JP4457469B2 - Electric double layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric double-layer capacitor, in which the sealing part will not become loose, and no leakage of electrolyte solution occurs, despite repeated expansions and contractions of the filler inside the cell during long term usage. SOLUTION: A positive-polarity polarizable electrode 7 containing an electrolyte solution, a negative-polarity polarizable electrode 7 containing an electrolyte solution, and an electrolyte solution of a gel state arranged between the polarizable electrodes, are accommodated in a space sandwiched by collector electrodes 4, 6 and surrounded by packing 2. All these are sealed hermetically by pressing from both ends, to form an electric double-layer capacitor, where a gaseous layer 8 for absorbing expansion and contraction is arranged in the space by an amount of 6% or higher and 20% or lower (under an atmospheric pressure and at 25 deg.C) of the total volume of the gas layer and the liquid layer inside the space.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric double layer capacitor having an activated carbon electrode as a polarizable electrode.
[0002]
[Prior art]
The withstand voltage of the unit capacitor is determined by the electrolysis voltage of the electrolytic solution (electrolyte, solvent) that is a component of the unit capacitor, and is about 1.2 V for an aqueous electrolyte and 2.8 to 3 V for an organic electrolyte. .
Since a capacitor is destroyed when a voltage higher than the solvent decomposition voltage is applied, a plurality of unit capacitors are connected in series for applications requiring a high voltage.
[0003]
Structurally, there are a wound type in which an electrode and a separator are spirally wound and accommodated in a cylindrical case, and a flat plate type in which the electrode separator is a flat plate.
The flat plate type can take a bipolar structure in which electrodes, separators, electrodes and separators are alternately stacked, and is suitable for high voltage applications.
[0004]
A cross-sectional view of a flat type two-cell multilayer capacitor is shown in FIG.
As shown in FIG. 1, the cell surrounded by the collector electrodes 4 and 6 and the packing 2 contains an electrolyte as a liquid layer, an activated carbon electrode as a solid layer, and nitrogen gas as a gas layer 8; Argon gas or dry air is included.
[0005]
[Problems to be solved by the invention]
In the electric double layer capacitor described above, the capacitor temperature changes to -20 to 70 ° C. due to environmental temperature changes and charge / discharge current conditions, and the in-cell liquid layer repeatedly expands and contracts.
Therefore, there has been a problem that, due to long-term use of the capacitor, the filling inside the cell is repeatedly expanded and contracted, the sealing portion is loosened, and electrolyte leakage occurs.
[0006]
[Means for Solving the Problems]
The electric double layer capacitor according to claim 1 of the present invention that solves the above problems is disposed between a positive polarizable electrode containing an electrolytic solution, a negative polarizable electrode containing an electrolytic solution, and the polarizable electrode. In an electric double layer capacitor that has a gel electrolyte solution, is housed in a space sandwiched between a collector electrode and packing, and is sealed by tightening from both ends, a gas layer for expansion and contraction absorption is provided in the space On the other hand, the amount of the electrolyte solution is determined in advance, and the gas layer for expansion and contraction absorption is 14% or more and 19% or less (at atmospheric pressure at 25 ° C.) with respect to the sum of the gas layer and the liquid layer in the space. characterized in that there.
[0007]
The electric double layer capacitor according to claim 2 of the present invention that solves the above problem is the electric double layer capacitor according to claim 1 , wherein the packing material is organic peroxide vulcanized ethylene propylene rubber (PO-EPDM). It is characterized by doing.
[0008]
The electric double layer capacitor according to claim 3 of the present invention for solving the above-mentioned problems is characterized in that in the electric double layer capacitor according to claim 1 , a fastening rib is provided on the packing.
[0009]
[Action]
Since the volume of gas and liquid changes with pressure change, but the solid does not change, the ratio of gas layer to the sum of gas layer and liquid layer (= gas layer volume / (liquid layer volume + gas layer volume)) It is theoretical to use it as an indicator.
If the sealing structure is strengthened to increase the durability against pressure increase, the weight of the capacitor will increase as a result.
Moreover, since the amount of the electrolyte solution stored in the cell is determined, when the proportion of the gas layer is increased, the capacitor volume is increased correspondingly and the volume energy density is reduced.
Therefore, the optimal ratio of the gas layer is considered to be 6% to 20%.
[0010]
In the examples described below, the ratio of the gas layer was set to 20%, and as a comparative example, the ratio was set to 5%. However, it was confirmed that good results were obtained when the ratio was set to 14%.
Also, in calculation, when the pressure is 5%, 6%, 7%, and 8% at 70 ° C, the pressure becomes 4 times, 3 times, 2.5 times, and 2.2 times respectively. It turns out that this is a point that changes.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
[Example 1]
A first embodiment of the present invention is shown in FIG.
In this embodiment, expansion of the electrolyte in the cell is suppressed by using a specified amount of gas in the cell as a buffer, and the leakage occurrence rate is reduced.
That is, in the electric double layer capacitor shown in FIG. 1, the end collector electrode 4 and the intermediate collector electrode 6 are alternately stacked with two cells sandwiched between the separators 5 and the packing 2 is interposed on the outer peripheral portion thereof. Is clamped with a tightening bolt 3 with the end plate 1 sandwiched from both sides.
[0012]
The cell surrounded by the end collector electrode 4, the intermediate collector electrode 6 and the packing 2 contains an electrolytic solution as a liquid layer, an activated carbon electrode as a solid layer, and nitrogen gas, argon gas or Contains dry air.
An aluminum foil was used as the intermediate collector electrode 6 and an activated carbon fiber cloth ACC561-25 manufactured by Nihon Kynol Co., Ltd. having an outer shape of 195 mm × 195 mm was used as the polarizable electrode 7 and both were bonded together with a conductive adhesive.
The polarizable electrode 7 was impregnated with 8 cm ^{3 of} an electrolytic solution in which tetraethylammonium tetrafluoroborate was dissolved in 1 mol / dm ³ propylene carbonate.
[0013]
A gel electrolyte solution (205 mm in length, 205 mm in width, 0.2 mm in thickness) using polyacrylonitrile as a gelling agent as the gelling agent was used as the separator 5.
As the packing 2, an elastomer having a thickness of 0.8 mm and an inner dimension of 212 mm × 212 mm was used, and 5.6 cm ³ of argon gas was sealed inside the cell.
Here, the prescribed amount of argon gas was 19% with respect to the total of the gas layer and the liquid layer.
If the specified amount is too small, the internal pressure at a high temperature increases and the leakage rate increases, and if it is too large, the cell volume increases and the capacitor has a low volume energy density. % Or more and 20% or less is desirable.
[0014]
For example, when laminating in an argon gas atmosphere (1 atm), the volume of the internal volume on the structure excluding the internal solid layer and the liquid layer is the gas filling amount.
In this embodiment, 7 cells were stacked to produce a capacitor unit.
As a comparative example, a 7-cell multilayer capacitor unit in which the amount of electrolyte impregnated in the polarizable electrode 7 was 10 cm ³ and the amount of sealed gas was 1.6 cm ³ (5% with respect to the sum of the gas layer and the liquid layer) was manufactured.
[0015]
20 units of the above two units are tested at 70 ° C for 2 hours, 25 ° C for 2 hours, -20 ° C for 2 hours, and a temperature change rate of 45 ° C / h for 100 cycles. The rate of occurrence of leakage was determined.
[0016]
As a result, the leakage rate was 80% in the comparative example, whereas it was reduced to 0% in Example 1.
The number of man-hours can be reduced by providing the cell through hole 10 of the multilayer capacitor not in the collector electrode 6 but in the packing 2.
For example, a rectangular through hole 10 of 2 mm × 2 mm is provided in the packing 2 at one location in the four corners of the thin portion inside the fastening rib, assembled as shown in FIG. 2, and tightened as shown in FIG. Capacitor unit with structure can be manufactured.
[0017]
[Example 2]
In this embodiment, by using a packing material having a small compression set, the durability at high temperature of the packing material is improved, and the leakage rate is reduced when the temperature range is widened. Other configurations are the same as those in the above-described embodiment.
A capacitor unit having the structure of Example 1 was manufactured using an organic peroxide vulcanized ethylene propylene rubber (PO-EPDM) (compression set 7%: compression rate 25% -100 ° C.-70 hours) as the packing material.
[0018]
As a comparative example, a capacitor unit having the structure of Example 1 was manufactured as a sulfur compound vulcanized ethylene propylene rubber (S-EPDM) (compression set 44%: compression rate 25% -100 ° C.-70 hours).
20 units of the above two units are each 90 ° C for 2 hours, 35 ° C for 2 hours, -20 ° C for 2 hours, and 100 cycles of heat change at a temperature change rate of 55 ° C / h. The rate of occurrence of leakage was determined.
As a result, the leakage rate was 20% in the comparative example, whereas it was reduced to 0% in Example 2.
[0019]
The number of man-hours can be reduced by providing the cell through hole 10 of the multilayer capacitor not in the collector electrode 6 but in the packing 2.
For example, a rectangular through hole 10 of 2 mm × 2 mm is provided in the packing 2 at one location in the four corners of the thin portion inside the fastening rib, assembled as shown in FIG. 2, and tightened as shown in FIG. Capacitor unit with structure can be manufactured.
[0020]
[Example 3]
A third embodiment of the present invention is shown in FIG.
In this embodiment, the sole characteristic is improved by providing a fastening rib on the packing, and the leakage rate is reduced when the temperature range is widened.
That is, in the electric double layer capacitor shown in FIG. 2, a plurality of end collector electrodes 4 and intermediate collector electrodes 6 are alternately stacked with the separator 5 interposed therebetween, and the packing 2 is interposed on the outer peripheral portion thereof. Is clamped with a tightening bolt 3 between the end plate 1 and both ends.
[0021]
Here, the packing 2 is a flat plate packing having a thickness of 0.8 mm provided with fastening ribs 9 having a width of 2.5 mm and a height of 0.2 mm.
However, FIG. 2 shows the fastening rib 9 in the assembled and laminated state, and FIG. 3 shows the fastening rib 9 in the state fastened by the fastening bolt 3.
[0022]
As a comparative example, a capacitor unit having the structure of Example 1 using a flat packing without ribs was manufactured.
20 units of the above two units are each 90 ° C for 2 hours, 35 ° C for 2 hours, -20 ° C for 2 hours, and 100 cycles of heat change at a temperature change rate of 55 ° C / h. The rate of occurrence of leakage was determined.
As a result, the leakage occurrence rate in the comparative example was 20%, whereas in Example 3, it was reduced to 0%.
[0023]
The number of man-hours can be reduced by providing the cell through hole 10 of the multilayer capacitor not in the collector electrode 6 but in the packing 2.
For example, a rectangular through hole 10 of 2 mm × 2 mm is provided in the packing 2 at one location in the four corners of the thin portion inside the fastening rib, assembled as shown in FIG. 2, and tightened as shown in FIG. Capacitor unit with structure can be manufactured.
[0024]
【The invention's effect】
As specifically described above based on the examples, in the present invention, since the sealing portion is prevented from loosening due to temperature change and the electrolyte is prevented from leaking out, the leakage resistance is excellent and the compact electric A double layer capacitor can be provided.
[Brief description of the drawings]
FIG. 1 is a structural diagram of an electric double layer capacitor according to a first embodiment of the present invention.
FIG. 2 is a structural diagram of an assembly and lamination stage of an electric double layer capacitor according to a third embodiment of the present invention.
FIG. 3 is a structural diagram after tightening of an electric double layer capacitor according to a third embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 End plate 2 Packing 3 Clamping bolt 4 End collector electrode 5 Separator 6 Intermediate current collection virtual 7 Polarizing electrode containing electrolyte 8 Gas layer 9 Clamping rib 10 Cell through hole

Claims (3)

It has a positive polarizable electrode containing an electrolytic solution, a negative polarizable electrode containing an electrolytic solution, and a gel electrolyte placed between the polarizable electrodes, and these are sandwiched between a collector electrode and a packing In an electric double layer capacitor which is accommodated in a space and sealed by tightening from both ends, a gas layer for expansion / contraction absorption is provided in the space, while the amount of the electrolyte is predetermined, and the gas for expansion / contraction absorption An electric double layer capacitor, wherein the layer is 14% or more and 19% or less (under atmospheric pressure at 25 ° C.) with respect to the sum of the gas layer and the liquid layer in the space . Electric double layer capacitor according to claim 1, characterized in that the material of the packing and organic peroxide vulcanization of ethylene propylene rubbers. Electric double layer capacitor according to claim 1, characterized in that a clamping rib on the packing.

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