Electrode slurry

Abstract

The present disclosure generally relates to an electrode slurry composition comprising an electrode active material, a binder, and a microemulsion comprising an aqueous phase, a water-immiscible phase, and an amphiphilic substance, wherein the electrode active material and the binder are incorporated within the microemulsion, and the electrode slurry composition can be used to prepare an electrode, including for the production of an electrochemical cell.

Description

Technical Field

[0001] The present disclosure generally relates to electrode slurry compositions. Specifically, the present disclosure relates to electrode slurry compositions that can be used to prepare electrodes, including for the production of electrochemical cells. The present disclosure also relates to a process for preparing an electrode slurry composition and a process for preparing an electrode from an electrode slurry composition. The present disclosure also relates to the use of an electrode slurry composition for preparing an electrode for an electrochemical cell. The present disclosure also relates to an electrochemical cell comprising an electrode prepared from an electrode slurry composition.

Background Art

[0002] Energy consumption / production that relies on the combustion of fossil fuels is predicted to have a profound impact on the world economy and the ecological environment in the future. Electrochemical energy production is being seriously considered as an alternative energy / power source as long as this energy consumption is designed to be more sustainable and environmentally friendly (Winter et al., Chem. Rev. 2004, 104, 10, 4245-4270). Systems for electrochemical energy storage and conversion include electrochemical cells such as batteries (e.g., lithium-ion batteries), fuel cells, and supercapacitors. Although the energy storage and conversion mechanisms are different, there is an "electrochemical similarity" among these electrochemical cells. A common feature is that each requires a positive electrode and a negative electrode, the energy-providing process occurs at the phase boundary of the electrode / electrolyte interface, and the transport of electrons and ions is separated.

[0003] One important process that is almost universally used in the production of electrochemical cells such as batteries (e.g., lithium-ion batteries), fuel cells, and supercapacitors is to prepare the electrodes by applying a slurry made from an electrode active material, optionally a conductive agent, a binder, and a solvent onto a metal current collector. This coated current collector then passes through an oven at a high temperature that removes the solvent and leaves behind a film of only the solid materials. Ideally, this film is robust, uniform, and has good adhesion to the metal.

[0004] The solvents typically used in the industry are almost exclusively N-methylpyrrolidone (NMP), which is widely used in the industry and academic research because it gives the best results with respect to the above-mentioned desirable electrode properties. Since NMP is an expensive, moisture-sensitive, and environmentally harmful organic solvent, finding alternatives to it is a high priority. It is industry practice to include an NMP recovery system in the production line that can recapture the evaporated NMP and recycle it. The recovery of NMP is an energy-intensive process, and these systems are expensive. Therefore, there is a need for alternative or improved electrode slurry compositions for use in the production of electrodes, and for electrodes used in electrochemical cells that can address one or more of the above problems and / or provide socially useful alternatives.

[0005] It will be understood that the prior art publications referred to herein do not admit that any of these documents form part of the common general knowledge in the art in Australia or any other country. SUMMARY OF THE INVENTION

[0006] The present disclosure provides certain electrode slurry compositions that can be used to prepare electrodes. The electrode slurry compositions described herein include an electrode active material and a microemulsion instead of NMP as a solvent. Water is an ideal solvent to use, but this often results in insufficient dispersion of solid materials and films of insufficient quality that crack during drying. After extensive research and development, the inventors have surprisingly found that a microemulsion can be used in the electrode slurry composition to prepare high-quality electrodes. Advantageously, the microemulsion replaces the expensive and dangerous NMP in the electrode slurry composition, providing a cheaper and more environmentally considerate alternative. Furthermore, the physical and / or chemical properties of the microemulsion can be adjusted to develop an electrode slurry composition specially designed to produce high-quality films for a given electrode active material, providing a highly versatile system for preparing a wide variety of electrodes.

[0007] In one aspect, there is provided an electrode slurry composition comprising an electrode active material, a binder, and a microemulsion comprising an aqueous phase, a water-immiscible phase, and an amphiphilic substance, wherein the electrode active material and the binder are incorporated within the microemulsion.

[0008] In another aspect, there is provided a process for preparing an electrode slurry composition described herein, comprising mixing a microemulsion, an active material, and a binder under conditions effective to form the electrode slurry composition.

[0009] In another aspect, there is provided a process for preparing an electrode, comprising coating a first surface of a current collector with an electrode slurry composition described herein and heating the electrode slurry composition at a temperature and for a period effective to dry the electrode slurry composition to form an electrode layer on the surface of the current collector, wherein the electrode layer comprises an electrode active material, a conductive material, and a binder.

[0010] In another aspect, provided is the use of the electrode slurry composition described herein when preparing an electrode for an electrochemical cell.

[0011] In another aspect, provided is an electrochemical cell including a positive electrode (e.g., a cathode), a negative electrode (e.g., an anode), and an electrolyte, wherein the positive electrode and / or the negative electrode is prepared using the electrode slurry composition described herein.

[0012] These and other aspects and embodiments related to the present disclosure are further described herein. Any one or more of the aspects, embodiments, and examples described herein for the electrode slurry composition may be applied to any one or more of the process for preparing the electrode slurry composition, the process for preparing an electrode, the use of the electrode slurry composition, the aspects, embodiments, and examples of the electrode and / or the electrochemical cell described herein, and vice versa. Unless otherwise specifically stated, any embodiment, aspect, or example described herein is considered to be applicable with modifications to each and all of the other embodiments, aspects, or examples. It is also understood that other aspects, embodiments, and examples of the electrode slurry composition, process, use, electrode, and / or electrochemical cell are described herein.

[0013] Also, some features of the electrode slurry composition, process, use, electrode, and / or electrochemical cell in some of the aspects, embodiments, or examples described herein may not be required in all of the aspects, embodiments, or examples described herein, and it is understood that this specification should be read in this context. It is also understood that in various aspects, embodiments, or examples, the order of the method or process steps is not essential and may vary.

Brief Description of the Drawings

[0014] Preferred embodiments of the present disclosure are further described and illustrated below, by way of example only, with reference to the accompanying drawings.

[0015]

Figure 1

Figure 2

DETAILED DESCRIPTION OF THE INVENTION

[0016] The present disclosure describes the following various non-limiting embodiments related to electrode slurries and electrode slurry compositions that can be used in the production of electrodes and electrochemical cells. The electrode slurry compositions described herein include an electrode active material and a microemulsion, which are further described below according to various non-limiting embodiments and examples. The electrode slurry compositions described herein have surprisingly been found to provide one or more advantages, including the preparation of high-quality electrodes for electrochemical cells.

[0017] Those skilled in the art will understand that numerous variations and / or modifications can be made to the above embodiments without departing from the broad general scope of the present disclosure. Accordingly, the present embodiments are to be considered in all respects as illustrative and not restrictive.

[0018] Term In the following description, reference is made to the accompanying drawings which form a part hereof and which illustrate, by way of example, several embodiments. It is understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present disclosure.

[0019] For the definitions provided in this specification, unless otherwise stated or implied by context, the defined terms and phrases include the provided meanings. Unless otherwise explicitly stated or not apparent from the context, the following terms and phrases do not exclude the meanings obtained by those skilled in the relevant art for the term or phrase. The definitions are provided to assist in describing specific embodiments and are not intended to limit the claimed disclosure as the scope of the present disclosure is limited only by the claims. Further, unless otherwise required by context, singular terms shall include the plural and plural terms shall include the singular.

[0020] All publications discussed and / or referenced herein are hereby incorporated by reference in their entirety.

[0021] Any discussion of documents, acts, materials, devices, articles, etc. contained herein is for the purpose of providing context for the present disclosure only. It is not admitted that any of these matters form part of the prior art base or are common general knowledge in the field relevant to the present disclosure that existed before the priority date of each claim of this application.

[0022] Throughout the present disclosure, unless otherwise specifically stated or required by context, references to a single step, composition of matter, group of steps, or group of compositions of matter shall be considered to include one and more (i.e., one or more) of those steps, compositions of matter, groups of steps, or groups of compositions of matter. Thus, as used herein, the singular forms "a", "an", and "the" include plural aspects unless the context clearly dictates otherwise. For example, a reference to "a" includes one as well as two or more, a reference to "an" includes one as well as two or more, a reference to "the" includes one as well as two or more, and so forth.

[0023] Those skilled in the art will understand that the disclosure herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the disclosure includes all such variations and modifications. The disclosure also includes all of the examples, steps, features, methods, compositions, coatings, processes, and coated substrates individually or collectively mentioned or shown herein, as well as any and all combinations, or any two or more of such steps or features.

[0024] The term "and / or", e.g., "X and / or Y", is understood to mean either "X and Y" or "X or Y", and is considered to explicitly support both meanings or either meaning.

[0025] Unless otherwise indicated, terms such as "first", "second", etc. are used herein merely as labels and are not intended to impose sequential, positional, or hierarchical requirements on the items they refer to. Further, a reference to a "second" item does not require or exclude the presence of a lower numbered item (e.g., a "first" item) and / or a higher numbered item (e.g., a "third" item).

[0026] As used herein, the phrase "at least one" when used with a list of items means that different combinations of one or more of the listed items may be used and only one of the items in the list may be required. An item can be a particular object, thing, or category. In other words, "at least one" means that any combination of items or number of items may be used from the list, but not all items in the list may be required. For example, "at least one of item A, item B, and item C" can mean item A; item A and item B; item B; item A, item B, and item C; or item B and item C. In some cases, "at least one of item A, item B, and item C" can mean, for example, but not limited to, two of item A, one of item B, and ten of item C, four of item B, and seven of item C, or some other suitable combination.

[0027] As used herein, the term "about" typically refers to + / - 10% of the specified value, e.g., + / - 5%, unless stated otherwise.

[0028] It should also be understood that, for clarity, the specific features described herein with respect to separate embodiments may be provided in combination in a single embodiment. Conversely, for brevity, the various features described with respect to a single embodiment may be provided separately or in any partial combination.

[0029] Throughout this specification, various aspects and components of the disclosure may be presented in a range format. The range format is included for convenience only and should not be construed as an immutable limitation on the scope of the disclosure. Accordingly, a range description should be considered to specifically disclose all possible sub-ranges within that range, as well as individual numerical values, unless a specific indication is given. For example, a range description such as 1 to 5 should be considered to specifically disclose sub-ranges such as 1 to 3, 1 to 4, 1 to 5, 2 to 4, 2 to 5, 3 to 5, and individual numbers and sub-numbers within the recited range, such as 1, 2, 3, 4, 4.5, and 5, unless integers are required or are implied from the context. This applies regardless of the width of the disclosed range. If specific values are required, these are indicated in the specification.

[0030] Throughout this specification, the word "comprise", or variations such as "comprises" or "comprising", is understood to mean including the recited element, integer or step, or group of elements, integers or steps, but not excluding any other element, integer or step, or group of elements, integers or steps.

[0031] The reference to "substantially free of" generally refers to the absence of that compound or component in a composition other than any trace amounts or impurities that may be present. For example, this may be an amount less than about 1 wt%, about 0.1 wt%, about 0.01 wt%, about 0.001 wt%, or about 0.0001 wt% in the total composition.

[0032] The term "immiscibility" means, with respect to two or more materials, that the materials do not dissolve or combine with another material. With respect to immiscible liquids in a two-phase system such as the microemulsions described herein, "immiscibility" means that the liquids are insoluble or very poorly soluble in each other, such that for all practical purposes, these liquids are conventionally considered to be insoluble in each other. When two immiscible liquids are combined within a system, they form a two-phase system of immiscible liquids.

[0033] The terms "water" and "oil" (as used, for example, in connection with water-in-oil microemulsions and oil-in-water microemulsions) are understood to represent an aqueous phase and a water-immiscible phase. The term "water-immiscible phase" is used to describe any liquid that is immiscible with the aqueous phase. As used herein, "water phase" and "aqueous phase" may be used interchangeably.

[0034] The term "slurry" refers to a liquid mixture containing solid particles.

[0035] Electrode slurry composition The present disclosure encompasses various research and developments related to the identification of electrode slurry compositions that can be used in the preparation of electrodes, including those used in electrochemical cells. The electrode slurry compositions of the present disclosure include an electrode active material, a binder, and a microemulsion comprising an aqueous phase, a water-immiscible phase, and an amphiphilic substance, wherein the electrode active material and the binder are incorporated within the microemulsion. According to some embodiments or examples, the microemulsion and / or the electrode slurry composition is substantially free of N-methyl-2-pyrrolidone (NMP).

[0036] One or more advantages of the present disclosure according to at least some embodiments or examples as described herein is that the microemulsion can replace expensive and dangerous NMP in the electrode slurry composition that provides a more inexpensive and environmentally friendly system for preparing high-quality electrodes. The physical and / or chemical properties of the microemulsion can be adjusted to develop an electrode slurry composition specifically designed to produce a high-quality film for a given electrode active material, providing a highly versatile system for preparing a wide variety of electrodes.

[0037] The presence of at least an electrode active material, a binder, and an optional conductive material incorporated (e.g., dissolved / suspended / dispersed) within the microemulsion causes the slurry to have a solids content. In one embodiment, the slurry has a solids content of at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, or 90 (% weight / weight) based on the total weight of the slurry. In one embodiment, the slurry has a solids content of less than about 90, 80, 70, 60, 50, 40, 30, 20, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 (% weight / weight) based on the total weight of the slurry. The solids content can be in a range provided by any two of these upper and / or lower limits. For example, the slurry can have a solids content of about 1 to about 90, about 10 to about 90, about 20 to about 60, about 30 to about 50, about 1 to about 50, or about 1 to about 10 (% weight / weight) based on the total weight of the slurry.

[0038] Any amount of electrode active material can be used to prepare the slurries described herein. In one embodiment, the slurry comprises from about 25 wt / wt% to about 90 wt / wt% electrode active material, based on the total weight of the solids incorporated within the microemulsion. The slurry can comprise at least about 25, 50, 55, 60, 65, 70, 75, 80, 85, or 90 wt / wt% electrode active material, based on the total weight of the solids incorporated within the microemulsion. The slurry can comprise less than about 90, 85, 80, 75, 70, 65, 60, 55, 50, or 25 wt / wt% electrode active material, based on the total weight of the solids incorporated within the microemulsion. The wt / wt% of electrode active material based on the total weight of the solids incorporated within the microemulsion can be in a range provided by any two of these upper and / or lower values. For example, the slurry can comprise from about 50 wt / wt% to about 90 wt / wt% or from about 80 wt / wt% to about 90 wt / wt% electrode active material, based on the total weight of the solids incorporated within the microemulsion. Any amount of binder can be used to prepare the slurries described herein. In one embodiment, the slurry comprises from about 1 wt / wt% to about 20 wt / wt% binder, based on the total weight of the solids incorporated within the microemulsion. The slurry can comprise at least about 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, or 20 wt / wt% binder, based on the total weight of the solids incorporated within the microemulsion. The slurry can comprise less than about 20, 18, 16, 14, 12, 10, 8, 6, 4, 2, or 1 wt / wt% binder, based on the total weight of the solids incorporated within the microemulsion. The wt / wt% of binder based on the total weight of the solids incorporated within the microemulsion can be in a range provided by any two of these upper and / or lower values. For example, the slurry can comprise from about 1 wt / wt% to about 10 wt / wt% binder, based on the total weight of the solids incorporated within the microemulsion.

[0039] If present, any amount of the conductive material can be used to prepare the slurries described herein. In one embodiment, the slurry comprises from about 1 wt / wt% to about 30 wt / wt% of the conductive material, based on the total weight of the solids incorporated within the microemulsion. The slurry can comprise at least about 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 25, or 30 wt / wt% of the conductive material, based on the total weight of the solids incorporated within the microemulsion. The slurry can comprise less than about 30, 25, 20, 18, 16, 14, 12, 10, 8, 6, 4, 2, or 1 wt / wt% of the conductive material, based on the total weight of the solids incorporated within the microemulsion. The wt / wt% of the conductive material based on the total weight of the solids incorporated within the microemulsion can be in a range provided by any two of these upper and / or lower values. For example, the slurry can comprise from about 5 wt / wt% to about 20 wt / wt% of the conductive material, based on the total weight of the solids incorporated within the microemulsion.

[0040] microemulsion The electrode slurry composition comprises a microemulsion. Other optional additives, such as an electrode active material, a binder, and a conductive agent, are incorporated within the microemulsion. As used herein, the term "incorporated" generally refers to the microemulsion's ability to act as a suitable carrier for one or more of the listed components. For example, the electrode active material can be dispersed (e.g., suspended) within the microemulsion as solid particles. The binder can be dissolved within the microemulsion, depending on its properties (e.g., can be dissolved in the aqueous and / or water immiscible phase of the microemulsion). Nevertheless, dissolved or suspended components within the microemulsion are understood to be "incorporated" as used herein.

[0041] As used herein, the term "microemulsion" refers to a thermodynamically stable mixture of two immiscible liquid phases. A microemulsion can be of the "oil-in-water" (O / W) type, "water-in-oil" (W / O) type, or "bicontinuous", and these terms defining the microemulsion structure are well known in the art. In an oil-in-water microemulsion, the water-immiscible phase is dispersed in the continuous aqueous phase. In a water-in-oil microemulsion, the aqueous phase is dispersed in the continuous water-immiscible phase. In a bicontinuous microemulsion, the aqueous phase and the water-immiscible phase are each interconnected and dispersed throughout the mixture. Typically, a microemulsion has a fine and heterogeneous liquid biphasic structure, which appears homogeneous at the macroscopic level. The aqueous phase and the water-immiscible phase of a microemulsion are immiscible at the desired operating temperature (usually room temperature or near it). Microemulsions are thermodynamically stable and can thus be formed spontaneously (without applying energy) and, once formed, do not separate into their constituent phases over time.

[0042] "Emulsion", despite the similar nomenclature, should be emphasized as being very different from microemulsion. An emulsion is a thermodynamically unstable (kinetically stable) mixture of immiscible liquids. This means, in contrast to microemulsion, that the two immiscible phases of the emulsion will separate over time. Unlike microemulsion which exists without surfactants, emulsions of immiscible liquids almost always require the presence of stabilizers, particularly surfactants or viscosity modifiers, to prevent phase separation. For example, viscosity modifiers (e.g., thickeners such as polysaccharides) have been used previously to stabilize emulsions by retarding the coalescence of droplets as the immiscible phases separate, and as such, these viscosity modifiers, although not surfactants / amphiphilic substances as understood in the art, have come to be referred to as emulsifiers or stabilizers. Such highly viscous, concentrated emulsions may be more stable, but often it is difficult to uniformly disperse the electrode active material and the binder throughout, and when these components are incorporated, due to the thickener, the overall slurry can become such highly viscous that it is difficult to blade coat onto the current collector, resulting in a non-uniform electrode layer that leads to a decrease in performance.

[0043] The microemulsion contains an aqueous phase and a water-immiscible phase. In one embodiment, the microemulsion is an oil-in-water (O / W) type microemulsion (i.e., the water-immiscible phase is dispersed in the aqueous phase and the aqueous phase is the continuous phase). In an alternative embodiment, the microemulsion is a bicontinuous microemulsion (i.e., the water-immiscible phase and the aqueous phase are bicontinuous). In yet another embodiment, the microemulsion is a water-in-oil (W / O) type microemulsion (i.e., the water-immiscible phase is the continuous phase and the aqueous phase is the dispersed phase). The type of microemulsion (e.g., O / W type, W / O type, or bicontinuous) may depend on the properties of the electrode active material and can be adjusted to develop an electrode slurry composition specifically designed to produce a high-quality film of a given electrode active material. According to some embodiments or examples, it has been found that high-quality electrodes can be prepared using an electrode slurry composition containing an oil-in-water (O / W) type microemulsion as shown in the examples.

[0044] The solvent used as the water-immiscible phase of the microemulsion may include a water-immiscible solvent or a combination of two or more water-immiscible solvents. In one embodiment, the water-immiscible phase includes an organic solvent (e.g., a water-immiscible organic solvent). By way of example only, a non-limiting list of solvents suitable for use as the water-immiscible phase of the microemulsion includes aliphatic solvents (e.g., hexane, cyclohexane, and petroleum ether, cyclic and acyclic, branched and unbranched alkanes such as alkenes, alkynes), aromatic solvents (e.g., benzene, toluene, p-xylene, 1,2-dichlorobenzene), halogenated solvents (e.g., dichloromethane, chloroform, dichloroethane), ether solvents (e.g., diethyl ether, diphenyl ether), ketone solvents (e.g., acetophenone), ester solvents (e.g., ethyl benzoate, ethyl acetate), or combinations thereof.

[0045] In one embodiment, the organic solvent is selected from the group consisting of aliphatic solvents, aromatic solvents, halogenated solvents, ketone solvents that are substantially immiscible with water, ether solvents that are substantially immiscible with water, ester solvents that are substantially immiscible with water, or combinations thereof.

[0046] In one embodiment, the organic solvent is selected from the group consisting of hexane, cyclohexane, petroleum ether, benzene, toluene, p-xylene, 1,2-dichlorobenzene, dichloromethane, chloroform, dichloroethane, ethyl acetate, and diethyl ether, or combinations thereof.

[0047] In some embodiments, the organic solvent has a boiling point of less than about 150 °C, which is close to the boiling point of water (a preferred component of the aqueous phase) and relatively low compared to other high-boiling long-chain compounds used to prepare the emulsion. In some embodiments, the organic solvent has a boiling point of about 20 to about 150 (in °C).

[0048] In some embodiments, the water-immiscible phase and the water-miscible phase have a boiling point difference of about 1 °C to about 100 °C (i.e., the difference between the boiling points of each phase). For example, if the water-miscible phase is water (boiling point of about 100 °C) and the water-immiscible phase is toluene (boiling point of about 110 °C), the boiling point difference is about 10 °C. In some examples, the boiling point difference (in °C) between the water-immiscible phase and the water-miscible phase is about 1 to about 100, 1 to about 80, 10 to about 70.

[0049] In some examples, by preparing a microemulsion using a water-immiscible phase having a boiling point close to or lower than that of water, which is a preferred component of the aqueous phase, further advantages such as the formation of a uniform electrode coating due to the low heat required during the drying process described herein are provided. In some preferred cases, the organic solvent as the water-immiscible layer can have a boiling point equal to or lower than that of water, which is a preferred component of the aqueous phase.

[0050] According to some embodiments or examples described herein, an organic solvent having a relatively low boiling point, along with a suitable aqueous phase such as water, enables an electrode slurry once coated on the surface of a current collector to be heated at a relatively low temperature and still be effectively dried, thereby forming a uniform electrode layer on the surface of the current collector. Specifically, the inventors of the present application have surprisingly found that using such a low-boiling organic solvent as a water-immiscible phase can provide a more uniform electrode at a lower drying temperature (e.g., less than about 200°C). In contrast, a water-immiscible phase containing, for example, a long-chain higher alkane, carboxylic acid, or fatty acid has a substantially higher boiling point compared to water (e.g., a boiling point exceeding 300°C), which means that the temperature required to dry an electrode slurry containing these long-chain compounds is much higher and may affect the integrity of the electrode, and thus does not result in a more uniform electrode obtained at a lower drying temperature. Additionally, water-immiscible and water-immiscible phases having similar boiling points mean that the microemulsion composition remains similar throughout the drying process (e.g., one phase is not preferentially removed over another), which is in contrast to an emulsion that contains phases with very different boiling points such as water and a long-chain carboxylic acid, where water is removed first and takes more time to be (completely) removed, leaving the long-chain carboxylic acid that can affect how the electrode progresses as it dries. The fact that the microemulsion phase has a slurry that dries at approximately the same rate (due to similar boiling points) maintains the formation of the electrode layer that occurs under the same conditions throughout the drying, rather than passing through a stepwise drying regime (i.e., a significantly higher boiling point phase removal regime following a water removal regime). In one embodiment, the concentration (% weight / weight) of the water-immiscible phase is at least about 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 99 based on the total weight of the microemulsion. In one embodiment, the concentration (% weight / weight) of the water-immiscible phase is less than about 99, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, or 1 based on the total weight of the microemulsion.The % weight / weight concentration of the water-immiscible phase in the microemulsion can be in the range provided by any two of these upper and / or lower limit values. For example, the concentration (% weight / weight) of the water-immiscible phase can be about 5 to about 95, about 25 to about 75, or about 40 to about 60, based on the total weight of the microemulsion. It will be understood that the concentration of the water-immiscible phase varies depending on the type of microemulsion. For example, an O / W type microemulsion contains less water-immiscible phase compared to a W / O type emulsion.

[0051] In embodiments where the microemulsion is an O / W type microemulsion, the concentration (% weight / weight) of the water-immiscible phase can be about 1 to about 60, about 1 to about 50, about 1 to about 40, or about 1 to about 20, based on the total weight of the microemulsion.

[0052] In embodiments where the microemulsion is a bicontinuous microemulsion, the concentration (% weight / weight) of the water-immiscible phase can be about 20 to about 80, based on the total weight of the microemulsion.

[0053] In embodiments where the microemulsion is a W / O type microemulsion, the concentration (% weight / weight) of the water-immiscible phase can be about 40 to about 99, about 50 to about 99, about 60 to about 99, or about 80 to about 99, based on the total weight of the microemulsion.

[0054] In one embodiment, the aqueous phase contains water. In another embodiment, the aqueous phase contains a water-miscible solvent. In one embodiment, the aqueous phase contains a mixture of water and a water-miscible solvent. The water-miscible solvent can be an alcohol, such as methanol, ethanol, propanol, or pentanol, or a mixture thereof. It will be understood that the aqueous phase of the microemulsion electrolyte composition must be immiscible with the water-immiscible phase.

[0055] In one embodiment, the concentration (% weight / weight) of the aqueous phase is at least about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 99 based on the total weight of the microemulsion. In one embodiment, the concentration (% weight / weight) of the aqueous phase is less than about 99, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5 based on the total weight of the microemulsion. The % weight / weight concentration of the aqueous phase in the microemulsion can be in a range provided by any two of these upper and / or lower limits. For example, the concentration (% weight / weight) of the aqueous phase can be about 5 to about 95, about 25 to about 75, or about 40 to about 60. It will be understood that the concentration of the aqueous phase varies depending on the type of microemulsion. For example, an O / W type microemulsion contains more aqueous phase compared to a W / O type emulsion.

[0056] In an embodiment where the microemulsion is an O / W type microemulsion, the concentration (% weight / weight) of the aqueous phase can be about 40 to about 99, about 50 to about 99, about 60 to about 99, or about 80 to about 99 based on the total weight of the microemulsion.

[0057] In an embodiment where the microemulsion is a bicontinuous microemulsion, the concentration (% weight / weight) of the aqueous phase can be about 20 to about 80 based on the total weight of the microemulsion.

[0058] In an embodiment where the microemulsion is a W / O type microemulsion, the concentration (% weight / weight) of the aqueous phase can be about 1 to about 60, about 1 to about 50, about 1 to about 40, or about 1 to about 20 based on the total weight of the microemulsion.

[0059] The relative proportions of the aqueous phase and the water-immiscible phase in the microemulsion are naturally limited by the overall thermodynamic stability of the mixture of components (e.g., aqueous phase, water-immiscible phase) that make up the microemulsion. There are natural limitations to the relative proportions of the phases for which it is thermodynamically favorable for the composition to exist as a microemulsion. To achieve an oil-in-water microemulsion or a bicontinuous microemulsion, there are further natural limitations to the relative proportions of the phases. The relative proportions of the phases can be determined theoretically or by routine experimentation by those skilled in the art. It will also be understood that the relative proportions of the aqueous phase and the water-immiscible phase include any and all proportions and ranges for which a microemulsion is formed. Since oil-in-water and bicontinuous microemulsion systems are preferred, the preferred proportions of the aqueous phase and the water-immiscible phase are those that result in oil-in-water and bicontinuous microemulsions.

[0060] The microemulsion further comprises one or more amphiphilic substances. As is understood in the art, amphiphilic substances are molecules that have both hydrophobic and hydrophilic regions that stabilize the microemulsion. Suitable amphiphilic substances are described herein and the selection of amphiphilic substances is used in the examples, but the disclosure is not limited to these particular compounds. As will be understood by those skilled in the art, the selection of the amphiphilic substance depends on the type of microemulsion desired (e.g., O / W type, W / O type, or bicontinuous), and / or the chemical nature and composition of the microemulsion or its components, and / or the specific identity and proportions of the components in the electrode slurry composition. In some cases, a suitable phase diagram for the target microemulsion can facilitate specifying the appropriate amounts of the phases used and / or the type / amount of the amphiphilic substance.

[0061] The amphiphilic substance can be a surfactant, a co-surfactant, or a co-solvent. In one embodiment, the microemulsion further comprises a surfactant. As is understood in the art, a surfactant is a chemical compound that can reduce the surface tension or interfacial tension between the water-miscible phase and the water-immiscible phase of the microemulsion due to the presence of both a hydrophobic region and a hydrophilic region.

[0062] In one embodiment, the microemulsion further comprises a co-solvent. A co-solvent is often completely or at least partially miscible with each phase of the microemulsion, which results in improved phase stability.

[0063] Suitable surfactants, co-surfactants, and co-solvents that can be used as amphiphilic substances for the preparation of microemulsions will be known to those skilled in the art. Examples of suitable surfactants include anionic surfactants, cationic surfactants, zwitterionic surfactants, and nonionic surfactants. Examples of preferred surfactants include Triton X-100, cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride (CTAC), cetylpyridinium chloride (CPC), benzalkonium chloride, benzetonium chloride, sodium dodecyl sulfate (SDS), and sodium lauryl ether sulfate (SLES). Examples of suitable co-surfactants or co-solvents include aliphatic alcohols such as C2-C6 alcohols, amines such as C2-C6 alkylamines, and short-chain carboxylic acids (C2-C6). Preferred co-surfactants and / or co-solvents of the present disclosure include ethanol, propanol, butanol, and pentanol. As will be understood by those skilled in the art, the selection of the amphiphilic substance depends on the type of microemulsion desired (oil-in-water, bicontinuous, or water-in-oil), as well as the specific identity and proportion of the components in the electrode slurry composition (e.g., electrode active material, binder, optional conductive material, etc.).

[0064] The factors for determining the preferred relative proportions of the aqueous phase and the water-immiscible phase are for the purpose of achieving the required incorporation of the electrode active material, the binder material, and, if present, the conductive material in the microemulsion.

[0065] From the foregoing description, it will be apparent that the amounts of the respective components in the microemulsion (e.g., the aqueous phase, the water-immiscible phase, and the amphiphilic substance, etc.) can be configured or adjusted to optimize the parameters so as to be able to customize the microemulsion from the perspective of physical and chemical properties, and microemulsions can be developed that are specifically designed to achieve the required incorporation of the electrode active material, the binder material, and, if present, the conductive material in the microemulsion. This possibility of customization is beneficial because it can enable the production of high-quality films of various materials. Such optimization is a matter of routine experimentation and is within the scope of the present disclosure.

[0066] The microemulsion can be prepared according to known methods for preparing microemulsions well known to those skilled in the art. The microemulsion of the present disclosure can be prepared by combining the individual components. Since the microemulsion is thermodynamically stable, it can form spontaneously. However, agitation of the microemulsion components can be carried out so that the microemulsion is preferably formed in a short time. For example, the combined components can be agitated by stirring, shaking, or sonication.

[0067] The microemulsion can be prepared under ambient conditions, i.e., at room temperature and in the presence of ambient moisture, oxygen, carbon dioxide, and other atmospheric constituents.

[0068] In one embodiment, the concentration (% weight / weight) of the microemulsion is at least about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 99 based on the total weight of the electrode slurry composition. In one embodiment, the concentration (% weight / weight) of the microemulsion is less than about 99, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5 based on the total weight of the electrode slurry composition. The % weight / weight concentration of the microemulsion in the electrode slurry composition can be in a range provided by any two of these upper and / or lower limits. For example, the concentration (% weight / weight) of the microemulsion can be about 5 to about 99, about 10 to about 90, about 40 to about 80, about 50 to about 70, about 50 to about 99, about 60 to about 99, about 70 to about 99, about 80 to about 99, or about 90 to about 99 based on the total weight of the electrode slurry composition.

[0069] Electrode active material The electrode slurry composition includes an electrode active material incorporated (e.g., dispersed) within the microemulsion. The electrode active material can be any electrochemically active species that can be used as an electrode (e.g., a positive or negative electrode such as a cathode or anode) in an electrochemical cell. The electrode active material can be selected from any known in the art. In one embodiment, the electrode active material includes a positive electrode material (e.g., a cathode material). In one embodiment, the electrode active material includes a negative electrode material (e.g., an anode material).

[0070] In one embodiment, the electrode active material may be selected from the group consisting of transition metal oxides or mixed metal oxides (e.g., lithium cobalt oxide, sodium metatitanate, lithium titanate, vanadium pentoxide), transition metal salts including phosphates and sulfates of transition metals (e.g., lithium iron phosphate, sodium iron sulfate), vanadates (e.g., ammonium metavanadate), elements (e.g., sulfur), main group nitrides (e.g., boron nitride), main group oxides (e.g., boric anhydride), perylene and other organic substances (e.g., 3,4,9,10 - perylenetetracarboxylic dianhydride), Prussian blue, its analogs (e.g., iron(III) hexacyanoferrate), and carbon - based materials (e.g., carbon black, graphite, and activated carbon). However, it is understood that the electrode slurry composition may essentially contain any electrode active material and represents a highly versatile system for preparing a wide range of electrodes.

[0071] In one embodiment, the concentration (% weight / weight) of the electrode active material is at least about 1, 2, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or 95 based on the total weight of the electrode slurry composition. In one embodiment, the concentration (% weight / weight) of the electrode active material is less than about 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 4, 2, or 1 based on the total weight of the electrode slurry composition. The % weight / weight concentration of the electrode active material in the electrode slurry composition can be in a range provided by any two of these upper and / or lower limits. For example, the concentration (% weight / weight) of the electrode active material can be about 1 to about 90, about 8 to about 60, about 10 to about 50, about 1 to about 50, about 1 to about 20, or about 1 to about 10 based on the total weight of the electrode slurry composition.

[0072] Binder The electrode slurry composition includes a binder incorporated (e.g., dissolved) within the microemulsion. The binder holds the electrode active materials together and promotes the adhesion of the electrode active materials to the current collector. According to some embodiments or examples described herein, by introducing the binder into the microemulsion, it becomes possible for the electrode coating to start directly from the slurry formation, requiring a single drying step to remove the microemulsion, solidify the binder, and adhere the electrode active materials to the current collector, providing a simple process for preparing the electrode layer.

[0073] The binder can be selected from any known in the art. In one embodiment, the binder is a polymer binder. In one embodiment, the binder is selected from the group consisting of polyvinylidene difluoride (PVDF), polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), or combinations thereof (e.g., a mixture of SBR and CMC).

[0074] In one embodiment, the concentration (% weight / weight) of the binder is at least about 0.01, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 12, 14, 16, 18, 20, or 30 based on the total weight of the electrode slurry composition. In one embodiment, the concentration (% weight / weight) of the binder is less than about 30, 20, 18, 16, 14, 12, 10, 5, 2, 1, 0.5, 0.2, 0.1, 0.05, or 0.01 based on the total weight of the electrode slurry composition. The % weight / weight concentration of the binder in the electrode slurry composition can be in a range provided by any two of these upper and / or lower limits. For example, the concentration (% weight / weight) of the binder can be about 0.1 to about 30, 0.2 to about 30, about 0.5 to about 20, about 0.7 to about 15, about 0.1 to about 20, about 0.1 to about 10, about 0.1 to about 5, or about 0.1 to about 1 based on the total weight of the electrode slurry composition.

[0075] In one embodiment, the binder is dissolved in the aqueous or water-immiscible phase of the microemulsion. The advantage of having a microemulsion-based slurry system is that the binder can be dissolved in either the aqueous phase or the water-immiscible phase. This allows a wide range of possible binders and amounts of binder to be used. For example, binders with different solubility characteristics can be used without changing the entire solvent system of the slurry, provided that it is soluble in at least one of the phases of the microemulsion.

[0076] Conductive material The electrode slurry composition, if present, may further include a conductive material incorporated (e.g., dispersed) within the microemulsion. Typically, the conductive material is added to improve the resulting charge-discharge performance of the electrode by forming a percolation network for electron transport within the electrode, which significantly improves the conductivity of the electrode. However, if the electrode active material is also conductive (e.g., graphite), a conductive material may not be required.

[0077] The conductive material can be selected from any known in the art. In one embodiment, the conductive material is a carbon-based material. In a further embodiment, the conductive material is carbon black. There can be various types of carbon black, such as "Super P" or "Ketjenblack 600JD". Carbon black is particularly useful for improving the conductivity of the electrode and reducing the resistance of the interactions. In another embodiment, the conductive material is graphite.

[0078] In one embodiment, the concentration (% weight / weight) of the conductive material is at least about 0.01, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 12, 14, 16, 18, 20, or 30 based on the total weight of the electrode slurry composition. In one embodiment, the concentration (% weight / weight) of the conductive material is less than about 30, 20, 18, 16, 14, 12, 10, 5, 2, 1, 0.5, 0.2, 0.1, 0.05, or 0.01 based on the total weight of the electrode slurry composition. The % weight / weight concentration of the conductive material in the electrode slurry composition can be in a range provided by any two of these upper and / or lower limits. For example, the concentration (% weight / weight) of the conductive material can be about 0.2 to about 30, about 0.5 to about 20, about 0.7 to about 15, 0.1 to about 30, about 0.1 to about 10, about 0.1 to about 5, or about 0.1 to about 2 based on the total weight of the electrode slurry composition.

[0079] Additive The electrode slurry composition may further include one or more additional additives. The additives can be added as components of the microemulsion or as separate components.

[0080] In one embodiment, the microemulsion may further contain a dissolved salt. The dissolved salt may be selected from the group consisting of Group 1 salts, Group 2 salts, transition metal salts, aluminum salts, or combinations thereof. Examples of dissolved salts include, but are not limited to, LiCl, NaCl, KCl, LiOH, NaOH, KOH, MgSO4, MgCl2, Zn(NO3)2, and AlCl3. The aqueous phase may contain a dissolved salt. The aqueous phase may also contain dissolved Group 1 ions, Group 2 ions, transition metal ions, aluminum ions, or combinations thereof. Examples of dissolved ions include lithium, sodium, potassium, magnesium, aluminum, calcium, chromium, manganese, iron, cobalt, copper, nickel, zinc, silver, halogen ions (e.g., fluoride, chloride, chlorate, bromide, iodide, iodate), sulfate ions, nitrate ions, and combinations thereof. The concentration of the dissolved salt or ions in the aqueous phase can be between 0% and a saturated aqueous solution. Exemplary ranges of dissolved salts or ions include 0 to 10 M, more preferably about 0.01 M to 5 M, more preferably 0.05 M to 1 M, and most preferably about 0.05 M to 0.5 M.

[0081] In one embodiment, the salt can be added to the microemulsion after the microemulsion has already been formed or added to the aqueous component prior to the preparation of the microemulsion. In one embodiment, the salt is added to the aqueous component prior to the preparation of the microemulsion.

[0082] Process for preparing an electrode slurry composition In a further aspect of the present disclosure, a process for preparing an electrode slurry composition is provided. The process for preparing an electrode slurry composition includes mixing a microemulsion, an electrode active material, a binder, and, if present, a conductive agent under conditions effective to form the electrode slurry composition.

[0083] The microemulsion, binder, electrode active material, and, if present, the conductive material can be mixed at any suitable temperature effective to form a slurry. For example, the mixing can be at a temperature of at least about 10, 15, 20, 25, 30, 35, 40, 45, or 50 °C. The mixing can be at a temperature of less than about 50, 45, 40, 35, 30, 25, 20, 15, or 10 °C. The mixing temperature can be in a range provided by any two of these upper and / or lower limits. For example, the microemulsion, electrode active material, binder, and, if present, the conductive agent can be mixed at a temperature of about 10 to about 50 °C.

[0084] The microemulsion, binder, electrode active material, and, if present, the conductive material can be mixed for a period of time effective to form a slurry. For example, the mixing can be for a period of at least about 5, 10, 15, 20, 30, 60, or 120 minutes. The mixing can be for a period of less than about 120, 60, 30, 20, 15, 10, or 5 minutes. The mixing time can be in a range provided by any two of these upper and / or lower limits. For example, the microemulsion, electrode active material, binder, and, if present, the conductive agent can be mixed for a period of about 5 to 120 minutes.

[0085] In one embodiment, the microemulsion, electrode active material, binder, and, if present, the conductive agent are mixed for a period of time effective to form a homogeneous dispersion of the electrode active material, binder, and, if present, the conductive agent within the microemulsion.

[0086] In one embodiment, the process includes adding the microemulsion to the electrode active material, binder, and, if present, the conductive agent and mixing under conditions effective to form an electrode slurry composition. In an alternative embodiment, the process includes dissolving / suspending the binder in the microemulsion and then adding it to the electrode active material and, if present, the conductive agent and mixing under conditions effective to form an electrode slurry composition.

[0087] Mixing can be carried out using any suitable method, such as magnetic stirring, planetary mixing, or manual mixing. Alternatively or additionally, the slurry can be mixed under vacuum or placed under vacuum after preparation. By doing so, further advantages are provided, such as removing (i.e., degassing) any dissolved gas present in the slurry. In one embodiment, the process includes degassing the slurry.

[0088] Electrode The present disclosure also provides an electrode prepared using the electrode slurry composition described herein.

[0089] In one aspect, a process for preparing an electrode, coating a first surface of a current collector with an electrode slurry composition comprising an electrode active material, a binder, optionally a conductive material, and a microemulsion comprising an aqueous phase and a water-immiscible phase, wherein the electrode active material, the binder, and, if present, the conductive material are incorporated within the microemulsion; heating the electrode slurry composition at a temperature effective to dry the electrode slurry composition and for a period effective to form an electrode layer on the surface of the current collector, the electrode layer comprising the electrode active material, the binder, and, if present, a conductive agent, is provided.

[0090] The electrode can be used as a positive electrode (e.g., cathode) and / or a negative electrode (e.g., anode).

[0091] The electrode slurry composition can be applied to the first surface of the current collector by any suitable method. In one embodiment, the electrode slurry composition is coated onto the first surface of the current collector by transfer coating, slot die coating, doctor blading, dip coating, screen printing, spray coating, or brush coating. The coating is typically performed at ambient temperature. The coating can be performed one or more times if necessary to obtain an electrode slurry coating layer of a suitable thickness. In one embodiment, the electrode slurry composition is applied to the first surface of the current collector to provide an electrode slurry coating having a thickness of at least about 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, 5000, or 10,000 thickness (μm). In one embodiment, the electrode slurry composition is applied to the first surface of the current collector to provide an electrode slurry coating having a thickness (μm). The thickness of the electrode slurry coating can be in the range provided by any two of these upper and / or lower limit values, for example, from about 1 μm to about 1 mm, preferably from about 50 μm to about 200 μm.

[0092] The electrode slurry composition and the current collector are typically heated together (e.g., by placing the coated current collector in an oven). The electrode slurry composition can be heated at a temperature effective to form the electrode layer and for a period effective thereto. This can include a temperature effective to solidify the binder and / or dry and remove the microemulsion. The heating step can substantially remove at least the aqueous phase of the microemulsion (i.e., substantially remove water). In one embodiment, the electrode layer is substantially free of water.

[0093] In one embodiment, the electrode slurry composition is heated at a temperature of at least about 50, 70, 100, 110, 130, 150, 180, or 200 °C. In one embodiment, the electrode slurry composition is heated at a temperature of less than about 200, 180, 150, 130, 110, 70, or 50 °C. The heating temperature can be in a range provided by any two of these upper and / or lower limits, for example, from about 50 to about 200, or from about 100 to about 150. Such lower temperatures can provide a more uniform electrode. It will be understood that the duration of heating depends on the temperature, with lower temperatures requiring longer heating times and higher temperatures requiring shorter heating times. In one embodiment, the electrode slurry composition is heated for a period of at least about 0.1, 0.5, 1, 2, 4, 6, 9, 12, 18, 24, or 48 hours. In one embodiment, the electrode slurry composition is heated for a period of less than about 48, 24, 18, 12, 9, 6, 4, 2, 1, 0.5, or 0.1 hours. The heating time can be in a range provided by any two of these upper and / or lower limits, for example, from about 0.1 to about 48 hours, or from about 6 to about 48 hours. In one embodiment, the slurry can be heated under vacuum.

[0094] It will be understood that the electrodes can be provided in any shape, size, thickness, or configuration. The electrodes can be provided in various thicknesses depending on the application. The thickness of the electrode can be controlled, in part, by the thickness of the electrode slurry coating.

[0095] The amount of slurry for coating the first surface of the current collector can vary depending on the overall target thickness of the electrode layer. In one embodiment, the electrode layer has a thickness of at least about 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, 5000, or 10,000 μm. In one embodiment, the electrode layer has a thickness of less than about 10,000, 5000, 1000, 500, 200, 1, 5, 2, or 1 μm. The thickness of the electrode layer can be in a range provided by any two of these upper and / or lower limits, for example, from about 1 μm to about 1 mm, preferably from about 50 μm to about 200 μm.

[0096] In one embodiment, in the process for preparing the electrode, the electrode layer and the current collector are compressed at a pressure effective to increase the density of the electrode layer and / or to facilitate contact between the surface of the current collector and the electrode layer. The electrode layer and the current collector can be compressed at a pressure of at least about 0.1, 1, 2, 5, 10, 20, 40, 60, 80, or 100 MPa. The electrode layer and the current collector can be compressed at a pressure of less than about 100, 80, 60, 40, 20, 10, 5, 2, 1, or 0.1 MPa. The compression pressure can be in the range provided by any two of these upper and / or lower limit values. For example, the pressure (MPa) can be from about 0.1 to about 100.

[0097] The current collector can be any suitable current collector used for preparing the electrode. The current collector can have a form and / or properties effective to support the electrode slurry composition. In one embodiment, the current collector is a metal (e.g., steel) or carbon-based (e.g., graphite) current collector. In one embodiment, the current collector includes an aluminum or copper current collector. In one embodiment, the current collector includes aluminum or copper. In one embodiment, the current collector is in the form of a foil.

[0098] The current collector can have any suitable thickness. In one embodiment, the current collector has a thickness of from about 10 μm to about 1000 μm. The current collector can have a thickness of at least about 10, 20, 50, 70, 100, 120, 150, 200, 250, 300, 350, 400, 500, 600, 800, or 1000 μm. The current collector can have a thickness of less than about 1000, 800, 600, 500, 400, 350, 300, 250, 200, 150, 120, 100, 70, 50, 20, or 10 μm. The thickness can be in the range provided by any two of these upper and / or lower limit values, for example, from about 50 μm to about 500 μm.

[0099] The current collector may have a roughened or textured surface, which may provide an enhanced surface area that promotes the dispersion, incorporation, or embedding of the electrode layer on or within the current collector. Such surface roughening or texturing is understood to mean that the surface of the current collector has been manipulated (i.e., roughened or textured) and does not include a natural "perfectly smooth" or polished surface that may have some form of microscopic roughness. In other words, surface roughening is achieved by some physical or mechanical treatment of the substrate surface, for example, through polishing.

[0100] The current collector may initially be a sheet, and then, after the electrode layer is formed on the surface of the current collector, it is cut to an appropriate size to form an electrode that can be incorporated into an electrochemical cell.

[0101] In some embodiments, at least about 50, 60, 70, 80, 90, 95, or 98% of the surface of the current collector is coated with the electrode slurry composition / electrode layer.

[0102] In one embodiment, the process further includes forming an electrochemical cell using the electrode.

[0103] Electrochemical cell In a further aspect of the present disclosure, an electrochemical cell is provided. It will be understood that the electrochemical cell includes a positive electrode (e.g., cathode) and a negative electrode (e.g., anode) in fluid communication with an electrolyte. The positive electrode and / or the negative electrode may be prepared using the electrode slurry composition described herein.

[0104] In one aspect, an electrochemical cell is provided that includes a positive electrode (e.g., cathode), a negative electrode (e.g., anode), and an electrolyte, and the anode and / or the cathode are prepared using the electrode slurry composition and process described herein. For example, the positive electrode and / or the negative electrode may include a current collector coated with an electrode layer prepared using the electrode slurry composition described herein.

[0105] The electrochemical cell can be suitable for any type of battery. For example, the electrochemical cell can be an ion battery or a flow battery. In one embodiment, the electrochemical cell is a lithium-ion battery, a magnesium-ion battery, a sodium-ion battery, an aluminum-ion battery, or a supercapacitor.

[0106] In one embodiment, the electrochemical cell can be an ion battery or a flow battery. Preferably, the electrochemical cell can be a lithium-ion battery, a magnesium-ion battery, a sodium-ion battery, an aluminum-ion battery, or a redox flow battery.

[0107] The electrochemical cell can be prepared using the electrodes described herein according to known methods. For example, a typical battery is made from a suitable material for containing an electrolyte such as aluminum or steel, usually not plastic, in any suitable shape, a battery case of a standard or other shape, battery terminals of a typical configuration, a positive electrode, a negative electrode, a separator for separating the positive electrode from the negative electrode, and an electrolyte.

[0108] The electrode includes a current collector. At least one of the positive electrode and / or the negative electrode includes an electrode layer on the current collector, which is prepared using the electrode slurry composition described herein.

[0109] Ion batteries such as lithium-ion batteries can be constructed under ambient conditions using at least one electrode prepared by the process described herein. For example, a first electrode including an electrode layer on the surface of a current collector is disposed in a body (e.g., a plastic cell) with the electrode layer facing inward. A glass microfiber filter is cut to size and then placed on top of the first electrode to function as a separator. In the case of a small battery, before a second electrode including an electrode layer on the surface of a current collector is disposed in the cell such that the electrode layer faces the inside of the cell, about 0.1 mL to about 1 mL of a suitable electrolyte is added on top of the glass microfiber. The components are fixed and the cell is closed, for example, by closing and screwing the cell.

[0110] Typically, the battery is in the form of a single cell, although multiple cells are possible. The cell can be in plate or spiral form, or any other form. The positive and negative electrodes are electrically connected to the battery terminals.

[0111] The electrolyte can be any suitable electrolyte known to those skilled in the art and can be selected according to the type of electrochemical cell being developed. In one embodiment, the electrolyte comprises or consists of the microemulsion described herein. Microemulsion electrolytes are also disclosed in PCT / NZ2019 / 050164, the contents of which are incorporated by reference. Alternatively, the electrolyte can include water, an organic solvent, or a mixture thereof. In one embodiment, the electrolyte can include water or one or more solvents selected from ether, ester, carbonate, and acetal. In one example, one or more electrolyte solvents are selected from 1,2-dimethoxyethane, diglyme, triglyme, tetraglyme, ethylene carbonate, propylene carbonate, dimethyl carbonate, tetrahydrofuran, acetonitrile, and dioxolane, or a mixture thereof.

[0112] In one aspect, there is provided the use of the electrode slurry composition described herein when preparing an electrode for an electrochemical cell. In another aspect, there is provided the electrode slurry composition described herein for use in preparing an electrochemical cell.

[0113] This application claims priority from AU2022 / 902023, filed on 20 July 2022, the entire contents of which are incorporated herein by reference.

Examples

[0114] The present disclosure is further described by the following examples. It should be understood that the following description is for the purpose of describing specific embodiments only and is not intended to be limiting with respect to the above description.

[0115] Example 1: Microemulsion Microemulsion samples were prepared according to the following method. Each microemulsion sample contained an aqueous component and a water-immiscible component, optionally a co-solvent, optionally a surfactant, and / or optionally a co-surfactant. The components of each microemulsion sample are shown in Table 1.

[0116] The surfactant was weighed in an Erlenmeyer flask to which the water-immiscible component and co-surfactant were added. The mixture was stirred thoroughly to form a homogeneous slurry, and then the aqueous component was added. The mixture was turbid, but ultrasonic treatment or stirring in an ultrasonic bath resulted in the formation of a transparent microemulsion.

[0117] ME2 and ME2i were prepared according to the method described in Menger, F.M. & Elrington, A.R. “Organic reactivity in microemulsion systems” J. Am. Chem. Soc. 113, 9621 - 9624 (1991). The preparation method of ME2i is based on this disclosure. ME4 was prepared according to the method described in Mukherjee, K., Mukherjee, D.C. & Moulik, S.P. “Thermodynamics of Microemulsion Formation” J. Colloid Interface Sci. 187, 327 - 333 (1997). ME14a and ME14b were prepared according to the method described in Gorel, F. “Assessment of agar gel loaded with microemulsion for the cleaning of porous surfaces” CeROArt Conserv. Expo. Restaur. D’Objets D’Art (2010).

[0118] For the microemulsion with dissolved salts, the required amount of salt was weighed and added to the prepared microemulsion. [Table 1]

[0119] Example 2: Preparation of Electrode Slurry First, 300 mg of the dry slurry components were weighed and added to a dry sample vial. Then, the microemulsion was added to the same vial together with a magnetic stir bar. The resulting slurry was stirred vigorously until the desired consistency was reached and all materials were well dispersed. This was all done under ambient conditions. The % weight / weight of the electrode active material, conductive carbon, and binder that make up a total of 300 mg of the dry slurry components, as well as the mL volume of the microemulsion used to prepare the slurry, are summarized in Tables 2 - 5.

[0120] Example 3: Fabrication of Electrodes Next, the slurry is coated onto the graphite foil with a wet film thickness of 200 microns using a blade coater (MSK-AFA-HC100, MTICorp.). This is done with the aid of a mask. Then, the coated film is placed in an extraction oven (UT20P, Heraeus Instruments) at 80 °C for 2 hours and then in a vacuum oven (AI, PRDC3000, MTICorp.) at 180 °C for 12 hours. Next, electrodes of appropriate size are cut from a larger sheet and weighed to confirm the mass of the electrode slurry on the electrodes. These electrodes are then stored until needed or used immediately.

[0121] Example 4: Fabrication of Test Cells All the prepared cells were of the Swagelok type. First, the electrodes were placed on the glassy carbon current collector inside the cell casing with the active material facing the inside of the cell. Then, one or two glass microfiber (Whatman, GF-D) separators cut to size were placed on top of the first electrode inside the cell casing. Then, an appropriate electrolyte of usually 1 - 2 ml was added. Then, the final electrode was placed on top of the glass separator with the active material facing the inside of the cell. Then, the second current collector was placed on top of the second electrode, and the complete cell was compressed to ensure good contact and sealed.

[0122] Example 5: Performance of Electrodes The assembled cells were attached to a battery analyzer (Neware BTS4000 Series 5V 12A) capable of performing "galvanostat charge-discharge" experiments. The positive lead was attached to the positive electrode and the negative lead to the negative electrode. The cells were cycled 10 times at 500 milliamperes per gram of electrode material (MW1, MW2) and 100 milliamperes per gram of electrode material (MW3). Then, the results were analyzed for suitable performance. The performance of the test cells containing the fabricated electrodes is summarized in Tables 2 - 5. [Table 2] [Table 3]

Table 4-1

Table 4-2

Table 5-1

Table 5-2

[0123] Referring to FIGS. 1 and 2, the voltage vs. time graph demonstrates that the test cell containing the fabricated electrodes is stable and can be repeatedly charged to a voltage of 2.5V without visible signs of degradation, and would be observed as long, irregular plateaus at or near the maximum voltage if present. The absence of visible degradation emphasizes the stability of the fabricated electrodes. Additionally, the time taken for the charge-discharge cycles is constant over the test period, which also emphasizes the stability of the electrodes. Low-quality electrodes degrade, their capacity rapidly decreases, and the cycles become shorter over time.

Claims

1. An electrode slurry composition comprising: an electrode active material; a binder; an aqueous phase, a water-immiscible phase, and a microemulsion containing an amphiphilic substance, wherein the electrode active material and the binder are incorporated within the microemulsion.

2. The electrode slurry composition according to claim 1, wherein the electrode slurry composition further comprises a conductive material.

3. The electrode slurry composition according to claim 1 or 2, wherein the microemulsion substantially does not contain N-methyl-2-pyrrolidone (NMP).

4. The electrode slurry composition according to any one of claims 1 to 3, wherein the electrode slurry has a solids content (% weight / weight) of about 1 to about 90, about 1 to about 50, or about 1 to about 10 based on the total weight of the slurry.

5. The electrode slurry composition according to any one of claims 1 to 4, wherein the microemulsion is an oil-in-water (O / W) type microemulsion, a water-in-oil (W / O) type microemulsion, or a bicontinuous microemulsion.

6. The electrode slurry composition according to any one of claims 1 to 5, wherein the aqueous phase is water.

7. The electrode slurry composition according to any one of claims 1 to 6, wherein the water-immiscible phase contains an organic solvent.

8. The electrode slurry composition according to any one of claims 1 to 7, wherein the organic solvent is selected from the group consisting of an aliphatic solvent, an aromatic solvent, a halogenated solvent, a substantially water-immiscible ketone solvent, a substantially water-immiscible ether solvent, a substantially water-immiscible ester solvent, or a combination thereof.

9. The electrode slurry composition according to any one of claims 1 to 8, wherein the organic solvent is selected from the group consisting of hexane, cyclohexane, petroleum ether, benzene, toluene, p-xylene, 1,2-dichlorobenzene, dichloromethane, chloroform, dichloroethane, ethyl acetate, and diethyl ether, or a combination thereof.

10. The electrode slurry composition according to any one of claims 1 to 9, wherein the water-immiscible phase and the water-miscible phase have a boiling point difference of about 1°C to about 100°C.

11. The electrode slurry composition according to claim 10, wherein the amphiphilic substance is a surfactant or a co-solvent, or a mixture thereof.

12. The electrode slurry composition according to any one of claims 1 to 11, wherein the surfactant is a cationic surfactant, an anionic surfactant, an amphoteric ion surfactant, or a nonionic surfactant.

13. The electrode slurry composition according to any one of claims 1 to 12, wherein the surfactant is selected from the group consisting of Triton X-100, cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride (CTAC), cetylpyridinium chloride (CPC), benzalkonium chloride, benzetonium chloride, sodium dodecyl sulfate (SDS), and sodium lauryl ether sulfate (SLES).

14. The electrode slurry composition according to claim 13, wherein the co-solvent is an alcohol, an amine, or a short-chain carboxylic acid.

15. The electrode slurry composition according to claim 13 or 14, wherein the co-solvent is selected from the group consisting of ethanol, propanol, butanol, and pentanol.

16. The electrode slurry composition according to any one of claims 1 to 15, wherein the microemulsion preferably further contains a dissolved salt selected from the group consisting of lithium salts, sodium salts, potassium salts, magnesium salts, calcium salts, and aluminum salts.

17. The electrode slurry composition according to any one of claims 1 to 16, wherein the amount (% weight / weight) of the electrode active material in the electrode slurry composition is about 1 to about 90, about 1 to about 50, about 1 to about 20, or about 1 to about 10 based on the total weight of the slurry.

18. The electrode slurry composition according to any one of claims 1 to 17, wherein the electrode active material includes a positive electrode material (for example, a cathode material).

19. The electrode slurry composition according to any one of claims 1 to 18, wherein the electrode active material includes a negative electrode material (for example, an anode material).

20. The electrode slurry composition according to any one of claims 1 to 19, wherein the electrode active material is selected from the group consisting of transition metal oxides or mixed metal oxides, transition metal salts, vanadates, elements, main group nitrides, main group oxides, perylene and other organic substances, Prussian blue, its analogs, and carbon-based materials.

21. The amount (% weight / weight) of the binder in the electrode slurry composition is about 0.1 to about 30, about 0.1 to about 20, about 0.1 to about 10, or about 0.1 to about 5 based on the total weight of the electrode slurry composition. The electrode slurry composition according to any one of claims 1 to 20.

22. The electrode slurry composition according to any one of claims 1 to 21, wherein the binder is dissolved in the aqueous phase or the water-immiscible phase.

23. The electrode slurry composition according to any one of claims 1 to 22, wherein the binder is selected from the group consisting of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene butadiene rubber, or a mixture of styrene butadiene rubber and carboxymethyl cellulose, or a combination thereof.

24. The amount (% weight / weight) of the conductive material in the electrode slurry is about 0.1 to about 30, about 0.1 to about 10, or about 0.1 to about 5 based on the total weight of the electrode slurry composition. The electrode slurry composition according to any one of claims 1 to 23.

25. The electrode slurry composition according to any one of claims 2 to 24, wherein the conductive material is a carbon-based conductive material.

26. The electrode slurry composition according to claim 25, wherein the carbon-based conductive material is carbon black or a derivative thereof, or graphene, or a combination thereof.

27. A process for preparing the electrode slurry composition according to any one of claims 1 to 26, comprising mixing the microemulsion, the electrode active material, the binder, and, if present, the conductive agent under conditions effective to form the electrode slurry composition.

28. The process for preparing the electrode slurry composition according to claim 27, wherein the microemulsion, the electrode active material, the binder, and, if present, the conductive agent are mixed at a temperature of about 10°C to about 50°C.

29. The process for preparing the electrode slurry composition according to claim 27 or 28, wherein the microemulsion, the electrode active material, the binder, and, if present, the conductive agent are mixed for a period effective to form a homogeneous dispersion of the electrode active material, the binder, and, if present, the conductive agent within the microemulsion.

30. A process for preparing the electrode slurry composition according to any one of claims 27 to 29, wherein the microemulsion, the electrode active material, the binder, and, if present, the conductive agent are mixed for a period of about 5 minutes to about 120 minutes.

31. A process for preparing an electrode, comprising: coating a first surface of a current collector with the electrode slurry composition according to any one of claims 1 to 26; heating the electrode slurry composition at a temperature effective to dry the electrode slurry composition and for a period effective thereto to form an electrode layer on the surface of the current collector. A process for preparing an electrode, wherein the electrode layer comprises the electrode active material, a binder, and, if present, a conductive material.

32. A process for preparing an electrode according to claim 31, wherein the electrode layer has a thickness of about 1 μm to about 1 mm, preferably about 50 μm to about 200 μm.

33. A process for preparing an electrode according to claim 31 or 32, wherein the electrode layer is substantially free of water.

34. A process for preparing an electrode according to any one of claims 31 to 33, wherein the electrode slurry composition is coated on the first surface of the current collector by transfer coating, slot die coating, doctor blading, dip coating, screen printing, spray coating, or brush coating.

35. A process for preparing an electrode according to any one of claims 31 to 34, wherein the electrode slurry composition is heated at a temperature of about 50°C to 200°C.

36. A process for preparing an electrode according to any one of claims 31 to 35, wherein the electrode slurry composition is heated for a period of about 0.1 to about 48 hours.

37. A process for preparing an electrode according to any one of claims 31 to 36, wherein the electrode layer and the current collector are compressed at a pressure effective to increase the density of the electrode layer and / or to promote contact between the surface of the current collector and the electrode layer.

38. A process for preparing an electrode according to any one of claims 31 to 37, wherein the electrode layer and the current collector are compressed at a pressure of about 0.1 MPa to about 100 MPa.

39. A process for preparing an electrode according to any one of claims 31 to 38, wherein the current collector is a metal or carbon-based current collector.

40. A process for preparing an electrode according to any one of claims 31 to 39, wherein the metal-based current collector contains aluminum or copper.

41. A process for preparing an electrode according to any one of claims 31 to 40, wherein the carbon-based current collector contains graphite or graphene.

42. A process for preparing an electrode according to any one of claims 31 to 41, wherein the current collector is in the form of a foil.

43. A process for preparing an electrode according to any one of claims 31 to 42, wherein the electrode is a positive electrode (e.g., cathode).

44. A process for preparing an electrode according to any one of claims 31 to 43, wherein the electrode is a negative electrode (e.g., anode).

45. Use of an electrode slurry composition according to any one of claims 1 to 26 in preparing an electrode for an electrochemical cell.

46. An electrochemical cell comprising a cathode, an anode, and an electrolyte, wherein the positive electrode and / or the negative electrode is prepared using the process according to any one of claims 31 to 44.

47. The electrochemical cell according to claim 46, wherein the electrochemical cell is a lithium-ion battery, a magnesium-ion battery, a sodium-ion battery, an aluminum-ion battery, or a supercapacitor.

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