With the invention of the high-temperature sodium-sulfur batteries, Na metal-based chemistries remained in oblivion. However, due to increasing concerns over the safety of the high-temperature sodium-sulfur batteries, Na metal anode is revived in recent years with the ever-growing demands for high energy density and improved safety. Despite that current Na metal anode still lacks high-reversibility, efficiency, and room-temperature stability due to limited or no control over the interfacial chemistry of the Na metal anode. The electrochemical reduction of Na+ ions is accompanied by the inevitable reduction of organic species, which leads to the growth of the solid-electrolyte interphase (SEI) with Na-deposits. The SEI is inherently unstable due to the localized fluctuations in its chemical and physical properties. A deep understanding of the challenges associated with the SEI's localized interfacial chemistry is of prime importance towards developing the practical Na metal anodes for RT-Na/S batteries. This mini-review highlights critical challenges in developing a stable Na metal anode and further sheds light on its mechanistic aspects. In addition to that, novel approaches to precisely tune the interphase's physicochemical properties are highlighted to pave path for developing a stable and long-life Na-metal anode for RT-Na/S batteries.
Prof. Vipin Kumar