Kraft Lignin as Electrode Material for Sustainable Electrochemical Energy Storage

Electrochemical energy storage using lignin as a renewable electrode material is a cheap and sustainable approach for future organic batteries. Previous reports mainly focus on lignosulfonates (LS) or composites with conductive polymer additives with inherent problems, such as still expensive monomers. Here, composite electrodes are used from more available Kraft lignin and sustainable conductive carbon. Charge storage is evaluated in terms of electrical double layer storage and redox reactions, aiming at a better understanding of desired lignin properties for electrochemical energy storage. Using unmodified, commercial lignin and high surface area conductive carbon, reasonable capacity of ≈80 mAh g−1 is achieved in samples in which a thin layer of lignin covers the interface of high surface area carbon. Non‐faradaic contribution to charge storage is as large as in comparable pure carbon electrodes, and redox reactions in lignin contribute to additional, faradaic charge storage, significantly enhancing capacity in these systems. Resulting electrodes are cheap, reliable, and stable. Composite electrode materials from lignin and high surface area conductive carbon are described. The combination of faradaic and non‐faradaic charge storage is evaluated. Charge transfer between lignin and conductive carbon mainly determines capacity of such electrodes. Combined faradaic/non‐faradaic charge storage makes them promising for future sustainable, reliable, and cheap energy storage devices.