Theoretical study of electron transfer reaction in the anode of Li-Air battery with Cn(mim)22(NTF2) ionic liquid electrolyte: Effect of alkyl chain length

In this research, the electron transfer rate of the anodic reaction of the lithium-air battery was theoretically investigated in the presence of the imidazolium-based dicationic ionic liquids (ILs), Cn(mim)22(NTF2), as an electrolyte. For this purpose, the electron transfer rate constant (ket) of the related reaction was calculated using Marcus' theory. Gibbs free energy of the reaction (ΔG0), reorganization energy (λ), and electron coupling energy (VRP) calculated using the density functional theory (DFT) method. All calculations performed using DFT with GGA/revPBE and B3LYP exchange-correlation functional and 6- 311++G** basis set, using NWchem software. Results show that the ket at the anode depends on the solvent dielectric constant. The longer alkyl chains in the ILs resulted in a decrease in dielectric constant and, consequently, a decrease in ket. Calculated ket values for dicationic ILs ranged from 1.312 to 1.416, which are higher values than those of mono-cationic ILs. The findings of this study are important because the ILs are green solvents with tunable properties.