Chemical diffusion in intermediate phases in the lithium-silicon system

The equilibrium coulometric titration curve shows four intermediate phases in the LiSi system at 415°C. The nominal compositions for these phases are Li12Si7, Li7Si3, Li13Si4, and Li22Si5, respectively. They all have quite narrow ranges of homogeneity. The compositional variations of the chemical diffusion coefficients within the various intermediate phases are similar to each other and closely resemble those of the thermodynamic enhancement factor for each phase. The chemical diffusion coefficients across all four intermediate phases are essentially of the same order, about 6.0 × 10−5 cm2/sec at 415°C.