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

Abstract

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.