Double-confined nanoheterostructure Sb/Sb₂S₃@Ti₃C₂T_x@C toward ultra-stable Li-/Na-ion batteries

Antimony-based materials with high capacities and moderate potentials are promising anodes for lithium-/sodium-ion batteries. However, their tremendous volume expansion and inferior conductivity lead to poor structural stability and sluggish reaction kinetics. Herein, a double-confined nanoheterostructure Sb/Sb₂S₃@Ti₃C₂T_x@C has been fabricated through a solvothermal method followed by low-temperature heat treatment. The dual protection of “MXene” and “carbon” can better accommodate the volume expansion of Sb/Sb₂S₃. The strong covalent bond (Ti–S, Ti–O–Sb, C–O–Sb) can firmly integrate Sb-based material with Ti₃C₂T_x and carbon, which significantly improves the structure stability. In addition, the carbon layer can restrain the oxidation of MXenes, and the nano-Sb/Sb₂S₃ can facilitate electron/ion transport and suppress the restacking of MXenes. The heterogeneous interface between Sb and Sb₂S₃ can further promote interfacial charge transfer. The MXene-Sb/Sb₂S₃@C-1 with the optimal Sb content shows high specific capacities, comparable rate properties and ultra-stable cycling performances (250 mAh·g⁻¹ after 2500 cycles at 1 A·g⁻¹ for sodium-ion batteries). Ex situ X-ray diffractometer (XRD) test reveals the storage mechanism including the conversion and alloying process of MXene-Sb/Sb₂S₃@C-1. Cyclic voltammetry (CV) test results demonstrate that the pseudocapacitance behavior is dominant in MXene-Sb/Sb₂S₃@C-1, especially at large current. This design paves the way for exploring high-performance alloy-based/conversion-type anode for energy storage devices.