1. Beijing Key Laboratory of Environmental Science and Engineering School of Materials Science and Engineering Beijing Institute of Technology Beijing 100081 P. R. China
2. Key Laboratory of Materials Processing and Mold Ministry of Education Zhengzhou University Zhengzhou 450002 P. R. China
3. Institute of Physics Chinese Academy of Science Beijing 100190 China
4. Collaborative Innovation Center of Electric Vehicles in Beijing Beijing 100081 P. R. China