A new group-contribution model based on both the modified double-lattice theory and the Debye-Huckel theory extended by Guggenheim theory is developed to interpret the phase behaviors of solid polymer electrolyte/salt systems at various temperatures and compositions. The model includes a 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 specific energy contribution from hydrogen bonding. Quantitative description according to the proposed model is in good agreement with the experimentally observed transition temperatures of the given systems. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 2884-2890, 2008