Large-scale preparation of black phosphorus by molten salt method for energy storage

Black phosphorus (BP) is a new layered material in concept, which has attracted great interest due to its fascinating optical and electrochemical properties. Here, we report the large scale synthesis of BP (20 g) by reducing PCl5 with metallic Al in melt AlCl3 at 300 °C. X-ray diffraction indicates the orthorhombic structure of BP and Raman spectrum shows that there is no obvious impurities. BP samples consist of micron-sized clusters of about 2 µm aggregated by flake-like nanoparticles with 20–100 nm. When used as anode materials for lithium ion battery, it exhibits a high specific capacity of 1610 m Ah g−1 at a current density of 0.1C, and cycle life up to 1000 cycles at a current density of 5C. In addition, through gradient centrifugation of as-prepared BP samples, gram-scale BP quantum dots can be obtained.