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Dive into the research topics where Gwi Ok Park is active.

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Featured researches published by Gwi Ok Park.


Nature Communications | 2016

Discovery of abnormal lithium-storage sites in molybdenum dioxide electrodes

Jeong Kuk Shon; Hyo Sug Lee; Gwi Ok Park; Jeongbae Yoon; Eunjun Park; Gyeong Su Park; Soo Sung Kong; Mingshi Jin; Jae-Man Choi; Hyuk Chang; Seok-Gwang Doo; Ji Man Kim; Won-Sub Yoon; Chanho Pak; Hansu Kim; Galen D. Stucky

Developing electrode materials with high-energy densities is important for the development of lithium-ion batteries. Here, we demonstrate a mesoporous molybdenum dioxide material with abnormal lithium-storage sites, which exhibits a discharge capacity of 1,814 mAh g−1 for the first cycle, more than twice its theoretical value, and maintains its initial capacity after 50 cycles. Contrary to previous reports, we find that a mechanism for the high and reversible lithium-storage capacity of the mesoporous molybdenum dioxide electrode is not based on a conversion reaction. Insight into the electrochemical results, obtained by in situ X-ray absorption, scanning transmission electron microscopy analysis combined with electron energy loss spectroscopy and computational modelling indicates that the nanoscale pore engineering of this transition metal oxide enables an unexpected electrochemical mass storage reaction mechanism, and may provide a strategy for the design of cation storage materials for battery systems.


ACS Nano | 2015

In Operando Monitoring of the Pore Dynamics in Ordered Mesoporous Electrode Materials by Small Angle X-ray Scattering.

Gwi Ok Park; Jeongbae Yoon; Eunjun Park; Su Bin Park; Hyunchul Kim; Kyoung Ho Kim; Xing Jin; Tae Joo Shin; Hansu Kim; Won-Sub Yoon; Ji Man Kim

To monitor dynamic volume changes of electrode materials during electrochemical lithium storage and removal process is of utmost importance for developing high performance lithium storage materials. We herein report an in operando probing of mesoscopic structural changes in ordered mesoporous electrode materials during cycling with synchrotron-based small angel X-ray scattering (SAXS) technique. In operando SAXS studies combined with electrochemical and other physical characterizations straightforwardly show how porous electrode materials underwent volume changes during the whole process of charge and discharge, with respect to their own reaction mechanism with lithium. This comprehensive information on the pore dynamics as well as volume changes of the electrode materials will not only be critical in further understanding of lithium ion storage reaction mechanism of materials, but also enable the innovative design of high performance nanostructured materials for next generation batteries.


RSC Advances | 2016

Mesoporous transition metal dichalcogenide ME2 (M = Mo, W; E = S, Se) with 2-D layered crystallinity as anode materials for lithium ion batteries

Yoon Yun Lee; Gwi Ok Park; Yun Seok Choi; Jeong Kuk Shon; Jeongbae Yoon; Kyoung Ho Kim; Won-Sub Yoon; Hansu Kim; Ji Man Kim

Mesoporous transition metal dichalcogenides (TMDCs), composed of group VI metals (Mo and W) and chalcogens (S and Se), with 2-D layered crystalline frameworks and 3-D pore structures were successfully prepared via a melting-infiltration assisted nano-replication method using a mesoporous template KIT-6 with cubic Ia3d symmetry. Combined analysis using X-ray diffraction, N2 adsorption–desorption and electron microscopy indicated that the mesoporous TMDCs, thus obtained, exhibited high surface areas (87–105 m2 g−1), large pore volumes (0.21–0.25 cm3 g−1) and well-defined mesopores about 20 nm in diameters. The mesoporous TMDCs showed outstanding rate capabilities up to 2C as well as high reversible lithium storage capacities (MoS2 710 mA h g−1; MoSe2 744 mA h g−1; WS2 501 mA h g−1; WSe2 427 mA h g−1) without a remarkable fading of capacity.


NANO | 2015

Highly Ordered Mesoporous Antimony-Doped SnO2 Materials for Lithium-ion Battery

Gwi Ok Park; Eunbyeol Hyung; Jeong Kuk Shon; Hansu Kim; Ji Man Kim

Highly ordered mesoporous antimony-doped tin oxide (ATO) materials, containing different amount of antimony in the range of 0–50mol%, are prepared via a nanoreplication method using a mesoporous silica template. The mesoporous ATO materials thus obtained exhibit high electrical conductivity, high reversible capacity, superior cycle stability and good rate capability as anode materials for lithium-ion batteries, compared to those of pure mesoporous tin oxide. Amongst the ATO materials in this work, the mesoporous ATO material with 10mol% of antimony has highest discharge capacity of 1940mAhg-1 (charge capacity of 1049) at the 1st cycle, best cycle performance (716mAhg-1 at 100th cycle) and excellent rate capability, which are probably due to the enhanced electrical conductivity as well as reduced crystalline size.


ACS Nano | 2018

Exceptional Lithium Storage in a Co(OH)2 Anode: Hydride Formation

Hyunchul Kim; Woon Ih Choi; Yoonjung Jang; Mahalingam Balasubramanian; Wontae Lee; Gwi Ok Park; Su Bin Park; Jaeseung Yoo; Jin Seok Hong; Youn Suk Choi; Hyo Sug Lee; In Tae Bae; Ji Man Kim; Won-Sub Yoon

Current lithium ion battery technology is tied in with conventional reaction mechanisms such as insertion, conversion, and alloying reactions even though most future applications like EVs demand much higher energy densities than current ones. Exploring the exceptional reaction mechanism and related electrode materials can be critical for pushing current battery technology to a next level. Here, we introduce an exceptional reaction with a Co(OH)2 material which exhibits an initial charge capacity of 1112 mAh g-1, about twice its theoretical value based on known conventional conversion reaction, and retains its first cycle capacity after 30 cycles. The combined results of synchrotron X-ray diffraction and X-ray absorption spectroscopy indicate that nanosized Co metal particles and LiOH are generated by conversion reaction at high voltages, and Co xH y, Li2O, and LiH are subsequently formed by hydride reaction between Co metal, LiOH, and other lithium species at low voltages, resulting in a anomalously high capacity beyond the theoretical capacity of Co(OH)2. This is further corroborated by AIMD simulations, localized STEM, and XPS. These findings will provide not only further understanding of exceptional lithium storage of recent nanostructured materials but also valuable guidance to develop advanced electrode materials with high energy density for next-generation batteries.


Small | 2018

Nanostructural Uniformity of Ordered Mesoporous Materials: Governing Lithium Storage Behaviors

Gwi Ok Park; Jeongbae Yoon; Su Bin Park; Zhenghua Li; Yun Seok Choi; Won-Sub Yoon; Hansu Kim; Ji Man Kim

Nanostructured materials make a considerable impact on the performance of lithium-storage characteristics in terms of the energy density, power density, and cycle life. Direct experimental observation, by a comparison of controlled nanostructural uniformity of electrode materials, reveals that the lithium-storage behaviors of mesoporous MoO2 and CuO electrodes are linearly correlated with their nanostructural uniformity. Reversible capacities of mesoporous MoO2 and CuO electrodes with well-developed nanostructures (1569 mA h g-1 for MoO2 and 1029 mA h g-1 for CuO) exceed their theoretical capacity based on the conversion reaction (838 mA h g-1 for MoO2 and 674 mA h g-1 for CuO). Given that exact understanding of the origin of the additional capacity is essential in maximizing the energy density of electrode material, this work may help to gain some insights into the development of high energy-density lithium-storage materials for next-generation lithium rechargeable batteries.


Chemistry of Materials | 2014

New Insight into the Reaction Mechanism for Exceptional Capacity of Ordered Mesoporous SnO2 Electrodes via Synchrotron-Based X-ray Analysis

Hyunchul Kim; Gwi Ok Park; Yunok Kim; Shoaib Muhammad; Jaeseung Yoo; Mahalingam Balasubramanian; Yong-Hun Cho; Min-Gyu Kim; Byungju Lee; Kisuk Kang; Hansu Kim; Ji Man Kim; Won-Sub Yoon


Chemistry Letters | 2010

Highly Ordered Mesoporous .ALPHA.-Mn2O3 for Catalytic Decomposition of H2O2 at Low Temperatures

Jung-Nam Park; Jeong Kuk Shon; Mingshi Jin; Seong Hee Hwang; Gwi Ok Park; Jin-Hyo Boo; Tae Hee Han; Ji Man Kim


Advanced Functional Materials | 2016

Discovering a Dual-Buffer Effect for Lithium Storage: Durable Nanostructured Ordered Mesoporous Co–Sn Intermetallic Electrodes

Gwi Ok Park; Jeongbae Yoon; Jeong Kuk Shon; Yun Seok Choi; Jong Gu Won; Su Bin Park; Kyoung Ho Kim; Hansu Kim; Won-Sub Yoon; Ji Man Kim


Journal of Physical Chemistry C | 2017

Visible-Light Driven Photocatalytic Degradation of Organic Dyes over Ordered Mesoporous CdxZn1–xS Materials

Yoon Yun Lee; Jong Hun Moon; Yun Seok Choi; Gwi Ok Park; Mingshi Jin; Long Yi Jin; Donghao Li; Jin Yong Lee; Seung Uk Son; Ji Man Kim

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Ji Man Kim

Sungkyunkwan University

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Won-Sub Yoon

Sungkyunkwan University

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Su Bin Park

Sungkyunkwan University

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Hyunchul Kim

Chonnam National University

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Yunok Kim

Sungkyunkwan University

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