FeSb/FeS heterostructures anchored on exfoliated graphite nanosheets as an advanced anode for sodium-ion batteries

Abstract

Research on sodium-ion battery (SIB) anodes has made significant progress, but there are still considerable challenges in developing materials that combine fast charge–discharge capabilities with long cycling stability. To overcome this challenge, guided by theoretical calculations, this study designed and synthesized a multi-phase FeSb/FeS nanocomposite anchored on exfoliated graphite nanosheets (denoted as FeSb/FeS-G). The material is prepared through a simple and efficient two-step process involving calcination and ball milling. The results show that FeSb/FeS-G exhibits better electrochemical performance compared to FeSb/FeS. Specifically, at a current density of 6 A g⁻¹, the initial discharge capacity of FeSb/FeS-G is 269.88 mA h g⁻¹, and after 900 cycles, it retains a reversible capacity of 233.57 mA h g⁻¹, with a capacity retention of 86.55%. Both theoretical calculations and experimental results indicate that the incorporation of exfoliated graphite not only effectively accelerates the Na⁺ diffusion rate but also significantly enhances the structural stability of the material, thereby prolonging the battery's cycling life. Notably, the full cell assembled with a Na₃V₂(PO₄)₃ cathode (Na₃V₂(PO₄)₃‖FeSb/FeS-G) retained 94.53% of its capacity after 20 cycles at a current density of 0.1 A g⁻¹. Through a simple two-step preparation process, this study successfully obtained FeSb/FeS-G composite materials that combine high capacity and long cycle life at high current densities, providing new insights and approaches for the design and development of advanced SIB anode materials.