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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.
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>
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, 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>
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>
Highly Stable Iron- and Manganese-Based Cathodes for Long-Lasting Sodium Rechargeable Batteries
Kim, Hyungsub,Yoon, Gabin,Park, Inchul,Hong, Jihyun,Park, Kyu-Young,Kim, Jongsoon,Lee, Kug-Seung,Sung, Nark-Eon,Lee, Seongsu,Kang, Kisuk American Chemical Society 2016 Chemistry of materials Vol.28 No.20
<P>The development of long-lasting and low-cost rechargeable batteries lies at the heart of the success of large-scale energy storage systems for various applications. Here, we introduce Fe- and Mn-based Na rechargeable battery cathodes that can stably cycle more than 3000 times. The new cathode is based on the solid-solution phases of Na4MnxFe3-x(PO4)(2)-(P2O7) (x = 1 or 2) that we successfully synthesized for the first time. Electrochemical analysis and ex situ structural investigation reveal that the electrodes operate via a one phase reaction upon charging and discharging with a remarkably low volume change of 2.1% for Na4MnFe2(PO4)(P2O7), which is one of the lowest values among Na battery cathodes reported thus far. With merits including an open framework structure and a small volume change, a stable cycle performance up to 3000 cycles can be achieved at 1C and room temperature, and almost 70% of the capacity at C/20 can be obtained at 20C. We believe that these materials are strong competitors for large-scale Na-ion battery cathodes based on their low costs, long-term cycle stability, and high energy density.</P>
Kim, Jongsoon,Kim, Hyungsub,Myung, Seung-Taek,Yoo, Jung-Keun,Lee, Seongsu Elsevier Sequoia 2018 Journal of Power Sources Vol. No.
<P><B>Abstract</B></P> <P>Mn-rich olivine LiFe<SUB>0.3</SUB>Mn<SUB>0.7</SUB>PO<SUB>4</SUB> is homogenously encapsulated by an ∼3-nm-thick conductive nanolayer composed of the glassy lithium fluorophosphate through simple non-stoichiometric synthesis using additives of small amounts of LiF and a phosphorus source. The coating of the glassy lithium fluorophosphate nanolayer is clearly verified using transmission electron microscopy and X-ray photoelectron spectroscopy. It enables significant decrease in charge transfer resistance of LiFe<SUB>0.3</SUB>Mn<SUB>0.7</SUB>PO<SUB>4</SUB> and improvement of its sluggish Li diffusion. At a rate of 10C, the LiFe<SUB>0.3</SUB>Mn<SUB>0.7</SUB>PO<SUB>4</SUB> encapsulated by conductive glassy lithium fluorophosphate (LiFe<SUB>0.3</SUB>Mn<SUB>0.7</SUB>PO<SUB>4</SUB>-GLFP) electrode delivers a capacity of ∼130 mAh g<SUP>−1</SUP>, which is ∼77% of its theoretical capacity (∼170 mAh g<SUP>−1</SUP>) and ∼1.5 times higher than that of the pristine counterpart at 10C. Furthermore, LiFe<SUB>0.3</SUB>Mn<SUB>0.7</SUB>PO<SUB>4</SUB>-GLFP achieves outstanding cycle stability (∼75% retention of its initial capacity over 500 cycles at 1C). The proposed olivine LiFe<SUB>0.3</SUB>Mn<SUB>0.7</SUB>PO<SUB>4</SUB>-GLFP battery is thus expected to be a promising candidate for large-scale energy storage applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Simple coating of glassy lithium fluorophosphates. </LI> <LI> Excellent power capability (∼130 mAh g<SUP>−1</SUP> at 10C). </LI> <LI> Great cyclability (∼75% retention of its initial capacity over 500 cycles at 1C). </LI> </UL> </P>
Kim, Jongsoon,Kim, Hyungsub,Lee, Seongsu American Chemical Society 2017 Chemistry of materials Vol.29 No.8
<P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2017/cmatex.2017.29.issue-8/acs.chemmater.6b04557/production/images/medium/cm-2016-045575_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm6b04557'>ACS Electronic Supporting Info</A></P>