RESEARCH PAPER Poly ethylene oxide (PEO)–LiI polymer electrolytes embedded with CdO nanoparticles A. Karmakar • A. Ghosh Received: 22 July 2010 / Accepted: 20 December 2010 / Published online: 5 January 2011 Ó Springer Science+Business Media B.V. 2010 Abstract Improvement of electrical conductivity of poly ethylene oxide (PEO)–LiI polymer electrolytes is necessary for their use in solid state lithium ion battery. In this study a new kind of PEO–LiI-based polymer electrolytes embedded with CdO nanoparti- cles with improved electrical conductivity has been prepared and characterized. The electron microscopic studies confirm that CdO nanoparticles of average size 2.5 nm are dispersed in the PEO matrix. The glass transition temperature of the PEO–LiI electro- lyte decreases with the introduction of CdO nano- particle in the polymer matrix. X-ray diffraction, electron microscopic, and differential scanning calo- rimetry studies show that the amorphous phase of PEO increases with the introduction of CdO nano- particle and that the increase in amorphous phase is maximum for 0.10 wt% CdO doping. The electrical conductivity of the sample with 0.10 wt% CdO increases by three orders in magnitude than that of the PEO–LiI electrolyte. The electrical conductivity of PEO–LiI electrolyte embedded with CdO nano- particle exhibits VTF behavior with reciprocal tem- perature indicating a strong coupling between the ionic and the polymer chain segmental motions. Keywords Polymer nanocomposite electrolytes  Structure  Ionic conductivity  Lithium battery  Energy storage Introduction Ion conducting polymer electrolytes have drawn much attention because of their high energy density, good flexibility, mechanical strength, good cyclabil- ity, etc., for use as electrolytes in solid state lithium ion rechargeable batteries (Scrosati et al. 2001; Tarascon and Armand 2001; Dias et al. 2000). Mainly poly ethylene oxide (PEO)–lithium salt-based polymer electrolytes (Croce et al. 1998; Meyer 1998; Xi and Tang 2004; Gadjourova et al. 2001; Stoeva et al. 2003) have been studied extensively and the ionic conductivity is the key parameter of their performance. The dissolution of lithium salt in PEO electrolyte is due to the fact that PEO chains coil around the Li ? ions and thus separates the cations from the counter anions (Dias et al. 2000). It is well established (Mao et al. 2000) that at room temper- ature the nature of PEO is biphasic containing both crystalline and amorphous phases and the transport of Li ? cations in the polymer matrix is related to the local relaxation and segmental motion of PEO chains. These two mechanisms are achieved when the amorphous phase of PEO is dominant. Generally PEO tends to crystallize below its melting tempera- ture (mp 60 °C) and thus shows much higher A. Karmakar  A. Ghosh (&) Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India e-mail: sspag@iacs.res.in 123 J Nanopart Res (2011) 13:2989–2996 DOI 10.1007/s11051-010-0194-x