Discharge Li-O2 batteries with intermittent current

This study periodically rests Li-O2 batteries (for 5-10 min) between each 2-10 min discharge to improve the oxygen transfer within the porous electrode. Periodically resting the battery increases the specific discharge capacity by at least 50% at various current densities (0.1-1.5 mA/cm2). Multistep discharge at decreasing current rates (2.0, 1.5, and 1.0 mA/cm2) is also proposed to increase the overall discharge capacity with a given cutoff voltage. The performance improvement is mainly due to the enhanced O2 diffusion during rest between intermittent discharge. The lyophilic electrode has the highest increase rate of discharge capacity after applying intermittent current while the electrode with mixed wettability achieves the highest specific discharge capacity. The resting and discharging time of electrodes with mixed wettability are then optimized at 1.0 mA/cm2. Cycling tests with 1000 mA h/g and 1500 mAh/g cut-off capacities at 1.0 mA/cm2 are also performed. The batteries completed similar numbers of cycles with a higher cut-off capacity (1500 mAh/g) applying intermittent discharge, compared with applying continuous current (1000 mAh/g cut-off capacity). This study emphasizes the importance of O2 diffusion and provides practical strategies to improve the deep discharge capacity of Li-O2 batteries, especially at high current rates (>1.0 mA/cm2).