Magneli-Phase Ti4O7 Nanosphere Electrocatalyst Support for Carbon-Free Oxygen Electrodes in Lithium-Oxygen Batteries

Lithium-oxygen batteries have been considerably researched due to their potential for high energy density compared to some rechargeable batteries. However, it is known that the stability of a carbon-based oxygen electrode is insufficient owing to the promotion of carbonate formation, which results in capacity fading and large overpotential in lithium-oxygen batteries. To improve the chemical stability in organic-based electrolytes, alternative electrocatalyst support materials are required. The Ti-O crystal system appears to provide a good compromise between electrochemical performance and cost and is thus an interesting material for further investigation. Here, we investigate a carbon-free electrode with the goal of identifying routes for its successful optimization. To replace carbon materials as an electrocatalyst support, Magneli Ti4O7 nanospheres were synthesized from anatase TiO2 nanospheres via a controlled thermochemical reduction. The Magna Ti4O7 nanospheres demonstrated effective overpotential characteristics (1.53 V) compared to the anatase TiO2 nanospheres (1.91 V) during charge-discharge cycling at a current rate of 100 mA g(-1). Additionally, RuO2@Magneli-Ti4O7 nanospheres were prepared as a bifunctional catalyst-containing oxygen electrode for lithium-oxygen batteries, providing a remarkably reduced overpotential (0.9 V).