The Decisive Role of Li<sub>2</sub>O<sub>2</sub> Desorption for Oxygen Reduction Reaction in Li–O<sub>2</sub> Batteries
Chengyang Xu, Aimin Ge, Koki Kannari, Baoxu Peng, Min Xue, Bing Ding, Ken‐ichi Inoue, Xiaogang Zhang, Shen Ye
Abstract
Fundamental issues relevant to the oxygen reduction reaction (ORR) mechanism and reaction interface are ambiguous in Li–O 2 batteries. Herein, we utilized highly sensitive surface-enhanced Raman spectroscopy (SERS) to reveal the spontaneous desorption behavior of insoluble products of lithium peroxide (Li 2 O 2 ) from the electrode surface. Furthermore, the electrochemical ORR mechanism is elucidated at the electrode/Li 2 O 2 interface based on a dynamic equilibrium between the generation and desorption of Li 2 O 2 . The desorption of adsorbed Li 2 O 2 species (Li 2 O 2 *) is crucial to releasing surface sites and maintaining the electrochemical ORR process at the electrode substrate surface instead of the Li 2 O 2 /electrolyte interface. The proceeding of Li 2 O 2 * desorption can guarantee the stability of Li 2 O 2 * concentration and the discharge plateau in the galvanostatic ORR process. The suppression of Li 2 O 2 * desorption is proved to induce the termination of Li 2 O 2 * generation, which is accompanied by the growth of adsorbed lithium superoxide (LiO 2 *), leading to rapid potential attenuation.