Lithium-ion battery drying method and lithium battery

Abstract

This application discloses a method for drying lithium-ion batteries and a lithium battery pack, which includes the following steps: Step 1: Place the cells to be dried in an oven; Step 2: Perform the following drying steps multiple times; Adjust the temperature and vacuum level in the oven, and when performing the next drying step, readjust the temperature and vacuum level in the oven so that the temperature is gradually decreased and the vacuum level is gradually increased compared to the previous drying step; Step 3: Test the cells to be dried for moisture.

Description

[Technical Field]

[0001] This application claims priority from a Chinese patent application bearing application number 202310163857.4, filed with the China Patent Office on February 24, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the technical field of battery manufacturing, and in particular to a method for drying a lithium ion battery and a lithium battery. [Background technology]

[0003] The moisture content has a significant impact on battery performance, including initial discharge capacity, SEI film quality, internal resistance, and cycle life, so it is necessary to strictly control the moisture content during the lithium battery manufacturing process.

[0004] Two baking processes are used in the manufacturing of lithium batteries. One is baking after coating is complete. This typically involves airflow baking, which bakes out the NMP (N-methylpyrrolidone) in the slurry, converting the slurry from a wet film to a dry film that adheres to the current collector. This post-coating baking reduces the wet weight and residual NMP. The other is baking after assembly, typically involving contact or airflow baking under vacuum conditions. This further reduces the moisture content of the assembled cell pole pieces and separators, meeting moisture content requirements. These baking processes have problems with long baking times, low efficiency, and high equipment costs. Summary of the Invention [Problem to be solved by the invention]

[0005] The present application provides a method for drying lithium ion batteries and lithium batteries that can overcome the technical problems of conventional drying techniques, such as long baking times, low efficiency, and high equipment investment costs. [Means for solving the problem]

[0006] In a first aspect, the present application provides a method for drying a lithium-ion battery, the method comprising the steps of:

[0007] Step 1: Place the cell to be dried in the oven.

[0008] Step 2: Adjust the temperature and vacuum level in the oven, and vacuum-dry the cell to be dried in the oven at a predetermined temperature and vacuum level for a preset time. Then, perform a drying step of breaking the vacuum in the oven multiple times. When the drying step is performed next time, readjust the temperature and vacuum level in the oven, and gradually decrease the temperature in the oven and gradually increase the vacuum level in the oven compared to the previous execution of the drying step.

[0009] Step 3: A moisture test is performed on the cell to be dried. If the test result is pass, the drying is terminated. If the test result is fail, Step 2 is repeated.

[0010] In a second aspect, the present application further provides a lithium battery, the lithium battery cell of which is manufactured using the method for drying a lithium ion battery described above. [Effects of the Invention]

[0011] The beneficial effect of the present invention is that the drying step is repeated multiple times in the order of adjusting the temperature and vacuum, drying for a predetermined time, and breaking the vacuum. Each time the drying step is performed, the temperature and vacuum are readjusted, and compared to the previous drying step, the temperature is gradually lowered and the vacuum is gradually increased. This shortens the overall baking time, increases the baking efficiency, and reduces the required energy consumption. After performing the drying step multiple times, the cell moisture baking consistency is good and the failure rate of moisture after baking is low. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present application provides a method for drying a lithium-ion battery, the method comprising the steps of:

[0013] Step 1: Place the cell to be dried in the oven.

[0014] Step 2: Perform the following drying steps multiple times:

[0015] (1) Adjust the temperature and vacuum level inside the oven.

[0016] (2) The cell to be dried is vacuum-dried in an oven at a predetermined temperature and vacuum level for a predetermined time.

[0017] (3) Break the vacuum on the oven.

[0018] When the drying steps (1) to (3) are performed next time, the temperature and vacuum level in the oven are readjusted, and the temperature in the oven is gradually decreased and the vacuum level in the oven is gradually increased compared to the previous execution of the drying steps (1) to (3).

[0019] Step 3: A moisture test is performed on the cell to be dried. If the test result is pass, the drying is terminated. If the test result is fail, Step 2 is repeated.

[0020] In some embodiments, the drying step is performed three times in step 2. When the drying step is performed the first time, the temperature in the oven is adjusted to T1, the vacuum level to P1, and the time for which the cell to be dried is vacuum-dried in the oven to h1. When the drying step is performed the second time, the temperature in the oven is adjusted to T2, the vacuum level to P2, and the time for which the cell to be dried is vacuum-dried in the oven to h2. When the drying step is performed the third time, the temperature in the oven is adjusted to T3, the time for which the cell to be dried is vacuum-dried in the oven to h3, and the vacuum level to P3. Here, T1>T2>T3, P1 <P2<P3である。

[0021] The temperature in the oven is adjusted to T2, the degree of vacuum to P2, and after the vacuum is broken, the temperature in the oven is adjusted to T3 again, and the degree of vacuum to P3. Here, T1>T2>T3, P1 <P2<P3である。

[0022] Here, 80°C≦T1≦120°C, 60°C≦T2≦100°C, 40°C≦T3≦80°C; 10 Pa≦P1≦100 Pa, 100 Pa≦P2≦300 Pa, 200 Pa≦P3≦500 Pa; 60 min≦h1≦200 min, 10 min≦h2≦300 min, 200 min≦h3≦500 min.

[0023] In some embodiments, the oven is preheated before step 2. The oven preheat temperature is T1, and 80°C < T1 < 120°C.

[0024] In some embodiments, the oven preheat time is h4, where 40 min≦h4≦100 min.

[0025] In some embodiments, in step 2 above, the vacuum is broken by filling the oven with an inert gas to displace the baked-out moisture.

[0026] In some embodiments, the inert gas may be at least one of helium gas, neon gas, argon gas, krypton gas, xenon gas, and nitrogen gas.

[0027] In some embodiments, the nitrogen gas has a purity of ≧99.9%.

[0028] The present application further provides a lithium battery, the lithium battery cell of which is manufactured using the above-mentioned method for drying a lithium ion battery. Example 1

[0029] The present application provides a method for drying a lithium-ion battery, the method comprising the steps of:

[0030] Step 1: Place the cell to be dried in the oven.

[0031] Step 2: Perform the drying step three times.

[0032] When the drying step is performed for the first time, the temperature in the oven is adjusted to T1, the degree of vacuum to P1, and the time for vacuum drying the cell to be dried to h1, where T1 is 120°C, P1 is 10 Pa, and h1 is 200 min, and then the vacuum is broken.

[0033] When the drying step is performed for the second time, the temperature in the oven is adjusted to T2, the vacuum level to P2, and the time for vacuum drying the cell to be dried to h2, where T2 is 100°C, P2 is 100 Pa, and h2 is 300 min, and then the vacuum is broken.

[0034] When the drying step is performed for the third time, the temperature in the oven is adjusted to T3, the vacuum level to P3, and the time for vacuum drying the cell to be dried to h3, where T3 is 80°C, P3 is 200 Pa, and h3 is 500 min, and then the vacuum is broken.

[0035] Step 3: A moisture test is performed on the cell to be dried. If the test result is pass, the drying is terminated. If the test result is fail, Step 2 is repeated. Example 2

[0036] The difference from Example 1 is that In step 2, when the drying step is performed for the first time, the temperature in the oven is adjusted to T1, the vacuum level is adjusted to P1, and the time for vacuum-drying the cell to be dried is adjusted to h1, where T1 is 110°C, P1 is 10 Pa, and h1 is 200 min. In step 2, when the drying step is performed for the second time, the temperature in the oven is adjusted to T2, the vacuum degree is adjusted to P2, and the time for vacuum drying the cell to be dried is adjusted to h2, where T2 is 90°C, P2 is 100 Pa, and h2 is 300 min; In step 2, when the drying step is performed for the third time, the temperature in the oven is adjusted to T3, the vacuum degree to P3, and the time for vacuum drying the cell to be dried to h3, where T3 is 70°C, P3 is 200 Pa, and h3 is 500 min. Example 3

[0037] The difference from Example 1 is that In step 2, when the drying step is performed for the first time, the temperature in the oven is adjusted to T1, the vacuum degree is adjusted to P1, and the time for vacuum-drying the cell to be dried is adjusted to h1, where T1 is 100°C, P1 is 10 Pa, and h1 is 200 min. In step 2, when the drying step is performed for the second time, the temperature in the oven is adjusted to T2, the vacuum degree is adjusted to P2, and the time for vacuum drying the cell to be dried is adjusted to h2, where T2 is 80°C, P2 is 100 Pa, and h2 is 300 min; In step 2, when the drying step is performed for the third time, the temperature in the oven is adjusted to T3, the vacuum level to P3, and the time for vacuum drying the cell to be dried to h3, where T3 is 60°C, P3 is 200 Pa, and h3 is 500 min. Example 4

[0038] The difference from Example 1 is that In step 2, when the drying step is performed for the first time, the temperature in the oven is adjusted to T1, the vacuum level to P1, and the time for vacuum-drying the cell to be dried to h1, where T1 is 90°C, P1 is 10 Pa, and h1 is 200 min; In step 2, when the drying step is performed for the second time, the temperature in the oven is adjusted to T2, the vacuum degree is adjusted to P2, and the time for vacuum drying the cell to be dried is adjusted to h2, where T2 is 70°C, P2 is 100 Pa, and h2 is 300 min; In step 2, when the drying step is performed for the third time, the temperature in the oven is adjusted to T3, the vacuum level to P3, and the time for vacuum drying the cell to be dried to h3, where T3 is 50°C, P3 is 200 Pa, and h3 is 500 min. Example 5

[0039] The difference from Example 1 is that In step 2, when the drying step is performed for the first time, the temperature in the oven is adjusted to T1, the vacuum level is adjusted to P1, and the time for vacuum-drying the cell to be dried is adjusted to h1, where T1 is 80°C, P1 is 10 Pa, and h1 is 200 min; In step 2, when the drying step is performed for the second time, the temperature in the oven is adjusted to T2, the vacuum degree is adjusted to P2, and the time for vacuum drying the cell to be dried is adjusted to h2, where T2 is 60°C, P2 is 100 Pa, and h2 is 300 min; In step 2, when the drying step is performed for the third time, the temperature in the oven is adjusted to T3, the vacuum degree to P3, and the time for vacuum drying the cell to be dried to h3, where T3 is 40°C, P3 is 200 Pa, and h3 is 500 min. Example 6

[0040] The difference from Example 1 is that In step 2, when the drying step is performed for the first time, the temperature in the oven is adjusted to T1, the vacuum degree to P1, and the time for vacuum-drying the cell to be dried to h1, where T1 is 120°C, P1 is 50 Pa, and h1 is 100 min; In step 2, when the drying step is performed for the second time, the temperature in the oven is adjusted to T2, the vacuum degree is adjusted to P2, and the time for vacuum drying the cell to be dried is adjusted to h2, where T2 is 100°C, P2 is 150 Pa, and h2 is 200 min; In step 2, when the drying step is performed for the third time, the temperature in the oven is adjusted to T3, the vacuum level to P3, and the time for vacuum drying the cell to be dried to h3, where T3 is 80°C, P3 is 250 Pa, and h3 is 300 min. Example 7

[0041] The difference from Example 1 is that In step 2, when the drying step is performed for the first time, the temperature in the oven is adjusted to T1, the vacuum level to P1, and the time for vacuum-drying the cell to be dried to h1, where T1 is 110°C, P1 is 50 Pa, and h1 is 100 min; In step 2, when the drying step is performed for the second time, the temperature in the oven is adjusted to T2, the vacuum degree is adjusted to P2, and the time for vacuum drying the cell to be dried is adjusted to h2, where T2 is 90°C, P2 is 150 Pa, and h2 is 200 min; In step 2, when the drying step is performed for the third time, the temperature in the oven is adjusted to T3, the vacuum level to P3, and the time for vacuum drying the cell to be dried to h3, where T3 is 70°C, P3 is 250 Pa, and h3 is 300 min. Example 8

[0042] The difference from Example 1 is that In step 2, when the drying step is performed for the first time, the temperature in the oven is adjusted to T1, the vacuum degree to P1, and the time for vacuum-drying the cell to be dried to h1, where T1 is 100°C, P1 is 50 Pa, and h1 is 100 min; In step 2, when the drying step is performed for the second time, the temperature in the oven is adjusted to T2, the vacuum degree is adjusted to P2, and the time for vacuum drying the cell to be dried is adjusted to h2, where T2 is 80°C, P2 is 150 Pa, and h2 is 200 min; In step 2, when the drying step is performed for the third time, the temperature in the oven is adjusted to T3, the vacuum degree to P3, and the time for vacuum drying the cell to be dried to h3, where T3 is 60°C, P3 is 250 Pa, and h3 is 300 min. Example 9

[0043] The difference from Example 1 is that In step 2, when the drying step is performed for the first time, the temperature in the oven is adjusted to T1, the vacuum degree is adjusted to P1, and the time for vacuum-drying the cell to be dried is adjusted to h1, where T1 is 90°C, P1 is 50 Pa, and h1 is 100 min; In step 2, when the drying step is performed for the second time, the temperature in the oven is adjusted to T2, the vacuum degree is adjusted to P2, and the time for vacuum drying the cell to be dried is adjusted to h2, where T2 is 70°C, P2 is 150 Pa, and h2 is 200 min; In step 2, when the drying step is performed for the third time, the temperature in the oven is adjusted to T3, the vacuum degree to P3, and the time for vacuum drying the cell to be dried to h3, where T3 is 50°C, P3 is 250 Pa, and h3 is 300 min. Example 10

[0044] The difference from Example 1 is that In step 2, when the drying step is performed for the first time, the temperature in the oven is adjusted to T1, the vacuum degree is adjusted to P1, and the time for vacuum-drying the cell to be dried is adjusted to h1, where T1 is 80°C, P1 is 50 Pa, and h1 is 100 min; In step 2, when the drying step is performed for the second time, the temperature in the oven is adjusted to T2, the vacuum degree is adjusted to P2, and the time for vacuum drying the cell to be dried is adjusted to h2, where T2 is 60°C, P2 is 150 Pa, and h2 is 200 min; In step 2, when the drying step is performed for the third time, the temperature in the oven is adjusted to T3, the vacuum level to P3, and the time for vacuum drying the cell to be dried to h3, where T3 is 40°C, P3 is 250 Pa, and h3 is 300 min. Example 11

[0045] The difference from Example 1 is that In step 2, when the drying step is performed for the first time, the temperature in the oven is adjusted to T1, the vacuum level is adjusted to P1, and the time for vacuum-drying the cell to be dried is adjusted to h1, where T1 is 120°C, P1 is 100 Pa, and h1 is 60 min; In step 2, when the drying step is performed for the second time, the temperature in the oven is adjusted to T2, the vacuum degree is adjusted to P2, and the time for vacuum drying the cell to be dried is adjusted to h2, where T2 is 100°C, P2 is 300 Pa, and h2 is 10 min; In step 2, when the drying step is performed for the third time, the temperature in the oven is adjusted to T3, the vacuum degree to P3, and the time for vacuum drying the cell to be dried to h3, where T3 is 80°C, P3 is 500 Pa, and h3 is 200 min. Example 12

[0046] The difference from Example 1 is that In step 2, when the drying step is performed for the first time, the temperature in the oven is adjusted to T1, the vacuum degree to P1, and the time for vacuum-drying the cell to be dried to h1, where T1 is 110°C, P1 is 100 Pa, and h1 is 60 min; In step 2, when the drying step is performed for the second time, the temperature in the oven is adjusted to T2, the vacuum degree is adjusted to P2, and the time for vacuum drying the cell to be dried is adjusted to h2, where T2 is 90°C, P2 is 300 Pa, and h2 is 10 min; In step 2, when the drying step is performed for the third time, the temperature in the oven is adjusted to T3, the vacuum level to P3, and the time for vacuum drying the cell to be dried to h3, where T3 is 70°C, P3 is 500 Pa, and h3 is 200 min. Example 13

[0047] The difference from Example 1 is that In step 2, when the drying step is performed for the first time, the temperature in the oven is adjusted to T1, the vacuum degree is adjusted to P1, and the time for vacuum-drying the cell to be dried is adjusted to h1, where T1 is 100°C, P1 is 100 Pa, and h1 is 60 min; In step 2, when the drying step is performed for the second time, the temperature in the oven is adjusted to T2, the vacuum degree is adjusted to P2, and the time for vacuum drying the cell to be dried is adjusted to h2, where T2 is 80°C, P2 is 300 Pa, and h2 is 100 min; In step 2, when the drying step is performed for the third time, the temperature in the oven is adjusted to T3, the vacuum degree to P3, and the time for vacuum drying the cell to be dried to h3, where T3 is 60°C, P3 is 500 Pa, and h3 is 200 min. Example 14

[0048] The difference from Example 1 is that In step 2, when the drying step is performed for the first time, the temperature in the oven is adjusted to T1, the vacuum degree is adjusted to P1, and the time for vacuum-drying the cell to be dried is adjusted to h1, where T1 is 90°C, P1 is 100 Pa, and h1 is 60 min; In step 2, when the drying step is performed for the second time, the temperature in the oven is adjusted to T2, the vacuum degree is adjusted to P2, and the time for vacuum drying the cell to be dried is adjusted to h2, where T2 is 70°C, P2 is 300 Pa, and h2 is 10 min; In step 2, when the drying step is performed for the third time, the temperature in the oven is adjusted to T3, the vacuum degree to P3, and the time for vacuum drying the cell to be dried to h3, where T3 is 50°C, P3 is 500 Pa, and h3 is 200 min. Example 15

[0049] The difference from Example 1 is that In step 2, when the drying step is performed for the first time, the temperature in the oven is adjusted to T1, the vacuum level is adjusted to P1, and the time for vacuum-drying the cell to be dried is adjusted to h1, where T1 is 80°C, P1 is 100 Pa, and h1 is 60 min; In step 2, when the drying step is performed for the second time, the temperature in the oven is adjusted to T2, the vacuum degree is adjusted to P2, and the time for vacuum drying the cell to be dried is adjusted to h2, where T2 is 60°C, P2 is 300 Pa, and h2 is 10 min; In step 2, when the drying step is performed for the third time, the temperature in the oven is adjusted to T3, the vacuum degree to P3, and the time for vacuum drying the cell to be dried to h3, where T3 is 40°C, P3 is 500 Pa, and h3 is 200 min. Comparative Example 1

[0050] The cell to be dried is placed in an oven, and the temperature and vacuum level are constant in the oven, where the temperature is 95° C. and the vacuum level is 10 Pa. Comparative Example 2

[0051] The cell to be dried is placed in an oven, and the temperature and vacuum level are constant in the oven, where the temperature is 95°C and the vacuum level is 50Pa. Comparative Example 3

[0052] The cell to be dried is placed in an oven, and the temperature and vacuum level are constant in the oven, where the temperature is 95°C and the vacuum level is 100Pa. Conclusions and Analysis

[0053] The effects of each example and comparative example on the drying effect are shown in Table 1. [Table 1]

[0054] As can be seen from Table 1, in the examples of the present application, the temperature and vacuum level are readjusted each time the drying step is performed. Compared with the previous drying step, the temperature is gradually decreased, the vacuum level is gradually increased, the overall baking time is shorter, the baking efficiency is higher, the required energy consumption is lower, and the moisture content after baking is lower, all of which meet the standard requirements and have a high pass rate.

[0055] In the above embodiments, the description of each embodiment is focused on its own, and for parts that are not described in detail in one embodiment, reference may be made to the relevant descriptions of other embodiments.

[0056] In the description of this application, the terms "first" and "second" are for descriptive purposes only and should not be understood as indicating or implying the relative importance or the number of the indicated technical features, whereby a feature qualified as "first" or "second" may explicitly or implicitly include one or more features.

Claims

1. A method for drying a lithium ion battery, comprising: Step 1: Place the cell to be dried in the oven; a step 2 in which a drying step is performed multiple times, in which the temperature and degree of vacuum in the oven are adjusted, the cells to be dried are vacuum-dried in the oven at a predetermined temperature and degree of vacuum for a preset time, and then the vacuum in the oven is broken, and when the drying step is performed next time, the temperature and degree of vacuum in the oven are readjusted, and the temperature in the oven is gradually lowered and the degree of vacuum in the oven is gradually increased compared to the previous execution of the drying step; a step 3 of conducting a moisture test on the cell to be dried, terminating the drying if the test result is a pass, and repeating step 2 if the test result is a fail.

2. In step 2, the drying step is performed three times, and when the drying step is performed for the first time, the temperature in the oven is adjusted to T1 and the vacuum degree is adjusted to P1; when the drying step is performed for the second time, the temperature in the oven is adjusted to T2 and the vacuum degree is adjusted to P2; and when the drying step is performed for the third time, the temperature in the oven is adjusted to T3 and the vacuum degree is adjusted to P3, where T1>T2>T3 and P1<P2<P3; Here, 80°C ≦ T1 ≦ 120°C, 60°C ≦ T2 ≦ 100°C, and 40°C ≦ T3 ≦ 80°C, 2. The method for drying a lithium ion battery according to claim 1, wherein the pressures are 10 Pa≦P1≦100 Pa, 100 Pa≦P2≦300 Pa, and 200 Pa≦P3≦500 Pa.

3. 3. The method for drying a lithium ion battery according to claim 2, wherein the length of the predetermined time for vacuum-drying the cell to be dried in the oven varies each time the drying step is performed.

4. When the drying step is performed for the first time, the predetermined length of time for vacuum-drying the drying target cell is h1, when the drying step is performed for the second time, the predetermined length of time for vacuum-drying the drying target cell is h2, and when the drying step is performed for the third time, the predetermined length of time for vacuum-drying the drying target cell is h3, 4. The method for drying a lithium ion battery according to claim 3, wherein 60 min≦h1≦200 min, 10 min≦h2≦300 min, and 200 min≦h3≦500 min.

5. 2. The method for drying a lithium ion battery according to claim 1, wherein the oven is preheated before step 2.

6. 6. The method for drying lithium ion batteries according to claim 5, wherein the preheating time of the oven is h4, where 40 min≦h4≦100 min.

7. 2. The method for drying a lithium ion battery according to claim 1, wherein in step 2, the vacuum is broken by filling the oven with an inert gas.

8. 8. The method for drying a lithium ion battery according to claim 7, wherein the inert gas is at least one of helium gas, neon gas, argon gas, krypton gas, xenon gas, and nitrogen gas.

9. 9. The method for drying a lithium ion battery according to claim 8, wherein the purity of the nitrogen gas is 99.9% or more.

10. 2. The method for drying a lithium ion battery according to claim 1, wherein in step 2, the drying step is performed 3 to 6 times.

11. A lithium battery, characterized in that the lithium battery is manufactured using the method for drying a lithium ion battery according to any one of claims 1 to 10.

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