Composition for forming active material composite material, active material composite material and method for producing the same

Abstract

The present invention provides a composition for forming an active material composite material, from which an active material composite material can be obtained. This active material composite material can be used in electrodes of lithium-ion secondary batteries and the like, and can improve the battery's cycle and rate characteristics. The composition for forming an active material composite material is characterized by comprising an active material, a conductive material, a dispersant, a solvent, and a crosslinking agent, wherein the active material is at least one selected from the group consisting of a metal, a semimetal, a metal alloy, a metal oxide, a semimetal oxide, a metal phosphate, a metal sulfide, and a metal nitride.

Description

Technical Field

[0001] The present invention relates to a composition for forming an active material composite material (active material complex), an active material composite material obtained from the composition, and a method for producing the active material composite material. Background Art

[0002] In recent years, the trend toward miniaturization and lightweighting of electronic devices has led to a demand for smaller and lighter batteries, which serve as their power sources. Non-aqueous electrolyte secondary batteries, such as lithium-ion batteries, are small, lightweight, and capable of high-capacity charge and discharge. They are now practically used in portable electronic devices such as small cameras, mobile phones, and laptop computers, as well as in communications equipment.

[0003] Lithium-ion secondary batteries offer advantages such as high energy density, higher capacity, and higher operating voltage than other batteries. However, this high energy density can also pose a risk of overheating and fire, depending on usage, necessitating high safety requirements for lithium-ion secondary batteries. Hybrid vehicles, in particular, are attracting significant attention, demanding even higher energy density and output characteristics, thus requiring even greater safety.

[0004] Typically, a lithium-ion secondary battery consists of a positive electrode, a negative electrode, and an electrolyte. During charging, lithium ions are released from the positive electrode active material into the electrolyte and then inserted into the negative electrode active material, such as carbon particles. During discharge, lithium ions are released from the negative electrode active material into the electrolyte and then inserted into the positive electrode active material, allowing current to be output to an external circuit. In this way, within a lithium-ion secondary battery, lithium ions travel back and forth between the positive and negative electrodes through the electrolyte, thereby causing charging and discharging.

[0005] On the other hand, with the improvement of the performance of portable electronic devices, etc., higher capacity batteries are required. As negative electrode active materials, the capacity per unit weight is much higher than that of Sn, Si, etc. compared with existing carbon. However, when Si or Si alloys are used as negative electrode active materials, there is a problem of increased volume expansion and deterioration of cycle characteristics. In order to solve this problem, graphite is mixed, but when the graphite is unevenly distributed during mixing, there is a situation where the cycle characteristics (lifespan) are reduced.

[0006] Furthermore, with the increasing versatility of lithium-ion secondary batteries in recent years, there is a demand for further improvements in rate characteristics. Research is also underway to use these secondary batteries as high-output power sources, particularly for plug-in hybrid vehicles, hybrid electric vehicles, and power tools. Batteries used as these high-output power sources are required to be able to charge and discharge at high speeds.

[0007] The electrode active material used in such a battery, such as an electrode material containing a lithium phosphate compound or a lithium-containing metal oxide having the property of enabling lithium ions to be reversibly deintercalated, has the problem of low electrical conductivity. Therefore, when charging and discharging with a large current, there is a situation where the resistance overvoltage and activation overvoltage increase, the voltage of the battery decreases, and sufficient charge and discharge capacity cannot be obtained. In contrast, in order to improve the electronic conductivity of the electrode material, an electrode material as described below is proposed, wherein the particle surface of the electrode active material is covered with an organic compound as a carbon source, and then a carbonaceous film is formed on the surface of the electrode active material by carbonizing the organic compound, and the carbon of the carbonaceous film is sandwiched therein as an electronic conductive material (for example, patent document 1).

[0008] However, further improvements in cycle characteristics and rate characteristics are required, and the carbonization step requires a long-term heat treatment at a high temperature of 500° C. or higher in an inert gas atmosphere.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-15111 Summary of the Invention

[0012] Problems to be solved by the invention

[0013] The present invention is completed in view of the above situation. The purpose of the present invention is to provide a composition for forming an active material composite material, an active material composite material obtained from the composition, and a method for manufacturing the active material composite material. Based on the composition for forming the active material composite material, an active material composite material can be obtained. The active material composite material can be used for electrodes of lithium-ion secondary batteries, etc. and can improve the cycle characteristics and rate characteristics of the battery.

[0014] Means used to solve problems

[0015] As a result of in-depth research to solve the above problems, the inventors found that: a composition for forming an active material composite material, which includes an active material, a conductive material, a dispersant, a solvent and a cross-linking agent, wherein the active material is selected from at least one of a metal, a semi-metal, a metal alloy, a metal oxide, a semi-metal oxide, a metal phosphate, a metal sulfide and a metal nitride, and an active material composite material having a thermally cured layer containing a conductive material on the surface of the active material particles and having good conductivity and excellent durability can be obtained from the active material composite material. The active material composite material is used to form a battery electrode, thereby providing a secondary battery with excellent cycle characteristics and rate characteristics. In addition, the inventors also found that by using the above-mentioned active material composite material composition and performing a heat treatment at a lower temperature than before, the above-mentioned thermally cured layer can be easily formed, and the above-mentioned active material composite material can be obtained even without performing a carbonization process. The inventors completed the present invention based on this.

[0016] That is, the present invention provides the following compositions for forming an active material composite material, active material composite materials, methods for producing the active material composite materials, and the like.

[0017] Item 1. A composition for forming an active material composite material, characterized in that the composition for forming an active material composite material contains an active material, a conductive material, a dispersant, a solvent and a cross-linking agent, and the active material is selected from at least one of metals, semi-metals, metal alloys, metal oxides, semi-metal oxides, metal phosphates, metal sulfides and metal nitrides.

[0018] Item 2. In the active material composite material forming composition of Item 1, the active material is selected from FeS2, TiS2, MoS2, LiFePO4, V2O6, V6O 13 , MnO2, LiCoO2, LiMnO2, LiMn2O4, LiMo2O4, LiV3O8, LiNiO2, Li z Ni y M 1-y O2 (wherein M represents at least one metal element selected from Co, Mn, Ti, Cr, V, Al, Sn, Pb, and Zn, 0.05≦z≦1.10, 0.5≦y≦1.0), Li(Ni a Co b Mn c )O2(where 0 <a<1,0<b<1,0<c<1,a+b+c=1)、Li4Ti5O 12 、Si、SiO x 、AlO x 、SnO x, SbO x , BiO x , GeO x , AsO x , PbO x , ZnO x , CdO x , InO x , TiO x and GaO x (where 0 < x ≦ 2), at least one of them.

[0019] Item 3. In the composition for forming the active material composite of Item 1 or Item 2, the above conductive material is conductive carbon.

[0020] Item 4. In the composition for forming the active material composite of Item 3, the above conductive carbon is carbon nanotubes.

[0021] Item 5. An active material composite obtained from the composition for forming the active material composite of any one of Items 1 to 4.

[0022] Item 6. In the active material composite of Item 5, a thermosetting layer is provided on the surface of the particles of the active material selected from at least one of metals, semimetals, metal alloys, metal oxides, semimetal oxides, metal phosphides, metal sulfides, and metal nitrides, and the thermosetting layer contains a conductive material, a dispersant, and a crosslinking agent.

[0023] Item 7. An active material composite, characterized in that it contains an active material, a conductive material, a dispersant, and a crosslinking agent, and the active material is selected from at least one of metals, semimetals, metal alloys, metal oxides, semimetal oxides, metal phosphides, metal sulfides, and metal nitrides.

[0024] Item 8. In the active material composite of Item 7, the above active material is selected from FeS2, TiS2, MoS2, LiFePO4, V2O6, V6O 13 , MnO2, LiCoO2, LiMnO2, LiMn2O4, LiMo2O4, LiV3O8, LiNiO2, Li z Ni y M 1-y O2 (where M represents at least one metal element selected from Co, Mn, Ti, Cr, V, Al, Sn, Pb, and Zn, 0.05 ≦ z ≦ 1.10, 0.5 ≦ y ≦ 1.0), Li(Ni a Co b Mn c )O2 (where 0 < a < 1, 0 < b < 1, 0 < c < 1, a + b + c = 1), Li4Ti5O 12, Si, SiO x , AlO x , SnO x , SbO x , BiO x , GeO x , AsO x , PbO x , ZnO x , CdO x , InO x , TiO x and GaO x (where 0 < x ≦ 2) at least one of them.

[0025] Item 9. In the active material composite of Item 7 or 8, the conductive material is conductive carbon.

[0026] Item 10. In the active material composite of Item 9, the conductive carbon is carbon nanotubes.

[0027] Item 11. A composition for forming an electrode, which comprises the active material composite of any one of Items 5 to 10, a conductive aid, and a binder.

[0028] Item 12. An electrode, which has an active material layer composed of the composition for forming an electrode of Item 11.

[0029] Item 13. A secondary battery, which includes the electrode of Item 12.

[0030] Item 14. A method for manufacturing a composition for forming an active material composite, which is a method for manufacturing the composition for forming an active material composite of any one of Items 1 to 4, and includes: preparing an active material dispersion liquid and a conductive material dispersion liquid separately and then mixing them, wherein the active material dispersion liquid contains an active material and a solvent, and the conductive material dispersion liquid contains a conductive material, a dispersant, a crosslinking agent, and a solvent.

[0031] Item 15. A method for manufacturing an active material composite, which includes: preparing a composition for forming an active material composite by mixing an active material, a conductive material, a dispersant, a solvent, and a crosslinking agent, and performing heat treatment at a temperature at which carbonization of the composition does not occur; wherein the active material is selected from at least one of metals, semi-metals, metal alloys, metal oxides, semi-metal oxides, metal phosphides, metal sulfides, and metal nitrides.

[0032] Item 16. In the method for manufacturing an active material composite of Item 15, heat treatment is performed at 120 - 220 °C.

[0033] Item 17. In the method for manufacturing the active material composite of Item 15 or 16, it includes drying after preparing the composition for forming the above-mentioned active material composite.

[0034] Item 18. In the method for manufacturing the active material composite of Item 17, the above-mentioned drying is carried out by the spray drying method.

[0035] Item 19. In the method for manufacturing the active material composite of any one of Items 15 to 18, the above-mentioned active material is selected from the group consisting of FeS2, TiS2, MoS2, LiFePO4, V2O6, V6O 13 , MnO2, LiCoO2, LiMnO2, LiMn2O4, LiMo2O4, LiV3O8, LiNiO2, Li z [[ID=IO]]Ni y M 1-y O2 (where M represents at least one metal element selected from Co, Mn, Ti, Cr, V, Al, Sn, Pb, and Zn, 0.05 ≦ z ≦ 1.10, 0.5 ≦ y ≦ 1.0), Li(Ni a Co b Mn c )O2 (where 0 < a < 1, 0 < b < 1, 0 < c < 1, a + b + c = 1), Li4Ti5O 12 , Si, SiO x , AlO [[ID=2S]] x , SnO x , SbO x , BiO x , GeO x , AsO x , PbO x , ZnO x , CdO x , InO x , TiO x and GaO x (where 0 < x ≦ 2) and at least one of the group.

[0036] Item 20. In the method for manufacturing the active material composite of any one of Items 15 to 19, the above-mentioned conductive material is conductive carbon.

[0037] Item 21. In the method for manufacturing the active material composite of Item 20, the above-mentioned conductive carbon is carbon nanotubes.

[0038] Item 22. In the method for manufacturing an active material composite material of any one of items 15 to 21, an active material dispersion containing an active material and a solvent and a conductive material dispersion containing a conductive material, a dispersant and a cross-linking agent are prepared separately and then mixed to prepare the composition for forming the above-mentioned active material composite material.

[0039] Effects of the Invention

[0040] The present invention can be used to heat-treat the active material composite material composition at a lower temperature than conventional methods, thereby obtaining an active material composite material in which the surface of active material particles is covered with a thermally cured layer containing a conductive material, a dispersant, and a cross-linking agent. Furthermore, the resulting active material composite material can be used to produce a secondary battery with excellent cycle and rate characteristics. DETAILED DESCRIPTION

[0041] Hereinafter, the present invention will be described in further detail.

[0042] The composition for forming an active material composite material of the present invention comprises an active material, a conductive material, a dispersant, a solvent and a crosslinking agent, wherein the active material is selected from at least one of metals, semi-metals, metal alloys, metal oxides, semi-metal oxides, metal phosphates, metal sulfides and metal nitrides.

[0043] As the active material, various active materials that have been conventionally used for electrodes for energy storage devices can be used. Specific examples include the following active materials.

[0044] Examples of the metal active material include Al, Sn, and Zn.

[0045] Examples of semimetal active materials include Si, Ge, and As.

[0046] Examples of the metal alloy active material include Li—Al alloys, Li—Mg alloys, Li—Al—Ni alloys, Na—Hg alloys, and Na—Zn alloys.

[0047] As the active material of metal oxide, AlO x 、SnO x , SbO x 、BiO x , PbO x 、ZnO x , CdO x 、InO x 、TiO x and GaO x (where 0 <x≦2)、V2O6、V6O 13, MnO2, LiCoO2, LiMnO2, LiMn2O4, LiMo2O4, LiV3O8, LiNiO2, Li z Ni y M 1-y O2 (where M represents at least one metal element selected from Co, Mn, Ti, Cr, V, Al, Sn, Pb, and Zn, 0.05 ≦ z ≦ 1.10, 0.5 ≦ y ≦ 1.0), ternary system active material (Li(Ni a Co b Mn c )O2 (where 0 < a < 1, 0 < b < 1, 0 < c < 1, a + b + c = 1)), tin silicate (SnSiO3), lithium bismuth oxide (Li3BiO4), lithium zinc oxide (Li2ZnO2), and lithium titanium oxide (Li4Ti5O 12 ) etc.

[0048] As active materials for half - metal oxides, SiO x , GeO x , and AsO x (where 0 < x ≦ 2) etc. can be cited.

[0049] As active materials for metal phosphides, LiFePO4 etc. can be cited.

[0050] As active materials for metal sulfides, FeS2, TiS2, MoS2, Li2S, lithium iron sulfide (Li x FeS2 (where 0 < x ≦ 3)) and lithium copper sulfide (Li x CuS (where 0 < x ≦ 3)) etc. can be cited.

[0051] As active materials for metal nitrides, Li x M y N (where M = Co, Ni, Cu, 0 ≦ x ≦ 3, 0 ≦ y ≦ 0.5, x and y are not both 0) and lithium iron nitride (Li3FeN4) etc. can be cited.

[0052] In the present invention, among these active materials, FeS2, TiS2, MoS2, LiFePO4, V2O6, V6O 13 , MnO2, LiCoO2, LiMnO2, LiMn2O4, LiMo2O4, LiV3O8, LiNiO2, Li z Ni y M 1-yO2 (where M represents at least one metal element selected from Co, Mn, Ti, Cr, V, Al, Sn, Pb, and Zn, 0.05 ≦ z ≦ 1.10, 0.5 ≦ y ≦ 1.0), Li(Ni a Co b Mn c )O2 (where 0 < a < 1, 0 < b < 1, 0 < c < 1, a + b + c = 1), Li4Ti5O 12 、Si、SiO x 、AlO x 、SnO x 、SbO x 、BiO x 、GeO x 、AsO x 、PbO x 、ZnO x 、CdO x 、InO x 、TiO x 以及GaO x (where 0 < x ≦ 2), more preferably TiO x (where 0 < x ≦ 2).

[0053] In addition, for Li(Ni a Co b Mn c )O2, it is further preferably satisfied that 1 / 3 ≦ a < 1, 0 < b ≦ 1 / 3, 0 < c ≦ 1 / 3, a + b + c = 1.

[0054] In addition, the above-mentioned Li(Ni a Co b Mn c )O2 can also be obtained as a commercial product. As such a commercial product, for example, NCM111 (manufactured by Beijing Easping Material Technology Co., Ltd., a = 1 / 3, b = 1 / 3, c = 1 / 3), NCM523 (manufactured by Beijing Easping Material Technology Co., Ltd., a = 0.5, b = 0.2, c = 0.3), NCM622 (manufactured by Beijing Easping Material Technology Co., Ltd., a = 0.6, b = 0.2, c = 0.2), NCM811 (manufactured by Beijing Easping Material Technology Co., Ltd., a = 0.8, b = 0.1, c = 0.1), etc. can be cited.

[0055] The average particle size (primary particle size) of the active material is preferably 10 nm to 15 μm, more preferably 20 nm to 8 μm. By making the active material particles smaller in average primary particle size, it is easier to increase the reaction area for the active material. The above average particle size is measured using a scanning electron microscope (SEM).

[0056] The amount of active material added varies depending on the required electrical and thermal properties, slurry viscosity, production cost, etc., but is preferably 0.1 to 80 mass %, more preferably 1 to 60 mass %, and even more preferably 1 to 50 mass % in the composition.

[0057] As the conductive material, for example, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon nanotubes (CNTs), natural graphite, artificial graphite, carbon fibers and other conductive carbons, carbon fluorides, and polyphenylene derivatives can be cited. These conductive materials can be used alone or in combination of two or more. In the present invention, from the perspective of allowing the above-mentioned conductive material to cover the surface of the active material particles, fibrous carbon is preferred, and carbon nanotubes are more preferred. In addition, the conductive material in the present invention does not use a flaky carbon-based conductive material.

[0058] CNTs are typically produced by arc discharge, chemical vapor deposition (CVD), laser ablation, and the like. The CNTs used in the present invention can be obtained by any of these methods. Furthermore, CNTs include single-layer CNTs (hereinafter also referred to as SWCNTs) obtained by rolling a single carbon film (graphene sheet) into a cylindrical shape, double-layer CNTs (hereinafter also referred to as DWCNTs) obtained by rolling two graphene sheets into concentric circles, and multilayer CNTs (hereinafter also referred to as MWCNTs) obtained by rolling multiple graphene sheets into concentric circles. In the present invention, SWCNTs, DWCNTs, and MWCNTs can be used individually or in combination.

[0059] In addition, when using the above-mentioned method to produce SWCNT, DWCNT or MWCNT, since catalyst metals such as nickel, iron, cobalt, and iridium may remain, purification may be necessary to remove these impurities. To remove impurities, acid treatment with nitric acid, sulfuric acid, etc. and ultrasonic treatment are effective. However, during acid treatment with nitric acid, sulfuric acid, etc., there is a possibility that the π-conjugated system constituting the CNT will be destroyed, thereby compromising the original properties of the CNT. Therefore, it is preferably purified and used under appropriate conditions.

[0060] Specific examples of CNTs that can be used in the present invention include super-grown CNTs (manufactured by the New Energy and Industrial Technology Development Agency, a national research and development organization), eDIPS-CNTs (manufactured by the New Energy and Industrial Technology Development Agency, a national research and development organization), SWNT series (trade name, manufactured by Meijo Nanocarbon Co., Ltd.), VGCF series (trade name, manufactured by Showa Denko K.K. [abbreviated as: KK]), FloTube series (trade name, manufactured by CNano Technology Co., Ltd.), AMC (trade name, manufactured by Ube Industries, Ltd.), NANOCYL NC7000 series (trade name, manufactured by Nanocyl SA), Baytubes (trade name, manufactured by Bayer AG), GRAPHISTRENGTH (trade name, manufactured by Arkema), MWNT7 (trade name, manufactured by Hodogaya Chemical Industry Co., Ltd.), Hyperion CNT (trade name, manufactured by Hyperion Catalysis International Co., Ltd.), TC-2010 (trade name, manufactured by Toda Industry Co., Ltd.), etc.

[0061] The amount of conductive material incorporated varies depending on the required electrical properties, thermal properties, slurry viscosity, manufacturing costs, etc., and in the case of CNTs, at least a portion thereof is optional only in isolated dispersion, but is preferably 0.0001 to 50% by mass in the composition, more preferably 0.001 to 20% by mass, and even more preferably 0.001 to 10% by mass.

[0062] As a dispersant, it is possible to appropriately select and use from well-known dispersants. In the present invention, surfactants, various polymer materials, etc. can be used. By adding a dispersant, the dispersibility and dispersion stabilization performance of the conductive material can be improved during the preparation of the composition.

[0063] The surfactants are classified into ionic surfactants and nonionic surfactants, and any surfactant can be used in the present invention. Specifically, the following surfactants can be mentioned.

[0064] Examples of the cationic surfactant include alkylamine salts, quaternary ammonium salts, alkylpyridinium salts, and alkylimidazolium salts.

[0065] Examples of the amphoteric surfactant include alkyl betaine-based surfactants and amine oxide-based surfactants.

[0066] Examples of the anionic surfactant include fatty acid salts, alkyl dicarboxylates, alkyl sulfate ester salts, polysulfate ester salts, alkylnaphthalene sulfates, alkylbenzene sulfates, alkylnaphthalene sulfate ester salts, alkyl sulfosuccinates, naphthoates, alkyl ether carboxylates, titanium acylates, alpha olefin sulfates, N-acylmethyl taurates, alkyl ether sulfates, secondary polyol ethoxysulfates, polyoxyethylene alkylphenyl ether sulfates, monoglyceride sulfates (glycerol fatty acid ester sulfates), alkyl ether phosphates, alkyl phosphates, alkylbenzenesulfonates such as dodecylbenzenesulfonic acid, aromatic sulfonic acid surfactants such as dodecylphenyl ether sulfonate, monoacid soap anionic surfactants, ether sulfate surfactants, phosphate surfactants, and carboxylic acid surfactants.

[0067] Among them, aromatic ring-containing anionic surfactants, i.e., aromatic ionic surfactants, are preferred due to their excellent dispersibility, dispersion stability, and ability to achieve high concentrations. Aromatic ionic surfactants such as alkylbenzenesulfonates and dodecylphenylethersulfonates are particularly preferred.

[0068] Examples of the nonionic surfactant include sugar ester surfactants such as sorbitan fatty acid esters and polyoxyethylene sorbitan fatty acid esters, fatty acid ester surfactants such as polyoxyethylene resin acid esters and polyoxyethylene fatty acid diethyl ester, ether surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene polypropylene glycol, and aromatic nonionic surfactants such as polyoxyalkylene octylphenyl ether, polyoxyalkylene nonylphenyl ether, polyoxyalkyldibutylphenyl ether, polyoxyalkylstyrylphenyl ether, polyoxyalkylbenzylphenyl ether, polyoxyalkyldiphenyl ether, and polyoxyalkylcumylphenyl ether. In the above, the alkyl group may be an alkyl group having 1 to 20 carbon atoms.

[0069] Among them, nonionic surfactants are preferred due to their excellent dispersibility, dispersion stability, and ability to achieve high concentrations. Polyoxyethylene phenyl ether, which is an aromatic nonionic surfactant, is particularly preferred.

[0070] On the other hand, examples of polymer materials include fluorine-based acrylic polymers, silicone-based acrylic polymers, polyoxyethylene alkyl ethers, polyoxyethylene sterol ethers, polyoxyethylene linoleic acid derivatives, polyoxyethylene-polyoxypropylene copolymers, polyoxyethylene sorbitan fatty acid esters, monoglyceride fatty acid esters, sucrose fatty acid esters, alkylolamide fatty acids, polyoxyethylene fatty acid amides, polyoxyethylene alkylamines, polyvinyl alcohol, polyethylene cellulose resins, acrylic resins, butadiene resins, styrene-acrylic copolymer resins, polyester resins, polyamide resins, and polyurethanes. The present invention also can be used as the conductive polymer of the present invention.The conductive polymer of the present invention can be alkyl amine, phosphatidyl choline, polystyrene sulfonic acid, polyacrylamide, acrylic resin emulsion, water-soluble acrylic polymer, styrene emulsion, silicone emulsion, acrylic silicone emulsion, fluororesin emulsion, EVA emulsion, vinyl acetate emulsion, vinyl chloride emulsion, carbamate resin emulsion, polyvinyl alcohol, polyvinyl pyrrolidone, polystyrene sulfonic acid ammonium salt, polystyrene sulfonic acid sodium salt and the water-soluble polymers, carboxymethyl cellulose and its salt (sodium salt, ammonium salt etc.), methyl cellulose, hydroxyethyl cellulose, amylose, macrocyclic starch (cyclic amylose) and chitosan etc..In addition, conductive polymers and derivatives thereof such as polythiophene, polyethylene dioxythiophene, polyisobenzothiophene, polyaniline, polypyrrole and polyacetylene can also be used.In the present invention, the ethylene polymer with oxazoline group in side chain of triarylamine series highly branched polymer, International Publication No. 2015 / 029949 record is suitable.

[0071] Specific examples of the triarylamine-based hyperbranched polymer include those obtained by polycondensing triarylamines represented by the following formulas (1) and (2) with aldehydes and / or ketones under acidic conditions.

[0072]

[0073] In the above formulas (1) and (2), Ar 1 ~Ar 3 Each independently represents any divalent organic group represented by formulae (3) to (7), and is particularly preferably a substituted or unsubstituted phenylene group represented by formula (3).

[0074]

[0075] In the formula, R 5 ~R 38 Each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms which may have a branched structure, an alkoxy group having 1 to 5 carbon atoms which may have a branched structure, a carboxyl group, a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, or a salt thereof.

[0076] In addition, in formulas (1) and (2), Z 1 and Z2 Each independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms which may have a branched structure, or any monovalent organic group represented by formula (8) to (11) (wherein Z 1 and Z 2 are not the above alkyl groups), as Z 1 and Z 2 Each of them is independently preferably a hydrogen atom, a 2- or 3-thienyl group, or a group represented by formula (8), and Z is more preferably 1 and Z 2 Any one of them is a hydrogen atom and the other is a hydrogen atom, a 2- or 3-thienyl group, a group represented by formula (8) (especially R 41 is phenyl or R 41 is a methoxy group).

[0077] In addition, in R 41 In the case of a phenyl group, in the acidic group introduction method described later, there is a case where the acidic group is introduced after the polymer is produced, and the acidic group is introduced into the phenyl group.

[0078] Examples of the alkyl group having 1 to 5 carbon atoms and which may have a branched structure include the same alkyl groups as exemplified above.

[0079]

[0080] In these formulas, R 39 ~R 62 Each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms which may have a branched structure, a halogenated alkyl group having 1 to 5 carbon atoms which may have a branched structure, a phenyl group, OR 63 、COR 63 NR 63 R 64 、COOR 65 (In these formulas, R 63 and R 64 Each independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms which may have a branched structure, a halogenated alkyl group having 1 to 5 carbon atoms which may have a branched structure, or a phenyl group, and R 65 represents an alkyl group having 1 to 5 carbon atoms which may have a branched structure, a halogenated alkyl group having 1 to 5 carbon atoms which may have a branched structure, or a phenyl group), a carboxyl group, a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, or a salt thereof.

[0081] In the above formulas (2) to (7), R 1 ~R 38 Each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms which may have a branched structure, an alkoxy group having 1 to 5 carbon atoms which may have a branched structure, a carboxyl group, a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, or a salt thereof.

[0082] Here, examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0083] Examples of the alkyl group having 1 to 5 carbon atoms which may have a branched structure include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, and n-pentyl.

[0084] Examples of the alkoxy group having 1 to 5 carbon atoms and which may have a branched structure include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, and n-pentoxy.

[0085] Examples of salts of carboxyl groups, sulfonic acid groups, phosphoric acid groups, and phosphonic acid groups include: salts of alkali metals such as sodium and potassium; salts of Group II metals such as magnesium and calcium; ammonium salts; salts of aliphatic amines such as propylamine, dimethylamine, triethylamine, and ethylenediamine; salts of alicyclic amines such as imidazoline, piperazine, and morpholine; salts of aromatic amines such as aniline and diphenylamine; and pyridinium salts.

[0086] In the above formulas (8) to (11), R 39 ~R 62 Each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms which may have a branched structure, a halogenated alkyl group having 1 to 5 carbon atoms which may have a branched structure, or a phenyl group, 63 、COR 63 NR 63 R 64 、COOR 65 (In these formulas, R 63 and R 64 Each independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms which may have a branched structure, a halogenated alkyl group having 1 to 5 carbon atoms which may have a branched structure, or a phenyl group, and R 65 represents an alkyl group having 1 to 5 carbon atoms which may have a branched structure, a halogenated alkyl group having 1 to 5 carbon atoms which may have a branched structure, or a phenyl group), or a carboxyl group, a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, or a salt thereof.

[0087] Here, examples of the halogenated alkyl group having 1 to 5 carbon atoms which may have a branched structure include a difluoromethyl group, a trifluoromethyl group, a bromodifluoromethyl group, a 2-chloroethyl group, a 2-bromoethyl group, a 1,1-difluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, a 2-chloro-1,1,2-trifluoroethyl group, a pentafluoroethyl group, a 3-bromopropyl group, a 2,2,3,3-tetrafluoropropyl group, a 1,1,2,3,3,3-hexafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropane-2-yl group, a 3-bromo-2-methylpropyl group, a 4-bromobutyl group, and a perfluoropentyl group.

[0088] Examples of the halogen atom and the alkyl group having 1 to 5 carbon atoms which may have a branched structure include the same groups as exemplified in the above formulae (2) to (7).

[0089] Examples of the aldehyde compound used in the production of the highly branched polymer include: saturated aliphatic aldehydes such as formaldehyde, paraformaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde, valeraldehyde, hexanal, 2-methylbutyraldehyde, hexanal, undecanal, 7-methoxy-3,7-dimethyloctylaldehyde, cyclohexanecarboxaldehyde, 3-methyl-2-butyraldehyde, glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, and adipaldehyde; unsaturated aliphatic aldehydes such as acrolein and methacrolein; and heteroaryl aldehydes such as furfural, pyridinecarboxaldehyde, and thiophenealdehyde. Cyclic aldehydes; benzaldehyde, tolualdehyde, trifluoromethylbenzaldehyde, phenylbenzaldehyde, o-hydroxybenzaldehyde, p-anisaldehyde, acetoxybenzaldehyde, terephthalaldehyde, acetylbenzaldehyde, formylbenzoic acid, methyl formylbenzoate, aminobenzaldehyde, N,N-dimethylaminobenzaldehyde, N,N-diphenylaminobenzaldehyde, naphthylaldehyde, anthracenylaldehyde, phenanthrenylaldehyde and other aromatic aldehydes, phenylacetaldehyde, 3-phenylpropanal and other aralkylaldehydes, among which aromatic aldehydes are preferably used.

[0090] Ketone compounds used for producing the highly branched polymers are alkyl aryl ketones and diaryl ketones, for example, acetophenone, propiophenone, diphenyl ketone, phenylnaphthyl ketone, dinaphthyl ketone, phenyltolyl ketone, and xylyl ketone.

[0091] As shown in the following Scheme 1, the highly branched polymer used in the present invention can be obtained by polycondensing a triarylamine compound such as that represented by the following formula (A) that can impart the above-mentioned triarylamine skeleton with an aldehyde compound and / or a ketone compound such as that represented by the following formula (B) in the presence of an acid catalyst.

[0092] When a bifunctional compound (C) such as phthalaldehyde, for example, is used as the aldehyde compound, not only the reaction shown in Scheme 1 but also the reaction shown in Scheme 2 below may occur, and a highly branched polymer having a cross-linked structure in which both functional groups contribute to the condensation reaction may be obtained.

[0093] Solution 1

[0094]

[0095] In the formula, Ar 1 ~Ar 3 and Z 1 ~Z 2 Means the same as above.

[0096] Option 2

[0097]

[0098] In the formula, Ar 1 ~Ar 3 and R 1 ~R 4 Means the same as above.

[0099] In the polycondensation reaction, the aldehyde compound and / or ketone compound may be used in a ratio of 0.1 to 10 equivalents relative to 1 equivalent of the aryl group of the triarylamine compound.

[0100] Examples of the acid catalyst include mineral acids such as sulfuric acid, phosphoric acid, and perchloric acid; organic sulfonic acids such as p-toluenesulfonic acid and p-toluenesulfonic acid monohydrate; and carboxylic acids such as formic acid and oxalic acid.

[0101] The amount of the acid catalyst used can be selected in various ways depending on the type, but is generally 0.001 to 10,000 parts by mass, preferably 0.01 to 1,000 parts by mass, and more preferably 0.1 to 100 parts by mass, relative to 100 parts by mass of the triarylamines.

[0102] Even in the absence of a solvent, the above-mentioned condensation reaction can be carried out, but a solvent is usually used for the above-mentioned condensation reaction. As a solvent, all solvents can be used as long as they do not damage the reaction, for example, cyclic ethers such as tetrahydrofuran and 1,4-dioxane; amides such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP); ketones such as methyl isobutyl ketone and cyclohexanone; halogenated hydrocarbons such as dichloromethane, chloroform, 1,2-dichloroethane, and chlorobenzene; aromatic hydrocarbons such as benzene, toluene, and xylene. Cyclic ethers are particularly preferred. These solvents can be used alone or in combination of two or more.

[0103] Furthermore, if the acid catalyst used is a liquid acid catalyst such as formic acid, the acid catalyst may also function as a solvent.

[0104] The reaction temperature during condensation is usually 40 to 200° C. The reaction time can be selected in various ways depending on the reaction temperature, but is usually about 30 minutes to 50 hours.

[0105] The weight average molecular weight Mw of the polymer obtained as described above is usually 1,000 to 2,000,000, and preferably 2,000 to 1,000,000.

[0106] When introducing an acidic group into a hyperbranched polymer, the acidic group can be introduced by a method of previously introducing the acidic group into the aromatic ring of the above-mentioned triarylamine compound, aldehyde compound, or ketone compound as a polymer raw material and using the polymer raw material to produce the hyperbranched polymer. Alternatively, the acidic group can be introduced by treating the obtained hyperbranched polymer with a reagent capable of introducing the acidic group into the aromatic ring. However, considering the simplicity of production, the latter method is preferably used.

[0107] In the latter method, the method for introducing the acidic group into the aromatic ring is not particularly limited and may be appropriately selected from various conventionally known methods depending on the type of the acidic group.

[0108] For example, when introducing a sulfonic acid group, a method of sulfonation using excess sulfuric acid can be employed.

[0109] The average molecular weight of the highly branched polymer is not particularly limited, but is preferably 1,000 to 2,000,000, more preferably 2,000 to 1,000,000.

[0110] In addition, the weight average molecular weight in the present invention is a value measured based on gel permeation chromatography (polystyrene conversion).

[0111] Specific examples of the highly branched polymer include those represented by the following formulae, but the present invention is not limited to these highly branched polymers.

[0112]

[0113] On the other hand, as ethylene polymers having an oxazoline group in the side chain (hereinafter referred to as oxazoline polymers), there can be cited polymers obtained by free radical polymerization of an oxazoline monomer having a polymerizable carbon-carbon double bond group at the 2-position as shown in the following formula (12), which has a repeating unit bonded to the polymer main chain or a spacer at the 2-position of the oxazoline ring.

[0114]

[0115] The above X represents a group containing a polymerizable carbon-carbon double bond, and R 100 ~R 103 Each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms which may have a branched structure, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms.

[0116] The group containing a polymerizable carbon-carbon double bond as an oxazoline monomer is not particularly limited as long as it contains a polymerizable carbon-carbon double bond. Preferably, it is a chain hydrocarbon group containing a polymerizable carbon-carbon double bond, for example, preferably an alkenyl group having 2 to 8 carbon atoms such as a vinyl group, an allyl group, and an isopropenyl group.

[0117] Examples of the halogen atom and the alkyl group having 1 to 5 carbon atoms which may have a branched structure include the same ones as mentioned above.

[0118] Specific examples of the aryl group having 6 to 20 carbon atoms include phenyl, xylyl, tolyl, biphenylyl, and naphthyl.

[0119] Specific examples of the aralkyl group having 7 to 20 carbon atoms include benzyl, phenylethyl, and phenylcyclohexyl.

[0120] Specific examples of the oxazoline monomer having a polymerizable carbon-carbon double bond-containing group at the 2-position represented by formula (12) include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-4-ethyl-2-oxazoline, 2-vinyl-4-propyl-2-oxazoline, 2-vinyl-4-butyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-vinyl-5-ethyl-2-oxazoline, 2-vinyl-5-propyl-2-oxazoline, 2-vinyl-5-butyl-2-oxazoline, oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-4-ethyl-2-oxazoline, 2-isopropenyl-4-propyl-2-oxazoline, 2-isopropenyl-4-butyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2-isopropenyl-5-propyl-2-oxazoline, 2-isopropenyl-5-butyl-2-oxazoline, and 2-isopropenyl-2-oxazoline are preferred; from the viewpoint of easy availability, 2-isopropenyl-2-oxazoline is preferred.

[0121] Furthermore, when an aqueous solvent is used as a solvent described later in the preparation of the active material composite material-forming composition, the oxazoline polymer is preferably water-soluble.

[0122] Such a water-soluble oxazoline polymer can be a homopolymer of the oxazoline monomer represented by the above formula (12). In order to further improve the solubility in water, it is preferably a polymer obtained by free radical polymerization of the above oxazoline monomer and at least two monomers of a (meth)acrylate monomer having a hydrophilic functional group.

[0123] Specific examples of (meth)acrylic monomers having a hydrophilic functional group include (meth)acrylic acid, 2-hydroxyethyl acrylate, methoxypolyethylene glycol acrylate, monoesters of acrylic acid and polyethylene glycol, 2-aminoethyl acrylate and its salts, 2-hydroxyethyl methacrylate, methoxypolyethylene glycol methacrylate, monoesters of methacrylic acid and polyethylene glycol, 2-aminoethyl methacrylate and its salts, sodium (meth)acrylate, (meth)acrylamide, (meth)acrylonitrile, (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, N-(2-hydroxyethyl) (meth)acrylamide, and sodium styrenesulfonate. These monomers can be used alone or in combination of two or more. Among them, methoxypolyethylene glycol (meth)acrylate and monoesters of (meth)acrylic acid and polyethylene glycol are suitable.

[0124] Furthermore, other monomers other than the above-mentioned oxazoline monomer and the (meth)acrylic monomer having a hydrophilic functional group may be used in combination within a range that does not adversely affect the dispersibility of the oxazoline polymer in the conductive material.

[0125] Specific examples of other monomers include (meth)acrylate monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octadecyl (meth)acrylate, perfluoroethyl (meth)acrylate, and phenyl (meth)acrylate; α-olefin monomers such as ethylene, propylene, butene, and pentene; halogenated olefin monomers such as vinyl chloride, vinylidene chloride, and vinyl fluoride; styrene monomers such as styrene and α-methylstyrene; carboxylic acid vinyl ester monomers such as vinyl acetate and vinyl propionate; and vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether. These monomers may be used alone or in combination of two or more.

[0126] In the monomeric component of the manufacturing that is used for above-mentioned oxazoline polymer, from the such viewpoint of the dispersion property of the oxazoline polymer that further improves that obtains at conductive material, the content of oxazoline monomer is preferably more than the 10 quality %, more preferably more than the 20 quality %, further be preferably more than the 30 quality %.In addition, the upper limit value of the content of the oxazoline monomer of monomeric component is 100 quality %, in this case, can obtain the homopolymer of oxazoline monomer.

[0127] On the other hand, from the viewpoint of further improving the water solubility of the obtained oxazoline polymer, the content of the (meth)acrylic monomer having a hydrophilic functional group in the monomer component is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more.

[0128] In addition, as described above, within the range that does not affect the dispersion performance of the obtained oxazoline polymer for the conductive material, although it cannot be generally determined because it varies depending on its type, the content of other monomers in the monomer component can be appropriately set within the range of 5 to 95 mass %, preferably 10 to 90 mass %.

[0129] The average molecular weight of the oxazoline polymer is not particularly limited, but the weight average molecular weight is preferably 1,000 to 2,000,000, and more preferably 2,000 to 1,000,000.

[0130] The oxazoline polymer that can be used in the present invention can be synthesized by subjecting the above-mentioned monomers to conventional free radical polymerization, but can also be obtained as a commercially available product. Examples of such commercially available products include: EPOCROS WS-300 (manufactured by Nippon Shokubai, solid content concentration 10% by mass, aqueous solution); EPOCROS WS-700 (manufactured by Nippon Shokubai, solid content concentration 25% by mass, aqueous solution); EPOCROS WS-500 (manufactured by Nippon Shokubai, solid content concentration 39% by mass, water / 1-methoxy-2-propanol solution); poly(2-ethyl-2-oxazoline) (Aldrich); poly(2-ethyl-2-oxazoline) (Alfa Aesar); poly(2-ethyl-2-oxazoline) (VWR International, LLC), etc.

[0131] In addition, when the solution is a commercial product, it may be used as it is or after replacing it with the target solvent.

[0132] In the present invention, the above-mentioned dispersants may be used alone or in combination of two or more.

[0133] The amount of the dispersant incorporated is not particularly limited as long as it is a concentration sufficient to disperse the conductive material in the solvent, but is preferably 0.001 to 30% by mass, more preferably 0.002 to 20% by mass, of the composition. Furthermore, the mixing ratio of the conductive material to the dispersant is preferably in the range of 1000:1 to 1:100 by mass.

[0134] As the crosslinking agent, a crosslinking agent that causes a crosslinking reaction with the above-mentioned dispersant or a crosslinking agent that performs self-crosslinking can be used. In addition, these crosslinking agents are preferably dissolved in the solvent used.

[0135] Examples of the cross-linking agent that causes a cross-linking reaction with the dispersant include the following triarylamine-based highly branched polymers and oxazoline polymers.

[0136] As cross-linking agents for triarylamine-based highly branched polymers, for example, melamine-based, substituted urea-based, or polymer-based cross-linking agents thereof can be cited, and these cross-linking agents can be used alone or in combination of two or more. In addition, cross-linking agents having at least two cross-linking-forming substituents are preferred, and examples thereof include CYMEL (registered trademark), methoxymethylated glycoluril, butoxymethylated glycoluril, hydroxymethylated glycoluril, methoxymethylated melamine, butoxymethylated melamine, hydroxymethylated melamine, methoxymethylated benzoguanamine, butoxymethylated benzoguanamine, hydroxymethylated benzoguanamine, methoxymethylated urea, butoxymethylated urea, hydroxymethylated urea, methoxymethylated thiourea, methoxymethylated thiourea, hydroxymethylated thiourea, and the like, as well as condensation products of these compounds.

[0137] As the cross-linking agent of oxazoline polymer, for example, as long as there are two or more carboxyl, hydroxyl, thiol group, amino, sulfinic acid group, epoxy group(ing) etc. and the compound of the reactive functional group with oxazoline group just do not have particular limitation, be preferably the compound with two or more carboxyl.In addition, also can use the compound such as sodium salt, potassium salt, lithium salt, ammonium salt etc. with carboxylic acid etc. when film forms heating, the existence of acid catalyst can produce above-mentioned functional group and cause the functional group of cross-linking reaction as cross-linking agent.

[0138] Specific examples of compounds that cause a cross-linking reaction with an oxazoline group include synthetic polymers such as polyacrylic acid and its copolymers, which exhibit cross-linking reactivity in the presence of an acid catalyst, metal salts of natural polymers such as carboxymethyl cellulose and alginic acid, and ammonium salts of the above-mentioned synthetic polymers and natural polymers that exhibit cross-linking reactivity by heating. Particularly preferred are sodium polyacrylate, lithium polyacrylate, polyacrylic acid amine, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, carboxymethyl cellulose amine, and the like, which exhibit cross-linking reactivity in the presence of an acid catalyst and under heating conditions.

[0139] Such compounds that cause cross-linking reactions with oxazoline groups can also be obtained as commercial products. Examples of such commercial products include sodium polyacrylate (manufactured by Wako Pure Chemical Industries, Ltd., with a degree of polymerization of 2700 to 7500), sodium carboxymethylcellulose (manufactured by Wako Pure Chemical Industries, Ltd.), sodium alginate (manufactured by Kanto Chemical Co., Ltd., Cica (Deer) first-class product), ARONA-30 (polyacrylic acid amine, manufactured by Toagosei Co., Ltd., solid content concentration 32% by mass, aqueous solution), DN-800H (carboxymethylcellulose amine, manufactured by Daicel FineChem Co., Ltd.), and alginate amine (manufactured by Kimica Co., Ltd.).

[0140] Examples of cross-linking agents that self-crosslink include compounds having cross-linkable functional groups that react with each other within the same molecule (such as an aldehyde group, epoxy group, vinyl group, isocyanate group, alkoxy group relative to a hydroxyl group, an aldehyde group, amino group, isocyanate group, epoxy group relative to a carboxyl group, and an isocyanate group, aldehyde group relative to an amino group); compounds having a hydroxyl group (dehydration condensation), a mercapto group (disulfide bond), an ester group (Claisen condensation), a silanol group (dehydration condensation), a vinyl group, an acrylic group, etc. that react with each other through the same cross-linkable functional group; and the like.

[0141] Specific examples of self-crosslinking crosslinking agents include multifunctional acrylates that exhibit crosslinking reactivity in the presence of an acid catalyst, tetraalkoxysilanes, block copolymers of monomers having blocked isocyanate groups and monomers having at least one of hydroxyl groups, carboxylic acid groups, and amino groups.

[0142] Such self-crosslinking crosslinking agents are commercially available. Examples of such commercially available products include, among the polyfunctional acrylates, A-9300 (ethoxylated isocyanurate triacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.), A-GLY-9E (polyoxyethylene ether glycerol triacrylate (EO9 mol), manufactured by Shin-Nakamura Chemical Co., Ltd.), and A-TMMT (pentaerythritol tetraacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.); among the tetraalkoxysilanes, tetramethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) and tetraethoxysilane (manufactured by Toyoko Chemical Co., Ltd.); and among the polymers having blocked isocyanate groups, ELASTRON series E-37, H-3, H38, BAP, NEW BAP-15, C-52, F-29, W-11P, MF-9, and MF-25K (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.).

[0143] The amount of crosslinking agent incorporated varies depending on the target thickness of the active material layer, the required mechanical properties, electrical properties, thermal properties, etc., but is preferably 0.001 to 80% by mass, more preferably 0.01 to 50% by mass, and even more preferably 0.05 to 40% by mass relative to the total amount of the crosslinking agent and the dispersant. These crosslinking agents may also cause a crosslinking reaction based on self-condensation, but they are substances that cause a crosslinking reaction with the dispersant. When a crosslinking substituent is present in the dispersant, the crosslinking reaction is promoted by the crosslinking substituent.

[0144] In the present invention, as a catalyst for promoting the cross-linking reaction, an acidic compound such as p-toluenesulfonic acid, trifluoromethanesulfonic acid, pyridinium p-toluenesulfonic acid, salicylic acid, sulfosalicylic acid, citric acid, benzoic acid, hydroxybenzoic acid, or naphthalenecarboxylic acid and / or a thermal acid generator such as 2,4,4,6-tetrabromocyclohexadienonone, benzoin p-toluenesulfonate, 2-nitrobenzyl p-toluenesulfonate, or an organic alkyl sulfonate may be added.

[0145] The amount of these catalysts added is preferably 0.0001 to 20% by mass, more preferably 0.0005 to 10% by mass, and even more preferably 0.001 to 3% by mass, relative to the total amount of the catalyst and the dispersant.

[0146] The solvent (dispersion medium) that can be used when preparing the active material composite material forming composition is not particularly limited as long as it is a solvent conventionally used for preparing a dispersion containing a conductive material such as CNT, and examples thereof include: water; ethers such as tetrahydrofuran (THF), diethyl ether, and 1,2-dimethoxyethane (DME); halogenated hydrocarbons such as dichloromethane, chloroform, and 1,2-dichloroethane; N,N-dimethylformamide (DMF), N, Organic solvents include amides such as N-dimethylacetamide (DMAc) and N-methyl-2-pyrrolidone (NMP); ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, isopropyl alcohol, and n-propyl alcohol; aliphatic hydrocarbons such as n-heptane, n-hexane, and cyclohexane; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; glycol ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and propylene glycol monomethyl ether; and glycols such as ethylene glycol and propylene glycol. These solvents can be used alone or as a mixture of two or more.

[0147] In particular, when using CNTs as the conductive material, from the viewpoint of increasing the ratio of their isolated dispersion, the solvent is preferably water, NMP, DMF, THF, methanol, isopropyl alcohol, or cyclohexanone. These solvents can be used alone or as a mixture of two or more.

[0148] In the production of the active material composite material, when the spray drying method described below is used, since the solvent needs to be rapidly volatilized, alcohols such as methanol and isopropyl alcohol or water are preferred; water is more preferred from the perspective of safety during production.

[0149] Furthermore, the active material composite material-forming composition may contain a matrix polymer as needed.

[0150] Specific examples of the matrix polymer include: fluorine-based resins such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer [P(VDF-HFP)], and vinylidene fluoride-chlorotrifluorinated ethylene copolymer [P(VDF-CTFE)]; polyolefin resins such as polyvinyl pyrrolidone, ethylene-propylene-diene terpolymer, PE (polyethylene), PP (polypropylene), EVA (ethylene-vinyl acetate copolymer), and EEA (ethylene-ethyl acrylate copolymer); and polystyrene such as PS (polystyrene), HIPS (high-strength polystyrene), AS (acrylonitrile-styrene copolymer), ABS (acrylonitrile-butadiene-styrene copolymer), MS (methyl methacrylate-styrene copolymer), and styrene-butadiene rubber. Styrene resins; polycarbonate resins; vinyl chloride resins; polyamide resins; polyimide resins; (meth)acrylic resins such as polyacrylic acid, polyacrylamide, sodium polyacrylate, and PMMA (polymethyl methacrylate); PET (polyethylene terephthalate), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, PLA (polylactic acid), poly-3-hydroxybutyric acid, polycaprolactone, and polybutylene succinate Polyester resins such as polyethylene succinate / adipate; polyphenylene ether resins; modified polyphenylene ether resins; polyacetal resins; polysulfone resins; polyphenylene sulfide resins; polyvinyl alcohol resins; polyglycolic acid; modified starch; cellulose acetate, carboxymethyl cellulose, cellulose triacetate; chitin, chitosan; thermoplastic resins such as lignin; polyaniline and its semi-acid derivatives, namely emeraldine base; polythiophene; polypyrrole; polystyrene vinylene; polyphenylene; polyacetylene; and conductive polymers such as polyacetylene. Other examples include epoxy resins; urethane acrylates; phenolic resins; melamine resins; urea resins; alkyd resins and other thermosetting resins, as well as photocurable resins. In the composition for forming the active material composite material of the present invention, since it is appropriate to use water as a solvent, even as a matrix polymer, a water-soluble polymer is preferably used, for example, polyacrylic acid, polyacrylic amine, sodium polyacrylate, sodium carboxymethyl cellulose, water-soluble cellulose ether, sodium alginate, polyvinyl alcohol, polystyrene sulfonic acid, polyethylene glycol, etc.; particularly suitable are polyacrylic acid, polyacrylic amine, sodium polyacrylate, sodium carboxymethyl cellulose, etc.

[0151] The matrix polymer can also be obtained as a commercial product. Examples of such commercial products include ARON A-10H (polyacrylic acid, manufactured by Toagosei Co., Ltd., solid content concentration 26% by mass, aqueous solution), ARON A-30 (polyacrylamide, manufactured by Toagosei Co., Ltd., solid content concentration 32% by mass, aqueous solution), sodium polyacrylate (manufactured by Wako Pure Chemical Industries, Ltd., polymerization degree 2700 to 7500), sodium carboxymethylcellulose (manufactured by Wako Pure Chemical Industries, Ltd.), sodium alginate (manufactured by Kanto Chemical Co., Ltd., Cica first grade), METOLOSE SH series (hydroxypropyl methylcellulose, manufactured by Shin-Etsu Chemical Co., Ltd.), METOLOSE SE series (hydroxyethyl methylcellulose, manufactured by Shin-Etsu Chemical Co., Ltd.), JC-25 (completely saponified polyvinyl alcohol, manufactured by Japan VAM & POVAL Co., Ltd.), and JM-17 (intermediately saponified polyvinyl alcohol, manufactured by Japan VAM & POVAL Co., Ltd.). VAM & POVAL CO., LTD.), JP-03 (partially saponified polyvinyl alcohol, manufactured by JAPAN VAM & POVAL CO., LTD.), polystyrene sulfonic acid (manufactured by Aldrich, solid content concentration 18% by mass, aqueous solution), etc.

[0152] The amount of the matrix polymer to be added is not particularly limited, but is preferably 0.0001 to 99% by mass, more preferably 0.001 to 90% by mass, in the composition.

[0153] There are no particular limitations on the method for producing the active material composite material composition. It is sufficient to mix the components in a specified ratio. However, in the present invention, it is preferred to prepare an active material dispersion containing an active material and a solvent, and a conductive material dispersion containing a conductive material, a dispersant, a cross-linking agent, and a solvent, and then mix the two dispersions to produce the composition. This allows for the production of an active material composite material in which the surface of the active material particles is covered with dispersed conductive material. Furthermore, when using the matrix polymer, it is sufficient to incorporate it into the conductive material dispersion.

[0154] At this time, when the active material or the conductive material is not made into a dispersion but mixed in a powdered manner, when the active material and the conductive material are dry-mixed, or when a dispersion medium is added to the dry mixture to prepare a dispersion, etc., it is possible to obtain a non-uniform active material composite material in which the microparticles or the conductivity imparting agent are not dispersed and have a conductivity imparting agent attached to a microparticle aggregate, or it is possible to obtain an active material composite material having a structure in which the conductivity imparting agent aggregate and the microparticle aggregate are respectively localized (localized). Therefore, in order to obtain the active material composite material of the present invention, it is preferred to prepare a dispersion of the active material or the conductive material respectively and mix the dispersions.

[0155] There is no particular limitation on the method for preparing the active material dispersion, as long as the active material is placed in a predetermined solvent and dispersed. In addition, if necessary, a dispersion treatment described below may be performed to efficiently disperse the active material in the solvent.

[0156] On the other hand, the method for preparing the conductive material dispersion is not particularly limited, and the conductive material such as CNTs, a dispersant, a crosslinking agent, a solvent (dispersion medium) as needed, and a matrix polymer may be mixed in any order.

[0157] At this time, the mixture is preferably subjected to a dispersion treatment, which can further increase the dispersion ratio of the conductive material such as CNT. Examples of the dispersion treatment include wet treatment using a ball mill, a bead mill, a jet mill, etc., as a mechanical treatment, and ultrasonic treatment using a bathtub-type or probe-type sonicator. Wet treatment or ultrasonic treatment using a jet mill is particularly suitable.

[0158] The time for the dispersion treatment is arbitrary, but is preferably about 1 minute to 10 hours, and more preferably about 5 minutes to 5 hours. At this time, a heat treatment may be performed as needed.

[0159] In addition, the crosslinking agent and the matrix polymer may be prepared by preliminarily mixing a conductive substance, a dispersant, and a solvent to disperse the conductive substance in the solvent, and then adding the crosslinking agent and the matrix polymer to the resulting mixture.

[0160] The active material composite material of the present invention can be produced by drying the above-mentioned active material composite material forming composition and then heat-treating it at a predetermined temperature without carbonizing it. At this time, for the obtained active material composite material, the covering layer containing the conductive material, dispersant and cross-linking agent is heat-cured by heat treatment to obtain an active material composite material having a heat-cured layer on the surface of the active material particles, wherein the heat-cured layer contains the conductive material, dispersant and cross-linking agent. As described later, compared with the case of implementing a conventional carbonization process that requires heat treatment at 500°C or above, the above-mentioned heat treatment of the present invention can be carried out at a low temperature, and an active material composite material with excellent characteristics can be more easily obtained.

[0161] As a drying method for the active material composite material composition, a well-known drying method can be used, without particular limitation. For example, in addition to natural drying, heating and drying can be carried out in the atmosphere, in an inert gas such as nitrogen, or in a vacuum using a heating device such as a hot plate or an oven. In the present invention, from the viewpoint of obtaining miniaturized spherical particles, a spray drying method can be suitably used.

[0162] Drying conditions can be appropriately set depending on the composition and amount of the target composition, the equipment used, etc., and are not particularly limited. For example, when drying in the air using a heating device such as a hot plate or an oven, drying at 120 to 250°C for 1 minute to 2 hours is preferred. The spray drying method is described in detail below.

[0163] The spray drying method is a method of making a liquid into a mist and drying it in a short time with hot air to obtain spherical particles. In the spray drying method, a commercially available spray dryer can be used, and any of the nozzle type and disk type (rotary atomizer type) can be used; in the present invention, the fluid spray type (fluid nozzle spray type) spray drying method is particularly suitable. The fluid spray drying method is a method of making a fluid into a fine mist by spraying compressed air and drying it with warm air. Compared with mechanical granulation drying methods such as the rotary atomizer type, it can obtain fine secondary particles. Depending on the number of spray nozzles, there are two-fluid type, four-fluid type and other methods; in the present invention, any method can be used. According to the structure of the spray drying device, the spray drying conditions (primary particle concentration, organic matter concentration, dispersion flow rate, drying gas flow rate, drying temperature, etc.) of the particle dispersion of the spray drying method are appropriately set so that the average particle size of the granulated particles becomes within the specified range.

[0164] When spray drying is used for granulation, the solid content of the slurry is preferably in the range of 1 to 50% by mass. Considering production efficiency, a slurry with a high solid content is preferred. Considering the sufficient and uniform dispersion of the active material particles and the conductive carbon, the range of 1 to 20% by mass is more preferred.

[0165] As the above-mentioned spray dryer, for example, as a device using a two-fluid nozzle, the spray dryer "Pulvis Mini Spray GB210-A" manufactured by Yamato Science Co., Ltd., the spray dryers "RJ-10", "RJ-25", "RJ-50", and "TJ-100" manufactured by Okawara Chemical Machinery Co., Ltd. can be used; as a device using a four-fluid nozzle, the spray dryers "MDL-050B", "MDL-050BM", "MDL-015CM-H", and "MDL-015MGC" manufactured by Fujisaki Electric Co., Ltd. can be used.

[0166] For heat treatment, there is no particular limitation as long as the heating is carried out in the atmosphere, in an inert gas such as nitrogen, or in a vacuum using a well-known heating device. In the present invention, for example, heating devices such as a dryer, a vacuum dryer, an oven, a tubular furnace, and a muffle furnace can be used. In the above-mentioned heat treatment, the treatment temperature and treatment time are the conditions required for thermally curing the conductive material, dispersant, and cross-linking agent dispersed on the surface of the particles of the active material, but can be appropriately set according to the components and the amount contained in the composition. For example, when a vacuum dryer or an oven is used, the treatment temperature can be set to a temperature that does not carbonize the composition, and can be preferably set to 60 to 500°C, more preferably to 120 to 300°C, and the treatment time can be preferably set to 1 minute to 24 hours, more preferably to 5 minutes to 2 hours. In addition, when a vacuum dryer is used, there is no particular limitation on the air pressure, as long as it is reduced to about 0.1 to 20 kPa. In addition, when the same device as the drying device is used as the heating device, the above-mentioned heat treatment can be carried out in conjunction with the above-mentioned drying integration.

[0167] From the viewpoint of dispersibility and filling properties of the electrode slurry, the average particle size of the active material composite material thus obtained is preferably 0.1 to 20 μm, more preferably 1 to 10 μm. The above average particle size is a value measured using a scanning electron microscope.

[0168] As described above, the active material composite material obtained using the active material composite material-forming composition has a thermally cured layer on the surface of the active material particles, obtained by thermally curing a coating layer containing a conductive material, a dispersant, and a crosslinking agent.

[0169] At this time, the surface of the particles of the active material is covered with a conductive material dispersed by a dispersant. If the conductive material exists in an aggregated state, a deviation in resistance may occur in the composite material, which may in some cases cause a decrease in the conductivity of the composite material as a whole. On the other hand, if the conductive material exists in a dispersed state in the composite material and covers the surface of the particles of the active material, a deviation in resistance will not occur in the composite material, and there will be no adverse effect such as a decrease in conductivity. The so-called dispersion here refers to the state in which the carbon nanotubes in the carbon nanotube assembly are scattered one by one, in a state in which several are gathered and formed into a bundle, or in a state in which bundles ranging from one to various thicknesses are mixed, as long as the conductive material is evenly distributed in the composite material, it can be expressed as dispersion. In addition, the particle surface does not need to be completely covered, as long as it is covered to the extent that a conductive path can be formed between the particles. For example, it can be covered to the extent that it is covered with a conductivity-imparting agent in a mesh shape.

[0170] The active material composite material produced using the manufacturing method of the present invention has a heat-cured layer on the surface of the active material particles, where the conductive material and dispersant are uniformly dispersed. This layer can significantly improve conductivity. Furthermore, the uniform dispersion of the conductive material allows for improved performance without the need for conventional carbonization treatment, thus simplifying the manufacturing process.

[0171] The present invention also provides an electrode-forming composition using the active material composite material. The electrode-forming composition can be used for both positive and negative electrodes by selecting the type of active material, and comprises the active material composite material, a conductive additive, and a binder.

[0172] Examples of the conductive additive include carbon materials such as graphite, carbon black, acetylene black, vapor grown carbon fibers (VGCF), carbon nanotubes, carbon nanohorns, and graphene, and conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, and polyacene. These conductive additives may be used alone or as a mixture of two or more.

[0173] The amount of the conductive additive is not particularly limited, but is preferably 1 to 20 parts by mass, more preferably 2 to 12 parts by mass, relative to 100 parts by mass of the active material composite material. By adjusting the amount of the conductive additive within the above range, good conductivity can be achieved.

[0174] As the above-mentioned adhesive, it can be appropriately selected from well-known materials for use without particular limitation; as the adhesive that can be used in the present invention, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer (P(VDF-HFP)), vinylidene fluoride-chlorinated trifluoroethylene copolymer (P(VDF-CTFE)), polyvinyl alcohol, polyimide, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyaniline, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene and polypropylene etc. can be cited. These adhesives can be used alone or in combination of two or more.

[0175] The amount of the binder is not particularly limited, but is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, relative to 100 parts by mass of the active material composite material. By adjusting the binder amount within this range, good adhesion to the current collector substrate can be achieved without reducing capacity.

[0176] The adhesive can be dissolved in a solvent for use as needed. In this case, examples of the solvent include N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, tetrahydrofuran, dioxolane, cyclopentane, dimethylformamide, and dimethylacetamide.

[0177] In addition, in order to further improve the conductivity of the active material layer, the above-mentioned conductive material may be further blended into the electrode-forming composition of the present invention during the mixing of the active material composite material, the conductive auxiliary agent, and the binder.

[0178] When a conductive material is further added, the amount thereof is preferably 0.1 to 20 parts by mass, more preferably 0.1 to 5 parts by mass, relative to 100 parts by mass of the active material composite material.

[0179] The electrode of the present invention is an electrode having an active material layer (thin film) composed of the electrode-forming composition described above on a substrate as a current collector, or an electrode having the electrode-forming composition alone formed into a thin film.

[0180] In the case where the above-mentioned active material layer is formed on a substrate, as a method for forming the active material layer, it is possible to cite: a method in which an electrode-forming composition prepared without a solvent is press-formed on a substrate (dry method), or a method in which an electrode-forming composition is prepared using a solvent and the electrode-forming composition is applied to a collector for drying (wet method). There are no particular limitations on these methods, and various methods well known in the past can be used. For example, as a wet method, various printing methods such as offset printing, screen printing, etc. using a varnish obtained by dissolving or suspending the material comprising the above-mentioned active material composite material in an organic solvent, dip coating, spin coating, rod coating, slit coating, inkjet method, etc. can be cited.

[0181] As substrates for the above-mentioned electrodes, for example, there can be mentioned: metal substrates such as platinum, gold, iron, stainless steel, copper, aluminum, lithium, alloy substrates composed of any combination of these metals, oxide substrates such as indium tin oxide (ITO), indium zinc oxide (IZO), antimony tin oxide (ATO), or carbon substrates such as glassy carbon, pyrolytic graphite, carbon felt, etc.

[0182] When the electrode-forming composition is formed into a thin film, the film can be formed by appropriately using the above-mentioned wet method and dry method on a substrate that can be peeled off after the film is formed. Alternatively, a method of thinly extending the electrode-forming composition on the substrate using a glass rod or the like can be adopted. As the substrate, a substrate that has no adhesion to the film, such as a glass plate, can be used. In addition, even a substrate that has adhesion to the film can be used as long as the surface thereof has been treated to enable the film to be peeled off (such as by attaching a release paper or forming a release layer).

[0183] The thickness of the active material layer (thin film) is not particularly limited, but is preferably about 0.01 to 1000 μm, more preferably about 1 to 100 μm. When the thin film alone serves as an electrode, the thickness is preferably 10 μm or more.

[0184] In order to further suppress the dissolution of the active material contained in the electrode, the active material layer (thin film) may contain a polyalkylene oxide and an ion-conductive salt, or the electrode may be covered with a protective film. The protective film preferably contains a polyalkylene oxide and an ion-conductive salt.

[0185] The polyalkylene oxide is not particularly limited, but polyethylene oxide, polypropylene oxide, and the like are preferred.

[0186] The number average molecular weight of the polyalkylene oxide is preferably 300,000 to 900,000, and more preferably 500,000 to 700,000. The number average molecular weight is a value measured in terms of polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent.

[0187] Examples of the ion-conductive salt include lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium trifluoromethanesulfonate (LiCF3SO3), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), and lithium hexafluorophosphate (LiPF6). The ion-conductive salt is preferably contained in an amount of 5 to 50 parts by mass per 100 parts by mass of the polyalkylene oxide.

[0188] The protective film can be formed, for example, by applying a composition containing a polyalkylene oxide, an ion-conductive salt, and a solvent onto the substrate having the active material layer (thin film) formed thereon by a dipping method or the like, and drying the composition at 40 to 60° C. for 30 to 120 minutes.

[0189] As the above-mentioned solvent, acetonitrile, dichloromethane, etc. are preferable.

[0190] The thickness of the protective film is not particularly limited, but is preferably about 10 to 1000 μm, more preferably about 50 to 500 μm.

[0191] The secondary battery of the present invention comprises the aforementioned electrodes, more specifically, at least one pair of positive and negative electrodes, a separator interposed between the electrodes, and an electrolyte, with at least one of the positive and negative electrodes being composed of the aforementioned electrodes. Other components of the battery element may be appropriately selected from conventionally known components.

[0192] Examples of the material used for the separator include porous polyolefin, polyamide, and polyester.

[0193] As the electrolyte, an electrolytic solution composed of an electrolyte salt as a main component of ion conduction and a solvent can be preferably used from the viewpoint of being able to easily exhibit sufficient performance in practical use.

[0194] Examples of the electrolyte salt include lithium salts such as LiPF6, LiBF4, LiN(C2F5SO2), LiAsF6, LiSbF6, LiAlF4, LiGaF4, LiInF4, LiClO4, LiN(CF3SO2), LiCF3SO3, LiSiF6, and LiN(CF3SO2)(C4F9SO2), metal iodides such as LiI, NaI, KI, CsI, and CaI2, iodide salts of quaternary imidazolinium compounds, iodide salts of tetraalkylamine compounds, and metal bromides such as perchlorates, LiBr, NaBr, KBr, CsBr, and CaBr2. These electrolyte salts may be used alone or in combination of two or more.

[0195] As the above-mentioned solvent, there is no particular limitation as long as it is a solvent that does not corrode or decompose the materials constituting the battery so as to degrade their performance and can dissolve the above-mentioned electrolyte salt. For example, as the non-aqueous solvent, cyclic esters such as ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, ethers such as tetrahydrofuran, dimethoxyethane, chain esters such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, etc. can be used. These solvents can be used alone or in combination of two or more.

[0196] Compared with conventional secondary batteries, a battery produced using the electrode-forming composition of the present invention has excellent cycle characteristics and rate characteristics.

[0197] The secondary battery's form and electrolyte type are not particularly limited, and any form such as lithium-ion battery, nickel-metal hydride battery, manganese battery, or air battery may be employed, but lithium-ion battery is particularly suitable. There are also no particular limitations on the stacking method or production method.

[0198] Example

[0199] The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[0200] [Probe type ultrasonic irradiation device]

[0201] Apparatus: UIP1000 manufactured by Hielscher Ultrasonics

[0202] [Spray Dryer]

[0203] Equipment: Spray dryer Pulvis Mini Spray GB210-A manufactured by Yamato Science Co., Ltd.

[0204] [Scanning electron microscope]

[0205] Apparatus: Manufactured by JEOL Ltd., field emission scanning electron microscope JSM-7400F

[0206] The particles were observed at a magnification of 2000 times, the diameters of 50 particles were measured, and the number-average particle diameter was determined.

[0207] [Planetary mixer]

[0208] Apparatus: Manufactured by THINKY Corporation, THINKY MIXER (Awatori Rentaro) ARE-310

[0209] [Roll press]

[0210] Apparatus: Manufactured by TAKUMI Giken Co., Ltd., pressure / heating roll press SA-602

[0211] [Button cell sealer]

[0212] Apparatus: Manufactured by Hozen Co., Ltd., manual button sealer CR2032

[0213] [Micrometer]

[0214] Apparatus: Manufactured by Mitutoyo Corporation, IR54

[0215] [Charge-discharge measurement device]

[0216] Apparatus: Manufactured by Toyo System Co., Ltd., TOSCAT 3100

[0217] (1) Preparation of conductive material dispersion

[0218] [Example 1-1] Preparation of conductive material dispersion A2

[0219] An aqueous solution containing an oxazoline polymer as a dispersant, namely EPOCROS WS-700 (manufactured by Nippon Shokubai Co., Ltd., solid component concentration 25% by mass, weight-average molecular weight 4×10 4 , oxazoline group amount 4.5 mmol / g) 2.0 g was mixed with 47.5 g of distilled water, and further 0.5 g of MWCNT (TC-2010, manufactured by Toda Kogyo Corporation) as a conductive material was mixed with the above mixed solution. For the obtained mixture, ultrasonic treatment was performed at room temperature for 30 minutes using a probe-type ultrasonic irradiation device, and a black conductive material dispersion A1 in which MWCNT was uniformly dispersed without sediment was obtained.

[0220] To 50 g of the obtained conductive material dispersion A1, 0.7 g of Aron A-30 (Toagosei Co., Ltd., solid content concentration 31.6 mass %), an aqueous solution containing polyacrylamide (PAA-NH4) as a crosslinking agent, and 49.3 g of distilled water were added and stirred to obtain a conductive material dispersion A2 (solid content concentration 1.22 mass %).

[0221] [Example 1-2] Preparation of Conductive Material Dispersion Liquid A3

[0222] A conductive substance dispersion A3 was obtained by the same method as in Example 1-1 except that MWCNT was changed to Nanocyl-7000 (manufactured by Nanocyl Corporation).

[0223] [Comparative Example 1-1] Preparation of Conductive Material Dispersion Liquid A4

[0224] 0.25 g of MWCNTs (TC-2010, manufactured by Toda Kogyo Co., Ltd.) was mixed with a solution prepared by dissolving 0.36 g of polyvinyl alcohol JP-18 (partially saponified polyvinyl alcohol, manufactured by Japan VAM & POVAL Co., Ltd.) as a dispersant in 49.39 g of distilled water. The resulting mixture was ultrasonically treated at room temperature for 30 minutes using a probe-type ultrasonic irradiation device, yielding a black conductive material dispersion A4 (solids concentration 1.22% by mass) in which the MWCNTs were uniformly dispersed without sediment.

[0225] (2) Manufacturing of active material composite materials

[0226] [Example 2-1] Production of active material composite material P1

[0227] Mix 490 g of water with 10 g of anatase titanium oxide (product number 637254, manufactured by Sigma-Aldrich, with a primary particle size of 25 nm or less). The obtained mixture was ultrasonically treated at room temperature for 30 minutes using a bathtub-type ultrasonic device to obtain a white active material dispersion. 105 g of the conductive material dispersion A2 prepared in Example 1-1 and 499 g of distilled water were mixed with the above-mentioned active material dispersion. The obtained mixture was ultrasonically treated at room temperature for 30 minutes to obtain a black dispersion (composition for forming active material composite materials). Then, the obtained dispersion was dried using a spray dryer. The drying conditions were set as follows: the drying gas was air, the inlet temperature was 210°C, the atomizing gas pressure was 0.1 MPa, and the aspirator flow rate was 0.50 m 3 / minute, and the liquid feeding rate of the mixed liquid was 3.5 g / minute. The outlet temperature at this time was 85±3°C. A gray solid was obtained by drying the dispersion. The obtained solid was further heat-treated in a dryer (150°C, 2 hours) to obtain the active material composite material P1.

[0228] The average particle size of the obtained active material composite material P1 was 4.5 μm.

[0229] [Example 2-2] Production of active material composite material P2

[0230] An active material composite material P2 was produced by the same method as in Example 2-1, except that A3 prepared in Example 1-2 was used instead of the conductive material dispersion A2 prepared in Example 1-1.

[0231] The average particle size of the obtained active material composite material P2 was 3.7 μm.

[0232] [Comparative Example 2-1] Production of Active Material Composite Material P3

[0233] An active material composite material P3 was produced by the same method as in Example 2-1, except that A4 prepared in Comparative Example 1-1 was used instead of the conductive material dispersion A2 prepared in Example 1-1.

[0234] The average particle size of the obtained active material composite material P3 was 5.8 μm.

[0235] (3) Manufacturing of electrodes and lithium-ion batteries

[0236] [Example 3-1]

[0237] 2.06g of the active material composite material P1 manufactured in the above Example 2-1, 0.048g of acetylene black (AB, manufactured by Electric Chemical Industry (Strain)) as a conductive aid, and 2.88g of NMP solution of PVDF as a binder (solid content concentration 12% by mass, manufactured by Kishida Chemical (Strain)) were mixed in a mass ratio of 86:2:12, and NMP3.49g was further mixed so that the solid content concentration became 30% by mass. The above mixture was mixed using a rotary revolution mixer (2000rpm, 10 minutes 2 times) to manufacture an electrode forming slurry (negative electrode slurry). After the electrode forming slurry was evenly spread onto aluminum foil (1085, manufactured by (Strain) UACJ, substrate thickness 15μm) using a scraper method (wet film thickness 100μm), it was dried at 80°C for 30 minutes and then dried at 120°C for 30 minutes to form an active material layer. The active material layer was compressed (pressure-bonded) using a roll press to produce an electrode C1 (film thickness 40 μm).

[0238] The obtained electrode was punched into a disk shape with a diameter of 10 mm, and after measuring its mass, it was vacuum-dried at 120° C. for 12 hours and transferred to a glove box filled with argon gas.

[0239] An overlapping layer of 6 lithium foils punched out to a diameter of 14 mm (manufactured by Honjo Chemical Co., Ltd., with a thickness of 0.17 mm) is placed on a cover welded with a gasket and a gasket of a 2032-type button battery (manufactured by Hohsen Co., Ltd.), and then a separator (manufactured by CELGARD Co., Ltd., 2400) that has been immersed in an electrolyte (manufactured by Kishida Chemical Co., Ltd., ethylene carbonate: diethyl carbonate = 1:1 (volume ratio), containing 1 mol / L of lithium hexafluorophosphate as an electrolyte) for more than 24 hours and punched out to a diameter of 16 mm is stacked on it. Electrode C1 is then stacked on it so that the surface coated with the active material faces down. After dripping 1 drop of electrolyte, the outer shell and gasket are placed and sealed with a button battery sealing machine. It is then left to stand for 24 hours to obtain a secondary battery for the test.

[0240] [Example 3-2]

[0241] An electrode C2 was manufactured by the same method as in Example 3-1, except that the composite material P2 manufactured in Example 2-2 was used instead of the active material composite material P1 manufactured in Example 2-1.

[0242] Using the obtained electrode C2, a secondary battery for a test was produced in the same manner as in Example 3-1.

[0243] [Comparative Example 3-1]

[0244] An electrode C3 was manufactured by the same method as in Example 3-1, except that the composite material P3 manufactured in Comparative Example 2-1 was used instead of the active material composite material P1 manufactured in Example 2-1.

[0245] Using the obtained electrode C3, a secondary battery for a test was produced in the same manner as in Example 3-1.

[0246] [Comparative Example 3-2]

[0247] An electrode C4 was produced by the same method as in Example 3-1, except that titanium oxide powder that did not form a composite material was used as the active material instead of the active material composite material P1 produced in Example 2-1.

[0248] Using the obtained electrode C4, a secondary battery for a test was produced in the same manner as in Example 3-1.

[0249] The electrode properties of the lithium-ion secondary batteries produced in Examples 3-1 and 3-2 and Comparative Examples 3-1 and 3-2 were evaluated using a charge-discharge measurement device under the following conditions. The discharge capacity (rate characteristics) of each secondary battery at various discharge rates (0.1C, 0.5C, 1C, 2C, 3C, and 5C) is shown in Table 1. Furthermore, the capacity retention (cycle characteristics) at each cycle of 0.5C constant current discharge is shown in Table 2.

[0250] [Measurement conditions]

[0251] Rate characteristics:

[0252] Current: 0.1C constant current charge, 0.1C, 0.5C, 1C, 2C, 3C, 5C constant current discharge (the capacity of TiO2 is set to 336mAh / g, and after increasing the discharge rate every three cycles, the final discharge rate is set to 0.5C)

[0253] Cycle characteristics:

[0254] Current: 0.1C constant current charging, 0.5C constant current discharging (the capacity of TiO2 is set to 336mAh / g)

[0255] Cut-off voltage: 3.00V~1.00V

[0256] Temperature: room temperature

[0257] [Table 1]

[0258]

[0259] [Table 2]

[0260]

[0261] According to the results in Table 1 above, the secondary batteries of Examples 3-1 and 3-2, in which the active material composite materials of Examples 2-1 and 2-2 are used as negative electrode active materials, have been confirmed to have excellent discharge capacity at high rates compared to the secondary batteries of Comparative Examples 3-1 and 3-2, in which the negative electrode active material of Comparative Example 2-1 or commercially available particles are used.

[0262] Therefore, it was confirmed that by using an active material composite material having a thermosetting layer (the thermosetting layer contains a conductive material, a dispersant and a cross-linking agent) on the surface of the active material particles for the negative electrode active material, the conductivity can be improved compared to the negative electrode active material without the thermosetting layer, thereby improving the cycle characteristics and rate characteristics of the secondary battery.

Claims

1. A composition for forming an active material composite material, characterized in that: The active material composite material forming composition comprises an active material, a conductive material, a dispersant, a solvent and a cross-linking agent, wherein the active material is selected from at least one of metals, semi-metals, metal alloys, metal oxides, semi-metal oxides, metal phosphates, metal sulfides and metal nitrides; wherein, The dispersant is an ethylene polymer having an oxazoline group in the side chain, The cross-linking agent is at least one selected from the group consisting of the following compounds: Sodium polyacrylate, lithium polyacrylate, ammonium polyacrylate, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, and carboxymethyl cellulose amine.

2. The composition for forming an active material composite material according to claim 1, wherein The active material is selected from FeS2, TiS2, MoS2, LiFePO4, V2O6, V6O 13 , MnO2, LiCoO2, LiMnO2, LiMn2O4, LiMo2O4, LiV3O8, LiNiO2, Li z Ni y M 1-y O2、Li(Ni a Co b Mn c )O2、Li4Ti5O 12 、Si、SiO x 、AlO x 、SnO x , SbO x 、BiO x 、GeO x 、AsO x , PbO x 、ZnO x , CdO x 、InO x 、TiO x and GaO x At least one of Among them, in the formula Li z Ni y M 1-y In O2, M represents at least one metal element selected from Co, Mn, Ti, Cr, V, Al, Sn, Pb, and Zn, 0.05≦z≦1.10, 0.5≦y≦1.0; Among them, in the formula Li(Ni a Co b Mn c )O2, 0 <a<1,0<b<1,0<c<1,a+b+c=1; Among them, in the formula SiO x 、AlO x 、SnO x , SbO x 、BiO x 、GeO x 、AsO x , PbO x 、ZnO x , CdO x 、InO x 、TiO x and GaO x Medium, 0 <x≦2。 3. The composition for forming an active material composite material according to claim 1 or 2, wherein The conductive substance is conductive carbon.

4. The composition for forming an active material composite material according to claim 3, wherein The conductive carbon is carbon nanotube. 5 . An active material composite material obtained from the composition for forming an active material composite material according to claim 1 .

6. The active material composite material according to claim 5, wherein: A thermally cured layer is provided on the surface of particles of at least one active material selected from metals, semi-metals, metal alloys, metal oxides, semi-metal oxides, metal phosphates, metal sulfides and metal nitrides, wherein the thermally cured layer contains a conductive material, a dispersant and a cross-linking agent.

7. An active material composite material comprising an active material, a conductive material, a dispersant, and a cross-linking agent, wherein the active material is selected from at least one of metals, semi-metals, metal alloys, metal oxides, semi-metal oxides, metal phosphates, metal sulfides, and metal nitrides; wherein: The dispersant is an ethylene polymer having an oxazoline group in the side chain, The cross-linking agent is at least one selected from the group consisting of the following compounds: Sodium polyacrylate, lithium polyacrylate, ammonium polyacrylate, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, and carboxymethyl cellulose amine.

8. The active material composite material according to claim 7, wherein: The active material is selected from FeS2, TiS2, MoS2, LiFePO4, V2O6, V6O 13 , MnO2, LiCoO2, LiMnO2, LiMn2O4, LiMo2O4, LiV3O8, LiNiO2, Li z Ni y M 1-y O2、Li(Ni a Co b Mn c )O2、Li4Ti5O 12 、Si、SiO x 、AlO x 、SnO x , SbO x 、BiO x 、GeO x 、AsO x , PbO x 、ZnO x , CdO x 、InO x 、TiO x and GaO x At least one of Among them, in the formula Li z Ni y M 1-y In O2, M represents at least one metal element selected from Co, Mn, Ti, Cr, V, Al, Sn, Pb, and Zn, 0.05≦z≦1.10, 0.5≦y≦1.0; Among them, in the formula Li(Ni a Co b Mn c )O2, 0 <a<1,0<b<1,0<c<1,a+b+c=1; Among them, in the formula SiO x 、AlO x 、SnO x , SbO x 、BiO x 、GeO x 、AsO x , PbO x 、ZnO x , CdO x 、InO x 、TiO x and GaO x Medium, 0 <x≦2。 9. The active material composite material according to claim 7 or 8, wherein: The conductive substance is conductive carbon.

10. The active material composite material according to claim 9, wherein: The conductive carbon is carbon nanotube. 11 . An electrode-forming composition comprising the active material composite material according to claim 5 , a conductive additive, and a binder. 12 . An electrode comprising an active material layer comprising the electrode-forming composition according to claim 11 . 13 . A secondary battery comprising the electrode according to claim 12 .

14. A method for producing a composition for forming an active material composite material, for producing the composition according to any one of claims 1 to 4, the method comprising: An active material dispersion and a conductive material dispersion are prepared separately and then mixed, wherein the active material dispersion comprises an active material and a solvent, and the conductive material dispersion comprises a conductive material, a dispersant, a cross-linking agent and a solvent.

15. A method for producing an active material composite material, comprising: An active material, a conductive material, a dispersant, a solvent, and a cross-linking agent are mixed to prepare a composition for forming an active material composite material, and heat-treated at a temperature at which the composition is not carbonized; Here, the active material is selected from at least one of metal, semi-metal, metal alloy, metal oxide, semi-metal oxide, metal phosphate, metal sulfide and metal nitride; wherein, The manufacturing method further comprises performing heat treatment at 120°C to 220°C, The dispersant is an ethylene polymer having an oxazoline group in the side chain, The cross-linking agent is at least one selected from the group consisting of the following compounds: Sodium polyacrylate, lithium polyacrylate, ammonium polyacrylate, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, and carboxymethyl cellulose amine.

16. The method for producing the active material composite material according to claim 15, comprising: After the active material composite material-forming composition is prepared, it is dried.

17. The method for producing an active material composite material according to claim 16, wherein: The drying is performed by spray drying.

18. The method for producing an active material composite material according to any one of claims 15 to 17, wherein the active material is selected from FeS2, TiS2, MoS2, LiFePO4, V2O6, V6O 13 , MnO2, LiCoO2, LiMnO2, LiMn2O4, LiMo2O4, LiV3O8, LiNiO2, Li z Ni y M 1-y O2、Li(Ni a Co b Mn c )O2、Li4Ti5O 12 、Si、SiO x 、AlO x 、SnO x , SbO x 、BiO x 、GeO x 、AsO x , PbO x 、ZnO x , CdO x 、InO x 、TiO x and GaO x At least one of in, In the formula z Ni y M 1-y In O2, M represents at least one metal element selected from Co, Mn, Ti, Cr, V, Al, Sn, Pb, and Zn, 0.05≦z≦1.10, 0.5≦y≦1.0; Among them, in the formula Li(Ni a Co b Mn c )O2, 0 <a<1,0<b<1,0<c<1,a+b+c=1; Among them, in the formula SiO x 、AlO x 、SnO x , SbO x 、BiO x 、GeO x 、AsO x , PbO x 、ZnO x , CdO x 、InO x 、TiO x and GaO x Medium, 0 <x≦2。 19. The method for producing an active material composite material according to any one of claims 15 to 17, wherein: The conductive substance is conductive carbon.

20. The method for producing an active material composite material according to claim 19, wherein: The conductive carbon is carbon nanotube.

21. The method for producing an active material composite material according to any one of claims 15 to 17, wherein: An active material dispersion containing an active material and a solvent and a conductive material dispersion containing a conductive material, a dispersant, and a crosslinking agent are separately prepared and then mixed to prepare the active material composite material forming composition.

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