PNNL

Abstract

Irreversible parasitic reactions and the accumulation of insulating side products are two of the main barriers for practical application of rechargeable Li-O2 batteries. Therefore, it is critical to develop multifunctional oxygen electrodes suitable for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and decomposition of side reaction products. Here we report the application of ultrafine ruthenium-deposited boron carbide (Ru/B4C) with remarkably multifunctional activities as non-carbon-based oxygen electrodes for Li-O2 batteries. Li2CO3 and LiOH can be completely decomposed by Ru/B4C at 3.97 V and 4.1 V, respectively, within the stability window of the ether-based electrolyte. A Li-O2 battery using a Ru/B4C oxygen electrode achieves a high discharge voltage plateau of 2.8 V, a significantly low charge voltage of 3.7 V, and good cycling performance under a limited capacity of 300 mAh gRu/B4C-1. In-situ gas chromatography analysis reveals that O2 is the major gas product during charge. Only a negligible amount of CO2 is observed in the first charge, in either a shallowly or a deeply discharged cell. Therefore, Ru/B4C can be used as a very promising oxygen-electrode material for Li-O2 batteries and Li-air batteries operated in ambient air.