JP4748438B2 - Binder resin solution for lithium battery electrode and electrode and battery manufactured from this solution and active material - Google Patents

Description

  The present invention relates to a binder resin solution for a lithium battery electrode, an electrode and a battery obtained from this solution and an active material, and methods for producing them.

Advances in electronic technology have improved the performance of electronic devices, making them smaller and more portable, and secondary batteries with high energy density are desired as the power source. Conventional secondary batteries include lead-acid storage, nickel-cadmium batteries, and the like, which are insufficient in terms of high energy density batteries. Therefore, as an alternative to these batteries, in recent years, an organic electrolyte lithium secondary battery (hereinafter simply referred to as “lithium battery”) that can greatly improve the energy density has been developed and rapidly spread.
Lithium-containing metal composite oxides such as lithium-cobalt composite oxide are mainly used as the active material for the positive electrode of the lithium battery, and lithium ions are mainly inserted between the layers as the active material (lithium intercalation compound). Carbon materials having a multilayer structure capable of forming and releasing lithium ions from the interlayer are used. The positive and negative electrodes are prepared by dispersing these active materials and binder resin components in a solvent such as N-methyl-2-pyrrolidone or water, and applying this to the surface of a metal foil as a current collector. Then, after the solvent is removed by drying, a mixture layer is formed, and this is compression-molded with a roll press. As the binder resin, polyvinylidene fluoride (hereinafter simply referred to as “PVDF”) is generally used for both electrodes.
However, when PVDF is used as a binder resin component, the adhesion between the current collector and the mixture layer and the adhesion between the active materials in the mixture layer, particularly the former adhesion, are inferior. ) A part or all of the mixture layer is peeled off or removed from the current collector during the battery manufacturing process such as cutting of the electrode plates of each electrode or winding the electrode plates of both electrodes in a spiral shape through a separator. (2) Since the carbon material of the negative electrode active material expands / shrinks as lithium ions are inserted / released due to charging / discharging of the battery, part or all of the mixture layer is peeled off / dropped from the current collector by repeated charging / discharging, Such a lack of adhesion has been one cause of battery capacity reduction.
As a fluorine-containing binder resin component that can solve the above-mentioned adhesion problem of PVDF, for example, in JP-A-6-172452, a main component is vinylidene fluoride, and a small amount of unsaturated dibasic monoester is added thereto. It has been proposed to use a vinylidene fluoride copolymer obtained by copolymerization. When such a vinylidene fluoride copolymer is used as a binder resin component, a current collector, a mixture layer, While the adhesion at the interface is greatly improved, due to the decrease in crystallinity, the resistance to the electrolyte injected after winding (hereinafter referred to as “electrolytic solution resistance”) decreases, and it tends to swell. The contact at the interface between the current collector and the mixture layer and the contact between the active materials in the mixture layer become loose. This leads to the collapse of the conductive network of the entire electrode, and the capacity of the battery decreases. It has been pointed out that the battery does not function properly, and has not yet solved the essential problem.
These fluorine-containing binder resin components are used in a form dissolved in an organic solvent such as N-methyl-2-pyrrolidone (NMP). However, this NMP has problems in terms of cost and environmental load.
On the other hand, as binder resin components other than fluorine-containing binders such as PVDF, for example, JP-A-5-74461 uses a diene synthetic rubber such as styrene-butadiene rubber (hereinafter abbreviated as “SBR”). Proposed. The diene rubber is in the form of an aqueous dispersion, and has a lower environmental impact than the case where an organic solvent is used, so that a battery can be manufactured at a low cost. Further, when such a diene synthetic rubber is used as a binder resin component, the adhesion at the interface between the current collector and the mixture layer is relatively good. However, since diene rubber also has low electrolysis resistance and easily swells, it leads to the collapse of the conductive network of the electrode due to repeated charging and discharging, and when lithium batteries are repeatedly charged and discharged, it is a cause that capacity decreases with time. It was.
On the other hand, there is a nitrile group-containing resin as a binder resin which is a binder resin component other than the above and excellent in electrolytic solution resistance and swelling resistance that does not dissolve in the electrolytic solution. In particular, JP-A-2003-132893 discloses a repeating unit derived from acrylonitrile or methacrylonitrile and a formula (I): CH ₂ = CR ¹ -COOR ² (wherein R ¹ is a hydrogen atom or a methyl group, R ² includes a polymer (A) containing a repeating unit derived from a monomer of an alkyl group having 3 or less carbon atoms) and a polymer (B) such as a butyl acrylate-acrylonitrile-diethylene glycol dimethacrylate copolymer. Disclosed is a slurry composition for an electrode. However, when two types of polymers as described above are used as the electrode slurry composition, the binder resin formed by applying and drying the slurry composition including the active material on the electrode (current collector) is formed. There were problems of cracking and peeling from the current collector. In particular, when the binder resin formed by applying and drying on the current collector is further subjected to roll press molding, or when the positive electrode and the negative electrode are wound in a spiral shape via a separator, the mixture layer may be peeled and cracked. There was a concern that defects would occur. In other words, it was difficult to say that the flexibility and flexibility of the obtained battery electrode were sufficiently improved.

Japanese Patent Laid-Open No. 6-175252 JP-A-5-74461 JP 2003-132893 JP

The objective of this invention is providing the binder resin solution for lithium battery electrodes which can manufacture the electrode excellent in electrolyte solution resistance, a softness | flexibility, and flexibility. In addition, electrolyte solution resistance means the tolerance with respect to electrolyte solution as mentioned above, for example, when a binder resin and electrolyte solution are made to contact, binder resin does not expand | swell, and the swelling degree of binder resin with respect to electrolyte solution is When it is low, it can be said that the resistance to the electrolytic solution is high, that is, the electrolytic solution is resistant.
The object of the present invention is to apply the above-mentioned binder resin solution for a lithium battery electrode mixed with an active material to the current collector of the electrode, and to dry the mixture layer obtained by subjecting the mixture layer to electrolyte resistance, flexibility, and flexibility. It is to make it excellent in flexibility.
A further object of the present invention is to provide a battery, particularly a lithium battery, which is excellent in resistance to electrolyte, flexibility and flexibility.

The present inventor used a binder resin solution for a lithium battery electrode containing a polymer and a monomer, and applied and dried a slurry obtained by adding an active material to this solution to a current collector of a lithium battery electrode. By polymerizing the components, as described in JP-A-2003-132893, two types of prepolymerized polymers are mixed, and this is far more than when applied to the current collector of the electrode and dried. The present inventors have found that it has excellent flexibility and flexibility, and at the same time has resistance to electrolytic solution that hardly dissolves or swells in the electrolytic solution, and has led to the present invention.
Accordingly, the present invention relates to a binder resin solution for a lithium battery electrode comprising (A) a polymer containing a nitrile group, (B) an acrylic monomer and / or a methacrylic monomer, and a solvent.
The present invention further includes a current collector and a mixture layer provided on at least one surface of the current collector, and the mixture layer includes the following steps: (a) the binder resin for lithium battery electrodes Applying a slurry containing a solution and an active material onto the current collector; (b) removing a solvent from the applied slurry; and (c) (B) polymerizing an acrylic monomer and / or a methacrylic monomer. And a lithium battery electrode obtained from the step.
Furthermore, this invention relates to the lithium battery containing the said electrode for lithium batteries.
In addition, the present invention is a method for producing an electrode for a lithium battery, comprising the following steps: (a) a slurry containing the binder resin solution for a lithium battery electrode and an active material on at least one surface of a current collector And (b) removing the solvent from the applied slurry; and (c) (B) polymerizing an acrylic monomer and / or a methacrylic monomer. It relates to a method of manufacturing.

The present invention uses a binder resin solution for a lithium battery electrode containing the polymer (A) and the monomer (B) as described above, and a slurry obtained by adding an active material to this solution is used as a current collector for an electrode of a lithium battery. And then (B) by polymerizing the monomer components, it has much better flexibility and flexibility compared to the case where two types of prepolymerized polymers are applied to the electrode current collector and dried. The present inventors have found that it has flexibility, and at the same time, has an electrolyte solution resistance that is difficult to dissolve and swell in the electrolyte solution. In particular, the monomer (B) is prepared by applying a binder resin solution for a lithium battery electrode of the present invention containing an active material on a current collector, drying the resultant mixture layer, and optionally rolling the resultant mixture layer, followed by vacuum drying or the like. It is polymerized using a method. In this way, by polymerizing the monomer (B) at the final stage of electrode production, the mixture layer and the binder resin contained therein are not cracked and peeled off from the current collector, thereby being flexible and possible. An electrode having a mixture layer with excellent flexibility can be provided. Furthermore, by adjusting the composition of the binder resin, it is possible to provide a mixture layer having an electrolytic solution resistance that hardly dissolves and swells in the electrolytic solution, and a binder resin contained therein. In particular, an electrode manufactured using this binder resin solution is compatible with electrolyte resistance and flexibility, and even when used at high temperatures, the electrode has a long interface between the current collector and the mixture layer. The contact and the contact between the active materials in the mixture layer can be satisfactorily maintained, and an excellent capacity retention rate is exhibited even when the charge / discharge cycle is repeated.
Furthermore, the binder resin obtained by using the binder resin solution for a lithium battery electrode of the present invention is a polymer obtained by polymerizing the monomer (B) with a strong bond of the nitrile group (A). Since it can be relaxed, the electrode manufactured using the binder resin solution of the present invention has an excellent plastic effect.

(1) Binder resin solution for lithium battery electrode The binder resin solution for lithium battery electrode of the present invention (hereinafter sometimes simply referred to as “binder resin solution”) is (A) a polymer containing a nitrile group, and (B) acrylic. A binder resin component containing a monomer and / or a methacryl monomer, and other additives, and a solvent are included. In the present invention, the binder resin solution is a mixture (varnish) of the binder resin component and the solvent before being applied to the current collector of the electrode.
(1-1) Binder resin component The binder resin component of the present invention comprises (A) a polymer containing a nitrile group and (B) an acrylic monomer and / or a methacrylic monomer as essential components. Moreover, the binder resin component of the present invention optionally contains other additives.
(1-1-1) Nitrile group-containing polymer (component (A))
The polymer containing a nitrile group (A) of the present invention is not particularly limited, and examples thereof include acrylic polymers such as polyacrylonitrile, polymethacrylonitrile and copolymers of acrylonitrile and methacrylonitrile, and cyanoacrylates such as polycyanoacrylate. Based polymers and the like. Of these, acrylonitrile or methacrylonitrile homopolymers and / or copolymers are preferred in view of the dispersion stability of the filler.

The mass average molecular weight of the polymer containing a nitrile group can be measured, for example, by gel permeation chromatography. Specifically, from a calibration curve prepared using standard polystyrene using N-methyl-2-pyrrolidone solution prepared by adding sodium chloride as a relaxation agent to a concentration of 0.1 mol / liter, the polystyrene equivalent value (Hereinafter, unless otherwise specified, the mass average molecular weight is a value measured by such gel permeation chromatography.) The mass average molecular weight of the polymer containing a nitrile group is, for example, 10, It is preferably 000 to 5,000,000, more preferably 30,000 to 3,000,000, particularly preferably 50,000 to 2,000,000, and 100,000 to 1 It is very preferable that it is 1,000,000. If this mass average molecular weight is 10,000 or more, the dispersibility of the filler does not decrease, and if it is 5,000,000 or less, there is a problem of increasing the viscosity of the slurry, and the binder resin solution or activity. This is preferable because it does not become difficult to apply a binder resin solution containing a substance (ie, slurry).
The polymer containing a nitrile group of the present invention is produced by polymerizing a nitrile group-containing monomer and any other monomer. Examples of the nitrile group-containing monomer include acrylic monomers such as acrylonitrile and methacrylonitrile, and cyan monomers such as α-cyanoacrylate and dicyanovinylidene. Other monomers include acrylate compounds such as n-butyl acrylate, isobutyl acrylate and t-butyl acrylate; methacrylate compounds such as methyl methacrylate, ethyl methacrylate and propyl methacrylate; unsaturated compounds such as acrylic acid and methacrylic acid Examples thereof include monocarboxylic acid monomers, unsaturated dicarboxylic acids such as maleic acid, fumaric acid and citraconic acid, and crosslinkable monomers such as divinylbenzene. As a polymerization method for producing the binder resin of the present invention, existing methods such as bulk suspension polymerization, suspension polymerization, dispersion polymerization, and emulsion polymerization can be applied.

  Moreover, there is no restriction | limiting in particular as a catalyst used arbitrarily in superposition | polymerization, For example, a triethylamine, a triethylenediamine, N, N-dimethylaniline, N, N-diethylaniline, N, N-ditylbenzylamine, N-methyl Morpholine, N-ethylmorpholine, N, N-dimethylpiperazine, pyridine, picoline, tertiary amines such as 1,8-diazabicyclo [5,4,0] undecene-7, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-methyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 2-phenyl-4-methyl-15-hydroxymethylimidazole, 2-Phenyl-4,5-dihydroxymethylimida , Imidazoles such as 1-azine-2-methylimidazole, ditintin dilaurate, organotins such as 1,3-diacetoxytetrabutyl distanoxane, tetraethylammonium bromide, tetrabutylammonium bromide, benzyl chloride Triethylammonium chloride, trioctylmethylammonium chloride, cetyltrimethylammonium bromide, tetrabutylammonium iodide, dodecyltrimethylammonium iodide, benzyldimethyltetradecylammonium acetate, tetraferphosphonium chloride, triphenylmethylphosphonium chloride, tetramethylphosphonium bromide Quaternary onium salts such as, organic phosphorus compounds such as 3-methyl-1-phenyl-2-phospholene-1-oxide, sodium benzoate, potassium benzoate Alkali metal salts of organic acids, inorganic salts such as zinc chloride, iron chloride, lithium chloride and lithium bromide, metal carbonyl compounds such as octacarbonyl dicobalt (cobalt carbonyl), metal ether compounds such as tetrabutoxy titanium, Benzoyl oxide, lauroyl peroxide, di-t-butylperoxyhexahydroterephthalate, t-butylperoxy-2-ethylhexanoate, 1,1-t-butylperoxy-3,3,5-trimethylcyclohexane, Organic peroxides such as t-butylperoxyisopropyl carbonate, azo compounds such as azobisisobutyronitrile, azobis-4-methoxy-2,4-dimethylvaleronitrile, azobiscyclohexanone-1-carbonitrile, azodibenzoyl Persulfate such as potassium peroxodisulfate Potassium acid and ammonium persulfate can be used. The usage-amount of these catalysts is about 0.01-10 mass% with respect to solid content in the said binder resin solution for lithium battery electrodes, for example.

（式中、Ｒ₁はH又はCH₃、Ｒ₂は炭素数１〜100の炭化水素基である） (1-1-2) Acrylic monomer and / or methacrylic monomer (component (B))
The acrylic monomer and / or methacrylic monomer of the present invention is preferably selected so that the polymer obtained by polymerizing the component (B) is not the same as the polymer of the component (A). In particular, in order to improve the plasticity of the binder resin obtained from the binder resin solution of the present invention, the polymer obtained by polymerizing the component (B) is more plastic than the polymer of the component (A). preferable. Examples of the component (B) include acrylic acid esters, diacrylic acid esters, methacrylic acid esters, and dimethacrylic acid esters.
For example, examples of the (B) acrylic monomer and / or methacrylic monomer include monomers represented by the general formula (Ι).

(Wherein R ₁ is H or CH ₃ , and R ₂ is a hydrocarbon group having 1 to 100 carbon atoms)

Specific examples of the (B) acrylic monomer and / or methacrylic monomer include the following compounds.
Methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, Cyclohexyl acrylate, 2-ethylhexyl acrylate, n-heptyl acrylate, n-octyl acrylate, isooctyl acrylate, isodecyl acrylate, lauryl acrylate, isomyristyl acrylate, tridecyl acrylate, dodecyl acrylate, stearyl acrylate Fluorine-containing acrylic monomers such as isobornyl acrylate, phenyl acrylate, benzyl acrylate, naphthyl acrylate, glycidyl acrylate, 2-hydroxyethyl acrylate, trifluoroethyl acrylate,

Ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, pentaethylene glycol diacrylate, hexaethylene glycol diacrylate, heptaethylene glycol diacrylate, octaethylene glycol diacrylate, nonaethylene glycol diacrylate , Decaethylene glycol diacrylate, undecaethylene glycol diacrylate, dodecaethylene glycol diacrylate, tridecaethylene glycol diacrylate, tetradecaethylene glycol diacrylate, pentadecaethylene glycol diacrylate, hexadecaethylene glycol diacrylate, diacrylic acid Heptadecaethylene glycol, diacrylate Decaethylene glycol, nonadecaethylene glycol diacrylate, 1,3-butanediol diacrylate, methanediol diacrylate, 1,2-ethanediol diacrylate, 1,3-propanediol diacrylate, 1,4-butane diacrylate Diol, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, 1,7-heptanediol diacrylate, 1,8-octanediol diacrylate, 1,9-nonanediol diacrylate, diacrylic acid 1 , 10-decanediol, neopentyl diacrylate, zinc diacrylate, dimethylol tricyclodecane diacrylate,

Trimethylolpropane triacrylate, diacrylic acid bisphenol A ethylene oxide adduct, diacrylic acid bisphenol A propylene oxide adduct, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, trimethylolpropane acrylic acid benzoate, 2- Hydroxy-3-acryloyloxypropyl acrylate, propylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, tetrapropylene glycol diacrylate, pentapropylene glycol diacrylate, hexapropylene glycol diacrylate, heptapropylene glycol diacrylate , Octapropyl diacrylate Glycol, dipropylene glycol diacrylate, decapropylene glycol diacrylate, undecapropylene glycol diacrylate, dodecapropylene glycol diacrylate, tridecapropylene glycol diacrylate, tetradecapropylene glycol diacrylate, pentadecapropylene glycol diacrylate, diacryl Acid hexadecapropylene glycol, heptadecapropylene glycol diacrylate, octadecapropylene glycol diacrylate, nonadecapropylene glycol diacrylate,

Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, Cyclohexyl methacrylate, 2-ethylhexyl methacrylate, n-heptyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, isodecyl methacrylate, lauryl methacrylate, isomyristyl methacrylate, tridecyl methacrylate, dodecyl methacrylate, stearyl methacrylate , Isobornyl methacrylate, phenyl methacrylate, benzyl methacrylate, naphthyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, triflate methacrylate Fluorine-containing methacrylic monomers such as oloethyl, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, pentaethylene glycol dimethacrylate, hexaethylene glycol dimethacrylate, dimethacrylate Acid heptaethylene glycol, octaethylene glycol dimethacrylate, nonaethylene glycol dimethacrylate, decaethylene glycol dimethacrylate, undecaethylene glycol dimethacrylate, dodecaethylene glycol dimethacrylate, tridecaethylene glycol dimethacrylate, di Tetradecaethylene glycol methacrylate, pentadecaethylene glycol dimethacrylate, hexadecadimethacrylate Lenglycol, heptadecaethylene glycol dimethacrylate, octadecaethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, methanediol dimethacrylate, 1,2-ethanediol dimethacrylate, dimethacrylate 1, 3-propanediol, 1,4-butanediol dimethacrylate, 1,5-pentanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,7-heptanediol dimethacrylate, 1, methacrylic acid 1, 8-octanediol, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, neopentyl dimethacrylate, zinc dimethacrylate, dimethyloltricyclodecane dimethacrylate,

Trimethylolpropane trimethacrylate, dimethacrylic acid bisphenol A ethylene oxide adduct, dimethacrylic acid bisphenol A propylene oxide adduct, pentaerythritol trimethacrylate, pentaerythritol tetrametallate, dipentaerythritol hexamethacrylate, trimethylolpropane methacrylic acid benzoate 2-hydroxy-3-acryloyloxypropyl methacrylate, propylene glycol dimethacrylate, dipropylene glycol dimethacrylate, tripropylene glycol dimethacrylate, tetrapropylene glycol dimethacrylate, pentapropylene glycol dimethacrylate, dimethacrylic acid Hexapropylene glycol, heptapropylene glycol dimethacrylate , Octapropylene glycol dimethacrylate, nonapropylene glycol dimethacrylate, decapropylene glycol dimethacrylate, undecapropylene glycol dimethacrylate, dodecapropylene glycol dimethacrylate, tridecapropylene glycol dimethacrylate, tetradecamethacrylate Propylene glycol, pentadecapropylene glycol dimethacrylate, hexadecapropylene glycol dimethacrylate, heptadecapropylene glycol dimethacrylate, octadecapropylene glycol dimethacrylate, nonadecapropylene glycol dimethacrylate, and the like.

As the acrylic monomer and / or methacrylic monomer which is the component (B) of the present invention, the above compounds may be used alone or in combination of two or more. Among them, R ₂ in formula (I) preferably has a saturated aliphatic hydrocarbon group having 1 to 50 carbon atoms in terms of imparting flexibility, and a saturated aliphatic hydrocarbon group having 2 to 25 carbon atoms. It is more preferable to have

(1-1-3) Other additives In the binder resin solution for lithium battery electrodes of the present invention, if necessary, curing agents such as epoxy resin, melamine resin, polyblock isocyanate, polyoxazoline, polycarbodiimide, Various additives such as ethylene glycol, glycerin, polyether polyol, polyester polyol, acrylic oligomer, phthalic acid ester, dimer acid-modified product, and polybutadiene-based compound may be included. You may mix | blend this additive individually or in combination of 2 or more types.

(1-1-4) Content of component (A) and component (B) (A) A polymer containing a nitrile group and (B) an acrylic monomer and / or methacrylic monomer, for example, 100 parts by mass of component (A) Part, the component (B) is preferably contained in a proportion of 1 to 50 parts by mass, particularly preferably 2 to 40 parts by mass, and most preferably 5 to 30 parts by mass. . If it is 50 parts by mass or less, good electrolytic solution resistance can be achieved, and if it is 1 part by mass or more, it contributes sufficiently to improving the flexibility of the binder resin obtained from the binder resin solution of the present invention. Therefore, it is preferable.
The usage-amount of the said other additive is about 0.01-15 mass% with respect to solid content in the said binder resin solution for lithium battery electrodes, for example. If it is 0.01 mass% or more and 15 mass% or less, since sufficient adhesiveness between an active material and binder resin or between a collector and a mixture layer is obtained, it is preferable.

(1-2) Solvent The binder resin solution for a lithium battery electrode of the present invention is obtained by adding a solvent to the binder resin component. Examples of the solvent include water and organic solvents.
Examples of the organic solvent include amides such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, N, N-dimethylethyleneurea, N, N-dimethylpropyleneurea, tetra Ureas such as methyl urea, lactones such as γ-butyrolactone, γ-caprolactone, carbonates such as propylene carbonate, ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl acetate, n-butyl acetate, butyl cellosolve acetate, butyl Esters such as carbitol acetate, ethyl cellosolve acetate and ethyl carbitol acetate, glymes such as diglyme, triglyme and tetraglyme, hydrocarbons such as toluene, xylene and cyclohexane, sulfolane And the like.
Of these, amides and ureas are preferable in that the binder resin component is excellent in solubility. N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylethyleneurea, N, N-dimethyl Propylene urea and tetramethyl urea are more preferable, and among them, N-methyl-2-pyrrolidone is particularly preferable.
These solvents are used alone or in combination of two or more.

  The amount of the solvent used is preferably 50 to 10,000 parts by mass, more preferably 200 to 5,000 parts by mass, with respect to 100 parts by mass of the total solid content in the binder resin solution, 300 It is especially preferable to set it as -3,000 mass parts. If the amount used is 50 parts by mass or more, sufficient solubility is obtained, and the reaction system is less likely to be non-uniform or highly viscous. It is preferable because it proceeds and the reaction is easily completed.

(1-3) Method for Producing Binder Resin Solution for Lithium Battery Electrode The binder resin solution for lithium battery electrode of the present invention is obtained by dispersing the binder resin component containing the above (A) component, (B) component and other additives in a solvent. Alternatively, it is manufactured by dissolving it into a varnish. Specifically, for example, first, a monomer for synthesizing the polymer (A) is dissolved in a solvent, and the polymer (A) is synthesized by heat or light. Subsequently, component (B) and other additives are added to the solvent containing the polymer (A) to obtain a binder resin solution for a lithium battery electrode.

(2) Electrode The electrode of the present invention has a current collector and a mixture layer provided on at least one surface of the current collector, and the mixture layer comprises the following steps:
(a) applying a slurry containing the binder resin solution for a lithium battery electrode and an active material on the current collector;
(b) removing the solvent from the applied slurry; and
(c) (B) a step of polymerizing an acrylic monomer and / or a methacrylic monomer,
Is obtained from
The above steps are performed in the order of (a), (b), (c). Between the steps (b) and (c), the following steps are further performed:
(d) You may include the process of rolling the laminated body of the obtained electrical power collector and mixture layer.
(2-1) Current Collector The current collector of the present invention may be any material having conductivity, and for example, metals, conductive plastics and the like can be used. More specifically, aluminum, copper, or nickel can be used as the metal. Moreover, polyaniline, polythiol, etc. can be used as a conductive plastic. Further, the shape of the current collector is not particularly limited, but a thin film shape is preferable from the viewpoint that the capacity of the battery can be increased and the volume of the current collector can be reduced. The thickness of the current collector is, for example, 5 to 100 μm, preferably 10 to 30 μm. If it is 5 μm or more, it is easy to handle, and if it is 100 μm or less, the capacity of the battery can be increased, which is preferable.

(2-2) Mixture Layer The mixture layer of the present invention is produced from a slurry in which an active material is added to the binder resin solution.
(2-2-1) Active Material The active material used in the present invention is not particularly limited as long as it can reversibly insert and release lithium ions by charging and discharging a lithium battery. However, the positive electrode has a function of releasing lithium ions at the time of charging and receiving lithium ions at the time of discharging, while the negative electrode has a function opposite to that of the positive electrode of receiving lithium ions at the time of charging and releasing lithium ions at the time of discharging. Therefore, it is preferable that the active materials used in the positive electrode and the negative electrode are different types of active materials in accordance with the respective functions.
The positive electrode active material may be any transition metal oxide that can reversibly insert and release lithium ions by charge and discharge, and may be a lithium cobalt composite oxide, lithium, nickel composite oxide, or a mixture thereof. Also, in the lithium nickel composite oxide, lithium nickel or lithium site substituted with at least one metal selected from Al, V, Cr, Fe, Co, Sr, Mo, W, Mn, B, and Mg. A complex may also be used. In addition, in the lithium manganese composite oxide, the manganese site or the lithium site is substituted with at least one metal selected from Al, V, Cr, Fe, Co, Sr, Mo, W, Mn, B, and Mg. A composite oxide may be used.

  On the other hand, as the active material of the negative electrode, for example, carbon materials such as amorphous carbon, graphite, carbon fiber, coke, activated carbon and the like are preferable. Other than the carbon material, metals such as silicon, tin, silver or the like These oxides can be used. These active materials are used alone or in combination of two or more. The average particle diameter of the negative electrode active material is preferably 1 to 100 μm, more preferably 5 to 50 μm, and particularly preferably 10 to 40 μm.

(2-2-2) Solvent Further, a solvent may be added to the slurry to adjust the viscosity and the like. There is no restriction | limiting in particular as a solvent, The solvent for binder resin solutions mentioned above can be used. For example, N-methyl-2-pyrrolidone and N-methyl-2-pyrrolidone and ester solvents (ethyl acetate, n-butyl acetate, butyl cellosolve acetate, butyl carbitol acetate, etc.) or glyme solvents (diglyme, triglyme, tetraglyme) Etc.) is particularly preferred. These solvents may be used alone or in combination of two or more.

(2-2-3) Other additives A thickener can be added to the slurry for producing the mixture layer of the present invention in order to improve the dispersion stability and coating property of the slurry. Thickeners include celluloses such as carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, and ammonium salts or alkali metal salts thereof, polyacrylic acid and alkali metal salts thereof, polyvinyl alcohol, ethylene / vinyl alcohol copolymer Examples thereof include polyvinyl alcohol copolymers such as coalescence.
In addition, you may add to the slurry of a positive electrode further conductive support agents, such as carbon black and graphite, individually or in combination of 2 or more types.
(2-2-4) Composition of components constituting the mixture layer The active material constituting the mixture layer is, for example, 50 to 99 mass%, preferably with respect to the mixture layer obtained by removing the solvent. Is preferably added in an amount of 80 to 99% by mass.
The solvent depends on the amount of the solvent in the binder resin solution, but the solid content of the binder resin solution after adding the solvent is, for example, 20 to 1% by mass, preferably 10 to 2% by mass. It is preferable that it exists in.

(2-3) Electrode production method The electrode of the present invention,
(a) applying a slurry containing the binder resin solution for a lithium battery electrode and an active material on the current collector;
(b) removing the solvent from the applied slurry; and
(c) (B) a step of polymerizing an acrylic monomer and / or a methacrylic monomer,
Obtained from.
The above steps are performed in the order of (a), (b), (c). Between the steps (b) and (c), the following steps are further performed:
(d) The method may include a step of rolling the obtained current collector / mixture layer laminate.

(a) The step of applying the slurry containing the binder resin solution for lithium battery electrodes and the active material on the current collector includes, for example, the active material, the binder resin solution, and any solvent and other additives. The slurry is prepared, and the slurry is applied to at least one surface, preferably both surfaces of the current collector. Application | coating can be performed using a comma coater, a wire coater, etc., for example. The application is suitably performed so that the active material utilization rate per unit area is not less than negative electrode / positive electrode = 1 in the opposing electrode.
The coating amount of the mixture layer, for example, a dry weight for example, from 60 to 500 g / m ^2, preferably, is suitably a 70~400g / m ^2.

  (b) For the step of removing the solvent from the applied slurry, for example, a method of drying in air and a drying method such as vacuum drying can be used. Drying is performed by exposing the applied slurry at, for example, 60 to 160 ° C., preferably 70 to 130 ° C. for 3 to 20 minutes, preferably 5 to 15 minutes.

(c) (B) The process of superposing | polymerizing an acrylic monomer and / or a methacryl monomer is performed by vacuum-drying the slurry apply | coated on the electrical power collector, for example.
The vacuum drying is performed, for example, under conditions of 13.2 KPa or less, preferably 6.6 KPa or less; 100 to 200 ° C., preferably 120 to 150 ° C .; 1 to 36 hours, preferably 3 to 24 hours.
The removal of the solvent performed in the step (b) may be performed together in the step of polymerizing the monomer of the component (B) in the step (c). That is, the residual solvent and adsorbed water in the electrode sheet, that is, the mixture layer applied to the electrode may be removed by utilizing vacuum drying in this step. When the removal of the solvent and the polymerization of the monomer of the component (B) are simultaneously performed, for example, the heating may be performed at 100 to 200 ° C., preferably 120 to 150 ° C. for 1 to 36 hours.
In the binder resin on the mixture layer thus obtained, the polymer of the component (A) and the polymer polymerized from the component (B) preferably have an mutual network structure (IPN). By having such a structure, the polymer polymerized from the component (B) serves as a plasticizer for the polymer of the component (A). Furthermore, the effect of the polymer polymerized from the component (B) as a plasticizer depends on the glass transition temperature (Tg) of the polymer. That is, the lower the Tg of the polymer polymerized from the component (B), the better the plasticizer.

(d) The step of rolling the laminate of the obtained current collector and the mixture layer is performed using, for example, a roll press machine, and the bulk density of the mixture layer is, for example, 0.5 to 4.0 g / cm ^3, preferably suitably be pressed so that 1.0~3.5g / cm ^3.

(3) Battery The electrode of the present invention can be further combined with an electrolytic solution to produce a battery, particularly a lithium battery.
(3-1) Electrolytic Solution The electrolytic solution used in the present invention is not particularly limited as long as it can function as a battery, but a solution in which an electrolyte is dissolved in an organic solvent can be used.
Examples of the organic solvent include carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, lactones such as γ-butyrolactone, trimethoxymethane, 1,2-dimethoxyethane, and diethyl. Ethers, ethers such as 2-ethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, sulfoxides such as dimethyl sulfoxide, oxolanes such as 1,3-dioxolane, 4-methyl-1,3-dioxolane, acetonitrile, nitromethane, N -Nitrogens such as methyl-2-pyrrolidone, esters such as methyl formate, methyl acetate, butyl acetate, methyl propionate, ethyl propionate, phosphate triester, diglyme Glymes such as triglyme and tetraglyme, ketones such as acetone, diethyl ketone, methyl ethyl ketone, and methyl isobutyl ketone, sulfolanes such as sulfolane, oxazolidinones such as 3-methyl-2-oxazolidinone, 1,3-propane sultone Sultone such as 1,4-butane sultone and naphtha sultone. An organic solvent is used individually or in combination of 2 or more types.
As the electrolyte, for _{example, LiCl, LiBF 4, LiI,} LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiAlCl 4, LiCl, LiBr, LiB (C 2 H 5) 4, LiCH 3 SO ₃ , LiC ₄ F ₉ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N can be mentioned. Among these, an electrolytic solution in which LiPF ₆ is dissolved in carbonates is preferable.

(3-2) Battery Manufacturing Method The lithium battery manufacturing method of the present invention is not particularly limited, but any known method can be used. For example, first, the electrode is wound through a separator made of a polyethylene microporous membrane. The obtained spiral wound group is inserted into a battery can, and a tab terminal previously welded to a negative electrode current collector is welded to the bottom of the battery can. Inject the electrolyte into the resulting battery can, weld the tab terminal that was previously welded to the positive electrode current collector to the battery lid, and place the lid on the top of the battery can via an insulating gasket A battery is obtained by caulking and sealing the part where the lid and the battery can are in contact.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not restrict | limited to these Examples.
<Manufacture of binder resin solution>
Binder resin solution 1
In a 0.5 liter separable flask equipped with a stirrer, thermometer, cooling pipe, distilling pipe and nitrogen gas introduction pipe, 27.0 g of polyacrylonitrile in a nitrogen atmosphere (component (A), mass average molecular weight 82,600 manufactured by Aldrich) 270 g of N-methyl-2pyrrolidone was added and dissolved by stirring at 80 ° C. for 8 hours. After dissolution, the mixture was cooled to 25 ° C., and 3 g of butyl acrylate (component (B)) was added to obtain a binder resin solution 1.

Binder resin solution 2
A binder resin solution 2 was obtained in the same manner as the binder resin solution 1 except that 25.0 g of polyacrylonitrile (component (A)) and 5 g of butyl acrylate (component (B)) were used.

Binder resin solution 3
The binder resin solution 3 was prepared in the same manner as the binder resin solution 1 except that 27.5 g of polyacrylonitrile (component (A)) was used and 2.5 g of lauryl acrylate was used instead of butyl acrylate (component (B)). Obtained.

Binder resin solution 4
A binder resin solution 4 was obtained in the same manner as the binder resin solution 1 except that polyacrylonitrile (component (A)) was 25.0 g and lauryl acrylate 5 g was used as the component (B) instead of butyl acrylate. .

Binder resin solution 5
In a 0.5 liter separable flask equipped with a stirrer, thermometer, cooling pipe, distilling pipe and nitrogen gas introduction pipe, under a nitrogen atmosphere, 27 g of acrylonitrile, 1 g of lauryl acrylate, 0.2 g of potassium peroxodisulfate, and 200 g of water The mixture was heated to 80 ° C. and stirred at the same temperature for 8 hours. After completion of the reaction, the reaction mixture was filtered and vacuum dried at 60 ° C. to obtain 29.7 g of a solid content (component (A)) of the binder resin solution. The mass average molecular weight of this solid content was measured by gel permeation chromatography and found to be 200,000.
27 g of the obtained solid content and 270 g of N-methyl-2pyrrolidone were added, and the mixture was stirred at 80 ° C. for 3 hours in a 0.5 liter separable flask equipped with a stirrer, thermometer, cooling pipe, distillation pipe and nitrogen gas introduction pipe. While dissolving. After dissolution, the mixture was cooled to 25 ° C., and 3 g of butyl acrylate (component (B)) was added to obtain a binder resin solution 5.

Binder resin solution 6
Add 25 g of solid content (component (A)) of the binder resin solution obtained in the section of the binder resin solution 5 and 270 g of N-methyl-2-pyrrolidone, stirrer, thermometer, cooling pipe, distilling pipe and nitrogen gas introducing pipe. Was dissolved in a 0.5 liter separable flask equipped with No. 3 at 80 ° C. with stirring for 3 hours. After dissolution, after cooling to 25 ° C., 5 g of butyl acrylate (component (B)) was added to obtain a binder resin solution 6.

Binder resin solution 7
Add 27.5 g of the solid content of the binder resin solution obtained in the section of the binder resin solution 5 (component (A)) and 270 g of N-methyl-2-pyrrolidone, and introduce a stirrer, thermometer, cooling pipe, distilling pipe and nitrogen gas The sample was dissolved in a 0.5-liter separable flask equipped with a tube at 80 ° C. with stirring for 3 hours. After dissolution, the mixture was cooled to 25 ° C., and then 2.5 g of lauryl acrylate (component (B)) was added to obtain a binder resin solution 7.

<Preparation of electrode for positive electrode>
Example 1
A lithium manganese composite oxide having a composition of Li _1.12 Mn _1.88 O ₄ having an average particle diameter of 10 μm as an active material for a positive electrode, a carbon powder having an average particle diameter of 3 μm as a conductive additive, and a binder resin solution 1 are prepared as follows: Mixing at a ratio of 10: 10% by volume (the volume% of the binder resin solution is the volume% of the binder resin component in the binder resin solution), and N-methyl-2-pyrrolidone has a solid content of 4%. Was added and mixed to prepare a slurry. This slurry was applied on both sides of an aluminum foil having a thickness of 20 μm and dried at 120 ° C. for 10 minutes. The coating amount of the mixture layer was 290 g / m ² in terms of dry mass. Thereafter, the mixture layer was rolled with a roll press so that the bulk density was 2.6 g / cm ³ , and cut into 420 mm × 54 mm to produce a short positive electrode sheet. An aluminum current collecting tab is ultrasonically welded to the end of the obtained electrode sheet for positive electrode, and then for polymerization of the component (B) in the binder resin solution, removal of residual solvent and adsorbed water in the electrode sheet The electrode for positive electrode of Example 1 was obtained by vacuum drying at 150 ° C. for 16 hours.

Examples 2-7
Except having used binder resin solution 2-7 as binder resin solution, it carried out similarly to Example 1, and obtained the electrode for positive electrodes of Examples 2-7.

Example 8
A volume of 80:10:10 of a lithium cobalt composite oxide having a composition of LiCoO ₂ having an average particle diameter of 10 μm as an active material for a positive electrode, a carbon powder having an average particle diameter of 3 μm as a conductive additive, and a binder resin solution 1 %, And N-methyl-2-pyrrolidone was added and mixed so that the solid content of the binder resin solution was 4% to prepare a slurry. This slurry was applied to both sides of an aluminum foil (current collector) having a thickness of 20 μm and dried at 120 ° C. for 10 minutes. The coating amount of the mixture layer was 290 g / m ² in terms of dry mass. Then, it rolled with the roll press machine so that the bulk density of a mixture layer might be 2.6 g / cm < ³ >, and cut to 54 mm width, and produced the electrode sheet for positive electrodes of a short shape. An aluminum current collector tab was ultrasonically welded to the end of the obtained electrode sheet for positive electrode, and then the polymerization of component (B) in the binder resin solution, removal of residual solvent and adsorbed water in the electrode sheet Therefore, the electrode for positive electrode of Example 8 was obtained by vacuum drying at 150 ° C. for 16 hours.

Example 9
A volume of 80:10:10 of a lithium cobalt composite oxide having a composition of LiNiO ₂ having an average particle diameter of 10 μm as an active material for a positive electrode, a carbon powder having an average particle diameter of 3 μm as a conductive additive, and a binder resin solution 1 %, And N-methyl-2-pyrrolidone was added and mixed so that the solid content of the binder resin solution was 4% to prepare a slurry. This slurry was applied to both sides of an aluminum foil (current collector) having a thickness of 20 μm and dried at 120 ° C. for 10 minutes. The coating amount of the mixture layer was 220 g / m ² in terms of dry mass. Thereafter, the mixture layer was rolled with a roll press so that the bulk density was 3.5 g / cm ³ and cut into a width of 54 mm to produce a short positive electrode sheet. An aluminum current collector tab was ultrasonically welded to the end of the obtained electrode sheet for positive electrode, and then the polymerization of component (B) in the binder resin solution, removal of residual solvent and adsorbed water in the electrode sheet Therefore, the electrode for positive electrode of Example 9 was obtained by vacuum drying at 150 ° C. for 16 hours.

Comparative Example 1
Lithium manganese composite oxide with a composition of Li _1.12 Mn _1.88 O _{4 with} an average particle size of 10 μm as an active material for positive electrode, carbon powder with an average particle size of 3 μm as a conductive additive, and binder resin component in a binder resin solution Polyvinylidene fluoride (# 1120 manufactured by Kureha Chemical Industry Co., Ltd.) as a corresponding component is mixed at a volume ratio of 80:10:10, and N-methyl-2-pyrrolidone has a solid content of 4 in the binder resin solution. % Was added and mixed to prepare a slurry. This slurry was applied to both sides of an aluminum foil (current collector) having a thickness of 20 μm and dried at 120 ° C. for 10 minutes. The coating amount of the mixture layer was 290 g / m ² in terms of dry mass. After that, the mixture layer was rolled with a roll press to a bulk density of 2.6 g / cm ³ and cut into a width of 54 mm to produce a short positive electrode sheet. The aluminum current collector tab was ultrasonically welded to the end of the electrode sheet for the positive electrode, and then vacuum-dried at 150 ° C. for 16 hours to remove residual solvent and adsorbed water in the electrode sheet. A positive electrode was obtained.

Comparative Example 2
A positive electrode for Comparative Example 2 was obtained in the same manner as Comparative Example 1, except that a lithium cobalt composite oxide having a composition of LiCoO ₂ having an average particle diameter of 10 μm was used as the positive electrode active material.
Comparative Example 3
A positive electrode for Comparative Example 3 was obtained in the same manner as Comparative Example 1 except that a lithium nickel composite oxide having a composition of LiNiO ₂ having an average particle diameter of 10 μm was used as the positive electrode active material.
Comparative Example 4
A positive electrode for Comparative Example 4 was obtained in the same manner as in Comparative Example 1 except that polyacrylonitrile (manufactured by Aldrich, mass average molecular weight 82,600) was used as the binder resin component in the binder resin solution.

Comparative Example 5
A positive electrode for Comparative Example 5 was obtained in the same manner as Comparative Example 4 except that a lithium cobalt composite oxide having a composition of LiCoO ₂ having an average particle diameter of 10 μm was used as the positive electrode active material.
Comparative Example 6
A positive electrode for Comparative Example 6 was obtained in the same manner as Comparative Example 4 except that a lithium nickel composite oxide having a composition of LiNiO ₂ having an average particle diameter of 10 μm was used as the positive electrode active material.

<Preparation of electrode for negative electrode>
Example 10
Amorphous carbon (PIC (F) manufactured by Kureha Chemical Industry Co., Ltd.) having an average particle diameter of 20 μm as an active material for a negative electrode and binder resin solution 1 were mixed at 90: 10% by volume (volume% of the binder resin solution is The binder resin solution was mixed at a ratio of volume% of the binder resin component), and N-methyl-2-pyrrolidone was added and mixed so that the solid content of the binder resin solution was 4% to prepare a slurry. This slurry was applied to both sides of a 10 μm thick copper foil (current collector) and dried at 120 ° C. for 10 minutes. The coating amount of the mixture layer was set to 65 g / m ² on one side in terms of dry mass. The mixture layer was rolled with a roll press so that the bulk density was 1.0 g / cm ³ , and cut to a width of 56 mm to prepare a short negative electrode mixture electrode sheet. A nickel current collector tab was ultrasonically welded to the end of the obtained electrode sheet for negative electrode, and then polymerization of component (B) in the binder resin solution, removal of residual solvent and adsorbed water in the electrode sheet were performed. Therefore, the electrode for negative electrode of Example 10 was obtained by vacuum drying at 120 ° C. for 16 hours.

Examples 11-16
Negative electrode for Examples 11 to 16 was obtained in the same manner as Example 10 except that binder resin solutions 2 to 7 were used as the binder resin solution.

Example 17
Artificial graphite (MCMB manufactured by Osaka Gas Co., Ltd.) having an average particle diameter of 20 μm as the negative electrode active material and binder resin solution 1 were mixed at 90: 10% by mass (volume% of the binder resin solution is the binder in the binder resin solution). (Volume% of resin component), and N-methyl-2-pyrrolidone was added and mixed so that the solid content of the binder resin solution was 4% to prepare a slurry. This slurry was applied to both sides of a 10 μm thick copper foil (current collector) and dried at 120 ° C. for 10 minutes. The coating amount of the mixture layer was 70 g / m ² on one side in terms of dry mass. Then, it rolled with the roll press machine so that the bulk density of a mixture layer might be set to 1.5 g / cm < ³ >, and cut to 56 mm width, and produced the electrode sheet for negative electrodes of a short shape. A nickel current collector tab was ultrasonically welded to the end of the obtained electrode sheet for negative electrode, and then polymerization of component (B) in the binder resin solution, removal of residual solvent and adsorbed water in the electrode sheet were performed. Therefore, it was vacuum-dried at 120 ° C. for 16 hours to obtain a negative electrode.

Example 18
Artificial graphite (MCMB manufactured by Osaka Gas Co., Ltd.) having an average particle diameter of 20 μm as the negative electrode active material and binder resin solution 1 were mixed at 90: 10% by mass (volume% of the binder resin solution is the binder in the binder resin solution). (Volume% of resin component), and N-methyl-2-pyrrolidone was added and mixed so that the solid content of the binder resin solution was 4% to prepare a slurry. This slurry was applied to both sides of a 10 μm thick copper foil (current collector) and dried at 120 ° C. for 10 minutes. The coating amount of the mixture layer was 75 g / m ² on one side in terms of dry mass. Then, it rolled with the roll press machine so that the bulk density of a mixture layer might be set to 1.5 g / cm < ³ >, and cut to 56 mm width, and produced the electrode sheet for negative electrodes of a short shape. A nickel current collector tab was ultrasonically welded to the end of the obtained electrode sheet for negative electrode, and then polymerization of component (B) in the binder resin solution, removal of residual solvent and adsorbed water in the electrode sheet were performed. Therefore, it was vacuum-dried at 120 ° C. for 16 hours to obtain a negative electrode.

Comparative Example 7
Amorphous carbon having an average particle diameter of 20 μm as the negative electrode active material and polyvinylidene fluoride as a component corresponding to the binder resin component in the binder resin solution were mixed at a ratio of 90: 10% by volume, and N— Methyl-2-pyrrolidone was added and mixed so that the solid content of the binder resin solution was 4% to prepare a slurry. This slurry was applied to both sides of a 10 μm thick copper foil (current collector) and dried at 120 ° C. for 10 minutes. The coating amount of the mixture layer was set to 65 g / m ² on one side in terms of dry mass. The mixture layer was rolled with a roll press so that the bulk density was 1.0 g / cm ³ , and cut into a width of 56 mm to produce a short negative electrode sheet. A nickel current collector tab was ultrasonically welded to the end of the obtained electrode sheet for negative electrode, and then vacuum-dried at 120 ° C. for 16 hours for removal of residual solvent and adsorbed water in the electrode sheet. An electrode was obtained.

Comparative Example 8
Amorphous carbon having an average particle diameter of 20 μm as the negative electrode active material and polyvinylidene fluoride as a component corresponding to the binder resin component in the binder resin solution were mixed at a ratio of 90: 10% by volume, and N— Methyl-2-pyrrolidone was added and mixed so that the solid content of the binder resin solution was 4% to prepare a slurry. This slurry was applied to both sides of a 10 μm thick copper foil (current collector) and dried at 120 ° C. for 10 minutes. The coating amount of the mixture layer was 50 g / m ² on one side in terms of dry mass. The mixture layer was rolled with a roll press so that the bulk density was 1.0 g / cm ³ , and cut into a width of 56 mm to produce a short negative electrode sheet. A nickel current collector tab was ultrasonically welded to the end of the obtained electrode sheet for negative electrode, and then vacuum-dried at 120 ° C. for 16 hours for removal of residual solvent and adsorbed water in the electrode sheet. An electrode was obtained.

Comparative Example 9
A negative electrode was obtained in the same manner as in Example 18 except that polyvinylidene fluoride resin was used instead of the binder resin solution 1 as a component corresponding to the binder resin component in the binder resin solution.
Comparative Example 10
A negative electrode was obtained in the same manner as in Comparative Example 7 except that polyacrylonitrile (manufactured by Aldrich, mass average molecular weight 82,600) was used as a component corresponding to the binder resin component in the binder resin solution.
Comparative Example 11
A negative electrode was obtained in the same manner as in Comparative Example 9 except that polyacrylonitrile (manufactured by Aldrich, mass average molecular weight 82,600) was used as a component corresponding to the binder resin component in the binder resin solution.

<Evaluation>
It was visually confirmed and evaluated whether peeling and cracks occurred in the electrodes of each Example and Comparative Example. In addition, in order to evaluate the resistance to electrolytic solution, a mixed solution (manufactured by Kishida Chemical Co., Ltd.) of ethylene carbonate / dimethyl carbonate = 1/2 (volume ratio) in which LiPF ₆ having a concentration of 1M was dissolved was used as the electrolytic solution. The electrode of the example or comparative example was immersed in this mixed solution at 50 ° C. for 24 hours. The state of the electrode after immersion was evaluated for the presence or absence of appearance abnormality using an electron microscope (1000 times magnification). These results are shown in Table 1.

Table 1

  As shown in Table 1, when polyvinylidene fluoride was used as the binder resin component in the binder resin solution (Comparative Examples 1 to 3 and 7 to 9), It was observed that the binder resin on the surface of the electric conductor swelled and peeled off from the current collector, or the active material that had appeared on the surface of the binder resin was taken into the binder resin and covered with this resin. When polyacrylonitrile is used as the binder resin component in the binder resin solution (Comparative Examples 4 to 6, 10 and 11), the mixture layer lacks the flexibility of the mixture layer. Peeled off. Therefore, the evaluation of the resistance to electrolytic solution and the subsequent battery production were not performed. In contrast, in Examples 1 to 17, the resistance of the binder resin to the electrolytic solution was improved, and these phenomena were not observed.

<Production of battery>
The positive electrode and the negative electrode of the combination examples or comparative examples shown in Table 2 below were wound through a separator made of a polyethylene microporous film having a thickness of 25 μm and a width of 58 mm to produce a spiral wound group. . This wound group was inserted into a battery can, and a tab terminal previously welded to the negative electrode current collector was welded to the bottom of the battery can. Next, 5 ml of an electrolytic solution in which LiPF ₆ was dissolved at a concentration of 1 mol / l was poured into a solution mixed with ethylene carbonate / dimethyl carbonate = 1/2 (volume ratio). After that, the tab terminal that has been previously welded to the positive electrode current collector is welded to the battery lid, and the lid is placed on the top of the battery can via an insulating gasket, and the battery can and the lid are crimped and sealed. A cylindrical battery having a diameter of 18 mm and a height of 65 mm was produced.

<Battery evaluation>
The batteries 1 to 15 and the comparative battery 1 were charged at a constant current of a charging current of 400 mA and a limiting voltage of 4.2 V, and then discharged to a discharge end voltage of 2.7 V at a discharging current of 800 mA to measure the initial capacity.
The batteries 16 and 18 and the comparative battery 2 were charged at a constant current of a charging current of 750 mA and a limiting voltage of 4.2 V, then discharged at a charging current of 1500 mA until reaching a final discharge voltage of 2.5 V, and the initial capacity was measured.
The batteries 17 and 19 and the comparative battery 3 were charged at a constant current of a charging current of 900 mA and a limiting voltage of 4.15 V, then discharged to a discharge end voltage of 3.0 V at a charging current of 1800 mA, and the initial capacity was measured.
Charging / discharging under these conditions was taken as one cycle and charging / discharging was repeated at an ambient temperature of 50 ° C., and the number of cycles when the discharge dose reached 70% of the initial discharge dose was defined as the life cycle number. The results are shown in Table 2.

Table 2

  As can be seen from Table 2, a positive electrode using lithium manganate as an active material, a polyvinylidene fluoride resin as a binder resin component in a binder resin solution, amorphous carbon as an active material, and polyvinylidene fluoride resin as a binder resin component. The comparative battery 1 combined with the negative electrode used was manufactured by using the binder resin solution according to the present invention for the binder resin of at least one of the positive electrode and the negative electrode, despite the fact that the life was reached in 50 cycles ( The batteries 1 to 11) have an extended life of 200 cycles or more. In particular, batteries using the binder resin solution of the present invention for the negative electrode (batteries 1, 3, 4, 6, 8, 10, 12, 14) are compared with those using PVDF (comparative batteries 1 to 3). Thus, the cycle life characteristics are improved. When the battery after the end of life was disassembled, the comparative battery 1 had the negative electrode mixture layer peeled off from the current collector, and deposition of metallic lithium was confirmed in this portion. On the other hand, deposition of metallic lithium was not observed in the electrode produced using the binder resin solution of the present invention. From this, the battery produced using the binder resin solution of the present invention maintains excellent adhesion between the electrode current collector and the mixture layer interface and the active material, and can suppress the decrease in capacity to a small level. Think.

Claims (8)

(A) a polymer containing a nitrile group, (B) an acrylic monomer and / or methacrylic monomer represented by the general formula (I) , and a solvent ,
When the component (A) is 100 parts by mass, the binder resin solution for a lithium battery electrode contains 1 to 50 parts by mass of the component (B).

(Wherein R ₁ is H or CH ₃ , and R ₂ is a saturated aliphatic hydrocarbon group having 2 to 25 carbon atoms). (A) The binder resin solution for a lithium battery electrode according to claim 1, wherein the polymer containing a nitrile group is a homopolymer of acrylonitrile or methacrylonitrile and / or a copolymer thereof. The current collector has a mixture layer provided on at least one surface of the current collector, and the mixture layer has the following steps:
(a) The process of apply | coating the slurry containing the binder resin solution for lithium battery electrodes and active material of Claim 1 or 2 on the said electrical power collector;
(b) removing the solvent from the applied slurry; and
(c) (B) a step of polymerizing an acrylic monomer and / or a methacrylic monomer,
An electrode for a lithium battery obtained from the above. The lithium battery electrode according to claim 3 , wherein the active material can reversibly insert and release lithium ions by charge and discharge. The lithium battery electrode according to claim 3 or 4 , wherein the active material is a negative electrode active material, and the negative electrode active material is a carbon material. The active material is an active material for a positive electrode, and the active material for a positive electrode is selected from a lithium cobalt composite oxide, a lithium nickel composite oxide, a lithium manganese composite oxide, and a mixture of two or more thereof. 3. The electrode for a lithium battery according to 3 or 4 . The lithium battery containing the electrode for lithium batteries of any one of Claims 3-6 . A method for producing an electrode for a lithium battery, comprising the following steps:
(a) The process of apply | coating the slurry containing the binder resin solution for lithium battery electrodes and active material of Claim 1 or 2 to at least 1 surface of an electrical power collector;
(b) removing the solvent from the applied slurry; and
(c) (B) a step of polymerizing an acrylic monomer and / or a methacrylic monomer,
A method for producing an electrode for a lithium battery, comprising: