Rigid Framework-Constrained Membranes: A Key to Long-Life Polysulfide/Polyiodide Redox Flow Batteries

The emerging polysulfide/polyiodide redox flow batteries (PSIBs) attract much attention owing to their high capacity and low cost. However, severe polysulfide/polyiodide crossover and insufficient cycle life caused by membrane swelling impede their large-scale applications. Herein, we constructed a rigid framework-constrained membrane, where rigid carbonylated polymer of intrinsic microporosity (cPIM-1) chains were introduced to bind the movement of the flexible perfluorosulfonic acid (PFSA) polymer chain. Quartz crystal microbalance and positron annihilation techniques demonstrated optimizing the PFSA/cPIM (P/cPIM) composite membrane structure and channel size. In the PSIB test, the battery with the P/cPIM membrane operated stably for over 780 h, which significantly improved over the 165 h recorded for the PFSA membrane.