Revealing the CO2 Conversion at Electrode/Electrolyte Interfaces in Li–CO2 Batteries via Nanoscale Visualization Methods

Abstract Lithium–carbon dioxide (Li–CO 2 ) battery technology presents a promising opportunity for carbon capture and energy storage. Despite tremendous efforts in Li–CO 2 batteries, the complex electrode/electrolyte/CO 2 triple‐phase interfacial processes remain poorly understood, in particular at the nanoscale. Here, using in situ atomic force microscopy and laser confocal microscopy‐differential interference contrast microscopy, we directly observed the CO 2 conversion processes in Li–CO 2 batteries at the nanoscale, and further revealed a laser‐tuned reaction pathway based on the real‐time observations. During discharge, a bi‐component composite, Li 2 CO 3 /C, deposits as micron‐sized clusters through a 3D progressive growth model, followed by a 3D decomposition pathway during the subsequent recharge. When the cell operates under laser (λ=405 nm) irradiation, densely packed Li 2 CO 3 /C flakes deposit rapidly during discharge. Upon the recharge, they predominantly decompose at the interfaces of the flake and electrode, detaching themselves from the electrode and causing irreversible capacity degradation. In situ Raman shows that the laser promotes the formation of poorly soluble intermediates, Li 2 C 2 O 4 , which in turn affects growth/decomposition pathways of Li 2 CO 3 /C and the cell performance. Our findings provide mechanistic insights into interfacial evolution in Li–CO 2 batteries and the laser‐tuned CO 2 conversion reactions, which can inspire strategies of monitoring and controlling the multistep and multiphase interfacial reactions in advanced electrochemical devices.