Preparação e caracterização de supercapacitor sólido birredox baseado em eletrodos de óxido de grafeno reduzido e eletrólitos poliméricos géis

Abstract

In this work, the synthesis and characterization of different materials were performed: graphene oxides and poly(ionic liquids), aiming to develop electrodes and electrolytes for the preparation of solid-state supercapacitors. The thermal, morphologic, textural, spectroscopic, and electric properties of those materials were studied aiming to establish structure-property correlations. Three thermally reduced graphene oxides (Tr-GOs) and two poly(ionic liquid)/ionic liquid (PIL/IL) redox gel electrolytes based on the active molecules anthraquinone (AQ) and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) were synthesized. Those materials were utilized in the construction of solid-state supercapacitors containing redox activity. The Tr-GO materials, utilized as electrodes, were characterized by aiming to evaluate their structures and properties, to confirm and optimize the reduction process. The poly(ionic liquids) synthesized: PIL AQ and PIL TEMPO were characterized to attest to the success of their synthesis process and then utilized in the preparation of the two PIL/IL electrolytes, that were evaluated in three-electrode cells to enable the comprehension of the redox activity electrolytes in the presence of the graphene oxide electrodes. Three-electrode cell measurements have shown that the three Tr-GOs prepared were suitable for utilization as electrode materials within each of the developed electrolytes. The Tr-GO reduced at the temperature of 950oC (Tr-GO 950) has shown the best electrochemical performance among the three materials, based on the correlation with its morphological properties. The electrolytes PIL AQ/BMPYRRO TFSI and PIL TEMPO/BMPYRRO TFSI were successfully synthesized and have shown electrochemically active, being able to transfer electrons at the interface with the electrodes. The three-electrode cell measurements were fundamental to comprehending the electron transfer processes for each of the redox electrolytes and allowed to obtain good capacitance values in this configuration. Finally, a solid-state supercapacitor was developed by combining the two redox electrolytes synthesized (bielectrolyte) containing Tr-GO 950 as electrode material, PIL AQ/BMPYRRO TFSI as the electrolyte in the negative semi-cell (anolyte) and PIL TEMPO/BMPYRRO TFSI as the electrolyte in the positive semi-cell (catholyte). The device has presented an 81.4 F g-1 capacitance, 59.9W h g-1 energy density, and 281W kg-1 power density, which are among the best values in the literature. This demonstrates that the utilization of poly(ionic liquid)/ionic liquid redox gel electrolytes in the solid-state for the development of supercapacitors have shown to be an excellent strategy for the development of high-performance solid-state energy storage devices.