V2CTx 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 V2CTx 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 V2CTx 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 V2CTx 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 V2CTx//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 V2CTx MXene electrode promising in aqueous energy storage devices.