Synergistically enhanced lithium storage performance based on titanium carbide nanosheets (MXene) backbone and SnO₂ quantum dots

Titanium carbide MXene (Ti₃C₂T_x) possesses a metallic conductivity and an opened nanostructure, being an ideal host for transition metal oxide (TMO) to construct advanced lithium-ion battery anodes. However, Ti₃C₂T_x is prone to be oxidized under hydrothermal treatment, which limits the growth of TMO/MXene composites through a wet-chemistry approach. Here, we take advantage of the strong electrostatic interaction between SnO₂ quantum dots (QDs) and delaminated Ti₃C₂T_x to protect the latter from oxidation under the hydrothermal condition. The in-situ heterogeneously nucleated SnO₂ QDs are tightly anchored on the Ti₃C₂T_x nanosheets, while the Ti₃C₂T_x nanosheets effectively limit the growth/aggregation of SnO₂. Further freeze-drying of the colloidal mixture results in the SnO₂ QDs@Ti₃C₂T_x composite with conductive Ti₃C₂T_x nanosheets as backbone, which displays a high specific surface area and abundant voids. The unique architecture design renders SnO₂ QDs@Ti₃C₂T_x a high capacity (1021 mAh g⁻¹ at 100 mA g⁻¹ in the 2.6 mg cm⁻² electrode) and long lifetime performance, which maintains 810 mAh g⁻¹ after 200 cycles (100 mA g⁻¹), 697 mAh g⁻¹ after 520 cycles (200 mA g⁻¹) and 500 mAh g⁻¹ after 700 cycles (at 500 mA g⁻¹). More importantly, this wet-chemistry/freeze-drying approach is general, and can be extended to other TMOs and MXenes to fabricate corresponding TMO QDs/MXene composites for various applications.