Mwcnts-COOH/Cotton Flexible Supercapacitor Electrode Prepared By Improvement One-Time Dipping and Carbonization Method

Abstract

In the field of soft electronic devices, flexible supercapacitor has received dramatical attention due to their appealing properties like lightweight, flexible, and environment friendly. To get the ideal flexibility of the supercapacitor, it is a key point to get a solid flexible substrate, which not only preserve the original physical properties of fabric but also offers self-supported scaffold for active materials. Among the different flexible substrate, cotton fabric is a good choice owing to the properties like low price, easily available and hydrophilicity, in which the hydroxyl groups make it favorable for adsorbing water and reacting with active materials. Carbon nanotubes are widely used electrode materials with the merits of high specific surface area, good chemical stability, low resistance, thermal stability, high flexibility and excellent electrical properties. However, it is hard to obtain ideal properties only combining carbon nanotubes with cotton, because the low capacity of carbon nanomaterials. Herein, we proposed a new method to prepare flexible carbon materials with high capacitance. First, we prepared flexible supercapacitor electrode based on carboxyl functionalized multiwalled carbon nanotubes (MWCNTs-COOH) and cotton fabric by a facile and highly efficient one-time dipping method under the condition of high pressure and temperature. After this process, MWCNTs-COOH coated on cotton fiber uniformly and winding together because of the presence of electrostatic interaction, van der Waals’ force and hydrogen bond between the oxygen-containing functional groups on MWCNTs-COOH and cotton fibers. Second, the sample was dipped in solution of poly(ethylene oxide) (PEO) for improving the carbon content and strengthen the composite structure after carbonization. At last, the above sample was dealt with pre-oxidation and carbonization to get the final composite. Pre-oxidation was used to induce oxygen-containing groups and obtain stable skeleton. Carbonization is beneficial to increase the carbon content and get stable structure with bitter melon surface-shape, which can supply large specific area and mesoporous to store and transport electrons, leading to a high capacitance. Therefore, the composite possessed excellent electrochemical performance with a high capacitance of 94.3 F g-1 at a current rate of 0.81 A g-1, and a good capacitance retention with over 96% after 3000 cycles. The prepared flexible supercapacitor electrode also showed good flexibility (93% capacitance retention after bending 60 times). Considering these good electrochemical performances, they are expected to be useful for practical applications in the field of supercapacitor. Figure 1