A comparative study on the thermal runaway process mechanism of a pouch cell based on Li-rich layered oxide cathodes with different activation degrees.

Li-rich layered oxide (LLO) is regarded as one of the most promising candidates for the next-generation batteries. At present, most of the research studies are focusing on the normal electrochemical properties of LLOs, while safety issues of the cells are neglected. To address this problem, this article systematically investigates the thermal runaway (TR) process of the pouch cell based on LLOs and elucidates how different activation degrees influence the thermal stability of the cathode material and cell, through various thermal analysis methods. Results prove that for the cell with higher activation degrees, more vulnerable solid electrolyte interfaces (SEI) are formed, leading to the occurrence of a self-heat process at lower temperatures. Then, more exothermic reactions are strengthened due to the weakened stability of the cathode material, releasing more heat and triggering TR processes at lower temperatures. Finally, during the period of uncontrolled TR, more oxidative O is released, responsible for the intensified exothermic redox reactions. Therefore, moderate activation of LLOs should be a reasonable and practical application strategy, considering the balance between the high energy density and safety of the cells.