Design of parallel double-chain fibrous electrode using electrospinning technique for vanadium redox flow battery with boosted performance

This article proposes a parallel double-chain fibrous electrode structure with dual fibers of different diameters by electrospinning technique for vanadium redox flow battery to improve the battery performance. The larger diameter fibers contribute to the formation of larger pores, enhancing electrolyte flow and mass transfer. Meanwhile, the smaller diameter fibers provide abundant reaction sites. Different fiber diameters are fabricated by using precursor solutions with different concentration ratios. For a single concentration ratio electrode, as the concentration of PAN (Polyacrylonitrile) solution in syringe A increases, the performance of the battery significantly improves. The best performance is achieved by employing a concentration ratio of 20%:10%, i.e., ECF (Electrospun Carbon Fibers)-20%/10% electrode, at various current densities due to largest pore diameter and enough reaction sites. At current densities of 100 mA cm−2 and 200 mA cm−2, the ECF-20%/10% electrode achieves energy efficiencies of 88% and 80.5%, which are twice the energy efficiency of traditional carbon felt electrodes. Moreover, after 200 cycles, the battery capacity decay of ECF-20%/10% electrode only is 27.5%, which is 20.3% lower than that of the carbon felt electrode after 100 cycles. Dual concentration ratio electrode is also fabricated and found to show lower performance than the best single concentration ratio electrode for the reason that the second fabrication stage decreases the pore sizes.