(104f) Thin-Film Composite Membranes for High-Efficiency Nonaqueous Organic Redox Flow Batteries with Enhanced Stability

Nonaqueous organic redox flow batteries (NAORFBs) are an emerging class of energy storage systems by featuring high cell voltage, a wide range of operation temperature, and potentially high energy density with low cost. Polymer membrane is a key component to determining efficiencies of NAORFBs by allowing fast transport of supporting ions (i.e., low area-specific resistance, ASR) while preventing crossover of redox species (i.e., low permeance). However, developing a fast and selective membrane has been challenging due to the harsh organic solvent environments which will swell or even dissolve a wide range of polymer structures. Inspired by the industrial success in water purification, herein, we report high-performance thin-film composite (TFC) membranes by in situ interfacial polymerization for NAORFBs. Owing to its ultrathin (~200 nm) and crosslinked structure, the prepared TFC membranes exhibited a very low ASR (<2.3 Ω cm²) coupled with excellent solvent stability compared to those of commercial membranes. Also, a gas chromatography (GC)-based protocol was introduced to screen the small redox species (100–350 g/mol) by evaluating their permeance. Ultimately, we demonstrate the great potential of the developed TFC membranes to boost the efficiency and cycle life of NAORFBs.