Dual-porous structured membrane for ion-selection in vanadium flow battery

Porous membranes based on low-cost, chemically robust and non-ionic polymers are found to be promising as ion-selective membranes in redox flow batteries. Herein, we fabricate a dual-porous structured membrane where micro and macro pores are formed in the Nafion/poly(vinylidene fluoride) hybrid matrix. The dual-porous structure of the membranes is constructed by using polyethylene glycol as a pore-forming template. It is revealed that Nafion resin has significant impacts on both pore formation and ion conduction. The proton conductivity of the dual-porous membrane reaches 49.1 mS cm−1, and its vanadium permeation can be notably suppressed. Result of the single cell test indicates that, with the dual-porous structured membrane, coulombic efficiency and energy efficiency of the cells can achieve 96.1% and 83.8%, respectively, at 100 mA cm−2. The characteristics of low cost (approximately 50% of the material cost of Nafion), suppressed vanadium permeation, good chemical stability and competitive electrochemical performance make the dual-porous blend membranes promising candidate for redox flow batteries.