Polymer electrolytes for unlocking the potential of room-temperature sodium-sulfur batteries: a review

Room-temperature sodium-sulfur (RT Na-S) batteries are gaining attention for large-scale energy storage due to the high abundance of sodium, low cost of the constituents, and high energy density. However, challenges such as dendrite formation, polysulfide shuttling, interfacial instability, and safety concerns remain major hurdles to the commercialization of this battery chemistry. Polymer electrolytes offer an effective pathway to address these issues by combining the benefits of liquid and solid systems. Studies on polymer electrolytes for RT Na-S batteries have reported ionic conductivities in the range of 10 –4 -10 −2 S cm⁻ 1 , electrochemical stability windows exceeding 3.5 V, and sufficient Na⁺ transport to support good reversible capacities and prolonged cycling. Recent studies show that higher liquid loading, functional fillers, and crosslinked polymer networks can enhance ionic conductivity while limiting dendrite growth and polysulfide migration. Despite noteworthy advancement over the last decade, challenges continue in balancing high ionic conductivity with controlling polysulfide migration, ensuring long-term stability, and achieving scalability. More systematic studies are needed to clearly link polymer structure with sodium-ion transport and polysulfide confinement. This review outlines preparation techniques for polymer electrolytes and emerging strategies, particularly multifunctional polymer designs and interface engineering, for advancing practical RT Na-S batteries. It also discusses key polymer hosts and functional additives that improve conductivity and enhance overall battery stability, while connecting electrolyte structure, fabrication methods, and electrochemical performance to overall battery efficiency.