Enabling high-energy-density aqueous batteries with hydrogen bond-anchored electrolytes

Conventional aqueous electrolytes suffer from a narrow voltage window due to water decomposition. Highly concentrated electrolytes expand the voltage window; however, they are limited by high cost and potential toxicity. Here, we develop a hydrogen bond-anchored electrolyte by introducing sulfolane as hydrogen bond acceptor to limit water activity. The designed electrolyte expands the voltage window to 3.4 V (1.3–4.7 V versus Li⁺/Li) and forms a hierarchical anode-electrolyte interphase to suppress the hydrogen evolution reaction. An aqueous Li₄Ti₅O₁₂/LiMn₂O₄ full cell achieved 141 W h kg⁻¹ for 300 cycles at 1 C and 125 W h kg⁻¹ for 1,000 cycles at 5 C with a high Coulombic efficiency of 99.5%–99.9%. On-line electrochemical mass spectroscopy shows negligible hydrogen/oxygen gas evolution upon cycling, further confirming the stability of the designed electrolyte. This work demonstrates a rational and effective approach to suppress the hydrogen evolution reaction and achieve stable high-voltage aqueous batteries.