Correlation of aging and thermal stability of commercial 18650-type lithium ion batteries

• Published in: Journal of power sources Vol. 342; pp. 382 - 392
• Main Authors: Börner, M., Friesen, A., Grützke, M., Stenzel, Y.P., Brunklaus, G., Haetge, J., Nowak, S., Schappacher, F.M., Winter, M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 28.02.2017
• Subjects: Aging; Lithium deposition; NCM; Post-mortem; Safety; Thermal stability; Aging; Post-mortem; NCM; Safety; Lithium deposition; Thermal stability
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2016.12.041

Established safety of lithium ion batteries is key for the vast diversity of applications. The influence of aging on the thermal stability of individual cell components and complete cells is of particular interest. Commercial 18650-type lithium ion batteries based on LiNi0.5Co0.2Mn0.3O2/C are investigated after cycling at different temperatures. The variations in the electrochemical performance are mainly attributed to aging effects on the anode side considering the formation of an effective solid-electrolyte interphase (SEI) during cycling at 45 °C and a thick decomposition layer on the anode surface at 20 °C. The thermal stability of the anodes is investigated including the analysis of the evolving gases which confirmed the severe degradation of the electrolyte and active material during cycling at 20 °C. In addition, the presence of metallic lithium deposits could strongly affect the thermal stability. Thermal safety tests using quasi-adiabatic conditions show variations in the cells response to elevated temperatures according to the state-of-charge, i.e. a reduced reactivity in the discharged state. Furthermore, it is revealed that the onset of exothermic reactions correlates with the thermal stability of the SEI, while the thermal runaway is mainly attributed to the decomposition of the cathode and the subsequent reactions with the electrolyte. [Display omitted] •Comprehensive study on the thermal stability of commercial 18650-type LIBs.•Strong influence of cycling temperature on the thermal stability of the SEI.•Onset temperatures for exothermic reactions correlate with SOC for fresh LIBs.•Metallic lithium deposits on the anode reduce safety properties of the cell.•Thermally stable SEI impedes de-intercalation of lithium ions.