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Surface dipole enhanced instantaneous charge pair generation in triboelectric nanogenerator
Kim, Kyeong Nam,Jung, Yun Kyung,Chun, Jinsung,Ye, Byeong Uk,Gu, Minsu,Seo, Eunyong,Kim, Seongsu,Kim, Sang-Woo,Kim, Byeong-Su,Baik, Jeong Min Elsevier 2016 Nano energy Vol.26 No.-
<P><B>Abstract</B></P> <P>Developing a successful strategy to maximize the surface charge density is crucial to speed-up the commercialization success of triboelectric nanogenerator. Here, for the first time, the fabrication of positive triboelectric material to donate electrons efficiently to dielectrics is reported, by increasing the stretchability for the uniform contact and by introducing a functional group for the surface potential control. A highly stretchable and conductive film with Ag nanowires and PDMS was fabricated as a base material, in which the portion of nanowires exposed above the embedding surface should be accurately controlled. In specific, positively charged 4-(dimethylamino)pyridine (DMAP) coated Au nanoparticles, prepared by phase transfer method, are coated. The DMAP lowers the effective work function of the nanoparticles by a permanent dipole induced at the DMAP-Au interface and enhances the electron transfer to the dielectrics, confirmed by the Kelvin probe force microscope measurement. The designed nanogenerator gives an output performance up to 80V and 86μA, and 2.5mW in output power, 2.5 times enhancement compared with the conventional TENG. With the integration with AC to DC converting circuit and buck-boost circuit, the nanogenerator produces a constant voltage of 2.6V. The wireless sensing system, which operates the remote controller, were also demonstrated, turning on a siren.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A positive triboelectric material to donate electrons efficiently to dielectrics is developed. </LI> <LI> The keynote is to increase the stretchability and to introduce a functional group. </LI> <LI> It was proven to be effective for the uniform contact and surface potential control. </LI> <LI> The TENG gave an output performance up to 80 V and 86 μA, and 2.5 mW in output power. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Seongsu Kang,Bolam Kim,Se-Jun Yim,Jin-Oh Kim,Dong-Pyo Kim,Yeu-Chun Kim 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.88 No.-
Electroporation technique has recently emerged as a tool for delivery of foreign molecules into cells. However, the electroporation has many critical hurdles to overcome in cell viability, delivery efficiency,and productivity. To overcome the hurdles with a single platform, we devised a polyimide (PI)film-basedon- chip electroporation system that shields the cells from the electrodes with four sheathflows,enabling a 3Dflow focusing. This on-chip electroporation with a double forced-flow (OE-DFF)configuration enhances the cell viability to such an extent that even with a long spiral channel for highmolecular delivery efficiency, which is detrimental to the cell viability due to longer exposure to theelectricfield, the cell viability is still increased substantially. The advantages provided by the OE-DFFsystem is demonstrated with afluorescent probe molecule (FITC-BSA) and pPtCrCFP plasmid deliveredinto Chlamydomonas reinhardtii, one of the challenging cell lines to transform. The continuous nature oftheflow system assures high throughput. This novel approach in microfluidic science is expected togreatly contribute to algal research as an efficient electroporation tool as well as to broad applications.
SEONGSU KIM,DANIEL C. FELDMAN 한국고용노사관계학회 2001 한국노사관계학회 학술대회 Vol.2001 No.6
This study uses a continuity theory of aging to understand when individuals will pursue bridge employment and the role which bridge employment plays in adjustment to retirement. Results suggest that employees with better health, greater organizational tenure, working spouses, and dependent children were more likely to take bridge employment, while age and salary at time of retirement were inversely related to extent of bridge employment. Moreover, bridge employment is strongly related to both retirem ent satisfaction and overall life satisfaction. In addition, volunteer work and leisure activity complement bridge employment in facilitating adjustment to retirement. Implications of the results for future theory development, methodological improvement, and management practice are discussed as well.
Kim, Hyungsub,Park, Inchul,Seo, Dong-Hwa,Lee, Seongsu,Kim, Sung-Wook,Kwon, Woo Jun,Park, Young-Uk,Kim, Chul Sung,Jeon, Seokwoo,Kang, Kisuk American Chemical Society 2012 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.134 No.25
<P>New iron-based mixed-polyanion compounds Li<SUB><I>x</I></SUB>Na<SUB>4–<I>x</I></SUB>Fe<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>(P<SUB>2</SUB>O<SUB>7</SUB>) (<I>x</I> = 0–3) were synthesized, and their crystal structures were determined. The new compounds contained three-dimensional (3D)sodium/lithium paths supported by P<SUB>2</SUB>O<SUB>7</SUB> pillars in the crystal. First principles calculations identified the complex 3D paths with their activation barriers and revealed them as fast ionic conductors. The reversible electrode operation was found in both Li and Na cells with capacities of one-electron reaction per Fe atom, 140 and 129 mAh g<SUP>–1</SUP>, respectively. The redox potential of each phase was ∼3.4 V (vs Li) for the Li-ion cell and ∼3.2 V (vs Na) for the Na-ion cell. The properties of high power, small volume change, and high thermal stability were also recognized, presenting this new compound as a potential competitor to other iron-based electrodes such as Li<SUB>2</SUB>FeP<SUB>2</SUB>O<SUB>7</SUB>, Li<SUB>2</SUB>FePO<SUB>4</SUB>F, and LiFePO<SUB>4</SUB>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2012/jacsat.2012.134.issue-25/ja3038646/production/images/medium/ja-2012-038646_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja3038646'>ACS Electronic Supporting Info</A></P>
Anomalous Jahn–Teller behavior in a manganese-based mixed-phosphate cathode for sodium ion batteries
Kim, Hyungsub,Yoon, Gabin,Park, Inchul,Park, Kyu-Young,Lee, Byungju,Kim, Jongsoon,Park, Young-Uk,Jung, Sung-Kyun,Lim, Hee-Dae,Ahn, Docheon,Lee, Seongsu,Kang, Kisuk The Royal Society of Chemistry 2015 ENERGY AND ENVIRONMENTAL SCIENCE Vol.8 No.11
<P>We report a 3.8 V manganese-based mixed-phosphate cathode material for applications in sodium rechargeable batteries; i.e., Na4Mn3(PO4)(2)(P2O7). This material exhibits a largest Mn2+/Mn3+ redox potential of 3.84 V vs. Na+/Na yet reported for a manganese-based cathode, together with the largest energy density of 416 W h kg (1). We describe first-principles calculations and experimental results which show that three-dimensional Na diffusion pathways with low-activation-energy barriers enable the rapid sodium insertion and extraction at various states of charge of the Na4-xMn3(PO4)(2)(P2O7) electrode (where x = 0, 1, 3). Furthermore, we show that the sodium ion mobility in this crystal structure is not decreased by the structural changes induced by Jahn-Teller distortion (Mn3+), in contrast to most manganese-based electrodes, rather it is increased due to distortion, which opens up sodium diffusion channels. This feature stabilizes the material, providing high cycle stability and high power performance for sodium rechargeable batteries. The high voltage, large energy density, cycle stability and the use of low-cost Mn give Na4Mn3(PO4)(2)(P2O7) significant potential for applications as a cathode material for large-scale Na-ion batteries.</P>
LiFePO<sub>4</sub> with an alluaudite crystal structure for lithium ion batteries
Kim, Jongsoon,Kim, Hyungsub,Park, Inchul,Park, Young-Uk,Yoo, Jung-Keun,Park, Kyu-Young,Lee, Seongsu,Kang, Kisuk The Royal Society of Chemistry 2013 Energy & environmental science Vol.6 No.3
<P>A novel Na-pillared LiFePO<SUB>4</SUB> with an alluaudite structure is reported and its structure is investigated. The alluaudite-LiFePO<SUB>4</SUB> allowed fast lithium diffusion with stable electrochemical cycling in lithium batteries. ∼0.8 Li<SUP>+</SUP> could be extracted and reinserted reversibly for extended cycles <I>via</I> one-phase reaction in contrast to the well-known two-phase reaction in olivine-LiFePO<SUB>4</SUB>.</P> <P>Graphic Abstract</P><P>The novel alluaudite-LiFePO<SUB>4</SUB> allows fast lithium diffusion with stable electrochemical cycling as a cathode in lithium batteries. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3ee24393a'> </P>
New 4V-Class and Zero-Strain Cathode Material for Na-Ion Batteries
Kim, Jongsoon,Yoon, Gabin,Lee, Myeong Hwan,Kim, Hyungsub,Lee, Seongsu,Kang, Kisuk American Chemical Society 2017 Chemistry of materials Vol.29 No.18
<P>Here, we introduce Na<SUB>3</SUB>V(PO<SUB>3</SUB>)<SUB>3</SUB>N as a novel 4V-class and zero-strain cathode material for Na-ion batteries. Structural analysis based on a combination of neutron and X-ray diffraction (XRD) reveals that the Na<SUB>3</SUB>V(PO<SUB>3</SUB>)<SUB>3</SUB>N crystal contains three-dimensional channels that are suitable for facile Na diffusion. The Na (de)intercalation is observed to occur at ∼4 V vs Na/Na<SUP>+</SUP> in the Na cell via the V<SUP>3+</SUP>/V<SUP>4+</SUP> redox reaction with ∼67% retention of the initial capacity after over 3000 cycles. The remarkable cycle stability is attributed to the near-zero volume change (∼0.24%) and unique centrosymmetric distortion that occurs during a cycle despite the large ionic size of Na ions for (de)intercalation, as demonstrated by <I>ex situ</I> XRD analysis and first-principles calculations. We also demonstrate that the Na<SUB>3</SUB>V(PO<SUB>3</SUB>)<SUB>3</SUB>N electrode can display outstanding power capability with ∼84% of the theoretical capacity retained at 10C, even though the particle sizes are on the micrometer scale (>5 μm), which is attributed to its intrinsic three-dimensional open-crystal framework. The combination of this high power capability and extraordinary cycle stability makes Na<SUB>3</SUB>V(PO<SUB>3</SUB>)<SUB>3</SUB>N a new potential cathode material for Na-ion batteries.</P> [FIG OMISSION]</BR>
Kim, Jongsoon,Kim, Hyungsub,Lee, Seongsu,Myung, Seung-Taek Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.42
<▼1><P>Na2Fe1.96V0.96(PO4)3 (NFVP) that exhibits outstanding cycle life and great power capability with a high redox potential for the first time.</P></▼1><▼2><P>We report Na2Fe1.96V0.96(PO4)3 (NFVP) as a new cathode material for Na ion batteries with outstanding cycle life and high power density for the first time. Structural characterization of NFVP was performed using Rietveld refinement of X-ray diffraction and neutron diffraction patterns, which revealed large Na diffusion paths in the structure that enabled rapid Na (de)intercalation without a large volume change. Using X-ray diffraction and X-ray photoelectron spectroscopy with charge/discharge measurements, it was confirmed that based on redox reactions of Fe and V ions, ∼2 Na ions are reversibly (de)intercalated from the structure with an average voltage of ∼3.1 V (<I>vs.</I> Na<SUP>+</SUP>/Na). At 30C, which denotes the rapid charge/discharge, ∼74% of the theoretical capacity was delivered. Furthermore, NFVP exhibited an outstanding cycle life of over 2500 cycles (∼70% retention of the initial capacity), which can be attributed to the low volume change (∼1%) during charge/discharge.</P></▼2>