Proposing lithium pump mechanism for observing Ag-Li two-phase interface reaction of in-situ Li-O2 battery by two-step method

In this study, we established a new lithiation-oxidation method (two-step method) to explore the Ag-Li solid–solid interface reaction mechanism during the discharge process in a lithium oxygen nanobattery assembled within a spherical aberration-corrected transmission electron microscope. A continuous Ag-Ag3Li10-Ag solid–solid interface conversion process has been observed during the lithiation reaction, clarifying a typical lithium pump effect. [Display omitted] •We established a new lithiation-oxidation method (two-step method) to explore the Ag-Li solid–solid interface reaction mechanism during the discharge process in a Li-O2 nanobattery assembled within a spherical aberration-corrected ETEM.•The intermediate product Ag3Li10 accelerates the kinetic performance of the interface reaction.•A continuous Ag-Ag3Li10-Ag solid-solid interface conversion process has been observed during the reaction, clarifying a typical lithium pump effect. Silver (Ag) plays an important role as a cathode catalyst in lithium-oxygen batteries (Li-O2 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 Ag3Li10, while the oxidation process precipitates Ag nanoparticles (Ag NPs). The alternating reactions of Ag-Ag3Li10-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-O2 batteries, offering valuable guidance for strategies to monitor and control complex, multi-step interfacial reactions.