Temperature-dependent safety behavior of LiFePO4 pouch cells under mechanically induced localized short circuits

Ambient temperature is a key factor affecting the safety performance of lithium-ion batteries and becomes increasingly important as their application scenarios and operating conditions continue to expand. This study systematically investigates the influence of ambient temperature (−20 °C–60 °C) on the safety behaviors of two LiFePO4 pouch cells with different capacities and manufacturers. Using an experimental platform that synchronously integrates thermal, mechanical, and electrical measurements, localized indentation was applied to induce internal short circuits (ISC) and analyze the multiphysics coupling responses. The results show that temperature significantly affects the mechanical strength and failure mechanisms of the batteries: as temperature increases, the maximum load and stress decrease, and the displacement required to trigger a short circuit becomes larger; at higher temperatures, voltage drops and temperature rise rates accelerate, whereas the peak temperature decreases. The state of charge (SOC) also plays a crucial role—at high SOC levels, the voltage and temperature responses are more sensitive to temperature, while at low SOC levels, mechanical characteristics are more affected. The early-unloading experiments further verify that the failure process proceeds sequentially from localized short circuit to temperature rise and ultimately to thermal runaway, emphasizing the decisive influence of ambient temperature on battery damage and short-circuit evolution behavior. This research not only deepens understanding of the nonlinear, multi-physics behaviors in lithium batteries but also provides foundational data for safety standards and engineering strategies.