Supercapacitor applications of some metal / graphene based materials

Nowadays, supercapacitors have gained importance in energy storage. It has higher power and energy density and longer life cycle than conventional capacitors. Supercapacitor electrode materials are chosen from carbonaous materials with high surface area, transition metal oxides, and conductive polymers. In this thesis, it is aimed to synthesize new nanocomposites and to develop supercapacitor devices with superior electrochemical performances. NiO, MnO2, Co3O4, GO, rGO, PANI, rGO/NiO, rGO/MnO2, rGO/Co3O4, rGO/NiO/PANI, rGO/MnO2/PANI, rGO/Co3O4/PANI materials were synthesized to show the applicability on equivalent circuits. The synthesized materials were characterized by various methods, such as SEM-EDX, FTIR-ATR, thermal gravimetric analysis (TGA-DTA), 4-point probe solid conductivity measurements, surface analysis (BET) and Atomic force microscopy (AFM). Electrochemical performances of supercapacitor devices were measured by various methods, such as cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), electrochemical impedance spectroscopy (EIS). MnO2 and NiO based materials were tested by ladder equivalent circuit model [R1(C1(R2(C2(R2(C3R3))))]. However, Co3O4 based materials were tested by circuit model [R1(C1(R2(C2R3)))] using ZSimpWin 3.22 simulation programme.