JPH03220713A - Manufacture of electric double layer capacitor - Google Patents

Abstract

PURPOSE:To provide a title condenser reduced in size and increased in capacitance by manufacturing active charcoal by carbonizing thermosetting resin at 500-700 deg.C. CONSTITUTION:When polarizable electrodes are formed of mixture of active charcoal 1 and electrolyte solution, and a current collector 2, and a capacitor is manufactured, the charcoal is manufactured by carbonizing thermosetting resin at 500-700 deg.C. When the resin is carbonized, a transition point for varying from resin to carbon precursor exists between 400 and 500 deg.C. Thus, a large difference exists at equivalent series resistances at between 400 and 500 deg.C. On the other hand, when the carbonizing temperature is raised to advance carbonization, weight is reduced and contraction occurs. Since the influence of the reduction in the weight is large up to the vicinity of 650 deg.C, the surface area of the carbide becomes maximum near at 650 deg.C. Since the influence of the contraction of the carbide at 650 deg.C or higher is large, pores are gradually vanished. Accordingly, its capacitance is apparently large, and a range of the carbonizing temperature having no problem at the value of the equivalent series resistance is 500 deg.C or higher and 700 deg.C or lower. Thus, a large capacitance is provided with small size.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing an electric double layer capacitor, and particularly to a method for manufacturing an electric double layer capacitor, which is characterized in manufacturing activated carbon, which is an electrode material for an electric double layer capacitor. It is related to.

[Prior art and its problems] The basic configuration of an electric double layer capacitor (hereinafter referred to as the basic element) consists of an activated carbon layer 1 and a current collector 2 as unit polarizable electrodes, and a pair of An electrolyte solution is impregnated between the polarizable electrodes, and electronic short circuits are prevented by a porous separator 3 that is electronically insulating and ion permeable.
4 is an insulating gasket. Electric double layer capacitors have a structure in which one or more capacitors are laminated depending on the voltage used, since the maximum operating voltage of the basic element is lower than the electrolytic voltage of the electrolyte solution.

By the way, electric double layer capacitors are small, large-capacity capacitors that are widely used for backup of microcomputers, memories, etc., and for auxiliary power supplies that can instantaneously supply large currents. As devices become smaller and lighter, there is a strong desire for smaller electric double layer capacitors to be used there. In order to realize miniaturization of this electric double layer capacitor, it is very important to increase the electric double layer capacitance per unit volume.

Conventionally, the activated carbon used in electric double layer capacitors was originally developed for adsorption or catalyst use. For this reason, materials have not been designed that are suitable for the polarizable electrodes of electric double layer capacitors, and no matter which activated carbon is used, capacitor characteristics such as capacitance two-equivalent dot series resistance do not change much.

Furthermore, although many proposals regarding the form of polarizable electrodes have been made up to now, there have not been many proposals regarding the manufacturing conditions for activated carbon suitable for electric double layer capacitors, and none have been fully satisfactory.

The present invention has been made to solve the above-mentioned conventional problems, and provides a method for manufacturing a small and large-capacity electric double layer capacitor with a large electric double layer capacitance per unit volume of polarizable electrodes. There is a particular thing.

[Means for Solving the Problems] The present invention comprises forming a polarizable electrode with a mixture of activated carbon and an electrolyte solution and a current collector, and stacking a pair of the polarizable electrodes facing each other with a separator interposed therebetween. In the method for manufacturing electric double layer capacitors, activated carbon is made of thermosetting resin.
This is a method for manufacturing an electric double layer capacitor, which is characterized by carbonizing the capacitor at a temperature of 00 to 700°C.

[Function] When the thermosetting resin is carbonized, there is an inflection point between 400'C and 500'C where the resin changes to a carbon precursor, so the value of the equivalent series resistance is 400'C. and 500°
There is a big difference between C. On the other hand, if carbonization is promoted by lowering the carbonization temperature by -L, weight loss and shrinkage occur, but 650
Up to around 'C, the effect of weight loss is large, so 650
The surface area of carbides is maximum near 'C. and 650
At temperatures above 0.degree. C., the pores gradually disappear due to the large effect of shrinkage of carbides. It is thought that these pores play an important role in the reaction during activation. Therefore, it can be said that the range of carbonization humidity where the capacitance is clearly large and the value of equivalent series resistance is not a problem is 500° C. or higher and 700° C. or lower.

[Example] Next, examples of the present invention will be described.

Examples 1 to 3, Comparative Examples 1 to 5 Phenol resin, which is a thermosetting resin, was used as a raw material. 20g of this resin was placed in an alumina SEC and heated in a tubular electric furnace in a nitrogen atmosphere to produce 4
Carbonized at 00-1400'C.

Carbonization time is 2 hours, temperature increase rate is 100℃ per hour
It is. After the obtained carbide was pulverized in a planetary ball mill, the carbon powder was placed in an alumina SEC and activated in a tubular electric furnace. The activation temperature is 900°C, and the heating rate is 200''G per hour.The activation method is a gas activation method using water vapor, and after reaching a predetermined temperature, nitrogen gas is used as a carrier gas to raise the dew point temperature. Steam was introduced into the furnace at room temperature.The activation time was 4 hours.

An electric double layer capacitor was manufactured using the above sample as activated carbon for a basic element to be described later.

Example 4 Fibers of phenolic resin, which is a thermosetting resin, were used as a raw material. 20 g of this phenolic resin fiber was placed in an alumina pot, placed in a nitrogen atmosphere, and carbonized at 600'C in a tubular electric furnace. The carbonization time was 2 hours, and the temperature increase rate was 100°C per hour. The obtained carbon fibers were directly placed in an alumina SEC and activated in a tubular electric furnace.

The activation process is the same as in Example 1.

An electric double layer capacitor was manufactured using the above sample as activated carbon for a basic element to be described later.

Example 5 The same phenolic thermosetting resin used in Example 1 was used as a raw material. This resin was immersed in a zinc chloride solution with a specific gravity of 1.8, and after drying, chemical activation was performed in a tubular electric furnace. The weight ratio of zinc chloride to resin is 1
．． It is 65. The activation temperature is 600°C, and the heating rate is 1
ioo'c per hour. Moreover, the activation time was 4 hours. After washing and drying the obtained activated carbon, an electric double layer capacitor was manufactured by using it as activated carbon for a basic element to be described later.

Comparative Example 6 Polyvinyl chloride, which is a thermoplastic resin, was used as a raw material. The activated carbon production conditions other than the raw materials were the same as in Example 1.

An electric double layer capacitor was manufactured using the above sample as activated carbon for a basic element to be described later.

The method for manufacturing the electric double layer capacitors of the above-mentioned Examples and Comparative Examples is as follows.

In FIG. 2, the current collector 2 has a film thickness of 200IIIn.
An unvulcanized conductive butyl rubber having a diameter of 8.2 mm was used. In addition, the film thickness of the insulating gasket 4 is 500JJ.
, unvulcanized butyl rubber with a diameter of 8.2 mm and concentric holes of 3.8 mm was used. The porous separator 3 was made of polyethylene and had a thickness of 100mm and a diameter of 60mm.

In all cases other than Example 4, the recesses formed by crimping the current collector 2 and the insulating gasket 4 were filled with a paste containing a mixture of activated carbon and electrolyte solution obtained in each Example and Comparative Example. A unit polarizable electrode was obtained. In Example 4, the activated carbon cloth obtained in Example was punched into a circular shape with a diameter of 3.8 mm and impregnated with an electrolyte solution in the recess formed by pressing the current collector 2 and the insulating gasket 4 together. A unit polarizable electrode was obtained by filling the solution with . The electrolyte solution contains 4
A 0% by weight aqueous sulfuric acid solution was used. A pair of unit polarizable electrodes is crimped with the paste facing each other through a porous separator 3, and a pressure of 'j/Cm2 is applied to 7, and the mixture is left at a temperature of 120°C for 3 hours. The electric body 2, the insulating gasket 4, and the insulating gasket 4 were bonded together by vulcanization to obtain a basic element 8 of an electric double layer capacitor. Six basic elements 8 are laminated as shown in FIG.
By taking out the terminals to the outside, an electric double layer capacitor with an operating voltage of 5V was manufactured.

Capacitance and equivalent series resistance, which are capacitor characteristics, were measured for the electric double layer capacitors manufactured in each Example and Comparative Example. The capacitance was measured by inserting a 1Ω resistor in series with the capacitor and calculating from the time constant when a constant voltage of 5Ω was applied.

Also, the equivalent series resistance is 1 k for the electric double layer capacitor.
It was determined by flowing a constant current of Hz/10 mA and measuring the voltage across the electric double layer capacitor.

Table 1 shows the characteristics of the electric double layer capacitors obtained in each example and comparative example. Further, FIG. 1 shows the relationship between carbonization temperature and capacitance. The numbers in FIG. 1 correspond to the sample numbers in Table 1.

As is clear from Figure 1, the lower the carbonization temperature, the larger the capacitance, but the value of the equivalent series resistance is 400°C.
It can be seen that there is a large difference between 500℃ and 500℃. According to the research and investigation conducted by the present inventors, when resin is carbonized, the inflection point at which the resin changes into a carbon precursor is 400°C and 500°C.
exists between. Then, when the carbonization temperature is increased and carbonization is progressed, weight loss and shrinkage occur, but the effect of weight loss is large up to around 650°C, so E) The surface area of the carbide reaches its maximum at around 50°C. At temperatures above 650° C., the pores gradually disappear due to the large effect of shrinkage of the carbide. It is thought that these pores play an important role in the reaction during activation. Therefore, the carbonization temperature range where the capacitance is clearly large and the value of equivalent series resistance is not a problem is 50
It can be said that the temperature is above 0°C and below 700'l.

In Examples 4 and 5, the capacitances were also approximately the same as in Example 2. From this result, it can be said that the carbonization conditions have a greater influence on the performance of electric double layer capacitors than the form of the resin or the activation method.

Comparative Example 6 did not show much effect on capacitor properties compared to thermosetting resin. This is thought to be because the resin has fluidity during the carbonization process, so there are fewer pores after carbonization.

(The following is a margin) Condolences 1 Table] [Effects of the Invention] As explained above, according to the method of the present invention, it is possible to obtain a small-sized, large-capacity electric double layer capacitor.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram showing the relationship between the carbonization temperature of the resin and the capacitance of the electric double layer capacitor, Fig. 2 is a sectional view of the basic element of the electric double layer capacitor, and Fig. 3 is an embodiment of the present invention. FIG. 2 is a cross-sectional view of an electric double layer capacitor obtained by the method.

Claims (1)

[Claims] (1) A method for manufacturing an electric double layer capacitor in which a polarizable electrode is formed with a mixture of activated carbon and an electrolyte solution and a current collector, and a pair of the polarizable electrodes are laminated to face each other with a separator in between. 50% thermosetting resin
A method for manufacturing an electric double layer capacitor, which comprises carbonizing the capacitor at a temperature of 0 to 700°C.