All the current energy technologies focus on the development of energy conversion and storage systems with higher power/energy density, longer cycle life, and competitive costs. Nevertheless, there have hardly been any major scientific breakthroughs to replace the much more economical fossil fuel systems. Successfully improving durability and continually searching for alternative materials is essential to spurring commercialization of further energy systems, by decreasing cost of the energy systems and increasing life time. Energy conversion and storage systems such as fuel cells and batteries are governed by electrochemistry and their performance and durability are ascribed to electrochemically induced mechanisms during operation. Therefore, in order to improve the performance and durability of the electrochemical energy systems, it is necessary to clearly understand the electrochemistry and develop suitable materials and prevention techniques. In the group (EESL), we study electrochemical mechanism of various energy systems and develop advanced energy materials and systems with excellent performance and long-term stability.