Highly conductive, organic plastic crystals based on pyrazolium imides

In this work we report on a new family of organic plastic crystals based on ringed pyrazolium cations. Three of the reported compounds displayed a single plastic crystalline phase. Temperature dependence of the conductivity was measured in the neat state and at various doping levels with lithium bistrifluoromethanesulfonimide salt (LiTFSI). The conductivity is correlated with the phase transitions as observed by DSC and varies as a binomial function of temperature, within the plastic range. Solid state conductivity values up to 10−3 S cm−1 were observed. Initial battery testing demonstrated that the studied compounds are true Li+ conductors, and promising contenders as new solid state electrolytes for secondary lithium batteries.