NiS 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 porous hollow spheres (NiS PHSs) and porous NiS hollow cages (NiS PHCs) with high yield are designed and selectively fabricated via a simple solvothermal and subsequent annealing approach. The obtained NiS PHSs display long-term cycling stability (127 mAh g after 6000 cycles at 8 A g) and excellent rate performance (605 mAh g at 1 A g and 175 mAh g at 15 A g). NiS 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. It is also worth noting that the NiS PHSs//FeFe(CN) full cell is successfully assembled and exhibits an initial reversible capacity of 460 mAh g at 0.5 A g, which further evidence that NiS is a kind of prospective anode material for SIBs.