Vertical-MXene based micro-supercapacitors with thickness-independent capacitance.

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• MXenes are promising two-dimensional (2D) materials for micro-supercapacitors (MSCs) due to excellent conductivity and capacity.
• Conventional MXene films exhibit thickness-dependent electrochemical properties because sheet stacking hinders ion transport.
• Vertical alignment of MXene sheets is needed to overcome ion accessibility limitations.

Purpose of the Study:

• To develop a micro-supercapacitor (MSC) with vertically aligned MXene sheets.
• To investigate the effect of vertical alignment on ion transport and electrochemical performance.
• To demonstrate a scalable method for fabricating vertically aligned MXene structures.

Main Methods:

• Fabrication of vertically aligned Ti₃C₂T_x MXene films using a liquid nitrogen-assisted freeze-drying method.
• Assembly of vertically aligned MXene films into micro-supercapacitors (MSCs).
• Electrochemical characterization, including areal capacitance and cycling stability measurements.

Main Results:

• The vertically aligned MXene structure facilitates directional ion transport, leading to thickness-independent electrochemical properties.
• The fabricated MSCs achieved a high areal capacitance of 87 mF cm^-2 at 10 mV s^-1.
• Excellent cycling stability was observed, with approximately 87.4% capacitance retention after 10,000 charge-discharge cycles.

Conclusions:

• Vertically aligned MXene sheets offer a promising strategy for enhancing MSC performance by enabling efficient ion transport.
• The liquid nitrogen-assisted freeze-drying method provides a scalable approach for fabricating vertically aligned MXene structures.
• This approach can be extended to other 2D materials for applications requiring directional transport.