The rechargeable lithium–oxygen (Li–O2) battery has the highest theoretical specific energy density of any rechargeable batteries and could transform energy storage systems if a practical device could be attained. However, among numerous challenges, which are all interconnected, are polarization due to sluggish kinetics, low cycle life, small capacity, and slow rates. In this study, we report on use of KMnO4to generate a colloidal electrolyte made up of MnO2nanoparticles. The resulting electrolyte provides a redox mediator for reducing the charge potential and lithium anode protection to increase cycle life. This electrolyte in combination with a stable binary transition metal dichalcogenide alloy, Nb0.5Ta0.5S2, as the cathode enables the operation of a Li–O2battery at a current density of 1 mA·cm–2and specific capacity ranging from 1000 to 10 000 mA·h·g–1(corresponding to 0.1–1 mA·h·cm–2) in a dry air environment with a cycle life of up to 150. This colloidal electrolyte provides a robust approach for advancing Li–air batteries.