1. Graduate School of Informatics and Engineering, The University of Electro-Communication, Tokyo 182-8585, Japan
2. Institute of Molecular Science, Key Laboratory of Materials for Energy Conversion and Storage of Shanxi Province, Shanxi University, Taiyuan 030006, P. R. China
3. Analytical and Testing Center, Chongqing University, Chongqing 401331, P. R. China