Failure mechanisms in lithium-ion batteries under high-velocity impact: Experiments and modeling across multiple velocities

High-velocity impacts pose critical safety risks to lithium-ion batteries (LIBs) used in transportation systems, yet the underlying failure mechanisms remain unclear. This study investigates the mechanical, electrical, and thermal responses of pouch-type LIBs under ballistic impacts from 300 to 1300 m/s. Experiments on cells with and without electrolyte isolate the effects of mechanical damage, revealing velocity-dependent fracture patterns, rapid voltage drop-recovery behavior, localized heating near the penetration zone, and a substantial rise in internal resistance. To capture the transient failure process, a thermo-mechanically coupled FE-SPH model is developed and validated against ballistic tests. The simulation reproduces stress-wave propagation, adiabatic heating, and the transition from mixed tension-compression failure to compression-dominated pulverization at higher velocities. The intact region sharply decreases with velocity (94% to 16%), indicating increased susceptibility to internal short circuits. Comparison with needle penetration clarifies the dominant factors in batteries failure under extreme mechanical abuse. Material-level strategies—strengthening the separator and enhancing separator-electrode interfacial bonding—are shown to effectively suppress short-circuit pathways. These results offer actionable guidance for improving the impact safety of LIBs in transportation applications.