Plastic separators with improved properties for portable power device applications
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ORIGINAL PAPER
Plastic separators with improved properties for portable power device applications A. L. Sharma & Awalendra K. Thakur
Received: 11 March 2012 / Revised: 8 June 2012 / Accepted: 8 June 2012 / Published online: 19 September 2012 # Springer-Verlag 2012
Abstract We report a novel clay-intercalated polymer nanocomposites (PNC) having very high ionic conductivity (~10−3 S cm−1) and improved stability properties. The suitability of the PNC films for subsequent use as a separator component in energy storage devices has been explored in terms of desirable voltage (~4.3 V), thermal (~290 °C) and mechanical (~55 MPa) stability, and ion transport (tion, ~0.99) properties. Intercalation of (polyacrylonitrile (PAN)8LiPF6 complex into nanometric channels of organophilic clay has been confirmed by X-ray diffraction analysis. These observations agree well with transmission electron microscopy results. Impedance spectroscopy indicated bulk electrical conduction in the high-frequency region followed by electrode polarization effects at lower frequencies. The latter effect is clearly noticed in the admittance plots. Estimated value of ionic conductivity and stability is invariably higher in PNCs compared with clay-free polymer–salt complex film. The feasibility of ionic conduction in the PNC separators has been explained in terms of hopping mechanism. The optimized PNC film may be expected to serve the dual purpose A. L. Sharma Centre for Applied Physics, Central University of Jharkhand, Brambe, Ranchi 835205, India A. K. Thakur (*) Department of Physics, Indian Institute of Technology (I. I. T.), Patna 800013, India e-mail: [email protected] A. K. Thakur e-mail: [email protected] A. L. Sharma : A. K. Thakur Department of Physics and Meteorology, Indian Institute of Technology (I. I. T.), Kharagpur 721302, India
of electrolyte as well as separator in portable energy storage/ conversion devices. Keywords AC conductivities . Cationic conductors . DC conductivities . Ionic conductivities . Lithium batteries
Introduction Development of plastic separators having mechanical stability, physical flexibility, and feasibility of fast ion transport (Li+ ion conduction) has ever been a desired R&D goal for both the academia and industry working for efficient energy storage devices (high-energy-density lithium battery, supercapacitors, PEM fuel cells, etc.) [1–3]. There has been continuous effort, over the last three decades, to develop optimized materials combination (appropriate electrolyte/ separator with suitable electrodes) for design of miniaturized devices with high energy density and power density. The state-of-the-art problems of the existing brands such as: bulky design, low-energy density, high self discharge, instability towards electrode reaction at the electrode–electrolyte interface, and performance degradation at sub-ambient (≤55 °C) and also at elevated temperatures (≥55 °C) [4–6] need serious attention. In order to address the challenges mentioned above, soft polymeric electrolytes that may serve the dual pur
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