Numerical Analysis of Explosion Characteristics of Vent Gas from 18650 LiFePO₄ Batteries with Different States of Charge

Abstract

The combustion and explosion characteristics of lithium-ion battery vent gas is a key factor in determining the fire hazard of lithium-ion batteries. Investigating the combustion and explosion hazards of lithium-ion batteries vent gas can provide guidance for rescue and protection in explosion accidents in energy storage stations and new energy vehicles, thereby promoting the application and development of lithium-ion batteries. Based on this understanding and combined with previous research on gas production from lithium-ion batteries, this article conducted a study on the combustion and explosion risks of vent gas from thermal runaway of 18650 LFP batteries with different states of charge (SOCs). The explosion limit of mixed gases affected by carbon dioxide inert gas is calculated through the "elimination" method, and the Chemkin-Pro software is used to numerically simulate the laminar flame speed and adiabatic flame temperature of the battery vent gas. And the concentration of free radicals and sensitivity coefficients of major elementary reactions in the system are analyzed to comprehensively evaluate the combustion explosion hazard of battery vent gas. The study found that the 100% SOC battery has the lowest explosion limit of the vent gas. The inhibitory elementary reaction sensitivity coefficient in the reaction system is lower and the concentration of free radicals is higher. Therefore, it has the maximum laminar flame speed and adiabatic flame temperature. The combustion and explosion hazard of battery vent gas increases with the increase of SOC, and the risk of explosion is the greatest and most harmful when SOC reaches 100%. However, the related hazards decrease to varying degrees with overcharging of the battery. This article provides a feasible method for analyzing the combustion mechanism of vent gas from lithium-ion batteries, revealing the impact of SOC on the hazardousness of battery vent gas. It provides references for the safety of storage and transportation of lithium-ion batteries, safety protection of energy storage stations, and the selection of related fire extinguishing agents.

Keywords

Combustion and explosion characteristics / Explosion limit / Laminar flame speed / Adiabatic flame temperature / Sensitivity analysis

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