Adhesive composition for electrode preparation, electrode material layer composition for dry process including the same, and secondary battery including the same

Abstract

This invention relates to an electrode material layer composition for secondary batteries and a secondary battery comprising the same, and more specifically, to a novel adhesive composition, an electrode material layer composition for dry processing comprising the adhesive composition, and a secondary battery comprising the same. The novel adhesive composition comprises a terpolymer, which, regardless of whether a wet or dry process is used, can improve the adhesion between the electrode and the metal plate serving as a current collector, as well as the adhesion between the components within the electrode, and stably maintain conductivity, thereby resulting in excellent electrochemical characteristics.

Description

Technical Field

[0001] This invention was supported by the Korean National Research and Development Program.

[0002] Project ID: 1415187718

[0003] Project Number: 20023145

[0004] Department Name: Ministry of Trade, Industry and Energy of Korea

[0005] Name of the project management (specialized) agency: Korea Institute of Industrial Technology Evaluation and Management

[0006] Research Project Title: Materials and Components Technology Development

[0007] Research Project Title: Development of Adhesives and Preparation Processes for Carbon Reduction Dry Process in Secondary Batteries

[0008] This invention relates to electrode material layer compositions for secondary batteries and technologies for secondary batteries containing the same, and more specifically, to novel adhesive compositions, dry-process electrode material layer compositions containing the adhesive compositions, and secondary batteries containing the same. The novel adhesive compositions contain terpolymers, which, regardless of whether a wet or dry process is used, can improve the adhesion between the electrode and the metal plate serving as a current collector, as well as the adhesion between the components within the electrode, thereby stabilizing conductivity and exhibiting excellent electrochemical characteristics. Background Technology

[0009] The following description of the present invention will focus on lithium-ion batteries. However, it should be noted that the scope of the present invention is not limited to lithium-ion batteries, but is applicable to all rechargeable batteries.

[0010] Lithium-ion batteries are manufactured as follows: Lithium-containing compound particles are used as the positive electrode active material. A negative electrode active material, typically graphite, is mixed with a binder and then formed into an active material layer on a metal foil (plate) such as aluminum or copper. An electrolyte is then impregnated within this layer, and a separator (also called a separator membrane) is placed in the middle and the batteries are laminated. In this process, lithium ions repeatedly move between the positive and negative electrode layers (lithiation and delithiation). When different types of ions are used, a secondary battery that operates using those ions can be manufactured by using positive and negative electrode active materials and electrolytes (if necessary) adapted to those ion types.

[0011] Existing techniques for preparing electrode plates involve a wet process: active materials, binders, conductive materials, and other additives are dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP) or water to prepare an electrode composition slurry. This slurry is then coated onto a metal electrode plate at a specified thickness and dried to prepare an active material electrode plate. This process requires an additional step of completely removing and recovering the evaporated solvent. Therefore, the wet process, which requires significant energy consumption and is costly, necessitates the re-collection of evaporated solvent. In contrast, the increasingly popular dry process involves preparing an electrode composition by dry mixing of active materials, binders, and other additives without using solvents. The electrode composition is then directly formed onto the electrode plate at a specified thickness, thus preparing the electrode plate without solvents. In the dry method, high-speed stirring or stirring with heat and pressure is used to uniformly mix the active material with the binder and other additives, but no solvent is used and there is no need for additional steps to remove and recycle the solvent, so it can be said to be environmentally friendly.

[0012] To prepare an electrode composition, an electrode layer should be formed on a metal plate. In this case, the substance that imparts adhesion between the active materials or between the active materials and the plate is the adhesive. While bonding the active materials to the conductive materials, the adhesive should not impede the movement of lithium ions from the positive electrode active material (e.g., lithium-nickel-cobalt-manganese: NCM) to the negative electrode active material (e.g., graphite, silicon, etc.) or from the negative electrode active material to the positive electrode active material. To facilitate the smooth movement of lithium ions through the adhesive, it is advantageous to use an adhesive that promotes ion conduction. Currently used adhesives, in wet processes, primarily use polyvinylidene fluoride (PVDF) in the positive electrode and carboxymethyl cellulose / styrene-butadiene rubber (CMC / SBR) mixtures in the negative electrode. These adhesives are effective in terms of adhesion between the active materials or to the plate, but they do not contain ion-conducting components. Therefore, although the adhesion between the active materials or to the plate is good, there are limitations in increasing ion conductivity. Furthermore, the main binder used in the dry process is a fluorinated resin called polytetrafluoroethylene (PTFE). When using PTFE as a binder to prepare the electrode composition, high pressure is required for coating the electrode sheets, which is unsuitable for preparing thinner electrode layers smaller than 100 micrometers. Moreover, fluorinated resins are known to have weak adhesive strength. In this situation, although electrode layers can be prepared under high pressure, the repeated expansion and contraction during battery use, due to repeated charging and discharging, reduces the adhesion between the various structural components, ultimately leading to a significant problem of degraded electrochemical performance.

[0013] Therefore, it is necessary to develop the following novel adhesives: when preparing the electrode material layer of secondary batteries by dry process, the adhesives can improve the bonding force of structural components such as active materials and conductive materials and their adhesion to the electrode plates, while also exhibiting excellent electrochemical properties. Summary of the Invention

[0014] Technical issues

[0015] Therefore, the object of the present invention is to provide an adhesive composition for electrode preparation and an electrode material layer composition for dry process comprising the adhesive composition, wherein the adhesive composition for electrode preparation comprises a terpolymer, which can increase the adhesion between the components in the electrode regardless of whether a wet process or a dry process is used, is soft and has excellent adhesion to the electrode plate metal, does not hinder the movement of lithium ions, and thus has excellent electrochemical characteristics.

[0016] A positive electrode material layer or a negative electrode material layer can be prepared using an electrode preparation binder composition. Therefore, another object of the present invention is to provide an electrode for a miniaturized secondary battery.

[0017] Another objective of this invention is to provide a variety of secondary batteries, including lithium-ion batteries, wherein the lithium-ion batteries comprise electrodes made of an electrode material layer composition for dry processing, which eliminates the complex process of solvent removal and subsequent collection, and offers excellent environmental and economic benefits.

[0018] The purpose of this invention is not limited to the purposes mentioned above. Those skilled in the art to which this invention pertains will clearly understand other purposes not mentioned through the following description.

[0019] Technical solution

[0020] To achieve the above-mentioned objective of the present invention, firstly, the present invention provides an adhesive composition for electrode preparation, comprising a terpolymer composed of a diol compound, a maleic acid compound, and a third monomer.

[0021] In a preferred embodiment, the third monomer is a compound having a main chain containing vinyl (CH2=CH-) and other functional groups attached thereto.

[0022] In a preferred embodiment, the compound is one or more selected from the group consisting of acrylic acid compounds, acrylonitrile compounds, ethylene compounds, imidazole compounds, imidazoleonium compounds, propylene compounds, and vinylidene compounds.

[0023] In a preferred embodiment, the third monomer is an acrylic compound having the following chemical formula 1.

[0024] Chemical Formula 1

[0025] CH2=CH-COO-R

[0026] In the above chemical formula 1, R is any one of -H, alkyl, alkenyl, alkynyl, phenyl, and amino.

[0027] In a preferred embodiment, the molar ratio of diol compound to maleic acid compound in the terpolymer is 99:1 to 1:99, and the weight ratio of diol compound and maleic acid compound to third monomer is 99:1 to 1:99.

[0028] In a preferred embodiment, the diol compound is a compound whose main chain is composed of ethylene glycol (HO-(CH2-CH2-O)nH) or ethylene oxide (-(CH2-CH2-O)n-) (where n is a natural number greater than 0), and the maleic acid compound is a compound containing a 5-membered ring structure with two carboxyl groups.

[0029] In a preferred embodiment, the diol compound is selected from one or more of the group consisting of ethylene glycol, ethylene oxide, propylene glycol, and propylene oxide, and the maleic acid compound is selected from one or more of the group consisting of maleic acid, its salt, and its anhydride.

[0030] In a preferred embodiment, the third copolymer is ethylene glycol-maleic acid-acrylonitrile or ethylene glycol-maleic acid-acrylic acid.

[0031] In a preferred embodiment, the number-average molecular weight of the terpolymer is 10,000-1,000,000 g / mol.

[0032] In a preferred embodiment, the terpolymer is further comprising one or more other types of adhesives, wherein the weight ratio of the terpolymer to the adhesive is 90:10 to 10:90.

[0033] In a preferred embodiment, the adhesive is one or more of carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and polyacrylic acid (PAA).

[0034] Furthermore, the present invention provides an electrode material layer composition for dry process, comprising: an active material for positive or negative electrode; any of the above-mentioned binder compositions; and a conductive material.

[0035] In a preferred embodiment, the material comprises 85-99.4% by weight of the positive or negative electrode active material, 0.5-10% by weight of the binder composition, and 0.1-5% by weight of the conductive material.

[0036] In a preferred embodiment, the conductive material is selected from one or more of the group consisting of conductive carbon black, graphene, single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, branched carbon nanotubes, carbon nanosheets, and carbon nanoribbons.

[0037] In a preferred embodiment, the compound further comprises an acrylate compound that is liquid at room temperature and can be post-cured, and a curing agent for the acrylate compound.

[0038] In a preferred embodiment, the acrylate compound contains 2 to 16 functional groups, and the main chain is a monomer or oligomer composed of 2 to 1000 carbon atoms.

[0039] In a preferred embodiment, the functional group is selected from one or more of the group consisting of methylene, carbamate, ester, ether, oxide, ethylene oxide, propylene oxide, ethylene glycol, propylene glycol, butadiene, imide, amino, amide, epoxy, olefin, sulfonic acid, or combinations thereof.

[0040] In a preferred embodiment, the active material for the positive or negative electrode comprises 0.1 to 10 parts by weight of the acrylate compound, based on 100 parts by weight.

[0041] In a preferred embodiment, the curing agent is one or more of a thermosetting agent and a photocuring agent, and comprises 0.1 to 20 parts by weight of the curing agent based on 100 parts by weight of the acrylate compound.

[0042] In a preferred embodiment, the thermosetting agent comprises a peroxide or an azo compound, and the photocuring agent comprises a phenyl ketone compound or a phosphine oxide compound.

[0043] In a preferred embodiment, the active material for the positive or negative electrode comprises one or more selected from the group consisting of lithium, manganese, nickel, cobalt, aluminum, iron, phosphorus, tin, titanium, carbon materials, silicon, silicon oxide, sulfur, and combinations thereof.

[0044] Furthermore, the present invention provides a primer composition comprising, based on 100 parts by weight of any of the above-mentioned adhesive compositions, 0.05 to 300 parts by weight of nano-carbon material and solvent, and the content of solid components is 0.2-40% by weight.

[0045] In a preferred embodiment, the nano-carbon material is selected from one or more of the group consisting of conductive carbon black, graphene, single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, branched carbon nanotubes, carbon nanosheets, and carbon nanoribbons.

[0046] Furthermore, the present invention provides an electrode for a secondary battery, comprising a positive electrode material layer or a negative electrode material layer formed from the above-described electrode material layer composition for dry processing.

[0047] Furthermore, the present invention provides a method for preparing an electrode for a secondary battery, comprising: a composition preparation step of preparing the electrode material layer composition for dry process as described in claim 15; a sheet formation step of forming a positive electrode material sheet or a negative electrode material sheet using the electrode material layer composition for dry process; an attachment step of attaching the positive electrode material sheet or a negative electrode material sheet to a metal electrode plate; a curing step of curing the attached positive electrode material sheet or a negative electrode material sheet; and a rolling step of rolling the electrode obtained by performing the curing step.

[0048] In a preferred embodiment, the adhesion step includes: forming a primer layer on the metal electrode plate; and pressing the positive electrode material sheet or the negative electrode material sheet onto the primer layer.

[0049] In a preferred embodiment, the curing step is performed by one or more of thermal curing at a temperature of 50°C to 180°C for 5 to 30 minutes and photocuring by light irradiation.

[0050] Furthermore, the present invention provides a lithium-ion battery including the aforementioned electrodes for secondary batteries.

[0051] Furthermore, the present invention provides a lithium-ion battery comprising an electrode for a secondary battery prepared by the above-described preparation method.

[0052] The effects of the invention

[0053] The above-described electrode preparation adhesive composition and electrode material layer composition containing the present invention contain terpolymers. Regardless of whether a wet or dry process is used, it can enhance the adhesion between the components in the electrode, is soft and has excellent adhesion to the electrode metal, does not hinder the movement of lithium ions, thereby stably maintaining conductivity and exhibiting excellent electrochemical characteristics.

[0054] Furthermore, the secondary battery of the present invention includes electrodes prepared by a dry process, which eliminates the complex process of collection after solvent removal, resulting in excellent environmental friendliness and economy.

[0055] Therefore, the secondary battery of the present invention has the advantage of being able to stably maintain electrochemical properties such as capacity and charge-discharge cycle characteristics.

[0056] The effects of the present invention are not limited to those mentioned above. Those skilled in the art to which this invention pertains can clearly understand other effects not mentioned through the following description. Attached Figure Description

[0057] Figure 1a and Figure 1b Examples of chemical structural formulas for ethylene glycol-maleic acid-acrylic acid copolymer and ethylene glycol-maleic acid-acrylonitrile copolymer, respectively, prepared as terpolymers in Examples 1 and 2 of the present invention.

[0058] Figure 2 This is a photograph of the copolymer obtained in Example 2 of the present invention.

[0059] Figure 3 The results of charge-discharge cycle tests are shown for the positive electrode prepared by a wet process according to Example 5 of the present invention.

[0060] Figure 4 The results of charge-discharge cycle tests are shown for the negative electrode prepared by a wet process according to Example 6 of the present invention.

[0061] Figure 5 The results of charge-discharge cycle tests are shown for the positive electrode 1 prepared by a dry process according to Example 7 of the present invention.

[0062] Figure 6 The results of charge-discharge cycle tests are shown for the positive electrode 2 prepared by a dry process according to Example 9 of the present invention.

[0063] Figure 7 The results of charge-discharge cycle tests are shown for the comparative example positive electrode 2 prepared by the dry process in Comparative Example 2 of the present invention.

[0064] Figure 8 The results of charge-discharge cycle tests are shown for the positive electrode 4 prepared by dry process according to Example 11 of the present invention. Detailed Implementation

[0065] While taking into account the functionality of this invention, the terminology used in this invention is selected as commonly used terms as much as possible, but may vary depending on the intentions, conventions, and emerging technologies of those skilled in the art. Furthermore, in certain cases, there may be terms arbitrarily chosen by the applicant; in such cases, their meanings will be described in detail in the description of the relevant invention.

[0066] In this invention, when referring to terms such as "comprising," "having," or "forming," other parts may be added if not limited by "only." Unless otherwise expressly stated, the use of the singular to express structural elements includes the plural.

[0067] When interpreting structural elements, if not explicitly stated, it should be interpreted as including the range of error.

[0068] The various features of the multiple embodiments of the present invention can be partially or completely combined or integrated with each other, and can be linked and driven in various ways. Each embodiment can be implemented independently or together through related relationships.

[0069] The technical structure of the present invention will now be described in detail with reference to the accompanying drawings and preferred embodiments.

[0070] However, the present invention is not limited to the embodiments described herein, and may be embodied in other forms. Throughout the specification, the same reference numerals used to describe the invention denote the same structural elements.

[0071] The technical feature of this invention lies in providing a new application for ternary copolymers prepared by synthesizing diol compounds and maleic acid compounds, or complexes of which are chemically bonded together, with a third monomer. This allows for use not only in dry processes but also as adhesives in wet processes. The copolymers are flexible, enhance the adhesion between components within the electrode, exhibit excellent adhesion to the electrode metal, and do not impede lithium-ion movement. This provides an adhesive composition for electrode preparation containing ternary copolymers, as well as electrode material layer compositions and primer layer compositions for dry processes containing the copolymers. Furthermore, the invention is characterized by the ability to prepare thinner electrode layers using the electrode material layer compositions for dry processes, thereby providing electrodes for effectively miniaturized secondary batteries and secondary batteries prepared thereby that stably maintain electrochemical properties such as capacity and charge-discharge cycle characteristics.

[0072] Thus, the technical feature of this invention lies in a novel adhesive composition that serves to bond the active material and conductive material, which are structural components of a secondary battery, and to adhere the electrode layer (or electrode composition layer) formed therefrom to a metal electrode plate, which serves as a current collector. This adhesive composition for electrode preparation is not limited to lithium-ion batteries, but is applicable to all types of secondary batteries, including negative and / or positive electrodes containing active materials, conductive additives, and the adhesive composition. Hereinafter, the description will primarily use lithium-ion batteries. Furthermore, the description will primarily use the positive electrode, but it should be understood that this is independent of the type of active material; that is, it is equally applicable to active materials used for both positive and negative electrodes.

[0073] Therefore, the present invention provides a binder composition for dry process electrode preparation, comprising a terpolymer composed of a glycol compound, a maleic acid compound and a third monomer.

[0074] As compounds with ion conductivity, glycol compounds are components introduced to facilitate the movement of lithium ions within a battery or to minimize the obstacles to lithium ion movement. These compounds can be compounds containing ethylene glycol (HO-(CH2-CH2-O)nH) or ethylene oxide (-(CH2-CH2-O)n-) as their main chain. These two compounds, having essentially the same chemical structure, are called ethylene glycol (EG) if their molecular weight is less than 20,000 g / mol, and ethylene oxide (EO) if their molecular weight is above this value. Therefore, they will be referred to as glycol compounds in this invention. As an example, glycol compounds, as compounds composed of olefins such as ethylene or propylene and oxygen, have a main chain consisting of 2-1000 carbon atoms and can be one or more selected from the group consisting of ethylene glycol, ethylene oxide, propylene glycol, and propylene oxide.

[0075] Maleic acid compounds are components used to increase the adhesion between metal electrodes and active materials. For example, maleic anhydride is a compound with two carboxyl groups and a so-called five-membered ring structure consisting of five carbon atoms and an oxygen atom. It can be a compound that can combine with other compounds to form copolymers. As an example, it can be one or more selected from the group consisting of maleic acid, its salts, and its anhydrides.

[0076] When needed, these diol compounds and maleic acid compounds can be prepared in advance as copolymers (hereinafter referred to as diol-maleic acid complexes) through chemical reactions using organic acid reaction initiators.

[0077] As a compound that forms the terpolymer of the present invention by copolymerization with the above-mentioned diol compounds and maleic acid compounds or diol-maleic acid complexes, the third monomer is a compound having a vinyl (CH2=CH-) backbone and other functional groups attached thereto, and any monomer that is formed by binding other components to the vinyl group can be used.

[0078] The third monomer includes representative compounds such as propenyl, methpropenyl, acrylonitrile, imidazole, vinylpyrrolidone, ethylene, propylene, or monomers with double bonds in the side chain, and any one or more of these compounds can be used.

[0079] As an example, it can be one or more compounds selected from the group consisting of acrylic acid compounds, acrylonitrile compounds, ethylene compounds, imidazole compounds, imidazoleonium compounds, propylene compounds, and vinylidene compounds.

[0080] As another example, the third monomer can be one or more monomers selected from the group consisting of acrylic acid compounds, imidazoles, imidazoles, acrylates, methacrylates, acrylonitrile, pyrrolidones, ethylene, propylene, or monomers with double bonds in the side chain. Therefore, it goes without saying that the actual synthesis methods for each component will vary to some extent.

[0081] Among them, acrylic compounds can be compounds having the following chemical formulas.

[0082] Chemical Formula 1

[0083] CH2=CH-COO-R

[0084] In this case, R is any one of -H, alkyl, alkenyl, alkynyl, phenyl, and amino.

[0085] Furthermore, as compounds with a cyano group (-CN) attached to the vinyl (CH2=CH-) backbone, a typical acrylonitrile compound can be acrylonitrile (CH2=CH-CN).

[0086] The following description of the terpolymers of the present invention focuses on the use of acrylic or acrylonitrile compounds as the third monomer. However, the scope of the present invention is not limited to acrylic or acrylonitrile compounds.

[0087] The terpolymer contained in the electrode preparation adhesive composition of the present invention can be synthesized by two methods using the above-mentioned compounds, namely, using a diol compound and a maleic acid compound or a diol-maleic acid complex and a third monomer.

[0088] The first method is a one-step synthesis method: all components, including glycol compounds, maleic acid compounds, and the third monomer, are mixed in a solvent. Then, two reaction initiators are added separately: one for the glycol-maleic acid complex reaction and another for the subsequent synthesis reaction with the third monomer. Alternatively, one reaction initiator that can participate in both reactions can be added to synthesize the terpolymer. The final terpolymer is then synthesized through appropriate filtration and washing processes.

[0089] The second method is a two-step synthesis method: a reaction initiator is used to first react a diol compound with a maleic acid compound to prepare a diol-maleic acid complex. This complex is then placed in a solvent with a third monomer formed from vinyl groups and a reaction initiator is added before the reaction is repeated to synthesize a terpolymer.

[0090] Both methods involve reacting a glycol compound with a maleic acid compound to generate a glycol-maleic acid complex during the synthesis reaction, followed by copolymerization with a third monomer to ultimately prepare a terpolymer. Therefore, in the one-step synthesis method, the total weight of the glycol compound and the maleic acid compound initially added can be considered as the weight of the glycol-maleic acid complex.

[0091] Therefore, in the terpolymer contained in the electrode preparation adhesive composition of the present invention, the component ratios of each component, the component ratios of diol compounds and maleic acid compounds are calculated in molar ratios, and the component ratios of diol-maleic acid complex and third component are calculated in weight ratios, which facilitates experiments.

[0092] As a result, in the terpolymer synthesized by the above method, the molar ratio of the glycol compound to the maleic acid compound can be from 99:1 to 1:99, and the weight ratio of the glycol compound and the maleic acid compound to the third monomer can be from 99:1 to 1:99. More preferably, the molar ratio of the glycol compound to the maleic acid compound can be from 90:10 to 10:90, and the weight ratio of the glycol compound and the maleic acid compound to the third monomer can be from 90:10 to 10:90. If the molar ratio or weight ratio is below the lower limit or above the upper limit, the final product will be indistinguishable from one component, which is not conducive to well representing the characteristics of both components.

[0093] Furthermore, the terpolymer contained in the electrode preparation adhesive composition of the present invention can be synthesized using the aforementioned compounds, i.e., using glycol compounds and maleic acid compounds or glycol-maleic acid complexes with a third monomer through various methods. For example, the glycol-maleic acid complex can be synthesized using reaction initiators such as acetic acid or p-toluenesulfonic acid as organic acid systems. Furthermore, the synthesis of the glycol-maleic acid complex with acrylonitrile or acrylic acid monomers as the third component can be achieved using various methods such as free radical polymerization using free radical generating compounds such as 2,2-azobisisobutyronitrile (AIBN), peroxides, or oxidative polymerization using ammonium persulfate. In addition, the terpolymer can be synthesized by combining reaction initiators or using them sequentially, using any one or more of the following methods: photoinitiator method, ionic polymerization method, redox polymerization method using oxygen reduction reaction, or thermal polymerization method. The detailed reaction conditions for each polymerization method, namely the reaction temperature and time, the content of the reaction initiator, and other reaction conditions, such as using various solvents such as dimethylformamide (DMF) or water at a temperature of 60-120 degrees Celsius for 4-48 hours, are well known to those skilled in the art to which this invention pertains. This invention is not limited to any particular method.

[0094] The number-average molecular weight of the terpolymer contained in the adhesive composition for electrode preparation of the present invention is preferably in the range of 10,000-1,000,000 g / mol. If the number-average molecular weight of the copolymer is 10,000 g / mol, the physical properties of the electrode layer are poor due to the low molecular weight, which is disadvantageous. If it is below 1,000,000 g / mol, it is not only difficult to obtain by conventional free radical polymerization, but also difficult to mix with active materials and conductive materials due to the high molecular weight and viscosity, which is also disadvantageous.

[0095] In other embodiments, in addition to the terpolymer described above, the electrode preparation binder composition of the present invention may also contain other types of binders, wherein the weight ratio of the terpolymer to the other type of binder may be 90:10 to 10:90. In this case, the properties of each binder composition are enhanced, which is beneficial for obtaining better results. If the upper or lower limit is exceeded, it is not actually a mixture, but almost equivalent to a single binder, and its role as a mixed binder is negligible, which is therefore disadvantageous.

[0096] Other types of adhesives may use all known adhesives. As an example, one or more adhesives may contain polyolefins, polyalkylenes, polyethers, styrene-butadiene rubber (SBR), polysiloxanes and their copolymers, branched polyethers, polyvinyl ethers, polyacrylic acid, polyvinylcarbonate, their copolymers and / or mixtures thereof. In another example, the adhesive may also include guar gum, alginate, poly[(isobutylene-alt-maleic acid, ammonium salt)-co-isobutylene-alt-maleic anhydride], poly(ethylene-alt-maleic anhydride), poly(methyl vinyl ether-alt-maleic anhydride), polyacrylonitrile (PAN), acrylonitrile-acrylic acid-maleic anhydride copolymer, acrylic acid-acrylonitrile copolymer, imidazole polymers and copolymers, poly(methyl methacrylate) (PMMA), polyvinyl chloride (PVC), and polyvinyl ether. The adhesive may contain cellulose. In some embodiments, the polyolefin may include polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), copolymers thereof, and / or mixtures thereof. In another example, one or more adhesives may comprise polyvinylidene chloride, poly(phenylene oxide) (PPO), polyethylene-block-poly(ethylene glycol), polyethylene oxide (PEO), poly(phenylene oxide) (PPO), polyethylene-block-poly(ethylene glycol), polydimethylsiloxane (PDMS), polydimethylsiloxane-co-alkylmethyl siloxane, copolymers thereof, and / or mixtures thereof. In a particular embodiment, the fibrous adhesive is PTFE. One or more adhesives may comprise cellulose or cellulose derivatives.For example, cellulose derivatives may include: cellulose esters, such as cellulose acetate; cellulose ethers, such as methyl cellulose, ethyl cellulose, hydroxylpropyl cellulose (HPC), hydroxylpropylmethylcellulose (HPMC), or hydroxyethyl cellulose (HEC); cellulose nitrate; cellulose chitosan, such as carboxymethyl cellulose chitosan; or carboxyalkyl cellulose, such as carboxymethyl cellulose (CMC), carboxyethyl cellulose, carboxypropyl cellulose, or carboxyisopropyl cellulose. In an additional embodiment, cellulose or cellulose derivatives may include cellulose salts. In yet another embodiment, the cation of the cellulose salt may be selected from sodium, ammonium, calcium, or lithium. For example, cellulose or cellulose derivatives may comprise sodium cellulose salts or sodium cellulose derivative salts selected from sodium cellulose ester salts, sodium cellulose ether salts, sodium cellulose nitrate salts, or sodium carboxyalkyl cellulose salts. CMC may comprise sodium carboxymethyl cellulose salts. In one embodiment, an adhesive comprises CMC, PVDF, and / or PTFE.

[0097] The electrode preparation adhesive composition of the present invention having the above-described structure can be used not only as an adhesive for existing wet and dry processes, but also as a primer layer composition.

[0098] Next, the electrode material layer composition for dry process of the present invention comprises: an active material for a positive or negative electrode; the binder composition configured as described above; and a conductive material. As mentioned above, the binder composition may comprise one or more of terpolymers or other types of binders. In particular, it may comprise 85-99.4% by weight of the active material for the positive or negative electrode, 0.5-10% by weight of the binder composition, and 0.1-5% by weight of the conductive material.

[0099] The active material used for the positive or negative electrode can be any active material known in the technical field to which this invention pertains, suitable for use as the positive or negative electrode in a secondary battery. As an example, it can be one or more elements selected from the group consisting of alkali metals such as lithium, alkaline earth metals, manganese, nickel, cobalt, aluminum, iron, tin, graphite, titanium, silicon, silicon oxide, sulfur, and combinations thereof. If the active material percentage is less than 85% by weight, it is disadvantageous due to the low capacity of the secondary battery; if it is greater than 99.4% by weight, the low binder content reduces the adhesion between components and the adhesion to the electrode plates, resulting in poor mechanical properties, which is also disadvantageous.

[0100] If the content of the adhesive composition is less than 0.5% by weight, the active material electrode layer formed on the electrode plate will easily fall off due to insufficient adhesive, which is disadvantageous. If it is greater than 10% by weight, although there is the advantage of strong adhesion of the active material electrode layer to the electrode plate, the relatively low content of active material will ultimately result in a small electrode volume capacitance, which is also disadvantageous.

[0101] Conductive materials are structural elements that contribute to the electrical conductivity between components within the electrode layer and to the conductivity of the electrode layer and the metal plate acting as a current collector. Carbon-based nanomaterials can be used. In one example, one or a combination of several nanomaterials such as conductive carbon black, graphene, carbon nanotubes (single-walled, double-walled, multi-walled, branched, etc.), carbon nanoribbons, and carbon nanosheets can be used. It is generally preferred to use carbon nanotubes with a high aspect ratio and nano-carbon materials with an aspect ratio of less than 100 (e.g., conductive carbon black).

[0102] If the content of conductive material is less than 0.1% by weight, it will be unfavorable due to the low conductivity. If it is greater than 5% by weight, it will be unfavorable because it will reduce the content of active material and thus reduce the capacity of the final secondary battery.

[0103] If necessary, the electrode material layer composition for dry process of the present invention may further include acrylate compounds and a curing agent for said acrylate compounds.

[0104] That is, when forming the electrode material layer through the dry process, pressure and heat should first be applied to the dry-mixed components to prepare a thin film. In the process of preparing the electrode material layer composition by mixing active materials, binder compositions and conductive materials, acrylate compounds and their curing agents, which exist in a liquid state at room temperature and change to solids when cured by appropriate methods, are also included. They act as liquid processing aids in the mixing process of the dry process, which can make the active material sheet thinner and easier to prepare, and make the surface of the prepared electrode layer more beautiful, which is beneficial to the preparation of electrode plates for secondary batteries.

[0105] Among these, acrylate compounds are not limited as long as they exist in a liquid state at room temperature and can be solidified through additional processing, i.e., a curing process. This is because they have the following characteristics: when an acrylate compound existing in a liquid state at room temperature is combined with a curing agent of appropriate form and cured under appropriate conditions, it transforms into a solid polymer with a three-dimensional network structure. The acrylate compound does not dissolve in the electrolyte and does not adversely affect the battery performance. In the case of acrylate compounds with more suitable functional groups, the polymer morphology with a three-dimensional network structure formed after curing can also increase adhesion to the metal electrode plate, which is advantageous. On the other hand, while acrylate compounds are mainly used in the examples, it is self-evident that methacrylate compounds with similar properties are also included. Therefore, it should be understood that the acrylate compounds used in this invention include not only acrylate compounds and methacrylate compounds, but also compounds of the same class with other substituents.

[0106] Acrylic ester compounds are not limited as long as they contain two or more functional groups. The functional groups are also not limited as long as they can react with heat or light. They can be selected from one or more of the group consisting of methylene, urethane, ester, ether, oxide, ethylene oxide, propylene oxide, ethylene glycol, propylene glycol, butadiene, imide, amino, amide, epoxy, olefin, sulfonic acid, or combinations thereof. In particular, they can be acrylate compounds containing 2 to 16 functional groups. If there are two or fewer functional groups, it is a monofunctional acrylate, resulting in a low curing point and a slow curing reaction, which is disadvantageous. If there are 16 or more functional groups, the curing reaction is too fast due to the excessive number of functional groups, making it difficult to regulate the reaction rate, or there is a risk of the polymer transforming into a hard polymer in a short time, which is also disadvantageous.

[0107] Furthermore, unless otherwise specified, the acrylate compounds used in this invention refer to acrylate compounds in all forms, including monomers and oligomers. As an example, they can be monomers or oligomers with a main chain consisting of 2 to 1000 carbon atoms. If the main chain has fewer than 2 carbon atoms, it becomes a very brittle polymer during post-curing and is unsuitable as an adhesive, which is disadvantageous. If the main chain has more than 1000 carbon atoms, steric hindrance hinders its function as an adhesive, which is also disadvantageous. This invention uses acrylate compounds that are liquid at room temperature and cured through additional treatment as adhesives as its main technical feature; therefore, the mentioned functional groups are merely illustrative and not intended to be limiting.

[0108] The acrylate compounds used in this invention can be selected from various aliphatic and aromatic acrylate monomers such as triethylene glycol acrylate, trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, trimethylolpropane trimethacrylate, and bisphenol A ethylene oxide dimethacrylate, as well as complexes (i.e., oligomers, such as methylene, urethane, ester, ether, oxide, ethylene oxide, propylene oxide, ethylene glycol, propylene glycol, butadiene, imide, amino, amide, epoxy, olefin, and sulfonic acid groups) formed by the main chain monomers constituting these acrylates with two or more units.

[0109] The active material used for the positive or negative electrode may contain 0.1 to 10 parts by weight of the acrylate compound per 100 parts by weight. If the content of the acrylate compound is less than 0.1 parts by weight, the effect of the acrylate will be negligible due to the low content of the acrylate compound, which is disadvantageous. If it is more than 10 parts by weight, the capacity per unit volume will be low because the content of the acrylate compound is higher than the required content, which is also disadvantageous.

[0110] Acrylic ester curing agents are structural elements used to transform acrylate compounds, which are liquid at room temperature, into polymers with a three-dimensional network structure through separate curing processes. One or more thermosetting and photocuring agents can be used. This is because, when photocuring is readily achieved, especially with thick electrode layers, the parallel use of photocuring agents (photoinitiators) and thermosetting agents is more effective. These curing agents can be used regardless of their type, as long as they generate free radicals through heat or light.

[0111] More specifically, the thermal initiator, as a curing agent containing peroxides or azo compounds, is not particularly limited in type, as long as it decomposes at a temperature between 50°C and 180°C to generate a reaction initiator. For example, a peroxide-containing curing agent could be benzoyl peroxide (BP), which generates oxygen free radicals, and an azo compound-containing curing agent could be 2,2-azobisisobutyronitrile (AIBN), etc. In this case, if the curing agent's decomposition temperature is less than 50°C, the reaction initiator is generated too easily due to the low decomposition temperature, which is disadvantageous. If the decomposition temperature is above 180°C, the cost is disadvantageous due to the excessively high temperature required for the curing reaction. Preferably, a curing agent that decomposes at a temperature between 50°C and 150°C is used.

[0112] Photoinitiators can be curing agents containing phenyl ketone compounds or phosphine oxide compounds that generate free radicals when exposed to ultraviolet (UV) light. In one example, solid or liquid photoinitiators such as hydroxycyclohexylphenyl ketone, hydroxydimethyl acetophenone, trimethylbenzoyl diphenylphosphine oxide, or methyl benzoylformate can be used.

[0113] Based on 100 parts by weight of acrylate compound, it may contain 0.1 to 20 parts by weight of curing agent. If the content of curing agent is less than 0.1 parts by weight, there is a high possibility that the acrylate compound will remain in a liquid state after curing because it is not cured, which is disadvantageous. If it is more than 20 parts by weight, it will become too hard due to over-curing, or the adhesive contained therein will deteriorate due to side reactions caused by the free radicals generated by the remaining curing agent that did not participate in the curing reaction.

[0114] On the other hand, the electrode preparation binder composition containing ternary copolymers of the present invention can be used not only in the aforementioned dry process but also as a binder in existing wet processes. For example, the ethylene glycol-maleic acid-acrylonitrile copolymer of the present invention can be dissolved in a solvent such as NMP, and then an NCM-type positive electrode active material and a conductive material such as conductive carbon black or carbon nanotubes can be added and dispersed to prepare an electrode composition slurry. This slurry is then coated onto a metal electrode plate and dried to prepare a positive electrode plate. Furthermore, it goes without saying that in the case of all-solid-state batteries, the ternary copolymer of the present invention can also be used with the active material or other structural components to prepare an electrode composition, which can then be used to prepare an electrode.

[0115] Next, the primer composition of the present invention comprises a terpolymer and a carbon nanomaterial. The carbon nanomaterial is used to impart conductivity to the primer layer, and there is no limitation on any carbon-based material of nanoscale size. As an example, the carbon nanomaterial can be one or a combination of more than one of conductive carbon black, carbon nanotubes (single-walled, double-walled, or multi-walled), graphene, carbon nanotubes (CNP), carbon nanoribbons, etc.

[0116] Based on 100 parts by weight of the terpolymer, the content of nano-carbon material can range from 0.05 to 300 parts by weight. If the content of nano-carbon material is less than 0.05 parts by weight, the conductivity will be poor due to the low content of the conductivity enhancer, which is unfavorable. If it is more than 300 parts by weight, the viscosity of the primer material will be too high due to the high content of the conductivity enhancer, which will reduce the coatability and is also unfavorable. Any organic solvent and aqueous solvent can be used in the preparation of the primer layer composition, and it is not limited to any particular solvent.

[0117] The method for preparing the primer composition involves dispersing the terpolymer of the present invention with nano-carbon materials in a solvent such as NMP or water under high pressure and high speed. The content of solid components in the primer composition can be 0.2-40% by weight relative to the total weight of the solution. If the solid component content is less than 0.2%, the wet film thickness must be too thick to obtain a primer layer of the specified thickness, which is disadvantageous. If it is above 40%, the viscosity is too high, making it difficult to obtain a thin primer layer, which is also disadvantageous.

[0118] As described later, the thickness of the primer layer formed on the surface of the metal electrode can be in the range of 0.05-5 μm. Preferably, when a primer layer with a thickness of 1 μm is formed on a polyester film, the surface resistivity is 10 Ω·cm. 7 Below ohms per area. This is to ensure smooth movement of electrons through the primer layer. If the surface resistance of the primer layer is 10... 7 If the ratio of ohms to area exceeds a certain threshold, the movement of mutually attracted electrons will be somewhat restricted, ultimately leading to a decrease in battery performance, which is therefore detrimental.

[0119] As described above, when an electrode composition sheet is prepared by a dry process and then attached to a metal electrode plate to form an electrode plate, it is advantageous to form a primer layer on the surface of the metal electrode plate as needed, and then attach the electrode composition layer thereon. The primer layer used should have high conductivity. The primer composition is prepared by using the terpolymer of the present invention as a binder and mixing nano-carbon materials therein. The reason for using a primer composition prepared by using a binder composition containing the terpolymer of the present invention is that maximizing the adhesion between the two layers is achieved by using the same binder for both the primer layer and the active material layer.

[0120] Next, the electrode for secondary batteries of the present invention comprises a positive electrode material layer or a negative electrode material layer formed from any of the above-described dry process electrode material layer compositions. The positive electrode material layer or the negative electrode material layer has a thickness of less than 100 μm. In particular, when the dry process electrode material layer composition comprises an acrylate compound, a thinner electrode film with excellent properties can be prepared.

[0121] As described below, when preparing the electrode for the secondary battery of the present invention using a dry process, that is, when attaching a sheet prepared from the electrode material layer composition for the dry process to a metal electrode plate, a metal electrode plate (positive electrode: aluminum, negative electrode: copper) forming a primer layer is used. However, unlike the dry process, in the wet process, even without a primer layer, the adhesion of the electrode layer is excellent; therefore, an electrode layer is formed on a metal electrode plate without a primer layer.

[0122] Next, the method for preparing an electrode for a secondary battery according to the present invention may include: the steps of forming a positive electrode material sheet or a negative electrode material sheet using any of the dry process electrode material layer compositions; an attachment step of attaching the positive electrode material sheet or a negative electrode material sheet to a metal electrode plate; a curing step of curing the attached positive electrode material sheet or a negative electrode material sheet; and a rolling step of rolling the electrode obtained by performing the curing step. These steps can be performed in batches or by a continuous process to prepare the final electrode plate. Adopting a continuous process may be the most efficient preparation process.

[0123] The composition preparation step can be carried out using any known mixing method as long as all the constituent components can be added, i.e., the active material for the negative or positive electrode, the binder composition for electrode preparation, and the conductive additive are added, followed by dry shearing and mixing. Liquid acrylate compounds and curing agents for acrylate compounds can be added if necessary. Various mixing methods can be used, and mixing equipment includes mixers (low-speed or high-speed mixers) such as Henschel mixers with appropriately shaped blades, or mixing containers in the form of extruders capable of continuous processes. Representative mixing devices such as single-screw extruders, twin-screw extruders, or continuous kneaders with added mixing functions are effective.

[0124] The aforementioned continuous mixing apparatus uses a die at the end capable of producing sheet-like shapes of appropriate thickness to prepare active substance composition sheets of a specified thickness. These sheets are then subjected to multiple rolling processes to achieve the desired thickness, thus enabling the sheet formation step. In the embodiments and comparative examples described later, a calendering method using two rollers installed at a specified interval was used.

[0125] The adhesion step may include the following steps: forming a primer layer on the metal electrode plate; and pressing the positive or negative electrode material sheet onto the primer layer. In a continuous process, the adhesion step can be performed on a metal electrode plate supplied by a separate supply device. The primer layer can be formed with a thickness of 0.05-5 μm by coating the primer layer composition described above. If the thickness is less than 0.05 μm, the coating operation itself is difficult due to the thinness of the primer layer, and the improvement in adhesion is negligible, which is disadvantageous. If the thickness is greater than 5 μm, the excessive thickness of the conductive layer may hinder the movement of lithium ions, which is also disadvantageous.

[0126] The curing step acts as an adhesive by solidifying the acrylate compound on the positive or negative electrode layer attached to the metal plate in the curing adhesion step. It is also a process used to strengthen the adhesion of the sheet to the metal plate. It can be carried out by either heat curing at a temperature of 50°C to 150°C for 5 to 30 minutes or by light curing by irradiation with ultraviolet light.

[0127] The rolling step can be a step performed to increase electrode density by finally extruding the electrode material layer obtained by the curing step with appropriate force.

[0128] Example 1

[0129] Electrode preparation adhesive composition 1 is prepared by synthesizing ethylene glycol-maleic acid-acrylic acid copolymer as a terpolymer in one or two steps as follows.

[0130] 1. One-step synthesis

[0131] Ethylene glycol (4000 g / mol) and maleic acid (116 g / mol) were weighed in a 1:1 molar ratio and added to dimethylformamide. Acrylic acid was then mixed in the solution in a 1:1 weight ratio to the total weight of ethylene glycol and maleic acid. The mixture was then heated to 70°C and stirred for 10 minutes. While maintaining this temperature, 1.5% by weight of ammonium persulfate (APS) was slowly added dropwise as a reaction initiator, and the reaction proceeded for 5 hours. After the reaction was complete, ethanol was added to solidify the mixture, which was then filtered / purified and vacuum dried (40°C, 24 hours) to obtain the final terpolymer.

[0132] 2. Two-step synthesis

[0133] First, ethylene glycol (4000 g / mol) and maleic acid (116 g / mol) were weighed in a 1:1 molar ratio and added to dimethylformamide to achieve a solid content of 5% by weight. The mixture was stirred at 90°C for 10 minutes to mix. Then, at the same temperature, 1.5% by weight of p-toluenesulfonic acid (p-CH3CH6CH4SO3H) (reaction initiator) was slowly added dropwise to the mixture while reacting for at least 6 hours until the mixture turned white. The reacted mixture was then slowly introduced into ether to precipitate the synthesized product, which was then filtered and vacuum dried (50°C, 24 hours) to obtain the ethylene glycol-maleic acid complex.

[0134] The ethylene glycol-maleic acid complex, weighed at a 1:1 ratio, was mixed with acrylic acid and placed in water. The mixture was then heated to 70°C with stirring. Ammonium persulfate, acting as a reaction initiator, was then added dropwise over 10 hours to synthesize the ethylene glycol-maleic acid-acrylic acid terpolymer. In this case, the content of ammonium persulfate as the reaction initiator was 1.5% by weight relative to the total solids composition. After all reactions were completed, the solid obtained by pressure filtration of the reactants was vacuum dried (40°C, 24 hours) to obtain the ethylene glycol-maleic acid-acrylic acid terpolymer.

[0135] Example 2

[0136] Electrode preparation adhesive composition 2 is prepared by synthesizing ethylene glycol-maleic acid-acrylonitrile copolymer as a terpolymer in one step as follows.

[0137] Except for one step of the synthesis process in Example 1, which uses acrylonitrile (53 g / mol) instead of acrylic acid, the ethylene glycol-maleic acid-acrylonitrile copolymer was obtained in the same manner as in Example 1.

[0138] Example 3

[0139] In the manner described below, the ethylene glycol-maleic acid-acrylonitrile copolymer synthesized in Example 2 also contains PTFE as another type of binder to prepare an electrode preparation adhesive composition 3.

[0140] ethylene glycol-maleic acid-acrylonitrile copolymer and PTFE were uniformly mixed at a weight ratio of 3:1.

[0141] Example 4

[0142] Except for using ethylene glycol-maleic acid-acrylonitrile copolymer and PTFE in a 1:1 weight ratio, the electrode preparation adhesive composition 4 was prepared in the same manner as in Example 3.

[0143] Example 5

[0144] Using electrode preparation binder composition 2, a positive electrode composition slurry, a positive electrode, and a button cell are prepared by a wet process in the following manner.

[0145] 1. Prepare the electrode composition slurry for the positive electrode.

[0146] To prepare a positive electrode composition slurry, 2.0% by weight of electrode preparation binder composition 2, 96.0% by weight of active material (NCM811), and 2.0% by weight of conductive carbon black (solid content in the slurry: 70%) are placed in NMP and mixed in a C-mixer at 2000 rpm for 20 minutes.

[0147] 2. Prepare the positive electrode

[0148] The electrode composition slurry for the positive electrode is coated onto an aluminum foil serving as the positive electrode plate and dried to prepare a 40-micrometer-thickness electrode (loading: 10 mg / cm²). 2 The positive electrode plate of the electrode material layer.

[0149] 3. Prepare button batteries

[0150] A coin cell (CR2032) with a half-cell structure was fabricated using a positive electrode plate. In this case, lithium metal foil was used as the counter electrode, and 1.15 moles of LiPF6 were dissolved in a mixed solvent of carbonates (EC, PC, DEC, VC, and FEC, weight ratio: EC / PC / DEC / VC / FEC = 2 / 1 / 7 / 0.05 / 0.05) to serve as the electrolyte. The coin cell was fabricated in an argon-filled glove box.

[0151] Example 6

[0152] Using an electrode preparation binder composition 1 synthesized in two steps, a negative electrode composition slurry, a negative electrode, and a button cell are prepared by a wet process as follows.

[0153] 1. Prepare the electrode composition slurry for the negative electrode.

[0154] A negative electrode composition slurry was prepared by mixing 2.7% by weight of the binder composition 1 for electrode preparation, 96.3% by weight of the mixed active material (graphite / SiOx = 90 / 10 by weight, theoretical capacity ~470mAh / g), 1.0% by weight of carbon black, and 0.3% by weight of single-walled carbon nanotubes in a DMF / water mixed solvent (weight ratio: 8:2) (solid content in the slurry: 70%) and kneading once. Then, the mixture was put back into a C-Mixer and mixed at 2000 rpm for 10 minutes.

[0155] 2. Prepare the negative electrode

[0156] A negative electrode plate is prepared by coating the electrode composition slurry for the negative electrode onto a copper foil and drying it. The negative electrode plate is formed by an electrode layer with a thickness of 20 micrometers.

[0157] 3. Prepare button batteries

[0158] A charge-discharge cycle test battery (type 2032) was prepared using a negative electrode plate. The electrolyte used was the electrolyte from Example 5.

[0159] Example 7

[0160] Using an electrode preparation binder composition 2, a dry process electrode material layer composition 1, a secondary battery positive electrode 1, and a button cell are prepared by a dry process as follows.

[0161] 1. Preparation of electrode material layer composition for dry process

[0162] A dry process positive electrode material layer composition 1 is prepared by mixing 3.5% by weight of electrode preparation binder composition 2, positive electrode active material (NCM811, 95% by weight) and 1.5% by weight of conductive carbon black, and kneading them at 120°C and 40 rpm for 20 minutes using a kneader.

[0163] 2. Prepare the positive electrode

[0164] After preparing an 80-micron-thick positive electrode sheet by rolling the prepared dry-process positive electrode material layer composition at room temperature, it was then pressed onto an electrode plate forming a primer layer (8 kgf / cm²). 2 To prepare the positive electrode plate.

[0165] 3. Prepare button batteries

[0166] A coin cell (CR2032) with a half-cell structure was fabricated using the positive electrode plate. The remaining configuration is the same as in Example 5.

[0167] Example 8

[0168] Using an electrode preparation binder composition 1 synthesized in two steps, a dry process negative electrode material layer composition 1, a negative electrode 1, and a button cell are prepared by a dry process as follows.

[0169] 1. Preparation of negative electrode material layer composition for dry process

[0170] A negative electrode material layer composition for dry process was prepared by mixing 3.5% by weight of electrode preparation binder composition 1, 95.0% by weight of mixed active material (graphite / SiOx = 90 / 10 by weight, theoretical capacity 470 mAh / g), 1.0% by weight of carbon black, and 0.5% by weight of single-walled carbon nanotubes using the same method as in Example 7.

[0171] 2. Prepare the negative electrode

[0172] After preparing an 80-micrometer-thick negative electrode layer by rolling the dry process negative electrode material layer composition at room temperature, it is attached to a copper foil forming a primer layer to prepare a negative electrode plate with a thickness of about 65 micrometers.

[0173] 3. Prepare button batteries

[0174] A charge-discharge cycle test battery (type 2032) was prepared using a negative electrode plate. The electrolyte used was the electrolyte from Example 5.

[0175] Example 9

[0176] 1. Preparation steps of electrode material layer composition for dry process

[0177] A dry-process positive electrode material layer composition 2 is prepared by mixing 1.5% by weight of an electrode preparation binder composition 2, 2% by weight of an acrylate compound (a mixture of ethylene glycol bifunctional monomers and hexafunctional 6-ethylene glycol oligomers in a 1:1 weight ratio), 2 parts by weight of AIBN (thermosetting agent) relative to the acrylate compound, 5 parts by weight of a phosphine oxide curing agent (photocuring agent), a positive electrode active material (NCM811, 95% by weight), and 1.5% by weight of conductive carbon black, and kneading the mixture at 120°C and 40 rpm for 20 minutes using a kneader.

[0178] 2. Steps for forming positive electrode material sheets

[0179] Apply 7 kgf / cm to the positive electrode material layer composition 2 2 The pressure is applied and the material is rolled multiple times to form a 70μm thick positive electrode material sheet.

[0180] 3. Attachment Steps

[0181] ① Steps for forming the primer layer

[0182] To attach the positive electrode material layer to the aluminum electrode plate, a primer layer was formed on the electrode plate surface as follows: Carbon nanotubes and ethylene glycol-maleic anhydride-acrylonitrile copolymer (CNP Solutions, Korea) were placed in NMP with the primer and stirred at room temperature for 10 minutes. The mixture was then re-dispersed using a pressure spray method to prepare the primer layer composition. The carbon nanotube content in the binder was 20% by weight relative to the total weight of the copolymer, and the solid content in the dispersion was 4% by weight. The primer layer was formed on an aluminum foil (thickness: 12 micrometers) with a thickness of approximately 1.0 μm using a bar coater (drying: 130°C, 2 minutes). Tape testing of the primer layer confirmed good adhesion and no peeling from the electrode plate. Furthermore, the surface resistivity of the electrode plate with the primer layer was 400 ohms / area.

[0183] ② Pressing steps

[0184] A temporary positive electrode is formed by placing a positive electrode material layer on an aluminum electrode plate that forms a primer layer and pressing them together.

[0185] 4. Curing Steps

[0186] After treating the temporary positive electrode at 120 degrees Celsius for 10 minutes, it was then irradiated with ultraviolet light (700 mJ / cm²). 2 This process cures ethylene glycol bifunctional monomers and hexafunctional ethylene glycol oligomers, which are acrylate compounds, so that the acrylate compounds used as adhesives do not dissolve in the electrolyte and thus act as adhesives.

[0187] 5. Rolling Steps

[0188] The electrode density of the positive electrode material layer composition 2, after the curing step, is 1.0 g / cm³ through a rolling process. 3 To finally prepare a positive electrode 2 for a secondary battery containing a positive electrode material sheet with a thickness of 70 μm.

[0189] Example 10

[0190] Except for the use of 2 parts by weight of electrode preparation adhesive composition 2, 1.5 parts by weight of acrylate compound (mixed with ethylene glycol bifunctional monomer and hexafunctional ethylene glycol oligomer in a 1:1 weight ratio), 2 parts by weight of AIBN (thermosetting agent) relative to the weight of the acrylate compound, and 5 parts by weight of phosphine oxide curing agent (photocuring agent) in the preparation of the electrode material layer composition for dry process in Example 9, the positive electrode 3 for secondary battery was finally prepared in the same manner as in Example 9.

[0191] Example 11

[0192] Except for the use of the binder composition 3 for electrode preparation, the positive electrode 4 for secondary batteries was prepared in the same manner as in Example 7.

[0193] Example 12

[0194] Except for using the electrode preparation binder composition 4, the positive electrode 5 for secondary batteries was prepared in the same manner as in Example 7.

[0195] Example 13

[0196] Except for the use of the electrode preparation binder composition 3, the positive electrode 6 for secondary batteries was prepared in the same manner as in Example 10.

[0197] Comparative Example 1

[0198] Comparative Example Positive Electrode 1 was obtained using the same method as in Example 7, except that an electrode plate without a primer coating was used.

[0199] Comparative Example 2

[0200] The comparative example positive electrode 2 was obtained by the same method as in Example 7, except that polytetrafluoroethylene was used instead of the electrode preparation adhesive composition 2. In this case, in order to prepare an electrode layer with a thickness of less than 90-100 micrometers, 15-20 ton / cm² is required. 2 High pressure on the left and right.

[0201] Experimental Example 1

[0202] Infrared spectrometer (Fourier transform infrared spectrometer) was used to confirm whether the ethylene glycol-maleic acid-acrylic acid terpolymer synthesized in Example 1 through one or two steps was synthesized into the same substance.

[0203] The ethylene glycol-maleic acid-acrylic acid synthesized in both one-step and two-step processes were white particles. The presence or absence of the ketone peak of acrylic acid was used to confirm that the ethylene glycol-maleic acid-acrylic acid synthesized in both processes was a terpolymer.

[0204] The molecular weight of the terpolymer synthesized in one step was measured by chromatography, and the number average molecular weight was 22,500 g / mol. The molecular weight of the terpolymer synthesized in two steps was measured by chromatography, and the molecular weight was 25,000 g / mol.

[0205] As mentioned above, the infrared absorption spectra of the terpolymers synthesized by one-step and two-step methods are very similar to each other. Therefore, it can be confirmed that the one-step and two-step synthesis methods are the same methods for synthesizing the same copolymer.

[0206] And, as Figure 2 As shown, the terpolymer synthesized in Example 2, namely the ethylene glycol-maleic acid-acrylonitrile copolymer, appears as ivory-colored particles upon visual observation. The synthesis of this copolymer was confirmed by the presence or absence of an acrylonitrile peak using Fourier transform infrared spectroscopy (FTIR), indicating successful copolymerization of the three components. The number-average molecular weight, measured by chromatography, was 31600 g / mol.

[0207] Experiment Example 2

[0208] To verify whether the electrode material layer adheres well to the metal electrode plate using positive and negative electrodes prepared by a wet process, and positive electrodes 1 to 6 for secondary batteries and negative electrodes prepared by a dry process, as well as comparative example positive electrode 1 and comparative example positive electrode 2, an adhesion test was conducted using Scotch tape. For this purpose, after attaching 3M Scotch tape to the surface of the electrode material layer, the degree of adhesion was determined by whether the electrode material layer peeled off from the electrode plate during the peeling process. That is, if the electrode layer peels off from the electrode plate after the tape is attached to the surface, the adhesion is considered poor.

[0209] The results of the adhesion test using Scotch tape confirmed that, whether the positive and negative electrodes were prepared by wet process or the positive electrode 1 to the positive electrode 6, the negative electrode and the comparative example positive electrode 2 were prepared by dry process, the electrode material layer was well attached to the electrode plate.

[0210] However, in Comparative Example 1, the positive electrode used an electrode plate without a primer layer. When forming the electrode composition sheet, the tape test results confirmed that the electrode composition layer was completely peeled off. Thus, since the electrode composition layer was peeled off from the electrode plate due to the lack of a primer layer, further testing was meaningless. Therefore, no further testing was conducted on Comparative Example 1.

[0211] Furthermore, in the case of positive electrodes 1 to 6 for secondary batteries prepared by dry process, it was found that the surface appearance of the electrode layers of positive electrodes 2, 3 and 6 prepared by using an acrylate compound and an electrode material layer composition containing the acrylate curing agent is significantly cleaner, and the thickness of the electrode layer sheet can be thinner when using acrylate and its curing agent.

[0212] In particular, the positive electrode material sheets of the positive electrodes 2, 3, and 6 for secondary batteries exhibit excellent processability. Since acrylate compounds are liquid at room temperature, it is anticipated that the mixing and rolling processes of the active material compositions, which are mostly composed of inorganic particles, will be significantly easier. Therefore, when the electrode material layer compositions of the present invention contain acrylate compounds and their curing agents, they can not only function as processing aids or mixing binders for dry processes but also further improve the performance of lithium-ion batteries.

[0213] In the preparation of positive electrodes 4 and 5 in Examples 11 and 12, the appearance of the electrode layer was neat during the rolling process. The pressure used to attach the electrode layer to the electrode plate was also lower than that used in the preparation of the positive electrode 2 in Comparative Example 2, i.e., lower than that used only PTFE. Therefore, the electrode plate can be prepared more easily compared to using only PTFE. This demonstrates that the terpolymer of the present invention can be used in combination with PFTE, a prior art adhesive, without significant problems.

[0214] Experimental Example 3

[0215] Based on the results of Experiment 2, charge-discharge cycle tests were conducted on the positive and negative electrode plates with well-attached electrode layers. During the charge-discharge cycle tests, the formation process was initially performed at a rate of 0.1-1.0C, followed by lifetime tests at 0.2C or 1.0C. For all positive and negative electrodes prepared by wet or dry processes, the discharge capacity after 3 or 4 cycles was used as the initial capacity, and these initial capacities were compared with the discharge capacity after 50 cycles to calculate the capacity retention. The cycle test results are as follows: Figures 3 to 8 As shown.

[0216] First, the results of charge-discharge cycle tests were conducted using the coin cell fabricated with the positive electrode prepared by the wet process in Example 5, such as... Figure 3 As shown, the discharge capacity was 182 mAh / g after 4 cycles and 176 mAh / g after 50 cycles, with almost no capacity reduction (capacity retention: ~97%).

[0217] Furthermore, for the button cell prepared using the negative electrode produced by the wet process in Example 6, after initialization, a cycle test was conducted at a rate of 0.5C. The results of the charge-discharge cycle test for the negative electrode cell are shown below. Figure 4 It can be seen that the discharge capacity is 435 mAh / g after 3 cycles and 420 mAh / g after 50 cycles, with a capacity retention of approximately 97%.

[0218] The results of charge-discharge cycle tests on the button cell prepared using the positive electrode 1 prepared by the dry process in Example 7 are as follows: Figure 5 As shown, the discharge capacity is 189 mAh / g after 4 cycles and 179 mAh / g after 50 cycles, with a capacity retention of approximately 95%.

[0219] Although not illustrated, the results of charge-discharge cycle tests on the button cell prepared using the negative electrode prepared by the dry process in Example 8 show that the discharge capacity is 412 mAh / g after 4 cycles and 395 mAh / g after 50 cycles, indicating a capacity retention of approximately 95%.

[0220] The results of charge-discharge cycle tests on the button cell prepared using the positive electrode 2 prepared by the dry process in Example 9 are as follows: Figure 6 As shown, the discharge capacity after 4 cycles is 189 mAh / g and the discharge capacity after 50 cycles is 180 mAh / g, showing a capacity retention of approximately 95%. Although not shown, it is confirmed that the button cell prepared using the positive electrode 3 prepared by the dry process in Example 10 shows a capacity retention of approximately 94%.

[0221] The results of charge-discharge cycle tests were performed on the coin cell prepared using the positive electrode 2 of Comparative Example 2, which was prepared by the dry process in Comparative Example 2. Figure 7 As shown, the discharge capacity was 192 mAh / g after 4 cycles, but only 150 mAh / g after 50 cycles, indicating a sharp decrease in capacity. As mentioned above, PTFE, used as a binder in the prior art, requires extremely high pressure to prepare the electrode layer, and in charge-discharge cycle tests, it was observed that the battery capacity continuously decreased with each charge-discharge cycle.

[0222] The results of charge-discharge cycle tests on the button cell (type 2032) prepared using the positive electrode 4 prepared by the dry process in Example 11 are as follows: Figure 8 As shown, the initial capacity is approximately 185 mAh / g or higher, and the capacity retention rate after 50 cycles is 94%. The results of charge-discharge cycle tests on the button cell (type 2032) prepared using the positive electrode 5 prepared by the dry process in Example 12, although not illustrated, confirmed a similarity to Example 11: an initial capacity of approximately 185 mAh / g or higher, and a capacity retention rate of approximately 95% after 50 cycles.

[0223] Although not illustrated, the results of charge-discharge cycle tests on the button cell prepared using the positive electrode 6 prepared by the dry process in Example 13 showed a discharge capacity of 190 mAh / g after 4 cycles and a capacity retention of 94% after 50 cycles. This indicates that acrylate compounds are also effective in the preparation of active material composition sheets when mixed with a binder.

[0224] The above experimental results confirm that the adhesive composition containing the glycol-maleic acid-based terpolymer of the present invention can be used not only in adhesives for electrode preparation in dry processes, but also in adhesives for electrode preparation in wet processes, and can also be used in primer compositions, and can be mixed with other existing adhesives for use.

[0225] Furthermore, it is known that the binder composition for electrode preparation containing the terpolymer of the present invention has good dry processability and can prepare electrodes with relatively thin thickness (less than 100 micrometers), thereby producing electrodes with excellent electrochemical properties.

[0226] In particular, it was confirmed that when acrylate compounds and curing agents for acrylate compounds are used in the dry-processing electrode material layer composition containing the adhesive composition for electrode preparation, the acrylate compounds are liquid at room temperature, making it possible to uniformly mix the electrode material layer composition containing positive or negative electrode active materials. The electrode sheet formed from the electrode material layer composition, i.e., the positive or negative electrode material sheet, also exhibits excellent processability, with a strength of less than 10 kgf / cm². 2 Thin electrode material compositions with a thickness of less than 100 micrometers can be prepared under relatively low pressure. Ultimately, not only does the electrode material composition exhibit excellent adhesion to the metal electrode plate after the curing process, but it also maintains a high capacity retention rate during charge-discharge cycle tests.

[0227] As described above, the electrode material layer composition comprising the binder composition for electrode preparation of the present invention can be used to form a positive electrode material layer and a negative electrode material layer, thereby enabling its use in conventional secondary batteries, including lithium-ion batteries using active materials.

[0228] The present invention has been illustrated by the preferred embodiments described above, but is not limited to the embodiments described. Various changes and modifications can be made by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A binder composition for electrode preparation, characterized in that, It contains terpolymers composed of diol compounds, maleic acid compounds and a third monomer.

2. The binder composition for electrode preparation according to claim 1, characterized in that, The third monomer is a compound having a main chain containing vinyl groups and other functional groups attached to it.

3. The binder composition for electrode preparation according to claim 2, characterized in that, The compound is selected from one or more of the group consisting of acrylic acid compounds, acrylonitrile compounds, ethylene compounds, imidazole compounds, imidazoleonium compounds, propylene compounds, and vinylidene compounds.

4. The binder composition for electrode preparation according to claim 1, characterized in that, The third monomer is an acrylic acid compound having the following chemical formula 1. Chemical Formula 1: CH2=CH-COO-R, In the above chemical formula 1, R is any one of -H, alkyl, alkenyl, alkynyl, phenyl, and amino.

5. The binder composition for electrode preparation according to claim 2, characterized in that, The molar ratio of diol compounds to maleic acid compounds in the terpolymer is 99:1 to 1:99, and the weight ratio of diol compounds and maleic acid compounds to the third monomer is 99:1 to 1:

99.

6. The binder composition for electrode preparation according to claim 1, characterized in that, The diol compounds are compounds whose main chain is composed of ethylene glycol or ethylene oxide. The chemical formula of ethylene glycol is HO-(CH2-CH2-O)nH, and the chemical formula of ethylene oxide is -(CH2-CH2-O)n-, where n is a natural number greater than 0. The maleic acid compounds are compounds containing a five-membered ring structure with two carboxyl groups.

7. The binder composition for electrode fabrication according to claim 6, characterized in that, The diol compound is selected from one or more of the group consisting of ethylene glycol, ethylene oxide, propylene glycol, and propylene oxide. The maleic acid compounds are selected from one or more of the group consisting of maleic acid, its salts and its anhydrides.

8. The binder composition for electrode preparation according to claim 1, characterized in that, The terpolymer is ethylene glycol-maleic acid-acrylonitrile or ethylene glycol-maleic acid-acrylic acid.

9. The binder composition for electrode preparation according to claim 1, characterized in that, The number-average molecular weight of the terpolymer is 10,000-1,000,000 g / mol.

10. The binder composition for electrode preparation according to claim 1, characterized in that, It also contains one or more other types of adhesives, wherein the weight ratio of the terpolymer to the adhesive is 90:10 to 10:

90.

11. The binder composition for electrode fabrication according to claim 10, characterized in that, The adhesive is one or more of carboxymethyl cellulose, polyvinylidene fluoride, polytetrafluoroethylene, and polyacrylic acid.

12. An electrode material layer composition for dry process, characterized in that, Include: The positive or negative electrode uses an active material; The adhesive composition according to any one of claims 1 to 11; and Conductive materials.

13. The electrode material layer composition for dry processes according to claim 12, characterized in that, It comprises 85-99.4% by weight of the active material for the positive or negative electrode, 0.5-10% by weight of the binder composition, and 0.1-5% by weight of the conductive material.

14. The electrode material layer composition for dry processes according to claim 12, characterized in that, The conductive material is selected from one or more of the group consisting of conductive carbon black, graphene, single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, branched carbon nanotubes, carbon nanosheets, and carbon nanoribbons.

15. The electrode material layer composition for dry processes according to claim 12, characterized in that, It also includes an acrylate compound that is liquid at room temperature and can be post-cured, and a curing agent for the acrylate compound.

16. The electrode material layer composition for dry processes according to claim 15, characterized in that, The acrylate compounds contain 2 to 16 functional groups, and the main chain is a monomer or oligomer composed of 2 to 1000 carbon atoms.

17. The electrode material layer composition for dry processes according to claim 16, characterized in that, The functional group is selected from one or more of the group consisting of methylene, carbamate, ester, ether, oxide, ethylene oxide, propylene oxide, ethylene glycol, propylene glycol, butadiene, imide, amine, amide, epoxy, olefin, sulfonic acid, or combinations thereof.

18. The electrode material layer composition for dry processes according to claim 15, characterized in that, The active material for the positive or negative electrode contains 0.1 to 10 parts by weight of the acrylate compound, based on 100 parts by weight.

19. The electrode material layer composition for dry processes according to claim 18, characterized in that, The curing agent is one or more of a thermosetting curing agent and a photocuring agent, and contains 0.1 to 20 parts by weight of the curing agent per 100 parts by weight of the acrylate compound.

20. The electrode material layer composition for dry processes according to claim 19, characterized in that, The thermosetting agent contains peroxide or azo compound, and the photocuring agent contains phenyl ketone compound or phosphine oxide compound.

21. The electrode material layer composition for dry processes according to claim 12, characterized in that, The active material used for the positive or negative electrode comprises one or more of the group consisting of lithium, manganese, nickel, cobalt, aluminum, iron, phosphorus, tin, titanium, carbon materials, silicon, silicon oxide, sulfur, and combinations thereof.

22. A primer composition, characterized in that, The adhesive composition according to any one of claims 1 to 11, based on 100 parts by weight, comprises 0.05 parts by weight to 300 parts by weight of nano-carbon material and solvent, and the content of solid components is 0.2-40% by weight.

23. The primer composition according to claim 22, characterized in that, The nano-carbon material is selected from one or more of the group consisting of conductive carbon black, graphene, single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, branched carbon nanotubes, carbon nanosheets, and carbon nanoribbons.

24. An electrode for a secondary battery, characterized in that, It comprises a positive electrode material layer or a negative electrode material layer formed by the electrode material layer composition for dry process as described in claim 12.

25. A method for preparing an electrode for a secondary battery, characterized in that, include: The composition preparation step involves preparing the electrode material layer composition for the dry process as described in claim 15. The sheet formation step involves using the dry process to form a positive electrode material sheet or a negative electrode material sheet using the electrode material layer composition. The attachment step involves attaching the positive electrode material layer or the negative electrode material layer to the metal electrode plate. The curing step involves curing the attached positive or negative electrode material layer; and The rolling step rolls the electrode obtained by performing the curing step.

26. The method for preparing an electrode for a secondary battery according to claim 25, characterized in that, The attachment step includes: The step of forming a primer layer on the metal electrode plate; and The step of laminating the positive electrode material sheet or the negative electrode material sheet after setting the primer layer.

27. The method for preparing an electrode for a secondary battery according to claim 25, characterized in that, The curing step is performed by one or more of the following methods: heat curing at a temperature of 50°C to 180°C for 5 to 30 minutes and light curing by light irradiation.

28. A lithium-ion battery, characterized in that, Includes the electrode for a secondary battery as described in claim 24.

29. A lithium-ion battery, characterized in that, This includes electrodes for secondary batteries prepared by the method for preparing electrodes for secondary batteries as described in claim 25.

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