Direct Visualization of Dynamic Mobility of Li2O2 in Li-O2 Batteries: A Differential Interference Microscopy Study

The reversibility and the discharge/charge performance in nonaqueous lithium-oxygen (Li-O-2) batteries are critically dependent on the kinetics of interfacial reactions. However, the interfacial reaction dynamic behaviors, especially the quantitative analysis, are still far from deep understanding. Using the method of laser confocal microscopy combined with differential interference contrast microscopy (LCM-DIM), we monitored the Li-O-2 interfacial reaction and in situ traced the Li2O2 migration processes promoted by the solution catalyst. Different dynamic behaviors exist when regulating the concentration of the redox mediator. Quantitative analysis of the discharged Li2O2 particles shows high mobility at the early discharge stage and decayed motion in the subsequent process, indicating the solution-mediated pathway participating Li2O2 formation in the low-concentration redox mediator addition, while particles/aggregates confined into the amorphous film demonstrate simultaneous solution and surface route-mediated pathway participation in the high-concentration case. These distinctive observations of Li2O2 formation and decomposition processes present the advantage of LCM-DIM to fundamentally understand the dynamic evolution in Li-O-2 batteries.

Automated summary

The kinetics of interfacial reactions play a critical role in the reversibility and discharge/charge performance of nonaqueous lithium-oxygen (Li-O-2) batteries. This study used laser confocal microscopy combined with differential interference contrast microscopy (LCM-DIM) to monitor the Li-O-2 interfacial reaction and trace the Li2O2 migration processes. The concentration of the redox mediator was found to affect the dynamic behavior of the reaction. In low concentrations, Li2O2 particles showed high mobility at the early discharge stage, while in high concentrations, both solution and surface routes participated in Li2O2 formation.