Binder composition for secondary battery

Abstract

The invention discloses a binder composition which can be used in a dry electrode mixture or an electrode slurry to prepare an electrode. The binder composition includes a water-compatible copolymer and has a liquid content of less than 85% by weight based on the total weight of the binder composition. The lower liquid content binder composition improves the efficiency of transportation and storage as compared to conventional wet binder compositions. The binder compositions disclosed herein are versatile and can be successfully used in dry electrode mixtures and electrode pastes. Batteries comprising electrodes prepared using the binder compositions disclosed herein have electrochemical properties comparable to those of batteries comprising electrodes prepared by conventional wet binder compositions.

Description

[0001] This invention is a divisional application of a Chinese patent application with the application number 202180024379.8, the application date of June 10, 2021, and the invention title "Binder Composition for Secondary Batteries". Technical Field

[0002] This invention relates to the field of batteries. Specifically, this invention relates to a binder composition for electrode slurries or dry electrode mixtures that can be used in lithium-ion batteries and other metal-ion batteries. Background Art

[0003] In the past few decades, lithium-ion batteries (LIBs) have been widely used in various applications, especially in consumer electronics, due to their excellent energy density, long cycle life, and high discharge capacity. Due to the rapid development of the markets for electric vehicles (EVs) and grid energy storage, high-performance and low-cost LIBs are currently one of the most promising options for large-scale energy storage devices.

[0004] Generally, a lithium-ion battery electrode contains an electrode active material, conductive carbon, and a binder composition. The binder composition provides good electrochemical stability to the electrode layer, holds the electrode layer materials together, and adheres the electrode layer materials to the current collector. Usually, a slurry is used to form the electrode, and a solvent is used in the slurry to suspend or dissolve various electrode components for easy processing and coating. Polyvinylidene fluoride (PVDF) is one of the most commonly used binder polymers in the commercial lithium-ion battery industry, and it can be used as the binder composition by itself. However, PVDF can only be dissolved in some specific organic solvents such as N-methyl-2-pyrrolidone (NMP). Therefore, these organic solvents are used as solvents in the electrode slurry containing PVDF. However, NMP is flammable and toxic, so special treatment is required. During the drying process, an NMP recovery system must be installed to recover NMP vapor. This will incur a huge cost in the manufacturing process because a large amount of capital needs to be invested.

[0005] Considering the disadvantages of using organic solvent-based slurries to form electrodes, it has been considered to switch to water-based slurries, that is, aqueous solvents (most commonly water) are used in the slurries. Since PVDF is insoluble in water and has poor dispersibility in water, in water-based electrode slurries, a binder polymer compatible with water is used instead of PVDF. Since a large amount of aqueous solvent is required during the polymerization process, the binder composition that is most easily manufactured by conventional methods contains the polymer and a large amount of aqueous solvent.

[0006] When scaled up to industrial scale, the presence of a large amount of aqueous solvent in the binder composition poses problems for storage because even storing a normal quantity of the binder composition requires a large amount of space. In addition, in an industrial environment, the production of the binder composition and the electrodes may not be carried out at the same location, so it may be necessary to transport the finished binder composition to another facility for electrode production. In such cases, the high liquid content also makes it difficult to transfer the binder composition from one facility to another. Clearly, the presence of a large amount of aqueous solvent in the binder composition presents significant challenges to the logistics of high-efficiency electrode production.

[0007] U.S. Patent Application Publication No. US10741843 discloses a process for producing an electrode layer in which an electrode active material, conductive carbon, and dry PVDF as a binder composition are mixed and then directly calendered onto a current collector without adding any solvent. In other words, a dry electrode mixture is used to produce the electrode layer, but the water-incompatible polymer PVDF must be used. PVDF is water-incompatible, making it easy to be in a dry state, which helps to manufacture the dry electrode mixture. This makes PVDF particularly suitable for the production of dry electrode mixtures and can explain why dry PVDF is chosen to produce the dry electrode layer in this patent.

[0008] On the other hand, polymers that are compatible with water are more difficult to be in a dry state. It is quite challenging to separate and dry a water-compatible polymer to form a substantially liquid-free binder composition because some water-compatible polymers undergo irreversible morphological changes after drying. That is, even when re-wetted, these polymers may not return to their pre-dried morphology, resulting in a permanent deterioration of their binder properties once they are dried. In addition, for some binder compositions containing water-compatible polymers, it may be difficult to reduce the liquid content of the binder composition, even if it is not completely dry, because the polymer has a high affinity for the aqueous solvent and is not easily separated from it.

[0009] However, the inventors of the present invention have conducted in-depth research on this subject and found that, as disclosed herein, a water-compatible binder composition with a low liquid content (even substantially free of residual liquid) can be simply produced by treating a wet binder composition containing a water-compatible copolymer and an aqueous solvent. A battery comprising an electrode produced using the binder composition disclosed herein has electrochemical properties comparable to those of a battery comprising an electrode produced using a conventional wet binder composition. Therefore, one object of the present invention is to provide a binder composition comprising a water-compatible copolymer, having a low liquid content and capable of maintaining binder properties comparable to those of a conventional wet binder composition. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a flowchart showing an overview of various aspects disclosed herein. SUMMARY OF THE INVENTION

[0011] The above needs are met by various aspects and embodiments disclosed herein. In one aspect, provided herein is a binder composition that can be used in a dry electrode mixture or an electrode slurry to produce an electrode, wherein the binder composition comprises a copolymer compatible with water, and based on the total weight of the binder composition, the liquid content of the binder composition is less than 85% by weight. In another aspect, various dry electrode mixtures and electrode slurries using such binder compositions are disclosed. Despite its low liquid content, the binder composition disclosed herein can maintain binder properties comparable to those of conventional wet binder compositions. In addition, a battery comprising an electrode produced using the binder composition disclosed herein has electrochemical properties comparable to those of a battery comprising an electrode produced by a wet binder composition. DETAILED DESCRIPTION

[0012] In one aspect, provided herein is a binder composition that can be used in a dry electrode mixture or an electrode slurry to produce an electrode, wherein the binder composition comprises a copolymer compatible with water, and the binder composition has a lower liquid content compared to a conventional wet binder composition. In another aspect, various dry electrode mixtures and electrode slurries using such binder compositions are disclosed. In yet another aspect, electrodes prepared using the dry electrode mixture and the electrode slurry are disclosed.

[0013] The term "electrode" refers to a "cathode" or an "anode". In some embodiments, the electrode comprises a current collector and an electrode layer.

[0014] The term "positive electrode" can be used interchangeably with "cathode". Similarly, the term "negative electrode" can be used interchangeably with "anode".

[0015] The term "current collector" refers to any conductive substrate that contacts the electrode layer and can conduct current to the electrode during discharge or charging of a secondary battery. Some non-limiting examples of current collectors include a single conductive metal layer or substrate and a single conductive metal layer or substrate coated with a conductive coating (such as a carbon black-based coating). The conductive metal layer or substrate can be in the form of a foil or a porous body having a three-dimensional network structure, and can be a polymer or a metal material or a metallized polymer. In some embodiments, the three-dimensional porous current collector is coated with a conformal carbon layer.

[0016] The term "electrode layer" refers to a layer that contacts a current collector and contains an electrochemically active material. In some embodiments, the electrode layer is made by applying a coating on the current collector. In some embodiments, the electrode layer is located on the surface of the current collector. In other embodiments, a three-dimensional porous current collector is covered with a conformal electrode layer.

[0017] The term "polymer" refers to a polymeric compound prepared by polymerizing monomers, whether the monomers are of the same or different types. The general term "polymer" includes the terms "homopolymer" and "copolymer".

[0018] The term "homopolymer" refers to a polymer prepared by polymerizing monomers of the same type.

[0019] The term "copolymer" refers to a polymer prepared by polymerizing two or more different types of monomers. In some embodiments, the copolymer is a random copolymer, periodic copolymer, statistical copolymer, alternating copolymer, block copolymer, stereoblock copolymer, gradient copolymer, graft copolymer, star copolymer, brush copolymer, comb copolymer, or a combination thereof.

[0020] The term "water-compatible" when describing a compound, a mixture of compounds, or a polymer means that the compound, the mixture of compounds, or the polymer can be well dispersed in water to form a solution or a colloid.

[0021] The term "binder composition" refers to a compound, a mixture of compounds, or a polymer used to fix materials in place and adhere the materials to a substrate. In some embodiments, the binder composition is used to fix electrode components in place and adhere them to a conductive metal part to form an electrode. In some embodiments, the binder composition contains a polymer. Such a polymer can be referred to as a "binder polymer". In some embodiments, the binder composition contains a polymer that is a copolymer. Such a copolymer can be referred to as a "binder copolymer". In some embodiments, the binder composition contains a liquid, where the liquid is an aqueous solvent. In some embodiments, the binder composition is substantially free of liquid. In other embodiments, the binder composition does not contain liquid.

[0022] For a mixture, the term "dry" means that the mixture is substantially free of liquid, or contains no liquid. For a mixture, the term "substantially free of liquid" means that the liquid content of the mixture is very low. In certain embodiments, "substantially free of liquid" means that, based on the total weight of the mixture, the liquid content in the mixture is less than 1%, less than 0.8%, less than 0.6%, less than 0.5%, less than 0.4%, less than 0.3%, less than 0.2%, less than 0.15%, less than 0.1%, less than 0.05%, less than 0.03%, less than 0.02%, less than 0.015%, less than 0.01%, less than 0.1%, less than 0.075%, less than 0.05%, less than 0.025%, less than 0.02%, less than 0.015%, less than 0.01%, less than 0.0075%, less than 0.005%, less than 0.0025%, less than 0.002%, less than 0.0015% or less than 0.001% by weight.

[0023] The term "conductive agent" refers to a material having good electrical conductivity. Thus, when forming an electrode, a conductive agent is often mixed with an electrode active material to improve the electrical conductivity of the electrode. In some embodiments, the conductive agent is chemically active. In some embodiments, the conductive agent is chemically inert.

[0024] The term "dry electrode mixture" refers to a mixture of materials that can be used to form an electrode layer, wherein the material mixture is substantially free of liquid, or contains no liquid. In some embodiments, the dry electrode mixture contains an electrode active material and a binder composition. In some embodiments, the dry electrode mixture further contains a conductive agent.

[0025] The term "electrode slurry" refers to a mixture of materials that can be used to form an electrode layer, wherein the mixture contains a liquid solvent. In some embodiments, the electrode slurry contains an electrode active material and a binder composition. In some embodiments, the electrode slurry further contains a conductive agent.

[0026] The term "particle size D50" refers to the volume-based cumulative 50% size (D50), which is the particle size at the 50% point on the cumulative curve when the cumulative curve is plotted from a volume-based particle size distribution and the total volume is 100% (i.e., the particle diameter at the 50th percentile (median) of the particle volume). Further, with respect to the electrode active material of the present invention, the particle size D50 refers to the volume average particle size of secondary particles formed by the mutual aggregation of primary particles, and in the case where the particles consist only of primary particles, it refers to the volume average particle size of the primary particles.

[0027] As used herein, the term "unsaturated" refers to a moiety having one or more carbon-carbon double or triple bonds.

[0028] The term "alkyl" or "alkyl group" refers to a monovalent group having the general formula C n H 2n+1 which is derived by removing one hydrogen atom from a saturated unbranched or branched aliphatic hydrocarbon, where n is an integer. Some examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, 2-methyl-1-propyl, 2-methyl-2-propyl, 2-methyl-1-butyl, 3-methyl-1-butyl, 2-methyl-3-butyl, 2,2-dimethyl-1-propyl, 2-methyl-1-pentyl, 3-methyl-1-pentyl, 4-methyl-1-pentyl, 2-methyl-2-pentyl, 3-methyl-2-pentyl, 4-methyl-2-pentyl, 2,2-dimethyl-1-butyl, 3,3-dimethyl-1-butyl, 2-ethyl-1-butyl, butyl, isobutyl, tert-butyl, pentyl, isopentyl, neopentyl, hexyl, heptyl, and octyl. Longer alkyl groups include nonyl and decyl groups. The alkyl group can be unsubstituted or substituted with one or more suitable substituents. In addition, the alkyl group can be branched or unbranched.

[0029] The term "alkenyl" refers to a monovalent group derived by removing one hydrogen atom from an unsaturated aliphatic hydrocarbon having at least one carbon-carbon double bond, which can be branched or unbranched. Non-limiting examples of alkenyl include vinyl, 1-propenyl, 2-propenyl, isobutenyl, and butadienyl. Similarly, the term "alkynyl" refers to a monovalent group derived by removing one hydrogen atom from an unsaturated aliphatic hydrocarbon having at least one carbon-carbon triple bond, which can be branched or unbranched. Non-limiting examples of alkynyl include ethynyl, 3-methyl-1-pentyn-3-yl (HC≡C-C(CH3)(C2H5)-), and butadiynyl.

[0030] The term "alkylene" refers to a saturated divalent hydrocarbon group derived by removing two hydrogen atoms from a straight-chain or branched saturated hydrocarbon. Examples of alkylene groups include methylene (-CH2-), ethylene (-CH2CH2-), isopropylidene (-CH(CH3)CH2-), etc. The alkylene group can optionally be substituted with one or more substituents described herein.

[0031] The term "cycloalkyl" or "cycloalkyl group" refers to a saturated or unsaturated cyclic non-aromatic hydrocarbon group having a single ring or multiple fused rings. Examples of cycloalkyl groups include, but are not limited to, cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cycloheptyl; cycloalkenyl groups such as cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, and cycloheptenyl; and cyclic terpenes and bicyclic terpenes. The cycloalkyl group can be unsubstituted or substituted with one or two suitable substituents.

[0032] The term "alkoxy" refers to an alkyl group attached to the main carbon chain through an oxygen atom. Some non-limiting examples of alkoxy groups include methoxy, ethoxy, propoxy, butoxy, etc. The alkoxy group can be substituted or unsubstituted, where the substituent can be, but is not limited to, deuterium, hydroxyl, amino, halogen, cyano, alkoxy, alkyl, alkenyl, alkynyl, mercapto, nitro, etc.

[0033] The term "aryl" or "aryl group" refers to an organic group derived by removing one hydrogen atom from a monocyclic or polycyclic aromatic hydrocarbon. Non-limiting examples of aryl groups include phenyl, naphthyl, benzyl, tolanyl, sexiphenyl, phenanthrenyl, anthracenyl, coronenyl, and tolanylphenyl. The aryl group can be unsubstituted or substituted with one or more suitable substituents.

[0034] The term "aliphatic" refers to a non-aromatic hydrocarbon or a group derived therefrom. Non-limiting examples of aliphatic compounds include alkanes, alkenes, alkynes, alkyl, alkenyl, alkynyl, alkylene groups, alkenylene groups, or alkynylene groups.

[0035] The term "aromatic" refers to a group containing an aromatic hydrocarbon ring, which optionally includes heteroatoms or substituents. Examples of such groups include, but are not limited to, phenyl, tolyl, biphenyl, o-terphenyl, m-terphenyl, p-terphenyl, naphthyl, anthryl, phenanthryl, pyrenyl, triphenylenyl, and their derivatives.

[0036] The term "substituted" refers to a compound or chemical moiety in which at least one hydrogen atom is replaced by a second chemical moiety. This second chemical moiety is referred to as a "substituent". Examples of substituents include, but are not limited to, halogen; alkyl; heteroalkyl; alkenyl; alkynyl; aryl; heteroaryl; hydroxy; alkoxy; amino; nitro; mercapto; thioether; imino; cyano; amido; phosphonato; phosphinato; carboxy; thiocarbonyl; sulfonyl; sulfonamide; acyl; formyl; acyloxy; alkoxycarbonyl; carbonyl; haloalkyl (e.g., trifluoromethyl); carbocyclic cycloalkyl, which may be monocyclic or fused or unfused polycyclic (e.g., cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl); heterocycloalkyl, which may be monocyclic or fused or unfused polycyclic (e.g., pyrrolidinyl, piperidinyl, piperazinyl, morpholinyl or thiazinyl); monocyclic or fused or unfused polycyclic aryl, which may be carbocyclic or heterocyclic (e.g., phenyl, naphthyl, pyrrolyl, indolyl, furyl, thiophenyl, imidazolyl, oxazolyl, isoxazolyl, thiazolyl, triazolyl, tetrazolyl, pyrazolyl, pyridyl, quinolinyl, isoquinolinyl, acridinyl, pyrazinyl, pyridazinyl, pyrimidinyl, benzimidazolyl, benzothiophenyl or benzofuryl); amino (primary, secondary or tertiary); o-lower alkyl; o-aryl, aryl; aryl-lower alkyl; -CO2CH3; -CONH2; -OCH2CONH2; -NH2; -SO2NH2; -OCHF2; -CF3; -OCF3; -NH(alkyl); -N(alkyl)2; -NH(aryl); -N(alkyl)(aryl); -N(aryl)2; -CHO; -CO(alkyl); -CO(aryl); -CO2(alkyl); and -CO2(aryl); and these moieties may also optionally be substituted by a fused ring structure or a bridging structure (e.g., -OCH2O-). These substituents may optionally be further substituted by substituents selected from these groups. Unless otherwise specified, all chemical groups disclosed herein may be substituted.

[0037] The term "halogen" or "hal" refers to F, Cl, Br or I.

[0038] The term "monomer unit" refers to the constitutional unit provided by a single monomer to the structure of a polymer.

[0039] The term "structural unit" refers to the total monomer units provided by the same monomer type in a polymer.

[0040] The "number average molecular weight" M of a polymer n is mathematically defined as: where N iis the number of polymer molecules having a specific molecular weight M i .

[0041] The "weight-average molecular weight" M of a polymer w is mathematically defined as: where N i is the number of polymer molecules having a specific molecular weight M i .

[0042] The "polydispersity index" (PDI) of a polymer refers to the ratio of the weight-average molecular weight to the number-average molecular weight of the polymer (i.e., Mw / M n ). It represents the distribution of molecular weights in a polymer sample.

[0043] The term "homogenizer" refers to a device that can be used for material homogenization. The term "homogenization" refers to the process of uniformly distributing a material throughout a mixture. Any conventional homogenizer can be used in the methods disclosed herein. Some non-limiting examples of homogenizers include stirring mixers, planetary mixers, tumblers, and mills.

[0044] The term "tumbler" refers to a device that can be used for mixing or stirring different materials to form a homogeneous mixture, where the device includes a container that rotates along a fixed axis and the container contains the materials to be stirred. In some embodiments, the tumbler does not contain an impeller. In some embodiments, the tumbler contains freely moving components such as balls or pebbles to reduce particle aggregation. The rotational speed can be expressed in units of revolutions per minute (rpm), which refers to the number of revolutions completed by a rotating body in one minute.

[0045] The term "stirring mixer" refers to a device that can be used for mixing or stirring different materials to form a homogeneous mixture, which includes one or more impellers that rotate along a fixed axis within a container. The term "planetary mixer" refers to a device that can be used for mixing or stirring different materials to form a homogeneous mixture, which includes two or more impellers that rotate along their respective axes and also continuously rotate within the container. In some embodiments, the planetary mixer includes at least one planetary paddle and at least one high-speed dispersing paddle as impellers. The rotational speed can be expressed in rpm.

[0046] The term "mill" refers to a device that can reduce the particle size of a material, which includes a mixer that can be used for mixing or stirring different materials to form a homogeneous mixture. The particle size can be reduced by wearing down the particles using various objects, including but not limited to the surface of the container, pressurized gas, and heavy spheres.

[0047] The term "applying" refers to the action of laying or spreading a substance on a surface.

[0048] The term "roll press" refers to a device that compacts a powdered material into a uniform coating by using rollers. In some embodiments, the rollers compact the powder into separate layers, which can then be pressed onto a substrate. In some embodiments, the rollers directly compact the powder onto the substrate to form a coating.

[0049] The term "molding press" refers to a device that forms a coating or pellets from a powder by using one or more molds and applying mechanical force to generate high pressure. In some embodiments, the force can be provided by a pneumatic or hydraulic piston. The term "tablet press" refers to a molding press that forms small pellets from a powder.

[0050] The term "transfer coating" refers to a process for preparing a large-area film on a rigid or flexible substrate. Instead of directly coating a slurry onto the substrate to form a coating, the slurry is first coated onto a release film, and then the release film with the coating is brought into contact with the substrate to place the coating on the substrate. The term "transfer coater" refers to a device capable of performing transfer coating.

[0051] The term "doctor blading" refers to a process for preparing a large-area film on a rigid or flexible substrate. The coating blade, also known as a "doctor blade", controls the thickness of the coating by adjusting the width of the gap between the coating blade and the substrate surface. This allows coatings of different thicknesses to be formed. The term "doctor blade coater" refers to a device capable of performing doctor blading.

[0052] The term "slot-die coating" refers to a process for preparing a large-area film on a rigid or flexible substrate. The substrate is supported on rollers and continuously fed to a nozzle, through which a slurry is continuously pumped onto the substrate to apply the slurry to the substrate. The thickness of the coating can be controlled by various methods, such as changing the flow rate of the slurry or the speed of the rollers. The term "slot-die coater" refers to a device capable of performing slot-die coating.

[0053] The term "room temperature" refers to an indoor temperature of about 18°C to about 30°C, such as 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30°C. In some embodiments, room temperature refers to a temperature of about 20°C + / - 1°C or + / - 2°C or + / - 3°C. In other embodiments, room temperature refers to a temperature of about 22°C or about 25°C.

[0054] The term "specific humidity" of a certain region refers to the mass of water vapor present in the air per unit mass in that region.

[0055] The term "solid content" refers to the amount of non-volatile material remaining after evaporation of the mixture. The term "solid portion" of a mixture refers to this non-volatile material. The term "liquid content" refers to the amount of material evaporated from the mixture. The term "liquid portion" of a mixture refers to this evaporated material. The sum of the solid content and the liquid content of a mixture is equal to the total mass of the mixture. The solid content and / or liquid content of a mixture are usually expressed as a ratio or percentage of the total mass of the mixture. When the mixture contains no liquid, the solid content of the mixture is 100% and the liquid content is 0%.

[0056] The term "peel strength" refers to the force required to separate two adhesively bonded materials (such as a current collector and an electrode layer coated on the current collector). It is a measure of the bond strength between these two materials and is usually expressed in N / cm.

[0057] The term "C-rate" refers to the charge or discharge rate of a battery whose total storage capacity is expressed in ampere-hours (Ah) or milliampere-hours (mAh). For example, a rate of 1C means using all the stored energy in one hour; 0.1C means using 10% of the energy in one hour or using all the energy in 10 hours; and 5C means using all the energy in 12 minutes.

[0058] The term "ampere-hour (Ah)" is the unit used to describe the storage capacity of a battery. For example, a battery with a capacity of 1Ah can supply a current of 1 ampere for 1 hour or a current of 0.5 ampere for 2 hours, and so on. Thus, 1 ampere-hour (Ah) is equivalent to 3,600 coulombs of charge. Similarly, the term "milliampere-hour (mAh)" is also a unit for the storage capacity of a battery and is 1 / 1,000 of an ampere-hour.

[0059] The term "capacity" is a characteristic of an electrochemical cell and refers to the total amount of electric charge that an electrochemical cell (such as a battery) can hold. Capacity is usually expressed in ampere-hours. The term "specific capacity" refers to the capacity output per unit weight of an electrochemical cell (such as a battery) and is usually expressed in Ah / kg or mAh / g.

[0060] In the following description, all numerical values disclosed herein are approximate values, regardless of whether the words "about" or "approximate" are combined. They can vary by 1%, 2%, 5% or sometimes 10% to 20%. Whenever a numerical range with a lower limit R L and an upper limit R U is disclosed, then any numerical value within that range has been specifically disclosed. Specifically, the following numerical values within that range are particularly disclosed: R = RL +k*(R U -R L ), where k is a variable ranging from 0% to 100%. Additionally, any numerical range defined by two R values determined in the above manner is also specifically disclosed.

[0061] In this specification, all cases described in the singular also include the plural cases, and vice versa.

[0062] Currently, electrodes are typically prepared by forming an electrode paste by dispersing an electrode active material, a binder composition, and a conductive agent in a solvent, and then coating the electrode paste onto a current collector and drying it.

[0063] A widely used electrode paste formulation contains PVDF as the binder composition and NMP as the solvent, but the use of NMP poses significant environmental, health, and safety risks. To reduce these risks, a vapor recovery system must be installed when using NMP, resulting in additional costs. Therefore, water-based electrode pastes containing a water-compatible binder polymer and an aqueous solvent have been proposed as a safer and more environmentally friendly alternative.

[0064] However, such water-compatible polymers can typically be in the form of a wet binder composition, which contains the polymer and a large amount of aqueous solvent derived from the polymer production process. This poses a problem for logistics because the large amount of aqueous solvent makes it difficult to store or transport any large quantity of the wet binder composition.

[0065] For polymers that are not water-compatible, such as PVDF, substantially anhydrous binder compositions are readily available. In fact, these binder compositions have been successfully used in dry electrode mixtures. However, it may be difficult to convert a wet binder composition into a dry binder composition because a water-compatible polymer may irreversibly change form upon dehydration, resulting in poor binder performance even upon rewetting. Due to the inherent affinity of a water-compatible polymer for the aqueous solvent in the binder composition, it may be challenging to reduce the liquid content of the wet binder composition by removing the aqueous solvent.

[0066] The present disclosure relates to a binder composition comprising a water-compatible copolymer, wherein the binder composition has a lower liquid content compared to conventional wet binder compositions. In some embodiments, the binder composition is produced by treating a wet binder composition comprising the copolymer and the aqueous solvent remaining from the polymerization process. In some embodiments, the treated binder composition is a dry binder composition, i.e., a binder composition that is substantially free of liquid or contains no liquid. In certain embodiments, the treated binder composition is a semi-dry binder composition, i.e., it still contains liquid, but its liquid content is less than that of the wet binder composition. The liquid portion of the semi-dry binder composition is referred to herein as its aqueous solvent. The binder composition disclosed herein has been found to have excellent binder properties.

[0067] In some embodiments, the water-compatible copolymer disclosed herein is produced by the polymerization of monomers, polymers, or monomer-polymer complexes dispersed in an aqueous medium, which is initiated by free radicals generated by a water-soluble radical initiator. Any suitable reaction conditions can be used during the polymerization process as long as the copolymer can be successfully formed.

[0068] The aqueous medium during the polymerization process serves as a solvent for the radical initiator and other chemicals required during the polymerization process. In some embodiments, the aqueous medium is water. In some embodiments, the aqueous medium is selected from the group consisting of tap water, bottled water, purified water, pure water, distilled water, deionized water, D2O, and combinations thereof.

[0069] In some embodiments, the aqueous medium is a mixture of water and minor components. In some embodiments, the volume ratio of water to the minor components is from about 51:49 to about 99:1. Any water-miscible solvent or volatile solvent can be used as the minor component of the aqueous medium. Some non-limiting examples of water-miscible solvents or volatile solvents include alcohols, lower aliphatic ketones, lower alkyl acetates, and combinations thereof.

[0070] Some non-limiting examples of alcohols include C1-C4 alcohols such as methanol, ethanol, isopropanol, n-propanol, tert-butanol, n-butanol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, ethylene glycol, propylene glycol, glycerol, and combinations thereof. Some non-limiting examples of lower aliphatic ketones include acetone, dimethyl ketone, methyl ethyl ketone (MEK), and combinations thereof. Some non-limiting examples of lower alkyl acetates include ethyl acetate (EA), isopropyl acetate, propyl acetate, butyl acetate (BA), and combinations thereof. Other non-limiting examples of water-miscible or volatile solvents include 1,4-dioxane, diethyl ether, methyl tert-butyl ether, cyclopentyl methyl ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran, acetonitrile, dimethyl sulfoxide (DMSO), sulfolane, nitromethane, propylene carbonate, ethylene carbonate, dimethyl carbonate, pyridine, acetaldehyde, formic acid, acetic acid, propionic acid, butyric acid, γ-valerolactone (GVL), furfuryl alcohol, methyl lactate, ethyl lactate, diethanolamine, dimethylacetamide (DMAc), dimethylformamide (DMF), N-methylpyrrolidone (NMP), dihydrolevoglucosenone (Cyrene TM ), N,N'-dimethylpropyleneurea (DMPU), and isosorbide dimethyl ether (DMI). In some embodiments, there are no minor components in the aqueous medium.

[0071] In some embodiments, the water-compatible copolymer comprises a structural unit (a) derived from a monomer containing an acid group, where the acid group is selected from the group consisting of carboxylic acid, sulfonic acid, sulfuric acid, phosphonic acid, phosphoric acid, nitric acid, salts of these acids, derivatives of these acids, and combinations thereof. In some embodiments, the salt of the acid comprises an alkali metal cation. Examples of alkali metals include lithium, sodium, and potassium. In some embodiments, the salt of the acid comprises an ammonium cation. In some embodiments, the acid group is specifically a combination of one or more of the above acids and one or more of the above salts of the acids.

[0072] In some embodiments, the carboxylic acid is acrylic acid, methacrylic acid, crotonic acid, 2-butylcrotonic acid, cinnamic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, 4,4-dimethylitaconic acid or a combination thereof. In certain embodiments, the carboxylic acid is 2-ethylacrylic acid, isocrotonic acid, cis-2-pentenoic acid, trans-2-pentenoic acid, angelic acid, tiglic acid, 3,3-dimethylacrylic acid, 3-propylacrylic acid, trans-2-methyl-3-ethylacrylic acid, cis-2-methyl-3-ethylacrylic acid, 3-isopropylacrylic acid, trans-3-methyl-3-ethylacrylic acid, cis-3-methyl-3-ethylacrylic acid, 2-isopropylacrylic acid, trimethylacrylic acid, 2-methyl-3,3-diethylacrylic acid, 3-butylacrylic acid, 2-butylacrylic acid, 2-pentylacrylic acid, 2-methyl-2-hexenoic acid, trans-3-methyl-2-hexenoic acid, 3-methyl-3-propylacrylic acid, 2-ethyl-3-propylacrylic acid, 2,3-diethylacrylic acid, 3,3-diethylacrylic acid, 3-methyl-3-hexylacrylic acid, 3-methyl-3-tert-butylacrylic acid, 2-methyl-3-pentylacrylic acid, 3-methyl-3-pentylacrylic acid, 4-methyl-2-hexenoic acid, 4-ethyl-2-hexenoic acid, 3-methyl-2-ethyl-2-hexenoic acid, 3-tert-butylacrylic acid, 2,3-dimethyl-3-ethylacrylic acid, 3,3-dimethyl-2-ethylacrylic acid, 3-methyl-3-isopropylacrylic acid, 2-methyl-3-isopropylacrylic acid, trans-2-octenoic acid, cis-2-octenoic acid, trans-2-decenoic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid or a combination thereof. In some embodiments, the carboxylic acid is methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, bromomaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, difluoromaleic acid, nonyl hydrogen maleate, decyl hydrogen maleate, dodecyl hydrogen maleate, octadecyl hydrogen maleate, fluoroalkyl hydrogen maleate or a combination thereof. In some embodiments, the carboxylic acid is maleic anhydride, methylmaleic anhydride, dimethylmaleic anhydride, acrylic anhydride, methacrylic anhydride, methacrolein, methacryloyl chloride, methacryloyl fluoride, methacryloyl bromide or a combination thereof.

[0073] In some embodiments, the sulfonic acid is vinylsulfonic acid, methylvinylsulfonic acid, allylvinylsulfonic acid, allylsulfonic acid, methylallylsulfonic acid, styrenesulfonic acid, 2-sulfoethyl methacrylate, 2-methyl-2-propen-1-sulfonic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-allyloxy-2-hydroxy-1-propanesulfonic acid, or a combination thereof.

[0074] In some embodiments, the sulfuric acid is allyl hydrogen sulfate, vinyl hydrogen sulfate, 4-allylphenyl sulfate, or a combination thereof.

[0075] In some embodiments, the phosphonic acid is vinylphosphonic acid, allylphosphonic acid, vinylbenzylphosphonic acid, acrylamidealkylphosphonic acid, methacrylamidealkylphosphonic acid, acrylamidealkyldiphosphonic acid, acrylylphosphonic acid, 2-methacryloyloxyethylphosphonic acid, bis(2-methacryloyloxyethyl)phosphonic acid, ethylene 2-methacryloyloxyethylphosphonic acid, ethyl-2-methacryloyloxyethylphosphonic acid, or a combination thereof.

[0076] In some embodiments, the phosphoric acid is mono(2-acryloyloxyethyl) phosphate, mono(2-methacryloyloxyethyl) phosphate, diphenyl(2-acryloyloxyethyl) phosphate, diphenyl(2-methacryloyloxyethyl) phosphate, phenyl(2-acryloyloxyethyl) phosphate, 2-phosphoryloxyethyl methacrylate, 3-chloro-2-phosphoryloxypropyl methacrylate, phosphoryloxypoly(ethylene glycol) monomethacrylate, phosphoryloxypoly(propylene glycol) methacrylate, (meth)acryloyloxyethyl phosphate, (meth)acryloyloxypropyl phosphate, (meth)acryloyloxy-2-hydroxypropyl phosphate, (meth)acryloyloxy-3-hydroxypropyl phosphate, (meth)acryloyloxy-3-chloro-2-hydroxypropyl phosphate, allyl hydrogen phosphate, vinyl hydrogen phosphate, allyl pyrophosphate, vinyl pyrophosphate, allyl tripolyphosphate, vinyl tripolyphosphate, allyl tetrapolyphosphate, vinyl tetrapolyphosphate, allyl metaphosphate, vinyl metaphosphate, isopentenyl phosphate, isopentenyl pyrophosphate, or a combination thereof, wherein (meth)acryloyl refers to acryloyl or methacryloyl.

[0077] In some embodiments, the nitric acid is allyl hydrogen nitrate, vinyl hydrogen nitrate, or a combination thereof.

[0078] In some embodiments, based on the total molar amount of monomer units in the copolymer, the proportion of structural unit (a) in the water-compatible copolymer is about 35% to about 85%, about 35% to about 80%, about 35% to about 75%, about 35% to about 70%, about 35% to about 65%, about 35% to about 60%, about 35% to about 55%, about 40% to about 85%, about 40% to about 80%, about 40% to about 75%, about 40% to about 70%, about 40% to about 65%, about 40% to about 60%, about 45% to about 85%, about 45% to about 80%, about 45% to about 75%, about 45% to about 70%, about 45% to about 65%, about 50% to about 85%, about 50% to about 80%, about 50% to about 75%, about 50% to about 70%, about 55% to about 85%, about 55% to about 80%, about 55% to about 75%, about 60% to about 85%, about 60% to about 80%, or about 65% to about 85% by mole.

[0079] In some embodiments, based on the total molar amount of monomer units in the copolymer, the proportion of structural unit (a) in the water-compatible copolymer is about 33%, about 34%, about 35%, about 36%, about 37%, about 38%, about 39%, about 40%, about 41%, about 42%, about 43%, about 44%, about 45%, about 46%, about 47%, about 48%, about 49%, about 50%, about 51%, about 52%, about 53%, about 54%, about 55%, about 56%, about 57%, about 58%, about 59%, about 60%, about 61%, about 62%, about 63%, about 64%, about 65%, about 66%, about 67%, about 68%, about 69%, about 70%, about 71%, about 72%, about 73%, about 74%, about 75%, about 76%, about 77%, about 78%, about 79%, about 80%, about 81%, about 82%, about 83%, about 84%, or about 85% by mole.

[0080] In some embodiments, based on the total molar amount of monomer units in the copolymer, the proportion of structural unit (a) in the water-compatible copolymer is less than 85%, less than 80%, less than 75%, less than 70%, less than 65%, less than 60%, less than 55%, less than 50%, less than 45%, or less than 40% by mole. In some embodiments, based on the total molar amount of monomer units in the copolymer, the proportion of structural unit (a) in the water-compatible copolymer is greater than 30%, greater than 35%, greater than 40%, greater than 45%, greater than 50%, greater than 55%, greater than 60%, greater than 65%, greater than 70%, greater than 75%, or greater than 80% by mole.

[0081] In some embodiments, the water-compatible copolymer further comprises a structural unit (b) derived from a monomer selected from the group consisting of monomers containing an amide group, monomers containing a hydroxyl group, and combinations thereof.

[0082] In some embodiments, the monomer containing an amide group is acrylamide, methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N-n-propylmethacrylamide, N-isopropylmethacrylamide, isopropylacrylamide, N-n-butylmethacrylamide, N-isobutylmethacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N-hydroxymethylmethacrylamide, N-(methoxymethyl)methacrylamide, N-(ethoxymethyl)methacrylamide, N-(propoxymethyl)methacrylamide, N-(butoxymethyl)methacrylamide, N-(3-(dimethylamino)propyl)methacrylamide, N-(2-(dimethylamino)ethyl)methacrylamide, N,N-(dihydroxymethyl)methacrylamide, diacetonemethacrylamide, diacetoneacrylamide, methacryloylmorpholine, N-hydroxymethacrylamide, N-methoxymethacrylamide, N-methoxymethylmethacrylamide, N,N'-methylenebisacrylamide (MBA), N-hydroxymethylacrylamide, or combinations thereof.

[0083] In some embodiments, the monomer containing a hydroxyl group contains a hydroxyl group and is an acrylate or methacrylate containing a C1 to C 20 alkyl or a C5 to C 20 cycloalkyl. In some embodiments, the monomer containing a hydroxyl group is 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 5-hydroxypentyl acrylate, 6-hydroxyhexyl methacrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, 3-chloro-2-hydroxypropyl methacrylate, diethylene glycol mono(meth)acrylate, allyl alcohol, or combinations thereof.

[0084] In some embodiments, based on the total molar number of monomer units in the copolymer, the proportion of the structural unit (b) in the water-compatible copolymer is about 5% to about 35%, about 5% to about 30%, about 5% to about 25%, about 10% to about 35%, about 10% to about 30%, or about 15% to about 35% by mole.

[0085] In some embodiments, based on the total molar number of monomer units in the copolymer, the proportion of structural unit (b) in the water-compatible copolymer is about 5%, about 6%, about 7%, about 8%, about 9%, about 10%, about 11%, about 12%, about 13%, about 14%, about 15%, about 16%, about 17%, about 18%, about 19%, about 20%, about 21%, about 22%, about 23%, about 24%, about 25%, about 26%, about 27%, about 28%, about 29%, about 30%, about 31%, about 32%, about 33%, about 34% or about 35% by mole.

[0086] In some embodiments, based on the total molar number of monomer units in the copolymer, the proportion of structural unit (b) in the water-compatible copolymer is less than 35%, less than 30%, less than 25%, less than 20% or less than 15% by mole. In some embodiments, based on the total molar number of monomer units in the copolymer, the proportion of structural unit (b) in the water-compatible copolymer is greater than 5%, greater than 10%, greater than 15%, greater than 20%, greater than 25% or greater than 30% by mole.

[0087] In some embodiments, the water-compatible copolymer further comprises a structural unit (c) derived from a monomer selected from the group consisting of monomers containing a nitrile group, monomers containing an ester group, monomers containing an ether group, monomers containing an epoxy group, monomers containing a carbonyl group, fluorine-containing monomers, and combinations thereof.

[0088] In some embodiments, the monomer containing a nitrile group includes α,β-ethylenically unsaturated nitrile monomers. In some embodiments, the monomer containing a nitrile group is acrylonitrile, α-halopropionitrile, α-alkylacrylonitrile, or a combination thereof. In some embodiments, the monomer containing a nitrile group is α-chloropropionitrile, α-bromopropionitrile, α-fluoropropionitrile, methacrylonitrile, α-ethylacrylonitrile, α-isopropylacrylonitrile, α-n-hexylacrylonitrile, α-methoxyacrylonitrile, 3-methoxyacrylonitrile, 3-ethoxyacrylonitrile, α-acetoxyacrylonitrile, α-phenylacrylonitrile, α-tolylacrylonitrile, α-(methoxyphenyl)acrylonitrile, α-(chlorophenyl)acrylonitrile, α-(cyanophenyl)acrylonitrile, vinylidenecyanide, or a combination thereof.

[0089] In some embodiments, the monomer containing an ester group is a C1-C 20 alkyl acrylate, a C1-C 20An alkyl methacrylate, a cycloalkyl acrylate, or a combination thereof. In some embodiments, the monomer containing an ester group is methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, tert-butyl acrylate, amyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 3,3,5-trimethylhexyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate, or a combination thereof. In some embodiments, the monomer containing an ester group is cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, 3,3,5-trimethylcyclohexyl acrylate, or a combination thereof. In some embodiments, the monomer containing an ester group is methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, stearyl methacrylate, 2,2,2-trifluoroethyl methacrylate, phenyl methacrylate, benzyl methacrylate, or a combination thereof.

[0090] In some embodiments, the monomer containing an ether group is vinyl ether, allyl ether, allyl vinyl ether, allyl glycidyl ether, 2H-hexafluoroisopropyl allyl ether, hydroxy polyethoxy(10) allyl ether, allyl phenetole, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, or a combination thereof.

[0091] In some embodiments, the epoxy group-containing monomer is vinyl glycidyl ether, allyl glycidyl ether, allyl-2,3-epoxypropyl ether, butenyl glycidyl ether, butadiene monoepoxide, chloroprene monoepoxide, 3,4-epoxy-1-butene, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexane, 1,2-epoxy-4-vinylcyclohexane, 3,4-epoxycyclohexyl ethylene, epoxy-4-vinylcyclohexene, 1,2-epoxy-5,9-cyclododecadiene, or a combination thereof. In some embodiments, the epoxy group-containing monomer is 1,2-epoxy-5-hexene, 1,2-epoxy-9-decene, glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl 2,4-dimethylpentenoate, glycidyl 4-hexenoate, glycidyl 4-heptenoate, glycidyl 5-methyl-4-heptenoate, glycidyl sorbate, glycidyl linoleate, glycidyl oleate, glycidyl 3-butenoate, glycidyl 3-pentenoate, glycidyl 4-methyl-3-pentenoate, or a combination thereof.

[0092] In some embodiments, the carbonyl group-containing monomer is methyl vinyl ketone, ethyl vinyl ketone, acrolein, acryloyl chloride, cinnamaldehyde, E-crotonaldehyde, 2-hexenal, 2-octenal, 2-methyl-2-pentenal, 4-methyl-3-penten-2-one, 1-octen-3-one, 2-pentyl-1-buten-3-one, or a combination thereof.

[0093] In some embodiments, the fluorine-containing monomer is an acrylate or methacrylate containing a C1-C 20 alkyl group or a combination thereof, wherein the monomer contains at least one fluorine atom. In some embodiments, the fluorine-containing monomer is a perfluoroalkyl acrylate, such as perfluorododecyl acrylate, perfluorooctyl acrylate, perfluorobutyl acrylate, perfluorohexylethyl acrylate, and perfluorooctylethyl acrylate; a perfluoroalkyl methacrylate, such as perfluorododecyl methacrylate, perfluorooctyl methacrylate, perfluorobutyl methacrylate, perfluorohexylethyl methacrylate, and perfluorooctylethyl methacrylate; a perfluorooxyalkyl acrylate, such as perfluorododecyloxyethyl acrylate and perfluorodecyloxyethyl acrylate; a perfluorooxyalkyl methacrylate, such as perfluorododecyloxyethyl methacrylate and perfluorodecyloxyethyl methacrylate, or a combination thereof. In some embodiments, the fluorine-containing monomer is a C1-C 20Carboxylates of alkyl groups and fluorine atoms, wherein the carboxylates are selected from the group consisting of crotonates, malates, fumarates, itaconates, and combinations thereof. In some embodiments, the fluorinated monomer is vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, fluoroalkyl vinyl ether, perfluoroalkyl vinyl ether, hexafluoropropylene, 2,3,3,3-tetrafluoropropene, vinylidene fluoride, tetrafluoroethylene, 2-fluoroacrylate, or a combination thereof.

[0094] In some embodiments, based on the total molar number of monomer units in the copolymer, the proportion of structural unit (c) in the water-compatible copolymer is about 10% to about 85%, about 10% to about 80%, about 10% to about 75%, about 10% to about 70%, about 10% to about 65%, about 10% to about 60%, about 10% to about 55%, about 10% to about 50%, about 10% to about 45%, about 10% to about 40%, about 10% to about 35%, about 10% to about 30%, about 15% to about 85%, about 15% to about 80%, about 15% to about 75%, about 15% to about 70%, about 15% to about 65%, about 15% to about 60%, about 15% to about 55%, about 15% to about 50%, about 15% to about 45%, about 15% to about 40%, about 15% to about 35%, about 20% to about 85%, about 20% to about 80%, about 20% to about 75%, about 20% to about 70%, about 20% to about 65%, about 20% to about 60%, about 20% to about 55%, about 20% to about 50%, about 20% to about 45%, about 20% to about 40%, about 25% to about 85%, about 25% to about 80%, about 25% to about 75%, about 25% to about 70%, about 25% to about 65%, about 25% to about 60%, about 25% to about 55%, about 25% to about 50%, about 25% to about 45%, about 30% to about 85%, about 30% to about 80%, about 30% to about 75%, about 30% to about 70%, about 30% to about 65%, about 30% to about 60%, about 30% to about 55%, about 30% to about 50%, about 35% to about 85%, about 35% to about 80%, about 35% to about 75%, about 35% to about 70%, about 35% to about 65%, about 35% to about 60%, about 35% to about 55%, about 40% to about 85%, about 40% to about 80%, about 40% to about 75%, about 40% to about 70%, about 40% to about 65%, about 40% to about 60%, about 45% to about 85%, about 45% to about 80%, about 45% to about 75%, about 45% to about 70%, about 45% to about 65%, about 50% to about 85%, about 50% to about 80%, about 50% to about 75%, about 50% to about 70%, about 55% to about 85%, about 55% to about 80%, about 55% to about 75%, about 60% to about 85%, about 60% to about 80%, or about 65% to about 85% by mole.

[0095] In some embodiments, based on the total molar number of monomer units in the copolymer, the proportion of structural unit (c) in the water-compatible copolymer is about 10%, about 11%, about 12%, about 13%, about 14%, about 15%, about 16%, about 17%, about 18%, about 19%, about 20%, about 21%, about 22%, about 23%, about 24%, about 25%, about 26%, about 27%, about 28%, about 29%, about 30%, about 31%, about 32%, about 33%, about 34%, about 35%, about 36%, about 37%, about 38%, about 39%, about 40%, about 41%, about 42%, about 43%, about 44%, about 45%, about 46%, about 47%, about 48%, about 49%, about 50%, about 51%, about 52%, about 53%, about 54%, about 55%, about 56%, about 57%, about 58%, about 59%, about 60%, about 61%, about 62%, about 63%, about 64%, about 65%, about 66%, about 67%, about 68%, about 69%, about 70%, about 71%, about 72%, about 73%, about 74%, about 75%, about 76%, about 77%, about 78%, about 79%, about 80%, about 81%, about 82%, about 83%, about 84% or about 85% by mole.

[0096] In some embodiments, based on the total molar number of monomer units in the copolymer, the proportion of structural unit (c) in the water-compatible copolymer is less than 85%, less than 80%, less than 75%, less than 70%, less than 65%, less than 60%, less than 55%, less than 50%, less than 45%, less than 40%, less than 35%, less than 30%, less than 25%, less than 20% or less than 15% by mole. In some embodiments, based on the total molar number of monomer units in the copolymer, the proportion of structural unit (c) in the water-compatible copolymer is greater than 10%, greater than 15%, greater than 20%, greater than 25%, greater than 30%, greater than 35%, greater than 40%, greater than 45%, greater than 50%, greater than 55%, greater than 60%, greater than 65%, greater than 70% or greater than 75% by mole.

[0097] In other embodiments, the water-compatible copolymer further comprises a structural unit derived from an olefin. Any hydrocarbon containing at least one carbon-carbon double bond can be used as the olefin. In some embodiments, the olefin includes C2-C 20 aliphatic compounds, C8-C containing vinyl unsaturated bonds 20 aromatic or cyclic compounds, C4-C 40Dienes and their combinations. In some embodiments, the olefin is styrene, ethylene, propylene, isobutene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 3-methyl-1-butene, cyclobutene, 3-methyl-1-pentene, 4-methyl-1-pentene, 4,6-dimethyl-1-heptene, 4-vinylcyclohexene, vinylcyclohexane, norbornene, norbornadiene, ethylidene norbornene, cyclopentene, cyclohexene, dicyclopentadiene, cyclooctene, or a combination thereof. In some embodiments, the water-compatible copolymer does not contain structural units derived from olefins. In some embodiments, the water-compatible copolymer does not contain structural units derived from styrene, ethylene, propylene, isobutene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 3-methyl-1-butene, cyclobutene, 3-methyl-1-pentene, 4-methyl-1-pentene, 4,6-dimethyl-1-heptene, 4-vinylcyclohexene, vinylcyclohexane, norbornene, norbornadiene, ethylidene norbornene, cyclopentene, cyclohexene, dicyclopentadiene, or cyclooctene.

[0098] Conjugated dienes belong to olefins. In some embodiments, the conjugated diene is selected from C4-C 40 Dienes; aliphatic conjugated dienes such as 1,3-butadiene, 1,3-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 1,7-octadiene, 1,9-decadiene, isoprene, myrcene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene; substituted linear conjugated pentadienes; substituted branched conjugated hexadienes, and combinations thereof. In some embodiments, the water-compatible copolymer does not contain structural units derived from C4-C 40 Dienes; aliphatic conjugated dienes (especially 1,3-butadiene, 1,3-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 1,7-octadiene, 1,9-decadiene, isoprene, myrcene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, or 2-chloro-1,3-butadiene); substituted linear conjugated pentadienes or substituted side-chain conjugated hexadienes.

[0099] In other embodiments, the water-compatible copolymer further comprises structural units derived from monomers containing aromatic vinyl groups. In some embodiments, the monomers containing aromatic vinyl groups are styrene, α-methylstyrene, vinyltoluene, divinylbenzene, or combinations thereof. In some embodiments, the copolymer does not contain structural units derived from monomers containing aromatic vinyl groups. In some embodiments, the copolymer does not contain structural units derived from styrene, α-methylstyrene, vinyltoluene, or divinylbenzene.

[0100] Copolymers having the above structural unit ratios have excellent binder properties. In addition, these copolymers are water-compatible and can be well dispersed in aqueous solvents, making them easy to handle when used in water-based electrode slurries. In addition, a battery comprising an electrode containing the water-compatible copolymer disclosed herein has excellent capacity and electrochemical performance.

[0101] After the polymerization process, a post-reaction mixture is formed. The post-reaction mixture mainly comprises the aqueous medium used in the polymerization process and a solid portion. In some embodiments, the solid portion of the post-reaction mixture comprises the water-compatible copolymer.

[0102] In some embodiments, based on the total weight of the post-reaction mixture, the solid content of the post-reaction mixture is about 1% to about 20%, about 2% to about 20%, about 3% to about 20%, about 4% to about 20%, about 5% to about 20%, about 6% to about 20%, about 7% to about 20%, about 8% to about 20%, about 9% to about 20%, about 10% to about 20%, about 1% to about 18%, about 2% to about 18%, about 3% to about 18%, about 4% to about 18%, about 5% to about 18%, about 6% to about 18%, about 7% to about 18%, about 8% to about 18%, about 9% to about 18%, about 10% to about 18%, about 1% to about 15%, about 2% to about 15%, about 3% to about 15%, about 4% to about 15%, about 5% to about 15%, about 6% to about 15%, about 7% to about 15%, about 8% to about 15%, about 1% to about 12%, about 2% to about 12%, about 3% to about 12%, about 4% to about 12%, about 5% to about 12%, about 1% to about 10%, about 2% to about 10%, about 3% to about 10%, about 4% to about 10%, or about 5% to about 10% by weight.

[0103] In some embodiments, based on the total weight of the post-reaction mixture, the solids content of the post-reaction mixture is less than 20 wt%, less than 19 wt%, less than 18 wt%, less than 17 wt%, less than 16 wt%, less than 15 wt%, less than 14 wt%, less than 13 wt%, less than 12 wt%, less than 11 wt%, less than 10 wt%, less than 9 wt%, less than 8 wt%, less than 7 wt%, less than 6 wt% or less than 5 wt%. In some embodiments, based on the total weight of the post-reaction mixture, the solids content of the post-reaction mixture is more than 1 wt%, more than 2 wt%, more than 3 wt%, more than 4 wt%, more than 5 wt%, more than 6 wt%, more than 7 wt%, more than 8 wt%, more than 9 wt%, more than 10 wt%, more than 11 wt%, more than 12 wt%, more than 13 wt%, more than 14 wt% or more than 15 wt%.

[0104] When the weight average molecular weight of the water-compatible copolymer is within the following range, the electrode layer containing the copolymer has good adhesion strength, and the battery containing the electrode layer exhibits good cycle characteristics.

[0105] In some embodiments, the weight-average molecular weight of the water-compatible copolymer is from about 10,000 g / mol to about 1,000,000 g / mol, from about 10,000 g / mol to about 800,000 g / mol, from about 10,000 g / mol to about 500,000 g / mol, from about 10,000 g / mol to about 400,000 g / mol, from about 10,000 g / mol to about 300,000 g / mol, from about 10,000 g / mol to about 200,000 g / mol, from about 10,000 g / mol to about 180,000 g / mol, from about 10,000 g / mol to about 150,000 g / mol, from about 10,000 g / mol to about 120,000 g / mol, from about 10,000 g / mol to about 100,000 g / mol, from about 10,000 g / mol to about 80,000 g / mol, from about 10,000 g / mol to about 50,000 g / mol, from about 50,000 g / mol to about 1,000,000 g / mol, from about 50,000 g / mol to about 800,000 g / mol, from about 50,000 g / mol to about 500,000 g / mol, from about 50,000 g / mol to about 400,000 g / mol, from about 50,000 g / mol to about 300,000 g / mol, from about 50,000 g / mol to about 200,000 g / mol, from about 50,000 g / mol to about 180,000 g / mol, from about 50,000 g / mol to about 150,000 g / mol, from about 100,000 g / mol to about 1,000,000 g / mol, from about 100,000 g / mol to about 800,000 g / mol, from about 100,000 g / mol to about 500,000 g / mol, from about 100,000 g / mol to about 400,000 g / mol, from about 100,000 g / mol to about 300,000 g / mol, from about 100,000 g / mol to about 200,000 g / mol, from about 100,000 g / mol to about 180,000 g / mol, from about 100,000 g / mol to about 150,000 g / mol, from about 120,000 g / mol to about 1,000,000 g / mol, from about 120,000 g / mol to about 800,000 g / mol, from about 120,000 g / mol to about 600,000 g / mol, from about 120,000 g / mol to about 500,000 g / mol, from about 120,000 g / mol to about 400,000 g / mol, from about 120,000 g / mol to about 300,000 g / mol, from about 120,000 g / mol to about 200,000 g / mol, from about 120,from about 000 g / mol to about 190,000 g / mol, from about 120,000 g / mol to about 180,000, from about 140,000 g / mol to about 1,000,000 g / mol, from about 140,000 g / mol to about 800,000 g / mol, from about 140,000 g / mol to about 500,000 g / mol, from about 140,000 g / mol to about 400,000 g / mol, from about 140,000 g / mol to about 300,000 g / mol, from about 140,000 g / mol to about 200,000 g / mol, from about 140,000 g / mol to about 190,000 g / mol, from about 140,000 g / mol to about 180,000 g / mol, from about 150,000 g / mol to about 1,000,000 g / mol, from about 150,000 g / mol to about 800,000 g / mol, from about 150,000 g / mol to about 500,000 g / mol, from about 150,000 g / mol to about 400,000 g / mol, from about 150,000 g / mol to about 300,000 g / mol, from about 150,000 g / mol to about 200,000 g / mol, from about 150,000 g / mol to about 190,000 g / mol, from about 150,000 g / mol to about 180,000 g / mol, from about 200,000 g / mol to about 1,000,000 g / mol, from about 200,000 g / mol to about 800,000 g / mol, from about 200,000 g / mol to about 600,000 g / mol, from about 200,000 g / mol to about 500,000 g / mol, from about 200,000 g / mol to about 400,000 g / mol, from about 500,000 g / mol to about 1,000,000 g / mol, from about 500,000 g / mol to about 900,000 g / mol or from about 500,000 g / mol to about 800,000 g / mol.,

[0106] In some embodiments, the weight-average molecular weight of the water-compatible copolymer is less than 1,000,000 g / mol, less than 800,000 g / mol, less than 600,000 g / mol, less than 500,000 g / mol, less than 400,000 g / mol, less than 300,000 g / mol, less than 200,000 g / mol, less than 190,000 g / mol, less than 180,000 g / mol, less than 170,000 g / mol, less than 160,000 g / mol, less than 150,000 g / mol, less than 140,000 g / mol, less than 130,000 g / mol, less than 120,000 g / mol, less than 110,000 g / mol, less than 100,000 g / mol, less than 90,000 g / mol, less than 80,000 g / mol, less than 70,000 g / mol, less than 60,000 g / mol, or less than 50,000 g / mol. In some embodiments, the weight-average molecular weight of the water-compatible copolymer is greater than 10,000 g / mol, greater than 20,000 g / mol, greater than 30,000 g / mol, greater than 40,000 g / mol, greater than 50,000 g / mol, greater than 60,000 g / mol, greater than 70,000 g / mol, greater than 80,000 g / mol, greater than 90,000 g / mol, greater than 100,000 g / mol, greater than 110,000 g / mol, greater than 120,000 g / mol, greater than 130,000 g / mol, greater than 140,000 g / mol, greater than 150,000 g / mol, greater than 160,000 g / mol, greater than 170,000 g / mol, greater than 180,000 g / mol, greater than 190,000 g / mol, greater than 200,000 g / mol, greater than 300,000 g / mol, greater than 400,000 g / mol, greater than 500,000 g / mol, greater than 600,000 g / mol, or greater than 700,000 g / mol.

[0107] In some embodiments, the number average molecular weight of the water-compatible copolymer is from about 10,000 g / mol to about 500,000 g / mol, from about 10,000 g / mol to about 300,000 g / mol, from about 10,000 g / mol to about 200,000 g / mol, from about 10,000 g / mol to about 100,000 g / mol, from about 10,000 g / mol to about 90,000 g / mol, from about 10,000 g / mol to about 80,000 g / mol, from about 10,000 g / mol to about 70,000 g / mol, from about 10,000 g / mol to about 60,000 g / mol, from about 10,000 g / mol to about 50,000 g / mol, from about 10,000 g / mol to about 40,000 g / mol, from about 20,000 g / mol to about 500,000 g / mol, from about 20,000 g / mol to about 300,000 g / mol, from about 20,000 g / mol to about 200,000 g / mol, from about 20,000 g / mol to about 100,000 g / mol, from about 20,000 g / mol to about 90,000 g / mol, from about 20,000 g / mol to about 80,000 g / mol, from about 20,000 g / mol to about 70,000 g / mol, from about 20,000 g / mol to about 60,000 g / mol, from about 20,000 g / mol to about 50,000 g / mol, from about 30,000 g / mol to about 500,000 g / mol, from about 30,000 g / mol to about 300,000 g / mol, from about 30,000 g / mol to about 200,000 g / mol, from about 30,000 g / mol to about 100,000 g / mol, from about 30,000 g / mol to about 90,000 g / mol, from about 30,000 g / mol to about 80,000 g / mol, from about 30,000 g / mol to about 70,000 g / mol, from about 40,000 g / mol to about 500,000 g / mol, from about 40,000 g / mol to about 300,000 g / mol, from about 40,000 g / mol to about 200,000 g / mol, from about 40,000 g / mol to about 100,000 g / mol, from about 40,000 g / mol to about 90,000 g / mol, from about 40,000 g / mol to about 80,000 g / mol, from about 40,000 g / mol to about 70,000 g / mol, from about 50,000 g / mol to about 500,000 g / mol, from about 50,000 g / mol to about 300,000 g / mol, from about 50,000 g / mol to about 200,000 g / mol, from about 50,000 g / mol to about 100,000 g / mol, from about 50,000 g / mol to about 90,000 g / mol, from about 50,000 g / mol to about 80,000 g / mol, from about 60,000 g / mol to about 500,000 g / mol, from about 60,000 g / mol to about 300,000 g / mol, from about 60,000 g / mol to about 200,000 g / mol, from about 60,000 g / mol to about 150,000 g / mol, from about 60,000 g / mol to about 100,000 g / mol, from about 60,000 g / mol to about 90,000 g / mol, from about 70,000 g / mol to about 500,000 g / mol, from about 70,000 g / mol to about 300,000 g / mol, from about 70,000 g / mol to about 200,000 g / mol, from about 70,000 g / mol to about 150,000 g / mol, from about 70,000 g / mol to about 100,000 g / mol, from about 80,000 g / mol to about 500,000 g / mol, from about 80,000 g / mol to about 300,000 g / mol, from about 80,000 g / mol to about 200,000 g / mol, from about 80,000 g / mol to about 150,000 g / mol, from about 90,000 g / mol to about 500,000 g / mol, from about 90,000 g / mol to about 300,000 g / mol, from about 90,000 g / mol to about 200,000 g / mol, from about 90,000 g / mol to about 150,000 g / mol, from about 100,000 g / mol to about 500,000 g / mol, from about 100,000 g / mol to about 300,000 g / mol or from about 100,000 g / mol to about 200,000 g / mol.,

[0108] In some embodiments, the number-average molecular weight of the water-compatible copolymer is less than 500,000 g / mol, less than 400,000 g / mol, less than 300,000 g / mol, less than 200,000 g / mol, less than 150,000 g / mol, less than 100,000 g / mol, less than 90,000 g / mol, less than 80,000 g / mol, less than 70,000 g / mol, less than 60,000 g / mol, less than 50,000 g / mol, less than 45,000 g / mol or less than 40,000 g / mol. In some embodiments, the number-average molecular weight of the water-compatible copolymer is greater than 10,000 g / mol, greater than 20,000 g / mol, greater than 30,000 g / mol, greater than 40,000 g / mol, greater than 45,000 g / mol, greater than 50,000 g / mol, greater than 60,000 g / mol, greater than 70,000 g / mol, greater than 80,000 g / mol, greater than 90,000 g / mol, greater than 100,000 g / mol, greater than 150,000 g / mol, greater than 200,000 g / mol, greater than 300,000 g / mol or greater than 400,000 g / mol.

[0109] In some embodiments, the polydispersity index (PDI) of the water-compatible copolymer is from about 1 to about 20, from about 1 to about 15, from about 1 to about 10, from about 1 to about 5, from about 1 to about 4.8, from about 1 to about 4.5, from about 1 to about 4.2, from about 1 to about 4, from about 1 to about 3.8, from about 1 to about 3.5, from about 1 to about 3.2, from about 1 to about 3, from about 1.2 to about 20, from about 1.2 to about 15, from about 1.2 to about 10, from about 1.2 to about 5, from about 1.2 to about 4.8, from about 1.2 to about 4.5, from about 1.2 to about 4.2, from about 1.2 to about 4, from about 1.2 to about 3.8, from about 1.2 to about 3.6, from about 1.2 to about 3.4, from about 1.2 to about 3.2, from about 1.2 to about 3, from about 1.4 to about 20, from about 1.4 to about 15, from about 1.4 to about 10, from about 1.4 to about 5, from about 1.4 to about 4.8, from about 1.4 to about 4.5, from about 1.4 to about 4.2, from about 1.4 to about 4, from about 1.4 to about 3.8, from about 1.4 to about 3.5, from about 1.4 to about 3.2, from about 1.4 to about 3, from about 1.6 to about 20, from about 1.6 to about 15, from about 1.6 to about 10, from about 1.6 to about 5, from about 1.6 to about 4.8, from about 1.6 to about 4.5, from about 1.6 to about 4.2, from about 1.6 to about 4, from about 1.6 to about 3.8, from about 1.6 to about 3.5, from about 1.8 to about 20, from about 1.8 to about 15, from about 1.8 to about 10, from about 1.8 to about 5, from about 1.8 to about 4.8, from about 1.8 to about 4.5, from about 1.8 to about 4.2, from about 1.8 to about 4, from about 1.8 to about 3.8, from about 1.8 to about 3.5, from about 2 to about 20, from about 2 to about 15, from about 2 to about 10, from about 2 to about 5, from about 2 to about 4.8, from about 2 to about 4.5, from about 2 to about 4.2, from about 2 to about 4, from about 2 to about 3.8, from about 2 to about 3.5, from about 2.5 to about 20, from about 2.5 to about 15, from about 2.5 to about 10, from about 2.5 to about 5, from about 2.5 to about 4.8, from about 2.5 to about 4.5, from about 2.5 to about 4.2, from about 2.5 to about 4, from about 3 to about 20, from about 3 to about 15, from about 3 to about 10, from about 3 to about 5, from about 3 to about 4.8, from about 3 to about 4.6 or from about 3 to about 4.5.

[0110] In some embodiments, the polydispersity index of the water-compatible copolymer is less than 20, less than 15, less than 10, less than 5, less than 4.8, less than 4.5, less than 4.2, less than 4, less than 3.8, less than 3.5, less than 3.2, less than 3, less than 2.8, less than 2.5, less than 2.2, less than 2, less than 1.8 or less than 1.5. In some embodiments, the polydispersity index of the water-compatible copolymer is greater than 1, greater than 1.2, greater than 1.5, greater than 1.8, greater than 2, greater than 2.2, greater than 2.5, greater than 2.8, greater than 3, greater than 3.2, greater than 3.5, greater than 3.8, greater than 4, greater than 4.2, greater than 4.5, greater than 4.8, greater than 5, greater than 10 or greater than 15.

[0111] When the polydispersity index of the water-compatible copolymer is within the above range, each molecule of the copolymer has a similar weight, so the copolymer can be more evenly distributed in the dry electrode mixture or the electrode paste.

[0112] In the conventional method for preparing the water-based binder composition, the post-reaction mixture obtained after polymerization will be a wet binder composition. This wet binder composition will be the final product and will be directly used in the electrode paste. However, the wet binder composition contains a large amount of aqueous medium: in some cases, the liquid content of the wet binder composition can be more than 80% of the total weight of the wet binder composition. Although such a high liquid content enables the water-compatible copolymer to have excellent dispersibility, it makes the storage and transportation of the binder composition very inefficient. Therefore, a binder composition with a lower liquid content is preferably selected.

[0113] Therefore, in some embodiments, the post-reaction mixture is dried to remove the liquid and form a binder composition with a lower liquid content. In some embodiments, a dry binder composition is formed by drying the post-reaction mixture until it is substantially free of remaining liquid. In certain embodiments, a dry binder composition is formed by drying the post-reaction mixture until it is completely free of liquid.

[0114] In some embodiments, based on the total weight of the dry binder composition, the liquid content of the dry binder composition is less than 1%, less than 0.8%, less than 0.6%, less than 0.5%, less than 0.4%, less than 0.3%, less than 0.25%, less than 0.2%, less than 0.15%, less than 0.1%, less than 0.05%, less than 0.04%, less than 0.03%, less than 0.025%, less than 0.02%, less than 0.015%, less than 0.01%, less than 0.008%, less than 0.005%, less than 0.003%, less than 0.002% or less than 0.001% by weight.

[0115] The dryer used is not particularly limited, but the dryer should be capable of reducing the liquid content of the reaction mixture without degrading the copolymer in the mixture. In some embodiments, the dryer is a spray dryer, a freeze dryer, a tray dryer, a rotary dryer, a screw dryer, a fluidized bed dryer, a drum dryer, a vacuum dryer, or a combination thereof.

[0116] In some embodiments, the dry binder composition is in the form of particles. In some embodiments, the particle size D50 of the dry binder composition particles is from about 10 μm to about 50 μm, from about 12 μm to about 50 μm, from about 14 μm to about 50 μm, from about 16 μm to about 50 μm, from about 18 μm to about 50 μm, from about 20 μm to about 50 μm, from about 20 μm to about 48 μm, from about 20 μm to about 46 μm, from about 20 μm to about 44 μm, from about 20 μm to about 42 μm, from about 20 μm to about 40 μm, from about 22 μm to about 40 μm, from about 22 μm to about 38 μm, from about 24 μm to about 38 μm, from about 24 μm to about 36 μm, from about 26 μm to about 34 μm, from about 28 μm to about 34 μm, or from about 28 μm to about 32 μm.

[0117] In some embodiments, the particle size D50 of the dry binder composition particles is less than 50 μm, less than 48 μm, less than 46 μm, less than 44 μm, less than 42 μm, less than 40 μm, less than 38 μm, less than 36 μm, less than 34 μm, less than 32 μm, less than 30 μm, less than 28 μm, less than 26 μm, less than 24 μm, less than 22 μm, less than 20 μm, less than 18 μm, less than 16 μm, less than 14 μm, or less than 12 μm. In some embodiments, the particle size D50 of the dry binder composition particles is greater than 10 μm, greater than 12 μm, greater than 14 μm, greater than 16 μm, greater than 18 μm, greater than 20 μm, greater than 22 μm, greater than 24 μm, greater than 26 μm, greater than 28 μm, greater than 30 μm, greater than 32 μm, greater than 34 μm, greater than 36 μm, greater than 38 μm, greater than 40 μm, greater than 42 μm, greater than 44 μm, greater than 46 μm, or greater than 48 μm.

[0118] By drying the binder composition to substantially no remaining liquid, maximum storage and transportation efficiency can be achieved because the mass and volume occupied by any remaining liquid in the dry binder composition are negligible. The dry binder composition can be used to produce a dry electrode mixture or an electrode slurry, which can then be coated on a current collector to form an electrode.

[0119] In other embodiments, the binder composition is a semi-dry binder composition. In some embodiments, the semi-dry binder composition is obtained by directly drying the post-reaction mixture to a desired solid content percentage. In this case, the semi-dry binder composition will have an aqueous solvent that is the same as or derived from the aqueous medium during the polymerization process. In other embodiments, to more precisely control the liquid content of the binder composition, the dry binder composition disclosed above is partially re-wetted to obtain a semi-dry binder composition.

[0120] In some embodiments, an aqueous solvent is added to the dry binder composition to re-wet it into a semi-dry binder composition. Any aqueous solvent suitable as the aqueous medium during the polymerization process is also suitable for re-wetting the dry binder composition into a semi-dry binder composition. In some embodiments, the aqueous solvent of the dry binder composition for re-wetting and the aqueous medium during the polymerization process have the same composition. In other embodiments, the aqueous solvent of the dry binder composition for re-wetting and the aqueous medium during the polymerization process have different compositions.

[0121] In other embodiments, to re-wet the dry binder composition into a semi-dry binder composition, the dry binder composition is placed in a humid environment to absorb moisture from the humid environment. This moisture then serves as the aqueous solvent for re-wetting. In some embodiments, the binder composition is stirred while being re-wetted to ensure that all of the binder composition can be re-wetted in the humid environment. There is no particular limitation on the stirring speed when re-wetting the binder composition, but the stirring speed should be fast enough to cause all of the binder composition to be re-wetted. In other embodiments, the binder composition is not stirred when being re-wetted.

[0122] In some embodiments, the humid environment is a controlled environment. In some embodiments, the controlled environment is a glove box. In some embodiments, the controlled environment is an incubator. In some embodiments, the controlled environment is at room temperature. In other embodiments, as long as the humidity of the open environment is high enough, the humid environment can refer to the open environment.

[0123] There is no particular limitation on the humidity of the humid environment, but the specific humidity of the humid environment should be greater than the liquid content of the dry binder composition to ensure that the dry binder composition indeed absorbs moisture from the humid environment to form a semi-dry binder composition. In some embodiments, the specific humidity of the humid environment is higher than 0.1 g / kg, higher than 0.15 g / kg, higher than 0.2 g / kg, higher than 0.25 g / kg, higher than 0.5 g / kg, higher than 1 g / kg, higher than 1.5 g / kg, higher than 2 g / kg, higher than 3 g / kg, higher than 4 g / kg, higher than 5 g / kg, higher than 6 g / kg, higher than 8 g / kg, higher than 10 g / kg, higher than 12.5 g / kg, higher than 15 g / kg, higher than 20 g / kg, higher than 30 g / kg, higher than 40 g / kg, higher than 50 g / kg, higher than 75 g / kg or higher than 100 g / kg.

[0124] There is no particular limitation on the period of time for leaving the dry binder composition in the humid environment, but the period of time should be long enough to allow the dry binder composition to absorb moisture from the humid environment to form a semi-dry binder composition. In some embodiments, the period of time for leaving the dry binder composition in the humid environment is 5 minutes, 15 minutes, 30 minutes, 45 minutes, 60 minutes, 2 hours, 4 hours, 6 hours, 12 hours, 1 day, 2 days, 3 days, 1 week or 2 weeks.

[0125] In some embodiments, based on the total weight of the semi-dry binder composition, the liquid content of the semi-dry binder composition is about 1% to about 85%, about 1% to about 80%, about 1% to about 75%, about 1% to about 70%, about 1% to about 65%, about 1% to about 60%, about 1% to about 55%, about 1% to about 50%, about 1% to about 45%, about 1% to about 40%, about 1% to about 35%, about 1% to about 30%, about 1% to about 25%, about 1% to about 20%, about 10% to about 85%, about 10% to about 80%, about 10% to about 75%, about 10% to about 70%, about 10% to about 65%, about 10% to about 60%, about 10% to about 55%, about 10% to about 50%, about 10% to about 45%, about 10% to about 40%, about 10% to about 35%, about 10% to about 30%, about 10% to about 25%, about 20% to about 85%, about 20% to about 80%, about 20% to about 75%, about 20% to about 70%, about 20% to about 65%, about 20% to about 60%, about 20% to about 55%, about 20% to about 50%, about 20% to about 45%, about 20% to about 40%, about 30% to about 85%, about 30% to about 80%, about 30% to about 75%, about 30% to about 70%, about 30% to about 65%, about 30% to about 60%, about 30% to about 55%, about 30% to about 50%, about 40% to about 85%, about 40% to about 80%, about 40% to about 75%, about 40% to about 70%, about 40% to about 65% or about 40% to about 60% by weight.

[0126] In some embodiments, based on the total weight of the semi-dry binder composition, the liquid content of the semi-dry binder composition is about 1%, about 2%, about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about 9%, about 10%, about 11%, about 12%, about 13%, about 14%, about 15%, about 16%, about 17%, about 18%, about 19%, about 20%, about 21%, about 22%, about 23%, about 24%, about 25%, about 26%, about 27%, about 28%, about 29%, about 30%, about 31%, about 32%, about 33%, about 34%, about 35%, about 36%, about 37%, about 38%, about 39%, about 40%, about 41%, about 42%, about 43%, about 44%, about 45%, about 46%, about 47%, about 48%, about 49%, about 50%, about 51%, about 52%, about 53%, about 54%, about 55%, about 56%, about 57%, about 58%, about 59%, about 60%, about 61%, about 62%, about 63%, about 64%, about 65%, about 66%, about 67%, about 68%, about 69%, about 70%, about 71%, about 72%, about 73%, about 74%, about 75%, about 76%, about 77%, about 78%, about 79%, about 80%, about 81%, about 82%, about 83%, about 84% or about 85% by weight.

[0127] In some embodiments, based on the total weight of the semi-dry binder composition, the liquid content of the semi-dry binder composition is less than 85%, less than 80%, less than 75%, less than 70%, less than 65%, less than 60%, less than 55%, less than 50%, less than 45%, less than 40%, less than 35%, less than 30%, less than 25%, less than 20%, less than 15% or less than 10% by weight. In some embodiments, based on the total weight of the semi-dry binder composition, the liquid content of the semi-dry binder composition is more than 1%, more than 5%, more than 10%, more than 15%, more than 20%, more than 25%, more than 30%, more than 35%, more than 40%, more than 45%, more than 50%, more than 55%, more than 60%, more than 65%, more than 70% or more than 75% by weight.

[0128] Although the lack of liquid content in the dry binder composition helps to improve logistics efficiency, it does not necessarily mean that keeping the liquid content of the binder composition as low as possible is always the best. The aqueous solvent in the semi-dry binder composition can reduce the risk of powder explosion and reduce the effect of static electricity. The semi-dry binder composition can be used to produce an electrode paste, which can then be coated on a current collector to form an electrode.

[0129] In some embodiments, in addition to the binder composition, the dry electrode mixture or the electrode paste contains an electrode active material. Such an electrode active material can be a cathode active material or an anode active material. When the dry electrode mixture or the electrode paste contains a cathode active material, the dry electrode mixture or the electrode paste can be referred to as a cathode mixture and a cathode paste, respectively. When the dry electrode mixture or the electrode paste contains an anode active material, the dry electrode mixture or the electrode paste can be referred to as an anode mixture and an anode paste, respectively. In some embodiments, the dry electrode mixture or the electrode paste further contains a conductive agent.

[0130] Many cathode active materials are unstable in water and react with it to form unwanted impurities such as lithium hydroxide (LiOH). The presence of these impurities can lead to a reduction in the electrochemical performance of the battery. Methods have been designed to make these cathode active materials water-proof, such as coating the cathode active material to form a core-shell cathode active material. However, these methods can increase production costs and time, and even have an adverse effect on battery performance. By using a dry electrode mixture to form the electrode, deterioration of the cathode active material due to reaction with water can be prevented.

[0131] The dry electrode mixture can be prepared using the dry binder composition disclosed herein, and no solvent is added during the preparation of the dry electrode mixture. The dry electrode mixture thus contains an electrode active material and a dry binder composition, and optionally a conductive agent, but the dry electrode mixture is substantially free of or contains no any liquid.

[0132] In some embodiments, based on the total weight of the dry electrode mixture, the liquid content of the dry electrode mixture is less than 1%, less than 0.8%, less than 0.6%, less than 0.5%, less than 0.4%, less than 0.3%, less than 0.25%, less than 0.2%, less than 0.15%, less than 0.1%, less than 0.05%, less than 0.04%, less than 0.03%, less than 0.025%, less than 0.02%, less than 0.015%, less than 0.01%, less than 0.008%, less than 0.005%, less than 0.003%, less than 0.002%, or less than 0.001% by weight.

[0133] In contrast, the electrode paste contains a liquid. The electrode paste can be prepared using the dry or semi-dry binder composition disclosed herein. The liquid portion of the electrode paste consists of an aqueous solvent, such as water, at least a part of which can be derived from the aqueous solvent in the semi-dry binder composition.

[0134] Since the electrode paste contains liquid, it can be easily applied to the current collector to form an electrode without using extreme conditions such as high temperature and high pressure. This improves the safety of the coating process itself and saves the cost of taking additional safety measures during the coating process. Safety is also improved due to the reduced risk of powder explosion.

[0135] In addition, in an electrode paste with a relatively low liquid content, for example, the liquid content is less than 30% of the total weight of the paste, water is mainly embedded in the polymer chains and is not directly exposed to other electrode components in the paste. Therefore, problems caused by the presence of water in the electrode paste, such as the reaction of water with the cathode active material, can be reduced.

[0136] Therefore, in some embodiments, an electrode paste is prepared with a semi-dry binder composition, where no solvent is added during the preparation of the electrode paste. In this case, the liquid portion of the semi-dry binder composition containing an aqueous solvent is sufficient to provide the liquid portion of the electrode paste. Thus, the electrode paste will contain an electrode active material and a semi-dry binder composition, and optionally a conductive agent. In other embodiments, an electrode paste is prepared with a dry or semi-dry binder composition disclosed herein, where an additional solvent is added during the preparation of the electrode paste. Then, the electrode paste will contain an electrode active material, a dry binder composition or a semi-dry binder composition, an additional solvent, and optionally a conductive agent.

[0137] As described above, it can be seen that both the dry electrode mixture and the electrode paste have their respective advantages. Therefore, the binder compositions disclosed herein can be used as the binder composition in the dry electrode mixture or the electrode paste according to production needs.

[0138] There is no particular limitation on the method for preparing the dry electrode mixture or the electrode paste, but all the electrode components should be sufficiently mixed to form a homogenized dry electrode mixture or electrode paste; for example, this can be achieved by using a homogenizer. In some embodiments, all the materials used to produce the dry electrode mixture or the electrode paste are added to the homogenizer at one time. In other embodiments, each component of the dry electrode mixture or the electrode paste (e.g., the electrode active material, the binder composition, and optionally the conductive agent) can be added to the homogenizer in several batches, and each batch can contain more than one electrode component.

[0139] In some embodiments, when an additional solvent is added to the electrode paste, the additional solvent is an aqueous solvent. Any aqueous solvent suitable as the aqueous medium in the polymerization process and / or as the aqueous solvent for rewetting the dry binder composition into a semi-dry binder composition is also suitable as the additional solvent in the electrode paste. In some embodiments, when an additional solvent is added in the preparation of the electrode paste, the additional solvent can be added in one or more batches before, after, and / or during the homogenization of the electrode components.

[0140] In some embodiments, when an additional solvent is added to the electrode paste, the additional solvent has the same composition as the aqueous medium in the polymerization process. In some embodiments, when an additional solvent is added to the electrode paste, the additional solvent has the same composition as the aqueous solvent for rewetting the dry binder composition into a semi-dry binder composition. In some embodiments, when an additional solvent is added to the electrode paste, the additional solvent, the aqueous medium in the polymerization process, and the aqueous solvent for rewetting the dry binder composition into a semi-dry binder composition all have the same composition. In other embodiments, when an additional solvent is added to the electrode paste, two or more of the additional solvent, the aqueous medium in the polymerization process, and the aqueous solvent for rewetting the dry binder composition into a semi-dry binder composition have different compositions.

[0141] In other embodiments, the electrode paste is formed by placing the dry electrode mixture in a humid environment to absorb moisture from the humid environment. This moisture then serves as the additional solvent. When this method is used, the liquid content of the electrode paste may be relatively low compared to conventional electrode pastes. In some embodiments, the humid environment is a controlled environment. In some embodiments, the controlled environment is a glove box. In some embodiments, the controlled environment is an incubator. In some embodiments, the controlled environment is at room temperature. In other embodiments, the humid environment can refer to an open-air environment as long as the humidity of the open-air environment is high enough.

[0142] There is no particular limitation on the humidity of the humid environment, but the specific humidity of the humid environment should be greater than the liquid content of the dry electrode mixture to ensure that the dry electrode mixture will indeed absorb moisture from the humid environment to form an electrode paste. In some embodiments, the specific humidity of the humid environment is higher than 0.1 g / kg, higher than 0.15 g / kg, higher than 0.2 g / kg, higher than 0.25 g / kg, higher than 0.5 g / kg, higher than 1 g / kg, higher than 1.5 g / kg, higher than 2 g / kg, higher than 3 g / kg, higher than 4 g / kg, higher than 5 g / kg, higher than 6 g / kg, higher than 8 g / kg, higher than 10 g / kg, higher than 12.5 g / kg, higher than 15 g / kg, higher than 20 g / kg, higher than 30 g / kg, higher than 40 g / kg, higher than 50 g / kg, higher than 75 g / kg or higher than 100 g / kg.

[0143] There is no particular limitation on the period of time for leaving the dry electrode mixture in the humid environment, but the period of time should be long enough to allow the dry electrode mixture to absorb moisture from the humid environment to form an electrode paste. In some embodiments, the period of time for leaving the dry electrode mixture in the humid environment is 5 minutes, 15 minutes, 30 minutes, 45 minutes, 60 minutes, 2 hours, 4 hours, 6 hours, 12 hours, 1 day, 2 days, 3 days, 1 week or 2 weeks.

[0144] In some embodiments, the cathode active material is a cathode active material selected from the group consisting of LiCoO2, LiNiO2, LiNi x Mn y O2, LiCo x Ni y O2, Li 1+z Ni x Mn y Co 1-x-y O2 (NMC), LiNi x Co y Al z O2 (NCA), LiV2O5, LiTiS2, LiMoS2, LiMnO2, LiCrO2, LiMn2O4, Li2MnO3, LiFeO2, LiFePO4, and combinations thereof, where each x is independently from 0.1 to 0.9; each y is independently from 0 to 0.9; and each z is independently from 0 to 0.4. In some embodiments, each x, y, and z in the above general formula independently has an interval of 0.01. In other embodiments, the cathode active material is not LiCoO2, LiNiO2, LiV2O5, LiTiS2, LiMoS2, LiMnO2, LiCrO2, LiMn2O4, LiFeO2, or LiFePO4. In further embodiments, the cathode active material is not LiNi xMn y O2, Li 1+z Ni x Mn y Co 1-x-y O2, LiNi x Co y Al z O2 or LiCo x Ni y O2, where each x is independently from 0.1 to 0.9; each y is independently from 0 to 0.9; and each z is independently from 0 to 0.4. In some embodiments, the cathode active material is Li 1+x Ni a Mn b Co c Al (1-a-b-c) O2; where -0.2 ≤ x ≤ 0.2, 0 ≤ a < 1, 0 ≤ b < 1, 0 ≤ c < 1 and a + b + c ≤ 1. In some embodiments, the cathode active material has the general formula LiMPO4, where M is selected from the group consisting of Fe, Co, Ni, Mn, Al, Mg, Zn, Ti, La, Ce, Sn, Zr, Ru, Si, Ge or combinations thereof. In some embodiments, the cathode active material is selected from the group consisting of LiFePO4, LiCoPO4, LiNiPO4, LiMnPO4, LiMnFePO4, LiMn x Fe (1-x) PO4 and combinations thereof; where 0 < x < 1. In some embodiments, the cathode active material is LiNi x Mn y O4; where 0.1 ≤ x ≤ 0.9 and 0 ≤ y ≤ 2. In certain embodiments, the cathode active material is xLi2MnO3·(1 - x)LiMO2, where M is selected from the group consisting of Ni, Co, Mn and combinations thereof; and where 0 < x < 1. In some embodiments, the cathode active material is Li3V2(PO4)3 or LiVPO4F. In certain embodiments, the cathode active material has the general formula Li2MSiO4, where M is selected from the group consisting of Fe, Co, Mn, Ni and combinations thereof.

[0145] In certain embodiments, the cathode active material is doped with a dopant selected from the group consisting of Co, Cr, V, Mo, Nb, Pd, F, Na, Fe, Ni, Mn, Al, Mg, Zn, Ti, La, Ce, Sn, Zr, Ru, Si, Ge and combinations thereof. In some embodiments, the dopant is not Co, Cr, V, Mo, Nb, Pd, F, Na, Fe, Ni, Mn, Mg, Zn, Ti, La, Ce, Ru, Si or Ge. In certain embodiments, the dopant is not Al, Sn or Zr.

[0146] In some embodiments, the cathode active material comprises or is itself a core-shell composite material having a core and a shell structure. In some embodiments, the core comprises one or more lithium transition metal oxides. In some embodiments, the shell comprises one or more lithium transition metal oxides and / or one or more transition metal oxides. In some embodiments, the one or more lithium transition metal oxides are selected from the group consisting of Li 1+x Ni a Mn b Co c Al (1-a-b-c) O2, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li2MnO3, LiCrO2, Li4Ti5O 12 , LiV2O5, LiTiS2, LiMoS2, LiCo a Ni b O2, LiMn a Ni b O2, and combinations thereof, where -0.2 ≤ x ≤ 0.2, 0 ≤ a < 1, 0 ≤ b < 1, 0 ≤ c < 1, and a + b + c ≤ 1. In some embodiments, each lithium transition metal oxide is independently doped with one or more dopants selected from the group consisting of Co, Cr, V, Mo, Nb, Pd, F, Na, Fe, Ni, Mn, Al, Mg, Zn, Ti, La, Ce, Sn, Zr, Ru, Si, Ge, and combinations thereof. In some embodiments, the one or more transition metal oxides are selected from the group consisting of Fe2O3, MnO2, Al2O3, MgO, ZnO, TiO2, La2O3, CeO2, SnO2, ZrO2, RuO2, and combinations thereof.

[0147] In some embodiments, the core and the shell each comprise one or more lithium transition metal oxides. In some embodiments, the lithium transition metal oxides in the core and the shell can be the same, different, or partially different. In some embodiments, when the core or the shell comprises two or more lithium transition metal oxides, the two or more lithium transition metal oxides are uniformly distributed on the core or the shell. In certain embodiments, when the core or the shell comprises two or more lithium transition metal oxides, the two or more lithium transition metal oxides are non-uniformly distributed on the core or the shell. In some embodiments, the cathode active material is not a core-shell composite material.

[0148] In some embodiments, the thickness of the shell and the diameter of the core are each independently about 1 μm to about 45 μm, about 1 μm to about 25 μm, about 1 μm to about 15 μm, about 1 μm to about 5 μm, about 3 μm to about 15 μm, about 5 μm to about 10 μm, about 10 μm to about 35 μm, about 15 μm to about 30 μm, about 15 μm to about 25 μm, or about 20 μm to about 30 μm. In some embodiments, the diameter or thickness ratio of the core to the shell is in the range of 15:85 to 85:15, 25:75 to 75:25, 30:70 to 70:30, or 40:60 to 60:40. In some embodiments, the volume or weight ratio of the core to the shell is 95:5, 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, or 30:70.

[0149] In some embodiments, the electrode active material is an anode active material selected from the group consisting of natural graphite particles, synthetic graphite particles, hard carbon, soft carbon, mesocarbon microbeads (MCMB), Sn particles, SnO2, SnO, Li4Ti5O 12 particles, Si particles, Si-C composite particles, and combinations thereof.

[0150] In certain embodiments, the anode active material is doped with a dopant. In some embodiments, the dopant is selected from the group consisting of Fe, Ni, Mn, Al, Mg, Zn, Ti, La, Ce, Sn, Zr, Ru, and combinations thereof. In some embodiments, the dopant is B, Si, Ge, N, P, F, S, Cl, I, Se, or combinations thereof. In other embodiments, the anode active material is not doped. In some embodiments, the anode active material is not doped with Fe, Ni, Mn, Al, Mg, Zn, Ti, La, Ce, Sn, Zr, Ru, B, Si, Ge, N, P, F, S, Cl, I, or Se.

[0151] In some embodiments, the anode active material comprises or itself is a core-shell composite material having a core and a shell structure. In some embodiments, the core is selected from the group consisting of natural graphite particles, synthetic graphite particles, hard carbon, soft carbon, mesocarbon microbeads (MCMB), Sn particles, SnO2, SnO, Li4Ti5O 12 particles, Si particles, Si-C composite particles, and combinations thereof. In some embodiments, the shell is selected from the group consisting of soft carbon, hard carbon, natural graphite particles, synthetic graphite particles, mesocarbon microbeads (MCMB), Kish graphite, pyrolytic carbon, mesophase pitch, mesophase pitch-based carbon fiber, Sn particles, SnO2, SnO, Li4Ti5O 12 particles, Si particles, Si-C composite particles, and combinations thereof.

[0152] In some embodiments, the dry electrode mixture or the electrode paste may further comprise a conductive agent. The conductive agent is used to enhance the electrical conductivity of the electrode. Therefore, it may be advantageous to include a conductive agent in the dry electrode mixture or the electrode paste. Any suitable material can be used as the conductive agent. In some embodiments, the conductive agent is a carbonaceous material. Some non-limiting examples include carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fibers, carbon nanofibers, graphitized carbon flakes, carbon tubes, carbon nanotubes, activated carbon, Super P, KS6, vapor grown carbon fiber (VGCF), mesoporous carbon, and combinations thereof. In certain embodiments, the conductive agent does not comprise a carbonaceous material.

[0153] In some embodiments, the conductive agent is a conductive polymer selected from the group consisting of polypyrrole, polyaniline, polyacetylene, polyphenylene sulfide (PPS), polyphenylacetylene (PPV), poly(3,4-ethylenedioxythiophene) (PEDOT), polythiophene, and combinations thereof. In some embodiments, the conductive agent also acts as a binder composition. In some embodiments, the conductive agent is a mixture of a carbonaceous material and a conductive polymer. In other embodiments, the conductive agent does not comprise a conductive polymer.

[0154] The dry electrode mixture or the electrode paste may contain additives as needed to obtain the desired electrode properties. In certain embodiments, the additive is a conductive polymer used in addition to the conductive agent. In some embodiments, the additive is a dispersant or a surfactant to promote the homogenization of the electrode mixture or paste.

[0155] In some embodiments, based on the total weight of each of the solid portions of the dry electrode mixture or the electrode paste, the proportion of the binder copolymer in the solid portion of the dry electrode mixture or the electrode paste is by weight about 1% to about 50%, about 2% to about 50%, about 5% to about 50%, about 8% to about 50%, about 10% to about 50%, about 15% to about 50%, about 20% to about 50%, about 25% to about 50%, about 30% to about 50%, about 1% to about 40%, about 2% to about 40%, about 5% to about 40%, about 8% to about 40%, about 10% to about 40%, about 15% to about 40%, about 20% to about 40%, about 25% to about 40%, about 1% to about 30%, about 2% to about 30%, about 5% to about 30%, about 8% to about 30%, about 10% to about 30%, about 15% to about 30%, about 20% to about 30%, about 1% to about 20%, about 2% to about 20%, about 5% to about 20%, about 8% to about 20%, about 10% to about 20%, about 15% to about 20%, about 1% to about 10%, about 2% to about 10%, about 5% to about 10%, about 1% to about 5%, or about 2% to about 5%.

[0156] In some embodiments, based on the respective total weight of the solid portion of the dry electrode mixture or the electrode paste, the proportion of the binder copolymer in the solid portion of the dry electrode mixture or the electrode paste is less than 50%, less than 45%, less than 40%, less than 35%, less than 30%, less than 25%, less than 20%, less than 15%, less than 10%, less than 8% or less than 5% by weight. In some embodiments, based on the respective total weight of the solid portion of the dry electrode mixture or the electrode paste, the proportion of the binder copolymer in the solid portion of the dry electrode mixture or the electrode paste is greater than 1%, greater than 2%, greater than 5%, greater than 8%, greater than 10%, greater than 15%, greater than 20%, greater than 25%, greater than 30%, greater than 35% or greater than 40% by weight.

[0157] In some embodiments, based on the respective total weight of the solid portion of the dry electrode mixture or the electrode paste, the proportion of the conductive agent in the solid portion of the dry electrode mixture or the electrode paste is about 1% to about 20%, about 2% to about 20%, about 5% to about 20%, about 8% to about 20%, about 10% to about 20%, about 15% to about 20%, about 1% to about 10%, about 2% to about 10%, about 5% to about 10%, about 1% to about 5% or about 2% to about 5% by weight.

[0158] In some embodiments, based on the respective total weight of the solid portion of the dry electrode mixture or the electrode paste, the proportion of the conductive agent in the solid portion of the dry electrode mixture or the electrode paste is less than 20%, less than 15%, less than 10%, less than 8% or less than 5% by weight. In some embodiments, based on the respective total weight of the solid portion of the dry electrode mixture or the electrode paste, the proportion of the conductive agent in the solid portion of the dry electrode mixture or the electrode paste is more than 1%, more than 2%, more than 5%, more than 8%, more than 10% or more than 15% by weight.

[0159] In some embodiments, based on the respective total weight of the solid portion of the dry electrode mixture or the electrode paste, the proportion of the electrode active material in the solid portion of the dry electrode mixture or the electrode paste is about 40% to about 99%, about 45% to about 99%, about 50% to about 99%, about 55% to about 99%, about 60% to about 99%, about 65% to about 99%, about 70% to about 99%, about 75% to about 99%, about 80% to about 99%, about 40% to about 95%, about 45% to about 95%, about 50% to about 95%, about 55% to about 95%, about 60% to about 95%, about 65% to about 95%, about 70% to about 95%, about 75% to about 95%, about 80% to about 95%, about 40% to about 90%, about 45% to about 90%, about 50% to about 90%, about 55% to about 90%, about 60% to about 90%, about 65% to about 90%, about 70% to about 90%, about 75% to about 90%, about 80% to about 90%, about 40% to about 85%, about 45% to about 85%, about 50% to about 85%, about 55% to about 85%, about 60% to about 85%, about 65% to about 85%, about 70% to about 85%, or about 75% to about 85% by weight.

[0160] In some embodiments, based on the respective total weight of the solid portion of the dry electrode mixture or the electrode paste, the proportion of the electrode active material in the solid portion of the dry electrode mixture or the electrode paste is less than 99%, less than 95%, less than 90%, less than 85%, less than 80%, less than 75%, less than 70%, less than 65%, less than 60%, less than 55%, or less than 50% by weight. In some embodiments, based on the respective total weight of the solid portion of the dry electrode mixture or the electrode paste, the proportion of the electrode active material in the solid portion of the dry electrode mixture or the electrode paste is greater than 40%, greater than 45%, greater than 50%, greater than 55%, greater than 60%, greater than 65%, greater than 70%, greater than 75%, greater than 80%, or greater than 85% by weight.

[0161] In some embodiments, based on the total weight of the slurry, the proportion of additional solvent added to the electrode slurry is about 0% to about 60%, about 2% to about 60%, about 5% to about 60%, about 8% to about 60%, about 10% to about 60%, about 12% to about 60%, about 15% to about 60%, about 18% to about 60%, about 20% to about 60%, about 22% to about 60%, about 25% to about 60%, about 28% to about 60%, about 30% to about 60%, about 32% to about 60%, about 35% to about 60%, about 38% to about 60%, about 40% to about 60%, about 42% to about 60%, about 45% to about 60%, about 0% to about 50%, about 2% to about 50%, about 5% to about 50%, about 8% to about 50%, about 10% to about 50%, about 12% to about 50%, about 15% to about 50%, about 18% to about 50%, about 20% to about 50%, about 22% to about 50%, about 25% to about 50%, about 28% to about 50%, about 30% to about 50%, about 32% to about 50%, about 35% to about 50%, about 0% to about 40%, about 2% to about 40%, about 5% to about 40%, about 8% to about 40%, about 10% to about 40%, about 12% to about 40%, about 15% to about 40%, about 18% to about 40%, about 20% to about 40%, about 22% to about 40%, about 25% to about 40%, about 28% to about 40%, about 30% to about 40%, about 0% to about 30%, about 2% to about 30%, about 5% to about 30%, about 8% to about 30%, about 10% to about 30%, about 12% to about 30%, about 15% to about 30%, about 18% to about 30%, about 20% to about 30%, about 0% to about 20%, about 2% to about 20%, about 5% to about 20%, about 8% to about 20%, about 10% to about 20%, about 0% to about 15%, about 3% to about 15%, or about 5% to about 15% by weight.

[0162] In some embodiments, based on the total weight of the slurry, the proportion of additional solvent added to the electrode slurry is less than 60 wt%, less than 58 wt%, less than 55 wt%, less than 52 wt%, less than 50 wt%, less than 48 wt%, less than 45 wt%, less than 42 wt%, less than 40 wt%, less than 38 wt%, less than 35 wt%, less than 32 wt%, less than 30 wt%, less than 28 wt%, less than 25 wt%, less than 22 wt%, less than 20 wt%, less than 18 wt%, less than 15 wt%, less than 12 wt%, less than 10 wt%, less than 8 wt% or less than 5 wt%. In some embodiments, based on the total weight of the slurry, the proportion of additional solvent added to the electrode slurry is greater than 0 wt%, greater than 2 wt%, greater than 5 wt%, greater than 8 wt%, greater than 10 wt%, greater than 12 wt%, greater than 15 wt%, greater than 18 wt%, greater than 20 wt%, greater than 22 wt%, greater than 25 wt%, greater than 28 wt%, greater than 30 wt%, greater than 32 wt%, greater than 35 wt%, greater than 38 wt%, greater than 40 wt%, greater than 42 wt%, greater than 45 wt%, greater than 48 wt%, greater than 50 wt% or greater than 52 wt%.

[0163] In some embodiments, based on the total weight of the slurry, the liquid content of the electrode slurry is about 1% to about 60 wt%, about 3% to about 60 wt%, about 5% to about 60 wt%, about 8% to about 60 wt%, about 10% to about 60 wt%, about 12% to about 60 wt%, about 15% to about 60 wt%, about 18% to about 60 wt%, about 20% to about 60 wt%, about 23% to about 60 wt%, about 25% to about 60 wt%, about 28% to about 60 wt%, about 30% to about 60 wt%, about 33% to about 60 wt%, about 35% to about 60 wt%, about 38% to about 60 wt%, about 40% to about 60 wt%, about 43% to about 60 wt%, about 45% to about 60 wt%, about 1% to about 50 wt%, about 3% to about 50 wt%, about 5% to about 50 wt%, about 8% to about 50 wt%, about 10% to about 50 wt%, about 12% to about 50 wt%, about 15% to about 50 wt%, about 18% to about 50 wt%, about 20% to about 50 wt%, about 23% to about 50 wt%, about 25% to about 50 wt%, about 28% to about 50 wt%, about 30% to about 50 wt%, about 33% to about 50 wt%, about 35% to about 50 wt%, about 1% to about 40 wt%, about 3% to about 40 wt%, about 5% to about 40 wt%, about 8% to about 40 wt%, about 10% to about 40 wt%, about 12% to about 40 wt%, about 15% to about 40 wt%, about 18% to about 40 wt%, about 20% to about 40 wt%, about 23% to about 40 wt%, about 25% to about 40 wt%, about 1% to about 30 wt%, about 3% to about 30 wt%, about 5% to about 30 wt%, about 8% to about 30 wt%, about 10% to about 30 wt%, about 12% to about 30 wt%, about 15% to about 30 wt%, about 1% to about 20 wt%, about 3% to about 20 wt%, about 5% to about 20 wt%, about 8% to about 20 wt%, about 10% to about 20 wt%, about 1% to about 15 wt%, about 3% to about 15 wt%, about 5% to about 15 wt% or about 1% to about 10 wt%.

[0164] In some embodiments, based on the total weight of the slurry, the liquid content of the electrode slurry is less than 60 wt%, less than 58 wt%, less than 55 wt%, less than 53 wt%, less than 50 wt%, less than 48 wt%, less than 45 wt%, less than 43 wt%, less than 40 wt%, less than 38 wt%, less than 35 wt%, less than 33 wt%, less than 30 wt%, less than 28 wt%, less than 25 wt%, less than 23 wt%, less than 20 wt%, less than 18 wt%, less than 15 wt%, less than 12 wt%, less than 10 wt%, less than 8 wt% or less than 5 wt%. In some embodiments, based on the total weight of the slurry, the liquid content of the electrode slurry is greater than 1 wt%, greater than 3 wt%, greater than 5 wt%, greater than 8 wt%, greater than 10 wt%, greater than 12 wt%, greater than 15 wt%, greater than 18 wt%, greater than 20 wt%, greater than 23 wt%, greater than 25 wt%, greater than 28 wt%, greater than 30 wt%, greater than 33 wt%, greater than 35 wt%, greater than 38 wt%, greater than 40 wt%, greater than 43 wt%, greater than 45 wt%, greater than 48 wt%, greater than 50 wt%, greater than 53 wt% or greater than 55 wt%.

[0165] The homogenizer can be equipped with a temperature control system, and the temperature of the dry electrode mixture or the electrode slurry can be controlled by the temperature control system. Any homogenizer that can reduce or eliminate particle aggregation and / or promote the uniform distribution of electrode components in the dry electrode mixture or the electrode slurry can be used herein. Uniform distribution is important for preparing a battery with good electrochemical performance. In some embodiments, the homogenizer is a rotary drum, a grinder, a stirring mixer or a planetary mixer. In some embodiments, the homogenizer is grounded to reduce the influence of static electricity on the dry electrode mixture.

[0166] In some embodiments, the total homogenization time for preparing the dry electrode mixture or the electrode paste is from about 1 minute to about 24 hours, from about 5 minutes to about 24 hours, from about 10 minutes to about 24 hours, from about 15 minutes to about 24 hours, from about 30 minutes to about 24 hours, from about 60 minutes to about 24 hours, from about 2 hours to about 24 hours, from about 4 hours to about 24 hours, from about 6 hours to about 24 hours, from about 8 hours to about 24 hours, from about 10 hours to about 24 hours, from about 12 hours to about 24 hours, from about 16 hours to about 24 hours, from about 1 minute to about 16 hours, from about 5 minutes to about 16 hours, from about 10 minutes to about 16 hours, from about 15 minutes to about 16 hours, from about 30 minutes to about 16 hours, from about 60 minutes to about 16 hours, from about 2 hours to about 16 hours, from about 4 hours to about 16 hours, from about 6 hours to about 16 hours, from about 8 hours to about 16 hours, from about 10 hours to about 16 hours, from about 12 hours to about 16 hours, from about 1 minute to about 12 hours, from about 5 minutes to about 12 hours, from about 10 minutes to about 12 hours, from about 15 minutes to about 12 hours, from about 30 minutes to about 12 hours, from about 60 minutes to about 12 hours, from about 2 hours to about 12 hours, from about 4 hours to about 12 hours, from about 1 minute to about 6 hours, from about 5 minutes to about 6 hours, from about 10 minutes to about 6 hours, from about 15 minutes to about 6 hours, from about 30 minutes to about 6 hours, from about 60 minutes to about 6 hours, from about 2 hours to about 6 hours, from about 1 minute to about 2 hours, from about 5 minutes to about 2 hours, from about 10 minutes to about 2 hours, from about 15 minutes to about 2 hours, or from about 30 minutes to about 2 hours.

[0167] In some embodiments, the total homogenization time for producing the dry electrode mixture or the electrode paste is less than 24 hours, less than 16 hours, less than 12 hours, less than 10 hours, less than 8 hours, less than 6 hours, less than 4 hours, less than 2 hours, less than 60 minutes, less than 30 minutes, or less than 15 minutes. In some embodiments, the total homogenization time for producing the dry electrode mixture or the electrode paste is more than 1 minute, more than 5 minutes, more than 10 minutes, more than 15 minutes, more than 30 minutes, more than 60 minutes, more than 2 hours, more than 4 hours, more than 6 hours, more than 8 hours, more than 10 hours, more than 12 hours, or more than 16 hours.

[0168] In some embodiments, the temperature of the mixed dry electrode mixture or electrode slurry is from about 20°C to about 90°C, from about 25°C to about 90°C, from about 30°C to about 90°C, from about 35°C to about 90°C, from about 40°C to about 90°C, from about 50°C to about 90°C, from about 60°C to about 90°C, from about 70°C to about 90°C, from about 20°C to about 80°C, from about 25°C to about 80°C, from about 30°C to about 80°C, from about 35°C to about 80°C, from about 40°C to about 80°C, from about 50°C to about 80°C, from about 60°C to about 80°C, from about 20°C to about 70°C, from about 25°C to about 70°C, from about 30°C to about 70°C, from about 35°C to about 70°C, from about 40°C to about 70°C, from about 50°C to about 70°C, from about 20°C to about 60°C, from about 25°C to about 60°C, from about 30°C to about 60°C, from about 35°C to about 60°C, or from about 40°C to about 60°C.

[0169] In some embodiments, the temperature of the mixed dry electrode mixture or electrode slurry is less than 90°C, less than 80°C, less than 70°C, less than 60°C, less than 50°C, or less than 40°C. In some embodiments, the temperature of the mixed dry electrode mixture or electrode slurry is greater than 20°C, greater than 25°C, greater than 30°C, greater than 35°C, greater than 40°C, greater than 50°C, greater than 60°C, or greater than 70°C.

[0170] In certain embodiments, the rotational speed of each rotating component in the homogenizer is independently from about 100 rpm to about 3000 rpm, from about 500 rpm to about 3000 rpm, from about 1000 rpm to about 3000 rpm, from about 1500 rpm to about 3000 rpm, from about 100 rpm to about 2500 rpm, from about 500 rpm to about 2500 rpm, from about 1000 rpm to about 2500 rpm, from about 1500 rpm to about 2500 rpm, from about 100 rpm to about 2000 rpm, from about 500 rpm to about 2000 rpm, from about 1000 rpm to about 2000 rpm, from about 100 rpm to about 1500 rpm, or from about 500 rpm to about 1500 rpm.

[0171] In certain embodiments, the rotational speed of each rotating component in the homogenizer is independently less than 3000 rpm, less than 2500 rpm, less than 2000 rpm, less than 1500 rpm, or less than 1000 rpm. In certain embodiments, the rotational speed of each rotating component in the homogenizer is independently greater than 100 rpm, greater than 500 rpm, greater than 1000 rpm, greater than 1500 rpm, or greater than 2000 rpm.

[0172] After homogenization, the dry electrode mixture or electrode slurry can be used to fabricate an electrode. In some embodiments, the electrode comprises a current collector and an electrode layer formed on one or more surfaces of the current collector.

[0173] In some embodiments, after homogenizing the dry electrode mixture or the electrode slurry, the dry electrode mixture or the electrode slurry can be coated on one or both sides of the current collector to form a coated electrode film. In some embodiments, the dry electrode mixture or the electrode slurry is directly applied or calendered onto the current collector. In some embodiments, the dry electrode mixture or the electrode slurry is applied or calendered onto a release film to form a self-supporting layer. Then, the self-supporting layer is combined with the current collector and pressed to form a coated electrode film on the current collector.

[0174] In some embodiments, a press, a roller press, an extruder, or a powder coater can be used to perform the coating process of the dry electrode mixture. In some embodiments, the press is a tablet press. In some embodiments, the extruder is a granulator or a screw extruder. In certain embodiments, a knife coater, a slot die coater, a transfer coater, a roll coater, a reverse coater, or a gravure coater can be used to perform the coating process of the electrode slurry.

[0175] The current collector is used to collect electrons generated by the electrochemical reaction of the cathode active material or to provide electrons required for the electrochemical reaction. In some embodiments, the current collector can be in the form of a foil, a sheet, or a film. In certain embodiments, the current collector is stainless steel, titanium, nickel, aluminum, copper, or an alloy thereof; or a conductive resin. In certain embodiments, the current collector has a two-layer structure including an outer layer and an inner layer, where the outer layer includes a conductive material and the inner layer includes an insulating material or another conductive material; for example, aluminum covered with a conductive resin layer or a polymer insulating material coated with an aluminum film. In some embodiments, the current collector has a three-layer structure including an outer layer, an intermediate layer, and an inner layer, where the outer layer and the inner layer include a conductive material and the intermediate layer includes an insulating material or another conductive material; for example, a plastic substrate coated with metal films on both sides. In certain embodiments, each of the outer layer, the intermediate layer, and the inner layer is independently stainless steel, titanium, nickel, aluminum, copper, or an alloy thereof; or a conductive resin. In some embodiments, the insulating material is a polymeric material selected from the group consisting of polycarbonate, polyacrylate, polyacrylonitrile, polyester, polyamide, polystyrene, polyurethane, polyepoxy resin, poly(acrylonitrile-butadiene-styrene), polyimide, polyolefin, polyethylene, polypropylene, polyphenylene sulfide, poly(vinyl ester), polyvinyl chloride, polyether, polyphenylene ether, cellulose polymer, and combinations thereof. In certain embodiments, the current collector includes a structure with more than three layers.

[0176] In some embodiments, a conductive layer can be coated on the current collector to improve its electrical conductivity. In certain embodiments, the conductive layer comprises a material selected from the group consisting of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fibers, carbon nanofibers, graphitized carbon flakes, carbon tubes, carbon nanotubes, activated carbon, mesoporous carbon, and combinations thereof. In some embodiments, the conductive layer does not comprise carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fibers, carbon nanofibers, graphitized carbon flakes, carbon tubes, carbon nanotubes, activated carbon, or mesoporous carbon.

[0177] In some embodiments, the thickness of the conductive layer is from about 0.5 μm to about 5.0 μm. The thickness of the conductive layer affects the volume occupied by the current collector within the battery and the amount of electrode active material required, thereby affecting the capacity of the battery.

[0178] In certain embodiments, the thickness of the conductive layer on the current collector is about 0.5 μm to about 4.5 μm, about 1.0 μm to about 4.0 μm, about 1.0 μm to about 3.5 μm, about 1.0 μm to about 3.0 μm, about 1.0 μm to about 2.5 μm, about 1.0 μm to about 2.0 μm, about 1.1 μm to about 2.0 μm, about 1.2 μm to about 2.0 μm, about 1.5 μm to about 2.0 μm, about 1.8 μm to about 2.0 μm, about 1.0 μm to about 1.8 μm, about 1.2 μm to about 1.8 μm, about 1.5 μm to about 1.8 μm, about 1.0 μm to about 1.5 μm, or about 1.2 to about 1.5 μm. In some embodiments, the thickness of the conductive layer on the current collector is less than 4.5 μm, less than 4.0 μm, less than 3.5 μm, less than 3.0 μm, less than 2.5 μm, less than 2.0 μm, less than 1.8 μm, less than 1.5 μm, or less than 1.2 μm. In some embodiments, the thickness of the conductive layer on the current collector is greater than 1.0 μm, greater than 1.2 μm, greater than 1.5 μm, greater than 1.8 μm, greater than 2.0 μm, greater than 2.5 μm, greater than 3.0 μm, or greater than 3.5 μm.

[0179] The thickness of the current collector affects the volume it occupies in the battery, thereby affecting the energy density of the battery. In some embodiments, the thickness of the current collector is from about 5 μm to about 30 μm. In certain embodiments, the thickness of the current collector is about 5 μm to about 20 μm, about 5 μm to about 15 μm, about 10 μm to about 30 μm, about 10 μm to about 25 μm, or about 10 μm to about 20 μm.

[0180] In some embodiments, after a dry electrode mixture or an electrode slurry is coated onto a current collector to form a coated film, the coated film is heated and / or dried. Any device that can heat and / or dry the coated film to adhere the coated film layer to the current collector can be used herein. Some non-limiting examples of devices that can be used to heat and / or dry the coated film include batch drying ovens, conveyor belt drying ovens, and microwave drying ovens. Some non-limiting examples of conveyor belt drying ovens include conveyor belt hot air drying ovens, conveyor belt resistance drying ovens, conveyor belt induction drying ovens, and conveyor belt microwave drying ovens. When a dry electrode mixture is used to manufacture the coated film, its initial liquid content is already negligible, so drying may not be required. However, heating is still necessary or advantageous to ensure that the coated film is firmly fixed to the current collector. Even if the coated film is made of a dry electrode mixture, drying can still be performed to further reduce the liquid content of the coated film.

[0181] There are no particular restrictions on the conditions for heating and / or drying the coated film, but after the heating and / or drying process, the coated film should be firmly fixed to the current collector without deformation or peeling. Therefore, the temperature should be high enough to ensure that the heating and / or drying process can be completed within a reasonable time frame. At the same time, the temperature should be low enough to ensure that the electrode components in the coated electrode film do not deteriorate due to heat and to reduce the risk of significant temperature gradients caused by uneven heating, which may lead to electrode deformation or peeling.

[0182] In some embodiments, the temperature at which the coating film on the current collector is heated and / or dried is about 50°C to about 160°C, about 60°C to about 160°C, about 70°C to about 160°C, about 80°C to about 160°C, about 90°C to about 160°C, about 95°C to about 160°C, about 100°C to about 160°C, about 105°C to about 160°C, about 110°C to about 160°C, about 115°C to about 160°C, about 120°C to about 160°C, about 125°C to about 160°C, about 130°C to about 160°C, about 140°C to about 160°C, about 60°C to about 150°C, about 70°C to about 150°C, about 80°C to about 150°C, about 90°C to about 150°C, about 95°C to about 150°C, about 100°C to about 150°C, about 105°C to about 150°C, about 110°C to about 150°C, about 115°C to about 150°C, about 120°C to about 150°C, about 60°C to about 140°C, about 70°C to about 140°C, about 80°C to about 140°C, about 90°C to about 140°C, about 95°C to about 140°C, about 100°C to about 140°C, about 105°C to about 140°C, about 110°C to about 140°C, about 115°C to about 140°C, about 120°C to about 140°C, about 60°C to about 130°C, about 70°C to about 130°C, about 80°C to about 130°C, about 90°C to about 130°C, about 95°C to about 130°C, about 100°C to about 130°C, about 105°C to about 130°C, about 110°C to about 130°C, about 60°C to about 120°C, about 70°C to about 120°C, about 80°C to about 120°C, about 90°C to about 120°C, about 95°C to about 120°C, about 100°C to about 120°C, about 60°C to about 110°C, about 70°C to about 110°C, about 80°C to about 110°C, about 90°C to about 110°C, about 60°C to about 100°C, about 70°C to about 100°C or about 80°C to about 100°C.

[0183] In some embodiments, the temperature at which the coating film on the current collector is heated to and / or dried is lower than 160°C, lower than 150°C, lower than 140°C, lower than 130°C, lower than 120°C, lower than 115°C, lower than 110°C, lower than 105°C, lower than 100°C, lower than 95°C, lower than 90°C, lower than 80°C or lower than 70°C. In some embodiments, the temperature at which the coating film on the current collector is heated to and / or dried is higher than 60°C, higher than 70°C, higher than 80°C, higher than 90°C, higher than 95°C, higher than 100°C, higher than 105°C, higher than 110°C, higher than 115°C, higher than 120°C, higher than 130°C or higher than 140°C.

[0184] After heating and / or drying, an electrode layer is formed. In some embodiments, after heating and / or drying, the electrode layer is mechanically compressed to increase the density of the electrode layer. In some embodiments, when the coating film contains a cathode active material, the electrode layer is specifically a cathode electrode layer. In some embodiments, when the coating film contains an anode active material, the electrode layer is specifically an anode electrode layer.

[0185] The proportion of the binder copolymer in the electrode layer can be the same as that in the solid part of the dry electrode mixture or the electrode paste as described above. Similarly, the proportions of the conductive agent and the electrode active material in the electrode layer can be the same as those of the conductive agent and the electrode active material in the solid part of the dry electrode mixture or the electrode paste as described above.

[0186] In certain embodiments, the thickness of the electrode layer is about 5 μm to about 90 μm, about 5 μm to about 50 μm, about 5 μm to about 25 μm, about 10 μm to about 90 μm, about 10 μm to about 50 μm, about 10 μm to about 30 μm, about 15 μm to about 90 μm, about 20 μm to about 90 μm, about 25 μm to about 90 μm, about 25 μm to about 80 μm, about 25 μm to about 70 μm, about 25 μm to about 50 μm, about 30 μm to about 90 μm or about 30 μm to about 80 μm. In some embodiments, the thickness of the electrode layer is greater than 5 μm, greater than 10 μm, greater than 15 μm, greater than 20 μm, greater than 25 μm, greater than 30 μm, greater than 40 μm, greater than 50 μm, greater than 60 μm, greater than 70 μm or greater than 80 μm. In some embodiments, the thickness of the electrode layer is less than 90 μm, less than 80 μm, less than 70 μm, less than 60 μm, less than 50 μm, less than 40 μm, less than 30 μm, less than 25 μm, less than 20 μm, less than 15 μm or less than 10 μm.

[0187] In some embodiments, the surface density of the electrode layer is about 1 mg / cm 2 to about 50 mg / cm 2 、about 3 mg / cm 2 to about 50 mg / cm 2 、about 5 mg / cm 2 to about 50 mg / cm 2 、about 10 mg / cm 2 to about 50 mg / cm 2 、about 15 mg / cm 2 to about 50 mg / cm 2 、about 20 mg / cm 2 to about 50 mg / cm 2 、about 30 mg / cm 2to about 50 mg / cm 2 、about 1 mg / cm 2 to about 30 mg / cm 2 、about 3 mg / cm 2 to about 30 mg / cm 2 、about 5 mg / cm 2 to about 30 mg / cm 2 、about 10 mg / cm 2 to about 30 mg / cm 2 、about 15 mg / cm 2 to about 30 mg / cm 2 、about 20 mg / cm 2 to about 30 mg / cm 2 、about 1 mg / cm 2 to about 20 mg / cm 2 、about 3 mg / cm 2 to about 20 mg / cm 2 、about 5 mg / cm 2 to about 20 mg / cm 2 、about 10 mg / cm 2 to about 20 mg / cm 2 、about 1 mg / cm 2 to about 15 mg / cm 2 、about 3 mg / cm 2 to about 15 mg / cm 2 、about 5 mg / cm 2 to about 15 mg / cm 2 or about 10 mg / cm 2 to about 15 mg / cm 2 。

[0188] In some embodiments, the surface density of the electrode layer is less than 50 mg / cm 2 、less than 40 mg / cm 2 、less than 30 mg / cm 2 、less than 20 mg / cm 2 、less than 15 mg / cm 2 、less than 10 mg / cm 2 、less than 5 mg / cm 2 or less than 3 mg / cm 2 。In some embodiments, the surface density of the electrode layer is greater than 1 mg / cm 2 、greater than 3 mg / cm 2 、greater than 5 mg / cm 2 、greater than 10 mg / cm 2 、greater than 15 mg / cm 2 、greater than 20 mg / cm2 、 greater than 30 mg / cm 2 or greater than 40 mg / cm 2 。

[0189] In some embodiments, the density of the electrode layer is from about 0.5 g / cm 3 to about 7.5 g / cm 3 、 from about 1 g / cm 3 to about 7.5 g / cm 3 、 from about 1.5 g / cm 3 to about 7.5 g / cm 3 、 from about 2 g / cm 3 to about 7.5 g / cm 3 、 from about 2.5 g / cm 3 to about 7.5 g / cm 3 、 from about 3.5 g / cm 3 to about 7.5 g / cm 3 、 from about 4.5 g / cm 3 to about 7.5 g / cm 3 、 from about 0.5 g / cm 3 to about 5.5 g / cm 3 、 from about 1 g / cm 3 to about 5.5 g / cm 3 、 from about 1.5 g / cm 3 to about 5.5 g / cm 3 、 from about 2 g / cm 3 to about 5.5 g / cm 3 、 from about 2.5 g / cm 3 to about 5.5 g / cm 3 、 from about 0.5 g / cm 3 to about 2.5 g / cm 3 、 from about 1 g / cm 3 to about 2.5 g / cm 3 or from about 1.5 g / cm 3 to about 2.5 g / cm 3 。 In some embodiments, the density of the electrode layer is less than 7.5 g / cm 3 、 less than 6.5 g / cm 3 、 less than 5.5 g / cm 3 、 less than 4.5 g / cm 3 、 less than 3.5 g / cm 3 、 less than 2.5 g / cm 3 、 less than 2 g / cm 3 or less than 1.5 g / cm 3 。 In some embodiments, the density of the electrode layer is greater than 0.5 g / cm 3 、 greater than 1 g / cm3 , greater than 1.5 g / cm 3 , greater than 2 g / cm 3 , greater than 2.5 g / cm 3 , greater than 3.5 g / cm 3 , greater than 4.5 g / cm 3 or greater than 5.5 g / cm 3 .

[0190] In addition, the electrodes prepared from the dry electrode mixture or electrode slurry produced by using the binder composition of the present invention exhibit strong adhesion of the electrode layer to the current collector. It is important that the electrode layer has good peel strength against the current collector because this can prevent electrode peeling or separation, which would greatly affect the mechanical stability of the electrode and the cycle performance of the battery. Therefore, the electrode should have sufficient peel strength to withstand the rigors of the battery manufacturing process.

[0191] In some embodiments, the peel strength between the current collector and the electrode layer is about 1.0 N / cm to about 8.0 N / cm, about 1.0 N / cm to about 6.0 N / cm, about 1.0 N / cm to about 5.0 N / cm, about 1.0 N / cm to about 4.0 N / cm, about 1.0 N / cm to about 3.0 N / cm, about 1.0 N / cm to about 2.5 N / cm, about 1.0 N / cm to about 2.0 N / cm, about 1.2 N / cm to about 3.0 N / cm, about 1.2 N / cm to about 2.5 N / cm, about 1.2 N / cm to about 2.0 N / cm, about 1.5 N / cm to about 3.0 N / cm, about 1.5 N / cm to about 2.5 N / cm, about 1.5 N / cm to about 2.0 N / cm, about 1.8 N / cm to about 3.0 N / cm, about 1.8 N / cm to about 2.5 N / cm, about 2.0 N / cm to about 6.0 N / cm, about 2.0 N / cm to about 5.0 N / cm, about 2.0 N / cm to about 3.0 N / cm, about 2.0 N / cm to about 2.5 N / cm, about 2.2 N / cm to about 3.0 N / cm, about 2.5 N / cm to about 3.0 N / cm, about 3.0 N / cm to about 8.0 N / cm, about 3.0 N / cm to about 6.0 N / cm or about 4.0 N / cm to about 6.0 N / cm.

[0192] In some embodiments, the peel strength between the current collector and the electrode layer is greater than 1.0 N / cm, greater than 1.2 N / cm, greater than 1.5 N / cm, greater than 2.0 N / cm, greater than 2.2 N / cm, greater than 2.5 N / cm, greater than 3.0 N / cm, greater than 3.5 N / cm, greater than 4.0 N / cm, greater than 4.5 N / cm, greater than 5.0 N / cm, greater than 5.5 N / cm, greater than 6.0 N / cm, greater than 6.5 N / cm, or greater than 7.0 N / cm. In some embodiments, the peel strength between the current collector and the electrode layer is less than 8.0 N / cm, less than 7.5 N / cm, less than 7 N / cm, less than 6.5 N / cm, less than 6.0 N / cm, less than 5.5 N / cm, less than 5.0 N / cm, less than 4.5 N / cm, less than 4.0 N / cm, less than 3.5 N / cm, less than 3.0 N / cm, less than 2.8 N / cm, less than 2.5 N / cm, less than 2.2 N / cm, less than 2.0 N / cm, less than 1.8 N / cm, or less than 1.5 N / cm.

[0193] Figure 1 A flowchart showing a simplified overview of some embodiments illustrating various aspects of the invention disclosed herein. As shown in the figure, after polymerization, the reaction mixture is dried until it is substantially anhydrous. When the desired binder composition is a dry binder composition, the dried reaction mixture is the binder composition. When the desired binder composition is a semi-dry binder composition, the dried reaction mixture is re-wetted to form the binder composition. The dry binder composition is mixed with the electrode active material and an optional conductive agent to form a dry electrode mixture from the dry binder composition. The dry binder composition is mixed with the electrode active material, an additional solvent, and an optional conductive agent to form a semi-dry electrode paste from the dry binder composition. The semi-dry binder composition is mixed with the electrode active material, an optional conductive agent, and / or an additional solvent to form a semi-dry electrode paste from the semi-dry binder composition.

[0194] The binder compositions disclosed herein have several advantages. Most importantly, compared to conventional wet binder compositions, the lower liquid content of the binder compositions disclosed herein ensures that higher storage and transportation efficiency of the binder compositions can be achieved, thus contributing to the simplification of the supply chain for electrode manufacturing. It has been found that the dry binder compositions disclosed herein can be directly used in dry electrode mixtures and in electrode slurries after rewetting to form semi-dry binder compositions. In both cases, it has been found that batteries comprising electrodes produced using the dry or semi-dry binder compositions disclosed herein have similar mechanical and electrochemical properties compared to batteries comprising electrodes produced using conventional wet binder compositions. Overall, this indicates that the binder compositions disclosed herein have excellent binder properties and that the binder copolymers in the binder compositions disclosed herein are effective in both the dry state and in the rewet form, thus demonstrating the versatility of the copolymer.

[0195] The following examples are given to illustrate embodiments of the invention and are not intended to limit the invention to the specific embodiments recited. Unless otherwise indicated, all parts and percentages are by weight. All values are approximate. When a numerical range is given, it should be understood that embodiments outside the stated range still fall within the scope of the invention. The specific details described in each example should not be construed as essential features of the invention. Example

[0196] The peel strength of the electrode layer was measured using a tensile tester (DZ-106A, from Dongguan Zonhow Test Equipment Co., Ltd., China). This test measures the average force required to peel the electrode layer from the current collector at an angle of 180°, expressed in Newtons (N). The average roughness depth (R z ) of the current collector was 2 μm. A tape (3M; USA; model 810) 18 mm wide and 20 mm long was adhered to the surface of the electrode layer. The electrode strip was clamped in the testing machine, the tape was folded back 180°, then placed in the movable jaws, and pulled at a peel rate of 200 mm / minute at room temperature. The maximum peel force measured was taken as the peel strength. The measurement was repeated three times and the average value was taken.

[0197] The solid content of the binder composition, dry electrode mixture, or electrode paste is calculated based on the mass change of the binder composition, dry electrode mixture, or electrode paste before and after drying. Weigh approximately 1 g of the binder composition, dry electrode mixture, or electrode paste in a weighing bottle, and dry it in a vacuum dryer at 110 + 5 °C and -0.09 MPa for more than 5 hours. The dried binder composition, dry electrode mixture, or electrode paste is cooled in the dryer for about 15 minutes, and then its mass is measured. The mass difference of the binder composition, dry electrode mixture, or electrode paste before and after drying is obtained, and the solid content of the binder composition, dry electrode mixture, or electrode paste is calculated according to the following formula: where x can refer to the binder composition, dry electrode mixture, or electrode paste.

[0198] The weight-average molecular weight and number-average molecular weight of the water-compatible copolymer are measured by gel permeation chromatography. First, dissolve the binder composition containing the copolymer in dimethylformamide at room temperature. After the dissolution of the binder composition is completed, filter the solution using a filter with a pore size of 0.45 μm to prepare a test sample. Use a standard made of polystyrene to prepare a calibration curve, and calculate the weight-average molecular weight and number-average molecular weight of the copolymer according to the curve. Use an Agilent PLgel 5 μm MIXED-C chromatographic column to analyze the obtained test sample, with a flow rate of 1 ml / min and a sample weight of 2 mg. The detector used is a Waters 2414 refractive index (RI) detector, and the detection temperature is 35 °C. Example 1 A) Preparation of Binder Composition

[0199] Add 17.96 g of sodium hydroxide (NaOH) to a round-bottom flask containing 380 g of distilled water. Stir the mixture at 80 rpm for 30 minutes to obtain a first suspension.

[0200] Add 35.67 g of acrylic acid to the first suspension. Further stir the mixture at 80 rpm for 30 minutes to obtain a second suspension.

[0201] Dissolve 18.84 g of acrylamide in 10 g of deionized water to form an acrylamide solution. Thereafter, add all of the acrylamide solution to the second suspension. Heat the mixture to 55 °C and stir at 80 rpm for 45 minutes to obtain a third suspension.

[0202] Add 12.73 g of acrylonitrile to the third suspension. Further stir the mixture at 80 rpm for 10 minutes to obtain a fourth suspension.

[0203] After that, 0.015 g of a water-soluble free radical initiator (ammonium persulfate, APS; from Aladdin Industries Corporation, China) was dissolved in 3 g of deionized water, and 0.0075 g of a reducing agent (sodium bisulfite; from Tianjin Damao Chemical Reagent Factory, China) was dissolved in 1.5 g of deionized water. All the APS solution and sodium bisulfite solution were added to the fourth suspension. The mixture was stirred at 200 rpm at 55 °C for 24 h to obtain a fifth suspension.

[0204] After complete reaction, the temperature of the fifth suspension was lowered to 25 °C. 3.72 g of NaOH was dissolved in 400 g of deionized water, and the entire sodium hydroxide solution was added dropwise to the fifth suspension to adjust the pH to 7.3, forming a sixth suspension. The sixth suspension was filtered using a 200 μm nylon mesh. The solid content of the filtered sixth suspension was 9.00 wt.%.

[0205] The filtered sixth suspension was dried overnight in a vacuum dryer at 60 °C and then ground using a mortar and pestle to form a powdered dry binder composition. The weight-average molecular weight, number-average molecular weight, and polydispersity index of the binder composition were 140,300 g / mol, 61,500 g / mol, and 2.28, respectively. B) Preparation of Positive Electrode

[0206] First, 0.9 g of a conductive agent (KS6; from ANR Technologies Pte. Ltd., Singapore), 0.90 g of the binder composition, and 28.2 g of NMC532 (from Shandong Tianjiao New Energy Co., Ltd., China) were ground using a grinder to form a homogeneous mixture. After that, 20.0 g of deionized water was added to the mixture and further ground to form a homogeneous cathode slurry. The solid content of the cathode slurry was 60 wt.%.

[0207] The cathode slurry was coated on one side of an aluminum foil with a thickness of 16 μm as the current collector. The coated film on the aluminum foil was dried at about 80 °C for 120 min using a hot air dryer (DHG10H, Huyue Equipment Co., Ltd., China) to form a cathode electrode layer. Then the electrode was pressed to reduce the thickness and surface density of the cathode electrode layer to 34 μm and 5 mg / cm 2 。 C) Assembly of Button Battery

[0208] The CR 2032 button-type Li battery was assembled in a glove box filled with argon gas. The coated cathode sheet was cut into a disc-shaped positive electrode. Lithium metal foil with a thickness of 500 μm was used as the negative electrode. The cathode and anode were separated by a separator, which was a non-woven fabric (MPM, Japan) microporous membrane with a ceramic coating, with a thickness of about 25 μm. The electrode assembly was dried in a box-type resistance furnace (DZF-6020, from Shenzhen Kejing Star Technology Co., Ltd., China) under vacuum conditions at 105 °C for about 16 hours. After drying, the water contents of the separator and the electrode assembly were 200 ppm and 300 ppm, respectively.

[0209] After that, in an environment of high-purity argon gas with humidity and oxygen content less than 3 ppm respectively, the electrolyte was injected into the housing containing the electrodes. The electrolyte was a solution containing LiPF6 (1M) in a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) with a volume ratio of 1:1:1. After injecting the electrolyte, the button battery was mechanically stamped using a stamping tool with a standard circle. D} Electrochemical Measurement

[0210] The button battery was analyzed using a multi-channel battery tester (BTS-4008-5V10mA, from Neware Electronics Co., Ltd., China) in a constant current mode. The initial cycle was carried out between 3.0 and 4.3 V under the conditions of C / 20 and 25 °C, and the corresponding discharge capacity of the cycle was measured. The electrochemical performance of the button battery of Example 1 was measured, and the results are shown in Table 1 below. Example 3

[0211] The positive electrode was prepared in the same manner as in Example 1, except that when preparing the binder composition, 30.10 g of sodium hydroxide was added in the preparation of the first suspension, 56.92 g of acrylic acid was added in the preparation of the second suspension, 7.19 g of acrylamide was added in the preparation of the third suspension, and 5.90 g of acrylonitrile was added in the preparation of the fourth suspension. The solid content of the filtered sixth suspension was 9.82 wt.%. Example 5

[0212] The positive electrode was prepared in the same manner as in Example 1, except that when preparing the binder composition, 11.90 g of sodium hydroxide was added in the preparation of the first suspension, 24.50 g of acrylic acid was added in the preparation of the second suspension, 7.19 g of acrylamide was added in the preparation of the third suspension, and 29.71 g of acrylonitrile was added in the preparation of the fourth suspension. The solid content of the filtered sixth suspension was 8.38 wt.%. Example 7 A) Preparation of Binder Composition

[0213] The binder composition was prepared in the same manner as in Example 1, except that after the filtered sixth suspension was dried and ground, the resulting dry powder was mixed with deionized water to form the binder composition. The mass ratio of deionized water to the dry powder was 1:2, and the binder composition was a semi-dry binder composition with a liquid content of 33.3 wt.%. B) Preparation of Positive Electrode

[0214] The positive electrode was prepared in the same manner as in Example 1, except that when preparing the homogenized cathode slurry, 1.35 g of the above binder composition (liquid content 33.3 wt.%) and 19.55 g of deionized water were added. Example 8 A) Preparation of Binder Composition

[0215] The binder composition was prepared in the same manner as in Example 1, except that after the filtered sixth suspension was dried and ground, the resulting dry powder was mixed with deionized water to form the binder composition. The mass ratio of deionized water to the dry powder was 1:1, and the binder composition was a semi-dry binder composition with a liquid content of 50 wt.%. B) Preparation of Positive Electrode

[0216] The positive electrode was prepared in the same manner as in Example 1, except that when preparing the homogenized cathode slurry, 1.80 g of the above binder composition (liquid content 50 wt.%) and 19.10 g of deionized water were added. Example 9 A) Preparation of Binder Composition

[0217] The binder composition was prepared in the same manner as in Example 1, except that after the filtered sixth suspension was dried and ground, the resulting dry powder was mixed with deionized water to form the binder composition. The mass ratio of deionized water to the dry powder was 2:1, and the binder composition was a semi-dry binder composition with a liquid content of 66.7 wt.%. B) Preparation of Positive Electrode

[0218] The positive electrode was prepared in the same manner as in Example 1, except that when preparing the homogenized cathode slurry, 2.70 g of the above binder composition (liquid content 66.7 wt.%) and 18.20 g of deionized water were added. Example 10 A) Preparation of Binder Composition

[0219] The binder composition was prepared in the same manner as in Example 1, except that after the filtered sixth suspension was dried and ground, the resulting dry powder was mixed with deionized water to form a binder composition. The mass ratio of deionized water to the dry powder was 4:1, and the binder composition was a semi-dry binder composition with a liquid content of 80 wt.%. B) Preparation of Positive Electrode

[0220] The positive electrode was prepared in the same manner as in Example 1, except that when preparing the homogenized cathode slurry, 4.50 g of the above binder composition (liquid content 80 wt.%) and 17.30 g of deionized water were added. Example 11 A) Preparation of Binder Composition

[0221] The binder composition was prepared in the same manner as in Example 1. B} Preparation of Positive Electrode

[0222] 0.24 g of a conductive agent (KS6; from ANR Technologies Pte.Ltd., Singapore), 0.36 g of the binder composition, and 0.60 g of NMC532 (from Shandong Tianjiao New Energy Co., Ltd., China) were ground using a grinder to form a homogenized dry cathode mixture.

[0223] 0.2 g of the homogenized cathode mixture was pressed onto one side of an aluminum foil with a thickness of 16 μm as a current collector using a hot press. The coating film on the aluminum foil was vacuum dried at about 80 °C for 6 hours to form a cathode electrode layer. Example 13

[0224] The positive electrode was prepared in the same manner as in Example 1, except that the same weight of LCO was used instead of NMC532. Example 14

[0225] The positive electrode was prepared in the same manner as in Example 1, except that the same weight of LFP (Tianjin Sitelan Energy Technology Co., Ltd., China) was used instead of NMC532. Assembly of Button Batteries of Examples 3, 5, 7 - 11 and 13 - 14

[0226] The button cells of Examples 3, 5, 7 - 11, and 13 - 14 were assembled in the same manner as in Example 1. Electrochemical Measurements of Examples 3, 5, 7 - 11 and 13

[0227] The button cells of Examples 3, 5, 7 - 11 and 13 were analyzed in the same manner as in Example 1. The electrochemical performances of the button cells of Examples 3, 5, 7 - 11 and 13 were measured, and the results are shown in Table 1 below. Electrochemical Measurement of Example 14

[0228] The button cell of Example 14 was analyzed in the same manner as in Example 1, except that cycling was carried out between 2.0 and 3.65 V. The electrochemical performance of the button cell of Example 14 was measured, and the results are shown in Table 1 below. Comparative Example 1

[0229] The positive electrode was prepared in the same manner as in Example 1, except that 0.9 g of dry sodium polyacrylate (Sigma - Aldrich, Germany) was used as the binder composition. Comparative Example 2

[0230] The positive electrode was prepared in the same manner as in Example 1, except that 0.9 g of dry polyacrylamide (Sigma - Aldrich, Germany) was used as the binder composition. Ratio Comparative Example 3

[0231] The positive electrode was prepared in the same manner as in Example 1, except that 0.9 g of dry polyacrylonitrile (Sigma - Aldrich, Germany) was used as the binder composition. Comparative Example 4

[0232] The positive electrode was prepared in the same manner as in Example 1, except that when preparing the binder composition, 24.14 g of sodium hydroxide was added in the preparation of the first suspension, 46.84 g of acrylic acid was added in the preparation of the second suspension, acrylamide was not added in the preparation of the third suspension, and 18.57 g of acrylonitrile was added in the preparation of the fourth suspension. The solid content of the filtered sixth suspension was 9.63 wt.%. Comparative Example 5

[0233] The positive electrode was prepared in the same manner as in Example 1, except that when preparing the binder composition, 26.13 g of sodium hydroxide was added in the preparation of the first suspension, 50.44 g of acrylic acid was added in the preparation of the second suspension, 21.32 g of acrylamide was added in the preparation of the third suspension, and acrylonitrile was not added in the preparation of the fourth suspension. The solid content of the filtered sixth suspension was 9.92 wt.%. Comparative Example 6

[0234] The positive electrode was prepared in the same manner as in Example 1, except that when preparing the binder composition, 1.86 g of sodium hydroxide was added in the preparation of the first suspension, acrylic acid was not added in the preparation of the second suspension, 21.32 g of acrylamide was added in the preparation of the third suspension, 37.14 g of acrylonitrile was added in the preparation of the fourth suspension, and sodium hydroxide was not added in the preparation of the sixth suspension. The solid content of the filtered sixth suspension was 7.15 wt.%. Comparative Example 7 A) Preparation of Binder Composition

[0235] The binder composition was prepared in the same manner as in Comparative Example 4, except that after the filtered sixth suspension was dried and ground, the obtained dry powder was mixed with deionized water to form a binder composition. The mass ratio of deionized water to the dry powder was 2:1, and the binder composition was a semi-dry binder composition with a liquid content of 66.7 wt.%. B) Preparation of Positive Electrode

[0236] The positive electrode was prepared in the same manner as in Example 1, except that 2.70 g of the above binder composition (liquid content 66.7 wt.%) and 18.20 g of deionized water were added when preparing the homogenized cathode slurry. Comparative Example 8

[0237] The positive electrode was prepared in the same manner as in Example 11, except that 0.9 g of dry sodium polyacrylate (Sigma-Aldrich, Germany) was used as the binder composition. Comparative Example 9

[0238] The positive electrode was prepared in the same manner as in Example 11, except that 0.9 g of dry polyacrylamide (Sigma-Aldrich, Germany) was used as the binder composition. Comparative Example 10

[0239] The positive electrode was prepared in the same manner as in Example 11, except that 0.9 g of dry polyacrylonitrile (Sigma-Aldrich, Germany) was used as the binder composition. Comparative Example 11

[0240] The positive electrode was prepared in the same manner as in Example 11, except that the binder composition was prepared in the same manner as in Comparative Example 4. Comparative Example 12

[0241] The positive electrode was prepared in the same manner as in Example 11, except that the binder composition was prepared in the same manner as in Comparative Example 5. Comparative Example 13

[0242] The positive electrode was prepared in the same manner as in Example 11, except that the binder composition was prepared in the same manner as in Comparative Example 6. Assembly of Button Batteries of Comparative Examples 1 - 13

[0243] The button cells of Comparative Examples 1-13 were assembled in the same manner as in Example 1. Electrochemical Measurements of Comparative Examples 1 - 13

[0244] The button cells of Comparative Examples 1-13 were analyzed in the same manner as in Example 1. The electrochemical performances of the button cells of Comparative Examples 1-13 were measured, and the results are shown in Table 2 below.

[0245] Although the present invention has been described in connection with a limited number of embodiments, the specific features of one embodiment should not limit the other embodiments of the present invention. In some embodiments, the method may include a plurality of steps not mentioned herein. In other embodiments, the method does not include or substantially does not contain any steps not enumerated herein. There are variations and changes based on the described embodiments. The appended claims are intended to cover all such variations and changes falling within the scope of the present invention.

Claims

1. A binder composition comprising a water-compatible copolymer, wherein based on the total weight of the binder composition, the aqueous solvent content of the binder composition is less than 70% by weight, wherein the water-compatible copolymer comprises a structural unit (a) derived from an acid group-containing monomer, wherein the acid group is selected from the group consisting of carboxylic acid, sulfonic acid, sulfuric acid, phosphonic acid, phosphoric acid, nitric acid, salts of these acids, derivatives of these acids, and combinations thereof, and wherein based on the total molar number of monomer units in the copolymer, the proportion of the structural unit (a) in the copolymer is about 33% to about 85% by mole; wherein the water-compatible copolymer further comprises a structural unit (b) derived from a monomer selected from the group consisting of amide group-containing monomers, hydroxyl group-containing monomers, and combinations thereof, and wherein based on the total molar number of monomer units in the copolymer, the proportion of the structural unit (b) in the copolymer is about 5% to about 35% by mole; wherein the water-compatible copolymer further comprises a structural unit (c) derived from a monomer selected from the group consisting of nitrile group-containing monomers, ester group-containing monomers, ether group-containing monomers, epoxy group-containing monomers, carbonyl group-containing monomers, fluorine-containing monomers, and combinations thereof, and wherein based on the total molar number of monomer units in the copolymer, the proportion of the structural unit (c) in the copolymer is about 10% to about 85% by mole.

2. The binder composition according to claim 1, wherein based on the total weight of the binder composition, the liquid content of the binder composition is less than 50% or less than 25% by weight.

3. The binder composition according to claim 1, wherein based on the total weight of the binder composition, the liquid content of the binder composition is less than 1% by weight.

4. The binder composition according to claim 1, wherein the aqueous solvent comprises water.

5. The binder composition according to claim 1, wherein the weight-average molecular weight of the water-compatible copolymer in the binder composition is about 10,000 g / mol to about 1,000,000 g / mol.

6. The binder composition according to claim 1, wherein the number-average molecular weight of the water-compatible copolymer in the binder composition is about 10,000 g / mol to about 500,000 g / mol.

7. The binder composition according to claim 1, wherein the polydispersity index of the water-compatible copolymer in the binder composition is about 1 to about 5.

8. The binder composition according to claim 1, wherein the binder composition is used for a lithium-ion secondary battery.

9. An electrode paste, which comprises a binder composition according to any one of claims 1-8 and an electrode active material, wherein based on the total weight of the electrode paste, the liquid content of the electrode paste is about 1% to about 60% by weight.

10. The electrode paste according to claim 9, wherein the electrode paste further comprises a conductive agent.

11. The electrode paste according to claim 9, wherein the liquid content of the electrode paste is derived from an aqueous solvent.

12. The electrode paste according to claim 11, wherein the aqueous solvent comprises water.

13. The electrode paste according to claim 9, wherein based on the total weight of the solid portion of the electrode paste, the proportion of the electrode active material in the solid portion of the electrode paste is about 40% to about 99% by weight.

14. The electrode paste according to claim 9, wherein the cathode active material is selected from the group consisting of LiCoO2, LiNiO2, LiNi x Mn y O2, LiCo x Ni y O2, Li 1+z Ni x Mn y Co 1-x-y O2 (NMC), LiNi x Co y Al z O2 (NCA), LiV2O5, LiTiS2, LiMoS2, LiMnO2, LiCrO2, LiMn2O4, Li2MnO3, LiFeO2, LiFePO4, and combinations thereof, wherein each x is independently 0.1 to 0.9; each y is independently 0 to 0.9; and each z is independently 0 to 0.

4.

15. A dry electrode mixture, which comprises a binder composition according to claim 3 and any one of claims 5-8 and an electrode active material.

16. The dry electrode mixture according to claim 15, wherein the dry electrode mixture further comprises a conductive agent.

17. The dry electrode mixture according to claim 15, wherein based on the total weight of the dry electrode mixture, the proportion of the electrode active material in the dry electrode mixture is about 40% to about 99% by weight.

18. The dry electrode mixture according to claim 15, wherein based on the total weight of the dry electrode mixture, the liquid content of the dry electrode mixture is less than 1% by weight.

19. The dry electrode mixture according to claim 15, wherein the cathode active material is selected from the group consisting of LiCoO2, LiNiO2, LiNi x Mn y O2, LiCo x Ni y O2, Li 1+z Ni x Mn y Co 1-x-y O2 (NMC), LiNi x Co y Al z O2 (NCA), LiV2O5, LiTiS2, LiMoS2, LiMnO2, LiCrO2, LiMn2O4, Li2MnO3, LiFeO2, LiFePO4, and combinations thereof, wherein each x is independently from 0.1 to 0.9; each y is independently from 0 to 0.9; and each z is independently from 0 to 0.4.

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