Lignin as a Sustainable Building Block for Electrochemical Energy Devices: A Critical Review

Lignin, the most abundant aromatic biopolymer on Earth, has gained significant attention as a sustainable precursor for materials used in advanced energy storage technologies. Its intrinsic chemical complexity, featuring phenolic, methoxy, and quinone-like functionalities, enables multiple valorization pathways, including the production of carbon materials, redox-active polymers, polymer electrolytes, and functional binders. Recent advances in lignin extraction, fractionation, targeted chemical modification, and controlled carbonization have significantly broadened the functional scope and electrochemical performance of lignin-based components across a wide range of systems, including batteries, supercapacitors, and hybrid devices. This review consolidates recent progress in the development of lignin-derived materials for electrochemical energy storage, emphasizing structure–function relationships and the influence of lignin source and processing route on final material properties. Finally, we outline emerging prospects for integrating lignin-based materials into next-generation sustainable energy storage systems and present a roadmap for accelerating future scientific and industrial development.