Self-Templated Formation of Fluffy Graphene-Wrapped Ni₅P₄ Hollow Spheres for Li-Ion Battery Anodes with High Cycling Stability

Abstract

Transition-metal phosphides have gained great importance in the field of energy conversion and storage such as electrochemical water splitting, fuel cells, and Li-ion batteries. In this study, a rationally designed novel fluffy graphene (FG)-wrapped monophasic Ni₅P₄ (Ni₅P₄@FG) is in-situ-synthesized using a chemical vapor deposition method as a Li-ion battery anode material. The porous and hollow structure of Ni₅P₄ core is greatly helpful for lithium-ion diffusion, and at the same time, the cilia-like graphene nanosheet shell provides an electron-conducting layer and stabilizes the solid electrolyte interface formed on the Ni₅P₄ surface. The Ni₅P₄@FG sample shows a high reversible capacity of 739 mAh g^-1 after 300 cycles at a specific current density of 500 mA g^-1. The high capacity, superior cycling stability, and improved rate capability of Ni₅P₄@FG are ascribed to its unique hierarchical structure. Moreover, the present efficient fabrication methodology of Ni₅P₄@FG has potential to be developed as a general method for the synthesis of other transition-metal phosphides.