Development of Tailored Hydrocarbon‐Based Pentablock Copolymer Membranes for Sodium‐Polysulfide Flow Batteries

Abstract Long‐duration energy storage (LDES) technologies are pivotal for the adoption of renewables like wind and solar. Non‐aqueous redox flow batteries (NARFBs) with a sodium‐polysulfide hybrid system feature high energy density independent of power density, yet face challenges with polysulfide shuttling. This study investigates a hydrocarbon‐based penta‐block copolymer membrane, Nexar, to mitigate crossover effects by balancing TFSI conversion and their crosslink density. The membranes are annealed to induce crosslinking for reducing electrolyte uptake and enhancing mechanical stability while demonstrating excellent ionic conductivity. The hydrocarbon‐based membranes address environmental concerns associated with perfluoroalkyl substances and improve the performance and durability of NARFBs. Our findings suggest that annealed Nexar membranes with tailored TFSI functionality offer a scalable, cost‐effective solution for enhancing the efficiency of high‐capacity energy storage systems, pivotal for grid integration of renewable sources.