Unlocking Kinetic Limitations in Hard‐Carbon Anodes to Enable Practical Fast‐Charging Sodium‐Ion Batteries

ABSTRACT Hard carbons are considered to be the most promising anode materials for sodium‐ion batteries (SIBs) because of their low cost and high sodium storage performance. However, the inadequate rate performance of hard carbon remains a critical bottleneck hindering high‐power applications of SIBs. Herein, we elucidate the key structural descriptors underlying the rate‐performance failure mechanism by constructing hard carbon with tailored microstructures, achieved via precise regulation of precursor composition. It is worth noting that the hard carbons engineered with the aforementioned differentiated structural design exhibit similar thermodynamic behaviors for sodium storage, but markedly different kinetic properties. At a current density of 2 A g −1 , the reversible capacity of ABP‐L‐1400 is 304.6 mAh g −1 , which is 1.24 times of ABP‐H‐1400. Systematic characterization reveals that the kinetic difference is primarily attributable to variations in low‐plateau capacity, with key influencing factors identified through in‐depth analysis as the uniform organic/inorganic hybrid solid electrolyte interphase and the micro‐open pore structure. Additionally, practical applications can be extended to high‐power Prussian blue//hard carbon cylindrical cells, demonstrating a capacity of 702.2 mAh at 5 C. This work provides guidance for the design of advanced fast‐charging SIBs.