Measurement and regression of solid-liquid binary equilibrium data for lithium battery additive FEC-VC system
The solid-liquid equilibrium data for binary mixtures of fluoroethylene carbonate-vinylene carbonate(FEC-VC)were determined by differential scanning calorimetry(DSC)for the lack of basic theoretical data in separation of lithium battery electrolyte additive by melt crystallization.The experimental data showed that the binary system presented a lowest eutectic point.On this basis,the activity coefficient data of binary system were calculated by activity coefficient method.With the data regression function of Aspen Plus process simulation software,the solid-liquid equilibrium data of the binary system were regressed using van laar,NRTL and Redlich-Kister models,and the regression parameters of each model were obtained.The binary solid-liquid equilibrium data were calculated by the models and the lowest eutectic type solid-liquid phase diagrams were plotted.The comparison of regression results of each model indicated that the deviation of van laar model was large,and the regression results of Redlich-Kister model were more in line with the experimental data with a standard deviation of equilibrium temperature of less than 0.005 and an average deviation of less than 1.0K.The solid-liquid equilibrium data and thermodynamics parameters were provided for the crystallization separation technology of FEC-VC system.