Synergistic Engineering of Defects and Heterostructures Enhance Lithium/Sodium Storage Properties of F-SnO2-x -SnS2-x Nanocrystals Supported on N,S-Graphene.

ABSTRACT

Phase engineering of the electrode materials in terms of designing heterostructures, introducing heteroatom and defects, improves great prospects in accelerating the charge storage kinetics during the repeated Li+ /Na+ insertion/deintercalation. Herein, a new design of Li/Na-ion battery anodes through phase regulating is reported consisting of F-doped SnO2 -SnS2 heterostructure nanocrystals with oxygen/sulfur vacancies (VO /VS ) anchored on a 2D sulfur/nitrogen-doped reduced graphene oxide matrix (F-SnO2-x -SnS2-x @N/S-RGO). Consequently, the F-SnO2-x -SnS2-x @N/S-RGO anode demonstrates superb high reversible capacity and long-term cycling stability. Moreover, it exhibits excellent great rate capability with 589 mAh g-1 for Li+ and 296 mAh g-1 at 5 A g-1 for Na+ . The enhanced Li/Na storage properties of the nanocomposites are not only attributed to the increase in conductivity caused by VO /VS and F doping (confirmed by DFT calculations) to accelerate their charge-transfer kinetics but also the increased interaction between F-SnO2-x -SnS2-x and Li/Na through heterostructure. Meanwhile, the hierarchical F-SnO2-x -SnS2-x @N/S-RGO network structure enables fast infiltration of electrolyte and improves electron/ion transportation in the electrode, and the corrosion resistance of F doping contributes to prolonged cycle stability.