JP4593493B2 - Electric double layer capacitor - Google Patents

Description

  The present invention relates to an electric double layer capacitor.

  The electric double layer capacitor is provided with polarizable electrodes (positive electrode and negative electrode) facing each other with a separator interposed therebetween, and utilizes the capacitance of the electric double layer formed on the surface of the polarizable electrode in the electrolytic solution. . Electric double layer capacitors are characterized by extremely large capacitance compared to ordinary capacitors such as aluminum capacitors. They are used for backup of electronic devices, power storage for home appliances and copiers, and for automobiles. A wide range of uses has begun, including power supplies for starting during idle stops, power supplies for hybrid vehicles, and power storage for peak shaving and leveling of wind power and solar power generation. This is a key to save energy and reduce carbon dioxide. Expected as a device.

  The electric double layer capacitor has different shapes such as a button type and a laminated type, but in either case, a positive electrode and a negative electrode made of a polarizable electrode mainly composed of carbon particles such as activated carbon, and a separator that separates these two electrodes Are alternately laminated in the outer case and impregnated with an electrolytic solution (such as an electrolyte dissolved in a solution or an ionic liquid).

  Since the electric double layer capacitor does not involve a chemical reaction during charging and discharging, there is an advantage that a large current can be charged and discharged instantaneously and charging and discharging efficiency is good. In addition, it has the advantages that it can be charged and discharged more than 100,000 times, has a lifetime of 10 years or more, and is highly reliable. On the other hand, compared with a lithium ion battery etc., there exists a fault that an energy density is low.

  Therefore, in order to increase the energy density of the electric double layer capacitor, a device for optimizing the combination of the pore diameter of carbon and the size of the electrolyte, or increasing the energy density by using nanogate carbon or nanocarbon has been devised.

  For example, Patent Document 1 discloses that the energy density can be improved to nearly six times that of the prior art by using non-porous charcoal with a developed multi-layer graphene layer. It is also known that the energy density can be increased by using nanocarbon such as carbon nanotubes.

  Patent Document 2 discloses that the use of specially activated alkali-activated activated carbon increases the electrostatic capacity and increases the energy density.

JP 2004-289130 A JP 2005-129924 A

  However, when carbon having a high energy density is used as the electrode material, the electrode expands during charging and contracts during discharging. This is because intercalation causes the volume to expand due to the electrolyte being absorbed by the carbon of the electrode during charging, and the electrolyte absorbed by the electrode is discharged outside the electrode during discharging. This is because the volume shrinks. For example, when nanogate carbon or alkali activated carbon is used as the electrode material, expansion of about 20 to 30% occurs during charging, and contraction of about 20 to 30% occurs during discharging.

  When the electrode expands during charging, the electrolyte solution impregnated in the separator moves to the electrode side, so that the electrolyte solution impregnated in the separator is insufficient and voids are generated in the pores of the separator. As a result, there exists a problem that the electrical resistance of a separator becomes high.

  In addition, when the electrode contracts during discharge, the electrolyte discharged from the electrode moves to the separator side, and the electrolyte that can no longer be stored in the separator is discharged from the discharge valve provided in the outer case to the outside of the outer case. Overflowing. As a result, there is a problem in that the electrolyte in the outer case is insufficient and the life is shortened, and the overflowed electrolyte causes the external circuit to be electrically short-circuited and corroded.

  On the other hand, since the expansion / contraction of the electrode occurs only in the stacking direction, the electrode is expanded / contracted in order to suppress the change in the amount of the electrolyte in the separator by applying a surface pressure to the main part of the large cell part. Although it can be reduced to about 10%, if the expansion / contraction of the electrode is suppressed, the electrolytic solution and electrolyte do not enter the electrode, so the electric double layer is not sufficiently expanded in area. The increase in the electrostatic capacity in comparison with the above is only about 1.5 times. However, 20-30% expansion / contraction is allowed, and if the electrode is quickly filled with sufficient electrolyte and electrolyte and charged quickly when discharged, the capacitance can be tripled. Expanding.

  Therefore, the present invention has been made in view of the above points, and while increasing the electrostatic capacity, the electrolyte solution impregnated in the separator is maintained at a constant amount, and the electrical resistance of the separator is increased or the outside is increased. An object of the present invention is to obtain an electric double layer capacitor capable of avoiding leakage of electrolyte.

An electric double layer capacitor according to the present invention has a positive electrode and a negative electrode which are opposed to each other with a porous separator impregnated with an electrolyte interposed therebetween, expands by charging and contracts by discharging, and contacts the separator, and cushions A porous electrolyte reservoir that can be impregnated with the electrolyte, and the electrolyte reservoir is made of a foamed plastic having both closed pores and open pores, and the positive electrode and the negative electrode When at least one of them expands, it contracts, and when at least one of them contracts, it expands.

  According to the electric double layer capacitor of the present invention, since the electrolyte reservoir contracts when the positive electrode and the negative electrode expand, the positive electrode and the negative electrode absorb the electrolyte by expansion due to charging, and are sandwiched between the positive electrode and the negative electrode. Even when the separator is short of electrolyte, the electrolyte can be quickly supplied to the separator by the electrolyte reservoir. In addition, the electrolyte reservoir expands when the positive electrode and the negative electrode contract, so the positive electrode and the negative electrode release the electrolyte due to contraction due to discharge, and the electrolyte overflows from the separator sandwiched between the positive electrode and the negative electrode However, the electrolyte reservoir can quickly absorb and hold the electrolyte from the separator. Therefore, the electrolyte solution impregnated in the separator can be maintained at a constant amount while allowing sufficient expansion and contraction of the positive electrode and the negative electrode during charging and discharging. As a result, it is possible to avoid an increase in the electrical resistance of the separator and leakage of the electrolyte solution to the outside while increasing the capacitance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure, the element which attached | subjected the same code | symbol shall show the same or equivalent element.

Embodiment 1 FIG.
1 and 2 are sectional views showing the structure of the electric double layer capacitor according to Embodiment 1 of the present invention. FIG. 1 shows the structure of the electric double layer capacitor at the time of complete discharge, and FIG. 2 shows the structure of the electric double layer capacitor at the time of full charge. As shown in FIGS. 1 and 2, the electric double layer capacitor according to the first embodiment includes an outer case 1, an electrolyte reservoir 4 and a cell unit 5 housed in the outer case 1, and a positive electrode terminal 2. And a negative electrode terminal 3.

  The cell unit 5 includes a positive electrode 6 and a negative electrode 7 that are opposed to each other with a porous separator 10 interposed therebetween, and a positive electrode current collector plate 8 and a negative electrode current collector plate 9 that are connected to the positive electrode 6 and the negative electrode 7 from the outside, respectively. Yes. The positive electrode 6, the negative electrode 7, and the separator 10 are impregnated with an electrolytic solution.

As the positive electrode 6 and the negative electrode 7, an alkali activated carbon or nanogate carbon having a diameter of about 10 μm is used with a fluorine resin such as PTFE (polytetrafluoroethylene) or an SBR (styrene butadiene rubber) synthetic rubber as a binder. A layer having a thickness of several tens of μm to several mm is used. The shape of each main surface of the positive electrode 6 and the negative electrode 7 is a square of 10 cm × 10 cm, for example, and the area thereof is 100 cm ² . Hereinafter, the positive electrode 6 and the negative electrode 7 may be collectively referred to simply as “electrodes”.

  The positive electrode 6 is formed on the positive electrode current collector plate 8, and the negative electrode 7 is formed on the negative electrode current collector plate 9. The positive electrode current collector plate 8 is formed of, for example, an aluminum foil and is connected to the positive electrode terminal 2. The negative electrode current collector plate 9 is made of, for example, aluminum foil or copper foil, and is connected to the negative electrode terminal 3. The positive electrode terminal 2 and the negative electrode terminal 3 are drawn out from the upper surface side to the outside of the outer case 1 while being sealed by a seal portion 11 provided on the upper surface of the outer case 1.

  The separator 10 exists between the positive electrode 6 and the negative electrode 7 and is provided in contact with the main surface so as to cover most of the main surface of the positive electrode current collector plate 8 opposite to the positive electrode 6. . Further, the separator 10 is provided in contact with the main surface so as to cover most of the main surface of the negative electrode current collector plate 9 opposite to the negative electrode 7. The separator 10 is provided so as to cover the bottom surfaces of the positive electrode 6 and the positive electrode current collector plate 8 and the negative electrode 7 and the negative electrode current collector plate 9.

  Examples of the separator 10 include cellulose-based materials such as natural pulp, natural cellulose, solvent-spun cellulose, and bacterial cellulose, and non-woven fabric containing glass fibers and non-fibrillated organic fibers, as well as nylon 66, aromatic polyamide, wholly aromatic polyamide, Aromatic polyester, wholly aromatic polyester, wholly aromatic polyester amide, wholly aromatic polyether, wholly aromatic polyazo compound, polyphenylene sulfide (PPS), poly-p-phenylenebenzobisthiazole (PBZT), poly-p-phenylene Philylated forms such as benzobisoxazole (PBO), polybenzimidazole (PBI), polyetheretherketone (PEEK), polyamideimide (PAI), polyimide, polytetrafluoroethylene (PTFE), or Porous film is used. The separator 10 has a thickness of about 20 μm to 50 μm, a porosity (porosity) of about 60% to 80%, and an average pore diameter of several μm to several tens of μm. There are various average pore diameters, and the same material can be easily changed with the basis weight. The average pore diameter can be easily measured using an analytical instrument such as a commercially available mercury intrusion porosimeter or gas adsorption. It is also possible to entrust the analysis by handing the sample to the analysis manufacturer.

The electrolyte reservoir 4 is made of a porous material having a cushioning property that can be impregnated with the electrolyte, and is provided in contact with the separator 10. The electrolyte reservoir 4 according to the first embodiment is disposed between the inner side surface 1 a of the outer case 1 and the side surface that is the main surface of the cell portion 5 so as to come into contact therewith. Specifically, the electrolyte reservoir 4 is in contact between the side surface of the separator 10 formed on the main surface of the positive electrode current collector plate 8 opposite to the positive electrode 6 and the inner side surface 1 a of the outer case 1. And formed between the side surface of the separator 10 formed on the main surface opposite to the negative electrode 7 in the negative electrode current collector plate 9 and the inner side surface 1a of the outer case 1 in contact with them. Has been. The electrolyte reservoir 4 can be composed of various materials and structures as long as it is stable under the conditions of the electrolyte, electrolyte, electrochemical potential, and temperature used. The shape of the main surface of the electrolyte reservoir 4 is, for example, a 10 cm × 10 cm square that is the same as the shape of the main surfaces of the positive electrode 6 and the negative electrode 7, and the area thereof is 100 cm ² .

As the electrolyte, for example, a combination of a cation and an anion is used. The cation is quaternary ammonium, 1,3-dialkylimidazolium, or 1,2,3-trialkylimidazolium, and the anion is BF ₄ ⁻ , PF. ₆ ⁻ , ClO ₄ ⁻ , or CF ₃ SO ₃ ^— , AlCl ₄ ⁻ or BF of 1-ethyl-3-methylimidazolium (EMI), 1,2-dimethyl-3-propylimidazolium (DMPI) ₄ ^- and salts, such as are used. As the solvent, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxymethane, diethoxyethane, γ-butyllactone, acetonitrile, a mixed solvent of two or more of these selected from propionitrile, and the like are used. ing. In the present invention, the electrolytic solution means a liquid electrolyte solution containing these.

  As a material for the outer case 1, a laminate film in which a resin such as polyethylene is bonded to the surface of an aluminum foil is used. The outer case 1 is provided with a discharge valve (not shown). The discharge valve is provided with a small through hole, which is normally closed by the valve, but when the internal pressure of the outer case 1 increases, the valve opens and the through hole opens, The gas in the outer case 1 is released to the outside.

  In the electric double layer capacitor according to the first embodiment configured as described above, when the positive electrode 6 and the negative electrode 7 expand during charging or contract during discharging, the electrolyte reservoir 4 and the separator 10 are mutually connected. The electrolyte solution is delivered at the contacting portion. At the time of charging, as shown in FIG. 2, the positive electrode 6 and the negative electrode 7 absorb the electrolytic solution and expand, and the electrolytic solution impregnated in the separator 10 moves to the positive electrode 6 and the negative electrode 7. Then, the electrolytic solution moves from the electrolytic solution reservoir 4 to the separator 10 via the contact surface between the electrolytic solution reservoir 4 and the separator 10. When fully charged, the positive electrode 6 and the negative electrode 7 are expanded most, and the electrolyte reservoir 4 is contracted most.

  On the contrary, at the time of discharging, as shown in FIG. 1, the positive electrode 6 and the negative electrode 7 discharge and reduce the electrolytic solution, and the electrolytic solution moves to the separator 10. Then, the electrolyte moves from the separator 10 to the electrolyte reservoir 4 via the contact surface between the electrolyte reservoir 4 and the separator 10. At the time of complete discharge, the positive electrode 6 and the negative electrode 7 are most contracted, and the electrolyte reservoir 4 is most expanded.

  In the first embodiment, since the main surface of the electrolyte reservoir 4 and the main surface of the separator 10 are in contact with each other, the electrolyte can be exchanged between the charge solution reservoir 4 and the separator 10 using a large area. It can be realized instantly.

  FIG. 3 shows the pore size distribution (S10) of the separator 10, the pore size distribution (S4) of the electrolyte reservoir 4, the pore size distribution (S7) of the electrode, and the pore occupancy ratio of the electrolyte during complete discharge. FIG. 4 shows the pore size distribution (S10) of the separator 10, the pore size distribution (S14) of the electrolyte reservoir 4, the pore size distribution (S17) of the electrode, and the pore occupancy ratio of the electrolyte during full charge. FIG. Here, the pore occupation ratio (hereinafter simply referred to as “occupancy ratio”) means the pore volume filled with the electrolyte with respect to the total pore volume. 3 and 4, the pore occupancy ratio of the electrolytic solution is indicated by hatching.

  As shown in FIGS. 3 and 4, the average pore diameter of the electrolyte reservoir 4 is set larger than the average pore diameter of the electrode and the average pore diameter of the separator 10. Therefore, the occupancy rate of the electrolyte solution in the pores of the electrode and the separator 10 is kept high by the difference in pore suction force. This is because, when the contact angle between the electrode, the separator 10 and the surface of the electrolyte reservoir 4 and the electrolyte is less than 90 degrees, a force for drawing the electrolyte into the electrode, the separator 10 and the electrolyte reservoir 4 is generated by capillary action. However, the smaller the pore diameter, the stronger the force. If the contact angle is the same, the electrolyte solution is filled in order from the pores with the smallest pore diameter. And since the average pore diameter of the electrode is set smaller than the average pore diameter of the separator 10, the electrolyte solution of the electrode is always kept in a full state. If the electrolyte is less than the total pore volume of the electrode, electrolyte reservoir 4 and separator 10, pores with a large diameter of the electrolyte reservoir 4 are left as areas not filled with the electrolyte.

  At the time of charging, when the electrolytic solution is sucked into the carbon of the electrode by a mechanism such as intercalation and the volume of the electrode is increased as indicated by an arrow 100 in FIG. 4, from the separator 10 to the electrode as indicated by an arrow 110. The electrolytic solution moves, and voids are generated in some of the pores of the separator 10. When a gap is generated in the separator 10, the electrical resistance is increased, the charging efficiency is decreased, the heat generated by charging is increased, the temperature is increased, and the life is shortened. However, in the electric double layer capacitor according to the first embodiment, as indicated by an arrow 111, the electrolytic solution present in the large pores in the electrolytic solution reservoir 4 moves to the gap of the separator 10, The gap is filled with the electrolytic solution.

  Further, when the electrode expands, the surface pressure applied to the electrolytic solution reservoir 4 increases, and as shown by an arrow 101 in FIG. 4, the electrolytic solution reservoir 4 having cushioning properties is crushed and contracted. Then, as indicated by an arrow 111, the electrolytic solution held by the electrolytic solution reservoir 4 is quickly released to the separator 10. Therefore, the gap formed in the separator 10 can be quickly filled with the electrolytic solution. Further, since the expansion of the electrode is absorbed by the electrolyte reservoir 4, it is possible to mitigate the expansion of the outer case 1.

  Thus, by providing the electrolytic solution reservoir 4 having a cushioning property, the electrode can be allowed to expand, and the electrolytic solution is absorbed into the electrode by an allowable amount, so that a high capacitance can be realized.

  In the example shown in FIG. 4, the occupancy rate of the electrolyte solution in the pores of the separator 10 at the time of full charge is 100%. In this case, the electrical resistance of the separator 10 does not increase at all. However, if the occupancy ratio of the electrolyte in the pores of the separator 10 is 50% or more, the electrolytes in adjacent pores in the separator 10 are connected to each other, and the increase in electrical resistance is within an allowable range. Since the electrolyte solution in the separator 10 is the least during full charge, if the occupancy rate of the electrolyte solution in the pores of the separator 10 during full charge is 50% or more, the increase in the electrical resistance of the separator 10 is It will be within the allowable range.

  On the other hand, when the electrode contracts during discharge as indicated by an arrow 200 in FIG. 3, the electrolyte discharged from the electrode moves to the separator 10 as indicated by an arrow 210. When the occupancy ratio of the electrolytic solution in the pores of the separator 10 exceeds 100%, the electrolytic solution that cannot be accommodated in the separator 10 as indicated by an arrow 211 is absorbed by the electrolytic solution reservoir 4. As a result, it is possible to avoid a situation in which the electrolyte overflows from the discharge valve to the outside of the outer case 1. Since the electrolytic solution in the separator 10 is the largest during complete discharge, as shown in FIG. 3, the occupation ratio of the electrolytic solution to the pores of the electrolytic solution reservoir 4 during complete discharge is 100% or less. In this case, leakage of the electrolyte solution to the outside of the outer case 1 can be prevented.

  As described above, the electrolyte reservoir 4 has an electrolyte occupancy ratio of 50% or more in the pores of the separator 10 at the time of complete charging, and an occupancy ratio of 100% of the electrolyte solution in the pores of the electrolyte reservoir 4 at the time of complete discharge. It suffices that the electrolyte solution is impregnated with a predetermined amount so as to be not more than%. Thereby, the leakage of the electrolyte solution to the outside at the time of discharging can be prevented while keeping the increase in the electrical resistance of the separator 10 at the time of charging within an allowable range.

  As an example of Embodiment 1, separator paper for electric double layer capacitor “TF40” manufactured by Nippon Kogyo Paper Industry Co., Ltd. can be used as separator 10. As the electrolyte reservoir 4, a 1.5 mm thick porous membrane obtained by stacking five polypropylene porous membranes having a thickness of 0.3 mm can be used. As the porous membrane made of polypropylene, for example, “MPF45AC” manufactured by Nippon Kogyo Paper Industry Co., Ltd. can be used.

  TF40 is a solvent-spun regenerated cellulose fiber having an average pore diameter of 0.3 micrometers and a porosity of 73%. MPF45AC is a polypropylene fiber having an average pore diameter of 4 micrometers and a porosity of 75%. Since the separator 10 and the electrolyte reservoir 4 have an average pore diameter that differs by about 10 times or more, the electrolyte is preferentially occupied by the separator 10 having a large pore suction force.

Electrolyte reservoir 4 having a thickness of 1.5mm in a state where not applied surface pressure, when applying a surface pressure of 2 kg / cm ² become a thickness of 1.0 mm, 0.7 mm at a surface pressure of 5 kg / cm ² The thickness becomes. Such an electrolyte reservoir 4 has a sufficient cushioning property against a change in surface pressure accompanying a change in electrode thickness due to charge / discharge.

  It is desirable that the average pore diameter of the electrolyte reservoir 4 is larger than the average pore diameter of the separator 10, but conversely if the contact angle with the electrolyte is smaller than that of the electrolyte reservoir 4, Since the pore suction force of the separator 10 is higher than that of the electrolyte reservoir 4, the same effect as that obtained when the average pore diameter is different can be obtained.

  Even if the average pore diameter of the electrolyte reservoir 4 is smaller than that of the separator 10 and the contact angle with the electrolyte is larger than that of the electrolyte reservoir 4, the electrolyte reservoir 4 is crushed as the electrode expands. If the electrolytic solution that has contracted and cannot be accommodated in the electrolytic solution reservoir 4 moves to the separator 10, the separator 10 is electrolyzed while mitigating expansion of the outer case due to expansion of the electrode during charging. A shortage of electrolyte at the electrode can be compensated by supplying a solution.

  In order to allow the electrode to expand and contract, it is desirable that the separator 10 has a sufficient length during full discharge as shown in FIG. 1, and the positive electrode current collector plate 8 during full charge as shown in FIG. It is desirable that the negative electrode current collector plate 9 has a sufficient length. These most desirable lengths can be precisely designed from the amount of change in the thickness of the electrode during charging and discharging.

  As described above, in the electric double layer capacitor according to the first embodiment, since the electrolyte reservoir 4 contracts when the positive electrode 6 and the negative electrode 7 expand, the positive electrode 6 and the negative electrode 7 are electrolyzed by expansion due to charging. Even when the electrolyte is absorbed by the separator 10 sandwiched between the positive electrode 6 and the negative electrode 7 and the electrolytic solution is insufficient, the electrolytic solution reservoir 4 can quickly supply the electrolytic solution to the separator 10. In addition, since the electrolyte reservoir 4 according to the first embodiment expands when the positive electrode 6 and the negative electrode 7 contract, the positive electrode 6 and the negative electrode 7 release the electrolyte due to contraction due to discharge, and the positive electrode 6 and the negative electrode 7 Even when the electrolyte overflows from the separator 10 sandwiched between the separators 7, the electrolyte reservoir 4 can quickly absorb and hold the electrolyte from the separator 10. Therefore, the electrolyte solution impregnated in the separator 10 can be maintained at a constant amount while allowing sufficient expansion / contraction of the positive electrode 6 and the negative electrode 7 during charge / discharge. As a result, it is possible to avoid an increase in the electrical resistance of the separator 10 and leakage of the electrolytic solution to the outside while increasing the capacitance.

  Further, since the electrolyte reservoir 4 having cushioning properties is disposed between the inner surface 1a of the outer case 1 and the cell portion 5, the expansion of the positive electrode 2 or the negative electrode 3 can be absorbed by the electrolyte reservoir 4. it can. Therefore, the exterior case 1 can be prevented from expanding due to the expansion of the positive electrode 2 or the negative electrode 3.

  As a result of conducting a charge / discharge test on the electric double layer capacitor according to the first embodiment, it was confirmed that the thickness of the outer case was hardly changed. Moreover, it confirmed that the initial value of an electrostatic capacitance improved 3 times compared with the electric double layer capacitor which has the activated carbon electrode in the past. In addition, it was confirmed that when the electric double layer capacitor was subjected to 3000 charge / discharge cycles with 10 minutes as one cycle, the decrease in capacitance showed stable operation within 5%.

Embodiment 2. FIG.
FIG. 5 is a front view showing the structure of the electric double layer capacitor according to the second embodiment of the present invention, and FIG. 6 is a cross-sectional view showing the structure of the electrolyte reservoir 4 and the cell unit 5 according to the second embodiment. is there. In FIG. 6, each element is shown separated, but actually each element is stored in the outer case 1 in close contact with each other as in the first embodiment.

  In the first embodiment, the electric double layer capacitor having only one set of the positive electrode 6 and the negative electrode 7 has been described. However, in the second embodiment, the electric double layer having a plurality of sets of the positive electrode 6 and the negative electrode 7 is used. The capacitor will be described.

  As shown in FIG. 6, the cell unit 5 according to the second embodiment has a structure in which a plurality of sets of positive electrodes 6 and negative electrodes 7 facing each other with the separator 10 interposed therebetween are stacked. A positive electrode current collector plate 8 and a negative electrode current collector plate 9 are connected to each set of the positive electrode 6 and the negative electrode 7 from the outside.

  One unit cell 50 is composed of a pair of positive electrode 6 and negative electrode 7 facing each other across the separator 10, and a positive electrode current collector plate 8 and a negative electrode current collector plate 9 connected to the set of positive electrode 6 and negative electrode 7, respectively. It is configured. The cell unit 5 includes a plurality of unit cells 50. In the second embodiment, a plurality of positive electrodes 6 and negative electrodes 7 are arranged so that electrodes of the same polarity are adjacent to each other in two unit cells 50 adjacent to each other. A current collector plate is arranged at the boundary between two unit cells 50 adjacent to each other, and two electrodes of the same polarity adjacent to each other share the current collector plate. That is, the two unit cells 50 share one current collecting plate.

  Each positive current collector plate 8 is connected to the positive electrode terminal 2, and each negative current collector plate 9 is connected to the negative electrode terminal 3. Thereby, the some positive electrode 6 and the some negative electrode 7 are electrically connected in parallel. Similarly to the first embodiment, the positive electrode terminal 2 and the negative electrode terminal 3 are sealed by a seal portion (not shown) provided on the upper surface of the outer case 1, and as shown in FIG. Has been pulled from.

  The separator 10 is a continuous body and is configured by bending a single member. The positive electrode 6 and the positive electrode current collector plate 8, and the negative electrode 7 and the negative electrode current collector plate 9 are alternately sandwiched between the folded separators 10.

  In Embodiment 2, porous electrolyte rubber having a thickness of 2 mm is used as the electrolyte reservoir 4. The electrolyte reservoir 4 is disposed between the inner side surface of the outer case 1 and the side surface of the cell part 5 in the same manner as in the first embodiment.

  The exchange of the electrolytic solution between the electrolytic solution reservoir 4 and the separator 10 is the same as in the first embodiment, and the separator 10 provided in each of the plurality of unit cells 50 is also connected to the electrolytic solution reservoir 4. The electrolyte can be exchanged. Therefore, the same effect as in the first embodiment can be obtained.

  The material of the electrolyte reservoir 4 may be porous silicone rubber or the like in addition to porous fluorine rubber, and the same effect can be obtained in this case.

Embodiment 3 FIG.
FIG. 7 is a front view showing the structure of the electric double layer capacitor according to the third embodiment of the present invention, and FIG. 8 is a cross-sectional view showing the structure of the electrolyte reservoir 4 and the cell unit 5 according to the third embodiment. is there. In FIG. 8, each element is shown separated, but actually each element is stored in the outer case 1 in close contact with each other as in the first embodiment.

  In the electric double layer capacitor according to the above-described first and second embodiments, the positive electrode terminal 2 and the negative electrode terminal 3 are taken out from the same side of the outer case 1, but in the electric double layer capacitor according to the third embodiment, The positive electrode terminal 2 and the negative electrode terminal 3 are taken out from the opposite side of the outer case.

  As shown in FIG. 8, valley folds and mountain folds are alternately applied to the separator 10, and the separator 10 has valley fold portions 150 and mountain fold portions 160 alternately. The positive electrode 6 and the positive electrode current collector plate 8 are sandwiched between the valley folds 150 of the separator 10, and the negative electrode 7 and the negative electrode current collector plate 9 are sandwiched between the mountain folds 160 of the separator 10.

  The positive electrode terminal 2 is drawn from the upper surface side to the outside of the outer case 1 as shown in FIG. 7 while being sealed by a seal portion (not shown) provided on the upper surface of the outer case 1. On the other hand, the negative electrode terminal 3 is pulled out from the bottom surface side to the outside of the exterior case 1 as shown in FIG. 7 while being sealed by a seal portion (not shown) provided on the bottom surface of the exterior case 1.

  In the third embodiment, a gel electrolyte having a thickness of 2 mm is used as the electrolyte reservoir 4. As the gel electrolyte, for example, a precursor in which polyvinylidene fluoride and hexafluoropropylene are mixed is heated in a vacuum oven, and then the precursor is converted into an organic electrolytic solution (TEMABF4: triethylmethylammonium tetrafluoroborate) containing an electrolyte (TEMABF4: triethylmethylammonium tetrafluoroborate). It is formed by impregnating propylene carbonate). Gel electrolyte compresses and squeezes and releases the electrolyte when it receives a strong surface pressure, absorbs the electrolyte again when the surface pressure is reduced, and acts as a cushion against the surface pressure and has a reserve function for the electrolyte. ing.

  Even when the positive electrode terminal 2 and the negative electrode terminal 3 are taken out to the opposite side of the outer case 1 as in the second embodiment, there is no problem and the same effect as in the first and second embodiments is obtained. can get.

Embodiment 4 FIG.
9 and 10 are cross-sectional views showing the structure of the electrolyte reservoir 4 according to Embodiment 4 of the present invention. FIG. 9 shows the electrolyte reservoir 4 in an expanded state, and FIG. 10 shows the electrolyte reservoir 4 in a contracted state. The electrolyte reservoir 4 according to Embodiment 4 includes a metal cushion plate 4a and a porous body 4b made of carbon fiber that holds the metal cushion plate 4a.

  As a material of the metal cushion plate 4a, a stainless plate, a copper plate, an aluminum plate, or the like can be used. As a material of the porous body 4b made of carbon fibers, carbon cloth, carbon felt, or the like can be used.

  Carbon cloth and carbon felt are excellent in electrochemical corrosion resistance, have stability against electrolytes, have a large pore diameter, and are suitable as a reservoir. Although it is possible to configure the electrolyte reservoir 4 with only carbon cloth or carbon felt, in the fourth embodiment, the metal cushion plate 4a is used to reinforce the function of the electrolyte reservoir 4 to buffer the surface pressure. Is used. The shape of the metal cushion plate 4a can be freely selected such as a rectangle or a wave shape. The electrolytic solution reservoir 4 is not constituted only by the carbon cloth or carbon felt, but by placing the metal cushion plate 4a between them, there is an effect that a greater cushioning property against the surface pressure can be obtained. As a result, the outer case 1 can be further suppressed from expanding. Moreover, even if the same material is used for the carbon cloth and the carbon felt constituting the porous body 4b, the cushioning property of the electrolyte reservoir 4 is changed by changing the shape, thickness, and material of the metal cushion plate 4a. This also has the effect of increasing the degree of freedom in designing the electrolyte reservoir 4.

  Such electrolyte reservoir 4 can be used for any of the electric double layer capacitors according to the above-described first to third embodiments.

Embodiment 5 FIG.
11 and 12 are sectional views showing the structure of the electrolyte reservoir 4 according to the fifth embodiment of the present invention. FIG. 11 shows the electrolyte reservoir 4 in an expanded state, and FIG. 12 shows the electrolyte reservoir 4 in a contracted state. The electrolyte reservoir 4 according to the fifth embodiment is made of foamed plastic having both closed pores 4c and open pores 4d. Such an electrolyte reservoir 4 can be easily formed by foaming a polymer material such as polyethylene, polypropylene, or polystyrene with a gas, and then opening holes in the material to create open pores.

  The closed pores 4c, ie, pores not communicating with the outside, serve as cushions, and the open pores 4d, ie, pores communicating with the outside, serve as an electrolyte reservoir. As the above-described polymer material, a copolymer or a composite material can be used in addition to a single material, and the same effect can be obtained.

  The electrolyte reservoir 4 according to the fifth embodiment can be used for any of the electric double layer capacitors according to the first to third embodiments.

  In the above first to fifth embodiments, the case where the present invention is applied to a multilayer electric double layer capacitor has been described. However, the present invention is also applied to a button type, box type, or cylindrical type electric double layer capacitor. Is possible, and the same effect can be obtained.

  As described above, by providing the electric double layer capacitor with the electrolytic solution reservoir 4 according to the present invention, the electrode expands and contracts as much as 30% every time charging / discharging and absorbs and discharges the electrolytic solution. This makes it possible to achieve harsh operating conditions that are not present in the market and to achieve a significant increase in capacitance.

It is sectional drawing which shows the structure of the electric double layer capacitor which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the structure of the electric double layer capacitor which concerns on Embodiment 1 of this invention. It is a figure which shows the pore diameter distribution of a separator at the time of complete discharge, the pore diameter distribution of an electrolyte solution reservoir, the pore diameter distribution of an electrode, and the pore occupation rate of an electrolyte solution. It is a figure which shows the pore diameter distribution of a separator, the pore diameter distribution of an electrolyte solution reservoir, the pore diameter distribution of an electrode, and the pore occupancy rate of an electrolyte solution during full charge. It is a front view which shows the structure of the electric double layer capacitor which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the structure of the electrolyte solution reservoir and cell part which concern on Embodiment 2 of this invention. It is a front view which shows the structure of the electric double layer capacitor which concerns on Embodiment 3 of this invention. It is sectional drawing which shows the structure of the electrolyte solution reservoir and cell part which concerns on Embodiment 3 of this invention. It is sectional drawing which shows the structure of the electrolyte reservoir which concerns on Embodiment 4 of this invention. It is sectional drawing which shows the structure of the electrolyte reservoir which concerns on Embodiment 4 of this invention. It is sectional drawing which shows the structure of the electrolyte reservoir which concerns on Embodiment 5 of this invention. It is sectional drawing which shows the structure of the electrolyte reservoir which concerns on Embodiment 5 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exterior case, 1a Inner side surface, 4 Electrolyte reservoir, 4a Metal cushion board, 4b Porous body, 4c Closed pore, 4d Open pore, 5 Cell part, 6 Positive electrode, 7 Negative electrode, 10 Separator.

Claims (4)

A cell part having a positive electrode and a negative electrode that face each other across a porous separator impregnated with an electrolytic solution, expand by charging and contract by discharging, and
A porous electrolyte reservoir in contact with the separator and having a cushioning property and capable of being impregnated with the electrolyte;
The electrolyte reservoir is made of a foamed plastic having both closed and open pores, and contracts when at least one of the positive electrode and the negative electrode expands, and when at least one of them contracts An electric double layer capacitor that expands. The electric double layer capacitor according to claim 1,
An outer case in which the cell part and the electrolyte reservoir are stored;
The electrolyte reservoir is an electric double layer capacitor disposed between an inner surface of the outer case and the cell portion. The electric double layer capacitor according to any one of claims 1 and 2,
The electric double layer capacitor , wherein an average pore diameter of the electrolyte reservoir is larger than an average pore diameter of the separator . The electric double layer capacitor according to claim 3 ,
The electrolyte reservoir has an occupancy rate of the electrolyte in the pores of the separator of 50% or more during full charge, and an occupancy rate of the electrolyte in the pores of the electrolyte reservoir of 100% or less during complete discharge. become such, the electrolyte of the predetermined amount that has been impregnated, the electric double layer capacitor.

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