Laser-induced graphene and its modification with polypyrrole for increasing microsupercapacitor capacitance

Laser-induced graphene (LIG) films were synthesized by line-by-line scanning of cw CO$_2$ laser focused radiation on the surface of industrial polyimide film as a result of pyrolysis of its near-surface layer. The structure of the synthesized film material is shown to be heterogeneous in thickness by Raman spectroscopy. The results of the study of the effect of the laser power and the distance between the lines on the specific electrical capacitance c of the synthesized material in aqueous solution of sulfuric acid are presented. It is shown that modification of LIG with polypyrrole (PPy) allows to increase c up to 60 mF/cm$^2$. PPy-modified LIG films were used to make a prototype of a flexible film microsupercapacitor with an area of 8 cm$^2$, using a gel electrolyte based on sulfuric acid and polyvinyl alcohol, with a 230 mF capacitance.