Synergistic coupling of a self-defense redox mediator and anti-superoxide disproportionator in lithium-oxygen batteries for high stability

In this study, a detailed analysis of the characteristics of lithium–oxygen batteries (LOBs) combined with cobalt iodide as a self-defense redox mediator is conducted, and their synergistic effect with propagermanium as an anti-superoxide disproportionator is explored. Cobalt iodide acts as a self-defense redox mediator for the electrodes and nonaqueous electrolytes. The Li anode is coated with Co metal by cobalt cations to prevent the growth of dendrites and passivation layers, while the iodide anions lower the overpotential, acting as a typical redox mediator. However, as the number of cycles increased, the iodide anions become oxidized and its function as a redox mediator is inhibited. To prevent this degradation, as an effective anti-superoxide disproportionator, propagermanium is proposed as a means of effectively inhibiting the parasitic reaction in LOBs. Consequently, the simultaneous use of a self-defensive redox mediator and anti-superoxide disproportionator yielded LOBs with a low discharge–charge overpotential (0.48 V) and long-term cycling performance (300 cycles).