Separator for aluminum electrolytic capacitor and aluminum electrolytic capacitor

Abstract

To provide a separator for an aluminum electrolytic capacitor that has high short-circuit resistance and can improve impregnation properties of aqueous dispersion liquid of conductive polymer or polymerization solution.SOLUTION: A separator that is interposed between a pair of electrodes and is used in an aluminum electrolytic capacitor having a conductive polymer as a cathode material is made only of cellulose fibers, and has a multilayer structure including a layer having an air resistance of 3 to 10 sec / 100 ml and a layer having an air resistance of 0.05 to 1 sec / 100 ml.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a separator for an aluminum electrolytic capacitor and an aluminum electrolytic capacitor using the separator.

Background Art

[0002] In recent years, in automotive applications, the use of aluminum electrolytic capacitors (hereinafter, hybrid electrolytic capacitors) using a conductive polymer and an electrolytic solution as cathode materials has been increasing. A hybrid electrolytic capacitor is a capacitor that combines the advantages of a conventional aluminum electrolytic capacitor using an electrolytic solution as a cathode material and an aluminum electrolytic capacitor using a conductive polymer as a cathode material (hereinafter, solid electrolytic capacitor).

[0003] Compared with conventional aluminum electrolytic capacitors, hybrid electrolytic capacitors have a low equivalent series resistance (hereinafter, ESR), good frequency characteristics, and can pass a high ripple current. Further, since a hybrid electrolytic capacitor also uses an electrolytic solution unlike a solid electrolytic capacitor, it has a function of repairing an anode foil, and thus high reliability has also been attracting attention.

[0004] Hybrid electrolytic capacitors are used in electronic control units (ECUs) such as electric power steering and advanced driver assistance systems in automobiles. In recent years, as efforts towards carbon neutrality progress in various countries, it is predicted that electrification and electronic control of automobiles will further progress. With the progress of electrification and electronic control of automobiles, the number of ECUs installed in automobiles increases, but since the installation space is limited, miniaturization of each component used in the ECU is required. For hybrid electrolytic capacitors used in ECUs, it is required to miniaturize while maintaining the capacitance or to increase the capacitance while maintaining the same size.

[0005] In addition, with the progress of the electrification and electronic control of automobiles, it is predicted that the power supply voltage of automobiles will also increase. In order to cope with this, hybrid electrolytic capacitors are required to have a higher rated voltage and improved short-circuit resistance.

[0006] To increase the capacitance of a hybrid electrolytic capacitor, it is effective to increase the foil length of the electrode foil. However, in order to maintain the outer diameter of the capacitor, it is necessary to make the separator thinner. However, when the separator is made thinner, the distance between the electrode foils becomes narrower, so the risk of short-circuit failure increases. Therefore, in order to use a thinner separator, it is necessary to improve the short-circuit resistance of the separator.

[0007] In solid electrolytic capacitors and hybrid electrolytic capacitors, a water dispersion or polymerization solution of a conductive polymer (a mixed solution of a monomer of a conductive polymer before polymerization and an oxidizing agent) is impregnated into the separator. However, when improving the short-circuit resistance of the separator, the density of the separator increases, the impregnation property of the water dispersion or polymerization solution of the conductive polymer deteriorates, and the ESR and productivity of the capacitor may deteriorate.

[0008] To increase the rated voltage and improve the short-circuit resistance of a hybrid electrolytic capacitor, it is effective to improve the short-circuit resistance of the separator. However, as described above, when improving the short-circuit resistance of the separator, the ESR and productivity of the capacitor may deteriorate.

[0009] For separators for hybrid electrolytic capacitors, separators containing fibers such as cellulose fibers and synthetic fibers, such as those in Patent Documents 1 to 4, are used.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

[0011] Patent Document 1 discloses a separator having a multilayer structure made of natural fibers and having fine pinholes uniformly dispersed therein. When this separator is applied to a hybrid electrolytic capacitor, it is considered that it can impregnate a water dispersion or polymerization solution of a conductive polymer well. However, since there are holes (pinholes) that are minute but penetrate from the front surface to the back surface of the separator, short-circuit failures occur, and it is not possible to make the separator thinner.

[0012] Patent Document 2 discloses a highly dense separator made of solvent-spun regenerated cellulose. This separator is highly dense and can impregnate the electrolytic solution well, but when applied to a hybrid electrolytic capacitor, it is difficult to impregnate a water dispersion or polymerization solution of a conductive polymer. This is due to the very high density of the separator. However, if the density of the separator is decreased in order to improve impregnability, short-circuit failures of the capacitor will occur. Also, when the density of the separator is decreased, the mechanical strength of the separator decreases, resulting in poor workability during capacitor manufacturing and a decrease in productivity.

[0013] Patent Document 3 discloses a technique for reducing the ESR of a capacitor by using a separator having a two-layer structure in which regenerated cellulose fibers are laminated at different densities. The impregnability of the water dispersion or polymerization solution of the conductive polymer of this separator is better than that of the separator disclosed in Patent Document 2, but worse than that of the separator disclosed in Patent Document 1. In order to improve the impregnability of the separator disclosed in Patent Document 3, there is a method of reducing the density of the separator to reduce the density, but reducing the density causes a short circuit failure and causes the constituent fibers to fall off due to the reduction of the density, and the productivity also deteriorates.

[0014] Patent Document 4 discloses a separator composed of a synthetic fiber and a binder, which can suppress the short circuit failure of a capacitor while maintaining the impregnability of the water dispersion or polymerization solution of the conductive polymer to the separator. The separator disclosed in this Patent Document 4 can suppress the short circuit failure of the capacitor as compared with the separator disclosed in Patent Document 1, but is inferior to the separators disclosed in Patent Document 2 and Patent Document 3. When the separator disclosed in Patent Document 4 is made thinner, the short circuit resistance further decreases and the risk of short circuit failure of the capacitor increases, so it is also difficult to make it thinner than a certain thickness. In order to suppress the short circuit failure of the capacitor using the separator disclosed in Patent Document 4, there is a method of increasing the density by increasing the fibrillated synthetic fiber contained in the separator, but when the density of the separator is increased beyond the range disclosed in Patent Document 4, it becomes difficult to impregnate the water dispersion or polymerization solution of the conductive polymer, and the ESR of the capacitor deteriorates.

[0015] As described above, in the conventional separator, it has not been possible to improve the impregnability of the water dispersion or polymerization solution of the conductive polymer and the short circuit resistance at the same time.

[0016] The viscosity of the aqueous dispersion or polymerization solution of the conductive polymer is about several tens to 150 mPa·s, which is higher than that of the main electrolytic solution (viscosity of about 10 mPa·s or less) of an electrolytic capacitor used at the same rated voltage as a capacitor using the conductive polymer as an electrolyte. Therefore, when impregnating the separator with the dispersion or polymerization solution, it is impregnated gradually over time under a reduced pressure environment. At this time, there were cases where the dispersion or polymerization solution of the conductive polymer only impregnated the ends of the capacitor element and could not impregnate the entire element. This is considered to be due to the following reasons. The impregnation of the conductive polymer dispersion or polymerization solution into the capacitor element is a process of sequentially sucking up the solution into the element by immersing the capacitor element in the solution. However, the previously impregnated dispersion or polymerization solution accumulates between the fibers and acts as a weir, inhibiting subsequent sucking up. Furthermore, the fibers constituting the separator swell when immersed in the dispersion or polymerization solution, and the fiber gaps become too narrow, resulting in resistance to the impregnation of the solution and making it impossible to impregnate the solution.

[0017] The present invention has been made in view of the above-described problems, and an object thereof is to provide a separator that has high short-circuit resistance and improves the impregnation property of an aqueous dispersion or polymerization solution of a conductive polymer. Another object is to suppress the occurrence of short-circuit defects in a hybrid electrolytic capacitor and reduce the ESR by using this separator.

Means for Solving the Problems

[0018] The present invention is intended to solve the above-described problems and has, for example, the following configuration. That is, a separator used for an aluminum electrolytic capacitor having a conductive polymer in the cathode material and interposed between a pair of electrodes, the separator being composed only of cellulose fibers and having a multilayer structure of a layer with an air permeability resistance of 3 to 10 seconds / 100 ml and a layer with an air permeability resistance of 0.05 to 1 second / 100 ml.

[0019] The separator of the present invention is a separator with improved impregnation properties for aqueous dispersions or polymerization solutions of conductive polymers due to the above configuration. By using this separator in a capacitor, the previously impregnated aqueous dispersion or polymerization solution accumulates between the fibers constituting the separator and no longer inhibits subsequent suction, enabling impregnation of the entire element. In addition, since the layer with an air permeability resistance of 0.05 to 1 second / 100 ml has many large voids inside the layer, even when the fibers constituting the separator swell during impregnation, sufficient voids are maintained inside the separator, allowing impregnation of the aqueous dispersion or polymerization solution of the conductive polymer up to the center of the capacitor element. Furthermore, the layer with an air permeability resistance of 3 to 10 seconds / 100 ml provides high short-circuit resistance for the separator and suppresses short-circuit failures when applied to a capacitor.

Advantages of the Invention

[0020] According to the present invention described above, it is possible to obtain a separator with high short-circuit resistance while improving the impregnation properties of aqueous dispersions or polymerization solutions of conductive polymers. Moreover, by using this separator, the occurrence of short-circuit failures in hybrid electrolytic capacitors can be suppressed and the ESR can be reduced. Furthermore, since the separator of the present invention has high short-circuit resistance, it is possible to make the separator thinner than before, and using this thinner separator can also contribute to increasing the capacitance and reducing the diameter of the capacitor.

Embodiments for Carrying Out the Invention

[0021] Hereinafter, a detailed description will be given of an exemplary embodiment of the present invention.

[0022] The separator of the present invention is a separator having a multilayer structure with a layer having an air permeability resistance of 3 to 10 seconds / 100 ml and a layer having an air permeability resistance of 0.05 to 1 second / 100 ml. The layer with an air permeability resistance of 3 to 10 seconds / 100 ml (highly dense layer) of the separator of the present invention is a layer in which fibers are densely deposited and contributes to improving the short-circuit resistance of the separator. In addition, the layer (low-density layer) of the separator of the present invention with an air permeability resistance of 0.05 to 1 second / 100 ml is a layer in which fibers are deposited coarsely compared to the high-density layer, and contributes to improving the impregnation property of the separator. Since this low-density layer is easily impregnated with an aqueous dispersion or polymerization solution of a conductive polymer, it can also be called a "high-impregnation layer". And by laminating one or more of these layers respectively, the separator of the present invention can be obtained.

[0023] Note that the high-density layer in the present invention refers to a layer with an air permeability resistance of 3 to 10 seconds / 100 ml in "JIS P 8117 'Paper and Paperboard - Test Methods for Air Permeability and Air Permeability Resistance (Intermediate Region) - Gurley Method'". Also, the low-density layer in the present invention refers to a layer with an air permeability resistance of 0.05 to 1 second / 100 ml in "JIS P 8117 'Paper and Paperboard - Test Methods for Air Permeability and Air Permeability Resistance (Intermediate Region) - Gurley Method'".

[0024] The separator of the present invention consists only of cellulose fibers. Therefore, the above high-density layer and low-density layer are each composed only of cellulose fibers. The reason for limiting to only cellulose fibers in the separator of the present invention will be explained below. Cellulose fibers have hydrogen bonds, and cellulose fibers are bound to each other by hydrogen bonds. When the fibers are bound to each other, the interval between the fibers becomes narrow, and the density of the sheet can be increased. In addition, cellulose fibers can be refined by beating. By refining cellulose fibers, it is possible to increase the specific surface area of the fibers, and it is also possible to increase the hydrogen bond sites when forming a sheet. That is, by controlling the degree of refinement of the fibers, the degree of density can be controlled within a desired range. On the other hand, synthetic fibers do not have hydrogen bonds unlike cellulose fibers. Also, synthetic fibers are difficult to be refined by beating. Even fibrillated synthetic fibers do not form hydrogen bonds, so the fibers are only physically entangled with each other, and the density cannot be increased beyond a certain level. For the above reasons, it is preferable that the separator of the present invention contains only cellulose fibers.

[0025] When the separator of the present invention is applied to a hybrid electrolytic capacitor and impregnated with an aqueous dispersion or polymerization solution of a conductive polymer, the aqueous dispersion or polymerization solution of the conductive polymer first impregnates the low-density layer. Then, it is gradually impregnated in the thickness direction, and the conductive polymer connects between the two electrode foils. In addition, since the impregnation of the aqueous dispersion or polymerization solution of the conductive polymer is sufficiently achieved by the low-density layer, even if the short-circuit resistance of the high-density layer is improved, the impregnation of the entire separator is not inhibited.

[0026] The high-density layer of the separator of the present invention can be formed, for example, by sheet-forming a material obtained by beating regenerated cellulose fibers such as solvent-spun cellulose fibers or natural cellulose fibers such as abaca pulp, cotton pulp, and jute pulp. From the viewpoint of denseness, the fibers used for the high-density layer of the present invention are preferably beaten fibers. If the average fiber length is less than 1 mm, it is preferable because it is easy to increase the denseness.

[0027] The low-density layer of the separator of the present invention can be formed, for example, by sheet-forming regenerated cellulose fibers such as solvent-spun cellulose fibers or natural cellulose fibers such as abaca pulp, cotton pulp, jute pulp, and esparto pulp. The fibers used for the low-density layer of the present invention may or may not be beaten as long as they do not adversely affect the impregnation of the aqueous dispersion or polymerization solution of the conductive polymer. If the average fiber length is 1 mm or more, it is difficult to become overly dense, which is preferable. Among them, solvent-spun cellulose fibers are preferable because it is easy to obtain a desired fiber diameter and fiber length depending on the degree of beating and it is easy to control the denseness of the sheet.

[0028] The beating method of the fiber used in the separator of the present invention can be used without particular limitation as long as it is used for ordinary papermaking raw materials. Generally, a disk refiner, a conical refiner, a high-pressure homogenizer, etc. can be mentioned. Also, there is no particular limitation on the beating conditions as long as a layer with a desired air permeability resistance can be obtained.

[0029] When forming the high-density layer into a sheet, various methods such as a papermaking method using a Fourdrinier paper machine or a cylinder paper machine, and a casting method can be used. When forming the low-density layer into a sheet, various methods such as a papermaking method using a cylinder paper machine and a casting method can be used. Also, for both the high-density layer and the low-density layer, when forming into a sheet, an antifoaming agent, a dispersant, or a paper strength enhancer may be added as long as it does not adversely affect the capacitor performance.

[0030] The lamination method of the separator of the present invention is not particularly limited. For example, the high-density layer and the low-density layer may be laminated on a paper machine to form a sheet, or after obtaining each layer, they may be laminated using a laminating device or the like, or each layer may be overlapped and wound together with a foil and laminated in a capacitor. Also, for example, after obtaining the high-density layer, a laminated sheet may be obtained by casting the low-density layer on the high-density layer.

[0031] Although there is no particular limitation on the thickness of the separator of the present invention, from the recent environment where miniaturization and high capacitance of capacitors are required, 60 μm or less is preferable. Also, in order to surely isolate between the two electrodes, 20 μm or more is preferable.

[0032] The density of the separator of the present invention is not particularly limited as long as it satisfies the short-circuit resistance and does not adversely affect the impregnation property of the aqueous dispersion or polymerization solution of the conductive polymer. However, from the viewpoints of handling during capacitor manufacturing and short-circuit resistance, 0.25 to 0.50 g / cm 3 is preferable.

[0033] 〔Measurement Method of Characteristics of Separator and Aluminum Electrolytic Capacitor〕 Specific measurements of the characteristics of the separator and aluminum electrolytic capacitor of this embodiment were performed under the following conditions and methods.

[0034] 〔Thickness〕 Using the micrometer specified in "5.1.1 Measuring instrument and measuring method a When using an outside micrometer" of "JIS C 2300-2 'Cellulose paper for electrical use - Part 2: Test methods' 5.1 Thickness", and folding the paper in accordance with the method of folding ten sheets in "5.1.3 Measuring the thickness by folding the paper", the thickness (μm) of the separator was measured.

[0035] 〔Density〕 The density (g / cm 3 ) of the separator in the absolutely dry state was measured by the method specified in Method B of "JIS C 2300-2 'Cellulose paper for electrical use - Part 2: Test methods' 7.0A Density".

[0036] 〔Average fiber length〕 Measured using the apparatus described in "JIS P 8226-2 'Pulp - Method for measuring fiber length by automated optical analysis - Part 2: Unpolarized light method'" (ISO16065-2 'Pulps - Determination of Fibre length by automated optical analysis - Part2: Unpolarized light method'), specifically Fiber Tester PLUS (manufactured by Lorentzen & Wettre) in this case.

[0037] 〔Air resistance〕 The air resistance (seconds / 100ml) of each of the high-density layer and the low-density layer was measured by the method described in "JIS P 8117 'Paper and paperboard - Test methods for air permeability and air resistance (intermediate range) - Gurley method'" (ISO5636-5 'Paper and board - Determination of air resistance(medium range) - Part5:Gurlay method'). If the air resistance could not be measured before laminating each layer, it was measured after peeling off the layers after lamination.

[0038] [Manufacturing Process of Capacitor Element] As the electrode foils, an anode foil with a thickness of 100 μm, a length of 170 mm, and a width of 5 mm, and a cathode foil with a thickness of 50 μm, a length of 190 mm, and a width of 5 mm were used. They were wound with separators having lengths of 200 mm × width of 6 mm and 250 mm × width of 6 mm interposed therebetween to fabricate a capacitor element with a height of 6 mm. The fabricated capacitor element was pre-dried at 105°C for 2 hours before the hybrid electrolytic capacitor manufacturing process.

[0039] [Manufacturing Process of Hybrid Electrolytic Capacitor] Using the separators of each example, a capacitor element was fabricated as in the above [Manufacturing Process of Capacitor Element], followed by a reformation process. After impregnating and drying with a dispersion liquid of a conductive polymer, it was impregnated with an ethylene glycol-based electrolytic solution. Then, it was inserted into a case, sealed, and subjected to an aging process to obtain a hybrid electrolytic capacitor with a rated voltage of 35 V, a diameter of 10.0 mm × a height of 10.0 mm.

[0040] [Short Circuit Defect Rate] The short circuit defect rate was obtained by counting the number of short circuit defects during aging using capacitor elements that could be wound without breakage defects, and dividing the number of elements that became these short circuit defects by the number of elements that could be wound without breakage defects, and expressing it as a percentage as the short circuit defect rate.

[0041] [ESR] The ESR of the fabricated hybrid electrolytic capacitor was measured at a frequency of 100 kHz at 20°C using an LCR meter.

[0042] [Capacitance] The capacitance of the fabricated hybrid electrolytic capacitor was measured at a frequency of 120 Hz at 20°C using an LCR meter.

Examples

[0043] Hereinafter, each specific example, each comparative example, and each conventional example according to the present invention will be described in detail.

[0044] Example 1 Using solvent-spun cellulose fibers beaten to an average fiber length of 0.5 mm, a high-density layer with an air permeability resistance of 4 seconds / ml was obtained by Fourdrinier papermaking. Using solvent-spun cellulose fibers beaten to an average fiber length of 1.2 mm, a low-density layer with an air permeability resistance of 0.1 second / 100 ml was obtained by cylinder papermaking. Each layer was laminated on a paper machine to obtain a two-layer separator. The thickness of this separator was 35 μm, and the density was 0.35 g / cm 3 It was.

[0045] Example 2 Using solvent-spun cellulose fibers beaten to an average fiber length of 0.6 mm, a high-density layer with an air permeability resistance of 5 seconds / ml was obtained by Fourdrinier papermaking. Using solvent-spun cellulose fibers beaten to an average fiber length of 1.3 mm, a low-density layer with an air permeability resistance of 1 second / 100 ml was obtained by cylinder papermaking. Using a laminating machine, the low-density layers were laminated on both sides of the high-density layer to obtain a three-layer separator. The thickness of this separator was 60 μm, and the density was 0.40 g / cm 3 It was.

[0046] Example 3 Using solvent-spun cellulose fibers beaten to an average fiber length of 0.45 mm, a paper strength enhancer was added and a high-density layer with an air permeability resistance of 3 seconds / ml was obtained by Fourdrinier papermaking. After mixing solvent-spun cellulose fibers beaten to an average fiber length of 1.2 mm and un-beaten solvent-spun cellulose fibers with an average fiber length of 2 mm, a low-density layer with an air permeability resistance of 0.05 second / 100 ml was obtained by cylinder papermaking. Each layer was laminated on a paper machine to obtain a two-layer separator. The thickness of this separator was 20 μm, and the density was 0.30 g / cm 3 It was.

[0047] Example 4 Using the solvent-spun cellulose fibers beaten to an average fiber length of 0.45 mm, a high-density layer with an air permeability resistance of 9 seconds / ml was obtained by Fourdrinier papermaking. After mixing 50% by mass of the solvent-spun cellulose fibers beaten to an average fiber length of 1.2 mm and 50% by mass of the unbeaten cotton pulp with an average fiber length of 1.6 mm, a low-density layer with an air permeability resistance of 0.5 seconds / 100 ml was obtained by cylinder papermaking. Each layer was laminated on a paper machine to obtain a two-layer separator. The thickness of this separator was 40 μm and the density was 0.45 g / cm 3 .

[0048] 〔Example 5〕 Using the same separator as in Example 3, the length of the electrode foil and the separator was extended during the production of the capacitor to produce a capacitor.

[0049] 〔Comparative Example 1〕 Using the same raw materials as the high-density layer in Example 1, a high-density layer was obtained by Fourdrinier papermaking, and a single-layer separator with the same thickness and density as in Example 1 was obtained. The air permeability resistance of this separator was 8 seconds / ml.

[0050] 〔Comparative Example 2〕 Using the same raw materials as the low-density layer in Example 1, a low-density layer was obtained by cylinder papermaking, and a single-layer separator with the same thickness and density as in Example 1 was obtained. The air permeability resistance of this separator was 0.2 seconds / ml.

[0051] 〔Conventional Example 1〕 Referring to Example 1 of Patent Document 1, a separator was produced by changing the thickness and density. This separator contains 40% by mass of Manila hemp pulp and 60% by mass of esparto pulp. The thickness of this separator was 50 μm and the density was 0.40 g / cm 3 . The air permeability resistance of this separator was 0.1 seconds / ml.

[0052] 〔Conventional Example 2〕 Referring to Example 7 of Patent Document 3, a separator was produced. This separator is formed by a layer (high-density layer) in which solvent-spun cellulose fibers are made into a fourdrinier sheet and a layer (low-density layer) in which solvent-spun cellulose fibers are made into a cylinder mold sheet. The thickness of this separator was 40 μm and the density was 0.40 g / cm 3 In addition, the air permeability resistance of the fourdrinier sheet layer of this separator was 7 seconds / 100 ml, and the air permeability resistance of the cylinder mold sheet layer was 1.5 seconds / 100 ml.

[0053] 〔Conventional Example 3〕 With reference to Example 7 of Patent Document 4, a separator was produced. This separator contains 45% by mass of fibrillated aramid fibers, 40% by mass of acrylic fibers, and 15% by mass of polyvinyl alcohol binder fibers. The thickness of this separator was 50 μm and the density was 0.35 g / cm 3 In addition, the air permeability resistance of this separator was 0.8 seconds / ml.

[0054] The raw materials, formulations, average fiber lengths, number of laminations, separator thickness, density, and performance evaluation results of the hybrid electrolytic capacitors using the separators of the examples, comparative examples, and conventional examples described above are shown in Table 1.

[0055]

Table 1

[0056] Hereinafter, the physical properties of the separators of each example, each comparative example, and each conventional example, and the evaluation results of the hybrid electrolytic capacitors using each separator will be described in detail.

[0057] The separator of Conventional Example 1 is a separator produced with reference to Patent Document 1. In the capacitor using this separator, a short circuit defect has occurred.

[0058] The separator of Comparative Example 3 is a separator manufactured with reference to Patent Document 4. In the capacitor using this separator, a short circuit failure has occurred. This is presumably due to fine pinholes penetrating the front and back surfaces existing in the separator. Also, the separator of Comparative Example 3 contains synthetic fibers. The synthetic fiber of Comparative Example 3 is fibrillated aramid fiber, which is a fiber that easily achieves high tightness among synthetic fibers. However, in the capacitor using the separator of Comparative Example 3, a short circuit failure has occurred. This is presumably because the tightness has decreased due to the influence of the synthetic fiber.

[0059] The separator of Comparative Example 2 is a separator manufactured with reference to Patent Document 3. The capacitor using this separator has a significantly higher ESR compared to Comparative Example 1 and Comparative Example 3. This is presumably because in the low-tightness layer of the separator of Comparative Example 2, the tightness is higher compared to the low-tightness layer of each example of the present application, and the impregnation of the conductive polymer is insufficient.

[0060] On the other hand, in the capacitors using the separators of Examples 1 to 4, no short circuit failure occurred and the ESR was also sufficiently low. It can be understood that by using the separator of the present invention, the short circuit failure of the capacitor can be suppressed and the ESR can be reduced.

[0061] As described above, in the capacitor using the separator of Comparative Example 3, a short circuit failure has occurred. From the comparison between each example and Comparative Example 3, it can be understood that by configuring the separator only with cellulose fibers without containing synthetic fibers, the tightness can be increased and the occurrence of short circuit failures can be prevented.

[0062] The capacitor using the separator of Comparative Example 1 has a significantly higher ESR of the capacitor compared to each example. Also, in the capacitor using the separator of Comparative Example 2, a short circuit failure has occurred. From the comparison between each example and Comparative Example 1 and Comparative Example 2, it can be understood that a multilayer structure of a high-tightness layer and a low-tightness layer is important to achieve both short circuit resistance and impregnation properties and suppress short circuit failures of the capacitor and reduce the ESR.

[0063] Also, in Example 5, without changing the case size of the capacitor, the capacitance of the capacitor can be improved compared with each example. By using the separator of the present invention, it can be seen that it can contribute not only to reducing the short-circuit failure and lowering the ESR of the capacitor, but also to improving the capacitance.

[0064] As described above, according to the present invention, it is possible to obtain a separator that is highly dense and has improved impregnation properties of the conductive polymer. Also, by using this separator, the occurrence of short-circuit failure in the hybrid electrolytic capacitor can be suppressed and the ESR can be reduced. Furthermore, since the separator of the present invention has high short-circuit resistance, by using a separator thinner than before, it can contribute to increasing the capacitance and reducing the diameter of the capacitor.

Claims

1. A separator used in an aluminum electrolytic capacitor having a conductive polymer in a cathode material and interposed between a pair of electrodes, wherein the separator consists only of cellulose fibers and has a multilayer structure of a layer having an air permeability resistance of 3 to 10 seconds / 100 ml and a layer having an air permeability resistance of 0.05 to 1 second / 100 ml A separator for an aluminum electrolytic capacitor, characterized by the above.

2. An aluminum electrolytic capacitor, characterized by using the separator for an aluminum electrolytic capacitor according to Claim 1.

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