A High-Performance Sintered Iron Electrode for Rechargeable Alkaline Batteries to Enable Large-Scale Energy Storage

Abstract

Iron-based alkaline rechargeable batteries such as iron-air and nickel-iron batteries are particularly attractive for large-scale energy storage because these batteries can be relatively inexpensive, environment-friendly, and also safe. Therefore, our study has focused on achieving the essential electrical performance and cycling properties needed for the widespread use of iron-based alkaline batteries in stationary and distributed energy storage applications. We have demonstrated for the first time, an advanced sintered iron electrode capable of 3500 cycles of repeated charge and discharge at the 1-hour rate and 100% depth of discharge in each cycle, and an average Coulombic efficiency of over 97%. Such a robust and efficient rechargeable iron electrode is also capable of continuous discharge at rates as high as 3C with no noticeable loss in utilization. We have shown that the porosity, pore size and thickness of the sintered electrode can be selected rationally to optimize specific capacity, rate capability and robustness. These advances in the electrical performance and durability of the iron electrode enables iron-based alkaline batteries to be a viable technology solution for meeting the dire need for large-scale electrical energy storage. Electrical energy storage systems will enable the seamless integration of the electricity generated from wind turbines and solar photovoltaics into the electricity grid. Rechargeable batteries are particularly good candidates for such large-scale energy storage because of their high round-trip efficiency, inherent scalability, and flexibility for being located almost anywhere.1-6 Batteries such as vanadiumredox, lead-acid and lithium-ion are under consideration for this application because of their commercial availability. Yet, the widespread deployment of these battery systems is limited by their materials cost, lifetime, safety concerns, and the high cost of delivered energy. 7,8Rechargeable iron-based alkaline batteries such as nickel-iron and iron-air have unique advantages that make them particularly attractive for meeting the emerging demands of grid-scale electrical energy storage systems.6,9-12 Iron, the primary raw material for these battery systems, is globally abundant, relatively inexpensive, eco-friendly and is recycled readily. Thus, iron is particularly attractive as a raw material for batteries required at such a large scale.6 Iron-based batteries such as the nickel-iron battery are historically well known for their extraordinary robustness to thousands of cycles of charge and discharge, and tolerance to overcharge and over-discharge. [13][14][15][16] Such robustness is generally uncommon among rechargeable batteries; other types of batteries in use today degrade in about 1000 cycles.17 For example, lead-acid batteries typically offer 500-800 cycles, and lithium-ion batteries usually last no more than 1000 cycles especially when subjected to deep discharge.18 Despite these striking attributes of iron-based batteries, the large-scale use of these batteries ...

Development of the Iron Electrode for Utility Scale Energy Storage

“…A slurry or dry iron powder can be heated at temperatures approaching the melting temperature in order to sinter the iron. Yang et al, referencing much earlier work by Vassie and Tseung, noted that sintered electrodes were likely to be more mechanically robust than pressed electrodes and this has importance for attaining long cycle lives [19], [135]. In this work, Vassie and Tseung refer to electrodes being produced from either iron or iron oxide, but both routes require a reducing atmosphere ( 2 ) to avoid excessive oxidation of the iron active material at sintering temperatures.…”

“…More recently, Narayanan et al have published extensively on various production methods of iron electrodes and additives for improving their performance in work primarily published in the Journal of the Electrochemical Society and funded by the U.S. [19], [22], [52], [79]- [85]. In this same time period, Posada and Hall et al of the University of Sheffield have written several articles on iron electrode additives [54], [86]- [91] and have completed a review on aqueous batteries with contribution from this author [18].…”

“…Various studies have demonstrated the suppression of the hydrogen evolution reaction by incorporating additives and reducing impurities within the iron electrode [54], [62], [75], [79]- [81], [112]. Sulfide additions in the form of iron sulfide have been reported to have a beneficial effect [19], [22], [67]. The overpotential for hydrogen evolution is also said to be increased along with capacity [113].…”

“…The temperatures involved in sintering iron are inherently expensive and the author considers that, ideally, a temperature should be chosen such that iron could be sintered evenly in less than five minutes, to be sympathetic to the needs of mass production via a semi-continuous roll to roll production line. Sintering in reviewed literature was not achieved in less than 15 minutes [19], [75], [76], [135]. This author considers there to be merit in research into rapid sintering of iron electrodes.…”

“…Hydrogen evolution (Equation 1.6-2) is the main reason for the poor faradaic efficiency of the iron electrode and occurs preferentially to the charging (iron reduction) reaction (Equation 1.6-1) as it is more favorable [19]:…”