Biomass‐Derived Carbon and Their Composites for Supercapacitor Applications: Sources, Functions, and Mechanisms

Biomass‐derived carbons are eco‐friendly and sustainable materials, making them ideal for supercapacitors due to their high surface area, excellent conductivity, cost‐effectiveness, and environmental benefits. This review provides valuable insights into biomass‐derived carbon and modified carbon for supercapacitors, integrating both experimental results and theoretical calculations. This review begins by discussing the origins of biomass‐derived carbon in supercapacitors, including plant‐based, food waste‐derived, animal‐origin, and microorganism‐generated sources. Then, this review presents strategies to improve the performance of biomass‐derived carbon in supercapacitors, including heteroatom doping, surface functionalization, and hybrid composite construction. Furthermore, this review analyzes the functions of biomass‐derived carbon in supercapacitors both in its pure form and as modified materials. The review also explores composites derived from biomass‐based carbon, including carbon/MXenes, carbon/MOFs, carbon/graphene, carbon/conductive polymers, carbon/transition metal oxides, and carbon/hydroxides, providing a thorough investigation. Most importantly, this review offers an innovative summary and analysis of the role of biomass‐derived carbon in supercapacitors through theoretical calculations, concentrating on four key aspects: energy band structure, density of states, electron cloud density, and adsorption energy. Finally, the review concludes the future research directions for biomass carbon‐based supercapacitors, including the discovery of novel biomass materials, tailoring surface functional groups, fabricating high‐performance composite materials, exploring ion transfer mechanisms, and enhancing practical applications. In summary, this review offers a thorough exploration of the sources, functions, and mechanisms of biomass‐derived carbon in supercapacitors, providing valuable insights for future research.