Eco-Friendly Tetrahydropyran Enables Weakly Solvating "4S" Electrolytes for Lithium-Metal Batteries

The growth of lithium dendrites hinders the commercial applications of lithium-metal batteries. Electrolytes play a crucial role in influencing electrode/electrolyte interfacial chemistry. Traditional electrolytes adopt strongly solvating solvents to dissolve Li salts, creating an organic-rich solid electrolyte interface (SEI). The Li+ conductivity and mechanical strength of the organic-rich SEI are poor, so the derived SEI cannot effectively suppress the growth of Li dendrites. The weakly solvating electrolyte (WSE) system can realize an inorganic-rich SEI, demonstrating improved compatibility with the Li metal. However, the design rules for the WSE are not clear. Here, four kinds of "4S" (single salt and single solvent) WSE are designed to investigate interface chemistry. The SEI thickness, pore volume, and porosity are revealed via a reactive force field. The results show the heterocyclic and symmetric tetrahydropyran has the most suitable solvating power and the best interfacial stability in the lithium-metal battery system. This research provides a weakly solvating electrolyte design route for bridging the molecular thermodynamic and interfacial chemistry gap.