Adiabatic Thermal Runaway Behaviors of Lithium-Ion Batteries with High-Capacity Cathodes (LiNi0.9Co0.05Mn0.05 O2 and LiFePO4) at the Cell Level: A Comparative Study

To address the research gap in adiabatic thermal runaway (TR) characteristics of large - capacity (>100 Ah) lithium - ion batteries—LiFePO4 (LFP) and LiNi0.9Co0.05Mn0.05O2 (NCM90.50.5) cells—this study systematically investigated the TR processes of 129 Ah NCM and 107 Ah LFP cells via an accelerating rate calorimeter (ARC) under a unified experimental environment, aiming to reveal their differential TR mechanisms.ARC tests divided cell TR into four stages, and an Arrhenius - based heat generation model was established. Results showed that for the NCM cell: self - heating onset temperature (T1) = 102.3 °C, TR trigger temperature (T2) = 156.5 °C (coinciding with valve - opening temperature, Tvent/ = T2), voltage - fluctuation - to - TR warning time = 256 s, and maximum TR temperature (T3) = 1000 °C. In contrast, LFP cell: T1 = 90.7 °C, T2 = 189.7 °C, warning time = 8600 s, T3 = 491 °C. Moreover, the LFP cell's double - jellyroll structure induced a secondary thermal reaction at TR's final stage. Kinetic fitting indicated the NCM heat generation model: y = 7.2×10−22·(T(t)/T)9.77. Its temperature sensitivity (b = 9.77) was significantly higher than LFP's (b = 3.195), demonstrating more intense TR reactions and faster reaction acceleration in NCM cells.