WCU Seminar


1. 제목 : Nanotechnology-based Synthetic and Analytic Ways for Advanced Electrode Materials of LAB

2. 연사 : Professor Yong-Mook Kang (Department of Energy & Materials Engineering, Dongguk University-Seoul)

3. 일시 : 2013년 5월 29일(수) 오후 4시-6시

4. 장소 : 301동 1512-2호

5. 내용 :

 Rechargeable lithium batteries have the potential to provide an energy storage solution to depletion of fossil fuel resources and global warming because they are also considered as clean power sources from renewable energy sources for next-generation electric applications such as electric vehicle (EV), portable electric appliances, and large-scale energy storage system. The energy density of the conventional lithium ion battery cannot meet the stringent requirements for these applications, whereas lithium-air batteries have significantly high theoretical specific energy coming up to 11,140 Wh/kg because lithium–air batteries are based on discharge reaction between Li and oxygen to yield Li₂O₂. However, regardless of its high energy density, low cycling capability remained as an important hurdle for commercialization. A major drawback about lithium-air batteries is its low round trip efficiency coming from very large potential difference between ORR and OER (Oxygen evolution reaction). Various types of materials have been adopted for the catalysts to reduce potential hysteresis and thus attain high round-trip efficiency. In particular, α-MnO₂ has received great attention as an oxide catalyst for lithium-air batteries since its superior catalytic activity was introduced by P.G. Bruce et al.. Because the relatively good catalytic activity of α-MnO₂ among various metal oxides results from easy accommodation of Li₂O₂ inside its large 2x2 tunnel structure, many researchers have tried to vary the macrophysical properties such as porosity, surface-to-volume ratio and so on to enhance the electrochemical properties of lithium-air batteries using α-MnO₂. However, such kind of piecemeal approaches without detailed understanding on the fundamental physical properties governing the catalytic activity of materials failed to make a breakthrough in the development of commercially available catalysts.

Hence, we here report on the [200]-oriented α-MnO₂ nanowires having thermodynamically metastable surface with significant instability and more open-structured surface frame ascribed to its cross-sectionally orderded 2x2 channel resultantly enabling more homogeneous nucleation of Li₂O₂ without toroidal growth and more effective Li₂O₂ accommodation compared to the [002]-oriented α-MnO₂ nanotubes. The dependence of catalytic activity on the growth direction has been predicted based on the state-of-the-art first principles calculation on low miller index planes as main sidewall surface planes. To experimentally confirm the calculation results, very facile route based on hydrothermal reaction will be also introduced to abnormally grow α-MnO₂ nanowires along [200] direction

6. 약력:

-Ph.D. KAIST 공과대학 신소재공학과

-M.S.  KAIST 공과대학 신소재공학과

-B.S.   KAIST 공과대학 신소재공학과

-동국대학교 융합에너지신소재공학과 교수

7. 문의:  기계항공공학부 조경재 교수 (880-1709)