Nitrogen-Doped graphene coated FeS2 microsphere composite as high-performance anode materials for sodium-ion batteries enhanced by the chemical and structural synergistic effect

Developing high-performance anode materials for sodium-ion batteries with high rate capability and long-term cyclability remains challenging. FeS2, one of the most potential candidates, is massively hindered by its intrinsically low electronic conductivity, poor ionic diffusivity, and severe volume change during cycling. Considering these issues, FeS2/nitrogen-doped graphene composite (FeS2/N-G) has been proposed, where in-situ growth of FeS2 microspheres among N-doped graphene are confined into a diameter of 1-3 mu m and coated with the intact and uniform N-doped graphene decoration. Through the kinetic analysis and first-principles calculations, the heterointerface between FeS2 and N-doped graphene is found to play an essential role in improving electronic conductivity and facilitating Na+ diffusion kinetics. The uniform N-doped graphene coating also helps sustain good structural stability, which is revealed in morphology evolution examination. Because of the chemical and structural synergistic effect, FeS2/N-G can realize the robust and fast sodium-ion storage with delivering a reversible capacity of 251.7 mAh g(-1) over 10,000 cycles at 5 A g(-1). The superior electrochemical performance and simple synthetic procedure of FeS2/N-G demonstrate the feasibility of applying FeS2/N-G as a potential anode material for sodium-ion batteries.