The enthalpies of formation for various Cu–Li–Sb compounds

Abstract

The system Cu–Li–Sb has recently gained much attention with regard to Cu–Sb alloys being used as electrode materials for lithium ion batteries. Only few data exists however on the thermodynamics governing the lithiation of such electrode materials. A theoretical model of the corresponding phase diagrams, as provided by the CALPHAD approach, would give tremendous insights, not only into the thermodynamics but also to certain kinetic aspects governing these materials. However in order to develop a reliable model, fundamental experimental data is necessary. Especially the Gibbs energies and enthalpies of formation for the encountered intermetallic phases are essential building blocks for modeling of the system.In this work, the enthalpies of formation of four ternary compounds, i.e. CuLi2−xSb, Cu2−xLi1−xSb, Cu1.5−xLi1+xSb, Cu4+xLi1−xSb2 (i.e. T1–T4), were determined by two different experimental methods. Drop solution calorimetry using a tin bath was used to derive the enthalpies of formation from the limiting partial molar enthalpies of solution of the different ternary compounds as well as of their constituent components. Emf measurements at temperatures ranging from 642 K to 754 K were applied to calculate the enthalpies of formation from the integrated partial enthalpies of reaction with respect to liquid lithium. An electrochemical cell which can be represented as W|”Al, LiAl”|LiCl–KCl|CuxLiySbz|W was used for these measurements.