Realizing Spherical Lithium Deposition by In Situ Formation of a Li₂S/Li–Sn Alloy Mixed Layer on Carbon Paper for Stable and Safe Li Metal Anodes

Abstract

Uncontrollable formation of Li dendrites and volume expansion have always been serious obstacles to the practical application of Li metal anodes. Three-dimensional (3D) frameworks are proven to accommodate Li to suppress volume expansion, but the lithiophobic surface tends to cause uncontrollable formation of Li dendrites. Here, uniform SnS₂ nanosheets are coated on the carbon paper (SnS₂@CP) skeleton and then transformed into a mixed layer of Li₂S/Li-Sn after lithiation. Under the joint action of the lithiophilic Li-Sn alloy and low-diffusion energy barrier Li₂S, the dual effects of strong adsorption and rapid diffusion of Li are realized. As a result, Li deposits homogeneously within the whole framework; as the plating amount increases, dendrite-free spherical Li is demonstrated, and the thickness of the electrode stays almost unchanged even at a high areal capacity of 10 mA h cm^-2. The SnS₂@CP electrodes present an ultralow nucleation overpotential (ca. 4 mV), high Coulombic efficiency (above 96.6% for more than 450 cycles), and stable cycle life (>1500 h), indicating that the 3D framework with the Li₂S/Li-Sn alloy mixed coating has excellent lithiophilicity and fast Li transport kinetics, thus effectively inhibiting the formation of Li dendrites. All the findings give new insights into the design strategy for stable and safe Li metal anodes.