Nonlinearity of the heterogeneous process of zinc release in flow Batteries

Abstract

Currently, there is a worldwide search for technologies allowing to use alternative (renewable) energy sources. It is related to both the environmental degradation and the growing demand for electricity. In recent times, concerning the transition to “alternative” types of energy, there was a great interest in flow hybrid-type batteries, specifically, zinc ones. Since these energy batteries have a number of issues associated with the formation of zinc dendrites, the hydrogen release and the corrosion, research is being conducted to improve technologies. Mathematical modeling is one of the methods for studying fundamental processes occurring at the interface in heterogeneous systems. In this article, it is proposed a numerical algorithm that allows to find rate constants of near-electrode processes, predict the yield and study the influence of separate processes. The algorithm is exemplified by the problem of zinc release predicting with competing reaction of hydrogen release during the electrolysis of a sodium hydroxide solution containing sodium tetrahydroxozicate. This algorithm is verified using full-scale experiments. Thus, in this article, there are found the constants of cathodic stepwise electrochemical reactions of zinc powder production using direct search method. In order to solve a direct problem consisting of kinetic equations describing stepwise cathodic reactions, it was tested explicit and implicit Runge-Kutta methods. Calculations have shown that at the initial phase of nucleus growth (teeting) has a great influence. Therefore, at the initial phase during the formation of zinc nucleus on steel electrode it is observed a delinearity of process. Further, the linearity of the process is eventually established.