Laser irradiation illuminates uncertain degradation, leading to thermal runaway of 18650 cells charged/discharged at low temperatures

• Published in: Journal of power sources Vol. 542; p. 231767
• Main Authors: Shironita, Sayoko, Li, Shuo, Tsuruga, Hideki, Honda, Keizoh, Koshika, Kenichiroh, Umeda, Minoru
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.09.2022
• Subjects: Accelerating rate calorimeter; Battery safety; Li deposition; Lithium-ion secondary battery; Thermal stability; Lithium-ion secondary battery; Battery safety; Li deposition; Thermal stability; Accelerating rate calorimeter
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2022.231767

The safety of Li-ion secondary cells decreases during charging and discharging at low temperatures due to the deposition of Li metal that reduces the cell thermal stability. Generally, the thermal stability of Li-ion cells is evaluated by an accelerating rate calorimeter (ARC). Therefore, in this study, degraded cells with low capacities have been prepared by charge/discharge cycling at a low temperature. After confirming the decrease in thermal stability by ARC heating, the degraded cells are charged at room temperature, and a thermal runaway is initiated by both ARC heating and laser irradiation. During ARC heating, the exothermic behavior of the degraded cell is identical to that of a new cell; however, the degraded cell undergoes a thermal runaway after laser irradiation at an input energy 100 times lower than that required to induce the runaway of a new cell. Therefore, the degradation of cells due to charge/discharge cycling at low temperatures can be detected by the laser irradiation method despite the decreased thermal stability undetectable by the ARC. •Laser irradiation detects the decreased thermal stability undetectable by the ARC.•Thermal runaway of degraded cells easily occurs due to rapid heating.•Thermal runaway of degraded cells requires low input energy.•Li deposition on the anode surface is observed by disassembling a degraded cell.