Electrolyte Development for Non-Aqueous Redox Flow Batteries Using a High-Throughput Screening Platform

Though 2,5-di-tert-butyl-1,4-bis(2-methoxyethoxy)benzene (DBBB) is a promising active species for non-aqueous redox flow batteries, the development and optimization of suitable electrolytes is still required to realize this potential. Given the breadth and diversity of non-aqueous electrolytes, combinatorial screening using automated platforms offers an efficient means of mapping out the design space. Employing an automated electrolyte synthesis and characterization system, we studied electrolytes consisting of DBBB, various alkali ion salts, and carbonate solvents, with an overarching goal of improving DBBB solubility and ionic conductivity. Via this high-throughput approach, mixtures of linear and cyclic carbonates were found to improve solubility and conductivity including certain mixtures that demonstrated both improved DBBB solubility (>0.5 M) and electrolyte conductivity (>5 mS/cm), over the base case scenario. In general, the addition of LiTFSI as a salt (or co-salt) improved DBBB solubility in electrolytes and the ionic conductivity of solutions. Furthermore, the electrochemical behavior of DBBB was systematically investigated over a range of concentrations (0.005 M to 0.3 M) in an optimized electrolyte using both macroelectrode and ultramicroelectrode techniques. Determining the trends of key electrochemical parameters may help bridge the gap between low concentration screening experiments and higher concentration energy storage applications.