Li-ion conductivity in PEO-graphene oxide nanocomposite polymer electrolytes: A study on effect of the counter anion

Graphene oxide (GO) has been prepared by modified Hummer's method for their incorporation as nanofiller in designing nanocomposite polymer electrolytes (NCPEs). Prior to use the GO nanofillers has been characterized by TEM, FTIR, and Raman studies to elucidate their nanostructure, functionality, and purity. The various poly(ethylene oxide) (PEO)-based NCPEs has been prepared by incorporating GO nanofillers in presence of three different lithium salts, viz., CF3SO3Li, LiTFSI, and LiNO3 as the source of Li-ions and then casted into free standing polymeric films. The change in PEO crystallinity has been studied considering their full width half maximum values of respective diffraction peaks in the XRD spectra. The Li-ion conductivity of various NCPEs has been studied from impedance spectroscopy. All the NCPE films show optimum value of Li-ion conductivity with 0.3% GO nanofiller content irrespective of the source of Li-ions used. But, variation of the Li-ion conductivity values is occurred for all the three studied lithium salts. Both LiTFSI and LiNO3 salts display Li-ion conductivity in the order of 10(-4) Scm(-1) whereas CF3SO3Li in the order of 10(-6) Scm(-1), all in presence of 0.3% GO nanofillers. The change in conductivity values of the NCPEs has been explained by correlating with Argand plots and also with change in PEO crystallinity, which occurs due to various relaxation processes. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46336.