Graphene quantum dots based flexible planar micro-supercapacitors with different bending angles.

The development of micro-electronic products and the increase in demand for portable devices have driven the research of planar micro-supercapacitors (PMSCs). Flexible PMSCs have the advantages of high energy and power density, stable cycling performance and good flexibility, which makes the flexible PMSCs valuable for the research in the field of wearable electronic devices. In this paper, graphene quantum dots were selected as the electrode material for the flexible devices and PET as the flexible substrate, and the flexible PMSCs with interdigital electrode width to gap ratio of 60 μm/60 μm were prepared using modified liquid-air interface self-assembly, photolithography and oxygen plasma etching. Cyclic voltammetry, galvanostatic charge-discharge, electrochemical impedance spectroscopy and cyclic stability were performed on the devices with the bending angles of 0°, 60°, 90°, 150° and 180°, respectively, using electrochemical workstation. Redox peaks appeared in the CV curves of the devices at the very low scan rates, indicating that redox reaction occurred and pseudocapacitance effect appeared. The area capacitance, energy density and power density of the devices decreased and the charging time was longer than discharging time after the bending angle was increased. After 10,000 cycles, the cyclic stability for the five bending angles was maintained at more than 71%. In short, the larger the bending angles, the greater the impact on some performance of the devices, and when the devices were placed in non-vacuum environment for too long, some performance after bending but better. [ABSTRACT FROM AUTHOR]