Structural and thermal regulation of strain behavior in batteries under air and immersion cooling

Immersion cooling (IC) for battery thermal management has become an emerging trend in recent years, but research on battery strain behavior in liquid-immersed environments remains limited. To address this gap, the strain evolution of cylindrical, pouch and prismatic cells was experimentally studied under two cooling conditions. The results show that structural variations among battery types significantly influence their primary strain distribution patterns. Cylindrical and prismatic batteries display stronger strain responses near their negative electrode tabs due to mechanical constraints from rigid metal casings, whereas the pouch battery shows high strain concentration mainly in its center because of its flexible packaging. Additionally, as the C-rate increases, strain responses vary significantly among different cell types, and the impact of immersion cooling on strain magnitude depends on the battery format. At a 3C rate with IC, cylindrical cells experienced a strain increase of 9.1 με along with a temperature drop of 14.3 °C; pouch cells showed a 2 με strain increase and a 9.5 °C temperature decrease; while prismatic cells had a 12 με decrease in strain with a 5 °C temperature reduction. Moreover, IC significantly reduces strain reversal at high C-rates; cylindrical cells are the most sensitive, while the other two types are less affected. These differences could be linked to their structural flexibility and improved thermal diffusion. Analysis of differential capacity versus differential strain curves shows that, under different cooling conditions, mechanical signals generally lag behind electrochemical signals during charging. This study investigates the mechanical behavior of lithium-ion batteries under different immersion cooling conditions, focusing on their similarities and differences.