JPS6164113A - Electric doulbe 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 the Invention The present invention relates to a small, thin, large capacity wet type electric double layer capacitor.

Structure of a conventional example and its problems FIG. 1 shows an example of the structure of a conventional wet electric double layer capacitor. Using activated carbon fiber cloth as the polarizable electrode 1,
A metal layer such as aluminum, titanium, nickel, stainless steel, or a conductive resin layer is formed on the polarizable electrode 1 as a current collector 2, and after facing each other with a separator 3 interposed therebetween, an electrolytic solution is injected, After that, a case 4, a sealing plate 5, and a gasket 6 are used to seal the casing.

Here, the activated carbon fibers used for the polarizable electrodes are phenol-based (hardened novolac fiber) and rayon-based.

Obtained by carbonizing and activating acrylic or pitch fiber cloth. Electrical resistance 2 strength of activated carbon fiber.

Considering the activation yield, etc., among the above-mentioned fibers, phenolic fibers are most suitable for polarizable electrodes.

The metal conductive layer is formed by plasma spraying, arc spraying or gas spraying. Further, a conductive layer made of conductive resin or the like can be easily formed by a screen printing method, a press method, or a dipping method. The polarizable electrode having the above shape can be punched to a desired diameter, and the first
It is possible to realize the small coin-shaped flat plate large-capacity capacitor shown in the figure.

Further, such polarizable electrodes do not require the use of a binder, and can reduce internal resistance. In particular, when the conductive layer is formed by a thermal spraying method, the adhesion strength between the thermal sprayed metal layer and the activated carbon fiber layer is good, the contact resistance is small, and good capacitor characteristics can be obtained.

However, today there has been a remarkable improvement in the characteristics of electronic devices, especially semiconductor memories, and there is a strong demand for capacitors with a smaller capacity than before and with excellent charge/discharge characteristics (rapid charging). In addition, as equipment becomes lighter, thinner, and smaller,
Double layer capacitors are also required to be smaller and thinner. As long as conventional activated carbon fiber cloth is used, it is extremely difficult to reduce the thickness of the capacitor to less than one tone after sealing the casing.

Further, although the activated carbon fiber cloth 7 shown in FIG. 2 does not use a binding medium, the void portion 8 is too large to improve the volumetric efficiency. Furthermore, during the manufacturing process, fibers fly off during the punching process of polarizable electrodes, causing dust pollution. Furthermore, as is well known, the electric charge accumulated in the double layer is proportional to its formation area, but the more activated carbon fibers are activated, the more their specific surface area and pore volume increase.

On the other hand, the fiber strength is significantly reduced and becomes unusable.

OBJECTS OF THE INVENTION The present invention aims to improve the charging and discharging characteristics of conventional electric double layer carriers and to make them thinner, more compact, and with higher energy density.

Structure of the Invention To achieve this object, the present invention provides a polarizable electrode with a bulb having a thickness of 400 mm, which is made by a papermaking method using a bulb as a coupling medium.
μm or less, density is o, 1? A conductive layer is formed on at least one side of this polarizable electrode using paper-like activated carbon fibers of /cri or more, and the electrolyte is injected while facing each other with a separator interposed therebetween.
Description of Example 0 In which the charging/discharging characteristics are improved and the energy density per unit volume is improved while maintaining the strength.The following will explain based on specific examples.

(Example 1) A coin-shaped capacitor shown in FIG. 3 was created using the constituent materials and steps shown below.

Tow-shaped phenolic novolac resin fiber (φ15μm
) using a catalyst and steam to activate carbonization, and the specific surface area obtained was measured by the BET method to be 2400 m/7. Pore volume 1
．． 5 cc/S', 50% when the pore size is 20~4°A
The activated carbon fibers present above are finely pulverized using a mixer, and then a polarizable electrode of paper-like activated carbon fibers having a basis weight and density shown in Table 1 is formed using a bulb (cellulose fiber) calendar, roller, or press. An aluminum layer having a thickness of 3Q μm is formed on at least one side of this polarizable electrode by plasma spraying. The polarizable electrode having the conductive layer is placed in such a way that the conductive layer is in contact with the case 4 and the sealing plate 5, and spot welded to form a 1 mol (C2H6) electrode.
)4NBF6, after injecting the propylene carbonate solution, a sealed casing is placed with a gasket 6 interposed to insulate the positive and negative electrodes. The polarizable electrode in this example has a disk shape with a diameter of 14 mm. Table 1 shows the initial characteristics of capacitors that exploded using polarizable electrodes prepared under each condition. From this table, it is clear that the higher the density, the higher the energy density and the lower the impedance. In addition, it can be seen that the polarizable electrode has a thickness of 400 μm or less, a density of o1f/crt1 or more, and a coupling medium of 50% or less, preferably 20 to 30%, which can maintain strength and exhibit good capacitor characteristics. Below is a blank space (Example 2) A polarizable electrode having the same composition as Nα4 in Example 1,
■ Acrylic resin instead of the valve as the binding medium.

■We prototyped a capacitor similar to the one shown in Figure 3 using polyethylene oxide resin. The results are shown in Table 2.
, 0, it is possible to easily form a thin polarizable electrode, but it can be seen that the capacitor has a large impedance.

Below is a blank space (Example 3) A polarizable electrode having the same composition as N14 in Example 1 was used as an activated carbon fiber.■ Polyacrylonitrile resin was used as a starting material and the specific surface area was e o o m7y.■ Rayon was used as a starting material. Using a fiber with a specific surface area of 600 rn''/g, we prototyped a capacitor similar to that shown in Figure 3. The results are shown in Table 3. Phenolic activated carbon fibers have a large specific surface area and can form capacitors with high energy density. .

The following blank space (Example 4) A conductive paint layer containing carbon as conductive particles was applied and formed on the surface of a polarizable electrode having the same composition as Example 1 ONI14, and the electrolyte contained 1 mol (C2H5)4NCR○.
Using a propylene carbonate solution, a coin-shaped carriage seat shown in FIG. 3 was prepared. Compared to Nα4 of Example 1, the impedance was increased to 25.10,
The other properties were almost the same (Example 5) Nickel was thermally sprayed to a thickness of about 30 μm on the polarizable electrode having the Nα4 composition and basis weight of Example 1 to form a conductive layer. Then, capacitors shown in FIGS. 4a and 4b were produced. Figure 4 shows a cross section taken along line X-X'. 1 is a 250μm polarizable electrode, 9 is a 30μm polarizable electrode
m conductive layer of nickel, 10 is 50 pm; 2 is current collector plate, 11 is 50 μm thick polypropylene separator, 12 is polyethylene terephthalate); The film sheet 13 is a lead. The electrolyte contains 24wt%
of potassium hydroxide was used. The capacitor of this example has good current collecting ability and strong polarizable electrode strength, and has 1oO×
Even with a size of 2 o -, it can be assembled with sufficient workability. Table 4 shows various characteristics of the capacitor of this example.

Table 4 [''- (Example 6) 100μ
A cylindrical capacitor shown in FIG. 5 was fabricated by thermally spraying an aluminum layer of 1.m and using an etched aluminum foil as the current collector 2. Since such a cylindrical capacitor can have a large electrode area, it is possible to discharge a large current. However, when using the polarizable electrode of the present invention,
If the original is 1000 μmK, it becomes a capacitor with a large internal resistance, so it is better to use a polarizable electrode with a diameter of 400 μm or less. In the figure, 13 is a lead,
14 is a case, 16 is a sealing lever king, and 16 is a gasket. The electrolyte contains 1 mol KPF6. A propylene carbonate solution was used.

The size of the polarizable electrode body used was 30×200−. Table 5 shows the characteristics of the capacitor of this example. From this table, it can be seen that the capacitor of the present invention is a small-sized, large-capacity capacitor with excellent charging and discharging characteristics.

Table 5 Effects of the Invention As described above, according to the present invention, it is possible to obtain a thin, compact, large-capacity electric double layer capacitor that has excellent charging and discharging characteristics and is easy to work with.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a conventional electric double layer capacitor, FIG. 2 is a schematic diagram of an activated carbon fiber cloth, and FIG. 3 is a sectional view showing an example of the electric double layer capacitor of the present invention. , FIGS. 4a and 4b are a plan view and a sectional view showing another embodiment, and FIG. 5 is a partially sectional front view of still another embodiment. 1... Polarizable electrode, 2... Current collector, 3...
...Section silator, 4,14...Case, 5...Sealing plate, 6゜16...Gasket, 7...Activated carbon fiber , 9... conductive layer,
1Q... Current collector plate, 11... Polypropylene separator, 12... Film sheet, 1
3...Lead, 15...Sealed Robano King. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4 (Q)

Claims (6)

[Claims] (1) The thickness is 400 μm or less and the density is 0.1 g/c, made by the papermaking method using a polarizable electrode and a bulb as a coupling medium.
An electric double layer that uses paper-like activated carbon fibers of m^3 or more and has a structure in which a conductive layer is formed on at least one side of a polarizable electrode, these are opposed to each other via a separator, and an electrolyte is injected. capacitor. (2) The electric double layer capacitor according to claim 1, wherein the binding medium accounts for 50% or less by weight of the polarizable electrode without a current collector. (3) The electric double layer capacitor according to claim 1, wherein the conductive layer formed on at least one side of the polarizable electrode is in contact with a conductive case or a current collector. (4) The activated carbon fibers constituting the polarizable electrode have a specific surface area of 1500 m^2/g and a pore volume of 0.5 cc/g or more by the BET method, obtained by carbonizing and activating a phenolic resin. The electric double layer capacitor according to claim 1, characterized in that: (5) A patent claim characterized in that the activated carbon fiber constituting the polarizable electrode has a specific surface area of 600 m^2/g or more by the BET method, obtained by carbonizing and activating polyacrylonitrile resin or rayon fiber. The electric double layer capacitor according to item 1. (6) Claim 1, characterized in that the binding medium for the activated carbon fibers constituting the polarizable electrode is an acrylic resin or a synthetic resin such as polyethylene terephthalate.
The electric double layer capacitor described in Section 1.