Nitrogen-doping of graphene enhancing sodium storage of SnO2 anode

Currently, challenges are still pervasive in developing excellent new materials for sodium-ion batteries (SIBs). In this work, we design SnO2/nitrogen-doped graphene (SnO2/NG) composites for SIBs. The SnO2/NG anodes with the optimal nitrogen-doping level exhibit enhanced reversible capacities and rate capabilities over undoped anodes. More importantly, the results reveal that the pyridinic-N is the main contributor to excellent cycling capacity of SnO2/NG. Consequently, the resultant SnO2/NG composite with higher content of pyridinic-N (1.97%) delivers outstanding reversible capacity of 409.6 mAh g−1 at 50 mA g−1 when the cycling numbers increase to 100 cycles, and it also presents superior rate capabilities of 416.5, 366.9, and 318.7 mAh g−1 at 200, 400, and 800 mA g−1, respectively. Furthermore, the conspicuous improvement of electrochemical performance of SnO2/NG is rooted in its high Na+ diffusion coefficient and small electrochemical reaction polarization. Our strategies might allow development of new avenues for the design of advanced electrode materials in SIBs.