Porous electrode foil and dynamic rotation heat treatment process thereof

Abstract

The invention discloses a porous electrode foil and a dynamic rotation heat treatment process thereof. The process comprises the following steps of: rolling a composite aluminum foil and wrapping the composite aluminum foil into a foil roll by using a shaping piece; transversely placing the foil roll with a material shaft in the center into the sintering furnace, and connecting the material shaft with the output end of the circumferential driver; and starting the circumferential driver to enable the foil roll to be subjected to heat treatment in a continuous swinging or rotating state. The foil coil is transversely placed in the sintering furnace, and the material shaft and the circumferential driver are matched to enable the foil coil to receive a heat treatment procedure in the swinging or rotating process, so that the influence of the gravity of the foil coil on the model can be effectively reduced, and the deformation of the foil coil caused by heating is uniformly distributed on the circumference of the whole foil coil; the condition of local deformation accumulation is prevented; therefore, the defects such as creases, wrinkles and piebaldness on the foil surface can be effectively reduced, the formation production stability can be improved, and the qualified rate of electrode foil production can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of capacitors, and in particular relates to a porous electrode foil and a dynamic rotation heat treatment process thereof. Background Art

[0002] Electrode foil is a key raw material for preparing capacitors. In order to increase the specific volume of electrode foil, a sintered foil (i.e., porous electrode foil) has been proposed in recent years to replace the traditional etched foil. Sintered foil is made by covering a layer of aluminum powder or aluminum powder mixture on the surface of an aluminum foil substrate in a variety of optional ways, and then sintering it; after sintering, the aluminum powder or aluminum powder mixture layer is transformed into a porous sintered body. Due to the increase in surface area, the specific volume of sintered foil is at least 20% higher than that of etched foil; and the sintering process does not involve environmentally polluting raw materials such as hydrochloric acid, sulfuric acid, and nitric acid, and is more environmentally friendly.

[0003] It can be seen that the rapid development of sintered foil and its gradual replacement of traditional corrosion foil has become an inevitable trend. However, in the preparation process of sintered foil, it is inevitable to sinter the aluminum foil at high temperature. The foil roll will deform under the action of high temperature, tension and gravity, resulting in creases, wrinkles, spots and other defects on the foil surface, increasing the risk of broken foil and cracking during chemical production, seriously affecting the production qualification rate of porous electrode foil.

[0004] In order to reduce the deformation of the foil roll during the sintering process, a Chinese invention patent with the announcement number CN 117900480 B discloses a heat treatment process for porous electrode foil, which first uses a shaping piece to wrap the foil roll, and then places the foil roll vertically in a sintering furnace for sintering. This sintering method can reduce the deformation of the foil roll caused by gravity at high temperature (lateral prevention of the foil roll) to a certain extent, but it will still introduce longitudinal folds and extrusion marks at the contact position between the shaping piece and the foil roll.

[0005] To date, there is no effective process that can significantly improve the shape of foil coils after heat treatment. Summary of the invention

[0006] The purpose of the invention is to provide a porous electrode foil and a dynamic rotation heat treatment process thereof, so as to improve the shape of the foil roll after heat treatment and improve the yield of the porous electrode foil.

[0007] To achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows: A dynamic rotary heat treatment process for a porous electrode foil comprises the steps of rolling up a composite aluminum foil and wrapping it with a forming member into a foil roll; and further comprising: The step of placing the foil roll with the material shaft in the center transversely in the sintering furnace and connecting the material shaft to the output end of the circumferential drive; and, a step of activating a circumferential drive to allow the foil coil to be subjected to heat treatment in a state of continuous oscillation or rotation.

[0008] The present invention places the foil roll horizontally in the sintering furnace, and adopts the cooperation of the material shaft and the circumferential driver to make the foil roll undergo a heat treatment procedure during the swinging or rotating process. This method can effectively reduce the influence of the gravity of the foil roll on the template, so that the deformation of the foil roll caused by heat is evenly distributed on the entire circumference of the foil roll, and the accumulation of local deformation is prevented; thereby, the occurrence of creases, wrinkles, spots and other defects on the foil surface can be effectively reduced, which is beneficial to improving the stability of chemical production and improving the qualified rate of electrode foil production.

[0009] Preferably, in the above-mentioned dynamic rotation heat treatment process of the porous electrode foil, the sintering furnace comprises a furnace body with an inlet and outlet, the furnace body is provided with at least one heat treatment platform, and the fixed shaft is rotatably connected to the heat treatment platform.

[0010] As a further preferred embodiment, in the above-mentioned dynamic rotation heat treatment process of the porous electrode foil, the heat treatment platform comprises a support table fixedly arranged in the furnace body, and a material rack movably connected to the support table; the material rack is rotatably connected to at least one material shaft and all the material shafts are arranged in parallel; The circumferential driver is fixed on the outer wall of the furnace body. The output end of the circumferential driver passes through the furnace body and has a connecting piece inside the furnace body. The connecting piece is detachably connected or sleeved with the end of the material shaft to ensure that the material shaft and the circumferential driver rotate synchronously.

[0011] The movably arranged material rack facilitates both the assembly of the material shaft with the foil roll and the separation or connection of the material shaft with the circumferential drive.

[0012] Preferably, in the above-mentioned dynamic rotary heat treatment process of the porous electrode foil, the inlet and outlet are located on the peripheral side of the furnace body, and the support platform is provided with at least one Y-guide rail for guiding the material rack to enter and exit the furnace body and a plurality of X-guide rails communicating with the Y-guide rail; The material rack is provided with a plurality of rolling elements rollingly matched with the Y guide rail and the X guide rail. The Y guide rail has a first travel end point opposite to the entrance and exit, and the X guide rail has a second travel end point opposite to the Y guide rail.

[0013] When the rolling element moves along the Y guide rail to the first end of the stroke, at least one rolling element also reaches the position opposite to the X guide rail. At this time, the material rack is pushed along the X guide rail, and the rolling element enters the X guide rail. When the rolling element moves to the second end of the stroke, the end of the material shaft is engaged or sleeved with the above-mentioned connecting element. Due to the circumferential limit between the connecting element and the material shaft, when the circumferential drive is working, the material shaft and the connecting element will swing or rotate synchronously.

[0014] Preferably, in the above-mentioned dynamic rotation heat treatment process of the porous electrode foil, the swing amplitude of the foil roll is between ±15° and 360°.

[0015] The present invention has found that the optimal swing amplitude and optimal swing speed are different for foil rolls with different roll diameters. Specifically, as a preferred embodiment, the swing amplitude of a foil roll with a roll diameter greater than 600 mm is ±15°~360°, and the swing speed is 1~2 rpm; The swing amplitude of foil coils with a coil diameter between 400-600 mm is ±45°~360°, and the swing speed is 4-6 rpm; The swing amplitude of foil coils with a coil diameter between 300-400 mm is ±60°~360°, and the swing speed is 1-20 rpm; The swing amplitude of foil coils with a coil diameter between 200-300 mm is ±90°~360°, and the swing speed is 8-12 rpm; The foil coils with a coil diameter between 100 and 200 mm are rotated through 360° at a speed of 12 to 18 rpm.

[0016] As a further preferred embodiment, the swing amplitude of the foil roll with a roll diameter greater than 600 mm is ±15° and the swing speed is 1 rpm; The swing amplitude of foil coils with a coil diameter between 400-600 mm is ±45° and the swing speed is 5 rpm; The swing amplitude of foil coils with a coil diameter between 300-400 mm is ±60° and the swing speed is 5-10 rpm; The swing amplitude of foil coils with a coil diameter between 200-300 mm is ±90° and the swing speed is 10 rpm; The foil coils with a coil diameter between 100 and 200 mm are rotated through 360° at a speed of 15 rpm.

[0017] In the above-mentioned dynamic rotation heat treatment process of the porous electrode foil, the heat treatment includes a heating stage, a heat preservation stage and a cooling stage which are carried out in sequence. In each stage, the swing amplitude and the swing speed of the foil roll can remain unchanged or change regularly, that is: as the heating stage, the heat preservation stage and the cooling stage occur in sequence, the swing amplitude of the foil roll increases in sequence and the swing speed of the foil roll decreases in sequence.

[0018] For example, for a foil roll with a roll diameter between 300-400 mm, the swing amplitude of the foil roll in the heating stage is more preferably ±60°, and the swing speed is more preferably 5 rpm; the swing amplitude of the foil roll in the heat preservation stage is more preferably ±90°, and the swing speed is more preferably 1 rpm; in the cooling stage, the foil roll preferably rotates 360°, and the rotation speed is more preferably 1 rpm.

[0019] The present invention also provides a porous electrode foil, which is manufactured by adopting the above-mentioned dynamic rotation heat treatment process.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention places the foil roll horizontally in the sintering furnace, and adopts the cooperation of the material shaft and the circumferential driver to make the foil roll undergo the heat treatment process during the swinging or rotating process. This method can effectively reduce the influence of the weight of the foil roll on the template, so that the deformation of the foil roll caused by heat is evenly distributed around the entire circumference of the foil roll, thereby preventing the accumulation of local deformation. This can effectively reduce the appearance of defects such as creases, wrinkles, and spots on the foil surface, which is beneficial to improving the stability of chemical production and the qualified rate of electrode foil production.

[0021] (2) The present invention sets different swing amplitudes and swing speeds for foil rolls with different roll diameters, finds the balance point of foil roll tension, gravity, torsion and the restraining force of the outer ring forming part, so that the foil rolls with different roll diameters can reach the optimal state.

[0022] (3) The present invention sets different swing amplitudes and swing speeds according to the different deformation characteristics of the foil roll in the heating, insulation and cooling stages of the heat treatment process, thereby specifically improving the deformation in each stage of the heat treatment process, which is beneficial to further improve the yield of the porous electrode foil. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the structure of a sintering furnace used in a dynamic rotary heat treatment process of a porous electrode foil according to the present invention; Figure 2 A schematic diagram of the structure of a sintering furnace used in a dynamic rotary heat treatment process of a porous electrode foil according to the present invention; Figure 3 It is a schematic diagram of the swinging or rotating state of the foil roll. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0025] Example 1 The present embodiment provides a porous electrode foil, and its preparation process includes the following steps: (1) 50 wt.% aluminum powder, 3.0 wt.% valve metal oxide powder, 5 wt.% binder and 42.0 wt.% solvent are uniformly mixed to obtain a fluid mixture; The average particle size of the aluminum powder is 3.5 μm, the valve metal oxide powder is titanium dioxide powder with an average particle size of 100 nm, the binder is polyvinylidene fluoride, and the solvent is N-methylpyrrolidone; (2) using an extrusion coater to symmetrically coat the fluid mixture on both sides of an aluminum foil substrate having a thickness of 30-40 μm, and coating thickness on one side of the substrate is 45-65 μm, so that the total thickness of the composite aluminum foil obtained after drying reaches 130 μm; (3) rolling up the composite aluminum foil and wrapping it with a forming piece to form a foil roll; Specifically, the composite aluminum foil is rolled up by a winding machine, the rolling tension is 15 kg, and the rolling length is 300-1000 m; after the rolling is completed, it is wrapped with a 200-mesh 304 stainless steel mesh, and the sealing is fixed with an aluminum foil tape to obtain a foil roll; (4) placing the foil roll with the material shaft 4 in the center transversely in the sintering furnace and connecting the material shaft 4 to the output end of the circumferential drive 5; Specifically, Figure 1 As shown, the foil roll tube core is first passed through the material shaft 4, and the material shaft 4 and the foil roll tube core are fixed with an inclined iron clamp, and then the material shaft 4 with the foil roll is placed horizontally in the sintering furnace; like Figure 1 As shown, the sintering furnace of this embodiment includes a furnace body 1 with a heating chamber 100 therein, and an entrance 200 for loading or unloading a foil roll is provided on the peripheral side of the furnace body 1; at least one heat treatment platform is provided in the heating chamber 100, and each heat treatment platform includes a support platform 2 fixed in the furnace body 1 and a material rack 3 movably connected to the support platform 2; Among them, multiple pairs of brackets are arranged on the material rack 3, and the two ends of the material shaft 4 are rotatably connected to a pair of brackets respectively; a plurality of circumferential drivers 5 are fixedly installed on the outer wall of the furnace body 1. In this embodiment, a motor is adopted, and the output shaft of each circumferential driver 5 passes through the furnace body 1 and is provided with a connecting piece 6 in the heating chamber. The connecting piece 6 is detachably connected or sleeved with the end of the material shaft 4 to ensure that the material shaft 4 and the circumferential driver 5 swing or rotate synchronously. The swing or rotation is shown as follows Figure 3 ,; It can be seen that the number of circumferential drivers 5 is consistent with the number of material shafts 4, which facilitates targeted adjustment of the swing amplitude and swing speed of each material shaft 4; accordingly, the roll diameters of multiple foil rolls on the same material shaft 4 are preferably consistent; In addition, if Figure 2 As shown, the support platform 2 includes two parallel Y guide rails 21, which are opposite to the entrance 200 and are used to guide the material rack 3 to enter and exit the furnace body 1. Each Y guide rail 21 is connected to two X guide rails 22, and the X guide rail 22 is used to guide the material rack 3 to move in the direction of the circumferential drive 5. The bottom of the material rack 3 is provided with a plurality of rolling elements that roll with the Y guide rail 21 and the X guide rail 22. The Y guide rail 21 has a first travel end point that is opposite to the entrance 200, and the X guide rail 22 has a second travel end point that is opposite to the Y guide rail 21. When the rolling element moves along the Y guide rail 21 to the first travel end point, at least one rolling element also reaches a position opposite to the X guide rail 22. At this time, the material rack 3 is pushed along the X guide rail 22, and the rolling element enters the X guide rail 22. When the rolling element moves to the second travel end point, the end of the material shaft 4 is engaged or sleeved with the above-mentioned connecting element 6. Due to the circumferential limit between the connecting element 6 and the material shaft 4, when the circumferential drive 5 is working, the material shaft 4 and the connecting element 6 will swing or rotate synchronously. Those skilled in the art can select various forms of connecting elements 6, and the present invention has no special requirements for this. It is only necessary to ensure that the material shaft 4 and the connecting element 6 can be quickly connected or disconnected, and that the material shaft 4 can rotate when the circumferential drive 5 rotates. (5) starting the circumferential drive 5 so that the foil roll is subjected to heat treatment in a state of continuous swinging or rotation; Specifically, after the swing amplitude and swing speed corresponding to the foil roll are set, each motor is started; (6) Heat treating the foil coil; The heat treatment procedure is as follows: first, a 450°C debinding atmosphere (argon) is supplied to the sintering furnace for 5 h; then, a 620°C sintering atmosphere (argon) is supplied to the sintering furnace, and the sintering atmosphere circulates and passes through the foil roll axially in the sintering furnace for 10 h; The heat treatment procedure includes a heating stage, a heat preservation stage and a cooling stage, wherein the heating stage is from room temperature to 450°C and from 450°C to 620°C, the heat preservation stage is sintering at 620°C for 10 h, and the cooling stage is the process of cooling to 50°C or room temperature after sintering. (7) The sintered foil roll is anodized by conventional chemical process to obtain the porous electrode foil of this embodiment.

[0026] In each embodiment of the present invention, steps (1), (2), (3), (6) and (7) are conventional processes, and reference may be made to the Chinese invention patent publication number CN115608986B. Therefore, for the above steps, the present invention only lists one implementation mode as an example, but it is obvious that this part of the content should not limit the protection scope of the present invention. For step (5), the present invention will use different foil roll diameters, swing amplitudes, and swing speeds for examples, and evaluate the appearance of the porous electrode foil obtained in each embodiment. The results are shown in Table 1.

[0027] Table 1 It can be seen from Table 1 that for foil rolls with different roll diameters, in order to obtain a higher yield, appropriate swing amplitude and swing speed should be set. Specifically, for foil rolls with a roll diameter of 100-200mm, the best swing amplitude is 360°, and the best rotation speed is 15 rpm. At this time, the yield of the porous electrode foil reaches 96.0%; for foil rolls with a roll diameter of 200-300mm, the best swing amplitude is ±90°, and the best swing speed is 10 rpm. At this time, the yield of the porous electrode foil reaches 97.7%; for foil rolls with a roll diameter of 300-400mm, the best swing amplitude is ±60°, and the best swing speed is 5 rpm. At this time, the yield of the porous electrode foil reaches 98.4% (compared with Comparative Example 1, the yield is increased by 6.4%); for foil rolls with a roll diameter of 400-600mm, the best swing amplitude is ±45°, and the best swing speed is 5 rpm. rpm, at this time the yield of the porous electrode foil reaches 98.0%; for the foil roll with a roll diameter greater than 600mm, the best swing amplitude is ±15°, and the best swing speed is 1rpm, at this time the yield of the porous electrode foil reaches 97.6%.

[0028] At the same time, it can be seen from Example 20 that when different swing amplitudes and swing speeds are set in different stages of the heat treatment process, the yield of the porous electrode foil is further improved to 99.0% compared with Example 2; it is speculated that this is because the deformation characteristics of the foil roll are different in different stages of the heat treatment process, and the adapted swing speed and swing amplitude are conducive to targeted improvement of the deformation in each stage of the heat treatment process.

Claims

1. A dynamic rotary heat treatment process for porous electrode foil, comprising the steps of rolling up a composite aluminum foil and wrapping it with a forming member into a foil roll; characterized in that: Also includes: The step of placing the foil roll with the material shaft (4) in the center transversely in the sintering furnace and connecting the material shaft (4) to the output end of the circumferential drive (5); And, the step of starting the circumferential drive (5) to allow the foil roll to be subjected to heat treatment in a state of continuous swinging or rotation.

2. The dynamic rotation heat treatment process of porous electrode foil according to claim 1, characterized in that: The sintering furnace comprises a furnace body (1) with an inlet and outlet (200), at least one heat treatment platform is arranged in the furnace body (1), and the fixed shaft is rotatably connected to the heat treatment platform.

3. The dynamic rotation heat treatment process of porous electrode foil according to claim 2, characterized in that: The heat treatment platform comprises a support platform (2) fixedly arranged in the furnace body (1), and a material rack (3) movably connected to the support platform (2); at least one material shaft (4) is rotatably connected to the material rack (3), and all the material shafts (4) are arranged in parallel; The circumferential drive (5) is fixedly mounted on the outer wall of the furnace body (1); the output end of the circumferential drive (5) passes through the furnace body (1) and is provided with a connecting piece (6) located inside the furnace body (1); the connecting piece (6) is detachably engaged or sleeved with the end of the material shaft (4) to ensure that the material shaft (4) and the circumferential drive (5) rotate synchronously.

4. The dynamic rotation heat treatment process of porous electrode foil according to claim 3, characterized in that: The entrance and exit (200) is located on the peripheral side of the furnace body (1), and the support platform (2) is provided with at least one Y-direction guide rail (21) for guiding the material rack (3) to enter and exit the furnace body (1) and a plurality of X-direction guide rails (22) connected to the Y-direction guide rail (21); The material rack (3) is provided with a plurality of rolling elements that roll with the Y guide rail (21) and the X guide rail (22); the Y guide rail (21) has a first travel end point opposite to the entrance (200); and the X guide rail (22) has a second travel end point opposite to the Y guide rail (21).

5. The dynamic rotation heat treatment process of porous electrode foil according to claim 1, characterized in that: The swing amplitude of the foil roll is between ±15° and 360°.

6. The dynamic rotation heat treatment process of porous electrode foil according to claim 5, characterized in that: The swing amplitude of foil rolls with a roll diameter greater than 600 mm is ±15°~360°, and the swing speed is 1~2 rpm; The swing amplitude of foil coils with a coil diameter between 400-600 mm is ±45°~360°, and the swing speed is 4-6 rpm; The swing amplitude of foil coils with a coil diameter between 300-400 mm is ±60°~360°, and the swing speed is 1-20 rpm; The swing amplitude of foil coils with a coil diameter between 200-300 mm is ±90°~360°, and the swing speed is 8-12 rpm; The foil coils with a coil diameter between 100 and 200 mm are rotated through 360° at a speed of 12 to 18 rpm.

7. The dynamic rotation heat treatment process of porous electrode foil according to claim 6, characterized in that: For foil coils with a coil diameter greater than 600 mm, the swing amplitude is ±15° and the swing speed is 1 rpm; The swing amplitude of foil coils with a coil diameter between 400-600 mm is ±45° and the swing speed is 5 rpm; The swing amplitude of foil coils with a coil diameter between 300-400 mm is ±60° and the swing speed is 5-10 rpm; The swing amplitude of foil coils with a coil diameter between 200-300 mm is ±90° and the swing speed is 10 rpm; The foil coils with a coil diameter between 100 and 200 mm are rotated through 360° at a speed of 15 rpm.

8. The dynamic rotation heat treatment process of porous electrode foil according to claim 6, characterized in that: The heat treatment includes a heating stage, a heat preservation stage and a cooling stage which are performed in sequence. As the heating stage, the heat preservation stage and the cooling stage occur in sequence, the swing amplitude of the foil roll increases in sequence and the swing speed of the foil roll decreases in sequence.

9. The dynamic rotation heat treatment process of porous electrode foil according to claim 8, characterized in that: For foil rolls with a roll diameter between 300-400 mm, the swing amplitude of the foil roll in the heating stage is ±60° and the swing speed is 5 rpm; the swing amplitude of the foil roll in the insulation stage is ±90° and the swing speed is 1 rpm; in the cooling stage, the foil roll rotates 360° and the speed is 1 rpm.

10. A porous electrode foil, characterized in that: It is prepared by the dynamic rotation heat treatment process described in any one of claims 1 to 9.

Images