Cell Design and Electrode Material for All Vanadium Redox Flow Battery
Date
2018-03-09
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Abstract
The all-vanadium redox flow battery (VRFB) is one of the most promising renewable energy storage systems due to its high energy efficiency, reliability, design flexibility and environmental friendly. In order to improve the performance of VRFB, cell design and electrode materials were studied in this project. A novel flow field design using a flow going through the porous electrode for the VRFB has been evaluated. By dividing the flow between flow-by and a portion of the flow going through the electrode, a significant improvement in the performance was obtained. A vanadium electrolyte system was used and charging and discharging cycles were performed and compared with the flow-by design. With a portion of flow going through the electrode, the voltage efficiency was increased from 74% to 80% and the voltage loss was decreased by 23%. The results indicate that the “flow through” condition can enhance the mass transfer rate at the surface of electrode. A templated nano-carbon scaffold (NCS) electrode material was evaluated for using in the VRFB. Scanning electron microscopy (SEM) was used to characterize the morphology of the electrode materials. This material has an organized nanoporous structure and the pore size can be as small as 22 nm. To investigate the performance of NCS as an electrode material, the NCS was attached to the surface of conventional carbon paper electrodes. The charge discharge performance of the VRFB was determined using a flow through mode of operation. The performance of nano carbon scaffold (NCS) with different pore size and thickness was compared with a conventional heat-treated carbon paper. The results show that by using nano carbon scaffold (NCS-85-HT), the voltage efficiency increased from 74% to 91% at 10 mA cm-2. The energy efficiency also increased from 56% to 70% at 10 mAcm-2 due to the increased voltage efficiency. The results indicate that the large surface area of the NCS, associated with its nano structure, lead to a reduction in overpotential of around 65%, and thus higher battery efficiencies. Cell performance under different current density was also explored and the improved efficiencies for NCS were maintained at all the current densities studied.
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Keywords
all-vanadium redox flow battery, cell design, electrode material, flow through condition, carbon nano materials
Citation
Li, J. (2018). Cell Design and Electrode Material for All Vanadium Redox Flow Battery (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/22446