V2O3-decorated carbon nanofibers as a robust interlayer for long-lived, high-performance, room-temperature sodium–sulfur batteries

We developed a V2O3 nanoparticle–decorated carbon nanofiber (V2O3@CNF) interlayer for room-temperature sodium–sulfur batteries (RT/NaSBs), inserted on the cathode side of the separator to inhibit the shuttling of sodium polysulfides, i.e., their migration to the sodium anode, and thus realize high-performance RT/NaSBs. The V2O3 adsorbs polysulfides and catalytically promotes polysulfide trapping, while the CNFs provide conductive channels that facilitate ion transport and accelerate reaction kinetics. The electrochemical performance of the resulting Na–S cells are superior to those of cells with a CNF interlayer and without an interlayer. A cell with a V2O3@CNF interlayer utilizes almost 70% of its active material at 0.1C, while cells with a CNF interlayer and without an interlayer utilize 54 and 33%, respectively. It demonstrates superior rate performance, achieving a capacity of 268 mA h g−1 at 2.0C, and its diffusion coefficient (∼10−11cm2 s−1) is an order of magnitude higher than those of cells with a CNF interlayer or without an interlayer (∼10−12 cm2 s−1), indicating fast reaction kinetics. Moreover, it delivers a discharge capacity of 406 mA h g−1 after 500 cycles at 1.0C with a high coulombic efficiency of 100%. Even at a high C-rate of 2.0C, the capacity of the cell decays at a low rate of 0.076% per cycle over 1000 cycles, indicating exceptional capacity retention. The outstanding electrochemical performance is mainly attributed to the effective sodium polysulfide confinement, improved active material utilization, and accelerated reaction kinetics associated with the V2O3@CNF interlayer.