High-Throughput Methods to Identifying and Probing High Concentration Redox Electrolytes

Non-aqueous redox flow batteries (RFBs) are attractive candidates for grid storage applications.  The development of highly conductive electrolytes with high charge carrier concentrations is key to enabling cost-effective electrochemical devices.  However, given the breadth and diversity of non-aqueous electrolytes in terms of both salts and solvents, the systematic exploration required for the electrolyte optimization could be time-consuming and materials intensive when performed via traditional manual bench-scale methods.  In principle, automation may offer a means of performing such tasks in a high-throughput manner with exceptional reproducibility and minimal materials investment.

To this end, we herein demonstrate the applicability of an automated electrolyte synthesis and characterization system in the electrolyte optimization for non-aqueous RFBs in a high-throughput fashion.  Promising, down-selected formulations were investigated via electroanalytical methods.  Specifically, we study electrolytes consisting of 2,5-di-tert-butyl-1,4-bis(2-methoxyethoxy)benzene (DBBB), which has been identified as a promising redox active compound for non-aqueous RFB, and various alkali ion salts (LiBF₄, LiPF₆, LiTFSI, LiTf, NaBF₄, and NaPF₆) in carbonate-based (EC, PC, DEC, and DMC) or ether-based (DME, DOL, TEGDME, and DEGDME) solvents, with an overarching goal of improving DBBB solubility and ionic conductivity.  In addition, cyclic voltammetry of DBBB in the pre-optimized salt and solvent combination was investigated to supplement the solution properties from the high-throughput platform, and to complete the electrolyte screening for non-aqueous RFBs.