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Experimental Investigation of Zinc Bromine Flow Batteries

Moshakker, Hossein | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57021 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Molaei Dehkordi, Asghar
  7. Abstract:
  8. Given the necessity of energy storage in today's world, various technologies have been developed to expand energy storage systems on a large scale. Electrochemical-based technologies, due to their high efficiency, are among the most suitable energy storage systems that have attracted the attention of scientists and researchers. Rechargeable zinc bromine flow batteries are one of the most powerful candidates for next-generation energy storage due to their high energy density, lower material costs, deep discharge capability, non-flammable electrolytes, relatively long lifespan, and good reversibility. However, there are many challenges to improving the efficiency and stability of these batteries for long-term operation. Zinc deposition during the charging process and the use of complexing agents are among the most important challenges for these batteries. In this research, sodium sulfate was used as a supporting electrolyte with high conductivity, and tetrapropylammonium was used as a complexing agent. The results indicate that high concentrations of tetrapropylammonium bromide lead to the solidification of the liquid electrolyte, converting the flow battery into a static battery. If the concentration of this substance in the electrolyte is optimized, it does not solidify the flow battery electrolyte but can improve the deposition of bromine. Additionally, according to the results obtained, the use of sodium sulfate improves the voltage and coulombic efficiency of the system. After determining the supporting electrolyte and suitable complexing agent for optimizing the flow battery system for bromine, and investigating the effects of known factors such as current density, electrolyte flow rate, and base electrolyte concentration, a response surface methodology with 20 experimental design runs was performed. The results show that current density has the greatest impact on the performance of the zinc bromine flow battery. Following that, electrolyte concentration and flow rate have a greater impact on the performance of this battery, respectively. The R2Reg and R2Adj values for the fitted model on the bromine flow battery system were obtained as 0.87 and 0.71, respectively. To validate the battery model, two experiments were conducted over 10 cycles at optimal values. The energy efficiency of the bromine flow battery at a concentration of 2.75 Molar bromide, a current density of 13.23 mA cm-2, and an electrolyte flow rate of 10 mL min-1 was determined to be approximately 61%, with an error of about 15% compared to the fitted model. The effect of graphite flow channel on the performance of the zinc bromine flow battery was also investigated at optimal factor levels. The results indicate that graphite electrode without flow channels performs better compared to graphite electrode with flow channels. The reason for this issue was attributed to the lower resistance of this graphite plate. The developed zinc bromine flow battery showed good stability for 70 charge/discharge cycles
  9. Keywords:
  10. Energy Storage ; Electrochemistry ; Hybrid Flow Battery ; Zinc-Bromine Flow Battery ; Buttery Life

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