The SOLVOMET group is the laboratory of metallurgical chemistry in the Department of Chemistry of KU Leuven and is led by Prof. Koen Binnemans. SOLVOMET’s vision is that metallurgical chemistry expertise allows to develop circular hydrometallurgical processes to provide the metals that are needed for the transition to a climate-neutral society. SOLVOMET’s dual mission is (1) to perform excellent research in metallurgical chemistry & solvent extraction, while training young researchers in these domains and (2) to support companies worldwide in the development of (solvent extraction-based) circular hydrometallurgical processes, and to provide training in solvent extraction. SOLVOMET’s is also applying its expertise in hydrometallurgy to the development of new electrolytes for redox flow batteries.
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Project
Within the SOLVOMET group of KU Leuven, a PhD student will be hired to work on the development of new electrolytes for cerium-titanium redox flow batteries (RFBs).
The large-scale deployment of renewable technologies will require cost-effective battery technologies to support the electrical grid for industry and society. Solving this fundamental problem will enable the further expansion of renewable energy technologies, thus contributing to a CO2-neutral electricity supply. Such a technology needs to be scalable to a national grid level, demands a long service lifetime, and requires a low cost per kWh. Lithium-based battery technology has a good energy and power density, ideal for transport and small domestic applications. However, since it suffers from rapid performance degradation, production that is primarily reserved for automotive applications, high cost, and a strict safety management, they are not suitable for grid-scale storage applications. RFBs are an exciting alternative for large-scale applications: their performance is constant, without inherent degradation over time. With routine maintenance, even at the end of their theoretical lifetime (15 to 20.000 charge cycles), their performance will still be close to its original value. Moreover, the storage capacity of an RFB is not dependent on the electrode size but only on the volume of the electrolyte.6 State-of-the-art RFBs combine vanadium (V) electrolytes with fluorinated proton-conducting membranes. Although they have been studied for decades, their cost (esp. the electrolyte and membrane) is still a challenge for commercialization. In addition, vanadium is moderately toxic, and not really abundant and would need to be replaced to improve the safety of the system.
Titanium and cerium electrolytes are very promising to replace vanadium in next generation RFBs. They are much less toxic than vanadium and titanium is about 40 times more abundant than vanadium. Cerium’s abundance is comparable to that of copper and a large oversupply of cerium currently exists as a side product of mining and processing of rare-earth ores for the production of neodymium for permanent magnets. So far, cerium is used only for low-added value applications, such as glass polishing powder and "flint" ignition devices. At this moment, most mining companies, separate cerium from the other rare earths and are just stockpiling it. Finding a useful application of this ‘waste product’ has been a long-standing challenge. This is the so-called “Balance Problem” of rare-earth markets. As a result not only, titanium but also cerium is much cheaper than vanadium.
The objective of this PhD project is to develop new cerium and titanium-containing electrolytes that will be used to construct cerium-titanium RFBs with a Ce4+/Ce3+ catholyte in combination with a Ti4+/Ti3+ anolyte. Special attention will be paid to mixed-acid electrolytes that show higher solubilities, higher stability and faster redox kinetics compared to single-anion electrolytes. The targets are stable electrolytes with metal concentration above 2 mol L-1, resulting in a higher cell potential (1.7-1.75 V) than the all-vanadium system (1.2-1.3 V). The new electrolytes will be mixtures of methanesulphonic acid (MSA) and other inorganic acids. The research activities involve the determination of the solubility of the different salts as a function of the acid concentration and the temperatures, with special attention to the effect of mixed anions. The metal species present in the electrolyte solutions will be identified by a combination of different spectroscopic techniques, yielding complementary information, such as UV-VIS absorption spectroscopy, FTIR, Raman, 1D and 2D heteronuclear NMR spectroscopy (17O, 49Ti NMR for this project), electrospray ionisation mass spectrometry (ESI-MS), magnetic susceptibility measurements and X-ray absorption fine structure (XAFS, performed at ESRF in Grenoble (F) or at a beamline of another European synchrotron facility. The measured water activity is an indication of the deviation from ideal thermodynamic behavior. The information gathered will be used to build a thermodynamic model within the Mixed Solvent Electrolyte (MSE) framework. To determine the electrochemical properties of the electrolytes, different electrochemical techniques will be used, including cyclic voltammetry (CV) using stationary or rotating disk electrodes and spectroelectrochemistry. The diffusion coefficients and the radius of the diffusing electroactive species can be determined via chronoamperometric measurements and by application of the Cottrell and Stokes-Einstein equations. Experiments with a rotating disk electrode will allow the determination of limiting current, via the Levich equation.
This PhD project is a combination of experimental work and modelling, but the focus can be shifted towards the experimental work or the modelling, depending on the skills and interests of the student. The supervisor will be Prof. Koen Binnemans and the project is part of the Flemish research project REBBID.
Profile
We are looking for a highly motivated and talented candidate who meets the following requirements:
- You hold a Master’s degree in Chemistry or Material Sciences
- You have a strong interest in sustainable technologies, electrochemistry, solution chemistry and batteries
- You have a passion for science and technology
- You enjoy both experimental laboratory work and modelling activities
- You are able to work independently while contributing to a collaborative research team
- You have good communication skills in English (written and spoken)
- Experience in redox flow batteries is an asset, but not a requirement
Offer
We offer:
- A fully funded 4-year PhD position at KU Leuven
- A stimulating international research environment within a leading research groups in metallurgical chemistry and non-aqueous coordination chemistry
- Access to state-of-the-art laboratory infrastructure and modelling tools
- Opportunities to present your work at international conferences and to build an academic and industrial network
- A comprehensive doctoral training programme within the Arenberg Doctoral School
Interested?
For more information please contact Prof. dr. Koen Binnemans, mail: [email protected].
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