JPH06124708A - Conductive composition containing polyvinylidene fluoride and battery using the composition - Google Patents

Abstract

PURPOSE:To provide a battery having high current density and long cycle lifetime via the use of a conductive composition having enhanced strength and adhesive quality as a positive electrode by applying a conductive composition containing polyvinylidene fluoride or the like as a binding agent. CONSTITUTION:A soluble conductive high polymer and polyvinylidene fluoride are evenly dissolved in a solvent, and thereafter the solvent is removed. As a result, a conductive composition having an adhesive conductive component is formed. In this case, when a composition used concurrently with polyaniline is applied as a binding agent, the strength and binding quality of the polyaniline are enhanced, while the characteristics thereof being maintained. Thus, when a positive electrode made of the composition is used, a battery having high current density and long cycle lifetime can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive composition composed of a soluble conductive polymer and polyvinylidene fluoride, and a battery using the same as a binder for a battery electrode.

[0002]

2. Description of the Related Art Since polyaniline has conductivity and redox properties, it is used as a conductive material, an electromagnetic wave shield, a sensor,
Applications to batteries, capacitors, etc. are under consideration. However, since polyaniline is inferior in strength as a film, various studies have been conducted. For example, in P125 (1987) of the 28th Battery Symposium Proceedings, polyaniline was used as N-
A method of obtaining a polyaniline film by dissolving it in methylpyrrolidone and casting it has been proposed. However, the strength of the polyaniline film is not sufficient, and the adhesion with the substrate is not sufficient. Further, WO 90/13601 proposes a method of obtaining a high-strength polyaniline / polyamide composition by dissolving polyaniline and polyamide in formic acid and casting. However, since formic acid must be used as a solvent, there is a problem of corrosion of substrates and equipment. Further, in a battery using a powdered active material, it has been used as a binder for electrodes by utilizing the excellent stability, solvent resistance and binding property of polyvinylidene fluoride. However, in order to carry out the electrode reaction, it is necessary to increase the conductivity of the electrode, but since polyvinylidene fluoride is insulative, it is necessary to use a large amount of a conductive agent for electrode preparation, and it has conductivity. A binder was sought.

[0003]

SUMMARY OF THE INVENTION One object of the present invention is to provide a composition which has the characteristics of polyaniline while improving its strength and adhesiveness. Another object of the present invention is to provide a composition that takes advantage of the characteristics of polyvinylidene fluoride. Another object of the present invention is to use the composition as a binder for forming electrodes.

[0004]

The present invention relates to a conductive composition comprising a soluble conductive polymer and polyvinylidene fluoride.

The soluble conductive polymer means a conductive polymer soluble in a solvent of polyvinylidene fluoride.
Specifically, polyvinylidene fluoride may be a conductive polymer soluble in a solvent such as dimethylformamide, N-methylpyrrolidone and tetrahydrofuran. This type of conductive polymer can be obtained, for example, by polymerizing the following monomers. That is, (1) anilines, JP-A-61-197633, JP-A-1-301714,
See JP-A-2-166165, JP-A-2-211230, JP-A-2-220373, and JP-A-3-505892. (2) Anilinoanilines For example, the formula

[Chemical 1] (In the formula, R ¹ and R ² can be hydrogen, alkyl or alkoxy.) (3) Pyrroles

[Chemical 2] (In the formula, R ³ , R ⁴ and R ⁵ are groups selected from the group consisting of hydrogen, alkyl and alkoxy, and R ³ , R ⁴ and R 5
^At least one of ⁵ is alkyl or alkoxy) (4) Thiophenes

[Chemical 3] (In the formula, R ⁶ and R ⁷ are groups selected from the group consisting of hydrogen, alkyl and alkoxy, but at least one of R ⁶ and R ⁷ is alkyl or alkoxy) and the like. . From the monomer of [Chemical Formula 1],
formula

[Chemical 4] From the monomer of the above [Chemical formula 2]

[Chemical 5] From the monomer of the above [Chemical formula 3]

[Chemical 6] Polymers are obtained respectively. Polyanilines are preferable in consideration of conductivity and strength.

The soluble conductive polymer in the conductive composition of the present invention may be in a doped or undoped state. The soluble conductive polymer in the undoped state has a high solubility in a solvent, but in order to impart conductivity, it is necessary to perform doping after compounding with polyvinylidene fluoride. As a dopant used for doping, Japanese Patent Laid-Open No. 3-505892 and Japanese Patent Laid-Open No. 30171/1991.
4, JP-A-2-166165, JP-A-2-21123
No. 0, a dopant as described in JP-A-2-220373 can be used. Specific examples include halogen anions such as hydrochloric acid, sulfuric acid, perchloric acid, nitric acid, borofluoric acid, chlorine, bromine, iodine and hydrogen chloride, halide anions such as hexafluoroline, hexafluoroarsenic and tetrafluoroboron, and alkylbenzene. Sulfonic acid, benzenesulfonic acid, nitrobenzenesulfonic acid, sulfonate anion such as β-naphthalenesulfonic acid, perchloric acid, perchlorate anion such as potassium perchlorate, sulfate anion such as sulfuric acid, chromanyl, bromanil, dichlorobenzoquinone, Benzoquinone, anthraquinone, toluquinone, tetramethyl-p-benzoquinone, tetrafluorotetracyanoquinodimethane, tetracyanoquinodimethane, tetracyanoethylene, 2,3-dichloro-5,6
Examples thereof include organic acceptors such as -dicyano-p-benzoquinone, which may be used alone or in combination, and the doping treatment may be performed by any of the treatment methods described in the above publications. As one specific method, it can be obtained by contacting a compound containing the dopant with a soluble conductive polymer in a dedoped state. Among these, organic acceptors are most preferable in consideration of conductivity, corrosiveness and strength. When using a soluble conductive polymer in a doped state prepared by the above-mentioned doping method, the solubility in a solvent is generally inferior to that in a dedoped state, but a soluble conductive polymer doped with an organic acceptor does not dissolve in a solvent. High solubility,
The composition is preferable because of its high conductivity and strength.

The amount of the soluble conductive polymer in the composition of the present invention is 1 to 99% by weight, preferably 5 to 95%.
%, Particularly preferably 20 to 90% by weight.

Next, a method for producing the composition of the present invention will be described. The composition of the present invention can obtain a homogeneous soluble conductive polymer / polyvinylidene fluoride composition by dissolving the soluble conductive polymer and polyvinylidene fluoride in a solvent and then removing the solvent. Examples of the solvent for the soluble conductive polymer and polyvinylidene fluoride include N-methylpyrrolidone, tetrahydrofuran, dimethylformamide and the like. As a method for removing the solvent, the solvent can be removed by evaporation by heating or reduced pressure, contact with a solvent that hardly dissolves both the soluble conductive polymer and polyvinylidene fluoride, and the shape and strength of the desired composition. The law is selected. The composition of the present invention can be processed into a film, powder or fiber.
Further, since the composition of the present invention has a binding property, it can be processed into various shapes by performing pressure molding, heat molding, etc., and various powder active materials (eg, inorganic oxide powder, inorganic chalcogen). Compound powder, conductive polymer powder, etc.).

Further, any other powder can be dispersed in the solution containing the soluble conductive polymer, polyvinylidene fluoride and the solvent, and the solvent is removed from the solution in which the powder is dispersed. A soluble conductive polymer / polyvinylidene fluoride composition containing powder can be obtained. The amount of powder that can be contained in the composition of the present invention is 0 to
95%, preferably 5 to 90%. As the powder to be contained in the composition of the present invention, various conductive materials, optical functional materials, battery materials and the like can be used.

The most effective case of the composition of the present invention is when it is used as a binder for battery electrodes. This will be described below. As the positive electrode active material as the electrode active material, the soluble conductive polymer / polyvinylidene fluoride composition of the present invention also functions as the active material, but Mn, C
oxides of transition metals such as o, Ni, V, Mo and W, chalcogen compounds, composite oxides with alkali metals, conductive polymers such as polyacetylene, polypyrrole, polythiophene, polycarbazole and polyazulene, carbon bodies, etc. It can be illustrated. Li and A as the negative electrode active material
Examples thereof include alloys such as 1, Mn, and Pb, carbon bodies, and the like.

Next, a battery using the above electrode will be described. This battery is basically composed of a positive electrode, a negative electrode and an electrolyte. In the battery of the present invention, an electrode formed by using the composition of the present invention as a binder is used as the positive electrode. As the negative electrode, in addition to the above electrodes, alkali metals such as Li, Na and K
An alloy of Li and Al, Mn, Pb, or the like, a carbon body, or the like can be used.

The following anions or cations are used as the electrolyte. Examples of the anion include halide anions of Va group elements such as PF ₆ ⁻ , SbF ₆ ⁻ , As ₆ ⁻ , BF ₄ ⁻ , BR ₄ ⁻ (R is a phenyl group,
Anions of group IIIa elements such as alkyl groups), Cl ⁻ , Br
^- , I-, ^and other halogen anions, perchlorate anions, trifluoromethanesulfonate anions, and the like.
For example Li + as a cation, Na +, K +, etc. of an alkali metal _{cation, (R 4 N) + (} R is a hydrocarbon group having 1 to 20 carbon atoms) and the like. Examples of the compound that provides the electrolyte include LiPF ₆ , LiSbF ₆ , and LiAs.
₆ , LiBF ₄ , LiClO ₄ , LiCF ₃ SO ₃ , Li
I, KPF ₆ , KClO ₄ , NaPF ₆ , [(n-Bu) ₄
N] BF ₄ , [(n-Bu) ₄ N] ClO ₄ , LiAlC
Examples thereof include l _{4 and the} like, but the invention is not limited thereto.

The solvent constituting the electrolyte solution is not particularly limited, but a solvent having a relatively large polarity is preferably used. Specifically, propylene carbonate, ethylene carbonate, benzonitrile, acetonitrile,
Tetrahydrofuran, 2-methyltetrahydrofuran,
One or a mixture of two or more organic solvents such as γ-butyl lactone, dioxolane, triethyl phosphite, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, dimethoxyethane, polyethylene glycol, sulfolane, dichloroethane, chlorobenzene and nitrobenzene. Is mentioned.

As the separator, one having a low resistance to the movement of ions of the electrolyte solution and an excellent solution holding property is used. For example, a polymer such as a glass fiber filter, polyester, Teflon, polyflon, polypropylene or the like is used. Examples thereof include a bore filter non-woven fabric or a non-woven fabric made of glass fiber and these polymers. A solid electrolyte is used as a substitute for the electrolytic solution and the separator. For example, in an inorganic system, A
Examples thereof include metal halides such as gCl, AgBr, AgI and LiI, RbAg ₄ I ₅ and RbAg ₄ I ₄ CN.
Further, in the organic system, polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyacrylamide and the like as a polymer matrix, a complex in which the electrolyte salt is dissolved in the polymer matrix, or a gel cross-linked product thereof, a low molecular weight polyethylene oxide,
Examples thereof include a polymer solid electrolyte in which an ionic dissociation group such as crown ether is grafted to the polymer main chain, or a gel polymer solid electrolyte in which the electrolyte solution is contained in a high molecular weight polymer. One specific example thereof is a separator described in Japanese Patent Application No. 60-172036 of the present applicant. The form of the battery of the present invention is not particularly limited, but the battery can be mounted on various batteries such as a coin type, a sheet type, a cylinder type and a gum type.

[0015]

【Example】

Production of polyaniline A. from ammonium persulfate and hydrochloric acid. G. MacDiar
mid et al. , Conducting Pol
ymers. , 105 (1987) to synthesize polyaniline. Example 1 0.45 g of polyaniline and 0.05 g of polyvinylidene fluoride manufactured by Showa Denko were dissolved in 10 ml of n-methylpyrrolidone. After applying this solution to the SUS304 substrate, 1
It heated at 70 degreeC and removed n-methyl pyrrolidone. S
A homogeneous polyaniline / polyvinylidene fluoride composition film was obtained on a US304 substrate. Example 2 0.3 g of polyaniline and 0.2 g of polyvinylidene fluoride manufactured by Showa Denko were dissolved in 10 ml of n-methylpyrrolidone. After applying this solution to a glass substrate, it was heated at 170 ° C. to remove n-methylpyrrolidone. A homogeneous polyaniline / polyvinylidene fluoride composition film was obtained on the glass substrate. Example 3 0.1 g of polyaniline and 0.4 g of polyvinylidene fluoride manufactured by Showa Denko were dissolved in 10 ml of dimethylformamide. After applying this solution to an aluminum substrate, 170
Heated at ° C to remove dimethylformamide. A homogeneous polyaniline / polyvinylidene fluoride composition film was obtained on an aluminum substrate.

Example 4 The polyaniline / polyvinylidene fluoride composition film prepared in Example 1 was immersed in a 1M aqueous solution of HClO ₄ perchlorate for 12 hours. After washing and drying, the electric conductivity was measured and found to be 1 S / cm. Example 5 The polyaniline / polyvinylidene fluoride composition film produced in Example 2 was immersed in a 1M sulfuric acid aqueous solution for 12 hours. After washing and drying, the electric conductivity was measured and found to be 0.4.
It was S / cm. Example 6 0.45 g of polyaniline and 0.05 g of polyvinylidene fluoride manufactured by Showa Denko were dissolved in 10 ml of n-methylpyrrolidone in which 50 mM tetracyanoquinodimethane (TCNQ) was dissolved. After applying this solution to a SUS304 substrate, it was heated at 170 ° C. to remove n-methylpyrrolidone. A homogeneous polyaniline / polyvinylidene fluoride composition film was obtained on the SUS304 substrate. When the electric conductivity of this composition film was measured, it was 2 × 10 ^−4.
It was S / cm.

Example 7 0.3 g of polyaniline and 0.2 g of polyvinylidene fluoride manufactured by Showa Denko were dissolved in 10 ml of n-methylpyrrolidone. This solution was put into 500 ml of water which was stirred with a magnetic stirrer. The precipitate was filtered and dried to obtain a homogeneous polyaniline / polyvinylidene fluoride composition powder. This powder was immersed in a 1M sulfuric acid aqueous solution for 12 hours. After washing and drying, a molded product was obtained by pressing at ² t / cm ² . The electric conductivity of this molded body is 0.3 S / cm
Met.

Example 8 1.2 g of Mn-Li composite oxide obtained by mixing MnO ₂ and LiNO ₃ at a molar ratio of 7: 3 and calcined at 400 ° C., 0.2 g of polyaniline, 0.2 g of polyvinylidene fluoride manufactured by Showa Denko.
Was mixed with 10 ml of n-methylpyrrolidone in which 50 mM tetracyanoquinodimethane (TCNQ) was dissolved, stirred with a magnetic stirrer, applied on a SUS304 substrate, and then heated at 170 ° C. to remove n-methylpyrrolidone. Then, a positive electrode for a secondary battery was produced. Secondary battery characteristics were measured using Li as the negative electrode and a 1 mol LiClO ₄ / propylene carbonate solution as the electrolytic solution. Charge and discharge is 2
When carried out at 0.2 mA / cm ² in a voltage range of up to 3.7 V, a discharge capacity of 159 mAh / g per positive electrode weight was obtained, and a cycle life of 100 times or more was obtained. Example 9 In Example 8, V ₂ was used instead of the Mn—Li composite oxide.
A positive electrode for a secondary battery was produced in the same manner as in Example 8 except that O ₅ was used, and the characteristics of the secondary battery were evaluated. 161mAh /
A discharge capacity of g was obtained, and a cycle life of 100 times or more was obtained.

Example 10 0.5 g of polyaniline and 0.5 g of polyvinylidene fluoride
Was dissolved in 10 ml of n-methylpyrrolidone. This solution was poured into a petri dish having a diameter of 3 cm and heated at 170 ° C. to remove n-methylpyrrolidone to obtain a film having a thickness of 300 μm and a diameter of 3 cm. 10 this film in water
When it was dried after being left for one day, the thickness was 280 μm and the diameter was 2.7 cm, and the deformation was small. This film is 1N-
It was immersed in an HBF ₄ aqueous solution for 12 hours. The dried film has a thickness of 305 μm, a diameter of 3.1 cm, and a conductivity of 7 × 10.
It was ^-2 S / cm. Comparative Example 1 g of polyaniline was dissolved in 10 ml of n-methylpyrrolidone. This solution was poured into a petri dish having a diameter of 3 cm and heated at 170 ° C. to remove n-methylpyrrolidone to obtain a film having a thickness of 300 μm and a diameter of 3 cm. This film was left in water for 10 days and then dried to obtain a thickness of 12
The deformation was very large at 0 μm and a diameter of 1.4 cm.

[0020]

[Effect] According to the present invention, a novel conductive composition containing polyvinylidene fluoride can be provided. This composition is useful as an electrode-forming binder because it is electrically conductive but has a binding property. In particular, when a composition used in combination with polyaniline is used as a binder, the properties of polyaniline are improved. It was possible to improve the strength and adhesion of polyaniline while making the best use of it. Further, the battery using the positive electrode made using the composition of the present invention has a high current density,
It has the characteristic of long cycle life.

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Claims (7)

[Claims] 1. A conductive composition comprising a soluble conductive polymer and polyvinylidene fluoride. 2. The conductive composition according to claim 1, wherein the soluble conductive polymer is polyaniline. 3. The conductive composition according to claim 2, wherein the polyaniline forms a complex with an organic acceptor. 4. The conductive composition according to claim 1, 2 or 3, wherein the composition is in the form of a film. 5. A method for producing a conductive composition, which comprises uniformly dissolving both a soluble conductive polymer and polyvinylidene fluoride in a soluble solvent and then removing the solvent. 6. A binder for forming an electrode, which comprises the composition according to claim 1, 2, or 3. 7. A battery using the electrode formed by using the binder according to claim 6 as a positive electrode.