Free-Standing Type Mixed Oxide Oxygen Electrode for Rechargeable Li–O2 Batteries
In this study, for the first time we introduce a free-standing type oxygen electrode design, where additional carbon and binders are no longer necessary in the oxygen electrode of Li–O2 battery. A simple and cost effective solvo-thermal techniques was used to fabricate free standing carbon-free electrodes. The highly porous structure of the electrode allows electrolyte and oxygen to diffuse effectively into the catalytic active sites and hence improve the performance. The discharge products would precipitate and decompose on the pores of the free-standing catalyst nanorods. In this study, Mn-based composite oxide was selected as the catalyst candidate and directly deposited on the metallic nickel foam which was applied as the current collector. The electrochemical examination demonstrates that the free-standing electrode without carbon support gives almost the highest cell potential during discharge (2.85 V), the lowest cell potential during charge (3.54 V), almost the highest specific capacity (when considering all active mass in the cathode) and the minimum capacity fading among the rechargeable Li–O2 batteries reported to date. The Li-O2 battery demonstrated cyclability for more than 100 cycles while maintaining a moderate specific capacity of 1000 mAh g-1. Further, the synergistic effect of the fast kinetics of electron transport provided by the free standing structure and the high electro-catalytic activity of the composite oxide enabled the excellent performance of the oxygen electrode for Li-O2 batteries.