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 mgS ⁻¹ ), delivering 394 Wh kg⁻¹ energy density based on electrodes and electrolyte mass.