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Summary Recent breakthroughs in aqueous electrolytes made highly safe 3.0 V class aqueous Li-ion batteries possible. However, the formed solid-electrolyte interphase therein still cannot effectively support the desired energy-dense anode and cathode materials. In this work, we report a new class of electrolytes, by hybridizing aqueous with non-aqueous solvents, that inherits the non-flammability and non-toxicity characteristics from aqueous and better electrochemical stability from non-aqueous systems. The secondary interphasial ingredient (alkylcarbonate) introduced by non-aqueous component helps to expand the electrochemical window of the hybridized electrolyte to 4.1 V, which supports the operation of a 3.2 V aqueous Li-ion battery based on Li 4 Ti 5 O 12 and LiNi 0.5 Mn 1.5 O 4 to deliver a high energy density of 165 Wh/kg for >1,000 cycles. The understanding of how a better interphase could be tailored by regulating the inner-Helmholtz interfacial structures of the hybridized electrolyte provides important guidelines for designing future electrolytes and interphases for new battery chemistries.