Electrospun Biomass‐Derived Flexible Anodes With Hierarchical Structure via Cobalt <scp>MOF</scp> Integration for Sodium‐Ion Batteries

To develop a green, sustainable, and high‐performance anode for sodium‐ion batteries (SIBs), flexible biomass‐based carbon nanofiber membranes as a self‐standing and structurally stable anode for SIBs were designed and fabricated by incorporating cellulose (CE) and chitosan (CS) with a cobalt‐based metal–organic framework (ZIF‐67) through two facile strategies: blending electrospinning–carbonization (CBNFM/ZIF‐67) and electrospinning in situ growth–carbonization (CISNFM/ZIF‐67). Compared with CISNFM/ZIF‐67, the CBNFM/ZIF‐67 anode displayed superior specific capacity, rate performance, and cycling stability, corresponding to 384.2 mAh g −1 at 20 mA g −1 , and maintaining a discharge capacity of 336.1 mAh g −1 with a high Coulombic efficiency of 95.5% after 700 cycles at 100 mA g −1 . The specific discharge capacity at 100 mA g −1 and cycling stability of CBNFM/ZIF‐67 significantly improved by 65.95% and 69.49% than the control (CNFM), respectively. The enhanced mechanism of sodium‐ion insertion and desertion through construction and design of hierarchical pore structure, nitrogen‐doping, and sodium‐cobalt alloy was revealed by combining in situ Raman spectroscopy with density functional theory (DFT) calculation. CBNFM/ZIF‐67 exhibited significantly higher binding energy (−774 kcal mol −1 ) and diffusion coefficient (12.88 e −7 cm 2 s −1 ) than those of CISNFM/ZIF‐67, revealing its superior ion transport kinetics. In addition, life cycle assessment demonstrates that the synthesis route offers an eco‐friendly and low‐carbon pathway for producing biomass‐derived anodes. This study provides fundamental insights into sodium‐ion insertion and extraction mechanisms, establishes a structure–property relationship for biomass‐based electrodes, and presents a sustainable strategy for the large‐scale development of sodium‐ion batteries. These findings highlight the environmental and technological potential of green electrode materials for next‐generation energy storage systems.