Acetal as a class of co-intercalation-free electrolytes for lithium-ion batteries

The success of lithium-ion batteries has relied on the application of ethylene carbonate-based electrolytes, but their high freezing point and strong solvating power frustrate operation under low-temperature and fast-charging conditions. Here, we report that a class of acetal electrolytes can support reversible lithium-ion intercalation into graphite without solvent co-intercalation at conventional concentrations, which comes from the unique four-membered-ring coordination structure of lithium and anion-rich inner solvation shells resulting in the weaker solvation energy of acetal electrolytes. Furthermore, the anion-rich solvation structures also contribute to the formation of a stable inorganic-compound-dominated solid electrolyte interphase. The graphite anode retains 80% of its capacity for more than 200 cycles with single-solvent/single-salt electrolytes. The co-intercalation-free nature and wide liquid region of acetal molecules show promise for broadening the environmental suitability of batteries.