Magnesium anodes in ionic liquid electrolytes (DTP)
Magnesium metal is an ideal rechargeable battery anode material because of its high volumetric energy density which is almost double that of lithium metal (3833 vs. 2277mAh cm-3), high negative reduction potential (-2.7V vs SHE), high melting point (650°C) and natural abundance (sixth most abundant element in the Earth’s crust). Compared to lithium, magnesium tends to grow smooth surfaces due to lower diffusion barriers and, as an hcp metal, it favours higher-coordinated configurations (in contrast to the bcc lithium). These characteristics hinder the dendrite nucleation process, in which unrestrained growth results in dreadful short circuit, fire, or explosion, and is therefore one of the most severe limitations to the commercial deployment of Li-metal batteries. Unfortunately, the low solubility of magnesium salts in non-aqueous solvents and the passivation of the magnesium surface by oxidized species (i.e. MgO, Mg(OH)2 and MgCO3) limits the electrolyte choice. Ionic liquids (ILs) represent a very exciting new class of room temperature fluids. The main advantages of ILs compared to organic solvents are their non-flammability, negligible vapor pressure, and high chemical and thermal stability. Therefore, ILs have been recently investigated as electrolytes for electrochemical devices including rechargeable lithium batteries due to their high ionic conductivity and electrochemical stability. Bis(fluorosulfonyl)imide (FSI) ILs, show particular promise as they exhibit low viscosity, high chemical stability, and form robust solid−electrolyte interphase.
In this project, the student will investigate trifluoromethanesulfonylimide (FSI) based ionic liquids as electrolytes in magnesium-metal batteries: from their physico-chemical properties (i.e. viscosity, thermal stability), to their bulk electrochemistry (i.e. conductivity, diffusion coefficient, transference number), to the surface chemistry of the magnesium metal
IL interface with the aim of understanding the role of improving its cycle life and rate capability. Advanced electrochemical characterization, NMR, XPS and electron microscopy, both in-situ and ex-situ, are some of the techniques that the student will be trained on during the PhD studies.
Any questions concerning the project can be addressed to Professor Mauro Pasta ([Email Address Removed]). General enquiries on how to apply can be made by e‑mail to [Email Address Removed]. You must complete the standard Oxford University Application for Graduate Studies. Further information and an electronic copy of the application form can be found at http://www.ox.ac.uk/admissions/postgraduate_courses/apply/index.html.
This EPSRC-funded 3.5 year DPhil in Materials DTP studentship will provide full fees and maintenance for a student with home fee status (this status includes an EU student who has spent the previous three years (or more) in the UK undertaking undergraduate study). Candidates with EU fee status are eligible for a fees-only award, but normally would have to provide funding for their living costs from another source such as personal funds or a scholarship. The stipend will be approximately £15,777 per year. Information on fee status can be found at http://www.ox.ac.uk/admissions/graduate/fees-and-funding/fees-and-other-charges.