1. Key
Laboratory of Physics and Technology for Advanced Batteries (Ministry
of Education), College of Physics, Jilin University, Changchun 130012, China
2. Department
of Physics, College of Science, Yanbian University, Yanji 133002, China
3. Department
of Materials Science and Engineering, and A. J. Drexel Nanotechnology
Institute, Drexel University, Philadelphia, Pennsylvania 19104, United States