JP2001015388A - Electric double layer capacitor - Google Patents

Abstract

(57) Abstract: Provided is an electric double layer capacitor capable of connecting cells in parallel, reducing internal resistance, and maintaining a stable connection between current collectors. A plurality of current collectors (5, 6) are connected to a connecting portion (1), respectively.
The conductive bands for the positive electrode and the negative electrode connected by the positive and negative current collectors 5 and 6 are alternately stacked by bending the connecting portions 15 and 16 to alternately stack the current collector portions 5 and 6 for the positive electrode and the negative electrode.
And a laminate structure 12 in which a plurality of polarizable electrodes 2 and a separator 3 disposed between the polarizable electrodes 2 are disposed between the current collector portions 5 and 6, respectively. The connecting portions 15 and 16 are formed to project in different directions from the side surfaces of the laminated structure 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric double layer capacitor, and more particularly to an electric double layer capacitor suitable as a high voltage power supply.

[0002]

2. Description of the Related Art An electric double layer capacitor is a capacitor using an electric double layer formed by polarization of ions at an interface between an electrode and an electrolytic solution, and has both functions of a capacitor and a battery. Compared to a large-capacity electrostatic charge and a rapid charge / discharge operation, it has attracted attention as an auxiliary power supply for a large-capacity motor, such as a small-sized memory backup power supply or a drive source for a car.

As a general example of such an electric double layer capacitor, there is a structure in which current collectors are disposed on the upper and lower surfaces of a laminate of two polarizable electrodes and a separator provided between the electrodes. As a unit cell, a plurality of the cells are stacked and housed in a gasket, and the cells are connected in series.

In the case of using a power supply requiring a high voltage, a current collector is alternately connected to a conductor layer provided on the inner wall surface of a gasket as disclosed in Japanese Patent Application Laid-Open No. 7-94374. Thus, it is disclosed that the cells can be connected in parallel.

[0005]

However, in the electric double layer capacitor having the above structure, it is possible to connect a plurality of basic cells in parallel. However, the electric current collector is disposed on the inner wall surface of the gasket. It is necessary to electrically connect to the two conductor layers, and the internal resistance increases due to the large resistance at the connection part, causing a large voltage drop when discharging a large current, Since the polar electrode expands and a large displacement occurs in the current collector, the connection state between the current collector and the conductor layer connected to the current collector may be deteriorated.

Accordingly, Japanese Patent Application Laid-Open No. 9-7893 discloses that
A current collector for positive and negative electrodes is formed by folding two conductor bands having a connection portion made of a metal foil or the like having a thickness of 20 to 50 μm at the connection portion so as to alternately overlap with each other, and forming a current collector for the positive and negative electrodes. By adopting a structure in which the connecting portion is shifted and protruded in the same direction so as not to contact, the cells can be connected in parallel, and the connection between the current collector and the conductor layer as described above is not required, It is disclosed that the internal resistance can be reduced.

However, in the electric double-layer capacitor having such a configuration, there is a possibility that the connection between the positive and negative electrode connecting portions may be in contact with each other and short-circuited when a voltage is applied. In addition, since the conductor band is made of thin metal foil and the width of the connection portion must be narrowed so that the connection between the positive and negative electrode connection portions does not contact, the connection portion is easily cracked and the internal resistance increases, In some cases, there was a risk of breaking.

The present invention provides an electric double layer capacitor in which cells suitable for an electric double layer capacitor requiring a high voltage are connected in parallel.
An object is to provide an electric double layer capacitor that can maintain a stable connection state between current collectors.

[0009]

Means for Solving the Problems The inventors of the present invention have studied the method of arranging the current collector in the electric double layer capacitor having the above-mentioned structure. As a result, two conductive bands having a connecting portion are alternately formed at the connecting portion. In an electric double-layer capacitor that is folded to form a parallel-connected current collector, the internal resistance can be reduced by projecting the connection portions for the positive electrode and the negative electrode in different directions on the side surfaces of the laminate, and It has been found that, since the width can be increased, the risk of cracks and disconnections occurring in the conductor band forming the current collector, particularly at the connection portion, is reduced.

That is, in the electric double layer capacitor of the present invention, the positive and negative conductive bands in each of which a plurality of current collectors are connected by connecting portions are bent, and the connecting portions are bent to collect the positive and negative current collectors. While alternately stacking the electrical parts,
It consists of a laminated structure in which a plurality of polarizable electrodes and a separator disposed between the polarizable electrodes are disposed between the current collector portions of the laminate, respectively, for a positive electrode and a negative electrode. The connecting portion may be projected in a different direction from a side surface of the laminated structure.

Here, the width of the connecting portion is not less than 0.5 of the width of the current collector, and the width of the boundary between the connecting portion and the current collector portion is equal to the width of the current collector portion. The number of the connecting portions is formed between the two current collector portions, between the positive current collector portion and the negative electrode connection portion, and the negative electrode. It is desirable that an insulator is provided between the current collector portion for the battery and the connecting portion for the positive electrode.

[0012]

FIG. 1 is a schematic sectional view showing an example of an electric double layer capacitor according to the present invention. According to FIG. 1, the electric double layer capacitor 1 has a positive electrode current collector 5 on one surface of a laminate 4 in which a separator 3 is provided between two positive and negative polarizable electrodes 2a and 2b. The negative electrode current collector 6 is provided on the other surface.

According to FIG. 1, the positive electrode current collector 5, the laminated body 4, and the negative electrode current collector 6 are regarded as one unit of cell 7, and a laminated structure 12 in which a plurality of cells 7 are laminated is provided. Are formed and housed in the gasket 8. Further, pressing plates 10 and 11 are disposed on the upper and lower surfaces of the laminated structure 12, and are fixed by the fixing member 9. , 11.

A connecting portion 1 is provided between the positive electrode current collector portions 5 and 5.
5, the collectors 6 and 6 for the negative electrode are connected continuously by the connecting portion 16, and the cells 7 are connected in parallel. FIG.
In FIG. 5, only the connecting portion 16 arranged on the front side of the drawing is shown, and those arranged on the back side of the drawing are omitted.

According to the present invention, FIG. 3 is a schematic perspective view showing a part of the assembling process of the main part, and the positive electrode current collector part 5 and the connecting part 15 as shown in FIG. Are formed by conductive bands alternately formed, and similarly, the patterns of the current collector 6 for the negative electrode and the connecting portion 16 are formed by conductive bands alternately formed. Are bent at the connecting portions 15 and 16, and the positive electrode current collector portions 5 and the negative electrode current collector portions 6 are superposed while sandwiching the cells 7 so as to be alternately stacked via the cells 7. However, a significant feature is that the two conductive bands are arranged so as to be different in direction so that the connecting portions 15 and 16 project from different directions of the side surfaces of the stacked body 4 and overlap each other.

In FIG. 1, the positive electrode connecting portion 15 protrudes in two opposing directions from two opposing side surfaces of the laminated structure 12 having a rectangular shape, and the negative electrode connecting portion 16 opposes from the other two side surfaces. A straight line protruding in two directions and connecting the two protruding portions of the positive electrode connecting portion 15 and a straight line connecting the two protruding portions of the negative electrode connecting portion 16 are perpendicular to each other.

With this configuration, the connecting portions 15 and 16 do not come into contact with each other and short-circuit, and the connecting portions 15 and 1 are not short-circuited.
6 can be widened, and the mechanical strength of the connecting portion is improved, so that stable electrical connection can be maintained.

Further, according to FIG. 1, contact portions between the current collector 5 and the connection portion 16 and between the current collector portion 6 and the connection portion 15 are provided on the protruding side surfaces of the connection portions 15 and 16 on the outer peripheral side surface of the laminate 4. In order to prevent the current collector from being connected to the connecting portion to include the side of the current collector, and if necessary, the insulator over the side of the laminate located on the upper and lower surfaces of the current collector 18 are provided. An electrolyte injection port 20 is formed in the gasket, and is sealed by a sealing member 21.

More specifically, each portion in the electric double layer capacitor 1 will be described. The polarizable electrode 2 has a structure in which an activated carbon-containing structure containing activated carbon is impregnated with an electrolytic solution. The activated carbonaceous structure constituting the polarizable electrode 2 is provided with activated carbon particles having a high specific surface area, and is blended as a binder for binding the activated carbon particles, and comprises a carbon component subjected to a carbonization treatment. It is desirable to become. Further, in order to obtain the necessary strength as a structure while maintaining the high capacitance of the capacitor, the specific surface area of the polarizable electrode 2 is desirably 1000 to 2500 m ² / g.

The carbon component added as a binder is present between the activated carbon particles, but preferably accounts for 5 to 50% by weight of the activated carbon layer, thereby increasing the binding between the activated carbon particles. Thus, the shape retention of the structure can be improved.

Furthermore, the polarizable electrode 2 is desirably plate-shaped, and its shape is not particularly limited, such as a rectangle or a circle. In order to increase the mounting density of the device, a rectangular shape is desirable.

The thickness of the polarizable electrode 2 is desirably 1.5 mm or less, particularly 0.5 mm or less, since the capacitance increases as the distance between the current collectors of the capacitor decreases. JISR1 in terms of mechanical reliability that can withstand vibration and shock during handling and use
The three-point bending strength at room temperature according to 601 is 300 gf
/ Mm ² or more, particularly preferably 600 gf / mm ² or more.

As the electrolytic solution impregnated in the polarizable electrode 2, an aqueous solution such as sulfuric acid or nitric acid, propylene carbonate,
γ-butyrolactone, N, N-dimethylformamide,
An organic solution containing an organic solvent such as ethylene carbonate, sulfolane, and 3-methylsulfolane and an electrolyte such as a quaternary ammonium salt, a quaternary sulfonium salt, and a quaternary phosphonium salt can be used.

The separator 3 is formed of at least one selected from an organic film of pulp, polyethylene, polypropylene or the like or a glass fiber nonwoven fabric and ceramics, and is formed to insulate the polarizable electrodes 1 and 2 from each other. However, it is formed of a porous material capable of transmitting ions in the electrolytic solution contained in the polarizable electrode.

On the other hand, the current collectors 5 and 6 are made of conductive butyl rubber having conductivity, aluminum foil, stainless steel, metal fiber,
The polarizable electrodes 2a, 2a are formed of a carbon material or the like.
Although electric charges are exchanged between the electrodes b, it is desirable to use a metal having high corrosion resistance to the electrolytic solution. As the electrolyte,
It is desirable to use an organic electrolytic solution having a high decomposition voltage, and the organic electrolytic solution also has an advantage that deterioration of a metal such as an aluminum foil can be suppressed as compared with an aqueous electrolytic solution. The thickness of the current collector is preferably thin in order to prevent the current from flowing in the thickness direction of the current collector and increasing the internal resistance due to the resistance of the current collector, but in consideration of damage due to handling during assembly and the like. It is desirably about 0.01 to 0.30 mm.

As shown in the schematic diagram of the current collector portion and the conductive band having the connection portion in FIG. 4, the connection portions 15 and 16 are formed by continuously or stepwise increasing the width of the connection portion at the boundary with the current collector portion. (A) a method of tapering a boundary portion between the connection portion and the current collector portion,
(B) a method in which a boundary portion between the connection portion and the current collector portion has a curved portion having a curvature radius R of 0.5 to 2 mm, for example;
Thereby, it is possible to suppress the occurrence of cracks particularly at boundaries where cracks are likely to occur. Further, two or more connecting portions may be formed as shown in (c), so that even if one of the connecting portions is disconnected, electrical connection can be maintained by the remaining connecting portions.

Further, when the laminate 4 is disk-shaped,
A circular current collector portion and a connecting portion as shown in FIG.

The pressing members 10 and 11 function to press and fix the stacked cells 7 from above and below, but are preferably made of a highly rigid metal plate in order to make the pressing stress uniform. Further, as shown in FIG. 1, the pressing members 10 and 11 may be a conductive metal plate or the like having a function as a connection electrode to an external circuit.

At four corners of the pressing members 10 and 11, through holes are formed through the pressing members 10 and 11 and the gasket 8. A fixing member 9 is inserted into the through holes. The plurality of stacked cells 7 and the pressing members 10 and 11 can be pressed and held by the fixing member 9 and caulked. Further, as the fixing member 9, there are methods such as screwing or injecting a resin into the through hole, and then curing and shrinking the resin.

Further, the gasket 8 prevents the electrolyte impregnated in the polarizable electrode 2 from leaking to the outside,
A non-conductive material for protecting the cell 7;
For example, it is formed of plastic such as polypropylene or acrylic, glass, ceramics, or the like.

The connecting portion 15 on the outer peripheral side surface of the laminate 4
The insulator 18 formed on the protruding side surface 16 to prevent contact between the current collector portion 5 and the connecting portion 16 and between the current collector 6 and the connecting portion 15 has high insulating properties and relaxes against stress. An elastic material that can be used is preferable. For example, the elastic material is made of silicone rubber, urethane rubber, or the like, and may be adhered and fixed with an insulating adhesive.

In FIG. 1, the cell 7 has a rectangular shape, but the present invention is not limited to this.
The cell 7 may be circular, in which case the connection 15,
16 are formed in two opposing directions, and in this case, the angle at which the straight line connecting the two connecting parts 15 and 15 and the straight line connecting the two connecting parts 16 and 16 intersects with each other. It may be formed smaller than 90 °.

[0033]

EXAMPLE A polyvinyl butyral (PV) was used for 100 parts by weight of an activated carbon powder sample having a BET value of 2000 m ² / g.
B) was mixed with 50 parts by weight and stirred with a high-speed mixing stirrer,
After the obtained powder was subjected to a mesh pass with 40 mesh, a sheet-like molded body was produced by roll molding.

Then, after forming a molded body for forming a solid active electrode by cutting the sheet into a predetermined shape, a heat treatment is performed at 900 ° C. in a vacuum to obtain 100 mm ×
A rectangular activated carbonaceous structure having a rectangular shape of 50 mm and a thickness of 0.5 mm was produced.

On the other hand, a current collector 1 of 100 mm × 50 mm
A conductive band made of aluminum foil having a thickness of 50 μm in which connecting portions having a width of 50 mm and a length of 6.5 mm are arranged between the six pieces;
A width of 50 mm x between 16 current collectors of mm x 100 mm
A conductive band made of aluminum foil having a thickness of 50 μm and having a connecting portion having a length of 6.5 mm is prepared, and the two conductive bands are vertically arranged so that the current collectors overlap each other. , The above-mentioned solid activated carbonaceous structure, a separator made of polyolefin-based papermaking, and a laminate made of the above-mentioned solid activated carbonaceous structure were arranged.

Then, the above-mentioned two conductive bands are laminated on the surface of the current collector for the positive electrode, and the connecting portion of the conductive bands for forming the current collector for the negative electrode is formed into an arc. After being bent so as to draw, the negative electrode current collector was laminated on the upper surface of the laminate. Similarly, the laminate is laminated on the surface of the negative electrode current collector, and the conductive band connecting portion for forming the positive electrode current collector is bent so as to draw an arc, and the positive electrode current collector is formed. The body was laminated on the upper surface of the laminate.

Then, this lamination is repeated in the same manner as above.
The laminated bodies were laminated so as to be a positive electrode current collector part-laminate-negative electrode current collector part-laminate. Also, a negative electrode connecting portion between the laminate and the positive electrode current collector portion so that a short circuit does not occur between the positive electrode current collector portion and the negative electrode connecting portion, and between the negative electrode current collector portion and the positive electrode connecting portion. 0.3 mm × 0.3 mm on the formation surface, and on the formation surface of the connection portion for the positive electrode between the laminate and the current collector portion for the negative electrode
A silicone rubber of × 100 mm was inserted and fixed with an adhesive.

This is housed in a plastic gasket having a through hole formed at a predetermined position, and further sandwiched between the upper and lower surfaces of the gasket by pressing members made of an aluminum plate, and screwed with bolts and nuts. The body and the current collector are fixed and integrated, and the pressure is 100 kgf / cm.
Caulked to be ² .

After this was dried at 100 ° C. in a vacuum atmosphere, 1 mol / l was supplied from an electrolyte injection port provided in a gasket.
Of tetraethylammonium tetrafluoroborate (Et ₄ NBF ₄ ) was injected into the solid activated carbonaceous structure to impregnate the electrolyte.

With respect to the obtained electric double layer capacitor,
After charging at a voltage of 3.0 V for 30 minutes, 3 mA / cm ²
When the capacitance of the capacitor was calculated by the constant current discharge method with the current of, the value was 40 F / g. Also, as a result of measuring the impedance at 1 kHz as the internal resistance, 8 m
Ω.

(Comparative Example) The width of the connecting portion between the two conductive strips in the example was 15 mm, and the two conductive strips were arranged so as to be in the same direction, and were laminated in the same manner as in the example. Except that the connection portion of the current collector portion and the connection portion of the negative electrode current collector portion are formed so as to protrude so as not to contact the same side surface of the laminate of the two solid activated carbonaceous structures and the separator. When an electric double layer capacitor was manufactured in exactly the same manner as in the example, a crack was generated at a part of the boundary between the current collector portion and the connection portion, and the capacitance was 35 F / g and the internal resistance was 350 mΩ.

[0042]

As described in detail above, in the electric double layer capacitor of the present invention, the two conductive bands for the positive electrode and the negative electrode having the current collector part and the connecting part are superimposed on each other to collect the positive electrode and the negative electrode. By forming the current collector, the cells can be connected in parallel, the connection resistance between the current collectors can be reduced, the internal resistance can be reduced, and a short circuit due to the contact between the connecting portions can be avoided. Further, since the width of the connecting portion can be increased, a crack in the connecting portion can be prevented, and stable electrical connection can be maintained. Further, by changing the width of the boundary portion between the connection portion and the current collector portion continuously or stepwise, or by forming a plurality of connection portions, cracks in the connection portion can be further reduced.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an example of an electric double layer capacitor of the present invention.

FIG. 2 is a partially enlarged view of the electric double layer capacitor of FIG.

FIG. 3 is a schematic perspective view showing one example of a manufacturing process in the electric double layer capacitor of the present invention.

FIG. 4 is a schematic view showing an example of a conductive band for forming the electric double layer capacitor of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electric double layer capacitor 2 ... Polarizable electrode 3 ... Separator 4 ... Laminated body 5 ... Positive electrode collector part 6 ... Negative electrode collector part 7 ... Cell 8 ... Gasket 9 ... Fixing member 10, 11 ... Pressure member 12 ... Laminated structure 15 ... Positive electrode connecting portion 16 ... Positive electrode connecting portion 18 ... Insulator 20 ... Electrolyte inlet 21 ... Sealing member

Continuing from the front page (72) Inventor Yuichi Hori 1-4-4 Yamashita-cho, Kokubu-shi, Kagoshima Inside Kyocera Research Institute (72) Inventor Shinya Matsuno 1-4-4 Yamashita-cho, Kokubu-shi, Kagoshima Kyocera Corporation In the laboratory

Claims (5)

[Claims] 1. A positive and negative conductive band in which a plurality of current collectors are connected by connecting portions, and a positive and negative current collector portion are alternately laminated by bending each connecting portion. An electric double-layer capacitor comprising a multilayer structure in which a plurality of polarizable electrodes and a separator provided between the polarizable electrodes are provided between current collector portions of the laminate, and each of which is for an anode and a cathode. Wherein the connecting portion protrudes in a different direction from a side surface of the multilayer structure. 2. The method according to claim 1, wherein the width of the connecting portion is 0.5 times the width of the current collector.
The electric double layer capacitor according to claim 1, wherein: 3. The current collector according to claim 1, wherein the width of the connecting portion at the boundary with the current collector is increased continuously or stepwise toward the current collector. The electric double-layer capacitor as described. 4. The electric double layer capacitor according to claim 1, wherein a plurality of said connecting portions are formed between said two current collector portions. 5. An insulator is provided between the current collector for the positive electrode and the connection for the negative electrode and between the current collector for the negative electrode and the connection for the positive electrode. The electric double-layer capacitor according to any one of claims 1 to 4, wherein