(255b) Electrospun Carbon Nanotube/Sulfonated Poly (ether ether ketone) Proton Conductive Membranes for Vanadium Redox Flow Battery

Vanadium redox flow battery (VFB) is a promising large-scale energy storage techniques for most renewable energy resources. As one of the key components in VFB, proton conductive membrane faces the challenge of improving selectivity of proton to vanadium ions (H/V selectivity), because both vanadium ions and proton transport through the similar pathway of hydrophilic domains in polymer matrix. Inorganic additives has intrinsically good vanadium ions barrier, while are likely to agglomerate or peeling away from the polymer materials due to poor compatibility. In this work, carbon nanotube (CNT) hybrid sulfonated poly (ether ether ketone) (SPEEK) is nano-fiberized through electrospinning. High electric field inducesthree-dimensional interconnected SPEEK nanofiber networks and thealignment of fibrous CNTs along SPEEK nanofiber axis, which provide long-range proton conductive pathways,good dispersion of CNT in SPEEK nanofibers and maximum vanadium ions and swelling blocking effect. Area resistance of Spun 0.5 is reduced to 0.23 ohm/cm², which is 20.7% lower than that of Cast0.5.Vanadium ions permeation decreases by about 67.6% at CNT content of 0.5 wt% comparing to 0 wt.%. Good H/V selectivity and tensile strength in hydrated state make the electrospun MWCNT/SPEEK membrane exhibit good VFB performance.At current density of 100 mA cm^-2, energy efficiency of Spun0.5 is about 86.2%, much better than that of Cast0.5 (77.7%) and Nafion211 (74.9%). Even after 100 cyclic operation, Spun0.5 shows higher capacity stability (0.47% per cycle decay), which is much better than that of Nafion 211 (0.84% per cycle decay) with similar membrane thickness.