Electrolytic capacitor and method for manufacturing electrolytic capacitor

Abstract

To provide an electrolytic capacitor which is capable of reducing an ESR while improving the suppression effect of liquid leakage than before and is capable of being used at voltages of 50 V or more.SOLUTION: An electrolytic capacitor 1 includes a wound-type capacitor element 2 and an electrolyte 2e introduced into the capacitor element 2. An anode foil 2a has a film withstand voltage of 65 V or more. The electrolyte 2e contains 25 wt.% or less of a quaternized cyclic amidinium salt comprising acid anions and quaternized cyclic amidinium cations, and also contains 5 wt.% or more of 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.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 quaternary ammonium salt-based electrolytic solution has been known, and an electrolytic capacitor has been proposed in which boric acid and a sugar alcohol such as mannitol are further blended in the electrolytic solution to increase the withstand voltage and correspond to a rated voltage of 50 to 100 [V] (Patent Document 1: Japanese Patent Application Laid-Open No. 9-213583, Patent Document 2: Japanese Patent Application Laid-Open No. 2011-204949, Patent Document 3: WO2014 / 051129).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] For an electrolytic capacitor using an electrolytic solution, improvement in reliability is always required, and in particular, it is required to enhance the liquid leakage suppression effect. However, the electrolytic solutions of the above patent documents could not sufficiently meet such high reliability requirements.

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 that can achieve a lower ESR while enhancing the liquid leakage suppression effect as compared with the conventional one and can be used at a voltage of 50 V or higher.

[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 film breakdown voltage of the anode foil is 65 V or more, and the electrolytic solution contains γ-butyrolactone 70~80 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 and organic acid and and a first composition composed of a non-quaternary amine, and the pKa of the conjugate acid of the non-quaternary amine is 12 or less. triethylamine phthalate which is The electrolytic solution 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 is the phthalic acid amidinium salt 5 to 20% by weight contains, and contains 5% by weight or more of triethylamine phthalate which is the first composition and is characterized by this.

[0008] The inventors of the present invention have found that when a specific electrolytic solution is used, the liquid leakage resistance is improved and the low ESR can be achieved, and thus the present invention has been completed. That is, according to this configuration, the low specific resistance characteristics of the electrolytic solution containing the quaternized cyclic amidinium salt can achieve a low ESR, and the electrolytic solution containing 5% by weight or more of the first composition can obtain good liquid leakage resistance and can be sufficiently used even at a voltage of 50 [V] or more. That is, by using a non-quaternary amine having 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] The electrolytic solution preferably contains 50% by weight or more of γ-butyrolactone and 2% by weight or more of the quaternized cyclic amidinium salt. With this configuration, an increase in specific resistance in a low temperature range can be effectively suppressed. As an example, the solvent of the electrolytic solution may be γ-butyrolactone alone.

[0010] In the quaternized cyclic amidinium salt, it is preferable that an alkyl group is added to all nitrogen atoms constituting the ring among the atoms in the quaternized cyclic amidinium cation. Thereby, the electrolytic solution can have a low specific resistance. As such a cation component, as an 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 types 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 5 [% by weight] or more, or 10 [% by weight] or more. On the other hand, in the electrolytic solution, it is preferable that the total value of the ratio of the quaternized cyclic amidinium salt and the ratio of the first composition is 40 [% by weight] or less, and more preferably 30 [% by weight] or less. Thereby, a phenomenon in which a part of the electrolytic solution components precipitates in a low temperature range can be prevented.

[0011] 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 liquid leakage resistance is 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.

[0012] As the quaternized cyclic amidinium salt, as an example, a salt of a carboxylic acid anion and a quaternized cyclic amidinium cation can be mentioned. Further, a salt of an anion of a polyvalent carboxylic acid such as phthalic acid and a quaternized cyclic amidinium cation 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] From the viewpoint of enabling use at a higher voltage than conventional products, the film breakdown voltage of the anode foil may be 80 [V] or more, or may be 120 [V] or more. Also, from the viewpoint of enabling use at a higher voltage, the proportion of the quaternized cyclic amidinium salt in the electrolytic solution may be 20 [wt%] or less, or may be 15 [wt%] or less. In particular, in order to enable use at a voltage of 100 [V], the film breakdown voltage of the anode foil may be 120 [V] or more, and the proportion of the quaternized cyclic amidinium salt in the electrolytic solution may be 15 [wt%] or less.

[0016] The manufacturing method of the 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 film breakdown voltage of the anode foil is 65 V or more, The electrolytic solution contains γ-butyrolactone 70~80 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 and contains a phthalic acid amidinium salt and organic acid and and a non-quaternary amine, and is a manufacturing method of an electrolytic capacitor containing a first composition in which the conjugate acid of the non-quaternary amine has a pKa of 12 or less. The method includes a first step of preparing a first solution in which the phthalic acid amidinium salt is contained in an organic solvent, and the first composition triethylamine phthalate which is triethylamine phthalate which is ​Adding it to the first solution in A second step of adjusting the molar ratio of the non-quaternary amine to the quaternized cyclic amidinium cation to 0.2 or more and corresponding to a rated voltage of 50 V or more, and the electrolyte is The phthalic acid amidinium salt 5 to 20% by weight contains, and contains 5% by weight or more of triethylamine phthalate which is the first composition It is characterized by the above.

[0017] According to this production method, the concentration of the quaternized cyclic amidinium salt in the first solution can be adjusted to correspond to a rated voltage of 50 V or more, and a desired electrolyte can be adjusted. And, due to the low specific resistance characteristics of the electrolyte containing the quaternized cyclic amidinium salt, the ESR can be lowered, and good liquid leakage resistance can be obtained with the electrolyte containing the first composition.

Effects of the Invention

[0018] According to the present invention, due to the low specific resistance characteristics of the electrolyte containing the quaternized cyclic amidinium salt, the ESR can be lowered, and good liquid leakage resistance can be obtained with the electrolyte containing the first composition, enabling use at a voltage of 50 V or more. Therefore, an electrolytic capacitor having a configuration with low ESR, good liquid leakage resistance, and enhanced reliability can be realized.

Brief Description of the Drawings

[0019] [Figure 1] FIG. 1 is a partial cross-sectional view showing the schematic structure of an electrolytic capacitor according to an embodiment of the present invention from the side. [Figure 2] FIG. 2A is a schematic diagram showing the positional relationship between the lead terminal, the anode foil, and the lead terminal and the cathode foil, and FIG. 2B is a schematic diagram of a state in which the anode foil, the first separator, the cathode foil, and the second separator are wound in this order and stacked.

Modes for Carrying Out the Invention

[0020] 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 through-holes formed at two locations, 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 ingress 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 and shaping a metal such as aluminum, and the sealing body 3 is made of an insulating rubber composition.

[0021] The anode foil 2a is made of a valve metal such as aluminum. After the surface is roughened by an etching treatment, an oxide film is formed by a forming treatment. The cathode foil 2c is made of a valve metal such as aluminum. After the surface is roughened by an etching treatment, an oxide film is formed by natural oxidation or a forming treatment. 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 an example of the raw material of natural fibers, wood, Manila hemp, esparto, etc. can be mentioned. As an example of chemical fibers, rayon, etc. can be mentioned, and recycled fibers may also be used.

[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, and contains a quaternized cyclic amidinium salt composed of an acid anion and a quaternized cyclic amidinium cation in an equimolar ratio at a ratio of 5% by weight or more and 25% by weight or less, and contains 5% by weight 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 not containing the first composition is replaced with the first composition.

[0024] Subsequently, Examples A1, A2, B, C1, C2, D1, and D2 of the electrolytic solution will be described below.

[0025] [Example A1 of the electrolytic solution] It has a configuration containing 80 [wt%] of γ-butyrolactone and 20 [wt%] of a quaternized cyclic amidinium salt composed of an acid anion and a quaternized cyclic amidinium cation in an equimolar ratio. The quaternized cyclic amidinium salt is a salt of phthalic acid and 1,2,3,4-tetramethylimidazolinium. It does not contain the first composition. It does not contain boric acid. It does not contain sugar alcohols.

[0026] [Example A2 of the electrolytic solution] It has a configuration containing 85 [wt%] of γ-butyrolactone, 5 [wt%] of a quaternized cyclic amidinium salt composed of an acid anion and a quaternized cyclic amidinium cation in an equimolar ratio, 4 [wt%] of boric acid added, and 6 [wt%] of mannitol added. 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 B of the electrolytic solution] It has a configuration containing 73 [wt%] of γ-butyrolactone, 20 [wt%] of a quaternized cyclic amidinium salt composed of an acid anion and a quaternized cyclic amidinium cation in an equimolar ratio, 3 [wt%] of boric acid added, and 4 [wt%] of mannitol added. The quaternized cyclic amidinium salt is a salt of phthalic acid and 1,2,3,4-tetramethylimidazolinium. It does not contain the first composition.

[0028] [Example C1 of the electrolyte solution] It contains 70 [wt%] of γ-butyrolactone, 20 [wt%] of a quaternized cyclic amidinium salt composed of an acid anion and a quaternized cyclic amidinium cation in equimolar amounts, and further contains 10 [wt%] of a first composition composed of adipic acid and triethylamine in a weight ratio of 8:2. The quaternized cyclic amidinium salt is a salt of phthalic acid and 1,2,3,4-tetramethylimidazolinium. Example C1 of the electrolyte solution is configured such that, using Example A1 of the electrolyte solution as a reference electrolyte solution, a part of γ-butyrolactone in the reference electrolyte solution is replaced with the first composition at the same weight ratio to make the specific resistance about 1.6 times that of the reference electrolyte solution. A first solution containing γ-butyrolactone and a quaternized cyclic amidinium salt was prepared, and then adipic acid and triethylamine constituting the first composition were added to the first solution to prepare Example C1 of the electrolyte solution.

[0029] [Example C2 of the electrolyte solution] It contains 70 [wt%] of γ-butyrolactone, 20 [wt%] of a quaternized cyclic amidinium salt composed of an acid anion and a quaternized cyclic amidinium cation in equimolar amounts, and further contains 10 [wt%] of a first composition composed of azelaic acid and triethylamine in a weight ratio of 8.5:1.5. The quaternized cyclic amidinium salt is a salt of phthalic acid and 1,2,3,4-tetramethylimidazolinium. Example C2 of the electrolyte solution is configured such that, using Example A1 of the electrolyte solution as a reference electrolyte solution, a part of γ-butyrolactone in the reference electrolyte solution is replaced with the first composition at the same weight ratio to make the specific resistance about 1.6 times that of the reference electrolyte solution. A first solution containing γ-butyrolactone and a quaternized cyclic amidinium salt was prepared, and then azelaic acid and triethylamine constituting the first composition were added to the first solution to prepare Example C2 of the electrolyte solution.

[0030] [Example D1 of the electrolyte solution] It contains 80 wt% of γ-butyrolactone, 5 wt% of a quaternized cyclic amidinium salt composed of an acid anion and a quaternized cyclic amidinium cation in equimolar amounts, 4 wt% of boric acid is added, 6 wt% of mannitol is added, and further contains 5 wt% of a first composition composed of equimolar phthalic acid and triethylamine. The quaternized cyclic amidinium salt is a salt of phthalic acid and 1,2,3,4-tetramethylimidazolinium. Example D1 of the electrolyte is a configuration in which a part of γ-butyrolactone in the reference electrolyte is replaced with the first composition at the same weight ratio based on Example A2 of the electrolyte, and the specific resistance is about 0.9 times that of the reference electrolyte. 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 D1 of the electrolyte.

[0031] [Example D2 of the electrolyte] It contains 75 wt% of γ-butyrolactone, 5 wt% of a quaternized cyclic amidinium salt composed of an acid anion and a quaternized cyclic amidinium cation in equimolar amounts, 4 wt% of boric acid is added, 6 wt% of mannitol is added, and further contains 10 wt% of a first composition composed of equimolar phthalic acid and triethylamine. The quaternized cyclic amidinium salt is a salt of phthalic acid and 1,2,3,4-tetramethylimidazolinium. Example D2 of the electrolyte is a configuration in which a part of γ-butyrolactone in the reference electrolyte is replaced with the first composition at the same weight ratio based on Example A2 of the electrolyte, and the specific resistance is about 1.1 times that of the reference electrolyte. 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 D2 of the electrolyte.

[0032] Subsequently, Examples E to H of the capacitor element will be described below.

[0033] [Example E of the 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% by weight or more of rayon. The film breakdown voltage of the anode foil is 65 V or more. 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 50 μm, and the thickness of the second separator 2d2 is 50 μm. The total thickness of the anode foil 2a, the first separator 2d1, the cathode foil 2c, and the second separator 2d2 is 240 μm.

[0034] [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 60% by weight or more of rayon. The film breakdown voltage of the anode foil is 65 V or more. The thickness of the anode foil 2a is 70 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 200 μm.

[0035] [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 60% by weight or more of rayon. The film breakdown voltage of the anode foil is 65 V or more. The thickness of the anode foil 2a is 65 μm, the thickness of the cathode foil 2c is 40 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 185 μm.

[0036] [Example H 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% by weight or more of rayon. The film breakdown voltage of the anode foil is 120 V or more. The thickness of the anode foil 2a is 70 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 200 μm.

[0037] Subsequently, 10 electrolytic capacitors each with a rated voltage of 50 V and a capacitance of 33 μF were prototyped by combining Example A1, B, C1, C2 of the electrolytic solution with Examples E - G of the capacitor element. Then, the ESR at a temperature of 25 °C and a frequency of 100 kHz was measured and the average value was calculated. After that, a load test of applying a rated voltage of 50 V for 1,000 hours was carried out in a thermo - hygrostat at a temperature of 85 °C and a humidity of 85%RH, and the presence or absence of liquid leakage after the test was confirmed. The performance evaluation results are shown in Table 1 below.

[0038]

Table 1

[0039] According to Table 1, in Reference Examples 1 to 3 using Example A1 and Example B of the electrolytic solution, liquid leakage occurred in all cases. In addition, in Reference Example 1 using Example A1 of the electrolytic solution, the withstand voltage of the electrolytic solution was insufficient, and the yield rate in a predetermined aging process of applying a voltage equal to or higher than the rated voltage was inferior to other examples. On the other hand, in Examples 1 to 6 using Example C1 and Example C2 of the electrolytic solution, no liquid leakage occurred. Moreover, the yield rate in a predetermined aging process of applying a voltage equal to or higher than the rated voltage was also good, and it was confirmed that good liquid leakage resistance and sufficient withstand voltage characteristics could be obtained with the electrolytic solution 2e containing the first composition. In particular, by using Example F of the capacitor element or Example G of the capacitor element, the ESR became 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 became even lower than that of the configuration using Example F of the capacitor element.

[0040] Subsequently, 10 electrolytic capacitors each with a rated voltage of 100 [V] and a capacitance of 22 [μF] were prototyped by combining Example A2, D1, and D2 of the electrolytic solution with Example H of the capacitor element. Then, the ESR at a temperature of 25 [°C] and a frequency of 100 [kHz] was measured and the average value was calculated. 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 100 [V] was carried out for 5,000 [hours], and the presence or absence of liquid leakage after the test was confirmed. The performance evaluation results are shown in Table 2 below.

[0041]

Table 2

[0042] According to Table 2, in Reference Example 4 using Example A2 of the electrolytic solution, liquid leakage occurred. On the other hand, in Examples 7 to 8 using Example D1 and Example D2 of the electrolytic solution, no liquid leakage occurred, and it was confirmed that good liquid leakage resistance could be obtained with the electrolytic solution 2e containing the first composition. In particular, it was confirmed that good low ESR could be achieved by using Example H of the capacitor element. Therefore, the effect of the liquid leakage resistance improvement action by the electrolytic solution 2e containing the first composition is remarkable.

[0043] 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

[0044] 1 Electrolytic capacitor 2 Capacitor element 2a Anode foil 2c Cathode foil 2e Electrolyte 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 film breakdown voltage of the anode foil is 65 V or more, the electrolytic solution contains 70 to 80% by weight of γ-butyrolactone, is composed of an acid anion and a quaternized cyclic amidinium cation, and is composed of phthalic acid and 1,2,3,4-tetramethylimidazolinium, and contains phthalic acid amidinium salt, and a first composition composed of an organic acid and a non-quaternary amine and having a pKa of the conjugate acid of the non-quaternary amine of 12 or less, triethylamine phthalate, and the molar ratio of the non-quaternary amine to the quaternized cyclic amidinium cation is 0.2 or more, and the electrolytic solution contains 5 to 20% by weight of the phthalic acid amidinium salt and 5% by weight or more of triethylamine phthalate which is the first composition. An electrolytic capacitor characterized by the above.

2. A method for manufacturing an electrolytic capacitor, which 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, wherein the film breakdown voltage of the anode foil is 65 V or more, the electrolytic solution contains 70 to 80% by weight of γ-butyrolactone, is composed of an acid anion and a quaternized cyclic amidinium cation, and is composed of phthalic acid and 1,2,3,4-tetramethylimidazolinium, and contains phthalic acid amidinium salt, and a first composition composed of an organic acid and a non-quaternary amine and having a pKa of the conjugate acid of the non-quaternary amine of 12 or less, triethylamine phthalate, the method comprising: a first step of preparing a first solution containing the phthalic acid amidinium salt in an organic solvent; and a second step of adding triethylamine phthalate which is the first composition to the first solution to adjust the molar ratio of the non-quaternary amine to the quaternized cyclic amidinium cation to 0.2 or more to correspond to a rated voltage of 50 V or more, and the electrolytic solution contains 5 to 20% by weight of the phthalic acid amidinium salt and 5% by weight or more of triethylamine phthalate which is the first composition. A method for manufacturing an electrolytic capacitor characterized by the above.

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