Abstract
Long-Duration Energy Storages (LDES), with the ability to store excess energy generated by renewable sources such as solar and wind, play a vital role in ensuring a continuous and reliable power supply, which is crucial in promoting a more sustainable future. Redox flow batteries (RFBs) have attracted a great deal of attention as a highly suitable system for LDES, because of offering easy scalability, great flexibility by decoupling power and energy capacity, long cycle life, and enhanced safety. While all-vanadium RFBs are widely used as the most mature technology currently, for further market development, the research on novel RFB electrolytes aims to explore resource-unconstrained materials, such as titanium or manganese, that can achieve longer-duration capacity at reduced cost compared to vanadium [1][2].Complex-type Fe-Cr materials have gained traction as RFB electrolytes due to their high electromotive force exceeding 1.6V [3]. In this report, we investigate KCrPDTA and K4[Fe(CN)6] aqueous solutions as electrolytes by conducting over 400 hours of charge-discharge operations in a RFB system with the total electrolyte volume of 6L, yielding excellent results including coulombic efficiency >99.9%, cell resistance of 0.95Ω・cm2, and energy density of 16.7 kWh/m3.However, there are still several challenges to overcome for the practical application of these active materials. These identified challenges encompass limited solubility of positive electrolyte that restricts the energy density, serious pH stability of charged negative electrolyte, hydrogen generation due to the extremely low redox reaction potential, and issues with the current separator membranes.[1] Y. Dong, et al. "A novel titanium/manganese redox flow battery." ECS Transactions 69.18 (2015): 59.[2] H. Kaku, et al. "Enhanced performance of Ti/Mn redox flow battery." ECS Transactions 77.11 (2017): 173.[3] B. Robb, et al. "Chelated chromium electrolyte enabling high-voltage aqueous flow batteries." Joule 3.10 (2019): 2503-2512.
Published Version
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