Synthesis and characterization of a hierarchically structured three-dimensional conducting scaffold for highly stable Li metal anodes

Herein, the lithiophilicity of Li₂O and the capillary action-induced absorption of molten Li are employed to fabricate a hierarchically structured three-dimensional (3D) Li metal electrode comprising Li₂O-coated Cu foam (Li₂O@Cu foam), the unique structural characteristics of which allow one to suppress Li dendrite formation and confine Li movement within the foam matrix. The lithiophilicity of Li₂O@Cu foam is ascribed to the occurrence of in situ interfacial reactions between Li and Cu oxides formed on the surface of Cu foam, and the formation of the Li₂O@Li@Cu hierarchical structure is shown to significantly stabilize the interfacial characteristics of the Li metal anode even in harsh electrochemical environments. In addition to being lithiophilic, Li₂O@Cu foam allows for homogeneous plating and stripping of Li ions, since the nucleation overpotential of Li₂O toward Li ions is low, e.g., the lowest overpotential of 13 mV is observed during Li plating/stripping at 1.0 mA cm^-2. At a total capacity of 1.0 mA h cm^-2, Li₂O@Cu foam exhibits a coulombic efficiency of >99.0% over 150 cycles at 0.5 mA cm^-2, whereas a slightly smaller value of ∼97.5% is observed for 100 cycles at 5 mA cm^-2.