Pseudocapacitive Charge Storage in MXene–V 2 O 5 for Asymmetric Flexible Energy Storage Devices

Pseudocapacitive asymmetric supercapacitors are promising candidates for achieving high energy density in flexible energy storage devices. However, seeking suitable positive electrode materials that are compatible with negative electrode materials remains a considerable challenge. In the current study, a pseudocapacitive Ti 3 C 2 T x MXene used as negative electrodes is rationally compatible with redox-type V 2 O 5 as positive electrodes, resulting in the assembly of an all-pseudocapacitive Ti 3 C 2 T x MXene//V 2 O 5 asymmetric flexible energy storage device. The solid-state asymmetric device can deliver an energy density of 8.33 mW h cm –3 at a current density of 0.5 A g –1 . Moreover, it can operate in an expanded voltage window of 1.5 V, with dominant surface-capacitive charge-storage mechanisms. Additionally, the device can power a yellow light-emitting diode for up to 7 s, indicating the potential of the device for use in practical applications. This study demonstrates the possibility of using other two-dimensional transition-metal carbide nanosheets for high-energy density flexible energy storage devices.