Compression Experiment and Simulation on Prismatic Lithium-ion Batteries

Abstract

In order to understand the mechanical characteristics and failure modes of prismatic lithium-ion battery under mechanical loading conditions, flat plate compression and hemispherical punch indentation test were performed on 186570 prismatic LiFePO4 lithium-ion batteries and bare cells (cells without shell casing). Load and displacement of the cells and bare cells were measured in all tests. Additionally, temperature and voltage of the battery cells were also recorded. In flat plate compression condition, the battery shell casing cracked and electrolyte was squeezed from the cells. In hemispherical punch indentation condition, the punch displacements were stopped when a drop in force and voltage of the cell, as well as a rise in temperature indicated an internal short circuit in the cell. From the measured load-displacement data of the bare cell under flat compression condition, the individual compression stress-strain curves were calculated for the bare cells and used to develop a finite element model for the prismatic LiFePO4 battery. The bare cell is modeled as compressible foam material in LS-Dyna. This model can successfully predicted the load displacement relation of the cell under compression condition. On the other hand, this model can closely predict the force and punch displacement corresponding to the onset of short circuit in the cell under hemispherical punch indentation condition. The present tests and simulation can help to understand the deformation shape and internal short circuit mechanism of the prismatic lithium-ion cells under mechanical abuse conditions.