Promoting polysulfide conversion by catalytic separator with LiNiPO4 and rGO hybrids for high performance Li–S batteries

Abstract

As a promising next-generation energy storage system, lithium–sulfur batteries (LSBs) have been the focus of much attention due to their high energy density and high theoretical specific capacity. However, the application of LSBs is still hindered by the “shuttle effect” of soluble lithium polysulfides (LiPSs) and their sluggish reaction kinetics. Herein, a novel strategy for suppressing the “shuttle effect” of LiPSs and facilitating the reaction kinetics is achieved using reduced graphene oxide (rGO) with incorporated polar LiNiPO₄ (LNPO) nanoparticles as a functional coating layer for the separator in LSBs. The synergy between polar LNPO nanoparticles and rGO endowed the cell with enhanced chemical adsorption for LiPSs and promoted the electrochemical kinetics. The cell with the LNPO/rGO-modified separator exhibited ultra-long cycling stability (629 mA h g⁻¹ at 1.5C after 1400 cycles) and a high areal capacity of 4.2 mA h cm⁻². Furthermore, the reaction mechanism and kinetics of LSBs were revealed by in situ X-ray diffraction (XRD) and catalytic kinetics measurement, while the enhanced chemical anchoring of LiPSs was demonstrated by density functional theory (DFT) calculations and UV-vis spectroscopy. This work provides a new approach for LSBs with ultra-long cycling life and high areal capacity.