Structure and Dynamics in Liquid Battery Electrolytes
The introduction of Sony’s rechargeable lithium-ion battery in 1991 sparked a transformation of our everyday life, enabling wide-spread use of portable electronics, such as smartphones and laptops. Furthermore, in recent years the increased usage of electrical vehicles and the on-going change to transient renewable energy sources has created a large interest in cheaper, safer, more sustainable, long-lasting and energy denser batteries. Next generation batteries – batteries beyond the traditional lithium-ion battery chemistries – offers possible routes towards the for-mentioned sought performance, societal and economical improvements. In this thesis several next generation battery concepts are studied. In particular, i) the sodium-ion battery, offering similar energy densities to that of the modern-day lithium-ion battery, but showing better power performance, is cheaper, more sustainable and safer, and ii) highly concentrated electrolytes, enabling higher energy densities, improved safety features, and improved cycling stability, are studied.
Several of the improvements in safety and performance seen in these next generation battery technologies stem from the local environment in the electrolyte. In this work I present a comprehensive study of the local cationic environment in several next generation battery electrolytes employing computational methods such as semi-empirical methods, density functional theory, and ab initio molecular dynamics. Furthermore, novel methods for studying the dynamics of the solvation shell are presented. The results of these studies are compared to what I and others have found in conventional lithium-ion battery electrolytes, and the connection between the local electrolyte structure and dynamics and the macroscopic electrolyte and battery properties is discussed.