Preparation Of PANI/Graphene Composites And Their Application In Supercapacitors

Energy is the crucial foundation for the survival and development of human beings. Effective energy storage and conversion is becoming one of the key problems in the sustainable development of the society. As a new energy storage and conversion device, supercapacitor has a series of advantages such as fast charging and discharging, high power density and excellent cycle performance, which has shown promising applications in the area of portable electronics, medical equipment and hybrid electrical vehicles. Based on different energy storage mechanisms, supercapacitor can be divided into two categories, one is double layer capacitor such as graphene that has good rate and cycle stability but low specific capacitance value; another one is pseudo capacitor such as polyaniline that has the advantage of high specific capacitance value but poor rate capability. In order to combine the advantages of the above two different materials and overcome their shortcomings, this research focuses on the design of PANI/graphene composites for supercapacitors and eventually the electrochemical performance of the composites was improved by the synergistic effect of the two components. The main contents are as follows:(1) The PANI/graphene composites were obtained by introducing phytic acid as the crosslinking agent. By field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) characterizations, it is revealed that the introduction of phytic acid can facilitate the formation of three-dimensional polyaniline/graphene networks. The obtained composite was utilized as the electrode for supercapacitors. Due to the interconnected 3D network, quick ion diffusion and electron transfer was obtained. As a result, the composite exhibited excellent specific capacitance. Experimental parameters, such as the phytic acid content, aniline content, reduction time, polymerization time, were optimized systematically. High capacity of 536 F/g at scan rate of 2 mv/s was achieved under the optimal conditions.(2) A novel approach to synthesize PANI/graphene composites by oxidative polymerization of aniline in the confined space between graphene layers has been developed. This method employs 2D graphene films derived from 3D graphene hydrogel (SGH) as the precursor. The direct growth of PANI nanorods in the confined space between the graphene layers can produce a binder-free PANI/graphene electode. The present of the confined space can effectively guide the growth of PANI nanorods between the graphene layers. Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Raman spectroscopy (Raman) and X-ray photoelectron spectroscopy (XPS) characterizations confirm that the PANI nanowires were successfully grown in the confined space. This was well defined PANI/graphene sandwich structure can be effectively used as the electrode for supercapacitors directly. The synergistic effect between the graphene matics and the loaded PANI nanorod makes this kind of PANI/graphene composite a good candidate for supercapacitors, which delivered high specific capacitance of 465 F/g(0.1 A/g) and retain 80% of the pristine capacitance after 3000 cycles as the charge discharge current of 1 A/g.