Enabling high-performance room-temperature sodium/sulfur batteries with few-layer 2H-MoSe2 embellished nitrogen-doped hollow carbon spheres as polysulfide barriers

Abstract

Room-temperature sodium/sulfur (RT-Na/S) batteries are of considerable interest for next-generation energy storage systems because of their earth-abundant electrode materials, low cost, and high energy density. However, the widespread application of RT-Na/S batteries is severely hindered by the dissolution, shuttling, and sluggish kinetics conversion of sodium polysulfides (SPSs) during electrochemical processes. Herein, we prepare a powerful functional separator to suppress the shuttle effect by directly coating 2H-MoSe₂/nitrogen-doped hollow carbon spheres/graphene oxide (2H-MoSe₂/N-HCS/GO) onto a standard glass fiber separator. The rational design of the functional separator effectively suppresses the migration of SPSs and promotes the conversion reactions of SPSs. Meanwhile, N-HCS decorated with few-layer 2H-MoSe₂ nanoflakes is used as the sulfur host. As verified by a series of density functional theory calculations and experimental characterization, a RT-Na/S battery with a functional separator and a high sulfur content of 71.4 wt% delivers a high discharge capacity of 787 mA h g⁻¹ at 0.1C after 100 cycles and exhibits outstanding long-term cycling stability (484 mA h g⁻¹ at 0.5C after 500 cycles), with a low capacity fading rate of 0.077% per cycle. This study demonstrates an effective strategy to develop functional separators for shuttle suppression and provides a promising path for high-performance RT-Na/S batteries.