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

Abstract To address the research gap in the adiabatic thermal runaway (TR) characteristics of large-capacity lithium-ion battery cells (>100 Ah)—specifically lithium iron phosphate (LiFePO4, LFP) and LiNi0.9Co0.05Mn0.05O2 (NCM90.50.5) cells—this study systematically investigated the TR processes of 129 Ah NCM90.50.5 cells and 107 Ah LFP cells under a unified experimental environment using an accelerating rate calorimeter (ARC). The aim was to reveal the differential mechanisms of TR between the two cell types. Through ARC testing, the TR process of the cells was divided into four stages, and a heat generation model based on the Arrhenius equation was established. The results showed that for the NCM90.50.5 cell: the self-heating onset temperature (T1) was 102.3 °C, the TR trigger temperature (T2) was 156.5 °C, and the valve-opening temperature coincided with the trigger temperature (Tvent = T2). The warning time from voltage fluctuation to TR was only 256 s, and the maximum TR temperature (T3) reached up to 1000 °C. In contrast, for the LFP cell: T1 was 90.7 °C, and T2 was 189.7 °C. The early warning time from the first battery voltage fluctuation to thermal runaway reaches as long as 8600 s, and T3 peaked at 491 °C. Additionally, the double-jellyroll structure of the LFP cell induced a secondary thermal reaction at the final stage of TR. Kinetic fitting results indicated that the heat generation model for the NCM90.50.5 cell was y = 7.2 × 10−22·(T(t)/T)9.77. Its temperature sensitivity (exponent b = 9.77) was significantly higher than that of the LFP cell (b = 3.195), demonstrating that the NCM cell exhibits more intense TR reactions and a faster rate of reaction acceleration.