Herein we present an alternative indicator to DN that controls the discharge capacity in the Li-O2 batteries. We focused on the effect of the range of combinations of cathode substrates and electrolytes on the discharge capacity. When we used Au-mesh as cathode, higher discharge capacity was obtained in a higher DN of dimethyl sulfoxide (DMSO) electrolytes (LiTFSI in DMSO) than that obtained in a lower DN of acetonitrile (MeCN) electrolyte, as reported previously.6 However, interestingly, higher capacity was obtained in the MeCN electrolytes when a carbon material was applied as the cathode. Through these experiments, we also found that the negative differential resistance (NDR), which appears when the coverage of the inhibitor on the electrode depends on the potential of the electrode, is a critical indicator determining the discharge capacity of Li-O2 batteries. The NDR in the oxygen reduction reaction (ORR) potential region implies that LiO2 works as an inhibitor of ORR. The higher discharge capacity can be obtained when the ORR proceeds at higher potential than NDR region, because LiO2 is desorbed from the electrode and the solution pathway is promoted. Our results indicate that this correlation between the NDR and the discharge capacity is generally applied to Li-O2 battery system.
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