Although Li–air rechargeable batteries offer higher energy densities than lithium-ion batteries, the insulating Li₂O₂ formed during discharge hinders rapid, efficient re-charging. Redox mediators are used to facilitate Li₂O₂ oxidation; however, fast kinetics at a low charging voltage are necessary for practical applications and are yet to be achieved. We investigate the mechanism of Li₂O₂ oxidation by redox mediators. The rate-limiting step is the outer-sphere one-electron oxidation of Li₂O₂ to LiO₂, which follows Marcus theory. The second step is dominated by LiO₂ disproportionation, forming mostly triplet-state O₂. The yield of singlet-state O₂ depends on the redox potential of the mediator in a way that does not correlate with electrolyte degradation, in contrast to earlier views. Our mechanistic understanding explains why current low-voltage mediators (<+3.3 V) fail to deliver high rates (the maximum rate is at +3.74 V) and suggests important mediator design strategies to deliver sufficiently high rates for fast charging at potentials closer to the thermodynamic potential of Li₂O₂ oxidation (+2.96 V).

尽管锂空气充电电池比锂离子电池提供更高的能量密度，但放电过程中形成的绝缘Li ₂ O ₂阻碍了快速、有效的再充电。氧化还原介体用于促进Li ₂ O ₂氧化；然而，低充电电压下的快速动力学对于实际应用是必要的，但尚未实现。我们研究了氧化还原介质氧化Li ₂ O ₂的机制。限速步骤是Li ₂ O ₂的外球单电子氧化为LiO ₂，​​其遵循Marcus理论。第二步以LiO2_为主歧化，主要形成三重态O ₂。与早期观点相反，单线态 O ₂的产率取决于介体的氧化还原电位，而与电解质降解无关。我们的机制理解解释了为什么当前的低压介体 (<+3.3 V) 无法提供高速率（最大速率为 +3.74 V），并提出了重要的介体设计策略，以提供足够高的速率，以接近充电电压的电位进行快速充电。 Li ₂ O ₂氧化的热力学势(+2.96 V)。