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Hierarchical Porous Carbon Nanotube Particles for Lithium-Sulfur Batteries
권동휘,문준혁 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
A carbon host capable of effective sulfur loading is the key for lithium-sulfur(Li-S) batteries. Despite the various application of porous carbon materials, the carbon hosts capable of uniformly impregnating sulfur is still challenging. To address this issue, we demonstrate a CNT particles containing spherical macropores. The spherical macropores improve the penetration of sulfur into the carbon nanotube matrix. Consequently, The S-loaded CNT particle cathode shows a highly reversible capacity of 1343 mAh/g at a current density even with 70wt% of sulfur contents.
권동휘,문준혁,주민영 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-
Fully-incorporated and high-content sulfur in porous carbon is crucial for high performance Li-S batteries. To this end, unlike conventional methods to control the pore of carbon hosts, we demonstrate controlling the surface tension of the solution in the process of penetrating the sulfur-dissolved solution. We find, experimentally and theoretically, that the interfacial energy with the carbon surface of the sulfur solution is the key to driving complete encapsulation of sulfur. In the penetration of sulfur solutions with N-methyl-2-pyrrolidone, we obtain complete encapsulation of sulfur, even up to 85 wt %. The sulfur fully incorporated cathode achieves remarkably high volumetric capacity and stable cycle property in its Li-S battery applications. We achieve a volumetric capacity of 855 mAh/㎤ at 0.2C and a capacity reduction of 0.071% per cycle up to 300 cycles at 1C.
Si nanoparticle-nested CNT particles for high capacity Li-ion Batteries
권동휘,문준혁 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
Silicon-porous carbon is the most promising anode material for high capacity lithium batteries. Previous approaches have been complicated and usually hard to making scale-up production. To address this issue, we present simple but rationally designed nanostructured anodes comprised of Si nanoparticle-nested CNT particles (Si/CNTPs). Additionally, the Si / CNTP was coated with polydopamine (PD) to inhibit the formation of a solid-electrolyte interphase layer. Our Si/CNTP anode showed a capacity of 795 mAh/g after 300 cycles.
High Performance Supercapacitors based on CNT/MnO<sub>2</sub> Nanoflake particles
황정태,권동휘,문준혁 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
We introduce CNT/MnO<sub>2</sub> particles for high-performance supercapacitors. We prepare the CNT particles and grow MnO<sub>2</sub> shell on the particle. We control the amount of MnO<sub>2</sub> content on the CNT particles and characterize the effect on specific capacitance. We observe the capacitance 14 times higher than that of bare CNT particles. We apply CNT / MnO<sub>2</sub> particles to supercapacitors. We achieve high power density, which is attributed to the contribution of the high pseudocapacitance of a compact MnO<sub>2</sub> nanoflake and the high electrical conductivity of CNT particles with dense packing.
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형남원,최경욱,권동휘 금융감독원 2018 금융감독연구 Vol.5 No.2
As early warning indicators of systemic risk, 'Credit/GDP ratio' and ' Credit/GDP gap' forecasting models are developed and compared in this study. To use all possible information, we combine the dynamic factor model and the MIDAS model to improve predictive power. In conclusion, the ‘Credit/GDP ratio’ forecast, the GRS-dms model and the GRS-MIDAS models predictability are relatively superior. In the forecast of 'Credit/GDP gap', the GRS-dms model predictability is superior to that of other models.