Towards Determining an Engineering Stress-Strain Curve and Damage of the Cylindrical Lithium-Ion Battery Using the Cylindrical Indentation Test

Abstract

Mechanical internal short circuit (ISC) is one of the significant safety issues in lithium-ion battery design. As a result, it is possible to subject LIB cells to thorough mechanical abuse tests to determine when and why failure may occur. The indentation test is a recommended loading condition for evaluating mechanical damage and ISC. In this study, 18,650 cylindrical battery cells underwent indentation tests and a voltage reduction following the peak force identified by the ISC. Due to the complexity of the contact surface shape between two cylinders (LIB cell and indenter), a new phenomenological analytical model is proposed to measure the projected contact area, which the FEM model confirms. Moreover, the stress-strain curve and Young’s modulus reduction were calculated from the load-depth data. In contrast to previously published models, the model developed in this paper assumes anisotropic hyperelasticity (the transversely isotropic case) and predicts the growing load-carrying capacity (scalar damage), whose variation is regulated by the Caputo-Almeida fractional derivative.