JPS6027113A - 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] Industrial Application Field The present invention relates to an electric double layer capacitor using activated raw carbon as a polarizable electrode, and is capable of higher power and rapid charging and discharging than conventional capacitors of this type. Electricity, automobiles, cameras,
It can be used in a wide range of industrial fields such as machinery and combiners.

Conventional structure and its problems The basic structure of an electric double layer canoshiter using activated carbon as a polarizable electrode is as shown in Fig. 1, in which an activated carbon layer 1 and a collector electrode 2 of this layer are used as unit polarizable electrodes. A separator 3 impregnated with an electrolyte is interposed between the pair of polarizable electrodes. Conventional configurations of this type of electric double layer capacitor include the following types, and their configurations and problems are outlined below.

The first one uses an aluminum punching metal ring as the current collector 4, as shown in FIG. The polar electrode material is mold-pressed or supported on four rolling rollers, a pair of current collectors and polarizable electrodes are wound through a separator 3, and an electrolytic solution is injected.

In polarizable electrodes manufactured using such current collectors, the metal current collector and activated carbon electrode are basically only in physical contact, and in particular, polarizable electrodes manufactured by winding the polarizability into a spiral structure are , stress is applied to the activated carbon electrode layer on the outside of the current collector and the activated carbon electrode layer on the inside of the current collector, so the contact between the current collector and the activated carbon electrode becomes weaker, and the internal resistance of the electric double layer capacitor increases. There were drawbacks such as a gradual increase in the number of active carbon electrode layers and a gradual decrease in the utilization efficiency of the activated carbon electrode layer.

The second is a polarized electrode 6, which is a cloth 7 mainly composed of N activated carbon fibers, paper, felt, etc. as shown in Figure 3, and a metal layer such as aluminum as a current collector γ on one side. It is constructed by thermal spraying, vapor deposition, etc., and a pair of polarizable electrodes are impregnated with an electrolytic solution and then separated through a separator 8.
The outer case 9 and the gas foot 10 can be configured into a coin shape.

In fact, this type of material can be wound into a spiral structure and formed into a chip-like structure as shown in FIG. 2, which is an advantageous method that allows it to be formed into any desired shape.

The disadvantage of this method is that activated carbon fibers are extremely costly (approximately 1
Since the fiber diameter is small, the electric resistance is large and current cannot flow through it.

Therefore, charging takes a long time, and discharging can only be performed with a weak current.

The third method is to activate carbonize glassy graphite and use it for polarizable electrodes. The problem with this method is that it is extremely difficult to synthesize glassy carbon, takes a long time, and since glass carbon is not currently produced in the world, it is even more costly than the fiber method. Because it is difficult to process into any shape, electric double layer canopies using this method have not yet been manufactured.

OBJECTS OF THE INVENTION It is an object of the present invention to provide an electric double layer carrier in which a polarizable electrode made of activated carbon is low in cost and is capable of providing a large amount of electricity.

Structure of the Invention The present invention is characterized in that a phenolic resin molded sheetra, which is mainly composed of a powdered phenol resin having thermal fusibility, is directly carbonized and activated carbonized and used for a polarizable electrode.

Description of Examples The basics of the present invention are to obtain a molded body in the form of a film or sheet using a powdered phenolic resin with heat-fusible properties and high molecular weight, and to directly carbonize this phenolic resin molded body. It is activated carbonized and used for polarizable electrodes of electric double layers.

The characteristics of this phenolic resin will be explained in detail later, but the phenol sheet obtained from heat-fusible powdered phenol has a lower three-dimensional crosslink density than the phenol sheet synthesized from conventional liquid phenol (novolak and resol resin) resin. , it has flexibility, and when the phenol sheet is activated for carbonization, the gas generated by decomposition easily dissipates out of the sheet, so there are fewer cracks, cracks, blisters, etc. in the carbonization activated sheet, and even when carbonization is activated in sheet form, surface area is 10
00 to 2600 m2/P has characteristics that can be obtained relatively easily.

However, the mechanical strength and current collecting ability of the phenolic resin /-1. Therefore, the invention can be further improved as in the embodiment shown in FIG.

FIG. 4 is a cross-sectional view of a phenolic resin sheet reinforced with a metal substrate. Reference numeral 11 in FIG. 4a is a chopped nickel wire, and reference numeral 13 in FIG. 4 is a nickel net knitted with nickel wire. In both figures,
Reference numeral 12 denotes a phenol resin layer in which a heat-fusible powdered phenol resin used in the present invention is fused at a pressure of 200 K47 cnL for 1 s at 0°C.

In this way, the surface of the metal substrate made of a transition element is completely coated with the phenolic resin to obtain a reinforced phenolic resin sheet with the metal substrate, and this composite sheet is
Carbonization activation is performed at a temperature of 1100°C.

According to these examples, the metal substrate improves the reinforcement and flexibility of the phenolic resin in the form of a film or sheet, and after carbonization activation, the metal becomes an excellent current collector, and also works well with activated carbon. In addition to providing an extremely strong bond with the current collector, the activated carbon polarizable electrode also has improved flexibility and mechanical strength, and when the electrode is anodically polarized, the surface layer of the metal substrate is completely covered with carbon. Because of this, the anode potential can be polarized more positively than in the conventionally known method, and electrode dissolution during charging and storage is still extremely small.

When the activated carbon polarized electrode reinforced with the metal substrate obtained in this way is used as an electric double layer electrode, the internal resistance can be improved to an extremely low value compared to conventionally known electric double layer capacitors, and instantaneous charging can be achieved in an extremely short time. This makes it possible to perform instantaneous discharge.

The necessary conditions for carrying out the present invention will be explained in detail.

[Phenol resin]

Generally, phenolic resin refers to phenol formaldehyde resin, and this phenolic resin is broadly classified into novolak resin and resol resin.

However, the phenol resin mainly used in the present invention is a powdered phenol resin that has heat-fusible properties and consists of fine particles of 1 to 20 μφ. This new heat-fusible, powdered phenolic resin is described in Japanese Patent Publication No. 177011/1988 and 58
-17114 and is sold by Kanebo Co., Ltd. as Bell Pearl S.

This resin differs greatly from conventional phenolic resins in the following points.

(1) It has good storage stability and is reactive when molded or heated, either by itself or when mixed with other resins, and is thermally fused.

(2) Since the particles are spherical fine particles with a size of 1 to 20 μφ, they have good fluidity and can uniformly and completely coat the metal substrate of the present invention.

(3) Since the free phenol content is 50 ppm or less, it is safe and easy to handle, and it can be thermally fused at a low temperature of 100 to 200°C, making it extremely useful industrially.

Conventionally, cured phenolic resin products have an excessively high three-dimensional crosslinking density, making the phenol resin molded sheet hard and brittle and requiring a long time of 4 to 7 days for carbonization and activated carbonization. Such heat-fusible phenolic resin molded products can be carbonized and activated carbonized in 1 to 3 hours. This seems to be due to the fact that the three-dimensional crosslinking density is low, so that thermal decomposition products can be easily dissipated out of the molded sheet during carbonization.

In other words, in conventional phenol molded products, cracks and cracks occur during carbonization.
It cracked and fell apart, so even a thin sheet was carbonized over a long period of time (4 to 7 days). In order to carbonize and activate carbonize in a short time, the specific surface area of the cured phenolic resin must be increased, as with novolac fibers, otherwise cracks would occur.

When using a metal substrate, which is an embodiment of the present invention, emphasis is placed on the adhesion between the metal substrate and the cured phenol, and even after carbonization and activated carbonization, the adhesion and electrical conductivity between the metal substrate and activated carbon are important. In order to industrially produce these products in a short period of time, a powdered phenol resin having this heat-fusibility is most suitable.

However, this resin mixes well with novolac resin, resol resin, epoxy resin, furan resin, as well as paper, pulp, asbestos, wood flour, and PVA, and these mixtures can be used to improve the properties of phenolic resin sheets and activated carbon sheets. It is possible to improve the flexibility, porosity, and workability of the sheet of the present invention depending on the intended use by adding as necessary.

[Type and shape of metal base]

The role of the metal substrate used in the present invention is to strengthen the phenolic resin sheet at the resin stage and the activated carbonization stage, and to provide current collection properties. Therefore, the metal substrate is 600 to 110
Requires heat resistance of 0°C.

In addition, as a polarizable electrode, it is necessary to have corrosion resistance that can withstand an anodic polarization potential.

To meet these requirements, nickel,
The substrate must be made of a single metal made of a transition element such as chromium, cobalt, copper, titanium, tantalum, hannium, zirconium, etc. or an alloy of these metals.

In addition, the shapes of these metal substrates include thin wire net shapes,
Preferably, the shape is felt, chopped, nonwoven fabric, punched thin plate, lath wire mesh, or the like. Further, the diameter and film thickness of the thin wires constituting these substrates are also influenced by the capacity of the electric double layer, charge/discharge conditions, mass production scale, etc. The diameter of the thin wire is 5
~10oOμmφ is preferable, especially 2o~20oIin
Chopped, net, felt, and nonwoven fabrics made of φ are preferable, and the film thickness is preferably about 50 to 300 μm. The practical thickness of the foam is about 10 to 2 oolim, and the porosity is preferably in the range of 20 to 90%. Punched and lath-shaped electrodes have small polarizable electrodes and are suitable for small-capacity coin-shaped and sheet-shaped electrodes.

The weight ratio of the metal base to the resin is about 60 to 70% when using metal powder, and if it is not added, the resin will not have conductivity. However, carbonization or activated carbonization can sufficiently improve the conductivity even with a thickness of about 15 to 50 cm. However, for the purpose of the present invention, powder form, net form, chopped form, and foam form are preferable, and the addition rate of the metal base is about 15 to 50%.
It is possible to improve current collection resistance by ~3 orders of magnitude.

Next, a method for preparing the polarizable electrode of j according to the present invention will be described in detail using the aforementioned metal substrate and heat-fusible phenolic resin.

FIG. 5 is a manufacturing process diagram for implementing the present invention. First, as an example, a chopped metal substrate of 30 .mu.m.phi.

The fine nickel wire chops are pre-treated, degreased, washed and dried, and 30 parts by weight of the nickel chops are mixed with a powdered phenol resin (with thermal fusibility).
Mix Belpar S).

When mixing, since there is a difference in specific gravity, a mixer such as an omnibus is appropriate. A mixture of fine metal wire and resin is thoroughly mixed and applied to the cloth. Press condition id180℃X1
Preferable conditions are a press pressure of about 2ooKg/crA for 0 minutes.

For the purpose of the present invention, the thickness of the molded sheet is preferably about 200 μm, so the phenol resin is cured by heat-sealing to obtain a molded film thickness of 200 pm. The phenol composite sheet thus obtained is activated for carbonization at a temperature of 600 to 11 oo'C in an inert gas atmosphere. The conditions for carbonization activation include the temperature raising conditions for carbonization activation, the amount of activation catalyst added, etc., depending on the type, film thickness, application, and shape of the phenol composite material.

As an example of carbonization activation conditions, carbonization is activated at 700°C in an argon gas atmosphere using ZnCl2 as a catalyst, and the specific surface area of activated carbon is 1500-2500C.
rl/P was obtained.

The carbonized activated carbon sheet is optionally provided with collector electrodes and lead terminals, and then cut into a desired shape and assembled to obtain an electric double layer capacitor product.

The above process is sufficient if the metal substrate is in the form of chops or flakes, but if it is difficult to fill small pores with particulate phenol because it has few pores, such as in the form of a wire mesh, nonwoven fabric, or manufacturer. Since this heat-fusible, powdered phenolic resin is soluble in methanol,
A methanol solution is prepared so that the amount of There is also a method of obtaining a desired phenolic composite sheet using powdered phenolic resin. As described above, the method for preparing the metal-reinforced phenolic resin composite sheet is arbitrarily selected depending on the type and shape of the metal substrate.

big.

In FIG. 5, the process from preparing the metal substrate to resin fusion bonding The advantages of the method of the present invention as described above are as follows.

(1) This resin is easy to carbonize.

(2) Activated carbon and collector electrode can be bonded extremely strongly, and the current collection resistance of the polarizable electrode can be reduced to 1/1o to 1/1oOo. (3) The surface of the metal base of the current collector is completely coated with carbon. This allows the anodic polarization potential to be higher than before, and also avoids anodic dissolution of the current collector during charging.

(4) Metal-reinforced phenolic resins and metal-reinforced activated carbon electrodes have flexibility and mechanical strength, and such configurations have extremely high industrial value in the continuous production of these sheets.

[Separator]

A layer is interposed between a pair of metal-reinforced polarizable electrodes to prevent mutual electron conduction, but in the present invention, a porous layer made of polypropylene, nylon, polyester, polyethylene chloride, etc. It is possible to use a porous sheet or the like.

The following margin [Electrolyte] In the examples of the present invention, a mixed solution of proprene carbonate and tetraethylammonium verchlorate is used.
When charging and discharging at a large current density, KOH, Na
It is preferable to use an electrolyte with low electrical resistance, such as OH, H2S O4.

EXAMPLE As a specific example of the present invention, 16 types of tests conducted under the conditions shown in Table 1 will be compared with a conventional meter.

First of all, Examples JI6.1 to JI3 show cases in which only a heat-sealable resin is used without using a metal substrate. AI is a case in which a sheet is produced using only a heat-sealable resin.

Carbonization activation shrinkage is about 28%, so taking that into consideration,
Approximately 28 mm so that the sheet film thickness after carbonization activation is 200 μm.
Preparation of 0 μm heat-fused phenolic resin sheets L, Z
n C12 catalyst under argon gas at 800
Carry out carbonization activation at ℃ and crack.

An excellent activated carbon sheet without blisters, deformation, etc. was obtained.

Section 2 uses novolac fiber and has a basis weight of 27o9/lr? The case where a heat-sealable sheet having a thickness of about 280 μm was prepared using the woven fabric as a base material, similar to Flat 1, is shown. A3 is about 30μ of PVA
A heat-sealing sheet was obtained by adding 10 parts of powder or granular material of m. Since the flat plate 3 can be made porous by the amount of PVA added, the time required for carbonization activation can be shortened.

In the case of 1 to 4.3 ox, only heat-sealing resin is mainly used and no metal substrate is used. Therefore, electric double layer capacitors prepared with resin sheets of size 1 to size 3 require time to charge and discharge, and are used for relatively small currents.

For short-term charging and discharging, nickel, copper, and chromium 30
Introducing a chop-shaped wire of μmφ, using nickel net, nickel foam, etc. as a metal base.

Phenol resin is heat-fusible and powdered Bell Pearl S.
based on. For sizes A4 to 7, thin metal wires and heat-fusible resin were mixed and heat-fused under the conditions described above to obtain phenolic resin sheets.

Flats 8 to 16 are made using nickel foam and nickel net. First, as mentioned above, 1 to 2
Material impregnated with phenolic resin? After that, fill the remaining porous parts with heat-sealing resin,
The phenol resin was cured by heat-sealing pressing so that the sheet had a total thickness of 200 μm.

In order to investigate the effect of adding resins other than the heat-fusible phenolic resin of the present invention, general fujin resin, novolac resin,
Products to which resol resin, nylon, etc. were added are also shown. This is the flexibility and workability of the resin sheet and activated carbon sheet film after carbonization activation.

The aim is to take advantage of the excellent overall characteristics with total cost performance, even if the characteristics of the electric double layer capacity are reduced, such as mass productivity and porosity, by adding a resin that is suitable for the intended product. can do.

The film thickness of the nickel foam is 200 μm, and when using a fine wire chop, the film thickness of the activated carbon sheet after carbonization activation is 200 μm.
00 μm.

When preparing a polarizable electrode using a phenol resin and a resin filler, the phenol resin was filled and carbonized and activated carbonized using the method detailed using FIG. 6.

The activated carbonization in Table 1 was carried out using a Z n C12 catalyst at 800°C in argon. After spot welding, a mixed solution of propylene carbonate and tetraedylammonium perchlorate was injected as an electrolyte through a polypropylene separator, and the metal case was sealed through a gasket.

The capacitance, internal resistance, and high temperature load life of the button-type capacitor prepared as described above were measured, and the performance was compared with a conventional example whose rating is close to that of the example.

A conventional cylinder type example using powdered activated carbon had poor characteristics, so it was not compared. Since this type of capacitor using glass carbon is not yet commercially available, it was not possible to make a comparison.

From the results in Table 1, it can be seen that all of the inventive examples shown in A1 to A16 have the same or higher polarizable electrode capacity, and are significantly different from the conventional method, especially in terms of internal resistance and high-temperature load life. It can be seen that it is effective. According to the present invention, the bond between the current collector and the resin is extremely excellent, and in order to carbonize and activate carbonize the current collector, the current collector is almost completely coated with carbonaceous material, so when used as a polarizable electrode, Because it behaves almost exactly as if it were a highly conductive carbon electrode, it exhibits the excellent characteristics of an electric double layer capacitor.

Thus, according to the present invention, it can be easily seen that even when an organic electrolyte is used, the internal resistance of the electric double layer capacitor is one to three orders of magnitude lower than that of the conventional capacitor.

Next, an electric double layer capacitor was adjusted using caustic force 1,1 (KOH) to enable rapid charging and rapid discharging, and its characteristics were tested.

FIG. 6 is a schematic diagram of a high-power electric double layer capacitor suitable for rapid charging and discharging, and FIG. 7 is a cross-sectional view taken along the line AA in FIG. 6. In FIGS. 6 and 7, 16 and 16 are polarizable electrodes having a film thickness of 200 μm, and have lead terminals 19 and 20, respectively.
are overlapped with a separator 17 interposed therebetween, and then sealed in a thermally welded sheet 18 having a thickness of 100 μm, and completely sealed with a seal portion 21.

As a polarizable electrode, use the one under the condition of flat 5 in Table 1 at 40
It was cut into a size of 100 mm, and 8NKOH was used as the electrolyte. The area of the polarizable electrode was approximately 40 C11f.

Charge this electric double layer capacitor at 6A for about 60 seconds,
When the battery was discharged at a constant current of 3A, the discharge was completed in about 112 seconds.

Next, constant current charging at 12A for 30 seconds and constant current discharging at 3A completes discharging in about 115 seconds.
The discharge was completed in about 59 seconds.

As described above, when an electrolytic solution with excellent conductivity such as KOH, NaOH, or H2SO4 is used, the electric double layer capacitor according to the present invention can achieve a large current density despite being an extremely small and lightweight electric double layer capacitor. This makes it possible to commercialize high-power electric double layer capacitors that can be charged and discharged at

Effects of the Invention The electric double layer capacitor according to the present invention uses, as a polarizable electrode, a molded body mainly made of a heat-fusible phenolic resin that has been activated to carbonize, and therefore can be charged and discharged at a large current density. It is suitable as a starter power supply for starting liquid fuel in automobiles and machinery, and is also ideal for applications such as instantaneous large power discharge when driving the motor of fully automatic cameras and portable cameras.

It has great industrial value and is expected to be applied in all industrial fields such as machinery, cameras, electricity, and computers.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the basic configuration of an electric double layer capacitor, Figure 2 is a perspective view of an example of a conventional double layer capacitor, and Figure 3 is another example of a coin type double layer capacitor. 4 is a cross-sectional view of a metal-reinforced phenolic resin composite material according to an embodiment of the present invention; FIG. 6 is a manufacturing process diagram for implementing the present invention; FIGS. 6 and 7 are 1A and 1B are a plan view and a cross-sectional view of a portion thereof, respectively, of a sheet type electric double layer capacitor for high power, which is an embodiment of the present invention. 11...Chopped metal wire, 13...Fine wire net, 12...Phenol resin, 15.
16...Polarizable electrode, 17...Separator, 18...Exterior sheet. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 5
Zuka 6 Figure 7 Figure 7 I81 B

Claims (1)

[Scope of Claims] (1) An electric double layer capacitor characterized by carbonizing a phenolic resin molded body mainly consisting of a powdered phenolic resin having heat-fusible properties and using the activated carbonized product as a polarizable electrode. . 2)) The electric double layer capacitor according to claim 1, wherein the phenol resin molded body is a phenol resin molded composite material reinforced with a substrate made of a transition metal. (3M group has a melting point of 600°C or higher, and a machine for producing transition metal-based alloy carbon electrodes made of nickel, chromium, copper, cobalt, aluminum, titanium, tantalum, hafnium, or zirconium alone or based on these metals) A modified double-layer capacitor with electrical reinforcement and polarizable electrodes with a single current efficiency. (5) The substrate made of a transition metal has a configuration of chopped fine wires, netted wires, non-woven fabric, punched thin plates, or lath wire mesh. The electric double layer capacitor according to claim 2, characterized in that the capacitor is disposed in a composite material. (6) The phenol resin molded body contains, in addition to a powdered phenol resin having thermal fusibility, General resol resin, novolac resin, polyester resin, polyacrylic resin, P
The electric double layer capacitor according to claim 1, characterized in that it contains 3 to 60% of one or more of VA, pulp, and asbestos.