Synergistically enhanced lithium storage performance based on titanium carbide nanosheets (MXene) backbone and SnO^sub 2^ quantum dots

Titanium carbide MXene (Ti3C2Tx) 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, Ti3C2Tx 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 Ti3C2Tx to protect the latter from oxidation under the hydrothermal condition. The in-situ heterogeneously nucleated SnO2 QDs are tightly anchored on the Ti3C2Tx nanosheets, while the Ti3C2Tx nanosheets effectively limit the growth/aggregation of SnO2. Further freeze-drying of the colloidal mixture results in the SnO2 QDs@Ti3C2Tx composite with conductive Ti3C2Tx nanosheets as backbone, which displays a high specific surface area and abundant voids. The unique architecture design renders SnO2 QDs@Ti3C2Tx 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.