Enhanced laser scribed flexible graphene-based micro-supercapacitor performance with reduction of carbon nanotubes diameter

By making use of the induced transformation of graphite oxide (GO) to laser scribed graphene (LSG), the coated layers of GO/carbon nanotubes (CNTs) hybrid powders on flexible polyethylene terephthalate sheets were patterned into LSG/CNTs micro-supercapacitors (LSG/CNTs-MSCs). In the presence of CNTs with a smaller diameter, the laser-scribed LSG/CNTs-MSC was found to yield the better energy storage performance. This dependence on the CNT diameter can be attributed to the role of CNTs in prevention of restacking of LSG layers and thus the increase of ion-accessible surface area. The CNTs with a smaller diameter can be more easily inserted between the LSG layers, thus inhibiting the restacking phenomenon more effectively. By using the single-wall CNTs (SWCNTs) of 1–2 nm diameter, the laser-scribed LSG/SWCNTs-MSC was observed to exhibit the best electrochemical properties: The volumetric capacitance of 3.10 F cm−3 at a current density of 1000 mA cm−3, the volumetric energy density of 0.84 mW h cm−3 and power density of 1.0 W cm−3, and long-term cycling stability.