Structural adjustment on fluorinated graphene and their supercapacitive properties in KI-additive electrolyte

[Display omitted] •F content and porous structure are tuned by heating and chemical reduction of FG.•Semi-ionic C-F species enhance the supercapacitive properties in KI electrolyte.•The introduction of KI promotes the specific capacitance up to 583 from 17 F/g. To investigate the effect of structural properties of fluorinated graphene (FG) on the supercapacitive properties in KI additive electrolyte, the porous structure and surface F element content of FG were adjusted via chemical reduction by hydrazine and heating treatment. Systematically electrochemical measurements show that there is a dramatical increase of specific capacitance (583 F/g) in KI-additive electrolyte due to the pseudocapacitance brought by KI compared with that (17 F/g) in pure H2SO4 electrolyte. Investigation on the relationship between F content and areal capacitance show that small amount of F content, especially for semi-ionic C-F species with better electronic conductivity compared with covalent C-F species, can effectively promote the areal capacitance. With moderate F content and relatively high specific surface area, the assembled symmetric supercapacitor can deliver an energy density of 8.89 Wh kg−1 and exhibits a long cyclic stability.