Surfactant for Enhanced Rheological, Electrical, and Electrochemical Performance of Suspensions for Semisolid Redox Flow Batteries and Supercapacitors

A suspension of Li4Ti5O12 and of Ketjen black in a solution of 1M lithium bis(trifluoromethanesulfonyl)imide in propylene carbonate is studied as the anolyte for semisolid redox flow batteries. The rheological behavior and electronic conductivity are studied both at rest and under shear flow. The electrochemical behavior is evaluated at rest as a function of the charge/discharge rates and of the thickness of the suspension in the electrochemical cell. The highly beneficial influence of the addition of a non-ionic surfactant in the composition of the suspension is demonstrated. All practical properties are improved with respect to semisolid redox flow applications. The viscosity decreases, the electronic conductivity increases and is less affected by the shear flow, and the electrochemical performance is improved. Moreover, the suspension shows much better stability, so its performance is preserved over time.