Stabilized Li metal anode with robust C-Li3N interphase for high energy density batteries

Abstract

The combination of commercial high-voltage cathode and a thin lithium metal anode has emerged as a promising approach to realize rechargeable high energy density lithium batteries. However, abundant challenges, including huge volume change of Li metal and its severe side reactions with electrolyte for wide electrochemical potential window, hamper the practical application of lithium metal anode in high energy density batteries. In this work, we reported a Li/graphene composite electrode with in situ formed robust C/Li3N interphase (Li/graphene-C/Li3N electrode). Stabilized by the graphene framework, the electrode can endure large volume change during lithium stripping/plating cycles and realize stable cycling. The Li3N protection layer can not only help the composite electrode to avoid the direct physical contact between active metallic lithium and electrolyte, and suppress the side reactions between them, but also help to homogenize Li+ diffusion and plating/stripping behaviors due to its high ionic conductivity. As a result, the composite structure and electrochemical interphase stability enable superior electrochemical performance of the Li/graphene-C/Li3N electrodes. As a demonstration, the Li/graphene-C/Li3N symmetric cell displayed a low and stable overpotential for more than 1000 hours at 1 mA cm−2 and 1 mAh cm−2. LCoO2||Li/graphene-C/Li3N cell delivered a high energy density of 694.05 Wh kg−1 in the working potential range between 2.8 V and 4.6V and displayed high Coulombic efficiency of over 99% for more than 150 cycles, showing promising for practical high energy density lithium metal batteries.