In-situ imaging the electrochemical reactions of Li-CO₂ nanobatteries at high temperatures in an aberration corrected environmental transmission electron microscope

Rechargeable lithium-carbon dioxide (Li-CO₂) batteries have attracted much attention due to their high theoretical energy densities and capture of CO₂. However, the electrochemical reaction mechanisms of rechargeable Li-CO₂ batteries, particularly the decomposition mechanisms of the discharge product Li₂CO₃ are still unclear, impeding their practical applications. Exploring electrochemistry of Li₂CO₃ is critical for improving the performance of Li-CO₂ batteries. Herein, in-situ environmental transmission electron microscopy (ETEM) technique was used to study electrochemistry of Li₂CO₃ in Li-CO₂ batteries during discharge and charge processes. During discharge, Li₂CO₃ was nucleated and accumulated on the surface of the cathode media such as carbon nanotubes (CNTs) and Ag nanowires (Ag NWs), but it was hard to decompose during charging at room temperature. To promote the decomposition of Li₂CO₃, the charge reactions were conducted at high temperatures, during which Li₂CO₃ was decomposed to lithium with release of gases. Density functional theory (DFT) calculations revealed that the synergistic effect of temperature and biasing facilitates the decomposition of Li₂CO₃. This study not only provides a fundamental understanding to the high temperature Li-CO₂ nanobatteries, but also offers a valid technique, i.e., discharging/charging at high temperatures, to improve the cyclability of Li-CO₂ batteries for energy storage applications.