JP2023029570A - Electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic capacitor with high reliability.

SOLUTION: The electrolytic capacitor includes; a capacitor element including an anode body formed with a dielectric layer; a conductive polymer covering at least a portion of the surface of the dielectric layer; and an electrolyte containing a non-aqueous solvent, a glycerin compound, and an ionic solute. The non-aqueous solvent is at least one selected from the group consisting of lactones, glycols, cyclic carbonates, and sulfones. The content of the glycerin compound in the electrolytic solution is 5% by mass or more and 50% by mass or less.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention relates to electrolytic capacitors, and more particularly to electrolytic capacitors with high reliability.

With the digitization of electronic equipment, there is a growing demand for capacitors used therein to be small, large in capacity, and low in equivalent series resistance (ESR) in the high frequency region.

Electrolytic capacitors using conductive polymers such as polypyrrole, polythiophene, polyfuran, and polyaniline as cathode materials are promising as small-sized, large-capacity, and low-ESR capacitors. For example, an electrolytic capacitor has been proposed in which a conductive polymer layer is provided as a cathode material on an anode foil (anode body) on which a dielectric layer is formed.

In Patent Document 1, an element provided with a separator is impregnated with a conductive polymer dispersion to form a conductive solid layer, and then impregnated with an electrolytic solution to provide a conductive solid layer and an electrolytic solution. Methods have been proposed for manufacturing electrolytic capacitors.

JP 2008-010657 A

In recent years, electrolytic capacitors have been used not only in electronic equipment but also in automotive electrical equipment. In particular, since electrolytic capacitors used in automobile electrical equipment are used for a long period of time in a high-temperature environment, electrolytic capacitors are required to have higher reliability over a longer period of time than ever before. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electrolytic capacitor having higher reliability.

One aspect of the present invention provides a capacitor element comprising an anode body having a dielectric layer formed thereon;
a conductive polymer covering at least a portion of the surface of the dielectric layer;
an electrolytic solution comprising a non-aqueous solvent, a glycerin compound and an ionic solute;
The non-aqueous solvent is at least one selected from the group consisting of lactones, glycols, cyclic carbonates, and sulfones,
It relates to the electrolytic capacitor, wherein the content of the glycerin compound in the electrolytic solution is 10% by mass or more and 50% by mass or less.

According to the present invention, an electrolytic capacitor having high reliability can be obtained.

1 is a schematic cross-sectional view of an electrolytic capacitor according to one embodiment of the present invention; FIG. 2 is a schematic diagram for explaining the configuration of a capacitor element in the electrolytic capacitor of FIG. 1; FIG.

EMBODIMENT OF THE INVENTION Below, embodiment of the electrolytic capacitor of this invention is described, referring drawings suitably. However, the following embodiments do not limit the present invention.

≪Electrolytic Capacitor≫
FIG. 1 is a schematic cross-sectional view of an electrolytic capacitor according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing a part of a capacitor element included in the same electrolytic capacitor.

In FIG. 1, an electrolytic capacitor comprises a capacitor element 10 comprising an anode body 21 having a dielectric layer formed thereon, and a conductive high-electrolyte layer covering (or adhering to) at least part of the surface of the dielectric layer. It contains a molecule (not shown) and an electrolyte (not shown). Capacitor element 10 is housed in an exterior case together with an electrolytic solution in a state in which at least a portion of the surface of the dielectric layer is covered with a conductive polymer. The outer case includes a bottomed case 11 that accommodates the capacitor element 10 therein, an insulating sealing member 12 that closes the opening of the bottomed case 11 , and a seat plate 13 that covers the sealing member 12 . The vicinity of the open end of the bottomed case 11 is drawn inward, and the open end is curled so as to be crimped to the sealing member 12 .

For example, a capacitor element 10 as shown in FIG. 2 is called a wound body. This capacitor element 10 includes an anode body 21 connected to a lead tab 15A, a cathode body 22 connected to a lead tab 15B, and a separator 23. As shown in FIG. Anode body 21 and cathode body 22 are wound with separator 23 interposed therebetween. The outermost periphery of capacitor element 10 is fixed by winding stop tape 24 . Note that FIG. 2 shows a partially unfolded state before the outermost periphery of the capacitor element 10 is stopped.

Anode body 21 comprises a metal foil whose surface is roughened to have unevenness, and a dielectric layer is formed on the metal foil having unevenness.
In the electrolytic capacitor, the conductive polymer adheres so as to cover at least a part of the surface of the dielectric layer formed on anode body 21 , but is not limited to this case, and the anode body 21 and cathode body 22 can be attached anywhere between For example, the conductive polymer coats at least part of the surface of the dielectric layer formed on anode body 21, and furthermore, at least part of the surface of cathode body 22 and/or at least part of the surface of separator 23. part may be covered. In electrolytic capacitors, a conductive polymer layer (specifically, a film containing a conductive polymer) that covers at least a portion of the surfaces of the anode body, cathode body, separator, and the like is generally formed into a conductive polymer layer. It is sometimes called

Below, the configuration of the electrolytic capacitor according to the embodiment of the present invention will be described in more detail.
A capacitor element includes an anode body having a dielectric layer formed thereon. A conductive polymer adhered to the surface of the dielectric layer effectively functions as a cathode material. The capacitor element may optionally further include a cathode body and/or separator.

(capacitor element)
(Anode body)
Examples of the anode body include a metal foil having a roughened surface. The type of metal that constitutes the metal foil is not particularly limited, but it is preferable to use a valve metal such as aluminum, tantalum, or niobium, or an alloy containing a valve metal, because the dielectric layer can be easily formed.

Roughening of the metal foil surface can be performed by a known method. A plurality of irregularities are formed on the surface of the metal foil by roughening. Roughening is preferably performed by etching the metal foil, for example. The etching treatment may be performed by, for example, a DC electrolysis method or an AC electrolysis method.

(dielectric layer)
The dielectric layer is formed on the surface of the anode body (specifically, the surface of the roughened metal foil).
Although the method of forming the dielectric layer is not particularly limited, it can be formed by chemically converting a metal foil. The chemical conversion treatment may be performed, for example, by immersing the metal foil in a chemical conversion solution such as an ammonium adipate solution. In the chemical conversion treatment, if necessary, voltage may be applied while the metal foil is immersed in a chemical conversion solution.

Generally, from the viewpoint of mass production, a metal foil made of a large-sized valve metal or the like is subjected to roughening treatment and chemical conversion treatment. In that case, anode body 21 is prepared by cutting the foil after treatment to the desired size.

(Cathode body)
A metal foil may be used for the cathode body 22 as well as the anode body. Although the type of metal is not particularly limited, it is preferable to use a valve-acting metal such as aluminum, tantalum, or niobium, or an alloy containing a valve-acting metal. If necessary, the surface of the metal foil may be roughened.
Moreover, the surface of the cathode body 22 may be provided with a chemical conversion coating, or may be provided with a coating of a metal (dissimilar metal) different from the metal constituting the cathode body or a non-metal coating. Examples of dissimilar metals and non-metals include metals such as titanium and non-metals such as carbon.

(separator)
As the separator 23, for example, a nonwoven fabric containing fibers of cellulose, polyethylene terephthalate, vinylon, polyamide (for example, aromatic polyamide such as aliphatic polyamide and aramid) may be used.

Capacitor element 10 can be produced by a known method. For example, capacitor element 10 may be produced by stacking anode body 21 and cathode body 22 with separator 23 interposed therebetween. By winding the anode body 21 and the cathode body 22 with the separator 23 interposed therebetween, a wound body as shown in FIG. 2 may be formed. At this time, the lead tabs 15A and 15B may be erected from the wound body as shown in FIG. 2 by winding the lead tabs 15A and 15B.

The material of the lead tabs 15A and 15B is not particularly limited as long as it is a conductive material. The surfaces of the lead tabs 15A and 15B may be chemically treated. Also, the portions of the lead tabs 15A and 15B that come into contact with the sealing member 12 and the portions that connect to the lead wires 14A and 14B may be covered with a resin material.
The material of the lead wires 14A and 14B connected to the lead tabs 15A and 15B, respectively, is also not particularly limited, and a conductive material or the like may be used.

Of the anode body 21 , the cathode body 22 and the separator 23 , the outermost layer of the wound body (cathode body 22 in FIG. 2 ) is fixed with a winding stop tape 24 at the end of the outer surface. In the case where anode body 21 is prepared by cutting a large-sized metal foil, in order to provide a dielectric layer on the cut surface of anode body 21, the capacitor element in the form of a wound body or the like is further subjected to chemical conversion. processing may be performed.

(Conductive polymer)
Examples of conductive polymers include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylenevinylene, polyacene, and polythiophenevinylene. These may be used alone, may be used in combination of two or more, or may be a copolymer of two or more monomers.

In this specification, polypyrrole, polythiophene, polyfuran, polyaniline and the like mean polymers having polypyrrole, polythiophene, polyfuran, polyaniline and the like as basic skeletons, respectively. Therefore, polypyrrole, polythiophene, polyfuran, polyaniline, etc. may also include their respective derivatives. For example, polythiophenes include poly(3,4-ethylenedioxythiophene) and the like.

The conductive polymer may contain a dopant. Polyanions can be used as dopants. Specific examples of polyanions include polyvinylsulfonic acid, polystyrenesulfonic acid, polyallylsulfonic acid, polyacrylsulfonic acid, polymethacrylsulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprenesulfonic acid, poly Anions such as acrylic acid are included. Among them, polyanions derived from polystyrene sulfonic acid are preferred. These may be used alone or in combination of two or more. Moreover, these may be polymers of a single monomer, or copolymers of two or more monomers.

Although the weight average molecular weight of the polyanion is not particularly limited, it is, for example, 1,000 to 1,000,000. A conductive polymer containing such a polyanion is easily dispersed homogeneously in a liquid solvent and easily adheres uniformly to the surface of the dielectric layer.

The conductive polymer may be attached to at least a portion of the surface of the dielectric layer of the anode body 21 so as to cover the dielectric layer, but is preferably attached to cover as much of the area as possible. When the capacitor element includes a cathode body and/or a separator, the conductive polymer may adhere not only to the surface of the dielectric layer but also to the surface of the cathode body and/or the separator. That is, the conductive polymer may be in contact with the separator and/or the cathode body.

The conductive polymer is obtained by a step of impregnating a capacitor element having an anode body on which a dielectric layer is formed with a first treatment liquid containing a conductive polymer (first step), and, if necessary, a first step. After that, the capacitor element can be adhered through a step (second step) of impregnating the second treatment liquid. A conductive polymer is adhered to the surface of the dielectric layer through the first step or the first and second steps. The method for manufacturing an electrolytic capacitor may include a step (third step) of removing at least part of the solvent component contained in the first treatment liquid after the first step, and removing the first treatment liquid after the second step. and/or a step of removing at least part of the solvent component contained in the second treatment liquid (fourth step).

(i) Step of impregnating the capacitor element (wound body) 10 with the first treatment liquid (first step)
Impregnation of the capacitor element 10 with the first treatment liquid is not particularly limited as long as the first treatment liquid can be applied to at least the anode body (particularly, at least the dielectric layer). Alternatively, the capacitor element may be filled with the first treatment liquid. The impregnation may be performed under atmospheric pressure, but may also be performed under reduced pressure, for example, in an atmosphere of 10 kPa to 100 kPa, preferably 40 kPa to 100 kPa. Impregnation may optionally be performed under ultrasonic vibration. Although the impregnation time depends on the size of the capacitor element 10, it is, for example, 1 second to 5 hours, preferably 1 minute to 30 minutes. Through this step, the first treatment liquid is applied to the capacitor element 10 .

The first treatment liquid may contain a conductive polymer and a liquid solvent. The first treatment liquid may be either a solution of a conductive polymer dissolved in a liquid solvent or a dispersion of a conductive polymer dispersed in a liquid solvent. In a dispersion, the conductive polymer is dispersed in the form of particles in a liquid solvent. As a dispersion, a conductive polymer raw material (for example, a precursor such as a monomer and/or oligomer of a conductive polymer) is polymerized in a liquid solvent in the presence of a dopant to obtain a conductive polymer containing the dopant. You may use the thing obtained by producing|generating the particle|grains of. In addition, as the dispersion liquid, a material obtained by polymerizing a conductive polymer raw material in a liquid solvent to generate conductive polymer particles, or a previously synthesized conductive polymer in a liquid solvent You may use the thing obtained by dispersing the particle|grains of.

The liquid solvent of the first treatment liquid may contain the first solvent, or may contain the first solvent and a solvent other than the first solvent. The liquid solvent contained in the first treatment liquid may contain a plurality of first solvents of different types. The first solvent may account for, for example, 30% by mass or more, preferably 50% by mass or more, more preferably 70% by mass or more of the liquid solvent of the first treatment liquid.

The first solvent is not particularly limited, and may be water or a non-aqueous solvent. The non-aqueous solvent is a general term for liquids other than water and liquids containing water, and includes organic solvents and ionic liquids. Among them, the first solvent is preferably a polar solvent. A polar solvent may be a protic solvent or an aprotic solvent.

Examples of protic solvents include alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol (EG), propylene glycol, polyethylene glycol, diethylene glycol monobutyl ether, glycerin, 1-propanol, butanol, polyglycerin, formaldehyde and water. etc.

Examples of aprotic solvents include amides such as N-methylacetamide, N,N-dimethylformamide and N-methyl-2-pyrrolidone, esters such as methyl acetate, methyl ethyl ketone, γ-butyrolactone (γBL) and the like. ketones, ethers such as 1,4-dioxane, sulfur-containing compounds such as dimethylsulfoxide and sulfolane, and carbonate compounds such as propylene carbonate.

Among them, the first solvent is preferably a protic solvent. In particular, it is preferred that the first solvent is water. In this case, the handleability of the first treatment liquid and the dispersibility of the conductive polymer are improved. In addition, since water has a low viscosity, it can be expected that the contact between the conductive polymer and the second treatment liquid is improved in the second step, which is a subsequent step. When the first solvent is water, water preferably accounts for 50% by mass or more, more preferably 70% by mass or more, and particularly preferably 90% by mass or more of the liquid solvent of the first treatment liquid.

The conductive polymer particles dispersed in the dispersion have a median diameter in the volume particle size distribution measured by a particle size measuring device using dynamic light scattering (hereinafter simply referred to as the median diameter according to dynamic light scattering). ) is preferably 0.01 μm to 0.5 μm. The particle size of the conductive polymer can be adjusted by polymerization conditions, dispersion conditions, and the like.

The concentration of the conductive polymer (including dopants or polyanions) in the first treatment liquid is preferably 0.5 to 10% by mass. The first treatment liquid having such a concentration is suitable for adhering an appropriate amount of conductive polymer, and is easily impregnated into the capacitor element 10, which is advantageous in terms of improving productivity.

(ii) Step of impregnating the capacitor element with the second treatment liquid (second step)
In the second step, the capacitor element applied with the first treatment liquid is impregnated with the second treatment liquid. The second step is an optional step.

In the second step, it is preferable to impregnate the capacitor element (especially the anode body) with the second treatment liquid while at least part of the liquid solvent (such as the first solvent) of the first treatment liquid remains. A capacitor element having an anode body in which a liquid solvent remains has extremely high permeability to the second treatment liquid. Therefore, when the second treatment liquid is applied to the capacitor element in such a state, the second treatment liquid can penetrate further into the inside. Such an effect is particularly likely to be obtained when at least water remains. Therefore, it is preferable to use a liquid solvent containing water as at least the first solvent for the first treatment liquid. When a liquid solvent containing water is used as the first solvent, the stability of the first treatment liquid is also enhanced, which is also advantageous from this point of view.

In the capacitor element subjected to the second step, the residual amount of the liquid solvent is preferably 5% by mass or more (eg, 5 to 100% by mass), and 20% by mass or more (eg, 20 to 100% by mass). Alternatively, it is more preferably 50% by mass or more (eg, 50 to 100% by mass). When the residual amount of the liquid solvent is within such a range, the second treatment liquid tends to be uniformly mixed with the conductive polymer in the capacitor element in the second step. It becomes easy to make it adhere more uniformly.

The remaining amount of the liquid solvent is the ratio of the mass of the liquid solvent contained in the capacitor element subjected to the second step to the mass of the liquid solvent contained in the first treatment liquid with which the capacitor element is impregnated in the first step. It is a ratio (% by mass).

A solvent (second solvent) is used as the second treatment liquid. The impregnation of the capacitor element with the second treatment liquid can be carried out in the same manner as in the case of the first treatment liquid. The second solvent includes polar solvents and non-polar solvents. Non-polar solvents include, for example, hydrocarbons, ethyl acetate, diethyl ether and the like.

A polar solvent is preferable as the second solvent. Examples of polar solvents include protic solvents exemplified for the first solvent, as well as aprotic solvents.
Examples of the aprotic solvent include, among those exemplified for the first solvent, amides, lactones such as γBL, cyclic ethers such as 1,4-dioxane, sulfones such as dimethylsulfoxide and sulfolane, and propylene carbonate. Cyclic carbonate etc. are mentioned. The second treatment liquid may contain one second solvent, or two or more second solvents.

Examples of protic solvents include water, alcohols (specifically, alkanols such as methanol and ethanol, polyol compounds such as glycols (EG, PEG, etc.), glycerins (glycerin, polycerin, etc.)), diethylene glycol monobutyl ether, and the like. Protic organic solvents such as glycol monoethers are preferred.
The at least one second solvent is preferably a protic solvent, and the second processing liquid may be a mixture of protic and aprotic solvents. When using a plurality of second solvents, for example, combining a polyol compound having 3 or more hydroxyl groups per molecule and a polar solvent (protic organic solvent and/or aprotic solvent) other than the polyol compound good too. As protic organic solvents, alcohols other than polyol compounds (specifically, alkanols and glycols), glycol monoethers, and the like are preferable.

(iii) Step of removing the solvent component (third step, fourth step)
After the first step, solvent components remaining in the capacitor element can be removed in a third step. After the second step, the solvent component remaining in the capacitor element may be removed in the fourth step. In the third or fourth step, at least part of the solvent component may be removed, or all of the solvent component may be removed. By removing the solvent component in the fourth step, the conductive polymer can be adhered more uniformly to the surface of the dielectric layer.
The solvent component here means the liquid solvent contained in the first treatment liquid and the second solvent contained in the second treatment liquid. Among these, it is preferable to remove at least part of the first solvent and/or the second solvent (especially the first solvent) in the fourth step.

In each of the third step and the fourth step, the solvent component can be removed by evaporating under heating, may be removed under atmospheric pressure, or may be removed under reduced pressure if necessary. good. The temperature for removing the solvent component may be equal to or higher than the boiling point of the first solvent (or the second solvent). The solvent component may be removed, for example, in a plurality of stages with different temperatures (for example, 2 stages or 3 or more stages), or may be performed while increasing the temperature.
In this manner, the conductive polymer is attached between the anode body 21 and the cathode body 22 (in particular, the surface of the dielectric layer), and the capacitor element 10 with the conductive polymer attached is manufactured.

The conductive polymer is preferably attached so as to cover at least part of the surface of the dielectric layer. At this time, the conductive polymer may adhere not only to the surface of the dielectric layer but also to the surfaces of the cathode body 22 and/or the separator 23 . In addition, a first step (i) of impregnating the capacitor element 10 including the anode body 21 having a dielectric layer with the first treatment liquid, and a second step of removing the solvent component (liquid solvent such as the first solvent) after the first step. Three steps (optional step), a second step (ii) of impregnating the capacitor element with the second treatment liquid, and a second step of removing the solvent component (liquid solvent such as the first solvent and/or the second solvent) after the second step. At least one step selected from the group consisting of 4 steps (iv) (optional steps) may be repeated two or more times, if desired. A series of steps selected from these steps may be repeated two or more times. For example, after the first step is repeated multiple times, other steps may be performed, or the first step, optionally the third step, and the second step may be repeated multiple times as a series of steps. It is advantageous to repeat at least the first step multiple times from the viewpoint of easily increasing the coverage of the conductive polymer with respect to the dielectric layer.

All solvent components may be removed from the capacitor element 10 obtained in the second step or the fourth step. Moreover, the capacitor element 10 obtained in the second step or the fourth step may be in a state in which the solvent component remains. When the solvent component remains, the repair function of the dielectric layer can be further improved. In addition, since the remaining solvent component exists between the particles of the conductive polymer, the electrolytic solution easily permeates between the particles of the conductive polymer when the capacitor element is impregnated with the electrolytic solution. Therefore, it becomes easy to obtain the function of repairing the dielectric layer by the electrolytic solution. By enhancing the repair function of the dielectric layer, it is also possible to effectively suppress short circuits even when the guaranteed life of the electrolytic capacitor has passed.

(Electrolyte)
The electrolytic solution contains a non-aqueous solvent containing γBL and at least one glycerin compound selected from the group consisting of glycerin and polyglycerin. Moreover, the electrolytic solution may further contain an ionic substance (solute), or may contain no solute. As the ionic substance, one that dissolves in a glycerin compound and/or a non-aqueous solvent is used.

By including γBL in the electrolytic solution, it is possible to improve the impregnation of the electrolytic solution into the capacitor element despite the use of a relatively high-viscosity glycerin compound. The electrolytic solution containing a glycerin compound can swell the conductive polymer. Therefore, the conductive polymer can be present in every corner of the plurality of irregularities formed by roughening the anode foil. As a result, in addition to being able to reduce the ESR at the initial stage of charging and discharging, the low ESR can be maintained even when the electrolytic capacitor is used for a long period of time, and high reliability can be obtained.

The electrolytic solution refers to the electrolytic solution (solvent component) contained in the assembled electrolytic capacitor (specifically, in the exterior case). The electrolytic solution also contains a solvent component remaining in the electrolytic capacitor during the manufacturing process of the electrolytic capacitor. Such a solvent component includes a solvent component contained in the first treatment liquid and/or the second treatment liquid (for example, a liquid medium contained in the first treatment liquid and/or a liquid medium contained in the first solvent and the second treatment liquid). second solvent, etc.).

Polyglycerin, for example, contains 2 to 20 (preferably 2 to 12, 2 to 10, or 2 to 6) glycerin units. As polyglycerin, diglycerin, triglycerin and the like are also preferable.

The glycerin compound has a high affinity for the conductive polymer and tends to stably exist between particles of the conductive polymer. Glycerin compounds also have low volatility. Therefore, when the electrolytic solution contains a glycerin compound, the electrolytic solution can be easily retained around the dielectric layer, the film repairability of the dielectric layer can be enhanced, and the effect of suppressing leakage current can be enhanced. Therefore, short circuits can be effectively suppressed even when the guaranteed life of the electrolytic capacitor has passed.

The content of the glycerin compound in the electrolytic solution is, for example, 5% by mass or more, and may be 10% by mass or more or 20% by mass or more. The content of the glycerin compound in the electrolytic solution may be, for example, 50% by mass or less, preferably 30% by mass or less. These lower and upper limits can be combined arbitrarily. The content of the glycerin compound in the electrolytic solution may be, for example, 5-50 mass %, or 10-30 mass %.
Higher reliability is obtained when the content of the glycerin compound in the electrolytic solution is within the above range.

In the electrolytic capacitor, the mass of the glycerin compound contained in the electrolyte may be 2 to 100 times or 3 to 80 times the mass of the conductive polymer impregnated in the capacitor element. good. When the mass ratio is within such a range, the effect of swelling the conductive polymer is likely to be obtained.

The non-aqueous solvent may include a non-aqueous solvent (organic solvent and/or ionic liquid) other than γBL. Organic solvents (organic solvents other than γBL) are preferably used. Such a nonaqueous solvent preferably has a high boiling point, and the high boiling point nonaqueous solvent includes an ionic liquid and/or a high boiling point organic solvent. The boiling point of the non-aqueous solvent is, for example, higher than 100°C, preferably 150°C or higher, and more preferably 200°C or higher. Examples of the organic solvent include the organic solvents exemplified for the first solvent of the first treatment liquid and the second solvents exemplified for the second treatment liquid. A non-aqueous solvent can be used individually by 1 type or in combination of 2 or more types.

As the non-aqueous solvent, it is preferable to use one that dissolves the glycerin compound (or one that is miscible or compatible with the glycerin compound). Examples of such non-aqueous solvents include protic organic solvents and aprotic solvents such as amides, lactones, cyclic ethers, sulfones, and cyclic carbonates. As protic organic solvents, alcohols other than glycerins (specifically, alkanols and glycols), glycol monoethers, and the like are preferable. Among non-aqueous solvents, at least one selected from the group consisting of glycols, lactones, sulfones, and cyclic carbonates is preferred. The non-aqueous solvent may contain γBL and at least one selected from the group consisting of EG, sulfolane, and PC.

Such aprotic solvents and protic organic solvents have high affinity with glycerin compounds and can be uniformly mixed with glycerin compounds. Therefore, when such a solvent is used, the electrolytic solution can easily permeate between the particles of the conductive polymer.

Salts of anions and cations are used as the solute, and organic salts in which at least one of the anions and cations is an organic substance are preferred. Examples of organic salts include trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolinium phthalate, and mono-1,3-dimethyl-2-ethylimidazolium phthalate. Linium and the like can be exemplified. A solute may be used singly or in combination of two or more.

Impregnation of the electrolytic solution into the capacitor element 10 is not particularly limited and can be performed by a known method. For example, the capacitor element may be immersed in the electrolytic solution, or the electrolytic solution may be poured into a container containing the capacitor element. Impregnation of the electrolytic solution into the capacitor element may be performed under reduced pressure (for example, 10 to 100 kPa), if necessary.

(others)
Capacitor element 10 may be encapsulated. More specifically, first, capacitor element 10 is housed in bottomed case 11 so that lead wires 14A and 14B are positioned on the open upper surface of bottomed case 11 . As the material of the bottomed case 11, metals such as aluminum, stainless steel, copper, iron, and brass, or alloys thereof can be used.

Next, the sealing member 12 formed so that the lead wires 14A and 14B pass therethrough is arranged above the capacitor element 10 to seal the capacitor element 10 in the bottomed case 11 . The sealing member 12 may be made of an insulating material. As the insulating material, an elastic body is preferable, and among them, silicone rubber, fluororubber, ethylenepropylene rubber, chlorosulfonated polyethylene rubber (Hypalon rubber, etc.), butyl rubber, isoprene rubber, etc., having high heat resistance are preferable.

Next, the vicinity of the open end of the bottomed case 11 is laterally drawn, and the open end is crimped to the sealing member 12 to be curled. By arranging the seat plate 13 on the curled portion, the electrolytic capacitor as shown in FIG. 1 is completed. After that, aging treatment may be performed while applying the rated voltage.

In the above embodiments, a wound type electrolytic capacitor has been described, but the scope of application of the present invention is not limited to the above. It can also be applied to capacitors and laminated electrolytic capacitors using a metal plate as an anode.

EXAMPLES The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

<<Example 1>>
A wound electrolytic capacitor (diameter 6.3 mm, length 5.8 mm) having a rated voltage of 35 V and a rated capacitance of 47 μF as shown in FIG. 1 was manufactured and evaluated by the following procedure.

(1) Production of electrolytic capacitor (preparation of anode body having dielectric layer)
An aluminum foil having a thickness of 100 μm was subjected to an etching treatment to roughen the surface of the aluminum foil. Thereafter, a dielectric layer was formed on the surface of the aluminum foil by chemical conversion treatment using an aqueous solution of ammonium adipate to prepare an anode body having a dielectric layer.

(Preparation of cathode body)
An aluminum foil having a thickness of 50 μm was etched to roughen the surface of the aluminum foil to prepare a cathode body.

(Production of capacitor element (wound body))
An anode lead tab and a cathode lead tab were connected to the anode body and the cathode body, and the anode body and the cathode body were wound through a separator while winding the lead tab, to obtain a capacitor element. An anode lead wire and a cathode lead wire were connected to the ends of each lead tab protruding from the capacitor element. Then, the manufactured capacitor element was subjected to chemical conversion treatment again to form a dielectric layer on the cut end of the anode body. Next, the ends of the outer surface of the capacitor element were fixed with a winding tape.

(Impregnation of first treatment liquid)
A mixed solution was prepared by dissolving 3,4-ethylenedioxythiophene and polystyrene sulfonic acid as a dopant in ion-exchanged water (first solvent). While stirring the resulting mixed solution, ferric sulfate and sodium persulfate (oxidizing agent) dissolved in ion-exchanged water were added to carry out a polymerization reaction. After the reaction, the resulting reaction solution is dialyzed to remove unreacted monomers and excess oxidizing agent, and poly3,4-ethylenedioxythiophene (PEDOT) doped with about 5% by mass of polystyrenesulfonic acid is obtained. A dispersion liquid (first treatment liquid) containing
The obtained first treatment liquid was impregnated into the capacitor element for 5 minutes. The solvent component was then removed by heating the capacitor element at 150° C. for 20 minutes.
Thus, a capacitor element to which the conductive polymer was attached was produced.

(Electrolyte impregnation)
Then, the capacitor element was impregnated with the electrolytic solution under reduced pressure. As the electrolytic solution, a solution containing γBL:glycerin:mono(ethyldimethylamine) phthalate (solute)=50:25:25 (mass ratio) was used.

(sealing of capacitor element)
The capacitor element impregnated with the electrolytic solution was housed in an exterior case as shown in FIG. 1 and sealed to produce an electrolytic capacitor. A total of 300 electrolytic capacitors were produced in the same manner.

(2) Performance Evaluation (a) Capacitance and ESR Values As initial characteristics of electrolytic capacitors, capacitance (μF) and ESR values (mΩ) were measured. Specifically, the initial capacitance (μF) at a frequency of 120 Hz was measured for the electrolytic capacitor using an LCR meter for four-terminal measurement. Also, the ESR value (mΩ) of the electrolytic capacitor at a frequency of 100 kHz was measured using an LCR meter for four-terminal measurement.
As an accelerated test, the capacitance (μF) and ESR value (mΩ) after leaving the electrolytic capacitor at 125° C. for 4000 hours were also measured in the same manner as the initial characteristics.
The capacitance and ESR values were each measured for 120 randomly selected electrolytic capacitors, and the average value was calculated.

<<Comparative example 1>>
An electrolytic capacitor was produced in the same manner as in Example 1, except that a solution containing γBL: mono(ethyldimethylamine) phthalate (solute) = 75:25 (mass ratio) was used as the electrolytic solution. made an evaluation.

<<Example 2>>
As the electrolytic solution, the same procedure as in Example 1 was performed except that a solution containing γBL: sulfolane: glycerin: mono(ethyldimethylamine) phthalate (solute) = 25:25:25:25 (mass ratio) was used. , electrolytic capacitors were fabricated and their performance was evaluated.

<<Example 3>>
An electrolytic capacitor was fabricated in the same manner as in Example 1, except that a solution containing γBL: glycerin: phthalic acid mono(ethyldimethylamine) (solute) = 70:5:25 (mass ratio) was used as the electrolytic solution. It was produced and the performance was evaluated.
Table 1 shows the results of Examples and Comparative Examples.

As shown in Table 1, in the example, the capacitance can be secured and the ESR can be kept low even after the accelerated test. On the other hand, in Comparative Example 1, the capacitance decreased and the ESR increased after the accelerated test.

INDUSTRIAL APPLICABILITY The present invention can be applied to electrolytic capacitors using conductive polymers as cathode materials.

10: capacitor element, 11: bottomed case, 12: sealing member, 13: seat plate, 14A, 14B: lead wire, 15A, 15B: lead tab, 21: anode body, 22: cathode body, 23: separator, 24 : Winding stop tape

Claims (8)

a capacitor element having an anode body on which a dielectric layer is formed;
a conductive polymer covering at least a portion of the surface of the dielectric layer;
an electrolytic solution comprising a non-aqueous solvent, a glycerin compound and an ionic solute;
Concavities and convexities are formed on the surface of the anode body,
the conductive polymer comprises polystyrene sulfonic acid;
The non-aqueous solvent is at least one selected from the group consisting of lactones, glycols, cyclic carbonates, and sulfones,
The content of the glycerin compound in the electrolytic solution is 5% by mass or more and 50% by mass or less,
An electrolytic capacitor, wherein the mass of the non-aqueous solvent contained in the electrolytic solution is larger than the mass of the glycerin compound. 2. The electrolytic capacitor according to claim 1, wherein the mass of said glycerin compound contained in said electrolytic solution is in the range of 2 to 100 times the mass of the conductive polymer adhering to said capacitor element. the ionic solute comprises a cationic component and an anionic component;
The cation component is at least one selected from the group consisting of maleic acid, borodisalicylic acid and phthalic acid,
3. The electrolytic capacitor according to claim 1, wherein said anion component is at least one selected from the group consisting of amine compounds and amidine compounds. the glycerin compound comprises polyglycerin;
The electrolytic capacitor according to any one of claims 1 to 3, wherein said polyglycerin contains 2 to 20 glycerin units. 5. The electrolytic capacitor according to claim 4, wherein the content of said polyglycerin in the electrolytic solution is 10% by mass or more and 50% by mass or less. 4. The electrolytic capacitor according to claim 1, wherein said glycerin compound comprises glycerin. 7. The electrolytic capacitor according to claim 6, wherein the glycerin content in the electrolytic solution is 10% by mass or more and 50% by mass or less. The conductive polymer covering at least a part of the surface of the dielectric layer,
8. The electrolytic capacitor according to claim 1, which is formed by applying a first treatment liquid containing said conductive polymer to said anode body having said dielectric layer formed thereon.

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