The solid-electrolyte interphase (SEI) is one of the most important components of a Li-ion battery. The SEI forms from the breakdown of the electrolyte and anode during early cycling and serves as a passivating layer, leading to a longer battery lifespan. While many different compounds can form on the SEI, selective electrolyte choice can be used to control their formation. The use of fluorinated solvents allows for the formation of LiF, which allows for fast ion transport and suppresses non-beneficial reactions. The Bedrov group has conducted research on a newly proposed fluorinated solvent, 3,3,3-trifluoropropylmethyldimethoxysilane (TFPMDS). This solvent was compared to an traditional electrolyte cosolvent system using ethylene carbonate (EC) and ethyl methyl carbonate (EMC). Both solvents were studied with LiFSI molarity varying between 1 and 3 M. Molecular dynamics simulations of the systems found differing lithium-ion transport mechanisms. In the EC-EMC systems solubility of the LiFSI salt was high, leading to Li+ ions to be move highly independent of the FSI- molecules; this behavior was consistent over all concentrations. The TFPMDS systems, on the other hand, underwent a structural change as the concentration increased. At 1 M the LiFSI salt clustered together, stifling Li+ transport. However, as the concentration increased to 3 M the FSI- molecules began to form percolating 'bridges', creating new pathways for Li+ transport. Due to this, the conductivity of the two electrolyte systems had opposing trends. While the EC-EMC systems decreased in conductivity, from 7.59 mS/cm at 1 M to 4.22 M at 3 M, the TFPMDS systems increased in conductivity, from 0.103 mS/cm at 1 M to 0.230 mS/ cm at 3 M. These results matched well with experimental data from collaborators at South China Normal University. The understanding gained from this study will allow for further design of new fluorinated solvents utilizing this new transport method.
University / Institution: University of Utah
Format: In Person
SESSION D (3:30-5:00PM)
Area of Research: Science & Technology
Faculty Mentor: Dmitry Bedrov