JP2002075806A - Electric double-layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric double-layer capacitor which can prevent an external case from breakage and minimize the leakage of an electrolyte solution even if a gas is generated during actual usage, and can be used for a long time without reducing electric characteristics. SOLUTION: This electric double-layer capacitor 1 is sealed in a bag made of packaging material as an external case 60. At least one laminated body, in which polarizable electrodes made mainly of carbon are arranged in a pair of current collecting bodies made of metallic material, and an electron insulating separator is interposed between the polarizable electrodes, is dipped in an electrolyte solution. The capacitor 1 is provided with a buffer part 64 which is made integral with the external case 60 and is communicated therewith through a flow passage 66.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an electric double layer capacitor.

[0002]

2. Description of the Related Art An electric double layer capacitor (or "capacitor") has a farad-class large capacity,
Because of its excellent charge / discharge cycle characteristics, its use as a backup power source for electronic equipment and as a battery for various transport vehicles, such as automobiles, and for storage of nighttime power from the viewpoint of effective use of energy are being studied. .

As shown in FIG. 4, a single electrode cell 10, which is one of the basic structures of such an electric double layer capacitor, is generally connected to current collectors 20 and 22 made of a metal material on the positive electrode side, respectively. The polarizable electrode 24 and the polarizable electrode 26 on the negative electrode side are formed, and the polarizable electrodes 24 and 26 are
8 and a polarizable electrode 2
The electrolyte solution composed of a solvent and an electrolyte is impregnated into the separators 4 and 26 and the separator 28.

FIG. 5 shows the structure of a single capacitor cell 12 in which a plurality of single electrode cells 10 are
It has a structure in which the electrode lead-out portions 30 and 32 formed on the reference numerals 0 and 22 are electrically connected in parallel, respectively. Usually, the electrode take-out parts 30, 32 are connected to electrode terminals.
Each of the single electrode cell 10 and the single capacitor cell 12 is a flat plate type, and has a feature that high filling and large area are easy. Further, as an electric double layer capacitor having a relatively large capacity used for an automobile or the like, a capacitor module in which a plurality of such single capacitor cells 12 are stacked is preferably used.

When an electric double layer capacitor as described above is actually used, strict packaging suitability (sealing) is applied to portions other than the connection portion between the electrode terminals in order to prevent intrusion of moisture which causes leakage or deterioration of the electrolyte from outside air. It is important to package in a manner such as resistance, barrier properties, abrasion resistance, and expansion resistance.
For this reason, sealing is conventionally performed in an outer case made of a robust metal, but there is a disadvantage that the outer case is large and heavy. Therefore, in recent years, the use of a soft case, which is a bag made of a laminated film in which a resin film and an aluminum foil are laminated, as an outer case has been studied.

In the electric double layer capacitor manufactured as described above, depending on the use conditions, for example, use at a large current, use at a high temperature exceeding 60 ° C., or use for a long time, Gas generated by the decomposition of the solvent or solute of the electrolytic solution enclosed in the case,
Since the internal pressure of the outer case is increased, not only the electrical characteristics of the electric double layer capacitor are reduced, but also the outer case is expanded and deformed. In particular, in the case of an outer case made of a laminated film bag, there is some degree of deformation, but beyond that, the outer case is ruptured, and the electrolyte in the outer case leaks out. was there.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the related art,
Its purpose is to prevent the rupture of the outer case and minimize the leakage of the electrolyte even if gas is generated during actual use and the internal pressure of the outer case rises, and to improve the electrical characteristics. An object of the present invention is to provide an electric double layer capacitor that can be used for a long time without lowering.

[0008]

Means for Solving the Problems According to the present invention, a pair of current collectors made of a metal material is provided with a polarizable electrode formed mainly of a carbon material, and the polarizable electrode is An electric double-layer capacitor in which at least one laminate having an electronic insulating separator interposed therebetween is immersed in an electrolyte and sealed in a bag made of a package material as an outer case, wherein the outer case is provided. An electric double layer capacitor is provided, which is formed integrally with the outer case and has a buffer portion that communicates with the outer case via a flow path.

At this time, in the present invention, it is preferable that the buffer portion is a bag obtained by sealing the same package material as the outer case.

[0010] In the present invention, it is preferable that the buffer unit has a pressure releasing unit that releases gas to the outside when the pressure inside the outer case rises. At this time, the pressure release portion is preferably formed integrally with the normal seal by a seal having a weaker adhesive force than the normal seal. For example, a no-seal portion is provided outside the notch structure or the weak seal portion. Preferably, it is

In the present invention, it is preferable that a buffer material such as a moisture absorbing material, a gas absorbing material, and an electrolyte retaining material that does not affect the electrical characteristics of the capacitor is sealed in the buffer unit.

Further, in the present invention, it is preferable that the flow path has a pressure release mechanism for releasing gas to the buffer section when the pressure in the outer case rises, and the pressure release mechanism has an adhesive force higher than that of a normal seal. It is preferable that a weak seal is formed integrally with a normal seal.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An electric double layer capacitor according to the present invention comprises a pair of current collectors made of a metal material, each of which is provided with a polarizable electrode formed mainly of a carbon material, and between the polarizable electrodes. An electric double-layer capacitor in which at least one laminate sandwiching an electronic insulating separator is sealed in a bag made of a package material as an outer case in a state of being immersed in an electrolytic solution, and integrated with the outer case. And has a buffer portion which is communicated with the outer case via a flow path. Thereby, even when gas is generated at the time of actual use and the internal pressure of the outer case increases, the rupture of the outer case is prevented, and leakage of the electrolyte is minimized, and the electric characteristics are not reduced. Can be used for a long time.

Hereinafter, the present invention will be described in more detail with reference to the drawings. 1 and 2 are front views showing examples of the electric double layer capacitor of the present invention. Here, the main features of the electric double layer capacitor of the present invention are, as shown in FIGS. 1 and 2, formed integrally with an outer case (bag body made of a package material) 60 and through a flow path 66. It has a buffer portion 64 communicated with the outer case 60. This allows
Even when gas is generated during actual use and the internal pressure of the outer case 60 increases, the internal pressure of the outer case 60 can be maintained in a steady state by storing the generated gas in the buffer portion 64. It can be used for a long time without deteriorating the electrical characteristics of the capacitor. The buffer 6
No. 4, buffer materials such as a water absorbing material, a gas absorbing material (for example, molecular sieve, etc.) and an electrolyte holding material (for example, alumina / silica inorganic fiber material, etc.) which do not affect the electrical characteristics of the capacitor. Is more preferable to maintain the above effect.

The cushioning portion 64 used in the present invention is a bag obtained by sealing the same package material as the outer case 60, so that it is easy to form integrally with the outer case 60 in the manufacturing process, and the cost is low. Is preferable. The arrangement of the buffer 64 in the present invention is not particularly limited. However, as shown in FIGS. 1 and 2, it is preferable that the buffer 64 be attached to the electrode terminal because it can be folded and stored in the electrode when modularized.

Further, it is preferable that the buffer 64 used in the present invention has a pressure release part 68 for releasing gas to the outside when the pressure inside the outer case rises. Accordingly, the rupture of the outer case 60 and the buffer 64 can be prevented, and the electrolyte leaked from the outer case 60 can be trapped by the buffer 64, so that leakage of the electrolyte to the outside can be minimized. Can be minimized.

Further, in the present invention, it is preferable that the flow path 66 has a pressure release mechanism that releases gas to the buffer section 64 when the pressure inside the outer case 60 increases. That is, the flow path 66 between the outer case 60 and the buffer 64 is closed in a normal state, and can be set to open when the pressure in the outer case increases. Thereby, the gas generated in the outer case is accommodated in the buffer portion 64, and the pressure rise is once suppressed. In the subsequent pressure increase, the pressure release section 6
8 can be a two-stage mechanism. In this case, the contact between the buffer material sealed in the buffer portion 64 and the electrolytic solution can be prevented in a normal state, which is preferable.

Incidentally, the pressure release section 68 is, as shown in FIG.
It is preferable that the seal is formed integrally with the normal seal 80 by a seal (weak seal portion) 82 having a weaker adhesive force than the normal seal 80 because it can be manufactured at low cost. Further, it is preferable to reduce the seal width t of the pressure release portion 68 in order to reliably release the gas due to the peeling of the weak seal portion 82. As shown in FIG.
Or as shown in FIG. 3B,
In order to make the seal width smaller than the normal seal 80 width,
It is more preferable to provide the no-seal portion 86 outside the weak seal portion 82.

As the package material used in the present invention, a laminated film obtained by laminating films having different characteristics is used because it is lightweight, has good workability, and has a function suited to the purpose. In particular, an aluminum laminated film is preferably used. be able to.

The aluminum laminated film used in the present invention is a multilayer film in which both surfaces of an aluminum foil are covered with a resin film, and the aluminum foil blocks moisture permeation from the outside. The inner resin in contact with the electrolyte is a polyolefin-based resin with excellent heat sealing properties and solvent resistance (for example, polypropylene resin, polyethylene resin, etc.)
Preferably, the outer resin is polyethylene terephthalate or the like from the viewpoint of weather resistance and abrasion resistance.

When this aluminum laminated film is used, the outer case having the buffer section and the pressure release section of the present invention can be easily formed by a heat sealing method. The heat sealing conditions in the heat sealing method include temperature, time, and pressure.
By controlling these conditions, a difference occurs in the adhesive strength, and this can be used to easily form a weak seal portion of the pressure release portion. Specifically, as shown in FIG. 6, a characteristic is used in which the adhesive strength of the seal portion can be changed by changing the heat fusion temperature at the time of heat sealing. Further, it is possible to change the pressure at the time of pressure release by changing the adhesive strength of the weak seal portion.

The seal width is determined so as to minimize the moisture permeating from the cross section of the resin layer of the aluminum laminate film. However, experimentally, the seal width of the entire outer case is considered in consideration of the pressure release portion. Is about 10 mm, a life of about 10 years can be secured as a capacitor.

The polarizable electrode used in the present invention is formed by using activated carbon industrialized for a capacitor as a carbon material, adding a conductive material such as carbon black or an organic binder, mixing, kneading, and forming a sheet. is there. As the current collector, an aluminum foil whose surface has been subjected to an etching treatment can be suitably used. For the electrode terminal, high-purity aluminum can be suitably used from the viewpoint of electric conductivity and stability against an electrolytic solution. As the separator, a paper separator for a capacitor or a porous resin film made of polyethylene, polypropylene, or Teflon can be used.

The electrolyte may be either organic or aqueous. However, an organic electrolyte which has a high withstand voltage and a high energy density as a capacitor is preferable. As the solvent for the organic electrolyte, propylene carbonate, γ
-Butyl lactone, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, sulfolane, and these alone, or a mixture of two or more, or a solvent to which additives such as other solvents and surfactants are added Is preferably used. As the electrolyte, a quaternary ammonium salt such as tetraethylammonium, tetrabutylammonium, triethylmethylammonium boron tetrafluoride or hexafluorophosphate, or a quaternary phosphonium boron tetrafluoride or hexafluoride A phosphate or the like can be used.

Next, an example of a method for packaging an electric double layer capacitor of the present invention will be described. Electrode terminal 2,
The single-capacitor cell 12 connected to 3 and the electrolytic solution are charged into the outer case 60 provided with the buffer 64. Thereafter, the outer case 60 and the electrode terminals 2 and 3 are adhered to each other by performing heat fusion while keeping the electrode terminals 2 and 3 at predetermined positions of the outer case 60. Further, the insertion port of the outer case is sealed, and the capacitor cell is sealed in the outer case 60 (see FIGS. 1 and 2).

After the single capacitor cell 12, the electrode terminals 2, 3, and the electrolyte are sealed in the outer case 60, the aluminum laminate film of the connection portions 4, 5 of the electrode terminals 2, 3 is removed. As a result, FIGS.
Is completed.

[0027]

EXAMPLES Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. (Example) An outer case having a buffer portion and a pressure release portion
A capacitor cell composed of a pair was packaged to produce the capacitor shown in FIG. Here, the pressure release part 68 provided in the buffer part 64 was manufactured by changing the heat fusion condition when forming the outer case 60 to make it a weak seal. The pressure release section 68 has a seal width T of 10 mm, a temperature of 165 ° C.,
Sealing was performed for 10 seconds at a pressure of 10 ⁶ Pa (10 kgf / cm ² ). Thereafter, the seal portion of the outer case 60 other than the pressure release portion 68 has a seal width T of 10 mm and a temperature of 210 mm.
° C, time 10 seconds, pressure 10 ⁶ Pa (10 kgf / cm ² )
Sealed with.

The seal length L serving as the pressure release section 68 is 20 m
As shown in FIG. 3A, a notch 84 was formed in the portion m, and the seal width t was set to 5 mm. In addition, the buffer 64 includes
Alumina-silica inorganic fiber material was encapsulated. A tensile strength test was performed on the strip-shaped test sample sealed under the above heat fusion conditions, and it was confirmed that the weak seal portion 82 serving as the pressure release portion 68 had approximately half the adhesive strength as compared with the normal seal 80. .

Next, an internal pressure rise test due to gas generation was performed on the capacitor (see FIG. 1). By applying an overvoltage of 3.6 V at 70 ° C. to the capacitor, gas was forcibly generated to increase the internal pressure. At this time, a pressure gauge was attached to the outer case 60 to monitor the internal pressure. As a result, the outer case 60 and the buffer 64 expanded due to gas generation with the application of the overvoltage, and the internal pressure increased. Then, when the internal pressure became 0.15 MPa, the weak seal portion 82 of the pressure release section was peeled off, the gas was released and the internal pressure decreased, but there was almost no leakage of the electrolytic solution.

(Comparative Example) A packaged capacitor cell without a buffer portion and a pressure release portion was similarly manufactured, and an internal pressure rise test was performed. As a result, the package of the outer case was ruptured on the side surface of the capacitor cell, and leakage of the electrolyte was observed.

[0031]

As described above, according to the present invention, even when gas is generated during actual use and the internal pressure of the outer case increases, the outer case is prevented from rupture and leakage of the electrolyte is minimized. While suppressing, without lowering the electrical characteristics,
Can be used for a long time.

[Brief description of the drawings]

FIG. 1 is a front view showing an example of an electric double layer capacitor of the present invention.

FIG. 2 is a front view showing another example of the electric double layer capacitor of the present invention.

FIGS. 3A and 3B show examples of a pressure release section used in the present invention, wherein FIG. 3A is a cutaway structure, and FIG. is there.

FIG. 4 is a perspective view showing an example of the structure of a single electrode cell.

FIG. 5 is a perspective view showing an example of the structure of a single capacitor cell.

FIG. 6 is a diagram showing a relationship between a sealing temperature and an adhesive strength.

[Explanation of symbols]

1: Electric double layer capacitor, 2, 3: Electrode terminal, 4, 5
... Connecting portion (for connecting an external circuit), 10 ... Single electrode cell (laminated body), 12 ... Single capacitor cell, 20, 22 ... Current collector,
24, 26: Polarizable electrode, 28: Separator, 30, 3
2 ... Electrode take-out part, 60 ... Outer case (package), 64 ... Buffer part, 66 ... Flow path, 68 ... Pressure release part, 80
... normal seal, 82 ... weak seal part, 84 ... notch part, 8
6 No seal part.

Claims (9)

[Claims] 1. A pair of current collectors made of a metal material, a polarizable electrode formed mainly of a carbon material is disposed, and at least one polarizer sandwiching an electronic insulating separator between the polarizable electrodes. An electric double-layer capacitor in which two laminates are immersed in an electrolytic solution and sealed in a bag made of a package material serving as an outer case, which is formed integrally with the outer case and provided with a flow path. An electric double-layer capacitor having a buffer portion connected to the outer case. 2. The electric double layer capacitor according to claim 1, wherein the buffer section is a bag obtained by sealing the same package material as the outer case. 3. The electric double layer capacitor according to claim 1, wherein the buffer section has a pressure release section for releasing gas to the outside when the pressure inside the outer case rises. 4. The electric double layer capacitor according to claim 1, wherein the pressure release portion is formed integrally with the normal seal by a seal having a weaker adhesive force than the normal seal. . 5. The electric double layer capacitor according to claim 4, wherein the pressure release section has a cutout structure. 6. The electric double layer capacitor according to claim 4, wherein a no-seal portion is provided outside the weak seal portion so that the pressure release portion has a seal width smaller than a normal seal width. 7. The buffer section according to claim 1, wherein a buffer material such as a water absorbing material, a gas absorbing material, and an electrolyte retaining material which does not affect the electrical characteristics of the capacitor is sealed.
An electric double layer capacitor according to the item. 8. When the pressure in the outer case rises, the flow path
A pressure release mechanism for releasing gas to the buffer section has a pressure release mechanism.
8. The electric double layer capacitor according to any one of items 7 to 7. 9. The electric double layer capacitor according to claim 8, wherein the pressure release mechanism is formed integrally with the normal seal by a seal having a weaker adhesive force than the normal seal.