Complete Decomposition of Li₂CO₃ in Li-O₂ Batteries Using Ir/B₄C as Noncarbon-Based Oxygen Electrode.

Abstract

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.