Inês GOMES DA SILVA1, Meriem ANOUTI2, Fatima MONTEMOR1, Isabel MARRUCHO1
1Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
2Université François Rabelais, Laboratoire PCMB (EA 4244), équipe de Chimie-physique des Interfaces et des Milieux Electrolytiques (CIME), Parc de Grandmont, 37200 Tours, France, Tours, France
The world’s energy demand is increasing as a consequence of a growing and highly technological population that highly relies on fossil fuels, therefore, engaging renewable energy in the energy world supply is highly requirable. However, since most of renewable energy are intrinsically intermittent, energy harvest and distribution will largely depend on energy storage devices, namely supercapacitors [1]. Along with this aspiring goal, is desirable that the materials used to develop these devices are not only high-performance but also the most environmentally friendly possible [2]. In this work, mixtures of water with eutectic systems of sodium hexanoate with different carboxyl acids (hexanoic acid, octanoic acid, nonanoic acid and decanoic acid) are studied as potential electrolytes for Electrical Double Layer Supercapacitors (EDLCs).
In the first part of this study, physical characterization of these mixtures is studied through measurement and exploration of several properties, namely the conductivity, viscosity, density, surface tension and pH.
In the second part, the electrochemical performance of these mixtures is tested in EDLC cells with microporous activated carbon electrodes through Cyclic Voltammetry (CV), Galvanostatic Charge-Discharge (GCD) and Electrochemical Impedance Spectroscopy (EIS).
From this study the eutectic system of sodium hexanoate and hexanoic acid with 60% molar composition in acid (NaC6:C6(0.6)), showed the highest conductivity, 22.3 mS/cm at 20 °C, the highest electrode specific capacitance, 71.6 F/g at 0.2 A/g, and the lowest internal resistance, 1.83 Ω, for a weight water composition of 60%.
AcknowledgementsI.G. Silva gratefully acknowledges the financial support of FCT/MCTES (Portugal) for the fellowship 2021.07949.BD. This project was financed through FCT/MCTES (Portugal) within the project PTDC/EQU-EQU/4893/2021 and the CQE project (UIDB/00100/2020).
References
[1] C. Zhong, Y. Deng, W. Hu, D. Sun, X. Han, J. Qiao, J. Zhang, Electrolytes for electrochemical supercapacitors, 2016. https://doi.org/10.1201/b21497-6.
[2] M. Anouti, E. Couadou, L. Timperman, H. Galiano, Protic ionic liquid as electrolyte for high-densities electrochemical double layer capacitors with activated carbon electrode material, Electrochim. Acta. 64 (2012) 110–117. https://doi.org/10.1016/J.ELECTACTA.2011.12.120.