High-Voltage Aqueous Asymmetric Supercapacitor Based on Mo1.33CTx i-MXene and Hydrated V2O5 in LiCl Electrolyte

Recently, aqueous asymmetric supercapacitors (ASCs) have attracted considerable attention as safe and high-power energy storage devices. However, achieving high energy density while maintaining long-term cycling stability remains a significant challenge. Herein, an aqueous ASC employing a Mo1.33CTx/CNT negative electrode and a hydrated V2O5·nH2O/CNT positive electrode in a 5 M LiCl electrolyte is reported. The Mo1.33CTx i-MXene was synthesized via hydrothermal selective etching of an i-MAX precursor, whereas hydrated V2O5·nH2O nanoflakes were prepared with peroxide-assisted hydrothermal treatment. The ordered-vacancy Mo1.33CTx i-MXene provides a stable negative potential window, redox-active sites, and favorable conditions for reversible Li+ intercalation/deintercalation, thereby contributing to pseudocapacitive charge storage. The assembled ASC delivered a stable operating voltage of 1.7 V, a specific capacitance of 61 F·g−1 at 1 A·g−1, an energy density of 25.2 Wh·kg−1 at 883 W·kg−1 and 86% capacitance retention after 10,000 cycles. Electrochemical impedance spectroscopy revealed relatively low internal resistance and efficient ion transport within the layered electrode architectures. These results highlight the strong potential of ordered-vacancy MXene/vanadium oxide systems for advanced aqueous energy storage applications.