Electrode foil, preparation method thereof and aluminum electrolytic capacitor
By combining vacuum and oxygen alternating degreasing treatment with sintering, boiling and formation treatment, the problem of high leakage current of electrode foil was solved, and electrode foil with low residual carbon content and long life was prepared, reducing environmental pollution.
Patent Information
- Application Number
- CN202510957179.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-11
- Publication Date
- 2025-11-11
AI Technical Summary
Electrode foils prepared by existing sintering methods have the problem of large leakage current, and traditional degreasing methods have the problems of high residual carbon content and environmental pollution.
A degreasing process using alternating vacuum and oxygen environments was employed to treat aluminum foil rolls. A vacuum state was created under vacuum conditions and oxygen was introduced. The pressure difference was used to drive oxygen into the gaps between the aluminum foil rolls for thorough degreasing. Combined with sintering, boiling, and formation treatments, electrode foils were prepared.
It effectively reduces the residual carbon content of the electrode foil, decreases leakage current, extends the service life of the electrode foil, and reduces environmental pollution.
Smart Images
Figure CN120933072A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of electrode material technology, and in particular to an electrode foil, a method for preparing the same, and an aluminum electrolytic capacitor. Background Technology
[0002] Aluminum electrolytic capacitors are widely used in the manufacture of important electronic components due to their higher specific capacitance compared to other capacitors of the same volume. Electrode foil is one of the key components of aluminum electrolytic capacitors, and its preparation methods include acid etching and sintering. Acid etching uses an acid-containing system to electrochemically create tunnels on the aluminum foil surface, increasing its specific surface area. Alumina dielectric layer is then formed on the surface of these tunnels through a chemical oxidation process. However, acid etching has low raw material utilization and generates waste acid, causing environmental pollution. The sintering process mainly involves slurry preparation, coating, drying, degreasing, sintering, and oxidation. While it does not generate waste acid, it still suffers from a relatively high leakage current. Summary of the Invention
[0003] Based on this, in order to solve the technical problem of large leakage current in electrode foils prepared by sintering, this application provides an electrode foil, a method for preparing the same, and an aluminum electrolytic capacitor.
[0004] A first aspect of this application provides a method for preparing an electrode foil, the method comprising the following steps:
[0005] The aluminum foil roll is degreased to obtain degreased foil. The degreasing process is carried out in alternating atmospheres of a first atmosphere and a second atmosphere. The first atmosphere is a vacuum state, and the second atmosphere is oxygen introduced into the first atmosphere. The aluminum foil roll includes a substrate foil and a coating layer disposed on at least one surface of the substrate foil. The coating layer includes aluminum powder and an organic binder.
[0006] The degreased foil was subjected to sintering, boiling and formation treatments in sequence to prepare electrode foil.
[0007] In some embodiments, the pressure of the first atmosphere is 1 Pa to 100 Pa; and / or,
[0008] The pressure of the second atmosphere is 4000 Pa to 200000 Pa, optionally 80000 Pa to 150000 Pa; and / or,
[0009] The degreasing treatment temperature is 200℃~400℃.
[0010] In some embodiments, the degreasing process includes alternating vacuum degreasing steps in a first atmosphere and oxygen degreasing steps in a second atmosphere;
[0011] The holding time for each vacuum degreasing step is 10 min to 60 min; and / or,
[0012] The holding time for a single oxygen defatting step is 10 min to 180 min; and / or,
[0013] The total time for degreasing is 1 to 8 hours.
[0014] In some embodiments, the vacuum degreasing step is performed ≥3 times, the oxygen degreasing step is performed ≥3 times; and / or,
[0015] The degreasing process ends with an oxygen degreasing step.
[0016] In some embodiments, the average particle size D50 of the aluminum powder is 1 μm to 8 μm; and / or,
[0017] Organic binders include at least one of ethyl cellulose, polypropylene carbonate, and polyvinyl butyral resin; and / or,
[0018] The mass ratio of aluminum powder to organic binder is 4~70:1.
[0019] In some embodiments, the thickness of the substrate foil is 10 μm to 50 μm; and / or,
[0020] The thickness of the coating layer is 10μm~100μm.
[0021] In some embodiments, the coating preparation slurry includes aluminum powder, an organic binder, and an organic solvent;
[0022] The slurry is prepared to meet at least one of the following conditions:
[0023] (1) The organic solvent includes at least one of ethyl acetate, tributyl citrate, dimethyl adipate, diethylene glycol dimethyl ether, dibutyl phthalate, diethylene glycol butyl ether acetate, diethylene glycol butyl ether, diethylene glycol dibutyl ether and terpineol;
[0024] (2) Based on the total mass of organic binder and organic solvent, the amount of organic binder is 1wt~10wt.
[0025] In some embodiments, the sintering process includes: sintering the degreased foil at 560°C to 650°C for 1 hour to 24 hours in a vacuum or inert atmosphere; and / or,
[0026] The boiling process includes immersing the sintered foil obtained from the sintering process in pure water at 90℃~99℃ for 3min~30min.
[0027] In some implementations, the formation process includes:
[0028] The water-boiled foil obtained by water boiling treatment is placed in a forming solution and formed to a voltage of 510V~530V; then it is left to stand in an air atmosphere at 400℃~600℃ for 1min~5min; then it is placed in the forming solution and kept at a constant voltage of 510V~530V for 8min~12min.
[0029] The formation solution is a mixed solution containing 80 g / L to 120 g / L boric acid and 0.8 g / L to 1.2 g / L ammonium pentaborate.
[0030] A second aspect of this application provides an electrode foil prepared using the above-described electrode foil preparation method.
[0031] In some embodiments, the residual carbon content of the electrode foil is 0.01 wt% to 0.1 wt%; and / or,
[0032] The leakage current of the electrode foil is 0.12 mA / cm. 2 ~0.35mA / cm 2 .
[0033] A third aspect of this application provides an aluminum electrolytic capacitor, including the aforementioned electrode foil.
[0034] Compared with related technologies, this application has the following advantages:
[0035] In the above-mentioned method for preparing electrode foil, the aluminum foil roll is treated by a degreasing process under alternating vacuum and oxygen environments. In the first atmosphere, a vacuum is formed between the layers of the aluminum foil roll. When oxygen is introduced, it is easier for oxygen to enter the gaps between the layers of the aluminum foil roll under the drive of the pressure difference, thereby reducing the residual carbon content of the electrode foil. This effectively reduces the leakage current of the electrode foil and extends its service life. Attached Figure Description
[0036] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0037] Figure 1 This is a flowchart of a method for preparing electrode foil in some embodiments of this application. Detailed Implementation
[0038] To facilitate understanding of this application, a more comprehensive description of the application will be provided below in conjunction with specific embodiments. Preferred embodiments of the application are given in the specific embodiments. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.
[0039] 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 application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0040] Unless otherwise stated or in case of conflict, the terms or phrases used in this application shall have the following meanings:
[0041] In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.
[0042] In this application, terms such as "further," "even more," "particularly," "for example," "like," "example," and "exemplary" are used for descriptive purposes to indicate a connection in the coverage of different technical solutions presented earlier and later, but should not be construed as limiting the preceding technical solution or restricting the scope of protection herein. Unless otherwise specified herein, A (e.g., B) indicates that B is a non-limiting example of A, and it can be understood that A is not limited to B.
[0043] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it is selected from either "present" or "absent." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent. In this application, descriptions such as "optionally contains" and "optionally includes" indicate "contains or does not contain." "Optional component X" indicates whether component X exists or does not exist, or whether component X is contained or not.
[0044] When a numerical range is disclosed in this application, the range is considered continuous and includes the minimum and maximum values of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed in this application should be understood to include any and all subranges to which they are included.
[0045] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.
[0046] The terms "comprising" and "having," and any variations thereof, used in the embodiments of this application, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or components inherent to such processes, methods, products, or devices.
[0047] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.
[0048] In the flowchart of this application, although the steps are shown sequentially according to the arrows, these steps are not necessarily performed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps. They can be executed in other orders. Moreover, at least some of the steps in the diagram may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. Their execution order is not necessarily sequential, but can be performed alternately or in turn with at least some of other steps or other sub-steps or stages.
[0049] The traditional sintering method for preparing electrode foil mainly includes slurry preparation, coating, drying, degreasing, sintering, and formation. The slurry typically contains aluminum powder, solvent, and organic binder. Degreasing primarily removes the organic binder and can be performed in a vacuum, inert atmosphere, or oxygen environment. The inventors of this application have discovered that degreasing under vacuum and inert atmospheres easily leads to decarburization of the organic binder, forming elemental carbon and resulting in a high residual carbon content in the electrode foil. Furthermore, degreasing under an oxidizing atmosphere results in uneven removal of the organic binder.
[0050] Based on this, the first aspect of this application provides a method for preparing an electrode foil, the method comprising the following steps:
[0051] S1: The aluminum foil roll is degreased to obtain degreased foil; the degreasing process is carried out in alternating atmospheres of a first atmosphere and a second atmosphere; the first atmosphere is a vacuum state, and the second atmosphere is oxygen introduced into the first atmosphere; the aluminum foil roll includes a substrate foil and a coating layer disposed on at least one surface of the substrate foil, the coating layer including aluminum powder and an organic binder.
[0052] S2: The degreased foil is subjected to sintering, boiling and formation treatments in sequence to prepare electrode foil.
[0053] In the above-mentioned method for preparing electrode foil, the aluminum foil roll is treated by a degreasing process under alternating vacuum and oxygen environments. In the first atmosphere, a vacuum is formed between the layers of the aluminum foil roll. When oxygen is introduced, it is easier for oxygen to enter the gaps between the layers of the aluminum foil roll under the drive of the pressure difference, thereby reducing the residual carbon content of the electrode foil. This effectively reduces the leakage current of the electrode foil and extends its service life.
[0054] In some embodiments, the average particle size D50 of the aluminum powder is 1 μm to 8 μm. Exemplarily, the average particle size D50 of the aluminum powder can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, or any value within a range formed by any two of these point values as end values.
[0055] In some embodiments, the organic binder includes at least one of ethyl cellulose, polypropylene carbonate, and polyvinyl butyral resin.
[0056] In some specific examples, the organic binder is ethyl cellulose.
[0057] In some embodiments, the substrate foil includes at least one of aluminum alloy foil and aluminum foil.
[0058] In some specific examples, the purity of the aluminum alloy foil is greater than 99.7%.
[0059] In some specific examples, the purity of the aluminum foil is >99.9%.
[0060] In some embodiments, the thickness of the substrate foil is 10 μm to 50 μm; for example, it can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm or any value within the range formed by any two of these point values as end values.
[0061] In some embodiments, the size of the substrate foil is 500mm~550mm×1km~5km.
[0062] In some embodiments, the substrate foil has a first surface and a second surface opposite to the first surface, and the coating layer may be disposed on one of the surfaces or on both surfaces simultaneously.
[0063] In some embodiments, the thickness of the coating layer is 10 μm to 100 μm; for example, it can be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm or any value within the range formed by any two of these point values as end values.
[0064] In some embodiments, the slurry for preparing the coating layer includes aluminum powder, an organic binder, and an organic solvent. Understandably, the coating layer is a layer obtained by drying the slurry to remove the organic solvent.
[0065] In some embodiments, the organic solvent includes at least one selected from ethyl acetate, tributyl citrate, dimethyl adipate, diethylene glycol dimethyl ether, dibutyl phthalate, diethylene glycol butyl ether acetate, diethylene glycol butyl ether, diethylene glycol dibutyl ether, and terpineol.
[0066] In some embodiments, the total mass of the organic binder and organic solvent is used as a basis, wherein the amount of organic binder is 1 wt% to 10 wt%; for example, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or any value within a range formed by any two of these point values as endpoints.
[0067] In some embodiments, the mass ratio of aluminum powder to organic binder is 4 to 70:1. Exemplarily, it can be 4:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 55:1, 60:1, 65:1, or 70:1.
[0068] In some embodiments, the method for preparing aluminum foil rolls includes:
[0069] The slurry is coated onto at least one surface of the substrate foil and dried to form a coating layer, thereby obtaining a composite foil;
[0070] The composite foil is wound up to obtain an aluminum foil roll.
[0071] In some embodiments, the coating method described above is not limited and can be a coating method commonly used in the art, including but not limited to at least one of blade coating, extrusion coating and brush coating.
[0072] In some implementations, the slurry can be coated onto one or both surfaces of the substrate foil.
[0073] In some embodiments, the drying conditions described above are not particularly limited and can be carried out according to conventional conditions in the art.
[0074] In some embodiments, the diameter of the aluminum foil roll can be 50cm to 100cm, and the width can be 500mm to 520mm.
[0075] In some embodiments, the degreasing temperature is 200°C to 400°C. Exemplarily, the degreasing temperature can be 200°C, 250°C, 300°C, 350°C, 400°C, or any value within a range formed by any two of these point values as endpoints.
[0076] Understandably, in this application, oxygen is not introduced into the first atmosphere.
[0077] In some implementations, the pressure of the first atmosphere is lower than the pressure of the second atmosphere.
[0078] In some implementations, the pressure of the first atmosphere is 1 Pa to 100 Pa. For example, it can be 1 Pa, 5 Pa, 10 Pa, 20 Pa, 30 Pa, 40 Pa, 50 Pa, 60 Pa, 70 Pa, 80 Pa, 90 Pa, 100 Pa, or any value within a range formed by any two of these point values as endpoints.
[0079] In some embodiments, the pressure of the second atmosphere is 4000 Pa to 200000 Pa. For example, the pressure of the second atmosphere is 4000 Pa to 200000 Pa. 4000 Pa, 5000 Pa, 10000 Pa, 20000 Pa, 30000 Pa, 40000 Pa, 50000 Pa, 60000 Pa, 80000 Pa, 100000 Pa, 150000 Pa, 200000 Pa, or any value within a range formed by any two of these point values as endpoints.
[0080] In some specific examples, the pressure of the second atmosphere is 80,000 Pa to 150,000 Pa.
[0081] In some embodiments, the degreasing process includes alternating vacuum degreasing steps in a first atmosphere and oxygen degreasing steps in a second atmosphere.
[0082] In some embodiments, the holding time for a single vacuum degreasing step is 10 min to 60 min. Exemplarily, the holding time can be 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, or any value within a range formed by any two of these point values as endpoints.
[0083] In some embodiments, the specific process of the vacuum degreasing step includes: evacuating the processing environment to a pressure of 1 Pa to 100 Pa and maintaining it for 10 min to 60 min.
[0084] In some embodiments, the single holding time of the oxygen degreasing step is 10 min to 180 min; for example, the holding time can be 10 min, 20 min, 30 min, 60 min, 80 min, 90 min, 120 min, 150 min, 180 min, or any value within a range formed by any two of these point values as endpoints.
[0085] In some embodiments, the specific process of the oxygen degreasing step includes: introducing oxygen into an environment with a pressure of 1 Pa to 100 Pa until the pressure reaches 4000 Pa to 200000 Pa and maintaining it for 10 min to 180 min.
[0086] Understandably, in this application, the total degreasing time is the sum of the holding time of the vacuum degreasing step and the holding time of the oxygen degreasing step. In some embodiments, the total degreasing time is 1 hour to 8 hours. Exemplarily, it can be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours.
[0087] In some implementations, the vacuum degreasing step is performed ≥3 times, and the oxygen degreasing step is performed ≥3 times.
[0088] In some specific examples, the vacuum degreasing step is performed 3 to 6 times.
[0089] In some specific examples, the oxygen degreasing step is performed 3 to 6 times.
[0090] Understandably, the degreasing process ends with an oxygen degreasing step, that is, the degreasing process alternates between vacuum degreasing and oxygen degreasing steps, and the processing atmosphere of the last processing step is the second atmosphere, which can improve the degreasing effect and thus reduce the leakage current of the electrode foil.
[0091] In some embodiments, the sintering process includes sintering the degreased foil at 560°C to 650°C for 1 hour to 24 hours in a vacuum or inert atmosphere. Exemplarily, the sintering temperature can be 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, or any value within a range consisting of any two of these values as endpoints. The inert atmosphere can be provided by nitrogen or an inert gas, such as argon, which is commonly used in the art.
[0092] In some embodiments, the method for preparing the electrode foil further includes a step of unfolding between the sintering treatment and the boiling treatment, thereby changing the sintered foil from a rolled state to a flat state.
[0093] In some embodiments, the boiling process includes immersing the sintered foil obtained from the sintering treatment in pure water at 90°C to 99°C for 3 to 30 minutes. Exemplarily, the temperature of the pure water can be 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, or 99°C, and the immersion time can be 3 minutes, 5 minutes, 8 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, or 30 minutes.
[0094] In some implementations, the formation process includes:
[0095] The water-boiled foil obtained by water boiling treatment is placed in a forming solution and formed to a voltage of 510V~530V; then it is left to stand in an air atmosphere at 400℃~600℃ for 1min~5min; then it is placed in the above forming solution and kept at a constant voltage of 510V~530V for 8min~12min.
[0096] The above-mentioned chemical solution is a mixed solution containing 80 g / L to 120 g / L boric acid and 0.8 g / L to 1.2 g / L ammonium pentaborate.
[0097] In some specific examples, during the process of forming the boiled foil obtained by boiling in water to a voltage of 510V~530V in a forming solution, a load of 0.1A / cm can be applied. 2 ~1A / cm 2 The current is converted to a voltage of 510V~530V.
[0098] In some specific examples, during the formation process, a water-boiled foil obtained from the boiling process is used as the anode, and stainless steel or graphite is used as the cathode.
[0099] In some specific examples, the temperature of the formation solution can be 85℃~95℃ during the formation process.
[0100] A second aspect of this application provides an electrode foil prepared using the above-described electrode foil preparation method.
[0101] A third aspect of this application provides an aluminum electrolytic capacitor, including the aforementioned electrode foil.
[0102] Understandably, the aluminum electrolytic capacitor described above, using electrode foil prepared by the above method as the electrode, can have a long service life.
[0103] To make the objectives and advantages of this application clearer, the preparation method and effects of the electrode foil of this application are further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only for explaining this application and should not be used to limit this application. Unless otherwise specified, the following embodiments do not include components other than unavoidable impurities. Unless otherwise specified, the drugs and instruments used in the embodiments are conventional choices in the art. Experimental methods in the embodiments that do not specify specific conditions are implemented according to conventional conditions, such as those described in literature, books, or methods recommended by the manufacturer.
[0104] Example 1
[0105] This embodiment provides an electrode foil, the preparation method of which includes the following steps:
[0106] S1: Aluminum powder (average particle size D50 is 3µm, purity >99.99wt%), ethyl acetate and ethyl cellulose are mixed evenly in a mass ratio of 45:50:5 and homogenized for 10 min at 1700 rpm using a homogenizer to obtain a slurry.
[0107] The slurry is uniformly coated onto the first surface of a 30µm thick substrate aluminum foil using a doctor blade coating method, and then dried in an oven at 100℃ to control the coating thickness to 50µm. The slurry is then uniformly coated onto the second surface of the aluminum foil using a doctor blade coating method, and then dried in an oven at 100℃ to control the coating thickness to 50µm, thus obtaining a composite foil.
[0108] The composite foil is wound up to obtain an aluminum foil roll with a width of 500 mm and a diameter of 300 mm.
[0109] The aluminum foil rolls were degreased by performing six unit degreasing processes at 300°C to obtain degreased foil. The unit degreasing process was as follows: the processing environment was evacuated to a pressure of 1 Pa and maintained for 10 min, and then oxygen was introduced into the processing environment to a pressure of 80000 Pa and maintained for 50 min. The total degreasing time was 6 h.
[0110] S2: The above degreased foil is sintered in a vacuum environment at 560°C for 24 hours to obtain a sintered foil;
[0111] The sintered foil was unfolded and then immersed in pure water at 95°C for 5 minutes to obtain a boiled foil.
[0112] Using the aforementioned boiled foil as the anode and stainless steel as the cathode, a forming solution containing 100 g / L boric acid and 0.9 g / L ammonium pentaborate was prepared at 88°C, with a loading of 0.5 A / cm. 2The current was converted for 20 minutes, and after conversion to 520V, it was placed in air at 500℃ for 2 minutes, and then placed in the above conversion solution at a constant voltage of 520V for 10 minutes.
[0113] Example 2
[0114] S1: Aluminum powder (average particle size D50 is 3µm, purity >99.99wt%), ethyl acetate and ethyl cellulose are mixed evenly in a mass ratio of 45:50:5 and homogenized for 10 min at 1700 rpm using a homogenizer to obtain a slurry.
[0115] The slurry is uniformly coated onto the first surface of a 30µm thick substrate aluminum foil using a doctor blade coating method, and then dried in an oven at 100℃ to control the coating thickness to 50µm. The slurry is then uniformly coated onto the second surface of the aluminum foil using a doctor blade coating method, and then dried in an oven at 100℃ to control the coating thickness to 50µm, thus obtaining a composite foil.
[0116] The composite foil is wound up to obtain an aluminum foil roll with a width of 500 mm and a diameter of 300 mm.
[0117] The above aluminum foil roll was degreased. At 300°C, the treatment environment was pre-vacuumed to a pressure of 50 Pa, then oxygen was introduced to a pressure of 80000 Pa and maintained for 60 min. The treatment environment was then evacuated to a pressure of 50 Pa and maintained for 30 min. Oxygen was introduced to the treatment environment to a pressure of 80000 Pa and maintained for 90 min. The treatment environment was then evacuated to a pressure of 50 Pa and maintained for 30 min. Oxygen was introduced to the treatment environment to a pressure of 80000 Pa and maintained for 90 min. The treatment environment was then evacuated to a pressure of 50 Pa and maintained for 30 min. Oxygen was introduced to the treatment environment to a pressure of 80000 Pa and maintained for 30 min, resulting in degreased foil.
[0118] S2: The above degreased foil is sintered in a vacuum environment at 560°C for 24 hours to obtain a sintered foil;
[0119] The sintered foil was unfolded and then immersed in pure water at 95°C for 10 minutes to obtain a boiled foil.
[0120] Using the aforementioned boiled foil as the anode and stainless steel as the cathode, a forming solution containing 100 g / L boric acid and 0.9 g / L ammonium pentaborate was prepared at 88°C, with a loading of 0.5 A / cm. 2 The current was converted for 20 minutes, and after conversion to 520V, it was placed in air at 500℃ for 2 minutes, and then placed in the above conversion solution at a constant voltage of 520V for 10 minutes.
[0121] Example 3
[0122] S1: Aluminum powder (average particle size D50 is 3µm, purity >99.99wt%), ethyl acetate and ethyl cellulose are mixed evenly in a mass ratio of 45:50:5 and homogenized for 10 min at 1700 rpm using a homogenizer to obtain a slurry.
[0123] The slurry was uniformly coated onto the first surface of a 30µm thick aluminum foil substrate using a doctor blade coating method, and then dried in an oven at 100℃ to control the coating thickness to 50µm. The slurry was then uniformly coated onto the second surface of the aluminum foil using the same method, and dried in an oven at 100℃ to control the coating thickness to 50µm, resulting in a composite foil.
[0124] The composite foil is wound up to obtain an aluminum foil roll with a width of 520 mm and a diameter of 800 mm.
[0125] The degreasing treatment of the above aluminum foil roll is as follows: at 300°C, the treatment environment is pre-vacuumed to a pressure of 100 Pa, then oxygen is introduced into the treatment environment to a pressure of 80000 Pa and maintained for 120 min, the treatment environment is evacuated to a pressure of 100 Pa and maintained for 60 min, oxygen is introduced into the treatment environment to a pressure of 80000 Pa and maintained for 120 min, the treatment environment is evacuated to a pressure of 100 Pa and maintained for 60 min, the total degreasing treatment time is 6 h, and degreased foil is obtained;
[0126] S3: The above degreased foil is sintered in a vacuum environment at 560°C for 24 hours to obtain a sintered foil;
[0127] The sintered foil was unfolded and then immersed in pure water at 95°C for 10 minutes to obtain a boiled foil.
[0128] Using the aforementioned boiled foil as the anode and stainless steel as the cathode, a forming solution containing 100 g / L boric acid and 0.9 g / L ammonium pentaborate was prepared at 88°C, with a loading of 0.5 A / cm. 2 The current was converted for 20 minutes, and after conversion to 520V, it was placed in air at 500℃ for 2 minutes, and then placed in the above conversion solution at a constant voltage of 520V for 10 minutes.
[0129] Example 4
[0130] The process is basically the same as in Example 1, except that the specific steps of the degreasing treatment are as follows:
[0131] At 300°C, the treatment environment was evacuated to a pressure of 1 Pa and maintained for 120 min. Then, oxygen was introduced into the treatment environment to a pressure of 80000 Pa and maintained for 60 min. The treatment environment was evacuated to a pressure of 1 Pa and maintained for 120 min. Then, oxygen was introduced into the treatment environment to a pressure of 80000 Pa and maintained for 60 min.
[0132] Example 5
[0133] The process is basically the same as in Example 1, except that the specific steps of the degreasing treatment are as follows:
[0134] At 300℃, the treatment environment was evacuated to a pressure of 1 Pa and maintained for 120 min. Then, oxygen was introduced into the treatment environment to a pressure of 80000 Pa and maintained for 60 min. Then, the environment was evacuated to a pressure of 1 Pa and maintained for 120 min. The total time for degreasing treatment was 5 h.
[0135] Example 6
[0136] It is basically the same as Example 1, except that only 3 unit degreasing treatments are performed, and the total time for degreasing treatment is 3 hours.
[0137] Comparative Example 1
[0138] The process is basically the same as in Example 1, except that the degreasing process is carried out entirely in an oxygen environment. The specific steps of the degreasing process are as follows:
[0139] Maintain at 300℃ and oxygen pressure of 80000Pa for 6 hours.
[0140] Comparative Example 2
[0141] The process is basically the same as in Example 1, except that the degreasing process is carried out entirely in a vacuum environment. The specific steps of the degreasing process are as follows:
[0142] At 300°C, the treatment environment was evacuated to a pressure of 1 Pa and maintained for 6 hours.
[0143] Test case
[0144] 1. The residual carbon content in the edge and center regions of the electrode foils prepared in the examples and comparative examples was detected. Samples were taken 2 cm from the edge (referred to as edge samples) with dimensions of 1 cm × 5 cm; samples were taken from the center region (referred to as center samples) with dimensions of 1 cm × 5 cm. The residual carbon content of the obtained samples was detected using a carbon-sulfur analyzer.
[0145] The test results are shown in Table 1.
[0146] Table 1
[0147]
[0148] 2. The residual carbon content in the edge and center regions of the electrode foils prepared in the examples and comparative examples was detected. A sample was taken 2 cm from the edge and recorded as the edge sample, with a size of 1 cm × 5 cm. A sample was taken in the center region and recorded as the center sample, with a size of 1 cm × 5 cm.
[0149] The leakage current of the obtained sample was tested using a leakage current detector under the following conditions:
[0150] The leakage current of the sample was detected using a 4mA current in a boric acid solution with a concentration of 70g / L at 65℃.
[0151] The test results are shown in Table 2.
[0152] Table 2
[0153]
[0154] As can be seen from Tables 1 and 2, the degreasing treatment in the examples involved alternating between vacuum and oxygen atmospheres, resulting in electrode foils with low residual carbon content and leakage current at both the center and edges. In contrast, Comparative Example 1 involved degreasing in an oxygen atmosphere throughout, resulting in electrode foils with low residual carbon content and leakage current at the edges, but high residual carbon content and leakage current at the center. Comparative Example 2 involved degreasing in a vacuum without oxygen, resulting in electrode foils with high residual carbon content and leakage current at both the edges and center.
[0155] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0156] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification and drawings can be used to interpret the content of the claims.
Claims
1. A method for preparing an electrode foil, characterized in that, The method includes the following steps: The aluminum foil roll is degreased to obtain degreased foil. The degreasing process is carried out in alternating atmospheres of a first atmosphere and a second atmosphere. The first atmosphere is a vacuum state, and the second atmosphere is oxygen introduced into the first atmosphere. The aluminum foil roll includes a substrate foil and a coating layer disposed on at least one surface of the substrate foil. The coating layer includes aluminum powder and an organic binder. The degreased foil is subjected to sintering, boiling and formation treatments in sequence to obtain the electrode foil.
2. The preparation method according to claim 1, characterized in that, The pressure of the first atmosphere is 1 Pa to 100 Pa; and / or, The pressure of the second atmosphere is 4000 Pa to 200000 Pa, optionally 80000 Pa to 150000 Pa; and / or, The degreasing treatment is performed at a temperature of 200℃~400℃.
3. The preparation method according to claim 1 or 2, characterized in that, The degreasing process includes alternating vacuum degreasing steps in the first atmosphere and oxygen degreasing steps in the second atmosphere; The holding time for each vacuum degreasing step is 10 min to 60 min; and / or, The single holding time for the oxygen degreasing step is 10 min to 180 min; and / or, The total time for the degreasing treatment is 1 to 8 hours.
4. The preparation method according to claim 3, characterized in that, The vacuum degreasing step is performed ≥3 times, and the oxygen degreasing step is performed ≥3 times; and / or, The degreasing process ends with an oxygen degreasing step.
5. The preparation method according to claim 1 or 2, characterized in that, The average particle size D50 of the aluminum powder is 1μm~8μm; and / or, The organic binder includes at least one of ethyl cellulose, polypropylene carbonate, and polyvinyl butyral resin; and / or, The mass ratio of the aluminum powder to the organic binder is 4~70:
1.
6. The preparation method according to claim 1 or 2, characterized in that, The thickness of the substrate foil is 10μm~50μm; and / or, The thickness of the coating layer is 10μm to 100μm.
7. The preparation method according to claim 1 or 2, characterized in that, The coating preparation slurry includes aluminum powder, organic binder, and organic solvent; The prepared slurry satisfies at least one of the following conditions: (1) The organic solvent includes at least one of ethyl acetate, tributyl citrate, dimethyl adipate, diethylene glycol dimethyl ether, dibutyl phthalate, diethylene glycol butyl ether acetate, diethylene glycol butyl ether, diethylene glycol dibutyl ether and terpineol; (2) The amount of organic binder used is 1 wt to 10 wt, based on the total mass of organic binder and organic solvent.
8. The preparation method according to claim 1 or 2, characterized in that, The sintering process includes: sintering the degreased foil at 560℃~650℃ for 1h~24h in a vacuum or inert atmosphere; and / or, The boiling treatment process includes: immersing the sintered foil obtained from the sintering treatment in pure water at 90℃~99℃ for 3min~30min; and / or, The formation process includes: The water-boiled foil obtained by boiling is placed in a forming solution and formed to a voltage of 510V~530V; then it is left to stand in an air atmosphere at 400℃~600℃ for 1min~5min; then it is placed in the forming solution and kept at a constant voltage of 510V~530V for 8min~12min. The formation solution is a mixed solution containing 80 g / L to 120 g / L boric acid and 0.8 g / L to 1.2 g / L ammonium pentaborate.
9. An electrode foil, characterized in that, The electrode foil is prepared by the method described in any one of claims 1 to 8.
10. The electrode foil according to claim 9, characterized in that, The residual carbon content of the electrode foil is 0.01wt%~0.1wt%; and / or, The leakage current of the electrode foil is 0.12 mA / cm. 2~ 0.35mA / cm 2 .
11. An aluminum electrolytic capacitor, characterized in that, Includes the electrode foil as described in claim 10.