Anti-bubble coating system and method for lithium battery pole piece coating

Abstract

The invention provides an anti-bubble coating system and method for lithium battery pole piece coating, and belongs to the technical field of battery manufacturing, and the system comprises a main coating system which comprises a coating feeding tank, a screw pump, a filter and a coating die head; the material receiving backflow unit comprises a material receiving funnel, a backflow pipeline, a backflow conveying pump, an auxiliary tank, a transfer pipeline and a transfer pump, the material receiving funnel is arranged on one side of the coating die head, a feeding port of the material receiving funnel faces the coating die head, one end of the backflow pipeline is connected with a discharging port of the material receiving funnel, and the other end of the backflow pipeline is connected with a feeding port of the auxiliary tank; the backflow conveying pump is arranged on the backflow pipeline; one end of the transfer pipeline is connected with a discharge port of the auxiliary tank, the other end of the transfer pipeline is connected with a feed port of the coating feeding tank, and the transfer pump is arranged on the transfer pipeline; the auxiliary tank is connected with a vacuum pump. According to the anti-bubble coating system and method for coating the lithium battery pole piece, the situation that the pole piece is scrapped can be reduced, the production cost is reduced, and meanwhile the quality of the battery pole piece is improved.

Description

Technical Field

[0001] This application relates to the field of battery manufacturing technology, and more specifically, to an anti-bubble coating system and method for lithium battery electrode coating. Background Technology

[0002] In the coating process of lithium-ion battery electrodes, slot extrusion coating technology is widely used. The slurry passes through a screw pump, filter, and branch pipe, and is finally precisely coated onto the current collector by the coating die. However, after each cleaning of the coating die, branch pipe, feeding trolley, and screw pump, or after replacing the main filter element, a large amount of air is introduced into the entire closed slurry delivery system. This air mixes into the slurry in the form of bubbles, or accumulates in "dead corners" such as high points in the pipeline, filters, valves, and pump bodies.

[0003] The commonly used technique in related technologies is "circulation," which involves circulating the slurry between the loading trolley and the coating die, attempting to carry away air bubbles through the flow of the slurry. However, this method has inherent drawbacks: cyclic shearing may generate new microbubbles; for static bubbles attached to the tube wall or trapped in dead corners, the laminar flow of the slurry lacks sufficient scouring force to effectively entrain and remove them; furthermore, the circulation process cannot actively eliminate air bubbles already mixed into the slurry. The direct consequence is uneven slurry distribution and the presence of air bubbles at the start of coating, leading to "metal leakage" defects after coating, resulting in the scrapping of the electrode sheets and creating a safety hazard of internal short circuits in the battery. Summary of the Invention

[0004] This application aims to provide an anti-bubble coating system and method for lithium battery electrode coating, which aims to reduce electrode scrap, lower production costs, and improve the quality of battery electrodes.

[0005] The first aspect of this application provides an anti-bubble coating system for lithium battery electrode coating, comprising: The main coating system includes a coating feed tank, a screw pump, a filter, and a coating die. One end of the screw pump is connected to the outlet of the coating feed tank, and the other end is connected to the coating die. The filter is disposed between the screw pump and the coating die. The material receiving and reflux unit includes a material receiving funnel, a reflux pipe, a reflux conveying pump, a secondary tank, a transfer pipe, and a transfer pump. The material receiving funnel is located on one side of the coating die head, with its inlet facing the coating die head. One end of the reflux pipe is connected to the outlet of the material receiving funnel, and the other end is connected to the inlet of the secondary tank. The reflux conveying pump is located on the reflux pipe. One end of the transfer pipe is connected to the outlet of the secondary tank, and the other end is connected to the inlet of the coating feed tank. The transfer pump is located on the transfer pipe. A vacuum pump is connected to the secondary tank, and the vacuum pump is used to maintain the internal pressure of the secondary tank at a preset pressure.

[0006] Optionally, a first filter device is provided between the return pipe and the feed inlet of the auxiliary tank, the first filter device being used for initial filtration of the negative electrode slurry.

[0007] Optionally, a second filter device is provided between the transfer pipe and the inlet of the coating feed tank, the second filter device being used to filter the recovered negative electrode slurry.

[0008] Optionally, the receiving funnel, the return pipe, and the transfer pipe are made of stainless steel.

[0009] Optionally, the preset pressure is between -0.08 MPa and -0.06 MPa.

[0010] The second aspect of this application provides a method for preventing bubble-induced coating initiation in lithium battery electrode coating, applied to an anti-bubble coating initiation system for lithium battery electrode coating as provided in the first aspect of this application, the method comprising: Inject the negative electrode slurry into the coating feed tank and adjust the discharge port of the coating die head to face the receiving funnel; Start the main screw pump and the return delivery pump so that the negative electrode slurry flows through the main screw pump, the filter and the coating die in sequence, and enters the auxiliary tank through the receiving funnel and the return pipe until the first preset time period is reached. Then, adjust the discharge port direction of the coating die again and start coating the lithium battery electrode. When the negative electrode slurry in the auxiliary tank accumulates to the preset liquid level, the vacuum pump and the agitator in the auxiliary tank are turned on to maintain the internal pressure of the auxiliary tank at the preset pressure and continuously stir the negative electrode slurry in the auxiliary tank until the second preset time period is reached. Then, the transfer pump is started to re-inject the negative electrode slurry in the auxiliary tank into the coating loading tank through the transfer pipeline.

[0011] Optionally, the first time period is 5 hours.

[0012] Optionally, the preset liquid level is two-thirds of the volume of the auxiliary tank.

[0013] Optionally, the second time period is 2 hours.

[0014] Beneficial effects: This application provides an anti-bubble coating system and method for lithium battery electrode coating. The system includes a main coating system and a receiving and recycling unit. The main coating system includes a coating feed tank, a screw pump, a filter, and a coating die. The receiving and recycling unit includes a receiving funnel, a return pipe, a return transfer pump, a secondary tank, a transfer pipe, and a transfer pump. After cleaning the main coating system, negative electrode slurry is added to the coating feed tank and driven by the screw pump to flow sequentially through the screw pump, filter, and coating die. During this process, the negative electrode slurry can expel air from the system. The negative electrode slurry containing air enters the secondary tank through the receiving funnel, and after bubble removal treatment in the secondary tank, it re-enters the coating feed tank. This achieves venting of the main coating system, thereby reducing electrode scrap during subsequent electrode coating, and the negative electrode slurry containing air in the secondary tank is also recycled, thus reducing production costs. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of an anti-bubble coating system for lithium battery electrode coating according to an embodiment of this application; Figure 2 This is a flowchart illustrating the steps of an embodiment of this application for an anti-bubble coating method for lithium battery electrode coating.

[0017] Explanation of reference numerals in the attached drawings: 1. Coating feed tank; 2. Screw pump; 3. Filter; 4. Coating die; 5. Receiving funnel; 6. Return pipe; 7. Return transfer pump; 8. Auxiliary tank; 9. Transfer pipe; 10. Transfer pump; 11. First filter device; 12. Vacuum pump; 13. Second filter device. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] Reference Figure 1 As shown in the figure, an anti-bubble coating system for lithium battery electrode coating is provided in an embodiment of this application. The system includes a main coating system and a material receiving and recycling unit.

[0020] Specifically, the main coating system includes a coating feed tank 1, a screw pump 2, a filter 3, and a coating die 4. One end of the screw pump 2 is connected to the outlet of the coating feed tank 1, and the other end is connected to the coating die 4. The screw pump 2 pumps the negative electrode slurry from the coating feed tank 1 to the coating die 4. The coating die 4 is a slit extrusion die, which can extrude the negative electrode slurry into sheets and coat them onto the battery electrode. The filter 3 is located between the screw pump 2 and the coating die 4. The filter 3 is used to filter the negative electrode slurry. In this embodiment, the filtration accuracy of the filter 3 is 50 μm.

[0021] Reference Figure 1 As shown, the material receiving and recycling unit includes a material receiving funnel 5, a return pipe 6, a return conveying pump 7, a secondary tank 8, a transfer pipe 9, and a transfer pump 10.

[0022] Specifically, the receiving funnel 5 is located directly below the discharge lip of the coating die head 4. The receiving funnel 5 is made of 316L stainless steel, and its outlet diameter is DN50. The inlet of the receiving funnel 5 faces the coating die head 4. One end of the return pipe 6 is connected to the discharge port of the receiving funnel 5, and the other end is connected to the inlet of the auxiliary tank 8. The return pipe 6 is made of stainless steel. The return transfer pump 7 is a screw pump and is located on the return pipe 6. The return transfer pump 7 can pump the negative electrode slurry in the receiving funnel 5 into the auxiliary tank 8. At the same time, a first filter device 11 is provided between the return pipe 6 and the inlet of the auxiliary tank 8. The first filter device 11 can perform initial filtration on the negative electrode slurry. In this embodiment, the first filter device 11 is a filter equipped with a disposable polypropylene filter element.

[0023] Reference Figure 1 As shown, the auxiliary tank 8 has a volume of 100 liters and is a jacketed mixing tank. The auxiliary tank 8 is equipped with an anchor-type agitator driven by a variable frequency motor, and the speed can be adjusted within the range of 30 rpm to 60 rpm. The top of the auxiliary tank 8 is connected to a vacuum pump 12 through a pipe. The vacuum pump 12 can keep the internal pressure of the auxiliary tank 8 at a preset pressure. In this embodiment, the preset pressure is -0.08 MPa to -0.06 MPa. By establishing and maintaining a negative pressure environment in the auxiliary tank 8, air bubbles in the negative electrode slurry can be eliminated.

[0024] Reference Figure 1As shown, one end of the transfer pipe 9 is connected to the outlet of the auxiliary tank 8, and the other end is connected to the inlet of the coating feed tank 1. The transfer pipe 9 is made of stainless steel. The transfer pump 10 is installed on the transfer pipe 9. The transfer pump 10 is a pneumatic diaphragm pump. The transfer pump 10 can pump the negative electrode slurry in the auxiliary tank 8 into the coating feed tank 1. At the same time, a second filter device 13 is provided between the transfer pipe 9 and the inlet of the coating feed tank 1. The second filter device 13 can filter the recovered negative electrode slurry to ensure the cleanliness of the reused slurry. In this embodiment, the second filter device 13 is a filter equipped with a disposable polypropylene filter element.

[0025] In this embodiment of the application, after cleaning the main coating system and replacing the filter element, a three-stage processing flow can be performed.

[0026] In the first stage, the negative electrode slurry is added to the coating feed tank 1, and the screw pump 2 and the return transfer pump 7 are started to make the negative electrode slurry continuously flow into the auxiliary tank 8. During this process, the continuously flowing negative electrode slurry is used as a carrier to systematically fill the entire delivery pipeline, and its viscous shear force is used to "capture" and expel the air trapped in dead corners such as the filter 3, the screw pump 2 cavity, and the pipe weld. The purpose of this stage is not circulation, but "displacement" and "cleaning". After displacement, starting from the 2-meter electrode, the coating is of high quality and free of metal defects.

[0027] In the second stage, the vacuum pump 12 and the agitator in the auxiliary tank 8 are activated to apply a negative pressure environment to the negative electrode slurry collected in the auxiliary tank 8, supplemented by mechanical stirring. The negative pressure causes the bubbles in the negative electrode slurry to expand in volume and increase the internal and external pressure difference, thereby rapidly accelerating their rise, escape, and collapse. Stirring breaks the surface tension of the slurry and promotes the coalescence of microbubbles, thereby achieving efficient and deep defoaming treatment.

[0028] In the third stage, the clean slurry that has been thoroughly defoamed and is in a uniform state is transported back to the coating feed tank 1 and can be used as normal slurry.

[0029] It should be noted that, in the embodiments of this application, the processing flow of the first stage can be carried out synchronously with the processing flow of the second and third stages.

[0030] Thus, the anti-bubble coating system for lithium battery electrode coating provided in this application embodiment can achieve at least the following technical effects: 1. Eliminate the source of bubbles: Through long-term directional emission in the first stage, the air accumulated in the dead corners of the system is actively discharged, rather than passively waiting for it to dissolve or be carried away by chance, thus reducing the total amount of bubbles from the source.

[0031] 2. Deep purification guarantee: Through the proprietary negative pressure stirring process in the second stage, the slurry is subjected to centralized and enhanced defoaming treatment, which is far superior to simple static or normal pressure stirring.

[0032] 3. Achieve zero-waste production: In the third stage, the treated slurry is recycled for production, completely avoiding material waste, conforming to the concept of green manufacturing, and directly reducing production costs.

[0033] 4. Comprehensive improvement in quality and safety: It fundamentally eliminates metal leakage during the initial coating stage, improving electrode consistency, battery yield, and safety performance.

[0034] Reference Figure 2 As shown in the embodiments of this application, a method for preventing bubble-induced coating initiation in lithium battery electrode coating is also provided. This method is applied to the anti-bubble coating initiation system for lithium battery electrode coating as described above. The method includes: Step 201: Inject negative electrode slurry into coating feed tank 1 and adjust the outlet of coating die head 4 to face the receiving funnel 5.

[0035] Step 202: Start the screw pump 2 and the return conveying pump 7 so that the negative electrode slurry flows sequentially through the screw pump 2, the filter 3 and the coating die head 4, and enters the auxiliary tank 8 through the receiving funnel 5 and the return pipe 6 until the first preset time period is reached. Then, adjust the discharge port direction of the coating die head 4 again and start the coating of the lithium battery electrode sheet.

[0036] Specifically, after cleaning the main coating system, venting is required. During this process, the negative electrode slurry continuously flows through the screw pump 2, filter 3, and coating die 4, and then through the receiving funnel 5 and return pipe 6 into the auxiliary tank 8. During this time, the flowing slurry acts like a "cleaning piston," systematically filling the entire pipeline volume from the pump to the die, and using its viscous shear force to thoroughly "capture" and expel air previously trapped inside the filter element of filter 3, the cavity of screw pump 2, pipe welds, and valve dead zones into the auxiliary tank 8. It is important to note that the rotational speed of screw pump 2 remains exactly the same as during normal coating to simulate the flow field under real-world conditions.

[0037] The first preset time period is 5 hours. This time period is the shortest time required to completely replace the system volume and stabilize the flow state, as determined by fluid mechanics and extensive practical experience.

[0038] After 5 hours, the slurry in the entire main coating system was in a stable flow state with no obvious bubbles.

[0039] At this point, the operator rotates the switching valve of coating die head 4, guiding the negative electrode slurry to the running copper foil substrate. From this moment on, the coated electrode sheets (starting from the 2nd meter at the production line speed) have a uniform and dense surface. After online CCD inspection and confirmation by subsequent processes, there are no "metal leakage" defects, and the electrode sheets can be directly entered into the drying oven as qualified products.

[0040] Step 203: When the negative electrode slurry in the auxiliary tank 8 accumulates to the preset liquid level, turn on the vacuum pump 12 and the agitator in the auxiliary tank 8 to maintain the internal pressure of the auxiliary tank 8 at the preset pressure, and continue to stir the negative electrode slurry in the auxiliary tank 8 until the second preset time period is reached. Then, start the transfer pump 10 to re-inject the negative electrode slurry in the auxiliary tank 8 into the coating loading tank 1 through the transfer pipe 9.

[0041] Specifically, the preset liquid level is two-thirds of the volume of the auxiliary tank 8. At this point, the vacuum pump 12 and the agitator inside the auxiliary tank 8 can be turned on to maintain the internal pressure of the auxiliary tank 8 at -0.07MPa. The agitator speed is set to 50rpm to perform deep defoaming treatment on the negative electrode slurry containing a large number of air bubbles that has accumulated in the auxiliary tank 8. Under negative pressure, the air bubbles in the slurry expand and burst rapidly, and the stirring action further breaks the surface tension of the slurry and promotes the coalescence of microbubbles, thereby achieving efficient and thorough defoaming.

[0042] The second preset time period is 2 hours, which ensures that different batches of slurry entering the auxiliary tank can be fully processed.

[0043] After the slurry in the auxiliary tank 8 has completed the defoaming treatment for 2 hours, turn off the vacuum pump 12 and the agitator, and break the air to restore the auxiliary tank 8 to normal pressure.

[0044] The transfer pump 10 is started, and the slurry that has become uniform, fine, and free of visible bubbles in the auxiliary tank 8 is safely transported back to the coating feed tank 1 through the transfer pipe 9 and the second filter device 13. This batch of recycled slurry has stable physicochemical properties and is no different from fresh slurry. It can be used immediately for subsequent normal coating production as a supplement to the slurry in the feed tank, achieving zero waste of materials.

[0045] The method for preventing bubble formation during coating of lithium battery electrodes provided in this application can achieve at least the following technical effects: 1. Achieved "qualified upon coating start": After the system is vented for 5 hours, the second-meter electrode is qualified, completely eliminating batch scrap during the coating start stage. 2. “Waste resource utilization” has been achieved: the initial slurry that originally had to be discarded due to the presence of air bubbles can be 100% reused after being processed in the auxiliary tank, which significantly reduces production costs. 3. Improved product consistency and safety: It fundamentally eliminates metal leakage defects caused by air bubbles, improving the quality consistency of battery electrodes and the final safety performance of the battery.

[0046] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0047] It should also be noted that, in this document, the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and 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. Furthermore, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations, nor should they be construed as indicating or implying relative importance. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. In the absence of further restrictions, an element defined by the phrase "includes a..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes the element.

[0048] The technical solutions provided in this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand this application, and the content of this specification should not be construed as a limitation of this application. Furthermore, for those skilled in the art, there will be different forms of changes in the specific implementation methods and application scope based on this application. It is neither necessary nor possible to exhaustively list all implementation methods here, and obvious changes or modifications derived therefrom are still within the protection scope of this application.

Claims

1. A system for preventing bubble formation and coating failure in lithium battery electrode coating, characterized in that, include: The main coating system includes a coating feed tank, a screw pump, a filter, and a coating die. One end of the screw pump is connected to the outlet of the coating feed tank, and the other end is connected to the coating die. The filter is disposed between the screw pump and the coating die. The material receiving and reflux unit includes a material receiving funnel, a reflux pipe, a reflux conveying pump, a secondary tank, a transfer pipe, and a transfer pump. The material receiving funnel is located on one side of the coating die head, with its inlet facing the coating die head. One end of the reflux pipe is connected to the outlet of the material receiving funnel, and the other end is connected to the inlet of the secondary tank. The reflux conveying pump is located on the reflux pipe. One end of the transfer pipe is connected to the outlet of the secondary tank, and the other end is connected to the inlet of the coating feed tank. The transfer pump is located on the transfer pipe. A vacuum pump is connected to the secondary tank, and the vacuum pump is used to maintain the internal pressure of the secondary tank at a preset pressure.

2. The anti-bubble coating system for lithium battery electrode coating according to claim 1, characterized in that: A first filter device is provided between the return pipe and the feed inlet of the auxiliary tank. The first filter device is used to perform initial filtration of the negative electrode slurry.

3. The anti-bubble coating system for lithium battery electrode coating according to claim 1, characterized in that: A second filter device is provided between the transfer pipe and the inlet of the coating feed tank. The second filter device is used to filter the recovered negative electrode slurry.

4. The anti-bubble coating system for lithium battery electrode coating according to claim 1, characterized in that: The receiving funnel, the return pipe, and the transfer pipe are made of stainless steel.

5. The anti-bubble coating system for lithium battery electrode coating according to claim 1, characterized in that: The preset pressure ranges from -0.08 MPa to -0.06 MPa.

6. A method for preventing bubble-induced coating in lithium battery electrode coating, applied to the anti-bubble coating system for lithium battery electrode coating as described in any one of claims 1-5, characterized in that, The method includes: Inject the negative electrode slurry into the coating feed tank and adjust the discharge port of the coating die head to face the receiving funnel; Start the main screw pump and the return delivery pump so that the negative electrode slurry flows through the main screw pump, the filter and the coating die in sequence, and enters the auxiliary tank through the receiving funnel and the return pipe until the first preset time period is reached. Then, adjust the discharge port direction of the coating die again and start coating the lithium battery electrode. When the negative electrode slurry in the auxiliary tank accumulates to the preset liquid level, the vacuum pump and the agitator in the auxiliary tank are turned on to maintain the internal pressure of the auxiliary tank at the preset pressure and continuously stir the negative electrode slurry in the auxiliary tank until the second preset time period is reached. Then, the transfer pump is started to re-inject the negative electrode slurry in the auxiliary tank into the coating loading tank through the transfer pipeline.

7. The method for preventing bubble formation during coating of lithium battery electrodes according to claim 6, characterized in that: The first time period is 5 hours.

8. The anti-bubble coating system for lithium battery electrode coating according to claim 6, characterized in that: The preset liquid level is two-thirds of the volume of the auxiliary tank.

9. The anti-bubble coating system for lithium battery electrode coating according to claim 6, characterized in that: The second time period is 2 hours.

Images