JP2018133479A - Solid electrolytic capacitor, and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor which can achieve the reduction in ESR and leakage current.SOLUTION: A solid electrolytic capacitor comprises: an anode body 11; a dielectric layer 12 disposed on a surface of the anode body 11; a solid electrolyte layer 13 disposed on a surface of the dielectric layer 12; and a cathode layer 16 disposed on a surface of the solid electrolyte layer 13. The cathode layer 16 includes a carbon layer 14 covering at least a part of the solid electrolyte layer 13 and including a graphene oxide; in the graphene oxide, the quantity of oxygen atoms to carbon atoms included in the graphene oxide is 0.1-52 mass%.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a solid electrolytic capacitor and a method for manufacturing the solid electrolytic capacitor, and more particularly to a solid electrolytic capacitor using graphene oxide as at least a part of a carbon layer and a method for manufacturing the solid electrolytic capacitor.

  The carbon layer of the solid electrolytic capacitor is formed by applying a paste made of a conductive component, a solvent, and a binder to the surface of the solid electrolyte layer and drying it. As the conductive component of the carbon layer, for example, ketjen black or graphite is used. Patent Document 1 discloses a solid electrolytic capacitor containing graphene as a conductive component of a carbon layer.

JP-A-2015-195313

  As described in the background art, ketjen black or graphite is used for the carbon layer of the solid electrolytic capacitor. On the other hand, in the solid electrolytic capacitor disclosed in Patent Document 1, graphene is used for the carbon layer for the purpose of reducing the equivalent series resistance (ESR) of the solid electrolytic capacitor.

  However, when graphene is used for the carbon layer of the solid electrolytic capacitor, moisture is not sufficiently permeated through the graphene, so that moisture necessary for regenerating the dielectric oxide film layer is not sufficiently supplied to the dielectric oxide film layer. There is a problem that the leakage current deteriorates.

  The present invention has been made in view of the above problems, and provides a solid electrolytic capacitor and a method for manufacturing the solid electrolytic capacitor capable of realizing a reduction in ESR and a reduction in leakage current.

  A solid electrolytic capacitor according to the present invention includes an anode body, a dielectric layer disposed on the surface of the anode body, a solid electrolyte layer disposed on the surface of the dielectric layer, and a surface of the solid electrolyte layer. The cathode layer includes a carbon layer containing graphene oxide covering at least a part of the solid electrolyte layer, and the graphene oxide contains oxygen atoms with respect to carbon atoms contained in the graphene oxide Is 0.1 to 52% by mass.

  The method of manufacturing a solid electrolytic capacitor according to the present invention includes a step of oxidizing a surface of an anode body to form a dielectric layer, a step of forming a solid electrolyte layer on the surface of the dielectric layer, and a step of forming the solid electrolyte layer. Forming a cathode layer on a surface, and the step of forming the cathode layer includes a step of forming a carbon layer containing graphene oxide so as to cover at least a part of the solid electrolyte layer, and the graphene oxide Is adjusted so that the amount of oxygen atoms relative to the carbon atoms contained in the graphene oxide is 0.1 to 52 mass%.

  According to the present invention, it is possible to provide a solid electrolytic capacitor and a method for manufacturing the solid electrolytic capacitor capable of realizing reduction of ESR and reduction of leakage current.

It is a schematic sectional drawing of the solid electrolytic capacitor concerning embodiment. It is a schematic sectional drawing of the solid electrolytic capacitor concerning an Example. It is a table | surface which shows the evaluation result of the solid electrolytic capacitor concerning an Example. It is a schematic diagram showing a synthesis process of graphene oxide and graphene.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiment. In addition, the drawings are simplified as appropriate for the detailed description.

  FIG. 1 is a schematic cross-sectional view of a solid electrolytic capacitor according to an embodiment. As shown in FIG. 1, the solid electrolytic capacitor 1 according to the present embodiment includes an anode body 11, a dielectric layer 12, a solid electrolyte layer 13, and a cathode layer 16. Here, the cathode layer 16 has a carbon layer 14 and a silver layer 15 and functions as a cathode lead layer for connecting the solid electrolyte layer 13 and the cathode (not shown). The cathode is formed by bending a band-shaped metal plate.

  The anode body 11 is formed using a valve action metal. Examples of the valve action metal include aluminum, tantalum, niobium, titanium, zirconium, hafnium, tungsten, and alloys containing these. These are merely examples, and any material may be used as long as it is a valve metal that can be used as the anode body 11.

  A dielectric layer 12 is formed on the surface of the anode body 11. The dielectric layer 12 can be formed, for example, by anodizing the anode body 11 which is the valve action metal described above. For example, when tantalum is used for the anode body 11, a tantalum oxide film (dielectric layer 12) can be formed on the surface of the anode body 11 by anodizing the anode body 11. For example, the thickness of the dielectric layer 12 is about 1 nm to 500 nm.

  A solid electrolyte layer 13 is formed on the surface of the dielectric layer 12. For the solid electrolyte layer 13, for example, a conductive polymer such as manganese dioxide or PEDOT (poly (3,4-ethylenedioxythiophene)) can be used. In addition, these are examples and will not be specifically limited if it can be used as a solid electrolyte. For example, the thickness of the solid electrolyte is about 1 nm to 200 μm.

  In the solid electrolytic capacitor 1 according to the present embodiment, a precoat layer may be provided between the dielectric layer 12 and the solid electrolyte layer 13. The thickness of a precoat layer can be 1 micrometer or less, for example. Examples of the precoat layer include silicon, silicone, various resins (polyvinyl alcohol, polyvinyl acetate, polycarbonate, polyacrylate, polymethacrylate, polystyrene, polyurethane, polyacrylonitrile, polybutadiene, polyisoprene, polyether, polyester, polyethylene terephthalate, Polybutylene terephthalate, polyamide, polyimide, butyral resin, silicone resin, melamine resin, alkyd resin, bisphenol A type epoxy, bisphenol F type epoxy, alicyclic epoxy) and the like, but is not limited thereto. In the case where the solid electrolyte layer 13 is formed under high temperature conditions, it is preferable to use silicon or silicone resin. Moreover, when using various resin, it is desirable that the hydrophilic functional group is contained, for example. By including functional groups in various resins, self-healing of the dielectric layer 12 can be promoted when defects occur in the dielectric layer 12 that is an oxide film.

  As a method for forming the precoat layer, any method may be used as long as the precoat layer can be formed on the surface of the dielectric layer 12. For example, the precoat layer can be formed on the surface of the dielectric layer 12 by repeating the step of immersing and drying the element formed up to the dielectric layer 12 in a solution containing the components of the precoat layer.

  A cathode layer 16 composed of a carbon layer 14 and a silver layer 15 is formed on the surface of the solid electrolyte layer 13. The carbon layer 14 is formed so as to cover at least a part of the surface of the solid electrolyte layer 13. The carbon layer 14 contains graphene oxide. The carbon layer 14 may contain graphene. The carbon layer 14 may contain a resin material. The details of the carbon layer 14 containing graphene oxide in the present embodiment will be described later.

  A silver layer 15 is formed on the surface of the carbon layer 14. The silver layer 15 is made of a silver paste in which silver and a resin are mixed. The silver layer 15 functions as a conductive binder. Although silver is used for the silver layer 15 in the present embodiment, it is not particularly limited as long as it is a material that functions as a conductive binder, and any material may be used. For example, the thickness of the silver layer 15 is about 10 μm to 300 μm.

  The solid electrolytic capacitor 1 according to the present embodiment is characterized in that the carbon layer 14 contains graphene oxide. Below, the carbon layer 14 with which the solid electrolytic capacitor 1 concerning this Embodiment is provided is demonstrated in detail. First, before describing graphene oxide, problems of graphene and graphite will be described.

  Graphene refers to a carbon sheet having a two-dimensional hexagonal lattice structure in which carbon atoms are SP2 bonded with a thickness of one atom. Since the specific properties of graphene are manifested in a laminate of 30 or less carbon sheets, graphene may be formed of one carbon sheet layer, or may be formed of 2 or more and 30 or less layers. Good. Note that graphite and carbon black, which are carbon materials, are formed using graphene, which is a carbon sheet, as a basic structure. For example, a carbon material in which more than 30 carbon sheets are laminated is graphite, which is greatly different from graphene in electrical characteristics, thermal characteristics, and mechanical characteristics.

  As described in the background art, ketjen black or graphite is used for the carbon layer of the solid electrolytic capacitor. On the other hand, in the solid electrolytic capacitor disclosed in Patent Document 1, graphene is used for the carbon layer for the purpose of reducing the ESR of the solid electrolytic capacitor.

  However, when graphene is used for the carbon layer of the solid electrolytic capacitor, moisture is not sufficiently permeated through the graphene, so that moisture necessary for regenerating the dielectric oxide film layer is not sufficiently supplied to the dielectric oxide film layer. There was a problem that the leakage current deteriorated. Thus, in this embodiment, the above problem is solved by using graphene oxide as a material constituting the carbon layer.

Graphene oxide refers to a state in which a functional group such as a hydroxyl group (—OH), a carboxy group (—COOH), or a sulfo group (—SO ₃ H) is added to the graphene that is the above-described carbon sheet. With the addition of functional groups, graphene oxide exhibits solubility in polar solvents such as water. Furthermore, graphene oxide that has become soluble in polar solvents can easily retain and permeate moisture (water molecules). Self-healing function of dielectric oxide film that repairs defects in oxide film by oxidation of acid component and moisture near oxide film when external force or overvoltage is applied to cause a defect in oxide film of dielectric layer 12 Is expressed. Here, when the water | moisture content of an oxide film vicinity is insufficient, the self-repair function is expressed by supplying the water | moisture content which the solid electrolyte layer 13 has to an oxide film. When the moisture in the vicinity of the oxide film and the moisture in the solid electrolyte layer 13 are insufficient, the moisture held by the graphene oxide contained in the carbon layer 14 passes through the solid electrolyte layer 13 and enters the oxide film of the dielectric layer 12. Supplied with. In the case of further lack of moisture, moisture present in the silver layer 15 which is the upper layer of the carbon layer 14 passes through the carbon layer 14 and the solid electrolyte layer 13 and is supplied to the oxide film of the dielectric layer 12. . Such a self-repairing function of the oxide film of the dielectric layer 12 can suppress the occurrence of leakage current due to the defect of the oxide film. In other words, since graphene having a functional group, that is, graphene oxide has sufficient moisture, when a defect occurs in the oxide film of the dielectric layer 12, a repair function is exhibited, and the leakage current of the solid electrolytic capacitor is reduced. It becomes possible to reduce.

  The inventors of the present application have also found that there is a correlation between the amount of oxygen atoms contained in graphene oxide and the value of ESR. Specifically, the amount of oxygen atoms with respect to carbon atoms contained in graphene oxide is 1 to 52% by mass, preferably 1 to 40% by mass, more preferably 1 to 30% by mass, still more preferably 5 to 30% by mass, It has been found that the reduction of the ESR and the reduction of the leakage current of the solid electrolytic capacitor can be realized by setting the content to 10 to 30% by mass most preferably.

  Note that when the amount of oxygen atoms (oxygen content) with respect to the carbon atoms contained in the graphene oxide is more than 52 mass%, the conductivity is remarkably lowered and the ESR is deteriorated. On the other hand, when the oxygen content is less than 0.1% by mass, the chemical conversion ability is not sufficiently exhibited, and the function of repairing the oxide film is hardly exhibited, so that the leakage current increases.

  In this embodiment, the content of oxygen atoms contained in graphene oxide is measured by elemental analysis. As the elemental analysis, for example, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, or the like can be used. In addition, the oxygen content of graphene oxide can be adjusted by reducing the graphene oxide using a reducing agent. Examples of the reducing agent include hydrazine, iodine, sodium, and an amine compound. However, the reducing agent is not limited to this, and any reducing agent may be used.

  Graphene oxide can be synthesized by using a graphene synthesis method such as the Hummers method, the modified Hummers method, the Brodie method, the Staudenmaier method, and the like. Graphene oxide synthesized by these methods is in a solution state. The carbon layer 14 is formed using the graphene oxide in a solution state.

  The carbon layer 14 can be formed by, for example, a method in which graphene oxide in a solution state is immersed in a solid electrolyte layer and dried, or a method using chemical vapor deposition (CVD). For example, the surface of the solid electrolyte layer 13 is obtained by immersing an element formed up to the solid electrolyte layer 13 (that is, an element having the anode body 11, the dielectric layer 12, and the fixed electrolyte layer 13) in a graphene oxide solution and drying it. Alternatively, a carbon layer 14 containing graphene oxide may be formed. Further, for example, the carbon layer 14 containing graphene may be formed on the surface of the solid electrolyte layer 13 using a CVD method, and the carbon layer containing graphene oxide may be formed by performing functional group addition treatment.

  The graphene oxide layer constituting the carbon layer 14 may be a single layer or multiple layers. In the case of a multilayer structure, the step of forming a graphene oxide layer by immersing in a graphene oxide solution and drying may be repeated. Further, when forming the graphene oxide layer, a step of forming the graphene oxide layer by dipping in a graphene oxide solution and drying may be combined with a step of forming the graphene oxide using another method. The number of graphene oxide layers is preferably 1 to 15 layers. Note that the carbon layer may include not only graphene oxide but also graphene or a resin material described below.

  The carbon layer 14 may contain a resin material. By including the resin material, the binding property is improved. Resin materials include polyvinyl alcohol, polyvinyl acetate, polycarbonate, polyacrylate, polymethacrylate, polystyrene, polyurethane, polyacrylonitrile, polybutadiene, polyisoprene, polyether, polyester, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyimide, butyral Resins, silicone resins, melamine resins, alkyd resins, cellulose, nitrocellulose, bisphenol A type epoxies, bisphenol F type epoxies, alicyclic epoxies and the like are included, but are not limited thereto.

  The temperature at which the carbon layer 14 is formed may be high or may be room temperature. Further, the element formed up to the solid electrolyte layer 13 may be heated in a range where the solid electrolyte layer 13 does not deteriorate.

  The atmosphere for forming the carbon layer 14 may be either air or an inert gas atmosphere, and a preferable one is selected depending on the forming method. Argon, helium, and nitrogen gas can be used as the inert gas. When it is desired to reduce the solid electrolyte layer simultaneously with the formation of the carbon layer 14, hydrogen gas, ammonia gas, or the like can be used. Moreover, the pressure at the time of forming the carbon layer 14 may be any of reduced pressure, atmospheric pressure, and increased pressure. For example, in the case of forming a graphene oxide layer by dipping in a graphene oxide solution and drying, the reaction can be performed under atmospheric pressure. In addition, when a graphene oxide layer is formed by a CVD method, it can be performed under reduced pressure.

  In the present embodiment, the graphene oxide contained in the carbon layer 14 has a conductivity of 1 (S / cm) or more, more preferably a conductivity of 10 (S / cm) or more, and even more preferably 100 (S / cm). It has the above conductivity. The conductivity can be adjusted by adjusting the amount of the functional group.

  As described above, in the solid electrolytic capacitor according to the present embodiment, graphene oxide is used as the material constituting the carbon layer. Since graphene oxide has a functional group, it has a property of easily holding and transmitting moisture. For this reason, moisture permeates through the graphene oxide and moisture necessary for regeneration of the dielectric oxide film layer is supplied to the dielectric oxide film layer, so that the self-repair function of the dielectric oxide film can be exhibited. Therefore, it is possible to suppress the occurrence of leakage current due to a defect in the dielectric oxide film. In addition, since graphene oxide has low resistance, ESR of the solid electrolytic capacitor can be reduced.

  Therefore, according to the invention according to the present embodiment described above, it is possible to provide a solid electrolytic capacitor and a method for manufacturing the solid electrolytic capacitor that can realize reduction of ESR and reduction of leakage current.

  In the present invention, the synthesis of graphene oxide is performed during the synthesis of graphene. Here, a series of graphene synthesis flows will be described with reference to FIG. FIG. 4 is a schematic diagram illustrating a synthesis process of graphene oxide and graphene. The modified Hammers method is used for the synthesis of graphene. In the modified Hummers method, first, graphite having a multilayer structure is oxidized using sulfuric acid and potassium permanganate to synthesize graphene oxide. Oxidation of graphite causes functional groups to enter the gaps in the layer structure, thereby increasing the gap between the layers and facilitating separation between the layers. And graphene is obtained by reducing using reducing agents, such as hydrazine.

  However, the process of once oxidizing graphite to obtain graphene oxide and reducing graphene oxide to obtain graphene is complicated. Furthermore, in order to completely remove the functional group from the graphene oxide to which the functional group has been added by oxidation, a single reduction is not sufficient, and it is necessary to perform the reduction repeatedly. From the viewpoint of practical use, the cost increases. In addition, graphene oxide has high resistance (in fact, if the oxygen content is high, the ESR defect rate increases as shown in Example 5). Normally, from the viewpoint of conductivity, graphene oxide is used as a solid electrolytic capacitor. do not use. However, the inventor of the present application has found the usefulness of using graphene oxide in a solid electrolytic capacitor by adjusting the oxygen content of graphene oxide, and is capable of simultaneously realizing ESR reduction and leakage current reduction. It came to offer.

Next, examples of the present invention will be described.
EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited only to these Examples. Although the powder sintered body is evaluated in the following examples, the same effect can be expected with a single plate element or an etched foil.

<Example 1>
FIG. 2 is a schematic cross-sectional view of the solid electrolytic capacitor according to the example. Tantalum powder (Ta), which is a valve metal, was used for the anode body of the solid electrolytic capacitor 2. When forming the anode body, the tantalum powder was formed and then sintered to form a tantalum powder sintered body. Then, the tantalum powder sintered body was electrolytically oxidized at 10 V in a phosphoric acid aqueous solution, and tantalum oxide (Ta ₂ O ₅ ) was formed as a dielectric layer (oxide film layer) on the entire surface of the tantalum powder sintered body. Next, PEDOT was applied to the surface of the dielectric layer and dried to form a solid electrolyte layer (conductive polymer layer).

  Then, the element which formed the solid electrolyte layer in the graphene oxide solution was repeatedly immersed and dried, and the carbon layer was formed. The graphene oxide solution is a solution synthesized using an improved Hummers method in which graphite is oxidized using sulfuric acid and a potassium permanganate solution. Graphite became graphene oxide by the modified Hummers method. This graphene oxide was reduced and redissolved before use. The number of graphene layers is 10 on average, the oxygen content is 0.1% by mass, and the thickness of the carbon layer is 1 μm.

  The amount of oxygen atoms (oxygen content) relative to the carbon atoms contained in the graphene oxide in the produced carbon layer was measured. The oxygen content of the carbon layer was specified by XPS analysis (measuring instrument: Quantum 2000 manufactured by ULVAC-PHI, X-ray source: Al). The range of 50 μm on the measurement surface of the carbon layer 14 is scanned, and the result of conversion into the mass ratio (mass%) from the measurement result of the element ratio (at%) of carbon (C) and oxygen (O) is shown in FIG. Shown in the table. The oxygen content shown in the table of FIG. 3 shows the result after adjusting the oxygen content using hydrazine as a reducing agent.

  Furthermore, a silver paste layer (thickness: 30 μm) was formed on the carbon layer to obtain a solid electrolytic capacitor according to Example 1. ESR and leakage current were evaluated for 100 manufactured capacitors. The table showing the percentage of the number of capacitors showing the leakage current failure rate and the ESR failure rate at each oxygen content measured above in 100 capacitors is shown in the table of FIG.

<Example 2>
As the solid electrolytic capacitor according to Example 2, a solid electrolytic capacitor in which a carbon layer was formed using graphene oxide having an oxygen content of 1% by mass was manufactured. The oxygen content was adjusted by adjusting the reduction time of hydrazine. The rest is the same as in the first embodiment.

<Example 3>
As a solid electrolytic capacitor according to Example 3, a solid electrolytic capacitor in which a carbon layer was formed using graphene oxide having an oxygen content of 5% by mass was manufactured. The oxygen content was adjusted by adjusting the reduction time of hydrazine. The rest is the same as in the first embodiment.

<Example 4>
As a solid electrolytic capacitor according to Example 4, a solid electrolytic capacitor in which a carbon layer was formed using graphene oxide having an oxygen content of 10% by mass was manufactured. The oxygen content was adjusted by adjusting the reduction time of hydrazine. The rest is the same as in the first embodiment.

<Example 5>
As a solid electrolytic capacitor according to Example 5, a solid electrolytic capacitor in which a carbon layer was formed using graphene oxide having an oxygen content of 52% by mass was manufactured. The oxygen content was adjusted by adjusting the reduction time of hydrazine. The rest is the same as in the first embodiment.

<Example 6>
As a solid electrolytic capacitor according to Example 6, a solid electrolytic capacitor in which a carbon layer was formed using graphene oxide having an oxygen content of 41% by mass was manufactured. The oxygen content was adjusted by adjusting the reduction time of hydrazine. The rest is the same as in the first embodiment.

<Example 7>
As a solid electrolytic capacitor according to Example 7, a solid electrolytic capacitor in which a carbon layer was formed using graphene oxide having an oxygen content of 30% by mass was manufactured. The oxygen content was adjusted by adjusting the reduction time of hydrazine. The rest is the same as in the first embodiment.

<Example 8>
As a solid electrolytic capacitor according to Example 8, graphene / graphene oxide having an oxygen content of 10% by mass by mixing graphene oxide having an oxygen content of 52% by mass and graphene having an oxygen content of 0.05% by mass A solid electrolytic capacitor having a carbon layer formed using the mixture was produced. The rest is the same as in the first embodiment.

<Comparative Example 1>
As a solid electrolytic capacitor according to Comparative Example 1, a solid electrolytic capacitor in which a carbon layer was formed using graphite was produced. The rest is the same as in the first embodiment.

<Comparative example 2>
As a solid electrolytic capacitor according to Comparative Example 2, a solid electrolytic capacitor was produced in which a carbon layer was formed using graphene to which no functional group was added. The rest is the same as in the first embodiment.

<Examination of evaluation results: Leakage current>
Examples 1-8 and Comparative Examples 1-2 are compared about the relationship between oxygen content and a leakage current defect rate. Examples 1 to 8 have an oxygen content of 0.1% by mass or more by addition of a functional group, but Comparative Examples 1 and 2 have no oxygen content because no such functional group is added. 0.05% by mass. Therefore, when the leakage current is examined, in Examples 1 to 8 in which the oxygen content is 0.1% by mass or more, the leakage current failure rate is suppressed to 5% or less, whereas in Comparative Examples 1 to 2, the leakage current is The current failure rate is as high as 12% or more. In addition, when oxygen content was adjusted to 10 mass% or more (Examples 4-8), the leakage current defect rate showed the most preferable value with 2%. According to this result, the functional group is added in Examples 1 to 8 to express a self-repair function, and when a defect occurs in the tantalum oxide (oxygen film) that is the dielectric layer, leakage occurs. It is thought that the current was reduced. Therefore, compared with Comparative Examples 1 and 2 in which no functional group is added and the leakage current defect rate is high, in the solid electrolytic capacitor of the present invention, the functional group is added and the oxygen content is adjusted to 0.1% by mass or more. The leakage current can be reduced by forming a carbon layer using graphene oxide. In Example 8 using a mixture of graphene oxide and graphene for the carbon layer, the leakage current was reduced as in Examples 1 to 7 using graphene oxide for the carbon layer.

<Examination of evaluation results: ESR>
Examples 1-8 and Comparative Examples 1-2 are compared about the relationship between oxygen content and ESR defect rate. First, as shown in Comparative Example 2 in FIG. 3, when graphene having an oxygen content of 0.05 mass% was used for the carbon layer, the ESR failure rate was 2%. However, as shown in Comparative Example 1, when graphite was used for the carbon layer, the ESR defect rate increased significantly to 18%. Therefore, when graphite was used for the carbon layer, the ESR was higher than when graphene was used for the carbon layer.

  In Examples 1 to 7, since graphene oxide was used for the carbon layer, the ESR defect rate was lower than that of Comparative Example 1 in which graphite was used for the carbon layer. Specifically, in Examples 1 to 7, the ESR defect rate was in the range of 2 to 6%. In Example 8 using a mixture of graphene oxide and graphene for the carbon layer, the ESR defect rate was low (2%) as in Examples 1-7. On the other hand, as shown in Example 5, when the oxygen content of graphene oxide was 52% by mass, the ESR defect rate was 6%. That is, when the oxygen content of graphene oxide is further increased, the ESR defect rate is increased. Therefore, in consideration of the results of Examples 1 to 8, the oxygen content of graphene oxide needs to be 52% by mass or less, more preferably 40% by mass or less, and further preferably 30% by mass or less in order to reduce ESR. There is.

<Examination of evaluation results: Leakage current and ESR>
From the above results, the oxygen content and the leakage current have a correlation, and at the same time, the oxygen content and the ESR also have a correlation. When these results are combined, the oxygen content is 0.1 to 52% by mass, preferably 1 to 40% by mass, more preferably 1 to 30% by mass, further preferably 5 to 30% by mass, and most preferably 10 to 10% by mass. By forming the carbon layer using graphene oxide that is 30% by mass, it is possible to provide a solid electrolytic capacitor that can reduce ESR and leakage current.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention.

1, 2 Solid electrolytic capacitor 11 Anode body 12 Dielectric layer 13 Solid electrolyte layer 14 Carbon layer 15 Silver layer 16 Cathode layer

Claims (8)

An anode body;
A dielectric layer disposed on a surface of the anode body;
A solid electrolyte layer disposed on a surface of the dielectric layer;
A cathode layer disposed on the surface of the solid electrolyte layer,
The cathode layer includes a carbon layer containing graphene oxide covering at least a part of the solid electrolyte layer,
In the graphene oxide, the amount of oxygen atoms relative to the carbon atoms contained in the graphene oxide is 0.1 to 52 mass%.
Solid electrolytic capacitor.   2. The solid electrolytic capacitor according to claim 1, wherein the graphene oxide has an oxygen atom content of 1 to 40 mass% with respect to carbon atoms contained in the graphene oxide.   2. The solid electrolytic capacitor according to claim 1, wherein the graphene oxide has an oxygen atom content of 1 to 30 mass% with respect to carbon atoms contained in the graphene oxide.   The solid electrolytic capacitor according to claim 1, wherein the graphene oxide has an oxygen atom content of 5 to 30 mass% with respect to carbon atoms contained in the graphene oxide.   2. The solid electrolytic capacitor according to claim 1, wherein the graphene oxide has an oxygen atom content of 10 to 30 mass% with respect to carbon atoms contained in the graphene oxide.   The solid electrolytic capacitor according to claim 1, wherein the carbon layer includes a plurality of graphene oxide layers.   The solid electrolytic capacitor according to claim 1, wherein the carbon layer includes a resin material. Oxidizing the surface of the anode body to form a dielectric layer;
Forming a solid electrolyte layer on the surface of the dielectric layer;
Forming a cathode layer on the surface of the solid electrolyte layer,
The step of forming the cathode layer includes the step of forming a carbon layer containing graphene oxide so as to cover at least a part of the solid electrolyte layer,
The graphene oxide is adjusted so that the amount of oxygen atoms with respect to carbon atoms contained in the graphene oxide is 0.1 to 52 mass%.
A method for producing a solid electrolytic capacitor.

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