An electrode foil and a coiled sintering process thereof

Abstract

The application discloses an electrode foil and a coiled sintering process thereof, and the coiled sintering process comprises the step of spacing and coiling a base layer foil and a sandwich layer foil to form a foil coil; and the sandwich layer foil is provided with micropores. The sandwich layer foil is provided with micropores, so that, on the one hand, the shrinkage range of the sandwich layer foil is larger than that of the sandwich layer foil without the micropores, and the shrinkage range of the sandwich layer foil is more matched with that of the base layer foil, which is beneficial to reducing the difference in coiling tension, reducing the problems of adhesion and bulging caused by difficult glue discharge, and on the other hand, the micropores can adsorb the binder gasified from the base layer foil, make the binder volatilize more quickly, make the glue discharge more complete, and improve the glue discharge efficiency; and on the third hand, the sandwich layer foil with the micropores has better heat conduction performance, so that it is beneficial to reducing the temperature difference between the inside and the outside of the foil coil during the coiled sintering, and reducing the electric performance difference of the electrode foil.

Description

Technical Field

[0001] This invention belongs to the field of capacitor technology, specifically relating to an electrode foil and its roll-forming and sintering process. Background Technology

[0002] The quality of the anode foil not only affects the lifespan of the capacitor, but also directly impacts the lifespan of the entire electronic device.

[0003] Currently, there are two main production processes for anode foil: etching and sintering. The sintering process involves coating aluminum powder onto the surface of an aluminum foil substrate, followed by high-temperature melting and bonding of the aluminum powder with each other and with the substrate, forming a porous aluminum foil with a three-dimensional structure. This porous foil helps increase the specific surface area of ​​the anode foil, improving its electrochemical performance. Therefore, with increasing national emphasis on ecological and environmental issues, the sintering process is favored by enterprises due to its environmental friendliness, lack of pollution, and the high performance of the resulting electrode foil.

[0004] It can be seen that the correct and effective implementation of the sintering step in the sintering foil process is one of the key factors determining the performance of the sintered foil. Currently, the following three sintering methods can be used in the sintering foil process:

[0005] The first type, such as the porous electrode foil preparation process disclosed in Chinese invention patent application CN114523112A, involves heat treatment (i.e. sintering) being carried out while the composite aluminum foil is in a moving state. During sintering, there is a large transmission tension, which can easily cause the aluminum foil to deform or break. This process has drawbacks such as slow foil feeding speed and low production efficiency.

[0006] The second method, as disclosed in Chinese invention patent CN117900480A, involves a heat treatment process for porous electrode foil. This process first winds up the composite aluminum foil and wraps it into a foil roll using a shaping component, then places the foil roll in a sintering furnace for sintering. Compared to the aforementioned process of sintering while the foil is being wound, this method uses a roll-to-roll sintering approach, which is not only energy-efficient and high-performing but also avoids foil deformation and breakage. However, after winding, the inner and outer composite aluminum foils come into contact with each other, leading to interlayer adhesion after sintering. This can still cause tearing and breakage of the sintered foil during subsequent unwinding.

[0007] The third method, such as the Chinese invention patent CN115274304B, discloses a sintered foil and its preparation method. This method involves winding a base foil with a slurry layer and an interlayer foil alternately to form a roll foil, and then sintering the roll foil. This interlayer foil effectively blocks the diffusion of aluminum atoms between adjacent base foils during the sintering process, thus alleviating the problem of adhesion between adjacent base foils. However, this sintering process still has shortcomings: the interlayer foil uses a complete aluminum alloy foil, titanium alloy foil, or steel foil. When this interlayer foil is wound together with the base foil, it not only increases the temperature difference between the inside and outside of the roll, but also causes the interlayer foil and the base foil to shrink at different rates during sintering. This makes core glue removal difficult and easily leads to adhesion between the base foil and the interlayer foil. Once adhesion occurs, it will further affect subsequent glue removal, causing foil bulging, poor pattern formation, and impacting subsequent chemical formation properties. Summary of the Invention

[0008] The purpose of this invention is to provide an electrode foil and its rolling and sintering process to prevent adhesion between base foils or between base foils and interlayer foils, thereby ensuring the performance of the electrode foil.

[0009] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows:

[0010] An electrode foil is prepared using the above-mentioned roll-to-sintering process, which includes the step of winding a base foil and an interlayer foil alternately to form a foil roll; the interlayer foil has micropores.

[0011] The sandwich foil used in this invention has micropores. On the one hand, during the sintering process, the shrinkage of the sandwich foil is greater than that without micropores, which better matches the shrinkage of the base foil, thus reducing the difference in winding tension and mitigating adhesion and bulging problems caused by adhesive removal difficulties. On the other hand, the micropores can adsorb the vaporized adhesive from the base foil, allowing it to evaporate more quickly, resulting in more complete adhesive removal and improved adhesive removal efficiency. Thirdly, the sandwich foil with micropores has better thermal conductivity, which helps to reduce the temperature difference between the inside and outside of the foil roll during sintering and reduces the differences in electrical properties at various points on the electrode foil.

[0012] Preferably, in the above-mentioned coiling and sintering process, the pore size of the micropores is between 0.01 and 0.5 μm, more preferably between 0.1 and 0.5 μm; and the density of micropores on the sandwich foil is 100-1000 per cm. 2 More preferably, 300-700 per cm 2 The interlayer foil is aluminum foil or aluminum alloy foil; the thickness of the interlayer foil is 10-200 μm, more preferably 50-200 μm. Suitable interlayer foil thickness, micropore density and pore size are beneficial to further reduce bulging during sintering and rewinding, and to further improve the leakage current, specific capacitance and other properties of the electrode foil.

[0013] Preferably, in the above-mentioned coiling and sintering process, the micropores are formed by irradiating the interlayer foil with a laser, and the micropores are formed after the laser melts through the interlayer foil. Laser-formed micropores have the characteristics of high precision, smooth inner walls, and no need for secondary processing. They are also environmentally friendly, simple to operate, and have high production efficiency, making them suitable for processing high-density hole groups.

[0014] As a further preferred embodiment, the parameters of the laser irradiation are as follows: the laser frequency of the laser is 50KHz, the laser pulse width is 7-11ns, the pattern fill density is 1-0.03mm, and the scanning speed is 300-500mm / s.

[0015] Compared with the prior art, the technical effects of the present invention are reflected in:

[0016] The coil sintering process of this invention uses a sandwich foil with micropores. On the one hand, during the sintering process, the shrinkage of the sandwich foil with micropores is greater than that without micropores, which better matches the shrinkage of the base foil, thus reducing the difference in winding tension and mitigating adhesion and bulging problems caused by difficulty in debinding. On the other hand, the micropores can adsorb the vaporized binder from the base foil, allowing it to evaporate more quickly, resulting in more complete debinding and improved debinding efficiency. Thirdly, the sandwich foil with micropores has better thermal conductivity, which helps to reduce the temperature difference between the inside and outside of the foil roll during coil sintering and reduces the differences in electrical properties at various points on the electrode foil. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of using laser irradiation of aluminum foil to prepare sandwich foil;

[0018] Figure 2 This is a real image of the sandwich foil used in the coiling and sintering process of an electrode foil according to the present invention. Detailed Implementation

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0020] This embodiment describes a coiling and sintering process for electrode foil, which includes the following steps:

[0021] (1) Coat the aluminum powder paste onto the surface of the aluminum foil substrate and dry it to obtain the base foil.

[0022] Specifically, by mass percentage, the aluminum powder slurry comprises: 50-60 wt.% aluminum powder (in this embodiment, 50 wt.% aluminum powder with an average particle size of 3 μm is used), 0.02-3 wt.% valve metal oxide powder (in this embodiment, 3 wt.% titanium dioxide powder with an average particle size of 100 nm is used), 3-10 wt.% binder (in this embodiment, 5 wt.% polyvinylidene fluoride is used), and 30-45 wt.% solvent (in this embodiment, 42 wt.% N-methylpyrrolidone is used).

[0023] Aluminum powder paste is symmetrically coated on both sides of an aluminum foil substrate with a thickness of 30μm, and the coating thickness on one side is 50μm; after coating, drying is performed to obtain the base foil.

[0024] (2) Preparation of sandwich foil with micropores

[0025] Specifically, the interlayer foil (material is aluminum foil or aluminum alloy foil) is first oxidized (using oxygen as the oxidizing atmosphere, oxidation temperature 230℃, oxidation time 20min) to form a layer of aluminum oxide on its surface. Then, the interlayer foil is irradiated with a laser (e.g., Figure 1 As shown), after laser melting through the sandwich foil, a sandwich foil with micropores is obtained (e.g. Figure 2 (As shown in Table 1), the thickness, micropore density, and micropore diameter of the interlayer foil are shown in Table 1.

[0026] (3) The base foil and the interlayer foil are wound alternately to form a foil roll, and then sintered to obtain a sintered foil.

[0027] Specifically, the base foil and the laminated foil are wound alternately to form a foil roll with alternating layers of "base foil-laminated foil-base foil". The foil roll is then placed vertically in a sintering furnace and sintered under vacuum or an inert atmosphere (such as argon). The sintering temperature is 550℃~650℃ (605℃ in this embodiment) and the sintering time is 8h~20h (15h in this embodiment). During the sintering process, the sintering atmosphere circulates and convects in the sintering furnace and passes through the foil roll axially.

[0028] After the sintered foil was formed according to the formation steps disclosed in publication number CN114525565B, the electrode foil of this embodiment was obtained. The appearance and electrochemical performance of each electrode foil were tested, and the results are shown in Table 1.

[0029] Table 1

[0030]

[0031] Note: No micropores were found on the sandwich foil in Comparison 1 and Comparison 2.

[0032] As can be seen from Table 1, compared with the non-microporous sandwich foil, when micropores are opened on the sandwich foil, the electrode foil only shows slight bulging or no bulging when it is spun and rolled up. The c content of the sintered electrode foil is also reduced accordingly, indicating that the glue removal effect is better during the sintering process.

[0033] Furthermore, as can be seen from Table 1, when the micropore diameter is 0.1-0.5 μm and the micropore density is 300-700 pores / cm³, 2 When the interlayer foil thickness is 50-200μm and the interlayer foil is aluminum foil or aluminum alloy foil, the electrode foil has further improved performance data such as leakage current, specific capacitance, and specific capacitance difference.

[0034] Examples 14-18

[0035] This embodiment describes a coiled sintering process for electrode foil, which is basically the same as that in Embodiment 7, except for the composition of the aluminum powder slurry and the sintering conditions, as listed in Table 2.

[0036] Table 2

[0037]

[0038] As can be seen from Table 2, under the established aluminum powder slurry and sintering conditions, the performance of each electrode foil remains basically consistent.

Claims

1. A sintering process for electrode foil, comprising the step of alternately winding a base foil and a sandwich foil to form a foil roll; characterized in that, The interlayer foil has micropores.

2. The coiling and sintering process as described in claim 1, characterized in that, The pore size of the micropores is between 0.01 and 0.5 μm.

3. The coiling and sintering process as described in claim 2, characterized in that, The pore size of the micropores is between 0.1 and 0.5 μm.

4. The coiling and sintering process as described in claim 1, characterized in that, The density of micropores on the sandwich foil is 100-1000 per cm. 2 .

5. The coiling and sintering process as described in claim 4, characterized in that, The density of micropores on the sandwich foil is 300-700 per cm. 2 .

6. The coiling and sintering process as described in claim 1, characterized in that, The micropores are formed by irradiating the interlayer foil with a laser, and the micropores are formed after the laser melts through the interlayer foil.

7. The coiling and sintering process as described in claim 6, characterized in that, The parameters for laser irradiation are as follows: the laser frequency of the laser is 50KHz, the laser pulse width is 6-12ns, the pattern fill density is 1-0.03mm, and the scanning speed is 200-500mm / s.

8. The coiling and sintering process as described in claim 1, characterized in that, The thickness of the interlayer foil is 10-200 μm.

9. The coiling and sintering process as described in claim 8, characterized in that, The thickness of the interlayer foil is 50-200 μm.

10. An electrode foil, characterized in that, Prepared using the rolling and sintering process described in any one of claims 1-9.

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