(459a) Flow Batteries for Grid-Scale Energy Storage: A Historical Perspective, More Recent Approaches, and Specific Research Issues Addressed

Large-scale electrochemical energy storage is required to meet a multitude of current energy challenges. These challenges include modernizing the grid, incorporating intermittent renewable energy sources (so as to dispatch continuous electrical energy), improving the efficiency of electricity transmission and distribution, and providing flexibility of storage independent of geographical and geological location. In addition, electrochemical storage would be scalable for centralized or distributed use.

Flow batteries are a type of electrochemical energy storage system where the chemicals used to store charge are stored externally in tanks. These chemicals are pumped to a fuel cell like device for conversion of electricity to chemical energy for energy storage, and vice versa for energy dispatch. I will summarize the chemistries and features of various flow batteries, and provide an historical perspective, especially with respect to the early work in the field.^1,2 I will then describe some of the more recent flow battery chemistries reported in the literature such as Quinone couples, non-aqueous couples⁴, and couples in deep eutectic solvents^5,6.

In recent years, redox flow batteries have been advanced by incorporating design features from PEM fuel cells. For example, the introduction of serpentine and interdigitated flow fields have minimized ohmic losses and enhanced mass transfer so high power densities are achievable. I will summarize some of the advances reported in power densities, and will discuss modeling work in our group that clarifies the mechanism of performance enhancement in these designs.^7,8

Over the years, reports on electrode materials performance in flow batteries has shown much variability, this being especially the case for the vanadium system. We have studied electrochemical pretreatments of carbon felt materials for vanadium flow battery electrodes that explain some of the variation seen in the literature. The experiments and results will be summarized^9,10,11.

Finally, I will describe a technology approach based on using very low cost iron electrolytes with a carbon slurry negative electrode that will be economically competitive for large scale energy storage. Additional advantages of this approach are that abundant, non-toxic, and non-corrosive materials are used to provide an energy storage solution that has inherently safe operation and is environmentally friendly. This approach will further reduce downstream lifecycle costs (including maintenance and disposal) that are often underestimated. I will describe our work on developing the all iron flow battery technology and our work on understanding the factors that control or limit energy storage performance.

Acknowledgements

This work is supported in-part by the flow battery project (DE-AR0000352) funded from ARPA-E program of Department of Energy (DOE) of the United States.

References

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9. Buckley, D.N., Bourke, A., Lynch, R.P., Quill, N., Miller, M.A., Wainright, J.S. and R.F. Savinell, “Influence of Pretreatment on Kinetics at Carbon Electrodes and Consequences for Flow Battery Performance”, MRS Advances, 2(21-22), pp. 1131-1142 (2017).
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