Looking to design next-gen aqueous electrolytes beyond water-in-salt electrolytes, aqueous electrolytes with a lower salt concentration of &lt;5.0 m (mol kg–1) and wider electrochemical stability window of &gt;3.0 V are urgently needed. Here we develop a 4.5 m LiTFSI–KOH–CO(NH2)2–H2O non-flammable ternary eutectic electrolyte that expands the electrochemical stability window to &gt;3.3 V. The ternary eutectic electrolyte can reduce the number of H2O in a Li+ solvation shell to 0.7 and the reduction of LiTFSI and CO(NH2)2 under KOH catalyst formed a robust LiF/polymer bilayer solid–electrolyte interphase. Moreover, Li-rich Li1.5Mn2O4 is used as a lithium reservoir, which compensates for the Li-loss in the anode and converts to LiMn2O4 at the same time. Ultimately, the assembled pouch cells with practical settings (an areal capacity of 2.5 mAh cm–2, a low positive/negative capacity ratio of 1.14, and a lean electrolyte (3 g Ah–1)) achieve a high average Coulombic efficiency of 99.96% and capacity retention of 92% over 470 cycles. This battery chemistry – in addition to superior performance – is safe/non-flammable, low cost, and environmentally friendly, thus paving the way for the use of aqueous lithium-ion batteries in everyday applications.

Aqueous electrolyte design for 2.5 V LiMn2O4 || Li4Ti5O12 pouch cells

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ACS Fall 2022

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