1. Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education) College of Physics Jilin University Changchun 130012 P. R. China
2. A. J. Drexel Nanomaterials Institute and Department of Materials Science and Engineering Drexel University Philadelphia PA 19104 USA
3. Comprehensive Energy Saving School of Electrical and Electronic Information Engineering Jilin Jianzhu University Changchun 130118 P. R. China
4. State Key Laboratory of Superhard Materials Jilin University Changchun 130012 P. R. China
5. Institute for Materials Discovery University College London London WC1E 7JE UK