Anion exchange membranes based on long side-chain quaternary ammonium-functionalized poly(arylene piperidinium)s for vanadium redox flow batteries

Ether-Free Poly(p-terphenyl-co-acetylpyridine) Membranes with Different Thicknesses for Vanadium Redox Flow Batteries

“…Figure A shows the vanadium ion permeability of various membranes. Apparently, Nafion 212 and Nafion 115 exhibited significant vanadium ion permeability values equal to 8.6 × 10 –7 cm 2 min –1 and 4.1 × 10 –7 cm 2 min –1 , which are in agreement with previous reports. , Consistent with the trend of Nafion series membranes, either PTAP or PBI membrane with a thinner thickness exhibited a higher vanadium ion permeability, which is due to the significant vanadium crossover in a thinner membrane . As a result, the PTAP-55μm membrane occupied a slightly higher vanadium ion permeability (4.6 × 10 –8 cm 2 min –1 ) than PTAP-125μm (3.8 × 10 –8 cm 2 min –1 ).…”

“…For the membrane for VRFBs, it should be of both good ion conductivity and low vanadium ion permeability. For the sake of comprehensively considering the AR and vanadium ion permeability, ion selectivity ( S ) was calculated by dividing the ionic conductivity by the vanadium ion permeability. , When the ion selectivity value of the membrane was higher, it indicates that the membrane facilitates the transport of charged ions rather than vanadium ions. , For the same type membranes, the membrane with a thinner thickness displayed a lower ion selectivity, owing to its higher vanadium ion permeability. Among all the membranes, PTAP-55μm and PTAP-125μm membranes displayed high ion selectivity values equal to 2.5 × 10 5 and 6.2 × 10 5 S·min·cm –3 , which were nearly 10 times higher than those of Nafion 212 and Nafion 115 (i.e., 2.7 × 10 4 and 5.2 × 10 4 S·min·cm –3 ).…”

“…The membranes were cut evenly to a size of 4 mm × 25 mm. The area resistance (AR) of PTAP and PBI membranes was determined using electronic impedance spectroscopy (EIS) over a frequency range from 100 MHz to 1 Hz as reported in the literature. , The acid-doped membranes (effective area ( A ) of 2.27 cm 2 ) were clamped between two diffusion cells containing a 3.0 M SA solution. The resistances ( R 1 and R 2 ) were measured in the testing cell without and with a membrane, which was calculated with the eq . …”

“…With the development of society and economy, the energy crisis and the impact of massive carbon dioxide emissions on the environment are becoming more and more serious. The exploration and utilization of large-scale energy storage devices have attracted widespread attention, when unstable and intermittent renewable energies are being used efficiently worldwide. , Among many energy storage devices, the vanadium redox flow battery (VRFB) gets the attention of researchers, which brings in advantages including quick response, flexible design, high safety, green environmental protection, and long cycle life. , One of the most important components in VRFBs is the separation membrane, which not only provides ion transport channels to form electrical circuits but also separates the cathode and anolyte to avoid cross-infiltration of vanadium ions. , In order to reduce energy loss and improve cell efficiency, membranes are required to have low vanadium ion permeability, low area resistance, excellent chemical stability, and low cost. , …”

“…Jannasch et al recently synthesized a series of ether-free poly­(arylene piperidine)­s (PAPs) through a superelectrophilic activation . Subsequently, different side chains quaternized PAP membranes have been successfully developed for anion exchange membrane fuel cell and high temperature proton exchange membrane fuel cell. , Inspired by the above works, our group prepared different quaternized poly­(triphenylpiperidine) (PTP) membranes for VRFBs, using (5-bromopentyl)­trimethylammonium bromide and 3-chloro-2-hydroxypropyltrimethyl­ammonium chloride as quaternization reagents, respectively. The obtained long side-chain quaternary ammonium grafted poly­(terphenylpiperidinium) membranes (i.e., PTP-QA and PTP-CHPTMA) exhibited much lower vanadium ion permeability and higher ion selectivity than Nafion 115.…”