Proposing lithium pump mechanism for observing Ag-Li two-phase interface reaction of in-situ Li-O battery by two-step method.

Silver (Ag) plays an important role as a cathode catalyst in lithium-oxygen batteries (Li-O batteries). However, the catalytic mechanism of Ag remains unclear. Despite efforts dedicated to studying interfacial reactions, observing efficient reactions and ion transport at the Ag-Li solid-solid interface continues to be a challenge. Here, we used Ag nanowires (Ag NWs) as working electrodes, creating a lithiation-oxidation microenvironment within spherical aberration-corrected transmission electron microscopy (ETEM) through a two-step method to investigate the reaction mechanisms at the Ag-Li interface. The lithiation process generates AgLi, while the oxidation process precipitates Ag nanoparticles (Ag NPs). The alternating reactions of Ag-AgLi-Ag form a cycle process, elucidating the transport pathway of Li at the Ag-Li solid-solid interface during discharge process and demonstrating a typical lithium pump effect. Density Functional Theory (DFT) calculations also confirm these results. This work provides novel insights into the interfacial mechanisms of Ag catalysts in Li-O batteries, offering valuable guidance for strategies to monitor and control complex, multi-step interfacial reactions.