Résumé
Air stable copper phosphide was synthesized as a thick film over a copper foil by a very simple solid-state reaction at low temperature. X-ray diffraction confirms that the layer is pure Cu
3P. Scanning electron microscopy reveals a porous microstructure consisting of agglomerated particles with 10 μm of diameter. Electrochemical reaction of Cu
3P with lithium leads to an amorphisation of the thick film during the first discharge, and Cu
3P does not seem to recover upon subsequent charge. Structural and microstructural analyses coupled with electrochemical tests emphasize a complex behavior of the copper phosphide material. An initial capacity of 415 mAh/g has been measured with a stable reversible capacity close to 200 mAh/g on subsequent cycles without the help of binder and/or conductive additives. Although the gravimetric capacity values obtained with Cu
3P are slightly below the graphite capacity, the volumetric capacity of Cu
3P (1473 Ah/L) is 80% higher than those of graphite (800 Ah/L).