Designing Cation–Solvent Fully Coordinated Electrolyte for High‐Energy‐Density Lithium–Sulfur Full Cell Based On Solid–Solid Conversion

Sulfur chemistry based on solid–liquid dissolution‐deposition route inevitably encounters shuttle of lithium polysulfides, its parasitic interaction with lithium (Li) anode and flood electrolyte environment. The sulfurized pyrolyzed poly(acrylonitrile) (S@pPAN) cathode favors solid‐solid conversion mechanism in carbonate ester electrolytes but fails to pair high‐capacity Li anode. Herein, we rationally design a cation‐solvent fully coordinated ether electrolyte to simultaneously resolve the problems of both Li anode and S@pPAN cathode. Raman spectroscopy reveals a highly suppressed solvent activity and a cation‐solvent fully coordinated structure (molar ratio 1:1). Consequently, Li electrodeposit evolves into round‐edged morphology, LiF‐rich interphase, and high reversibility. Moreover, S@pPAN cathode inherits a neat solid‐phase redox reaction and fully eliminated the dissolution of lithium polysulfides. Finally, we harvest a long‐life Li‐S@pPAN pouch cell with slight Li metal excessive (0.4 time) and ultra‐lean electrolyte design (1 μL mg S −1 ), delivering 394 Wh kg −1 energy density based on electrodes and electrolyte mass.