Formation of stable phosphorus-carbon bond for enhanced performance in black phosphorus nanoparticle-graphite composite battery anodes.

High specific capacity battery electrode materials have attracted great research attention. Phosphorus as a low-cost abundant material has a high theoretical specific capacity of 2596 mAh/g with most of its capacity at the discharge potential range of 0.4-1.2 V, suitable as anodes. Although numerous research progress have shown other high capacity anodes such as Si, Ge, Sn, and SnO2, there are only a few studies on phosphorus anodes despite its high theoretical capacity. Successful applications of phosphorus anodes have been impeded by rapid capacity fading, mainly caused by large volume change (around 300%) upon lithiation and thus loss of electrical contact. Using the conducting allotrope of phosphorus, "black phosphorus" as starting materials, here we fabricated composites of black phosphorus nanoparticle-graphite by mechanochemical reaction in a high energy mechanical milling process. This process produces phosphorus-carbon bonds, which are stable during lithium insertion/extraction, maintaining excellent electrical connection between phosphorus and carbon. We demonstrated high initial discharge capacity of 2786 mAh·g(-1) at 0.2 C and an excellent cycle life of 100 cycles with 80% capacity retention. High specific discharge capacities are maintained at fast C rates (2270, 1750, 1500, and 1240 mAh·g(-1) at C/5, 1, 2, and 4.5 C, respectively).