1. Key Laboratory of Physics and Technology for Advanced Batteries of Ministry of EducationCollege of PhysicsJilin University Changchun 130012 P. R. China
2. State Key Laboratory of Superhard MaterialsJilin University Changchun 130012 P. R. China
3. Department of Materials Science and EngineeringA. J. Drexel Nanomaterials InstituteDrexel University Philadelphia PA 19104 USA
4. Institute for Materials DiscoveryUniversity College London London WC1E 7JE UK