(324c) Solid State Electrolytes for Energy-Dense Lithium Metal Batteries

Lithium metal batteries promise high energy densities. However, lithium metal deposits nonuniformly and forms high surface area dendrites that react continuously with the electrolyte. Solid state electrolytes have been developed with ionic conductivities that rival liquids and have been proposed as one solution to mechanically suppress dendrite growth. Inorganic solid state electrolytes have the highest ionic conductivities, but are brittle and have poor ionic contact with the electrodes. In contrast, polymer electrolytes have flexible mechanical properties, but have poor ionic conductivities. We hypothesize that hybrid polymer-inorganic electrolytes can combine the conductivity of sulfides with the tunable mechanical properties of polymers. Firstly, we develop design rules for polymer selection and understand the influence of polymer type on lithium ion transport in the hybrid electrolyte and eventual effect on lithium metal cycling. Secondly, we synthesize novel fluoroether oligomers to understand the effect of building block connectivity (ethers and fluorinated moieties), molecular structure and ion solvation on oligomer ion conductivity and oxidative stability. Insights gained from our work will enable solid state lithium metal batteries with high energy densities.