Insulating layer composition for lithium secondary battery and lithium secondary battery containing same

Abstract

The object of the present invention is to provide an insulating layer composition for a lithium secondary battery that can perform insulating liquid coating simultaneously with positive electrode coating by replacing water, which is a dispersion solvent of an aqueous conjugated dienes copolymer latex, with a non-aqueous organic solvent (e.g., N-methyl-pyrrolidone). The present invention relates to an insulating layer composition for a lithium secondary battery, comprising a conjugated diene copolymer as a binder polymer and a non-aqueous organic solvent as a dispersion solvent, the conjugated diene copolymer having a Tg of -10° C. to 40° C., and a lithium secondary battery comprising the same. According to one embodiment of the present invention, an insulating layer that simultaneously satisfies flexibility, insulating properties, and electrolyte resistance properties is formed on a tab portion of a positive electrode, thereby preventing physical short-circuiting between the positive electrode and the negative electrode when defects such as separator shrinkage and electrode folding occur in a lithium secondary battery, and insulating liquid coating can be performed simultaneously with positive electrode coating.

Description

[Technical Field]

[0001] The present invention relates to an insulating layer composition for a lithium secondary battery and a lithium secondary battery including the same. [Background technology]

[0002] As technological development and demand for mobile devices increases, the demand for secondary batteries as an energy source is growing rapidly, and accordingly, much research is being conducted on batteries that can meet various needs.

[0003] Typically, in terms of battery shape, there is high demand for thin prismatic and pouch-shaped batteries that can be used in products such as mobile phones, and in terms of materials, there is high demand for lithium secondary batteries such as lithium-cobalt polymer batteries, which have excellent energy density, discharge voltage, and safety.

[0004] One of the main research topics for secondary batteries is improving their safety. The primary cause of safety-related battery accidents is the abnormally high temperature caused by a short circuit between the positive and negative electrodes. Under normal circumstances, a separator is located between the positive and negative electrodes to maintain electrical insulation. However, under abnormal conditions, such as overcharging or overdischarging a battery, internal short circuiting caused by dendritic growth of the electrode material or foreign matter, penetration by sharp objects such as nails or screws, or excessive deformation caused by external forces, conventional separators alone begin to show their limitations.

[0005] Generally, microporous membranes made of polyolefin resin are used as separators, but their heat resistance is insufficient, with a temperature limit of around 120-160°C. Therefore, when an internal short circuit occurs, the separator shrinks due to the short circuit reaction heat, expanding the short circuit area and leading to a thermal runaway state in which more reaction heat is generated. Therefore, various methods have been researched to reduce the possibility of cell deformation, external impact, or physical short circuit between the positive and negative electrodes.

[0006] For example, to prevent a short circuit caused by the electrode tab coming into contact with the upper end of the electrode assembly due to movement of the electrode assembly after the battery is assembled, a method of attaching a predetermined size of insulating tape to the electrode tab adjacent to the upper end of the current collector is known. However, the winding process of this insulating tape is very cumbersome, and if the insulating tape is wound to a length that extends slightly downward from the upper end of the current collector, this portion may increase the thickness of the electrode assembly. Furthermore, there is a problem that the electrode tab is easily loosened when bent.

[0007] Another method involves forming an insulating layer on the positive electrode tab using a non-aqueous binder (such as PVDF) or aqueous styrene-butadiene copolymer (SBL). However, when using a non-aqueous binder (such as PVDF), the wet adhesion strength is reduced, and lithium ion migration to the electrode overlay region cannot be prevented, resulting in capacity development. In particular, when capacity development occurs in the electrode overlay region, lithium ions can precipitate, which can reduce the stability of the battery cell. Furthermore, when using an aqueous styrene-butadiene copolymer (SBL) binder, simultaneous coating with the positive electrode mixture layer slurry can result in gelation of the organic binder used as the positive electrode binder, penetration of the positive electrode slurry into the insulating liquid boundary, and side reactions due to moisture, resulting in reduced battery performance. This makes simultaneous coating of the positive electrode mixture layer slurry and the insulating coating layer slurry impossible.

[0008] Therefore, there is a strong need for the development of an insulating liquid that allows simultaneous coating of a slurry for a positive electrode mixture layer and a slurry for an insulating coating layer while simultaneously satisfying flexibility, insulating properties, and electrolyte resistance properties. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Korean Patent No. 10-1586530 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an insulating layer composition for a lithium secondary battery that can perform insulating liquid coating simultaneously with positive electrode coating by replacing water, which is the dispersion solvent of an aqueous conjugated diene copolymer latex, with a non-aqueous organic solvent (e.g., N-methyl-pyrrolidone).

[0011] Another object of the present invention is to provide a method for producing a positive electrode for a lithium secondary battery using the insulating layer composition for a lithium secondary battery.

[0012] Another object of the present invention is to provide a positive electrode for a lithium secondary battery formed from the insulating layer composition for a lithium secondary battery.

[0013] Another object of the present invention is to provide a lithium secondary battery including the above-mentioned positive electrode for a lithium secondary battery.

[0014] Other objects and advantages of the present invention will be more clearly set forth in the following detailed description of the invention and claims. [Means for solving the problem]

[0015] To achieve the above technical objectives, the present invention provides an insulating layer composition for a lithium secondary battery, which comprises a conjugated diene copolymer as a binder polymer and a non-aqueous organic solvent as a dispersion solvent, and the conjugated diene copolymer has a Tg of -10°C to 40°C.

[0016] The present invention also provides a method for manufacturing a positive electrode for a lithium secondary battery, the method comprising: preparing a water-dispersible conjugated diene latex; adding a non-aqueous organic solvent to the water-dispersible conjugated diene latex and heating and reducing the pressure to prepare a slurry for an insulating coating layer; applying a slurry for a positive electrode mixture layer, the slurry including a positive electrode active material, a conductive material, and a non-aqueous binder, to one or both sides of a positive electrode current collector; applying the slurry for the insulating coating layer from a portion of an uncoated area of ​​the positive electrode current collector to cover a portion of the slurry for the positive electrode mixture layer applied to the current collector; and drying the slurry for the positive electrode mixture layer and the slurry for the insulating coating layer applied to the positive electrode current collector.

[0017] The present invention also provides a positive electrode for a lithium secondary battery, comprising a positive electrode current collector, a positive electrode tab protruding from the positive electrode current collector, and an insulating layer coated on the positive electrode tab with an insulating material, wherein the insulating material comprises the insulating layer composition for a lithium secondary battery according to the present invention.

[0018] The present invention also provides a lithium secondary battery including the positive electrode for the lithium secondary battery. [Effects of the Invention]

[0019] According to one embodiment of the present invention, by forming an insulating layer that simultaneously satisfies flexibility, insulating properties, and electrolyte resistance properties on the tab portion of the positive electrode, it is possible to prevent a physical short circuit between the positive electrode and the negative electrode when defects such as separator shrinkage and electrode breakage occur in a lithium secondary battery.

[0020] According to one embodiment of the present invention, by providing a slurry for an insulating coating layer in which water, which is a dispersion solvent for conjugated diene latex particles used in forming the insulating layer, is replaced with a non-aqueous organic solvent (e.g., N-methyl-pyrrolidone), it is possible to perform insulating liquid coating simultaneously with positive electrode coating.

[0021] The effects of the present invention are not limited to the above-mentioned examples, and more diverse effects are included in this specification. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 10 is a diagram showing the results of evaluating brittleness according to Experimental Example 4. [Figure 2] FIG. 10 is a diagram showing the results of evaluating the influence of moisture according to Experimental Example 7. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be described in detail below.

[0024] All terms (including technical and scientific terms) used in this specification may be used in the sense commonly understood by those skilled in the art to which the present invention pertains, unless otherwise defined. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless clearly and specifically defined.

[0025] Throughout this specification, when a part is said to "comprise" certain elements, this should be understood as open-ended terms that do not exclude other elements but that include the possibility of further including other elements, unless specifically stated to the contrary.

[0026] As used herein, the terms "preferred" and "preferably" refer to embodiments of the invention that may offer certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or different circumstances. Furthermore, the reference to one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.

[0027] In the present invention, the term "insulating coating layer" refers to an insulating member formed by coating and drying from at least a portion of the uncoated area of ​​the electrode current collector to at least a portion of the electrode mixture layer.

[0028] In the present invention, "wet adhesion" refers to the adhesion of an insulating coating layer measured while immersed in an electrolyte. If the insulating coating layer swells or peels off while immersed in an electrolyte, reducing the wet adhesion, the insulating properties of the electrode are difficult to maintain. This can be confirmed by coating an insulating coating layer on an electrode specimen and measuring the insulating properties.

[0029] In the present invention, the term "metal test piece" refers to a metal current collector used in manufacturing an electrode, which is a space where an insulating coating layer is formed, and may be a metal current collector punched to have a predetermined width and length. For example, the metal test piece may be aluminum, copper, or an aluminum alloy.

[0030] <Insulating layer composition for lithium secondary batteries>

[0031] One example of the present invention is an insulating layer composition for a lithium secondary battery, which comprises a conjugated diene copolymer as a binder polymer and a non-aqueous organic solvent as a dispersion solvent, and the conjugated diene copolymer has a Tg of -10°C or more and 40°C or less.

[0032] The insulating layer composition for a lithium secondary battery according to the present invention comprises conjugated diene copolymer particles having an average particle size of 50 to 500 nm, present as an independent phase, and the conjugated diene copolymer may be contained in an amount of 20 to 100 wt % based on the total solid mass of the composition. When the content of the conjugated diene copolymer is 20 to 100 wt %, the conjugated diene copolymer particles can exert an insulating effect while maintaining adhesive properties even in an electrolyte, thereby providing a certain insulating effect.

[0033] The insulating layer composition may further contain inorganic particles or dyes insofar as the insulating properties are not impaired.

[0034] In one embodiment of the present invention, the inorganic particles may be alumina, boehmite, silica, titanium dioxide, etc.

[0035] The conjugated diene copolymer may contain (a) a conjugated diene monomer or a conjugated diene polymer, (b) one or more monomers selected from the group consisting of acrylate monomers, vinyl monomers, and nitrile monomers, and (c) a polymer of one or more monomers selected from the group consisting of unsaturated carboxylic acid monomers and hydroxy group-containing monomers.

[0036] The conjugated diene monomer may be one monomer selected from the group consisting of 1,3-butadiene, isoprene, chloroprene, and piperylene.

[0037] The conjugated diene polymer may be, for example, a polymer of two or more monomers selected from the group consisting of 1,3-butadiene, isoprene, chloroprene, and piperylene; a styrene-butadiene copolymer; an acrylonitrile-butadiene copolymer; a styrene-isoprene copolymer; an acrylate-butadiene rubber; an acrylonitrile-butadiene-styrene rubber; an ethylene-propylene-diene polymer; a partially epoxidized or brominated polymer of any of these polymers; or a mixture thereof.

[0038] The acrylate monomer may be one or more monomers selected from the group consisting of methyl ethacrylate, methyl methacrylate, methacryloxyethyl ethylene urea, β-carboxyethyl acrylate, aliphatic monoacrylate, dipropylene diacrylate, ditrimethylolpropane tetraacrylate, dipentaerythriol hexaacrylate, pentaerythriol triacrylate, pentaerythriol tetraacrylate, and glycidyl methacrylate.

[0039] The vinyl monomer may be at least one monomer selected from the group consisting of styrene, α-methylstyrene, β-methylstyrene, pt-butylstyrene, and divinylbenzene.

[0040] The nitrile monomer may be at least one monomer selected from the group consisting of acrylonitrile, methacrylonitrile, and allyl cyanide.

[0041] The unsaturated carboxylic acid monomer may be at least one monomer selected from the group consisting of maleic acid, fumaric acid, methacrylic acid, acrylic acid, glutaric acid, itaconic acid, tetrahydrophthalic acid, crotonic acid, isocrotonic acid, and nadic acid, but is not limited thereto.

[0042] The hydroxy group-containing monomer may be one or more monomers selected from the group consisting of hydroxyacrylate, hydroxyethyl acrylate, hydroxybutyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate, but is not limited thereto.

[0043] The method for producing the conjugate diene copolymer particles is not particularly limited and can be performed by known methods such as suspension polymerization, emulsion polymerization, and seed polymerization. The monomer mixture used to produce the copolymer particles can contain one or more other components, such as a polymerization initiator, a crosslinking agent, a coupling agent, a buffer solution, a molecular weight modifier, and an emulsifier. Specifically, the copolymer particles can be produced by emulsion polymerization. In this case, the average particle size of the copolymer particles can be controlled by the amount of emulsifier. Generally, the particle size tends to decrease as the amount of emulsifier increases, and the particle size tends to increase as the amount of emulsifier decreases. The desired average particle size can be achieved by adjusting the amount of emulsifier used, taking into account the desired particle size, reaction time, reaction stability, and the like. The polymerization temperature and polymerization time can be appropriately determined depending on the polymerization method, the type of polymerization initiator, and the like. For example, the polymerization temperature can be 10°C to 150°C, and the polymerization time can be 1 to 20 hours.

[0044] The polymerization initiator may be an inorganic or organic peroxide, such as a water-soluble initiator including potassium persulfate, sodium persulfate, or ammonium persulfate, or an oil-soluble initiator including cumene hydroperoxide or benzoyl peroxide. In addition, an activator may be further included to promote the initiation reaction of the peroxide together with the polymerization initiator, and the activator may be at least one selected from the group consisting of sodium formaldehyde sulfoxylate, sodium ethylenediaminetetraacetate, ferrous sulfate, and dextrose.

[0045] The crosslinking agent is a substance that promotes crosslinking of the binder, and examples thereof include amines such as diethylene triamine, triethylene tetramine, diethylamino propylamine, xylene diamine, and isophorone diamine, dodecyl succinic anhydride, and phthalic anhydride. Examples of suitable grafting agents include acid anhydrides such as methyl anhydride, polyamide resins, polysulfide resins, phenolic resins, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolmethane triacrylate, and glycidyl methacrylate. Examples of suitable grafting agents include aryl methacrylate (AMA), triaryl isocyanurate (TAIC), triarylamine (TAA), and diarylamine (DAA).

[0046] The coupling agent is a material for increasing the adhesive strength between the active material and the binder, and is characterized by having two or more functional groups, one of which reacts with a hydroxyl group or a carboxyl group on the surface of the silicon, tin, or graphite-based active material to form a chemical bond, and the other functional group is a material that forms a chemical bond through a reaction with the nanocomposite according to the present invention, and is not particularly limited. For example, silane coupling agents such as triethoxysilylpropyl tetrasulfide, mercaptopropyl triethoxysilane, aminopropyl triethoxysilane, chloropropyl triethoxysilane, vinyltriethoxysilane, methacryloxypropyl triethoxysilane, glycidoxypropyl triethoxysilane, isocyanatopropyl triethoxysilane, and cyanatopropyl triethoxysilane may be used.

[0047] The buffer (buffering agent) may be, for example, one selected from the group consisting of NaHCO3, Na2CO3, K2HPO4, KH2PO4, Na2HPO4, NaOH, and NH4OH.

[0048] Examples of the molecular weight modifier that can be used include mercaptans, terfins such as terpinolene, dipentene, and t-terpiene, and halogenated hydrocarbons such as chloroform and carbon tetrachloride.

[0049] The emulsifier is a substance having both a hydrophilic group and a hydrophobic group, and in one specific example, may be at least one selected from the group consisting of anionic emulsifiers and nonionic emulsifiers.

[0050] The use of nonionic emulsifiers in conjunction with anionic emulsifiers can help control particle size and distribution and can provide additional colloidal stabilization through van der Waals forces of the polymer particles in addition to the electrostatic stabilization of the ionic emulsifiers. Nonionic emulsifiers are not often used alone because they produce particles that are less stable than anionic emulsifiers.

[0051] The anionic emulsifier may be selected from the group consisting of phosphates, carboxylates, sulfates, succinates, sulfosuccinates, sulfonates and disulfonates. For example, the anionic emulsifier may be selected from the group consisting of sodium alkyl sulfate, sodium polyoxyethylene sulfate, sodium lauryl ether sulfate, sodium polyoxyethylene lauryl ether sulfate, sodium lauryl sulfate, sodium alkyl sulfonate, sodium alkyl ether sulfonate, sodium alkyl benzene sulfonate, sodium linear alkyl benzene sulfonate, sodium alpha olefin sulfonate, sodium alcohol polyoxyethylene ether sulfonate, sodium dioctyl sulfosuccinate, sodium perfluorooctane sulfonate, sodium perfluorobutane sulfonate, alkyl diphenyloxide disulfonate, sodium dioctyl sulfosuccinate (DOSS), sodium alkyl-aryl phosphate, alkyl ether phosphate, and sodium lauryl sarcosinate, but is not limited to these. All known anionic emulsifiers are encompassed within the scope of the present invention.

[0052] The nonionic emulsifier may be an ester type, an ether type, an ester-ether type, etc. Examples include polyoxyethylene glycol, polyoxyethylene glycol methyl ether, polyoxyethylene monoallyl ether, polyoxyethylene bisphenol-A ether, polypropylene glycol, polyoxyethylene alkenyl ether, etc. However, the present invention is not limited to these, and all known nonionic emulsifiers may be included in the scope of the present invention.

[0053] The conjugated diene copolymer may contain, based on the total weight, 20 to 45 wt% of the (a) conjugated diene monomer or conjugated diene polymer, 50 to 70 wt% of the (b) one or more monomers selected from the group consisting of acrylate monomers, vinyl monomers, and nitrile monomers, and 1 to 20 wt% of the (c) one or more monomers selected from the group consisting of unsaturated carboxylic acid monomers and hydroxyl group-containing monomers. Other components such as the emulsifier, buffer, and crosslinker may optionally be included within the range of 0.1 to 10 wt%.

[0054] When the content ratio between the monomers constituting the conjugate diene copolymer falls within the above-mentioned range, Tg can be -10°C or more and 40°C or less.

[0055] When the content ratio between the monomers constituting the conjugate diene copolymer falls within the above-mentioned range, the flexibility, insulating properties, and electrolyte resistance properties of the insulating layer can be significantly improved.

[0056] In the experimental examples of the present invention, it was confirmed that when the content ratio between each monomer constituting the conjugate diene copolymer falls within the above-mentioned range, the initial adhesive strength, brittleness, and insulating properties are all excellent.

[0057] On the other hand, the average particle size of the copolymer may be 50 nm to 500 nm, where an average particle size of less than 50 nm or more than 500 nm is not preferred because it may result in a decrease in dispersion stability.

[0058] Meanwhile, since the copolymer particles in the composition according to the present invention exhibit a greater adhesive strength when present as an independent phase, it is very important to prevent agglomeration between the particles. Therefore, the composition according to the present invention includes a dispersion solvent for dispersing the copolymer particles. In the present invention, a non-aqueous organic solvent is used as the dispersion solvent.

[0059] The non-aqueous organic solvent may be at least one selected from the group consisting of N-methyl-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate (BC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), acetonitrile, dimethoxyethane, tetrahydrofuran (THF), gamma-butyrolactone, methyl alcohol, ethyl alcohol, and isopropyl alcohol.

[0060] Preferably, the non-aqueous organic solvent may be N-methyl-pyrrolidone (NMP), but is not limited thereto.

[0061] The water content of the insulating layer composition for a lithium secondary battery according to an embodiment of the present invention may be 10,000 ppm or less, preferably 5,000 ppm or less, and more preferably 3,000 ppm or less. When the water content is within this range, the insulating layer composition is coated separately from the electrode mixture layer, and the physical properties of the electrode are not deteriorated.

[0062] <Method of manufacturing a positive electrode for a lithium secondary battery>

[0063] Another example of the present invention is a method for manufacturing a positive electrode for a lithium secondary battery, comprising: preparing a water-dispersible conjugated diene latex; adding a non-aqueous organic solvent to the water-dispersible conjugated diene latex and heating and reducing the pressure to prepare a slurry for an insulating coating layer; applying a slurry for a positive electrode mixture layer, the slurry including a positive electrode active material, a conductive material, and a non-aqueous binder, to one or both surfaces of a positive electrode current collector; applying the slurry for the insulating coating layer from a portion of an uncoated area of ​​the positive electrode current collector to cover a portion of the slurry for the positive electrode mixture layer applied to the current collector; and drying the slurry for the positive electrode mixture layer and the slurry for the insulating coating layer applied to the positive electrode current collector.

[0064] The step of preparing the slurry for the insulating coating layer may include replacing water, which is a dispersion medium for conjugated diene latex particles, with a non-aqueous organic solvent.

[0065] In one embodiment of the present invention, the step of preparing the slurry for the insulating coating layer may be a step of adding a non-aqueous organic solvent to the water-dispersible conjugated diene latex, heating to a temperature of 40°C to 100°C, and reducing the pressure to less than 200 torr for 1 hour to 20 hours.

[0066] In one embodiment of the present invention, the conjugate diene latex may be styrene-butadiene latex particles, and the non-aqueous organic solvent may be NMP (N-methyl-pyrrolidone).

[0067] A non-aqueous organic solvent is added to the water-dispersed conjugated diene latex, and the mixture is heated and decompressed to replace the water, which is the dispersion solvent for the conjugated diene latex particles, with the non-aqueous organic solvent.

[0068] In a preferred embodiment, the water-based styrene-butadiene latex (SBL) and NMP (N-methyl-pyrrolidone) are mixed, heated to a set temperature of 40°C to 100°C, and then the pressure is reduced to less than 200 torr to replace the solvent of the water-based styrene-butadiene latex (SBL) with NMP (N-methyl-pyrrolidone).

[0069] Conjugated diene latex particles, in which the water dispersion solvent is replaced with a non-aqueous organic solvent, maintain their particle shape even after the replacement with the non-aqueous organic solvent. Whether or not the particle shape is maintained can be confirmed by particle size measurement. The particle size can be confirmed using, but is not limited to, a DLS particle size analyzer, a laser diffraction particle size analyzer, or an electron transmission microscope.

[0070] The positive electrode current collector for the lithium secondary battery according to the present invention may be made of a material that has high conductivity and does not cause chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, etc. may be used. In the case of aluminum or stainless steel, the surface may be treated with carbon, nickel, titanium, silver, etc. For example, the current collector may be aluminum.

[0071] In addition, in the slurry for the positive electrode mixture layer, any positive electrode active material that is commonly used in a positive electrode can be used as the positive electrode active material, and examples thereof that can be used include, but are not limited to, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, and lithium composite oxides that are combinations of these.

[0072] The non-aqueous binder contained in the positive electrode active material slurry may include one or more resins selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, and copolymers thereof. For example, the binder may include polyvinylidene fluoride.

[0073] The conductive material is used to improve the performance of the positive electrode, such as electrical conductivity, and may be at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber. For example, the conductive material may include acetylene black.

[0074] Furthermore, the solvent used for the slurry for the positive electrode mixture layer is a non-aqueous organic solvent, such as N-methyl-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate (BC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), acetonitrile, dimethoxyethane, tetrahydrofuran (THF), gamma butyrolactone, methyl alcohol, ethyl alcohol, and isopropyl alcohol. The solvent may be one or more selected from the group consisting of N-methyl-2-pyrrolidone (NMP), for example.

[0075] In the step of applying the slurry for the insulating coating layer to the current collector, the slurry for the insulating layer may be applied while the slurry for the positive electrode mixture layer is still wet, or the slurry for the positive electrode mixture layer and the slurry for the insulating layer may be applied simultaneously.

[0076] The step of drying the slurry for the positive electrode mixture layer and the slurry for the insulating coating layer may be performed using a drying method commonly known in the art to completely dry the slurry for the positive electrode mixture layer and the slurry for the insulating coating layer and remove the solvent. In a specific example, the drying may be performed using a hot air method, a direct heating method, an induction heating method, or the like at a temperature at which the solvent is completely evaporated, but is not limited to these. For example, the step of drying the insulating coating liquid may be performed using a hot air method.

[0077] In this case, the drying temperature may be in the range of 50° C. to 300° C., or may be 60 to 200° C. or 70 to 150° C. Meanwhile, if the drying temperature of the insulating coating liquid is less than 50° C., the temperature may be too low to completely dry the insulating coating liquid, and if it exceeds 300° C., the drying temperature may be too high to cause deformation of the electrode.

[0078] A positive electrode mixture layer and an insulating coating layer are formed on the current collector, and the current collector is rolled to manufacture a positive electrode for a lithium secondary battery.

[0079] <Positive electrodes for lithium secondary batteries>

[0080] Another example of the present invention is a positive electrode for a lithium secondary battery, comprising: a positive electrode current collector; a positive electrode tab protruding from the positive electrode current collector; and an insulating layer formed by coating an insulating material on the positive electrode tab, wherein the insulating material includes the insulating layer composition for a lithium secondary battery according to the present invention.

[0081] According to one embodiment of the present invention, a positive electrode including an insulating layer on a positive electrode tab can significantly shorten the battery manufacturing process, ultimately reducing battery manufacturing costs. It also has a wider insulating area, further improving battery safety. Furthermore, it has the advantage of being highly unlikely to detach when bending the positive electrode tab to attach it to the insulating area, which is a problem that occurs when using conventional insulating films or tapes, and does not increase the thickness of the electrode assembly. Furthermore, it solves the problem of reduced wet adhesion when using non-aqueous binders (e.g., PVDF) and the problem of gelation of the organic binder PVDF used as the positive electrode binder when using an aqueous styrene-butadiene copolymer (SBL) binder, which makes simultaneous coating of the positive electrode mixture layer slurry and the insulating coating layer slurry impossible.

[0082] <Lithium secondary battery>

[0083] Another example of the present invention is a lithium secondary battery including the positive electrode for lithium secondary batteries.

[0084] In addition to the electrodes, the lithium secondary battery generally further includes a separator and a non-aqueous electrolyte containing a lithium salt.

[0085] The separator is interposed between the positive electrode and the negative electrode, and is a thin insulating membrane with high ion permeability and mechanical strength. The pore size of the separator is generally 0.01 to 10 μm, and the thickness is generally 5 to 300 μm. Examples of such separators include sheets or nonwoven fabrics made of chemically resistant and hydrophobic olefin polymers such as polypropylene, glass fiber, or polyethylene. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte can also serve as the separator.

[0086] The lithium-containing non-aqueous electrolyte solution comprises a non-aqueous electrolyte solution and a lithium salt.

[0087] Examples of the non-aqueous electrolyte solution include non-quantum organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran (franc), 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0088] The lithium salt is a substance that is easily dissolved in the non-aqueous electrolyte solution, and examples thereof include LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, (CF3SO2)2NLi, lithium chloroborane, lithium lower aliphatic carboxylates, lithium 4-phenylborate, imides, etc. are used.

[0089] In some cases, an organic solid electrolyte, an inorganic solid electrolyte, or the like may be used.

[0090] Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and polymers containing ionic dissociative groups.

[0091] Examples of the inorganic solid electrolyte that can be used include nitrides, halides, and sulfates of Li, such as LiN, LiI, LiNI, LiN-LiI-LiOH, LiSiO, LiSiO-LiI-LiOH, LiSiS, LiSiO, LiSiO-LiI-LiOH, and LiPO-LiS-SiS.

[0092] In addition, for the purpose of improving charge / discharge characteristics, flame retardancy, etc., non-aqueous electrolytes may contain additives such as pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, and aluminum trichloride. In some cases, halogen-containing solvents such as carbon tetrachloride and trifluoroethylene may be added to impart non-flammability, and carbon dioxide may be added to improve high-temperature storage properties. Fluoro-ethylene carbonate (FEC), propenesultone (PRS), etc. may also be added.

[0093] The secondary battery according to the present invention is not only used as a battery cell used as a power source for small devices, but is also preferably used as a unit battery for medium- to large-sized battery modules containing a number of battery cells used as a power source for medium- to large-sized devices.

[0094] Preferred examples of the medium- to large-sized devices include, but are not limited to, power tools powered by battery motors, electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc., electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters, electric golf carts, and energy storage systems.

[0095] The present invention will be described in detail below with reference to examples, but the following examples are merely illustrative of the present invention and are not intended to limit the scope of the present invention.

[0096] [Example 1]

[0097] Five parts by weight of styrene-butadiene seed latex with a 55 nm particle size was placed in a reactor and heated to 80°C. Then, 38 g of 1,3-butadiene (as monomer), 59 g of styrene, 3 g of acrylic acid, 30.5 g of NaHCO3 (as buffer), 1 g of alkyldiphenyloxide disulfonate (as emulsifier), 1 g of dodecyl mercaptan (as molecular weight modifier), and 1 g of potassium persulfate (as polymerization initiator) were added to the reactor for 4 hours. The reaction was continued for another 4 hours at 80°C to produce a 50% solids styrene-butadiene copolymer latex. The pH was adjusted to neutral (7) using sodium hydroxide. After polymerization, copolymer particle size analysis using a submicron particle sizer (Nicomp™ 380) revealed an average particle size of 150 nm.

[0098] 100 g of the prepared styrene-butadiene copolymer latex was placed in a reactor, and 600 g of NMP (N-methylpyrrolidone) was added and mixed. The temperature was raised to 90°C, and the pressure was reduced to 15 torr within 1-4 hours to replace the water dispersing solvent for the styrene-butadiene copolymer particles with NMP, producing a composition containing styrene-butadiene copolymer dispersed in NMP. The final moisture content was adjusted to 10,000 ppm or less, and the NMP was further adjusted to a final solids content of 8%. The moisture content of the final product was measured using a Karl Fischer moisture meter.

[0099] [Example 2]

[0100] A composition containing a styrene-butadiene copolymer dispersed in NMP was prepared in the same manner as in Example 1, except that 30 g of 1,3-butadiene, 60 g of styrene, 5 g of methyl methacrylate, 2 g of acrylonitrile, 1 g of hydroxyacrylate, and 3 g of itaconic acid were used as monomers.

[0101] [Example 3]

[0102] A composition containing a styrene-butadiene copolymer dispersed in NMP was prepared in the same manner as in Example 1, except that 45 g of 1,3-butadiene, 50 g of styrene, and 5 g of acrylic acid were used as monomers, and 0.2 g of dodecyl mercaptan was used as a molecular weight modifier.

[0103] [Example 4]

[0104] A composition containing a styrene-butadiene copolymer dispersed in NMP was prepared in the same manner as in Example 1, except that 22 g of 1,3-butadiene, 68 g of styrene, 5 g of methyl methacrylate, 2 g of hydroxyacrylate, and 3 g of itaconic acid were used as monomers.

[0105] [Comparative Example 1]

[0106] A composition containing a styrene-butadiene copolymer dispersed in NMP was prepared in the same manner as in Example 1, except that 48 g of 1,3-butadiene, 47 g of styrene, 1 g of methyl methacrylate, 2 g of hydroxyacrylate, and 2 g of acrylic acid were used as monomers.

[0107] Comparative Example 2

[0108] A composition containing a styrene-butadiene copolymer dispersed in NMP was prepared in the same manner as in Example 1, except that 20 g of 1,3-butadiene, 75 g of styrene, 2 g of methyl methacrylate, and 3 g of acrylic acid were used as monomers.

[0109] Comparative Example 3

[0110] A styrene-butadiene copolymer latex having a solid content of 50% was produced in the same manner as in Example 2.

[0111] 100 g of the prepared styrene-butadiene copolymer latex was placed in a reactor, and 530 g of NMP (N-methylpyrrolidone) was added and mixed. The temperature was raised to 85°C, and the pressure was reduced to 180 torr within 1 hour to replace the water dispersing solvent for the styrene-butadiene copolymer particles with NMP, producing a composition containing a styrene-butadiene copolymer dispersed in NMP. NMP was added to achieve a final solids content of 8%, and the final moisture content was 50,010 ppm. The moisture content of the final product was measured using a Karl Fischer moisture meter.

[0112] Comparative Example 4

[0113] A styrene-butadiene copolymer latex having a solid content of 50% was produced in the same manner as in Example 2.

[0114] 100 g of the prepared styrene-butadiene copolymer latex was placed in a reactor, and 530 g of NMP (N-methyl-pyrrolidone) was added and mixed. The temperature was raised to 90°C, and the pressure was reduced to 100 torr over 7 hours to replace the water dispersing solvent for the styrene-butadiene copolymer particles with NMP, producing a composition containing a styrene-butadiene copolymer dispersed in NMP. NMP was added to achieve a final solids content of 8%, and the final moisture content was 12,201 ppm. The moisture content of the final product was measured using a Karl Fischer moisture meter.

[0115] Comparative Example 5 Preparation of compositions containing styrene butadiene latex without dispersing solvent replacement

[0116] To compare with a composition containing styrene-butadiene latex without solvent replacement, the styrene-butadiene latex prepared in Example 4 was mixed with carboxymethyl cellulose at a weight ratio of 9:1 without solvent replacement to prepare a composition. Carboxymethyl cellulose is used as a thickener to improve the coatability of styrene-butadiene latex without solvent replacement.

[0117] The types and amounts of monomers used in Examples 1 to 4 and Comparative Examples 1 to 5 are summarized in the following Table 1. The amounts used are expressed in weight % based on the total weight of the monomers.

[0118] [Table 1]

[0119] The compositions containing styrene-butadiene copolymers dispersed in NMP prepared in Examples 1 to 4 and Comparative Examples 1 to 5 were evaluated for water content, viscosity, and Tg according to the methods described in Experimental Examples 1, 2, and 5 below, and the results are shown in Table 2 below.

[0120] To confirm the excellent physical properties of the compositions containing styrene-butadiene copolymer dispersed in NMP prepared in Examples 1 to 4, the compositions containing styrene-butadiene copolymer dispersed in NMP prepared in Comparative Examples 1 and 2, a composition containing PVDF (Comparative Example 6), a composition in which hydrogenated nitrile rubber was dissolved in NMP (Comparative Example 7), and a composition in which styrene-butadiene rubber was dissolved in NMP (Comparative Example 8) were evaluated for initial tackiness and brittleness according to the methods described in Experimental Examples 3 and 4 below, and the results are shown in Table 2 below. In Comparative Example 8, the styrene-butadiene rubber did not completely dissolve in NMP, but partially dissolved, and gelled at 8% solids. In the following experimental examples, the gelled portion was removed, and only the dissolved portion was obtained and the results of the experiment are shown.

[0121] The compositions containing styrene-butadiene copolymer dispersed in NMP prepared in Examples 1 to 4 and Comparative Examples 1 and 2, and the composition containing PVDF (Comparative Example 6) were subjected to evaluation of insulation properties and moisture influence by the methods described in Experimental Examples 6 and 7 below, and the results are shown in Table 2 below. The compositions prepared in Comparative Examples 3 and 4 had the same composition as Example 2 except for the moisture content, so only the moisture influence evaluation, which may be affected by the moisture content, was carried out. In order to compare the properties of a state in which the dispersion solvent of styrene-butadiene latex was not replaced with a non-aqueous organic solvent and a state in which it was replaced, the composition containing styrene-butadiene latex without dispersion solvent replacement prepared in Comparative Example 8 was subjected to evaluation of brittleness and moisture influence.

[0122] [Experimental Example 1] Moisture content

[0123] For the compositions prepared in Examples 1 to 4 and Comparative Examples 1 to 8, a Metrohm 899 Coulometer connected to an 860KF Thermoprep oven was used to set the oven temperature to 220°C, and 0.1 to 0.4 g of sample was weighed to measure the moisture content. In the case of Comparative Example 5, the product was prepared in an aqueous solution without replacing the dispersion solvent, and the moisture content was so high that it was impossible to measure using an instrument. Therefore, the solid content was measured and the remaining content was calculated and expressed as moisture.

[0124] [Experimental Example 2] Tg measurement

[0125] The compositions prepared in Examples 1 to 4 and Comparative Examples 1 to 8 were subjected to two cycles from -80°C to 80°C at 5°C / min using DSC, and the glass transition temperature was calculated from the midpoint of the transition range in the second cycle. Using a TA Instruments DSC25, 3 to 20 mg of sample was weighed and Tg was measured, and the results are shown in Table 2 below.

[0126] [Experimental Example 3] Initial Tackiness Evaluation

[0127] The compositions prepared in Examples 1 to 4, Comparative Examples 1 to 2, and Comparative Examples 5 to 8 were coated on aluminum foil and dried at 130°C to prepare metal samples with an insulating coating layer of approximately 10 μm in thickness. The metal samples were cut into 2 cm x 12 cm pieces and laminated on SUS plates (SUS plates), and the 90° adhesive strength was measured. The results are shown in Table 2 below.

[0128] [Experimental Example 4] Brittleness measurement

[0129] The compositions prepared in Examples 1 to 4, Comparative Examples 1 to 2, and Comparative Examples 5 to 8 were coated onto substrates to a final thickness of 20 μm, dried at 130°C, cut into 2 cm widths, and then measured for brittleness. The samples were folded in half at room temperature, pressed once with a 1 kg roller, and then unfolded. The coating film was visually inspected for cracks and the presence or absence of cracks was confirmed, and the results are shown in Table 2 below.

[0130] [Experimental Example 5] Viscosity measurement

[0131] The viscosity of the compositions prepared in Examples 1 to 4 and Comparative Examples 1 to 8 was measured. The viscosity was measured at 25°C using a Brookfield LV viscometer with a No. 63 spindle, rotated at 12 rpm, and then measured 1 minute later. If the viscosity was outside the measurement range, the rpm was lowered and the measurement was continued. The results are shown in Table 2 below. In Table 2 below, 8% viscosity means the viscosity at a solids content of 8%.

[0132] [Experimental Example 6] Insulation characteristic measurement

[0133] LiNi as the positive electrode active material 0.8 Co 0.2 Mn 0.2 A positive electrode mixture layer slurry was prepared by weighing 96 parts by weight of O2, 2 parts by weight of PVdF as a binder, and 2 parts by weight of carbon black as a conductive material in an N-methylpyrrolidone (NMP) solvent. The mixture layer slurry was applied to an aluminum foil, dried, and then rolled to prepare a positive electrode having a 60 μm-thick positive electrode mixture layer.

[0134] Thereafter, an insulating liquid, which is a composition containing the styrene-butadiene copolymer produced in Examples 1 to 4, an insulating liquid, which is a composition containing the styrene-butadiene copolymer produced in Comparative Examples 1 and 2, and an insulating liquid containing PVDF (Comparative Example 6), were applied onto the positive electrode mixture layer and then dried to form a positive electrode insulating layer having a thickness of 10 μm.

[0135] Coin-type half cells were fabricated using the above cathode, lithium foil as the anode, and an electrolyte containing 1M LiPF4 in a solvent of EC:EMC=3:7. The coin-type half cells were stored in an oven at 60°C for 15 days, and then the discharge capacity of the half cells was measured to confirm the insulating effect of the insulating layer. For comparison, half cells were fabricated using cathodes without an insulating coin layer, and the 0.1C discharge capacity was set at 100. The discharge capacity ratios of cathodes with insulating coating layers formed using the insulating solutions of Examples 1 to 4, Comparative Examples 1 and 2, and Comparative Example 6 were calculated, and the results are shown in Table 2 below.

[0136] [Table 2]

[0137] As shown in Table 2 above, in Examples 1 to 4, the initial adhesive strength, brittleness, and insulating properties were all excellent.

[0138] On the other hand, in the case of Comparative Examples 1, 7, and 8, where the Tg is less than -10°C, the initial adhesive strength is high, so the electrodes stick to each other after coating, and the electrodes stick to each other during the winding process, making it difficult to carry out the process.

[0139] Furthermore, as shown in Figure 1, in Comparative Example 2, where the Tg exceeds 40°C, cracking occurred despite low initial adhesion. Cracking also occurred in Comparative Example 5, because even the addition of a small amount of carboxymethyl cellulose as a thickener caused high brittleness and affected the insulating liquid. For these reasons, even when styrene butadiene latex is coated separately without simultaneous coating, the insulating layer may crack or detach during the winding and slitting processes.

[0140] In addition, in the case of Comparative Example 6 using PVDF, the initial adhesive strength was low, but the high-temperature discharge capacity ratio was high.

[0141] In particular, the positive electrodes with insulating coating layers formed using the insulating liquids of Comparative Examples 1, 2, and 6 to 8 exhibited higher discharge rates than the positive electrodes with insulating coating layers formed using the insulating liquids of Examples 1 to 4. When wet adhesion strength in the electrolyte is low, the insulating liquid may detach and swell during high-temperature storage, resulting in the positive electrode's capacity being exerted. It appears that the higher the high-temperature discharge capacity ratio, the lower the insulating effect. It can be seen that the insulating liquids of Comparative Examples 1, 2, and 6 to 8 exhibited low wet adhesion strength in the electrolyte, which led to the insulating liquid detachment and swelling during high-temperature storage, resulting in the positive electrode's capacity being exerted.

[0142] [Experimental Example 7] Moisture Impact Assessment

[0143] LiNi as the positive electrode active material 0.8 Co 0.2 Mn 0.2 96 parts by weight of O2, 2 parts by weight of PVdF as a binder, and 2 parts by weight of carbon black as a conductive material were weighed and mixed in an N-methylpyrrolidone (NMP) solvent to prepare a slurry for a positive electrode mixture layer.

[0144] The positive electrode mixture layer slurry and the insulating coating layer slurries prepared in Examples 1 to 4 and Comparative Examples 3 to 5 were simultaneously applied to a current collector using a doctor blade so as to overlay each other. The results were compared immediately after application and one minute after application, and the results are shown in Table 2 and Figure 2. As shown in Figure 2, Examples 1 to 4 maintained their initial coated state without penetration into the overlay both immediately after application and one minute after application. However, in Comparative Examples 3 to 5, which had a water content of 10,000 ppm or more, the electrode slurry penetrated into the insulating layer, making it impossible to reliably maintain the coating boundary. In particular, in Comparative Example 5, where the dispersion solvent was not replaced, the contact area between the positive electrode slurry and the insulating liquid coagulated due to water immediately after application, confirming that the aqueous insulating liquid without solvent replacement could not be simultaneously coated with the positive electrode slurry.

[0145] The higher the water content of the slurry for the positive electrode insulating coating layer, the more difficult it is for the slurry for the positive electrode mixture layer to penetrate into the slurry for the positive electrode insulating coating layer when the slurry for the positive electrode mixture layer and the slurry for the insulating layer are coated simultaneously, making it difficult to achieve the expected insulating effect.

Claims

1. A conjugated diene copolymer as a binder polymer; a non-aqueous organic solvent as a dispersion solvent, The conjugate diene copolymer has a Tg of −10° C. or more and 40° C. or less, An insulating layer composition for a lithium secondary battery, having a moisture content of 10,000 ppm or less.

2. Conjugated diene copolymer particles having an average particle size of 50 nm to 500 nm are present as a separate phase; The insulating layer composition for a lithium secondary battery according to claim 1 .

3. The conjugate diene copolymer comprises a polymer of (a) a conjugated diene monomer or a conjugated diene polymer, (b) at least one monomer selected from the group consisting of an acrylate monomer, a vinyl monomer, and a nitrile monomer, and (c) at least one monomer selected from the group consisting of an unsaturated carboxylic acid monomer and a hydroxy group-containing monomer. The insulating layer composition for a lithium secondary battery according to claim 1 .

4. the conjugated diene monomer is one monomer selected from the group consisting of 1,3-butadiene, isoprene, chloroprene, and piperylene; The conjugated diene polymer is a polymer of two or more monomers selected from the group consisting of 1,3-butadiene, isoprene, chloroprene, and piperylene, a styrene-butadiene copolymer, an acrylonitrile-butadiene copolymer, a styrene-isoprene copolymer, an acrylate-butadiene rubber, an acrylonitrile-butadiene-styrene rubber, an ethylene-propylene-diene polymer, a partially epoxidized or brominated polymer of any of these polymers, or a mixture thereof. The insulating layer composition for a lithium secondary battery according to claim 3 .

5. The acrylate monomer is at least one monomer selected from the group consisting of methyl ethacrylate, methacryloxyethyl ethylene urea, β-carboxyethyl acrylate, aliphatic monoacrylate, dipropylene diacrylate, ditrimethylolpropane tetraacrylate, dipentaerythriol hexaacrylate, pentaerythriol triacrylate, pentaerythriol tetraacrylate, and glycidyl methacrylate. The insulating layer composition for a lithium secondary battery according to claim 3 .

6. The vinyl monomer is at least one monomer selected from the group consisting of styrene, α-methylstyrene, β-methylstyrene, pt-butylstyrene, and divinylbenzene. The insulating layer composition for a lithium secondary battery according to claim 3 .

7. The nitrile monomer is one or more monomers selected from the group consisting of acrylonitrile, methacrylonitrile, and allyl cyanide. The insulating layer composition for a lithium secondary battery according to claim 3 .

8. The unsaturated carboxylic acid monomer is at least one monomer selected from the group consisting of maleic acid, fumaric acid, methacrylic acid, acrylic acid, glutaric acid, itaconic acid, tetrahydrophthalic acid, crotonic acid, isocrotonic acid, and nadic acid. The insulating layer composition for a lithium secondary battery according to claim 3 .

9. The hydroxy group-containing monomer is one or more monomers selected from the group consisting of hydroxyacrylate, hydroxyethyl acrylate, hydroxybutyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate. The insulating layer composition for a lithium secondary battery according to claim 3 .

10. The conjugate diene copolymer comprises, based on the total weight, 20 to 45% by weight of the (a) conjugated diene monomer or conjugated diene polymer, 50 to 70% by weight of the (b) at least one monomer selected from the group consisting of acrylate monomers, vinyl monomers, and nitrile monomers, and 1 to 20% by weight of the (c) one or more monomers selected from the group consisting of unsaturated carboxylic acid monomers and hydroxy group-containing monomers. The insulating layer composition for a lithium secondary battery according to claim 1 .

11. The non-aqueous organic solvent is at least one selected from the group consisting of N-methyl-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate (BC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), acetonitrile, dimethoxyethane, tetrahydrofuran (THF), gamma butyrolactone, methyl alcohol, ethyl alcohol, and isopropyl alcohol. The insulating layer composition for a lithium secondary battery according to claim 1 .

12. the conjugated diene copolymer is a styrene-butadiene copolymer; The non-aqueous organic solvent is NMP (N-methyl-pyrrolidone). The insulating layer composition for a lithium secondary battery according to claim 1 .

13. preparing a water-dispersible conjugated dienes latex; Adding a non-aqueous organic solvent to the water-dispersed conjugated diene latex, and heating and reducing the pressure to prepare a slurry for an insulating coating layer comprising the composition of claim 1; applying a slurry for a positive electrode mixture layer, the slurry including a positive electrode active material, a conductive material, and a non-aqueous binder, to one or both surfaces of a positive electrode current collector; applying the slurry for the insulating coating layer to a portion of an uncoated area of ​​the positive electrode current collector so as to cover a portion of the slurry for the positive electrode mixture layer applied to the current collector; and drying the slurry for the positive electrode mixture layer and the slurry for the insulating coating layer applied to the positive electrode current collector. A method for manufacturing a positive electrode for a lithium secondary battery.

14. The step of preparing the slurry for the insulating coating layer includes replacing water, which is a dispersion medium for the conjugated diene latex particles, with a non-aqueous organic solvent. The method for producing a positive electrode for a lithium secondary battery according to claim 13.

15. The conjugate diene latex particles maintain their particle shape even after the dispersion solvent is replaced with a non-aqueous organic solvent. The method for producing a positive electrode for a lithium secondary battery according to claim 14.

16. the conjugated diene latex is a styrene-butadiene latex particle; The non-aqueous organic solvent is NMP (N-methyl-pyrrolidone). The method for producing a positive electrode for a lithium secondary battery according to claim 13.

17. a positive electrode current collector; a positive electrode tab protruding from the positive electrode current collector; an insulating layer coated with an insulating material on the positive electrode tab; The insulating material comprises the composition of claim 1. Positive electrode for lithium secondary batteries.

18. The positive electrode for a lithium secondary battery according to claim 17, Lithium secondary battery.

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