JP4627874B2 - 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

[0001]
BACKGROUND 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 source.
[0002]
[Prior art]
An electric double layer capacitor is a capacitor that uses an electric double layer formed by the polarization of ions at the interface between the electrode and the electrolyte, and combines the functions of both a capacitor and a battery. Since it can charge a large capacitance and can be rapidly charged and discharged, it has been attracting attention as an auxiliary power source for large-capacity motors such as small memory backup power sources and automobile drive sources.
[0003]
As a general example of such an electric double layer capacitor, a laminate of two polarizable electrodes, a separator provided between the electrodes, and a current collector provided on each of the other surfaces of the polarizable electrode is provided. As a single unit cell, a plurality of layers of the cells are stacked and accommodated in an exterior material, filled in the exterior material, and impregnated in a pair of polarizable electrodes and a separator disposed therebetween. Capacitance can be generated in the polarizable electrode by the movement of ions in the electrolyte.
[0004]
[Problems to be solved by the invention]
However, such an electric double layer capacitor generates gas from the surface of the polarizable electrode due to deterioration of the polarizable electrode or decomposition of impurities in the electrolyte due to repeated charge and discharge, and the gas causes the gas between the polarizable electrode and the current collector. As a result, the internal resistance of the entire electric double layer capacitor increases, the internal pressure of the exterior material rises, the exterior material itself expands locally, and eventually the exterior material bursts. There was a problem.
[0005]
The present invention has been made to solve the above-mentioned problems, and its purpose is to change the contact state between the polarizable electrode and the current collector even by the generation of gas accompanying repeated charging and discharging of the 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, suppressing expansion of the exterior material, and preventing the exterior material from bursting.
[0006]
[Means for Solving the Problems]
As a result of examining the above problems, the present inventors have provided a pressure-resistant member having a higher Young's modulus than the exterior material between the upper and lower surfaces of the laminate of the polarizable electrode, the separator, and the current collector, and the exterior material. The exterior material does not swell locally due to the generation of gas due to repeated charging and discharging of the electric double layer capacitor, and the partial unevenness of the pressure applied to the laminate of the polarizable electrode, the separator and the current collector is reduced. As a result, the contact state between the polarizable electrode and the current collector can be made uniform without deteriorating, and as a result, an increase in the internal resistance of the electric double layer capacitor can be suppressed.
[0007]
That is, covered electric double layer capacitor of the present invention, arranged separator between a pair of polarizable electrodes, and the respective other surface in the laminated body obtained by laminating a current collector of the polarizable electrode, filled with electrolyte solution A member that is housed in a material and has a higher Young's modulus than the exterior material comprising a plate-like body having a zigzag or wavy cross section between the upper and lower surfaces of the laminate and the exterior material. the provided Rutotomoni, between the side surface of the laminated body and the exterior material, and is characterized in that formed by providing other members Young's modulus is higher than the outer member.
[0008]
Here, it is desirable that the flat plate is disposed between the Young's modulus than before Kigaiso material is higher member and the laminate.
[0009]
Furthermore, it is desirable to provide another member having a Young's modulus higher than that of the exterior material between the side surface of the laminate and the exterior material.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
An example of the 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 includes 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. A cell stack 5 in which a plurality of cells are stacked is stacked using the stack of the current collectors 4 a and 4 b forming a single unit as a unit cell, and this is housed in an exterior material 7.
[0011]
Further, according to FIG. 1, a terminal part is formed at one end of the current collector 4, and the terminal part of the current collector 4a forming the positive electrode and the terminal part of the current collector 4b forming the negative electrode are converged to converge the positive electrode and the positive electrode, respectively. A connection terminal 8a and a connection terminal 8b that form a negative electrode are formed, and the connection terminals 8a and 8b penetrate the wall surface of the exterior member 7 and project outside. 2, the terminal portions 9 (9a, 9b) of the current collector 4 penetrate through the insulating layer 10 disposed on the side surface of the cell stack 5 every other layer. The terminals 9a (9a are not shown) and the terminals 9b are converged and integrated by welding or the like, and are bent toward the exterior material 7 side. Thus, the connection terminal 8 is formed.
[0012]
According to the present invention, a major feature is that the pressure-resistant member 12 having a Young's modulus higher than that of the exterior material 7 is provided between the upper and lower surfaces of the cell laminate 5 and the exterior material 7. The outer packaging material 7 does not swell locally due to the generation of gas due to repeated charging and discharging of the multilayer capacitor 1, and local unevenness of the pressure applied to the cell stack 5 is eliminated, so that the polarizable electrode 2 and the current collector are removed. As a result of not deteriorating the contact state with 4, the increase in the internal resistance of the electric double layer capacitor 1 can be suppressed, and the burst due to the local expansion of the exterior material 7 can be prevented.
[0013]
That is, if the pressure member 12 is not provided or if the Young's modulus of the pressure member 12 is equal to or less than that of the exterior material 7, the center portion of the exterior material 7 protrudes due to gas generated by repeated charge and discharge. As a result, the contact pressure between the polarizable electrode 2 and the current collector 4 fluctuates and finally ruptures due to the expansion of the outer packaging material 7. .
[0014]
Further, according to FIG. 1, the pressure-resistant member 12 is a plate-like body having a zigzag-like or wavy cross section, and on both surfaces between the pressure-resistant member 12 and the cell stack 5 (the pressure-resistant member 12 in FIG. 1). Is provided with a flat plate 13 having a Young's modulus equal to or greater than that of the pressure-resistant member 12, so that even when gas is generated, a uniform and stable pressure can be applied regardless of the location of the cell stack 5. Since the contact state between the polar electrode 2 and the current collector 4 does not fluctuate, fluctuations in internal resistance due to the contact state between them can be prevented. Note that at least the flat plate 13 disposed between the pressure-resistant member 12 and the cell stack 5 is made of an insulator.
[0015]
Further, according to FIG. 1, the pressure-resistant member 12 is disposed between the side surface of the cell laminate 5 and the exterior material 7 in addition to the both ends of the cell laminate 5 and the exterior material 7. Thus, local expansion of the surface of the exterior material 7 located on the side surface of the cell stack 5 can be prevented, and the exterior material 7 can be prevented from bursting.
[0016]
In addition, it is desirable that the corner portion of the exterior material 7 is firmly bonded by screwing, welding, or the like and has a structure that can withstand the internal pressure of the exterior material 7.
[0017]
The exterior material 7 is made of rubber such as silicon rubber, urethane rubber, butadiene rubber, or at least one selected from the group of metals such as aluminum, silver, tin, and duralumin. It is desirable to consist of. Furthermore, the shape of the exterior material 7 is desirably 0.5 to 3 mm in terms of heat dissipation, shock buffering properties, and miniaturization of the electric double layer capacitor 1.
[0018]
The pressure-resistant member 12 is made of a material having a higher Young's modulus than the exterior material 7, and is made of, for example, a metal such as stainless steel, copper, iron, or tungsten, or a ceramic such as alumina, mullite, zirconia, silicon nitride, or silicon carbide. It is desirable to use stainless steel that is particularly inexpensive and highly rigid. The exterior material 7 is preferably caulked with a screw member 14.
[0019]
Furthermore, in order to prevent fluctuations in the caulking pressure applied to the cell stack 5, the shape of the pressure-resistant member 12 is such that the distance (d) between the apexes o and p adjacent to each other is 5 to 30 mm as shown in FIG. In particular, it is desirable that the height (t) between 10 to 20 mm and the opposing apexes p and q is 5 to 50 mm, particularly 10 to 20 mm, and the corner portion is particularly preferable in terms of preventing stress concentration. It is desirable to have a wavy shape that does not exist.
[0020]
The flat plate 13 interposed between the cell laminate 5 and the pressure-resistant member 12 is made of at least one selected from the group consisting of stainless steel, copper, iron, tungsten, alumina, mullite, zirconia, silicon nitride, and silicon carbide. Is desirable.
[0021]
On the other hand, the polarizable electrode 2 contains, for example, activated carbon having a high specific surface area, and can be suitably used in combination with a bonding agent for bonding with the activated carbon, which improves capacitance and reduces internal resistance. It may be carbonized in terms. Further, in order to increase the capacitance of the electric double layer capacitor 1 and maintain the strength necessary for the structure, the specific surface area of the polarizable electrode 2 excluding the electrolyte is 500 to 3000 m ² / g, particularly 1000. It is desirable to be ˜3000 m ² / g.
[0022]
In addition, although the carbon component added as a binder exists between activated carbon particles, when performing the carbonization treatment, it is desirable that the proportion of the carbon component in the activated carbon structure is 5 to 50% by weight. Thus, the sinterability and bondability between the activated carbon particles can be enhanced.
[0023]
Furthermore, the polarizable electrode 2 is preferably a disk, a rectangular plate (rectangular shape in FIG. 1) or the like, and can withstand vibrations, shocks, etc. during the manufacture and use of the electric double layer capacitor 1. From the point of reliability of mechanical strength, the three-point bending strength at room temperature according to JIS R1601 is preferably 30 kPa or more, particularly preferably 60 kPa or more. 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 internal resistance.
[0024]
The separator 3 can be made of an organic film such as pulp, polyethylene, polypropylene, polyvinylidene fluoride (PVdF), a glass fiber nonwoven fabric, ceramics, or the like, and is formed to insulate between the polarizable electrodes 2. However, it is formed of a porous body that can transmit ions in the electrolytic solution contained in the polarizable electrode 2. In addition, the thickness of the separator 3 is preferably 0.02 to 0.15 mm in order to prevent a short circuit and reduce internal resistance.
[0025]
Further, in the polarizable electrode 2 and the separator 3, an aqueous solution such as sulfuric acid and nitric acid, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), γ-butyrolactone (γ-BL), N, Non-aqueous electrolytes combining non-aqueous solvents such as N-dimethylformamide, sulfolane, 3-methylsulfolane and the like and electrolytes such as quaternary ammonium salts such as tetraethylammonium tetrafluoroborate, quaternary sulfonium salts, and quaternary phosphonium salts Although the electrolyte is impregnated, it is desirable to use a non-aqueous electrolyte having a high decomposition voltage in the present invention. The amount of the electrolyte dissolved in the non-aqueous solvent is preferably 0.5 to 2 mol / l in order to stably obtain a high capacitance.
[0026]
The current collector 4 is formed of conductive aluminum, titanium, tantalum, platinum, gold or other metal foil, stainless steel, etc., and exchanges electric charges between the polarizable electrodes 2 and 2. In addition, it is desirable to use a metal foil mainly composed of aluminum from the viewpoint of corrosion resistance against a non-aqueous electrolyte having a high decomposition voltage. The current collector 4 is preferably thin in order to reduce the internal resistance, but is preferably about 0.02 to 0.10 mm in consideration of damage due to handling during assembly.
[0027]
In addition, an electrolyte solution injection port (not shown) for injecting and impregnating the electrolyte solution into the polarizable electrode 2 and the separator 3 is formed on the outer peripheral surface of the outer packaging material 7. After removing impurities such as water adhering to the body 5, the non-aqueous electrolyte solution is injected and sealed, thereby reducing the amount of water in the electric double layer capacitor 1 and preventing deterioration of the electrolyte solution, The reliability of the electric double layer capacitor 1 can be increased.
[0028]
【Example】
Example 1
50 parts by weight of polyvinyl butyral (PVB) is mixed with 100 parts by weight of activated carbon powder sample having a BET value of 2000 m ² / g and stirred with a high-speed mixing stirrer. After that, a sheet-like molded body is produced by roll molding, cut into a predetermined shape, and heat treated at 900 ° C. in a vacuum to produce a rectangular activated carbon structure having a size of 100 mm × 100 mm and a thickness of 0.3 mm. did.
[0029]
On the other hand, a current collector made of an aluminum foil having a size of 100 mm × 100 mm and a thickness of 50 μm and having a terminal portion with a width of 30 mm at one end thereof was prepared. In addition, a separator made of cellulose pulp having a size of 105 mm × 105 mm and a thickness of 50 μm was prepared.
[0030]
And the laminated body laminated | stacked in order of FIG. 1 using 32 sheets of the said activated carbonaceous structures, 32 electrical power collectors, and 16 separators is formed, and the terminal part formation surface of the said electrical power collector of the side surface of this laminated body is formed. An insulator made of a polyethylene film was disposed, and the insulator was fixed by penetrating every other connection terminal of the current collector from the insulator. Moreover, the connection terminal was formed by bundling and welding the terminal portions of every other current collector.
[0031]
On the other hand, it is made of stainless steel with a Young's modulus of 350 GPa (made of SUS304), has a corrugated shape of 110 mm × 110 mm, thickness 5 mm, distance (d) between adjacent tops is 10 mm, and height (t) between opposing tops is 3 mm. A pressure-resistant member was prepared. Moreover, two flat plate-shaped bodies made of stainless steel and having a size of 110 mm × 110 mm and a thickness of 0.5 mm were prepared. Furthermore, an exterior material comprising a container and a lid made of metallic aluminum having a Young's modulus of 70 GPa, an inner wall shape of 120 mm × 120 mm × 120 mm, and a wall thickness of 3 mm was prepared.
[0032]
Next, while storing the said laminated body in the inner surface of the said exterior material container, the said plate-shaped body and the pressure | voltage resistant member were inserted between the inner wall face of the said exterior material container, and the said laminated body. Then, the lid 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 the electrolyte inlet formed in the exterior material container, and then the exterior A propylene carbonate (PC) solution of 1 mol / l tetraethylammonium tetrafluoroborate (Et ₄ NBF ₄ ) was injected into the material as an electrolyte. Further, after the injection of the electrolyte, the laminate was caulked with a screw member of the outer packaging container so that the caulking pressure was 400 kPa.
[0033]
With respect to the obtained electric double layer capacitor, the impedance at 1 kHz was measured as an internal resistance, and it was 1.5 mΩ. The internal resistance before and after repeated charging / discharging for 1000 hours at 70 ° C., 3.0 V, and current 5 A was 1.8 mΩ. Further, the outer packaging material did not rupture even when charging and discharging were repeated for 3000 hours.
[0034]
(Example 2)
With respect to the electric double layer capacitor of Example 1, an electric double layer capacitor was produced in the same manner as in Example 1 except that the pressure-resistant member and the plate-like body were not provided on the side surface of the laminate, and the results were evaluated in the same manner. The initial internal resistance was 1.5 mΩ, the internal resistance after 1000 hours of charge / discharge was 15 mΩ, and leakage of the electrolyte was observed due to the rupture of the exterior material after 500 hours of charge / discharge.
[0035]
(Comparative Example 1)
The electric double layer capacitor of Example 1 was manufactured in the same manner as in Example 1 except that a pressure-resistant member and a plate-like member were not formed at all. The internal resistance was 5 mΩ and the internal resistance after charging / discharging for 1000 hours was 15 mΩ, and leakage of the electrolyte solution was observed due to the bursting of the exterior material after 800 hours charging / discharging.
[0036]
(Comparative Example 2)
For the electric double layer capacitor of Example 1, an electric double layer capacitor was prepared in the same manner as in Example 1 except that the pressure-resistant member and the plate-like body were replaced with the same material as the exterior material. The internal resistance was 1.5 mΩ, the internal resistance after charging / discharging for 1000 hours was 18 mΩ, and the leakage of the electrolyte was observed due to the rupture of the exterior material after charging / discharging for 600 hours.
[0037]
【The invention's effect】
As described in detail above, in the electric double layer capacitor of the present invention, a pressure-resistant member having a Young's modulus higher than that of the exterior material is provided between the upper and lower surfaces of the laminate of the polarizable electrode, the separator, and the current collector, and the exterior material. By providing, the exterior material does not swell locally due to the generation of gas due to repeated charging and discharging of the electric double layer capacitor, and the pressure applied to the laminate of the polarizable electrode, the separator and the current collector is partially As a result, the increase in the internal resistance of the electric double layer capacitor can be suppressed, the position accuracy of the internal laminate is not lowered, and the exterior Rupture due to expansion of the material can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of an electric double layer capacitor of the present invention.
2 is an enlarged view of a main part for explaining the structure of a terminal portion of a current collector of the electric double layer capacitor of FIG. 1;
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 Insulating layer 12 Pressure-resistant member 13 Flat plate 14 Screw member

Claims (2)

Disposing a separator between a pair of polarizable electrodes, and the respective other surface in the laminated body obtained by laminating a current collector of the polarizable electrode, an electric double layer capacitor comprising housed in an outer material filled with electrolyte a is, the respective zigzag or wavy cross-section the outer Young's modulus is higher than the material member consisting of a plate-like body having a between the upper and lower surfaces and the outer member of the laminate is provided Rutotomoni, the laminate An electric double layer capacitor , wherein another member having a Young's modulus higher than that of the exterior material is provided between the side surface of the exterior material and the exterior material . The electric double layer capacitor according to claim 1, wherein the flat plate is disposed between the Young's modulus than the outer package is higher member and the laminate.

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