2024 AIChE Annual Meeting
(569ak) Density Functional Study for Deep Eutectic Solvent Based Solid Polymer Electrolyte
Solid polymer electrolytes (SPEs) consist of polymers and lithium salts without any solvent, enhancing the efficiency of batteries due to their safety and low internal resistance. Although SPEs exhibit segmental motion allowing for lithium ion transport through electrostatic interactions between the negatively charged segments of the polymer and Li+ cations, their ionic conductivity is limited. Unlike conventional liquid electrolytes, ion conduction in SPEs occurs via a hopping mechanism based on electrostatic interactions between polymer segments, rather than migration. Consequently, the mobility of ions and thus the ionic conductivity are reduced. In this study, we aim to investigate a novel mechanism of ion conduction by synthesizing a polymer electrolyte based on a Deep Eutectic Solvent (DES). DES forms a bicontinuous structure composed of nano-domains and elastomers. Within DES domains, ion conduction occurs via migration, while between domains, the hopping mechanism is prevalent. The DES is formed by mixing Dimethyl Sulfone (DMS) and LiFSi. In this process, the sulfur (S) in DMS interacts with the fluorine (F) in FSi, while the oxygen (O) in DMS is expected to interact with Li+ cations. These interactions lead to a transition into the liquid state. To elucidate the interactions between ions and the hopping mechanism through which ions conduct, the system analyzed using Molecular Dynamics (MD) and Density Functional Theory (DFT). By calculating Radial Distribution Functions (RDFs), diffusion rates, interaction energies, and energy surface diagrams, to elucidate the ion conduction mechanism and the behavior of individual molecules in each system, the aim is to unveil the structure and behavior of molecules involved in ion conduction upon DES formation.