A Hierarchical Hybrid MXenes Interlayer with Triple Function for Room-Temperature Sodium-Sulfur Batteries

Room temperature sodium sulfur (RT Na-S) batteries with high theoretical energy density and low cost have recently gained extensive attention for potential large-scale energy storage applications. However, the shuttle effect of sodium polysulfides is still the main challenge that leads to poor cycling stability, which hinders the practical application of RT Na-S batteries. Herein, a multifunctional hybrid MXene interlayer is designed to stabilize the cycling performance of RT Na-S batteries. The hybrid MXene interlayer comprises a large-sized Ti3C2Tx nanosheets inner layer followed by a small-sized Mo2Ti2C3Tx nanoflake outer layer on the surface of the glass fiber (GF) separator. The large-sized Ti3C2Tx nanosheet inner layer provides an effective physical block and chemical confinement for the soluble polysulfides. The small-sized Mo2Ti2C3Tx outer layer offers an excellent polysulfide trapping capability and accelerates the reaction kinetics of polysulfide conversion, due to its superior electronic conductivity, large specific surface area, and Mo-rich catalytic surfaces. As a result, RT Na-S batteries with this hybrid MXene interlayer modified glass fiber separator deliver a stable cycling performance over 200 cycles at 1 C with an enhanced capacity retention of 71%. This unique structure design provides a novel strategy to develop 2D material-based functional interlayer for high-performance metal-sulfur batteries.