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Songgang-dong, South Korea

Yoon Y.S.,Yonsei University | Jee S.H.,Yonsei University | Lee S.H.,Yonsei University | Nam S.C.,GS NanoTech Co.
Surface and Coatings Technology | Year: 2011

Nano-sized silicon particles were uniformly coated onto a natural graphite surface by a 1 ton/month-based semi-mass production ball milling method in order to prepare Si-based anodes for Li ion batteries. The structure, surface morphology and Si coating properties of the as-synthesized powders were analyzed by XRD, Raman, SEM, TEM and EDS mapping tools. The initial gravimetric discharge capacity of the Si-coated graphite measured using a half cell was 761 mAh/g at a rate of 0.2. C. Additionally, the discharge capacity retention of a full cell system was 71.4% at a 1 C rate even after 300 cycles as well as 96.6% of initial coulombic efficiency. The cycled composite powders were further analyzed by SEM and EDS mapping techniques. This method is proposed for commercial extension to the manufacture of lithium secondary batteries. © 2011 Elsevier B.V.

Yoon Y.S.,Yonsei University | Cho S.B.,Agency for Defense Development | Nam S.C.,GS NanoTech Co.
Electrochimica Acta | Year: 2012

A module with 11 thin film battery (TFB) stacks was fabricated to investigate its internal resistance and charging characteristics to a real capacitor with 150 uF. Each cell consisted of thin layers of LiCoO 2, LiPON and Li on a ceramic substrate, and each layer was deposited by radio frequency (RF) + direct current (DC) hybrid magnetron sputtering, RF reactive sputtering, and thermal evaporation, respectively. In order to increase the effective surface area of the TFB in a limited small volume, 11 cells were stacked and connected in parallel. By designing the thermal switch with a heating source, its capacitor charging performance was well maintained, even at temperatures below -30 °C, as well as at room temperature. Charging to greater than 4 V was completed within 0.06 sec at room temperature and within 0.13 s at -30 ° C due to the heat-up process. A novel battery system consisting of the TFB module with a thermal switch and a heating source proved to be a promising substitute for the ampoule type reserve battery in small sized electrical fuses, even at very low temperatures. © 2012 Elsevier Ltd. All rights reserved.

Lee S.H.,Yonsei University | Jee S.H.,Yonsei University | Lee K.S.,Yonsei University | Nam S.C.,GS NanoTech Co. | Yoon Y.S.,Yonsei University
Electrochimica Acta | Year: 2013

SnPxOy thin films were deposited on stainless steel substrates by electron-beam evaporation for use as anodes in thin-film lithium ion batteries. The thin films were heat-treated at various temperatures for 4 h, and their composition, microstructure, and electrochemical properties were characterized by Rutherford backscattering spectroscopy (RBS), X-ray diffraction (XRD), cyclic voltammetry (CV), and AC impedance spectroscopy. The specific discharge capacity of the as-deposited SnPxOy thin film anode decreased rapidly to 12 μAh cm-2-μm within 10 cycles. However, after heat treatment for 4 h at 500 °C, it maintained a high specific discharge capacity of 136 μAh cm-2-μm and excellent cyclability even after 300 cycles, in contrast to pure SnOx thin film. © 2012 Elsevier Ltd.

Hossain M.M.,Kyungpook National University | Faisal S.N.,Kyungpook National University | Kim C.S.,Pohang University of Science and Technology | Cha H.J.,Pohang University of Science and Technology | And 2 more authors.
Electrochemistry Communications | Year: 2011

A novel strip-based disposable amperometric proton sensor that can selectively detect organophosphate neurotoxins (i.e., paraoxon) is described. The detection methodology is based on measuring the current change involved in the assisted proton transfer by a proton selective ligand (e.g., ETH 1778) across a microelliptic hole interface between the aqueous and polyvinylchloride-2-nitrophenyloctylether gel phase. The selective detection of paraoxon is achieved by measuring protons released by the specific hydrolysis of paraoxon with the organophosphorus hydrolase enzyme. A two-step process involving the hydrolysis and proton transfer reaction was characterized using cyclic voltammetry and differential pulse stripping voltammetry. A strip-based sensor fabricated using a simple polydimethylsiloxane (PDMS) mold with the resulting device was found to exhibit a linear response over a wide range of paraoxon concentrations (0.5 μM-100 μM) present in aqueous samples. In addition to the excellent detection limit and a wide dynamic range, a superb selectivity in the presence of common interfering agents in agricultural samples is achieved. © 2011 Elsevier B.V. All Rights Reserved.

Lee B.G.,Inha University | Nam S.-C.,GS NanoTech Co. | Choi J.,Inha University
Current Applied Physics | Year: 2012

We investigate the possibility of using a TiO 2 anode as an alternative to the Li electrode in Li-air and Li-ion rechargeable batteries. TiO 2 nanotube layer is fabricated by the anodization method and optional thermal treatment is conducted. The electrochemical charge/discharge profile of the TiO 2/liquid electrolyte/LiCoO 2 structured cell is measured under the flowing of O 2, N 2 and Ar, respectively. The elevation of the upper cut-off voltage from 3 to 4.5 V leads to an increase in the specific capacity by a factor of more than three. We suppose this to be a novel mechanism in which the TiO 2/LiCoO 2 system under the oxygen atmosphere works in Li-air battery mode up to 3 V and then works in Li-ion battery mode from 3 V to 4.5 V. This idea is confirmed by ICP-OES analysis. © 2012 Elsevier B.V. All rights reserved.

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