Insight into the Synergistic Effect of N, S Co-Doping for Carbon Coating Layer on Niobium Oxide Anodes with Ultra-Long Life

Multi-heteroatoms co-doped carbon coating can significantly enhance the electronic conductivity and mass transfer rate of the electrode materials due to the synergistic effect. In this study N, S co-doped carbon coating is introduced on the surface of niobium oxides (GNO@NSC) by using a convenient thiourea evaporation method. Theory calculations and experimental results confirm the synergistic effect of N, S co-doping in GNO@NSC composite. N, S co-doping not only enlarges the layer distance of the carbon materials but also leads to more activation sites for lithium storage; meanwhile, the introduction of the co-doping carbon layer on GNO significantly enhances the bonding interaction with GNO, leading to excellent structural stability and conductivity of the composite. As a result, the GNO@NSC composite possesses excellent structural reversibility, a large specific capacity, and high-rate performance. GNO@NSC nanowires deliver a highly reversible capacity of 288 mAh g(-1) and display excellent cycling stability, and its capacity retention is 78.9% after 6000 cycles at a high current density of 1 A g(-1). This study reveals the functional mechanism of N, S co-doped carbon coating and the origin of performance improvement of niobium oxides, which can be used for reference to design and develop relevant materials.