Hierarchically Designed Nitrogen-Doped MoS/Silicon Oxycarbide Nanoscale Heterostructure as High-Performance Sodium-Ion Battery Anode.

Molybedenum disulfide (MoS) is regarded as a promising anode material for next-generation sodium-ion batteries (SIBs) owing to its high theoretical capacity. However, its low conductivity, large volume changes, and undesirable phase transformation hinder its practical applications. In this study, we synthesize a hierarchically designed core-shell heterostructure based on nitrogen-doped MoS/C and silicon oxycarbide (SiOC) (N-MoS/C@SiOC) via the facile pyrolysis of a suspension of an N-MoS/polyfurfural precursor in silicone oil. The nitrogen doping in a two-dimensional MoS structure with carbon incorporation leads to the enlargement of the interlayer spacing and enhancement of the electronic conductivity and mechanical stability, which allows the facile, highly reversible insertion and extraction of sodium ions upon cycling. Further, the nanoscale SiOC shell with surface capacitive reactivity provides a conductive pathway, preventing unfavorable side reactions at the electrode/electrolyte interface and acting as a structure-reinforcing buffer against severe volume expansion issues. As a result, the N-MoS/C@SiOC composite exhibits high reversible capacity (540.7 mAh g), high-capacity retention (>100% after 200 cycles), and excellent rate capability up to 10 A g. The simple hierarchical core-shell design strategy developed in this study allows for the fabrication of high-performance metal sulfide anodes as well as other high-capacity anode materials for energy storage applications.