Improved conductivity of single-component, ion-condensed smectic liquid crystalline electrolytes

Fast Li+ conductors with enhanced thermal stability are sought for next-generation lithium batteries. Li+ transport within percolated polymeric ionic aggregates has been a novel focus recently due to the possible fast hopping process observed in atomistic and coarse-grained simulations. This fast ion hopping is decoupled from polymer structural relaxations. In this work, we discuss the synthesis and conductivity performance of single-component ionic liquid crystalline (ILC) materials where morphological control via molecular structure variations is more facile than with ionic polymers. A smectic LC phase can be readily achieved with an easily synthesized ILC having a -trifluoromethanesulfonylimide (-TFSI-) head group and an octadecane tail. The smectic ILC with regular ionic aggregate phase has improved (10 to 1000 times) ionic conductivity compared with an isotropic version of a counterpart having decane tail. Through the analysis of the phase behavior and physiochemical properties of ionic liquid molecules having -sulfonylazanide (-SA-) and -sulfonylphenylsulfonylimide (-PSI-) head groups, it is also found that lower electrostatic interaction between ion-pairs and smaller size of anion has a positive influence on conductivity due to faster relaxation of ion pairs.