JP2002190432A - Electric double-layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric double-layer capacitor that can inhibit increase in the internal resistance, without deteriorating the contact state between a polarization electrode and a collector, even if gas is generated by the repetition of chargings and discharging, can inhibit expansion in an outer covering material, and can prevent the decrease of positional accuracy in a laminate at the inside and at the same time, rupture due to the expansion of the outer covering material. SOLUTION: In this electric double-layer capacitor 1, a cell laminate 5 of a cell is accommodated in the outer covering material 7 filled with an electrolyte. In the cell laminate 5 of the cell, a separator 3 is arranged between a pair of polarization electrodes 2a and 2b, and at the same time, collectors 4a and 4b are laminated to each of other surfaces of the polarization electrodes 2a and 2b. Also, in the electric double-layer capacitor 1, a pressure resistant member 12 is provided at each portion between the upper and lower surfaces of the cell laminate 5 and armor material 7. The pressure resistance member 12 has a Young's modulus which is larger than the armor material 7.

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 utilizing 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. In addition to being able to charge a large amount of electrostatic capacity and capable of rapid charging and discharging as compared with the above, it has attracted attention as an auxiliary power supply for a large-capacity motor, such as a small memory backup power supply or a driving source of a car.

As a general example of such an electric double layer capacitor, there are two polarizable electrodes, a separator provided between the electrodes, and a current collector provided on each of the other surfaces of the polarizable electrodes. The stacked body as one unit cell, a configuration in which the cells are stacked in multiple layers and housed in an exterior material, filled in the exterior material, and in a pair of polarizable electrodes and a separator disposed therebetween. The capacitance can be generated in the polarizable electrode by the movement of ions in the impregnated electrolyte.

[0004]

However, in such an electric double layer capacitor, gas is generated from the surface of the polarizable electrode due to deterioration of the polarizable electrode and decomposition of impurities in the electrolytic solution due to repetition of charge and discharge. As a result, the contact state between the polarizable electrode and the current collector deteriorates, and the internal resistance of the entire electric double layer capacitor increases, or the internal pressure of the external material increases, and the external material itself expands locally. There was a problem that the exterior material burst.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a method for producing a gas between a polarizable electrode and a current collector by generating gas accompanying repetition of charging and discharging of an electric double layer capacitor. An object of the present invention is to provide an electric double layer capacitor capable of suppressing an increase in internal resistance without deteriorating a contact state, suppressing expansion of an exterior material, and preventing rupture of the exterior material.

[0006]

The inventors of the present invention have studied the above-mentioned problems, and as a result, have found that, between the upper and lower surfaces of the laminate of the polarizable electrode, the separator and the current collector, and the outer packaging material, the Younger material is used. By providing a pressure-resistant member with a high rate, the exterior material does not locally expand even when gas is generated due to repeated charging and discharging of the electric double layer capacitor, and a laminate of a polarizable electrode, a separator, and a current collector It has been found that as a result of eliminating the partial unevenness of the pressure applied to the electrode and making the contact state between the polarizable electrode and the current collector uniform without deteriorating, an increase in the internal resistance of the electric double layer capacitor can be suppressed.

That is, in the electric double layer capacitor of the present invention, a separator is disposed between a pair of polarizable electrodes, and a current collector is laminated on each of the other surfaces of the polarizable electrodes. Characterized in that a member having a higher Young's modulus than the exterior material is provided between the upper and lower surfaces of the laminated body and the exterior material, respectively. is there.

Here, it is desirable that the member having a higher Young's modulus than the exterior material is a plate-like body having a zigzag or wavy cross section. In particular, the member having a higher Young's modulus than the exterior material and the laminate are preferably used. It is desirable to arrange a flat plate between them.

Further, it is preferable that another member having a higher Young's modulus than the exterior material is provided between the side surface of the laminate and the exterior material.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One example of an electric double layer capacitor of the present invention will be described with reference to FIG. According to FIG. 1, the electric double layer capacitor 1 has a separator 3 disposed between a pair of polarizable electrodes 2a and 2b forming a positive electrode and a negative electrode, and a positive electrode and a negative electrode on the other surfaces of the polarizable electrodes 2a and 2b, respectively. The cell stack 5 in which a plurality of cells are stacked is stacked with the stacked body in which the current collectors 4a and 4b are stacked as one unit cell, and this is stored in the exterior material 7.

According to FIG. 1, a terminal portion is formed at one end of the current collector 4 so that the terminal portion of the current collector 4a forming a positive electrode and the terminal portion of the current collector 4b forming a negative electrode converge. Connection terminal 8a and connection terminal 8b respectively forming a positive electrode and a negative electrode
Are formed, and the connection terminals 8a and 8b penetrate the wall surface of the exterior material 7 and protrude to the outside. As shown in the enlarged view of the main part of FIG. 2, the terminal portions 9 (9a, 9b) of the current collector 4
It penetrates the insulating layer 10 provided on the side surface of the cell stack 5 every other layer, is bent along the insulating layer 10, and further connects the terminal portions 9a (9a is not shown) and the terminal portions 9b. Are converged, integrated by welding or the like, and bent toward the exterior material 7 to form the connection terminal 8.

According to the present invention, a significant feature is that a pressure-resistant member 12 having a higher Young's modulus than the exterior material 7 is provided between the upper and lower surfaces of the cell laminate 5 and the exterior material 7 respectively.
As a result, the exterior material 7 does not locally expand due to the generation of gas due to repeated charging and discharging of the electric double layer capacitor 1, eliminating the local unevenness of the pressure applied to the cell stack 5, As a result, the internal resistance of the electric double layer capacitor 1 can be prevented from increasing and the rupture due to the local expansion of the exterior material 7 can be prevented.

That is, whether the pressure-resistant member 12 is provided,
Alternatively, if the Young's modulus of the pressure-resistant member 12 is lower than that of the exterior material 7, the gas generated by the repetition of charging and discharging causes the central portion of the exterior material 7 to protrude so as to protrude,
The caulking pressure applied to the cell laminate 5 is uneven, the contact state between the polarizable electrode 2 and the current collector 4 fluctuates, and finally, the package 7 ruptures due to expansion.

According to FIG. 1, the pressure-resistant member 12 is a plate-like body having a zigzag or wavy cross section, and is located between the pressure-resistant member 12 and the cell stack 5 (in FIG. 1, the pressure-resistant member 12). A flat plate 13 having a Young's modulus equal to or higher than the pressure-resistant member 12 is disposed on both surfaces of the cell stack 5, whereby even and stable gas can be applied regardless of the location of the cell stack 5. Since the contact state between the polarizable electrode 2 and the current collector 4 does not change, it is possible to prevent a change in internal resistance due to the contact state between the two. Note that at least the flat plate 13 provided between the pressure-resistant member 12 and the cell stack 5 is made of an insulator.

Further, according to FIG. 1, a pressure-resistant member 12 is disposed between the side surfaces of the cell laminate 5 and the exterior material 7 in addition to between the both ends of the cell laminate 5 and the exterior material 7. Thus, it is possible to prevent local expansion of the surface of the exterior material 7 located on the side surface of the cell laminate 5 and prevent the exterior material 7 from being ruptured.

It is desirable that the corners of the exterior material 7 are firmly adhered by screwing, welding, or the like, and have a structure that can withstand the internal pressure of the exterior material 7.

Further, silicone rubber,
It is made of rubber such as urethane rubber or butadiene rubber, or at least one selected from the group consisting of metals such as aluminum, silver, tin, and duralumin, and is preferably made of inexpensive and lightweight metal aluminum. Furthermore, the exterior material 7
Is desirably 0.5 to 3 mm in thickness in terms of heat dissipation, shock buffering, and miniaturization of the electric double layer capacitor 1.

The pressure-resistant member 12 is made of a material having a Young's modulus higher than that of the exterior material 7.
It is desirable to use metals such as iron and tungsten, ceramics such as alumina, mullite, zirconia, silicon nitride, and silicon carbide, and it is particularly desirable to use inexpensive and highly rigid stainless steel. The exterior member 7 is a screw member 1
Desirably, caulking by 4 is performed.

Further, in order to prevent the fluctuation of the caulking pressure applied to the cell stack 5, the shape of the pressure-resistant member 12 is, as shown in FIG.
Is 5 to 30 mm, especially 10 to 20 mm, and the height (t) between opposing tops p and q is 5 to 50 mm, particularly 10 to 20 mm.
It is preferably a zigzag shape or a wavy shape of mm, and particularly preferably a wavy shape having no corners in order to prevent stress concentration.

The flat plate 13 interposed between the cell laminate 5 and the pressure-resistant member 12 is at least one selected from the group consisting of stainless steel, copper, iron, tungsten, alumina, mullite, zirconia, silicon nitride, and silicon carbide. Desirably, it consists of

On the other hand, the polarizable electrode 2 contains, for example, activated carbon having a high specific surface area, and a compounding agent for bonding to the activated carbon can be suitably used. May be subjected to a carbonization treatment in terms of reduction of the carbon content. In order to increase the capacitance of the electric double layer capacitor 1 and maintain the strength required for the structure, the specific surface area of the polarizable electrode 2 excluding the electrolytic solution is 500
3,000 m ² / g, preferably 1000-3000 m ² / g.

The carbon component added as a binder is present between the activated carbon particles. However, when the carbonization treatment is performed, the ratio of the carbon component contained in the activated carbonaceous structure is 5 to 50.
% Of the activated carbon particles, thereby improving the sinterability and bonding between the activated carbon particles.

Further, the polarizable electrode 2 is preferably in the form of a disk, a flat plate of a rectangular shape (rectangular shape in FIG. 1), or the like. J in terms of reliability of mechanical strength that can withstand
Three-point bending strength at room temperature according to ISR1601 is 3
It is preferably at least 0 kPa, particularly preferably at least 60 kPa. In addition, the thickness of the polarizable electrode 2 is preferably 1.5 mm or less, particularly 1.0 mm or less, and more preferably 0.6 mm or less from the viewpoint of reducing the internal resistance.

The separator 3 is made of pulp, polyethylene, polypropylene, polyvinylidene fluoride (P
An organic film such as VdF) or a glass fiber nonwoven fabric and ceramics can be used, and are formed to insulate the polarizable electrodes 2 from each other. It is formed of a porous body through which ions can pass. The separator 3
Is preferably 0.02 to 0.15 mm in order to prevent a short circuit or the like and reduce the internal resistance.

Further, the polarizable electrode 2 and the separator 3
An aqueous solution of sulfuric acid or nitric acid, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), γ-butyrolactone (γ-
BL), N, N-dimethylformamide, sulfolane,
An electrolyte such as a non-aqueous electrolyte obtained by combining a non-aqueous solvent such as 3-methylsulfolane and an electrolyte such as a quaternary ammonium salt such as tetraethylammonium tetrafluoroborate or a quaternary sulfonium salt or a quaternary phosphonium salt is impregnated. In the present invention, it is desirable to use a non-aqueous electrolyte having a high decomposition voltage. The amount of the electrolyte dissolved in the non-aqueous solvent is desirably 0.5 to 2 mol / l in order to stably obtain a high capacitance.

The current collector 4 is made of conductive metal foil such as aluminum, titanium, tantalum, platinum, or gold, stainless steel, or the like, and exchanges electric charges between the polarizable electrodes 2 and 2. In particular, it is desirable to use a metal foil mainly composed of aluminum from the viewpoint of heat dissipation and corrosion resistance to a non-aqueous electrolyte having a high decomposition voltage. The current collector 4
The thickness is preferably thin in order to reduce the internal resistance, but in consideration of breakage due to handling during assembly, etc.
About 02 to 0.10 mm is desirable.

Further, an electrolyte injection port (not shown) for injecting and impregnating the electrolyte into the polarizable electrode 2 and the separator 3 is formed on the outer peripheral surface of the exterior material 7. After removing impurities such as moisture adhering to the inside of the cell laminate 5, the non-aqueous electrolytic solution is injected and sealed to reduce the amount of moisture in the electric double layer capacitor 1 and reduce the deterioration of the electrolytic solution. This can improve the reliability of the electric double layer capacitor 1.

[0028]

(Example 1) To 100 parts by weight of an activated carbon powder sample having a BET value of 2000 m ² / g, 50 parts by weight of polyvinyl butyral (PVB) was mixed and stirred with a high-speed mixing stirrer. After the powder was subjected to a mesh pass with 40 mesh, a sheet-like molded body was prepared by roll molding, cut into a predetermined shape, and heat-treated at 900 ° C. in vacuum, and 100 mm × 100 mm, thickness 0.3 mm
A rectangular activated carbonaceous structure was produced.

On the other hand, 100 mm × 100 mm, thickness 50
made of aluminum foil with a width of 30 mm at one end
A current collector formed with the terminal portions was prepared. Also, 105m
A separator made of cellulose pulp having a size of mx 105 mm and a thickness of 50 m was prepared.

Then, a laminate is formed by using the activated carbonaceous structure 32, the current collector 32 and the separator 16 in the order shown in FIG. 1, and a terminal portion of the current collector on a side surface of the laminate is formed. An insulator made of a polyethylene-based film was provided on the formation surface, and connection terminals of the current collector were pierced every other layer from the insulator to fix the insulator. Also,
Connection terminals were formed by bundling and welding the terminal portions of every other current collector.

On the other hand, it is made of stainless steel (made of SUS304) having a Young's modulus of 350 GPa, and is 110 mm × 110 m
m, thickness 5 mm, and distance (d) between adjacent tops is 10
mm, a wave-shaped pressure-resistant member having a height (t) between opposing tops of 3 mm was prepared. Also, made of stainless steel
Two flat plate-like bodies having a size of 10 mm × 110 mm and a thickness of 0.5 mm were prepared. Furthermore, it is made of metallic aluminum having a Young's modulus of 70 GPa and has an inner wall shape of 120 mm × 120 mm.
An outer package consisting of a container having a size of 120 mm and a thickness of 3 mm and a lid was prepared.

Next, the laminate was housed on the inner surface of the exterior material container, and the plate-like body and the pressure-resistant member were inserted between the inner wall surface of the exterior material container and the laminate. Then, the cover of the exterior material is screwed to the exterior material container via the plate-like body and the pressure-resistant member, and the interior of the exterior material is evacuated at an electrolyte injection port formed in the exterior material container. A 1 mol / l solution of tetraethylammonium tetrafluoroborate (Et ₄ NBF ₄ ) in propylene carbonate (PC) was injected into the material as an electrolyte. After the injection of the electrolytic solution, the laminate was caulked with a screw member of the exterior material container to a pressure of 400 kPa.

With respect to the obtained electric double layer capacitor,
When the impedance at 1 kHz was measured as the internal resistance, it was 1.5 mΩ. The internal resistance before and after repeated charging and discharging at 70 ° C., 3.0 V, and current of 5 A for 1000 hours was 1.8 mΩ. Further, the exterior material did not burst even after repeated charge and discharge for 3000 hours.

(Embodiment 2) An electric double layer capacitor is manufactured in the same manner as in Embodiment 1 except that the pressure-resistant member and the plate-shaped member are not arranged on the side surfaces of the laminate. As a result of the same evaluation, the initial internal resistance was 1.
The internal resistance after charging and discharging for 5 hours was 5 mΩ and the internal resistance was 15 mΩ after charging and discharging for 1000 hours.

(Comparative Example 1) An electric double layer capacitor was produced in the same manner as in Example 1 except that no pressure-resistant member and a plate-like member were formed at all with respect to the electric double layer capacitor of Example 1, and evaluated similarly. As a result, the initial internal resistance was 1.5 mΩ, 100
The internal resistance after charging / discharging for 0 hour was 15 mΩ, and after charging / discharging for 800 hours, leakage of the electrolyte was observed due to the rupture of the exterior material.

Comparative Example 2 An electric double layer capacitor was manufactured in the same manner as in Example 1 except that the pressure-resistant member and the plate were replaced with the same material as the exterior material. As a result of the same evaluation, the initial internal resistance was 1.5 m.
Ω, the internal resistance after charging and discharging for 1000 hours is 18 mΩ,
After charging and discharging for 600 hours, leakage of the electrolyte was observed due to the rupture of the exterior material.

[0037]

As described in detail above, in the electric double layer capacitor of the present invention, the Young's modulus of the electric double layer capacitor between the upper and lower surfaces of the laminate of the polarizable electrode, the separator and the current collector and the outer packaging material is smaller than that of the outer packaging material. By providing a high withstand pressure member, the exterior material does not locally swell even due to the generation of gas due to repeated charging and discharging of the electric double layer capacitor, and the laminate of the polarizable electrode, the separator and the current collector As a result of eliminating the partial unevenness of the pressure and not deteriorating the contact state between the polarizable electrode and the current collector, it is possible to suppress an increase in the internal resistance of the electric double layer capacitor and to reduce the positional accuracy of the internal laminated body. Without rupture due to expansion of the exterior material.

[Brief description of the drawings]

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

FIG. 2 is an enlarged view of a main part for describing a structure of a terminal portion of a current collector of the electric double layer capacitor of FIG.

FIG. 3 is a view for explaining the shape of a pressure-resistant member of the electric double-layer capacitor of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric double layer capacitor 2 Polarized electrode 3 Separator 4 Current collector 5 Cell laminated body 7 Exterior material 8 Connection terminal 9 Terminal part 10 Insulation layer 12 Withstand pressure member 13 Flat plate 14 Screw member

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Kazuo Ikuta 1-4-4 Yamashita-cho, Kokubu-shi, Kagoshima Inside the Kyocera Research Institute

Claims (4)

[Claims] Claims: 1. A separator is arranged between a pair of polarizable electrodes,
An electric double-layer capacitor in which a laminate obtained by laminating a current collector on each of the other surfaces of the polarizable electrode is housed in an exterior material filled with an electrolytic solution, wherein upper and lower surfaces of the laminate and the exterior An electric double layer capacitor comprising a member having a Young's modulus higher than that of the exterior material between the two members. 2. The electric double layer capacitor according to claim 1, wherein the member having a Young's modulus higher than that of the exterior material is a plate having a zigzag or wavy cross section. 3. The electric double layer capacitor according to claim 2, wherein a flat plate is provided between the member having a higher Young's modulus than the exterior material and the laminate. 4. The semiconductor device according to claim 1, further comprising another member having a higher Young's modulus than the exterior material between the side surface of the laminate and the exterior material. The electric double-layer capacitor as described.