Highly Porous NiCoSe₄ Microspheres as High-Performance Anode Materials for Sodium-Ion Batteries

Binary transition metal selenides have been more promising than single transition metal selenides as anode materials for sodium-ion batteries (SIBs). However, the controlled synthesis of transition metal selenides, especially those derived from metal-organic-frameworks with well-controlled structure and morphology is still challenging. In this paper, highly porous NiCoSe₄ @NC composite microspheres were synthesized by simultaneous carbonization and selenization of a Ni-Co-based metal-organic framework (NiCo-MOF) and characterized by scanning electron microscopy, transition electron microscopy, X-Ray diffraction, X-Ray photoelectron spectroscopy and electrochemical techniques. The rationally engineered NiCoSe₄ @NC composite exhibits a capacity of 325 mAh g^-1 at a current density of 1 A g^-1 , and 277.8 mAh g^-1 at 10 A g^-1 . Most importantly, the NiCoSe₄ @NC retains a capacity of 293 mAh g^-1 at 1 A g^-1 after 1500 cycles, with a capacity decay rate of 0.025 % per cycle.