JP7407371B2 - Electrolytic capacitor - Google Patents

Description

The present invention relates to an electrolytic capacitor, and more particularly, to an electrolytic capacitor having high reliability.

With the digitalization of electronic devices, capacitors used therein are required to be small, large in capacity, and have low equivalent series resistance (ESR) in a high frequency range.

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.

Patent Document 1 discloses that an element including a separator is impregnated with a dispersion of a conductive polymer to form a conductive solid layer, and then impregnated with an electrolyte to provide the conductive solid layer and the electrolyte. A method of manufacturing an electrolytic capacitor has been proposed.

Japanese Patent Application Publication No. 2008-010657

In recent years, electrolytic capacitors have been used not only in electronic devices but also in automobile electrical equipment. In particular, since electrolytic capacitors used in automobile electrical equipment are used for long periods of time in high-temperature environments, electrolytic capacitors are required to have higher reliability over a longer period of time than conventional capacitors. Therefore, an object of the present invention is to provide an electrolytic capacitor having even higher reliability.

One aspect of the present invention is to provide a capacitor element including 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 containing a nonaqueous 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 electrolyte is 10% by mass or more and 50% by mass or less.

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

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

Embodiments of the electrolytic capacitor of the present invention will be described below with appropriate reference to the drawings. 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 an embodiment of the present invention. FIG. 2 is a partially developed schematic diagram of a capacitor element included in the electrolytic capacitor.

In FIG. 1, an electrolytic capacitor includes a capacitor element 10 that includes an anode body 21 on which a dielectric layer is formed, and a conductive layer that covers at least a part of the surface of the dielectric layer (or that is attached to at least a part of the surface). It includes molecules (not shown) and an electrolyte (not shown). The capacitor element 10 is housed in an exterior case together with an electrolytic solution, with at least a portion of the surface of the dielectric layer covered with a conductive polymer. The exterior 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 onto 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. The anode body 21 and the cathode body 22 are wound together with a separator 23 in between. The outermost periphery of the capacitor element 10 is fixed with a winding tape 24. Note that FIG. 2 shows a partially expanded state of the capacitor element 10 before its outermost circumference is stopped.

The anode body 21 includes a metal foil whose surface is roughened to have an uneven surface, and a dielectric layer is formed on the uneven metal foil.
In the electrolytic capacitor, the conductive polymer is attached to cover at least a part of the surface of the dielectric layer formed on the anode body 21, but this is not limited to this case. It may be attached anywhere between. For example, the conductive polymer covers at least a portion of the surface of the dielectric layer formed on the anode body 21, and further coats at least a portion of the surface of the cathode body 22 and/or the surface of the separator 23. may be covered. In general, in electrolytic capacitors, a conductive polymer layer (specifically, a film containing a conductive polymer) that covers at least a portion of the surfaces of an anode body, a cathode body, a separator, etc. It is sometimes called.

Below, the structure of the electrolytic capacitor according to the embodiment of the present invention will be explained in more detail.
The capacitor element includes an anode body on which a dielectric layer is formed. The conductive polymer attached to the surface of the dielectric layer effectively functions as a cathode material. The capacitor element may further include a cathode body and/or a separator, if necessary.

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

The surface of the metal foil can be roughened by a known method. Due to the roughening, a plurality of irregularities are formed on the surface of the metal foil. It is preferable to roughen the surface by etching the metal foil, for example. The etching process may be performed by, for example, a direct current electrolysis method or an alternating current electrolysis method.

(dielectric layer)
The dielectric layer is formed on the surface of the anode body (specifically, the roughened surface of the metal foil).
Although the method for forming the dielectric layer is not particularly limited, it can be formed by subjecting metal foil to a chemical conversion treatment. 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, a voltage may be applied while the metal foil is immersed in the chemical conversion liquid.

Generally, from the viewpoint of mass production, surface roughening treatment and chemical conversion treatment are performed on a large-sized metal foil formed of a valve metal or the like. In that case, the anode body 21 is prepared by cutting the treated foil into a desired size.

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

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

Capacitor element 10 can be manufactured by a known method. For example, capacitor element 10 may be manufactured by stacking anode body 21 and cathode body 22 with separator 23 in between. By winding the anode body 21 and the cathode body 22 with the separator 23 in between, a wound body as shown in FIG. 2 may be formed. At this time, by winding the lead tabs 15A, 15B while being rolled in, the lead tabs 15A, 15B may be made to stand up from the wound body, as shown in FIG.

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

Out of the anode body 21, the cathode body 22, and the separator 23, the outermost layer of the wound body (the cathode body 22 in FIG. 2) has an end portion of the outer surface fixed with a winding tape 24. Note that when the anode body 21 is prepared by cutting a large metal foil, the capacitor element in the form of a wound body or the like is further coated with a chemical compound in order to provide a dielectric layer on the cut surface of the anode body 21. Processing may be performed.

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

In this specification, polypyrrole, polythiophene, polyfuran, polyaniline, etc. each mean a polymer having a basic skeleton of polypyrrole, polythiophene, polyfuran, polyaniline, etc. Therefore, polypyrrole, polythiophene, polyfuran, polyaniline, etc. may also include their respective derivatives. For example, polythiophene includes poly(3,4-ethylenedioxythiophene) and the like.

The conductive polymer may contain a dopant. A polyanion can be used as the dopant. Specific examples of polyanions include polyvinylsulfonic acid, polystyrenesulfonic acid, polyallylsulfonic acid, polyacrylsulfonic acid, polymethacrylsulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprenesulfonic acid, and polysulfonic acid. Examples include anions such as acrylic acid. Among these, 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 types of monomers.

The weight average molecular weight of the polyanion is not particularly limited, but 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 is easily adhered uniformly to the surface of a dielectric layer.

The conductive polymer may be attached to at least a portion of the surface of the dielectric layer in the anode body 21 so as to cover the dielectric layer, but it is preferable that the conductive polymer be attached so as 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 be attached 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 prepared in a step (first step) of impregnating a capacitor element including an anode body with a dielectric layer formed thereon with a first treatment liquid containing the conductive polymer, and, if necessary, in the first step. After that, the second treatment liquid can be attached to the capacitor element through a step (second step) of impregnating the capacitor element with the second treatment liquid. A conductive polymer is attached 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 a part of the solvent component contained in the first treatment liquid after the first step, and after the second step, the first treatment liquid is removed. and/or a step of removing at least a portion 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 (in particular, at least the dielectric layer); for example, the capacitor element 10 may be immersed in the first treatment liquid. Alternatively, the first treatment liquid may be injected into the capacitor element. Impregnation may be carried out under atmospheric pressure, but may also be carried out under reduced pressure, for example in an atmosphere of 10 kPa to 100 kPa, preferably 40 kPa to 100 kPa. Impregnation may be carried out under ultrasonic vibration if necessary. The impregnation time depends on the size of the capacitor element 10, but 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 include a conductive polymer and a liquid solvent. The first treatment liquid may be either a solution in which a conductive polymer is dissolved in a liquid solvent or a dispersion in which a conductive polymer is dispersed in a liquid solvent. In a dispersion, the conductive polymer is dispersed in the form of particles in a liquid solvent. The dispersion liquid is prepared by polymerizing a conductive polymer raw material (for example, a precursor such as a monomer and/or oligomer of a conductive polymer) in the presence of a dopant in a liquid solvent to form a conductive polymer containing a dopant. You may use the one obtained by producing particles of. In addition, as a dispersion liquid, one obtained by polymerizing the raw material of the conductive polymer in a liquid solvent to generate conductive polymer particles, or a dispersion liquid obtained by polymerizing the raw material of the conductive polymer in a liquid solvent, or a conductive polymer synthesized in advance in a liquid solvent. You may use the one obtained by dispersing the particles.

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 include a plurality of different types of first solvents. The first solvent may account for, for example, 30% by mass or more, preferably 50% by mass or more, and 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. Note that the non-aqueous solvent is a general term for liquids excluding water and liquids containing water, and includes organic solvents and ionic liquids. Among these, the first solvent is preferably a polar solvent. The 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, and polyglycerin, formaldehyde, and water. Examples include.

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, and γ-butyrolactone (γBL). Examples include ketones, ethers such as 1,4-dioxane, sulfur-containing compounds such as dimethyl sulfoxide and sulfolane, and carbonate compounds such as propylene carbonate.

Among these, the first solvent is preferably a protic solvent. In particular, it is preferable that the first solvent is water. In this case, the ease of handling the first treatment liquid and the dispersibility of the conductive polymer are improved. Furthermore, since water has a low viscosity, it can be expected that the contact between the conductive polymer and the second treatment liquid will be 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, particularly 90% by mass or more of the liquid solvent of the first treatment liquid.

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

The concentration of the conductive polymer (including the dopant or polyanion) in the first treatment liquid is preferably 0.5 to 10% by mass. The first treatment liquid having such a concentration is suitable for attaching an appropriate amount of conductive polymer, and is also advantageous in improving productivity because it is easily impregnated into the capacitor element 10.

(ii) Step of impregnating the capacitor element with the second treatment liquid (second step)
In the second step, the capacitor element to which the first treatment liquid has been applied 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 (particularly the anode body) with the second treatment liquid while at least a portion of the liquid solvent (first solvent, etc.) of the first treatment liquid remains. A capacitor element including an anode body in which 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 deeper into the capacitor element. Such an effect is particularly likely to be obtained when the treatment is carried out in a state where at least water remains. Therefore, it is preferable to use a liquid solvent containing water as at least the first solvent in 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 increased, which is advantageous from this point of view.

In the capacitor element subjected to the second step, the remaining amount of the liquid solvent is preferably 5% by mass or more (for example, 5 to 100% by mass), and preferably 20% by mass or more (for example, 20 to 100% by mass). Or, it is more preferably 50% by mass or more (for example, 50 to 100% by mass). If the remaining amount of the liquid solvent is within this range, the second treatment liquid will be more likely to mix uniformly with the conductive polymer in the capacitor element in the second step. It becomes easier to adhere more uniformly.

Note that the remaining amount of liquid solvent is the mass of the liquid solvent contained in the capacitor element subjected to the second step relative to the mass of the liquid solvent contained in the first treatment liquid that impregnated the capacitor element in the first step. The ratio (mass%).

A solvent (second solvent) is used as the second treatment liquid. Impregnation of the capacitor element with the second treatment liquid can be performed in the same manner as in the case of the first treatment liquid. The second solvent includes polar solvents and non-polar solvents. Examples of nonpolar solvents include hydrocarbons, ethyl acetate, diethyl ether, and the like.

As the second solvent, a polar solvent is preferred. Examples of the polar solvent include, in addition to the protic solvents exemplified for the first solvent, 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 dimethyl sulfoxide and sulfolane, and propylene carbonate. Examples include cyclic carbonate. The second treatment liquid may contain one type of second solvent, or may contain two or more types of second solvents.

Protic solvents include water, alcohols (specifically, alkanols such as methanol and ethanol, polyol compounds such as glycols (EG, PEG, etc.), glycerins (glycerin, polyserine, etc.)), diethylene glycol monobutyl ether, etc. Protic organic solvents such as glycol monoethers are preferred.
The at least one second solvent is preferably a protic solvent, and the second treatment liquid may be a mixture of a protic solvent and an aprotic solvent. When using multiple second solvents, for example, a polyol compound having three or more hydroxyl groups per molecule and a polar solvent other than the polyol compound (protic organic solvent and/or aprotic solvent) are combined. Good too. Preferred examples of the protic organic solvent include alcohols other than polyol compounds (specifically, alkanols and glycols), glycol monoethers, and the like.

(iii) Step of removing solvent components (third step, fourth step)
After the first step, the solvent component remaining in the capacitor element can be removed in a third step. Furthermore, after the second step, the solvent component remaining in the capacitor element may be removed in a fourth step. In the third or fourth step, at least a portion 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 more uniformly adhered to the surface of the dielectric layer.
Note that the solvent component herein refers to 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 a portion of the first solvent and/or the second solvent (especially the first solvent) in the fourth step.

In each of the third and fourth steps, the solvent component can be removed by evaporation under heat, may be removed under atmospheric pressure, and optionally may be removed under reduced pressure. good. The temperature at which the solvent component is removed may be equal to or higher than the boiling point of the first solvent (or second solvent). The removal of the solvent component may be performed, for example, in a plurality of stages (for example, two stages or three or more stages) at different temperatures, or may be performed while increasing the temperature.
In this way, the conductive polymer is attached between the anode body 21 and the cathode body 22 (particularly on the surface of the dielectric layer), and the capacitor element 10 to which the conductive polymer is attached is manufactured.

The conductive polymer is preferably attached so as to cover at least a portion of the surface of the dielectric layer. At this time, the conductive polymer may be attached not only to the surface of the dielectric layer but also to the surface of the cathode body 22 and/or the separator 23. Further, 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 step (i) of removing the solvent component (liquid solvent such as the first solvent) after the first step. 3 steps (optional steps), 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 four steps (iv) (optional steps) may be repeated two or more times, if necessary. A series of steps selected from these steps may be repeated two or more times. For example, after repeating the first step multiple times, other steps may be performed, or the first step, if necessary, the third step, and the second step may be repeated multiple times as a series of steps. From the viewpoint of easily increasing the coverage of the conductive polymer on the dielectric layer, it is advantageous to repeat at least the first step multiple times.

All solvent components may be removed from the capacitor element 10 obtained in the second step or the fourth step. Further, the capacitor element 10 obtained in the second step or the fourth step may have a solvent component remaining therein. When the solvent component remains, the repair function of the dielectric layer can be further improved. Further, since the remaining solvent component exists between the particles of the conductive polymer, when impregnating the capacitor element with the electrolyte, the electrolyte easily penetrates between the particles of the conductive polymer. Therefore, the repair function of the dielectric layer by the electrolytic solution can also be easily obtained. By increasing 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 includes a nonaqueous solvent containing γBL and at least one glycerin compound selected from the group consisting of glycerin and polyglycerin. Further, the electrolytic solution may further contain an ionic substance (solute) or may not contain a solute. As the ionic substance, a glycerin compound and/or a substance soluble in a non-aqueous solvent is used.

When the electrolytic solution contains γBL, it is possible to improve the impregnating property of the electrolytic solution into the capacitor element even though a glycerin compound having a relatively high viscosity is used. When the electrolytic solution contains a glycerin compound, the conductive polymer can be swollen. 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 ESR at the initial stage of charging and discharging, low ESR can be maintained even when the electrolytic capacitor is used for a long period of time, resulting in high reliability.

Note that the electrolytic solution refers to an electrolytic solution (solvent component) housed inside the assembled electrolytic capacitor (specifically, inside the exterior case). The electrolytic solution also includes solvent components 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 and/or a first solvent contained in the first treatment liquid, a solvent contained in the second treatment liquid), second solvent, etc.).

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

Glycerin compounds have a high affinity for conductive polymers and tend to stably exist between particles of conductive polymers. 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 improved, and the effect of suppressing leakage current can be increased. Therefore, even if the guaranteed life of the electrolytic capacitor has passed, short circuits can be effectively suppressed.

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 limit values and upper limit values can be arbitrarily combined. The content of the glycerin compound in the electrolytic solution may be, for example, 5 to 50% by mass, or 10 to 30% by mass.
When the content of the glycerin compound in the electrolytic solution is within the above range, higher reliability can be obtained.

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 into the capacitor element. good. When the mass ratio is within such a range, the effect of swelling the conductive polymer can be easily 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 non-aqueous solvent preferably has a high boiling point, and examples of the high-boiling non-aqueous solvent include ionic liquids and/or high-boiling organic solvents. The boiling point of the nonaqueous 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. The non-aqueous solvent can be used alone or in combination of two or more.

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 nonaqueous solvents include protic organic solvents and aprotic solvents such as amides, lactones, cyclic ethers, sulfones, and cyclic carbonates. Preferred examples of the protic organic solvent include alcohols other than glycerin (specifically, alkanols and glycols), glycol monoethers, and the like. Among the nonaqueous solvents, at least one selected from the group consisting of glycols, lactones, sulfones, and cyclic carbonates is preferred. The nonaqueous 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 the glycerin compound and can be uniformly mixed with the glycerin compound. Therefore, when such a solvent is used, the electrolytic solution can easily penetrate between particles of the conductive polymer.

As the solute, salts of anions and cations are used, and organic salts in which at least one of the anion and the cation 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-ethylimidazo phthalate. An example is linium. One type of solute may be used alone or two or more types may be used in combination.

Impregnation of the capacitor element 10 with the electrolytic solution 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. The capacitor element may be impregnated with the electrolytic solution under reduced pressure (for example, 10 to 100 kPa), if necessary.

(others)
Capacitor element 10 may be sealed. More specifically, first, the capacitor element 10 is housed in the bottomed case 11 so that the lead wires 14A and 14B are located on the open top surface of the 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 through is placed above the capacitor element 10, and the capacitor element 10 is sealed in the bottomed case 11. The sealing member 12 may be any insulating material. As the insulating substance, an elastic body is preferable, and among them, silicone rubber, fluororubber, ethylene propylene rubber, chlorosulfonated polyethylene rubber (such as Hypalon rubber), butyl rubber, and isoprene rubber, which have high heat resistance, are preferable.

Next, a horizontal drawing process is applied to the vicinity of the open end of the bottomed case 11, and the open end is crimped to the sealing member 12 and curled. Then, by placing the seat plate 13 on the curled portion, an electrolytic capacitor as shown in FIG. 1 is completed. Thereafter, aging treatment may be performed while applying the rated voltage.

Although the above embodiment describes a wound type electrolytic capacitor, the scope of application of the present invention is not limited to the above, and is applicable to other electrolytic capacitors, such as a chip type electrolytic capacitor using a sintered metal body as an anode body. It can also be applied to capacitors and multilayer electrolytic capacitors that use a metal plate as an anode body.

EXAMPLES Hereinafter, the present invention will be specifically explained based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

《Example 1》
A wound type electrolytic capacitor (diameter 6.3 mm, length 5.8 mm) with a rated voltage of 35 V and a rated capacitance of 47 μF as shown in FIG. 1 was produced and evaluated using the following procedure.

(1) Manufacture of electrolytic capacitor (preparation of anode body with dielectric layer)
An etching treatment was performed on an aluminum foil having a thickness of 100 μm 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 ammonium adipate solution, thereby preparing an anode body having a dielectric layer.

(Preparation of cathode body)
An aluminum foil having a thickness of 50 μm was subjected to etching treatment to roughen the surface of the aluminum foil, thereby preparing 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 with a separator interposed therebetween while the lead tab was being wound around the anode body and the cathode body 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, respectively. Then, the produced capacitor element was again subjected to a chemical conversion treatment 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 tape.

(Impregnation with first treatment liquid)
A mixed solution was prepared in which 3,4-ethylenedioxythiophene and polystyrene sulfonic acid as a dopant were dissolved 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 was dialyzed to remove unreacted monomers and excess oxidizing agent, and poly3,4-ethylenedioxythiophene (PEDOT) doped with about 5% by mass of polystyrene sulfonic acid was obtained. A dispersion liquid (first treatment liquid) containing the above was obtained.
The capacitor element was impregnated with the obtained first treatment liquid for 5 minutes. Next, the solvent component was removed by heating the capacitor element at 150° C. for 20 minutes.
In this way, a capacitor element to which a conductive polymer was attached was produced.

(Impregnation of electrolyte)
The capacitor element was then impregnated with an 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)
A capacitor element impregnated with an 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 manufactured in the same manner.

(2) Performance evaluation (a) Capacitance and ESR value As initial characteristics of the electrolytic capacitor, capacitance (μF) and ESR value (mΩ) were measured. Specifically, the initial capacitance (μF) of the electrolytic capacitor at a frequency of 120 Hz was measured using a four-terminal LCR meter. Furthermore, the ESR value (mΩ) of the electrolytic capacitor at a frequency of 100 kHz was measured using a four-terminal LCR meter.
As an accelerated test, the capacitance (μF) and ESR value (mΩ) after the electrolytic capacitor was left at 125° C. for 4000 hours were measured in the same manner as in the case of the initial characteristics.
The capacitance and ESR value 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 electrolyte, and the performance was evaluated. We conducted an evaluation.

《Example 2》
The same procedure as in Example 1 was used, except that a solution containing γBL: sulfolane: glycerin: mono(ethyldimethylamine) phthalate (solute) = 25:25:25:25 (mass ratio) was used as the electrolyte. , we fabricated an electrolytic capacitor and evaluated its performance.

《Example 3》
An electrolytic capacitor was prepared in the same manner as in Example 1, except that a solution containing γBL: glycerin: mono(ethyldimethylamine) phthalate (solute) = 70:5:25 (mass ratio) was used as the electrolyte. It was manufactured and its performance was evaluated.
Table 1 shows the results of Examples and Comparative Examples.

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

INDUSTRIAL APPLICATION This invention can be utilized for the electrolytic capacitor which uses a conductive polymer as a cathode material.

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 tape

Claims (6)

a capacitor element including 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 containing a nonaqueous solvent, a glycerin compound, and an ionic solute;
unevenness is formed on the surface of the anode body,
The conductive polymer includes at least one selected from the group consisting of polythiophene and derivatives thereof and polystyrene sulfonic acid,
The non-aqueous solvent contains lactones,
The glycerin compound includes at least one selected from the group consisting of glycerin and polyglycerin,
The content of the glycerin compound in the electrolytic solution is 10% by mass or more and 50% by mass or less,
The electrolytic capacitor, wherein the mass of the glycerin compound contained in the electrolytic solution is in a range of 2 to 100 times the mass of the conductive polymer attached to the capacitor element. The electrolytic capacitor according to claim 1 , wherein the non-aqueous solvent further contains sulfones. The glycerin compound includes the polyglycerin,
The electrolytic capacitor according to claim 1 or 2 , wherein the polyglycerin contains 2 to 20 glycerin units. The electrolytic capacitor according to claim 3 , wherein the content of the polyglycerin in the electrolytic solution is 10% by mass or more and 50% by mass or less. The electrolytic capacitor according to claim 1 or 2 , wherein the glycerin compound includes the glycerin. The electrolytic capacitor according to claim 5 , wherein the content of the glycerin in the electrolytic solution is 10% by mass or more and 50% by mass or less.

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