JPH10188991A - Binder composition for lithium ion secondary battery electrode, electrode and battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery having excellent charge and discharge cycle characteristics, high capacity maintaining ratio and excellent battery performance by forming an electrode of a low-gel type binder composition, which is composed of a rubber polymer having polyethylene type saturated main chain and non-aromatic group organic compound solvent having a specified number of carbon and a specified boiling point. SOLUTION: An active material is mixed in a binder composition, which is composed of a rubber polymer and an organic compound solvent to obtain the slurry, and this slurry is coated on a collector, and the solvent is eliminated by drying to obtain a lithium ion secondary battery electrode. As a described rubber group polymer, a rubber group polymer, which has a polyethylene type saturated main chain and which does not include fluorine, is used. An organic compound solvent, which has 2-20 carbon and a boiling point at 85-350 deg.C and which does not have an aromatic group nucleus, is used. Furthermore, percentage content of gel of the rubber polymer in the binder composition is set at a value less than 50%. With this composition, excellent adhesiveness can be obtained between the collector and the active material, and between each active material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a binder composition for a lithium ion secondary battery electrode, an electrode and a battery.

[0002]

2. Description of the Related Art A binder composition for an electrode of a lithium ion secondary battery (hereinafter, sometimes referred to as a binder composition) is obtained by dissolving a substance to be a binder in a solvent. A mixture of the binder composition and the active material (hereinafter, sometimes referred to as a slurry) is applied to the current collector of the electrode, and the solvent is removed by a method such as drying to bind the active material to the current collector. At the same time, the active materials are bound together to form an electrode of the lithium ion secondary battery.

[0003] The capacity of a lithium ion secondary battery (hereinafter sometimes referred to as a battery) is determined by a number of factors such as the type and amount of an active material, the type and amount of an electrolyte, and the like. Composition performance is also an important factor. If the binder can bind a sufficient amount of the active material to the current collector and cannot bind the active materials to each other, a battery with a large initial capacity cannot be obtained. This is because the active material falls off and the capacity of the battery decreases. Such a difference in performance may be caused by, for example, a difference in the solvent of the binder composition, in addition to a difference in the type of the binder.

[0004] As the binder composition, two types of organic solvent-based binder composition and water-dispersed binder composition are known, and the water-dispersed binder is used for non-aqueous electrolyte batteries such as lithium ion secondary batteries. When used in the manufacture of an electrode, if the water is insufficiently dried and even a very small amount of water remains on the electrode, lithium ions react violently with the remaining water to deteriorate battery performance. Therefore, it is very important to completely remove water when manufacturing an electrode using a water-dispersed binder, but a high level of technology is required to completely remove water industrially.

Therefore, an organic solvent-based binder composition in which a polyvinylidene fluoride-based polymer is dissolved in N-methylpyrrolidone or the like has been industrially frequently used (for example, see JP-A-4-249860). Such).
However, when this binder composition is used, the binding property between the current collector and the active material is not always sufficient, and there is a problem that the active material is dropped off due to volume fluctuation of the active material due to repetition of charge and discharge. As described in Japanese Patent Application Laid-Open No. H6-163031, a rise in battery temperature decomposes a polyvinylidene fluoride-based polymer to generate hydrogen fluoride, reacts with lithium ions in the system, Damage or rupture may occur.

Under these circumstances, in recent years, it has been proposed to use a rubber-based polymer as a binder for an electrode for a lithium ion battery (JP-A-5-62668,
JP-A-8-124561, JP-A-8-15767
No. 7 publication). However, even if it is a rubber-based polymer, a fluorine-based rubber as described in JP-A-8-157677 has a chemical structure similar to that of a polyvinylidene fluoride-based polymer, and There is the same problem as the fluoride-based polymer. JP-A-5-62668 and JP-A-8-124561 exemplify a rubber-based binder composition in which a rubber-based polymer is dissolved in an aromatic organic compound solvent such as benzene or toluene. However, the present inventors have further studied and found that when an aromatic solvent is used as the solvent, the binding property between the current collector and the active material is significantly reduced, and the binding between the active material particles is also poor. Was obtained. This is considered to be because the rubber-based polymer is concentrated on the electrode surface when a slurry containing a binder, an active material, and the like is applied to the current collector and dried.

As described above, a binder composition used for an electrode for a lithium ion secondary battery has not yet obtained a binder composition having sufficient performance, and further improvement is required.

[0008]

Based on such prior art, the present inventors have conducted intensive studies in order to provide a further excellent binder composition. The inventors have found that a binder composition obtained by dissolving a fluorine-based rubber in a non-aromatic compound organic solvent has excellent performance, and have completed the present invention.

[0009]

According to the present invention, there is provided a binder composition for a lithium ion secondary battery electrode comprising a rubber-based polymer and an organic compound solvent,
(A) the rubber-based polymer is a rubber-based polymer having a polymethylene-type saturated main chain and containing no fluorine atom, and (b) the organic compound solvent has 2 to 20 carbon atoms and a boiling point of 85 to 350 ° C. And an organic compound solvent having no aromatic nucleus, and (c) a gel content of a rubber-based polymer in the binder composition is less than 50%. Provided are a binder composition for use, a lithium-ion secondary battery electrode manufactured using the binder composition, and a lithium-ion secondary battery using the electrode.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. (A) Rubber-Based Polymer The rubber-based polymer used in the present invention is a rubber-based polymer having a polymethylene-type saturated main chain and containing no fluorine atom. Such polymers include AC
Acrylate rubbers such as M, AEM, ANM, etc .;
Chlorinated polyethylene rubber such as CM, CSM, etc .;
Specific examples include copolymer rubber of a monomer containing ethylene and propylene such as EPDM and EPM; ternary rubber containing styrene such as SEBM and SEPM; and EVM. ACM, AEM, ANM, CM, CSM, EPDM,
ETM, EVM, SEBM, SEPM are ASTM D
It is a polymer according to the notation specified by 1418-94, and is a polymer that does not contain a fluorine atom among polymers classified into the M class. Of course, these polymers may be used alone, or two or more of them may be mixed and used by appropriately setting the mixing ratio according to the purpose. Hereinafter, these polymers will be specifically described.

The acrylate rubber used in the present invention includes AC acrylate, which is a copolymer of ethyl acrylate or other acrylate and a small amount of a monomer for vulcanization.
M, AEM which is a copolymer of ethyl acrylate or other acrylate and ethylene, and ANM which is a copolymer of ethyl acrylate or other acrylate and acrylonitrile are exemplified. Examples of the acrylate include an alkyl acrylate having 1 to 8 carbon atoms, an alkyl acrylate having 1 to 4 carbon atoms having an alkoxy group, and an alkylene group having 2 to 5 carbon atoms. At least one acrylate monomer selected from the group consisting of alkyl acrylates having 1 to 8 carbon atoms having the following formula (I) is preferable.
It is at least 0% by weight, preferably at least 40% by weight, more preferably at least 60% by weight.

100 ° C. of such an acrylate rubber
Is preferably from 10 to 150, more preferably from 20 to 80. Also,
Glass transition temperature (measured by differential scanning calorimeter; Tg)
Is preferably from 10 to -60C, more preferably from 0 to-
40 ° C.

Specific examples of the acrylate rubber used in the present invention include Nipol AR series (manufactured by Nippon Zeon Co., Ltd .; trade name) and JSR-AREX series (manufactured by Nippon Synthetic Rubber Co., Ltd .; trade name). Noxtite series (manufactured by Nippon Mektron Ltd .; trade name), Toa Akron series (manufactured by Toa Paint Co., Ltd .; trade name), Nissin acrylic rubber RV-2500 series (manufactured by Nissin Chemical Co., Ltd.); (Trade name), Baymac series (Dupont Co., Ltd .; trade name) and the like.

The chlorinated polyethylene rubber used in the present invention includes chlorinated polyethylene (CM) and chlorsulfonated polyethylene (CSM).

Specific examples of the chlorinated polyethylene rubber used in the present invention include Tyrin series (trade name, manufactured by Dow Chemical Co., Ltd.), Eraslen series (trade name, manufactured by Showa Denko KK), Daisorak series (manufactured by Daiso Corporation; trade name), Hypalon (HYP)
ALON) series (manufactured by Dupont Co .; trade name), Ectos series (manufactured by Tosoh Corporation; trade name) and the like.

The copolymer rubber of a monomer containing ethylene and propylene used in the present invention includes EPM, which is a copolymer of ethylene and propylene, and ethylene-propylene.
EPDM, which is a terpolymer composed of dienes, and the like. The ethylene / propylene ratio (weight ratio) of EPM and EPDM used in the present invention is not particularly limited, but is usually 30/70 to 80/20, preferably 50/70.
It is 50-70 / 30.

The diene as a raw material of the EPDM used in the present invention includes dicyclopentadiene, ethylidene norbornene, cyclopentadiene, 1,3-cyclohexadiene, 1,4-cyclohexadiene,
Any cyclic diene such as 5-norbornadiene can be arbitrarily selected, but dicyclopentadiene and ethylidene norbornene are particularly preferred examples. Further, such a diene is used in an EPDM synthesis at a ratio of 15% by weight or less, preferably 10% by weight or less.

The weight average molecular weight in terms of styrene of these EPM and EPDM measured by gel permeation chromatography using toluene is as follows:
2,000 to 1,000,000, preferably 4,000
0 to 500,000, particularly preferably 5,000 to 30
It has a Mooney viscosity of 5 to 200, preferably 10 to 150, measured at 100 ° C.

Specific examples of the copolymer rubber of a monomer containing ethylene and propylene used in the present invention include JSR E
P series (manufactured by Nippon Synthetic Rubber Co., Ltd .; trade name), Mitsui EPT series, Bestabrene series, Mybren series (all 3 series are Mitsui Petrochemicals Co., Ltd.)
Company name; Esplen EPR series, Esplen EPDM series (two or more series manufactured by Kyo Sumitomo Chemical Co., Ltd .; brand name), Kertan series (manufactured by Idemitsu DSM Corporation; brand name), Loyallen series EPM such as (Uniroyal Corp .; trade name), Nodell series (Dupont Corp .; trade name), Dutralter series (Montecatini Co .; trade name), etc.
And EPDM.

Examples of the styrene-containing block copolymer used in the present invention include styrene / ethylene / butylene terpolymers such as SEBM (SEB and SEB).
S), SEPM (SEP and SEPS) which is a styrene-ethylene-propylene ternary block copolymer, and the like.

The weight average molecular weight in terms of styrene of the block copolymer of a monomer containing styrene used in the present invention, as measured by gel permeation chromatography using toluene, is from 2,000 to 1,000,000.
000, preferably 4,000 to 500,000, particularly preferably 5,000 to 300,000. The styrene content of the copolymer is 5 to 80% by weight, preferably 8 to 50% by weight, more preferably 10 to 30% by weight.

The iodine value of SEBM and SEPM is usually 120 or less, preferably 50 or less, more preferably 30 or less.

Specific examples of the block copolymer of a monomer containing styrene used in the present invention include Rheostomer series (manufactured by Riken Vinyl Industry Co., Ltd .; trade name) and Lavalon series (manufactured by Mitsubishi Chemical Corporation; Name), Sumitomo TP
E-SB series (manufactured by Sumitomo Chemical Co., Ltd .; trade name), Kraton G series (manufactured by Shell Japan Co., Ltd .; trade name), Elastomer AR series (manufactured by Aron Kasei Co., Ltd .; trade name), Tuftec series (manufactured by Asahi Kasei Corporation; trade name), Septon series (manufactured by Kuraray Co., Ltd .; trade name) and the like.

In addition, examples of the polymer which can be used in the present invention include EVM which is a copolymer of ethylene and vinyl acetate. Specific examples thereof include EVALATE series (manufactured by Sumitomo Chemical Co., Ltd .; Name), Ebaslen series (manufactured by Dainippon Ink and Chemicals, Inc .; trade name), Ultracene series (manufactured by Tosoh Corporation; trade name), Suntech-EVA series (manufactured by Asahi Kasei Corporation); product Name) etc.

Among these rubbers, ACM, AEM, EPM, EPDM, SE which do not contain chlorine as a constituent element
BM and SEPM are preferred.

(B) Organic Compound Solvent The organic compound solvent used in the present invention is an organic compound solvent having 2 to 20 carbon atoms, a boiling point of 85 to 350 ° C., and having no aromatic nucleus.

It is important that the organic compound solvent used in the present invention is a non-aromatic organic compound solvent containing no benzene ring in the compound molecule. Aromatic organic compound solvents containing a benzene ring in the organic compound molecules used as the solvent, for example, benzene, toluene, xylene, ethylbenzene, aniline, chlorobenzene and the like are often good solvents for rubber-based polymers, A binder composition was prepared using these aromatic organic compounds as a solvent,
When mixed with the active material to form a slurry, which is applied to the current collector and dried, a rubber-based polymer as a binder moves during the drying, causing a phenomenon of localization on the electrode surface. This is not preferred, because the binding property with the polymer significantly decreases and a phenomenon such as poor binding force between the active material particles easily occurs.

The non-aromatic organic compound solvent used in the present invention has 2 to 20 carbon atoms, preferably 2 to 15 carbon atoms,
More preferably, 3 to 13 non-aromatic organic compounds are used. When a slurry using a non-aromatic organic compound having 1 carbon atom is applied to a current collector, thixotropic properties become strong, and it is difficult to apply the active material uniformly. A slurry using a non-aromatic organic solvent having a carbon number of 21 or more has a high melting point and is inferior in operability in a coating process at about room temperature, which is not preferable.

The boiling point of the non-aromatic organic compound solvent used in the present invention is usually 85 to 350 ° C., preferably 90 to 350 ° C.
It is 300 degreeC, More preferably, it is 100-270 degreeC, Especially preferably, it is 110-250 degreeC. Boiling point is 85
When the temperature is lower than ℃, similar to the aromatic organic compound solvent,
A phenomenon in which the rubber-based polymer as a binder migrates and localizes on the electrode surface occurs, and the binding property between the current collector and the active material is significantly reduced, and the binding force between the active material particles is poor. In addition to the above phenomenon, the solvent tends to evaporate and the slurry is not stable. As a result, the battery performance is reduced. On the other hand, if the boiling point is higher than 350 ° C., the solvent is difficult to evaporate, and it takes a long time to dry the slurry after applying the slurry to the current collector. Is not preferred.

The non-aromatic organic compound solvent used in the present invention may be a hydrocarbon compound, an oxygen-containing hydrocarbon compound, a chlorine-containing hydrocarbon compound, as long as it satisfies the above-mentioned conditions.
Any of a nitrogen-containing hydrocarbon compound and a sulfur-containing hydrocarbon compound may be used.

Specific examples include (i) hydrocarbon compounds such as heptane, isoheptane, octane, isooctane, methylcyclohexane, ethylcyclohexane, nonane, decane, decalin, dodecane; and (ii) n-propyl alcohol, n-butyl alcohol , Isobutyl alcohol, secondary butyl alcohol, amyl alcohol,
Isoamyl alcohol, methyl isobutyl carbinol, 2-ethylbutanol, 2-ethylhexanol,
Cyclohexanol, furfuryl alcohol, tetrahydrofurfuryl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, hexylene glycol, glycerin; n
-Butyl ether, dichloroethyl ether, 1,4-
Dioxane, ethylene glycol monomethyl ether,
Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, dithylene glycol monoethyl ether, diethylene glycol monobutyl ether; formic acid,
Acetic acid, acetic anhydride, butyric acid, butyl formate, amyl formate, isopropyl acetate, butyl acetate, sec-butyl acetate, amyl acetate, isoamyl acetate, 2-ethylhexyl acetate, cyclohexyl acetate, butylcyclohexyl acetate, ethyl propionate, butyl propionate, Amyl propionate,
Butyl butyrate, diethyl carbonate, diethyl oxalate, methyl lactate, ethyl lactate, butyl lactate, triethyl phosphate; furfural, acetal, methyl isopropyl ketone,
Oxygenated hydrocarbon compounds such as methyl isobutyl ketone, diisobutyl ketone, acetylacetone, diacetone alcohol, cyclopentanone, cyclohexanone, methylcyclohexanone, cycloheptanone, 1,4-dioxane and isophorone; (iii) tetrachloroethane, trichloroethylene Chlorinated hydrocarbon compounds such as perchlorethylene, dichloropropane, amyl chloride and dichloropentane; (iv) nitroethane, 1-nitropropane, 2-nitropropane, acetonitrile, triethylamine, cyclohexylamine, pyridine, pyricon, mono Nitrogen-containing hydrocarbon compounds such as ethanolamine, diethanolamine, morpholine, N, N-dimethylformamide and N-methylpyrrolidone; (v) thiophene, sulfolane, Chirusuruhekishido like sulfur-containing hydrocarbon compounds such. Among them, hydrocarbon compounds such as heptane, octane, nonane, dodecane, methylcyclohexane, ethylcyclohexane; methyl isopropyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, cycloheptanone, 1,4-dioxane, n-butyl alcohol Oxygenated hydrocarbon compounds such as, isobutyl alcohol, secondary butyl alcohol, amyl alcohol, isoamyl acetate, methyl lactate, ethyl lactate, butyl lactate, butyl acetate;
Nitrogen-containing compounds such as N, N-dimethylformamide and N-methylpyrrolidone; and sulfur-containing hydrocarbon compounds such as dimethylsulfoxide are preferred. Such a non-aromatic organic compound solvent may be used alone or as a mixed solvent in which two or more kinds are arbitrarily combined by appropriately setting a mixing ratio according to the purpose.

(C) Binder composition The binder composition of the present invention is a binder composition for a lithium ion secondary battery electrode, and the gel content of the rubber polymer in the binder composition is less than 50%, preferably It is 20% or less, more preferably 10% or less.
In addition, the gel content referred to here is 50% of the binder composition.
This is a value calculated as a percentage by dividing the weight of the rubber-based polymer in the solid material remaining on the screen through a 200-mesh sieve at a temperature of 0 ° C. by the weight of the total rubber-based polymer in the binder composition. .

The concentration of the rubber polymer contained in the binder composition is 0.1 to 50% by weight, preferably 0.5 to 4% by weight.
0% by weight, more preferably 1 to 20% by weight. 0.
If the concentration is lower than 1% by weight, the binder composition becomes too large during the production of the slurry, making it difficult to apply the active material to the current collector. Conversely, if it exceeds 50% by weight, the binder composition becomes too small during the production of the slurry. There is a problem that a uniform slurry cannot be obtained.

(D) Electrode The electrode according to the present invention is obtained by first mixing the binder composition and the positive electrode active material or the negative electrode active material used in the present invention with the active material 10
With respect to 0 parts by weight, the above-mentioned rubber-based polymer is 0.05 to
The slurry may be mixed to be 30 parts by weight, preferably 0.1 to 20 parts by weight, more preferably 0.3 to 15 parts by weight to form a slurry. If the amount of the rubber-based polymer is less than 0.05 part by weight, a good binding force cannot be obtained, while if it exceeds 30 parts by weight, the overvoltage is significantly increased and the battery performance is reduced.

Various additives can be added to the slurry as required. Various additives include (i) graphite, carbon black, acetylene black,
Conductive agent such as metal powder, (ii) polyvinylpyrrolidone, polyacrylic acid, polymethacrylic acid, polyacrylamide, poly-N-isopropylacrylamide, poly-N, N-dimethylacrylamide, polyethyleneimine, polyoxyethylene, poly (2 -Methoxyethylene), polyvinyl alcohol, poly (3-morpholinylethylene), polyvinyl sulfonic acid, polyvinylidene fluoride, amylose, amylopectin, polysaccharides such as starch, carboxymethylcellulose, carboxymethylethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose Thickeners such as cellulose-based compounds such as carboxyethylcellulose (including their sodium salts and lithium salts), (iii)
Sulfur such as powdered sulfur, precipitated sulfur, colloidal sulfur, and surface-treated sulfur; sulfur compounds such as sulfur chloride, sulfur dichloride, and polymer polysulfide; inorganic granules other than sulfur such as magnesium oxide, lead monochloride, and zinc white Oximes such as p, p'-dibenzoyl quinone dioxime; hexamethylene diamine, triethylene tetramine, tetraethylene
Pentamine, hexamethylenediamine carbamate,
Polyamines such as N, N'-dicinnamylidene-1,6-hexanediamine, 4,4'methylenebis (cyclohexylamine) carbamate; tert-butyl hydroperoxide, 2,5-dimethylhexane-2,5-hydroperoxide, dicumyl Peroxide, tert-butylcumyl peroxide, 1,1-bis (tert-butylperoxy)
Cyclododecane, 2,2-bis (tert-butylperoxy) octane, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 2,5-dimethyl-2,5
-(Tert-butylperoxy) hexyne-3,1,3-bis (tert-butylperoxyisopropyl) benzene,
2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 1,1-bis (tert-butylperoxy)
-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis (tert-butylperoxy) valerate,
Benzoyl peroxide, m-toluyl peroxide,
Organic peroxides such as tertiary butyl peroxybenzoate, tertiary butyl peroxyisopropyl carbonate, and acrylic cross-linking agents; cross-linking agents such as (iv) casein, glue, soap, gluten, alkyl fiber, starch, and various surfactants Stabilizers such as (v) stearic acid, monostearate of diethylene glycol,
Examples include dispersants such as monoethanolamine, diethylene glycol, and pine tar, various vulcanization accelerators, vulcanization acceleration aids, activators, scorch inhibitors, antioxidants, tackifiers, and the like.

Next, the slurry is made of copper, aluminum,
The electrode is applied to a current collector made of a metal foil film of nickel, iron, lithium, or the like, and then the non-aromatic organic compound solvent is dried to produce an electrode. Examples of the coating method include a reverse roll method, a comma bar method, a gravure method, and an air knife method. Although the drying method of the non-aromatic organic compound solvent used in the present invention is not particularly limited, the drying temperature is usually 50 to 400 ° C, preferably 80 to 300 ° C. When a crosslinking agent is added to the slurry, it is preferable to dry at a temperature equal to or higher than the crosslinking temperature.

[0037] As the negative electrode active material, carbon fluoride, graphite, natural graphite, PAN-based carbon fibers such as MCMB, carbonaceous materials such as pitch-based carbon fibers, conductive polymers such as polyacene, Li _x M _y N _z (However, Li represents a lithium atom, M represents Mn, Fe, Co, Sn, B, A
1, at least one selected from Si and Ni, wherein x, y and z are respectively 7.0 ≧ x ≧ 1.0, 4
Lithium nitride represented by ≧ y ≧ 0, 5 ≧ z ≧ 0.5), and AxMyOz (where A
Is Li, M is at least one selected from Co, Ni, Al, Sn and Mn, O represents an oxygen atom, x,
y and x are 1.10 ≧ x ≧ 0.05 and 4.00, respectively.
≧ y ≧ 0.85, 5.00 ≧ z ≧ 1.5). As the positive electrode active material, TiS _2, TiS _3, amorphous _{MoS 3, Cu 2 V 2 O} 3, amorphous V ₂ O ₅ -P
₂ O ₅ , MoO ₃ , V ₂ O ₅ , V ₆ O ₁₃ , AxMyNz
Op (where A is Li, M is at least one selected from Co, Ni and Mn, N is at least one selected from Al and Sn, O represents an oxygen atom, x,
y, z, and p are 1.10 ≧ x ≧ 0.05, respectively.
00 ≧ y ≧ 0.85, 2.00 ≧ z ≧ 0, 5.00 ≧ p
And a conductive polymer such as polyacetylene and poly-p-phenylene.

(E) Battery In the present invention, a lithium ion secondary battery is a lithium secondary battery that does not use an alkali metal such as lithium or a metal such as an alkali metal alloy as an active material, and is preferably a carbonaceous material. And a lithium compound such as lithium nitride or a metal oxide as an active material. Of course, as long as this condition is satisfied, a lithium polymer battery using an organic solid electrolyte is also included.

When a non-aqueous electrolyte battery is manufactured using the electrode of the present invention, an insulating thin film having high ion permeability, being chemically stable and having a predetermined mechanical strength is used as a separator. For example, olefin-based nonwoven fabrics such as polypropylene and polyethylene, glass fibers, and the like are used. The electrolyte is not particularly limited, and a non-aqueous electrolyte 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, L as an electrolyte
iClO ₄ , LiBF ₄ , CF ₃ SO ₃ Li, LiI,
LiAlCl ₄ , LiPF ₆ , NsClO ₄ , NaBF
₄ , NaI, (n-Bu) ₄ ClO _{4 and the} like.
As solvents, ethers, ketones, lactones, nitriles, amines, amides, sulfur compounds, chlorinated hydrocarbons, esters, carbonates, nitro compounds, phosphate compounds, sulfolane compounds And the like, and ethylene carbonate, propylene carbonate and diethyl carbonate are generally suitable.

The electrode produced using the binder composition of the present invention, when used in a lithium ion secondary battery,
Especially excellent battery performance can be exhibited,
It is also useful for electrodes of non-aqueous electrolyte capacitors.

[0041]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In this example, the gel content was measured by the method described above, and the viscosity was 25 ° C. measured by a B-type viscometer.
Is the value of

(Examples 1-1 to 1-14) Production of Negative Electrode ACM- (1) (Zeon Corporation) as a rubber polymer
“Nipol AR-31”) was dissolved in N, N-dimethylformamide, and the concentration of the rubber-based polymer in the solution was 5%.
% By weight of the binder composition A was obtained. The gel content in the binder composition A was 0.6% by weight. Carbon (Lonza "KS-15"; used as negative electrode active material)
To 100 parts by weight, the binder composition A was added so that the amount of the rubber-based polymer was 3 parts by weight, and the viscosity was about 6000 cp.
s to obtain a slurry composition for a negative electrode.
This negative electrode slurry composition was applied to one surface of a copper foil having a thickness of 8 μm, dried under vacuum at 150 ° C. for 72 hours, and dried to a thickness of 0.1 μm.
mm of the negative electrode active material layer was formed to produce a negative electrode of a lithium ion secondary battery. In the same manner as in Table 1, Example No. 1-
Each negative electrode was produced using a binder composition having the composition shown in 2-1-14. The following evaluation was performed using this electrode.

Production of Positive Electrode A rubber-based polymer EPM- (1) (“Mitsui EPT 0045”, manufactured by Mitsui Petrochemical Co., Ltd.) was dissolved in dodecane,
A binder composition B having a concentration of EPM- (1) in the solution of 5% by weight was obtained. The gel content of the binder composition B was 1.5%. To 100 parts by weight of LiCoO ₂ (used as a positive electrode active material), the binder composition B obtained so that the amount of EPM- (1) was 2 parts by weight was added, and 10 parts by weight of acetylene black was further added. About 40
The slurry was adjusted to 00 cps to obtain a positive electrode slurry composition. This slurry composition for a positive electrode was 0.02 mm thick.
Was coated on one side of an aluminum foil and vacuum dried at 150 ° C. for 24 hours to form a 0.4 mm thick positive electrode active material layer, thereby producing a positive electrode of a lithium ion secondary battery. The positive electrodes used for the following evaluations were all the positive electrodes.

Production of Lithium-Ion Secondary Battery The above positive electrode and negative electrode were cut out into a circle having a diameter of 15 mm, and a separator made of a circular polypropylene microporous film (fiber non-woven fabric) having a diameter of 18 mm and a thickness of 25 μm was interposed. The stainless steel coin-type outer container (with a spring (expanded metal) placed on the copper foil and a polypropylene packing installed, with the active material layer facing and the aluminum foil in contact with the bottom of the outer container) Diameter 20mm, height 1.8mm, stainless steel thickness 0.2
5 mm). An electrolyte in which LiPF ₆ was dissolved at a concentration of 1 mol / liter as an electrolyte was injected into a container in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 so that no air remained. A stainless steel cap with a thickness of 0.2 mm is put on and fixed to the outer container via a polypropylene packing, the battery can is sealed, and the diameter is 20 mm and the thickness is about 2 m.
20 coin type batteries were manufactured. In each of the following evaluations, 20 coin-type batteries manufactured by the same method were used.

Measurement of Battery Performance Each of 20 cells was measured by a constant current method (current density: 0.1
The battery was charged and discharged at 4.0 V at mA / cm ² ) and discharged to 3.0 V, and the electric capacity was measured. The average value is shown in Table 1 as an evaluation result.

[Table 1]

From Table 1, it can be seen that the lithium ion secondary battery using the binder composition of the present invention does not show a substantial decrease in electric capacity even when charging and discharging are repeated 50 times.
It was found that the variation in the electric capacity of the 20 cells was stable at a maximum of ± 5%.

(Examples 2-1 to 2-9) Production of Negative Electrode Rubber-based polymer ACM- (2) (manufactured by Zeon Corporation)
"Nipol AR-32") is dissolved in methyl isobutyl ketone, and the concentration of ACM- (2) in the solution is 7% by weight.
Was obtained. The gel content in this binder composition was 1.1% by weight. To 100 parts by weight of carbon ("KS-15" manufactured by Lonza; used as a negative electrode active material), the binder composition C obtained so that the amount of ACM- (2) becomes 4 parts by weight was added, and the viscosity was about 4000 cp.
s to obtain a slurry composition for a negative electrode.
This negative electrode slurry composition was applied to one surface of a copper foil having a thickness of 8 μm, dried under vacuum at 120 ° C. for 24 hours, and then dried to a thickness of 0.1 μm.
mm of the negative electrode active material layer was formed to produce a negative electrode of a lithium ion secondary battery. The negative electrodes used for the following evaluations were all the negative electrodes.

ACM- (1) (manufactured by Zeon Corporation) as a rubber-based polymer
(“Nipol AR-31” manufactured by KK) was dissolved in methyl isobutyl ketone to obtain a binder composition D having a rubber-based polymer concentration of 25% by weight in the solution. The gel content in this binder composition D was 0.5% by weight. LiCoO ₂
(Used as positive electrode active material) To 100 parts by weight, a binder composition D obtained so that the rubber-based high molecular weight was 3 parts by weight, and 10 parts by weight of acetylene black were further added.
The viscosity was adjusted to about 4000 cps to obtain a slurry composition for a positive electrode. This slurry composition for a positive electrode was applied to one surface of an aluminum foil having a thickness of 25 μm,
After drying for 4 hours under vacuum, a positive electrode active material layer having a thickness of 0.4 mm was formed to produce a positive electrode of a lithium ion secondary battery. In the same manner, each positive electrode was produced using a binder composition having the composition shown in Table 2 Example Nos. 2-2 to 2-9. The following evaluation was performed using this electrode. The abbreviations in the column of the rubber-based polymer in Table 2 correspond to Table 1.

Production of Lithium Ion Secondary Battery The above positive electrode and negative electrode were cut out into a circle having a diameter of 15 mm, respectively, and a separator composed of a circular polypropylene microporous membrane (fiber non-woven fabric) having a diameter of 18 mm and a thickness of 25 μm was interposed. A stainless steel coin-type outer container in which the active material layer faces and the aluminum foil is in contact with the bottom of the outer container, a spring (expanded metal) is placed on the copper foil, and a polypropylene packing is installed. (Diameter 20mm, height 1.8mm, stainless steel thickness 0.2
5 mm). An electrolyte in which LiPF ₆ was dissolved at a concentration of 1 mol / liter as an electrolyte was injected into a container in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 so that no air remained. A stainless steel cap with a thickness of 0.2 mm is put on and fixed to the outer container via a polypropylene packing, the battery can is sealed, and the diameter is 20 mm and the thickness is about 2 m.
20 coin type batteries were manufactured. In each of the following evaluations, 20 coin-type batteries manufactured by the same method were used.

Measurement of Battery Performance A 20-cell battery was subjected to a constant current method (current density: 0.1
The battery was charged and discharged at 4.0 V at mA / cm ² ) and discharged to 3.0 V, and the electric capacity was measured. The average value is shown in Table 2 as an evaluation result.

[Table 2]

From Table 2, it can be seen that the lithium ion secondary battery using the binder composition of the present invention does not show a substantial decrease in electric capacity even after repeating charge and discharge 50 times.
It was found that the variation in electric capacity of the 20 cells was stable at a maximum of ± 5%.

(Examples 3-1 to 3-7) Table 3
Except for using the various solvents shown in Table 1, seven lithium ion secondary batteries were prepared and evaluated in the same manner as in Example 1-1. Table 3 shows the results.

[Table 3]

From these results, it was found that the solvent has 2 to 2 carbon atoms.
When an organic compound solvent having a boiling point of 85 to 350 ° C. and having no aromatic nucleus is used, a substantial decrease in electric capacity is not observed even when charging and discharging are repeated 50 times. It was found that the variation in the electric capacity was extremely stable at a maximum of ± 3%. From the results in Table 3, it was also found that the solvent had an effect on the binder performance.

(Examples 4-1 to 4-3) The same as Example 1-1 except that the additives described in Table 4 were added so that the concentration in the solution was 2% by weight. A lithium ion secondary battery was prepared by the method and evaluated. The results are shown in Table 4 (Example 1 in which no additives were added in Table 4).
The results of evaluation 1 are also shown).

[Table 4]

From these results, it was found that the use of the cellulose-based additive did not lower the battery performance.

(Comparative Examples 1-1 to 1-8) A lithium ion secondary battery was prepared in the same manner as in Example 1-1, except that the rubber-based polymer and the solvent shown in Table 5 were used. , Respectively. Table 5 shows the results. still,
The abbreviations in the column of rubber-based polymer in Table 5 correspond to Table 1.

[Table 5]

From these results, it was found that when the organic compound solvent was an organic compound solvent having an aromatic nucleus or an organic compound having no aromatic nucleus had a boiling point lower than 85 ° C., the charge was repeated 50 times. It was found that the electric capacity was significantly reduced by repeated discharge. In addition, the dispersion of the 20 cells was large, and in some cases, the active material was peeled off from the current collector during the production of the battery, resulting in poor productivity (Comparative Example 1-).
2, 1-8).

[0058]

As is clear from the above examples, according to the binder composition of the present invention, the binding property between the current collector and the active material and the binding property between the active materials are excellent. A lithium ion secondary battery having a high capacity retention rate and excellent battery performance in a charge / discharge cycle can be obtained.

Claims (3)

[Claims] 1. A binder composition for a lithium ion secondary battery electrode comprising a rubber polymer and an organic compound solvent, wherein (a) the rubber polymer has a polymethylene-type saturated main chain, and (B) an organic compound solvent having 2 to 20 carbon atoms and a boiling point of 8
An organic compound solvent having no aromatic nucleus at 5 to 350 ° C., and (c) a gel content of a rubber polymer in the binder composition is less than 50%. A binder composition for a secondary battery electrode. 2. A lithium ion secondary battery electrode produced using the binder composition according to claim 1. 3. A lithium ion secondary battery using the electrode according to claim 2.