Anionic Se-Substitution toward High-Performance CuS_{1- x} Se_x Nanosheet Cathode for Rechargeable Magnesium Batteries

Rechargeable magnesium batteries (rMBs) are promising as the most ideal further energy storage systems but lack competent cathode materials due to sluggish redox reaction kinetics. Herein, developed is an anionic Se-substitution strategy to improve the rate capability and the cycling stability of 2D CuS_{1- x} Se_x nanosheet cathodes through an efficient microwave-induced heating method. The optimized CuS_{1- x} Se_x (X = 0.2) nanosheet cathode can exhibit high reversible capacity of 268.5 mAh g^-1 at 20 mA g^-1 and good cycling stability (140.4 mAh g^-1 at 300 mA g^-1 upon 100 cycles). Moreover, the CuS_{1- x} Se_x (X = 0.2) nanosheet cathode can deliver remarkable rate capability with a reversible capacity of 119.2 mAh g^-1 at 500 mA g^-1 , much higher than the 21.7 mAh g^-1 of pristine CuS nanosheets. The superior electrochemical performance can be ascribed to the enhanced reaction kinetics, enriched cation storage active sites, and shortened ion diffusion pathway of the CuS_{1- x} Se_x nanosheet. Therefore, tuning anionic chemical composition demonstrates an effective strategy to develop novel cathode materials for rMBs.