Covalent‐Organic‐Framework‐Based Li–CO₂ Batteries

Abstract

Covalent organic frameworks (COFs) are an emerging class of porous crystalline materials constructed from designer molecular building blocks that are linked and extended periodically via covalent bonds. Their high stability, open channels, and ease of functionalization suggest that they can function as a useful cathode material in reversible lithium batteries. Here, a COF constructed from hydrazone/hydrazide‐containing molecular units, which shows good CO2 sequestration properties, is reported. The COF is hybridized to Ru‐nanoparticle‐coated carbon nanotubes, and the composite is found to function as highly efficient cathode in a Li–CO2 battery. The robust 1D channels in the COF serve as CO2– and lithium‐ion‐diffusion channels and improve the kinetics of electrochemical reactions. The COF‐based Li–CO2 battery exhibits an ultrahigh capacity of 27 348 mAh g−1 at a current density of 200 mA g−1, and a low cut‐off overpotential of 1.24 V within a limiting capacity of 1000 mAh g−1. The rate performance of the battery is improved considerably with the use of the COF at the cathode, where the battery shows a slow decay of discharge voltage from a current density of 0.1 to 4 A g−1. The COF‐based battery runs for 200 cycles when discharged/charged at a high current density of 1 A g−1.

Electroactive Covalent Organic Frameworks: Design, Synthesis, and Applications

“…For example, Loh and co-workers designed hydrazone-linked COF (Tf-DHzOPr COF) and then hybridized it with Ru@CNT (COF-Ru@CNT) as a cathode in Li-CO 2 batteries. [131] In this electrode design, the channel of COF acted as CO 2 collector and diffusion channels for both ion and gas (once interfaced to Ru@CNT). At the same time, Ru was a catalyst that was responsible for both CO 2 reduction and Li 2 CO 3 /C decomposition.…”

Single crystal of a one-dimensional metallo-covalent organic framework

“…In this regard, COFs are among the most difficult to crystallise, owing to the lesser reversibility of their covalent linkages compared to coordination bonds and hydrogen bonds in MOFs and HOFs. The ease of encoding functionalities in COFs and their structural robustness render them potentially useful in wide-ranging applications [13][14][15][16][17][18][19] . However, an in-depth understanding of the structure-property correlation in COFs is lacking, owing to the fact that most synthesised COFs are polycrystalline, which hampers structural determination.…”

Recent Advances in Lithium–Carbon Dioxide Batteries

“…Li et al first reported a COF catalyst designed from hydrazide/hydrazone‐containing units for Li–CO 2 batteries ( Figure a). [ 121 ] The COF was incorporated into Ru (nanoparticles)‐decorated CNTs. The 1D channels in the catalyst could provide free paths for the diffusion of Li + ions and CO 2 , thus improving the kinetics of CO 2 reactions.…”

“…With this COF catalyst, the Li–CO 2 cell showed superior rate capability (even sustaining a high current density of 4.0 A g −1 ). [ 121 ] Huang et al developed a graphene@COF material as a cathode catalyst for Li–CO 2 batteries. [ 122 ] A uniform and thin imine COF was loaded onto graphene to assist CO 2 reactions.…”

“…Reproduced with permission. [ 121 ] Copyright 2019, Copyright 2019, Wiley‐VCH. b) Scheme of Li + deposition on cathode, reaction with the nanoenriched and nanoconfined CO 2 , and small‐sized Li 2 CO 3 formation.…”