Solid electrolytic capacitor element and solid electrolytic capacitor

Abstract

A capacitor element included in a solid electrolytic capacitor includes an anode body including a porous portion in at least a surface layer, a dielectric layer, a solid electrolyte layer, and a cathode extraction layer. The solid electrolyte layer contains a first polymer component including a monomer unit that corresponds to a thiophene compound, and a second polymer component including a polymer anion. The solid electrolyte layer has a first portion filled in a void of the porous portion, and a second portion protruding from a main surface of the anode body having the dielectric layer. The second portion is divided into an A portion on the first portion side and a B portion on the opposite side to the first portion. When Raman spectra of the first portion and the second portion are measured, a first peak specific to the first polymer component is observed in the first portion and the A portion, and the first peak is not observed in the B portion.

Description

Solid electrolytic capacitor element and solid electrolytic capacitor

[0001] The present disclosure relates to a solid electrolytic capacitor element and a solid electrolytic capacitor.

[0002] The solid electrolytic capacitor includes, for example, a solid electrolytic capacitor element and a resin outer casing or case that seals the solid electrolytic capacitor element. The solid electrolytic capacitor element includes, for example, an anode body, a dielectric layer formed on the surface of the anode body, and a cathode portion that covers at least a portion of the dielectric layer. The cathode portion includes a conductive polymer (e.g., a conjugated polymer and a dopant) that covers at least a portion of the dielectric layer. The conductive polymer is also called a solid electrolyte.

[0003] Patent Document 1 proposes a method for manufacturing an electrolytic capacitor, which includes the steps of impregnating an anode body having a dielectric coating formed on its surface with a first dispersion solution containing particles of a first conductive polymer and a first solvent, and then impregnating the anode body with a second dispersion solution containing particles of a second conductive polymer and a second solvent, wherein the pH of the first dispersion solution is closer to 7 than the pH of the second dispersion solution.

[0004] JP 2013-58807 A

[0005] Solid electrolytic capacitors are required to have low equivalent series resistance (ESR) in addition to excellent charge / discharge characteristics and voltage resistance.

[0006] a cathode extraction layer covering at least a portion of the surface of the solid electrolyte layer; a first polymer component including a monomer unit corresponding to a thiophene compound; and a second polymer component including a polymer anion; the solid electrolyte layer having, in the anode body having the dielectric layer, a first portion filling voids in the porous portion and a second portion protruding from a main surface of the anode body having the dielectric layer; and a cross section of the solid electrolyte layer taken parallel to a thickness direction of the solid electrolyte layer, the second portion being divided into a portion A on the first portion side and a portion B on the opposite side to the first portion; and when Raman spectra of the first portion and the second portion are measured in the cross section, a first peak characteristic of the first polymer component is observed in the first portion and the portion A, but the first peak characteristic of the first polymer component is not observed in the portion B.

[0007] A second aspect of the present disclosure relates to a solid electrolytic capacitor including at least one of the above-described solid electrolytic capacitor elements.

[0008] A solid electrolytic capacitor having excellent charge / discharge characteristics and voltage resistance, as well as low ESR, can be provided.

[0009] FIG. 1 is a cross-sectional schematic view of a solid electrolytic capacitor according to an embodiment of the present disclosure.

[0010] The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0011] In solid electrolytic capacitors, increasing the thickness of the solid electrolyte layer improves the voltage resistance, but decreases the capacitance and increases the ESR. Reducing the thickness of the solid electrolyte results in high capacitance and low ESR, but decreases the voltage resistance. There is a demand for solid electrolytic capacitors that can maintain high capacitance after repeated charging and discharging (in other words, that have excellent charge and discharge characteristics) while also exhibiting high voltage resistance and low ESR.

[0012] (Technology 1) In view of the above, a solid electrolytic capacitor element according to the present disclosure includes an anode body including a porous portion at least in a surface layer thereof, a dielectric layer covering at least a portion of the surface of the anode body, a solid electrolyte layer covering at least a portion of the dielectric layer, and a cathode extraction layer covering at least a portion of the surface of the solid electrolyte layer. The solid electrolyte layer includes a first polymer component including a monomer unit corresponding to a thiophene compound and a second polymer component including a polymer anion. In the anode body having the dielectric layer, the solid electrolyte layer has a first portion filling the voids of the porous portion and a second portion protruding from a main surface of the anode body having the dielectric layer. In a cross section of the solid electrolyte layer taken parallel to the thickness direction of the solid electrolyte layer, the second portion is divided into a portion A on the side of the first portion and a portion B on the opposite side of the first portion. When the Raman spectra of the first and second portions of the cross section are measured, a first peak specific to the first polymer component is observed in the first and second portions, while a first peak specific to the first polymer component is not observed in the second portion. Hereinafter, the solid electrolytic capacitor element may be simply referred to as a capacitor element. Furthermore, a monomer corresponding to a thiophene compound may be referred to as a first monomer, and a monomer unit corresponding to a thiophene compound may be referred to as a first monomer unit.

[0013] In the capacitor element of the present disclosure, at least a first peak characteristic of the first polymer component is observed in the Raman spectra of the first portion and portion A of the solid electrolyte layer. The first polymer component is a conjugated polymer. The Raman spectra of the first portion and portion A are characterized by the highest peak (first peak) attributed to the CC stretching vibration derived from the conjugated polymer. The solid electrolyte constituting the first portion and portion A exhibits high crystallinity due to the high orientation of the conjugated polymer. Furthermore, the conjugated polymer is energetically stabilized in the first portion and portion A. Therefore, the first portion and portion A exhibit characteristic Raman spectra in which the above-described first peak is observed. Such Raman spectra indicate that the first portion and portion A were formed by three-electrode electropolymerization using a precursor of the first polymer component (e.g., a first monomer) and a second polymer component.

[0014] In the first portion and the portion A, a first peak characteristic of a conjugated polymer is observed due to the inclusion of the first monomer unit in the conjugated polymer, and the first peak is attributed to the CC stretching vibration of the thiophene ring in the first monomer unit.

[0015] On the other hand, although part B contains the first polymer component and the second polymer component, the Raman spectrum of part B does not exhibit a characteristic peak such as the first peak. This is thought to be because fluorescence inhibits the observation of Raman scattered light from the polymer components. Such a Raman spectrum indicates that part B is formed from a liquid dispersion containing the first polymer component and the second polymer component. In preparing the liquid dispersion, polymerization of a conjugated polymer precursor proceeds in the presence of polymer anions in a liquid phase, resulting in a liquid dispersion in which particles of a conductive polymer (more specifically, a conductive polymer containing the first polymer component and the second polymer component) are dispersed. It is thought that the high-molecular-weight polymer anions are more likely to segregate in the resulting conductive polymer particles than in the conjugated polymer precursor. When a liquid dispersion is used, part B is formed by conductive polymer particles with segregated polymer anions, and therefore, the Raman spectrum of part B does not exhibit a characteristic peak such as the first peak due to fluorescence emission from the segregated polymer anions.

[0016] In this way, in the capacitor element of the present disclosure, by forming the first portion and the portion A by electrolytic polymerization, the voids of the porous portion can be densely filled with solid electrolyte and the adhesion between the first portion and the second portion can be enhanced. Therefore, excellent charge / discharge characteristics can be ensured. Furthermore, in addition to the high adhesion between the first portion and the second portion, by forming the second portion from a liquid dispersion, a low ESR and a high voltage resistance can be obtained.

[0017] (Technology 2) In the above (Technology 1), when the average thickness of the second portion from the main surface is T, the average thickness of the portion B may be 0.15 T or more. In this case, higher voltage resistance can be ensured.

[0018] (Technology 3) In the above (Technology 1) or (Technology 2), the cathode extraction layer may include a carbon particle-containing layer covering at least a portion of the surface of the solid electrolyte layer, and a metal-containing layer covering at least a portion of the surface of the carbon particle-containing layer. Even in this case, it is possible to ensure high voltage resistance while ensuring low ESR.

[0019] (Technology 4) In the above (Technology 1) or (Technology 2), the portion B may further contain carbon particles. In this case, the adhesion between the second portion and a cathode extraction layer such as a metal-containing layer can be improved, eliminating the need to provide a carbon particle-containing layer covering the solid electrolyte layer. This allows the thickness of the cathode extraction layer to be reduced, thereby increasing the capacitance per unit volume of the solid electrolytic capacitor.

[0020] (Technology 5) In the above (Technology 4), the cathode extraction layer may include a metal-containing layer covering at least a portion of the surface of the solid electrolyte layer. By including carbon particles in portion B, high adhesion between the second portion and the metal-containing layer is achieved, resulting in a low ESR. Furthermore, the thickness of the cathode extraction layer can be reduced, ensuring a high capacitance per unit volume of the solid electrolytic capacitor.

[0021] (Technology 6) In any one of the above (Technology 1) to (Technology 5), in the Raman spectrum, the position of the first peak is 1200 cm －１ More than 1600cm －１ In this case, high conductivity of the solid electrolyte is easily obtained, which is advantageous in further reducing the ESR.

[0022] (Technology 7) The present disclosure also encompasses a solid electrolytic capacitor. The solid electrolytic capacitor of the present disclosure includes at least one solid electrolytic capacitor element according to any one of (Technology 1) to (Technology 6) above. Such a solid electrolytic capacitor can ensure high charge / discharge characteristics. It also achieves low ESR and high voltage resistance.

[0023] The capacitor element and solid electrolytic capacitor of the present disclosure will be described in more detail below, including the above-mentioned (Technology 1) to (Technology 7), with reference to the drawings as necessary. At least one of the above-mentioned (Technology 1) to (Technology 7) may be combined with at least one of the elements described below, provided that no technical contradiction exists. Note that the drawings are schematic illustrations, and the dimensional ratios (e.g., thickness) of each component may differ from the actual ratios.

[0024] [Solid Electrolytic Capacitor] A solid electrolytic capacitor includes one or more capacitor elements. In the present disclosure, at least one of the capacitor elements included in the solid electrolytic capacitor has the characteristics described in any one of (Technology 1) to (Technology 7) above. It is preferable that 50% or more (more preferably 75% or more) of the capacitor elements included in the solid electrolytic capacitor have the above characteristics, and it is even more preferable that all of the capacitor elements have the above characteristics.

[0025] (Capacitor element) (Anode body) The anode body may contain a valve metal, an alloy containing a valve metal, or a compound containing a valve metal. These materials may be used alone or in combination of two or more. Preferred valve metals include, for example, aluminum, tantalum, niobium, and titanium.

[0026] The anode body includes a porous portion at least in a surface layer. An anode body having a porous portion in a surface layer can be obtained by roughening the surface of a substrate (such as a sheet-like (e.g., foil-like, plate-like) substrate) containing a valve metal by, for example, etching. The roughening can be performed by, for example, etching.

[0027] The anode body may be a compact or a sintered body of particles containing a valve metal. Each of the compact and the sintered body has a porous structure. Each of the compact and the sintered body may be in the form of a sheet, a rectangular parallelepiped, a cube, or a similar shape.

[0028] Typically, the anode body has an anode lead portion including a first end and a cathode forming portion including a second end opposite the first end. The cathode portion is typically formed on the cathode forming portion of the anode body via a dielectric layer. An anode lead terminal may be connected to the anode lead portion.

[0029] (Dielectric Layer) The dielectric layer is formed so as to cover at least a portion of the surface of the anode body. The dielectric layer is an insulating layer that functions as a dielectric. The dielectric layer is formed by anodizing the valve metal on the surface of the anode body using a chemical conversion treatment or the like. The surface of the dielectric layer has a fine uneven shape corresponding to the surface shape of the porous portion of the anode body.

[0030] The dielectric layer may be formed of a material that functions as a dielectric layer. Such a material includes, for example, an oxide of a valve metal. For example, when tantalum is used as the valve metal, the dielectric layer may be Ta. ２ O ５ When aluminum is used as the valve metal, the dielectric layer contains Al ２ O ３ However, the dielectric layer is not limited to these specific examples.

[0031] (Cathode portion) The cathode portion included in the capacitor element includes a solid electrolyte layer covering at least a portion of the dielectric layer and a cathode extraction layer covering at least a portion of the surface of the solid electrolyte layer. The cathode portion is usually formed on at least a portion of the surface of the anode body via a dielectric layer. The solid electrolyte layer and the cathode extraction layer will be described below.

[0032] (Solid Electrolyte Layer) In the present disclosure, the solid electrolyte layer includes a first polymer component including a monomer unit corresponding to a thiophene compound and a second polymer component including a polymer anion. The first polymer component is a π-conjugated polymer. The second polymer component acts as a dopant for the first polymer component. This allows the first polymer component and the second polymer component to function as conductive polymers, resulting in high conductivity of the solid electrolyte layer.

[0033] In the present disclosure, the solid electrolyte layer has a first portion filling voids in a porous portion in an anode body having a dielectric layer and a second portion protruding from a main surface of the anode body having a dielectric layer. In a cross section (hereinafter sometimes referred to as cross section A) of the solid electrolyte layer cut parallel to the thickness direction of the solid electrolyte layer, the second portion is divided into a portion A on the first portion side and a portion B on the opposite side to the first portion.

[0034] (First Polymer Component) Examples of thiophene compounds corresponding to the first monomer unit include compounds having a thiophene ring and capable of forming a repeating structure of the first monomer unit. Thiophene compounds can be linked at the 2- and 5-positions of the thiophene ring to form a repeating structure of the first monomer unit, thereby making it possible to form a polymer in which the π-electron cloud is spread throughout the molecule. Thiophene compounds also include those having a substituent. The substituent may be, for example, at least one of the 3- and 4-positions of the thiophene ring. The substituent at the 3-position and the substituent at the 4-position may be linked to form a ring fused to the thiophene ring. Examples of thiophene compounds include thiophenes that may have a substituent at at least one of the 3- and 4-positions, alkylenedioxythiophene compounds (C such as ethylenedioxythiophene compounds), etc. ２－４ The alkylenedioxythiophene compounds include those having a substituent in the alkylene group portion. The substituent in the thiophene compound is an alkyl group (C alkyl group such as a methyl group or an ethyl group). １－４ alkyl groups, alkoxy groups (C groups such as methoxy groups and ethoxy groups) １－４ alkoxy group, hydroxy group, hydroxyalkyl group (hydroxy C such as hydroxymethyl group) １－４ Preferred examples of the thiophene compound include, but are not limited to, two or more substituents. When the thiophene compound has two or more substituents, the substituents may be the same or different.

[0035] In particular, using a first polymer component containing at least a first monomer unit corresponding to a 3,4-ethylenedioxythiophene compound makes it easier to ensure higher conductivity of the solid electrolyte layer. In addition, it makes it easier to obtain high heat resistance of the solid electrolyte layer. Hereinafter, 3,4-ethylenedioxythiophene may be referred to as EDOT, and poly(3,4-ethylenedioxythiophene) may be referred to as PEDOT.

[0036] Thiophene compounds generally have a higher polymerization potential than pyrrole compounds, making in situ electropolymerization technically difficult. The use of at least a thiophene compound in which an electron-donating group, such as an alkylenedioxythiophene or alkoxy group, is substituted on the thiophene ring can reduce the polymerization potential. Therefore, the polymerization reaction of the thiophene compound can proceed rapidly even in the presence of a polymer anion. As a result, despite the use of a polymer anion, a solid electrolyte containing a first polymer component and a second polymer component containing a polymer anion can be densely packed into the fine recesses on the surface of the dielectric layer, with each polymer component more uniformly dispersed. In this way, a first portion and a portion A can be obtained in which the polymer components are more uniformly dispersed and a first peak is observed in the Raman spectrum.

[0037] In the solid electrolyte layer (or each of the first portion, portion A, and portion B), the first polymer component may contain one type of first monomer unit or may contain two or more types of first monomer units. The solid electrolyte layer (or each of the first portion, portion A, and portion B) may contain one type of first polymer component or may contain two or more types.

[0038] In the solid electrolyte layer (or each of the first portion, portion A, and portion B), the first polymer component may contain a second monomer unit other than the first monomer unit, as necessary. From the viewpoint of easily ensuring a higher capacitance, the molar ratio of the first monomer unit in the first polymer component is preferably 90 mol% or more. The molar ratio of the first monomer unit in the first polymer component is 100 mol% or less. The first polymer component may be composed only of a repeating structure of the first monomer unit.

[0039] In the solid electrolyte layer (or each of the first portion, portion A, and portion B), the weight average molecular weight (Mw) of the first polymer component is 1,000 or more and 1,000,000 or less. However, the Mw of the first polymer component is not limited to this range.

[0040] (Second Polymer Component) In the solid electrolyte layer (or each of the first portion, the A portion, and the B portion), the polymer anion contained in the second polymer component may be, for example, a polymer having a plurality of anionic groups. Such a polymer may include a polymer containing a monomer unit having an anionic group.

[0041] Examples of the anionic group include a sulfonic acid group and a carboxy group. In the solid electrolyte layer, the anionic group may be contained in a free form, an anionic form, or a salt form, or may be contained in a form bonded to or interacting with the first polymer component. In this specification, all of these forms may be referred to simply as an "anionic group," "sulfonic acid group," or "carboxy group."

[0042] In the solid electrolyte layer (or each of the first portion, portion A, and portion B), the second polymer component may contain one type of polymer anion or two or more types of polymer anions. Note that the second polymer component contains only polymer anions.

[0043] Examples of polymer anions having a carboxy group include polyacrylic acid, polymethacrylic acid, and copolymers using at least one of acrylic acid and methacrylic acid, but the polymer anions having a carboxy group are not limited to these.

[0044] In the solid electrolyte layer (or each of the first portion, the A portion, and the B portion), the second polymer component preferably contains a polymer anion having at least a sulfonic acid group. In this case, higher conductivity of the solid electrolyte layer or each portion can be ensured, and dedoping from the solid electrolyte layer or each portion can be easily suppressed.

[0045] The polymer anion having a sulfonic acid group includes a monomer unit M corresponding to an organic sulfonic acid compound. １ The organic sulfonic acid compound may be any of aliphatic, alicyclic, aromatic and heterocyclic. The polymer anion may be a monomer unit M １It may also be a homopolymer containing only the monomer unit M １ and other monomer units.

[0046] Specific examples of polymer anions having sulfonic acid groups include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic sulfonic acid, polymethacrylic sulfonic acid, poly(2-acrylamido-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, polyester sulfonic acid, and phenolsulfonic acid novolac resin. However, the polymer anions having sulfonic acid groups are not limited to these.

[0047] In particular, when the polymer anion has an aromatic ring, dedoping is easily suppressed. However, polymer anions having an aromatic ring tend to emit strong fluorescence when aggregated. In the present disclosure, even when a polymer anion having an aromatic ring is used, segregation in the first portion and the A portion is suppressed, and a more uniform dispersion state of each of the first polymer component and the second polymer component can be ensured. This excellent dispersion state can be confirmed by Raman spectroscopy. The first portion and the A portion having such a dispersion state can achieve high charge / discharge characteristics and low ESR. Furthermore, by forming the B portion as a liquid dispersion, high voltage resistance can be ensured.

[0048] As the polymer anion having an aromatic ring, for example, a monomer unit M corresponding to an organic sulfonic acid compound can be used. １ Among the polymer anions containing the monomer unit M, those containing an aromatic ring are exemplified. １ as the monomer unit corresponding to the aromatic sulfonic acid compound (monomer unit M ２(sometimes referred to as "polymer anions"). Such polymer anions include, among the above-mentioned polymer anions, polystyrene sulfonic acid (including copolymers and substituted products having a substituent), aromatic polyester sulfonic acid, and phenol sulfonic acid novolac resin. However, polymer anions having an aromatic ring are not limited to these.

[0049] In the solid electrolyte layer or each portion, the Mw of the polymer anion is, for example, 100 or more and 500,000 or less. The Mw of the polymer anion constituting at least the first portion is preferably 100,000 or less, more preferably 1,000 or more and 100,000 or more and 10,000 or less. In these cases, electrolytic polymerization of the precursor of the first polymer (such as raw material monomer) in the presence of the polymer anion in the voids of the porous portion is easily carried out, making it easy to ensure a high filling rate of the solid electrolyte in the voids. Furthermore, in the first portion and portion A, higher dispersibility of the polymer anion and a relatively high doping rate are easily obtained, which is advantageous in ensuring higher conductivity. In addition, high stability of the solid electrolyte is easily obtained.

[0050] The amount of the second polymer component contained in the solid electrolyte layer or each portion may be 10 parts by mass or more and 1,000 parts by mass or less, or 50 parts by mass or more and 200 parts by mass or less, relative to 100 parts by mass of the first polymer component.

[0051] (Raman Spectrum) In the present disclosure, when the Raman spectrum of the first and second portions of cross section A is measured, a first peak characteristic of the first polymer component is observed in the first and A portions. On the other hand, the first peak characteristic of the first polymer component is not observed in the B portion. These characteristics indicate that the solid electrolyte in the first and A portions is formed by three-electrode electrolytic polymerization (in situ polymerization), and the B portion is formed from a liquid dispersion containing the first and second polymer components. These characteristics allow the solid electrolyte to be highly packed in the porous portion of the first portion, and the A portion ensures high adhesion between the first and second portions. This results in high charge / discharge characteristics, and the high conductivity of the solid electrolyte ensures low ESR. Furthermore, the B portion, which is highly adhesively integrated with the first and A portions, ensures high voltage resistance.

[0052] In the capacitor element of the present disclosure, at least a first peak characteristic of the first polymer component (conjugated polymer) is observed in the Raman spectrum of the first portion and portion A in cross section A. Furthermore, a second peak characteristic of the second polymer component is also observed in the Raman spectrum.

[0053] Since the first polymer component contains the first monomer unit, the Raman spectrum of the first portion and the A portion shows a peak at 1200 cm －１ More than 1600cm －１ When the polymer anion, which is the second polymer component, contains a monomer unit corresponding to an aromatic sulfonic acid compound, the first peak is observed in the range of 800 cm. －１ More than 1100cm －１ A second peak is observed in the following range. The second peak is attributed to the C-S stretching vibration between the aromatic ring in the monomer unit corresponding to the aromatic sulfonic acid compound and the S element of the sulfonic acid group. For example, when the first polymer component contains at least a monomer unit corresponding to EDOT, the position of the first peak is at 1400 cm －１ More than 1450cm －１ or less, 1410 cm －１ 1435cm or more －１When the polymer anion contains at least polystyrene sulfonic acid, the position of the second peak may be 900 cm or less. －１ More than 1050cm －１ It may be 950 cm or less, －１ More than 1050cm －１ On the other hand, in the Raman spectrum of the solid electrolyte of part B formed using a liquid dispersion containing the first polymer component and the second polymer component, no characteristic peaks such as the first peak and the second peak are observed.

[0054] In the capacitor element of the present disclosure, the Raman spectrum of the first portion has an intensity I of a first peak specific to the first polymer component (conjugated polymer). ｐ１ The intensity I of the second peak characteristic of the second polymer component (polymer anion) ｐ２ Ratio to: I ｐ１ / I ｐ２ may be 4.0 or more. ｐ１ / I ｐ２ When the ratio is in this range, the orientation and crystallinity of the conjugated polymer in the first portion are relatively high. Therefore, it is easy to ensure high conductivity of the solid electrolyte in the first portion. From the viewpoint of easily ensuring higher crystallinity and conductivity, I ｐ１ / I ｐ２ The ratio may be 5.0 or greater. ｐ１ / I ｐ２ The ratio is, for example, 10.0 or less. The intensity of each peak corresponds to the peak height obtained by subtracting the background height from the peak height.

[0055] In this specification, the Raman spectrum of the solid electrolyte in each portion is measured for the solid electrolyte present at a predetermined position in each portion of the cross section A of the capacitor element under the following conditions: Raman spectrometer: NanoPhoton RamanFORCE PAV Diffraction grating: 600 gr / cm Measurement wavenumber range: 0 cm －１ More than 2500cm －１Temperature: 25°C The wavelength of the irradiated laser light, the laser power density, and the exposure time are determined depending on the type of conjugated polymer. For example, when the conjugated polymer is PEDOT, the wavelength of the irradiated laser light is 784.73 nm, and the laser power density is 870 W / cm ２ and the exposure time is 60 seconds.

[0056] For Raman spectroscopy, samples collected using the following procedure can be used. First, a solid electrolytic capacitor is embedded in a curable resin, and the curable resin is cured. The cured product is polished or cross-section polished to expose a cross section perpendicular to the longitudinal direction of the capacitor element and parallel to the thickness direction. Cross section A is defined as a cross section located 0 to 0.05 from the end of the solid electrolyte region opposite the anode lead (the end on the second end side), where the length of the region parallel to the longitudinal direction of the capacitor element is 1. In this manner, a sample for measurement is obtained. In the exposed cross section A of the sample, Raman spectra are measured for an 8 μm × 8 μm region of the solid electrolyte (first portion) on the surface of each portion. The intensities of the first and second peaks are determined by averaging the measured values ​​for 12 locations in an 8 μm × 8 μm region of each portion. More specifically, for the first portion, the measurement region is selected for the solid electrolyte formed within the pits on the surface of the porous portion. For part A, a measurement region is selected for a portion of the solid electrolyte in contact with the main surface of the anode body having a dielectric layer. For part B, a measurement region is selected for a portion of the solid electrolyte layer opposite the anode body (e.g., a portion 0.15 T thick or less from the surface of the solid electrolyte layer opposite the anode body).

[0057] (Others) When the average thickness of the second portion is T, the average thickness of portion B may be 0.15T or more, 0.30T or more, or 0.50T or more. The average thickness T of the second portion is the average thickness of the second portion from the main surface of the anode body having the dielectric layer. The thickness T is determined by measuring the distance from the main surface of the anode body having the dielectric layer to the outer edge of the solid electrolyte layer at multiple locations (e.g., 10 locations) on cross section A and averaging the measured values.

[0058] The average thickness T of the second portion may be 5 μm or more and 30 μm or less, or 10 μm or more and 25 μm or less. From the viewpoint of easily obtaining a lower ESR, the thickness T may be 5 μm or more and 20 μm or less, or 10 μm or more and 20 μm or less.

[0059] Part B may or may not contain carbon particles. Because the second polymer component is prone to segregation in Part B, adhesion to the cathode extraction layer tends to be lower than in a case where segregation is not present. However, when Part B contains carbon particles, adhesion between the second part and the cathode extraction layer, such as a metal-containing layer, can be improved without providing a carbon particle-containing layer covering the solid electrolyte layer. Because a carbon particle-containing layer is not required, the thickness of the cathode extraction layer can be reduced, ensuring high voltage resistance without increasing the thickness of the capacitor element. Furthermore, a high capacitance per volume of the solid electrolytic capacitor can be ensured. In particular, when the solid electrolytic capacitor includes a laminate of multiple capacitor elements, the inclusion of carbon particles in Part B provides significant benefits.

[0060] The phrase "Part B contains or does not contain carbon particles" means that at least the region of part B that is in contact with part A contains or does not contain carbon particles.

[0061] Examples of the carbon particles include conductive carbon, and examples of the conductive carbon include graphite (artificial graphite, natural graphite, etc.).

[0062] The average particle diameter of the carbon particles may be 0.1 μm or more and 3 μm or less, or 0.3 μm or more and 2 μm or less. When the average particle diameter is in this range, the carbon particles can be easily dispersed in portion B while ensuring high adhesion between the second portion and a cathode extraction layer such as a metal-containing layer. The average particle diameter of the carbon particles is the 50% particle diameter D50 (i.e., median diameter) in a volume-based particle size distribution determined using a laser diffraction / scattering particle size distribution analyzer.

[0063] When part B contains carbon particles, the content of carbon particles in part B may be 10% by mass or more and 80% by mass or less, 20% by mass or more and 60% by mass or less, or 30% by mass or more and 50% by mass or less. The carbon particle content is determined for a region of part B that contacts part A (e.g., a region from the interface between parts A and B to a thickness of 0.20T). When the carbon particle content is within the above range, it is easy to ensure higher adhesion between the second part and the cathode extraction layer (e.g., a metal-containing layer) while suppressing leakage current.

[0064] In the present disclosure, the anode body may be an anode foil containing aluminum, and the solid electrolyte layer may contain sulfur. The sulfur may be derived from a second polymer component or the like. In such an embodiment, elemental mapping of a cross section of the first portion using an electron probe microanalyzer (EPMA) may indicate that the sulfur content, relative to the aluminum content of 100%, may be 0.50% or more, 0.65% or more, or 0.70% or more. By ensuring that the sulfur content falls within this range, the porous portion is highly filled with a highly conductive solid electrolyte, suppressing deterioration of the solid electrolyte during repeated charge and discharge. This allows the contact between the first portion or the porous portion and the second portion to be maintained, thereby suppressing capacity loss. Furthermore, the resistance of the first portion can be kept low from the initial stage, thereby reducing the initial ESR and ensuring a relatively high initial capacity. Considering the volume of the voids in the porous portion, the abundance ratio of the S element is, for example, 5.00% or less.

[0065] The EPMA analysis was performed using a sample in which a cross section of a porous portion of a capacitor element where a cathode containing a solid electrolyte was formed was exposed and a platinum film was formed. In the cross-sectional image of the porous portion where the solid electrolyte was formed, elemental mapping was performed using EPMA on a 5 μm-wide region extending from the main surface of the anode foil to the bottom of the porous portion (in other words, a region measuring the entire thickness of the porous portion on one side of the anode foil × 5 μm in width) based on the difference in wavelength of characteristic X-rays, and the net intensity of the contained elements was measured. The net intensity was calculated by subtracting background (noise) from the measured value of each element. The ratio (%) of the net intensity of the S element was calculated when the net intensity of the Al element was set to 100%. The ratio (%) of the net intensity of the S element was calculated for multiple regions (e.g., five regions), and the average value was calculated. This was used as the abundance ratio (%) of the S element when the abundance ratio of the Al element in the porous portion was set to 100%. The EPMA analysis conditions were as follows: Measurement environment: 25°C, atmospheric pressure Acceleration voltage: 15.0 kV Beam current: 20.1 nA Integration time: 180.0 ms / point (12-minute mode) Analyzing crystals: AP / CH1, PbST / CH2, PET / CH3, LiF / CH4, LSA80 / CH5

[0066] An analytical sample can be prepared, for example, by the following procedure. First, a solid electrolytic capacitor is embedded in a curable resin and the curable resin is cured. The anode foil has a first end and a second end opposite the first end, and a solid electrolyte is formed on the second end of the anode foil. At a predetermined position in the direction from the first end to the second end of the anode foil (i.e., the longitudinal direction of the anode foil or capacitor element), the cured product obtained above is wet- or dry-polished to expose a cross-section perpendicular to the longitudinal direction of the capacitor element and parallel to the thickness direction. The exposed cross-section is smoothed by ion milling. A platinum film with a thickness of 1 nm to 2 nm is formed on the smoothed cross-section using a sputtering device. In this way, an analytical sample is obtained. Note that the cross-section is measured at a position between 0 and 0.05 mm from the end of the solid electrolyte region on the second end side, where 1 is the length of the region parallel to the longitudinal direction of the capacitor element.

[0067] (Formation of Solid Electrolyte Layer) (Formation of First Portion and A Portion) The first portion and A portion can be formed on the surface of the dielectric layer by electropolymerizing a precursor of the first polymer component (such as a first monomer) in the presence of a second polymer component in a three-electrode system. For example, electropolymerization is performed while immersing the cathode-forming portion of an anode body having a dielectric layer formed on its surface in a liquid mixture containing a precursor of the first polymer component and a second polymer component. By performing such electropolymerization, the precursor of the first polymer component grows on the surface of the dielectric layer and forms a first polymer in a state where it interacts with the second polymer component. The first portion is formed in the voids of the porous portion, and A portion is formed on the main surface of the anode body having the dielectric layer.

[0068] Three-electrode electropolymerization is performed using three electrodes: an anode body with a dielectric layer formed on its surface, a counter electrode, and a reference electrode. In three-electrode electropolymerization, the use of a reference electrode allows for precise control of the anode potential without being affected by changes in the counter electrode's natural potential. The three-electrode electropolymerization allows for more precise control of the electropolymerization reaction than a two-electrode electropolymerization using an anode body and a counter electrode. Furthermore, adjusting the polymerization potential can control the degree of interaction with the polymer anion and the growth rate of the polymer chains of the first polymer component (conjugated polymer). This can improve the orientation of the resulting conjugated polymer and enhance the dispersion of the polymer anion. As a result, a more uniform and dense solid electrolyte is believed to be formed with a high filling rate in the voids of the porous portion. Furthermore, the formation of a dense solid electrolyte on the major surface of the anode body with a dielectric layer can enhance adhesion between the first and second portions. Additionally, the high dispersion of the polymer anion facilitates a relatively high doping rate, thereby enhancing the conductivity of the solid electrolyte itself.

[0069] Examples of precursors of conjugated polymers include raw material monomers (such as first monomers) of conjugated polymers, and oligomers and prepolymers in which multiple molecular chains of raw material monomers (such as first monomer units) are linked together. The precursor contains at least a first monomer unit. One type of precursor may be used, or two or more types may be used in combination. From the viewpoint of easily achieving higher orientation of the conjugated polymer, it is preferable to use at least one type (particularly a monomer) selected from the group consisting of monomers and oligomers as the precursor.

[0070] The liquid composition usually contains a solvent, such as water, an organic solvent, or a mixed solvent of water and an organic solvent (such as a water-soluble organic solvent).

[0071] When other conductive materials, additives, etc. are used, they may be added to the liquid composition.

[0072] The liquid composition may contain an oxidizing agent, if necessary. The oxidizing agent may be applied to the anode body before or after contacting the liquid composition with the anode body on which the dielectric layer has been formed. Examples of such an oxidizing agent include Fe ３＋ Examples of the oxidizing agent include compounds capable of generating ferric sulfate, persulfates (sodium persulfate, ammonium persulfate, etc.), and hydrogen peroxide. One type of oxidizing agent may be used alone, or two or more types may be used in combination.

[0073] The counter electrode may be, but is not limited to, a Ti electrode. The reference electrode may be a silver / silver chloride electrode (Ag / Ag ＋ ) is preferably used.

[0074] In electropolymerization, the voltage (polymerization voltage) applied to the anode foil is, for example, 0.6 V or more and 1.5 V or less. From the viewpoint of facilitating high filling of the voids of the porous portion and ensuring relatively high crystallinity of the solid electrolyte, the polymerization voltage is preferably greater than 0.9 V and less than 1.2 V (or less than 1.1 V), and may be 1 V or more (e.g., 1.0 V or more) and less than 1.2 V, or 1 V or more (e.g., 1.0 V or more) and less than 1.1 V. By performing electropolymerization using a three-electrode system at such a polymerization voltage, the polymerization reaction in the voids can be precisely controlled. Therefore, polymer chains of the conjugated polymer can be grown in a state in which the polymer anions are highly dispersed in the voids, allowing the solid electrolyte to be highly filled in the voids and forming part A with a dense solid electrolyte. Furthermore, since the polymerization can proceed slowly, the orientation and crystallinity of the conjugated polymer can be further improved and relatively high conductivity can be easily ensured. The polymerization voltage was measured using a reference electrode (silver / silver chloride electrode (Ag / Ag ＋ )). In electropolymerization, a power supply (such as a power supply tape) is electrically connected to the anode lead, and a voltage is applied to the anode foil via the power supply. The potential of the anode foil is the potential of the power supply electrically connected to the anode foil.

[0075] The temperature at which the electropolymerization is carried out is, for example, 5°C or higher and 60°C or lower, and may be 15°C or higher and 35°C or lower.

[0076] Prior to electropolymerization, a precoat layer may be formed on the surface of the dielectric layer. The precoat layer may include, for example, a conductive material. The precoat layer may be formed using a liquid dispersion containing a conductive polymer (such as a conjugated polymer and a dopant). However, the liquid dispersion used to form the precoat layer has a smaller particle size and lower concentration of the conductive polymer compared to the liquid dispersion used to form the solid electrolyte constituting the cathode portion. For example, the average primary particle size of the conductive polymer particles contained in the liquid dispersion for the precoat layer may be, for example, 100 nm or less, or even 60 nm or less. The dry solids concentration of the liquid dispersion is, for example, 1.2 mass% or less. Note that the average primary particle size of the conductive polymer particles in the liquid dispersion used to form the solid electrolyte constituting the cathode portion is typically 200 nm or more, and the dry solids concentration is 2 mass% or more. The conjugated polymer of the precoat layer and the conjugated polymer formed by electropolymerization may be the same or different. The dopant of the precoat layer and the dopant used in the electrolytic polymerization may be the same or different. In the present disclosure, since the first portion and the portion A are formed by electrolytic polymerization, even if the precoat layer is formed using a liquid dispersion, the polymerization liquid can be sufficiently permeated into the fine voids, and the first portion can be formed with a high filling rate.

[0077] (Part B) Part B is formed using a liquid dispersion (or solution) containing a first polymer component and a second polymer component. The liquid dispersion (or solution) usually contains a liquid medium. Examples of the liquid medium include water, an organic solvent, and a mixed solvent of water and an organic solvent (such as a water-soluble organic solvent).

[0078] More specifically, part B may be formed by immersing the anode body on which the first part and part A have been formed in the liquid dispersion (or solution), removing the anode body from the liquid dispersion (or solution), and then drying the anode body. Alternatively, part B may be formed by applying the liquid dispersion (or solution) to the surface of the solid electrolyte part of the anode body on which the first part and part A have been formed, followed by drying the liquid dispersion (or solution). The drying may be performed under heating or under reduced pressure. If necessary, after forming the first part and part A, part B may be formed after applying a treatment liquid containing an anionic component or a treatment liquid containing an anionic component and a cationic component to the solid electrolyte part.

[0079] The portion B may have a single layer structure or a multi-layer structure.

[0080] (Others) Each of the first and second parts may further contain at least one selected from the group consisting of known additives and known conductive materials other than conductive polymers, as necessary. Examples of the conductive material include at least one selected from the group consisting of conductive inorganic materials such as manganese dioxide and TCNQ complex salts.

[0081] The additives include known additives added to solid electrolytes (e.g., coupling agents and silane compounds), known conductive materials other than conductive polymers, and water-soluble polymers. Each part constituting the solid electrolyte may contain one of these additives or a combination of two or more of them.

[0082] When the portion B is composed of a plurality of layers, the types, compositions, contents, etc. of the conductive polymers, additives, etc. contained in the respective layers may be the same or different. A layer for improving adhesion may be interposed between the dielectric layer and the solid electrolyte layer.

[0083] The solid electrolytes constituting the first portion and the portions A and B can be distinguished, for example, by EPMA analysis of a cross-sectional image. For example, EPMA analysis can be performed at equal intervals on a cross-sectional image of the entire solid electrolyte layer, and the interface between adjacent solid electrolytes can be determined from the difference in wavelength of characteristic X-rays at each measurement point. The sample for measurement is prepared using the same procedure as for the sample for Raman spectrum measurement.

[0084] (Cathode Extraction Layer) The cathode extraction layer may include at least a first layer that is in contact with the solid electrolyte and covers at least a portion of the solid electrolyte, and may include a first layer and a second layer that covers the first layer. Examples of the first layer include a layer containing conductive particles and metal foil. Examples of the conductive particles include at least one selected from conductive carbon and metal powder. For example, the cathode extraction layer may be composed of a first layer containing conductive carbon (also referred to as a carbon particle-containing layer) and a second layer containing metal (e.g., a layer containing metal powder or metal foil). When a metal-containing layer is used as the first layer, the cathode extraction layer may be composed of this metal-containing layer.

[0085] For example, when portion B contains carbon particles, the cathode extraction layer may include a metal-containing layer covering at least a portion of the surface of the solid electrolyte layer. In this case, the cathode extraction layer may be formed using the metal-containing layer as the first layer. When portion B does not contain carbon particles, the cathode extraction layer may include a carbon particle-containing layer covering at least a portion of the surface of the solid electrolyte layer and a metal-containing layer covering at least a portion of the surface of the carbon particle-containing layer.

[0086] Examples of conductive carbon contained in the carbon particle-containing layer include graphite (artificial graphite, natural graphite, etc.).

[0087] Among the metal-containing layers, a layer containing metal powder can be formed, for example, by laminating a composition containing metal powder on the surface of the first layer or the solid electrolyte layer. Examples of such a layer containing metal powder include a metal paste layer formed using a composition containing metal powder such as silver particles and a resin (binder resin). While a thermoplastic resin can be used as the resin, it is preferable to use a thermosetting resin such as an imide resin or an epoxy resin.

[0088] When a metal foil is used in the metal-containing layer, the type of metal is not particularly limited. It is preferable to use a valve metal (aluminum, tantalum, niobium, etc.) or an alloy containing a valve metal as the metal foil. If necessary, the surface of the metal foil may be roughened. The surface of the metal foil may be provided with a chemical conversion coating, or may be provided with a coating of a metal (dissimilar metal) or a nonmetal different from the metal constituting the metal foil. Examples of dissimilar metals and nonmetals include metals such as titanium and nonmetals such as carbon (e.g., conductive carbon).

[0089] The coating of the dissimilar metal or non-metal (for example, conductive carbon) may be the first layer, and the metal foil may be the second layer.

[0090] (Separator) When a metal foil is used for the cathode extraction layer, a separator may be disposed between the metal foil and the anode body (particularly the anode foil). The separator is not particularly limited, and examples thereof include a nonwoven fabric containing fibers of cellulose, polyethylene terephthalate, vinylon, or polyamide (e.g., aliphatic polyamide, aromatic polyamide such as aramid).

[0091] (Other) A solid electrolytic capacitor includes at least one capacitor element. The solid electrolytic capacitor may be a wound type, and may be either a chip type or a stacked type. For example, the solid electrolytic capacitor may include two or more stacked capacitor elements. The solid electrolytic capacitor may also include two or more wound capacitor elements. The configuration of the capacitor element may be selected depending on the type of solid electrolytic capacitor.

[0092] In the capacitor element, one end of a cathode lead terminal is electrically connected to the cathode extraction layer. The cathode lead terminal is bonded to the cathode extraction layer, for example, by applying a conductive adhesive to the cathode extraction layer via this conductive adhesive. One end of the anode lead terminal is electrically connected to the anode foil. The other end of the anode lead terminal and the other end of the cathode lead terminal are each extended from the resin exterior body or the case. The other end of each terminal exposed from the resin exterior body or the case is used for soldering to a substrate on which the solid electrolytic capacitor is to be mounted, for example.

[0093] The capacitor element is sealed using a resin outer casing or case. For example, the capacitor element and the resin material of the outer casing (e.g., an uncured thermosetting resin and a filler) may be placed in a mold, and the capacitor element may be sealed in the resin outer casing by transfer molding, compression molding, or the like. At this time, the other end portions of the anode lead terminal and the cathode lead terminal connected to the anode lead drawn from the capacitor element are exposed from the mold. Alternatively, the capacitor element may be housed in a bottomed case such that the other end portions of the anode lead terminal and the cathode lead terminal are positioned on the opening side of the bottomed case, and the opening of the bottomed case may be sealed with a sealant to form a solid electrolytic capacitor.

[0094] Fig. 1 is a cross-sectional view schematically illustrating the structure of a solid electrolytic capacitor according to an embodiment of the present disclosure. As shown in Fig. 1, the solid electrolytic capacitor 1 includes a capacitor element 2, a resin outer casing 3 that seals the capacitor element 2, and an anode lead terminal 4 and a cathode lead terminal 5, at least a portion of which is exposed outside the resin outer casing 3. The anode lead terminal 4 and the cathode lead terminal 5 may be made of a metal such as copper or a copper alloy. The resin outer casing 3 has a substantially rectangular parallelepiped outer shape, and the solid electrolytic capacitor 1 also has a substantially rectangular parallelepiped outer shape.

[0095] The capacitor element 2 includes an anode foil 6 made of Al foil, a dielectric layer 7 covering the anode foil 6, and a cathode portion 8 covering the dielectric layer 7. The cathode portion 8 includes a solid electrolyte layer 9 covering the dielectric layer 7 and a cathode extraction layer 10 covering the solid electrolyte layer 9. The anode foil 6 has porous portions formed by etching or the like on both surfaces. The solid electrolyte layer 9 contains S element, and in the anode foil 6 having the dielectric layer 7, the anode foil 6 has a first portion filling the voids in the porous portion and a second portion protruding from the main surface of the anode foil. The second portion is divided into a portion A on the first portion side and a portion B on the opposite side from the first portion.

[0096] Cathode extraction layer 10 may be composed of a carbon particle-containing layer (first layer) 11 that covers at least a portion of solid electrolyte layer 9, and a metal-containing layer (second layer) 12 that covers at least a portion of the first layer. When part B of the second portion does not contain carbon particles, such cathode extraction layer 10 is used. When part B contains carbon particles, the carbon particle-containing layer is not particularly necessary, and cathode extraction layer 10 may be composed of a metal-containing layer. Such a metal-containing layer may be a layer containing metal powder (e.g., a metal paste layer).

[0097] The anode foil 6 includes an area facing the cathode portion 8 and an area not facing the cathode portion 8. Of the area of ​​the anode foil 6 not facing the cathode portion 8, an insulating separator 13 is formed in a strip-like shape on the surface of the anode foil 6 in a portion adjacent to the cathode portion 8, thereby restricting contact between the cathode portion 8 and the anode foil 6. Of the area of ​​the anode foil 6 not facing the cathode portion 8, another part is electrically connected to the anode lead terminal 4 by welding. The cathode lead terminal 5 is electrically connected to the cathode portion 8 via an adhesive layer 14 formed of a conductive adhesive.

[0098] EXAMPLES The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0099] <Solid Electrolytic Capacitor E1> A solid electrolytic capacitor E1 was fabricated in the following manner, and its characteristics were evaluated.

[0100] (1) Preparation of anode foil: Both surfaces of an aluminum foil (thickness: 130 μm) were roughened by etching to prepare an anode foil. The thickness of the porous portions formed on both surfaces of the anode foil was 50 μm.

[0101] (2) Formation of Dielectric Layer The cathode forming portion of the anode foil was immersed in an anodizing solution, and a DC voltage of 70 V was applied for 20 minutes to form a dielectric layer containing aluminum oxide.

[0102] (3) Formation of Solid Electrolyte Layer A separator was formed between a region of the anode foil on which the dielectric layer was formed, where the solid electrolyte layer was to be formed, and a region on which the solid electrolyte layer was not to be formed, by attaching an insulating resist tape. The anode foil on which the separator was formed was immersed in a liquid composition containing a conductive material, and then removed and dried to form a precoat layer (not shown).

[0103] A mixed solution was prepared by dissolving EDOT monomer and a polymer anion, polystyrene sulfonic acid (PSS, Mw: 100,000), in ion-exchanged water. Iron (III) sulfate (oxidant) dissolved in ion-exchanged water was added to the mixed solution while stirring to prepare a polymerization solution. The resulting polymerization solution was then subjected to three-electrode electropolymerization. Specifically, an anode foil with a precoat layer formed thereon, a counter electrode, and a reference electrode (a silver / silver chloride reference electrode) were immersed in the polymerization solution. A voltage was applied to the anode foil so that the potential of the anode foil (more specifically, the power supply attached to the anode lead) relative to the reference electrode was 1.1 V. Electropolymerization was then performed at 25°C to form the first and second portions.

[0104] Next, portion B was formed using the following procedure. The anode foil on which portion A and portion B had been formed was immersed in a liquid dispersion containing a conductive polymer and dried at 120°C for 10 to 30 minutes. The process of immersion in the liquid dispersion and drying was repeated four more times. In this way, portion B was formed so as to cover the surface of the anode foil on which portion A and portion B had been formed. The liquid dispersion used was an aqueous dispersion containing a conductive polymer (PEDOT as the first polymer component and polystyrene sulfonic acid (PSS, Mw = 160,000) as the second polymer component) at a concentration of 2 to 4% by mass.

[0105] (4) Formation of Cathode Extraction Layer The anode foil obtained in (3) above was immersed in a dispersion of graphite particles in water, removed from the dispersion, and then dried to form a carbon particle-containing layer (first layer) at least on the surface of the solid electrolyte layer. The drying was carried out at 130 to 180°C for 10 to 30 minutes.

[0106] Next, a silver paste containing silver particles and a binder resin (epoxy resin) was applied to the surface of the first layer, and the binder resin was cured by heating at 150 to 200°C for 10 to 60 minutes to form a metal-containing layer (second layer). In this way, a cathode extraction layer composed of the first layer and the second layer was formed, and a cathode part composed of the solid electrolyte layer and the cathode extraction layer was formed. In this manner, a capacitor element was produced.

[0107] (5) Assembly of a Solid Electrolytic Capacitor The cathode portion of the capacitor element obtained in (4) above was joined to one end of the cathode lead terminal with an adhesive layer of conductive adhesive. One end of the anode foil protruding from the capacitor element was joined to one end of the anode lead terminal by laser welding. Next, a resin outer casing made of insulating resin was formed around the capacitor element by molding. At this time, the other end of the anode lead terminal and the other end of the cathode lead terminal were pulled out from the resin outer casing. In this way, a solid electrolytic capacitor E1 was completed. A total of 20 solid electrolytic capacitors E1 were produced in the same manner as above.

[0108] <Solid electrolytic capacitor E2> A liquid dispersion containing a conductive polymer and carbon particles (artificial graphite, D50: 0.8 μm) was used as the liquid dispersion for forming portion B. The proportion of the carbon particles in the dry solid content of the liquid dispersion was 50 mass %. A total of 20 solid electrolytic capacitors E2 were fabricated in the same manner as solid electrolytic capacitor E1, except for these points.

[0109] <<Solid electrolytic capacitor C1>> The entire solid electrolyte layer (first portion and portion A) was formed by electrolytic polymerization, and portion B was not formed. The average thickness (corresponding to thickness T) of portion A (the solid electrolyte layer extending beyond the main surface) was 18.0 μm. Other than these, the solid electrolytic capacitor was fabricated in the same manner as solid electrolytic capacitor E1.

[0110] [Evaluation] The solid electrolytic capacitors were evaluated as follows.

[0111] (a) Thickness T The average thickness T of the second portion was determined by the procedure described above.

[0112] (b) Measurement of Raman Spectrum of Each Part Using a solid electrolytic capacitor, the Raman spectra of the solid electrolyte in the first part and the B part in the cross section A were measured by the procedure described above. In the Raman spectra of the first part of the solid electrolytic capacitors E1 and E2, a peak (first peak) specific to the five-membered ring of PEDOT was observed at 1420 cm －１ The peak (second peak) specific to the aromatic ring-S element bond of PSS is observed at 1000 cm －１ The intensity of the first peak I ｐ１ and the intensity of the second peak I ｐ２ I ｐ１ / I ｐ２ The ratio was calculated.

[0113] (c) Charge-Discharge Characteristics The initial capacitance (μF) of each solid electrolytic capacitor was measured at a frequency of 120 Hz using a four-terminal LCR meter under an environment of 20°C. The average value (C ０ ) was sought.

[0114] Next, the solid electrolytic capacitors were charged and discharged 60,000 times under the following conditions, and then the capacitance was measured in a 20°C environment using the same procedure as for the initial capacitance, and the average value (C １ The capacitance change rate (ΔC) was calculated from the following formula: １ -C ０ ) / C ０×100 (%) The capacitance change rate is a negative value, and the smaller the value, the lower the capacity after repeated charge and discharge, indicating poor charge and discharge characteristics.

[0115] (d) ESR The initial ESR (mΩ) of the capacitor element was measured at a frequency of 100 kHz using a four-terminal LCR meter in an environment of 20° C. Then, the average value of the initial ESR of 20 capacitor elements was calculated.

[0116] (e) Voltage Withstand Property A voltage was applied to the solid electrolytic capacitor while increasing it at a rate of 1.0 V / sec, and the breakdown voltage (BVD) (unit: V) at which an overcurrent of 0.5 A flows was measured. The voltage withstand property was expressed as a relative value when the BVD (V) of the solid electrolytic capacitor of Comparative Example 1 was set to 100. A larger value indicates a higher voltage withstand property.

[0117] The evaluation results are shown in Table 1. E1 and E2 are examples, and C1 is a comparative example. Initial capacity C ０ The initial ESR is shown as a relative value when the value of C1 is set to 100.

[0118]

[0119] As shown in Table 1, the examples (E1 and E2) achieved high charge / discharge characteristics and voltage resistance, while also ensuring a relatively low ESR. In E1, the ESR was kept relatively low despite the large thickness T of the second portion. Furthermore, in E1, the ESR was further reduced because the second portion contained carbon particles. In contrast, the comparative example C1 had a low ESR but low voltage resistance.

[0120] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

[0121] According to the present disclosure, a solid electrolytic capacitor can be provided with high charge / discharge characteristics and voltage resistance, while also ensuring low ESR. Therefore, the solid electrolytic capacitor of the present disclosure can be used in a variety of applications requiring reliability, long life, excellent voltage resistance, etc. However, the applications of the solid electrolytic capacitor element and the solid electrolytic capacitor are not limited to these.

[0122] 1: Solid electrolytic capacitor 2: Capacitor element 3: Resin exterior body 4: Anode lead terminal 5: Cathode lead terminal 6: Anode foil 7: Dielectric layer 8: Cathode portion 9: Solid electrolyte layer 10: Cathode extraction layer 11: First layer 12: Second layer 13: Separation portion 14: Adhesive layer

Claims

1. A solid electrolytic capacitor element comprising: an anode body including a porous portion at least in a surface layer thereof; a dielectric layer covering at least a portion of the surface of the anode body; a solid electrolyte layer covering at least a portion of the dielectric layer; and a cathode extraction layer covering at least a portion of the surface of the solid electrolyte layer; wherein the solid electrolyte layer comprises a first polymer component including a monomer unit corresponding to a thiophene compound and a second polymer component including a polymer anion; wherein the solid electrolyte layer has, in the anode body having the dielectric layer, a first portion filling voids in the porous portion and a second portion protruding from a main surface of the anode body having the dielectric layer; in a cross section obtained by cutting the solid electrolyte layer parallel to a thickness direction of the solid electrolyte layer, the second portion is divided into a portion A on the first portion side and a portion B on the opposite side to the first portion; and when Raman spectra of the first portion and the second portion of the cross section are measured, a first peak characteristic of the first polymer component is observed in the first portion and the portion A, but the first peak characteristic of the first polymer component is not observed in the portion B.

2. The solid electrolytic capacitor element according to claim 1, wherein, when the average thickness of said second portion from said main surface is T, the average thickness of said portion B is 0.15T or more.

3. The solid electrolytic capacitor element according to claim 1, wherein the cathode extraction layer includes a carbon particle-containing layer covering at least a portion of the surface of the solid electrolyte layer, and a metal-containing layer covering at least a portion of the surface of the carbon particle-containing layer.

4. The solid electrolytic capacitor element according to claim 1, wherein said portion B further contains carbon particles.

5. The solid electrolytic capacitor element according to claim 4, wherein the cathode extraction layer includes a metal-containing layer covering at least a portion of the surface of the solid electrolyte layer.

6. In the Raman spectrum, the position of the first peak is 1200 cm －１ More than 1600cm －１ 2. The solid electrolytic capacitor element according to claim 1, wherein:

7. A solid electrolytic capacitor comprising at least one solid electrolytic capacitor element according to any one of claims 1 to 6.

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