Thermal runaway behavior of lithium-ion batteries in aerospace mobility systems

Lithium iron phosphate (LFP) batteries are widely regarded as intrinsically safer than other lithium-ion chemistries due to the structural stability of the olivine cathode. However, their behavior under aerospace operating environments—characterized by reduced pressure and oxygen-limited conditions—remains insufficiently understood. In this work, the thermal runaway characteristics of LFP batteries were investigated through a combined experimental–thermochemical approach to assess potential hazards in aerospace mobility applications. Differential scanning calorimetry (DSC) experiments were conducted on full LFP cells at multiple states of charge (SOC = 25–100%) under high heating rates (40–100 °C min−1) to examine thermal decomposition behavior. Kinetic analysis revealed two dominant exothermic reactions associated with solid electrolyte interphase (SEI) decomposition and subsequent cathode degradation. The activation energy for the primary reaction ranged from approximately 55–65 kJ mol−1, with increasing SOC leading to earlier onset temperatures and greater heat release, indicating enhanced reactivity at high charge states. To evaluate the combustion consequences of thermal runaway gases, experimentally derived parameters were integrated with thermochemical equilibrium calculations using NASA Chemical Equilibrium with Applications (CEA). Simulations were performed for representative ambient (φ = 1.0, ~1 bar) and aerospace (φ = 1.3, 0.4–0.8 bar) conditions. Results indicate that although adiabatic flame temperatures exceed 2500 K under both environments, aerospace conditions promote significantly higher fractions of incomplete combustion products. The combined mole fraction of CO and H2 increased from approximately 0.007–0.008 under ambient conditions to ~0.019–0.020 in the aerospace scenario, nearly three times higher due to oxygen-limited combustion. These findings demonstrate that while LFP cathodes exhibit strong structural stability, the combustion behavior of their thermal runaway gases can become more hazardous in aerospace environments. The study highlights the importance of SOC management, ventilation control, and thermal mitigation strategies for next-generation aerospace battery systems.