Chemical Exfoliation as a Controlled Route to Enhance the Anodic Performance of COF in LIB

摘要

A covalent organic framework (COF), built from light atoms with a graphitic structure, could be an excellent anodic candidate for lightweight batteries, which can be of use in portable devices. But to replace the commercial graphite anode, they need more Li-interactive sites/unit-cell and all such sites should be made to participate. The compromise made in the volumetric density to gain the gravimetric advantage should be minimal. Exfoliation enhances surface/functional group accessibility yielding high capacity and rapid charge storage. A chemical strategy for simultaneous exfoliation and increase of Li-loving active-pockets can deliver a lightweight Li-ion battery (LIB). Here, anthracene-based COFs are chemically exfoliated into few-layer-thick nanosheets using maleic anhydride as a functionalizing exfoliation agent. It not only exfoliates but also introduces multiple Li-interactive carbonyl groups, leading to a loading of 30 Li/unit-cell (vs one Li per C-6). The exfoliation enhances the specific capacity by approximate to 4 times (200-790 mAh g(-1) @100 mA g(-1)). A realistic full-cell, made using the exfoliated COF against a LiCoO2 cathode, delivers a specific capacity of 220 mAh g(-1) over 200 cycles. The observed capacity stands highest among all organic polymers. For the first report of a COF derived full-cell LIB, this is a windfall.