Dr. Won-Sub Yoon is a professor in the Department of Energy Science at Sungkyunkwan University (SKKU). He received his Ph.D. in materials science and engineering from Yonsei University, Korea. He worked at Brookhaven National Laboratory in USA as a principal investigator and Kookmin University in Korea as a professor. His research group is specialized in studying electrode materials and the structural properties for energy conversion and storage systems including rechargeable batteries, fuel cells, and supercapacitors. Most of his publications (more than 120 papers) have been focused on developing and applying in situ synchrotron-based X-ray techniques to investigate electrode materials and the reaction mechanisms for rechargeable battery systems attacking current issues in rechargeable battery R&D. He has extensive experience with in situ synchrotron X-ray research. Especially, he has pioneered in the application of in situ time-resolved XRD, in situ temperature dependent XRD, in situ soft X-ray absorption spectroscopy, and in situ SAXS studying on the structural and electronic changes of ion storage materials during real time operation.