Challenges and advances of redox flow batteries utilizing sustainable and cost-effective non-vanadium active materials

Abstract

The key parameters for grid-scale energy storage systems (ESS) are safety, longevity, and cost-effectiveness. Aqueous redox flow batteries (RFB) are good candidates for grid-scale ESS because of the prospect of long-term stability while offering cost-effectiveness due to the use of cheap, non-volatile aqueous electrolytes. The currently most widely used RFB, the vanadium RFB (VRFB), is limited for even wider commercialization by its high acquisition cost and temperature sensitivity of vanadium electrolytes. To solve those limitations, RFBs, utilizing redox-active materials that can be cheaply prepared and have strong resistance against temperature, are a viable option. As the new redox-active materials, current trends for low-cost redox active materials, quinones, iron-based complex, and iodide are estimated. Their pros and cons are summarized, and proper preparation of their electrolytes are summarized, while the performance and stability of RFBs operated with the electrolytes are scrutinized.