Engineering towards stable sodium metal anodes in room temperature sodium-sulfur batteries: challenges, progress and perspectives

Room temperature sodium-sulfur batteries (RT Na-S batteries) are regarded as promising power sources particularly for grid-scale energy storage, owing to their high theoretical capacity and low-cost electrode materials. Currently, numerous studies have focused on the S-cathode. Moreover, it is identified that the dissolution/shuttle of sodium polysulfides (NaPSs) in ether-based electrolytes and the grievous nucleophilic reaction in ester-based electrolytes are the most pivotal challenges for RT Na-S batteries. Nevertheless, the practical advancement of RT Na-S batteries is equally hampered by significant obstacles associated with Na anodes. This review starts with the discussion on the origin, cell chemistries and principles of RT Na-S batteries. Afterwards, severe challenges confronted by Na anodes especially in RT Na-S batteries are concluded. Then, we provide an exhaustive overview of the present stabilization strategies for Na anodes in polysulfides-rich environments, including electrolyte, interface and separator. Moreover, theoretical investigations to foundational data concerning stable NaPSs, surface structure, charge transfer kinetics and sodium deposition/dissolution dynamics in polysulfide-rich electrolytes are summarized. Finally, this article also provides suggestions on underscoring fundamental scientific challenges and considerations necessitating attention in order to promote comprehensive development of RT Na-S batteries.