Investigation of the Li solubility in the intermediate phase Li17Sn4 relevant to understanding lithiation mechanisms in Sn-based anode materials

• Published in: Journal of alloys and compounds 2017-08, Vol.714, p.593-602
• Main Authors: Reichmann, Thomas L., Gebert, C., Cupid, Damian M.
• Format: Article
• Language: English
• Subjects: Alloys; Anodes; Chemical compounds; Coulometers; Coulometry; Crystal structure; Crystallography; Differential scanning calorimetry; Electrode materials; Experimental thermodynamics; Experiments; Heat measurement; Lattice parameters; Lithium compounds; Phase diagram; Solid electrolytes; Trapping
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2017.04.232

A comprehensive study of the Li-rich phase boundary of the intermediate Li17Sn4 compound is given based on thermochemical and electrochemical investigations. From the results a partial phase diagram showing the homogeneity range of this phase could be constructed. Using these results, the defect mechanism for the compound Li17Sn4 could also be clarified. Galvanostatic coulometry with potential limitation (GCPL) was performed using 2032 coin cell equipment. This allowed for the determination of the amount of Li insertion on special crystallographic sites at 25 °C, which is 0.41 ± 0.04 at.%. The respective Li loss mechanisms (solid electrolyte interface formation, Li plating, Li trapping) are discussed. Irreversible capacity according to Li trapping could be excluded due to the limited voltage window of the experiments. Moreover, differential scanning calorimetry (DSC) was carried out on two individual Tian-Calvet type calorimeters. The Li-rich boundary of the Li17Sn4 compound was determined at 81.31 ± 0.04 (C-80) and 81.28 ± 0.05 at.% Li (M-HTC) at 427 °C. In addition, the latter results were compared to the change of lattice parameters of alloys with compositions Li17+xSn4. [Display omitted] •Structural data about Li17Sn4 is collected and discussed.•A narrow homogeneity range Li17+xSn4 is presented.•Open circuit potentials and charge capacities of Li17Sn4 vs. Li are given.•Irreversible capacity losses dedicated to the material are discussed.