Seed-mediated atomic-scale reconstruction of silver manganate nanoplates for oxygen reduction towards high-energy aluminum-air flow batteries

A Mechanistic Overview of the Current Status and Future Challenges in Air Cathode for Aluminum Air Batteries

Aluminum air batteries (AABs) are a desirable option for portable electronic devices and electric vehicles (EVs) due to their high theoretical energy density (8100 Wh K-1 ), low cost, and high safety compared to state-of-the-art lithium-ion batteries (LIBs). However, numerous unresolved technological and scientific issues are preventing AABs from expanding further. One of the key issues is the catalytic reaction kinetics of the air cathode as the fuel (oxygen) for AAB is reduced there. Additionally, the performance and price of an AAB are directly influenced by an air electrode integrated with an oxygen electrocatalyst, which is thought to be the most crucial element. In this study, we covered the oxygen chemistry of the air cathode as well as a brief discussion of the mechanistic insights of active catalysts and how they catalyze and enhance oxygen chemistry reactions. There is also extensive discussion of research into electrocatalytic materials that outperform Pt/C such as nonprecious metal catalysts, metal oxide, perovskites, metal-organic framework, carbonaceous materials, and their composites. Finally, we provide an overview of the present state, and possible future direction for air cathodes in AABs.

Low-Index Facet Polyhedron-Shaped Binary Cerium Titanium Oxide for High-Voltage Aqueous Zinc-Vanadium Redox Flow Batteries

Aqueous zinc-vanadium hybrid redox flow battery systems are an efficient strategy to address the problems of low voltage and high cost of conventional all-vanadium redox flow batteries. However, the low electrochemical activity of carbon-based electrodes toward a vanadium redox reaction limits the performance of redox flow batteries. In this study, polyhedral binary cerium titanium oxide (Ce2/3TiO3, CTO) is synthesized using molten salt synthesis. CTO is fabricated by adjusting the temperature and composition. Notably, the prepared CTO obtained at 1000 °C shows the highest catalytic activity for a VO2+/VO2+ redox reaction. Further, CTO is prepared as a composite electrocatalyst and applied to a high-voltage aqueous zinc-vanadium redox flow battery. The cell adopts an alkali zinc electrolyte containing a Zn/[Zn(OH)4]2- redox pair and exhibits a high operating voltage of 2.26 V. Remarkably, a zinc-vanadium redox flow battery using the composite electrocatalyst exhibits a high energy density of 42.68 Wh L-1 at 20 mA cm-2 and an initial voltage efficiency of 90.3%. The excellent cell performance is attributed to structural defects caused by A-site deficiency in the perovskite oxide structure as well as oxygen vacancies resulting from the low valence state of the metal ion, which enhance the catalytic activity of the vanadium ions.

Solid-Solution-Based Metal Coating Enables Highly Reversible, Dendrite-Free Aluminum Anode

Aluminum-ion batteries have attracted great interest in the grid-scale energy storage field due to their good safety, low cost and the high abundance of Al. However, Al anodes suffer from severe dendrite growth, especially at high deposition rates. Here, we report a simple strategy for constructing a highly reversible, dendrite-free, Al-based anode through directly introducing a solid-solution-based metal coating to a Zn foil substrate. Compared with Cu foil substrates and bare Al, a Zn foil substrate shows a lower nucleation barrier of Al deposition due to the intrinsic, definite solubility between Al and Zn. During Al deposition, a thin, solid-solution alloy phase is first formed on the surface of the Zn foil substrate and then guides the parallel growth of flake-like Al on Zn substrate. The well-designed, Zn-coated Al (Zn@Al) anode can effectively inhibit dendrite growth and alleviate the corrosion of the Al anode. The fabricated Zn@Al–graphite battery exhibits a high specific capacity of 80 mAh·g−1 and an ultra-long lifespan over 10,000 cycles at a high current density of 20 A·g−1 in low-cost molten salt electrolyte. This work opens a new avenue for the development of stable Al anodes and can provide insights for other metal anode protection.

A Review of Energy Storage Mechanisms in Aqueous Aluminium Technology

This systematic review covers the developments in aqueous aluminium energy storage technology from 2012, including primary and secondary battery applications and supercapacitors. Aluminium is an abundant material with a high theoretical volumetric energy density of –8.04 Ah cm−3. Combined with aqueous electrolytes, which have twice the ionic storage potential as non-aqueous versions, this technology has the potential to serve many energy storage needs. The charge transfer mechanisms are discussed in detail with respect to aqueous aluminium-ion secondary batteries, where most research has focused in recent years. TiO2 nanopowders have shown to be promising negative electrodes, with the potential for pseudocapacitive energy storage in aluminuim-ion cells. This review summarises the advances in Al-ion systems using aqueous electrolytes, focusing on electrochemical performance.

An Efficient Rechargeable Aluminium-Amine Battery Working Under Quaternization Chemistry

Rechargeable aluminium (Al) batteries (RABs) have long-been pursued due to the high sustainability and three-electron-transfer properties of Al metal. However, limited redox chemistry is available for rechargeable Al batteries, which restricts the exploration of cathode materials. Herein, we demonstrate an efficient Al-amine battery based on a quaternization reaction, in which nitrogen (radical) cations (R3 N.+ or R4 N+ ) are formed to store the anionic Al complex. The reactive aromatic amine molecules further oligomerize during cycling, inhibiting amine dissolution into the electrolyte. Consequently, the constructed Al-amine battery exhibits a high reversible capacity of 135 mAh g-1 along with a superior cycling life (4000 cycles), fast charge capability and a high energy efficiency of 94.2 %. Moreover, the Al-amine battery shows excellent stability against self-discharge, far beyond conventional Al-graphite batteries. Our findings pave an avenue to advance the chemistry of RABs and thus battery performance.

Silver nanomaterials: synthesis and (electro/photo) catalytic applications

In view of their unique characteristics and properties, silver nanomaterials (Ag NMs) have been used not only in the field of nanomedicine but also for diverse advanced catalytic technologies. In this comprehensive review, light is shed on general synthetic approaches encompassing chemical reduction, sonochemical, microwave, and thermal treatment among the preparative methods for the syntheses of Ag-based NMs and their catalytic applications. Additionally, some of the latest innovative approaches such as continuous flow integrated with MW and other benign approaches have been emphasized that ultimately pave the way for sustainability. Moreover, the potential applications of emerging Ag NMs, including sub nanomaterials and single atoms, in the field of liquid-phase catalysis, photocatalysis, and electrocatalysis as well as a positive role of Ag NMs in catalytic reactions are meticulously summarized. The scientific interest in the synthesis and applications of Ag NMs lies in the integrated benefits of their catalytic activity, selectivity, stability, and recovery. Therefore, the rise and journey of Ag NM-based catalysts will inspire a new generation of chemists to tailor and design robust catalysts that can effectively tackle major environmental challenges and help to replace noble metals in advanced catalytic applications. This overview concludes by providing future perspectives on the research into Ag NMs in the arena of electrocatalysis and photocatalysis.

Atomic, Molecular and Hybrid Oxygen Structures on Silver

Interactions between oxygen and silver are important in many areas of science and technology, including materials science, medical, biomedical and environmental applications, spectroscopy, photonics, and physics. In the chemical industry, identification of oxygen structures on Ag catalysts is important in the development of environmentally friendly and sustainable technologies that utilize gas-phase oxygen as the oxidizing reagent without generating byproducts. Gas-phase oxygen adsorbs on Ag atomically by breaking the O-O bond and molecularly by preserving the O-O bond. Atomic O structures have Ag-O vibrations at 240-500 cm^-1. Molecular O₂ structures have O-O vibrations at significantly higher values of 870-1150 cm^-1. In this work, we identify hybrid atomic-molecular oxygen structures, which form when one adsorbed O atom reacts with one lattice O atom on the surface or in the subsurface of Ag. Thus, these hybrid structures require dissociation of adsorbed molecular oxygen into O atoms but still possess the O-O bond. The hybrid structures have O-O vibrations at 600-810 cm^-1, intermediate between the Ag-O vibrations of atomic oxygen and the O-O vibrations of molecular oxygen. The hybrid O-O structures do not form by a recombination of two adsorbed O atoms because one of the O atoms in the hybrid structure must be embedded into the Ag lattice. The hybrid oxygen structures are metastable and, therefore, serve as active species in selective oxidation reactions on Ag catalysts.

Defect engineering of oxide perovskites for catalysis and energy storage: synthesis of chemistry and materials science

Oxide perovskites have emerged as an important class of materials with important applications in many technological areas, particularly thermocatalysis, electrocatalysis, photocatalysis, and energy storage. However, their implementation faces numerous challenges that are familiar to the chemist and materials scientist. The present work surveys the state-of-the-art by integrating these two viewpoints, focusing on the critical role that defect engineering plays in the design, fabrication, modification, and application of these materials. An extensive review of experimental and simulation studies of the synthesis and performance of oxide perovskites and devices containing these materials is coupled with exposition of the fundamental and applied aspects of defect equilibria. The aim of this approach is to elucidate how these issues can be integrated in order to shed light on the interpretation of the data and what trajectories are suggested by them. This critical examination has revealed a number of areas in which the review can provide a greater understanding. These include considerations of (1) the nature and formation of solid solutions, (2) site filling and stoichiometry, (3) the rationale for the design of defective oxide perovskites, and (4) the complex mechanisms of charge compensation and charge transfer. The review concludes with some proposed strategies to address the challenges in the future development of oxide perovskites and their applications.

Plasma-Assisted Synthesis of Defect-Rich O and N Codoped Carbon Nanofibers Loaded with Manganese Oxides as an Efficient Oxygen Reduction Electrocatalyst for Aluminum-Air Batteries

The oxygen reduction reaction (ORR) with sluggish kinetics on the cathode of aluminum-air (Al-air) batteries greatly limits their further development. Here, a new strategy is proposed to synthesize oxygen and nitrogen codoped carbon nanofibers loaded with manganese oxides (MnO/Mn₂O₃/ONCNF-n) as an efficient electrocatalyst for ORR by using oxygen plasma surface etching. The MnO/Mn₂O₃/ONCNF-3 exhibit superior ORR performance in an alkaline electrolyte, which is attributed to various active sites including N and O heteroatoms, vacancies, and manganese oxides. Additionally, the fabricated homemade Al-air battery (AAB) with MnO/Mn₂O₃/ONCNF-3 exhibits a maximum power density of 129.7 mW cm^-2, demonstrating comparable performance to AABs based on the commercial Pt/C catalyst. This work provides a new approach of using O₂ plasma for enhancing the ORR catalytic activities of carbon materials.

Pristine and Modified Porous Membranes for Zinc Slurry-Air Flow Battery

The membrane is a crucial component of Zn slurry–air flow battery since it provides ionic conductivity between the electrodes while avoiding the mixing of the two compartments. Herein, six commercial membranes (Cellophane™ 350PØØ, Zirfon^®, Fumatech^® PBI, Celgard^® 3501, 3401 and 5550) were first characterized in terms of electrolyte uptake, ion conductivity and zincate ion crossover, and tested in Zn slurry–air flow battery. The peak power density of the battery employing the membranes was found to depend on the in-situ cell resistance. Among them, the cell using Celgard^® 3501 membrane, with in-situ area resistance of 2 Ω cm² at room temperature displayed the highest peak power density (90 mW cm⁻²). However, due to the porous nature of most of these membranes, a significant crossover of zincate ions was observed. To address this issue, an ion-selective ionomer containing modified poly(phenylene oxide) (PPO) and N-spirocyclic quaternary ammonium monomer was coated on a Celgard^® 3501 membrane and crosslinked via UV irradiation (PPO-3.45 + 3501). Moreover, commercial FAA-3 solutions (FAA, Fumatech) were coated for comparison purpose. The successful impregnation of the membrane with the anion-exchange polymers was confirmed by SEM, FTIR and Hg porosimetry. The PPO-3.45 + 3501 membrane exhibited 18 times lower zincate ions crossover compared to that of the pristine membrane (5.2 × 10⁻¹³ vs. 9.2 × 10⁻¹² m² s⁻¹). With low zincate ions crossover and a peak power density of 66 mW cm⁻², the prepared membrane is a suitable candidate for rechargeable Zn slurry–air flow batteries.

A general MOF-intermediated synthesis of hollow CoFe-based trimetallic phosphides composed of ultrathin nanosheets for boosting water oxidation electrocatalysis

Engineering an electrode material for boosting reaction kinetics is highly desired for the oxygen evolution reaction (OER) in the anodic half reaction, and is still a grand challenge for energy conversion technologies. By taking inspiration from the catalytic properties of transition metal phosphides (TMPs) and metal-organic frameworks (MOFs), we herein propose a general MOF-intermediated synthesis of a series of hollow CoFeM (M = Bi, Ni, Mn, Cu, Ce, and Zn) trimetallic phosphides composed of ultrathin nanosheets as advanced electrocatalysts for the OER. A dramatic improvement of electrocatalytic performance toward the OER is observed for hollow CoFeM trimetallic phosphides compared to bimetallic CoFe phosphides. Remarkably, composition-optimized CoFeBiP hollow microspheres could deliver superior electrocatalytic performance, achieving a current density of 10 mA cm^-2 with an overpotential of only 273 mV. Mechanistic investigations reveal that the Bi and P doping effectively optimizes the electronic structure of Co and Fe by charge redistribution, which significantly lowers the adsorption energy of oxygen intermediates. Moreover, the hollow microsphere structures composed of ultrathin nanosheets also enable them to provide rich surface active sites to boost the electrocatalytic OER.

Surface Facet Engineering in Nanoporous Gold for Low-Loading Catalysts in Aluminum-Air Batteries

The performance of metal-air batteries and fuel cells depends on the speed and efficiency of electrochemical oxygen reduction reactions at the cathode, which can be improved by engineering the atomic arrangement of cathode catalysts. It is, however, difficult to improve upon the performance of platinum nanoparticles in alkaline electrolytes with low-loading catalysts that can be manufactured at scale. Here, the authors synthesized nanoporous gold catalysts with increased (100) surface facets using electrochemical dealloying in sodium citrate surfactant electrolytes. These modified nanoporous gold catalysts achieved an 8% higher operating voltage and 30% greater power density in aluminum-air batteries over traditionally prepared nanoporous gold, and their performance was superior to commercial platinum nanoparticle electrodes at a 10 times lower mass loading. The authors used rotation disc electrode studies, backscattering of electrons, and underpotential deposition to show that the increased (100) facets improved the catalytic activity of citrate dealloyed nanoporous gold compared to conventional nanoporous gold. The citrate dealloyed samples also had the highest stability and least concentration of steps and kinks. The developed synthesis and characterization techniques will enable the design and synthesis of metal nanostructured catalysts with controlled facets for low-cost and mass production of metal-air battery cathodes.

Boosting Oxygen Electroreduction over Strained Silver

Manipulating the strain effect of Ag without any foreign metals to boost its intrinsic oxygen reduction reaction (ORR) activity is intriguing, but it remains a challenge. Herein, we developed a class of Ag-based electrocatalysts with tunable strain structures for efficient ORR via ligand-assisted competitive decomposition of Ag-organic complexes (AgOCs). Benefiting from the superior coordination capability, 4,4'-bipyridine as a ligand triggered a stronger competition with NaBH₄ for Ag ions during reduction-induced decomposition of AgOCs in comparison with the counterparts of the pyrazine ligand and the NO₃^- anion, which moderately modulated the compressive strain structure to upshift the d-band center of the catalyst and increase the electron density of Ag. Accordingly, the O₂ adsorption was obviously improved, and the stronger repulsion effect between the Ag sites and the 4e ORR product, i.e., the electron-rich OH^-, was generated to promote the desorption of OH^- via the Ag-OH bond cleavage, which enabled more Ag sites to be regenerated after ORR. Both of these led to an enhancement to the intrinsic ORR activity of the Ag-based catalyst. This competitive decomposition of metal-organic complex strategy would provide a facile method to design other catalysts with the well-tuned strain structures for energy conversion and heterocatalysis.

Architecting a Stable High-Energy Aqueous Al-Ion Battery

Aqueous Al-ion batteries (AAIBs) are the subject of great interest due to the inherent safety and high theoretical capacity of aluminum. The high abundancy and easy accessibility of aluminum raw materials further make AAIBs appealing for grid-scale energy storage. However, the passivating oxide film formation and hydrogen side reactions at the aluminum anode as well as limited availability of the cathode lead to low discharge voltage and poor cycling stability. Here, we proposed a new AAIB system consisting of an Al_xMnO₂ cathode, a zinc substrate-supported Zn-Al alloy anode, and an Al(OTF)₃ aqueous electrolyte. Through the in situ electrochemical activation of MnO, the cathode was synthesized to incorporate a two-electron reaction, thus enabling its high theoretical capacity. The anode was realized by a simple deposition process of Al³⁺ onto Zn foil substrate. The featured alloy interface layer can effectively alleviate the passivation and suppress the dendrite growth, ensuring ultralong-term stable aluminum stripping/plating. The architected cell delivers a record-high discharge voltage plateau near 1.6 V and specific capacity of 460 mAh g^-1 for over 80 cycles. This work provides new opportunities for the development of high-performance and low-cost AAIBs for practical applications.

Recent Developments for Aluminum–Air Batteries

Abstract

Environmental concerns such as climate change due to rapid population growth are becoming increasingly serious and require amelioration. One solution is to create large capacity batteries that can be applied in electricity-based applications to lessen dependence on petroleum. Here, aluminum–air batteries are considered to be promising for next-generation energy storage applications due to a high theoretical energy density of 8.1 kWh kg−1 that is significantly larger than that of the current lithium-ion batteries. Based on this, this review will present the fundamentals and challenges involved in the fabrication of aluminum–air batteries in terms of individual components, including aluminum anodes, electrolytes and air cathodes. In addition, this review will discuss the possibility of creating rechargeable aluminum–air batteries.

Graphic Abstract

High-Capacity Dual-Electrolyte Aluminum–Air Battery with Circulating Methanol Anolyte

Aluminum–air batteries (AABs) have recently received extensive attention because of their high energy density and low cost. Nevertheless, a critical issue limiting their practical application is corrosion of aluminum (Al) anode in an alkaline aqueous electrolyte, which results from hydrogen evolution reaction (HER). To effectively solve the corrosion issue, dissolution of Al anode should be carried out in a nonaqueous electrolyte. However, the main cathodic reaction, known as oxygen reduction reaction (ORR), is sluggish in such a nonaqueous electrolyte. A dual-electrolyte configuration with an anion exchange membrane separator allows AABs to implement a nonaqueous anolyte along with an aqueous catholyte. Thus, this work addresses the issue of anode corrosion in an alkaline Al–air flow battery via a dual-electrolyte system. The battery configuration consisted of an Al anode | anolyte | anion exchange membrane | catholyte | air cathode. The anolytes were methanol solutions containing 3 M potassium hydroxide (KOH) with different ratios of water. An aqueous polymer gel electrolyte was used as the catholyte. The corrosion of Al in the anolytes was duly investigated. The increase of water content in the anolyte reduced overpotential and exhibited faster anodic dissolution kinetics. This led to higher HER, along with a greater corrosion rate. The performance of the battery was also examined. At a discharge current density of 10 mA·cm−2, the battery using the anolyte without water exhibited the highest specific capacity of 2328 mAh/gAl, producing 78% utilization of Al. At a higher content of water, a higher discharge voltage was attained. However, due to greater HER, the specific capacity of the battery decreased. Besides, the circulation rate of the anolyte affected the performance of the battery. For instance, at a higher circulation rate, a higher discharge voltage was attained. Overall, the dual-electrolyte system proved to be an effective approach for suppressing anodic corrosion in an alkaline Al–air flow battery and enhancing discharge capacity.

Interrogation of the Reaction Mechanism in a Na-O2 Battery Using In Situ Transmission Electron Microscopy

Critical factors that govern the composition and morphology of discharge products are largely unknown for Na-O₂ batteries. Here we report a reversible oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) process in a sodium-oxygen battery observed using in situ environmental-transmission electron microscopy (TEM) experiment. The reaction mechanism and phase evolution are probed using in situ electron diffraction and TEM imaging. The reversible ORR and OER cycling lies upon the nanosized copper clusters that were formed in situ by sodiation of CuS. In situ electron diffraction revealed the formation of NaO₂ initially, which then disproportionated into orthorhombic and hexagonal Na₂O₂ and O₂. Na₂O₂ was the major final ORR product that uniformly covered the whole wire-shape cathode. This uniform product morphology largely increased the application feasibility of Na-O₂ batteries in industry. In the following OER process, the Na₂O₂ transformed to NaO₂, which resulted in volume expansion at first, and then the NaO₂ decomposed to sodium ions and O₂ gas. Galvanostatic charge/discharge profiles of CuS in real Na-O₂ cells revealed a maximum capacity over 3 mAh cm^-2 with a discharge cutoff voltage of 1.8 V and high cycling stability. The nanosized copper catalyst plays a dominating role in controlling the morphology, chemical composition of discharge products, and reversibility of this Na-O₂ battery. Our finding shines light on the exploration of effective catalysts for the Na-O₂ battery.

Turning on electrocatalytic oxygen reduction by creating robust Fe-Nx species in hollow carbon frameworks via in situ growth of Fe doped ZIFs on g-C3N4

Iron-nitrogen-carbon (Fe-N-C) electrocatalysts have been demonstrated to be promising candidates to substitute conventional Pt/C electrocatalysts in the oxygen reduction reaction (ORR) due to the benefits of high efficiency and affordable price. Unfortunately, Fe is prone to aggregation upon high-temperature treatment, which may cover the active sites of the Fe-Nx species and further affect the ORR performance. Thus, the key issue is to avoid Fe aggregation and keep it uniformly dispersed as much as possible. In this work, Fe-N-C catalysts with robust Fe-Nx species in hollow carbon frameworks were created via in situ growth of Fe doped Zn based zeolitic imidazolate frameworks (ZIFs) on g-C3N4 with the subsequent pyrolysis treatment. The developed catalysts demonstrate superb ORR activity, high resistance to methanol and ultralong stability as compared with traditional Pt/C catalysts in alkaline solution. The brilliant performance benefits from the firm connection and robust structure of the optimal Fe-Nx species that are homogeneously dispersed in the hollow carbon frameworks. This work presents a facile and reasonable strategy for the development of excellent ORR electrocatalysts.

Paper-based microfluidic aluminum-air batteries: toward next-generation miniaturized power supply

Paper-based microfluidics (lab on paper) emerges as an innovative platform for building small-scale devices for sensing, diagnosis, and energy storage/conversions due to the power-free fluidic transport capability of paper via capillary action. Herein, we report for the first time that paper-based microfluidic concept can be employed to fabricate high-performing aluminum-air batteries, which entails the use of a thin sheet of fibrous capillary paper sandwiched between an aluminum foil anode and a catalyst coated graphite foil cathode without using any costly air electrode or external pump device for fluid transport. The unique microfluidic configuration can help overcome the major drawbacks of conventional aluminum-air batteries including battery self-discharge, product-induced electrode passivation, and expensive and complex air electrodes which have long been considered as grand obstacles to aluminum-air batteries penetrating the market. The paper-based microfluidic aluminum-air batteries are not only miniaturized in size, easy to fabricate and cost-effective, but they are also capable of high electrochemical performance. With a specific capacity of 2750 A h kg-1 (@20 mA cm-2) and an energy density of 2900 W h kg-1, they are 8.3 and 12.6 times higher than those of the non-fluidic counterpart and significantly outperform many other miniaturized energy sources, respectively. The superior performance of microfluidic aluminum-air batteries originates from the remarkable efficiency of paper capillarity in transporting electrolyte along with O2 to electrodes.

Advanced Technologies for High-Energy Aluminum-Air Batteries

Aluminum-air batteries are considered as next-generation batteries owing to their high energy density with the abundant reserves, low cost, and lightweight of aluminum. However, there are several hurdles to be overcome, such as the sluggish rate of the oxygen reduction reaction (ORR) at the air electrode, precipitation of aluminum hydroxides and oxides at the anode, and severe hydrogen evolution problems at the interface of the anode and the electrolyte. Here, recent advances in silver metal and metal-nitrogen-carbon-based ORR electrocatalysts, aluminum anodes, electrolytes, and the requirements of future research directions are mainly summarized.

Semi-solid-state aluminium-air batteries with electrolytes composed of aluminium chloride hydroxide with various hydrophobic additives

Semi-solid-state Al-air batteries with solid electrolytes prepared by mixing AlCl3·6H2O and various hydrophobic additives were prepared and tested. All of the prepared Al-air batteries exhibited higher current 48 hours after battery preparation. This might be due to a decrease in battery resistance as AlCl3·6H2O melted and penetrated into the air cathode as a result of its hygroscopic property. Among the batteries tested, when commercial vaseline and butyl methyl imidazolium hexafluorophosphate were mixed with AlCl3·6H2O and used as the solid electrolyte, the prepared Al-air battery exhibited a stable high current and electrochemical property.