A Stable Lithium–Oxygen Battery Electrolyte Based on Fully Methylated Cyclic Ether

Full methyl jacket: A fully methylated cyclic ether 4,4,5,5‐hexamethyl‐1,3‐dioxolane is used as an electrolyte solvent for Li–O₂ batteries. It exhibits excellent stability in the presence of superoxide or singlet oxygen because all the active α‐H atoms are substituted with methyl groups. The cycling performance is 4 times greater that of conventional ether electrolytes.

Abstract

Ether‐based electrolytes are commonly used in Li–O₂ batteries (LOBs) because of their relatively high stability. But they are still prone to be attacked by superoxides or singlet oxygen via hydrogen abstract reactions, which leads to performance decaying during long‐term operation. Herein we propose a methylated cyclic ether, 2,2,4,4,5,5‐hexamethyl‐1,3‐dioxolane (HMD), as a stable electrolyte solvent for LOBs. Such a compound does not contain any hydrogen atoms on the alpha‐carbon of the ether, and thus avoids hydrogen abstraction reactions. As the result, this solvent exhibits excellent stability with the presence of superoxide or singlet oxygen. In addition the CO₂ evolution during charge process is prohibited. The LOB with HMD‐based electrolyte was able to run up to 157 cycles, 4 times more than with 1,3‐dioxolane (DOL) or 1,2‐dimethoxyethane (DME) based electrolytes.

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