Development of organic-based flow batteries, determination of chemical/electrochemical characterization and performance

Energy demand is increasing day by day due to the increasing population and technology in the world. Energy sources with high carbon footprints are used to meet the increasing energy demand, and this returns to humanity as environmental and atmospheric pollution. In order to keep the environment clean by preventing pollution and to prevent it from having a negative impact on the lives of living things, efforts are being made to increase the use of economically attractive renewable energy resources (RES). However, since RES is not continuous, such as solar energy panels and wind turbines, there are problems in integrating the produced energy into the grid and the produced energy cannot always be used. For this reason, as in every field, there is a need to store city grid electrical energy where there is high energy demand. Thus, the stored energy can be transferred to the grid in certain flows and energy can be supplied to the grid during hours when the energy produced by RES is not continuous. The importance given to RES and energy storage in our country is increasing day by day, as in the world. In this thesis, the use of organic redox flow batteries to store city electricity was studied. Redox flow batteries are batteries with high electrical energy storage properties. In these batteries, which are based on the principle of storing energy through the flow of liquid electrolyte, it is sufficient to increase the amount of electrolyte to increase the amount of energy storage. Electrolyte can be prepared using aqueous or non-aqueous solvent. The solute must be an electroactive organic material in which redox reactions occur. Various organic materials were examined within the scope of the thesis. These organic materials are polyaniline boronic acid (PABA), polythiophene boronic acid (PTBA), ferrocene disulfonic acid (FcDS), ferrocene - 1,4-disubstituted 1,2,3-triazole (1,2,3-TAFc), and 2,2,6,6-tetramethylpiperidine (TEMPOL) compounds. The potential of using PTBA, PABA, FcDS, 1,2,3-TAFc organic materials as electroactive materials in flow batteries was examined. The electrochemical properties of relevant organic materials were examined through tests performed in solutions at different pH levels. In tests carried out in aqueous environment, the charge/discharge behavior was investigated by establishing a flow battery system with the 1,2,3-TAFc compound. It was determined that the relevant organic material was extremely stable and battery tests were carried out successfully for the first time in the literature. TEMPOL compound was used to perform performance tests of graphite felts used as electrodes in flow batteries. Graphite felt electrodes were coated with graphene and tested with TEMPOL material and performance changes were examined.