1. Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, P. R. China
2. School of Materials Science and Engineering, Peking University, Beijing 100871, P. R. China
3. Beijing Graphene Institute (BGI), Beijing 100095, P. R. China
4. Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, Peking University, Beijing 100871, P. R. China
5. Institute of Advanced Materials, Key Lab of Fluorine and Silicon for Energy Materials and Chemistry of Ministry of Education, Jiangxi Normal University, Nanchang 330022, P. R. China
6. Electron Microscopy Laboratory and International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P. R. China
7. Collaborative Innovation Center of Quantum Matter, Beijing 100871, P. R. China
8. Center for Nanochemistry, Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China