Self-assembled VN/Ti3C2Tx composites for asymmetric supercapacitors

Abstract

MXenes have gained significant recognition due to their outstanding electrical conductivity, abundant surface functional groups, and distinctive two-dimensional layered structure. However, restacking of nanoflakes hinders the electrochemical performance of Ti₃C₂T_x-based supercapacitors. Herein, a Ti₃C₂T_x/VN composite is fabricated using a one-step in situ nitriding method. The presence of VN within the Ti₃C₂T_x nanoflakes results in an increased interlayer spacing, providing additional electrochemically active sites for charge storage. In addition, the Ti₃C₂T_x nanosheets form a continuous metallic skeleton that suppresses the formation of soluble salts from VN during charging and discharging resulting in better cycling stability. As the negative electrode in supercapacitors, Ti₃C₂T_x/VN demonstrates an outstanding specific capacity of 382.1 F g⁻¹ at a current density of 1 A g⁻¹ and exceptional cycling endurance, retaining 93.5% of its capacity after 5000 cycles. An asymmetric supercapacitor comprising Co₃O₄ and Ti₃C₂T_x/VN as the positive and negative electrodes, respectively, shows high energy and power densities of 69.1 W h kg⁻¹ (1 A g⁻¹) and 7.6 kW kg⁻¹ (8 A g⁻¹). The results reveal a promising strategy to design composite anodes with high energy and power densities for supercapacitors.