JP3624921B2 - Binder for battery, binder composition, electrode, and battery - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a battery binder composition, an electrode using the same, and a battery, and more specifically, a battery binder composition having a large battery capacity and little deterioration even after repeated charge and discharge, an electrode using the same, And battery.
[0002]
[Prior art]
The battery binder is bonded to the surface of the electrode substrate, and the active material is fixed to the electrode surface by fixing the active material in the binder structure. The capacity of the battery is determined by multiple factors such as the type and amount of the active material, the type and amount of the electrolyte, but if the binder cannot fix a sufficient amount of active material to the electrode, a battery with a large initial capacity cannot be obtained. In addition, the capacity of the battery decreases as the active material is removed from the electrode due to repeated charging and discharging.
[0003]
The binder for a battery is usually obtained by dispersing an active material in a binder composition in which a polymer serving as a binder is dissolved or dispersed in a solvent, applying the active material to the surface of the electrode substrate, and volatilizing the solvent. Fix it.
[0004]
There are two types of binder compositions, an organic solvent-based binder composition and an aqueous binder composition. As the organic solvent-based binder composition, a polyvinylidene fluoride-based polymer such as polyvinylidene fluoride is usually N-. Those dissolved in an organic solvent such as methylpyrrolidone are used (for example, JP-A-4-249860, JP-A-7-201315, JP-A-7-201316, etc.). When an electrode manufactured by applying a slurry in which an active material is dispersed in this organic solvent binder composition to an electrode substrate and removing the organic solvent can be used, the initial capacity of the battery can be increased. When charging and discharging are repeated in the used battery, there is a problem that the active material fixed to the electrode is easily dropped. When the active material is improved so as not to easily fall off from the electrode substrate by copolymerizing a comonomer having a polar group (for example, JP-A-7-201315, JP-A-7-201316, etc.) ), The binder made of the polyvinylidene fluoride-based polymer has a small improvement effect, and since the strength is easily lowered by swelling in the electrolytic solution, the drop-off cannot be sufficiently suppressed.
[0005]
As an aqueous binder composition, an aqueous dispersion of a latex of a styrene / butadiene copolymer rubber produced by using an emulsion polymerization method using a surfactant as a solvent and carboxymethyl cellulose or the like as a thickener is added. Used (for example, JP-A-4-342966, JP-A-2-21068, JP-A-5-74461, etc.). When an electrode manufactured by applying a slurry in which an active material is dispersed in this aqueous binder composition to an electrode substrate and removing moisture is used, the active material is less likely to fall off. Although the active material did not easily fall off, a battery having a large capacity could not be obtained.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a battery binder composition that can increase the capacity of the battery and that does not deteriorate even after repeated charge and discharge, an electrode having the active material fixed thereon, and a battery.
[0007]
[Means for Solving the Problems]
As a result of diligent efforts, the present inventors have found that a composition in which a rubbery polymer is blended with a polyvinylidene fluoride polymer is less likely to drop off an active material as a binder, and the present invention has been completed.
[0008]
Thus, according to the present invention, a battery binder comprising a polyvinylidene fluoride polymer and a rubbery polymer, a binder comprising the battery binder and a solvent, an electrode having an active material fixed by the battery binder, and the A battery using the electrode is provided.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
(Polyvinylidene fluoride polymer)
The polyvinylidene fluoride polymer used in the present invention contains 50% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and usually 100% by weight of repeating structural units derived from vinylidene fluoride. Is most preferred. If the number of repeating structural units derived from vinylidene fluoride is too small, the flexibility is insufficient or the solvent resistance is low, and it becomes difficult to sufficiently fix the active material and maintain it without dropping off.
[0010]
If necessary, a copolymer may be used using a comonomer copolymerizable with vinylidene fluoride as long as the active material is sufficiently fixed and can be held without dropping. Examples of such comonomers include ethylenically unsaturated monomers such as aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, pt-butylstyrene, and chlorostyrene; (Meth) acrylate esters such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate Monomers; (meth) acrylamide monomers such as (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide; glycidyl such as glycidyl (meth) acrylate and allyl glycidyl ether Group-containing monomers; (meth) acrylonitriles and other (meth) acrylic Ronitrile monomers; carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, fumaric acid and itaconic acid; sulfonic acid group-containing monomers such as styrene sulfonic acid sword and acrylamidomethylpropane sulfonic acid; Amino group-containing monomers such as dimethylaminoethyl and diethylaminoethyl methacrylate; Most of these are monomers having a polar group, but in order to make the binder excellent in adhesiveness, as a comonomer when a polyvinylidene fluoride polymer is used as a copolymer, a polar group is used. It is preferable to use the monomer which has. In that case, copolymerization is performed so that the repeating structural unit derived from the comonomer is 50% by weight or less, preferably 20% by weight or less, more preferably 10% by weight or less. When there are too many repeating structural units derived from a comonomer, there are too many repeating structural units derived from vinylidene fluoride, the solvent resistance is low, and there arises a problem that the active material tends to fall off from the electrode substrate due to a volume change due to charge and discharge.
[0011]
The polyvinylidene fluoride polymer of the present invention is a persulfate, a perphosphate, or the like as a polymerization initiator in an aqueous solvent or an organic solvent. It can be obtained by copolymerization using 14 MPa, a polymerization initiator, an emulsifier, and a chain transfer agent. The degree of polymerization is preferably 500 or more, more preferably 800 or more, and preferably 3000 or less, more preferably 2000 or less. When the degree of polymerization is too small, the strength is insufficient as a binder, and when it is too large, the viscosity becomes too high and it becomes difficult to apply the binder composition.
[0012]
(Rubber polymer)
In the present invention, in order to make the binder more flexible, a rubbery polymer is blended with the polyvinylidene fluoride polymer to obtain a binder. The rubbery polymer is not particularly limited, and a rubbery polymer having polarity is preferable as the binder because it has excellent adhesion to the active material and is excellent in adhesion between the electrode substrate and the active material.
[0013]
The polar rubbery polymer is preferably 5% by weight or more, more preferably 10% by weight or more, particularly preferably 30% by weight of a repeating structural unit derived from a monomer having polarity (hereinafter referred to as polar monomer). The rubber polymer containing 100% by weight or less. If the number of repeating structural units derived from the polar monomer is small, the polarity may be small and the active material may easily peel off from the electrode substrate, and it may be difficult to disperse in the organic solvent. As polar monomers, ethylenic nitrile compounds such as (meth) acrylonitrile, crotonnitrile, allylnitrile; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylonitrile, hydroxyethyl (Meth) acrylate and other ethylenically unsaturated carboxylic acid esters; acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid and other ethylenically unsaturated carboxylic acids; maleic anhydride and other ethylenically unsaturated carboxylic acid anhydrides Can be used. In particular, dicarboxylic acids such as itaconic acid, fumaric acid and maleic acid, and dicarboxylic acid anhydrides such as maleic anhydride are preferred in terms of increasing the adhesive strength of the electrode.
[0014]
In addition, since the balance between strength and flexibility is good, the polar rubbery polymer is preferably an aromatic vinyl / conjugated diene polymer. This preferred aromatic vinyl / conjugated diene polymer has a repeating structural unit derived from the polar monomer of 5% by weight or more, preferably 10% by weight or more, more preferably 30% by weight or more, and preferably 50%. % By weight or less, more preferably 40% by weight or less, particularly preferably 35% by weight or less, and a repeating structure derived from an aromatic vinyl monomer such as styrene, α-methylstyrene, vinyltoluene, or pt-butylstyrene. The unit is preferably 15% by weight or more, more preferably 20% by weight or more, particularly preferably 25% by weight or more, and preferably 50% by weight or less, more preferably 45% by weight or less, particularly preferably 40% by weight or less, Conjugated diene monomers such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene The repeating structural unit is preferably 15% by weight or more, more preferably 20% by weight or more, particularly preferably 30% by weight or more, and preferably 80% by weight or less, more preferably 50% by weight or less, particularly preferably 40% by weight. % Or less. If the amount of the polar monomer is too large, the characteristics of the aromatic vinyl / conjugated diene polymer are hardly exhibited and the flexibility is poor. Too little aromatic vinyl monomer or too much conjugated diene monomer will result in insufficient strength, and too much aromatic vinyl monomer or too little conjugated diene monomer will provide flexibility. Run short. If the strength is insufficient, the active material is likely to fall off the electrode substrate due to volume change such as swelling / shrinkage of the active material due to charge / discharge, and if the flexibility is insufficient, the electrode is thin and the electrode is thin. As a result, the binder easily peels off from the electrode substrate, and the active material easily falls off the electrode substrate.
[0015]
The method for producing the rubbery polymer used in the present invention is not particularly limited, and in the case of an aromatic vinyl / conjugated diene polymer that is a polar rubbery polymer, solution polymerization or emulsion polymerization may be used, but it is usually simple. For some reason, it is polymerized as latex particles by emulsion polymerization. In the case of emulsion polymerization, generally, 100 parts by weight of the monomer mixture is dispersed in 60 parts by weight or more, preferably 100 parts by weight or more and 300 parts by weight or less, preferably 200 parts by weight of a dispersion medium mainly composed of water. 1 part by weight or more of the emulsifier, preferably 2 parts by weight or more and 10 parts by weight or less, preferably 7 parts by weight or less, 0.1 parts by weight or more of the polymerization initiator, preferably 0.2 parts by weight or more, and 1 part by weight. Part or less, preferably 0.6 parts by weight or less, and a necessary amount of molecular weight regulator is added, and the polymerization is conducted with stirring at a temperature of 30 ° C. or higher, preferably 50 ° C. or higher and 100 ° C. or lower, preferably 90 ° C. or lower . A batch method in which all monomers are dispersed in a dispersion medium in advance and then polymerized, a semi-batch method in which a part of the monomers is polymerized and then the remaining monomers are continuously added to the dispersion medium for polymerization. The polymerization may be carried out by any continuous method in which a monomer is continuously added to a dispersion medium for polymerization. As the emulsifier, nonionic emulsifiers such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene oxide / polypropylene oxide copolymers; alkyl sulfonates, alkyl allyl sulfonates, alkyl sulfates, alkyl sulfone Examples include anionic emulsifiers such as succinates and polyoxyethylene alkylphenyl ether sulcates. As a polymerization initiator, persulfates such as potassium persulfate and ammonium persulfate; peroxides such as hydrogen peroxide, benzoyl peroxide, cumene peroxide and tert-butyl hydroperoxide; Reducing agents such as sodium bisulfite and ascorbic acid; polymerization aids such as disodium phosphate may be used in combination.
[0016]
When an aromatic vinyl / conjugated diene polymer, which is a polar rubber polymer, is obtained by emulsion polymerization, the particle size of the polymer obtained as latex particles is 0.01 μm or more, preferably 0.05 μm or more. Preferably they are 0.10 micrometer or more and 10 micrometers or less, Preferably it is 1 micrometer or less, More preferably, it is 0.5 micrometer or less. Further, when an aromatic vinyl / conjugated diene polymer that is a polar rubbery polymer is obtained by solution polymerization, a weight average molecular weight of 20,000 or more in terms of polystyrene by gel permeation chromatography using tetrahydrofuran as a solvent, Preferably it is 30,000 or more, More preferably, it is 50,000 or more and 1,000,000 or less, Preferably it is 800,000 or less, More preferably, it is 500,000 or less. If the particle size or molecular weight is too small, the adhesiveness is inferior, the active material tends to fall off from the electrode substrate, and if it is too large, polymerization is difficult.
[0017]
(Binder for battery)
The battery binder of the present invention is 5 parts by weight or more, preferably 20 parts by weight or more, more preferably 40 parts by weight or more and 100 parts by weight with respect to 100 parts by weight of the polyvinylidene fluoride polymer. Hereinafter, it is preferably 90 parts by weight or less, more preferably 80 parts by weight or less. If the amount of the rubbery polymer is too small, there is no flexibility, so that the binder is easily peeled off from the electrode substrate due to slight distortion of the electrode, and the active material layer on the electrode surface may be cracked or chipped. On the other hand, if the amount is too large, the strength is insufficient, and the active material is likely to fall off due to the volume change of the active material due to charge / discharge.
[0018]
(Binder composition for batteries)
The battery binder composition of the present invention is a battery binder solution or dispersion, but is usually simple, so that a polyvinylidene fluoride polymer and a rubbery polymer are prepared without preparing a binder in advance. The other optional components are dissolved or dispersed in one solvent to prepare a binder composition.
[0019]
The solvent is not particularly limited as long as it can dissolve or disperse the polyvinylidene fluoride polymer and the rubbery polymer. In particular, by making a rubbery polymer into a polar rubbery polymer, the rubbery polymer is added to a polar organic solvent such as N-methylpyrrolidone or dimethylfluoride that can dissolve or disperse the polyvinylidene fluoride polymer well. Can also be dispersed. Usually, ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, in which polyvinylidene fluoride does not dissolve; Furans such as tetrahydrofuran and rufurfural; Esters such as ethyl acetate and methyl acetate; Nitriles such as acetonitrile and propionitrile , Etc., become soluble depending on the type and amount of the comonomer used in the polyvinylidene fluoride polymer, and these solvents can be used as long as the rubbery polymer can be dissolved and dispersed.
[0020]
The amount of the solvent is not particularly limited, but usually the solvent is preferably 400 parts by weight or more, more preferably 500 parts by weight or more, particularly preferably 800 parts by weight or more, and preferably 10,000 parts by weight or less, in 100 parts by weight of the binder. More preferably, it is 5,000 parts by weight or less, particularly preferably 2,000 parts by weight or less. If it is too much or too little, it becomes difficult to apply the binder composition.
[0021]
(electrode)
In the electrode of the present invention, an active material is blended into the binder composition for a battery to prepare a slurry, which is applied to the electrode substrate, and the solvent is removed, whereby the active material is incorporated into the binder matrix formed on the electrode substrate surface. Is obtained by fixing.
[0022]
The active material used in the present invention is not particularly limited as long as it functions as an active material. Usually, carbon is used as a negative electrode active material, and oxides such as molybdenum, vanadium, titanium, niobium, sulfides, and Ce are used as a positive electrode active material. Les In addition to nitride, lithium-containing composite oxides such as lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, and lithium iron oxide are used. As the active material to be fixed, carbon is preferable because it is particularly firmly fixed in the binder matrix and hardly falls off during use as a battery electrode.
[0023]
The amount of the active material of the slurry used in the present invention is not particularly limited, but is preferably 5 times or more, more preferably 7 times or more, and 1000 times or less, more preferably 100 times or less, on a weight basis with respect to the battery binder. An active material is blended in the binder composition for batteries. If the amount of the active material is too small, there are many inactive portions on the surface of the binder layer on which the active material is fixed, and the function as an electrode may be insufficient. It becomes easy to drop off without being fixed enough. In addition, the slurry is used by adding a solvent to a concentration that facilitates coating.
[0024]
The electrode substrate used in the present invention is not particularly limited as long as it is made of a conductive material, but generally a metal substrate such as iron, copper or aluminum is used. Although the shape is not particularly limited, a sheet having a thickness of about 0.05 to 0.5 mm is usually used because a large electrode surface area is preferable.
[0025]
The method for applying the slurry is not particularly limited. For example, it is applied by dipping or brushing. The amount to be applied is preferably 0.1 mm or more, more preferably 0.5 mm or more, preferably 5 mm or less, more preferably 2 mm or less, with the thickness of the binder layer fixing the active material formed after removing the organic solvent. To be. The method for removing the organic solvent is not particularly limited, but usually, the organic solvent is volatilized as soon as possible within a speed range that does not cause stress concentration to crack the binder layer or peel off from the electrode substrate. The organic solvent is removed by adjusting the degree of decompression and the degree of heating.
[0026]
(battery)
The battery of the present invention uses the electrode of the present invention for at least one of a positive electrode and a negative electrode. This battery has a structure in which an active material is fixed between a positive electrode and a negative electrode (a binder layer side in the electrode of the present invention) face each other, and an electrolyte solution is filled between both electrodes. In the case of a large battery, the electrode is tape-shaped, the separator sheet is sandwiched between the negative electrode and the positive electrode, wound, and immersed in a case filled with electrolyte. In this case, it is easy to use the battery as a battery by a method such as making the electrode into a circular sheet and immersing it in a coin-shaped case filled with the electrolyte, and a battery with a large capacity can be obtained.
[0027]
There is no particular limitation on the electrolytic solution, and a material that functions as a battery may be selected according to the types of the negative electrode active material and the positive electrode active material. For example, as an electrolyte, LiClO ₄ , LiBF ₄ , CF ₃ SO ₃ Li, LiI, LiAlCl ₄ , LiPF ₆ , NaClO ₄ , NaBF ₄ , NaI, (n-Bu) ₄ NClO ₄ Examples of solvents include ethers, ketones, lactones, nitriles, amines, amides, sulfur compounds, chlorinated hydrocarbons, esters, carbonates, nitro compounds, and phosphate esters Examples thereof include compounds and sulfolane compounds, and generally, ethylene carbonate, diethyl carbonate and the like are widely used.
[0028]
(Aspect)
As an aspect of the present invention,
(1) a battery binder comprising a polyvinylidene fluoride polymer and a rubbery polymer;
(2) The battery binder according to (1), wherein the rubber polymer is a polar rubber polymer,
(3) The battery binder according to (1) or (2), wherein the rubbery polymer contains 5 to 100% by weight of a repeating structural unit derived from a monomer having a polar group,
(4) The battery binder according to any one of (1) to (3), wherein the rubbery polymer is an aromatic vinyl / conjugated diene copolymer,
(5) The rubbery polymer has 5 to 50% by weight of repeating structural units derived from monomers having polar groups, 15 to 50% by weight of repeating structural units derived from aromatic vinyl monomers, and conjugated. The battery binder according to any one of (1) to (4), wherein the repeating structural unit derived from a diene monomer contains 15 to 80% by weight,
(6) The battery binder according to any one of (1) to (5), wherein the rubbery polymer is latex particles having a particle diameter of 0.01 to 10 μm.
(7) The rubbery polymer according to any one of (1) to (5), which has a weight average molecular weight of 20,000 to 1,000,000 in terms of polystyrene by gel permeation chromatography using tetrahydrofuran as a solvent. Battery binder,
(8) The binder for batteries according to any one of (1) to (7), wherein the polyvinylidene fluoride-based polymer contains 50 to 100% by weight of repeating structural units derived from vinylidene fluoride,
(9) The binder for batteries according to any one of (1) to (8), wherein the degree of polymerization of the polyvinylidene fluoride polymer is 500 to 3,000,
(10) The battery binder according to any one of (1) to (9), wherein 5 to 100 parts by weight of a rubbery polymer is blended with 100 parts by weight of the polyvinylidene fluoride polymer.
(11) A battery binder composition comprising a solvent and the battery binder according to any one of (1) to (10),
(12) The battery binder composition according to (11), which is obtained by adding 400 to 10,000 parts by weight of a solvent to 100 parts by weight of a battery binder,
(13) An electrode in which an active material is fixed by the battery binder according to any one of (1) to (10),
(14) The electrode according to (13), wherein the active material is preferably fixed 5 to 1000 times by weight based on the binder for the battery,
(15) An electrode in which the active material is uniformly dispersed in the battery binder composition according to any one of (1) to (10), applied to an electrode substrate, and the solvent is removed.
(16) A battery using the electrode according to any one of (13) to (15) as at least one of a positive electrode and a negative electrode,
Etc. are exemplified.
[0029]
【Example】
The present invention will be specifically described below with reference examples, examples and comparative examples.
[0030]
Reference example 1
To 1 liter of water, 400 g of styrene, 300 g of butadiene, 200 g of methyl methacrylate, 50 g of acrylonitrile, 50 g of itaconic acid, 4 g of ammonium lauryl sulfate and 10 g of sodium bicarbonate were added and stirred to prepare a monomer emulsion.
[0031]
Add 3.4 liters of water, 10 g of ethylenediaminetetraacetic acid, 10 g of ammonium lauryl sulfate, 20 g of potassium persulfate and 10% by weight of the above monomer emulsion, heat to 80 ° C. with stirring, and react for 1 hour to obtain 80 g of potassium persulfate. After addition with 200 ml of water, the remaining monomer was added continuously at a constant rate over 4 hours and allowed to react for an additional 4 hours. The remaining monomer was removed under reduced pressure, and the pH was adjusted to 7 with lithium hydroxide. The conversion rate was about 99%.
[0032]
2000 g of N-methylpyrrolidone was added to 250 ml of the obtained latex dispersion, and water was removed using an evaporator to obtain a latex particle organic solvent dispersion. This latex particle organic solvent dispersion had a solid content of 9.3% by weight, a water content of about 180 ppm, and the average particle size of the latex particles was 0.18 μm.
[0033]
Reference example 2
Latex particle organic solvent dispersion in the same manner as in Example 1 except that styrene 400 g, butadiene 300 g, methyl methacrylate 200 g, acrylonitrile 50 g, and itaconic acid 50 g were used instead of styrene 500 g, butadiene 250 g, methyl methacrylate 150 g, and acrylonitrile 100 g. A liquid was obtained. This latex particle organic solvent dispersion had a solid content concentration of 7.0% by weight, a water content of about 200 ppm, and the average particle size of the latex particles was 0.18 μm.
[0034]
Reference example 3
Example 1 is used except that instead of styrene 400 g, butadiene 300 g, methyl methacrylate 200 g, acrylonitrile 50 g, and itaconic acid 50 g, styrene 350 g, butadiene 200 g, methyl methacrylate 200 g, acrylonitrile 100 g, itaconic acid 100 g, and fumaric acid 50 g are used. Similarly, a latex particle organic solvent dispersion was obtained. This latex particle organic solvent dispersion had a solid content concentration of 4.0% by weight, a water content of 180 ppm, and the average particle size of the latex particles was 0.18 μm.
[0035]
Example 1
By adding 30 parts by weight of N-methylpyrrolidone to 5 parts by weight of polyvinylidene fluoride (polymerization degree: about 1000) and the latex particle organic solvent dispersion obtained in Reference Example 1 so that the solid content is 3 parts by weight, A binder composition was obtained.
[0036]
To this binder composition, 100 parts by weight of carbon (NG-12L, manufactured by Kansai Thermal Engineering) as a negative electrode active material is added to 8 parts by weight of the solid content in the composition, and N-methyl is added so that the viscosity is about 7000 cps. Pyrrolidone was added to prepare a slurry, which was applied onto a copper foil having a thickness of 0.1 mm, dried by holding at 130 ° C. for 5 hours, and an active material having a uniform thickness of 0.5 mm was fixed by a roll press. A binder layer was formed to provide an electrode (negative electrode) of the present invention.
[0037]
Further, in the same binder composition, LiCo as a positive electrode active material with respect to 4 parts by weight of the solid content in the composition ₂ 90 parts by weight and 10 parts by weight of acetylene black (Denka Black, Denki Kagaku Kogyo) were added, N-methylpyrrolidone was added so that the viscosity was about 7000 cps, and a slurry was prepared. An electrode (positive electrode) was manufactured by applying the coating layer on the substrate, drying it while maintaining at 130 ° C. for 5 hours, and forming a binder layer on which an active material having a uniform thickness of 0.5 mm was fixed by a roll press.
[0038]
Both the negative electrode and the positive electrode were cut into a circle having a diameter of 15 mm on a Teflon plate using a cylindrical blade. No cracks or chips were observed at the cut portion of the active material layer fixed with the binder.
[0039]
A polypropylene packing was disposed with the active material layers fixed to each other facing each other with a separator made of a circular polypropylene microporous membrane (fiber nonwoven fabric) having a diameter of 16 mm and a thickness of 50 μm interposed between the two electrodes. It was stored in a stainless steel outer container (cylindrical container having only one bottom surface having a diameter of 20 mm, a height of 1.8 mm, and a stainless steel thickness of 0.2 mm). In a container, LiPF was added to a solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1. ₆ An electrolyte solution dissolved in a concentration of 1 mol / liter is poured so that no air remains, and a stainless steel cap with a thickness of 0.2 mm is covered, and the outer container and the cap are fixed via a polypropylene-made packing. The contents were sealed so that the copper foil was in contact with the cap and the aluminum foil was in contact with the bottom of the container, thereby producing a coin-type battery having a diameter of 20 mm and a thickness of 2.0 mm.
[0040]
In this battery, the constant current method (current density: 1.0 mA / cm ² ) Was charged to 4.0V and discharged to 3.0V, and the change in capacity was measured. The capacity at the first charge was 180 mAh (100%), 170 mAh (reduced to about 94%) at the 50th charge, and 160 mAh (reduced to about 89%) at the 100th charge.
[0041]
Example 2
An electrode was prepared in the same manner as in Example 1 except that the latex particle organic solvent dispersion obtained in Reference Example 2 was used instead of the latex particle organic solvent dispersion obtained in Reference Example 1, and a battery was obtained and the performance was examined. It was.
[0042]
In the cut portion of the active material layer fixed by the binder of both electrodes cut into a circle having a diameter of 15 mm, no cracks or chips were observed. The capacity at the first charge was 175 mAh (100%), 160 mAh (reduced to about 91%) at the 50th charge, and 155 mAh (reduced to about 89%) at the 100th charge.
[0043]
Example 3
An electrode was prepared in the same manner as in Example 1 except that the latex particle organic solvent dispersion obtained in Reference Example 3 was used instead of the latex particle organic solvent dispersion obtained in Reference Example 1, a battery was obtained, and the performance was examined. It was.
[0044]
In the cut portion of the active material layer fixed by the binder of both electrodes cut into a circle having a diameter of 15 mm, no cracks or chips were observed. The capacity at the first charge was 185 mAh (100%), 170 mAh (decreased to about 92%) at the 50th charge, and 160 mAh (decreased to about 86%) at the 100th charge.
[0045]
Comparative Example 1
An electrode was produced in the same manner as in Example 1 except that a binder composition in which 10 parts by weight of polyvinylidene fluoride was added to 90 parts by weight of N-methylpyrrolidone instead of the prepared binder composition was obtained, and a battery was obtained. I investigated.
[0046]
Cracks were observed at the cut portion of the active material layer fixed by the binder of both electrodes cut into a circle having a diameter of 15 mm, and chipping was observed at a considerable portion. Moreover, although the capacity | capacitance by the 1st charge was 180 mAh, since it fell to 20 mAh or less by the 40th time, the measurement was stopped.
[0047]
【The invention's effect】
In a battery in which an electrode having an active material fixed using the battery binder composition of the present invention is used for either the positive electrode or the negative electrode, since the active material is less likely to fall off from the electrode, the capacity decrease is small, and the initial capacity In addition, since the electrode surface to which the active material is fixed is less likely to crack or chip, the performance is stable.

Claims (5)

A binder for an organic electrolyte secondary battery electrode comprising a polyvinylidene fluoride polymer and a rubbery polymer which is an aromatic vinyl / conjugated diene copolymer. 2. The binder for an organic electrolyte secondary battery electrode according to claim 1, wherein the rubber polymer is a polar rubber polymer. The binder which consists of the binder for organic electrolyte secondary battery electrodes of Claim 1 or 2, and a solvent. According to claim 1 or 2 organic electrolyte secondary battery electrode with a fixed active material with an organic electrolyte secondary battery electrode binder according. An organic electrolyte secondary battery using the organic electrolyte secondary battery electrode according to claim 4.