Early emergency cooling for mitigating the onset of battery thermal runaway

Immersion coolants are an emerging and promising technology for battery thermal management and the prevention and mitigation of battery fires. This study investigates the effect of four immersion coolants (water, HFE-7200, silicone oil, and transformer oil) and their coolant-battery volumes ratio (1/16–100) on the onset time of thermal runaway following safe venting in cylindrical batteries (SOC from 40 % to 100 %). Results reveal that within a critical time window (1–2 min after venting), a small amount of immersion coolant (1 mL and volume ratio < 1/16) can effectively suppress the battery post-venting self-heating and prevent the onset of thermal runaway. The critical immersion cooling rate versus coolant-battery ratio is quantified at different battery SOCs. As the coolant-battery ratio increases, battery mass loss, maximum temperature, maximum cooling rate, and the critical time window all decrease linearly, regardless whether thermal runaway occurs. The five-dimensional evaluation suggests the overall effect on preventing thermal runaway ranks as water, transformer oil, silicone oil, and HFE-7200. This study quantifies the optimal emergency cooling strategy to prevent or delay the onset of battery thermal runaway, providing support for the design of future battery safety management systems.