Lithium phosphorus oxynitride as an efficient protective layer on lithium metal anodes for advanced lithium-sulfur batteries

Developing high-energy-density Li-S batteries are highly promising for next-generation electrochemical energy storage. The unstable solid electrolyte interphase (SEI) formed on the Li metal anode and the subsequent notorious growth of Li dendrites during the cycle inevitably plague the practical application in the field. Herein, a facile and mass-produced method to modify the Li metal anode is proposed by establishing a dense and homogenous LiPON coating on the Li metal anode via nitrogen plasma-assisted deposition of electron-beam reaction evaporation. This method enables a high deposition rate up to 66 nm min-1. For Li metal, the LiPON coating serves as a highly ionic conductive, chemically stable and mechanically robust protective layer, which suppresses the corrosion reaction with organic electrolytes and promotes uniform Li plating/stripping, thus enabling a stable and dendrite-free cycling of the symmetric Li metal cells for over 900 cycles under a current density up to 3 mA cm-2. Using the LiPON-coated Li as anode, the Li-S pouch cell (sulfur loading: 7 mg cm-2) was obtained with a specific energy density of ~300 Wh kg-1, a relatively stable Coulombic efficiency of ~91% and an extended lifespan of over 120 cycles with respect to 1.0 Ah capacity retention. Our approach could lead to the practical application of high-energy-density Li-metal-based batteries.