Simulation and Analysis of Sulfone-Based Localized High-Concentration Electrolyte Systems for Lithium-Ion Batteries

Lithium (Li)-ion batteries (LIBs) are a state-of-the-art energy storage technology and have been found in many aspects of our daily life, including portable electronics, electric vehicles, and power grid storage. The electrolyte of the LIB serves as the media for the transport of Li ions within the cell and the source for the formation of effective solid electrolyte interphase (SEI). This makes the electrolyte crucial for operation of LIBs. Conventional electrolytes are usually dilute organic-based solutions of Li salt (more specifically, LiPF6), which are often incompatible with high-energy-density LIBs and pose safety risks due to their high-flammability. Li metal batteries (LMB), cells with Li metal anode, the optimal electrode, also deplete conventional electrolytes rapidly. Localized high concentration electrolytes (LHCEs) have recently emerged as a promising class of electrolytes for LIBs and LMBs, utilizing the electrochemical stability and safety benefits associated with high concentration electrolytes, but also sustaining improved viscosity and electrode contact. Sulfone-based LHCEs can utilize the benefits of good stability on high-voltage cathodes, high dielectric constant, and low flammability associated with sulfone solvents. They can also solve the issues of high viscosity and poor wettability associated with sulfone-based high concentration electrolytes. Additives can offer increased performance and improve SEI stability. Greater understanding of microscopic interactions within LHCE systems is critical to explaining many of their macroscopic properties. Here, we describe the use of molecular dynamics to investigate the theoretically predicted properties of tetramethylene sulfone based LHCEs with additives, such as solvation structure and dielectric constant, and compare them with experimental measurement. We also present microscopic images and electrochemical cycling data demonstrating their high performance in LIBs. Our investigations will lead to greater fundamental understanding of LHCEs and offer first principle guidelines for developing advanced electrolytes for rechargeable Li batteries.