1. State Key Laboratory of Silicon Materials Key Laboratory of Advanced Materials and Applications for Batteries of Zhejiang Province, and Department of Materials Science and Engineering Zhejiang University Hangzhou 310027 P. R. China
2. State Key Laboratory of Coal Conversation Institute of Coal Chemistry Chinese Academy of Sciences Taiyuan 030001 P. R. China
3. Department of Optical Science and Engineering Fudan University Shanghai 200433 P. R. China
4. Department of Physics City University of Hong Kong Hong Kong 999077 P. R. China
5. Department of Materials Chemistry Huzhou University Huzhou 313000 P. R. China