JPH05109586A - Electrolytic capacitor and manufacture thereof - Google Patents

Abstract

PURPOSE:To decrease an impedance by employing special compound as polymer electrolyte footing material and further forming it of a special composition ratio. CONSTITUTION:An electrolytic capacitor comprises electrolyte containing crosslinked polymer compound in which polyetherpolyol represented by a formula is as a basic skeleton and polyether part contains random copolymer of oxyethylene and oxypropylene and ammonium salt, a dielectric element 3 made of metal oxide, and electrically conductive electrodes 1, 4. A method for manufacturing the capacitor comprises the steps of dissolving electrolyte material containing crosslinked polymer compound represented by a formula and ammonium salt in organic solvent, impregnating it with porous carrier 6 made of electrically insulating material, bringing the carrier 6 into close contact with the element 3 and the electrodes 1, 4, and thermally curing it. Thus, the capacitor having a low impedance, a high capacity and a long life can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic capacitor and its manufacturing method.

[0002]

2. Description of the Related Art Conventionally, in the construction of electrolytic capacitors, oxides such as aluminum oxide have been used as a dielectric, and an organic electrolyte prepared by dissolving an ammonium salt in a high boiling organic solvent such as ethylene glycol has been used as an electrolyte. However, a capacitor using such an electrolytic solution cannot obtain long-term reliability due to leakage or evaporation of the electrolytic solution.

In order to solve such a problem, instead of the electrolytic solution constituting the capacitor, a polymer composed of a mixture of siloxane-alkylene oxide copolymer and polyethylene oxide is used as a base material, and an alkali metal salt is dissolved in the polymer to carry out ion conduction. There is proposed an electrolytic capacitor (Japanese Patent Laid-Open No. 1-503425) in which the element is solidified by using a hydrophilic polymer electrolyte and leakage or evaporation of the electrolytic solution is prevented.

[0004]

However, in an electrolytic capacitor using an ion-conductive polymer electrolyte having an alkali metal as a mobile ion as an electrolyte, the alkali metal ion diffuses into a dielectric material forming the electrolytic capacitor, Therefore, there is a problem that the dielectric constant of the dielectric is lowered, and eventually electrical short circuit occurs.

In order to solve such a problem, it is conceivable to use ammonium ions as mobile ions of the electrolyte constituting the electrolytic capacitor. However, in general, it has been conventionally known that an ion conductive polymer electrolyte in which an ammonium salt is dissolved has extremely low ionic conductivity. (Conductive polymer Naoya Ogata, Kodansha Scientific, 1990) In addition, the ionic conductivity of the electrolyte that constitutes the electrolytic capacitor acts as impedance of the capacitor,
If the ionic conductivity of the electrolyte is too low, it is difficult to use it in practice.

When such an ion conductive polymer electrolyte is used as an electrolyte of an electrolytic capacitor, how to achieve high ion conductivity by combining a polymer base material and an ammonium salt is a very important requirement. However, this specific example is not described in the electrolytic capacitor described in Japanese Patent Publication No. 1-503425.

At present, aluminum oxide is widely used as a dielectric material for electrolytic capacitors. In an actual configuration, by immersing a metal aluminum electrode whose surface is etched in a weakly acidic electrolytic solution and anodizing it electrochemically, aluminum oxide in a micropore state of about several hundred angstroms is created. , We are trying to improve the surface area.

However, when an electrolyte that is not a liquid, for example, the above-mentioned polymer electrolyte is used, the bonding area between the aluminum oxide micropores and the solid-state electrolyte is considerably smaller than that of the liquid electrolyte, and the filling area is small. It is easily conceivable that peeling will gradually occur when the discharge cycle is repeated.

That is, in an electrolytic capacitor using a solid electrolyte as a constituent element, a method of joining the electrolyte and the dielectric in a large area while maintaining a strong joining force is a manufacturing problem.

[0010]

In order to solve the above problems, as a constituent material of the polymer electrolyte, which is a constituent element of the present invention, the specific compound described in the claims is used, and the specific compound is used in a specific composition ratio. With the configuration, the above-mentioned problems can be effectively solved.

Further, as a manufacturing method, a material obtained by dissolving the constituent material of the electrolyte with the organic solvent described in the claims is permeated into the above-mentioned aluminum oxide micropores,
A more practical device can be manufactured by using a method of thermosetting this.

[0012]

When the specific compound described in the claims is used as a constituent material of the polymer electrolyte which is a constituent element of the present invention,
We have found that it is possible to create an electrolytic capacitor that has a low impedance and that does not deteriorate in performance even after repeated charge and discharge cycles.

As a manufacturing method, a method is also used in which the constituent material of the electrolyte is dissolved in the specific organic solvent described in the claims is permeated into the above-mentioned aluminum oxide micropores, and the composition is heat-cured. And an electrolytic capacitor with a large capacity can be created.

Further, the electrolyte material is dissolved in an organic solvent,
After impregnating this with a porous carrier made of an electrically insulating material, it was brought into close contact with the dielectric and the electrically conductive electrode and cured by heating, whereby the stability of the element quality could be improved.

[0015]

[Examples] Specific examples of electrolytic capacitors prepared by the manufacturing method according to claim 7 using a polymer electrolyte in which an ammonium salt is dissolved as a constituent element will be described in detail below.

(Embodiment 1) FIG. 1 is a sectional view of the configuration of an electrolytic capacitor of this embodiment. Thickness 0.1mm, etching hole diameter about 1 to 5 microns, size 1cm x 1cm
The anode connector 2 is spot-welded to one surface of the electrode 1 made of aluminum foil. Next, this is immersed in an aqueous boric acid solution (concentration 80 g / l) kept at a temperature of 90 ° C.,
An anode was prepared by forming the dielectric layer 3 composed of aluminum oxide by oxidizing the aluminum surface described above for 15 minutes with a current of 100 mA.

Further, a cathode connector 5 is provided on one side of an electrode 4 made of aluminum foil having a thickness of 0.1 mm, an etching hole diameter of about 1 to 5 μm, and a size of 1 cm × 1 cm.
An electrode for a cathode was prepared by spot welding. .

Next, the structural formula

[0019]

[Chemical 2]

4.4 g of the polymer compound represented by (l + m) × n = 50, 0.52 g of ammonium borodisalicylate, and 0.175 of diethylene glycol.
A stock solution of the polymer electrolyte was prepared by stirring and mixing g and 4 ml of methyl ethyl ketone. The material composition ratio is the number of molecules of ammonium salt contained in the electrolyte, which is A
And the total number B of oxygen atoms constituting the polymer compound (Chemical Formula 2) contained in the electrolyte is B / A = 50.

Subsequently, this was made of polypropylene having a porosity of 50%, a thickness of 0.1 mm, and a size of 1 cm × 1 cm.
After being impregnated into the separator 6 of FIG.
And press-bonding the aluminum surface 4 of the cathode to face each other,
The electrolyte stock solution was cured by storing at a temperature of ° C for 3 hours to form a polymer electrolyte layer 7.

Finally, an electrolytic capacitor A of Example 1 was prepared by sealing the whole with epoxy resin 8.

Next, as a comparative example, an electrolytic capacitor B prepared by using a polymer electrolyte in which a metal salt was dissolved as a constituent element was prepared.

The manufacturing method is as follows. Instead of 0.52 g of ammonium borodisalicylate, which is a constituent material of the electrolyte in the preparation of the electrolytic capacitor A, 0.18 of lithium perchlorate is used.
The same material and construction method were used except that g was used.

Further, a comparative electrolytic capacitor C having a different manufacturing method was prepared. The constituent materials used were all the same as those of the electrolytic capacitor A.

The manufacturing method is such that the method for forming the electrolyte layer 7 is stored in advance at a temperature of 90 ° C. for 3 hours to obtain 0.1 m.
After being cured to a thickness of m, all the steps were the same as the method for producing the electrolytic capacitor A, except that the anode and the cathode were thermocompression bonded at a temperature of 100 ° C. for 1 hour.

With respect to the electrolytic capacitor A of the example and the electrolytic capacitors B and C of the comparative example prepared as described above, the frequency characteristics of impedance and capacity and the cycle life characteristics of charging / discharging were evaluated. The results are shown in FIGS. 2, 3 and 4.

In FIG. 2, the vertical axis and the horizontal axis are respectively
The impedance and the measurement frequency are shown. From this evaluation, it was found that the impedance of the electrolytic capacitor C of the comparative example having a different method of forming the electrolyte layer was extremely higher than that of the electrolytic capacitor A of the example.

In FIG. 3, the vertical axis and the horizontal axis are respectively
The capacity and the measured frequency are shown. From this evaluation, it was found that the capacitance of the electrolytic capacitor C of the comparative example having a different method of forming the electrolyte layer was extremely smaller than that of the electrolytic capacitor A of the example.

From the above results, the manufacturing method described in claim 7 is extremely useful as a method for manufacturing an electrolytic capacitor using a polymer electrolyte for lowering impedance and increasing capacitance. I understood.

In FIG. 4, the vertical axis represents the relative value with respect to the initial discharge capacity, and the horizontal axis represents the number of charge / discharge cycles.
The discharge capacity of electrolytic capacitors A and B is 10 at 500V.
It was evaluated by measuring the amount of electricity flowing when short-circuited for 5 minutes after charging for a minute.

From these results, the electrolytic capacitor B of the comparative example
It was found that the electrolytic capacitor A of the example maintained the initial performance even after 1000 cycles or more, whereas the capacity deteriorates early in the charging / discharging cycle.

In this embodiment, methyl ethyl ketone was used as the solvent when preparing the electrolyte stock solution, but the same effect can be obtained by using acetone, tetrahydrafuran, propylene carbonate, ethylene carbonate or polyalkylene glycol dimethyl ether. I found it to have.

(Example 2) In the electrolytic capacitor A of Example 1 described above, ammonium borodisalicylate was used as the ammonium salt contained in the electrolyte, and the number of molecules X
And the relationship between the total number Y of oxygen atoms constituting the polymer compound (Chemical Formula 2) contained in the electrolyte is Y / X = 50,
A polyelectrolyte was created.

In this Example, ammonium adipate, ammonium azelate, ammonium benzoate, tetramethylammonium borodisalicylate, tetraethylammonium paratoluenesulfonate and ammonium γ-resorcylate described in claim 4 were used as ammonium salts. Using the same constituent materials and manufacturing method as the electrolytic capacitor A of Example 1, electrolytic capacitors D, E,
F, G, H and I were created. The impedance values of these electrolytic capacitors at 100 Hz are shown in FIG.

In FIG. 5, the vertical axis represents the impedance value at 100 Hz, and the horizontal axis represents the above composition ratio Y /.
X was shown. From this result, the relationship between the number X of molecules of ammonium salt contained in the electrolyte and the total number Y of oxygen atoms constituting the polymer compound (Chemical Formula 2) contained in the electrolyte is 2
It has been found that 0 ≦ (Y / X) ≦ 50 is optimal.

(Embodiment 3) Thickness is 0.05 mm, diameter of etching hole is about 1 to 5 microns, and size is 1 cm × 10 c.
Spot weld an anode connector to one side of an electrode made of aluminum foil. Next, this was immersed in an aqueous boric acid solution (concentration: 80 g / l) kept at a temperature of 90 ° C., and the aluminum surface was oxidized at a current of 1 A for 15 minutes to obtain a dielectric material composed of aluminum oxide. The anode was created by forming the layers.

Further, a cathode connector is spot-welded to one side of an electrode made of an aluminum foil having a thickness of 0.05 mm, an etching hole diameter of about 1 to 5 μm, and a size of 1 cm × 10 cm, to thereby form a cathode electrode. It was created. .

Next, in the structural formula (Formula 2), (l +
m) × n = 4.4 g of the polymer compound represented by 50,
Further, a polyelectrolyte stock solution was prepared by stirring and mixing polyethylene glycol dimethyl ether having a molecular weight of 275 with various weights in 0.52 g of ammonium borodisalicylate, 0.175 g of diethylene glycol and 4 ml of acetone with stirring. This material composition ratio corresponds to the relation W / Z between the weight Z of the polymer compound (Chemical Formula 2) that constitutes the electrolyte and the weight W of the polyalkylene glycol dimethyl ether described in claim 5. is there.

Subsequently, this was made of polypropylene with a porosity of 50%, a thickness of 0.05 mm, and a size of 1 cm × 10.
After impregnating into the separator of cm, the dielectric surface of the anode and the aluminum surface of the cathode are pressed against each other at 90 ° C.
After storing at 30 ° C for 30 minutes, it was wound into a roll and further stored at the same temperature for 3 hours to cure the electrolyte stock solution into a roll electrode to form a polymer electrolyte layer.

Finally, store this in an aluminum tube,
The electrolytic capacitor of Example 3 was prepared by sealing the connector portion with epoxy resin.

With respect to the electrolytic capacitors of the examples prepared as described above, 100H against the composition ratio W / Z of the electrolyte.
Impedance and capacity at z Further, impedance deterioration at 30 ° C. after storage at 80 ° C. was evaluated. The results are shown in FIGS. 6, 7 and 8, respectively.

In FIG. 6, the vertical axis and the horizontal axis are respectively
Impedance at 100 Hz and composition ratio of electrolyte W /
Z is indicated. From this evaluation, it was found that the larger the composition ratio W / Z of the weight Z of the polymer compound (Formula 2) constituting the electrolyte and the weight W of the polyalkylene glycol dimethyl ether, the smaller the impedance.

Further, in FIG. 7, the vertical axis and the horizontal axis respectively show the capacity and the composition ratio W / Z of the electrolyte at 100 Hz. From this evaluation, it was found that the capacitance of the capacitor increased with an increase in the composition ratio W / Z of the electrolyte, and was saturated at a certain amount or more.

Further, in FIG. 8, the ordinate and the abscissa respectively represent the impedance at 30 ° C. after storage at 80 ° C. and the number of storage days. From this evaluation, it was found that the deterioration of the impedance of the capacitor increased as the composition ratio W / Z of polyethylene glycol dimethyl ether in the electrolyte increased.

From the above results, the relationship between the weight Z of the polymer compound (Chemical Formula 2) constituting the electrolyte and the weight W of the polyalkylene glycol dimethyl ether is 0 ≦ (W / Z)
When ≦ 1, it was possible to produce an electrolytic capacitor having good initial performance and long-term high reliability.

[0047]

According to the present invention, it is possible to obtain a capacitor which has a low impedance and a high capacity and which has a long life.

[Brief description of drawings]

FIG. 1 is a sectional view showing the configuration of an electrolytic capacitor according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of the electrolytic capacitor of Example 1.

FIG. 3 is a characteristic diagram of the electrolytic capacitor of Example 1.

FIG. 4 is a characteristic diagram of the electrolytic capacitor of Example 1.

FIG. 5 is a characteristic diagram of the electrolytic capacitor of Example 2.

FIG. 6 is a characteristic diagram of the electrolytic capacitor of Example 3.

FIG. 7 is a characteristic diagram of the electrolytic capacitor of Example 3.

FIG. 8 is a characteristic diagram of the electrolytic capacitor of Example 3.

[Explanation of symbols]

 1 Electrode 2 Connector for Anode 3 Dielectric Layer 4 Electrode 5 Connector for Cathode 6 Polymer Electrolyte Layer 7 Seal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichi Takeyama Inventor Kenichi Takeyama 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (10)

[Claims] 1. A basic skeleton of polyether polyol,
A polymer compound in which the polyether moiety is a random copolymer of oxyethylene and oxypropylene An electrolytic capacitor comprising at least an electrolyte having a crosslinked body of the above and an ammonium salt, a dielectric made of a metal oxide, and an electrically conductive electrode. 2. The electrolytic capacitor according to claim 1, which contains polyalkylene glycol dimethyl ether as a material constituting the electrolyte. 3. The electrolytic capacitor according to claim 1, wherein the terminal group of the polymer compound (Formula 1) is crosslinked with a diol compound. 4. A single ammonium salt selected from ammonium adipate, ammonium azelate, ammonium benzoate, ammonium borodisalicylate, tetramethylammonium borodisalicylate, tetraethylammonium paratoluenesulfonate, and ammonium γ-resorcylate. 4. The electrolytic capacitor according to claim 1, which is a compound or a mixture thereof. 5. The relationship between the weight Z of the polymer compound (Chemical Formula 1) constituting the electrolyte and the weight W of the polyalkylene glycol dimethyl ether is 0 ≦ (W / Z) ≦ 1. Item 2. The electrolytic capacitor according to Item 2. 6. The relationship between the number X of molecules of ammonium salt contained in the electrolyte and the total number Y of oxygen atoms constituting the polymer compound (Formula 1) contained in the electrolyte is 20 ≦ (Y / X) ≦.
The electrolytic capacitor according to claim 4, wherein the electrolytic capacitor is 50. 7. The method for producing an electrolytic capacitor according to claim 1, wherein the electrolyte material is dissolved in an organic solvent, the solution is cast on a dielectric, and then the composition is heated and cured. 8. An electrolytic material is dissolved in an organic solvent and impregnated into a porous carrier made of an electrically insulating material, and then the porous carrier impregnated with the electrolytic material is used as a dielectric and an electrically conductive electrode. 2. The method for producing an electrolytic capacitor according to claim 1, wherein the method is closely adhered to and heat-cured. 9. An electrolyte material is dissolved in at least one organic solvent selected from acetone, methyl ethyl ketone, tetrahydrafuran, propylene carbonate, ethylene carbonate, and polyalkylene glycol dimethyl ether, which is cast on a dielectric and then heated. The method for producing an electrolytic capacitor according to claim 4, wherein the method is a hardening process. 10. An electrolyte material comprising acetone, methyl ethyl ketone, tetrahydrafuran, propylene carbonate,
After dissolving in at least one kind of organic solvent selected from ethylene carbonate and polyalkylene glycol dimethyl ether and impregnating it with a porous carrier made of an electrically insulating material, the porous carrier impregnated with the electrolyte material is used as a dielectric. The method for producing an electrolytic capacitor according to claim 4, wherein the method is in close contact with the body and the electrically conductive electrode and heat curing is performed.