Modelling of Battery Electrolyte Interactions

Licentiate thesis, 2018

The rechargeable lithium-ion battery (LIB), powering our portable electronics, has transformed our everyday lives. Even though the success of the LIB there is a need for next generation batteries, due to a lack of abundant lithium and a need for greater performance and sustainable chemistries, in order to move towards a sustainable society with applications such as hybrid and electrical vehicles (EVs) and large scale energy storage for solar and wind power. Therefore, there is a large interest in various next generation batteries, such as sodium-ion, Li-S, and Li-air batteries.

In this thesis the structure of Li+ and Na+ solvation shells, as functions of salt concentrations, is studied using a semi-empirical method. Overall, this shows that: i) The first solvation shell of the Na-ion is larger and more disordered than the Li-ion first solvation shell, ii) The coordination number (CN) remain quite constant as a function of concentration, while the disorder, as measured by the variance of the CN, increases with concentration, and iii) The choice of solvent influences the disorder. Moreover, the interaction of O2 with several anions is computed, showing a correlation between the interaction energy and the O2 solubility, with application to Li-air batteries. Finally, a novel approach employing ab initio molecular dynamics to study solvation shell dynamics is presented.