1. Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China
2. School of Engineering Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
3. Institute of Electrical Engineering and Advanced Electromagnetic Drive Technology, Qilu Zhongke, Jinan 250013, China
4. CAS Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, Shanxi 030001, China