Synthesis, crystal and electronic structure of Li13Ag5Si6, a potential anode for Li-ion batteries

The ternary system lithium–silver–silicon has been analyzed in a domain close to the composition Li2AgSi. The new compound Li13Ag5Si6 has been characterized by both powder and single crystal X-ray diffraction. It crystallizes in the R3¯m rhombohedral system with the hexagonal cell parameters a = 4.3906(6), c = 42.293(5) Å, Z = 2. The pseudo-tetrahedral structure is made up of [SiAg], hexagon-based, corrugated layers that are cross-linked via Si–Ag, Si–Si or Ag–Ag connections. Lithium atoms not only fill the interlayer space but also partially (∼19%) substitute for silver within the layers. The band structure indicates an anisotropic metallic character. Li13Ag5Si6 behaves fairly well as an anodic material for lithium-ion batteries, with a reversible specific capacity around 800 mA h g−1.

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