Master thesis presentation Sofia Reiner, MPPHS

Abstract: The lithium-ion battery is the fastest growing energy storage technology and dominates in demand for smaller portable applications and electric vehicles due to its high energy density, small weight, and long lifespan. New developments in the materials used as positive electrodes enable the battery cells to operate under higher voltages than their predecessors, increasing the maximal power output. However, the voltage range of these cells extends beyond the reduction and oxidation limits on conventional solvents used in the electrolyte, causing the degradation of cell components and the subsequential failure of the battery. In this work, a dual electrolyte concept is proposed and evaluated in which each electrode has its own catered electrolyte, reducing the voltage window each electrolyte must be electrochemically stable in. Pairs of immiscible electrolytes consisting of both organic solvents and room temperature ionic liquids were evaluated and the diffusion between them in a battery cell setting was studied by Raman confocal spectroscopy, showing no or little diffusion under mechanical pressure. Furthermore, the electrochemical properties of the electrolyte pairs were tested in galvanostatic cycling, using lithium manganese nickel oxide and graphite as cathode and anode respectively.

Examiner: Patrik Johansson
Supervisor: Clément Pechberty
Opponent: Erik Brusewitz