Recent advances of biomass-derived hard carbon as anode materials for sodium-ion batteries

With the growing demand for clean energy storage, sodium-ion batteries (SIBs) have emerged as a critical alternative to lithium-ion batteries (LIBs) attributable to their resource abundance and cost-effectiveness. Biomass-derived hard carbon (BHC) materials exhibit significant potential as anode materials for SIBs, owing to their renewability, environmental compatibility, and unique microstructures. This review systematically provides a systematic overview of synthetic methods, characterization techniques and regulation strategies of BHC. Then the enhancement mechanism for sodium-ion storage performance was further analyzed and discussed. Despite significant advancements in capacity and cycling stability, some challenges remain, including low initial Coulombic efficiency and insufficient understanding on storage mechanisms at the microscopic level. Future progress in green synthesis processes, multiscale structural design, and investigation under realistic conditions are expected to propel the practical application of BHC toward high-performance and low-cost SIBs, thereby facilitating large-scale storage of sustainable energy.