Enhanced reversibility and electrochemical performances of mechanically alloyed Cu3P achieved by Fe addition

Cu3P is a potential anode material for lithium-ion batteries with its comparable gravimetric capacity, but several times higher volumetric capacity (4732 mA h cm(-3)) than graphite. However, the cycling stability of Cu3P is poor at low discharge potentials and high current densities. In this work, Fe addition is employed as a simple strategy to modulate the composition and phase constitution of Cu3P nanopowders synthesized by wet mechanical alloying, and thereby to tune the electrochemical performance of the anode. The addition of Fe results in a composite constitute containing Cu3P as the major phase and some other minor phases including Cu, a-Fe and FeP, which are combinationally determined by X-ray diffraction, energy dispersive X-ray spectroscopy and Mossbauer spectroscopy. Electrochemical tests reveal that both the cycling stability and the rate capability of the electrodes are improved by Fe addition. The Cu3P electrode with 10% Fe addition shows the best cell performance, with the capacity being remarkably improved by over 100%, from 82 mA h g(-1) to 178 mA h g(-1) after 50 cycles at 0.75C between 2.0 V and 0.5 V vs. Li/Li+. The improvement of the electrochemical performance is engendered by a synergetic effect of the microstructure change of the powders and the presence of Fe-related minor phases, leading to increased electronic conductivity as well as enhanced electrochemical reversibility of the electrode.