Carbonates are frequently used as solvent systems in making nonaqueous electrolytes for lithium batteries. In the present work, the thermodynamic property of the dimethyl carbonate (DMC), ethylene carbonate (EC), and propylene carbonate (PC) system was modeled using a computerized optimization procedure. Based on experimental data in the literature, the thermodynamic properties of the pure DMC, EC, and PC phases and the thermodynamic interaction parameters in the liquid phase in the three binary systems, DMC-EC, DMC-PC, and EC-PC, were evaluated. The thermodynamic property of the ternary DMC-EC-PC system was predicted by combining the three binary systems. The liquidus projection and isothermal and isopleth sections were calculated. The results provide a base for modeling the interaction between solvent systems and various salts used in lithium batteries. (C) 2003 The Electrochemical Society.