Patent Application
20200335767
Rechargeable batteries based on the Li metal anode have reemerged as an area of intense scientific and practical interest in the last decade. The source of this interest is on the one-hand—the specific capacity of the Li anode is one order of magnitude higher than graphite (3860 v.s. 372 mAh/g) and the standard potential for reducing Li ions in solution to the metal (Li++e−=Li(s)) is fully (200-300)mV lower than the corresponding intercalation reaction with graphite to form LiC6. The interest is on the other hand problematic because the practical energy density of a battery is dependent not only on the anode chemistry, but also on subtle and often ignored parameters, including the negative to positive electrode capacity ratio (N:P ratio), electrolyte to electrodes mass ratio and weight of other battery components, e.g., separator, etc. There are tradeoffs between the often times conflicting design parameter choices that must be made in creating Li metal batteries that live up to the promise offered by the anode. A Li metal cell that uses a conventional intercalating cathode can only truly outperform a conventional Li-ion battery when the N:P ratio is kept below 5:1. Unfortunately, because some fraction of Li in the battery will inevitably be lost to parasitic reactions in forming the solid electrolyte interface (SEI) on the metal anode and because the specific capacity of Li metal is about 20 to 30 times higher than that of conventional intercalation Li-ion cathode (usually around 150 mAh/g), it is extremely difficult to evaluate Li metal anodes under the stringent N:P conditions that will be required to establish practical cell viability.
Of the conventional approaches towards increasing the N:P ratio in a lithium metal battery, strategies which (a) use a thin Li foil (e.g., as created by roll pressing or Physical Vapor Deposition (PVD)) to lower the areal capacity of the anode, 3 or (b) utilize layered cathode architectures to introduce non-planarity and thereby higher areal capacity are the most practiced. Comparing the two approaches, the disadvantages of the former are as plentiful as they are fundamental. First, as the Li foil becomes thinner, more of the active material in the anode is present at the interface with the electrolyte, meaning that a greater fraction of the active anode mass is loss in creating the SEI on Li. Second, the mechanical robustness of anode will deteriorate, meaning that its ability to accommodate cyclic volume changes associated with the large change in specific volume associated with the reversible reaction Li++e−=Li(s) during charge and discharge cycles. Third, the weight of the current collector, separator and the electrolyte needed to wet these battery parts will correspondingly increase. Finally, the cost of fabricating thin Li anodes by either approach will add substantially to the overall unit cost. Currently, most conventional cathode structures are based on 2D/planar deposition on a thin metallic current collector, e.g., Al foil. Due to the limited electron transport length scale, the areal loading is rarely higher than 20 mg/cm2 which corresponds to an areal capacity of 2-3 mAh/cm2. For a 3 mAh/cm2 cathode, if the N:P ratio is set to 3:1, the resulting thickness of Li foil is 25 μm, whose commercial availability remains limited. Physical vapor deposition, rather than the conventional casting and rolling procedure, will be necessary to prepare Li foil with this thickness, which makes batteries of this type uncompetitive in terms of cost and ability to be scaled up. For the aforementioned reasons, designing a novel electrode structure that can accommodate a high areal mass loading of active material and can thus offer a high areal capacity comparable with Li foil is a desirable route towards high energy density Li metal batteries.
The present disclosure provides electrodes (e.g., cathodes or anodes) or electrode materials (e.g., cathode materials or anode materials), catalysts, and catalysts, and methods for forming electrodes (e.g., cathodes or anodes) or electrode materials (e.g., cathode materials or anode materials), catalysts and catalyst materials. The present disclosure also provides electrochemical devices comprising an electrode (e.g., cathode or anode) or electrode material (e.g., cathode material or and materials) or catalyst or catalyst material, which may be formed using a composition or method of the present disclosure.
In an aspect, the present disclosure provides electrodes (e.g., cathodes or anodes), electrode materials (e.g., cathode materials or anode materials), catalysts, and catalyst materials. Electrodes, electrode materials, catalysts, and catalyst materials can be made by methods of the present disclosure. An electrode (e.g., a cathode or an anode) or electrode material (e.g., a cathode material or an anode material) or catalyst or catalyst material may comprise: an electrically conducting 3-dimensional (3-D) matrix comprising a plurality of porous regions (e.g., voids); an active material, and optionally, a carbon conductivity aid. The active material may be disposed in and/or on (e.g., infiltrated in) at least a portion of the porous regions of the electrically conducting 3-D matrix. An electrodes, electrode material, catalyst, or catalyst material may be a multilayer structure. The electrically conducting 3-D matrix may be surface modified. An active material may be an electrically-conducting active material and/or a catalytically-active active material.
In an aspect, the present disclosure provides methods of forming electrodes (e.g., cathodes or anodes), electrode materials (e.g., cathode materials or anode materials), and catalysts, and catalyst materials. The methods may be used to form an electrode (e.g., cathode or anode), electrode material (e.g., cathode material or anode material), catalyst, or catalyst material of the present disclosure. The electrode or electrode material or catalyst or catalyst material may be made by contacting an electrically conducting 3-D matrix with additive material dispersed thereon with a liquid. The liquid may be a non-aqueous liquid. Force can be applied in various ways. In various examples, the force is applied by a member.
In an aspect, the present disclosure provides devices. The devices comprise one or more electrode (e.g., cathode or anode), electrode material (e.g., cathode material or anode material), catalyst, catalyst material, or a combination of thereof, of the present disclosure and/or one or more electrode (e.g., cathode or anode), electrode material (e.g., cathode material or anode material), catalyst, catalyst material, or a combination of thereof, formed by a method of the present disclosure. A device may be an electrochemical device. Non-limiting examples of electrochemical devices include batteries, supercapacitors, fuel cells, electrolyzers, electrolytic cells, and the like.
For a fuller understanding of the nature and objects of the disclosure, reference should be made to the following detailed description taken in conjunction with the accompanying figures.
The coin cell was closed according to a conventional coin-cell assembling procedure (e). The pressure applied by the coin cell crimper is about 100 bar. In order to examine the non-planar cathode, the coin cell was then opened. The morphology of the non-planar cathode is reported by f, g, and h. (h) demonstrates the flexibility of the non-planar cathode against bending.
Although subject matter of the present disclosure is described in terms of certain embodiments and examples, other embodiments and examples, including embodiments and examples that do not provide all of the benefits and features set forth herein, are also within the scope of this disclosure. For example, various structural, logical, and process step changes may be made without departing from the scope of the disclosure.
Ranges of values are disclosed herein. The ranges set out a lower limit value and an upper limit value. Unless otherwise stated, the ranges include all values to the magnitude of the smallest value of the stated range (either lower limit value or upper limit value) and all ranges between the values of the stated range.
The present disclosure provides electrodes (e.g., cathodes or anodes) or electrode materials (e.g., cathode materials or anode materials), catalysts, and catalysts, and methods for forming electrodes (e.g., cathodes or anodes) or electrode materials (e.g., cathode materials or anode materials), catalysts and catalyst materials. The present disclosure also provides electrochemical devices comprising an electrode (e.g., cathode or anode) or electrode material (e.g., cathode material or and materials) or catalyst or catalyst material, which may be formed using a composition or method of the present disclosure.
The present disclosure provides non-planar electrode and catalyst architectures, which, in the case of electrodes, enables desirable areal mass loading and capacity. In certain embodiments, the present disclosure relates to the design of a battery electrode/electrode material or catalyst/catalyst material architecture in which ionic and electronic transport pathways are continuous, and span the entire volume of a thick, three-dimensional electrode. In this electrode architecture, active materials (e.g., LiCoO2, LiFePO4, etc.) are dispersed into a porous 3-D conductive matrix (e.g., carbon cloth, metal foam, etc.), and an areal capacity of, for example, 28 mAh/cm2 is manifested.
The porous, electronically conductive matrixes are, in certain embodiments, able to support a desirable loading of active material particles and, in certain embodiments, infiltration of a liquid electrolyte provides a mechanism for constraining electron and ion transport length scales below the critical values for any arbitrary thickness of the electrode. In some examples, a commercial carbon cloth comprised of interwoven carbon fibers as the electron transport medium. In certain embodiments, a powder-compaction technique in which a composites of nano-sized, commercial battery-grade active materials particles, e.g., LCO, LFP, etc., with a carbon conductivity aid were loaded in the electrolyte-free dry state into the carbon framework. Without intending to be bound by any particular theory, it is considered that once exposed to a liquid electrolyte, capillary forces draw the electrolyte into the interparticle region to enable fast, complete, and desirable (e.g., electrolyte to electrodes mass ratio=0.6:1) wetting of the active material interfaces by a process analogous to wicking.
In an aspect, the present disclosure provides electrodes (e.g., cathodes or anodes), electrode materials (e.g., cathode materials or anode materials), catalysts, and catalyst materials. Electrodes, electrode materials, catalysts, and catalyst materials can be made by methods of the present disclosure. In various examples, an electrode (e.g., cathode or anode), electrode material (e.g., cathode material or anode material), catalyst, or catalyst material is made by a method of the present disclosure. Non-limiting examples of electrodes, electrode materials, catalysts, and catalyst materials are provided herein.
An electrode (e.g., a cathode or an anode) or electrode material (e.g., a cathode material or an anode material) or catalyst or catalyst material may comprise: an electrically conducting 3-dimensional (3-D) matrix comprising a plurality of porous regions (e.g., voids); an active material, and optionally, a carbon conductivity aid. The active material may be disposed in and/or on (e.g., infiltrated in) at least a portion of the porous regions of the electrically conductive matrix.
An electrode, electrode material, catalyst, or catalyst material may be a multilayer structure. A multilayer structure may comprise multiple layers comprising electrical/catalytic materials. In various examples, each individual layer comprises electrical materials and/or catalytic materials. In various examples, a multilayer structure comprises multiple electrical material layers, multiple catalytic material layers, or a combination of electrical material layers and catalytic material layers. In various examples, a multilayer structure comprises two or more electrode material layers(s) or two or more catalytic material layer(s) or one or more electrode material layers (s) and one or more catalytic material layer(s). The layers may be the same or two or more layers may be structurally and/or compositionally different.
An electrode, electrode material, catalyst, or catalyst material may comprise various electrically conducting 3-D matrixes. An electrically conducting 3-D matrix may be referred to as an electronically conductive matrix, porous electronically conductive matrix 3-D electronically conductive matrix, or porous 3-D electronically conductive matrix. An electrically conducting 3-D matrix may be planar or non-planar. An electrically conducting 3-D matrix may be a single layer electrically conducting 3-D matrix or a multiple layer electrically conducting 3-D matrix. In an example, the electrically conducting 3-D matrix is not a ceramic foam.
The electrically conducting 3-D matrix material may have various sizes. In an example, the smallest dimension of the matrix material is 10 microns or greater and/or the porosity of current collector is 20% or greater. The electrically conducting 3-D matrix may have at least one dimension (e.g., a dimension perpendicular to the longest dimension of the electrically conducting 3-D matrix) of at least 10 microns.
An electrically conducting 3-D matrix may comprise (or be) a carbon matrix. A matrix may comprise (or be) a carbon cloth or fabric. In various examples, a carbon cloth or fabric comprises (or is) a single layer of carbon cloth or fabric or multiple layers of a carbon cloth or fabric. A cloth or fabric may be woven or non-woven. A woven cloth or fabric may have a 3-D weave pattern. A non-woven cloth or fabric may be perforated.
An electrically conducting 3-D matrix may comprise a plurality of porous regions (e.g., voids). The porous regions may comprise a plurality of pores (e.g., voids), a portion of which or all of which may be continuous (e.g., in fluid contact). In various examples, the porous regions are continuous such that two or more surfaces (which may two surfaces opposed to each other) of the matrix are in fluid contact. In various examples, the porous regions are continuous throughout the volume of the electrode, electrode material, catalyst, or catalyst material. The porous regions (e.g., voids) may be at least partially, substantially (which may be that a majority of the porous regions/voids are continuous), or completely continuous (which may be that porous regions/voids are in fluid contact). The porous regions (e.g., voids) may, independently or all, have one or more dimension(s) or all dimensions (e.g., one or more linear dimension(s)) of 100 nm to 200 microns, including all integer nm values and ranges therebetween. The porous regions (e.g., voids) may be 30% or more, 50%, 90% or more, or 95% or more of the total volume of the electrically conducting 3-D matrix.
An electrically conducting 3-D matrix may be have various forms. Non-limiting examples of matrixes include carbon frameworks, metal frameworks, and other frameworks formed from other conductive materials, and the like, and combinations thereof. Non-limiting examples of carbon frameworks include carbon fabrics, carbon cloths, graphene aerogels, and the like, and combinations thereof. Non-limiting examples of metal frameworks include metal foams, such as, for example, nickel foams, copper foams, and the like, and combination thereof, and the like, and combinations thereof
The electrically conducting 3-D matrix may be surface modified. At least a portion of or all of the electrically conducting 3-D matrix may be surface modified. In various examples, at least a portion of a surface or all of the surfaces of the electrically conducting 3-D matrix (e.g., a least a portion of a surface of the porous regions/pores and/or at least a portion of an exterior surface of the electrically conducting 3-D matrix) is surface modified. The surface modification may provide desirable electrolyte wettability. The surface modification may provide a hydrophilic and/or metal ion-philic surface. Non-limiting examples of surface modification include surfactant modification, oxidation modification, electrodeposition modification, nano-particle modification, and the like, and combinations thereof.
An electrically conducting 3-D matrix may have desirable electrical conductivity. In various examples, the electrically conducting 3-D matrix has a conductivity of 1 to 108 S/m, including all integer S/m values and ranges therebetween.
An electrode, electrode material, catalyst, or catalyst material may comprise various active materials. An active material may be an electrically-conducting active material and/or a catalytically-active active material. An active material may be a combination of active materials (e.g., two or more structurally and/or compositionally different active materials). The active material may be particulate. An active material may be a nanosized powder. An active material may be a battery-grade powder, such as, for example, a battery-grade nanopowder. Suitable active materials are commercially available. Non-limiting examples of active materials are known in the art.
The active material may be disposed on a portion of or all of a surface or the surfaces of the electrically conducting 3-D matrix and/or in the porous regions/voids. In an example, 70% or more of the active material is in the porous regions (e.g., voids). The active material may not be present only on an exterior surface of the electrically conducting 3-D matrix (e.g., carbon cloth).
An electrode, electrode material, catalyst, or catalyst material may comprise various amounts of active material(s). In various examples, the active material is present at 5 to 90% by weight (based on the total weight of the electrode) and the carbon conductivity aid may be the remainder.
The active material may be an anode material, a cathode material, or a catalyst material. In the case where the electrode or electrode material is a cathode or cathode material, the active material may be one or more ion-conducting material(s), which may be ion-conducting material(s), ion-conducting material(s), lithium ion-conducting material(s), potassium ion-conducting material(s), sodium ion-conducting material(s), magnesium ion-conducting material(s), zinc ion-conducting material(s), aluminum ion-conducting material(s), and the like. Non-limiting examples of lithium-ion conducting materials include LCO, LFP, NCM, LMNO, sulfur, selenium and the like, combinations thereof. Non-limiting examples of potassium-ion conducting materials include cyanoperovskite, and the like, and combinations thereof. Non-limiting examples of sodium-ion conducting materials include Na3V2(PO4)3, and the like, and combinations thereof. Non-limiting examples of magnesium-ion conducting materials include V2O5, and the like, and combinations thereof. Non-limiting examples of zinc-ion conducting materials include MnO2, and the like, and combinations thereof. Non-limiting examples of aluminum-ion conducting materials include graphite, sulfur, MnO2, and the like, and combinations thereof, and the like.
In the case where the electrode or electrode material is an anode or anode material, the active material may be a metal or a semi-metal. Non-limiting examples of metals include tin, aluminum, magnesium, lithium, sodium, potassium, zinc, and the like). Non-limiting examples of semi-metals include silicon, MoS2, and the like.
In the case of catalysts and catalyst materials, the active material may be a catalyst material or catalytic material. A catalyst material or catalytic material may be one or more metal(s), one or more metal alloy(s), one or more metal oxide(s) or a combination thereof. Non-limiting examples of metals and metal oxides include catalytically active metals, catalytically active metal alloys, catalytically active metal oxides, and the like, and combinations thereof. Non-limiting examples of catalytically active metals include late transition metals, such as, for example, noble metals, and combinations thereof. Other non-limiting examples of catalytically active metals include Group 8, Group 9, Group 10, Group 11 metals, and combinations thereof. Non-limiting examples of catalytically active metal oxides include early transition metal oxides and combinations thereof. Other non-limiting examples of catalytically active metal oxides include oxides of Group 4, Group 5, Group 6, Group 7 metals, and combinations thereof. The catalyst material may catalyze reactions, such as, for example, oxygen reduction, carbon dioxide reduction, hydrogen evolution, hydrogen oxidation, and the like.
In the case of catalysts and catalytic materials, the active material may be present in various amounts. In various examples, where the catalyst or catalytic material comprises one or more carbon conductivity aid(s), the ratio of catalyst material to carbon conductivity aid is 5:95 to 95:5 (e.g., 45:55 to 55:45, and 50:50), including all 0.1 catalyst material to carbon conductivity aid ratio values and ranges therebetween.
In cases where the electrically conducting 3-D matrix is a carbon matrix, the active material may be present at 0.01 to 98% by weight, including all 0.01% by weight values and ranges therebetween, (e.g., 0.01 to 20% by weight, 1 to 90% by weight, 1 to 95% by weight, 10 to 95% by weight, or 30 to 98% by weight) based on the total weight of the electrode or electrode material or catalyst or catalyst material (e.g., active material and matrix material and, if present carbon conductivity aid) (e.g., carbon materials, such as, for example, carbon matrix and, if present, carbon conductivity aid).
An electrode, electrode material, catalyst, or catalyst material may comprise various carbon conductivity aid(s). The carbon conductivity aid may be a carbon material or a combination thereof. Non-limiting examples of carbon materials include graphite, Super P, carbon nanotubes, carbon fibers, ketjen black, and the like, and combinations thereof.
The carbon conductivity aid may be a combination of an anisotropic carbon conductivity aid and an isotropic carbon conductivity aid. Non-limiting examples of anisotropic carbon conductivity aids include graphites, carbon fibers, carbon nanotubes, graphenes, and the like). Non-limiting examples of isotropic carbon conductivity aids include ketjen black, Super P, and the like. An isotropic carbon conductivity aid may have a high aspect ratio (e.g., rod-like) structure. Without intending to be bound by any particular theory, it is considered the isotropic carbon conductivity aid may provide increased percolation and/or surface area. Further, the combination of anisotropic carbon conductivity aid and the isotropic carbon conductivity aid may provide a hierarchical structure (e.g., a combination or electrical conductivity and conductive framework).
The anisotropic carbon conductivity aid and isotropic carbon conductivity aid may be present in various amounts. In various examples, the ratio of anisotropic carbon conductivity aid(s) to isotropic carbon conductivity aid(s) is from 40:60 to 60:40 (e.g., 45:55 to 55:45, or 50:50), including 0.1 anisotropic carbon conductivity aid(s) to isotropic carbon conductivity aid(s) ratio values and ranges therebetween.
An electrode, electrode material, catalyst, or catalyst material may comprise various amounts of carbon conductivity aid(s). In various examples, the carbon conductivity aid(s) is/are present at of 1% to 50% by weight, including all integer % by weight values and ranges therebetween, based on the total weight of the electrode or electrode material or catalyst or catalyst material.
An electrode or a catalyst may comprise one or more electrode material(s) and/or one or more catalyst material(s) and/or one or more electrode material layers(s) and/or one or more catalyst material layers(s). In various examples, the electrodes (e.g., cathodes or anodes), electrode materials (e.g., cathode materials or anode materials), are part of rechargeable/secondary batteries, such as, for example, Li-ion batteries, Li metal batteries, sodium-ion batteries, sodium metal batteries, and the like, or primary batteries. The electrodes (e.g., cathodes or anodes), electrode materials (e.g., cathode materials or anode materials), catalysts, and catalyst materials may comprise an active material, which may be a catalytic material and/or an anode material or a cathode material. Suitable examples of active materials are known in the art and non-limiting examples of active materials provided herein. In various examples, an electrode or electrode material does not exhibit metal orphaning. In various examples, an electrode, electrode material, catalyst, or catalyst material does not comprise a binder.
An electrode may comprise one or more electrode material(s) and/or one or more catalyst material(s). The electrode may comprise a current collector other than the electrode material. In an example, an electrode does not comprise a metal current collector. The electrode material may be disposed on a current collector (e.g., a metal current collector). The electrode (e.g., a cathode or an anode) or electrode material may be free of other conducting materials (e.g., carbon-based conducting materials and the like).
In an aspect, the present disclosure provides methods of forming electrodes (e.g., cathodes or anodes), electrode materials (e.g., cathode materials or anode materials), and catalysts, and catalyst materials. The methods may be used to form an electrode (e.g., cathode or anode), electrode material (e.g., cathode material or anode material), catalyst, or catalyst material of the present disclosure. Non-limiting examples of methods are provided herein.
The electrode or electrode material or catalyst or catalyst material may be made by contacting an electrically conducting 3-D matrix with additive material dispersed thereon with a liquid. In various examples, a method of making an electrode or an electrode material or catalyst or catalyst material (e.g., an electrode or an electrode material or catalyst or catalyst material of the present disclosure) comprises: contacting an active material (e.g., an active material powder) and an electrically conducting 3-D matrix; contacting the electrically conducting 3-D matrix and the active material (e.g., the active material powder) with a layer of a material; optionally, contacting the electrically conducting 3-D matrix, the active material (e.g., the active material powder), and the layer of the material with a liquid; and optionally, applying a force to the electrically conducting 3-D matrix, the active material (e.g., the active material powder), the layer of the material, and the liquid, where the and the electrode or electrode material or catalyst or catalyst material is formed. At least a portion of the active material may be infiltrated into the electrically conducting 3-D matrix. The electrically conducting 3-D matrix may be an electrically conducting 3-D matrix described herein. The active material may be a powder, which may be a nanosized powder, of an active material described herein.
The electrically conducting 3-D matrix and the active material powder may be contacted with a layer comprising (or of) various materials. The layer may comprise a sacrificial material and/or be a sacrificial layer. Non-limiting examples layers (or layer materials) include glasses, metals, polymers, plastics, or the like, or a combination thereof The material may be a non-functional material.
A multilayer structure may be formed. A multilayer structure may comprise one or more or two or more electrode material layer(s) and/or one or more or two or more catalytic material layer(s). In various examples, prior to contacting the electrically conducting 3-D matrix, the active material (e.g., the active material powder), and the layer of the material with a liquid and, applying a force, if performed, at least a portion of an exterior surface of the second electrically conducting 3-D matrix may be contacted with a second active material powder and the second layer of a material may be contacted with the second electrically conducting 3-D matrix and a second active material powder. These further contacting steps may be independently repeated a desired number of times to form a multilayer structure.
Various liquids may be used. The liquid may be an electrolyte. The liquid may be an aqueous liquid. In various examples, an aqueous liquid comprises (or is) ZnSO4, which may be present at, for example, 2 M, in H2O. The liquid may be a non-aqueous liquid. In various examples, a non-aqueous liquid comprises (or is) LiPF6, which may be present at, for example, 1 M, in ethylene carbonate.
Force can be applied in various ways. In various examples, the force is applied by a member. The member may have a planar surface. In various examples, force is applied using a press or using any hard solid material, such as, for example, a tweezer, a doctor blade, and the like. It is desirable that the force does not damage the 3-D matrix material(s). In various examples, the force applied does not degrade one or more electrical property(ies) of the 3-D matrix material(s) by more than 10%, more than 5%, more than 1%, or more than 0.1% and/or structurally damage the 3-D matrix material(s).
In an aspect, the present disclosure provides devices. The devices comprise one or more electrode (e.g., cathode or anode), electrode material (e.g., cathode material or anode material), catalyst, catalyst material, or a combination of thereof, of the present disclosure and/or one or more electrode (e.g., cathode or anode), electrode material (e.g., cathode material or anode material), catalyst, catalyst material, or a combination of thereof, formed by a method of the present disclosure. Non-limiting examples of devices are provided herein.
A device may be an electrochemical device. Non-limiting examples of electrochemical devices include batteries, supercapacitors, fuel cells, electrolyzers, electrolytic cells, and the like.
A device can be various batteries. Non-limiting examples of batteries include secondary/rechargeable batteries, primary batteries, and the like. A battery may be an ion conducting battery. Non-limiting examples of ion-conducting batteries include lithium-ion conducting batteries, potassium-ion conducting batteries, sodium-ion conducting batteries, magnesium-ion conducting batteries, aluminum-ion conducting batteries, and the like. A battery may be a metal battery, such as, for example, a lithium-metal battery, a sodium metal battery, magnesium metal battery, or the like. A device may be a solid-state battery or a liquid electrolyte battery.
In the case of a device, which may be a battery, comprising an anode material or anode of the present disclosure, the device may comprise one or more cathode material(s). Examples of suitable cathode materials are known in the art. In various examples, the cathode material(s) is/are one or more lithium-containing cathode material(s), one or more potassium-containing cathode material(s), one or more sodium-containing cathode material(s), one or more magnesium-containing cathode material(s), one or more aluminum-containing cathode material(s), or the like. Examples of suitable cathode materials are known in the art. Non-limiting examples of lithium-containing cathode materials include lithium nickel manganese cobalt oxides, LiCoO2, LiNi1/3Co1/3Mn1/3O2, LiNi0.5Co0.2Mn0.3O2, lithium manganese oxides (LMOs), lithium iron phosphates (LFPs), LiMnPO4, LiCoPO4, and Li2MMn3O8, where M is chosen from Fe, Co, and the like, and combinations thereof, and the like, and combinations thereof. Non-limiting examples of sodium-containing cathode materials include Na2V2O5, P2-Na2/3Fe1/2Mn1/2O2, Na3V2(PO4)3, NaMn1/3Co1/3Ni1/3PO4, Na2/3Fe1/2Mn1/2O2@graphene composites, and the like, and combinations thereof. Non-limiting examples of magnesium-containing cathode materials include magnesium-containing materials (such as, for example, MgMSiO4 (M=Fe, Mn, Co) materials and MgFePO4F materials, and the like), FeS2 materials, MoS2 materials, TiS2 materials, and the like. Any of these cathodes/cathode materials may comprise a conducting carbon aid.
In the case of a device, which may be a battery, comprising a cathode material or cathode of the present disclosure, the device may comprise one or more anode material(s). Examples of suitable anode materials are known in the art. Non-limiting examples of anode material(s) include metals, such as, for example, lithium metal, potassium metal, sodium metal, magnesium metal, aluminum metal, and the like, lithium-ion conducting anode materials, sodium-ion conducting anode materials, magnesium-ion conducting anode materials, aluminum-ion conducting anode materials, and the like. Examples of suitable anode materials are known in the art. Non-limiting examples of lithium containing materials include lithium carbide, Li6C, lithium titanates (LTOs), and the like, and combinations thereof), and combinations thereof. Non-limiting examples of sodium-ion conducting anode material include Na2C8H4O4 and Na0.66Li0.22Ti0.78O2, and the like, and combinations thereof. Non-limiting examples of magnesium-containing anode materials include Mg2Si, and the like, and combinations thereof. The device, which may be a battery, may comprise a material chosen from silicon-containing materials, tin and its alloys, tin/carbon, phosphorus, and the like.
The device, which may be a battery, may comprise a conversion-type electrode (e.g., anode or cathode, depending on which electrode/electrode material of the present disclosure is used). Non-limiting examples of conversion-type electrode materials include air (e.g., oxygen), iodine, sulfur, sulfur composite materials, polysulfides, metal sulfides, such as, for example, MoS2, FeS2, TiS2, and the like, and combinations thereof.
A device, which may be a battery, may further comprise a solid electrolyte or liquid electrolyte. Examples of suitable electrolytes are known in the art.
A device may further comprise a current collector disposed on at least a portion of the cathode and/or the anode. In various examples, the current collector is a conducting metal or metal alloy.
A solid-state electrolyte, cathode, anode, and, optionally, the current collector may form a cell of a battery. The battery may comprises a plurality of the cells and each adjacent pair of the cells is separated by a bipolar plate. The number of cells in the battery is determined by the performance requirements (e.g., voltage output and the like) of the battery and is limited only by fabrication constraints. For example, the battery comprises 1 to 500 cells, including all integer number of cells and ranges therebetween.
The steps of the methods described in the various embodiments and examples disclosed herein are sufficient to produce an electrode or electrode material or catalyst or catalyst material of the present disclosure. Thus, in an embodiment, a method consists essentially of a combination of the steps of the methods disclosed herein. In another embodiment, a method consists of such steps.
The following Statements are examples of electrodes, electrode materials, catalysts, catalyst materials, methods of making electrodes, electrode materials, catalysts, and catalyst materials, and devices of the present disclosure:
Statement 1. An electrode (e.g., a cathode or an anode) or electrode material (e.g., a cathode material or an anode material) or catalyst or catalyst material comprising: an electrically conducting 3-dimensional (3-D) (e.g., planar or non-planar) matrix comprising a plurality of porous regions (e.g., voids); an active material, and optionally, a carbon conductivity aid, where the active material is disposed in and/or on (e.g., infiltrated in) at least a portion of the porous regions of the electrically conducting 3-D matrix. The electrode (e.g., a cathode or an anode) or electrode material may be free of other conducting materials (e.g., carbon-based conducting materials.
Statement 2. An electrode or electrode material or catalyst or catalyst material according to Statement 1, where the porous regions/voids are at least partially, substantially (e.g., a majority of the porous regions/voids are continuous), or completely continuous (e.g., in fluid contact).
Statement 3. An electrode or electrode material or catalyst or catalyst material according to Statement 1 or 2, where the porous regions/voids has one or more or all dimensions of 100 nm to 200 microns, including all integer nm values and ranges therebetween.
Statement 4. An electrode or electrode material or catalyst or catalyst material according to any one of the preceding Statements, where the porous regions/voids are 30% or more, 50% or more, 75% or more, 90% or more, or 95% or more of the total volume of the electrically conducting 3-D matrix.
Statement 5. An electrode or electrode material or catalyst or catalyst material according to any one of the preceding Statements, where the electrically conducting 3-D matrix has a conductivity of 1 to 108 S/m, including all integer S/m values and ranges therebetween.
Statement 6. An electrode or electrode material or catalyst or catalyst material according to any one of the preceding Statements, where the electrically conducting 3-D matrix is a single layer electrically conducting 3-D matrix or a multiple layer electrically conducting 3-D matrix.
Statement 7. An electrode or electrode material or catalyst or catalyst material according to any one of the preceding Statements, where the electrically conducting 3-D matrix is carbon matrix.
Statement 8. An electrode or electrode material or catalyst or catalyst material according to Statement 7, where in the carbon matrix is a carbon cloth/fabric (e.g., a single layer of carbon cloth/fabric or multiple layers of a carbon cloth/fabric).
Statement 9. An electrode or electrode material or catalyst or catalyst material according to Statement 8, where the cloth/fabric is woven or non-woven.
Statement 10. An electrode or electrode material or catalyst or catalyst material according to Statement 9, where the woven cloth/fabric has a 3-D weave pattern.
Statement 11. An electrode or electrode material or catalyst or catalyst material according to Statement 9, where the non-woven cloth/fabric is perforated.
Statement 12. An electrode or electrode material or catalyst or catalyst material according to any one of the preceding Statements, where the electrically conducting 3-D matrix is a carbon matrix and the active material is present at 0.01 to 98% by weight, including all 0.1% by weight values and ranges therebetween, (e.g., 0.01 to 20% by weight, 1 to 90% by weight, 1 to 95% by weight, 10 to 95% by weight, or 30 to 98% by weight) based on the total weight of the electrode or electrode material or catalyst or catalyst material (e.g., active material and matrix material and, if present carbon conductivity aid) (e.g., carbon materials, such as, for example, carbon matrix and, if present, carbon conductivity aid).
Statement 13. An electrode or electrode material or catalyst or catalyst material according to any one of Statements 1-6, where the electrically conducting 3-D matrix is chosen from carbon frameworks (e.g., carbon fabrics, carbon cloths, graphene aerogels, and the like), metal frameworks (e.g., metal foams, such as, for example, nickel foam, a copper foam, and the like, and the like), and other frameworks formed from other conductive materials, and combinations thereof, and the like.
Statement 14. An electrode or electrode material or catalyst or catalyst material according to any one of the preceding Statements, where the active material is disposed on a surface of the electrically conducting 3-D matrix and/or in the porous regions/voids (e.g., 70% or more of the active material is in the porous regions/voids). The active material is not present only on an exterior surface of the electrically conducting 3-D matrix (e.g., carbon cloth).
Statement 15. An electrode or electrode material or catalyst or catalyst material according to any one of the preceding Statements, where the active material is a particulate active material.
Statement 16. An electrode or electrode material or catalyst or catalyst material according to any one of the preceding Statements, where the active material is present at 5 to 90% by weight (based on the total weight of the electrode) and the carbon conductivity aid is the remainder.
Statement 17. An electrode or electrode material or catalyst or catalyst material according to any one of the preceding Statements, where the active material is an anode material, a cathode material, or a catalyst material.
Statement 18. An electrode or electrode or catalyst material or catalyst material according to Statement 17, where the electrode is a cathode and the active material is an ion-conducting material (e.g., one or more lithium-ion conducting material (such as, for example, LCO, LFP, NCM, LMNO, sulfur, selenium and the like, combinations thereof), one or more potassium-ion conducting material (such as, for example, cyanoperovskite, and the like, and combinations thereof), one or more sodium-ion conducting material (such as, for example, Na3V2(PO4)3, and the like, and combinations thereof), one or more magnesium-ion conducting material (such as, for example, V2O5, and the like, and combinations thereof), one or more zinc-ion conducting material (such as, for example, MnO2, and the like, and combinations thereof), one or more aluminum-ion conducting material, such as, for example, graphite, sulfur, MnO2, and the like, and combinations thereof), and the like).
Statement 19. An electrode or electrode material or catalyst or catalyst material according to Statement 17, where the electrode is an anode and the active material is a metal (e.g., tin, aluminum, magnesium, lithium, sodium, potassium, zinc, and the like), a semi-metal (e.g., silicon, MoS2, and the like), or the like.
Statement 20. An electrode or electrode material or catalyst or catalyst material according to Statement 17, where the active material is a catalyst material chosen metals and metal oxides. Non-limiting examples of metals and metal oxides include catalytically active metals, catalytically active metal oxides, and the like, and combinations thereof. Non-limiting examples of catalytically active metals include late transition metals, such as, for example, noble metals, and combinations thereof. Other non-limiting examples of catalytically active metals include Group 8, Group 9, Group 10, Group 11 metals, and combinations thereof. Non-limiting examples of catalytically active metal oxides include early transition metal oxides and combinations thereof. Other non-limiting examples of catalytically active metal oxides include oxides of Group 4, Group 5, Group 6, Group 7 metals, and combinations thereof. The catalyst material may catalyze reactions, such as, for example, oxygen reduction, carbon dioxide reduction, hydrogen evolution, hydrogen oxidation, and the like.
Statement 21. An electrode or electrode material or catalyst according to any one of the preceding Statements, where the active material is a catalyst material and the ratio of catalyst material to carbon conductivity aid is 5:95 to 95:5 (e.g., 45:55 to 55:45, and 50:50).
Statement 22. An electrode or electrode material or catalyst or catalyst material according to any one of the preceding Statements, where the carbon conductivity aid is a carbon material (e.g., graphite, Super P, carbon nanotubes, carbon fibers, ketjen black, and the like).
Statement 23. An electrode or electrode material or catalyst or catalyst material according to any one of the preceding Statements, where the carbon conductivity aid is present at of 1% to 50% by weight, including all integer % by weight values and ranges therebetween, based on the total weight of the electrode or electrode material or catalyst or catalyst material.
Statement 24. An electrode or electrode material or catalyst or catalyst material according to any one of the preceding Statements, where the carbon conductivity aid is a combination of an anisotropic carbon conductivity aid (e.g., graphite, carbon fibers, carbon nanotubes, graphene, and the like) and an isotropic carbon conductivity aid (e.g., ketjen black, Super P, and the like). The isotropic carbon conductivity aid may have a rod-like (e.g., high aspect ratio) structure, which may provide increased percolation and/or surface area). The combination of anisotropic carbon conductivity aid and the isotropic carbon conductivity aid may provide a hierarchical structure (e.g., a combination or electrical conductivity and conductive framework).
Statement 25. An electrode or electrode material or catalyst or catalyst material according to Statement 24, where the ratio of anisotropic carbon conductivity aid to isotropic carbon conductivity aid is from 40:60 to 60:40 (e.g., 45:55 to 55:45, or 50:50).
Statement 26. An electrode or electrode material or catalyst or catalyst material according to any one of the preceding Statements, where the electrically conducting 3-D matrix has at least one dimension (e.g., a dimension perpendicular to the longest dimension of the electrically conducting 3-D matrix) of at least 10 microns.
Statement 27. An electrode or electrode material or catalyst or catalyst material according to any one of the preceding Statements, where the electrode material is disposed on a current collector (e.g., a metal current collector).
Statement 28. An electrode or electrode material or catalyst or catalyst material according to any one of the preceding Statements, where at least a portion of a surface of the electrically conducting 3-D matrix (e.g., a least a portion of a surface of the porous regions/pores and/or at least a portion of an exterior surface of the electrically conducting 3-D matrix) is surface modified. The surface modification may provide desirable electrolyte wettability. The surface modification may provide a hydrophilic and/or metal ion-philic surface. Non-limiting examples of surface modification include surfactant modification, oxidation modification, electrodeposition modification, nanoparticle modification, and the like, and combinations thereof.
Statement 29. A method of making an electrode or an electrode material or catalyst or catalyst material (e.g., an electrode or an electrode material or catalyst or catalyst material according to any one of Statements 1-28) comprising: contacting an active material powder an electrically conducting 3-D matrix; contacting the electrically conducting 3-D matrix and the active material (e.g., the active material powder) with a layer of a material (which may be a conducting 3-D matrix or a sacrificial material); optionally, contacting the electrically conducting 3-D matrix, the active material powder, and the layer of the material with a liquid; and optionally, applying a force to the electrically conducting 3-D matrix, the active material powder, the layer of the material, and the liquid (if present), where at least a portion of the active material may be infiltrated into the electrically conducting 3-D matrix and the electrode or electrode material or catalyst or catalyst material is formed.
Statement 30. A method according to Statement 29, where the layer of the material is a second electrically conducting 3-D matrix.
Statement 31. A method according to Statement 29, where, prior to contacting the electrically conducting 3-D matrix, the active material (e.g., the active material powder), and the layer of the material with a liquid and, applying a force, if performed, at least a portion of an exterior surface of the second electrically conducting 3-D matrix is contacted with a second active material (e.g., second active material powder) and a second layer of a material is contacted with the second electrically conducting 3-D matrix and a second active material powder, and, optionally, repeating the contacting steps a desired number of times to form a multilayer structure.
Statement 32. A method according to any one of Statements 29-31, where the active material (e.g., the active material powder) is and active material described herein or a combination thereof (e.g., LCO, LFP, NCM, LMNO, sulfur, selenium, Na3V2(PO4)3, V2O5, MnO2, and the like).
Statement 33. A method according to any one of Statements 29-32, where the liquid is an aqueous liquid (e.g., 2 M ZnSO4, at, for example, 2 M, in H2O or non-aqueous liquid (e.g., LiPF6, at, for example, 1M, in ethylene carbonate.
Statement 34. A method according to any one of Statements 29-33, where the liquid is an electrolyte.
Statement 35. A method according to any one of Statements 29-34, where the layer of material comprises (e.g., is) glass, metal, polymer, plastic, or the like, or a combination thereof. The material may be a non-functional material.
Statement 36. A method according to any one of Statements 29-35, where force is applied by a member, which may have a planar surface (e.g., using a press or using any hard solid material, such as, for example, a tweezer, a doctor blade, and the like). It is desirable that the force does not damage the 3-D matrix material(s).
Statement 37. A device comprising one or more electrode (e.g., one or more cathode/cathode material and/or anode/anode material) or catalyst according to any one of Statements 1-28 or an electrode (e.g., one or more cathode/cathode material and/or anode/anode material) made by a method according to any one of Statements 29-36.
Statement 38. A device according to Statement 37, where the device is an electrochemical device.
Statement 39. A device according to Statement 38, where the electrochemical device is a battery (e.g., a secondary/rechargeable battery, a primary battery, or the like), a supercapacitor, a fuel cell, an electrolyzer, an electrolytic cell, or the like.
Statement 40. A device according to any one of Statements 37-39, where the battery is an ion-conducting battery.
Statement 41. A device according to Statement 40, where the ion-conducting battery is a lithium-ion conducting battery, a potassium-ion conducting battery, a sodium-ion conducting battery, a magnesium-ion conducting battery, or an aluminum-ion conducting battery.
Statement 42. A device according to any one of Statements 39-41, where the battery further comprises an anode (e.g., a metal anode, such as, for example, a lithium metal anode, a potassium metal anode, a sodium metal anode, a magnesium metal anode, an aluminum metal anode, or the like) and/or one or more electrolyte (e.g., liquid electrolyte, such as, for example, carbonate-based or ether-based electrolyte) and/or one or more current collector and/or one or more additional structural components.
Statement 43. A device according to Statement 42, where the one or more additional structural component is chosen from bipolar plates, external packaging, electrical contacts/leads to connect wires, and combinations thereof.
Statement 44. A device according to any one of Statements 39-43, where the battery comprises a plurality of cells, each cell comprising one or more electrode (e.g., one or more cathode and/or anode) or one or more electrode material (e.g., one or more cathode material and/or anode material), and optionally, one or more anode(s), electrolyte(s), current collector(s), or a combination thereof.
Statement 45. A device according to Statement 44, where the battery comprises 1 to 500 cells.
Statement 46. A device according to any one of Statements 37-45, where battery exhibits one or more of the following: a N:P ratio of at least 1.1 (e.g., 1:1 to 10:1); a mass loading of at least 10 mg/cm2 (e.g., 10 mg/cm2 to 300 mg/cm2); an areal capacity of 5 to 30 mAh/cm2; a current density of at least 1 mA/cm2; at least 70%, at least 80%, at least 90%, at least 95%, at least 99%, or 100% (e.g., 70 to 100%) of the active material is electrochemically active and/or reversibly electrochemically active; cycle life of at least 100 cycles, at least 500 cycles, at least 1000 cycles, at least 2500 cycles, at least 5000 cycles, at least 7500 cycles, or at least 10,000 cycles; or 60% or greater (e.g., 60 to 90%, 60 to 95%, or 60 to 100%) capacity retention, any one or more of which may be determined under conditions typically used in the art.
The following examples are presented to illustrate the present disclosure. They are not intended to be limiting in any matter.
This example provides a description of electrodes and electrode materials, methods of making electrodes, electrode materials, catalysts, and catalyst materials, and devices of the present disclosure.
Described is design of a battery electrode architecture in which ion and electronic transport pathways are continuous, and span the entire volume of a thick, non- planar electrode. It was shown that for a range of active materials conductivities, the length scale for electronic transport in such an architecture can be tuned by simple manipulations of the electrode design to enable good access to the active material. Benefits of such electrodes were demonstrated in low-N:P ratio cells in which a conventional (300-800 μm) Li foil was successfully cycled with LiCoO2 cathodes with high areal capacities (10-28 mAh/cm2).
It was hypothesized that a porous, electronically conductive matrix, able to support high loading of active material particles and full infiltration of a liquid electrolyte provides a mechanism for constraining electron and ion transport length scales below the critical values (
Results from galvanostatic charge-discharge experiments reported in
1Thickness of the cathode was measured under ~100 bar pressure by caliper.
2LCO content was calculated on the basis of LCO, KB carbon and carbon cloths.
3Volumetric energy density of cathode was calculated using measured cathode thickness.
A beneficial attribute of the LCO cathode is that the theoretical specific capacity can be improved by charging to a higher voltage. By charging to 4.5 V specific and areal capacities of 188 mAh/g and a 13.3 mAh/cm2, respectively, are achieved (
In addition to LCO particles, whose intrinsic electron conductivity is high, the electrode architecture was also compatible with LiNi1/3Co1/3Mn1/3O2 and, particularly, LiFePO4 that is reported to have a lower electronic conductivity (10−8 S/cm) (
The galvanostatic cycling performance of the Li∥high loading LCO full cells are reported in
By designing the electron wiring length scales in electrode, a non-planar electrode architecture that enables battery cathodes with areal capacity as high as 28 mAh/cm2 was demonstrated. The cells can be cycled stably against a Li anode over a range of current densities and that because of the high Li throughput (10˜30 mAh/cm2) per (dis)/charge, the cells provide an important tool for evaluating long-term stability of Li metal anodes.
Materials and methods, detailed calculation of energy density, Li metal plating/stripping Coulombic efficiency measurements, details about fabrication of non-planar cathodes and coin cell assembling, SEM morphology of electrode composites, rheological measurements, discharge voltage profiles of LCO charged to different voltages, XANES data, SEM images of cycled Li metal and table summarizing the parameters of nonplanar LCO cathodes.
Materials: Battery grade 1.0 M LiPF6 in ethylene carbonate/dimethyl carbonate (EC:DMC=50:50 volume ratio; Gen-2 electrolyte) and vinylene carbonate (1,3-Dioxol-2-one, VC) were purchased from Sigma Aldrich. 750 μm lithium foil was purchased from Alfa Aesar. Fluoroethylene carbonate (4-Fluoro-1,3-dioxolan-2-one, FEC) was purchased from AstaTech, Inc. Plain carbon cloth 1071 was purchased from Fuel Cell Store. LiCoO2 (LCO) powder was purchased from Electrodes and More. LiFePO4 (LFP) powder and LiNi1/3Co1/3Mn1/3O2 (NCM111) were purchased from MTI. Ketjen Black (KB) carbon was purchased from AkzoNobel.
Characterization of materials and batteries: Field-emission scanning electron microscopy (FESEM) was carried out on Zeiss Gemini 500 Scanning Electron Microscope equipped with Bruker energy dispersive spectroscopy (EDS) detector. Shear rheology measurement was performed using Anton Paar MCR 501. X-ray absorption near edge spectroscopy (XANES) measurements of Li/LFP experimental cells were acquired at beamline 5-ID of the National Synchrotron Light Source II (NSLS II) at Brookhaven National Laboratory. XANES measurements were collected using fluorescence geometry at the Fe edge, and data were aligned and normalized using Athena software.
Electrochemical studies were performed using CR2032 coin cell. The area of carbon cloth is 1.27 cm2. The areal density of carbon cloth is 12 mg/cm2. The carbon cloth exhibits a tensile strength of 345 MPa (Product Specification). Electrode thickness was measured by MARATHON digital caliper. In N:P=4:1 full cell test, the area of the 750 μm Li foil was 0.32 cm2. Separator used in coin cells was Celgard 3501. Galvanostatic charge/discharge performance of coin cells were tested on Neware battery test systems at room temperature. In lithium plating/stripping Coulombic efficiency test (Li∥Cu cell), a certain amount of lithium metal (1 mAh v.s. 10 mAh) was plated on 1.27 cm2 copper foil at 0.8 mA/cm2 from Gen-2 electrolyte The cutoff voltage for lithium stripping was 0.5 V.
Fabrication of non-planar cathodes and coin cell assembling are described in
Calculation of Li-LCO energy density: To evaluate the minimal requirements of design parameters for a Li metal battery, we calculate the dependency of energy density on these parameters as follows. The energy density of Li-LCO battery with different negative:positive capacity ratios (rNP) and electrolyte:electrodes(rEE) mass ratios are plotted according to:
where Cdis is discharge capacity; Edis is average discharge voltage; mLCO is the mass of LCO; mLi is the mass of Li that has the same capacity as LCO; ract is the content of active material in cathode.
For example, set WLCO=1 g, which provides a Cdis=140 mAh if it is charged to 4.2V.
The average discharge voltage Edis is 3.8V. Hence, the energy density of an anode-free (rNP=0) Li-90% LCO/10% KB (ract=0.9) battery with electrolyte whose mass is 60% of the electrodes (rEE=0.6) charged to 4.2V can be calculated as follows:
rEE=0 means that the energy density is calculated based merely on the mass of the electrodes. For example, the energy density of an anode-free Li-LCO battery calculated based on electrode mass is:
Of note, currently, the commercial availability of thin lithium (˜30 μm) is limited. Most Li metal studies use lithium foils of conventional thickness, i.e., 250˜750 μm (areal capacity: 50˜150 mAh/cm2); while the cathode areal capacity is rarely above 3 mAh/cm2, meaning that the N:P ratio is larger than 17.
In the plating/stripping of Li metal on copper foil, a portion of Li was reacted with electrolyte and causes the formation of SEI; this portion of Li cannot be stripped away. The plating/stripping Coulombic inefficiency is, therefore, a characterization of the amount of reacted lithium.
Cathode material powders (LCO, LFP and NCM111; as received) were ball milled with KB carbon for 20 minutes and were dried in an oven before use. The mass ratio between active material and KB carbon was 90:10, unless specified otherwise (
The lithium foil anode and the non-planar cathode was separated by a piece of Celgard 3501 polypropylene separator (˜25 μm). A piece of carbon cloth was placed on the separator (
In order to examine the non-planar cathode, the coin cell was then opened. The morphology of the non-planar cathode shown in
The slurry exhibited a storage modulus that is one order of magnitude higher than its loss modulus, indicating that the concentration of the solids was well above the percolation threshold. The slurry is a yield stress fluid with a yield stress of 9×10′ Pa. Therefore, the forces used to drive the slurry should be able to generate a shear stress larger than the yield stress, i.e., 9×102 Pa.
This example provides a description of electrodes and electrode materials, methods of making electrodes and electrode materials, and devices of the present disclosure.
The dendritic electrodeposition of lithium, leading to physical orphaning and chemical instability, is considered responsible for the poor reversibility and premature failure of electrochemical cells that utilize Li metal anodes. The roles of physical orphaning and chemical instability of electrodeposited Li on electrode reversibility using planar and non-planar electrode architectures were assessed. The non-planar electrodes allowed the morphology of electrodeposited Li to be interrogated in detail and in the absence of complications associated with cell stacking pressure. Physical orphaning is an important determinant of the poor reversibility of Li. Fiber-like, dendritic electrodeposition is an intrinsic characteristic of Li—irrespective of the electrolyte solvent chemistry. With guaranteed electronic access to prevent physical loss, it was shown that a Li metal electrode exhibits desirable levels of reversibility (99.4% CE), even when the metal electrodeposits are in obvious, dendritic morphologies. These findings were used to create high-loading (7 mAh/cm2) Li∥LFP full cells with nearly unity N:P ratio and demonstrate that these cells exhibit good reversibility.
Suppression of mossy/dendritic deposition during recharge is considered a requirement for progress towards practical LMBs. Described is using planar and non-planar electrodes that allow the morphology of Li to be interrogated in detail. With guaranteed electronic access that prevents physical loss of active Li (orphaning,
The main results of the study are summarized in
which is close to the measured values. This means that nearly full capacity of both electrodes was achieved in this cycling study. These findings therefore show that a non-planar anode enhances the long-term reversibility of Li metal.
On the basis of these observations, it was concluded that it is possible to sustain stable, high-CE cycling of Li even when the deposition is fiber-like or dendritic. It is further hypothesized that factors other than the electrolyte chemistry or electrodeposit morphology are dominantly responsible for the high CE measured for non-planar electrodes.
Lithium orphaning occurs when the metal becomes electronically disconnected from the current collector; while the ionic connection is maintained by contact with electrolyte. It has been extensively discussed in the literature as a failure mode for the Li anode, but has received scant consideration as a dominant factor in the poor reversibility of Li.
The plateau implies that there is an interplay of multiple factors—e.g., the reduced chemical instability is offset by increasingly prominent Li orphaning at the higher Li throughputs. This explanation is supported by results reported in
The erratic CE and voltage fluctuations is ascribed to the possibility that orphaned Li in one plating/stripping cycle can be reconnected when Li is deposited appropriately 6 cycles. This random breakage and rebuilding of electronic access to Li (see scheme in
As a final step, the separator from the planar Li∥Cu cells was removed and the CE and morphology of Li electrodeposits were evaluated. An O-Ring separated coin cell was designed (
By interrogating the electrochemical properties and morphology of Li electrodeposits formed in a non-planar, carbon-cloth electrode in various liquid electrolytes, it was found that relative to the more commonly studied chemical and morphological instabilities, physical orphaning of Li is the key cause of poor reversibility of Li metal anodes. With successful prevention of physical orphaning by building robust non-planar electronic pathways in the anode, it was further shown that Li anodes with high levels of reversibility can be created even when the metal electrodeposits in obviously dendritic morphologies.
Materials and methods: Materials: Battery grade 1.0 M LiPF6 in ethylene carbonate/dimethyl carbonate (EC:DMC=50:50 volume ratio; Gen-2 electrolyte) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were purchased from Sigma Aldrich. 750 μm lithium foil was purchased from Alfa Aesar. Fluoroethylene carbonate (4-Fluoro-1,3-dioxolan-2-one, FEC) was purchased from AstaTech, Inc. 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL) were purchased from Oakwood Chemical. Plain carbon cloth 1071 was purchased from Fuel Cell Store. LiFePO4 (LFP) powder was purchased from MTI. Ketjen Black (KB) carbon was purchased from AkzoNobel.
Characterization of materials: Field-emission scanning electron microscopy (FESEM) was carried out on Zeiss Gemini 500 Scanning Electron Microscope equipped with Bruker energy dispersive spectroscopy (EDS) detector. X-ray photon spectroscopy (XPS) SSX-100 was applied to study the chemistry information of SEI of Li deposits on nonplanar carbon cloth and on planar Cu foil. The x-ray diffraction (XRD) pattern of Li anodes were performed on a Bruker D8 Powder Diffractometer.
Electrochemical measurements: Galvanostatic charge/discharge performance of coin cells were tested on Neware battery test systems at room temperature. Electrochemical studies were performed using CR2032 coin cells. The area of electrodes in this study is 1.27 cm2. Electrodes are separated by Celgard 3501. Cu foil and carbon cloth were washed by ultrasonication in deionized water and acetone. In each coil cell, ˜60 μL electrolyte was added by pipette. The current density in this study was kept at 0.8 mA/cm2. The thickness of the Teflon O-ring was ˜0.8 mm. For the O-Ring measurements, ˜200 μL electrolyte was added into the cells to make sure the space was filled. In a lithium plating/stripping Coulombic efficiency measurement (Li∥Cu cell or Li∥carbon cloth cell), a certain amount of lithium metal was plated on the substrate of interest.
The detailed fabrication procedures of high loading nonplanar LFP cathode (˜7 mAh/cm2) are described in our recent publication. The concept in designing this ultrahigh loading LFP electrode is that with nonplanar electronic pathways that expand throughout the cathode chamber, particulate active materials can be electronically and ionically wired to the electrochemical system. Electrolyte served as a fluid that drives particulate active materials into a nonplanar porous medium. 90 wt % LFP and 10 wt % KB were ball milled for 40 minutes before being infiltrated into carbon cloth. No polymer binder, e.g., PVdF, was added.
This example provides a description of electrodes and electrode materials, methods of making electrodes and electrode materials, and devices of the present disclosure.
This example describes creating Na metal anodes that can be reversibly cycled at room temperature. Specifically, by studying the plating and stripping reactions at a Na metal anode using in-situ optical visualization, it was found that orphaning of Na metal is a source of irreversibility in liquid electrolytes. It was further shown that orphaning is triggered by a root-breakage process during the stripping cycle, which is exacerbated by the fragility of mossy Na electrodeposits formed spontaneously during electrodeposition. As an initial step towards electrode designs that are able to accommodate these fragile deposits, electrodeposition of Na was studied in non-planar electrode architectures that provide continuous and morphology agnostic access to the metal at all stages of electrochemical cycling. On this basis, it was found non-planar Na electrodes that exhibit high levels of reversibility (Coulombic Efficiency>99% for 1 mAh/cm2 Na throughput) in room-temperature, liquid electrolytes.
Direct, in-situ optical visualization and complementary surface analysis studies of electrochemical processes at a Na anode to elucidate failure mechanisms of the anode were performed. It was found that while morphological and chemical instability of Na lead to decidedly low-efficiency and non-planar/mossy deposition of the metal during battery recharge, orphaning (physical loss of Na) during anode discharge is an important determinant of anode reversibility. Specifically, it was found that the low Coulombic Efficiency (CE) of
Na electrodes is principally a result of mechanical breakage and consequent electronic disconnection of large fragments of low-density, mossy Na electrodeposits from the electrode mass. It was further found that by constraining the deposition in a generic structured electrode architecture composed of interwoven carbon fibers (i.e. a carbon cloth) and a limited pore spacings (about 10 μm for the carbon cloth used in this study) comparable to the diameter of the mossy deposits (about 400 μm in the case of free growth, and 50 μm in the case with constraints by the anode framework), it is possible to completely arrest orphaning of Na without application of mechanical pressure to the electrode. High CE values, exceeding 99% in many cases, can be achieved in plate-strip cycling of a Na anode in liquid electrolytes, confirming that orphaning of Na plays a dominant role in its notoriously poor reversibility. Finally, it was shown that rechargeable batteries that pair a highly reversible Na anode with a sulfur/carbon composite (MOFS) cathode exhibit desirable overall reversibility and cycling.
Result and Discussion: Optical Visualization of Na Deposition: The apparatus shown in
However, the leaving mechanism of Na dendrites remained not understood. Because Na dendrites have less density than the carbonate electrolyte used in this experiment, orphaned Na dendrite naturally floated up in the electrolyte. The setup in
These results suggest that difference in density does not trigger the detachment of a Na dendrite, but the possible accumulation of charges in the Na dendrite is the key of the tearing after the connection between dendrites and bulk gets weaker. However, after the detaching, the orphaned Na carries very few net charges, the connection to the electrode is completely lost, all the previously accumulated charges are quickly neutralized by the environment (mainly the electrolyte), and the orphaned Na dendrites move around follows the buoyancy and the flow of electrolyte.
Visualization cell results suggest a low reversibility of a Na metal cell. To qualify this result and to test if such dramatic surface-cleaning event happens in a coin cell setup, a Coulombic efficiency (CE) test was performed on a Na-stainless steel (SS) coin cell using a Teflon washer (O-ring) as the spacer to completely eliminate the effect of mechanical pressure. The averaged CE for this coin cell is only about 2.98%. Although such low CE value was not reported by others, yet it matches with visualization observations well, confirming the surface-cleaning pheromone that was previously seen in a visualization cell.
It is then not difficult to imagine how much orphaning Na deposits can be generated after a good amount of cycling time.
The activity of the mossy Na dendrites remained to be interesting. An X-ray photoelectron spectroscopy (XPS) analysis was done to study the composition of the mossy Na dendrite with comparison to that of the pristine Na metal. The soft and porous nature of glass fiber helps to catch and preserve the orphaned mossy Na dendrites (as shown in
Architecture and Full Cell Cycling Performance: The choice of separator and the design of anode was investigated to determine if they can improve the reversibility of Na metal during cycling by providing better connection to the electrodes and fixing the dendrites to the surface to avoid loss of Na.
The CE of a Na∥Stainless Steel cell using a Teflon washer (O-ring) to hold electrolyte was only about 2.98%. However, while keeping the same O-ring setup, but switching from the planar SS electrode to carbon cloth (CC), which is a 3-D frame with good elasticity, it was found that the CE was improved from 2.98% to 54.6%. The performance of this 3-D electrode was tested in a more conventional coin cell setup, in which the O-ring was replaced by glass fiber. By switching to a separator that provided some extra constraints to dendritic growth, the CE for cell employing an SS counter electrode was improved from 2.98% to 38.6%, as shown in
An X-ray powder diffraction (XRD) test was done to further study the reversibility of the Na deposits on CC. The two peaks associating with plating were matched with the (0 0 4) and (1 1 1) peaks of orthorhombic NaOH from the literature reference. Na is highly sensitive to air. Although the XRD sample preparation was done in an argon glovebox, complete inhibition of oxidation of Na metal was not achieved. The oxidation of Na under air had not yet process to Na2CO3 by the time the XRD was performed, yet essentially the majority of Na had been oxidized to NaOH, which is understandable as the theoretical thickness of Na coated on the surface of carbon fibers is less than 0.1 μm. The disappearing of the (0 0 4) and (1 1 1) peaks of orthorhombic NaOH for the stripped sample confirms the high reversibility of Na deposits on CC.
A scanning electron microscope (SEM) imaging with energy-dispersive X-ray (EDX) mapping investigation was done with the goal to visually support and explain the surprising improvement of employing a 3-D electrode. As shown in
Another unique feature of CC is that Na ion intercalation happens with the metallic deposition. For the CE values reported in
To further prove the benefits of employing a 3-D framework for Na deposition, a Na/CC hybrid 3-D anode was created by first electrochemically depositing Na to CC in a Na∥CC cell, and then it was paired with a carbon-sulfur composite cathode. In
While the cell with Na/Cu anode completely lost its capacity within the first 20 cycles, Na metal plate anode with greater N/P ratio survived until 350 cycles. However, the cell with Na/CC anode kept 80% of its capacity at the 450th cycle, comparing with its capacity at the 2nd cycle.
The extremely soft and fragile nature of Na dendrites has been described. These observations provided a new thought on designing a hybrid Na metal anode. Unlike Li metal batteries, where the hard dendrite can break the separator and cause short-circuits, most Na metal batteries fail due to the physical loss of anode materials. The problem of orphaning Na during battery cycling can be largely reduced by using a 3-D framework anode as described herein.
Experimental methods: Materials: Electrolyte used in this study was NaClO4 in EC/PC solution (50:50 by volume), prepared in our laboratory. All materials were kept under argon gas, and the electrolyte was extra dried with molecular sieve for overnight before using. Na metal used was purchased from Sigma Aldrich (cubes, under mineral oil, 99.9% trace metals basis).
Visualization: Visualization cells are quartz 3.5 mL cuvette purchased from Science Outlet (schematic shown in
Coin cell electrochemical tests: Two types of coin cells were assembled in this study. One used O-ring washer as the separator, with thickness about 0.8 mm and a hole in the center with diameter of ⅜″. The other type used glass fiber GF/B, purchased from Sigma Aldrich. Glass fiber plates were kept in 100° C. oven overnight for water removal. Electrolyte and Na plates used were as described in Materials. Plain carbon cloth 1071 HCB (from Fuel Cell Store) was used as purchased for making the CC counter electrode and CC/Na anodes. All tests were performed on Neware CT-3008W coin cell testing system.
Characterization: SEM and EDX images were taken on Zeiss GEMINI 500 Scanning Electron Microscope. XPS data was collected by technician at Cornell Center for Materials Research Shared Facilities.
Although the present disclosure has been described with respect to one or more particular embodiments and/or examples, it will be understood that other embodiments and/or examples of the present disclosure may be made without departing from the scope of the present disclosure.
This application claims priority to U.S. Provisional Application No. 62/836,486, filed on Apr. 19, 2019, the disclosure of which is incorporated herein by reference.
This invention was made with government support under grant no. DE-SC0012673 awarded by the Department of Energy. The government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 62836486 | Apr 2019 | US |
