Unlocking the Role of Carbon Microstructure in MOF-Mediated Interfacial Engineering for Fast-Charging Sodium-Ion Batteries

The performance of hard carbon anodes in sodium-ion batteries is restricted by the inherent trade-off between rate capability and capacity due to uncoordinated ion-electron transport. This research indicates that the microstructure of the carbon host crucially determines the interfacial reconstruction behavior and electrochemical outcome of MOF modification. For porous cellulose-derived carbon, the integration of MOF induces a continuous composite interface, enhancing the Na + diffusion coefficient by an order of magnitude below 0.1 V (reaching 10 −9 cm 2 s −1 ), and yielding a high reversible capacity of 667.2 mAh g −1 with 79% capacity retention. In contrast, on commercial hard carbon with a higher degree of graphitization, MOF forms a discontinuous physical coating that obstructs intrinsic ion pathways, restricting rate performance of hard carbon despite the improvement in its cycling stability. In-situ EIS and distribution of relaxation time analyses disclose lower charge-transfer resistance and optimized SEI evolution in MOF@cellulose-derived carbon, facilitating efficient ion-electron dual transport. The full cell utilizing MOF@cellulose-derived carbon attains a high energy density of 172.8 Wh kg −1 at a power density of 2065 W kg −1 . This work offers mechanistic insights into the correlations among carbon microstructure, interface, and performance, guiding the rational anodes design of high-power and high-energy density sodium-ion batteries.