Mechanistic Insights and Engineering Strategies of Biomass‐Derived Carbon Anodes for Sodium‐Ion Batteries

ABSTRACT Sodium‐ion batteries (SIBs) have emerged as a compelling next‐generation technology to complement or replace lithium‐ion batteries, primarily due to their lower cost and enhanced safety features, positioning them as strong candidates for grid‐scale energy storage. Among diverse anode candidates, hard carbon has emerged as a leading contender for commercialization, thanks to its cost‐effectiveness and amorphous structure, which supports stable reversible capacity in the low‐voltage plateau region. Biomass‐derived hard carbon, in particular, has attracted considerable research interest due to its abundant raw material sources and superior cost competitiveness compared to traditional precursors. However, the pyrolysis of biomass during carbonization often leads to uncontrollable behavior, resulting in an increased number of surface defects, varied pore structures, and excessive functional groups. These characteristics typically result in poor initial coulombic efficiency (ICE) and suboptimal reversible capacity. This review delves into the sodium storage mechanisms within hard carbon, starting from structural models, and investigates the physical and chemical transformations that occur during biomass pyrolysis. Additionally, various strategies are explored to improve ICE, reversible capacity, rate capability, and long‐term cycling stability. By systematically analyzing pyrolysis behavior and optimizing performance, this work aims to enhance performance and reduce the cost of biomass‐derived hard carbon, thereby promoting its industrial adoption for SIBs applications.