JP2001244148A - Electric double-layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric double-layer capacitor, which can reduce the size and the cost and prevent the positional deviation of polarized electrodes from each other between the electrodes and the positional deviation of a separator from the electrodes prevent from being generated and also maintain stable electrostatic capacity over a long period. SOLUTION: In an electric double-layer capacitor 1, which is provided with a pair of polarized electrodes 2 and 2, a separator 3 which is interposed between the electrodes 2 and 2, and current collecting bodies 4 which are respectively laminated on the other surfaces of the electrodes 2 and 2, the separator 3 has each recessed part 11 in both surfaces thereof and at the same time, the one pair of the polarized electrodes 2 and 2 are respectively housed in the recessed parts 11.

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 useful as a chargeable / dischargeable 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 an electric double layer capacitor, a plate-like separator is interposed between a pair of plate-like polarizable electrodes, and a current collector is laminated on each of the other surfaces of the polarizable electrodes. And a structure in which a non-conductive gasket is arranged on the outer periphery of the laminate.

[0004]

However, in the method using the gasket, there is a problem that the formation of the gasket separately increases the volume and size of the electric double layer capacitor and increases the cost.

In order to reduce the size and cost of the electric double-layer capacitor, a laminate of a plate-shaped polarizable electrode, a separator and a current collector is sealed with a bag-shaped aluminum laminate or the like. Are known, polarizable electrodes,
The separator and the current collector may be easily displaced, and the capacitance may be reduced. In some cases, the positive and negative polarizable electrodes may be in contact with each other and short-circuited.

Therefore, a method is known in which a polarizable electrode and a current collector are sealed in a bag-like separator to prevent contact between the positive and negative polarizable electrodes.
Even in such a method, there is a problem that the displacement between the polarizable electrodes cannot be prevented, and the capacitance decreases. Further, when charging and discharging are performed for a long time, the electrolyte volatilizes from the polarizable electrode and the side surface of the separator of the laminate, and the amount of the electrolytic solution in the polarizable electrode decreases, that is, a so-called liquid withdrawal phenomenon occurs. , Causing a decrease in capacitance. The present invention has been made to solve the above-described problems, and an object of the present invention is to make it possible to reduce the size and cost of an electric double-layer capacitor, and to prevent displacement between polarizable electrodes and a separator. Another object of the present invention is to provide an electric double layer capacitor capable of maintaining stable capacitance for a long period of time.

[0007]

Means for Solving the Problems The present inventors have studied a method which can be reduced in size and cost and can prevent displacement between the polarizable electrodes and the position of the separator. By forming a concave portion and accommodating the pair of polarizable electrodes in the concave portion, the above problem can be solved, and the electrolytic solution is volatilized from the polarizable electrode and stable for a long time without running out of the electrolytic solution. It was found that the capacity could be maintained.

That is, an electric double layer capacitor according to the present invention comprises a pair of polarizable electrodes, a separator interposed between the pair of polarizable electrodes, and a current collector laminated on each of the other surfaces of the polarizable electrodes. Wherein the separator has concave portions on both surfaces, and the pair of polarizable electrodes are accommodated in the concave portions.

Here, it is desirable that the current collector be housed in the recess of the separator together with the polarizable electrode.

It is preferable that a notch is provided in a peripheral portion of the concave portion of the separator, and a terminal formed on the current collector is projected from the notch.

[0011]

FIG. 1 is a schematic sectional view of an example of an electric double layer capacitor according to the present invention, and FIG. 2 is an exploded perspective view thereof. According to FIGS. 1 and 2, the electric double-layer capacitor 1 has a separator 3 disposed and interposed between polarizable electrodes 2 and 2 serving as a positive electrode and a negative electrode. Current collectors 4 and 4 forming a positive electrode and a negative electrode are respectively laminated and bonded to the opposite surfaces.

According to FIGS. 1 and 2, the polarizable electrode 2,
The laminate of the separator 2, the current collectors 4, 4 is hermetically sealed by the exterior material 5.

The activated carbonaceous structure constituting the polarizable electrode 2 is mainly composed of a mixture of activated carbon particles having a high specific surface area and a binder for binding the activated carbon particles. May be carbonized.

In addition, maintaining a high capacitance of the capacitor,
In order to obtain the required strength as a structure, the activated carbon desirably has a specific surface area of 1,000 to 1,800 m ² / g.

The carbon component added as the binder is present between the activated carbon particles, but when the carbonization treatment is performed, the ratio of the carbon component to the activated carbonaceous structure is 5 to 5.
The content is preferably 50% by weight, whereby the sinterability and bonding between the activated carbon particles can be enhanced.

Further, the polarizable electrode 2 is preferably in the form of a plate.
JIS in terms of reliability of mechanical strength that can withstand impacts etc.
30k 3-point bending strength at room temperature according to R1601
It is preferably at least Pa, especially at least 60 kPa.
Further, the thickness of the polarizable electrode 2 is preferably 1.5 mm or less, particularly 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.

According to the present invention, it is a major feature that the separator 3 has the concave portions 6 on both surfaces and the polarizable electrode 2 is housed in the concave portions 6, thereby enabling downsizing and cost reduction. And the polarizable electrode 2,
It is possible to prevent the displacement between the two and the separator 3 and to maintain a stable capacitance for a long time.

The width of the peripheral portion 7 of the concave portion 6 in the separator 3 is increased in order to improve the capacitance by increasing the volume ratio of the polarizable electrode 2 and to maintain the shape of the separator 3. Electrolyte volatilization from the polarizable electrode 2 due to long-term use of the electric double layer capacitor causes the polarizable electrode 2
In order to prevent a decrease in capacitance due to a shortage of the electrolyte solution therein, it is desirable that the thickness is 1 to 4 mm, particularly 2 to 3 mm. Further, the thickness of the separator 3 located in the concave portion 6 is preferably 0.02 to 0.15 mm in order to prevent a short circuit or the like and reduce the internal resistance. The depth of the concave portion 6 of the separator 3 is desirably the thickness of the polarizable electrode 2 or the total thickness of the polarizable electrode 2 and the current collector 4 in order to reduce the internal resistance.

The current collector 4 is made of a conductive metal foil such as aluminum, titanium, tantalum, platinum, or gold, or stainless steel, 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 corrosion resistance against a non-aqueous electrolyte having a high decomposition voltage. It is preferable to use various metals having electrolytic resistance. The thickness of the current collector 4 is preferably thin in order to reduce the internal resistance, but is 0.02 to 0.10 m in consideration of damage due to handling during assembly.
It is desirable that the terminal portion 7 be formed on the outer peripheral portion of the current collector 4 from the viewpoint of ease of assembling the electric double layer capacitor 1.

According to the present invention, the current collector 4 may be in contact with the polarizable electrode 2 and the peripheral edge 7 of the separator 3 as shown in FIG. However, as shown in the schematic sectional view of FIG. 3 and the exploded perspective view of FIG. 4, it is desirable that the current collector 8 be housed in the concave portion 11 of the separator 10 together with the polarizable electrode 2. The displacement of the body 8 can also be prevented.

Further, a terminal portion 9 is provided on the outer peripheral portion of the current collector 8, and the terminal portion 9 is projected outside of the separator 10 from a cutout portion 13 provided in a part of a peripheral edge portion 12 of the separator 10. Can be prevented, and damage to the terminal portion 9 can be reduced.

Further, according to the present invention, as shown in FIG. 5, the concave portion 11 is provided only on one side, and two of the concave portions 11
For example, the separator 14 is formed in a shape that connects the shared peripheral portion 15 with a width of 2 to 10 mm, particularly 4 to 6 mm, and, if desired, is a peripheral portion other than the shared peripheral portion 15 and is shared. Notched portions 13 of the terminal portion are provided at positions where they are located on the same side surface when folded back at the peripheral edge portion 15 and do not overlap each other.

The polarizer 2 and the current collector 8 may be formed so as to be folded at the peripheral portion 15 which shares the separator 14 so as to house the polarizable electrode 2 and the current collector 8 in the respective concave portions 11. If this is the case, assembly during manufacture becomes easy.

On the other hand, the polarizable electrode 2 and the separators 3, 1
Examples of the electrolytic solution impregnated in the liquids 0 and 14 include aqueous solutions of sulfuric acid and nitric acid, ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (B
C) Combination of a non-aqueous solvent such as γ-butyrolactone (γ-BL), N, N-dimethylformamide, sulfolane, 3-methylsulfolane and an electrolyte such as quaternary ammonium salt, quaternary sulfonium salt and quaternary phosphonium salt Although a non-aqueous electrolyte solution can be used, it is desirable to use a non-aqueous electrolyte solution having a high decomposition voltage in the present invention. In addition,
The amount of the electrolyte dissolved in the non-aqueous solvent is 0.5 m
ol / l to 2.0 mol / l is preferable from the viewpoint of obtaining a stable and high capacitance.

The exterior material 5 is formed of a bag-like body, and the laminated body of the polarizable electrode 2, the separators 3, 10, 14, and the current collectors 4, 8 is sealed except for a part of the terminal portions 7, 9. It has a barrier function against the outside air and moisture.

Examples of the exterior material 5 include a laminate film in which a resin exhibiting heat fusibility is disposed at least in a sealing portion and a metal foil such as aluminum is interposed inside. Specifically, acid-modified polypropylene (PP) laminated from the sealing portion side to the outer surface
/ Polyethylene terephthalate (PET) / Al foil / PE
T laminated film, acid-modified polyethylene (PE)
/ Nylon / Al foil / PET laminated film, Ionomer / Ni foil / PE / PET laminated film,
Ethylene vinyl acetate (EVA) / PE / Al foil / P
ET laminated film, ionomer / PET / Al
A foil / PET laminate film or the like can be used. Here, the acid-denatured polyethylene (PE), acid-denatured polypropylene (PP), ionomer, and ethylene vinyl acetate (EVA) on the sealing side have moisture resistance, air resistance, and chemical resistance.

[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 of 40 mesh, a sheet-like molded body was produced by roll molding. After forming a molded body for forming a solid activated carbon electrode by cutting the sheet into a predetermined shape, a heat treatment is performed at 900 ° C. in vacuum to form an activated carbonaceous structure having a size of 50 mm × 50 mm and a thickness of 0.5 mm. Produced.

On the other hand, polyvinylidene fluoride (PVd)
F) was stirred and mixed in acetone at 70 ° C. to prepare a paste, and the obtained paste was poured into a 55 × 55 mm mold having a convex inner bottom surface, and was dried, so that concave portions were present on both surfaces. A separator was obtained. The shape of the separator is 55 mm × 55 mm × 0.10 mm in thickness,
The recess was 50 mm × 50 mm × 0.80 mm in depth, and the width of the peripheral edge was 2.5 mm.

Further, tetraethylammonium is used as an electrolyte.
Um tetrafluoroborate (Et _FourNBF_FourNon-water soluble)
Dissolved in propylene carbonate (PC) as a medium, and the concentration was 1.
It was adjusted to be 0 mol / l.

Then, the two activated carbonaceous structures are accommodated in the recesses of the separator, and an aluminum foil having a thickness of 0.05 mm is attached to both sides of the activated carbonaceous structure and the periphery of the recesses of the separator. Laminated on
From the outermost layer, polyethylene terephthalate (PET), Al foil, polyethylene terephthalate (P)
ET), inserted into a bag-shaped exterior body made of a laminated film laminated in the order of a heat-fusible resin film, and after adding a predetermined amount of an electrolytic solution to the bag-shaped body, the positive and negative electrodes were inserted into the opening of the bag-shaped body. An electric double layer capacitor having a capacitance of 30 F was produced by sealing the negative electrode current collector with the terminal portion sandwiched therebetween.

Regarding the obtained electric double layer capacitor,
When activation was performed by applying a predetermined amount of charge and discharge, the voltage did not increase even after charging, that is, the number of short-circuited capacitors was 2/20. As a result of observing the internal lamination state, it was confirmed that it was due to the contact between the terminals of the current collector. Also,
The battery was charged at 3 mA / cm ² to a voltage (V) of 3.0 V, and further charged at a constant voltage for 2 hours.
^The time t required for discharging to 0 V at ² was measured, and the capacitance was measured by the following formula: capacitance (C) = current (I) × voltage (V) / time (t). g. The charge / discharge cycle is defined as one cycle, and
After repeating the charge and discharge for 00 cycles, the rate of decrease in the capacitance relative to the initial value was measured, and as a result, the rate of decrease was 7%.

(Embodiment 2) With respect to the separator of Embodiment 1, the depths of the recesses formed on both sides were 0.10 mm, respectively.
And a shape similar to that of Example 1 except that one end of the peripheral edge of the concave portion has a notch for accommodating a terminal portion of a current collector having a width of 10 mm and a thickness of 0.05 mm. Except that the activated carbonaceous structure and the current collector are sequentially housed in the recesses of the separator,
An electric double layer capacitor was manufactured in the same manner as in Example 1.

As a result of evaluation in the same manner as in Example 1, the number of short-circuited capacitors was 0/20 and the capacitance was 23.
8F / g and the rate of decrease in capacitance was 5%.

(Example 3) Only one side of the separator shape of Example 2 was formed with a concave portion having the shape of Example 2 so that the width of the peripheral portion between the concave portions was 2.5 mm and the thickness of the peripheral portion was 6 mm. A separator was produced in the same manner as in Example 2, except for performing the above. The cutouts of the respective recesses are peripheral portions other than the shared peripheral portion, and are formed so as to be located on the same side surface when folded back at the shared peripheral portion and not overlap with each other.

After the obtained separator is folded at the common peripheral portion, the same operation as in Example 2 is performed except that the activated carbonaceous structure and the current collector are housed in the recess of the separator in the same manner as in Example 2. As a result of producing and evaluating a double-layer capacitor, the number of short-circuited capacitors is 0/20,
The capacitance was 23.8 F / g, and the rate of decrease in capacitance was 5%.

(Comparative Example) The separator of Example 1 was 55 m
An electric double layer capacitor was manufactured and evaluated in the same manner as in Example 1 except that the shape was a flat plate having an m square × 0.10 mm thickness. As a result, the number of shorted capacitors was 6/20, and the capacitance was 22.5F. / G, the rate of decrease in capacitance was 10%. As for this short-circuited capacitor, the laminate film was peeled off and the internal laminated state was observed.
It was confirmed that in addition to the contact between the terminals of the current collector, the displacement was caused by the displacement between the polarizable electrodes and the position of the separator.

That is, the electric double-layer capacitor in which the separator has a flat plate shape is displaced between the polarizable electrodes and the separator as compared with the electric double-layer capacitor in which the polarizable electrode is housed in the recess according to the present invention. It was found that the frequency was high, and that the polarizable electrode ran out of liquid due to long-term use, and the rate of decrease in capacitance increased.

[0039]

As described in detail above, according to the present invention,
By providing a concave portion on the surface of the separator and accommodating the polarizable electrode in the concave portion, it is possible to prevent short-circuiting between the polarizable electrodes and a displacement of the separator, and to prevent the electrolytic solution of the polarizable electrode from prolonged use. As a result, the rate of change in capacitance can be reduced, and the life of the electric double layer capacitor can be extended.

[0040]

[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 an exploded perspective view of the electric double layer capacitor of FIG.

FIG. 3 is a schematic sectional view of another example of the electric double layer capacitor of the present invention.

FIG. 4 is an exploded perspective view of the electric double layer capacitor of FIG.

FIG. 5 is an exploded perspective view showing still another example of the electric double layer capacitor of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric double layer capacitor 2 Polarized electrode 3, 10, 14 Separator 4, 8 Current collector 5 Exterior material 6, 11 Concave part 7, 9 Terminal part 12, 15 Peripheral part 13 Notch

Claims (3)

[Claims] An electric double-layer capacitor comprising: a pair of polarizable electrodes; a separator interposed between the pair of polarizable electrodes; and a current collector laminated on each of the other surfaces of the polarizable electrodes. An electric double-layer capacitor, wherein the separator has concave portions on both surfaces, and the pair of polarizable electrodes is accommodated in the concave portions. 2. The electric double layer capacitor according to claim 1, wherein said current collector is housed in a recess of said separator together with said polarizable electrode. 3. The electric double layer capacitor according to claim 2, wherein a notch is provided at a peripheral edge of the concave portion of the separator, and a terminal portion formed on the current collector is projected from the notch. .