Open Positions

Investigation of the electrochemical performance and the surface layer formation of cycled thin films of amorphous Si in carbonate and ionic liquid based electrolytes

Li-ion batteries are considered to have the highest gravimetric and volumetric energy densities among commercialized rechargeable batteries. However, there are still windows for improvements in the electrochemical performance, durability and safety. To achieve this purpose, a lot of effort still needs to be dedicated to the bulk and surface side of the electrodes as well as to the electrolyte. It’s quite urgent to use and develop further characterization techniques on simplified models to study the electrodes, the electrolyte and the interface electrode/electrolyte in order to understand the mechanism and the origin of any modification occurring during cycling.

In this context, the master thesis project will be dealing with thin films of amorphous Si used as a model simplified negative electrode free of any binder and conductive carbon. The silicon will be cycled in half cell configuration versus lithium by using two types of electrolytes; (I) a carbonate based one, "the most common used in Li ion battery" and an ionic liquid "promising electrolyte for high voltage and temperature". The aim of the study is to compare the electrochemical performance of the silicon thin films and correlate that with the evolution of the surface layer during the early stage of cycling by using X-ray photoemission spectroscopy (XPS).

For further information please contact Dr Mario El Kazzi, phone +41 56 310 51 49 or Prof. Dr Petr Novak, phone +41 56 310 24 57.
Operando XPS measurements to investigate the interface electrode/electrolyte in Li-ion batteries

In the framework of developing operando characterization techniques to investigate lithium-ion batteries; operando XPS cell was developed at PSI in order to be able to investigate the evolution of the interface "electrode/electrolyte" during the early stage of cycling. The operation of this cell requires the use of ionic liquid as an electrolyte thanks to its low vapor pressure and its compatibility with the UHV system.

In this context, the master thesis project will deal with operando XPS measurements performed on model electrodes like graphite flakes or thin film of amorphous silicon cycled versus Li+/Li. The aim of the study is to put in evidence the possibility of probing the interface ionic liquid / electrode and follow the electrolyte decomposition as well as the Li ion intercalation in the case of the "graphite" or the Li-Si alloy in the case of "silicon".

For further information please contact Dr Mario El Kazzi, phone +41 56 310 51 49 or Prof. Dr Petr Novak, phone +41 56 310 24 57.

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