Instability of carbon-based oxygen electrodes and incomplete decomposition of Li2CO3 during charge process are critical barriers for rechargeable Li-O2 batteries. Here we report the complete decomposition of Li2CO3 in Li-O2 batteries using the ultrafine iridium-decorated boron carbide (Ir/B4C) nanocomposite as a noncarbon based oxygen electrode. The systematic investigation on charging the Li2CO3 preloaded Ir/B4C electrode in an ether-based electrolyte demonstrates that the Ir/B4C electrode can decompose Li2CO3 with an efficiency close to 100% at a voltage below 4.37 V. In contrast, the bare B4C without Ir electrocatalyst can only decompose 4.7% of the preloaded Li2CO3. Theoretical analysis indicates that the high efficiency decomposition of Li2CO3 can be attributed to the synergistic effects of Ir and B4C. Ir has a high affinity for oxygen species, which could lower the energy barrier for electrochemical oxidation of Li2CO3. B4C exhibits much higher chemical and electrochemical stability than carbon-based electrodes and high catalytic activity for Li-O2 reactions. A Li-O2 battery using Ir/B4C as the oxygen electrode material shows highly enhanced cycling stability than those using the bare B4C oxygen electrode. Further development of these stable oxygen-electrodes could accelerate practical applications of Li-O2 batteries.
Keywords: Li2CO3 decomposition; boron carbide; iridium catalyst; lithium−oxygen battery; noncarbon oxygen electrode.