Rational Engineering of Amide-Based Electrolytes for “True”-Lithium–Air Batteries Working by Atmospheric Oxygen

Lithium–air batteries (LABs) offer ultrahigh energy density, but their practical use is limited by the sluggish oxygen reduction reaction, which requires operation under pure oxygen and yields extremely low power output. Herein, to boost both the power and energy under air oxygen, we investigated the discharge performance of LAB cells with low-viscosity amide-based electrolytes, N,N-dimethylacetamide (DMA) and N,N-dimethylformamide (DMF), dissolving lithium nitrate (LiNO3) or lithium bis(trifluloromethanesulfonyl)imide (LiTFSI). With viscosities 1/3–1/4 lower than that of the typical LAB solvent of tetraethylene glycol dimethyl ether (TEG), the amide-based electrolytes ensure rapid transport of oxygen and Li+ ions, thereby enhancing battery output. Raman spectroscopy revealed that LiNO3-based electrolytes exhibit weaker solvation, explaining their lower viscosity with slightly reduced ionic conductivity compared to LiTFSI-based electrolytes, with this effect more evident in DMF. As a result, LAB cells with DMF electrolyte dissolving 1.0 M LiNO3 (DMF-NO3) achieved the highest current density discharge of 23 mA cm–2 with a capacity of 2.2 mAh cm–2 under dry air, corresponding to an “engine-like” power of 2200 W kg–1 and an energy density of 210 Wh kgenergy–1. Galvanostatic discharge–charge cycling tests revealed better cyclability for DMA-based electrolytes due to reduced solvent volatilization. Anion mixing further suppressed the solvent loss and minimized side reactions, providing 200 Wh kgenergy–1 over 14 cycles. Due to the milder oxidative conditions, LAB cells increased the rechargeability under dry air rather than under pure oxygen. This work paves the way for the development of “true” LABs capable of operating efficiently using atmospheric oxygen.