Co-Doped CoxCu6 − xSn5 Alloys as Negative Electrode Materials for Rechargeable Lithium Batteries

Abstract

A series of Co-doped alloys were prepared by mechanical alloying, followed by annealing at . The Co-doped alloys show the same structure as the , which can be indexed to a hexagonal NiAs-type cell, but differ in the electrochemical performance as the anodes of Li-ion batteries. The results of ex situ X-ray diffraction analysis indicate the different Li alloying mechanism among . The metastable intermediate phases of formed during the Li-ion insertion process of become unstable and even undetectable with increasing amounts of Co substituted. A proper amount of Co-doped alloy, , showed improved cycling stability at the expense of capacity, whereas a heavy Co-doped alloy, , resulted in poor cycling ability. The crystal and electronic structure, thermodynamic stability of and half-lithiated alloy, , as well as the average voltage of alloying reaction in terms of different discharge depths were investigated using first-principles density-functional theory with pseudopotentials and plane wave basis.