Preparation method of anode foil for aluminum electrolytic capacitors and aluminum electrolytic capacitors

Abstract

This disclosure relates to a method for preparing an anode foil for an aluminum electrolytic capacitor and an aluminum electrolytic capacitor, belonging to the field of capacitor technology. The method includes: uniformly mixing spherical aluminum powder and a mixed solution to obtain a mixed slurry; coating the mixed slurry onto the surface of an aluminum foil substrate to obtain an aluminum foil substrate with a slurry film layer; pre-drying the aluminum foil substrate with the slurry film layer to obtain an aluminum foil blank; freezing the aluminum foil blank to obtain a frozen aluminum foil blank; subjecting the frozen aluminum foil blank to secondary directional drying to form a coated initial anode foil; sintering the initial anode foil under an inert atmosphere to obtain a sintered anode foil; sequentially subjecting the sintered anode foil to ultrasonic cleaning, pure water rinsing, and boiling in water to obtain a boiled anode foil; and performing a formation treatment on the boiled anode foil to form an oxide layer on the boiled anode foil to obtain the target anode foil. This disclosure improves the bending performance of the target anode foil.

Description

Technical Field

[0001] This disclosure relates to the field of capacitor technology, and more specifically, to a method for preparing an anode foil for an aluminum electrolytic capacitor and an aluminum electrolytic capacitor. Background Technology

[0002] The aluminum electrolytic capacitor anode foil prepared by existing methods has insufficient bending performance.

[0003] It should be noted that the information in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] The purpose of this disclosure is to provide a method for preparing the anode foil of an aluminum electrolytic capacitor and an aluminum electrolytic capacitor, thereby overcoming, at least to some extent, the problem of insufficient bending performance caused by the limitations and defects of related technologies.

[0005] According to one aspect of this disclosure, a method for preparing an anode foil for an aluminum electrolytic capacitor is provided, comprising the following steps: Step S101, uniformly mixing spherical aluminum powder and a mixed solution to obtain a mixed slurry, and coating the mixed slurry onto the surface of an aluminum foil substrate to obtain an aluminum foil substrate with a slurry film layer; Step S102, pre-drying the aluminum foil substrate with the slurry film layer to obtain an aluminum foil blank, and freezing the aluminum foil blank to obtain a frozen aluminum foil blank; Step S103, subjecting the frozen aluminum foil blank to secondary directional drying to form a coated initial anode foil, and sintering the initial anode foil under an inert atmosphere to obtain a sintered anode foil; Step S104, sequentially subjecting the sintered anode foil to ultrasonic cleaning, pure water rinsing, and boiling in water to obtain a boiled anode foil, and subjecting the boiled anode foil to a formation treatment to form an oxide layer on the boiled anode foil, thereby obtaining a target anode foil for a high-capacity and high-toughness aluminum electrolytic capacitor.

[0006] In an exemplary embodiment of this disclosure, the purity of the spherical aluminum powder is ≥99.9%, and the particle size D50 of the spherical aluminum powder is 1~10μm; the mass ratio between the spherical aluminum powder and the mixed solution is (40~70):(30~60); the mixed solution is prepared by mixing organic solvent, binder and dispersant, and the mass ratio between the organic solvent, binder and dispersant in the mixed solution is (25~42):(2~8):(1~6).

[0007] In one exemplary embodiment of this disclosure, the organic solvent is one or more of terpineol, ethylene glycol, isopropanol, and propylene glycol methyl ether; the binder is one or more of ethyl cellulose, polyvinyl butyral, polyvinylidene fluoride, and hydroxypropyl cellulose; and the dispersant is one or more of polyacrylic acid, ammonium polycarboxylate, and triammonium citrate.

[0008] In an exemplary embodiment of this disclosure, the thickness of the aluminum foil substrate is 20 μm to 100 μm; the process of coating the mixed slurry onto the surface of the aluminum foil substrate is achieved by coating the aluminum foil substrate on both sides with the mixed slurry to form a slurry film layer of the same thickness on the surface of the aluminum foil substrate.

[0009] In an exemplary embodiment of this disclosure, the aluminum foil preform is obtained by: adjusting the drying temperature of the hot air oven to 80°C~160°C, and pre-drying the aluminum foil substrate with the slurry film layer for 1~10 minutes at the temperature of 80°C~160°C in the hot air oven to obtain the aluminum foil preform; wherein, in the obtained aluminum foil preform, the single-layer thickness of the slurry film layer is 20μm~60μm.

[0010] In one exemplary embodiment of this disclosure, the freezing device used in the freezing process of the aluminum foil blank includes at least one of the following: a liquid nitrogen spraying device, a freezing box, or a tunnel freezing device.

[0011] In an exemplary embodiment of this disclosure, the required drying conditions for the secondary directional drying of the frozen aluminum foil blank are as follows: the temperature of the oven is raised from room temperature to 100-450°C at a heating rate of 2-10°C / min, and held at that temperature for 5-60 minutes; simultaneously, the moving direction of the heating tube forms an angle of 10-80° with the length direction of the powdered aluminum foil blank; during the secondary directional drying process, by controlling the heating rate of the oven and the moving direction of the heating tube, the network microcracks of the frozen aluminum foil blank are arranged obliquely and regularly.

[0012] In an exemplary embodiment of this disclosure, the inert atmosphere used in the sintering process includes at least one of nitrogen, argon, and high vacuum; the sintered anode foil is obtained by: raising the temperature of the sintering apparatus from room temperature to 350-450°C at a heating rate of 1-20°C / min in the inert atmosphere and holding it at that temperature for 1-8 hours, and then raising the temperature of the sintering apparatus from 350-450°C to 580-655°C at a heating rate of 1-20°C / min and holding it at that temperature for 1-12 hours to obtain the sintered anode foil.

[0013] In an exemplary embodiment of this disclosure, the boiled anode foil is obtained by the following method: the sintered anode foil is sequentially ultrasonically cleaned, rinsed with pure water, and then boiled in water at 95-100°C for 5-15 minutes to remove residual organic matter and stabilize the oxide film, thereby obtaining the boiled anode foil; the formation voltage used in the formation treatment of the boiled anode foil to obtain the target anode foil is 520V; the target anode foil has a specific capacity ≥0.95μF / cm² under the 520V empowerment condition, and has a 90° reciprocating bending count ≥90 times in both the transverse and longitudinal directions.

[0014] According to one aspect of this disclosure, an aluminum electrolytic capacitor is provided, the aluminum electrolytic capacitor comprising a target anode foil obtained by the method for preparing the anode foil of the aluminum electrolytic capacitor according to any one of the preceding claims.

[0015] This disclosure provides a method for preparing an anode foil for an aluminum electrolytic capacitor. Firstly, a slurry is obtained by uniformly mixing spherical aluminum powder and a mixed solution. This slurry is then coated onto the surface of an aluminum foil substrate to obtain an aluminum foil substrate with a slurry film layer. Next, the aluminum foil substrate with the slurry film layer is pre-dried to obtain an aluminum foil blank. The aluminum foil blank is then subjected to freeze treatment to obtain a frozen aluminum foil blank. The frozen aluminum foil blank is then subjected to secondary directional drying to form a coated initial anode foil. The initial anode foil is then sintered under an inert atmosphere to obtain a sintered anode foil. Finally, the sintered anode foil is sequentially subjected to ultrasonic cleaning, pure water rinsing, and boiling in water to obtain a boiled anode foil. Boiled anode foil undergoes a formation process to form an oxide layer on it, resulting in a target anode foil for high-capacity and high-toughness aluminum electrolytic capacitors. During the preparation of the target anode foil, a freezing followed by a secondary directional drying process creates uniformly distributed network microcracks on the anode foil surface, significantly releasing bending stress and improving both longitudinal and transverse bending capabilities. This fundamentally solves the industry problem of poor toughness and brittle fracture in high-specific-capacity sintered foils. Furthermore, since the network microcracks on the aluminum foil are fully preserved during subsequent sintering, a dual-functional microstructure of conductive and crack-damping properties can be formed. This provides oxide film deformation margin while maintaining a high specific surface area, helping to prevent crack propagation.

[0016] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0018] Figure 1 The flowchart schematically illustrates a method for preparing an anode foil for an aluminum electrolytic capacitor according to an exemplary embodiment of the present disclosure.

[0019] Figure 2 The diagram illustrates an SEM image of an anode foil obtained according to an exemplary embodiment of the present disclosure, based on the preparation method described in Example 1.

[0020] Figure 3 The illustration shows an SEM image of an anode foil obtained according to an exemplary embodiment of the present disclosure, based on the preparation method described in Comparative Example 1. Detailed Implementation

[0021] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided to make this disclosure more comprehensive and complete, and to fully convey the concept of the example embodiments to those skilled in the art. The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a full understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced with one or more of the specific details omitted, or other methods, components, apparatus, steps, etc., can be employed. In other instances, well-known technical solutions are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0022] Furthermore, the accompanying drawings are merely illustrative of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities may be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0023] Aluminum electrolytic capacitors are widely used in core functional modules of various electronic circuits, such as filtering, bypassing, coupling, timing, tuning, rectification, and energy storage, due to their high specific capacitance per unit volume, strong breakdown resistance, self-healing properties during operation, and low cost. Meanwhile, with the continuous pursuit of miniaturization and lightweighting in downstream electronic devices, the market has placed more stringent requirements on the specific capacitance of capacitors, making the high specific capacitance of the anode foil a major direction for technological upgrading in the industry.

[0024] Furthermore, compared to high-purity aluminum foil etching and expansion technology, powder-coated electronic aluminum foil technology has advantages such as higher specific capacitance, lower cost, energy saving and emission reduction, and environmental friendliness. However, it still suffers from drawbacks such as insufficient bending strength, making mass production difficult. Extensive experimental analysis reveals that the insufficient bending strength stems from the porous structure formed by aluminum powder sintering on the aluminum substrate surface. This porous structure easily diminishes during the subsequent anodizing process of the powder-coated electronic aluminum foil as the oxide film grows. Furthermore, the dense and brittle oxide film, with its three-dimensional network structure, severely weakens its bending performance, making it difficult for the electronic aluminum foil anode to meet the standard performance requirements for capacitor winding. It should also be noted that while some related technical solutions can improve the bending performance of the powder-coated electronic aluminum anode foil, they result in severe surface damage, affecting its surface quality and overall performance. Therefore, there is an urgent need to provide a high-capacity, high-toughness aluminum electrolytic capacitor anode foil.

[0025] Based on the problems described above, this disclosure first provides a method for preparing the anode foil of an aluminum electrolytic capacitor. Specifically, refer to... Figure 1 As shown, the method for preparing the anode foil of the aluminum electrolytic capacitor may include the following steps: Step S101: The spherical aluminum powder and the mixed solution are uniformly mixed to obtain a mixed slurry, and the mixed slurry is coated on the surface of the aluminum foil substrate to obtain an aluminum foil substrate with a slurry film layer; Step S102: The aluminum foil substrate with the slurry film layer is pre-dried to obtain an aluminum foil blank, and the aluminum foil blank is frozen to obtain a frozen aluminum foil blank. Step S103: The frozen aluminum foil blank is subjected to secondary directional drying to form a coated initial anode foil, and the initial anode foil is sintered in an inert atmosphere to obtain a sintered anode foil. Step S104: The sintered anode foil is subjected to ultrasonic cleaning, pure water rinsing and boiling in water in sequence to obtain a boiled anode foil. The boiled anode foil is then subjected to formation treatment to form an oxide layer on the boiled anode foil, thereby obtaining the target anode foil for a high-capacity and high-toughness aluminum electrolytic capacitor.

[0026] In the above-described method for preparing the anode foil of an aluminum electrolytic capacitor, on one hand, a slurry is obtained by uniformly mixing spherical aluminum powder and a mixed solution, and the slurry is coated onto the surface of an aluminum foil substrate to obtain an aluminum foil substrate with a slurry film layer; then, the aluminum foil substrate with the slurry film layer is pre-dried to obtain an aluminum foil blank, and the aluminum foil blank is frozen to obtain a frozen aluminum foil blank; then, the frozen aluminum foil blank is subjected to secondary directional drying to form a coated initial anode foil, and the initial anode foil is sintered under an inert atmosphere to obtain a sintered anode foil; finally, the sintered anode foil is subjected to ultrasonic cleaning, pure water rinsing, and boiling in water to obtain a boiled anode foil, and the boiled anode foil is... The anode foil undergoes a formation process to form an oxide layer on the boiled anode foil, resulting in a target anode foil for high-capacity and high-toughness aluminum electrolytic capacitors. During the preparation of the target anode foil, a freezing followed by a secondary directional drying process can be used to form uniformly distributed network microcracks on the anode foil surface, significantly releasing bending stress and improving both longitudinal and transverse bending capabilities. This fundamentally solves the industry problem of poor toughness and brittle fracture in high-specific-capacity sintered foils. Furthermore, since the network microcracks on the aluminum foil are fully preserved during subsequent sintering, a bifunctional microstructure of conductive and crack-inhibiting properties can be formed. This provides oxide film deformation margin while maintaining a high specific surface area, helping to prevent crack propagation.

[0027] The following will provide a detailed explanation and description of the method for preparing the anode foil of the aluminum electrolytic capacitor as described in the exemplary embodiments of this disclosure, in conjunction with the accompanying drawings.

[0028] First, the technical implementation principle of the exemplary embodiments of this disclosure will be explained and described. Specifically, the preparation method of the anode foil of the aluminum electrolytic capacitor described in the exemplary embodiments of this disclosure firstly involves uniformly mixing spherical high-purity aluminum powder, organic solvent, binder, and dispersant to obtain a mixed slurry; secondly, coating the mixed slurry onto the surface of a high-purity aluminum foil substrate and pre-drying it to obtain an aluminum foil blank with a powder layer; then, freezing the dried powder layer aluminum foil blank; further, performing a secondary directional drying treatment on the frozen powder layer aluminum foil blank; even further, sintering the powder layer aluminum foil blank after secondary directional drying to obtain a sintered anode foil; finally, cleaning and boiling the sintered anode foil; and then performing an energy-forming treatment on the boiled anode foil to ultimately obtain a high-capacity, high-toughness aluminum electrolytic capacitor anode foil. In practical applications, the exemplary embodiments of this disclosure utilize a process of first freezing and then secondary directional drying to form uniformly distributed network microcracks on the surface of the anode foil, which significantly improves the toughness of the anode foil. At the same time, the preparation method is simple, easy to implement, green and environmentally friendly, and suitable for large-scale production.

[0029] Secondly, for Figure 1The method for preparing the anode foil of the aluminum electrolytic capacitor shown will be further explained and illustrated. Specifically: In step S101, spherical aluminum powder and a mixed solution are uniformly mixed to obtain a mixed slurry, and the mixed slurry is coated on the surface of an aluminum foil substrate to obtain an aluminum foil substrate with a slurry film layer.

[0030] Specifically, the purity of the spherical aluminum powder described herein is ≥99.9%, and the particle size D50 of the spherical aluminum powder is 1~10μm; based on this, the mass ratio between the spherical aluminum powder and the mixed solution is (40~70):(30~60); furthermore, the mixed solution described herein is prepared by mixing organic solvent, binder and dispersant, and the mass ratio between the organic solvent, binder and dispersant in the mixed solution can be (25~42):(2~8):(1~6).

[0031] In one example embodiment, the organic solvents described above may include, but are not limited to, terpineol, ethylene glycol, isopropanol, and propylene glycol methyl ether; the binders may include, but are not limited to, ethyl cellulose, polyvinyl butyral, polyvinylidene fluoride, and hydroxypropyl cellulose; and the dispersants may include, but are not limited to, polyacrylic acid, polyammonium carboxylate, and triammonium citrate.

[0032] In one example embodiment, the thickness of the aluminum foil substrate described above is 20μm to 100μm; meanwhile, the process of coating the mixed slurry onto the surface of the aluminum foil substrate is achieved by coating the aluminum foil substrate on both sides using the mixed slurry to form a slurry film layer of the same thickness on the surface of the aluminum foil substrate.

[0033] In step S102, the aluminum foil substrate with the slurry film layer is pre-dried to obtain an aluminum foil blank, and the aluminum foil blank is frozen to obtain a frozen aluminum foil blank.

[0034] In this embodiment of the disclosure, the aluminum foil preform is obtained by the following method: in a hot air drying oven, the drying temperature of the hot air drying oven is adjusted to 80℃~160℃, and the aluminum foil substrate with the slurry film layer is pre-dried for 1~10 minutes under the condition of 80℃~160℃ in the hot air drying oven to obtain the aluminum foil preform; wherein, in the obtained aluminum foil preform, the single layer thickness of the slurry film layer is 20μm~60μm; at the same time, the obtained aluminum foil preform is an aluminum foil preform with a powder layer.

[0035] In this embodiment of the disclosure, the freezing device used in the freezing process of the aluminum foil blank includes, but is not limited to, a liquid nitrogen spraying device, a freezing box or a tunnel freezing device, etc.

[0036] In step S103, the frozen aluminum foil blank is subjected to secondary directional drying to form a coated initial anode foil, and the initial anode foil is sintered under an inert atmosphere to obtain a sintered anode foil.

[0037] In this embodiment, the required drying conditions for the secondary directional drying of the frozen aluminum foil blank are as follows: the oven temperature is raised from room temperature to 100-450°C at a heating rate of 2-10°C / min, and held for 5-60 minutes; simultaneously, the moving direction of the heating tube forms an angle of 10-80° with the length direction of the powdered aluminum foil blank; and during the secondary directional drying process, by controlling the heating rate of the oven and the moving direction of the heating tube, the network microcracks of the frozen powdered aluminum foil blank are arranged obliquely and regularly. It should be noted that the secondary directional drying is necessary to form a uniformly distributed network microcracks on the surface of the initial coated anode foil, thereby significantly improving the toughness of the anode foil. Furthermore, this method is simple, easy to implement, environmentally friendly, and suitable for large-scale production.

[0038] In this embodiment of the disclosure, the inert atmosphere used in the sintering process may include, but is not limited to, nitrogen, argon, and high vacuum; at the same time, the sintered anode foil is obtained by the following method: in the inert atmosphere, the temperature of the sintering device is raised from room temperature to 350-450°C at a heating rate of 1-20°C / min and held for 1-8 hours, and then the temperature of the sintering device is raised from 350-450°C to 580-655°C at a heating rate of 1-20°C / min and held for 1-12 hours to obtain the sintered anode foil.

[0039] In step S104, the sintered anode foil is sequentially subjected to ultrasonic cleaning, pure water rinsing, and boiling in water to obtain a boiled anode foil. The boiled anode foil is then subjected to a formation treatment to form an oxide layer on the boiled anode foil, thereby obtaining the target anode foil for a high-capacity and high-toughness aluminum electrolytic capacitor.

[0040] In this embodiment of the disclosure, the boiled anode foil is obtained by the following method: the sintered anode foil is sequentially ultrasonically cleaned and rinsed with pure water, and then boiled in water at 95-100°C for 5-15 minutes to remove residual organic matter and stabilize the oxide film, thereby obtaining the boiled anode foil; simultaneously, in the process of forming the boiled anode foil to obtain the target anode foil, the forming voltage used is 520V; the target anode foil has a specific capacity ≥0.95μF / cm² under the 520V empowerment condition, and has a 90° reciprocating bending count ≥90 times in both the transverse and longitudinal directions.

[0041] In one example embodiment, this disclosure also provides an aluminum electrolytic capacitor comprising a target anode foil obtained according to the aforementioned method for preparing an aluminum electrolytic capacitor anode foil.

[0042] Thus, the preparation method of the aluminum electrolytic capacitor anode foil described in the exemplary embodiments of this disclosure has been fully realized. Based on the foregoing description, it can be understood that the preparation method of the aluminum electrolytic capacitor anode foil described in the exemplary embodiments of this disclosure, although simple in process, can reduce defects on the anode foil surface; furthermore, it can improve the bending resistance of the anode foil, ensuring the integrity of the anode foil surface and resulting in excellent bending resistance; specifically, this can be reflected in the following aspects: ① The anode foil obtained in the exemplary embodiments of this disclosure produces directional network microcracks on its surface, which can improve the bending resistance of the anode foil after subsequent formation treatment; ② This preparation method first dries the surface of the aluminum foil blank through pre-drying treatment, providing a basis for the freeze-drying process; in addition, this preparation method applies internal stress inside the powder layer through cooling freeze-drying treatment, and increases the unevenly distributed internal stress in the slurry film layer through secondary directional drying treatment, and then superimposes the sintering stress formed during sintering, making... After sintering, the slurry film layer can form directional multi-directional microcracks, which can effectively avoid the foil surface damage caused by applying stress or strain through direct contact with the foil, thus avoiding specific capacitance loss and improving the production quality of the anode foil. This preparation method can produce anode foils with intact surfaces, high quality, and good bending resistance. ③ The synergistic processing technology of "pre-drying-freezing-secondary directional drying" induces the formation of regular network microcracks on the powder layer surface, which can significantly release bending stress and significantly improve the bending performance of the anode foil in both the longitudinal and transverse directions, fundamentally solving the industry problem of poor toughness and brittle fracture of high specific capacitance sintered foils. ④ The network microcracks on the powder layer aluminum foil are fully preserved in the subsequent sintering process, forming a conductive-cracking dual-function microstructure. This maintains a high specific surface area and provides oxide film deformation margin, helping to prevent crack propagation and achieving a specific capacitance ≥0.95. While achieving μF / cm², both longitudinal and transverse bending strength are significantly improved, achieving a balance between high capacity and high toughness; ⑤ The process route is simple and efficient, requiring no additional expensive equipment. Freezing + directional drying can be integrated online with existing coating lines, shortening the sintering process, significantly reducing energy consumption, making it green and environmentally friendly, and suitable for mass production; ⑥ The resulting anode foil has good compatibility with 400-600V high-voltage electrolyte systems and can be directly used in long-life, high-ripple applications such as automotive and blockchain computers, expanding the high-end market space for sintered anode foil.

[0043] Furthermore, it should be added here that the aluminum electrolytic capacitor prepared based on the anode foil obtained in the example embodiments of this disclosure has good mechanical properties and good overall device performance.

[0044] The following will further explain and illustrate the preparation method of the aluminum electrolytic capacitor anode foil described in the exemplary embodiments of this disclosure, with reference to specific examples.

[0045] Example 1: A method for preparing the anode foil of an aluminum electrolytic capacitor, comprising the following steps: 1) Slurry preparation: 65wt% spherical high-purity aluminum powder (D50=3μm, purity≥99.9%) is mixed with 3wt% ethyl cellulose, 1wt% polyacrylic acid dispersant, and 31wt% terpineol, and stirred in a planetary mixer for 2 hours to obtain a uniform aluminum slurry with a solid content of 65wt%; 2) Coating and pre-baking: The aluminum slurry is coated on both sides of a 50μm high-purity aluminum foil substrate using a coating machine, with a single-sided coating thickness of 40μm; it is pre-baked in a 120℃ hot air oven for 3 minutes to obtain a powder-coated aluminum foil blank with a total thickness of approximately 130μm; 3) Freezing treatment: The blank is placed in a liquid nitrogen spraying device tunnel and kept at -20℃ for 20 minutes; 4) Secondary directional drying: The temperature is increased to 300℃ at 5℃ / min and held for 10 minutes, with the heating tube of the oven at 60° to the length of the foil; 5) Sintering: A Under an R2 atmosphere (O2 < 30 ppm), the temperature was increased to 450℃ at 5℃ / min and held for 4 hours, then increased to 620℃ at 5℃ / min and held for 6 hours to obtain a sintered anode foil; 6) Cleaning and boiling: ultrasonic cleaning for 5 minutes → pure water rinsing → boiling in water at 98℃ for 10 minutes; 7) Five-stage formation: ① 85℃, 120V, 5 minutes; ② 85℃, 250V, 8 minutes; ③ 85℃, 520V, 15 minutes; the formation solution contained 5 wt% boric acid and 0.5 wt% ammonium pentaborate; the current density was 25 mA / cm²; where, in the five-stage formation process described here, ①, ②, and ③ correspond to the first, third, and fifth stages of formation, respectively, the second stage of formation is the pause time between the first and third stages of formation, and the fourth stage of formation is the pause time between the third and fifth stages of formation. Meanwhile, the SEM image of the anode foil obtained in Example 1 can be referenced. Figure 2 As shown; 8) Performance test: 520V specific capacitance 1.153μF / cm 2 ; Bend back and forth 125 times in the 90° coating direction and bend 108 times in the lateral direction.

[0046] Example 2: A method for preparing the anode foil of an aluminum electrolytic capacitor, comprising the following steps: 1) Slurry preparation: Mix 55wt% spherical high-purity aluminum powder (D50=5μm, purity≥99.9%) with 5wt% polyvinyl butyral, 2wt% polyacrylic acid dispersant, and 38wt% ethylene glycol, and stir planetarily for 2 hours to obtain a uniform aluminum slurry with a solid content of 55wt%; 2) Coating and pre-baking: Use a coating machine to coat the aluminum slurry onto both sides of a 100μm high-purity aluminum foil substrate, with a coating thickness of 20μm on one side; pre-baking is carried out in a 150℃ hot air oven for 2 minutes to obtain a powder-coated aluminum foil blank with a total thickness of approximately 140μm; 3) Freezing treatment: Place the blank in a freezer and keep it at -50℃ for 10 minutes; 4) Secondary directional drying: 5) Sintering: Under N2 atmosphere (O2<30ppm), heat to 410℃ at 10℃ / min and hold for 1h, then heat to 615℃ at 5℃ / min and hold for 4h to obtain sintered anode foil; 6) Cleaning and boiling: Ultrasonic cleaning for 5min → pure water rinsing → boiling in 95℃ water for 15min; 7) Five-stage formation: ① 85℃, 120V, 5min; ② 85℃, 250V, 8min; ③ 85℃, 520V, 15min; the formation solution contains 5wt% boric acid and 0.5wt% ammonium pentaborate; the current density is 25mA / cm. 2 ; In the five-stage formation process described here, ①, ② and ③ correspond to the first, third and fifth stages of formation, respectively. The second stage of formation is the pause time between the first and third stages of formation, and the fourth stage of formation is the pause time between the third and fifth stages of formation; 8) Performance test: 520V specific capacitance 1.372μF / cm²; 90° coating direction reciprocating bending 165 times, transverse bending 126 times.

[0047] Example 3: A method for preparing the anode foil of an aluminum electrolytic capacitor, comprising the following steps: 1) Slurry preparation: 40wt% spherical high-purity aluminum powder (D50=1μm, purity ≥99.9%), 8wt% ethyl cellulose, 4% hydroxypropyl cellulose, 6wt% ammonium polycarboxylate dispersant, and 42wt% isopropanol are mixed and stirred in a planetary mixer for 2 hours to obtain a uniform aluminum slurry with a solid content of 40wt%; 2) Coating and pre-baking: The aluminum slurry is coated onto both sides of a 60μm high-purity aluminum foil substrate using a coating machine, with a coating thickness of 50μm on one side; it is pre-baked in a 100℃ hot air oven for 4 minutes to obtain a powder-coated aluminum foil blank with a total thickness of approximately 160μm; 3) Freezing treatment: The blank is placed in a liquid nitrogen spraying device tunnel and kept at -25℃ for 30 minutes; 4) II 5) Directional Drying: Heat to 100℃ at 2℃ / min and hold for 60 min, with the heating tube of the oven at 30° to the length of the foil; 6) Sintering: Under a high vacuum atmosphere (O2 < 30ppm), heat to 350℃ at 1℃ / min and hold for 8 h, then heat to 655℃ at 20℃ / min and hold for 1 h to obtain sintered anode foil; 7) Cleaning and Boiling: Ultrasonic cleaning → pure water rinsing → boiling in 100℃ water for 5 min; 8) Five-stage Formation: ① 85℃, 120V, 5 min; ② 85℃, 250V, 8 min; ③ 85℃, 520V, 15 min; the formation solution contains 5wt% boric acid and 0.5wt% ammonium pentaborate; current density 25mA / cm². 2 ; In the five-stage formation process described here, ①, ②, and ③ correspond to the first, third, and fifth stages of formation, respectively. The second stage of formation is the pause time between the first and third stages of formation, and the fourth stage of formation is the pause time between the third and fifth stages of formation; 8) Performance test: 520V specific capacitance 1.165μF / cm 2 ; Bending back and forth 142 times in the 90° coating direction and bending laterally 113 times.

[0048] Example 4: A method for preparing the anode foil of an aluminum electrolytic capacitor, comprising the following steps: 1) Slurry preparation: Mix 60wt% spherical high-purity aluminum powder (D50=4μm, purity≥99.9%) with 4wt% polyvinylidene fluoride, 2wt% triammonium citrate dispersant, and 34wt% propylene glycol methyl ether, and stir planetarily for 2 hours to obtain a uniform aluminum slurry with a solid content of 60wt%; 2) Coating and pre-baking: Use a coating machine to coat the aluminum slurry onto both sides of a 20μm high-purity aluminum foil substrate, with a coating thickness of 60μm on one side; pre-baking is carried out in an 80℃ hot air oven for 10 minutes to obtain a powder-coated aluminum foil blank with a total thickness of approximately 140μm; 4) Freezing treatment: Place the blank in a freezer and keep it at -10℃ for 45 minutes; 5) Secondary directional drying 6) Sintering: Under Ar2 atmosphere (O2<30ppm), heat to 420℃ at 20℃ / min and hold for 6h, then heat to 635℃ at 1℃ / min and hold for 2h to obtain sintered anode foil; 7) Cleaning and boiling: Ultrasonic cleaning → pure water rinsing → boiling in 98℃ water for 5min; 8) Five-stage formation: ① 85℃, 120V, 5min; ② 85℃, 250V, 8min; ③ 85℃, 520V, 15min; The formation solution contains 5wt% boric acid and 0.5wt% ammonium pentaborate; Current density 25mA / cm 2 ; In the five-stage formation process described here, ①, ②, and ③ correspond to the first, third, and fifth stages of formation, respectively. The second stage of formation is the pause time between the first and third stages of formation, and the fourth stage of formation is the pause time between the third and fifth stages of formation; 8) Performance test: 520V specific capacitance 0.957μF / cm 2 ; 90° coating direction repeated bending 195 times, transverse bending 137 times.

[0049] Example 5: A method for preparing the anode foil of an aluminum electrolytic capacitor, comprising the following steps: 1) Slurry preparation: 62wt% spherical high-purity aluminum powder (D50=2μm, purity ≥99.9%) is mixed with 2wt% hydroxypropyl cellulose, 1wt% polycarboxylate ammonium dispersant, and 35wt% terpineol, and stirred in a planetary mixer for 2 hours to obtain a uniform aluminum slurry with a solid content of 62wt%; 2) Coating and pre-baking: The aluminum slurry is coated on both sides of a 50μm high-purity aluminum foil substrate using a coating machine, with a coating thickness of 40μm on one side; it is pre-baked in a 130℃ hot air oven for 5 minutes to obtain a powder-coated aluminum foil blank with a total thickness of 130μm; 3) Freezing treatment: The blank is placed in a tunnel freezing device and kept at -15℃ for 40 minutes; 4) Secondary directional drying: The temperature is increased to 400℃ at 4℃ / min and held for 5 minutes, with the heating tube of the oven at 50° to the length of the foil; 5) Sintering: Under a N2 atmosphere (O2<30ppm), the temperature is increased to 400℃ at 5℃ / min. 6) Cleaning and boiling: ultrasonic cleaning → pure water rinsing → boiling in water at 98℃ for 15 min; 7) Five-stage formation: ① 85℃, 120V, 5 min; ② 85℃, 250V, 8 min; ③ 85℃, 520V, 15 min; the formation solution contains 5wt% boric acid and 0.5wt% ammonium pentaborate; the current density is 25mA / cm²; in the five-stage formation process described here, ①, ② and ③ correspond to the first, third and fifth stages of formation, respectively. The second stage of formation is the pause time between the first and third stages of formation, and the fourth stage of formation is the pause time between the third and fifth stages of formation; 8) Performance test: 520V specific capacity 0.963μF / cm²; 187 reciprocating bends in the 90° coating direction and 134 transverse bends.

[0050] Example 6: A method for preparing the anode foil of an aluminum electrolytic capacitor, comprising the following steps: 1) Slurry preparation: 70wt% spherical high-purity aluminum powder (D50=10μm, purity ≥99.9%) is mixed with 4wt% ethyl cellulose, 1wt% polycarboxylate ammonium dispersant, and 25wt% isopropanol, and stirred in a planetary mixer for 2 hours to obtain a uniform aluminum slurry with a solid content of 70wt%; 2) Coating and pre-baking: The aluminum slurry is coated on both sides of a 60μm high-purity aluminum foil substrate using a coating machine, with a coating thickness of 35μm on one side; it is pre-baked in a 125℃ hot air oven for 3 minutes to obtain a powder-coated aluminum foil blank with a total thickness of approximately 140μm; 3) Freezing treatment: The blank is placed in a liquid nitrogen spraying device tunnel and kept at -5℃ for 60 minutes; 4) Secondary directional drying Drying: Heat to 350℃ at 8℃ / min and hold for 20 min, with the heating tube of the oven at 80° to the length of the foil; 5) Sintering: Under a high vacuum atmosphere (O2<30ppm), heat to 400℃ at 6℃ / min and hold for 6 h, then heat to 625℃ at 10℃ / min and hold for 3 h to obtain sintered anode foil; 6) Cleaning and boiling: Ultrasonic cleaning → pure water rinsing → boiling in water at 95℃ for 5 min; 7) Five-stage formation: ① 85℃, 120V, 5 min; ② 85℃, 250V, 8 min; ③ 85℃, 520V, 15 min; The formation solution contains 5wt% boric acid and 0.5wt% ammonium pentaborate; Current density 25mA / cm 2 ; In the five-stage formation process described here, ①, ② and ③ correspond to the first, third and fifth stages of formation, respectively. The second stage of formation is the pause time between the first and third stages of formation, and the fourth stage of formation is the pause time between the third and fifth stages of formation; 8) Performance test: 520V specific capacitance 1.176μF / cm²; 90° coating direction reciprocating bend 129 times, lateral bend 99 times.

[0051] Example 7: A method for preparing the anode foil of an aluminum electrolytic capacitor, comprising the following steps: 1) Slurry preparation: 67wt% spherical high-purity aluminum powder (D50=3μm, purity≥99.9%) is mixed with 2wt% hydroxypropyl cellulose, 1wt% polyacrylic acid dispersant, and 30wt% terpineol, and stirred in a planetary mixer for 2 hours to obtain a uniform aluminum slurry with a solid content of 67wt%; 2) Coating and pre-baking: The aluminum slurry is coated on both sides of a 50μm high-purity aluminum foil substrate using a coating machine, with a coating thickness of 45μm on one side; it is pre-baked in a 160℃ hot air oven for 1 minute to obtain a powder-coated aluminum foil blank with a total thickness of approximately 140μm; 3) Freezing treatment: The blank is placed in a liquid nitrogen spraying device tunnel and kept at -30℃ for 15 minutes; 4) Secondary directional drying 5) Sintering: Under Ar2 atmosphere (O2<30ppm), heat to 450℃ at 5℃ / min and hold for 4h, then heat to 610℃ at 8℃ / min and hold for 6h to obtain sintered anode foil; 6) Cleaning and boiling: Ultrasonic cleaning → pure water rinsing → boiling in 100℃ water for 15min; 7) Five-stage formation: ① 85℃, 120V, 5min; ② 85℃, 250V, 8min; ③ 85℃, 520V, 15min; the formation solution contains 5wt% boric acid and 0.5wt% ammonium pentaborate; the current density is 25mA / cm. 2 ; In the five-stage formation process described here, ①, ②, and ③ correspond to the first, third, and fifth stages of formation, respectively. The second stage of formation is the pause time between the first and third stages of formation, and the fourth stage of formation is the pause time between the third and fifth stages of formation; 8) Performance test: 520V specific capacitance 1.161μF / cm 2 ; Bending back and forth 124 times in the 90° coating direction and 94 times in the transverse direction.

[0052] Comparative Example 1: A method for preparing the anode foil of an aluminum electrolytic capacitor, comprising the following steps: 1) Slurry preparation: Mix 65wt% spherical high-purity aluminum powder (D50=3μm, purity ≥99.9%) with 3wt% ethyl cellulose, 1wt% polyacrylic acid dispersant, and 31wt% terpineol, and stir planetarily for 2 hours to obtain a uniform aluminum slurry with a solid content of 65wt%; 2) Coating and pre-baking: Use a coating machine to coat the aluminum slurry onto both sides of a 50μm high-purity aluminum foil substrate, with a single-sided coating thickness of 40μm; pre-bake in a 120℃ hot air oven for 3 minutes to obtain a powder-coated aluminum foil preform with a total thickness of approximately 130μm; 3) No freezing treatment is required; 4) No need for... 5) Sintering: Under Ar2 atmosphere (O2<30ppm), heat to 450℃ at 5℃ / min and hold for 4h, then heat to 620℃ at 5℃ / min and hold for 6h to obtain sintered anode foil; 6) Cleaning and boiling: Ultrasonic cleaning for 5min → pure water rinsing → boiling in 98℃ water for 10min; 7) Five-stage formation: ① 85℃, 120V, 5min; ② 85℃, 250V, 8min; ③ 85℃, 520V, 15min; The formation solution contains 5wt% boric acid and 0.5wt% ammonium pentaborate; Current density 25mA / cm 2 8) Performance test: 520V specific capacitance 1.146μF / cm 2 ; Bend back and forth once in the 90° coating direction, and bend horizontally once.

[0053] Furthermore, the performance test results obtained after performance testing of the anode foils obtained in Examples 1-7 and Comparative Example 1 are shown in Table 1 below: Table 1. Performance test results of the anode foil after 520V energy formation treatment.

[0054] As can be seen from the contents recorded in Table 1 above, the anode foil prepared in Comparative Example 1, after coating and drying and direct sintering, has a specific capacitance of 1.146 μF / cm at 520V after formation and energy-enhancing treatment. 2 The anode foil prepared in Example 1, obtained by pre-drying, freeze-drying, and secondary directional drying followed by sintering, exhibits a specific capacitance of 1.153 μF / cm³ at 520V after formation and energy-enhancing treatment. 2The anode foil prepared in Example 1 was bent 125 times in the 90° coating direction and 108 times in the lateral direction compared to the anode foil prepared in Comparative Example 1, and its specific capacitance was also slightly improved. Furthermore, the anode foils prepared in Examples 1-7 showed significantly increased bending times in both the 90° coating direction and the lateral direction compared to the anode foil prepared in Comparative Example 1, greatly improving the bending resistance of the anode foil and meeting the requirements of subsequent processing. Therefore, the anode foil preparation method provided by this invention can improve the bending resistance of the anode foil, thereby improving the overall performance of aluminum electrolytic capacitor components.

[0055] Furthermore, although the steps of the method in this disclosure are described in a specific order in the accompanying drawings, this does not require or imply that the steps must be performed in that specific order, or that all the steps shown must be performed to achieve the desired result. Additional or alternative steps may be omitted, multiple steps may be combined into one step, and / or a step may be broken down into multiple steps.

[0056] Furthermore, the above figures are merely illustrative of the processes included in the method according to exemplary embodiments of this disclosure and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0057] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention described herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not invented by this disclosure. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the claims.

Claims

1. A method for preparing the anode foil of an aluminum electrolytic capacitor, characterized in that, Includes the following steps: Step S101: The spherical aluminum powder and the mixed solution are uniformly mixed to obtain a mixed slurry, and the mixed slurry is coated on the surface of the aluminum foil substrate to obtain an aluminum foil substrate with a slurry film layer; Step S102: Pre-dry the aluminum foil substrate with the slurry film layer to obtain an aluminum foil blank, and then freeze the aluminum foil blank to obtain a frozen aluminum foil blank. Step S103: The frozen aluminum foil blank is subjected to secondary directional drying to form a coated initial anode foil, and the initial anode foil is sintered in an inert atmosphere to obtain a sintered anode foil. Step S104: The sintered anode foil is subjected to ultrasonic cleaning, pure water rinsing and boiling in water in sequence to obtain a boiled anode foil. The boiled anode foil is then subjected to formation treatment to form an oxide layer on the boiled anode foil, thereby obtaining the target anode foil for a high-capacity and high-toughness aluminum electrolytic capacitor.

2. The method for preparing the anode foil of an aluminum electrolytic capacitor according to claim 1, characterized in that, The purity of the spherical aluminum powder is ≥99.9%, and the particle size D50 of the spherical aluminum powder is 1~10μm; The mass ratio of the spherical aluminum powder to the mixed solution is (40~70):(30~60). The mixed solution is prepared by mixing organic solvent, binder and dispersant, and the mass ratio of organic solvent, binder and dispersant in the mixed solution is (25~42):(2~8):(1~6).

3. The method for preparing the anode foil of an aluminum electrolytic capacitor according to claim 2, characterized in that, The organic solvent is one or more of terpineol, ethylene glycol, isopropanol, and propylene glycol methyl ether; The binder is one or more of ethyl cellulose, polyvinyl butyral, polyvinylidene fluoride, and hydroxypropyl cellulose. The dispersant is one or more of polyacrylic acid, ammonium polycarboxylate, and triammonium citrate.

4. The method for preparing the anode foil of an aluminum electrolytic capacitor according to claim 1, characterized in that, The thickness of the aluminum foil substrate is 20μm~100μm; The process of coating the mixed slurry onto the surface of the aluminum foil substrate is achieved by coating the aluminum foil substrate on both sides with the mixed slurry to form a slurry film layer of the same thickness on the surface of the aluminum foil substrate.

5. The method for preparing the anode foil of an aluminum electrolytic capacitor according to claim 1, characterized in that, The aluminum foil blank is obtained by the following method: in the case of a hot air oven, the drying temperature of the hot air oven is adjusted to 80℃~160℃, and the aluminum foil substrate with the slurry film layer is pre-dried for 1~10 minutes under the condition of 80℃~160℃ in the hot air oven to obtain the aluminum foil blank. In the obtained aluminum foil blank, the thickness of the single layer of the slurry film is 20μm~60μm.

6. The method for preparing the anode foil of an aluminum electrolytic capacitor according to claim 1, characterized in that, The freezing device used in the freezing process of the aluminum foil blank includes at least one of the following: liquid nitrogen spraying device, freezing box or tunnel freezing device.

7. The method for preparing the anode foil of an aluminum electrolytic capacitor according to claim 1, characterized in that, During the secondary directional drying process of the frozen aluminum foil blank, the required drying conditions are as follows: the temperature of the oven is raised from room temperature to 100-450℃ at a heating rate of 2-10℃ / min, and held for 5-60 minutes; at the same time, the moving direction of the heating tube is at an angle of 10-80° to the length direction of the powdered aluminum foil blank. During the secondary directional drying process, by controlling the heating rate of the oven and the moving direction of the heating tubes, the mesh-like microcracks of the frozen powder aluminum foil blank are arranged obliquely and regularly.

8. The method for preparing the anode foil of an aluminum electrolytic capacitor according to claim 1, characterized in that, During the sintering process, the inert atmosphere used includes at least one of nitrogen, argon, and high vacuum. The sintered anode foil is obtained by the following method: in the inert atmosphere, the temperature of the sintering apparatus is raised from room temperature to 350-450°C at a heating rate of 1-20°C / min and held for 1-8 hours, and then the temperature of the sintering apparatus is raised from 350-450°C to 580-655°C at a heating rate of 1-20°C / min and held for 1-12 hours to obtain the sintered anode foil.

9. The method for preparing the anode foil of an aluminum electrolytic capacitor according to claim 1, characterized in that, The boiled anode foil is obtained by the following method: the sintered anode foil is subjected to ultrasonic cleaning and pure water rinsing in sequence, and then boiled in water at 95-100°C for 5-15 minutes to remove residual organic matter and stabilize the oxide film, thereby obtaining the boiled anode foil. In the process of forming the water-boiled anode foil to obtain the target anode foil, the forming voltage used is 520V; the target anode foil has a specific capacity ≥0.95μF / cm² under the 520V empowerment condition, and has ≥90 90-fold reciprocating bends in both the transverse and longitudinal directions.

10. An aluminum electrolytic capacitor, characterized in that, The aluminum electrolytic capacitor includes the target anode foil obtained by the method for preparing the anode foil of the aluminum electrolytic capacitor according to any one of claims 1-9.

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