JPH01241110A - Electric double layer capacitor - Google Patents

Abstract

PURPOSE:To reduce internal resistance and the degree of deterioration of capacitance by composing a metallic case and a metallic cover body of a metal having the same composition selected from aluminum, tantalum, zirconium, titanium and niobium or a clad material using the metal. CONSTITUTION:A metallic case 5 and a metallic cover body 4 consist of a metal having the same composition selected from aluminum, tantalum, zirconium, titanium and niobium or a clad material employing the metal. The clad material of aluminum-stainless is most preferable from the viewpoint of profitability and workability at that time. Accordingly, an electric double layer capacitor, internal resistance of which is hardly increased because the material having high corrosion resistance is used and which has the excellent long-term reliability even of the little degree of deterioration of capacitance, can be acquired.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electric double layer capacitor.

[Prior Art] Various reports have been made regarding current collectors that extract electricity from polarizable electrodes in electric double layer capacitors and case materials that house the constituent elements of the electric double layer capacitor. (For example, see Japanese Patent Publication No. 64-18730.) These inventions are mainly characterized by using a metal with high corrosion resistance on the anode (positive electrode during charging) side so that the anode does not melt when a high voltage is applied. . This is mainly because metals with high corrosion resistance are expensive, and as a result, inexpensive materials with poor corrosion resistance have been used on the cathode side.

[Problems to be Solved by the Invention] However, when such a configuration is adopted, the capacitor inevitably becomes polarized, and if it is reverse mounted on a circuit board, corrosion of the metal storage case, decomposition of the electrolyte, and accompanying problems occur. However, the problem was that the electrolyte solution leaked.

In addition, in order to avoid this, a polarity check is required in the mounting process, which has the disadvantage of complicating the process.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems. Namely, the present invention provides a pair of polarizable electrodes impregnated with an electrolyte and a separator impregnated with an electrolyte. placed through,
One polarizable electrode is housed in electrical contact with the metal case, and the metal case and metal lid are caulked together via a gasket.In an electric double layer capacitor, the metal case and metal lid are made of aluminum. The present invention provides an electric double layer capacitor made of a metal having the same composition selected from tantalum, zirconium, titanium, and niobium, or a cladding material using the metal.

That is, in the present invention, it is important to use the metals described above for the metal case and the metal lid. Aluminum, niobium, titanium, and tantalum can be used as such metals and their cladding materials, but their economic efficiency and
From the viewpoint of workability, aluminum-stainless steel cladding material is most preferred.

The polarizable electrode used in the present invention is not particularly limited, and various conventionally known and known polarizable electrodes can be employed. For example, activated carbon powder, carbon black, activated carbon fiber, etc. having a large specific surface area can be preferably used.

In particular, activated carbon powder contains polytetrafluoroethylene (PT).
The electrode is made by adding a binder such as FE), roll-forming it into a sheet, and subjecting it to stretching treatment as necessary.
It is preferably used because it has excellent capacity per unit volume, strength, and long-term reliability.

As the separator used in the present invention, a usual separator for electric double layer capacitors, such as a separator made of polypropylene fiber nonwoven fabric or glass fiber mixed nonwoven fabric, can be used.

The electrolytic solution used in the present invention is not particularly limited, and those normally used for electric double layer capacitors, that is, those in which an electrochemically stable solute (electrolyte) is dissolved in a polar organic solvent, can be used as appropriate. be done. As the solvent for the electrolytic solution, propylene carbonate, butylene carbonate, γ-butyrolactone, acetonitrile, dimethylformamide, 1,2-dimethoxyethane, sulfolane, nitromethane, etc. are preferably used.

Examples of solutes in the electrolytic solution include alkali metal salts such as perchloric acid, hexafluorophosphoric acid, tetrafluoroboric acid, perfluoroalkylsulfonic acid, tetraalkylammonium salts, and tetraalkylphosphonium salts. of solute in the above solvent at 0.1 to 3.0 M/Q,
Preferably, an electrolytic solution dissolved at a concentration of 0.5 to 1.5 Vi/Q is suitably used.

Furthermore, the method of collecting current from the polarizable electrode used in the present invention is not particularly limited, and conventionally well-known methods can be used. For example, a metal mesh is welded to a metal case and an electrode is crimped onto it, or a metal current collecting layer is formed on the electrode by plasma spraying, plating, etc. A method of bonding with a conductive adhesive can be preferably used. In particular, a method using a conductive adhesive containing carbon is preferred.

The conductive adhesive used in the present invention is preferably a high-purity, high-lead adhesive containing almost no binder.
A graphite or carbon black-based conductive adhesive containing a resin binder such as phenol or an inorganic binder such as water glass may also be used.

[Example] Example 1 As a unit cell of a coin-shaped electric double layer capacitor (diameter 20 mm, thickness 2, (1 mm)) as shown in FIG. First, activated carbon powder (specific surface area: 2
．． 10% by weight of polytetrafluoroethylene was added to 000m"7g) and formed into a sheet by wet blending.The sheet thus obtained was punched out into a disk shape to form polarizable electrode 1 (diameter 15mm, thickness Q, 7mm),
A polarizable electrode 1 and a polarizable electrode 2 having the same composition and shape are connected via a separator 3 made of polypropylene fiber nonwoven fabric to a metal lid 4 made of aluminum with a purity of 99.99% and a metal case 5. They are adhered to each other with a graphite-based conductive adhesive at 7° and 7°, respectively, and housed in an outer container made of the same material.

A propylene carbonate solution of tetraethylphosphonium tetrafluoroborate ((CIH8), PBF,) with a concentration of 0.5 mol/Q was injected into the unit cell as an electrolyte, and the polarizable electrode 1.2 and separator 3 were injected into the unit cell. After sufficiently impregnating with this electrolytic solution, the ends of the metal case 5 and the metal lid 4 were caulked and sealed via the polypropylene backing 6.

Using this electric double layer capacitor unit cell, we measured the initial capacitance (Fo) and internal resistance of each cell when a voltage of 2.8v was applied, and then applied a voltage of 2.8v to this cell. 1000 at 70℃ while applying
Measure the capacity ffi (F) and internal resistance after storage for a period of time, and calculate the capacity deterioration rate ((F, -F)/
F,) was calculated and shown in Table 1. The internal resistance was measured by the AC two-terminal method (frequency: 1 koz).

The results are shown in Table 1.

Example 2 As a metal lid body and a metal case, the side to which the polarizable electrode is attached is made of aluminum ram with a purity of 99.99%, and the outside of the coin cell is made of M
A cladding material made of stainless steel containing 2% O, 18% Cr, and 12% Cr was used. Other conditions are the same as in Example 1. The results are shown in Table 1.

Example 3 As a metal lid body and a metal case, a 99.99% pure aluminum laminate was used on the side to which the polarizable electrode was bonded, and a 99.99% aluminum ram was used on the outside of the coin cell.
A cladding material of 9% nickel was used. Other conditions are the same as in Example 1. The results are shown in Table 1.

Comparative Example I Nickel with a purity of 99% was used for the metal lid and metal case. Other conditions are the same as in Example I. Results first
Shown in the table.

Comparative Example 2 Stainless steel (Mo2%
, containing 18% Cr and 12% old) was used. Other conditions are the same as in Example 1.

The results are shown in Table 1.

Table 1 [Effects of the Invention] The present invention has excellent long-term reliability in that the increase in internal resistance is small and the rate of capacity deterioration is small because high corrosion resistance is used. Furthermore, since it can be used without polarity, conventional problems such as reverse mounting on a circuit board are eliminated.

Therefore, a large practical ripple effect can be expected.

[Brief explanation of the drawing]

FIG. 1 shows the structure of a unit cell of an example of the present invention and a comparative example. 1.2 Bipolar electrode 3: Separator 4: Lid 5: Case 6: Backing 7.7': Adhesive

Claims (2)

[Claims] (1) A pair of polarizable electrodes impregnated with an electrolytic solution are arranged through a separator impregnated with an electrolytic solution, one polarizable electrode is housed in electrical contact with a metal case, and the other polarizable electrode is In an electric double layer capacitor that is housed in electrical contact with a metal lid and has a structure in which the metal case and the metal lid are caulked together via a gasket, the metal case and the metal lid are made of aluminum, tantalum, zirconium, titanium, An electric double layer capacitor made of a metal with the same composition selected from niobium or a cladding material using that metal. (2) The electric double layer capacitor according to claim 1, wherein the polarizable electrode is made of carbon powder or activated carbon fiber.