Study of the influence of the type of pores present in the electrodes on the behaviour of a SWAGELOK-type supercapacitor

Abstract

The sharp increase in energy consumption in recent years has increased the demand for new energy storage systems or the improvement of existing ones. Supercapacitors are the answer to this great challenge needed by any industrialized society. In this work, to improve the storage system of these supercapacitors, the composition of carbon-based electrodes has been modified by adding carbon carbonaceous materials and the influence of porous texture (porosity and porosity distribution) on carbonaceous electrodes. Thus, a commercial activated carbon-based electrode PCO-1000 was modified by adding structured carbons TEG, TEG-B92, and carbon black V3. For this purpose, three PCO-1000 (commercial activated carbon) base electrodes were prepared, to which 5 % Teflon was added as a binder and 5 % TEG (structured carbon), TEG-B92 (92 h heat-treated structured carbon) and V3 (carbon black), to provide the electrodes with carbon porous structures, as well as graphitic structures with carbon separation between lamellar layers. The structured carbons (TEG and TEG-B92) have carbon structures formed by interlamellar layers at carbon spacing distances and micro, macroporous pore distributions versus V3 carbon black with meso-macroporous distributions. Furthermore, carbon black V3 was selected as it has a pore distribution (meso-macroporous) greater than 50 Å which is electrochemically accessible by aqueous solutions of H2SO4, in an organic medium large solvated ions are not accessible to small pores. The supercapacitor prepared on the PCO-1000 basis with V3 (E-V3), is the best performing, with capacity, power, and energy parameters far superior to the other samples. This seems to indicate that E-V3 supercapacitors with a varied pore structure perform better than those with a predominantly micropore distribution. It seems to be deduced that it is the wide mesopores present in V3 that favour the diffusion of ions inside the carbons. In conclusion, the resistance of the supercapacitor cell is strongly dependent on the resistance of the electrolyte used, the size of the electrolyte ions in which it diffuses, and the size of the electrode pores, so the characteristics of the electrode material and the electrolyte must be considered together and not separately. Finally, this study could be of great importance in the fabrication of electrodes with a certain porosity distribution and predominance of wide mesopores and macropores to achieve important energy storage capacities in this type of supercapacitors and their application to hybrid electric vehicles, computers, uninterruptible power supply systems (UPS), motor starters, etc.