JP3488957B2 - Electric double layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high capacity electric double-layer capacitor capable of extracting large current and improving energy density. SOLUTION: A low-density polarized electrode 10, having the density in the large of 0.50 to 0.70 g/cm3 provided by mixing and sintering an active carbon powder and phenol resin and a high-density polarized electrode 9 having a density in the large of 0.60 to 0.75 g/cm3 provided by mixing and sintering the active carbon powder and phenol resin are laminated, and made into a polarized electrode and arranged on both the sides of a separator 2, and a current collector 3 is arranged outside the high-densitypolarized electrode 9.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric double layer capacitor, and more particularly to an internal electrode structure of a large capacity electric double layer capacitor. 2. Description of the Related Art A conventional electric double-layer capacitor is disclosed in Japanese Patent No. 2,054,380. As shown in FIG. 2, an electric double layer capacitor disclosed in Japanese Patent No. 2054380 (hereinafter referred to as Conventional Example 1) is a polarizable electrode using a composite of activated carbon powder and a polyacene-based material, particularly activated carbon. The capacitor structure has a polarizable electrode 1 obtained by mixing a powder and a granular or powdery phenolic resin and heat-curing, and using an electric double layer generated at the polarizable electrode interface. [0004] The electric double layer capacitor shown in FIG.
A separator 2 is sandwiched between two polarizable electrodes 1 from both sides, and a current collector 3 is in contact with each of the polarizable electrodes 1. A gasket is formed between the separator 2, the polarizable electrode 1, and the current collector 3. 4 and is used as the basic cell 5. Dilute sulfuric acid is used as a medium for polarization. As shown in FIG. 3, the basic cell 5 shown in FIG. 2 is laminated in a plurality of layers in accordance with a required voltage, and terminal plates 8 are arranged on both sides thereof to constitute a large-capacity electric double layer capacitor. . According to the conventional example 1 shown in FIG. 2, a capacitor having a low internal resistance and a large capacity can be constructed, and the charge and discharge mechanism does not involve a chemical reaction unlike a battery. In principle, the number of times of charge / discharge is unlimited, and rapid charge / discharge with a large current is possible. Accordingly, the electric double-layer capacitor shown in FIG. 2 has a storage amount that is inferior to that of a conventional secondary battery such as a Pb storage battery, but makes use of the above-mentioned features to make it possible to use a maintenance-free power supply or a large current. Applications in various fields are being studied as power sources for storage. By the way, in the conventional example 1 shown in FIG.
From the application point of view, the following performance may be required. [0009] That is, from the viewpoint of the application, the power is low during normal use, but there is a case where the performance is required for supplying power for a long time and supplying a large current instantaneously. Considering the structure and performance of the electric double layer capacitor, the higher the density of the polarizable electrode 1, the more
Since the movement of ions inside is hindered, it is difficult to extract a large current. Also, if the density is lowered, a large current can be taken out, but the energy density will be low,
In order to extract the energy required, the volumetric efficiency is poor
Inevitably, the volume must be increased. As a technique for improving this point, Japanese Patent Laid-Open Publication No. Hei.
The technology disclosed in JP-A-201519 (hereinafter referred to as Conventional Example 2)
There is). As shown in FIG. 4, the technique disclosed in Japanese Patent Application Laid-Open No. Hei 3-201519 is a porous sintering method comprising first activated carbon 7 and second activated carbon 6 having different densities by sintering activated carbon particles. A structure is used in which the sintered body is used as a polarizable electrode and a porous sintered body made of the second activated carbon 6 having a high density is in close contact with the current collector 3. The density is adjusted by controlling the average particle size of the powdered activated carbon. For the low-density first activated carbon, a powder having an average particle size of 20 μm is used.
It is adjusted to 61 g / cm ³ , and powder having an average particle size of 5 μm is used for the high density second activated carbon, and the sintering density is 0.82 g.
/ Cm ³ . In Conventional Example 2, the purpose of adjusting the density is to use only low-density activated carbon to increase the contact resistance with the current collector and prevent the internal resistance from increasing. A high-density activated carbon 6 is arranged on the third side to reduce the contact resistance and prevent the internal resistance from increasing. According to the conventional example 2, when a large current is required, power is supplied by supplying ions from the low-density first activated carbon 7 and the energy density is increased by the high-density second activated carbon 6. It has a secure structure. Therefore, according to the conventional example 2, it is possible to use it for an application having a large load fluctuation. However, the conventional example 2 shown in FIG. 4 has a problem that a sufficiently large current cannot be supplied. The reason will be described. That is, as shown in FIG. 4, the contact resistance between the polarizable electrode 6 and the current collector 3, the contact resistance of the material particles in the polarizable electrodes 6 and 7, and the ion movement in the polarizable electrodes 6 and 7. This is due to the difficulty and the contact resistance between activated carbons due to the structure in which activated carbons having different densities are stacked. Further, in the conventional example 2, since the high-density activated carbon is used on the current collector 3 side, the effect of reducing the contact resistance with the current collector 3 is obtained, but the polarizable electrodes 6 and 7 Since only activated carbon is used as the material, the contact resistance between particles in the sintered body is large. In the above publication showing Conventional Example 2, low-density activated carbon is said to have a high contact resistance with the current collector, which indicates that the particles on the surface of the activated carbon are rough. . This is partly due to the use of a powder having a large particle size, which results in insufficient connection between the particles and, as a result, a high internal contact resistance. Naturally, it is not possible to reduce the contact resistance between high-density activated carbon and low-density activated carbon. For the above reasons, in the conventional example 2, since the reduction of the internal resistance is insufficient, a sufficiently large current cannot be taken out. An object of the present invention is to provide a high energy density,
Another object of the present invention is to provide a large-capacity electric double-layer capacitor having a small internal resistance for extracting a large current. In order to achieve the above object, an electric double layer capacitor according to the present invention is an electric double layer capacitor having a polarizable electrode, wherein the polarizable electrode comprises a powder Activated carbon and a phenolic resin are mixed and fired, and one surface of the polarizable electrode is in contact with the separator, and the other surface is in contact with the current collector, and the polarizable electrode is formed of powdered activated carbon having the same particle size. Using activated carbon
And a phenol resin in different weight ratios, a low-density polarizable electrode having a density of 0.50 to 0.70 (g / cm ³ ) was formed on the separator side, and 0.6% on the current collector side.
A high-density polarizable electrode having a density of 0 to 0.95 (g / cm ³ ) is formed and the bipolar electrodes are laminated ;
Since the energy density is high and the internal resistance is low, it is possible to take out a large current. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an electric double layer capacitor according to an embodiment of the present invention. The electric double layer capacitor according to the embodiment of the present invention shown in FIG. 1 uses, as the polarizable electrodes, polarizable electrodes 9 and 10 obtained by mixing and firing powdered activated carbon and a phenol resin, and using the polarizable electrodes 9 and 10 as separators 2. Are arranged on both sides of the body. In the embodiment shown in FIG. 1, polarizable electrodes 9 and 10 having different densities are laminated in two layers and arranged on both sides of the separator 2. The inner polarizable electrode 10 is in contact with one surface of the separator 2, and the outer polarizable electrode 9 is in contact with the current collector 3. These are sealed by the gasket 4 and have the inside for polarization. Medium fluid is being injected. The structure shown in FIG. 1 forms a basic cell 5. Further, in the structure according to the embodiment of the present invention shown in FIG. 1, of the polarizable electrodes 9, 10, the low-density polarizable electrode 10 is provided on the separator side, and the high-density polarizable electrode 9 is provided on the current collector. It has a structure in which it is arranged and laminated on three sides. The low-density polarizable electrode 10 is 0.50
The density is set to 0.70 (g / cm ³ ), and the density of the high-density polarizable electrode 9 is set to 0.60 to 0.95 (g / cm ³ ). Next, a specific example of the structure according to the embodiment of the present invention will be described as an example. In the embodiment of the present invention, the activated carbon powder and the phenol resin powder are mixed at a ratio of 8: 2 by weight and molded by a press mold at a pressure of 1000 kgf / cm ² , and then, under a vacuum atmosphere. Bake to 900 ° C, 100
A low-density polarizable electrode 10 of mm × 100 mm × 6 mm was obtained. Its density was 0.49 g / cm ³ . On the other hand, the activated carbon powder and the phenol resin powder were mixed in a ratio of 3: 7 by weight, and the mixture was mixed with a press mold to obtain 10 parts.
Molded at a pressure of 00 kgf / cm 2, and then fired in a vacuum atmosphere at a temperature of 900 ° C.
A high-density polarizable electrode 9 of 0 mm × 6 mm was obtained. Its density was 0.91 g / cm ³ . High density polarizable electrode 9 and low density polarizable electrode 1
0, and the high-density polarizable electrode 9 was brought into contact with the current collector 3 made of conductive rubber. A glass fiber cloth is used as the separator 2, and a thermoplastic resin is used as the gasket 4.
The basic cell 5 was configured. The weight of the internal polarization medium is 40% by weight.
Was used. As in the conventional example, the basic cells 5 were stacked as shown in FIG. 3, and terminal plates 8 were attached to both ends to obtain a large-capacity electric double layer capacitor. In order to see the effect for an application having a load fluctuation, data was acquired with the following configuration. DC / with high voltage electric double layer capacitor as input and voltage 6V as output
After extracting a current of 10 A as a load for 2 minutes through a DC converter, the number of hours that the battery can be discharged at 0.1 A was measured. The large-capacity electric double layer capacitor was fully charged at 12 V in advance. The terminal voltage at which the DC / DC converter operates was 5V. That is, the terminal voltage of the large-capacity electric double layer capacitor is used from 12 V to 5 V. In the same configuration, the maximum current is set to 0.
The current which can express 1/2 as the capacitance at the time of 1A discharge was investigated. As a result, 10 A discharge is possible, and 0.
5.8 (h) as 1 A discharge time, 22 as maximum current
A large-capacity electric double layer capacitor A was obtained. In Example 1, a large-capacity electric double layer capacitor was formed with the low-density polarizable electrode 10 having a weight ratio of activated carbon and phenolic resin of 6: 4, and the same measurement was performed. As a result, 10 A discharge is possible and 0.1 A discharge is possible.
A capacitor having a discharge time of 6.3 (h) and a maximum current of 18 A was obtained. Similarly, the parts by weight of the activated carbon and the phenol resin of the low density polarizable electrode 9 and the high density polarizable electrode 10
Table 1 and Table 3 show the results of adjusting the density by adjusting the parts by weight of the activated carbon and the phenol resin. (Comparative Example 1) An example in which the prior art 1 is used will be described. The differences from the first embodiment of the present invention will be described. Without separating into a low-density polarizable electrode and a high-density polarizable electrode, a polarizable electrode was produced integrally with a ratio of activated carbon to phenolic resin of 8: 2 by weight, and the same as Example 1 as an electric double layer capacitor. Similar measurements were made. The results are shown in Tables 2 and 4. (Comparative Example 2) In Comparative Example 2, an integrated type polarizable electrode was prepared in the prior art 1 in which the ratio of activated carbon and phenolic resin was 4: 6 by weight and an electric double layer capacitor was used. The same measurement as in Example 1 of the present invention was performed.
The results are shown in Tables 2 and 4. (Comparative Example 3) In Comparative Example 3, a monolithic polarizable electrode was prepared in a ratio of 5: 5 by weight of activated carbon and a phenolic resin to obtain an electric double layer capacitor. The same measurement as in Example 1 of the present invention was performed.
The results are shown in Tables 2 and 4. (Comparative Example 4) In the prior art 2, the low-density polarizable electrode 9 had a density of 0.61 formed only with activated carbon.
(G / cm ³ ) using the activated carbon sintered body in Comparative Example 4
It was produced as. When manufactured under the same pressing conditions and firing conditions as in Example 1 of the present invention, the density is 0.42 (g / c).
m ³ ). Therefore, the pressing pressure is set to 2200 (kg)
f / cm ² ), the firing temperature was 950 ° C., and the above activated carbon sintered body (Comparative Example 4) was obtained. In Comparative Example 4, the high-density polarizable electrode 10 was formed of only activated carbon and had a density of 0.82 (g / cm ³ ).
Was used. Press pressure 3500 (kg
f / cm ² ), the firing temperature was 1030 ° C., and the activated carbon sintered body was obtained. As a result, an electric double layer capacitor having a maximum current of 5 A was obtained. In the examples and comparative examples of the present invention, activated carbon powder having an average particle diameter of 5 μm was used. Due to the lower activity of the powder, conditions that accelerate sintering, such as higher temperatures, must be selected to obtain the same density. As a result, the pores inside the activated carbon are blocked by surface diffusion or volume diffusion during sintering, and the energy density becomes lower. As shown in the table, in the prior art, unlike the first embodiment of the present invention, the output is 6.0 V, 10 A and 2 V.
It is impossible to construct an electric double layer capacitor capable of supplying 0.1 A for 5 hours or more. On the other hand, according to the present invention, for example,
A large-capacity electric double layer capacitor capable of supplying energy of 10 A for 2 minutes and 0.1 A of 6.8 h can be formed. [Table 1] [Table 2] [Table 3] [Table 4] It should be noted that the present invention is not limited to the above-described embodiments, and it is apparent that the embodiments can be appropriately modified within the scope of the technical idea of the present invention. As described above, according to the present invention, the density of the polarizable electrode obtained by mixing and firing the activated carbon powder and the phenol resin is 0.50 to 0.70 (g / cm ³ ).
By disposing a low-density polarizable electrode adjusted to a density of 0.60 to 0.95 (g / cm ³ ) on the current collector side, a high-density polarizable electrode adjusted to a density of 0.60 to 0.95 (g / cm ³ ) is disposed on the current collector side. And a high energy density can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view showing a basic cell of an electric double layer capacitor according to one embodiment of the present invention. FIG. 2 is a longitudinal sectional view showing a basic cell of an electric double layer capacitor according to a conventional example. FIG. 3 is a perspective view showing an electric double layer capacitor according to a conventional example. FIG. 4 is a longitudinal sectional view showing a basic cell of an electric double layer capacitor according to a conventional example. [Description of Signs] 9 High density polarizable electrode 10 Low density polarizable electrode

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01G 9/058

Claims (1)

(57) An electric double layer capacitor having a polarizable electrode, wherein the polarizable electrode is obtained by mixing powdered activated carbon and a phenol resin and firing the mixture. One side of the electrode contacts the separator and the other side contacts the current collector.
And further wherein the polarizable electrode, with powdered activated carbon of the same particle size
To make the weight ratio of activated carbon and phenolic resin different
More, the separator side 0.50 to 0.70 (g / c
m ³⁾ density to form a polarizable electrode of low density with a, to form a high density of the polarizable electrodes having a density of 0.60~0.95 (g / cm ³⁾ in the current collector side bisect An electric double layer capacitor characterized by laminating polar electrodes .