1. 제목 : In-situ Lithiation Test of Si nanostructure

2. 연사 : IN-SUK CHOI, Ph. D (Korea Institute of Science and Technology, Seoul, Korea)

3. 일시 : 2013년 6월 14일(금) 오후 4:30 - 6시 

4. 장소 : 301동 101호

5. 내용 : 

Understanding lithiation process of Si at nanoscale becomes of prime importance to develop next generation Li-ion batteries since the nanostructured Si such as Si nanowires and porous nanostrcutrues were reported to enhance charging rate and avoid mechanical degradation due to the dramatic volume expansion of Si during lithiation. However, affirmative description of Li kinetics in nanostructured Si anode is still very limited. In the present work, we demonstrated a new method to characterize nanoscale lithiation process without electrolyte and external electrical potential. Our in-situ lithiation test showed for the first time unprecedentedly fast lithiation of a pristine Si nanowire by direct contact between the Si nanowire and the bulk Li. It was very surprising that the speed of external potential-free lithiation was even faster than the recent record-high electro-chemical lithiation rate assisted by a carbon coating. The measured diffusivity is even faster than the upper-bound of Li for the ex-situ electrochemical tests but comparable to the theoretically calculated diffusivity values. The mechanical properties of lithiated Si nanowires were also investigated using in-situ tensile testing, which provides a guidance of new nanostructure design of Si anode. Subsequently, we introduced a new design of nanostructured Si anode on a Polyimide (PI) substrate for future applications of flexible energy storage devices. Unlike other technique to fabricate nanostructure Si anodes, amorphous-Si was deposited directly on the polymer substrate having nano-hair like surface structure. This unique nanostructured Si anode hinders the delamination of an anode component resulting in higher capacity and longer life cycle than that of a-Si on the non- PI substrate or on a typical Cu foil substrate.

6. 약력:

2009.09-present   Senior Research Scientist (KIST)

2006.10-2009.08   Forschungszentrum Karlsruhe (KIT), Germany 

2002.08-2006.10   Massachusetts Institute of Technology, Cambridge, MA

                         (Ph. D. in Materials Science and Engineering) 

2000.09-2002.06   Stanford University, Palo Alto, CA

                         (S.M. in Materials Science and Engineering)

1994.03-2000.08   Seoul National University, Seoul, Korea

                         (B.S. in Materials Science and Engineering )

7. 문의:  기계항공공학부 조경재 교수 (880-1709)