1. Department of Chemical Engineering, Chungnam National University, 220 Gung-Dong, Yuseong-Gu, Daejeon 305-764, Korea
2. Bioneer Co. 49-3, Munpyeong-Dong, Daedeok-Gu, Daejeon 306-220, Korea
3. Energy Storage Research Center, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650, Korea