Fluorine-induced dual defects in nip2 anode with robust sodium storage performance

Metal phosphides have shown great application potential as anode for sodium-ion batteries (NIBs) owing to high theoretical capacity, suitable operation voltage and abundant resource. Unfortunately, the application of NiP2 anode is severely impeded by low practical capacity and fast capacity decay due to the huge volume variation and low reactivity of internal phosphorus (P) component towards Na+. Herein, electronic structure modulation of NiP2 via heteroatoms doping and introducing vacancies defects to enhance Na+ adsorption sites and diffusion kinetics is successfully attempted. The as-synthesized three-dimensional (3D) bicontinuous carbon matrix decorated with well-dispersed fluorine (F)-doped NiP2 nanoparticles (F-NiP2@carbon nanosheets) delivers a high reversible capacity (585 mAh.g(-1) at 0.1 A.g(-1)) and excellent long cycling stability (244 mAh.g(-1) over 1,000 cycles at 2 A.g(-1)) when tested as anode in NIBs. Density functional theory (DFT) calculations reveal that F doping in NiP2 induces the formation of P vacancies with increased Na+ adsorption energy and accelerates the alloying of internal P component. The F-NiP2@carbon nanosheets//Na3V2(PO4)(3) full cell is evaluated showing stable long cycling life. The heteroatoms dopinginduced dual defects strategy opens up a new way of metal phosphides for sodium storage.

Automated summary

The study successfully modulated the electronic structure of NiP2 through heteroatoms doping and introducing vacancies defects, enhancing Na+ adsorption sites and diffusion kinetics, leading to high reversible capacity and excellent long cycling stability as an anode in NIBs.