Impact response of prismatic Li-ion battery jellyrolls and cells

Abstract

Understanding the damage behavior of lithium-ion batteries subjected to dynamic loading is crucial for electric vehicle safety design. In this work, jellyrolls and prismatic cells of a typical commercial vehicle battery module were impacted using a drop tower impact system with three different stainless-steel indenters at two different speeds (2.5 m/s and 7.5 m/s). The indenter shapes included flat and hemispherical punches as well as a round end wedge with an identical diameter of 25.4 mm (1 in). Impact force and displacement responses were measured for jelly rolls while additional measurement of voltage change during impact was performed for cells. Testing results suggest that the peak force of the jellyrolls increases with increase in speed for flat and hemispherical punches and decreases for wedge, but the impact speed does not seem to have much influence on the damage mode. Impact of cells using flat and hemispherical punches ruptured the cover plate and copper current collector layer beneath the cover plate whereas cover plate was intact in wedge tests. Critical displacement for short-circuit in the cells was influenced by both speed and indenter type, which is the result of different damage mechanisms. It decreases with impact speed for the low-speed tests because of increased jellyroll brittleness and increases at high speeds due to jellyroll inertia. The findings in this work can potentially be applied as the basis for future numerical model development and battery module safety design.