Multi-parameter thermal runaway monitoring platform unraveling SOC-dependent thermal runaway mechanisms in LiNi0.8Co0.1Mn0.1O2 batteries

Thermal runaway (TR) propagation in lithium-ion batteries, particularly in high-nickel LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) batteries, poses critical safety concerns for energy storage system. The state of charge (SOC) is a critical factor influencing battery safety. This study systematically investigates TR behaviors in 18650-type NCM811 batteries under 0%, 50%, and 100% SOC conditions using an integrated multi-parameter monitoring platform. The platform combines programmable thermal stimulation, synchronized thermocouple arrays, infrared imaging (capturing spatial-temporal temperature gradients), and cone calorimetry (quantifying heat and smoke release rates). Results reveal a strong SOC-dependent TR response: Fully charged batteries (100% SOC) show a 73.9% increase in total heat release (16.1 MJ/m² vs. 4.2 MJ/m² at 50% SOC) and accelerated CO/CO₂ emissions due to intensified electrolyte decomposition. Paradoxically, fully discharged batteries (0% SOC) produce higher cumulative smoke, which is attributed to incomplete oxidation of carbonaceous anode materials under moderated TR conditions. These quantitative correlations help resolve conflicting combustion behaviors across SOC levels and provide mechanistic insights for SOC-specific thermal management strategies in battery safety design. The novel TR testing platform enables comprehensive analysis of battery failure progression and supports in-depth investigations into lithium-ion battery safety enhancement.