Remedies for Polysulfide Dissolution in Room-Temperature Sodium–Sulfur Batteries

Rechargeable room-temperature sodium–sulfur (RT-NaS) batteries represent one of the most attractive technologies for future stationary energy storage due to their high energy density and low cost. The S cathodes can react with Na ions via two-electron conversion reactions, thus achieving ultrahigh theoretical capacity (1672 mAh g−1) and specific energy (1273 Wh kg−1). Unfortunately, the sluggish reaction kinetics of the nonconductive S, severe polysulfide dissolution, and the use of metallic Na are causing enormous challenges for the development of RT-NaS batteries. Fatal polysulfide dissolution is highlighted, important studies toward polysulfide immobilization and conversion are presented, and the reported remedies in terms of intact physical confinement, strong chemical interaction, blocking layers, and optimization of electrolytes are summarized. Future research directions toward practical RT-NaS batteries are summarized.