Analysis of Ion Transport in Glyme-Based Electrolyte Solutions for Li-Air Batteries

Abstract

To clarify the relationship between ion transport behavior and Li deposition/dissolution reaction at Li metal negative electrode (NE) for Li-air batteries, 1.0 M of LiSO3CF3/tetraglyme(G4) and LiN(SO2CF3)2/G4 electrolytes were selected, and the Li+ transport were evaluated from two aspects, i.e. i) Li+ supplying rate to the Li metal NE and ii) charge transfer rate through solid state interphase (SEI) films at Li metal NE. For the former aspect, self-diffusion coefficients D of Li+, anion and G4 solvent together with viscosity η, density ρ, ionic conductivity σ of electrolytes were measured, and the degree of apparent dissociation α app of Li salts was also estimated from the D and σ. On the other hand, the later aspect was examined with Li | Li symmetric cells containing the glyme-based electrolytes. As a result, the LiN(SO2CF3)2/G4 having a higher supplying rate, i.e. σ, owing to its higher α app exhibited an excellent Li deposition/dissolution and Li-air cell performance.