This work reports on a novel electrode prepared with electrospun nano- and micro-scale carbon fibers for aqueous redox flow batteries. Larger fibers, ~10 μm in diameter, form larger pores to provide pathways for electrolyte flow, while smaller fibers, ~1 μm in diameter, increase active surface area for redox reactions. Brunauer-Emmett-Teller and pressure drop tests show that the specific surface area of the prepared dual-diameter electrode is doubled as compared with the large-fiber electrode, while the estimated permeability is enhanced by 1.4 times as opposed to the small-fiber electrode. The application of the dual-diameter electrodes to a vanadium redox flow battery allows the battery to achieve an energy efficiency of 84.78% at the current density of 100 mA cm⁻², which is 13.57% higher than that with small-fiber electrodes, and 3.91% higher than that with large-fiber electrodes. Even at a high current density of 200 mA cm⁻², the battery with the prepared electrode can still maintain the energy efficiency of 74.18%, which is 5.5% higher than that with large-fiber electrodes, and the battery with small-fiber electrodes cannot be operated at such high current density. This dual-diameter fibrous structure provides inspirations for the future electrode design in aqueous redox flow batteries.

这项工作报告了一种新型的电极，该电极用电纺纳米和微米级碳纤维制备，用于水性氧化还原液流电池。直径约10μm的较大纤维形成较大的孔，以提供电解质流动的路径，而直径约1μm的较小纤维则增加了氧化还原反应的活性表面积。Brunauer-Emmett-Teller和压降测试表明，与大纤维电极相比，制备的双直径电极的比表面积增加了一倍，而估计的渗透率比小纤维电极提高了1.4倍。将双直径电极应用于钒氧化还原液流电池可使电池在100 mA cm ^-2的电流密度下实现84.78％的能量效率，比小纤维电极高13.57％，比大纤维电极高3.91％。即使在200 mA cm ^-2的高电流密度下，带有制备电极的电池仍可以保持74.18％的能量效率，这比大纤维电极和小纤维电极的电池高5.5％。无法在如此高的电流密度下运行。这种双直径的纤维结构为水性氧化还原液流电池的未来电极设计提供了灵感。