Facile Preparation and Boosted Electrochemical Properties of Carbon/Carbon Composite Electrodes for Supercapacitors

Herein, a kind of carbon/carbon composite electrode is prepared using polyimide (PI)/3D sphere-like polyimide composite films as precursors, followed by carbonization. 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride are polymerized and thermally imidized to form the matrix, and 3D sphere-like PI particles synthesized by the solvothermal process are introduced via the in situ polymerization method. The electrochemical behaviors of C/C composites are examined in relation to the loading of the 3D sphere-like PI crystals and carbonization temperatures. The C/C composite PI/5%3D-PI-800 demonstrates a specific capacitance maximum of 322.7 F g(-1) at 0.5 A g(-1) due to synergistic effects between different types of PIs. The specific capacitance decreases to 214 F g(-1) with a retention rate of 66.3% as the current density increases to 10 A g(-1). Moreover, the symmetrical supercapacitor (SC) assembled by PI/5%3D-PI-800 shows a specific capacitance of 244.4 F g(-1) at 0.5 A g(-1), with a high energy density of 33.94 Wh kg(-1) and a power density of 500 W kg(-1). In addition, after 6 months of storage, the button SC is retested and still shows fantastic capacitance retention rate of above 99.5%. Thus, this work proposes a facile method to fabricate the C/C composite electrodes with outstanding electrochemical properties.