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//O-2 battery, showing good stability against both the O-2 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 O-2. 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.

Automated summary

The use of a hybrid electrolyte of DMA and concentrated nitrate has shown potential in providing good electrochemical stability while using fewer dissolved salts. Through analysis and molecular dynamics simulation, it was found that the stability of the electrolyte can be attributed to the weakened Li+/Zn2+ solvation sheath caused by the low permittivity of DMA. This work demonstrates the feasibility of utilizing a relatively dilute electrolyte dissolved in oxygen for a highly stable aqueous rechargeable battery.