A method of making a high capacity high strength powder sintered foil

Abstract

The present application relates to the technical field of powder sintered foil, and particularly relates to a preparation method of high-capacity high-strength powder sintered foil. The present application adds active powder and gas pore-forming agent into aluminum powder to prepare mixed powder, then the mixed powder is pressed onto the surface of pure aluminum foil substrate in two times through pressing, and then the aluminum powder is pressed onto the surface of the mixed powder layer, and the high-capacity high-strength powder sintered foil is obtained after discharge plasma sintering and formation. Compared with the prior art, the powder sintered foil prepared by the present application has higher strength, higher porosity and capacity, and therefore has wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of powder sintered foil preparation, and more particularly to a method for preparing high-capacity, high-strength powder sintered foil. Background Technology

[0002] Aluminum electrolytic capacitors are widely used in industrial frequency converters, inverters, 5G base stations, and new energy charging piles, making them an important electronic device. Traditional aluminum electrolytic capacitors use electrode foils primarily manufactured through electrochemical etching and anodizing. The former utilizes large amounts of corrosive acids, such as hydrochloric acid, sulfuric acid, and nitric acid, to etch the foil surface, thereby increasing the specific surface area. However, the large amounts of acid waste require expensive environmental protection systems for treatment or recycling, increasing environmental disposal costs and environmental pressure. In recent years, methods have emerged that use sintered aluminum powder on the aluminum substrate to replace electrochemical etching to obtain high specific surface areas. This process avoids the use of various corrosive acids, significantly reducing environmental burden and economic costs. For example, patent document CN114724858B discloses a method for preparing high specific surface area and high dielectric sintered foil. This invention obtains sintered foil by coating aluminum powder onto the surface of aluminum foil. While this process avoids the use of large amounts of waste acid, the final sintered foil exhibits significant powder shedding.

[0003] To address the aforementioned issues, patent document CN116598141B discloses a method for preparing surface-hydroxylated sintered foil. This invention involves first coating the surface of aluminum foil with aluminum powder and adhesive, then subjecting the coated aluminum foil surface to hydroxylation treatment, and finally forming it using a conventional formation process. While this method addresses the issue of powder shedding from the sintered foil to some extent, it offers relatively limited improvement in the specific surface area and porosity of the sintered foil, severely restricting further enhancement of its dielectric properties.

[0004] Therefore, in response to the aforementioned technologies, there is an urgent need to develop a method for preparing high-capacity, high-strength powder sintered foil. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for preparing high-capacity, high-strength powder sintered foil, so as to provide a powder sintering technology that does not require the use of corrosive acid for electrochemical etching, and to obtain high-capacity, high-strength powder sintered foil.

[0006] To achieve the above objectives, the present invention provides a method for preparing a high-capacity, high-strength powder sintered foil, characterized by comprising the following steps: S1: Aluminum foil is pickled and washed with water to obtain aluminum foil substrate; S2: Spread the mixed powder A evenly on one surface of the aluminum foil substrate, press it into a cold-pressed blank by cold isostatic pressing, with a pressure of 10-50MPa, holding pressure for 10-30min, pressing 1-3 times to form the first powder layer; S3: Spread the mixed powder B evenly on the surface of the first powder layer, press it into a cold-pressed blank by cold isostatic pressing, with a pressure of 10-50MPa, holding pressure for 10-30min, pressing 1-3 times to form the second powder layer. S4: Aluminum powder is evenly spread on the surface of the second powder layer, and then pressed into a cold-pressed blank by cold isostatic pressing at a pressure of 10-50MPa, holding pressure for 10-30min, pressing 1-3 times to form the third powder layer. S5: Repeat steps S2-S4 to obtain aluminum foil with powder coating on both sides; S6: The double-sided powder-coated aluminum foil is subjected to discharge plasma sintering to form a high-strength powder-sintered electrode foil. The mixed powder A is obtained by mixing aluminum powder, active powder and gas pore-forming agent in a weight ratio of 10:0.8-1:0.8-1; The mixed powder B is obtained by mixing aluminum powder, active powder and gas pore-forming agent in a weight ratio of 10:0.1-0.3:0.1-0.3; Preferably, the active powder is one or more of magnesium powder, silicon powder, and rare earth powder; Preferably, the gaseous pore-forming agent is one or more of CaCO3, NaHCO3, NH4HCO3, MgCO3 and CaMg(CO3)2.

[0007] Preferably, the gaseous pore-forming agent is NaHCO3.

[0008] Preferably, the rare earth powder is one or more of yttrium powder, cerium powder, and neodymium powder.

[0009] Preferably, the specific steps of step S1 are as follows: immerse a 10-50μm thick aluminum foil in a 60-150g / L sulfuric acid solution, soak it in a constant temperature water bath at 40℃-60℃ for 1-5 minutes to remove organic matter and grease from the surface, and quickly remove it after soaking and rinse it with deionized water.

[0010] Preferably, in step S2, the spreading amount of mixed powder A is 0.4-0.5 g / cm³. 3 In step S3, the spreading amount of mixed powder B is 0.4-0.5 g / cm³. 3 In step S4, the aluminum powder spreading amount is 0.6-1.2 g / cm³. 3 .

[0011] Preferably, the specific steps of the spark plasma sintering in step S6 are as follows: The double-sided powder-coated aluminum foil is placed into a graphite mold, then placed into a spark plasma sintering furnace; the vacuum pump is turned on, and a vacuum of 1×10⁻⁶ is drawn. -2Pa, sintering temperature set at 500-650℃, heating rate controlled at 30-60℃ / min, holding time at 10-20min.

[0012] Preferably, the specific steps of the formation in step S6 are as follows: S61: Place the sintered aluminum foil coated with powder on both sides in water at 90-98℃ and boil for 8-10 minutes; S62: Then place it in a solution of boric acid with a mass percentage concentration of 2%-10% and ammonium citrate with a mass percentage of 0.5%-2%, and at 70-90℃ and a current density of 10-20 mA / cm². 2 Perform a single-stage formation at a voltage of 180V for 10-20 minutes, and then remove and rinse with water. S63: Then place it in a solution of boric acid with a mass percentage concentration of 2%-10% and ammonium citrate with a mass percentage concentration of 0.2%-1.5%, and at 70-90℃ and a current density of 10-20 mA / cm². 2 Perform two-stage formation under 360V conditions, with the formation time controlled at 10-15 min, and then remove and rinse with water; S64: Then place it in a solution of boric acid with a mass percentage concentration of 4%-15% and ammonium pentaborate with a mass percentage concentration of 0.1%-1%, and at 80-95℃ and a current density of 10-20 mA / cm². 2 Perform three-stage formation under 500V conditions, with the formation time controlled at 8-15 minutes, and then remove and rinse with water; S65: Then place it in a solution of boric acid with a mass percentage concentration of 4%-15% and ammonium pentaborate with a mass percentage concentration of 0.1%-1%, and at 80-95℃ and a current density of 10-20 mA / cm². 2 Perform four-stage formation at 640V for 20-30 minutes, then remove and rinse with water. S66: Place it in a 5%-10% phosphoric acid solution, control the temperature at 50-80℃, control the immersion time at 5-10 min, and then take it out and wash it with water. S67: Then place it in a solution of boric acid with a mass percentage concentration of 10%-12% and ammonium pentaborate with a mass percentage concentration of 1%-1.5%, and at 80-95℃ and a current density of 10-20 mA / cm². 2 The subsequent formation is carried out under conditions of 640V, with the formation time controlled at 5-10 minutes, and then the product is removed and rinsed with water. S68: Place it in an oven, with the temperature controlled at 400-550℃ and the time controlled at 3-5 minutes; S69: Then place it in a solution of boric acid with a mass percentage concentration of 4%-15% and ammonium pentaborate with a mass percentage concentration of 0.1%-1%, and at 80-95℃ and a current density of 10-20 mA / cm². 2 The second formation was carried out under 640V conditions, with the formation time controlled at 5-10 min, and then the product was taken out and rinsed with water. S70: Place it in a 1%-5% ammonium dihydrogen phosphate solution and immerse it at 60-80℃ for 5-10 minutes. Then remove it, wash it with water, and dry it.

[0013] The beneficial effects of this invention are: This invention eliminates the need for large amounts of corrosive acid during the preparation of high-capacity, high-strength powder sintered foil, effectively reducing environmental disposal costs and environmental pressure, and better meeting the requirements of green manufacturing. This invention employs spark plasma sintering, which has a fast sintering speed. Adding an appropriate amount of active powder to pure aluminum powder can promote the formation of more sintering necks between aluminum powder particles, resulting in a higher degree of bonding between the aluminum foil matrix and the powder, further enhancing the strength of the powder sintered foil. At the same time, a gaseous pore-forming agent is added, which can increase the specific surface area and porosity of the powder sintered foil after powder sintering. Compared with the pure aluminum powder sintered foil in the prior art, the powder sintered foil prepared by this invention has a higher capacity. This invention employs a three-stage layered pressing method. The first two layers are mixed powders of active powder and gas pore-forming agent with gradient content, which can improve the bonding degree between the mixed powder and the aluminum foil substrate. The third layer is pure aluminum powder, which can form a high dielectric oxide layer. Furthermore, this gradient structure design enables the powder sintered foil to have higher capacity and mechanical properties. Detailed Implementation

[0014] In a specific embodiment of the present invention, the particle size of aluminum powder is 5.4 μm; the particle size of magnesium powder is 6.3 μm; the particle size of silicon powder is 5.8 μm; and the particle size of cerium powder is 5.2 μm.

[0015] Example 1: Preparation of high-capacity, high-strength powder sintered foil: (1) Immerse a 20μm thick aluminum foil in a 100g / L sulfuric acid solution and soak it in a constant temperature water bath at 50℃ for 3min to remove organic matter and grease from the surface. After soaking, take it out quickly and rinse it with deionized water to obtain the aluminum foil substrate. (2) Mix 10g of aluminum powder, 0.8g of magnesium powder and 0.8g of NH4HCO3 to obtain mixed powder A. Then, evenly spread mixed powder A on one surface of the aluminum foil substrate, with a spreading amount of 0.5g / cm. 3 The powder is formed by cold isostatic pressing at a pressure of 120 MPa for 120 min, and pressing twice to form the first powder layer. (3) Mix 10g of aluminum powder, 0.1g of magnesium powder and 0.1g of NH4HCO3 to obtain mixed powder B. Then, evenly spread mixed powder B on the surface of the first powder layer with a spreading amount of 0.5g / cm. 3 The powder is pressed into a cold-pressed blank by cold isostatic pressing at a pressure of 20 MPa for 20 min, and pressed twice to form the second powder layer. (4) Spread aluminum powder evenly on the surface of the second powder layer, with a spreading amount of 1 g / cm. 3 The powder is pressed into a cold-pressed blank by cold isostatic pressing at a pressure of 20 MPa for 20 min, and pressed twice to form the third powder layer. (5) Repeat steps S2-S4 to obtain aluminum foil with powder coating on both sides; (6) Place the double-sided powder-coated aluminum foil into a graphite mold, then place it into a spark plasma sintering furnace, turn on the vacuum pump, and evacuate to 1×10⁻⁶. -2 Pa, sintering temperature set at 600℃, heating rate controlled at 40℃ / min, holding time at 20min.

[0016] (7) Then place the sintered aluminum foil coated with powder on both sides into water at 95°C and boil for 10 minutes; (8) Then place it in a solution of 5% boric acid and 1% ammonium citrate by mass percentage, and heat it at 80°C and a current density of 15 mA / cm². 2 The first-stage formation was carried out under a voltage of 180V, and the formation time was controlled within 20 minutes. The product was then removed and rinsed with water. (9) Then place it in a solution of 5% boric acid and 1% ammonium citrate by mass, and heat it at 80°C and a current density of 15 mA / cm². 2 Two-stage formation was performed under 360V conditions, with the formation time controlled within 15 minutes, and the sample was then removed and rinsed with water. (10) Then place it in a solution of 10% boric acid and 0.5% ammonium pentaborate, and heat it at 90°C and a current density of 15 mA / cm². 2 Three-stage formation was performed under 500V conditions, with the formation time controlled within 10 minutes, and the sample was then rinsed with water. (11) Then place it in a solution of 10% boric acid and 0.5% ammonium pentaborate, and heat it at 90°C and a current density of 15 mA / cm². 2 Perform four-stage formation at 640V for 25 minutes, then remove and rinse with water. (12) Then place it in a phosphoric acid solution with a mass percentage concentration of 8%, control the temperature at 70℃, control the immersion time at 8 min, and take it out and wash it with water; (13) Then place it in a solution of boric acid with a mass percentage concentration of 10% and ammonium pentaborate with a mass percentage concentration of 1%, and at 90°C and a current density of 15 mA / cm². 2 The subsequent formation was carried out under conditions of 640V, with the formation time controlled at 8 minutes, and then the product was removed and rinsed with water. (14) Place it in an oven and heat it at 500°C for 4 minutes. (15) Then place it in a solution of 10% boric acid and 0.5% ammonium pentaborate, and heat it at 90°C and a current density of 15 mA / cm². 2 The second formation was carried out under 640V conditions, with the formation time controlled at 8 minutes, and then the product was taken out and rinsed with water. (16) Then place it in a 3% ammonium dihydrogen phosphate solution, immerse it at 70°C for 8 minutes, take it out, wash it with water, and dry it to obtain a high-capacity, high-strength powder sintered foil.

[0017] Example 2: Preparation of high-capacity, high-strength powder sintered foil: (1) Immerse a 20μm thick aluminum foil in a 100g / L sulfuric acid solution and soak it in a constant temperature water bath at 50℃ for 3min to remove organic matter and grease from the surface. After soaking, take it out quickly and rinse it with deionized water to obtain the aluminum foil substrate. (2) Mix 10g of aluminum powder, 1g of magnesium powder and 1g of NH4HCO3 to obtain mixed powder A. Then, evenly spread mixed powder A on one surface of the aluminum foil substrate, with a spreading amount of 0.5g / cm. 3 The powder is formed by cold isostatic pressing at a pressure of 120 MPa for 120 min, and pressing twice to form the first powder layer. (3) Mix 10g of aluminum powder, 0.3g of magnesium powder and 0.3g of NH4HCO3 to obtain mixed powder B. Then, evenly spread mixed powder B on the surface of the first powder layer with a spreading amount of 0.5g / cm. 3 The powder is pressed into a cold-pressed blank by cold isostatic pressing at a pressure of 20 MPa for 20 min, and pressed twice to form the second powder layer. (4) Spread aluminum powder evenly on the surface of the second powder layer, with a spreading amount of 1 g / cm. 3 The powder is pressed into a cold-pressed blank by cold isostatic pressing at a pressure of 20 MPa for 20 min, and pressed twice to form the third powder layer. (5) Repeat steps S2-S4 to obtain aluminum foil with powder coating on both sides; (6) Place the double-sided powder-coated aluminum foil into a graphite mold, then place it into a spark plasma sintering furnace, turn on the vacuum pump, and evacuate to 1×10⁻⁶. -2Pa, sintering temperature set at 600℃, heating rate controlled at 40℃ / min, holding time at 20min.

[0018] (7) Then place the sintered aluminum foil coated with powder on both sides into water at 95°C and boil for 10 minutes; (8) Then place it in a solution of 5% boric acid and 1% ammonium citrate by mass percentage, and heat it at 80°C and a current density of 15 mA / cm². 2 The first-stage formation was carried out under a voltage of 180V, and the formation time was controlled within 20 minutes. The product was then removed and rinsed with water. (9) Then place it in a solution of 5% boric acid and 1% ammonium citrate by mass, and heat it at 80°C and a current density of 15 mA / cm². 2 Two-stage formation was performed under 360V conditions, with the formation time controlled within 15 minutes, and the sample was then removed and rinsed with water. (10) Then place it in a solution of 10% boric acid and 0.5% ammonium pentaborate, and heat it at 90°C and a current density of 15 mA / cm². 2 Three-stage formation was performed under 500V conditions, with the formation time controlled within 10 minutes, and the sample was then rinsed with water. (11) Then place it in a solution of 10% boric acid and 0.5% ammonium pentaborate, and heat it at 90°C and a current density of 15 mA / cm². 2 Perform four-stage formation at 640V for 25 minutes, then remove and rinse with water. (12) Then place it in a phosphoric acid solution with a mass percentage concentration of 8%, control the temperature at 70℃, control the immersion time at 8 min, and take it out and wash it with water; (13) Then place it in a solution of boric acid with a mass percentage concentration of 10% and ammonium pentaborate with a mass percentage concentration of 1%, and at 90°C and a current density of 15 mA / cm². 2 The subsequent formation was carried out under conditions of 640V, with the formation time controlled at 8 minutes, and then the product was removed and rinsed with water. (14) Place it in an oven and heat it at 500°C for 4 minutes. (15) Then place it in a solution of 10% boric acid and 0.5% ammonium pentaborate, and heat it at 90°C and a current density of 15 mA / cm². 2 The second formation was carried out under 640V conditions, with the formation time controlled at 8 minutes, and then the product was taken out and rinsed with water. (16) Then place it in a 3% ammonium dihydrogen phosphate solution, immerse it at 70°C for 8 minutes, take it out, wash it with water, and dry it to obtain a high-capacity, high-strength powder sintered foil.

[0019] Example 3: Preparation of high-capacity, high-strength powder sintered foil: (1) Immerse a 20μm thick aluminum foil in a 100g / L sulfuric acid solution and soak it in a constant temperature water bath at 50℃ for 3min to remove organic matter and grease from the surface. After soaking, take it out quickly and rinse it with deionized water to obtain the aluminum foil substrate. (2) Mix 10g of aluminum powder, 0.8g of silicon powder and 0.8g of NH4HCO3 to obtain mixed powder A. Then, evenly spread mixed powder A on one surface of the aluminum foil substrate, with a spreading amount of 0.5g / cm. 3 The powder is formed by cold isostatic pressing at a pressure of 120 MPa for 120 min, and pressing twice to form the first powder layer. (3) Mix 10g of aluminum powder, 0.1g of silicon powder and 0.1g of NH4HCO3 to obtain mixed powder B. Then, evenly spread mixed powder B on the surface of the first powder layer with a spreading amount of 0.5g / cm. 3 The powder is pressed into a cold-pressed blank by cold isostatic pressing at a pressure of 20 MPa for 20 min, and pressed twice to form the second powder layer. (4) Spread aluminum powder evenly on the surface of the second powder layer, with a spreading amount of 1 g / cm. 3 The powder is pressed into a cold-pressed blank by cold isostatic pressing at a pressure of 20 MPa for 20 min, and pressed twice to form the third powder layer. (5) Repeat steps S2-S4 to obtain aluminum foil with powder coating on both sides; (6) Place the double-sided powder-coated aluminum foil into a graphite mold, then place it into a spark plasma sintering furnace, turn on the vacuum pump, and evacuate to 1×10⁻⁶. -2 Pa, sintering temperature set at 600℃, heating rate controlled at 40℃ / min, holding time at 20min.

[0020] (7) Then place the sintered aluminum foil coated with powder on both sides into water at 95°C and boil for 10 minutes; (8) Then place it in a solution of 5% boric acid and 1% ammonium citrate by mass percentage, and heat it at 80°C and a current density of 15 mA / cm². 2 The first-stage formation was carried out under a voltage of 180V, and the formation time was controlled within 20 minutes. The product was then removed and rinsed with water. (9) Then place it in a solution of 5% boric acid and 1% ammonium citrate by mass, and heat it at 80°C and a current density of 15 mA / cm². 2 Two-stage formation was performed under 360V conditions, with the formation time controlled within 15 minutes, and the sample was then removed and rinsed with water. (10) Then place it in a solution of 10% boric acid and 0.5% ammonium pentaborate, and heat it at 90°C and a current density of 15 mA / cm². 2 Three-stage formation was performed under 500V conditions, with the formation time controlled within 10 minutes, and the sample was then rinsed with water. (11) Then place it in a solution of 10% boric acid and 0.5% ammonium pentaborate, and heat it at 90°C and a current density of 15 mA / cm². 2 Perform four-stage formation at 640V for 25 minutes, then remove and rinse with water. (12) Then place it in a phosphoric acid solution with a mass percentage concentration of 8%, control the temperature at 70℃, control the immersion time at 8 min, and take it out and wash it with water; (13) Then place it in a solution of boric acid with a mass percentage concentration of 10% and ammonium pentaborate with a mass percentage concentration of 1%, and at 90°C and a current density of 15 mA / cm². 2 The subsequent formation was carried out under conditions of 640V, with the formation time controlled at 8 minutes, and then the product was removed and rinsed with water. (14) Place it in an oven and heat it at 500°C for 4 minutes. (15) Then place it in a solution of 10% boric acid and 0.5% ammonium pentaborate, and heat it at 90°C and a current density of 15 mA / cm². 2 The second formation was carried out under 640V conditions, with the formation time controlled at 8 minutes, and then the product was taken out and rinsed with water. (16) Then place it in a 3% ammonium dihydrogen phosphate solution, immerse it at 70°C for 8 minutes, take it out, wash it with water, and dry it to obtain a high-capacity, high-strength powder sintered foil.

[0021] Example 4: Preparation of high-capacity, high-strength powder sintered foil: (1) Immerse a 20μm thick aluminum foil in a 100g / L sulfuric acid solution and soak it in a constant temperature water bath at 50℃ for 3min to remove organic matter and grease from the surface. After soaking, take it out quickly and rinse it with deionized water to obtain the aluminum foil substrate. (2) Mix 10g of aluminum powder, 0.8g of magnesium powder and 0.8g of NH4HCO3 to obtain mixed powder A. Then, evenly spread mixed powder A on one surface of the aluminum foil substrate, with a spreading amount of 0.5g / cm. 3 The powder is formed by cold isostatic pressing at a pressure of 120 MPa for 120 min, and pressing twice to form the first powder layer. (3) Mix 10g of aluminum powder, 0.1g of cerium powder and 0.1g of NH4HCO3 to obtain mixed powder B. Then, evenly spread mixed powder B on the surface of the first powder layer with a spreading amount of 0.5g / cm. 3 The powder is pressed into a cold-pressed blank by cold isostatic pressing at a pressure of 20 MPa for 20 min, and pressed twice to form the second powder layer. (4) Spread aluminum powder evenly on the surface of the second powder layer, with a spreading amount of 1 g / cm. 3 The powder is pressed into a cold-pressed blank by cold isostatic pressing at a pressure of 20 MPa for 20 min, and pressed twice to form the third powder layer. (5) Repeat steps S2-S4 to obtain aluminum foil with powder coating on both sides; (6) Place the double-sided powder-coated aluminum foil into a graphite mold, then place it into a spark plasma sintering furnace, turn on the vacuum pump, and evacuate to 1×10⁻⁶. -2 Pa, sintering temperature set at 600℃, heating rate controlled at 40℃ / min, holding time at 20min.

[0022] (7) Then place the sintered aluminum foil coated with powder on both sides into water at 95°C and boil for 10 minutes; (8) Then place it in a solution of 5% boric acid and 1% ammonium citrate by mass percentage, and heat it at 80°C and a current density of 15 mA / cm². 2 The first-stage formation was carried out under a voltage of 180V, and the formation time was controlled within 20 minutes. The product was then removed and rinsed with water. (9) Then place it in a solution of 5% boric acid and 1% ammonium citrate by mass, and heat it at 80°C and a current density of 15 mA / cm². 2 Two-stage formation was performed under 360V conditions, with the formation time controlled within 15 minutes, and the sample was then removed and rinsed with water. (10) Then place it in a solution of 10% boric acid and 0.5% ammonium pentaborate, and heat it at 90°C and a current density of 15 mA / cm². 2 Three-stage formation was performed under 500V conditions, with the formation time controlled within 10 minutes, and the sample was then rinsed with water. (11) Then place it in a solution of 10% boric acid and 0.5% ammonium pentaborate, and heat it at 90°C and a current density of 15 mA / cm². 2 Perform four-stage formation at 640V for 25 minutes, then remove and rinse with water. (12) Then place it in a phosphoric acid solution with a mass percentage concentration of 8%, control the temperature at 70℃, control the immersion time at 8 min, and take it out and wash it with water; (13) Then place it in a solution of boric acid with a mass percentage concentration of 10% and ammonium pentaborate with a mass percentage concentration of 1%, and at 90°C and a current density of 15 mA / cm². 2 The subsequent formation was carried out under conditions of 640V, with the formation time controlled at 8 minutes, and then the product was removed and rinsed with water. (14) Place it in an oven and heat it at 500°C for 4 minutes. (15) Then place it in a solution of 10% boric acid and 0.5% ammonium pentaborate, and heat it at 90°C and a current density of 15 mA / cm². 2 The second formation was carried out under 640V conditions, with the formation time controlled at 8 minutes, and then the product was taken out and rinsed with water. (16) Then place it in a 3% ammonium dihydrogen phosphate solution, immerse it at 70°C for 8 minutes, take it out, wash it with water, and dry it to obtain a high-capacity, high-strength powder sintered foil.

[0023] Example 5: Preparation of high-capacity, high-strength powder sintered foil: (1) Immerse a 20μm thick aluminum foil in a 100g / L sulfuric acid solution and soak it in a constant temperature water bath at 50℃ for 3min to remove organic matter and grease from the surface. After soaking, take it out quickly and rinse it with deionized water to obtain the aluminum foil substrate. (2) Mix 10g of aluminum powder, 0.5g of magnesium powder, 0.4g of silicon powder and 0.8g of NH4HCO3 to obtain mixed powder A. Then, evenly spread mixed powder A on one surface of the aluminum foil substrate, with a spreading amount of 0.5g / cm. 3 The powder is formed by cold isostatic pressing at a pressure of 120 MPa for 120 min, and pressing twice to form the first powder layer. (3) Mix 10g aluminum powder, 0.1g magnesium powder, 0.1g silicon powder and 0.1g NH4HCO3 to obtain mixed powder B. Then, evenly spread mixed powder B on the surface of the first powder layer with a spreading amount of 0.5g / cm. 3 The powder is pressed into a cold-pressed blank by cold isostatic pressing at a pressure of 20 MPa for 20 min, and pressed twice to form the second powder layer. (4) Spread aluminum powder evenly on the surface of the second powder layer, with a spreading amount of 1 g / cm. 3 The powder is pressed into a cold-pressed blank by cold isostatic pressing at a pressure of 20 MPa for 20 min, and pressed twice to form the third powder layer. (5) Repeat steps S2-S4 to obtain aluminum foil with powder coating on both sides; (6) Place the double-sided powder-coated aluminum foil into a graphite mold, then place it into a spark plasma sintering furnace, turn on the vacuum pump, and evacuate to 1×10⁻⁶. -2Pa, sintering temperature set at 600℃, heating rate controlled at 40℃ / min, holding time at 20min.

[0024] (7) Then place the sintered aluminum foil coated with powder on both sides into water at 95°C and boil for 10 minutes; (8) Then place it in a solution of 5% boric acid and 1% ammonium citrate by mass percentage, and heat it at 80°C and a current density of 15 mA / cm². 2 The first-stage formation was carried out under a voltage of 180V, and the formation time was controlled within 20 minutes. The product was then removed and rinsed with water. (9) Then place it in a solution of 5% boric acid and 1% ammonium citrate by mass, and heat it at 80°C and a current density of 15 mA / cm². 2 Two-stage formation was performed under 360V conditions, with the formation time controlled within 15 minutes, and the sample was then removed and rinsed with water. (10) Then place it in a solution of 10% boric acid and 0.5% ammonium pentaborate, and heat it at 90°C and a current density of 15 mA / cm². 2 Three-stage formation was performed under 500V conditions, with the formation time controlled within 10 minutes, and the sample was then rinsed with water. (11) Then place it in a solution of 10% boric acid and 0.5% ammonium pentaborate, and heat it at 90°C and a current density of 15 mA / cm². 2 Perform four-stage formation at 640V for 25 minutes, then remove and rinse with water. (12) Then place it in a phosphoric acid solution with a mass percentage concentration of 8%, control the temperature at 70℃, control the immersion time at 8 min, and take it out and wash it with water; (13) Then place it in a solution of boric acid with a mass percentage concentration of 10% and ammonium pentaborate with a mass percentage concentration of 1%, and at 90°C and a current density of 15 mA / cm². 2 The subsequent formation was carried out under conditions of 640V, with the formation time controlled at 8 minutes, and then the product was removed and rinsed with water. (14) Place it in an oven and heat it at 500°C for 4 minutes. (15) Then place it in a solution of 10% boric acid and 0.5% ammonium pentaborate, and heat it at 90°C and a current density of 15 mA / cm². 2 The second formation was carried out under 640V conditions, with the formation time controlled at 8 minutes, and then the product was taken out and rinsed with water. (16) Then place it in a 3% ammonium dihydrogen phosphate solution, immerse it at 70°C for 8 minutes, take it out, wash it with water, and dry it to obtain a high-capacity, high-strength powder sintered foil.

[0025] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that the amount of magnesium powder added in step (3) is 1g; Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that the amount of NH4HCO3 added in step (3) is 1g; Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that the amount of magnesium powder added in step (3) is 1g and the amount of NH4HCO3 added is 1g.

[0026] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that NH4HCO3 was not added in steps (2) and (3).

[0027] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that the aluminum foil substrate surface is only covered with a layer of aluminum powder, with a coverage amount of 2 g / cm³. 3 .

[0028] Performance testing methods: Flexural strength: The sintered foils prepared in the examples and comparative examples were cut into rectangular samples of 150mm×10mm. The samples were clamped in the chuck of the bending machine. The test conditions were: load weight of 2.5N, chuck curvature R of 1.0mm, bending angle of 90±2°, and bending speed of 6 times / s. After the sample broke, the reading on the bending machine was read. The results are shown in Table 1. Pressure resistance test: The test solution is 70 g / L boric acid with a conductivity of 133.3 μs / cm and a pH of 3.2. The sample is immersed in the test solution with the tested part 6-8 mm below the liquid surface. The data is read in the computer of the pressure resistance tester. The results are shown in Table 1. Specific volume test: The test solution was 80 g / L ammonium pentaborate with a conductivity of 3.3 × 10⁻⁶. 4 μs / cm, pH 7.4, the sample was clamped into the capacitance tester circuit, the test frequency was 120Hz, and the test results were read directly. The results are shown in Table 1.

[0029] Table 1 Performance Test Results

[0030] Data Analysis: As can be seen from Examples 1-5 in Table 1, the high-capacity, high-strength powder sintered foil prepared by the present invention has high specific volume and flexural strength, and the specific volume and flexural strength of the powder sintered foil can be controlled by adding different active powders, which has broad application prospects.

[0031] As can be seen from Example 2 and Comparative Examples 1-5 in Table 1, the gradient content of active powder and gas pore-forming agent in the three-layer segmented pressing of the present invention can effectively improve the specific volume and flexural strength of the powder sintered foil. This may be because the gradient structure design can effectively reduce the accumulation of internal stress and over-sintering of the powder during the sintering process, and construct a uniform channel and pore distribution, thereby optimizing the electrochemical performance and mechanical properties.

[0032] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0033] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing a high-capacity, high-strength powder sintered foil, characterized in that, Includes the following steps: S1: Aluminum foil is pickled and washed with water to obtain aluminum foil substrate; S2: The mixed powder A is evenly spread on one surface of the aluminum foil substrate and pressed into a cold-pressed blank by cold isostatic pressing to form the first powder layer; S3: The mixed powder B is evenly spread on the surface of the first powder layer, and then pressed into a cold-pressed blank by cold isostatic pressing to form the second powder layer; S4: Aluminum powder is evenly spread on the surface of the second powder layer, and then pressed into a cold-pressed blank by cold isostatic pressing to form the third powder layer; S5: Repeat steps S2-S4 to obtain aluminum foil with powder coating on both sides; S6: Double-sided powder-coated aluminum foil is subjected to discharge plasma sintering to form a high-capacity, high-strength powder sintered foil. The mixed powder A is obtained by mixing aluminum powder, active powder and gas pore-forming agent in a weight ratio of 10:0.8-1:0.8-1; The mixed powder B is obtained by mixing aluminum powder, active powder and gas pore-forming agent in a weight ratio of 10:0.1-0.3:0.1-0.3; The active powder is one or more of magnesium powder, silicon powder, and rare earth powder.

2. The method for preparing high-capacity, high-strength powder sintered foil according to claim 1, characterized in that, In step S2, the spreading amount of mixed powder A is 0.4-0.5 g / cm³. 3 In step S3, the spreading amount of mixed powder B is 0.4-0.5 g / cm³. 3 In step S4, the aluminum powder spreading amount is 0.6-1.2 g / cm³. 3 .

3. The method for preparing high-capacity, high-strength powder sintered foil according to claim 1, characterized in that, The gaseous pore-forming agent is NH4HCO3.

4. The method for preparing high-capacity, high-strength powder sintered foil according to claim 1, characterized in that, The process parameters for cold isostatic pressing are: pressure 10-50 MPa, holding pressure for 10-30 min, pressing 1-3 times.

5. The method for preparing high-capacity, high-strength powder sintered foil according to claim 1, characterized in that, The rare earth powder is one or more of yttrium powder, cerium powder, and neodymium powder.

6. The method for preparing high-capacity, high-strength powder sintered foil according to claim 1, characterized in that, The process conditions for the spark plasma sintering are: vacuum degree 1×10⁻⁶. -2 Pa, temperature 500-650℃, heating rate 30-60℃ / min, holding time 10-20min.

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