HK1116914A - Electrolyte capacitors with polymeric outer layer and process for producing thereof - Google Patents

Description

Electrolytic capacitor with polymer outer layer and method for making same

RELATED APPLICATIONS

The present application claims the benefit of german application No. 102005033839 filed on 20/7/2005, which is incorporated by reference in its entirety for all useful purposes.

Technical Field

The invention relates to a method for producing an electrolytic capacitor having a low equivalent series resistance and a low residual current, said capacitor consisting of a solid electrolyte made of a conductive polymer and an outer layer containing a conductive polymer, to an electrolytic capacitor produced by said method and to the use of said electrolytic capacitor.

Description of the related Art

Conventional commercial solid electrolytic capacitors are typically composed of porous metal electrodes, an oxide layer on the metal surface, an electrically conductive solid introduced into the porous structure, an outer electrode (contact) such as a silver layer, and other electrical contacts and packaging.

Examples of solid electrolytic capacitors are tantalum, aluminum, niobium and niobium oxide capacitors with charge transfer complexes, manganese dioxide or polymeric solid electrolytes. The use of porous bodies has the advantage of a very high capacity density, i.e. a high capacitance that can be obtained in a small space due to the large surface area.

Owing to their high conductivity, pi-conjugated polymers are particularly suitable for use as solid electrolytes. Pi-conjugated polymers are also known as conducting polymers or synthetic metals. The importance of pi-conjugated polymers in terms of economy is increasing due to the advantages of polymers compared to metals in terms of the targeted adjustment of processability, weight and chemical modification properties. Examples of known pi-conjugated polymers are polypyrrole, polythiophene, polyaniline, polyacetylene, polyphenylene and poly (p-phenylene vinylene), poly-3, 4- (ethylene-1, 2-dioxy) thiophene, also commonly referred to as poly (3, 4-ethylenedioxythiophene), being the very industrially used polythiophene, because of its very high conductivity in oxidized form.

The development of electronic technology has increased the demand for solid electrolytic capacitors having very low Equivalent Series Resistance (ESR). This is due to, for example, the need for reduced logic voltages, higher integration densities and increased clock frequencies in integrated circuits. Low ESR also reduces energy consumption and this is particularly advantageous for mobile battery operating applications. Therefore, it is desirable to reduce ESR of the solid electrolytic capacitor as much as possible.

European patent specification EP-A340512 describes a process for preparing solid electrolytes from 3, 4-ethylene-1, 2-dioxythiophene and the use of cationic polymers thereof prepared by oxidative polymerization as solid electrolytes in electrolytic capacitors. Due to the higher conductivity, the replacement of manganese dioxide or charge transfer complexes with poly (3, 4-ethylenedioxythiophene) in solid electrolytic capacitors reduces the equivalent series resistance of the capacitor and increases the frequency behavior.

In addition to low ESR, modern solid electrolytic capacitors require low residual current and good stability against external stresses. High mechanical stresses that can greatly increase the residual current of the capacitor anode occur especially during the manufacturing process when encapsulating the capacitor anode.

The stability against such stresses and the resulting low residual current can be achieved mainly by an outer layer of about 5-50 μm thick made of a conductive polymer on the capacitor anode. This layer acts as a mechanical buffer layer between the anode and cathode side electrodes of the capacitor. This prevents the silver layer (contact) from directly contacting the dielectric, for example when mechanically stressed, or from damaging the dielectric and thereby increasing the residual current of the capacitor. The conductive polymer outer layer should itself exhibit known self-healing behavior: relatively small defects in the dielectric on the outer anode surface, which occur despite the buffer effect, are electrically insulated by the current breaking the conductivity of the outer layer at the defect points.

It is very difficult to form a thick polymer outer layer by in situ polymerization. The formation of layers in this process requires a very large number of coating cycles. As a result of said multiple coating cycles, the coating of the outer layer is very uneven, in particular the edges of the capacitor anode are often improperly covered. It is stated in japanese patent application JP-a 2003-. However, this makes the production process very prone to interruptions. The addition of binder materials for forming layers more quickly is also difficult because the binder materials hinder oxidation in the in situ polymerization. In addition, the in situ polymerized layer must be free of residual salts by washing, thereby forming pinholes in the polymer layer.

A dense conductive outer layer with good edge coverage can be formed by electrochemical polymerization. Electrochemical polymerization, however, requires that a conductive sheet be first deposited on the insulating oxide layer of the capacitor anode, and that layer then be in electrical contact with each individual capacitor. Such contacts are very expensive in mass production and may damage the oxide layer.

The conductive outer layer on the capacitor can also be prepared by mixing a powder of a conductive polymer with a binder and applying the mixture to the capacitor body. However, the high contact resistance between the individual powder particles creates additional resistance, preventing the production of solid electrolytic capacitors with low ESR.

In EP- ｃA-637043, the addition of the conductive powder significantly increases the non-uniformity of the outer layer produced by chemical in situ polymerisation, improves the adhesion between the outer graphite layer and the polymer film and thus achieves lower ESR values and loss factors. However, this method has a disadvantage in that the polymer outer layer becomes very uneven (unevenness: 10 to 50 μm). Since the total thickness of the polymeric outer layer should not exceed 5-50 μm in order to achieve a low ESR, this high inhomogeneity leads to locally very thin outer layers and thus to high residual currents. Voltage peaks and electrical breakdowns may also occur at non-uniform points of the polymer outer layer.

In Japanese patent applications JP-A2001-102255 and JP-A2001-060535, a layer of polyethylene dioxythiophene/polystyrene sulfonic acid (PEDT/PSS) (also referred to as polyethylene dioxythiophene/polystyrene sulfonic acid complex or PEDT/PSS complex) is applied directly onto an oxide film to protect the oxide film and improve adhesion between the solid electrolyte and the oxide film. An outer layer is then applied over the layer by in situ polymerization or by dipping the capacitor anode in a tetracyanoquinodimethane salt solution. However, this method has the following drawbacks: the PEDT/PSS complex does not cross the porous anode body having pores. Modern highly porous anode materials cannot be used.

US-P6,001,281 describes in the examples solid capacitors with a solid electrolyte prepared in situ from polyethylene dioxythiophene (PEDT) and an outer layer prepared from PEDT/PSS complexes. However, these capacitors have a drawback of having an ESR of 130m Ω or more.

In EP-A-1524678, the outer polymer layer is produced by applying ｃA dispersion containing at least one polymeric anion and at least one optionally substituted polyaniline and/or at least one polythiophene having repeating units of the general formulae (I), (II) or repeating units of the general formulae (I) and (II) with ｃA binder. Although this method improves edge coverage, it cannot be used to produce polymeric outer layers with reliable repeat density.

Disclosure of Invention

There is therefore still a need for an improved method for producing solid electrolytic capacitors having a low Equivalent Series Resistance (ESR), which is capable of producing dense polymer outer layers with good edge coverage in a simple and reliable reproducible manner. The object therefore provides such a method and a capacitor improved thereby.

It has now surprisingly been found that dispersions containing polyaniline and/or polythiophene particles having a diameter of less than 700nm, a binder and solid particles having a diameter of 0.7 to 20 μm meet these requirements.

Surprisingly, coarse solid particles having a diameter of 0.7 to 20 μm in the dispersion have a significant influence on the formation of the outer layer on the electrolytic capacitor. The corner and edge coverage is significantly improved by these particles. Polyaniline and/or polythiophene particles with a diameter of less than 700nm not only contribute to good conductivity of the layer and thus low ESR of the capacitor, but also smooth out the inhomogeneities produced by these solid particles. This results in a dense and compact layer with a uniform thickness, i.e. low inhomogeneity, and thus in a capacitor with low residual current.

The invention therefore relates to a process for preparing an electrolytic capacitor, comprising applying a dispersion a) to a capacitor body comprising at least:

a porous electrode body of an electrode material,

a dielectric covering the surface of the electrode material,

a solid electrolyte comprising at least a conductive material, preferably a conductive polymer, covering all or part of the electrolyte surface,

the dispersion (a) comprises at least:

conductive polymer particles b) containing at least one optionally substituted polyaniline and/or at least one polythiophene having repeating units of the general formula (I) or (II) or repeating units of the general formula (I) and (II)

Wherein

A represents optionally substituted C₁-C₅An alkylene group or a substituted alkylene group,

r represents a linear or branched optionally substituted C₁-C₁₈Alkyl, optionally substituted C₅-C₁₂Cycloalkyl, optionally substituted C₆-C₁₄Aryl, optionally substituted C₇-C₁₈Aralkyl, optionally substituted C₁-C₄A hydroxyalkyl group or a hydroxyl group,

x represents an integer of 0 to 8, and

if a plurality of radicals R are bonded to A, which may be identical or different,

and contains a binder c) and a dispersant d),

and, in order to form the outer layer of the conductive polymer, the dispersant d) and/or the curing binder c) are at least partially removed,

characterized in that the proportion of conductive polymer particles b) having a diameter of less than 700nm in dispersion a) constitutes a solids content of at least 5% by weight of the solids content of the dispersion,

and, in addition to components b) to d), solid particles e) having a diameter of 0.7 to 20 μm are also contained in the dispersion.

Drawings

FIG. 1 is a schematic view showing a structure of a solid electrolytic capacitor in an example of a tantalum capacitor.

Fig. 2 shows an enlarged detail 10 of fig. 1, which reproduces the schematic layer structure of a tantalum capacitor.

Detailed Description

The invention therefore relates to a process for preparing an electrolytic capacitor comprising applying dispersion a) to a capacitor body, wherein the capacitor body comprises:

a porous electrode body of an electrode material,

a dielectric covering the surface of the electrode material,

a solid electrolyte comprising at least a conductive material, preferably a conductive polymer,

and the dispersion a) comprises at least:

conductive polymer particles b) containing at least one optionally substituted polyaniline and/or at least one polythiophene having repeating units of the general formula (I) or (II) or repeating units of the general formula (I) and (II)

Wherein

A represents optionally substituted C₁-C₅An alkylene group or a substituted alkylene group,

r represents a linear or branched optionally substituted C₁-C₁₈Alkyl, optionally substituted C₅-C₁₂Cycloalkyl, optionally substituted C₆-C₁₄Aryl, optionally substituted C₇-C₁₈Aralkyl, optionally substituted C₁-C₄A hydroxyalkyl group or a hydroxyl group,

x represents an integer of 0 to 8, and

if a plurality of radicals R are bonded to A, which may be identical or different,

and contains a binder c) and a dispersant d),

and, in order to form the outer layer of conductive polymer, the dispersing agent d) and/or the curing binder c) are at least partially removed,

wherein the proportion of conductive polymer particles b) having a diameter of less than 700nm in dispersion a) constitutes a solids content of at least 5% by weight of the solids content of the dispersion,

and, in addition to components b) to d), solid particles e) having a diameter of 0.7 to 20 μm are also contained in the dispersion.

The proportion of particles e) in the dispersion is preferably at least 5% by weight of the solids content of the dispersion.

The general formulae (I) and (II) are to be understood such that x substituents R can be attached to the alkylene radical A.

The diameter of the particles b) is measured, for example, by an ultracentrifuge device. The diameter distribution of the particles b) relates to the mass distribution in the dispersion as a function of the particle diameter.

The diameter of the solid particles e) in the dispersion is measured, for example, by laser diffraction. The diameter distribution of these solid particles relates to the volume distribution of the solid particles e) in the dispersion as a function of the particle diameter.

In dispersion a), the proportion of particles b) having a diameter of less than 700nm, based on their solids content, is preferably at least 10% by weight, particularly preferably at least 15% by weight, based on the solids content of the dispersion.

The proportion of particles b) having a diameter of less than 500nm, based on their solids content, is particularly preferably at least 5% by weight, more preferably at least 10% by weight, and very particularly preferably at least 15% by weight, based on the solids content of the dispersion a).

The proportion of particles b) having a diameter of less than 400nm, based on their solids content, is particularly preferably at least 5% by weight, more preferably at least 10% by weight, and very particularly preferably at least 15% by weight, based on the solids content of the dispersion a).

In the process, the conductive polymer particles b) in the dispersion a) preferably have an average diameter of from 5 to 500nm, particularly preferably from 10 to 300 nm.

The proportion of solid particles e) having a diameter of from 0.7 to 20 μm is preferably at least 10% by weight, particularly preferably at least 15% by weight, based on the solids content of dispersion a).

The proportion of solid particles e) having a diameter of from 1 to 10 μm is particularly preferably at least 5% by weight, more preferably at least 10% by weight, and very particularly preferably at least 15% by weight, based on the solids content of dispersion a).

The proportion of solid particles e) having a diameter of from 1 to 5 μm is particularly preferably at least 5% by weight, more preferably at least 10% by weight, and very particularly preferably at least 15% by weight, based on the solids content of dispersion a).

In the dispersion a), the solid particles e) preferably have an average diameter of from 1 to 10 μm, particularly preferably from 1 to 5 μm.

In dispersion a), the solid particles e) preferably have a diameter distribution d10 value of more than 0.9 μm and a d90 value of less than 15 μm, particularly preferably have a d10 value of more than 1 μm and a d90 value of less than 10 μm, very particularly preferably have a d10 value of more than 1.2 μm and a d90 value of less than 8 μm.

The value of the diameter distribution d10 means that the particles having a diameter which is less than or equal to the value of d10 represent 10% of the total volume of all solid particles e) in dispersion a). The diameter distribution d90 means that the particles having a diameter of less than or equal to the value d90 represent 90% of the total volume of all solid particles e) in dispersion a).

The conductive polymer particles b), binder c) and solid particles e) preferably form a stable dispersion. However, unstable dispersions can also be used, provided that they are used, for example, by stirring, tumbling or shaking, to ensure uniform distribution of the components before use.

The solid particles e) can be inorganic particles, organic particles or a mixture of organic and inorganic particles and in particular have a composition which is different from that of components b) and c).

The solid particles e) used may be conventional fillers, for example carbonates such as calcium carbonate, silicates, silica, calcium sulfate or barium sulfate, aluminum hydroxide, glass fibers or glass spheres, wood flour, cellulose powder or carbon black.

Particularly suitable inorganic solid particles e) consist, for example, of carbon, graphite, carbon black, metals, metal oxides, ceramics, silicates, silicon oxides, preferably silicon dioxide, for example precipitated silicon dioxide, fumed silicon dioxide, silica gel, quartz or glass. Precipitated silica, fumed silica and silica gel are particularly preferred.

The organic solid particles e) consist, for example, of polymers, in particular electrically conductive polymers, or cellulose.

The solid particles e) are preferably introduced into the dispersion a) in powder form, but may also be present in other forms, for example in the form of fibers or spheres.

Conductive polymers as the basis of solid particles include, for example, polythiophene, polypyrrole and polyaniline, which may be substituted or unsubstituted.

Preferred conductive polymers for the solid particles e) include polythiophenes having recurring units of the general formulae (I), (II) or recurring units of the general formulae (I) and (II), where A, R and x have the meanings specified above for the general formulae (I) and (II).

A particularly preferred electrically conductive polymer in the solid particles e) is poly (3, 4-ethylenedioxythiophene).

The electrode material is preferably formed into a porous body having a large surface area in the electrolytic capacitor produced by the method of the present invention, for example, in the form of a porous calcined pellet or an etched sheet. Hereinafter, the porous body is also shortened to an electrode body.

The electrode body covered with the dielectric is also shortened to an oxidized electrode body below. The term "oxidized electrode body" also includes an electrode body covered by a dielectric, which is not prepared by oxidation of the electrode body.

The electrode body covered with the dielectric and entirely or partially covered with the solid electrolyte is also shortened below as the capacitor main body.

The electrically conductive layer, which is produced by the inventive method from dispersion a) and comprises at least one optionally substituted polyaniline and/or at least one polythiophene having a repeating unit of the general formula (I) or (II) or repeating units of the general formulae (I) and (II), and at least one binder c) and solid particles s), is also referred to below as polymer outer layer.

The dispersion a) preferably comprises at least one polymeric organic binder c). Examples of particularly preferred polymeric organic binders c) include polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl chloride, polyvinyl acetate, polyvinyl butyrate, polyacrylates, polyacrylamides, polymethacrylates, polymethacrylamides, polyacrylonitrile, styrene/acrylates, vinyl acetate/acrylates and ethylene/vinyl acetate copolymers, polybutadiene, polyisoprene, polystyrene, polyethers, polyesters, polycarbonates, polyurethanes, polyamides, polyimides, polysulfones, melamine-formaldehyde resins, epoxy resins, silicone resins or celluloses. Other preferred polymeric organic binders c) also include those which can be produced by addition of crosslinking agents, such as melamine compounds, blocked isocyanates or functional silanes, such as 3-glycidoxypropyltrialkoxysilane, tetraethoxysilane and tetraethoxysilane hydrolysates or crosslinkable polymers, such as polyurethanes, polyacrylates or polyolefins, and subsequent crosslinking. Such crosslinked products suitable as polymeric binders c) can also be formed, for example, by reacting added crosslinking agents with any polymeric anions contained in dispersion a). Preferably one that is sufficiently thermally stable to withstand the temperatures to which the finished capacitor is subsequently exposed (e.g., soldering temperatures of 220 ℃ C. and 260 ℃ C.).

The solids content of the preferred polymeric binders c) in the dispersion a) is from 0.1 to 90% by weight, preferably from 0.5 to 30% by weight, particularly preferably from 0.5 to 10% by weight.

Preferably, sufficient binder c) is added to dispersion a) to effectively bind the polymeric outer layer to the capacitor body and to obtain a high degree of stability within the polymeric outer layer. The ratio of the solids content (% by weight) of the binder c) to the solids content of the solid particles e) is therefore preferably greater than 1: 2, particularly preferably greater than 1: 1. Thereby further increasing the mechanical stability of the layer and the adhesion of the layer to the capacitor body.

The dispersion a) may contain one or more dispersants d). Examples of the dispersant d) include the following solvents. Aliphatic alcohols such as methanol, ethanol, isopropanol, and butanol; aliphatic ketones such as acetone and methyl ethyl ketone; aliphatic carboxylic acid esters such as ethyl acetate and butyl acetate; aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as hexane, heptane and cyclohexane; chlorinated hydrocarbons such as dichloromethane and dichloroethane; aliphatic nitriles such as acetonitrile; aliphatic sulfoxides and sulfones, such as dimethyl sulfoxide and sulfolane; aliphatic carboxylic acid amides such as methylacetamide, dimethylacetamide and dimethylformamide; aliphatic and araliphatic ethers, such as diethyl ether and anisole. The dispersants d) used may also be water or mixtures of water with the abovementioned organic solvents.

Preferred dispersants d) include water or other protic solvents, for example alcohols such as methanol, ethanol, isopropanol and butanol, and also mixtures of water with these alcohols; a particularly preferred solvent is water.

The binder c) can also optionally act as a dispersant d).

According to the invention, the term "polymer" includes all compounds having more than one identical or different repeating unit.

Conductive polymers are used to denote in particular a class of pi-conjugated polymers which are electrically conductive after oxidation or reduction. Conductive polymers are preferably used to mean having at least about 1 μ S cm after oxidation^-1A conductive pi-conjugated polymer.

Within the scope of the present invention, the prefix "poly" is used to indicate that more than one identical or different repeating unit is contained in the polymer or polythiophene. The polythiophenes contain a total of n recurring units of the formula (I) or (II) or of the formulae (I) and (II), n being an integer from 2 to 2,000, preferably from 2 to 100. The recurring units of the general formulae (I) and/or (II) in the polythiophenes may each be identical or different. Preference is given in each case to polythiophenes having identical recurring units of the general formula (I), (II) or (I) and (II).

Each end group of the polythiophene preferably has H.

The solid electrolyte may contain, as a conductive polymer, an optionally substituted polythiophene, an optionally substituted polypyrrole or an optionally substituted polyaniline.

Preferred conductive polymers for the solid electrolyte are polythiophenes having recurring units of the general formulae (I), (II) or recurring units of the general formulae (I) and (II), where A, R and x have the definitions given above for the general formulae (I) and (II).

Particularly preferably wherein A represents optionally substituted C₂-C₃Alkylene and x represents 0 or 1, a polythiophene having a repeating unit of the general formula (I), (II) or repeating units of the general formulae (I) and (II).

Most preferably poly (3, 4-ethylenedioxythiophene) is used as the conductive polymer of the solid electrolyte.

C₁-C₅Alkylene A is preferably methylene, ethylene, n-propylene, n-butylene or n-pentylene. C₁-C₁₈Alkyl preferably represents straight or branched chainC₁-C₁₈Alkyl, for example methyl, ethyl, n-or i-propyl, n-, i-, s-or t-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1-ethylpropyl, 1-dimethylpropyl, 1, 2-dimethylpropyl, 2-dimethylpropyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl, C₅-C₁₂Cycloalkyl R denotes, for example, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl or cyclodecyl, C₅-C₁₄Aryl R represents, for example, phenyl or naphthyl, and C₇-C₁₈Aralkyl represents, for example, benzyl, o-, m-, p-tolyl, 2, 3-, 2, 4-, 2, 5-, 2, 6-, 3, 4-, 3, 5-xylyl or 2, 4, 6-trimethylphenyl. The above list is used by way of example to illustrate the invention and should not be construed as exhaustive.

Various organic radicals are conceivable as optional further substituents for the radicals A and/or the radicals R, for example alkyl, cycloalkyl, aryl, aralkyl, alkoxy, halogen, ether, thioether, disulfide, sulfoxide, sulfone, sulfonate, amino, aldehyde, ketone, carboxylate, carboxylic acid, carbonate, carboxylate, cyano, alkylsilane and alkoxysilane groups and carboxamide groups.

For example, the above-mentioned groups a and R and/or other substituents for the groups a and R may be considered, for example, as substituents for polyaniline. Unsubstituted polyaniline is preferred.

The polythiophenes used as solid electrolytes in the preferred process can be neutral or cationic. In a preferred embodiment they are cationic, "cationic" refers only to the charge located on the polythiophene backbone. Depending on the substituents on the group R, the polythiophene can have positive and negative charges on the main unit, the positive charge being located on the polythiophene main chain and the negative charge optionally being located on the group R which is substituted by sulfonate or carboxylate groups. In this case, the positive charge on the polythiophene main chain can be partially or completely saturated by the negative charge optionally present on the radical R. In these cases, the polythiophene can be cationic, neutral or even anionic, as described above. However, within the scope of the present invention they are considered to be cationic polythiophenes, since the positive charge on the polythiophene main chain is of crucial importance. The positive charge is not illustrated by chemical formula because its exact number and position is not precisely determined. However, the number of positive charges is at least 1 and at most n, n being the total number of repeating units (identical or different) within the polythiophene.

To balance the positive charge, cationic polythiophenes require anions as counterions if this has not occurred as a result of the optional sulfonate or carboxylate substitution and thus the negative charge of R.

The counter ion may be a monomeric or a polyanionic, the latter hereinafter also referred to as polymeric anion.

The polymeric anion for the solid electrolyte may be, for example, an anion of: polymeric carboxylic acids, such as polyacrylic acid, polymethacrylic acid or polymaleic acid or polysulfonic acids, such as polystyrenesulfonic acid and polyvinylsulfonic acid. These polycarboxylic and sulfonic acids may also be copolymers of vinylcarboxylic and vinylsulfonic acids with other polymerizable monomers (for example acrylates and styrenes).

Preferably, monomeric ions are used for the solid electrolyte, since they penetrate better through the oxidized electrode body.

Suitable monomeric anions include, for example: c₁-C₂₀Alkanesulfonic acids, such as methane, ethane, propane, butane or higher sulfonic acids, such as dodecanesulfonic acid; aliphatic perfluorosulfonic acids such as trifluoromethanesulfonic acid, perfluorobutanesulfonic acid, or perfluorooctanesulfonic acid; aliphatic C₁-C₂₀Carboxylic acids, such as 2-ethylhexyl carboxylic acid; aliphatic perfluorocarboxylic acids such as trifluoroacetic acid or perfluorooctanoic acid; optionally is covered with C₁-C₂₀Alkyl-substituted aromatic sulfonic acids such as benzenesulfonic acid, o-toluenesulfonic acid, p-toluenesulfonic acid or dodecylbenzenesulfonic acid; and cycloalkanesulfonic acids, e.g. camphorsulfonic acid or tetrafluoroborate, hexafluorophosphatePerchlorate, hexafluoroantimonate, hexafluoroarsenate or hexachloroantimonate.

Preference is given to the anion of p-toluenesulfonic acid, methanesulfonic acid or camphorsulfonic acid.

Cationic polythiophenes containing anions as counterions for charge compensation are generally known as polythiophene/(poly) anion complexes.

In addition to the conductive polymer and optional counter-ions, the solid electrolyte may contain binders, cross-linking agents, surface-active substances, such as ionic or non-ionic surfactants or binders and/or other additives.

The binder is, for example, an organofunctional silane and its hydrolysis products, such as 3-glycidoxypropyltrialkoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane or octyltriethoxysilane.

The solid electrolyte preferably includes a conductive polymer and a monomeric anion as the counter ion.

The solid electrolyte preferably forms a layer with a thickness of less than 200nm, particularly preferably less than 100nm, more preferably less than 50nm, on the dielectric surface.

The coverage of the dielectric with the solid electrolyte can be determined as follows: the capacitance of the capacitor was measured at 120Hz in both the dry and wet state. The degree of coverage is the ratio of the capacitance in the dry state to the capacitance in the wet state, expressed as a percentage. The dry state means that the capacitor has been dried at a high temperature (80-120 ℃) for several hours before the measurement. The wet state indicates that the capacitor has been exposed to saturated ambient humidity for several hours at high pressure, for example in a steam pressure vessel. The moisture penetrates into the pores not covered with the solid electrolyte and serves as a liquid electrolyte therein.

The coverage of the dielectric by the solid electrolyte is preferably greater than 50%, particularly preferably greater than 70%, more preferably greater than 80%.

As shown in the figures and by way of example in fig. 1 and 2, the polymeric outer layer is preferably located on all or part of the outer surface of the capacitor body. The outer surface refers to the outside of the capacitor body.

Fig. 1 is a schematic view showing a structure of a solid electrolytic capacitor in an embodiment of a tantalum capacitor, comprising:

1 capacitor body

5 outer layer of polymer

6 graphite/silver layer

7 lead wire in contact with the electrode body 2

8 external joint

9 Package

10 detailed view

Fig. 2 shows an enlarged detail 10 of fig. 1, which reproduces a schematic layer structure of a tantalum capacitor, comprising:

10 detailed view

2 porous electrode body (Anode)

3 dielectric

4 solid electrolyte (cathode)

5 outer layer of polymer

6 graphite/silver layer

7 solid particles

The geometric surface area is hereinafter referred to as the outer surface of the capacitor body 1, which is derived from the geometric dimensions. For a right parallelepiped sintered compact, the geometric surface area corresponds to:

geometric surface area 2(L B + L H + B H),

where L is the length of the body, B is the width of the body, and H is the height of the body, and x denotes the multiplication. Only a portion of the capacitor body 1 having the polymer outer layer placed thereon was tested.

If a plurality of capacitor bodies 1 are used in the capacitor, the individual surface areas are added to give a total geometric surface area.

For a solid electrolytic capacitor containing, for example, a wound coil as a porous electrode body, the size (length, width) of the unwound coil was used for measurement.

Instead of a solid electrolyte containing a conductive polymer, a solid electrolyte containing a non-polymeric conductive material, such as a charge transport complex, for example TCNQ (7, 7, 8, 8-tetracyano-1, 4-quinodimethane), manganese oxide or a salt, such as those that can form an ionic liquid, may also be contained in the solid electrolytic capacitor. The polymer outer layer also produces a lower residual current in this type of solid electrolytic capacitor.

The same preferred structural features as for the polythiophenes used in the solid electrolyte apply to the polythiophenes of the conductive polymer particles b) located in dispersion a) having recurring units of the general formula (I), (II) or recurring units of the general formulae (I) and (II).

Polymeric or monomeric anions can be used as counterions for the polyaniline and/or the polythiophene of the abovementioned particles b) having recurring units of the general formula (I), (II) or recurring units of the general formulae (I) and (II). However, additional counter ions may also be provided in this layer. Polymeric anions are preferably used as counterions in dispersion a).

The polymeric anion may be, for example, the anion of a polymeric carboxylic acid, such as polyacrylic acid, polymethacrylic acid or polymaleic acid, or a polysulfonic acid, such as polystyrenesulfonic acid and polyvinylsulfonic acid. These polycarboxylic and sulfonic acids can also be copolymers of vinylcarboxylic and vinylsulfonic acids with other polymerizable monomers (e.g. acrylates and styrene).

Anions of polymeric carboxylic or sulfonic acids are preferred as polymeric anions in the above particles b).

The anion of polystyrene sulfonic acid (PSS) is particularly preferred as the polymeric anion.

The molecular weight of the polyacid which provides the polymeric anion is preferably 1,000-2,000,000, particularly preferably 2,000-500,000. Polyacids or alkali metal salts thereof are commercially available, for example polystyrenesulfonic acids or polyacrylic acids and the like can be prepared by known methods (see, for example, Houben Weyl, Prozessen der organischen Chemie, vol. E20 Markromolekulare Stoffe, second part (1987), p.1141 ff).

The polymeric anionic and electrically conductive polymers may be present in the dispersion a) in a weight ratio of from 0.5: 1 to 50: 1, preferably from 1: 1 to 30: 1, particularly preferably from 2: 1 to 20: 1. The weight of the electrically conductive polymer here corresponds to the weight fraction of the monomers used, provided that there is complete conversion during the polymerization.

The dispersion a) may also contain monomeric anions. The same preferred anions as listed above for the solid electrolyte apply to the monomeric anions.

The dispersion a) may also contain further components, for example surface-active substances, such as ionic and nonionic surfactants or additives, for example organofunctional silanes or their hydrolysis products, for example 3-glycidoxypropyltrialkoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane or octyltriethoxysilane.

The thickness of the outer polymer layer is preferably from 1 to 1,000. mu.m, particularly preferably from 1 to 100. mu.m, very particularly preferably from 2 to 50 μm, and even more preferably from 4 to 20 μm. The layer thickness may vary on the outer surface. In particular, the layer thickness at the edges of the capacitor body may be thicker or thinner than on the side surfaces of the capacitor body. However, a substantially uniform layer thickness is preferred.

The polymeric outer layer may have a uniform or non-uniform distribution with respect to the composition associated with the binder c) and the conductive polymer. Preferably uniformly distributed.

The polymeric outer layer may be a component of a multilayer system that forms the outer layer of the capacitor body. Thus, while the electrical function of the polymer outer layer should not be limited, one or more other functional layers (e.g., an adhesive layer) may be located between the solid electrolyte and the polymer outer layer. Other functional layers may also be located on the polymeric outer layer. A plurality of polymeric outer layers may also be located on the capacitor body.

The polymer outer layer is preferably located directly on the solid electrolyte. The polymer outer layer preferably penetrates the edge region of the capacitor body to achieve good electrical contact with the solid electrolyte and to increase adhesion to the capacitor body without penetrating the entire depth of all pores (see, e.g., fig. 2).

In a particularly preferred embodiment, the electrolytic capacitor produced by the process of the invention contains a solid electrolyte comprising poly (3, 4-ethylenedioxythiophene) (PEDT) and a polymeric outer layer comprising polystyrene sulfonic acid (PSS) and poly (3, 4-ethylenedioxythiophene), the latter also commonly referred to in the literature as PEDT/PSS or PEDT/PSS.

In a particularly preferred embodiment, the electrolytic capacitors produced by the process of the invention comprise a solid electrolyte made from poly (3, 4-ethylenedioxythiophene) and monomeric counterions and a polymeric outer layer made from PEDT/PSS, a binder c) and solid particles e).

Also preferred is a method of producing an electrolytic capacitor, characterized in that the electrode material is a valve metal or a compound having electrical properties comparable to valve metals.

Within the scope of the present invention, valve metal is used to denote a metal whose oxide layer does not cause current to flow equally in both directions. The oxide layer of the valve metal blocks the flow of current for the voltage applied by the anode, whereas for the voltage applied by the cathode there is an excess current that may damage the oxide layer. Valve metals include Be, Mg, Al, Ge, Si, Sn, Sb, Bi, Ti, Zr, Hf, V, Nb, Ta and W, and alloys or compounds of at least one of these metals with other elements. The most typical valve metals known are Al, Ta and Nb. Compounds having electrical properties comparable to valve metals are those having metallic conductivity, which can be oxidized and whose oxide layer has the properties described above. For example, NbO has metallic conductivity but is not generally considered a valve metal. However, oxidized NbO layers have typical valve metal oxidizing properties, and thus NbO or alloys or compounds of NbO with other elements are typical examples of compounds having electrical properties comparable to valve metals.

Thus, the term "oxidizable metal" is used to refer not only to a metal, but also to an alloy or compound of a metal with other elements, provided that it has metallic conductivity and can be oxidized.

The invention therefore particularly preferably relates to a process for producing electrolytic capacitors, characterized in that the valve metal or a compound having electrical properties comparable to those of the valve metal is tantalum, niobium, aluminum, titanium, zirconium, hafnium, vanadium, an alloy or compound of at least one of these metals with other elements, NbO or an alloy or compound of NbO with other elements.

The dielectric preferably consists of an oxide of the electrode material. Optionally containing other elements and/or compounds.

In addition to the kind of dielectric, the capacitance of the oxidation electrode body depends on the surface area and thickness of the dielectric. The charge-to-mass ratio is a measure of the amount of charge that can be absorbed by the oxidized electrode body per unit weight. The charge-to-mass ratio is calculated as follows:

charge-to-mass ratio (capacitance voltage)/weight of the oxidation electrode body

The capacitance is derived from the capacitance of the finished capacitor measured at 120Hz and the voltage is the operating voltage (nominal voltage) of the capacitor. The weight of the oxidized electrode body is based only on the weight of the dielectric coated porous electrode body and does not include polymers, contacts, and packaging.

The electrolytic capacitors produced by the novel process preferably have a charge to mass ratio of more than 10,000. mu.C/g, particularly preferably more than 20,000. mu.C/g, more preferably more than 30,000. mu.C/g, most preferably more than 40,000. mu.C/g.

The solid electrolytic capacitors produced by the process according to the invention are characterized by a low residual current and a low equivalent series resistance. The capacitor body is more robust to mechanical stress since the outer polymer layer forms a dense layer around the capacitor body and covers its edges well. Furthermore, the polymer outer layer shows good adhesion to the capacitor body and high conductivity, whereby a low equivalent series resistance can be obtained. The polymer outer layer shows only a low degree of inhomogeneity with respect to the layer thickness. The outer layer does not contain any thin areas where high residual currents may occur.

The invention preferably relates to electrolytic capacitors prepared by the novel process having an ESR of less than 50m Ω measured at 100 kHz. The ESR of the electrolytic capacitors produced by the novel process is particularly preferably below 31 m.OMEGA.when measured at a frequency of 100kHz, more preferably below 21 m.OMEGA.and most preferably below 16 m.OMEGA.. In a particularly preferred embodiment of the electrolytic capacitor, the ESR is less than 11m Ω.

The equivalent series resistance of a solid electrolytic capacitor is inversely proportional to the geometric surface area of the capacitor. The product of the equivalent series resistance and the geometric surface area thus provides a variable independent of the overall size.

The invention therefore also preferably relates to an electrolytic capacitor produced by the novel process, wherein the product of the equivalent series resistance measured at 100kHz and the geometric surface area of the capacitor body is less than 4,000 m.OMEGA.mm². The product of the equivalent series resistance and the geometric surface area is particularly preferably less than 3,000 m.OMEGA.mm²More preferably less than 2,000 m.OMEGA.mm²Most preferably less than 1,000m Ω mm². In a particularly preferred embodiment of the electrolytic capacitor, the product of the equivalent series resistance and the geometric surface area is less than 600 m.OMEGA.mm²。

An electrolytic capacitor of this type according to the invention can be prepared essentially as follows: first, a valve metal powder having a large surface area is, for example, pressed and sintered to form a porous electrode body. Conductive wires made of the same metal as the powder (e.g. tantalum) are usually pressed into an electrode body. The metal foil may also be etched to obtain a porous foil.

The electrode body is then covered with a dielectric, i.e. an oxide layer, by e.g. electrochemical oxidation. The conductive polymer forming the solid electrolyte is chemically or electrochemically deposited on the dielectric, for example by oxidative polymerization. The precursors for preparing the conductive polymer, the oxidizing agent(s) and optionally the counter-ions are then applied simultaneously or consecutively to the dielectric of the porous electrode body and polymerized by chemical oxidation at a certain temperature, or the precursors for preparing the conductive polymer and the counter-ions are polymerized on the dielectric of the porous electrode body by electrochemical polymerization. According to the invention, a layer containing at least one optionally substituted polyaniline and/or a polythiophene having a repeating unit of the general formulae (I), (II) or repeating units of the general formulae (I) and (II) and at least one binder c) and solid particles e) is then applied from the dispersion to the capacitor body. Additional layers are optionally applied to the polymeric outer layer. Coatings with readily conductive layers, such as graphite and silver, or metallic cathode bodies are used as electrodes for discharging the current. And finally, connecting the capacitor and packaging.

The precursor for preparing the conductive polymer, hereinafter also referred to as precursor, is used to represent the corresponding monomer or its derivative. Mixtures of different precursors may also be used. Suitable monomer precursors include, for example, optionally substituted thiophenes, pyrroles or anilines, preferably optionally substituted thiophenes, particularly preferably optionally substituted 3, 4-alkylenedioxythiophenes.

Examples of substituted 3, 4-alkylenedioxythiophenes include compounds of the general formulae (III), (IV) or mixtures of thiophenes of the general formulae (III) and (IV)

Wherein

A represents optionally substituted C₁-C₅Alkylene, preferably optionally substituted C₂-C₃An alkylene group or a substituted alkylene group,

r represents a linear or branched optionally substituted C₁-C₁₈Alkyl, preferably straight or branched, optionally substituted C₁-C₁₄Alkyl, optionally substituted C₅-C₁₂Cycloalkyl, optionally substituted C₆-C₁₄Aryl, optionally substituted C₇-C₁₈Aralkyl, optionally substituted C₁-C₄Hydroxyalkyl, preferably optionally substituted C₁-C₂A hydroxyalkyl group, or a hydroxyl group,

x represents an integer from 0 to 8, preferably an integer from 0 to 6, particularly preferably 0 or 1, and

if a plurality of radicals R are attached to A, they may be identical or different.

A more particularly preferred monomer precursor is optionally substituted 3, 4-ethylenedioxythiophene.

Examples of substituted 3, 4-ethylenedioxythiophenes include compounds of the general formula (V)

Wherein R and x have the meanings given for the general formulae (III) and (IV).

According to the invention, derivatives of these monomer precursors are understood to include, for example, dimers or trimers of these monomer precursors. Higher molecular weight derivatives, such as tetramers, pentamers, etc. of the monomer precursors are also possible as derivatives.

A compound of the general formula (VI)

Examples of substituted 3, 4-alkylenedioxythiophene derivatives,

wherein

n represents an integer from 2 to 20, preferably from 2 to 6, particularly preferably 2 or 3,

and is

A. R and x have the meanings given for the general formulae (III) and (IV).

The derivatives may consist of the same or different monomer units and may be used in pure form and in the form of mixtures with one another and/or with monomer precursors. If the same conductive polymers as the above-mentioned precursors are produced during their polymerization, the oxidized or reduced forms of these precursors are also covered by the term "precursor" within the scope of the present invention.

C within the scope of the invention₁-C₅Alkylene A is methylene, ethylene, n-propylene, n-butylene or n-pentylene. C within the scope of the invention₁-C₁₈Alkyl represents a straight or branched chain C₁-C₁₈Alkyl, for example methyl, ethyl, n-or i-propyl, n-, i-, s-or t-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1-ethylpropyl, 1-dimethylpropyl, 1, 2-dimethylpropyl, 2-dimethylpropyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl, C₅-C₁₂Cycloalkyl R denotes, for example, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl or cyclodecyl, C₅-C₁₄Aryl R represents, for example, phenyl or naphthyl, and C₇-C₁₈Aralkyl represents, for example, benzyl, o-, m-, p-tolyl, 2, 3-, 2, 4-, 2, 5-, 2, 6-, 3, 4-, 3, 5-xylyl or 2, 4, 6-trimethylphenyl. The above list is used by way of example to illustrate the invention and should not be construed as exhaustive.

The groups R and a may be substituted with a variety of organic groups such as alkyl, cycloalkyl, aryl, aralkyl, alkoxy, halogen, ether, thioether, disulfide, sulfoxide, sulfone, sulfonate, amino, aldehyde, ketone, carboxylate, carboxylic acid, carbonate, carboxylate, cyano, alkylsilane, and alkoxysilane groups and carboxamide groups.

The substituents R mentioned in the general formulae (III) and (IV) can be considered as substituents for the above-mentioned precursors, in particular for thiophenes, preferably for 3, 4-alkylenedioxythiophenes.

For example, the above-mentioned groups A and R and/or further substituents for the groups A and R can be considered as substituents for pyrroles and anilines.

Methods for preparing monomer precursors for the production of conductive polymers and derivatives thereof are well known to those skilled in the art and are described, for example, in l.groenendaal, f.jonas, d.freitag, h.pielartzik & j.r.reynolds, adv.mater.12(2000)481-494 and references cited therein.

The 3, 4-alkyleneoxythiophenes of the formula (III) required for preparing the polythiophenes to be used are known to the person skilled in the art or can be prepared by known methods (e.g. according to P.Blancard, A.Cappon, E.Levillain, Y.Nicolas, P.Frere and J.Roncali, org.Lett.4(4), 2002, pp.607-609).

The electrically conductive polymer is preferably prepared on the electrode body covered with the dielectric by oxidative polymerization of a precursor for producing the electrically conductive polymer, for which purpose the precursor, the oxidizing agent and optionally counter ions are applied, preferably in solution form, separately or successively or simultaneously, to the dielectric of the electrode body, and the oxidative polymerization is optionally completed by heating the coating, depending on the activity of the oxidizing agent used.

The application of the electrode body dielectric can be carried out directly or using a binder, for example a silane, such as an organofunctional silane or its hydrolysis products, for example 3-glycidoxypropyltrialkoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane or octyltriethoxysilane, and/or one or more different functional layers.

Depending on the oxidizing agent used and the desired reaction time, the chemical oxidative polymerization of the thiophenes of the formula (HI) or (IV) is generally carried out at temperatures of from-10 ℃ to 250 ℃, preferably from 0 ℃ to 200 ℃.

As solvents for the precursors and/or oxidizing agents and/or counterions for the preparation of the conductive polymers, the following organic solvents which are inert under the reaction conditions can be mentioned in principle: aliphatic alcohols such as methanol, ethanol, isopropanol, and butanol; aliphatic ketones such as acetone and methyl ethyl ketone; aliphatic carboxylic acid esters such as ethyl acetate and butyl acetate; aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as hexane, heptane and cyclohexane; chlorinated hydrocarbons such as dichloromethane and dichloroethane; aliphatic nitriles such as acetonitrile; aliphatic sulfoxides and sulfones, such as dimethyl sulfoxide and sulfolane; aliphatic carboxylic acid amides such as methylacetamide, dimethylacetamide and dimethylformamide; aliphatic and araliphatic ethers, such as diethyl ether and anisole. Water or mixtures of water with the abovementioned organic solvents can also be used as solvents.

Any metal salt suitable for the oxidative polymerization of thiophenes, anilines or pyrroles and well known to the person skilled in the art may be used as oxidizing agent.

Suitable metal salts include salts of the main group metals and the sub-group metals of the periodic table of the elements, which are also referred to hereinafter as transition metal salts. Suitable transition metal salts include in particular salts of inorganic or organic acids, or transition metals comprising organic groups, for example mineral acids of iron (III), copper (II), chromium (VI), cerium (IV), manganese (VII) and ruthenium (III).

Preferred transition metal salts include iron (III) salts. Conventional iron (III) salts are inexpensive, readily available and easy to handle, e.g. iron (III) salts of mineral acids, such as iron (III) halides (e.g. FeCl)₃) Or iron (III) salts of other mineral acids, e.g. Fe(ClO₄)₃Or Fe₂(SO₄)₃And Iron (III) salts of organic acids and inorganic acids including organic groups.

Mention may be made, as examples of iron (III) salts of mineral acids comprising organic radicals, of sulfuric acid mono C₁-C₂₀Iron (III) salts of alkanol esters, for example of lauryl sulphate.

Particularly preferred transition metal salts include organic acid salts, particularly iron (III) salts of organic acids.

Examples of iron (III) salts of organic acids include C₁-C₂₀Iron (III) salts of alkanesulfonic acids, for example of methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid or higher sulfonic acids, for example of dodecanesulfonic acid; iron (III) salts of aliphatic perfluorosulfonic acids, such as trifluoromethanesulfonic acid, perfluorobutanesulfonic acid, or perfluorooctanesulfonic acid; aliphatic C₁-C₂₀Iron (III) salts of carboxylic acids, for example iron (III) salt of 2-ethylhexyl carboxylic acid; iron (III) salts of aliphatic perfluorocarboxylic acids, for example iron (III) salts of trifluoroacetic acid or perfluorooctanoic acid; and optionally is C₁-C₂₀Iron (III) salts of alkyl-substituted arylsulfonic acids, such as iron (III) salts of benzenesulfonic acid, o-toluenesulfonic acid, p-toluenesulfonic acid or dodecylbenzenesulfonic acid; and Iron (III) salts of cycloalkanesulfonic acids, such as iron (III) salts of camphorsulfonic acid.

Any mixture of iron (III) salts of the above organic acids may also be used.

The use of iron (III) salts of organic acids and of inorganic acids comprising organic groups has the advantage that they are not corroded.

More particularly preferred as the metal salt is iron (III) p-toluenesulfonate, iron (III) o-toluenesulfonate or a mixture of iron (III) p-toluenesulfonate and iron (III) o-toluenesulfonate.

Peroxo compounds, such as hydrogen peroxosulphates (persulfates), in particular ammonium peroxosulphate and alkali metal peroxosulphates, such as sodium peroxosulphate and potassium peroxosulphate, or alkali metal perborates, optionally in the presence of catalytic amounts of metal ions, such as iron, cobalt, nickel, molybdenum or vanadium ions, and transition metal oxides, such as manganese dioxide (manganese (IV) oxide) or cerium (IV) oxide, are also suitable oxidizing agents.

Theoretically, for the oxidative polymerization of thiophenes of the general formula (III) or (IV), 2.25 equivalents of oxidizing agent per mole of thiophene are required (see, for example, j.polymer.sc.part.a Polymer Chemistry vol.26, p.1287 (1988)). However, lower or higher equivalents of oxidizing agent may also be used. According to the invention, 1 equivalent or more, particularly preferably 2 equivalents or more, of oxidizing agent is used per mole of thiophene.

For the separate application of the precursor, the oxidizing agent and the optional counter ions, the dielectric of the electrode body is preferably initially coated with a solution of the oxidizing agent and the optional counter ions and then coated with the precursor solution. For the preferred joint application of precursor, oxidizing agent and optionally counter-ion, the dielectric of the electrode body is coated with only one solution, i.e. a solution containing precursor, oxidizing agent and optionally counter-ion.

Other components may also be added to the solution, such as one or more organic binders dissolved in an organic solvent, such as polyvinyl acetate, polycarbonate, polyvinyl butyral, polyacrylate, polymethacrylate, polystyrene, polyacrylonitrile, polyvinyl chloride, polybutadiene, polyisoprene, polyether, polyester, silicone, styrene/acrylate, vinyl acetate/acrylate, and ethylene/vinyl acetate copolymers, or a water soluble binder, such as polyvinyl alcohol; crosslinkers such as melamine compounds, blocked isocyanates, functional silanes, for example tetraethoxysilane, alkoxysilane hydrolysates, for example based on tetraethoxysilane, epoxysilanes, for example 3-glycidoxypropyltrialkoxysilane, polyurethanes, polyacrylates or polyolefin dispersions, and/or additives, for example surface-active substances, for example ionic or nonionic surfactants, or additives, for example organofunctional silanes or hydrolysates thereof, for example 3-glycidoxypropyltrialkoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, octyltriethoxysilane.

The solution applied to the dielectric of the electrode body preferably contains 1 to 30% by weight of the thiophene of the general formula (III) or of the thiophene mixtures of the general formulae (III) and (IV) and 0 to 50% by weight of binders, crosslinkers and/or additives, all percentages by weight being based on the total weight of the mixture.

The solution can be applied to the dielectric of the electrode body by known methods, for example by dipping, casting, drop application, pouring, spraying, knife coating, brushing, spin coating, or printing, for example inkjet, screen printing, contact printing or embossing.

The solvent can be removed by simple evaporation at ambient temperature after application of the solution. However, in order to achieve higher processing speeds, it is more advantageous to remove the solvent at elevated temperatures, for example at temperatures of from 20 to 300 ℃ and preferably from 40 to 250 ℃. The heat post-treatment may be performed directly after the solvent is removed, or may be performed after a certain period of time after the coating is completed.

The duration of the heat treatment is 5 seconds to several hours, depending on the kind of polymer used at the time of coating. Temperature profiles with different temperatures and residence times may also be used in the heat treatment.

For example, the heat treatment may be performed in such a way that the coated oxidized electrode body is passed through a heating chamber at a desired temperature at a speed to achieve a desired dwell time at the selected temperature, or is brought into contact with a heated plate at the desired temperature for a desired dwell time. For example, the heating treatment may also be performed in a heating furnace or a plurality of heating furnaces each having a different temperature.

After removal of the solvent (drying) and optional thermal after-treatment, excess oxidizing agent and residual salts can advantageously be washed from the coating using a suitable solvent, preferably water or alcohol. Residual salts here refer to the salts of the reduced form of the reducing agent and optionally other salts.

For metal oxide dielectrics, such as the oxides of valve metals, after polymerization and preferably during or after washing, the oxide films can advantageously be electrochemically simulated to modify defects that may be present in the oxide films and subsequently reduce the residual current of the finished capacitor. During this reforming, the capacitor body is immersed in the electrolyte and a positive voltage is applied to the electrode body. The flowing current mimics the oxidation of the defect sites in the oxide film and destroys the conductive polymer where the high current defects flow.

Depending on the kind of oxidation electrode body, it is advantageous to impregnate the oxidation electrode body more times with the mixture, preferably after the washing process, to produce a thicker polymer layer.

The polythiophenes of the solid electrolyte can likewise be prepared from precursors by electrochemical oxidative polymerization.

During electrochemical polymerization, the dielectric-coated electrode body may first be coated with a thin layer of a conductive polymer. After applying a voltage to the layer, a layer containing the conductive polymer grows thereon. Other conductive layers may also be used as the deposited layer. Thus, Y.Kudoh et al describe the use of manganese oxide deposits in Journal of Power Sources 60(1996)157 and 163.

The electrochemical oxidative polymerization of the precursor can be carried out at a temperature of-78 ℃ to the boiling point of the solvent used. The electrochemical polymerization is preferably carried out at temperatures of from-78 ℃ to 250 ℃ and particularly preferably from-20 ℃ to 60 ℃.

The reaction time is from 1 minute to 24 hours, depending on the precursor used, the electrolyte used, the temperature selected and the current density applied.

If the precursor is a liquid, the electropolymerization may be carried out in the presence or absence of a solvent which is inert under the electropolymerization conditions. The electropolymerization of the solid precursor is carried out in the presence of a solvent which is inert under the electrochemical polymerization conditions. In some cases it is advantageous to use a solvent mixture and/or to add a solubilizer (detergent) to the solvent.

Examples of solvents that are inert under electropolymerization conditions include: water; alcohols such as methanol and ethanol; ketones such as acetone; halogenated hydrocarbons such as dichloromethane, chloroform, carbon tetrachloride and fluorinated hydrocarbons; esters such as ethyl acetate and butyl acetate; carbonates, such as propylene carbonate; aromatic hydrocarbons such as benzene, toluene, xylene; aliphatic hydrocarbons such as pentane, hexane, heptane and cyclohexane; nitriles such as acetonitrile and benzonitrile; sulfoxides such as dimethyl sulfoxide; sulfones, such as dimethyl sulfone, phenyl methyl sulfone, and sulfolane; liquid aliphatic amides such as methylacetamide, dimethylacetamide, dimethylformamide, pyrrolidone, N-methylpyrrolidone, N-methylcaprolactam; aliphatic and mixed aliphatic-aromatic ethers, such as diethyl ether and anisole; liquid ureas, for example tetramethylurea or N, N-dimethylimidazolidinone.

To perform the electropolymerization, an electrolyte additive is added to the precursor or a solution thereof. Free acids or conventional carrier electrolytes having a certain solubility in the solvents used are preferably used as electrolyte additives. The following have been demonstrated as electrolyte additives: free acids, for example p-toluenesulfonic acid, methanesulfonic acid and salts with alkanesulfonates, aromatic sulfonates, tetrafluoroborates, hexafluorophosphates, perchlorates, hexafluoroantimonates, hexafluoroarsenates and hexafluoroantimonate anions and alkali metal, alkaline earth metal or optionally alkylated ammonium, *, sulfonium and oxonium cations.

The concentration of the precursor may be 0.01 to 100 wt% (100 wt% means containing only the precursor), and the concentration is preferably 0.1 to 20 wt%.

The electropolymerization can be carried out batchwise or continuously.

The current density used for electropolymerization can vary within a wide range; usually, 0.0001 to 100mA/cm is used³The current density of (A) is preferably 0.01 to 40mA/cm³. Voltages of about 0.1-50V are obtained from these current densities.

For metal oxide dielectrics, it is advantageous to electrochemically mimic the oxide film after electrochemical polymerization to modify defects that may be present in the oxide film and subsequently reduce the residual current (reforming) of the finished capacitor.

The monomeric or polymeric anions already mentioned before are suitable as counterions, preferably the anions of monomeric or polymeric alkanesulfonic or cycloalkanesulfonic acids or aromatic sulfonic acids. The anions of the monomeric alkanesulfonic acids or cycloalkanesulfonic acids or aromatic sulfonic acids are particularly preferred for use in the electrolytic capacitors according to the invention, since the solutions containing them are more permeable into the dielectric-coated porous electrode material and thus allow a larger contact area to be formed between the dielectric and the solid electrolyte. The counter ion is added to the solution, for example in the form of its alkali metal salt or its free acid. During the electrochemical polymerization, these counterions are added to the solution or the thiophene, optionally as electrolyte additives or carrier electrolytes.

Furthermore, the optionally present anions of the oxidizing agents used can be used as counterions, so that in the case of chemical oxidative polymerization no further counterions have to be added.

After the solid electrolyte was prepared, the polymer outer layer was applied as described above.

The addition of a binder has the great advantage that it increases the adhesion between the polymer outer layer and the capacitor body. The adhesive may also bind solid particles in the outer polymer film. Solid particles of 0.7-20 μm enable complete coverage of the dispersion with a suitable outer layer even at edges and corners.

The dispersion a) may also contain crosslinking agents, surface-active substances, for example ionic or nonionic surfactants or binders and/or additives. The above-mentioned crosslinking agent for the solid electrolyte, the surface additive substance and/or the binder may be used.

The dispersion a) preferably contains further additives which increase the conductivity, for example compounds containing ether groups, such as tetrahydrofuran, compounds containing lactone groups, such as γ -butyrolactone, γ -valerolactone, compounds containing amide or lactam groups, such as caprolactam, N-methylcaprolactam, N-dimethylacetamide, N-methylacetamide, N-Dimethylformamide (DMF), N-methylformamide, N-methylformanilide, N-methylpyrrolidone (NMP), N-octylpyrrolidone, pyrrolidone, sulfones and sulfoxides, such as sulfolane (tetramethylene sulfone), dimethyl sulfoxide (DMSO), sugars or sugar derivatives, such as sucrose, glucose, fructose, lactose, sugar alcohols, such as sorbitol, mannitol, furan derivatives, such as 2-furancarboxylic acid, 3-furancarboxylic acid, and/or di-or polyhydric alcohols, such as ethylene glycol, glycerol, di-or triethylene glycol. Particular preference is given to using tetrahydrofuran, N-methylformamide, N-methylpyrrolidone, ethylene glycol, dimethyl sulfoxide or sorbitol as additive for increasing the conductivity.

The dispersion a) may have a pH of from 1 to 14, preferably a pH of from 1 to 8. For corrosion sensitive dielectrics, such as alumina, dispersions with a pH of 4 to 8 are preferred so as not to damage the dielectric.

The dispersion is preferably thixotropic to promote good edge and corner coverage of the capacitor body.

The dispersions are prepared from optionally substituted anilines, thiophenes of the general formulae (III), (IV) or mixtures of thiophenes of the general formulae (III) and (IV), for example analogously to the conditions described in EP-A440957. The above listed oxidizing agents and solvents may be used. The diameter distribution of the particles b) can be adjusted, for example, by high-pressure homogenization.

It is also possible to prepare polyaniline/polyanion or polythiophene/polyanion complexes and subsequently disperse or redisperse them in one or more solvents.

The dispersion is applied to the capacitor body by known methods, for example by spin coating, dipping, casting, drop application, injection, spraying, knife coating, brushing or printing, for example ink-jet printing, screen printing or embossing.

Depending on the type of application, the viscosity of the dispersions a) may be from 0.1 to 100,000 mPas (at 100 s)^-1Measured at a shear rate of). The viscosity is preferably from 1 to 10,000 mPas, particularly preferably from 10 to 1,500 mPas, very particularly preferably 100 mPas 1,000 mPas.

When the dispersion a) is applied to the capacitor body by impregnation, it is advantageous to form a film having a higher viscosity on the surface of the dispersion a) before impregnation. If the capacitor body is subsequently impregnated successively deeper into such a dispersion a) in one or more impregnation and drying cycles, the coverage of the edges and corners of the capacitor body is even more improved and blistering in the dried polymer film is prevented. Thus, the capacitor body can be dipped, for example, in the first step only half as deep into dispersion a) and then dried. In a second impregnation step, the capacitor body can then be completely impregnated in dispersion a) and subsequently dried. A thin film having a higher viscosity can be formed on the surface of the dispersion a), for example, by simply placing it in open air. The formation of the film can be accelerated by, for example, heating the dispersion a) or heating the dispersion surface with hot air or heat radiation.

Preference is given to using dispersions a) which in the dry state have a specific conductivity of more than 1S/cm, particularly preferably more than 10S/cm, more preferably more than 20S/cm and most preferably more than 50S/cm.

As already described above for the production of solid electrolytes, drying, washing of the layers by washing, reforming and repeated application can also be used for applying the outer polymer layer. In the case of a drying process, the dispersant d) is preferably removed. However, it is also possible that at least a part of the dispersant d) remains in the outer polymer layer. Depending on the dispersant c) or crosslinking agent used, further processing steps, for example curing or crosslinking by heat or light, may also be used. Other layers may also be applied to the polymeric outer layer.

For metal oxide dielectrics, it has surprisingly been found that, in order to produce solid electrolytic capacitors having a low ESR and a low residual current, no additional treatment step of the associated layer is required after application and drying of dispersion a). In other methods of preparing the polymer outer layer, the oxide layer must generally be reformed after application of the conductive polymer outer layer to achieve low residual current. As a result of this reforming in the electrolyte, the polymer outer layer may separate from the capacitor body at some point, thereby increasing the ESR. When using the method according to the invention, the reforming step may not be used, so that the residual current is not increased.

Preferably, once the polymeric outer layer is made, any other existing conductive layers, such as graphite and/or silver layers, may be applied to the capacitor, the capacitor connected and encapsulated.

Valve metals listed above for electrolytic capacitors or compounds having comparable electrical properties are preferably used for the production of the electrode body. Therefore, the preferable range is also applicable.

For example, oxidizable metals are sintered in powder form to form a porous electrode body, or the porous structure is compacted on a metal body. This can be done, for example, by etching the wafer.

For example, the porous electrode body is oxidized in a suitable electrolyte such as phosphoric acid by applying a voltage. The level of this formation voltage depends on the thickness of the resulting oxide layer or the subsequent applied voltage of the capacitor. The voltage is preferably from 1 to 300V, particularly preferably from 1 to 80V.

Preferably, metal powders having a charge to mass ratio of more than 35,000 μ C/g, particularly preferably more than 45,000 μ C/g, more preferably more than 65,000 μ C/g, most preferably more than 95,000 μ C/g, are used for the preparation of the electrode body. In a preferred embodiment according to the invention, a metal powder having a charge to mass ratio of more than 140,000 μ C/g is used.

The charge-to-mass ratio is calculated as follows:

charge-to-mass ratio (capacitance voltage)/weight of the oxidation electrode body

The capacitance here is measured in the aqueous electrolyte at 120Hz from the capacitance of the oxidation electrode body. The conductivity of the electrolyte here is sufficiently large that no capacitance drop occurs at 120Hz because of the resistance of the electrolyte. For example, using an 18% aqueous sulfuric acid electrolyte. The voltage in the above equation corresponds to the maximum formation voltage (oxidation voltage).

In particular, solid electrolytic capacitors having a dense polymer outer layer and having good edge coverage and adhesion can be produced simply using the process according to the invention. The capacitor is also characterized by low residual current and low ESR.

Due to their low residual current and low ESR, the electrolytic capacitors prepared in accordance with the present invention are outstandingly suitable for use as components in electrical circuits. The invention also relates to the use of such a capacitor. Digital circuits of this type are preferred, for example for use in computers (desktop, laptop, server), portable electronic devices, such as mobile telephones and digital cameras, electronic entertainment devices, such as CD/DVD players and computer game consoles, navigation systems and communication devices.

Examples

Example 1: preparation of the dispersions of the invention

1.1 preparation of the conductive particles b)

868g of deionized water, 330g of an aqueous solution of polystyrenesulfonic acid having an average molecular weight of 70,000 and a solids content of 3.8 wt.% were placed in a 21-neck flask with a stirrer and an internal thermometer. The reaction temperature was maintained at 20-25 ℃.

5.1g of 3, 4-ethylenedioxythiophene are added while stirring. The solution was stirred for 30 minutes. Then 0.03g of iron (III) sulfate and 9.5g of sodium persulfate were added and the resulting solution was stirred for a further 24 hours.

Once the reaction was completed, 100ml of a strong acid cation exchanger and 250ml of a weak base anion exchanger were added to remove inorganic salts, and the solution was stirred for another 2 hours. The ion exchanger is filtered off.

The resulting poly (3, 4-ethylenedioxythiophene) styrene sulfonate dispersion had a solids content of 1.2% by weight and the following particle size distribution:

d10 100nm

d50 141nm

d90 210nm

the diameter distribution of the conductive polymer particles b) is related to the mass distribution of the particles b) in the dispersion and is a function of the particle diameter. The diameter was determined using ultracentrifuge measurements.

1.2 preparation of solid particles e) (PEDT-tosylate powder)

2.51 demineralized water was placed in a 51 glass reactor with stirrer and thermometer. While stirring, 214.2g of p-toluenesulfonic acid monohydrate and 2.25g of iron (III) sulfate heptahydrate were added. Once the entire mixture has dissolved, 85.8g of 3, 4-ethylenedioxythiophene are added and stirring is continued for 30 minutes. 192.9g of sodium peroxosulphate were then added while stirring, and the mixture was stirred at ambient temperature for a further 24 hours. After the reaction was complete, the PEDT/tosylate powder was filtered off on a porcelain suction filter, washed with 3 l of demineralized water and finally dried at 100 ℃ for 6 hours. 89 g of blue-black PEDT tosylate powder was obtained.

1.3 preparation of inventive Dispersion a)

In a beaker with stirrer, 170g of PEDT/PSS dispersion prepared according to example 1.1, 15g of sulfopolyester (Eastek 1100, Eastman), 8g of dimethyl sulfoxide, 1g of 3-glycidoxypropyltrimethoxysilane (Silquest A-187, Osi Specialities) and 0.4g of wetting agent (Dynol 604, Air Products) were mixed vigorously for 1 hour. 6g of PEDT/tosylate powder (prepared according to example 1.2) were then dispersed with a ball mill dissolution unit. For this purpose, 300g of zirconia beads (. PHI.1 mm) were added and the mixture was stirred at 7000rpm for 1 hour while cooling with water. Finally the milled beads were separated with a 0.8 μm screen. The dispersion had a solids content of 7.0%.

Example 2: preparation of capacitors

2.1 preparation of Oxidation capacitors

Tantalum powder having a specific capacitance of 50,000 μ FV/g was pressed into pellets comprising tantalum wires 7 and sintered to form a porous electrode body 2 having a size of 4.2mm by 3mm by 1.6 mm. The electrode body 2 was anodized to 30V in a phosphoric acid electrolyte.

2.2 chemical in-situ coating of electrode bodies

Preparation of 1 part by weight of 3, 4-ethylenedioxythiophene (BAYTRON)^®M, H.C.Starck GmBH) and 20 parts by weight of iron (III) p-toluenesulfonate (BAYTRON)^®C-E, h.c. starck GmBH) in 40 wt% ethanol.

The solution was used to impregnate 9 anodized electrode bodies 2. The electrode body 2 was immersed in this solution and then dried at ambient temperature (20 ℃) for 30 minutes. Then heat treated in a drying oven at 50 ℃ for 30 minutes. The electrode body was then washed with a2 wt% aqueous solution of p-toluic acid for 30 minutes. The electrode body was reformed in a 0.25 wt% aqueous solution of p-toluenesulfonic acid for 30 minutes, and then rinsed in deionized water and dried. The impregnation, drying, heat treatment and reforming were repeated two additional times using the same electrode body.

2.3 preparation of the outer Polymer layer

9 electrode bodies which had been coated in situ were then dipped once into the dispersion according to example 1.3 of the invention and subsequently dried at 120 ℃ for 10 minutes.

After application of the polymer outer layer 5, the lower electrode body was observed under an optical microscope: the entire outer surface of the electrode body is covered with a dense polymer film. Corners and edges also show a continuous polymer film coating. The thickness of the outer polymer film was about 40 μm.

The electrode body is then coated with graphite and silver layers.

Comparative example 1

Preparation of non-inventive Dispersion

In a beaker with stirrer, 170g of PEDT/PSS dispersion prepared according to example 1.1, 15g of sulfopolyester (Eastek 1100, Eastman), 8g of dimethyl sulfoxide, 1g of 3-glycidoxypropyltrimethoxysilane (Silquest A-187, Osi Specialities) and 0.4g of wetting agent (Dynol 604, Air Products) were mixed vigorously for 1 hour.

Preparation of capacitors

An oxidized electrode body was prepared analogously to examples 2.1 and 2.2 and applied in situ. 9 electrode bodies were dipped once in the dispersion from comparative example 1 and subsequently dried at 120 ℃ for 10 minutes.

After application of the polymer outer layer 5, the electrode body was observed under an optical microscope: the electrode body comprising the polymer outer layer 5 shows no polymer film, especially at the corners and edges of the anode.

The electrode body is then coated with graphite and silver layers.

The 9 capacitors from example 2 and comparative example 1 each had an average of the following residual currents:

	residual current [ mu A ]]	Coating with a polymeric outer layer
			Example 2 (Dispersion according to the invention)	11.6	110％
Comparative example 1	64.8	Exposing corners and edges

After applying a voltage of 10V, the residual current was measured for 3 minutes using a Keithley 199 multimeter.

The capacitors produced by the process according to the invention show a significantly lower residual current with the use of the dispersion containing solid particles e) due to the improved coating with the polymer outer layer 5. In a non-inventive process using a dispersion without solid particles e), the graphite and silver layers are in direct contact with the dielectric, thereby generating a high residual current.

Example 3: preparation of the dispersions of the invention

In a beaker with stirrer, 180g of PEDT/PSS dispersion prepared according to example 1.1, 10g of sulfopolyester (Eastek 1100, Eastman), 8g of dimethyl sulfoxide, 1g of 3-glycidoxypropyltrimethoxysilane (Silquest A-187, Osi Specialities) and 0.4g of wetting agent (Dynol 604, Air Products) were mixed vigorously for 1 hour. 2g of PEDT/tosylate powder (prepared according to example 1.2) were then dispersed with a ball mill dissolution unit. For this purpose, 300g of zirconia beads (. PHI.1 mm) were added and the mixture was stirred at 7000rpm for 1 hour while cooling with water. Finally, the milled beads were separated with a 0.8 μm screen. The dispersion had a solids content of 4.7%.

The distribution of solid particles in the dispersion was determined by laser diffraction (MS 2000 Hydro S). The following diameter distribution values were obtained:

d₁₀： 1.5μm

d₅₀: 3.0 μm (mean diameter)

d₉₀： 6.6μm

Example 4: preparation of the dispersions of the invention

In a beaker with stirrer, 180g of PEDT/PSS dispersion prepared according to example 1.1, 10g of sulfopolyester (Eastek 1100, Eastman), 8g of dimethyl sulfoxide, 1g of 3-glycidoxypropyltrimethoxysilane (Silquest A-187, Osi Specialities) and 0.4g of wetting agent (Dynol 604, Air Products) were mixed vigorously for 1 hour. Then 2g of precipitated silica (Acematt OK 607, Degussa, average particle diameter 4.5 μm) were added, and the resulting mixture was stirred for 1 hour with cooling using a dissolver (disk diameter 6cm, 5000 rpm). The resulting dispersion had a solids content of 4.2%.

Example 5: preparation of the dispersions of the invention

In a beaker with stirrer, 180g of PEDT/PSS dispersion prepared according to example 1.1, 10g of sulfopolyester (Eastek 1100, Eastman), 8g of dimethyl sulfoxide, 1g of 3-glycidoxypropyltrimethoxysilane (Silquest A-187, Osi Specialities) and 0.4g of wetting agent (Dynol 604, Air Products) were mixed vigorously for 1 hour. 2g of pyrogenic silica (Acematt TS 100, Degussa, mean particle diameter 10 μm) are then added and the resulting mixture is stirred for 1 hour with cooling using a dissolver (disk diameter 6cm, 5000 mm). The resulting dispersion had a solids content of 4.3%.

Comparative example 2:

in a beaker with stirrer, 180g of PEDT/PSS dispersion prepared according to example 1.1, 10g of sulfopolyester (Eastek 1100, Eastman), 8g of dimethyl sulfoxide, 1g of 3-glycidoxypropyltrimethoxysilane (Silquest A-187, Osi Specialities) and 0.4g of wetting agent (Dynol 604, Air Products) were mixed vigorously for 1 hour. 2g of pyrogenic silica (Acematt TS 100, Degussa, mean particle diameter 0.012 μm) are then added and the resulting mixture is stirred for 1 hour with cooling using a dissolver (disk diameter 6cm, 5000 rpm). The resulting dispersion had a solids content of 4.2%.

An oxidized electrode body was prepared analogously to examples 2.1 and 2.2 and applied in situ. All 9 electrode bodies were dipped once in the dispersions from examples 3, 4 and 5 and comparative example 2 and subsequently dried at 120 ℃ for 10 minutes.

After application of the polymer outer layer 5, the electrode body was observed using an optical microscope, and the coating layer having the polymer outer layer 5 was visually evaluated.

The electrode body is then coated with graphite and silver layers.

The residual current was measured for 3 minutes after applying 10V using a Keithley 199 multimeter. Equivalent Series Resistance (ESR) was measured at 100kHz using an LCR meter (Agilent 4284A).

	Average diameter of solid particles [ mu m ]]	Coverage rate	Residual current [ mu A ]]	ESR[mΩ]
					Example 3	3	100％	7	17.1
Example 4	4.5	100％	6	16.0
					Example 5	10	100％	10	15.5
Comparative example 2	0.012	Exposing corners and edges	78	17.7

The capacitors prepared by the process of the invention (examples 3, 4 and 5) showed 100% external polymer film coverage and low residual current. The very fine solid particles in the dispersion from which the outer polymer film was prepared did not give good coverage (comparative example 2). In particular, in this case, corners and edges of the electrode body are exposed, resulting in high residual current.

Example 6: preparation of the dispersions of the invention

182.2g of PEDT/PSS dispersion prepared according to example 1.1, 1.1g of dimethylethanolamine (50% solution in water), 6.4g of Novolak epoxy resin (EPI-REZ 6006W-70, Resolution), 10g of ethylene glycol, 1g of 3-glycidoxypropyltrimethoxysilane (SilquestA-187, Osi Specialities) and 0.4g of wetting agent (Surfynol E-104, Air Products) were mixed vigorously for 1 hour in a beaker with a stirrer. 4g of PEDT/tosylate powder (prepared according to example 1.2) were then dispersed with a ball mill dissolution unit. For this purpose, 300g of zirconia beads (. PHI.1 mm) were added and the mixture was stirred at 7000rpm for 1 hour while cooling with water. Finally the milled beads were separated with a 0.8 μm screen. The dispersion had a solids content of 4.8%.

Comparative example 3: preparation of non-inventive Dispersion

Dispersions were prepared analogously to example 6, but without addition and dispersion of the PEDT/tosylate powder.

Example 7: preparation of the dispersions of the invention

161.1g of PEDT/PSS dispersion prepared according to example 1.1, 30g of perfluorosulphonic acid/tetrafluoroethylene copolymer (Liquion 1115, Ion Power), 8g of dimethyl sulphoxide and 0.4g of wetting agent (Zonyl FS-300, DuPont) are mixed vigorously for 1 hour in a beaker with a stirrer. 5g of PEDT/tosylate powder (prepared according to example 1.2) were then dispersed with a ball mill dissolution unit. For this purpose, 300g of zirconia beads (. PHI.1 mm) were added and the mixture was stirred at 7000rpm for 1 hour while cooling with water. Finally the milled beads were separated with a 0.8 μm screen. The dispersion had a solids content of 5.8%.

Comparative example 4: preparation of non-inventive Dispersion

Dispersions were prepared analogously to example 7, but without addition and dispersion of the PEDT/tosylate powder.

Example 8: preparation of the dispersions of the invention

In a beaker with a stirrer, 186.6g of PEDT/PSS dispersion prepared according to example 1.1, 1.1g of dimethylethanolamine (50% solution in water), 5.0g of an aqueous phenolic resin dispersion (Phenodur VPW 1942, Cytec Industries), 8g of dimethyl sulfoxide and 0.4g of a wetting agent (Dynol 604, air products) were mixed vigorously for 1 hour. 5g of PEDT/tosylate powder (prepared according to example 1.2) were then dispersed with a ball mill dissolution unit. For this purpose, 300g of zirconia beads (. PHI.1 mm) were added and the mixture was stirred at 7000rpm for 1 hour while cooling with water. Finally the milled beads were separated with a 0.8 μm screen. The dispersion had a solids content of 5.5% and a pH of 6.8.

Comparative example 5: preparation of non-inventive Dispersion

Dispersions were prepared analogously to example 8, but without addition and dispersion of the PEDT/tosylate powder.

Example 9: preparation of the dispersions of the invention

183g of PEDT/PSS dispersion prepared according to example 1.1, 8.6g of an aqueous acrylate copolymer dispersion (Carbopol Aqua 30, Noveon), 8g of ethylene glycol and 0.4g of a wetting agent (Dynol 604, Air Products) were mixed vigorously for 1 hour in a beaker with a stirrer. Then 5g of PEDT/tosylate powder (prepared according to example 1.2) were dispersed with a ball mill dissolution unit. For this purpose, 300g of zirconia beads (. PHI.1 mm) were added and the mixture was stirred at 7000rpm for 1 hour while cooling with water. Finally the milled beads were separated with a 0.8 μm screen. The dispersion had a solids content of 5.0%.

Comparative example 6: preparation of non-inventive Dispersion

Dispersions were prepared analogously to example 9, but without addition and dispersion of the PEDT/tosylate powder.

An oxidized electrode body was prepared analogously to examples 2.1 and 2.2 and applied in situ. The electrode bodies were then in each case immersed once in the dispersion from examples 6 to 9 or from comparative examples 3 to 6 and subsequently dried at 120 ℃ for 10 minutes.

After the application of the polymer outer layer 5, the electrode body was observed under an optical microscope, and the coverage covered by the polymer outer layer was visually evaluated.

	Covering
		Example 6	110％
Comparative example 3	Exposing corners and edges
		Example 7	100％
Comparative example 4	Exposing corners and edges
		Example 8	100％
Comparative example 5	Exposing corners and edges
		Example 9	100％
Comparative example 6	Exposing corners and edges

After application to the electrode body, the formulations according to examples 6 to 9 of the present invention all formed a polymer outer layer covering 100% of the electrode body. After coating with the formulations prepared in comparative examples 3 to 6, which are not according to the invention, which do not contain any solid particles e, the electrode bodies were exposed at the edges and corners.

Example 10: preparation of the dispersions of the invention

In a beaker with stirrer, 180g of PEDT/PSS dispersion prepared according to example 1.1, 10g of sulfopolyester (Eastek 1100, Eastman), 8g of dimethyl sulfoxide, 1g of 3-glycidoxypropyltrimethoxysilane (Silquest A-187, Osi Specialities) and 0.4g of wetting agent (Dynol 604, Air Products) were mixed vigorously for 1 hour. 2g of PEDT/tosylate powder (prepared according to example 1.2) were then dispersed with a ball mill dissolution unit. For this purpose, 300g of zirconia beads (. PHI.1 mm) were added and the mixture was stirred at 7000rpm for 1 hour while cooling with water. Finally the milled beads were separated with a 0.8 μm screen. The viscosity was then adjusted to 390mPas by evaporating water in vacuo, measured at 100Hz using HaakeRotovisco 1.

Comparative example 7: preparation of non-inventive Dispersion

In a beaker with stirrer, 180g of PEDT/PSS dispersion prepared according to example 1.1, 10g of sulfopolyester (Eastek 1100, Eastman), 8g of dimethyl sulfoxide, 1g of 3-glycidoxypropyltrimethoxysilane (Silquest A-187, Osi Specialities) and 0.4g of wetting agent (Dynol 604, Air Products) were mixed vigorously for 1 hour. The viscosity was then adjusted to 360mPas by evaporating water in vacuo, measured at 100Hz using Haake Rotovisco 1.

An aluminum oxide body consisting of a matte surface having dimensions of 4 mm × 1mm and an aluminum oxide foil was then immersed in the dispersion according to example 10 of the present invention or in the dispersion of comparative example 7, which is not of the present invention, followed by drying at 120 ℃ for 10 minutes, and then again immersed and dried. After the application of the polymer outer layer 5, the electrode body was observed under an optical microscope, and the coverage covered by the polymer outer layer 5 was visually evaluated: the electrode bodies coated with the dispersion from example 10 showed complete coverage of all edges. The electrode body coated with the dispersion of comparative example 7 did not have any polymer film at the edges. The dispersion according to the invention thus allows even sharper edges, for example electrode bodies made of thin sheets, to be covered highly effectively.

An oxidized electrode body was prepared analogously to examples 2.1 and 2.2 and applied in situ. The electrode bodies were then in each case immersed once in the dispersion from example 10 or from comparative example 7 and subsequently dried at 120 ℃ for 10 minutes. After the application of the polymer outer layer 5, the electrode body was observed under an optical microscope, and the coverage covered by the polymer outer layer 5 was visually evaluated: the electrode body coated with the dispersion from example 10 is characterized by a uniform polymer outer layer. Electrode bodies coated with the dispersion from comparative example 7 showed craters and cracks in the outer polymer film. The dispersions according to the invention allow high viscosities to be used for coating purposes without cracks or craters being formed as a result.

Example 11: preparation of aluminum capacitor

Preparation of 1 part by weight of 3, 4-ethylenedioxythiophene (BAYTRON)^®M, H.C.Starck GmBH) and 20 parts by weight of iron (III) p-toluenesulfonate (BAYTRON)^®C-E, h.c. starck GmBH) in 40 wt% ethanol. The solution was used to impregnate 12 oxidized electrode bodies made of etched and anodized aluminum foil having dimensions of 4 mm by 1 mm. The oxidized electrode body was immersed in this solution and dried at ambient temperature (20 ℃) for 30 minutes. Then heat treated in a drying oven at 50 ℃ for 30 minutes. The electrode body was then washed in water for 30 minutes and then dried.

A dispersion according to example 10 was prepared. The pH of the dispersion was adjusted to 6.7 by the addition of trimethylethanolamine. The electrode body was immersed in the dispersion and then dried at 120 ℃ for 10 minutes, and then immersed again and dried again. The electrode body is then coated with graphite and silver layers.

The 12 aluminum capacitors had the following average electrical values:

capacitance: 3.5 μ F

ESR： 73mΩ

Residual current: 7 muA

The residual current was measured for 3 minutes after applying a voltage of 6V using a Keithley 199 multimeter. The capacitance was determined at 120Hz and the Equivalent Series Resistance (ESR) was determined at 100kHz using an LCR meter (Agilent 4284A).

Example 12: measurement of average inhomogeneity of the Polymer outer layer

An oxidized electrode body was prepared analogously to examples 2.1 and 2.2 and applied in situ. Part of the electrode body was then dipped once in the dispersion from example 10 and subsequently dried at 120 ℃ for 10 minutes.

The average unevenness of the coated electrode body was determined using a Tencor Alpha Step 500 Surface Profile. For those electrode bodies coated only in situ, it was 0.4 μm. For those electrode bodies additionally coated with the dispersion according to the invention, the average inhomogeneity was 0.5 μm. Although the dispersion according to the invention contains solid particles e), the inhomogeneity of the electrode body is not increased significantly. The conductive polymer particles b) fill the gaps between the solid particles and thus make the outer polymer film smoother.

Example 13: preparation of the conductive layer

The conductive layers were prepared from the dispersions from example 1.3 and example 10. For this purpose, a part of the dispersion was spin-coated on a glass stage (26 mm. times.26 mm. times.1 mm) using a spin coater (Chemat Technology KW-4A) rotating at 1000rpm for 5 seconds. The sample was dried at 120 ℃ for 10 minutes. The two opposing sides of the stage were then coated with conductive silver. After the conductive silver was dried, the two silver strips were connected and the surface resistance was determined using a Keithley 199 multimeter. Layer thickness was determined using a Tencor Alpha Step 500 Surface Profile. The specific conductivity is determined by the sheet resistance and the layer thickness.

The following layer thicknesses and specific conductivity values were obtained:

	layer thickness [ mu ] m]	Specific conductivity [ S/cm ]]
			Example 1.3	1.5	28
Example 10	1.3	63

All of the above documents are incorporated by reference in their entirety for all useful purposes.

While certain specific structures embodying the invention have been shown and described, it will be apparent to those skilled in the art that various changes and rearrangements may be made without departing from the spirit and scope of the inventive concept, and it is not intended to be limited to the specific forms shown and described herein.

Claims (36)

1. A process for preparing an electrolytic capacitor comprising applying dispersion a) to a capacitor body, wherein the capacitor body comprises:

a porous electrode body of electrode material,

a dielectric covering the surface of the electrode material,

a solid dielectric comprising at least a conductive material, which covers the dielectric surface partially or totally,

and the dispersion a) comprises at least

Conductive polymer particles b) containing at least one optionally substituted polyaniline and/or a polythiophene having a recurring unit of the general formula (I) or (II) or recurring units of the general formulae (I) and (II)

Wherein

A represents optionally substituted C₁-C₅An alkylene group or a substituted alkylene group,

r represents a linear or branched optionally substituted C₁-C₁₈Alkyl, optionally substituted C₅-C₁₂Cycloalkyl, optionally substituted C₆-C₁₄Aryl, optionally substituted C₇-C₁₈Aralkyl, optionally substituted C₁-C₄A hydroxyalkyl group or a hydroxyl group,

x represents an integer of 0 to 8, and

if a plurality of radicals R are attached to A, they may be identical or different,

and contains a binder c) and a dispersant d),

and, optionally, at least partially removing the dispersant d) and/or curing the binder c) in order to form an outer layer of the conductive polymer,

wherein the proportion of conductive polymer particles b) having a diameter of less than 700nm in dispersion a) constitutes a solids content of at least 5% by weight of the solids content of the dispersion,

and, in addition to components b) to d), solid particles e) having a diameter of 0.7 to 20 μm are also contained in the dispersion.

2. The process according to claim 1, wherein the conductive polymer particles b) in dispersion a) have an average diameter of from 5 to 500 nm.

3. The process according to claim 1, wherein the solid particles e) are based on electrically conductive polymers, in particular on poly (3, 4-ethylenedioxythiophene).

4. The process according to claim 1, wherein the solid particles e) are based on fillers.

5. The method according to claim 1, wherein the filler is a carbonate, a silicate, silica, calcium sulfate, barium sulfate, aluminum hydroxide, glass fiber, glass spheres, wood chips, cellulose powder, carbon black, silica or silica.

6. The method of claim 1, wherein the filler is calcium carbonate, carbon, graphite, carbon black, metal oxide, ceramic, silicate, silicon, quartz, glass, precipitated silica, fumed silica, or silica gel.

7. The process according to claim 1, wherein the polythiophene of the particles b) in dispersion a) is poly (3, 4-ethylenedioxythiophene).

8. The process according to claim 1, wherein the dispersion a) additionally contains at least one polyanion.

9. The process according to claim 8, wherein said polyanion is an anion of a polycarboxylic acid or a sulfonic acid.

10. The process according to claim 1, wherein the binder c) contained in the dispersion a) is a polymeric organic binder.

11. The process according to claim 1, wherein the ratio of the weight% solids content of the binder c) to the solids content of the solid particles e) is greater than 1: 2.

12. The process according to claim 1, wherein the pH of dispersion a) is adjusted to 1 to 8 before application.

13. The method according to claim 1, wherein the reaction is carried out for 100s^-1The viscosity of the dispersion a) measured at a shear rate of (b) is from 10 to 1500 mPas.

14. The process according to claim 1, wherein the dispersant d) contained in the dispersion a) is an organic solvent, water or a mixture of an organic solvent and water.

15. The process according to claim 1, wherein the dispersion a) additionally contains crosslinking agents and/or surface-active substances and/or further additives.

16. The process according to claim 15, wherein the further additives contained in dispersion a) are ethers, lactones, amides or compounds containing lactam groups, sulfones, sulfoxides, sugars, sugar derivatives, sugar alcohols, furan derivatives and/or di-or polyols.

17. The process according to claim 1, wherein the pH of dispersion a) is adjusted to 4 to 8 in a pH-sensitive dielectric.

18. The process according to claim 1, wherein the proportion of particles e) in dispersion a) is at least 5% by weight of the solids content of dispersion a).

19. The process according to claim 1, wherein in dispersion a) the proportion of particles b) having a diameter of less than 700nm is at least 10% by weight, based on their solids content, of the solids content of the dispersion.

20. The process according to claim 1, wherein in dispersion a) the proportion of particles b) having a diameter of less than 500nm, preferably less than 400nm, based on their solids content, is at least 5% by weight, preferably at least 10% by weight, particularly preferably at least 15% by weight, based on the solids content of the dispersion.

21. The process according to claim 1, wherein the solid particles e) in the dispersion a) have an average diameter of from 1 to 10 μm.

22. The process according to claim 1, wherein the solid particles e) in dispersion a) have a diameter distribution d10 value of more than 0.9 μm, and a d90 value of less than 15 μm, and a d90 value of less than 10 μm.

23. The process according to claim 8, wherein the polymeric anion is polystyrenesulphonic acid, wherein the ratio of the% by weight solids content of binder c) to the solids content of the solid particles e) is greater than 1: 1, the proportion of particles e) in dispersion a) is at least 15% by weight of the solids content of dispersion a) and has a mean diameter of from 1 to 5 μm, and the solid particles e) in dispersion a) have a diameter distribution with a d10 value of greater than 1.2 μm and a d90 value of less than 8 μm, the proportion of particles b) having a diameter of less than 700nm in dispersion a) being based on their solids content at least 15% by weight of the solids content of the dispersion, and the proportion of particles b) having a diameter of less than 400nm being based on their solids content at least 15% by weight of the solids content of the dispersion.

24. The method according to claim 1, wherein the conductive material of the solid electrolyte is a conductive polymer.

25. The method according to claim 24, wherein the conductive polymer contained in the solid electrolyte is polythiophene, polypyrrole or polyaniline, which are optionally substituted.

26. The method according to claim 25, wherein the conductive polymer contained in the solid electrolyte is a polythiophene having a repeating unit of the general formula (I) or the general formula (II), or repeating units of the general formulae (I) and (II):

wherein A represents optionally substituted C₁-C₅An alkylene group or a substituted alkylene group,

r represents a linear or branched optionally substituted C₁-C₁₈Alkyl, optionally substituted C₅-C₁₂Cycloalkyl, optionally substituted C₆-C₁₄Aryl, optionally substituted C₇-C₁₈Aralkyl, optionally substituted C₁-C₄A hydroxyalkyl group or a hydroxyl group,

x represents an integer of 0 to 8, and

if a plurality of radicals R are attached to A, they may be identical or different.

27. The method according to claim 26, wherein the conductive polymer contained in the solid electrolyte is poly (3, 4-ethylenedioxythiophene).

28. The method of claim 1, wherein the solid electrolyte contains monomeric anions.

29. A method according to claim 1, wherein the electrode material of the electrode body is a valve metal or a compound having electrical properties comparable to those of the valve metal.

30. The method of claim 29, wherein the valve metal or compound having electrical properties comparable to those of the valve metal is tantalum, niobium, aluminum, titanium, zirconium, hafnium, vanadium, an alloy or compound of at least one of these metals with other elements, NbO or an alloy or compound of NbO with other elements.

31. A method according to claim 1, wherein the dielectric is an oxide of a valve metal, or an oxide of a compound having electrical properties comparable to those of a valve metal.

32. The method according to claim 1, wherein after application of dispersion a) and formation of the conductive polymer outer layer, the capacitor is optionally provided with further conductive external contacts and optionally connected and encapsulated.

33. An electrolytic capacitor produced by the method of claim 1.

34. Electrolytic capacitor according to claim 33, characterized in that the average thickness of the polymeric outer layer is 1-100 μm.

35. The electrolytic capacitor as recited in claim 33, wherein the electrolytic capacitor has a charge-to-mass ratio of more than 10000 μ C/g based on the weight of the dielectric-coated electrode body.

36. An electrical circuit comprising the electrolytic capacitor of claim 33.