Solid electrolytic capacitor element and solid electrolytic capacitor

Abstract

A capacitor element contained in a solid electrolytic capacitor includes an anode body including a porous portion at least in a surface layer, a dielectric layer, a solid electrolyte layer, and a cathode lead-out layer. The solid electrolyte layer contains 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 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 of the first portion. When Raman spectra of the first portion and the second portion are measured, a first peak peculiar 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

Technical Field

[0001] This disclosure relates to solid electrolytic capacitor elements and solid electrolytic capacitors. Background Technology

[0002] Solid electrolytic capacitors include, for example, solid electrolytic capacitor elements and a resin casing or housing that seals the solid electrolytic capacitor elements. The solid electrolytic capacitor element includes, for example, an anode, a dielectric layer formed on the surface of the anode, and a cathode covering at least a portion of the dielectric layer. The cathode comprises a conductive polymer (e.g., a conjugated polymer and a dopant) covering at least a portion of the dielectric layer. The conductive polymer is also referred to as a solid electrolyte.

[0003] Patent Document 1 discloses a method for manufacturing an electrolytic capacitor, comprising: impregnating an anode body having a dielectric film formed on its surface with a first dispersion solution containing particles of a first conductive polymer and a first solvent; and impregnating 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] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2013-58807 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In solid electrolytic capacitors, in addition to excellent charge and discharge characteristics and voltage withstand capability, a low equivalent series resistance (ESR) is also required.

[0009] Methods for solving problems

[0010] The first aspect of this disclosure relates to a solid electrolytic capacitor element, comprising: an anode body having at least a porous surface layer, 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 lead-out layer covering at least a portion of the surface of the solid electrolyte layer.

[0011] The aforementioned solid electrolyte layer comprises a first polymer component and a second polymer component, wherein the first polymer component comprises monomer units corresponding to the thiophene compound, and the second polymer component comprises polymer anions.

[0012] The aforementioned solid electrolyte layer has a first portion that fills the voids within the porous portion of the anode body having the aforementioned dielectric layer, and a second portion that protrudes from the main surface of the anode body having the aforementioned dielectric layer.

[0013] In a cross-section obtained by cutting the solid electrolyte layer parallel to its thickness direction, the second part is divided into part A on the side of the first part and part B on the side opposite to the first part.

[0014] When the Raman spectra of the first and second parts of the cross section were measured, a first peak characteristic of the first polymer component was observed in the first and second parts, but no first peak characteristic of the first polymer component was observed in the second part.

[0015] The second aspect of this disclosure relates to a solid electrolytic capacitor comprising at least one of the aforementioned solid electrolytic capacitor elements.

[0016] Invention Effects

[0017] Solid electrolytic capacitors that offer excellent charge / discharge characteristics and voltage withstand capability, and have low ESR. Attached Figure Description

[0018] Figure 1 This is a cross-sectional schematic diagram of a solid electrolytic capacitor according to one embodiment of the present disclosure. Detailed Implementation

[0019] Novel features of the invention are set forth in the appended claims, but both the structure and content of the invention, together with its other objects and features, can be better understood from the following detailed description taken in conjunction with the accompanying drawings.

[0020] In solid electrolytic capacitors, increasing the thickness of the solid electrolyte layer improves voltage withstand capability but reduces capacitance and increases ESR. Conversely, decreasing the thickness of the solid electrolyte layer results in high capacitance and low ESR, but reduces voltage withstand capability. The desired outcome is a solid electrolytic capacitor that maintains high capacitance (in other words, excellent charge-discharge characteristics) under repeated charge-discharge conditions, while exhibiting high voltage withstand capability and low ESR.

[0021] (Technology 1)

[0022] In view of the above, the solid electrolytic capacitor element of this disclosure includes: an anode body with at least a porous surface layer, 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 lead-out layer covering at least a portion of the surface of the solid electrolyte layer. The solid electrolyte layer includes a first polymer component and a second polymer component, the first polymer component including monomer units corresponding to a thiophene compound, and the second polymer component including polymer anions. The solid electrolyte layer has a first portion filling the voids of the porous surface in the anode body having the dielectric layer, and a second portion protruding from the main surface of the anode body having the dielectric layer. In a cross-section cutting the solid electrolyte layer parallel to its thickness direction, the second portion is divided into a portion A on the side of the first portion and a portion B on the side opposite to the first portion. When the Raman spectra of the first and second portions of the above-mentioned cross sections were measured, a first peak characteristic of the first polymer component was observed in the first portion and the first portion A, but the first peak characteristic of the first polymer component was not observed in the first portion B. Hereinafter, the solid electrolytic capacitor element will sometimes be simply referred to as a capacitor element. Additionally, the monomer corresponding to the thiophene compound is sometimes referred to as the first monomer, and the monomer unit corresponding to the thiophene compound is sometimes referred to as the first monomer unit.

[0023] In the capacitor element of this disclosure, at least a first peak characteristic of the first polymer component is observed in the Raman spectra of the first part and the A part of the solid electrolyte layer. The first polymer component is a conjugated polymer. In the Raman spectra of the first part and the A part, the peak attributable to the C-S stretching vibration originating from the conjugated polymer (the first peak) has the highest height and is characteristic. The solid electrolyte constituting the first part and the A part exhibits high crystallinity due to the high orientation of the conjugated polymer. In addition, in the first part and the A part, the conjugated polymer is in an energy-stabilized state. Therefore, the first part and the A part exhibit characteristic Raman spectra in which the first peak described above can be observed. Such Raman spectra indicate that the first part and the A part are formed by three-pole electrolytic polymerization using a precursor (first monomer, etc.) of the first polymer component and a second polymer component, etc.

[0024] In Part 1 and Part A, the characteristic first peak of the conjugated polymer was observed because the conjugated polymer contains a first monomer unit. The first peak is attributed to the C-S stretching vibration of the thiophene ring in the first monomer unit.

[0025] On the other hand, part B contains both polymer components 1 and 2, but no characteristic peak like the first peak was observed in the Raman spectrum of part B. This is believed to be because fluorescence emission hinders the observation of the Raman scattered light from the polymer components. Such Raman spectra indicate that part B is formed from a liquid dispersion containing both polymer components 1 and 2. In the preparation of the liquid dispersion, the polymerization of a conjugated polymer precursor is carried out in the liquid phase in the presence of polymer anions, resulting in a liquid dispersion containing particles of a conductive polymer (more specifically, a conductive polymer containing both polymer components 1 and 2). It is believed that, compared to the conjugated polymer precursor, the high molecular weight polymer anions tend to segregate more easily among the obtained conductive polymer particles. In the case of using a liquid dispersion, the conductive polymer particles segregated by polymer anions form part B; therefore, it is believed that the characteristic peak like the first peak is not observed in the Raman spectrum of part B due to the fluorescence emission of the segregated polymer anions.

[0026] Thus, in the capacitor element of this disclosure, the first part and the second part are formed by electrolytic polymerization, thereby enabling a high degree of solid electrolyte filling within the pores of the porous portion and improving the adhesion between the first part and the second part. Therefore, high charge-discharge characteristics can be ensured. Furthermore, in addition to the high adhesion between the first part and the second part, forming the second part from a liquid dispersion results in low ESR and high voltage withstand capability.

[0027] (Technology 2)

[0028] Based on the above (Technology 1), when the average thickness of the second part from the main surface is set to T, the average thickness of the B part can be 0.15T or more. In this case, higher voltage withstand capability can be ensured.

[0029] (Technology 3)

[0030] Based on the above (Technology 1) or (Technology 2), the cathode lead-out layer may comprise a carbon-containing particle 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-containing particle layer. In this case, high voltage withstand capability can be ensured while maintaining low ESR.

[0031] (Technology 4)

[0032] Based on (Technology 1) or (Technology 2) described above, part B may further contain carbon particles. In this case, the adhesion between part 2 and the cathode lead-out layer, such as the metal layer, can be improved, thus eliminating the need for a carbon particle-containing layer covering the solid electrolyte layer. Therefore, the thickness of the cathode lead-out layer can be reduced, and the capacity per unit volume of the solid electrolytic capacitor can be increased.

[0033] (Technology 5)

[0034] Based on the above (Technology 4), the cathode lead-out 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 part B, high adhesion between part B and the metal-containing layer can be achieved, resulting in low ESR. Furthermore, the thickness of the cathode lead-out layer can be reduced, ensuring high capacitance per unit volume of the solid electrolytic capacitor.

[0035] (Technology 6)

[0036] Based on any one of the above (Technology 1) to (Technology 5), in the above Raman spectrum, the position of the first peak can be 1200 cm⁻¹. -1 Above and 1600cm -1 The following applies. In this case, the high conductivity of the solid electrolyte is readily obtained, which is advantageous for further reducing ESR.

[0037] (Technology 7)

[0038] This disclosure also includes solid electrolytic capacitors. The solid electrolytic capacitor of this disclosure includes at least one solid electrolytic capacitor element described in any one of the above (Technique 1) to (Technique 6). In such a solid electrolytic capacitor, high charge-discharge characteristics can be ensured. Furthermore, low ESR and high voltage withstand capability can be obtained.

[0039] Hereinafter, with reference to the accompanying drawings as needed, the capacitor elements and solid electrolytic capacitors of this disclosure will be described in more detail, including (Technique 1) to (Technique 7) described above. To the extent that there is no technical inconsistency, at least one of (Technique 1) to (Technique 7) described above may be combined with at least one of the elements described below. It should be noted that the drawings are schematic, and the proportions of the dimensions (e.g., thickness) of the constituent components may differ from the actual dimensions.

[0040] [Solid electrolytic capacitors]

[0041] A solid electrolytic capacitor comprises one or more capacitor elements. In this disclosure, at least one capacitor element in a solid electrolytic capacitor has the features described in any one of (Technology 1) to (Technology 7) above. Preferably, 50% or more (more preferably 75% or more) of the capacitor elements in a solid electrolytic capacitor have the above features, and even more preferably, all capacitor elements have the above features.

[0042] (Capacitor element)

[0043] (Anode)

[0044] The anode body may contain a valve-acting metal, an alloy containing a valve-acting metal, or a compound containing a valve-acting metal. These materials may be used individually or in combination of two or more. For example, aluminum, tantalum, niobium, and titanium are preferred valve-acting metals.

[0045] The anode body contains a porous portion at least in its surface layer. An anode body having a porous surface layer is obtained, for example, by roughening the surface of a substrate (sheet-like (e.g., foil-like, plate-like) material containing a valve-acting metal) using etching or the like. Roughening can be performed, for example, by etching.

[0046] The anode body can be a shaped body or a sintered body containing particles of valve-acting metal. Both the shaped body and the sintered body have a porous structure. Both the shaped body and the sintered body can be sheet-like, cuboid, cubic, or similar shapes.

[0047] Typically, the anode body has an anode lead-out portion including a first end and a cathode forming portion including a second end opposite to the first end. The cathode portion is typically formed in the cathode forming portion of the anode body via a dielectric layer. Anode lead terminals can be connected to the anode lead-out portion.

[0048] (Dielectric layer)

[0049] The dielectric layer is formed in such a way that it covers 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-acting metal on the surface of the anode body using a chemical conversion treatment or similar method. The surface of the dielectric layer has a finely textured surface, depending on the shape of the porous portion of the anode body.

[0050] The dielectric layer can be formed from a material that functions as a dielectric layer. Such a material may include, for example, an oxide containing a valve-acting metal. For instance, when tantalum is used as the valve-acting metal, the dielectric layer contains Ta₂O₅; when aluminum is used as the valve-acting metal, the dielectric layer contains Al₂O₃. However, the dielectric layer is not limited to these specific examples.

[0051] (Cathode section)

[0052] The cathode portion of a capacitor element includes a solid electrolyte layer covering at least a portion of a dielectric layer and a cathode lead-out layer covering at least a portion of the surface of the solid electrolyte layer. The cathode portion is typically formed on at least a portion of the surface of the anode body via the dielectric layer. The solid electrolyte layer and the cathode lead-out layer will be described below.

[0053] (Solid electrolyte layer)

[0054] In this disclosure, the solid electrolyte layer comprises a first polymer component and a second polymer component. The first polymer component contains monomer units corresponding to a thiophene compound, and the second polymer component contains polymer anions. The first polymer component is a π-conjugated polymer. The second polymer component acts as a dopant on the first polymer component. Thus, both the first and second polymer components function as conductive polymers, resulting in high conductivity of the solid electrolyte layer.

[0055] In this disclosure, the solid electrolyte layer has a first portion that fills the voids in the porous portion of the anode body having a dielectric layer and a second portion that protrudes from the main surface of the anode body having a dielectric layer. In a cross section (hereinafter, sometimes referred to as section A) obtained by cutting the solid electrolyte layer 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 side opposite to the first portion.

[0056] (Polymer component 1)

[0057] 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 form a repeating structure of the first monomer unit by connecting at positions 2 and 5 of the thiophene ring, thereby forming a polymer in which the π electron cloud extends to the entire molecule. Thiophene compounds also include those with substituents. For example, at least one of the 3 and 4 positions of the thiophene ring may have a substituent. The substituent at position 3 and the substituent at position 4 can connect to form a ring fused with the thiophene ring. Examples of thiophene compounds include thiophene, alkylene dioxythiophene compounds (such as ethylene dioxythiophene compounds C...), which may have substituents at at least one of the 3 and 4 positions. 2-4 Alkylene dioxythiophene compounds, etc.). Alkylene dioxythiophene compounds also include alkylene dioxythiophene compounds in which the alkylene portion has a substituent. The substituents in the thiophene compound are preferably alkyl groups (methyl, ethyl, etc.). 1-4 Alkyl groups, etc.), alkoxy groups (methoxy, ethoxy, etc. C 1-4 alkoxy, hydroxyl, hydroxyalkyl (hydroxymethyl, etc. hydroxy C 1-4Alkyl groups, etc., but not limited to these. In the case of thiophene compounds having more than two substituents, the substituents may be the same or different.

[0058] In this regard, if a first polymer component containing at least a first monomer unit corresponding to a 3,4-ethylenedioxythiophene compound is used, higher conductivity of the solid electrolyte layer can be easily ensured. Furthermore, high heat resistance of the solid electrolyte layer is readily obtained. Hereinafter, 3,4-ethylenedioxythiophene will sometimes be referred to as EDOT, and poly(3,4-ethylenedioxythiophene) will be referred to as PEDOT.

[0059] Thiophene compounds typically have higher polymerization potentials compared to pyrrole compounds, making in-situ polymerization via electrolytic polymerization technically difficult. However, by using thiophene compounds formed by substituting electron-donating groups such as alkylene dioxythiophene or alkoxy groups into the thiophene ring, the polymerization potential can be lowered. Therefore, even in the presence of polymer anions, the polymerization reaction of thiophene compounds can proceed rapidly. As a result, despite the use of polymer anions, a solid electrolyte containing a first polymer component and a second polymer component containing polymer anions can be more uniformly dispersed in the fine recesses on the surface of the dielectric layer. This results in a more uniform dispersion of the polymer components, and the observation of the first and A portions of the first peak in Raman spectroscopy.

[0060] In the solid electrolyte layer (or each of Part 1, Part A, and Part B), the first polymer component may contain one first monomer unit or two or more first monomer units.

[0061] In the solid electrolyte layer (or each of Part 1, Part A, and Part B), the first polymer component may, as needed, include a second monomer unit in addition to the first monomer unit. From the viewpoint of easily ensuring higher electrostatic 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 consist solely of a repeating structure of the first monomer unit.

[0062] In the solid electrolyte layer (or each of Part 1, Part A, and Part 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 such a range.

[0063] (Second polymer component)

[0064] In the solid electrolyte layer (or each of Part 1, Part A, and Part B), the polymer anion contained in the second polymer component can be, for example, a polymer having multiple anionic groups. As such a polymer, a polymer comprising monomer units having anionic groups can be cited.

[0065] Examples of anionic groups include sulfonic acid groups and carboxyl groups. In a solid electrolyte layer, anionic groups can be contained in a free form, anionic form, or salt form, or in a form that is bonded to or interacts with the first polymer component. In this specification, all of these forms are sometimes simply referred to as "anionic group," "sulfonic acid group," or "carboxyl group."

[0066] In the solid electrolyte layer (or each of Part 1, Part A, and Part B), the second polymer component may contain one polymer anion or two or more polymer anions. It should be noted that the second polymer component contains only polymer anions.

[0067] Examples of polymeric anions containing carboxyl groups include polyacrylic acid, polymethacrylic acid, and copolymers using at least one of acrylic acid and methacrylic acid. However, polymeric anions containing carboxyl groups are not limited to these.

[0068] In the solid electrolyte layer (or each of Part 1, Part A, and Part B), the second polymer component preferably contains polymer anions having at least sulfonic acid groups. In this case, higher conductivity of the solid electrolyte layer or its parts can be ensured, and dedoping from the solid electrolyte layer or its parts can be easily suppressed.

[0069] Examples of polymer anions containing sulfonic acid groups include polymer anions comprising monomer units M1 corresponding to organic sulfonic acid compounds. Organic sulfonic acid compounds can be aliphatic, alicyclic, aromatic, or heterocyclic. The polymer anion can be a homopolymer containing only monomer unit M1, or a copolymer containing monomer unit M1 and other monomer units besides it.

[0070] Specific examples of polymeric anions containing sulfonic acid groups include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polypropylene sulfonic acid, polymethyl methacrylate sulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, polyester sulfonic acid, and phenolic sulfonic acid resins. However, polymeric anions containing sulfonic acid groups are not limited to these.

[0071] Especially when the polymer anion has an aromatic ring, dedoping is easily suppressed. However, polymer anions with aromatic rings tend to emit strong fluorescence upon aggregation. In this disclosure, even when using polymer anions with aromatic rings, segregation in the first and second portions can be suppressed, ensuring a more uniform dispersion of both the first and second polymer components. Furthermore, this excellent dispersion can be confirmed by Raman spectroscopy. With the first and second portions having such a dispersion, high charge-discharge characteristics and low ESR can be obtained. Moreover, by forming the second portion from a liquid dispersion, high voltage withstand capability can be ensured.

[0072] Examples of polymer anions containing aromatic rings include polymer anions containing a monomer unit M1 corresponding to an organic sulfonic acid compound. Preferably, polymer anions containing at least a monomer unit (sometimes referred to as monomer unit M2) corresponding to an aromatic sulfonic acid compound as monomer unit M1 are preferred. Examples of such polymer anions include polystyrene sulfonic acid (including copolymers and substituted derivatives with substituents), aromatic polyester sulfonic acid, and phenol sulfonic acid phenolic resin. However, polymer anions containing aromatic rings are not limited to these.

[0073] In the solid electrolyte layer or its components, the Mw of the polymer anions is, for example, 100 or more and 500,000 or less. The Mw of the polymer anions constituting at least the first component is preferably 100,000 or less, more preferably 1,000 or more and 100,000 or less, or 10,000 or more and 100,000 or less. In these cases, the electrolytic polymerization of the precursor of the first polymer (raw material monomers, etc.) is easily carried out in the pores of the porous portion in the presence of the polymer anions, easily ensuring a high filling rate of the solid electrolyte within the pores. Furthermore, in the first component and the A component, higher dispersion and a relatively high doping rate of the polymer anions are easily obtained, which is advantageous in ensuring higher conductivity. In addition, high stability of the solid electrolyte is easily obtained.

[0074] Relative to 100 parts by mass of the first polymer component, the amount of the second polymer component contained in the solid electrolyte layer or its components may be 10 parts by mass or more and 1000 parts by mass or less, or 50 parts by mass or more and 200 parts by mass or less.

[0075] (Raman spectroscopy)

[0076] In this disclosure, when the Raman spectra of the first and second portions were measured at cross section A, a first peak characteristic of the first polymer component was observed in both portions. However, the first peak characteristic of the first polymer component was not observed in portion B. This characteristic indicates that the solid electrolytes of portions 1 and A are formed via a three-electrode electrolytic polymerization (in-situ polymerization), and portion B is formed from a liquid dispersion containing both the first and second polymer components. This characteristic ensures that the solid electrolyte is highly packed within the porous portion in portion 1, and that portion A ensures high adhesion between portion 1 and portion 2. Consequently, high charge-discharge characteristics and high conductivity of the solid electrolyte are achieved, thereby ensuring low ESR. Furthermore, high voltage withstand capability is ensured by portion B, which is integrated with portions 1 and A with high adhesion.

[0077] In the capacitor element of this disclosure, at least a first peak characteristic of the first polymer component (conjugated polymer) is observed in the Raman spectra 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 aforementioned Raman spectra.

[0078] Since the first polymer component contains the first monomer unit, the Raman spectra of part 1 and part A show a high concentration of 1200 cm⁻¹. -1 Above and 1600cm -1 The first peak was observed within the following range. Furthermore, when the polymer anion, which is the second polymer component, contains a monomer unit corresponding to an aromatic sulfonic acid compound, a peak was observed at 800 cm⁻¹. -1 Above and 1100cm -1 The second peak was observed within the following range. The second peak is attributed to the CS stretching vibration between the aromatic ring and the sulfur element of the sulfonic acid group in the monomer unit corresponding to the aromatic sulfonic acid compound. For example, if the first polymer component contains at least the monomer unit corresponding to EDOT, the position of the first peak can be 1400 cm⁻¹. -1 Above and 1450cm -1 The following can also be 1410cm -1 Above and 1435cm -1 Below. When the polymeric anion contains at least polystyrene sulfonic acid, the position of the second peak can be 900 cm⁻¹. -1 Above and 1050cm -1 The following can also be 950cm -1 Above and 1050cm -1 Below. On the other hand, in the Raman spectrum of the solid electrolyte of part B formed by using a liquid dispersion containing the first polymer component and the second polymer component, no characteristic peaks like the first and second peaks were observed.

[0079] In the capacitor element of this disclosure, in the Raman spectrum of Part 1, the intensity I of the first peak characteristic of the first polymer component (conjugated polymer) is... p1 The intensity I of the second peak characteristic of the second polymer component (polymer anion) p2 Ratio: I p1 / I p2 It can be 4.0 or higher. In I p1 / I p2 Within this range, the conjugated polymers in Part 1 exhibit higher orientation and crystallinity. Therefore, it is easier to ensure high conductivity of the solid electrolyte in Part 1. From the viewpoint of easily ensuring higher crystallinity and conductivity, I p1 / I p2 The ratio can be 5.0 or higher. p1 / I p2 For example, values ​​below 10.0. It should be noted that the intensity of each peak is equivalent to the peak height obtained by subtracting the background height from the peak height.

[0080] In this specification, the Raman spectra of the solid electrolyte in each part are obtained by measuring the solid electrolyte at specified positions in each part of the cross section A of the capacitor element under the following conditions.

[0081] Raman spectrometer: NanoPhoton RamanFORCE PAV

[0082] Diffraction grating: 600gr / cm

[0083] Wavenumber range for measurement: 0 cm -1 Above and 2500cm -1 the following

[0084] Temperature: 25℃

[0085] The wavelength, power density, and exposure time of the irradiating laser are determined based on the type of conjugated polymer. For example, when the conjugated polymer is PEDOT, the irradiating laser wavelength is 784.73 nm and the laser power density is 870 W / cm². 2 The exposure time is 60 seconds.

[0086] Raman spectroscopy measurements can be performed using a sample acquired through the following steps. First, a solid electrolytic capacitor is embedded in a curable resin and the resin is cured. The cured material is ground or its cross-section is polished to expose a cross-section perpendicular to the length direction of the capacitor element and parallel to its thickness direction. With the length of the region containing the solid electrolyte in the direction parallel to the length direction of the capacitor element defined as 1, cross-section A is defined as a position from 0 to 0.05 units measured from the end of the region containing the solid electrolyte on the side opposite to the anode lead (the end on the second end side). This yields the sample for measurement. In the exposed cross-section A of the sample, the Raman spectrum of an 8 μm × 8 μm region of the solid electrolyte (part 1) on the surface of each part is measured. The intensities of the first and second peaks are determined by averaging the measurements at 12 locations within the 8 μm × 8 μm region of each part. More specifically, for part 1, the measurement area is selected for the solid electrolyte formed within the pits on the surface of the porous portion. Regarding Part A, the measurement area is selected for the portion of the solid electrolyte that is in contact with the main surface of the anode body having a dielectric layer. Regarding Part B, the measurement area is selected for the portion of the solid electrolyte layer opposite to the anode body (such as the portion opposite to the anode body with a thickness of 0.15T or less measured from the surface of the solid electrolyte layer).

[0087] (other)

[0088] When the average thickness of the second part is set as T, the average thickness of part B can be 0.15T or more, 0.30T or more, or 0.50T or more. The average thickness T of the second part is the average thickness of the second part measured from the main surface of the anode body with the dielectric layer. The thickness T is obtained by measuring and averaging the distance from the main surface of the anode body with the dielectric layer to the outer edge of the solid electrolyte layer at multiple locations (e.g., 10 locations) in section A.

[0089] The average thickness T of Part 2 can 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 can be 5 μm or more and 20 μm or less, or 10 μm or more and 20 μm or less.

[0090] Part B can be either carbon-free or carbon-particle-free. In Part B, the second polymer component tends to segregate, resulting in lower adhesion to the cathode lead-out layer compared to the case without segregation. However, when Part B contains carbon particles, the adhesion between Part B and the cathode lead-out layer, such as the metal layer, can be improved even without a carbon-particle-containing layer covering the solid electrolyte layer. Since a carbon-particle-containing layer is not required, the thickness of the cathode lead-out layer can be reduced, ensuring high voltage withstand capability without increasing the thickness of the capacitor element. Furthermore, high capacitance per unit volume of the solid electrolytic capacitor can be ensured. This effect is particularly significant when the solid electrolytic capacitor is a laminate containing multiple capacitor elements, as evidenced by the inclusion of carbon particles in Part B.

[0091] Part B containing or not containing carbon particles means that at least the area of ​​Part B that is in contact with Part A contains or does not contain carbon particles.

[0092] Examples of carbon particles include conductive carbon. Examples of conductive carbon include graphite (artificial graphite, natural graphite, etc.).

[0093] The average particle size of the carbon particles can be greater than or equal to 0.1 μm and less than 3 μm, or greater than or equal to 0.3 μm and less than 2 μm. With an average particle size in this range, high adhesion between Part 2 and the cathode lead-out layer containing the metal layer is ensured, and carbon particles are easily dispersed within Part B.

[0094] The average particle size of carbon particles is the 50% particle size D50 (i.e., the median particle size) in the particle size distribution of the volume reference determined by a particle size distribution measuring device using laser diffraction scattering.

[0095] When part B contains carbon particles, the carbon particle content in part B can 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 the region of part B that is in contact with part A (e.g., the region from the interface between part A and part B to a thickness of 0.20T). When the carbon particle content is within the above range, leakage current is easily suppressed, and a higher seal is easily ensured between part 2 and the cathode lead-out layer (including metal layers, etc.).

[0096] In this disclosure, the anode body may be an anode foil containing aluminum, and the solid electrolyte layer may contain sulfur. The sulfur originates from a second polymer component, etc. In this manner, in the elemental mapping of the cross-section of the first part using an electron probe microanalyzer (EPMA), the sulfur content when the aluminum content is set to 100% can be 0.50% or more, 0.65% or more, or 0.70% or more. By setting the sulfur content within such a range, a highly conductive solid electrolyte is highly packed in the porous portion, thus suppressing the degradation of the solid electrolyte during repeated charge-discharge cycles, maintaining the contact between the first part or the porous portion and the second part, and suppressing capacity reduction. Furthermore, the resistance of the first part can be kept low from the initial stage, the initial ESR can be kept low, and a high initial capacity can be ensured. Considering the volume of the pores in the porous portion, the sulfur content is, for example, 5.00% or less.

[0097] EPMA-based analysis was performed using a sample in a capacitor element where a cross-section of the porous portion containing the cathode containing a solid electrolyte was exposed, and a platinum film was formed. In the cross-sectional image of the porous portion containing the solid electrolyte, for a region 5 μm wide, including the bottom of the porous portion from the main surface of the anode foil (in other words, the total thickness of the porous portion on one side of the anode foil × a 5 μm wide region), elemental mapping was performed based on the wavelength differences of characteristic X-rays based on EPMA, and the net intensity of the contained elements was measured. The net intensity is obtained by removing background (noise) from the measured values ​​of each element. The percentage (%) of the net intensity of S element was calculated when the net intensity of Al element was set to 100%. For multiple regions (e.g., 5 regions), the percentage (%) of the net intensity of S element was calculated, and the average value was taken as the percentage (%) of the presence of S element when the presence ratio of Al element in the porous portion was set to 100%.

[0098] The conditions for EPMA analysis are as follows.

[0099] The environment during the measurement was 25℃ and atmospheric pressure.

[0100] Accelerating voltage: 15.0kV

[0101] Beam current: 20.1 nA

[0102] Integrating time: 180.0ms / point (12-minute mode)

[0103] Spectroscopic crystals: AP / CH1, PbST / CH2, PET / CH3, LiF / CH4, LSA80 / CH5

[0104] The analytical sample can be prepared, for example, by the following steps. First, a solid electrolytic capacitor is embedded in a curable resin and the resin is cured. The anode foil has a first end and a second end opposite to the first end, and the solid electrolyte is formed on the portion of the anode foil at the second end. At a predetermined position in the direction from the first end of the anode foil toward the second end (in other words, the length direction of the anode foil or capacitor element), the cured material obtained above is wet-ground or dry-ground in such a way that a cross-section perpendicular to the length direction of the capacitor element and parallel to the thickness direction is exposed. The exposed cross-section is smoothed by ion milling. Platinum (Pt) is sputtered onto the smoothed cross-section using a sputtering device to form a platinum film with a thickness of 1 nm or more and 2 nm or less. The analytical sample is thus obtained. It should be noted that when the length of the region where the solid electrolyte is formed in the direction parallel to the length direction of the capacitor element is set to 1, the cross-section is set at a position of 0 or more and 0.05 or less from the end of the region where the solid electrolyte is formed.

[0105] (Formation of a solid electrolyte layer)

[0106] (The formation of Part 1 and Part A)

[0107] Part 1 and Part A can be formed by electrolytic polymerization of a precursor of the first polymer component (such as a first monomer) on the surface of the dielectric layer in the presence of the second polymer component. For example, electrolytic polymerization is performed while the cathode forming portion of an anode body on which the dielectric layer is formed is immersed in a liquid mixture containing the precursor of the first polymer component and the second polymer component. By performing such electrolytic polymerization, the precursor of the first polymer component grows on the surface of the dielectric layer, forming a first polymer in a state that interacts with the second polymer component. Part 1 is formed within the voids of the porous portion, and Part A is formed on the main surface of the anode body having the dielectric layer.

[0108] Three-electrode electropolymerization utilizes three electrodes: an anode, a counter electrode, and a reference electrode, all with a dielectric layer formed on their surface. In three-electrode electropolymerization, the anode potential can be precisely controlled regardless of changes in the natural potential of the counter electrode by using the reference electrode. Compared to the two-electrode method using only an anode and a counter electrode, the three-electrode method provides more precise control over the electropolymerization reaction. Furthermore, adjusting the polymerization potential allows for the regulation of the interaction with the polymer anions and the growth rate of the polymer chains in the first polymer component (conjugated polymer). This improves the orientation of the formed conjugated polymer and enhances the dispersion of the polymer anions. As a result, a more uniform and dense solid electrolyte is formed with a high filling rate within the porous structure. Additionally, forming a dense solid electrolyte on the main surface of the anode with the dielectric layer improves the adhesion between the first and second parts. Moreover, the high dispersion of the polymer anions facilitates a higher doping rate, thereby improving the conductivity of the solid electrolyte itself.

[0109] Examples of precursors for conjugated polymers include monomers (such as first monomers), oligomers formed by linking multiple molecular chains (such as first monomer units) of the monomers, and prepolymers. The precursor must contain at least one first monomer unit. One type of precursor may be used, or a combination of two or more may be used. From the viewpoint of easily obtaining higher orientation of the conjugated polymer, at least one precursor selected from monomers and oligomers (especially monomers) is preferred.

[0110] Liquid compositions typically contain a solvent. Examples of solvents include water, organic solvents, and mixtures of water and organic solvents (such as water-soluble organic solvents).

[0111] When using other conductive materials, additives, etc., it can be added to the liquid composition.

[0112] The liquid composition may contain an oxidizing agent as needed. Furthermore, the oxidizing agent may be coated onto the anode body before or after contacting the liquid composition with the anode body having a dielectric layer formed. Examples of such oxidizing agents include those capable of generating Fe. 3＋ Compounds (such as ferric sulfate), persulfates (such as sodium persulfate and ammonium persulfate), and hydrogen peroxide. Oxidizing agents can be used alone or in combination of two or more.

[0113] As the counter electrode, a Ti electrode can be used, but it is not limited to this. As the reference electrode, a silver / silver chloride electrode (Ag / Ag) is preferably used. ＋ ).

[0114] In electrolytic polymerization, the voltage applied to the anode foil (polymerization voltage) is, for example, 0.6V or higher and 1.5V or lower. From the viewpoint of easily achieving high filling within the pores of the porous material and easily ensuring relatively high crystallinity of the solid electrolyte, the polymerization voltage is preferably greater than 0.9V and less than 1.2V (or less than 1.1V), and can be greater than 1V (e.g., greater than 1.0V) and less than 1.2V, or greater than 1V (e.g., greater than 1.0V) and less than 1.1V. By performing electrolytic polymerization in a three-electrode configuration at such a polymerization voltage, the polymerization reaction within the pores can be precisely controlled. Therefore, within the pores, the polymer chains of the conjugated polymer can grow in a highly dispersed state of polymer anions, the solid electrolyte can be highly filled within the pores, and the A-part can be formed with a dense solid electrolyte. In addition, since the polymerization can proceed slowly, the orientation and crystallinity of the conjugated polymer can be further improved, and high conductivity can be easily ensured. It should be noted that the polymerization voltage is the voltage of the anode foil relative to the reference electrode (silver / silver chloride electrode (Ag / Ag)). ＋ The potential of the anode foil is the electrical potential of the anode foil. In electrolytic polymerization, a power supply (such as a power supply strip) 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 refers to the potential of the power supply that is electrically connected to the anode foil.

[0115] The temperature for electrolytic polymerization is, for example, above 5°C and below 60°C, or above 15°C and below 35°C.

[0116] A pre-coating can be formed on the surface of the dielectric layer prior to electrolytic polymerization. The pre-coating may contain, for example, a conductive material. The pre-coating can be formed using a liquid dispersion containing conductive polymers (conjugated polymers and dopants, etc.). However, the liquid dispersion used in forming the pre-coating has a smaller particle size and lower concentration of conductive polymers compared to the liquid dispersion used in forming the solid electrolyte constituting the cathode portion. For example, the average primary particle size of the conductive polymer particles contained in the liquid dispersion used for the pre-coating may be 100 nm or less, and may be 60 nm or less. Furthermore, the dry solids content of the liquid dispersion is, for example, 1.2% by mass or less. It should be noted that in the case of forming the solid electrolyte constituting the cathode portion, the average primary particle size of the conductive polymer particles in the liquid dispersion is typically 200 nm or more, and the dry solids content is 2% by mass or more. The conjugated polymer in the pre-coating may be the same type or a different type as the conjugated polymer formed by electrolytic polymerization. The dopants in the pre-coating may be the same type or a different type than the dopants used in the electrolytic polymerization. In this disclosure, since Part 1 and Part A are formed by electrolytic polymerization, even if a pre-coating is formed using a liquid dispersion, the polymer liquid can fully penetrate into the fine pores, and Part 1 can be formed with a high filling rate.

[0117] (Part B)

[0118] Part B is formed using a liquid dispersion (or solution) comprising a first polymer component and a second polymer component. The liquid dispersion (or solution) typically contains a liquid medium. Examples of liquid media include water, organic solvents, and mixtures of water and organic solvents (such as water-soluble organic solvents).

[0119] More specifically, part B can be formed by immersing the anode body, on which parts 1 and A are formed, in the aforementioned liquid dispersion (or solution), removing it, and drying it. Alternatively, it can be formed by coating the surface of the solid electrolyte portion of the anode body on which parts 1 and A are formed with the aforementioned liquid dispersion (or solution) and then drying it. Drying can be performed under heating or under reduced pressure. If necessary, part B can be formed by adhering a treatment solution containing anionic components, or a treatment solution containing both anionic and cationic components, to the solid electrolyte portion after forming parts 1 and A.

[0120] Part B can be a single-layer structure or a multi-layer structure.

[0121] (other)

[0122] Part 1 and Part 2 may each further include, as needed, at least one selected from known additives and known conductive materials other than conductive polymers. Examples of conductive materials include, for instance, at least one selected from conductive inorganic materials such as manganese dioxide and TCNQ complex salts.

[0123] Examples of additives include known additives added to solid electrolytes (e.g., coupling agents, silane compounds), known conductive materials other than conductive polymers, and water-soluble polymers. The components of a solid electrolyte may contain one of these additives, or a combination of two or more.

[0124] When Part B consists of multiple layers, the types, compositions, and contents of conductive polymers, additives, etc., contained in each layer can be the same or different. A layer to improve adhesion can also be sandwiched between the dielectric layer and the solid electrolyte layer.

[0125] The differences between the individual solid electrolytes constituting Part 1 and Part A or Part B can be determined, for example, by EPMA analysis of cross-sectional images. For instance, EPMA analysis can be performed at equal intervals in a cross-sectional image of the entire solid electrolyte layer, and the interfaces between adjacent solid electrolytes can be determined based on the differences in the wavelengths of characteristic X-rays at each measurement point. The samples used for measurement are prepared using the same procedures as those used for Raman spectroscopy measurements.

[0126] (Cathode lead-out layer)

[0127] The cathode lead-out layer may have at least a first layer that is in contact with and covers at least a portion of the solid electrolyte, or it may have a first layer and a second layer covering the first layer. Examples of the first layer include a layer containing conductive particles, a metal foil, etc. Examples of conductive particles include at least one selected from conductive carbon and metal powder. For example, the cathode lead-out layer may be composed of a layer containing conductive carbon as the first layer (also called a carbon particle-containing layer) and a metal-containing layer (a layer containing metal powder or a metal foil, etc.) as the second layer. When a metal-containing layer is used as the first layer, the cathode lead-out layer may also be composed of this metal-containing layer.

[0128] For example, if part B contains carbon particles, the cathode lead-out 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 lead-out layer may also be formed from the metal-containing layer as the first layer. If part B does not contain carbon particles, the cathode lead-out layer may also include a carbon-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-containing layer.

[0129] Conductive carbon contained in a layer of carbon particles can be exemplified by graphite (artificial graphite, natural graphite, etc.).

[0130] In a metal-containing layer, the layer containing metal powder can be formed, for example, by laminating a composition containing metal powder onto the surface of the first layer or the solid electrolyte layer. Examples of such a metal powder-containing layer include a metal paste layer formed using a composition containing metal powder such as silver particles and a resin (binder resin). Thermoplastic resins can also be used as the resin, but thermosetting resins such as imide resins and epoxy resins are preferred.

[0131] When using metal foil in a metal-containing layer, the type of metal is not particularly limited. Valve-acting metals (aluminum, tantalum, niobium, etc.) or alloys containing valve-acting metals are preferred. The surface of the metal foil can be roughened as needed. A chemical conversion coating or a coating of a different metal (dissimilar metal) or non-metal can be applied to the surface of the metal foil. Examples of dissimilar metals or non-metals include metals such as titanium and non-metals such as carbon (conductive carbon, etc.).

[0132] Alternatively, the film of the aforementioned dissimilar metal or non-metal (e.g., conductive carbon) can be used as the first layer, and the aforementioned metal foil can be used as the second layer.

[0133] (Diaphragm)

[0134] When a metal foil is used as the cathode lead-out layer, a diaphragm can also be disposed between the metal foil and the anode body (especially the anode foil). There are no particular limitations on the diaphragm; for example, a nonwoven fabric containing fibers such as cellulose, polyethylene terephthalate, vinylon, or polyamides (e.g., aliphatic polyamides, aromatic polyamides such as aramid) can be used.

[0135] (other)

[0136] A solid electrolytic capacitor contains at least one capacitor element. Solid electrolytic capacitors can be wound, chip-type, or multilayered. For example, a solid electrolytic capacitor can also contain two or more multilayered capacitor elements. Alternatively, a solid electrolytic capacitor can also contain two or more wound capacitor elements. The configuration of the capacitor elements can be selected based on the type of solid electrolytic capacitor.

[0137] In a capacitor element, one end of the cathode lead terminal is electrically connected to the cathode lead layer. For example, a conductive adhesive is applied to the cathode lead layer, and the cathode lead terminal is bonded to the cathode lead layer via this conductive adhesive. One end of the anode lead terminal is electrically connected to the anode foil. The other ends of the anode lead terminal and the other ends of the cathode lead terminal extend from the resin casing or housing, respectively. The other ends of each terminal exposed from the resin casing or housing are used for welding connections to the substrate on which the solid electrolytic capacitor is to be mounted, etc.

[0138] Capacitor elements are sealed using a resin casing or housing. For example, the capacitor element and the resin material of the casing (e.g., uncured thermosetting resin and filler) can be contained in a mold, and the capacitor element can be sealed with a resin casing using transfer molding, compression molding, or similar methods. In this case, the anode lead terminal connected to the anode lead extending from the capacitor element, and the other end portion of the cathode lead terminal, are exposed from the mold. Alternatively, the capacitor element can be contained in a bottomed housing with the other end portions of the anode and cathode lead terminals located on the opening side of the bottomed housing, and the opening of the bottomed housing can be sealed using a sealing material, thereby forming a solid electrolytic capacitor.

[0139] Figure 1 This is a schematic cross-sectional view illustrating the structure of a solid electrolytic capacitor according to one embodiment of the present disclosure. Figure 1 As shown, the solid electrolytic capacitor 1 includes a capacitor element 2, a resin casing 3 that seals the capacitor element 2, and at least a portion of an anode lead terminal 4 and a cathode lead terminal 5 exposed outside the resin casing 3. The anode lead terminal 4 and the cathode lead terminal 5 may be made of metals such as copper or copper alloys. The resin casing 3 has a generally cuboid shape, and the solid electrolytic capacitor 1 also has a generally cuboid shape.

[0140] The capacitor element 2 includes an anode foil 6 formed 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 lead-out layer 10 covering the solid electrolyte layer 9. The anode foil 6 has porous portions formed by etching or the like on both of its surfaces. The solid electrolyte layer 9 contains sulfur and has a first portion that fills the voids in the porous portions of the anode foil 6 having the dielectric layer 7, and a second portion that protrudes from the main surface of the anode foil. The second portion is divided into a portion A on the side of the first portion and a portion B on the side opposite to the first portion.

[0141] The cathode lead-out layer 10 may also consist of a carbon particle-containing layer (first layer) 11 covering at least a portion of the solid electrolyte layer 9 and a metal-containing layer (second layer) 12 covering at least a portion of the first layer. This type of cathode lead-out layer 10 is used when portion B of the second part does not contain carbon particles. When portion B contains carbon particles, a carbon particle-containing layer is not particularly necessary, and the cathode lead-out layer 10 may be composed of a metal-containing layer. Such a metal-containing layer may be a layer containing metal powder (such as a metal paste layer).

[0142] The anode foil 6 includes a region opposite to the cathode portion 8 and a region not opposite to it. In the region of the anode foil 6 not opposite to the cathode portion 8, an insulating separation portion 13 is formed adjacent to the cathode portion 8, covering the surface of the anode foil 6 in a strip-like manner to restrict contact between the cathode portion 8 and the anode foil 6. Another portion of the region of the anode foil 6 not opposite to the cathode portion 8 is electrically connected to the anode lead terminal 4 by soldering. The cathode lead terminal 5 is electrically connected to the cathode portion 8 via an adhesive layer 14 formed of a conductive adhesive.

[0143] [Example]

[0144] The present invention will now be described in detail based on embodiments and comparative examples, but the present invention is not limited to the following embodiments.

[0145] Solid Electrolytic Capacitor E1

[0146] Construct a solid electrolytic capacitor E1 according to the following instructions and evaluate its characteristics.

[0147] (1) Preparation of anode foil

[0148] An anode foil is fabricated by roughening both surfaces of an aluminum foil (thickness: 130 μm) through etching. The porous portions formed on the two surfaces of the anode foil are each 50 μm thick.

[0149] (2) Formation of the dielectric layer

[0150] The cathode forming part of the anode foil is immersed in a chemical conversion solution, and a DC voltage of 70V is applied for 20 minutes to form a dielectric layer containing aluminum oxide.

[0151] (3) Formation of solid electrolyte layer

[0152] A separation portion is formed by attaching an insulating resist tape between the regions where a solid electrolyte layer is formed and the regions where a solid electrolyte layer is not formed on the anode foil in which a dielectric layer is formed. The anode foil with the separation portion is then immersed in a liquid composition containing a conductive material, removed, and dried, thereby forming a pre-coating (not shown).

[0153] A mixed solution was prepared by dissolving EDOT monomer and polystyrene sulfonic acid (PSS, Mw: 100,000) as the polymeric anion in ion-exchanged water. Ferric sulfate (III) (an oxidant) dissolved in the ion-exchanged water was added while stirring the mixed solution to prepare a polymerization solution. Electrolytic polymerization was carried out using the obtained polymerization solution in a three-electrode configuration. More specifically, a pre-coated anode foil, a counter electrode, and a reference electrode (silver / silver chloride reference electrode) were impregnated in the polymerization solution. A voltage was applied to the anode foil (more specifically, the power supply attached to the anode lead) with a potential of 1.1V relative to the reference electrode, and electrolytic polymerization was carried out at 25°C to form Part 1 and Part A.

[0154] Next, follow the steps below to form Part B.

[0155] The anode foil having portions 1 and A is immersed in a liquid dispersion containing a conductive polymer and dried at 120°C for 10–30 minutes. The immersion and drying in the liquid dispersion are repeated four times each. This forms portion B by covering the surface of the anode foil having portions 1 and A. The liquid dispersion is an aqueous dispersion containing conductive polymers (PEDOT as the first polymer component and polystyrene sulfonic acid (PSS, Mw = 160,000) as the second polymer component) at a concentration of 2–4% by mass.

[0156] (4) Formation of the cathode lead-out layer

[0157] The anode foil obtained in (3) above is immersed in a dispersion of graphite particles in water, removed from the dispersion, and dried, thereby forming at least a carbon particle layer (layer 1) on the surface of the solid electrolyte layer. The drying is carried out at 130-180°C for 10-30 minutes.

[0158] Next, a silver paste containing silver particles and an adhesive resin (epoxy resin) is applied to the surface of the first layer, and heated at 150–200°C for 10–60 minutes to cure the adhesive resin, forming a metal-containing layer (second layer). In this way, a cathode lead-out layer consisting of the first and second layers is formed, and a cathode portion consisting of a solid electrolyte layer and the cathode lead-out layer is formed.

[0159] To manufacture capacitor components, proceed as described above.

[0160] (5) Assembly of solid electrolytic capacitors

[0161] The cathode portion of the capacitor element obtained in (4) above is joined to one end of the cathode lead terminal using an adhesive layer of conductive adhesive. One end of the anode foil protruding from the capacitor element is joined to one end of the anode lead terminal by laser welding.

[0162] Next, a resin casing made of insulating resin is 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 are positioned to extend out from the resin casing.

[0163] This completes the solid electrolytic capacitor E1. Using the same procedure as above, a total of 20 solid electrolytic capacitors E1 were manufactured.

[0164] Solid Electrolytic Capacitor E2

[0165] As the liquid dispersion used to form part B, a liquid dispersion containing conductive polymers and carbon particles (artificial graphite, D50: 0.8 μm) was used. The proportion of carbon particles in the dry solid component of the liquid dispersion was set to 50% by mass. In addition, a total of 20 solid electrolytic capacitors E2 were manufactured by operating in the same manner as in the case of solid electrolytic capacitor E1.

[0166] Solid Electrolytic Capacitor C1

[0167] The entire solid electrolyte layer (part 1 and part A) was formed by electrolytic polymerization, but part B was not formed. The average thickness (equivalent to thickness T) of part A (the solid electrolyte layer protruding from the main surface) was 18.0 μm. Otherwise, a solid electrolytic capacitor was fabricated using the same procedure as in the case of solid electrolytic capacitor E1.

[0168] [evaluate]

[0169] The following evaluation was conducted using solid electrolytic capacitors.

[0170] (a) Thickness T

[0171] Following the steps above, calculate the average thickness T of the second part.

[0172] (b) Raman spectroscopy determination of each part

[0173] Using a solid electrolytic capacitor, the Raman spectra of the solid electrolyte in sections A, specifically parts 1 and B, were determined following the steps outlined above. In the Raman spectra of parts 1 of the solid electrolytic capacitors E1 and E2, the Raman spectrum at 1420 cm⁻¹... -1 A peak characteristic of the 5-membered ring of PEDOT (peak 1) was observed at 1000 cm⁻¹. -1 A peak characteristic of the aromatic ring -S bond in PSS (the second peak) was observed. The intensity I of the first peak was determined. p1 and the intensity of the second peak I p2 , calculate I p1 / I p2 Compare.

[0174] (c) Charge and discharge characteristics

[0175] At 20°C, the initial electrostatic capacitance (μF) of each solid electrolytic capacitor at a frequency of 120 Hz was measured using a 4-terminal LCR meter. Then, the average value (C0) of the 20 solid electrolytic capacitors was calculated.

[0176] Next, after repeating the charge-discharge cycle of the solid electrolytic capacitors 60,000 times under the following conditions, the electrostatic capacitance was measured at 20°C following the same procedure as the initial electrostatic capacitance, and the average value (C1) of the 20 solid electrolytic capacitors was calculated. The rate of change of electrostatic capacitance (ΔC) was then calculated using the following formula.

[0177] The rate of change of electrostatic capacitance ΔC: (C1-C0) / C0×100 (%)

[0178] The rate of change of electrostatic capacitance is negative. The smaller the rate of change of electrostatic capacitance, the lower the capacity after repeated charging and discharging, and the lower the charge and discharge characteristics.

[0179] (d) ESR

[0180] The initial ESR (mΩ) of the capacitor elements at a frequency of 100kHz was measured using a 4-terminal LCR meter at an environment of 20°C. Then, the average value of the initial ESR of 20 capacitor elements was calculated.

[0181] (e) Withstand voltage

[0182] A voltage was applied to a solid electrolytic capacitor while increasing the voltage at a rate of 1.0 V / s, and the breakdown voltage (BDV) (unit: V) was measured when an overcurrent of 0.5 A flowed through it. The breakdown voltage is represented by a relative value when the BDV (V) of the solid electrolytic capacitor of Comparative Example 1 is set to 100. The larger the value, the higher the breakdown voltage.

[0183] The evaluation results are shown in Table 1. E1 to E2 are examples, and C1 is a comparative example. The initial capacity C0 and the initial ESR are expressed as relative values ​​when C1 is set to 100.

[0184] [Table 1]

[0185]

[0186] As shown in Table 1, high charge-discharge characteristics and voltage withstand capability were obtained in the embodiments, and relatively low ESR (E1 and E2) was ensured. In E1, it can be said that despite the large thickness T of the second part, the ESR was suppressed to a relatively low level. In addition, in E2, the second part contains carbon particles, so the ESR is suppressed even more. In contrast, in Comparative Example C1, although the ESR is low, the voltage withstand capability is low.

[0187] Preferred embodiments of the present invention have been described, but such disclosure should not be interpreted as restrictive. Various modifications and alterations will be readily apparent to those skilled in the art upon reading the above disclosure. Therefore, the scope of the appended claims should be interpreted as including all modifications and alterations without departing from the true spirit and scope of the invention.

[0188] Industrial availability

[0189] According to this disclosure, a solid electrolytic capacitor can be obtained with high charge-discharge characteristics and voltage withstand capability, and low ESR can be ensured. Therefore, the solid electrolytic capacitor of this disclosure can be used in a variety of applications requiring reliability, long life, and excellent voltage withstand capability. However, the applications of solid electrolytic capacitor elements and solid electrolytic capacitors are not limited to these.

[0190] Explanation of reference numerals in the attached figures

[0191] 1: Solid electrolytic capacitor

[0192] 2: Capacitor Components

[0193] 3: Resin outer casing

[0194] 4: Anode lead terminal

[0195] 5: Cathode lead terminal

[0196] 6: Anode foil

[0197] 7: Dielectric layer

[0198] 8: Cathode section

[0199] 9: Solid electrolyte layer

[0200] 10: Cathode lead-out layer

[0201] 11: Level 1

[0202] 12: Level 2

[0203] 13: Separation section

[0204] 14: Adhesive layer

Claims

1. A solid electrolytic capacitor element comprising: an anode body having at least a porous surface layer; 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 lead-out layer covering at least a portion of the surface of the solid electrolyte layer. The solid electrolyte layer comprises a first polymer component and a second polymer component, the first polymer component comprising monomer units corresponding to the thiophene compound, and the second polymer component comprising polymer anions. The solid electrolyte layer has a first portion that fills the voids in the porous portion of the anode body having the dielectric layer, and a second portion that protrudes from the main surface of the anode body having the dielectric layer. In a cross-section obtained by cutting the solid electrolyte layer parallel to its thickness direction, the second portion is divided into portion A on the side of the first portion and portion B on the opposite side of the first portion. When the Raman spectra of the first and second portions of the cross section were measured, a first peak characteristic of the first polymer component was observed in the first and second portions, but no first peak characteristic of the first polymer component was observed in the second portion.

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

3. The solid electrolytic capacitor element according to claim 1, wherein, The cathode lead-out layer comprises a carbon-containing particle 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-containing particle layer.

4. The solid electrolytic capacitor element according to claim 1, wherein, Part B also contains carbon particles.

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

6. The solid electrolytic capacitor element according to claim 1, wherein, In the Raman spectrum, the position of the first peak is 1200 cm⁻¹. -1 Above and 1600cm -1 the following.

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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