Non-woven pitch-based carbon fiber electrodes for low-cost redox flow battery†

Redox flow batteries (RFBs) are promising energy storage systems to support renewable energy sources and overcome the limitations imposed by their intermittent and unpredictable nature. As a developing technology, the cost of key components, namely the membrane, electrolyte, and electrodes, present a major hurdle to widespread integration. This work describes the performance of non-woven carbon fiber (NWCF) electrodes derived from low-cost petroleum pitch and produced using a scalable, inexpensive melt-blowing process. Compared to commercial polyacrylonitrile (PAN)-based carbon fiber felt, pitch-based carbon fibers have increased graphitic content, tensile strength, and electrical conductivity. Greenhouse gas emissions for pitch-based carbon fibers are estimated to be significantly lower than that of PAN-based carbon fibers. When RFBs with unoptimized NWCF electrodes are evaluated in zinc iodide electrolytes, the voltage and power density (83 mW cm⁻²) are slightly lower compared to RFBs with PAN-derived carbon felts (104 mW cm⁻²) @ 100 mA cm⁻². RFBs fabricated with oxidized low-cost NWCF electrodes show nearly identical battery performance to those prepared with commercial PAN-derived carbon felts in vanadium electrolytes (peak power density of 137 mW cm⁻²vs. 139 mW cm⁻², respectively). Because of their low-cost precursor and cheaper processing methods, NWCF electrodes offer a promising solution to reducing the cost of RFB electrode materials, and with further optimization, these electrodes will likely result in improved battery performance.