JP2000048805A - Manufacture of positive electrode or negative electrode for nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a positive electrode or a negative electrode for a nonaqueous electrolyte secondary battery, which can easily provide the nonaqueous electrolyte secondary battery which can be used suitably for a mobile power source for a portable electronic equipment, and has high capacity, improved charge and discharge characteristics and high capacity maintenance rate in long repeated use. SOLUTION: Coating liquid comprising an active material, a binder and a solvent dispersed therein is applied as coating onto a collector. The collector is then dried up with the coated surface faced down. The binder is preferably composed of particulate resin of 0.05-100 μm particle size, and the particulate resin is further preferably made of configuration swollen by the solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a positive electrode or a negative electrode of a non-aqueous electrolyte secondary battery capable of easily obtaining a non-aqueous electrolyte secondary battery having high capacity and excellent charge / discharge characteristics.

[0002]

2. Description of the Related Art In recent years, with the spread of portable electronic devices such as portable video cameras and portable personal computers, demand for batteries as a portable power supply has been rapidly increasing. Furthermore, there is a very high demand for such batteries to be reduced in size, weight, and high energy density, and in response to such demands, lithium, which is a negative electrode active material, has been converted to a negative electrode active material by a chemical or physical method. A non-aqueous electrolyte secondary battery in which a carbon material as a support is used as a negative electrode and a composite oxide of lithium as a positive electrode active material is used as a positive electrode has attracted attention.

[0003] In the battery structure, a limited space is filled with as much active material as possible, and a positive electrode and a negative electrode are formed in a strip shape in order to withstand use under heavy load.
It is preferable to form a spiral wound electrode body structure that is formed by winding in the length direction through a band-shaped separator. In order to have such a structure, the positive electrode and the negative electrode need to be flexible and have a thin film shape.

A non-aqueous electrolyte secondary battery having a flexible, thin-film electrode is disclosed, for example, in JP-A-4-24.
No. 9860 discloses that a carbon material provided on a metal foil as a current collector with polyvinylidene fluoride as a binder is used as a negative electrode, and a composite oxide of lithium is provided on a metal foil with polyvinylidene fluoride. A non-aqueous electrolyte secondary battery using the battery as a positive electrode is disclosed.

[0005] However, in the nonaqueous electrolyte secondary battery described in the above publication, when the charge and discharge are repeated several hundred times or more, the carbon material or the composite oxide is peeled off from the metal foil or cracks are generated on the electrode surface. For this reason, the capacity is reduced, so that long-term repeated use is difficult.

To solve this problem, Japanese Patent Application Laid-Open No. Hei 9-18596
No. 0 publication discloses that an active material layer is formed by applying and drying a coating solution comprising an active material and a binder on a current collector surface,
Overcoating using two or more types of coating liquids in which the ratio of the binder in the coating liquid applied first is greater than the ratio of the binder in the coating liquid applied later A method of changing the composition of an active material layer in the thickness direction has been proposed. JP-A-9-
JP-A-320569 also discloses a method of bonding a current collector and an active material layer by changing the composition and structure of the active material layer and the particle size and type of the active material. However, these methods complicate the steps required for coating and the design of the active material. Also, since the specific gravity of the active material is larger than that of the binder or the solvent, sedimentation tends to occur in the coating film before and during drying, and the amount of the binder at the contact point between the current collector and the active material layer should be increased. It is difficult.

[0007]

SUMMARY OF THE INVENTION In view of the above, the present invention can be suitably used as a portable power source for portable electronic devices, etc., has a high capacity, has excellent charge / discharge characteristics, and can be used for a long period of repeated use. An object of the present invention is to provide a method for manufacturing a positive electrode or a negative electrode of a nonaqueous electrolyte secondary battery, which can easily obtain a nonaqueous electrolyte secondary battery having a high capacity retention rate.

[0008]

According to the first aspect of the present invention, a current collector is coated with a coating liquid in which an active material, a binder and a solvent are dispersed, and the coated surface faces downward. And producing a positive electrode or a negative electrode of a non-aqueous electrolyte secondary battery.

According to a second aspect of the present invention, there is provided the positive electrode or the negative electrode of the non-aqueous electrolyte secondary battery according to the first aspect, wherein the binder comprises a particulate resin having a particle size of 0.05 to 100 μm. It is a manufacturing method of.

According to a third aspect of the present invention, there is provided the method for producing a positive electrode or a negative electrode of a non-aqueous electrolyte secondary battery according to the second aspect, wherein the particulate resin has a form swollen by a solvent. The coating liquid used in the present invention has an active material, a binder, and a solvent dispersed therein. If necessary, a conductive additive may be added to the coating liquid.

[0011] When the positive electrode active material above active material for the positive electrode, usually, and the general formula LiMO2 (where, M represents at least one selected Co, Ni, from the group consisting of Mn and V), Lix MyMn2 -y
O4 (wherein, M represents at least one selected from the group consisting of Cr, Co, Ni and Mn. 0 <x≤1,
0 <y ≦ 2) or a composite oxide represented by LiVO5 is used.

The composite oxide represented by LiMO2 is not particularly limited, and examples thereof include a lithium-cobalt composite oxide, a lithium-nickel composite oxide, a lithium-cobalt-nickel composite oxide, and a lithium-manganese composite oxide. And a lithium-vanadium composite oxide. The composite oxide represented by Lix My Mn2-y O4 is not particularly limited, and examples thereof include lithium-manganese-chromium composite oxide, lithium-manganese-cobalt composite oxide, and lithium-manganese-nickel composite oxide. No.

These may be used alone or in combination of two or more. When two or more of the above lithium oxides are used in combination, they may be used in the form of a mixture or may be used as a solid solution. In the present invention, lithium-cobalt composite oxide, lithium
Nickel composite oxide, lithium-cobalt-nickel composite oxide, and lithium-manganese composite oxide are preferably used.

The anode active material above active material for negative electrode, usually, crystalline or low-crystalline carbon material is used. In the present invention, the negative electrode is made of a mixture of a crystalline or low-crystalline carbon material and a negative electrode binder. As the crystalline carbon material, X
It is preferable that the spacing between (002) planes in line diffraction is 3.7 Å or more. If it is less than 3.7 angstroms, the doping amount of lithium is small, and the current capacity per unit weight of carbon is small. The crystalline carbon material is not particularly limited, for example, natural graphite,
Artificial graphite, carbon fiber, and coke such as pitch coke and needle coke.

The crystalline carbon material is, for example, 700 to
It can be produced by carbonizing an organic material by a method such as firing at a temperature of about 3000 ° C. The organic material is not particularly limited, for example, furan resin composed of a homopolymer of furfuryl alcohol or furfural, furan resin composed of a copolymer of furfuryl alcohol and furfural, cellulose, phenol resin, acrylic resin such as polyacrylonitrile, poly Examples thereof include a halogenated vinyl resin such as vinyl chloride, a polyamideimide resin, a polyamide resin, and an organic polymer compound such as polyacetylene and polyparaphenylene. Among them, in the present invention, a furan resin composed of a homopolymer of furfuryl alcohol or furfural and a furan resin composed of a copolymer of furfuryl alcohol and furfural are preferably used.

Further, as the organic material, a petroleum pitch having a hydrogen atom / carbon atom ratio of 0.6 to 0.8 is used,
By subjecting this to oxygen crosslinking for introducing a functional group containing oxygen, a precursor having an oxygen content of 10 to 20% by weight is obtained, and then a crystalline carbon material obtained by firing this precursor is also used. It is preferably used.

Further, as the organic material, for example, two or more monocyclic hydrocarbon compounds having three or more ring members such as naphthalene, phenanthrene, anthracene, triphenylene, pyrene, chrysene, naphthacene, picene, pyrylene, pentaphene, and pentacene are used. Condensed cyclic hydrocarbon compounds formed by condensation, derivatives thereof; 3-membered or more heterocyclic heterocyclic compounds such as indole, isoindole, quinoline, isoquinoline, quinoxaline, phthalazine, carbazole, acridine, phenazine, phenanthridine and the like. Condensed heterocyclic compounds formed by condensing at least two or more heterocyclic monocyclic compounds having three or more rings with one or more monocyclic hydrocarbon compounds having three or more rings, or derivatives thereof; Can also be used.

Examples of the low crystalline carbon material include a graphitizable carbon material and a non-graphitizable carbon material. The graphitizable carbon material is obtained by performing a heat treatment at 500 to 1000 ° C. using tar pitch obtained from petroleum or coal as a raw material. Also,
The non-graphitizable material is obtained by firing and carbonizing an organic compound such as a phenol resin, and has a turbostratic structure in which carbon net surfaces are randomly stacked. This is because graphitization does not proceed even if the heat treatment temperature is increased, and the interlayer distance is considerably wider than natural graphite.

Binders Examples of the binder include polyester resin, polyamide resin, polyacrylate resin, polycarbonate resin, polyurethane resin, cellulose resin, polyolefin resin, polyvinyl chloride resin, polyvinyl butyral resin, polyvinylidene fluoride, and the like. A thermoplastic resin such as a fluororesin such as polytetrafluoroethylene or polyhexafluoroethylene, or a rubber-based resin, an acrylate monomer or an oligomer, or a homopolymer obtained by polymerizing a mixture thereof, or obtained by copolymerized fat. Can be used. These resins can be used alone or as a mixture of two or more. As the binder in the present invention, a polyamide elastomer, which is a kind of polyamide resin, is preferable among the above binders, and this point will be described in detail later.

Solvent The solvent is not particularly restricted but includes water, alcohols such as methanol, ethanol, propanol and butanol, ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, ethylene glycol monomethyl ether,
Glycols such as ethylene glycol monoethyl ether; aromatic hydrocarbons such as toluene and xylene; esters such as ethyl acetate, propyl acetate and butyl acetate; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran and dioxane; Formamide,
Use is made of amides such as N, N-dimethylformamide, N, N-dimethylacetamide, N, N-dimethylacetylacetamide, pyrrolidone, N-methylpyrrolidone, and halogenated hydrocarbon compounds such as chloroform, carbon tetrachloride, and tetrachloroethane. it can. These solvents and liquid dispersants can be used alone or as a mixture of two or more.

Conductive Aids Examples of the conductive aid include carbon compounds such as graphite, carbon black, acetylene black and carbon fiber, and conductive polymers such as polyaniline and polypyrrole.

[0022] In a specific gravity above coating liquid is preferably the specific gravity of the components consisting of the solvent and the binder is less than 0.98 times the density of the active material, more preferably 0.95 times or less . The above ratio is 0.98 or less in a usual combination of a solvent and a binder. For example, when N-methylpyrrolidone is used as a solvent, a polyamide elastomer is used as a binder, and a carbon material is used as an active material, the value is about 0.4 to 0.7. The present invention
By positively utilizing this property, the amount of the binder present at the interface between the current collector and the active material layer is increased to prevent peeling due to charge and discharge, thereby enabling long-term use.

Current Collector Metal foil is usually used as the current collector in the present invention. The material of the metal foil is not particularly limited. For example, gold, silver, copper, nickel, so-called stainless steel (for example, S
US), aluminum and the like. The metal foil having a thickness of several μm to several hundred μm is preferably used.

Coating conditions The method for preparing a coating solution from the above active material, binder and solvent is not particularly limited. Usually, a planetary stirring device is prepared by adding an active material and a binder to a solvent. , A planetary mixer, a disperser, a sand mill, a ball mill, a kneader and the like. The method for applying the coating liquid to the current collector is not particularly limited, and a doctor blade, a knife coater, an applicator, a comma coater, a gravure coater, a roll coater, a lip coater, or the like can be used.
The viscosity of the coating liquid is preferably from 500 to 40,000 cps when measured at 1 rpm using an E-type viscometer. This is because if the viscosity is too low, the coating liquid tends to drip when the liquid is turned downward, and if the viscosity is too high, the workability deteriorates.

Drying conditions The drying method is not particularly limited, and hot air, infrared rays, far infrared rays and the like can be used. The temperature is preferably 30 to 200 ° C.,
-180 ° C is more preferred, and 80-160 ° C is even more preferred. Further, drying under reduced pressure can be further performed as necessary. Further, a method of performing pressure pressing using a roll press after forming the electrode coating film may be employed.

Polyamide-based Elastomer As the binder in the present invention, among the above-mentioned binders, a polyamide-based elastomer, which is a kind of polyamide-based resin, is preferable in terms of achieving both flexibility and adhesiveness. In the present invention, the polyamide-based elastomer refers to a thermoplastic elastomer having a polyamide content of 5 to 90% by weight, and a polyamide as a hard segment responsible for physical crosslinking and a polyether as a soft segment responsible for elastomer properties. And a block copolymer composed of an aliphatic polyester.

Commercially available polyamide-based elastomers used in the present invention include, for example, Mitsubishi Chemical Corporation (trade name "NOVAMID PAE"), Ube Industries, Ltd. (trade name "PAE"), and Daicel Huls ( Product name "Diamid PAE"), manufactured by Toray Industries (product name "Pebax"),
And Dainippon Ink Co., Ltd. (trade name “Greak A”).

As the polyamide-based elastomer,
At least one selected from dicarboxylic acids represented by the following general formula (1) and at least one selected from diols represented by the following general formula (2), and a reduced viscosity (1 g / d
L98% sulfuric acid solution, measured at 20 ° C.) is 0.5 to 7 dL /
It is preferable to use a polyesteramide obtained by reacting g with the polyamide.

HOOC-R1-COOH (1) wherein R1 is an alkylene group having 2 to 8 carbon atoms.

HO-R2-OH (2) wherein R2 is an alkylene group having 2 to 6 carbon atoms.

The dicarboxylic acid represented by the above general formula (1) is not particularly restricted but includes, for example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid,
Suberic acid, azelaic acid, sebacic acid and the like can be mentioned.

In the present invention, various other dicarboxylic acids can be appropriately used in combination with the dicarboxylic acid represented by the general formula (1) as long as the physical properties of the obtained polyamide elastomer are not impaired.

The diol represented by the above general formula (2) is not particularly restricted but includes, for example, ethylene glycol,
Examples thereof include 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, and 1,6-hexanediol. Among these, a branched diol such as 1,2-propanediol and neopentyl glycol is preferably used in order to improve the flexibility of the obtained polyamide elastomer.

In addition to the diol represented by the general formula (2), glycol and polyalkylene oxide can be appropriately used as a diol component as long as the physical properties of the obtained polyamide elastomer are not impaired. .

The glycol is not particularly restricted but includes, for example, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, cyclopentane-1,2-diol. Diol, cyclohexane-1,2-diol, cyclohexane-
Examples thereof include 1,3-diol, cyclohexane-1,4-diol, and cyclohexane-1,4-dimethanol.

The polyalkylene oxide is not particularly restricted but includes, for example, polyethylene oxide, polypropylene oxide, polytetramethylene oxide, polyhexamethylene oxide and the like.

In addition to the above-mentioned dicarboxylic acids and diols, a trifunctional or higher functional carboxylic acid or a trifunctional or higher functional polyol can be appropriately used in combination as long as the physical properties of the obtained polyamide elastomer are not impaired.

As the above trifunctional or higher carboxylic acid, for example, trimellitic acid or benzenetetracarboxylic acid is preferable, and as the trifunctional or higher functional polyol, for example,
Trimethylolpropane, pentaerythritol and the like are preferred. The amount of the above trifunctional or higher carboxylic acid or trifunctional or higher functional polyol to be used is preferably 0.01 to 2% by weight based on the total amount of the above dicarboxylic acid and diol.

The polyamide has an amide bond in the main chain of the polymer, and is soluble in dicarboxylic acids and diols, which are constituents of polyester, and
Those which can be heated and melted are preferred.

The reduced viscosity of the polyamide is 0.5 to 7
dL / g (1 g / dL 98% sulfuric acid solution, measured at 20 ° C.)
Is preferred. If it is less than 0.5 dL / g, the resulting polyesteramide will have insufficient mechanical strength at high temperatures, and
If it exceeds L / g, the solubility will decrease and the synthesis will be difficult. The molecular weight of the polyamide is 1,000 to 60,0.
00, more preferably 2,000 to 50,000.
00.

The polyamide is not particularly restricted but includes, for example, 4-nylon, 6-nylon, 6,6-nylon, 11-nylon, 12-nylon, 6,10-nylon.
Aliphatic nylons such as nylon and 6,12-nylon; dicarboxylic acids such as isophthalic acid and terephthalic acid, metaxylylenediamine, 2,2-bis (paraaminocyclohexyl) propane, and 4,4'-diaminodicyclohexylmethane; Aromatic, alicyclic or side-chain substituted aliphatic diamines such as 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine,
Examples include polycondensed polyamides.

The content of the polyamide in the polyesteramide is preferably 5 to 90% by weight, more preferably 10 to 85% by weight. If the polyamide content is less than 5% by weight, the resulting polyesteramide will have insufficient mechanical strength, and if it exceeds 90% by weight, the hard segment content will increase and the polyesteramide will be hardened and will have good rubber elasticity. It tends to be impossible to obtain.

The polyester amide can be synthesized by any method, and is obtained, for example, by polymerizing a dicarboxylic acid and a diol in the presence of a polyamide. This polymerization reaction is usually performed in a two-stage reaction consisting of an esterification reaction and a polycondensation reaction.

The first stage of the esterification reaction is carried out in a transparent and homogeneous solution by dissolving the above polyamide in dicarboxylic acid and diol which are raw materials for the polyester component.
In a heterogeneous state, the reaction does not proceed efficiently. The melting temperature is preferably from 150 to 230C. If the temperature is lower than 150 ° C., it is difficult to dissolve, and if the temperature exceeds 230 ° C., a decomposition reaction may occur.

The second stage polycondensation reaction is preferably carried out under reduced pressure, preferably at 10 mmHg or less, at a temperature of 180 to 260 ° C. When the temperature is lower than 180 ° C., the reaction rate is low and the polymerization viscosity is high, so that efficient polymerization becomes difficult. When the temperature is higher than 260 ° C., a decomposition reaction or coloring may occur.

In the above polycondensation reaction, it is preferable to charge 1.2 to 3 moles of the diol per 1 mole of the dicarboxylic acid. For 1 mole of the dicarboxylic acid,
When the amount of the diol is less than 1.2 mol, the esterification reaction does not proceed efficiently. When the amount of the diol is more than 3 mol, the excess diol component is used, which is disadvantageous in terms of cost. Since the reaction easily occurs, the blocking property is reduced, and the heat resistance is reduced.

In the above-mentioned polycondensation reaction, a catalyst usually used in the production of polyester may be used. The catalyst is not particularly limited and includes, for example, lithium, sodium, potassium, cesium, magnesium, calcium, barium, strontium, zinc, aluminum,
Titanium, cobalt, germanium, tungsten, tin,
Metals such as lead, antimony, arsenic, cerium, boron, cadmium, manganese, and zirconium; and organic metal compounds, organic acid salts, metal alkoxides, and metal oxides thereof. These may be used alone,
More than one species may be used in combination.

Among the above catalysts, particularly, calcium acetate,
Stannous diacyl, stannous tetraacyl, dibutyltin oxide, dibutyltin dilaurate, dimethyltin malate, tin dioctanoate, tin tetraacetate, triisobutylaluminum, tetrabutyltitanate, tetrapropoxytitanate, titanium (oxy) acetylacetate, germanium dioxide , Tungstic acid, antimony trioxide and the like are preferably used.

[0049] In the particle size present invention of the binder, as described in claim 2, it is preferred that the binder consists of particulate resin having a particle size 0.05～100Myuemu. When the binder is in the form of particles, the thixotropy of the coating liquid is increased, so that the coating liquid is prevented from dripping even when the coating surface faces downward.

The particle size is preferably 0.05 to 100 μm, more preferably 0.08 to 50 μm, and still more preferably 1 to 20 μm. If the particle size is less than 0.05 μm, it is difficult to exhibit the effect of suppressing dripping against the coating liquid, and if it exceeds 100 μm, it is difficult to uniformly mix the active material. The particulate resin can be obtained by pulverizing the resin, or by a method such as suspension polymerization, emulsion polymerization, seed polymerization, or phase separation from a resin solution.

Form of Binder and Solvent In the present invention, the particulate resin is preferably in a form swollen by a solvent. By adopting such a form, many active materials can be bound with a small amount of the binder. The solvent used for preparing the gel particles swollen by the solvent in the polyamide elastomer is preferably one having a low solubility in the polyamide elastomer at room temperature and a high solubility at high temperature. The index of solubility is preferably 7% or less at 23 ° C, more preferably 5% or less, and 100% or more preferably 10% or more, more preferably 12% or more.

Therefore, a suitable solvent differs depending on the polyamide elastomer used. When the above polyesteramide is used, examples of suitable solvents in terms of solubility include cyclic amides such as N-methylpyrrolidone;
Linear amides such as dimethylformamide and N, N-dimethylacetamide; aromatic hydrocarbons such as anisole, toluene and xylene; alcohols such as butanol and cyclohexanol. These solvents may be used alone or in combination of two or more.

In preparing the gel particles of the polyamide elastomer, a solvent having a low solubility at a high temperature of the polyamide elastomer may be added to the solvent. As such a solvent having a low solubility at a high temperature, for example,
Halogenated hydrocarbons such as carbon tetrachloride, trichloroethylene and chloroform; ketones and esters such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, ethyl acetate and butyl acetate; ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, diethylene glycol monomethyl ether; Ethers such as diethylene glycol dimethyl ether; and alcohols such as methanol, ethanol and isopropanol. These may be used alone or in combination of two or more.

The polyamide elastomer gel particles are prepared, for example, by the following method. It is preferable to dissolve the polyamide-based elastomer at a high temperature in a solvent having low solubility at room temperature and increasing at a high temperature. The dissolution temperature is not particularly limited as long as it is a temperature at which the solubility required for uniform dissolution is obtained. If dissolved above the boiling point of the solvent,
It is preferable to use a pressure-resistant container such as an autoclave. The dissolution temperature is preferably 50 ° C, more preferably 60 to 240 ° C, and still more preferably 80 to 240 ° C.
200 ° C.

Next, the temperature of the polyamide elastomer solution obtained at a high temperature is lowered while stirring. At this time, if the stirring is not carried out, the polyamide elastomer tends to be in a solid gel state as a whole, and a granular elastomer cannot be obtained. Further, the particle size of the gel particles can be adjusted by the stirring speed, and the higher the stirring speed, the smaller the gel particles become.

If the rate of lowering the temperature of the polyamide-based elastomer solution, that is, the temperature-fall rate exceeds 50 ° C./hour, uniform temperature reduction becomes impossible, and coarse polyamide elastomer gel particles are formed. Speed is 5
0 ° C./hour or less is preferred. Normally, when cooling at room temperature, the cooling rate exceeds 50 ° C./hour. Therefore, it is preferable to control the cooling rate by performing heating or the like.
For example, when the above gel particles are prepared in a cylindrical container having a diameter of 10 cm using a stirring blade having a clearance of 2 mm between the inner wall of the container (the distance between the inner wall and the stirring blade), the stirring speed is 50 rpm. Or more, more preferably 80 rpm or more.

Battery Assembly The above-mentioned negative electrode and the above-mentioned positive electrode can be formed into a sheet shape, a square shape, a cylindrical shape, or the like, and can be used as an electrode of the secondary battery of the present invention. In this case, the negative electrode is opposed to the positive electrode via the separator. For example, a strip-shaped positive electrode, a separator, a negative electrode, and a separator may be sequentially stacked and wound from the end of the strip to form a cylindrical shape.

Other Battery Components For the separator, a material having excellent liquid retention properties is used. Such is not particularly limited, for example,
A nonwoven fabric of a polyolefin-based resin may be used. These are preferably used after being impregnated with an electrolytic solution.

As the electrolyte for the non-aqueous electrolyte secondary battery of the present invention, an electrolyte in which an electrolyte is dissolved in an organic solvent is used. The organic solvent is not particularly limited, for example,
Examples thereof include carbonates, sulfolane, chlorinated hydrocarbons, ethers, esters, ketones, lactones, and nitriles. Specific examples include, for example, propylene carbonate, ethylene carbonate, butylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolan, 4- Methyl-1,3-dioxolan, methyl formate, methyl acetate, methyl propionate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, and the like. These may be used alone or in combination of two or more.

The electrolyte is not particularly restricted but includes, for example, LiClO 4, LiPF 6, LiBF 4, LiBP
h4, LiCl, LiBr, MeSO3 Li, CF3 S
O3Li, LiAsF6, Li (CF3 SO) 2N, Li
C4F9SO3 and the like. In the formula, Ph represents a phenyl group, and Me represents a methyl group.

(Function) The present invention is characterized in that a coating liquid in which an active material, a binder and a solvent are dispersed is applied to a current collector, and the current collector is dried with the coated surface facing down. I do. In general, the specific gravity of the active material is larger than that of the binder or the solvent.By drying the coated surface on the lower side, the active material in the active material layer increases as the distance from the current collector increases. The closer the agent to the current collector, the more the agent, and the better the adhesiveness. That is,
Adhesion between the coating film containing the active material and the current collector is improved, and peeling of the active material from the current collector during production of the nonaqueous electrolyte secondary battery can be prevented.

Therefore, according to the method of the present invention, high capacity, excellent charge / discharge cycle characteristics, and repetitive use for a long period of time are possible. For example, high capacity can be maintained even in several hundred charge / discharge cycles. A water electrolyte secondary battery is obtained, and can be suitably used for portable video cameras, portable personal computers, portable telephones, transceivers, cameras, headphone stereos, portable televisions, and the like.

According to a second aspect of the present invention, the binder is made of a particulate resin having a particle size of 0.05 to 100 μm. The more the active material becomes farther away from the current collector, the more the binder becomes closer to the current collector, so that the above-mentioned action is surely exhibited, and the adhesiveness is further improved, so that a more excellent effect is brought about.
The present invention according to claim 3 is characterized in that the particulate resin has a form swollen by a solvent. According to the present invention, the active material in the active material layer is separated from the current collector. In addition to the above-mentioned effect of increasing the number of binders and increasing the amount of binder near the current collector, the adhesiveness is improved and an even more excellent effect is brought about.

[0064]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. (1) Synthesis of polyamide elastomer (A) 146 parts by weight of adipic acid, 108 parts by weight of butylene glycol, 125 parts by weight of neopentyl glycol [butylene glycol / neopentyl glycol = 50/50 (molar ratio), adipic acid at the time of preparation Component / diol component = 1
/2.4 (molar ratio)], 6-nylon (T
3.5 dL reduced viscosity at 20 ° C. in 850, 98% sulfuric acid
/ G) 120 parts by weight, tetrabutyl titanate 0.25 parts by weight as a catalyst, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4) as a stabilizer
-Hydroxybenzyl) benzene (0.4 parts by weight) and tris (2,4-di-t-butylphenyl) phosphite (0.4 parts by weight) were added, and the reaction system was heated at 200 ° C. under a nitrogen atmosphere.
The temperature rose. After 10 minutes, the 6-nylon dissolved and became a clear solution.

The esterification reaction was carried out at this temperature for another hour. The progress of the esterification reaction was confirmed by measuring the amount of distilled water. After the progress of the esterification reaction, the temperature was raised to 240 ° C. in 20 minutes, and the pressure was reduced. The polymerization system reached a reduced pressure of 1 mmHg or less in 10 minutes. In this state, a polycondensation reaction was performed for 1 hour to obtain 327 parts by weight of a transparent polyesteramide.

(2) Polyamide elastomer (B)
Instead of 120 parts by weight of synthetic 6-nylon T850 (manufactured by Toyobo), 6-nylon A1050 (2% in 98% sulfuric acid)
(Reduced viscosity at 0 ° C. 6.2 dL / g, manufactured by Unitika) 40
607 parts by weight of a polyesteramide was obtained in the same manner as in the polyesteramide (A) except that 0 part by weight was used.

With respect to the polyamide elastomers (A) and (B), intrinsic viscosity [η], polyamide content, melting point and heat of crystal fusion were measured by the following methods, and the results are shown in Table 1. (A) Intrinsic viscosity [η] of polyamide-based elastomer In o-chlorophenol using an Ubbelohde viscosity tube,
It was measured at 30 ° C. (B) Polyamide content (% by weight) It was calculated from the weight of the polyamide at the time of charging with respect to the weight of the produced amide-based elastomer. (C) Melting point and heat of crystal fusion First, from room temperature to 2 ° C using a differential scanning calorimeter (DSC).
After the temperature was raised to 40 ° C., and then the temperature was lowered to −100 ° C. at a rate of 20 ° C./min, the measurement was performed at a rate of 10 ° C./min.

[0068]

[Table 1]

(3) Preparation of Gel Particle Dispersion (a) 5 parts by weight of polyamide elastomer (A) and 95 parts by weight of N-methylpyrrolidone (hereinafter abbreviated as NMP) were equipped with a reflux tower and a stirrer. The NMP solution of the polyamide elastomer (A) was prepared in a flask at 180 ° C. for 1 hour under a nitrogen stream. Heating was performed to control the cooling rate, and stirring was performed while maintaining the cooling rate at 20 ° C./hour, followed by cooling to room temperature to obtain a gel particle dispersion (a). The solution became turbid from 90 ° C. to 50 ° C., and precipitation of gel-like particles (a1) was observed.

The particle size of the gel-like particles (a1) was measured with a phase-contrast microscope and found to be 2.5 μm. The gel particle dispersion (a) was coated on a glass plate with a 200 μm doctor blade and dried in an air circulating oven at 150 ° C. for 5 minutes to obtain a uniform film having a thickness of 10 μm. Was.

(4) Preparation of Gel Particle Dispersion (b ) 5 parts by weight of polyamide elastomer (B) and NMP9
5 parts by weight were charged into a flask equipped with a reflux tower and a stirrer, and were placed in a nitrogen stream at 180 ° C. for 1 hour. An NMP solution of the polyamide elastomer (B) was prepared over 5 hours. Heating was performed to control the cooling rate, and the mixture was stirred while maintaining the cooling rate at 20 ° C./hour, and cooled to room temperature. 100 ℃
To 60 ° C., the solution became turbid, and precipitation of gel-like particles (b1) was observed. Next, the gel-like particles are centrifuged.
The gel-like particles obtained by separating (b1) from the sol component (b
1) was washed with NMP to recover gel-like particles (b1).
The particle size of the recovered gel particles (b1) was measured by a phase contrast microscope and found to be 2 μm. Further, the sol component is a polyamide-based elastomer, and the solid content NM
It was confirmed from R and IR spectra.

50 parts by weight of the gel particles (b1) were added to 50 parts by weight of xylene, and the mixture was stirred with a planetary stirrer to obtain a uniform gel particle dispersion (b). The particle size of the gel particles (b2) in the gel particle dispersion (b) was measured by a phase contrast microscope and found to be 1.5 μm. This gel-like particle dispersion (b) was coated on a glass plate with a doctor blade of 200 μm, and was coated in an air-circulating oven at 100 μm.
After drying at 5 ° C. for 5 minutes, a uniform film having a thickness of 5 μm was obtained.

Example 1 Natural graphite (“L” manufactured by Nippon Graphite Co., Ltd.)
B-CG ", 95 parts by weight of a negative electrode active material) powder, and gel-like particle dispersion (a) (binder dispersion for electrode coating film) 10
0 parts by weight were mixed and dispersed to obtain a slurry negative electrode coating solution. The viscosity of the coating solution was 15000 cps (E-type viscometer, 23 ° C., 1 rpm). The coating solution for a negative electrode was applied to a copper foil having a thickness of 10 cm × 30 cm × 15 μm, and then dried in an oven at 120 ° C. with the coated surface facing down to evaporate the solvent to prepare a negative electrode.

Separately, 0.5 mol of lithium carbon and 1 mol of carbon cobalt were mixed and calcined in air at 900 ° C. for 5 hours to obtain LiCoO 2. Li obtained
90 parts by weight of CoO2 and 5 parts by weight of acetylene black as a conductive agent are dispersed in 100 parts by weight of the gel particle dispersion (a) (binder dispersion for electrode coating), and a slurry-like coating solution for the positive electrode is dispersed. I got The viscosity of the coating liquid is 30,000 cps
(E-type viscometer, 23 ° C., 1 rpm). This coating solution for a positive electrode was applied to an aluminum foil having a thickness of 10 cm × 30 cm × 15 μm, and then was applied at 105 ° C. with the coated surface facing down.
After drying in an oven, the solvent was evaporated to produce a positive electrode.

Non-aqueous electrolytic solution [dissolved in a microporous propylene film separator at a ratio of 1 mol of lithium salt (LiPF6) to 1 mol of an equivalent mixture of propylene carbonate and 1,2-dimethoxyethane] After impregnation, the negative electrode and the positive electrode were arranged via the separator to prepare a test battery.

Example 2 Example 2 was repeated except that the gel particle dispersion (b) was used instead of the gel particle dispersion (a) as a binder and a solvent for the positive and negative electrodes. A test battery was prepared and evaluated in the same manner as in Example 1.

Example 3 A gel particle dispersion (b) was used instead of the gel particle dispersion (a) as a binder and a solvent for the positive and negative electrodes. A test battery was prepared and evaluated in the same manner as in Example 1, except that the amount used in was changed to 200 parts by weight.

Comparative Example 1 An NMP solution of polyvinylidene fluoride (“KF-1300” manufactured by Kureha Chemical Co., Ltd.) for the positive and negative electrodes instead of the gel particle dispersion (a) as a binder and a solvent. And a test battery was prepared and evaluated in the same manner as in Example 1 except that drying was performed in an oven with the coated side facing up. The performance of the test battery obtained above was evaluated with respect to the following items, and the results are shown in Table 2.

(1) Discharge capacity (Ah / kg) After charging the test battery at a constant voltage of 4.2 V for 5 hours, 1 m
The charge / discharge cycle was repeated, with one cycle of discharging at a constant current of A / cm @ 2 at a final voltage of 2.75 V, and the discharge capacity at the tenth cycle was measured.

(2) Capacity maintenance rate (%) After charging the test battery at a constant voltage of 4.2 V for 5 hours, 1 m
The charge / discharge cycle was repeated with one cycle of discharging at a constant current of A / cm 2 at a final voltage of 2.75 V. The discharge capacity at the 10th cycle and the discharge capacity at the 300th cycle were measured. And the ratio of the 10th cycle (300 cycles / 10 cycles) was expressed in percentage.

(3) Adhesiveness of coating film A 10 × 10 square was put on the coating surface with a knife, and a cellophane tape was stuck thereon with a rubber roller having a width of 3 cm and 2 kg, and the coating film after the cellophane tape was peeled off. And the number of remaining coating films were examined. The state in which the coating film was broken between the active materials was referred to as material destruction, and the state in which the coating film was peeled off on the surface of the metal foil was referred to as interface peeling. (4) Distribution of Binder Amount in Coating Film The coating film was cut to a depth of about 40 μm from the side remote from the current collector and from the side in contact with the current collector, and the binder was removed at 160 ° C. Extracted with NMP, and measured the weight after drying to measure the distribution of the amount of binder in the coating film, which was in contact with the current collector with respect to the amount of binder on the side away from the current collector The ratio of the amount of binder on the side was determined.

[0082]

[Table 2]

[0083]

According to the method for producing a positive electrode or a negative electrode of a non-aqueous electrolyte secondary battery of the present invention, a current collector is coated with a coating liquid in which an active material, a binder and a solvent are dispersed. Because the surface is dried with the side down, the more the active material in the active material layer is away from the current collector, the more the binder becomes closer to the current collector, and the better the adhesiveness, so the active material is included Adhesion between the coating film and the current collector is improved, and peeling of the active material from the current collector during production of the nonaqueous electrolyte secondary battery can be prevented.

Therefore, according to the method of the present invention, a non-aqueous electrolyte secondary battery having a high capacity and excellent charge / discharge cycle characteristics and which can be used repeatedly for a long period of time can be easily obtained as described above, and is practically large. It has the following effects. Specifically, for example, a high capacity can be maintained even in several hundred charge / discharge cycles, and the nonaqueous electrolyte secondary battery including the positive electrode or the negative electrode obtained by the present invention is a portable video camera, Portable computers, mobile phones, transceivers,
It can be suitably used for cameras, headphone stereos, portable televisions and the like.

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Claims (3)

[Claims] 1. A non-aqueous electrolyte secondary, characterized in that a current collector is coated with a coating liquid in which an active material, a binder and a solvent are dispersed, and the coated surface of the current collector is dried. A method for producing a positive electrode or a negative electrode of a battery. 2. The method for producing a positive electrode or a negative electrode of a non-aqueous electrolyte secondary battery according to claim 1, wherein the binder comprises a particulate resin having a particle size of 0.05 to 100 μm. 3. The method for producing a positive electrode or a negative electrode of a non-aqueous electrolyte secondary battery according to claim 2, wherein the particulate resin has a form swollen by a solvent.