Metal-organic frameworks derived hollow NiS2 spheres encased in graphene layers for enhanced sodium-ion storage

Nickel disulfide (NiS2) is a promising anode material for sodium-ion batteries (SIBs). Due to the volume expansion issue and intrinsic low conductivity, conventional NiS2-based anodes exhibit unsatisfactory Na+ storage performance far below their high theoretical specific capacity. Here, hollow NiS2 microspheres assembled from small NiS2 nanoparticles embedded in graphene layers (hollow NiS2@G) were successfully prepared by one-step annealing of Ni-MOFs involving simultaneous carbonization and sulfidation. Benefitting from the hollow and porous structure, highly graphitized carbon protective layers and large mass loading of NiS2, the as-prepared hollow NiS2@G is developed as a high-performance anode for SIBs, and delivers an increased capacity of 848 mA h g(-1) at 0.1 A g(-1) after 100 cycles and an excellent rate capability of 527.8 mA h g(-1) at 2 A g(-1). The comprehensive material characterization and electrochemical investigations demonstrate the one-step calcination as a simple and effective strategy in fabricating MOFs-derived nanocomposites for energy storage and conversion.