How Do Mild Mechanical Shocks Influence the Electrical Behaviors of Lithium-Ion Batteries?

Electric vehicles or onboard devices are possibly subjected to mechanical shocks in either the working lives or some collision scenarios. The mechanical shocks often non-negligibly affect the performance of devices. Regarding this, we investigate influences of mild shock waves that do not cause visible deformation on lithium-ion batteries and reveal the mechanisms. Shocked pouch cell samples were prepared by drop tower, and then subjected to short- and long-term cycles under different C-rates. By comparing their capacity retention and energy efficiency, abnormal electrical behaviors were observed. The aging mechanisms are revealed by quantification of internal variables of cells. Anomalous degradation in shocked cells is dominated by particle cracking, which is validated by scanning electron microscopy and gas generation detection. Furthermore, controlled stack compression tests validate the hypothesis that mechanical shock induces microcracks of graphite anode. Graphite particles containing shock-induced microcracks leads to the anomalous electrical behavior. Finally, we summarize several easy-to-detect electrical characteristics that can be applied to identify the shocked cells from the intact ones. This study clarifies the potential influence of shock waves on electrical behavior as well as durability of lithium-ion batteries, contributing to the quality diagnosis of spent batteries and their secondary use.