Designing solvate ionogel electrolytes with very high room-temperature conductivity and lithium transference number

Abstract

Free-standing electrolytes based on Li(G4)TFSI and chemically-crosslinked poly(ethylene glycol), as well as functional co-monomers and/or small amounts of volatile diluent, are demonstrated to reach very high room-temperature ionic conductivities (>2 × 10⁻³ S cm⁻¹) and electrochemically-measured lithium transference numbers (>0.5). An unexpected dependence of properties on polymer length/crosslinking is observed and explained in terms of competing Li⁺ transport processes. These electrolytes enable lithium symmetric cells to cycle >600 h at low overpotential and without dendrite growth. Future optimization routes are also discussed.