Proton Exchange Membranes from Sulfonated Lignin Nanocomposites for Redox Flow Battery Applications

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 20; no. 24; pp. e2309459 - n/a
• Main Authors: dos Santos, Fernanda Brito, McMichael, Philip Spencer, Whitbeck, Alex, Jalaee, Adel, Gyenge, Elod, Foster, E. Johan
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01-06-2024
• Subjects: Clean energy; Dimensional stability; Efficiency; Electrochemical analysis; Energy storage; enery production; Ion exchange; ion‐conductiong nanochannels; ion‐exchange membrane; Lignin; Membranes; Miscibility; modified lignin nanoparticles; Nanocomposites; Nanoparticles; Perfluoro compounds; Polyvinyl alcohol; Protons; Pulping; Rechargeable batteries; Waste management; zinc‐Iodine redox flow battery; ion‐conductiong nanochannels; modified lignin nanoparticles; zinc‐Iodine redox flow battery; enery production; ion‐exchange membrane
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202309459

Redox flow batteries (RFBs) are increasingly being considered for a wide range of energy storage applications, and such devices rely on proton exchange membranes (PEMs) to function. PEMs are high‐cost, petroleum‐derived polymers that often possess limited durability, variable electrochemical performance, and are linked to discharge of perfluorinated compounds. Alternative PEMs that utilize biobased materials, including lignin and sulfonated lignin (SL), low‐cost byproducts of the wood pulping process, have struggled to balance electrochemical performance with dimensional stability. Herein, SL nanoparticles are demonstrated for use as a nature‐derived, ion‐conducting PEM material. SL nanoparticles (NanoSLs) can be synthesized for increased surface area, uniformity, and miscibility compared with macrosized lignin, improving proton conductivity. After addition of polyvinyl alcohol (PVOH) as a structural backbone, membranes with the highest NanoSL concentration demonstrated an ion exchange capacity of 1.26 meq g−1, above that of the commercial PEM Nafion 112 (0.98 meq g−1), along with a conductivity of 80.4 mS cm−1 in situ, above that of many biocomposite PEMs, and a coulombic efficiency (CE), energy efficiency (EE) and voltage efficiency (VE) of 91%, 68% and 78%, respectively at 20 mA cm−2. These nanocomposite PEMs demonstrate the potential for valorization of forest biomass waste streams for high value clean energy applications.
Sulfonated lignin (SL), a byproduct of wood pulping, may be treated to produce chemically and morphologically uniform nanospheres encompassed by hydrophilic sulfonate groups. A percolated network of these sulfonated lignin nanoparticles (NanoSLs), within a polyvinyl alcohol (PVOH) matrix, functions as proton‐conducting channels for use in a separator layer for redox flow battery applications, with thermal and structural stability.