V₂CT_x MXene as novel anode for aqueous asymmetric supercapacitor with superb durability in ZnSO₄ electrolyte

Despite of great interests in aqueous asymmetric supercapacitors (ASC), their performance is often restricted by unsatisfactory specific capacitance of anode materials. Herein, accordion-like V₂CT_x MXene has been prepared and exploited as novel anode material for aqueous ASC in neutral ZnSO₄ electrolyte. Profitting from the layered structure with expanded interlayer distance, the V₂CT_x electrode exhibits a high specific capacitance of 481F g^-1 at 1 A g^-1, a reasonable rate performance and intriguing cycling stability with capacitance retention of 84.3% after 60,000 cycles at 10 A g^-1 in 2 M ZnSO₄ electrolyte. Furthermore, an ASC device based on the V₂CT_x as anode and activated carbon (AC) as cathode was successfully assembled in the ZnSO₄ electrolyte, which achieves a wide potential window up to 1.8 V. Remarkably, the V₂CT_x//AC ASC delivers a high energy density of 34 W h kg^-1 at a power density of 954 W kg^-1, as well as superb cycling stability with capacitance retention of 79% even after 100,000 charge/discharge cycles at 10 A g^-1. The intriguing electrochemical performance, especially the ultralong cycling life, make the V₂CT_x MXene electrode promising in aqueous energy storage devices.