Ultrafast Na⁺ Diffusion Enabled by Defective 3D in₂S₃/MXene Nanostructure toward High‐Rate Sodium Ion Batteries

Abstract Slow diffusion kinetics caused by the low conductivity and large volume changes of metal sulfides (MSs) during repeated sodiation/desodiation processes greatly limit the implementation of high‐rate sodium ion batteries (SIBs). To address this, inspired by vacancy diffusion and defect engineering, for the first time, the defective 3D In 2 S 3 /MXene nanostructure with high‐density vacancies and strong interface bonding is developed as the fast‐charging anode for SIBs. This design enables the material to have a low Na + diffusion energy barrier (0.28 eV) and absorption energy (−1.68 eV), resulting in the high Na + diffusion coefficient (5.01 × 10 −12 cm 2 s −1 ) and pseudocapacitive contribution of 97.3%. Moreover, the nanostructure exhibits a reversible multistep intercalation‐conversion reaction mechanism and superior electrochemical reaction kinetics. Consequently, the assembled SIBs display superior high‐rate performance (202.2 mAh g −1 at 100 A g −1 ) and long‐term cycling stability over 5000 cycles with a 0.0074% decay per cycle at 20 A g −1 . On this basis, the Na‐ion full cell is assembled, indicating the practical application of this material. This study sheds light on the design of functional electrode materials for high‐rate and long‐lifespan sodium storage devices.