Heteroatom‐Doped Biopolymer Nanocomposites: A Sustainable Pathway Towards High‐Performance Supercapacitors

ABSTRACT Biopolymers‐derived nanocomposites have emerged as sustainable electrodes for supercapacitors due to their natural abundance, biodegradability and intrinsic functional groups. However, their electrochemical performance varies significantly depending upon heteroatom doping. Undoped biopolymers such as cellulose and lignin typically exhibit moderate specific capacitance values ranging from ~254 to 357 Fg −1 with cyclic stability between ~80%–85%. In contrast, heteroatom‐doped biopolymer nanocomposites, those enriched with nitrogen, sulfur, phosphorus, oxygen, boron and fluorine exhibit enhanced capacitance, improved wettability and ion transport. For instance, N‐doped chitosan composites show specific capacitance up to 2479 Fg −1 , with cyclic stability reaching ~110%. This review presents varied reports on heteroatom‐doped biopolymer nanocomposites, highlighting the role of surface area, porosity and functional groups (COOH, NH etc.) in optimizing electrode performance. It also discusses the integration of different biopolymers with nanomaterials and their application as both electrode and electrolytes. Challenges in synthesis reproducibility, scalability and long‐term stability are shown. Lastly, futuristic potential of AI‐ML based electrode design for development of high‐performance, eco‐friendly and flexible supercapacitor is also highlighted.