Decoupling the influence of impact energy and velocity on dynamic failure of cylindrical lithium-ion batteries

Abstract

Ensuring battery safety in electric vehicles during crashes is crucial due to the complexities of battery failure under dynamic loading. This study presents a dynamic test apparatus that isolates the effects of impact energy and velocity. Experiments show that impact energy primarily drives battery failure, with impact velocity also influencing outcomes. Notably, the battery demonstrates mitigated electrical failure within a specific impact energy range, which is lower than the threshold for failure characterized by a sudden voltage drop due to major fractures. The self-discharging rate of the impaired batteries within this range exhibits randomness, likely caused by complex electrode contact conditions following minor separator fractures and subsequent deformation recovery. Interestingly, under similar impact energy, electro-mechanical failure exhibits a nonlinear “severe-mild-severe” pattern as velocity increases, differing from the typical strain-rate effect observed in components like separators. X-ray computerized tomography and dynamic material behavior analysis reveal this anomaly as a competition between strain-rate hardening of materials and inertia effect of electrolyte flow and wound structure. The findings highlight that different factors dominate battery failure under varying impact velocities. This research enhances understanding of the energy- and velocity-dependent responses of lithium-ion batteries, aiding in optimizing battery designs for improved safety during collisions.