Preparation of Ag-CNTs and Ag-Graphene nanocomposite and their combination with MnO2 bath deposition for flexible supercapacitor development.

Abstract

Nowadays, researchers have made great efforts on the development of flexible and light weight energy storage devices for their practical applications and the advancement of modern electronic devices. Owing to the promising feathers of high specific power, high rate capability, and long-term cycling life, the supercapacitors (SCs) are considered as highly suitable for various flexible applications. In general, the carbon-based nanomaterials such as carbon nanotubes and graphene nanosheets, exhibit good supercapacitor performance. Manganese dioxide (MnO2) are widely studied for pseudocapacitors owing to their high specific capacitance, high power, and energy density. Thus, MnO2 was applied to increase the supercapacitor performance of carbon materials. However, most of the reported SCs are bulk, heavy, and non-flexible, which are not suitable for wearable energy technology. To overcome these challenges, flexible supercapacitors (FSCs) are developed to meet the wearable electronics. The cotton cloth materials are widely considered for flexible substrates due to inexpensive natural fiber, highly hydrophilic and light weight. In this work, the conductive cotton was successfully prepared by the screen-printing method using the developed ink. The designed textile ink and silver powder mixture demonstrates an outstanding conductivity. The prepared conductive cotton reached a low resistance of less than 15 ohm/cm2. Furthermore, the supercapacitor electrodes were also fabricated by mixing the active materials (CNT, and graphene) into the developed ink. Among these different carbon electrodes, the CNT electrodes show superior electrochemical performance (78.49 mF/cm2 at 0.1 mA/cm2). To further enhance the specific capacitance, the MnO2 was coated on the electrodes by chemical bath deposition (CBD) using potassium permanganate and sulfuric acid solution. The specific capacitance of as high as 741.83 mF/cm2 at 0.1 mA/cm2 was achieved. Finally, the flexible supercapacitor device was also successfully fabricated, which exhibited a high specific areal capacitance of 677.12 mF/cm2 at 0.0125 mA/cm2 for CNT electrodes. The flexible device also shows excellent rate performance and cyclic stability with capacitance retention of 80% for 3000 cycles, demonstrating that advanced flexible energy storage devices can be achieved.