Material box mechanism and coating device

Abstract

The utility model relates to a material box mechanism and a coating device. The material box mechanism is used for providing coating slurry for a coating roller, the material box mechanism comprises a material box, the material box is provided with a containing cavity used for storing the coating slurry, and a part of the coating roller is located below the liquid level of the coating slurry in the containing cavity; and the ultrasonic generator is arranged in the accommodating cavity of the material box. Compared with the prior art in which defoaming treatment is carried out in a previous process (such as a stirring process) of the material box, the ultrasonic generator is directly arranged in the accommodating cavity of the material box, so that the ultrasonic generator is used for directly defoaming the coating slurry in the material box; the risk that the coating slurry attached to the roller surface of the coating roller contains bubbles is greatly reduced, so that the coating defects such as coating omission and explosion points are greatly reduced, and the coating qualification rate is greatly improved.

Description

Technical Field

[0001] This application relates to the field of battery manufacturing equipment technology, specifically to a material box mechanism and a coating device. Background Technology

[0002] Lithium-ion batteries are widely used in electronic devices, new energy vehicles, and energy storage due to their advantages such as environmental friendliness, high operating voltage, large specific capacity, and long cycle life. The safety performance and lifespan of lithium-ion batteries are crucial for their future applications.

[0003] In the manufacturing process of lithium batteries, gravure coating technology is a common method for preparing electrodes, which involves coating a carbon layer onto foil using gravure coating technology. During the coating process of a gravure coating machine, air bubbles in the slurry within the hopper often cause abnormalities in the carbon-coated foil manufacturing process, such as missed coating and bursting defects, affecting the yield of the carbon-coated foil. Utility Model Content

[0004] Therefore, it is necessary to provide a material box mechanism and coating device that can eliminate air bubbles in the slurry, avoid defects such as missed coating and bursting during coating, and thus improve the product qualification rate.

[0005] On one hand, this application provides a feed hopper mechanism for supplying coating slurry to a coating roller, the feed hopper mechanism comprising:

[0006] A material box having a receiving cavity for storing coating slurry, wherein a portion of the coating roller is located below the liquid level of the coating slurry within the receiving cavity; and

[0007] An ultrasonic generator is disposed within the receiving cavity of the material box.

[0008] In some embodiments, two ultrasonic generators are provided, and the two ultrasonic generators are arranged at intervals in the receiving cavity along a first preset direction;

[0009] In the first preset direction, the coating roller is located between the two ultrasonic generators.

[0010] In some embodiments, the ultrasonic generator is located at the bottom of the receiving cavity.

[0011] In some embodiments, the material box mechanism further includes a baffle disposed within the receiving cavity, the baffle being partially located below the liquid surface of the coating slurry within the receiving cavity, and a gap being present between the baffle and the bottom wall of the receiving cavity, with the coating roller located on one side of the baffle.

[0012] In some embodiments, the baffle includes a first baffle and a second baffle, both disposed within the receiving cavity. The first baffle and the second baffle are both partially located below the liquid surface of the coating slurry within the receiving cavity and are spaced apart from the bottom wall of the receiving cavity. The coating roller is located between the first baffle and the second baffle.

[0013] In some embodiments, the material box further has a first sidewall and a second sidewall, which respectively serve as the inner walls of the receiving cavity on both sides in a second preset direction, and the first baffle and the second baffle both extend from the first sidewall to the second sidewall, and the second preset direction is parallel to the axial direction of the coating roller.

[0014] In some embodiments, the ultrasonic generator extends longitudinally along the second preset direction.

[0015] In some embodiments, the first baffle and the second baffle are arranged at intervals along a first preset direction, and the first preset direction is perpendicular to the axial direction of the coating roller;

[0016] In the first preset direction, the distance between the first baffle and the coating roller is 5cm-10cm, and the distance between the second baffle and the coating roller is 5cm-10cm.

[0017] On the other hand, this application provides a coating apparatus, including a coating roller, a pressure roller, and a material box mechanism as described in any of the above embodiments;

[0018] A portion of the coating roller is located below the liquid surface of the coating slurry within the receiving cavity, and the pressure roller is used to press the strip to be coated against the portion of the coating roller located above the liquid surface of the coating slurry within the receiving cavity. Both the coating roller and the pressure roller can be controlled to rotate in opposite directions about their own axes.

[0019] In one embodiment, the coating apparatus further includes a buffer tank and a feed pipe. The buffer tank has a buffer cavity for storing coating slurry and a discharge port communicating with the buffer cavity. The slurry box also has a feed port communicating with the receiving cavity. The feed pipe is connected between the discharge port and the feed port for conveying the coating slurry in the buffer cavity to the receiving cavity.

[0020] Compared with the prior art, this application has the following beneficial effects:

[0021] Compared with the prior art where defoaming is performed in a process before the material box (such as a stirring process), the above-mentioned material box mechanism and coating device directly install an ultrasonic generator in the receiving cavity of the material box, thereby using the ultrasonic generator to directly defoam the coating slurry in the material box. This greatly reduces the risk of air bubbles in the coating slurry adhering to the roller surface of the coating roller, thereby greatly reducing coating defects such as missed coating and bursting points, and greatly improving the coating qualification rate. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the coating apparatus in one embodiment of this application;

[0023] Figure 2 for Figure 1 The diagram shows the structure of the coating apparatus from another perspective. Detailed Implementation

[0024] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0025] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0027] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0028] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0029] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0030] Please see Figure 1 and Figure 2This application provides a coating apparatus, including a coating roller 101, a pressure roller 102, and a cartridge mechanism 100. The cartridge mechanism 100 includes a cartridge 10 having a receiving cavity 11 for storing coating slurry. A portion of the coating roller 101 is located below the liquid surface b of the coating slurry in the receiving cavity 11, that is, a portion of the roller surface of the coating roller 101 is immersed in the coating slurry in the receiving cavity 11. The pressure roller 102 is used to press the material strip a to be coated against the portion of the coating roller 101 above the liquid surface b of the coating slurry, and both the coating roller 101 and the pressure roller 102 can be controlled to rotate in opposite directions about their own axes. Thus, in actual use, the pressure roller 102 presses the material strip a to be coated against the part of the coating roller 101 above the liquid surface b of the coating slurry. At the same time, the coating roller 101 and the pressure roller 102 are controlled to rotate in opposite directions. On the one hand, the roller surface of the coating roller 101 rotates from below the liquid surface of the coating slurry to above the liquid surface, and the coating slurry adhering to the roller surface is applied to the material strip a that is passing by. On the other hand, the material strip a is driven to continuously pass between the pressure roller 102 and the coating roller 101 and then be conveyed downstream. When passing between the pressure roller 102 and the coating roller 101, the side of the material strip a facing the coating roller 101 is coated.

[0031] It should be noted that the pressure roller 102 presses against the coating roller 101, and the material strip a is pressed between the pressure roller 102 and the coating roller 101. In some embodiments, the coating roller 101 is the driving roller and the pressure roller 102 is the driven roller. That is, the coating roller 101 rotates around its own axis under the driving action of a driving member (e.g., a motor), thereby driving the pressure roller 102 to rotate in the opposite direction under the action of friction. At the same time, the material strip a is coated on the surface of one side facing the coating roller 101 and conveyed downstream under the combined action of the coating roller 101 and the pressure roller 102. Of course, in other embodiments, both the coating roller 101 and the pressure roller 102 can be driving rollers. That is, the coating roller 101 rotates actively under the driving action of a driving member, and at the same time, the pressure roller 102 also rotates actively under the driving action of a driving member, and their rotation directions are opposite. As long as continuous coating of the material strip a can be achieved, it is not limited here.

[0032] It should also be noted that the aforementioned strip a can be a foil used to prepare electrodes, such as copper foil, aluminum foil or composite foil, etc. Of course, it can also be other types of strips, which are not limited here.

[0033] Furthermore, the material box mechanism 100 also includes an ultrasonic generator 20, which is disposed within the receiving cavity 11 of the material box 10. The ultrasonic generator 20 emits ultrasonic waves into the receiving cavity 11, utilizing the high-frequency vibration characteristics of the ultrasonic waves to disrupt the bubble structure in the coating slurry, causing the bubbles in the coating slurry to collapse rapidly, thereby eliminating the bubbles in the coating slurry. Thus, compared to the prior art where defoaming is performed in a process preceding the material box (e.g., a stirring process), this application directly places the ultrasonic generator 20 within the receiving cavity 11 of the material box 10, thereby directly defoaming the coating slurry within the material box 10. This significantly reduces the risk of bubbles in the coating slurry adhering to the roller surface of the coating roller 101, thereby greatly reducing coating defects such as missed coating and bursts, and significantly improving the coating pass rate.

[0034] It should be noted that, in this application, by directly installing an ultrasonic generator 20 for defoaming in the receiving cavity 11 of the material box 10, coating defects such as missed coating and bursting points are greatly reduced, ensuring better uniformity and consistency of coating. On the one hand, it reduces material waste caused by uneven coating, which can save production costs and improve production efficiency; on the other hand, it reduces the quality risk of batteries made using the coated material strip, which is conducive to improving the cycle stability and safety of the battery.

[0035] Specifically, in this embodiment, two ultrasonic generators 20 are configured, and these two ultrasonic generators 20 are arranged at intervals along a first preset direction X1 within the receiving cavity 11. The coating roller 101 is located between the two ultrasonic generators 20 along this first preset direction X1. Thus, by utilizing the two ultrasonic generators 20 located on opposite sides of the coating roller 101 along the first preset direction X1 for ultrasonic defoaming treatment, the risk of air bubbles in the coating slurry entering the area between the two ultrasonic generators 20 (i.e., the area where the coating roller 101 is located) is further reduced, thereby significantly reducing the risk of air bubbles in the coating slurry adhering to the roller surface of the coating roller 101.

[0036] It should be noted that in some other embodiments, the number of ultrasonic generators 20 may be two or more, as long as the defoaming effect meets the process requirements, and no special limitation is made here.

[0037] In a specific embodiment, the ultrasonic generator 20 is located at the bottom of the receiving cavity 11. The ultrasonic generator 20 emits ultrasonic waves from the bottom to the left, right and top sides, thereby maximizing the ultrasonic radiation range and improving the ultrasonic debubbling effect.

[0038] In the embodiments of this application, the material box mechanism 100 further includes a baffle 30 disposed within the receiving cavity 11. A portion of the baffle 30 is located below the liquid surface b of the coating slurry within the receiving cavity 11, and a certain distance exists between the baffle 30 and the bottom wall of the receiving cavity 11, forming a bottom channel c for the coating slurry to pass through. The coating roller 101 is located on one side of the baffle 30, thereby using the baffle 30 to prevent air bubbles that rise to near the liquid surface b from drifting towards the coating roller 101, further reducing the risk of air bubbles in the coating slurry adhering to the roller surface of the coating roller 101.

[0039] Furthermore, the number of baffles 30 can be set to two, namely a first baffle 30a and a second baffle 30b. Both the first baffle 30a and the second baffle 30b are partially located below the liquid surface b of the coating slurry within the receiving cavity 11, and both the first baffle 30a and the second baffle 30b have a certain distance between them and the bottom wall of the receiving cavity 11, such that a bottom channel c for the coating slurry to pass through is formed between the first baffle 30a and the second baffle 30b and the bottom wall of the receiving cavity 11. The coating roller 101 is located between the first baffle 30a and the second baffle 30b. Thus, by arranging the coating roller 101 between the first baffle 30a and the second baffle 30b, the first baffle 30a and the second baffle 30b can prevent air bubbles that rise to the vicinity of the liquid surface b from entering the area between the first baffle 30a and the second baffle 30b. Therefore, it can prevent air bubbles from drifting toward the coating roller 101 and further reduce the risk of air bubbles in the coating slurry adhering to the roller surface of the coating roller 101.

[0040] Furthermore, the material box 10 also has a first sidewall d1 and a second sidewall d2, which respectively serve as the inner walls of the receiving cavity 11 on both sides in a second preset direction X2, which is parallel to the axial direction of the coating roller 101. The first baffle 30a and the second baffle 30b both extend from the first sidewall d1 to the second sidewall d2. That is, there are no gaps between the first sidewall d1 and the second sidewall d2 and the first baffle 30a, and there are no gaps between the first sidewall d1 and the second sidewall d2 and the second baffle 30b. This prevents air bubbles from passing between the first baffle 30a and the first sidewall d1 or the second sidewall d2, and also prevents air bubbles from passing between the second baffle 30b and the first sidewall d1 or the second sidewall d2, further reducing the risk of air bubbles in the coating slurry adhering to the roller surface of the coating roller 101.

[0041] Furthermore, the ultrasonic generator 20 extends longitudinally along the second preset direction X2, thereby ensuring that ultrasonic waves are present at all positions within the receiving cavity 11 along the second preset direction X2, which is beneficial for improving the ultrasonic debubbling effect. Specifically, the length of the ultrasonic generator 20 along the second preset direction X2 is equal to or slightly smaller than the distance between the first sidewall d1 and the second sidewall d2.

[0042] Optionally, the first baffle 30a and the second baffle 30b are arranged at intervals along a first preset direction X1, and the first preset direction X1 is perpendicular to the axial direction of the coating roller 101. In the first preset direction X1, the distance between the first baffle 30a and the coating roller 101 is 5cm to 10cm, and the distance between the second baffle 30b and the coating roller 101 is 5cm to 10cm.

[0043] Optionally, the height of the first baffle 30a (i.e., the height in the third preset direction X3, which is perpendicular to both the first preset direction X1 and the second preset direction X2) can be 10cm, the height of the first baffle 30a below the liquid surface b of the coating slurry is 5cm, and the height of the first baffle 30a above the liquid surface b of the coating slurry is 5cm.

[0044] The height of the second baffle 30b (i.e., the dimension in the third preset direction X3, which is perpendicular to both the first preset direction X1 and the second preset direction X2) can be 10cm. The height of the second baffle 30b below the liquid surface b of the coating slurry is 5cm, and the height of the second baffle 30b above the liquid surface b of the coating slurry is 5cm.

[0045] It should be noted that the height dimensions of the first baffle 30a and the second baffle 30b below the liquid surface b and above the liquid surface b are not limited to these. They can be set according to process requirements, as long as they can prevent air bubbles from drifting toward the coating roller 101.

[0046] In a specific embodiment, the material box 10 also has an overflow port that communicates with the receiving cavity 11. When the liquid level b of the coating slurry in the receiving cavity 11 is higher than the overflow port, the coating slurry is discharged from the overflow port, ensuring that the liquid level b of the coating slurry in the receiving cavity 11 remains stable, which is beneficial to improving the coating quality.

[0047] Furthermore, an electrically controlled valve 15 is installed at the overflow port, which automatically controls the opening and closing of the overflow port. When the liquid level b of the coating slurry in the receiving cavity 11 is too high, the electrically controlled valve 15 controls the overflow port to open, allowing the coating slurry to be discharged from the overflow port. When the liquid level b of the coating slurry in the receiving cavity 11 is at a preset height, the electrically controlled valve 15 controls the overflow port to close, preventing the coating slurry from continuing to be discharged from the overflow port.

[0048] Specifically, in this embodiment, the coating roller 101 has a material strip entry side and a material strip exit side on its two sides in the first preset direction X1, respectively. During coating, the material strip a enters between the coating roller 101 and the pressure roller 102 on the material strip entry side of the coating roller 101, and exits between the coating roller 101 and the pressure roller 102 on the material strip exit side of the coating roller 101.

[0049] The coating apparatus also includes a doctor blade 107, which is arranged on the tape exit side of the coating roller 101 and contacts the roller surface of the coating roller 101 to scrape off the coating slurry adhering to the roller surface of the coating roller 101 as the coating roller 101 rotates. Thus, during coating, the coating slurry adhering to the roller surface of the coating roller 101 rotates with the coating roller 101 to a position facing the pressure roller 102, so that a portion of the adhering coating slurry is coated onto the passing tape a, while the other portion remains on the roller surface of the coating roller 101 and continues to rotate with the coating roller 101 to the tape exit side. At this point, the doctor blade 107 scrapes off the remaining coating slurry on the coating roller 101 to facilitate subsequent coating and improve coating quality.

[0050] In embodiments of this application, the coating apparatus further includes a buffer tank 103 and a delivery pipe 104. The buffer tank 103 has a buffer cavity for storing coating slurry and a discharge port c1 communicating with the buffer cavity. The material box 10 also has a feed port c2 communicating with a receiving cavity 11. The delivery pipe 104 is connected between the discharge port c1 and the feed port c2 for conveying the coating slurry in the buffer cavity of the buffer tank 103 to the receiving cavity 11 of the material box 10.

[0051] It should be noted that the opening and closing of the feed pipe 104 can be controlled by a control valve, and the flow of the coating slurry along the feed pipe 104 can be powered by a delivery pump. When it is necessary to inject coating slurry into the material box 10, the control valve opens, allowing the feed pipe 104 to open. At this time, under the pumping action of the delivery pump, the coating slurry in the buffer chamber of the buffer tank 103 can flow through the feed pipe 104 to the receiving chamber 11 of the material box 10. When it is not necessary to inject coating slurry into the material box 10, the control valve closes, allowing the feed pipe 104 to close. At this time, the coating slurry in the buffer chamber of the buffer tank 103 cannot flow through the feed pipe 104 to the receiving chamber 11 of the material box 10.

[0052] Furthermore, the outlet c1 is located at the bottom of the buffer chamber, allowing the coating slurry inside the buffer chamber to flow out through the outlet c1 at the bottom. Since air bubbles (especially large air bubbles) in the coating slurry will rise to the surface, the outlet c1, being located at the bottom of the buffer chamber, can effectively prevent air bubbles from rising.

[0053] The feed inlet c2 is located at the bottom of the receiving cavity 11, so that the coating slurry in the conveying pipe 104 enters the receiving cavity 11 through the feed inlet c2 at the bottom, thus preventing the flowing coating slurry from being exposed to the air and forming air bubbles.

[0054] Optionally, the distance between the discharge port c1 and the bottom wall of the buffer cavity is 2 cm, and the distance between the inlet port c2 and the bottom wall of the receiving cavity 11 is 2 cm. Of course, in other embodiments, the distance between the discharge port c1 and the bottom wall of the buffer cavity can be other values, as long as the discharge port c1 is approximately located at the bottom of the buffer cavity; this is not limited here. Similarly, the distance between the inlet port c2 and the bottom wall of the receiving cavity 11 can also be other values, as long as the inlet port c2 is approximately located at the bottom of the receiving cavity 11; this is not limited here.

[0055] 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.

[0056] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. 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 protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A feed box mechanism for supplying coating slurry to a coating roller (101), characterized in that, The material box mechanism (100) includes: The material box (10) has a receiving cavity (11) for storing the coating slurry, and a portion of the coating roller (101) is located below the liquid level (b) of the coating slurry within the receiving cavity (11); and An ultrasonic generator (20) is disposed in the receiving cavity (11) of the material box (10).

2. The material box mechanism according to claim 1, characterized in that, The ultrasonic generator (20) is configured as two, and the two ultrasonic generators (20) are arranged at intervals in the receiving cavity (11) along a first preset direction (X1); In the first preset direction (X1), the coating roller (101) is located between the two ultrasonic generators (20).

3. The material box mechanism according to claim 1, characterized in that, The ultrasonic generator (20) is located at the bottom of the receiving cavity (11).

4. The material box mechanism according to any one of claims 1 to 3, characterized in that, The material box mechanism (100) further includes a baffle (30) disposed in the receiving cavity (11). The baffle (30) is partially located below the liquid surface (b) of the coating slurry in the receiving cavity (11), and there is a gap between the baffle (30) and the bottom wall of the receiving cavity (11). The coating roller (101) is located on one side of the baffle (30).

5. The material box mechanism according to claim 4, characterized in that, The baffle (30) includes a first baffle (30a) and a second baffle (30b) both disposed in the receiving cavity (11). The first baffle (30a) and the second baffle (30b) are both partially located below the liquid surface (b) of the coating slurry in the receiving cavity (11) and are spaced apart from the bottom wall of the receiving cavity (11). The coating roller (101) is located between the first baffle (30a) and the second baffle (30b).

6. The material box mechanism according to claim 5, characterized in that, The material box (10) also has a first sidewall (d1) and a second sidewall (d2) that serve as the inner walls of the receiving cavity (11) on the second preset direction (X2), respectively. The first baffle (30a) and the second baffle (30b) both extend from the first sidewall (d1) to the second sidewall (d2). The second preset direction (X2) is parallel to the axial direction of the coating roller (101).

7. The material box mechanism according to claim 6, characterized in that, The ultrasonic generator (20) extends longitudinally along the second preset direction (X2).

8. The material box mechanism according to claim 5, characterized in that, The first baffle (30a) and the second baffle (30b) are arranged at intervals along a first preset direction (X1), and the first preset direction (X1) is perpendicular to the axial direction of the coating roller (101); In the first preset direction (X1), the distance between the first baffle (30a) and the coating roller (101) is 5cm-10cm, and the distance between the second baffle (30b) and the coating roller (101) is 5cm-10cm.

9. A coating apparatus, characterized in that, It includes a coating roller (101), a pressure roller (102), and a material box mechanism (100) as described in any one of claims 1 to 8; A portion of the coating roller (101) is located below the liquid surface (b) of the coating slurry in the receiving cavity (11), and the pressure roller (102) is used to press the strip (a) to be coated against the portion of the coating roller (101) located above the liquid surface (b) of the coating slurry in the receiving cavity (11), and both the coating roller (101) and the pressure roller (102) can be controlled to rotate in opposite directions about their own axes.

10. The coating apparatus according to claim 9, characterized in that, The coating apparatus further includes a buffer tank (103) and a conveying pipe (104). The buffer tank (103) has a buffer cavity for storing coating slurry and a discharge port (c1) communicating with the buffer cavity. The material box (10) also has a feed port (c2) communicating with the receiving cavity (11). The conveying pipe (104) is connected between the discharge port (c1) and the feed port (c2) for conveying the coating slurry in the buffer cavity to the receiving cavity (11).

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