Fluorine‐Containing Branched Sulfonated Polyimide Membrane for Vanadium Redox Flow Battery Applications. Issue 23 (27th September 2018) - Yang, Pan
Abstract: A series of fluorine‐containing branched sulfonated polyimide (Fb‐SPI) membranes with different degrees of branching (0–12 %) were synthesized through polycondensation. The chemical structure of Fb‐SPI‐10 membrane was confirmed using ATR‐FTIR and 1 H NMR spectroscopy. The physico‐chemical properties of Fb‐SPI membranes were systematically investigated and compared to linear SPI (l‐SPI) and Nafion 117 membranes. The vanadium‐ion permeabilities of Fb‐SPI membranes (2.45–0.99×10 −7 cm 2 min −1 ) are much lower than that of Nafion 117 (17.1×10 −7 cm 2 min −1 ) membranes. Besides, the chemical stability of Fb‐SPI membranes is superior to that of l‐SPI membranes. During 500‐time continuous cyclic charge‐discharge measurements, the VRFB assembled with a Fb‐SPI‐10 membrane shows higher coulombic efficiency (98.4–99.7 %), higher or close energy efficiency (69.0–79.7 %) from 40 to 80 mA cm −2, and higher or close capacity retention (52.8–100 %) from 40 to 70 mA cm −2 compared with a device using a Nafion 117 membrane. All of these results demonstrate that the as‐selected Fb‐SPI‐10 membrane has promising potential for VRFB applications. Abstract : Root and branch : fluorine‐containing branched sulfonated polyimide membranes (Fb‐SPI) with different degrees of branching are prepared from a fluorine‐containing "Y" type monomer. Fb‐SPI membranes show better chemical stability, higher proton selectivity and higher tensile strength than linear SPI and Nafion 117 membranes. The Fb‐SPI‐10 membrane shows outstanding and stable performance in vanadium redox flow batteries.