MXene quantum dots-guided construction of superstable telluride electrodes for supercapacitors with excellent rate performance

For a considerable period, the development and preparation of electrode materials for supercapacitors have primarily focused on enhancing energy density and voltage window, often at the expense of rate capability. Transition metal tellurides (TMTe) possess inherent advantages for achieving exceptional rate performance due to their high intrinsic electronic conductivity, open ion diffusion channels, and rapid surface pseudocapacitive reactions. To maximize the conductivity and structural stability of transition metal tellurides, the introduction of a conductive MXene quantum dots (MQDs) substrate presents an excellent strategy. Accordingly, in this work, a Co 0.32 Fe 0.32 Te/MQDs composite was synthesized via a two-step hydrothermal tellurization process, using MQDs as the conductive substrate and a MOF material with fast ion channels as the precursor. Benefiting from high electrical conductivity and a loose, porous surface structure, the charge storage mechanism of Co 0.32 Fe 0.32 Te/MQDs is not limited to slow bulk diffusion-controlled redox reactions, but also encompasses significant contributions from both surface-controlled and diffusion-controlled pseudocapacitive behavior. Moreover, the relatively large tellurium atoms act as structural “pillars”, helping to buffer volume changes during high-rate charge/discharge processes, which is highly favorable for high rate performance. As anticipated, in a three-electrode configuration, Co 0.32 Fe 0.32 Te/MQDs delivers a specific capacitance of 279.4 F g⁻ 1 at 1 A g⁻ 1 and retains 214 F g⁻ 1 even at a current density of 10 A g⁻ 1 , demonstrating an impressive rate capability of 76.5%. After 10,000 cycles at 10 A g⁻ 1 , the capacitance retention remains at 57.14%. Furthermore, an asymmetric supercapacitor assembled with Co 0.32 Fe 0.32 Te/MQDs as the positive electrode and activated carbon (AC) as the negative electrode (AC//Co 0.32 Fe 0.32 Te/MQDs) exhibits superior electrochemical performance. It achieves an energy density of 12.075 Wh kg⁻ 1 at a power density of 750 W kg⁻ 1 , and maintains a high capacitance retention of 78.78% after 10,000 charge/discharge cycles at 10 A g⁻ 1 . In summary, this work expands the selection of supercapacitor electrode materials that combine high cycling stability with excellent rate capability, resulting in a promising faradaic electrode material for asymmetric supercapacitors with substantial application potential.