Investigation of Electrolyte Concentration Effects on the Performance of Lithium–Oxygen Batteries

Abstract

A combined experimental and computational study has been performed in order to elucidate the effect of electrolyte salt concentration on the performance of Li–O2 batteries. Four electrolyte solutions with varying lithium triflimide (LiTFSI) content in 1,2-dimethoxyethane (DME) were studied to identify principal failure mechanisms in Li–O2 batteries for dilute and concentrated electrolytes (0.1 M to saturation) in cells cycled with high overpotentials and/or deep discharge. Quantitative 19F NMR was employed to determine that in 0.1 M electrolyte solutions salt decomposition can contribute to limitations in cell recycling arising from low ionic conductivity due to a decrease in available soluble Li+ over multiple cycles. In contrast, increased salt decomposition in high-concentration electrolytes can result in cathode passivation by insoluble Li salts that impact capacity by hindering Li2O2 production and further inhibiting electronic conductivity. By employing first-principles calculations, we modeled diff...