Single Crystal Growth and Thermodynamic Stability of Li₁₇Si₄

Abstract

Single crystals of Li 17 Si 4 were synthesized from melts Li x Si 100– x ( x > 85) at various temperatures and isolated by isothermal centrifugation. Li 17 Si 4 crystallizes in the space group F 4̅3 m ( a = 18.7259(1) Å, Z = 20). The highly air and moisture sensitive compound is isotypic with Li 17 Sn 4 . Li 17 Si 4 represents a new compound and thus the lithium-richest phase in the binary system Li–Si superseding known Li 21 Si 5 (Li 16.8 Si 4 ). As previously shown Li 22 Si 5 (Li 17.6 Si 4 ) has been determined incorrectly. The findings are supported by theoretical calculations of the electronic structure, total energies, and structural optimizations using first-principles methods. Results from melt equilibration experiments and differential scanning calorimetry investigations suggest that Li 17 Si 4 decomposes peritectically at 481 ± 2 °C to “Li 4 Si” and melt. In addition a detailed investigation of the Li–Si phase system at the Li-rich side by thermal analysis using differential scanning calorimetry is given.