Hierarchical micro-composite assembled from Bi spheres and expanded graphite flakes as anodes for sodium-ion half/full cells with excellent comprehensive electrochemical performance

Abstract

Developing anode materials with both excellent comprehensive electrochemical performance and low cost is critical for the large-scale practical application of sodium-ion batteries. Herein, a novel hierarchical micro-composite assembled from Bi nano/submicron spheres and expanded graphite flakes (labelled as H-BiS/EGF) is fabricated by facile and scalable methods, using low-cost starting materials. As anodes for sodium-ion half cells, the H-BiS/EGF micro-composite exhibits a first coulombic efficiency of 85% with a reversible capacity of around 288 mAh g−1 at 0.5 A g−1, outstanding cycle stability (95% capacity retention for 17,300 cycles at 5 A g−1) and superior rate capability (228 mAh g−1 at 25 A g−1). The sodium-ion full cell, which was constructed with the H-BiS/EGF anode and the synthesized C coated Na3V2(PO4)3/rGO as the cathode, delivers a high energy density (180 Wh kg−1 at 1C) and good cycle performance (95.9% capacity retention after 600 cycles at 10C).