Carbon-doped Cu1.96S/C hollow microspheres for high-rate sodium storage performance

Currently, transition metal sulfides (TMSs) have attached great attention of researchers due to their various structural types and outstanding electrochemical activities. As one of typical TMSs, Cu _x S materials owes advantages of abundant reserves, lower material cost, excellent electronic conductivity when applied for sodium ion batteries (SIBs). However, Cu _x S materials inevitably suffer from the differentiation and volume expansion caused by the transformation reaction, which leads to poor electrochemical performance (especially the inferior cycling stability) in low voltage charge-discharge process. Herein, we utilized a facile way to synthesize Cu _1.96 S/C hollow microspheres by using a carbon-doped strategy. The Cu _1.96S/C electrode was tested with optimized cut-off voltage range, demonstrating a remarkable reversible capacity of 351 mAh g ⁻¹ after 1500 cycles at 20 A g ⁻¹ current density, along with an average coulombic efficiency close to 100%. The outstanding rate performance and long-term cyclic performance of Cu _1.96 S/C electrode can be attributed to its carbon doped structure and pseudocapacitance behavior. These findings suggest that Cu _1.96S/C composites exhibit the potential to enhance the high-rate capability of SIBs for industrial applications.