Mechanism of gas generation and explosion in full lifecycle lithium-ion batteries considering free radical reactions

The rapid growth in power battery deployment foresees a significant surge in retired batteries, with cascade utilization representing the most environmentally friendly and cost-effective approach. However, such batteries pose substantial safety risks. This study established a gas generation testing platform for both new and aged lithium-ion batteries (LIBs). Through gas generation tests, 20 L spherical explosion tests, and CHEMKIN simulations, we analyzed the thermal runaway (TR) gas generation behavior, explosion characteristics, and underlying mechanisms. The results reveal distinct gas generation stages depending on the state of health (SOH), with flammable gas yields decreasing in the order: 100 % SOH > 70 % SOH > 60 % SOH > 80 % SOH. Explosion behavior occurs in four distinct phases, with batteries at 70 % and 100 % SOH presenting the highest hazard levels. Key elementary reactions driving explosions are R1 (H + O₂ = O + OH) and R31 (CO + OH = CO₂ + H), with the H radical identified as the most critical factor. This research enhances the understanding of LIB gas generation and explosion characteristics across their lifecycle, providing crucial support for early warning systems and hazard prevention strategies.