Structural inheritance in biomass-derived hard carbon for sodium-ion batteries

Hard carbon is one of the most promising anode materials for sodium-ion batteries. Among various hard carbon precursors, biomass-derived hard carbons have attracted significant attention due to their abundance, renewability, and low cost. Nevertheless, biomass-based hard carbons still face considerable challenges, as their carbon structures largely inherit features from the precursor, making precise control of the microstructure difficult and leaving the sodium storage mechanism poorly understood. This review highlights the critical role of structural inheritance from biomass precursors in shaping the carbon architecture, providing insights for structural design and performance optimization of hard carbon anodes. We summarize the structural characteristics of the main components of biomass (cellulose, hemicellulose, lignin and minor constituents), so as to clarify the advantages and disadvantages of each component when applied to the preparation of hard carbon anodes. We further discuss how the structural features of different precursors affect the electrochemical performance of the resulting hard carbon, aiming to improve its performance through various preparation strategies. Recent advances in sodium storage mechanisms and preparation strategies are also reviewed. This work aims to clarify the structural inheritance of biomass-derived hard carbons and offer a theoretical basis for the design of high-performance anode materials for sodium-ion batteries.