Dajian Li

Heat capacities and an updated thermodynamic model for the Li–Sn system

Phase-pure Li17Sn4 and Li7Sn3 intermetallic compounds were synthesized using defined heat treatment procedures in specially designed Ta crucibles. The products were characterized by inductively coupled plasma optical emission spectroscopy (ICP-OES) and powder X-ray diffraction (powder-XRD) techniques to determine their composition and phase purity. The heat capacities of the synthesized compounds were measured via the step method in sealed Ta crucibles using a Setaram C80 Tian-Calvet calorimeter. The experimentally determined heat capacities were then used to develop restricted Maier-Kelley models for each phase and to incorporate these data into the re-optimization of an existing thermodynamic description of the Li-Sn system. The new models for the intermetallic and liquid phases result in improved agreement between the calculated and experimental heat capacity, thermodynamic, electrochemical and phase diagram data. Since the re-optimized Gibbs free energy expressions are based on reliable heat capacity data, the models can now be used to predict emf values in the Li-Sn system at a variety of operation temperatures and active material compositions.

Phase diagram, thermodynamic investigations, and modelling of systems relevant to lithium-ion batteries

Abstract This article reports on two consecutive joint projects titled “Experimental Thermodynamics and Phase Relations of New Electrode Materials for Lithium-Ion Batteries”, which were performed in the framework of the WenDeLIB 1473 priority program “Materials with new Design for Lithium Ion Batteries”. Hundreds of samples were synthesized using experimental techniques specifically developed to deal with highly reactive lithium and lithium-containing compounds to generate electrochemical, phase diagram and crystal structure data in the Cu–Li, Li–Sn, Li–Sb, Cu–Li–Sn, Cu–Li–Sb and selected oxide systems. The thermochemical and phase diagram data were subsequently used to develop self-consistent thermodynamic descriptions of several binary systems. In the present contribution, the experimental techniques, working procedures, results and their relevance to the development of new electrode materials for lithium ion batteries are discussed and summarized. The collaboration between the three groups has resulted in more than fifteen (15) published articles during the six-year funding period.