Hydrogen/Vanadium Hybrid Redox Flow Battery with enhanced electrolyte concentration

Abstract A high energy density Hydrogen/Vanadium (6 ​M HCl) system is demonstrated with increased vanadium concentration (2.5 ​M vs. 1 M), and standard cell potential (1.167 vs. 1.000 ​V) and high theoretical storage capacity (65 ​W h L−1) compared to previous vanadium systems. The system is enabled through the development and use of HER/HOR catalysts with improved chemical stability towards the halogen-containing electrolyte within which the usual catalyst (Pt/C) is shown to quickly degrade during potential hold experiments. The implementation of an Ir/C catalyst at the negative side enables a system with high achievable energy density of 45 ​W ​h ​L−1 at 75 ​mA ​cm−2 associated with 67% electrolyte utilization. Based on such a promising performance, the system here presented could be a suitable solution for medium and large-scale energy storage with lower cost and volume footprint than existing batteries, particularly all-vanadium RFBs.