Comparative study of mechanical-electrical-thermal responses of pouch, cylindrical, and prismatic lithium-ion cells under mechanical abuse

In the study, mechanical abuse tests mainly in the form of indentation were performed on the cylindrical cell, pouch cell, and prismatic cell. The mechanical force-displacement response, open circuit voltage (OCV), and temperature distribution were recorded and compared. In spherical head indentation tests of the pouch and prismatic cell and lateral indentation of the cylindrical cell, the peak force is strongly correlated with OCV drop and local temperature increase. However, in flat-end cylinder indentation tests, the internal mechanical damage is progressively developed, and the OCV drop and the temperature increase occur before the peak force. The fracture surfaces of the post-mortem samples were examined to investigate the correlation between fracture patterns and internal short circuit (ISC) behaviors (OCV and temperature distribution). Two distinct fracture patterns were observed that the in-plane fracture induced by biaxial stretching and inter-layers' fracture induced by shearing. A strong correlation is observed between the number of shear fractures and OCV drop. An increase in the number of inter-layers' fractures increases the rate of OCV drop. Additionally, the fracture patterns influence the ISC area and location, thereby affecting the heat generation and conduction as well as the temperature distribution.