JPH04206914A - Electric double layer capacitor and electrode - Google Patents

Abstract

PURPOSE:To facilitate the manufacture of apparatus, to improve characteristics thereof and to make a high capacity possible by forming a polarizable electrode through the use of an activated carbon block obtained by carbonization and activation of a resin foam and specified in bulk density and specific surface area. CONSTITUTION:A resin foam is a porous body having a cellular structure obtained by mixing, foaming and hardening a prepolymer mainly of thermosetting resin, foaming agent and hardener, which porous body forms a plate body as it is or is cut into the plate body and thereafter is carbonized by burning in a non-oxidizing atmosphere. An activated carbon block obtained by activation of this carbon porous body in the presence of an oxidizing gas is 0.1g/cm<3> or more in bulk density and 500m<2>/g or more in specific surface area. This activated carbon block is cut to a predetermined thickness in the direction of foaming, i.e., in the direction toward a counter electrode, one surface of the block is plasma-sprayed with an aluminum collector layer 2 to form a polarizable electrode 1, and a pair of such electrodes are caused to face each other, covered with a pair of electrode side cases 7 and housed via packing 6 composed of insulating material so that an electric double layer capacitor is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an electric double layer capacitor and a polarized/r11 electrode, and more specifically, using a polarizable electrode of the charcoal type; Conventional lead nj battery, Ni-Cd
The present invention relates to an electric double layer capacitor having a human capacity of 1, which can be used as a primary battery of a storage battery, and a polarizable electrode used therein.

(Prior Art) In recent years, electric knee multilayer capacitors, which can be charged and discharged at high speed over long periods of time, have been used as backup power sources for electronic devices. Examples of this type of electrode include a polarizable electrode in which a metal electrode is disposed on one side of activated carbon fiber instead of the conventional hanging metal electrode, and a polarizable electrode in which active=1<charcoal powder paste is pressed onto a conductive rubber electrode. In addition, a powdered phenolic resin having heat-fusibility is formed on a fabric made of activated carbon fibers and conductive cotton, and a substrate made of fiber metal.
There are carbonized and activated products, for example, Tokko Sho 63-1.
r1574 publication, Japanese Patent Application Laid-open No. 61-110416,
and Special Publication No. 14492, Special Publication No. 14492, Special Publication No. 63-
The one described in Japanese Patent No. 55205 is known.

Among these, the special public official publication 6:11 f15745- was published as 1
:1! As shown in Figure 1, the product listed here has a conductive electrode formed by spraying a metal such as aluminum on the surface of activated carbon fiber such as 7fi.
A composite polarizable electrode is formed by bringing the polarizable electrode having the r5 structure into surface contact with a polarizable electrode having no conductive electrode, and using this composite polarizable electrode as at least one electrode,
Electro-Φ' layer capacitors are disclosed that are opposed to each other with a separator in between.

(Problems to be Solved by the Invention and Problems to be Solved by the Invention) By the way, this fΦ electric double layer capacitor is a polarizable electrode in order to effectively draw out the electric double layer accumulated in the polarizable electrode. The electrical resistance of the activated carbon layer is low, the activated carbon is easy to collect current, the bulk specific gravity of the activated carbon is high for making liquid, and it is electrically inert. Furthermore, it is required to be low cost.

Conventionally, in order to use these conditions as a microbial extraction electrode, aluminum metal is plasma sprayed on one side of activated carbon fiber cloth, or a fabric made of activated carbon fiber and conductive 1fi wire is used. Or, a material made of fiber metal (made of powdered phenolic resin with heat-adhesive properties, carbonized, and activated) was used.

However, in cloth made of activated carbon fibers, the thickness of the polarized electrodes is necessarily the thickness that allows the material, synthetic fiber cloth, to be woven, i.e., the carbonized, atl activated thickness. , 11. It can only be shaped to a thickness of fimm culm.

Moreover, cloth made of activated carbon fibers is very expensive, has a porosity of more than 90% unless pressurized (occupies more than 60% even when pressurized), and has a large loss of space. Because of this, there is a problem that there is little contact between the fibers and the book, resulting in high contact resistance (Japanese Patent Application Laid-Open No. 63-194
3+9 Publication).

For this reason, with activated carbon fiber cloth, the contact resistance between the fibers is determined in the first step of caulking the case when used as a capacitor, and the electrical resistance of the polarizable electrode becomes unstable. There is a risk that it will happen. However, in order to avoid such inconveniences, as a method of lowering internal resistance using carbon fiber 1, fabrics with conductive cotton were used for polarizable electrodes (Japanese Patent Publication No. 14492/1983). Powdered phenolic resin made of fiber metal is molded, carbonized and activated and used for polarizable electrodes (Japanese Patent Publication No. 63-5'', > 205-inch publication) has been developed.

However, unlike 4F, although these JJ methods are effective in reducing internal resistance, they are not suitable for human body resistance due to the low content of activated carbon, and they are not suitable for reducing internal resistance. The problem of economy 1- that pressurization is expensive cannot be ignored.

In addition, as a method for manufacturing capacitors using activated carbon fiber cloth, a method has been developed in which activated carbon fiber cloths are layered and brought into surface contact to achieve horizontal composite polarization (Japanese Patent Publication No. 63). -10574 publication).

However, in this case as well, since the activated carbon fibers are in contact with each other and are in composite face-to-face contact, polarization and ['1
The problem is that the electrodes have high electrical resistance and are unstable.

The present invention has been made in view of the problems of the prior art mentioned above, and its technical object is to provide a large-capacity, @-layer capacitor that is easy to manufacture and has good characteristics.

(Means for Solving the Problems) The present invention has been proposed to solve the above problems, and is characterized by a polarizable electrode having a specific structure and an electric double layer capacitor using this polarizable electrode. That is, according to the present invention, a polarizable electrode consisting of an activated carbon block made of a carbonized and activated resin foam and having a bulk density of 0.1 g/cm3 or more]-1 specific surface area of 500 m27 g or more, Furthermore, an electric double layer capacitor characterized in that the activated carbon block is used as a polarizable electrode is provided.

Furthermore, according to the present invention, there is provided an electric quadruple layer capacitor using a polarized l-electrode having a substantially open cell structure in which the bubbles of the activated carbon block are oriented in the direction toward the counter electrode. Ru.

(Specific structure of the invention) Hereinafter, a specific example configuration of the present invention will be explained.

Resin foam Resin foams include, for example, polyurethane, phenol resin, furfural resin, epoxy resin, furan resin, polyisocyanurate resin, polyimide resin, urea resin, and biranyl resin. A porous body having a cellular structure obtained by mixing, foaming, and curing a prepolymer of a thermosetting resin such as a thermosetting resin, a foaming agent, and a curing agent is used. Among these resin foams, phenolic resins, especially resol, are preferred as prepolymers because they have a uniform cell shape, are easy to manufacture, and can be carbonized and recovered. It is preferable to use a resol-type phenolic resin foam to be used as a foam.Resols can be obtained by reacting phenols and aldehydes in the presence of an alkali catalyst according to a known method. Specifically, phenol, cresol,
Gyslenol, resorxin, etc. are used.

Specifically, the aldehydes include formaldehyde,
Acetaldehyde, furfural, etc. are used. Specifically, examples of the alkali catalyst include 1. iol,
Examples include KOII, Na011, NHl, Nl+4DH, ethanolamine, ethylenediamine, and triethylamine. As a blowing agent for obtaining a resin foam, a blowing agent of G: i or 11 can be used, but among these, it is preferable to use a G: single blowing type blowing agent. Physically, paraffin hydrocarbons such as butane, pentane, hexano, heptane, alcohols such as methanol, ethanol, butanol, halogenated hydrocarbons such as Freon 123 (dichlorotrifluoroethane), ethers, and these I can give you a mixture. In order to foam and harden resins such as resol type phenolic resins,
A curing agent is used along with a blowing agent. As this curing agent, a conventionally known curing agent is selected and used depending on the type of prepolymer. The prepolymer is resol II; 1
In the case of 4-phenol resin, specifically, inorganic acids such as sulfuric acid, phosphoric acid, and hydrochloric acid, and organic acids such as cresol sulfonic acid are used. The resin foam can be obtained, for example, by mixing a foaming agent, a curing agent, and if necessary, a foam stabilizer, a filler, etc. all at once or sequentially into the resol phenolic resin prepolymer described in 1. For example, by supplying a cream-like material into a heated metal container, wooden container, or cardboard box, or into a double-belt conveyor belt, foaming and curing it, and cutting it as necessary. 4W
I can do it. Among these, a method of supplying a creamy material into a mold and gradually foaming it at a slow rate is preferably employed. In contrast, the cellular structure of a foam that is rapidly expanded, for example on a conveyor belt, is non-uniform and does not vary in direction from one place to another.
There is a problem that the internal resistance value varies, so it cannot be suitably used for the purpose of the present invention.

In the present invention, the bulk density of this resin foam is usually 1
1.1 g/cm” VU l-2 preferably G o f1.
I7 to [18 g/e m''.

Carbonization method In order to carbonize the obtained resin foam, the foamed resin foam is carbonized by firing it in a non-oxidizing atmosphere F' after forming the foam as it is or cutting it into a plate-shaped body.

That is, under reduced pressure, Δr gas, 11 (! gas, N
2 gas, CO gas, halogen gas, ammonia gas, 1
12 gases or mixed gases thereof, preferably from 500 to 1200°C, especially from 600°C to 900°C.
Baking at a temperature of °C. In this way, the foam is carbonized and a porous carbon body is obtained. Although there is no particular limit to the rate of gastric temperature during firing, the decomposition of the resin generally begins20.
It is preferable to gradually increase the temperature between 0 and 600°C.

In the present invention, the bulk density of the carbon porous material is usually [1,
1 g/cmll or more 1 preferably (II7 to 0.8
g/cm3.

Activation Method The activated carbon block used in the present invention is obtained by 1) activating a carbon porous body subjected to 4r and 7 by the Jj method described in 11 in the presence of an oxidizing gas. Although this activated carbon block can be formed into various shapes and vines, it is preferably formed into a plate shape in the present invention. The treatment temperature is usually preferably 800 to +200°C. If the processing temperature is too low, 1. i (Katsu does not progress sufficiently, and only a small amount of 1 page ¥ can be obtained. On the other hand,
If the treatment temperature is too high, cracks will easily form in the carbon porous body.

The oxidizing gas in the present invention refers to oxygen-containing gases such as water vapor, carbon oxide, static electricity, oxygen, etc., but these gases are usually replaced by inert gases such as combustion gas, N2 gas, etc. for ease of operation. It is preferable to use it as a mixed electric material with etc. The exposure time to the oxidizing gas depends on the concentration of the oxidizing gas and the processing temperature, but it must be within a range that does not damage the 1fa state of the porous carbon material. Generally, 30 minutes to 30 hours is preferred.

Furthermore, the activation may be a chemical activation method other than the gas activation described in L, or a method (j) that uses both methods in combination. The chemical activation method is a method in which chemicals such as zinc chloride, phosphoric acid, potassium sulfide, etc. are added to the resin foam, and then heated in an inert gas atmosphere to simultaneously carbonize and activate. Activation is also performed by a method that uses both the activation method and the chemical activation method.

Activated carbon block used in the present invention The activated carbon block that can be used in the present invention has a bulk density of 0.1 g/cm31. , J, preferably o, +5
1<10m” or old 70 (z, / (: m 3,
The specific surface area is 5 fl Om 2/ +XX humans, preferably 700 m27g or more, more preferably 700 to 2
0n [1 m2/g. An activated carbon block with a bulk density in this range will have high strength and will not break even if the ratio 1r+1 product is increased? l[I. Furthermore, since the carbon matrix is continuous, it does not warp and has high strength. Therefore, it has the characteristics that it can be easily impregnated with an electrolytic solution, has low electrical resistance, and is stable.

It is particularly preferable that the activated carbon block used in the present invention has a substantially open cell structure. In other words, when an activated carbon block having a substantially open cell structure is used as a polarizable electrode, the volume per unit wall of the electrode can be increased, which has important technical significance. In the present invention, the bubble structure in the polarizable electrode (activated carbon b[-knock) is preferably used in a direction in which the bubble direction is directed toward the counter electrode.The Jj direction toward the counter electrode is defined as 60° or less with respect to the line, preferably 45° or less, more preferably L < Let
l O” VU F, HoIf++'+'fQ Mki?Flji directional Ka lF; Cyu taste the state that is being achieved.

That is, in the present invention, when the bubbles are used in a direction toward the counter electrode, a large-capacity electric double layer capacitor can be obtained because the bubble structure has communicating holes on both the inner and outer surfaces of the activated carbon block. It is something.

In the present invention, the term "substantially open cells" means that the volume of the electrolyte impregnated into the activated carbon block under the Lier atmosphere (10-' t, orr) is the spatial volume of the polarizable electrode that can be theoretically determined. 60% or more 1, preferably 80n or more [-1, more preferably 90% or more 1-] in terms of volume ratio.

The type of electrolyte used during measurement is, for example, 30% sulfuric acid (density 1.215g/cc, 25°C
), or an electrolytic solution containing 1% of propylene carbonate and 1% of tetraedylammonium tetrafluoroboric acid IH, 0 ton).

In the present invention, the open cell ratio was determined as follows.

The theoretical space volume (■1) is the body ij'1 (V
), the bulk density of the polarizable electrode (80), and the true density of activated carbon (D, c), it is calculated by the formula F.

□ = (1-AD/DC) did.

The volume of the electrolyte impregnated into the polarizable electrode (V, , ) is determined by the volume of the polarizable electrode before impregnation (Wl) and the post-impregnation type Fit (W
It is calculated from the following formula from 2'I and the density of the electrolytic solution (D, , ).

v, = (w2-W,)/D.

Therefore, the open cell ratio is It is calculated as V, /V□×100%.

In addition, the bubble direction means the direction of the major diameter of the pores formed by the foaming agent, and can be easily observed using an electron beam stirrup or the like.

Furthermore, the activated carbon block of the present invention is characterized in that it is easy to manufacture large-sized products. By simply cutting this block (preferably in the direction in which the air direction is toward the counter electrode) to a desired thickness and shape, it becomes a polarizable electrode for an electro-intermediate layer capacitor. On the other hand, when making a polarization/I'I electrode using activated carbon fiber cloth,
The fabrics must be laminated, which leads to high resistance at each point in surface contact and between fibers in point contact, and has the fatal disadvantage of unstable electrical resistance. The excellent features of the polarizable electrode of the present invention will be understood from this explanation.

That is, the present invention has excellent features in that it is possible to easily manufacture an electric double layer capacitor that has a large plane noise of polarizable electrodes, is thick, and has a high capacity.

In addition, the activated carbon book of the present invention has a high density of Y'Hi, so when manufacturing a capacitor with high capacity, the volume of the polarizable electrode can be reduced, and the size of the entire capacitor can therefore be reduced. Furthermore, since it is a strong I-ray polarizable electrode, the current collector can be used to directly apply plasma to the activated carbon block. It is extremely easy to install by surface contacting or adhesive composite of conductive materials such as metal plates, graphite plates, conductive resin plates, etc., and can be used as large-capacity storage capacitors for energy storage etc. It can be manufactured at a low cost and has extremely high industrial value.

Manufacture of electrical multi-layer capacitor Figure 2 shows an example of an electrical multi-layer capacitor using the activated carbon block according to the present invention as a polarizable electrode. For Ji,
That is, it is cut to a predetermined thickness in the direction toward the counter electrode, and an aluminum collector electrode layer is plasma-melted on one side of the cut.

Plasma spraying the activated carbon blocks of the present invention was found to be easy and to adhere firmly. Then, it is cut into a predetermined Jfa shape, degassed, impregnated with a solution in which propylene hexacarbonate borate is dissolved, and an electrolytic solution such as sulfuric acid, and a plasma-sprayed aluminum collector electrode is placed on the outside with a separator in between. By placing two polarizable electrodes facing each other, covering them with a case on one electrode side and a case on the other electrode side, and housing both cases with a gasket made of an insulating material interposed therebetween, an electric-7 A double layer capacitor is manufactured.

In addition, since the activated carbon block of the present invention has strength, the metal case can also be used as a collector electrode to easily generate electricity.
[A layer capacitor is manufactured.]

Furthermore, an electric knee multilayer capacitor can be easily manufactured by using a graphite plate as a collector electrode, placing a pair of polarizable electrodes in a polyethylene bag, and pulling out lead wires from the graphite plate.

(Example) Hereinafter, the present invention will be explained based on Examples.

Example 1 100 parts by weight of resol (phenol-formaldehyde resin prepolymer), 10 parts of para-toluenesulfonic acid as curing agent! After thoroughly stirring 1.5 parts of dichlorotrifluoroethane as a blowing agent with a high-speed mixer, the mixture was mixed with gold! l;! After pouring it into a container and putting a lid on it, leave it in an air oven at 80'C for 30 minutes to create a product with a length of 30 cm, a width of 30 cm, a thickness of 3 cm, and a bulk density of 0.
．． A plate-shaped phenolic resin foam of 3 g/cm" was obtained.

This formation F[a board is 20cm long and IOcm wide. l';sa2
．． After cutting into 50m lengths, they were placed in a Matsufuru furnace and heated under a nitrogen atmosphere. Heat the product at a vortex rate of 0°C/hour to a temperature of 600°C, maintain this temperature for 1 hour, and then cool it.
1.6cm long, 80m wide, 2cm thick, bulk density 0.2
A plate-like carbon porous body of 9H</cm3 was obtained.

Furthermore, this plate-shaped carbon porous body was heated to 95% in kerosene combustion gas.
After raising the temperature to 0℃, water vapor is introduced into this gas,
After holding for 16 hours, the mixture was cooled to obtain an activated carbon block.

The appearance, bulk density, strength, specific surface area, and open cell rate of the obtained activated carbon block were examined.

The results are shown in Table 1.

Example 2 A plate-shaped phenol resin having a bulk density of [1.4 g/cm' Bulk density n 39.</cm3
A plate-like porous carbon material and an activated carbon block were obtained. The appearance, bulk density, strength, specific surface area, and open cell ratio of the obtained activated carbon block were investigated, and the activity was shown to the first person.

(Margins below this page) Table 1 * Electrolyte used for measurement: * 130% by weight sulfuric acid (density 1.215 g/cc) *2
Thinning of brobylene carposite
Density: 1.088 g/cc) Example 3 The activated carbon block obtained in Example 1 was arranged so as to be perpendicular to the bubble direction or the cut surface of the activated carbon block, and cut into pieces with a band saw of 12 cm in length and 7.5 cm in width. , thickness 0.5 (: m,
After cutting two pieces of each, the cut surfaces were smoothed with sandpaper to form polarizable electrodes.

Next, the polarizable electrode was degassed, and the inorganic electrolyte was
Contains wt% sulfuric acid in Teikucho (10-'1.orr or less)
I turned on. A pair of polarizable electrodes impregnated with an electrolyte and a polypropylene non-woven fabric as a separator are placed opposite each other, and a lead plate is used as a current collector (opposing electrode). Surface contact was made with the outside of the electrode. The direction of the bubbles in the activated carbon block, which is the bundle and polarizable electrode, is perpendicular to the counter electrode. A lead wire was taken out from one part of the graphite plate, placed in a polyethylene bag, and then covered with Fuji 1 to form a basic cell. Furthermore, this basic cell is sandwiched between acrylic plates from both sides, and an electrician's φ-layer capacitor 414 as shown in FIG. 3 is installed.

(The capacitor was charged and discharged with a constant current until the withstand voltage IV, and the capacity and internal resistance were measured.The internal resistance was determined by charging with a constant current and discharging immediately after the ml/1 voltage reached IV.) It was calculated from the voltage drop at that time.

The results are shown in Table 2.

Example 4 The activated carbon block obtained in Example 2 was cut with a band saw to a length of 7.5 cm, a width of 2 cm, and a thickness of 0.5 cm so that the bubble direction of the activated carbon block was perpendicular to the cut surface. After cutting two sheets of each of the activated carbon blocks, an IH7 electric double layer capacitor was measured in the same manner as in Example C3 so that the air bubble direction of the activated carbon block was perpendicular to the electrodes ffi and I, and its capacity and internal resistance were measured. .

The results are shown in Table 2.

Example 5 The activated carbon block obtained in Example 2 was cut into 2 pieces each with a length of 7.5 cm, a width of 20 m, and a thickness of 0.5 cm using a bandsaw so that the bubble direction of the activated carbon block was parallel to the cut surface.
After cutting, an electric-Φ' layer capacitor was obtained in the same manner as in Example 3. In this capacitor, the activated carbon block of the polarizable electrode is in an IL row with the counter electrode. Its capacity and internal resistance were measured.

The results are shown in Table 2.

Table 2 A: 30% by weight sulfuric acid Example 6 The activated carbon block obtained in Example 2 was cut vertically with a band saw so that the bubble direction of the activated carbon block was perpendicular to the cut surface. After cutting into two pieces each 5 cm wide, 2 cm wide, and 0.5 cm thick, instead of the electrolytic solution of Example 3, as an organic electrolytic solution, propylene carbonate and tetraethylammonium tetrafluoroboric acid Iu l Ow t% were added. An electric double layer capacitor was obtained in the same manner as in Example 3, except that the added and dissolved solution was used and the voltage was changed to 3 V.
Its capacity and internal resistance were measured.

The results are shown in Table 3.

Example 7 The activated carbon block obtained in Example 2 was cut into 2 pieces each with a length of 7.5 cm, a width of 2 cm, and a thickness of 0.5 cm using a bandsaw so that the bubble direction of the activated carbon block was parallel to the cut surface.
After cutting the sheets, instead of the electrolyte in Example 3, a solution prepared by adding and dissolving 10 wt% of tetraethylammonium tetrafluoroborate in propylene carbonate was used as an organic electrolyte, and the dielectric strength was 3. An electric F layer capacitor was obtained in the same manner as in Example 3, except that charging and discharging was carried out at a constant current up to (1), and its capacitance and internal resistance were measured.

The prefectures are shown in Table 3.

(1ζ margin directly above this) Table 3 B: Provirene carbonei! - Tetraedylammonium tetrafluoroborate 1 [Contains 1wt% (Effects of the invention) According to the present invention, by using an activated carbon block obtained by carbonizing and activating a resin foam as a polarizable electrode. Since large-sized electrodes with high bulk density can be easily obtained, it has become easy to manufacture large-capacity electric double layer capacitors.

In addition, the activated carbon block of the present invention has low electric resistance and high strength because the activated carbon is three-dimensionally continuous, and has good malleability, so it is suitable for use in accommodation capacitors. It has become easier to manufacture polarizable electrodes with large surface sizes.

Furthermore, since it is made from synthetic resin, it has a low content of impurities (and is electrochemically inactive, so it
The energy storage properties can be maintained for a long time, making it suitable for energy storage.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional electric double layer capacitor, Fig. 2 is a sectional view showing an example of an electric double layer capacitor of the present invention, and Fig. 3 is an example of an electric double layer capacitor of the present invention. FIG. FIG. 4 is an electron micrograph (251'?) showing the cell structure (bubble direction) of the activated carbon block of the present invention. In the figure, 1: Polarizable electrode body 2: Conductive electrode 3: Separator 4: Polarizable electrode body 5: Composite polarizable electrode 6: Packing 7: Case 8: Screw (insulating) 9: Lead wire 1O2 lead Lead plate 1: polyethylene bag 12, acrylic plate 13: bolt-'' Ku Qtsu-ha 4th figure hand Itotori Nefu official book (method) % formula % ■, Indication of patent application 1990 Patent Application No. 338776 2 , Name of the invention Electric double layer capacitor and electrode 3゜Relationship with the case of the person who amends the patent applicant His Majesty the Patent Applicant "i T, r%2 4th attorney" 〒113 5, Date of amendment order I 1 March 12, 1991 (shipment date)

Claims (4)

[Claims] (1) The resin foam is carbonized and activated, and the bulk density is 0.
．． An electric double layer capacitor characterized in that an activated carbon block having a specific surface area of 1 g/cm^3 or more and a specific surface area of 500 m^2/g or more is used as a polarizable electrode. (2) The electric double layer capacitor according to claim 1, wherein the activated carbon block has a substantially open cell structure. (3) Claim 1, wherein the polarizable electrode is one in which the bubbles of an activated carbon block are oriented in the direction toward the counter electrode.
The electric double layer capacitor described in Section 1. (4) The resin foam is carbonized and activated, and the bulk density is 0.
．． An electrode comprising an activated carbon block having a specific surface area of 1 g/cm^3 or more and a specific surface area of 500 m^2/g or more.