A　thermodynamic　model　was　developed　in　particular　for　nanocrystalline　partially　ionic　solids,　which　represent　a　group　of　Li　ion　battery　anode　materials.　The　lithium　compounds　were　used　as　examples　to　demonstrate　the　model　applications　in　studies　of　phase　stability　and　phase　transformation　behavior　in　the　nanoscale　anode　system.　The　peritectic　and　eutectic　transformations　were　described　systematically　concerning　the　reaction　temperatures　and　liquid　concentrations　at　various　equilibria,　in　which　the　grain　size　effects　on　the　equilibrium,　stability　and　transformation　of　Li-containing　phases　were　quantified.　To　verify　the　model　predictions,　a　series　of　experiments　were　performed　using　the　nanocrystalline　Li-Si　system　as　sample　materials.　The　experimental　finding　confirmed　the　model　calculations,　based　on　which　the　correlation　of　phase　stability,　temperature,　grain　size　and　critical　grain　size　was　proposed.