Effects of addition of BMIMCF₃SO₃ ionic liquid on electrical, thermal and structural properties of PVC-LiCF₃S0₃-BMIMCF₃S0₃ polymer electrolyte / Nik Aisyah Suraya Nik Zulkepeli

In this study, poly(vinyl) chloride (PVC) is used as polymer host, lithium triflate (LiCFsSOa) as doping salt, and l-butyl-3-methylimidazolium trifluoromethasulfonate (BMIMCF3SO3), an ionic liquid is used as plasticiser for preparation of plasticised polymer electrolyte PVC-LiCF3S03-BMIMCF3S03. The polymer electrolytes were prepared by using solution cast technique. Characterisation techniques of EIS, XRD, DSC, FTIR, and TNM were used to study the properties of the PVC-based electrolyte. Conductivity for pure PVC at room temperature is found to be 5.23 x 10"10 Scm"1 . A system composed of PVC with just ionic liquid which served as a control, recorded conductivity of 1.50 x 10'9 Scm"1 .The conductivity of PVC rose to 1.07 x 10"8 Scm"1 upon addition of LiCF3S03, which is an increase of about two orders of magnitude. Further increase of ionic conductivity is obtained when ionic liquid is added to the salted system. The highest conductivity achieved is 1.12 x 10"7 Scm"1 for 3 wt.% of ionic liquid. The increment of conductivity is attributed to increase in number of mobile ions as evidenced by deconvolution of FTIR and decrease in crystallinity of the films as evidenced by XRD, while DSC indicates that the system is more flexible due to the plasticising effect of ionic liquid. Temperature dependence of conductivity study showed that the system PVC-LiCF3S03-BMIMCF3S03 increased in conductivity up to its Tg value after which it decreased. This is attributed to the presence of ionic liquid which implies that motion of polymer segments are limited where ions are triggered by hopping mechanism at temperatures below Tg and at temperatures above Tg, cations were reduced to particles. Transference number of this system is found to be -0.92.