Regulation of Molecular Microheterogeneity in Electrolytes Enables Ampere‐Hour‐Level Aqueous LiMn₂O₄||Li₄Ti₅O₁₂ Pouch Cells

Abstract Aqueous batteries are attractive due to their high safety and fast reaction kinetics, but the narrow electrochemical stability window of H₂O limits their applications. It is a big challenge to broaden the electrochemical operation window of aqueous electrolytes while retaining fast reaction kinetics. Here, a new organic aqueous mixture electrolyte of manipulatable (3D) molecular microheterogeneity with H₂O‐rich and H₂O‐poor domains is demonstrated. H₂O‐poor domains molecularly surround the reformed microclusters of H₂O molecules through interfacial H‐bonds, which thus not only inhibit the long‐range transfer of H₂O but also allow fast and consecutive Li⁺ transport. This new design enables low‐voltage anodes reversibly cycling with aqueous‐based electrolytes and high ionic conductivity of 4.5 mS cm⁻¹. LiMn₂O₄||Li₄Ti₅O₁₂ full cells demonstrate excellent cycling stability over 1000 cycles under various C rates and a low temperature of −20 °C. 1 Ah pouch cell delivers a high energy density of 79.3 Wh kg⁻¹ and high Coulombic efficiency of 99.4% at 1 C over 200 cycles. This work provides new insights into the design of electrolytes based on the molecular microheterogeneity for rechargeable batteries.