Thermally stable benzimidazole based co-polyimides and derived LIG for flexible supercapacitors

Laser-induced graphene (LIG) derived from the polymers has captured a great deal of attention owing to its high efficiency, low-cost fabrication and prospect applications in the flexible energy storage devices. Polyimides have been explored as one of the most popular LIG substrates for the last couple of years. In this work, a novel LIG material has been reported which is prepared from a novel copolyimide. A series of new thermally stable polyimides has been synthesized via copolymerization of diamine containing benzimidazole derivative, namely N¹-(4-aminophenyl)-N¹-(4-(2-phenyl-1H-benzo[d]imidazole-1-yl)phenyl)benzene-1,4-diamine with four different aromatic anhydrides. Graphene formation and morphology have been examined and confirmed by employing several techniques including Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray and Raman spectroscopy. LIG obtained using these newly reported polyimides was reproducible as well as stable with negligible to no difference in properties and appearance over a long period of time. At 1 mA cm^-2, the 11a-LIG electrode displays capacitance of 136 mF cm^-2 in KOH electrolyte. Consequently, the symmetric supercapacitor device with LIG electrodes, achieves capacitance of 216 mF cm^-2 at 2.5 mA cm^-2 using PVA-KOH electrolyte. Newly fabricated supercapacitor device exhibits good cycling stability and excellent mechanical flexibility hence, making it a potential candidate for wearable electronics.