Li-air batteries (LABs) operated in ambient air containing moisture and CO2 highly desire the oxygen electrodes to have capability of Li2CO3 and LiOH decomposition and electro-chemical stability. Here we report the application of a stable non-carbon based oxygen electrode based on boron carbide supported ruthenium (Ru/B4C) for ambient LABs. LABs using Ru/B 4 C deliver a discharge capacity of 2689 mA h g(-1) and voltage plateaus of 2.7 V and 3.8 V for discharge and charge process, respectively at 0.1 mA cm(-2), which are comparable to those for Ru/B 4 C-based Li-O-2 battery (2796 mA h g(-1), 2.8 V and 3.7 V, respectively). Under limited capacity of 300 mA h g(-1), LAB exhibits 45 stable cycles, close to the 50 cycles for its Li-O-2 battery counterpart. The typical product for the first discharge for LAB is the mixture of Li2CO3 and Li2O2 with relative content ratio of 62:38, which cannot be detected after the first charge. The non-carbon based Ru/B4C oxygen electrode provides a promising approach for the stable operation of LABs in ambient air. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.