NiS_1.03 Hollow Spheres and Cages as Superhigh Rate Capacity and Stable Anode Materials for Half/Full Sodium-Ion Batteries

Nickle sulfides as promising anode materials for sodium-ion batteries have attracted tremendous attention owing to their large specific capacity and good electrical conductivity. However, the relative large volume changes during the sodiation/desodiation process usually result in a fast capacity decay, poor cycling stability, and sluggish electrode kinetics which hinder their practical applications. Herein, NiS_1.03 porous hollow spheres (NiS_1.03 PHSs) and porous NiS_1.03 hollow cages (NiS_1.03 PHCs) with high yield are designed and selectively fabricated via a simple solvothermal and subsequent annealing approach. The obtained NiS_1.03 PHSs display long-term cycling stability (127 mAh g^-1 after 6000 cycles at 8 A g^-1) and excellent rate performance (605 mAh g^-1 at 1 A g^-1 and 175 mAh g^-1 at 15 A g^-1). NiS_1.03 PHCs also show high rate capability and outstanding cycling stability. In addition, the analyses results of in situ and ex situ XRD patterns and HRTEM images reveal the reversible Na-ion conversion mechanism of NiS_1.03. It is also worth noting that the NiS_1.03 PHSs//FeFe(CN)₆ full cell is successfully assembled and exhibits an initial reversible capacity of 460 mAh g^-1 at 0.5 A g^-1, which further evidence that NiS_1.03 is a kind of prospective anode material for SIBs.