The characterisation and optimisation of the zinc bromine hybrid redox flow battery

Student thesis: Doctoral Thesis

Abstract

The zinc-bromine hybrid redox flow battery (RFB) is one of the few battery systems that have seen implementation on the medium to large scale energy storage. However, there still exist financial barriers to allow this technology to be fully utilised on the market. To improve this system, several potential areas could be improved from cell design, additive chemistries and electrode materials.Throughout this study, work was carried out on identifying new novel additives with the objective to complex the bromine without forming an immiscible phase. This work identified the use of a variety of ammonium- and phosphonium-based additives with appropriate carboxylic, sulphonate and hydroxyl functional groups to aid in the solubility of the complex. These additives were analysed in terms of their electrochemical response and on their physical characteristics. The data obtained were compared the industry standard complex, N-methyl-N-ethylpyrrolidinium.Carbon felt electrode materials and activated carbon electrode coatings were also investigated to examine their potential applications in this flow battery. The felt electrodes although providing a greater surface area, caused the immiscible phase to become trapped within it which led to an increase in flow pressure which ultimately was detrimental to the performance of the battery. This shows an even greater need to develop the additive chemistries to make use of the large surface areas offered by the felts. The activated carbon coating was found to be preferable with improved electrode kinetics and ease of the immiscible phase removal once charged.Finally, experience was gained on two large scale batteries which were characterised in terms of performance optimisation as part of this work. The ZnBr2 25 kW/ 50 kWh RFB was characterised at the Power Network Demonstration Centre, Scotland, and the all-vanadium 200 kW/ 400 kWh RFB was characterised at the École Polytechnique Fédérale de Lausanne - Laboratory of Physical and Analytical Electrochemistry, Switzerland. This has led to a better understanding of potential complications and differences that occur from scaling up redox chemistries from a lab bench to an industrial level.
Date of Award1 Apr 2018
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorLeonard Berlouis (Supervisor) & (Supervisor)

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