Critical Challenges and Recent Advances Toward Practical Room-Temperature Sodium–Sulfur Batteries

Room-temperature sodium–sulfur (RT Na–S) batteries are gaining renewed interest as a cost-effective, high-energy-density candidate for next-generation storage, owing to their high theoretical specific energy (1274 Wh kg−1) and the earth abundance of sodium. However, their practical application continues to be hampered by persistent challenges such as the polysulfide shuttle effect, uncontrolled growth of sodium (Na) dendrites and electrolyte-induced interfacial instability. This review summarizes recent progress in several key areas: cathode design (including defect engineering, single-atom catalysts, heterostructures), anode interfacial regulation (through SEI/CEI engineering and additive chemistry), and electrolyte formulation (notably localized high-concentration electrolytes and solvation-structure tuning). Although promising results have been achieved at the laboratory scale, critical challenges remain for practical deployment, particularly under high-sulfur-loading and lean-electrolyte conditions, along with fundamental interfacial issues inherent to all-solid-state battery architectures.