JP2008060199A - Electric double layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric double layer capacitor in which long life can be attained by suppressing corrosion by hydrofluoric acid on the interface of a polarizing electrode and a collector electrode. <P>SOLUTION: In an electric double layer capacitor 1 comprising a cell 5 having a separator 2, a pair of polarizing electrodes 3A and 3B arranged on the opposite sides of the separator 2, and a pair of collector electrodes 4A and 4B arranged on the outside of the pair of polarizing electrodes 3A and 3B wherein the cell 5 is filled with electrolyte 6 containing hydrofluoric acid, hydrophobic silica is blended in the polarizing electrodes 3A and 3B. Alternatively, a separator blended hydrophobic silica may be used. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electric double layer capacitor (hereinafter also simply referred to as a capacitor).

  The electric double layer capacitor includes a separator, a pair of polarizable electrodes (activated carbon electrodes) disposed on both sides of the separator, and a pair of collector electrodes (aluminum foil) disposed on the outside of the pair of polarizable electrodes, respectively. ), And a pair of conductors (output terminals) for extracting electricity are connected to the pair of collector electrodes, respectively.

  As the separator, a nonwoven fabric made of cellulose fiber or the like is generally used. The pair of polarizable electrodes (activated carbon electrodes) is a mixture of activated carbon, a conductive auxiliary agent, and a binder, and there are one applied on the collector electrode and one formed into a sheet shape. . The inside of the cell is filled with an electrolytic solution, and this electrolytic solution penetrates into the polarizable electrode and the separator.

JP 2001-233694 A

  In order to extend the life of the electric double layer capacitor, it is necessary to control the electrochemical reaction inside the capacitor. Examples of this electrochemical reaction include the following (1) to (3).

(1) Decomposition of the electrolytic solution.
(2) Oxidation of the surface functional group of the carbon material contained in the polarizable electrode.
(3) Corrosion of the constituent material of the electric double layer capacitor by hydrofluoric acid generated due to moisture remaining inside the capacitor.

  Among these, the electrochemical reaction (1) can be controlled by appropriately maintaining the working voltage of the electric double layer capacitor. In order to control the electrochemical reaction of (2), it is necessary to adjust the amount of surface functional groups of the polarizable electrode. This adjustment of the amount of surface functional groups requires man-hours and the cost required for the treatment is polarizable. Since this is added to the cost of the electrode and causes an increase in the cost of the electric double layer capacitor, the current level is limited. Moreover, it is necessary to perform appropriate pH control with respect to the polarizable electrode after manufacture. Furthermore, when the separator is a cellulosic material, since the separator also has a surface functional group containing oxygen, there is a problem that it is difficult to obtain an effect even if the surface functional group of the electrode is adjusted.

  As for the control of the electrochemical reaction of (3), moisture is removed from the polarizable electrode and the like more thoroughly than vacuum drying or the like in the member drying step in the manufacturing process of the electric double layer capacitor. However, even after such drying treatment, trace amounts of moisture below the ppm order remain inside the electric double layer capacitor (polarizable electrodes, etc.), and this residual moisture reacts with the electrolyte containing fluorine. Then hydrofluoric acid is generated. And this hydrofluoric acid causes the increase in the internal resistance of the electric double layer capacitor by corroding the interface between the polarizable electrode and the collecting electrode, and this increase in the internal resistance deteriorates the performance of the electric double layer capacitor, The life of the electric double layer capacitor is shortened. Therefore, if the corrosion of the interface between the polarizable electrode and the collecting electrode due to the hydrofluoric acid can be controlled, the life of the electric double layer capacitor can be extended. That is, the control of hydrofluoric acid is a key point for extending the life of the electric double layer capacitor.

  Therefore, in view of the above circumstances, an object of the present invention is to provide an electric double layer capacitor capable of suppressing the corrosion of the interface between a polarizable electrode and a collecting electrode due to hydrofluoric acid and extending the life.

An electric double layer capacitor according to a first aspect of the present invention that solves the above problems includes a separator, a pair of polarizable electrodes disposed on both sides of the separator, and a pair disposed on the outside of the pair of polarizable electrodes, respectively. And an electric double layer capacitor having a structure in which the inside of the cell is filled with an electrolyte containing fluorine.
The polarizable electrode is mixed with hydrophobic silica.

  An electric double layer capacitor according to a second aspect of the invention is the electric double layer capacitor according to the first aspect of the invention, wherein the polarizable electrode is a mixture of activated carbon, a conductive aid, a binder, and the hydrophobic silica. It is characterized by that.

  The electric double layer capacitor of the third invention is the electric double layer capacitor of the second invention, wherein the blending ratio of the hydrophobic silica is 0.1 wt% to 70 wt%.

  The electric double layer capacitor according to a fourth aspect of the invention is the electric double layer capacitor according to the second aspect of the invention, wherein the blending ratio of the hydrophobic silica is 1 wt% to 30 wt%.

Moreover, the electric double layer capacitor of the fifth invention is the electric double layer capacitor of any of the second to fourth inventions,
The hydrophobic silica has an average particle size of 30 μm or less.

Moreover, the electric double layer capacitor of the sixth invention is the electric double layer capacitor of any one of the second to fourth inventions,
The hydrophobic silica has an average particle size of 10 μm or less.

The electric double layer capacitor according to the seventh aspect of the invention includes a separator, a pair of polarizable electrodes respectively disposed on both sides of the separator, and a pair of collector electrodes respectively disposed outside the pair of polarizable electrodes. In an electric double layer capacitor in which the inside of the cell is filled with an electrolyte containing fluorine,
The separator is mixed with hydrophobic silica.

An electric double layer capacitor according to an eighth aspect of the invention includes a separator, a pair of polarizable electrodes disposed on both sides of the separator, and a pair of collector electrodes respectively disposed outside the pair of polarizable electrodes. In an electric double layer capacitor in which the inside of the cell is filled with an electrolyte containing fluorine,
The separator is a stack of two sheets,
Of these two separators, the separator located on the positive electrode side is characterized by blending hydrophobic silica.

  According to the electric double layer capacitor of the first or second invention, even if water remaining in the capacitor reacts with the electrolytic solution to generate hydrofluoric acid, the hydrofluoric acid is generated at the interface between the polarizable electrode and the collector electrode, etc. It reacts with the hydrophobic silica compounded in the polarizable electrode before it is corroded. For this reason, the concentration of hydrofluoric acid is suppressed, and corrosion of the interface between the polarizable electrode and the collecting electrode due to hydrofluoric acid is suppressed. Therefore, increase in the internal resistance of the capacitor due to the corrosion is suppressed and the life of the capacitor is extended. It becomes possible. And since the lifetime of a capacitor can be extended without performing management of the surface functional group and pH of a troublesome polarizable electrode, the cost of the capacitor can be reduced.

  Further, according to the electric double layer capacitor of the third invention, since the blending ratio of the hydrophobic silica is 0.1 wt% to 70 wt%, the silica blended in an appropriate range that does not cause a decrease in the capacitance of the capacitor. Thus, the concentration of hydrofluoric acid can be suppressed, and the increase in the internal resistance of the capacitor can be suppressed.

  Further, according to the electric double layer capacitor of the fourth invention, since the blending ratio of the hydrophobic silica is 1 wt% to 30 wt%, the silica blended in a more suitable range that does not cause a decrease in the capacitance of the capacitor. Thus, the concentration of hydrofluoric acid can be suppressed, and the increase in the internal resistance of the capacitor can be suppressed.

  Further, according to the electric double layer capacitor of the fifth invention, since the average particle diameter of the hydrophobic silica is 30 μm or less, an appropriate average particle diameter that does not cause a decrease in the strength of the polarizable electrode and a decrease in the specific surface area of the silica. With this silica, the concentration of hydrofluoric acid can be suppressed, and the increase in the internal resistance of the capacitor can be suppressed.

  Further, according to the electric double layer capacitor of the sixth invention, since the average particle size of the hydrophobic silica is 10 μm or less or 1 μm to 10 μm, it does not cause a decrease in the strength of the polarizable electrode and a decrease in the specific surface area of the silica. The silica having a more appropriate average particle diameter can suppress the concentration of hydrofluoric acid and suppress the increase in the internal resistance of the capacitor.

  Further, according to the electric double layer capacitor of the seventh invention, even if moisture remaining in the capacitor reacts with the electrolytic solution to generate hydrofluoric acid, the hydrofluoric acid acts on the interface between the polarizable electrode and the collecting electrode. It reacts with the hydrophobic silica compounded in the separator before it corrodes. For this reason, the concentration of hydrofluoric acid is suppressed, and corrosion of the interface between the polarizable electrode and the collecting electrode due to hydrofluoric acid is suppressed. Therefore, increase in the internal resistance of the capacitor due to the corrosion is suppressed and the life of the capacitor is extended. It becomes possible. And since the lifetime of a capacitor can be extended without performing management of the surface functional group and pH of a troublesome polarizable electrode, the cost of the capacitor can be reduced.

  According to the electric double layer capacitor of the eighth aspect of the invention, even if moisture remaining in the capacitor reacts with the electrolytic solution to generate hydrofluoric acid, the hydrofluoric acid forms the interface between the polarizable electrode and the collecting electrode. It reacts with the hydrophobic silica compounded in the positive electrode separator before it corrodes. For this reason, since the concentration of hydrofluoric acid is suppressed and corrosion of the polarizable electrode-collector electrode interface due to hydrofluoric acid is suppressed, the increase in the internal resistance of the capacitor due to the corrosion is suppressed and the life of the capacitor is extended. It becomes possible. And since the lifetime of a capacitor can be extended without performing management of the surface functional group and pH of a troublesome polarizable electrode, the cost of the capacitor can be reduced.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

<Embodiment 1>
FIG. 1 is a cross-sectional view showing a configuration of an electric double layer capacitor according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the electric double layer capacitor 1 of the first embodiment has a cell 5. The cell 5 includes a separator 2, a pair of polarizable electrodes 3A and 3B disposed on both sides of the separator 2, and a pair of collector electrodes 4A disposed outside the pair of polarizable electrodes 3A and 3B, respectively. , 4B. The inside of the cell 5 is filled with the electrolytic solution 6, and this electrolytic solution 6 penetrates into the polarizable electrodes 3 </ b> A and 3 </ b> B and the separator 2.

  A pair of pressing plates 7A and 7B are disposed on both sides of the collecting electrodes 4A and 4B, respectively. Further, a packing 8 as a sealing material for the electrolytic solution 6 is interposed between the peripheral portions of the pressing plates 7A and 7B. The packing 8 surrounds the polarizable electrodes 3A and 3B and the outer periphery of the separator 2.

  In the state where the packing 8 is interposed, the peripheral portions of the pressing plates 7A and 7B are fastened by screws 9. For this reason, the electrolytic solution 6 is sealed in the cell 5, and the separator 2, the polarizable electrodes 3A and 3B, and the collector electrode 4 constituting the cell 5 are pressed from both sides by the pressing plates 7A and 7B. Further, the capacitor body 10 is shielded from the outside air by being wrapped by the aluminum laminate film 11. The collector electrodes 4A and 4B are connected to the proximal ends of a pair of conductors (output terminals) 12A and 12B, respectively, and the distal ends of these conductors (output terminals) 12A and 12B go out of the aluminum laminate film 11. Yes.

  The screw 9 and the collector electrodes 4A and 4B and the output terminals 12A and 12B and the aluminum laminate film 11 are electrically insulated by an insulating material (not shown). The separator 2, the polarizable electrodes 3A and 3B, the collector electrodes 4A and 4B, and the pressing plates 7A and 7B are rectangular, and the packing 8 is an ethylene butadiene rubber thin film sheet cut out in a square shape. I am using it.

  As the separator 2, an appropriate one such as a cellulose separator is used, and for example, a nonwoven fabric made of cellulose fiber or the like is used. As the collector electrodes 4A and 4B, for example, an aluminum foil is used. The electrolytic solution 6 is an electrolytic solution containing fluorine. Examples of the electrolytic solution 6 include an electrolytic solution of SBPBF4 / PC (1.4 mol / L) using spirobipyrrolidinium tetrafluoroborate (SBPBF4) as an electrolyte containing fluorine and propylene carbonate (PC) as a solvent. Used.

  In the electric double layer capacitor 1 of the first embodiment, silica is blended in the polarizable electrodes 3A and 3B. That is, the polarizable electrodes 3A and 3B are made of, for example, the same activated carbon (for example, coconut shell activated carbon powder), conductive auxiliary agent (for example, carbon black such as acetylene black) and binder (for example, PTFE (tetrafluoroethylene resin)). Further, silica is mixed with the above and is applied to the collector electrodes 4A and 4B or formed into a sheet shape. In addition, as silica blended in the polarizable electrodes 3A and 3B, hydrophobic silica (for example, hydrophobic silica from Tosoh Silica Co., Ltd .: NIPSIL-SS, etc.) is used instead of hydrophilic silica in order to suppress the moisture content inside the capacitor. Is preferably used.

  According to the electric double layer capacitor 1 of the first embodiment, moisture remaining in the capacitors (the polarizable electrodes 3A and 3B and the separators 4A and 4B) and the electrolytic solution 6 at or near the polarizable electrodes 3A and 3B. Even if hydrofluoric acid is generated by reacting with the hydrofluoric acid, the hydrofluoric acid is mixed with the hydrophobic silica 3A, 3B before corroding the interface between the polarizable electrodes 3A, 3B and the collecting electrodes 4A, 4B. React with. For this reason, since the concentration of hydrofluoric acid is suppressed and the corrosion of the polarizable electrodes 3A, 3B and the collector electrodes 4A, 4B due to the hydrofluoric acid is suppressed, the internal resistance of the electric double layer capacitor 1 is increased by the corrosion. Is suppressed, and the life of the electric double layer capacitor 1 can be extended. And since the lifetime of the electric double layer capacitor 1 can be extended without managing the surface functional groups and pH of the troublesome polarizable electrodes 3A and 3B, the cost of the electric double layer capacitor 1 can be reduced. It becomes possible.

  In addition, when the particle diameter of the silica mix | blended with polarizable electrode 3A, 3B is too large, in addition to reducing the intensity | strength of polarizable electrode 3A, 3B, the specific surface area per unit weight of silica will also fall. Therefore, the average particle diameter of the silica is preferably 30 μm or less, and more preferably 10 μm or less. For example, it is good also as an average particle diameter range of 1 micrometer-30 micrometers, Furthermore, it is good also as an average particle diameter range of 1 micrometer-10 micrometers.

  Moreover, when the compounding ratio (mixing ratio) of the silica compounded in the polarizable electrodes 3A and 3B is too large, the ratio of the activated carbon in the polarizable electrodes 3A and 3B is decreased to cause a decrease in the capacitance of the electric double layer capacitor 1. . On the other hand, if the mixing ratio of silica is too small, the hydrofluoric acid concentration cannot be suppressed. Accordingly, the compounding ratio (weight ratio) of silica is preferably 0.1 wt% to 70 wt%, and more preferably 1 wt% to 30 wt%. Even when 0.1 wt% to 70 wt% function as a capacitor and the effect of adding hydrophobic silica is also seen, the practical range is 1 wt% to 30 wt%.

<Embodiment 2>
FIG. 2 is a cross-sectional view showing a configuration of an electric double layer capacitor according to Embodiment 2 of the present invention. In the electric double layer capacitor 21 of FIG. 2, the same reference numerals are given to the same parts as those of the electric double layer capacitor 1 (FIG. 1) of the first embodiment.

  As shown in FIG. 2, the electric double layer capacitor 21 of the second embodiment is provided with two-layer separators 22A and 22B instead of the separator 2 of the electric double layer capacitor 1 of the first embodiment. ing. A pair of polarizable electrodes 3A and 3B are disposed on both sides of these separators 22A and 22B. That is, one polarizable electrode 3A is disposed outside one separator 22A, and the other polarizable electrode 3B is disposed outside the other separator 22B.

  However, the polarizable electrodes 3A and 3B according to the second embodiment do not contain silica. For example, the same activated carbon (for example, coconut shell activated carbon powder) and conductive auxiliary agent (for example, carbon black such as acetylene black) are used. ) And a binder (for example, PTFE), which are applied to the collector electrodes 4A and 4B or formed into a sheet shape.

  In the electric double layer capacitor 21 of the second embodiment, silica is blended in the separators 22A and 22B. The separators 22A and 22B are both polyolefin-based separators containing silica. As such separators 22A and 22B, for example, a polyethylene separator having a porosity of 80% to 90% mixed with silica can be used. In addition, as silica to be mixed in separators 22A and 22B, hydrophobic silica (for example, hydrophobic silica from Tosoh Silica Co., Ltd .: NIPSIL-SS) is used instead of hydrophilic silica in order to suppress the moisture content inside the capacitor. It is preferable to do.

  Since the other configuration of the electric double layer capacitor 21 is the same as that of the electric double layer capacitor 1 (FIG. 1) of the first embodiment, description thereof is omitted here.

  According to the electric double layer capacitor 1 of the second embodiment, even if the water remaining in the capacitor reacts with the electrolytic solution 6 to generate hydrofluoric acid, the hydrofluoric acid is separated from the polarizable electrodes 3A and 3B. It reacts with the hydrophobic silica blended in the separators 22A and 22B before corroding the interface of the collecting electrodes 4A and 4B. For this reason, since the concentration of hydrofluoric acid is suppressed and corrosion of the interfaces between the polarizable electrodes 3A and 3B and the collecting electrodes 4A and 4B due to hydrofluoric acid is suppressed, the internal resistance of the electric double layer capacitor 21 is increased due to the corrosion. As a result, the life of the electric double layer capacitor 21 can be extended. And since it is possible to extend the life of the electric double layer capacitor 21 without managing the surface functional groups and pH of the troublesome polarizable electrodes 3A and 3B, the cost of the electric double layer capacitor 21 can be reduced. It becomes possible.

  In addition, as a separator which mix | blended the silica used for this invention, not only the above two-sheet separator but the separator of 1 sheet or 3 sheets or more may be sufficient.

<Embodiment 3>
FIG. 3 is a sectional view showing a configuration of an electric double layer capacitor according to Embodiment 3 of the present invention. In addition, in the electric double layer capacitor 31 of FIG. 3, the same code | symbol is attached | subjected to the part similar to the electric double layer capacitor 1 (FIG. 1) of the said Example 1. FIG.

  As shown in FIG. 3, the electric double layer capacitor 31 of the third embodiment is provided with two-layer separators 32A and 32B instead of the separator 2 of the electric double layer capacitor 1 of the first embodiment. ing. The pair of polarizable electrodes 3A and 3B are disposed on both sides of the separators 32A and 32B. That is, one polarizable electrode 3A is disposed outside one separator 32A, and the other polarizable electrode 3B is disposed outside the other separator 32B.

  However, the polarizable electrodes 3A and 3B of the third embodiment do not contain silica. For example, activated carbon (for example, coconut shell activated carbon powder) and a conductive auxiliary agent (for example, carbon black such as acetylene black) are used in the same manner as in the past. ) And a binder (for example, PTFE)), which are applied on the collector electrodes 4A and 4B or formed into a sheet shape.

  In the electric double layer capacitor 31 of the third embodiment, silica is blended in one separator 32A disposed so as to be positioned on the positive electrode side (polarizable electrode 3A side). The separator 32A is a polyolefin-based separator containing silica. As the separator 32A, for example, a polyethylene separator having a porosity of 80% to 90% mixed with silica can be used. In addition, as silica to be mixed in the separator 32A, hydrophobic silica (for example, hydrophobic silica from Tosoh Silica Co., Ltd .: NIPSIL-SS, etc.) should be used instead of hydrophilic silica in order to suppress the moisture content inside the capacitor. Is preferred.

  The other separator 32B disposed so as to be located on the negative electrode side (polarizable electrode 3B side) is a cellulose separator. Since the penetration of the electrolytic solution is poor only with the polyethylene separator, the electrolytic solution is guided by the cellulose separator to improve the permeability.

  Since the other configuration of the electric double layer capacitor 31 is the same as that of the electric double layer capacitor 1 (FIG. 1) of the first embodiment, description thereof is omitted here.

  According to the electric double layer capacitor 31 of the third embodiment, even if water remaining in the capacitor reacts with the electrolytic solution 6 to generate hydrofluoric acid, the hydrofluoric acid is separated from the polarizable electrodes 3A and 3B. It reacts with the hydrophobic silica blended in the separator 32A before corroding the interface of the collecting electrodes 4A and 4B. For this reason, since the concentration of hydrofluoric acid is suppressed and the corrosion of the interfaces between the polarizable electrodes 3A, 3B and the collecting electrodes 4A, 4B due to the hydrofluoric acid is suppressed, the internal resistance of the electric double layer capacitor 31 is increased by the corrosion. Is suppressed, and the life of the electric double layer capacitor 31 can be extended. And since it is possible to extend the life of the electric double layer capacitor 31 without managing the surface functional groups and pH of the troublesome polarizable electrodes 3A and 3B, the cost of the electric double layer capacitor 31 can be reduced. It becomes possible. It has been empirically confirmed (by test) that the characteristics are improved when the polyethylene separator 32A blended with hydrophobic silica is disposed on the positive electrode side.

  The configurations of the first to third embodiments may be combined as appropriate. That is, the configuration using the polarizable electrodes 3A and 3B blended with silica and the separators 22A and 22B blended with silica, the polarizable electrodes 3A and 3B blended with silica, the separator 32A and the separator 32B blended with silica, It is good also as the structure used.

  Here, first, Examples 1 to 9 related to the first embodiment and Comparative Examples 1 and 2 will be described.

<Comparative Example 1>
An electric double layer capacitor having a structure as shown in FIG. 1 was produced. However, the polarizable electrode was prepared by mixing activated carbon, carbon black, and PTFE in the same manner as in the past without using silica. The compounding ratio (weight ratio) of activated carbon: carbon black: PTFE was 8: 1: 1. Then, a thermal acceleration voltage application test of the electric double layer capacitor was performed, and the characteristics (life) of the electric double layer capacitor were evaluated from the characteristic deterioration. The characteristic evaluation results are shown in the table of FIG. 4 and the graphs of FIGS. The capacitance retention rate and the internal resistance increase rate shown in these are expressed as percentages with respect to the initial value.

<Comparative example 2>
An electric double layer capacitor having a structure as shown in FIG. 1 was produced. However, as for the polarizable electrode, hydrophilic silica (hydrophilic silica of Tosoh Silica Co., Ltd .: NIPSIL-LP, average particle size 1 μm) is added to activated carbon, carbon black and PTFE prepared at the same mixing ratio as in Comparative Example 1. It was prepared by adding. The amount of hydrophilic silica added was such that the blending ratio of hydrophilic silica was 10 wt%. Then, a thermal acceleration voltage application test of the electric double layer capacitor was performed, and the characteristics (life) of the electric double layer capacitor were evaluated from the characteristic deterioration. The characteristic evaluation results are shown in the table of FIG. 4 and the graphs of FIGS.

<Example 1>
An electric double layer capacitor having the same configuration as in FIG. 1 was produced. The polarizable electrode was prepared by mixing the activated carbon, carbon black and PTFE prepared in the same mixing ratio as in Comparative Example 1 with hydrophobic silica (hydrophobic silica manufactured by Tosoh Silica Co., Ltd .: NIPSIL-SS, average particle size 1 μm). It was prepared by adding. The amount of hydrophobic silica added was such that the blending ratio of hydrophobic silica was 1 wt%. The electric double layer capacitor was subjected to a thermal acceleration voltage application test, and the characteristic (life) of the electric double layer capacitor was evaluated from the deterioration of the characteristic. The characteristic evaluation results are shown in the table of FIG. 4 and the graphs of FIGS.

<Example 2>
An electric double layer capacitor having the same configuration as in FIG. 1 was produced. The polarizable electrode was prepared by mixing the activated carbon, carbon black and PTFE prepared in the same mixing ratio as in Comparative Example 1 with hydrophobic silica (hydrophobic silica manufactured by Tosoh Silica Co., Ltd .: NIPSIL-SS, average particle size 1 μm). It was prepared by adding. The amount of hydrophobic silica added was such that the blending ratio of hydrophobic silica was 10 wt%. The electric double layer capacitor was subjected to a thermal acceleration voltage application test, and the characteristic (life) of the electric double layer capacitor was evaluated from the deterioration of the characteristic. The characteristic evaluation results are shown in the table of FIG. 4 and the graphs of FIGS.

<Example 3>
An electric double layer capacitor having the same configuration as in FIG. 1 was produced. The polarizable electrode was prepared by mixing the activated carbon, carbon black and PTFE prepared in the same mixing ratio as in Comparative Example 1 with hydrophobic silica (hydrophobic silica manufactured by Tosoh Silica Co., Ltd .: NIPSIL-SS, average particle size 1 μm). It was prepared by adding. The amount of hydrophobic silica added was such that the blending ratio of hydrophobic silica was 30 wt%. The electric double layer capacitor was subjected to a thermal acceleration voltage application test, and the characteristic (life) of the electric double layer capacitor was evaluated from the deterioration of the characteristic. The characteristic evaluation results are shown in the table of FIG. 4 and the graphs of FIGS.

<Example 4>
An electric double layer capacitor having the same configuration as in FIG. 1 was produced. Then, the polarizable electrode was prepared by adding hydrophobic silica (hydrophobic silica of Tosoh Silica Co., Ltd .: NIPSIL-SS, average particle size of 5 μm) to activated carbon, carbon black and PTFE prepared at the same mixing ratio as in Comparative Example 1. It was prepared by adding. The amount of hydrophobic silica added was such that the blending ratio of hydrophobic silica was 1 wt%. The electric double layer capacitor was subjected to a thermal acceleration voltage application test, and the characteristic (life) of the electric double layer capacitor was evaluated from the deterioration of the characteristic. The characteristic evaluation results are shown in the table of FIG. 4 and the graphs of FIGS.

<Example 5>
An electric double layer capacitor having the same configuration as in FIG. 1 was produced. Then, the polarizable electrode was prepared by adding hydrophobic silica (hydrophobic silica of Tosoh Silica Co., Ltd .: NIPSIL-SS, average particle size of 5 μm) to activated carbon, carbon black and PTFE prepared at the same mixing ratio as in Comparative Example 1. It was prepared by adding. The amount of hydrophobic silica added was such that the blending ratio of hydrophobic silica was 10 wt%. The electric double layer capacitor was subjected to a thermal acceleration voltage application test, and the characteristic (life) of the electric double layer capacitor was evaluated from the deterioration of the characteristic. The characteristic evaluation results are shown in the table of FIG. 4 and the graphs of FIGS.

<Example 6>
An electric double layer capacitor having the same configuration as in FIG. 1 was produced. Then, the polarizable electrode was prepared by adding hydrophobic silica (hydrophobic silica of Tosoh Silica Co., Ltd .: NIPSIL-SS, average particle size of 5 μm) to activated carbon, carbon black and PTFE prepared at the same mixing ratio as in Comparative Example 1. It was prepared by adding. The amount of hydrophobic silica added was such that the blending ratio of hydrophobic silica was 30 wt%. The electric double layer capacitor was subjected to a thermal acceleration voltage application test, and the characteristic (life) of the electric double layer capacitor was evaluated from the deterioration of the characteristic. The characteristic evaluation results are shown in the table of FIG. 4 and the graphs of FIGS.

<Example 7>
An electric double layer capacitor having the same configuration as in FIG. 1 was produced. The polarizable electrode was prepared by mixing the activated carbon, carbon black and PTFE prepared in the same mixing ratio as in Comparative Example 1 with hydrophobic silica (hydrophobic silica of Tosoh Silica Co., Ltd .: NIPSIL-SS, average particle size 9 μm). It was prepared by adding. The amount of hydrophobic silica added was such that the blending ratio of hydrophobic silica was 1 wt%. The electric double layer capacitor was subjected to a thermal acceleration voltage application test, and the characteristic (life) of the electric double layer capacitor was evaluated from the deterioration of the characteristic. The characteristic evaluation results are shown in the table of FIG. 4 and the graphs of FIGS.

<Example 8>
An electric double layer capacitor having the same configuration as in FIG. 1 was produced. The polarizable electrode was prepared by mixing the activated carbon, carbon black and PTFE prepared in the same mixing ratio as in Comparative Example 1 with hydrophobic silica (hydrophobic silica of Tosoh Silica Co., Ltd .: NIPSIL-SS, average particle size 9 μm). It was prepared by adding. The amount of hydrophobic silica added was such that the blending ratio of hydrophobic silica was 10 wt%. The electric double layer capacitor was subjected to a thermal acceleration voltage application test, and the characteristic (life) of the electric double layer capacitor was evaluated from the deterioration of the characteristic. The characteristic evaluation results are shown in the table of FIG. 4 and the graphs of FIGS.

<Example 9>
An electric double layer capacitor having the same configuration as in FIG. 1 was produced. The polarizable electrode was prepared by mixing the activated carbon, carbon black and PTFE prepared in the same mixing ratio as in Comparative Example 1 with hydrophobic silica (hydrophobic silica of Tosoh Silica Co., Ltd .: NIPSIL-SS, average particle size 9 μm). It was prepared by adding. The amount of hydrophobic silica added was such that the blending ratio of hydrophobic silica was 30 wt%. The electric double layer capacitor was subjected to a thermal acceleration voltage application test, and the characteristic (life) of the electric double layer capacitor was evaluated from the deterioration of the characteristic. The characteristic evaluation results are shown in the table of FIG. 4 and the graphs of FIGS.

  Next, Examples 10 and 11 related to Embodiments 2 to 4 and Comparative Example 3 will be described.

<Comparative Example 3>
An electric double layer capacitor having a structure as shown in FIG. 1 was produced. As the electrolytic solution, SBPBF4 / PC (1.4 mol / L) was used. However, the polarizable electrode was prepared by mixing coconut shell activated carbon powder, acetylene black, and PTFE without blending silica. The separator was not a compound containing silica, and a cellulose separator was used. Then, a thermal acceleration voltage application test of the electric double layer capacitor was performed, and the characteristics (life) of the electric double layer capacitor were evaluated from the characteristic deterioration. The characteristic evaluation results are shown in the table of FIG.

The test conditions were further described in detail. The prepared sample (electric double layer capacitor) was charged at a constant voltage of 2.8 V under an environment of a temperature of 50 ° C., and discharged at a constant current occasionally to measure the characteristics. The current density was 32 mA / cm ² and the final discharge voltage was 1.1V. The change with time of voltage was obtained from the result of the constant current discharge test, and the capacitance and internal resistance were calculated. Capacitance and internal resistance were calculated by converting per unit time. The test was conducted for up to 1000 hours. Of course, these test conditions are the same in Examples 10 and 11 described later.

<Example 10>
An electric double layer capacitor having the same configuration as in FIG. 2 was produced. And the polyethylene separator with the porosity of 80%-90% which mix | blended the hydrophobic silica as a separator was used by overlapping two sheets. The electric double layer capacitor was subjected to a thermal acceleration voltage application test, and the characteristic (life) of the electric double layer capacitor was evaluated from the deterioration of the characteristic. The characteristic evaluation results are shown in the table of FIG.

<Example 11>
An electric double layer capacitor having the same configuration as in FIG. 3 was produced. Then, a polyethylene separator having a porosity of 80% to 90% blended with hydrophobic silica as a separator and a cellulose separator were used, one in total, and two in total. The electric double layer capacitor was subjected to a thermal acceleration voltage application test, and the characteristic (life) of the electric double layer capacitor was evaluated from the deterioration of the characteristic. The characteristic evaluation results are shown in the table of FIG.

  As shown in the table of FIG. 7, the rate of change (capacitance retention rate) from the initial stage of the capacitance of the capacitor was the same as in Examples 10 and 11 and Comparative Example 3, but the internal resistance of the capacitor In Examples 10 and 11 and Comparative Example 3, there was a clear difference in the increase ΔR in internal resistance.

  The present invention relates to an electric double layer capacitor, and is useful when applied to extend the life and cost reduction of an electric double layer capacitor.

It is sectional drawing which shows the structure of the electrical double layer capacitor which concerns on Example 1 of Embodiment of this invention. It is sectional drawing which shows the structure of the electrical double layer capacitor which concerns on Example 2 of embodiment of this invention. It is sectional drawing which shows the structure of the electrical double layer capacitor which concerns on Example 3 of Embodiment of this invention. It is a table | surface which shows the list of the characteristic evaluation result (an electrostatic capacitance retention rate, an internal resistance increase rate) of the electric double layer capacitor of Examples 1-9. It is a graph which shows the characteristic evaluation result (electrostatic capacity retention) of the electric double layer capacitor of Examples 1-9. It is a graph which shows the characteristic evaluation result (electrostatic capacity retention) of the electric double layer capacitor of Examples 1-9. It is a table | surface which shows the list of the characteristic evaluation result (an electrostatic capacitance retention, an internal resistance increase part) of the electric double layer capacitor of Examples 10-12.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric double layer capacitor 2 Separator 3A, 3B Polarization electrode 4A, 4B Collector electrode 5 Cell 6 Electrolyte 7A, 7B Holding plate 8 Packing 9 Screw 10 Capacitor body 11 Aluminum laminate film 12A, 12B Conductor (output terminal)
21 Electric Double Layer Capacitor 22A, 22B Separator 31 Electric Double Layer Capacitor 32A, 32B Separator 41 Electric Double Layer Capacitor

Claims (8)

A cell having a separator, a pair of polarizable electrodes respectively disposed on both sides of the separator, and a pair of collector electrodes respectively disposed outside the pair of polarizable electrodes; and In an electric double layer capacitor having a configuration in which the inside of the cell is filled with an electrolyte containing fluorine,
The electric double layer capacitor, wherein the polarizable electrode is mixed with hydrophobic silica. The electric double layer capacitor according to claim 1,
The electric double layer capacitor, wherein the polarizable electrode is formed by mixing activated carbon, a conductive auxiliary agent, a binder, and the hydrophobic silica. The electric double layer capacitor according to claim 2,
The electric double layer capacitor according to claim 1, wherein a blending ratio of the hydrophobic silica is 0.1 wt% to 70 wt%. The electric double layer capacitor according to claim 2,
The electric double layer capacitor according to claim 1, wherein a blending ratio of the hydrophobic silica is 1 wt% to 30 wt%. The electric double layer capacitor according to any one of claims 2 to 4,
The electric double layer capacitor, wherein the hydrophobic silica has an average particle diameter of 30 μm or less. The electric double layer capacitor according to any one of claims 2 to 4,
The electric double layer capacitor, wherein the hydrophobic silica has an average particle diameter of 10 μm or less. A cell having a separator, a pair of polarizable electrodes disposed on both sides of the separator, and a pair of collector electrodes respectively disposed on the outside of the pair of polarizable electrodes; In an electric double layer capacitor in which the inside of the cell is filled with an electrolyte containing fluorine,
An electric double layer capacitor, wherein the separator is blended with hydrophobic silica. A cell having a separator, a pair of polarizable electrodes disposed on both sides of the separator, and a pair of collector electrodes respectively disposed on the outside of the pair of polarizable electrodes; In an electric double layer capacitor in which the inside of the cell is filled with an electrolyte containing fluorine,
The separator is a stack of two sheets,
An electric double layer capacitor characterized in that hydrophobic silica is blended in a separator located on the positive electrode side of these two separators.

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