Temperature Dependency of Swelling Force in Prismatic Lithium-Ion Cells Under Fixed Mechanical Constraints Over Lifetime

The performance and integrity of large-format lithium-ion cells are strongly influenced by the swelling and mechanical deformation that occurs during operation. In this study the influence of ambient temperature and cell design on the mechanical swelling stresses and degradation behavior of prismatic lithium-ion cells during cyclic aging has been investigated. Mechanical stresses were monitored in-situ during C/2 cycling at temperatures ranging from 15 °C to 45 °C for two different commercial prismatic cell types ≥ 60 Ah. Increasing temperature from 15 °C to 45 °C resulted in higher maximum stresses at end of test by factors of 1.85 and 3.69 depending on cell type. The minimum stress exhibited a bilinear trend, where the gradient correlated positively with temperature. The intercalation induced stress amplitude showed three stages: rapid initial increase, plateau, and decreasing amplitude, with higher temperatures shortening the plateau duration. However, the temperature sensitivity of mechanical stresses could not be directly attributed to differences in degradation modes but rather to capacity- and resistance-neutral effects, most likely related to solid-electrolyte interphase layer growth and electrolyte gassing. The findings from this study contribute to a better understanding of the complex interplay between temperature, mechanical stresses, and the degradation of prismatic lithium-ion cells.