Unveiling the interaction of reactions and phase transition during thermal abuse of Li-ion batteries

• Published in: Journal of power sources Vol. 522; p. 230881
• Main Authors: Baakes, F., Lüthe, M., Gerasimov, M., Laue, V., Röder, F., Balbuena, P.B., Krewer, U.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 28-02-2022
• Subjects: Boiling; Endothermic and exothermic degradation reactions; Phase equilibria; Self-heating; Solid electrolyte interphase; Water; Water; Phase equilibria; Endothermic and exothermic degradation reactions; Solid electrolyte interphase; Boiling; Self-heating
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2021.230881

Safety considerations have always accompanied the development of new battery chemistries; this holds especially for the Li-ion battery with its highly reactive components. An overall assessment and decrease of risks of catastrophic failures such as during thermal runaway, requires an in-depth and quantitative understanding of the ongoing processes and their interaction. This can be provided by predictive mathematical models. Thus, we developed a thermal runaway model that focuses on rigorous modelling of thermodynamic properties and reactions of each component within a Li-ion battery. Moreover, the presented model considers vapour–liquid equilibria of a binary solvent mixture for the first time. Simulations show a fragile equilibrium between endothermic and exothermic reactions, such as LiPF6 and LEDC decomposition, in the early phases of self-heating. Further, an autocatalytic cycle involving the production of HF and the SEI component Li2CO3 could be revealed. Additionally, the unpredictability of the thermal runaway could be directly correlated to availability of LEDC or contaminants such as water. Also, solvent boiling can have a significant influence on the self-heating phase of a Li-ion battery, due to its endothermic nature. Further analysis revealed that the rising pressure, stemming from gassing reactions, can suppress solvent boiling until the thermal runaway occurs.
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•First time consideration of phase equilibria in Li-ion battery thermal runaway.•Complex interaction of SEI degradation, reformation and solvent boiling revealed.•Fragile equilibrium of endo- and exothermic processes in self-heating phase.•Unpredictability of thermal runaway related to presence of LEDC or water.•Rising pressure from reaction gases can suppress solvent boiling.