Monodispersed copper phosphide nanocrystals in situ grown in a nitrogen-doped reduced graphene oxide matrix and their superior performance as the anode for lithium-ion batteries†
Abstract
A nanocomposite anode material consisting fully of monodispersed copper phosphide (Cu3P) nanocrystals in situ grown in three-dimensional (3D) nitrogen-doped reduced graphene oxide (N-RGO) matrices has been manufactured via a “heating-up” synthesis, which involves nucleation, nitrogen-doping, crystallization and ligand exchange. The “heating-up” synthesis approach, using stable and relatively low-toxicity precursors and 3D porous N-RGO as the matrix, is straightforward, cost-effective and up-scalable. The Cu3P nanocrystals with an average size of 25–40 nm are wrapped, without aggregation, within the interior and on the surface of the curling N-RGO matrices. The resultant Cu3P/N-RGO nanocomposites possess a 3D porous nanostructure with a BET surface area as high as 405.71 m2 g−1. In this nanostructure, the N-RGO's properties of excellent conductivity and an interconnected porous network enable the Cu3P/N-RGO nanocomposites to provide pathways for rapid electron transfer and lithium ion transport, and the Cu3P nanocrystals with their small size and monodispersed phase can accommodate the volume change during charging/discharging processes. Hence, Cu3P/N-RGO nanocomposites reveal an excellent lithium-storage performance in terms of a long-life cycling stability (705.5 mA h g−1 at 10C, 88.8% capacity retention over 1000 cycles at 25 °C), a high heat-resistance capability (674.6 mA h g−1 under 10C, 88.9% capacity retention over 1000 cycles at 55 °C), and a high rate capability (604.6 mA h g−1 at 50C).