All the current energy technologies for future vehicles 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 engines. Successfully improving durability as well as continually searching for alternative materials is essential to spurring commercialization of further energy systems for electric vehicles, by increasing life time and decreasing cost. Energy conversion and storage systems such as batteries and fuel-cells are governed by electrochemistry and their degradations are ascribed to electrochemically induced corrosion during operation. Therefore, in order to improve stability in electrochemical energy systems, it is necessary to clearly understand the electrochemical degradation mechanisms, and then develop suitable prevention techniques. In the presentation, I will demonstrate my researches including designing novel electrode for high-performance lithium ion battery with excellent long-term stability and developing highly durable fuel cell membrane electrolyte assembly.