1. College of Physics, Qingdao University, No. 308 Ningxia Road, Qingdao 266071, China
2. State Key Laboratory of Bio Fibers and Eco Textiles, Qingdao University, No. 308 Ningxia Road, Qingdao 266071, China
3. College of Mechanical and Electrical Engineering, National Engineering Research Center for Intelligent Electrical Vehicle Power System (Qingdao), Qingdao University, Qingdao 266071, China
4. National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan