Thermodynamic properties and prediction of viscosity for ternary solution (VOSO4 + PAA + H2O) in vanadium flow battery

A number of additives have been proven to improve the performance of vanadium redox flow batteries (VRFBs). Polyacrylic acid (PAA) is considered to be one of the promising candidates because of its beneficial effects on the stability of batteries . This paper studied the influence of PAA on viscosity, which is one of the electrolyte transport properties. The viscosity of VOSO 4  + PAA + H 2 O ternary solution was measured at different temperature, ionic strength , and ionic strength fractions in the temperature range of 283.15 K–318.15 K. Several thermodynamic parameters of the PAA aqueous solution were calculated, such as the viscosity B -coefficients, the apparent molar volume of infinite dilution and the free energy of activation . In addition, two different semi-empirical prediction equations were established for ternary solution viscosity on the basis of the Eyring's theory , and the better one was determined through comparison. The average relative deviation is 0.74% between the predicted and the experimental values, which indicates this function can be used to predict the viscosity of VOSO 4  + PAA + H 2 O ternary solution.