Laser-induced carbonization of carbon nanofibers free-standing electrodes for flexible interdigitated micro-supercapacitors

A versatile one-step laser writing technique is introduced in this work for carbonizing and patterning polymeric nanofibers mat to produce a free-standing laser carbonized nanofibers (LCNFs) electrode for flexible interdigitated microsupercapacitors. A large-area polyacrylonitrile nanofibers mat was first prepared with the facile electrospinning technique on a collecting drum followed by a stabilizing step. A high-power CO2 laser beam is used to carbonize the stabilized nanofibers into highly conductive LCNFs at ambient atmospheric conditions and draw the interdigitated pattern at the same time. The complete carbonization of the nanofibers is confirmed by the nearly complete disappearance of polyacrylonitrile peaks in the FTIR measurements and from the high-intensity characteristic peaks of carbon materials obtained in the Raman scattering measurements of the LCNFs. The SEM microscopy showed that the LCNFs were able to survive their fibrous structure after the laser carbonization process and without any significant damage. Also, the TEM microscopy revealed that the LCNFs are composed of graphene sheets that are axially ordered to form such a unique fibrous structure. Owing to its outstanding structural and electrical properties, the LCNFs interdigitated supercapacitor attained an aerial specific capacitance of 20.38 mF/cm2, a high energy density of 0.64 μWh/cm2, and a high-power density of 224.6 μW/cm2 which are almost two-fold higher than those of the laser-induced graphene (LIG) on a polyamide substrate assembled with the same conditions. This was accompanied by an excellent capacitance retention of 95.3 % after 10,000 electrochemical cyclic stability and impressive mechanical stability and flexibility.