fig3

Figure 3. (A) Schematic diagram of reactions in a Li-O₂ cathode (O₂ + 2Li⁺ + 2e^- ↔ Li₂O₂) during charge/discharge process in a typical electrolyte. Li₂O₂, an insulating and insoluble discharge product, develops on the surface of the conducting porous substrate and suppresses the electron transport. (B) The mediators M and M' mediate electron/hole transport. In an inner sphere process, the reduction mediator M can transfer electrons to O₂ via an O₂-binding transition state or in an outer sphere process via an O₂-binding transition state. Reproduced with permission from Ref.^[48] (Copyright 2017, Royal Society of Chemistry).