Growth of nanostructured MNO2 on ionic liquid-graphene composite paper as free-standing electrodes for supercapacitor applications

• Main Author: K. R. Rakhitha Malinga, Ariyawansha
• Other Authors: School of Chemical and Biomedical Engineering
• Format: Theses and Dissertations
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/61130
• Institution: Nanyang Technological University

Energy storage devices are receiving extensive attention in recent years due to the increasing demand of energy. Supercapacitor is one of the energy storage devices with high specific power density and wide applications in electronic vehicles, commercial mobile electronics, and military devices. In this dissertation, we design and fabricate a high-performance flexible supercapacitor electrode based on MnO2 nanonest (MNNs) modified ionic liquid (IL) functionalized graphene composite paper (IL-GP). The nanohybrid paper was fabricated by first functionalizing graphene nanosheet with a new type of amine-terminated IL to form freestanding IL-GP and then modifying IL-GP with unique MNNs structure via a facile template-free electrodeposition method, which allowed for better structural integration of MNNs with IL-GP, We have shown that conductive and hydrophilic ILs 1-(3-amainopropyl)-3-methylimidazolium bromide) that covalent attached on the graphene nanosheets effectively prevented graphene aggregation from forming paper structure and provided highly conductive channels and expected hydrophilic property to facilitate the access of the aqueous electrolyte ions onto the grephene surface. The freestanding IL-GP with large specific surface area then served as electrochemical active substrates for electrodeposition of pseudocapacitive MNNs. The resultant MNN modified IL-GP (MNN/Il-GP) combining unique pseudocapacity of metal oxide high conductivity and electric double layer charging/discharging of IL-Graphene composite exhibited an enhanced supercapacitor performance. The maximum specific capacitance of 411 Fg-1 was achieved by chronopotentiometry at a current of 1 Ag-1. The nanohybrid MNN/IL-GP electrode also exhibited rate capacity and cycling stability. Its specific capacitance preserves 70% as the current densities increase from 1 to 20 Ag-1 and 95% at a current density of 10 Ag-1 after 1000 cycles. More importantly, MNN/IL-GP displayed distinguished mechanical stability and flexibility as well. These interesting findings collectively demonstrated the potential of MNN/IL-GP as high-performance the electrode to realize high-energy density and high-power density characteristics for flexible electrochemical capacitor applications.