JP2000068166A - Electric-double-layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make increasable the capacity of an electric-double-layer capacitor, by using in it an electrode wherein the mixture of conductive fine grains with a bonding agent containing hydrophilic/lipophilic polymers is bonded to its collector electrode. SOLUTION: By a mixer, the mixture (slurry) of conductive fine grains with a bonding agent is prepared. Hereupon, as the bonding agent, hydrophilic/ lipophilic polymers are used. Applying this slurry to a collector electrode by a roll coater, its solvent is dried to create a sheet-form active carbon electrode. As the hydrophilic/lipophilic polymers, one or more kinds of polypropylene, polyethylene, butyl rubber, ethylene propylidene rubber, natural rubber, and nitryl rubber are used. Also, the bonding agent is obtained by mixing the hydrophilic/lipophilic polymers with a bridging agent. Further, the mixing ratio of the conductive fine grains to the bonding agent is set favorably to the conductive fine grains : the bonding agent = 95:5-50:50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric double layer capacitor.

[0002]

2. Description of the Related Art An electric double layer capacitor is composed of a carbon electrode mainly composed of activated carbon and a liquid electrolyte, and stores electric charge by using an electric double layer formed at the solid-liquid interface when electricity is supplied. I do. Electric double-layer capacitors use activated carbon with a large surface area, and as a device utilizing the so-called capacitor phenomenon that does not involve electrochemical changes in materials, currently have the largest power storage capacity. It has been attracting attention for use in regenerative energy systems for automobiles. As the electrolyte, an organic electrolyte obtained by dissolving a tetraalkylammonium perchlorate or a borofluoride in an ethylene carbonate-based solvent or a lactone-based solvent, or an aqueous electrolyte such as an aqueous solution of sulfuric acid or potassium hydroxide is used. .
The organic electrolytic solution has a feature that it is advantageous in energy because the oxidation potential is higher and the breakdown voltage can be increased, and the aqueous electrolyte solution has an advantage in output because the resistance can be reduced while the breakdown voltage is low. In addition, since it operates according to the principle that does not involve electrochemical change, it also has the feature that its life is extremely long as compared with a secondary battery. However, since the capacity is smaller than that of a secondary battery such as a lithium ion secondary battery, it is difficult for the battery to be used alone as a main power source, and further higher capacity has been desired.

[0003]

The capacity of an electric double layer capacitor depends on the main material, activated carbon, or its surface area, and it is necessary that the pore size sufficient to form an electric double layer be distributed in the activated carbon. is there. In recent years, various efforts have been made to increase the capacity, and with the advent of porous conductive polymers such as polyacene, the capacity of electric double layer capacitors has been increased. However, when theoretically considering the maximum capacity that an electric double layer capacitor can have based on the surface area of activated carbon, a capacity of about 150 F / g is generally feasible, but the actual capacity is about 10 to 15 F / g. However, the capacity of activated carbon has not been fully drawn out. This is due to the water and oil repellency of polytetrafluoroethylene (PTFE) used as an adhesive (binder). PTFE is a polymer with high chemical stability and high oxidation resistance, and has the excellent properties of forming a network by mechanical stretching, binding strongly conductive fine particles, and ensuring high conductivity. There is a problem that the contact between the liquid and the activated carbon is prevented.

In order to solve this problem, it is effective to relatively reduce the ratio of PTFE to the conductive fine particles. However, if the ratio of the PTFE to the activated carbon electrode is less than 10%, the bonding force is weakened and the resistance increases. There is a problem that the mechanical strength is reduced.

[0005]

The present invention solves the above-mentioned problems by using a polymer having hydrophilicity or lipophilicity as an adhesive. By using a polymer having hydrophilicity or lipophilicity for the adhesive, the electrolyte permeates into the pores of the conductive fine particles due to the hydrophilicity or lipophilicity of the polymer, and the capacity of the electric double layer capacitor can be increased. That is, an electric double layer capacitor using an electrode obtained by binding a mixture of conductive fine particles and an adhesive containing a hydrophilic and / or lipophilic polymer to a current collecting electrode.

Alternatively, a polarizing electrode formed by mixing conductive fine particles and an adhesive containing a hydrophilic and / or lipophilic polymer and molding using a mold, and an electrode obtained by laminating a current collecting electrode are used. It is an electric double layer capacitor characterized by the following.

The above-mentioned hydrophilic and / or lipophilic polymer is selected from the group consisting of polypropylene (PP), polyethylene (PE), butyl rubber (IIR), ethylene propylene diene rubber (EPDM), natural rubber (NR), and nitrile rubber (NBR). ), Wherein the electric double layer capacitor is at least one of the following.

[0008] Further, there is provided an electric double layer capacitor, wherein the mixing ratio of the conductive fine particles and the adhesive is 5:95 to 50:50.

Further, the above-mentioned adhesive is an electric double layer capacitor in which a hydrophilic and / or lipophilic polymer is mixed with a crosslinking agent.

[0010] In the electric double layer capacitor, the current collecting electrode is a foil or a mesh mainly containing at least one of aluminum, nickel and copper.

[0011] The electric double layer capacitor is characterized in that the current collecting electrode is formed by applying a conductive rubber to a foil or a mesh mainly composed of at least one of aluminum, nickel and copper. .

[0012] An electric double layer capacitor, wherein the current collecting electrode is a conductive rubber sheet.

Further, the conductive fine particles are at least one of activated carbon, conductive polymer, carbon black, ketjen black, acetylene black, furnace black, nickel, titanium nitride, ruthenium oxide and vanadium pentoxide. An electric double layer capacitor characterized by the following.

The above-mentioned polarization electrode is made of aluminum,
An electric double layer capacitor formed by forming a current collecting electrode by plasma spraying a metal containing at least one of nickel and copper as a main component.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS By using a hydrophilic or lipophilic polymer as an adhesive for conductive fine particles, an electrolytic solution can be permeated into the pores of activated carbon to increase the capacity of an electric double layer capacitor. . In addition, when a polymer and a cross-linking agent are mixed to form an adhesive, the cross-linking agent tends to strongly bond and shrink the polymers, thereby improving the bonding between the carbon powders and reducing the resistance. There is.

[0016]

EXAMPLE A mixture (slurry) of conductive fine particles and an adhesive was prepared with the composition shown in Table 1 using a mixer. The slurry was applied onto a collecting electrode using a roll coater, and the solvent was dried to prepare a sheet-like activated carbon electrode. Note that an aluminum foil that had been etched and subjected to a chemical conversion treatment at about 2 V in advance was used as a collecting electrode.

[0017]

[Table 1]

[0018] 0.01 ml of propylene carbonate was dropped on the produced electrode, and the contact angle was measured with a cassette meter. The results shown in Table 2 were obtained. It is clear that the wettability of each of the examples is higher than that of the comparative example.

[0019]

[Table 2]

Next, as shown in FIG. 1, two activated carbon electrodes each having a lead wire connected to an activated carbon electrode cut out so as to have a fixed area were wound through a separator paper to obtain a capacitor element. After drying the capacitor element, the capacitor element was impregnated with an electrolyte obtained by dissolving 0.6 mol / l of tetraethylammonium tetrafluoroborate in a solvent in which propylene carbonate and ethylene carbonate were in a ratio of 1: 1. Sealing was performed using an aluminum case and rubber packing, and 50 electric double layer capacitors were produced. The capacitance and resistance were measured, and the results shown in Table 3 were obtained. As is clear from Table 3, the electric double layer capacitor of the example has a larger capacity and a lower resistance value than the comparative example. From the results shown in Table 2, it is considered that the electrode according to the present invention is easily wetted by an ethylene carbonate-based solvent which is a main component of the electrolytic solution. Further, 2.3 V was applied to these capacitors at 85 ° C., and the change over time in the characteristics was measured. The result is shown in FIG. The embodiment has the same reliability as the comparative example.

[0021]

[Table 3]

The mixing ratio between the conductive fine particles and the adhesive is a problem because if the amount of the adhesive is smaller than the conductive fine particles: adhesive = 95: 5, the conductive fine particles cannot be bonded. Also, if the amount of the adhesive is larger than 50:50 of the conductive fine particles: adhesive, the resistance of the electrode becomes too high, which is a problem. Therefore, the mixing ratio of the conductive fine particles and the adhesive is preferably from 95: 5 to 50:50.

Although sulfur powder was used as a cross-linking agent, its addition amount is preferably 0.1 to 7.0% by weight of the polymer. Further as a crosslinking accelerator ZnO, metal oxide powder such as MgO, hexamethylenetetramine, 1,3-diphenylguanidine, N-butyraldehyde aniline, di-o-tolylguanidine, 1-o-tolylbiguanide, N, N- A general rubber cross-linking accelerator such as diphenylthiourea, 2-mercaptobenzothiazole, tetramethyltyrium disulfide or the like may be added in an amount of 0.1 to 3.0% by weight of the polymer. In addition, as other crosslinking agents, phenolic thermosetting resins such as tackylol and titanol and known resin crosslinking agents, p-quinonedioxime, 2,4,6-trimercapto-s-triazine, p, p'-diazine Benzoylquinone dioxime and the like can be mentioned, and the addition amount of the resin crosslinking agent is preferably 5 to 15% by weight of the polymer, and the others are preferably 0.1 to 7.0% by weight of the polymer.

Further, after the slurry is applied to the collecting electrode and dried,
5000kg / cm activated carbon electrode ^TwoWithin the range of
May be processed.

In the examples, IIR, NB
Although R is used, the same effect can be obtained by using PP, PE, EPDM, and NR, and a plurality of them may be mixed and used.

In the examples, activated carbon and acetylene black were used as the conductive fine particles. However, conductive polymers, carbon black, Ketjen black, furnace black, nickel, titanium nitride, ruthenium oxide,
The same effect is obtained by using vanadium pentoxide, and a plurality of them may be used in combination. When other substances are mixed with activated carbon, the amount of activated carbon is preferably set to 30 to 95 wt%.

In the embodiment, a chemically formed aluminum foil was used as a current collecting electrode. However, a foil, a mesh, or a foil or a mesh mainly composed of at least one of aluminum, nickel and copper coated with conductive rubber. The same effect can be obtained by using a metal having at least one of aluminum, nickel and copper as the main component by plasma spraying.

[0028]

According to the electric double layer capacitor of the present invention, for example, a conductive element and a hydrophilic and / or lipophilic polymer are added to a capacitor element in which an electrolyte is impregnated into an electrode via a separator, as in the embodiment. By using an electrode formed by binding a mixture with an adhesive containing the current collecting electrode, the electrolyte can easily penetrate into the pores of the conductive fine particles,
It is possible to increase the capacity of the electric double layer capacitor, and it is of great industrial value.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an electric double layer capacitor.

FIG. 2 Capacitance change at 85 ° C. and 2.3 V applied

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Activated carbon electrode 2 Separator paper 3 Rubber packing 4 Lead wire 5 Capacitor element 6 Aluminum case

Claims (10)

[Claims] 1. An electric double-layer capacitor using an electrode formed by binding a mixture of conductive fine particles and an adhesive containing a hydrophilic and / or lipophilic polymer to a current collecting electrode. 2. A polarizing electrode formed by mixing conductive fine particles and an adhesive containing a hydrophilic and / or lipophilic polymer and molding using a mold, and an electrode obtained by laminating a current collecting electrode. An electric double layer capacitor. 3. The hydrophilic and / or lipophilic polymer according to claim 1, wherein the hydrophilic and / or lipophilic polymer is polypropylene (P).
P), polyethylene (PE), butyl rubber (IIR),
At least one of ethylene propylene diene rubber (EPDM), natural rubber (NR), and nitrile rubber (NBR)
An electric double layer capacitor characterized by being a seed. 4. The mixing ratio between the conductive fine particles and the adhesive according to claim 1 and 2, wherein the conductive fine particles: adhesive = 9.
An electric double layer capacitor having a ratio of 5: 5 to 50:50. 5. An electric double layer capacitor comprising the adhesive according to claim 1 and a mixture of a hydrophilic and / or lipophilic polymer and a crosslinking agent. 6. An electric double layer capacitor, wherein the current collecting electrode according to claim 1 is a foil or a mesh mainly composed of at least one of aluminum, nickel and copper. 7. The current collecting electrode according to claim 1 or 2, wherein a conductive rubber is applied to a foil or a mesh mainly composed of at least one of aluminum, nickel and copper. Characteristic electric double layer capacitor. 8. The electric double layer capacitor according to claim 1, wherein the current collecting electrode is a conductive rubber sheet. 9. The conductive fine particles according to claim 1, wherein the conductive fine particles are activated carbon, conductive polymer, carbon black, Ketjen black, acetylene black, furnace black, nickel, titanium nitride, ruthenium oxide, pentoxide. An electric double layer capacitor comprising at least one of vanadium. 10. An electric double layer capacitor comprising a current collecting electrode formed by plasma spraying a metal containing at least one of aluminum, nickel and copper on the polarized electrode according to claim 2.