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Kim, Jongsoon,Lee, Byungju,Kim, Hyungsub,Kim, Hyunah,Kang, Kisuk American Chemical Society 2016 Chemistry of materials Vol.28 No.19
<P>Defects in crystals such as antisites generally lead-to the deterioration of the ionic conductivity of solid-state ionic conductors. Herein, using first principles calculations, we demonstrate that the Li diffusion in Li2MP2O7 (M = Fe or Mn), a promising battery material, is sensitively affected by the presence of Li/M antisites; however, unexpectedly, the antisites significantly promote Li diffusion. The calculations reveal that the presence of antisites reduces the barrier of Li hopping and opens new paths for Li diffusion in the Li2MP2O7 crystal. In our experimental verification, we succeeded in synthesizing crystalline Li2MnP2O7 with varying Li/Mn antisite contents and demonstrated that the inclusion of antisites results in improved power capability with faster Li diffusion for Li-ion battery electrodes. We believe that this unexpected finding of increasing the ionic conductivity by introducing antisite defects broadens our understanding of solid-state ionic conductors and provides a new strategy for improving Li diffusion in conventional electrode materials for Li rechargeable batteries.</P>
Kim, Hyeri,Kim, Jongsoon,Jeong, Hee-Sung,Kim, Hyungsub,Lee, Hoyeon,Ha, Jae-Min,Choi, Sung-Min,Kim, Tae-Ho,Nah, Yoon-Chae,Shin, Tae Joo,Bang, Joona,Satija, Sushil K.,Koo, Jaseung The Royal Society of Chemistry 2018 Chemical communications Vol.54 No.41
<P>We demonstrate that hybrid structures of graphene and single-walled carbon nanotubes (SWNTs) are precisely controlled at the liquid-gas interface. The functionalized SWNT Langmuir monolayers anchor single-layer graphene nanosheets (GNSs) suspended in water <I>via</I> Coulomb interaction at the interface. This GNS/SWNT hybrid multilayer electrode can be a promising anode material for Li-ion batteries, offering high specific capacity, outstanding power capability, and excellent cyclability.</P>
Kim, Jinsoo,Yoon, Sanghoon,Yoo, Jung-Keun,Kim, Jongsoon,Kim, Haegyeom,Kang, Kisuk The Korean Electrochemical Society 2012 Journal of electrochemical science and technology Vol.3 No.2
The electrospinning technique is a revolutionary template-catalyst-free method that can generate 1D nanostructure with the tunability and the potential for the mass production. This approach received a great deal of attention due to its ability to give direct pathways for electrical current and has been utilized in various electronic applications. However, the delamination of inorganic electrospun film has prevented the intense utilization due to the thermal expansion/contraction during the calcination. In this study, we propose an electrical grounding method for transparent conducting oxide and electrospun nanowires to enhance the adhesion after the calcination. Then, we examined the potential of the technique on ZnO based dye-sensitized solar cells.
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>
Kim, Haegyeom,Seo, Dong-Hwa,Kim, Sung-Wook,Kim, Jongsoon,Kang, Kisuk Elsevier 2011 Carbon Vol.49 No.1
<P><B>Graphical abstract</B></P><P><ce:figure id='f0045'></ce:figure></P><P><B>Research highlights</B></P><P>► Co<SUB>3</SUB>O<SUB>4</SUB>/graphene hybrid is fabricated using a simple in situ reduction process. ► The hybrid consists of 5nm size Co<SUB>3</SUB>O<SUB>4</SUB> particles uniformly dispersed on graphene. ► The hybrid showed excellent electrochemical performance as an anode.</P> <P><B>Abstract</B></P><P>A Co<SUB>3</SUB>O<SUB>4</SUB>/graphene hybrid material was fabricated using a simple in situ reduction process and demonstrated as a highly reversible anode for lithium rechargeable batteries. The hybrid is composed of 5nm size Co<SUB>3</SUB>O<SUB>4</SUB> particles uniformly dispersed on graphene, as observed by transmission electron microscopy, atomic force microscopy, Raman spectroscopy and X-ray diffraction analysis. The Co<SUB>3</SUB>O<SUB>4</SUB>/graphene anode can deliver a capacity of more than 800mAhg<SUP>−1</SUP> reversibly at a 200mAg<SUP>−1</SUP> rate in the voltage range between 3.0 and 0.001V. The high reversible capacity is retained at elevated current densities. At a current rate as high as 1000mAg<SUP>−1</SUP>, the Co<SUB>3</SUB>O<SUB>4</SUB>/graphene anode can deliver more than 550mAhg<SUP>−1</SUP>, which is significantly higher than the capacity of current commercial graphite anodes. The superior electrochemical performance of the Co<SUB>3</SUB>O<SUB>4</SUB>/graphene is attributed to its unique nanostructure, which intimately combines the conductive graphene network with uniformly dispersed nano Co<SUB>3</SUB>O<SUB>4</SUB> particles.</P>
Understanding Phytosanitary Irradiation Treatment of Pineapple Using Monte Carlo Simulation
Kim, Jongsoon,Kwon, Soon-Hong,Chung, Sung-Won,Kwon, Soon-Goo,Park, Jong-Min,Choi, Won-Sik Korean Society for Agricultural Machinery 2013 바이오시스템공학 Vol.38 No.2
Purpose: Pineapple is now the third most important tropical fruit in world production after banana and citrus. Phytosanitary irradiation is recognized as a promising alternative treatment to chemical fumigation. However, most of the phytosanitary irradiation studies have dealt with physiochemical properties and its efficacy. Accurate dose calculation is crucial for ensuring proper process control in phytosanitary irradiation. The objective of this study was to optimize phytosanitary irradiation treatment of pineapple in various radiation sources using Monte Carlo simulation. Methods: 3-D geometry and component densities of the pineapple, extracted from CT scan data, were entered into a radiation transport Monte Carlo code (MCNP5) to obtain simulated dose distribution. Radiation energy used for simulation were 2 MeV (low-energy) and 10 MeV (high-energy) for electron beams, 1.25 MeV for gamma-rays, and 5 MeV for X-rays. Results: For low-energy electron beam simulation, electrons penetrated up to 0.75 cm from the pineapple skin, which is good for controlling insect eggs laid just below the fruit surface. For high-energy electron beam simulation, electrons penetrated up to 4.5 cm and the irradiation area occupied 60.2% of the whole area at single-side irradiation and 90.6% at double-side irradiation. For a single-side only gamma- and X-ray source simulation, the entire pineapple was irradiated and dose uniformity ratios (Dmax/Dmin) were 2.23 and 2.19, respectively. Even though both sources had all greater penetrating capability, the X-ray treatment is safer and the gamma-ray treatment is more widely used due to their availability. Conclusions: These results are invaluable for optimizing phytosanitary irradiation treatment planning of pineapple.