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Sb-AlxCy-C Nanocomposite Alloy Anodes for Lithium-Ion Batteries
허재현 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0
We present a facile approach to make Al-Sb, carbon-modified (Al-Sb-C) nanocomposites for use as new anode materials in lithium-ion batteries (LIB). Alloying is achieved by one step synthesis using high energy mechanical milling (HEMM), producing nanometer-sized alloy particles, Sb-AlxCy-C. Based on electrochemical analyses, we determined that Sb acts as an active material, and both Al and carbon create a hybrid buffering matrix that mitigates the volume expansion of the active material during lithiation/delithiation to a greater degree as compared to that by a pure metallic matrix (AlSb). In addition, we optimized the stoichiometric ratio of Al and Sb concerning specific capacity and cycling performance. AlSb-C anodes also showed good rate capability and volumetric capacity. Overall, the new AlSb-C composite is a promising candidate for use as the negative electrode in lithium-ion batteries, providing an alternative to commercially available graphite electrodes.
허재현,김일태 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.6
Antimony (Sb)-containing intermetallic alloy compound consisting of molybdenum (Mo) and Sb dispersed in an amorphous carbon matrix was developed via high-energy mechanical milling and utilized as an anode for a sodium-ion battery. The structure and morphology of the as-prepared material were characterized using X-ray diffraction (XRD) and transmission electron microscope. Ex situ XRD measurement confirmed the formation of a Na3Sb phase during sodiation. The electrochemical performance of the as-prepared Mo3Sb7C composite demonstrated stable cyclability up to 40 cycles at a current rate of 100 mA/g. When a fluoroethylene carbonate additive was introduced into the electrolyte, the Mo3Sb7 C anodes exhibited a longer cyclic life with a capacity retention of ~90% at 100 cycles, as well as superior rate-cyclic performance corresponding to a capacity retention of more than 70% at 10 000 mA/g. This enhanced electrochemical performance could be ascribed to the formation of a stable solid electrolyte interphase layer, smaller charge-transfer resistance, and better dispersion of Mo3Sb7 nanoparticles in the carbon matrix.
허재현,김일태 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.12
The reduced graphene oxide(rGO)/aluminum phosphate(AlPO4)-coated LiMn1.5Ni0.5O4 (LMNO) cathode material has been developed by hydroxide precursor method for LMNO and by a facile solution based process for the coating with GO/AlPO4 on the surface of LMNO, followed by annealing process. The amount of AlPO4 has been varied from 0.5 wt % to 1.0 wt %, while the amount of rGO is maintained at 1.0 wt %. The samples have been characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. The rGO/AlPO4-coated LMNO electrodes exhibit better cyclic performance compared to that of pristine LMNO electrode. Specifically, rGO(1%)/AlPO4(0.5%)- and rGO(1%)/AlPO4(1%)-coated electrodes deliver a discharge capacity of, respectively, 123 mAh g−1 and 122 mAh g−1 at C/6 rate, with a capacity retention of, respectively, 96% and 98% at 100 cycles. Furthermore, the surface-modified LMNO electrodes demonstrate higher-rate capability. The rGO(1%)/AlPO4(0.5%)-coated LMNO electrode shows the highest rate performance demonstrating a capacity retention of 91% at 10 C rate. The enhanced electrochemical performance can be attributed to (1) the suppression of the direct contact of electrode surface with the electrolyte, resulting in side reactions with the electrolyte due to the high cut-off voltage, and (2) smaller surface resistance and charge transfer resistance, which is confirmed by total polarization resistance and electrochemical impedance spectroscopy.
Solvent induced conversion of microdomain structure in block copolymer electrolyte thin films
허재현,배준원 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1
The block copolymer electrolytes have become interesting owing to their potential applications forproton exchange membranes in fuel cells. Thus an attention has been paid to understand the structure–property relation in block copolymer electrolytes. In particular, the morphology–performancecorrelation is one of the most important characteristics of block copolymer electrolytes, because theprimary performances such as transport properties are strongly dependent on the morphology. Therefore, in this study, the solvent induced microstructure conversion in sulfonated polystyrene-bhydrogenatedpolybutadiene-b-polystyrene block copolymer electrolyte was examined with transmissionelectron microscopy and atomic force microscopy. The introduction of hydrophilic solventmethanolto hydrophilic-tetrahydrofuran modified the internal structure of the block copolymerelectrolyte, then generated a unique morphology. This work will be of help to understand theinteractions between block copolymer electrolytes and solvents.
허재현,송용원 사단법인 미래융합기술연구학회 2021 아시아태평양융합연구교류논문지 Vol.7 No.5
Amid the era of convergence and innovation that requires more creativity than human labor, a growing number of companies and schools are introducing TRIZ, a creativity-based problem-solving tool. However, it is not easy to learn and apply TRIZ theories that are different from existing methods. In particular, if the cases used in education are different from those of students' interests or if the learning content is too difficult, the learning effect will be even worse. In this paper, we conduct research on how to induce immersion of trainees and learn TRIZ theory efficiently. The effectiveness of education can be increased if students combine hobbies that they are interested in or examples of solving real problems at hand. Using DIY (Do It Yourself) production activities, which anyone can easily participate in with interest, the curriculum that solves various problems in the production process directly through TRIZ theory has gained active participation and excellent learning effects. It is a way to effectively understand Learning in conjunction with TRIZ and areas of interest is an effective way to understand TRIZ tools such as invention principles, material-field, and FORS(Function oriented Resource Search). 인간의 노동력보다 창의력이 더욱 필요한 융합과 혁신의 시대가 된 가운데 창의력기반의 문제해결 도구인 트리즈를 도입하는 기업이나 학교가 많이 증가하고 있다. 하지만 기존의 방법과 다른 트리즈 이론을 배우고 현장에 적용하는 것은 쉽지 않다. 특히 교육에 활용되는 사례가 교육생들의 관심분야와 다르거나 학습 내용이 너무 어려울 경우 학습효과는 더욱 떨어진다. 본 논문에서는 교육생들의 몰입을 유도하고 효율적으로 트리즈 이론을 배울 수 있는 방법에 대한 연구를 진행하였다. 교육생들이 관심을 가지고 있는 취미활동이나 당면한 현실 문제해결 사례를 접목한다면 교육의 효과가 증가할 수 있다. 누구나 흥미를 느끼고 쉽게 참여할 수 있는 악기 DIY(Do It Yourself) 제작활동을 활용하여 제작과정에서 발생하는 다양한 문제를 트리즈 이론을 통해 직접 해결해 보는 교육 과정은 교육생들의 능동적 참여와 뛰어난 학습효과를 얻게 했다. 트리즈와 관심 분야를 연계하는 것은 발명원리, 물질-장, FORS(Function oriented Resource Search) 같은 트리즈 도구들을 효과적으로 이해할 수 있는 방법이다.