Zinc-air Flow Batteries Research Articles

Enhancing Zinc-Air Flow Batteries: Single-Atom Catalysis within Cobalt-Encapsulated Carbon Nanotubes for Superior Efficiency.

Amid the world's escalating energy needs, rechargeable zinc-air batteries stand out because of their environmental sustainability, with their performance being critically dependent on the oxygen reduction reaction (ORR). The inherent slow kinetics of the ORR at air electrodes frequently constrains their operational efficiency. Here, we develop a new self-catalytic approach for in situ growth of carbon nanotubes with new cathode material Co@CoN3/CNTs-800 without external additives. Density functional theory calculation reveals this method integrates nonprecious single-atom catalysis with spatial confinement, facilitating large-scale, in situ fabrication of CNTs, which can support dispersed atomic CoN3 sites and enforce spatial confinement on Co nanoparticles. The Co@CoN3/CNTs-800 electrode achieves an electron transfer number close to ideal (3.9 out of 4.0). In rechargeable zinc-air flow batteries, it achieves a peak power density of 169.5 mW cm-2 and a voltage gap that is only 1.6% larger than the original after 700 h. This work surmounts critical challenges in the ORR kinetics for zinc-air batteries.

Balancing current density and electrolyte flow for improved zinc-air battery cyclability

Zinc-air batteries (ZABs), known for their high energy density and environmental friendliness, are emerging as promising solutions for sustainable energy storage. However, the irregular deposition of zinc on electrodes hinders the widespread utilization of rechargeable ZABs due to limited durability and stability. This study investigates the role of electrolyte flow in enhancing zinc electrodeposition and overall performance in zinc-air flow batteries (ZAFBs) at high current densities. We explore the interplay between current density, flow rate, and their influence on electrode surface morphology and the removal of the passivating zinc oxide layer to improve battery efficiency and lifespan. Using advanced in-situ synchrotron radiation x-ray tomography, we found that incorporating flowing electrolyte at specific current densities results in rounded dendrite tips, thinner and more uniform deposition layers, and improved zinc adhesion. Imaging and electrochemical analyses further reveal that flowing electrolyte enhances zinc morphology, reduces charge transfer resistance, diminishes passivation, and lowers galvanostatic charge/discharge polarization across various current densities, thereby improving battery cycling performance. Notably, the impact of flowing electrolyte is more pronounced at a moderate current density of 50 mA/cm2 compared to lower or higher currents. Our findings underscore the importance of electrolyte flow and current density management in developing high-performance ZAFBs, providing valuable insights for their future commercialization.

Chemical Vapor Deposition Toward Efficient Bimetallic Atomically Dispersed Oxygen Reduction Catalysts.

Non-precious metal-based nitrogen-doped carbon (M-Nx/C) shows great potential as a substitute for precious metal Pt-based catalysts. However, the conventional pyrolytic methods for forming M-Nx/C active sites are prone to issues such as the lack of synergistic interactions among bimetallic atoms and the potential encasement of active sites, leading to compromised catalytic efficiency and hindered mass transfer. In this work, a highly active FeCo-N-C@U-AC electrocatalyst is developed with a high density of active sites, adequate exposure of catalytic sites, and robust mass transfer capability using the chemical vapor-phase deposition (CVD) technique. The resulting catalyst demonstrates impressive oxygen reduction reaction (ORR) catalytic performance and stability, with half-wave potentials of 0.820V (0.1M HClO4) and 0.911V (0.1M KOH), respectively. It also exhibits significantly enhanced stability, retaining 93.25% and 98.38% of current after continuous 50000 s of durability testing, surpassing the retention rates of Pt/C (80.31% in HClO4 and 84.96% in KOH electrolytes). Notably, when employed as a cathode catalyst in proton exchange membrane fuel cells (PEMFCs) and zinc-air flow batteries (ZAFBs), the FeCo-N-C@U-AC catalyst delivers peak power densities of 859 and 162mW·cm-2, respectively, showcasing competitive performance comparable to benchmarkPt/C.

Hierarchical pore engineering of MOF-5 derived electrocatalysts with high mass transfer for zinc-air flow batteries

From micro to macro level, the performance of zinc-air flow battery (ZAFB) hinges on two crucial factors: the effective oxygen reduction reaction (ORR) electrocatalysts, and the durable triple-phase electrodes. However, sluggish kinetic process always occurs due to insufficient active sites and hysteretic mass transfer. In this work, a well-confined iron phthalocyanine (FePc) structure onto carbonized metal-organic framework (C-MOF5) electrocatalyst is constructed through a pyrolysis-free strategy. The macrocyclic skeleton of MOF-5 has been confirmed to offer a stronger and more abundant environment for hosting FePc molecules. Attributing to the hierarchical pore engineering of MOF-5, the FePc@C-MOF5 electrocatalyst reveals a high content of Fe (5.68 wt%) with multiple exposed active sites. Notably, the FePc@C-MOF5 exhibits a remarkably high half-wave potential of 0.915 V for ORR in 0.1 M KOH, surpassing that of commercial Pt/C by nearly 60 mV. From a higher-level device perspective, the highest oxygen diffusion velocity and local current density of the FePc@C-MOF5 electrode is verified by computational fluid dynamics (CFD) simulations. As a result, the as-assembled ZAFB demonstrates long-term stability with 200 h’ cycling. This work not only presents the hierarchical pore tailoring strategy for designing ORR electrocatalysts but also offers a deeper understanding of the essence of interfacial mass transfer.

Feasibility Study of a Novel Secondary Zinc‐Flow Battery as Stationary Energy Storage System: From Design to Environmental Assessment

Herein, a zinc‐air flow battery (ZAFB) as an environmentally friendly and inexpensive energy storage system is investigated. For this purpose, an optimized ZAFB for households is designed based on the most recent publications, and an economic and ecological analysis of the system is carried out. The results show that the customer price of the designed ZAFB is estimated at ≈5000 € and is thus about one‐third lower than the quoted price for a comparable vanadium flow battery (VFB). The carbon footprint (CF) analysis shows that especially the alkaline electrolyte and the silver‐containing gas diffusion electrode have a high share of the greenhouse gas emissions of the ZAFB system. However, the CF is 41% lower than that of the VFB, highlighting the great potential of the ZAFB as an alternative home storage system.

Macrocycle-based covalent-organic-polymer as efficient oxygen electrocatalysts for zinc-air flow batteries

Covalent organic polymers (COPs), as emerging porous materials with well-defined architectures and high hydrothermal stability, have attracted extensive attention in the field of electrocatalysis. Herein, we report a rational design method for preparing oxygen reduction reaction electrocatalysts with the assistance of a predesigned macrocyclic COP model molecular. With the predesigned nitrogen position and structural features in macrocyclic chain-like COP-based materials, the obtained COPMCT-Co-900 catalyst provided excellent oxygen reduction performance, where the half-wave potential (E1/2) reaches 0.85 V (vs . RHE), comparable to commercial Pt/C. We also extended the strategy to similar macrocycle COPs and Fe-based and Ni-based metal sources and studied the oxygen reduction reaction performance of corresponding catalysts, proving the universality of the method. Interestingly, we assemble COPMCT-Co-900 catalyst as air electrode catalyst of the self-made rechargeable zinc-air flow batteries, which exhibit outstanding power density (155.6 mW·cm-2) and long cycle life (90 h, 270 cycles at 10 mA·cm-2). Our studies provide a new method for the development of high-performance oxygen electrodes applied in zinc-air flow battery devices.

EX-SITU-EVALUATION OF NEW MATERIALS SUCH AS COPPER COMPOUNDS FOR ZINC-AIR BATTERY WITH THE AIM OF GETTING A SECONDARY ZINC-AIR BATTERY

Zinc airflow batteries are popular for large-scale energy storage due to their high-volume density, environmental safety, and economic feasibility of production and recycling. There is going to be a lot of research in order to realize a zinc-air battery as a secondary battery. One potential option in order to overcome this challenge is to use other anode materials, which are stable in the alkaline medium. The main objective of this work is to present the most influencing factors for the production of copper compounds with thermoplastic as binder and graphite as a secondary filler material. In addition, copper compounds are evaluated based on chemical and electrical tests.

D-Orbital steered FeN4 moiety through N, S dual-site adjustation for zinc-air flow battery

The implementation of pristine covalent organic polymer (COP) with well-defined structure as air electrode may spark fresh vitality to rechargeable zinc-air flow batteries (ZAFBs), but it still remains challenges in synergistically regulating their electronic states and structural porosity for the great device performance. Here, we conquer these issues by exploiting N and S co-doped graphene with COP rich in metal–ligand nitrogen to synergistically construct an effective catalyst for oxygen reduction reaction (ORR). Among them, the N and S co-doped sites with high electronegativity properties alter the number of electron occupations in the d orbital of the iron centre and form electron-transfer bridges, thereby boosting the selectivity of the ORR-catalysed four-electron pathway. Meanwhile, the introduction of COP materials aids the formation of pore interstices in the graphene lamellae, which both adequately expose the active sites and facilitate the transport of reactive substances. Benefiting from the synergistic effect, as-prepared catalyst exhibits excellent half-wave potentials (E1/2 = 912 mV) and stability (merely 8.8% drop after a long-term durability test of 50000 s). Further, ZAFBs assembled with the N/SG@COP catalyst demonstrate exceptional power density (163.8 mW cm−2) and continuous charge and discharge for approximately 140 h at 10 mA cm−2, outperforming the noble-metal benchmarks.

Polarization Behaviors and Morphology during Zinc Deposition and Dissolution in Zinc Flow Battery

A zinc flow battery is one of the candidates of secondary batteries for stationary energy storage system, and a zinc-air flow battery is the most promising device because of its high theoretical energy density, low cost of anode material, air-breathing cathode, and high safety of non-flammable aqueous electrolyte. The flow of the electrolyte, which is mostly KOH solutions, is believed to be effective to suppress the generation of zinc dendrite and non-uniform distribution of zinc and zinc oxide, while there has been little information on the effects of the charge-discharge conditions and the dimensions, design, and flow parameters of the cell on the polarization behaviors of the zinc anode and on the morphology during zinc deposition and dissolution in zinc flow secondary batteries.1,2 This paper reports the results on the potential measurements of the zinc anode at the current density up to 500 mA/cm2 and the observation of the morphology of zinc growth and dissolution during charge and discharge.The zinc anode was electrodeposited zinc alloy film supplied by Mitsui Mining & Smelting, Co., Ltd, which produces less than 1/100 of hydrogen compared to conventional rolled zinc film, indicating a high hydrogen overpotential and a quite low self-discharge rate. Two-electrode or three-electrode cells were equipped with the zinc film anode and a zinc wire reference electrode, of which the electrolyte was 6 mol/L KOH solutions saturated with ZnO. The electrolyte was pumped into the cell and the flow rate was changed. The potential of the zinc anode during charge and discharge was monitored while constant current electrolysis was performed at 100 mA/cm2 to 500 mA/cm2. The morphological change for zinc deposition and dissolution was observed by video camera during charge and discharge and by SEM after the operation.The results on the polarization of the zinc anode obtained at different current densities are shown in Fig. 1, in which the increase in polarization at the current density from 100 mA/m2 to 500 mA/cm2 was less than 50 mV for both of charge and discharge at 25 mL/min, suggesting that the electrolyte flow enhances the mass transport of zincate ions and suppresses the concentration overpotential. This is also supported by the fact that charge failed with no electrolyte flow. The dependence of the anode’s potential on the flow rate also indicated that the potential hardly increased when the flow rate changed from 250 mL/min to 25 mL/min. The observation of zinc deposition and dissolution was further carried out and some interesting features on the relationship between the morphology of zinc deposits and the operating conditions was found, implying the conditions to suppress zinc dendrite formation.This work was partly supported by JSPS Grant-in-Aid for Scientific Research No. 22H02187.References1) A. L. Zhu, D. P. Wilkinson, X. Zhang, Y. Xing, A. G. Rozhin, S. A. Kulinich, J. Energy Storage, 8, 35-50 (2016).2) A. Abbasi, S. Hosseini, A. Somwangthanaroj, R. Cheacharoen, S. Olaru, S. Kheawhom, Sci. Data, 7, 196 (2020). Figure 1

Directly assembling initial metal–organic framework and covalent organic polymer toward bifunctional oxygen electrocatalysts for Zn-air flow battery

Developing highly efficient bifunctional oxygen electrocatalysts is important but still remains a challenge for Zn-air flow battery. Metal-organic frameworks (MOFs) and covalent organic polymers (COPs) materials have emerged as promising alternatives to the benchmark precious metal electrocatalysts due to their designable and controllable structures at the atomic level. However, their catalytic performances are limited by the conductivity and catalytic activity using initial materials. Moreover, these materials are generally developed either as single oxygen reduction reaction (ORR) or oxygen evolution reaction (OER) electrocatalysts. Herein, we utilize the π-π stacking effect to directly assemble initial nanosheet FeNi-MOF and iron phthalocyanine rich COP hybrid materials toward the highly efficient bifunctional electrocatalysts via pyrolysis-free strategy. The carbon black is added to the composite as support to limit the stacking of composites and increase the conductivity. The obtained catalyst, named as NSFeNi@COPFe-C, exhibits superior catalytic performance with an ORR onset potential of 0.99 V (vs. reversible hydrogen electrode: RHE), half-wave potential of 0.9 V (vs. RHE), and the OER potential of 1.65 V at 10 mA cm−2 in alkaline electrolyte. The assembled zinc-air flow battery with NSFeNi@COPFe-C as the bifunctional oxygen electrocatalyst shows a discharge power up to 115 mW cm−2 and a long-term stability.

Trifunctional catalyst of FeCo,N-doped mixed-dimensional carbon for the high-performance zinc-air flow battery

Exploring efficient and highly stable non-precious metal trifunctional catalysts is imperative for the practical application of zinc-air flow batteries (ZAFBs) and overall water splitting (OWS). Herein, the FeCo and nitrogen-rich codoped one-dimensional carbon nanotubes cross-interpenetrated with birdhouse-like carbon nanosheets in mixed-dimensional carbon structure (FeCo,N-MDC) is constructed by a facile and universal method. Benefiting from the merits of hyper-dispersed FeCo-N/Ox and FeCo alloy active sites, high density of pyridine and graphitic nitrogen, ultra-high conducting carbon nanotubes, large surface area, and massive mass transfer channels can synergistically promote multifunctional catalysis. The resulting FeCo,N-MDC exhibits superior trifunctional activities with onset potential and half-wave potential of 0.994 V and 0.861 V for oxygen reduction reaction in 0.1 M KOH, oxygen evolution reaction and hydrogen evolution reaction overpotentials of 0.341 V and 0.272 V at 10 mA·cm−2 in 1 M KOH, respectively, and have long electrochemical stability. Moreover, the FeCo,N-MDC-based ZAFB has an open-circuit voltage of 1.517 V, a specific capacity of 808 mAh·g−1, the remarkable running stability for 300 h, which surpassed that of commercial Pt/C + RuO2 hybrid-driven device. Additionally, the hydrophilic FeCo,N-MDC, as both the anode and cathode electrodes, also display a hydrolysis reaction voltage of 1.603 V to deliver a current density of 10 mA·cm−2 and outstanding durability. What is more, the continuously mass-produced FeCo,N-MDC, and the alternative CoFe, N-MDC catalysts exhibit excellent performance in the same water-solvent environment. This effort presents a facile strategy for rationally designing economical and efficient mixed-dimensional catalysts for zinc-air flow batteries and more energy devices.

Zinc–Air Flow Batteries at the Nexus of Materials Innovation and Reaction Engineering

Zinc–Air Flow Batteries at the Nexus of Materials Innovation and Reaction Engineering

ZIF-derived Fe,Co coordinated N/O-codoped three-dimensional tungsten–carbon matrix for the performance-enhanced zinc-air flow battery and water splitting

Constructing efficient and cost-effective electrocatalysts with oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) for the development of zinc-air flow batteries (ZAFBs) and overall water splitting (OWS) is significant, but still challenging. Herein, we have fabricated a heterojunction catalyst (Fe,CoZn9+9-NO/WC) featuring uniformly dispersed Fe and Co coordinated with riched-nitrogen/oxygen codoped into a three-dimensional highly porous tungsten–carbon matrix modified carbon nanotube by a simple stepwise construction route using water as the solvent. The resultant Fe,CoZn9+9-NO/WC exhibits a positive half-wave potential (E1/2) of 0.889 V for ORR, a low overpotential at 10 mA·cm−2 for OER (290 mV) and HER (84 mV), and excellent electrochemical durability in alkaline electrolyte, outperforming even benchmark catalysts. Moreover, Fe,CoZn9+9-NO/WC as a bifunctional air cathode for ZAFBs delivers higher open circuit voltage, peak power density (190 mW·cm−2), and specific capacity (814 mAh·g−1), lower charge/discharge voltage gap and prolonged operational cycles durability, largely exceeding those of the hybrid Pt/C+RuO2 bifunctional catalyst. The alkaline OWS electrolyzer is constructed by Fe,CoZn9+9-NO/WC with good stability and requires only 1.556 V cell voltage at 10 mA·cm−2. Impressively, the self-constructed Fe,CoZn9+9-NO/WC electrodes were applied to practical ZAFBs and OWS devices, demonstrating superior performance to the recently reported ZIF/MOF-derived catalysts in organic solvents. This work offers an economical synthetic strategy to prepare highly efficient multifunctional catalysts with practical potential for commercial production, promising to facilitate the development of clean energy storage and conversion devices.

High current density charging of zinc-air flow batteries: Investigating the impact of flow rate and current density on zinc electrodeposition

Rechargeable zinc-based batteries (RZABs) show much promise over a wide range of applications due to their scalability, safety, and low cost. However, achieving stable and uniform zinc electrodeposition, particularly at high current densities, remains a significant challenge. Herein, the mechanism of charging zinc-air flow batteries under high current density conditions is investigated in detail. Through a combination of experimental and computational methods, both the individual and combined effects of current density and electrolyte flow rate on zinc electrodeposition are studied. Critical aspects of zinc electrodeposition, including ion concentration gradients, overpotential, mass transfer impedance, and gas evolution are scrutinized. Findings demonstrate that flow velocity profoundly affects current density regulation and mass transfer, while bubble formation at high current densities has implications for induced overpotential and overall charging performance. The surface morphology of electrodeposited zinc, as well as the formation and motion of bubbles, are evaluated using both in-situ and ex-situ microscopic imaging techniques. Optimal uniformity of zinc deposition is achieved by combining a current density of 60 mA cm−2 with a flow rate of 0.021 m s−1. Applying these conditions to a zinc-air battery results in excellent durability, maintaining commendable performance throughout 78 h of charge/discharge cycling. This research provides valuable insights into the correlation between operating parameters and surface properties of zinc electrodeposition, thus supporting the development of high-performance rechargeable zinc-based energy storage devices incorporating flow systems.

High-Power-Density and High-Energy-Efficiency Zinc-Air Flow Battery System for Long-Duration Energy Storage

To achieve long-duration energy storage (LDES), a technological and economical battery technology is imperative. Herein, we demonstrate an all-around zinc-air flow battery (ZAFB), where a decoupled acid-alkaline electrolyte elevates the discharge voltage to ∼1.8 V, and a reaction modifier KI lowers the charging voltage to ∼1.8 V. This ZAFB exhibits a long discharge duration of over 4 h, a high power density of 178 mW cm−2 (about 76 % higher than conventional ZAFB), and unprecedented energy efficiency of nearly 100 %. Moreover, the ZAFB demonstrates outstanding fast charging ability, mitigated zinc dendrite growth and parasitic hydrogen evolution, enhanced cathode protection, and good resistance to environmental disturbance. This all-around ZAFB will not only become a very promising option for LDES but also promote the development of other LDES systems.

Efficient synergistic effect of trimetallic organic frameworks derived as bifunctional catalysis for the rechargeable zinc-air flow battery

Precise design of oxygen electrode catalysts can alleviate the problems of slow kinetic reaction and high overpotential in the rechargeable zinc-air flow batteries (ZAFBs). Herein, an ideal 3D carbon-based material for FeCo alloy inlaid to Fe/Co and N co-doped bamboo-like carbon nanotubes (CNTs) is prepared by means of a one-pot high-temperature pyrolysis strategy of three metal organic frameworks (MOFs) mixed-precursors. The concentration of active metal species, the amount of conductive CNTs and the hierarchical porous structure with high specific surface area in this material are regulated. The optimal catalyst, Fe/12Zn/Co-NCNTs, demonstrates excellent electrochemical activity with a high half-wave potential of 0.879 V for oxygen reduction reaction (ORR) and low overpotential of 340 mV at 10 mA cm−2 for oxygen evolution reaction (OER) in the half-cell. Moreover, the smaller bifunctional ΔE value of Fe/12Zn/Co-NCNTs and Fe/(12Zn/Co)-NCNTs catalyst are 0.693 V and 0.717 V, respectively, less than the commercial Pt/C+IrO2 (ΔE = 0.77 V). The ZAFB yields a high open circuit voltage of 1.518 V, peak power density of 166 mW cm−2, and specific capacity of 809.1 mAh g−1 when employing Fe/12Zn/Co-NCNTs as air cathode because of the synergistic effect that improves both OER and ORR. More importantly, both Fe/12Zn/Co-NCNTs and Fe/(12Zn/Co)-NCNTs as the bifunctional catalysts produce a low charge-discharge voltage gap and high cycle lifespan of more than 320 h at 10 mA cm−2. This work provides a facile strategy for fabricating high-efficiency and low-cost bifunctional electrocatalysts for ZAFBs and other clean energy applications.

Improve the Zinc Slurry-Air Battery Performance: New Operational Mode to Separate Effects

In recent years, zinc air batteries received substantial interest as a viable next generation of batteries based on their merits of high energy densities, high performance, environmentally friendly, inexpensive, and abundant electrode material. Traditional secondary zinc air flow batteries use zinc metal as an anode. Severe dendrite growth and passivation limits the cycling behavior, which hinders commercialization in the industry. By substituting the zinc plate with a zinc slurry (zinc particles suspended in the alkaline media, typically with a high concentration of potassium hydroxide), the battery can in principle achieve higher energy density and attain more cycles but with very limited performance. Important questions related to such systems include the accessible percentage of Zn capacity, controlled by the formation of passivating layers on the particle and the intrinsic resistance of the slurry.Here, we present a new operational mode to investigate the performance of zinc slurry air battery. The anode of the test battery system consists of 5 cm2 nickel plate as current collector for 5 cm3 zinc slurry. The cathode consists of air electrode, bipolar plate, and current collector. Zinc particles (Spectrum) were suspended in 4M KOH stabilized by polyacrylic acid (PAA). In our testing, the polarization loss was measured and is separated from that associated with the air electrode using a reference electrode. The conductivity of the slurry was measured by the simply modified configuration of the cell. The utilization of zinc is measured by chronopotentiometry. The battery can work at 1.1 V with 200mA/cm2, and the slurry can achieve 48.7% utilization. Acknowledgements The authors gratefully acknowledge the support of the US Department of Energy Office of Electricity Storage Systems Program directed by Dr. Imre Gyuk and the University of Tennessee Governor’s Chair Fund for support of this work. Figure 1

Proton Exchange Membrane for Iron Air/Flow Battery Application

Iron air/redox flow battery is the next promising battery system that can bridge the drawbacks of a static battery, at least in medium to high storage systems, due to the distinguishing difference from its static counterpart. It comes with the main advantages: the high current discharge and a flowing electrolyte, which can significantly suppress the formation of dendrite and passivation without imposing permanent damage to the cell structure. Iron, the fourth most abundant metal on the earth's crust, comes at a lower cost and requires less corrosion protection.This technology has received less attention than others due to overpotential/overvoltage and high Hydrogen evolution reaction on the anode. Different promising approach has been explored to improve the cycling stability of iron air batteries; by adding different electrolyte additives to suppress passivation and hydrogen evolution during discharge, improving the air cathode design by including dual or bifunctional electrocatalyst, and recent modification of the anode has helped realize a better iron air battery by facilitating a high surface area iron electrode using nanosized iron particle, and these create more electrode available to electrolyte and further adding a suitable additive to the electrode and electrolyte and increase charge capacity.Nonetheless, the battery working components begin to degrade as they interact; these cannot be stopped as batteries are consumable objects, but they can be delayed by improving the membrane separator's physical-chemical properties like conductivity, swelling ratio, selectivity, and membrane stability. Membrane's critical role aid in the improvement of the battery performance by separating the air cathode and metal anode electrode compartments to prevent short-circuiting, facilitate proton transfer, act as an electron insulator, and prevent fuel crossover, therefore improving the battery cycle life. The presentation will cover the basic working principle of the iron-air/redox flow battery and its prospective future in grid application and a brief report on the role of composite proton exchange membrane and their influence on cycle stability. ReferencesSakai, T., Inoishi, A., Ogushi, M., Ida, S., & Ishihara, T. (2016). Characteristics of fe-air battery using Y2O3-stabilized-ZrO2 electrolyte with Ni–Fe electrode and Ba0.6La0.4CoO3-δ electrode operated at intermediate temperature. Journal of Energy Storage, 7, 115-120.Abbasi, A., Hosseini, S., Somwangthanaroj, n., Cheacharoen, R., Olaru, S., & Kheawhom, S. (2020). Discharge profile of a zinc-air flow battery at various electrolyte flow rates and discharge currents. Scientific Data, 7(1), 196.Leung, P., Li, X., De León, C. P., Berlouis, L., Low, C. J., & Walsh, F. C. (2012). Progress in redox flow batteries, remaining challenges and their applications in energy storage. Rsc Advances, 2(27), 10125-10156.Karomah, A. (2021). Iron-air batteries: A breakthrough in green energy. . Retrieved 17 march, 2022, from https://www.azom.com/article.aspx?ArticleID=20872.McKerracher, R., Ponce de León, C., Wills, R. G. A., Shah, A., & Walsh, F. (2014). A review of the Iron–Air secondary

Prediction of charge-discharge behavior and state of charge estimation for tri-electrode rechargeable zinc-air flow batteries

An effective state of charge (SOC) estimation is essential for the development of a battery management system. At present, the provision of a SOC estimation for zinc-air flow batteries (ZAFBs) is still at its early stage of development. This work sets out to develop the SOC estimator for ZAFBs. The estimator is based-on a linear parameter varying (LPV) model integrated with an extended Kalman filter (EKF). The LPV model is constructed from multiple linear time-invariant (LTI) models with battery current and SOC as scheduling parameters. It is observed that the response data for ZAFBs have an exceptionally flat profile related to SOC change; dynamic differentiation only occurs when SOC is almost depleted. For this reason, the estimation of SOC converges to the true value when SOC is near depletion. In this work, it is shown that by appropriate tuning, the SOC estimation performance of the LPV model combined with EKF performs well as the absolute errors of soc. estimation lie under 2 % after true SOC convergence. The LPV model with the EKF algorithm is also compared with the Luenberger observer (LO). The proposed estimator can surpass the LO estimator. Overall, this SOC estimator provides a systematic way to fulfill the requirements of a battery management system.

Investigating the Role of the Triple-Phase Boundary in Zinc-Air Cathodes Using Pore Network Modeling

Zinc-air flow batteries are a promising energy storage technology. Their performance depends on their porous cathodes where the oxygen reduction reaction (ORR) occurs. A key feature of the cathode is the invasion of electrolyte, creating the so-called triple phase boundary between air, electrolyte and catalyst, which is shown in this work to be an overly simplified picture. In this study a mathematical framework based on pore network modeling (PNM) was developed to better understand the interplay between electrode structure, transport of species and electrolyte invasion. The results suggest that increasing electrolyte volume provides highly branched invasion pattern and enhances performance up to a saturation of whereas further invasion reduces air-liquid interfacial area and lowers the performance. Interestingly, at lower saturations (<0.3) the liquid structure is so excessively branched that hydroxide ions are unable to diffuse to the anode at a sufficient rate, resulting in supersaturation, which is a degradation problem. The pore size distribution of the catalyst layer also affects the performance with wider pore size distributions generally performing better. This work represents the first 3D PNM of a zinc-air cathode that includes all the key physics and transport mechanisms, enabling prediction of the structure-performance relationship of porous cathodes.