The effect of lithium salt concentration in an aprotic solvent on the oxygen reaction

Abstract Characteristics of LiClO4/TTG and LiClO4/DMF electrolytes at different salt concentrations have been experimentally determined by conductometry, 7Li, 1H, 13C NMR. It has been demonstrated that the influence of these parameters on the oxygen reaction is due to solvation and electrical conductivity, which, determine the transport characteristics of the reaction participants. In DMF the formation of Li2O2 proceeds predominantly through the solution bulk. In TTG the reaction proceeds predominantly on the electrode surface and does not depend on LiClO4 concentration, which is likely due to the formation of Li2O2 on the electrode surface without passing into the solution bulk with a weak concentration dependence of LiClO4 dissociation in TTG. It cannot be ruled out that the LiClO4 concentration in TTG has an effect on the oxygen reduction mechanism at higher concentrations (> 2 M) because of the complex formation. At any LiClO4 concentration in TTG, the amount of electricity in the cathodic process is lower and the reaction reversibility is higher than in DMF solutions. The key factor responsible for the change in the characteristics of the oxygen reaction in TTG is the decrease in the electrical conductivity and diffusion coefficients of O2 and Li+ with increasing concentration, due to the viscosity of the solution and low dielectric constant.