Proposals for Master level thesis work during 2017
– Ångström Advanced Battery Centre
1. Salt dissolution and ion conduction in polymers for advanced battery applications
There are a number of polymers which can dissolve salts and conduct ions; mostly explored have been polymers for Li-based salts. With the advancement of alternative battery chemistries (Na-based, Mg-based, etc), there is a need to investigate systems also based on other cations. At the same time, the advancement of high-voltage cathode materials leads to a need for electrolyte systems which are prone not to dissolve and complex transition metal ions (primarily Mn and Ni). The proposed project will explore different salts in different polymer hosts to find chemistries which would be suitable for conduction of alkali metal ions, but less prone to dissolve transition metal ions.
2. Block-copolymers based on polycarbonates
Polycarbonates constitute a promising class of new host materials for polymer electrolyte systems. Their mechanical properties can be significantly improved by block-copolymerisation strategies, while conductivity is not compromised. A limited number of different carbonates and block-sizes will be explored to find the best conductivity. The project will involve polymer synthesis, polymer characterisation, impedance spectroscopy and battery prototype construction and testing.
3. Polymer electrolytes on a large scale
We have recently developed a high-performance polymer electrolyte that shows stable cycling with high efficiency and excellent capacity retention in prototype cells. We would like to develop the material and the manufacturing processes further to be able to more easily produce the electrolyte in larger quantities. This would also enable more consistent and reproducible materials properties. The aim of this project is to accomplish this and use the resulting material to produce larger-scale batteries with optimized capacity and energy density.
4. Polymer electrolytes for high-voltage cathodes
One key to solving our future renewable energy needs is improving the energy density of Li-ion batteries. This can be accomplished through increasing the battery voltage by using cathode materials with a higher electrochemical potential. This puts tougher demands on the electrochemical stability of the electrolyte and it is currently difficult to find electrolytes that are sufficiently stable. We have recently been working with a polycarbonate electrolyte platform that has the potential of showing improved electrochemical stability compared to standard materials. In addition, recent results by other research groups show that at high salt concentrations, such electrolytes can show even higher cathodic stability. This project will explore this further in order to develop a material suitable for use with next-generation high-voltage cathode materials.
5. Non-aqueous Zinc (Zn) Batteries: A new field in rechargeable batteries
Studies have very recently shown that Zn metal can reversibly be used in non-aqueous based electrolytes. This new achievement will open a new field in the technology of rechargeable batteries. Although the gravimetric capacity of Zn-ion batteries is relatively lower than Li-ion batteries, Zn batteries have several advantages such as efficient Zn plating-stripping, much higher volumetric capacity, multivalent charge ions, etc. In this project, we will try to explore this new field of rechargeable batteries by studying Zn plating/stripping reaction in different non-aqueous electrolytes. Electrochemical tests such as galvanostatic cycling and cyclic voltammetry will be used to find out the efficiency of Zn plating/stripping reaction. In addition, different characterization techniques such as XRD, XPS, and SEM will be employed to analyze composition of deposited products.
6. Advanced anode materials for sodium (Na) batteries
Contrary to Li, sodium (Na) has abundant natural resources both in Earth’s crust and sea water. Therefore, Na-ion batteries (NIBs), which have comparable energy densities to LIBs, can guarantee sustainable development of rechargeable batteries. In this respect, there have been vast efforts in recent years to build efficient NIBs. The project will focus on the development of anode materials for Na-ion batteries. In particular, anode composites based on antimony (Sb) will be studied. Electrochemical tests as well as XRD and XPS techniques will be used to analyze the cycling performance and reaction products in Na-ion half cells.
7. Solid electrolyte interphase (SEI) on lithium metal anode
The gravimetric and volumetric energy densities of lithium batteries could be increased by using lithium metal as anode instead of the conventional anode materials such as graphite. However, Li-metal anodes suffer from 2 main problems: i) the formation of dendrites, and ii) poor cycling efficiency. In this project, the formation and properties of SEI on Li-metal anode and the parameter influence performance of Li-metal in aprotic electrolytes will be studied. Operando light microscopy, XPS, SEM, and electrochemical test are the main techniques to analyze the performance of Li-metal anode.
8. Sustainable electrodes for hybrid batteries
The project aims at developing the first hybrid organic-inorganic lithium-ion full cell which can be prepared and recycled using only non-polluting solvents such as water and ethanol. Preliminary results from our laboratory have already demonstrated the feasibility of the concept with organic lithium-ion half cell (ChemSusChem 2014, 7 (10), 2859-2867) and recent literature has shown similar approach with inorganic lithium-ion half cell (J Mat Chem 2015, 3, 11493-11502). The idea here is to combine these two approaches and develop strategies for recycling of the materials.
9. Developing Large Format Lithium Ion Cells for In Operando Neutron Diffraction
To expand our understanding of the reactions occurring in lithium ion cells new techniques of analysis need to be utilised. One such technique which is currently rapidly growing in popularity is in operando neutron diffraction. It enables one to see inside a battery and track the reactions which take place on the atomic scale while the cell is in operation. Thus a direct correlation can be made between battery performance and the actual changes taking place to the battery electrodes during cycling. However, designing a cell for neutron diffraction is no trivial task and has been a major road block for the wide spread utilisation of this technique. This project will thus focus on exploring whether a large format cylindrical cell containing the commercial electrodes LiNi0.5Mn1.5O4 and Li4Ti5O12 can be built. Electrochemical testing such as galvanostatic cycling will be performed to assess the quality of the cell in addition to post-mortem ex situ X-ray diffraction to explore if the electrochemical reaction is homogeneous throughout the cell.