JPH02240908A - 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 Field of Industrial Application The present invention has a characteristic of high capacitance using an electric double layer formed at the interface between a polarizable electrode and an electrolyte (liquid), and mainly has the following characteristics: Volatile semiconductor memory (e.g. RM...
This relates to electric double layer capacitors used as backup for power outages (random access memory).

BACKGROUND ART Conventional electric double layer capacitors of this type have a structure called a disk shape (coin shape, button shape), as shown in the attached drawing, and are made of graphite, activated carbon, carbon black, some binder, etc. A pair of carbon electrodes 1.1' made of molded material, electrodes supported on an aluminum or stainless steel net, or carbon fibers, especially activated carbon fiber cloth.
A separator 3 impregnated with electrolyte 2 is interposed between the two,
These are sealed by a metal case 4 that serves as a current collector and an exterior material, a metal lid 6, and a packing 6 that serves as an insulator and a sealing material. Furthermore, in the case of an electrode made of activated carbon fiber cloth, an aluminum layer is formed by plasma spraying or the like on the surface that contacts the metal case and metal lid in order to improve current collection.

Problems to be Solved by the Invention In the case of the electric double layer capacitor having the above-mentioned structure, electrodes made of activated carbon fiber cloth obtained by carbonizing and activating phenol fiber cloth are usually used. The reasons for this include the fact that the raw material is a chemical product and contains little impurities, that activated carbon can be obtained with a high specific surface area, and that most of the shapes for electrodes are already available. However, this is more expensive than other general-purpose activated carbons, and current carbonization and
Problems with the activation technology include relatively large variations in thickness and area weight (g/ll2). In particular, since the developed capacitance is determined by the weight (diameter and thickness) of the electrode used, several thicknesses (
It is necessary to prepare electrodes with different fabric weights), prepare several types of parts with different diameters and thicknesses, and have multi-product manufacturing equipment or several single-function machines that can handle this. Furthermore, low capacitance products have the disadvantage that the thickness (fabric weight) and diameter of the electrodes used are less than the values required for manufacturing, making transportation, positioning, etc. difficult. Furthermore, in terms of characteristics, the electrodes made of activated carbon fiber cloth, the separator therebetween, and the internal elements made of electrolyte must be appropriately compressed by a metal lid and a metal case that also serve as current collectors. The reason is that if the compression is weak, the internal resistance will increase and become unstable.)
Conversely, if the compression is strong, part of the electrode will easily penetrate the separator, resulting in a large leakage current. Therefore,
It was necessary to make the thickness of each member constant, or to adjust the distance between the metal lid and the metal case so that an appropriate compressive force could be achieved depending on the total thickness of the members.

However, all of these methods lead to high costs and decreased productivity.

As a solution to the above problem, we focused on the fact that the activated carbon used is in the form of fibers, and by pulverizing activated carbon fiber cloth or using activated carbon fiber in the form of chips, we added this to the valve, carbon fiber, and Polarizable electrodes made into paper using binders and dispersants have already been proposed. By changing the ratio of activated carbon, which determines the capacitance, carbon fiber, which is a conductive material, and a bulb binder, which maintains the properties of paper, several types of electrodes with the same electrode diameter and thickness can be made. It is possible to produce products with a capacitance value of .

The present invention solves the above-mentioned conventional problems, and aims to provide an electric double layer capacitor that can improve the withstand voltage as an electrode, has stable aging characteristics, and has an extended lifespan. It is something to do.

Means for Solving the Problems In order to achieve the above object, the electric double layer capacitor of the present invention uses a nonwoven fabric made of carbon fiber, activated carbon, and heat-fusible synthetic resin fiber as a polarizable electrode. .

Effects According to the above configuration, the electrodes are manufactured using non-woven fabric manufacturing technology instead of conventional paper manufacturing technology, which eliminates the need for water dispersants and binders, which were previously required, and also eliminates the need for water dispersants and binders, which are required in the past. Since there are no constituent substances, it is possible to obtain an electrode with very low moisture content.As a result, the withstand voltage as an electrode is improved, and its characteristics over time are stable.
Moreover, it is possible to extend the service life.

EXAMPLES The present invention will be described in detail below. First, as a polarizable electrode, an activated carbon nonwoven fabric (the ratio of constituent materials will be described later) with a diameter φCSW and a basis weight of 140 g/Im was used.

On one side of this activated carbon nonwoven fabric, an aluminum layer of about 0.05 fl is formed by plasma spraying. Its total thickness is 0.6M. Also, outer diameter φ11
A metal case No. 6, a corresponding metal lid, and a sealing body were prepared. 5U8304 is used for the metal lid that has a negative potential, and the inner surface of the metal case that has a positive potential is made of aluminum, and the outer surface is made of 5UI9304, and both are clad and integrated. The separator is made of a nonwoven fabric made of polypropylene fibers, and this nonwoven fabric is a porous sheet with a thickness of 0.35jil and a basis weight of 50 g/ll2f). The sealing body is a polypropylene resin molded product. The electrolytic solution was propylene carpenate to which 1 mol of tetraethylammonium tetrafluoroborate was added, and 30 μl of this was used.

Next, the sealed single cell has a withstand voltage of 3V,
In order to cope with the driving voltage of semiconductor memory, two sheets are laminated and the product uses 6.6V. Comparisons between the electrodes of the present invention and conventional electrodes were conducted as (1) initial characteristics (capacitance, internal resistance, leakage current, and low-temperature characteristics) and (2) reliability tests of products using each electrode. This is based on a high temperature load test (70'C, electrical characteristics after 3000 hours of 5.5V application).

Table 1 shows the initial values (measuring temperature: 20°C) and low-temperature characteristics (-26 ℃) and high temperature load test (70℃, s
, sV application) shows a comparison of characteristics after 3000 hours.

The materials used are (&) Fibrous activated carbon (MUCF), which uses phenolic resin fibers as a starting material, and has a specific surface area of 1
90011"7g, fiber diameter: 11μm, fiber length: 3.
It is 0m11. In this case, pitch-based activated carbon fibers were also examined, but no particular difference was found as long as they had the above characteristics. (b) Finely powdered activated carbon (MUCP) is made from coconut and has a specific surface area of 1800112/K and an average particle size of 300 mesh. In this case, activated carbon using sawdust as a starting material was also considered, but no particular difference was found as long as it had the above characteristics. However, it is currently not economical to obtain the required specific surface area due to low yields. (0) As the carbon fiber (air), highly conductive graphitized fiber was used. Thread diameter: 13μ weight, thread length: aos
ag, volume resistivity; 1, exlo (Ω·cN), carbon content; MIN, 95% (wt%). Although the fibers were straight, there was no significant difference in the curled fibers. In this case as well, phenolic resin fibers were used as the starting material, but as long as they also had the above-mentioned characteristics, there was no particular difference. (d) Polyethylene resin fiber (pm), polyester resin fiber (pp), polyester resin fiber (PIT/
...Polyethylene terephthalate, or PBτ
...Polybutylene terephthalate) has a fiber diameter;
3 μm, fiber length: 6 fl.

(O) The bulb (P) is the same bulb as kraft paper used as a separator material for ordinary aluminum electrolytic capacitors. In this case, Manila hemp fiber as other natural fibers,
Regenerated fibers such as rayon and synthetic fibers such as polyethylene, polypropylene, and polyester can also be used.

The dispersant is also an antifoaming agent/dispersant used in ordinary paper making, and the amount added is 1 tre or less.

(The following is a blank space) Effects of the Invention As described above, according to the present invention, electrodes are manufactured using nonwoven fabric manufacturing technology instead of conventional paper manufacturing technology, so water consumption, which is necessary with conventional paper manufacturing technology, is reduced. 1 dispersant,
Since there is no need for a binder and there is no water component like in bulbs, an electrode with lower moisture content can be obtained.As a result, products using the nonwoven fabric electrode of the present invention have excellent initial characteristics It is also possible to maintain more stable characteristics in terms of characteristics and reliability (high temperature load test).

[Brief explanation of drawings]

The figure is a sectional view showing a conventional electric double layer capacitor. 1.1'...electrode, 2...electrolyte, 3
...Separator, 4...Metal case,
6...Metal lid, 6...Putskin. Name of agent: Patent attorney Shigetaka Awano and one other person 1.
1”-11 Electrode 2-11 Electrolyte 3--e> Maretaro -11 No. Wakin

Claims (5)

[Claims] (1) An electric double layer capacitor characterized in that a nonwoven fabric made of carbon fiber, activated carbon, or heat-fusible synthetic resin fiber is used as a polarizable electrode. (2) The electric double layer capacitor according to claim 1, wherein the carbon fiber is a phenol or pitch-based carbon fiber. (3) The electric double layer capacitor according to claim 1, wherein the activated carbon is phenol or pitch-based fibrous activated carbon. (4) The electric double layer capacitor according to claim 1, wherein the activated carbon is finely powdered activated carbon using coconut husk or sawdust as a starting material. (5) The electric double layer capacitor according to claim 1, wherein the heat-fusible synthetic resin fiber is polyethylene, polypropylene, or polyester.