Holey aligned electrodes through in-situ ZIF-8-assisted-etching for high-performance aqueous redox flow batteries

Fabricating electrodes with large specific surface area (SSA) and high permeability has been the long-standing target in redox flow batteries (RFBs). In this work, we propose a novel ZIF-8-assisted etching approach to form holey fibers in the electrospinning process of aligned electrode structures. The etching approach allows the formation of holey fibers with small pores of similar to 50 nm, offering large active surface areas for redox reactions, while the aligned macrostructure with the holey fibers of 3-5 mu m in diameter ensures a high permeability along the fiber direction. The application of the prepared electrodes to a vanadium redox flow battery (VRFB) enables an energy efficiency (EE) of 87.2% at the current density of 200 mA cm(-2), which is 13.3% higher than that with conventional electrospun carbon electrodes. Even at high current densities of 300 and 400 mA cm(-2), the battery still maintains energy efficiencies of 83.3% and 79.3%. More excitingly, the prepared electrode yields a high limiting current density of 4500 mA cm(-2) and a peak power density of 1.6Wcm(-2). It is anticipated that the present electrospinning method combining the ZIF-8-assisted etching approach with a way to form ordered fiber structures will allow even more high-performance electrodes for RFBs in the future. (C) 2020 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.