Abstract
Covalent organic framework (COF) based proton permselective membranes are for the first time designed to break through the trade-off between proton permeability and selectivity for improved efficiencies of acid supporting redox flow batteries (the representative one is all vanadium redox flow battery). The precise hydrated proton (<0.24 nm)/vanadium (>0.6 nm) sieving is achieved originating from the appropriate pore size (0.48 nm) of COF prepared here. As a result, no vanadium permeation can be detected for the membrane. While, the presences of micropores and the amino groups in COF lead to a low area resistance. The cell assembled with this membrane presents very high coulombic efficiency (CE: 98.7–99.6%) and energy efficiency (EE: 93.5–76.4%) at 40–180 mA cm−2. In addition, the membrane is free of ion exchange groups, leading to excellent chemical stability. The membrane structure shows no changes after the cell steadily runs over 500 cycles (>1300 h) at 80 mA cm−2. This work provides a new orientation to design a membrane with an ultrahigh proton permselectivity for redox flow batteries.
Published Version
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