Evaluating Biomass‐Derived Electrospun Electrodes Using Nonaqueous Redox Flow Cells

Electrochemical energy storage technologies can enable reliable electricity delivery from variable assets. Among them, flow batteries are excellent candidates for stationary, long‐duration energy storage due to their flexible design, durability, and environmental friendliness. Nevertheless, this technology is nascent, with opportunities for performance improvements and cost reductions through materials development. In particular, the carbon electrodes influence performance by providing active sites for electrochemical reactions and a permeable structure for electrolyte flow. In this work, the performance of a commercial carbon paper (Freudenberg, FH 23) is compared to that of a lignin‐derived electrode and a polyacrylonitrile (PAN)‐derived electrode, both manufactured via electrospinning. The electrodes are tested using a nonaqueous electrolyte to ensure complete electrode wetting, minimize kinetic resistances, and better investigate mass transport efficiency and effective area utilization. The electrospun electrodes exhibit smaller fiber diameters, resulting in larger electrochemically active surface areas (ECSA) per unit mass, but also decreased permeabilities. At the same volumetric flow rates, polarization and electrochemical impedance spectroscopy measurements are similar for all electrodes. When normalized to superficial velocities, FH 23 performs best, followed by lignin‐derived electrodes, with PAN‐derived electrodes exhibiting the worst performance. The differences are largely attributed to electrode effective area utilization.