Iron-air Batteries Research Articles

Demonstration of 10+ hour energy storage with ϕ1′′ laboratory size solid oxide iron–air batteries

Long duration electricity storage (LDES) with 10+ hour cycle duration is an economically competitive strategy to accelerate the penetration of renewable energy into the utility market.

Synthesis of Fe2O3 nanomaterials for a rechargeable battery anode

Iron electrode plays an important role in iron-air batteries. Mastering the fabrication technology of this electrode material is a key step in improving capacity, cycling efficiency, and lowering the cost of commercial batteries. The sol-gel method is known to be simple and easy to implement for producing nanomaterials. In this study, α-Fe2O3 nanoparticles with various shapes were synthesised by the sol-gel method for iron-air battery anodes. Electrochemical characteristic measurements performed on Fe2O3/AB electrodes using synthesised Fe2O3nanomaterials showed that the size and morphology of iron particles strongly affect their cycleability. Optimisation of the fabrication process to obtain the suitable Fe2O3 particle size and shape for the best electrochemical properties was performed. Additionally, the effect of the K2S additive in electrolyte solution on the electrochemical properties of the Fe2O3/AB electrode was also studied.

High Performance Iron Electrodes with Metal Sulfide Additives

Iron-based alkaline rechargeable batteries are promising candidates for large-scale energy storage applications owing to their low cost, robustness and environmental-friendliness. However, the widespread deployment of iron-based batteries has been limited by the low charging efficiency and poor discharge rate capability of the iron electrode. Our previous efforts on iron electrodes based on carbonyl iron powder and iron (II) sulfide have shown promise in overcoming these limitations. With the goal of understanding the role of sulfide additives, in this study, we have compared the performance of iron electrodes with iron (II) sulfide, iron (II) disulfide, copper (I) sulfide and zinc sulfide. The electrode containing zinc sulfide outperformed all other electrodes with a remarkable faradaic efficiency of 95% at C/2 rate and a specific discharge capacity close to 0.24 Ah g−1 at 1 C rate. The electrode did not lose any capacity for 750 cycles of repeated deep discharge at C/2 charge and discharge rates. Further, these electrodes could be cycled at 55 degrees Celsius with no noticeable change in performance. We attributed the excellent performance of zinc sulfide containing electrode to the low solubility of zinc sulfide in the electrolyte and the stability of zinc sulfide towards electro-reduction under the operating conditions of the iron electrode. These insights indicate that zinc sulfide is a promising additive for designing highly efficient and robust iron electrodes for alkaline nickel-iron and iron-air batteries.

Improved battery capacity and cycle life in iron-air batteries with ionic liquid

Hydrogen releasing and electrode passivation are the major factors resulting in low cycling stability of Fe-air batteries with battery capacity deterioration. Here we introduce a new approach to restrain these drawbacks by adding ionic liquid (1-ethyl-3-methylimidazolium L-(+)-lactate, abbrev. EML) as an electrolyte additive to suppress both hydrogen releasing and passivation formation on the electrode surface during battery discharge. By utilizing hydrogen volume, electrochemical, and battery capacity measurements, the impact of ionic liquid EML on the performance of the Fe-air battery has been clearly demonstrated. The introduction of EML as an electrolyte additive allows for the inhibition of hydrogen releasing with an efficiency of over 97%. The nature of ionic liquid EML enables to prevent the passive layer formation on the Fe electrode surface by forming iron (II) lactate instead of iron oxides. As a result, a Fe-air battery with ionic liquid EML achieves capacity retention after 1000 cycles higher than 94% with a nominal capacity of 0.416 Ah g−1 at C/5. This approach provides a promising direction for the future development of ionic liquids as electrolyte additives that can be used to improve the cycling life of Fe-air batteries.

Effect of carbon material additives on hydrogen evolution at rechargeable alkaline iron battery electrodes

In recent years a renewed interest in developing iron electrode for iron based accumulators has risen, govern by the progress in nano-materials research that could bring iron based accumulators nearer to their theoretical energy density and capacity. In this aspect, Iron-Air battery chemistry is best suited for current energy crisis in combination with the cost effectiveness, eco-friendliness, recyclability, non-toxicity of the iron materials. The possibility of Iron-Air battery to function as a rechargeable battery makes this electrochemical systems for engaging development. However, some challenges related to the performance of iron electrode needs to be addressed such as the passivation of the iron electrode on discharge due to the accumulation of iron hydroxide and the low efficiency due to the parasitic hydrogen evolution that occurs during the charging. So the proper engineering and the formulation of iron electrodes are necessary to attain the maximum efficiency for Iron-Air battery. In this exertion, different Fe2O3/Carbon (Fe/C) composites are tested as electrodes for Iron air battery. In addition to this, the prepared materials were comprehensively characterized by X-ray diffraction (XRD). The electrochemical effectiveness of the prepared samples were tested in a three electrode configuration.Fe2O3/MWCNT electrode show the best electrochemical performance exhibits a specific capacity of about 350 mAhg−1 at 10 mA cm−2 compared to the Fe2O3/Graphene of 300 mAhg−1, Fe2O3/Acetylene black of 225 mAhg−1 and Fe2O3/Vulcan carbon of 180 mAhg−1.

Quasi-solid-state electrolyte for rechargeable high-temperature molten salt iron-air battery

Molten salts are a unique type of electrolyte enabling high-temperature electrochemical energy storage (EES) with unmatched reversible electrode kinetics and high ion-conductivities, and hence impressive storage capacity and power capability. However, their high tendency to evaporate and flow at high temperatures challenges the design and fabrication of the respective EES devices in terms of manufacturing cost and cycling durability. On the other hand, most of these EES devices require lithium-containing molten salts as the electrolyte to enhance performances, which not only increases the cost but also demands a share of the already limited lithium resources. Here we report a novel quasi-solid-state (QSS) electrolyte, consisting of the molten eutectic mixture of Na2CO3-K2CO3 and nanoparticles of yttrium stabilized zirconia (YSZ) in a mass ratio of 1:1. The QSS electrolyte has relatively lower volatility in comparison with the pristine molten Na2CO3-K2CO3 eutectic, and therefore significantly suppresses the evaporation of molten salts, thanks to a strong interaction at the interface between molten salt and YSZ nanoparticles at high temperatures. The QSS electrolyte was used to construct an iron-air battery that performed excellently in charge-discharge cycling with high columbic and energy efficiencies. We also propose and confirm a redox mechanism at the three-phase interlines in the negative electrode. These findings can help establish a simpler and more efficient approach to designing low-cost and high-performance molten salt metal-air batteries with high stability and safety.

Combined microbial electrolysis cell–iron-air battery system for hydrogen production and swine wastewater treatment

Swine wastewater is a typical high-strength animal wastewater. For treatment, it often requires combined processes (i.e., integrated units), such as multiple anaerobic reactors and advanced treatments. Microbial electrolysis cells (MECs) are a promising technology for wastewater treatment and simultaneous hydrogen harvesting. In this study, we constructed a MEC powered by an iron-air battery to treat swine wastewater and produce hydrogen efficiently. The performance of iron-air batteries with different electrolyte concentrations was compared in terms of coagulant production and power generation. The highest coagulation performance was obtained with coagulants generated using a battery with 35 g/L NaCl, which achieved 54 % ± 3%, 27 % ± 2%, 49 % ± 1%, and 34 % ± 3% removal of ammonia, chemical oxygen demand (COD), suspended solids (SS) and turbidity, respectively. Powered by the iron-air battery with 35 g/L NaCl, the hydrogen generation rate of MEC reached approximately 6 L/m3·d using raw swine wastewater and 57 L/m3·d using coagulated swine wastewater. The reduction of organics by coagulating helped improve hydrogen production. The total COD removal by the coagulation process integrated with MEC reached 98 % ± 0.2 %. The iron-air battery–MEC system is a promising method for simultaneous hydrogen production and wastewater treatment without any additional energy input.

Effects of pore morphology on the cyclical oxidation/reduction of iron foams created via camphene-based freeze casting

Solid-oxide iron-air batteries have potential for applications in large-scale energy storage systems, but their storage materials, iron and iron oxides, have limited cycle life due to powder sintering and choking of gas flow. To address this issue, Fe foams are synthesized with either equiaxed or directional dendritic pore structures by camphene-based freeze casting of Fe2O3 powders, followed by H2 reduction to Fe and sintering. For each pore architecture, Fe foams are created with three different initial porosities, ranging from 47 to 63 vol %, and are then cycled at 800 °C under alternating oxidation (via H2O) and reduction (via H2) conditions. The redox-cycled foams are examined by optical microscopy, scanning electron microscopy, and synchrotron X-ray tomography to assess the evolution of their porosity driven by the redox volume changes, sintering, and micropore formation via the Kirkendall effect. After 5 redox cycles, the Fe foams have lost the majority (39 ± 2 vol %) of their initial porosity.

Finite Element Model for Coupled Diffusion and Elastoplastic Deformation during High-Temperature Oxidation of Fe to FeO

Solid-oxide iron-air batteries are an emerging technology for large-scale energy storage, but mechanical degradation of Fe-based storage materials limits battery lifetime. Experimental studies have revealed cycling degradation due to large volume changes during oxidation/reduction (via H2O/H2 at 800 °C), but degradation has not yet been correlated with the microstructural stress and strain evolution. Here, we implement a finite element model for oxidation of a Fe lamella to FeO (74% volumetric expansion), in a lamellar Fe foam designed for battery applications. Growth of FeO at the Fe/gas interface is coupled, via an oxidation reaction and solid-state diffusion, with the shrinkage rate of the Fe lamellar core. Using isotropic linear elasticity and plastic hardening, the model simulates deformation of a continuously growing FeO layer by dynamically switching “gas” elements into new “FeO” elements along a sharp FeO/gas interface. As oxidation progresses, the effective plastic strain and von Mises stress increase in FeO. Distribution of tensile and compressive stresses along the Fe/FeO interface are validated by oxidation theory and explain interface delamination, as observed during in operando X-ray tomography experiments. The model explains the superior stability of lamellar vs dendritic foam architectures and the improved redox lifetime of Fe-Ni foams.

In operando tomography reveals degradation mechanisms in lamellar iron foams during redox cycling at 800 °C

The lifetime of iron-based active materials in high-temperature redox applications (e.g., solid-oxide iron-air batteries, chemical looping) is limited by sintering, accelerated by oxidation/reduction volume changes. Here, in operando X-ray microtomography is used to reveal the evolution of structure, porosity, and extent of reaction in freeze-cast, lamellar iron foams during five redox cycles between Fe and FeO/Fe3O4 (via H2 and H2O) at 800 °C. Foam porosity decreases during oxidations but only partially recovers during reductions, with a net decrease from 77 to 52%. A gas-blocking surface layer, or shell, forms around the foam exterior. By correlating SEM microanalysis with in operando data, the Kirkendall effect is identified as the primary mechanism underlying these degradations. These insights suggest that material lifetime can be improved by measures that prevent the Kirkendall effect, such as combining iron with elements (in solid solution or as a second, redox-inactive phase) that lessen the imbalance of diffusional fluxes.

Silicon and Iron as Resource-Efficient Anode Materials for Ambient-Temperature Metal-Air Batteries: A Review.

Metal-air batteries provide a most promising battery technology given their outstanding potential energy densities, which are desirable for both stationary and mobile applications in a “beyond lithium-ion” battery market. Silicon- and iron-air batteries underwent less research and development compared to lithium- and zinc-air batteries. Nevertheless, in the recent past, the two also-ran battery systems made considerable progress and attracted rising research interest due to the excellent resource-efficiency of silicon and iron. Silicon and iron are among the top five of the most abundant elements in the Earth’s crust, which ensures almost infinite material supply of the anode materials, even for large scale applications. Furthermore, primary silicon-air batteries are set to provide one of the highest energy densities among all types of batteries, while iron-air batteries are frequently considered as a highly rechargeable system with decent performance characteristics. Considering fundamental aspects for the anode materials, i.e., the metal electrodes, in this review we will first outline the challenges, which explicitly apply to silicon- and iron-air batteries and prevented them from a broad implementation so far. Afterwards, we provide an extensive literature survey regarding state-of-the-art experimental approaches, which are set to resolve the aforementioned challenges and might enable the introduction of silicon- and iron-air batteries into the battery market in the future.

Improving the stability and discharge capacity of nanostructured Fe2O3/C anodes for iron-air batteries and investigation of 1-octhanethiol as an electrolyte additive

Iron-based aqueous batteries, such as the iron-air and nickel-iron chemistries, are limited by passivation and hydrogen evolution at the iron anode, especially at high current densities. In this paper, strategies to minimise these issues are investigated with iron electrodes composed of 20–50 nm Fe2O3 nanoparticles produced by the Adams and Oxalate methods. The strategies include ball milling the Fe2O3 with Ketjenblack carbon to improve conductivity, addition of bismuth sulphide to the electrode and 1-octanethiol to the electrolyte, and addition of potassium carbonate as a pore-forming agent. The ratio of Fe/C in the electrode and the 1-octanethiol additive have the greatest impact on the electrode capacity. The Fe/C ratio should be below 2.0 to ensure conductivity of the discharged electrode. The presence of 1-octanethiol can protect the electrodes from passivation during discharge; at very high 2C discharge rates adding 1-octanethiol increases the electrode specific capacity from 17 to 171 mAh/gFe. The synthesis method and use of pore former do not have a significant effect on the capacity. In all electrodes, the Fe2O3 nanoparticles are in the same crystalline phase after cycling and do not undergo significant crystal growth and passivation, demonstrating the stability and suitability of these materials for iron-based batteries.

Performance and degradation behavior of carbonyl Fe – MoS2 composite as anode material in Fe-air batteries

The two technical limitations of iron-air batteries are: (1) Hydrogen evolution reaction (HER) and (2) Passivation. HER account for low charging efficiency while passivation in Fe-air batteries account for its inability to fully discharge at a high rate due to the formation of iron hydroxide. As a result of this, many studies has been dedicated to inhibit these problems. Just like in recent literature, the enhancement of Fe-air anode for commercialization is not trivial. With high purity carbonyl Fe–MoS2 composites electrode and the influence of 2 mM Na2S additives in 6 M KOH electrolyte solution and 1.88 wt % polyacrylic acid as the gelling agent, we have demonstrated a high performance carbonyl Fe anodes comprising of 3 wt % MoS2 (F3M), 5 wt % MoS2 (F5M), and 10 wt % MoS2 (F10 M) additives in Fe anodes. The result of the various electrodes characterized via field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) reveals a distinct surface morphology that correspond to fundamental crystallographic growth patterns. Additionally, Energy dispersive spectroscopy (EDS) and SEM mapping affirms that both the Fe and additive (weight (Wt. %) and atomic percent (At. %)) were well dispersed in the electrode. According to Tafel test, F3M, F5M, and F10 M exhibits corrosion inhibition efficiency of 51.2%, 21.1% and 5.6% respectively. Thus, the corrosion rate decreased in the order of bare Fe > F10 M > F5M > F3M. While drastic capacity retention drops occur in the bare Fe electrode around 300th cycle, we were able to regenerate the battery back to full capacity via our choice of additives (F3M). During regeneration at 800th cycles, the capacity retention of F3M, F5M and F10 M electrodes were 97%, 93%, and 76% respectively. Therefore, in conjunction with the unique structure and synergistic effect that characterizes two excellent anode materials, F3M is best choice for a high-performance Fe-air battery due to its excellent performance, low side effects (corrosion and passivation), low float current, superior capacity retention and efficiency during cycling compare to F5M and F10 M.

Electrode thickness-dependent formation of porous iron electrodes for secondary alkaline iron-air batteries

Secondary iron-air batteries re-gained considerable scientific attention due to their excellent energy densities, pronounced environmental friendliness and exceptional reversibility compared to other metal-air batteries. In order to exploit the energy density of iron on full-cell level, the ratio between anode- and overall battery material should be as large as possible, aiming at practically competitive iron-air battery performances in the future. Therefore, here, we report the investigation of comparatively thick, pressed-plate, carbonyl iron-anodes and the distinctive attempt to further elucidate the processes behind the electrochemical formation. In order to do so, the electrode thickness-dependent charge-/discharge performance, the wetting behavior and the specific surface area of the electrodes were examined. In addition to the established dissolution and precipitation mechanism of iron, we propose that a gradually increasing number of electrochemically active carbonyl iron particles may be an additional source of active iron surface for the steeply increasing discharge capacity during the formation, which is particularly relevant for thick rather than thin electrodes. Furthermore, substantiated by cross-section SEM-images, we propose that the increasing number of active carbonyl iron particles is induced by microstructural changes of the electrode, hypothetically driven by hydrogen evolution during the formation period. Bound to the access of electrolyte, the process suggests the presence of active material on the outside and inactive, since non-wetted, material on the inside of porous carbonyl iron-anodes depending on their state of formation.

Improvement of Negative Electrodes for Iron-Air Batteries: Comparison of Different Iron Compounds as Active Materials

For iron-air batteries, it has yet to be established which iron-containing material is the best candidate for producing iron electrodes. Galvanostatic charge-discharge cycling up to a potential of −0.55 V vs. Hg/HgO was carried out for at least 20 cycles on steel mesh-coated hot pressed iron electrodes. Five different iron active materials were tested: carbonyl iron, Fe3O4 (magnetite), Fe2O3 (hematite), FeOOH (goethite) and iron sulfide, resulting in five hot pressed electrodes. In addition, five hot pressed electrodes were prepared using the same iron active materials but with further processing by ball milling. The specific capacity and voltage of the electrodes is compared, where possible, with similar iron electrodes reported in the literature. This paper reports the maximum, mean value and standard deviation of the specific discharge capacity for each electrode; the highest mean discharge capacity was achieved with the ball milled Fe3O4 electrode with a value of 610 mA h g−1Fe. The shortest formation period was observed for the goethite iron electrode, which achieved a maximum discharge capacity after just 3 cycles with a standard deviation of only 9 mA h g−1Fe over 21 cycles.

Synthesis and electrochemical properties of Fe2O3@C composite

Fe2O3@C material was prepared by one-step hydrothermal method for use as a negative electrode in an iron-air battery. The structure of Fe2O3@C was determined by X-ray diffraction (XRD) measurement while their morphology was observed by scanning electron microscopy (SEM). The electrochemical properties of the Fe2O3@C electrode in alkaline solution were investigated using cyclic voltammetry (CV) measurement. The results showed that Fe2O3@C material with α-Fe2O3 structure and amorphous carbon were successfully synthesized by one-step hydrothermal method. CV measurements indicate that the redox reaction rate of the Fe2O3@C electrode is higher than that of the Fe2O3@AB electrode using commercial Fe2O3 and AB (Acetylene Black Carbon).

Electrical Energy of Iron-Air Battery with Carbon Cathodes Using Sea Water Electrolyte

Iron is chosen for the manufacture of air batteries because it is cheap, widely available in nature. One solution currently being developed is the creation of air batteries. This study aims to determine the effect of electrolyte of seawater and the temperature of air that is in direct contact with carbon cathodes and iron anodes of air batteries as a source of electrical energy.The method used in the voltaic cell which is an electrolyte, anode and cathode solution. It is this anode and cathode that causes a reduction and oxidation reaction, as well as an electrolyte as a conduit to produce electrical energy from chemical reactions. The higher the temperature of the air in contact with the battery will reduce the battery's electrical power.The decreasing air density will reduce the amount of air mass, so that the air mass that is in direct contact with the electrode gets less.

High performance solid-state iron-air rechargeable ceramic battery operating at intermediate temperatures (500–650 °C)

An efficient, reliable and cost-effective energy storage is necessary to increase the use of renewables and to contribute in reducing the carbon footprint of the electricity grid. A novel iron-air battery characterized by high performance, safety and reliability for operation at intermediate temperatures (500–650 °C) is demonstrated. The iron-air rechargeable battery is based on a new configuration where both the nickel-electrode and the hydrogen/water redox processes, generally utilized in high temperature ceramic batteries, are avoided in this system completely operating in the solid state. This can increase the durability and reliability of the battery while providing excellent performance (specific energy of 0.46 Wh g−1, specific capacity of 0.5 Ah g−1, faradaic efficiency 80%). These characteristics favourably compare to low temperature iron-air batteries. Excellent performance and cyclability are achieved at 650 °C for the iron-air solid-state battery showing no relevant degradation after more than 100 cycles. The concept is based on a composite iron-ceria anode in contact with an oxygen anion-conducting lanthanum gallate electrolyte and a mixed conductivity lanthanum ferrite perovskite-based cathode. This combines both simplicity of operation and intrinsic safety with high energy density and durability. The excellent dynamic behaviour, the absence of influence of external environmental conditions and the use of cost-effective ceramic materials, with the possibility to produce high quality heat to cover the chain of electrical and thermal energy, make such systems largely appealing for applications related to renewable power sources.

Structural evolution of directionally freeze-cast iron foams during oxidation/reduction cycles

Cyclical oxidation/reduction behavior of iron-based powders and porous pellets is of great interest for iron-air batteries, steam-iron, and chemical looping processes, but extended cycling is limited by degradation via sintering or pulverization. To address these problems, we use directional freeze casting to fabricate porous iron foams, consisting of colonies of parallel iron lamellae and open channels of sufficient width (20–40 and 20–50 μm, respectively) to accommodate iron/iron oxide volume changes during redox cycling. Iron foams of three different initial channel porosities (48, 61 and 65 vol.%) are fabricated via water-based freeze casting of Fe2O3 powders followed by reduction with H2 and sintering. The evolution of these iron foams is examined after 5 and 10 redox cycles between Fe3O4 and Fe at 800 °C (via steam and H2) using optical microscopy, scanning electron microscopy, and synchrotron X-ray tomography. Redox cycling causes a macroscopic foam shrinkage as the iron lamellae grow closer together, decreasing (and even sometimes eliminating) the channel width between lamellae. Smaller micropores within individual iron lamellae are partially preserved, consistent with new porosity formation via vacancy diffusion and clustering in the oxide phase. Additionally, a dense Fe shell forms on the exterior surface of most samples, caused by lamellae contacting and sintering during oxidation, followed by formation of an impermeable Fe layer during reduction. Strategies are proposed to reduce both channel constriction and shell formation, which are undesirable as they restrict gas phase transport.

Iron Air Batteries: Design Construction and Characterisation

In recent years a renewed interest in developing metal air batteries has arisen, driven by the advances in nanomaterials research that could bring metal air batteries closer to their theoretical specific energy density. For the particular case of the iron-air battery a theoretical energy density of 764 W h kg-1 in combination with the abundance, low cost, eco-friendliness, recyclability, non-toxicity of the materials, and the possibility to work as a secondary battery makes this electrochemical system appealing to develop [1]. Nevertheless, there are several challenges that requires to be improved such as the development of a high efficient iron electrode formulation that reduces the amount of parasitic hydrogen evolution during charge, with a highly porous structure; the development of a good performing bifunctional gas diffusion electrode [2] and the design of a lightweight battery cell design that reduces ohmic losses, electrolyte leaks, allow sufficient air supply to the gas diffusion electrodes and allows evolved gas to be vented [3]. More particular challenges related to the performance of the iron electrodes includes the passivation of the iron electrode at high discharge rates and the low faradaic efficiency due to the parasitic H2 evolution that takes places during the charging process. The engineering of the electrodes in an efficient way to avoid adding extra weight and a way to efficiently supply air are challenging engineering design aspects that have to be addressed to achieve a new level of development. In this work, the individual iron and air electrodes performance in half-cell configurations will be presented (Fig1) together with a comparison between various iron electrode formulations and some considerations about the engineering design of an iron air battery using additive manufacturing. References R. D. McKerracher, C. Ponce de Leon, R. G. A. Wills, A. A. Shah, and F. C. Walsh, “A Review of the Iron–Air Secondary Battery for Energy Storage,” Chempluschem, vol. 80, no. 2, pp. 323–335, 2015.R. D. McKerracher, H. A. Figueredo-Rodríguez, C. Ponce de León, C. Alegre, V. Baglio, A. S. Aricò, and F. C. Walsh, “A high-performance, bifunctional oxygen electrode catalysed with palladium and nickel-iron hexacyanoferrate,” Electrochim. Acta, vol. 206, pp. 127–133, Jul. 2016.H. A. Figueredo-Rodríguez, R. D. McKerracher, C. Ponce de León, and F. C. Walsh, “Current distribution in a rectangular flow channel manufactured by 3-D printing,” AIChE J., Aug. 2016. Figure 1