JPS63173311A - Electric double-layer capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an electric double layer capacitor.

(Prior Art) An electric double layer capacitor in which a conductive adhesive is interposed between a polarizable electrode and a metal case housing the electrode is conventionally described in, for example, Japanese Patent Laid-Open No. 59-3915. There is something.

(Problems to be Solved by the Invention) However, in such conventional electric double layer capacitors, cellulose derivatives such as methyl cellulose, polyvinyl alcohol (
Because they use materials such as PVA), polyvinyl butyral, and polyvinyl acetate, the electrodes and case are often bonded by point adhesion, which tends to increase internal resistance and degrade capacitance, resulting in insufficient long-term reliability. There was a problem.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide an electric double layer capacitor that exhibits less capacity deterioration and excellent long-term reliability.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention accommodates a polarizable electrode in a case to prevent an electric double layer formed at the interface between the polarizable electrode and the electrolyte. Provided is an electric double layer capacitor for use in which a layer made of a conductive adhesive containing a heat-fusible resin is interposed between the polarizable electrode and the inner surface of the case. It is something to do.

As the conductive adhesive used in the present invention, one containing carbonaceous, metal, or other conductive material and heat-fusible resin can be used. It is preferable to use carbon as a main component, particularly graphite or a carbon blank such as acetylene black.

The heat-fusible resin contained in the conductive adhesive preferably has heat-fusibility that allows bonding the inner surface of the case and the polarizable electrode by heating to 150 to 330"C. Often, for example, tetrafluoroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer resin, trifluorochloroethylene resin, vinyl chloride resin, vinyl fluoride resin, vinylidene chloride resin, vinylidene fluoride resin, polyethylene resin. , ethylene-vinyl acetate copolymer resin,
Examples include polypropylene resins, but in terms of chemical resistance and heat fusion properties, fluorinated alkylene resins such as tetrafluoroethylene-hexafluoropropylene copolymer resins, 37fluorochlorinated ethylene resins, and vinyl fluoride resins Resin, vinylidene fluoride resin, polyethylene resin, etc. are preferably used.

In the composition of the conductive adhesive, the content of the heat-fusible resin is preferably 1 to 200% by weight, preferably 10 to 150% by weight, based on the weight of the carbonaceous material.

Also, water, acetone, methanol,
Organic solvents such as ethanol can be suitably used, and it is preferable to prepare the adhesive using these diluents so that the solid content of the adhesive is 30 to 50% by weight.

The method for bonding the polarizable electrode to the case is to apply the conductive adhesive to at least one of the inner surface of the case and the polarizable electrode, heat the adhesive, and preferably maintain fluidity before solidifying the adhesive. Crimp the polarizable electrode to the inner surface of the case.

This pressure bonding is carried out at a temperature near or above the melting point of the heat-fusible resin, preferably 150 to 330°C, particularly 170 to 300°C.
1 to 100 kg/c at a temperature of °C - preferably 1
Perform at a pressure of ~20 kg/cl.

Note that a current collector such as a metal mesh may be fixed in advance to the surface of the case that comes into contact with the electrode by means such as welding or adhesion.

In such a case, a conductive adhesive may be applied to the inner surface of the current collector in advance.

The material of the polarizable electrode used in the present invention is not particularly limited, but is electrochemically inert to the electrolyte,
It is also preferable to use activated carbon powder or activated carbon fibers that have a large specific surface area.

In particular, activated carbon powder contains polytetrafluoroethylene (PT).
Electrodes that are made by adding a binder such as FE), roll-formed into a sheet, and preferably stretched in a uniaxial or biaxial direction have excellent capacity per unit volume, strength, and long-term reliability. Preferably used.

The electrolytic solution used in the present invention is not particularly limited, and may be one commonly used for electric double layer capacitors, that is, an electrochemically stable solute (electrolyte).
Dissolved in a polar organic solvent is appropriately used.

As a solvent for the electrolytic solution, propylene carbonate, butylene carbonate, sulfolane, β-butyrolactone,
γ-butyrolactone, acetonitrile, dimethylformamide, 1,2-dimethoxyethane, nitromethane and the like are preferably used.

Examples of solutes in the electrolytic solution include cations such as alkali metals, alkaline earth metals, ammonium, tetraalkylammonium, and tetraalkylphosphonium;
Examples include salts formed in combination with anions such as fluorinated boric acid, 6-fluorinated phosphoric acid, perchloric acid, 6-fluorinated arsenic acid, tetrachloroaluminic acid, 6-fluorinated antimonic acid, and trifluoroalkylsulfonic acid. and these solutes are added to the above solvent at a rate of 0.1 to 3.0 M/p, preferably 0.5 to 1.5 M/f.
An electrolytic solution dissolved at a concentration of f is preferably used.

As the separator used in the present invention, a usual separator for electric double layer capacitors, such as a separator made of polypropylene fiber nonwoven fabric or glass fiber mixed paper nonwoven fabric, is suitably used.

(Example) Examples and comparative examples of the present invention will be specifically described below with reference to the drawings.

Example 1 To 100 parts by weight of activated carbon powder having a specific surface area of 2.000 m/g, 10 parts by weight of a polytetrafluoroethylene dispersion was added and formed into a sheet by wet kneading.

The sheet-like material obtained in this way was punched out into a disk shape to make a polarizable electrode 1.2 (diameter 151 m, thickness 0.7 weight).
And so. Next, 5 wt.
Graphite-based conductive adhesive (solid content 20% by weight) containing 56m
The conductive adhesive layer 7 was formed by applying g/cIil, and the polarizable electrodes 1 and 2 were placed inside the case 4.5, respectively, and pressure bonded at 175°C, 120 kg/self, and 10 minutes.

A polarizable electrode 1 fixed to the inside of the case 4 and a polarizable electrode 2 fixed to the inside of the case 5 are arranged facing each other with a separator 3 made of polypropylene fiber nonwoven fabric having a thickness of 80 μm interposed therebetween. .2 and Separate Lake 3 are impregnated with an electrolytic solution (tetrabutylphosphonium fluoroborate dissolved in propylene carbonate at a concentration of 0.5 M/I!), and then case 4 and case 5 are inserted through a polypropylene backing 6. The ends were caulked and sealed to integrate.

Using the electric double layer capacitor unit cell prepared as described above, the initial capacitance (F/c♂) and initial internal resistance (Ω) when a voltage of 2.8 V is applied are as follows:
Subsequently, apply a voltage of 2.8μ to this cell and
The capacity and internal resistance after storage at °C for 1000 hours were measured, and the rate of capacity deterioration (%) from the initial capacity was calculated.

Example 2 The same processing and measurements as in Example 1 were performed, except that a graphite-based conductive adhesive containing 10% by weight of polyvinylidene fluoride (vinylidene fluoride resin) was used as the heat-fusible resin.

Example 3 A graphite-based conductive adhesive containing 5% by weight of tetrafluoroethylene-67-propylene copolymer resin was used as a heat-fusible resin, and the adhesive was heated at 280°Cl2Okg/cffl, 1
The same treatments and measurements as in Example I were performed except that the electrodes were crimped for 0 minutes.

Example 4 Except for using a carbon blank conductive adhesive containing 5% by weight of polyethylene resin as the heat-fusible resin,
The same treatments and measurements as in Example 1 were performed.

Comparative Example The same treatments and measurements as in Example 1 were carried out, except that a graphite-based conductive adhesive containing no heat-fusible resin was used.

The measurement results of the above Examples and Comparative Examples are shown in Table 1.

(Tree page, blank space below) Table 1 As is clear from the results in Table 1, the electric double layer capacitors of Examples 1 to 4 had a smaller increase in internal resistance after long-term use than those of the comparative example, and the capacitance Deterioration rate is extremely low.

(Effects of the Invention) According to the present invention, by interposing a layer made of a conductive adhesive containing a heat-fusible resin between the polarizable electrode and the case, there is little capacity deterioration and long-term reliability is ensured. It is possible to obtain an excellent electric double layer capacitor.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing one embodiment of an electric double layer capacitor according to the present invention. 1.2... Polarizable electrode, 3... Separator, 4... Anode side case, 5... Cathode side case, 6... - Banking, 7... Conductive adhesive layer.

Claims (6)

[Claims] (1) In an electric double layer capacitor that houses a polarizable electrode in a case and utilizes an electric double layer formed at the interface between the polarizable electrode and an electrolyte, there is a gap between the polarizable electrode and the inner surface of the case. An electric double layer capacitor characterized by interposing a layer made of a conductive adhesive containing a heat-fusible resin. (2) The heat-fusible resin is made of at least one resin selected from the group consisting of tetrafluoroethylene-hexafluoropropylene copolymer resin, vinyl fluoride resin, vinylidene fluoride resin, and polyethylene resin. The electric double layer capacitor according to claim 1, characterized in that: (3) The electric double layer capacitor according to claim 1 or 2, wherein the conductive substance of the conductive adhesive has carbon as a main component. (4) The electric double layer capacitor according to claim 3, wherein the carbonaceous material is graphite or carbon black. (5) Claims 1 to 3, wherein the polarizable electrode is made of a sheet-like material containing activated carbon and/or carbon black and polytetrafluoroethylene powder.
The electric double layer capacitor according to any one of Item 4. (6) The electric double layer capacitor according to any one of claims 1 to 5, wherein the sheet-like material is obtained by roll molding.