Suppressing Singlet Oxygen Formation during the Charge Process of Li-O-2 Batteries with a Co3O4 Solid Catalyst Revealed by Operando Electron Paramagnetic Resonance

Aprotic lithium-oxygen (Li-O-2) batteries promise high energy, but the cycle life has been plagued by two major obstacles, the insulating products and highly reactive singlet oxygen (O-1(2)), which cause higher overpotential and parasitic reactions, respectively. A solid-state catalyst is known to reduce overpotential; however, it is unclear whether it affects O-1(2) generation. Herein, Co3O4 was employed as the representative catalyst in Li-O-2 batteries, and O-1(2) 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 O-1(2) generation in the charge process can be suppressed by the Co(3)O(4 )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 O-1(2) generation during the early charge stage. The Co(3)O(4 )catalyst reduces the amount of LiO2-like species in discharge products, and thus the O-1(2) formation is suppressed.