Thin copper phosphide films as conversion anode for lithium-ion battery applications

Air stable copper phosphide of thicknesses (0.2, 0.4 μm) was synthesized over copper plates (of 10 mm diameter) by hybrid electrochemical deposition and low temperature solid-state reaction. Stoichiometric amount of red phosphorus (P) were sprayed over electrodeposited copper and followed by annealing at 250 °C under inert gas atmosphere for different durations (5 h, 7 h and 12 h). During this process, phosphorus particles diffuse by excavating into the copper deposits, producing holes, where the Cu3P crystallites nucleate and lead to conglomeration of several agglomerates and hence resulted in non-homogeneous morphology. A small extend of Cu3P oxidation occurs over the film's top surface. X-ray diffraction (XRD) patterns confirm that the layer to be pure Cu3P. Scanning electron microscopy (FEG-SEM) reveals a porous microstructure consisting of agglomerated particles with ∼10 μm size. The as-prepared carbon-free Cu3P electrodes exhibited significantly improved capacity retention and rate capability characteristics over 40 cycles when electrochemically tested against lithium at constant 20 μA/cm2 rendering it as possible negative electrode for high energy density lithium-ion battery (LiB) applications.