Polymeric Electrolyte Comprising a NAFION Membrane Plasticized by Dimethyl Sulfoxide and the Transport Specifics of Alkali Metal Ions in It: Quantum-Chemical Simulation

The first theoretical study of alkali-metal ion transport in a polymeric inorganic electrolyte based on a dimethyl sulfoxide-plasticized Nafion membrane is reported. The structure and intermolecular interactions in XNafion · nDMSO (X = Li, Na, K, Rb, and Cs; n = 8 and 12) ionomers are simulated by the DFT method with hybrid density functionals B3LYP, wB97XD, and PBE taking into account periodic boundary conditions and the projector augmented wave (PAW) method in the VASP and GAUSSIAN program packages. According to the calculations, the barriers rise from 0.2 to 0.4 eV in the series Li–K but lower to 0.3–0.2 eV as the radius increases further in the series Rb, Cs. These results are quantitatively consistent with experimental conductivity activation energy data: 0.26 (Li+), 0.37–0.38 (Na+, K+), 0.27 (Rb+), and 0.20 (Cs+) eV. The conclusion is drawn about the structure and conductivity of the electrolyte depending on the nature of the cations.