Anode-Free Lithium-Sulfur Batteries with a Rare-Earth Triflate as a Dual-Function Electrolyte Additive.

Anode-free lithium-sulfur batteries feature a cell design with a fully lithiated cathode and a bare current collector as an anode to control the total amount of lithium in the cell. The lithium stripping and deposition are key factors in designing an anode-free full cell to realize a practical cell configuration. To realize effective anode protection and achieve a good performance of the anode-free full cell, manipulation of the electrolyte chemistry toward the modification of the solid-electrolyte interphase on the anode is considered a feasible approach. In this study, the use of neodymium triflate, Nd(OTf), as a dual-function electrolyte additive is demonstrated to promote homogeneous catalysis on the cathode conversion reactions and the anode stabilization. Nd(OTf) not only facilitates the conversion reaction by promoting the polysulfide adsorption but also effectively protects the lithium-metal anode and stabilizes the lithium stripping and deposition during cycling. With this electrolyte modification, both Li∥LiS half cells and Ni∥LiS anode-free full cells support a high areal capacity of 5.5-7.0 mA h cm and maintain a high Coulombic efficiency of 94-95% during cycling.