JPH02210810A - Electric double layer capacitor - Google Patents

Abstract

PURPOSE:To improve impregnating properties an increase leak current characteristics and the like by previously washing a separator by using liquid of at least either one of solvent or solute of impregnant. CONSTITUTION:On both surfaces of a separator 1, a polarizing electrode 2 is deposited and impregnated with organic system electrolyte as impregnate. This one is contained in a case 3. The separator 1 formed of polypropylene is impregnated with surface-active agent, which can be eliminated by washing process using organic system electrolyte or organic solvent for electrolyte. In the organic system electrolyte, the same solute as the impregnant is used, and in the organic solvent for electrolyte, the same solvent as the impregnant is used, so that the compatibility with the impregnatnt is excellent, and the impregnant is sufficiently absorbed. When the separator 1 is dried, impregnating properties are not decreased, and each of the characteristics is not affected. Thereby, characteristic of electrostatic capacitance, equivalent series resistance, leak current, etc., can be improved.

Description

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

(Prior Art) Electric double layer capacitors are used as backup power sources for computers during power outages, batteries for solar clocks, and power sources for motor drives.

This electric double layer capacitor, for example, has polarizable electrodes laminated on both sides of a separator, which is impregnated with an electrolytic solution and then stored in a stainless steel case, or by placing a layer between the polarizable electrode and the inner surface of the case. It is inverted with one layer of karai body.

In particular, separators require heat resistance, chemical resistance, and low water absorption, so polypropylene nonwoven fabrics or porous films are used, and they are impregnated with surfactants to improve electrolyte impregnation. There is.

(Problem to be solved by the invention) However, since the surfactant impregnated into the separator accelerates the deterioration of the electrolyte, it has the disadvantage that various characteristics such as capacitance, equivalent series resistance, and leakage current tend to deteriorate. there were.

An object of the present invention is to provide an electric double layer capacitor which can improve the above-mentioned drawbacks and improve various characteristics such as capacitance.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a case in which polarizable electrodes are layered on both sides of a separator, and the separator is impregnated with an organic electrolyte as an impregnating agent. The present invention provides an electric double layer capacitor characterized in that the separator is provided with a separator washed with at least one of a solvent and a solute of an impregnating agent.

(Function) A commercially available separator made of polypropylene or the like is impregnated with a surfactant, but the surfactant can be removed by washing it with an organic electrolyte or an organic solvent for the electrolyte.

Since the organic electrolyte has the same solute as the impregnating agent, and the organic solvent for the electrolyte has the same solvent as the impregnating agent,
It has good compatibility with the impregnating agent and is easily impregnated with the impregnating agent.

Incidentally, the surfactant can also be washed with water or lower alcohol, but if the separator is subsequently dried, the impregnating property will deteriorate. In this respect, in the case of the present invention, the impregnating property is not reduced and each property is hardly affected.

(Example) Hereinafter, the present invention will be explained based on illustrated embodiments.

In Fig. 1, numeral 1 is a polypropylene separator that has been cleaned in advance with an electrolyte such as an organic solvent such as propylene carbonate or γ-butyl lactone, lithium tetrafluoroborate, or tetraalkyl ammonium tetrafluoroborate to make the surface active. The agent has been removed. 2 is a polarizable electrode laminated on both sides of the separator 1, which is made by mixing conductive carbon black or Ketchen black with a binder such as tetrafluoroethylene, polyvinyl alcohol, or polyvinylpyrrolidone, and processing it into a sheet. be. This polarizable electrode 2 is impregnated with an electrolytic solution in which an electrolyte such as lithium tetrafluoroborate or tetraalkylammonium tetrafluoroborate is dissolved in an organic solvent such as propylene carbonate or γ-butyl lactone. 3 is a coin-shaped case made of stainless steel, which houses a separator 1 and a polarizable electrode 2.
It houses elements consisting of.

Next, the initial characteristics and changes in characteristics after the life test were measured for the above example and the conventional example.

The manufacturing conditions of the example and the conventional example are as follows.

Example 1) Separator: A polypropylene strip porous film (Type 340, manufactured by Celanese Co., Ltd.) washed with propylene carbonate, a solvent for electrolyte (moisture content: 3 Q PP8 or less), with a thickness of 25 to 100 μm and a diameter of 1711 # I is formed into a circular shape.

Polarizable electrode: A material prepared by adding about 25% of Teflon binder to carbon black is formed into a sheet with a thickness of 500μ and punched into a circular shape with a diameter of 14a.

Electrolyte: A solution prepared by dissolving tetraethylammonium tetrafluoroborate as a solute in propylene carbonate as a solvent.

Case: A coin-shaped stainless steel case with a thickness of 1.6 m and a diameter of 20 mm.

Example 2) The conditions were the same as in Example 1) except that the separator was washed with propylene carbonate having a water content of 5QPPH or less.

Example 3) The conditions were the same as in Example 2) except that a 25 μm thick boria-0-birene nonwoven fabric (type MU-4010 manufactured by Nippon Vilene Co., Ltd.) was used as the separator.

Conventional Example 1) The same conditions as in Example 1) were used except that the separator was used without cleaning.

Conventional Example 2) The conditions are the same as in Example 3) except that the separator is used without being washed.

In addition, in the life test, a voltage of 2 [V] was applied and the temperature was 85°C.
Leave it in an atmosphere of

The initial characteristics were as shown in the table.

As is clear from the table, according to Examples 1 to 3 of the present invention, the leakage current can be reduced to 2/3 to 115 times as compared to Conventional Examples 1 to 2.

Further, the characteristics of capacitance change rate, equivalent series resistance (hereinafter referred to as ESR), and leakage current in the life test are as shown in FIGS. 1 to 3. 1600 from Figure 10) W after leaving for 1r
The p lightning capacity change rate was 14% for Examples 1 and 2, and 4% for Example 3.
-12%, conventional example 1 -20%, conventional example 2 -132%
According to Examples 1 to 3, it is 1/8 to 1/8 of Conventional Examples 1 to 2.
It can be reduced to 315. Also, from the main figure, the ESR change rate is 1.5 times in Examples 1 to 3, 3 times in Conventional Example 1, and 5.5 times in Conventional Example 2. 1~
It can be reduced to 1/11 to 1/2 of 2. Furthermore, according to the cylinder diagram, the leakage current is 8 μA for Examples 1 and 2, and 8 μA for Example 3.
is 11μA1 Conventional example 1 is 18μA1 Conventional example 2 is 22μA
According to Examples 1 to 3, it is 4/1 of Conventional Examples 1 to 2.
It can be reduced to 1 to 11/18.

In addition, when comparing Examples 1 to 3, Examples 1 to 2 using a porous film made of polypyrene as a separator have better capacitance change rate and leakage current characteristics than Example 3 using a nonwoven fabric. It can be further improved.

(Effects of the Invention) As described above, according to the present invention, since the separator is cleaned in advance with at least one of the solvent and the solute of the impregnating agent, the impregnating property can be improved and the leakage current characteristics can be improved. Thus, an electric double layer capacitor can be obtained which can improve the characteristics such as the following.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view of an embodiment of the present invention, FIG. 2 is a capacitance change rate, FIG. 3 is an equivalent series resistance change rate, and FIG. 4 is a leakage current characteristic. 1...Separator, 2...Polarizable electrode, 3...
Case. Patent Applicant: Hitachi Capacitor Co., Ltd. Figure 2 () C4 Hoban 1 field!

Claims (1)

[Claims] (1) An electric double layer capacitor in which polarizable electrodes are laminated on both sides of a separator and impregnated with an organic electrolyte as an impregnating agent is housed in a case, and the capacitor is cleaned with at least one of the solvent or solute of the impregnating agent. An electric double layer capacitor characterized by being provided with a separator.