Facile synthesis of Cu7.2S4/RGO composites for an ultrastable and high-rate sodium storage anode

Metal sulfides with high capacity, morphology-controlled, and facile synthesis are considered as potential anodes for Na-ion batteries. However, the conductivity and structural stability of electrode materials are still hampered by its inherent low conductivity and obvious volume changes during cycling. Herein, Cu 7.2 S 4 nanoparticles anchored on reduced graphene oxide (Cu 7.2 S 4 /RGO) are successfully prepared by solvothermal and thermal processes. The product, Cu 7.2 S 4 /RGO-10, not only features optimized the amount of RGO , but also delivers a large reversible capacity (314.4 mAh g −1  at 2 A g −1 ), good cycling stability (with a capacity fading of 0.11% per cycle from 2nd to 400th) and excellent rate capability (209 mAh g −1  at a high current density of 20 A g −1 ), making it the promising anode material for SIBs . Kinetics analysis clarifies that the high ion diffusion coefficient and the pseudo-capacitance contribution are important reasons for the superior performance. As expected, sodium-ion full cells (Cu 7.2 S 4 /RGO//Na 3 V 2 (PO 4 ) 3 ) also show good cycling stability.