Sulphur-doped carbon nanosheets derived from biomass as high-performance anode materials for sodium-ion batteries

Sodium-ion batteries (SIBs) have attracted enormous attention as a promising alternative to lithium-ion batteries in recent years due to the richness and low cost of sodium (Na) resource. The SIBs performance is essentially determined by the electrode materials applied. Due to the difficulty of intercalating the large Na ions, developing competent anode materials (AMs) has become particularly fascinating and critical for SIBs. Herein, three-dimensional (3D) scaffolding framework of carbon nanosheets heavily-doped with sulphur (S–CNS) has been fabricated from plant biomass using a facile thermal method. The S–CNS affords an ultrahigh reversible capacity of 605 mAh g−1 at 50 mA g−1, high rate performance 133 mAh g−1 at 10 A g−1, and long-term cycling stability at 5 A g−1 (~94% retention upon 2000 cycles). These values are among the best results based on AMs of doped carbon derived from biomass ever reported. Moreover, we demonstrate that such S-doped carbon materials with competent electrochemical properties can be easily produced from diverse plant wastes using this method. This work thus introduces a universal strategy and a fertile ground to produce high-performance AMs by using the mixture of biomass and S powder, which may hold considerable potential for scalable production of commercial SIBs.