Recent advances in zinc-air batteries.

Zinc systems | Zinc–air

Metal-air batteries (MABs) have attracted considerable attention as promising next-generation energy storage technology candidates due to their high theoretical energy densities and potential for sustainable applications. Recently, two-dimensional (2D) MBenes have gained significant importance as advanced electrocatalytic materials due to their outstanding features, including excellent thermal and chemical stability, moderate surface area, suitable magnetic and mechanical properties, and tunable electronic structure. In this review, a comprehensive overview of MAB technology, with particular focus on lithium-air batteries (LABs) and zinc-air batteries (ZABs), has been presented. The fundamental components of ZABs and LABs, as well as the operating mechanisms of these systems, are discussed in detail, followed by an in-depth exploration of the mechanistic pathways and kinetics of the OER and ORR. Moreover, the latest research on emerging 2D MBene-based materials as electrocatalysts for MAB electrode modification, particularly for air-cathode applications, is also included in this review. Main approaches to improving stability, conductivity, and electrocatalytic activity through electronic and structural modulation of MBenes are also highlighted. Furthermore, this review article provides future suggestions for the application of 2D MBenes in MABs. Finally, the present review bridges the existing knowledge gap and offers valuable insights into the growing class of materials for zinc-air and lithium-air batteries. MBenes (Two-dimensional transition metal borides) based materials for MABs (M = Zn and Li). • Components of metal air batteries. • Exploration of OER and ORR mechanisms. • Explanation of electrolytes. • Efficiencies of electrolyte additives. • Latest development of MBenes-based materials as an electrocatalyst for ZABs and LABs.

Zinc–air is a century-old battery technology but has attracted revived interest recently. With larger storage capacity at a fraction of the cost compared to lithium-ion, zinc–air batteries clearly represent one of the most viable future options to power electric vehicles. Despite of their great potential, the development of zinc–air batteries has been impeded by problems associated with the metal electrode like self-corrosion, dendrite formation on zinc electrode, and poor discharge characteristics. It is therefore urgent to improve their overall device performance. In the present research, an attempt is made to investigate the application of ionic liquid (IL) modified Metal Organic Frameworks (MOFs) in zinc-air batteries. The use of MOF-5 (IL) in zinc-air batteries have never been studied so far, so in this research we will focus on the use of electrochemically modified zinc electrode decorated with MOF-5 (IL) for the fabrication of zinc-air batteries. It can solve issues like self-corrosion and improve discharge performance which would result into high performance zinc-air batteries with prolonged cyclability. The research also deals with the use of polythiophene in zinc air batteries. Electro-polymerization of a conducting polymer like polythiophene [1] proves to be an efficient approach for modification of the Zn anodes as it provides high thermal and chemical stability. Hence, electropolymerized polythiophene coating can aid in the binding of MOF-5 film over the Zn electrode which would provide stability to the latter. Synthesis of MOF-5 (IL) decorated zinc anodes - Modified MOF-5 (IL) was successfully synthesized over zinc electrode by a mild in-situ electrochemical method [2] using 1-butyl-3-methylimidazolium chloride (IL) ionic liquid as a templating agent employing a modified procedure of reported method [2]. Synthesis of the MOF-5 (IL) was achieved by a constant dissolution of Zn2+ ion from Zn anode. The dissolution was carried out by applying a constant direct current of 0.20 A. A titanium electrode was employed as cathode. The electrolyte used in this procedure was a solution containing 0.07 M terephthalic acid and 0.04 M zinc nitrate hexahydrate in DMF. The electrochemical galvanostatic procedure was carried out for 1hr to get uniform coating of MOF (IL) over the zinc electrode. After that, the electrode was kept for drying at room temperature for 6 hours. Synthesis of MOF-5 (IL) / polythiophene decorated zinc anodes – After the synthesis of MOF-5 (IL), thiophene was added in the solution described above and cyclic voltammetry was performed using Ag/Ag+ as reference electrode for 10 cycles. The electrode was then, kept for drying. Similarly, controlled electropolymerization of thiophene was also done over the zinc electrodes for polythiophene coated Zn anodes. The X-ray diffractogram of synthesized MOF-5 (IL) (Fig. 1) was indexed and was found to be in good agreement with the indices of conventional MOF-5. To investigate the corrosion behavior of Zn anode with different surface modifications, potentiodynamic experiment was performed using a three electrode cell including Zn-based electrode as a working electrode, Ag/AgCl as reference electrode and platinum served as counter electrode. The experiment was performed at room temperature in 0.1 M NaOH aq. at a scan rate of 3.6 mV/s in the range of -0.25 V to 0.50 V. To study discharge characteristics, zinc-air battery was fabricated using carbon cloth as air electrode, zinc based electrodes as anode and nickel mesh as current collector. 5.0 M KOH aq. was used as electrolyte. Chronopotentiometry experiment was performed to see the discharge behavior of different Zn based anodes. The potential went down abruptly in case of pure zinc anode while the potential with zinc anodes decorated with MOF-5 (IL) sustained for a longer cycle. The zinc-air battery with pure zinc as anode showed current density of ~ 7 mA cm-2. On the contrary, zinc-air batteries with zinc anodes decorated with MOF-5 (IL) showed 4 times enhanced current density of ~ 30 mA cm-2. Considering corrosion current and corrosion potential, MOF-5 (IL) decorated Zn anodes and MOF-5 (IL) / polythiophene coated Zn anodes showed the most favorable characteristics to be used in zinc-air batteries. The enhanced discharge performance may be due to the formation of conducting passive layer of MOF-5 (IL) and MOF-5 (IL) / polythiophene on the surface of pure zinc electrode which prevented the active Zn metal from direct exposure to the KOH electrolyte and thus, minimizing the spontaneous side reactions that occur in conventional zinc-air batteries like hydrogen evolution. Efforts are underway to study the discharge characteristics of MOF-5 (IL) / polythiophene coated Zn and polythiophene coated Zn materials. Figure 1

Perovskite‐based catalysts have received a lot attention as bifunctional oxygen evolution reaction and oxygen reduction reaction (ORR/OER) catalysts in secondary rechargeable zinc–air batteries due to their tunable structure, stability at high current densities, low cost, lightweight, and nontoxicity. This paper investigates a new perovskite material, Sr2TiMnO6 (STMO), for a rechargeable zinc–air battery (ZAB). The crystalline structure, morphology, and adsorption/desorption behavior of STMO are thoroughly studied and investigated their catalytic processes. The perovskite catalyst shows high catalytic activities, durability, and endurance in the alkaline medium, resulting in the power density of 97 mW·cm−2, and a specific capacity of 705.21 mAh·g−1. The rechargeable STMO ZAB exhibited good cycling stability with the current density of 3.5 mA·cm−2 for 6.66 h and low overpotential. The observed results promise STMO to be a viable candidate as a functional (ORR/OER) electrocatalyst which can be successfully used for commercial fuel‐cells and metal air batteries.

Incorporating intermittent renewable energy sources into the power grid will require large amounts of grid-scale energy storage. Electrochemical batteries are a versatile and scalable energy storage option and, hence, Li-ion batteries have been widely adopted to store excess wind and solar energy [1]. Li-ion batteries, however, have a relatively low energy density and serious safety concerns. An alternative electrochemical battery option lies with zinc-air batteries. This technology uses lower cost materials and is overall much safer. Furthermore, zinc-air batteries have a much larger theoretical energy density than Li-ion batteries [2]. The major impediment to wide-scale adoption of zinc-air batteries is the low energy efficiency because of the poor reaction kinetics at the air electrode. Both the charge and discharge reactions at the air electrode are sluggish and require the use of catalysts to obtain practicable performance. However, many catalysts active towards the charge reaction are not active towards the discharge reaction, and vice versa. The development of a catalyst active towards both the charge and discharge reactions, known as a bifunctional catalyst, is therefore a high priority [3]. Furthermore, catalysts employed in zinc-air batteries often show instability, with performance degradation evident after a few cycles. Ultimately, a highly stable bifunctional zinc-air battery catalyst is of the utmost importance.The aim of this work is to develop highly stable bifunctional catalysts for zinc-air batteries using atomic layer deposition (ALD). With ALD, extremely conformal catalyst coatings can be deposited directly on the air electrode of a zinc-air battery. The self-limiting surface reactions of ALD ensure that electrode porosity is maintained while maximizing the total coating surface area [4]. Since ALD operates in the gas phase, catalytic coatings can be deposited deep within the pores of the air electrode. This will help maintain the three-phase boundary necessary for the discharge reaction and ultimately improve the stability of a zinc-air battery [5]. To create a bifunctional catalyst, two ALD processes, one for manganese oxide and another for iron oxide, is combined into one ALD supercycle, depositing a mixed manganese-iron oxide. Since manganese oxide is a well-established discharge catalyst [6], and iron oxide demonstrates activity towards the charge reaction [7], this mixed manganese-iron oxide exhibits bifunctional activity in a zinc-air battery. An optimized supercycle process will be discussed and full-cell battery test results showcased. Specifically, the bifunctional efficiency of a zinc-air battery can be improved by more than 10% by using the mixed manganese-iron oxide catalyst. In addition, the high stability of the manganese-iron oxide catalyst is demonstrated, where bifunctional efficiency can be maintained at over 95% of the initial value over 200 cycles. Materials characterization of the mixed manganese-iron oxide, deposited through ALD, is also included.[1] L. Trahey, F. R. Brushett, N. P. Balsara, G. Ceder, L. Cheng, Y. M. Chiang, N. T. Hahn, B. J. Ingram, S. D. Minteer, J. S. Moore, K. T. Mueller, L. F. Nazar, K. A. Persson, D. J. Siegel, K. Xu, K. R. Zavadil, V. Srinivasan, and G. W. Crabtree, “Energy Storage Emerging: A Perspective from the Joint Center for Energy Storage Research,” Proc. Natl. Acad. Sci. U. S. A., vol. 117, no. 23, pp. 12550–12557, 2020.[2] J. Fu, R. Liang, G. Liu, A. Yu, Z. Bai, L. Yang, and Z. Chen, “Recent Progress in Electrically Rechargeable Zinc – Air Batteries,” Adv. Mater., vol. 31, no. 31, p. 1805230, 2019.[3] E. Davari and D. G. Ivey, “Bifunctional electrocatalysts for Zn – air batteries,” Sustain. Energy Fuels, vol. 2, no. 1, pp. 39–67, 2018.[4] C. Detavernier, J. Dendooven, S. Pulinthanathu Sree, K. F. Ludwig, and J. A. Martens, “Tailoring nanoporous materials by atomic layer deposition,” Chem. Soc. Rev., vol. 40, no. 11, pp. 5242–5253, 2011.[5] M. P. Clark, M. Xiong, K. Cadien, and D. G. Ivey, “High Performance Oxygen Reduction/Evolution Electrodes for Zinc − Air Batteries Prepared by Atomic Layer Deposition of MnOx,” ACS Appl. Energy Mater., vol. 3, no. 1, pp. 603–313, 2020.[6] M. P. Clark, T. Muneshwar, M. Xiong, K. Cadien, and D. G. Ivey, “Saturation Behavior of Atomic Layer Deposition MnOx from Bis(Ethylcyclopentadienyl) Manganese and Water: Saturation Effect on Coverage of Porous Oxygen Reduction Electrodes for Metal-Air Batteries,” ACS Appl. Nano Mater., vol. 2, no. 1, pp. 267–277, 2019.[7] M. Labbe, M. P. Clark, Z. Abedi, A. He, K. Cadien, and D. G. Ivey, “Atomic layer deposition of iron oxide on a porous carbon substrate via ethylferrocene and an oxygen plasma,” Surf. Coatings Technol., vol. 421, p. 127390, 2021.

Recently, zinc–air batteries (ZABs) have been receiving attention due to their theoretically high energy density, excellent safety, and the abundance of zinc resources. Typically, the performance of the zinc air batteries is determined by two catalytic reactions on the cathode—the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Therefore, intensive effort has been devoted to explore high performance electrocatalysts with desired morphology, size, and composition. Among them, single-atom catalysts (SACs) have emerged as attractive and unique systems because of their high electrocatalytic activity, good durability, and 100% active atom utilization. In this review, we mainly focus on the advance application of SACs in zinc air batteries in recent years. Firstly, SACs are briefly compared with catalysts in other scales (i.e., micro- and nano-materials). A main emphasis is then focused on synthesis and electrocatalytic activity as well as the underlying mechanisms for mono- and dual-metal-based SACs in zinc air batteries catalysis. Finally, a prospect is provided that is expected to guide the rational design and synthesis of SACs for zinc air batteries.

Implementation of renewable energy into the power grid is a necessary step for a more sustainable future. However, this process is strongly dependent on the capacity of practical energy storage technologies available. Zinc-air batteries show great promise for energy storage, boasting high theoretical energy density, inexpensive electrode materials, and excellent safety. Current development of zinc-air batteries is, however, stifled by the sluggish oxygen kinetics occurring both during discharge and charge. While precious metals such as platinum and ruthenium are considered to be good catalysts, more abundant, inexpensive transition metal catalysts have been found to perform just as well and with better cycling stability [1], [2].This work focuses on the development of transition metal oxide catalysts using atomic layer deposition (ALD). ALD is a gas phase deposition technique that generates conformal thin films through the use of self-terminating surface reactions. In particular, iron oxide catalysts, which promote the oxygen evolution reaction, are synthesized via ALD using an ethylferrocene precursor. Iron oxide growth from this precursor is enabled by an oxygen plasma reactant. Recipe development is showcased, demonstrating saturating behaviour for the growth of iron oxide films.The synthesized catalytic films are deposited directly onto a porous carbon substrate (gas diffusion layer or GDL), which is used as the air electrode in metal-air batteries. The high surface area GDL takes full advantage of ALD’s conformal nature to maximize the surface area of the deposited catalytic film, optimizing catalytic performance. As well, compared with other deposition techniques, ALD increases the depth of catalytic loading into the pores of the electrode. This increases the three-phase boundary volume consisting of gaseous oxygen, aqueous hydroxide ions, and solid catalytic active sites, thereby improving battery performance [3]. Deposited iron oxide films are tested through various electrochemical techniques to quantify catalytic activity. Iron oxide is combined with other transition metal oxides with the goal of creating a bifunctional catalyst, which is active for both the charge and discharge reactions in a zinc-air battery.[1] M. Xiong, M. P. Clark, M. Labbe, and D. G. Ivey, “A horizontal zinc-air battery with physically decoupled oxygen evolution/reduction reaction electrodes,” J. Power Sources, vol. 393, pp. 108–118, 2018.[2] D. Aasen, M. Clark, and D. G. Ivey, “A Gas Diffusion Layer Impregnated with Mn3O4 -Decorated N-Doped Carbon Nanotubes for the Oxygen Reduction Reaction in Zinc-Air Batteries,” Batter. Supercaps, vol. 2, pp. 1–13, 2019.[3] Y. Li and H. Dai, “Recent advances in Zinc-air batteries,” Chem. Soc. Rev., vol. 43, no. 15, pp. 5257–5275, 2014.

Recent advances of micro-nanofiber materials for rechargeable zinc-air batteries

As one of the proposed post lithium-ion battery technologies, metal-air batteries have received revived interest recently. Among the different types of metal-air batteries, rechargeable zinc-air battery (RZAB) is a promising electrochemical energy storage device with the advantages of high theoretical energy density of 1086 Wh kg-1, high abundance, low toxicity and intrinsic safety.1 However, current RZAB still suffer from poor energy efficiency and cycle life, owing mainly to the zinc-anodes, electrolytes, and air-cathodes. To improve the low energy efficiency, many efforts have been made to promote both of the sluggish oxygen reduction/evolution reactions in the air-cathodes by engineering bifunctional catalyst materials with high reactivity. Although significant progress has been made in developing suitable catalyst materials for the air-cathode, many technical challenges still remain in electrolyte to achieve the long cycle life while maintaining high performance. Aqueous electrolytes, predominantly alkaline electrolytes, have been adopted by the RZAB system since its birth. Potassium hydrogen (KOH) is the most commonly used alkaline electrolyte because of its high ionic conductivity, high activity for both the zinc and air electrodes as well as good low temperature performance.2 Despite its desirable properties, the usage of KOH in RZAB raises several technical problems: i) zinc dendrite formation, shape change, surface passivation from complicated reaction between zinc and OH- as well as the dissolution and migration of Zn(OH)4 2-; ii) corrosion of the carbon-based air cathode in concentrated alkaline electrolyte; iii) formation of insoluble K2CO3 arising from the reaction of aerial CO2 with KOH; iv) reduced cell shelf due to the high corrosive ability of concentrated alkaline electrolyte to the stainless steel used in the experimental cell component. In this work, specific attention is given to the obstacles caused by the alkaline electrolytes with the focus on the fundamental understanding of zinc-anode reaction mechanisms, carbonization of electrolyte as well as the precipitation of carbonates on the air cathode. Furthermore, the effects of the practical operating conditions on battery performance and durability are discussed, including the experimental cell configuration for RZAB as well as the contaminants commonly encountered in ambient air (e.g. carbon dioxide). The approaches to overcome the challenges are also presented and analyzed for facilitating further research and development of the electrolyte for RZAB. Reference Li, Y.; Dai, H., Recent advances in zinc-air batteries. Chemical Society reviews 2014, 43 (15), 5257-75.R. Mainar, A.; Leonet, O.; Bengoechea, M.; Boyano, I.; de Meatza, I.; Kvasha, A.; Guerfi, A.; Alberto Blázquez, J., Alkaline aqueous electrolytes for secondary zinc-air batteries: an overview. International Journal of Energy Research 2016, 40 (8), 1032-1049.

As one of the proposed post lithium-ion battery technologies, metal-air batteries have received revived interest recently. Among the different types of metal-air batteries, rechargeable zinc-air battery (RZAB) is a promising electrochemical energy storage device with the advantages of high theoretical energy density of 1086 Wh kg-1, high abundance, low toxicity and intrinsic safety.1 However, current RZAB still suffer from poor energy efficiency and cycle life, owing mainly to the zinc-anodes, electrolytes, and air-cathodes. To improve the low energy efficiency, many efforts have been made to promote both of the sluggish oxygen reduction/evolution reactions in the air-cathodes by engineering bifunctional catalyst materials with high reactivity. Although significant progress has been made in developing suitable catalyst materials for the air-cathode, many technical challenges still remain in electrolyte to achieve the long cycle life while maintaining high performance. Aqueous electrolytes, predominantly alkaline electrolytes, have been adopted by the RZAB system since its birth. Potassium hydrogen (KOH) is the most commonly used alkaline electrolyte because of its high ionic conductivity, high activity for both the zinc and air electrodes as well as good low temperature performance.2 Despite its desirable properties, the usage of KOH in RZAB raises several technical problems: i) zinc dendrite formation, shape change, surface passivation from complicated reaction between zinc and OH- as well as the dissolution and migration of Zn(OH)4 2-; ii) corrosion of the carbon-based air cathode in concentrated alkaline electrolyte; iii) formation of insoluble K2CO3 arising from the reaction of aerial CO2 with KOH; iv) reduced cell shelf due to the high corrosive ability of concentrated alkaline electrolyte to the stainless steel used in the experimental cell component. In this work, specific attention is given to the obstacles caused by the alkaline electrolytes with the focus on the fundamental understanding of zinc-anode reaction mechanisms, carbonization of electrolyte as well as the precipitation of carbonates on the air cathode. Furthermore, the effects of the practical operating conditions on battery performance and durability are discussed, including the experimental cell configuration for RZAB as well as the contaminants commonly encountered in ambient air (e.g. carbon dioxide). The approaches to overcome the challenges are also presented and analyzed for facilitating further research and development of the electrolyte for RZAB. Reference Li, Y.; Dai, H., Recent advances in zinc-air batteries. Chemical Society reviews 2014, 43 (15), 5257-75.R. Mainar, A.; Leonet, O.; Bengoechea, M.; Boyano, I.; de Meatza, I.; Kvasha, A.; Guerfi, A.; Alberto Blázquez, J., Alkaline aqueous electrolytes for secondary zinc-air batteries: an overview. International Journal of Energy Research 2016, 40 (8), 1032-1049.

Rechargeable zinc–air batteries (ZABs) are presently attracting a lot of attention for electrical energy storage, owing to their low manufacturing cost and very high theoretical specific energy density. Currently, the large‐scale application of ZABs is hampered by the sluggish kinetics of the oxygen‐reduction reaction (ORR) and oxygen evolution reaction (OER), which underpin battery discharging and charging processes, respectively. In recent years, metal single‐atom catalysts (SACs) have emerged as promising candidates for driving oxygen electrocatalysis in ZABs, offering both high electrocatalytic activity and high metal atom utilization through unique metal coordination environments (typically porphyrin‐like MNx species on N‐doped carbon supports). Herein, recent breakthroughs in the design of SACs for ORR and OER electrocatalysis are summarized, with a general view towards improving ZAB performance. This Review begins by introducing the operating principles of ZABs and the reaction mechanisms of the ORR and the OER on the air electrode, after which the various types of SAC‐based materials developed to date for oxygen electrocatalysis and ZABs are discussed. Special emphasis is placed on the relationships between the structure of the SAC active site and electrocatalytic performance. Finally, challenges and opportunities for SACs in practical ZABs are explored.

Zinc air batteries use very cheap raw materials (Zinc, Carbon, Potassium Hydroxide) with material costs less than 10€/kWh. The fact that they are water based batteries also makes them much safer and they use environmentally benign and recyclable materials. There is no possibility of thermal runaway or fire either. Zinc-air batteries are therefore an interesting option for the electric vehicle, but also for lower cost stationary storage. High energy density zinc-air batteries are already on the market with energy densities above 400 Wh/kg but they are not rechargeable. The technology to make zinc-air batteries on an industrial scale therefore already exists. The challenge now is to be able to make zinc-air batteries rechargeable. Attempts to develop such a battery have failed due to the poor reversibility of the air electrode and due to the formation of zinc dendrites during charge. By using 3D electrode structures and a protected air electrode, an electrically rechargeable zinc-air battery has been developed which has solved these problems and which has high cycle efficiencies. One of the disadvantages of metal-air batteries is their poor discharge power performance compared to Lithium-ion batteries. The culprit is the air electrode, the zinc electrode is not limited on discharge. Oxygen reduction is a multi-electron reaction with slow kinetics. The reaction is further impaired by the low concentration of the active material (oxygen from the air) and the low molar density of a gaseous reactant. The addition of a second high power cathode has solved this problem and has brought very interesting power and energy performances to our zinc-air battery. High energy densities have also been achieved using zinc electrodes with very high loadings, up to 630 mAh/cm². These zinc-air cells are tested under standard cycling conditions, but also using normalised electric vehicle driving cycles.

Current status and technical challenges of electrolytes in zinc–air batteries: An in-depth review

Rechargeable zinc-air batteries, which are cost-effective, environmental compatibility, and have high energy density, are promising energy storage devices for renewable energy and power sources for electric transportation. However, the critical issues that impede the commercialization of rechargeable zinc–air batteries are limited charge and discharge cycles and the sluggish kinetics of oxygen reduction and evolution reactions, which affect the round trip efficiency. Over the past years, numerous efforts have been devoted to develop earth-abundant materials as bifunctional catalysts towards both OER and ORR. But a suitable bifunctional catalyst has not really been found yet. Therefore, the rechargeable zinc–air battery with cobalt oxide nanoparticles as a bifunctional catalyst are investigated. The result shows that the rechargeable zinc-air batteries in a two-electrode configuration exhibited a small charge–discharge voltage polarization of ~0.70 V at 5 mA cm−2, high reversibility and stability during battery discharge, charge, and cycling processes.

SECONDARY BATTERIES – METAL-AIR SYSTEMS | Zinc–Air: Electrical Recharge