Densification, Precipitation, and Dissolution of Vanadium Electrolyte for Vanadium Redox Flow Battery Systems

Abstract

The all-vanadium redox flow battery system (VRFB) is the most mature RFB technology since it uses a single active species, which does not degrade. Rebalancing electrolytes to maintain maximum energy capacity in an RFB system that uses a single active species, or symmetrical electrolytes, is simple and enables the use of relatively low-selectivity separators, which have higher ionic conductivities.1 Conversely, finite-lifetime RFB chemistries, especially asymmetric chemistries, result in significant negative impacts on the levelized cost of storage (LCOS).2 Currently, the vanadium electrolyte used in a MWh-scale VRFB system is typically shipped to the installation site in liquid form in multiple totes and the VRFB-system tanks are filled onsite. A new approach explored in this study is to densify and precipitate the electrolyte in a solid form, which can then be quickly dissolved to its intended concentration onsite by the addition of de-ionized water.3 This approach can enable multiple benefits. First, shipping the electrolyte in solid form provides more stability and higher density during shipping, which significantly reduces shipping costs. Second, the solid electrolyte can be shipped in the actual containers that will be used onsite, which thus simplifies the required onsite work. This presentation will discuss a method used to densify the vanadium electrolyte, as well as nucleation and precipitation processes that generate the solid electrolyte form, which will quickly dissolve when deionized water is added onsite. The nucleation and precipitation process leverages recent work on the solid-liquid high-energy storage density method for RFB systems.4 References M. L. Perry, J. D. Saraidaridis, and R. Darling, “Crossover Mitigation Strategies for Redox-Flow Batteries,” Current Opinion in Electrochemistry, 21 (2020). 10.1016/j.coelec.2020.03.024 K. E. Rodby, M. L. Perry, and F. R. Brushett, “Assessing Capacity Loss Remediation Methods for Asymmetric Redox Flow Battery Chemistries Using Levelized Cost of Storage,” J. Power Sources, 506 (2021). 10.1016/j.jpowsour.2021.230085 M. L. Perry, Provisional U.S. Patent Application 63/312,999 filed on Feb. 2, 2022.Yuanchao Li and Trung Van Nguyen, “A Solid/Liquid High-Energy-Density Storage Concept for Redox Flow Batteries and Its Demonstration in an H2-V System,” J. Electrochem. Soc., 169 (2022). 10.1149/1945-7111/ac97c6