Porous Membrane with High Selectivity for Alkaline Quinone-Based Flow Batteries.

Aqueous organic-based flow batteries are increasingly receiving attention owing to their appealing traits of high safety and low cost. An economic and high-performance membrane is always regarded as the heart of the batteries. Here, we introduce a cost-effective, homemade porous membrane with high performance for alkaline quinone-based flow batteries. The membrane is constituted by highly stable poly(ether sulfone) (PES) and sulfonated poly(ether ether ketone) (SPEEK) that serves dual functions of (1) adjusting the membrane microstructure and (2) endowing the membrane with a charge trait. Benefiting from the well-tuned structure and charge property of the membrane, a high ion selectivity and transport of OH- with much higher mobility serving as the primary charge-balancing ion can be realized. By employing alkaline alizarin red (ARS)/ferro-ferricyanide flow battery as the platform, a battery delivers a coulombic efficiency (CE) of 98.28% and an energy efficiency (EE) of 85.81% at 40 mA cm-2, which is higher than that of the battery with a Nafion 212 membrane (CE ∼ 99.19%, EE ∼ 84.60%), however, with much lower cost. The successful application of homemade porous membrane may provide a new strategy to engineer and fabricate membranes with high efficiency for alkaline quinone-based flow batteries and further decrease the batteries' cost.