High-performance electrode foil and sintering process thereof

Abstract

The invention discloses a high-performance electrode foil and a sintering process thereof. The sintering process comprises the following steps: carrying out hydration treatment on an aluminum-containing interlayer foil to obtain a hydrated interlayer foil; winding the base layer foil and the hydrated interlayer foil at intervals to form a foil roll; and sintering the foil roll. The adopted interlayer foil is the aluminum-containing interlayer foil, and when the aluminum-containing interlayer foil is subjected to hydration treatment, hydrated aluminum hydroxide can be formed on the surface of the aluminum-containing interlayer foil; when sintering is carried out, on one hand, hydrated aluminum hydroxide on the surface of the hydrated interlayer foil can be decomposed, generated water can react with aluminum powder on the surface of the base layer foil at a high temperature, aluminum oxide and hydrogen are generated, and therefore the purposes of promoting the aluminum powder on the surface of the base layer foil to generate aluminum oxide and promoting the sintering process are achieved, and aluminum powder oxidation is more uniform; and on the other hand, generation and decomposition of aluminum hydroxide can cause a large number of pores to be generated in the interlayer foil, so that the adhesive gasified from the base layer foil is better adsorbed, adhesive discharging is more complete, and improvement of the performance of the electrode foil is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of capacitors, and in particular relates to a high-performance electrode foil and a sintering process thereof. Background Art

[0002] Currently, anode foil production processes primarily include etching and sintering. The sintering process involves coating the surface of a base foil (aluminum foil) with a slurry containing aluminum particles to form a slurry layer. This is then followed by drying, sintering, and chemical conversion to produce the finished anode foil. During the sintering process, the slurry-coated base foil is typically wound into a coil, which is then sintered under a specific temperature. The sintered coil is then separated into separate coils before undergoing the next chemical conversion process.

[0003] For example, Chinese invention patent publication number CN117900480A discloses a heat treatment process for porous electrode foil. This process involves first rolling a composite aluminum foil and wrapping it with a preformed piece into a foil roll. The roll is then placed in a sintering furnace for sintering. However, this sintering process has drawbacks: after rolling, the inner and outer composite aluminum foils come into contact with each other, leading to interlayer adhesion after sintering. Furthermore, the sintered foil can still tear and break during unwinding.

[0004] For example, Chinese invention patent publication number CN115274304B discloses a sintered foil and its preparation method. This method involves winding a base foil with a slurry layer and a laminated foil at intervals to form a foil roll, which is then sintered. The interlayer foil effectively blocks the diffusion of aluminum atoms between adjacent base foils during the foil roll sintering process, thereby alleviating the problem of adhesion between adjacent base foils.

[0005] However, the above sintering process still has shortcomings: the laminated foil uses aluminum foil, and its addition will increase the sintering difference between the inside and outside of the roll; it also makes it difficult to remove the glue from the core, and it is easy for the base foil and the interlayer foil to stick together. Once adhesion occurs, it will further affect the subsequent debinding, resulting in bulging of the foil surface and poor pattern, which will affect the subsequent performance of the formed product. Summary of the Invention

[0006] The purpose of the present invention is to provide a high-performance electrode foil and a sintering process thereof, which can prevent adhesion between the base foil and the interlayer foil and prevent adverse debonding at the core of the foil roll; the obtained electrode foil has a good shape and is not bulging.

[0007] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows: A sintering process for high-performance electrode foil, comprising: a step of hydrating the aluminum-containing interlayer foil to obtain a hydrated interlayer foil; The step of alternately winding the base foil and the hydrated interlayer foil to form a foil roll; The step of sintering the foil roll.

[0008] The interlayer foil used in the present invention is an aluminum-containing interlayer foil. The surface of such an aluminum-containing interlayer foil usually has a layer of aluminum oxide film. When it is hydrated, this aluminum oxide film will slightly dissociate in water and react with hydrogen ions in the water, thus destroying the aluminum oxide film and exposing the aluminum inside the interlayer foil. At this time, this part of the aluminum will react with water to form aluminum hydroxide and hydrogen, and the aluminum hydroxide will further hydrate to form hydrated aluminum hydroxide. When the base foil and the hydrated interlayer foil are rolled into a foil roll and sintered at high temperature, On the one hand, the hydrated aluminum hydroxide on the surface of the hydrated interlayer foil will decompose, and the generated water will react with the aluminum powder on the surface of the base foil at high temperature to generate aluminum oxide and hydrogen, thereby promoting the formation of aluminum oxide from the aluminum powder on the surface of the base foil, promoting the sintering process, and making the oxidation of the aluminum powder more uniform; on the other hand, for the interlayer foil, the generation and decomposition of aluminum hydroxide on its surface will lead to a large number of pores inside the interlayer foil, thereby better absorbing the vaporized binder from the base foil, making the debinding more complete and improving the debinding efficiency, thereby improving the performance of the electrode foil.

[0009] Preferably, in the above sintering process, the aluminum-containing interlayer foil is an aluminum foil with an aluminum purity greater than 97%.

[0010] Preferably, in the above sintering process, the step of hydrating the aluminum-containing interlayer foil to obtain a hydrated interlayer foil comprises: The aluminum-containing interlayer foil is placed in a hydration tank for hydration treatment, the hydration temperature is 50-100° C., and the hydration time is 1-25 minutes; after hydration, the hydrated interlayer foil is obtained by drying.

[0011] As a further preference, in the above sintering process, the step of hydrating the aluminum-containing interlayer foil to obtain a hydrated interlayer foil comprises: placing the aluminum-containing interlayer foil in a hydration tank for hydration treatment at a hydration temperature of 85-100° C. and a hydration time of 1-15 minutes; drying after hydration to obtain the hydrated interlayer foil; more preferably, the hydration temperature is 95-100° C. and the hydration time is 3-8 minutes; Alternatively, the aluminum-containing interlayer foil is placed in a hydration tank for hydration treatment at a hydration temperature of 50-85° C. and a hydration time of 15-25 minutes; and after hydration, it is dried to obtain the hydrated interlayer foil.

[0012] Under the above-mentioned hydration conditions, the thickness of the hydration layer and the oxygen content of the hydration layer on the surface of the hydrated interlayer foil are both relatively good, which can not only release more water to promote the formation of aluminum oxide on the surface of the base foil, but also form more pores, which can better adsorb the binder and prevent adhesion to the base foil during sintering.

[0013] Preferably, in the above sintering process, the aluminum-containing interlayer foil is an aluminum foil with an aluminum purity greater than 99.9%.

[0014] Preferably, in the above sintering process, the length of the foil roll is 300-1000m, and the roll diameter is 300-800mm.

[0015] Preferably, in the above sintering process, the step of sintering the foil roll includes: sintering the vertically placed foil roll under vacuum conditions or inert atmosphere protection, with a sintering temperature of 550-650° C. and a sintering time of 5-30 hours.

[0016] The present invention also provides a high-performance aluminum foil, which is produced by adopting the above-mentioned sintering process.

[0017] Compared with the prior art, the technical effects of the present invention are embodied in: (1) The interlayer foil used in the present invention is an aluminum-containing interlayer foil. The surface of the aluminum-containing interlayer foil usually has a layer of aluminum oxide film. When it is hydrated, the aluminum oxide film will slightly dissociate in water and react with hydrogen ions in the water, so that the aluminum oxide film is destroyed, exposing the aluminum inside the interlayer foil. At this time, this part of the aluminum will react with water to form aluminum hydroxide and hydrogen, and the aluminum hydroxide will further hydrate to form hydrated aluminum hydroxide. When the base foil and the hydrated interlayer foil are rolled into a foil roll and sintered at high temperature, During the sintering process, on the one hand, the hydrated aluminum hydroxide on the surface of the hydrated interlayer foil will decompose, and the generated water will react with the aluminum powder on the surface of the base foil at high temperature to generate aluminum oxide and hydrogen, thereby promoting the aluminum powder on the surface of the base foil to generate aluminum oxide, promoting the sintering process, and making the oxidation of the aluminum powder more uniform; on the other hand, for the interlayer foil, the generation and decomposition of aluminum hydroxide on its surface will lead to a large number of pores inside the interlayer foil, thereby better absorbing the binder vaporized from the base foil, making the debinding more complete and improving the debinding efficiency, thereby improving the performance of the electrode foil.

[0018] (2) Under the hydration conditions set by the present invention, the thickness of the hydration layer and the oxygen content of the hydration layer on the surface of the hydrated interlayer foil are both better, which can not only release more water to promote the formation of aluminum oxide on the surface of the base foil, but also form more pores, which can better absorb the binder and prevent adhesion to the base foil during sintering.

[0019] (3) The electrode foil of the present invention not only does not bulge or stick when rolled after sintering, but also has a low C content and a good pattern, indicating that the debinding effect during the sintering process is good; and the performance such as leakage current, specific capacitance, specific capacitance dispersion, and loss are further improved. DETAILED DESCRIPTION

[0020] The following examples are given to further illustrate the technical solution of the present invention.

[0021] Examples 1-16 This embodiment provides a sintering process for a high-performance electrode foil, and the sintering process includes the following steps: S1: coating the aluminum powder slurry on the surface of the aluminum foil substrate and drying it to obtain a base foil; This embodiment has no restrictions on the specific composition of the aluminum powder slurry and the coating thickness. In addition to aluminum powder, the aluminum powder slurry generally contains a solvent and a binder. Aluminum powder slurries that meet the above conditions and can be used in the present invention can be found in CN114523112A. To facilitate subsequent data comparison, the aluminum powder slurries used in various embodiments of the present invention all have the following compositions: 50 wt.% aluminum powder with an average particle size of 3 μm, 3 wt.% titanium dioxide powder with an average particle size of 100 nm, 5 wt.% polyvinylidene fluoride (binder), and 42 wt.% N-methylpyrrolidone (solvent). The aluminum powder slurry is symmetrically coated on both sides of an aluminum foil substrate with a thickness of 30 μm, and the coating thickness on one side is 50 μm; after the coating is completed, the base foil is obtained by drying; S2: hydrating the aluminum-containing interlayer foil to obtain a hydrated interlayer foil; Specifically, the aluminum-containing interlayer foil is placed in a hydration tank for a certain period of time, and the portion that has passed through the hydration tank is dried to obtain a hydrated interlayer foil; The hydration time and water temperature in the hydration tank are shown in Table 1; S3: Winding the base foil and the hydrated interlayer foil alternately to form a foil roll; Specifically, the base foil and the hydrated interlayer foil are alternately wound to form a base foil-interlayer foil-base foil form, and then wound to form a foil roll, the foil roll has a length of 300-1000m and a roll diameter of 300-800mm; S4: sintering the foil roll; Specifically, the foil roll placed vertically in a sintering furnace is sintered under vacuum conditions or under the protection of an inert atmosphere; This embodiment has no special requirements for the sintering temperature and sintering time. The sintering temperature in the range of 550-650°C and the sintering time in the range of 5-30 hours are applicable to the present invention. This sintering condition has been verified in the Chinese invention patent publication number CN115608986B. To facilitate subsequent data comparison, the embodiments of the present invention all adopt a sintering temperature of 605°C and a sintering time of 15 hours.

[0022] The subsequent chemical formation process of the sintered foil may refer to known or unknown technologies, and the present invention has no special requirements for this. To facilitate subsequent data comparison, each embodiment of the present invention is formed according to the chemical formation steps published in publication number CN114525565B, and then the high-performance electrode foil of this embodiment can be obtained.

[0023] Comparative Example 1 This comparative example provides a sintering process for an electrode foil. The sintering process is the same as that of Example 1, except that: there is no step S2, and the aluminum-containing interlayer foil is directly used in step S3.

[0024] Comparative Example 2 This comparative example provides a sintering process for an electrode foil. The sintering process is the same as that of Example 5, except that: there is no step S2, and the aluminum-containing interlayer foil is directly used in step S3.

[0025] Table 1 Step parameters of various embodiments and comparative examples and various performance tests of electrode foil As can be seen from Table 1, compared with the interlayer foil that has not been hydrated, when the interlayer foil is hydrated, the electrode foil obtained in Examples 1-16 does not bulge when rolled after sintering, has a good shape, and the C content of the electrode foil after sintering is also reduced accordingly, indicating that the debinding effect during the sintering process is better.

[0026] Furthermore, it can be seen that the hydration temperature has a certain influence on both the hydration time and the hydration effect. When the hydration temperature is between 85-100°C, a relatively short hydration time (1-15 minutes) is required to form a hydrated aluminum hydroxide layer with a certain thickness (above 1.65μm) and oxygen content (above 0.276%) on the surface of the interlayer foil. This allows the hydrated aluminum hydroxide layer to release more water during high-temperature sintering. This water actively reacts with the aluminum on the surface of the base foil to form aluminum oxide, prompting the rapid and uniform formation of aluminum oxide on the surface of the base foil. Moreover, the hydrated aluminum hydroxide layer with sufficient thickness will create more pores inside the interlayer foil during the generation and decomposition process, better adsorbing the binder during sintering, making the debinding more complete and improving the debinding efficiency, further preventing the base foil from sticking, and beneficially improving the performance of the electrode foil.

[0027] When the hydration temperature is between 65-85°C, a longer hydration time (at least 10 minutes or more) is required to obtain a hydrated aluminum hydroxide layer equivalent to the above. The lower the hydration temperature, the longer the corresponding hydration time (when the hydration temperature is 65°C and the hydration time is 25 minutes, the thickness of the hydrated aluminum hydroxide layer is 1.61μm and the oxygen content is 0.198%).

[0028] It can be seen that compared with comparative examples 1-2, the electrode foils of each embodiment of the present invention have further improved performance data such as leakage current, specific capacitance, and specific capacitance dispersion. In particular, the leakage current of the electrode foils of Examples 3-5 is between 106-118 μA, and the specific capacitance is between 1.20-1.25 μF / cm 2 The specific volume dispersion is between 0.5-0.9%, and the loss is between 3.75-4.03.

Claims

1. A sintering process for high-performance electrode foil, characterized in that: include: a step of hydrating the aluminum-containing interlayer foil to obtain a hydrated interlayer foil; The step of alternately winding the base foil and the hydrated interlayer foil to form a foil roll; The step of sintering the foil roll.

2. The interlayer foil according to claim 1, characterized in that The aluminum-containing interlayer foil is an aluminum foil with an aluminum purity greater than 97%.

3. The sintering process according to claim 1, wherein: The step of hydrating the aluminum-containing interlayer foil to obtain a hydrated interlayer foil comprises: The aluminum-containing interlayer foil is placed in a hydration tank for hydration treatment at a hydration temperature of 50-100° C. and a hydration time of 1-25 minutes. After hydration, the hydrated interlayer foil is dried to obtain the hydrated interlayer foil.

4. The sintering process according to claim 3, characterized in that The step of hydrating the aluminum-containing interlayer foil to obtain a hydrated interlayer foil comprises: The aluminum-containing interlayer foil is placed in a hydration tank for hydration treatment, the hydration temperature is 85-100° C., and the hydration time is 1-15 minutes; after hydration, it is dried to obtain the hydrated interlayer foil.

5. The sintering process according to claim 4, characterized in that The hydration temperature is 95-100℃ and the hydration time is 3-8min.

6. The sintering process according to claim 3, characterized in that The step of hydrating the aluminum-containing interlayer foil to obtain a hydrated interlayer foil comprises: The aluminum-containing interlayer foil is placed in a hydration tank for hydration treatment, the hydration temperature is 50-85° C., and the hydration time is 15-25 minutes; after hydration, the foil is dried to obtain the hydrated interlayer foil.

7. The sintering process according to claim 1, wherein: The base foil and the hydrated interlayer foil are alternately wound to form a base foil-interlayer foil-base foil form, and then wound to form a foil roll. The foil roll has a length of 300-1000m and a roll diameter of 300-800mm.

8. The sintering process according to claim 1, wherein: The step of sintering the foil roll includes: sintering the vertically placed foil roll under vacuum conditions or inert atmosphere protection, with a sintering temperature of 550-650° C. and a sintering time of 5-30 hours.

9. A high performance aluminum foil, characterized in that: The sintering process is adopted as claimed in any one of claims 1 to 8.

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