Study of Electrochemical Impedance Spectroscopy and Cyclic Voltammetry of Commercial Lithium-ion Battery at Elevated Temperature

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.