Abstract:
Li-ion batteries have become essential in everything from consumer electronics to
renewable energy systems. However, they also suffer from some key performance
and safety challenges, mainly arising at high temperatures. In general, high
temperatures increase the kinetics of various degradation processes such as gas
production, lithium plating, and electrolyte breakdown, resulting in capacity loss
and safety risks. Cyclic voltammetry (CV) and electrochemical impedance
spectroscopy (EIS) are the most powerful techniques for investigating LIBs, which
provide insight into redox behaviors, electrode kinetics, and internal resistance,
respectively. In this study, the electrochemical performance and degradation
mechanisms of a commercial 600mAh lithium-ion pouch cell were examined under
controlled cycling conditions. The cell was subjected to 100 charge-discharge cycles at
room temperature and 100°C, with current rates of 100mA, 300mA, and 500mA
individually. The charge-discharge cycling, in particular at higher current rates and
elevated temperatures, results in significant capacity fade, fluctuating Coulombic
efficiency, and internal short circuits. EIS analysis showed high initial impedance due
to incomplete SEI formation, and from the CV, it was concluded that the reaction
kinetics and ion mobility were enhanced at higher temperatures. Severe structural
degradation, such as roughening, dendritic growth, and lithium plating on the anode
surface, was observed using optical microscopy, especially after high current cycling.
