ZnSxSe1-x/N-C (x = 0.24) hierarchical nanosphere with improved energy storage capability as sodium-ion battery anode

Anode materials are demonstrated to essentially affect the electrochemical performance of sodium-ion batteries (SIBs), which are considered as a promising large-scale energy storage device. In this work, alloying ZnSxSe1-x (x = 0.24) and N doped carbon composite (ZnSxSe1-x/N-C (x = 0.24)) hierarchical nanospheres are prepared by selenizing the ZnS precursor. The corresponding X-ray diffraction and high-resolution transmission electron microscopy results prove the formation of an alloyed phase, resulting in a wider lattice compared with ZnS. Benefitting from the coexistence of S2− and Se2− in the ZnSxSe1-x lattice, the weaker Zn-Se bonds and wider lattice spacing facilitate ultrafast pseudocapacitive sodium storage capability and enhanced cycling stability, when ZnSxSe1-x/N-C is used as anode material for SIBs. At current of 1.0 A g−1, it delivers a capacity of 378 mAh g−1 after 130 cycles with capacity retention of 87.9%, which is much higher than 34.3% for the ZnS/N-C electrode. In addition, for the rate performance, it can maintain an impressive capacity of 233 mAh g−1 at 10.0 A g−1 with a capacity retention of 55.9% in comparison with the capacity at 0.2 A g−1. This work provides us common thoughts to enhance the electrochemical performance of transition metal chalcogenide anode through anion substitution.