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 μm 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.