Probing the Self-Boosting Catalysis of LiCoO2 in Li-O2 Battery with Multiple In Situ/Operando Techniques

Designing high-activity catalysts and revealing the in-depth structure-property relationship is particularly important for Li-O-2 batteries. Herein, the self-boosting catalysis of LiCoO2 as an electrocatalyst for Li-O-2 batteries and the investigation of its self-adjustment mechanism using in situ X-ray absorption spectroscopy and other operando characterization techniques is reported. The intercalation/extraction of Li+ in LiCoO2 not only induces the change in Co valence and modulates the electronic/crystal structure but also tunes the surface disorder degree, lattice strain, and local symmetry, which all affect the catalysis activity. In a discharge, highly ordered LiCoO2 acts as a catalyst to boost oxygen reduction reaction. During charging, the initial extraction of Li+ from LiCoO2 induces Li/oxygen vacancy and Co4+, which deforms CoO6 octahedron as well as lowers the symmetry, and accordingly promotes oxygen evolution reaction. This article offers insights into tuning the activity of catalysts for Li-O-2 batteries with the intercalation/extraction of alkali metal ions in traditional cathodes.