SOC-Dependent Compression of Lithium-Ion Battery Electrodes

Young’s modulus is a key parameter to describe the compressive behavior of battery electrodes and is therefore frequently employed in mechanical models. In most studies, this property is determined using pristine electrodes. However, during electrochemical cycling, lithium insertion and extraction can alter the mechanical response of the active materials. The literature lacks SOC-dependent compression data of electrodes with different active materials. Especially for LFP electrodes, no SOC dependencies have been reported. This study closes this gap by performing compression tests on graphite, NMC, and LFP electrodes at different states of charge. The results show that the stiffness of graphite and NMC electrodes increases with higher lithium contents, whereas the compressive behavior of LFP remains independent of the lithium content. These findings are consistent with material-level properties reported in the literature. Two hypotheses are proposed to explain this behavior: one hypothesis is related to the contribution of active material particles to electrode deformation and the other hypothesis is related to microstructural changes governed by particle diameter.