Lithium battery drying process

Abstract

The present application relates to the manufacturing field of secondary battery, especially to the drying process of lithium battery. The drying process of the present application can reduce the time of breaking vacuum and the time of next vacuum pumping when performing the breathing action, and can avoid the damage of the temperature environment in the drying box caused by the breaking vacuum gas, so that the battery needs to be heated for a long time, thus the time required for a single breathing is reduced, more breathing actions can be performed in a limited time, and the high-frequency breathing action can strengthen the size of the gap between the battery pole piece and the diaphragm, which is helpful to the more efficient evaporation of water in the battery. Therefore, the cooperation of different steps in the drying method of the present application can efficiently dry the battery, which not only helps to reduce the drying time and improve the drying efficiency, but also can reduce the water content in the battery after drying.

Description

Technical Field

[0001] This invention relates to the field of secondary battery manufacturing, and more particularly to lithium battery drying processes. Background Technology

[0002] Battery drying is a critical process in battery manufacturing, and current technologies primarily employ vacuum drying. Existing vacuum drying processes typically involve placing the lithium battery in a vacuum drying chamber, heating it to a certain temperature, and then evacuating it; the vacuum is then broken back to atmospheric pressure, followed by another vacuuming process; this cycle is repeated to dry the battery. However, this vacuum drying process requires a long drying time, has low drying efficiency, and the battery still retains a high moisture content after drying, indicating incomplete drying. Furthermore, with advancements in battery material systems, the evaporation of moisture contained within the materials has become increasingly difficult. Summary of the Invention

[0003] The purpose of this invention is to provide a lithium battery drying process to solve the problems of low drying efficiency and poor drying effect in existing lithium battery drying processes.

[0004] The lithium battery drying process of the present invention includes the following steps:

[0005] Heat the battery placed in the drying chamber to the initial drying temperature;

[0006] Evacuate the drying oven to 30-100 Pa and maintain the pressure for the set time. Then, break the vacuum in the drying oven to 10-50 KPa using hot drying gas and maintain the vacuum for a certain time to complete one breath.

[0007] The vacuum cycle is repeated to complete the set number of breaths.

[0008] This invention provides a novel lithium battery drying process. After heating the battery in the drying chamber to the initial drying temperature, the moisture inside the battery will evaporate to the outside of the battery and enter the gas in the drying chamber at the initial drying temperature. Then, through the breathing action, the size of the gap between the battery electrode and the separator can be rhythmically adjusted, which makes it easier for the moisture in the center of the electrode to evaporate. At the same time, it can replace the gas in the drying chamber and the battery to extract the moisture.

[0009] During the breathing action, the vacuum is broken to 10Kpa-50Kpa, which is much lower than atmospheric pressure. This reduces the vacuum breaking time and the time required for the next vacuuming. Furthermore, using hot drying gas for vacuum breaking avoids disrupting the temperature environment inside the drying chamber, which would otherwise require a longer time to reheat the cells. This also shortens the vacuum breaking time. Overall, this reduces the time required for a single breathing action, allowing for more breathing actions within a limited time. The high-frequency breathing action also enhances the rhythmic movement of the gaps between the battery electrodes and the separator, which helps the moisture in the battery evaporate more efficiently. Therefore, the coordination of different steps in the drying method of this invention can efficiently dry the battery, not only helping to reduce drying time and improve drying efficiency, but also reducing the moisture content in the cells after drying. Attached Figure Description

[0010] Figure 1 This is a process flow diagram of one embodiment of the lithium battery drying process of the present invention;

[0011] Figure 2 This is a dry respiration curve;

[0012] Figure 3 for Figure 2 Enlarged view of point A in the middle. Detailed Implementation

[0013] The existing vacuum drying process used in battery drying generally involves placing the lithium battery in a vacuum drying chamber, heating it to a certain temperature to accelerate the evaporation of moisture inside the battery, and then performing a vacuuming process to remove the water-containing gas. Next, the vacuum chamber is broken down to atmospheric pressure, allowing external gas to enter the chamber, and the battery is heated again to a certain temperature to promote further evaporation of moisture. This process is repeated, allowing the vacuum drying chamber to "breathe" multiple times, thus achieving the desired battery drying.

[0014] However, this vacuum drying process involves restoring the vacuum drying chamber to atmospheric pressure before evacuating, which takes a considerable amount of time. Furthermore, the vacuum is often broken using ambient temperature workshop drying gas, which is cold and disrupts the temperature environment inside the vacuum drying chamber. This necessitates a further temperature recovery process for the batteries within the chamber, requiring a lengthy heating time. Therefore, the current drying technology requires a long drying time and has low drying efficiency. Even after a certain drying time, the batteries still retain a high moisture content, indicating incomplete drying.

[0015] To address the problems existing in the prior art, this invention dries the battery through a "high-frequency" and "shallow breathing" method. The "shallow breathing" shortens the time required for a single breath, thereby increasing the breathing frequency and achieving "high-frequency" breathing. High-frequency breathing can enhance the rhythmic movement of the gap between the battery electrodes and the separator, which helps the moisture in the battery to evaporate more efficiently, thus improving the drying effect and efficiency of the battery.

[0016] Specifically, one embodiment of the lithium battery drying process of the present invention is as follows:

[0017] The lithium battery drying process of the present invention includes the following steps, such as: Figure 1 ;

[0018] The lithium batteries to be dried are placed in a vacuum drying oven, and then heated for 60 minutes to the initial drying temperature, preferably between 100℃ and 110℃. During this heating process, the moisture in the batteries can continuously diffuse and evaporate into the vacuum drying oven.

[0019] The vacuum drying oven is evacuated. The evacuation time varies depending on the size of the oven's cavity, but typically does not exceed 30 minutes. The vacuum pressure is evacuated to 30-100 Pa. In different embodiments, the vacuum pressure varies, for example, 30 Pa, 40 Pa, 50 Pa, 60 Pa, 80 Pa, or 100 Pa. Vacuuming helps to remove moisture that diffuses from the battery during the heating process. Then, a vacuum holding time is set, generally between 10 and 25 minutes. During the holding time, moisture-containing gases inside the battery are continuously expelled and removed, accelerating the removal of moisture. During the vacuuming process, the lithium batteries inside the vacuum drying oven are maintained at 105°C.

[0020] This process can be understood as the vacuum drying oven exhaling once.

[0021] The vacuum drying oven is ruptured, meaning the vacuum state of the oven is released and hot, dry gas is introduced. The rupture stops when the pressure inside the oven reaches the set rupture pressure. The rupture time varies depending on the size of the oven's internal cavity, but typically does not exceed 10 minutes. The rupture cutoff pressure ranges from 10 kPa to 50 kPa. In different embodiments, the specific rupture pressure can be 10 kPa, 20 kPa, 30 kPa, 40 kPa, or 50 kPa. Furthermore, the battery temperature must be maintained below 100°C to 110°C during rupture.

[0022] When breaking the vacuum, the temperature of the hot drying gas introduced into the vacuum drying chamber is preferably between 70°C and 100°C. In different embodiments, it can be 70°C, 80°C, 90°C, or 100°C, preferably 100°C. This temperature is closer to the initial drying temperature of the lithium battery, which will not disrupt the temperature environment inside the vacuum drying chamber. Moreover, even if further heating is required after introducing the hot drying gas, the required heating temperature rise is lower and the heating time is shorter.

[0023] This process can be understood as the vacuum drying oven undergoing one air intake.

[0024] Cycle inhalation and exhalation, allowing the vacuum drying chamber to complete multiple breaths. Specifically, a breath count of 15-30 breaths is preferred. Of course, in different embodiments, the breath count can be set as needed, such as 15, 20, 25, or 30 breaths.

[0025] Based on the above description of the breathing process, combined with Figure 2-3 As shown in the drying breathing curve (taking breaking the vacuum to 10 kPa and then evacuating to 100 kPa as an example), since the vacuum state in the vacuum drying chamber is not completely released to atmospheric pressure when breaking the vacuum, but is in the range of 10 kPa-50 kPa, the vacuum is not started from atmospheric pressure when evacuating again. That is, the breathing pressure range of the present invention is between 30-100 Pa and 10 kPa-50 kPa, which is shallow breathing. The time required for one breathing is short. The pressure holding time for each vacuum evacuation is set according to the number of breathings. The overall completion of one breathing usually takes about 1 hour. Moreover, the lithium battery in the vacuum drying chamber is generally maintained at about 105°C during the breathing process, that is, a relatively stable drying temperature can be maintained throughout the breathing process, achieving constant temperature breathing, which is conducive to the continuous output of moisture in the battery.

[0026] Breathing displaces the gas inside the vacuum drying chamber and the battery, thereby extracting moisture from both. This frequent, shallow breathing also creates a rhythmic movement between the battery electrodes and the separator, facilitating the rapid removal of moisture from the center of the electrodes. During these repeated shallow breaths, as... Figure 3 The vacuum level changes shown indicate that the moisture inside the battery is continuously released. After 15-30 cycles of drying, a good drying effect is finally achieved, resulting in a low water content inside the dried battery.

[0027] When breaking the vacuum, the preferred hot drying gas is hot air with a low dew point, which can reduce the micropore temperature difference contraction effect of the internal battery materials and facilitate the evaporation of internal moisture.

[0028] After the last breath is completed, that is, after the last inhalation is finished, break the vacuum to normal pressure. After cooling down, open the door of the vacuum drying oven, take out the dried battery from the vacuum drying oven, and the drying of the battery is completed.

[0029] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A lithium battery drying process, characterized by: Includes the following steps: Heat the battery placed in the drying chamber to the initial drying temperature, which is 100℃-110℃. Then, the drying chamber is evacuated to 30-100 Pa and held for a set time. After that, the vacuum in the drying chamber is broken to 10 kPa-50 kPa by hot drying gas at a temperature of 70°C-100°C to ensure that the battery temperature is 100°C-110°C when the vacuum is broken and to maintain a certain vacuum breaking time, thus completing one breath. The vacuuming and vacuum breaking processes are repeated cyclically to complete the set number of breaths.

2. The lithium battery drying process according to claim 1, characterized in that, The set breathing rate is 15-30 breaths.

3. The lithium battery drying process according to claim 1, characterized in that, During the breathing process, the pressure holding time after vacuuming is 10-25 minutes.

4. The lithium battery drying process according to claim 3, characterized in that, During the breathing process, the vacuuming time shall not exceed 30 minutes.

5. The lithium battery drying process according to claim 1, characterized in that, During the breathing process, the drying chamber is evacuated to 30-50 Pa.

6. The lithium battery drying process according to any one of claims 1-5, characterized in that, During the breathing process, the vacuum is broken down to 10 kPa.

7. The lithium battery drying process according to any one of claims 1-5, characterized in that, During the breathing process, the time for breaking the vacuum does not exceed 10 minutes.

8. The lithium battery drying process according to any one of claims 1-5, characterized in that, The initial drying temperature is 100℃-110℃, and the heating time is 30min-60min.

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