FINAL REPORT For Japan-Korea Joint Research Project

Transcription

1 FINAL REPORT For Japan-Korea Joint Research Project AREA 1. Mathematics & Physics 2. Chemistry & Material Science 3. Biology 4. Informatics & Mechatronics 5. Geo-Science & Space Science 6. Medical Science 7. Humanities & Social Sciences 1. Research Title: Basic Research on Nano-carbon Electrode for High Power Lithium-ion Batteries 2. Term of Research: From July 1, 2008 To June 30, Total Budget a. Financial Support by JSPS: Total amount: 2,400 thousand yen 1 st Year 1,200 thousand yen 2 nd Year 1,000 thousand yen 3 rd Year 200 thousand yen b. Other Financial Support : Total amount: 0 thousand yen 4. Project Organization a. Japanese Principal Researcher Takeshi ABE Name Institution / Department Position Graduate School of Engineering, Kyoto University / Department of Energy & Hydrocarbon Chemistry/ Professor b. Korean Principal Researcher Name JEONG Soonki Institution / Department Position Associate Professor 1

2 c. List of Japanese-side Participants (Except for Principal Researcher) Name Institution/Department Position Kohei Miyazaki Graduate School of Engineering, Kyoto University/ Department of Energy & Hydrocarbon Chemistry Research Associate d. List of Korean-side Participants (Except for Principal Researcher) Name Institution/Department Position Donggui Choi Master Course Student Pogyom Kim Master Course Student 2

3 5. Number of Exchanges during the Final Fiscal Year* a. from Japan to Korea *Japanese fiscal year begins April 1. Name Home Institution Duration Host Institution Total: 0 persons Total: 0 man-days Numbers of Exchanges during the past fiscal years FY2008: Total 2 persons FY2009: Total 0 persons b. from Korea to Japan Name Home Institution Duration Host Institution Total: 0 persons Total: 0 man-days Numbers of Exchanges during the past fiscal years FY2008: Total 2 persons FY2009: Total 2 persons 3

4 6. Objective of Research Lithium-ion batteries have been used in the portable electronic devices for almost 20 years. In addition, lithium-ion batteries have attracted much attention for a practical use in hybrid electric vehicles (HEV), plug-in HEV, and EV. For these EV s, high safety, longer lives, faster charge-discharge reactions of lithium-ion batteries are required. The R&D of lithium-ion batteries to meet the above requirements has been extensively done in the world. So far, Asian countries, in particular, Japan and Korea are superior in the production of portable lithium-ion batteries. Therefore, industrial and academic activities on Li-ion batteries are very high in Japan and Korea. The high activity in the research of Li-ion batteries enables us to the basic studies of Li-ion batteries for HEV of the next generation. The rapid development of EV s is one of the most important issues to protect the worldwide pollution. Then, the cooperation between Japan and Korea in the field of Li-ion batteries is meaningful since the both countries are in the frontier for R&D of Li-ion batteries. Based on the collaboration between Japan and Korea, the objective of this research is to conduct the basic studies on nano-carbons for a practical use in lithium-ion batteries for HEV since HEV requires higher rate performance. In particular, we focused on the preparation of nano-carbons, compatibilities between nano-carbons and electrolytes, and the formation mechanism of solid electrolyte interface. Also, we focused on the use of propylene carbonate (PC) as a solvent of electrolyte. Since the high performance of lithium-ion batteries in the lower temperature region is required for EV s, we need solvent with lower melting points. 4

5 7. Methodology Graphitized nano-carbons were prepared by an electrospray pyrolyzed method, and their electrochemical properties as a negative electrode were studied. In addition, electrochemical properties of various nano-carbons with the various microstructures were studied by cyclic voltammetry, charge-discharge measurements, AC impedance spectroscopy. The fabrication of nano-carbons was mainly done in Kyoto University, Japan, and the electrochemical studies were made by our master course students in each country. After the evaluation of the electrochemical properties of various nano-carbons, the solid electrolyte interface (SEI) formed during the first charge was studied by scanning electron microscopy, transmission electron microscopy, and "in-situ" electrochemical scanning probe microscopes to find out the detail formation mechanism of SEI. These observations were cooperated by our master and doctor course students using the equipments in Kyoto University. Based on the understanding of the formation mechanism of SEI, surface structures of graphitized nano-carbons were modified. The electrochemical properties of nano-carbons in concentrated propylene carbonate-based electrolyte were studied. In the concentrated PC-based electrolyte, charge and discharge reactions are available for graphite negative electrolyte. However, due to the large viscosity, high rate performance was not obtained for a typical graphite electrode. Therefore, we used the nano-carbons in the concentrated PC-based electrolyte to attain fast charge and discharge reactions. Also, the SEI formation of nano-carbons in the concentrated PC-based electrolyte was studied by using the above equipments in Kyoto University. 5