Copper sulfide for high-rate and long-life sodium storage through conversion–displacement chemistry

A conversion–displacement chemistry is reported in CuS that inherits the high capacity of the conversion reaction and the excellent reversibility of displacement, enabling CuS to deliver high-capacity, high-rate and long-life sodium storage properties. • Copper sulfide hollow nanospheres were synthesized via facile solvothermal and subsequent annealing methods. • Copper sulfide electrodes deliver high-rate and long-life sodium storage properties. • Electrochemical Na + displacement reaction in copper sulfide anode for sodium-ion batteries is proposed for the first time. For the displacement process, Cu ions in the S 2− based sub-lattices are just electrochemically displaced by Na + , which does not involve lattice reconfiguration and collapse. Transition metal sulfides based on multielectron conversion chemistries promise substantially high capacity for sodium-ion batteries (SIBs). However, significant volume changes and drastic structural reorganization caused by breaking bonds of the parent phase and reforming completely different compounds pose challenges to their cycle life. Herein, we report that CuS@N-doped carbon (CuS@NC) hollow nanospheres, synthesized via solvothermal and subsequent annealing methods, used as anode materials for high-rate, high-capacity, and long-life sodium storage. In this composite, CuS undergoes a two-step redox reaction of conversion–displacement chemistry that inherits the high capacity of the conversion reaction and the excellent reversibility of displacement. N-doped carbon can enhance electrical conductivity and buffer structural change of CuS during cycling. Consequently, hollow nanospherical CuS@NC composites exhibit excellent sodium storage properties, with high specific capacity of 439.8 mAh g −1 after 800 cycles at a current density of 1 A g −1 , long cycling stability of more than 4400 cycles at 4 A g −1 , and a high-rate capability of 241.7mAh g −1 at 30 A g −1 . This work opens a new avenue for exploring high-capacity, high-rate and long-life anode materials for SIBs through conversion − displacement chemistry.