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

Abstract

Lithium-carbon dioxide (Li-CO₂ ) battery technology presents a promising opportunity for carbon capture and energy storage. Despite tremendous efforts in Li-CO₂ batteries, the complex electrode/electrolyte/CO₂ 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 CO₂ conversion processes in Li-CO₂ batteries at the nanoscale, and further revealed a laser-tuned reaction pathway based on the real-time observations. During discharge, a bi-component composite, Li₂ CO₃ /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 Li₂ CO₃ /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, Li₂ C₂ O₄ , which in turn affects growth/decomposition pathways of Li₂ CO₃ /C and the cell performance. Our findings provide mechanistic insights into interfacial evolution in Li-CO₂ batteries and the laser-tuned CO₂ conversion reactions, which can inspire strategies of monitoring and controlling the multistep and multiphase interfacial reactions in advanced electrochemical devices.