JPS63213914A - Electric double-layer capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

(Prior Art) Conventionally, electrolytes used in electric double layer capacitors include electrochemical solutions such as perchloric acid, 6-fluorinated phosphoric acid, 47-fluorinated boric acid, or alkali metal salts and tetraalkylammonium salts of trifluoromethanesulfonic acid. It is known that a stable solute is dissolved in a polar organic solvent (Japanese Unexamined Patent Publication No. 4
9-68254, JP-A-50-44463, JP-A-59-232409, etc.).

(Problems to be Solved by the Invention) However, electric double layer capacitors using these known solutes have the problem that sufficient performance cannot be obtained in terms of withstand voltage, capacitance value, long-term reliability, etc. there were.

An object of the present invention is to solve the above-mentioned problems and provide an electric double layer capacitor that has excellent withstand voltage, capacity, and long-term reliability.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides an electric double layer capacitor that utilizes an electric double layer formed at the interface between a polarizable electrode and an electrolyte. The solute is of general formula (I)
An electric double layer capacitor characterized by being a salt represented by any one of -(I[+)] is provided.

(CHz) - R3P (CHz) ,,PRx' ・2X(
III) However, in the above general formula, R and R' are each Hl or an alkyl group having 1 to 15 carbon atoms, allyl (
aryl) group or an aryl group having 6 to 15 carbon atoms (a
ryl) group, n is an integer of 1 to 20, and X is BF4
,PF, ,Cl0a% AsFb,SbF, ,
A7ICl, or RfSCh (Rf has 1 or more carbon atoms
8) is shown.

The solute of the electrolytic solution used in the present invention is represented by the above general formula (1).
, (II) or (I[I). In the above general formula, R and R' are H (not all H), an alkyl group having 1 to 15 carbon atoms, preferably 1 to 4 carbon atoms, an allyl group, or an allyl group having 6 to 4 carbon atoms.
15 is preferably an aryl group of 6 to 10, and n is 1 to 10.
20, preferably an integer from 1 to 15.

Examples of preferable alkyl groups include methyl group, ethyl group, propyl group, butyl group, and examples of preferable aryl groups include phenyl group (C6H5), tolyl group (CHff・C,H4−), and naphthyl group. Group (C1゜H
, -), etc.

In addition, in the above general formula, X is BF, PF, CIO
4, A S F b 1 S b F & , A I C
l4 or Rrsox, and Rf represents a fluoroalkyl group having 1 to 8 carbon atoms.

Preferred salts include, for example, diethyl trispropylene diphosphonium bistetrafluoroborate, (CH.).tetraethyldibropylene diphosphonium bistetrafluoroporate hexaethylpropylene diphosphonium bistetrafluoroborate Et Et hexaethylhexylene diphosphonium bistetra Examples include fluoroborate.

The concentration of such a solute (electrolyte) in the electrolyte is:
0.1 to 3.0 M/1 is suitable for tearing, especially NiO.

It is suitable to set it as 5-1.5M, #. If this concentration is too low, the internal resistance will increase and the capacity will decrease, while if it is too high, problems such as precipitation of solutes and decreased stability may occur in cold weather.

The solvent for the electrolytic solution used in the present invention is not particularly limited, and propylene carbonate, butylene carbonate, T-butyrolactone, acetonitrile, dimethylformamide, 1,2-dimethoxyethane, sulfolane, nitromethane, etc. may be used alone or as appropriate. They are preferably used in combination.

The material of the polarizable electrode used in the present invention is not particularly limited, but it is preferable to use activated carbon powder or activated carbon fiber that is electrochemically inert to the electrolyte and has a large specific surface area.

In particular, activated carbon powder contains polytetrafluoroethylene (P).
Electrodes that are added with a binder such as TFE), roll-formed into a sheet, and preferably stretched uniaxially or biaxially have excellent capacity per unit volume, strength, and long-term reliability. Therefore, it is suitable for use.

As the separator interposed between the pair of polarizable electrodes in the present invention, a normal separator made of polypropylene fiber nonwoven fabric, glass fiber mixed nonwoven fabric, etc. can be used.

(Example) Next, Examples and Comparative Examples will be specifically described with reference to the drawings.

Common to the examples and comparative examples of the present invention is the coin type electric double layer capacitor shown in FIG.
A cell (diameter 20cm, thickness 2.01m) was prepared as follows. First, activated carbon powder (specific surface area 200O
10% by weight of polytetrafluoroethylene was added to n(/g) and formed into a sheet by wet mixing. The sheet thus obtained was punched out into a disk shape to form polarizable electrodes 1 and 2 (diameter 15 mm, thickness 0.7 mm),
The polarizable electrodes 1.2 are housed in an outer container made of a stainless steel cap 4 and a stainless steel can 5, facing each other with a separator 3 made of a nonwoven polypropylene fiber fabric interposed therebetween. Next, a predetermined electrolyte is injected into the unit cell, and the polarizable electrode 1.2 and separator 3 are
After sufficiently impregnating the inside with this electrolytic solution, the ends of the cap 4 and can 5 were caulked and sealed via a polypropylene backing 6 to integrate them.

2. For each cell using the electric double layer capacitor unit cell produced as described above and using various electrolytes as shown in Table 1 at a concentration of 1.0 M/ff.
After measuring the initial capacity and internal resistance when a voltage of 8V was applied, the capacity after being stored at 70°C for 1000 hours while applying a voltage of 2.8V to the cell was measured. The capacity deterioration rate (%) was calculated from These measurement results are shown in Table 1 as Examples 1 to 8 and Comparative Examples 1.2.

Note that the internal resistance was measured by an AC two-terminal method (frequency IKHz).

(This page, blank space below) (Effects of the invention) As explained above, according to the present invention, an electric 21I layer capacitor has a high withstand voltage, a low capacity deterioration rate under high temperature conditions, and a high long-term reliability. is obtained.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing one embodiment of an electric double layer capacitor according to the present invention. 1.2... Polarizable electrode, 3... Separator, 4... Cap, 5... Can, 6... Puffing.

Claims (2)

[Claims] (1) In an electric double layer capacitor that utilizes an electric double layer formed at the interface between a polarizable electrode and an electrolyte, the solute of the electrolyte is a salt represented by one of the general formulas (I) to (III). An electric double layer capacitor characterized by: ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(III) However, in the above general formula, R, R' are respectively H,
or an alkyl group having 1 to 15 carbon atoms, allyl
l) Group or aryl having 6 to 15 carbon atoms
group, n is an integer from 1 to 20, and X is BF_4, PF
_6, ClO_4, AsF_6, SbF_6, AlCl
_4 or RfSO_3 (Rf is a fluoroalkyl group having 1 to 8 carbon atoms). (2) The electric double layer capacitor according to claim 1, wherein the concentration of the solute is 0.1 to 3.0 M/l.