  Ionic liquids (ILs) are salts that are liquid close to room temperature.
Their possible applications are numerous, e.g., as solvents for green chemistry
in various electrochemical devices, and even for such "exotic" purposes as
spinning-liquid mirrors for lunar telescopes. Here we concentrate on their use
for new advancements in energy-storage and -conversion devices: Batteries,
supercapacitors or fuel cells using ILs as electrolytes could be important
building blocks for the sustainable energy supply of tomorrow. Interestingly,
ILs show glassy freezing and the universal, but until now only poorly
understood dynamic properties of glassy matter, dominate many of their physical
properties. We show that the conductivity of ILs, an essential figure of merit
for any electrochemical application, depends in a systematic way not only on
their glass temperature but also on the so-called fragility, characterizing the
non-canonical super-Arrhenius temperature dependence of their ionic mobility.
