Fabrication of porous graphene/polyimide composites using leachable poly-acrylic resin for enhanced electrochemical and energy storage capabilities

Abstract

Specific capacitance of graphene–polyimide composites is significantly enhanced by incorporation of porous structures in the polymer composite. The selective decomposition of thermally labile poly-acrylic resin introduced into the composite during synthesis creates pores of varying size and shapes. It is noted that samples synthesized with lower weight percent acrylic polymer produced more uniform sized pores than those with higher weight percent. The presence of pores increased available surface area of the stacked graphene sheets available for ion adsorption and double layer formation. Scanning electron microscope (SEM) images confirms the presence of pores and reveals filler orientation around porous regions. Cyclic voltammetry (CV) show an increase in specific capacitance from 39 F g⁻¹ to 133 F g⁻¹ and electrochemical impedance spectroscopy (EIS) shows significant decrease in bulk resistance and a 100% increase in theoretical porosity when tested in 0.4 M potassium hexaflorophosphate VI (KPF6)/propylene carbonate electrolyte solution. Shifts in imide peaks to lower wave numbers in Raman and Fourier transform spectroscopy (FTIR) suggests presence of chemical interaction between filler and matrix confirming uniform dispersion of fillers in the material. Thermogravimetric analysis (TGA) shows thermal stability for the composite systems at temperatures above 700 °C. The material is investigated for use in super capacitor applications especially in devices which require high end-use temperatures.