Electrolytic capacitor and its manufacturing method

Abstract

Disclosed is an electrolytic capacitor 100 comprising a capacitor element 10. The capacitor element 10 includes an anode body 21 having a dielectric layer on a surface thereof, and an electrolyte layer disposed adjacent to the dielectric layer. The electrolyte layer includes a self-doping first conductive polymer and a non-aqueous solvent.

Description

[Technical field]

[0001] The present disclosure relates to electrolytic capacitors and methods for manufacturing the same. [Background technology]

[0002] Capacitors used in electronic devices are required to have a large capacity and a low equivalent series resistance (ESR) value in the high frequency range. As a capacitor with a large capacity and a low ESR, an electrolytic capacitor using a conductive polymer such as polypyrrole, polythiophene, polyfuran, or polyaniline is promising. Patent Document 1 (International Publication No. 2012 / 117994) discloses a conductive polymer solution for forming a solid electrolyte layer, which contains "a conductive polymer, polysulfonic acid or a salt thereof that functions as a dopant for the conductive polymer, a mixture of a polyacid and a carbon material, and a solvent" (claim 1 of Patent Document 1). Patent Document 1 also discloses a solid electrolytic capacitor manufactured using the conductive polymer solution. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2012 / 117994 Summary of the Invention [Problem to be solved by the invention]

[0004] Currently, there is a demand for electrolytic capacitors with a low rate of increase in ESR over a long period of time. In this situation, one of the objects of the present disclosure is to provide an electrolytic capacitor with a low rate of increase in ESR over a long period of time. [Means for solving the problem]

[0005] One aspect of the present disclosure relates to an electrolytic capacitor including a capacitor element, the capacitor element including an anode body having a dielectric layer on a surface thereof and an electrolyte layer disposed adjacent to the dielectric layer, the electrolyte layer including a self-doping first conductive polymer and a non-aqueous solvent.

[0006] Another aspect of the present disclosure relates to a method for producing an electrolytic capacitor, the method comprising the steps of: (i) preparing a capacitor element precursor including an anode body having a dielectric layer on a surface thereof; (ii) forming a polymer layer including a self-doping first conductive polymer by an impregnation process so as to be adjacent to the dielectric layer; and (iii) impregnating the polymer layer with a non-aqueous solvent. . Effect of the Invention

[0007] According to the present disclosure, an electrolytic capacitor having a low rate of increase in ESR over a long period of time can be obtained. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view illustrating a schematic example of an electrolytic capacitor according to the present disclosure. [Diagram 2] FIG. 2 is a diagram illustrating a schematic view of a portion of the electrolytic capacitor illustrated in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In the following, the embodiment of the present disclosure will be described with reference to examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and materials may be applied as long as the effects of the present disclosure can be obtained.

[0010] (Electrolytic capacitor) The electrolytic capacitor of the present disclosure includes a capacitor element including an anode body having a dielectric layer on a surface thereof and an electrolyte layer disposed adjacent to the dielectric layer, the electrolyte layer including a self-doping first conductive polymer and a non-aqueous solvent.

[0011] The capacitor element may include a foil-shaped anode body having a dielectric layer on its surface, a foil-shaped cathode body, a separator disposed between the anode body and the cathode body, and an electrolyte layer disposed between the anode body and the cathode body. Such a capacitor element may be referred to as a "first capacitor element" below. The first capacitor element may be a wound type or a laminated type. In one example of a wound type capacitor element, a foil-shaped anode body, a foil-shaped cathode body, and a separator are wound so that the separator is disposed between the anode body and the cathode body. In one example of a laminated type capacitor element, a foil-shaped anode body, a foil-shaped cathode body, and a separator are folded in a zigzag shape so that the separator is disposed between the anode body and the cathode body.

[0012] Alternatively, the capacitor element may include a porous anode body having a dielectric layer on its surface, a cathode layer, and an electrolyte layer disposed between the anode body and the cathode layer. Such a capacitor element may be hereinafter referred to as a "second capacitor element." In the first and second capacitor elements, the electrolyte layer is adjacent to the dielectric layer of the anode body.

[0013] The electrolyte layer may further include a second conductive polymer doped with a dopant.

[0014] The first and second conductive polymers contained in the electrolyte layer will be described below. Note that in this specification, the term "conductive polymer" may be read as "conductive polymer."

[0015] (First conductive polymer) The first conductive polymer is a self-doping conductive polymer. Here, the self-doping conductive polymer means a polymer in which a functional group functioning as a dopant is directly or indirectly bonded to the backbone of the conductive polymer by a covalent bond. Examples of the functional group functioning as a dopant include an anionic group. The anionic group is a group that becomes negatively charged by dissociation of a cation. The anionic group may be at least one selected from the group consisting of a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, and a carboxyl group, or may be a salt thereof (such as a salt with an inorganic base or a salt with an organic base). A preferred example of the anionic group is a sulfonic acid group or a salt thereof.

[0016] The amount of functional groups (such as anionic groups) functioning as dopants may be in the range of 0.2 to 3, 0.5 to 2, or even 1 per structural unit constituting a polymer.

[0017] The first conductive polymer may be used alone or in combination of two or more kinds.

[0018] Examples of the skeleton of the first conductive polymer include polypyrrole, polythiophene, polyaniline, etc. These skeletons may have an atomic group (e.g., a functional group) other than the functional group that functions as a dopant bonded thereto. Examples of the first conductive polymer include polypyrroles having an anionic group (polypyrrole and its derivatives), polythiophenes having an anionic group (polythiophene and its derivatives), polyanilines having an anionic group (polyaniline and its derivatives), etc. In these examples, an example of a preferred anionic group is a sulfonic acid group or a salt thereof. The first conductive polymer is a polymer that is composed of two or more monolayers. The polymer may be a copolymer of the above monomers.

[0019] The first conductive polymer may be poly(3,4-ethylenedioxythiophene) (PEDOT) to which an atomic group containing a sulfonic acid group has been introduced, since this has a high effect of suppressing an increase in ESR and a decrease in capacitance even in a high temperature environment. For example, the first conductive polymer may be the following: Shown by chemical formula It may contain the constitutional units Shown by chemical formula It may be made up of structural units.

[0020] [ka]

[0021] In the above formula, R represents an organic chain. R may be composed of a hydrocarbon chain, or may contain, in addition to the hydrocarbon chain, an ether bond, a branched alkyl group, or other substituents. In the above formula, the sulfonic acid group may be converted into a salt. Examples of R include (skeleton side) -CH 2 -O-(CH 2 ) 2 -(CHCH 3 )- (sulfonic acid group side) and the like.

[0022] Alternatively, the first conductive polymer may be a polyaniline having an atomic group containing a sulfonic acid group introduced therein, for example, polyaniline sulfonic acid.

[0023] The weight average molecular weight of the first conductive polymer may be in the range of 1,000 to 100,000, or in the range of 1,000 to 30,000.

[0024] (Second conductive polymer) The second conductive polymer is a polymer whose conductivity is improved by doping with a dopant. Examples of the second conductive polymer include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, and derivatives thereof. The derivatives include polymers having polypyrrole, polythiophene, polyfuran, polyaniline, and polyacetylene as a basic skeleton. For example, derivatives of polythiophene include poly(3,4-ethylenedioxythiophene). The second conductive polymer may be used alone or in combination of two or more types. The second conductive polymer may be a copolymer of two or more types of monomers. The weight-average molecular weight of the second conductive polymer is not particularly limited, and may be in the range of 1,000 to 100,000, for example. A preferred example of the second conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0025] Unlike the first conductive polymer, in the second conductive polymer, the functional group functioning as a dopant is not covalently bonded to the backbone of the conductive polymer. The second conductive polymer is doped with a dopant. In order to suppress dedoping from the second conductive polymer, As the dopant, it is preferable to use a polymer dopant. Examples of the polymer dopant include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacryl sulfonic acid, polymethacryl sulfonic acid, poly(2-acrylamido-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, etc. These may be used alone or in combination of two or more. These may be included in the electrolyte layer in the form of a salt. A preferred example of the dopant is polystyrene sulfonic acid (PSS).

[0026] The weight-average molecular weight of the dopant is not particularly limited, but may be in the range of 1,000 to 100,000 in order to facilitate the formation of a homogeneous electrolyte layer.

[0027] In the electrolytic capacitor of the present disclosure, the dopant may be polystyrene sulfonic acid, and the second conductive polymer may be poly(3,4-ethylenedioxythiophene). That is, the electrolyte layer may include poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid.

[0028] (Liquid component) The electrolyte layer of the electrolytic capacitor of the present disclosure includes a nonaqueous solvent. The electrolyte layer may include an electrolytic solution (nonaqueous electrolyte solution) including a nonaqueous solvent and a base component dissolved in the nonaqueous solvent. That is, the electrolyte layer of the electrolytic capacitor of the present disclosure may include a liquid component. Hereinafter, the liquid component (nonaqueous solvent or electrolyte solution) included in the electrolyte layer may be referred to as "liquid component (L)". In this specification, the liquid component (L) may be a component that is liquid at room temperature (25°C) or a component that is liquid at the temperature during use of the electrolytic capacitor. An electrolytic capacitor having an electrolyte layer including the liquid component (L) may be called a hybrid capacitor.

[0029] The non-aqueous solvent contained in the electrolyte layer may be an organic solvent or an ionic liquid. Examples of the non-aqueous solvent include polyhydric alcohols such as ethylene glycol and propylene glycol, cyclic sulfones such as sulfolane (SL), lactones such as γ-butyrolactone (γBL), amides such as N-methylacetamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone, esters such as methyl acetate, carbonate compounds such as propylene carbonate, ethers such as 1,4-dioxane, ketones such as methyl ethyl ketone, and formaldehyde.

[0030] Also, a polymer-based solvent may be used as the non-aqueous solvent. Examples of polymer-based solvents include polyalkylene glycol, derivatives of polyalkylene glycol, and compounds in which at least one hydroxyl group in a polyhydric alcohol is substituted with polyalkylene glycol (including derivatives). Specifically, examples of polymer-based solvents include polyethylene glycol (PEG), polyethylene glycol glyceryl ether, polyethylene glycol diglyceryl ether, polyethylene glycol sorbitol ether, polypropylene glycol, polypropylene glycol glyceryl ether, polypropylene glycol diglyceryl ether, polypropylene glycol sorbitol ether, and polybutylene glycol. Examples of polymer-based solvents further include ethylene glycol-propylene glycol copolymers, ethylene glycol-butylene glycol copolymers, and propylene glycol-butylene glycol copolymers. The non-aqueous solvent may be used alone or in combination of two or more.

[0031] As described above, the electrolyte layer may include a non-aqueous solvent and a base component (base) dissolved in the non-aqueous solvent. The electrolyte layer may also include a non-aqueous solvent and a base component and / or an acid component (acid) dissolved in the non-aqueous solvent.

[0032] The acid component can be a polycarboxylic acid or a monocarboxylic acid. Examples of the polycarboxylic acid include aliphatic polycarboxylic acids (saturated polycarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, and 5,6-decanedicarboxylic acid; unsaturated polycarboxylic acids such as maleic acid, fumaric acid, and icosanoic acid), aromatic polycarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, and pyromellitic acid), and alicyclic polycarboxylic acids (cyclohexane-1,2-dicarboxylic acid, cyclohexene-1,2-dicarboxylic acid, and the like).

[0033] Examples of the monocarboxylic acid include aliphatic monocarboxylic acids (having 1 to 30 carbon atoms) ([saturated monocarboxylic acids, such as formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, lauric acid, myristic acid, stearic acid, and behenic acid]; [unsaturated monocarboxylic acids, such as acrylic acid, methacrylic acid, and oleic acid]), aromatic monocarboxylic acids (such as benzoic acid, cinnamic acid, and naphthoic acid), and oxycarboxylic acids (such as salicylic acid, mandelic acid, and resorcylic acid).

[0034] Among these, maleic acid, phthalic acid, benzoic acid, pyromellitic acid, and resorcylic acid are preferably used because they are thermally stable.

[0035] An inorganic acid may be used as the acid component. Representative examples of inorganic acids include phosphoric acid, phosphorous acid, hypophosphorous acid, alkyl phosphate esters, boric acid, borofluoric acid, tetrafluoroboric acid, hexafluorophosphoric acid, benzenesulfonic acid, and naphthalenesulfonic acid. In addition, a composite compound of an organic acid and an inorganic acid may be used as the acid component. Examples of such a composite compound include borodiglycolic acid, borodioxalic acid, and borodisalicylic acid.

[0036] The base component may be a compound having an alkyl-substituted amidine group, such as an imidazole compound, a benzimidazole compound, or an alicyclic amidine compound (pyrimidine compound, imidazoline compound). Specifically, 1,8-diazabicyclo[5,4,0]undecene-7, 1,5-diazabicyclo[4,3,0]nonene-5, 1,2-dimethylimidazolinium, 1,2,4-trimethylimidazoline, 1-methyl-2-ethyl-imidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-heptyl imidazoline, 1-methyl-2-(3'heptyl)imidazoline, 1-methyl-2-dodecyl imidazoline, 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, 1-methylimidazole, or 1-methylbenzimidazole is preferred. By using these, a capacitor with excellent impedance performance can be obtained.

[0037] As the base component, a quaternary salt of a compound having an alkyl-substituted amidine group may be used. Examples of such base components include imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds) quaternized with an alkyl group or arylalkyl group having 1 to 11 carbon atoms. Specifically, 1-methyl-1,8-diazabicyclo[5,4,0]undecene-7, 1-methyl-1,5-diazabicyclo[4,3,0]nonene-5, 1,2,3-trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,2-dimethyl-3-ethyl-imidazolinium, 1,3,4-trimethyl-2-ethylimidazolinium, 1,3-dimethyl-2-heptylimidazolinium, 1,3-dimethyl-2-(3'heptyl)imidazolinium, 1,3-dimethyl-2-dodecylimidazolinium, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidium, 1,3-dimethylimidazolium, 1-methyl-3-ethylimidazolium, and 1,3-dimethylbenzimidazolium are preferred. By using these, a capacitor with excellent impedance performance can be obtained.

[0038] Tertiary amines may also be used as the base component. Examples of tertiary amines include trialkylamines (trimethylamine, dimethylethylamine, methyldiethylamine, triethylamine, dimethyl-n-propylamine, dimethylisopropylamine, methylethyl-n-propylamine, methylethylisopropylamine, diethyl-n-propylamine, diethylisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, tri-tert-butylamine, etc.), and phenyl group-containing amines (dimethylphenylamine, methylethylphenylamine, diethylphenylamine, etc.). Among these, trialkylamines are preferred in terms of increasing the conductivity of the electrolyte layer, and it is more preferred to include at least one selected from the group consisting of trimethylamine, dimethylethylamine, methyldiethylamine, and triethylamine. Secondary amines such as dialkylamines, primary amines such as monoalkylamines, and ammonia may also be used as the base component.

[0039] The liquid component (L) may contain a salt of an acid component and a base component. The salt may be an inorganic salt and / or an organic salt. An organic salt is a salt in which at least one of the anion and the cation contains an organic substance. As the organic salt, for example, trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolinium phthalate, mono-1,3-dimethyl-2-ethylimidazolinium phthalate, etc. may be used.

[0040] In order to suppress dedoping of the dopant, the pH of the liquid component (L) may be less than 7, or may be 5 or less (for example, in the range of 2 to 5).

[0041] It is important for electrolytic capacitors to have a low ESR. A low ESR can be achieved by using an electrolyte layer containing a conductive polymer doped with a dopant. However, the inventors of the present application have found that when an electrolyte layer containing a conductive polymer doped with a dopant and a liquid component (L) is used, the initial ESR is low, but the degradation phenomenon in which the ESR increases over time is large. When the cause of this is examined, it is found that the dopant may be easily de-doped in an electrolyte layer containing a liquid component (L). It is believed that this de-doping causes the ESR to increase over time. Therefore, it is important to suppress the increase in ESR over time in an electrolytic capacitor containing a liquid component (L) compared to a solid electrolytic capacitor containing a solid electrolyte that does not contain a liquid component (L).

[0042] Since the self-doping first conductive polymer is unlikely to be dedoped, its conductivity does not deteriorate much over time, and therefore, by including the first conductive polymer in the electrolyte layer, it is possible to suppress the increase in ESR over time.

[0043] In the electrolytic capacitor of the present disclosure, the dopant may be a dopant containing an acidic group, or a polymer dopant containing an acidic group. Through investigation, the present inventors have newly found that when a dopant containing an acidic group is used, dedoping may occur significantly with an increase in pH. Therefore, when a dopant containing an acidic group is used, it is particularly important to suppress the increase in ESR over time.

[0044] In the electrolytic capacitor of the present disclosure using the second conductive polymer, the dopant may be a polymer dopant containing an acidic group, and the electrolyte layer may contain an electrolyte solution containing a non-aqueous solvent and a base component dissolved in the non-aqueous solvent. In this case, since de-dopantization is likely to occur due to the base component, it is particularly important to suppress the increase in ESR over time. As described above, since the electrolytic capacitor of the present disclosure contains a self-doping type first conductive polymer, the increase in ESR over time can be suppressed.

[0045] Examples of the base component include the above-mentioned base components. Examples of the acidic group include a sulfonic acid group, a carboxyl group, and the like. The polymer dopant containing an acidic group is a polymer in which at least a part of the constituent units contains an acidic group. Examples of such a polymer dopant include the above-mentioned polymer dopant.

[0046] In the electrolytic capacitor of the present disclosure, the amount of the base component in the electrolytic solution may be 0.1% by mass or more and 20% by mass or less. When the amount of the base component is 0.1% by mass or more, it is particularly important to use a self-doping first conductive polymer. In addition, by setting the amount of the base component to 20% by mass or less, it becomes easy to dissolve the base component in the electrolytic solution.

[0047] The content of the liquid component (L) in the electrolyte layer is in the range of 60 to 99 mass % (for example, 70 to 95 mass %). %of range ) The content of the first conductive polymer in the solid content of the electrolyte layer may be in the range of 1 to 100 mass % (for example, 1 to 45 mass %). %of range ) The total content of the second conductive polymer and the dopant in the solid content of the electrolyte layer may be in the range of 1 to 99 mass % (for example, 55 to 99 mass %). %of range ) In the electrolyte layer, the relationship of (mass of the first conductive polymer):(total mass of the second conductive polymer and the dopant)=10:90 to 45:55 may be satisfied.

[0048] In the electrolytic capacitor of the present disclosure, the total mass of the second conductive polymer and the dopant contained in the electrolyte layer may be greater than the mass of the first conductive polymer contained in the electrolyte layer. That is, the total content rate (mass %) of the second conductive polymer and the dopant in the electrolyte layer may be greater than the content rate (mass %) of the first conductive polymer in the electrolyte layer. The conductive polymer doped with the dopant generally has higher conductivity than the self-doped conductive polymer. Therefore, increasing the content rate of the second conductive polymer doped with the dopant is effective for reducing the initial ESR.

[0049] The mass W1 (g) of the first conductive polymer contained in the electrolyte layer and the total mass W2 (g) of the second conductive polymer and the dopant contained in the electrolyte layer may satisfy the relationship of 1 < W2 / W1, or may satisfy the relationship of 1.1 ≦ W2 / W1 ≦ 9.

[0050] The electrolytic capacitor of the present disclosure may satisfy the following condition (1). (1) The electrolyte layer includes a polymer layer (conductive polymer layer) composed of a first conductive polymer and a second conductive polymer doped with a dopant, and the polymer layer includes a first polymer layer formed on the dielectric layer on the surface of the anode body and a second polymer layer formed on the first polymer layer.

[0051] The conductive polymer contained in the first polymer layer and the conductive polymer contained in the second polymer layer may be the same or different. When both the first and second polymer layers contain the second conductive polymer, the dopant contained in the first polymer layer and the dopant contained in the second polymer layer may be the same or different.

[0052] In one example, the first polymer layer is composed of a second conductive polymer doped with a dopant, and the second polymer layer is composed of the first conductive polymer. In another example, the first polymer layer is composed of the first conductive polymer, and the second polymer layer is composed of a second conductive polymer doped with a dopant.

[0053] The electrolytic capacitor of the present disclosure may satisfy the above (1) and the following (2) conditions. (2) The content rate (mass %) of the second conductive polymer in the first polymer layer is larger than the content rate (mass %) of the second conductive polymer in the second polymer layer. In addition, in this item (2), the "content rate (mass %) of the second conductive polymer" may be replaced with the "total content rate (mass %) of the second conductive polymer and the dopant".

[0054] The condition of the above (2) may be replaced with the condition that (2') the content rate (mass %) of the first conductive polymer in the first polymer layer is smaller than the content rate (mass %) of the first conductive polymer in the second polymer layer. According to the configuration of the above (2), the ratio of the second conductive polymer in the portion close to the dielectric layer on the surface of the anode body can be increased. As a result, it is possible to lower the initial ESR.

[0055] The electrolytic capacitor of the present disclosure may satisfy the following conditions (A) and (B), and may further satisfy the requirement of (C). (A) The first conductive polymer is poly(3,4-ethylenedioxythiophene) into which a sulfonic acid group is introduced, for example, the polymer described above. (B) The second conductive polymer is poly(3,4-ethylenedioxythiophene), and the dopant doped into the second conductive polymer is polystyrene sulfonic acid. (C) The mass W1 (g) of the first conductive polymer contained in the electrolyte layer and the total mass W2 (g) of the second conductive polymer and the dopant contained in the electrolyte layer satisfy the relationship of 1 < W2 / W1, for example, satisfy the relationship of 1.1 ≦ W2 / W1 ≦ 9.

[0056] There are no particular limitations on the components (anode body, cathode body, separator, etc.) of the capacitor element other than the electrolyte, and known ones may be used. Examples of those of the first capacitor element will be described below.

[0057] (Anode body) The anode body may be a metal foil having a dielectric layer formed on its surface. The type of metal constituting the metal foil is not particularly limited. In terms of ease of forming the dielectric layer, examples of metals constituting the metal foil include valve metals such as aluminum, tantalum, niobium, and titanium, and alloys of valve metals. A preferred example is aluminum and an aluminum alloy. Usually, the surface of the anode body is roughened (porous). The dielectric layer of the anode body is formed on the porous portion (roughened surface). The electrolyte layer is in contact with the dielectric layer of the anode body.

[0058] (cathode body) A metal foil may be used for the cathode body. The type of metal constituting the metal foil is not particularly limited. Examples of metals constituting the metal foil include valve metals such as aluminum, tantalum, niobium, and titanium, and alloys of valve metals. A preferred example is aluminum and an aluminum alloy. A chemical conversion film may be provided on the surface of the cathode body, and a coating of a metal (heterogeneous metal) different from the metal constituting the cathode body or a nonmetal may be provided. Examples of the heterogeneous metal and nonmetal include metals such as titanium and nonmetals such as carbon.

[0059] (Separator) The separator may be a sheet-like material that can be impregnated with an electrolyte, for example, a sheet-like material that has insulating properties and can be impregnated with an electrolyte. The separator may be a woven fabric, a nonwoven fabric, or a porous membrane. Examples of the separator material include cellulose, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, vinylon, nylon, aromatic polyamide, polyimide, polyamideimide, polyetherimide, rayon, and glass.

[0060] The components of the second capacitor element other than the electrolyte layer will be described below by way of example. The capacitor element includes a porous anode body having a dielectric layer on a surface thereof, a cathode layer, and an electrolyte layer disposed between the anode body and the cathode layer.

[0061] The porous anode body may be, for example, a porous sintered body obtained by sintering material particles containing a valve metal. The anode body may be in the shape of a rectangular parallelepiped. Examples of the valve metal include titanium (Ti), tantalum (Ta), and niobium (Nb). The material particles may be made of an alloy containing a valve metal. For example, an alloy containing a valve metal and silicon, vanadium, boron, or the like may be used. The valve metal alloy contains a valve metal as a main component, for example, 50 atomic % or more of the valve metal. Also, material particles made of a compound containing a valve metal and a typical element such as nitrogen may be used. One type of material particle may be used alone, or two or more types may be mixed and used.

[0062] The anode body of the second capacitor element is porous, and has a porous portion on its surface, and the dielectric layer is formed in the porous portion. The electrolyte layer is in contact with the dielectric layer of the anode body. The dielectric layer is formed, for example, by subjecting the sintered body that will become the anode body to a chemical conversion treatment and growing an oxide film on the surface of the sintered body.

[0063] The cathode layer has a current collecting function. The cathode layer is formed, for example, of a conductive material. The cathode layer may be a conductive layer formed to cover the electrolyte layer. The cathode layer may include a carbon layer formed to cover the electrolyte layer, and a metal paste layer formed on the carbon layer. The carbon layer may include a conductive carbon material such as graphite and a resin. The metal paste layer may include metal particles (for example, silver particles) and a resin. The cathode layer can be formed by applying the above-mentioned materials, or the like.

[0064] (Method of manufacturing electrolytic capacitor) The method of the present disclosure for manufacturing an electrolytic capacitor is described below. According to this manufacturing method, the electrolytic capacitor of the present disclosure can be manufactured. Note that the matters described for the electrolytic capacitor of the present disclosure can be applied to the manufacturing method below, and therefore duplicated descriptions may be omitted. For example, the components of the capacitor element have been described above, and therefore duplicated descriptions may be omitted. Also, the matters described in the manufacturing method below can be applied to the electrolytic capacitor described above.

[0065] The manufacturing method according to the present disclosure includes steps (i), (ii), and (iii). These are explained below.

[0066] (Step (i)) Step (i) is a step of preparing a capacitor element precursor including an anode body having a dielectric layer on a surface thereof. About The step (i) may be a step of forming a capacitor element precursor by a known method.

[0067] When manufacturing an electrolytic capacitor including a first capacitor element, step (i) may be a step of forming a capacitor element precursor including a foil-shaped anode body having a dielectric layer on its surface, a foil-shaped cathode body, and a separator disposed between the anode body and the cathode body. In this case, as described above, the capacitor element precursor may be of a wound type or a laminated type. When manufacturing an electrolytic capacitor including a second capacitor element, the capacitor element precursor may be composed of an anode body (porous anode body) having a dielectric layer on its surface, and an anode wire partly embedded in the anode body.

[0068] (Step (ii)) In step (ii), a polymer layer containing a self-doping first conductive polymer is formed by impregnation. The step of forming the insulating film adjacent to the dielectric layer.

[0069] The polymer layer formed in step (ii) may include a first conductive polymer and a second conductive polymer doped with a dopant. That is, step (ii) may be a step of forming a polymer layer including the first conductive polymer and the second conductive polymer doped with a dopant by an impregnation treatment so as to be adjacent to the dielectric layer.

[0070] The impregnation treatment in step (ii) may be an impregnation treatment (x) in which a liquid (dispersion liquid or solution; the same applies below) containing a first conductive polymer and a second conductive polymer doped with a dopant is impregnated into the capacitor element precursor. For example, the liquid can be impregnated by immersing the capacitor element precursor in the liquid. By removing (drying) the dispersion medium or solvent of the liquid impregnated into the capacitor element precursor, a polymer layer containing the first conductive polymer and the second conductive polymer doped with a dopant can be disposed adjacent to the dielectric layer. The impregnation treatment (x) may be performed multiple times. In this case, a drying step for removing the dispersion medium or solvent of the impregnated liquid may be performed before the second or subsequent impregnation treatments (x).

[0071] The liquid dispersion medium or solvent is not particularly limited, and any known dispersion medium or solvent may be used. For example, an aqueous liquid containing water may be used as the dispersion medium or solvent, or water may be used.

[0072] By adjusting the mass (content) of the first conductive polymer and the mass (content) of the second conductive polymer (and dopant) in the liquid, it is possible to adjust their ratio in the formed electrolyte layer. For example, by making the mass (content) of the second conductive polymer (and dopant) in the liquid larger than the mass (content) of the first conductive polymer in the liquid, it is possible to make the mass of the second conductive polymer (and dopant) contained in the electrolyte layer larger than the mass of the first conductive polymer contained in the electrolyte layer.

[0073] The impregnation treatment in step (ii) may include an impregnation treatment (y) in which a first liquid containing a first conductive polymer is impregnated into the capacitor element precursor, and an impregnation treatment (z) in which a second liquid containing a second conductive polymer doped with a dopant is impregnated into the capacitor element precursor. The impregnation treatment (y) and the impregnation treatment (z) may be performed first, the impregnation treatment (y) may be performed first, or the impregnation treatment (z) may be performed simultaneously. In a preferred example, the impregnation treatment (y) is performed after the impregnation treatment (z). The impregnation treatment (y) and the impregnation treatment (z) may each be performed multiple times independently. In addition, a drying step for removing the dispersion medium (or solvent) of the impregnated liquid may be performed after each of the impregnation treatments (y) and (z).

[0074] As for the dispersion medium (or solvent) of the first and second liquids and the impregnation method in the impregnation treatment (y) and the impregnation treatment (z), the dispersion medium (or solvent) and the impregnation method described in the impregnation treatment (x) may be applied.

[0075] In one example, the first liquid does not include a second conductive polymer doped with a dopant and the second liquid does not include the first conductive polymer, but the first liquid may include a second conductive polymer doped with a dopant and the second liquid may include the first conductive polymer.

[0076] Either the impregnation treatment (y) or the impregnation treatment (z) may be followed by drying, and then the other impregnation treatment may be carried out. In this manner, a polymer layer including a first polymer layer and a second polymer layer can be formed. In addition, the type and content of the conductive polymer (and dopant) in the first liquid and the conductive polymer (and By adjusting the type and content of the conductive polymer (and dopant) in the first polymer layer, it is possible to adjust the type and content of the conductive polymer (and dopant) in the second polymer layer.

[0077] (Step (iii)) Step (iii) is a step of impregnating the polymer layer formed in step (ii) with a non-aqueous solvent. In this way, an electrolyte layer containing a self-doping first conductive polymer and a non-aqueous solvent is formed. In step (iii), an electrolyte solution (containing a non-aqueous solvent) is added to the polymer layer formed in step (ii). That is, the step (iii) may be a step of impregnating the cellulose acylate formed in the step (ii) with the cellulose acylate. It may be a step of impregnating the polymer layer with a liquid component (L).

[0078] When the polymer layer formed in step (ii) includes a second conductive polymer doped with a dopant, a self-doped first conductive polymer and a dopant-doped second conductive polymer are formed in step (iii). An electrolyte layer is formed that includes the doped second conductive polymer and a non-aqueous solvent.

[0079] The method of impregnation in step (iii) is not particularly limited, and any known method may be used. For example, the capacitor element precursor that has been subjected to the step (ii) may be immersed in a non-aqueous solvent (or an electrolytic solution). The non-aqueous solvent (or an electrolytic solution) used in the step (iii) may be any of those mentioned above. Cut.

[0080] In the manufacturing method of the present disclosure, the dopant may be a polymer dopant containing an acidic group, and the step (iii) is a step of subjecting an electrolyte solution containing a non-aqueous solvent and a base component dissolved in the non-aqueous solvent to high temperature. It may be a step of impregnating a molecular layer.

[0081] Step (iii) provides a first capacitor element. Alternatively, step (iii) provides an anode body and an electrolyte layer of a second capacitor element. The components obtained in step (iii) may be used to fabricate an electrolytic capacitor. There is no limitation on the method, and any known method can be used.

[0082] In the following, an example of the electrolytic capacitor according to the present disclosure will be specifically described with reference to the drawings, but the electrolytic capacitor of the present disclosure is not limited to the following drawings. The above-mentioned components can be applied to the components of the example electrolytic capacitor described below. In addition, the components of the example electrolytic capacitor described below can be modified based on the above description. In addition, the matters described below may be applied to the above embodiment. Note that the same reference numerals may be used for similar parts, and duplicated descriptions may be omitted.

[0083] (Embodiment 1) In embodiment 1, an example of an electrolytic capacitor according to the present disclosure will be described. This electrolytic capacitor is an electrolytic capacitor including a first capacitor element. Fig. 1 shows a schematic cross-section of an example of an electrolytic capacitor 100 of embodiment 1. Fig. 2 shows a schematic view in which a part of a capacitor element 10 included in the electrolytic capacitor 100 shown in Fig. 1 is developed.

[0084] 1, electrolytic capacitor 100 includes capacitor element 10, bottomed case 11 that houses capacitor element 10, sealing member 12 that closes the opening of bottomed case 11, seat plate 13 that covers sealing member 12, lead wires 14A and 14B that are led out from sealing member 12 and pass through seat plate 13, and lead tabs 15A and 15B that connect lead wires 14A and 14B to electrodes of capacitor element 10. Capacitor element 10 is housed in bottomed case 11. The vicinity of the open end of bottomed case 11 is drawn inward, and the open end of bottomed case 11 is curled so as to crimp sealing member 12.

[0085] 2, capacitor element 10 includes a foil-shaped anode body 21 having a dielectric layer on its surface, a foil-shaped cathode body 22, and a separator 23 and an electrolyte layer (not shown) disposed therebetween. Anode body 21 and cathode body 22 are wound with separator 23 disposed therebetween. The outermost periphery of the wound body is fixed by a stop tape 24. Note that FIG. 2 shows a partially unfolded state of the wound body before the outermost periphery is fixed. EXAMPLES

[0086] Hereinafter, the embodiments of the present disclosure will be described in more detail with reference to examples.

[0087] Example 1 In Example 1, a number of electrolytic capacitors (capacitors A1 to A7 and capacitor C1) were fabricated and evaluated. The manufacturing method and evaluation method for these capacitors are described below. In the description of the manufacturing method for the capacitors of the comparative examples, conditions different from the above-mentioned conditions of steps (ii) and (iii) may be used. For convenience, these conditions will also be referred to as steps (ii) and (iii). ) and step (iii).

[0088] [Preparation of capacitor A1] Capacitor A1 is a wound-type electrolytic capacitor with a rated voltage of 35 V and a rated capacitance of 270 μF. Capacitor A1 was produced by the following procedure.

[0089] (Preparation of the cathode body) For the cathode body, an Al foil (aluminum foil) having a thickness of 70 μm was used.

[0090] (Preparation of anode body) An Al foil having a thickness of 120 μm was prepared. This Al foil was subjected to a DC etching treatment to roughen the surface. Next, the Al foil was subjected to a chemical conversion treatment to form a dielectric layer (thickness: about 70 nm) to obtain an anode body. The dielectric layer was formed by immersing the Al foil in an ammonium adipate solution and performing a chemical conversion treatment at 70° C. for 30 minutes while applying a voltage of 50 V to the Al foil. The anode body was then cut to a predetermined size to prepare an anode body for capacitor A1.

[0091] (Preparation of liquid containing self-doped first conductive polymer) As a liquid containing a self-doping type first conductive polymer, the following aqueous solution was prepared. (Liquid AL containing conductive polymer A) An aqueous solution (liquid AL) containing poly(4-(2,3-dihydrothieno-[3,4-b][1,4]dioxin-2-ylmethoxy)-1-propanesulfonic acid) as the conductive polymer A at a concentration of 5 mass % was prepared. (Liquid BL containing conductive polymer B) As the conductive polymer B, an aqueous solution (liquid BL) containing N-position-substituted sulfonated polyaniline at a concentration of 5 mass % was prepared.

[0092] (Preparation of PEDOT:PSS dispersion) A dispersion of a second conductive polymer doped with a dopant was prepared by the following method. A mixed solution of 3,4-ethylenedioxythiophene and polystyrene sulfonic acid as a dopant was prepared by dissolving them in ion-exchanged water. While stirring the resulting mixed solution, iron (III) sulfate (oxidizing agent) dissolved in ion-exchanged water was added to cause a polymerization reaction. After the reaction, the resulting reaction solution was dialyzed to remove unreacted monomers and excess oxidizing agent, and a dispersion containing poly(3,4-ethylenedioxythiophene) doped with about 5% by mass of polystyrene sulfonic acid (PSS) was obtained. In the following, poly(3,4-ethylenedioxythiophene) doped with about 5% by mass of polystyrene sulfonic acid (PSS) was This may be referred to as "PEDOT:PSS". The dispersion in which PEDOT:PSS is dispersed may be referred to as "PEDOT:PSS dispersion". In this way, a PEDOT:PSS dispersion with a PEDOT:PSS content of 2 mass% was prepared.

[0093] (Preparation of wound body (step (i))) An anode lead tab and a cathode lead tab connected to a lead wire were connected to the prepared anode body and cathode body, respectively. The anode body and the cathode body were then wound with a separator sandwiched therebetween, and the outer surface was fixed with a winding stop tape. A nonwoven fabric made of cellulose was used as the separator. In this manner, a wound body (capacitor element precursor) was produced. The wound body produced was immersed in an ammonium adipate solution, and a chemical conversion treatment was performed again at 70°C for 60 minutes while a voltage of 50 V was applied to the anode body, thereby forming a dielectric layer mainly on the end surface of the anode body.

[0094] (Step (ii)) First, liquid AL containing the above-mentioned self-doped conductive polymer A was placed in a container. Next, the wound body was immersed in the liquid AL in the container for 15 minutes at room temperature in a reduced pressure atmosphere (40 kPa), and then the wound body was pulled out of the liquid AL. In this way, the wound body was impregnated with the liquid AL. Next, the wound body was dried in a drying furnace at 60°C for 30 minutes, and then dried at 150°C for 15 minutes. This allowed the liquid AL to dry. In this way, a polymer layer (conductive polymer layer) was formed.

[0095] (Electrolyte Impregnation) The wound body that had been subjected to step (iii) was impregnated with an electrolyte at room temperature and atmospheric pressure. A solution of polyethylene glycol, γ-butyrolactone, sulfolane, and mono(ethyldimethylamine) phthalate (solute) mixed in a mass ratio of polyethylene glycol:γ-butyrolactone:sulfolane:mono(ethyldimethylamine) phthalate = 30:30:20:20 was used. In this way, a capacitor element including an electrolyte layer was obtained. This capacitor element was sealed to complete an electrolytic capacitor. Thereafter, an aging treatment was performed at 130°C for 2 hours while applying the rated voltage. In this way, a capacitor A1 was obtained.

[0096] [Making capacitors A2 to A7] Capacitors A2 to A7 were produced using the same materials and conditions as capacitor A1, except that the liquid used in step (ii) was different. In producing capacitors A2 to A7, a mixture of liquid AL containing the above-mentioned self-doping conductive polymer A and the above-mentioned PEDOT:PSS dispersion was used as the liquid used in step (ii). Capacitors A2 to A7 were produced by changing the ratio of the mass of the self-doping conductive polymer contained in the mixture (dispersion) to the mass of PEDOT:PSS. This mass ratio corresponds directly to the mass ratio of the self-doping conductive polymer to PEDOT:PSS in the electrolyte layer to be formed.

[0097] [Creating capacitor C1] Capacitor C1 was fabricated using the same materials and conditions as capacitor A1, except that the liquid used in step (ii) was different. In fabricating capacitor C1, the above-mentioned PEDOT:PSS dispersion was used as the liquid used in step (ii). Therefore, the electrolyte layer of capacitor C1 contained PEDOT:PSS but did not contain a self-doped conductive polymer.

[0098] [Fabrication of capacitors B1 to B7] Capacitors B1 to B7 were fabricated using the same materials and under the same conditions as Capacitors A1 to A7, except that the liquid used in step (ii) was different. In fabricating Capacitors B1 to B7, Liquid BL was used instead of Liquid AL.

[0099] (ESR measurement) The equivalent series resistance (ESR) of the electrolytic capacitors fabricated as described above was measured. The ESR was measured using a four-terminal LCR meter in an environment of 20°C. The ESR was measured at the initial value after fabrication and after leaving the electrolytic capacitors at high temperature (165°C for 500 hours). The long-term characteristic evaluation value F was calculated as an index of long-term characteristics using the following formula. Long-term characteristic evaluation value F = (ESR value after exposure to high temperature) / (initial ESR value)

[0100] The ratio of the mass of the self-doped conductive polymer to the mass of PEDOT:PSS in the electrolyte layer of the above electrolytic capacitor is shown in Tables 1 and 2. The evaluation results of the ESR of the above electrolytic capacitor are also shown in Tables 1 and 2.

[0101] [Table 1]

[0102] [Table 2]

[0103] As shown in Tables 1 and 2, capacitors A1 to A7 and B1 to B7 of the present disclosure had small evaluation value F. That is, in these capacitors, the rate of increase in ESR due to long-term exposure to high temperature was small. When the ratio of (mass of first conductive polymer):(total mass of second conductive polymer and dopant) in the electrolyte layer was 10:90 to 45:55, the ESR was low both initially and after exposure to high temperature.

[0104] Example 2 In Example 2, a number of electrolytic capacitors (capacitors A8 and A9) were fabricated and evaluated. The manufacturing method and evaluation method for these capacitors are described below.

[0105] [Capacitor A8] Capacitor A8 was produced using the same materials and conditions as capacitor A1, except for step (ii). In step (ii) of capacitor A8, the impregnation treatment (z) described above was performed, followed by the impregnation treatment (y) described above. Step (ii) of capacitor A8 will be described below.

[0106] (Impregnation process (z) and drying process) Specifically, first, the above-mentioned dispersion liquid of PEDOT:PSS was placed in a container. Next, the wound body formed in step (i) was immersed in the dispersion liquid in the container for 5 minutes at room temperature in a reduced pressure atmosphere (40 kPa), and then the wound body was pulled out of the dispersion liquid. In this way, the wound body was impregnated with the dispersion liquid. Next, the wound body was dried at 60°C for 30 minutes in a drying oven, and then dried at 155°C for 15 minutes. This allowed the dispersion liquid to dry. In this way, a first polymer layer composed of PEDOT:PSS was formed.

[0107] (Impregnation process (y) and drying process) Next, impregnation with Liquid AL and drying were carried out under the same conditions as for the formation of the first polymer layer, except that Liquid AL containing the above-mentioned self-doped conductive polymer A was used instead of the PEDOT:PSS dispersion liquid. In this way, a second polymer layer composed of the self-doped conductive polymer A was formed.

[0108] In this manner, the step (ii) was carried out. By the step (ii), the first polymer layer (PEDOT:PSS layer) formed on the dielectric layer of the anode body and the second polymer layer (self-doped conductive polymer layer) formed on the first polymer layer were An electrolyte layer containing Formed.

[0109] [Capacitor A9] Capacitor A9 was produced using the same materials and under the same conditions as Capacitor A8, except that the order of impregnation treatment (z) and impregnation treatment (y) was reversed. That is, in step (ii) of Capacitor A9, impregnation treatment (y) was performed before impregnation treatment (z). The drying step was carried out under the same conditions as the drying step of Capacitor A8.

[0110] In the above manner, the step (ii) was carried out. By the step (ii), the first polymer layer (self-doped conductive polymer layer) formed on the dielectric layer of the anode body and the second polymer layer (PEDOT:PSS layer ) was formed.

[0111] The ESR of the electrolytic capacitor thus fabricated was measured under the same conditions as those for electrolytic capacitor A1. The evaluation results are shown in Table 3.

[0112] [Table 3]

[0113] As shown in Table 3, both capacitors A8 and A9 had low ESR and evaluation value F. Comparing capacitors A8 and A9, capacitor A9 had a lower evaluation value F. was low. [Industrial Applicability]

[0114] The present disclosure can be used for an electrolytic capacitor and a manufacturing method thereof. [Explanation of symbols]

[0115] 10 Capacitor element 21 Anode body 22 Cathode body 23 Separator 100 Electrolytic capacitor

Claims

1. 1. An electrolytic capacitor including a capacitor element, the capacitor element includes an anode body having a dielectric layer on a surface thereof, and an electrolyte layer disposed adjacent to the dielectric layer; the electrolyte layer includes a first conductive polymer of a self-doping type, a second conductive polymer doped with a polymer dopant containing an acidic group, and a non-aqueous solvent; the polymer dopant is polystyrene sulfonic acid; the second conductive polymer is poly(3,4-ethylenedioxythiophene); an electrolytic capacitor, wherein a ratio of a total mass of the second conductive polymer and the polymer dopant to a total mass of the second conductive polymer and the polymer dopant contained in the electrolyte layer and a mass of the first conductive polymer is 55% or more and 90% or less.

2. An electrolytic capacitor as described in claim 1, wherein the proportion of the sum of the mass of the second conductive polymer and the mass of the polymer dopant to the sum of the mass of the second conductive polymer and the mass of the polymer dopant contained in the electrolyte layer and the mass of the first conductive polymer is 80% or less.

3. 3. The electrolytic capacitor according to claim 1, wherein the electrolyte layer contains an electrolyte solution containing the non-aqueous solvent and a base component dissolved in the non-aqueous solvent.

4. the electrolyte layer includes a polymer layer constituted by the first conductive polymer and the second conductive polymer doped with the polymer dopant; the polymer layer includes a first polymer layer formed on the dielectric layer and a second polymer layer formed on the first polymer layer; the first polymer layer includes the first conductive polymer, 4. The electrolytic capacitor according to claim 1, wherein the second polymer layer includes the second conductive polymer doped with the polymer dopant.

5. An electrolytic capacitor described in any one of claims 1 to 4, wherein the capacitor element is formed by winding a foil-shaped anode body and a foil-shaped cathode body with a separator sandwiched between them.

6. A method for manufacturing an electrolytic capacitor, comprising the steps of: (i) preparing a capacitor element precursor including an anode body having a dielectric layer on a surface thereof; (ii) forming a polymer layer comprising a self-doped first conductive polymer and a second conductive polymer doped with a polymer dopant containing an acidic group by an impregnation process so as to be adjacent to the dielectric layer; (iii) impregnating the polymer layer with a non-aqueous solvent; the polymer dopant is polystyrene sulfonic acid; the second conductive polymer is poly(3,4-ethylenedioxythiophene); a ratio of a total mass of the second conductive polymer and the polymer dopant to a total mass of the second conductive polymer and the polymer dopant contained in the polymer layer and a mass of the first conductive polymer is 55% or more and 90% or less.

7. The manufacturing method described in claim 6, wherein the ratio of the sum of the mass of the second conductive polymer and the mass of the polymer dopant to the sum of the mass of the second conductive polymer and the mass of the polymer dopant contained in the polymer layer and the mass of the first conductive polymer is 80% or less.

8. The manufacturing method described in claim 6 or 7, wherein the step (ii) includes a step (x) of impregnating the capacitor element precursor with a solution or dispersion in which both the first conductive polymer and the second conductive polymer doped with the polymer dopant are dissolved or dispersed in a solvent or dispersion medium, and then removing at least a portion of the solvent or dispersion medium.

9. The step (ii) a step (y) of impregnating the capacitor element precursor with a solution or dispersion in which the first conductive polymer is dissolved or dispersed in a solvent or dispersion medium, and then removing at least a part of the solvent or dispersion medium; and (z) a step of impregnating the capacitor element precursor with a solution or dispersion in which the second conductive polymer doped with the polymer dopant is dissolved or dispersed in a solvent or dispersion medium, and then removing at least a part of the solvent or dispersion medium.

10. The manufacturing method described in claim 9, wherein the step (z) is performed after the step (y).

11. The manufacturing method described in any one of claims 6 to 10, wherein the step (iii) is a step of impregnating the polymer layer with an electrolyte solution containing the non-aqueous solvent and a base component dissolved in the non-aqueous solvent.

12. A manufacturing method described in any one of claims 6 to 11, wherein the capacitor element precursor is formed by winding a foil-shaped anode body and a foil-shaped cathode body with a separator sandwiched between them.

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