JPH03280518A - Electric double layer capacitor and its manufacturing method - 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 Field of the Invention The present invention relates to an electric double layer capacitor using activated carbon as a polarizable electrode and a method for manufacturing the same.

Conventional electric double layer capacitors use activated carbon as polarizable electrodes.
＼ Large-capacity capacitors that utilize the electric double layer capacitance accumulated in the interfacial electric double layer between activated carbon and electrolyte. Conventionally, there are two types of electric double layer capacitors: One uses an aqueous electrolyte such as an aqueous solution, and the other uses an organic solution electrolyte in which an electrolyte is added to an organic solvent such as propylene carbonate. This shows the configuration of a typical example. As shown in Figure 4, the separator 41
Activated carbon powder electrodes 42, 43 are opposed to each other through an insulating rubber case 44, 45 and a conductive electrode 46, 40. Activated carbon powder electrodes 42, 43 are made by molding activated carbon powder into pellets using a concentrated sulfuric acid aqueous solution. The sulfuric acid aqueous solution also acts as a binder.The organic electrolyte-based capacitor has the structure shown in Figure 5.Activated carbon powder A paste consisting of fluorine polymer and methyl alcohol is applied onto an aluminum net 50.51 and dried to form a film. The activated carbon electrodes 52 and 53 are wound with a separator 54 in between and are impregnated with a mixed solution of propylene carbonate and tetraethylammonium barchlorate for cleaning. 55, 56, 57, 5
8 are anode lead, cathode lead, and rubber cap respectively.
Problems that the invention aims to solve with an aluminum case The two conventional electrolyte-based capacitors each have the following characteristics (advantages and disadvantages).a The advantage of the aqueous solution type is that the electrolyte has low electrical resistance. It is suitable for large current load discharge, and the disadvantage is that the withstand voltage of the capacitor, which depends on the decomposition voltage of the electrolyte, can only be obtained up to 1.0 ■. The advantage of the organic solution system is that the electrolyte has a high withstand voltage (~3
V), it is possible to use higher voltages than aqueous solutions.Disadvantages: Due to the electrical resistance of the electrolyte, the internal resistance of the capacitor is 5 to 10 times that of an aqueous solution, resulting in a large current load. The purpose of the present invention is to create a capacitor that combines the advantages of the two conventional types of electrolyte capacitors, which have been difficult to use in such applications. By obtaining a capacitor with low resistance, a means for solving the problem according to the present invention 1 is intended to achieve the above object, and is made of a conductive substrate, activated carbon on the conductive substrate, and a water-soluble binder. It is an electric double layer capacitor consisting of a layer of Otori or a layer containing a conductivity imparting agent and placed facing each other with a separator interposed therebetween, and an electrolyte.
A solution prepared by mixing and dispersing a solution of methylcellulose or carboxymethylcellulose in water, activated carbon, and a conductivity imparting agent is coated, supported on an aluminum substrate by either dipping or printing, dried, and the substrates are placed facing each other with a separator in between. According to the present invention, an activated carbon polarizable electrode supported on a foil-like conductive substrate has low electrical resistance and good electrical contact with the foil-like conductive substrate. The electrical resistance of the obtained capacitor is significantly lowered in order to provide an activated carbon electrode composition which is excellent in film formation properties and self-shape retention of an activated carbon film. In addition, in the activated carbon electrode composition of the present invention, the thickness of the activated carbon layer can be made very thin, which is difficult to achieve due to the geometrical form factor of the electrode (the surface area of the electrode that allows a thin layer to be accommodated in a unit capacitor volume). A capacitor with large capacity and low resistance can be obtained.

Examples Next, specific examples of the present invention will be described (Example-
1) 10 parts by weight of activated carbon powder (specific surface area: 2000 m'/g, average particle size: 2 μm) and 2 parts by weight of acetylene black are uniformly dispersed in a mixed solution of water and methanol.

Dissolve 2 parts by weight of carboxymethyl cellulose (CMC, a product in which some of the carboxyl group protons have been replaced with Na ions) in water a. Mix and stir both solutions to form an activated carbon slurry. As shown in Figure 1. Aluminum foil roughened by chemical etching method with a thickness of 20 μm (1
0mm! Activated carbon slurry is applied to both sides of (40 mm length) 1 by dipping method, dried in air for 30 minutes, and then dried with far infrared rays at 100°C for 60 minutes to form activated carbon electrodes 2 and 3 to a thickness of 50 μm.This film pressure If the diameter is 100 μm or less, a preferable result can be obtained. However, a pair of 4.5 pieces of the obtained foil-like electrode body is wound through a separator 6. As an electrolytic solution, 1 mol/1 of tetraethylammonium tetrafluoroborate is added to a propylene carbonate solution. The housing is completed with the melted aluminum case 7, aluminum lead electrodes 8 and 9, and rubber gasket 10 (Example-2) Same configuration as Example-1, but without acetylene black (Example-3) Example- Same configuration as in Example 1, but using CMC in which some of the protons of the carboxyl group are replaced with NH4 ions (Example-4) With the same configuration as in Example-1, phenolic resin-based activated carbon fiber was used instead of activated carbon powder. Chop (fiber diameter is 10μm, average chop length is 0.511L, specific surface area is 230
0/g) (Example-5) Same configuration as Example-1 Ruthenium oxide powder (average particle size: 0.5μ) was used instead of acetylene black (Example-6) Activated carbon powder (Specific surface area: 2000/& Average particle size: 2 μm) 10 parts by weight and 2 parts by weight of acetylene black are uniformly dispersed in aqueous ammonia (concentration 5% by weight). Dissolve 2 parts by weight of (2 parts by weight) in water. Mix and stir both solutions to form an activated carbon slurry. Spread the activated carbon slurry on both sides of an aluminum foil with a thickness of 2 μm that has been roughened by chemical etching. Apply with a roll coater, dry in air for 30 minutes, and then heat at 100℃ for 6 days.
Dry with far infrared rays for 0 minutes to form an activated carbon electrode.A As shown in Figure 2, a pair of the obtained foil-like electrode bodies is wound through a separator to obtain the electrode body 20. Add propylene carbonate solution as an electrolyte. A stainless steel case 21 and a stainless steel lid 23 having an aluminum layer 22 are prepared by dissolving 1 mol/l of tetraethylammonium tetrafluoroborate.
However, this configuration is a hermetic sealing element, and aluminum 1 and cathode lead 2 are used to complete the housing.
4 and 25 are joined to the lid 23 at glass layers 26 and 27, and 21 and 23 are welded at the joint 28 (Example-7) Activated carbon fiber chop (specific surface area: 2500 m'/g
, average length 0.2 ma, fiber diameter 8 μm) and 2 parts by weight of acetylene black were uniformly dispersed in a mixed solution of water and methanol. Two parts by weight of carboxymethylcellulose (CMC, a product in which some of the protons of carboxyl groups are replaced with Na ions) is dissolved in water. Both solutions are further mixed and stirred to form an activated carbon slurry.As shown in Figure 3, the activated carbon slurry is applied by a printing method to one side of an aluminum foil 30 whose surface has been roughened by a chemical etching method to a thickness of 20 μm. After drying for 30 minutes in
Activated carbon electrodes 31 and 32 are formed by drying with far infrared rays for 0 minutes.
The obtained foil-shaped electrode body is punched to a diameter of 15 mm and placed through a separator 33. 1 mol/l of propylene carbonate solution nitetraethylammonium tetrafluoroborate is dissolved as an electrolytic solution, and a housing is formed with cases 34, 35 and a gasket 36. Characteristics of the coin-shaped capacitor obtained in the above examples are shown in the table along with comparative examples.

However, Comparative Example 1i & A wound capacitor having a layer (thickness: 200 μm) composed of activated carbon and a water-insoluble organic binder (fluororesin) on one side of a 60 μm thick aluminum foil. Comparative Example-2 (Yo) Comparative Example-3
(Characteristics of capacitors using sulfuric acid as electrolyte) In addition, in the table, the capacities of Examples 1 to 6 and Comparative Example 1 are expressed in seconds to reach 1.OV at 100 mA discharge, and other is expressed in farads.Reliability (1.8V
The capacitance change after 1000 hours of negative storage at 70°C is shown in %.The conductive substrate is aluminum.A plate of an element selected from tantalum and titanium.The net and holes are maple.Expanded plates or etched surfaces of these. The water-soluble binder ζ can also be composed of at least one of the following: methylcellulose, polyvinylpyrrolidone, hydroxyethylcellulose, polyurethane, vinyl chloride/k, vinyl acetate, polyacrylonitrinok, and polyester. Cellulose cellulose carboxyethyl cellulose Hydroxyethyl cellulose can be used by replacing at least one proton of the carboxyl group with either Na ion, ammonium ion, or aluminum ion. It is also possible to use carbon fiber, etc. to ruthenium oxide, and it is also possible to use carbon fiber, etc., as a conductivity imparting agent. Effects of the Invention As described above, according to the present invention, it is possible to maintain a high withstand voltage, which is a characteristic of organic electrolytes, while achieving an internal resistance equal to or higher than that of a capacitor using an aqueous electrolyte. Discharge characteristics can be obtained, and the frequency dependence of impedance is also very small.

[Brief explanation of drawings]

1@ FIGS. 2 and 3 are configuration diagrams of a capacitor according to an embodiment of the present invention. FIGS. 4 and 5 are configuration diagrams of a conventional capacitor. 1, 2. 3. Aluminum knife 4.5... Foil electric maple 6
・・Separate length 7・・Aluminum 8, 9・・Lead.

Claims (6)

[Claims] (1) Conductive substrates facing each other, a layer consisting of activated carbon and a water-soluble binder formed on at least opposing surfaces of both conductive substrates, a separator disposed between the opposing electrodes, and an electrolytic solution. An electric double layer capacitor consisting of. (2) The electric double layer capacitor according to claim 1, further comprising a conductivity imparting agent in the layer on the conductive substrate or in the electrolytic solution. (3) The electric double layer capacitor according to claim 1, wherein the water-soluble binder is carboxymethyl cellulose. (4) The electric double layer capacitor according to claim 3, wherein carboxyethyl cellulose is substituted with any one of Na ions, ammonium ions, and aluminum ions. (5) Applying, dipping, printing, roll coating, spin coating, doctor blading a solution prepared by mixing and dispersing a solution of one or more of methylcellulose, carboxymethylcellulose, ethylcellulose, or carboxyethylcellulose and activated carbon in water. 1. A method for producing an electric double layer capacitor, comprising supporting the capacitor on an aluminum substrate by any of the coatings, drying, and arranging the substrates facing each other with a separator in between. (6) The method for manufacturing an electric double layer capacitor according to claim 5, characterized in that at least one of alcohol and ammonia is added during dissolution, mixing, and dispersion.