Electrochemical behavior and morphological evolution of Li metal anode under high cycling capacity

Despite the high theoretical capacity and low reduction potential of Li metal, low Coulombic efficiency and safety issues of Li metal batteries have hindered their commercialization. In this work, we explore the processes significantly impacting on Coulombic efficiency and overpotential in Li||Cu asymmetric cells depending on “cycling capacity”. To understand this behavior, we focused on three overshooting peaks in voltage profiles, and as each peak involves both Li plating and stripping at two electrodes, we could extract the six individual processes. Among them, the decreasing values of overpotential with increasing cycling capacity (or equivalently, “cycling time” at a fixed current density) are clearly observed, confirming their influence on cell performance. This comprehensive understanding of Coulombic efficiency, overpotential and morphological evolutions from the perspective of time provides new insight to the performance of Li metal batteries.