Biomass-derived hard carbon anodes: From structural engineering to industrial sodium-ion battery applications

Abstract

Biomass-derived hard carbon has emerged as a promising anode material for sodium-ion batteries (SIBs) owing to its tunable microstructure, sustainability, and cost-effectiveness. Although extensive research and industrial practices have validated its sodium storage feasibility, the inherent structural complexity poses significant challenges for practical implementation. This review systematically correlates the structural characteristics of hard carbon, including microcrystalline regions, defects, and nanopores, with their sodium storage mechanisms, analyzing the electrochemical behaviors arising from distinct structural configurations. The enhanced low-voltage plateau capacity and cycling stability critically depend on the pivotal role of short-range ordered carbon layers and closed-pore architectures. In light of this, a rigorous framework is established for selecting high-carbon-yield biomass precursors, with particular focus on precursor composition-structure relationships and their effects on electrochemical performance. Advanced engineering strategies are comprehensively evaluated, including pyrolysis parameter optimization, closed-pore construction, heteroatom doping and surface functionalization. Furthermore, synergistic optimization approaches such as electrolyte formulation, conductive network design, and aqueous binder systems are highlighted for generating thin and stable solid electrolyte interphase (SEI) layers. This work provides a roadmap for transforming biomass waste into high-performance anodes, bridging fundamental insights on sodium storage mechanisms with scalable manufacturing strategies for next-generation SIBs.