A High Efficiency Iron-Chloride Redox Flow Battery for Large-Scale Energy Storage

Abstract

We report advances on a novel membrane-based iron-chloride redox flow rechargeable battery that is based on inexpensive, earthabundant, and eco-friendly materials. The development and large-scale commercialization of such an iron-chloride flow battery technology has been hindered hitherto by low charging efficiency resulting from parasitic hydrogen evolution at the negative electrode and high overpotential losses. We have demonstrated a high charging efficiency of 97% by maintaining the negative electrolyte at a pH value of 2 and by using indium chloride as an electrolyte additive. The high charging efficiency of the negative electrode was found to be stable over at least 50 cycles. Further, we have demonstrated that with a graphite felt electrode, the overpotential losses were substantially mitigated at the positive and negative electrodes allowing the electrodes to be operated at current densities as high as 100 mA/cm 2 . With these technical advancements, the iron-chloride redox flow battery has an increased prospect of being a sustainable and efficient solution for large-scale energy storage. Large-scale energy storage systems that are inexpensive, robust, and highly efficient are essential for the integration of renewable energy sources like solar and wind into the electrical power grid. Rechargeable batteries are particularly promising for such grid-scale applications because of their efficiency, modularity, and flexibility to siting.1-4 Several battery systems including lithium-ion, lead-acid, sodium-sulfur, and the all-vanadium redox flow battery have been deployed at the mega-watthour scale.4-8 However, the levelized cost of energy delivered (LCOE) for these state-of-art battery systems is about ten to fifty times higher than the target values identified by the U.S. Department of Energy (DoE). [9][10][11] In addition, the aforementioned battery systems pose challenges from the standpoint of sustainability and environmental friendliness because of the relatively expensive and toxic materials used. Therefore, the development of high-performance and long-life batteries that use inexpensive, eco-friendly, and abundantlyavailable materials is an important topic of current research.Redox flow batteries for large-scale energy storage.-Redox flow batteries are particularly well-suited for large-scale energy storage applications. 3,4,[12][13][14][15][16] Unlike conventional battery systems, in a redox flow battery, the positive and negative electroactive species are stored in tanks external to the cell stack. Therefore, the energy storage capability and power output of a flow battery can be varied independently to suit the desired application. For example, if an application requires a battery with high energy content, the amount of electroactive species in the tanks can be increased without significant modification to the cell stack. As the electroactive material is held in the external tanks, an increase in the amount of electroactive species does not require an increase in the volume of the cell stack. Thus, m...

Effects of Temperature and Composition on Catholyte Stability in Vanadium Flow Batteries: Measurement and Modeling

“…[5][6][7][15][16][17] The chemistry of this system is perhaps the most thoroughly characterized and the cell design has been considerably optimized. 2,18,19 It has seen the widest commercial deployment 17 and systems as large as 250-1000 kWh have been demonstrated.…”

Techno-economic analysis of a process for CO2-free coproduction of iron and hydrocarbon chemical products

“…Whilst the individual reactions presented in Table 1 have been the subject of investigation by others (halogenation of methane using metal chlorides [30,[33][34], more specifically ferric chloride [35], coupling of methyl halides [25,[36][37][38], leaching of iron ore with HCl [39][40][41], iron-chloride redox flow batteries [42][43]), in this report we present a unique process intensification which couples each of these individual concepts. …”

“…The molten iron chloride salt leaving the ore-halide slurry reactor is sent to an iron-chloride redox electrolyser, which operates according to Figure 3 [42]. The redox chemistry is based on the iron (II) chloride/iron (III) chloride redox couple at the positive electrode and the iron (II) chloride/metallic iron couple at the negative electrode [42].…”

“…The redox chemistry is based on the iron (II) chloride/iron (III) chloride redox couple at the positive electrode and the iron (II) chloride/metallic iron couple at the negative electrode [42]. The open-circuit voltage is 1.21 V; however, an overpotential must be expected to drive acceptable current densities.…”

“…The 'all-iron' redox flow battery has been the subject of much interest in the field of large-scale energy storage systems since its conceptualization by Hruska and Savinell in 1981 [57]. Many of the technical and process challenges of the all-iron battery have since been well defined and significant technological and commercialization progress has been made [42,58] and is not explored further here.…”