Methanesulfonate in phosphate superionic electrolyte enables ampere-hour practical aqueous batteries

Present high-voltage Li-ion aqueous batteries largely rely on highly concentrated (up to 63 <i>m</i>) "water-in-salt" electrolyte with limited cycle life (<1,000 cycles) and little hope in practical application. To date, no dilute aqueous electrolyte (salt molality < 2 <i>m</i>) can reliably operate beyond 2 V with cycling life over 1,000 cycles. Here, we introduce a "methanesulfonate in phosphate" superstructure that simultaneously tailors Li⁺ migration in molecular crowding solvent and electrode surfaces, which enables an unprecedented electrochemical stability window (up to 4.5 V) and cyclability (up to 10,000 cycles) in a dilute 1.1-<i>m</i> aqueous electrolyte. In addition, Such methanesulfonate in phosphate electrolyte can be also applied in various high-voltage electrode couples, and the assembled 60-V, 15-A·h LiMn₂O₄/LiTi₂(PO₄)₃ aqueous battery can drive an electric bike for 70 km, highlighting the power of such electrolyte design in the commercialization of high-voltage aqueous batteries.