Recent Progress in Aqueous Organic or Inorganic-Based Redox Flow Batteries at Pnnl

Abstract

Redox flow batteries (RFBs), as one of the most promising electrical energy storage systems, provide an alternative solution to the problems of balancing power generation and consumption. RFBs are designed to convert and store electrical energy into chemical energy and release it in a controlled fashion when required. In particular, aqueous RFBs are attracting more attentions because of their good safety, low cost and high power density comparing with non-aqueous RFBs. Therefore, aqueous RFB chemistries with appropriate redox potential, high soluble and low-cost active species are critically required.1 During the past few years, PNNL invented several aqueous RFB systems: inorganic and organic-based systems. Here, we will present the electrode development for zinc-polyiodide RFBs2 (inorganic-based). Two kinds of metal-organic frameworks (MOFs) acting as catalysts were in-situ grown at the cathode carbon electrode.3 The flow cell with MOFs showed largely improved energy efficiency. The chemical stability of MOFs in electrolytes was studied in detail. Also, we will introduce a kind of methyl viologen-based RFBs (organic-based). It represents a great potential to replace expensive vanadium flow batteries because of low-cost active materials. The cell performance and the chemical stability of electrolytes will be discussed.