Explosion dynamics for thermal runaway gases of 314 Ah LiFePO4 lithium-ion batteries triggered by overheating and overcharging

Abstract

Thermal runaway (TR) of LiFePO₄ lithium-ion batteries (LFPs) can produce significant amounts of smoke, posing serious explosion hazards. This paper systematically investigated TR gas generation, explosion limits, explosion overpressure, and post-explosion gas compositions of 314 Ah LFPs under overcharging and overheating. Quantum chemical and explosion reaction kinetics calculations clarified the elementary reactions and compositional alterations occurring in gases and free radicals during the explosion process. The findings revealed that H₂ constituted the primary component of TR gases, comprising 47.64 % and 53.12 % of the overcharging and overheating, respectively, followed by CO₂ and CO. The ranges of explosion concentration for TR gases, when subjected to overheating and overcharging conditions, were 6.32–29.3 % and 6.83–26.91 %, respectively. At the point of maximum explosion overpressure (P_max), the gas concentrations peaked at 15.86 % and 16.25 %. The elementary reaction R1 held a pivotal position in enhancing the explosion overpressure. As the TR gas concentration escalated, the Rate of Production (ROP) of R31 and R35 also surged, ultimately resulting in elevated concentrations of CO. The reactions R123, R250, and R279 facilitated the generation of H₂ while simultaneously consuming hydrocarbon gases. This resulted in a risk of secondary explosion of the TR gas after the explosion. Post-explosion gas residual quantities followed the order: C₂H₆ < C₂H₄ < CH₄ < H₂ < CO. The results revealed crucial insights for developing explosion prevention and suppression in the process safety industry and Energy Storage Systems.