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

Abstract

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.