Heterostructures of MoO₃ nanobelts assembled on delaminated V₄C₃T_x MXene nanosheets for supercapacitors with excellent room/high temperature performance

A novel flexible delaminated vanadium carbide MXene (d-V₄C₃T_x) and molybdenum trioxide (MoO₃) are promising electrode materials. However, the re-stacking of the d-V₄C₃T_x nanosheets and the poor conductivity and cyclic stability of MoO₃ seriously restrict their development for supercapacitors application. Constructing heterostructures to obtain a synergistic property enhancement is an effective strategy to solve it. Herein, the free-standing d-V₄C₃T_x/MoO₃ heterostructure composite films are fabricated by combining hydrothermal, electrostatic assembly with vacuum-assisted filtration methods, and the energy storage mechanism is dominated by diffusion-controlled process. Results indicate that the as-prepared composite film electrode has high specific capacity of 645 0 C g⁻¹ at current density of 1 A g⁻¹. Even at 40 °C, it also has 639.2 C g⁻¹ at a scan rate of 2 mV s⁻¹. This impressive electrochemical performance can be attributed to the enhanced conductivity and high pseudocapacitance offered by the heterostructures. The as-fabricated asymmetric supercapacitor (ASC), in which the d-V₄C₃T_x/MoO₃ composite film is used as negative electrode and the active carbon (AC) is used as positive electrode, exhibits maximum energy density of 22.2 Wh kg⁻¹ and maximum power density of 5289.9 W kg⁻¹, and the capacity retention rate can still up to 97.0% even after 10,000 cycles at a current density of 10 A g⁻¹. Furthermore, the assembled ASC device successfully drives the small alarm clock and lights the light emitting diode (LED), which facilitates the development of applications for such high-performance supercapacitors.