Sacrificial Co-solvent Electrolyte to Construct a Stable Solid Electrolyte Interphase in Lithium–Oxygen Batteries

Lithium-oxygen batteries are vital devices for electrochemical energy storage. The electrolyte is a crucial factor for improving battery performance. The high reactivity of lithium metal induces side reactions with organic electrolytes, thus leading to an unstable interface between the anode and electrolyte and poor performance of batteries. In this work, to compensate for the above shortcomings, 1-methylimidazole (MeIm) is introduced to the tetraethylene glycol dimethyl ether (TEGDME) electrolyte to form the TEGDME/MeIm co-solvent electrolyte. Because of the high donor number value of MeIm, the solution-based pathway of discharge products can be triggered. Compared with the single TEGDME electrolyte, the discharge capacity with the TEGDME/MeIm co-solvent electrolyte is increased by more than 2 times. Moreover, the TEGDME/MeIm co-solvent electrolyte can promote the dissociation of Li salt due to the high dielectric constant of MeIm and thus make up for the shortcomings of TEGDME. In addition, due to the lower energy than the lowest unoccupied molecular orbital (LUMO) level of TEGDME, MeIm is decomposed preferentially, and a dense solid electrolyte interphase (SEI) layer is constructed. Then, the decomposition of TEGDME is suppressed. Therefore, the cycle performance of the battery with the TEGDME/MeIm co-solvent electrolyte is 18 times compared to that with the single TEGDME electrolyte.