JPH08203499A - Conductive composition and electrode using this composition - Google Patents

Abstract

PURPOSE: To provide an electrode in which carbon particles are hardly separated, high adhesion is kept, an electrode is not separated from a current collector, and high capacity is held. CONSTITUTION: A conductive composition contains an organic resin and conductive carbon particles. The organic resin is an alkali metal salt of an organic polymer compound having a carboxyl group, and the carbon particles are covered with the alkali metal salt of the organic polymer compound in a mixed solution of ethanol and water, whose pH is controlled to 6-9 to form the conductive composition, then an electrode is prepared by using the conductive composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive composition suitable for electrodes such as lithium batteries. The invention also relates to an electrode obtained with such a conductive composition.

[0002]

2. Description of the Related Art It is well known to use a carbon material for the negative electrode of a lithium battery (see JP-A-63-24555 and JP-A-64-7258). This type of battery is summarized in Osaka Industrial Laboratory Report, Volume 42, pages 150-159 (1992). A lithium battery is assembled into a battery by, for example, sandwiching a separator made of porous polyolefin between a positive electrode and a negative electrode, winding both electrodes in a spiral shape. At this time, as a binding agent for adhering the electrode and the current collector, polytetrafluoroethylene, polyvinylidene fluoride, etc. are mixed with the carbon particles and used for the electrode.

These fluororesins have a weak adhesion to metal, and the outermost periphery of the electrode is peeled off from the current collector during repeated charging and discharging, resulting in a decrease in battery capacity.

[0004]

The object of the present invention is to prevent peeling between the electrode and the aggregate when used as an electrode mixture and to separate carbon particles during coating. It is to provide a conductive composition that is unlikely to occur. Another object of the present invention is to provide an electrode using such a conductive composition as a mixture.

[0005]

Means for Solving the Problems As a result of repeated studies to solve this problem, the present inventors have used an alkali metal salt of an organic polymer compound having a carboxyl group as an organic resin binder, and The inventors have found that the above-mentioned problems can be achieved by using, as conductive particles, carbon particles having a pH range and having a surface coated with an alkali metal salt of a polymer compound, and have completed the present invention.

That is, the present invention provides a conductive composition containing (A) an organic resin and (B) carbon particles,
(A) is an alkali metal salt of an organic polymer compound having a carboxyl group, and (B) is the following (a) and (b):
The present invention relates to a conductive composition which satisfies the requirement of 1) and the amount of (A) in the composition is 1 to 10% by weight, and an electrode using the conductive composition as a mixture. (A) The pH of the liquid prepared by dispersing 10% by weight of the carbon particles in a mixed liquid of ethanol-water at a weight ratio of 1: 1 is 6-9. (B) The surface is coated with an alkali metal salt of a polymer compound.

The organic resin (A) used as a binder in the conductive composition of the present invention is an alkali metal salt of an organic polymer compound having a carboxyl group. Examples of such an organic resin include (a ') a vinyl-based or dienyl-based copolymer having a carboxyl group, (b') a polyamic acid, or (c ') an alkali metal salt of a carboxyl group-containing cellulose derivative (a). , (B) and (c)
Are particularly effective.

The vinyl-based or dienyl-based copolymer having a carboxyl group (a ') from which (a) is derived is
(1) One or more kinds of aliphatic hydrocarbon monomers having an ethylenically unsaturated double bond or a conjugated double bond 7
0-99.99 mol% and (2) one or more ethylenically unsaturated double bond-containing monomers having one or two carboxyl groups or hydrolyzable acid anhydride groups in the molecule. It is a copolymer of 0.01 to 20 mol%. The copolymer may contain units derived from other monomers, if necessary. Further, it may be directly obtained by copolymerization of the monomer (1) and the monomer (2), or may be synthesized through further hydrolysis and / or hydrogenation.

By using the copolymer (a ') having such a structure, the unit derived from the monomer (1) absorbs the stress of the expansion and contraction of the electrode due to the charge / discharge cycle or the heat cycle. A conductive composition suitable for use as an electrode mixture, which has an excellent adhesiveness to the metal of the current collector by forming an alkali metal salt by the unit derived from the monomer (2) as described below. Is obtained.

As the aliphatic hydrocarbon monomer (1), an aliphatic hydrocarbon having an ethylenically unsaturated double bond or a conjugated double bond is used. Specifically, ethylene, propylene, butene-1, isobutene, pentene-
Examples include 1,1-methylpentene-1, butadiene and isoprene. When butadiene or isoprene is used, it may be used as an alkali metal salt as it is, or may be saturated by hydrogenation after copolymerization. These may be used alone or in combination of two or more, and ethylene, propylene and butadiene (saturated after copolymerization) are preferable.

This monomer (1) is 70 to 99.99 of the monomers that participate in the copolymerization for synthesizing (a ').
Mol%, preferably 75 to 99.9 mol%, and more preferably 77 to 99.5 mol%. (1) is 7
If it is less than 0 mol%, the copolymer lacks the ability to absorb the stress due to volume expansion and contraction of the electrode, and peeling occurs during use due to charge / discharge cycle or heat cycle of the electrode. 9
If it exceeds 9.9 mol%, the adhesion to a metal such as a current collector will be poor.

Examples of the monomer (2) include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid and 4-carboxystyrene. Examples of the monomer having an acid anhydride group which later yields two carboxyl groups by hydrolysis include maleic anhydride, itaconic anhydride and the like; and Diels-Alder reaction adduct of cyclopentadiene and itaconic anhydride and the like. To be done. These may be used alone or in combination of two or more, and acrylic acid and maleic anhydride are preferable. When a monomer having an acid anhydride group is used as (2), it can be converted into two carboxyl groups by adding a hydrolysis step. Further, without undergoing such a conversion step, the copolymer obtained by using the monomer having an acid anhydride group as (2) is reacted with an alkali metal hydroxide in the presence of water. It is also possible to obtain an alkali metal salt by hydrolysis.

This monomer (2) is 0.01 to 20 mol% of the monomer involved in the copolymerization for synthesizing (a '), preferably 0.05 to 10 mol%,
-5 mol% is more preferable. If it is less than 0.01 mol%, the adhesiveness to a metal such as a current collector is poor, and it is 20 mol%.
If it exceeds, the stress due to volume expansion and contraction of the electrode cannot be absorbed.

If desired, the copolymer (a ') may be copolymerized with 30 mol% or less of another monomer having an ethylenically unsaturated double bond. Examples of the monomer for introducing such a unit include styrene, acrylonitrile, and alcohol esters of (meth) acrylic acid, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, and butyl methacrylate. When the content of these exceeds 30 mol%, the copolymer swells or dissolves in the electrolytic solution and fails to function as a binder. Another example of another monomer is vinylidene fluoride. If this content exceeds 30 mol%, the adhesive strength of the copolymer will decrease and peeling from a metal such as a current collector will occur.

Such a copolymer (a ') can be obtained by copolymerizing the monomer (1), the monomer (2) and, if necessary, other monomer by a conventional method. Furthermore, a conjugated diene such as butadiene or isoprene is used as a part or all of the monomer of (1), and the monomer of (2) having an acid anhydride group such as maleic anhydride in the double bond remaining in the polymer chain. May be added and then hydrolyzed to be converted into a maleic acid unit. Also, the double bond of the polymer chain similarly obtained by using the conjugated diene may be saturated by hydrogenation.

The polyamic acid (b ') from which (b) is derived is a polymer having a carboxyl group and an amide bond in the molecule, and various aromatic polyamic acids are known as precursors of polyimide. However, it is not limited to these, and an aliphatic polyamic acid can also be used.
(B ') polyamic acid includes carboxylic acid dianhydride and diamine such as N, N-dimethylformamide, N,
N-dimethylacetamide, dimethyl sulfoxide, N
It can be synthesized by polycondensation in the presence of an aprotic polar solvent such as -methyl-2-pyrrolidone or tetramethylurea.
Examples of the carboxylic acid dianhydride include pyromellitic acid anhydride, naphthalene-2,3,6,7-tetracarboxylic acid dianhydride, naphthalene-1,2,5,6-tetracarboxylic acid dianhydride and diphenyl-3. , 3 ', 4,4'-Tetracarboxylic acid dianhydride, Diphenyl-2,2', 3,3'-tetracarboxylic acid dianhydride, Perylene-3,4,9,10
-Tetracarboxylic acid dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, benzophenone-
Aromatic carboxylic dianhydrides such as 3,3 ′, 4,4′-tetracarboxylic dianhydride; and ethylene tetracarboxylic dianhydride, cyclohexane tetracarboxylic dianhydride, methyl cyclohexane tetracarboxylic dianhydride Illustrative are aliphatic tetracarboxylic dianhydrides such as anhydrides. On the other hand, as the diamine, m-phenylenediamine, p-phenylenediamine, 4,4'-methylenedianiline, 2,2-bis (4-aminophenyl) propane, 4,4'-diaminodiphenyl ether, m-xylylenediamine. Examples include amines, aromatic diamines such as p-xylylenediamine; and aliphatic diamines such as tetramethylenediamine, hexamethylenediamine, octamethylenediamine, decamethylenediamine, and 1,4-diaminocyclohexane.

The carboxyl group-containing cellulose derivative (c ') from which (c) is derived is one in which a substituent having a carboxyl group is introduced into cellulose, and is a carboxyalkyl cellulose such as carboxymethyl cellulose, carboxyethyl cellulose or carboxypropyl cellulose. Are exemplified, and carboxymethyl cellulose is preferable. The number of carboxyl groups introduced is 1 to 30 mol%, preferably 1 to 30 mol% based on the cellulose unit, from the effect and the solubility in the organic solvent used for preparing the binder.
It is 10 mol%.

In the present invention, the organic resin (A) used as a binder in the conductive composition is one of these (a)
′), (B ′) and (c ′) are alkali metal salts (a), (b) and (c) of organic polymer compounds having a carboxyl group. By using the alkali metal salt as the binder, the charge / discharge cycle life becomes longer than that of a conventional lithium battery using, for example, polyvinylidene fluoride as the binder. Examples of the alkali metal salt include lithium salt, sodium salt, potassium salt, rubidium salt and cesium salt,
Lithium salts are particularly preferred because they have the same cations as the electrolyte used.

Such an alkali metal salt can be obtained by reacting the above organic polymer compound having a carboxyl group or an acid anhydride group with a corresponding alkali metal hydroxide. The reaction is preferably carried out with an equivalent amount of the hydroxide depending on the type of the organic polymer compound, for example, a monohydric or polyhydric lower alcohol such as methanol, ethanol, propanol, isopropanol, ethylene glycol or glycerin; or N. -Methyl-
It is carried out by dissolving it in an aprotic polar solvent such as 2-pyrrolidone, adding it to the organic polymer compound, and stirring. In the case of the alkali metal salt of (a),
It can also be obtained by treating the copolymer of the monomer of (1) and the alkyl ester or nitrile derivative of the acid mentioned in (2) with the corresponding alkali metal hydroxide. In the case of the alkali metal salt of (c), it can also be synthesized by reacting alkali cellulose with a corresponding alkali metal chloroalkane salt, for example, lithium monochloroacetate.

The carbon particles used as conductive particles in the conductive composition of the present invention have a pH of 6 to 6 when dispersed in a mixture of ethanol and water at a weight ratio of 1: 1 by 10% by weight. It is a neutral to weakly alkaline one, which is adjusted to 9, preferably 6.5 to 8.8. When the pH is less than 6, the carbon particles are likely to settle and separate, and particularly when a conductive paste having an apparent viscosity of 20 Pa · s or less is prepared, the carbon particles aggregate during standing.
Separation of carbon particles from organic resin and solvent. On the other hand, pH
Even if the value exceeds 9, carbon particles aggregate and settle. The shape of the carbon particles may be spherical, flaky or fibrous. The size, that is, the spherical one has the diameter, the scaly one has the average of the major axis and the minor axis of the flat surface, and the fibrous one has the length of preferably 0.1 to 50 μm, more preferably 2 to 30 μm. Is. If the thickness is less than 0.1 μm, it is difficult to apply the conductive composition uniformly, and the binding strength, coating strength, and especially bending strength are poor. If it exceeds 30 μm, the surface of the formed composition loses smoothness, the packing density decreases, and the discharge capacity per unit volume decreases. Alternatively, the size of each carbon particle is 0.02 to 0.1 μ.
The m 2 particles may be aggregated in the form of chains or agglomerates to form the secondary particles of the above size.

In the present invention, the surface of such carbon particles is coated with an alkali metal salt of a polymer compound, preferably an alkali metal salt of a water-soluble polymer compound. As a result, the dispersibility of the carbon particles in the organic resin, which is the binder, can be increased and sedimentation can be prevented. Further, this increases the binding force between the organic resin that is the binder and the carbon particles, and withstands the expansion and contraction of the electrode due to the charge / discharge cycle of the lithium battery using this conductive composition for the electrode, The discharge cycle life is extended.

As the alkali metal salt of such a polymer compound, a salt in which the carboxyl group or the sulfone group of the polymer compound having a carboxyl group or a sulfone group is substituted with an alkali metal is preferable. Examples of the alkali metal salt of the polymer compound having a carboxyl group include the same as those described as the above-mentioned (A) organic resin. 30 to 100 mol% of an ethylenically unsaturated monomer having a carboxyl group or a sulfone group, a hydrocarbon not containing the above group in the molecule and having an ethylenically unsaturated double bond or a conjugated double bond, its ether and its Monomers 0 to 70 selected from the group consisting of esters
Water-soluble alkali metal salts of copolymers with mol% are more preferred. This facilitates intercalation of lithium ions. Examples of the alkali metal salt include lithium salt, sodium salt, potassium salt, rubidium salt and cesium salt, and the lithium salt is particularly preferable because it has the same cation as the electrolyte used.

As the above-mentioned monomer unit having a carboxyl group, acrylic acid, methacrylic acid, crotonic acid,
Examples thereof include carboxyl group-containing monomers such as maleic acid, itaconic acid and 4-carboxystyrene. Also,
As in the case of (a ′) above, after polymerizing a double bond-containing acid anhydride such as maleic anhydride and itaconic anhydride, hydrolysis is performed to form a carboxyl group on the side chain of the polymer. May be. On the other hand, the sulfone group can be introduced by sulfonating polystyrene, for example.

Further, as a monomer used for copolymerization in the range of up to 70 mol%, if necessary, ethylene, propylene, butene-1, isobutene, pentene-1, 1-methylpentene-1, styrene, α-methyl Olefins such as styrene; conjugated dienes such as butadiene and isoprene; ethers such as methyl vinyl ether; acrylic acid esters such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate and corresponding methacrylic acid esters. It is illustrated.

Such an alkali metal salt of a polymer compound is obtained by reacting a carboxyl group or a sulfone group of the polymer compound with a corresponding hydroxide of an alkali metal, as in the case of an organic resin used as a binder. Obtained. The reaction is preferably carried out by adding an equivalent amount of a solution of the hydroxide, such as the same lower alcohol as described above, to the polymer compound and stirring. Further, like the above-mentioned organic resin, it can be directly synthesized without passing through the polymer compound having the above group.

Preferred specific examples of such alkali metal salts of polymer compounds include alkali metal salts of hydrolyzed styrene-maleic anhydride copolymers and alkalis of hydrolyzed methyl vinyl ether-maleic anhydride copolymers. Examples thereof include metal salts, alkali metal salts of copolymers of poly (meth) acrylic acid and poly (meth) acrylic acid ester, and alkali metal salts of sulfonated or partially sulfonated polystyrene.

The surface of the carbon particles is coated by, for example, immersing the carbon particles in an aqueous solution of an alkali metal salt of a polymer compound, stirring, filtering, and drying. The amount of the alkali metal salt used for coating is preferably 0.005 to 1% by weight, more preferably 0.01 to 0.5% by weight, based on the carbon particles. If it is less than 0.005% by weight, sedimentation or separation of carbon particles will occur, and if it exceeds 5% by weight, the battery capacity will decrease.

The conductive composition of the present invention contains an organic resin and carbon particles which satisfy the above-mentioned conditions. The content of the organic resin in the composition is 1 to 10% by weight, preferably 2 to
6% by weight. If it is less than 1% by weight, the binding force of the carbon particles is weak, and the carbon particles are peeled and desorbed by charge / discharge cycles and heat cycles, resulting in a decrease in battery capacity. On the other hand, if it exceeds 10% by weight, the filling amount of carbon particles in the electrode is small and the battery capacity is also small.

In the conductive composition of the present invention, a solvent may be added to dissolve an organic resin and disperse carbon particles to prepare a conductive paste having an apparent viscosity suitable for treatment. As the solvent, depending on the type of organic resin, aromatic hydrocarbons such as toluene, xylene, ethylbenzene, aromatic components of petroleum fractions; and hexane, heptane, octane, cyclohexane, mineral spirits, kerosene, etc. Aliphatic hydrocarbons are exemplified. When the organic resin contains many carboxyl groups in the form of an alkali metal salt, it may be added in an amount of 5 to 2 to help the dissolution of the organic resin.
You may use together 0 weight% of propanol or butanol. When a poorly soluble organic resin is used in a general solvent, such as an alkali metal salt of polyamic acid, the same aprotic polar solvent used for its synthesis is used.

The apparent viscosity of the conductive paste varies depending on the purpose of use, but when it is used for forming an electrode, it is preferably in the range of 5 to 20 Pa · s so that the electrode is formed by one application. If it is less than 5 Pa · s, the coating thickness becomes insufficient, and if it exceeds 20 Pa · s, the coating becomes uneven.

The conductive composition of the present invention may be blended with nitrile rubber, isoprene rubber, ethylene propylene rubber and the like, if necessary, as long as the purpose is not violated.

The conductive composition of the present invention comprises an organic resin, carbon particles and, if necessary, other components, and a mixing / dispersing machine such as a propeller stirrer, a desolver, a kneader, a crusher, a three-roll mill and a ball mill. It can be prepared by mixing and dispersing.

The coating may be carried out by any method capable of coating in a thin film form such as coating with a doctor blade or an applicator; printing by screen printing or stencil printing. The thickness of the applied layer is preferably 70 to 200 μm,
More preferably, it is 80 to 150 μm. If it is less than 70 μm, the battery capacity per volume is low, and if it exceeds 200 μm,
The bending strength of the coating film is poor and cracks occur.

By using the conductive composition of the present invention as an electrode mixture, various electrodes such as a negative electrode and a positive electrode of a lithium battery can be produced. The other elements of these batteries can be used as known. For example, an electrolytic solution used in a lithium battery includes non-aqueous solvents such as ethers, ketones, lactones, nitriles, esters,
Carbonates or sulfolanes are used, especially cyclic carbonates. Examples of such non-aqueous solvent include ethylene carbonate, propylene carbonate, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, dimethoxyethane and the like. Further, as the electrolyte to be dissolved therein, LiClO ₄ , LiBF ₄ , LiPF ₆ , Li
Such as AsF _6, CF ₃ SO ₃ Li and the like. Support of lithium as an active material may be carried out by a conventional method.

[0035]

Industrial Applicability According to the present invention, a conductive composition having excellent adhesiveness and stable conductivity, in which carbon particles are less likely to be separated during storage and during coating, can be obtained. Various batteries using the electrode produced using the conductive composition of the present invention can maintain a high discharge capacity without peeling between the electrode and the current collector due to charge / discharge cycle or heat cycle. Therefore, the conductive composition of the present invention is useful as an electrode of various batteries including a negative electrode of a lithium battery.

[0036]

EXAMPLES The present invention will be described in detail below with reference to Reference Examples, Examples and Comparative Examples. In these examples, parts represent parts by weight. The invention is not limited by these examples.

In the following examples, the pH of carbon particles was measured as follows. That is, 10% by weight of carbon particles were dispersed in a mixed solution of ethanol and water at a weight ratio of 1: 1 and left for 5 minutes. Then, the carbon particles were removed by centrifugation, and the pH of the mixed solution was measured with a pH meter.

Reference Example 1: Surface treatment of carbon material 50 parts of an aqueous solution in which 0.05 parts of lithium polymethacrylate having an average molecular weight of 20,000 was dissolved, and the size was 20 μm.
, 100 parts of spherical carbon particles having a pH of 7.6 are mixed and stirred,
After the dispersion, the carbon particles were filtered off and dried at 150 ° C. for 30 minutes to obtain surface-treated carbon particles C1. Similarly, carbon particles having the size, shape and pH shown in Table 1 were surface-treated with lithium salts of various polymer compounds shown in Table 1 to obtain surface-treated carbon particles C2 to C6. For these surface-treated carbon particles, the weight loss of the particles up to 400 ° C. by TG-DTA was determined. On the other hand, the treated carbon particles were dispersed in water, boiled, the amount of lithium salt attached was determined by an ion chromatogram, and the value obtained by adding this to the above-mentioned weight loss was taken as the surface treatment amount. In addition, in Table 1, the untreated carbon particles C7 used for comparison are also described.

[0039]

[Table 1]

Reference Example 2: Synthesis of Copolymer-Based Organic Resins Copolymers B1 to B7 having the monomer compositions shown in Table 2 were used in "Experimental Method for Polymer Synthesis" written by Takayuki Otsu, Masayoshi Kinoshita, Kagaku Dojin). According to the method described, using an autoclave, under high pressure, in the presence of azobisisobutyronitrile,
It was synthesized by radical polymerization in benzene. The obtained copolymer was purified by pouring it into anhydrous diethyl ether to cause precipitation, and was dried. B7 is an ethylene propylene rubber for comparison, which does not contain a carboxyl group.

[0041]

[Table 2]

To the copolymers B1 to B6 having a carboxyl group in the molecule thus obtained, a 5% by weight solution of lithium hydroxide in isopropanol was added in an equivalent amount, and the mixture was neutralized by stirring and then isopropanol. After being washed with and dried, organic resins B'1 to B'6 for binders were obtained.

Reference Example 3: Synthesis of lithium polyamic acid salt 66.1 parts of pyromellitic anhydride and 33.9 parts of p-phenylenediamine were dissolved in 900 parts of N-methyl-2-pyrrolidone, and the mixture was heated to 80 ° C. with stirring. After heating for 3 hours, a solution B9 of polyamic acid was obtained. To this, a 5% solution of lithium hydroxide in isopropanol was added in an equivalent amount to synthesize a polyamic acid lithium salt B'9.

Reference Example 4: Synthesis of carboxymethylcellulose lithium salt Carboxymethylcellulose in which 0.2 hydroxyl groups were carboxymethylated per 1 cellulose unit of cellulose was added with a 5% solution of lithium hydroxide in isopropanol for carboxyl groups. To the carboxymethylcellulose lithium salt B ′ was added an equivalent amount to the mixture and stirred.
10 was synthesized.

Examples 1 to 9, Comparative Examples 1 to 5 Organic resins B'1 to B'6 synthesized in Reference Example 2 and ethylene propylene rubber B7 for comparison were respectively used as n.
-Dissolved in xylene containing 10% by weight of butanol. In addition, polyvinylidene fluoride B8 was added to N-methyl-2
-Dissolved in pyrrolidone. Carbon particles C1 to C1 obtained by surface-treating these solutions with an alkali metal salt of a polymer compound in Reference Example 1 so as to have the formulations shown in Table 3
A conductive paste was prepared by adding C6 and carbon particles C7 for comparison, respectively, and stirring with a muller to mix until the carbon particles were uniformly dispersed in the system. Leave this conductive paste at room temperature for 24 hours,
The degree of separation of carbon particles was observed. The results are shown in Table 3.
It was as shown in.

This conductive paste was applied to a copper foil having a thickness of 12 μm using an applicator so that the coating film thickness after drying would be 100 μm, and dried at 50 ° C. for 10 minutes,
A negative electrode was formed. The following evaluation was performed on this negative electrode.

Volume resistivity: 1 cm area on the carbon layer of the negative electrode
Another copper foil of No. ² was placed, and the resistance value between the copper foil of the negative electrode and the copper foil of the negative electrode was measured by the four-terminal method. The thickness of the carbon layer was measured with a micrometer, and the volume resistivity was calculated.

Bending strength: Using a bending tester (manufactured by Yasuda Seiki Seisakusho) having a diameter of 2 mm, the negative electrode was bent with the copper foil facing down and the carbon layer facing up, and the state of cracks and peeling was observed with a 20 × microscope. did.

2 cm in size formed as described above
Using a 1 cm negative electrode, the negative electrode; manganese dioxide 85% by weight, pH 7.5, 10% by weight of carbon particles having a size of 760Å, and 5% by weight of the organic resin B1 synthesized in Reference Example 2 were applied to a copper foil. A lithium battery of a three-electrode method (see SANYO TECHNICAL REVIEW Vol. 20, No. 3, p. 76 (November 1988)) equipped with a positive electrode obtained by drying; and a lithium metal was assembled. As the electrolyte, 1,000 ml of a mixed solution of propylene carbonate and dimethoxyethane with a molar ratio of 1: 1 was added to L
IClO ₄ was used after 1 mole dissolved. The initial value of the discharge capacity, the value after the heat cycle test, and the value after the charge / discharge cycle test of the battery thus manufactured were measured. In addition, the state of the negative electrode after the heat cycle test and the charge / discharge cycle test was observed.

The heat cycle test was conducted at a temperature of -20 ° C for 3 hours.
One cycle of 0 minutes, 30 minutes at 90 ℃, 5 cycles
0 cycles were performed. Also, the charge / discharge cycle test is conducted at a temperature of 2
At 5 ℃, current 0.5mA / cm ² up to maximum voltage 3.5V
0.5mA current with up to 2.5V cutoff voltage
The discharge at / cm ² was set as one cycle, and 50 cycles were performed.

These results show that Examples 1 to 9 using the conductive composition of the present invention, Comparative Example 1 containing a large amount of an organic resin as a binder, Comparative Example 2 using ethylene propylene rubber, and surface treatment. Comparative Examples 3 and 4 using carbon particles not subjected to the above and Comparative Example 5 using a combination of polyvinylidene fluoride and carbon particles not subjected to the surface treatment,
It shows in Table 3.

[0052]

[Table 3]

Examples 10 and 11 As shown in Table 4, an N-methyl-2-pyrrolidone solution B'9 of the lithium polyamic acid salt obtained in Reference Example 3 was obtained.
And a solution prepared by dissolving carboxymethylcellulose lithium B′10 obtained in Reference Example 4 in the same mixed solvent as used in Examples 1 to 9 were used as binders and used in Example 3. Same surface-treated carbon particles C3
And conductive paste was prepared in the same manner as in Examples 1 to 9. Using this, experiments similar to those in Examples 1 to 9 were performed. The results are shown in Table 4.

Examples 12 and 13 Polyamic acid lithium salt B'obtained in Reference Examples 3 and 4
9 and carboxymethyl cellulose lithium salt B'1
0 using 0.1 part each, size of 20 μm, pH
100 parts of 7.6 spherical carbon particles were treated in the same procedure as in Reference Example 1 to obtain surface-treated carbon particles C8 (treated with B'9).
And C9 (treated with B'10) were obtained. As shown in Table 4, these surface-treated carbon particles were combined with the binder B′2 to prepare conductive pastes in the same manner as in Examples 1 to 9. Using this, experiments similar to those in Examples 1 to 9 were performed. The results are shown in Table 4.

[0055]

[Table 4]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01M 4/62 Z

Claims (6)

[Claims] 1. A conductive composition containing (A) an organic resin and (B) carbon particles, wherein (A) is an alkali metal salt of an organic polymer compound having a carboxyl group,
A conductive composition in which (B) satisfies the following requirements (a) and (b), and the amount of (A) in the composition is 1 to 10% by weight. (A) The pH of the liquid prepared by dispersing 10% by weight of the carbon particles in a mixed liquid of ethanol-water at a weight ratio of 1: 1 is 6-9. (B) The surface is coated with an alkali metal salt of a polymer compound. 2. (A) is one or more of (a) (1) an aliphatic hydrocarbon monomer having an ethylenically unsaturated double bond or a conjugated double bond, and 70 to 99.99 mol% (2) One or more kinds of ethylenically unsaturated double bond-containing monomers having one or two carboxyl groups or hydrolyzable acid anhydride groups in the molecule, 0.01 to 2
The electroconductive composition according to claim 1, which is an alkali metal salt of a copolymer with 0 mol%; (b) an alkali metal salt of a polyamic acid; or (c) an alkali metal salt of a carboxyl group-containing cellulose derivative. 3. The conductive composition according to claim 1, wherein (A) is a lithium salt. 4. An ethylenically unsaturated monomer having a carboxyl group or a sulfone group as an alkali metal salt of a polymer compound which coats the surface of (B) is 30 to 100 mol%.
And a hydrocarbon having no ethylenically unsaturated double bond or conjugated double bond in the molecule and having 0 to 70 mol% of a monomer selected from the group consisting of ethers and esters thereof. The conductive composition according to claim 1, which is a water-soluble alkali metal salt of a polymer. 5. The conductive composition according to claim 4, wherein the alkali metal salt of the polymer compound that coats the surface of (B) is a lithium salt. 6. An electrode using the conductive composition according to claim 1 as a mixture.