Ion Effects on Vanadium Transport in Nafion Membranes for Vanadium Redox Flow Batteries

Abstract

Vanadium diffusion through Nafion membranes was investigated under conditions applicable to vanadium redox flow batteries (VRFBs). In this case, we examine the effects of interdiffusion of VO2+ with protons, V3+ and VO2+ by a 'cross-diffusion' experiment in which VO2+ and the other ion diffuse from opposite sides of the membrane. Vanadium concentrations in reservoirs designed to flow solution over both sides of the membrane were monitored using UV/vis and EPR spectroscopies. The permeability of each ion was determined and diffusion coefficients determined from permeability and measurements of ion uptake by the membrane. The VO2+ permeability is highest when H+ is the only ion on the counter side, and decreases in the following order: H+ > VO2+ > V3+.