1. State Key Laboratory of Power Transmission Equipment & System Security and New TechnologyDepartment of Applied PhysicsSchool of Chemistry and Chemical EngineeringChongqing University Chongqing 400044 China
2. Beijing Institute of Nanoenergy and NanosystemsChinese Academy of Sciences Beijing 100083 China
3. School of Materials Science and EngineeringUniversity of Science and Technology Beijing Beijing 100083 China