Anode foil material for electrolytic capacitor and preparation method and application thereof

Abstract

The invention discloses an anode foil material for an electrolytic capacitor and a preparation method and application thereof, and the method comprises the steps: uniformly mixing metal powder, a binder, a solvent and a fluxing agent, coating an aluminum foil substrate with the mixture, and drying to obtain a powder accumulation coating foil; the metal powder is aluminum powder or composite aluminum powder; and sintering the powder accumulation coating foil to prepare the anode foil material for the electrolytic capacitor. According to the method, a fluxing system is introduced, a sintering neck regulation and control mechanism based on atomic diffusion kinetics is constructed, the fluxing agent initiates the activation effect on the surfaces of powder particles in a sub-high-temperature interval, the metallurgical bonding process dominated by grain boundary migration is promoted, and the problems that in an existing sintering process, high-temperature sintering energy consumption is high, a surface oxide layer cannot grow in a controlled mode, and the service life of the sintering neck is prolonged are effectively solved. And the metallurgical bonding strength among powder particles is insufficient due to low-temperature sintering.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolytic capacitors and relates to an anode foil material for electrolytic capacitors and a preparation method and application thereof. Background Art

[0002] Capacitors are one of the most widely used electronic components in electronic circuits. Based on the dielectric material, they can be divided into three categories: ceramic capacitors, film capacitors, and electrolytic capacitors. Electrolytic capacitors stand out for their high specific capacitance and low raw material costs, making them widely used in communications equipment, automotive electronics, household appliances, and industrial electrical applications. Capacitance, a core performance parameter of electrolytic capacitors, is theoretically modeled according to the double-layer coupling mechanism, where the series relationship between the specific capacitances of the anode and cathode foils contributes to the total capacitance. Because the cathode foil has only an extremely thin oxide layer on its surface, its specific capacitance per unit area is significantly higher than that of the anode foil, resulting in the system's total capacitance being primarily determined by the specific capacitance of the anode foil. This characteristic dictates that the technological bottleneck for achieving higher capacitance and miniaturization of electrolytic capacitors lies in increasing the specific capacitance of the anode material. In the aluminum electrolytic capacitor market, the mainstream anode foil material is currently produced using a chemical / electrochemical surface etching process. This technology suffers from two key drawbacks: first, the process involves the discharge of acidic electrolyte, which conflicts with the concept of green manufacturing; second, the specific capacitance increase based on the corrosion surface etching mechanism has reached its limit, and further advancements are limited by the intrinsic properties of the material. In comparison, powder sintered foil can obtain a higher effective specific surface area by constructing a three-dimensional porous structure, and theoretically has better specific volume development potential.

[0003] However, the existing sintering process faces two technical barriers. First, the sintering temperature currently used in industry is relatively high. High-temperature sintering not only leads to huge energy consumption, but also easily causes uncontrollable growth of surface oxide layers under non-ideal atmospheres, such as air, non-absolute vacuum environment, and non-ultra-pure protective atmosphere. Such oxides significantly deteriorate the film quality of subsequent anodization. Although low-temperature sintering can inhibit oxidation, it leads to insufficient metallurgical bonding strength between powder particles, which manifests as incomplete development of sintering necks and low interfacial bonding energy, which directly affects the mechanical stability of the material and the efficiency of constructing an effective dielectric layer. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides an anode foil material for electrolytic capacitors, a preparation method and application thereof, thereby solving the technical problems in the existing sintering process, such as high energy consumption and uncontrollable growth of the surface oxide layer during high-temperature sintering, and insufficient metallurgical bonding strength between powder particles caused by low-temperature sintering.

[0005] The present invention is achieved through the following technical solutions: A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: S1: mixing metal powder, a binder, a solvent, and a flux uniformly, coating the mixture on an aluminum foil substrate, and drying the mixture to obtain a powder-coated foil; the metal powder is aluminum powder or composite aluminum powder; S2: sintering the powder stack coating foil to obtain the anode foil material for electrolytic capacitors.

[0006] Preferably, the mass ratio of the metal powder, binder, solvent and flux is (30~70):(0.5~10):(30~60):(0.1~5).

[0007] Preferably, the aluminum foil substrate is cleaned with an alkaline solution before being coated with the metal powder, binder, solvent and flux.

[0008] Preferably, the composite aluminum powder comprises aluminum alloy powder or composite powder of aluminum powder and high dielectric material; The diameter of the composite aluminum powder is 0.5-30 μm, and the purity of the aluminum powder is not less than 99.5%; The high dielectric material includes at least one of titanium dioxide, hafnium dioxide, tantalum pentoxide, niobium pentoxide, barium titanate, strontium titanate, barium strontium titanate, lead zirconate titanate, and bismuth ferrite.

[0009] Preferably, the flux is at least one of acetic acid, phosphoric acid, boric acid, adipic acid, nitrous acid, sulfurous acid, citric acid, phosphorus pentoxide, phosphorus trioxide, ammonium pentaborate, ammonium acetate, sodium acetate, ammonium phosphate, ammonium adipate, ammonium nitrite, sodium nitrite, ammonium sulfite, sodium sulfite, ammonium citrate and sodium citrate.

[0010] Preferably, the coating thickness is 30-200 μm.

[0011] Preferably, the drying temperature is 60-150° C. and the drying time is 10-600 min.

[0012] Preferably, in step S2, the specific sintering process is: raising the temperature to 350~500°C at a heating rate of 2~20°C / min, maintaining it in an air atmosphere for 0.5~30h, then raising the temperature to 610~660°C at a heating rate of 2~20°C / min, and maintaining it in a vacuum state or in an inert atmosphere for 0.5~30h.

[0013] An anode foil material for electrolytic capacitors is prepared by the above method; when the anode foil material is formed at 520V, the withstand voltage value is greater than 520V and the electrostatic capacitance is greater than 0.8μF / cm 2 .

[0014] Application of the above-mentioned anode foil material for electrolytic capacitors in electrolytic capacitors.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention discloses a method for preparing anode foil materials for electrolytic capacitors. By introducing a fluxing system of specific components, a sintering neck control mechanism based on atomic diffusion dynamics is constructed. The flux induces an activation effect on the surface of powder particles in the sub-high temperature range, promoting the metallurgical bonding process dominated by grain boundary migration, and achieving dual technological breakthroughs: first, it significantly reduces the sintering activation energy threshold, lowers the process temperature, and effectively suppresses the uncontrollable growth of the oxide layer while reducing energy consumption; second, by optimizing the metallurgical bonding strength between particles and the three-dimensional structure of the sintering neck, the mechanical strength and electrical properties of the sintered body are simultaneously improved. This innovative process based on flux-assisted sintering is beneficial for solving the problems of energy consumption and surface oxidation caused by high-temperature sintering, and provides a reliable technical path for the industrial preparation of high-performance sintered foils. The method of the present invention has universal expansion value in valve metal electrolytic capacitor systems. For porous sintered bodies used in tantalum, titanium, and niobium electrolytic capacitors, the traditional pressing-sintering process needs to be carried out in a higher temperature range. Therefore, a flux that effectively promotes the growth of sintering necks can also significantly reduce the production energy consumption of industrial production of tantalum, titanium, and niobium porous sintered body anodes, and improve their mechanical strength and electrical properties.

[0016] Furthermore, the mass ratio of the metal powder, the binder, the solvent and the flux is (30-70):(0.5-10):(30-60):(0.1-5), which can enable the flux to exert the best effect.

[0017] Furthermore, before coating the aluminum foil substrate with metal powder, binder, solvent and flux, the aluminum foil substrate is cleaned with an alkaline solution to remove impurities such as oil stains attached to the surface of the aluminum foil.

[0018] Furthermore, the composite aluminum powder includes aluminum alloy powder or a composite powder of aluminum powder and a high-dielectric material; wherein the diameter of the composite aluminum powder is 0.5~30μm, which can make the specific surface area of ​​the composite aluminum powder moderate and have a suitable specific volume value; the purity of the aluminum powder is not less than 99.5%, which can avoid the impurities in the aluminum powder from adversely affecting the electrical properties of the anode foil; the high-dielectric material includes at least one of titanium dioxide, hafnium dioxide, tantalum pentoxide, niobium pentoxide, barium titanate, strontium titanate, barium strontium titanate, lead zirconate titanate and bismuth ferrite, which can effectively improve the specific volume on the basis of pure aluminum powder.

[0019] Furthermore, the flux includes at least one of acetic acid, phosphoric acid, boric acid, adipic acid, nitrous acid, sulfurous acid, citric acid, phosphorus pentoxide, phosphorus trioxide, ammonium pentaborate, ammonium acetate, sodium acetate, ammonium phosphate, ammonium adipate, ammonium nitrite, sodium nitrite, ammonium sulfite, sodium sulfite, ammonium citrate and sodium citrate, which can significantly reduce the sintering activation energy threshold and promote the growth of sintering neck.

[0020] Furthermore, the coating thickness is 30 to 200 μm, which can reduce the probability of the aluminum powder layer falling off due to excessive thickness.

[0021] Furthermore, the drying temperature is 60-150° C. and the drying time is 10-600 min, so that the solvent in the powder accumulation coating foil can be fully volatilized.

[0022] Furthermore, in step S2, the specific sintering process is: raising the temperature to 350-500°C at a heating rate of 2-20°C / min, maintaining it in an air atmosphere for 0.5-30 hours, and then raising the temperature to 610-660°C at a heating rate of 2-20°C / min, maintaining it in a vacuum state or in an inert atmosphere for 0.5-30 hours, thereby obtaining a sintered foil with good mechanical strength and electrical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is an optical micrograph of a powder stacked sintered foil prepared in Comparative Example 1 without adding flux; Figure 2 This is an optical micrograph of the powder stacked sintered foil prepared by adding flux in Example 3; Figure 3 This is the SEM image of the powder stacked sintered foil prepared without adding flux; Figure 4 SEM image of powder stacked sintered foil prepared with the addition of flux. DETAILED DESCRIPTION

[0025] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0026] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0027] All features, such as values, amounts, contents, and concentrations, described herein as numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values ​​within the range (including integers and fractions).

[0028] In this document, unless otherwise specified, “include,” “including,” “contains,” “has” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0029] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0030] The present invention provides a method for preparing a powder sintered anode for electrolytic capacitors and flux-assisted sintering thereof to address the problems of high energy consumption, uncontrollable growth of surface thermal oxide films, and insufficient mechanical properties in existing sintering technologies. The method introduces a flux system containing acetic acid, phosphoric acid, boric acid, adipic acid, nitrous acid, sulfurous acid, citric acid, phosphorus pentoxide, phosphorus trioxide, ammonium pentaborate, ammonium acetate, sodium acetate, ammonium phosphate, ammonium adipate, ammonium nitrite, sodium nitrite, ammonium sulfite, sodium sulfite, ammonium citrate, or sodium citrate, thereby effectively lowering the sintering temperature of the powder anode, reducing the formation of thermal oxide films on its surface, promoting the growth of powder sintering necks, and improving the mechanical strength and electrical properties of the powder sintered foil. This technical solution provides a new path for producing high-performance powder sintered anode materials for electrolytic capacitors.

[0031] In order to achieve the above object, the present invention adopts the following technical solutions: A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: (1) Clean an aluminum foil substrate with a purity of 99.5% or more and a thickness of 20-50 μm with an alkaline solution of 0.1-1 mol / L for 10-60 min; The alkaline solution includes at least one of sodium carbonate solution, sodium bicarbonate solution, potassium carbonate solution, potassium bicarbonate, sodium hydroxide solution, potassium hydroxide solution and ammonia solution; (2) mixing metal powder, binder, solvent and flux in a mass ratio of (30-70):(0.5-10):(30-60):(0.1-5), preferably a mass ratio of 59:3:37:1, to prepare a slurry; the metal powder includes aluminum powder or composite aluminum powder; The composite aluminum powder includes aluminum alloy powder or composite powder of aluminum powder and high dielectric material; The purity of the aluminum powder is not less than 99.5%, and the particle size of the aluminum powder, aluminum alloy powder, and composite powder of aluminum and high dielectric material is 0.5-30 μm; The high dielectric material has a dielectric constant greater than 20 and can be composited with aluminum powder. The high dielectric material includes at least one of titanium dioxide, hafnium dioxide, tantalum pentoxide, niobium pentoxide, barium titanate, strontium titanate, barium strontium titanate, lead zirconate titanate, and bismuth ferrite.

[0032] The binder is at least one of polyethylene oxide, hydroxypropyl cellulose, carboxymethyl cellulose, acrylic resin, polyvinyl butyral, polyvinylidene fluoride, povidone, polyacrylic acid and polypropylene carbonate; The solvent is water, methanol, ethanol, ethylene glycol, propylene glycol, glycerol (i.e., glycerol), ether, tetrahydrofuran or dimethyl sulfoxide; The flux is at least one of acetic acid, phosphoric acid, boric acid, adipic acid, nitrous acid, sulfurous acid, citric acid, phosphorus pentoxide, phosphorus trioxide, ammonium pentaborate, ammonium acetate, sodium acetate, ammonium phosphate, ammonium adipate, ammonium nitrite, sodium nitrite, ammonium sulfite, sodium sulfite, ammonium citrate, and sodium citrate. The flux forms a liquid phase at high temperatures, reducing surface tension and viscosity, thereby significantly lowering the sintering activation energy threshold and lowering the process temperature. This reduces energy consumption while effectively inhibiting the uncontrolled growth of the oxide layer, and optimizing the metallurgical bonding strength between particles and the three-dimensional structure of the sintering neck.

[0033] (3) coating the slurry in step (2) onto an aluminum foil substrate cleaned with an alkaline solution to a thickness of 30 to 200 μm to obtain a powder-deposited coated foil; (4) drying the powder-coated foil prepared in step (3); wherein the drying temperature is 60-150° C., the drying time is 10-600 min, preferably the drying temperature is 60° C., the drying time is 25 min, and the drying atmosphere is air, argon, or nitrogen; (5) sintering the powder-stacked coated foil after drying in step (4) at 350-660° C. for 0.5-30 h to obtain a powder-stacked sintered foil with good sintering neck growth, i.e., the anode foil material for electrolytic capacitors in the present invention; The sintering process is specifically as follows: the temperature is raised to 350-500°C at a heating rate of 2-20°C / min and maintained in air for 0.5-30 hours; then the temperature is raised to 610-660°C at a heating rate of 2-20°C / min and maintained in vacuum (vacuum degree of 0.01Pa-0.1Pa) or in an inert gas (such as argon) for 0.5-30 hours. Preferably, during the sintering process, the temperature is raised to 440°C at a heating rate of 10°C / min, maintained in air for 1 hour, and then raised to 630°C at a heating rate of 10°C / min and maintained in vacuum for 4 hours.

[0034] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0035] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0036] Example 1 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and acetic acid are mixed uniformly in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate with a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0037] Example 2 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): uniformly mix titanium dioxide composite aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and acetic acid in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0038] Example 3 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0039] Example 4 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 59.9:3:37:0.1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0040] Example 5 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 55:10:30:5; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0041] Example 6 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 57.5:3:37:2.5; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0042] Example 7 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 5°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 5°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0043] Example 8 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 2°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 2°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0044] Example 9 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 420°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0045] Example 10 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 460°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0046] Example 11 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 2 hours; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0047] Example 12 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 50 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 2 hours; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0048] Example 13 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 200 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 2 hours; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0049] Example 14 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 150° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 2 hours; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0050] Example 15 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 10 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 2 hours; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0051] Example 16 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 150 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 2 hours; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0052] Example 17 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 2 hours; then raise the temperature to 610°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with a small sintering neck and poor mechanical properties.

[0053] Example 18 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil after drying in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 2 hours; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 0.5 hours to obtain a powder-stacked sintered foil with a small sintering neck and poor mechanical properties.

[0054] Example 19 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 2 hours; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 8 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0055] Example 20 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and phosphoric acid are mixed uniformly in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) at 60° C. in air for 25 min; Step (5): Sinter the powder-stacked coated foil after drying in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 2 hours; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in an argon atmosphere for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0056] Example 21 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and boric acid are mixed uniformly in a ratio of 58:3:37:2; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) in air at 60° C. for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in an argon atmosphere for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0057] Example 22 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and adipic acid are mixed uniformly in a ratio of 57:3:37:3; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) in air at 60° C. for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0058] Example 23 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and ammonium acetate are mixed uniformly in a ratio of 59:3:37:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) in air at 60° C. for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0059] Example 24 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, ultrapure water, and ammonium adipate are uniformly mixed in a ratio of 55:3:37:5; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) in air at 60° C. for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in an argon atmosphere for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0060] Example 25 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, hydroxypropyl cellulose, anhydrous ethanol, and phosphorus pentoxide are uniformly mixed in a ratio of 59.5:0.6:39.4:0.5; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) in air at 60° C. for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in an argon atmosphere for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0061] Example 26 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, hydroxypropyl cellulose, anhydrous ethanol, and ammonium citrate are uniformly mixed in a ratio of 59:0.6:39.4:1; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) in air at 60° C. for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0062] Example 27 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Mix barium titanate composite aluminum powder with a particle size of 2-3 μm, hydroxypropyl cellulose, anhydrous ethanol, and sodium nitrite in a ratio of 30:10:58:2; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) in air at 100° C. for 600 min; Step (5): Sinter the powder-stacked coated foil after drying in step (4), raise the temperature to 350°C at a heating rate of 20°C / min and maintain it in an air atmosphere for 30 hours; then raise the temperature to 630°C at a heating rate of 20°C / min and maintain it in a vacuum state for 30 hours to obtain a powder-stacked sintered foil with good sintering neck growth.

[0063] Example 28 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): mixing aluminum alloy powder with a particle size of 2-3 μm, hydroxypropyl cellulose, anhydrous ethanol, and phosphorus trioxide in a ratio of 30:10:58:2; Step (3): coating the slurry in step (2) onto an aluminum foil substrate to a coating thickness of 200 μm; Step (4): drying the powder-coated foil prepared in step (3) in air at 100° C. for 600 min; Step (5): Sinter the powder-stacked coated foil after drying in step (4), raise the temperature to 500°C at a heating rate of 20°C / min and maintain it in an air atmosphere for 0.5h; then raise the temperature to 660°C at a heating rate of 20°C / min and maintain it in a vacuum state for 10h to obtain a powder-stacked sintered foil with good sintering neck growth.

[0064] Comparative Example 1 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, and ultrapure water are mixed in a ratio of 60:3:37; Step (3): coating the slurry in step (2) onto an aluminum foil substrate with a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) in air at 60° C. for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with a small sintering neck and poor mechanical properties.

[0065] Comparative Example 2 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, hydroxypropyl cellulose, and anhydrous ethanol are mixed in a ratio of 60:0.6:39.4; Step (3): coating the slurry in step (2) onto an aluminum foil substrate with a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) in air at 60° C. for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in a vacuum state for 4 hours to obtain a powder-stacked sintered foil with a small sintering neck and poor mechanical properties.

[0066] Comparative Example 3 A method for preparing an anode foil material for an electrolytic capacitor comprises the following steps: Step (1): clean an aluminum foil substrate with a thickness of 30 μm and a purity of 99.9% with a 0.5 mol / L sodium carbonate solution for 20 min; Step (2): uniformly mix titanium dioxide composite aluminum powder with a particle size of 2-3 μm and a purity of 99.99%, polyethylene oxide, and ultrapure water in a ratio of 60:3:37; Step (3): coating the slurry in step (2) onto an aluminum foil substrate with a coating thickness of 100 μm; Step (4): drying the powder-coated foil prepared in step (3) in air at 60° C. for 25 min; Step (5): Sinter the powder-stacked coated foil dried in step (4), raise the temperature to 440°C at a heating rate of 10°C / min and maintain it in an air atmosphere for 1 hour; then raise the temperature to 630°C at a heating rate of 10°C / min and maintain it in an argon atmosphere for 4 hours to obtain a powder-stacked sintered foil with a small sintering neck and poor mechanical properties.

[0067] The aluminum capacitor sintered foils prepared in Examples 1 to 28 of the present invention and Comparative Examples 1 to 3 were chemically formed in a boric acid system solution at a forming voltage of 520 V and a current density of 0.05 A / cm 2 Then, the withstand voltage test was carried out in a 70 g / L boric acid solution, and the electrostatic capacitance test was carried out in an 80 g / L ammonium pentaborate solution. The results are described in Table 1 below.

[0068] Table 1 Test results of the products obtained in Examples 1 to 28 of the present invention and Comparative Examples 1 to 3 at 520V

[0069] As can be seen from Table 1, the flux significantly improves the performance of the powder stacked sintered foil prepared. Compared with comparative examples 1 to 3, the withstand voltage and specific volume value of the sintered foil prepared by adding the flux are greatly improved. From Examples 3 to 6, it can be observed that the performance improvement effect is best when the addition amount of the flux is 1% wt.; from Examples 1 to 2, it can be observed that when high dielectric constant material composite aluminum powder is used, its specific volume is significantly improved compared with pure aluminum powder; from Examples 3, 9 to 10, it can be observed that the debinding temperature, that is, the first temperature value in step (5), is too low or too high, which has an adverse effect on the performance of the sintered foil; from Examples 3, 11 to 28, it can be observed that the withstand voltage and specific volume value of the sintered foil prepared by adding the flux are greatly improved.

[0070] Figure 1This is an optical micrograph of a powder-stacked sintered foil prepared without adding flux in Comparative Example 1 of the present invention. As can be seen from the figure, when no flux is added, the sintered foil will shed powder when slightly bent, and the powder shed is severe during formation, resulting in a significant reduction in its electrostatic capacitance.

[0071] Figure 2 This is a light microscope image of the powder piled sintered foil prepared by adding flux in Example 3 of the present invention. As can be seen from the image, after adding the flux, the surface of the sintered foil is smooth and there is no powder falling.

[0072] Figure 3 This is the SEM image of the powder stacked sintered foil prepared without adding flux. It can be seen from the figure that at the experimental temperature, the sintering neck formed between the aluminum powder layers of the powder stacked sintered foil prepared without adding flux is small, and the bonding effect between the aluminum powders is weak, resulting in poor mechanical strength and electrical properties of the sintered foil.

[0073] Figure 4 This is the SEM image of the powder stacked sintered foil prepared with the addition of flux. At the experimental temperature, the sintering necks formed between the aluminum powders on the surface of the powder stacked sintered foil prepared with the addition of flux grew well, the bonding effect between the aluminum powders was strong, and the mechanical strength and electrical properties of the sintered foil were greatly improved.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing an anode foil material for an electrolytic capacitor, characterized in that: The following steps are involved: S1: mixing metal powder, a binder, a solvent, and a flux uniformly, coating the mixture on an aluminum foil substrate, and drying the mixture to obtain a powder-coated foil; the metal powder is aluminum powder or composite aluminum powder; S2: sintering the powder stack coating foil to obtain the anode foil material for electrolytic capacitors.

2. The method for preparing an anode foil material for an electrolytic capacitor according to claim 1, characterized in that: The mass ratio of the metal powder, the binder, the solvent and the flux is (30-70): (0.5-10): (30-60): (0.1-5).

3. The method for preparing an anode foil material for an electrolytic capacitor according to claim 1, wherein: Before coating the aluminum foil substrate with metal powder, adhesive, solvent and flux, the aluminum foil substrate is cleaned with an alkaline solution.

4. The method for preparing an anode foil material for an electrolytic capacitor according to claim 1, wherein: The composite aluminum powder includes aluminum alloy powder or composite powder of aluminum powder and high dielectric material; The diameter of the composite aluminum powder is 0.5-30 μm, and the purity of the aluminum powder is not less than 99.5%; The high dielectric material includes at least one of titanium dioxide, hafnium dioxide, tantalum pentoxide, niobium pentoxide, barium titanate, strontium titanate, barium strontium titanate, lead zirconate titanate, and bismuth ferrite.

5. The method for preparing an anode foil material for an electrolytic capacitor according to claim 1, wherein: The flux is at least one of acetic acid, phosphoric acid, boric acid, adipic acid, nitrous acid, sulfurous acid, citric acid, phosphorus pentoxide, phosphorus trioxide, ammonium pentaborate, ammonium acetate, sodium acetate, ammonium phosphate, ammonium adipate, ammonium nitrite, sodium nitrite, ammonium sulfite, sodium sulfite, ammonium citrate and sodium citrate.

6. The method for preparing an anode foil material for an electrolytic capacitor according to claim 1, characterized in that: The coating thickness is 30~200μm.

7. The method for preparing an anode foil material for an electrolytic capacitor according to claim 1, characterized in that: The drying temperature is 60~150℃ and the drying time is 10~600min.

8. The method for preparing an anode foil material for an electrolytic capacitor according to claim 1, characterized in that: In step S2, the specific sintering process is: raising the temperature to 350-500°C at a heating rate of 2-20°C / min, maintaining it in an air atmosphere for 0.5-30 hours, then raising the temperature to 610-660°C at a heating rate of 2-20°C / min, and maintaining it in a vacuum state or in an inert atmosphere for 0.5-30 hours.

9. An anode foil material for an electrolytic capacitor, characterized in that: The anode foil material is prepared by the method according to any one of claims 1 to 8; when formed at 520V, the withstand voltage is greater than 520V and the electrostatic capacitance is greater than 0.8μF / cm 2 .

10. Use of the anode foil material for electrolytic capacitors as claimed in claim 9 in electrolytic capacitors.

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