Soot formation and its hazards in battery thermal runaway

Abstract

As an increasingly important solution for the energy industry, batteries are widely used in electric vehicles and energy storage systems. However, thermal runaway of batteries is a serious safety hazard. In this process, the materials in the battery undergo thermal decomposition and combustion, resulting in the formation of soot and other harmful byproducts and posing a significant threat to the environment and human health. In this work, LiFePO₄ and ternary lithium batteries are selected as experimental subjects to comprehensively evaluate the soot hazard in the thermal runaway process. The LiFePO₄ and ternary lithium battery soot samples exhibited a typical "core-shell" structure, with lattice spacings ranging between 0.36-0.46 and 0.35–0.46 nm, respectively. The surfaces of these materials are covered with functional groups, including C–C, C–O, and O–H bonds. Soot samples taken from the thermal runaway of ternary lithium batteries also contain O–CO and π bonds, consistent with the functional groups in wood soot. Through EDS and XPS characterization, it is evident that the LiFePO₄ battery soot contains C, O, Li, F, P, and Fe, while the ternary lithium battery soot, in addition to these elements, also contains Ni, Co, and Mn. The battery soot samples exhibited significant cytotoxicity to human cells, such as lung cells (MRC-5) and neural cells (SH-SY5Y). With high concentrations of soot, the survival rate of lung cells and nerve cells is low. Compared to wood soot, battery soot causes greater damage to human lungs and neural cells. The research in this work contributes to a better understanding of the hazardous characteristics of soot in battery thermal runaway and its potential threats to human health, offering a crucial reference for enhancing battery safety and emergency responses.