Dispersion hydrophobic electrolyte enables lithium-oxygen battery enduring saturated water vapor

Abstract

Li–O2 batteries gain widespread attention as a candidate for next-generation energy storage devices due to their extraordinary theoretic specific energy. The semi-open structure of Li–O2 batteries causes many parasitic reactions, especially related to water. Water is a double-edged sword, which destroys Li anode and simultaneously triggers a solution-based pathway of the discharge product. In this work, hexamethyldisilazane (HMDS) is introduced into the electrolyte of an aprotic Li–O2 battery. HMDS has a strong ability to combine with a trace of water to generate a hydrophobic hexamethyldisiloxane (MM), which eliminates water from the electrolyte decomposition and then prevents the Li anode from producing the insulating LiOH with water. In this case, the hydrophobic MM disperses in the ether-based electrolyte, forming a dispersion hydrophobic electrolyte. This electrolyte can anchor water from the environment on the cathode side, which triggers a solution-based pathway and regulates the growth morphology of the discharge product and consequently increases the discharge capacity. Compared with the Li–O2 battery without the HMDS, the HMDS-containing Li–O2 battery contributes an about 13-fold increase of cyclability (400 cycles, 1800 h) in the extreme environment of saturated water vapor. This work opens a new approach for directly operating aprotic Li–O2 batteries in ambient air.