Pore Reconstruction of Fermented Biomass‐Derived Hard Carbon for High‐Plateau‐Capacity Sodium Storage

The plateau capacity of biomass‐derived hard carbon (HC) anodes for sodium‐ion batteries (SIBs) is largely limited by uncontrollable open porosity, which is closely related to the unregulated components and volatile substances in raw biomass. Herein, we propose an acid‐assisted pore reconstruction strategy using fermented biomass to engineer HC with abundant stable closed pores. The microbial fermentation combined with dilute acid etching effectively removes unstable components, inducing molecular‐level rearrangement. Subsequent KOH activation creates a uniform 2–4 nm mesopore network, which acts as a precise template for pitch infiltration to form dense closed pores during carbonization. Benefiting from this synergistic engineering, the resulting anode delivers a reversible capacity of 343 mAh g −1 at 0.2 C with a high plateau capacity of 217 mAh g −1 and an initial Coulombic efficiency of 87%. Furthermore, it exhibits extraordinary cycling stability, retaining a capacity of 203 mAh g −1 with 91.4% retention after 1000 cycles at 5 C. This work underscores the critical role of fermentation and offers a scalable, sustainable strategy for converting industrial biomass waste into high‐performance anodes for sodium storage.