Radical Passivation to Incubate Closed Pore Structure and Surface Functionalities of Hard Carbon for High‐Efficiency Sodium Storage

ABSTRACT Biomass‐derived hard carbon anodes receive remarkable prospects for use in sodium‐ion battery technology. However, precise regulation of carbon crystallites is extremely critical yet formidable, which seriously retards its scale‐up industrialization. Herein, a versatile radical passivation strategy is proposed to meticulously construct a desirable carbon architecture for high‐efficiency sodium storage. Volatile hydroxyl radicals are chemically passivated by oxygen‐rich functional species, which incubate the proliferation of pseudographitic carbon microdomains having increased closed pores, expanded carbon interlayer spacing, and enriched surface C═O functionalities. The architecture not only enables more available active sites and expedited sodiation kinetics, but also facilitates the building of a thin and robust inorganic‐rich interphase for inhibited side reactions and sustained working lifetime. The reversible capacity is greatly increased by 50% (up to 354.7 mAh g −1 at 0.02 A g −1 ) alongside an improved initial Coulombic efficiency of 85.8% and excellent rate/cycling capability. This work affords a radical‐oriented design insight for regulating closed pore structure and surface functionalities for hard carbon toward advanced sodium energy storage.