Method for producing an anode foil and aluminum electrolytic capacitor

Abstract

This disclosure relates to a method for preparing an anode foil and an aluminum electrolytic capacitor, belonging to the field of capacitor technology. The method includes: preparing a mixed slurry comprising aluminum powder and a mixed solution, the mixed solution being prepared by mixing an organic solvent, deionized water, a binder, and additives; coating the surface of an aluminum foil substrate with the mixed slurry to obtain an aluminum foil with a slurry film layer, and subjecting the aluminum foil with the slurry film layer to a first drying treatment to form an aluminum foil blank; subjecting the aluminum foil blank to directional heat treatment, and subjecting the directional heat-treated aluminum foil blank to vibration treatment and a second drying treatment to form an initial anode foil; subjecting the initial anode foil to sintering treatment and boiling treatment to form a first intermediate anode foil, and subjecting the first intermediate anode foil to a formation treatment to form an oxide layer on the first intermediate anode foil, thereby obtaining the target anode foil. This disclosure solves the problem of being unable to produce an anode foil with a complete surface and good bending performance.

Description

Technical Field

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

[0002] Aluminum electrolytic capacitors are widely used in various fields such as electronic communications, automotive industry, optoelectronic products, and high-speed rail. In practical applications, the anode foil is a key raw material that determines the overall performance of aluminum electrolytic capacitors. Meanwhile, as aluminum electrolytic capacitors further develop towards higher capacitance, miniaturization, and greener designs, the requirements for the bending performance of the anode foil are becoming increasingly stringent.

[0003] Currently, the bending performance of anode foil can be improved in several ways: The first method is to subject the aluminum foil to oblique stress when it passes through an inclined roller set in a conveying trough or a roller with balls on its circumferential surface that can rotate around their own center, thus obtaining an anode foil with multi-directional cracks on its surface; The second method is to use a shaped roller to roll-press the coated surface of the aluminum foil substrate after drying to obtain the anode foil; The third method is to use an anilox roller to heat-press the coated surface of the aluminum foil substrate after drying to obtain the anode foil; At the same time, the anode foil obtained by the above methods can generate irregular multi-directional cracks on the surface of the anode foil, thereby improving the bending performance of the anode foil in both the transverse and longitudinal directions.

[0004] However, the above-described processing methods all aim to improve bending performance by applying stress or strain to the foil with rollers to induce micro-cracks in the foil. During this process, the aluminum powder layer on the surface of the foil needs to come into contact with the rollers, which can easily lead to scratches and powder loss on the foil surface, causing the foil to stick together after sintering. This results in the inability to produce an anode foil with a complete surface and good bending performance.

[0005] 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

[0006] The purpose of this disclosure is to provide a method for preparing an anode foil and an aluminum electrolytic capacitor, thereby overcoming, to at least some extent, the inability to produce an anode foil with a complete surface and good bending performance due to limitations and defects in related technologies.

[0007] According to one aspect of this disclosure, a method for preparing an anode foil is provided, comprising: step S101, preparing a mixed slurry, the mixed slurry comprising aluminum powder and a mixed solution, the mixed solution being prepared by mixing an organic solvent, deionized water, a binder and additives; step S102, coating the surface of an aluminum foil substrate with the mixed slurry to obtain an aluminum foil having a slurry film layer, and subjecting the aluminum foil having the slurry film layer to a first drying treatment to form an aluminum foil blank; step S103, subjecting the aluminum foil blank to directional heat treatment, and subjecting the directional heat-treated aluminum foil blank to vibration treatment and a second drying treatment to form an initial anode foil; step S104, subjecting the initial anode foil to sintering treatment and boiling treatment to form a first intermediate anode foil, and subjecting the first intermediate anode foil to a formation treatment to form an oxide layer on the first intermediate anode foil, thereby obtaining a target anode foil.

[0008] In one exemplary embodiment of this disclosure, the mass ratio of aluminum powder to the mixed solution in the mixed slurry is 100:(40~150); and the mass ratio of organic solvent, deionized water, binder and additive in the mixed solution is 100:(2~20):(1.5~10):(0.5~10).

[0009] In one exemplary embodiment of this disclosure, the organic solvent is one or both of terpineol and diethylene glycol butyl ether acetate; the binder is ethyl cellulose; the additive includes one or more of defoamer, dispersant, and coupling agent; the defoamer is an organosilicon defoamer or a polyether defoamer, the dispersant is diethanolamine or triethanolamine, and the coupling agent is a silane coupling agent.

[0010] In an exemplary embodiment of this disclosure, the aluminum foil substrate has a thickness of 20 μm to 60 μm and has an upper surface and a lower surface disposed opposite to each other. The aluminum foil blank is obtained by: using the mixed slurry to double-sidedly coat the aluminum foil substrate to form a slurry film layer of the same thickness on the upper and lower surfaces of the aluminum foil substrate, thereby obtaining an aluminum foil with a slurry film layer; and performing a first drying treatment on the aluminum foil with the slurry film layer at a drying temperature of 100°C to 150°C to obtain the aluminum foil blank. During the first drying treatment, the axial direction of the heating element is perpendicular to the foil's forward direction. The heating element is a heating tube or a hot air nozzle. In the obtained aluminum foil blank, the thickness of the slurry film layer is 50 μm to 60 μm.

[0011] In an exemplary embodiment of this disclosure, the directional heat treatment of the aluminum foil blank is carried out in the following manner: 2 to 10 sets of heating devices are arranged above and below the aluminum foil blank, and each set of heating devices is configured with two heating elements for directional heat treatment; in each set of heating devices, the transverse axial direction of the two heating elements forms an angle of 30° to 60° and an angle of 120° to 150° with the length direction of the aluminum foil blank, respectively; the temperature of the two heating elements is set to 350°C to 500°C; the interval between the heating elements is cooled by room temperature air; and the speed at which the aluminum foil blank is conveyed along its length is 1 m / min to 10 m / min; the heating element is a heating tube or a hot air nozzle.

[0012] In one exemplary embodiment of this disclosure, the initial anode foil is obtained by immersing the oriented heat-treated aluminum foil blank in an immersion solution, then vibrating the aluminum foil blank in the immersion solution using sound waves as a vibration source, and then drying the vibrated aluminum foil blank a second time at a drying temperature of 100°C to 200°C to obtain the initial anode foil.

[0013] In one exemplary embodiment of this disclosure, the soaking solution includes one or more of polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400, ethylene glycol, and propylene glycol; the vibration source is ultrasound or megasonic waves.

[0014] In an exemplary embodiment of this disclosure, the first intermediate anode foil is obtained by heating the initial anode foil from room temperature to 600°C to 650°C at a heating rate of 0.1°C / min to 20°C / min in a nitrogen, argon, or vacuum atmosphere, and holding it at that temperature for 4h to 12h; after the holding period, cooling it in the furnace to obtain the sintered initial anode foil, and then boiling the sintered initial anode foil in deionized water at 100°C for 5min to 15min to obtain the first intermediate anode foil.

[0015] In one exemplary embodiment of this disclosure, the target anode foil is obtained by forming a first intermediate anode foil under a formation voltage of 200V to 700V to obtain the target anode foil.

[0016] According to one aspect of this disclosure, an aluminum electrolytic capacitor is provided, the aluminum electrolytic capacitor comprising a target anode foil prepared by the method for preparing the anode foil as described in any one of the preceding claims.

[0017] This disclosure provides a method for preparing an anode foil. On one hand, by adding deionized water to a slurry, the mixed slurry is coated onto the surface of an aluminum foil substrate and then dried for the first time to obtain an aluminum foil blank. Based on this, the aluminum foil blank undergoes directional heat treatment and vibration treatment, followed by sintering to obtain an initial anode foil. Finally, it undergoes boiling and formation treatment to obtain the target anode foil. Simultaneously, the target anode foil obtained by this preparation method has irregular multidirectional microcracks on its surface, which can improve the bending performance of the anode foil after subsequent formation treatment. On the other hand, by adding deionized water to the slurry, a hydrated alumina film is formed on the surface of the slurry film during the drying process. This hydrated alumina film can form a gap between adjacent aluminum foil blanks, preventing adhesion between the aluminum foil blanks during subsequent sintering, thereby reducing defects on the anode foil surface and ensuring the integrity of the anode foil surface. Furthermore, by controlling the slurry composition and drying process, this preparation method causes the slurry film coated on the surface of the aluminum foil substrate to form an orange peel texture during the drying process, thereby creating unevenly distributed internal stress within the slurry film.

[0018] 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

[0019] 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.

[0020] Figure 1 A flowchart illustrating a method for preparing an anode foil according to an exemplary embodiment of the present disclosure is shown.

[0021] Figure 2 The diagram illustrates a light microscope image of an anode foil formed using the preparation method provided in Comparative Example 1 according to an exemplary embodiment of the present disclosure.

[0022] Figure 3 The diagram illustrates a light mirror image of an anode foil formed using the preparation method provided in Comparative Example 2 according to an exemplary embodiment of the present disclosure.

[0023] Figures 4(a) and 4(b) schematically show optical micrographs of an anode foil formed using the preparation method provided in Example 1 according to an exemplary embodiment of the present disclosure. Detailed Implementation

[0024] 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.

[0025] 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.

[0026] In related technical solutions, to improve the bending performance of anode foil, aluminum foil can be tilted and placed on rollers in a conveying trough or on rollers with balls rotating around their own center on the circumferential surface; or a shaped roller can be used to roll-press the coated surface of the dried aluminum foil substrate, or a textured roller can be used to heat-press the coated surface of the dried aluminum foil substrate to generate irregular multi-directional cracks on the anode foil surface, thereby improving the bending performance of the anode foil in both the transverse and longitudinal directions. However, these methods all involve applying stress or strain to the foil through rollers to induce micro-cracks; during this process, scratches and powder shedding on the foil surface can easily occur, leading to adhesion of the foil after sintering, making it impossible to produce anode foil with a complete surface and good bending performance. Based on this, the exemplary embodiment of this disclosure first provides a method for preparing anode foil. Specifically, refer to... Figure 1 As shown, the method for preparing the anode foil may include the following steps: Step S101: Prepare a mixed slurry, the mixed slurry comprising aluminum powder and a mixed solution, the mixed solution being prepared by mixing organic solvent, deionized water, binder and additives; Step S102: The mixed slurry is coated on the surface of the aluminum foil substrate to obtain an aluminum foil with a slurry film layer, and the aluminum foil with the slurry film layer is subjected to a first drying treatment to form an aluminum foil blank. Step S103: The aluminum foil blank is subjected to directional heat treatment, and the aluminum foil blank after directional heat treatment is subjected to vibration treatment and a second drying treatment to form an initial anode foil. Step S104: The initial anode foil is subjected to sintering and boiling treatment to form a first intermediate anode foil, and the first intermediate anode foil is subjected to formation treatment to form an oxide layer on the first intermediate anode foil, thereby obtaining the target anode foil.

[0027] In the above-described method for preparing anode foil, on the one hand, deionized water is added to a slurry, the mixed slurry is coated onto the surface of an aluminum foil substrate, and then a first drying treatment is performed to obtain an aluminum foil blank; on this basis, the aluminum foil blank is subjected to directional heat treatment and vibration treatment, and then sintered to obtain an initial anode foil; finally, it is subjected to boiling and formation treatment to obtain the target anode foil; at the same time, the surface of the target anode foil obtained by this preparation method has irregular multidirectional microcracks, which can improve the bending performance of the anode foil after subsequent formation treatment; on the other hand, This preparation method involves adding deionized water to the slurry and forming a hydrated alumina film on the surface of the slurry film during the drying process. This hydrated alumina film can create a gap between adjacent aluminum foil blanks, preventing adhesion between the aluminum foil blanks during subsequent sintering, thereby reducing defects on the anode foil surface and ensuring the integrity of the anode foil surface. Furthermore, by controlling the slurry composition and drying process, this preparation method causes the slurry film coated on the aluminum foil substrate surface to form an orange peel texture during the drying process, thereby creating unevenly distributed internal stress in the slurry film.

[0028] The method for preparing the anode foil according to the exemplary embodiments of this disclosure will be explained and described in detail below with reference to the accompanying drawings. Specifically: In step S101, a mixed slurry is prepared, which includes aluminum powder and a mixed solution. The mixed solution is prepared by mixing organic solvent, deionized water, binder and additives.

[0029] In this embodiment of the present disclosure, the mass ratio between aluminum powder and the mixed solution in the obtained mixed slurry is 100:(40~150); for example, the mass ratio between aluminum powder and the mixed solution can be 100:40, 100:70, 100:100, 100:120 or 100:150, etc., and this example does not impose any special restrictions on this; at the same time, by limiting the mass ratio between aluminum powder and the mixed solution to the above range, the formation quality of the subsequent aluminum foil blank can be improved.

[0030] In this embodiment of the disclosure, the aluminum powder used in the preparation of the mixed slurry can be spherical or ellipsoidal particles with a particle size of 0.5 μm to 5 μm. For example, the particle size of the aluminum powder can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm, etc. It should also be noted that during the preparation of the aluminum powder, the resulting aluminum powder can contain multiple aluminum powders of different particle sizes, or it can contain aluminum powders of the same or approximately the same particle size. This example does not impose any special limitations on this. Furthermore, the purity of the aluminum powder used cannot be less than 99.99%.

[0031] In this embodiment of the present disclosure, the mass ratio of organic solvent, deionized water, binder and additive in the mixed solution is 100:(2~20):(1.5~10):(0.5~10); for example, the mass ratio of organic solvent, deionized water, binder and additive can be 100:2:1.5:0.5, 100:10:5:5, 100:20:10:5 or 100:20:10:10, etc. The mass ratio of each component in the mixed solution can be selected or adaptively adjusted according to the specific type and function of the component.

[0032] In this embodiment, the organic solvent described above may include, but is not limited to, terpineol, diethylene glycol butyl ether acetate, etc.; the binder described above may be ethyl cellulose; the additives described above may include, but are not limited to, defoamers, dispersants, coupling agents, etc.; the defoamer described above may include silicone defoamers or polyether defoamers, the dispersant described above may be diethanolamine or triethanolamine, and the coupling agent described above may be a silane coupling agent. It should be further noted that by controlling the type and mass ratio of each component in the mixed slurry, the mixed slurry can have characteristics such as low evaporation rate, easy storage, and moderate viscosity at room temperature; simultaneously, it can also ensure that the solvent in the mixed slurry is easily volatile during the drying process, so as to ensure that the surface of the obtained slurry film can form an orange peel texture; furthermore, it can also ensure that there is no or less residue of binder and additives during the sintering process, thereby achieving the purpose of reducing the impurity content of the obtained anode foil.

[0033] In this embodiment of the disclosure, no leveling agent is required during the preparation of the anode foil with orange peel texture. It should be noted that, in the industry, orange peel texture is considered a defect; however, experiments have shown that because the film thickness at the edge of the orange peel texture is smaller than that in the middle of the orange peel texture, the formation of orange peel texture on the film surface can cause micron-level thickness unevenness in the film layer. This can create unevenly distributed local stress in the film layer, which is beneficial for the formation of microcracks in the film layer after subsequent directional heat treatment, vibration treatment and sintering treatment, thereby improving the bending performance of the anode foil.

[0034] In step S102, the mixed slurry is coated on the surface of the aluminum foil substrate to obtain an aluminum foil with a slurry film layer, and the aluminum foil with the slurry film layer is subjected to a first drying treatment to form an aluminum foil blank.

[0035] In this embodiment, the thickness of the aluminum foil substrate used is 20μm to 60μm; for example, the thickness of the aluminum foil substrate can be 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm or 60μm, etc., and this example does not impose any special limitation on this; and, in the provided aluminum foil substrate, the aluminum foil substrate has an upper surface and a lower surface that are disposed opposite to each other; it should be noted that, since there may be subsequent differences between the various parts of the aluminum foil substrate, the thickness of the aluminum foil substrate can refer to one of the maximum distance, minimum distance or average distance between the upper surface and the lower surface. In this disclosure, the thickness of the aluminum foil substrate is described as the average distance between the upper surface and the lower surface.

[0036] In this embodiment of the disclosure, the aluminum foil blank described above is obtained by the following method: using the mixed slurry, the aluminum foil substrate is coated on both sides to form a slurry film layer of the same thickness on the upper and lower surfaces of the aluminum foil substrate, thereby obtaining an aluminum foil with a slurry film layer; the aluminum foil with the slurry film layer is subjected to a first drying treatment at a drying temperature of 100℃~150℃ to obtain the aluminum foil blank; wherein, during the first drying treatment, the axial direction of the heating element is perpendicular to the foil advancing direction; the heating element is a heating tube or a hot air nozzle; in the obtained aluminum foil blank, the thickness of the slurry film layer is 50μm~60μm.

[0037] In this embodiment, the double-sided coating of the aluminum foil substrate can be achieved using coating methods such as blade coating or slot extrusion coating. Based on this, a slurry film layer of the same thickness can be formed on both the upper and lower surfaces of the aluminum foil substrate. The thickness of the dried slurry film layer is 50μm to 60μm, for example, it can be 50μm, 52μm, 54μm, 56μm, 58μm, or 60μm, etc., and this example does not impose any special limitations on this. Furthermore, by controlling the thickness of the aluminum foil substrate and the slurry film layer, a porous layer of suitable thickness is formed on both sides of the aluminum foil blank, thereby preparing for subsequent irregular multidirectional microcracks. It should also be noted that the same thickness of the slurry film layer formed on the upper and lower surfaces of the aluminum foil substrate means that the thicknesses of the two layers are exactly the same or approximately the same. Due to process errors, a thickness difference of up to 1μm between the two layers can be considered as the same thickness.

[0038] In this embodiment of the present disclosure, after a slurry film layer is formed on the surface of the aluminum foil substrate, the aluminum foil with the slurry film layer is subjected to a first drying treatment. The drying temperature used in the first drying treatment can be 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, etc. The specific drying temperature can be adjusted according to the thickness of the slurry film layer. For example, when the slurry film layer is thicker, the drying temperature can be appropriately increased to shorten the drying time and improve efficiency.

[0039] In step S103, the aluminum foil blank is subjected to directional heat treatment, and the aluminum foil blank after directional heat treatment is subjected to vibration treatment and a second drying treatment to form an initial anode foil.

[0040] In this embodiment of the present disclosure, the directional heat treatment of the aluminum foil blank is carried out in the following manner: 2 to 10 sets of heating devices are set above and below the aluminum foil blank, and each set of heating devices is configured with two heating elements for directional heat treatment; in each set of heating devices, the transverse axial direction of the two heating elements forms an angle of 30° to 60° and an angle of 120° to 150° with the length direction of the aluminum foil blank, respectively; the temperature of the two heating elements is set to 350°C to 500°C; the interval between the heating elements is cooled by room temperature air; the speed at which the aluminum foil blank is conveyed along the length direction is 1m / min to 10m / min; the heating element is a heating tube or a hot air nozzle.

[0041] In this embodiment of the disclosure, directional heat treatment is a heat treatment process performed on the aluminum foil blank after the slurry coated on the surface of the aluminum foil substrate is dried. The purpose is to generate greater internal stress in the film layer by using hot and cold cycles. The coating process adopts a traditional drying method, that is, the axis of the heating element is perpendicular to the foil's forward direction, and there is no room temperature air between the heating elements to cool the foil.

[0042] In this embodiment, the heating devices arranged above and below the aluminum foil blank can be in groups of 2, 4, 6, 8, or 10, etc. Simultaneously, the transverse axial direction of one heating element in each group can be at an angle of 30°, 40°, 50°, or 60° to the length direction of the aluminum foil blank, and the transverse axial direction of the other heating element can be at an angle of 120°, 130°, 140°, or 150° to the length direction of the aluminum foil blank, etc. The temperature of the heating elements can be set to 350℃, 400℃, 450℃, or 500℃, etc. The conveying speed of the aluminum foil blank along its length direction can be 1 m / min, 3 m / min, 5 m / min, 7 m / min, or 10 m / min, etc. It should also be noted that this method, by controlling the number, temperature, angle, and conveying speed of the aluminum foil blank, generates unevenly distributed internal stress in the slurry film layer, thereby causing irregular multidirectional cracks in the slurry film layer during subsequent sintering, thus improving the bending performance of the anode foil.

[0043] In this embodiment of the disclosure, the initial anode foil described above is obtained by immersing the oriented heat-treated aluminum foil blank in an immersion solution, then vibrating the aluminum foil blank in the immersion solution using sound waves as a vibration source, and then performing a second drying treatment on the vibrated aluminum foil blank at a drying temperature of 100℃~200℃ to obtain the initial anode foil. Meanwhile, the immersion solution used here may include, but is not limited to, polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400, ethylene glycol, and propylene glycol; the vibration source used here is ultrasound or megasonic waves.

[0044] In this embodiment, the required drying temperature during the second drying process can be 100℃, 120℃, 140℃, 160℃, 180℃, or 200℃, etc. Simultaneously, vibration treatment can generate suitable internal stress in the slurry film layer, thereby causing irregular multidirectional cracks in the slurry film layer during subsequent sintering, thus improving the bending performance of the anode foil.

[0045] In step S104, the initial anode foil is subjected to sintering and boiling treatment to form a first intermediate anode foil, and the first intermediate anode foil is subjected to formation treatment to form an oxide layer on the first intermediate anode foil, thereby obtaining the target anode foil.

[0046] In this embodiment of the present disclosure, the first intermediate anode foil is obtained by heating the initial anode foil from room temperature to 600°C to 650°C at a heating rate of 0.1°C / min to 20°C / min in a nitrogen, argon, or vacuum atmosphere, and holding it at that temperature for 4h to 12h; after the holding period, the initial anode foil is cooled in the furnace to obtain the sintered initial anode foil, and then boiled in deionized water at 100°C for 5min to 15min to obtain the first intermediate anode foil.

[0047] In this embodiment, the heating rate can be 0.1℃ / min, 5℃ / min, 10℃ / min, 15℃ / min, or 20℃ / min, etc.; simultaneously, the holding temperature can be 600℃, 610℃, 620℃, 630℃, 640℃, or 650℃, etc.; and the holding time can be 4h, 6h, 8h, 10h, or 12h, etc. It should also be noted that by adjusting and controlling parameters such as the heating rate, sintering atmosphere, holding temperature, and holding time of the sintering process, the binder in the initial anode foil can be completely removed, while ensuring a smooth and non-adhesive surface of the anode foil, guaranteeing the flatness and integrity of the anode foil surface. Furthermore, irregular multidirectional microcracks can be generated on the surface and inside the anode foil to improve the bending performance of the anode foil after subsequent formation treatment.

[0048] In this embodiment, the temperature of the deionized water during the boiling treatment can be strictly 100°C; however, due to temperature error, a temperature within the range of 100°C ± 1°C can also be considered the required temperature for the boiling treatment. Furthermore, the boiling treatment time can be 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, or 15 min, etc., and this example does not impose any special limitations on this. Furthermore, by adjusting and controlling the boiling treatment time and temperature, a hydrated alumina layer of suitable thickness can be formed on the surface of the anode foil, which is beneficial for the formation of an oxide layer in subsequent formation processes.

[0049] In this embodiment of the disclosure, the target anode foil described above is obtained by performing a formation treatment on a first intermediate anode foil at a formation voltage of 200V to 700V to obtain the target anode foil. For example, the formation voltage can be 200V, 300V, 400V, 500V, 600V, or 700V, etc. The formation treatment can convert the hydrated alumina layer into an oxide layer, wherein the oxide layer is an alumina film layer. Furthermore, by adjusting and controlling the formation voltage, anode foils with various rated withstand voltage requirements can be produced.

[0050] Thus, the anode foil preparation method described in the exemplary embodiments of this disclosure has been fully implemented. Based on the foregoing description, it can be understood that the anode foil preparation method described in the embodiments of this disclosure, on the one hand, improves the bending performance of the anode foil after subsequent formation treatment by having irregular multidirectional microcracks on its surface; on the other hand, by adding deionized water to the slurry, a hydrated alumina film is formed on the surface of the slurry film during the drying process. This hydrated alumina film can form a gap between adjacent aluminum foil blanks, preventing adhesion between the aluminum foil blanks during subsequent sintering; furthermore, by controlling the slurry composition and drying process, the slurry film coated on the surface of the aluminum foil substrate forms an orange peel texture during the drying process, thereby creating unevenly distributed internal stress in the slurry film; further still, the preparation method further improves the bending performance of the anode foil after subsequent formation treatment by adding deionized water to the slurry film. The foil blank undergoes directional heat treatment, meaning the surface of the slurry film is confined and directionally heated along the transverse axis of the heating element. As the aluminum foil blank passes through the heating zone, the slurry film expands due to heat, generating thermal stress. The slurry film undergoes multiple directional heating and cooling processes to increase the unevenly distributed internal stress within it. Furthermore, this preparation method employs vibration treatment to further increase the unevenly distributed internal stress within the slurry film. This stress is then superimposed on the sintering stress generated during the sintering process, resulting in irregular, multidirectional microcracks forming in the slurry film after sintering. This effectively avoids the problem of surface scratches and powdering that occur when applying stress or strain to the foil using rollers, thus improving the surface quality of the anode foil. Finally, this preparation method can produce anode foils with intact surfaces and good bending performance.

[0051] This disclosure also provides an aluminum electrolytic capacitor, which includes a target anode foil prepared by the anode foil preparation method described in any one of the above-described embodiments. Furthermore, the aluminum electrolytic capacitor prepared in this manner exhibits good mechanical properties and overall device performance.

[0052] The following will further illustrate the preparation method of the anode foil provided in the example embodiments of this disclosure with reference to specific examples.

[0053] Example 1: A method for preparing an anode foil, comprising the following steps: Step 1: Mix organic solvent (terpineol), deionized water, ethyl cellulose, and additives (organosilicone defoamer, triethanolamine dispersant, and silane coupling agent) at a mass ratio of 100:20:10:2:1:5 to form a mixed solution; mix aluminum powder with the mixed solution at a mass ratio of 100:150 to form a mixed slurry; wherein the aluminum powder has a particle size of 0.5μm~5μm and a purity of 99.99%.

[0054] Step 2: The mixed slurry formed in Step 1 is applied to the upper and lower surfaces of the aluminum foil substrate using a slit extrusion process. After a first drying treatment, an aluminum foil blank is formed. The drying temperature for the first drying treatment is 140℃, the thickness of the aluminum foil substrate is 20μm, and the thickness of the slurry coated on the upper and lower surfaces after drying is 52μm. During the drying process, the axis of the heating tube is perpendicular to the direction of foil movement.

[0055] Step 3 involves directional heat treatment of the aluminum foil blank formed in Step 2, including: setting 10 sets of heating devices above and below the aluminum foil blank, with each set of heating devices consisting of two heating tubes. The axial directions of these two heating tubes are at 40° and 140° to the length direction of the aluminum foil blank, respectively. The temperature of the heating tubes is set to 400°C. The aluminum foil blank is cooled with room temperature air in the interval between each heating tube. The aluminum foil blank is conveyed along its length at a speed of 10 m / min.

[0056] Step 4: Immerse the aluminum foil blank formed in Step 3 into a mixed solution of polyethylene glycol 300 and propylene glycol, use megasonic waves as a vibration source to vibrate the aluminum foil blank, and then perform a second drying treatment at 180°C to form the initial anode foil.

[0057] Step 5: Sinter the initial anode foil formed in Step 4. Sintering is carried out in a bell-type furnace. The sintering process is as follows: the bell-type furnace is heated to 630°C in nitrogen at a heating rate of 10°C / min, held at that temperature for 10 hours, and then cooled with the furnace after the holding period.

[0058] Step 6: The anode foil formed in Step 5 is subjected to boiling water treatment and formation treatment. After washing with deionized water, it is dried at 100°C to form the target anode foil. The boiling water treatment uses deionized water at 100°C for 10 minutes; the formation treatment uses a 100 g / L boric acid solution and a formation voltage of 520 V.

[0059] Example 2: A method for preparing an anode foil, comprising the following steps: Step 1: Mix organic solvents (terpineol and diethylene glycol butyl ether acetate), deionized water, ethyl cellulose, and additives (diethanolamine and silane coupling agent) at a mass ratio of 30:70:15:8:2:8 until homogeneous to form a mixed solution. Then, mix aluminum powder with the mixed solution at a mass ratio of 100:120 until homogeneous to form a mixed slurry; wherein the aluminum powder has a particle size of 0.5μm~5μm and a purity of 99.99%.

[0060] Step 2: The mixed slurry formed in Step 1 is applied to the upper and lower surfaces of the aluminum foil substrate using a slit extrusion process. After a first drying treatment, an aluminum foil blank is formed. The drying temperature for the first drying treatment is 120℃, the thickness of the aluminum foil substrate is 60μm, and the thickness of the slurry coated on the upper and lower surfaces after drying is 56μm. During the drying process, the axis of the hot air nozzle is perpendicular to the foil's forward movement direction.

[0061] Step 3 involves directional heat treatment of the aluminum foil blank formed in Step 2, including: setting two sets of heating devices above and below the aluminum foil blank, with each set of heating devices consisting of two hot air nozzles. The axial directions of these two hot air nozzles are at 30° and 130° to the length direction of the aluminum foil blank, respectively. The temperature of the hot air nozzles is set to 350°C. The aluminum foil blank is cooled with room temperature air in the interval between each hot air nozzle. The aluminum foil blank is conveyed along its length at a speed of 1 m / min.

[0062] Step 4: Immerse the aluminum foil blank formed in Step 3 into a mixed solution of ethylene glycol and propylene glycol, use megasonic waves as a vibration source to vibrate the aluminum foil blank, and then perform a second drying treatment at 200°C to form the initial anode foil.

[0063] Step 5: Sinter the initial anode foil formed in Step 4. Sintering is carried out in a bell-type furnace. The sintering process is as follows: the bell-type furnace is heated to 640°C in a vacuum at a heating rate of 5°C / min, held at that temperature for 8 hours, and then cooled with the furnace after the holding period.

[0064] Step 6: The anode foil formed in Step 5 is subjected to boiling and formation treatments. After rinsing with deionized water, it is dried at 100°C to form the target anode foil. The boiling treatment uses deionized water at 100°C for 5 minutes; the formation treatment uses a 100 g / L boric acid solution at a formation voltage of 200 V.

[0065] Example 3: A method for preparing an anode foil, comprising the following steps: Step 1: Mix the organic solvent (diethylene glycol butyl ether acetate), deionized water, ethyl cellulose, and additives (organosilicone defoamer, triethanolamine, and silane coupling agent) at a mass ratio of 100:18:8:2:2:5 until homogeneous to form a mixed solution. Then, mix the aluminum powder with the mixed solution at a mass ratio of 100:60 until homogeneous to form a slurry; wherein the aluminum powder has a particle size of 0.5μm~5μm and a purity of 99.99%.

[0066] Step 2: The mixed slurry formed in Step 1 is applied to the upper and lower surfaces of the aluminum foil substrate using a slit extrusion process. After a first drying treatment, an aluminum foil blank is formed. The drying temperature for the first drying treatment is 110℃, the thickness of the aluminum foil substrate is 30μm, and the thickness of the slurry applied to the upper and lower surfaces after drying is 60μm. During the drying process, the axis of the heating tube is perpendicular to the direction of foil movement.

[0067] Step 3 involves directional heat treatment of the aluminum foil blank formed in Step 2, including: setting 5 sets of heating devices above and below the aluminum foil blank, with each set of heating devices consisting of two heating tubes. The axial directions of these two heating tubes are at 50° and 150° to the length direction of the aluminum foil blank, respectively. The temperature of the heating tubes is set to 400°C. The aluminum foil blank is cooled with room temperature air in the interval between each heating tube. The aluminum foil blank is conveyed along its length at a speed of 6 m / min.

[0068] Step 4: Immerse the aluminum foil blank formed in Step 3 into a mixed solution of polyethylene glycol 300, ethylene glycol and propylene glycol, and use ultrasound as a vibration source to vibrate the aluminum foil blank. Then, perform a second drying treatment at 160°C to form the initial anode foil.

[0069] Step 5: Sinter the initial anode foil formed in Step 4. Sintering is carried out in a bell-type furnace. The sintering process is as follows: the bell-type furnace is heated to 650°C in argon gas at a heating rate of 0.1°C / min, held at that temperature for 4 hours, and then cooled with the furnace after the holding period.

[0070] Step 6: The anode foil formed in Step 5 is subjected to boiling water treatment and formation treatment. After washing with deionized water, it is dried at 100°C to form the target anode foil. The boiling water treatment uses deionized water at 100°C for 15 minutes; the formation treatment uses a 100 g / L boric acid solution and a formation voltage of 700 V.

[0071] Example 4: A method for preparing an anode foil, comprising the following steps: Step 1: Mix the organic solvent (terpineol), deionized water, ethyl cellulose, and additives (organosilicone defoamer and silane coupling agent) at a mass ratio of 100:5:1.5:0.5:2 until homogeneous to form a mixed solution. Then, mix the aluminum powder with the mixed solution at a mass ratio of 100:40 until homogeneous to form a mixed slurry; wherein the aluminum powder has a particle size of 0.5μm~5μm and a purity of 99.99%.

[0072] Step 2: The mixed slurry formed in Step 1 is applied to the upper and lower surfaces of the aluminum foil substrate using a slit extrusion process. After a first drying treatment, an aluminum foil blank is formed. The drying temperature for the first drying treatment is 130℃, the thickness of the aluminum foil substrate is 30μm, and the thickness of the slurry applied to the upper and lower surfaces after drying is 50μm. During the drying process, the axis of the heating tube is perpendicular to the direction of foil movement.

[0073] Step 3 involves directional heat treatment of the aluminum foil blank formed in Step 2, including: setting up 8 sets of heating devices above and below the aluminum foil blank, with each set of heating devices consisting of two hot air nozzles. The axial directions of these two hot air nozzles are at 60° and 120° to the length direction of the aluminum foil blank, respectively. The temperature of the hot air nozzles is set to 450°C. The aluminum foil blank is cooled with room temperature air in the interval between each hot air nozzle. The aluminum foil blank is conveyed along its length at a speed of 5 m / min.

[0074] Step 4: Immerse the aluminum foil blank formed in Step 3 into a mixed solution of polyethylene glycol 400 and propylene glycol, use ultrasound as a vibration source to vibrate the aluminum foil blank, and then dry it for the second time at 140°C to form the initial anode foil.

[0075] Step 5: Sinter the initial anode foil formed in Step 4. Sintering is carried out in a bell-type furnace. The sintering process is as follows: the bell-type furnace is heated to 600°C in a vacuum at a heating rate of 20°C / min, held at that temperature for 12 hours, and then cooled with the furnace after the holding period.

[0076] Step 6: The anode foil formed in Step 5 is subjected to boiling water treatment and formation treatment. After washing with deionized water, it is dried at 100°C to form the target anode foil. The boiling water treatment uses deionized water at 100°C for 10 minutes; the formation treatment uses a 100g / L boric acid solution and a formation voltage of 200V.

[0077] Example 5: A method for preparing an anode foil, comprising the following steps: Step 1: Mix the organic solvent (terpineol and diethylene glycol butyl ether acetate), deionized water, ethyl cellulose, and additive (organic silicone defoamer) at a mass ratio of 50:50:2:5:0.5 until homogeneous to form a mixed solution. Then, mix the aluminum powder with the mixed solution at a mass ratio of 100:100 until homogeneous to form a mixed slurry; wherein the aluminum powder has a particle size of 0.5μm~5μm and a purity of 99.99%.

[0078] Step 2: The mixed slurry formed in Step 1 is applied to the upper and lower surfaces of the aluminum foil substrate using a slit extrusion process. After a first drying treatment, an aluminum foil blank is formed. The drying temperature for the first drying treatment is 100℃, the thickness of the aluminum foil substrate is 40μm, and the thickness of the slurry coated on the upper and lower surfaces after drying is 55μm. During the drying process, the axis of the hot air nozzle is perpendicular to the foil's forward movement direction.

[0079] Step 3 involves directional heat treatment of the aluminum foil blank formed in Step 2, including: setting up 6 sets of heating devices above and below the aluminum foil blank, with each set of heating devices consisting of two heating tubes. The axial directions of these two heating tubes are at 45° and 135° to the length direction of the aluminum foil blank, respectively. The temperature of the heating tubes is set to 500°C. The aluminum foil blank is cooled with room temperature air in the interval between each heating tube. The aluminum foil blank is conveyed along its length at a speed of 4 m / min.

[0080] Step 4: Immerse the aluminum foil blank formed in Step 3 into a mixed solution of polyethylene glycol 200 and ethylene glycol, use ultrasound as a vibration source to vibrate the aluminum foil blank, and then perform a second drying treatment at 120°C to form the initial anode foil.

[0081] Step 5: Sinter the initial anode foil formed in Step 4. Sintering is carried out in a bell-type furnace. The sintering process is as follows: the bell-type furnace is heated to 610°C in argon gas at a heating rate of 15°C / min, held at that temperature for 10 hours, and then cooled with the furnace after the holding period.

[0082] Step 6: The anode foil formed in Step 5 is subjected to boiling and formation treatments. After rinsing with deionized water, it is dried at 100°C to form the target anode foil. The boiling treatment uses deionized water at 100°C for 5 minutes; the formation treatment uses a 100 g / L boric acid solution at a formation voltage of 520 V.

[0083] Example 6: A method for preparing an anode foil, comprising the following steps: Step 1: Mix the organic solvent (diethylene glycol butyl ether acetate), deionized water, ethyl cellulose, and additives (organic silicone defoamer and triethanolamine) at a mass ratio of 100:10:3:1:5 until homogeneous to form a mixed solution. Then, mix the aluminum powder with the mixed solution at a mass ratio of 100:80 until homogeneous to form a mixed slurry; wherein the aluminum powder has a particle size of 0.5μm~5μm and a purity of 99.99%.

[0084] Step 2: The mixed slurry formed in Step 1 is applied to the upper and lower surfaces of the aluminum foil substrate using a slit extrusion process. After a first drying treatment, an aluminum foil blank is formed. The drying temperature for the first drying treatment is 150℃, the thickness of the aluminum foil substrate is 50μm, and the thickness of the slurry coated on the upper and lower surfaces after drying is 60μm. During the drying process, the axis of the hot air nozzle is perpendicular to the foil's forward movement direction.

[0085] Step 3 involves directional heat treatment of the aluminum foil blank formed in Step 2, including: setting up 4 sets of heating devices above and below the aluminum foil blank, with each set of heating devices consisting of two hot air nozzles. The axial directions of these two hot air nozzles are at 30° and 140° to the length direction of the aluminum foil blank, respectively. The temperature of the hot air nozzles is set to 350°C. The aluminum foil blank is cooled with room temperature air in the interval between each hot air nozzle. The aluminum foil blank is conveyed along its length at a speed of 2 m / min.

[0086] Step 4: Immerse the aluminum foil blank formed in Step 3 in ethylene glycol, use megasonic waves as a vibration source to vibrate the aluminum foil blank, and then perform a second drying treatment at 100°C to form the initial anode foil.

[0087] Step 5: Sinter the initial anode foil formed in Step 4. Sintering is carried out in a bell-type furnace. The sintering process is as follows: the bell-type furnace is heated to 620°C in nitrogen at a heating rate of 5°C / min, held at that temperature for 8 hours, and then cooled with the furnace after the holding period.

[0088] Step 6: The anode foil formed in Step 5 is subjected to boiling water treatment and formation treatment. After washing with deionized water, it is dried at 100°C to form the target anode foil. The boiling water treatment uses deionized water at 100°C for 15 minutes; the formation treatment uses a 100 g / L boric acid solution and a formation voltage of 700 V.

[0089] Comparative Example 1 (also known as Comparative Example 1): A method for preparing an anode foil, comprising the following steps: Step 1: Mix the organic solvent (terpineol), deionized water, ethyl cellulose, and additives (organosilicone defoamer, triethanolamine dispersant, and silane coupling agent) at a mass ratio of 100:20:10:2:1:5 until homogeneous to form a mixed solution. Then, mix the aluminum powder with the mixed solution at a mass ratio of 100:150 until homogeneous to form a mixed slurry; wherein the aluminum powder has a particle size of 0.5μm~5μm and a purity of 99.99%.

[0090] Step 2: The mixed slurry formed in Step 1 is applied to the upper and lower surfaces of the aluminum foil substrate using a slit extrusion process. After drying, an aluminum foil blank is formed. The drying temperature is 140℃, the thickness of the aluminum foil substrate is 20μm, and the thickness of the slurry coated on the upper and lower surfaces after drying is 52μm. During the drying process, the axis of the heating tube is perpendicular to the direction of foil movement.

[0091] Step 3: Cracks are created on the surface of the aluminum foil blank formed in Step 2 by passing it through a 12mm diameter roller. The process is as follows: First, the aluminum foil blank is passed through the roller at a 40° angle to the roller's axis, and this is repeated 10 times. Then, the aluminum foil blank is passed through the roller at a 140° angle to the roller's axis, and this is repeated 10 times.

[0092] Step 4: Sinter the aluminum foil blank formed in Step 3. Sintering is carried out in a bell-type furnace. The sintering process is as follows: the bell-type furnace is heated to 650°C in argon gas at a heating rate of 0.1°C / min, held at that temperature for 4 hours, and then cooled with the furnace after the holding period.

[0093] Step 5: The anode foil formed in Step 4 is subjected to boiling and formation treatments. After rinsing with deionized water, it is dried at 100°C to form the target anode foil. The boiling treatment uses deionized water at 100°C for 10 minutes; the formation treatment uses a 100 g / L boric acid solution at a formation voltage of 520 V.

[0094] Comparative Example 2 (also known as Comparative Example 2): A method for preparing an anode foil, comprising the following steps: Step 1: Mix the organic solvent (terpineol), deionized water, ethyl cellulose, and additives (organosilicone defoamer, triethanolamine dispersant, and silane coupling agent) at a mass ratio of 100:20:10:2:1:5 until homogeneous to form a mixed solution. Then, mix the aluminum powder with the mixed solution at a mass ratio of 100:150 until homogeneous to form a mixed slurry; wherein the aluminum powder has a particle size of 0.5μm~5μm and a purity of 99.99%.

[0095] Step 2: The mixed slurry formed in Step 1 is applied to the upper and lower surfaces of the aluminum foil substrate using a slit extrusion process. After drying, an aluminum foil blank is formed. The drying temperature is 140℃, the thickness of the aluminum foil substrate is 20μm, and the thickness of the slurry coated on the upper and lower surfaces after drying is 52μm. During the drying process, the axis of the heating tube is perpendicular to the direction of foil movement.

[0096] Step 3: Sinter the aluminum foil blank formed in Step 2. Sintering is carried out in a bell-type furnace. The sintering process is as follows: the bell-type furnace is heated to 630°C in nitrogen at a heating rate of 10°C / min, held at that temperature for 10 hours, and then cooled with the furnace after the holding period.

[0097] Step 4: The anode foil formed in Step 3 is subjected to boiling and formation treatments. After rinsing with deionized water, it is dried at 100°C to form the target anode foil. The boiling treatment uses deionized water at 100°C for 10 minutes; the formation treatment uses a 100 g / L boric acid solution at a formation voltage of 520 V.

[0098] Comparative Example 3 (also known as Comparative Example 3): A method for preparing an anode foil, comprising the following steps: Step 1: Mix organic solvents (terpineol and diethylene glycol butyl ether acetate), deionized water, ethyl cellulose, and additives (diethanolamine and silane coupling agent) at a mass ratio of 30:70:15:8:2:8 until homogeneous to form a mixed solution. Then, mix aluminum powder with the mixed solution at a mass ratio of 100:120 until homogeneous to form a mixed slurry; wherein the aluminum powder has a particle size of 0.5μm~5μm and a purity of 99.99%.

[0099] Step 2: The mixed slurry formed in Step 1 is applied to the upper and lower surfaces of the aluminum foil substrate using a slit extrusion coating method. After drying, an aluminum foil blank is formed. The drying temperature is 120℃, the thickness of the aluminum foil substrate is 60μm, and the thickness of the slurry coated on the upper and lower surfaces after drying is 56μm. During the drying process, the axis of the hot air nozzle is perpendicular to the foil's forward movement direction.

[0100] Step 3: Sinter the aluminum foil blank formed in Step 2. Sintering is carried out in a bell-type furnace. The sintering process is as follows: the bell-type furnace is heated to 640°C in a vacuum at a heating rate of 5°C / min, held at that temperature for 8 hours, and then cooled with the furnace after the holding period.

[0101] Step 4: The anode foil formed in Step 3 is subjected to boiling and formation treatments. After rinsing with deionized water, it is dried at 100°C to form the target anode foil. The boiling treatment uses deionized water at 100°C for 5 minutes; the formation treatment uses a 100 g / L boric acid solution at a formation voltage of 200 V.

[0102] Comparative Example 4 (also known as Comparative Example 4): A method for preparing an anode foil, comprising the following steps: Step 1: Mix the organic solvent (diethylene glycol butyl ether acetate), deionized water, ethyl cellulose, and additives (organosilicone defoamer, triethanolamine, and silane coupling agent) at a mass ratio of 100:18:8:2:2:5 until homogeneous to form a mixed solution. Then, mix the aluminum powder with the mixed solution at a mass ratio of 100:60 until homogeneous to form a mixed slurry; wherein the aluminum powder has a particle size of 0.5μm~5μm and a purity of 99.99%.

[0103] Step 2: The mixed slurry formed in Step 1 is applied to the upper and lower surfaces of the aluminum foil substrate using a slit extrusion coating method. After drying, an aluminum foil blank is formed. The drying temperature is 110℃, the thickness of the aluminum foil substrate is 30μm, and the thickness of the slurry coated on the upper and lower surfaces after drying is 60μm. During the drying process, the axis of the heating tube is perpendicular to the foil's forward movement direction.

[0104] Step 3: Sinter the aluminum foil blank formed in Step 2. Sintering is carried out in a bell-type furnace. The sintering process is as follows: the bell-type furnace is heated to 650°C in argon gas at a heating rate of 0.1°C / min, held at that temperature for 4 hours, and then cooled with the furnace after the holding period.

[0105] Step 4: The anode foil formed in Step 3 is subjected to boiling and formation treatments. After rinsing with deionized water, it is dried at 100°C to form the target anode foil. The boiling treatment uses deionized water at 100°C for 15 minutes; the formation treatment uses a 100 g / L boric acid solution at a formation voltage of 700 V.

[0106] Comparative Example 5 (also known as Comparative Example 5): A method for preparing an anode foil, comprising the following steps: Step 1: Mix the organic solvent (terpineol), deionized water, ethyl cellulose, and additives (organosilicone defoamer and silane coupling agent) at a mass ratio of 100:5:1.5:0.5:2 until homogeneous to form a mixed solution. Then, mix the aluminum powder with the mixed solution at a mass ratio of 100:40 until homogeneous to form a mixed slurry; wherein the aluminum powder has a particle size of 0.5μm~5μm and a purity of 99.99%.

[0107] Step 2: The mixed slurry formed in Step 1 is applied to the upper and lower surfaces of the aluminum foil substrate using a slit extrusion coating method. After drying, an aluminum foil blank is formed. The drying temperature is 130℃, the thickness of the aluminum foil substrate is 30μm, and the thickness of the slurry coated on the upper and lower surfaces after drying is 50μm. During the drying process, the axis of the heating tube is perpendicular to the foil's forward movement direction.

[0108] Step 3: Sinter the aluminum foil blank formed in Step 2. Sintering is carried out in a bell-type furnace. The sintering process is as follows: the bell-type furnace is heated to 600°C in a vacuum at a heating rate of 20°C / min, held at that temperature for 12 hours, and then cooled with the furnace after the holding period.

[0109] Step 4: The anode foil formed in Step 3 is subjected to boiling and formation treatments. After rinsing with deionized water, it is dried at 100°C to form the target anode foil. The boiling treatment uses deionized water at 100°C for 10 minutes; the formation treatment uses a 100 g / L boric acid solution at a formation voltage of 200 V.

[0110] Comparative Example 6 (also known as Comparative Example 6): A method for preparing an anode foil, comprising the following steps: Step 1: Mix the organic solvent (terpineol and diethylene glycol butyl ether acetate), deionized water, ethyl cellulose, and additive (organic silicone defoamer) at a mass ratio of 50:50:2:5:0.5 until homogeneous to form a mixed solution. Then, mix the aluminum powder with the mixed solution at a mass ratio of 100:100 until homogeneous to form a mixed slurry; wherein the aluminum powder has a particle size of 0.5μm~5μm and a purity of 99.99%.

[0111] Step 2: The mixed slurry formed in Step 1 is applied to the upper and lower surfaces of the aluminum foil substrate using a slit extrusion coating method. After drying, an aluminum foil blank is formed. The drying temperature is 100℃, the thickness of the aluminum foil substrate is 40μm, and the thickness of the slurry coated on the upper and lower surfaces after drying is 55μm. During the drying process, the axis of the hot air nozzle is perpendicular to the foil's forward movement direction.

[0112] Step 3: Sinter the aluminum foil blank formed in Step 2. Sintering is carried out in a bell-type furnace. The sintering process is as follows: the bell-type furnace is heated to 610°C in argon gas at a heating rate of 15°C / min, held at that temperature for 10 hours, and then cooled with the furnace after the holding period.

[0113] Step 4: The anode foil formed in Step 3 is subjected to boiling and formation treatments. After rinsing with deionized water, it is dried at 100°C to form the target anode foil. The boiling treatment uses deionized water at 100°C for 5 minutes; the formation treatment uses a 100 g / L boric acid solution at a formation voltage of 520 V.

[0114] Comparative Example 7 (also known as Comparative Example 7): A method for preparing an anode foil, comprising the following steps: Step 1: Mix the organic solvent (diethylene glycol butyl ether acetate), deionized water, ethyl cellulose, and additives (organic silicone defoamer and triethanolamine) at a mass ratio of 100:10:3:1:5 until homogeneous to form a mixed solution. Then, mix the aluminum powder with the mixed solution at a mass ratio of 100:80 until homogeneous to form a mixed slurry; wherein the aluminum powder has a particle size of 0.5μm~5μm and a purity of 99.99%.

[0115] Step 2: The mixed slurry formed in Step 1 is applied to the upper and lower surfaces of the aluminum foil substrate using a slit extrusion coating method. After drying, an aluminum foil blank is formed. The drying temperature is 150℃, the thickness of the aluminum foil substrate is 50μm, and the thickness of the slurry coated on the upper and lower surfaces after drying is 60μm. During the drying process, the axis of the hot air nozzle is perpendicular to the foil's forward movement direction.

[0116] Step 3: Sinter the initial anode foil formed in Step 2. Sintering is carried out in a bell-type furnace. The sintering process is as follows: the bell-type furnace is heated to 620°C in nitrogen at a heating rate of 5°C / min, held at that temperature for 8 hours, and then cooled with the furnace after the holding period.

[0117] Step 4: The anode foil formed in Step 3 is subjected to boiling and formation treatments. After rinsing with deionized water, it is dried at 100°C to form the target anode foil. The boiling treatment uses deionized water at 100°C for 15 minutes; the formation treatment uses a 100 g / L boric acid solution at a formation voltage of 700 V.

[0118] The target anode foils prepared in Examples 1-6 and Comparative Examples 1-7 will be tested below.

[0119] Specifically, during the testing process, a clamp with a curvature radius of 3.5 mm (referring to the electronic industry standard: SJ / T 11140-2022 Electrode Foil for Aluminum Electrolytic Capacitors) was used for bending performance testing. Based on this, the test results obtained are as follows: the anode foil formed in Comparative Example 1 underwent 162 longitudinal bends and 144 transverse bends; the anode foil formed in Comparative Example 2 underwent 6 longitudinal bends and 9 transverse bends; and the anode foil formed in Example 1 underwent 183 longitudinal bends and 167 transverse bends. Compared with Comparative Example 1 and Comparative Example 2, the anode foil formed in Example 1 had the highest number of bends. Furthermore, Figure 2 The image shows a light microscope image of the anode foil prepared using the method provided in Comparative Example 1. Figure 3 Figures 4(a) and 4(b) are optical micrographs of the anode foil formed using the preparation method provided in Comparative Example 2. Figure 2 It can be seen that the anode foil formed in Comparative Example 1 has irregular multidirectional microcracks, but the surface of the anode foil has defects such as scratches and powder shedding; from Figure 3 It can be seen that the surface of the anode foil formed in Comparative Example 2 is free of cracks; as can be seen from Figure 4, the surface of the anode foil formed in Example 1 has irregular multidirectional microcracks. Figure 4a ), and most of the cracks are formed along the indentations at the edges of the orange peel texture. Figure 4b The anode foil has a good surface quality and is free from defects such as scratches and powder shedding. The preparation method of Example 1 can form an anode foil with a complete surface and good bending performance.

[0120] Meanwhile, the bending performance test results (clamp curvature radius of 3.5 mm) of the anode foils prepared in Comparative Examples 1-7 and Examples 1-6 are shown in Table 1: Table 1

[0121] As shown in Table 1, the anode foil prepared in Comparative Example 1, treated with inclined rollers, had 162 longitudinal bends and 144 transverse bends. The anode foil prepared in Example 1, which underwent directional heat treatment and vibration treatment, had 183 longitudinal bends and 167 transverse bends. The anode foil prepared in Example 1 showed an increase in the number of bends compared to the anode foil prepared in Comparative Example 1. Furthermore, the anode foils prepared in Comparative Examples 2-7 without directional heat treatment and vibration treatment exhibited poor longitudinal and transverse bend performance, with each foil having fewer than 10 bends. The anode foils prepared in Examples 1-6, which underwent directional heat treatment and vibration treatment, achieved more than 170 longitudinal bends and more than 150 transverse bends. Comparative Examples 2-7 and Examples 1-6 show that, under the same test conditions, the anode foils prepared in Examples 1-6 have a bending count that is more than 15 times higher than those prepared in Control Examples 2-7, significantly improving the longitudinal and transverse bending performance of the anode foil and meeting machining requirements. Therefore, the anode foil preparation method provided in this disclosure can improve the bending performance of the anode foil, thereby improving the overall performance of the device.

[0122] 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.

[0123] 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.

[0124] 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 an anode foil, characterized in that, include: Step S101: Prepare a mixed slurry, the mixed slurry comprising aluminum powder and a mixed solution, the mixed solution being prepared by mixing organic solvent, deionized water, binder and additives; Step S102: The mixed slurry is coated on the surface of the aluminum foil substrate to obtain an aluminum foil with a slurry film layer, and the aluminum foil with the slurry film layer is subjected to a first drying treatment to form an aluminum foil blank. Step S103: The aluminum foil blank is subjected to directional heat treatment, and the directional heat-treated aluminum foil blank is subjected to vibration treatment and a second drying treatment to form an initial anode foil; wherein, the initial anode foil is obtained by: immersing the directional heat-treated aluminum foil blank in an immersion solution, then vibrating the aluminum foil blank in the immersion solution using sound waves as a vibration source, and then performing a second drying treatment on the vibrated aluminum foil blank at a drying temperature of 100℃~200℃ to obtain the initial anode foil; the directional heat treatment of the aluminum foil blank... The process is carried out as follows: 2 to 10 sets of heating devices are set above and below the aluminum foil blank. Each set of heating devices is set with two heating elements for directional heat treatment. In each set of heating devices, the transverse axial direction of the two heating elements forms an angle of 30° to 60° and an angle of 120° to 150° with the length direction of the aluminum foil blank, respectively. The temperature of the two heating elements is set to 350°C to 500°C. The interval between the heating elements is cooled with room temperature air. The aluminum foil blank is conveyed along the length direction at a speed of 1m / min to 10m / min. Step S104: The initial anode foil is subjected to sintering and boiling treatment to form a first intermediate anode foil, and the first intermediate anode foil is subjected to formation treatment to form an oxide layer on the first intermediate anode foil, thereby obtaining the target anode foil.

2. The preparation method according to claim 1, characterized in that, In the mixed slurry, the mass ratio of the aluminum powder to the mixed solution is 100:(40~150); In the mixed solution, the mass ratio of the organic solvent, deionized water, binder and additive is 100:(2~20):(1.5~10):(0.5~10).

3. The preparation method according to claim 2, characterized in that, The organic solvent is one or both of terpineol and diethylene glycol butyl ether acetate; The binder is ethyl cellulose; The additive includes one or more of the following: defoamer, dispersant, and coupling agent; The defoamer is an organosilicon defoamer or a polyether defoamer, the dispersant is diethanolamine or triethanolamine, and the coupling agent is a silane coupling agent.

4. The preparation method according to claim 1, characterized in that, The aluminum foil substrate has a thickness of 20μm to 60μm and has an upper surface and a lower surface that are disposed opposite to each other; the aluminum foil blank is obtained by the following method: Using the mixed slurry, the aluminum foil substrate is coated on both sides to form a slurry film layer of the same thickness on the upper and lower surfaces of the aluminum foil substrate, thereby obtaining an aluminum foil with a slurry film layer; The aluminum foil with a slurry film layer is subjected to a first drying treatment at a drying temperature of 100℃~150℃ to obtain the aluminum foil blank; wherein, during the first drying treatment, the axis of the heating element is perpendicular to the foil advancing direction; the heating element is a heating tube or a hot air nozzle; in the obtained aluminum foil blank, the thickness of the slurry film layer is 50μm~60μm.

5. The preparation method according to claim 1, characterized in that, The heating element is a heating tube or a hot air nozzle.

6. The preparation method according to claim 1, characterized in that, The soaking solution includes one or more of polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400, ethylene glycol, and propylene glycol; The vibration source is an ultrasonic wave or a megason.

7. The preparation method according to claim 1, characterized in that, The first intermediate anode foil is obtained in the following manner: The initial anode foil is heated from room temperature to 600℃ to 650℃ in a nitrogen, argon, or vacuum atmosphere at a heating rate of 0.1℃ / min to 20℃ / min, and held at that temperature for 4h to 12h. After the heat preservation is completed, the initial anode foil is cooled in the furnace to obtain the sintered initial anode foil. The sintered initial anode foil is then boiled in deionized water at 100°C for 5 to 15 minutes to obtain the first intermediate anode foil.

8. The preparation method according to claim 1, characterized in that, The target anode foil is obtained by forming the first intermediate anode foil under a formation voltage of 200V~700V.

9. An aluminum electrolytic capacitor, characterized in that, The aluminum electrolytic capacitor includes a target anode foil prepared by the method for preparing anode foil according to any one of claims 1-8.

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