Investigations on Three‐Dimensional (3D) Woven Carbon Fiber Electrodes for Vanadium Redox Flow Batteries

Three‐dimensional (3D) porous electrodes are known to enhance reaction rates due to their high surface areas and interconnected porous structures, which improve electrolyte flow, reduce concentration polarization, and lower ionic and electronic resistance, making them suitable for improving energy and system efficiencies in redox flow batteries (RFBs). In this study, 3D orthogonal woven electrodes made from continuous carbon filaments with varying warp and weft density were investigated to assess their impact on the vanadium RFB performance. Electrochemical impedance spectroscopy (EIS), including distribution of relaxation times (DRT), was employed to analyze resistance contributions in two different electrolytes: the ferro/ferricyanide system as a reference electrolyte in a symmetric configuration and the vanadium electrolyte as a commercially available option. The relationship between resistance components and electrode parameters—including warp, weft and binder density—is presented. Electrochemical behavior in the vanadium electrolyte was also assessed using polarization curves and charge–discharge cycles. Results demonstrate that 3D woven electrodes, especially those with higher weft density, exhibit superior hydraulic performance and tunable electrochemical properties, enabling system‐level energy efficiencies comparable to those of conventional felts under the investigated experimental conditions. These findings provide valuable insights for optimizing 3D porous carbon electrodes for vanadium redox flow batteries (VRFBs).