Chang Kee Lee

Korea Institute of Industrial Technology, Anzan, Gyeonggi Province, South Korea

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Publications (38)135.15 Total impact

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    ABSTRACT: Considerable attention has focused on the combination of carbon nanotubes (CNTs) and metal-organic frameworks (MOFs) since both nanomaterials have outstanding properties. We describe a method for the homogeneous decoration of an MOF (ZIF-8 was chosen) onto the surfaces of CNTs dispersed by polyvinylpyrrolidones (PVPs) in methanol, which was revealed by a scanning electron microscopic study. The homogeneous coating of the MOF on the CNTs, and nanostructures of the CNT-MOF were controlled by simply changing the concentrations of the MOFs. Furthermore, this method was also applicable to graphene and graphene oxide (GO). Selective CO2 uptakes of the CNT-MOF and graphene-MOF were significantly improved as compared to the nonhomogeneous composites synthesized without the PVP functionalization, and a good reproducibility of the CO2 adsorption was confirmed by the cycling test
    RSC Advances 09/2014; · 3.71 Impact Factor
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    ABSTRACT: The rapidly approaching smart/wearable energy era necessitates advanced rechargeable power sources with reliable electrochemical properties and versatile form factors. Here, as a unique and promising energy storage system to address this issue, we demonstrate a new class of heterolayered, one-dimensional (1D) nanobuilding block mat (h-nanomat) battery based on unitized separator/electrode assembly (SEA) architecture. The unitized SEAs consist of wood cellulose nanofibril (CNF) separator membranes and metallic current collector-/polymeric binder-free electrodes comprising solely single-walled carbon nanotube (SWNT)-netted electrode active materials (LiFePO4 (cathode) and Li4Ti5O12 (anode) powders are chosen as model systems to explore the proof of concept for h-nanomat batteries). The nanoporous CNF separator plays a critical role in securing the tightly interlocked electrode-separator interface. The SWNTs in the SEAs exhibit multifunctional roles as electron conductive additives, binders, current collectors and also non-Faradaic active materials. This structural/physicochemical uniqueness of the SEAs allows significant improvements in the mass loading of electrode active materials, electron transport pathways, electrolyte accessibility and misalignment-proof of separator/electrode interface. As a result, the h-nanomat batteries, which are easily fabricated by stacking anode SEA and cathode SEA, provide unprecedented advances in the electrochemical performance, shape flexibility and safety tolerance far beyond those achievable with conventional battery technologies. We anticipate that the h-nanomat batteries will open 1D nanobuilding block-driven new architectural design/opportunity for development of next-generation energy storage systems.
    Nano letters. 09/2014; 14(10):5677-5686.
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    ABSTRACT: The design and fabrication of oxygen barrier films is important for both fundamental and industrial applications. We prepared three different thin films composed of graphene oxide (GO) and laponite (LN), a typical low cost inorganic clay, with the GO/LN volume ratios of 1.9/0.1, 1.7/0.3 and 1.5/0.5 together with a double layer film of the GO and LN. We found that the films with GO/LN = 1.9/0.1 and the double layers exhibited high oxygen barrier and oxygen transmission rate values that reached 0.55 and 0.37 cm(3) per m(2) per atm per day, respectively, which were much lower than those of the films prepared from the pure GO, only LN and GO/LN = 1.7/0.3 and 1.5/0.5. This study is important for the design and fabrication of a film from GO-based all inorganic nanomaterials for applications in gas-barrier membranes.
    Nanoscale 06/2014; · 6.73 Impact Factor
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    ABSTRACT: A solid-state electrolyte with reliable electrochemical performance, mechanical robustness and safety features is strongly pursued to facilitate the progress of flexible batteries. Here, we demonstrate a shape-deformable and thermally stable plastic crystal composite polymer electrolyte (denoted as “PC-CPE”) as a new class of solid-state electrolyte to achieve this challenging goal. The PC-CPE is composed of UV (ultraviolet)-cured ethoxylated trimethylolpropane triacrylate (ETPTA) macromer/close-packed Al2O3 nanoparticles (acting as the mechanical framework) and succinonitrile-mediated plastic crystal electrolyte (serving as the ionic transport channel). This chemical/structural uniqueness of the PC-CPE brings remarkable improvement in mechanical flexibility and thermal stability, as compared to conventional carbonate-based liquid electrolytes that are fluidic and volatile. In addition, the PC-CPE precursor mixture (i.e., prior to UV irradiation) with well-adjusted rheological properties, via collaboration with a UV-assisted imprint lithography technique, produces the micropatterned PC-CPE with tunable dimensions. Notably, the cell incorporating the self-standing PC-CPE, which acts as a thermally stable electrolyte and also a separator membrane, maintains stable charge/discharge behavior even after exposure to thermal shock condition (=130 °C/0.5 h), while a control cell assembled with a carbonate-based liquid electrolyte and a polyethylene separator membrane loses electrochemical activity.
    J. Mater. Chem. A. 06/2014; 2(28).
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    ABSTRACT: Understanding and control of interfacial phenomena between electrode material and liquid electrolytes are of major scientific importance for boosting development of high-performance lithium ion batteries with reliable electrochemical/safety attributes. Here, as an innovative surface engineering approach to address the interfacial issues, a new concept of mixed ion/electron-conductive soft nanomatter-based conformal surface modification of the cathode material is presented. The soft nanomatter is comprised of an electron conductive carbonaceous (C) substance embedded in an ion conductive polyimide (PI) nanothin compliant film. In addition to its structural uniqueness, the newly proposed surface modification benefits from a simple fabrication process. The PI/carbon soft nanomatter is directly synthesized on LiCoO2 surface via one-pot thermal treatment of polyamic acid (=PI precursor) and sucrose (=carbon source) mixture, where the LiCoO2 powders are chosen as a model system to explore the feasibility of this surface engineering strategy. The resulting PI/carbon coating layer facilitates electronic conduction and also suppresses unwanted side reactions arising from the cathode material-liquid electrolyte interface. These synergistic coating effects of the multifunctional PI/carbon soft nanomatter significantly improve high-voltage cell performance and also mitigate interfacial exothermic reaction between cathode material and liquid electrolyte.
    Journal of Power Sources 01/2014; 263:209–216. · 5.26 Impact Factor
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    ABSTRACT: As a promising power source to boost up advent of next-generation ubiquitous era, high-energy density lithium-ion batteries with reliable electrochemical properties are urgently requested. Development of the advanced lithium ion-batteries, however, is staggering with thorny problems of performance deterioration and safety failures. This formidable challenge is highly concerned with electrochemical/thermal instability at electrode material-liquid electrolyte interface, in addition to structural/chemical deficiency of major cell components. Herein, as a new concept of surface engineering to address the abovementioned interfacial issue, multifunctional conformal nanoencapsulating layer based on semi-interpenetrating polymer network (semi-IPN) is presented. This unusual semi-IPN nanoencapsulating layer is composed of thermally-cured polyimide (PI) and polyvinyl pyrrolidone (PVP) bearing Lewis basic site. Owing to the combined effects of morphological uniqueness and chemical functionality (scavenging hydrofluoric acid that poses as a critical threat to trigger unwanted side reactions), the PI/PVP semi-IPN nanoencapsulated-cathode materials enable significant improvement in electrochemical performance and thermal stability of lithium-ion batteries.
    Scientific Reports 01/2014; 4:4602. · 5.08 Impact Factor
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    ABSTRACT: We have reported the fabrication of flexible graphene-paper electrode (GPE) with a flat surface, whose internal structure has been formed with gradient porous build-up (from the surface to the 2-hydroxyethyl cellulose (HC)-coated paper). HC solution was used as a binder to form the gradient porous graphene layer, enabling it to create an anchoring force between the porous graphene layer and the filter paper. The morphology of GPE was investigated using a scanning electron microscope, and the surface resistance of the GPE as a function of graphene content was determined using four-probe method. The electrochemical performance of the GPE was evaluated using a three-electrode test cell by cyclic voltammetry. The gravimetric capacitance of GPE was found to be 120 F per gram of graphene, and the capacitance retention was within ca. 96% for over 500 cycles. This could be attributed to both the low surface resistance resulting from the flat surface and the high electrochemical activity caused by the gradient porous structure. This unique structure not only offers an enhanced conductivity and good electrical contact between the electrode and electrolyte but also helps GPE to maintain good cyclic stability, proving its potential for use in various rechargeable and portable energy-storage devices.
    Journal of Nanoscience and Nanotechnology 11/2013; 13(11):7391-5. · 1.15 Impact Factor
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    ABSTRACT: The electrospray-deposited patterns of graphene onto filter paper were characterized to study the effect of cellulose acetate phthalate (CAP) binder on the surface resistance of the resulting paper. The amount of CAP determines the extent of penetration of graphene into the heterogeneous networks, because graphene gets anchored and crowded into the network with CAP. A graphene-dispersed ink was prepared in water using sodium dodecylbenzenesulfonate, and this ink was used to fabricate graphene-coated paper (GCP) by electrospray deposition technique. The SEM images of the GCP revealed the impregnation of graphene into the filter paper. The mechanical properties and surface resistance of the GCP were studied using a universal testing machine (UTM) and indigenous four-probe meter, respectively. The low-cost GCP prepared in this study showed relatively low surface resistance (96.2 omega/sq) owing to the effective electro-conducting pathway provided by the crowded and impregnated deposition of grapheme onto the filter paper. Consequently, CAP improved the electrical and mechanical characteristics of GCP, even though only a small amount of graphene was used during deposition.
    Journal of Nanoscience and Nanotechnology 10/2013; 13(10):7108-11. · 1.15 Impact Factor
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    ABSTRACT: We demonstrate a bendable plastic crystal polymer electrolyte (referred to as “B-PCPE”) for use in flexible lithium-ion batteries. The B-PCPE proposed herein is composed of a plastic crystal electrolyte (PCE, 1 M lithium bis-trifluoromethanesulphonimide (LiTFSI) in succinonitrile (SN)) and a UV (ultraviolet)-cured polymer network bearing long linear hydrocarbon chains (here, trimethylolpropane propoxylate triacrylate (TPPTA) polymer is exploited). The solid electrolyte characteristics of the B-PCPE are investigated in terms of plastic crystal behavior, mechanical bendability, ionic conductivity, and cell performance. Owing to the presence of long linear hydrocarbon chains attached to crosslinkable acrylate groups, the TPPTA polymer network in the B-PCPE acts as a compliant mechanical framework, thereby exerting a beneficial influence on bendability and also interfacial resistance with lithium metal electrodes. Meanwhile, the B-PCPE exhibits slightly lower ionic conductivity than a control sample (referred to as “R-PCPE”) incorporating a rigid and stiff polymer network of ethoxylated trimethylolpropane triacrylate (ETPTA). This unique behavior of the B-PCPE is discussed with an in-depth consideration of the polymer network structure and its specific interaction with the lattice defect phase of SN in the PCE. Although relatively sluggish ionic transport is observed in the B-PCPE, its intimate interfacial contact with electrodes (possibly due to the mechanically compliant TPPTA polymer network) may beneficially contribute to imparting satisfactory cycling performance.
    J. Mater. Chem. A. 04/2013; 1(17):5224-5231.
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    ABSTRACT: A facile approach to fabricate a highly bendable plastic crystal composite electrolyte (PCCE) for use in shape conformable all-solid-state lithium-ion batteries is demonstrated. This strategy is based on integration of a semi-interpenetrating polymer network (semi-IPN) matrix with a plastic crystal electrolyte (PCE, 1 M lithium bis-trifluoromethanesulfonimide in succinonitrile). In comparison to conventional carbonate-based electrolytes, salient benefits of the PCE are the thermal stability and nonflammability, which show promising potential as a safer electrolyte. The semi-IPN matrix in the PCCE is composed of a UV (ultraviolet)-crosslinked ethoxylated trimethylolpropane triacrylate polymer network and polyvinylidene fluoride-co-hexafluoropropylene (as a linear polymer). Solid electrolyte properties of the PCCE are investigated in terms of plastic crystal behavior, mechanical bendability, and ionic transport. Owing to the presence of the anomalous semi-IPN matrix, the PCCE exhibits unprecedented improvement in bendability, along with affording high ionic conductivity. Based on this understanding of the PCCE characteristics, feasibility of applying the PCCE to solid electrolytes for lithium-ion batteries is explored. The facile ionic transport of the PCCE, in conjunction with suppressed growth of cell impedance during cycling, plays a crucial role in providing excellence in cell performance. These advantageous features of the PCCE are further discussed with an in-depth consideration of the semi-IPN matrix architecture and its specific interaction with the PCE.
    Energy & Environmental Science 03/2012; 5(4):6491-6499. · 11.65 Impact Factor
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    ABSTRACT: The deoxyribonucleic acid (DNA)-coated multi-walled carbon nanotube (MWNT) hybrid fibers were fabricated by wet-spinning method. The fibers were made up with entangled nanowire networks of DNA-coated MWNTs, and it shows a strain of ∼0.15% as electrochemical actuators under low potential cycling between 0 and −0.9 V versus Ag/AgCl in 2 M NaCl solution. The fibers also show good electric conductivity (∼60 S/cm) and capacitance (50 ± 5 F/g) behaviors. Based on the appropriation of its electro-chemo-mechanical systems, the DNA/MWNT fiber can be one of the new intelligent materials for biomedical application.
    Sensors and Actuators B Chemical 01/2012; 162(1):173-177. · 3.84 Impact Factor
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    ABSTRACT: Maleic Anhydride (MAH) was grafted onto poly(L-lactic acid) (PLLA) in the presence of dicumyl peroxide (DCP) as a radical initiator. The effect of the MAH and DCP concentrations on the grafting and the physical and mechanical properties of PLLA films were investigated. The glass transition temperature and crystallinity significantly decreased with addition of MAH. The thermal decomposition of the PLLA films was affected by the MAH content while the mechanical properties were almost unchanged. A slight increase in molecular weight was found, which could be attributed to either the MAH branching reaction or a possible crosslinking reaction between the PLLA chains increasing the chain entanglements.
    Polymer Testing. 12/2011;
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    ABSTRACT: A high-surface-area material has recently attracted interest in actuator systems. We report on improved performance of the simultaneous electrochemical linear actuation of conducting polymer (CP)/carbon nanotube (CNT) hybrid fibers using porous structured deoxyribonucleic acid (DNA) hydrogels. It was deduced that individual DNA-wrapped CNTs had efficiently doped the PPy on its inner and outer surface through the association of PPy with the DNA via a supramolecular interaction. To assess the potential of the PPy/DNA/CNT hybrid fibers for use in electrochemical capacitors and actuators, we showed that the redox response of the hybrid fibers was improved by the addition of DNA to the PPy/CNT film. The values of the measured electrochemical capacitance (∼371 F/g in a lithium bis(trifluoromethylsulfonyl)imide aqueous solution, where the joint mass of PPy, DNA, and CNT was considered) were higher than those of previous CNT/PPy composite films with a controlled pore size (∼250 F/g). The fibers showed actuation stability with an expansion and contraction of ∼4.41% under a low potential (±1 V). DNA/PPy/CNT hybrid fibers will form the basis for new intelligent materials for applications such as bio-artificial muscles.
    Sensors and Actuators B: Chemical. 01/2010;
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    ABSTRACT: Tough and soft: Highly porous, spongelike materials self-assemble by calcium ion condensation of DNA-wrapped carbon nanotubes (SWNTs-DNA; see picture, IL = ionic liquid). The toughness, modulus, and swellability of the electrically conductive sponges can be tuned by controlling the density and strength of interfiber junctions. The sponges have compliances similar to the softest natural tissue, while robust interfiber junctions give high toughness.
    Angewandte Chemie International Edition 04/2009; 48(28):5116-20. · 11.34 Impact Factor
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    ABSTRACT: The switching electrochemical property of an SWNT/DNA hybrid can be produced through reversible conformational changes between the closed and open state originating from the pH-responding i-motif DNA which significantly improves its molecular switching and stability by hydrophobic interactions with SWNTs.
    Chemical Communications 04/2009; · 6.38 Impact Factor
  • Advanced Materials 03/2009; 21(19):1907 - 1910. · 14.83 Impact Factor
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    ABSTRACT: DNA hydrogels which are composed of an entangled network without a crosslinker are synthesized and examined in regards to their sensitivity to salt and pH changes. The DNA hydrogel fibers only exhibited a marked response - that is a fast and large change in length - under biological conditions ([Na(+) ] = 0.15 M at pH = 7) and are therefore suitable materials for bio-inspired devices.
    Macromolecular Rapid Communications 01/2009; 30(6):430 - 434. · 4.93 Impact Factor
  • Macromolecular Rapid Communications 01/2009; 30(6). · 4.93 Impact Factor
  • Advanced Materials 01/2009; 21(19). · 14.83 Impact Factor
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    ABSTRACT: A reversible and robust electrochemical pH oscillator was achieved using an ethyl viologen/ionic liquid (IL) aqueous solution under an applied redox potential in a batch reactor, where the IL incorporated into the pH oscillator increased the stability of the pH oscillation by acting as an electron buffer solution.
    Langmuir 05/2008; 24(7):3562-5. · 4.38 Impact Factor

Publication Stats

129 Citations
135.15 Total Impact Points

Institutions

  • 2011–2014
    • Korea Institute of Industrial Technology
      Anzan, Gyeonggi Province, South Korea
  • 2003–2012
    • Hanyang University
      • Department of Biomedical Engineering
      Sŏul, Seoul, South Korea
  • 2010
    • Sungkyunkwan University
      • Department of Physiology
      Sŏul, Seoul, South Korea
  • 2009
    • Seoul National University
      • Department of Physiology
      Seoul, Seoul, South Korea
  • 2006
    • University of Wollongong
      • ARC Centre of Excellence for Electromaterials Science
      Wollongong, New South Wales, Australia