Insights into the improved electrochemical performance of lithium-sulfur battery with free-standing SiO2/C composite nanofiber mat interlayer

A free-standing SiO2/C composite nanofiber mat (FS-SiO2/C-CNFM), prepared by electrospinning with heat treatments, is used as a multifunctional interlayer on the cathode side to suppress the polysulfide shuttle effect in lithium-sulfur batteries. The polysulfide adsorption and conversion capabilities of the interlayer are evaluated by a static polysulfide adsorption test and an electrochemical conversion test in an FS-SiO2/C-CNEM symmetric cell. The effects of the FS-SiO2/C-CNEM on the electrochemical properties of the lithium-sulfur batteries are studied by cyclic voltammetry, galvanostatic charge-discharge cycle tests, and electrochemical impedance spectroscopy. The FS-SiO2/C-CNEM interlayer significantly improves the specific capacity, long-cycling stability, and self-discharge behavior of the lithium-sulfur batteries. The cell with the FS-SiO2/C-CNEM interlayer has an initial discharge capacity of 1304 mA h g(-1) and retains 934 mA h g(-1) over 50 cycles at 0.1 C, corresponding to a capacity retention of 72% with 100% Coulombic efficiency. The improved properties are attributed to the suppression of the shuttle effect and the high reutilization of the trapped polysulfides. The adsorption/conversion mechanisms of the polysulfides of the FS-SiO2/C-CNEM interlayer are further elucidated from the results of ex situ X-ray photoelectron spectroscopy (XPS) and field-emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray spectroscopy (EDS) analysis.