Graded Solvation‐Structure Electrolyte for Synergistic Polysulfide Confinement and Interfacial Stabilization in Potassium‐Sulfur Batteries

Potassium‐sulfur (K‐S) batteries are promising candidates for high‐energy‐density and cost‐effective energy storage system, yet their practical deployment is hindered by poor cycling stability arising from severe potassium polysulfides (KPSs) shuttle effect and interfacial instability. Herein, we report a moderately solvating electrolyte (MSE) based on graded electrolyte design strategy to achieve an optimal balance between KPSs confinement, K‐metal stabilization, and redox kinetics. By leveraging the high polarity of tetraethylene glycol dimethyl ether, we ensure efficient salt dissociation and rapid KPSs redox kinetics, while a 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl ether‐rich outer solvation environment reinforces interfacial integrity and suppresses parasitic reactions. This graded solvation‐structure engineering facilitates a homogeneous K plating/stripping and promotes the formation of an inorganic‐rich, mechanically robust solid electrolyte interface. Consequently, the MSE facilitates stable K─S redox chemistry, delivering excellent cycling stability over 1000 cycles at 0.5 A g −1 . Furthermore, X‐ray photoelectron spectroscopy and in‐situ Raman spectroscopy analyses reveal that the reversible cleavage and reformation of C–S and S–S bonds within sulfurized polyacrylonitrile enable highly reversible K–S redox chemistry. This work provides new insights into electrolyte engineering for high‐performance K‐S batteries and offers a viable pathway toward safe and durable K‐based energy storage systems.