Lignin is an abundant natural polymer, as well as the main waste product of the paper-making industry. Potassium batteries are an emerging technology and could be a useful alternative to lithium-based batteries in some applications. They could, for example, be used to store the electricity produced from renewable sources. These types of batteries must, therefore, have low costs, be based on abundant materials, and guarantee adequate safety.

Gianmarco Griffini, Politecnico di Milano, Italy, National Interuniversity Consortium of Material Science and Technology (INSTM), Firenze, Italy, Federico Bella, Politecnico di Torino, Italy, and INSTM, and colleagues have developed a new use for lignin in a polymer electrolyte and separator for potassium batteries, i.e., as the battery component placed between the two electrodes.

The team first prepared oxidized lignin using FeCl₂·4H₂O as a catalyst and H₂O₂ as an oxidizing agent. Then they created lignin-based membranes (pictured) by crosslinking the pre-oxidized lignin with poly(ethylene glycol) diglycidyl ether (PEGDGE). They obtained self-standing membranes that can incorporate solvated potassium salts.

A laboratory-scale battery prototype using the membrane was stable for over 200 charge/discharge cycles and showed excellent ionic conductivity. This could open up a new application for lignin in the transition to sustainable energy.

• Lignin as Polymer Electrolyte Precursor for Stable and Sustainable Potassium Batteries,
  Sabrina Trano, Francesca Corsini, Giuseppe Pascuzzi, Elisabetta Giove, Lucia Fagiolari, Julia Amici, Carlotta Francia, Stefano Turri, Silvia Bodoardo, Gianmarco Griffini, Federico Bella,
  ChemSusChem 2022.
  https://doi.org/10.1002/cssc.202200294