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. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.