Thin-film composite membrane breaking the trade-off between conductivity and selectivity for a flow battery

Abstract

A membrane with both high ion conductivity and selectivity is critical to high power density and low-cost flow batteries, which are of great importance for the wide application of renewable energies. The trade-off between ion selectivity and conductivity is a bottleneck of ion conductive membranes. In this paper, a thin-film composite membrane with ultrathin polyamide selective layer is found to break the trade-off between ion selectivity and conductivity, and dramatically improve the power density of a flow battery. As a result, a vanadium flow battery with a thin-film composite membrane achieves energy efficiency higher than 80% at a current density of 260 mA cm ⁻², which is the highest ever reported to the best of our knowledge. Combining experiments and theoretical calculation, we propose that the high performance is attributed to the proton transfer via Grotthuss mechanism and Vehicle mechanism in sub-1 nm pores of the ultrathin polyamide selective layer.

Abstract

Low-cost flow batteries with high power density are promising for energy storage, but membranes with simultaneously high ion conductivity and selectivity should be developed. Here the authors report a thin-film composite membrane that breaks the trade-off between ion conductivity and selectivity.