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353 results on '"Kim, Ji Man"'

24. Discovery of abnormal lithium-storage sites in molybdenum dioxide electrodes.

Author

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

Abstract

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.

Published
2016

39. Facile Synthesis of Mesoporous Nanohybrid Two-Dimensional Layered Ni-Cr-S and Reduced Graphene Oxide for High-Performance Hybrid Supercapacitors.

Author

Bulakhe, Ravindra N., Nguyen, Anh Phan, Ryu, Changyoung, Kim, Ji Man, and In, Jung Bin

Subjects
ENERGY density, SUPERCAPACITORS, POWER density, MESOPOROUS materials, GRAPHENE synthesis, SURFACE area, IMPEDANCE spectroscopy
Abstract

This study describes the single-step synthesis of a mesoporous layered nickel-chromium-sulfide (NCS) and its hybridization with single-layered graphene oxide (GO) using a facile, inexpensive chemical method. The conductive GO plays a critical role in improving the physicochemical and electrochemical properties of hybridized NCS/reduced GO (NCSG) materials. The optimized mesoporous nanohybrid NCSG is obtained when hybridized with 20% GO, and this material exhibits a very high specific surface area of 685.84 m2/g compared to 149.37 m2/g for bare NCS, and the pore diameters are 15.81 and 13.85 nm, respectively. The three-fold superior specific capacity of this optimal NCSG (1932 C/g) is demonstrated over NCS (676 C/g) at a current density of 2 A/g. A fabricated hybrid supercapacitor (HSC) reveals a maximum specific capacity of 224 C/g at a 5 A/g current density. The HSC reached an outstanding energy density of 105 Wh/kg with a maximum power density of 11,250 W/kg. A 4% decrement was observed during the cyclic stability study of the HSC over 5000 successive charge–discharge cycles at a 10 A/g current density. These results suggest that the prepared nanohybrid NCSG is an excellent cathode material for gaining a high energy density in an HSC. [ABSTRACT FROM AUTHOR]

Published
2023
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