TW201342698A - Positive-electrode mixture, positive electrode, and non-aqueous electrolyte secondary battery using same - Google Patents

Abstract

Provided is an aqueous positive-electrode mixture that has excellent dispersibility of positive-electrode active materials, storage stability, and coatability when coated onto a charge collector, and that, after being coated onto a charge collector, can produce a positive electrode having excellent adhesion between the charge collector and the positive-electrode active materials. Also provided are a positive electrode and a non-aqueous electrolyte secondary battery using same. This positive-electrode mixture contains a positive-electrode active material, a water-dispersible polymeric binder resin, a conductive assistant, and a surfactant.

Description

Positive electrode mixture, positive electrode, and nonaqueous electrolyte battery using same

The present invention relates to a positive electrode mixture, a positive electrode, and a nonaqueous electrolyte secondary battery using the same, and more particularly to a water-based positive electrode mixture, which is a dispersibility of a positive electrode active material, a storage stability, and a coating applied to a current collector. It is excellent in the cloth property, and after being applied to a current collector, a positive electrode excellent in adhesion to a current collector and a positive electrode active material, a positive electrode, and a nonaqueous electrolyte secondary battery using the same can be obtained.

In recent years, with the development of miniaturization and multi-function of electronic components, many portable electronic devices have appeared. Since these devices are expected to be smaller and lighter, batteries used as power sources are also required to be smaller and lighter. In addition, in the context of environmental issues or resource issues, hybrid vehicles or electric vehicles have been developed and manufactured and sold. Such a so-called electric vehicle must also utilize a small, lightweight, rechargeable, and energy-intensive power supply unit. These power supply devices can use batteries such as lithium ion batteries or nickel hydrogen batteries, or electric double layer capacitors. In particular, non-aqueous electrolyte batteries, such as lithium ion batteries, are attracting attention as power supply devices because of their high energy density and high durability against repeated charge and discharge, and are being actively developed.

The electrode of the battery is composed of an active material, a conductive auxiliary agent, and a binder resin that bonds the current collector to the current collector. When the battery is charged and discharged, the volume of the positive or negative electrode will repeatedly expand or contract, so there will be active substances or The occurrence of peeling of the conductive auxiliary agent occurs, and the life of the charge and discharge cycle is shortened. Therefore, the binder resin for a battery needs to have flexibility to withstand swelling and shrinkage of the electrode. Conventionally, a fluororesin such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE) has been used for the positive electrode and the negative electrode.

However, the general fluororesin has insufficient adhesion to the current collector, and thus it is impossible to further increase the charge/discharge cycle life. In particular, when polyvinylidene fluoride is used as the binder resin, the adhesion to the current collector and the filler (positive electrode active material and conductive auxiliary agent) is weak, so that there is a set during battery manufacturing and battery use. The peeling of the electric body and the electrode mixture occurs, and the internal resistance of the battery increases.

For these problems, for example, in the fluororesin of the binder resin in Japanese Patent Document 1, a copolymer of a polar monomer such as a monoester of vinylidene fluoride and an unsaturated dibasic acid has been proposed. Thereby, the adhesion of the fluororesin to the current collector can be improved. Further, in Japanese Patent Publication No. 2 and Patent Document 3, a water-dispersible emulsion of styrene-butadiene copolymer (SBR) particles, or SBR particles and carboxymethyl fibers are proposed as a binder resin for a negative electrode active material. A composition consisting of a sodium salt or an ammonium salt of a compound (CMC). As shown in Patent Documents 2 and 3, by using the SBR particles in the binder resin, it is possible to prevent the negative electrode active material from falling off when used in a battery.

Further, Japanese Patent Document 4 proposes a technique of heating an acrylic resin and a crosslinking agent at the time of electrode production by adding a crosslinking agent to an acrylic resin dissolved in a solvent and serving as a binder resin. The reaction is carried out in the pressure bonding step to obtain a three-dimensional crosslinked structure, which prevents the active material or the conductive agent from falling off during charge and discharge of the battery. In addition, special in Japan In the literature 5, a technique is proposed in which a surface of a positive electrode active material having an average particle diameter of 0.01 to 0.5 μm is coated with a surfactant to increase the surface area of the positive electrode active material supplied to the reaction while preventing agglomeration of the positive electrode active material. And the battery has high output power.

Prior technical literature

Patent literature

Patent Document 1: Japanese Patent No. 3121943

Patent Document 2: Japanese Patent No. 3101775

Patent Document 3: Japanese Patent No. 3260972

Patent Document 4: Japanese Patent No. 3066682

Patent Document 5: JP-A-2008-21415

However, when the fluorine-based resin proposed in Japanese Patent Publication No. 1 is used under severe conditions such as the use of a binder resin for a non-aqueous battery electrode, solvent resistance and chemical resistance are still insufficient. In addition, when the binder resin described in Japanese Patent Publication No. 2 and 3 is used, the SBR particles have an advantage that they are less likely to fall off even when the negative electrode active material is repeatedly charged and discharged, but there is a problem that a battery having a large capacity cannot be obtained. Further, the SBR particles tend to coat the surface of the carbon material with a carbon material which is easily adsorbed to the negative electrode active material. Therefore, there is a case where an electrolyte containing lithium ions is difficult to permeate and sufficient electrical characteristics cannot be obtained. In addition, in the case of using the solvent-dissolving type binder resin proposed in Japanese Patent Publication No. 4, After the resin solution is applied to the electrode substrate, if the organic solvent is removed, the surface of the electrode active material is covered with the resin without a gap. Therefore, there is a problem that sufficient electrical characteristics cannot be obtained. Further, in the storage battery proposed in Japanese Patent Laid-Open No. 5, the adhesion of the positive electrode active material is easily hindered, and there is a problem that the durability of the positive electrode active material mixture layer is insufficient. Further, in Japanese Patent Publications 1 and 4, a fluororesin is used as the binder resin. However, the fluororesin is swelled and dissolved only in a specific solvent such as N-methylpyrrolidone, and therefore, an odor is generated during electrode production, and the like. Or problems that cause adverse effects in the environment.

In view of the above, an object of the present invention is to provide a water-based positive electrode mixture which is excellent in dispersibility, storage stability, and coating property when applied to a current collector, and is applied to a current collector. A positive electrode having excellent adhesion to a current collector and a positive electrode active material, a positive electrode, and a nonaqueous electrolyte secondary battery using the same are obtained.

In order to solve the above problems, the present inventors have found that a positive electrode active material is easily used in a solvent by using a surfactant in a positive electrode mixture and a specific polymer material as a water-dispersible polymer binder resin. The positive electrode mixture obtained is uniformly dispersed in the current collector, and the positive electrode obtained by drying the positive electrode mixture is excellent in adhesion to the current collector plate, so that the positive electrode mixture layer is excellent in adhesion. The present invention has been completed.

In addition, the inventors have found that by adding a specificity to the positive electrode mixture In the positive electrode active material, the positive electrode active material is easily and uniformly dispersed in a solvent, and the obtained positive electrode mixture is excellent in coating properties when applied to a current collector, and the positive electrode obtained by drying the positive electrode has a positive electrode. The mixture layer and the current collector plate are excellent in adhesion.

That is, the positive electrode mixture of the present invention is characterized by comprising a positive electrode active material, a water-dispersible polymer binder resin, a conductive auxiliary agent, and a surfactant.

In the positive electrode mixture of the present invention, the HLB value of the surfactant is preferably from 13.0 to 20.0. Further, in the positive electrode mixture of the present invention, it is preferred to contain water as a solvent.

Further, the positive electrode of the present invention is characterized in that the positive electrode mixture of the present invention is applied to a current collector.

Further, the nonaqueous electrolyte secondary battery of the present invention is characterized by using the above positive electrode of the present invention.

According to the present invention, it is possible to provide a water-based positive electrode mixture which is excellent in dispersibility, storage stability, and coating property when applied to a current collector, and can be obtained after application to a current collector. A positive electrode having excellent adhesion between a current collector and a positive electrode active material; a positive electrode; and a nonaqueous electrolyte secondary battery using the same.

Hereinafter, embodiments of the present invention will be described in detail.

<Positive electrode mixture>

The positive electrode mixture of the present invention contains a positive electrode active material, a water-dispersible polymer binder resin, a conductive auxiliary agent, and a surfactant. By adding a surfactant to the positive electrode mixture, the positive electrode active material and the water-dispersible polymer binder resin can be dispersed in the aqueous solvent for a short period of time and uniformly. Further, since the positive electrode active material and the water-dispersible polymer binder resin are less likely to aggregate and settle, the coatability to the current collector is also improved. Further, the positive electrode using the positive electrode mixture of the present invention is excellent in adhesion and flexibility to the current collector and the positive electrode active material. Even in the nonaqueous electrolyte secondary battery using the obtained positive electrode, even in a high temperature environment caused by repeated charging, discharging, or heat generation, it is possible to suppress a decrease in discharge capacity at the time of charge and discharge cycles, and a battery having a long life can be obtained. Hereinafter, each component of the positive electrode mixture of the present invention and a method for producing the same will be described in detail.

<Positive active material>

Among the positive electrode mixture of the present invention, for example, a transition metal oxide, a transition metal sulfide, a lithium-containing composite metal oxide, or the like can be used as the positive electrode active material. Examples of the transition metal include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, etc., and transition metal oxides such as MnO, MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , Cu are suitably used. ₂ V ₂ O ₃ , amorphous V ₂ OP ₂ O ₅ , MoO ₃ , V ₂ O ₅ , V ₆ O ₁₃ and the like. In particular, from the viewpoint of cycle stability and capacity, it is suitable for MnO, V ₂ O ₅ , V ₆ O ¹³ , and TiO ₂ . As the transition metal sulfide, TiS ₂ , TiS ₃ , amorphous MoS ₂ , FeS, or the like is suitably used. Further, the structure of the lithium-containing composite metal oxide is not particularly limited, and a layered structure or a spinel structure is suitably used, and an olivine structure or the like is also suitably used.

The lithium-containing composite metal oxide having a layered structure is mainly composed of a composite oxide containing lithium-containing cobalt oxide (LiCoO ₂ ), lithium-containing nickel oxide (LiNiO ₂ ), and Co-Ni-Mn. A lithium-containing composite metal oxide, a lithium-containing composite metal oxide mainly composed of a composite oxide of Ni-Mn-Al, and a lithium-containing composite metal oxide mainly composed of a composite oxide of Ni-Co-Al.

The lithium-containing composite metal oxide having a spinel structure may be exemplified by lithium manganate (LiMn ₂ O ₄ ), or Li[Mn _3/2 M _1/2 ]O _{4 in which} a part of Mn is substituted by another transition metal (here) M is Cr, Fe, Co, Ni, Cu, etc.).

The lithium-containing composite metal oxide having an olivine structure can be exemplified by LixMPO ₄ (wherein M is selected from the group consisting of Mn, Fe, Co, Ni, Cu, Mg, Zn, V, Ca, Sr, Ba, Ti, Al, An olivine-type lithium phosphate compound represented by at least one of Si, B and Mo, 0≦X≦2). Among the lithium-containing composite metal oxides, LiFePO ₄ and LiCoPO ₄ have low conductivity, and thus are used in a large amount in the form of fine particles. These materials have many pores, and therefore have a large surface area and are inferior in compatibility with a resin as a binder. However, since the positive electrode mixture of the present invention contains a surfactant, even LiFePO ₄ or LiCoPO _{4 is} suitably used.

In the positive electrode mixture of the present invention, the positive electrode active material is preferably one having an average particle diameter of 0.01 μm or more and less than 50 μm, and more preferably 0.1 μm to 30 μm. When the particle diameter is within the above range, the amount of the water-dispersible polymer binder resin blended can be reduced, and the capacity reduction of the battery can be suppressed while preventing The aggregation of the positive electrode active material is stabilized, and the dispersibility of the positive electrode mixture is good, and a uniform electrode can be obtained. Here, the particle diameter refers to the maximum distance L among the distances of any two points on the skeletal line of the particle, and the value of the average particle diameter refers to a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The observation means is a value calculated from the average value of the particle diameters of the particles observed in several to several tens of fields of view.

Further, when the positive electrode active material is an iron-based oxide having a lack of conductivity, it may be used as a positive electrode active material covered with a carbon material by presenting a carbon source material during reduction baking. The carbon source materials may also be partially substituted by elements. In addition, the positive electrode active material for a nonaqueous electrolyte secondary battery may be a mixture of the above inorganic compound and an organic compound of a conductive polymer such as polyacetylene or polyparaphenylene.

<Water Dispersible Polymer Adhesive Resin>

In the positive electrode mixture of the present invention, the water-dispersible polymer binder resin means a polymer binder resin which can be dispersed in an aqueous solvent to be described later. Examples of the water-dispersible polymer binder resin include a vinyl polymer, an acrylic polymer, a nitrile polymer, a polyurethane polymer, a non-fluorine polymer such as a diene polymer, or PVDF. Or a fluorine-based polymer such as PTFE. In particular, from the viewpoint of adhesion to a current collector or a positive electrode mixture, a non-fluorine-based polymer is preferred, an acrylic resin is preferred, and a weight average molecular weight of at least a polyol and a polyisocyanate is 8,000. ~1,500,000, preferably a polyurethane resin having a weight average molecular weight of 10,000 to 1,000,000.

When the water-dispersible polymer resin binder is an acrylic resin, a copolymer of an acrylate or a methacrylate and another functional monomer may be used. Further, when the water-dispersible polymer resin binder is a polyurethane resin, if the weight average molecular weight is less than 8,000, the durability of the binder may be lowered. On the other hand, if the weight average molecular weight exceeds At 1,500,000, although the durability of the binder is improved, the binder itself may agglomerate, and the dispersibility and coatability may be remarkably lowered. Further, the particle diameter is preferably 0.05 to 5 μm, more preferably 0.1 to 1 μm. When the particle diameter exceeds 5 μm, there is a concern that the adhesiveness is lowered. On the other hand, when the particle diameter is less than 0.05 μm, the surface of the positive electrode active material is covered and the internal resistance is increased. The polyol and the polyisocyanate used for the synthesis of the above polyurethane resin are not particularly limited, and a known one can be used. Further, the acrylic resin is not particularly limited, and a known one can be used. Further, the acrylate, methacrylate, and other monomers used in the synthesis of the acrylic resin are not particularly limited, and a known one can be used. Further, in the positive electrode mixture of the present invention, the polyurethane resin or the acrylic resin can also be used in the form of an aqueous emulsion or an aqueous dispersion.

The preparation method of the aqueous emulsion can be produced by, for example, a surfactant method using a surfactant such as soap, or an emulsion polymerization using a water-soluble polymer such as polyvinyl alcohol as a colloidal method of a protective colloid. A batch polymerization method, a pre-emulsification dropping method, a monomer dropping method, or the like may be used. Further, the average particle diameter of each of the polymers in the aqueous emulsion can be changed by controlling the monomer concentration, the reaction temperature, the stirring speed, and the like. Emulsified poly In combination, the particle size distribution of the polymer can be sharpened, and by using such an aqueous emulsion, various components in the electrode can be homogenized.

The aqueous dispersion is suitably a polytetrafluoroethylene aqueous dispersion. Further, a method of preparing an aqueous dispersion can be carried out by a known means, and a polytetrafluoroethylene-based aqueous dispersion can be obtained by dispersing polytetrafluoroethylene in water.

The polyol used in the synthesis of the polyurethane resin to which the positive electrode mixture of the present invention is used is preferably a polyester polyol. Examples of the polyester polyols include polyester polyols, polyester polycarbonate polyols, and polycarbonate polyols. Among these polyols, polyester polyols are suitable because they can impart good durability and strength when a polyurethane resin is used for a binder resin.

The polyester polyol may, for example, be an ester-forming derivative of a polyvalent carboxylic acid or an ester, an anhydride or a halide thereof, which is a stoichiometric amount less than a low molecular weight polyol. The esterification reaction and/or the transesterification reaction are carried out directly.

Examples of the low molecular polyol include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, and 2-butyl-2-ethyl-1,3-propanediol. 1,4-butanediol, neopentyl glycol, 3-methyl-2,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 3-methyl-1,5 - pentanediol, 2-methyl-2,4-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3,5-heptanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, diethylene glycol, An aliphatic diol such as triethylene glycol, an alicyclic diol such as cyclohexane dimethanol or cyclohexane diol, trimethylolethane, trimethylolpropane, hexitol or pentaerythritol Alcohol, glycerin, penta A trivalent or higher alcohol such as tetraol or tetramethylolpropane. These may be used alone or in combination of two or more.

Examples of the polyvalent carboxylic acid or an ester-forming derivative thereof include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, sebacic acid, and dodecane. Diacid, 2-methylsuccinic acid, 2-methyladipate, 3-methyladipate, 3-methylglutaric acid, 2-methyloctanedioic acid, 3,8-dimethylhydrazine Aliphatic dicarboxylic acids such as diacid, 3,7-dimethylsebacic acid, hydrogenated dimer acid, dimer acid, phthalic acid, terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, etc. a polyvalent carboxylic acid such as an alicyclic dicarboxylic acid such as an aromatic dicarboxylic acid or a cyclohexane dicarboxylic acid; a tricarboxylic acid such as a terpolymer of trimellitic acid, trimesic acid or a castor oil fatty acid; An acid anhydride of the polyvalent carboxylic acid, a chloride of the polyvalent carboxylic acid, a halide such as a bromide, or a methyl ester, an ethyl ester, a propyl ester, an isopropyl ester, a butyl ester or the like of the polyvalent carboxylic acid. Lower ester of ester, amyl ester, or the like, or γ-caprolactone, δ-caprolactone, ε-caprolactone, dimethyl-ε-caprolactone, δ-valerolactone, γ-valerolactone, a lactone such as γ-butyrolactone. These may be used alone or in combination of two or more.

Further, the polyisocyanate used for the synthesis of the polyurethane resin to which the positive electrode mixture of the present invention is used is not particularly limited, and a known polyisocyanate can be used. Since the obtained polyurethane resin is excellent in dispersibility and low in cost, the polyisocyanate is suitably a mixture of a diisocyanate and a triisocyanate.

The diisocyanate may, for example, be 2,4- and/or 2,6-methylphenylene diisocyanate, diphenylmethane-4,4'-diisocyanate, p-phenylene diisocyanate, benzoyl diisocyanate, 1, 5-naphthalene diisocyanate, 3,3'-dimethyl Aromatic diisocyanates such as diphenyl-4,4'-diisocyanate, diansidine diisocyanate, tetramethylxylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'- Alicyclic diisocyanates such as diisocyanate, trans-1,4-cyclohexyl diisocyanate, norbornene diisocyanate, 1,6-hexamethylene diisocyanate, 2, 2, 4 (2, 4, 4) An aliphatic diisocyanate such as trimethylhexamethylene diisocyanate or lysine diisocyanate. In particular, the alicyclic diisocyanate is suitable because it has excellent hydrolysis resistance. These may be used alone or in combination of two or more.

Examples of the triisocyanate include triphenylmethane triisocyanate, 1-methylbenzene-2,4,6-triisocyanate, the isocyanurate trimer of the above diisocyanate, the biuret trimer, and the trimethylol group. An adduct of propane, etc. In particular, the isocyanurate trimer is suitable because it can impart a stable dispersion state to the polyurethane resin. These may be used alone or in combination of two or more.

In the positive electrode mixture of the present invention, the polyurethane resin may also be a polyurethane resin obtained by polymerizing a chain extender. That is, in the case where the polyurethane resin must have a high molecular weight, a well-known chain extender used for the synthesis of the polyurethane resin can be used. The chain extender is preferably a polyvalent amine compound, a polyvalent primary alcohol compound or the like, and a polyvalent amine compound is preferred.

Examples of the polyvalent amine compound include low molecular polyamines, diethylenetriamine, triethylenetetramine, tetraethylene-5, which are substituted with an amine group of an alcoholic hydroxyl group of the above-exemplified low molecular polyol such as ethylenediamine or propylenediamine. Polyether polyamines such as amines, polyoxypropylenediamines, polyoxypropylene triamines, methane diamines, isophorone diamines, norborn diamines, Bis(4-amino-3-methyldicyclohexyl)methane, diaminodicyclohexylmethane, bis(aminomethyl)cyclohexane, N-aminomethylpiperazine, 3,9-double Alicyclic polyamines such as (3-aminopropyl) 2,4,8,10 tetraoxaspiro(5,5)undecane, m-xylenediamine, α-(m-/p-aminobenzene) Ethylamine, m-phenylenediamine, diaminodiphenylmethane, diaminodiphenylphosphonium, diaminodiethyldimethylmethane, diaminodiethylmethane , an aromatic polyamine such as dimethylthiotoluenediamine, diethyltoluenediamine, α,α'-bis(4-aminophenyl)-p-diisopropylbenzene or dithiodiphenylamine Class, hydrazine, ethylenediamine, propylenediamine, xylenediamine, diammonium adipate, isophoronediamine, piperazine and its derivatives, phenylenediamine, toluenediamine, xylenediamine , diisophthalic acid, etc. In the positive electrode mixture of the present invention, these may be used alone or in combination of two or more.

The method for producing the polyurethane resin to which the positive electrode mixture of the present invention is applied is not particularly limited, and a known production method can be used. For example, it is preferred to carry out a prepolymerization method in which a polyol, a diisocyanate, and a triisocyanate are reacted together to prepare a urethane prepolymer in advance to carry out chain extension in water in the presence of a chain extender.

The amount of the chain extender to be used is not particularly limited and may be selected in any amount. For example, in the case where the prepolymerization method is selected in the synthesis of the polyurethane resin, the obtained water-dispersible polyamine can be obtained. The ethyl formate composition has good dispersibility and no discoloration. Therefore, the number of active hydrogen of the chain extender is preferably 0.1 to 1.5, and preferably 0.5 to 1.0, relative to the number 1 of isocyanate groups in the prepolymer. .

The synthesis of the acrylic resin to which the positive electrode mixture of the present invention is used is used. Examples of the acrylate and methacrylate include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, n-butyl acrylate, and methacrylic acid. N-butyl ester, tert-butyl acrylate, tert-butyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, acrylic ring Hexyl ester, cyclohexyl methacrylate, stearyl acrylate, stearyl methacrylate, octadecyl acrylate, octadecyl methacrylate, phenyl acrylate, phenyl methacrylate, benzyl acrylate, Benzyl methacrylate, chloromethyl acrylate, chloromethyl methacrylate, 2-chloroethyl acrylate, 2-chloroethyl methacrylate, 2-hydroxyethyl acrylate, methacrylic acid-2- Hydroxyethyl ester, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 2,3,4,5,6-pentahydroxyhexyl acrylate, methacrylic acid-2,3,4,5 ,6-pentahydroxyhexyl ester, 2,3,4,5-tetrahydroxypentyl acrylate, 2,3,4,5-tetrahydroxypentyl methacrylate, aminoethyl acrylate Amino ethyl acrylate, propyl methacrylate, dimethylamino ethyl methacrylate, propyl amine group, an anilino group, ethyl methacrylate, cyclohexyl methacrylate, and ethyl group and the like. These may be used alone or in combination of two or more.

In the acrylic resin to which the positive electrode mixture of the present invention is related, a functional monomer may be added in addition to the above acrylate and the above methacrylate. Examples of the monofunctional monomer include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, and 4-dodecane. An aromatic vinyl monomer such as styrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene or halogenated styrene; cyanide such as acrylonitrile or methacrylonitrile Vinyl monomer; butadiene, isoprene Diene, 2,3-dimethylbutadiene, 2-methyl-3-ethylbutadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 2- Ethyl-1,3-pentadiene, 1,3-hexadiene, 2-methyl-1,3-hexadiene, 3,4-dimethyl-3,3-hexadiene, 1, A conjugated diene monomer such as 3-heptadiene, 3-methyl-1,3-heptadiene, 1,3-octadiene, cyclopentadiene, chloroprene or laurelene. Further, examples of the polyfunctional monomer include allyl methacrylate, allyl acrylate, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl malate , divinyl adipate, divinyl phenethylene glycol dimethacrylate, divinyl phenethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, Triethylene glycol dimethacrylate, triethylene glycol diacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, tetramethylol methane tetramethacrylate, four Methylol methane tetraacrylate, dipropylene glycol dimethacrylate, and dipropylene glycol diacrylate may be used in combination of two or more.

The method for producing the acrylic resin to which the present invention relates is not particularly limited, and a known production method can be used.

Further, in the positive electrode mixture of the present invention, other polymer particles may be added as necessary in the water-dispersible polymer-based binder resin. Examples of the polymer particles include a non-fluorine-based polymer such as a vinyl polymer, an acrylic polymer, a nitrile polymer, a polyurethane polymer, or a diene polymer; and a fluorine such as PVDF or PTFE. The polymer is preferably a non-fluorine-based polymer, especially from the viewpoint of adhesion. Further, in the positive electrode mixture of the present invention, the polymer particles may be used singly or in combination of two or more.

In the positive electrode mixture of the present invention, the content of the water-dispersible polymer binder resin (polymer particles) is preferably 0.1 to 10 parts by mass, preferably 0.5 to 5 parts by mass per 100 parts by mass of the positive electrode active material. Parts by mass. By setting the content ratio of the polymer particles in the above range, the adhesion and flexibility of the positive electrode mixture layer obtained by applying the positive electrode mixture of the present invention to the current collector and drying to the current collector plate can be improved.

Further, in the positive electrode mixture of the present invention, the average particle diameter of the water-dispersible polymer-based binder resin is preferably 0.05 to 5 μm, more preferably 0.1 to 1 μm. If the particle diameter is too large, there is a concern that the adhesiveness is lowered. When the particle diameter is too small, the surface of the positive electrode active material is covered and the internal resistance is increased.

<conductive additive>

In the positive electrode mixture of the present invention, the conductive auxiliary agent may be conductive carbon such as acetylene black, ketjen black, carbon black, graphite, vapor-grown carbon fiber, and carbon nanotube, graphene or fullerene. By using a conductive auxiliary agent, electrical contact between the positive electrode active materials can be improved, and in the case of using a nonaqueous electrolyte secondary battery, the discharge ratio characteristics can be improved. The amount of the conductive auxiliary agent to be added is preferably 0.1 to 20 parts by mass, preferably 0.1 to 10 parts by mass, per 100 parts by mass of the positive electrode active material.

<Surfactant>

In the positive electrode mixture of the present invention, the surfactant has high dispersibility in the electrolyte, low reactivity with lithium ions, and the like, and does not interfere with the electrolyte. The ion conduction in the medium is not particularly limited. For example, a surfactant, an anionic surfactant, an amphoteric surfactant, or a nonionic surfactant may be mentioned as the surfactant, and in particular, a nonionic surfactant is preferably used. This is because the nonionic surfactant has low reactivity with surrounding ions (such as lithium ions) and does not interfere with ion conduction in the electrolyte and on the surface of the active material. In the positive electrode mixture of the present invention, the surfactant may be used singly or in combination of two or more.

The cationic surfactant may, for example, be a mono/di long-chain alkyl type quaternary ammonium salt or an alkylamine salt. Further, the anionic interface active agent may, for example, be an alkylbenzenesulfonate, an alkyl sulfate, an alkyl ether sulfate, an alkenyl ether sulfate, an alkenyl sulfate, an α-olefinsulfonate or an α-sulfo group. Fatty acid or its ester salt, alkane sulfonate, saturated fatty acid salt, unsaturated fatty acid salt, alkyl ether carboxylate, alkenyl ether carboxylate, amino acid type surfactant, N-decylamino acid type interface An active agent, an alkyl phosphate or a salt thereof, an alkenyl phosphate or a salt thereof, an alkylsulfosuccinate or the like. The amphoteric surfactant may, for example, be a carboxyl type amphoteric surfactant or a sulfobetaine type amphoteric surfactant.

As the nonionic surfactant, a polyoxyethylene alkyl ether such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene higher alkyl ether or the like is suitable; Polyoxyethylene alkyl aryl ether such as oxyethylene decyl phenyl ether; polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopal Acid ester, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan oil Polyoxyethylene dehydrated sorbate Alcohol fatty acid ester; sucrose fatty acid ester; polyoxyethylene sorbitan fatty acid ester such as tetraoleic acid polyoxyethylene sorbitol; polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene Polyoxyethylene fatty acid esters such as diol distearate, polyethylene glycol monooleate; polyoxyethylene alkylamine; polyoxyethylene hardened castor oil; block of ethylene oxide and propylene oxide Copolymer; sorbitan monolaurate, sorbitan monomyristate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate , sorbitan fatty acid esters such as sorbitan monooleate, sorbitan trioleate, sorbitan sesquioleate, sorbitan distearate; A glycerin fatty acid ester such as stearate, glycerin monooleate, diglycerin monooleate or self-emulsifying glyceryl monostearate; alkylalkanolamine or the like.

In the positive electrode mixture of the present invention, when a nonionic surfactant is used as the surfactant, the nonionic surfactant is preferably a polymer material, and the weight average molecular weight of the nonionic surfactant is preferably 500 or more. . By setting the weight average molecular weight of the nonionic surfactant to 500 or more, the effect of dispersing the positive electrode active material by the surfactant can be favorably exhibited. This is considered to be because the affinity between the solvent and the surfactant is increased by the polymer surfactant, and the solvent is easily held in the vicinity of the particles, so that aggregation between the particles is suppressed. On the other hand, the upper limit of the weight average molecular weight is not particularly limited, and is preferably 100,000 or less. The nonionic surfactant in the positive electrode mixture of the present invention has a suitable weight average molecular weight in the range of 1,000 to 50,000. By setting the weight average molecular weight within this range, the dispersibility of the positive electrode active material becomes better, and The movement of ions will proceed smoothly.

Among the nonionic surfactants, a polyethylene glycol-based surfactant which is high in ion conductivity and can be used as an electrolyte for a lithium ion battery is preferable, and a polyethylene glycol fatty acid ester-based surfactant is preferred. More preferably, it is a stearate of polyethylene glycol. The stearic acid ester of polyethylene glycol has a high viscosity-increasing effect and an excellent effect of preventing sedimentation and aggregation of the active material. Further, by using a polyethylene glycol-based surfactant for coating the active material, the movement of lithium ions in the surfactant can be promoted. Further, in the present invention, the polyethylene glycol-based surfactant refers to a group containing an ethylene glycol chain in the active agent compound.

The surfactant used in the positive electrode mixture of the present invention preferably has an HLB system of 13 to 20, preferably 15 to 20, as measured by the Griffin method. In particular, in the case where the solvent does not use an organic solvent, the HLB system is preferably 16 to 20. When the surfactant having an HLB in this range is used, the hydrophilic group and the hydrophobic group of the surfactant are uniformly arranged, and thus the positive electrode active material having polarity and the binder resin can be uniformly dispersed in water as a solvent. In addition, the Griffin method is based on the formula and molecular weight of the hydrophilic group of the surfactant, and is defined according to the following formula: HLB value = 20 × sum of molecular formula of the hydrophilic portion / molecular weight

In the positive electrode mixture of the present invention, the blending amount of the surfactant is preferably 0.1 to 10 parts by mass, preferably 0.5 to 5 parts by mass, per 100 parts by mass of the positive electrode active material. By setting the blending amount of the surfactant in the above range, dispersibility and coating property of the positive electrode active material in the positive electrode mixture can be obtained. Excellent positive electrode mixture.

<solvent>

The solvent to be used in the positive electrode mixture of the present invention is not particularly limited as long as it is a substance which uniformly disperses the water-dispersible polymer binder resin and the positive electrode active material and interferes with sedimentation and aggregation. Or an organic solvent. Further, in the positive electrode mixture of the present invention, the solvent is particularly preferably water, and an organic solvent may be contained within a range not inhibiting the above effects. Examples of the organic solvent include cyclic aliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; acetone, ethyl methyl ketone, and diisopropyl ketone. a ketone such as cyclohexanone, methylcyclohexane or ethylcyclohexane; a chlorine-based aliphatic hydrocarbon such as methylene chloride, chloroform or carbon tetrachloride; ethyl acetate, butyl acetate, γ-butyl Esters such as lactones and ε-caprolactone; alkanonitriles such as acetonitrile and propionitrile; ethers such as tetrahydrofuran and ethylene glycol diethyl ether; methanol, ethanol, isopropanol, ethylene glycol, ethylene glycol An alcohol such as monomethyl ether; an amide such as N-methylpyrrolidone or N,N-dimethylformamide.

<Other additives>

The positive electrode mixture of the present invention mainly contains a positive electrode active material, a water-dispersible polymer binder resin, a conductive auxiliary agent, and a surfactant, and the others are not particularly limited, and may not affect the battery reaction in addition to the above components. The range contains additives. For example, in the positive electrode mixture of the present invention, in addition to the above components, it may also contain reinforcing materials, tackifiers, defoaming. whole A component such as a flat agent or an electrolyte decomposition inhibitor.

Reinforcing materials can also be used in a variety of inorganic and organic spherical, plate, rod or fibrous fillers. Further, a strong and flexible electrode can be obtained by using a reinforcing material, and excellent long-term cycle characteristics can be imparted. These may be used alone or in combination of two or more. The blending amount of the reinforcing material is usually 0.01 to 20 parts by mass, preferably 1 to 10 parts by mass, per 100 parts by mass of the positive electrode active material. By setting the blending amount of the reinforcing material within the above range, high capacity and high load characteristics can be imparted.

The tackifier is not particularly limited as long as it is a stable solvent for the solvent or electrolyte used in the production of the electrode and other materials used in the battery. For example, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and the like can be used. These may be used alone or in combination of two or more. The blending amount of the tackifier is usually 0.01 to 20 parts by mass, preferably 1 to 10 parts by mass, per 100 parts by mass of the positive electrode active material. By setting the blending amount of the tackifier in the above range, sedimentation and aggregation of the positive electrode active material having a large specific gravity can be favorably prevented.

Defoaming. As the leveling agent, a surfactant such as an alkyl-based surfactant, a polyfluorene-based surfactant, a fluorine-based surfactant, or a metal-based surfactant can be used. By mixing the surfactant, the backlash that occurs during coating can be prevented, and the smoothness of the electrode can be improved. Defoaming. The blending amount of the leveling agent is preferably 0.01 to 5 parts by mass based on 100 parts by mass of the positive electrode active material. By defoaming. The blending amount of the leveling agent is set to the above range, and the coating failure at the time of electrode coating can be prevented to improve productivity.

As the electrolyte decomposition inhibitor, vinylene carbonate or the like used in the electrolytic solution can be used. The blending amount of the electrolytic solution decomposition inhibitor in the electrode is preferably 0.01 to 5 parts by mass based on 100 parts by mass of the positive electrode active material. By setting the blending amount of the electrolytic solution decomposition inhibitor to the above range, the cycle characteristics and the high-temperature characteristics can be further improved. Other examples include nano fine particles such as fumed cerium oxide or fumed alumina. By mixing the nanoparticles, the shake of the mixture for electrode formation can be controlled. The blending amount of the nanoparticles in the positive electrode mixture of the present invention is preferably d.01 to 5 parts by mass based on 100 parts by mass of the positive electrode active material. By setting the blending amount of the nanoparticles in the above range, the mixture stability and productivity can be further improved, and high battery characteristics can be imparted.

<Method for Producing Positive Electrode Mixture>

The positive electrode mixture of the present invention can be obtained by mixing the above positive electrode active material, water-dispersible polymer binder resin, conductive auxiliary agent, surfactant, solvent, and other additives as necessary. In the production of the positive electrode mixture of the present invention, the mixing method is not particularly limited, and for example, a method using a stirring device such as a stirring type, a vibrating type, or a rotary type can be employed. Further, a method of using a dispersion kneading device such as a homogenizer, a ball mill, a sand mill, a roll mill, and a planetary kneader can be employed.

<positive>

Next, the positive electrode for a nonaqueous electrolyte secondary battery of the present invention will be described.

The positive electrode of the present invention is applied to a current collector to apply the above positive electrode mixture of the present invention. Made. The positive electrode of the present invention can be produced by a coating step of applying the positive electrode mixture of the present invention to a current collector, and drying the obtained current collector to form a positive electrode mixture layer. In the positive electrode of the present invention, the positive electrode mixture layer may be formed on one side of the current collector, and is preferably formed on both sides. Hereinafter, the constitution and manufacturing method of the positive electrode of the present invention will be described in detail.

<Collector>

The current collector used in the positive electrode of the present invention is not particularly limited as long as it is electrically conductive and has electrochemical durability, and is preferably a metal material having heat resistance. For example, iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, or the like can be cited. In particular, aluminum or an aluminum alloy is preferred from the viewpoint of less oxidative degradation during charging. The shape of the current collector is not particularly limited, and it is suitable to use a sheet having a thickness of about 5 to 100 μm.

In the positive electrode of the present invention, in order to increase the adhesion strength between the current collector and the positive electrode mixture layer, it is preferred to use a roughening treatment in advance and then use it. Examples of the roughening method include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method. In the mechanical polishing method, a polishing cloth to which abrasive particles are fixed, a grinding stone, a grinding wheel, a wire brush provided with a steel wire, or the like can be used. Further, in order to increase the adhesion strength or conductivity of the electrode layer, an intermediate layer may be formed on the surface of the current collector.

<Coating method>

The method of applying the positive electrode mixture of the present invention to a current collector is not particularly limited, and a known method can be used. The coating method may, for example, be a mold There are a coating method, a knife coating method, a dip coating method, a roll coating method, a spray coating method, a gravure coating method, a screen printing method, and an electrostatic coating method.

<Drying method>

The method of drying the current collector obtained by the above coating method is not particularly limited, and examples thereof include drying by warm air, hot air, low humidity, vacuum drying, and use of (far) infrared rays or electron beams. Drying method of irradiation. The drying time is usually 5 to 30 minutes, and the drying temperature is usually 40 to 180 °C.

<calendering>

In the production method of the present invention, after the coating step and the drying step, it is preferable to subject the calendering step, for example, by press treatment using metal mold calendering or roll calendering, to reduce the void ratio of the positive electrode mixture layer. The void ratio is suitably in the range of 5% to 15%, and the more suitable range is 7% to 13%. When the void ratio exceeds 15%, the charging efficiency or the discharge efficiency is deteriorated, which is not preferable. On the other hand, when the void ratio is less than 5%, there is a concern that it is difficult to obtain a high volume capacity, or the positive electrode mixture layer is easily peeled off by the current collector, and problems such as a problem are likely to occur. Further, in the case where the binder resin is a curable resin, it is preferred to include a step of curing the curable resin.

The thickness of the positive electrode of the present invention is usually 5 to 400 μm, preferably 30 to 300 μm. By setting the thickness of the positive electrode to the above range, a good electrode plate can be obtained with good flexibility and adhesion.

<Non-aqueous electrolyte battery>

Next, the nonaqueous electrolyte secondary battery of the present invention will be described.

The nonaqueous electrolyte secondary battery of the present invention uses the positive electrode of the present invention described above, and has a positive electrode, a negative electrode, a separator, and an electrolytic solution. Hereinafter, the constitution of the nonaqueous electrolyte secondary battery of the present invention and a method for producing the same will be described in detail.

<Negative Electrode for Nonaqueous Electrolyte Battery>

In the negative electrode for a non-aqueous electrolyte battery according to the present invention, a negative electrode mixture slurry can be prepared by mixing a negative electrode active material, a conductive auxiliary agent, a water-dispersible polymer binder resin, a solvent, and other necessary additives. It is applied to a current collector and dried, and it is produced by calendering as necessary.

As long as the negative electrode active material is an active material capable of absorbing and releasing lithium ions, a conventionally used material can be used, and any of a carbon-based active material and a non-carbon-based active material can be used. Examples of the carbon-based active material include graphite, soft carbon, and hard carbon. As the non-carbon-based active material, for example, a known substance such as a lithium metal, a lithium alloy, an oxide, a sulfide, or a lithium-containing metal composite oxide can be used.

As the conductive auxiliary agent and the solvent, the above-mentioned conductive auxiliary agent and the above solvent used in the production of the positive electrode of the present invention can be used. Further, as the binder resin, those generally used for nonaqueous electrolyte batteries such as SBR particles or PVDF resins may be used.

The current collector used for the negative electrode for a non-aqueous electrolyte battery according to the present invention is not particularly limited as long as it has electrical conductivity similar to the positive electrode for a non-aqueous electrolyte battery of the present invention and has electrochemical durability. The same material as the current collector used for the positive electrode for a nonaqueous electrolyte battery of the present invention described above is used.

<electrolyte>

The electrolytic solution used in the present invention is not particularly limited, and for example, an electrolytic solution obtained by dissolving a lithium salt as a supporting electrolyte in a nonaqueous solvent can be used. Examples of the lithium salt include LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlCl ₄ , LiClO ₄ , CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, CF ₃ COOLi, (CF ₃ CO) ₂ NLi, ( CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) NLi or the like. It is particularly suitable to use LiPF ₆ , LiClO ₄ , CF ₃ SO ₃ Li which is easily soluble in a solvent and exhibits high dissociation. These may be used alone or in combination of two or more. The amount of the supporting electrolyte to be added is usually 1% by mass or more, preferably 5% by mass or more, and usually 30% by mass or less, and preferably 20% by mass or less. If the amount of supporting electrolyte is too small or too much, the ionic conductivity will be lowered, and the charging characteristics and discharge characteristics of the battery will be lowered.

The solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte, and dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), and propylene carbonate (PC) can be used. , alkyl carbonates such as butylene carbonate (BC) and methyl ethyl carbonate (MEC); esters such as γ-butyrolactone and methyl formic acid; 1,2-dimethoxyethane Tetrahydrofuran Ethers such as ethers; sulfur-containing compounds such as cyclobutyl hydrazine and dimethyl hydrazine. In particular, since it is easy to obtain high ion conductivity and has a wide temperature range, it is preferably dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate or methyl ethyl carbonate. These may be used alone or in combination of two or more.

Further, other additives may be added to the electrolyte. The additive may, for example, be a carbonate-based compound such as vinylene carbonate (VC) or cyclohexylbenzene or diphenyl ether.

When the electrolyte solution other than the above is used for the nonaqueous electrolyte secondary battery of the present invention, for example, a colloidal polymer electrolyte obtained by immersing a polymer electrolyte such as polyethylene oxide or polyacrylonitrile in an electrolytic solution, or An inorganic solid electrolyte such as lithium sulfide, LiI, or Li ₃ N.

<spacer>

The spacer is a porous substrate having a pore portion, and may be (a) a porous spacer having a pore portion, (b) a porous spacer forming a polymer coating on one or both sides, and (c) The porous separator in which the porous resin coating layer containing the inorganic ceramic powder is formed may, for example, be coated with a polypropylene-based, polyethylene-based, polyolefin-based, aramid-based porous separator, polyvinylidene fluoride, or the like. a polymer electrolyte film for a polyethylene oxide, a polyacrylonitrile, a polyvinylidene fluoride-hexafluoropropylene copolymer, a polymer film for a colloidal polymer electrolyte, and a separator for a colloidal polymer coating, Further, a separator coated with a porous film layer composed of an inorganic filler or an inorganic filler dispersant may be used.

<Method of Manufacturing Nonaqueous Electrolyte Battery>

The method for producing the nonaqueous electrolyte secondary battery of the present invention is not particularly limited. For example, the negative electrode and the positive electrode are stacked with a separator interposed therebetween, and the battery is wound, folded, or the like in accordance with the shape of the battery, and placed in a battery container, and an electrolyte solution is injected into the battery container and sealed. In the nonaqueous electrolyte secondary battery of the present invention, an expansion metal plate, an element for preventing overcurrent such as a fuse or a PTC element, a lead plate, or the like may be added as necessary to prevent an increase in pressure inside the battery and overcharge and discharge. The shape of the battery may be any shape such as a laminated battery type, a coin type, a button type, a sheet type, a cylinder type, a rectangular shape, or a flat type.

[Examples]

The invention will now be described in more detail by way of examples.

<Example 1>

Cellseed NMC-111 (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) manufactured by Nippon Chemical Industry Co., Ltd., which is a ternary active material of a positive electrode active material, has a solid content ratio of 95% by mass, and is a conductive additive. Adeka Bontighter-HUX-822 (polyurethane emulsion resin: solid content 40) manufactured by ADEKA Co., Ltd. as a water-dispersible polymer binder resin, VGCF-H (vapor-grown carbon fiber) having a solid content ratio of 2% by mass Mass %) solid content ratio: 1.5% by mass, EMANON 3299RV (polyethylene glycol distearate) solid content ratio of 1.5% by mass of Kao Corporation as a surfactant, and water as a solvent of 60% by mass of a mixture solid content The mixture was blended and stirred at 1700 rpm for 10 minutes using a propeller to prepare a positive electrode mixture.

The prepared positive electrode mixture was allowed to stand for 24 hours, and then coated on a single side of an aluminum foil having a thickness of 20 μm using a 50 μm coater. Then, it was dried at 150 ° C for 20 minutes in a hot air circulating box type drying oven to remove water as a solvent. After cooling to room temperature, it was sandwiched between 1 mm stainless steel plates, and calendered at a normal temperature for 1 minute using a plate calender at a pressure of 1.5 ton/cm ² to prepare a positive electrode plate having an active material mixture layer having a surface of 80 μm on one side. Among the steps from the preparation of the positive electrode mixture to the production of the positive electrode plate, the dispersibility, the sedimentation and agglomeration stability, the appearance after drying, the adhesion after drying, the appearance of the electrode layer, and the adhesion of the electrode layer. And the resistance value of the electrode layer was evaluated. The details of the evaluation method are as follows. The results obtained are shown in Table 1.

<Examples 2 to 9, Comparative Examples 1, 2>

Stirring and mixing were carried out in the same manner as in Example 1 except that the water-dispersible polymer binder resin, the surfactant, the tackifier, the conductive auxiliary agent, and the positive electrode active material were changed in composition as shown in Tables 1 to 4. A positive electrode mixture was prepared, and the stability of the dispersibility and sedimentation agglutination was evaluated. The positive electrode mixture prepared was applied in the same manner as in Example 1. dry. Calendering was performed to produce a positive electrode plate. The results of the evaluation are combined and described in Tables 1 to 4.

<dispersibility>

When the prepared positive electrode mixture is applied to the positive electrode current collector of the aluminum foil, agglomeration failure, agglomeration of the coarse active material particles which are not dispersed, or agglomeration of the colloidal resin occurs, and a strip appears on the coated surface. The case of the trace was set to "poor", the case where some traces appeared was "ok", and the case where no traces appeared was designated as "good", and visual evaluation was performed.

<sedimentation agglutination stability>

The prepared positive electrode mixture was allowed to stand, and a sedimentation aggregate was generated on the bottom surface of the positive electrode mixture, or the case where the water was separated on the liquid surface was determined to be "defective", and the case where there was no change was determined as "good", and the evaluation was performed.

<Appearance after drying>

After the positive electrode mixture is applied to the positive electrode current collector and dried, the film defect such as foaming or backlash on the surface of the coating film is determined to be "defective", and the case where there is no abnormality is determined as "good", and the coating film is visually observed. Evaluation.

<Adhesiveness after drying>

After the positive electrode mixture was applied to the positive electrode current collector and dried, cross-cutting was performed on the surface of the coating film in accordance with JIS K-5600, and a lattice pattern of 25 squares was cut at intervals of 2 mm, and the case where the intersection point was significantly dropped was determined as "poor. The case where the amount of powder is small is "OK", and the case where there is no powder at all is "good" and is evaluated.

<Appearance of Electrode Layer>

The surface of the electrode plate to be formed was subjected to protrusion or cracking, and the like was determined to be "defective", and the case where it was smooth without an abnormality was determined to be "good", and the surface of the electrode was visually evaluated.

<Adhesion of Electrode Layer>

Using the prepared electrode plate, according to JIS K-5600, a lattice pattern of 25 grids was cut at intervals of 2 mm by a cross-cut method to test the adhesion between the current collector and the active material. The evaluation is carried out in six stages of 0 to 5. The smaller the number, the better the adhesion.

<resistance value of electrode layer>

The surface resistance value was measured using the electric meter (MILLIOHM HITESTER 3540 manufactured by Hioki Co., Ltd.) on the surface of the electrode plate produced.

1) Adeka Bontighter HUX-822 (molecular weight of polyurethane resin: 800,000~900,000) made by ADEKA Co., Ltd.

2) HSV-900 (polyvinylidene fluoride resin) manufactured by Arkema Co., Ltd.

3)Movinyl LDM7523 (acrylic/polyoxyl resin) manufactured by Nippon Synthetic Chemical Co., Ltd.

4) EMANON 3299RV (polyethylene glycol distearate nonionic surfactant HLB: 19.2 molecular weight: about 11200)

5) EMANON 3199V (polyethylene glycol monostearate nonionic surfactant HLB: 19.4 molecular weight: about 6800)

6) EMANON 1112 (polyethylene glycol monolaurate nonionic surfactant HLB: 13.7 molecular weight: about 730)

7) Adekamine 4MAG-30 (cationic surfactant) made by ADEKA Co., Ltd.

8) Daicel CMC#2200 Daicel FineChem Co., Ltd.

9) VGCF-H (vapor-grown carbon fiber) manufactured by Showa Denko Co., Ltd.

10) SP-270 (graphite powder) manufactured by Nippon Graphite Industries Co., Ltd.

11) Cellseed NMC111 (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) manufactured by Nippon Chemical Industry Co., Ltd.

12) LFP (lithium iron phosphate: LiFePO ₄ )

13) NMP (N-methylpyrrolidone)

In the positive electrode mixture of the present invention, the positive electrode active material of the present invention is excellent in dispersibility, storage stability, and coating property to a current collector, and the positive electrode mixture layer and set of the positive electrode produced using the mixture are used. The electrical body is excellent in adhesion. In the case of the comparative example, it was observed that the dispersion was good in the mud state, but coarse particulate agglomerates remained, and the dispersibility was poor, and it was difficult to form a coating film.

Claims (5)

A positive electrode mixture comprising a positive electrode active material, a water-dispersible polymer binder resin, a conductive auxiliary agent, and a surfactant. The positive electrode mixture of claim 1, wherein the surfactant has an HLB value of 13.0 to 20.0. The positive electrode mixture of claim 1 or 2, which contains water as a solvent. A positive electrode, which is characterized in that the current collector is coated with a positive electrode mixture according to any one of claims 1 to 3. A nonaqueous electrolyte secondary battery characterized by using a positive electrode as in the fourth aspect of the patent application.