Characteristics of CTAB as Electrolyte Additive for Vanadium Redox Flow Battery

Hexadecyl trimethyl ammonium bromide (CTAB) was used as the additive in electrolyte for vanadium redox flow battery. Its stability and electrochemical performance were investigated by UV-Vis absorption spectrophotometry, scanning electron microscope(SEM), square wave voltammetry(SWV), cyclic voltammetry(CV) and examination of stabilization. The results show that the quaternary ammonium headgroups of CTAB micelles interacting with V(V) ions in electrolyte prevents pentavalent vanadium from further polymerization, which leads to a good suppression of the crystallization. The stable hemispherical particles forming at the graphite-liquid interface catalyze the redox reaction of V(IV)/V(V), which is called Micellar catalysis. EIS and charge-discharge tests show that the adding of CTAB makes charge transfer resistance much smaller, and doubles double-layer capacitance, so that the electrochemical reaction activity of the electrolyte improved, which is consistent with CTAB micellar catalysis.