Single Metal Site and Versatile Transfer Channel Merged into Covalent Organic Frameworks Facilitate High-Performance Li-CO₂ Batteries

Abstract

The sluggish kinetics and unclear mechanism have significantly hindered the development of Li-CO₂ batteries. Here, a Li-CO₂ battery cathode catalyst based on a porphyrin-based covalent organic framework (TTCOF-Mn) with single metal sites is reported to reveal intrinsic catalytic sites of aprotic CO₂ conversion from the molecular level. The battery with TTCOF-Mn exhibits a low overpotential of 1.07 V at 100 mA/g as well as excellent stability at 300 mA/g, which is one of the best Li-CO₂ battery cathode catalysts to date. The unique features of TTCOF-Mn including uniform single-Mn(II)-sites, fast Li⁺ transfer pathways, and high electron transfer efficiency contribute to effective CO₂ reduction and Li₂CO₃ decomposition in the Li-CO₂ system. Density functional theory calculations reveal that different metalloporphyrin sites lead to different reaction pathways. The single-Mn(II) sites in TTCOF-Mn can activate CO₂ and achieve an efficient four-electron CO₂ conversion pathway. It is the first example to reveal the catalytic active sites and clear reaction pathways in aprotic Li-CO₂ batteries.