Laser transmission welding and surface modification of graphene film for flexible supercapacitor applications

Abstract

When a graphene film is coated onto a flexible polymer substrate, weak adhesion can cause delamination of the film under mechanical bending. Moreover, as each graphene layer restacks, the performance of the film as an electrode for a supercapacitor becomes limited. In this study, facile laser welding and surface modification processes are demonstrated to overcome these limitations. First, a continuous wave laser beam is applied to the interface between the coated graphene and the underlying transparent polycarbonate substrate. This welding process significantly improves their adhesion and enables excellent mechanical bendability. Second, surface modification of graphene is achieved under ambient conditions by irradiating the graphene film surface with a nanosecond pulsed laser. Sandwich-type supercapacitors are fabricated using these surface-modified graphene electrodes with a PVA-H3PO4 electrolyte. The effect of the laser fluence on the performance of the supercapacitor is investigated. At an optimal laser power, an areal capacitance of 4.7 mF/cm2 is achieved.