Improving sodium ion storage performance by heteroatom strategy with nitrogen and sulfur doping carbon sheets

Abstract

Carbon materials have been researched as a promising candidate anode for sodium-ion batteries (SIBs) because of its high structure stability and inexpensive. Whereas, the low specific capacity and sluggish transport mechanism hampers its practical uses. In here, we develop a facile heteroatom doping method to obtain N, S co-doped carbon sheets (NS-CS). Specifically, carbon nanosheet structure can effectively accelerate Na⁺ transport rate. Meanwhile, the abundant N, S heteroatom doping can highly boost the adsorption of Na⁺ on the surface of NS-CS. When served as anodes for SIBs, the NS-CS could show a senior specific capacity of 326.1 mAh g⁻¹ at 0.1 A g⁻¹, an admirable rate capability of 165.7 mAh g⁻¹ at 5 A g⁻¹, and an excellent long-life cycling stability at 5 A g⁻¹ (86% capacity retention after 3000 cycles). The density functional theory (DFT) calculations prove the N and S introducing in carbon skeleton avails the adsorption of Na⁺ during the sodiation procedure, which is explainable for the electrochemical performance improvement. Moreover, the galvanostatic intermittent titration technique (GITT) illustrates the fast Na⁺ diffusion kinetics of NS-CS.