N,N-Dimethylacetamide-Diluted Nitrate Electrolyte for Aqueous Zn//LiMn₂O₄ Hybrid Ion Batteries

N,N-Dimethylacetamide (DMA) cooperated with LiNO₃ salt has previously shown to be a promising electrolyte for a Li//O₂ battery, showing good stability against both the O₂ electrode reaction and Li stripping/plating. In this work, DMA is hybridized with a concentrated nitrate electrolyte [2.5 m Zn(NO₃)₂ + 13 m LiNO₃ aqueous solution] for better electrochemical stability while using less dissolved salts. The widest electrochemical stability window for this DMA-diluted electrolyte is determined as 3.1 V, the negative critical stability potential of which is -1.6 V versus Ag/AgCl, indicating desirable stability against hydrogen evolution and Zn deposition. The findings can be attributed to the weakened Li⁺/Zn²⁺ solvation sheath caused by low permittivity of DMA, as revealed through Raman spectra characterization and molecular dynamics simulation. A Zn//Zn symmetrical cell and Zn//LiMn₂O₄ hybrid ion batteries are assembled in air directly, attributed to the stability of DMA toward O₂. Zn stripping/plating with a dendrite-free morphology is delivered for 110 h and 200 charge/discharge cycles under 1 C rate, achieving 99.0% Coulombic efficiency. The maximum capacity of the battery is 121.0 mA h·g^-1 under 0.2 C rate (based on the mass of LiMn₂O₄), delivering an energy density of 165.8 W h·kg^-1 together with 2.0 V working voltage. This work demonstrates the feasibility and validity of utilizing a relatively dilute electrolyte dissolved in oxygen for a highly stable aqueous rechargeable battery.