JP2002043192A - Manufacturing method of sheet-like electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a configuration which improves the electrical characteristics of an internal resistance and the like, related to a manufacturing method of a sheet-like electrode using a conductive rubber. SOLUTION: At manufacturing of a sheet-like electrode 5 using an electric double layer capacitor 1, an aluminum foil 51 is submerged in a slurry-like liquid 520 where conductive fine particles, a silicone rubber compound, a curing agent, and a solvent are mixed together, and then it is lifted up, when the liquid 520 is coated on both surfaces of it. After the thickness of liquid 520 coated on both surfaces of it is adjusted, using a squeegee 26, the liquid 520 is subjected to thermally processing, so that the solvent contained in the liquid 520 is removed, while vulcanizing is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a sheet-like electrode used for an electric double layer capacitor or a lithium ion battery. More specifically, the present invention relates to a technique for manufacturing the sheet-like 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 formed using polytetrafluoroethane as a binder, an electric double layer capacitor can obtain only a considerably low capacitance in view of the capacitance expected from the surface area of activated carbon. However, there is a problem that the internal resistance of the electric double layer capacitor is not large. It is considered that the reason is that polytetrafluoroethane considerably hinders the electrical connection between activated carbons.

[0005] Such a carbon electrode is also used as a negative electrode of a lithium ion battery. However, an electrode formed by using polytetrafluoroethane as a binder as in the related art has a large internal resistance of the lithium ion battery. There is a problem.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a sheet-like electrode using a conductive rubber, which is capable of improving 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 electric double layer capacitor and the electrode of the lithium ion battery, a specific rubber is used as a binder. And that a specific manufacturing method is used to reduce the sheet resistance.

That is, the present invention relates to a method for manufacturing 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 at least the conductive fine particles, silicone rubber or After immersing the metal foil in a liquid material obtained by mixing a rubber compound of butyl rubber (isobutylene-isoprene copolymer), a vulcanizing agent, and a solvent, the metal foil is pulled up from the liquid material, and the metal foil is placed on the surface of the metal foil. The method further includes a coating step of applying a liquid material, and a heat treatment step of performing a heat treatment on the liquid material to laminate a conductive rubber on the surface of the metal foil.

In the present invention, the method may further include a film thickness adjusting step of adjusting a layer thickness of the liquid material applied on the surface of the metal foil by a squeegee after performing the applying step and before performing the heat treatment step. preferable.

According to another aspect of the present invention, there is provided a method of manufacturing 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 at least the conductive fine particles are formed. A rubber compound of silicone rubber or butyl rubber, a vulcanizing agent, a coating process of applying a liquid material mixed with a solvent to the surface of the metal foil by a squeegee, and performing a heat treatment on the liquid material applied to the surface of the metal foil. A heat treatment step of laminating a conductive rubber on the surface of the metal foil.

In the present invention, a sheet-like electrode using silicone rubber or butyl rubber (isobutylene-isoprene copolymer) in a conductive rubber using conductive fine particles such as activated carbon is a sheet-like electrode using other rubber or resin. As a result, it has been found that the electric double layer capacitor can improve the capacitance and reduce the internal resistance as compared with the electrode. In addition, the result that the internal resistance can be reduced also in the lithium ion battery was obtained. Further, according to the method of the present invention, it is possible to easily manufacture a sheet-like electrode in which conductive rubber is laminated on the surface of a metal foil, and in this sheet-like electrode, the adhesion between the conductive rubber and the metal foil is improved. Is high. 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.

[0012]

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

FIGS. 1A and 1B are an explanatory view showing the configuration of an electric double layer capacitor as an example of use 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 is generally a cylindrical case 2 having a bottom, a capacitor element 10 housed in the case 2, and a housing of the capacitor element 10. 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.

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

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%.

[Production Method 1 of Sheet Electrode 5] FIG.
With reference to (B) and FIG. 2, a method for manufacturing the sheet-like electrode 5 used for the electric double layer capacitor 1 of the present embodiment will be described.

FIG. 2 is an explanatory view schematically showing a method of manufacturing the sheet-like electrode 5 of the present embodiment. FIG. 2 shows a coating apparatus for forming a conductive rubber 52 on both surfaces of an aluminum foil 51. 20 are shown.

In FIG. 1B and FIG. 2, the thickness is 3
Aluminum foil 51 of about 0 μm to 50 μm (collecting electrode)
Prepare 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 liquid material 520 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 and supplied to the tank 21. Here, as the conductive fine particles, for example, activated carbon is used. As the solvent, an organic solvent such as toluene is used.

Next, in the coating apparatus 20, the aluminum foil 51 is driven by the rollers 22, 23, 24 and 25, immersed in the liquid material 520 in the tank 21, and then pulled up at a predetermined speed. As a result, a liquid material 520 containing a mixture of conductive fine particles, a silicone rubber compound, a vulcanizing agent, and a solvent is applied to both surfaces of the aluminum foil 51 to a predetermined thickness (application step).

Next, the surface of the liquid material 520 applied to both surfaces of the aluminum foil 51 is scraped by a pair of squeegees 26 to adjust the thickness of the liquid material 520 (layer thickness adjusting step).

Next, a heat treatment is performed on the liquid material 520 applied to both surfaces of the aluminum foil 51 (heat treatment step).

In this embodiment, as the heat treatment step, the liquid material 520 applied to both surfaces of the aluminum foil 51 is heated by the heater 27 to remove the solvent contained in the liquid material 520 and to a certain extent. Allow the sulfurization to proceed. As a result, the adhesiveness is lost from the surface of the aluminum foil 51. Therefore, the aluminum foil 51 is wound in a roll shape, and the rolled aluminum foil 51 is subjected to a heat treatment in a large heat treatment tank (not shown) to perform vulcanization. Complete.

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 silicone rubber is laminated in a state of being adhered to a thickness of, for example, about 80 μm. 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.

[Production Method 2 of Sheet Electrode 5] FIG.
With reference to (B) and FIG. 3, a method for manufacturing the sheet-like electrode 5 used for the electric double layer capacitor 1 of the present embodiment will be described.

FIG. 3 is an explanatory view schematically showing a method of manufacturing the sheet-like electrode 5 of the present embodiment. FIG. 3 shows a coating apparatus for forming a conductive rubber 52 on both surfaces of an aluminum foil 51. 30 is shown. Note that FIG. 3 illustrates only a main part of the coating apparatus 30 and does not illustrate a tension roller or the like.

In FIG. 1B and FIG. 3, the thickness is 3
Aluminum foil 51 of about 0 μm to 50 μm (collecting electrode)
Prepare 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 liquid material 520 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.
0 is supplied to the mesh drums 31 and 32. For example, coconut activated carbon is used as the conductive fine particles. Also,
An organic solvent such as toluene is used as the solvent.

Here, the mesh drums 31 and 32 have
Squeegees 33 and 34 are arranged, and in the coating device 30, the aluminum foil 51 is
7 and 38 to drive the mesh drums 31 and 32
When sequentially supplied to both sides of the aluminum foil 51,
Squeegees 33 and 34 via mesh drums 31 and 32
Conductive fine particles, silicone rubber compound,
The liquid material 520 in which the vulcanizing agent and the solvent are mixed is applied with a predetermined thickness (application step).

Next, a heat treatment is performed on the liquid material 520 applied to both surfaces of the aluminum foil 51 (heat treatment step).

In the heat treatment step, in the present embodiment, the liquid material 520 applied to both sides of the aluminum foil 51 is heated by the heater 39 to remove the solvent contained in the liquid material 520 and to a certain extent. Allow the sulfurization to proceed. As a result, the adhesiveness is lost from the surface of the aluminum foil 51. Therefore, the aluminum foil 51 is wound in a roll shape, and the rolled aluminum foil 51 is subjected to a heat treatment in a large heat treatment tank (not shown) to perform vulcanization. Complete.

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. 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.

[Other Embodiments] In the above embodiment, silicone rubber is used to form the polarization electrode made of the conductive rubber 52. However, even when butyl rubber is used, substantially the same results can be obtained. Was completed.

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.

[0038]

As described above, in the sheet-like electrode according to the present invention, since silicone rubber or butyl rubber (isobutylene-isoprene copolymer) is used in the conductive rubber using conductive fine particles such as activated carbon, As compared with the sheet-like electrode using rubber or resin, the internal resistance can be reduced also in the electric double layer capacitor and the lithium ion battery. Further, according to the method of the present invention, it is possible to easily manufacture a sheet-like electrode in which conductive rubber is laminated on the surface of a metal foil, and in this sheet-like electrode, the adhesion between the conductive rubber and the metal foil is improved. Is high. 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.

[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.

FIG. 2 is an explanatory view schematically showing a method for manufacturing a sheet-like electrode according to the present invention.

FIG. 3 is an explanatory view schematically showing another method for manufacturing a sheet-like electrode according to the present invention.

[Description of Signs] 1 Electric double layer capacitor 2 Case 3 Sealing material 4 Separator 5 Sheet electrode 6 Tab 7 Terminal 10 Capacitor element 20, 30 Coating device 21 Bath 22, 23, 24, 25, 35, 36, 37, 38 roller 26, 33, 34 squeegee 27, 39 heater 51 aluminum foil 52 conductive rubber 520 slurry-like liquid material

Continuation of the front page (72) Inventor Toshihiro Nakata 4009, Azakawa, Azusakawa-mura, Minamiazumi-gun, Nagano F-term (reference) in AW I Mach Co., Ltd. 5H050 AA12 BA17 CB07 CB08 CB09 DA04 DA10 DA11 EA02 EA10 EA28 EA29 FA02 GA02 GA10 GA13 GA22 HA04

Claims (3)

[Claims] 1. A metal foil is immersed in a liquid material obtained by mixing at least a conductive fine particle, a rubber compound of silicone rubber or butyl rubber, a vulcanizing agent, and a solvent, and then the metal foil is pulled up from the liquid material. An application step of applying the liquid material to the surface of the metal foil, and a heat treatment step of performing a heat treatment on the liquid material applied to the surface of the metal foil to laminate a conductive rubber on the surface of the metal foil. Of producing a sheet-like electrode to be formed. 2. A film thickness adjusting step according to claim 1, wherein after performing the applying step and before performing the heat treatment step, a layer thickness of the liquid material applied to the surface of the metal foil is adjusted by a squeegee. A method for producing a sheet-shaped electrode, comprising: 3. A coating step of applying a liquid material obtained by mixing at least a conductive fine particle, a rubber compound of silicone rubber or butyl rubber, a vulcanizing agent, and a solvent to the surface of the metal foil with a squeegee, and performing a heat treatment on the liquid material. A heat treatment step of laminating a conductive rubber on the surface of the metal foil.