Non-aqueous electrolytes are based on highly flammable solvents as well as thermally unstable and extremely toxic lithium salts. Their fabrication procedures as well as the components themselves incur substantial costs and safety concerns.
Water‐based electrolytes offer a safer, potentially cheaper alternative to organic solvent-based electrolytes. However, they are limited by the narrow electrochemical stability window of water which is only 1.23V due to the reduction potential and oxidation potentials of water. This has prevented aqueous high energy density LIBs to compete with their non‐aqueous counterparts operating above 4V.
Water-in-salt electrolytes refer to aqueous solvents with relatively high amounts of salt dissolved in solution. The presence of high salt concentrations alters the composition of the solid electrolyte interphase resulting in the expansion of the electrochemical stability window of water. This enables the possibility of high voltage aqueous based electrolytes. These electrolytes are currently being investigated by our group.