Transient Modeling of a Vanadium Redox Flow Battery and Real-Time Monitoring of Its Capacity and State of Charge

Abstract

The vanadium redox flow battery (VRFB) is a rechargeable flow battery that is one of the most promising large-scale energy storage systems making it suitable for grid-level energy storage. However, the self-discharge reactions along with the undesired side reactions and water transfer through the membrane cause imbalance in the electrolyte and state of charge, which can significantly reduce the capacity of these batteries. A first-principles, 2D electrochemical dynamic model of all-VRFB is developed. The electrochemical model includes self-discharge reactions caused by diffusion, convection, and migration of the vanadium ions from one half-cell to the other. In addition, side reactions leading to evolution of hydrogen and oxygen are modeled. Water transport through the membrane is modeled by considering transport of water along with vanadium ions due to electro-osmotic drag and diffusion between two electrolyte half-cells. The model is validated with the experimental data. A filtering approach is developed for co-estimation of state of charge and capacity. Using a state-space model identified using the data generated by the pseudo-random binary sequence in the current and electrolyte flowrates, the filtering approach is found to yield satisfactory estimation of the state of charge and capacity by using voltage as the only measured output variable.

Anion Exchange Membranes Based on Bis-Imidazolium and Imidazolium-Functionalized Poly(phenylene oxide) for Vanadium Redox Flow Battery Applications

“…Characterization. 1 H NMR spectra of ImPPO, BImPPO, BrPPO and 2,3-dimethyl-1-(6-(2-methylimidazol-1yl)hexyl)-imidazolium iodide were recorded on a Varian 400 MHz spectrometer (Varian CP-3800). The mechanical properties of ImPPO-and BImPPO-based membranes were studied using an Instron 3365 at 25 °C.…”

“…Vanadium redox flow batteries (VRFBs) have attracted great attention for their long service life, operational flexibility, and environmental friendliness. 1 − 3 An important component of VRFBs, the ion-exchange membrane (IEM), is used to separate the anode of VRFBs from their cathode. 4 , 5 The low vanadium permeability, high conductivity, and robust chemical stability are required for an ideal IEM in the application of VRFBs.…”

“…Vanadium redox flow batteries (VRFBs) have attracted great attention for their long service life, operational flexibility, and environmental friendliness. − An important component of VRFBs, the ion-exchange membrane (IEM), is used to separate the anode of VRFBs from their cathode. , The low vanadium permeability, high conductivity, and robust chemical stability are required for an ideal IEM in the application of VRFBs . Currently, Nafion membranes are commonly used as IEMs in VRFBs owing to their high conductivity. − However, the high vanadium permeability of Nafion significantly hinders its commercialization in this field. , Recently, sulfonated poly­(arylene ether) has been widely used as an IEM material for VRFBs because of its high conductivity and good chemical stability. , Nevertheless, the high vanadium permeability of sulfonated poly­(arylene ether) membranes remains unresolved. − …”