7 results on '"Jaegu Yoon"'
Search Results
2. Transition Metal Ordering Optimization for High-Reversible Capacity Positive Electrode Materials in the Li–Ni–Co–Mn Pseudoquaternary System
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Dong Hee Yeon, Fantai Kong, Chaoping Liang, Seok-Gwang Doo, Jaegu Yoon, Kyeongjae Cho, Jin Hwan Park, and Roberto C. Longo
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Electrode material ,Materials science ,Oxide ,Ionic bonding ,Thermodynamics ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Atomic units ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,General Energy ,Transition metal ,chemistry ,Structural stability ,Physical and Theoretical Chemistry ,0210 nano-technology ,Phase diagram - Abstract
The phase diagram of the Li–Ni–Co–Mn layered oxide pseudoquaternary system is used as starting point to elucidate the influence of transition metal (TM) ordering on the structures and electrochemistry of positive electrode materials with LiNi1–y–xCoyMnxO2 composition. Whereas our obtained phase diagram shows a comprehensive search of the most suitable target compositions for single-phase layered materials with large structural stability and reversible capacity, a detailed analysis of the transition metal ordering tries to fill the gap existing in the literature between transition metal composition and ordering, showing the effect on the electrochemical performance. Our results demonstrate that, in order to achieve high reversible capacities, control of the TM arrangement at the atomic scale seems to be crucial to enhance both ionic and electronic mobilities, thus maximizing the rate capability and structural stability during cycling.
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- 2016
3. A large-scale simulation method on complex ternary Li–Mn–O compounds for Li-ion battery cathode materials
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Kyeongjae Cho, Seok-Gwang Doo, Byeongchan Lee, Dong Hee Yeon, Fantai Kong, Hengji Zhang, Jin Hwan Park, Roberto C. Longo, and Jaegu Yoon
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Battery (electricity) ,Materials science ,General Computer Science ,Oxide ,Ab initio ,General Physics and Astronomy ,Ionic bonding ,Thermodynamics ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,law.invention ,chemistry.chemical_compound ,Computational chemistry ,law ,General Materials Science ,Phase diagram ,General Chemistry ,021001 nanoscience & nanotechnology ,Cathode ,0104 chemical sciences ,Computational Mathematics ,Chemical bond ,chemistry ,Mechanics of Materials ,0210 nano-technology ,Ternary operation - Abstract
To meet the requirement of large-scale simulation technics for Li-ion battery electrode materials, we introduce the charge-transfer modified embedded-atom method (CT-MEAM) in which the complex nature of the chemical bonding in transition metal (TM) oxides is described as a balance between metallic/covalent and ionic contributions by MEAM and a variable-charge model, respectively. The method is applied to Li 2 MnO 3 , and the parameterization is performed through fitting the energy–strain curves of Li 2 MnO 3 under uniaxial, biaxial and hydrostatic strains to a training set from ab initio density-functional theory calculations. The CT-MEAM prediction of the critical physical properties such as charge states and redox potentials match quite well with the ab initio results in various Li–Mn–O compounds beyond Li 2 MnO 3 . The constructed Li–Mn–O phase diagram is also qualitatively consistent with the ab initio reference work. The excellent transferability ensures use of the present method for a wide range of oxidation states in complex ternary TM oxides. Therefore, it will facilitate large-scale atomistic calculations required for the optimal design of many TM oxide applications including lithium-ion battery cathode materials.
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- 2016
4. Shape control of hierarchical lithium cobalt oxide using biotemplates for connected nanoparticles
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Kwangjin Park, Yoon-Sok Kang, Yongnam Ham, Jaegu Yoon, Gyusung Kim, Joung-Won Park, Meiten Koh, Insun Park, and Dongyoung Kim
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Materials science ,Fabrication ,Renewable Energy, Sustainability and the Environment ,Energy Engineering and Power Technology ,Nanoparticle ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Capacitance ,0104 chemical sciences ,Ion ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Electrode ,Particle ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,0210 nano-technology ,Lithium cobalt oxide ,Current density - Abstract
A new synthetic method using biotemplating for fabrication of LiCoO2 (LCO) for batteries of mobile products is developed. The LCO can be manufactured in various forms, and rapidly charged and discharged, even when using a thick electrode. Among three types of candidate biotemplates wood, cotton, and grass pollen, cotton was selected as the biotemplate considering its performance and potential for commercialization. Both the size of the primary particle and the shape of the secondary particle are controllable by using cotton. When using a thin electrode, the difference in capacitance between the LCO fabricated by the general method (solid-LCO) and the LCO made by using cotton (cotton-LCO) is within 3%, regardless of current density. On the other hand, the capacity difference in the case of a thick electrode between two samples is approximately 1.5 times higher than that observed for solid-LCO at very high current density (6C). The capacity retention values are 1.4% and 75.1% at 6C after the 100th cycle for solid-LCO and cotton-LCO, respectively. The superior performance at high current density for the cotton-LCO likely arises from decreasing the distance that the Li+ ion must diffuse in the solid-state by connected nanoparticles.
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- 2019
5. Phosphorus derivatives as electrolyte additives for lithium-ion battery: The removal of O 2 generated from lithium-rich layered oxide cathode
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In-Sun Jung, Seungyeon Lee, Young-Gyoon Ryu, Dong-Joon Lee, Seok-Soo Lee, Seok-Gwang Doo, Wan-Uk Choi, Jea-Woan Lee, Jaegu Yoon, and Dongmin Im
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Renewable Energy, Sustainability and the Environment ,Inorganic chemistry ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Electrolyte ,Cathode ,Lithium-ion battery ,Anode ,law.invention ,chemistry.chemical_compound ,Chemical state ,chemistry ,law ,Lithium ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,Phosphine ,Solid solution - Abstract
Direct internal pressure measurements of the cylindrical Li-ion cells with a mixture of LiCoO 2 and Li 1.167 Ni 0.233 Co 0.1 Mn 0.467 Mo 0.033 O 2 (a solid solution between 0.4 Li 2 Mn 0.8 Ni 0.1 Mo 0.1 O 3 and 0.6 LiNi 0.4 Co 0.2 Mn 0.4 O 2 ) as cathode and graphite as anode have been performed during cell charging. Cell internal pressure at the end of charging is greatly reduced from 2.85 to 0.84–1.84 bar by adding a small amount of phosphorus derivatives such as triphenyl phosphine (TPP), ethyl diphenylphosphinite (EDP), and triethyl phosphite (TEP) into a carbonate-based electrolyte. The phosphorus derivatives are supposed to react with O 2 generated from the decomposition of the Li 2 MnO 3 component. The chemical states of additive molecules before and after the charging process have been characterized with a nuclear magnetic resonance (NMR) spectroscopy and gas chromatography–mass spectrometry (GC–MS). It has also been shown that those additives improve the cycle life when applied in coin full cells.
- Published
- 2013
6. An in-situ gas chromatography investigation into the suppression of oxygen gas evolution by coated amorphous cobalt-phosphate nanoparticles on oxide electrode
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Sungjin Kim, Jin-Hwan Park, Donghan Kim, Jun Hee Han, Vinod Mathew, Jaekook Kim, Jihyeon Gim, Seokhun Kim, Jaegu Yoon, Suk-Gi Hong, Jeonggeun Jo, Jinju Song, and Sun-Ju Song
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Multidisciplinary ,Materials science ,Gas evolution reaction ,Oxide ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Cathode ,Article ,0104 chemical sciences ,Amorphous solid ,law.invention ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,law ,Electrode ,Surface modification ,0210 nano-technology - Abstract
The real time detection of quantitative oxygen release from the cathode is performed by in-situ Gas Chromatography as a tool to not only determine the amount of oxygen release from a lithium-ion cell but also to address the safety concerns. This in-situ gas chromatography technique monitoring the gas evolution during electrochemical reaction presents opportunities to clearly understand the effect of surface modification and predict on the cathode stability. The oxide cathode, 0.5Li2MnO3∙0.5LiNi0.4Co0.2Mn0.4O2, surface modified by amorphous cobalt-phosphate nanoparticles (a-CoPO4) is prepared by a simple co-precipitation reaction followed by a mild heat treatment. The presence of a 40 nm thick a-CoPO4 coating layer wrapping the oxide powders is confirmed by electron microscopy. The electrochemical measurements reveal that the a-CoPO4 coated overlithiated layered oxide cathode shows better performances than the pristine counterpart. The enhanced performance of the surface modified oxide is attributed to the uniformly coated Co-P-O layer facilitating the suppression of O2 evolution and offering potential lithium host sites. Further, the formation of a stable SEI layer protecting electrolyte decomposition also contributes to enhanced stabilities with lesser voltage decay. The in-situ gas chromatography technique to study electrode safety offers opportunities to investigate the safety issues of a variety of nanostructured electrodes.
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- 2016
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7. The effects of Mo doping on 0.3Li[Li0.33Mn0.67]O2·0.7Li[Ni0.5Co0.2Mn0.3]O2 cathode material
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Docheon Ahn, Jin Hwan Park, Jinju Song, Younkee Paik, Jinsub Lim, Min-Sik Park, Jaekook Kim, Jihyeon Gim, Jaegu Yoon, Hyosun Park, Dongmin Im, and Kyu-Sung Park
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Inorganic Chemistry ,chemistry.chemical_compound ,Differential scanning calorimetry ,Materials science ,Valence (chemistry) ,Transition metal ,X-ray photoelectron spectroscopy ,chemistry ,Doping ,Analytical chemistry ,Oxide ,Thermal stability ,Inductively coupled plasma - Abstract
Mo doped Li excess transition metal oxides formulated as 0.3Li[Li(0.33)Mn(0.67)]O(2)·0.7Li[Ni(0.5-x)Co(0.2)Mn(0.3-x)Mo(2x)]O(2) were synthesized using the co-precipitation process. The effects of the substitution of Ni and Mn with Mo were investigated for the density of the states, the structure, cycling stability, rate performance and thermal stability by tools such as first principle calculations, synchrotron X-ray diffraction, field-emission SEM, solid state (7)Li MAS nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), elemental mapping by scanning TEM (STEM), inductively coupled plasma atomic emission spectrometry (ICP-AES) and a differential scanning calorimeter (DSC). It was confirmed that high valence Mo(6+) doping of the Li-excess manganese-nickel-cobalt layered oxide in the transition metal enhanced the structural stability and electrochemical performance. This increase was due to strong Mo-O hybridization inducing weak Ni-O hybridization, which may reduce O(2) evolution, and metallic behavior resulting in a diminishing cell resistance.
- Published
- 2012
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