Electrolytic capacitor

Abstract

An electrolytic capacitor (1) includes: a capacitor element (10) in which a cathode foil (11) and an anode foil (12) are wound with a separator (13) interposed between the cathode foil (11) and the anode foil (12), and a prescribed solution is held between the cathode foil (11) and the anode foil (12); a main body case (3) that accommodates the capacitor element (10); and a sealing body (5) that seals the main body case (3). The solution is a fat-soluble antioxidant dissolved in a lipophilic solvent, and the separator (13) is configured to be in contact with the sealing body (5).

Description

[0001] This application is a divisional application of the application filed on September 20, 2018, with application number 201880097841.5 and invention title "Electrolytic Capacitor". Technical Field

[0002] This invention relates to an electrolytic capacitor sealed with a sealing member. Background Technology

[0003] Patent Document 1 discloses a known electrolytic capacitor. This electrolytic capacitor has a main body housing, a capacitor element, and a sealing member. The main body housing is formed of a cylindrical metal having a bottom, with one end of its cylindrical circumferential wall closed and the other end open to have an opening.

[0004] The capacitor element has an anode foil and a cathode foil, both housed within a main body housing. The anode and cathode foils have oxide coatings formed thereon, and a separator is wound between them. An electrolyte is held between the anode and cathode foils. Each anode and cathode foil has lead terminals connected to it. The opening of the main body housing containing the capacitor element is sealed with a sealing member, for example, formed of rubber, through which the lead terminals extend from the main body housing.

[0005] It is believed that when polymers such as rubber are exposed to heat or light energy in the presence of oxygen in the air or elsewhere, a series of oxidation reactions are triggered by the generation of free radicals, leading to performance degradation. To address this problem, the incorporation of anti-aging agents into sealing components to inhibit oxidation reactions is frequently mentioned.

[0006] On the other hand, Patent Document 2 discloses an electrolytic capacitor having a solid electrolyte instead of a liquid electrolyte. This electrolytic capacitor has a main body casing, capacitor elements, and sealing members similar to those of the electrolytic capacitor in Patent Document 1. A conductive polymer, serving as the solid electrolyte, is held between the anode and cathode foils of the capacitor element. A hydrophilic polymer compound containing water is also held between the anode and cathode foils.

[0007] Using the electrolytic capacitor constructed as described above, the conductive polymer helps to achieve low ESR. Furthermore, the moisture contained in the hydrophilic polymer compound helps to repair defects in the oxide coatings on the anode and cathode foils.

[0008] Citation List

[0009] Patent documents

[0010] Patent document 1: JP-A-2000-100670 (pages 2-4) Figure 1 )

[0011] Patent Document 2: WO 2014 / 050913 (pp. 9-23) Figure 2 ) Summary of the Invention

[0012] Today, with the trend of smaller size and improved performance of devices containing electrolytic capacitors, electrolytic capacitors are increasingly used in high-temperature environments, where they are placed near motors, engines, fast-running semiconductor devices, and other devices that generate a lot of heat.

[0013] In the electrolytic capacitor disclosed in Patent Document 1, the anti-aging agent mixed in the sealing component is consumed as it exerts its antioxidant effect; that is, it is gradually depleted. In electrolytic capacitors used in high-temperature environments, the sealing component deteriorates rapidly as the anti-aging agent is depleted. This usually causes the electrolyte to evaporate from the main casing, eventually resulting in a so-called dried-up state. Therefore, there is a problem that electrolytic capacitors cannot maintain their characteristics stably over a long period of time.

[0014] Similarly, for the electrolytic capacitor disclosed in Patent Document 2, its use in high-temperature environments leads to deterioration of the sealing components. Consequently, moisture held between the anode and cathode foils leaks out of the main casing, making it impossible to repair the oxide coating. Therefore, there is a problem that the electrolytic capacitor cannot maintain its characteristics stably over a long period.

[0015] This applies not only to moisture used to repair oxide coatings, but also, when functional liquids that enhance the properties of electrolytic capacitors are held within the capacitor element, the functional liquids leak as the sealing components deteriorate under high-temperature conditions. Therefore, there is a problem that electrolytic capacitors cannot maintain their properties stably over a long period.

[0016] The purpose of this invention is to provide an electrolytic capacitor that can maintain its characteristics stably over a long period of time.

[0017] To achieve the above objectives, according to one aspect of the present invention, an electrolytic capacitor includes: a capacitor element having an anode foil and a cathode foil and holding a predetermined solution between the anode foil and the cathode foil, a separator wound between the anode foil and the cathode foil; a main body housing housing the capacitor element; and a sealing member sealing the main body housing with the sealing member. Here, the solution contains a lipophilic antioxidant dissolved in a lipophilic solvent, and the separator is in contact with the sealing member.

[0018] According to another aspect of the invention, in an electrolytic capacitor constructed as described above, the capacitor element can retain a solid electrolyte.

[0019] According to another aspect of the invention, in the electrolytic capacitor constructed as described above, the solution may be an electrolyte having a lipophilic antioxidant and an electrolyte dissolved in a lipophilic solvent.

[0020] According to another aspect of the invention, in the electrolytic capacitor constructed as described above, the concentration of the fat-soluble antioxidant in the electrolyte can be from 1% to 30% by weight.

[0021] According to another aspect of the invention, in the electrolytic capacitor constructed as described above, the concentration of the fat-soluble antioxidant in the electrolyte can be from 3% to 30% by weight.

[0022] According to another aspect of the invention, in the electrolytic capacitor constructed as described above, the lipophilic solvent may be γ-butyrolactone.

[0023] According to another aspect of the invention, in the electrolytic capacitor constructed as described above, the lipophilic solvent may comprise: at least one selected from the group consisting of sulfolane, ethylene glycol and diethylene glycol; and a nonionic surfactant.

[0024] According to another aspect of the invention, in the electrolytic capacitor constructed as described above, the nonionic surfactant may be polyethylene glycol or polyglycerol coupled with a lipophilic group.

[0025] According to another aspect of the invention, in the electrolytic capacitor constructed as described above, the nonionic surfactant may be a copolymer of polyethylene glycol and polypropylene glycol.

[0026] According to another aspect of the invention, in the electrolytic capacitor constructed as described above, the fat-soluble antioxidant may be a fat-soluble vitamin.

[0027] According to another aspect of the invention, in the electrolytic capacitor constructed as described above, the fat-soluble vitamin may be tocopherol or tocotrienol.

[0028] According to another aspect of the invention, in the electrolytic capacitor constructed as described above, the width of the separator in its short side direction may be greater than the width of the anode foil and the cathode foil in their short side directions, and the separator may protrude further toward the sealing member than the anode foil and the cathode foil, thereby contacting the sealing member.

[0029] According to another aspect of the invention, in the electrolytic capacitor constructed as described above, the main housing may have a constricted portion protruding from its inner surface to press against the circumferential surface of the sealing member, and the ridge of the constricted portion is located further away from the capacitor element than the middle of the sealing member in its thickness direction.

[0030] According to the present invention, the capacitor element holds a solution containing a lipophilic antioxidant dissolved in a lipophilic solvent, and a separator is in contact with a sealing member. Therefore, the separator allows a continuous supply of the lipophilic antioxidant to the sealing member. The lipophilic antioxidant supplied to the sealing member permeates through the intermolecular gaps within the sealing member, thereby reaching both the interior and outer surface of the sealing member. Thus, the surface of the sealing member is covered with a lipophilic antioxidant in the form of an oil film, which helps to inhibit the deterioration of the sealing member over a long period. Therefore, leakage of the solution held by the capacitor element can be prevented, and the characteristics of the electrolytic capacitor can be maintained for a long time. Attached Figure Description

[0031] Figure 1 This is a perspective view of an electrolytic capacitor according to a first embodiment of the present invention, viewed from above.

[0032] Figure 2 This is a perspective view of an electrolytic capacitor according to a first embodiment of the present invention, viewed from below.

[0033] Figure 3 This is a front cross-sectional view showing the capacitor body of an electrolytic capacitor according to a first embodiment of the present invention.

[0034] Figure 4 This is a perspective view showing the capacitor element of an electrolytic capacitor according to a first embodiment of the present invention.

[0035] Figure 5 yes Figure 3 A detailed view of section H in the image.

[0036] Figure 6 This is a graph showing the rate of capacitance change of an electrolytic capacitor according to a first embodiment of the present invention, which has passed a durability test.

[0037] Figure 7 This is a diagram showing the sealing member of an electrolytic capacitor according to a first embodiment of the present invention after a durability test.

[0038] Figure 8 This is a diagram showing the sealing member of an electrolytic capacitor of a comparative example compared to the present invention after a durability test.

[0039] The annotations in the attached figures are explained as follows:

[0040] 1 Electrolytic capacitor

[0041] 2. Capacitor body

[0042] 3. Main body shell

[0043] 3c opening

[0044] 3D contraction section

[0045] 5. Sealing components

[0046] 5a, 5b through holes

[0047] 6-seat plate

[0048] Through holes 6a and 6b

[0049] 7 and 8 lead terminals

[0050] 10 Capacitor Components

[0051] 11 Anode foil

[0052] 12 Cathode foil

[0053] 13. Separators

[0054] 14 belts. Detailed Implementation

[0055] <First Embodiment>

[0056] Embodiments of the present invention will now be described with reference to the accompanying drawings. Figure 1 and Figure 2 This is a perspective view showing the electrolytic capacitor 1 according to the first embodiment, viewed from above and below, respectively. The electrolytic capacitor 1 includes a capacitor body 2 and a base plate 6. The base plate 6 is formed of synthetic resin and holds the capacitor body 2. The base plate 6 has a pair of through holes 6a and 6b formed therein. Lead terminals 7, 8 (described later) extending from the capacitor body 2 are inserted through the through holes 6a and 6b and are bent, thereby being soldered to a circuit board.

[0057] Figure 3 This is a front cross-sectional view of the capacitor body 2. The capacitor body 2 includes a main housing 3, a capacitor element 10, and a sealing member 5. The main housing 3 is formed of a metal such as aluminum, which is a cylindrical shape with a bottom and a circular cross-section, and is open at one end to have an opening 3c. The capacitor element 10 is housed inside the main housing 3, and the opening 3c is sealed by the sealing member 5.

[0058] Figure 4 This is a perspective view of capacitor element 10. Capacitor element 10 includes an anode foil 11, a cathode foil 12, and a separator 13. Both the anode foil 11 and the cathode foil 12 are formed of metal foil in the form of elongated strips. The separator 13 is formed of nonwoven fabric or the like in the form of elongated strips.

[0059] The capacitor element 10 is formed by winding an anode foil 11 and a cathode foil 12 (with a separator 13 between the anode foil 11 and the cathode foil 12) into a cylindrical shape. The end of the anode foil 11 or the cathode foil 12 is secured with a winding-end tape 14. A lead terminal 7 is connected to the anode foil 11; a lead terminal 8 is connected to the cathode foil 12.

[0060] The separator 13 is formed such that its width in the short side direction (axial direction) is greater than the widths of the anode foil 11 and the cathode foil 12 in the short side direction. Therefore, the separator 13 protrudes upward (away from the opening 3c) and downward (towards the opening 3c) relative to the anode foil 11 and the cathode foil 12, thereby preventing short circuits between the anode foil 11 and the cathode foil 12.

[0061] The anode foil 11 is formed of a valve metal such as aluminum, tantalum, niobium, or titanium. The cathode foil 12 faces the anode foil 11 across the separator 13 and is formed of aluminum or the like. Both the anode foil 11 and the cathode foil 12 have oxide coatings (not shown) formed on their surfaces.

[0062] An electrolyte is held between the anode foil 11 and the cathode foil 12 of the capacitor element 10. Immersing the capacitor element 10 in the electrolyte for a predetermined period of time allows the electrolyte to penetrate into the separator 13 and be held between the anode foil 11 and the cathode foil 12. The electrolyte effectively acts as the cathode. The electrolyte also helps to repair defects in the oxide coating on the anode foil 11 and the cathode foil 12.

[0063] An electrolyte is a solution of an electrolyte in a lipophilic solvent. Gamma-butyrolactone can be used as a lipophilic solvent. Liquids containing a nonionic surfactant in at least one of sulfolane, ethylene glycol, and diethylene glycol can also be used as lipophilic solvents. Nonionic surfactants include polyethylene glycol or polyglycerol coupled with lipophilic groups, copolymers of polyethylene glycol and polypropylene glycol, etc.

[0064] Electrolytes exert their electrical conductivity by dissolving into ions in a solvent. Examples of electrolytes include organic amine salts of boric acid compounds or carbonate compounds.

[0065] The electrolyte also contains a fat-soluble antioxidant dissolved in a lipophilic solvent. The fat-soluble antioxidant reacts with oxygen to inhibit oxidation of the sealing component 5, as will be described in detail later. Antioxidants soluble in lipophilic solvents (e.g., fat-soluble vitamins) can be used as fat-soluble antioxidants. Examples of fat-soluble vitamins include, for example, vitamin A (retinol, alpha-carotene, beta-carotene, beta-cryptoxanthin), vitamin D (vitamin D2, vitamin D3), vitamin E (tocopherol, tocotrienol), and vitamin K (vitamin K1, vitamin K2, menadione-7).

[0066] If the concentration of the fat-soluble antioxidant in the electrolyte is less than 1% by weight, it cannot maintain its antioxidant effect on the sealing component 5 for a long time. If the concentration of the fat-soluble antioxidant in the electrolyte is greater than 30% by weight, the electrolyte has such a high viscosity that it takes a long time to keep the electrolyte in the capacitor element 10, resulting in increased working time. For these considerations, it is preferable that the concentration of the fat-soluble antioxidant in the electrolyte is from 1% to 30% by weight. It is further preferred that the concentration of the fat-soluble antioxidant in the electrolyte is from 3% to 20% by weight, as this provides better antioxidant effect, thereby reducing working time.

[0067] exist Figure 3 In this design, the sealing member 5 is formed as a disc-shaped molded part of an electrically insulating elastic material such as rubber, having paired through holes 5a and 5b. The lead terminals 7 and 8 of the capacitor element 10 are pressed through the through holes 5a and 5b. Butyl rubber can be used for the sealing member 5, which exhibits high environmental resistance, such as heat aging resistance, chemical resistance, and light resistance, as well as high electrical resistance and low gas permeability. The sealing member 5 may contain an anti-aging agent to inhibit deterioration.

[0068] With the sealing member 5 placed in the opening 3c of the main body housing 3, the open end of the main body housing 3 folds onto the sealing member 5. The main body housing 3 is swaged to press against the circumferential surface of the sealing member 5, thereby forming a constricted portion 3d protruding into the interior of the main body housing 3. Therefore, the sealing member 5 is held in a fixed position together with the capacitor element 10 and prevented from falling off, and the opening 3c of the main body housing 3 is sealed by the sealing member 5.

[0069] Here, the ridge of the contraction portion 3d is positioned further away from the capacitor element 10 than the center of the sealing member 5 in its thickness direction. Therefore, as shown, the circumferential surface of the sealing member 5 is pressed from below, causing the top surface of the sealing member 5 (the surface near the capacitor element 10) to bulge upwards, with its central portion protruding toward the capacitor element 10.

[0070] Figure 5 yes Figure 3 Detailed view of section H. At least a portion of the separator 13 that protrudes downwards from the anode foil 11 and the cathode foil 12 contacts the sealing member 5. Here, because the central portion of the sealing member 5 bulges upwards, the separator 13 is positioned along the sealing member 5 such that the separator 13 is firmly in contact with the sealing member 5 at multiple points or over a region.

[0071] The sealing member 5 is continuously supplied with a lipid-soluble antioxidant from the electrolyte via the separator 13 in contact with it. The lipid-soluble antioxidant penetrates the intermolecular gaps within the sealing member 5 to reach the interior of the sealing member 5 and the outer surface of the sealing member 5 (the side opposite to the capacitor element 10). Therefore, the outer surface of the sealing member 5 is coated with a lipid-soluble antioxidant in the form of an oil film.

[0072] Lipid-soluble antioxidants have high boiling points and low melting points (e.g., tocopherol has a boiling point of 235°C and a melting point of 3°C). This inhibits the evaporation of the lipid-soluble antioxidants covering the surface of the sealing member 5. This allows the lipid-soluble antioxidants to remain in the liquid phase over a temperature range from 25°C (i.e., near room temperature) to 150°C, thereby stably maintaining the state of the oil film.

[0073] Therefore, while the contact between the sealing member 5 and oxygen in the air is suppressed, the fat-soluble antioxidant reacts with the oxygen on or inside the sealing member 5 through oxidation. This allows for long-term suppression of oxidation-induced deterioration of the sealing member 5. Consequently, evaporation of the electrolyte solution through cracks in the sealing member 5 can be prevented.

[0074] Figure 6 This is a graph showing how the capacitance of the electrolytic capacitor 1 in this embodiment changes during a durability test. In this graph, the vertical axis represents the rate of capacitance change (expressed as a percentage), and the horizontal axis represents the passage of time.

[0075] In this figure, "A" represents the electrolytic capacitor 1 of this embodiment, wherein the electrolyte contains γ-butyrolactone as a lipophilic solvent and tocopherol as a lipid-soluble antioxidant. The concentration of the lipid-soluble antioxidant in the electrolyte is 10% by weight. The sealing member 5 is formed of butyl rubber in which an anti-aging agent is added.

[0076] In this figure, "B" represents the electrolytic capacitor of the comparative example, in which the fat-soluble antioxidant is omitted compared with the electrolyte of electrolytic capacitor 1 represented by A.

[0077] The electrolytic capacitor 1 of this embodiment and the comparative example were subjected to a durability test at a high temperature of 150°C, and its capacitance was measured. Figure 7 It is a photographic image of the sealing component 5 of the electrolytic capacitor 1, represented by A, after 8000 hours. Figure 8 It is a photographic image of the sealing component 5 of the electrolytic capacitor 1, represented by B, after 4000 hours.

[0078] Durability tests on the comparative example electrolytic capacitors revealed the following: After 1500 hours, the anti-aging agent lost its effectiveness, leaving the surface of sealing member 5 dry. After 4000 hours, cracks appeared in sealing member 5 (see...). Figure 8Furthermore, the electrolyte evaporates rapidly, causing the capacitance to drop sharply.

[0079] In contrast, the electrolytic capacitor 1 of this embodiment has been demonstrated as follows. After 1500 hours or even 8000 hours, the surface of the sealing member 5 appears glossy due to the coating of a fat-soluble antioxidant in the form of an oil film. That is, at the surface of the sealing member 5, the evaporation of tocopherol is slower than that of γ-butyrolactone, and the fat-soluble antioxidant is stably maintained in an oil film state in a high-temperature range of around 150°C, at which temperature the sealing member 5 would rapidly deteriorate through oxidation.

[0080] Furthermore, in the electrolytic capacitor 1 of this embodiment, the capacitance change rate is less than 20% after 8000 hours. Therefore, this electrolytic capacitor 1 can provide stable characteristics over a long period of time in a high-temperature environment. At the same time, the ESR remains very low, indicating that the fat-soluble antioxidant has no adverse effect on the electrolyte in the electrolyte solution.

[0081] According to this embodiment, the capacitor element 10 can hold an electrolyte containing a lipophilic antioxidant dissolved in a lipophilic solvent, and the separator 13 is in contact with the sealing member 5. Therefore, the lipophilic antioxidant in the electrolyte is continuously supplied to the sealing member 5 via the separator 13, which helps to suppress the deterioration of the sealing member 5 over a long period. Thus, evaporation of the electrolyte held by the capacitor element 10 can be prevented, and the characteristics of the electrolytic capacitor 1 can be maintained stably over a long period.

[0082] The concentration of the fat-soluble antioxidant in the electrolyte can be from 1% to 30% by weight. This helps to inhibit the increase of working time and helps to maintain the antioxidant effect on the sealing component 5 for a long time.

[0083] The concentration of fat-soluble antioxidants in the electrolyte can be from 3% to 20% by weight. This helps prolong the antioxidant effect and reduce working hours.

[0084] The lipophilic solvent in the electrolyte can be readily achieved using γ-butyrolactone.

[0085] The lipophilic solvent in the electrolyte can be readily achieved by comprising at least one of sulfolane, ethylene glycol and diethylene glycol, and a nonionic surfactant.

[0086] Nonionic surfactants can be readily achieved through liquids containing polyethylene glycol or polyglycerol coupled with lipophilic groups.

[0087] Nonionic surfactants can be readily achieved through copolymers of polyethylene glycol and polypropylene glycol.

[0088] Lipid-soluble antioxidants in lipophilic solvents can be readily achieved through lipid-soluble vitamins.

[0089] Fat-soluble vitamins dissolved in lipophilic solvents can be readily obtained using tocopherols or tocotrienols.

[0090] The separator 13 can protrude further toward the sealing member 5 than the anode foil 11 and the cathode foil 12. Therefore, the separator 13 can easily reach contact with the sealing member 5.

[0091] The ridge of the contraction protruding from the inner surface of the main housing 3 can be located further away from the capacitor element 10 than the center of the sealing member in its thickness direction. This allows the middle portion of the sealing member 5 to protrude toward the capacitor element 10, so that the separator 13 is positioned along the sealing member 5 such that the separator 13 is in firm contact with the sealing member 5 at multiple points or over a region.

[0092] <Second Embodiment>

[0093] Next, a second embodiment will be described. In this embodiment, instead of an electrolyte, the capacitor element 10 holds a solid electrolyte (not shown) and a predetermined functional liquid. In other respects, this embodiment is similar to the first embodiment.

[0094] The solid electrolyte is composed of a conductive polymer, etc. The conductive polymer helps to reduce the ESR of the electrolytic capacitor 1. Examples of conductive polymers that can be used are polythiophene, polypyrrole, or any derivatives thereof. Polyethylene dioxythiophene is particularly preferred due to its high conductivity.

[0095] The capacitor element 10 is immersed in a dispersion of conductive polymer for a predetermined time, and then the result is dried so that a solid electrolyte composed of conductive polymer is held between the anode foil 11 and the cathode foil 12.

[0096] A functional liquid, which increases voltage withstand capability, is also maintained between the anode foil 11 and the cathode foil 12. The functional liquid is a solution containing a lipophilic antioxidant dissolved in a lipophilic solvent. γ-Butyrolactone can be used as a lipophilic solvent. Liquids containing a nonionic surfactant in at least one of sulfolane, ethylene glycol, and diethylene glycol can also be used as lipophilic solvents. Nonionic surfactants can be polyethylene glycol or polyglycerol coupled with a lipophilic group, copolymers of polyethylene glycol and polypropylene glycol, etc. Any of these lipophilic solvents contributes to increased voltage withstand capability and allows the lipophilic antioxidant to dissolve.

[0097] Antioxidants that are soluble in lipophilic solvents (e.g., fat-soluble vitamins) can be used as fat-soluble antioxidants. Examples of fat-soluble vitamins include, for example, vitamin A (retinol, alpha-carotene, beta-carotene, beta-cryptoxanthin), vitamin D (vitamin D2, vitamin D3), vitamin E (tocopherol, tocotrienol), and vitamin K (vitamin K1, vitamin K2, menadione-7).

[0098] The solid electrolyte swells with the functional liquid. This provides an increased degree of close contact between the solid electrolyte and the anode foil 11 and cathode foil 12, wherein the solid electrolyte remains between the anode foil 11 and cathode foil 12. This helps to reduce the ESR of the electrolytic capacitor 1. Therefore, the functional liquid also has the function of reducing the ESR of the electrolytic capacitor 1.

[0099] As in the first embodiment, the separator 13 of the capacitor element 10 contacts the sealing member 5, and the lipid-soluble antioxidant in the functional liquid is supplied to the sealing member 5 via the separator 13. The lipid-soluble antioxidant penetrates the intermolecular gaps within the sealing member 5 to reach the interior of the sealing member 5 and the outer surface of the sealing member 5 (the side opposite to the capacitor element 10). Therefore, the outer surface of the sealing member 5 is coated with a lipid-soluble antioxidant in the form of an oil film.

[0100] Therefore, while the contact between the sealing member 5 and oxygen in the air is suppressed, the fat-soluble antioxidant reacts with the oxygen on or inside the surface of the sealing member 5. This allows for the suppression of oxidation-induced deterioration of the sealing member 5 and prevents leakage of functional fluids.

[0101] In this embodiment, capacitor element 10 holds a functional liquid and a solid electrolyte. The functional liquid is formed by dissolving a lipophilic antioxidant in a lipophilic solvent, and the separator 13 is in contact with the sealing member 5. Therefore, the lipophilic antioxidant in the functional liquid is continuously supplied to the sealing member 5 via the separator 13, which helps to suppress the deterioration of the sealing member 5 over a long period. Thus, leakage of the functional liquid held by capacitor element 10 can be prevented, and the characteristics of the electrolytic capacitor 1 can be maintained for a long time.

[0102] In this embodiment, the electrolyte having an electrolyte dissolved in the aforementioned functional liquid can be maintained between the anode foil 11 and the cathode foil 12. Maintaining the solid electrolyte and electrolyte between the anode foil 11 and the cathode foil 12 helps to enhance the function of the repair oxide coating and further reduce the ESR of the electrolytic capacitor 1.

[0103] Industrial applicability

[0104] This invention discovers applications in electrolytic capacitors and in automobiles, electronic devices, etc., incorporating electrolytic capacitors in their control circuits.

Claims

1. An electrolytic capacitor, comprising: A capacitor element having an anode foil and a cathode foil, a separator being wound between the anode foil and the cathode foil, and a predetermined solution being maintained between the anode foil and the cathode foil; The main housing contains the capacitor element; as well as The sealing member is used to seal the main housing. in, The solution contains lipophilic antioxidants that dissolve in lipophilic solvents. The concentration of the fat-soluble antioxidant in the solution is from 1% to 30% by weight, and The separator contacts the sealing member, and the lipophilic antioxidant held by the capacitor element is supplied to the sealing member via the separator. The lipophilic antioxidant impregnated in the sealing member reaches the outer surface of the sealing member on the side opposite to the capacitor element and covers the outer surface in the form of an oil film.

2. The electrolytic capacitor according to claim 1, wherein, The capacitor element contains a solid electrolyte.

3. The electrolytic capacitor according to claim 1 or 2, wherein, The solution is composed of an electrolyte having the lipophilic antioxidant and the electrolyte dissolved in the lipophilic solvent.

4. The electrolytic capacitor according to claim 3, wherein, The concentration of the fat-soluble antioxidant in the electrolyte is from 1% to 30% by weight.

5. The electrolytic capacitor according to claim 3, wherein, The concentration of the fat-soluble antioxidant in the electrolyte is from 3% to 20% by weight.

6. The electrolytic capacitor according to claim 1 or 2, wherein, The lipophilic solvent is γ-butyrolactone.

7. The electrolytic capacitor according to claim 1 or 2, wherein, The lipophilic solvent comprises: Select at least one of the following groups: sulfolane, ethylene glycol, and diethylene glycol; and Nonionic surfactants.

8. The electrolytic capacitor according to claim 7, wherein, The nonionic surfactant is polyethylene glycol or polyglycerol bonded to a lipophilic group.

9. The electrolytic capacitor according to claim 7, wherein, The nonionic surfactant is a copolymer of polyethylene glycol and polypropylene glycol.

10. The electrolytic capacitor according to claim 1 or 2, wherein, The fat-soluble antioxidant is a fat-soluble vitamin.

11. The electrolytic capacitor according to claim 10, wherein, The fat-soluble vitamin is tocopherol or tocotrienol.

12. The electrolytic capacitor according to claim 1 or 2, wherein, The separator is wider than the anode foil and the cathode foil in their short side direction, and the separator protrudes further toward the sealing member than the anode foil and the cathode foil, and the separator contacts the sealing member.

13. The electrolytic capacitor according to claim 12, wherein, The main housing has a protrusion extending from its inner surface to press against the circumferential surface of the sealing member, and The ridge of the protrusion is positioned further away from the capacitor element than the center of the sealing member in its thickness direction.

Images