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Lee J.-H.,Korea NationalUniversity of Transportation | Park D.-S.,Korea NationalUniversity of Transportation | Lim J.-H.,Korea NationalUniversity of Transportation | Kim K.-M.,Korea NationalUniversity of Transportation
Molecular Crystals and Liquid Crystals | Year: 2015

Spherical bridged polysilsesquioxane nanoparticles with thiol groups (BPS-SH) were prepared by the reduction of BPS with disulfide groups after the base-catalyzed hydrolysis and condensation reaction of bis(triethoxysilylpropyl)disulfide. The average size of BPS was around 100∼300 nm. Hydroxyethyl methacrylate (HEMA)-initiated polycaprolactone (PCL) was synthesized by ring-opening polymerization of caprolactone under the co-initiation of HEMA and Sn(Oct)2. New nanocomposites of BPS-SH and HEMA-PCL were fabricated by the photo-induced chemical reaction under a photoradical generator and ultraviolet light. BPS was fully and continuously covered with PCL, which resulted in the rough surface of BPS nanoparticles as well as the connected BPS nanoparticles together. © 2015 Copyright Taylor & Francis Group, LLC.

Islam M.,Korea NationalUniversity of Transportation | Yoon M.S.,Korea NationalUniversity of Transportation | Park Y.M.,Daegu Gyeongbuk Institute of Science and Technology | Ur S.C.,Korea NationalUniversity of Transportation
Journal of Ceramic Processing Research | Year: 2015

Cathode materials have been the most important components of the Li-ion secondary battery research because they generally determine the capacity and safety of Li-ion battery (LIB). In order to decrease the cost of LIBs, main efforts are devoted to the cost reduction of the electrode materials. As a consequence, low cost raw materials are considered for cost reduction. Iron (III) phosphate has recently gained interest as a compatible source of both iron and phosphate in the field of LIB. It is prepared by a precipitation technique from aqueous solution. The starting material is Fe(NO3)3 • 9H2O, in this study, which is one of the cheapest iron sources for LiFePO4 cathode preparation. The olivine-type LiFePO4/C composites are synthesized by a solid state reaction process using pre-milled Li2CO3 and pre-synthesized amorphous FePO4 • xH2O powders. The pre-synthesized FePO4 • xH2O powders are mixed with pre-milled lithium carbonate and glucose (8 wt.%) using either water or alcohol solvent sequentially via ball-mill process. The main purpose of the present study is to investigate Fe(NO3)3 • 9H2O as a source material and explore the effect of precursor mixing solvent, if any, on the microstructure and electrochemical property of LiFePO4 cathode materials. The structural characteristics of LiFePO4/C composites are examined by XRD, SEM and TEM. To investigate the mixing solvent effect on the electrochemical property in LiFePO4/C composites, a Li[LiPF6 (ethylene carbonate + dimethyl carbonate)] LiFePO4/C model cell is used. It is demonstrated that the LiFePO4/C synthesize by using alcohol solvent exhibits the better electrochemical performance than that of water one. The reason of such kind of behavior is explicated by their corresponding TEM micrographs. © 2015, Hanyang University. All rights reserved.

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