Layered phosphorus-like GeP5: a promising anode candidate with high initial coulombic efficiency and large capacity for lithium ion batteries

In this work, we for the first time investigate GeP5 as an anode material for lithium ion batteries (LIBs). Using a facile high energy mechanical ball milling (HEMM) method, we successfully synthesize pure GeP5 and GeP5/C nanocomposite at ambient temperature and pressure. According to XRD Rietveld refinement and first principle calculations, GeP5 possesses a two-dimensional layered structure similar to that of black P and graphite, and a high conductivity that is 10 000 and 10 times that of black P and graphite, respectively. Serving as novel anode materials, both GeP5 and its carbon composite deliver an unprecedented high reversible capacity of ca. 2300 mA h g(-1), combined with a high initial coulombic efficiency of ca. 95%. Ex situ XRD and CV tests demonstrate that GeP5 undergoes conversion and alloying type lithium storage mechanism and that its capacity is co-contributed to by both the Ge and P components. In addition, GeP5/C exhibits superior cycle stability and excellent high-rate performance with a capacity of 2127 mA h g(-1) at 5 A g(-1). These properties suggest the promising application of these anode materials in next-generation high-energy and high-power LIBs.