Institute of Electrical Engineering Academy of Sciences 100190;
University of Chinese Academy of Sciences 100049;
Institute of Electrical Engineering and Advanced Electromagnetic Drive Technology Zhongke 250013;
Key Laboratory of Advanced Technologies of Materials of Education of Materials Science and Engineering Jiaotong University 6003 Sichuan;
School of Materials Science and Engineering University 450001;
Lithium-ion capacitors; Free-standing films; Reduced graphene oxide; Carbon materials;