Functionalized and tip-open carbon nanotubes for high-performance symmetric supercapacitors

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Carbon nanotubes (CNTs) possess excellent electrical and mechanical properties, making them promising for supercapacitor electrodes.
• However, their electrochemical performance is often limited by closed tips and a lack of active sites.

Purpose of the Study:

• To improve the electrochemical performance of CNTs by opening their tips and introducing functional groups.
• To investigate the performance of functionalized and tip-open CNTs (FTO-CNTs) in supercapacitors using different ion electrolytes.

Main Methods:

• A facile and efficient chemical-acid-etching method was used to functionalize and open CNT tips.
• Supercapacitors were fabricated using FTO-CNTs as electrodes in aqueous electrolytes with Li+, Na+, and Mg2+ ions.

Main Results:

• The Li+-based electrolyte demonstrated the best electrochemical performance with FTO-CNTs.
• Areal capacitances of 542 mF cm-2 (positive) and 410 mF cm-2 (negative) were achieved at 10 mV s-1.
• The positive electrode reached a maximum areal capacitance of 903 mF cm-2 at 1 mA cm-2.
• The symmetric supercapacitor exhibited an areal energy density of 39 μWh cm-2 and an areal power density of 10.2 mW cm-2 with excellent cycling stability.

Conclusions:

• Tip-opening and functionalization of CNTs significantly enhance supercapacitor performance.
• FTO-CNTs in Li+-based electrolytes offer a promising pathway for high-performance energy storage devices.
• The developed supercapacitor demonstrates excellent energy and power densities, along with remarkable cycling stability.