A vanillin bio-based redox polymer as a cathode material for lithium organic batteries

Abstract

Organic materials such as redox polymers have gained much attention as sustainable electrode materials for the next generation of batteries. Specifically, biomass-derived materials are intriguing due to their potential for their integration into a circular economy. Here we demonstrate a facile one-step polymerization reaction of vanillin, industrially produced by lignin-fueled biorefineries, which provides a bio-based catechol redox polymer. The insoluble poly(vanillin) is synthesized during a one-pot, acid-catalyzed polymerization reaction of vanillin in which auto-polycondensation, methyl-deprotection and crosslinking occur simultaneously. The electrochemical performance of poly(vanillin) was assessed as a cathode material in Li half-cells using either 1.0 M LiPF₆ in EC : DEC (1 : 1, v/v) or 1.0 M LiTFSI in DOL : DME (1 : 1, v/v) as the electrolyte. The latter displayed the best performance for poly(vanillin), with specific capacities of up to 101.25 mAh g⁻¹ and a capacity retention of 85.5% after 350 cycles. The dQ/dV plot exposes a well-defined reversible catechol redox at 3.2 V (vs. Li/Li⁺). Furthermore, the use of water as the processing solvent for electrode fabrication using a poly(ionic liquid) as the binder was demonstrated. This work shows a scalable synthetic route to a bio-based catechol redox polymer from vanillin to be used as a high-voltage organic electrode material.