Secondary battery coating composition and secondary battery using the same

Abstract

The secondary battery coating composition according to the present invention is a composition for coating an electrode and / or separator, comprising a flame retardant, a dispersant, and an aqueous solvent, wherein the flame retardant comprises at least one of an inorganic flame retardant containing a hydroxyl group, a phosphorus-based flame retardant, a halogen-based flame retardant, and a melamine-based flame retardant.

Description

[Technical Field]

[0001] The present invention claims the benefit of priority based on Korean Patent Application No. 10-2023-0033531 filed on March 14, 2023, and Korean Patent Application No. 10-2023-0186249 filed on December 19, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a coating composition for secondary batteries, and to an electrode, a separator, and a secondary battery produced using the same. [Background technology]

[0003] In recent years, technological developments and increased demand for mobile devices have led to a rapid increase in the demand for batteries as energy sources, and as a result, extensive research has been conducted on batteries that can meet various requirements. In particular, research has been actively conducted on lithium secondary batteries, which have high energy density and excellent life and cycle characteristics as power sources for such devices.

[0004] A lithium secondary battery includes a positive electrode containing a positive electrode active material capable of inserting / extracting lithium ions, a negative electrode containing a negative electrode active material capable of inserting / extracting lithium ions, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. The positive electrode and the negative electrode have a structure in which an electrode active material layer is formed on one or both sides of an electrode current collector.

[0005] On the other hand, in order to improve the safety of secondary batteries, improvements have been made to the characteristics of the positive electrode, negative electrode, electrolyte, and separator. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a coating composition for secondary batteries that can improve the dispersibility of flame retardants in aqueous solvents, and a secondary battery including a coating layer formed using the composition. [Means for solving the problem]

[0007] According to one embodiment of the present invention, there is provided a coating composition for a secondary battery, comprising a flame retardant, a dispersant, and an aqueous solvent, wherein the flame retardant comprises at least one of an inorganic flame retardant containing a hydroxyl group, a phosphorus-based flame retardant, a halogen-based flame retardant, and a melamine-based flame retardant.

[0008] According to one embodiment of the present invention, the inorganic flame retardant includes one or more selected from the group consisting of boehmite, pseudoboehmite, aluminum hydroxide, and magnesium hydroxide. 50 The thickness may be about 0.1 μm to 5.0 μm.

[0009] According to one embodiment of the present invention, the dispersant is a compound containing one or more carboxyl groups, and the dispersant includes one or more selected from the group consisting of citric acid, malic acid, oxalic acid, glutamic acid, aspartic acid, amino acid, malonic acid, and fatty acid.

[0010] According to one embodiment of the present invention, the dispersant and the flame retardant are included in a weight ratio of about 1:2 to 1:150.

[0011] According to one embodiment of the present invention, the aqueous solvent may be water.

[0012] In the coating composition for secondary batteries according to one embodiment of the present invention, the solid content is about 10% by weight to 70% by weight.

[0013] A secondary battery coating composition according to one embodiment of the present invention further includes a basic additive. The basic additive includes at least one selected from the group consisting of lithium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, ethylenediamine, diethylenetriamine, tris(2-aminoethyl)amine, vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, methylpropargyl carbonate, and allylmethyl carbonate. The basic additive is included in an amount of about 1 to 10 parts by weight based on 100 parts by weight of the secondary battery coating composition.

[0014] A secondary battery electrode according to one embodiment of the present invention includes a current collector, an electrode active material layer, and a coating layer, the electrode active material layer and the coating layer being disposed on the current collector, and the coating layer being formed from the aforementioned secondary battery coating composition. In the electrode according to one embodiment of the present invention, the coating layer has a thickness of approximately 2 μm to 30 μm.

[0015] According to one embodiment of the present invention, there is provided a lithium secondary battery including an electrode coated with the aforementioned secondary battery coating composition. According to one embodiment of the present invention, there is provided a sodium secondary battery including an electrode coated with the aforementioned secondary battery coating composition.

[0016] According to another embodiment of the present invention, there is provided a secondary battery separator comprising a porous polymer substrate and a coating layer, the coating layer being disposed on one side of the porous polymer substrate, and the coating layer being formed from the aforementioned coating composition for secondary batteries.

[0017] According to yet another embodiment of the present invention, there is provided a method for producing a coating composition for a secondary battery, the coating composition comprising a flame retardant, a dispersant, and an aqueous solvent, wherein the flame retardant comprises at least one of an inorganic flame retardant containing a hydroxyl group, a phosphorus-based flame retardant, a halogen-based flame retardant, and a melamine-based flame retardant.

[0018] Average particle size D of the inorganic flame retardant 50 The thickness is set to be approximately 0.1 μm to 5.0 μm.

[0019] The dispersant contains a compound containing one or more carboxy groups. [Effects of the Invention]

[0020] The secondary battery of the present invention has a coating composition for secondary batteries that contains at least one of an inorganic flame retardant containing a hydroxyl group, a phosphorus-based flame retardant, a halogen-based flame retardant, and a melamine-based flame retardant, so that the flame retardant is easily dispersed even in an aqueous solvent environment, thereby achieving the effect of relatively improving the coating properties and the heat resistance of the battery.

[0021] This provides a secondary battery containing a secondary battery coating composition that contains a flame retardant even in an aqueous solvent environment. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Example 1 was applied to a slide glass. [Figure 2] 1 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Example 2 was applied to a slide glass. [Figure 3] 1 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Example 3 was applied to a slide glass. [Figure 4] 1 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Example 4 was applied to a slide glass. [Figure 5] 1 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Example 5 was applied to a slide glass. [Figure 6]1 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Example 6 was applied to a slide glass. [Figure 7] 1 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Example 7 was applied to a slide glass. [Figure 8] 1 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Comparative Example 2 was applied to a slide glass. [Figure 9] 1 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Comparative Example 3 was applied to a slide glass. [Figure 10] 1 is a graph showing the battery capacity value as a function of the number of cycles after the lithium secondary batteries prepared in Example 3 and Comparative Example 1 were operated at a temperature of 25° C. DETAILED DESCRIPTION OF THE INVENTION

[0023] In some of the accompanying drawings, corresponding components are designated by the same reference numerals. Those skilled in the art will understand that the drawings illustrate elements simply and clearly and are not necessarily drawn to scale. For example, the dimensions of some elements shown in the drawings may be exaggerated relative to other elements to facilitate understanding of various embodiments. Furthermore, elements of known technology that are useful or essential in commercially feasible embodiments may not be depicted in order to avoid obscuring the scope of various embodiments of the present invention.

[0024] The advantages and features of the present invention, as well as methods for achieving them, will become apparent from the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be embodied in a variety of different forms. The present embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art to which the invention pertains. The present invention is defined solely by the claims. Like reference numerals refer to like elements throughout the specification.

[0025] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in the sense that they can be commonly understood by a person having ordinary skill in the art to which the present invention belongs. Furthermore, terms defined in commonly used dictionaries should not be interpreted ideally or excessively unless they are clearly and specifically defined.

[0026] The terms used in this specification are for describing the embodiments and are not intended to limit the present invention. In this specification, the singular form includes the plural form unless otherwise specified in the text. The words "comprise," "have," and "include" used in this specification do not exclude the presence or addition of one or more other elements in addition to the elements mentioned.

[0027] In this specification, when a part is said to include a certain component, this does not mean that it may further include other components, unless otherwise specified.

[0028] In this specification, the phrase "A and / or B" means A, or B, or A and B.

[0029] In this specification, "%" means % by weight unless expressly indicated otherwise.

[0030] In this specification, the average particle size D 50The average particle size D can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve. 50 can be measured by, for example, the laser diffraction method. The laser diffraction method is generally capable of measuring particle sizes from the submicron range to several mm, and can provide results with high reproducibility and high resolution.

[0031] As used in this specification, the terms "about," "approximately," and "substantially" are used to mean a numerical value, a range of degree, or a value close to that range, taking into account inherent manufacturing and material tolerances, and are used to prevent infringers from unfairly taking advantage of the disclosure content in which exact or absolute numerical values ​​provided for understanding the present invention are mentioned.

[0032] To improve the safety of electrodes and separators, research is being conducted into forming coating layers on the outer casings of the electrodes, active material layers, and separators. By forming coating layers on the outer casings of the electrode active material layers and separators, it is possible to protect the electrode active material layers and separators from heat generated when the secondary battery is in operation and to improve the insulation between the electrodes.

[0033] Research has been conducted into the use of insulating binders for coating layers on the electrodes and separators of secondary batteries. However, coating layers made of binders have relatively poor heat resistance, and the adhesive strength decreases under high-temperature conditions during battery operation, which can lead to a deterioration in battery safety.

[0034] In order to prevent such problems, a secondary battery is provided in which a flame retardant is added to the coating composition for the electrode or separator, thereby improving the heat resistance of the coating layer.

[0035] If a flame retardant is not uniformly dispersed in a coating composition for electrodes or separators used to improve the heat resistance of secondary battery coating layers, the flame retardant will settle to the bottom of the composition, resulting in an inconsistent distribution of the flame retardant in the coating layer formed from the composition, thereby reducing the effect of improving the heat resistance of the electrode. Furthermore, if the flame retardant is concentrated in the lower part of the coating layer, the binder content at the bottom of the coating layer will be reduced, making the coating layer more likely to detach from the electrode. Furthermore, if flame retardant particles aggregate to form particles with large diameters, the viscosity of the composition will increase, resulting in uneven thickness and / or surface of the coating layer, which will reduce the insulating performance of the coating layer and reduce battery safety. To address these and other problems, we provide a secondary battery using a dispersant containing one or more carboxyl groups that uniformly disperses the flame retardant in a coating composition for secondary batteries.

[0036] The present invention provides a secondary battery that is relatively inexpensive and environmentally friendly compared to organic solvents, using an aqueous solvent and / or binder as a solvent for uniformly dispersing a flame retardant in a coating composition for secondary batteries, in an amount that allows the coating composition to have an appropriate viscosity.

[0037] The present invention will be described below.

[0038] Secondary battery coating composition The coating composition for secondary batteries according to the present invention comprises a flame retardant, a dispersant, and an aqueous solvent, and the flame retardant comprises at least one of an inorganic flame retardant containing a hydroxyl group, a phosphorus-based flame retardant, a halogen-based flame retardant, and a melamine-based flame retardant.

[0039] Hereinafter, each component of the secondary battery coating composition according to the present invention will be described.

[0040] (1) Flame retardants The flame retardant is included in the secondary battery coating composition to improve the heat resistance of the coating layer described below. For example, the flame retardant has the property of not softening or melting even at high temperatures of 900°C or higher. Therefore, when the flame retardant is included in the coating layer, the electrode insulation properties are maintained even at very high temperatures.

[0041] The flame retardant includes at least one of an inorganic flame retardant, a phosphorous flame retardant, a halogen-based flame retardant, and a melamine-based flame retardant.

[0042] Inorganic flame retardants are decomposed by heat to release non-flammable gases such as water, carbon dioxide, sulfur dioxide, and hydrogen chloride, inducing an endothermic reaction, thereby diluting flammable gases and preventing the approach of oxygen, and are cooled by the endothermic reaction, thereby reducing the production of pyrolysis products, thereby exerting a flame retardant effect.

[0043] The inorganic flame retardant may be a compound containing a hydroxyl group. In one embodiment, the inorganic flame retardant includes one or more selected from the group consisting of boehmite (AlO(OH)), pseudoboehmite (Al2O3·nH2O), aluminum hydroxide (Alumina Trihydrate (ATH), Al(OH)3), and magnesium hydroxide (Mg(OH)2).

[0044] In one embodiment, the phosphorus-based flame retardant exhibits a flame retardant effect by forming a protective layer with polymetaphosphoric acid produced by pyrolysis or by blocking oxygen with a carbon coating produced by dehydration during polymetaphosphoric acid production. The phosphorus-based flame retardant includes one or more selected from the group consisting of red phosphorus, phosphates such as ammonium phosphate, phosphine oxide, phosphine oxide diols, phosphites, phosphonates, triaryl phosphate, alkyldiaryl phosphate, trialkyl phosphate, and resorcinol bisdiphenyl phosphate (RDP).

[0045] In one embodiment, the halogen-based flame retardant can exhibit a flame retardant effect by substantially stabilizing radicals generated on the gas, and the halogen-based flame retardant includes one or more selected from the group consisting of tribromophenoxyethane, tetrabromobisphenol-A (TBBA), octabromodiphenyl ether (OBDPE), brominated epoxy oligomer, brominated polycarbonate oligomer, chlorinated paraffin, chlorinated polyethylene, and alicyclic chlorinated flame retardant.

[0046] In one embodiment, the melamine-based flame retardant exhibits a flame retardant effect by absorbing energy as melamine sublimes while promoting the formation of char, lowering the temperature of the burning material and generating ammonia as a decomposition product, which dilutes oxygen and the combustion gas of the resin composition. For example, the melamine-based flame retardant includes one or more selected from the group consisting of melamine, melamine cyanurate, and melamine phosphate.

[0047] For example, the coating composition for secondary batteries according to the present invention contains an inorganic flame retardant. According to the present invention, the average particle size D of the inorganic flame retardant before being dissolved in the aqueous solvent is 50 The average particle size D of the inorganic flame retardant before being dissolved is about 0.1 μm to 5.0 μm, and in one embodiment, about 0.1 μm to 4.0 μm, or about 0.3 μm to 1.0 μm. 50 When the content of the inorganic flame retardant satisfies the above range, the occurrence of aggregation of the inorganic flame retardant particles in the composition is minimized, and a coating layer having a uniform thickness and surface is formed.

[0048] In one embodiment, the flame retardant is included in an amount of about 5 to 40 parts by weight, for example, about 15 to 30 parts by weight, or about 15 to 25 parts by weight, based on 100 parts by weight of the coating composition for secondary batteries. For example, when the content of boehmite is within the above range, the occurrence of agglomeration of boehmite particles is minimized, the viscosity of the coating composition for secondary batteries is appropriately maintained, and a coating layer having a uniform thickness and surface is formed.

[0049] (2) Dispersant The dispersant is intended to improve the dispersibility of the flame retardant in the secondary battery coating composition of the present invention. In one embodiment, the dispersant of the present invention improves the dispersibility of the flame retardant in an aqueous solvent environment.

[0050] The dispersant of the present invention includes a compound containing one or more carboxy groups. In one embodiment, when a compound containing one or more carboxy groups is used as a dispersant in a secondary battery coating composition containing an aqueous solvent and a flame retardant, the dispersibility of the flame retardant in the secondary battery coating composition and the coatability of the composition are relatively improved compared to when the present invention is not applied. For example, when the flame retardant is an inorganic flame retardant containing hydroxyl groups, the hydrophilic group moiety constituting the carboxylic acid compound bonds with the hydroxyl groups on the surface of the flame retardant particles, thereby improving the dispersibility of the flame retardant due to electrostatic repulsion between the carboxylic acid compounds located on the surface of each flame retardant particle.

[0051] The dispersant of the present invention is a compound containing one or more carboxy groups, and in one embodiment, a compound containing about 2 to 5 carboxy groups, or a compound containing about 2 to 4 carboxy groups. When the number of carboxy groups contained in the dispersant satisfies the above range, the carboxylic acid compound is uniformly and densely arranged on the particle surface of the flame retardant, thereby relatively improving the dispersibility of the flame retardant.

[0052] In one embodiment, the compound containing one or more carboxy groups includes one or more selected from the group consisting of citric acid, malic acid, oxalic acid, glutamic acid, aspartic acid, amino acid, malonic acid, and fatty acid. For example, the compound containing one or more carboxy groups is citric acid. Citric acid has the advantages of being easily soluble in aqueous solvents due to its many hydrophilic functional groups, excellent heat resistance due to its high melting point, and inexpensive.

[0053] The dispersant according to one embodiment is contained in an amount of about 0.1 to 10 parts by weight, for example, about 1 to 5 parts by weight, or about 1.9 to 2.5 parts by weight, relative to 100 parts by weight of the coating composition for secondary batteries. When the content of the dispersant satisfies the above range, the dispersibility of boehmite in the coating composition for secondary batteries containing an aqueous solvent is ensured.

[0054] Meanwhile, the dispersant and flame retardant of the present invention are contained in a weight ratio of about 1:2 to 1:150, for example, about 1:4 to 1:20, or about 1:5 to 1:10. When the weight ratio of the dispersant and flame retardant satisfies the above range, the dispersibility of the flame retardant in an aqueous solvent is increased, improving the coatability of the secondary battery coating composition, and the viscosity of the slurry is increased to increase the thickness of the coating layer, thereby improving the heat resistance of the secondary battery.

[0055] (3) Water-based solvents In the present invention, the aqueous solvent dissolves the flame retardant and dispersant, thereby ensuring the coatability of the secondary battery coating composition of the present invention. The aqueous solvent used in the present invention has the advantages of being cheaper to produce than organic solvents, being environmentally friendly, and being harmless to the human body.

[0056] The aqueous solvent is a solvent that can dissolve the flame retardant and dispersant to a certain level or more and is insoluble in the electrode active material layer. In one embodiment, water is used as the aqueous solvent. Alternatively, the aqueous solvent may further contain an alcohol compound such as ethanol or methanol in addition to water.

[0057] The aqueous solvent according to one embodiment is included in an amount that allows the composition to have an appropriate viscosity, taking into consideration the coating properties of the composition. For example, the aqueous solvent is included in an amount of about 20 to 90 parts by weight, about 23 to 80 parts by weight, or about 65 to 78 parts by weight, based on 100 parts by weight of the composition. Meanwhile, the coating composition for secondary batteries according to one embodiment of the present invention has a solids content of about 10 to 80% by weight, for example, about 20 to 77% by weight, or about 22 to 35% by weight. When the solids content is within the above range, the composition for secondary batteries minimizes aggregation of flame retardant particles and has a viscosity appropriate for forming a coating layer using the composition.

[0058] (4) Binder The coating composition for secondary batteries according to one embodiment of the present invention further includes a binder, which further improves the adhesive strength between the coating layer and the current collector and / or between the electrode active material layers.

[0059] The binder according to one embodiment includes a compound of a component that is not easily dissolved by the electrolyte of the secondary battery. The binder is a polymer binder, such as polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene, polyvinylpyrrolidone, polyacrylonitrile, polyacrylimide, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride-chlorotrifluoroethylene (PVdF-CTFE), polymethyl methacrylate, polyvinyl acetate, ethylene-co-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose (CMC), styrene butadiene copolymer (Styrene Butadiene Copolymer), etc. Aqueous or non-aqueous polymers are used, including a single material or a mixture of two or more selected from the group consisting of rubber (SBR), acrylonitrile styrene butadiene copolymer, and polyimide. In particular, when carboxymethyl cellulose and / or styrene butadiene copolymer are used, they are easily dissolved in aqueous solvents, increasing the binding strength and relatively reducing the amount of binder.

[0060] According to one embodiment, the binder is included in an amount of about 0.1 to 20 parts by weight, for example, about 0.1 to 10 parts by weight, or about 1 to 3 parts by weight, based on 100 parts by weight of the coating composition for secondary batteries of the present invention. When the binder content satisfies the above range, the adhesive strength between the coating layer and the electrode is relatively improved.

[0061] (5) Basic additives The coating composition for a secondary battery according to one embodiment of the present invention further includes a basic additive.

[0062] For example, the basic additive neutralizes the acidic dispersant, i.e., the compound containing one or more carboxy groups, in the composition of the present invention. Alternatively, by further including a basic additive in the electrode or separator coating composition of the present invention, acid-base neutralization in the composition can suppress acid-induced side reactions.

[0063] In one embodiment, the basic additive includes one or more selected from the group consisting of lithium carbonate (Li2CO3), sodium carbonate (Na2CO3), potassium carbonate (K2CO3), magnesium carbonate (MgCO3), calcium carbonate (CaCO3), ethylenediamine (EDA), diethylenetriamine (DETA), tris(2-aminoethyl)amine (TAEA), vinylene carbonate (VC), vinylethylene carbonate (VEC), fluoroethylene carbonate (FEC), methylpropargyl carbonate (MPC), and allylmethyl carbonate (AMC).

[0064] In one embodiment, the basic additive is included in an amount of about 0.1 to 10 parts by weight, for example, about 0.1 to 5 parts by weight, or about 0.2 to 2.3 parts by weight, based on 100 parts by weight of the coating composition for secondary batteries. When the content of the basic additive is within the above range, the dispersant included in the composition is sufficiently neutralized.

[0065] Meanwhile, a coating composition for a secondary battery according to one embodiment of the present invention is prepared by adding and mixing a flame retardant and a dispersant into an aqueous solvent, and then performing a dispersion process.

[0066] For example, the components of the composition are mixed by adding the flame retardant and dispersant to an aqueous solvent and mixing them together using a mixing device such as a homomixer.

[0067] Alternatively, the composition after the mixing step may be milled to disperse the composition. The milling may be performed using, for example, a ball mill, a bead mill, or a basket mill. The degree of dispersion of the composition can be controlled by adjusting milling conditions such as the number of passes (hereinafter referred to as "pass number") of the composition through the ball mill, bead mill, or basket mill, and the rotor speed.

[0068] On the other hand, the average particle size D of the solid particles in the composition according to one embodiment of the present invention 50 is about 0.1 μm to 10 μm, for example, about 0.3 μm to 3 μm, or about 0.3 μm to 1 μm. Here, the solid particles include at least one of a flame retardant and a dispersant. For example, the solid particles are in the form of flame retardant particles bonded to each other, or flame retardant particles bonded to a dispersant. Alternatively, the solid particles are in the form of flame retardant particles bonded to a dispersant and a binder. When the particle size of the solid particles in the composition satisfies the above range, the dispersibility of the flame retardant particles in the composition is improved, thereby relatively improving the coatability and adhesiveness of the coating layer. Meanwhile, the degree of dispersion of the solid particles in the composition according to one embodiment can be adjusted by adjusting the content of the solids in the composition, the type and content of the dispersant, and / or the dispersion process conditions.

[0069] The viscosity of the coating composition for secondary batteries according to one embodiment is about 10 cP to 16,000 cP, for example, about 20 cP to 4,000 cP, or about 30 cP to 600 cP. When the viscosity of the composition is within the above range, the coating layer is formed to an appropriate thickness, minimizing a decrease in cell life due to an increase in electrode resistance and ensuring the heat resistance of the battery.

[0070] Meanwhile, in a coating composition for secondary batteries according to an embodiment of the present invention, the content ratio of the flame retardant to the dispersant is controlled to ensure the dispersibility of the flame retardant and the coatability of the composition, and the viscosity of the composition can be adjusted to easily control the thickness of the coating layer. Therefore, when manufacturing a secondary battery that requires ensuring heat resistance, adjusting the viscosity of the composition can easily produce a thick coating layer.

[0071] The coating composition for secondary batteries according to one embodiment of the present invention is used to form a coating layer on an electrode. For example, the electrode coating layer is formed by applying the coating composition for secondary batteries described above onto a current collector and / or an electrode active material layer, followed by drying.

[0072] The composition of the present invention according to one embodiment can also be used to form a coating layer on a separator. For example, the separator coating layer can be formed by applying the composition of the present invention to a separator coated with an aqueous binder slurry, followed by drying.

[0073] electrode An electrode according to one embodiment of the present invention will be described. The electrode of the present invention includes a current collector, an electrode active material layer, and a coating layer, the electrode active material layer and the coating layer being disposed on the current collector, and the coating layer being formed from the aforementioned secondary battery coating composition. In this case, the secondary battery coating composition is as described above.

[0074] For example, the current collector is conductive and does not cause chemical changes in the battery, and may be made of copper, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like.

[0075] In the secondary battery of the present invention, an electrode active material layer containing a positive electrode active material or a negative electrode active material layer containing a negative electrode active material is used. As the positive electrode active material, for example, lithium cobalt-based oxides, lithium nickel-based oxides, lithium manganese-based oxides, lithium iron phosphate, lithium nickel manganese cobalt-based oxides, or combinations thereof are used. Alternatively, as the positive electrode active material, LiCoO2, LiNiO2, LiMn2O4, LiCoPO4, LiFePO4, and LiNi a Mn b Co c O2 (where 0 < a, b, c < 1) and the like are used. As the negative electrode active material, for example, natural graphite, artificial graphite, carbonaceous materials; lithium-containing titanium composite oxides (LTO), Si, Sn, Li, Zn, Mg, Cd, Ce, Ni, or metals (Me) such as Fe; alloys composed of the metals (Me); oxides (MeO x ); and one or more negative electrode active materials selected from the group consisting of composites of the metals (Me) and carbon are used.

[0076] The electrode active material layer according to one embodiment further includes a conductive material and a binder in addition to active materials such as a positive electrode active material and a negative electrode active material.

[0077] The conductive material according to one embodiment is electrically conductive and does not cause chemical changes in the battery. Examples of such conductive materials include graphite, carbon black (e.g., carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black), conductive fibers (e.g., carbon fiber and metal fiber), metal powders (e.g., carbon fluoride, aluminum, and nickel powder), conductive whiskers (e.g., zinc oxide and potassium titanate), conductive metal oxides (e.g., titanium oxide), and conductive materials (e.g., polyphenylene derivatives). Examples of conductive materials include acetylene black (e.g., acetylene black from Chevron Chemical Company, Denka Black (e.g., from Denka Singapore Private Limited, Gulf Oil Company), Ketjenblack, EC (e.g., from Armak Company), Vulcan XC-72 (e.g., from Cabot Company), and Super P (e.g., from Timcal).

[0078] The binder is a component that aids in binding the active material with the conductive material and the current collector, and in one embodiment, is added in an amount of about 1% to 30% by weight based on the total weight of the mixture including the positive electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butylene rubber, fluororubber, and various copolymerization agents.

[0079] Meanwhile, a coating layer according to one embodiment of the present invention is formed by applying the above-described coating composition for secondary batteries onto a current collector and then drying it. For example, the coating layer is formed on an uncoated portion of the current collector where no electrode active material layer is formed. In this case, the coating layer is formed so as to partially overlap the end of the electrode active material layer. The coating layer is formed to a uniform thickness on the current collector and the electrode active material layer. In this case, the thickness of the coating layer is about 2 μm to 30 μm, for example, about 2 μm to 20 μm, or about 5 μm to 13 μm. When the thickness of the coating layer satisfies the above range, the adhesion of the coating layer to the current collector and / or the electrode active material layer is relatively high.

[0080] The coating layer according to one embodiment of the present invention has relatively superior coating properties compared to conventional coating layers. For example, the coating layer has a relatively uniform thickness and / or surface. Alternatively, the flame retardant particles are uniformly dispersed on the coating layer. As a result, the heat resistance and battery life characteristics of the secondary battery are relatively improved.

[0081] secondary battery A lithium secondary battery according to one embodiment of the present invention will be described.

[0082] The lithium secondary battery of the present invention is a lithium secondary battery including the above-described electrodes. In this case, the electrodes are as described above. For example, the electrodes are positive electrodes and / or negative electrodes. A lithium secondary battery according to one embodiment of the present invention includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte.

[0083] The separator according to one embodiment of the present invention has low resistance to ion migration of the electrolyte and a relatively high electrolyte moisture-absorbing capacity. For example, a porous polymer film, such as a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof, can be used. Alternatively, a porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, can be used.

[0084] The electrolyte according to one embodiment includes an organic solvent and a lithium salt.

[0085] The organic solvent used in one embodiment can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. For example, the organic solvent can be an ester-based solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; an ether-based solvent such as dibutyl ether or tetrahydrofuran; a ketone-based solvent such as cyclohexanone; an aromatic hydrocarbon-based solvent such as benzene or fluorobenzene; or a carbonate-based solvent such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), or propylene carbonate (PC). For example, a carbonate-based solvent can be used, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and a high dielectric constant, and a low-viscosity linear carbonate-based compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) can be used, which can improve the charge / discharge performance of the battery.

[0086] Examples of lithium salts that may be used in one embodiment include LiPF, LiClO, LiAsF, LiBF, LiSbF, LiAlO, LiAlCl, LiCFSO, LiC4F9SO, LiN(C2F5SO3), LiN(C2F5SO2), LiN(CF3SO2).LiCl, LiI, and LiB(C2O4)2. For example, the lithium salt is contained in the electrolyte at a concentration of about 0.6 mol% to 2 mol%.

[0087] In addition to the constituent components of the electrolyte, the electrolyte according to one embodiment of the present invention further contains one or more additives such as pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the battery's life characteristics, suppressing a decrease in battery capacity, and improving the battery's discharge capacity.

[0088] A lithium secondary battery according to an embodiment of the present invention may be fabricated by forming an electrode assembly by disposing a separator between a positive electrode and a negative electrode, placing the electrode assembly in a cylindrical or prismatic battery case, and then injecting an electrolyte. Alternatively, the electrode assemblies may be stacked, impregnated with an electrolyte, and then placed in a battery case and sealed.

[0089] When manufacturing a lithium secondary battery according to an embodiment of the present invention, the electrode assembly is dried to remove one or more organic solvents selected from the group consisting of N-methyl-2-pyrrolidone (NMP), acetone, ethanol, propylene carbonate, ethyl methyl carbonate, ethylene carbonate, and dimethyl carbonate used in manufacturing the positive electrode. Alternatively, when an electrolyte having the same components as the organic solvent used in manufacturing the positive electrode is used, the process of drying the electrode assembly is omitted.

[0090] Meanwhile, although the coating composition has been described above in relation to a lithium secondary battery, the lithium secondary battery according to one embodiment of the present invention can also be applied to a sodium secondary battery in which sodium is used instead of lithium. For example, the coating composition of the present invention can also be applied to a sodium ion secondary battery manufactured using a material containing sodium instead of lithium as the positive electrode active material.

[0091] Also, unlike the above-described lithium secondary battery, the lithium secondary battery according to another embodiment of the present invention is an all-solid-state battery.

[0092] The battery case according to an embodiment of the present invention can be easily adapted to the shape of the battery depending on its intended use, and may be, for example, a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0093] The secondary battery according to one embodiment of the present invention exhibits relatively improved discharge capacity, output characteristics, and capacity retention rate, and is therefore useful in the fields of portable devices such as mobile phones, notebook computers, and digital cameras, energy storage systems (ESS), and electric vehicles such as hybrid electric vehicles (HEV).

[0094] The present invention will be described in more detail below with reference to examples. However, the following examples are merely illustrative for understanding the present invention and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope and technical concept of the present disclosure, and it goes without saying that such changes and modifications are within the scope of the appended claims.

[0095] In addition, in the examples and comparative examples described below, it is described that the coating composition of the present invention is applied to electrodes of secondary batteries. However, as described above, the coating composition of the present invention can be similarly applied to other structures of an electrode assembly, such as a separator, in addition to electrodes.

[0096] Examples and Comparative Examples Example 1 (1) Preparation of electrode coating composition 40 g of deionized water was used as a solvent, and boehmite (average particle size D 50After mixing 10 g of the powder (particle size: 0.2 μm) with 0.1 g of citric acid as a dispersant, the mixture was mixed for 10 minutes using a homomixer (product name: Dispermat LC, manufacturer: VMA).

[0097] (2) Manufacture of lithium secondary batteries Artificial graphite, carbon black, carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) were mixed in a weight ratio of 94.3:2.0:1.2:2.5 and distilled water was added to prepare anode slurry. The anode slurry was coated on one side of a 10 μm-thick copper (Cu) metal thin film and then vacuum-dried. The dried anode slurry was then rolled and dried in a vacuum oven at 130°C for 12 hours, and then punched out to prepare anode active material layers. The prepared electrode coating composition was then coated on each anode active material layer and vacuum-dried to prepare anodes with a coating layer (thickness: 12.4 μm).

[0098] As the positive electrode active material, Li[Ni 0.83 Co 0.11 Mn 0.06 ]O2, carbon nanotubes (CNTs), polyvinylidene fluoride (PVdF), and hydrogenated nitrile butadiene rubber (H-NBR) were added to N-methylpyrrolidone (NMP) solvent in a weight ratio of 97.0:1.0:1.5:0.5 and stirred to prepare a cathode slurry. The cathode slurry was coated on one side of a 15 μm-thick aluminum foil and then vacuum dried at 130°C for 10 hours. The dried cathode slurry was rolled and dried in a vacuum oven at 130°C for 12 hours, and then punched out to prepare a cathode.

[0099] The negative and positive electrodes prepared as described above and a porous polyethylene separator having a thickness of 10 μm were stacked to prepare an electrode assembly.

[0100] An electrolyte was prepared by dissolving LiPF6 to a concentration of 1.2 M in a solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a weight ratio of 20:80.

[0101] The electrode assembly was placed in a pouch-shaped battery case, the electrolyte was injected, and the case was sealed to manufacture a lithium secondary battery.

[0102] Example 2 An electrode coating composition was produced in the same manner as in Example 1, except that 0.5 g of citric acid was mixed instead of 0.1 g in the electrode coating composition of Example 1.

[0103] A lithium secondary battery was produced in the same manner as in Example 1, except that the above electrode coating composition was used.

[0104] Example 3 An electrode coating composition was produced in the same manner as in Example 1, except that 1.0 g of citric acid was mixed instead of 0.1 g in the electrode coating composition of Example 1.

[0105] A lithium secondary battery was produced in the same manner as in Example 1, except that the above electrode coating composition was used.

[0106] Example 4 An electrode coating composition was produced in the same manner as in Example 1, except that 2.0 g of citric acid was mixed instead of 0.1 g in the electrode coating composition of Example 1.

[0107] A lithium secondary battery was produced in the same manner as in Example 1, except that the above electrode coating composition was used.

[0108] Example 5 An electrode coating composition was produced in the same manner as in Example 1, except that 4.0 g of citric acid was mixed instead of 0.1 g in the electrode coating composition of Example 1.

[0109] A lithium secondary battery was produced in the same manner as in Example 1, except that the above electrode coating composition was used.

[0110] Example 6 An electrode coating composition was produced in the same manner as in Example 1, except that 0.1 g of ethylenediamine was additionally mixed as a basic additive in the electrode coating composition of Example 1.

[0111] A lithium secondary battery was produced in the same manner as in Example 1, except that the above electrode coating composition was used.

[0112] Example 7 In the preparation of the electrode coating composition, 40 g of deionized water was used as a solvent, and aluminum hydroxide (average particle size D 50 : 0.6 μm) 10 g and melamine (average particle size D 50 After mixing 3 g of the powder (fine particle size: less than 1 μm), 0.3 g of citric acid as a dispersant, and 0.3 g of ethylenediamine as a basic additive, the mixture was mixed for 10 minutes using a homomixer (product name: Dispermat LC, manufacturer: VMA).

[0113] Comparative Example 1 A lithium secondary battery was produced in the same manner as in Example 1, except that no coating layer was formed on the negative electrode of the lithium secondary battery.

[0114] Comparative Example 2 An electrode coating composition was produced in the same manner as in Example 1, except that citric acid was not mixed as a dispersant in the production of the electrode coating composition.

[0115] A lithium secondary battery was produced in the same manner as in Example 1, except that the above electrode coating composition was used.

[0116] Comparative Example 3 An electrode coating composition was produced in the same manner as in Example 1, except that silicon monoxide (SiO), which is not a flame retardant, was used instead of boehmite.

[0117] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the electrode coating composition was used.

[0118] [Table 1]

[0119] Experimental Example 1: Measurement of viscosity of electrode coating composition The viscosity of each of the electrode coating compositions produced in Examples 1 to 7 and Comparative Examples 2 and 3 was measured, and the measurement results are shown in Table 2 below.

[0120] The viscosity of the composition was measured using a viscometer (product name: DV2T, manufacturer: Brookfield) at 25°C and 12 rpm.

[0121] Experimental Example 2: Evaluation of the dispersibility of inorganic particles in electrode coating compositions The electrode coating compositions prepared in Examples 1 to 7 and Comparative Examples 2 and 3 were applied to a glass slide, and the dispersion of the inorganic particles in the compositions was evaluated using an optical microscope as follows: The results of the evaluation of dispersibility are shown in Table 2 below and Figures 1 to 9. ○: Good dispersibility (no aggregation of inorganic particles) ×: Poor dispersibility (aggregation of inorganic particles occurs)

[0122] FIG. 1 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Example 1 was applied to a slide glass.

[0123] FIG. 2 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Example 2 was applied to a slide glass.

[0124] FIG. 3 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Example 3 was applied to a slide glass.

[0125] FIG. 4 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Example 4 was applied to a slide glass.

[0126] FIG. 5 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Example 5 was applied to a slide glass.

[0127] FIG. 6 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Example 6 was applied to a slide glass.

[0128] FIG. 7 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Example 7 was applied to a slide glass.

[0129] FIG. 8 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Comparative Example 2 was applied to a slide glass.

[0130] FIG. 9 is an optical microscope image taken at 300x magnification after the electrode coating composition prepared in Comparative Example 3 was applied to a slide glass.

[0131] [Table 2]

[0132] Experimental Example 3: Evaluation of heat resistance characteristics of secondary batteries The lithium secondary batteries prepared in Examples 3 and 7 and Comparative Examples 1 and 3 were subjected to a hot box test in a fully charged state of SOC 100% (4.45V) while varying the temperature under the following conditions.

[0133] 1) Raise the temperature from 25°C to 130°C at a rate of 5°C / min, then maintain the temperature for 30 minutes. 2) The temperature was raised from 130°C to 200°C at a rate of 2°C / min, and then the temperature was maintained for 30 minutes. 3) The temperature was raised from 200°C to 260°C at a rate of 2°C / min, and then the temperature was maintained for 30 minutes.

[0134] At this time, the temperature at which the rapid temperature rise of the secondary battery started and the maximum temperature were measured using a thermocouple attached to the center of the pouch of the lithium secondary battery. In addition, the hot box test was conducted to check whether the secondary battery caught fire. The results are shown in Table 3 below. ○: Lithium secondary battery catches fire ×: Lithium secondary battery does not ignite

[0135] [Table 3]

[0136] Experimental Example 4: Evaluation of the room temperature life performance of secondary batteries The lithium secondary batteries manufactured in Example 3 and Comparative Example 1 were charged / discharged at a temperature of 25°C under the following conditions, and the battery capacity (unit: Ah) was measured according to the number of cycles, and the capacity retention rate (%) was calculated. - Charging conditions: CC (constant current) / CV (constant voltage) mode, charging at a rate of 0.2C, cut-off at 4.25V and 0.05C - Discharge conditions: CC mode, discharge rate 0.2C, cutoff at 3.0V

[0137] At this time, the battery capacity and the capacity retention rate at 100 cycles were measured using an IL-2C-525S manufactured by JEIO TECH Co., Ltd. The measurement results are shown in FIG.

[0138] FIG. 10 is a graph showing the battery capacity values ​​as a function of the number of cycles after the lithium secondary batteries manufactured in Example 3 and Comparative Example 1 were operated at a temperature of 25° C., respectively.

[0139] [Table 4]

[0140] As shown in Tables 1 and 2 and Figures 1 to 9, the electrode coating compositions of the present invention of Examples 1 to 6, in which boehmite and a compound containing one or more carboxyl groups are mixed in an aqueous solvent, have good dispersibility of boehmite, and it can be confirmed that aggregation of particles hardly occurs.

[0141] Example 7 is an electrode coating composition containing a flame retardant containing aluminum hydroxide and melamine, and a compound containing one or more carboxyl groups, mixed in an aqueous solvent. While aluminum hydroxide exhibits high endothermic energy, it can produce excessive water, potentially resulting in an explosive reaction with lithium. Melamine, on the other hand, has a higher endothermic effect than boehmite, an inorganic flame retardant. Therefore, it is expected that using melamine alone as a flame retardant would provide the best flame retardancy. However, because the inorganic flame retardant helps provide adequate insulation in the event of an internal short circuit through surface coating, and because melamine alone is difficult to prepare into a slurry, it is preferable to use a mixed flame retardant, as in Example 7.

[0142] In contrast, in the electrode coating composition of Comparative Example 2, which does not include a compound containing one or more carboxyl groups in the aqueous solvent of the present invention, the boehmite is not sufficiently dispersed, and aggregation of particles occurs, resulting in particle shapes with diameters of about 50 μm.Furthermore, in the electrode coating composition of Comparative Example 3, which does not include the present invention and uses silicon monoxide (SiO) instead of boehmite, the boehmite is not sufficiently dispersed, and aggregation of particles occurs.

[0143] As shown in Tables 1 and 3, in Comparative Example 1, to which the present invention was not applied, in which no coating layer was formed on the negative electrode, and Comparative Example 3, in which silicon monoxide (SiO) was included in the coating layer instead of boehmite, the temperature at which the secondary battery began to heat up rapidly was significantly lower than in Examples 3 and 7, and the maximum temperature of the secondary battery was significantly higher than in Examples 3 and 7. Therefore, unlike Examples 3 and 7, it was confirmed that the secondary battery ignited in the hot box test.

[0144] As shown in Table 1, Table 4, and FIG. 10, it can be seen that Example 3, in which a coating layer is formed using a composition in which boehmite and a compound containing one or more carboxyl groups are mixed in an aqueous solvent, has a relatively better capacity retention rate (%) at room temperature than Comparative Example 1, in which the present invention is not applied.

[0145] Although the present invention has been described above with reference to preferred embodiments, it will be understood by those skilled in the art or those having ordinary knowledge in the art that various modifications and changes can be made to the present invention without departing from the spirit and technical scope of the present invention as defined in the appended claims. Therefore, the technical scope of the present invention is not limited to the contents of the detailed description of the specification, but is defined by the claims.

Claims

1. A flame retardant; a dispersant; and an aqueous solvent; The flame retardant includes at least one of an inorganic flame retardant containing a hydroxyl group, a phosphorus-based flame retardant, a halogen-based flame retardant, and a melamine-based flame retardant.

2. 2. The coating composition for secondary batteries according to claim 1, wherein the inorganic flame retardant comprises one or more selected from the group consisting of boehmite, pseudoboehmite, aluminum hydroxide, and magnesium hydroxide.

3. Average particle size D of the inorganic flame retardant ５０ 2. The secondary battery coating composition according to claim 1, wherein the average particle size is about 0.1 μm to 5.0 μm.

4. The secondary battery coating composition according to claim 1 , wherein the dispersant comprises a compound containing one or more carboxy groups.

5. 2. The coating composition for secondary batteries according to claim 1, wherein the dispersant comprises at least one selected from the group consisting of citric acid, malic acid, oxalic acid, glutamic acid, aspartic acid, amino acid, malonic acid, and fatty acid.

6. 2. The coating composition for secondary batteries according to claim 1, wherein the dispersant and the flame retardant are contained in a weight ratio of about 1:2 to 1:

150.

7. The coating composition for secondary batteries according to claim 1 , wherein the aqueous solvent is water.

8. 2. The coating composition for secondary batteries according to claim 1, wherein the solid content is about 10% by weight to 70% by weight.

9. The secondary battery coating composition according to claim 1 , further comprising a basic additive.

10. 10. The secondary battery coating composition according to claim 9, wherein the basic additive comprises one or more selected from the group consisting of lithium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, ethylenediamine, diethylenetriamine, tris(2-aminoethyl)amine, vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, methylpropargyl carbonate, and allylmethyl carbonate.

11. The coating composition for secondary batteries according to claim 9, wherein the basic additive is included in an amount of about 1 part by weight to 10 parts by weight based on 100 parts by weight of the coating composition for secondary batteries.

12. a current collector, an electrode active material layer, and a coating layer; the electrode active material layer and the coating layer are disposed on the current collector, A secondary battery electrode, wherein the coating layer is formed from the secondary battery coating composition according to claim 1 .

13. 13. The secondary battery electrode according to claim 12, wherein the coating layer has a thickness of about 2 μm to 30 μm.

14. A lithium secondary battery comprising the secondary battery electrode according to claim 12.

15. A sodium secondary battery comprising the secondary battery electrode according to claim 12.

16. a porous polymer substrate and a coating layer; the coating layer is disposed on one side of the porous polymer substrate; A secondary battery separator, wherein the coating layer is formed from the coating composition for secondary batteries according to claim 1 .

17. A method for producing a coating composition for a secondary battery, comprising: The secondary battery coating composition comprises: A flame retardant; a dispersant; and an aqueous solvent; The flame retardant may include at least one of an inorganic flame retardant containing a hydroxyl group, a phosphorus-based flame retardant, a halogen-based flame retardant, and a melamine-based flame retardant.

18. 18. The method for producing a coating composition for a secondary battery according to claim 17, wherein the inorganic flame retardant comprises one or more selected from the group consisting of boehmite, pseudo-boehmite, aluminum hydroxide, and magnesium hydroxide.

19. Average particle size D of the inorganic flame retardant ５０ The method for producing a coating composition for secondary batteries according to claim 17, wherein the average particle size is about 0.1 μm to 5.0 μm.

20. The method for producing a coating composition for a secondary battery according to claim 17 , wherein the dispersant comprises a compound containing one or more carboxy groups.

Images