JP2001284186A - Manufacturing method of polarizable electrode for electric double-layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture thin and thick polarizable electrodes that are suitable for mass production and can be manufactured with satisfactory productivity, when manufacturing the polarizable electrodes that are used for a square electric double-layer capacitor having a large capacity. SOLUTION: In this manufacturing method of the polarizable electrode for the electric double-capacitor, that uses activated carbon as an electrode material, slurry containing activated carbon powder, a heatsetting resin, and pulp is used as a raw material, production is made for manufacturing a sheet-shaped forming body, the sheet-shaped forming body is subjected to hot pressing, and an obtained sheet-shaped forming body with high density is burned in non- oxidizing atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a polarizable electrode used in a rectangular large-capacity electric double layer capacitor.

[0002]

2. Description of the Related Art An electric double layer capacitor utilizes electric energy by electric charges accumulated in an electric double layer formed at an interface between a polarizable electrode mainly composed of activated carbon and an electrolytic solution, and is rapidly charged. It has features such as being capable of discharging, having an extremely long life because it is stable against repeated charging and discharging, and having no fear of environmental pollution because harmful heavy metals are not used.

Attention has been paid to these features, and a large-capacity so-called electric double-layer capacitor for power capable of discharging with a large current in the order of milliampere (mA) to ampere has been developed. A large-capacity electric double layer capacitor is known. This square large-capacity electric double-layer capacitor has a plurality of positive electrodes including a rectangular or square sheet-shaped (plate-shaped) polarizable electrode and an aluminum positive electrode current collector, and similarly has a sheet-like shape. A plurality of negative electrodes comprising a polarizable electrode and an aluminum negative electrode collector are formed, and the plurality of positive electrodes and the negative electrodes are alternately laminated with a porous separator interposed therebetween to form an electrode laminate. The electrode laminate was impregnated with an electrolytic solution and housed in a rectangular outer case.

[0004] The applicant of the present invention has previously proposed a method of manufacturing a polarizable electrode used for such a rectangular large-capacity electric double layer capacitor (Japanese Patent Laid-Open No. 10-24200).
No. 7). The method for producing this polarizable electrode comprises a mixing step of adding a granular or powdery phenol resin and a phenol resin dispersing solvent as a binder to activated carbon powder and mixing them to form a mixture, and using the mixture as a material. A granulating step of performing granulation to produce a granulated product, a pressure forming step of press-forming the granulated product to obtain a plate-shaped molded product, and firing the plate-shaped molded product in a non-oxidizing atmosphere And a firing step. In this case, in the pressure molding step, a hot plate having a heating plate embedded with a heating element is attached to the tip using a press machine with a hot plate equipped with a pressure punch, and the granulated product is filled in a mold. The pressure molding is performed by a press machine with a hot plate.

[0005]

However, in the above-mentioned conventional method for producing a polarizable electrode, granulation is performed using a mixture containing activated carbon powder as a material, and then a granulated product is filled in a mold, and a hot plate is prepared. Since the plate-shaped molded body is obtained by performing die molding of the granular granulated product with a press machine with
The productivity of the granulation itself is low, and in order to fill the granules with a uniform thickness in the mold in the pressure molding process, the extra granulated granules raised in the mold are removed. Careful "cutting work" by hand was necessary. As described above, there is a disadvantage that it takes time and labor and productivity is poor. Further, in the conventional method, when a thin polarizable electrode is to be obtained, it is difficult to take out the plate-like molded product from the mold, and the plate-like molded product is cracked at the time of mold release. With a thickness of about 5 mm, it was difficult to produce a thinner polarizable electrode.

Accordingly, an object of the present invention is to provide a polarizable electrode used for a square-shaped large-capacity electric double layer capacitor, which can be manufactured with good productivity suitable for mass production and from thin to thick polarizable electrodes. And a method of manufacturing a polarizable electrode for an electric double layer capacitor.

[0007]

Means for Solving the Problems To achieve the above object, the invention of claim 1 (first invention) relates to a method of manufacturing a polarizable electrode for an electric double layer capacitor using activated carbon as an electrode material. Using a slurry containing activated carbon powder, thermosetting resin and pulp as a raw material, papermaking is performed to produce a sheet-shaped molded body, and then the sheet-shaped molded body is hot-pressed,
Thereafter, the obtained sheet-like high-density molded body is fired in a non-oxidizing atmosphere to produce a polarizable electrode for an electric double layer capacitor.

According to a second aspect of the present invention, there is provided the method for manufacturing a polarizable electrode for an electric double layer capacitor according to the first aspect, wherein a plurality of the sheet-like molded bodies are integrated by hot pressing. Thereafter, the obtained sheet-like high-density compact is fired in a non-oxidizing atmosphere.

A third aspect of the present invention provides a method for manufacturing a polarizable electrode for an electric double layer capacitor using activated carbon as an electrode material, wherein a slurry containing activated carbon powder, a thermosetting resin and pulp is used as a raw material. A method for producing a polarizable electrode for an electric double-layer capacitor, comprising forming a sheet-like molded body by performing papermaking, and then firing the sheet-shaped molded body in a non-oxidizing atmosphere.

In the method for producing a polarizable electrode according to the first aspect of the invention, a sheet-forming apparatus, such as a paper-making apparatus, for producing a sheet-shaped molded body has an advantage that it has high productivity and is suitable for mass production. In addition, since a mold is not used for the production of a sheet-like high-density molded body by hot pressing, there is no need to perform operations of charging and releasing the mold into the mold. Then, since the sheet-like molded body is produced by performing papermaking with a papermaking apparatus used for the production of paper, etc., a sheet-like molded body having a thickness of approximately 0.2 to 1 mm is obtained. In addition, since a plurality of the obtained sheet-like molded bodies can be integrated by hot pressing, the thickness can be reduced from a thin wall to a thick wall in a range of approximately 0.1 to 2 mm. Polar electrodes can be stably manufactured with good productivity. In the conventional method, the lower limit of the thickness was about 0.5 mm as described above.

In the production method according to the first aspect of the invention, the slurry supplied as a raw material to the papermaking apparatus includes activated carbon powder (powder activated carbon), a thermosetting resin (eg, a powdered phenol resin) as a binder, and papermaking. Is prepared by mixing pulp, which is an essential raw material for carrying out the reaction, with water, which is a solvent. The pulp is indispensable for papermaking, and enhances the mechanical strength of a sheet-like molded product as an intermediate to facilitate the handling (handling).
It also exerts the effect of increasing the mechanical strength of the polarizable electrode as the final product.

Further, in the manufacturing method according to the first aspect of the invention, by performing hot pressing, the sheet-shaped molded body can be thermoset and appropriately compressed to have a high density.
A sheet-like high-density molded article having a higher density than the sheet-like molded article obtained by papermaking is obtained. For example, a sheet-like high-density molded article having a density about 10% larger than the density (g / ml) of the sheet-like molded article can be obtained. For the hot pressing of the sheet-like molded body, for example, a press with a hot plate may be used. In a press machine with a hot plate, a hot plate in which a heating element is buried inside is pressed by a pressure punch attached to the tip, and a sheet-like molded body placed on a flat platen is hot-pressed.
A sheet-like high-density molded product can be easily obtained. At this time, the temperature of the hot plate is set to 150 to 1 in order to thermoset the thermosetting resin.
A range of 80 ° C. is preferred. Further, the pressure is preferably 29.42 MPa (300 kgf / cm ² ) or more in order to increase the density, and the pressing time may be about 5 to 10 minutes.

Further, in the manufacturing method according to the first aspect of the invention, the firing of the sheet-shaped high-density molded body in a non-oxidizing atmosphere such as a nitrogen gas atmosphere is performed by carbonizing the thermosetting resin to a predetermined degree. This is performed to electrically connect the activated carbon particles to each other by giving conductivity to this, remove impurities in the sheet-like high-density molded body, or to further densify and obtain mechanical strength. It is. Firing temperature is 8
The range of 00-1200 degreeC is good.

On the other hand, in the production method according to the second invention, unlike the production method according to the first invention, the sheet-like molding obtained by papermaking without performing hot pressing for densification is performed. The body is fired without hot pressing.
As a result, although the density of the polarizable electrode is slightly reduced as compared with the manufacturing method of the first invention, the performance is slightly reduced in terms of the capacitance per unit volume of the capacitor (unit volume) and the internal resistance of the capacitor. By reducing the number of steps, the manufacturing cost can be reduced, and an inexpensive electric double layer capacitor can be provided.

In the manufacturing method according to the second invention, unlike the manufacturing method according to the first invention, the thermosetting of the sheet-shaped molded body is performed by firing, and the firing of the sheet-shaped molded body is performed by: The thermosetting resin is heat-cured and carbonized to a predetermined degree to impart conductivity to it, thereby electrically connecting the activated carbon particles, removing impurities in the sheet-shaped molded product, and further densifying the activated carbon particles. This is performed to obtain mechanical strength. The sintering temperature is in the range of 800 to 1200, as in the production method of the first invention.
The range of ° C is good.

[0016]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically showing a filter net portion (wire part) of a circular net (paper net) type papermaking apparatus used for carrying out the present invention, and FIG. 2 is a sheet in the papermaking apparatus shown in FIG. It is a figure which shows typically a mode that a state aggregate layer is transferred on a belt made of felt.

A polarizable electrode used in a square large-capacity electric double layer capacitor was manufactured by the following procedure. First, a slurry is prepared by mixing activated carbon powder (specific surface area: 3000 m ² / g), powdered phenol resin, pulp and water using a stirring tank (not shown) provided with stirring blades. In this case, the mixing ratio of activated carbon powder / powder phenol resin / pulp was 70/20/10 by weight. As the pulp, a conductive pulp made of synthetic fiber or the like is desirable. Then, as shown in FIG. 1, the slurry 1 is supplied to the papermaking vat 2 from the stirring tank.

As shown in FIG. 1, the papermaking bat 2 is provided therein with a papermaking drum 3 which is rotated in a counterclockwise direction in FIG. This papermaking drum 3
Is rotated in a state in which the lower half thereof is immersed in the slurry 1. The slurry 1 is scooped up to the papermaking drum 3 made of a wire mesh with this rotation, and is inwardly moved from the outer peripheral portion of the papermaking drum 3 to the inside. While being filtered and dewatered, it remains on the outer peripheral portion of the papermaking drum 3 and is formed as a sheet-like laminated layer 4. Activated carbon powder formed on the papermaking drum 3;
Sheet-shaped laminated layer 4 composed of phenol resin and pulp
Is transferred onto an endless or long felt belt 5 as shown in FIG.

Sheet-like laminated layer 4 on felt belt 5
Is conveyed to a downstream side (not shown), is squeezed out of moisture in a dewatering unit (press part) provided with a squeezing roll group, and is then dried in a drying unit (dryer part) provided with a heating roll group. The sheet is peeled off from the felt belt to form a long sheet-like molded body.

In this embodiment, the thickness is 0.19 mm
The long sheet-shaped molded product of the above was cut into a rectangle, and the thickness was 0.19 m.
The required number of sheet-shaped molded articles having a size of mx 50 mm in width x 100 mm in length were obtained.

The steps up to here are common in the first and second manufacturing methods according to the present invention. Regarding the subsequent steps, first, an embodiment according to the first manufacturing method will be described.

Next, in the first production method, the sheet-like molded body was hot-pressed. That is, in the present example, the sheet-like molded body placed on the flat platen by the press machine with the hot plate was heated at a temperature of 150 ° C. × a pressure of 29.42 MPa (300 k
(gf / cm ² ) × hot pressing under the condition of 10 minutes to obtain a sheet-like high-density molded article having a thickness of 0.13 mm × width 50 mm × length 100 mm.

Thereafter, the sheet-like high-density compact is fired in a nitrogen gas atmosphere at 1000 ° C. for 2 hours.
Dimensions are thickness 0.13mm x width 50mm x length 100mm
With the above, a polarizable electrode having a density of 0.45 g / ml was obtained. Thus, unlike the conventional method in which the lower limit of the thickness was about 0.5 mm, a thin polarizable electrode having a thickness of about 0.1 mm was able to be manufactured with high productivity.

Further, since a plurality of sheet-like molded articles obtained by papermaking can be integrated by hot pressing, the thickness can be reduced from a thin wall having a thickness of less than 0.5 mm to 1 mm.
Each polarizable electrode up to the above thickness can be produced.
For example, each polarizable electrode having a thickness of 0.2, 0.35, 0.6 and 1.2 mm in addition to the above-mentioned one having a thickness of 0.13 mm was obtained.

Further, when a sheet-like molded body is produced by carrying out paper-making with a paper-making apparatus, a plurality of paper-making bats 2 each having a paper-making drum 3 are arranged in series, and the number thereof is changed. Sheet-like molded articles having different thicknesses from thin to thick can also be produced. As described above, in the first manufacturing method according to the present invention, when manufacturing a polarizable electrode used for a rectangular large-capacity electric double layer capacitor, it can be manufactured with good productivity suitable for mass production and has a thickness of about 0.1 to 0.1. It is possible to manufacture a polarizable electrode from thin to thick as in the range of 2 mm.

On the other hand, in the second manufacturing method according to the present invention,
Unlike the first manufacturing method, the sheet-like molded body obtained by papermaking is fired in a nitrogen gas atmosphere at 1000 ° C. × 2 hours without performing hot pressing for densification, A polarizable electrode having a thickness of 0.19 mm × width 50 mm × length 100 mm and a density of 0.40 g / ml was obtained.

Thus, according to the second manufacturing method, unlike the conventional method in which the lower limit of the thickness is about 0.5 mm, a thin polarizable electrode having a thickness of about 0.2 mm is manufactured with high productivity. We were able to. In addition, since the sheet-like molded body is manufactured by performing papermaking, the first
Unlike the manufacturing method of the above, although the thickness is not increased by the hot pressing of a plurality of stacked sheet-like molded articles, the thickness from the thin to the thick wall is almost in the range of 0.2 to 1 mm. Polar electrodes can be manufactured.

[0028]

As described above, according to the method for manufacturing a polarizable electrode for an electric double layer capacitor according to the first invention,
When manufacturing polarizable electrodes used in square-type large-capacity electric double-layer capacitors, using a slurry containing activated carbon powder as a raw material, the paper is formed by a paper-making machine or the like to form a sheet-like molded body, and a press with a hot plate Since the sheet-like molded body is hot-pressed by a machine or the like to produce a sheet-like high-density molded body, a polarizable electrode suitable for mass production and with high productivity can be manufactured. With this,
Since a polarizable electrode having a thickness from about 0.1 to 2 mm can be manufactured from a thin wall to a thick wall, a thin polarizable electrode is required for an electric double layer capacitor requiring low resistance performance. In the case where high capacitance performance per unit volume of the capacitor is required, a thick polarizable electrode can be used, so that the polarizable electrodes can be easily formed according to the needs.

Further, according to the method for manufacturing a polarizable electrode for an electric double layer capacitor according to the second invention, the thickness of the polarizable electrode is substantially equal to 0.1.
It is possible to manufacture a polarizable electrode from a thin wall to a thick wall as in the range of 2 to 1 mm and, unlike the manufacturing method of the first invention, performs hot pressing for densification. Instead, since the sheet-like molded body obtained by papermaking is fired without hot pressing, although the performance in terms of the capacitance per unit volume of the capacitor and the internal resistance of the capacitor is slightly reduced, The manufacturing cost can be reduced by reducing the number of steps, and an inexpensive electric double layer capacitor can be provided.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a filter net portion (wire part) of a circular net type papermaking apparatus used for carrying out the present invention.

FIG. 2 is a diagram schematically showing a state in which a sheet-shaped laminated layer is transferred onto a felt belt in the papermaking apparatus shown in FIG.

[Explanation of symbols]

1. Slurry 2. Papermaking vat 3. Papermaking drum 4.
Sheet-like laminated layer 5: Belt made of felt

Claims (3)

[Claims] 1. A method for producing a polarizable electrode for an electric double layer capacitor using activated carbon as an electrode material, wherein a sheet containing a slurry containing activated carbon powder, a thermosetting resin and pulp is used as a raw material to form a sheet-like molded body. Produced, and then hot-pressed the sheet-shaped molded body, and thereafter, the obtained sheet-shaped high-density molded body is fired in a non-oxidizing atmosphere. Manufacturing method. 2. A method in which a plurality of the sheet-shaped compacts are stacked by hot pressing to integrate them, and thereafter, the obtained sheet-shaped high-density compact is fired in a non-oxidizing atmosphere. The method for producing a polarizable electrode for an electric double layer capacitor according to claim 1, wherein 3. A method for producing a polarizable electrode for an electric double layer capacitor using activated carbon as an electrode material, wherein a sheet containing a slurry containing activated carbon powder, a thermosetting resin and pulp is used as a raw material to form a sheet-like molded body. A method for producing a polarizable electrode for an electric double-layer capacitor, comprising: producing and then firing the sheet-shaped compact in a non-oxidizing atmosphere.