Laminated foil for aluminum electrolytic capacitor, method for producing the same, and aluminum electrolytic capacitor

Abstract

The present application belongs to the technical field of electrode material, and particularly relates to a laminated foil for aluminum electrolytic capacitor, a preparation method thereof and an aluminum electrolytic capacitor. The laminated foil for aluminum electrolytic capacitor comprises a substrate and a sintered layer composed of aluminum sintered body on at least one side surface of the substrate. The sintered layer on each side has a plurality of cracks. Along the thickness direction of the sintered layer, each of the plurality of cracks independently extends from the side surface of the sintered layer away from the substrate to the substrate surface, and the depth of the crack is less than the thickness of the sintered layer. In the laminated foil of the present application, the depth of the crack does not reach the substrate surface, does not cause damage to the continuity of the material, improves the bending strength and plasticity of the laminated foil, so that the stress is not concentrated in one point and released in the process of winding and cutting of the foil roll, reduces the risk of breaking during cutting, avoids the immersion of the electrolyte into the substrate surface during the formation process, and reduces the corrosion of the substrate.

Description

Technical Field

[0001] This invention belongs to the field of electrode material technology, specifically relating to a multilayer foil for aluminum electrolytic capacitors, its preparation method, and aluminum electrolytic capacitors. Background Technology

[0002] Since the 1990s, with the continuous development of electronic information technology and the expansion of application fields, aluminum electrolytic capacitors have been developing towards miniaturization, high performance, and high reliability.

[0003] Multilayer foil is a type of electrode foil, a core raw material for capacitors. It has a specific surface area 25%–35% larger than traditional etched foil, and its production process is pollution-free. It is expected to gradually replace most traditional etched foils in the future, showing promising development prospects. However, currently, multilayer foil has poor strength and is prone to cracking, breakage, and burrs during the cutting process, posing significant challenges to capacitor production. Summary of the Invention

[0004] The main objective of this invention is to provide a multilayer foil for aluminum electrolytic capacitors, its preparation method, and an aluminum electrolytic capacitor. In this invention, the depth of the cracks in the multilayer foil does not reach the surface of the substrate, thus not disrupting the continuity of the material. This improves the bending strength and plasticity of the multilayer foil, preventing stress concentration at a single point during the winding and cutting process, reducing the risk of breakage during cutting, and preventing the bath solution from seeping into the substrate surface during the formation process, thereby reducing corrosion of the substrate.

[0005] To achieve the above objectives, the present invention provides the following technical solutions.

[0006] The first aspect of the present invention provides a multilayer foil for aluminum electrolytic capacitors, comprising a substrate and a sintered layer formed of an aluminum sintered body on at least one surface of the substrate, wherein each side of the sintered layer has a plurality of cracks extending independently from the side of the sintered layer away from the substrate towards the substrate surface along the thickness direction of the sintered layer, and the depth of the cracks is less than the thickness of the sintered layer.

[0007] In some embodiments of the present invention, the sintered layer is present on both opposite surfaces of the substrate; based on the substrate, multiple cracks in the sintered layer located on both sides are independently and asymmetrically distributed.

[0008] In some embodiments of the present invention, based on the sintered layer on one side, the plurality of cracks are spaced apart along the length direction of the sintered layer.

[0009] In some embodiments of the present invention, based on the sintered layer on one side, the spacing between two adjacent cracks is independently 50 μm to 350 μm.

[0010] In some embodiments of the present invention, based on the sintered layer on one side, the spacing between two adjacent cracks is independently 100 μm to 320 μm.

[0011] In some embodiments of the present invention, based on the sintered layer on one side, the spacing between two adjacent cracks is independently 100 μm to 300 μm.

[0012] In some embodiments of the present invention, based on the sintered layer on one side, the spacing between two adjacent cracks is independently 100 μm to 250 μm.

[0013] In some embodiments of the present invention, multiple cracks in the sintered layer located on both sides are alternately distributed along the length of the sintered layer.

[0014] In some embodiments of the present invention, the width of each crack along the length direction of the sintered layer is independently 0.1 μm to 5 μm.

[0015] In some embodiments of the invention, the depth of each crack is independently less than or equal to 95% of the thickness of the sintered layer.

[0016] In some embodiments of the invention, the depth of each crack is independently 40% to 95% of the thickness of the sintered layer.

[0017] In some embodiments of the present invention, the depth of each crack is independently 50% to 95% of the thickness of the sintered layer.

[0018] In some embodiments of the present invention, the thickness of the sintered layer on each side is independently 45 μm to 200 μm.

[0019] In some embodiments of the present invention, the thickness of the substrate is 10 μm to 50 μm.

[0020] In some embodiments of the present invention, the substrate is selected from aluminum foil.

[0021] The second aspect of the present invention provides a method for preparing the multilayer foil for aluminum electrolytic capacitors as described in the first aspect. The method includes: coating a slurry prepared from aluminum powder onto at least one side surface of a substrate, and sequentially performing drying, straightening and sintering treatments to obtain the multilayer foil for aluminum electrolytic capacitors.

[0022] In some embodiments of the present invention, the tensioning process includes: passing the dried foil roll through a roller at a uniform speed under the tension of the roller. A roller is a mechanical element that transmits force through rotation, and is generally cylindrical in shape, often made of materials such as metal or rubber.

[0023] In some embodiments of the present invention, the diameter of the roller is 3 mm to 20 mm.

[0024] In some embodiments of the present invention, the tension of the roller is 5 kg to 50 kg.

[0025] In some embodiments of the present invention, the number of passes is 1 to 5.

[0026] In some embodiments of the present invention, the angle at which the foil roll passes through the roller is 90° to 180°.

[0027] In some embodiments of the present invention, the drying temperature is 30°C to 100°C, and the drying time is 1 min to 30 min.

[0028] In some embodiments of the present invention, the particle size D50 of the aluminum powder is 1 μm to 10 μm.

[0029] In some embodiments of the present invention, the particle size D50 of the aluminum powder is 3μm to 5μm.

[0030] In some embodiments of the present invention, the sintering temperature is 560°C to 650°C, and the sintering time is 2h to 20h.

[0031] A third aspect of the present invention provides an aluminum electrolytic capacitor comprising the multilayer foil for an aluminum electrolytic capacitor as described in the first aspect or the multilayer foil for an aluminum electrolytic capacitor prepared by the preparation method described in the second aspect.

[0032] Compared with the prior art, the present invention achieves the following technical effects:

[0033] In this invention, the crack depth in the sintered layer of the laminated foil does not reach the surface of the substrate, thus not damaging the continuity of the material. This improves the bending strength and plasticity of the laminated foil, so that stress will not be concentrated at one point during the winding and cutting process, reducing the risk of breakage during cutting. At the same time, it avoids the bath solution from immersing into the substrate surface during the formation process, thereby reducing corrosion of the substrate.

[0034] In this invention, the sintered layer of the laminated foil contains asymmetrically distributed cracks, which can further improve the bending strength of the laminated foil and enhance the plasticity of the material.

[0035] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0036] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. In the drawings:

[0037] Figure 1 This is a schematic cross-sectional view of a multilayer foil for an aluminum electrolytic capacitor according to some embodiments of the present invention;

[0038] Figure 2 This is a cross-sectional view of the multilayer foil for aluminum electrolytic capacitors prepared in Embodiment 1 of the present invention;

[0039] Figure 3 This is a cross-sectional view of the multilayer foil for aluminum electrolytic capacitors prepared in Embodiment 2 of the present invention;

[0040] Figure 4 This is a cross-sectional view of the multilayer foil for aluminum electrolytic capacitors prepared in Comparative Example 1 of the present invention.

[0041] Figure Labels

[0042] 100. Laminated foil;

[0043] 10. Substrate; 20. Sintered layer; 21. Crack. Detailed Implementation

[0044] Exemplary embodiments of the present invention will now be described in more detail with reference to specific examples. It should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the invention, are intended to cover non-exclusive inclusion.

[0046] In the description of the embodiments of the present invention, the technical terms "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0047] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0048] In the description of the embodiments of this invention, the term "and / or" is merely a description of the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists, A and B exist simultaneously, and B exists. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0049] In the description of the embodiments of the present invention, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0050] In the description of the embodiments of the present invention, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention.

[0051] In the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention according to the specific circumstances.

[0052] Existing multilayer foils have poor bending strength, and stress concentration during the cutting process makes them prone to cracking and breakage. Furthermore, the cutting process generates a lot of burrs, which brings great difficulties to the production of capacitors.

[0053] Furthermore, in existing technologies, most cracks in the cross-section of the sintered layer are symmetrically distributed, and the crack depth extends into the substrate. Cracks at symmetrical locations disrupt the continuity of the material, resulting in the weakest mechanical properties at those locations. In subsequent processing, such as formation, cutting, and winding, corrosion, fracture, and other adverse conditions are likely to occur.

[0054] This invention provides a multilayer foil for aluminum electrolytic capacitors, see [link to relevant documentation]. Figure 1 As shown, the laminated foil 100 includes a substrate 10 and a sintered layer 20 made of aluminum sintered body on at least one side surface of the substrate 10. Each side of the sintered layer 20 has a plurality of cracks 21. Along the thickness direction of the sintered layer 20, the plurality of cracks 21 extend independently from the side surface of the sintered layer 20 away from the substrate 10 toward the surface of the substrate 10, and the depth of the cracks 21 is less than the thickness of the sintered layer 20.

[0055] In embodiments of the present invention, a sintered layer 20 is provided on one side of the substrate 10, i.e., one side, or on opposite sides of the substrate 10, i.e., both sides. The sintered layer 20 is composed of an aluminum sintered body, and each side of the sintered layer 20 has a plurality of cracks 21. See also Figure 1 As shown, along the thickness direction of the sintered layer 20, the crack 21 extends from the side of the sintered layer 20 away from the substrate 10 to the surface of the substrate 10, and the depth of the crack 21 is less than the thickness of the sintered layer 20. This ensures that the crack depth on the sintered layer 20 does not reach the surface of the substrate 10, thus not disrupting the continuity of the material, improving the bending strength and plasticity of the laminated foil, so that the stress will not be concentrated at one point during the winding and cutting process of the foil roll, reducing the risk of foil roll breakage, and at the same time preventing the bath solution from immersing into the surface of the substrate 10 during the formation process, thereby reducing the corrosion of the substrate 10.

[0056] See also Figure 1 As shown, the sintered layer 20 located on any side of the substrate 10 has a plurality of cracks 21, each of which extends independently along the thickness direction of the sintered layer 20 and the depth of extension is less than the thickness of the sintered layer 20.

[0057] In some embodiments of the present invention, the depth H of each crack 21 is independently less than or equal to 95% of the thickness of the sintered layer 20, further reducing foil roll breakage and reducing corrosion of the substrate 10 by the bath solution. The depth H of each crack 21 provided by the present invention can be independently 40% to 95% of the thickness of the sintered layer 20; preferably, the depth H of each crack 21 is independently 50% to 95% of the thickness of the sintered layer 20. Exemplarily, the depth H of the crack 21 can be one of 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or 95% of the thickness of the sintered layer 20, or any value satisfying the above range.

[0058] In some embodiments of the present invention, during the straightening and sintering processes, a small number of cracks 21 may reach the surface of the aluminum foil in depth H. In the present invention, the proportion of cracks 21 reaching the surface of the aluminum foil in depth H is less than 5%. Exemplarily, the proportion of cracks 21 reaching the surface of the aluminum foil in depth H is one of 1%, 2%, 3%, or 4%, or any value satisfying the above range. That is, the proportion of cracks 21 not reaching the surface of the aluminum foil in depth H is greater than or equal to 95%. Exemplarily, the proportion of cracks 21 not reaching the surface of the aluminum foil in depth H is one of 95%, 96%, 97%, 98%, 99%, or 100%, or any value satisfying the above range.

[0059] In some embodiments of the present invention, the width L of each crack 21 along the length direction of the sintered layer 20 is independently 0.1 μm to 5 μm. The width L of the crack 21 provided by the present invention can be any value within the range of any two values ​​in the above range, for example, it can be 0.1 μm to 1.5 μm, or 1.5 μm to 3 μm, or 3 μm to 5 μm, and so on. The width L of the crack 21 provided by the present invention can also be one of 0.1μm, 0.2μm, 0.4μm, 0.5μm, 0.6μm, 0.8μm, 1.0μm, 1.2μm, 1.4μm, 1.5μm, 1.6μm, 1.8μm, 2.0μm, 2.2μm, 2.4μm, 2.5μm, 2.6μm, 2.8μm, 3.0μm, 3.2μm, 3.4μm, 3.5μm, 3.6μm, 3.8μm, 4.0μm, 4.2μm, 4.4μm, 4.5μm, 4.6μm, 4.8μm, and 5.0μm, or any value satisfying the above range.

[0060] See also Figure 1As shown, for any side of the sintered layer 20 of the substrate 10, that is, for a single side of the sintered layer 20, a plurality of cracks 21 are arranged at intervals along the length direction of the sintered layer 20.

[0061] In some embodiments of the present invention, for a single-sided sintered layer 20, the spacing D between two adjacent cracks 21 can each be independently 50 μm to 350 μm. The spacing D between two adjacent cracks 21 provided by the present invention can be a value within an interval consisting of any two values ​​in the above-mentioned range, such as 50 μm to 200 μm, 100 μm to 350 μm, 100 μm to 300 μm, 200 μm to 280 μm, 280 μm to 350 μm, and so on. The spacing between two adjacent cracks 21 provided by the present invention can also be one of 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm, 210μm, 220μm, 230μm, 240μm, 250μm, 260μm, 270μm, 280μm, 290μm, 300μm, 310μm, 320μm, 330μm, 340μm, 350μm or any value satisfying the above range.

[0062] See also Figure 1 As shown, the substrate 10 has sintered layers 20 on both sides of its opposite surfaces, i.e., on both sides of the substrate 10. Based on the substrate 10, multiple cracks 21 on the sintered layers 20 on both sides are independently and asymmetrically distributed.

[0063] In the embodiments of the present invention, the multiple cracks 21 in the sintered layer 20 located on the substrate A side and the multiple cracks 21 in the sintered layer 20 located on the substrate B side are each independently and asymmetrically distributed, and the depth H of the cracks 21 does not reach the surface of the substrate 10, so as not to damage the continuity of the material, further improving the bending strength and plasticity of the laminated foil. In addition, during the winding and cutting process of the foil roll, the stress will not be concentrated at one point, reducing the risk of foil roll breakage. At the same time, it avoids the bath liquid from immersing into the surface of the substrate 10 during the formation process, thereby reducing the corrosion of the substrate 10.

[0064] In some embodiments of the present invention, multiple cracks 21 on both sides of the sintered layer 20 are alternately distributed along the length direction of the sintered layer 20. This can be understood as multiple cracks 21 on the sintered layer 20 on the substrate A side and multiple cracks 21 on the sintered layer 20 on the substrate B side being alternately arranged along the length direction of the sintered layer 20, further improving the bending strength of the laminated foil and enhancing the plasticity of the material.

[0065] In embodiments of the present invention, for the sintered layer 20 on any side of the substrate 10, i.e., for each side of the sintered layer 20, the thickness of the sintered layer 20 can independently be 45 μm to 200 μm. The thickness of the sintered layer 20 provided by the present invention can be a value within the range formed by any two values ​​in the above range, for example, it can be 45 μm to 60 μm, 60 μm to 75 μm, 75 μm to 100 μm, 100 μm to 200 μm, and so on. The thickness of the sintered layer 20 provided by the present invention can also be one of 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm, 105μm, 110μm, 115μm, 120μm, 125μm, 130μm, 135μm, 140μm, 145μm, 150μm, 155μm, 160μm, 165μm, 170μm, 175μm, 180μm, 185μm, 190μm, 195μm, and 200μm, or any value satisfying the above range.

[0066] In embodiments of the present invention, the thickness of the substrate 10 can be from 10 μm to 50 μm. The thickness of the substrate 10 provided by the present invention can be any value within the range formed by any two values ​​within the aforementioned range, for example, it can be from 10 μm to 30 μm, or from 30 μm to 50 μm, and so on. The thickness of the substrate 10 provided by the present invention can also be one of 10 μm, 20 μm, 30 μm, 40 μm, and 50 μm, or any value satisfying the aforementioned range.

[0067] In embodiments of the present invention, the substrate 10 may be a substrate used as a multilayer foil for aluminum electrolytic capacitors, such as substrates known in the art.

[0068] In some embodiments of the present invention, the substrate 10 may be selected from aluminum foil made of pure aluminum or aluminum alloy.

[0069] The present invention also provides a method for preparing multilayer foil for aluminum electrolytic capacitors. The key is to perform tension straightening treatment on the substrate coated with slurry before sintering, thereby improving the bending strength and plasticity of the multilayer foil. In addition, the stress will not be concentrated at one point during the winding and cutting process of the foil roll, reducing the risk of foil roll breakage. At the same time, it avoids the bath liquid from immersing into the substrate surface during the formation process, thereby reducing corrosion of the substrate.

[0070] The method for preparing multilayer foil for aluminum electrolytic capacitors in this invention is carried out according to the following steps.

[0071] (1) Prepare slurry using aluminum powder as raw material.

[0072] In an embodiment of the present invention, aluminum powder is added to a colloid and mixed evenly to obtain a slurry.

[0073] In some embodiments of the present invention, the colloid may be colloid A formed by solvent and crosslinking agent A, colloid B formed by solvent and crosslinking agent B, or a mixed colloid formed by solvent, crosslinking agent A and crosslinking agent B.

[0074] In some embodiments of the present invention, the solvent is not particularly limited and may be one or more of water, ethanol, toluene, and acetone.

[0075] In some embodiments of the present invention, the crosslinking agent A is not particularly limited and may be one or more of natural resins, organic substances, inorganic substances, etc. Specifically, the crosslinking agent A may be one or more of epoxy resin, polyurethane, acrylic resin, and phthalic anhydride.

[0076] In some embodiments of the present invention, the crosslinking agent B is not particularly limited and may be one or more of natural resins, organic substances, inorganic substances, etc. Specifically, the crosslinking agent B may be one or more of epoxy resin, polyurethane, acrylic resin, and phthalic anhydride.

[0077] In some embodiments of the present invention, a mixed adhesive formed by solvent and crosslinking agent A and crosslinking agent B is used.

[0078] In some embodiments of the present invention, crosslinking agent A and crosslinking agent B may be the same or different.

[0079] In some embodiments of the present invention, the mass percentage of crosslinking agent A in colloid A is 5% to 30%. The mass percentage of crosslinking agent A in colloid A provided by the present invention can be any value within the range formed by any two values ​​within the above-mentioned range, for example, it can be 5% to 15%, or 15% to 30%, and so on. The mass percentage of crosslinking agent A in colloid A provided by the present invention can also be one of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or any value satisfying the above-mentioned range.

[0080] In some embodiments of the present invention, the mass percentage of crosslinking agent B in colloid B is 5% to 30%. The mass percentage of crosslinking agent B in colloid B provided by the present invention can be any value within the range formed by any two values ​​within the above-mentioned range, for example, it can be 5% to 15%, or 15% to 30%, and so on. The mass percentage of crosslinking agent B in colloid B provided by the present invention can also be one of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, and 30%, or any value satisfying the above-mentioned range.

[0081] In some embodiments of the present invention, the mixed adhesive may be prepared by first preparing colloid A and colloid B separately, and then mixing colloid A and colloid B; or it may be prepared by mixing crosslinking agent A and crosslinking agent B.

[0082] In some embodiments of the present invention, the mass of the mixed adhesive is 5% to 20% of the mass of the aluminum powder. The mass of the mixed adhesive provided by the present invention is the mass of aluminum powder within any two values ​​within the above-mentioned range, for example, it can be 5% to 10%, 10% to 15%, 15% to 20%, and so on. The mass of the aluminum mixed adhesive provided by the present invention is one of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20% of the mass of the aluminum powder, or any ratio satisfying the above range.

[0083] In some embodiments of the present invention, the particle size D50 of the aluminum powder can be 1 μm to 10 μm; preferably, the particle size D50 of the aluminum powder can be 3 μm to 5 μm. Exemplarily, the particle size D50 of the aluminum powder can be one of 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, and 10 μm, or any value satisfying the above range.

[0084] (2) A coating is formed on the surface of the substrate.

[0085] In an embodiment of the present invention, the slurry obtained in step (1) is coated on at least one side of the substrate to form a coating on the substrate surface.

[0086] In some embodiments of the present invention, a transfer coating machine is used to uniformly coat the slurry onto the opposite surfaces of a substrate with a thickness of 10 μm to 50 μm, and the coating thickness on one side is controlled to be 45 μm to 200 μm. The thickness of the substrate provided by the present invention can be any value within the range formed by any two values ​​within the above-mentioned range, for example, it can be 10 μm to 25 μm, or 25 μm to 50 μm, and so on. The thickness of the substrate provided by the present invention can also be one of 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, and 50 μm, or any value satisfying the above range. The coating thickness on one side provided by the present invention can be any value within the range formed by any two values ​​within the above-mentioned range, for example, it can be 45 μm to 60 μm, or 60 μm to 75 μm, or 75 μm to 100 μm, or 100 μm to 200 μm, and so on. The thickness of the substrate provided by the present invention can also be one of 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm, 105μm, 110μm, 115μm, 120μm, 125μm, 130μm, 135μm, 140μm, 145μm, 150μm, 155μm, 160μm, 165μm, 170μm, 175μm, 180μm, 185μm, 190μm, 195μm, and 200μm, or any value satisfying the above range.

[0087] (3) Drying treatment.

[0088] In an embodiment of the present invention, the substrate with the coating obtained after coating is dried.

[0089] In some embodiments of the present invention, the drying temperature can be between 30°C and 100°C. The drying temperature provided by the present invention can be any value within the range formed by any two values ​​within the above-mentioned range, for example, it can be 30°C to 60°C, or 60°C to 100°C, and so on. The drying temperature provided by the present invention can also be one of 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, and 100°C, or any value satisfying the above-mentioned range.

[0090] In some embodiments of the present invention, the drying time can be from 1 min to 30 min. The drying time provided by the present invention can be any value within the range formed by any two values ​​mentioned above, such as 1 min to 10 min, 10 min to 20 min, 20 min to 30 min, and so on. The drying time provided by the present invention can also be one of 1 min, 5 min, 10 min, 15 min, 20 min, 25 min, or 30 min, or any value satisfying the above range.

[0091] (4) Straightening treatment.

[0092] In an embodiment of the present invention, the tension straightening process includes passing the foil roll obtained after drying through the roller at a uniform speed under the tension of the roller.

[0093] In some embodiments of the present invention, the diameter of the roller is 3mm to 20mm. The diameter of the roller provided by the present invention can be any value within the range formed by any two values ​​in the above range, such as 3mm to 10mm, 10mm to 15mm, or 15mm to 20mm, and so on. For example, the diameter of the roller can be one of 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, and 20mm, or any value that satisfies the above range.

[0094] In some embodiments of the present invention, the tension of the roller is 5 kg to 50 kg. For example, the tension of the roller can be one of 5 kg, 10 kg, 15 kg, 20 kg, 25 kg, 30 kg, 35 kg, 40 kg, 45 kg, or 50 kg, or any value that satisfies the above range.

[0095] In some embodiments of the present invention, the number of passes can be 1 to 5. The number of passes will vary depending on the thickness of the foil roll. The appropriate number of passes can be selected according to actual needs, such as 1, 2, 3, 4 or 5 passes, without specific limitation.

[0096] In some embodiments of the present invention, the angle at which the foil roll passes through the roller is 90° to 180°. For example, the angle can be one of 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, 170°, and 180° or any value that satisfies the above range.

[0097] In some embodiments of the present invention, the foil roll is moved at a constant speed through a metal rod of 3mm to 20mm at an angle of 90° to 180° and under a tension of 5kg to 50kg. The number of times the foil roll passes through the metal rod varies depending on the thickness of the foil roll, and the number of times it passes through the metal rod can be 1 to 5.

[0098] (5) Sintering treatment.

[0099] In an embodiment of the present invention, the foil roll that has undergone tension straightening is subjected to sintering.

[0100] In some embodiments of the present invention, the sintering temperature can be 560℃ to 650℃. The sintering temperature provided by the present invention can be any value within the range formed by any two values ​​within the above-mentioned range, for example, it can be 560℃ to 600℃, or 600℃ to 650℃, and so on. The sintering temperature provided by the present invention can also be one of 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃, and 650℃, or any value satisfying the above-mentioned range.

[0101] In some embodiments of the present invention, the sintering time can be from 2 hours to 20 hours. The sintering time provided by the present invention can be any value within the range formed by any two values ​​mentioned above, such as 2 hours to 10 hours, or 10 hours to 20 hours, and so on. The sintering time provided by the present invention can also be one of 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, and 20 hours, or any value satisfying the above range.

[0102] The present invention also provides an aluminum electrolytic capacitor comprising the above-described multilayer foil for aluminum electrolytic capacitors or multilayer foil for aluminum electrolytic capacitors prepared by the above-described preparation method.

[0103] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are all conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or through existing methods; unless otherwise specified, the amounts of experimental reagents used are the amounts used in conventional experimental operations; unless otherwise specified, the experimental methods are all conventional methods.

[0104] Example 1

[0105] A multilayer foil for aluminum electrolytic capacitors and its preparation method are disclosed below.

[0106] (1) Preparation of slurry using aluminum powder as raw material

[0107] Aluminum powder with a particle size D50 of 4μm was added to a mixture of epoxy resin colloid (15% by mass, solvent: ethanol) and polyurethane colloid (20% by mass, solvent: ethanol), wherein the mass of the mixture was 10% of the mass of the aluminum powder. The mixture was mixed evenly to obtain a slurry.

[0108] (2) Forming a coating on the substrate surface

[0109] The slurry is uniformly coated on both sides of an aluminum foil with a thickness of 30 μm, and the coating thickness on one side is controlled at 60 μm.

[0110] (3) Drying treatment

[0111] The resulting coated substrate was dried at 100°C for 3 minutes.

[0112] (4) Straightening treatment

[0113] The dried foil roll is moved at a constant speed and angle of 130° on a 10mm metal rod with a tension of 40kg. This process is repeated twice.

[0114] (5) Sintering treatment

[0115] The foil rolls after straightening were then sintered at a temperature of 590℃ for 10 hours.

[0116] Samples of the sintered foil rolls were taken and stamped into 1cm×5cm specimens using an aluminum foil stamping machine. The specimens were then subjected to performance testing using a bending machine.

[0117] Example 2

[0118] A multilayer foil for aluminum electrolytic capacitors and its preparation method are disclosed below.

[0119] (1) Preparation of slurry using aluminum powder as raw material

[0120] Aluminum powder with a particle size D50 of 4μm was added to a mixture of acrylic resin colloid (15% by mass, solvent: ethanol) and phthalic anhydride (20% by mass, solvent: ethanol), wherein the mass of the mixture was 10% of the mass of the aluminum powder. The mixture was mixed evenly to obtain a slurry.

[0121] (2) Forming a coating on the substrate surface

[0122] The slurry is uniformly coated on both sides of an aluminum foil with a thickness of 30 μm, and the coating thickness on one side is controlled at 60 μm.

[0123] (3) Drying treatment

[0124] The resulting coated substrate was dried at 100°C for 3 minutes.

[0125] (4) Straightening treatment

[0126] The dried foil roll is moved at a constant speed and angle of 130° on a 10mm metal rod with a tension of 40kg. This process is repeated twice.

[0127] (5) Sintering treatment

[0128] The foil rolls after tension straightening are then sintered at 600℃ for 15 hours.

[0129] Samples of the sintered foil rolls were taken and stamped into 1cm×5cm specimens using an aluminum foil stamping machine. The specimens were then subjected to performance tests.

[0130] Comparative Example 1

[0131] The remaining operations are the same as in Example 1, except that the dried foil roll is directly sintered, and then tension straightened after sintering.

[0132] The processed foil rolls were sampled and stamped into 1cm×5cm specimens using an aluminum foil stamping machine, and the specimens were then subjected to performance tests.

[0133] Performance testing

[0134] The stamped samples are then subjected to bending tests using a bending machine, with a pass rate of ≥130 bends.

[0135] Table 1 shows the bending properties of the multilayer foil for aluminum electrolytic capacitors prepared in the examples and comparative examples.

[0136] Group Head left (back) Head (back) Beginning and end (return) Tail left (back) In the end (return) tail right (back) Example 1 161 164 164 160 164 164 Example 2 144 143 140 141 142 146 Comparative Example 1 61 59 63 60 63 61

[0137] Combination Figures 2 to 4 As can be seen from Table 1, compared with Comparative Example 1, Examples 1-2 show an improvement of nearly 2 times in bending performance testing. The cracks generated by the tensile straightening treatment before sintering in this invention exhibit an asymmetrical distribution. Figure 2 As shown, since the crack depth does not reach the substrate surface, the stress does not concentrate at a single point, thus significantly improving the bending strength of the foil roll. In contrast, in Comparative Example 1, the cracks generated by the tensioning process after sintering are symmetrically distributed. (See Figure 1 for details.) Figure 4 As shown, the crack depth reaches the surface of the substrate. During the winding and cutting process, the stress on the two sides of the substrate is concentrated at the same point and released. The foil roll is prone to problems such as powder shedding or even breakage at this position.

[0138] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A multilayer foil for an aluminum electrolytic capacitor, characterized in that, The substrate includes a substrate and sintered layers composed of aluminum sintered body on both opposite surfaces of the substrate, each side of the sintered layer having multiple cracks. Along the thickness direction of the sintered layer, each of the plurality of cracks extends independently from the side of the sintered layer away from the substrate towards the substrate surface, and the depth of each crack is less than the thickness of the sintered layer, and the depth of each crack is independently less than or equal to 95% of the thickness of the sintered layer; Based on the substrate, multiple cracks in the sintered layers on both sides are independently and asymmetrically distributed, and the multiple cracks in the sintered layers on both sides are alternately distributed along the length direction of the sintered layers. The multilayer foil for aluminum electrolytic capacitors is produced by straightening a substrate coated with slurry before sintering.

2. The multilayer foil for aluminum electrolytic capacitors as described in claim 1, characterized in that, Based on the sintered layer on one side, the plurality of cracks are spaced apart along the length direction of the sintered layer.

3. The multilayer foil for aluminum electrolytic capacitors as described in claim 1, characterized in that, Based on the sintered layer on one side, the spacing between two adjacent cracks is independently 50 μm to 350 μm.

4. The multilayer foil for aluminum electrolytic capacitors as described in claim 1, characterized in that, Based on the sintered layer on one side, the spacing between two adjacent cracks is independently 100 μm to 320 μm.

5. The multilayer foil for aluminum electrolytic capacitors as described in claim 1, characterized in that, The width of each crack along the length of the sintered layer is independently 0.1 μm to 5 μm.

6. The multilayer foil for aluminum electrolytic capacitors as described in claim 1, characterized in that, The depth of each crack is independently 40% to 95% of the thickness of the sintered layer.

7. The multilayer foil for aluminum electrolytic capacitors as described in claim 1, characterized in that, The depth of each crack is independently 50% to 95% of the thickness of the sintered layer.

8. The multilayer foil for aluminum electrolytic capacitors as described in claim 1, characterized in that, The thickness of the sintered layer on each side is independently 45 μm to 200 μm.

9. The multilayer foil for aluminum electrolytic capacitors as described in claim 1, characterized in that, The thickness of the substrate is 10 μm to 50 μm.

10. The multilayer foil for aluminum electrolytic capacitors as described in claim 1, characterized in that, The substrate is selected from aluminum foil.

11. A method for preparing multilayer foil for aluminum electrolytic capacitors according to any one of claims 1-10, characterized in that, The preparation method includes: A slurry prepared from aluminum powder is coated onto at least one side of a substrate, and then subjected to drying, straightening, and sintering processes in sequence to obtain the multilayer foil for the aluminum electrolytic capacitor.

12. The preparation method according to claim 11, characterized in that, The tension straightening process includes: passing the dried foil roll through the roller at a uniform speed under the tension of the roller.

13. The preparation method according to claim 12, characterized in that, The diameter of the roller is 3 mm to 20 mm.

14. The preparation method according to claim 12, characterized in that, The tension of the roller is 5 kg to 50 kg.

15. The preparation method according to claim 12, characterized in that, The number of passes is 1 to 5.

16. The preparation method according to claim 12, characterized in that, The angle at which the foil roll passes through the roller is 90° to 180°.

17. The preparation method according to claim 11, characterized in that, The drying temperature is 30℃~100℃, and the drying time is 1 min~30 min.

18. The preparation method according to claim 11, characterized in that, The particle size D50 of the aluminum powder is 1 μm to 10 μm.

19. The preparation method according to claim 11, characterized in that, The sintering temperature is 560℃~650℃, and the sintering time is 2 h~20 h.

20. An aluminum electrolytic capacitor, characterized in that, The multilayer foil for aluminum electrolytic capacitors comprises any one of claims 1-10 or the multilayer foil for aluminum electrolytic capacitors prepared by any one of claims 11-19.

Images