Two birds with one stone: engineering siloxane-based electrolytes for high-performance lithium–sulfur polyacrylonitrile batteries

Abstract

Sulfurized polyacrylonitrile (SPAN) has attracted considerable interest for high-energy lithium–sulfur batteries owing to its high specific capacity and remarkable cyclic stability. However, common electrolytes fail to stabilize both the lithium (Li) metal anode and SPAN cathode, thus affecting their practical applications. Herein, a lightweight siloxane solvent-based electrolyte (below 1 g mL⁻¹) comprising 1.5 M lithium bis(fluorosuflonyl) imide (LiFSI) in dimethyldimethoxysilane (DMMS) has been designed for linking metallic Li and high-capacity SPAN cathode simultaneously. The weakly solvating DMMS electrolyte with a moderate salt concentration of 1.5 M not only allows a remarkable Li stripping/plating CE of 99.6% but also retards the dissolution of polysulfides. As a result, the assembled Li‖SPAN cells delivered a superior cyclic stability of 513 mA h g⁻¹ at 0.2 A g⁻¹ with 96.9% capacity retention after 300 cycles. Depth-profiling X-ray photoelectron spectroscopy results confirm the generation of an inorganic-rich inner layer in electrode–electrolyte interphases with trace DMMS decomposition in the outer layer, thus enabling uniform Li deposition. Density functional theory result suggests weak affinity between the DMMS solvent and polysulfides, which minimizes polysulfide shuttling. This study provides a new avenue to explore novel solvents to simultaneously stabilize metallic Li and SPAN cathodes.