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.