Li22Si5

Li22Si5 is an intermetallic compound in the lithium–silicon system with the nominal composition Li22Si5. It represents a lithium-rich silicide phase that has been reported in phase‑diagram studies of Li–Si and is of interest for understanding lithiation behavior in silicon-containing materials.

Synthesis and structure: Li22Si5 is typically prepared by high‑temperature synthesis methods such as arc melting or solid‑state reaction of stoichiometric amounts of lithium and silicon under an inert atmosphere, followed by annealing and slow cooling. Crystallographic data have been derived from X-ray diffraction, and the compound is described as having a relatively complex lattice in which silicon and lithium occupy distinct crystallographic sites. The exact space group and lattice parameters depend on preparation conditions and sample history.

Properties and stability: The compound is metallic and expected to exhibit electrical conductivity characteristic of intermetallics. It is highly reactive toward air and moisture, and should be handled under inert atmosphere to avoid oxidation. Li22Si5 is stable at room temperature only under protective conditions; exposure to air can lead to rapid surface degradation and chemical transformation.

Occurrence and significance: In the Li–Si phase diagram, Li22Si5 appears in specific temperature–composition regions and contributes to understanding the range of lithium-rich silicides. It provides insight into phase transformations and diffusion processes relevant to lithium storage research and the broader study of silicon-rich materials, though it is primarily of academic and fundamental interest rather than a practical electrode material.

See also: Lithium silicides; Phase diagrams of lithium–silicon.

References: Crystallographic and phase-diagram studies of Li–Si systems discuss Li22Si5 and related silicides.