Why Does Edge Thickening Occur During Lithium Battery Anode Calendering?

As a vital technology in modern energy storage, lithium-ion batteries play a crucial role across various industries due to their superior performance and safety. However, the "edge bulging" phenomenon—occurring after the roll pressing of anodes—has become a key bottleneck limiting performance improvements in battery manufacturing.

This article provides an in-depth analysis of the causes of edge bulging during the anode roll pressing process and proposes a series of practical, effective solutions aimed at enhancing overall battery consistency and reliability, thereby driving the further advancement of lithium-ion battery technology.

During the coating and roll pressing of lithium-ion battery electrodes, a phenomenon known as the "thick edge effect" frequently occurs, characterized by thicker edges and a thinner center. This issue typically stems from uneven drying or compaction and can lead to foil breakage during subsequent winding or other processing stages. A detailed analysis follows:

Drying Rate Discrepancies: During the post-coating drying phase, the edge areas have a relatively larger surface area, causing them to dry faster than the center and resulting in a thicker film with lower moisture content.

Uneven Liquid Distribution: During drying, the coating fluid may migrate toward the edges, thinning the material in the center while thickening the edges due to fluid accumulation.

Roll Pressing Pressure Distribution: Uneven pressure application during roll pressing can result in insufficient compaction in the center and excessive pressure on the edges, leading to the thick-edge phenomenon.

ACEY-HR300 hydraulic balance electric Electrode Calendering Machine is aimed at high-precision rolling of positive and negative plates in the battery industry. The equipment has good horizontal and vertical rolling uniformity, and the appearance of the rolled product is high-quality. The equipment is provided by the hydraulic system to provide pressure for roll rolling. It is suitable for Where there is a higher requirement for the consistency of rolling force and rolling gap.

Optimize the Drying Process: Adjust the drying procedure to ensure a uniform drying rate across the entire electrode, thereby preventing the edges from drying too quickly and forming thick edges.

Improve Coating Die/Baffle Design: Optimize the shape of the coater's baffles or foam inserts to reduce the wet film thickness at the edges, preventing the thick-edge phenomenon at the source. Adjust coating parameters: Modify operating parameters such as coating speed and gap width to minimize liquid migration during drying and ensure coating uniformity.

Incorporate flow-guiding structures: Integrate flow-guiding structures into the coating equipment to promote even distribution of the coating slurry, reduce liquid accumulation at the edges, and prevent excessive edge thickness.

Optimize the calendering process: Adjust parameters—including speed, pressure, and temperature—to ensure uniform calendering pressure and prevent edge bulging caused by localized over-compaction.

Consider electrode design: Address edge effects during the electrode design phase to ensure that edge areas are properly managed throughout the drying and calendering processes.

Implement real-time process monitoring: Monitor the coating and calendering processes in real time to detect and adjust parameters promptly, preventing thick-edge issues caused by process fluctuations.

Apply post-processing measures: Employ techniques such as edge trimming to reduce the thickness of edge areas where thickening has occurred, thereby improving overall quality and consistency.

Implementing these preventive measures effectively mitigates the "thick-edge, thin-center" issue in lithium-ion battery electrodes during coating and calendering. This reduces the risk of foil breakage during winding and enhances the consistency and reliability of the batteries.