Solvation‐Hierarchy Electrolyte for Balancing Kinetics and Stability in Sodium–Sulfur Batteries

ABSTRACT Room‐temperature sodium–sulfur batteries hold immense promise for next‐generation energy storage, while hindered by the dilemma of sodium polysulfide (NaPS) shuttling and redox kinetic. Here, we propose a solvation hierarchy strategy for sodium–sulfur batteries to reconcile the intrinsic trade‐off between polysulfide confinement and reaction kinetics. The solvation hierarchy strategy includes the strong solvating, moderate solvating and weak solvating electrolyte, which establishes a tailored solvation environment that sterically excludes polysulfides to mitigate shuttling, while concurrently inducing a metastable state that lowers the desolvation energy barrier, promoting rapid charge transfer. The moderate solvating sec‐butyl ether (SBE) distinguished by its symmetric α‐methyl steric hindrance is chosen, compared to the highly solvating 1,2‐dimethoxyethane (DME) and the weakly solvating ethyl butyl ether (BEE). The designed solvation‐hierarchy electrolyte breaks the trade off in kinetic and stability, enabling a capacity decay rate of 0.015% per cycle after 800 cycles at 1C. Furthermore, the system demonstrates robust stability at practical conditions of high sulfur loadings of 6.8 mg cm − 2 and lean electrolyte of 5.1 µL mg − 1 and is also validated in pouch cell configurations. These findings highlight the efficacy of solvating hierarchy to balance the stability and kinetic dilemma, offering a valuable perspective for advancing high‐energy‐density metal‐sulfur batteries.