  Ionically-conducting plastic crystals are possible candidates for solid-state
electrolytes in energy-storage devices. Interestingly, the admixture of larger
molecules to the most prominent molecular PC electrolyte, succinonitrile, was
shown to drastically enhance its ionic conductivity. Therefore, binary mixtures
seem to be a promising way to tune the conductivity of such solid-state
electrolytes. However, to elucidate the general mechanisms of ionic charge
transport in plastic crystals and the influence of mixing, a much broader data
base is needed. In the present work, we investigate mixtures of two well-known
plastic-crystalline systems, cyclohexanol and cyclooctanol, to which 1 mol% of
Li ions were added. Applying differential scanning calorimetry and dielectric
spectroscopy, we present a thorough investigation of the phase behavior and the
ionic and dipolar dynamics of this system. All mixtures reveal
plastic-crystalline phases with corresponding orientational glass-transitions.
Moreover, their conductivity seems to be dominated by the "revolving-door"
mechanism, implying a close coupling between the ionic translational and the
molecular reorientational dynamics of the surrounding plastic-crystalline
matrix. In contrast to succinonitrile-based mixtures, there is no strong
variation of this coupling with the mixing ratio.
