JPS6050912A - Method of producing 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 relates to a method for producing an electric double layer capacitor using activated carbon, particularly activated carbon fibers, as a polarizable electrode.

(Conventional structure and its problems) Figure 1 shows the basic structure of an electric double layer capacitor that uses activated carbon as polarizable electrodes. It consists of conductive layers 3 and 4 that function as electrodes and a separator 5. The activated carbon layers 1 and 2 are impregnated with, for example, a mixed solution of propylene carbonate and tetraethylammonium barchlorate as an electrolyte.

Electric double layer capacitors having such a basic configuration can be roughly classified into the following three types of specific groove configurations. The first one is shown in FIG. 2, in which a mixed yeast 10 of activated carbon powder and an organic binder such as fluororesin powder is coated on an aluminum net 11, and the yeast is rolled up with a center layer 12. Items are placed in a metal can 13 and sealed with a rubber stopper 14. The wound material is impregnated with the electrolyte as described above, and 15 and 16 are electrodes. The second method is shown in FIG. 3, and uses viscous paste (20 and 21) obtained by mixing an aqueous electrolyte and activated carbon powder, and is insulated through a separator 22. It is composed of conductive elastic rings 23 and 24 and conductive elastic electrodes 25 and 26. These first. The second type uses activated carbon powder as a polarizable electrode, and each has characteristics such as high breakdown voltage and low internal resistance. On the other hand, as a third type, there is a structure in which activated carbon fibers are used as polarizing electrodes, developed by the present inventors (Japanese Unexamined Patent Publication No. 55-99714).

FIG. 4 shows this third type of canopy, in which activated carbon cloths 30 and 31 having metal sprayed films 32 and 33 are placed facing each other with a separator 34 in between, and a gasket 35 and metal cases 36 and 37 are sealed together. This is suitable for a small backup circuit for a microcomputer because it can be shaped like a flat coin and is easy to manufacture.

The present invention relates to the third type mentioned above,
First, we will describe the activation process of the polarizable activated carbon fiber cloth used as the pole.

Activated carbon fiber cloth is rayon-based, pinch-based, phenolic-based,
A woven fabric woven using PAN-based fibers or the like is carbonized in an inert gas to obtain a carbon fiber cloth, and then the carbon fiber is activated carbonized using an appropriate activating gas to obtain an activated carbon fiber.

FIG. 5 is a schematic diagram showing the process of carbonizing and activated carbonizing from the raw woven fabric, 40 is the raw woven fabric, 41 is the carbon fiber cloth, 42 is the activated carbon fiber cloth, (5) is the carbonization process, (B ) is the activation process,
(C) shows the carbonization activation process, in which the activated carbon fiber cloth is produced through a two-step process of carbonization and activation as shown in (A) and (B), and a carbonization and activation process as shown in (C). It is broadly divided into the process of obtaining. Appropriate activation conditions used here include, for example, introducing a mixed gas of hydrocarbon gas, carbon oxide, carbon dioxide, water vapor, etc. produced by combustion of carbon gas into a high-temperature furnace at 850°C, and then , or keeping the carbon fiber cloth in the furnace for a certain period of time.

FIG. 6 shows an example of an activation device, in which a woven fabric 51 to be carbonized or carbonized is housed in a furnace 50 maintained at a high temperature, and an activation gas generator 5 is inserted into an inlet 52 of the furnace 50.
Activation gas from No. 3 is introduced.

As shown in equation (1), the activation reaction is a process in which carbon is gradually removed from the carbon fiber by an oxidation reaction, creating pores of several X to several 10 times in size on the fiber surface.

cn+202→Cn-10Co↑ ・・・・・・(1)
In order for the oxidation reaction of formula (1) to proceed uniformly and quickly, contact between the activation gas and the fibers must be uniform throughout the system, and a sufficient amount of the activation gas must be supplied.

As can be seen from equation (1), the degree of progress of the activation reaction can also be determined by changes in the amount of fiber.

Figure 7 shows the activation time (
It shows the relationship between weight loss (horizontal axis) and weight loss (vertical axis). Here, (A), (B) and (C) each have a basis weight of 100. ! 9r/m2.300F/m2 and 500gr
/m2 plain weave using three types of woven fabrics using phenolic Norac fibers. From this figure,
It is clear that the weight of all fabrics gradually decreases as the activation time progresses, but in particular, the weight of fabrics with a small basis weight (4
It can be seen that the weight loss of the fabric (C), which has a large basis weight, is large, and the weight loss of the fabric (C), which has a large basis weight, is small. However, the activation conditions used here were a furnace at 800° C. and Pro-Gun combustion gas used as the activation gas. This difference in weight deceleration can be explained as shown in FIG.

FIG. 8 is a schematic diagram showing the relationship between the thickness of the original fabric and the degree of progress of the activation reaction. That is, l of the basis weight shown in FIG. 8(a)
”・The number of fibers per unit surface area of sai cloth is small,
Because the fabric is thin, the activation gas reacts uniformly and completely with the entire fabric in a short time, completing activation.

In addition, in the figure, the broken line part is the part where activation is completed. However, in a woven fabric with a large unit fabric area as shown in Figure 8 (b), the number of fibers per unit area is large and the thickness is thick, so (a)
The activation reaction progresses slowly when compared to In order to eliminate such differences in the way the fabric is activated, there are methods such as activating for a long time for fabrics with a large basis weight or increasing the amount of activating gas. However, if the total activation time is increased, the activation of the surface portion of the cloth progresses too much and the strength of the entire surface weakens. Furthermore, although increasing the amount of activating gas is an excellent method, there is a limit to the amount of gas that can actually be fed, and it is difficult to control the concentration with precision.

(Purpose of the Invention) The present invention aims to solve the above-mentioned problems by eliminating variations in the activation of the activated carbon fiber cloth used and obtaining an activated carbon cloth having uniform and excellent pores in a short time. The purpose of this invention is to provide a high-performance electric double layer capacitor using this activated carbon cloth.

(Structure of the Invention) The present invention provides a method for manufacturing an electric double layer capacitor in which a water-impregnated cloth is held in a high-temperature gas atmosphere to activate carbonization, and the obtained activated carbon cloth is used as a polarizable electrode. According to this method, water molecules that have been impregnated into the cloth in advance evaporate and act as an activating gas, and since the fibers are in a suitable state for wetting with water, they are introduced later. The catalytic oxidation reaction between the activation gas and the fibers proceeds smoothly. Even when activating thick fabrics with a large basis weight per unit fabric area for purposes of Activated carbon cloth can be obtained. Using this activated carbon cloth, it is possible to provide a large capacity electric double layer capacitor with excellent volumetric efficiency.

(Description of Examples) A major feature of the present invention is that the fiber cloth to be activated is impregnated with water prior to activation. Through this process, (1) the impregnated water is vaporized during activation and acts as an activation gas. ■Since the fibers are immersed in water in advance, the fibers are well wetted by water vapor gas, and the catalytic oxidation reaction with the activating gas proceeds smoothly. Excellent results can be obtained.

FIG. 9 is a characteristic diagram for detailed explanation of the present invention.
crnX 10cmz thickness 1mm, basis weight 2001r/m
This figure shows the relationship between the activation time and weight loss of the novolac fiber cloth in No. 2. The activation temperature is 800°C, and the activation gas is Pro-Gun combustion gas. In the figure (G) is data obtained when a cloth pre-impregnated with water is activated as in the present invention, and (B) is data obtained by a conventional method. As shown in this figure, (4) shows a weight loss of about 90 times in 20 minutes, while (B) shows a weight loss equivalent to (A) in about twice as much, 40 minutes.

This indicates that the activation progress rate according to the present invention is approximately twice as fast.

FIG. 10 shows the relationship between activation time and weight loss when the activation method according to the present invention is used, and corresponds to the conventional activation method shown in FIG. 7 above.

(A), (B) and (C) each have a basis weight of 100
11r 7m2゜300gr/m” and 5001/r/
These are the results when a cloth of m2 was used, and in both cases the cloth was impregnated with water before activation, but compared to the results in Figure 7, the weight reduction was 1.5 to 3 times with the same basis weight. It seems to be twice as fast,
The effect of cloth with a large basis weight is significant. Note that the longer the water impregnation time, the more effective it is, although it depends on the basis weight of the fiber cloth. In addition, alkali, alkaline earth metal ions,
By injecting ions, etc., the diameter of the pores generated by activation can be controlled by the catalytic action of these ions.

Next, specific examples of the present invention will be shown.

Example-1 Cloths (1) and (2) made of novolac phenolic fibers with a basis weight of 100 gr 7 m2 and 500.9 r 7 m2 are immersed in distilled water for 10 minutes. After being pulled out of the water and air-dried for 5 minutes, it was kept in a furnace at 800°C for 10 minutes. At this time, inside the furnace is (a) Pro Gun combustion gas, (b) 30III+l
A nitrogen gas containing 1 Hg of water vapor is introduced. After activation, an aluminum plasma sprayed film was formed on one side of the cloth, and two pieces of cloth were punched out to a diameter of 10 mm, a separator, and a mixture of propylene carbinate and tetraethylammonium glucorate. As an electrolyte, a coin-shaped cashier is completed using a case as shown in Figure 4. Table 1 lists the characteristics of the capacitor of this example. The same table also shows the characteristics of a capacitor using activated carbon cloth made by the conventional method, which is the same as this example, but without the step of impregnating it with water before activation.

Table 1 Example-2 A cloth composed of 7-virion phenol fibers with a basis weight of 5009 r/m2 was immersed in an 11 wt % calcium nitrate aqueous solution for 30 minutes. After being pulled up from water and air-dried for 10 minutes, it was kept in a furnace at 800°C for 30 minutes.

At this time, propane combustion gas is introduced into the furnace.

After activation, the cloth is washed with water for 10 minutes, dried, an aluminum plasma sprayed film is formed on one side of the cloth, and punched out to a diameter of 10 mm. The two surface electrodes made in this way and the separator,
Using an iowt% sulfuric acid aqueous solution as an electrolyte, a coin-shaped cashier is completed using a case as shown in FIG. Table 2 shows the characteristics of the capacitor of this example, and the same table shows the characteristics of the capacitor using the activated carbon cloth made by the conventional method, which is the same as this example, but without the step of immersing it in an aqueous calcium nitrate solution before activation.・Gushita characteristics are also listed.

Table 2 (Effects of the Invention) As explained above, according to the present invention, activation proceeds uniformly and quickly due to the water impregnated into the activated fibers in advance, and activated carbon has high strength and an optimum pore diameter. Cloth is obtained. A capacitor using this activated carbon cloth as a polarizable electrode has excellent volumetric efficiency and temperature characteristics, and has great industrial value.

[Brief explanation of the drawing]

Figure 1 shows the basic configuration of an electric double layer capacitor using activated carbon as a polarizable electrode, and Figures 2, 3, and 4 show specific configuration examples of conventional electric double layer capacitors. Figure 5 is a schematic diagram showing the process of carbonization and activated carbonization from raw woven fabric, Figure 6 is a diagram showing an example of an activation device, and Figure 7 is the activation of three types of woven fabrics using the conventional activation method. A diagram showing the relationship between time and weight loss, FIG. 8 is a schematic diagram showing the relationship between the thickness of the raw fabric and the degree of progress of the activation reaction, and FIG. 9 is a characteristic diagram for detailed explanation of the present invention. FIG. 10 is a diagram showing the relationship between activation time and weight loss when using the activation method according to the present invention. 1.2... activated carbon layer, 3.4... conductive layer, 5...
separator, 10...mixed paste, 11...aluminum net, 12...separator, 13...
Metal can, 14... Comb stopper, 15.16... Electrode,
20.21...Stowed, 22...Senogushiri,
23.24... Insulating ring, 25.26... Elastic electrode, 30... Activated carbon cloth, 32.33...
・Metal sprayed film, 34... Separator, 35... Gasket), 36° 37... Metal case, 4o... Original fabric fabric, 41... Carbon fiber, 42... Activated carbon fiber cloth ,
50...furnace, 51...woven fabric, 52...inlet, 5
3... Activating gas generator. Patent Applicant Matsushita Electric Industrial Co., Ltd. Managing Director Tsuneji Hoshino 5.1 1-I Figure 1 Figure 2 Figure 3 34 33 31 J'/ Figure 5 Figure 6'+1"1 Figure 7 Figure 8

Claims (5)

[Claims] (1) A method for producing an electric double layer capacitor, characterized in that a water-impregnated cloth is held in a gas atmosphere at high temperature to activate carbonization, and the obtained activated carbon cloth is used as a polarizable electrode. (2) The method for manufacturing an electric double layer capacitor according to claim (1), wherein the water contains ions of alkali metals and alkaline earth metals. (3) The method for manufacturing an electric double layer capacitor according to claim (1), wherein the gas contains at least nitrogen and water vapor. (4) The method for manufacturing an electric double layer capacitor according to claim (1), wherein the cloth contains at least phenolic novolac fiber as a constituent material. (5) The method for manufacturing an electric double layer capacitor according to claim (1), wherein the water vapor partial pressure of the gas is 20 mmH, 9 or more.