Facile synthesis of a biomass-based sustainable covalent organic network (CON) anode for high-performance LIBs†

Covalent organic networks (CONs) with reversible redox behaviour hold great promise as electrode materials for lithium-ion batteries (LIBs). However, the traditional synthesis of CONs relies heavily on organic monomers derived from fossil fuels, posing a significant challenge to the sustainable development of CON materials. In this study, we present a novel proof-of-concept CON material, named BIO, synthesized from biomass-derived monomers using a mild and straightforward process. This approach aligns with the principles of green and sustainable development while offering potential for large-scale preparation. The BIO-4C material was in situ grown on carbon nanotubes (CNTs) to enhance electronic conductivity. As a result, BIO-4C exhibited satisfactory long-cycle performance and high-rate capability. During the long cycle process, the maximum specific capacity of BIO-4C reached 804 mA h g⁻¹ (at 2000 mA g⁻¹), significantly surpassing most previous reports and commercial graphite anodes. Detailed analysis, including X-ray photoelectron spectroscopy (XPS), density functional theory (DFT) calculations, theoretical capacity, and capacity contribution studies, revealed a storage mechanism based on an 11-electron redox process. This mechanism involves the reversible interaction of lithium ions with benzene rings, furan rings, and imine linkages in the BIO monomer. This work represents a step forward in the development of biomass-based sustainable organic electrodes, offering high performance and practicality for future organic rechargeable batteries.