Synthesis of CoP–Co2P on graphene nanosheets for using as an anode material for lithium-ion batteries

In the present paper, we demonstrate a facile high-temperature solid-state route to synthesis two-phase cobalt phosphide/graphene nanocomposite and assess its potential as anode material for Li-ion batteries. The synthesized CoP–Co₂P/RGO composite shows a flake-like structure consisted of many cobalt phosphide nanospheres densely aggregated on the surface of the RGO nanosheets which in turn causes a twofold increase in the surface area from 15 m².g⁻¹ to 30 m².g⁻¹ and decreasing the mean pore diameter from ~ 2–95 nm to ~ 1–3 nm in comparison with the pristine CoP–Co₂P sample. The test results confirm the reversibility of the electrochemical reactions of the prepared anode material in the first 10 cycles. Compared to the pristine CoP–Co₂P sample, CoP–Co₂P/RGO nanocomposite exhibits 60 and 71% increase in the lithiation (118 mAh.g⁻¹) and delithiation (12 mAh.g⁻¹) capacities at 200 mA.g⁻¹. The improved battery performance of the CoP–Co₂P/RGO electrode is attributed to its highly-porous structure, high capacity of CoP, high electrical conductivity of graphene and Co₂P, and the ability of graphene in buffering the volume expansion during cycling.