A method for preparing sintered foil

Abstract

The present invention relates to the field of electrode foil manufacturing technology, in particular to a sintered foil preparation method, comprising the following steps: preparing aluminum powder slurry; cleaning an aluminum foil substrate and drying it; applying the aluminum powder slurry to the aluminum foil substrate and drying it; placing the aluminum foil substrate in a muffle furnace and performing a heating and heat preservation treatment according to a set process; cooling and chemical formation. In this way, on the one hand, during the slurry mixing process, the amine polymer used has a weak alkalinity, which can remove the oxide film formed on the surface of the aluminum-based powder in the air. In addition, during the sintering process, the ammonia generated by the decomposition of the amine polymer has a reducing effect, which can ensure that the aluminum-based powder is not oxidized, and the oxide film on the surface of the aluminum foil substrate is pre-cleared, thereby facilitating the enhancement of the bonding strength between the aluminum powder high-temperature sintering forming layer and the aluminum foil substrate; on the other hand, during the sintering process, the amine polymer decomposes into gaseous substances due to the high temperature and does not remain on the surface of the aluminum foil substrate.

Description

Technical Field

[0001] The invention relates to the technical field of electrode foil manufacturing, in particular to a method for preparing sintered foil. Background Art

[0002] Aluminum electrolytic capacitors are important electronic devices widely used in industrial frequency conversion, inverters, 5G base stations, and new energy charging stations. Anode foil, as a key component, plays a decisive role in the quality control of aluminum electrolytic capacitors.

[0003] Currently, high-voltage anode foil production in China mostly relies on an etching process, which involves chemically or electrochemically etching the aluminum foil using a sulfuric acid-hydrochloric acid system to create a certain density of tunnel holes on the foil surface, thereby increasing its specific surface area. This method has been extensively studied by numerous researchers, and its specific surface area increase has reached near theoretical limits. Furthermore, the sulfuric acid-hydrochloric acid system produces a large amount of waste acid during production, placing significant pressure on environmental protection.

[0004] With the emergence of new technologies, aluminum powder sintered foil, which is made by sintering aluminum powder or aluminum alloy powder on both sides of aluminum foil, has a higher specific surface area, and no waste acid or waste liquid is generated during its preparation process. At present, this process is still in its infancy in China, and the following problems arise during the preparation process: 1) The surface often turns black during the sintering process. The reason is that the detection found that the binder residue has not been completely removed, and the inert gas atmosphere needs to be maintained during the aluminum powder sintering process. Therefore, how to remove the binder under inert gas conditions has become one of the issues of concern to researchers; 2) The finished sintered foil has a serious "powder shedding" phenomenon. The reason is that a large number of studies have shown that this may be related to the fact that aluminum powder is easily oxidized when exposed to high temperatures in the air, and a dense oxide film is easily left on the surface of the aluminum foil, which in turn weakens the bonding strength of the subsequent aluminum powder high-temperature sintering molding layer with it. Therefore, technical personnel are urgently needed to solve the above problems. Summary of the Invention

[0005] Therefore, in view of the above existing problems and defects, the designers of the present invention collected relevant information, conducted multiple evaluations and considerations, and continued to experiment and modify the method after years of R&D experience in this industry, which ultimately led to the emergence of the sintered foil preparation method.

[0006] In order to solve the above technical problems, the present invention relates to a method for preparing a sintered foil, which comprises the following steps:

[0007] S1. Mixing aluminum-based powder, an organic solvent, and an amine polymer, and stirring them uniformly to prepare an aluminum powder slurry for later use;

[0008] S2. Flattening the rolled aluminum foil substrate layer by layer and feeding it into an ultrasonic cleaning tank; the cleaning liquid in the ultrasonic cleaning tank is a mixed aqueous solution of 0.3-0.5% by mass of NaOH and 5-6% by mass of acetone, the temperature is maintained below 25° C., and the reaction time is controlled within 2-3 minutes; the ultrasonic generator equipped in the ultrasonic cleaning tank has a power of 2000 W and a frequency controlled within 45-50 kHz;

[0009] S3, using high-pressure pure water to clean the aluminum foil substrate and then drying it;

[0010] S4, applying aluminum powder slurry to the front and back sides of the aluminum foil substrate, and performing a drying process until the moisture is completely vaporized and escapes;

[0011] S5. Placing the aluminum foil substrate obtained in step S4 in a muffle furnace, and maintaining its inner cavity in an inert gas atmosphere or a vacuum atmosphere. First, within 45 to 60 minutes, the furnace chamber temperature is uniformly increased to 250 to 300° C. and maintained at this temperature for 12 to 14 hours. Subsequently, within 25 to 30 minutes, the furnace chamber temperature is uniformly increased to 500 to 650° C., and then maintained at this temperature for 10 to 12 hours until sintering is completed.

[0012] S6. Take the aluminum powder sintered foil out of the muffle furnace and cool it naturally;

[0013] S7, the chemical formation stage, wherein the aluminum powder sintered foil is chemically treated to obtain a finished sintered foil.

[0014] As a further improvement of the technical solution disclosed in the present invention, in step S1, the mass ratio of the aluminum-based powder to the amine polymer is controlled at 80:1 to 100:1.

[0015] As a further improvement of the technical solution disclosed in the present invention, the aluminum-based powder is preferably pure aluminum powder with a purity of not less than 99.99%.

[0016] Of course, as another modified design of the above technical solution, the aluminum-based powder can also be preferably aluminum alloy powder, and one or more metals selected from copper, iron, cobalt, nickel, manganese, magnesium, titanium, tantalum, zirconium, niobium, etc. are mixed therein.

[0017] As a further improvement of the technical solution disclosed in the present invention, the organic solvent is preferably one or more of ethanol, ethylene glycol, acetone, N-methylpyrrolidone (NMP), and N,N-dimethylformamide (DMF), and the amine polymer is one or more of aminopolyethylene glycol, polyetheramine, polyacrylamide, polyethyleneamine, polyquaternary ammonium salt, polycaprolactone amino, diamino urea polymer, 4-aminomethylstyrene-styrene divinyl copolymer, etc.

[0018] As a further improvement of the technical solution disclosed in the present invention, in step S2, the initial thickness of the aluminum foil substrate is controlled to be 50 to 80 μm.

[0019] As a further improvement of the technical solution disclosed in the present invention, step S3a is added between step S3 and step S4, that is, before the coating operation is formally implemented, a laser etcher is used to form etching lines on the front and back sides of the aluminum foil substrate respectively.

[0020] As a further improvement of the technical solution disclosed in the present invention, the laser etcher is equipped with a Nd:YAG laser with a wavelength of 1064 nm, and an S-shaped scanning program is adopted during the etching process. The operating power is 8W, the laser frequency is 20KHZ, the pulse width is 100ns, the spot diameter is controlled at 38-40μm, and the scanning speed is controlled at 450-480mm / s.

[0021] As a further improvement of the technical solution disclosed in the present invention, in step S5, the inert gas is preferably either nitrogen or argon; when the inner cavity of the muffle furnace is maintained in a vacuum atmosphere, the vacuum degree is controlled at -100 KPa to -75 KPa.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] 1) During the slurry mixing process, the amine polymer used has a weak alkalinity, which can remove the oxide film formed on the surface of the aluminum-based powder in the air. The weak alkalinity will not destroy the structure of the aluminum-based powder itself, which is conducive to the formation of a sintering neck at high temperature, thereby enhancing the sintering strength;

[0024] 2) During the sintering process, the temperature rise process and precise temperature control of the muffle furnace chamber ensure that the amine polymer is decomposed into a large amount of ammonia (with reducing properties) under the action of high temperature, and the muffle furnace chamber is always maintained in an inert gas atmosphere or a vacuum atmosphere. This can reduce the oxidation effect of residual oxygen in the high-temperature muffle furnace and the sintering discharge of the binder on the aluminum-based powder to a certain extent. In addition, before the coating operation of the aluminum powder slurry is performed, the oxide film on the surface of the aluminum foil substrate is pre-removed with the help of an ultrasonic cleaning process, thereby enhancing the bonding strength between the subsequent aluminum powder high-temperature sintering forming layer and the aluminum foil substrate, and effectively eliminating the "powder shedding" phenomenon of the aluminum powder sintering layer;

[0025] 3) During the sintering process, amine polymers have a lower decomposition temperature than other organic polymers such as epoxy resins and polyvinylidene fluoride, and are more susceptible to decomposition when exposed to high temperatures. Taking polyetheramine as an example, since it contains oxygen atoms that can combine with carbon atoms, the carbon residue left after high-temperature decomposition in an inert atmosphere is less than that of oxygen-free binders such as polyvinylidene fluoride. In addition, the NH3 produced by the decomposition of polyetheramine is also a gaseous substance and will not remain on the surface of the aluminum foil substrate, nor will it generate substances that are difficult to remove. Therefore, the sintered foil surface has fewer residual impurities, which paves the way for improved low leakage performance.

[0026] It should also be noted here that, compared with the traditional preparation process, in Examples 1, 2, 3, and 4, a relatively low temperature is used in the first temperature control stage in step S5, and the insulation time is extended. On the one hand, this is conducive to ensuring that the amine polymer is more thoroughly decomposed, and the entire process is controllable, and eventually escapes and is discharged from the aluminum powder slurry solidified layer in the form of a gaseous substance; on the other hand, in the process of the heated amine polymer escaping in a gaseous form, a large number of penetrating "holes" can be formed in the aluminum powder slurry solidified layer, which is conducive to improving the electrical properties of the sintered foil product. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 This is a scanning electron microscope photograph (×1000, 15V) of an optional area of ​​a sintered foil prepared using the existing process method.

[0029] Figure 2 This is a scanning electron microscope photograph (×1000, 15V) of another area of ​​the sintered foil prepared using the existing process method.

[0030] Figure 3 This is a scanning electron microscope photograph (×3000, 20V) of an optional area of ​​a sintered foil prepared using the existing process method.

[0031] Figure 4 This is a scanning electron microscope photograph (×1000, 15V) of an optional area of ​​the sintered foil prepared in Example 1.

[0032] Figure 5 This is a scanning electron microscope photograph (×1000, 20V) of an optional area of ​​the sintered foil prepared in Example 1.

[0033] Figure 6This is a scanning electron microscope photograph (×2000, 15V) of an optional area of ​​the sintered foil prepared in Example 1. Implementation Method

[0034] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the examples, which are only used to illustrate the present invention and do not constitute a limitation on the scope of protection of the present invention. The methods described are all conventional methods unless otherwise specified.

[0035] Comparative Example (current industry-wide preparation process, small-batch trial production in the laboratory)

[0036] The sintered foil preparation method comprises the following steps:

[0037] S1. Mix 1 g aluminum powder, 2 ml NMP solvent, and 0.2 g polyvinylidene fluoride binder and grind them under high-speed ball mill for 0.5 h to form a uniform slurry.

[0038] S2, coating the prepared aluminum powder slurry on the surface of a 30 μm aluminum foil substrate, and drying the coating to an average dry film thickness of 50 μm;

[0039] S3, heating the coated aluminum foil in step 2 to 450 °C for 2 h and maintaining it for 2 h to remove the solvent and adhesive on the surface, then heating it to 550 °C for 1 h and sintering it for 4 h, using N2 protection during the sintering process;

[0040] S4. The sintered aluminum foil is washed with pure water and then chemically processed using a traditional chemical process, with a withstand voltage of 560Vf. Example

[0041] A method for preparing a sintered foil comprises the following steps:

[0042] S1. Mixing aluminum-based powder, an organic solvent, and an amine polymer, and stirring them uniformly to prepare an aluminum powder slurry for later use;

[0043] The mass ratio of the aluminum-based powder to the amine polymer is 80:1; the aluminum-based powder is preferably pure aluminum powder with a purity of not less than 99.99%;

[0044] The organic solvent is preferably ethanol, and the amine polymer is preferably polyetheramine;

[0045] S2. Flattening the rolled aluminum foil substrate (initial thickness controlled at 50-80 μm) layer by layer and feeding it into an ultrasonic cleaning tank; the cleaning solution in the ultrasonic cleaning tank is a mixed aqueous solution of 0.5% by mass NaOH and 5% by mass acetone, the temperature is maintained at 25°C, and the reaction time is set to 2 minutes; the ultrasonic generator equipped in the ultrasonic cleaning tank has a power of 2000W and a frequency controlled at 50 kHz;

[0046] S3, using high-pressure pure water to clean the aluminum foil substrate to remove the NaOH aqueous solution and acetone aqueous solution remaining on the surface; then, drying the aluminum foil substrate;

[0047] S4. Applying aluminum powder slurry to the front and back sides of the aluminum foil substrate and performing a drying process until the moisture is completely vaporized and escaped to form a solidified aluminum powder slurry layer; and the thickness of the solidified aluminum powder slurry layer is controlled to be 10 to 12 μm;

[0048] S5. The aluminum foil substrate obtained in step S4 is placed in a muffle furnace, and its inner cavity is always maintained in a nitrogen inert gas atmosphere. First, within 45 minutes, the furnace chamber temperature is uniformly increased to 250° C. and kept at this temperature for 14 hours. Then, within 30 minutes, the furnace chamber temperature is uniformly increased to 580° C. and kept at this temperature for another 10 hours until sintering is completed.

[0049] S6. Take the aluminum powder sintered foil out of the muffle furnace and cool it naturally in a nitrogen inert gas environment;

[0050] S7, the chemical formation stage, wherein the aluminum powder sintered foil is subjected to conventional chemical formation treatment to obtain a finished sintered foil. Example

[0051] A method for preparing a sintered foil comprises the following steps:

[0052] S1. Mixing aluminum-based powder, an organic solvent, and an amine polymer, and stirring them uniformly to prepare an aluminum powder slurry for later use;

[0053] The mass ratio of the aluminum-based powder to the amine polymer is 80:1; the aluminum-based powder may also preferably be an aluminum alloy powder, and one or more metals selected from the group consisting of copper, iron, cobalt, nickel, manganese, magnesium, titanium, tantalum, zirconium, and niobium may be mixed therein;

[0054] The organic solvent is preferably ethanol, and the amine polymer is preferably polyetheramine;

[0055] S2. Flattening the rolled aluminum foil substrate (initial thickness controlled at 50-80 μm) layer by layer and feeding it into an ultrasonic cleaning tank; the cleaning solution in the ultrasonic cleaning tank is a mixed aqueous solution of 0.3% by mass NaOH and 5% by mass acetone, the temperature is maintained at 25° C., and the reaction time is set to 3 minutes; the ultrasonic generator equipped in the ultrasonic cleaning tank has a power of 2000 W and a frequency controlled at 50 kHz;

[0056] S3, using high-pressure pure water to clean the aluminum foil substrate to remove the NaOH aqueous solution and acetone aqueous solution remaining on the surface; then, drying the aluminum foil substrate;

[0057] S4. Applying aluminum powder slurry to the front and back sides of the aluminum foil substrate and performing a drying process until the moisture is completely vaporized and escaped to form a solidified aluminum powder slurry layer; and the thickness of the solidified aluminum powder slurry layer is controlled to be 10 to 12 μm;

[0058] S5. The aluminum foil substrate obtained in step S4 is placed in a muffle furnace, and its inner cavity is always maintained in a nitrogen inert gas atmosphere. First, within 50 minutes, the furnace chamber temperature is uniformly increased to 280° C. and kept at this temperature for 13 hours. Then, within 25 minutes, the furnace chamber temperature is uniformly increased to 500° C. and kept at this temperature for another 12 hours until sintering is completed.

[0059] S6. Take the aluminum powder sintered foil out of the muffle furnace and cool it naturally in a nitrogen inert gas environment;

[0060] S7, the chemical formation stage, wherein the aluminum powder sintered foil is subjected to conventional chemical formation treatment to obtain a finished sintered foil. Example

[0061] A method for preparing a sintered foil comprises the following steps:

[0062] S1. Mixing aluminum-based powder, an organic solvent, and an amine polymer, and stirring them uniformly to prepare an aluminum powder slurry for later use;

[0063] The mass ratio of the aluminum-based powder to the amine polymer is 80:1; the aluminum-based powder may also preferably be an aluminum alloy powder, and one or more metals selected from the group consisting of copper, iron, cobalt, nickel, manganese, magnesium, titanium, tantalum, zirconium, and niobium may be mixed therein;

[0064] The organic solvent is preferably ethanol, and the amine polymer is preferably polyetheramine;

[0065] S2. Flattening the rolled aluminum foil substrate (initial thickness controlled at 50-80 μm) layer by layer and feeding it into an ultrasonic cleaning tank; the cleaning solution in the ultrasonic cleaning tank is a mixed aqueous solution of 0.4% by mass NaOH and 6% by mass acetone, the temperature is maintained at 25° C., and the reaction time is controlled to be 3 minutes; the ultrasonic generator equipped in the ultrasonic cleaning tank has a power of 2000 W and a frequency controlled at 45 kHz;

[0066] S3, using high-pressure pure water to clean the aluminum foil substrate to remove the NaOH aqueous solution and acetone aqueous solution remaining on the surface; then, drying the aluminum foil substrate;

[0067] S4. Applying aluminum powder slurry to the front and back sides of the aluminum foil substrate and performing a drying process until the moisture is completely vaporized and escaped to form a solidified aluminum powder slurry layer; and the thickness of the solidified aluminum powder slurry layer is controlled to be 10 to 12 μm;

[0068] S5. The aluminum foil substrate obtained in step S4 is placed in a muffle furnace, and the inner cavity thereof is always maintained in a vacuum atmosphere (the vacuum degree is controlled at -80 kPa). First, within 60 minutes, the furnace chamber temperature is uniformly increased to 300° C. and kept at this temperature for 12 hours. Subsequently, within 30 minutes, the furnace chamber temperature is uniformly increased to 650° C. and kept at this temperature for another 10 hours until sintering is completed.

[0069] S6. Take the aluminum powder sintered foil out of the muffle furnace and cool it naturally in a nitrogen inert gas environment;

[0070] S7, the chemical formation stage, wherein the aluminum powder sintered foil is subjected to conventional chemical formation treatment to obtain a finished sintered foil. Example

[0071] A method for preparing a sintered foil comprises the following steps:

[0072] S1. Mixing aluminum-based powder, an organic solvent, and an amine polymer, and stirring them uniformly to prepare an aluminum powder slurry for later use;

[0073] The mass ratio of the aluminum-based powder to the amine polymer is 80:1; the aluminum-based powder may also preferably be an aluminum alloy powder, and one or more metals selected from the group consisting of copper, iron, cobalt, nickel, manganese, magnesium, titanium, tantalum, zirconium, and niobium may be mixed therein;

[0074] The organic solvent is preferably ethanol, and the amine polymer is preferably polyetheramine;

[0075] S2. Flattening the rolled aluminum foil substrate (initial thickness controlled at 50-80 μm) layer by layer and feeding it into an ultrasonic cleaning tank; the cleaning solution in the ultrasonic cleaning tank is a mixed aqueous solution of 0.4% by mass NaOH and 6% by mass acetone, the temperature is maintained at 25° C., and the reaction time is controlled to be 3 minutes; the ultrasonic generator equipped in the ultrasonic cleaning tank has a power of 2000 W and a frequency controlled at 45 kHz;

[0076] S3, using high-pressure pure water to clean the aluminum foil substrate to remove the NaOH aqueous solution and acetone aqueous solution remaining on the surface; then, drying the aluminum foil substrate;

[0077] S3a, using a laser etching machine to form etching patterns on the front and back surfaces of the aluminum foil substrate;

[0078] The laser etching machine is equipped with a Nd:YAG laser with a wavelength of 1064 nm, and an S-shaped scanning program is adopted during the etching process. The working power is 8W, the laser frequency is 20KHZ, the pulse width is 100ns, the spot diameter is controlled at 38-40μm, and the scanning speed is controlled at 450-480mm / s.

[0079] S4. Applying aluminum powder slurry to the front and back sides of the aluminum foil substrate and performing a drying process until the moisture is completely vaporized and escaped to form a solidified aluminum powder slurry layer; and the thickness of the solidified aluminum powder slurry layer is controlled to be 10 to 12 μm;

[0080] S5. The aluminum foil substrate obtained in step S4 is placed in a muffle furnace, and the inner cavity thereof is always maintained in a vacuum atmosphere (the vacuum degree is controlled at -80 kPa). First, within 60 minutes, the furnace chamber temperature is uniformly increased to 300° C. and kept at this temperature for 12 hours. Subsequently, within 30 minutes, the furnace chamber temperature is uniformly increased to 650° C. and kept at this temperature for another 10 hours until sintering is completed.

[0081] S6. Take the aluminum powder sintered foil out of the muffle furnace and cool it naturally in a nitrogen inert gas environment;

[0082] S7, the chemical formation stage, wherein the aluminum powder sintered foil is subjected to conventional chemical formation treatment to obtain a finished sintered foil.

[0083] Table 1 is the test results of electrical properties of sintered foils obtained in Examples 1 to 4

[0084] Table 1

[0085]

[0086] In Examples 1, 2, 3, and 4, a large amount of experimental data demonstrates that the prepared sintered foils have excellent low leakage performance, and the aluminum powder sintered layer and the aluminum foil substrate have a higher bonding strength. The reasons for this are:

[0087] 1) During the slurry mixing process, the amine polymer used has a weak alkalinity, which can remove the oxide film formed on the surface of the aluminum-based powder in the air. The weak alkalinity will not destroy the structure of the aluminum-based powder itself, which is conducive to the formation of a sintering neck at high temperature, thereby enhancing the sintering strength;

[0088] 2) During the sintering process, the temperature rise process and precise temperature control of the muffle furnace chamber ensure that the amine polymer is decomposed into a large amount of ammonia (with reducing properties) under the action of high temperature, and the muffle furnace chamber is always maintained in an inert gas atmosphere or a vacuum atmosphere. This can reduce the oxidation effect of residual oxygen in the high-temperature muffle furnace and the sintering discharge of the binder on the aluminum-based powder to a certain extent. In addition, before the coating operation of the aluminum powder slurry is performed, the oxide film on the surface of the aluminum foil substrate is pre-removed with the help of an ultrasonic cleaning process, thereby enhancing the bonding strength between the subsequent aluminum powder high-temperature sintering forming layer and the aluminum foil substrate, and effectively eliminating the "powder shedding" phenomenon of the aluminum powder sintering layer;

[0089] 3) During the sintering process, amine polymers have a lower decomposition temperature than other organic polymers such as epoxy resins and polyvinylidene fluoride, and are more likely to decompose when subjected to high temperatures. Taking polyetheramine as an example, due to the presence of oxygen atoms that can combine with carbon atoms, the carbon residue left by high-temperature decomposition under an inert atmosphere will be less than that of oxygen-free binders such as polyvinylidene fluoride. In addition, the NH3 produced by the decomposition of polyetheramine is also a gaseous substance and will not remain on the surface of the aluminum foil substrate, and no substances that are difficult to remove will be generated. Therefore, the surface of the sintered foil formed has fewer residual impurities, which paves the way for improving low leakage performance (combined with the attached Figure 1-6 It can be clearly seen in the figure);

[0090] 4) In the traditional preparation process, in order to quickly and thoroughly decompose the NMP solvent and the polyvinylidene fluoride binder, the temperature of the muffle furnace chamber needs to be slowly raised to above 400°C and kept at this temperature for about 2 hours. In Examples 1, 2, 3, and 4, a relatively low temperature is used in the first temperature control stage in step S5, which greatly increases the temperature rise rate and correspondingly extends the holding time. On the one hand, this helps to ensure that the amine polymer is more thoroughly decomposed and the entire process is controllable, and eventually escapes and is discharged from the solidified aluminum powder slurry layer in the form of a gaseous substance; on the other hand, during the process of the heated amine polymer escaping in a gaseous form, a large number of penetrating "holes" can be formed in the solidified aluminum powder slurry layer, which helps to improve the electrical properties of the sintered foil product.

[0091] Table 2 is the test results of the element content in the sintered layer of sintered foil aluminum powder obtained in Examples 1 to 4

[0092] Table 2

[0093]

[0094] After analyzing the data in Table 2, the following conclusions can be drawn: After elemental energy spectrum analysis, the aluminum powder sintered layer of the sintered foil prepared by the new preparation method contains only Al and O elements, and no residual C and F elements are found, which means that the finished sintered foil maintains good purity, which is conducive to improving its low leakage performance.

[0095] Finally, the following points need to be explained:

[0096] 1) Compared with Examples 1, 2, and 3, in Example 4, before the aluminum powder slurry coating operation is officially performed, the aluminum foil substrate is laser etched to form etched lines on its front and back surfaces, and the depth is controlled to be 3-5 μm. In this way, after the coating is completed, the etched lines are filled with aluminum powder slurry, and when the aluminum powder slurry is subjected to high temperature to form an aluminum powder high-temperature sintered layer, the etched lines can variably play an "anchoring" role, thereby preventing the electrode foil from "peeling off" due to external forces in later practical applications;

[0097] 2) In both Examples 1, 2, 3, and 4, in step S2, the residual aluminum oxide film on the surface of the aluminum foil substrate is effectively removed by using a mixed aqueous solution of NaOH and acetone, supplemented by ultrasonic waves, allowing the solidified aluminum powder slurry layer to directly adhere to the surface of the aluminum foil substrate, ensuring excellent bonding strength between the aluminum powder high-temperature sintered layer and the aluminum foil substrate.

[0098] When the aluminum foil substrate flows through the ultrasonic cleaning tank, the sodium hydroxide solution can effectively dissolve the aluminum oxide film. The reaction formula is Al2O3 + 2NaOH +3H2O = 2NaAl(OH)4. Acetone is a polar solvent and contains carbonyl functional groups, which has good solubility. With its assistance, it can not only ensure that the sodium hydroxide solution has better dispersion uniformity in the mixed aqueous solution, but also facilitate the sodium hydroxide solution to more easily penetrate into the aluminum oxide film, which is beneficial to improve the reaction efficiency of the two. Moreover, under the set process parameters, the sodium hydroxide solution can only effectively dissolve the aluminum oxide film and will not undergo violent chemical reactions with the aluminum foil substrate. In this way, while ensuring that the aluminum oxide film is dissolved and removed, the outer shape regularity of the aluminum foil substrate can be maintained as much as possible.

[0099] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a sintered foil, characterized in that: The following steps are involved: S1. Mixing aluminum-based powder, an organic solvent, and an amine polymer, and stirring them uniformly to prepare an aluminum powder slurry for later use; S2. Flattening the rolled aluminum foil substrate layer by layer and feeding it into an ultrasonic cleaning tank; the cleaning liquid in the ultrasonic cleaning tank is a mixed aqueous solution of 0.3-0.5% by mass of NaOH and 5-6% by mass of acetone, the temperature is maintained below 25° C., and the reaction time is controlled within 2-3 minutes; the ultrasonic generator equipped in the ultrasonic cleaning tank has a power of 2000 W and a frequency controlled within 45-50 kHz; S3, using high-pressure pure water to clean the aluminum foil substrate and then drying it; S4, applying aluminum powder slurry to the front and back sides of the aluminum foil substrate, and performing a drying process until the moisture is completely vaporized and escapes; S5. Placing the aluminum foil substrate obtained in step S4 in a muffle furnace, and maintaining its inner cavity in an inert gas atmosphere or a vacuum atmosphere. First, within 45 to 60 minutes, the furnace chamber temperature is uniformly increased to 250 to 300° C. and maintained at this temperature for 12 to 14 hours. Subsequently, within 25 to 30 minutes, the furnace chamber temperature is uniformly increased to 500 to 650° C., and then maintained at this temperature for 10 to 12 hours until sintering is completed. S6. Take the aluminum powder sintered foil out of the muffle furnace and cool it naturally; S7, the chemical formation stage, wherein the aluminum powder sintered foil is chemically treated to obtain a finished sintered foil.

2. The method for preparing sintered foil according to claim 1, characterized in that: In step S1, the mass ratio of the aluminum-based powder to the amine polymer is controlled within a range of 80:1 to 100:

1.

3. The method for preparing sintered foil according to claim 2, characterized in that: The aluminum-based powder is pure aluminum powder with a purity of not less than 99.99%.

4. The method for preparing sintered foil according to claim 2, characterized in that: The aluminum-based powder is an aluminum alloy powder, and is mixed with one or more metals selected from the group consisting of copper, iron, cobalt, nickel, manganese, magnesium, titanium, tantalum, zirconium, and niobium.

5. The method for preparing sintered foil according to claim 2, characterized in that: The organic solvent is one or more of ethanol, ethylene glycol, acetone, N-methylpyrrolidone (NMP), and N,N-dimethylformamide (DMF), and the amine polymer is one or more of aminopolyethylene glycol, polyetheramine, polyacrylamide, polyethyleneamine, polyquaternary ammonium salt, polycaprolactone amino, diaminourea polymer, and 4-aminomethylstyrene-styrene divinyl copolymer.

6. The method for preparing sintered foil according to claim 1, characterized in that: In step S2, the initial thickness of the aluminum foil substrate is controlled to be 50-80 μm.

7. The method for preparing sintered foil according to claim 6, characterized in that: A step S3a is added between step S3 and step S4. Before the coating operation is formally carried out, a laser etching machine is used to form etching lines on the front and back surfaces of the aluminum foil substrate.

8. The method for preparing sintered foil according to claim 7, characterized in that: The laser etcher is equipped with a Nd:YAG laser with a wavelength of 1064nm, and an S-shaped scanning program is adopted during the etching process. The working power is 8W, the laser frequency is 20KHZ, the pulse width is 100ns, the spot diameter is controlled at 38-40μm, and the scanning speed is controlled at 450-480mm / s.

9. The method for preparing sintered foil according to claim 1, characterized in that: In step S5, the inert gas is either nitrogen or argon; when the inner cavity of the muffle furnace is maintained in a vacuum atmosphere, the vacuum degree is controlled at -100 KPa to -75 KPa.

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