JP2002043188A - Sheet electrode and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet electrode, using conductive rubber and method of manufacturing the same which can improve electrical characteristics, such as internal resistance. SOLUTION: When manufacturing the sheet electrode 5 which is to be used in an electric double-layer capacitor 1, conductive fine particles, silicone rubber compound, curing agent, and solvent are mixed by a mixer or the like to make a slurry-like kneaded material 50. Then, thick kneaded material 50 is applied in a prescribed thickness as a collector electrode on the surface of an aluminum foil 51. Thereafter, a heat treatment is conducted at a prescribed temperature and for a prescribed period of time, to completely evaporate the solvent, the then a curing processing is conducted. Thus, a polarized electrode formed of conductive rubber 52 is formed on the surface of the aluminum foil 51.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet-like electrode used for an electric double layer capacitor and a lithium ion battery, and a method for producing the same. More specifically, the present invention relates to a material technology for the sheet electrode.

[0002]

2. Description of the Related Art In general, an electric double layer capacitor is a capacitor using an electric double layer formed at an interface between a carbon electrode such as activated carbon and an electrolyte and has a large capacitance in the farad order. . For this reason, it has attracted attention as a memory backup for integrated circuits and a regenerative energy device for electric vehicles and hybrid vehicles.

In such an electric double layer capacitor, the carbon electrode has conventionally been formed by molding activated carbon using an adhesive such as polytetrafluoroethane as a binder.

[0004]

However, in an electrode using polytetrafluoroethane as a binder,
In the electric double layer capacitor, there is a problem that only a considerably low capacitance can be obtained in view of the capacitance expected from the surface area of the activated carbon, and the internal resistance of the electric double layer capacitor is large. It is considered that the reason is that polytetrafluoroethane considerably hinders the electrical connection between activated carbons.

Further, such a carbon electrode is also used as a negative electrode of a lithium ion battery. However, an electrode using polytetrafluoroethane as a binder has a large internal resistance of the lithium ion battery as in the related art. There is a problem.

An object of the present invention is to provide a sheet-like electrode using a conductive rubber and a method for manufacturing the same, which can improve the electrical characteristics such as internal resistance.

[0007]

According to the results of repeated experiments conducted by the present inventor to solve the above-mentioned problems, according to the results of manufacturing the electrodes of an electric double layer capacitor and a lithium ion battery, a specific binder is used as a binder. It has been found that the use of rubber can reduce the sheet resistance.

That is, according to the present invention, a sheet-like electrode in which conductive rubber in which conductive fine particles are held by rubber is laminated on the surface of a metal foil, wherein the rubber is silicone rubber or butyl rubber (isobutylene). -Isoprene copolymer).

In a sheet-like electrode using silicone rubber or butyl rubber in conductive rubber using conductive fine particles such as activated carbon, compared to a sheet-like electrode using other rubbers or resins, the electric double layer capacitor has a lower static electricity. The result was that the capacitance could be improved and the internal resistance could be reduced. In addition, the result that the internal resistance can be reduced also in the lithium ion battery was obtained.

In producing such a sheet-like electrode, at least conductive fine particles, a rubber compound,
After applying a kneaded material obtained by kneading the vulcanizing agent and the solvent to a predetermined thickness on the surface of the metal foil, a heat treatment is performed on the kneaded material,
A conductive rubber in which the conductive fine particles are dispersed in the rubber is laminated on the surface of the metal foil.
According to such a method, a sheet-like electrode in which conductive rubber is laminated on the surface of a metal foil can be easily manufactured, and the sheet-like electrode has high adhesion between the conductive rubber and the metal foil. In addition, since the vulcanizing agent is also kneaded and vulcanized during the heat treatment, the rubber molecules are strongly bonded to each other and the rubber molecules shrink, so that the degree of connection between the activated carbons is improved. Furthermore, since the solvent is blended, there is an advantage that the adhesiveness between the metal foil and the conductive rubber is high when the solvent is removed.

[0011]

Embodiments of the present invention will be described with reference to the drawings.

FIGS. 1A and 1B are an explanatory view showing a configuration of an electric double layer capacitor as a usage example of a sheet electrode to which the present invention is applied, and an enlarged sectional view showing the configuration of the sheet electrode. It is.

1 (A) and 1 (B), an electric double layer capacitor 1 generally has a bottomed cylindrical case 2, a capacitor element 10 housed in the case 2, and a housing Sealing material 3 for closing the opened case 2
It is composed of The capacitor element 10 includes a sheet electrode 5 in which a conductive rubber 52 as a polarizing electrode is formed on the surface of a metal foil such as an aluminum foil 51 as a collecting electrode, and a separator 4 made of nonwoven fabric or papermaking. The two tabs 6 pulled out from each sheet electrode 5 alternately are wound alternately one by one, and are electrically connected to the respective terminals 7 of the sealing material 3. Further, the separator 4 is impregnated with an electrolytic solution obtained by dissolving a tetraalkylammonium perchlorate or a fluoride in an ethylene carbonate-based solvent or a lactone-based solvent.

In the electric double layer capacitor 1 configured as described above, in this embodiment, both the polarizing electrodes of the two sheet electrodes 5 are made up of 50% by weight to 95% by weight of conductive fine particles such as activated carbon. The conductive rubber 52 is laminated on the surface of a metal foil such as the aluminum foil 51.

In this embodiment, the rubber used for the conductive rubber 52 as the polarization electrode is silicone rubber.

Activated carbon is, for example, coconut charcoal. The conductive rubber 52 as a polarization electrode includes, in addition to activated carbon, metal particles such as carbon black, acetylene black and nickel as conductive fine particles. Conductive oxide powder or the like may be used. Further, instead of the aluminum foil 51, a nickel foil or a copper foil may be used.

In such a polarized electrode (conductive rubber 52) of the sheet-like electrode 5, the rubber as a binder is silicone rubber unlike the conventional one, and this silicone rubber is
Most of the activated carbon is efficiently contacted with each other, and does not fill the fine pores formed on the surface of the activated carbon.
Therefore, the sheet-shaped electrode 5 to which the present invention is applied has a low sheet resistance value and the activated carbon has a large surface area. For this reason, in the electric double layer capacitor 1 using the sheet electrode 5 to which the present invention is applied, the internal resistance can be reduced by 30% to 60% as compared with the conventional one, and the capacitance is reduced by 30% to less than the conventional one. The result was that it could be increased by 70%.

Next, with reference to FIG. 1B, a method for manufacturing the sheet-like electrode 5 used for the electric double layer capacitor 1 of the present embodiment will be described.

First, an aluminum foil 51 (collecting electrode) having a thickness of about 30 μm to 50 μm is prepared. The aluminum foil 51 is subjected to a surface treatment such as an etching treatment for roughening the surface, if necessary.

Next, a slurry-like kneaded material in which conductive fine particles, a silicone rubber compound, a vulcanizing agent and a solvent are mixed by a mixer or the like is prepared. Here, as the conductive fine particles, for example, activated carbon is used. As the solvent, an organic solvent such as toluene is used.

Next, a slurry-like kneaded material 50 is applied to the surface of the aluminum foil 51 using a roll coater or the like. Next, the kneaded material 50 is roll-pressed to adjust its thickness.

Next, the kneaded material 50 is subjected to a heat treatment at a predetermined temperature for a predetermined time to completely evaporate the solvent, and then vulcanized.

As a result, on the surface of the aluminum foil 51, a conductive rubber 52 in which conductive fine particles such as activated carbon are held by a silicone rubber is laminated with a thickness of, for example, about 80 μm in close contact. Further, in the conductive rubber 52, since the rubber molecules are strongly bonded to each other by vulcanization, the rubber molecules shrink, and the degree of connection between the activated carbons is improved. Further, the sheet-like electrode 5 of the present embodiment
Since the conductive rubber 52 is laminated on the surface of the aluminum foil 51, it is deformable. For this reason,
As shown in FIG. 1A, it is easy to wind it into a cylindrical shape. Further, according to such a manufacturing method, a considerably long sheet-like electrode 5 can be easily manufactured. Therefore, when manufacturing the electric double-layer capacitor 1, the sheet-like electrode 5 wound in a coil shape has a predetermined size. The capacitor element 10 can be manufactured while cutting.

In the above embodiment, silicone rubber was used to form the polarization electrode made of the conductive rubber 52. However, even when butyl rubber was used, substantially the same results could be obtained.

In the above embodiment, the example in which the sheet electrode 5 is used for the electric double layer capacitor 1 has been described. However, when the sheet electrode 5 of this embodiment is used for the negative electrode of a lithium ion battery, its internal resistance is reduced. The result that it can be reduced was obtained.

[0026]

As described above, in the present invention, since the sheet-like electrode is formed using silicone rubber or butyl rubber as the rubber in which conductive fine particles such as activated carbon are dispersed, the electric double layer capacitor and the lithium ion battery are formed. In this case, the electrical characteristics can be improved, for example, the internal resistance can be reduced.

[Brief description of the drawings]

FIGS. 1A and 1B are an explanatory diagram showing a configuration of an electric double layer capacitor as a usage example of a sheet electrode to which the present invention is applied, and an enlarged sectional view showing the configuration of a sheet electrode. is there.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric double layer capacitor 2 Case 3 Sealing material 4 Separator 5 Sheet electrode 6 Tab 7 Terminal 10 Capacitor element 50 Kneaded material 51 Aluminum foil 52 Conductive rubber

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Toshihiro Nakata 4009-1, Yamato, Azusakawa-mura, Minamiazumi-gun, Nagano F-term (reference) 5H050 AA12 BA06 BA17 DA03 DA10 EA23 FA17 FA18 GA02 GA22

Claims (3)

[Claims] 1. A sheet-like electrode in which conductive rubber in which conductive fine particles are held by rubber is laminated on a surface of a metal foil, wherein the rubber is silicone rubber. . 2. A sheet-like electrode in which conductive rubber in which conductive fine particles are dispersed in rubber is laminated on a surface of a metal foil, wherein the rubber is butyl rubber. . 3. A kneaded material obtained by kneading at least conductive fine particles, a rubber compound, a vulcanizing agent, and a solvent is applied to a surface of a metal foil to a predetermined thickness, and then the kneaded material is subjected to a heat treatment to form the metal foil. A method for producing a sheet-like electrode, comprising laminating a conductive rubber on the surface of a sheet.