Nanocomposite polymer electrolytes comprising PVA-graft-PEGME/TiO 2 for Li-ion batteries
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Department of Chemistry, Fatih University, 34500 Büyükçekmece-I_stanbul, Turkey (Received 31 October 2013; accepted 27 January 2014)
The present work investigates inorganic–organic nanocomposite polymer electrolytes (NCPEs) for lithium-ion battery applications. Nanoscale TiO2 particles were dispersed into boron comprising poly(vinyl alcohol) (PVA)-g-poly(ethylene glycol) methyl ether (PEGME) host polymer at several percentages. During preparation, nanocomposite matrices were doped with CF3SO3Li at several compositions and homogeneous soft solid materials were obtained. The interactions between host copolymer and inorganic additive and dopant were studied by Fourier transform infrared spectroscopy. The surface morphology of the NCPEs was investigated by scanning electron microscopy and their thermal properties were studied by thermogravimetric analysis and differential scanning calorimetry. The ionic conductivity of these novel NCPEs was studied by dielectricimpedance spectroscopy. High ambient temperature Li1 ion conducting (;104 S/cm) NCPE matrices can be suggested for lithium battery applications.
I. INTRODUCTION
Energy storage has become more important in this century due to world’s increasing energy demand and energy supply ratio. Lithium polymer batteries are acquiring an important role as energy storage devices in various important markets, in particular, consumer electronics as well as electric or hybrid cars. However, safety issues surrounding these batteries must be addressed before they can be widely utilized, because highly flammable organic solvents pose significant fire hazards under the abuse condition.1,2 Therefore, the research for safer and more reliable electrolyte systems is urgent, and polymer electrolytes (PEs) are promising candidates in this context.3–5 Accordingly, there is an increasing trend in the preparation and characterization of gel PEs that exhibit high ionic conductivity, high energy density, good cyclability, flexible characteristics, and safety.2,6–10 Nanostructured materials are currently of interest for lithium-ion storage devices because of their high surface area, porosity, etc. Ceramic fillers such as SiO2, Al2O3, TiO2, ZrO2, and BaTiO3 have also been incorporated along with the host polymer to obtain composite PEs. They improved the ionic conductivity as well as enhanced the mechanical strength and stability of the materials.11–16 The ceramic fillers promote electrochemical properties, but only by physical action without directly contributing to the lithium-ion transport process. By suitable surface modification of the ceramic particles, they can also act as the source of charge carriers.17–19 It is of great interest to introduce inorganic materials containing dissociative lithium
ions, which are based on core–shell structure with unique advantages in terms of control of the final morphology. Over the years, borate and boronate esters have been studied for different applications.20 Mehta and Fujinami21,22 have produced polymers by the condensation reaction of boron trioxide and
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