A drying method and device for an electric cell

Abstract

This application provides a method and apparatus for drying battery cells. The method includes measuring the moisture content of the battery cell to be dried, determining the corresponding drying stage of the battery cell based on the moisture content, and performing the drying operation corresponding to the drying stage. This application achieves rapid moisture removal by drying the battery cell in stages according to the moisture distribution within the battery cell during the baking process. This effectively reduces the drying time of the battery cell and prevents damage to the battery cell as a whole. By using different process methods according to the three stages of moisture distribution within the battery cell during the baking process, the purpose of rapid moisture removal is achieved. The moisture content of the treated battery cell is less than 80 ppm, which is lower than the current standard. This effectively reduces the drying time of the battery cell and prevents damage to the battery cell as a whole.

Description

Technical Field

[0001] This application relates to the field of battery manufacturing technology, and in particular to a method and apparatus for drying battery cells. Background Technology

[0002] Moisture content significantly impacts battery performance. To ensure battery safety and cycle life, a cell drying process is typically required after cell fabrication to remove moisture. This drying process necessitates removing moisture from the internal components of the cell (including the positive and negative electrodes and the separator), requiring a moisture content of ≤150 PPM after drying – a stringent requirement. Existing cell drying processes generally require 10 to 20 hours to achieve the desired dryness. Furthermore, this process demands substantial amounts of production equipment and electricity, increasing costs related to equipment quantity, floor space, personnel, production time, and energy consumption. Summary of the Invention

[0003] In order to solve one or more of the technical problems existing in the prior art, this application provides a new method and apparatus for drying battery cells. The method and apparatus perform staged drying according to the distribution of moisture in the battery cell, which can effectively reduce the drying time of the battery cell and prevent the battery cell from being damaged as a whole.

[0004] To achieve the above objectives, the technical solution adopted by this application to solve its technical problem is as follows:

[0005] In a first aspect, this application provides a method for drying battery cells, the method comprising:

[0006] The moisture content of the battery cell to be dried is measured, and the drying stage corresponding to the battery cell to be dried is determined based on the moisture content. The drying operation corresponding to the drying stage is then performed on the battery cell to be dried. When the moisture content is greater than a first threshold, the drying stage corresponding to the battery cell to be dried is the first stage. The drying operation corresponding to the first stage includes at least: performing a first operation, which includes: heating the vacuum oven for processing the battery cell to be dried to a first temperature at a first heating rate under a first vacuum degree, maintaining it for a first time period, and then performing a second operation, which includes: introducing inert gas into the vacuum oven to a second vacuum degree, evacuating the vacuum oven to the first vacuum degree, maintaining it for a second time period, and repeating the second operation until the moisture content in the battery cell to be dried is lower than the first threshold.

[0007] In one specific embodiment, when the moisture content is between the first threshold and the second threshold, the drying stage corresponding to the battery cell to be dried is the second stage, and the drying operation corresponding to the second stage includes:

[0008] Repeat the third operation until the moisture content in the battery cell to be dried is lower than the second threshold. The third operation includes: heating the vacuum oven to the second temperature at the second heating rate under the first vacuum degree, baking for a third time period, introducing inert gas into the vacuum oven to the second vacuum degree, and then evacuating the vacuum oven to the third vacuum degree. The second temperature is greater than the first temperature, the third time period is greater than the second time period, the second threshold is less than the first threshold, and the third vacuum degree is not less than the first vacuum degree.

[0009] In one specific embodiment, when the moisture content is lower than the second threshold, the drying stage corresponding to the battery cell to be dried is the third stage, and the drying operation corresponding to the third stage includes:

[0010] Repeat the fourth operation until the moisture content in the battery cell to be dried meets the requirements. The fourth operation includes: introducing inert gas into the vacuum oven until the pressure of the inert gas is a preset pressure value, maintaining it for a fourth time period, and then evacuating the vacuum oven to the first vacuum level.

[0011] Preferably, the temperature difference between the inert gas and the temperature in the vacuum oven is ±10°C.

[0012] In one specific embodiment, the inert gas includes nitrogen.

[0013] In one specific embodiment, the first threshold is 400 ppm; and / or, the second threshold is 180 ppm.

[0014] In one specific embodiment, the first vacuum degree is 50-80 Pa; and / or, the second vacuum degree is 85000-100000 Pa.

[0015] Preferably, the second vacuum degree is 85000 Pa.

[0016] In one specific embodiment, the first heating rate is 0.8-1.5℃ / min; and / or, the first temperature is 65-70℃.

[0017] In one specific embodiment, the second heating rate is 5-10°C / min; and / or, the second temperature is 85-90°C.

[0018] Preferably, the second heating rate is 5°C / min.

[0019] In one specific embodiment, the second time period is 3-10 min; and / or, the third time period is 30-45 min; and / or, the fourth time period is 5-10 min.

[0020] In one specific embodiment, the preset pressure value is 0.2 MPa.

[0021] Secondly, corresponding to the above-mentioned cell drying method, this application also provides a cell drying apparatus, the apparatus comprising at least:

[0022] The measurement module is used to measure the moisture content of the battery cells to be dried.

[0023] A vacuum oven is used to perform the drying operation corresponding to the drying stage on the battery cells to be dried.

[0024] The processing module is configured to determine the drying stage corresponding to the battery cell to be dried based on the moisture content, and control the vacuum oven to perform the drying operation corresponding to the drying stage on the battery cell to be dried. Specifically, when the moisture content is greater than a first threshold, the drying stage corresponding to the battery cell to be dried is the first stage, and the drying operation corresponding to the first stage includes at least:

[0025] Perform a first operation, which includes: heating the vacuum oven for processing the battery cell to be dried to a first temperature at a first heating rate under a first vacuum level, maintaining it for a first time period, and then performing a second operation, which includes: introducing an inert gas into the vacuum oven to a second vacuum level, evacuating the vacuum oven to the first vacuum level, maintaining it for a second time period, and repeating the second operation until the moisture content in the battery cell to be dried is lower than the first threshold.

[0026] The beneficial effects of the technical solutions provided in this application are:

[0027] The present application provides a method and apparatus for drying battery cells. The method includes measuring the moisture content of the battery cell to be dried, determining the drying stage corresponding to the battery cell to be dried based on the moisture content, and performing a drying operation corresponding to the drying stage on the battery cell to be dried. When the moisture content is greater than a first threshold, the drying stage corresponding to the battery cell to be dried is a first stage. The drying operation corresponding to the first stage includes at least: performing a first operation, which includes: heating a vacuum oven for processing the battery cell to be dried to a first temperature at a first heating rate under a first vacuum level, maintaining this temperature for a first time period, and then performing a second operation, which includes: introducing an inert gas into the vacuum oven to a second vacuum level, evacuating the vacuum oven to the first vacuum level, maintaining this evacuation for a second time period, and repeating the second operation until the moisture content in the battery cell to be dried is lower than the first threshold. This application achieves rapid moisture removal by using a phased drying process based on the distribution of moisture within the battery cell. This effectively reduces the drying time of the battery cell and prevents damage to the entire battery cell. By employing different process methods according to the three stages of moisture distribution within the battery cell during the baking process, the goal of rapid moisture removal is achieved. The moisture content of the treated battery cell is less than 80 ppm, and the drying of the electrode sheets only requires 8-12 hours. The moisture content is lower than the current standard, and the existing baking time is shortened by 15%-50%. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0029] As described in the background section, the existing battery cell drying process typically requires ten to twenty hours to achieve the desired result, which places a large demand on production equipment and electricity, increasing costs such as the number of equipment, site area, supporting personnel, production time, and production energy consumption.

[0030] To address one or more of the aforementioned problems, this application creatively proposes a new method for drying battery cells. By dividing the battery cell into at least three stages—high moisture, medium moisture, and low moisture—based on its moisture content, the battery cell is then divided into three drying stages: a first stage, a second stage, and a third stage, corresponding to these three stages. Different drying operations are performed for each drying stage, which can effectively reduce the drying time of the battery cell and prevent damage to the battery cell as a whole.

[0031] It should be noted that the vacuum reading in this application is the dial reading of a high-vacuum oven, which differs from the vacuum level in the prior art. The vacuum oven in this application has a reading of 1,000,000 Pa at normal pressure. The 80 Pa mentioned below is equivalent to -101.3 kPa in the prior art. That is, the smaller the vacuum level value in this application, the higher the negative pressure.

[0032] The battery cell drying method provided in this application includes the following steps:

[0033] The moisture content of the battery cell to be dried is measured, and the drying stage corresponding to the battery cell is determined based on the moisture content. The drying operation corresponding to the drying stage is then performed on the battery cell. Wherein, when the moisture content is greater than a first threshold, the drying stage corresponding to the battery cell is the first stage. The drying operation corresponding to the first stage includes at least the following:

[0034] Perform a first operation, which includes: heating the vacuum oven for processing the battery cell to be dried to a first temperature at a first heating rate under a first vacuum, maintaining it for a first time period, and then performing a second operation, which includes: introducing an inert gas into the vacuum oven to a second vacuum, then evacuating the vacuum oven to the first vacuum, maintaining it for a second time period, and repeating the second operation until the moisture content in the battery cell to be dried is lower than the first threshold.

[0035] The first time period can be 0 minutes or the same as the second time period. The length of the first time period can be set according to the actual drying requirements, and there is no specific limitation here.

[0036] Specifically, in this embodiment, a high-moisture stage is defined as when the moisture content inside the battery cell exceeds a first threshold (e.g., 400 ppm). The battery cell in the high-moisture stage undergoes a first-stage drying operation. During this process, as the battery cell temperature gradually increases, the moisture inside the cell changes from a liquid state to a molecular state, causing rapid volume expansion. The water molecules begin to compress the substrate and each other, generating an overflow force F1. Meanwhile, the vacuum oven generates a force F2 that extracts moisture from the battery cell.

[0037] During the high-moisture stage, due to the high moisture content within the battery cell, the temperature rise rate within the vacuum oven needs to be strictly controlled. The preferred rise rate is 0.8-1.5℃ / min to prevent excessive and rapid moisture expansion that could damage or loosen the substrate pores. Under the combined action of the water molecule overflow force F1 and the vacuum environment's force F2 on the water molecules, water molecules can rapidly overflow. Therefore, it is necessary to quickly replace the nitrogen gas (99.999% purity) to promptly remove water molecules around the battery cell, preventing "blockage" in the overflow channels and improving the environment for water molecule overflow. Furthermore, the high vacuum level helps lower the boiling point of water, thereby reducing the requirement for high drying temperatures and achieving energy savings.

[0038] In practice, the battery cells to be dried are placed in a vacuum oven. The first operation involves turning on the vacuum device and evacuating the oven to a first vacuum level. Then, the temperature is raised to a first temperature at a first heating rate and maintained for a first time period, allowing the temperature of the battery cells to gradually increase. This causes the water inside the cells to change from a liquid state to a molecular state, resulting in rapid volume expansion. The water molecules begin to compress the substrate and each other, generating an overflow force F1. The second operation involves introducing an inert gas into the vacuum oven to achieve a second vacuum level. The inert gas includes, but is not limited to, nitrogen. Nitrogen will be used as an example in the following explanation. Finally, the vacuum oven is evacuated to the first vacuum level and maintained for a second time period. On one hand, the overflow force of the water molecules and the force exerted on the water molecules by the vacuum environment allow the water molecules in the battery cells to overflow rapidly. On the other hand, the rapid replacement of nitrogen gas removes the water molecules around the battery cells, preventing "blockage" in the overflow channels, improving the environment for water molecule overflow, and increasing drying efficiency. Repeat the process of "vacuuming → maintaining vacuum for the second time period → introducing nitrogen → vacuuming" 2-3 times until the moisture content inside the battery cell to be dried is lower than the first threshold, thus completing this stage of dehydration. The moisture content of the battery cell to be dried can be measured using a coulometric micro-water analyzer; there are no restrictions on this method, and users can choose the appropriate analyzer based on their actual needs.

[0039] It should be noted that in this embodiment, high-temperature nitrogen gas can be introduced into the vacuum oven. Preferably, the temperature of the introduced nitrogen gas can be ±10°C of the temperature inside the vacuum oven. This prevents the temperature inside the vacuum oven from dropping due to the introduction of nitrogen gas, and also avoids the need for reheating due to a drop in the temperature of the vacuum oven, reducing the drying time and improving drying efficiency. As a preferred implementation, in this embodiment, when the moisture content is between the first threshold and the second threshold, the drying stage corresponding to the battery cell to be dried is the second stage, and the drying operation corresponding to the second stage includes:

[0040] Repeat the third operation until the moisture content in the battery cell to be dried is lower than the second threshold. The third operation includes: heating the vacuum oven to a second temperature at a second heating rate under the first vacuum level; after baking for a third time period, introducing inert gas into the vacuum oven to a second vacuum level; and then evacuating the vacuum oven to a third vacuum level. The second temperature is greater than the first temperature, the third time period is greater than the second time period, the second threshold is less than the first threshold, and the third vacuum level can be equal to or greater than the first vacuum level. The magnitude of the third vacuum level can be determined based on the current moisture content of the battery cell to be dried and the drying requirements, and no specific restrictions are imposed here.

[0041] Specifically, in this embodiment, a medium moisture stage is defined as when the moisture content inside the battery cell is greater than a second threshold (e.g., 180 ppm) but less than a first threshold (e.g., 400 ppm). A second-stage drying operation is then performed on the battery cell in the medium moisture stage. At this point, since most of the water inside the battery cell has been converted into water molecules, with only a very small number remaining at deeper levels, the overflow force F1 has decreased. The main force at this point is the force F2 exerted by the vacuum environment on the water molecules.

[0042] Therefore, the drying operation for cells in the medium moisture stage needs to be different from that in the high moisture stage. In specific implementation, after the first stage of drying operation is completed, the vacuum degree in the vacuum oven is the first vacuum degree. Under the first vacuum degree, the temperature is raised to the second temperature at the second heating rate. At this time, since the moisture content in the cell is relatively low, the second heating rate can be appropriately increased compared with the first heating rate, thereby reducing the drying time and improving the overall drying efficiency. Then, after baking at the second temperature for a third time period, nitrogen gas is introduced into the vacuum oven to the second vacuum degree. Finally, the vacuum oven is evacuated to the third vacuum degree. The cycle of "heating and baking for a third time period → introducing nitrogen gas → evacuating vacuum" is repeated 2-4 times until the moisture content in the cell to be dried is lower than the second threshold, thus completing the dehydration of this stage.

[0043] Furthermore, in this embodiment, the second temperature is set higher than the first temperature, and the third time period is longer than the second time period. This is because the water content inside the battery cell has been significantly reduced compared to the high-moisture stage. Appropriately extending the heating time helps to convert the deep water into water molecules. Through high-temperature baking, the water molecules inside the battery cell become more active and more easily overflow from the depths of the substrate. It should be noted that because the moisture content in the vacuum oven is reduced in this stage, the frequency of nitrogen replacement can be reduced, thus reducing energy consumption.

[0044] In a preferred embodiment of this application, when the moisture content is lower than the second threshold, the drying stage corresponding to the battery cell to be dried is the third stage, and the drying operation corresponding to the third stage includes:

[0045] Repeat the fourth operation until the moisture content in the battery cell to be dried meets the requirements. The fourth operation includes: introducing inert gas into the vacuum oven until the pressure of the inert gas is a preset pressure value, maintaining it for a fourth time period, and then evacuating the vacuum oven to the first vacuum level.

[0046] Specifically, in this embodiment of the application, a low-moisture stage is defined as when the moisture content inside the battery cell is less than a second threshold (e.g., 180 ppm). A third-stage drying operation is then performed on the battery cell in the low-moisture stage. At this point, because there are very few water molecules left in the battery cell, the overflow force F1 almost disappears. Furthermore, since there are very few water molecules, an external molecule (e.g., nitrogen molecule) must be introduced to replace them before they can leave their original location.

[0047] Therefore, when performing the third stage drying operation on the battery cells in the low moisture stage, nitrogen gas is first introduced into the vacuum oven until the nitrogen pressure reaches the preset pressure value, preferably 0.2 MPa, and maintained for a fourth time period. Then, the vacuum oven is evacuated to the first vacuum degree, and the process of "introducing nitrogen gas → evacuating vacuum" is repeated 5-8 times until the moisture content in the battery cells to be dried meets the requirements, thus achieving the purpose of rapid water removal and cooling in this stage.

[0048] In a preferred embodiment of this application, the first threshold is 400 ppm; and / or the second threshold is 180 ppm.

[0049] Specifically, in this embodiment, the battery cell is divided into three stages for different drying processes based on its internal moisture content. Specifically, a high moisture content (greater than 400 ppm) is defined as the high moisture stage, and the high moisture stage is subjected to the first stage of drying. A medium moisture content (greater than 180 ppm but less than 400 ppm) is defined as the medium moisture stage, and the medium moisture stage is subjected to the second stage of drying. A low moisture content (less than 180 ppm) is defined as the low moisture stage, and the low moisture stage is subjected to the third stage of drying.

[0050] As a preferred implementation, in this embodiment of the application, the first vacuum degree is any value between 50-80 Pa. Optionally, the first vacuum degree is 50 Pa, 55 Pa, 60 Pa, 65 Pa, 70 Pa, 75 Pa, or 80 Pa, etc., which will not be listed here.

[0051] As a preferred embodiment, in this application embodiment, the second vacuum degree is 85000-100000 Pa, preferably, the second vacuum degree is 85000 Pa.

[0052] As a preferred implementation, in the embodiments of this application, the third vacuum degree is any value between 50-80 Pa. Optionally, the third vacuum degree is 50 Pa, 55 Pa, 60 Pa, 65 Pa, 70 Pa, 75 Pa, or 80 Pa, etc.

[0053] In a preferred embodiment of this application, the first heating rate is 0.8-1.5℃ / min. Optionally, the first heating rate can be 0.8℃ / min, 0.9℃ / min, 1.0℃ / min, 1.1℃ / min, 1.2℃ / min, 1.3℃ / min, 1.4℃ / min, or 1.5℃ / min, etc. The first temperature is any value between 65-70℃. Optionally, the first temperature can be 65℃, 66℃, 67℃, 68℃, 69℃, or 70℃, etc.

[0054] In a preferred embodiment of this application, the second heating rate is any value between 5-10℃ / min. Optionally, the first heating rate can be 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, etc. The second temperature is any value between 85-90℃. Optionally, the second temperature can be 85℃, 86℃, 87℃, 88℃, 89℃, or 90℃, etc. It should be noted that since the moisture content in the battery cell is relatively low during the medium moisture stage, the second heating rate can be appropriately increased compared to the first heating rate during the high moisture stage, thereby reducing the heating time and improving the drying efficiency.

[0055] In a preferred embodiment, the second time period is any value between 3 and 10 minutes. Optionally, the second time period can be 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes. The third time period is any value between 30 and 45 minutes. Optionally, the third time period can be 30 minutes, 35 minutes, 40 minutes, or 45 minutes. The fourth time period is any value between 5 and 10 minutes. Optionally, the fourth time period can be 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes. The vacuum holding time (i.e., the first time period) in each cycle during the high moisture stage can be the same or different. Preferably, the vacuum holding time gradually increases. For example, the second time period in the first cycle is 3 minutes, the second time period in the second cycle is 5 minutes, and the second time period in the third cycle is 7 minutes. Of course, the second time period can also be appropriately adjusted according to the thickness of the battery cell, the specific materials used, and the moisture content in the oven, which will not be elaborated here.

[0056] Corresponding to the above-described cell drying method, this application also provides a cell drying apparatus, the apparatus comprising at least:

[0057] The measurement module is used to measure the moisture content of the battery cells to be dried.

[0058] A vacuum oven is used to perform the drying operation corresponding to the drying stage on the battery cells to be dried.

[0059] The processing module is configured to determine the drying stage corresponding to the battery cell to be dried based on the moisture content, and control the vacuum oven to perform the drying operation corresponding to the drying stage on the battery cell to be dried. Specifically, when the moisture content is greater than a first threshold, the drying stage corresponding to the battery cell to be dried is the first stage, and the drying operation corresponding to the first stage includes at least:

[0060] The first operation includes: heating the vacuum oven for processing the battery cell to be dried to a first temperature at a first heating rate under a first vacuum level, maintaining it for a first time period, and then performing a second operation, which includes introducing an inert gas into the vacuum oven to a second vacuum level, evacuating the vacuum oven to the first vacuum level, maintaining it for a second time period, and repeating the second operation until the moisture content in the battery cell to be dried is lower than the first threshold.

[0061] Specifically, in the embodiments of this application, the measurement module can be implemented using a coulometric micro water analyzer or a measuring device using other measurement methods. The processing module can be implemented using the existing control module of the vacuum oven or by setting up a separate related functional module. No restrictions are placed here.

[0062] Example 1:

[0063] Perform the following operations on cell A to be dried:

[0064] Measure the moisture content of the battery cell A to be dried;

[0065] When the moisture content is greater than 400 ppm, the vacuum oven for the battery cell A to be dried is evacuated to 50 Pa, and then heated to 65 ℃ at a heating rate of 0.8 ℃ / min and held for 3 min. Then, the battery cell A to be dried is subjected to a second operation, which includes: introducing nitrogen gas to the vacuum oven to 85000 Pa, evacuating the vacuum oven to 50 Pa and holding for 3 min, and repeating the second operation 3 times.

[0066] When the moisture content is between 400ppm and 180ppm, the third operation is repeated twice for the cell A to be dried. The third operation includes: heating the vacuum oven to 85°C at a heating rate of 5°C / min under 50Pa, baking for 30 minutes, then introducing nitrogen to bring the vacuum oven to 85000Pa, and finally evacuating the vacuum oven to 50Pa.

[0067] When the moisture content is below 180ppm, repeat the fourth operation 5 times for the battery cell A to be dried. The fourth operation includes: introducing nitrogen into the vacuum oven until the nitrogen pressure is 0.2MPa, maintaining it for 5min, and then evacuating the vacuum oven to 50pa.

[0068] Example 2:

[0069] Perform the following operations on cell B to be dried:

[0070] Measure the moisture content of the battery cell B to be dried;

[0071] When the moisture content is greater than 400 ppm, the vacuum oven for the battery cell B to be dried is evacuated to 60 Pa, and then heated to 67 ℃ at a heating rate of 1.0 ℃ / min and held for 5 min. Then, the battery cell B to be dried is subjected to a second operation, which includes: introducing nitrogen gas to the vacuum oven to 90000 Pa, evacuating the vacuum oven to 60 Pa and holding for 5 min, and repeating the second operation twice.

[0072] When the moisture content is between 400ppm and 180ppm, the third operation is repeated 3 times for the cell B to be dried. The third operation includes: heating the vacuum oven to 87°C at a heating rate of 7°C / min under 60Pa, baking for 35 minutes, then introducing nitrogen to the vacuum oven to 90000Pa, and then evacuating the vacuum oven to 60Pa.

[0073] When the moisture content is below 180ppm, repeat the fourth operation 6 times for the battery cell B to be dried. The fourth operation includes: introducing nitrogen into the vacuum oven until the nitrogen pressure is 0.2MPa, maintaining it for 6min, and then evacuating the vacuum oven to 60pa.

[0074] Example 3:

[0075] Perform the following operations on the battery cell C to be dried:

[0076] Measure the moisture content of the battery cell C to be dried;

[0077] When the moisture content is greater than 400 ppm, the vacuum oven to be dried is evacuated to 70 Pa, and then heated to 68 ℃ at a heating rate of 1.2 ℃ / min and held for 7 min. Then, the second operation is performed on the cell C to be dried, which includes: introducing nitrogen gas to the vacuum oven to 95000 Pa, evacuating the vacuum oven to 70 Pa and holding for 7 min, and repeating the second operation 3 times.

[0078] When the moisture content is between 400ppm and 180ppm, the third operation is repeated 3 times for the cell C to be dried. The third operation includes: heating the vacuum oven to 88°C at a heating rate of 8°C / min under 70Pa, baking for 40 minutes, then introducing nitrogen to the vacuum oven to 95000Pa, and then evacuating the vacuum oven to 70Pa.

[0079] When the moisture content is below 180ppm, the fourth operation is repeated 7 times for the cell C to be dried. The fourth operation includes: introducing nitrogen into the vacuum oven to a pressure of 0.2MPa, maintaining it for 8 minutes, and then evacuating the vacuum oven to 70pa.

[0080] Example 4:

[0081] Perform the following operations on the battery cell D to be dried:

[0082] Measure the moisture content of the battery cell D to be dried;

[0083] When the moisture content is greater than 400 ppm, the vacuum oven to be dried is evacuated to 80 Pa, and then heated to 70 ℃ at a heating rate of 1.5 ℃ / min and held for 10 min. Then, the second operation is performed on the battery cell D to be dried, which includes: introducing nitrogen gas to the vacuum oven to 100000 Pa, evacuating the vacuum oven to 80 Pa and holding for 10 min. The second operation is repeated 3 times.

[0084] When the moisture content is between 400ppm and 180ppm, the third operation is repeated 4 times for the cell D to be dried. The third operation includes: heating the vacuum oven to 90℃ at a heating rate of 10℃ / min at 80pa, baking for 45min, then introducing nitrogen to the vacuum oven to 100000pa, and then evacuating the vacuum oven to 80pa.

[0085] When the moisture content is below 180ppm, the fourth operation is repeated 8 times for the cell D to be dried. The fourth operation includes: introducing nitrogen into the vacuum oven to a pressure of 0.2MPa, maintaining it for 10min, and then evacuating the vacuum oven to 80pa.

[0086] Among them, the battery cells AD to be dried are the same type of battery cells with the same initial moisture content.

[0087] The moisture content of the positive electrode, negative electrode, and the entire battery cell after being treated according to the methods of Examples 1-4 above was measured.

[0088] The test results are as follows:

[0089]

[0090] The test results show that the cell drying method provided in this application achieves the purpose of quickly removing moisture by using different process methods in three stages according to the moisture distribution of the cell during the baking process, and the moisture content in the cell after treatment is lower than the current standard.

[0091] In the description of this application, it should be understood that 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 indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "multiple" means two or more.

[0092] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for drying battery cells, characterized in that, The method includes: The moisture content of the battery cell to be dried is measured, and the drying stage corresponding to the battery cell is determined based on the moisture content. The drying operation corresponding to the drying stage is then performed on the battery cell. Specifically, when the moisture content is greater than a first threshold, the drying stage corresponding to the battery cell is the first stage; when the moisture content is between the first and second thresholds, the drying stage corresponding to the battery cell is the second stage; and when the moisture content is lower than the second threshold, the drying stage corresponding to the battery cell is the third stage. The drying operation corresponding to the first stage includes at least the following: Perform a first operation, the first operation including: heating the vacuum oven for processing the battery cell to be dried to a first temperature at a first heating rate under a first vacuum degree, maintaining it for a first time period, and then performing a second operation, the second operation including: introducing an inert gas into the vacuum oven to a second vacuum degree, evacuating the vacuum oven to the first vacuum degree, maintaining it for a second time period, and repeating the second operation until the moisture content in the battery cell to be dried is lower than the first threshold. The drying operations corresponding to the second stage include: Repeat the third operation until the moisture content in the cell to be dried is lower than the second threshold. The third operation includes: heating the vacuum oven to the second temperature at the second heating rate under the first vacuum degree, baking for a third time period, introducing inert gas into the vacuum oven to the second vacuum degree, and then evacuating the vacuum oven to the third vacuum degree. The second temperature is greater than the first temperature, the third time period is greater than the second time period, the second threshold is less than the first threshold, and the third vacuum degree is not less than the first vacuum degree. The second heating rate is greater than the first heating rate.

2. The method for drying battery cells according to claim 1, characterized in that, The drying operation corresponding to the third stage includes: Repeat the fourth operation until the moisture content in the battery cell to be dried meets the requirements. The fourth operation includes: introducing inert gas into the vacuum oven until the pressure of the inert gas is a preset pressure value, maintaining it for a fourth time period, and then evacuating the vacuum oven to the first vacuum level.

3. The method for drying battery cells according to claim 2, characterized in that, The first threshold is 400 ppm; and / or, the second threshold is 180 ppm.

4. The method for drying battery cells according to any one of claims 1 to 3, characterized in that, The first vacuum degree is 50-80 Pa; and / or, the second vacuum degree is 85000-100000 Pa.

5. The method for drying battery cells according to any one of claims 1 to 3, characterized in that, The first heating rate is 0.8-1.5℃ / min; and / or the first temperature is 65-70℃.

6. The method for drying battery cells according to claim 5, characterized in that, The second heating rate is 5-10℃ / min; and / or the second temperature is 85-90℃.

7. The method for drying battery cells according to claim 2, characterized in that, The second time period is 3-10 min; and / or, the third time period is 30-45 min; and / or, the fourth time period is 5-10 min.

8. The method for drying battery cells according to claim 2, characterized in that, The preset pressure value is 0.2 MPa.

9. A drying device for battery cells, characterized in that, The device includes at least: The measurement module is used to measure the moisture content of the battery cells to be dried. A vacuum oven is used to perform the drying operation corresponding to the drying stage on the battery cells to be dried. The processing module is used to determine the drying stage corresponding to the battery cell to be dried based on the moisture content, and control the vacuum oven to perform the drying operation corresponding to the drying stage on the battery cell to be dried. Specifically, when the moisture content is greater than a first threshold, the drying stage corresponding to the battery cell to be dried is the first stage; when the moisture content is between the first threshold and a second threshold, the drying stage corresponding to the battery cell to be dried is the second stage; and when the moisture content is lower than the second threshold, the drying stage corresponding to the battery cell to be dried is the third stage. The drying operation corresponding to the first stage includes at least: Perform a first operation, the first operation including: heating the vacuum oven for processing the battery cell to be dried to a first temperature at a first heating rate under a first vacuum degree, maintaining it for a first time period, and then performing a second operation, the second operation including: introducing an inert gas into the vacuum oven to a second vacuum degree, evacuating the vacuum oven to the first vacuum degree, maintaining it for a second time period, and repeating the second operation until the moisture content in the battery cell to be dried is lower than the first threshold. The drying operations corresponding to the second stage include: Repeat the third operation until the moisture content in the battery cell to be dried is lower than the second threshold. The third operation includes: heating the vacuum oven to the second temperature at the second heating rate under the first vacuum degree, baking for a third time period, introducing inert gas into the vacuum oven to the second vacuum degree, and then evacuating the vacuum oven to the third vacuum degree. The second temperature is greater than the first temperature, the third time period is greater than the second time period, the second threshold is less than the first threshold, and the third vacuum degree is not less than the first vacuum degree.

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