▎ 摘　　要

In this work, we demonstrate a facile and green hydrothermal process without using any surfactant or template to synthesize SnO2 nanoflowers (NFs)/graphene nanosheets (GNSs) composites as a high-performance electrode material for electric double layer capacitors (EDLCs). The crystal structure and morphology of the products were characterized by X-ray diffraction, scanning electron microscopy, and transition electron microscopy. The electrochemical properties were investigated by galvanostatic charge/discharge cycling and cycling voltammetry in a voltage range of 0.2-0.8 V. The results exhibit that the addition of GNSs did not change the tetragonal crystal structure of SnO2, and the GNSs were successfully coated on the flower-like surface of SnO2. The grain morphology of SnO2@GNSs composites has a flower-like appearance suggesting excellent electrochemical properties which were confirmed by electrochemical techniques. Compared with the GNSs, the SnO2@GNSs composites exhibit a high specific discharge capacitance of 126 F g(-1) at 0.2 A g(-1) and remains 98.2% after 2000 charge-discharge cycles. The combination of GNSs and SnO2 could significantly improve the electrical conductivity, enhance the interactions between GNSs and SnO2 NFs and provide more reaction sites, thereby resulting in improved electrochemical properties for the SnO2@GNSs composites in contrast with the pristine GNSs sample. The high specific capacity and long stability make the SnO2@GNSs nanocomposite as a electrode material for high-performance supercapacitors. (C) 2016 Elsevier B. V. All rights reserved.