JPH0216711A - Manufacture of electric double-layer capacitor - Google Patents

Abstract

PURPOSE:To obtain a thin capacitor having a large capacitance by a method wherein paper-type current collectors containing fibroid conductive material and organic binder are bonded to polarizing electrodes or outside connection current collectors, or provided between them and bonded to them. CONSTITUTION:PAN graphite fibers having a fiber diameter of 20mum and a fiber length of 5mm are used as fibroid conductive material 10a and polypropylene is used as organic binder 10b. The graphite fibers are processed into paper with the binder by a paper machine and the conductive material 10a is uniformly dispersed in the binder 10b and the paper is molded by compression to form a paper type current collector film 10 with a thickness of 50mum. The collector films 12 and 12' are put on polarizing electrodes 11 and 11' respectively and bonded to them by compression under a temperature of 130 deg.C and a pressure of 500kg/cm<2> to form a pair of compression-bonded units 13 and 13'. The polarization electrode sides of the units 13 and 13' are made to face each other with a porous separator 14 made of polypropylene between. The compression-bonded units 13 and 13' and the porous separator 14 are impregnated with electrolyte and housed in a stainless steel container 15 which is also used as outside connection current collectors and the container 15 is sealed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing an electric double layer capacitor in which a current collector is provided between a polarizable electrode and a metal current collector for external connection.

[Conventional technology]

Electric double-layer capacitors have a capacitance per unit volume that is several thousand times higher than that of conventional capacitors, so they can function as both a capacitor and a battery, and for example, they can be used as an application for the latter. It is used as a backup power source.

An electric double layer capacitor, for example, as shown in Fig. 5,
A polarizable electrode 2.2 is made of activated carbon fiber or made of a kneaded molded product of activated carbon, carbon blank, and binder (e.g., tetrafluoroethylene emulsion) through a non-electron-conducting and ion-permeable porous separator 1. It is known that a conductive current collector of 3.3° is formed on the top by thermal spraying or vapor deposition of a metal such as aluminum, and these are housed in a metal case 4, which has a large capacitance on the order of farads. can have.

Further, as shown in FIG. 6, a pair of polarizable electrodes 6.6° made of a layer made of activated carbon or the like impregnated with an electrolytic solution is provided on a gasket 8.8" facing each other with a porous separator 5 in between. An electron conductive current collecting electrode 7.7' made of conductive rubber such as conductive butyl rubber containing a carbon blank was provided on each of these polarizable electrodes to form a basic cell, and this basic cell was sealed. Those having a structure are also known.

Incidentally, recent electronic devices are required to have high density and high performance due to their small size and light weight, and there is a strong demand for electric double layer capacitors that are components of these devices to be thin and large in capacity.

[Problem to be solved by the invention]

In response to these demands, a conventional electric double layer capacitor with a structure in which a collector electrode is formed by thermal spraying aluminum as shown in Fig. 5 has a structure in which the aluminum metal layer of the collector electrode is
00 to 200 μ-, and therefore, when trying to create an electric double layer capacitor element with a certain thickness or less, the polarizable electrode.

The thickness must be reduced, which creates the problem of reducing capacitance. In addition, when the current collecting electrode made of an aluminum metal layer is created by aluminum vapor deposition or sputtering, the thickness is 5,000 or more.
It is possible to make the polarizable electrode as thin as 1 μm, making it possible to increase the thickness of the polarizable electrode, which is preferable from this point of view. If this is done, the current collecting electrode layer will undergo a chemical reaction, the aluminum layer will disappear, the internal resistance will increase, and the problem will arise that the amount of current that can be taken out will be reduced.

In addition, the current collecting electrode using the conductive rubber sheet shown in FIG. swells or
Melting increases the internal resistance, causing the problem of reducing the amount of current that can be taken out. Using an aqueous electrolyte such as sulfuric acid does not cause this problem, but from the perspective of reducing the contact resistance between the activated carbon powder of the polarizable electrode and the current collecting electrode made of conductive rubber, the current collecting electrode Normally, polarizable electrodes are sealed by compressing them, so if the thickness of the conductive rubber sheet is made too thin, the mechanical strength cannot be maintained, and making the sheet thinner is not recommended from a reliability point of view. There's a problem.

An object of the present invention is to obtain a thin, large-capacity electric double layer capacitor by making it possible to use a current collector that can be made thin while maintaining mechanical strength.

Furthermore, by selecting materials, it is possible to use a current collector that undergoes little chemical change and is not attacked by electrolyte, thereby obtaining an electric double layer capacitor with stable operating characteristics.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention provides at least one of the following features: An electric double layer capacitor that has a current collector for external connection, and a paper-like current collector containing a fibrous conductive substance and an organic binder is provided between the polarizable electrode and the current collector for external connection. The current collector of the paper-like body is adhered to at least one of the polarizable electrode and the external connection current collector by applying pressure (including thermocompression bonding), or the current collector of the paper-like body is An object of the present invention is to provide a method for producing an electric double layer capacitor, characterized in that the polarizable electrode and the current collector for external connection are provided by pressurizing and adhering the polarizable electrode and the current collector for external connection.

At this time, by selecting the material, it is possible to create a current collector that undergoes little chemical change and is not attacked by electrolyte, and by using this, it is possible to obtain an electric double layer capacitor with stable operating characteristics.

Next, the present invention will be explained in detail.

The conductive materials used in the present invention include Au, Cu,
Copper group such as Ag, platinum group such as pt, Ir, Ru, Pd,
Iron group metals such as N5sFe, stainless steel, A j! s Ta
s Nb1T11Zr, W1MO, etc., valve metals, alloys, or mixtures thereof, and SnO2
, RuO2, and other metal oxides alone or in mixtures. Further, conductive polymers such as rayon, polyacrylonitrile, phenol, carbonized or graphitized products such as fused polycyclic compounds such as coal tar pitch, polyaniline, and polythiophene may be mentioned. These are used in the form of fibers, and may be used alone or in a mixture of two or more.

Among these, when an aqueous electrolyte such as sulfuric acid is used, metal materials are likely to corrode and generate gas, so it is preferable to use fibrous carbonized materials of non-metallic materials.

The above-mentioned conductive substance is bound by an organic binder, and examples of this organic binder include cellulose, polypropylene, 6
Polyamides such as nylon, 6,6 nylon, and 6°lO nylon, polyesters, polyethylene, polyolefins other than those mentioned above, thermoplastic resins such as fluororesins such as tetrafluoroethylene alone or copolymers with others, or phenol;
Examples include single thermosetting resins such as epoxy and polyester, or mixtures thereof, modified products thereof, and natural fibers such as Manila hemp.

To bond the conductive substance with the organic binder,
For example, a conductive substance is dispersed in a solvent such as water together with an organic binder, this dispersion is made into paper using a paper machine, and this is further bonded under pressure to form a paper-like product in which the conductive substance is uniformly dispersed in the organic binder. A current collector for the body is formed, and this is bonded to, for example, an external connection current collector or a polarizable electrode under pressure to be integrated into a composite. Alternatively, the paper-like current collector may be interposed between the polarizable electrode and the external connection current collector, and the current collector may be bonded by applying pressure.

Pressure to form these paper-like bodies and composites is applied not only at room temperature but also when heated.The thickness of the current collector of the paper-like bodies is 5.
~200μ- is preferred, and 10-100μ is particularly preferred.

In this way, the paper-like current collector is provided between the polarizable electrode and the external connection current collector when assembling the electric double layer capacitor, but it may also be provided only on one of these.
It may be provided for both. The current collector provided in this way is conductive and can function as a current collecting electrode, but a separate current collecting electrode may be interposed, and in this case, the current collecting electrode is A current collector may be provided. As the current collector for external connection, a metal plate, conductive rubber, flexible graphite treated to be impermeable, etc. can be used.

As the polarizable electrode of the electric double layer capacitor of the present invention,
Activated carbon, electrolyte, etc. are contained, and activated carbon is made of synthetic polymer materials such as resol-type phenolic resin, resol/novolac-type phenolic resin, modified phenolic resin, rayon, polyacrylonitrile, pyrolytic resin, and 7-thi-based resin. Spherical, amorphous, fibrous, etc., coconut shell,
Activated carbon made from natural polymeric materials such as sawdust and coal may also be used.

In addition, the electrolyte includes esters such as propylene carbonate and T-butyrolactone, nitriles such as acetonitrile, halides such as chloroform, ketones such as acetone, amides such as dimethylformamide, amines such as pyridine, etc. Ethers such as tetrahydrofuran,
ClO4, BF4- PF6- AsF6, AlC in solvents such as alcohols such as butanol, nitro compounds such as nitromethane, and sulfur compounds such as dimethyl sulfoxide.
Lithium salts and other metal salts such as l4″, cp3so;
Examples include, but are not limited to, those obtained by melting an alkyl ammonium salt, an alkylphosphonium salt, or a mixture thereof, and an electrolyte solution such as an aqueous solution of an acid, an alkali, or a salt can also be used.

In addition, conductive substances such as carbon black and graphite, and binder resins such as acrylic, vinyl, cellulose, polyamide, polyester, and polytetrafluoroethylene (PTFE) may also be used in the polarizable electrode.

Further, the porous separator used in the present invention may be made of polymeric materials such as cellophane, polypropylene, and polyethylene, and natural fibers.

To manufacture the electric double layer capacitor of the present invention, for example, the above binder resin is heated and dissolved in an electrolytic solution, and the binder resin is heated as it is or cooled to form a gel state (a solid state that does not flow or deform unless force is applied), and then activated carbon, A polarizable electrode can be created by adding a conductive substance, or by simultaneously adding a resin, an electrolyte solution, activated carbon, and a conductive substance and kneading the mixture using, for example, a triple roll, or by combining the above binder resin, activated carbon, and conductive substance. After mixing to form a molded body, it is impregnated with an electrolytic solution to create polarizable electrodes, and the above-mentioned paper-like current collector is placed between these polarizable electrodes and the current collector for external connection. It is adhered as described above and assembled together with the porous separator into a predetermined structure according to a conventional method. Alternatively, a polarizable electrode and a porous separator are assembled, and the paper-like current collector is sandwiched between the polarizable electrode and an external connection current collector, and pressure is applied. In this case, heating can also be used. In addition, polarizable electrodes made by impregnating activated carbon, 30% H2S04 (sulfuric acid), etc. in a pair of gaskets made of plastic or rubber such as polypropylene are placed facing each other with a porous separator interposed therebetween, and the gaskets and paper-like material are separated. The current collector is pressure-bonded, or a paper-like current collector is pressure-bonded to the external connection current collector, and then assembled into a predetermined structure. Note that pressure bonding also includes the case of heating.

The electric double layer capacitor of the present invention includes not only a structure having polarizable electrodes on both sides of a porous separator and a current collecting electrode on each polarizable electrode, but also a structure in which a polarizable electrode is provided on one side of the porous separator. It also includes one in which the polarizable electrode and the porous separator are each provided with a current collecting electrode.

Function: Since the current collector of the paper-like material is adhered to the polar electrode, the external connection current collector, or a pressure bond between them, the contact at the interface is sufficiently good, and the contact electrical resistance at the interface is reduced. Not only can it be made smaller, but the contact area of the fibrous conductive material entangled inside the paper-like current collector can also be increased, making it possible to reduce the internal electrical resistance.

Furthermore, by compressing the organic binder, the density of the structure increases, and the mechanical strength of the current collector itself increases, allowing it to be made thinner. Furthermore, for example, carbonized fibers and Manila hemp are chemically stable and are not affected by electrolytes.

〔Example〕

Next, embodiments of the present invention will be described based on FIGS. 1 to 4.

Example 1 P with a wire diameter of 20 μm and a length of 511 as a fibrous conductive material
AN graphite fiber (graphitized polyacrylonitrile) is made with an organic binder of polypropylene in a paper machine,
As shown in Fig. 2, a paper-like material (PAN graphite fiber 80 g/m, density 0.7 g) is made by uniformly dispersing the conductive substance 10a in an organic binder and press-molding the paper to a thickness of 50 μm.
/ crj ) current collector film 10 is created. In addition, spherical activated carbon obtained by carbonizing spherical phenol, carbon powder (10:1 ratio), and tetrafluoroethylene resin are kneaded and formed into a sheet to form a polarizable electrode (diameter 1ofl, thickness 0.4m).
Create.

As shown in FIG. 1, the polarizable electrode 11. obtained above is shown.
A pair of crimped bodies 13.13゛ were made by stacking the current collector films 12 and 12 degrees obtained above on 11゛ and crimping them at 130°C and 500 Kg/a+1. They are made to face each other with a separator 14 in between. Add to this an electrolyte (a 0.5 molar propylene carbonate solution of tetraethylammonium perchlorate).
was injected into the stainless steel container 15 which also served as a current collector for external connection, and the container was sealed.

In this way, an electric double layer capacitor 16 having a cell thickness of 1.3 mm is obtained, which is connected to sample terminals 17 and 18 of the measuring circuit shown in FIG. In this state, the switch SW is connected to the terminal 19 side, and after reaching 2.4V, the voltage is switched to constant voltage charging, and the sample is charged for 30 minutes. Thereafter, the switch SW was switched to the terminal 20 side, and a constant current was discharged at 5 mA as shown in FIG. The time T2 at which OV is reached is measured. Calculate the capacitance from these measured values using the following formula. In addition, the electric double layer capacitor obtained above was heated at 70°C and 500°C.
After leaving it for a while, determine the capacitance in the same manner as above, calculate the rate of change in the capacitance, and show the results in the table, where 22 is the power supply, 23 is the ammeter, and 24 is the variable resistor. It is.

0.5 However, C: Capacitance (Farad) i: Current (Aa+p) 71, T2: Time (minutes) In addition, the electric double layer capacitor obtained above can be used as a commercially available LCR.
Using a meter (YHP 4274A), IKIIz, 1
0 mA, equivalent series resistance (initial internal resistance) at room temperature and applied voltage of 2.4 V at 70°C, charging and discharging for 1000
The rate of increase in the equivalent series resistance after repeated cycles with respect to the initial value was determined and the results are shown in the table.

Examples 2 to 4 Electric 2 mm capacitors were produced in the same manner as in Example 1, except that the thicknesses of the conductive fiber material, organic binder, and current collector sheet were as shown in the appropriate columns of the table. These were also measured in the same manner as in Example 1, and the results are shown in the table.

Examples 5 to 7 Current collectors obtained in the same manner as in Example 1, using stainless steel fiber coated with SnO211 as the fibrous conductive material and using the organic binder as shown in each column of the table. The body sheet was pressure-adhered on the external connection current collector of the anode side stainless steel container in the same manner as in Example 1, and the current collector sheet was similarly formed using the conductive substance and organic binder shown in each column of the table. A polarizable electrode was prepared in the same manner as in Example 1 by adhering it to a stainless steel container on the negative electrode side under pressure, and using fibrous activated carbon as the activated carbon of the polarizable electrode. The results were measured in the same manner as in Example 1, and the results are shown in the table.

Note that the pressure adhesion of the phenolic resin as the organic binder in Example 6 was carried out at 180°C and 500 kg/-, and the organic binder in Example 7 was made of Manila hemp with a small amount of polyethylene added.

Example 8 A current collector film was produced in the same manner as in Example 1, except that the organic binder of the current collector sheet was replaced with polyethylene. As shown in Figure 6, 30% H2 is placed in insulating polypropylene gasket rings facing each other through a separator.
Polarizable electrodes are formed by storing a paste containing SO4 electrolyte, coconut shell activated carbon, and carbon black, and the above-mentioned current collector film is applied to these polarizable electrodes, and an epoxy resin adhesive is used to connect the current collector film gasket and the separator. The results of measurements performed on the sealed electric double layer capacitor in the same manner as in Example 1 are shown in the table.

Comparative Example 1 Aluminum was thermally sprayed onto a polarizable electrode prepared in the same manner as in Example 5 to form a current collector layer with a thickness of 200 μm, which was placed facing each other with a separator in between as in Example 1, and then subjected to electrolysis. Impregnate with liquid. This was placed in a stainless steel container and sealed to produce an electric double layer capacitor, and the results were measured in the same manner as in Example 1 and are shown in the table.

Comparative Example 2 An electric double layer capacitor was prepared in the same manner as in Comparative Example 1, except that an aluminum current collector layer was formed to a thickness of 1 μm by vapor deposition, and the results were measured in the same manner as in Example 1, and the results are shown in the table. .

Comparative Example 3 A pair of current collectors are prepared by kneading carbon black powder and butyl rubber to form a sheet and vulcanizing it.

As in Example 1, polarizable electrodes are placed opposite to each other with a separator in between, and are impregnated with an electrolytic solution of 30% sulfuric acid solution.

In Example 8, an electric double layer capacitor prepared in the same manner as in Example 1 except that the above current collector was used instead of the current collector film was measured in the same manner as in Example 1, and the results are shown in the table.

(Margins below this page) (In the table, nylon is 6 nylon, 6.6 nylon, 6.
10 nylon) [Effects of the Invention] According to the present invention, a current collector made of a paper-like material containing a fibrous conductive substance and an organic binder can be used as a polarizable electrode, a current collector for external connection, or a current collector for these. By applying pressure between them and adhering them, it is possible to provide an electric double layer capacitor in which the current collector is interposed between the polarizable electrode and the external connection current collector. This increases the contact area. In addition, the contact between the entangled fibers inside the current collector is large, and the contact electrical resistance and internal resistance of the current collector can be reduced, and the mechanical strength of the current collector can be increased by being compressed, so its thickness can be reduced. ,
Since the thickness of the polarizable electrode can be increased accordingly, the capacitance of the electric double layer capacitor can be increased. As a result, it is possible to provide an electric double layer capacitor element that is thin, has a large capacity, and has a small resistance change.

In addition, the current collector using a non-metallic material as the conductive substance has high reactivity with the electrolyte like aluminum (and
By using a stable organic binder in the non-aqueous electrolyte,
Even after repeated long-term charging and discharging at high temperatures, there is no deterioration in its characteristics, and it can be made to have excellent stability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an electric double layer capacitor manufactured by a manufacturing method according to an embodiment of the present invention, FIG. 2 is a sectional view of its current collector, FIG. 3 is a measurement circuit diagram, and FIG. 4 is its Operation explanatory diagram, Figure 5 is a cross-sectional view of a conventional electric double layer capacitor, Figure 6
The figure is a sectional view of another conventional electric double layer capacitor. In the figure, 11.11'' is a polarizable electrode, 12.12'' is a current collector sheet, 13.13'' is a crimped body, 14 is a porous separator, and 15 is a stainless steel container that also serves as a current collector for external connection. July 5, 1988 Figure 2 70a bb 5 Figure 3 4 Figure T. Procedural amendment (spontaneous) March 9, 1999 Commissioner of the Patent Office Yoshi 1) Indication of the Moon Yi case 1988 Patent Application No. 165836 Name of the invention Relationship to the case of a person amending the manufacturing method of an electric double layer capacitor Patent applicant 6-16-20 Ueno, Taito-ku, Tokyo Taiyo Yuden Co., Ltd. Representative Kawa 1) Mitsugu

Claims (8)

[Claims] (1) At least a current collector for external connection is provided on both sides of a structure consisting of a non-electronically conductive and ion-permeable porous separator and a polarizable electrode provided on at least one side of the porous separator. , an electric double layer capacitor in which a paper-like current collector containing a fibrous conductive substance and an organic binder is provided between the polarizable electrode and the external connection current collector; A current collector was provided by pressurizing and adhering the current collector to at least one of the polarizable electrode and the external connection current collector, or applying pressure and adhering between the polarizable electrode and the external connection current collector. A method for manufacturing an electric double layer capacitor, characterized by: (2) The fibrous conductive material is a single substance, an alloy, or a mixture of valve metal elements such as copper group elements, platinum group elements, iron group elements, stainless steel, aluminum, and titanium. The method for manufacturing an electric double layer capacitor according to claim 1. (3) The method for manufacturing an electric double layer capacitor according to claim 1, wherein the fibrous conductive material is a single substance or a mixture of metal oxides such as SnO_2 and RuO_2. (4) The electric double layer capacitor according to claim 1, wherein the fibrous conductive material is one or a mixture of rayon, polyacrylonitrile, a carbonate such as phenol, and fluorinated graphite. manufacturing method. (5) The method for manufacturing an electric double layer capacitor according to any one of claims 1 to 4, wherein the organic binder is a thermoplastic resin such as cellulose, polypropylene, polyolefin, polyamide, or polyester. (6) The method for manufacturing an electric double layer capacitor according to any one of claims 1 to 4, wherein the organic binder is a thermosetting resin such as phenol or epoxy. (7) The method for manufacturing an electric double layer capacitor according to any one of claims 1 to 4, wherein the organic binder is a natural fiber such as Manila hemp. (8) The method for manufacturing an electric double layer capacitor according to any one of claims 1 to 4, wherein the organic binder is a fluororesin made of a homopolymer or copolymer of tetrafluoroethylene.