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 In₂S₃/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 cm² 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.