Probing the Origin of Viscosity of Liquid Electrolytes for Lithium Batteries.

Viscosity is an extremely important property for ion transport and wettability of electrolytes. Easy access to viscosity values and a deep understanding of this property remain challenging yet critical to evaluating the electrolyte performance and tailoring electrolyte recipes with targeted properties. We proposed a screened overlapping method to efficiently compute the viscosity of lithium battery electrolytes by molecular dynamics simulations. The origin of electrolyte viscosity was further comprehensively probed. The viscosity of solvents exhibits a positive correlation with the binding energy between molecules, indicating viscosity is directly correlated to intermolecular interactions. Salts in electrolytes enlarge the viscosity significantly with increasing concentrations while diluents serve as the viscosity reducer, which is attributed to the varied binding strength from cation-anion and cation-solvent associations. This work develops an accurate and efficient method for computing the electrolyte viscosity and affords deep insight into viscosity at the molecular level, which exhibits the huge potential to accelerate advanced electrolyte design for next-generation rechargeable batteries.

The Crucial Role of Electrode Potential of a Working Anode in Dictating the Structural Evolution of Solid Electrolyte Interphase.

The performance of rechargeable lithium (Li) batteries is highly correlated with the structure of solid electrolyte interphase (SEI). The properties of a working anode are vital factors in determining the structure of SEI; however, the correspondingly poor understanding hinders the rational regulation of SEI. Herein, the electrode potential and anode material, two critical properties of an anode, in dictating the structural evolution of SEI were investigated theoretically and experimentally. The anode potential is identified as a crucial role in dictating the SEI structure. The anode potential determines the reduction products in the electrolyte, ultimately giving rise to the mosaic and bilayer SEI structure at high and low potential, respectively. In contrast, the anode material does not cause a significant change in the SEI structure. This work discloses the crucial role of electrode potential in dictating SEI structure and provides rational guidance to regulate SEI structure.