Mechanical effects are ubiquitous in lithium-ion batteries, even during normal operation, and affect them at all scales from particle to electrode to cell level. At the cell level, various degradation processes contribute to cell internal mechanical stress; among the most important are breathing and swelling, along with their interaction with mechanical constraints such as the case or bracing.

Cylindrical 18650 and 21700 lithium-ion batteries are produced with small gaps between the jelly roll and the case. The size of these gaps and the mechanical attachment of the jelly roll to the case can have a significant impact on the thermal and mechanical properties of cells.

To investigate the influence of the state of charge (SOC) and state of health (SOH) on the size of the gap, computed tomography (CT) and gray-value analysis was conducted with various cell types at 0% and 100% SOC and after cycling. The results show a significant influence of the SOC on the gap for new cells and a substantial reduction in the gap during the first cycles.

Read more details in the published article.