Suppressing Singlet Oxygen Formation during the Charge Process of Li-O₂ Batteries with a Co₃O₄ Solid Catalyst...

Aprotic lithium-oxygen (Li-O₂) batteries promise high energy, but the cycle life has been plagued by two major obstacles, the insulating products and highly reactive singlet oxygen (¹O₂), which cause higher overpotential and parasitic reactions, respectively. A solid-state catalyst is known to reduce overpotential; however, it is unclear whether it affects ¹O₂ generation. Herein, Co₃O₄ was employed as the representative catalyst in Li-O₂ batteries, and ¹O₂ generation was investigated by ex-situ and operando electron paramagnetic resonance (EPR) spectroscopy. By comparing a carbon nanotube (CNT) cathode with a Co₃O₄/CNT cathode, we find that ¹O₂ generation in the charge process can be suppressed by the Co₃O₄ catalyst. After carefully studying the discharge products on the two electrodes and the corresponding decomposition processes, we conclude that a LiO₂-like species is responsible for the ¹O₂ generation during the early charge stage. The Co₃O₄ catalyst reduces the amount of LiO₂-like species in discharge products, and thus the ¹O₂ formation is suppressed.