CoxP compounds: electrochemical conversion/partial recombination reaction and partially disproportionated nanocomposite for Li-ion battery anodes

CoxP binary compounds, CoP and Co2P, were synthesized using simple solid-state synthetic routes, and their potential as anode materials for Li-ion batteries was investigated. Electrochemical Li reactivity was possible on the CoP electrode, whereas the Co2P electrode did not react with Li. The electrochemically driven partial recombination reaction of the CoP electrode was thoroughly demonstrated using ex situ X-ray diffraction and extended X-ray absorption fine structure analyses. To enhance the electrochemical performances of CoP, its carbon-modified nanocomposite was prepared. The nanocomposite consisted of well-dispersed CoP (active with Li) and Co2P (inactive with Li) nanocrystallites, as well as amorphous P within the amorphous carbon matrix. The partially disproportionated CoP/C nanocomposite electrode exhibited good electrochemical performance with a high initial charge capacity of 531 mA h g (-1) (or 855 mA h cm (-3)), a cycling durability of 407 mA h g (-1) (or 655 mA h cm (-3)) over 200 cycles, a good initial coulombic efficiency of ca. 75%, and a fast rate capability (2C: 435 mA h g (-1), 3C: 410 mA h g (-1)).