Biomass-based sustainable covalent organic framework (COF) anode for high-performance LIBs

COFs with reversible redox behaviours are promising lithium-ion batteries (LIBs) electrode materials. However, traditional COFs are synthesized from organic monomers primarily derived from fossil fuels, significantly hindering the sustainable development of COF materials. In this study, a novel proof-of-concept COF, named COF@bio, was constructed using two biomass-derived monomers under mild conditions and through a simple synthesis process, aligning with the principles of green sustainable development and showing potential for large-scale preparation. The COF@bio-40 was in-situ grown on carbon nanotubes (CNT) to enhance electronic conductivity. Consequently, COF@bio-40 exhibited satisfactory long-cycle performance and excellent high-rate capability. During the long cycle process, the maximum specific capacity of COF@bio-40 reached 804 mAh g⁻¹ (at 2,000 mA g⁻¹), significantly surpassing most previous reports and commercial graphite anodes. Analysis using X-ray photoelectron spectroscopy (XPS) of the anode during charge and discharge processes, DFT, and capacity contribution revealed that the storage mechanism is governed by 11-electron redox chemistry for the COF monomer, with one lithium ion per benzene ring, one lithium ion per furan ring, and one lithium ion per imine linkage. This work may pave the way for constructing biomass-based sustainable organic electrodes with high performance for organic rechargeable batteries.