State-of-Charge and Deformation-Rate Dependent Mechanical Behavior of Electrochemical Cells

The state-of-charge and deformation-rate dependent mechanical behavior of cylindrical lithium-ion battery cells was investigated. The research revealed that both state of charge and deformation rates affected the stiffness of the battery cells. Battery mechanical failure load was only weakly dependent on the state of charge. For the deformation-rate dependency on the mechanical integrity of battery cells, the battery mechanical failure load was either decreased significantly at high state of charge or decreased slightly at low state of charge as deformation rate increased. For the correlation between mechanical integrity and electrical failure, the displacement at the battery mechanical failure load coincided with a voltage drop. However, at high state of charge, premature and incomplete voltage drops were observed before the definite final voltage drop. No such premature voltage drop was observed in low state-of-charge specimens. The results of this research may be used as a reference for the design of impact and damage tolerant electric vehicle battery systems.