Nitrogen-Doped Graphene/Cellulose Fibers Double-Coated Asymmetric Separator for High-Performance Lithium-Sulfur Batteries

Abstract

Lithium-Sulfur (Li─S) batteries have the advantages of low cost and high capacity, but the cathode shuttle effect and the growth of anode lithium dendrites have hindered their development. Among the various modification strategies, separator modification offers a promising approach to address issues on both anodes and cathodes. In this study, a bifunctional asymmetric polypropylene (PP) separator is modified with nitrogen-doped reduced graphene oxide (N–rGO) on the cathode side and cellulose fibers (CF) on the anode side to address the challenges associated with both electrodes. CF effectively promotes the uniform deposition of lithium metal and significantly inhibits the growth of lithium dendrites. In addition, N–rGO with a porous structure and nitrogen-doped active sites can not only suppress lithium polysulfide shuttling by physical and chemical adsorption but also catalyze the kinetics of the redox reaction, leading to an increased specific capacity of the battery. The Li─S battery incorporating N–rGO@PP@CF separator exhibits an impressive specific capacity of 1294 mAh g⁻¹ at a current rate of 1 C, with a remarkably low average capacity decay of 0.076% per cycle over 500 cycles. The synergistic effect between CF and N–rGO modification on asymmetric separators provides a promising guideline for developing high-performance Li─S batteries.