| Summary: | Ionic liquid (IL) based gel polymer electrolytes (GPEs) are
being investigated extensively at present as substitutes for conventional
GPEs based on a polymer, a salt and solvents. The main reason behind
this is the drawbacks in usage of solvents. IL based GPEs have been
employed for energy storage devices such as batteries and super
capacitors due to their interesting mechanical, physical and
electrochemical properties. This study focused on synthesis preparation
and characterization of an IL based GPE consisting of poly(vinylidene
fluoride-co-hexafluoropropylene) (PVdF-co-HFP), zinc trifluoro metha
-nesulfonate (Zn(CF3SO3)2 - ZnTF) and 1-ethyl-3-methylimidazolium
trifluoromethanesulfonate (1E3MITF). Thin film samples were prepared
using solvent casting method. The optimized composition was found to
be 1 PVdF-co-HFP: 1 1E3MITF: 3 ZnTF (by weight basis). This
mechanically stable, thin film has the maximum room temperature
conductivity of 7.42×10-3 S cm-1. Conductivity variation with
temperature follows Vogel - Tamman - Fulcher (VTF) behavior
confirming the relation of conductivity mechanism with the free volume
theory. The IL based GPE is a purely an ionic conductor having a
considerable anionic contribution. It shows stability up to 2.5 V which
is very much convenient from a practical point of view. Oxidation and
reduction of Zn takes place at the potentials of 0.5 V and –0.5 V,
respectively. In addition, Zn platting and stripping occurs only on the
Zn electrodes but not on the stainless steel (SS) electrodes. Impedance
measurements taken for the GPE continuously for a long period of time
exhibited a satisfactory stability with Zn electrodes.
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