Characterization of non-aqueous electrolytes
Title: Characterization of non-aqueous electrolytes
SNIC Project: SNIC 2020/13-1
Project Type: SNIC Small Compute
Principal Investigator: Simon Colbin <simon.colbin@kemi.uu.se>
Affiliation: Uppsala universitet
Duration: 2020-01-21 – 2021-02-01
Classification: 10403
Keywords:

Abstract

The seemingly ever-increasing demand for lithium ion batteries has sparked an interest to find alternatives to the lithium-based technology, which apart from lithium also makes use of other non-abundant or expensive elements such as cobalt and nickel. In response to this, research on Sodium ion-batteries has emerged and intensified in recent years. While a fair amount of knowledge has been obtained about the electrode materials for sodium ion batteries, the knowledge about the electrolytes used in these systems are still to a large extent lacking. The aim of this project is to use DFT calculations as a complement to experimental characterization of different electrolyte systems. The focus will be on electrochemical stability, possible decomposition products from reduction and oxidation of electrolytes with different compositions, and the coordination of different solvent molecules to ions in non-aqueous electrolytes. The simulation of electrochemical stability will serv to complement and help interpret results from cyclic voltammetry and galvanostatic measurement. It is common in the literature to estimate the relative electrochemical stability of the electrolyte constituents by evaluating the HOMO and LUMO levels. However, it has been shown that this is an inaccurate method for evaluating the electrochemical stability. In this project, the Gibbs free energy of solvation will instead be used to evaluate the electrochemical stability of each constituent in different electrolytes. The resulting oxidation and reduction potentials will be compared with experimental data to evaluate the accuracy and transferability of this method. In relation to the electrochemical stability, possible fragmentations of the constituent particles upon reduction and oxidation will be investigated. This will aid the understanding of the solid electrolyte interface which is formed from electrolyte decomposition during cycling of the battery. Vibrational spectra will be simulated for ion-solvent model systems where the results will be compared with data from IR and Raman spectroscopy measurements, where both approaches are needed to evaluate how different solvent molecules coordinate to specific ions.