An aluminum electrolytic capacitor powder build-up sintered foil and a method of manufacturing the same

Abstract

The application discloses an aluminum electrolytic capacitor powder accumulation sintering foil and a preparation method thereof, and belongs to the technical field of aluminum electrolytic capacitors. The preparation method of the aluminum electrolytic capacitor powder accumulation sintering foil is as follows: taking aluminum powder and a dielectric substance precursor as raw materials, depositing the dielectric substance on the surface of the aluminum powder by a chemical vapor deposition method to obtain aluminum powder wrapped by the dielectric substance; the dielectric constant of the dielectric substance is greater than the dielectric constant of aluminum oxide; uniformly mixing the aluminum powder wrapped by the dielectric substance, a binder and a solvent, and then coating the mixture on an aluminum foil substrate; after drying, performing a degreasing treatment at 350 DEG C to 550 DEG C in an oxygen-containing atmosphere, and then performing a sintering treatment at 600 DEG C to 670 DEG C in an oxygen-free state, the aluminum electrolytic capacitor powder accumulation sintering foil is obtained after energization. The aluminum electrolytic capacitor powder accumulation sintering foil prepared by the application has excellent static capacity of the aluminum electrolytic capacitor powder accumulation sintering anode foil per unit area.

Description

Technical Field

[0001] This invention relates to the field of aluminum electrolytic capacitor technology, and more specifically to an aluminum electrolytic capacitor powder stacking sintered foil and its preparation method. Background Technology

[0002] Compared to other types of capacitors, aluminum electrolytic capacitors have advantages such as high volumetric energy density, controllable dielectric layer thickness, self-healing dielectric layer, and the ability to achieve very high rated capacitance. Therefore, they are widely used in consumer electronics, home appliances, and industrial control. Capacitance is a key parameter of a capacitor, and the capacitance of the anode foil determines the capacitance of the aluminum electrolytic capacitor. Therefore, increasing the specific capacitance of the anode foil is an effective way to improve the capacitance of electrolytic capacitors.

[0003] Currently, the anode foil of most aluminum electrolytic capacitors on the market is made from electrochemically etched foil. Electrochemical etching consumes a large amount of electrical energy during production and generates acidic waste liquid, causing environmental pollution. In terms of performance, anode foil etching technology is facing bottlenecks, and the capacitance is unlikely to see further breakthroughs in the short term. Compared to etched foil, powder-stabilized sintered foil has a higher specific surface area, resulting in greater capacitance per unit area. However, the preparation of powder-stabilized sintered foil is affected by the activity of aluminum powder, limiting the selection of binders and dispersants at room temperature. Most binders soluble in organic systems have high decomposition temperatures. Insufficient degreasing temperature leads to incomplete decomposition of the binder, easily resulting in carbon residue in the oxygen-free environment of sintering, leading to a large residual current after energization. Conversely, excessively high degreasing temperature results in complete decomposition of the binder, leading to an excessively thick thermal oxide film on the aluminum powder surface, which is detrimental to the formation of the sintering neck later. Some water-based binders have low decomposition temperatures, but the reaction between aluminum powder and dispersant results in hydrated alumina. High-temperature dehydration affects subsequent sintering and electrostatic capacitance. Furthermore, the reaction with water generates hydrogen gas, posing safety concerns. Therefore, surface coating of aluminum powder is an effective method to reduce its activity.

[0004] Common coating methods include solid-phase nanoparticle mixing and liquid-phase coating. In solid-phase nanoparticle physical mixing and doping, the high-dielectric nanoparticle coating is not dense and is easily detached. This mismatch with the sintering temperature of aluminum powder leads to the easy detachment of high-dielectric-constant nanoparticles, which then mix into the sintering neck, reducing the sintering strength. Liquid-phase coating results in a thicker surface coating, affecting the swelling during sintering. The sol-gel contains a large amount of organic matter, which carbonizes in an oxygen-free environment. The resulting dielectric layer is thick and dense, easily causing carbon residue and leading to a larger leakage current in the formed anode foil.

[0005] Chinese invention patent CN117594359B describes an anode sintered foil for an aluminum electrolytic capacitor and its preparation method. It uses spherical aluminum powder as the anode and a titanium target as the cathode, generating an aluminum-titanium composite powder via magnetron sputtering. The surface of the aluminum-titanium composite powder is coated with a titanium film. Magnetron sputtering uses high-energy ions to bombard the target material, imparting kinetic energy to the target atoms and molecules. The moving, electrically neutral target atoms or molecules are deposited on the substrate to form a thin film. Due to the poor diffraction properties of the moving target atoms and molecules, the coating properties and uniformity of the thin film are uncontrollable. The deposited titanium metal, after oxidation, results in a non-dense oxide film that cannot prevent the aluminum powder from reacting with the external environment.

[0006] Chinese invention patent CN117373830B describes a method for manufacturing anode foil of an aluminum electrolytic capacitor using a high dielectric constant composite film. This method involves incorporating a high dielectric constant metal oxide into the aluminum paste to improve the overall dielectric constant and specific capacitance of the composite film anode foil. However, the bonding of powders does not reduce the activity of the aluminum powder or prevent reactions with the external environment. To prevent agglomeration caused by surface tension, the introduced surfactant is prone to carbonization in a high-temperature, oxygen-free environment, which could lead to capacitor breakdown and failure. Summary of the Invention

[0007] To address the above problems, this invention provides an aluminum electrolytic capacitor powder-stabilized sintered foil and its preparation method. This invention introduces dielectric materials onto the surface of aluminum powder using chemical vapor deposition, avoiding direct contact between the aluminum powder and the dispersant, and suppressing side reactions that may be caused by the high activity of the aluminum powder. This solves the problem of reactions between highly active aluminum powder and some solvents and the external environment during the preparation of the aluminum electrolytic capacitor powder-stabilized sintered foil. The resulting aluminum electrolytic capacitor powder-stabilized sintered foil, prepared after coating, degreasing, and sintering treatments, exhibits excellent electrostatic capacitance per unit area.

[0008] The first objective of this invention is to provide a method for preparing aluminum electrolytic capacitor powder-stabilized sintered foil, comprising the following steps:

[0009] Using aluminum powder and dielectric precursor as raw materials, dielectric material is deposited on the surface of aluminum powder by chemical vapor deposition to obtain aluminum powder coated with dielectric material; the dielectric constant of the dielectric material is greater than that of aluminum oxide.

[0010] A paste is prepared by uniformly mixing aluminum powder coated with dielectric material, binder and solvent. The paste is coated on an aluminum foil substrate and dried. Then, it is degreased at 350℃~550℃ in an oxygen-containing atmosphere. Finally, it is sintered at 600℃~670℃ in an oxygen-free state. During the sintering process, the dielectric material combines with aluminum oxide to form a mixed dielectric layer. After sintering, aluminum electrolytic capacitor powder deposition sintered foil is obtained.

[0011] For example, the degreasing temperature is 350℃, 400℃, 450℃, 500℃, 550℃, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0012] If the degreasing temperature is insufficient during the degreasing process, carbon residue will be left behind, leading to powder sintering and accumulation, and increased leakage current of the anode foil.

[0013] During sintering, the sintering temperature is 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, etc., but is not limited to the listed values; other unlisted values ​​within the above range also apply. During sintering, the sintering atmosphere is any one or more of the following: vacuum atmosphere, argon atmosphere, nitrogen atmosphere, and hydrogen atmosphere.

[0014] The drying process involves a temperature of 60℃ to 150℃ and a drying time of 10 min to 600 min; the drying atmosphere is one or more of the following: air atmosphere, vacuum atmosphere, argon atmosphere, and nitrogen atmosphere.

[0015] In a preferred embodiment of the present invention, the deposition thickness is 0.1 nm to 1200 nm. For example, the deposition thickness is 0.1 nm, 10 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0016] In a preferred embodiment of the present invention, the slurry is composed of the following components by mass percentage: 40% to 80% aluminum powder coated with dielectric material, 0.1% to 10% binder, and the remainder being solvent, totaling 100%.

[0017] For example, the aluminum powder coated with dielectric material may be 40%, 50%, 60%, 70%, 80%, etc., the binder may be 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., and the solvent may be 10%, 20%, 30%, 40%, 50%, 59.9%, etc., but it is not limited to the values ​​listed above. Other unlisted values ​​within the above range are also applicable.

[0018] In a preferred embodiment of the present invention, double-sided coating is performed, with a coating thickness of 30 μm to 200 μm on each side. For example, the thickness of a single layer coating can be 30 μm, 50 μm, 70 μm, 90 μm, 110 μm, 130 μm, 150 μm, 170 μm, 190 μm, 200 μm, etc., but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0019] The specific surface area of ​​the aluminum foil substrate is improved by coating thickness, thereby improving the electrostatic capacitance of the aluminum electrolytic capacitor powder-stabilized sintered foil. The aluminum foil substrate used in this invention has a purity of 99.5% or higher and a thickness between 20 μm and 50 μm.

[0020] In a preferred embodiment of the present invention, the heating rate for the degreasing treatment is 2℃ / min to 20℃ / min, and the degreasing treatment time is 0.5h to 15h. For example, the heating rate for the degreasing treatment is 2℃ / min, 4℃ / min, 6℃ / min, 8℃ / min, 10℃ / min, 12℃ / min, 14℃ / min, 16℃ / min, 18℃ / min, 20℃ / min, etc., and the degreasing treatment time is 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, etc., but it is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0021] In a preferred embodiment of the present invention, the heating rate of the sintering treatment is 2℃ / min to 20℃ / min, and the sintering time is 0.5h to 15h. For example, the heating rate of the sintering treatment is 2℃ / min, 4℃ / min, 6℃ / min, 8℃ / min, 10℃ / min, 12℃ / min, 14℃ / min, 16℃ / min, 18℃ / min, 20℃ / min, etc., and the degreasing time is 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, etc., but it is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0022] In a preferred embodiment of the present invention, the dielectric material is one or more of titanium dioxide, hafnium oxide, tantalum pentoxide, niobium oxide, barium titanate, strontium titanate, barium strontium titanate, lead zirconate titanate, and bismuth ferrite. Typical but non-limiting examples of the combination include combinations of titanium dioxide and hafnium oxide, combinations of tantalum pentoxide and niobium oxide, combinations of barium titanate and strontium titanate, combinations of barium strontium titanate and lead zirconate titanate, combinations of bismuth ferrite and strontium titanate, etc., but are not limited to the values ​​listed. Other unlisted values ​​within the above range are also applicable.

[0023] In a preferred embodiment of the present invention, the binder is one or more selected from polyethylene oxide, hydroxypropyl cellulose, carboxymethyl cellulose, acrylic resin, and polypropylene carbonate. Typical but non-limiting examples of the combination include combinations of polyethylene oxide and hydroxypropyl cellulose, combinations of carboxymethyl cellulose and acrylic resin, combinations of polyethylene oxide and polypropylene carbonate, etc., but are not limited to the values ​​listed above; other unlisted values ​​within the above range are also applicable.

[0024] In preparing the slurry, the solvent of this invention is water, methanol, ethanol, terpineol, acetonitrile, acetone, dimethylformamide, N-methylpyrrolidone, n-butanol, or methyl ethyl ketone.

[0025] In a preferred embodiment of the present invention, atomic layer deposition is used for preparation during chemical vapor deposition.

[0026] A second objective of this invention is to provide an aluminum electrolytic capacitor powder stacked and sintered foil prepared by the above-described preparation method.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention involves the vapor deposition of dielectric materials on the surface of aluminum powder using a controllable chemical vapor deposition (CVD) method. This avoids direct contact between the aluminum powder and the dispersant, suppressing potential side reactions caused by the high activity of the aluminum powder. It solves the problem of reactions between highly active aluminum powder and some solvents and the external environment during the preparation of powder-stabilized sintered foil for aluminum electrolytic capacitors. After coating, sintering, and energizing, a high-dielectric composite powder-stabilized sintered anode foil for aluminum electrolytic capacitors is formed, further improving the capacitance per unit area of ​​the powder-stabilized sintered anode foil. The CVD method used in this invention results in a high bonding strength and uniform thickness between the vapor-phase dielectric coating layer and the aluminum powder surface, far superior to solid powder mixing coating and liquid phase coating. It solves the problems of nanoparticle detachment caused by mismatched sintering temperatures between aluminum powder and high-dielectric-constant nanoparticles in solid powder mixing coating, and excessively thick coating layers due to uncontrollable thickness in liquid phase coatings, which affect carbon removal and sintering neck formation during the sintering process. Attached Figure Description

[0029] Figure 1 In the diagram, a is a schematic diagram of aluminum powder, and b is a schematic diagram of aluminum powder coated with dielectric material.

[0030] Figure 2 This is a schematic diagram of aluminum powder coated with dielectric material after sintering.

[0031] Figure labels: 1-Dielectric material, 2-Aluminum powder. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] To address the problems described in the background art, this invention provides a method for preparing aluminum electrolytic capacitor powder stacking and sintering foil, such as... Figure 1 and Figure 2 As shown, during preparation, aluminum powder 2 and dielectric material precursor are used as raw materials, and dielectric material 1 is deposited on the surface of aluminum powder 2 by chemical vapor deposition to obtain aluminum powder coated with dielectric material.

[0034] Aluminum powder coated with dielectric material, binder and solvent are mixed evenly and coated onto aluminum foil substrate. After drying, degreasing is carried out at 350℃~550℃ in an oxygen-containing atmosphere. Then, sintering is carried out at 610℃~670℃ in an oxygen-free state. After sintering, aluminum electrolytic capacitor powder deposited sintered foil is obtained.

[0035] This invention employs chemical vapor deposition to introduce a dielectric material 1 onto the surface of aluminum powder 2. The dielectric material 1 on the surface of aluminum powder 2 exhibits high bonding strength and uniform thickness, far superior to solid powder mixing and coating, and liquid phase coating. This solves the problems of nanoparticle detachment caused by mismatched sintering temperatures between aluminum powder and high dielectric constant nanoparticles after solid powder mixing and coating, and excessively thick coating layers in liquid phase coatings due to uncontrollable thickness, which affect carbon removal and sintering neck formation during the sintering process.

[0036] Dielectric materials are stable in air and most solvents. When coated onto the surface of aluminum powder using chemical vapor deposition (CVD), a dense protective layer is formed, effectively preventing the highly reactive aluminum powder from reacting with the external environment and thus reducing its activity. The dielectric precursors and binders used in the CVD process contain a large amount of organic matter. Subsequent sintering in a high-temperature, oxygen-free environment causes carbonization, and residual carbon leads to increased leakage current in the sintered anode foil. Therefore, high-temperature air heat treatment effectively reduces residual carbon in the sintered foil. Then, high-temperature vacuum or inert atmosphere heat treatment and energy-enhancing treatment combine the dielectric material with alumina to form a mixed dielectric layer, effectively increasing the dielectric constant of the sintered foil and thus improving its capacitance.

[0037] The average molecular weight of the polyethylene oxide used in this invention is 10,000, the average molecular weight of hydroxypropyl cellulose is 40,000, the average molecular weight of carboxymethyl cellulose is 100,000, the average molecular weight of acrylic resin is 80,000, the average molecular weight of polyethylene oxide is 100,000, and the average molecular weight of polypropylene carbonate is 280,000. The purity of the aluminum foil substrate used in this invention is above 99.5%, and the thickness is between 20-50 μm.

[0038] Example 1

[0039] Step (1): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99% is placed in an ALD reaction chamber at a temperature of 200℃ and a vacuum degree of 5 mTorr. Nitrogen is used as the carrier gas, and isopropyl titanate is used as the titanium source. The titanium source temperature is maintained at 25℃. Nitrogen is introduced for 5 seconds, followed by purging with nitrogen for 30 seconds. Then, O3 is introduced for 10 seconds, followed by purging with nitrogen for 50 seconds. The above steps are repeated until the deposition thickness reaches 5 nm, resulting in aluminum powder coated with dielectric material.

[0040] Step (2): Weigh 60% of the aluminum powder coated with dielectric material prepared in step (1), 3% of polyethylene oxide and 37% of ultrapure water according to the mass percentage, mix them evenly to obtain a slurry.

[0041] Step (3): Coat the slurry prepared in step (2) onto the aluminum foil substrate. During coating, double-sided coating is performed, with a coating thickness of 50 μm on each side, to obtain powder-coated foil.

[0042] Step (4): Dry the powder-coated foil prepared in step (3) at 100°C in air for 30 minutes to obtain the dried powder-coated foil.

[0043] Step (5): The dried powder-coated foil prepared in step (4) is heated to 400°C at a heating rate of 10°C / min and degreased in air for 1 hour; then heated to 640°C at a heating rate of 10°C / min and sintered in vacuum for 4 hours to obtain aluminum electrolytic capacitor powder-coated sintered foil.

[0044] Example 2

[0045] Step (1): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99% is placed in an ALD reaction chamber at a temperature of 200℃ and a vacuum degree of 5 mTorr. Nitrogen is used as the carrier gas, and isopropyl titanate is used as the titanium source. The titanium source temperature is maintained at 25℃. Nitrogen is introduced for 5 seconds, followed by purging with nitrogen for 30 seconds. Then, O3 is introduced for 10 seconds, followed by purging with nitrogen for 50 seconds. The above steps are repeated until the deposition thickness reaches 5 nm, resulting in aluminum powder coated with dielectric material.

[0046] Step (2): Weigh out 60% of the aluminum powder coated with dielectric material prepared in step (1), 0.6% of hydroxypropyl cellulose and 39.4% of anhydrous ethanol by mass percentage, mix them evenly to obtain a slurry.

[0047] Step (3): Coat the slurry prepared in step (2) onto the aluminum foil substrate. During coating, double-sided coating is performed, with a coating thickness of 50 μm on one side, to obtain powder-coated foil.

[0048] Step (4): Dry the powder-coated foil prepared in step (3) at 100°C in air for 30 minutes to obtain the dried powder-coated foil.

[0049] Step (5): The dried powder-coated foil prepared in step (4) is heated to 500°C at a heating rate of 10°C / min and degreased in air for 1 hour; then heated to 640°C at a heating rate of 10°C / min and sintered in vacuum for 4 hours to obtain aluminum electrolytic capacitor powder-coated sintered foil.

[0050] Comparative Example 1

[0051] Step (1): Weigh 60% aluminum powder with a particle size of 2-3μm and a purity of 99.99%, 3% polyethylene oxide and 37% ultrapure water by mass percentage, mix them evenly to obtain a slurry.

[0052] Step (2): Coat the slurry prepared in step (1) onto the aluminum foil substrate. During coating, double-sided coating is performed, with a coating thickness of 50 μm on each side, to obtain a powder-coated foil.

[0053] Step (3): Dry the powder-coated foil prepared in step (2) at 100°C in air for 30 minutes to obtain the dried powder-coated foil.

[0054] Step (4): The dried powder-coated foil prepared in step (3) is heated to 400°C at a heating rate of 10°C / min and degreased in air for 1 hour; then heated to 640°C at a heating rate of 10°C / min and sintered in vacuum for 4 hours to obtain aluminum electrolytic capacitor powder-coated sintered foil.

[0055] Comparative Example 2

[0056] Step (1): Weigh 60% aluminum powder with a particle size of 2-3μm and a purity of 99.99%, 0.6% hydroxypropyl cellulose and 39.4% anhydrous ethanol by mass percentage, mix them evenly to obtain a slurry.

[0057] Step (2): Coat the slurry prepared in step (1) onto the aluminum foil substrate. During coating, double-sided coating is performed, with a coating thickness of 50 μm on each side, to obtain a powder-coated foil.

[0058] Step (3): Dry the powder-coated foil prepared in step (2) at 100°C in air for 30 minutes to obtain the dried powder-coated foil.

[0059] Step (4): The dried powder-coated foil prepared in step (3) is heated to 500°C at a heating rate of 10°C / min and degreased in air for 1 hour; then heated to 640°C at a heating rate of 10°C / min and sintered in vacuum for 4 hours to obtain aluminum electrolytic capacitor powder-coated sintered foil.

[0060] Example 3

[0061] Step (1): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99% is placed in an ALD reaction chamber at a temperature of 200℃ and a vacuum degree of 5 mTorr. Nitrogen is used as the carrier gas, and isopropyl titanate is used as the titanium source. The titanium source temperature is maintained at 25℃. Nitrogen is introduced for 5 seconds, followed by purging with nitrogen for 30 seconds. Then, O3 is introduced for 10 seconds, followed by purging with nitrogen for 50 seconds. The above steps are repeated until the deposition thickness reaches 10 nm, resulting in aluminum powder coated with dielectric material.

[0062] Step (2): Weigh 60% of the aluminum powder coated with dielectric material prepared in step (1), 3% of polyethylene oxide, and 37% of ultrapure water according to the mass percentage, and mix them evenly to obtain a slurry.

[0063] Step (3): Coat the slurry prepared in step (2) onto the aluminum foil substrate. During coating, double-sided coating is performed, and the coating thickness on one side is 50 μm.

[0064] Step (4): Dry the powder-coated foil prepared in step (3) at 100°C in air for 30 minutes to obtain the dried powder-coated foil.

[0065] Step (5): The dried powder-coated foil prepared in step (4) is heated to 400°C at a heating rate of 10°C / min and degreased in air for 1 hour; then heated to 640°C at a heating rate of 10°C / min and sintered in vacuum for 4 hours to obtain aluminum electrolytic capacitor powder-coated sintered foil.

[0066] Example 4

[0067] Step (1): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99% is placed in an ALD reaction chamber at a temperature of 200℃ and a vacuum degree of 5 mTorr. Nitrogen is used as the carrier gas, and isopropyl titanate is used as the titanium source. The titanium source temperature is maintained at 25℃. Nitrogen is introduced for 5 seconds, followed by purging with nitrogen for 30 seconds. Then, O3 is introduced for 10 seconds, followed by purging with nitrogen for 50 seconds. The above steps are repeated until the deposition thickness reaches 10 nm, resulting in aluminum powder coated with dielectric material.

[0068] Step (2): Weigh out 60% of the aluminum powder coated with dielectric material prepared in step (1), 0.6% of hydroxypropyl cellulose and 39.4% of anhydrous ethanol by mass percentage and mix them evenly to obtain a slurry.

[0069] Step (3): Coat the slurry prepared in step (2) onto the aluminum foil substrate. During coating, double-sided coating is performed, with a coating thickness of 50 μm on each side, to obtain a powder-coated foil.

[0070] Step (4): Dry the powder-coated foil prepared in step (3) at 100°C in air for 30 minutes to obtain the dried powder-coated foil.

[0071] Step (5): The dried powder-coated foil prepared in step (4) is heated to 500°C at a heating rate of 10°C / min and degreased in air for 1 hour; then heated to 640°C at a heating rate of 10°C / min and sintered in vacuum for 4 hours to obtain aluminum electrolytic capacitor powder-coated sintered foil.

[0072] Example 5

[0073] Step (1): Aluminum powder with a particle size of 4-5 μm and a purity of 99.99% is placed in an ALD reaction chamber at a temperature of 200℃ and a vacuum degree of 5 mTorr. Nitrogen is used as the carrier gas, and TTIP is used as the titanium source. The titanium source temperature is maintained at 25℃. Nitrogen is introduced for 5 seconds, followed by nitrogen purging for 30 seconds. Then, O3 is introduced for 10 seconds, followed by nitrogen purging for 50 seconds. The above steps are repeated 200 times to obtain aluminum powder coated with dielectric material.

[0074] Step (2): Weigh 60% of the aluminum powder coated with dielectric material prepared in step (1), 3% of polyethylene oxide and 37% of ultrapure water according to the mass percentage, mix them evenly to obtain a slurry.

[0075] Step (3): Coat the slurry prepared in step (2) onto the aluminum foil substrate. During coating, double-sided coating is performed, with a coating thickness of 50 μm on each side, to obtain powder-coated foil.

[0076] Step (4): Dry the powder-coated foil prepared in step (3) at 100°C in air for 30 minutes to obtain the dried powder-coated foil.

[0077] Step (5): The dried powder-coated foil prepared in step (4) is heated to 400°C at a heating rate of 10°C / min and degreased in air for 1 hour; then heated to 640°C at a heating rate of 10°C / min and sintered in vacuum for 4 hours to obtain aluminum electrolytic capacitor powder-coated sintered foil.

[0078] Example 6

[0079] Step (1): Aluminum powder with a particle size of 4-5 μm and a purity of 99.99% is placed in an ALD reaction chamber at a temperature of 200℃ and a vacuum degree of 5 mTorr. Nitrogen is used as the carrier gas, and isopropyl titanate is used as the titanium source. The titanium source temperature is maintained at 25℃. Nitrogen is introduced for 5 seconds, followed by purging with nitrogen for 30 seconds. Then, O3 is introduced for 10 seconds, followed by purging with nitrogen for 50 seconds. The above steps are repeated until the deposition thickness reaches 5 nm, resulting in aluminum powder coated with dielectric material.

[0080] Step (2): Weigh out 60% of the aluminum powder coated with dielectric material prepared in step (1), 0.6% of hydroxypropyl cellulose and 39.4% of anhydrous ethanol by mass percentage, mix them evenly to obtain a slurry.

[0081] Step (3): Coat the slurry prepared in step (2) onto the aluminum foil substrate. During coating, double-sided coating is performed, with a coating thickness of 50 μm on each side, to obtain powder-coated foil.

[0082] Step (4): Dry the powder-coated foil prepared in step (3) at 100°C in air for 30 minutes to obtain the dried powder-coated foil.

[0083] Step (5): The dried powder-coated foil prepared in step (4) is heated to 500°C at a heating rate of 10°C / min and degreased in air for 1 hour; then heated to 640°C at a heating rate of 10°C / min and sintered in vacuum for 4 hours to obtain aluminum electrolytic capacitor powder-coated sintered foil.

[0084] Comparative Example 3

[0085] Step (1): Weigh 60% aluminum powder with a particle size of 4-5μm and a purity of 99.99%, 3% polyethylene oxide and 37% ultrapure water by mass percentage, mix them evenly to obtain a slurry.

[0086] Step (2): Coat the slurry prepared in step (1) onto the aluminum foil substrate. During coating, double-sided coating is performed, with a coating thickness of 50 μm on each side, to obtain a powder-coated foil.

[0087] Step (3): Dry the powder-coated foil prepared in step (2) at 100°C in air for 30 minutes to obtain the dried powder-coated foil.

[0088] Step (4): The dried powder coating foil prepared in step (3) is sintered. The temperature is raised to 400°C at a heating rate of 10°C / min and held in air for 1 hour. Then the temperature is raised to 640°C at a heating rate of 10°C / min and held in vacuum for 4 hours to obtain aluminum electrolytic capacitor powder stacked sintered foil.

[0089] Comparative Example 4

[0090] Step (1): Weigh 60% aluminum powder with a particle size of 4-5μm and a purity of 99.99%, 0.6% hydroxypropyl cellulose and 39.4% anhydrous ethanol by mass percentage, mix them evenly to obtain a slurry.

[0091] Step (2): Coat the slurry prepared in step (1) onto the aluminum foil substrate. During coating, double-sided coating is performed, with a coating thickness of 50 μm on each side, to obtain a powder-coated foil.

[0092] Step (3): Dry the powder-coated foil prepared in step (2) at 100°C in air for 30 minutes to obtain the dried powder-coated foil.

[0093] Step (4): The dried powder-coated foil prepared in step (3) is heated to 500°C at a heating rate of 10°C / min and degreased in air for 1 hour; then heated to 640°C at a heating rate of 10°C / min and sintered in vacuum for 4 hours to obtain aluminum electrolytic capacitor powder-coated sintered foil.

[0094] Example 7

[0095] Step (1): Aluminum powder with a particle size of 4-5 μm and a purity of 99.99% is placed in an ALD reaction chamber at a temperature of 200℃ and a vacuum degree of 5 mTorr. Nitrogen is used as the carrier gas, and isopropyl titanate is used as the titanium source. The titanium source temperature is maintained at 25℃. Nitrogen is introduced for 5 seconds, followed by nitrogen purging for 30 seconds. Then, O3 is introduced for 10 seconds, followed by nitrogen purging for 50 seconds. The above steps are repeated until the deposition thickness reaches 10 nm, resulting in aluminum powder coated with dielectric material.

[0096] Step (2): Weigh 60% of the aluminum powder coated with dielectric material prepared in step (1), 0.6% of polyethylene oxide and 39.4% of ultrapure water according to the mass percentage and mix them evenly to obtain a slurry.

[0097] Step (3): Coat the slurry prepared in step (2) onto the aluminum foil substrate. During coating, double-sided coating is performed, with a coating thickness of 50 μm on each side, to obtain powder-coated foil.

[0098] Step (4): Dry the powder-coated foil prepared in step (3) at 100°C in air for 30 minutes to obtain the dried powder-coated foil.

[0099] Step (5): The dried powder-coated foil prepared in step (4) is heated to 400°C at a heating rate of 10°C / min and degreased in air for 1 hour; then heated to 640°C at a heating rate of 10°C / min and sintered in vacuum for 4 hours to obtain aluminum electrolytic capacitor powder-coated sintered foil.

[0100] Example 8

[0101] Step (1): Aluminum powder with a particle size of 4-5 μm and a purity of 99.99% is placed in an ALD reaction chamber at a temperature of 200℃ and a vacuum degree of 5 mTorr. Nitrogen is used as the carrier gas, and isopropyl titanate is used as the titanium source. The titanium source temperature is maintained at 25℃. Nitrogen is introduced for 5 seconds, followed by purging with nitrogen for 30 seconds. Then, O3 is introduced for 10 seconds, followed by purging with nitrogen for 50 seconds. The above steps are repeated until the deposition thickness reaches 10 nm, resulting in aluminum powder coated with dielectric material.

[0102] Step (2): Weigh out 60% of the aluminum powder coated with dielectric material prepared in step (1), 0.6% of hydroxypropyl cellulose and 39.4% of anhydrous ethanol by mass percentage, mix them evenly to obtain a slurry.

[0103] Step (3): Coat the slurry prepared in step (2) onto the aluminum foil substrate. During coating, double-sided coating is performed, with a coating thickness of 50 μm on each side, to obtain a powder-coated foil.

[0104] Step (4): Dry the powder-coated foil prepared in step (3) at 100°C in air for 30 minutes to obtain the dried powder-coated foil.

[0105] Step (5): The dried powder-coated foil prepared in step (4) is heated to 500°C at a heating rate of 10°C / min and degreased in air for 1 hour; then heated to 640°C at a heating rate of 10°C / min and sintered in vacuum for 4 hours to obtain aluminum electrolytic capacitor powder-coated sintered foil.

[0106] Example 9

[0107] Step (1): Aluminum powder with a particle size of 4-5 μm and a purity of 99.99% is placed in an ALD reaction chamber at a temperature of 200℃ and a vacuum degree of 5 mTorr. Nitrogen is used as the carrier gas, and isopropyl titanate is used as the titanium source. The titanium source temperature is maintained at 25℃. Nitrogen is introduced for 5 seconds, followed by purging with nitrogen for 30 seconds. Then, O3 is introduced for 10 seconds, followed by purging with nitrogen for 50 seconds. The above steps are repeated until the deposition thickness reaches 10 nm, resulting in aluminum powder coated with dielectric material.

[0108] Step (2): Weigh 80% of the aluminum powder coated with dielectric material prepared in step (1), 10% of the composite binder, and 10% of water according to the mass percentage, and mix them evenly to obtain a slurry. The composite binder is polyoxyethylene and hydroxymethyl cellulose in a mass ratio of 1:1.

[0109] Step (3): Coat the slurry prepared in step (2) onto the aluminum foil substrate. During coating, double-sided coating is performed, with a coating thickness of 80 μm on one side, to obtain powder-coated foil.

[0110] Step (4): Dry the powder-coated foil prepared in step (3) at 100°C in air for 30 minutes to obtain the dried powder-coated foil.

[0111] Step (5): The dried powder-coated foil prepared in step (4) is heated to 350°C at a heating rate of 10°C / min and degreased in air for 1 hour; then heated to 670°C at a heating rate of 10°C / min and sintered in vacuum for 4 hours to obtain aluminum electrolytic capacitor powder-coated sintered foil.

[0112] Example 10

[0113] Step (1): Aluminum powder with a particle size of 2-3 μm and a purity of 99.99% is placed in an ALD reaction chamber at a temperature of 200℃ and a vacuum degree of 5 mTorr. Nitrogen is used as the carrier gas, and isopropyl titanate is used as the titanium source. The titanium source temperature is maintained at 25℃. Nitrogen is introduced for 5 seconds, followed by purging with nitrogen for 30 seconds. Then, O3 is introduced for 10 seconds, followed by purging with nitrogen for 50 seconds. The above steps are repeated until the deposition thickness reaches 5 nm, resulting in aluminum powder coated with dielectric material.

[0114] Step (2): Weigh 40% of the aluminum powder coated with dielectric material prepared in step (1), 0.1% of polyethylene oxide, and 59.9% of ultrapure water according to the mass percentage and mix them evenly to obtain a slurry.

[0115] Step (3): Coat the slurry prepared in step (2) onto the aluminum foil substrate. During coating, double-sided coating is performed, with a coating thickness of 50 μm on each side, to obtain powder-coated foil.

[0116] Step (4): Dry the powder-coated foil prepared in step (3) at 100°C in air for 30 minutes to obtain the dried powder-coated foil.

[0117] Step (5): The dried powder-coated foil prepared in step (4) is heated to 400°C at a heating rate of 10°C / min and degreased in air for 1 hour; then heated to 640°C at a heating rate of 10°C / min and sintered in vacuum for 4 hours to obtain aluminum electrolytic capacitor powder-coated sintered foil.

[0118] The aluminum capacitor sintered foils prepared in Examples 1-8 and Comparative Examples 1-4 of this invention were formed in a boric acid system solution according to standard SJ / T11140-2022, with forming voltages of 500 and 700 V and a current density of 0.5 A / cm². 2 Then, the electrostatic capacity was tested in an 80 g / L ammonium pentaborate solution, and the withstand voltage was tested in a 70 g / L boric acid solution. The results are shown in Table 1 below.

[0119] Table 1 Experimental Results

[0120]

[0121]

[0122] It should be noted that "—" indicates that the test for this condition was not performed.

[0123] As shown in Table 1, the withstand voltage values ​​of Comparative Examples 1-4 and Examples 1-8 are all higher than the preset formation voltage. Compared with the capacitance and withstand voltage of the aluminum powder sintered stacked foil anodes in Comparative Examples 1-4, the capacitance and withstand voltage of the high dielectric constant powder sintered stacked foil anodes prepared by high dielectric constant coated aluminum powder in Examples 1-8 of this invention are significantly improved. This indicates that the introduction of dielectric material, after high-temperature heat treatment and energization, effectively improves the dielectric constant of the anode, thereby improving the capacitance. In Examples 1, 3, 5, and 7, compared with the aluminum electrolytic capacitor powder sintered stacked anode foil prepared by using organic solvents, the aluminum electrolytic capacitor powder sintered stacked anode foil prepared by using ultrapure water as solvent has significantly improved capacitance and withstand voltage. This indicates that the high dielectric constant coated aluminum powder is passivated after coating, suppressing side reactions that may be caused by the high activity of aluminum powder, and solving the problem of reactions between highly active aluminum powder and some solvents and the external environment during the preparation of aluminum electrolytic capacitor powder stacked sintered foil.

[0124] This invention introduces a dielectric material deposition layer larger than aluminum oxide onto the surface of aluminum powder, reducing the activity of the aluminum powder and expanding the selection range of binders and dispersants, while further improving the electrostatic capacitance of the powder sintered anode foil. The deposition layer formed by chemical vapor deposition is uniform and controllable in thickness, allowing for different deposition thicknesses to be selected according to different withstand voltage ranges. The coated aluminum powder has a stable deposition layer on its surface, which effectively prevents the aluminum powder from reacting with external air and water, reduces the formation of amorphous alumina, and preserves the aluminum core to a greater extent. Therefore, it helps to improve the electrostatic capacitance, while significantly increasing the safety factor during water-based slurry mixing.

[0125] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0126] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method of making an aluminum electrolytic capacitor powder build-up sintered foil, characterized by, Comprising the following steps: The dielectric substance-coated aluminum powder is obtained by depositing high dielectric substance on the surface of aluminum powder through chemical vapor deposition method, taking aluminum powder and dielectric substance precursor as raw materials; the dielectric constant of the dielectric substance is greater than the dielectric constant of aluminum oxide; the deposition thickness is 0.1 nm-1200 nm; the dielectric substance is one or more of titanium dioxide, hafnium oxide, tantalum pentoxide, niobium oxide, barium titanate, strontium titanate, barium strontium titanate, lead zirconate titanate, and bismuth ferrite; the chemical vapor deposition method is atomic layer deposition method; The slurry is obtained by uniformly mixing the dielectric substance-coated aluminum powder, the binder, and the solvent, the slurry is coated on the aluminum foil substrate, and after drying, the slurry is subjected to debinding treatment at 350℃-550℃ in an oxygen-containing atmosphere, and then sintering treatment at 600℃-670℃ in an oxygen-free state; during the sintering process, the dielectric substance combines with aluminum oxide to form a mixed dielectric layer, and after the sintering is completed, the aluminum electrolytic capacitor powder accumulation sintering foil is obtained.

2. The method for preparing aluminum electrolytic capacitor powder stacking and sintering foil according to claim 1, characterized in that, The slurry is composed of the following components in mass percentage: 40%-80% dielectric substance-coated aluminum powder, 0.1%-10% binder, and the rest is solvent, totaling 100%.

3. The method for preparing aluminum electrolytic capacitor powder stacking and sintering foil according to claim 1, characterized in that, Double-sided coating is performed during coating, and the coating thickness of a single side is 30μm-200μm.

4. The method for preparing aluminum electrolytic capacitor powder stacking and sintering foil according to claim 1, characterized in that, The heating rate of the debinding treatment is 2℃ / min-20℃ / min, and the debinding treatment time is 0.5h-15h.

5. The method for preparing aluminum electrolytic capacitor powder stacking and sintering foil according to claim 1, characterized in that, The heating rate of the sintering treatment is 2℃ / min-20℃ / min, and the sintering treatment time is 0.5h-15h.

6. The method for preparing aluminum electrolytic capacitor powder stacking and sintering foil according to claim 1, characterized in that, The binder is one or more of polyethylene oxide, hydroxypropyl cellulose, carboxymethyl cellulose, acrylic resin, or polypropylene carbonate; The solvent is water, methanol, ethanol, terpineol, acetonitrile, acetone, N,N-dimethylformamide, N-methylpyrrolidone, n-butanol, or methyl ethyl ketone.

7. An aluminum electrolytic capacitor powder accumulation sintering foil prepared by the preparation method of any one of claims 1-6.

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