LiI-doped N,N-Dimethyl-Pyrrolidinium iodide, an archetypal rotator-phase ionic conductor

N,N-Dimethyl-pyrrolidinium iodide, and the effect of doping with LiI, has been investigated using DSC, NMR, and impedance spectroscopy. It was found that the addition of a small amount of LiI enhances the ionic conductivity by up to 3 orders of magnitude for this ionic solid. Furthermore, a slight decrease in phase transition onset temperatures, as well as the appearance of a superimposed narrow line in the ¹H NMR spectra with dopant, suggest that the LiI facilitates the mobility of the matrix material, possibly by the introduction of vacancies within the lattice. ⁷Li NMR line width measurements reveal a narrow Li line width, decreasing in width and increasing in intensity with temperature, indicating mobile Li ions.