Improvements in ion transport property of polyethylene-oxide- (PEO-) based polymer electrolytes have been investigated, using different types of plasticizers. The effects of single and coupled plasticizers [i.e., EC, (EC + PC), and (EC + PEG)] on structural and electrical behavior of pristine electrolyte were studied by XRD, SEM technique, and impedance spectroscopy. The electrical conductivity of the best plasticized system was found to be 4？×？10？6？S/cm. Argand plots show dispersive nature of relaxation time or inhomogeneous space charge polarization of plasticized polymer electrolyte. 1. Introduction Recently, plasticized polymer electrolytes have been extensively used in the electrochemical devices, like secondary batteries, fuel cells, sensors, and smart windows. In order to improve their electrical and electrochemical properties for technical and industrial application, structural modification through plasticized polymer electrolytes is extensively used. Various techniques (like plasticization, copolymerization, etc.) have been adopted to achieve the desired objective of high ionic conduction and better stability of polymer composite electrolytes [1–3]. Large number of host polymer [e.g., polyethylene oxide (PEO), polymethylene methacrylate (PMMA), polypropylene oxide (PPO), polyvinyl alcohol (PVA), polyvinyl formal (PVF), etc.] [4–6] with different alkali and alkaline salts have been investigated in the past four decades. Among these polymers, PEO is the most studied polymeric system. The electrical conductivity of PEO is found relatively low at ambient temperature in comparison to the existing conventional liquid/hybrid electrolytes. The ionic conductivity of polymer electrolyte mainly depends upon (i) crystallinity of the material (ii) simultaneous cation and anion motion, and (iii) the ion-pair formation (anion complex-cation interaction). To overcome these problems, various approaches have been made to modify the structure of polymer electrolyte in the last three decades. Ammonium adipate (NH4)2C4H8(COO)2 contains smaller size cation (H+) with larger size anion which can easily dissociate and provide higher protonic conduction [7]. The addition of plasticizers in polymer electrolyte is one of the most effective approaches to improve the mobility of ionic or/and the interfacial interaction among ionic and polar groups in polymer chains. The choice of plasticizer and its concentration can affect film permeability and mechanical properties [8, 9]. The other advantage of plasticization is to modify the polymeric matrix and provide the enhanced
References
[1]
F. M. Gray, Solid Polymer Electrolyte Fundamental and Application, New York, NY, USA, 1991.
[2]
A. Chandra, P. C. Srivastava, and S. Chandra, “Ion transport studies in PEO:NH4I polymer electrolytes with dispersed Al2O3,” Journal of Materials Science, vol. 30, no. 14, pp. 3633–3638, 1995.
[3]
K. Pandey, M. M. Dwivedi, Asthana, Nidhi, M. Singh, and S. L. Agrawal, “Structural and ion transport studies in (100-x) PVdF + xNH4SCN Gel electrolyte,” Materials Sciences & Applications, vol. 2, no. 7, pp. 721–728, 2011.
[4]
P. K. Khare, P. L. Jain, and R. K. Pandey, “Charging transient in polyvinyl formal,” Bulletin of Materials Science, vol. 24, no. 4, pp. 401–406, 2001.
[5]
M. Kono, E. Hayashi, and M. Klantanabey, “Network polymer electrolytes with free chain ends as internal plasticizer,” Journal of The Electrochemical Society, vol. 145, no. 5, pp. 1521–1527, 1998.
[6]
Y. Kang, H. J. Kim, E. Kim, B. Oh, and J. H. Cho, “Photocured PEO-based solid polymer electrolyte and its application to lithium-polymer batteries,” Journal of Power Sources, vol. 92, no. 1-2, pp. 255–259, 2001.
[7]
M. A. S. Azizi Samir, A. M. Mateos, F. Alloin, J.-Y. Sanchez, and A. Dufresne, “Plasticized nanocomposite polymer electrolytes based on poly(oxyethylene) and cellulose whiskers,” Electrochimica Acta, vol. 49, no. 26, pp. 4667–4677, 2004.
[8]
M. H. Sheldon, M. D. Glasse, R. J. Latham, and R. G. Linford, “The effect of plasticiser on zinc polymer electrolytes,” Solid State Ionics, vol. 34, no. 1-2, pp. 135–138, 1989.
[9]
A. Roy, A. Ghosh, S. Datta et al., “Effects of plasticizers and surfactants on the film forming properties of hydroxypropyl methylcellulose for the coating of diclofenac sodium tablets,” Saudi Pharmaceutical Journal, vol. 17, no. 3, pp. 233–241, 2009.
[10]
A. Bhide and K. Hariharan, “Ionic transport studies on (PEO)6:NaPO3 polymer electrolyte plasticized with PEG400,” European Polymer Journal, vol. 43, no. 10, pp. 4253–4270, 2007.
[11]
M. Egashira, H. Todo, N. Yoshimoto, and M. Morita, “Lithium ion conduction in ionic liquid-based gel polymer electrolyte,” Journal of Power Sources, vol. 178, no. 2, pp. 729–735, 2008.
[12]
C. A. Entwistle and R. C. Rowe, “Plasticization of cellulose ethers used in the film coating of tablets,” Journal of Pharmacy and Pharmacology, vol. 31, pp. 269–272, 1979.
[13]
J. K. Sears and J. R. Darby, “Mechanism of plasticizer action,” in The Technology of Plasticizers, J. K. Sears and J. R. Darby, Eds., pp. 35–77, Wiley-Interscience, New York, NY, USA, 1982.
[14]
W. Barenswaard, V. M. Litvinov, F. Socrren, R. L. Scherreenberg, C. Gondard, and C. Colemonts, “Crystallinity and microstructure of plasticized poly(vinyl chloride). A 13C and 1H solid state NMR study,” Macromolecules, vol. 32, no. 1, pp. 167–180, 1999.
[15]
K. Pandey, M. M. Dwivedi, M. Tripathi, M. Singh, and S. L. Agrawal, “Structural, thermal and ion transport studies on nanocomposite polymer electrolyte-{(PEO + SiO2):NH4SCN} system,” Ionics, vol. 14, no. 6, pp. 515–523, 2008.
[16]
H.-M. Lai and G. W. Padua, “Properties and microstructure of plasticized zein films,” Cereal Chemistry, vol. 74, no. 6, pp. 771–775, 1997.
[17]
N. Baskaran, “Conductivity relaxation and ion transport processes in glassy electrolytes,” Journal of Applied Physics, vol. 92, no. 2, p. 825, 2002.
[18]
M. J. Rice and W. L. Roth, “Ionic transport in Superionic conductors: a theoretical model,” Journal of Solid State Chemistry, vol. 4, no. 2, pp. 294–310, 1972.
[19]
D. L. Sidebottom, “Universal approach for scaling the a.c. conductivity in ionic glasses,” Physical Review Letters, vol. 82, no. 18, pp. 3653–3656, 1999.
