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( Louishamenu ),원정하,이해수,( Latifatu Mohammed ),김광만,박종욱,백용구,남현국,고장면 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
In this work, poly[dimethylsiloxane-co-(siloxane-g-acrylate)] (PDMS-A) and lithium-modified silica nanosalt (Li202) are used together as lowtemperature electrolyte additives in lithium-ion batteries (LIBs), taking advantage of the electrochemical and interfacial stabilities due to their surface functional groups. Using these additives together improves the electrochemical stability and ionic conductivity of liquid electrolyte solution to over 5.5 V and 4``10-4Scm-1 at -20°C, respectively. The roomtemperature electrochemical performance of a conventional LIB(LiCoO2/ graphite)is improved by the addition (e.g., initial discharge capacity of 95.9 mAhg-1 obtained after charging at1.0C-rate and consequent discharging at5.0C-rate). The low-temperature performance is also enhanced, achieving a capacity retention ratio of 63.4% after 50cycles at -20°C, compared to 38.7% without the additives.
( Louishamenu ),이해수 ( Latifatu Mohammed ) 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
Three kinds of polydimethylsiloxane (PDMS)-based grafted and ungrafted copolymers such as poly[dimethylsiloxane-co-(siloxane-g-acrylate)] (PDMS-A), poly(dimethylsiloxane-co-phenylsiloxane) (PDMS-P), and poly[dimethylsiloxane-co-(siloxane-g-ethylene oxide)] (PDMS-EO) are used as additives to standard liquid electrolyte solutions to enhance the lithium-ion battery performance at low temperatures. Liquid electrolyte solutions with PDMS-based additives are electrochemically stable under 5.0 V and have adequate ionic conductivities of 10<sup>-4</sup> S cm<sup>-1</sup> at -20°C. Particularly, liquid electrolytes with PDMS-P and PDMS-EO exhibit higher ionic conductivities of around 5 × 10<sup>-4</sup> S cm-1 at -20°C, indicating a specific resisting property against the freezing of the liquid electrolyte components. As a result, the addition of PDMS-based additives to liquid electrolytes improves the capacity retention ratio and rate-capability of lithium-ion batteries at low temperatures.
( Louishamenu ),( Latifatu Mohammed ),이해수,( Alfred Madzamuse ),( Hu Mengyang ),( Kwang Man Kim ),( Jang Myoun Ko ) 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
In this work, lithium-modified silica nanosalt (Li202) is solution-synthesized and used as a gel-forming additive in 1.5 M tetraethylammonium tetrafluoroborate (TEABF4)/acetonitrile (ACN) electrolyte solution for the supercapacitor with activated carbon electrode. The electrochemical properties of the supercapacitor adopting the Li202 (5 wt.%) are investigated using linear sweep voltammetry, cyclic voltammetry, and complex impedance spectroscopy. By the addition of the Li202, the electrochemical stability of the electrolyte is improved over 4.0 V (cor responding to the current density below 0.6 mA cm-2) and higher specific capacitances at the scan rates of 10-500 mV s-1 are obtained. Thus, the Li202 can be considered as a promising electrolyte additive to enhance the supercapacitive properties of activated carbon electrode.
Louis Hamenu,Hae Soo Lee,Mohammed Latifatu,Kwang Man Kim,Jong Wook Park 한국물리학회 2016 Current Applied Physics Vol.16 No.6
The impact of random dopant fluctuation (RDF) on a 10-nm n-type silicon (Si) FinFET with a metalinsulator- semiconductor (M-I-S) source/drain (S/D) structure is investigated using three-dimensional TCAD simulation. To determine the optimal aspect ratio of the fin for a variation-robust FinFET with an M-I-S S/D structure, various metrics for device performance are quantitatively evaluated. It is found that variation in RDF-induced threshold voltage (Vth) in the FinFET can be suppressed with a taller fin (i.e., a fin with a higher aspect ratio) because of better gate-to-channel controllability and wider channel width. For a fin aspect ratio (i.e., fin height to fin width) of 5.25:1, the standard deviation for RDF-induced Vth in a FinFET with an S/D doping concentration (NS/D) of 5 1020 cm3 is 9.277 mV. In order to suppress RDF-induced Vth variation even further, an M-I-S structure with a heavily doped n-type ZnO interlayer can be introduced into the S/D region of the FinFET. For the tallest fin height, this M-I-S S/D structure (with an NS/D ¼ 5 1019 cm3) results in a standard deviation of 4.729 mV for RDF-induced Vth, while maintaining the on-state drive current (Ion) at a satisfactory level. Therefore, it is expected that a 10-nm n-type FinFET can be designed to be immune to Vth variation with the adoption of the proposed M-I-S S/D structure.
Louis Hamenu,Hae Soo Lee,Mohammed Latifatu 한국물리학회 2016 Current Applied Physics Vol.16 No.6
The Indium tin oxide (ITO) interlayer was deposited on the surface of n-Hg3In2Te6 (short for MIT) wafer by means of Pulsed Laser Deposition (PLD) method for improving the Au/n-MIT Schottky contact properties. Through the XPS depth profile analysis, it was found that the In3þ on the surface of MIT changed to In0 due to the reduction of O0 during the ITO deposition process. When the ITO interlayer was prepared between Au and MIT, the leakage current and series resistance of Au/n-MIT contact decreased and the Schottky barrier height increased. This phenomenon can be explained that the ITO passivation layer reduced the surface states of MIT wafer and weakened the Fermi level pining, which was caused by that In3þ on the surface of MIT changed into In0 due to the reduction of O0 and O2 obtained the electrons from In3þ occupied the Hg2þ vacancies.
Louis, Hamenu,Lee, Young-Gi,Kim, Kwang Man,Cho, Won Il,Ko, Jang Myoun Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.6
The corrosion property of aluminum by lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt is investigated in liquid and gel electrolytes consisting of ethylene carbonate/propylene carbonate/ethylmethyl carbonate/diethyl carbonate (20:5:55:20, vol %) with vinylene carbonate (2 wt %) and fluoroethylene carbonate (5 wt %) using conductivity measurement, cyclic voltammetry, scanning electron microscopy, and energy dispersive X-ray spectroscopy. All corrosion behaviors are attenuated remarkably by using three gel electrolytes containing 3 wt % of hydrophilic and hydrophobic fumed silica. The addition of silica particles contributes to the increase in the ionic conductivity of the electrolyte, indicating temporarily formed physical crosslinking among the silica particles to produce a gel state. Cyclic voltammetry also gives lower anodic current responses at higher potentials for repeating cycles, confirming further corrosion attenuation or electrochemical stability. In addition, the degree of corrosion attenuation can be affected mainly by the electrolytic constituents, not by the hydrophilicity or hydrophobicity of silica particles.
Louis Hamenu,Alfred Madzvamuse,Mengyang Hu,Latifatu Mohammed,Chris Yeajoon Bon,김상준,조원일,박종욱,고장면 한국물리학회 2017 Current Applied Physics Vol.17 No.12
Supercapacitors provide us with enormous power output for energy storage. Their energy output however still remains quite low compared to other energy storage materials like the batteries. This paper reports a highly stable liquid electrolyte which is composed of mixtures of 1-ethyl-3-methylimidazolium tetrafluoroborate(EMIBF4) ionic liquid with highly stable lithium bis(oxalate)borate LiBOB/acetonitrile( ACN). The electrolytes display remarkable supercapacitive performance at a high voltage of 3 V. The electrochemical impedance spectroscopy shows that EMIBF4 helps to reduce the bulk resistance and charge transfer resistance across the electrode surfaces by facilitating high ionic diffusions across the electrode/electrolyte interface. The high stability and high ionic conductivity of the electrolytes reflected in the good cycling performance tests at 2.8 V with a maximum delivery capacitance of 19.5Fg-1 after 1000cycles at a high scan rate of 200 mVs-1.
Lithium-silica nanosalt as a low-temperature electrolyte additive for lithium-ion batteries
Louis Hamenu,Hae Soo Lee,Mohammed Latifatu,Kwang Man Kim,박종욱,Yong Gu Baek,Jang Myoun Ko,Richard B. Kaner 한국물리학회 2016 Current Applied Physics Vol.16 No.6
A lithium-modified silica nanosalt (LieSiO2, coded Li202) of hydrophobic fumed silica (R202) is synthesized to use as an electrolyte additive for lithium-ion batteries (LIBs) under low temperature conditions. The synthesis method consists of reacting the silica nanoparticles with LiH and consequently quickly reacting the conjugate silicate ions with 1,3-propanesultone as a surface stabilizer. The obtained Li202 nanosalt (2.5 wt%) is added into an electrolyte solution of 1.0 M LiPF6 dissolved in ethylene carbonate/ propylene carbonate/ethylmethyl carbonate/diethyl carbonate (20:5:55:20 vol%) þ 2 wt% vinylene carbonate. The electrolyte solution including the Li202 nanosalt shows higher ionic conductivity and superior electrochemical stability over 5 V, which is due to the stabilized surface group. The high-rate capability at 20 C of the LiCoO2/graphite cell is particularly enhanced by adding Li202 nanosalt. In addition, excellent cycle performance at 20 C endorses the use of Li202 nanosalt as a low-temperature electrolyte additive for LIBs.
Benzotriazole as an electrolyte additive on lithium-ion batteries performance
Louis Hamenu,Alfred Madzvamuse,Latifatu Mohammed,이용민,고장면,Chris Yeajoon Bon,김상준,최원일,백용구,박종욱 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.53 No.-
Liquid electrolyte consisting of 1 M LiPF6 in ethylene carbonate (EC)/dimethyl carbonate (DMC) and 0.1 wt% benzotriazole (BzTz) is studied in LiCoO2//graphite battery system at room temperature. Benzotriazole addition introduces excellent electrochemical stability (5.6 V vs Li) and good ionic conductivity properties at room temperature. Also, this electrolyte shows good cycling performance and better discharge capacities at high C-rates relative to the pristine electrolyte. Furthermore, the additive allows the formation of a good solid electrolyte interphase (SEI) per cyclic voltammetry (CV) examination. These specialized properties make this liquid electrolyte ideal for high power and high voltage applications.
이해수,( Louishamenu ),( Latifatumohammed ),( Yeo Il Yoon ),( Alfred Madzamuse ),( Hu Mengyang ),( Jang Myoun Ko ) 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
Prepared are three types of composite supercapacitor electrode, such as electroactive polyaniline (PAN), PAN/multi-walled carbon nanotube (CNT), and PAN/CNT/RuO<sub>2</sub>. Cyclic voltammetry was performed to investigate the supercapacitive properties of these electrodes in an electrolyte solution of 1.0M H<sub>2</sub>SO<sub>4</sub>. The PAN/CNT/RuO<sub>2</sub> electrode showed the highest specific capacitance at all scan rates (e.g., 441 and 392 F g<sup>-1</sup> at 100 and 1,000 mV s<sup>-1</sup>, respectively). In cycle performance, however, the PAN/CNT electrode demonstrated the best capacitance retention (66%) at 104th cycle.