Metal-organic framework derived cobalt phosphide nanoparticles encapsulated within hierarchical hollow carbon superstructure for stable sodium storage

Abstract

Metal-organic framework (MOF) derivatives with controllable morphology, porosity, and high specific area are considered as potential anodes for sodium-ion batteries (SIBs). However, the poor conductivity and sluggish diffusion kinetics of Na+ of MOF-derived materials result in rapid capacity decline and inferior rate capability. Herein, a hierarchical hollow superstructure composed of CoP nanoparticles anchored on the N-doped carbon polyhedral frameworks with the epitaxial growth of carbon nanotubes (CoP@N-HP/CT), is prepared by MOF coating, and subsequent carbonization − oxidation − phosphorization strategy. Owing to the elaborate hierarchical hollow superstructure, the CoP@N-HP/CT composites achieve long cycling stability (over 2500 cycles), and good rate capability as SIBs anodes. The remarkable electrochemical performance of the CoP@N-HP/CT hybrids is attributed to their high capacitive contribution and fast sodium ion diffusion rate. Furthermore, the sodium storage behaviors of the CoP@N-HP/CT are revealed by ex-situ X-ray photoelectron spectroscopy and transmission electron microscope techniques. Thus, the well-designed hierarchical hollow CoP@N-HP/CT superstructure gives an insight into the superior anodes for sodium storage.