Influence of anion structure on thermal,mechanical, dielectric and electrochemical properties of ZrO2 nanoparticle-pyrrolidinium ionic liquid hybrid electrolytes for the application in energy storage devices

Influence of the two different anion structures viz. bis(fluorosulfonyl)imide (FSI^?) and bis(trifluoromethanesulfonyl) imide (TFSI^?), on the thermophysical, dielectric and electrochemical properties of ZrO₂-nanoparticle tethered pyrrolidinium based nanoscale hybrid ionic fluids (NHIFs) was investigated. Thermal and mechanical properties of NHIFs were found to depend strongly upon the structure of anions and TFSI^? comprising NHIF showed better thermal and mechanical stability then its FSI^? analogue. Temperature dependent electrical conductivity, dielectric and electrochemical properties of different NHIFs were studied. FSI-NHIF displayed higher ionic conductivity, associated with faster structural relaxation dynamics. At all the measured temperature, FSI-NHIF displayed superior electrochemical cycling performance than its TFSI-equivalent. While, electrochemical cell with TFSI-NHIF showed 81% capacitance retentivity after 5000 charge/discharge cycles, FSI-NHIF cell was found to retain >90% of its initial specific capacitance value after the same. Results obtained from the study optimize the applicability of pyrrolidinium based hybrid ionic fluids as electrolytes in secondary energy storage devices.