Electrode optimisation towards lowering self-discharge of carbon nanotubes-based supercapacitors

Abstract

Currently tremendous work is done to improve capacitance of supercapacitors. However, such important supercapacitor parameter as self-discharge is often overlooked, being a bottleneck issue in energy storage applications of supercapacitors. It requires more study and concrete methods to supress self-discharge of supercapacitors.

In this study self-discharge of carbon nanotubes-based supercapacitors is studied. Hydrogen and nitrogen annealing heat treatment is introduced a method of self-discharge improvement. Moreover, an optimal recipe of the annealing procedure is determined with temperature of 500°C, duration of 30 minutes and H2:N2 gas composition of 20 sccm: 200 sccm.

It is shown that for CNT-based supercapacitors with capacitance in the range of 20 mF the self-discharge has been improved by 62.3% by implementing introduced annealing heat treatment. In addition, FE-SEM, EDX and XRD sample characterisation has been performed to analyse the difference in electrodes before and after annealing.

Moreover, the studied annealed electrodes-based supercapacitors showed 6.6% better self-discharge performance than a commercial capacitor.

Furthermore, after consideration of challenges and limitations, certain methods to suppress self-discharge of CNT based supercapacitors even further are suggested for future work, including closer investigation of annealing parameters and usage of gold-plated coin cell cases for coin cell assembly.