Chitosan‐Organic Acids Functionalized as an Effective Sustainable and Scalable Binder for Lithium Sulfur Batteries

ABSTRACT This research focuses on enhancing chitosan's role as a binder in lithium‐sulfur (Li‐S) batteries through its modification with carboxylic acids. The structural analyses using FTIR and XRD reveal that incorporating specific poly‐substituted acids alters chitosan's molecular alignment and polymorph formation, inducing a mixture of Type I and Type II polymorphs. Mechanical testing shows that the Ch + Lactic binder provides improved toughness and ductility, properties essential for accommodating volume changes during Li‐S battery cycling. The electrochemical characterization demonstrates that chitosan‐aliphatic binders, particularly the Ch + Lactic binder, lead to higher specific capacities (e.g., 930 mAh·g −1 at C/10), improved rate capability, and notable long‐term cycling stability (0.057% capacity fade per cycle) compared to pristine chitosan. This enhanced performance is linked to more effective polysulfide management and structural integrity. Post‐mortem SEM analysis confirms the mechanical stability of the optimized cathodes, which remain crack‐free even after extensive cycling. This work illustrates that careful selection of carboxylic acids can effectively tailor chitosan's properties, contributing to the development of better performance of Li‐S battery technologies.