Liquid‐Based Janus Electrolyte for Sustainable Redox Mediation in Lithium–Oxygen Batteries

Abstract The discovery of a reliable electrolyte system remains one of the key challenges for the development of advanced lithium–oxygen batteries. To date, no single electrolyte is verified to be stable and compatible with both the cathode (e.g., oxygen radicals, lithium peroxide, etc.) and anode (lithium metal) for lithium–oxygen batteries. In this work, a novel liquid‐based Janus electrolyte system consisting of two different immiscible liquid phases is proposed and it is demonstrated that this system is remarkably effective in promoting the sustainable operation of redox‐mediated lithium–oxygen batteries. The liquid‐based Janus electrolyte is rationally designed by considering its compatibility with the lithium–oxygen cell environment, the solubility difference of target soluble species, and the mutual immiscibility of the two liquid phases. By combining spectral characterization, a phase‐separation experiment, and in situ observation of the electrochemical cell, it is revealed that the liquid‐based Janus electrolyte suppresses the migration of redox mediators from one liquid phase to the other, thereby preventing the detrimental shuttle effect. The enhanced stability of redox mediation leads to improved cycling performance of the cell. The various combinations possible for the liquid‐based Janus electrolyte open a new unexplored pathway for the design of advanced electrolyte systems for lithium–oxygen batteries.