Patent Application
20230282820
This invention relates to electrode materials useful for rechargeable lithium-based cells and battery systems.
Today, rechargeable lithium-ion batteries (LIBs) command a multi-billion-dollar industry. LIBs operate by shuttling lithium ions between the negative electrode (the anode) and the positive electrode (the cathode) during discharge and charge. Well-known examples of anode materials are carbon, particularly graphite, and the lithium-titanate spinel, Li4TisO12 (LTO). Well-known cathode products include materials with layered structures, compositional variations of the lithium-manganese-oxide spinel, and lithium-iron-phosphate, LiFePO4 (LFP), which has an olivine-type structure. Examples of layered materials include LiCoO2 (LCO), LiNi0.8Co0.15Al0.05O2 (NCA) and various lithium-nickel-manganese-oxide (NMC) compositions such as LiNi0.6Co0.2Mn0.2O2 (NMC622), LiNi0.33Co0.33Mn033O2 (NMC111), and lithium-rich variants, Li1+xM′1−xO2 (M=Ni, Mn, Co), alternatively designated in composite notation as wLi2MnO3·(1−w)LiM′O2. Examples of lithium-manganese-oxide spinel-type materials include LiMn2O4 (LMO) and substituted LiMn2−xNixO4 (0<x≤0.5, LMNO) materials, such as LiMn1.8Ni0.2O4 (x=0.2) and LiMn1.5Ni0.5O4 (x=0.5) and the lithium-rich spinel Li1.03Mn1.97O4. These materials represent stoichiometric spinel cathodes, in their stable discharged state, thereby enabling the safe assembly of lithium-ion cells and batteries, as well as the safe transport of these products from manufacturer to customer across the globe.
Gummow et al. reported the discovery of a new polymorphic form of lithium-cobalt-oxide (LiCoO2) in the Materials Research Bulletin, Volume 27, pages 327-337 (1992). This compound was designated LT-LiCoO2 because it was synthesized at a relatively low temperature (LT) of 400° C., compared to the previously known layered LiCoO2, which is prepared at a significantly higher temperature (HT), typically 900° C., i.e., HT-LiCoO2. Gummow et al. also reported in Solid State Ionics, Volume 53-56, pages 681-687 (1992) that nickel could be substituted for cobalt in the LT-LiCo1−xNixO2 system over the range (0<x≤0.2). From an X-ray structural analysis, it was concluded by Rossen et al. in Solid State Ionics, Volume 62, pages 53-60 (1993) that LT-LiCoO2 had a lithiated-spinel structure, while the refinements of Gummow et al. in the Materials Research Bulletin, Volume 28, pages 235-246 (1993) suggested that LT-LiCoO2 samples had a predominant lithiated-spinel-like structure that deviated from the ideal spinel arrangement of cations.
More recently, Lee et al. in ACS Applied Energy Materials, Volume 2, pages 6170-6175 (2019) revealed that Al-substitution for cobalt is also possible in LT-LiCo1−xAlxO2 for (0<x<0.5) but, in this case, the electrochemical signature differs from that provided by LT-LiCoO2 and LT-LiCo1−xNixO2 lithiated-spinel electrodes, exhibiting single-phase behavior on lithium extraction, rather than the typical two-phase behavior expected of spinel electrodes. A structural refinement of LT-LiCo0.85Al0.15O2 (x=0.15) by Lee et al. indicated that this behavior could be attributed to a small amount of cation disorder on the octahedral sites of the lithiated-spinel LT-LiCo1−xAlxO2 structure. Consequently, these slightly disordered lithiated-spinel LT-LiCo1−xAlxO2 materials can be defined as having slightly disordered rock salt structures. Like layered LiCoO2, LT-LiCoO2 and substituted derivatives are discharged cathodes. Lithium-ion cells with these cathode materials coupled to graphite (carbon) anodes can therefore be assembled safely in the discharged state, i.e., when all the lithium required for the electrochemical reaction is contained in the cathode. Such cells provide an attractive operating cell voltage of approximately 3.5 V.
Cobalt-containing lithiated-spinel electrode materials, for example, LiCo1−xMxO2, in which M is one or more metal ions, such as Ni and/or Al, are also of interest as stabilizers for layered lithium-rich and manganese-rich wLi2MnO3·(1−w)LiM′O2 (M′=Ni, Mn, and Co; i.e., NMC) electrodes, as described by Lee et al. in AppliedMaterials & Interfaces, Volume 8, pages 27720-27729 (2016). An advantage of these electrodes is that both lithiated-spinel and layered wLi2MnO3·(1−w)LiM′O2 components have a rock salt composition, in which the number of cations equals the number of anions, thereby facilitating their structural integration, particularly when the two components have closely-matched crystallographic lattice parameters. Furthermore, the discovery of LT-LiCo1−xAlxO2 electrode materials has heightened interest in developing all-solid-state ‘spinel-spinel’ cells, which can be assembled in their discharged state, for example, by coupling a Li4Ti5O12 spinel anode to a lithiated-spinel LT-LiCo1−xAlxO2 cathode with an appropriate lithium-ion conducting solid electrolyte, such as a solid inorganic electrolyte or a solid polymer electrolyte.
The generic family of materials with a spinel-type structure is broad and diverse. Numerous spinel-type compositions are found in nature while many others can be prepared synthetically in the laboratory, usually at elevated temperatures well above room temperature. The lithium spinels, such as LiMn2O4, Li4Mn5O12, LiMn1.5Ni0.5O4, and Li4Ti5O12, which are of interest as electrodes for Li-ion battery applications, are typically prepared at temperatures between 400 and 900° C. By contrast, lithiation of the above-mentioned spinels to form lithiated-spinel products has to be conducted at room temperature or at slightly higher temperatures, e.g., 50° C., by chemical reactions, for example with butyllithium, or by electrochemical reactions in an inert atmosphere because these lithiated-spinel structures are unstable at higher temperatures, particularly if heated in air or oxygen. In this respect, the family of lithiated cobalt-containing spinels, LiCo1−xMxO2, is distinct because they can be prepared at a moderately high temperature (for example, 400-500° C.) in air or oxygen, thereby offering the possibility of incorporating lithiated spinels as stabilizing components during the preparation of ‘layered-layered’ wLi2MnO3·(1−w)LiM′O2 (M′=Ni, Mn, and Co; “NMC”) electrode materials.
Of the cathode materials discussed above, LCO, NCA and NMC materials dominate the current global cathode materials market. All of these cathode materials contain cobalt, which is the most expensive and least abundant cathode component used in lithium-ion batteries. Major international efforts are therefore underway to find less expensive nickel-rich and manganese-rich alternatives that are cobalt-free, without compromising the electrochemical performance of lithium-ion cells. This has been a daunting task.
The materials, electrodes, cells and batteries described herein address the need for new cobalt-free, lithium-metal-oxide electrode structures and compositions.
Currently, there is great interest in developing new materials for lithium-ion cathodes, which are either low-Co, Co-free, or which contain Co but have other desired properties (e.g., improved cycling stability, improved coulombic efficiency; improved specific capacity, and the like relative to lithium cobalt oxide (LCO).
The cobalt-free cathode materials described herein have a lithiated-spinel-type structure. These novel materials open the door to the development and exploitation of lower cost and safer cobalt-free electrode materials for next generation lithium-ion cells and batteries. The cobalt-free lithiated spinel materials described herein have the general empirical formula LiMnxNiyMzO2, in which x+y+z=1, 0<x<1.0, 0<y<1.0, 0≤z≤0.5, or alternatively in lithiated-spinel notation, Li2Mn2xNi2yM2zO4, and in which M is selected from one or more metal cations, excluding Mn, Ni and Co. Preferably, M comprises Mg, Al, Ga, a combination of Mg and Ti in a 1:1 ratio, or a combination thereof. In general, the Mn:Ni ratio in the lithiated-spinel structures described herein is less than 2:1 and greater than 1:2, and in some embodiments close to 1:1. The lithiated spinel components of the materials described herein can adopt both ordered and partially-ordered cation configurations whereas the layered components are generally disordered.
In one aspect, the cobalt-containing lithium metal oxide materials described herein have a lithiated spinel-type structure (preferably predominately lithiated spinel; i.e., the material comprises greater than 50 mol % of the lithiated spinel structure; e.g., greater than 55 mol %, greater than 60 mol %, greater than 70 mol %, greater than 80 mol %, or 90 mol % of the lithiated spinel structure) and which have an overall empirical formula of LiMnxNiyMzO2; wherein M comprises Co and, optionally, other metals besides manganese and nickel; x+y+z=1; 0<x<1.0; 0<y<1.0; and 0≤z≤0.5; the Mn and Ni are present in a molar Mn:Ni ratio in the range of about 1:2 to about 2:1. In some embodiments, z≤0.2, or z≤0.4, or z≤0.5; and 0.05≤z, or 0.1≤z, or 0.15≤z. For example, in some embodiments, 0≤z≤0.2, or 0.05≤z≤0.2, or 0.1≤z≤0.2, or 0.15≤z≤0.2, or 0≤z≤0.4, or 0.05≤z≤0.4, or 0.1≤z≤0.4, or 0.15≤z≤0.4, or 0.2≤z≤0.4, or 0.3≤z≤0.4.
In another aspect, lithium-manganese-nickel-oxide electrode materials for lithium cells and batteries, notably rechargeable Li-ion batteries, are described herein, which are crystalline, structurally-integrated, lithium-metal-oxides of empirical formula LiM1O2 wherein M1 comprises a combination of Mn and Ni transition metal ions; the crystal structure of the materials comprises domains of an ordered or disordered lithiated-spinel component, a disordered layered component, and optionally a disordered rock salt component, in which the oxygen lattice of the components is cubic-close packed. In general, the Mn:Ni ratio in the lithiated-spinel structures described herein is less than about 2:1, and preferably about 1:1 (i.e., 1.05:1 to 0.95:1, or 1.02:1 to 0.98:1, or 1.01:1 to 0.99:1). Optionally, the lithium-manganese-nickel-oxide electrode materials can be blended or structurally-integrated or deposited as surface layers by, for example, wet chemical methods, with other cathode materials and structures, notably lithium-metal-oxide- and lithium-metal-polyanionic materials and structures, such as layered, spinel, lithiated-spinel, rock salt, olivine and partially disordered structures and/or partially-fluorinated derivatives to the extent of 10% of the O lattice in the bulk and at the surface thereof. Following the principles of this invention, selected examples and compositions of these materials and structures are: layered Li2MnO3, LiNi1−x−yMnxCoyO2 (NMC) and lithium-rich derivatives thereof, such as xLi2MnO3·(1−x)LiNi1−x−yMnxCoyO2; spinel LiMn2−xNixO4 (0≤x≤0.5), e.g., LiMn1.5Ni0.5O4 (x=0.5) and LiMn1.8Ni0.2O4; lithiated-spinel LiCo1−xAlxO2 and LiCo1−x−yNixAlyO2; disordered rock salt materials and structures, including lithium-rich compositions, and olivine LiFePO4. One method for identifying these component structures in the materials of this invention is to use high-resolution transmission electron microscopy, as demonstrated in a recent study by Shi et al of LT-LiMn0.5Ni0.5O2 published in Chemical Communications (2021) in which disordered layered, lithiated-spinel and rock salt components were identified. In some embodiments, M1 is M2(1−w)M3w, such that the material has the empirical formula LiM2(1−w)M3wO2, wherein M2 is a combination of Mn and Ni transition metal ions in a ratio of Mn to Ni ions of about 2:1 to about 1:1; M3 is one or more metal cations selected from the group consisting of an Al cation, a Ga cation, a Mg cation, a Ti cation, and a Co cation; and 0<w≤0.5.
In further embodiments, the lithium-manganese-nickel-oxide (LiM1O2) materials described herein can be blended or structurally-integrated with one or more ordered or disordered, layered (Li2M4O3) compositions and structures, in which M4 is one or more metal cations, selected preferably from Mn, Ti, and Zr cations. Alternatively, the lithium-manganese-nickel-oxide (LiM1O2) materials can be blended or structurally-integrated with one or more ordered or partially disordered, layered or lithiated-spinel (LiM5O2) materials and structures, in which M5 is different from M1 and comprises one or more metal cations, selected preferably from first-row transition metal cations, such as Mn, Ni, and Co cations, optionally substituted by minor amounts of one or more of Al, Ga and Mg cations, and partially-fluorinated derivatives thereof. In yet another alternative, the lithium-manganese-nickel-oxide-based LiM1O2 materials can be blended or structurally-integrated with a combination of the Li2M4O3 and LiM5O2 materials and structures and partially-fluorinated derivatives thereof. As such, these electrode materials can be generally described as having blended or integrated structures with layered- and lithiated-spinel character. In yet a further embodiment, the lithium-manganese-nickel-oxide (LiM1O2) materials described herein can be blended or structurally-integrated with one or more LiM82O4 materials with a spinel-type structure in which M8 is selected preferably from first-row transition metal cations, such as Mn, Ni, and Co cations, optionally substituted by minor amounts of one or more of non-transition cations, such as Li, Mg, and Al cations, and partially-fluorinated derivatives of LiM82O4 materials in which up to 10% of the O lattice in the bulk and at the surface thereof is replaced by F.
In another aspect, it is well known in the art that the cathode materials of lithium-ion cells, particularly those that operate at high potentials, such as between 3.0 and 5.0 V, require surface passivation to combat deleterious effects during electrochemical cycling, such as transition metal dissolution and oxygen loss, which can lead to capacity loss and structural degradation. Numerous passivating agents such as Al2O3, ZrO2, metal fluorides, glasses, carbon-based materials and more complex compounds have therefore been used to enhance electrochemical performance as described by G. Kaur and B. D. Gates in the Journal of the Electrochemical Society, volume 169, page 043504 (2022). The electrode materials described herein therefore can include surface-passivated materials with protective coatings as known in the art for other electrode materials.
In yet another aspect, a method for preparing a material of formula LiM2(1−w)M3wO2 is described herein. The method comprises the steps of (a) atomizing a precursor solution with oxygen to form liquid droplets; (b) spraying the liquid droplets into a methane/oxygen pilot flame of a flame-spray pyrolysis (FSP) unit to vaporize and oxidize the metal salts to produce a precursor powder; and (c) heating the precursor powder in air at a selected temperature in the range of about 400 to about 650° C. (preferably 400 to 600° C.) to form the material of empirical formula LiM2(1−w)M3wO2; wherein the precursor solution comprises stoichiometrically-required amounts of a Li salt, a M2 salt, and a M3 salt dissolved in non-aqueous solvent or an aqueous solvent, wherein optionally, the lithium salt is present in a molar excess of less than about 10 mol %; M2 is a combination of Mn and Ni transition metal ions in a ratio of Mn to Ni ions of about 2:1 to about 1:1; M3 is one or more metal cations selected from the group consisting of an Al cation, a Ga cation, a Mg cation, a Ti cation; and a Co cation; and 0<w≤0.5.
In yet a further embodiment, the electrode materials described herein can contain structurally-intergrown domains of lithiated spinel, layered and rock salt configurations, and disordered variations thereof, each of which can be represented by the generic formula LiMO2 (M=one or more metal ions, e.g., Mn, Ni, and/or Co with minor amounts of Mg, Al, Ti, and/or Fe). In some embodiments, LiMO2 can be LiM1O2, as described above. The LiMO2 is typically prepared as a separate composition by heating precursor materials (e.g., mixtures of metal salts and/or oxides in a stoichiometric ratio of metal ions suitable to form a targeted proportion of different M ions and Li stoichiometry) at 400 to 500° C. A significant advantage of these structurally-intergrown (i.e., structurally-integrated) materials is that they themselves can then be used as further precursors to fabricate other structurally integrated products.
In particular, a minor amount of the LiMO2 material is reacted with one or more layered lithium metal oxides materials (including simple layered materials, and structurally integrated layered-layered materials) at selected temperatures, e.g., in the range of about 500 to about 900° C. (preferably about 500 to 750° C.) to integrate the LiMO2 material with the layered lithium metal oxide to stabilize close-packed lithium-metal-oxide electrode structures. This integration and stabilization can occur because the LiMO2 material with the layered lithium metal oxide both have compatible oxygen lattices and metal layers, which facilitate structural integration. For example, the intergrown materials can be incorporated into layered manganese-rich and layered lithium- and manganese-rich metal oxide electrode materials, such as those represented by the formula xLi2MnO3·(1−x)LiMeO2 in which Me is one or more metal ions, at least one of which is selected from the group of Mn, Ni and Co ions, and in which 0≤x≤1. The resulting products can be represented by the formula (1−y)[xLi2MnO3·(1−x)LiMeO2]·yLiMO2 wherein 0≤x≤1, and 0<y<0.3 (e.g., O<y≤0.25; 0<y≤0.18; 0<y≤0.15; 0<y≤0.1, 0<y≤0.08; 0<y≤0.05; or 0<y≤0.03). Other metal ions, such as Mg, Al, Ti and Fe cations, can be included in small amounts relative to dominant M and/or Me transition metal cations. Partial substitution of oxygen by fluorine particularly at the electrode surface, can also contribute to the overall structural and electrochemical stability of (1−y)[xLi2MnO3·(1−x)LiMeO2]·yLiMO2 electrode materials.
Ideal, pure layered materials of formula LiMO2 have a 1:1 ratio of cations (Li and M) to anions (O2−) in a layered configuration having separate alternating layers of Li and M cations sharing an oxygen anion lattice. A partially-disordered layered structure is one in which some minor amount of Li and M is exchanged between the predominately Li and M layers, for example, typically less than 25% of Li:M exchange in the layered structure.
Ideal, pure lithiated-spinel materials of formula LiMO2 can be viewed as having a similar structure of alternating metal ion layers and oxygen lattice, but having layers of Li and M cations in which there is a 1:3 ratio of Li:M in one metal layer, and a 3:1 ratio of Li:M in one metal layer. Thus, the lithiated spinel structure is similar to the layered structure, but with 25% of the Li in the predominately M layers and 25% of the M in the predominately Li layers (i.e., 25% metal ion disorder).
A partially-disordered layered or lithiated spinel structure is one in which the distribution of Li and M differs from the ideal layered or lithiated spinel distribution by some amount, e.g., by about 25 percent or less, or between about 20 and 10 percent, about 10 percent or less, compared to the ideal structures. As used herein, a “disordered rock salt” or “rock salt” or “rock salt-like” structure refers to domains having the same 1:1 cation:anion rock salt stoichiometry as the layered and lithiated spinel materials, but in which the amount of Li/M layer exchange is greater than the 25% present in an ideal lithiated spinel structure.
The domains of layered, lithiated spinel, and rock salt structures can be identified by high-resolution transmission electron microscopy (TEM): for layered domains, the transition metal-containing layers (TM layers) show up as distinctly parallel lines, whereas for lithiated-spinel structures the TM-containing layers show up as strongly and uniformly cross-hatched lines because of the presence of M ions uniformly dispersed in the Li layers in a 1:3 ratio; rock salt domains (sometimes referred to as “disordered rock salt”) are less uniformly cross-hatched than the lithiated spinel structures, which is attributed to the higher degree of mixing of Li and M in the cation layers.
Heating structurally-intergrown LiMO2 materials such as LiCo0.85Al0.15O2, LiMn0.5Ni0.5O2 and LiMn0.33Ni0.33Co0.33O2 having structurally integrated domains of lithiated spinel, layered and rock salt configurations, and partially-disordered variations thereof, above about 400° C. gradually transforms the lithiated spinel and rock salt domains towards an ideal layered configuration, thereby increasing the concentration of the layered-like domains, while decreasing the concentration of the lithiated spinel- and rock-salt-like domains in the electrode material.
This process continues until the concentrations of the lithiated spinel and rock salt components reach values for the optimum stabilization of the layered domains. For example, a compound with an overall composition that lies between Li2MnO3 and LiNi(1−a−b)MnaCobO2 and substituted derivatives thereof can be prepared, such as xLi2MnO3·(1−x)LiNi(1−a−b)MnaCobO2 materials in which Ni1−a−bMnaCob represents Me, as defined above. In addition, substituted compositions in which the Ni, Mn and Co ions are replaced by minor amounts (i.e., 0.5 to 10%) of one or more other transition metal ions, such as Ti or Fe ions or non-transition metal ions, such as Al or Mg ions can also be prepared. In a preferred embodiment, the amount of the stabilized layered domains relative to the total amount of the lithiated spinel and rock salt domains in the LiMO2 can vary from about 99% to about 50%, preferably from about 99% to about 80%. Conversely, the total amount of the lithiated spinel and rock salt domains relative to the amount of the stabilized layered domains can vary from about 1% to about 50%, preferably from about 1% to about 20%.
The approach described above provides a new, controlled method of tailoring the relative amounts of layered, lithiated spinel and rock salt domains in order to optimize the electrochemical properties and stability of the composite (1−y)[xLi2MnO3·(1−x)LiMeO2]·yLiMO2 electrode materials described herein.
In another embodiment, synthesis methods and heat-treatment procedures to control and optimize the composition and structures of the stabilized (1−y)[xLi2MnO3·(1−x)LiMeO2]·yLiMO2 electrode materials are also provided. For example, one method involves the initial synthesis of an LiMO2 material with structurally-integrated and partially-disordered lithiated spinel, layered rock salt domains at about 400 to 500° C., or optionally at higher temperatures, for example, between about 400° C. and about 600° C. This LiMO2 material is then reacted with (1) another LiMO2 material (i.e., having a different M composition), or (2) a layered xLi2MnO3·(1−x)LiMeO2 (0≤x<1) material or, (3) with more with a mixture of precursor materials (e.g., such as metal hydroxides, carbonates and nitrates) that will form the layered xLi2MnO3·(1−x)LiMeO2 material mentioned above; by heating the materials at one or more consecutive temperatures in the range of about 500 to 900° C., preferably about 500 to 750° C., for a time sufficient to achieve a desired or optimum stabilization of the material. The desired or optimum stabilization level for a given composition can be determined by routine experimentation and evaluated by electrochemical methods, XRD, and/or TEM.
In addition, materials of formula xLi2MnO3·(1−x)LiMeO2, and/or LiMO2, optionally can be structurally integrated with a spinel material of formula LiM82O4 as described herein to form a material of formula: n[xLi2MnO3·(1−x)LiMeO2]·mLiMO2·zLiM82O4 wherein 0≤x<1; n+m+z=1; 0<n<1 (e.g., 0<n≤0.95; 0<n≤0.8; 0<n≤0.75; 0<n≤0.7, 0<n≤0.6; 0<n≤0.5; or 0<n≤0.45); 0≤m<1 (e.g., 0≤m≤0.5; 0≤m≤0.3; 0≤m≤0.15; 0≤m≤0.1, 0≤m≤0.08; 0≤m≤0.05; or 0≤m≤0.03); 0<z<0.3 (e.g., 0<z≤0.25; 0<z≤0.18; 0<z≤0.15; 0<z≤0.1, 0<z≤0.08; 0<z≤0.05; or 0<z≤0.03); the [xLi2MnO3·(1−x)LiMeO2] component comprises a layered (L) or layered-layered (LL) structure, the yLiMO2 component comprises an ordered or partially disordered lithiated spinel (LS) structure, and the LiM82O4 component comprises an ordered or partially disordered spinel (S) structure. Preferably, 0.5≤n<1. In some embodiments, 0<m<0.3, and 0<z<0.3, such that the material has a layered-lithiated spinel-spinel structure (i.e., x=0), or a layered-layered-lithated spinel-spinel structure (i.e., x>0).
In a preferred embodiment, the LiM82O4 spinel component is comprised of one or more spinel components containing manganese, optionally with or without nickel, such as those that are defined by the Li1+xMn2−xO4 system (0≤c≤1/3) with end members LiMn2O4 (x=0) and Li4Mn5O12, or alternatively, Li(Mn5/3Li1/3)O4 (x=1/3), and by the LiMn2−xNixO4 system 0≤x≤0.5) with end members LiMn2O4 (x=0) and LiMn1.5Ni0.5O4 (x=0.5) and substituted derivatives thereof that contain, for example, less than 10% of Al, Co, Mg, Ti cations and F anions. In this respect, it should be noted that it has been previously demonstrated that a spinel component (LiM2O4) can be used to improve the electrochemical performance of xLi2MnO3·(1−x)LiMeO2 electrodes, for example by Long et al. in the Journal of the Electrochemical Society, Volume 161, pages A2160-A2167 (2014), and by Croy et al. in the Journal of Power Sources, Volume 334, pages 213-220 (2016), but not in the presence of the lithiated spinel (rock salt) components (LiMO2) of this invention, which provide significantly higher capacities.
Selected periods of time can be used at different temperatures, which can vary from minutes to hours, to control and/or optimize (1) the amount of the stabilizing lithiated spinel domains in the product, (2) the extent of disorder in the composite electrode structure, and/or (3) the electrochemical performance of the product. The degree to which the structure is modified by the annealing can be assessed and/or monitored by XRD and high-resolution TEM, for example.
Materials of broad scope, both from compositional and structural points of view, can be prepared by the methods described herein. This versatility is illustrated by the following examples that contain one or more layered components (L), one or more lithiated-spinel components (LS), one or more spinel components (S) and typically some partially-disordered (rock salt) variations thereof The materials were prepared by annealing the LiMO2 with the appropriate stoichiometry of Li and M ions (i.e., M selected from Ni, Mn, and Co, with minor amounts of Al in some cases, at a temperature in the range of about 400 to 750° C.:
In practice, it is difficult to control and determine the exact composition of the individual components within these highly complex and structurally integrated composite electrode materials when made by the synthesis methods of this invention. In this respect, however, the layered and lithiated spinel components, and disordered variations thereof, can by identified by high-resolution TEM as described and presented herein.
Another aspect relates to LiMO2 materials, as described above, which have the composition LiMn0.75Ni0.25O2, which can be written in lithiated spinel notation as Li2Mn1.5Ni0.5O4. A lithiated spinel of this composition can be synthesized at room temperature by inserting lithium into the LiMn1.5Ni0.5O4 structure, either chemically, for example with n-butyllithium, or electrochemically in a Li/LiMn1.5Ni0.5O4 spinel cell. During this reaction, the manganese ions are reduced from a tetravalent, Mn4+, state to an average Mn3.33+ state, as well known in the art. It would be desirable to integrate this material with Li2MnO3; however, if Li2Mn1.5Ni0.5O4 is synthesized under conditions allowing integration with Li2MnO3, such as in air or under oxygen at moderate temperatures, e.g., at about 400° C., the lithiated spinel structure described above would be unstable because oxidation of the Mn3.33+ ions to tetravalent Mn4+ would occur. In order to overcome this difficulty, the desired integrated material can be produced directly by reacting suitable precursor materials in suitable stoichiometry, such as lithium, manganese, nickel and lithium carbonates, hydroxides, nitrates and the like, or mixtures thereof (e.g., Li2CO3, MnCO3, Ni(OH)2) using extra lithium, in the presence of oxygen or air, to increase the oxidation state of the Mn3.33+ ions in Li2Mn1.5Ni0.5O4 to a tetravalent Mn4+ state. In this case, the reaction at 400° C. would likely result in thermodynamically-stable components, as represented by the process:
Li2Mn1.5Ni0.5O4+½Li2CO3+½O2→Li2MnO3+LT-LiMn0.5Ni0.5O2.
In this reaction, the LT-LiMn0.5Ni0.5O2 product is composed of structurally-integrated and partially-disordered lithiated spinel, layered, and rock salt components as described herein. Heating the resulting structurally-integrated Li2MnO3·LiMn0.5Ni0.5O2 product to higher temperatures (e.g., from 400 to 700° C.) increases the concentration of the layered LiMn0.5Ni0.5O2 domains at the expense of the partially-disordered lithiated spinel and rock salt domains, thereby providing a controlled route to synthesize and tailor a new family of stabilized electrode materials with structurally-integrated Li2MnO3—, lithiated spinel-, layered- and rock salt components within a composite structure.
Alternatively, in yet another aspect of this invention, the lithium-manganese-nickel-oxide (LiM1O2) materials, which are comprised of one or more ordered or disordered lithiated spinel components and one or more disordered layered components, can be structurally integrated or blended with one or more ordered or disordered spinel (LiM82O4) components as expressed, for example, by the formula pLiNi0.5Mn0.5O2(L)·rLiMn0.5Ni0.5O2(LS)·wLiMn2−xNixO4(S) (0≤x≤0.5, e.g., LiMn1.5Ni0.5O4 (x=0.5) or LiMn1.8Ni0.2O4 (x=0.2)) without a Li2MnO3 component, where L, LS and S refer to layered, lithiated spinel and spinel configurations, respectively, and where p+r+w=1, such as p=0.8, r=0.1 and w=0.1.
The following non-limiting embodiments of the materials and methods described herein are provided below to illustrate certain aspects and features of the compositions and methods described herein.
Embodiment 1 is a cobalt-free lithium battery electrode active material of empirical formula LiMnxNiyMzO2; the material comprising a lithiated spinel structure; wherein M comprises one or more metal cations other than manganese, nickel and cobalt, x+y+z=1, 0<x<1.0, 0<y<1.0, 0<z≤0.5; and having a molar Mn:Ni ratio in the range of about 1:2 to about 2:1.
Embodiment 2 comprises the electrode active material of embodiment 1, wherein the Mn:Ni ratio is about or equal to 1:1.
Embodiment 3 comprises the electrode active material of embodiment 1 or embodiment 2, wherein M comprises one or more metal cation selected from the group consisting of an Al cation, a Ga cation, and a combination of Mg and Ti cations.
Embodiment 4 comprises the electrode active material of any one of embodiments 1 to 3, wherein at least two of the Li, Mn, Ni and M cations in the lithiated spinel are partially disordered over the octahedral sites of the lithiated-spinel structure.
Embodiment 5 is the electrode active material of any one of embodiments 1 to 4, wherein the lithiated-spinel structure contains cation and/or anion defects or deficiencies.
Embodiment 6 is the electrode active material of any one of embodiments 1 to 5, wherein the lithium, oxygen, and/or total non-lithium metal content of the lithiated-spinel composition LiMnxNiyMzO2 varies by up to about 5 percent from an ideal 1:1:2 respective elemental stoichiometry.
Embodiment 7 is the electrode active material of any one of embodiments 1 to 6, further comprising fluorine in place of a portion of the oxygen in the LiMnxNiyMzO2; wherein less than 10 mole percent of the oxygen is replaced by fluorine.
Embodiment 8 is an electrode active composition for an electrochemical cell comprising a first cobalt-free electrode active material with a lithiated spinel structure mechanically blended or structurally integrated with a second electrode active material; wherein the first electrode active material has the empirical formula LiMnxNiyMzO2; wherein M comprises one or more metal cations other than manganese, nickel and cobalt; x+y+z=1; 0<x<1.0; 0<y<1.0; 0≤z≤0.5; and having a molar Mn:Ni ratio in the range of about 1:2 to about 2:1; and the second electrode active material comprises one or more cobalt-containing lithium metal oxide material.
Embodiment 9 comprises the electrode active material of embodiment 8, wherein the cobalt-containing lithium metal oxide material comprises LiCoO2 with a layered-type structure and/or LiCoO2 with a lithiated-spinel-type structure.
Embodiment 10 comprises the electrode active material of embodiment 8 or embodiment 9, wherein Co comprises less than about 33 mol % of non-lithium metal ions in the electrode active material.
Embodiment 11 comprises the electrode active material of any one of embodiments 8 to 10, wherein Co comprises less than 20 mol % of non-lithium metal ions in the electrode active material.
Embodiment 12 comprises the electrode active material of any one of embodiments 8 to 11, wherein Co comprises less than 10 mol % of the non-lithium metal ions.
Embodiment 13 comprises the electrode active material of any of embodiments 8 to 12, wherein the lithiated-spinel structure contains cation and/or anion defects or deficiencies.
Embodiment 14 is an electrode for a lithium electrochemical cell comprising particles of the electrode active material of any one of embodiments 1 to 13 in a binder matrix coated on a current collector.
Embodiment 15 comprises the electrode of embodiment 14, wherein the current collector comprises a metal or carbon material.
Embodiment 16 comprises the electrode of embodiment 15, wherein the current collector comprises a conductive carbon fiber paper.
Embodiment 17 comprises the electrode of embodiment 15, wherein the current collector comprises aluminum foil.
Embodiment 18 comprises the electrode of any one of embodiments 14 to 17, wherein the binder matrix comprises poly(vinylidene difluoride).
Embodiment 19 comprise the electrode of any one of embodiments 14 to 18, wherein the electrode further comprises particles of a conductive carbon material mixed with the electroactive material in the binder matrix.
Embodiment 20 is an electrochemical cell comprising an anode, a cathode, and a lithium-containing electrolyte contacting the anode and cathode, wherein the cathode comprises the electrode of any one of embodiments 14 to 19.
Embodiment 21 is a battery comprising a plurality of electrochemical cells of embodiment 20, electrically connected in series, in parallel, or in both series and parallel.
Embodiment 22 is a method for preparing the electrode active material of any one of embodiments 1 to 7, comprising heating a mixture of precursor salts at a temperature in the range of about 200 to about 600° C. in an oxygen-containing atmosphere (e.g., air); wherein the precursor salts comprises salts of Li, Mn, Ni and M cations with anions selected from the group consisting of carbonate, hydroxide, oxide, and nitrate; and the Li, Mn, Ni and M salts are present in a stoichiometric ratio selected to provide a target lithiated spinel of formula LiMnxNiyMzO2; wherein M comprises one or more metal cations other than manganese, nickel and cobalt, x+y+z=1, 0<x<1.0, 0<y<1.0, 0≤z≤0.5; and having a molar Mn:Ni ratio in the range of about 1:2 to about 2:1.
Embodiment 23 comprises the method of embodiment 22, wherein the mixture of precursor salts temperature is in the range of about 400 to 600° C.
Embodiment 24 comprises the method of embodiment 22 or embodiment 23, wherein the lithium salt is lithium carbonate, and the Ni, Mn, M salts are single or mixed metal hydroxides of Ni, Mn, and M metal cations.
Embodiment 25 comprises an electrode active material of empirical formula LiMnxNiyMzO2; the material comprising (preferably predominately comprising) a lithiated spinel structure; wherein M comprises Co and, optionally, other metals besides manganese and nickel; x+y+z=1; 0<x<1.0; 0<y<1.0; 0≤z≤0.5; and having a molar Mn:Ni ratio in the range of about 1:2 to about 2:1. In some embodiments, 0≤z≤0.2, or 0.05≤z≤0.2, or 0.1≤z≤0.2, or 0.15≤z≤0.2, or 0≤z≤0.4, or 0.05≤z≤0.4, or 0.1≤z≤0.4, or 0.15≤z≤0.4, or 0.2≤z≤0.4, or 0.3≤z≤0.4.
Embodiment 26 comprises the electrode active material of embodiment 25, wherein 0≤z≤0.1.
Embodiment 27 comprises the electrode active material of embodiment 25 or 26, wherein at least two of the Li, Mn, Ni and M cations in the lithiated spinel are partially disordered over the octahedral sites of the lithiated-spinel structure.
Embodiment 28 is the electrode active material of any one of embodiments 25 to 27, wherein the lithiated-spinel structure contains cation and/or anion defects or deficiencies.
Embodiment 29 is the electrode active material of any one of embodiments 25 to 28, wherein the lithium, oxygen, and/or total non-lithium metal content of the lithiated-spinel composition LiMnxNiyMzO2 varies by up to about 5 percent from an ideal 1:1:2 respective elemental stoichiometry.
Embodiment 30 is the electrode active material of any one of embodiments 25 to 29, further comprising fluorine in place of a portion of the oxygen in the LiMnxNiyMzO2; wherein less than 10 mole percent of the oxygen is replaced by fluorine.
Embodiment 31 is the electrode active material of any one of embodiments 25 to 30 mechanically blended with or structurally integrated with another different electrode active material.
Embodiment 32 comprises an electrode active material comprising particles of the electrode active material of any one of embodiments 1 to 13 and 25 to 31 coated with a metal-oxide, a metal fluoride or a metal phosphate layer.
Embodiment 33 comprises the electrode active material of embodiment 32, wherein the metal oxide layer is a lithiated-spinel LiCo1−xAlxO2.
Embodiment 34 is an electrode active material comprising the electrode active material of any one of the embodiments 1 to 13 and 25-31 as a protective surface coating on an underlying lithium-metal-oxide electrode material.
Embodiment 35 comprises the lithium-metal-oxide electrode material of embodiment 34, wherein the underlying lithium-metal-oxide material has a layered or spinel structure.
Embodiment 36 is an electrode for a lithium electrochemical cell comprising particles of the electrode active material of any one of embodiments 25 to 35 in a binder matrix coated on a current collector.
Embodiment 37 comprises the electrode of embodiment 36, wherein the current collector comprises a metal or carbon material.
Embodiment 38 comprises the electrode of embodiment 37, wherein the current collector comprises a conductive carbon fiber paper.
Embodiment 39 comprises the electrode of embodiment 37, wherein the current collector comprises aluminum foil.
Embodiment 40 comprises the electrode of any one of embodiments 36 to 39, wherein the binder matrix comprises poly(vinylidene difluoride).
Embodiment 41 comprise the electrode of any one of embodiments 36 to 40, wherein the electrode further comprises particles of a conductive carbon material mixed with the electroactive material in the binder matrix.
Embodiment 42 is an electrochemical cell comprising an anode, a cathode, and a lithium-containing electrolyte contacting the anode and cathode, wherein the cathode comprises the electrode of any one of embodiments 36 to 41.
Embodiment 43 is a battery comprising a plurality of electrochemical cells of embodiment 42, electrically connected in series, in parallel, or in both series and parallel.
Embodiment 44 comprises a method for preparing the electrode active material of embodiment 25 to 29, comprising heating a mixture of precursor salts at a temperature in the range of about 200 to about 600° C. in an oxygen-containing atmosphere; wherein the precursor salts comprises salts of Li, Mn, Ni and M cations with anions selected from the group consisting of carbonate, hydroxide and nitrate, and the Li, Mn, Ni and M salts are present in a stoichiometric ratio selected to provide a target lithiated spinel of formula LiMnxNiyMzO2; wherein M comprises Co and, optionally, other metal cations besides manganese and nickel; x+y+z=1; 0<x<1.0; 0<y<1.0; 0≤z≤0.5; and having a molar Mn:Ni ratio in the range of about 1:2 to about 2:1. In some embodiments, 0≤z≤0.2, or 0.05≤z≤0.2, or 0.1≤z≤0.2, or 0.15≤z≤0.2, or 0≤z≤0.4, or 0.05≤z≤0.4 or0.1≤z≤0.4, or 0.15≤z≤0.4, or 0.2≤z≤0.4, or 0.3≤z≤0.4.
Embodiment 45 is a crystalline, structurally-integrated, lithium-metal-oxide composite electrode material of empirical formula LiM1O2, wherein M1 comprises a combination of Mn and Ni transition metal ions in a ratio of Mn to Ni ions of about 2:1 to about 1:1; the crystal structure of the material of empirical formula LiM1O2 comprises domains of a disordered lithiated-spinel component, a disordered layered component, and a disordered rock salt component, in which the oxygen lattice of the components is cubic-close packed, and in which greater than 0 percent and less than 20 percent (e.g., about, or up to about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19%) of lithium ions of the lithiated spinel and layered components are disordered among the octahedral sites normally occupied by the transition metal ions, and a corresponding percentage of the transition metal ions are disordered among the octahedral sites normally occupied by lithium ions, in fully-ordered, lithiated spinel and layered structures. In some preferred embodiments greater than 10 percent and less than 20 percent of the lithium ions of the lithiated spinel and layered components are disordered among the octahedral sites normally occupied by the transition metal ions, and a corresponding percentage of the transition metal ions are disordered among the octahedral sites normally occupied by lithium ions, in fully-ordered, lithiated spinel and layered structures.
Embodiment 46 is the material of Embodiment 1, wherein greater than 10 percent and less than 20 percent (e.g., about 11 to 19, 15 to 18, or 16 to 17 percent) of the lithium ions of the lithiated spinel and layered component structures are disordered among the octahedral sites normally occupied by the transition metals, and a corresponding percentage of the transition metal ions are disordered among the octahedral sites normally occupied by lithium ions, in fully ordered, lithiated spinel and layered structures.
Embodiment 47 is the material of Embodiments 45 or 46, wherein M1 comprises Mn and Ni ions in a ratio of Mn to Ni ions of about 1.5:1 to about 1:1.
Embodiment 48 is the material of any one of embodiments 45 to 47, wherein M1 comprises Mn and Ni ions in a ratio of Mn to Ni ions of about 1.1:1 to about 1:1.
Embodiment 49 is the material of any one of embodiments 45 to 48, wherein M1 comprises Mn and Ni ions in a ratio of about 1:1.
Embodiment 50 is the material of embodiment 49, wherein the disordered lithiated spinel and layered components of the material of formula LiM1O2 have X-ray diffraction (XRD) patterns in which the pattern of the disordered lithiated spinel component conforms to cubic space group symmetry Fd-3m with crystallographic formula: (Li0.83M0.17)2(16c)[Li0.83M10.17]2(16d)]O4(32e), the oxygen ions are cubic-close packed, about 16 to about 17 percent of lithium ions that would be located in 16c octahedral sites in a fully ordered lithiated spinel structure are located in 16d sites, and about 16 to 17 percent of the transition metal ions that would normally be located in 16d octahedral sites in a fully ordered lithiated spinel structure are present in 16c sites; the XRD pattern of the disordered layered component conforms to trigonal space group symmetry R-3m with crystallographic formula (Li0.83M10.17)(3a)[Li0.17M10.83](3b)]O2(6c), the oxygen ions are cubic-close-packed, about 16 to about 17 percent of lithium ions that would normally be located in 3a octahedral sites in a fully ordered layered material are located in 3b octahedral sites, and about 16 to 17 percent of the transition metal ions that would normally be located in 3b octahedral sites in the fully ordered layered structure are present in 3a octahedral sites.
Embodiment 51 is the material of any one of embodiments 45 to 50, wherein M1 in formula Li M1O2 is M2(1−w)M3w, M2 is a combination of Mn and Ni transition metal ions; M3 is one or more other metal cations selected from the group consisting of an Al cation, a Ga cation, a Mg cation, a Ti cation; and a Co cation; and 0<w≤0.1.
Embodiment 52 is the material of embodiment 51, wherein M2 is a combination of Mn and Ni transition metal ions in a Mn to Ni ratio of about 1:1 (i.e., 1.05:1 to 0.95:1, or 1.02:1 to 0.98:1, or 1.01:1 to 0.99:1).
Embodiment 53 is the material of embodiment 51 or 52, wherein M3 is an Al cation.
Embodiment 54 is the material of embodiment 51 or 52, wherein M3 is a Co cation.
Embodiment 55 is the material of any one of embodiments 45 to 54, wherein the lithium, M1, and/or oxygen, content of the material varies by up to about 5 percent from an ideal 1:1:2 respective elemental stoichiometry.
Embodiment 56 is the material of any one of embodiments 45 to 55, wherein the cubic-close-packed oxygen lattice deviates from ideal cubic-close-packing such that the crystal symmetry of one or more of the components is lowered by an anisotropic variation of at least one lattice parameter length of the unit cell by up to about 5%. Isotropic refers to a property of a material which is independent of spatial direction, whereas anisotropic is direction dependent. These two terms are commonly used to explain the properties of the material in basic crystallography, as is well known in the art.
Embodiment 57 is the material of any one of embodiments 45 to 55, wherein the cubic-close-packed oxygen lattice deviates from ideal cubic-close-packing such that the crystal symmetry of one or more of the components is lowered by an anisotropic variation of at least one lattice parameter length of the unit cell by up to about 2%.
Embodiment 58 is the material of any one of embodiments 45 to 57, further comprising fluorine in place of a portion of the oxygen in the material of formula LiM1O2; wherein less than 10 atom percent of the oxygen is replaced by fluorine.
Embodiment 59 is an electrode active composition for an electrochemical cell comprising a first electrode active material mechanically blended with or structurally integrated with a second electrode active material, wherein the first electrode active material is the material of any one of embodiments 45 to 58, and the second electrode active material comprises one or more additional lithium metal oxide materials different from the first electrode active material.
Embodiment 60 is an electrode for a lithium electrochemical cell comprising particles of an electrode active material in a binder matrix coated on a metal or carbon current collector; wherein the electrode active material comprises the material of any one of embodiments 45 to 59.
Embodiment 61 is an electrochemical cell comprising an anode, a cathode, and a lithium-containing electrolyte contacting the anode and cathode, wherein the cathode comprises the electrode of embodiment 60.
Embodiment 62 is a battery comprising a plurality of electrochemical cells of embodiment 61 electrically connected in series, in parallel, or in both series and parallel.
Embodiment 63 is a crystalline, structurally-integrated, lithium-metal-oxide composite electrode material of empirical formula LiM2(1−w)M3wO2, wherein M2 is a combination of Mn and Ni transition metal ions in a ratio of Mn to Ni ions of about 2:1 to about 1:1; M3 is one or more metal cations selected from the group consisting of an Al cation, a Ga cation, a Mg cation, a Ti cation; and a Co cation; and 0<w≤0.5; the crystal structure of the material of empirical formula LiM2(1−w)M3wO2 comprises domains of a disordered lithiated-spinel component, a disordered layered component, and optionally a disordered rock salt component, in which the oxygen lattice of the components is cubic-close packed, and in which greater than 0 and less than 20 percent of lithium ions of the lithiated spinel and layered components are disordered among the octahedral sites normally occupied by the transition metal ions, and a corresponding percentage of the transition metal ions are disordered among the octahedral sites normally occupied by lithium ions, in fully-ordered, lithiated spinel and layered structures. In some embodiments, w≤0.2, or w≤0.3, or w≤0.4, or w≤0.5; and 0.05≤w, or 0.1≤w, or 0.15≤w, or 0.3≤w.
Embodiment 64 is the material of embodiment 63, wherein greater than 10 percent and less than 20 percent of the lithium ions of the lithiated spinel and layered component structures are disordered among the octahedral sites normally occupied by the transition metals, and a corresponding percentage of the transition metal ions are disordered among the octahedral sites normally occupied by lithium ions, in fully ordered, lithiated spinel and layered structures.
Embodiment 65 is the material of embodiment 63 or 64, wherein the ratio of Mn to Ni ions is about 1:1.
Embodiment 66 is the material of any one of embodiments 63 to 65, wherein the ratio of Mn to Ni ions is in the range of 1.05:1 to 0.95:1.
Embodiment 67 is the material of any one of embodiments 63 to 66, wherein the ratio of Mn and Ni ions is in the range of 1.02:1 to 0.98:1.
Embodiment 68 is the material of any one of embodiments 63 to 67, wherein M3 is Co and 0<w≤0.35.
Embodiment 69 is the material of any one of embodiments 63 to 68, wherein M3 is Co and 0.3<w≤0.35.
Embodiment 70 is the material of embodiment 69, wherein the ratio of Mn to Ni ions is about 1:1.
Embodiment 71 is the material of embodiment 69, wherein the ratio of Mn to Ni ions is in the range of 1.05:1 to 0.95:1.
Embodiment 72 is the material of embodiment 69, wherein the ratio of Mn to Ni is in the range of 1.02:1 to 0.98:1.
Embodiment 73 is the material of any one of embodiments 63 to 72, wherein the lithium, M2, M2, and/or oxygen content of the material varies by up to about 5 percent from an ideal 1:(1−w):w:2 respective elemental stoichiometry.
Embodiment 74 is the material of any one of embodiments 63 to 73, wherein the cubic-close-packed oxygen lattice deviates from ideal cubic-close-packing such that the crystal symmetry of one or more of the components is lowered by an anisotropic variation of at least one lattice parameter length of the unit cell by up to about 5%.
Embodiment 75 is the material of any one of embodiments 63 to 73, wherein the cubic-close-packed oxygen lattice deviates from ideal cubic-close-packing such that the crystal symmetry of one or more of the components is lowered by an anisotropic variation of at least one lattice parameter length of the unit cell by up to about 2%.
Embodiment 76 is the material of any one of embodiments 63 to 75, further comprising fluorine in place of a portion of the oxygen in the material of formula LiM2(1−w)M3wO2; wherein less than 10 atom percent of the oxygen is replaced by fluorine.
Embodiment 77 is an electrode active composition for an electrochemical cell comprising a first electrode active material mechanically blended with or structurally integrated with a second electrode active material, wherein the first electrode active material is the material of any one of embodiments 63 to 76; and the second electrode active material comprises one or more additional lithium metal oxide materials different from the first electrode active material.
Embodiment 78 is an electrode for a lithium electrochemical cell comprising particles of an electrode active material in a binder matrix coated on a metal or carbon current collector; wherein the electrode active material comprises the material of any one of embodiments 63 to 76.
Embodiment 79 is an electrochemical cell comprising an anode, a cathode, and a lithium-containing electrolyte contacting the anode and cathode, wherein the cathode comprises the electrode of embodiment 78.
Embodiment 80 is a battery comprising a plurality of electrochemical cells of embodiment 79 electrically connected in series, in parallel, or in both series and parallel.
Embodiment 81 is a method for preparing a material of formula LiM2(1−w)M3wO2; the method comprising the steps of (a) atomizing a precursor solution with oxygen to form liquid droplet; (b) spraying the liquid droplets into a methane/oxygen pilot flame of a flame-spray pyrolysis (FSP) unit to vaporize an oxidize the metal salts to produce a precursor powder; and (c) heating the precursor powder in air at a selected temperature in the range of about 400 to about 650° C. (preferably 400 to 600° C.) to form the material of empirical formula LiM2(1−w)M3wO2; M2 is a combination of Mn and Ni transition metal ions in a ratio of Mn to Ni ions of about 2:1 to about 1:1; M3 is one or more metal cations selected from the group consisting of an Al cation, a Ga cation, a Mg cation, a Ti cation; and a Co cation; and 0<w≤0.5; and wherein the precursor solution comprises a Li salt, a M2 salt, and a M3 salt which are dissolved in a non-aqueous solvent or an aqueous solvent in stoichiometrically-required amounts required to achieve a target ratio of 1:(1−w):w:2, and optionally, the lithium salt is present in the precursor solution in a molar excess of less than about 10 mol %.
Embodiment 82 is the method of embodiment 81, wherein the precursor powder is heated at a selected temperature in the range of about 400 to about 600° C.
Embodiment 83 is the method of embodiment 81, wherein the precursor powder is heated at a selected temperature in the range of about 500 to about 600° C.
Embodiment 84 is the method of any one of embodiments 81 to 83, further comprising, before step (a), preparing the precursor solution by dissolving the Li salt, the M2 salt, and the M3 salt in an aqueous solvent or a non-aqueous solvent; wherein optionally the Li salt is included in an excess of up to about 10 mol %.
Embodiment 84 is the method of any one of embodiments 81 to 84, wherein each of the Li salt, the M2 salt, and the M3 salt is a salt of an organic acid.
Embodiment 85 is the method of any one of embodiments 81 to 84, wherein the organic acid is selected from the group consisting of acetic acid, propionic acid, and acetylacetic acid.
Embodiment 86 is the method of any one of embodiments 81 to 83, wherein the solvent is an organic solvent (e.g., a solvent selected from the group consisting of acetonitrile, 2-ethylhexanocid acid, and a combination thereof).
Embodiment 87 comprises a composite electrode active material comprising a first electrode active material blended or structurally-integrated with a second electrode active material that is different from the first electrode active material; wherein: the first electrode active material is a lithiated spinel selected from the group consisting of (a) a lithiated spinel of formula LiMnxNiyMzO2; wherein M comprises at least on metal cation other than manganese and nickel cations; x+y+z=1; 0<x<1.0; 0<y<1.0; 0≤z≤0.5; and the ratio of x:y is in the range of about 1:2 to about 2:1; and (b) a lithiated spinel of formula LiM1O2, wherein M1 comprises a combination of Mn and Ni transition metal ions in a ratio of Mn to Ni ions of about 2:1 to about 1:1; and the second electrode active material comprises at least one ordered or partially-disordered material selected from the group consisting of a lithium metal oxide, a lithium metal polyanionic material, a partially-fluorinated derivative of the lithium metal oxide, and a partially-fluorinated derivative of the lithium metal polyanionic material.
Embodiment 88 comprises the composite electrode active material of embodiment 87, wherein M comprises cobalt.
Embodiment 89 comprises the composite electrode active material of embodiment 87 to 88, wherein the lithium metal oxide has a structure selected from the group consisting of a layered structure, a spinel structure, a lithiated-spinel structure, rock salt structure, and a combination of two or more of the foregoing structures.
Embodiment 90 comprises the composite electrode active material of any one of embodiments 87 to 89, wherein the lithium metal polyanionic material has an olivine-type structure.
Embodiment 91 comprises the composite electrode active material of any one of embodiments 87 to 90, wherein 0≤z≤0.2, or 0.05≤z≤0.2, or 0.1≤z≤0.2, or 0.15≤z≤0.2, or 0≤z≤0.4, or 0.05≤z≤0.4, or 0.1≤z≤0.4, or 0.15≤z≤0.4, or 0.2≤z≤0.4, or 0.3≤z≤0.4.
Embodiment 92 comprises the composite electrode active material of any one of embodiments 87 to 91, wherein the second electrode active material comprises a layered compound of formula Li2M4O3, wherein M4 is at least one metal cation selected from the group consisting of a Mn cation, a Ti cation, and a Zr cation.
Embodiment 93 comprises the composite electrode active material of any one of embodiments 87 to 92, wherein the second electrode active material comprises a layered compound of formula LiM5O2, wherein M5 comprises at least one first row transition metal cation, and optionally at least one non-transition metal cation.
Embodiment 94 comprises the electrode active composite material of embodiment 87, wherein the electrode active composite material is a lithiated spinel-lithiated spinel of formula aLiM1O2·(1−a)LiM7O2 in which 0<a<1; wherein the first electrode active material is the lithiated spinel of formula LiM1O2, and the second electrode active material is a lithiated-spinel of formula LiM7O2 and wherein M7 comprises two or more cations selected from the group consisting of a Mn cation, a Ni cation, a Co cation, and a M6 cation; and M6 comprises at least one cation other than Mn Ni, and Co cations.
Embodiment 95 comprises the electrode active material of embodiment 94, wherein M6 is at least one cation of a metal selected from the group consisting of Al, Ga, Mg, and Ti.
Embodiment 96 comprises the electrode active composite material of embodiment 95, wherein the lithiated spinel-lithiated spinel is a material of formula 0.9LiMn0.5Ni0.5O2·0.1LiCo0.85Al0.15O2.
Embodiment 97 comprises a composite electrode active material comprising a first electrode active material that is structurally-integrated with second electrode active material; wherein: the first electrode active material is a layered material of empirical formula Li2M4O3, wherein M4 is at least one metal cation selected from the group consisting of a Mn cation, a Ti cation, and a Zr cation; the second electrode active material is a lithiated spinel of formula LiM1O2, wherein M1 comprises a combination of Mn and Ni transition metal ions in a ratio of Mn to Ni ions of about 2:1 to about 1:1; and the composite electrode active material is a layered-lithiated spinel material of formula bLi2M4O3·(1−b)LiM1O2, in which 0<b<1.
Embodiment 98 comprises the composite electrode active material of embodiment 97, wherein the material of formula LiM1O2 comprises domains of a disordered lithiated-spinel component, a disordered layered component, and a disordered rock salt component, in which the oxygen lattice of the components is cubic-close packed, and in which greater than 0 percent and less than 20 percent of lithium ions of the lithiated spinel and layered components are disordered among the octahedral sites normally occupied by the transition metal ions, and a corresponding percentage of the transition metal ions are disordered among the octahedral sites normally occupied by lithium ions, in fully-ordered, lithiated spinel and layered structures; Embodiment 99 comprises the composite material of embodiment 98, wherein greater than about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19 percent and less than 20 percent of the lithium ions of the material of formula bLi2M4O3·(1−b)LiM1O2 are disordered among the octahedral sites normally occupied by the transition metal ions, and a corresponding percentage of the transition metal ions are disordered among the octahedral sites normally occupied by lithium ions, in fully-ordered, lithiated spinel and layered structures.
Embodiment 100 comprises the composite material of embodiments 98 or 99, wherein greater than 10 percent and less than 20 percent of the lithium ions of the material of formula bLi2M4O3·(1−b)LiM1O2 are disordered among the octahedral sites normally occupied by the transition metal ions, and a corresponding percentage of the transition metal ions are disordered among the octahedral sites normally occupied by lithium ions, in fully-ordered, lithiated spinel and layered structures.
Embodiment 101 comprises the composite electrode active material of any one of embodiments 97 to 100, wherein in M1 is M21−wM3w; M2 comprises a combination of Mn and Ni transition metal ions; and M3 is at least one metal cation selected from the group consisting of an Al cation, a Ga cation, a Mg cation, a Ti cation; and a Co cation; and 0<w≤0.1.
Embodiment 102 comprises the composite electrode active material of any one of embodiments 97 to 101, wherein the composite electrode active material is a structurally integrated layered-lithiated spinel of formula 0.1Li2MnO3·0.9LiMn0.5Ni0.5O2.
Embodiment 103 comprises a electrode active material comprising the electrode active composite material of any one of embodiments 97 to 102, mechanically blended with or structurally integrated with a lithiated spinel of formula LiM7O2; wherein M7 comprises two or more cations selected from the group consisting of a Mn cation, a Ni cation, a Co cation, and a M6 cation; and M6 comprises at least one cation other than Mn Ni, and Co cations.
Embodiment 104 comprises the electrode active material of embodiment 103, wherein M6 is at least one cation of a metal selected from the group consisting of Al, Ga, Mg, and Ti.
Embodiment 105 comprises an electrode active material comprising the composite electrode active material of any one of embodiments 97 to 104, mechanically blended with or structurally integrated with a layered compound of formula LiM5O2, wherein M5 comprises at least one first row transition metal cation.
Embodiment 106 comprises the composite material of embodiment 105, wherein M5 further comprises at least one non-transition metal cation.
Embodiment 107 comprises an electrode active composite material comprising a first electrode active material that is mechanically blended with or structurally-integrated with a second electrode active material different from the first electrode active material, and a third electrode active material different from the first and second electrode active materials; wherein: the first electrode active material is a layered material of formula Li2M4O3, wherein M4 is at least one metal cation selected from the group consisting of a Mn cation, a Ti cation, and a Zr cation; the second electrode active material is a lithiated spinel of formula LiM1O2, wherein M1 comprises a combination of Mn and Ni transition metal ions in a ratio of Mn to Ni ions of about 2:1 to about 1:1; and the third electrode active material is selected from the group consisting of (a) a layered material of formula LiM5O2; wherein M5 comprises at least one first-row transition metal cation, and (b) a lithiated spinel of formula LiM7O2; wherein M7 comprises two or more cations selected from the group consisting of a Mn cation, a Ni cation, a Co cation, and a M6 cation; and M6 comprises at least one cation other than Mn Ni, and Co cations; Embodiment 108 comprises the electrode active composite material of embodiment 107, wherein M5 additionally comprises at least one non-transition metal cation.
Embodiment 109 comprises the electrode active composite material of embodiment 108 107, wherein M6 is at least one cation of a metal selected from the group consisting of Al, Ga, Mg, and Ti.
Embodiment 110 comprises the electrode active composite material of claim 109, wherein the composite electrode active material is a structurally integrated layered-lithiated spinel-lithiated spinel of formula cLi2M4O3·(1−c−d)LiMO2]·dLiM7O2 in which 0<|c−d|<1; 0<c<0.2; and 0<d<0.8.
Embodiment 111 comprises the composite material of claim 109, wherein the composite electrode active material is a structurally integrated layered-lithiated spinel-lithiated spinel material of formula 0.1Li2MnO3·0.8LiMn0.5Ni0.5O2·0.1LiCo0.85Al0.15O2.
Embodiment 112 comprises the electrode active composite material of embodiment 107, wherein the composite electrode active material is a structurally-integrated layered-lithiated spinel-layered material of formula eLi2M4O3·(1−e−f)LiM1O2]·fLiM5O2 in which 0<e−f|<1; 0<e<0.2; and 0<f<0.8.
Embodiment 113 comprises the electrode active composite material of embodiment 112, wherein M5 is a combination of at least one first-row transition metal cation and at least one non-transition metal cation selected from the group consisting of an Al cation, a Ga cation, and a Mg cation.
Embodiment 114 comprises the electrode active composite material of embodiment 112 or 113, wherein the layered-lithiated spinel-layered material is a compound of formula 0.1Li2MnO3·0.8LiMn0.5Ni0.5O2·0.1LiCo0.9Ti0.01Mg0.01O2.
Embodiment 115 comprises the electrode active composite material of any one of embodiments 87 to 114, wherein less than 10 mole percent of the oxygen is replaced by fluorine.
Embodiment 116 comprises the electrode active composite material of any one of embodiments 87 to 115, wherein the metal ions thereof are partially disordered relative to ideal lithiated spinel and layered structure.
Embodiment 117 comprises an electrochemical cell comprising an anode, a cathode, and a lithium-containing electrolyte contacting the anode and cathode, wherein the cathode comprises the electrode active composite material of any one of embodiments 87 to 116.
Embodiment 118 comprises a battery comprising a plurality of the electrochemical cell of embodiment 117 electrically connected in series, in parallel, or in both series and parallel.
Additional embodiments include:
(1) A structurally integrated composite electrode active material comprising a material of formula (1−y)[xLi2MnO3·(1−x)LiMeO2]·yLiMO2 wherein 0≤x≤1; 0<y<0.3, e.g., 0<y≤0.2 or 0<y≤0.1; M is one or more metal ions selected from Mn, Ni, and Co optionally with minor amounts of Mg, Al, Ti, and/or Fe; Me is one or more metal ions, at least one of which is selected from the group consisting of Mn, Ni and Co ions; and wherein the LiMO2 comprises domains of ordered or partially-disordered lithiated spinel structures, and domains of partially-disordered layered, and rock salt structures.
(2) A structurally-integrated composite electrode active material of formula xLi2MnO3·(1−x)LiMn0.5Ni0.5O2 in which 0≤x<1; wherein the LiMn0.5Ni0.5O2 comprises domains of ordered or partially-disordered lithiated spinel, and partially-disordered layered, and rock salt structures.
(3) A structurally-integrated composite electrode active material of formula Li2MnO3·LiMn0.5Ni0.5O2 wherein the LiMn0.5Ni0.5O2 comprises domains of ordered or partially-disordered lithiated spinel, and partially-disordered layered, and rock salt structures.
(4) A structurally-integrated composite electrode active material of formula n[xLi2MnO3·(1−x)LiMeO2]·mLiMO2·zLiM82O4 wherein 0≤x<1; n+m+z=1; 0<n<1 (e.g., 0<n≤0.95; 0n≤0.8; 0<n≤0.75; 0<n≤0.7, 0<n≤0.6; 0<n≤0.5; or 0<n≤0.45); 0≤m<1 (e.g., 0≤m≤0.5; 0≤m≤0.3; 0≤m≤0.15; 0≤m≤0.1, 0≤m≤0.08; 0≤m≤0.05; or 0≤m≤0.03); 0<z<0.3 (e.g., 0<z≤0.25; 0<z≤0.18; 0<z≤0.15; 0<z≤0.1, 0<z≤0.08; 0<z≤0.05; or 0<z≤0.03); the [xLi2MnO3·(1−x)LiMeO2] component comprises a layered (L) or layered-layered (LL) structure; the LiMO2 component comprises domains of partially-disordered lithiated spinel (LS), and optionally layered, and rock salt structures; and the LiM82O4 component comprises an ordered or partially disordered spinel (S) structure. Preferably, 0.5≤n<1. In some embodiments, 0<m<0.3, and 0<z<0.3, such that the material has a layered-lithiated spinel-spinel structure (i.e., x=0), or a layered-layered-lithated spinel-spinal structure (i.e., x>0).
(5) A structurally integrated composite electrode active material selected from the group consisting of:
(6) A structurally integrated composite electrode active material selected from the group consisting of:
(7) The materials of (1) to (6) in which up to about 10% of the G in the materials is replaced by F.
(8) The material of (4), wherein M8 of the LiM82O4 spinel component comprises Mn, a combination of Mn and Ni, a combination of Mn and Li, or a combination of Mn, Ni and Li.
(9) The material of (8) wherein the spinel component comprises one or more material selected from the group consisting of (a) Li1+xMn2−xO4, wherein 0≤x≤1/3; (b) LiMn2−xNixO4, wherein 0≤x≤0.5, (c) a substituted derivative of (a) in which less than 10% of the Mn is replaced by an element selected from the group consisting of Al, Co, Mg, Ti; (d) a substituted derivative of (b) in which less than 10% of the Mn, Ni, or both is replaced by an element selected from the group consisting of Al, Co, Mg, Ti; (e) a substituted derivative of (a) in which less than 10% of the O is replaced by F; and (f) and substituted derivatives of (b) in which less than 10% of the O is replaced by F.
(10) An electrochemical cell comprising an anode, a cathode, and a lithium-containing electrolyte contacting the anode and cathode, wherein the cathode comprises an electrode active composite material of (1) to (9), above.
(11) A battery comprising a plurality of the electrochemical cell of (10) electrically connected in series, in parallel, or in both series and parallel.
(12) A method for preparing a structurally-integrated composite electrode material comprising the steps of:
Materials with a spinel-type structure, as epitomized by the prototypic mineral spinel, having the formula MgAl2O4, are abundant in nature and they are diverse in their composition. For the lithium battery industry, lithium-metal-oxide electrodes with a spinel-type structure, such as lithium titanate, Li4Ti5O12 (Li[Li1/3Ti5/3]O4), and lithium manganate LiMn2O4 and substituted derivatives thereof, e.g., Li[Mn2−δLiδ]O4, can be prepared by a variety of synthetic techniques at elevated temperatures. High-temperature synthesis is important and necessary for fabricating electrode particles with an acceptably high packing density. On the other hand, it is well-known that lithiated spinels, such as Li7Ti5O12 (Li2[Li1/3Ti5/3]O4) and Li2[Mn2]O4 can be prepared electrochemically at room temperature and slightly elevated temperature (e.g., 60° C.). However, when heated at elevated temperatures, particularly in air or oxygen, these lithiated spinel structures are unstable and tend to transform to other structure types. Indeed, only a few examples of lithiated spinels that can be prepared at an elevated temperature of about 400° C. are known to exist, notably those in the family of lithiated-cobalt-oxide spinels LiCo1−xMxO2, alternatively in spinel notation, Li2Co2−2xM2xO4 (e.g., where M=Ni, Al, Ga), as described by Gummow et al. and by Lee et al. in references already provided herein.
As described herein, Co-free, lithiated-spinel electrode materials are described herein, which have the formula LiMnxNiyMzO2, alternatively Li2Mn2xNi2yM2zO4 in lithiated-spinel notation, in which x+y+z=1, 0<x<1.0, 0<y<1.0, 0≤z≤0.5, and M is a metal cation excluding Mn, Ni and Co. The reversible electrochemical capacity of these electrodes is generated predominantly from redox reactions that occur on the nickel ions, as it does in layered LiMn0.5Ni0.5O2 and spinel LiMn1.5Ni0.5O4 electrodes, while the tetravalent Mn ions operate predominantly as electrochemically-inactive spectator ions during charge and discharge of the cell. The strategy uses the LiMn0.5Ni0.5O2 composition as a building block to synthesize and stabilize a new family of Mn- and Ni-based lithiated-spinel electrode structures as emphasized in Table 1 in which the normalized and generalized lithiated-spinel notation, LiMnxNiyMzO2, is used for convenience to aid the discussion.
In a preferred embodiment, the Mn:Ni ratio in these lithiated-spinel structures is less than 2:1 and greater than 1:2, preferably close to 1:1, and more preferably 1:1, to yield fully-discharged LiMnxNiyMzO2 electrodes in which the Mn and Ni ions adopt tetravalent and divalent oxidation states, or oxidation states as close to those ideal values as possible. In another preferred embodiment, M is selected from one or more of Mg, Al and Ga or, alternatively, a combination of Mg and Ti in a 1:1 ratio also referred to herein as 1:1 Mg—Ti). In yet another embodiment; M can be a combination of two or more of Mg, Al, Ga, or 1:1 Mg—Ti.
The lithiated-spinel structures described herein may deviate slightly from their ideal stoichiometric composition by containing cation and/or anion defects or deficiencies, as is known for metal oxide structures. In this case, the sum of x+y+z in LiMnxNiyMzO2 may deviate slightly from 1 (e.g., up to about 5 mol % deviation), while the oxygen content may deviate slightly from 2 (e.g., up to about 5 mol % deviation). Moreover, it is well known that lithium metal oxides can be synthesized that are either slightly lithium-rich or slightly lithium-deficient, such as found within the Li1+xMn2−xO4 spinel (0<x<0.33) and Li1−xMn2O4 (0<x<1) spinel systems, respectively. Thus, the lithiated spinel LiMnxNiyMzO2 electrode materials may deviate from ideal stoichiometry by up to about 5 mol % in the lithium, oxygen or total non-lithium metal content thereof.
In a further embodiment, it is known that F ions can be substituted for the 0 ions in lithium-metal-oxides, especially near surfaces or within bulk environments, notably Li-rich environments as well as in the presence of oxygen vacancies and local disorder within defect-containing oxides.
These F ions can provide, for example, enhanced stability, particularly for Mn-containing compositions, against metal dissolution, surface damage, and reduced cycling and rate performance.
Therefore, another aspect of the materials described herein includes LiMnxNiyMzO2−δFδ electrode materials in which 0<δ<0.1.
The term “spinel” as used herein in reference to metal oxide materials refers to a material having a spinel-type crystal structure. The prototype “spinel” is the mineral MgA2O4. As explained in Thackeray, J. Am. Ceram. Soc; 1999; 82, 3347-54, spinels have a generic structure A[B2]X4 where A refers to cations in the 8a tetrahedral sites and B refers to cations in the 16d octahedral sites of the cubic space group symmetry Fd
Lithiated-spinel structures with the ideal spinel configuration of atoms also can be represented in spinel notation by the formula Li2(16c)[M2(16d)]O4(32e), where 16c and 16d refer to all the octahedral sites and 32e to the cubic-close-packed oxygen sites of the crystallographic space group, Fd-3m. This space group, is also adopted by the prototypic structure of the mineral ‘spinel’, Mg(8a)Al2(16d)O4(32e), in which the magnesium ions occupy the tetrahedral 8a sites and aluminum the octahedral 16d sites and by the lithium-manganese-oxide spinel structure, Li(8a)Mn2(16d)O4(32e), in which the lithium ions occupy the tetrahedral 8a sites and manganese ions the octahedral 16d sites. This cubic space group is used herein for convenience to simplify the structural discussion of the lithiated-spinel materials described herein and, particularly, because spinel and lithiated-spinel structures can adopt lower symmetry, as is the case for the spinel, Mn3O4, and the lithiated spinel, Li2[Mn2]O4, respectively, both of which have tetragonal symmetry, I41/amd. The crystallographic symmetry of the cobalt-free lithiated-spinel structures described herein is therefore not restricted to one space group.
It should be noted that lithiated spinels, Li2(16c)[M2(16d)]O4(32e), can also be regarded as having a rock-salt-type structure because the positively charged Li and M cations occupy all the octahedral sites (16c and 16d) of a cubic-close-packed oxygen lattice. The materials may include ordered and/or partially-disordered lithiated-spinel (rock salt) LiMnxNiyMzO2 electrode structures (alternatively Li2Mn2xNi2yM2zO4), in which the disorder occurs, for example, between the lithium ions on the octahedral 16c sites and the metal ions on the octahedral 16d sites of a structure with predominant lithiated-spinel character. Such disorder can result in structures with increasing layered character or, alternatively, to structures with a more random distribution of cations in localized regions of the electrode structure, thereby affecting the electrochemical signature and voltage profile of the cell during charge and discharge. Some localized disorder of the lithium and other metal ions between octahedral and tetrahedral sites may also be possible in these electrode structures.
During the electrochemical extraction of lithium during cell charging and reinsertion of lithium during cell discharge in the lithiated-spinel electrodes of described herein, the lithium ions diffuse predominantly through a 3-dimensional intersecting pathway of 8a tetrahedra and 16c octahedra (wherein 8a and 16c refer to crystallographic designations of specific spinel crystal lattice sites). It should, however, be recognized that any disorder of the Li, Mn, Ni or metal (M) ions, as well as the presence of a structurally-integrated layered component in the structure of the electrode material will likely affect these diffusion pathways and the profiles of the electrochemical charge and discharge reactions expected for ordered lithium-metal-oxide spinel electrodes, which are characterized by two-phase (constant voltage) behavior. It can therefore be understood that during electrochemical charge and discharge of the lithiated-spinel electrodes, the lithium-ions, in particular, will be disordered over both tetrahedral and octahedral sites of the structure.
The compositional space, structural features and atomic arrangements of the lithiated-spinel-related materials described herein are broad in scope, the electrochemical properties of which will be dependent on the selection of the metal cations, M, and the location of the electrochemically-active- and electrochemically-inactive metal ions within the ordered- or partially-disordered lithiated-spinel-related structures.
A further significant embodiment is the discovery of a remarkable crystallographic anomaly that was found to exist between a disordered lithiated-spinel LT-LiMn0.5Ni0.5O2 structure described herein, alternatively designated LT-Li2MnNiO4 for convenience, and a disordered layered LT-LiMn0.5Ni0.5O2 structure with the same chemical formula and composition overall, as described as follows.
A structural (Rietveld) refinement of the XRD pattern of a LT-Li2MnNiO4 sample (
Surprisingly, a second Rietveld refinement of the XRD peaks of the LT-Li2MnNiO4 (LT-LiMn0.5Ni0.5O2) sample showed that the pattern could also be matched to a disordered layered structure with cubic symmetry (Li0.17M0.83)[Li0.83M0.17]O2 in which approximately ⅚ (about 83%) of the M cations and approximately ⅙ (about 17%) of the Li+ ions resided in alternate layers of a cubic-close-packed structure, yielding an essentially identical XRD pattern to the disordered lithiated-spinel arrangement described above (
Small variations in the exact chemical composition and symmetry of electrode materials can occur, for example, during synthesis, and through experimental error when calculating composition or determining crystallographic lattice constants and crystal symmetry with high precision which will be dependent on the quality of the materials themselves and the instrumentation used for such analyses. Thus, there may be small deviations in crystallographic composition and symmetry of the electrode materials described herein. For example, the determined lithium, transition metal/M, and/or oxygen, content of the material can vary by up to about 5 percent from an ideal 1:1:2 respective elemental stoichiometry. In electrode materials containing substituted cations or anions, such as aluminum or fluorine ions, the degree of substitution can vary by less than 2 percent when less than 10 atom percent of the transition metal ions or oxygen ions are replaced by aluminum or fluorine ions, respectively. From a crystallographic standpoint, the cubic-close-packed oxygen lattice of the disordered lithiated spinel, disordered layered and disordered rock salt components can deviate slightly from ideal cubic-close-packing as a result of localized ordering of the cations, imperfections, dislocations or cationic or anionic defects. For example, localized ordering within a disordered layered component with trigonal symmetry, R-3m, may result in slight deviations from an ideally cubic-close-packed oxygen lattice in which the crystallographic ratio of the c and a lattice parameters of the unit cell (c a) is 4.90, by about 0.5 percent to a c a ratio of about 4.92. Furthermore, the cubic-close-packed oxygen lattice of the disordered lithiated spinel, disordered layered and disordered rock salt components can deviate from ideal cubic-close-packing such that the crystal symmetry of one or more of the components is lowered by an anisotropic variation of at least one lattice parameter length of the unit cell by up to about 5 percent, preferably by up to about 2 percent.
With respect to the Mn:Ni ratio in some embodiments of the materials described herein, it has been found that a 1:1 ratio provides good performance. In this case, the Mn:Ni ratio should deviate as little as possible, preferably by less than about 10 percent in the Mn or Ni content, i.e., less than a 1.1:1.0 Mn:Ni ratio. However, from a cost viewpoint, because manganese is less expensive than nickel, it could be advantageous to increase the Mn content in the Mn:Ni ratio to higher levels at the expense of lower performance, in which case the Mn:Ni ratio can vary between 2:1 and 1.1:1. As used herein in conjunction with numerical values for the ratios or proportions of elements in an empirical formula (e.g., 1:1, 2:1, or 1:1:2), the word “about” means that the specified values can vary by up to 5 percent from the stated value, which will not unduly affect the performance of the material in a lithium electrochemical cell. For example, “about 1:1 Mn to Ni” means to Mn and Ni components of the ratio can vary by up to 5%, such that the ratio of Ni to Mn can be from 1.05:1 to 0.95:1; and “about 1:1:2 Li to M to 0” means that each of the components of the ratio can vary by up to 5%, i.e., the Li and M components of the ratio can be from 1.05 to 0.95, and the 0 component of the ratio can be from 2.1 to 1.9.
Of the two structural models described above, it is believed that a partially disordered (17%) lithiated-spinel model, (Li0.83M0.17)2(16c)[Li0.17M0.3]2(16d)O4(32e), in which interconnected 3-D pathways for Li-ion transport are still likely to exist, may be the more favored structural model for LT-Li2MnNiO4 (LT-LiMn0.5Ni0.5O2). This finds some support in the voltage profile of the Li/LT-LiMn0.5Ni0.5O2 cell shown in
Unlike the two-plateau behavior of a Li/LT-LiMn0.5Ni0.5O2 cell (
The electrode materials described herein can include one or more disordered lithiated-spinel components, structurally integrated with one or more disordered layered components. Furthermore, because the cation-to-anion ratio in the disordered lithiated-spinel and disordered structures is about 1:1, both components can also be regarded as having partially disordered rock salt structures, such that disordered-layered- and/or disordered-rock salt components coexist with the disordered lithiated-spinel electrode components. Therefore, the LiMnxNiyMzO2 electrode materials of this invention can include one or more components comprising a partially disordered lithiated-spinel component and a partially-disordered layered component.
In an ideal, fully-ordered lithiated spinel of empirical formula Li[TM]O2, where TM stands for transition metal, the transition metal ions and lithium ions are arranged in two different types of alternating layers in which a first layer comprises 75% TM ions and 25% Li ions, and an adjacent second layer comprises 25% TM ions and 75% lithium ions. Similarly, in a fully-ordered, layered structure of empirical formula Li[TM]O2, the TM ions and Li ions are arranged in two different types of alternating layers in which a first layer comprises 100% TM ions, and a second adjacent layer comprises 100% Li ions. In the partially-disordered lithiated spinel and layered component structures of the material of empirical formula LiMnxNiyMzO2 described herein, a portion of the TM ions of the first layer are replaced by Li ions and a portion of the Li ions in the second layer are replaced by TM ions, leading to disorder among the ions in the different layers. Preferably, in terms of percentage, the extent of the disorder of the Mn/Ni/M cations relative to the Li cations in the alternating first and second layers ranges from 80:20 to 90:10, and more preferably from 81:19 to 85:15.
Some embodiments of the electrode materials described herein constitute a structurally-integrated, lithium-metal-oxide composite electrode material of empirical formula LiM1O2 for an electrochemical cell wherein M1 comprises a combination of Mn and Ni transition metal ions; the crystal structure of the material comprises domains of a disordered lithiated-spinel component, a disordered layered component, and a disordered rock salt component, in which the oxygen lattice of the components is cubic-close packed, and in which greater than 10 percent and less than 20 percent of lithium ions of the lithiated spinel and layered components are disordered among the octahedral sites normally occupied by the transition metal ions, and a corresponding percentage of the transition metal ions are disordered among the octahedral sites normally occupied by lithium ions in fully-ordered, lithiated spinel and layered structures.
In a further embodiment, any of the electrode materials described herein can be reacted further, or physically blended, with one or more other lithium metal oxide materials, e.g., cobalt-containing lithium-metal-oxide components, such as layered or lithiated-spinel LiCoO2 or substituted components such as LT-LiCo1−xAlxO2 reported by Lee et al. in ACS Applied Energy Materials, Volume 2, pages 6170-6175 (2019) to form either two-component- or multi-component electrode structurally integrated materials that contain the lithiated-spinel LiMnxNiyMzO2 materials described herein. Ideally, the cobalt content in these ‘mixed’ electrodes should be as low as possible, preferably close to zero, when it is possible that some Co may be incorporated within the lithiated-spinel structure. A specific embodiment, therefore, includes lithiated-spinel LiMnxNiyMzO2 materials in which M can be Co with z at most 0.2 for x+y+z=1, and preferably less than, or equal to z=0.1, or most preferably, less than or equal to 0.05 to keep the Co content as low as possible.
In a further aspect, the lithium-manganese-nickel-oxide (LiMnxNiyMzO2 or LiM1O2) materials of the invention can be mechanically blended with or structurally-integrated with one or more other ordered or disordered electrode active material such as a lithium metal oxide, a lithium metal polyanionic material, a partially-fluorinated derivative of the lithium metal oxide, and a partially-fluorinated derivative of the lithium metal polyanionic material. Such materials can have layered, spinel, lithiated spinel, and olivine-type structures. In one embodiment, the lithiated spinel of formula LiMnxNiyMzO2 or LiM1O2 is mechanically blended with or structurally-integrated with a layered Li2M4O3 materials and structures, in which M4 is one or more metal cations, selected preferably from Mn, Ti, and Zr cations. In another embodiment, the lithiated spinel of formula LiMnxNiyMzO2 or LiM1O2 is mechanically blended with or structurally-integrated with one or more ordered or disordered, layered (LiM5O2) or lithiated-spinel (LiM7O2) materials and structures, in which M5 is one or more metal cations, selected preferably from first-row transition metal cations and optionally one or more non-transition metal cations, such as, e.g., Mn, Ni, and Co cations, an Al cation, a Ga cation, and a Mg cation, and partially-fluorinated derivatives thereof; and M7 comprises two or more cations selected from the group consisting of a Mn cation, a Ni cation, a Co cation, and a M6 cation; and M6 comprises at least one cation other than Mn Ni, and Co cations (e.g., Al, Ga, Mg, and Ti, cations). Optionally, less than 10 atom percent of the oxygen of the electrode active materials can be exchanged by fluorine. As such, these electrode active materials can be generally described as having blended or integrated structures with layered- and lithiated-spinel character. Specific examples of composite aLi2M4O3·(1−b)LiM5O2 materials, represented in composite notation and by generalized LiM5O2 formulae, are provided below; the examples include a slightly disordered lithiated-spinel component structure, LiCo0.85Al0.15O2 and a layered component structure, LiCo0.9gTi0.01Mg0.01O2.
Non-limiting examples of structurally-integrated materials and compositions described herein include, e.g.:
The electrode materials described herein can include surface treatments and coatings to protect the surface of the electrode particles from undesirable reactions with the electrolyte, for example, by treating or coating the electrode particles with layers of metal-oxide, metal-fluoride or metal-phosphate materials to shield and protect the electrodes from highly oxidizing charging potentials and from other undesirable effects, such as electrolyte oxidation, oxygen loss, and/or dissolution. Such surface protection enhances the surface stability, rate capability and cycling stability of the electrode materials. In some embodiments the lithiated-spinel LiCo1−xAlxO2 (0<x<0.5) materials, may be used as protective layers or coatings for the lithiated-spinel LiMnxNiyMzO2 electrode materials described herein, particularly when formed by grinding or ball milling the electrode materials with lithiated-spinel LiCo1−xAlxO2 (0<x<0.5) compounds. Conversely, the lithiated-spinel LiMnxNiyMzO2 electrode materials described herein can be used as protective coatings for other underlying lithium-metal-oxide electrode materials, such as layered Li—Ni—Mn—O and Li—Mn—Ni—Co—O (NMC) electrode materials and spinel Li—Mn—O (LMO) electrode materials and substituted and compositional variations of these materials.
Non-limiting examples of cobalt-free, lithiated-spinel materials described herein are provided in Table 1, Section (a). Section (b) of Table 1 provides non-limiting examples of compositions comprising at least one cobalt-free lithiated spinel as described herein in combination with (e.g., structurally integrated with, or mixed with) at least one cobalt-containing component.
As used herein the term “lithium battery” refers to electrochemical cells and combinations of electrochemical cells in which lithium (e.g., lithium ion) shuttles between a Si anode and a cathode, and includes so-called full cells, as well as so-called half-cells (e.g. comprising a lithium metal anode).
Electrodes for lithium electrochemical cells typically are formed by coating a slurry of electrode active material in a solvent with a polymeric binder (e.g., poly(vinylidene difluoride); PVDF) onto a current collector (e.g., metal foil, conductive carbon fiber paper, and the like), and drying the coating to form the electrode. Some examples of electrode active materials can be found, e.g., in Mekonnen, Y., Sundararajan, A. & Sarwat, A. I. “A review of cathode and anode materials for lithium-ion batteries,” SoutheastCon 2016, Norfolk, Va., pp. 1-6, (2016), which is incorporated herein by reference in its entirety.
The electrodes utilize binders (e.g., polymeric binders) to aid in adhering cathode active materials to the current collectors. In some cases, the binder comprises a poly(carboxylic acid) or a salt thereof (e.g., a lithium salt), which can be any poly(carboxylic acid), such as poly(acrylic acid) (PAA), poly(methacrylic acid), alginic acid, carboxymethylcellulose (CMC), poly(aspartic acid) (PAsp), poly(glutamic acid) (PGlu), copolymers comprising poly(acrylic acid) chains, poly(4-vinylbenzoic acid) (PV4BA), and the like, which is soluble in the electrode slurry solvent system. The poly(carboxylic acid) can have a Mn, as determined by GPC, in the range of about 1000 to about 450,000 Daltons (preferably about 50,000 to about 450,000 Daltons, e.g., about 130,000 Daltons). In some other embodiments, the binder may comprise anionic materials or neutral materials such as fluorinated polymer such as poly(vinylidene difluoride) (PVDF), carboxymethylcellulose (CMC), and the like.
Lithium-ion electrochemical cells described herein comprise a cathode (positive electrode), an anode (negative electrode), and an ion-conductive separator between the cathode and anode, with the electrolyte in contact with both the anode and cathode, as is well known in the battery art. It is well understood that the function of a given electrode switches from being a positive or negative electrode depending on whether the electrochemical cell is discharging or charging. Nonetheless, for the sake of convenient identification, the terms “cathode” and “anode” as used herein are applied as identifiers for a particular electrode based only on its function during discharge of the electrochemical cell.
Cathodes typically are formed by combining a powdered mixture of the active material and some form of carbon (e.g., carbon black, graphite, or activated carbon) with a binder such as (polyvinylidene difluoride (PVDF), carboxymethylcellulose, and the like) in a solvent (e.g., N-methylpyrrolidone (NMP) or water) and the resulting mixture is coated on a conductive current collector (e.g., aluminum foil) and dried to remove solvent and form an active layer on the current collector.
The anode comprises a material capable of reversibly releasing and accepting lithium during discharging and charging of the electrochemical cell, respectively. Typically, the anode comprises a carbon material such as graphite, graphene, carbon nanotubes, carbon nanofibers, and the like, a silicon-based material such as silicon metal particles, a lead-based material such as metallic lead, a nitride, a silicide, a phosphide, an alloy, an intermetallic compound, a transition metal oxide, and the like. The anode active components typically are mixed with a binder such as (polyvinylidene difluoride (PVDF), carboxymethyl cellulose, and the like) in a solvent (e.g., NMP or water) and the resulting mixture is coated on a conductive current collector (e.g., copper foil) and dried to remove solvent and form an active layer on the current collector.
In some embodiments the anode comprises silicon-containing particles, preferably combined with carbon particles. The silicon-containing particles can be silicon nanoparticles, silicon/silicon oxide (Si/SiOx) nanocomposite particles, silicon nanotubes, microporous silicon, an alloy or intermetallic compound of silicon with a metal such as magnesium, calcium, nickel, iron, or cobalt. Some examples of useful silicon-containing materials are discussed in Ma et al., Nano-Micro Lett., 2014, 6(4):347-358, which is incorporated herein by reference in its entirety. Some other examples are mentioned in Zhu et al., Chemical Science, 2019 10, 7132., which is incorporated herein by reference in its entirety. Si/SiOx nanocomposite particles include e.g., materials described in co-owned application Ser. No. 15/663,268 to Wenquan Lu et al., filed on Jul. 28, 2017, now U.S. Pat. No. 10,714,745, which is incorporated herein by reference in its entirety.
Preferably, the silicon-containing particles, when utilized in the anode, have an average size in the range of about 50 to about 200 nm, more preferably about 70 to about 150 nm. The carbon particles can be carbon microparticles or nanoparticles. Non-limiting examples of carbon materials include, e.g., carbon black, graphite, carbon nanotubes, carbon nanofibers, and graphene. Preferably, the electrode includes silicon and carbon particles in a respective weight ratio (Si:C) of about 1:9 to about 9:1, more preferably about 1:5 to about 8:1. The binder typically comprises about 5 to about 30 percent by weight (wt %), preferably about 10 to about 20 wt %, of the active material coated on the current collector, based on the combined weight of the silicon, carbon and binder in the finished electrode (i.e., after drying). The loading of silicon and carbon particles and binder on the current collector typically is in the range of about 0.6 to about 3.2 mg/cm2, preferably about 0.8 to about 2.7 mg/cm2.
As used herein, the terms “structurally-intergrown”, “structurally-integrated” and “structurally-integrated composite” when used in relation to a lithium metal oxide a material refers to materials that include domains (e.g., locally ordered, nano-sized or micro-sized domains) indicative of different metal oxide compositions having different crystalline forms (e.g., layered or spinel forms) within a single particle of the composite metal oxide, in which the domains share substantially the same oxygen lattice and differ from each other by the elemental and spatial distribution of metal ions in the overall metal oxide structure. Structurally-integrated composite lithium metal oxides are different from and generally have different properties than mere mixtures or combinations of two or more metal oxide components (for example, mere mixtures do not share a common oxygen lattice).
In electrochemical cell and battery embodiments described herein, the electrolyte comprises an electrolyte salt (e.g., an electrochemically stable lithium salt or a sodium salt) dissolved in a non-aqueous solvent. Any lithium electrolyte salt can be utilized in the electrolyte compositions for lithium electrochemical cells and batteries described herein, such as the salts described in Jow et al. (Eds.), Electrolytes for Lithium and Lithium-ion Batteries; Chapter 1, pp. 1-92; Springer; New York, N.Y. (2014), which is incorporated herein by reference in its entirety.
Non-limiting examples of lithium salts include, e.g., lithium bis(trifluoromethanesulfonyl)imidate (LiTFSI), lithium 2-trifluoromethyl-4,5-dicyanoimidazolate (LiTDI), lithium 4,5-dicyano-1,2,3-triazolate (LiDCTA), lithium trifluoromethanesulfonate (LiTf), lithium perchlorate (LiClO4), lithium bis(oxalato)borate (LiB(C204)2 or “LiBOB”), lithium difluoro(oxalato)borate (LiF2BC2O4 or “LiDFOB”), lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium thiocyanate (LiSCN), lithium bis(fluorosulfonyl)imidate (LiFSI), lithium bis(pentafluoroethylsulfonyl)imidate (LiBETI), lithium tetracyanoborate (LiB(CN)4), lithium nitrate, combinations of two or more thereof, and the like. The lithium salt can be present in the electrolyte solvent at any concentration suitable for lithium battery applications, which concentrations are well known in the secondary battery art. As used herein the term “lithium battery” refers to electrochemical cells and combinations of electrochemical cells in which lithium (e.g., lithium ion) shuttles between an anode and a cathode, and includes so-called full cells with an anode material (e.g., graphite) that can accommodate intercalated lithium ions, as well as so-called half-cells in which the anode is lithium metal. In some embodiments, the lithium salt is present in the electrolyte at a concentration in the range of about 0.1 M to about 5 M, e.g., about 0.5 M to 2 M, or 1 M to 1.5 M. A preferred lithium salt is LiPF6.
The non-aqueous solvent for the electrolyte compositions include the solvents described in Jow et al. (Eds.), Electrolytes for Lithium and Lithium-ion Batteries; Chapter 2, pp. 93-166; Springer; New York, N.Y. (2014), which is incorporated herein by reference in its entirety. Non-limiting examples of solvents for use in the electrolytes include, e.g., an ether, a carbonate ester (e.g., a dialkyl carbonate or a cyclic alkylene carbonate), a nitrile, a sulfoxide, a sulfone, a fluoro-substituted linear dialkyl carbonate, a fluoro-substituted cyclic alkylene carbonate, a fluoro-substituted sulfolane, and a fluoro-substituted sulfone. For example, the solvent can comprise an ether (e.g., glyme or diglyme), a linear dialkyl carbonate (e.g., dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and the like), a cyclic alkylene carbonate (ethylene carbonate (EC), propylene carbonate (PC) and the like), a sulfolane (e.g., sulfolane or an alkyl-substituted sulfolane), a sulfone (e.g., a dialkyl sulfone such as a methyl ethyl sulfone), a fluoro-substituted linear dialkyl carbonate, a fluoro-substituted cyclic alkylene carbonate, a fluoro-substituted sulfolane, and a fluoro-substituted sulfone. The solvent can comprise a single solvent compound or a mixture of two or more solvent compounds.
In some embodiments, the non-aqueous solvent for a lithium electrochemical cell as described herein can be an ionic liquid. Any electrochemically stable ionic liquid solvent can be utilized in the electrolytes described herein, such as the solvents described in Jow et al. (Eds.), Electrolytes for Lithium and Lithium-ion Batteries; Chapter 4, pp. 209-226; Springer; New York, N.Y. (2014), which is incorporated herein by reference in its entirety. In the case of lithium electrochemical cells and batteries, the ionic liquid can optionally include a lithium cation, and can act directly as the electrolyte salt.
The electrolyte compositions for lithium electrochemical cells and batteries described herein also can optionally comprise an additive such as those described in Jow et al. (Eds.), Electrolytes for Lithium and Lithium-ion Batteries; Chapter 3, pp. 167-182; Springer; New York, N.Y. (2014), which is incorporated herein by reference in its entirety. Such additives can provide, e.g., benefits such as SEI, cathode protection, electrolyte salt stabilization, thermal stability, safety enhancement, overpotential protection, corrosion inhibition, and the like. The additive can be present in the electrolyte at any concentration, but in some embodiments is present at a concentration in the range of about 0.0001 M to about 0.5 M. In some embodiments, the additive is present in the electrolyte at a concentration in the range of about 0.001 M to about 0.25 M, or about 0.01 M to about 0.1 M.
Electrochemical cells typically comprise a cathode, an anode typically comprising carbon, silicon, lead, metallic lithium, some other anode active material, or a combination thereof; and a porous separator between the cathode and anode, with the electrolyte in contact with the anode, the cathode and the separator.
A battery can be formed by electrically connecting two or more such electrochemical cells in series, parallel, or a combination of series and parallel. The electrodes described herein preferably are utilized as the anode in a full-cell configuration in lithium-ion and sodium-ion cells and batteries. Electrochemical cells and battery designs and configurations, anode and cathode materials, as well as electrolyte salts, solvents and other battery or electrode components (e.g., separator membranes, current collectors), which can be used in the electrolytes, cells and batteries described herein, are well known in the secondary battery art, e.g., as described in “Lithium Batteries Science and Technology” Gholam-Abbas Nazri and Gianfranco Pistoia, Eds., Springer Science+Business Media, LLC; New York, N.Y. (2009), which is incorporated herein by reference in its entirety.
The separator component of the lithium-ion cell can be any separator used in the lithium battery art. A typical material is a porous polyalkylene material such as microporous polypropylene, microporous polyethylene, a microporous propylene-ethylene copolymer, or a combination thereof, e.g., a separator with layers of different polyalkylenes; a poly(vinylidene-difluoride)-polyacrylonitrile graft copolymer microporous separator; and the like. Examples of suitable separators are described in Arora et al., Chem. Rev. 2004, 104, 4419-4462, which is incorporated herein by reference in its entirety. In addition, the separator can be an ion-selective ceramic membrane such as those described in Nestler et al., AIP Conference Proceedings 1597, 155 (2014), which is incorporated herein by reference in its entirety.
Processes used for manufacturing lithium cells and batteries are well known in the art. The active electrode materials are coated on both sides of metal foil current collectors (typically copper for the anode and aluminum for the cathode) with suitable binders such as PVDF and the like to aid in adhering the active materials to the current collectors. In the cells and batteries described herein, the active cathodes are the lithiated-spinel materials, LiMnxNiyMzO2, defined herein, which optionally can be utilized with a carbon material such as graphite, and the anode active material typically is a lithium metal, carbon, and the like. Cell assembly typically is carried out on automated equipment. The first stage in the assembly process is to sandwich a separator between the anode and the cathode. The cells can be constructed in a stacked structure for use in prismatic cells, or a spiral wound structure for use in cylindrical cells. The electrodes are connected to terminals and the resulting sub-assembly is inserted into a casing, which is then sealed, leaving an opening for filling the electrolyte into the cell. Next, the cell is filled with the electrolyte and sealed under moisture-free conditions.
Once the cell assembly is completed, the cell typically is subjected to at least one controlled charge/discharge cycle to activate the electrode materials and in some cases form a solid electrolyte interface (SEI) layer on the anode. This is known as formation cycling. The formation cycling process is well known in the battery art and involves initially charging with a low voltage (e.g., substantially lower that the full-cell voltage) and gradually building up the voltage. The SEI acts as a passivating layer which is essential for moderating the charging process under normal use. The formation cycling can be carried out, for example, according to the procedure described in Long et al. J. Electrochem. Soc., 2016; 163 (14): A2999-A3009, which is incorporated herein by reference in its entirety. This procedure involves a 1.5 V tap charge for 15 minutes at C/3 current limit, followed by a 6-hour rest period, and then 4 cycles at C/10 current limit, with a current cutoff (i≤0.05 C) at the top of each charge.
Cathodes comprising the cobalt free lithiated spinel materials described herein can be utilized with any combination of anode and electrolyte in any type of rechargeable battery system that utilizes a non-aqueous electrolyte.
The following general methodology and non-limiting Examples are provided to illustrate certain features of the compositions and methods described herein.
A parent, unsubstituted LiMn0.5Ni0.5O2 electrode material (x=0.5; y=0) is prepared by a ‘low-temperature’ method reported previously by Gummow et al. in Mat. Res. Bull. 27, 327 (1992), and U.S. Pat. No. 5,160,712. Cation substituted materials of formula LiMnxNiyAlzO2, for x=0.45, 0.35, 0.30; y=0.45, 0.35, 0.30; and z=0.1, 0.2, 0.3, respectively, as listed in Table 1, are prepared by solid-state reaction of lithium carbonate (Li2CO3, >99%), manganese hydroxide, nickel hydroxide, and aluminum nitrate (Al(NO3)3·9H2O, >99%) precursors. Alternatively, mixed-metal precursors, such as manganese-nickel hydroxide, or metal oxide precursors, such as manganese dioxide, can be used. Stoichiometric amounts of the precursors are thoroughly mixed using a mortar and pestle, and fired in air at 400° C. in a furnace for approximately 6 days. The heating rate is about 2° C. per min. The samples are cooled in the furnace without controlling the cooling rate. Samples can also be prepared in air at higher temperature, i.e., at 450, 500, 550 and 600° C. to increase the layered character of the LiMn0.5Ni0.5O2 and LiMnxNiyAlzO2 electrode structures.
It should be noted that for materials in which the Mn:Ni ratio is 1:1, and in which the manganese and nickel ions are tetravalent and divalent, respectively, for example LiMn0.45Ni0.45Al0.10O2, the full electrochemical capacity of the electrode (260 mAh/g, Table 1) would, in principle, be associated with the oxidation of Ni2+ to Ni4+ and the extraction of 0.9 Li+ ions from an electrode structure in which only 45% of the non-lithium metal ions (Mn, Ni, Al) is nickel. It is anticipated that such an electrode composition would have significant cost and safety advantages over their nickel-rich NMC counterparts, for example, LiNi0.8Mn0.1Co0.1O2(NMC811) and LiNi0.6Mn0.2Co0.2O2(NMC622) in lithium-ion cells. In addition, nearest neighbor Mn—Ni interactions may assist electronic conductivity of these lithiated-spinel-related electrodes during electrochemical operation.
The materials of Example 1 are combined with a LT-LiCoO2 lithiated-spinel product that is prepared at 400° C. as described by Lee et al. in ACS Applied Energy Materials, Volume 2, pages 6170-6175 (2019), either by mechanical blending, for example, by high-energy ball milling at room temperature, or by reaction in air at temperatures between 400 and 600° C. to yield composite electrode structures with two or more lithium-metal-oxide components that can be integrated structures or blended mixtures having either lithiated-spinel character or a combination of lithiated-spinel and layered character, and disordered structural variations thereof.
A precursor solution is prepared by dissolving stoichiometric amounts of a nickel salt (e.g., nickel acetylacetonate), a cobalt salt (e.g., cobalt acetylacetonate), a manganese salt (e.g., manganese acetylacetonate) in the required Ni:Co:Mn_ratio for a target LT-LiM1O2 composition (where M1 comprises Ni, Mn and Co, e.g., LT-NMC111 where Ni:Co:Mn is 1:1:1) and a small excess of a lithium salt (e.g., lithium propionate) to compensate for lithium loss in the flame, in a solvent. Typically, about 1 to about 10% excess lithium salt, and preferably less than 10% excess lithium salt, are dissolved in an appropriate solvent (i.e., a solvent capable of dissolving the salts, such as water, or an organic solvent (e.g., a polar organic solvent) a C1 to C6 alcohol (e.g., methanol ethanol, or propanol, isopropanol), a nitrile such as acetonitrile or propionitrile and the like, an amide such as N,N-dimethylformamide, acetamide, and the like), a C1 to C10 organic acid, such as formic acid, acetic acid, propionic acid, hexanoic acid, 2-ethylhexanoic acid, and the like., or a combination of two or more such solvents. A preferred solvent is acetonitrile and 2-ethylhexanoic acid (5:5 by volume) at a concentration of 0.31 mol/L. The precursor solution is then atomized with oxygen to form liquid droplets, which are sprayed into the methane/oxygen pilot flame of a FSP unit, thereby vaporizing and oxidizing the metal salts to form a precursor powder comprising the requisite ratio of transition metal ions to lithium ion for the target composition. The resulting powder is subsequently sintered at a temperature in the range of about 400 to about 650° C. in air for about 3 to about 5 days. In some embodiments, the transition metal and lithium salts comprise organic acid anions such as, e.g., acetate, propionate, acetylacetonate, and the like. Some preferred solvents suitable for use with the FSP method include polar organic solvents such as acetonitrile, 2-ethylhexanoic acid, or a combination of thereof.
Coin-type cells (2032, Hohsen) are constructed in an argon-filled glovebox (<5 ppm O2 and H2O). The cathode consists of approximately 84 percent by weight (wt %) of LiMnxNiyMzO2 powder (M=Al), 8 wt % carbon, and 8 wt % PVDF binder on aluminum foil. The anode is metallic lithium foil or an alternative host electrode for lithium, such as graphite or Li4Ti5O12. The electrolyte is typically 1.2 M LiPF6 in a 3:7 (w/w) mixture of ethylene carbonate and ethyl-methyl carbonate. For the cycling experiments, Li/LiMnxNiyMzO2 cells (M=Al) are galvanostatically charged and discharged between 2.5 and 4.2 V at a current rate of either approximately 15 mA/g or approximately 60 mA/g. The electrochemical experiments are conducted at approximately 30° C.
In one aspect, a method of making the electrode materials described herein first involves the synthesis of low temperature lithium-metal-oxide (LT-LiMO2) materials with structurally-integrated lithiated spinel and layered structural domains and partially-disordered (rock salt) variations thereof. These materials are synthesized typically from about 400° C. to about 600° C., preferably about 400° C. to about 500° C. from a mixture of decomposable precursor salts and/or oxides. This process is followed by reaction of an intimate mixture (e.g., obtained by ball milling) of the LT-LiMO2 with, e.g., a layered xLi2MnO3·(1−x)LiMeO2 material (0≤x≤1) or, alternatively, with precursor materials such as metal hydroxides, carbonates, nitrates, and the like that decompose on heating to form metal oxides, and which will produce the layered xLi2MnO3·(1−x)LiMeO2 material. Next, the intimate mixture is heated at one or more consecutive temperatures between 500 and 900° C., preferably between 500 and 750° C., to yield stabilized (1−y)[xLi2MnO3·(1−x)LiMeO2]·yLiMO2 products in which 0<y≤0.3 (preferably 0<y≤0.1), which are stabilized by various amounts of partially disordered layered and lithiated spinel domains, and optionally partially disordered rock-salt domains within an integrated overall crystal structure.
LT-LiMn0.5Ni0.5O2 was prepared as follows: A Mn0.5Ni0.5(OH)2 precursor was first prepared by a co-precipitation reaction in an aqueous solution containing manganese sulfate (MnSO4) and nickel sulfate (NiSO4). A LT-LiMn0.5Ni0.5O2 electrode material was synthesized by a ‘low-temperature’ solid-state reaction of the Mn0.5Ni0.5(OH)2 precursor and lithium carbonate (Li2CO3, >99%). Stoichiometric amounts of the precursors were thoroughly mixed using a mortar and pestle, and fired in air at 400° C. for approximately 72 hours. The heating rate was about 2° C. per min, and the samples were cooled in the furnace without controlling the cooling rate. The X-ray diffraction (XRD) pattern (Cu Kα, radiation, λ=1.5406 Δ) of LT-LiMn0.5Ni0.5O2 is shown in
Li/LT-LiMn0.5Ni0.5O2 cells were assembled and evaluated as follows: Coin-type cells (2032, Hohsen) were assembled in an argon-filled glovebox (<5 ppm O2 and H2O) for electrochemical tests. The cathode electrode consisted of approximately 84 wt % of LT-LiMn0.5Ni0.5O2 powder, 8 wt % carbon, and 8 wt % polyvinylidene difluoride (PVDF) binder on an aluminum foil current collector. The anode was metallic lithium foil. The electrolyte was 1.2 M lithium hexafluorophosphate (LiPF6) in a 3:7 mixture of ethylene carbonate and ethyl methyl carbonate.
The coin cell was galvanostatically charged and discharged between 2.5 and 5.0 V at a constant current of approximately 15 mA/g. Electrochemical experiments were conducted at about 30° C. Voltage (V) vs. specific capacity (mAh/g) plots of a Li/LT-LiMn0.5Ni0.5O2 cell cycled between 5.0 and 2.5 V for the first 20 cycles are shown in
Ex situ synchrotron XRD patterns collected at different states of charge (SOC) showed that the LT-Li2MnNiO4 electrode structure maintains its cubic symmetry during the entire charge/discharge cycle and that the overall lattice volume change of 2.7% during cycling is significantly less than it is for the well-known spinels LixMn2O4 (16%) and LixMn1.5Ni0.5O4 (12%) when discharged to about 2.5 V (0≤x≤2).
LT-LiMn0.5Ni0.5O2 was prepared as described in Example 1.
Graphite/LT-LiMn0.5Ni0.5O2 cells were assembled following a similar procedure as described in Example 1, except that a graphite anode was used instead of metallic Li, and were evaluated as follows: Anode laminates were prepared by coating a graphite slurry on copper foil. The composition of the graphite slurry was 91.83 wt % graphite powder, 2 wt % carbon black, 6 wt % PVDF binder, and 0.17% oxalic acid. Coin cells were cycled between 2.0 to 4.9 V at a constant current of 100 mA/g. Voltage (V) vs. specific capacity (mAh/g) plots of a graphite/L,T-LiMn0.5Ni0.5O2 cell cycled between 4.9 and 2.0 V for the first 10 cycles are shown in
LT-LiMn0.45Ni0.45Al0.1O2 was prepared as follows: The LT-LiMn0.45Ni0.45Al0.1O2 powder was prepared following a similar procedure described in Example 1. Stoichiometric amounts of Li2CO3, Mn0.5Ni0.5(OH)2, and aluminum nitrate nonahydrate (Al(NO3)3·9H2O, >98%) precursors were thoroughly mixed with a planetary ball mill (RESTCH PM 200). The mixed powder was pressed into a pellet and fired in air at 400° C. for approximately 72 hours. The XRD pattern (Cu Kα, radiation, λ=1.5406 Δ) of the LT-LiMn0.45Ni0.45Al0.1O2 product is shown in
Li/LT-LiMn0.45Ni0.45Al0.1O2 cells with a metallic Li anode were assembled and evaluated as described in Example 1. The initial voltage (V) vs. specific capacity (mAh/g) plot of a Li/LT-LiMn0.45Ni0.45Al0.1O2 cell cycled between 5.0 and 2.5 V is shown in
Of particular note is that the voltage profile of the cell in which Al is used as a minor substituent in the LT-LiMn0.45Ni0.45Al0.1O2 electrode (
LT-LiMn0.5Ni0.5O2 was prepared by the method described in Example 1. LT-LiCo0.75Al0.25O2 was prepared as follows: Stoichiometric amounts of Li2CO3, CoCO3, and Al(NO3)3·9H2O were thoroughly mixed using a mortar and pestle. The mixture was then fired in air at 400° C. for 6 days. A blended electrode material was prepared by mechanically grinding the LT-LiMn0.5Ni0.5O2 and LT-LiCo0.75Al0.25O2 powders in a 90:10 percent ratio by mass using a mortar and pestle. The XRD pattern (Cu Kα, radiation, λ=1.5406 Δ) of a LT-LiMn0.5Ni0.5O2+LT-LiCo0.75Al0.25O2 electrode powder, blended in a 90:10 percent ratio by mass, respectively, is shown in
Li/LT-LiMn0.45Ni0.45Al0.1O2 cells with a metallic Li anode were assembled and evaluated as described in Example 1. The electrochemical profile of the initial charge and discharge of a Li/LT-LiMn0.5Ni0.5O2+LT-LiCo0.75Al0.25O2 cell when activated to 5.0 V and discharged to 2.5 V as a function of voltage (V) and specific capacity (mAh/g) is shown in
LT-LiMn0.475Ni0.475Co0.05O2 powder was prepared following a similar procedure to that described in Example 1. Stoichiometric amounts of Li2CO3 and Mn0.475Ni0.47ACo0.05(OH)2 precursors were thoroughly mixed using a mortar and pestle and fired in air at 400° C. for approximately 72 hours. The XRD pattern (Cu Kα, radiation, λ=1.5406 Å) of LT-LiMn0.475Ni0.475Co0.50O2 is shown in
LT-LiMn0.475Ni0.475Co0.05O2 cells were assembled and evaluated as in Example 1. The electrochemical profile of the initial charge and discharge of a Li/LT-LiMn0.475Ni0.475Co0.05O2 cell when activated to 5 V and discharged to 2.5 V as a function of voltage (V) and specific capacity (mAh/g) is shown in
In the above examples, the upper cut-off voltage was 5.0 V for the cells with a Li anode, and 4.9 V for the cell with a graphite anode. This high voltage was selected to maximize capacity and assess the stability of the electrode materials. In practice, it is anticipated that greater cycling stability of the cells will be achieved by lowering the upper cut-off voltage, for example to 4.75 V or lower, albeit with lower capacity. In this respect, improvements in the electrochemical properties of the electrode materials described herein can be expected by tailoring their synthesis and the voltage window of the cells during electrochemical cycling to achieve optimum cell performance.
Structural refinements of a LT-LiMn0.5Ni0.5O2 sample, prepared by the method described in Example 1, were undertaken to determine the structure-type and the extent of disorder, if any, between the lithium, manganese, and nickel ions in the structure. For these studies, high quality synchrotron X-ray diffraction data (λ=0.1173 Å) were collected at the Advanced Photon Source at Argonne National Laboratory (
Li/LT-LiMn0.5Ni0.5O2 cells were assembled and evaluated as described in Example 1.
A partially-disordered lithiated spinel material, LiNi1/3Mn1/3Co1/3O2, also hereafter referred to as LT-NMC111 (where LT refers to the ‘low-temperature’ at which the material was synthesized (400-650° C.) relative to conventional ‘high-temperature’ (HT) solid state synthesis (800-900° C.)), was prepared by a flame spray pyrolysis (FSP) method as follows.
Stoichiometric amounts of nickel acetylacetonate, manganese acetylacetonate, and cobalt acetylacetonate in the required 1:1:1 Ni:Mn:Co_ratio for LT-NMC111, and a small excess of lithium propionate to compensate for lithium loss in the flame, typically about 1 to about 10% excess lithium, and preferably less than 10% excess lithium, were dissolved in acetonitrile and 2-ethylhexanoic acid (5:5 by volume) at a concentration of 0.31 mol/L. The precursor solution was then sprayed into the flame of a flame-spraying pyrolysis unit at Argonne National Laboratory. Samples of the resulting powder were subsequently fired at various temperatures ranging from 400 to 650° C. in air for 3-5 days.
X-ray diffraction (XRD) patterns of the LT-NMC111 powders were obtained with a D8 ADVANCE, BRUKER diffractometer using Cu Kα radiation (λ=1.54178 Δ). Structural parameters of the materials were determined by Rietveld profile refinement using the FULLPROF program.
High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images of LT-NMC111 samples were obtained with an aberration-corrected JEOL electron microscope ARM200CF using an operation voltage of 200 kV. The image of an unheated precursor sample prepared by the flame spray pyrolysis (FSP) method, shown in
a) Cell Assembly and Testing
A slurry of 80 wt % LT-NMC111 material, 10 wt % carbon black (SUPER P, Timcal), and 10 wt % polyvinylidene fluoride (PVDF, Solvay), dissolved in N-methyl-2-pyrrolidone (NMP), was cast onto Al foil. The NMP was removed by drying the coated Al foil at 80° C. in an oven overnight. The electrode was calendared before use. Coin cells (CR2032, Hohsen) were assembled with a LT-NMC111 cathode, a lithium metal disc anode, a CELGARD 2325 separator, and an electrolyte consisting of a 1.2 M solution of LiPF6 in ethylene carbonate/ethyl methyl carbonate (EC/EMC, 3:7 by volume) in an Ar-filled glove box. The coin cells were charged and discharged using a MACCOR cycler (series 4000) between 2.7 and 4.3 V at 30° C. in a temperature-controlled chamber. Constant current, constant voltage charge and constant current discharge protocols were applied at a 0.2C rate (1C=100 mA/g) for the first 2 cycles to evaluate the relative electrochemical performance of the LT-NMC111 electrodes when heated to various temperatures.
b) Electrochemical Performance
The voltage profiles for the initial charge/discharge cycle of Li/LT-NMC111 cells with cathodes that had been annealed at 400, 500 and 625° C. are shown in
A Mn0.55Ni0.45(OH)2 precursor was first prepared by a co-precipitation reaction in an aqueous solution containing manganese sulfate (MnSO4) and nickel sulfate (NiSO4). Stoichiometric amounts of lithium carbonate (Li2CO3, >99%), Mn0.55Ni0.45(OH)2 precursor were thoroughly mixed using a mortar and pestle to produce an electrode composition, Li1.1Mn0.45Ni0.45O2, alternatively in composite notation, 0.1Li2MnO30.0.9LiMn0.5Ni0.5O2, and the mixture was then fired in air at 400° C. in a furnace for approximately 3 days. The heating rate was about 2° C. per min. The samples were cooled in the furnace without controlling the cooling rate. Thereafter, the product was washed with distilled water at room temperature (25° C.) to remove any unreacted lithium from the surface of the particles. The powder X-ray diffraction of the product is shown in
Li/LT-Li1.1Mn0.55Ni0.45O2.1 cells were assembled and evaluated as follows: Coin-type cells (2032, Hohsen) were assembled in an argon-filled glovebox (<5 ppm O2 and H2O) for electrochemical tests. The cathode electrode consisted of approximately 84 wt % of LT-Li1.1Mn0.55Ni0.45O2.1 powder, 8 wt % carbon, and 8 wt % polyvinylidene difluoride (PVDF) binder on an aluminum foil current collector. The anode was metallic lithium foil. The electrolyte was 1.2 M lithium hexafluorophosphate (LiPF6) in a 3:7 mixture of ethylene carbonate and ethyl methyl carbonate. The coin cell was galvanostatically charged and discharged between 2.5 and 5.0 V at a constant current of approximately 15 mA/g. Electrochemical experiments were conducted at about 30° C. Voltage (V) vs. specific capacity (mAh/g) plots of a Li/LT-Li1.1Mn0.55Ni0.45O2.1 cell cycled between 5.0 and 2.5 V for the first 3 cycles are shown in
LT-0.09Li2MnO3·0.81LiMn0.5Ni0.5O2·0.1LiCo0.85Al0.15O2 powder was prepared following a similar procedure described in Example 8. Stoichiometric amounts of lithium carbonate (Li2CO3, >99%), manganese(II) carbonate (MnCO3>99.9%), nickel(II) nitrate hexahydrate (Ni(NO3)2·6H20>99.999%), cobalt(II) carbonate hydrate (CoCO3·xH2O>99.99%), aluminum nitrate nonahydrate (Al(NO3)3·9H2O>98%) were thoroughly mixed by a planetary ball mill machine (RESTCH PM 200). The mixture powder was then fired in air at 400° C. for approximately 3 days. The heating rate was about 2° C. per min, and the samples were cooled in the furnace without controlling the cooling rate. The X-ray diffraction (XRD) pattern of LT-0.09Li2MnO3·0.81LiMn0.5Ni0.5O2·0.1LiCo0.85Al0.15O2 is shown in
Li/LT-0.09Li2MnO3·0.81LiMn0.5Ni0.5O2·0.1LiCo0.85Al0.15O2 cells with a metallic Li anode were assembled and evaluated as described in Example 8. The voltage (V) vs. specific capacity (mAh/g) profile of a Li/LT-0.1Li2MnO3·0.8LiMn0.5Ni0.5O2·0.1LiCo0.85Al0.15O2 cell, cycled between 5.0 and 2.5V for the five cycles, is consistent with the profile in Example 8, as shown in
LT-0.1LiCo0.85Al0.15O2·0.9LiMn0.5Ni0.5O2 was synthesized by the same method as described in Example 9. The X-ray diffraction (XRD) pattern of LT-0.1LiCo0.85Al0.15O2·0.9LiMn0.5Ni0.5O2 is shown in
In this example, the lithiated spinel-lithiated-spinel electrode of Example 10 delivers slightly less capacity than the layered-lithiated spinel-lithiated spinel electrode of Example 9. This result emphasizes the utility of the layered Li2MnO3 component in Example 9, consistent with Example 8.
LT-LiMn055Ni00.45O2 was prepared as follows: A Mn0.55Ni0.45(OH)2 precursor was first synthesized by the continuous stirred-tank reactor (CSTR) method. A stoichiometric amount of the hydroxide precursor was thoroughly mixed with lithium carbonate (Li2CO3>99%, Sigma-Aldrich) with a mortar and pestle. The mixture was then transferred to a furnace for solid state calcination in air. The calcination temperature was held at 400° C. for 72 hours after which the powder was cooled in the furnace to room temperature. The X-ray diffraction pattern of the LT-LiMn0.55Ni0.45O2 product is shown in
Li/LT-LiMn0.55Ni0.45O2 coin cells (size 2032) were assembled in an argon-filled glovebox for electrochemical testing. Cathode laminates were prepared by coating a slurry, consisting of 84 wt % active material: 8 wt % SUPER P carbon: 8 wt % polyvinylidene difluoride (Solvay) binder in a N-methyl-2-pyrrolidone solvent, on aluminum foil. Lithium metal was used as anode. The electrolyte consisted of 1.2 M lithium hexafluorophosphate (LiPF6) in a 3:7 mixture of ethylene carbonate and ethyl methyl carbonate. Coin cells were cycled between 2.0 to 5.0V at a constant current of 20 mA/g in a climate chamber held at 30° C. The voltage profile and dQ/dV plots of the Li/LT-LiMn0.55Ni0.45O2 cell for the first two cycles are shown in
LT-LiMn0.55Ni0.45O2 was prepared as follows: A Mn0.55Ni0.45(OH)2 precursor was first synthesized by the CSTR method. Stoichiometric amounts of the metal hydroxide and lithium carbonate precursors were thoroughly mixed using an automatic grinder equipped with an agate mortar and pestle. The mixture was then transferred to a furnace for solid state calcination during which the calcination temperature was held at 400° C. for 72 hours in air. The product was subsequently cooled in the furnace to room temperature. The X-ray diffraction pattern of the LT-LiMn0.55Ni0.45O2 product is shown in
Li/LT-LiMn0.55Ni0.45O2 cells were assembled and evaluated as described in Example 11a. The voltage profile and dQ/dV plots of the Li/LT-LiMn0.55Ni0.45O2 cell for the first two cycles are shown in
The following are additional structurally-integrated materials formed by the methods described herein:
Samples of 0.3Li2MnO3 (L)·0.7LiNi0.333Mn0.333Co0.333O2(L and LS) that can be described as having structurally-integrated domains of layered (L), lithiated-spinel (LS) and partially-disordered (rock salt) variations thereof were used to demonstrate the principles of this invention. The samples were synthesized and annealed at various temperatures between 400° C. and 750° C., as follows.
Stoichiometric amounts of manganese carbonate (MnCO3) and lithium carbonate (Li2CO3) precursors in a stoichiometric ratio sufficient to form Li2MnO3 were intimately mixed by ball milling for 90 minutes. The resulting powder was then mixed in a 3:7 molar ratio with LT-LiNi0.333Mn0.333Co0.333O2 that had been annealed at 400° C. This mixture was then ball-milled for another 2 minutes. Five individual samples of the resulting thoroughly-mixed material were then heated (i.e., annealed) again for 48 hours at temperatures of 400, 500, 600, 700 and 750° C., thereby yielding five LT-0.3Li2MnO3·0.7LiNi0.333Mn0.333Co0.333O2 products which had different amounts of layered, lithiated spinel and partially-disordered (rock salt) components depending on the temperature at which the materials were heated. In this regard, it should be noted that the composition and domain size of the layered, lithiated spinel, and rock salt domains within the composite structures of this invention are not uniform; instead, they vary across the structurally-integrated crystallites and secondary particles, as demonstrated herein by examples of high-resolution, transmission electron microscopy images and X-ray diffraction patterns of related materials.
X-ray diffraction (XRD) patterns of the five 0.3Li2MnO3·0.7LiNi0.333Mn0.333Co0.333O2 samples that had been annealed between 400, 500, 600, 700 and 750° C. were obtained with a D8 ADVANCE, BRUKER diffractometer using Cu Kα radiation (λ=1.54178 Δ, are shown in
The extent of ordering of the close-packed oxygen array is reflected by the crystallographic axial c a ratio of a trigonal unit cell, which varies from a value of 4.90 for an ideal cubic-close-packed oxygen lattice to >4.90 for a trigonal unit cell that deviates slightly from ideal cubic-close-packing; this ratio can therefore be used as a yardstick to monitor the amount of disorder between the lithium and transition metal ions in the layered component. In this respect, it should be noted that the split peaks in XRD pattern of the sample that had been annealed at 700° C., overlap with one another, implying that small domains of partially-disordered lithiated spinel and rock salt components may still exist in minor amounts in samples annealed at 750° C. and above, for example, between 750° C. and 900° C., particularly if the annealing process at such elevated temperatures is conducted for short periods of time (i.e., minutes to an hour) to optimize and minimize the amount of the stabilizing lithiated spinel component in the electrode structure.
The weak peak at approximately 21 °2θ in the X-ray diffraction patterns is a distinct characteristic of the Li2MnO3 component in the 0.3Li2MnO3·0.7LiNi0.333Mn0.333Co0.333O2 structure (
Electrochemistry The electrochemical performance of Li/0.3Li2MnO3·0.7LiNi0.333Mn0.333Co0.333O2 cells containing cathode materials that had been annealed at 400, 500, 600, 700 and 750° C. are shown in
A slurry containing 80 wt. % 0.3Li2MnO3·0.7LiNi0.333Mn0.333Co0.333O2, 10 wt. % carbon black (SUPER P, Timcal), and 10 wt. % polyvinylidene fluoride (Solvay), dissolved in N-methyl-2-pyrrolidone, was cast onto an aluminum foil, dried overnight in an oven at 80° C. and calendared before use. Coin cells (CR2032, Hohsen) containing a 0.3Li2MnO3·0.7LiNi0.333Mn0.333Co0.333O2 cathode, a lithium metal disc anode, a CELGARD 2325 separator, and an electrolyte solution of 1.2 M LiPF6 in ethylene carbonate/ethyl methyl carbonate (3:7 ratio vol/vol) were assembled in a glovebox under inert conditions (argon gas). Cells were operated and tested using a MACCOR cycler (series 4000) between 4.6 and 2.5 V at 30° C.; one cell was charged to 5.0 V to activate the Li2MnO3 component of the 0.3Li2MnO3·0.7LiNi0.333Mn0.333Co0.333O2 electrode and to monitor the capacity and stability of the electrode at high voltage. Cells were charged and discharged at a 15 mA/g rate.
The electrochemical data in
(1) annealing the stabilized 0.3Li2MnO3·0.7LiNi0.333Mn0.333Co0.333O2 electrode at higher temperatures increases the concentration of the more stable layered configuration at the expense of the lithiated spinel configuration.
(2) the overall capacity of the electrode increases when annealed at 700° C., where the XRD pattern shows the early onset of peak splitting at approximately 65 °2θ (
(3) the cycling stability of the electrode increases significantly when annealed above 600° C.
The principles of this invention can be extended to composite electrode structures containing layered, lithiated spinel and spinel components, as defined herein, notably those comprising layered LiMn0.5Ni0.5O2, lithiated spinel LiMn0.5Ni0.5O2, and spinel LiMn2−xNixO4 (0<x<0.5) components and the like, which are cobalt free, or those that contain a minimal amount of cobalt or stabilizing cations such as aluminum ions or stabilizing anions, such as fluorine ions, preferably less than 10% of the total transition metal content or oxygen content in the electrode structure, respectively.
All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
The use of the terms “a” and “an” and “the” and similar referents in the context of describing materials or methods (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The terms “consisting of” and “consists of” are to be construed as closed terms, which limit any compositions or methods to the specified components or steps, respectively, that are listed in a given claim or portion of the specification. In addition, and because of its open nature, the term “comprising” broadly encompasses compositions and methods that “consist essentially of” or “consist of” specified components or steps, in addition to compositions and methods that include other components or steps beyond those listed in the given claim or portion of the specification. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All numerical values obtained by measurement (e.g., weight, concentration, physical dimensions, removal rates, flow rates, and the like) are not to be construed as absolutely precise numbers, and should be considered to encompass values within the known limits of the measurement techniques commonly used in the art, regardless of whether or not the term “about” is explicitly stated. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate certain aspects of the materials or methods described herein and does not pose a limitation on the scope of the claims unless otherwise stated. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the claims.
Preferred embodiments are described herein, including the best mode known to the inventors for carrying out the claimed invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the claimed invention to be practiced otherwise than as specifically described herein. Accordingly, the claimed invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the claimed invention unless otherwise indicated herein or otherwise clearly contradicted by context.
This application claims the benefit of U.S. Provisional Application Ser. No. 63/346,491, filed on May 27, 2022; and this application is a continuation-in-part of U.S. application Ser. No. 17/351,944, filed on Jun. 18, 2021, which is a continuation-in-part of U.S. application Ser. No. 17/313,752, filed on May 6, 2021, which is a continuation-in-part of U.S. application Ser. No. 17/136,234, filed on Dec. 29, 2020, which claims the benefit of U.S. Provisional Application Ser. No. 63/055,993, filed on Jul. 24, 2020, each of which is incorporated herein by reference in its entirety.
The United States Government has rights in this invention pursuant to Contract No. DE-AC02-06CH11357 between the United States Government and UChicago Argonne, LLC representing Argonne National Laboratory.
| Number | Date | Country | |
|---|---|---|---|
| 63346491 | May 2022 | US | |
| 63055993 | Jul 2020 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 17351944 | Jun 2021 | US |
| Child | 18121785 | US | |
| Parent | 17313752 | May 2021 | US |
| Child | 17351944 | US | |
| Parent | 17136234 | Dec 2020 | US |
| Child | 17313752 | US |
