Lithium battery drying process

Abstract

The invention relates to the field of manufacturing of secondary batteries, in particular to a lithium battery drying process. According to the drying process, when the breathing action is carried out, the vacuum breaking degree is far smaller than the atmospheric pressure, the vacuum breaking time and the next breathing vacuumizing time can be shortened, vacuum breaking is carried out through hot drying gas, the temperature environment in the drying box can be prevented from being damaged by vacuum breaking gas, and the drying efficiency is improved. As a result, the battery cell in the drying box needs to be reheated for a long time, so that the time required by single breathing is shortened on the whole, more times of breathing actions can be carried out in limited time, and the size rhythm of the gap between the battery pole piece and the diaphragm is enhanced by the high-frequency breathing actions; according to the drying method disclosed by the invention, water in the battery can be more efficiently evaporated, so that the battery can be efficiently dried through mutual cooperation of different steps in the drying method disclosed by the invention, the drying time can be shortened, the drying efficiency can be improved, and the water content in a battery cell after drying can be reduced.

Description

Technical Field

[0001] The present invention relates to the field of manufacturing secondary batteries, and in particular to a drying process for lithium batteries. Background Art

[0002] Battery drying is a critical process in battery manufacturing. Existing technologies often utilize vacuum drying to dry batteries. This process typically involves placing lithium batteries in a vacuum drying oven, heating them to a certain temperature, and evacuating them. The vacuum is then broken to atmospheric pressure, and the process is then evacuated again, continuing this cycle to dry the batteries. However, this vacuum drying process requires a long drying time and has low drying efficiency. Furthermore, even after drying, the battery still contains a high moisture content, indicating incomplete drying. Furthermore, with the advancement of battery material systems, evaporating the moisture trapped within the materials becomes increasingly difficult. Summary of the Invention

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

[0004] The lithium battery drying process of the present invention comprises the following steps: Heat the battery in the drying oven to the initial drying temperature; The drying box is evacuated to 30-100 Pa and maintained for a set pressure holding time. The drying box is broken into 10K Pa-50K Pa by hot dry gas and maintained for a certain vacuum breaking time, completing one breath. The vacuum is pumped in and out in cycles to complete the set number of breaths.

[0005] The present invention provides a new lithium battery drying process. After the battery in the drying box is heated to the initial drying temperature, the moisture in the battery will evaporate to the outside of the battery at the initial drying temperature and enter the gas in the drying box. Then, through the breathing action, the size of the gap between the battery electrode and the diaphragm can be rhythmically adjusted, which makes it easier to evaporate the moisture in the center of the electrode. At the same time, it can replace the gas in the drying box and the battery to extract the moisture.

[0006] When performing the breathing action, the vacuum is broken to 10Kpa-50Kpa, which is much lower than the atmospheric pressure. This can shorten the vacuum breaking time and the time for the next breath vacuuming. The use of hot dry gas to break the vacuum can avoid the vacuum breaking gas from destroying the temperature environment in the drying box, resulting in a long time to reheat the battery cells in the drying box, which can also shorten the vacuum breaking time. In this way, the time required for a single breath is reduced as a whole, and more breathing actions can be performed within a limited time. The high-frequency breathing action strengthens the size rhythm of the gap between the battery pole piece and the diaphragm, which helps to evaporate the moisture in the battery more efficiently. Therefore, the mutual cooperation of different steps in the drying method of the present invention can efficiently dry the battery, which not only helps to reduce the drying time and improve the drying efficiency, but also can reduce the moisture content in the battery cell after drying. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is a process flow chart of an embodiment of the lithium battery drying process of the present invention; Figure 2 is the dry respiration curve; Figure 3 for Figure 2 Enlarged view of point A in the middle. DETAILED DESCRIPTION

[0008] The vacuum drying process used in the battery drying process in the prior art generally places the lithium battery in a vacuum drying oven, heats it to a certain temperature to evaporate the water in the battery faster, and then performs a vacuum treatment to extract the water-containing gas; then the vacuum drying oven is broken to atmospheric pressure to allow external air to enter the vacuum drying oven, and the battery in the drying oven is heated to a certain temperature again to promote the evaporation of the water in the battery, and then the vacuum operation is performed again; this cycle realizes multiple breathing of the vacuum drying oven, thereby achieving the drying of the battery.

[0009] However, this vacuum drying process requires the vacuum drying chamber to be restored to atmospheric pressure before vacuuming, which results in a relatively long time for both vacuuming and breaking. Furthermore, the vacuum is often broken using low-temperature workshop dry air, which disrupts the temperature environment within the vacuum drying chamber and reduces the temperature. The batteries within the vacuum drying chamber then need to be restored to their original temperature, requiring a long heating time. Consequently, the drying process employed in the prior art requires a long drying time and low drying efficiency. Even after the battery drying process is complete within a certain drying time, the water content remains high, indicating incomplete drying.

[0010] In response to the problems existing in the prior art, the present invention dries the battery through "high frequency" and "shallow breathing" methods. The "shallow breathing" shortens the time used for a single breath, thereby increasing the breathing frequency and achieving "high frequency" breathing. High frequency breathing can enhance the size rhythm of the gap between the battery pole piece and the diaphragm, which helps to evaporate the moisture in the battery more efficiently, thereby improving the drying effect and efficiency of the battery.

[0011] Specifically, a specific embodiment of the lithium battery drying process of the present invention is: The lithium battery drying process of the present invention comprises the following steps: Figure 1 ; Place the lithium battery to be dried in a vacuum drying oven and heat it for 60 minutes to the initial drying temperature, preferably within 100°C-110°C. During this heating process, the moisture in the battery can continuously diffuse outward and evaporate into the vacuum drying oven.

[0012] The vacuum drying box is evacuated. The evacuation time depends on the size of the inner cavity of the vacuum drying box, and is usually no more than 30 minutes. The vacuum is evacuated to 30-100 Pa. In different embodiments, the vacuum pressure is different, such as 30 Pa, 40 Pa, 50 Pa, 60 Pa, 80 Pa, 100 Pa, etc. The vacuum can be carried out to extract the moisture that diffuses outward from the battery during the heating process. Then the vacuum pressure is set for a time, and the pressure holding time is generally within 10 minutes to 25 minutes. During the pressure holding process, the water-containing gas in the battery is continuously discharged from the inside to the outside and is extracted, which can speed up the discharge of moisture in the battery. During the evacuation process, the lithium battery in the vacuum drying box is ensured to be at 105°C.

[0013] This process can be understood as the vacuum drying box performing an exhalation.

[0014] The vacuum drying box is broken, that is, the vacuum state of the vacuum drying box is released and air is inflated into the vacuum drying box. The gas filled during inflation is hot dry gas, and the inflation is stopped when the air pressure in the vacuum drying box reaches the set vacuum breaking pressure. The vacuum breaking time depends on the size of the inner cavity of the vacuum drying box and usually does not exceed 10 minutes. The pressure range for vacuum breaking is 10Kpa-50Kpa. In different embodiments, the specific vacuum breaking pressure can be 10Kpa, 20Kpa, 30Kpa, 40Kpa or 50Kpa, and the battery temperature must be within 100℃-110℃ when breaking the vacuum.

[0015] When breaking the vacuum, the temperature of the hot drying gas filled into the vacuum drying oven is preferably between 70°C and 100°C, and may be 70°C, 80°C, 90°C, or 100°C in different embodiments, with 100°C being preferred. This temperature is closer to the initial drying temperature of the lithium battery and will not disrupt the temperature environment within the vacuum drying oven. Furthermore, even if further heating is required after the hot drying gas is filled, the required temperature rise is relatively low and the heating time is relatively short.

[0016] This process can be understood as a vacuum drying box performing an air suction.

[0017] The cycle of exhalation and inspiration allows the vacuum drying box to complete multiple breaths. Specifically, the number of breaths is preferably within 15-30 times. Of course, in different embodiments, the number of breaths can be set as needed, such as 15 times, 20 times, 25 times or 30 times.

[0018] Through the above description of the breathing process, combined with Figure 2-3 As shown in the drying breathing curve (taking breaking vacuum to 10KPa and evacuating vacuum to 100Pa as examples), it can be seen that since the vacuum state in the vacuum drying box is not completely released to atmospheric pressure when breaking vacuum, but is within the range of 10KPa-50KPa, vacuuming is not started from atmospheric pressure during the next vacuuming. That is, the breathing pressure range of the present invention is between 30-100Pa and 10KPa-50KPa, which is shallow breathing. In this way, the time required for one breath is relatively short. The pressure holding time of each vacuuming is set according to the number of breaths. Generally, one breath is completed in about 1 hour. Moreover, the lithium batteries in the vacuum drying box are generally maintained at about 105°C during the breathing process. That is, a relatively stable drying temperature can be guaranteed throughout the breathing process, achieving constant temperature breathing, which is conducive to the continuous output of moisture in the battery.

[0019] Breathing can replace the gas in the vacuum drying box and the battery, thereby extracting the moisture in the battery and the vacuum drying box. Moreover, this high-frequency shallow breathing can achieve the rhythm of the gap between the battery pole piece and the diaphragm, which is conducive to the discharge of moisture in the center of the pole piece, and the discharge speed is faster. In the process of multiple shallow breathing, such as Figure 3 As shown in the figure, the moisture in the battery is continuously discharged. After 15-30 breaths, a better battery drying effect is finally achieved, so that the dried battery has a lower water content.

[0020] When breaking the vacuum, the hot drying gas is preferably hot air with a low dew point, which can reduce the micropore temperature difference shrinkage effect of the internal material of the battery and is conducive to the evaporation of internal moisture.

[0021] After the last breath is completed, that is, after the inhalation of the last breathing process is completed, the vacuum is broken to normal pressure. After the temperature drops, the door of the vacuum drying box can be opened and the dried batteries in the vacuum drying box can be taken out to complete the drying of the batteries.

[0022] The above description is only 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 based on the claims. Any equivalent structural changes made using the description and drawings of the present invention shall be included in the scope of protection of the present invention.

Claims

1. Lithium battery drying process, characterized by: The following steps are involved: Heat the battery in the drying oven to the initial drying temperature; The drying box is evacuated to 30-100 Pa and maintained for a set pressure holding time. The drying box is vacuumed to 10KPa-50KPa by hot dry gas and maintained for a certain vacuum breaking time, completing one breath; The vacuuming and the vacuum breaking are performed in a cycle to complete a set number of breathing times.

2. The lithium battery drying process according to claim 1, wherein: The set number of breaths is 15-30 times.

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

4. The lithium battery drying process according to claim 3, wherein: During the breathing process, the vacuuming time does not exceed 30 minutes.

5. The lithium battery drying process according to claim 1, wherein: During the breathing process, the drying box was evacuated to 30-50 Pa.

6. The lithium battery drying process according to any one of claims 1 to 5, characterized in that: During the breathing process, the vacuum was broken to 10 KPa.

7. The lithium battery drying process according to any one of claims 1 to 5, characterized in that: During the breathing process, the temperature of the hot dry gas is 70°C-100°C, and the battery temperature is ensured to be 100°C-110°C when the vacuum is broken.

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

9. The lithium battery drying process according to any one of claims 1 to 5, characterized in that: In the process of heating the battery to the initial drying temperature, the initial drying temperature is 100° C.-110° C.

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

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