MXene-derived TiO2 nanosheets/rGO heterostructures for superior sodium-ion storage

Transition metal oxides hold promise as electrode materials for energy-storage devices such as batteries and supercapacitors. However, achieving ideal electrode materials with high capacity, long-term cycling stability, and superb rate capability remains a challenge. In this study, we present a self-assembled heterogeneous structure consisting of TiO₂ nanosheets derived from Ti₃C₂T_x MXene and reduced graphene oxide. This structure facilitates the formation of heterogeneous structures while establishing a conductive network. The restacking of porous TiO₂ nanosheets and reduced graphene oxide within the heterostructure results in high porosity and excellent conductivity. Due to enhanced electron and Na⁺ transfer, as well as improved structural stability during the Na⁺ insertion/extraction process, this heterogeneous structure exhibited exceptional Na⁺ storage performance. Specifically, it exhibits a long-term cycling stability (217 mAh g⁻¹ at 10 C, 5000 cycles) and an ultrahigh rate capability (135 mAh g^–1, 40 C). Analysis of electrode reaction kinetics suggests that Na⁺ storage in the heterostructure is predominantly governed by a surface-controlled process. Our results provide a promising strategy for utilizing self-assembled heterostructures in advanced energy storage applications.