S-N-doping TiO2@ MXene heterostructure in-situ derived from MXene frameworks as high‑rate anodes for Lithium/Sodium-ion batteries

Titanium dioxide (TiO 2 ) shows promise as an anode material for Li/Na-ion batteries due to its low cost and good cycling stability. However, the limited rate capability and poor conductivity severely limit their practical application. Herein, the nitrogen-sulfur co-doping nano TiO 2 is in-situ constructed on the Ti 3 C 2 T x MXene substrate (SN-TiO 2 @MXene) via facile partial oxidation of MXene. The introduction of S-N heteroatoms, TiO 2 @MXene heterostructures and nanostructures can enhance electronic conductivity, improve ions diffusion kinetics and promote the contribution of pseudo-capacitance. Moreover, the employment of three-dimensional conductive layered MXene parent phase as a substrate material can not only construct the conductive network but also enhance the structural stability of the electrode. The SN-TiO 2 @MXene composite achieves an impressive reversible capacity of 306 mA/g after 1500 cycles at 500 mA/g, and 241.1 mAh/g after 2000 cycles even at a high current density of 2000 mA/g in LIBs. Furthermore, this electrode exhibits a discharge capacity of 105 mAh/g after 1000 cycles at 500 mA/g in SIBs. This study demonstrates that the three-dimensional layered SN-TiO 2 @MXene composites hold promising prospects as anode materials for ion batteries, and offer valuable insights for the fabrication of titanium matrix composites with exceptional electrochemical properties.