Phase stabilities, electronic and electrochemical properties of compounds in the LiAlSi system

We have previously concluded that at least four compounds exist in the ternary system lithium-aluminum-silicon, their complex crystal structures have all been determined without ambiguity from single crystal X-ray analysis. Compounds LiAlSi, Li5AlSi2 and Li9AlSi3 have been tested as potential anodic materials for lithium batteries. The best electrochemical behavior was found for Li9AlSi3 that affords a capacity of about 1040 mA h g−1, almost three times that of the carbon negative electrode used in commercial lithium-ion batteries. It is assumed that the significant disorder (atomic mixing and vacancies) that occurs in the tetragonal structure of Li9AlSi3 is responsible for this interesting property. First principle DFT calculations have been carried out to determine the energetic stabilities and electronic structures of these compounds.