Doctor of Philosophy (PhD)
In this dissertation, the structure and dynamics of battery electrolytes were investigated using atomistic molecular dynamics (MD) simulations. Battery electrolytes play a key role in transporting ions between the cathode and anode. The chemical stability and ionic conductivity of electrolytes influence battery performance. In order to design better electrolytes, one needs an understanding of the relationship between electrolyte structure, dynamics, and bulk properties. To bridge the gap between the macroscopic phenomenon and the hidden molecular physics, in the first project we focused on probing an ether-based electrolyte, chosen for its relevance in sodium-based batteries. Through studying the impact of concentration and glyme chain length in tandem with chelation, we were able to provide insights to develop guidelines for the design of better batteries. Examining the ion transport mechanism behind different glyme systems, we found a non-vehicular triflate hopping mechanism, which is attributed to the high conductivity at high concentration for the diglyme system. In the remaining two projects, we focused on polymer electrolytes and used MD simulations to complement and interpret experimental results. We studied how macromolecular architectures affect the polymer electrolytes' bulk properties from a molecular point of view. Block copolymer electrolytes (BCEs) have better ionic conductivity when compared to their random copolymer electrolytes (RCEs) counterpart and this is caused by the percolated water, which leads to faster ion migration, inside BCEs. Finally, nano-confined polymer electrolyte brushes exhibited excellent ionic conductivity that can be attributed to the low counterion condensation and faster ion transportation caused by a large concentration of water in the charged domains. The manner in which water molecules affect the counterion condensation and ion transport dynamics are also discussed in this dissertation.
Li, Ke, "Computational Investigations of Battery Electrolytes" (2020). LSU Doctoral Dissertations. 5406.