JP2006108159A - Electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolytic capacitor having high electrostatic capacitance characteristic. <P>SOLUTION: A capacitor element includes an electrode foil to which an aggregate of fine particles made of aluminum which is self-similar in the range of length of 2 μm to 0.01 μm and/or aluminum for forming an aluminum oxide layer is adhered to one side or both sides of smooth aluminum foil in which a foil thickness is 15 μm to less than 35 μm, and a separator wound on one side or both sides of smooth aluminum foil. Since the capacitor element contains water soluble metal complex containing a phosphoric acid and an electrolyte which contains water as a main solvent, the electrolytic capacitor having the high electrostatic capacity characteristic can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an electrolytic capacitor, and more particularly to an aluminum electrolytic capacitor realizing high capacitance characteristics.

    The electrolytic capacitor generally has the following configuration. That is, a high-purity aluminum foil formed in a band shape is chemically or electrochemically etched to expand the surface, and the expanded aluminum foil is subjected to chemical conversion in a chemical conversion solution such as an aqueous ammonium borate solution. By doing so, a capacitor element is formed by winding an anode foil in which an oxide film layer is formed on the surface of the aluminum foil and a cathode foil obtained by enlarging the same high-purity aluminum foil through a separator. The capacitor element is impregnated with a driving electrolyte solution and stored in a metal bottomed cylindrical outer case. Further, a sealing body made of elastic rubber is accommodated in the opening end portion of the outer case, and the opening end portion of the outer case is sealed by drawing to constitute an electrolytic capacitor.

As an electrolytic solution impregnated in a capacitor element of a small-sized, low-pressure electrolytic capacitor, conventionally, an ethylene glycol as a main solvent and an ammonium salt such as adipic acid or benzoic acid as a solute, or γ-butyrolactone As a main solvent, quaternary cyclic amidinium salts such as phthalic acid and maleic acid are used as solutes.

In recent years, electronic information devices have been digitized, and further, the driving frequency of a microprocessor (MPU), which is the heart of these electronic information devices, has been increased. Along with this, power consumption has increased, reliability problems due to heat generation have become obvious, and as a countermeasure, driving voltage has been reduced. Here, a DC-DC converter called a voltage control module (VRM) is widely used as a circuit for supplying high-precision power to a microprocessor, and a series equivalent resistance ( Many capacitors with low ESR) are used.

However, the increase in the driving frequency of the microprocessor is remarkable, and accordingly, the power consumption increases. In order to cope with this, the power supplied from the capacitor is required to be increased in order to prevent a voltage drop. That is, it is necessary to be able to supply a large amount of power in a short time. For this reason, the above-described electrolytic capacitor is required to have a lower ESR characteristic than before, along with an increase in capacity, size and voltage. The

Therefore, there is an attempt to further reduce the specific resistance of the electrolytic solution by adding a large amount of water to the electrolytic solution. However, in such an electrolytic capacitor, although the specific resistance of the electrolyte is low, the effect of reducing the ESR of the electrolytic capacitor is There is a problem in that it is not sufficient and the leaving characteristics are not good.

In the electrolytic capacitor as described above, an electrolytic capacitor in which the ESR characteristic is further reduced and the leaving characteristic is improved has been proposed (Patent Document 1).
JP 2003-297694 A

By the way, the demand for downsizing of electronic information equipment is constant, and there is always a problem of improving the capacitance for that purpose. Accordingly, an object of the present invention is to improve the capacitance of the electrolytic capacitor as described above.

The present invention relates to an agglomeration of fine particles made of aluminum having a self-similarity in a length range of 2 μm to 0.01 μm and / or aluminum having an aluminum oxide layer formed on the surface of one or both surfaces of a smooth aluminum foil in an electrolytic capacitor. A capacitor element in which an electrode foil to which an object is attached and a separator are wound includes a water-soluble metal complex containing phosphoric acid and an electrolytic solution containing water as a main solvent.

Here, “self-similarity within a length range of 2 μm to 0.01 μm” means that the particle diameter of fine particles made of aluminum and / or aluminum having an aluminum oxide layer formed on the surface is “2 μm to 0.01 μm”. Does not mean. Fine particles agglomerate or pile up. As a result, fine irregularities are formed on the surface of the smooth aluminum foil in a self-similar manner, that is, in a fractal shape, and the scale that makes this self-similarity is “2 μm to 0.01 μm”. It means that.

  Further, in the present invention, an electrode foil having an agglomerate of fine particles composed of aluminum with an aluminum oxide layer formed on the surface is used. However, an agglomerate of fine particles composed of aluminum adheres to the surface of the electrode foil. It is also possible to use an electrode foil that has improved adhesion to the aggregated electrode foil by using an electrode foil having an agglomerate of fine particles made of aluminum with an aluminum oxide layer formed on the surface.

The water-soluble metal complex containing phosphoric acid is a complex compound in which a chelating agent, a metal and phosphoric acid are complexed.

The thickness of the smooth electrode foil is preferably 15 μm or more and less than 35 μm, and the water-soluble metal complex containing phosphoric acid contained in the electrolytic solution used in the present invention is a water-soluble aluminum complex containing phosphoric acid. More preferably, the content of water in the solvent of the electrolytic solution used in the present invention is 35 to 100 wt%.

In addition, when water is used as a main solvent as an electrolytic solution, the resistance as an electrolytic solution is reduced by the action of water, which is the main component of the solvent, and the ESR characteristics as an electrolytic capacitor are improved. This water causes hydration deterioration of the electrode foil, which deteriorates the electrical characteristics after being left for a certain period of time, and in some cases, the pressure valve of the electrolytic capacitor opens. However, in the present invention, since a water-soluble metal complex containing phosphoric acid is contained in the capacitor element, this water-soluble metal complex releases phosphate ions into the electrolytic solution, and phosphorous in the electrolytic solution is discharged. Since it becomes possible to prevent the hydration deterioration of the electrode foil by maintaining an appropriate amount of acid ions, the electrical characteristics after being left for a certain period of time can be maintained in good condition, per unit area ESR characteristics can be greatly improved in combination with an electrode foil having a low resistance value.

Furthermore, in the electrolytic capacitor constructed by winding the electrode foil, the resistance of the electrode foil itself is essentially long because the electrode foil is long, so that the effect of reducing the ESR of the entire electrolytic capacitor becomes extremely large.

If the metal complex is an aluminum complex, a water-soluble metal complex containing phosphoric acid can be formed in the capacitor element of the electrolytic capacitor.

And when the content rate of the water in a solvent is 35-100 wt%, since ESR of an electrolytic capacitor reduces, it is preferable.

  In the present invention, an electrode foil having such a thickness is used, and the effect of agglomerates of fine particles composed of self-similar aluminum and / or aluminum having an aluminum oxide layer formed on the surface, and the static of the electrolyte used in the present invention. Due to the synergistic action with the capacitance increasing effect, an electrolytic capacitor having a high capacitance can be realized.

That is, the electrode foil used in the present invention has an aggregate of fine particles made of aluminum having self-similarity in a length range of 2 μm to 0.01 μm and / or aluminum having an aluminum oxide layer formed on the surface on one or both surfaces. Although it seems that it adheres and has a surface area equal to or larger than a layer having a smaller thickness than the etched portion of the conventional electrode foil, a large capacitance can be obtained. Further, since the electrolyte used in the present invention uses a solvent mainly composed of water, the foil capacity is increased from that in the non-aqueous electrolyte, and the dielectric oxide film becomes thinner due to the action of the chelating agent dissolving the oxide film. The capacitance increases due to the effect of increasing the capacitance. As described above, an unprecedented high capacitance electrolytic capacitor can be obtained by the synergistic action of the electrode foil and the electrode used in the present invention.

  The embodiment of the present invention will be specifically described. The aluminum foil is a high-purity foil having a purity of 99.9% or more with a foil thickness of 15 μm or more and less than 35 μm, and this aluminum foil is maintained at a temperature of 300 ° C. in a reduced-pressure atmosphere containing a mixed gas of nitrogen and oxygen. Aluminum is deposited at a deposition rate of 300 liters / sec, and the particles are made of aluminum that is self-similar in a length range of 2 μm to 0.01 μm on the surface of a smooth aluminum foil and / or aluminum that has an aluminum oxide layer formed on the surface. Aggregates were deposited. This aluminum foil was used as an electrode foil on the cathode side, and further, in order to form a dielectric film on the surface of this aluminum foil, it was subjected to chemical conversion in a chemical conversion solution comprising a phosphoric acid aqueous solution or the like to obtain an anode side electrode foil.

If necessary, a 0.1 to 10 V, preferably 0.3 to 5 V, chemical conversion film is formed on the cathode-side electrode foil, which is more preferable because ESR is reduced and high-temperature life characteristics are improved.

Further, if necessary, it is preferable to form a layer made of a metal compound or metal with low oxidizability such as titanium nitride or titanium on the surface of the electrode foil on the cathode side, because the capacitance increases. Here, it is more preferable that a chemical conversion film is formed on the cathode-side electrode foil, and a layer made of the above-mentioned metal or metal compound having low oxidizability is formed on the chemical conversion film.

The anode-side extraction terminal and the cathode-side extraction terminal are attached to the above-described anode-side electrode foil and cathode-side electrode foil, and are wound through a separator. Thereafter, a voltage is applied in the chemical conversion solution to repair the dielectric oxide film damaged in the previous steps. By using the anode-side electrode foil of the present invention and the conventional cathode-side electrode foil, the conventional anode-side electrode foil and the cathode-side electrode foil of the present invention, the effects of the present invention can be obtained. It goes without saying that the maximum effect can be obtained by using both the anode-side electrode foil and the cathode-side electrode foil of the present invention.

As the separator, Manila paper, kraft paper, glass separator, or the like, or a nonwoven fabric made of synthetic fibers such as vinylon or polyester, or a porous separator can be used.

Then, the capacitor element thus formed is impregnated with an electrolytic solution using a water-based solvent of the present invention, housed in a low and low cylindrical metal case, and a sealing rubber is attached to the opening end. And sealing by caulking.

The content of water in the solvent is 35 to 100 wt%, and since the low temperature characteristics are good at 75 wt% or less, it is preferably 35 to 75 wt%. Such an electrolytic solution improves the ESR characteristics of the electrolytic capacitor.

The capacitor element includes a water-soluble metal complex containing phosphoric acid and an electrolytic solution containing water as a main solvent. This water-soluble metal complex, which is a complex compound formed by complexing a chelating agent with a metal and phosphoric acid, is composed of a chelating agent and a metal or metal compound, and a compound that generates a phosphate ion in a solvent (phosphorus generating compound). Are mixed in a solvent, and the solvent is removed from this solution. The solvent used here may be any solvent that dissolves the chelating agent, metal or metal compound, or phosphorus-forming compound, and water, ethylene glycol, γ-butyrolactone, and the like are particularly preferable. The water-soluble metal complex thus formed can be added to the electrolytic solution and contained in the capacitor element. Alternatively, the water-soluble metal complex may be attached to the electrode foil or the separator by coating or the like and contained in the capacitor element.

The water-soluble metal complex containing phosphoric acid gradually releases phosphate ions into the electrolytic solution, and keeps the phosphate ions in the electrolytic solution in an appropriate amount over a long period of time. And even if it uses the electrolyte solution which made water the main solvent which improved the ESR characteristic with the phosphate ion held at this appropriate amount, deterioration of the electrode foil due to moisture can be suppressed, and various electrical characteristics can be obtained. It can be maintained well.

Moreover, a water-soluble metal complex can also be contained in a capacitor element by impregnating the capacitor element with an electrolytic solution to which a chelating agent and a metal or a metal compound and a phosphorus-forming compound are added. In this electrolytic solution, a water-soluble metal complex is formed by a reaction similar to the reaction in the solvent as described above. By impregnating this electrolytic solution into the capacitor element, the water-soluble metal complex is contained in the capacitor element. be able to. Further, when the electrode foil is aluminum, aluminum ions are dissolved from the electrode foil, so that a water-soluble aluminum complex containing phosphoric acid can be formed without adding a metal or a metal compound.

The following are mentioned as a chelating agent. That is, citric acid, tartaric acid, gluconic acid, malic acid, lactic acid, glycolic acid, α-hydroxybutyric acid, hydroxymalonic acid, α-methylmalic acid, α-hydroxycarboxylic acids such as dihydroxytartaric acid, γ-resorcylic acid, β- Resorcylic acid, trihydroxybenzoic acid, hydroxyphthalic acid, dihydroxyphthalic acid, phenol tricarboxylic acid, aurin tricarboxylic acid, aromatic hydroxycarboxylic acids such as eriochrome cyanine R, sulfocarboxylic acids such as sulfosalicylic acid, guanidines such as dicyandiamide, Sugars such as galactose and glucose, lignins such as lignosulfonate, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), glycol etherdiaminetetraacetic acid (GEDTA), diethylenetriamine Aminopolycarboxylic acids such as acetic acid (DTPA), hydroxyethylethylenediaminetriacetic acid (HEDTA), triethylenetetraminehexaacetic acid (TTHA), or salts thereof. And as these salts, ammonium salt, aluminum salt, sodium salt, potassium salt etc. can be used.

Examples of the metal or metal compound used for the water-soluble metal complex containing phosphoric acid include aluminum, iron, copper, nickel, manganese, zinc, calcium, magnesium, barium, lead, titanium, niobium, tantalum, and the like. A metal that forms a complex with a chelating agent can be used. In addition, as the metal compound, a compound that generates a metal ion in a solvent such as an oxide, a hydroxide, a chloride, or a metal salt such as a sulfate or carbonate can be used. Of these, aluminum is preferable.

And as a phosphorus production | generation compound, the phosphorus compound shown by general formula (Formula 1), these salts, these condensates, or the salt of these condensates can be mentioned.

(Wherein R ₁ and R ₂ are —H, —OH, —R ₃ , —OR ₄ : R ₃ and R ₄ are an alkyl group, an aryl group, a phenyl group, and an ether group)

Examples of these phosphorus-forming compounds include the following. Orthophosphoric acid, phosphorous acid, hypophosphorous acid, and salts thereof, and salts thereof include ammonium salt, aluminum salt, sodium salt, calcium salt, and potassium salt. Orthophosphoric acid and its salt decompose in aqueous solution to produce phosphate ions. In addition, phosphorous acid, hypophosphorous acid, and salts thereof are decomposed in an aqueous solution to generate phosphite ions and hypophosphite ions, and then oxidized to phosphate ions.

In addition, phosphoric acid compounds such as ethyl phosphate, diethyl phosphate, butyl phosphate, and dibutyl phosphate, phosphonic acid compounds such as 1-hydroxyethylidene-1,1-diphosphonic acid, aminotrimethylenephosphonic acid, and phenylphosphonic acid Is mentioned. Moreover, phosphinic acid compounds, such as methylphosphinic acid and butyl phosphinate, are mentioned.

Furthermore, the following condensed phosphoric acid or salts thereof can be mentioned. Linear condensed phosphoric acid such as pyrophosphoric acid, tripolyphosphoric acid and tetrapolyphosphoric acid, cyclic condensed phosphoric acid such as metaphosphoric acid and hexametaphosphoric acid, or such chain and cyclic condensed phosphoric acid are combined. . And as a salt of these condensed phosphoric acids, ammonium salt, aluminum salt, sodium salt, calcium salt, potassium salt etc. can be used.

These are also phosphate-forming compounds that generate phosphate ions in an aqueous solution, or generate phosphite ions and hypophosphite ions, which are then oxidized to phosphate ions.

Among these, normal phosphoric acid or a salt thereof, condensed phosphoric acid, or a phosphoric acid compound that easily generates phosphate ions is preferable. Further, normal condensed phosphoric acid, pyrophosphoric acid, tripolyphosphoric acid or the like that produces a large amount of phosphate ions relatively quickly with respect to the amount added, or a salt thereof is preferable. In addition, the effect of this invention can be acquired if it is a substance which produces a phosphate ion in aqueous solution other than these compounds.

The solute contained in the electrolyte includes ammonium salts, amine salts, quaternary ammonium salts, and quaternary salts of cyclic amidine compounds, which are usually used in electrolyte solutions for electrolytic capacitors and contain an acid conjugate base as an anion component. Can be mentioned. The amines constituting the amine salt include primary amines (methylamine, ethylamine, propylamine, butylamine, ethylenediamine, etc.), secondary amines (dimethylamine, diethylamine, dipropylamine, methylethylamine, diphenylamine, etc.), tertiary amines (trimethylamine). , Triethylamine, tripropylamine, triphenylamine, 1,8-diazabicyclo (5,4,0) -undecene-7, etc.). The quaternary ammonium constituting the quaternary ammonium salt includes tetraalkylammonium (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, methyltriethylammonium, dimethyldiethylammonium, etc.), pyridium (1-methylpyridium) 1-ethylpyridium, 1,3-diethylpyridium, etc.). Examples of the cation constituting the quaternary salt of the cyclic amidine compound include cations obtained by quaternizing the following compounds. That is, imidazole monocyclic compounds (1-methylimidazole, 1,2-dimethylimidazole, 1,4-dimethyl-2-ethylimidazole, imidazole homologues such as 1-phenylimidazole, 1-methyl-2-oxymethylimidazole, Oxyalkyl derivatives such as 1-methyl-2-oxyethylimidazole, nitro and amino derivatives such as 1-methyl-4 (5) -nitroimidazole, 1,2-dimethyl-5 (4) -aminoimidazole), benzimidazole (1-methylbenzimidazole, 1-methyl-2-benzylbenzimidazole, etc.), compounds having a 2-imidazoline ring (1-methylimidazoline, 1,2-dimethylimidazoline, 1,2,4-trimethylimidazoline, 1, 4-Dimethyl-2-ethylimidazoli , 1-methyl-2-phenylimidazoline, etc.), compounds having a tetrahydropyrimidine ring (1-methyl-1,4,5,6-tetrahydropyrimidine, 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine) 1,8-diazabicyclo [5.4.0] undecene-7, 1,5-diazabicyclo [4.3.0] nonene-5 and the like.

Anionic components include adipic acid, glutaric acid, succinic acid, benzoic acid, isophthalic acid, phthalic acid, terephthalic acid, maleic acid, toluic acid, enanthic acid, malonic acid, formic acid, 1,6-decanedicarboxylic acid, 5, Decane dicarboxylic acid such as 6-decanedicarboxylic acid, octane dicarboxylic acid such as 1,7-octane dicarboxylic acid, organic acid such as azelaic acid and sebacic acid, or polyvalent boric acid obtained from boric acid, boric acid and polyhydric alcohol Examples thereof include conjugate bases of inorganic acids such as alcohol complex compounds, phosphoric acid, carbonic acid, and silicic acid. Among these, decanedicarboxylic acid, octanedicarboxylic acid, azelaic acid, sebacic acid, adipic acid, glutaric acid, succinic acid, benzoic acid, isophthalic acid, formic acid and other organic carboxylic acids, or boric acid and boric acid are preferred. It is a polyhydric alcohol complex compound.

And when at least 1 type of adipic acid or its salt is used as a solute, ESR will reduce further. The content of this adipic acid or a salt thereof is 5 to 23 wt%, preferably 8 to 18 wt% in the electrolytic solution. Above this range, the specific resistance decreases, and below this range, the low temperature characteristics are good. The content of other solutes is also about 5 to 23 wt%, preferably 8 to 18 wt% of the entire electrolyte.

Here, it is preferable to use formic acid or a salt thereof as a solute because ESR is reduced. These contents are 3-15 wt% in an electrolyte solution, Preferably it is 6-12 wt%. Below this range, the effect of reducing ESR is small, and when this range is exceeded, blistering and valve opening occur due to gas generation. Furthermore, ESR is reduced when 3-15 wt% organic acids or their salts are added. Examples of the organic acid include the adipic acid and glutaric acid described above. Of these, adipic acid is preferred.

In the electrolytic solution of the present invention, water is the main solvent, but a protic polar solvent, an aprotic polar solvent, water, and a mixture thereof can be used as a secondary solvent. Protic polar solvents include monohydric alcohols (methanol, ethanol, propanol, butanol, hexanol, cyclohexanol, cyclopentanol, benzyl alcohol, etc.), polyhydric alcohols and oxyalcohol compounds (ethylene glycol, propylene glycol, glycerin). Methyl cellosolve, ethyl cellosolve, 1,3-butanediol, methoxypropylene glycol, etc.). Examples of aprotic polar solvents include amides (N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-dimethylformamide, N-methylacetamide, hexamethylphosphoric amide, etc.), lactones (Γ-butyrolactone, δ-valerolactone etc.), cyclic amides (N-methyl-2-pyrrolidone etc.), carbonates (ethylene carbonate, propylene carbonate etc.), nitriles (acetonitrile etc.), oxides (dimethyl sulfoxide etc. ), 2-imidazolidinone [1,3-dialkyl-2-imidazolidinone (1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, 1,3-di) (N-propyl) -2-imidazolidinone, etc.), 1,3,4-trialkyl A typical example is ru-2-imidazolidinone (1,3,4-trimethyl-2-imidazolidinone, etc.)].

In addition, in order to stabilize the life characteristics of electrolytic capacitors, fragrances such as nitrophenol, nitrobenzoic acid, nitroacetophenone, nitrobenzyl alcohol, 2- (nitrophenoxy) ethanol, nitroanisole, nitrophenetol, nitrotoluene, dinitrobenzene, etc. Group nitro compounds can be added.

In addition, for the purpose of improving the safety of electrolytic capacitors, nonionic surfactants that can improve the withstand voltage of electrolytic solutions, polyoxygens obtained by addition polymerization of polyhydric alcohols and ethylene oxide and / or propylene oxide An alkylene polyhydric alcohol ether compound and polyvinyl alcohol can also be added.

Further, the withstand voltage can be further improved by adding boric acid, polysaccharides (mannit, sorbit, pentaerythritol, etc.), complex compounds of boric acid and polysaccharides, colloidal silica, etc. to the electrolytic solution for electrolytic capacitors of the present invention. Can be measured.

In addition, an oxycarboxylic acid compound or the like can be added for the purpose of reducing leakage current.

Hereinafter, specific examples of the electrolytic capacitor of the present invention will be described. First, a high-purity foil having a thickness of 30 μm and a purity of 99.9% or more is used, and this aluminum foil is kept at a temperature of 300 ° C. in a reduced-pressure atmosphere containing a mixed gas of nitrogen and oxygen, and vapor deposition of about 300 liters / sec. Aluminum was vapor-deposited at a rate, and an aggregate of fine particles of aluminum oxide that was self-similar in a length range of 2 μm to 0.01 μm was adhered to both sides of a smooth aluminum foil to a thickness of 5 μm on each side. This aluminum foil was used as an electrode foil on the cathode side. Further, in order to form a dielectric film on the surface of the aluminum foil in which the agglomerates are adhered to each side with a thickness of 50 μm, the electrode foil on the anode side is formed by chemical conversion in a chemical conversion solution comprising a phosphoric acid aqueous solution or the like. . These electrode foils are wound through a separator to form a capacitor element.

The capacitor element configured as described above is impregnated with a driving electrolyte. The capacitor element impregnated with this electrolytic solution is accommodated in an outer case made of bottomed cylindrical aluminum, a sealing body made of butyl rubber or the like is inserted into the opening end of the outer case, and the end of the outer case is further squeezed. The aluminum electrolytic capacitor is sealed by processing. The prepared electrolytic capacitor has a rated voltage of 10 WV and a case size of 10φ × 12.5L.

The electrolyte used here was prepared as follows. First, 1 part of diethylenetriaminepentaacetic acid, 0.2 part of aluminum hydroxide and 1.5 parts of ammonium dihydrogen phosphate are added to 10 parts of water to complete the chelation reaction and phosphate ion binding reaction, and then the solvent is removed. A water-soluble metal complex containing phosphoric acid was prepared. Subsequently, this metal complex was added to an electrolytic solution composed of 50 parts of water, 18 parts of ethylene glycol, 10 parts of ammonium adipate, and 8 parts of ammonium formate.

On the other hand, as a comparative example, a commonly used etching foil, that is, a high-purity aluminum foil of 99.9% or more is roughened in an etching solution composed of an aqueous hydrochloric acid solution or the like so that the thickness of the unetched portion becomes 30 μm. And formed with fine hole-like etching pits.

As can be seen from (Table 1), the capacitance of the example of the present invention is 1.5 times that of the comparative example. That is, in the electrolytic capacitor of the present invention, since the capacitance per unit thickness of the electrode foil used in the present invention is large, the area of the electrode foil of the capacitor element that can be accommodated in the conventional case size can be increased. As a result, an electrolytic capacitor having good capacitance characteristics is obtained.

Claims (3)

Fine particles made of aluminum having a thickness of 15 μm or more and less than 35 μm on one or both sides of aluminum having a self-similarity in a length range of 2 μm to 0.01 μm and / or aluminum having an aluminum oxide layer formed on the surface. An electrolytic capacitor in which a capacitor element wound with an electrode foil to which aggregates are attached and a separator includes a water-soluble metal complex containing phosphoric acid and an electrolytic solution containing water as a main solvent. The electrolytic capacitor according to claim 1, wherein the metal complex is an aluminum complex. The electrolytic capacitor of Claim 1 or Claim 2 whose content rate of the water in a solvent is 35-100 wt%.