JPH02234349A - Secondary battery - Google Patents

Abstract

PURPOSE:To obtain a secondary battery with highly flexible, seat-like electrodes having excellent adhesiveness to metal sheets by utilizing powdery conductive high polymer. CONSTITUTION:A specified amount of conductive high polymer, conductive minute particles of an optional composition, steel balls, etc., are added to a binder solution and then dispersed. The dispersed liquid is applied on a conductive film, and then by drying it, a sheet-like electrode can be obtained. Conductive films include coating films on which metals such as iron and aluminum or alloys are evaporation-deposited or applied dud the film thickness should preferably be 5 to 50mum. Conductive high-polymers include polypillol and polythyophen, which are to be used conveniently as needed. The particle size of conductive high-polymer and conductive minute particles should preferably be from 0.1mu to 500mu. As a result, a secondary battery with highly flexible and highly reliable seat-like electrodes can be obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a secondary battery using a conductive polymer.

[Prior Art] Conventionally, sheet-like electrodes made of conductive polymers have been developed by electrolytically polymerizing them onto metal thin plates (current collectors) or metal meshes, as in JP-A-82-20243 and JP-A-61-133557. It is known to deposit a conductive polymer in the form of a film and use it as an electrode, but this method has low strength of the conductive polymer film itself or low adhesive strength between the film and the thin metal plate, making it difficult to conduct electricity. During assembly, there were problems such as the conductive polymer layer falling off. Furthermore, in electrolytic polymerization, it is difficult to control the thickness of the layer, and it is also difficult to increase the thickness.

In addition, although this electrolytic polymerization method can easily obtain a conductive polymer layer in the form of a film, the productivity is low. A method that uses molecules in the form of a film has been desired.

On the other hand, it is called a mixture type, and is a method in which a powdered or particulate conductive polymer is kneaded with a binder such as polytetrafluoroethylene and a conductive material such as carbon black, and then pressed to form a sheet electrode. (For example, Japanese Patent Application Laid-open No. 1983-
78260), the adhesiveness with the current collector is poor, and the seat body has poor flexibility and is easily broken by bending or the like.

[Problems to be Solved by the Invention] In view of these circumstances, the present invention utilizes a powdered conductive polymer, has excellent adhesion to thin metal plates, is highly flexible,
The present invention also provides a secondary battery having an excellent sheet-like electrode in which the conductive polymer layer does not fall off.

[Means for Solving the Problems] The present invention is characterized by having a sheet-like electrode formed by coating a thin metal plate with a coating layer made of conductive polymer fine particles, a binder, and optionally conductive fine particles. The invention relates to secondary batteries.

The conductive film used in the present invention includes metals or alloys such as aluminum, iron, nickel, and SUS, coating films deposited or coated with carbon bodies or metal oxides such as SnO2 and Inoz, and highly conductive films such as vorivirol. Examples include molecules. The form of the conductive film is a thin plate, a thin plate with through holes, or a two-dimensional mesh. The thickness of the conductive film is 1-100
Preferably, 5 to 50 microns is used.

Examples of conductive polymers include polypyrrole, polythiophene, poly-3-methylthiophene, polyrubazole, diphenylbenzidine polymer, polytriphenylamine, polythiazyl, polyacetylene, polyparaphenylene, polyparaphenylene sulfide, and polyaniline. , polyparaphenylene vinylene, polyisothianaphthene, polypyridazine, polyazulene, polyselenophene, polypyridine, boriacene, polyperinaphthalene, etc. are used as appropriate.

In addition, as a dopant for these conductive polymers, BF4-Cl04-PF6AsFS''''S
bFi CF3 So) CF 3 COO-
[(n-Bu)4Nl[(n-Et4)Nl”
, K"Li"Na◆, etc.

Further, binders used in the present invention include ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer,
Epoxy resin, vinylidene fluoride resin, polyvinyl alcohol, polyester resin, etc. are used. These binders have the ability to disperse conductive polymers (molecular structure consisting of polar groups and non-polar groups), have high adhesion ability to metals, do not dissolve in electrolytes, do not swell, and are flexible. Must be excellent.

In addition, conductive fine particles include conductive carbon powder such as Ketjen black and acetylene black, SUS short fibers,
Examples include fine metal particles such as platinum, gold, and silver, and short metal fibers.

A method for producing the sheet-like electrode of the present invention using these conductive films, conductive polymers, binders, and conductive fine particles will be exemplified below.

First, the binder is dissolved in a suitable solvent.

A predetermined amount of a conductive polymer and optional conductive fine particles are added to this solution, a solvent is further added if necessary, a steel ball or the like is added, and the mixture is dispersed using a ball mill, an attritor, etc.

The sheet-like electrode of the present invention can be obtained by coating the thus obtained dispersion onto a conductive film using a wire bar or the like and drying it.

The conductive polymer and conductive fine particles in the dispersion thus obtained preferably have a particle size of 0.1 μ to 500 μ.

The weight ratio of the binder, conductive polymer, and conductive fine particles is 5 to 40% by weight, preferably 10 to 40% by weight.
20% by weight, conductive polymer 60-95% by weight, preferably 80-90% by weight, conductive fine particles 0-15% by weight
, preferably 3 to 10m%.

The conductive polymer used in the present invention may be produced by either an electrolytic polymerization method or a chemical polymerization method, but a chemical polymerization method is more preferable because it is easy to obtain in powder form and can be mass-produced.

When the sheet electrode of the present invention is used as a positive electrode in a secondary battery, the negative electrode may include zinc, aluminum, magnesium, lithium, cadmium, etc., conductive polymers, etc. polymers) can be used.

When the sheet electrode of the present invention is used as a negative electrode in a secondary battery, the positive electrode may include manganese dioxide, silver oxide, graphite fluoride, thionyl chloride, activated carbon, titanium disulfide, molybdenum disulfide, conductive polymers, etc. And the sheet-like electrode of the present invention (using a different type of conductive polymer than the negative electrode) can be used.

As the electrolytic solution, an aqueous solution of a metal halide or a solution of an organic solvent can be suitably used. However, when the negative electrode is lithium, it is selected from organic solvents such as γ-butyrolactone, propylene carbonate, dimethylformamide, dimethoxyethane, and the like. Supporting salts include ammonium chloride for aqueous systems, lithium perchlorate for organic solvent systems, and
Lithium borofluoride, LiBr, LiCl, LiCF3
SO3, LiAsFs, L i CF 3 COO, L
lsbFG etc. are used.

[Example] The present invention will be explained in more detail with reference to Examples below.

Example 1 (1) Synthesis of chemically polymerized polyaniline 20.4 g of aniline (
0.219 sol) and while keeping it at 5 to 10°C under water cooling, (NH4)2S20sl
1.5g (0.0504mol) of 20011 IMH
Add the solution dissolved in cI aqueous solution dropwise and stir. Stirred. After the completion of the dropwise addition, stirring was continued at the same temperature for 2 hours, and the precipitated polyaniline (powder) was collected by filtration. 20Qm of the obtained borianiline
Washed 3 times with 1 ml of water, then 2 times with ioml of methanol and dried.

Next, this polyaniline was stirred in a 20% methanol solution of hydrazine 3001 at room temperature for 2 hours to perform dedoving and reduction, collected by filtration, and washed twice with methanol 10011,
10.1 g of pale blue polyaniline was obtained.

(2) Creation of polyaniline dispersion 2 g of the polyaniline synthesized above and 10 g of a lO% toluene solution of ethylene-vinyl acetate resin (Sumitomo Chemical ■, IIC-10), 5 g of toluene were placed in a steel ball.
Ball mill dispersion for 3 hours in a 0ml mayonnaise bottle,
A polyaniline dispersion was obtained.

<<3>> Preparation of sheet-like positive electrode A 20 μm thick SOS foil was coated with the above polyaniline dispersion using a wire bar so as to have a thickness of 8 μm when dried. The amount of solid matter deposited was 0.84 mg/cm'.

(4) Evaluation of battery characteristics The above sheet-like positive electrode, lithium foil (Honjo Metal ■, 50μ■
Thickness) Separator (Tonentapil Fukiyupilsu) and LiBF+ propylene carbonate 70 as the electrolyte
Using a 3M solution containing Jffi% and 30% dimethoxyethane by volume, the charge-discharge characteristics were investigated using a test cell as shown in FIG.

The evaluation method is as follows.

(1) Open-circuit voltage: Constant current charging (0.3 mA) was performed, and after standing for 10 minutes, the voltage between both electrode terminals was measured.

(2) Active material energy density: constant current (0.3mA
) was charged and discharged and measured. The open circuit voltage in this example is 3.8V. The active material energy density was 304 vh/kg. Also,
The sheet-like positive electrode of this example had good film-forming properties on the coated portion, was flexible, and did not come off even when bent or the like. Furthermore, no dissolution or swelling was observed in the coated part even after it was immersed in the electrolyte solution for one month in the test cell.

Example 2 A sheet-like positive electrode was prepared and evaluated in the same manner as in Example 1 except that the dispersion formulation was changed as shown below.

Borianiline 2g1 10% toluene solution of ethylene-vinyl acetate (Sumitomo Chemical ■, IC-10) tog, Ketjenblack (Lion ■, Ketjenblack E)
C) 0.2g, Tornine 5g0 open circuit voltage is a. g
v, the active material energy density is 359 wh/kg,
The film formability, flexibility, shedding, dissolution, swelling, etc. of the coated portion were the same as in Example 1.

Example 3 In Example 1, an aqueous IM zinc sulfate solution was used as the electrolyte, zinc foil was used as the negative electrode, and polyester resin (Toyobo Co., Ltd. Byron-300) was used as the polymer binder. went. The open circuit voltage is l. 2V
, the energy density of the active material is tooth/kg,
The film formability, flexibility, shedding, dissolution, swelling, etc. of the coated portion were the same as in Example 1.

Comparative Example 1 0.5M aniline, 5.5N H2SO as polymerization liquid
4 dissolved in water, 20u S as TEPCO
Using US foil as a working electrode, a polyaniline film with a thickness of 8 μm was deposited on the surface of the current collector by 0.75 V vs S C E constant potential polymerization method to prepare a sheet-like positive electrode. As in the synthesis of chemically polymerized polyaniline in Example 1, this positive electrode was reduced and dedoped with a 20% methanol solution of hydrazine.
A sheet-like positive electrode was created. Evaluation was performed in the same manner as in Example 1 except that the sheet-like positive electrode of Comparative Example 1 was used instead of the sheet-like positive electrode of Example 1.

Open circuit voltage is 3.8V, active material energy density is 4Q6
Vh/kg, but the surface of the borianiline layer was powdery, and the powder fell off and fell off heavily when bent, etc., making it impossible to wind the sheet-like positive electrode in a spiral shape, for example.

Comparative Example 2 As a sheet positive electrode, 0.5 g of polyaniline, 0.08 g of Teflon dispersion (including ffiBo%), 0.05 g of Ketjen black, and 0.5 g of water were kneaded,
A so-called mixture type positive electrode was created by pressurizing it at 200 kg/cs+2, but it was impossible to form it into a thin layer with a thickness of 100 μ1 or less. In addition, a sheet-shaped positive electrode was formed by forming a layer with a thickness of 150 μm and drying it under vacuum at 100°C, but this material easily broke or cracked when bent, making it impossible to wind it into a spiral shape. It was a state.

Furthermore, it was impossible to adhere this sheet-like positive electrode to Tokyo Electric Corporation's SUS foil by pressure bonding or the like.

Comparative Example 3 A sheet positive electrode was prepared in the same manner as in Example 1 except that low molecular weight polyethylene was used as the polymer binder in Example 1, but the polyaniline was poorly dispersed and did not form homogeneous fine particles. Ta. Furthermore, when this dispersion was applied to a SUS foil with 20μ dust, the adhesion was poor and it was easily peeled off from the SUS foil by bending or the like.

[Effects of the Invention] As explained above, the secondary battery using the sheet-like electrode of the present invention exhibits sufficient energy capacity and charge/discharge characteristics, and the sheet-like electrode has a flexible polyaniline-containing coating layer. It is a highly reliable sheet-like electrode that has excellent properties, has good adhesion to current collectors, can be wound spirally, and does not swell when dissolved in an electrolytic solution.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a test cell used for performance evaluation of the secondary battery of the present invention. ! ...Platinum lead wire for negative electrode, 2...Platinum wire mesh aggregate for negative electrode, 3...Lithium foil (negative electrode), 4...Yubirusu (separator), 5...Sheet-shaped positive electrode of the present invention (borianiline coated layer facing upward), G. Platinum wire mesh aggregate for positive electrode, 7. Platinum lead wire for positive electrode, 8. Polytetrafluoroethylene container.

Claims (1)

[Claims] A secondary battery comprising a sheet-like electrode formed by coating a conductive film with a coating layer comprising at least conductive polymer fine particles and a binder.