1. International Academy of Optoelectronics at Zhaoqing, South China Normal University, Zhaoqing 526238, Guangdong, P. R. China
2. Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
3. School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangdong 510631, P. R. China
4. Department of Chemical Engineering, Waterloo Institute for Nanotechnology, Waterloo Institute for Sustainable Energy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
5. Laboratory of Advanced Spectro-electrochemistry and Li-on Batteries, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023 Dalian, P. R. China
6. Shenyang National Laboratory for Material Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, P. R. China
7. Nanomaterials Centre, School of Chemical Engineering and Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St Lucia, QLD 4072 Australia