Nitrogen and Sulfur Co-Doped Graphene Nanosheets to Improve Anode Materials for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) attract more attention because of sodium's abundant availability, affordable price, and potential to be an effective anode material. Meanwhile, carbon-based materials provide the most promising anode materials. Because of the large radius of sodium ions, SIBs do not exhibit favorable electrochemical performance. Introducing heteroatoms into the carbon-lattice is an effective strategy to enlarge the interlayer space of carbon-based materials which can improve carbon's electrochemical performance. In addition, anode materials with a surface-induced capacitive process can enhance the SIB's electrochemical performance because its capacitive process increases the kinetics of ion diffusion. Here, we describe an SIB's anode material containing nitrogen and sulfur co-doped graphene sheets [denoted as poly(2,5-dimercapto-1,3,4-thiadiazole) (PDMcT)/reduced graphene oxide (RGO)] which are synthesized via carbonization of PDMcT polymerized on the surface of GO. PDMcT/RGO exhibited high capacities (240 mA h g at 500 mA g), improved rate performance (144 mA h g at 10 A g), and good cycling stability (153 mA h g after 5000 cycles at 5000 mA g). These unique results are attributed to the enlarged interlayer spacing and electronic conductivity from the heteroatoms which facilitate the sodium ion's insertion and electron transport. These results represent that PDMcT/RGO is a great potential anode material for SIBs.