Enhanced Cycling Performance of Li–O2 Battery by Highly Concentration Electrolyte of LiFSA/Methyl Pivalate

Abstract

Finding a stable organic electrolyte to improve the cycling life of lithium-oxygen (Li–O2) batteries is of primary importance. Tetra(ethylene) glycol dimethyl ether (TEGDME) based electrolytes are the most commonly used in Li–O2 batteries, however, they are still unstable in the presence of superoxides or singlet oxygen, and finally result in the performance reduction during long-term operation. Here a stable electrolyte designed to solve this issue is reported. By mixing dissociative LiFSA salt with methyl pivalate (MP) solvent at super-high concentration, an unusual three-dimensional network of FSA− anions and solvent molecules strongly complexed with Li+ ions is obtained. This unusual structure of the superconcentrated solution is different from the dilute and moderately concentrated solutions. Due to its special structural characteristics, the Li–O2 battery with the superconcentrated LiFSA/MP electrolyte exhibited excellent cycling stability, which was about 4 times higher than the battery with the conventional TEGDME based electrolyte.