Flexible freestanding all-MXene hybrid films with enhanced capacitive performance for powering a flex sensor

Abstract

Stacking different two-dimensional (2D) nanomaterials into composite structures opens an opportunity to fabricate electrodes combining the advantages of the individual nanomaterials. Here, different types of MXene nanosheets are combined to create flexible all-MXene hybrid films with high gravimetric capacitance and excellent rate performance for flexible supercapacitors. Ti₃C₂T_x nanosheets are introduced in between Nb₂CT_x layers, leading to a significantly increased interlayer spacing. The self-restacking of both types of MXene nanosheets is effectively impeded, accelerating the diffusion of electrolyte ions and enabling more accessible 2D nanochannels. The freestanding Ti₃C₂T_x/Nb₂CT_x films deliver a high gravimetric capacitance of 370 F g⁻¹ at a scan rate of 2 mV s⁻¹, good rate performance with 56.1% capacitance retention at 200 mV s⁻¹ and a long cycle life. Furthermore, the energy density of the assembled all-solid-state symmetric supercapacitor can reach up to 5.5 mW h g⁻¹ at a power density of 141.4 mW g⁻¹. Serving as a stable power source unit, the all-solid-state supercapacitor was also integrated with a flex sensor to fabricate a self-powered device. The route to fabricate Ti₃C₂T_x/Nb₂CT_x hybrid films with enhanced electrochemical performance is also applicable for other MXenes, promoting the application of MXenes in flexible supercapacitors and integrated electronic devices.