Study of a new polymer electrolyte poly(ethylene oxide): NaClO 3 with several plasticizers for battery application R Chandrasekaran and S Selladurai * Solid State Ionics Laboratory, Department of Physics, MIT campus, Anna University, Chromepet, Chennai-600 044, Tamil Nadu State, India Abstract: Sodium ion conducting thin ®lm polymer electrolytes based on poly(ethylene oxide) (PEO) complexed with NaClO 3 were prepared by a solution-casting method. Characterization by XRD, IR spectroscopy and AC conductivity has been carried out on these thin ®lm electrolytes to analyse their properties. The conductivity studies show that the conductivity value of PEO:NaClO 3 complex increases with the increase in salt concentrations. Increase in conductivity was found in the electrolyte system by the addition of low molecular weight polymer poly(ethylene glycol) (PEG) and the organic solvents dimethylformamide (DMF) and propylene carbonate (PC). Using these electrolyte systems, cell parameters were measured from the discharge study with the application of load 100 kV at room temperature with common cell con®guration NajelectrolytejC:I 2 :electrolyte. The open circuit voltage (OCV) ranges from 2.81 to 3.23 V and the short circuit current (SCC) ranges from 340 to 1180 mA. # 2001 Society of Chemical Industry Keywords: polymer electrolyte; PEO; PEG; conductivity INTRODUCTION Interest in solid polymeric electrolytes has increased the number of ion-conducting materials because of their possible applications (such as thin-®lm forma- tion, interfacial contacts and desirable sizes) as solid electrolytes in advanced high-energy electrochemical devices, eg batteries, fuel cells, electrochemical devices and photo-electrochemical solar cells poly(ethylene oxide) (PEO) in particular is an exceptional polymer which dissolves a wide variety of salts to form polymeric electrolytes; the chemical stability of the ether functional group strengthens the superiority of PEO as a host for a solid polymer electrolyte. 1±7 Temperature-dependent conductivity studies, surface analysis, glass transition temperature, structural changes, and cell studies of many sodium-ion-con- ducting polymer electrolytes based on PEO poly(pro- pylene oxide) (PPO) and poly(bis-methoxyethoxy- ethoxy phosphazene) (MEEP) complexed with, NaClO 4 , NaSCN, NaCF 3 SO 3 , NaPF 6 , NaI, NaYF 4 and NaNO 3 have been reported earlier. 8±15 To obtain moderate properties of polymer electrolytes (such as increase in conductivity, a wide redox stability, low melting point, change in amorphous phases, increase in ionic mobility, decrease in viscosity, high ability to dissolve salts), a new trend is the addition of plasticizers to the corresponding host polymers. Most plasticizers are low molecular weight organic solvents (eg propylene carbonate (PC), diethyl carbonate (DEC), ethylene carbonate (EC) and dimethyl carbo- nate (DMC)), studies on which have been reported earlier. 16±21 Enhanced conductivity was also obtained by using low molecular weight poly(ethylene glycol) (PEG). 22 Keeping this in view, the authors report here the effect of plasticizers on polymer conductivity and on cell performance by using polymer electrolytes based on PEO and NaClO 3 salt with the addition of the plasticizers PEG, PC and DMF. XRD and IR spectral analysis were used to characterize the resulting polymer electrolytes. EXPERIMENTAL The starting materials PEO (Aldrich, Mw=5  10 6 g mol 1 ), PEG (Aldrich, Mw = 4000 g mol 1 ) and NaClO 3 were dried well. Polymer thin ®lms of approximate thickness (100±140 mm) have been pre- pared by a solution-cast technique. 23 Thin PEO:Na- ClO 3 ®lms were prepared in the following molar ratios 90:10, 80:20 and 70:30 by a solution-cast technique using water-free methanol as solvent. To improve the conductivity of polymer electrolytes, PEG was intro- duced into the PEO:NaClO 3 matrix. Thin ®lms of PEG:PEO:NaClO 3 30:60:10, 45:45:10 and 60:30:10 were prepared using the solution-cast technique. 24 The prepared plasticized polymer electrolyte reduced (Received 1 February 2000; revised version received 7 June 2000; accepted 30 June 2000) * Correspondence to: S Selladurai, Solid State Ionics Laboratory, Department of Physics, MIT Campus, Anna University, Chrompet, Chennai- 600 044, Tamil Nadu State, India E-mail: sselladurai@mitindia.edu; ssdurai@yahoo.com # 2001 Society of Chemical Industry. Polym Int 0959±8103/2001/$30.00 89 Polymer International Polym Int 50:89±94 (2001)