S-Doped N-Rich Carbon Nanosheets with Expanded Interlayer Distance as Anode Materials for Sodium-Ion Batteries

2D composites with S doping into N-rich carbon nanosheets are fabricated, whose interlayer distance becomes large enough for Na+ insertion and diffusion. The large surface area and stable structure also provide more sites for Na+ adsorption, leading to high Na-storage capacity and excellent rate performance. More-over, Faradaic reactions between Na+ and tightly bound S is beneficial for further improvement of Na-storage capacity.