JP2898647B2 - Rechargeable battery - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a secondary battery using a conductive polymer.

[Prior art] Conventionally, as a sheet-like electrode made of a conductive polymer, as disclosed in JP-A-62-20243 and JP-A-61-133557, a conductive electrode is formed on a thin metal plate (collector) or metal mesh by electrolytic polymerization. It is known that a conductive polymer is deposited in the form of a film and used as an electrode, but the strength of the conductive polymer film itself or the adhesive strength between the film and the metal thin plate is low, so that the conductive polymer is used when assembling a battery. There was a problem such as dropping of the conductive polymer layer. In addition, it is difficult to control the thickness of the layer by electrolytic polymerization, and it is also difficult to increase the thickness.

In addition, in the present electropolymerization method, although the conductive polymer layer is easily obtained in the form of a film, the productivity is low. There has been a demand for a method of using molecules in a film form.

On the other hand, a method of kneading a powdery or fine-particle conductive polymer together with a binder such as polytetrafluoroethylene and a conductive material such as carbon black, which is called a mixture type, and pressing to form a sheet-like electrode is also available. Although there is (for example, JP-A-63-76
260), the adhesiveness to the current collector is poor, and the sheet itself has poor flexibility and is easily broken by bending or the like.

[Problems to be Solved by the Invention] In view of such circumstances, the present invention utilizes a powdery conductive polymer, has excellent adhesion to a thin metal plate, has high flexibility,
It is another object of the present invention to provide 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 provides a coating layer comprising a conductive polymer fine particle, a binder selected from an ethylene-vinyl acetate copolymer resin or a polyester resin and, if necessary, a conductive fine particle on a thin metal plate. The present invention relates to a secondary battery having a sheet electrode coated thereon.

The conductive film used in the present invention, aluminum, iron, nickel, or an alloy such as SUS, coated film was deposited or coated carbon body or SnO _2, InO metal oxide such as _2, conductive, such as polypyrrole Polymers and the like. The conductive film may be in the form of a thin plate, a thin plate having a through hole, or a two-dimensional mesh. The thickness of the conductive film is 1 to 100 μm, preferably 5 to 50 μm.

Further, as the conductive polymer, for example, polypyrrole,
Polythiophene, poly-3-methylthiophene, polycarbazole, diphenylbenzidine polymer, polytriphenylamine, polythiazyl, polyacetylene, polyparaphenylene, polyparaphenylene sulfide, polyaniline, polyparaphenylenevinylene, polyisothianaphthene, polypyridazine, Polyazulene, polyselenophene, polypyridine, polyacene, polyperinaphthalene, and the like are appropriately used.

Further, as dopants for these conductive polymers, BF ₄ ⁻ , ClO ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ COO
^{-, [(n-Bu)} 4 N] +, [(n-Et 4) N] +, K +, Li
⁺ , Na ^{+ and the} like.

The binder used in the present invention is ethylene-
A vinyl acetate copolymer resin or a polyester resin is used. These binders have the ability to disperse conductive polymers (molecular structure consisting of a polar group and a non-polar group) and a high ability to adhere to metals, and do not dissolve or swell in an electrolytic solution.
It must also have excellent flexibility.

Also, as conductive fine particles, conductive carbon powder such as Ketjen Black, acetylene black, SUS short fiber,
Fine metal particles such as platinum, gold, and silver, and short metal fibers are exemplified.

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

First, the binder is dissolved in a suitable solvent. A predetermined amount of a conductive polymer and conductive fine particles of an optional component are added to the solution, a solvent is further added as necessary, a steel ball or the like is added, and the mixture is dispersed by a ball mill, an attritor, or the like.

The thus obtained dispersion is coated on a conductive film using a wire bar or the like, and dried to obtain the sheet-like electrode of the present invention.

It is desirable that the particle diameter of the conductive polymer and the conductive fine particles in the dispersion liquid thus obtained is 0.1 μm to 500 μm.

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

The conductive polymer used in the present invention may be either an electrolytic polymerization method or a chemical polymerization method, but is preferably a chemical polymerization method from the viewpoint of easy production in powder form and mass productivity.

When the sheet-shaped electrode of the present invention is used as a positive electrode and used in a secondary battery, the negative electrode may be zinc, aluminum, magnesium, lithium, cadmium, or the like, a conductive polymer, or the like and the sheet-shaped electrode of the present invention (the positive electrode may be a different conductive (Using a conductive polymer).

When the sheet-shaped electrode of the present invention is used in a secondary battery as a negative electrode, manganese dioxide, silver oxide,
Graphite fluoride, thionyl chloride, activated carbon, titanium disulfide, molybdenum disulfide, a conductive polymer, and the like, and the sheet electrode of the present invention (using a different kind of conductive polymer from the negative electrode) can be used.

An aqueous solution of a metal halide or a solution of an organic solvent can be suitably used as the electrolytic solution. However, when the negative electrode is lithium, it is selected from organic solvents such as γ-butyrolactone, propylene carbonate, dimethylformamide, dimethoxyethane and the like. As the supporting salt, ammonium chloride is used in an aqueous solution system, and lithium perchlorate, lithium borofluoride, LiBr, LiCl, LiCF ₃ SO ₃ , and LiAs are used in an organic solvent system.
F ₆ , LiCF ₃ COO, LiSbF ₆ or the like is used.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 (1) Synthesis of Chemically Polymerized Polyaniline 20.4 g (0.219 mol) of aniline was dissolved in 300 ml of a 1M aqueous HCl solution, and (NH ₄ ) ₂ S ₂ O ₈ 1
A solution of 1.5 g (0.0504 mol) dissolved in 200 ml of an aqueous 1M HCl solution was added dropwise and stirred. After completion of the dropwise addition, stirring was continued at the same temperature for 2 hours, and the precipitated polyaniline (powder) was collected by filtration. The resulting polyaniline was washed three times with 200 ml of water, then twice with 100 ml of methanol and dried.

Next, this polyaniline was stirred in 300 ml of a 20% methanol solution of hydrazine at room temperature for 2 hours, dedoped and reduced, filtered, and washed twice with 100 ml of methanol to obtain 10.1 g of pale blue polyaniline.

(2) Preparation of Polyaniline Dispersion 10% toluene solution of 2 g of polyaniline synthesized above and ethylene-vinyl acetate resin (HC-10, Sumitomo Chemical Co., Ltd.)
g and 5 g of toluene were ball-milled in a 100 ml mayonnaise bottle containing steel balls for 3 hours to obtain a polyaniline dispersion.

(3) Preparation of Sheet-shaped Positive Electrode The above-mentioned polyaniline dispersion was dried on a SUS foil having a thickness of 20 μm with a wire bar and coated so as to have a thickness of 8 μm. The solid content was 0.84 mg / cm ² .

(4) Evaluation of battery characteristics The above sheet-shaped positive electrode and lithium foil (Honjo Metal Co., Ltd., 50
Using a test cell as shown in Fig. 1 using a separator (Tonentapyrs Co., Ltd. Tapils) and a 3M solution of LiBF ₄ in 70% by volume of propylene carbonate and 30% by volume of dimethoxyethane as an electrolyte. The charge / discharge characteristics were examined.

 The evaluation method is as follows.

(1) Open-circuit voltage: A constant current charge (0.3 mA) was performed, and after standing for 10 minutes, a voltage between both electrode terminals was measured.

(2) Active material energy density: Charged and discharged at a constant current (0.3 mA) and measured. The open-circuit voltage in this example was 3.8 V, and the energy density of the active material was 304 wh / kg. In addition, the sheet-shaped positive electrode of this example had good film-forming properties at the coated part, was flexible, and did not fall off the coated part even by bending or the like. Further, the coating portion did not dissolve, swell, or the like was observed in the test cell even when immersed in the electrolytic solution for one month.

Example 2 A sheet-shaped positive electrode was prepared and evaluated in the same manner as in Example 1 except that the formulation of the dispersion liquid in Example 1 was changed as follows.

2 g of polyaniline, 10 g of a 10% toluene solution of ethylene-vinyl acetate resin (Sumitomo Chemical Co., Ltd., HC-10), Ketjen Black (Lion Corporation, Ketjen Black EC)
2 g, toluene 5 g.

The open voltage was 3.8 V, the energy density of the active material was 359 Wh / kg, and the film forming property, flexibility, falling off, dissolving, swelling and the like of the coated portion were the same as in Example 1.

Example 3 In Example 1, a 1M aqueous solution of zinc sulfate was used as an electrolyte, a zinc foil was used as a negative electrode, a polyester resin was used as a polymer binder (Toyobo Co., Ltd., Byron-300), and all others were evaluated in the same manner as in Example 1. Was done. The open voltage is 1.2V,
The active material energy density was 100 Wh / kg, and the film forming property, flexibility, falling off, dissolving, swelling, and the like of the coated portion were the same as in Example 1.

Comparative Example 1 A solution prepared by dissolving 0.5 M aniline and 5.5 NH ₂ SO ₄ in water was used as a polymerization solution.
μ of a polyaniline film was deposited to form a sheet-shaped positive electrode. This positive electrode was reduced and de-doped with a 20% methanol solution of hydrazine as in the synthesis of the chemically polymerized polyaniline of Example 1 to prepare a sheet-shaped positive electrode. Evaluation was performed in the same manner as in Example 1 except that the sheet-shaped positive electrode of Comparative Example 1 was used instead of the sheet-shaped positive electrode of Example 1.

Although the open voltage was 3.8 V and the active material energy density was 406 Wh / kg, the surface of the polyaniline layer was powdery, and powdered and dropped off sharply due to bending and the like. Was in an impossible state.

Comparative Example 2 0.5 g of polyaniline, 0.08 g of Teflon dispersion (content 60%) as a sheet-shaped positive electrode, Ketjen Black
0.05 g of water and 0.5 g of water were kneaded and pressurized at 200 kg / cm ² to produce a so-called mixture type positive electrode. However, it was impossible to form a thin film having a thickness of 100 μm or less. In addition, the product molded into a thickness of 150 μm was dried at 100 ° C. under vacuum to obtain a sheet-shaped positive electrode. However, this product could not be easily bent or cracked by bending and could not be spirally wound. Met. Further, the sheet-like positive electrode could not be adhered to the current collector by pressure bonding to a SUS foil or the like.

Comparative Example 3 A sheet-shaped 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 dispersion state of polyaniline was poor, and the particles were not uniform. Was. In addition, this dispersion applied to a 20 μm SUS foil has poor adhesion,
It was easily peeled off from the SUS foil by bending or the like.

[Effects of the Invention] As described above, the secondary battery using the sheet-shaped electrode of the present invention exhibits a sufficient energy capacity and charge / discharge characteristics, and the sheet-shaped electrode has a flexible polyaniline-containing coating layer. It is a highly reliable sheet-shaped electrode that is rich in properties, has good adhesiveness to the current collector, can be wound in a spiral shape, has no swelling or the like dissolved in an electrolytic solution, and the like.

[Brief description of the drawings]

FIG. 1 is a diagram showing a test cell used for performance evaluation of a secondary battery of the present invention. DESCRIPTION OF SYMBOLS 1 ... Platinum lead wire for negative electrodes, 2 ... Platinum net current collector for negative electrodes, 3 ... Lithium foil (negative electrode), 4 ... Tapyrus (separator), 5 ... Sheet positive electrode of the present invention (polyaniline coat layer) 6) Platinum net current collector for positive electrode, 7 ... Platinum lead wire for positive electrode, 8 ... Polytetrafluoroethylene container.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01M 4/00-4/04 H01M 10/00-10/04 H01M 10/40

Claims (1)

(57) [Claims] 1. A sheet-like electrode having at least a conductive polymer fine particle and a coat layer comprising a binder selected from an ethylene-vinyl acetate copolymer resin or a polyester resin is provided on a conductive film. A secondary battery characterized by the above-mentioned.