Sodium-salt/amide based deep eutectic electrolytes for sodium ion batteries

Deep eutectic solvents (DESs) have been spotlighted as potential alternative electrolytes capable of solving the problems imposed by ionic liquids1, which are mainly, the cost and low ionic conductivity when compared to conventional organic electrolytes. The ability to manipulate the melting point and electrochemical stability is important as these features determine performance2. In this study, we report on a family of Na-salt/amide-based electrolytes (DEEs) comprised of two amide derivatives (N, N¿-dimethylpropyleneurea and 2-imidazolidinone) and two representative Na-salts (NaFSI and NaTFSI), in terms of thermal and electrochemical properties. We aim to develop a new family of DEEs based on sodium-salt/amide mixtures, which exhibit remarkable eutectic effects, good ionic conductivity and a wide electrochemical stability window. Another objective of this work is to provide guidelines for designing DEEs for NIB with characteristics that can be altered by selecting a suitable sodium salt- amide derivative pair