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![A review of the energy storage aspects of chemical elements for lithium-ion based batteries](https://image.oaes.cc/fca7603e-34c6-490b-93fd-d564f3994d92/4450.fig.3.jpg)
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).