Fabricação e caracterização de supercapacitores flexíveis com eletrodos compostos por multicamadas de grafeno e filmes finos de óxido metálico

Abstract

The goal of this study is the development of solid state and flexible electrodes and supercapacitors based on multilayer graphene and metallic oxides deposited by sputtering technique. Several tests were conducted in order to improve the electrolyte and electrode composition, increasing the electrical charge storage. The effect of compaction pressure (20 e 200 kgf.cm-2) used to obtain the MLG electrode using a constant mass of 80 mg, as well as the oxide used (VOx and NbOx) and oxide thickness were systematically evaluated. The most important studied parameters were specific capacitance, energy and potency density, stability over 1000 cycles, stability under flexibility and potential window. Capacitors constructed at minor compaction generated the better capacitance values. NbOx films appeared to be better than VOx. The effect of NbOx layer indicated certain influence over the specific capacitance. Using oxides deposited at 20 and 40 minutes, an increase in capacitance was observed, while for 60 minutes of deposition, the capacitance presented a decrease, indicating the influence of this parameter over the charge transfer in the electrolyte electrode interface. Other important studied characteristic was the device flexibility. For different bending angles, the device capacitance remained constant, indicating the electrochemical double layer capacitor behavior. The obtainer potential window was 2.45V with an intense water electrolysis above this value. Therefore, the process and the devices herein proposed have shown promise to be constructed in large scale.