Background
Driven by the rapid advancement of renewable energy and the global energy transition, sodium-ion batteries (SIBs) have emerged as a strong candidate for next-generation energy storage due to their resource abundance, low cost, and similarities to lithium-ion batteries. However, conventional graphite anodes suffer from poor sodium storage performance due to the larger ionic radius and specific thermodynamic properties of sodium. Hard carbon materials, with highly disordered structures, wide interlayer spacing, and high sodium storage capacity, are considered ideal anode candidates. A three-stage sodium storage mechanism, involving “adsorption-intercalation-pore filling”, provides a theoretical basis for performance optimization. However, hard carbon anodes face two key challenges: low initial Coulombic efficiency (ICE, typically 50%–80%) and insufficient reversible capacity (below 300 mAh g⁻¹). Early improvements focused on precursor modulation and carbonization processes, but high surface areas often led to excessive interfacial side reactions, reducing initial efficiency. Recent strategies, such as constructing closed ultramicropores (< 0.7 nm), enhance sodium-ion transport by excluding solvent molecules, thus preventing excessive electrolyte decomposition and SEI overgrowth, but they reduce surface adsorption capacity. Heteroatom doping (e.g., with N and S) has been used to introduce active sites, widen interlayer spacing, and improve electron conductivity, boosting reversible capacity. However, excessive mesopore formation can still compromise initial efficiency. Reports of biomass-derived hard carbon materials achieving both high ICE (> 80%) and high reversible capacity (> 350 mAh g⁻¹) remain scarce. The main challenge is to balance pore structure and surface chemistry to improve ICE without sacrificing reversible capacity.

Future Prospects
By pioneering a dual-modulation strategy that targets both pore architecture and electronic state in biomass-derived carbon, the research team has successfully developed a sodium-ion battery anode material that combines high initial Coulombic efficiency with high reversible capacity. To drive this material system toward practical use, the authors outline the following future research directions: (1) Investigating the interfacial evolution and performance degradation mechanisms under extreme conditions (e.g., ultra-low and high temperatures) to establish a theoretical foundation for broad-temperature operation; (2) Focusing on scaling up electrode fabrication and optimizing full-cell integration, with particular attention to validating long-term cycling stability and safety in practical pouch cell configurations; (3) Systematically evaluating the material performance limits under various operational conditions, targeting specific applications such as renewable energy storage and portable electronics. This work aims to bridge the gap between laboratory research and industrial application, accelerating the commercialization of high-performance, cost-effective sodium-ion batteries.

The complete study is accessible via DOI:10.34133/research.1039