JP2010226113A - High voltage electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolytic capacitor providing high voltages. <P>SOLUTION: A wet electrolytic capacitor is provided with: a porous anode body including a dielectric layer formed by anodization; a cathode including a metal base material covered with a conductive polymer; and an aqueous electrolyte disposed while abutting on the cathode and an anode. The electrolyte includes weak organic acid salt and water. The electrolyte has an ionic conductivity of approximately 0.5 to 80 mS/cm and approximately 5.0-8.0 pH, when measured at a temperature of 25°C. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  Electrolytic capacitors typically have a higher capacitance per unit volume than some other types of capacitors, which makes them useful in relatively high current, low frequency electrical circuits. One type of capacitor that has been developed is a “wet” electrolytic capacitor that includes a sintered tantalum powder anode. These tantalum “slags” have a very large internal surface area. These tantalum slags first undergo electrochemical oxidation to form an oxide layer that functions as a dielectric covering the entire outer and inner surfaces of the tantalum body. The anodized tantalum slag is then sealed in a high surface area can that contains a conductive and highly corrosive liquid electrolyte solution and includes a conductive lining that allows current to flow to the liquid electrolyte solution. The

The electrolyte solution used in wet tantalum electrolytic capacitors has traditionally consisted of one of two basic formulations. The first formulation consists of an aqueous solution of lithium chloride. The second electrolyte formulation conventionally used in wet tantalum capacitors consists of 35-40% aqueous sulfuric acid. Despite being corrosive, such sulfuric acid electrolytes have low resistance, wide temperature performance, and relatively high maximum operating voltage, which makes sulfuric acid electrolytes more common than conventional wet tantalum capacitors. Has become an option. Nevertheless, efforts have been made to develop other electrolytes for wet capacitors. For example, US Pat. No. 6,219,222 issued to Shah et al . Describes a solvent system comprising water and ethylene glycol, and an electrolyte using an ammonium salt. Shah et al. Show that this electrolyte has high conductivity and breakdown voltage, which reduces the equivalent series resistance. Unfortunately, the problem remains in that such capacitors are still difficult to reach high voltage values.

US Pat. No. 6,219,222 US Pat. No. 6,322,912 US Pat. No. 6,391,275 US Pat. No. 6,416,730 US Pat. No. 6,527,937 US Pat. No. 6,576,099 US Pat. No. 6,592,740 US Pat. No. 6,639,787 US Pat. No. 7,220,397 US Patent Application Publication No. 2005/0019581 US Patent Application Publication No. 2005/0103638 US Patent Application Publication No. 2005/0013765 US Pat. No. 6,197,252 US Pat. No. 6,191,936 US Pat. No. 5,949,639 U.S. Pat. No. 3,345,545 US Patent Application Publication No. 2005/0270725 US Patent No. 7,471,503 US Patent No. 7,411,779 US Patent No. 7,377,947 US Pat. No. 7,341,801 US Patent No. 7,297,015 US Pat. No. 7,154,740 US Pat. No. 6,987,663 U.S. Pat. No. 4,910,645 US Pat. No. 5,726,118 US Pat. No. 5,858,911 US Patent Application Publication No. 2003/0158342 US Pat. No. 5,457,862 US Pat. No. 5,473,503 US Pat. No. 5,729,428 US Pat. No. 5,812,367

Bruanauer, Emmet, and Teller, Journal of American Chemical Society, Vol. 60, 1938, p. 309.

  Therefore, there is a need for an electrolytic capacitor that can obtain a high voltage.

  According to one embodiment of the present invention, a porous anode body including a dielectric layer formed by anodization, a cathode including a metal substrate coated with a conductive polymer, and in contact with the cathode and the anode An electrolytic capacitor comprising an aqueous electrolyte disposed is disclosed. The electrolyte includes a salt of a weak organic acid and an aqueous solvent. The electrolyte has an ionic conductivity of about 0.1 to about 30 milliSiemens / centimeter and a pH of about 4.5 to about 7.0 when measured at a temperature of 25 ° C.

  Other features and aspects of the present invention are described in more detail below.

  The complete and practicable disclosure of the present invention, including the best mode of the present invention, directed to those skilled in the art will be described in further detail with reference to the accompanying drawings in the remainder of the specification.

1 is a cross-sectional view of one embodiment of a capacitor formed in accordance with the present invention.

  Repeat use of reference signs in the present specification and drawings is intended to indicate same or analogous features or elements of the invention.

  Those skilled in the art will appreciate that the discussion is merely illustrative of exemplary embodiments and is not intended to limit the broader aspects of the invention embodied in the exemplary configurations. Should.

  Broadly speaking, the present invention includes a porous anode body including a dielectric layer, a cathode including a metal substrate coated with a conductive polymer, and an aqueous electrolyte. The ionic conductivity of the electrolyte is selectively controlled within a specific range so that the capacitor can be charged to a high voltage. More specifically, the electrolyte is typically about 0.1 to about 30 milliSiemens / cm when measured using any known conductivity meter (such as Oakton Con Series 11) at a temperature of 25 ° C. Ion conductivity in meters (“mS / cm”), in some embodiments from about 0.5 to about 25 mS / cm, in some embodiments from about 1 to about 20 mS / cm, and in some embodiments from about 2 to about 15 mS / cm Have a rate. Within the above range, it is believed that the ionic conductivity of the electrolyte can extend the electric field into the liquid electrolyte to a length (Debye length) sufficient to provide significant charge separation. This spreads the potential energy of the dielectric to the electrolyte so that the resulting capacitor can store more potential energy than expected from the thickness of the dielectric oxide layer. In other words, the capacitor can be charged to a voltage exceeding the dielectric formation voltage. The ratio of the maximum voltage that can charge the capacitor to the forming voltage is, for example, from about 1.0 to 2.0, in some embodiments from about 1.1 to about 1.8, and in some embodiments from about 1.2 to about 1. .6. As an example, the maximum voltage to charge the capacitor may be about 200 to about 350V, in some embodiments about 220 to about 320V, and in some embodiments about 250 to about 300V.

The ionic conductivity of the electrolyte is achieved to some extent by selecting a particular type of salt within a certain concentration range. That is, the inventors have discovered that salts of weak organic acids are particularly effective for use in achieving the desired conductivity of the electrolyte. As salt cations, alkali metals (such as Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , or Cs ⁺ ), such as Be ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , or Ba ²⁺ ) Alkaline earth metals, monoatomic cations such as transition metals (such as Ag ⁺ , Fe ²⁺ , Fe ³⁺ ) and polyatomic cations such as NH ₄ ⁺ . Monovalent ammonium (NH ₄ ⁺ ), sodium (K + mistype Na ⁺ ), and lithium (Li ⁺ ) are particularly suitable cations for use in the present invention. The organic acid used to form the anion of the salt is usually from about 0 to about 11, in some embodiments from about 1 to about 10, and in some embodiments from about 2 to about 10, as measured at 25 ° C. It is “weak” in the sense that it has a single acid dissociation constant (pK _a1 ). In the present invention, acrylic acid, methacrylic acid, malonic acid, succinic acid, salicylic acid, sulfosalicylic acid, adipic acid, maleic acid, malic acid, oleic acid, gallic acid, tartaric acid (such as dextrotartaric acid, mesotartaric acid), citric acid, Formic acid, acetic acid, glycolic acid, oxalic acid, propionic acid, phthalic acid, isophthalic acid, glutaric acid, gluconic acid, lactic acid, aspartic acid, glutamic acid, itaconic acid, trifluoroacetic acid, barbituric acid, cinnamic acid, benzoic acid, 4 Any suitable weak organic acid, such as carboxylic acids such as hydroxybenzoic acid, aminobenzoic acid, and mixtures thereof can be used. For use in the formation of salts, (pK _a2 of pK _a1 and 5.41 4.43) adipic acid, alpha-tartaric acid (2.98 in pK _a1 and 4.34 pK _a2), meso-tartaric acid (3 .22 pK _a2 of pK _a1 and 4.82 of), pK _a2 of pKa1 and 4.19 of oxalic acid (1.23), pK _a1 of lactic acid (4.43, 5.41 of pK _a2, and 5. Polybasic acids (such as dibasic and tribasic) such as 41 pK _a3 ) are particularly desirable.

  The concentration of the weak organic acid salt in the electrolyte is selected to achieve the desired ionic conductivity. The actual amount may vary depending on the particular salt used, the solubility of the salt in the solvent (s) used in the electrolyte, and the presence of other components, but such weak organic acid salts. Typically within the electrolyte from about 0.1 to about 25% by weight, in some embodiments from about 0.2 to about 20% by weight, in some embodiments from about 0.3 to about 15% by weight, and in some embodiments. Is present in an amount of about 0.5 to about 5 weight percent.

  In general, the aqueous electrolyte can have any of a variety of forms such as solutions, dispersions, gels, and the like. However, regardless of its form, the aqueous electrolyte contains water (such as deionized water) as a solvent. For example, water (such as deionized water) can be from about 20% to about 95% by weight of the electrolyte, in some embodiments from about 30% to about 90%, and in some embodiments from about 40% to about 85%. % By weight can be constituted. In some cases, a secondary solvent can be used with water to form a solvent mixture. Suitable secondary solvents include, for example, glycols (such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, hexylene glycol, polyethylene glycol, ethoxydiglycol, dipropylene glycol), (methyl glycol ether, ethyl glycol ether) Glycol ethers (such as methanol, ethanol, n-propanol, isopropanol, and butanol), ketones (such as acetone, methyl ethyl ketone, and methyl isobutyl ketone), (ethyl acetate, butyl acetate, etc.) , Esters such as diethylene glycol ether acetate, methoxypropyl acetate, ethylene carbonate, propylene carbonate) (Dimethyl formamide de, dimethylacetamide, such as dimethyl caprylic / Kapurikku fatty acid amide and N- alkylpyrrolidones) amide, and (such as dimethyl sulfoxide (DMSO) and sulfolane) and the like sulfoxide or sulfone. Typically, such solvent mixtures are in an amount of from about 40% to about 80%, in some embodiments from about 50% to about 75%, and in some embodiments from about 55% to about 70% by weight. Contains water, in an amount of about 20% to about 60%, in some embodiments from about 25% to about 50%, and in some embodiments from about 30% to about 45% by weight. Contains a secondary solvent. For example, the secondary solvent (s) can be from about 5% to about 45% by weight of the electrolyte, in some embodiments from about 10% to about 40%, and in some embodiments from about 15% to about 35%. % Can be made up.

  The aqueous electrolyte is also relatively neutral, from about 4.5 to about 7.0, in some embodiments from about 5.0 to about 6.5, and in some embodiments from about 5.5 to about 6.0. Having a pH of If necessary, one or more pH adjusters (acid, base, etc.) can be used to help achieve the desired pH. In one embodiment, an acid is used to lower the pH to the desired range. Suitable acids include, for example, inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, polyphosphoric acid, boric acid, boronic acid, and acrylic acid, methacrylic acid, malonic acid, succinic acid, salicylic acid, sulfosalicylic acid, adipic acid, Maleic acid, malic acid, oleic acid, gallic acid, tartaric acid, citric acid, formic acid, acetic acid, glycolic acid, oxalic acid, propionic acid, phthalic acid, isophthalic acid, glutaric acid, gluconic acid, lactic acid, aspartic acid, glutamic acid, itacone Carboxylic acids such as acid, trifluoroacetic acid, barbituric acid, cinnamic acid, benzoic acid, 4-hydroxybenzoic acid, aminobenzoic acid, methanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, trifluoromethanesulfonic acid, styrenesulfone Acid, naphthalene disulfonic acid, hydroxybenzenesulfone And sulfonic acids such as poly (acrylic) or poly (methacrylic) acid and their copolymers (such as maleic-acrylic, sulfone-acrylic, and styrene-acrylic copolymers), polymeric acids such as carrageenic acid, carboxymethylcellulose, alginic acid, etc. And organic acids containing Although the total concentration of the pH adjuster may vary, the pH adjuster is typically about 0.01% to about 10% by weight of the electrolyte, and in some embodiments about 0.05% to about 5% by weight. %, And in some embodiments from about 0.1% to about 2% by weight.

  The electrolyte can also include other components that help improve the electrical performance of the capacitor. A depolarizer can be used in the electrolyte to help prevent the generation of hydrogen gas at the cathode of the electrolytic capacitor. If the depolarizer is not used, the hydrogen gas can expand the capacitor and eventually damage it. . When used, the depolarizer typically comprises about 1 to about 500 ppm of the electrolyte, in some embodiments about 10 to about 200 ppm, and in some embodiments about 20 to about 150 ppm. Suitable depolarizers include 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2-nitrobenzoic acid, 3-nitrobenzoic acid, 4-nitrobenzoic acid, 2-nitroacetophenone, 3-nitroacetophenone, 4-nitroacetophenone, 2-nitroanisole, 3-nitroanisole, 4-nitroanisole, 2-nitrobenzaldehyde, 3-nitrobenzaldehyde, 4-nitrobenzaldehyde, 2-nitrobenzyl alcohol, 3-nitrobenzyl alcohol, 4-nitro Mention may be made of nitroaromatic compounds such as benzyl alcohol, 2-nitrophthalic acid, 3-nitrophthalic acid, and 4-nitrophthalic acid. Particularly suitable nitroaromatic depolarizers for use in the present invention are nitrobenzoic acids substituted with one or more alkyl groups (such as methyl, ethyl, propyl, butyl, etc.), their anhydrides or salts . Specific examples of such alkyl-substituted nitrobenzoic acid compounds include, for example, 2-methyl-3-nitrobenzoic acid, 2-methyl-6-nitrobenzoic acid, 3-methyl-2-nitrobenzoic acid, 3-methyl Examples include -4-nitrobenzoic acid, 3-methyl-6-nitrobenzoic acid, 4-methyl-3-nitrobenzoic acid, and anhydrides or salts thereof. Without intending to be limited by theory, when the cathodic potential reaches a low region or the cell voltage is high, the alkyl-substituted nitrobenzoic acid compound preferentially adsorbs electrochemically to the active site on the cathode surface. It is believed that if the cathode potential rises or the cell voltage is low, it can then be desorbed from there into the electrolyte. Thus, this compound is “electrochemically reversible”, which can further suppress the generation of hydrogen gas.

The anode of the electrolytic capacitor is about 5,000 μF ^* V / g or higher, in some embodiments about 25,000 μF ^* V / g or higher, in some embodiments about 50,000 μF ^* V / g or higher, and in some embodiments about It includes a porous body that can be formed from a valve metal composition having a high specific charge such as 70,000 to about 300,000 μF ^* V / g. Valve metal compositions include valve metals (ie, metals that can be oxidized) or valve metal based compounds such as tantalum, niobium, aluminum, hafnium, titanium, alloys thereof, oxides thereof, and nitrides thereof. For example, the valve metal composition has an atomic ratio of niobium to oxygen of 1: 1.0 ± 1.0, in some embodiments 1: 10 ± 0.3, in some embodiments 1: 10 ± 0.1, and In some embodiments, a conductive oxide of niobium such as 1: 1 ± 0.05 niobium oxide can be included. For example, the niobium oxide may be NbO _0.7 , NbO _1.0 , NbO _1.1 , and NbO ₂ . Examples of such valve metal oxides, granted U.S. Patent No. 6,322,912 to Fife, No. 6,391,275, issued to Fife et first granted in Fife other 6,416 , 730, No. 6,527,937 granted to Fife , No. 6,576,099 granted to Kimmel et al ., No. 6,592,740 granted to Fife et al. , Granted to Kimmel et al. No. 6,639,787, and 7,220,397 to Kimmel et al., And US Patent Application Publication No. 2005/0019581 to Schnitter , US Patent Application Publication No. 2005/0103638 to Schnitter et al . No., are described in U.S. Patent application Publication No. 2005/0013765 to Thomas et al., these patents Their entirety by reference thereto by any object Te are incorporated herein.

In general, porous anode bodies can be formed using conventional fabrication procedures. In one embodiment, a tantalum or niobium oxide powder having a specific particle size is first selected. For example, the particles may be flaky, horned, knurled, and mixtures or variations thereof. The particles also typically have a sieve size distribution of at least about 60 mesh, in some embodiments from about 60 mesh to about 325 mesh, and in some embodiments from about 100 to about 200 mesh. Further, the specific surface area is from about 0.1 to about 10.0 m ² / g, in some embodiments from about 0.5 to about 5.0 m ² / g, and in some embodiments from about 1.0 to about 2.0 m ^2. / G. The term “specific surface area” refers to the physical gas adsorption method (B. E., et al., Branauer, Emmet, and Teller, Journal of American Chemical Society, Vol. 60, 1938, page 309, which uses nitrogen as the adsorption gas. T.) means the surface area measured. Similarly, the bulk (or Scott) density is typically about 0.1 to about 5.0 g / cm ³ , in some embodiments about 0.2 to about 4.0 g / cm ³ , and in some embodiments about 0.0. 5 to about 3.0 g / cm ³ .

  In order to facilitate the configuration of the anode body, another composition can be added to the conductive particles. For example, the conductive particles can optionally be mixed with a binder and / or lubricant to ensure that the particles adhere to each other correctly when pressurized to form the anode body. Suitable binders include camphor, stearic acid and other soapy fatty acids, Carbowax (Union Carbide), Glyptal (General Electric), polyvinyl alcohol, naphthalene, vegetable wax, and micro wax (purified paraffin). be able to. The binder can be dissolved or dispersed in the solvent. Exemplary solvents include water, alcohol, and the like. When utilized, the proportion of binder and / or lubricant may vary from about 0.1% to about 8% by weight of the total mass. However, it should be understood that binders and lubricants are not essential in the present invention.

The resulting powder can be compressed using any conventional powder press molding. For example, the press molding may be a single station compression press using a die and one or more punches. Alternatively, anvil-type compression press molding using only a die and a single lower punch can be used. Single station compression press molding includes single acting, double acting, floating die, movable platen, opposed ram, screw press, impact press, heating press, cam press with various capabilities such as casting or sizing, toggle / knuckle press and Available in several basic types such as eccentric / crank press. If necessary, any binder / lubricant can be removed after compression by heating the formed pellets under vacuum at a constant temperature (such as about 150 ° C. to about 500 ° C.) for several minutes. Alternatively, the binder / lubricant can be removed by contacting the pellet with an aqueous solution as described in US Pat. No. 6,197,252 to Bishop et al. Is hereby incorporated by reference in its entirety.

The thickness of the pressurized anode body is relatively thin, such as about 4 millimeters or less, in some embodiments from about 0.05 to about 2 millimeters, and in some embodiments from about 0.1 to about 1 millimeter. May be. The shape of the anode body can also be selected to improve the electrical properties of the resulting capacitor. For example, the anode body can have a shape such as a curve, a sine curve, a rectangle, a U-shape, or a V-shape. The anode body “grooves” in that it includes one or more ridges, grooves, recesses, or indentations to increase the surface to volume ratio to minimize ESR and broaden the frequency response of the capacitance. It can also have a “with” shape. Such “grooved” anodes are described, for example, in US Pat. No. 6,191,936 to Webber et al ., No. 5,949,639 to Maeda et al., And No. 5 to Bougault et al . No. 3,345,545 and U.S. Patent Application Publication No. 2005/0270725 to Hahn et al ., All of which are incorporated herein by reference for all purposes. .

The anode body may be anodically oxidized (“anodized”) so that a dielectric layer is formed over and / or within the anode. For example, a tantalum (Ta) anode can be anodized to tantalum pentoxide (Ta ₂ O ₅ ). Usually, anodic oxidation is performed by first adding a solution to the anode, such as by immersing the anode in an electrolyte. Generally, a solvent such as water (such as deionized water) is used. In order to increase the ionic conductivity, a compound that can be dissociated in a solvent to form ions can be used. Examples of such compounds include the acids as described above. For example, the acid (such as phosphoric acid) may be about 0.01% to about 5% by weight of the anodizing solution, about 0.05% to about 0.8% by weight, and in some embodiments, About 0.1% to about 0.5% by weight can be comprised. If necessary, an admixture of acids can also be used.

  A current passes through the anodizing solution to form a dielectric layer. The value of the formation voltage controls the thickness of the dielectric layer. For example, the power supply can be initially set to a constant current mode until the required voltage is reached. Thereafter, the power supply can be switched to the constant potential mode to ensure that the desired dielectric thickness is formed over the surface of the anode. Needless to say, other known methods such as pulsed or stepped potentiostatic methods can also be used. The voltage at which anodization is performed typically ranges from about 4 to about 250V, in some embodiments from about 9 to about 200V, and in some embodiments from about 20 to about 150V. During anodization, the anodization solution can be maintained at a temperature as high as about 30 ° C or higher, in some embodiments from about 40 ° C to about 200 ° C, and in some embodiments from about 50 ° C to about 100 ° C. Anodization can also be performed below atmospheric temperature. The resulting dielectric layer can be formed on the surface of the anode or in its pores.

  The cathodes of wet electrolytic capacitors are coated with tantalum, niobium, aluminum, nickel, hafnium, titanium, copper, silver, steel (such as stainless steel), alloys thereof (such as conductive oxides), and (conductive oxide) Metal substrates that can contain any metal, such as these composites (such as a modified metal). Titanium metal as well as its alloys are particularly suitable for use in the present invention. In general, the substrate geometry may vary as in the form of containers, cans, foils, sheets, screens, meshes, etc. as is well known to those skilled in the art. The surface area of the substrate can range from about 0.05 to about 5 square centimeters, in some embodiments from about 0.1 to about 3 square centimeters, and in some embodiments from about 0.5 to about 2 square centimeters. it can.

  There is also a conductive polymer coating on the metal substrate. Without intending to be limited by theory, we have charged the capacitors to a high voltage (e.g., higher than the forming voltage) to drive electrolyte ions into the polymer layer, which is conductive. It is believed to be facilitated by the small wetting angle of the aqueous electrolyte in the polymer system. The movement of ions causes the polymer to “swell” and increase the charge density by holding the ions close to the electrode surface. Nevertheless, since conductive polymers are generally amorphous and amorphous, conductive polymers can also dissipate and / or absorb heat associated with high voltages. During discharge, it is also believed that the conductive polymer “relaxes” to allow ions in the electrolyte to move out of the polymer layer. Through such swelling and relaxation mechanisms, the charge density near the electrode can be increased without chemical reaction with the electrolyte.

Generally speaking, a conductive polymer is a π-conjugated polymer that becomes conductive after oxidation or reduction. Examples of such conductive polymers include, for example, polypyrrole, polythiophene, polyaniline, polyacetylene, poly-p-phenylene (such as poly (p-phenylene sulfide) or poly (p-phenylene vinylene)), polyfluorene, polytetra Examples include thiafulvalene, polynaphthalene, derivatives of the aforementioned polymers, and mixtures thereof. One particularly suitable class of conductive polymers is poly (alkylene thiophenes) such as poly (3,4-ethylenedioxythiophene) (PEDT). Various suitable conducting polymer, Bruner other granted U.S. Patent Nos. 7,471,503, No. 7,411,779, issued to Merker other, first issued to Merker another 7,377, 947 No., No. 7,341,801, issued to Reuter et No. 7,297,015 issued to Merker other, No. 7,154,740, issued to Merker other, granted to Merker other No. 6,987,663 and 4,910,645 to Jonas et al ., All of which are hereby incorporated by reference in their entirety for all purposes. Is incorporated into.

Other materials can be used in the conductive polymer coating for various purposes. For example, the conductivity can be increased by using a conductive filler such as activated carbon, carbon black, or graphite. Some suitable forms of activated carbon and techniques for forming them are described in US Pat. No. 5,726,118 to Ivey et al., 5,858,911 to Wellen et al., And Shinozaki. All other granted U.S. Patent Application Publication No. 2003/0158342 are hereby incorporated by reference in their entirety for all purposes. In some cases, polymer anions can be used to handle any charge associated with the conducting polymer. For example, the anion may be a polymer carboxylic acid such as polyacrylic acid, polymethacrylic acid or polymaleic acid, or a polymer sulfonic acid such as polystyrene sulfonic acid (“PSS”) and polyvinyl sulfonic acid. When used, such polymer anions and conductive polymers are each about 0.5: 1 to about 50: 1, in some embodiments about 1: 1 to about 30: 1, and in some embodiments about 2: It can be present in a weight ratio of 1 to about 20: 1.

The conductive polymer can be applied to the metal substrate in the form of one or more layers and can be formed using various known techniques. For example, the coating can be formed using techniques such as screen printing, dipping, electrodeposition coating, and spraying. For example, in one embodiment, the monomer (s) used to form the conductive polymer (such as PEDT) is first mixed with the polymerization catalyst to form a dispersion. One suitable polymerization catalyst is CLEVIOS C (Bayer Corporation), which is iron (III) toluenesulfonate and n-butanol. CELVIOS C is a commercial catalyst for CELVIOS M, a monomer of PEDT also sold by Bayer Corporation, which is 3,4-ethylenedioxythiophene. When the dispersion liquid is generated, a conductive polymer can be formed by immersing the substrate in the dispersion liquid. Alternatively, the catalyst and the monomer (s) can be added separately. For example, the catalyst can be dissolved in a solvent (such as butanol) and then added as an immersion liquid. Although various methods have been described above, it should be understood that any other method for applying a coating, including a conductive polymer coating, can be utilized. For example, other methods for applying such a coating comprising one or more conductive polymer, granted to Sakata other U.S. Patent No. 5,457,862, issued to Sakata other 5,473 , 503, 5,724,428 granted to Sakata et al., And 5,812,367 granted to Kudoh et al. , These patents are incorporated by reference in their entirety for all purposes. Is incorporated herein.

  The physical arrangement of the capacitor's anode, cathode, and electrolyte may generally vary as is well known in the art. For example, referring to FIG. 1, one embodiment of an electrolytic capacitor 40 is shown that includes an aqueous electrolyte 44 disposed between an anode 20 and a cathode 43. The anode 20 includes a dielectric film 21 and is embedded with a lead 42 (such as a tantalum wire). The cathode 43 is formed from the base material 41 and the conductive polymer coating 49 as described above. In this embodiment, the cathode substrate 41 is in the form of a cylindrical “can” with a lid attached. A seal 23 (such as a glass metal seal) that connects and seals the anode 20 to the cathode 43 can also be used. If necessary, a separator (such as paper, plastic fiber, glass fiber, porous membrane, and ion-permeable material such as Nafion (registered trademark)) is disposed between the cathode 43 and the anode 20, and the anode Although direct contact between the cathode and the cathode is prevented, the flow of ionic current of the electrolyte 44 to the electrode can be allowed.

  The electrolytic capacitor of the present invention is not limited to the following, but is a medical device such as an implantable cardioverter defibrillator, a pacemaker, a cardiac defibrillator, a nerve stimulation device, a drug administration device, an automobile application, a RADAR system. It can be used for various uses including military use such as home appliances such as radio and television. In one embodiment, for example, a capacitor in an implantable medical device configured to provide a patient with a therapeutic high voltage (such as about 500 volts to about 850 volts, or desirably about 600 volts to about 800 volts) Can be used. The device can include a sealed biologically inert container or housing. One or more leads are electrically coupled via a vein between the device and the patient's heart. Cardiac electrodes are provided to detect cardiac activity and / or supply voltage to the heart. At least a portion of the lead (such as the tip of the lead) can be placed proximate to or in contact with one or more of the heart's ventricles and atria. The device also includes a capacitor bank that typically includes two or more capacitors that are connected in series and coupled to a battery that resides inside or outside the device and supplies energy to the capacitor bank. . The capacitors of the present invention can achieve superior electrical characteristics due in part to high electrical conductivity and are therefore suitable for use in capacitor banks of implantable medical devices.

  The invention can be better understood with reference to the following examples.

An electrolyte was formed by dissolving 10.65 grams of ammonium adipate (NH ₄ OC (O) (CH ₂ ) ₄ C (O) ONH ₄ ) in 55 milliliters of deionized water. Thereafter, 26 milliliters of ethylene glycol and 0.5 grams of H ₃ PO4 (85%) were added to the solution.

  The electrolyte was formed as described in Example 1 except that 5.3 grams of ammonium adipate was used.

  The electrolyte was formed as described in Example 1 except that 2.65 grams of ammonium adipate was used.

An electrolyte was formed by dissolving 10.65 grams of ammonium adipate in 55 milliliters of deionized water. Was then added ethylene glycol 26 ml of 0.1 grams of 3-methyl-4-nitrobenzoic acid and 0.5 grams of H ₃ PO4 (85%) to the solution.

  The electrolyte was formed as described in Example 4 except that 5.3 grams of ammonium adipate was used.

  The electrolyte was formed as described in Example 4 except that 2.65 grams of ammonium adipate was used.

An electrolyte was formed by dissolving 10.65 grams of ammonium acetate (NH ₄ OC (O) CH ₃ ) in 55 milliliters of deionized water. Thereafter, 26 milliliters of ethylene glycol and 0.5 grams of H ₃ PO4 (85%) were added to the solution.

  The electrolyte was formed as described in Example 7, except that 5.3 grams of ammonium acetate was used.

  The electrolyte was formed as described in Example 7, except that 2.65 grams of ammonium acetate was used.

An electrolyte was formed by dissolving 10.65 grams of sodium acetate (NaOC (O) CH ₃ ) in 55 milliliters of deionized water. Thereafter, 26 milliliters of ethylene glycol and 0.5 grams of H ₃ PO4 (85%) were added to the solution.

  The electrolyte was formed as described in Example 10, except that 5.3 grams of sodium acetate was used.

  The electrolyte was formed as described in Example 10, except that 2.65 grams of sodium acetate was used.

An electrolyte was formed by dissolving 5.3 grams of lithium acetate (LiOC (O) CH ₃ ) in 55 milliliters of deionized water. Thereafter, 26 milliliters of ethylene glycol and 0.5 grams of H ₃ PO4 (85%) were added to the solution.

  The electrolyte was formed as described in Example 13, except that 2.65 grams of lithium acetate was used.

An electrolyte was formed by dissolving 2.65 grams of lithium lactate (LiOC (O) CH (OH) CH ₃ ) in 55 milliliters of deionized water. Thereafter, 26 milliliters of ethylene glycol and 0.5 grams of H ₃ PO4 (85%) were added to the solution.

The electrolyte was formed by dissolving 2 grams of ammonium oxalate (NH ₄ OC (O) C (O) ONH ₄ ) in 54 milliliters of deionized water. Thereafter, 26 milliliters of ethylene glycol and 0.5 grams of H ₃ PO4 (85%) were added to the solution.

  The electrolyte was formed as described in Example 16, except that 1 gram of ammonium oxalate was used.

  An electrolyte was formed as described in Example 16, except that 0.5 grams of ammonium oxalate was used.

An electrolyte was formed by dissolving 2 grams of ammonium tartrate (NH ₄ OC (O) CH (OH) CH (OH) C (O) ONH ₄ ) in 54 milliliters of deionized water. Thereafter, 26 milliliters of ethylene glycol and 0.5 grams of H ₃ PO4 (85%) were added to the solution.

  The electrolyte was formed as described in Example 19, except that 1 gram of ammonium tartrate was used.

  An electrolyte was formed as described in Example 19, except that 0.5 grams of ammonium tartrate was used.

An electrolyte was formed by dissolving 2.7 grams of disodium tartrate (NH4OC (O) CH (OH) CH (OH) C (O) ONH4) in 54 milliliters of deionized water. Thereafter, 26 milliliters of ethylene glycol and 0.5 grams of H ₃ PO4 (85%) were added to the solution.

Example Testing Various properties of the electrolytes of Examples 1 to 14 and Examples 16 to 22 were tested. More specifically, a titanium base can is degreased, etched with oxalic acid (10% by weight aqueous solution), the plate is dried, and the inner surface of the can is roughened with sandpaper and a dremel tool to form a metal substrate. Formed. Thereafter, the roughened surface was coated with PEDT polymer. The coating was applied by immersing titanium metal in a solution of CLEVIOUS C dissolved in 1-butanol. After adding CLEVIOS C, the metal was immersed in CLEVIOUS M and placed in a humidity and temperature controlled box for 30 minutes. The relative humidity of the chamber was in the range of 75 to 85% and the temperature was in the range of 22 ° C to 25 ° C. The coated metal was then washed 4 times with methanol or ethanol to remove any unpolymerized material and residues from Baytron C. The final drying step was also performed in a chamber where the humidity was controlled to about 60% relative humidity. Coating, washing and drying were repeated four times to achieve a coating thickness of about 20 to about 50 μm on the titanium metal.

  Thereafter, the obtained cathode was immersed in the electrolyte. To test the electrolyte, a porous tantalum cylinder containing a tantalum pentoxide dielectric formed at 205V was used as the anode. A polypropylene separator material was wetted with electrolyte. The anode body was completely immersed in the electrolyte, and then taken out and a wet separator material was adhered. The assembly was placed in the electrolyte with a separator around the anode and then placed in a vacuum furnace for 15 minutes. Separately, the titanium cathode was filled with 1 milliliter of electrolyte. The anode / separator was then placed in a titanium can. The assembly was connected to a power supply ((+) pole to cylindrical anode and (−) pole to titanium can) and charged with a current in the range of 10-40 milliamps through a 1 kΩ resistor. The charging current affected the charging time, but ranged from 4.3 seconds at 10 mA to 1.3 seconds at 40 mA. The assembly was charged to the voltage set by the power supply. After charging the cell to the set voltage, it was held at the charging current for several minutes. Thereafter, the cell was discharged through a 100Ω resistor.

  The pH, voltage, charge time, and discharge time were measured. The results are shown in Tables 1 to 5 below.

Table 1: Characteristics of Examples 1 to 6

As a result of testing the ammonium adipate electrolyte, the cell could be charged to 280V. In comparison, it was confirmed that a similar cell using 5MH ₂ SO ₄ electrolyte could only be charged up to 140V. As shown in the table, as a result of reducing the amount of ammonium adipate in the basic compound electrolyte, the accumulated potential energy increased. Furthermore, the ionic conductivity of the ammonium adipate electrolyte was about 13.9 to 40.3 mS / cm, which was much smaller than the ionic conductivity of the 5 MH ₂ SO ₄ electrolyte (˜1000 mS / cm).

Table 2: Characteristics of Examples 7 to 9

  The ammonium acetate electrolyte showed the same behavior as the ammonium adipate electrolyte of Examples 1 to 6.

Table 3: Characteristics of Examples 10 to 14

  Sodium acetate and lithium electrolytes also behaved similarly to the ammonium adipate electrolytes of Examples 1-6.

Table 4: Characteristics of Example 16 to Example 21

  As shown in the table, the ammonium oxalate and ammonium tartrate electrolytes were easily charged to about 290V. It is believed that such a high voltage was achieved because of the low solubility limit of oxalic acid and tartaric acid ammonium salts, and thus limited maximum concentration in the electrolyte.

Table 5: Properties of Example 22

  The sodium tartrate electrolyte behaved similarly to the ammonium tartrate electrolytes of Examples 19-21.

  Those skilled in the art can make these and other modifications and changes to the present invention without departing from the spirit and scope of the present invention. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Further, those skilled in the art will appreciate that the above description is for illustrative purposes only and is not intended to limit the invention as further described in the claims appended hereto. I understand.

Claims (25)

A porous anode body including a dielectric layer formed by anodization;
A cathode comprising a metal substrate coated with a conductive polymer;
An aqueous electrolyte disposed in contact with the cathode and the anode;
The electrolyte comprises a salt of a weak organic acid and water, and the electrolyte has an ionic conductivity of about 0.1 to about 30 milliSiemens / centimeter when measured at a temperature of 25 ° C. the pH is from about 4.5 to about 7.0;
A wet electrolytic capacitor characterized by that. The electrolyte has an ionic conductivity of about 0.1 to about 20 milliSiemens / centimeter when measured at a temperature of 25 ° C .;
The wet electrolytic capacitor according to claim 1. The pH is from about 5.0 to about 6.5;
The wet electrolytic capacitor according to claim 1. The salt comprises a monoatomic cation,
The wet electrolytic capacitor according to claim 1. The monoatomic cation is an alkali metal ion,
The wet electrolytic capacitor according to claim 4. The salt comprises a polyatomic cation,
The wet electrolytic capacitor according to claim 1. The polyatomic cation is an ammonium ion;
The wet electrolytic capacitor according to claim 6. The organic acid has a first acid dissociation constant of about 2 to about 10 when measured at a temperature of 25 ° C .;
The wet electrolytic capacitor according to claim 1. The organic acid is a carboxylic acid,
The wet electrolytic capacitor according to claim 1. The carboxylic acid is polybasic,
The wet electrolytic capacitor according to claim 9. The polybasic carboxylic acid is adipic acid, tartaric acid, oxalic acid, citric acid, or a combination thereof;
The wet electrolytic capacitor according to claim 10. Weak organic acid salts comprise from about 0.1 to about 25 weight percent of the electrolyte;
The wet electrolytic capacitor according to claim 1. Weak organic acid salts comprise from about 0.3 to about 15 weight percent of the electrolyte;
The wet electrolytic capacitor according to claim 1. Water constitutes about 20 to about 95 weight percent of the electrolyte;
The wet electrolytic capacitor according to claim 1. The electrolyte further comprises a secondary solvent;
The wet electrolytic capacitor according to claim 1. The secondary solvent comprises ethylene glycol;
The wet electrolytic capacitor according to claim 15. The metal substrate comprises titanium;
The wet electrolytic capacitor according to claim 1. The conductive polymer is polythiophene,
The wet electrolytic capacitor according to claim 1. The polythiophene is poly (3,4-ethylenedioxythiophene) or a derivative thereof;
The wet electrolytic capacitor according to claim 18. The anode body is formed of tantalum or niobium oxide;
The wet electrolytic capacitor according to claim 1. The ratio of the maximum voltage that can charge the capacitor to the voltage at which the dielectric layer is formed is 1.0 to 2.0.
The wet electrolytic capacitor according to claim 1. A maximum voltage capable of charging the capacitor is about 200 to about 350V;
The wet electrolytic capacitor according to claim 1. A maximum voltage capable of charging the capacitor is about 250 to about 300V;
The wet electrolytic capacitor according to claim 1. A porous anode body formed of tantalum or niobium oxide and further comprising a dielectric layer formed by anodization;
A cathode comprising a titanium substrate coated with a conductive polymer comprising poly (3,4-ethylenedioxythiophene) or a derivative thereof;
An aqueous electrolyte disposed in contact with the cathode and the anode;
The electrolyte comprises a salt of a weak organic acid and water, and the electrolyte has an ionic conductivity of from about 0.5 to about 25 milliSiemens / centimeter when measured at a temperature of 25 ° C. the pH is about 4.0 to about 7.0;
A wet electrolytic capacitor characterized by that. The electrolyte has an ionic conductivity of from about 1 to about 20 milliSiemens / centimeter when measured at a temperature of 25 ° C .;
25. The wet electrolytic capacitor according to claim 24.

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