Stabilization of Lithium-Metal Batteries Based on the in Situ Formation of a Stable Solid Electrolyte Interphase Layer

Lithium (Li) metals have been considered most promising candidates as an anode to increase the energy density of Li-ion batteries because of their ultrahigh specific capacity (3860 mA h g–1) and lowest redox potential (−3.040 V vs standard hydrogen electrode). However, unstable dendritic electrodeposition, low Coulombic efficiency, and infinite volume changes severely hinder their practical uses. Herein, we report that ethyl methyl carbonate (EMC)- and fluoroethylene carbonate (FEC)-based electrolytes significantly enhance the energy density and cycling stability of Li-metal batteries (LMBs). In LMBs, using commercialized Ni-rich Li[Ni0.6Co0.2Mn0.2]O2 (NCM622) and 1 M LiPF6 in EMC/FEC = 3:1 electrolyte exhibits a high initial capacity of 1.8 mA h cm–2 with superior cycling stability and high Coulombic efficiency above 99.8% for 500 cycles while delivering a unprecedented energy density. The present work also highlights a significant improvement in scaled-up pouch-type Li/NCM622 cells. Moreover, the postmortem characterization of the cycled cathodes, separators, and Li-metal anodes collected from the pouch-type Li/NCM622 cells helped identifying the improvement or degradation mechanisms behind the observed electrochemical cycling.