Suppressing Shuttle Effect with a Size-Selective Covalent Organic Framework Based Bilayer Membrane

Organic batteries, while promising due to their abundant elements and minimal environmental impact, often suffer from capacity fade because of the shuttle effect of dissolved redox intermediates. To address this issue, we introduced a bilayer membrane, TpPa@PP, consisting of a 70-nm covalent organic framework (COF) thin film synthesized by interfacial condensation and subsequently deposited on a polypropylene substrate. This membrane allows solvent and ion transport, while rejecting soluble organic intermediates. When paired with pyrene-4,5,9,10-tetraone (PTO), an organic cathode with high capacity but notable dissolution issues, the TpPa@PP membrane effectively blocked the bulky PTO and Li-2-PTO species from crossover in an H-type cell, resulting in only a slight decrease in Li-ion flux. Furthermore, the membrane improved the first-cycle Coulombic efficiency. This work offers crucial insights into the membrane design for organic batteries.