Thermal Runaway Behavior and Gas Generation Characteristics Analysis for LiFePO ₄ Batteries with Various Capacities and States of Charge

The safety of lithium‐ion batteries raises significant safety concerns, and the batteries are developing in the direction of large capacity. However, the correlation between the thermal runaway (TR) behavior of the batteries and gas production characteristics and the capacity is not clear, it may lead to gaps in battery safety design. This article systematically investigates TR behavior and gas generation in lithium iron phosphate (LFP) batteries of varying capacities (1.6, 5, 10, 15 Ah) and states of charge (SOC: 25%, 50%, 75%, 100%). TR is induced via lateral heating in a sealed chamber, with temperature/voltage monitored. Gas chromatography identifies components and concentrations. Results show that, within the tested range, larger capacity batteries require more energy to trigger TR using a 200 W heater. The primary TR gas components and the proportions (H 2 ≈ 49%, CO ≈ 32%) are consistent across capacities, indicating minimal capacity impact on gas composition. Conversely, SOC significantly affects hazard severity: higher SOC shortens TR triggering time, accelerates temperature rise rates, and linearly increases combustible gas H 2 production and proportion (rising 5–11% per 25% SOC increment). This research clarifies the influence of LFP capacity and SOC on TR behavior and gas production, providing crucial data for battery safety design.