A new group-contribution model based on the lattice model is developed to interpret phase behaviors of solid polymer electrolyte/salt systems on the nonrandom mixing effect. The model includes the combinatorial energy contribution that is responsible for the revised Flory-Huggins entropy of mixing, the van der Waals energy contribution from dispersion, and the polar force and the specific energy contribution from hydrogen bonding. Lattice model gives a starting point for a theoretical description of thermodynamic properties of polymer solution systems. The proposed model in this study improves the configurational energy of mixing and correlates energy of mixing term including the effect of nonrandom mixing on the configurational thermodynamic properties of a binary mixture with experimental data. Our results show that good agreement is obtained upon comparison with experimental data of various PEO and salt systems in the interested ranges. (c) 2006 Published by Elsevier Ltd.