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

Abstract

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, α-Fe and FeP, which are combinationally determined by X-ray diffraction, energy dispersive X-ray spectroscopy and Mössbauer 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.