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Effects of Electrode Wettability on Discharge Capacity Li-O2 Batteries

Monday, 1 October 2018: 11:00
Galactic 1 (Sunrise Center)
F. Wang and X. Li (University of Kansas)
Three kinds of customized electrodes with various wettability are fabricated in this study. Results show that electrodes containing polyvinylidene fluoride (PVDF) binder are lyophilic while the binder of polytetrafluoroethylene (PTFE) results in the lyophobicity of electrodes. The electrode with mixed wettability is composed of two lyophobic carbon coatings on top and bottom and one lyophilic carbon coating in the middle. The intermittent current (1.0 – 0 mA/cm2) strategy indicates resting Li-O2 batteries (for 10 min) between each discharge (for 5 min) to improve the oxygen transfer within the porous electrode. 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 specific discharge capacity of the PVDF 15% electrode is 1664.8 ± 259.6 mAh/g at intermittent current but it is only 807.6 ± 137.6 mAh/g at continuous 1.0 mA/cm2. The discharge capacity is improved by 106.2%. The specific discharge capacity of Li-O2 battery with mixed binders increases from 1645.9 ± 98.3 mAh/g to 2256.7 ± 225.8 mAh/g when the operation changes from continuous discharge current to intermittent discharge current. The intermittent discharge strategy is optimized based on the mixed wettability electrode and results show that discharging at 1.0 mA/cm2 for 5 min and resting for 5 min periodically achieves highest discharge capacity. This study emphasizes that the lyophobicity of electrode and intermittent discharge strategy can both enhance the O2 diffusion and thus increase the discharge capacity of Li-O2 batteries.