Browsing by Subject "failure mechanism"

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    In Situ Temperature Evolution and Failure Mechanisms of LiNi0.33Mn0.33Co0.33O2 Cell under Over-Discharge Conditions
    (ECS, 2018-09) Wu, Linmin; Liu, Yadong; Cui, Yi; Zhang, Yi; Zhang, Jing; Mechanical Engineering, School of Engineering and Technology
    In this work, in situ study of commercial 18650 NMC (LiNi0.33Mn0.33Co0.33O2) cells under over-discharge charge conditions (100%, 110%, and 120%) has been performed. Both voltage and cell skin temperature evolutions were simultaneously monitored in situ during discharge process. The results show that there is a clear correlation between the voltage and temperature. For the NMC cell under 120% over-discharge condition, the cell failed after only 1 cycle. The voltage dropped to negative values at the end of the discharge. The skin temperature at the end of discharge increased dramatically to 73°C, indicating strong exothermal reactions happened inside the cell. For the 110% over-discharged cell, the cell failed after 10 cycles. The voltage at the end of the discharge process became negative after the 1st cycle. The cell skin temperature increased from 23.2°C to 61.7°C. The peak temperature in each cycle kept increasing until failure. These implies the micro short circuits were developed during the charge-discharge process. The failed components were examined by SEM/EDX and XRD. The results show substantial aluminum exists inside the failed separators. The results suggest that during the over-discharge process, the alumina inside the separator was reduced to aluminum. The electrons migrate through aluminum channel, leading to the failure of the cells.