Insight into preparation strategies of biomass-derived hard carbon anodes for sodium-ion batteries

Sodium-ion batteries (SIBs) have emerged as promising options for large-scale energy storage because of the affordability and resource abundance of raw materials. To date, considerable research has been directed toward developing hard carbon anodes for SIBs, among which biomass, a precursor of hard carbon, has gained widespread interest for its renewability and cost-effectiveness. Despite these advantages, there is still a significant lack of comprehensive and systematic review on biomass-derived hard carbon from the perspective of preparation strategies. Herein, this review comprehensively summarizes the different preparation strategies for biomass-derived hard carbon materials and their corresponding electrochemical performances in SIBs. Firstly, we carefully describe the structure and sodium storage mechanisms of hard carbon. Subsequently, the latest advances in synthesizing biomass-derived hard carbon materials are systematically discussed from different perspectives, including high-temperature pyrolysis, hydrothermal pretreatment, activation pretreatment, heteroatom-doped pretreatment, template pretreatment, and so on. Lastly, this review offers insights into the existing challenges and potential future research avenues for biomass-derived hard carbon materials, which may guide anode design for developing high-performance SIBs.