A 3D Carbon Architecture Encapsulation Strategy for Boosting the Performance of Nickel Disulfide as an Anode for Sodium-Ion Batteries

Nickel disulfide (NiS2) nanoparticles are encapsulated within nitrogen and sulfur co-doped carbon nanosheets, which are grown onto carbon nanofibers to form an array structure (NiS2/C@CNF), resulting in a self-supporting film. This encapsulated structure not only prevents the agglomeration of NiS2 nanoparticles, but also memorably buffers its volume changes during charge/discharge cycles, thereby maintaining structural integrity. The nitrogen and sulfur co-doping enhances electronic conductivity and facilitates the faster ion transport of the carbon backbone, improving the low conductivity of the NiS2/C@CNF anodes. Consequently, the NiS2/C@CNF electrode exhibits a remarkable rate ability, reaching 55.4% of its capacity at 5 A g-1 compared to that at 0.1 A g-1, alongside an impressive cycling stability, with 89.9% capacity retention over 1500 cycles at 2 A g-1. This work underscores the efficacy of the 3D carbon backbone encapsulation strategy for enhancing the sodium storage property of transition metal-based anodes.