Slurry-based electrodes for vanadium redox flow battery

  • Slurry-basierte Elektroden für Vanadium Redox Flow Batterien

Percin, Korcan; Wessling, Matthias (Thesis advisor); Breugelmans, Tom (Thesis advisor)

Aachen : RWTH Aachen University (2021)
Book, Dissertation / PhD Thesis

In: Aachener Verfahrenstechnik series - AVT.CVT - chemical process engineering 15 (2021)
Page(s)/Article-Nr.: 1 Online-Ressource : Illustrationen

Dissertation, RWTH Aachen University, 2021

Abstract

Energy storage systems play a significant role in developing network grids with the integration of renewable energy sources. Creating a stable electricity network supported by renewable energy sources is challenging due to the fluctuating nature. Vanadium redox flow battery is one of the electrochemical energy storage systems that store electrical energy in large amounts and capable of remediating the challenges oriented from using renewable energy sources. Up to now, vanadium redox flow technology has attracted considerable attention because of its simplicity and cost-effectiveness. However, electrode performance of the battery can be still improved. This thesis suggests replacing the standard electrodes used in a vanadium redox flow battery with the slurry electrodes. Slurry electrodes are conductive particles dispersed in electrolyte media. By replacing solid-static carbon electrodes from the standard cell, a dynamic flow cell is created, where the electrodes are also decoupled from the cell interiors. These electrodes are easy to produce, easy to scale-up, and easy to recycle without disassembling the cell. This dissertation aims to develop a slurry electrode-based vanadium redox battery by focusing on improving the electrochemical activity and the flow profile of the slurry electrodes. For the first time, a vanadium redox flow battery is presented using the slurry electrodes. However, the electrochemical activity of the slurry electrodes is limited due to the flow profile of the dispersion under laminar conditions. This thesis demonstrates the application of the static mixers to improve the slurry mixing in the flow cell, and thereby, increase the electrochemical activity significantly. Furthermore, having highly conductive static mixers expands the current density beyond the limits reaching highest in this work and closest to a standard vanadium redox flow battery. Besides the static mixers, the electrochemical activity of the slurry electrodes strongly depends on the particle properties. It has been shown that the particle size, porosity, and electrical conductivity indicates a considerable difference in the usage of slurry electrodes. Particles with the highest conductivity and the lowest porosity demonstrated to have the best activity for the redox reactions. The addition of nano-sized particles into the macro-sized slurries indicated an enhancement of the electrochemical activity by increasing the electrical conductivity between the particles. The dynamic nature of slurry electrodes allows the change of the planar cell designs of the classical electrochemical flow reactors. A tubular vanadium redox flow battery is manufactured to showcase a possible application of the slurry electrodes. The tubular-shaped cell demonstrates higher power density compared to the planar one because of the improved electrode surface area to the cell volume. Thereby, the slurry electrodes reveal the flexibility of their applications. It has been shown in this thesis that the slurry electrodes can be enabled and improved by considering complex flow and material properties. Many other electrochemical processes can benefit from the understanding gained from this work and encouraged to utilize the slurry electrodes.

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