Effect of TiO2 nano-filler on ionic conductivity of poly (ethylene oxide) based gel polymer electrolyte for magnesium ion batteries
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Date
2015
Journal Title
Journal ISSN
Volume Title
Publisher
Uva Wellassa University of Sri Lanka
Abstract
Gel polymer electrolytes (GPEs) have been identified as novel materials for magnesium ion
rechargeable batteries. Among different polymers, poly(ethylene oxide) (PEO) based systems
are the most studied candidates due to their solvation power, complexion ability, and proper
(Dissanayake et al.,
2012). However, ionic conductivity of PEO based polymer electrolytes at ambient temperature is
not high enough for most practical applications. In order to improve the ionic conductivity, the
addition of nano sized oxide fillers into the PEO-salt matrix have been regarded as the most
promising method (Agrawal et al., 2013). We here present the synthesis and characterization of PEO based Mg
ion conducting GPE by incorporating titanium dioxide nano filler (TiO 2).
Methodology
PEO (Mw~1×10 ), magnesium triflate (MgTf) (purity˃97%), ethylene carbonate (EC) (purity
˃99%), propylene carbonate (PC) (purity ˃99%) were purchased from sigma Aldrich and used
as starting materials along with titanium dioxide (TiO2) nano-filler. Prior to use, polymer, salt
and TiO2 were vacuum dried using appropriate temperatures. Nano composite polymer
electrolytes were prepared by adding different amounts of TiO2 (2,5,7.5,10,15 wt.%) in the
PEO:MgTf :EC/PC (1:1) mixture with weights of 0.20 g, 0.12 g, 0.30 g and 0.30 g respectivel y.
The mixtures were heated to 80 C and magnetically stirred for 12 hours without heating until a
homogenous gel was formed. The cathode film was prepared using vanadium pentoxide (V 2O5),
carbon black and polyvinylidene fluoride (PVdF) with the weight percentages of 76%, 14% and
10% respectively with the solvent of 1-methyl -1, 2-dipyrrolidine using doctor blade method.
The prepared electrolytes were characterized in order to obtain their ionic conductivity using
complex impedance spectroscopy whereas electrochemical tests were performed using the cells,
Mg/electrolyte/V2O5:C. DC polarization tests were done using both blocking (stainless steel) and
non-blocking (Mg) electrodes. Microscopic images of the electrolytes were taken using the
polarization microscope to investigate the change of crystallinity with the addition of nano-filler.
Figure 01(a) shows the temperature dependence of ionic conductivity for the GPEs,
PEO:MgTf:EC/PC (1:1), incorporating different wt. % of nano-sized TiO2 filler. Among studied
systems, highest ionic conductivity is observed for the GPE with 5 wt. % filler content. Figure
01(b) shows the variation of conductivity with different wt. % TiO2 at various temperatures
(conductivity isotherms) for the PEO:MgTf:EC /PC (1:1) GPEs. This plot also shows that the 5
wt.% filler containing electrolyte has the highest ionic conductivity in the studied temperature
range. A possible explanation to this effect could be the availability of extra hopping sites for
migrating ionic species due to formation of Lewis acid-base type interactions of ionic species with
O/OH surface groups on TiO2 nano filler (Pitawala et al., 2008).
Description
Keywords
Science and Technology, Technology, Polymer Science, Rubber Production, Rubber Technology