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- 검색키워드
- 저자 : Yongwon Lee (검색결과 201 건)
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Lee, Yongwon,Lee, Jaegi,Lee, Jeongmin,Kim, Koeun,Cha, Aming,Kang, Sujin,Wi, Taeung,Kang, Seok Ju,Lee, Hyun-Wook,Choi, Nam-Soon American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.17
<P>Sodium (Na) metal anodes with stable electrochemical cycling have attracted widespread attention because of their highest specific capacity and lowest potential among anode materials for Na batteries. The main challenges associated with Na metal anodes are dendritic formation and the low density of deposited Na during electrochemical plating. Here, we demonstrate a fluoroethylene carbonate (FEC)-based electrolyte with 1 M sodium bis(fluorosulfonyl)imide (NaFSI) salt for the stable and dense deposition of the Na metal during electrochemical cycling. The novel electrolyte combination developed here circumvents the dendritic Na deposition that is one of the primary concerns for battery safety and constructs the uniform ionic interlayer achieving highly reversible Na plating/stripping reactions. The FEC-NaFSI constructs the mechanically strong and ion-permeable interlayer containing NaF and ionic compounds such as Na<SUB>2</SUB>CO<SUB>3</SUB> and sodium alkylcarbonates.</P> [FIG OMISSION]</BR>
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Lee, Jaegi,Lee, Yongwon,Lee, Jeongmin,Lee, Sang-Min,Choi, Jeong-Hee,Kim, Hyungsub,Kwon, Mi-Sook,Kang, Kisuk,Lee, Kyu Tae,Choi, Nam-Soon American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.4
<P>We present an ultraconcentrated electrolyte composed of 5 M sodium bis(fluorosulfonyl)imide in 1,2-dimethoxyethane for Na metal anodes coupled with high-voltage cathodes. Using this electrolyte, a very high Coulombic efficiency of 99.3% at the 120th cycle for Na plating/stripping is obtained in Na/stainless steel (SS) cells with highly reduced corrosivity toward Na metal and high oxidation durability (over 4.9 V versus Na/Na+) without corrosion of the aluminum cathode current collector. Importantly, the use of this ultraconcentrated electrolyte results in substantially improved rate capability in Na/SS cells and excellent cycling performance in Na/Na symmetric cells without the increase of polarization. Moreover, this ultraconcentrated electrolyte exhibits good compatibility with high-voltage Na4Fe3(PO4)(2)(P2O7) and Na-0.7(Fe0.5Mn0.5)O-2 cathodes charged to high voltages (>4.2 V versus Na/Na+), resulting in outstanding cycling stability (high reversible capacity of 109 mAh g(-1) over 300 cycles for the Na/Na4Fe3(PO4)(2)(P2O7) cell) compared with the conventional dilute electrolyte, 1 M NaPF6 in ethylene carbonate/propylene carbonate (5/5, v/v).</P>
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Lee, Seungmin,Lee, Yohan,Lee, Jaehyoung,Lee, Huen,Seo, Yongwon American Chemical Society 2013 Environmental science & technology Vol.47 No.22
<P>The methane (CH<SUB>4</SUB>) – carbon dioxide (CO<SUB>2</SUB>) swapping phenomenon in naturally occurring gas hydrates is regarded as an attractive method of CO<SUB>2</SUB> sequestration and CH<SUB>4</SUB> recovery. In this study, a high pressure microdifferential scanning calorimeter (HP μ-DSC) was used to monitor and quantify the CH<SUB>4</SUB> – CO<SUB>2</SUB> replacement in the gas hydrate structure. The HP μ-DSC provided reliable measurements of the hydrate dissociation equilibrium and hydrate heat of dissociation for the pure and mixed gas hydrates. The hydrate dissociation equilibrium data obtained from the endothermic thermograms of the replaced gas hydrates indicate that at least 60% of CH<SUB>4</SUB> is recoverable after reaction with CO<SUB>2</SUB>, which is consistent with the result obtained via direct dissociation of the replaced gas hydrates. The heat of dissociation values of the CH<SUB>4</SUB> + CO<SUB>2</SUB> hydrates were between that of the pure CH<SUB>4</SUB> hydrate and that of the pure CO<SUB>2</SUB> hydrate, and the values increased as the CO<SUB>2</SUB> compositions in the hydrate phase increased. By monitoring the heat flows from the HP μ-DSC, it was found that the noticeable dissociation or formation of a gas hydrate was not detected during the CH<SUB>4</SUB> – CO<SUB>2</SUB> replacement process, which indicates that a substantial portion of CH<SUB>4</SUB> hydrate does not dissociate into liquid water or ice and then forms the CH<SUB>4</SUB> + CO<SUB>2</SUB> hydrate. This study provides the first experimental evidence using a DSC to reveal that the conversion of the CH<SUB>4</SUB> hydrate to the CH<SUB>4</SUB> + CO<SUB>2</SUB> hydrate occurs without significant hydrate dissociation.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2013/esthag.2013.47.issue-22/es403542z/production/images/medium/es-2013-03542z_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es403542z'>ACS Electronic Supporting Info</A></P>
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Lee, Yongwon,Lee, Tae Kyung,Kim, Saehun,Lee, Jeongmin,Ahn, Youngjun,Kim, Koeun,Ma, Hyeonsu,Park, Gumjae,Lee, Sang-Min,Kwak, Sang Kyu,Choi, Nam-Soon Elsevier 2020 Nano energy Vol.67 No.-
<P><B>Abstract</B></P> <P>Li metal anodes and Ni-rich layered oxide cathodes with high reversible capacities are promising candidates for the fabrication of high energy density batteries. However, low Coulombic efficiency, safety hazards from likely vertical Li growth, and morphological instability of Ni-rich cathodes hinder the practical applications of these electrodes. Here, we report that fluorinated compounds can be employed as interface modifiers to extend the applicable voltage range of ether-based electrolytes, which have been used specifically so far for lithium metal batteries with charging cut-off voltages lower than 4 V (vs. Li/Li<SUP>+</SUP>). A complementary electrolyte design using both 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and fluoroethylene carbonate in concentrated ether-based electrolytes significantly improves the capacity retention (99.1%) in a Li|LiNi<SUB>0.8</SUB>Co<SUB>0.1</SUB>Mn<SUB>0.1</SUB>O<SUB>2</SUB> full cell, with a high Coulombic efficiency of 99.98% after 100 cycles at 25 °C. Thus, the modified electrolyte system is promising for addressing the reductive and oxidative decompositions of labile ether-based electrolytes in high energy density Li metal batteries with Ni-rich cathodes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ether-based electrolyte formulation for 4V-class Li metal batteries is presented. </LI> <LI> FEC and TTE are employed as the electrode–electrolyte interface modifiers. </LI> <LI> Fluorine-enriched interfaces enable high-performance Li metal batteries. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Lee, In Hwan,Lee, Jeong Min,Jung, Yongwon American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.10
<P>Difficulties in stable conjugation of biomolecules to nanosilver surfaces have severely limited the use of silver nanostructures in biological applications. Here, we report a facile antibody conjugation onto gold/silver (Au/Ag) core–shell nanoparticles by stable and uniform embedment of an antibody binding protein, protein G, in silver nanoshells. A rigid helical peptide linker with a terminal cysteine residue was fused to protein G. A mixture of the peptide-fused protein G and space-filling free peptide was reacted with gold nanoparticles (AuNPs) to form a protein G-linked peptide layer on the particle surface. Uniform silver nanoshells were successfully formed on these protein G-AuNPs, while stably embedding protein G-linked peptide layers. Protein G specifically targets the Fc region of an antibody and thus affords properly orientated antibodies on the particle surface. Compared to Au nanoparticles of similar size with randomly adsorbed antibodies, the present immuno-labeled Au/Ag core–shell nanoparticles offered nearly 10-fold higher sensitivities for naked-eye detection of surface bound antigens. In addition, small dye molecules that were bonded to the peptide layer on Au nanoparticles exhibited highly enhanced surface-enhanced Raman scattering (SERS) signals upon Ag shell formation. The present strategy provides a simple but efficient way to conjugate antibodies to nanosilver surfaces, which will greatly facilitate wider use of the superior optical properties of silver nanostructures in biological applications.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-10/am500960b/production/images/medium/am-2014-00960b_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am500960b'>ACS Electronic Supporting Info</A></P>
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Lee, Bo Ram,Sa, Jeong-Hoon,Hong, Sang Yeon,Lee, Ju Dong,Lee, Kun-Hong,Seo, Yongwon,Sum, Amadeu K. American Chemical Society 2019 The Journal of Physical Chemistry Part C Vol.123 No.6
<P>The current knowledge of guest-guest interactions and co-occupation in clathrate hydrates is exclusive for the same guests (H<SUB>2</SUB> or N<SUB>2</SUB>) at moderate pressure. Here, we introduce the unusual co-occupation of distinct guests in the metastable state of hydrates. With controlled hydrate fraction, particle size, and intensification of the sintering of SF<SUB>6</SUB> hydrate particles formed from water and SF<SUB>6</SUB> gas as a help gas, we observed an abnormal but unique synchronous behavior in Raman intensities of two guest molecules (SF<SUB>6</SUB> and N<SUB>2</SUB>/H<SUB>2</SUB>) in hydrates consistently and repeatedly; over time, the scattering intensity for the guests (i) increases, (ii) decreases, and (iii) finally reaches the stable level. Without a concentration change of SF<SUB>6</SUB>, this abnormal behavior must arise from the possible changes in the scattering cross section of the molecules, suggesting that N<SUB>2</SUB>/H<SUB>2</SUB> strongly interacts with SF<SUB>6</SUB> in the large cages, resulting in a possible co-occupation during the metastable transition. These observations on the metastability of gas hydrate attest the importance of the sintering effect as a barrier to prevent fast gas diffusion for reaching equilibrium, which could have significant implication in increasing overall gas storage in clathrate hydrates.</P> [FIG OMISSION]</BR>
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Lee, Yohan,Choi, Wonjung,Seo, Young-ju,Lee, Joo Yong,Lee, Jaehyoung,Seo, Yongwon Elsevier 2018 APPLIED ENERGY Vol.228 No.-
<P><B>Abstract</B></P> <P>This study investigated a structural transition induced by cage-dependent guest exchange in the CH<SUB>4</SUB> + C<SUB>3</SUB>H<SUB>8</SUB> hydrate with CO<SUB>2</SUB> injection for CH<SUB>4</SUB> recovery and CO<SUB>2</SUB> sequestration. The influence of the CO<SUB>2</SUB> replacement on the crystalline structure of initial CH<SUB>4</SUB> + C<SUB>3</SUB>H<SUB>8</SUB> hydrates and the cage-dependent distribution of guest molecules were quantitatively investigated using powder X-ray diffraction, <SUP>13</SUP>C nuclear magnetic resonance spectroscopy, and gas chromatography. The quantitative analyses demonstrated that the CO<SUB>2</SUB> occupation caused the depletion of C<SUB>3</SUB>H<SUB>8</SUB> molecules in the large 5<SUP>12</SUP>6<SUP>4</SUP> cages of structure II hydrates, thereby resulting in the subsequent transformation into CO<SUB>2</SUB>-rich sI hydrates and the coexistence of structure I and structure II hydrates after the replacement. The guest-exchange behavior observed from time-dependent Raman spectra indicated that the replacement rate was increased with an increase in pressure of injected CO<SUB>2</SUB> and that the extent of the replacement was enhanced at higher pressure of injected CO<SUB>2</SUB>. Overall experimental evidence of the partial structural-transition replacement suggests that CO<SUB>2</SUB> molecules first occupied structure II hydrates predominantly with the rapid guest exchange at the surface and that the initial structure II hydrates were subsequently converted to the CO<SUB>2</SUB>-rich structure I hydrates from the surface to the inner side. Precise identification of the mechanism responsible for the partial structural transition occurring in the CH<SUB>4</SUB> + C<SUB>3</SUB>H<SUB>8</SUB> - CO<SUB>2</SUB> replacement will be very helpful in developing a strategy for actual CO<SUB>2</SUB> injection into structure II gas hydrate reservoirs for energy recovery and CO<SUB>2</SUB> sequestration.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The guest exchange behavior during replacement was quantitatively investigated. </LI> <LI> The CO<SUB>2</SUB> occupation induced the depletion of C<SUB>3</SUB>H<SUB>8</SUB> in the large 5<SUP>12</SUP>6<SUP>4</SUP> cages of sII. </LI> <LI> The partial structural transition occurred in the CH<SUB>4</SUB> + C<SUB>3</SUB>H<SUB>8</SUB> - CO<SUB>2</SUB> replacement. </LI> <LI> The replacement was more significant at higher pressure of injected CO<SUB>2</SUB>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Lee, Hyun Ho,Nam, Dongsik,Kim, Choon-Ki,Kim, Koeun,Lee, Yongwon,Ahn, Young Jun,Lee, Jae Bin,Kwak, Ja Hun,Choe, Wonyoung,Choi, Nam-Soon,Hong, Sung You American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.12
<P>Here, we report the first electrochemical assessment of organophosphonate-based compound as a safe electrode material for lithium-ion batteries, which highlights the reversible redox activity and inherent flame retarding property. Dinickel 1,4-benzenediphosphonate delivers a high reversible capacity of 585 mA h g<SUP>-1</SUP> with stable cycle performance. It expands the scope of organic batteries, which have been mainly dominated by the organic carbonyl family to date. The redox chemistry is elucidated by X-ray absorption spectroscopy and solid-state <SUP>31</SUP>P NMR investigations. Differential scanning calorimetry profiles of the lithiated electrode material exhibit suppressed heat release, delayed onset temperature, and endothermic behavior in the elevated temperature zone.</P> [FIG OMISSION]</BR>
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