- Title
- Microemulsion electrolytes for Redox flow batteries
- Creator
- Borah, Rohan
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2023
- Description
- Research Doctorate - Doctor in Philosophy (PhD)
- Description
- The energy crisis scenario of today and the near future presents challenges on several fronts, but the storage of excess energy is perhaps the most pressing. This demand on the small scale (from handheld devices to electric vehicles) has been met to a certain degree by the Li+ ion battery. For large scale applications like grid storage cheap, efficient and clean energy storage still remains an unanswered question. Despite all advantages, clean energy sources are not reliable due to the lack of efficient and cost-effective storage systems capable of handling immense charge volumes. In this regard, the Redox flow battery has emerged as a promising technology for large scale energy storage. Flow batteries are fundamentally distinct, in the aspect that the electroactive components instead of being coated onto electrodes are dissolved in solutions. These solutions are housed in storage tanks and not in the electrochemical cell allowing for decoupling of power and energy. This crucial feature of RFBs allow for easy and low-cost upscaling making them ideal candidates for energy storage in the MW scale and above. RFBs being based on solution electrochemistry are also much easier to maintain and thereby offer prolonged lifetimes compared to any other battery technology. The state-of-the-art Vanadium redox flow battery has come a long way in establishing the critical advantages that RFBs provide but are still pervaded with fundamental as well as economical concerns. The acidic Vanadium electrolyte, which is essential for the RFB to be feasible, poses risks of corrosion and gas evolution. Low abundance and fluctuating prices of Vanadium, coupled with the cost of expensive ion-exchange membranes impedes market uptake VRFBs. RFBs based on other chemistries such as All-Iron, Zinc bromide, etc. are commercialised but still have a much lower market share compared to VRFBs. RFB research has delved in numerous electrochemical systems to come at a stable, high-energy chemistry that can be scaled at a competitive levelized cost of storage. However, considering the intended scales of application where RFBs can be a highly competitive solution, finding low-cost chemistries is challenging. Organic electro-chemistries have gained popularity over the last decade, considering the fact organic compounds are not limited by material abundance and chemicals offering scalable production can be feasible with demand. Organic electro-chemistries although plenty to pick from, come with the disadvantage of requiring either structural modifications of the organic molecules or the use of non-aqueous electrolytes. Both the strategies are essential to achieve desired energy densities for RFBs but incur substantial cost increase. Research on alternative electrolyte systems, for organic chemistries has been less prominent compared to the alternate strategies mentioned above. Such an alternative electrolyte is preferably aqueous based to be cost competitive, but the current acidic aqueous-quinone electrolytes suffer from familiar problems such as electrolyte corrosivity and gas evolution. Other electrolytes include non-aqueous solvents, liquid active materi-als, ionic liquids and deep eutectic solvents, none of which are promising commercially yet. This work thereby focuses on the development of RFB electrolytes which are customisable to a specific organic active material. Micro-emulsions have been identified as highly tunable bi-phasic electrolyte system that offer the benefit of a wide range of organic material solubility. The electrochemistry of organic systems in such electrolytes has been assessed from the literature and fundamental aspects have been explored to determine feasibility as an RFB electrolyte. A variety of organic materials have been scanned for electrochemical characteristics and a proof-of-concept RFB has been demonstrated to study the effects of micro-emulsion electrolytes in practical applications. Overall, micro-emulsions can be promising electrolytes for ORFBs with exclusive advantages and with the further study outlined in this work, could become commercially feasible systems in the near future.
- Subject
- electrochemistry; flow batteries; energy; redox
- Identifier
- http://hdl.handle.net/1959.13/1471905
- Identifier
- uon:48742
- Rights
- This thesis is currently under embargo and will be available from 15.03.2024, Copyright 2023 Rohan Borah
- Language
- eng
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