# Review of Flexible Supercapacitors Using Carbon Nanotube-Based Electrodes
## 3 Conclusions and Perspective  
The summary of the various types of CNTs and their electrochemical performance are given in Table 1.  
CNT-based materials have emerged as promising materials for supercapacitor electrodes due to their high surface area, electrical conductivity, and mechanical strength. CNT-based materials can improve structural property which leads to enhanced electrochemical performance in the forms of 1D fiber, 2D film, and 3D composite. The larger surface area by porous structure of CNTs results in high areal capacitance, and intercalation of CNTs makes volumetric capacitance higher while their low density increases specific capacitance. Furthermore, there are huge potentials when combining with other materials expected to have sy synergetic effects because this creates various possibilities to combine with other active materials, sometimes with pre-treatment. Therefore, the scope of research regarding the use of CNTs as a supercapacitor material is expected to grow faster and broader in the future, while demands for flexible and wearable energy devices increase. There have been numerous studies aimed at improving the value of the specific capacitance, energy density, and rate performance of supercapacitors utilizing these materials. One strategy for enhancing performance has involved functionalizing the CNTs with conductive materials such as graphene and metal nanoparticles, while another method has \begin{table}
\begin{tabular}{c c c} \hline \hline
**Materials** & **Electrochemical Performance** & **[Ref]** \\ \hline \hline CNTFF & Areal capacitance of up to 353 mF/cm\({}^{2}\) and an energy density of up to & [39] \\  & 247 \(\mu\)W/cm\({}^{2}\) & [14] \\ \hline CNT-MnO\({}_{2}\) fiber fabrics & A specific capacitance reaching up to 231.3 F/g and an energy density of up & [1] \\  & to 86 nWh/cm & [1] \\ \hline CNT-graphene fiber fabrics & A specific capacitance of up to 350 mF/cm\({}^{2}\) & [10] \\ \hline CNT-NiO fiber fabrics & A specific capacitance of up to 402 F/g and an energy density of up to & [1] \\  & 28 Wh/kg & [1] \\ \hline Functionalizing CNTs on a Ti thin film & A specific capacitance of 535.7 F/g and an energy density up to 26.1 Wh/Kg & [40] \\   with graphene & & \\ \hline CNTs on Ni thin films & A specific capacitance of 1200 F/g & [2] \\ \hline MXene (Ti\({}_{3}\)C\({}_{2}\)T\({}_{x}\))-MWCNT electrodes & A specific capacitance of 0.94 F cm\({}^{-2}\) at scan rate of 2 mV s\({}^{-1}\) & [4] \\ \hline \hline A hybrid electrode combining CNTs, & & \\ Fe\({}_{3}\)O\({}_{4}\), and Ti\({}_{3}\)C\({}_{2}\)T\({}_{x}\) MXene & A specific capacitance of 5.52 F/cm\({}^{2}\) & [5] \\ \hline CNTs and Ti\({}_{3}\)C\({}_{2}\) MXene & A specific capacitance of 134 F/g & [13] \\ \hline VS\({}_{2}\)-MX-CNT-50//MWCNT & A specific capacitance of 505 F/g and an energy density of 7303 Wh/Kg & [42] \\ \hline NiCoO\({}_{2}\)/CNT@NF & A specific capacitance of 929 F g\({}^{-1}\) & [3] \\ \hline CNTs/NiCoO\({}_{2}\) system (3D) & A specific capacitance of 1587 F/g & [9] \\ \hline Self-assembled CNTs/NiCoO\({}_{2}\) system & A high specific capacitance of 1360 F/g & [15] \\ \hline SWNTs-coated Korean traditional paper & A specific capacitance of 366 F/g and energy density of 114 Wh/Kg & [44] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: A summary of the various types of CNTs and their electrochemical performances. involved controlling the morphology of the CNTs on thin metal films. CNT-FFs have shown impressive energy storage performance in many studies, including a specific capacitance of up to 402 F/g and an energy density of up to 28 Wh/kg. Similarly, CNTs on thin metal film electrodes have also demonstrated high specific capacitance and improved rate performance. Hybrid electrodes combining CNTs with Mxene or NiCoO\({}_{2}\) also showed excellent electrochemical performance. However, there are some challenges that need to be addressed, including the scalability of the synthesis processes and the long-term stability of the electrodes.