Lignin-Based Carbon Materials for Energy Storage Applications

The expanding electrification of transportation and other industrial sectors increases the demand of different chemistries and materials in energy storage devices. Carbon materials are common electrode constituents in in many energy storage devices, such as supercapacitors and Lithium-ion batteries. However, fossil-based or naturally mined carbon materials face a major sustainability problem due to the scarcity and depletion of their resources.

Sustainable energy storage devices need therefore alternative renewable carbon materials. The increasing volumes of lignins from paper mills and biorefineries offer an unprecedent opportunity for the design of future lignin-based renewable carbon materials. The aromatic nature of lignin and its high carbon yield upon thermal conversion makes it particularly attractive for this application. Turbostratic hard carbons, activated carbons and semi-graphitized carbons can be synthesized from lignins following different thermal conversion strategies and used as electrode materials in energy storage devices. The botanical and process heterogeneity of lignins, however, translates into different thermal reactivities and carbon materials with variable properties and performance. To better understand and control this variability, we devised a systematic approach based on the analysis of the lignin thermal reactivities, the in-depth characterization of their derived carbons, and the use of chemometric tools for performance optimization and structure-properties-performance relationship identification. Although little distinction is often made between lignins when used as precursor for carbon materials, their structural heterogeneity and purity are found to be key factors to consider in the design of ligninderived carbons.