Water-in-salt electrolytes for aqueous lithium-ion batteries with liquidus temperatures below -10 °C.

Crystallization near room temperature is a common challenge for water-in-salt electrolytes. We demonstrate that water-in-salt electrolytes based on lithium (pentafluoroethanesulfonyl)(trifluoromethanesulfonyl)imide remain thermodynamically in the liquid state down to at least -10 °C. Combined with their excellent chemical and electrochemical stability as well as high lithium-ion conductivity, these electrolytes represent a key enabler for the next generation of high-voltage aqueous lithium-ion batteries.