Electrolytic capacitor and method for manufacturing the same

Abstract

To provide an electrolytic capacitor which is capable of reducing an ESR while improving the suppression effect of liquid leakage than before.SOLUTION: An electrolytic capacitor 1 includes a wound-type capacitor element 2 and an electrolyte 2e introduced into the capacitor element 2. The electrolyte 2e contains: a quaternized cyclic amidinium salt comprising acid anions and a quaternized cyclic amidinium cations; and a first composition comprising one or more organic acids and one or more non-quaternary amines, a conjugate acid of the non-quaternary amine having a pKa of 12 or less. In the quaternized cyclic amidinium salt, an alkyl group is added to all nitrogen atoms constituting a ring among atoms in the quaternized cyclic amidinium cations.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electrolytic capacitor and a method for manufacturing the electrolytic capacitor.

Background Art

[0002] Conventionally, a configuration using an electrolytic solution containing 1,5-diazabicyclo[4,3,0]-5-nonene phthalate and N,N-dimethylaminoethanol phthalate has been proposed (Patent Document 1: Japanese Unexamined Patent Application Publication No. 2012-151377). Also, a configuration in which sulfolane is blended in a quaternized amidinium salt-based electrolytic solution has been proposed (Patent Document 2: Japanese Unexamined Patent Application Publication No. 11-126732).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the configuration described in Patent Document 1 has a high specific resistance of the electrolytic solution and cannot meet the requirement of reducing the ESR. Also, the configuration described in Patent Document 2 has a small effect of suppressing liquid leakage and cannot sufficiently meet the requirement of high reliability.

Means for Solving the Problems

[0005] In view of such circumstances, the present invention is made, and an object thereof is to provide an electrolytic capacitor having a configuration that can achieve a low ESR and can enhance the liquid leakage suppressing effect as compared with the conventional ones.

[0006] As one embodiment, the above problems are solved by the solution means disclosed below.

[0007] The electrolytic capacitor of the present invention includes a capacitor element in which an anode foil and a cathode foil are wound with a separator interposed therebetween, and an electrolytic solution introduced into the capacitor element. The electrolytic solution contains γ-butyrolactone 60~65 by weight % and contains a phthalic acid amidinium salt composed of an acid anion and a quaternized cyclic amidinium cation and composed of phthalic acid and 1,2,3,4 - tetramethylimidazolinium and 、 an organic acid and and a first composition composed of a non-quaternary amine, wherein the pKa of the conjugate acid of the non-quaternary amine is 12 or less. The molar ratio of the non-quaternary amine to the quaternized cyclic amidinium cation is 0.2 or more. The electrolytic solution contains the phthalic acid amidinium salt triethylamine phthalate which is by weight 20~25 and contains the first composition % by 5 triethylamine phthalate which is weight ~15 by weight % and is characterized by this.

[0008] The inventors of the present invention have found that when a specific electrolytic solution is used, the ESR can be lowered and the effect of suppressing liquid leakage is great, and thus the present invention has been completed. According to this configuration, the low specific resistance characteristic of the electrolytic solution containing the quaternized cyclic amidinium salt can reduce the ESR, and the good liquid leakage resistance can be obtained by the electrolytic solution containing the first composition. That is, by using a non-quaternary amine with a small pKa of the conjugate acid, the influence of the quaternized cyclic amidinium salt on the liquid leakage resistance is suppressed, and good liquid leakage resistance is obtained. The pKa of the conjugate acid of the non-quaternary amine is 12 or less, preferably the pKa of the conjugate acid of the non-quaternary amine is 11 or less, and more preferably the pKa of the conjugate acid of the non-quaternary amine is 10 or less.

[0009] In the quaternized cyclic amidinium salt, alkyl groups are added to all nitrogen atoms constituting the ring among the atoms in the quaternized cyclic amidinium cation. With this configuration, the electrolytic solution can have a low specific resistance. As such a cation component, for example, 1,2,3,4-tetramethylimidazolinium cation, other known quaternized imidazolinium cations, other known quaternized imidazolium cations, etc. can be mentioned. One of these may be used alone, or a plurality of them may be used in combination. Further, in order to make the specific resistance of the electrolytic solution lower and contribute to the low ESR characteristics of the electrolytic capacitor, the quaternized cyclic amidinium salt may be contained in an amount of 20 [wt%] or more, and may be contained in an amount of 25 [wt%] or more. On the other hand, it is preferable that the total value of the ratio of the quaternized cyclic amidinium salt and the ratio of the first composition is 60 [wt%] or less, and more preferably 50 [wt%] or less. Thereby, the phenomenon that a part of the electrolytic solution components precipitates in the low temperature range can be prevented.

[0010] The molar ratio of the moles of the non-quaternary amine to the moles of the quaternized cyclic amidinium cation is preferably 0.2 or more. By increasing the molar ratio, the influence of the quaternized cyclic amidinium salt on the liquid leakage property can be suppressed, and good liquid leakage resistance can be obtained. The molar ratio is more preferably 0.3 or more. The molar ratio is even more preferably 0.4 or more.

[0011] As an example, the electrolytic solution has a configuration in which γ-butyrolactone is contained in an amount of 50 wt% or more, the quaternized cyclic amidinium salt is contained in an amount of 15 wt% or more, and the first composition is contained in an amount of 5 wt% or more. Thereby, an increase in the specific resistance in the low temperature range can be effectively suppressed. As an example, the solvent of the electrolytic solution may be γ-butyrolactone alone.

[0012] Examples of the quaternized cyclic amidinium salt include salts of a carboxylic acid anion and a quaternized cyclic amidinium cation. Further, salts of anions of polyvalent carboxylic acids such as phthalic acid and quaternized cyclic amidinium cations can be preferably used.

[0013] Examples of the organic acid constituting the first composition include carboxylic acids, and in particular, polyvalent carboxylic acids such as phthalic acid, adipic acid, and azelaic acid can be preferably used. One of these may be used alone, or a plurality of them may be used in combination.

[0014] Examples of the non-quaternary amine constituting the first composition include tertiary amines such as triethylamine and ethyldimethylamine. Also, one of tertiary amines, secondary amines, and primary amines may be used alone, or a plurality of them may be used in combination. The first composition preferably contains a tertiary amine salt. At least one of the non-quaternary amines in the first composition is preferably a tertiary amine.

[0015] The method for manufacturing an electrolytic capacitor of the present invention includes a capacitor element in which an anode foil and a cathode foil are wound via a separator, and an electrolytic solution introduced into the capacitor element. The electrolytic solution contains γ-butyrolactone 60~65 by weight % and is composed of an acid anion and a quaternized cyclic amidinium cation and composed of phthalic acid and 1,2,3,4 - tetramethylimidazolinium phthalic acid amidinium salt 、 organic acid and a first composition composed of a non-quaternary amine and having a pKa of the conjugate acid of the non-quaternary amine of 12 or less triethylamine phthalate which is and contains the first composition, and the molar ratio of the non-quaternary amine to the quaternized cyclic amidinium cation is 0.2 or more. The electrolytic solution contains the phthalic acid amidinium salt 20~25 by weight % and contains the first composition triethylamine phthalate which is at 5 ~15 by weight % This is characterized.

[0016] According to this manufacturing method, the desired electrolytic solution can be adjusted by preparing the first solution in a direction of decreasing the concentration of the quaternized cyclic amidinium salt. And, the low specific resistance characteristic of the electrolytic solution containing the quaternized cyclic amidinium salt can achieve a low ESR, and good liquid leakage resistance can be obtained by the electrolytic solution containing the first composition.

Effect of the Invention

[0017] According to the present invention, the low specific resistance characteristic of the electrolytic solution containing the quaternized cyclic amidinium salt can achieve a low ESR, and the electrolytic solution containing the first composition can obtain good liquid leakage resistance. Therefore, an electrolytic capacitor having a configuration with a low ESR, good liquid leakage resistance, and enhanced reliability can be realized.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described in detail. As shown in FIGS. 1, 2A, and 2B, the electrolytic capacitor 1 includes a wound capacitor element 2 into which an electrolytic solution 2e is introduced, lead terminals 5 and 6, a sealing body 3 having two through holes formed therein, and a bottomed case 4 for housing the capacitor element 2. The opening side of the case 4 is sealed by the sealing body 3. The sealing body 3 has high airtightness to prevent the intrusion of moisture and the scattering of oxide film repair substances, and has a substantially cylindrical shape conforming to the inner shape of the case 4. The case 4 is formed by processing a metal such as aluminum, and the sealing body 3 is made of an insulating rubber composition.

[0020] The anode foil 2a is made of a valve metal such as aluminum, and after the surface is roughened by an etching process, an oxide film is formed by a forming process. The cathode foil 2c is made of a valve metal such as aluminum, and after the surface is roughened by an etching process, an oxide film is formed by natural oxidation or a forming process.

[0021] A first separator 2d1 or a second separator 2d2 is disposed between the anode foil 2a and the cathode foil 2c. As the first separator 2d1 and the second separator 2d2, paper, non-woven fabric, etc. containing natural fibers or chemical fibers can be used. As raw materials for natural fibers, examples include wood, Manila hemp, esparto, etc. As chemical fibers, examples include rayon, etc., and recycled fibers may be used in some cases.

[0022] As shown in FIG. 2B, the capacitor element 2 is wound by stacking the anode foil 2a having an oxide film formed thereon, the first separator 2d1, the cathode foil 2c, and the second separator 2d2 in this order. Then, the capacitor element 2 is impregnated with the electrolytic solution 2e.

[0023] As an example, the electrolytic solution 2e contains γ-butyrolactone as an organic solvent, contains 15 [wt%] or more of a quaternized cyclic amidinium salt composed of an acid anion and a quaternized cyclic amidinium cation in equimolar amounts, contains 5 [wt%] or more of a first composition composed of one or more organic acids and one or more non-quaternary amines, and has a configuration in which a part of γ-butyrolactone in a reference electrolytic solution containing the quaternized cyclic amidinium salt and not containing the first composition is replaced with the first composition at the same weight ratio to increase the specific resistance. That is, the specific resistance of the electrolytic solution 2e is higher than the specific resistance of the reference electrolytic solution.

[0024] Subsequently, Examples A to D of the electrolytic solution will be described below.

[0025] [Example A of Electrolytic Solution] It has a composition containing 75 [wt%] of γ-butyrolactone and 25 [wt%] of a quaternized cyclic amidinium salt composed of an acid anion and a quaternized cyclic amidinium cation in equimolar amounts. The quaternized cyclic amidinium salt is a salt of phthalic acid and 1,2,3,4-tetramethylimidazolinium. It does not contain sulfolane. It does not contain the first composition.

[0026] [Example B of the electrolyte solution] It has a composition containing 60 [wt%] of γ-butyrolactone, 15 [wt%] of sulfolane, and 25 [wt%] of a quaternized cyclic amidinium salt composed of an acid anion and a quaternized cyclic amidinium cation in equimolar amounts. The quaternized cyclic amidinium salt is a salt of phthalic acid and 1,2,3,4-tetramethylimidazolinium. It does not contain the first composition.

[0027] [Example C of the electrolyte solution] It has a composition containing 65 [wt%] of γ-butyrolactone, 25 [wt%] of a quaternized cyclic amidinium salt composed of an acid anion and a quaternized cyclic amidinium cation in equimolar amounts, and 10 [wt%] of the first composition composed of phthalic acid and triethylamine in equimolar amounts. The quaternized cyclic amidinium salt is a salt of phthalic acid and 1,2,3,4-tetramethylimidazolinium. Example C of the electrolyte solution is a composition in which a part of the γ-butyrolactone in the reference electrolyte solution is replaced with the first composition in the same weight ratio to make the specific resistance about 1.2 times that of the reference electrolyte solution, with the reference electrolyte solution being Example A of the electrolyte solution. A first solution containing γ-butyrolactone and a quaternized cyclic amidinium salt was prepared, and then phthalic acid and triethylamine constituting the first composition were added to the first solution to prepare Example C of the electrolyte solution.

[0028] [Example D of the electrolyte solution] It contains 60 wt% of γ-butyrolactone, 25 wt% of a quaternized cyclic amidinium salt composed of an acid anion and a quaternized cyclic amidinium cation in equimolar amounts, and 15 wt% of a first composition composed of phthalic acid and triethylamine in equimolar amounts. The quaternized cyclic amidinium salt is a salt of phthalic acid and 1,2,3,4-tetramethylimidazolinium. Example D of the electrolytic solution is configured such that, using Example A of the electrolytic solution as a reference electrolytic solution, a part of the γ-butyrolactone in the reference electrolytic solution is replaced with the first composition at the same weight ratio to make the specific resistance about 1.3 times that of the reference electrolytic solution. A first solution containing γ-butyrolactone and a quaternized cyclic amidinium salt was prepared, and then phthalic acid and triethylamine constituting the first composition were added to the first solution to prepare Example D of the electrolytic solution.

[0029] Subsequently, Examples E to G of the capacitor element will be described below.

[0030] [Example E of Capacitor Element] The anode foil 2a and the cathode foil 2c are made of aluminum, and the first separator 2d1 and the second separator 2d2 contain 60 wt% or more of rayon. The thickness of the anode foil 2a is 90 μm, the thickness of the cathode foil 2c is 50 μm, the thickness of the first separator 2d1 is 40 μm, and the thickness of the second separator 2d2 is 40 μm. The total thickness of the anode foil 2a, the first separator 2d1, the cathode foil 2c, and the second separator 2d2 is 220 μm.

[0031] [Example F of Capacitor Element] The anode foil 2a and the cathode foil 2c are made of aluminum, and the first separator 2d1 and the second separator 2d2 contain 95 wt% or more of rayon. The thickness of the anode foil 2a is 80 μm, the thickness of the cathode foil 2c is 50 μm, the thickness of the first separator 2d1 is 25 μm, and the thickness of the second separator 2d2 is 25 μm. The total thickness of the anode foil 2a, the first separator 2d1, the cathode foil 2c, and the second separator 2d2 is 180 μm.

[0032] [Example G of Capacitor Element] The anode foil 2a and the cathode foil 2c are made of aluminum, and the first separator 2d1 and the second separator 2d2 contain 95 [% by weight] or more of rayon. The thickness of the anode foil 2a is 60 [μm], the thickness of the cathode foil 2c is 40 [μm], the thickness of the first separator 2d1 is 25 [μm], and the thickness of the second separator 2d2 is 25 [μm]. The total thickness of the anode foil 2a, the first separator 2d1, the cathode foil 2c, and the second separator 2d2 is 150 [μm].

[0033] Subsequently, by combining Examples A to D of the electrolytic solution and Examples E to G of the capacitor element, ten electrolytic capacitors each with a rated voltage of 35 [V] and a capacitance of 33 [μF] were prototyped. Then, the ESR at a temperature of 25 [°C] and a frequency of 100 [kHz] was measured to calculate the average value. After that, they were placed in a thermo-hygrostat at a temperature of 85 [°C] and a humidity of 85 [%RH], and a load test of applying a rated voltage of 35 [V] was carried out for 1,000 [hours], and the presence or absence of liquid leakage after the test was confirmed. The performance evaluation results are shown in Table 1 below.

[0034]

Table 1

[0035] According to Table 1, in Reference Examples 1 to 3 using Example A or Example B of the electrolytic solution, liquid leakage occurred in all cases. In contrast, in Examples 1 to 6 using Example C or Example D of the electrolytic solution, no liquid leakage occurred. Therefore, it was confirmed that good liquid leakage resistance can be obtained by preparing the electrolytic solution 2e containing the first composition. Regarding low ESR, all were achieved. In particular, by using Example F or Example G of the capacitor element, the ESR becomes lower than that of the configuration using Example E of the capacitor element, and it was confirmed that by using Example G of the capacitor element, the ESR becomes even lower than that of the configuration using Example F of the capacitor element.

[0036] For Examples 1 to 6, subsequently, they were placed in a thermo-hygrostat at a temperature of 85 [°C] and a humidity of 85 [%RH], and a load test of applying a rated voltage of 35 [V] was carried out for a total of 4,800 [hours], and it was confirmed that no liquid leakage occurred. Therefore, the effect of the liquid leakage resistance improvement action by the electrolytic solution 2e containing the first composition is remarkable.

[0037] In addition to the above, by making the total thickness of the anode foil 2a, the first separator 2d1, the cathode foil 2c, and the second separator 2d2 185 [μm] or less, in particular, a low ESR can be achieved. Furthermore, by making the total thickness of the anode foil 2a, the first separator 2d1, the cathode foil 2c, and the second separator 2d2 155 [μm] or less, an even lower ESR can be achieved.

[0038] The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

Explanation of Reference Numerals

[0039] 1 Electrolytic capacitor 2 Capacitor element 2a Anode foil 2c Cathode foil 2e Electrolytic solution 3 Sealing body 4 Case 5 Lead terminal 6 Lead terminal

Claims

1. A capacitor element in which an anode foil and a cathode foil are wound with a separator interposed therebetween, and an electrolytic solution introduced into the capacitor element, wherein the electrolytic solution contains 60 to 65% by weight of γ-butyrolactone, is composed of an acid anion and a quaternized cyclic amidinium cation, and a phthalic acid amidinium salt composed of phthalic acid and 1,2,3,4-tetramethylimidazolinium, and contains phthalic acid triethylamine which is a first composition composed of an organic acid and a non-quaternary amine and has a pKa of the conjugate acid of the non-quaternary amine of 12 or less, the molar ratio of the non-quaternary amine to the quaternized cyclic amidinium cation is 0.2 or more, the electrolytic solution contains 20 to 25% by weight of the phthalic acid amidinium salt, and contains 5 to 15% by weight of phthalic acid triethylamine which is the first composition. An electrolytic capacitor characterized by the above.

2. A method for manufacturing an electrolytic capacitor, which comprises a capacitor element in which an anode foil and a cathode foil are wound with a separator interposed therebetween, and an electrolytic solution introduced into the capacitor element, wherein the electrolytic solution contains 60 to 65% by weight of γ-butyrolactone, is composed of an acid anion and a quaternized cyclic amidinium cation, and a phthalic acid amidinium salt composed of phthalic acid and 1,2,3,4-tetramethylimidazolinium, and contains phthalic acid triethylamine which is a first composition composed of an organic acid and a non-quaternary amine and has a pKa of the conjugate acid of the non-quaternary amine of 12 or less, the method having a first step of preparing a first solution containing the phthalic acid amidinium salt in an organic solvent, and a second step of adjusting the molar ratio of the non-quaternary amine to the quaternized cyclic amidinium cation in an increasing direction by adding phthalic acid triethylamine which is the first composition to the first solution, the electrolytic solution containing 20 to 25% by weight of the phthalic acid amidinium salt, and containing 5 to 15% by weight of phthalic acid triethylamine which is the first composition. A method for manufacturing an electrolytic capacitor characterized by the above.

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