Membranes employed bowl-like porous organic molecules for fast ion-selective transport

Membranes enabling fast ion-selective transport and safety operation in energy storage devices remain a significant challenge. In this work, a porous organic molecule of cyclodextrin (CD) with bowl-like structure is applied to design porous membrane for alkaline zinc-iron flow batteries. Benefiting from its clever alternating structure of hydrophilic outer wall and hydrophobic inner cavity, a large number of ion-transport nanotunnels are constructed for fast OH^– transmission, delivering high ion conductivity of 8.48 mS cm⁻¹. Meanwhile, the fixed cavity of CD effectively prevent the cross-contamination of large size active ions. What's more, CD with negatively charged outer wall act as a navigator to guide uniform zinc deposition, thus successfully addressing dendrite problem and achieving safety operation. The cell with the designed membrane present dendrite-free performance in 1,100 cycles with an average EE (88.9 %) at 80 mA cm⁻². This study advances the development of next-generation membranes for energy and power generation.