Self-discharge of the alkaline iron electrode

153

197

Inexpensive, robust and efficient large-scale electrical energy storage systems are vital to the utilization of electricity generated from solar and wind resources. In this regard, the low cost, robustness, and eco-friendliness of aqueous iron-based rechargeable batteries are particularly attractive and compelling. However, wasteful evolution of hydrogen during charging and the inability to discharge at high rates have limited the deployment of iron-based aqueous batteries. We report here new chemical formulations of the rechargeable iron battery electrode to achieve a ten-fold reduction in the hydrogen evolution rate, an unprecedented charging efficiency of 96%, a high specific capacity of 0.3 Ah/g, and a twenty-fold increase in discharge rate capability. We show that modifying high-purity carbonyl iron by in situ electro-deposition of bismuth leads to substantial inhibition of the kinetics of the hydrogen evolution reaction. The in situ formation of conductive iron sulfides mitigates the passivation by iron hydroxide thereby allowing high discharge rates and high specific capacity to be simultaneously achieved. These major performance improvements are crucial to advancing the prospect of a sustainable large-scale energy storage solution based on aqueous iron-based rechargeable batteries. Large-scale electrical energy storage systems are needed to accommodate the intrinsic variability of energy supply from solar and wind resources.1,2 Such energy storage systems will store the excess energy during periods of electricity production, and release the energy during periods of electricity demand. Viable energy storage systems will have to meet the following requirements: (i) low installed-cost of <$100/kWh, (ii) long operating life of over 5000 cycles, (iii) high round-trip energy efficiency of over 80%, and (iv) ease of scalability to megawatt-hour level systems.2 Rechargeable batteries are particularly suitable for such large-scale storage of electrical energy because of their high round-trip efficiency and scalability. Among the types of rechargeable batteries under consideration are vanadium-redox, sodium-sulfur, zinc-bromine, zinc-air and lithium-ion batteries. 3,4 In addressing the challenges of durability, cost, and large-scale implementation of the foregoing types of batteries, the beneficial features of iron-based alkaline batteries for large-scale energy storage have been largely overlooked. Nickel-Iron batteries have been used in various stationary and mobile applications for over 70 years in the USA and Europe until the 1980s when the iron-based batteries were largely supplanted by sealed lead-acid batteries. Iron-air batteries because of their high specific energy underwent active development for electric vehicles and military applications in the 1970s after the "oil shock" but major research in this area was abruptly discontinued after 1984. Except for some seminal research in India by Shukla et al. during the period 1986-1992, iron electrodes have not received any significant attention. [5][6][7] We e...

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confidence: 99%

A High-Performance Rechargeable Iron Electrode for Large-Scale Battery-Based Energy Storage

Manohar

Malkhandi

Yang

et al. 2012

153

197

“…13, 14 The sparingly soluble nature of iron (II) hydroxide ensures that the growth of iron crystals from the ferrite ion occurs adjacent to the iron (II) hydroxide phase. Also, the sparingly low solubility of the ferrite ion results in preferring nucleation over growth, leading to small crystallites of iron.…”

Section: Resultsmentioning

confidence: 99%

“…[13][14][15][16] Such robustness is generally uncommon among rechargeable batteries; other types of batteries in use today degrade in about 1000 cycles.…”

Section: 8mentioning

confidence: 99%

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

Yang

Manohar

Narayanan

2017

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 ...

“…The solution resistance was evaluated for the three-electrode setup by the current interrupt method before starting an experiment. The solution resistances obtained (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13) were neglected because of their insignificant effect on the measured potential. Cyclic voltammograms (CVs) were prepared by sweeping the potential between −1.4 and −0.7 V vs. Ag/Ag 2 O with a scan rate of 200 μVs −1 .…”

Section: Methodsmentioning

confidence: 99%

“…Thus, Fe electrodes are not resource-restricted and can contribute to large scale solutions when incorporating renewable energy in our electricity grids. The Fe electrode was first used as an anode in the alkaline Ni-Fe battery, developed by the Edison Company, [2][3][4][5] at the beginning of the 20th century. Despite the fact that the Fe electrode has been known and used for over a century, it suffers from long-term inefficiency.…”

mentioning

confidence: 99%

Stannate Increases Hydrogen Evolution Overpotential on Rechargeable Alkaline Iron Electrodes

Chamoun

Skårman

Vidarsson

et al. 2017

Alkaline iron electrodes present some challenges for use in secondary batteries that are associated with low coulombic efficiency and discharge utilization. Low coulombic efficiency is correlated to the hydrogen evolution reaction that takes place during charge. In this work, we demonstrate rechargeable alkaline iron electrodes with significant capacity retention over 150 cycles with high efficiency by suppressing the hydrogen evolution with stannate. Adding stannate to the alkaline electrolyte when cycling the iron electrode drastically changes the electrochemistry. The additive brings on two advantageous attributes for the iron electrode: increased hydrogen evolution overpotential, and a flat and prolonged discharge curve at typical battery operation. These attributes were provided by a novel intermediate phase that was detected from in situ neutron diffraction measurements. This phase was only detected in situ while it decomposed ex situ, and indicated a solid solution constituted by some of the elements present in the electrode.