Methods and applications for dehydration of lithium battery cells, and vacuum drying ovens

Abstract

This application relates to a method for removing water from a lithium battery cell, comprising the following steps: Step 1: Placing the cell in a drying chamber and preheating it to a preheated temperature; Step 2: Performing a first vacuum treatment on the drying chamber to reduce the pressure inside to a first atmospheric pressure; Step 3: Introducing a drying gas into the drying chamber to increase the pressure to a second atmospheric pressure; Step 4: Using a water removal mechanism to remove moisture mixed in the drying gas; Step 5: Performing a second vacuum treatment on the drying chamber to reduce the pressure to a third atmospheric pressure, and collecting the dehydrated gas; Step 6: Introducing the dehydrated gas into the drying chamber to increase the pressure to a fourth atmospheric pressure; Step 7: Repeating steps 4 to 6. This method allows for continuous moisture removal from the cell, thereby improving the water removal effect.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and in particular to a method for removing water from lithium battery cells and its application, as well as a vacuum drying oven. Background Technology

[0002] With the increasing demand for lithium-ion batteries from electric vehicles, energy storage, 3C products and other fields, lithium battery technology has entered a stage of rapid development.

[0003] In the manufacturing process of lithium batteries, the moisture content of the battery needs to be strictly controlled. Excessive moisture content can easily lead to increased internal resistance, low capacity, and poor cycle life, directly affecting battery performance. The key to controlling the internal moisture content of lithium batteries lies in the battery cell itself. Before the electrolyte filling process, removing as much moisture as possible from the electrodes and separators inside the cell effectively controls the moisture content of the final lithium battery product. During production, a baking process is typically used to evaporate the moisture, thus controlling the moisture content in the lithium battery cell. Therefore, the dehydration process is a crucial step in controlling the internal moisture content of lithium batteries.

[0004] There is currently a lot of research on the baking and dehydration process of lithium battery cells. For example, a domestic patent technology provides a rapid baking process for power battery cells. This process pre-baks the bare cells, and after the bare cells are assembled into batteries, a second baking is required. This solution is complex, involves adjustments to traditional process routes, and requires a large investment in equipment, resulting in high process costs. Another example is a domestic patent technology that provides a vacuum drying method for lithium battery cells. This solution requires nitrogen to be introduced during the baking process, and it needs to be charged to atmospheric pressure and frequently charged, which will result in a large consumption of nitrogen and also requires a large process cost. Summary of the Invention

[0005] Therefore, it is necessary to provide a method for dehydrating lithium battery cells that can simplify the process and reduce process costs, as well as its application and a vacuum drying oven.

[0006] One embodiment of this application provides a method for removing water from lithium battery cells. The method employs a vacuum drying oven, which has a drying chamber containing a water removal mechanism. The water removal method includes the following steps:

[0007] Step 1: Place the battery cell in the drying chamber and preheat the battery cell until it reaches the preheating temperature;

[0008] Step 2: Perform a first vacuum treatment on the drying chamber to reduce the air pressure inside the drying chamber to a first air pressure.

[0009] Step 3: Fill the drying chamber with drying gas to raise the gas pressure inside the drying chamber to the second pressure.

[0010] Step 4: Use the dehydration mechanism to remove moisture from the mixture in the drying gas;

[0011] Step 5: Perform a second vacuuming process on the drying chamber to reduce the air pressure inside the drying chamber to a third air pressure, and collect the dried gas after water removal treatment.

[0012] Step 6: Fill the drying chamber with the dehydrated gas to raise the pressure in the drying chamber to a fourth pressure.

[0013] Step 7: Repeat steps 4 through 6.

[0014] In one embodiment, the preheating temperature is 85°C to 105°C.

[0015] In one embodiment, the first pressure and the third pressure are each independently ≤100 Pa.

[0016] In one embodiment, the second pressure and the fourth pressure are each independently between 0.4 kPa and 30 kPa.

[0017] In one embodiment, in step 3, the dew point of the dry gas introduced is -60°C to -30°C.

[0018] In one embodiment, in step 4, after dehydration treatment, the moisture content mixed in the dry gas is controlled to not exceed 50 ppm.

[0019] In one embodiment, in step 7, the cycle is repeated 5 to 30 times.

[0020] In one embodiment, the drying gas is selected from at least one of nitrogen or dry air.

[0021] One embodiment of this application also provides a vacuum drying oven, which has a drying chamber and a water removal mechanism is provided in the drying chamber for removing moisture from the drying chamber.

[0022] An embodiment of this application also provides a lithium battery cell, which is obtained by the water removal method described in any of the above embodiments.

[0023] An embodiment of this application also provides a lithium battery, including the lithium battery cell described in the above embodiment.

[0024] This application provides a method for removing water from lithium battery cells. A water removal mechanism is installed in the drying chamber of a drying oven. When the battery cell is placed in the drying chamber for water removal, a vacuum process is first performed, followed by the introduction of a certain amount of drying gas. Then, the process repeats the steps of "water removal treatment - evacuation and collection of the water-removed drying gas - re-introduction of the water-removed drying gas". Under the dry gas atmosphere, water can be expelled from the battery cell. The water that evaporates from the battery cell is removed by the water removal mechanism, thereby controlling the moisture content mixed in the drying gas in the drying chamber to a low range. This maintains a high and continuous rate of water expulsion from the battery cell, greatly improving the water removal effect. Furthermore, the water-removed drying gas can be recycled, which can greatly reduce the consumption of drying gas. The above water removal method is simple and can effectively reduce the cost of the water removal process. Attached Figure Description

[0025] Figure 1 This is a flow chart of the dehydration process for a lithium battery cell provided in one embodiment. Detailed Implementation

[0026] To facilitate understanding of this application, a more comprehensive description will be provided below in conjunction with embodiments and accompanying drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0027] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0028] The terms "optionally," "preferredly," and "more preferably," as used in this application, refer to embodiments of the invention that may provide certain beneficial effects under certain circumstances. However, other embodiments may also be optional or preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this application.

[0029] When a numerical range is disclosed in this application, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed in this application should be understood to include any and all subranges to which they are included.

[0030] The term “and / or” as used in this application includes any and all combinations of one or more of the associated listed items.

[0031] like Figure 1 As shown, one embodiment of this application provides a method for removing water from a lithium battery cell. The water removal method is carried out using a vacuum drying oven, which has a drying chamber and a water removal mechanism installed inside the drying chamber. The water removal method includes the following steps:

[0032] Step 1: Place the battery cell in the drying chamber and preheat the battery cell until it reaches the preheating temperature;

[0033] Step 2: Perform a first vacuum treatment on the drying chamber to reduce the air pressure inside the drying chamber to the first air pressure.

[0034] Step 3: Fill the drying chamber with drying gas to raise the pressure inside the drying chamber to the second pressure.

[0035] Step 4: Use a dehydration device to remove moisture from the mixture in the dry gas;

[0036] Step 5: Perform a second vacuum treatment on the drying chamber to reduce the air pressure inside the drying chamber to a third air pressure, and collect the dried gas after water removal treatment.

[0037] Step 6: Fill the drying chamber with dehydrated gas to raise the pressure inside the drying chamber to the fourth pressure.

[0038] Step 7: Repeat steps 4 through 6.

[0039] This application provides a method for removing water from lithium battery cells. A water removal mechanism is installed in the drying chamber of a drying oven. When the battery cell is placed in the drying chamber for water removal, a vacuum process is first performed, followed by the introduction of a certain amount of drying gas. Then, the process repeats the steps of "water removal treatment - evacuation and collection of the water-removed drying gas - re-introduction of the water-removed drying gas". Under the dry gas atmosphere, water can be expelled from the battery cell. The water that evaporates from the battery cell is removed by the water removal mechanism, thereby controlling the moisture content mixed in the drying gas in the drying chamber to a low range. This maintains a high and continuous rate of water expulsion from the battery cell, greatly improving the water removal effect. Furthermore, the water-removed drying gas can be recycled, which can greatly reduce the consumption of drying gas. The above water removal method is simple and can effectively reduce the cost of the water removal process.

[0040] In one embodiment, the water-absorbing material of the dehydration mechanism is a molecular sieve. Molecular sieves have good water absorption properties and can effectively remove moisture mixed in the dry gas. Understandably, in other embodiments, the water-absorbing material of the dehydration mechanism may also be other substances with water-absorbing properties.

[0041] In one embodiment, the preheating temperature is 85°C to 105°C. Within this temperature range, the preheating temperature ensures that the moisture inside the battery cell is heated to a sufficient temperature to evaporate as water vapor, while also preventing the performance of internal materials such as the separator from being damaged by high temperatures. Understandably, the preheating temperature can be, but is not limited to, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C, 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, etc.

[0042] Furthermore, the preheating time is 1.5 to 2.5 hours to ensure that the inside of the battery cell is fully heated and heated evenly. Understandably, the preheating time can be, for example, but is not limited to, 1.5 hours, 2 hours, 2.5 hours, etc.

[0043] In one embodiment, the first and third pressures are each independently ≤100 Pa. By performing a first or second vacuuming process to remove as much gas as possible from the drying chamber and placing it in a low-pressure heating state, the boiling point of water can be significantly reduced, which is beneficial for promoting the evaporation of moisture in the battery cell. Furthermore, removing the original gas from the drying chamber helps to provide a clean, dry gas atmosphere for subsequent processes.

[0044] Furthermore, the first and third atmospheric pressures are each independently between 50 Pa and 100 Pa.

[0045] Further, in step 2, the air pressure inside the drying chamber is maintained at the first air pressure for 0.5 minutes to 45 minutes. Preferably, in step 2, the air pressure inside the drying chamber is maintained at the first air pressure for 0.5 minutes to 5 minutes.

[0046] Further, in step 5, the air pressure inside the drying chamber is maintained at the third air pressure for 0.5 minutes to 45 minutes. Preferably, in step 5, the air pressure inside the drying chamber is maintained at the third air pressure for 35 minutes to 45 minutes.

[0047] In one embodiment, the second and fourth pressures are each independently between 0.4 kPa and 30 kPa. After performing a first or second vacuum treatment on the drying chamber to remove as much of the original gas as possible, a certain amount of drying gas is then introduced. This drying gas helps adsorb water vapor volatilized from the battery cell, accelerating the drying and dehydration process and preventing oxidation. Furthermore, after introducing dehydrated or undehydrated drying gas, the pressure inside the drying chamber is only 0.4 kPa to 30 kPa, still far below atmospheric pressure. At lower pressures, the boiling point of water decreases, which is more conducive to water evaporation and reduces the amount of drying gas used, thus saving costs. Understandably, the second and fourth pressures can be, for example, but not limited to, independently between 0.4 kPa, 0.5 kPa, 2 kPa, 5 kPa, 10 kPa, 15 kPa, 20 kPa, 25 kPa, 30 kPa, etc.

[0048] In one embodiment, in step 3, the dew point of the introduced drying gas is -60°C to -30°C. Within this dew point range, the introduced drying gas has a low moisture content and is relatively dry, which is beneficial for promoting the evaporation of moisture inside the battery cell. Understandably, the dew point of the introduced drying gas can be, for example, but not limited to, -30°C, -35°C, -40°C, -45°C, -50°C, -55°C, -60°C, etc.

[0049] In one embodiment, in step 4, after dehydration treatment, the moisture content mixed in the drying gas is controlled to not exceed 50 ppm. By controlling the water content mixed in the drying gas to remain at a low level through dehydration treatment, a relatively dry gas atmosphere can be maintained continuously within the drying chamber, which is beneficial for promoting the continuous evaporation of water molecules from inside the battery cell and improving the baking and dehydration effect. It is understood that after dehydration treatment, the moisture content mixed in the drying gas can be controlled to be <50 ppm, <40 ppm, <30 ppm, <20 ppm, etc.

[0050] Furthermore, in step 4, the water removal treatment time is from 1 minute to 60 minutes. Controlling the water removal treatment within a certain time range ensures a good water removal and purification effect. Understandably, the water removal treatment time can be, for example, but not limited to, 1 minute, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, etc.

[0051] In one embodiment, the number of cycles in step 7 is 5 to 30. Controlling the number of cycles within a certain range ensures a good baking and dehumidification effect on the battery cell, greatly improving the dehumidification rate, while effectively avoiding the adverse effects of excessive cycles and repeated vacuuming operations on the vacuum pump. Understandably, the number of cycles can be, for example, but not limited to, 5, 8, 10, 13, 15, 18, 20, 22, 25, 30, etc.

[0052] In one embodiment, the drying gas is selected from at least one of nitrogen or dry air.

[0053] In one embodiment, the above-described water removal method further includes:

[0054] Step 8: After the cycle ends, fill the drying chamber with dry gas until atmospheric pressure is reached.

[0055] In one embodiment, the above-described water removal method further includes:

[0056] Step 9: After water removal is complete, cool the battery cell and remove it.

[0057] One embodiment of this application also provides a vacuum drying oven, which has a drying chamber and a dehydration mechanism provided in the drying chamber for removing moisture from the drying chamber.

[0058] An embodiment of this application also provides a lithium battery cell, which is obtained by the dehydration method in any of the above embodiments.

[0059] An embodiment of this application also provides a lithium battery, including the lithium battery cell of the above embodiment.

[0060] The following are specific examples.

[0061] Example 1

[0062] Taking a 300AH square aluminum-cased lithium iron phosphate battery as an example, a vacuum drying oven is used to remove water from the battery cells. The vacuum drying oven has a drying chamber, and a water removal mechanism is installed inside the drying chamber. The water removal method includes the following steps:

[0063] Step 1: Place the battery cell in the drying chamber and preheat it to the preheating temperature of 100℃ for 2 hours.

[0064] Step 2: Perform a first vacuum treatment on the drying chamber to reduce the air pressure inside the drying chamber to <100Pa and maintain it for 1 minute.

[0065] Step 3: Fill the drying chamber with nitrogen gas to raise the pressure inside the drying chamber to 20 kPa; the dew point of the nitrogen gas is -45°C.

[0066] Step 4: Use a dehydration device to remove moisture from the gas mixed in the drying chamber to continuously reduce the water content mixed in the nitrogen. After dehydration, the water content mixed in the nitrogen is controlled to be less than 50 ppm, and the dehydration time is 25 minutes.

[0067] Step 5: Perform a second vacuum treatment on the drying chamber to reduce the pressure inside the drying chamber to <100Pa, maintain this for 40 minutes, and then extract the nitrogen from the drying chamber and store it in a buffer tank.

[0068] Step 6: Refill the dried chamber with the stored and collected nitrogen gas to raise the pressure in the dried chamber to 10 kPa.

[0069] Step 7: Repeat steps 4 through 6 for a total of 8 times.

[0070] Step 8: After the cycle ends, fill the drying chamber with nitrogen gas to atmospheric pressure.

[0071] Step 9: After water removal is complete, cool the battery cell and remove it.

[0072] Example 2

[0073] Taking a 300AH square aluminum-cased lithium iron phosphate battery as an example, a vacuum drying oven is used to remove water from the battery cells. The vacuum drying oven has a drying chamber, and a water removal mechanism is installed inside the drying chamber. The water removal method includes the following steps:

[0074] Step 1: Place the battery cell in the drying chamber and preheat it to the preheating temperature of 85℃ for 2 hours.

[0075] Step 2: Perform a first vacuum treatment on the drying chamber to reduce the air pressure inside the drying chamber to <100Pa and maintain it for 1 minute.

[0076] Step 3: Fill the drying chamber with nitrogen gas to raise the pressure inside the drying chamber to 0.4 kPa; the dew point of the nitrogen gas is -60°C.

[0077] Step 4: Use a dehydration device to remove moisture from the gas mixed in the drying chamber to continuously reduce the water content mixed in the nitrogen. After dehydration, the water content mixed in the nitrogen is controlled to be less than 50 ppm, and the dehydration time is 20 minutes.

[0078] Step 5: Perform a second vacuum treatment on the drying chamber to reduce the pressure inside the drying chamber to <100Pa, maintain for 35 minutes, and then extract the nitrogen from the drying chamber and store it in the buffer tank.

[0079] Step 6: Refill the dried chamber with the collected nitrogen gas to raise the pressure inside the chamber to 0.4 kPa.

[0080] Step 7: Repeat steps 4 to 6 for a total of 30 times.

[0081] Step 8: After the cycle ends, fill the drying chamber with nitrogen gas to atmospheric pressure.

[0082] Step 9: After water removal is complete, cool the battery cell and remove it.

[0083] Example 3

[0084] Taking a 300AH square aluminum-cased lithium iron phosphate battery as an example, a vacuum drying oven is used to remove water from the battery cells. The vacuum drying oven has a drying chamber, and a water removal mechanism is installed inside the drying chamber. The water removal method includes the following steps:

[0085] Step 1: Place the battery cell in the drying chamber and preheat it until it reaches the preheating temperature; the preheating temperature is 105℃ and the preheating time is 2 hours.

[0086] Step 2: Perform a first vacuum treatment on the drying chamber to reduce the air pressure inside the drying chamber to <100Pa and maintain it for 1 minute.

[0087] Step 3: Fill the drying chamber with nitrogen gas to raise the pressure inside the drying chamber to 30 kPa; the dew point of the nitrogen gas is -30°C.

[0088] Step 4: Use a dehydration device to remove moisture from the gas mixed in the drying chamber to continuously reduce the water content mixed in the nitrogen. After dehydration, the water content mixed in the nitrogen is controlled to be less than 50 ppm, and the dehydration time is 30 minutes.

[0089] Step 5: Perform a second vacuum treatment on the drying chamber to reduce the pressure inside the drying chamber to <100Pa, maintain for 45 minutes, and then extract the nitrogen from the drying chamber and store it in the buffer tank.

[0090] Step 6: Refill the dried chamber with the stored and collected nitrogen gas to raise the pressure in the dried chamber to 30 kPa.

[0091] Step 7: Repeat steps 4 through 6 for a total of 5 times.

[0092] Step 8: After the cycle ends, fill the drying chamber with nitrogen gas to atmospheric pressure.

[0093] Step 9: After water removal is complete, cool the battery cell and remove it.

[0094] Example 4

[0095] It is largely the same as Example 1, except that:

[0096] Step 4: After dehydration treatment, the water content mixed in the nitrogen gas is controlled to be less than 150 ppm.

[0097] Example 5

[0098] It is largely the same as Example 1, except that:

[0099] Step 4: After dehydration treatment, the water content mixed in the nitrogen gas is controlled to be less than 250 ppm.

[0100] Example 6

[0101] It is largely the same as Example 1, except that:

[0102] Step 4: After dehydration treatment, the water content mixed in the nitrogen gas is controlled to be less than 350 ppm.

[0103] Comparative Example 1

[0104] Similar to Example 1, except that step 4 is omitted and a dehydration mechanism is not used to remove moisture from the mixture in the dry gas.

[0105] The main process parameters for baking lithium battery cells in Examples 1 to 6 and Comparative Example 1 are shown in Table 1 below.

[0106] Table 1 Baking process parameters for lithium battery cells

[0107]

[0108]

[0109] The moisture content of the lithium battery cells of Examples 1 to 6 and Comparative Example 1 before and after baking was tested, and the test results are shown in Table 2 below.

[0110] Table 2 Comparison of moisture content in lithium battery cells before and after baking

[0111]

[0112] As shown in Table 2, baking and dehydrating the lithium battery cells using the methods of Examples 1 to 6 can significantly reduce the moisture content of the cells, with a dehydration rate of 37.8% to 68.4%. However, in Comparative Example 1, since no dehydration mechanism was used, the dehydration rate of the lithium battery cells after baking was only 31%, indicating a significant decrease in the dehydration effect.

[0113] Compared with Examples 4, 5, and 6, Example 1 showed that after dehydration treatment, the water content mixed in nitrogen was controlled to be less than 50 ppm, 150 ppm, 250 ppm, and 350 ppm, respectively. The dehydration rates of the lithium battery cells after baking were 68.4%, 54.9%, 47.7%, and 37.8%, respectively. This indicates that controlling the water content mixed in nitrogen after dehydration treatment to less than 50 ppm helps to greatly improve the final dehydration effect.

[0114] 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.

[0115] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this 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 modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for removing water from a lithium battery cell, characterized in that, The dehydration method employs a vacuum drying oven, which has a drying chamber equipped with a dehydration mechanism. The dehydration method includes the following steps: Step 1: Place the battery cell in the drying chamber and preheat the battery cell until it reaches the preheating temperature; Step 2: Perform a first vacuum treatment on the drying chamber to reduce the air pressure inside the drying chamber to a first air pressure. Step 3: Fill the drying chamber with drying gas to raise the gas pressure inside the drying chamber to the second pressure. Step 4: Use the dehydration mechanism to remove moisture from the mixture in the drying gas; Step 5: Perform a second vacuuming process on the drying chamber to reduce the air pressure inside the drying chamber to a third air pressure, and collect the dried gas after water removal treatment. Step 6: Fill the drying chamber with the dehydrated gas to raise the pressure in the drying chamber to a fourth pressure. Step 7: Repeat steps 4 through 6.

2. The method for removing water from a lithium battery cell according to claim 1, characterized in that, The preheating temperature is 85℃~105℃.

3. The method for removing water from a lithium battery cell according to claim 1, characterized in that, The first pressure and the third pressure are each independently ≤100Pa.

4. The method for removing water from a lithium battery cell according to claim 1, characterized in that, The second pressure and the fourth pressure are each independently between 0.4 kPa and 30 kPa.

5. The method for removing water from a lithium battery cell according to claim 1, characterized in that, In step 3, the dew point of the dry gas introduced is -60℃ to -30℃.

6. The method for removing water from a lithium battery cell according to claim 1, characterized in that, In step 4, after dehydration treatment, the moisture content mixed in the dry gas is controlled to not exceed 50 ppm.

7. The method for removing water from a lithium battery cell according to any one of claims 1 to 6, characterized in that, In step 7, the loop is repeated 5 to 30 times.

8. The method for removing water from a lithium battery cell according to any one of claims 1 to 6, characterized in that, The drying gas is selected from at least one of nitrogen or dry air.

9. A lithium battery cell, characterized in that, The battery cell is obtained by the water removal method described in any one of claims 1 to 8.

10. A lithium battery, characterized in that, Including the lithium battery cell as described in claim 9.

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