Zinc - Iodine Rechargeable Flow Battery with Optimized Zn Solution for High Energy Density Devices

Abstract

Nowadays, electrochemical energy storage systems have gaining interest because they constitute an essential element in the development of sustainable energy technologies [1,2]. Among them, rechargeable flow batteries (RFBs) are one of the most promising technology for the integration in grid-connected electricity, especially if combined with unpredictable and intermittent renewable energy sources, due to their high efficiency, power/energy independent sizing and room temperature operation [3]. At the moment, among all RFBs systems, the most investigated and advanced technology is the vanadium based RFB, characterized by an energy efficiency equal to 80% and energy density ranging 15-45 Wh/l [4]. However, currently the main bulk of research is focused on finding an economically convenient and technically competitive flow battery chemistry, able to ensure long lifetime and high energy efficiency [5,6]. In this study, a zinc-iodine RFB with low cost and high energy density will be presented. In particular, inorganic electrolytes based on high soluble salts have been developed to increase the charge density of the device. Moreover, a deep study on the effects of organic additive for the proper zinc developed electrolyte, aiming to reduce the dendrites growth and to increase the current efficiency, have been analyzed. In order to investigate the effect of these chemical compounds, the developed solutions have been characterized by means of cyclic voltammetries while the obtained zinc metallic coatings have been morphological characterized using scanning electron microscopy. The combination of high energy efficiency of the Zn-I RFB, in the order of 70% at 20 mA cm-2, with its very high energy density ranging from 25 to 60 Wh/l, depending on the formulation of the electrolytes, its ability to withstand a large number of charge/discharge cycles and the low cost, makes this battery system suitable for large energy storage applications. References P. Alotto, M. Guarnieri, and F. Moro. Renewable and Sustainable Energy Reviews 29 (2014): 325-335.A. Z. Weber, M.M. Mench,, J.P. Meyers, P.N. Ross, J.T. Gostick and Q. Liu. Journal of Applied Electrochemistry (2011), 41(10), 1137.G. Kear, A.A Shah, and F.C. Walsh. International journal of energy research, (2012), 36(11), 1105-1120.C. Ding, H. Zhang, X. Li, T. Liu, and F. Xing. The Journal of Physical Chemistry Letters, (2013), 4(8), 1281-1294.C- Xie, Y. Duan, W. Xu, H. Zhang, and X Li. Angewandte Chemie International Edition, (2017) 56(47), 14953-14957.S. Selverston, R. F. Savinell, and J. S. Wainright. Journal of The Electrochemical Society 164.6 (2017): A1069-A1075.