Optimizing Discharge Capacity of Graphite Nanosheet Electrodes for Lithium-Oxygen Batteries.

Lithium-oxygen (Li-O₂) batteries require scalable air electrode concepts and a sensible choice of operation parameters to achieve their promised energy densities. Furthermore, different test parameters are often investigated individually, but rarely brought together in order to optimize the discharge process and unlock the full discharge capability of an air electrode. In this work, we present a highly porous electrode based on graphite nanosheets (GNS) and discuss the impact of the discharge current density and the oxygen pressure as battery test parameters, as well as the electrolyte salt and volume, on the discharge behavior. In particular, changing the electrolyte salt from LiNO₃ to LiTFSI proved to be an important step towards better cell performance, because synergistic effects of the electrolyte and GNS greatly enhance the carbon-specific capacity. The optimized combination of the aforementioned parameters enabled a remarkably high discharge capacity of 56.3 mAh/cm² (5860 mAh/gcarbon) obtained at 150 μA/cm² (15.6 mA/gcarbon), resulting in the almost complete conversion of the lithium anode. These experimental results are an important step towards practical high-capacity air electrodes for Li-O2 batteries. [ABSTRACT FROM AUTHOR]