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Lithium Dendrite Suppression with UV-Curable Polysilsesquioxane Separator Binders
Na, Wonjun,Lee, Albert S.,Lee, Jin Hong,Hwang, Seung Sang,Kim, Eunkyoung,Hong, Soon Man,Koo, Chong Min American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.20
<P>For the first time, an inorganic organic hybrid polymer binder was used for the coating of hybrid composites on separators to enhance thermal stability and to prevent formation of lithium dendrite in lithium metal batteries. The fabricated hybrid-composite-coated separators exhibited minimal thermal shrinkage compared with the previous composite separators (<5% change in dimension), maintenance of porosity (Gurley number 400 s/100 cm(3)), and high ionic conductivity (0.82 mS/cm). Lithium metal battery cell examinations with our hybrid-composite -coated separators revealed excellent C-rate and cyclability performance due to the prevention of lithium dendrite growth on the lithium anode even after 200 cycles under 0.2-5C (charge discharge) conditions. The mechanism for lithium dendrite prevention was attributed to exceptional nanoscale surface mechanical properties of the hybrid composite coating layer compared with the lithium metal anode, as the elastic modulus of the hybrid-composite-coated separator far exceeded those of both the lithium metal anode and the required threshold for lithium metal dendrite prevention.</P>
Kim, Taehyun,Gadotti, Dimitri A.,Sheth, Kartik,Athanassoula, E.,Bosma, Albert,Lee, Myung Gyoon,Madore, Barry F.,Elmegreen, Bruce,Knapen, Johan H.,Zaritsky, Dennis,Ho, Luis C.,Comeró,n, Sé IOP Publishing 2014 The Astrophysical journal Vol.782 No.2
<P>We have performed two-dimensional multicomponent decomposition of 144 local barred spiral galaxies using 3.6 mu m images from the Spitzer Survey of Stellar Structure in Galaxies. Our model fit includes up to four components (bulge, disk, bar, and a point source) and, most importantly, takes into account disk breaks. We find that ignoring the disk break and using a single disk scale length in the model fit for Type II (down-bending) disk galaxies can lead to differences of 40% in the disk scale length, 10% in bulge-to-total luminosity ratio (B/T), and 25% in bar-to-total luminosity ratios. We find that for galaxies with B/T >= 0.1, the break radius to bar radius, r(br)/R-bar, varies between 1 and 3, but as a function of B/T the ratio remains roughly constant. This suggests that in bulge-dominated galaxies the disk break is likely related to the outer Lindblad resonance of the bar and thus moves outward as the bar grows. For galaxies with small bulges, B/T < 0.1, r(br)/R-bar spans a wide range from 1 to 6. This suggests that the mechanism that produces the break in these galaxies may be different from that in galaxies with more massive bulges. Consistent with previous studies, we conclude that disk breaks in galaxies with small bulges may originate from bar resonances that may be also coupled with the spiral arms, or be related to star formation thresholds.</P>
Lee, Albert S.,Jo, Young Yeol,Choi, Seung-Sock,Baek, Kyung-Youl,Hwang, Seung Sang American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.8
<P>Through UV-initiated thiol-ene click chemistry, carbazole-substituted ladder-like structured polysilsesquioxane and cage-structured polyhedral oligomeric silsesquioxane (T8-POSS) compounds were synthesized and fully characterized. Perfectly carbazole-substituted T8-POSS was synthesized via post-modifications of a mercaptopropyl T8-POSS, while the ladder polysilsesquioxane was synthesized through a base-catalyzed hydrolysis-polycondensation reaction with a carbazole-substituted trialkoxysilane monomer. Through a comparative evaluation of the thermal, mechanical, and photophysical properties of the synthesized compounds, we demonstrate the utility and superiority of the ladder-like structure over the T8-POSS material.</P>
Intrinsic Flux Inequality in Forward Osmosis (FO) and Pressure-Retarded Osmosis (PRO) Processes
Albert S. Kim,Seung-won Lee 한국막학회 2015 멤브레인 Vol.25 No.4
정삼투와 압력지연삼투 공정에서 용매의 투과율은 용매와 막이 접촉하는 방식에 의존한다. 각각의 공정에서 막의 활성층이 고농도 용매와 접촉하는 경우를 압력지연삼투 방식이라 하고, 고농도 용매가 막의 다공성 지지하층과 직면해 있는 경우를 정삼투 방식이라고 한다. 압력지연삼투 방식과 정삼투 방식은 각각 희석형 그리고 농축형의 내부농도 분극 현상을 유발하는데, 동일한 조작 조건에서 정삼투 방식보다 압력지연삼투 방식이 높은 투과율을 나타내는 현상이 실험적으로 관측되었다. 본고에서는 정삼투방식과 압력지연삼투 방식에서 발생하는 본질적인 투과율 불균형을 수학적 귀류법을 이용하여 증명하고, 물리적인 원인을 규명한다. In pressure-retarded osmosis (PRO) and forward osmosis (FO) processes, solvent (permeate) flux depends on which surface the draw solution faces. There are two operation modes. PRO mode indicates that the active layer faces the draw solution, and FO mode means that the porous substrate fronts the draw stream. It is often observed that the PRO mode produces higher flux than that of FO under the same operating conditions. The current work uses the method of proof by contradiction, and mathematically proves the intrinsic flux inequality between the two modes.
Lee, Albert S.,Lee, Jin Hong,Lee, Jong-Chan,Hong, Soon Man,Hwang, Seung Sang,Koo, Chong Min American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.5
<P>The compatibility of diacrylate terminated polyethylene glycol-block-polydimethylsiloxane-block-polyethylene glycol was examined with an ionic liquid solution, 1 M LiTFSI in N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, and through mild UV-curing, hybrid gel polymer electrolytes were fabricated for lithium ion battery application. Obtained hybrid gel polymer electrolytes exhibited good ionic conductivity, electrochemical stability, thermal stability, and mechanical pliancy and the polyethylene glycol domains functioned to increase the ionic dissociation to improve ion conduction compared with gel polymer electrolytes fabricated with a conventional organic crosslinker. Lithium ion battery cell tests with these hybrid gel polymer electrolytes revealed that these hybrid gel polymer electrolytes hold promise as next generation electrolytes.</P>
Lee, Jin Hong,Lee, Albert S.,Lee, Jong-Chan,Hong, Soon Man,Hwang, Seung Sang,Koo, Chong Min American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.5
<P>Inorganic-organic hybrid ionogels fabricated with 1 M LiTFSI in N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide (BMPTFSI) crosslinked with a fully methacryl-substituted Polyhedral Oligomeric Silsesquioxane (T8-MMA-POSS) were investigated as gel polymer electrolytes for lithium ion batteries. The effect of T8-MMA-POSS on physical properties of the ionogels was characterized in terms of dimensional stability, ion transport behaviour, and thermal stability. A mere 5 wt% concentration of the cross-linker was able to produce non-flowing hybrid ionogels, leading to high ionic conductivity with good mechanical properties. The lithium battery cell fabricated with ionogels revealed high specific capacity and excellent cycling performance with high Coulombic efficiency at elevated temperature, demonstrating that hybrid ionogels could be a promising candidate electrolyte for use in lithium ion batteries.</P>
Albert S. Lee,백경열,최승석,장소현,황승상 한국고분자학회 2014 Macromolecular Research Vol.22 No.10
A series of azido-functionalized ladder-like structures was prepared by direct azidation of ladder-likestructured poly(p-chloromethylphenyl)silsesquioxane (LPCMPSQ) and poly(chloropropyl)silsesquioxane (LPAPSQ)in excellent yields with perfect substitution of the chloro-compounds. The azido-functionalized silsesquioxanesobtained were then photocured without additional photoinitiator to give highly cross-linked thin films with an exceptionallyhigh modulus (> 12 GPa). Furthermore, these materials were shown to be patterned through photolithographyto give impeccable micropatterned microstructures.
Lee, Albert S.,Choi, Seung-Sock,Lee, He Seung,Baek, Kyung-Youl,Hwang, Seung Sang The Royal Society of Chemistry 2012 Dalton transactions Vol.41 No.35
<P>Cage dodecaphenylsilsesquioxane (T12-Phenyl) was synthesized in a one batch, mildly basic aqueous solution under room temperature conditions using a trialkoxysilane precursor. Significant improvements in synthetic yield (>95%) were observed compared with previous reports. Kinetic studies of the hydrolysis of phenyltrimethoxysilane were conducted and the condensation was monitored by <SUP>29</SUP>Si NMR which revealed the presence of a transient, intermediary T1 species as the pathway to dodecaphenylsilsesquioxane spherulites, and the tendency for T12 structures over T8, T10, and other substructures was explained through MM2 simulations.</P> <P>Graphic Abstract</P><P>Cage dodecaphenylsilsesquioxane (T12-Phenyl) was synthesized in a one batch, mildly basic aqueous solution under room temperature conditions using a trialkoxysilane precursor. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2dt30659j'> </P>
Albert S. Lee,황승상,최승석,백경열 한국고분자학회 2015 Macromolecular Research Vol.23 No.1
A ladder-like structured poly(mercaptopropyl)silsesquioxane (LPMPSQ) was synthesized in one-bath,under mildly basic conditions at room temperature. Obtained LPMPSQ was utilized as a macroinitiator for thiol-enegraft photopolymerization of various vinyl monomers to give hard, soft, hydrophobic, and hydrophilic graft copolymerswith low PDI (<1.4). Synthesized hybrid graft copolymers were characterized by 1H NMR, 29Si NMR, FTIR,GPC, TGA, and DSC. Thermal studies with these hybrid graft copolymers revealed that the ladder-structure substantiallyincreased the thermal stabilities in the form of increased glass transition temperatures and higher degradationtemperatures over their organic analogues.