1. Department of Physics, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China
2. College of Chemistry and Molecular Science, Wuhan University, Wuhan, Hubei 430072, China
3. Sensor and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, Maryland 20783, United States
4. National Key Lab of Power Sources, Tianjin Institute of Power Sources, Tianjin, Tianjin 300381, China