Patent Application
20160218363
The field of the invention is energy storage devices, particularly non-aqueous electrochemical cells and batteries and, more particularly, non-aqueous rechargeable sodium electrochemical cells and batteries. Rechargeable ambient temperature sodium and sodium ion batteries of the invention are applicable to many energy storage applications, especially large-scale stationary electrical storage for electrical grid. Other example applications include, but are not limited to portable device, transportation, defense products, and aerospace products.
Worldwide demand to develop electrical energy storage is growing as a result of increased energy demand, rapid increases in the price of fossil fuels and the environmental consequences of their use. Renewable energy technologies such as wind and solar generated electricity are have great potential to generate energy. However, the renewable sources are not able to generate energy on demand in a manner that models traditional power plants. Wider success of the renewable sources therefore requires better energy storage systems.
Large-scale stationary electrical storage requires new battery systems, as current technology is ill-suited for this application.[1] Extensive research has focused on the lithium system for rechargeable batteries. The lithium system is in widespread use for small power consumption devices, such as electronics. It has also been adopted in electrically powered automobiles. The lithium is favored for its high energy and power density. Most research efforts are devoted to improving the lithium system for safety, power output, discharge cycle, and lifetime. Despite the widespread adoption of the lithium system, the energy, power density, lifetime, and costs are not well-suited for energy storage in a power distribution system. The limits of current lithium system technology also places a ceiling on performance of current applications, such as electrically powered vehicles.
In contrast, sodium intercalation chemistry has been explored considerably less than lithium intercalation system. Artisans have likely avoided the sodium battery system due to the lack of a high energy density cathode material that is safe and low cost.
Sodium is located below lithium in the periodic table. Sodium and lithium show similar chemical properties in many aspects. The fundamental principles of the sodium ion battery and lithium ion battery are identical, during charge and discharge the alkali ions move back and forth between the two electrodes. Sodium is available in high abundance and low cost, and has a very suitable redox potential (EΘNa+/Na=−2.7V only 0.3 V above that of EΘLi+/Li=−3.0V).
The abundance and low cost of Na in the earth can become an advantage when a large amount of alkali is demanded for large-scale applications. Research on sodium ion batteries began in the late 1970s and the early 1980s. [2-4] Sodium-based layered electrode materials can be categorized into two main groups[5]: O3 type or P2 type, in which the sodium ions are accommodated at octahedral and prismatic sites, respectively. A study by Lu and Dahn demonstrated that the P2-layered oxide, Na2/3[Ni1/3Mn2/3]O2, can reversibly exchange Na-ions in sodium cells [6, 7], but the voltage profile was complicated, showing single and two phase regions, and transformation to O2 structure at high voltage range. More recently, Li substituted Na1.0Li0.2Ni0.25Mn0.75O2 was studied by Kim et al. and displayed 95 mAh g−1 of specific capacity, excellent cycling and rate capabilities[8]. The TM layer is argued to improve the structural stability during the cycling.
Other P2-type phases provide higher capacity as electrode materials. P2-Na0.6MnO2 delivers a large initial capacity of 160 mAh g−1 [9], P2-Na2/3Fe0.5Mn0.5O2 delivers higher initial capacity of 190 mAh g−1 [10]. However the cyclability is insufficient.
O3-phases such as NaCoO2 [3], NaCrO2 [11], NaVO2 [12], and NaNi0.5Mn0.5O2 [13] are electrochemically active, but the repeatable reversible capacity cannot exceed 120 mAh g−1. Recently, Tarascon successfully synthesized O3-phase NaNi1/3Mn1/3Co1/3O2 which can deliver a reversible capacity of 120 mAh g−1. Their voltage profile shows complicated phase transformation during charge, followed the sequence O3→O1→P3→P1 which was proved by their in-situ XRD work.[14]
Embodiments of the invention include cathode materials and cathodes for sodium and sodium-ion cells and batteries including sodium, lithium and transition metal oxide cathode materials. In a preferred embodiment, the cathode is from of the composition NaxLiyNizMnuMvOw, with M being one or more metal cation, x+y≧0.9, (x+y)/(z+u+v)>1, O≦z≦0.9, O≦u≦0.9, 0≦v≦0.9, x+y+z+u+v is less than w, and the value of w depends on the proportions and average oxidation states of the metallic elements. The combined positive charge of the metallic elements is balanced by the number of oxygen anions, w. In preferred embodiments, w is less than or equal to 2, i.e., NaxLiyNizMnuMvO2−a, and preferably equal to or slightly less than 2. M is one or more metal cations selected preferably from one or more divalent, trivalent, tetravalent, pentavalent or hexavalent cations, such as Mg2+, Cu2+, Co3+, B3+, Fe3+, Al3+, Ti4+, Zr4+, V5+, and Cr6+ etc. The cathode material has a layered structure in which the Na is predominately present in sodium layer, and Ni, Mn and M are predominately present in a transition metal layer. The position of Li depends on the content of Li in the compounds, it can be present in sodium or transition metal layers or both, and it can also be present between the sodium and transition metal layers. In preferred embodiments, the Li content is 0.4 or less and preferably 0.2, or less. Preferred methods of forming electrode materials and electrodes of the invention include solid state mixing, co-precipitation reaction, calcination methods and ion exchange methods.
Embodiments of the invention provide cathode material, cathodes for energy storage devices and energy storage devices. Preferred embodiments provide non-aqueous electrochemical cells and batteries and, more particularly, non-aqueous rechargeable sodium and sodium ion electrochemical cells and batteries. Cells of the invention can operate at ambient temperature. Preferred embodiments also provide fuel cells including sodium, lithium and transition metal oxide cathode materials.
Preferred embodiments of the invention mix sodium-lithium nickel-manganese (or nickel-manganese-cobalt) metal oxide layered materials have been identified for use as cathode in ambient temperature sodium ion batteries.
Preferred embodiments of the invention provide cathode materials and cathodes for sodium and sodium-ion cells and batteries including sodium, lithium and transition metal oxide cathode materials. In a preferred embodiment, the cathode is from of the composition NaxLiyNizMnuMvOw, with M being one or more metal cation, x+y≧0.9, (x+y)/(z+u+v)>1, 0≦z≦0.9, 0≦u≦0.9, 0≦v≦0.9, x+y+z+u+v is less than w, and the value of w depends on the proportions and average oxidation states of the metallic elements. The combined positive charge of the metallic elements is balanced by the number of oxygen anions, w. In preferred embodiments, w is equal to or less than 2, i.e., NaxLiyNizMnuMvO2−a, and preferably equal to or slightly less than 2. M is one or more metal cations selected preferably from one or more divalent, trivalent, tetravalent, pentavalent or hexavalent cations, such as Mg2+, Cu2+, Co3+, B3+, Fe3+, Al3+, Ti4+, Zr4+, V5+, and Cr6+, and Cr6+ etc. The cathode material has a layered structure in which the Na is predominately present in sodium layer, and Ni, Mn and M are predominately present in a transition metal layer. The position of Li depends on the content of Li in the compounds, it can be present in sodium or transition metal layers or both, and it can also be present between the sodium and transition metal layers. The Li in the preferred material is 0.4 or less and most preferably 0.2 or less. This provides an advantage compared to the Li content in lithium ion battery cathodes, which is usually 1. The lower content of Li lowers the cost of cathodes produced by the invention. The Li ions in TM layer pin the oxygen layers by allowing the so-called tetrahedron dumbbell formation, in which the tetrahedral sites formed between the oxygen AB stacked layers can be occupied by either Li ion or Ni and Mn ions. The oxidation states of the Ni and Mn components are predominantly divalent and tetravalent, respectively.
A preferred method for formation of the cathode material includes thermal reaction of co-precipitated transition metal hydroxide/ carbonate precursors (including directly mixed transition metal oxides) mixed with sodium carbonate and lithium hydroxide/ carbonate or ion exchange with as-prepared O3 phase lithium transition metal oxides. Preferably, the NaxLiyNizMnuMvOw is present in a layer or casting on a current collector such as a metallic substrate (e.g., Al foil).
Preferred embodiments provide cathodes that are rich in sodium and manganese. The preferred cathodes are low in cost compared to similar lithium metal oxide compounds, and exhibit high power, high energy, and long cycle life times. Advances provided by cathodes and energy storage devices of the invention provide an attractive model for wide spread use of sodium and sodium ion batteries in many applications that presently rely upon the lithium system.
Preferred embodiment cathodes possess high-energy and high-power capabilities and can be used in rechargeable sodium and sodium ion cells and batteries that include a suitable anode and electrolyte (e.g., sodium metal anode, tin sulfite anode and sodium salt electrolyte) to form a full cell that is most preferably used in ambient temperature sodium electrochemical cells and batteries.
Preferred example cathode materials have been prepared in experiments. The example preferred materials have the general composition NaxLiyNizMnuMvOw, for example Na0.05Li1.15Ni0.2Mn0.6O2, Na0.8Li0.14Ni0.3Mn0.567Ow, Na0.8Li0.14Ni0.25Mn0.583Ow, Na0.8Li0.14Ni0.16Mn0.5Co0.16Ow, and NaLi0.133Ni0.2Mn0.467Co0.2O2. These materials are layered structures and were investigated as cathode active materials for sodium and sodium ion batteries. In these examples, the Na cations are predominately present in octahedral coordination in sodium layer, the Ni, Mn and M cations are preferentially located in octahedral coordination in the transition metal layer, and the Li cations are located in octahedral coordination in either transition metal layer or both transition metal layer and sodium layer depends on the amount of lithium ion in the structure. Preferably, the mixing between Na and transition metal cations is minimal and most preferably non-existent. Preferred prepared materials are believed to have had no Na/transition metal mixing. Li and Na can be in the same layer of the structure, however (at a relatively high state of charge). The metal stoichiometries were selected to include Li so that stabilize the O3 structure during electrochemical cycling. In lithium ion batteries, the charge-ordered state is known to stabilize the structure to reversible insertion/extraction of lithium between the TM layers.[15]
Preferred embodiments provide an cathode for sodium or sodium ion electrochemical cells and batteries and cells and batteries including the cathodes. The cathode comprises a material of composition NaxLiyNizMnuMvOw, where M compromises one or more metal cation, x+y>0.9, (x+y)/(z+u+v)>1, 0≦z≦0.9, 0≦u≦0.9, 0≦v≦0.9, x+y+z+u+v is less than w, and the value of w depends on the proportions and average oxidation states of the metallic elements. The combined positive charge of the metallic elements is balanced by the number of oxygen anions, w. The cathode material of composition NaxLiyNizMnuMvOw is layered, with preferably good separation between the layers. The Na cations are predominately present in octahedral coordination in sodium layer, the Ni, Mn and M cations are preferentially located in octahedral coordination in the transition metal layer, and the Li cations are located in octahedral coordination in either transition metal layer or both transition metal layer and sodium layer depends on the amount of lithium ion in the structure. The Li ions in TM layer pin the oxygen layers by allowing the so called tetrahedron dumbbell formation, the tetrahedral sites formed between the oxygen AB stacked layers can be occupied by either Li ion or Ni and Mn ions. They provide a pivoting role for preventing the oxygen layer shifting from AB (in O3 structure) to AA (in P2/P3 structure). In a preferred embodiment, little or no site-disorder takes place between the Na in sodium layers. The presence of Li in the structure beneficially leads to excellent electrochemical performance. This is associated with the structure's stability against phase transformation and a possibly correlated enhancement of Na ion diffusion therein, as observed by Meng et al in P2-Nax[Ni1/3Mn2/3]O2[16]. In a particular preferred embodiment, the NaxLiyNizMnuMvOw is present in a layer or casting on a current collector such as a metallic substrate (e.g., Al foil).
A preferred cathode for an electrochemical cell of the invention comprises an active material of composition NaxLiyNizMnuMvOw. In one preferred embodiment, v/w is 0, (x+y)/w is about 0.6, and (z+u)/w is about 0.4. In another preferred embodiment, v/w is 0, (x+y)/w is about 0.47, and (z+u)/w is about 0.433. In a third preferred embodiment, v/w is 0, (x+y)/w is about 0.47, and (z+u)/w is about 0.417. In a fourth preferred embodiment, v/w is about 0.08, (x+y)/w is about 0.47, and (z+u)/w is about 0.33. In a fifth preferred embodiment, v/w is about 0.1, (x+y)/w is about 0.567, and (z+u)/w is about 0.334.
In one preferred embodiment, ratio u/z is about 1.9, x/y is about 5.7, and (x+y)/ (z+u) is about 1.5, and the exists of Na, Ni and Mn in cathode material which extracted from cycled cathode are determined by EDX
In some preferred embodiments, M comprises one or more metal cations selected preferably from one or more divalent, trivalent, tetravalent, pentavalent or hexavalent cations, such as Mg2+, Cu2+, Co3+, B3+, Fe3+, Al3+, Ti4+, Zr4+, V5+, and Cr6+ etc. In preferred embodiments, Na is predominately present in sodium layer, and Ni, Mn and M are predominately present in a transition metal layer. Li is present in both sodium and transition metal layers. The Li ions reside in the TM layer, providing a pivoting role for preventing the oxygen layer shifting from AB (in O3 structure) to AA (in P2/P3 structure). The Li ions in TM layer pin the oxygen layers by allowing the so called tetrahedron dumbbell formation, the tetrahedral sites formed between the oxygen AB stacked layers can be occupied by either Li ion or Ni and Mn ions.
In preferred embodiment cathodes, Na cations are predominately present in octahedral coordination in the sodium layer, the Ni, Mn and M cations are preferentially located in octahedral coordination in the transition metal layer, and the Li cations are located in octahedral coordination in either transition metal layer or both transition metal layer and sodium layer depends on the amount of lithium ion in the structure. The Li present in transition metal layer, which makes local Li2MnO3 like character and preferably clusters with Ni and/or Mn. Preferably, the NaxLiyNizMnuMvOw exhibits a layering peak in the X-ray diffraction (XRD) pattern thereof, and also preferably has a repeating ABCABC layered, oxygen close-packed stacking structure.
In some preferred embodiments, the first electrochemical charge profile of the cathode exhibits a plateau at about 4.5V when used as the cathode in an electrochemical cell including a Li metal anode and an electrolyte including 1 M LiPF6 in a mixture of ethylenecarbonate (EC) and dimethylcarbonate (DMC) in a weight ratio of about 1:1 EC:DMC.
Preferred cathode materials of NaxLiyNizMnuMvOw can be prepared by a number of procedures, including solid state, co-precipitation, sol-gel, polyol, and hydrothermal methods. The co-precipitation and solid state methods are more readily scalable.
A preferred solid state method utilizes oxides, carbonate, hydroxides, or other starting materials including Na, Li, Mn, Ni and M can be thoroughly mixed in a ball milling or slow rotation mixer for a suitable period of time (e.g. 5 to 20 hours), followed by a calcination of the mixture at a temperature in range of 600° C. to 1100° C. for 2 to 24 h.
A preferred co-precipitation method utilizes salts of Mn, Ni and M that can be dissolved in a container. The base, for example, NaOH or Na2CO3, is dissolved in another container. The transition metal solution is dropped into the base solution to form the co-precipitation products, for example, NizMnuMy(OH)b or NizMnuMyCO3. The Li/Na carbonates or hydroxides are mixed with co-precipitated precursor, The pre-calcination is performed at a temperature in range of 480° C. to 500° C. for 2 to 24 h, the final calcination is performed at a temperature in range of 600° C. to 1100° C. for 2 to 24 h.
A preferred sol-gel method prepares the sol solution from the stoichiometric mixture of Ni, Mn, and M salts in distilled water. A solution of Li/Na salts in distilled water and aqueous solution of citric acid was added dropwise to the metal precursor mixture with a continuous stirring. Next, the pH of the mixed solution was adjusted to 7 by adding an ammonium hydroxide solution. As-prepared sol solution was dried at 70° C. with a vigorous mechanical stirring. After gel formation, the precursor was further dried in vacuum oven at 120° C. for overnight, eventually, the resulting gel precursors were decomposed at a temperature in range of 480° C. to 500° C. for 2 to 24 h in air and then calcinated at a temperature in range of 600° C. to 1100° C. for 2 to 24 h in air.
A preferred polyol method adds the stoichiometric mixture of Ni, Mn, Li, Na, and M salts and citric acid to 100 ml tetraethylene glycol (TTEG) in a stioichiometric molar ratio. The mixture was heated at 280° C. for 3 h in a round bottom flask connected to a refluxing condenser to ensure full activation of the polyol medium. The resulting solution was centrifuged several times with methanol and subsequently dried at 80° C. for overnight. The resulting precursors were decomposed at a temperature in range of 480° C. to 500° C. for 2 to 24 h in air and then calcinated at a temperature in range of 600° C. to 1100° C. for 2 to 24 h in air.
A preferred hydrothermal method loads stoichiometric amounts of Ni, Mn, Li, Na, and M salts and Polyvinylpyrrolidone (Mw=10,000 g mol−1) were loaded into a poly(tetrafluoroethylene)-lined stainless steel autoclave, which was then filled with 3/4 of a solution of ethylene glycol and water (v:v=1:1). The autoclave was sealed and maintained at 200° C. for 12 hrs. The precursor was heated on a hot plate to evaporate the ethylene glycol and water. The resulting precursors were decomposed at a temperature in range of 480° C. to 500° C. for 2 to 24 h in air and then calcinated at a temperature in range of 600° C. to 1100° C. for 2 to 24 h in air.
Calcination and sintering of suitable mixed combination of salts, oxides, carbonate, hydroxides, or other starting materials including Na, Li, Mn, Ni and M can also be used to prepare the material. For example, such starting materials can be mixed in a ball milling or slow rotation mixer for a suitable period of time (e.g. 5 to 20 hours), followed by grinding and thermal reaction of the mixture. In one preferred embodiment, the material is prepared by calcinations of a combination of sodium carbonate, lithium hydroxide monohydrate and a co-precipitated precursor Mn/Ni hydroxide, hereby releasing H2O and CO2 as shown in Equation (1): 1.15LiOH.H2O+0.025Na2CO3+0.8Ni0.25Mn0.75(OH)2+0.3O2→Li1.15Na0.05Ni0.2Mn0.6O2+2.525H2O+0.025CO2.
In another preferred embodiment, the material is prepared by calcinations of a combination of sodium carbonate, lithium carbonate and a co-precipitated precursor Mn/Ni/Co hydroxide, hereby releasing H2O and CO2 as shown in Equation (2): 0.0665Li2CO3+0.5Na2CO3+Ni0.2Mn0.467CO0.2(OH)1.734+0.2835O2→NaLi0.133Ni0.2Mn0.467Co0.2O2+0.867H2O+0.5665CO2.
Optionally, one or more additional metal hydroxide/carbonates (M hydroxide/ carbonate) can be included in the reaction of Equation (1) and (2), with appropriate adjustment of the stoichiomtries of the precursors. The temperature of the calcinations is selected such that the mixture of precursor hydroxides/carbonates decomposes to the active layered phase for the cathode material. In a preferred embodiment the pre-calcination is performed at a temperature in range of 480° C. to 500° C. for 2 to 24 h, the final calcinations is performed at a temperature in range of 600° C. to 1100° C. for 2 to 24 h. The stoichiometries of the hydroxides or carbonates are selected such that a material of composition NaxLiyNizMnuMvOw, where in M compromises one or more metal cation, x+y≧0.9, (x+y)/(z+u+v)>1, 0≦z≦0.9, 0≦u≦0.9, 0≦v≦0.9, x+y+z+u+v is less than w, and the value of w depends on the proportions and average oxidation states of the metallic elements. The combined positive charge of the metallic elements is balanced by the number of oxygen anions, w. The cathode material of composition NaxLiyNizMnuMvOw is layered, with preferably good separation between the layers. The Na cations are predominately present in octahedral coordination in sodium layer, the Ni, Mn and M cations are preferentially located in octahedral coordination in the transition metal layer, and the Li cations are located in octahedral coordination in either transition metal layer or both transition metal layer and sodium layer depends on the amount of lithium ion in the structure. Preferred example compositions are Na0.05Li1.15Ni0.2Mn0.6O2 and NaLi0.133Ni0.2Mn0.467Co0.2O2.
In another preferred embodiment, the O3 type NaxLiyNizMnuMvOw cathode material can be prepared by ion-exchange. In experiments, the NaxLiyNizMnuMvOw cathode containing more lithium (y>0.6) was charged with various cut off voltage between 4.6 and 4.95 V (vs. Li metal, using LiPF6 non-aqueous electrolyte) and discharged with various cut off voltage between 1.0 and 2.0 V (vs.Na metal, using NaPF6 non-aqueous electrolyte), and the O3 type NaxLiyNizMnuMvOw cathode which contains more sodium (x>0.6) cathode was obtained. Three preferred example compositions are Na0.8Li0.14Ni0.3Mn0.567Ow, Na0.8Li0.14Ni0.25Mn0.583Ow and Na0.8Li0.14Ni0.16Mn0.5Co0.16Ow.
Specifically, the ion-exchange procedure began with the NaxLiyNizMnuMvOw containing more lithium (y>0.6), which was made into a cathode and assembled with an Li anode. Then, this prepared cell is then charged with various cut off voltages between 4.6 and 4.95 V (vs. Li metal, using LiPF6 non-aqueous electrolyte) to remove most of the Li from the cathode. After the lithium removal, the cell was opened and the cathode was washed. In the experiments, the cathode was washed three times. Afterwards, the cathode was assembled with a Na anode and discharged with various cut off voltage between 1.0 and 2.0 V (vs. Na metal, using NaPF6 non-aqueous electrolyte) to insert Na, and produce the O3 type NaxLiyNizMnuMvOw cathode that contains more sodium (x>0.6). Three preferred example compositions achieved by ion exchange are Na0.8Li0.14Ni0.3Mn0.567Ow, Na0.8Li0.14Ni0.25Mn0.583Ow and Na0.8Li0.14Ni0.16Mn0.5Co0.16Ow, where w is less than 2.
An example O3 type layered NaxLiyNizMnuMvOw cathode of the invention generally exhibits a strongly intense (highly crystalline) (003) layering peak (Cu Kα) in its X-ray Diffraction (XRD) pattern. In a preferred embodiment, the layered structure of the material has an XRD pattern that is similar to that of the reference compound, NaFeO2 (ICSD reference code: 01-076-2299). The Na cations predominately are in an octahedral coordination between the close-packed, stacked oxygen anion layers, in an alternating three-layer arrangement, which can be designated as ABCABC packing. The Li cations are located in octahedral coordination in ABCABC packing structures, in either the transition metal layer or both the transition metal layer and sodium layer, which depends on the amount of lithium ion in the structure.
In a preferred embodiment, the oxidation state of Mn in the NaxLiyNizMnuMvOw is close to tetravalent. Preferably, the Ni in the NaxLiyNizMnuMvOw is cycled between about Ni2+ and about Ni4+ or oxidation states very close to these values in the preferred voltage window of approximately 1.5 to 4.5V vs. Na metal. The Ni oxidation state is close to Ni2+ in the discharged state, and preferably Ni4+ in the charged state, in order to maximize the capacity of the cathode and the amount of Na removed and inserted in to the structure. Preferably, the Na insertion and removal from the cathode has a charge balance that is limited to a theoretical value associated with redox change, therefore adding other M (metal cation) which may increase capacity or stabilize structure.
In a preferred embodiment, the voltage profile of an cathode of the present invention is a continuous single phase sloping intercalation shape after first charge, which is smooth between voltage cutoffs of about 1.5V to 4.5V. The O3 layer peaks of the XRD patterns of an cathode of the invention typically shifts as a function of the Na content. A single phase in evident after one charge/ discharge cycle, indicating that the NaxLiyNizMnuMvOw layered oxide generally retains its O3 single phase structure during charge-discharge cycle.
In another preferred embodiment, the voltage profile of an cathode of the present invention is a continuous single phase sloping intercalation shape after first charge, which is smooth between voltage cutoffs of about 1.5V to 4.5V. Then charge-discharge cycling between 1.5V to 4.2V. The O3 layer peaks of the XRD patterns of an cathode of the invention typically shifts as a function of the Na content. A single phase in evident after cycles, indicating that the NaxLiyNizMnuMvOw layered oxide generally retains its O3 single phase structure during charge-discharge cycles.
Embodiments of the invention were tested. An example electrochemical charge experiment of a cathode of the invention was in a lithium battery electrolyte with lithium metal as the anode. A typical battery exhibits a slope below 4.4V and a plateau at around 4.5V. After first charge, the battery was disassembled and the cathode was assembled in a sodium battery electrolyte with sodium metal as the anode. The sodium ions inserted into the structure during discharge with very reversible cycling of the battery at a capacity of about 205 mAh g−1 to about 241 mAh g−1 (depends on the composition).
Preferred embodiments of the invention will now be discussed with respect to experiments and experimental data. The invention is not limited to the details of the experiments, as will be understood by artisans.
An active layered phase Li1.15Na0.05Ni0.2Mn0.6O2, cathode material was prepared by heating a mixture of about 0.79821 g LiOH.H2O, 0.05306 g Na2CO3 and about 1.2 g Ni0.25Mn0.75(OH)2. The hydroxides and carbonates were thoroughly mixed for about 6 hours in a ball milling and then ground with a mortar and pestle for about 30 minutes prior to heating. The resulting powder was placed in to a box furnace, and then heated to a decomposition temperature, e.g. about 480-500° C., over about 2 hours and held there for a sufficient time to achieve decomposition, e.g., about 5-12 hours. In the experiments, 12 hours was a typical time. This heating achieves decomposition of Ni0.25Mn0.75(OH)2 to form Ni0.25Mn0.75Oe. The sample was allowed to cool to room temperature in the furnace. The pre-calcination product was then reground and placed in to a box furnace to react with LiOH, and then heated to a reaction temperature, e.g., about 800-1100° C., over about 3 hours and held there for a reaction time, e.g. about 3-24 hours. In the experiments, 12 hours was a typical time. This heating step reacts LiOH with with Ni0.25Mn0.75Ox and air to form the final product. The sample was allowed to cool to room temperature in the furnace. In each of the heating steps, a slow ramping rate is preferred, e.g., 5 degrees per minute.
A sample of the Li1.15Na0.05Ni0.2Mn0.6O2 cathode material was characterized by X-ray powder diffraction (XRD) using a Bruker D8 advance diffractometer with a Bragg—Brentano θ13 2θ geometry and a Cu Ka source. Samples were scanned from 10° to 80° with a scan rate of 0.025° per second. XRD spectra for the Li1.15Na0.05Ni0.2Mn0.6O2 is depicted in
The material synthesized in Example 1 is a powder and was processed into cathode laminates. Each cathode were prepared by mixing cathode material with a conductive additive of 10 wt % Carbon Black and 10 wt % PVDF binder (inactive component) then added N-methyl pyrrolidone solvent. The slurry was cast onto an Al foil using a doctor blade and dried in a vacuum oven at 80° C. for 12 hours. The cathode disks were punched and dried again at 80° C. before storing them in an argon-filled glove box (H2O level of <2 ppm). 2016 type coin cells were used to study the electrochemical behavior of the compounds. Lithium metal and 1 M LiPF6 in a 1:1 ethylene carbonate: dimethyl carbonate solution were used as the counter electrode and electrolyte, respectively. A Celgard model C480 separator was used as the separator. The coin cells were assembled in an argon-filled glove box and tested on an Arbin battery cycler in galvanostatic mode. The tests were conducted between 2.0 and 4.8 V at a constant current rate of 12.5 mA/g. The Li/Li1.15Na0.05Ni0.2Mn0.6O2 cell voltage profiles for the first cycle between 2.0 to 4.8V is shown in
Other methods can be used to prepare a cathode from the cathode materials of the invention. For example, the powders can be mixed with PTFE and carbon black and pressed to be a thin disk. Such a thin disk is often used in a Swagelok cell.
Following the reaction protocol in Example 1, the O3 type cathode material Li1.133Ni0.3Mn0.567O2 can be prepared using the appropriate mole stoichiometries of LiOH.H2O and Ni0.25Mn0.75(OH)2. Then, the Na0.8Li0.14Ni0.3Mn0.567Ow was prepared by ion-exchange. The Li1.133Ni0.3Mn0.567Ow cathode which contains more lithium (y>0.6) was charged with cut off voltage at 4.8 V (vs. Li metal, using 1M LiPF6, 1:1 EC:DMC) and discharged with cut off voltage 1.5 V (vs.Na metal, using 1M NaPF6, 1:1 EC:DEC), thus O3 type Na0.08Li0.14Ni0.3Mn0.567Ow cathode which contains more sodium (x>0.6) cathode was obtained. XRD spectra for the Na0.08Li0.14Ni0.3Mn0.567Ow is depicted in
Specifically, the reaction process in example 3, began with the Li1.133Ni0.3Mn0.567O2 containing more lithium (y>0.6), which was made into a cathode and assembled with Li anode. The prepared cell was charged with various cut off voltage at 4.8 V (vs. Li metal, using 1M LiPF6, 1:1 EC:DMC non-aqueous electrolyte) to remove of most Li in the electrode. Thirdly, this cell was opened and the electrode was washed with DMC for 3 times. In the last step, the electrode was assembled with Na anode and discharged to 1.5 V (vs.Na metal, using 1M NaPF6 , 1:1 EC:DEC non-aqueous electrolyte) to insert Na, and the O3 type Na0.8Li0.14Ni0.3Mn0.567Ow electrode which contains more sodium (x>0.6) electrode was obtained
The major diffraction peaks of are indexed according to the parent hexagonal structure with space group R-3m, is similar to that of the reference compound, NaFeO2 (ICSD reference code: 01-076-2w299). This indicates an alternating three-layer arrangement which can be designated as ABCABC packing structure. The existence of doublets at (006)/(102) and (108)/(110) showed that the sample is well-layered structure. Compared with low Na content O3 layered oxide, Na0.8Li0.14Ni0.3Mn0.567Ow shows expanded lattice. The “a” lattice parameter is 2.9238 Å, and the “c” lattice parameter is 16.1878 Å, therefore we observed large shift of (003) peaks, and the (101) (006) peak position change, due to different d-spacing in large Na content O3 layered oxide.
Na0.8Li0.14Ni0.3Mn0.567Ow prepared in Example 3 was tested in Na coin cells, using a cathode of the invention with an Na anode and an electrolyte of 1M NaPF6, 1:1 EC:DEC. The first cycle discharge voltage profile of a typical Na/Na0.8Li0.14Ni0.3Mn0.567Ow cell between 4.5 and 1.5 V vs. Na metal at a current rate of 12.5 mA/g, is shown in
The observed capacity was initially about 211 mAh g−1 at 12.5 mAh g−1, the discharge capacity at 25 mA g−1 was about 202 mAh g−1. This high capacity indicates a high energy density sodium ion battery cathode material. The charge/discharge profile within voltage window 1.5 to 4.5V is a smooth slope, which indicates that the Na0.8Li0.14Ni0.3Mn0.567Ow layered oxide generally retains its O3 single phase structure during charge-discharge cycle.
The Li1.13Ni0.3Mn0.567O2 and Na0.8Li0.14Ni0.3Mn0.567Ow were cycled in Li half cell and Na half cell respectively. The Li half-cell the cathode of the invention with an Li anode and an electrolyte of 1M LiPF6, 1:1 EC:DMC. TEM images were collected on these cathode material after first cycle, using an FEI Tecnai G2 Sphera cryoelectron microscope with an operation voltage of 200 kV. The powders (scratched from the electrodes) were suspended on a 300-mesh copper grid with lacey carbon.
Na0.8Li0.14Ni0.25Mn0.583Ow synthesized followed by Example 3 was made into Na coin cells. The first cycle discharge voltage profile of a typical Na/Na0.8Li0.14Ni0.25Mn0.583Ow cell to 1.5 V vs. Na metal at a current rate of 12.5 mA/g, is shown in
The specific synthesis in this example began with the Li1.167Ni0.25Mn0.583O2 containing more lithium (y>0.6), which was made into a cathode and assembled with an Li anode. The prepared cell was charged with various cut off voltages at 4.8 V (vs. Li metal, using 1M LiPF6, 1:1 EC:DMC non-aqueous electrolyte) to remove most of the Li from the cathode. The cell was opened and the electrode was washed with DMC for 3 times. In the last step, the electrode was assembled with Na anode and discharged to 1.5 V (vs. Na metal, using 1M NaPF6, 1:1 EC:DEC non-aqueous electrolyte) to insert Na, and the O3 type Na0.8Li0.14Ni0.25Mn0.583Ow electrode which contains more sodium (x>0.6) electrode was obtained.
The observed capacity was initially about 241 mAh g−1 at 12.5 mAh g−1, the corresponding energy density was calculated to be 674 Wh/kg. The discharge capacity at 125 mA g−1 between 1.5 and 4.2V was about 214 mAh g−1. After 12 cycles, the capacity retention is >98%, indicates good reversibility. Even charge/ discharge current density improved to 1.25 A/g, it still delivered 161 mAh/g capacity, indicated excellent rate capability. This high capacity indicates a high energy density sodium ion battery cathode material. The charge/discharge profile within voltage window 1.5V to 4.2V is a smooth slope, which indicates that the Na0.8Li0.14Ni0.25Mn0.583Ow layered oxide generally retains its O3 single phase structure during charge-discharge cycles.
Synchrotron XRD spectra (converted to Cu Kα) for the Na0.8Li0.14Ni0.25Mn0.583Ow after different cycles are shown in
Na0.8Li0.14Ni0.16Mn0.5Co0.16Ow synthesized followed by Example 3 was made into Na coin cells. The first cycle discharge voltage profile of a typical Na/Na0.8Li0.14Ni0.16Mn0.5Co0.16Ow cell to 1.5 V vs. Na metal at a current rate of 12.5 mA/g, is shown in
The specific synthesis began with the Li1.167Ni0.16Mn0.5Co0.16O2 containing more lithium (y>0.6), which was made into a cathode and assembled with an Li anode. Various cut off voltage at 4.8 V (vs. Li metal, using 1M LiPF6, 1:1 EC:DMC non-aqueous electrolyte) were applied to remove most of the Li from the electrode. The cathode was washed with DMC for 3 times. The cathode was assembled with an Na anode and discharged to 1.5 V (vs.Na metal, using 1M NaPF6, 1:1 EC:DEC non-aqueous electrolyte) to insert Na, producing the O3 type Na0.8Li0.14Ni0.16Mn0.5Co0.16Ow cathode which contains more sodium (x>0.6).
XRD spectra for the Na0.8Li0.14Ni0.16Mn0.5Co0.16Ow after cycles is depicted in
Na0.8Li0.14Ni0.25Mn0.583Ow synthesized followed by Example 3 was made into Na coin cells. The first cycle charge-discharge voltage profile of a typical SnS2-rGO/Na0.8Li0.14Ni0.25Mn0.583Ow full cell over a voltage range between 4.2V and 1.0 V vs. SnS2-rGO at a current rate of 17 mA/g, is shown in
Specifically, synthesis began with the Li1.167Ni0.25Mn0.583O2 containing more lithium (y>0.6) was made into a cathode and assembled with an Li anode. Charging with various cut off voltages at 4.8 V (vs. Li metal, using 1M LiPF6, 1:1 EC:DMC non-aqueous electrolyte) to remove most of the Li from the cathode. The cell was opened and the cathode was washed with DMC 3 times. The cathode was assembled with an Na anode and discharged to 1.5 V (vs.Na metal, using 1M NaPF6, 1:1 EC:DEC non-aqueous electrolyte) to insert Na, forming the O3 type Na0.8Li0.14Ni0.25Mn0.583Ow cathode which contains more sodium (x>0.6).
The half cell with Na as anode was opened to get the Na0.8Li0.14Ni0.25Mn0.583Ow cathode. A full cell was assembled with Sn2-rGO anode using 1M NaPF6 , 1:1 EC:DEC non-aqueous electrolyte.
The observed capacity was initially about 209 mAh g−1 at 17 mAh g−1, the energy density of this full cell was calculated to be 427 Wh/kg (considering both of the cathode and anode). This high capacity and high energy density sodium ion full battery can provide benefits to a wide variety of applications. The charge/discharge profile within voltage window 1.0V to 4.2V is a smooth slope, which indicates that the
Na0.8Li0.14Ni0.25Mn0.583Ow layered oxide generally retains its O3 single phase structure during charge-discharge cycles.
An active layered phase NaLi0.133Ni0.2Mn0.467Co0.2O2, material was prepared by heating a mixture of Li2CO3, Na2CO3 and Ni0.2Mn0.467Co0.2(OH)1.734. The hydroxides and carbonates were thoroughly mixed for about 6 hours in a ball milling and then ground with a mortar and pestle for about 30 minutes prior to heating. The resulting powder was placed into a box furnace, and then heated to about 480° C., over about 2 hours and held there for about 12 hours. The sample was allowed to cool to room temperature in the furnace. The pre-calcination product was then reground and placed in to a box furnace, and then heated to about 1000° C., over about 2 hours and held there for about 24 hours. The sample was quenched to room temperature in the furnace.
A sample of the NaLi0.133Ni0.2Mn0.467Co0.2O2 was characterized by X-ray powder diffraction (XRD) using a Bruker D8 advance diffractometer with a BraggBrentano θ—2θ geometry and a Cu Kα source. Samples were scanned from 10° to 80° with a scan rate of 0.025° per second. XRD spectra for the NaLi0.133Ni0.2Mn0.467Co0.2O2 is depicted in
The tests of NaLi0.133Ni0.2Mn0.467Co0.2O2 were conducted between 1.5 and 4.5 V at a constant current rate of 25 mA/g. The Na/NaLi0.133Ni0.2Mn0.467Co0.2O2 cell voltage profiles for the first cycle between 1.5 to 4.5V. The data are shown in
While specific embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims.
Various features of the invention are set forth in the appended claims.
The application claims priority under 35 U.S.C. §119 and applicable treaties from prior U.S. provisional application Ser. No. 61/875,456, which was filed Sep. 9, 2013.
This invention was made with government support under Award Number DE-SC0001294 from U.S. Department of Energy, Office of Basic Energy Sciences. The government has certain rights in the invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2014/054251 | 9/5/2014 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61875456 | Sep 2013 | US |
