The optimization of the drying process for lithium battery pack electrode sheets needs to be carried out from five core directions: temperature control, air flow organization, division of drying stages, solvent residue control, and process parameter monitoring. The following are the specific optimization strategies and analysis:

First, temperature control optimization

Segmented heating: The drying process is divided into three stages: preheating, constant-rate drying and reduced-rate drying. During the preheating stage, a low temperature (such as 60-80℃) is adopted for rapid heating to prevent the solvent from evaporating too quickly and causing the electrode sheets to crack. During the constant-rate drying stage, the temperature is raised (such as 100-120℃) to accelerate the evaporation of the solvent. During the deceleration drying stage, the temperature is reduced (such as 80-100℃) to minimize internal stress.

Gradient temperature control: Set a temperature gradient inside the drying oven, with a lower inlet temperature and a higher outlet temperature, to ensure that the electrode sheets gradually release the solvent during the drying process and avoid local overheating.

Second, optimization of air flow organization

Vertical air duct design: By adopting a vertical air duct, hot air is evenly blown down from above the electrode sheet, reducing the impact force of the airflow on the electrode sheet and preventing deformation or coating peeling of the electrode sheet.

Wind speed adjustment: Adjust the wind speed according to the drying stage. During the preheating stage, the wind speed should be relatively low (such as 0.5-1m/s) to prevent rapid evaporation of the solvent on the surface of the electrode sheet. During the constant-rate drying stage, increase the wind speed (such as 2-3m/s) to accelerate solvent evaporation. During the deceleration drying stage, the wind speed is reduced (such as 1-1.5m/s) to minimize the internal stress of the electrode sheets.

Third, division and optimization of the drying stage

Preheating stage: The time should be controlled at 5 to 10 minutes, and the temperature should gradually increase to 80℃ to allow the solvent on the surface of the electrode sheet to evaporate slowly and prevent surface crusting.

Constant-rate drying stage: The time is controlled at 20-30 minutes, and the temperature is maintained at 100-120℃ to ensure uniform evaporation of the solvent and avoid local drying being too fast.

Deceleration drying stage: The time is controlled at 10 to 15 minutes, and the temperature is reduced to 80 to 100℃, allowing the solvent inside the electrode sheet to evaporate slowly and reducing internal stress.

Fourth, solvent residue control

Vacuum drying assistance: Vacuum drying is introduced in the later stage of drying to lower the boiling point of the solvent and accelerate the evaporation of residual solvents. The vacuum degree should be controlled between -0.08 and -0.09MPa, and the time should be controlled within 5 to 10 minutes.

Solvent recovery system: A solvent recovery device is set up at the outlet of the drying oven to recover the volatile solvents, reduce environmental pollution and lower production costs at the same time.

Fifth, monitoring and adjustment of process parameters

Online monitoring system: Install temperature, humidity and wind speed sensors to monitor key parameters during the drying process in real time and ensure process stability.

Feedback regulation mechanism: Based on monitoring data, it automatically adjusts the heating power, wind speed and vacuum degree to achieve closed-loop control of the drying process.

Matching the thickness of the electrode sheet with the density of the coating: Adjust the drying temperature and time for electrode sheets of different thicknesses and coating densities. For instance, for thick electrode sheets (>150μm), the drying time should be extended by 10-15% and the temperature reduced by 5-10℃.

Sixth, post-drying treatment

Cooling stage: After the drying is completed, the electrode sheets need to be slowly cooled to room temperature under the protection of inert gas (such as nitrogen) to prevent cracking of the electrode sheets due to sudden temperature drops.

Quality inspection: The moisture content, thickness uniformity and surface morphology of the dried electrode sheets are inspected to ensure that the quality of the electrode sheets meets the requirements.