Superconcentrated Electrolytes for Aqueous Batteries Based on Alkali Metal Formates and Propionates

Theoretical approaches have been used to analyze the effectiveness of various ions in increasing the electrochemical potential window of aqueous electrolytes. The analysis results were used to select the most promising ions for potential electrolytes. Taking into account the theoretical estimates, the electrochemical stability and composition of aqueous superconcentrated electrolytes were investigated by experimental methods. As a result, the saturated 12 m sodium propionate solution and new formate eutectic 7.6 m LiOOCH +39.5 m KOOCH were selected. These electrolytes demonstrate high electrical conductivity and a potential window reaching 3 V, with fewer dissolved salts than in the acetate eutectics and other systems popular in literature. A formate eutectic and sodium propionate solution can be used as electrolytes for aqueous batteries and supercapacitors.