1. State Key Laboratory of Silicon Materials; Key Laboratory of Advanced Materials and Applications for Batteries of Zhejiang Province; Department of Materials Science and Engineering; Zhejiang University; Hangzhou 310027 P. R. China
2. Division of Physics and Applied Physics; School of Physical and Mathematical Sciences; Nanyang Technological University; Singapore 637371 Singapore
3. School of Engineering; Nanyang Polytechnic; Singapore 569830 Singapore