Methyl Tert‐Butyl Ether Induced Synergistic Engineering of Inner and Outer Solvation Shell for Practical Lithium–Sulfur Batteries

Abstract The electrolyte‐mediated electrochemistry of Li–S batteries dictates that electrolyte modifications regarding solvation structures of lithium polysulfides (LiPSs) are the core concerns. To accommodate the conversion kinetics of LiPSs and interfacial stability of Li‐metal anode upon lean electrolyte and high sulfur loading, a cosolvent of methyl tert‐butyl ether (MTBE) is screened for DME‐based electrolyte. The low solvating capability of MTBE enables it to principally construct the outer protective solvation shell of LiPSs. MTBE also promotes the incorporation of DME and anion into the inner solvation shell, facilitating effective solvation of LiPSs and a stable interfacial structure of the Li‐metal anode. Based on mutually corroborative measurements and theoretical calculations, the superiorities of optimized LWSE electrolyte from MTBE are firmly verified in protecting LiPSs against Li‐metal corrosion and improving interfacial stability of Li anode and electrochemical kinetics. In situ Raman/XRD results further support that LiPSs shuttling is greatly suppressed, and highly reversible electrochemical conversions of sulfur species involving a “α‐sulfur to α‐sulfur” mechanism are corroborated in LWSE. The physicochemical merits of LWSE enable pouch‐type Li–S full cell (N/P: 1.3) to achieve a high energy density of 385.3 Wh kg −1 at an E/S ratio of 3.0 µL mg −1 , and a high loading of 4.8 mg s cm −2 .