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리튬이온전지용 소프트카본 음극 소재의 인산 처리에 대한 연구
조용남,이은영,박민식,홍기주,이상익,정후영,이종훈,오승모,김영준,Jo, Yong-Nam,Lee, En-Young,Park, Min-Sik,Hong, Ki-Joo,Lee, Sang-Ick,Jeong, Hu-Young,Lee, Zonghoon,Oh, Seung M.,Kim, Young-Jun 한국전기화학회 2012 한국전기화학회지 Vol.15 No.4
Soft carbons are prepared by heat-treatment of cokes with different amounts of phosphoric acid (2, 4.5, and 10 wt% vs. cokes) at $900^{\circ}C$ to be used as anode materials for lithium ion batteries. From electrochemical measurements combined with structural analyses, we confirm that abundant nano-pores are existed in the microstructure of soft carbons prepared with the phosphoric acid, which are responsible for further lithium ion storage. Significant increase in reversible capacity of soft carbon is attained in proportion to added amount of the phosphoric acid. We also demonstrate the effect of structural modification with phosphoric acid on electrochemical performance of soft carbon to elucidate the origin of additional capacity. 코크스와 인산을 혼합한 뒤 $900^{\circ}C$에서 열처리하여 제조한 소프트카본의 구조적 특성 변화와 리튬이온전지용 음극 소재로서의 전기화학적 특성을 평가하였다. 입자 단면의 EDS 분석으로 phosphorus는 입자 내부에 전체적으로 존재하기는 하나 표면에 편재해 있었으며, $PO_x$(0 < x ${\leq}$ 4)의 결합 형태로 존재하고 있음을 XPS 분석을 통해 확인하였다. 인산 처리한 소프트카본의 방전 용량은 $390mAh\;g^{-1}$ 이상으로 인산을 처리하지 않은 소프트카본($336mAh\;g^{-1}$)보다 증가하였으며, 인산 처리량이 증가함에 따라 방전 용량이 증가하는 경향성을 나타내었다. 방전 용량 증가는 0.5 V vs. Li/$Li^+$ 이상에서 발현되는 용량 증가에 의한 것임을 확인하였고, 인산 처리로 생성된 $PO_x$(0 < x ${\leq}$ 4) 결합에 의해 소프트카본 내부에 생성된 나노 기공에 의한 것임을 충전 종료 전위별 실험을 통해 확인하였다. 또한 인산 2 wt%로 처리한 소프트카본이 가장 우수한 수명 특성을 나타내었다.
한지우,조용남,Han, Ji Woo,Jo, Yong Nam 한국재료학회 2019 한국재료학회지 Vol.29 No.12
The self-discharge behavior of zinc-air batteries is a critical issue induced by corrosion and hydrogen evolution reaction (HER) of zinc anode. The corrosion reaction and HER can be controlled by a gelling agent and concentration of potassium hydroxide (KOH) solution. Various concentrations of KOH solution and polyacrylic acid have been used for gel electrolyte. The electrolyte solution is prepared with different concentrations of KOH (6 M, 7 M, 8 M, 9 M). Among studied materials, the cell assembled with 6 M KOH gel electrolyte exhibits the highest specific discharge capacity and poor capacity retention. Whereas, 9 M KOH gel electrolyte shows high capacity retention. However, a large amount of hydrogen gas is evolved with 9 M KOH solution. In general, the increase in concentration is related to ionic conductivity. At concentrations above 7 M, the viscosity increases and the conductivity decreases. As a result, compared to other studied materials, 7 M KOH gel electrolyte is suitable for Zn-air batteries because of its higher capacity retention (92.00 %) and specific discharge capacity (351.80 mAh/g) after 6 hr storage.
아연-공기 전지용 전해질의 Gelling Agent 분자량에 따른 자가 방전 억제 효과
박정은,조용남,Park, Jeong Eun,Jo, Yong Nam 한국재료학회 2019 한국재료학회지 Vol.29 No.12
A zinc-air battery is one of most promising advanced batteries due to its high specific energy density, low cost, and environmental friendliness. However, zinc anodes in zinc-air batteries lead to several issues including self-discharge, corrosion reaction, and hydrogen evolution reaction (HER). In this paper, viscosity of electrolyte has been controlled to suppress the corrosion reaction, HER, and self-discharge behavior. Various viscosity average molecular weights of poly(acrylic acid) (PAA) are adopted to prepare the electrolyte. The evaporation of electrolytes is proportional to the increase in molecular weight. In addition, enhanced self-discharge behavior is obtained when the gelling agent with high molecular weight is used. In addition, the zinc-air cell assembled with lower viscosity average molecular weight of PAA (M<sub>v</sub> ~ 450,000) delivers 510.85 mAh/g and 489.30 mAh/g of discharge capacity without storage and with 6 hr storage, respectively. Also, highest capacity retention (95.78 %) is obtained among studied materials.
정민서,조용남,Jung, Min Seo,Jo, Yong Nam 한국재료학회 2020 한국재료학회지 Vol.30 No.12
For zinc-air batteries, there are several limitations associated with zinc anodes. The self-discharge behavior of zinc-air batteries is a critical issue that is induced by corrosion reaction and hydrogen evolution reaction (HER) of zinc anodes. Aluminum and indium are effective additives for controlling the hydrogen evolution reaction as well as the corrosion reaction. To enhance the electrochemical performances of zinc-air batteries, mechanically alloyed Zn-Al and Zn-In materials with different compositions are successfully fabricated at 500rpm and 5h milling time. Investigated materials are characterized by X-ray diffractometer (XRD), field emission scanning electron microscope (FE-SEM), and energy dispersive spectrometer (EDS). Alloys are investigated for the application as novel anodes in zinc-air batteries. Especially, the material with 3 wt% of indium (ZI3) delivers 445.37 mAh/g and 408.52 mAh/g of specific discharge capacity with 1 h and 6 h storage, respectively. Also, it shows 91.72 % capacity retention and has the lowest value of corrosion current density among attempted materials.
이주광,조용남,Lee, Ju Kwang,Jo, Yong Nam 한국재료학회 2020 한국재료학회지 Vol.30 No.12
A zinc-air battery consists of a zinc anode, an air cathode, an electrolyte, and a separator. The active material of the positive electrode is oxygen contained in the ambient air. Therefore, zinc-air batteries have an open cell configuration. The external condition is one of the main factors for zinc-air batteries. One of the most important external conditions is temperature. To confirm the effect of temperature on the electrochemical properties of zinc-air batteries, we perform various analyses under different temperatures. Under 60 ℃ condition, the zinc-air cell shows an 84.98 % self-discharge rate. In addition, high corrosion rate and electrolyte evaporation rate are achieved at 60 ℃. Among the cells stored at various temperature conditions, the cell stored at 50 ℃ delivers the highest discharge capacity; it also shows the highest self-discharge rate (65.33 %). On the other hand, the cell stored at 30 ℃ shows only 2.28 % self-discharge rate.
진위교,조용남 한국교육학회 2000 敎育學硏究 Vol.38 No.3
The purpose of this study is to diagnose the present state of college teaching and investigate the innovation strategy based on the instruction technology approach in the information era. As a result of questionnaire survey, the negative views on the college teaching represented by lecturing were scored high. And it was indicated that the effort to improve the college teaching was relatively behind. In the information era, the new paradigm of education is needed. So, to enhance the efficiency of college teaching, it is discussed that the innovative strategies such as the systematic design of instruction, instructional technology, and constructivism should be used. To make rich environments for active learning based on constructivism, zeitgeist at present, is needed. The generative learning in the meaningful contexts and social interaction through cooperative learning should be emphasized. Finally, it is suggested that the web, the star of information era, should be applied to the educational practice, especially to the teaching--learning process widely.