Enhanced performance of densified laser-induced graphene supercapacitor electrodes in dimpled polyimide

We fabricate a densified laser-induced graphene (d-LIG) electrode derived from a dimpled polyimide (PI) sheet. The fabrication process involves placing a PI sheet on a Si wafer and generating dimples on the PI surface via laser irradiation at the PI/Si interface. d-LIG is fabricated using the duplicated laser-induced carbonization, during which regular LIG is infiltrated with polyamic acid (PAA) and then irradiated with a CO2 laser. Compared to pristine PI, the LIG based on the dimpled PI facilitates deeper penetration of the PAA solution into the interior of the LIG, resulting in an increased amount of d-LIG and high nitrogen doping. When tested in a three-electrode configuration, the d-LIG derived from the dimpled PI (or d-LIG-D) exhibits a high specific capacitance of 67 mF/cm2 at 0.2 mA/cm2, which is almost twice that of the d-LIG derived from pristine PI (or d-LIG-P) (28.9 mF/cm2). When fabricated into a flexible solid-state supercapacitor with polyvinyl alcohol-H2SO4 gel-type electrolyte, d-LIG-D exhibits a higher specific capacitance (19.5 mF/cm2 at 0.05 mA/cm2) than d-LIG-P (8.4 mF/cm2). Furthermore, it possesses good capacitance retention, Coulombic efficiency, and mechanical flexibility. These properties make d-LIG-D a promising candidate for advanced supercapacitor applications, offering enhanced energy storage capabilities and robust performance.