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Lee, Soojeong,Cho, Mi Suk,Lee, Hyuck,Nam, Jae-Do,Lee, Youngkwan The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.5
<P>Thin multilayer graphene/PEDOT films were prepared by electrochemical deposition. PEDOT was deposited on gold electrodes by cyclic voltammetry, and p-doped graphene, which was synthesised from expanded and p-doped graphite, was assembled on the PEDOT-coated electrode by chronoamperometry at −1 V. The process was repeated as necessary to obtain the desired number of multilayers. Successful deposition of graphene/PEDOT layers was demonstrated by SEM. The maximum specific capacitance of the multilayer film was 154 F g<SUP>−1</SUP> for six graphene layers. Further, the multilayer film exhibited improved electrochemical stability with a retention life of 86% after 1000 cycles.</P> <P>Graphic Abstract</P><P>The graphene and PEDOT layers were electrodeposited alternately. The binder-free multilayer electrode with 6 graphene layers reached 2.7 times higher capacitance than that of PEDOT films. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1jm13739e'> </P>
Epoxidized Natural Rubber/Chitosan Network Binder for Silicon Anode in Lithium-Ion Battery
Lee, Sang Ha,Lee, Jeong Hun,Nam, Dong Ho,Cho, Misuk,Kim, Jaehoon,Chanthad, Chalathorn,Lee, Youngkwan American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.19
<P>Polymeric binder is extremely important for Si-based anode in lithium-ion batteries due to large volume variation during charging/discharging process. Here, natural rubber-incorporated chitosan networks were designed as a binder material to obtain both adhesion and elasticity. Chitosan could strongly anchor Si particles through hydrogen bonding, while the natural rubber could stretch reversibly during the volume variation of Si particles, resulting in high cyclic performance. The prepared electrode exhibited the specific capacities of 1350 mAh/g after 1600 cycles at the current density of 8 A/g and 2310 mAh/g after 500 cycles at the current density of 1 A/g. Furthermore, the cycle test with limiting lithiation capacity was conducted to study the optimal binder properties at varying degree of the volume expansion of silicon, and it was found that the elastic property of binder material was strongly required when the large volume expansion of Si occurred.</P> [FIG OMISSION]</BR>
Large Deformable Multiwalled Carbon Nanotube Core–Shell Structure on Polystyrene Beads
Lee, Jun-Ho,Lee, Youngkwan,Nam, Jae-Do WILEY-VCH Verlag 2009 Macromolecular rapid communications Vol.30 No.1
<P>Multiwalled carbon nanotube (MWCNT)-coated polystyrene (PS) beads have been prepared by dispersion polymerization followed by a layer-by-layer self-assembly method. The concentration of carboxylic acid groups on the MWCNTs increased from 1.81 × 10<SUP>21</SUP> to 3.43 × 10<SUP>22</SUP> COO<SUP>−</SUP> per g as the treatment time was increased from 3 to 9 h. The sulfonated polystyrene (SPS) beads changed from being negatively charged to positively charged when the cationic polyelectrolyte was self-assembled on their surface. The surface morphology of the adsorbed polyelectrolyte was smooth without any aggregation and the thickness of the polyelectrolyte coating on the SPS beads was ≈0.6 µm. The electrical conductivity and resistance of the MWCNT-coated SPS beads were measured to be 4.0 × 10<SUP>−2</SUP> S · cm<SUP>−1</SUP> and 12.8 Ω at a volume fraction of 91%, respectively.</P><P> <img src='wiley_img/10221336-2009-30-1-MARC200800531-gra001.gif' alt='wiley_img/10221336-2009-30-1-MARC200800531-gra001'> </P>
Lee, Sangyool,Lee, Youngkwan,Cho, Mi-Suk,Nam, Jae-Do American Scientific Publishers 2008 Journal of Nanoscience and Nanotechnology Vol.8 No.9
<P>Solid state redox supercapacitors were fabricated using a solid polymer electrolyte, nitrile butadiene rubber (NBR)-KCl and chemically deposited polypyrrole (PPy) as the conducting polymer electrodes on both surfaces of a NBR film. The optimal conditions for the preparation of the PPy/NBR electrode were confirmed as functions of the uptake of pyrrole monomer into the NBR matrix as well as the immersion time in an oxidant solution. The morphology of the PPy-NBR-KCl capacitor was observed using scanning electron microscopy. The performance of the capacitors was characterized using a galvanostatic charge-discharge technique.</P>
Lee, Hyuck,Kang, Junmo,Cho, Mi Suk,Choi, Jae-Boong,Lee, Youngkwan Royal Society of Chemistry 2011 Journal of materials chemistry Vol.21 No.45
<P>MnO<SUB>2</SUB>/graphene composites were prepared for the electrode material of supercapacitors. MnO<SUB>2</SUB> was synthesized on a gold plate by the electrodeposition method. Graphene prepared by thermal CVD was transferred onto the MnO<SUB>2</SUB> layer. These processes were repeated to make multilayer structures. The optimal performance of the MnO<SUB>2</SUB>/graphene composite was examined as a function of the number of graphene layers in MnO<SUB>2</SUB>. The morphology of MnO<SUB>2</SUB> on graphene was confirmed by SEM and TEM, and the capacitance of the electrode was investigated by cyclic voltammetry and galvanostatic charge/discharge test. The graphene layer provides the electro-conductivity of MnO<SUB>2</SUB>, and then leads to enhancement of the capacitance of MnO<SUB>2</SUB>.</P> <P>Graphic Abstract</P><P>A MnO<SUB>2</SUB>/graphene composite electrode was fabricated and its capacitive characteristics were studied. The graphene layer provides the electro-conductivity of MnO<SUB>2</SUB>, and then leads to enhancement of the capacitance of MnO<SUB>2</SUB>. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1jm13364k'> </P>
Lee, Jun‐,Ho,Lee, Youngkwan,Nam, Jae‐,Do John Wiley Sons, Ltd. 2010 Surface and interface analysis Vol.42 No.1
<P><B>Abstract</B></P><P>We investigated the delamination problem at the metal‐polymer interface and the mechanical buckling of the metal layer at a localized area of the metallic shell under compression between two parallel plates. First, polystyrene (PS) beads were synthesized by dispersion polymerization and then their sulfonation process. After sequential electroless deposition, the average size of multi‐metal coated sulfonated polystyrene (SPS) bead was <I>ca</I> 4.95 µm. Using the electromechanical indentation, the electrical resistance of a single metal‐coated SPS bead decreased with increasing compressive strain without delamination at the metal‐polymer interface, and its electrical resistance showed 5.65 Ω. Copyright © 2009 John Wiley & Sons, Ltd.</P>