Facile Fabrication of Flexible Graphene-Based Micro-Supercapacitors with Ultra-High Areal Performance

Micro-supercapacitors (MSCs) with high performance and flexibility could meet the demand of miniaturized electronic devices. The advantages of graphene and reduced graphene oxide (rGO), such as high specific surface area, good conductivity, mechanical properties, and electrochemical stability, make them promising candidates for flexible electrodes of MSCs. However, the low mass loading and electrical double-layer capacitor (EDLC) mechanism of graphene-based MSCs lead to a low areal electrochemical performance, which is a key parameter of miniaturized power sources. Here, we demonstrate a high-loading (21.1 mg cm–2) graphene-based MSC through hydrothermal, physical pressing and laser-engraving methods. Impressively, the symmetrical MSC can exhibit an areal capacitance as high as 569.5 mF cm–2. At the same time, the MSC exhibits an excellent areal energy density of 79.1 μWh cm–2, which is superior performance among graphene-based MSCs reported in research studies. Meanwhile, the MSC also demonstrates long-term cyclic stability (98.8% capacitance retention after 20 000 cycles) and robust flexibility (no attenuation of capacitance at bending angles from 0 to 180° and 98.4% capacitance retention after 2000 bending cycles). Therefore, this work offers a facile method to greatly promote the areal electrochemical performance of graphene-based MSCs, which are promising in broader applications.