Mechanical testing and macro-mechanical finite element simulation of the deformation, fracture, and short circuit initiation of cylindrical Lithium ion battery cells
A quasi-static mechanical abuse test program on cylindrical Lithium ion battery cells has been performed at a state of charge (SoC) of 0%. The investigated load cases involved radial crushing, local lateral indentation and global three-point bending of the cell. During the tests, the punch load, the punch displacement, the cell voltage and the temperature development of the cell have been monitored using an infrared camera and temperature sensors. After the test, the cells have been analysed using computer tomography.It is indicated that macroscopic jelly roll fracture on a global scale initiates the internal short circuits, revealed by a sudden decrease of the global mechanical load due to the rupture, followed by a drop of the measured voltage and immediate increase in cell temperature.A macro-mechanical finite element crash simulation model has been established for the cell housing and the jelly roll. The classical stress-based criterion after Mohr and Coulomb (MC) h as been applied to predict fracture and the initiation of an internal short circuit of the jelly roll. The MC criterion correctly represents the punch displacement to fracture, where the predicted fracture locations correspond to the observed locations of the internal short circuits of the cells.