MoP hollow nanospheres encapsulated in 3D reduced graphene oxide networks as high rate and ultralong cycle performance anodes for sodium-ion batteries.

Molybdenum phosphide (MoP), regarded as a promising anode material for sodium-ion batteries due to its superior conductivity and high theoretical specific capacity, still suffers from rapid capacity decay because of a large volume change and weak diffusion kinetics. Hollow nano-structures will be an effective solution to alleviate structural strain and improve cycling stability. Yet the preparation of MoP needs a high temperature phosphorization procedure which would cause agglomeration and structure collapse, making it difficult to achieve hollow nano-structures. Herein, caged by 3D graphene networks, MoP hollow nanospheres encapsulated in 3D reduced graphene oxide networks (H-MoP@rGO) were prepared successfully, and benefiting from the merits of the hollow nano-structure and flexibility of rGO, H-MoP@rGO demonstrates a superior cycle performance of 353.8 mA h g-1 at 1 A g-1 after 600 cycles and an extraordinary rate performance of 183.4 mA h g-1 at an ultrahigh current density of 10 A g-1 even after 3000 cycles.