M. Bahari, A.S Hamedi, V. Vallem, E. Beh
Quino Energy, Inc.,
United States
Keywords: organic flow batteries, aqueous flow batteries, anthraquinones, long lifetime
Summary:
Organic redox flow batteries (ORFBs) have shown significant promise as cost-effective alternatives to vanadium-based RFBs, with quinone derivatives emerging as the most extensively studied organic active materials. However, their practical applications have been hindered by two major challenges: rapid fade rates and high estimated cost of manufacture (COM). Addressing these obstacles is essential to enabling the scale-up of ORFBs and unlocking their potential for widespread energy storage applications. We previously identified an anthraquinone-based negolyte, 2,6-bis(carboxymethyl)-1,5-dihydroxyanthraquinone (1,5-DCDHAQ), which exhibits a degradation rate low enough to enjoy a useful life measured in decades. Additionally, we developed an in situ electrosynthesis process capable of producing this negolyte on a ton scale using a simple, zero-waste electrochemical strategy. The as-synthesized electrolyte has a purity of over 90%, requires no additional purification, and can be directly utilized in an RFB system. This streamlined approach significantly simplifies scale-up and achieves an estimated cost of manufacture (COM) of less than $30/kAh at scale. The performance of the as-synthesized DCDHAQ has been successfully validated in conventional RFB systems across various scales. These systems, originally designed for vanadium electrolytes, required no modifications for compatibility with organic electrolytes except replacing the PFAS membrane with a hydrocarbon membrane. This substitution resulted in up to 75% reduction in membrane costs without compromising performance. The tested commercial systems ranged in size from 5 kWh to 100 kWh, a 10^4 to 10^5-fold increase in battery capacity from the lab scale, thereby demonstrating the simple scalability of the DCDHAQ-based ORFB. In addition to membrane savings, the use of organic electrolytes enables more than 50% cost reduction for porous electrodes by allowing for inexpensive but effective alternatives. Since electrodes and membranes are the most costly components of RFBs, these changes significantly lower the overall system cost for ORFBs compared to vanadium systems. This cost reduction is achieved with minimal reengineering while avoiding the use of critical or fluorinated materials. Together, our straightforward electrosynthetic approach and the successful demonstration of stable ORFB performance in commercial RFB systems have enabled the commercialization of an affordable, practical, and viable ORFB chemistry that could rapidly replace vanadium as the chemistry of choice in flow batteries.