Lignin Nanoparticles as Biobased Redox Centers for Organic Battery Electrodes

Lignin, a central renewable carbon resource in the biosphere, has recently emerged as a promising redox-active material for organic batteries. Currently, the main challenge lies in finding a form of lignin that combines water-based processability with good cyclic stability, as the two industrially common forms, kraft lignin and lignosulfonate, each offers only one of these advantages. In this work, we demonstrate that lignin nanoparticles (LNPs) act as redox-active centers that are insoluble but exhibit colloidal stability in aqueous media, allowing for straightforward processing into electrodes for zinc-ion batteries. Electrodes based on conductive composites of LNPs with poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) were shown electrochemically to achieve specific capacities reaching 42.5 mAh/g at a current density of 1 A/g. A zinc-ion battery prototype using this composite demonstrated a specific energy of 54 Wh/kg, outperforming previous lignin-based energy storage devices. This zinc-lignin battery exhibited excellent Coulombic efficiency of around 100%, with a specific capacity of 82.5 mAh/g at 0.05 A/g and a capacity retention of approximately 61% after 2000 charge/discharge cycles. Our results highlight the potential of LNPs in advancing eco-friendly, cost-effective, and high-performance lignin-based energy storage devices.