Durability and performance improvements for metal-air batteries

Abstract

Improvements to metal-air batteries are disclosed including the provisioning of a reinforcing mesh to prevent electrolyte ingress to the anode, an inherently safe porous separator to slow leaks of aqueous electrolyte, nickel iron oxyhydroxide coatings to improve the oxygen evolution reaction cathode, and iron nitride or manganese oxide coatings to improve the oxygen reduction reaction cathode. Methods of making and using each of the improvements to form an improved metal-air battery are further disclosed.

Description

DURABILITY AND PERFORMANCE IMPROVEMENTS FOR METAL-ATR BATTERIESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the priority benefit of U.S. Provisional Patent Application Serial No. 63 / 533,618, filed August 19, 2023; U.S. Provisional Patent Application Serial No. 63 / 533,616, filed August 19, 2023; U.S. Provisional Patent Application Serial No. 63 / 533,617, filed August 19, 2023; U.S. Provisional Patent Application Serial No. 63 / 533,622, filed August 19, 2023; U.S. Provisional Patent Application Serial No. 63 / 559,818, filed February 29, 2024; and U.S. Provisional Patent Application Serial No. 63 / 559,824, filed February 29, 2024; the contents of each respective application hereby incorporated by reference herein in their respective entireties.STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH

[0002] This invention was made with government support under DE-SC0022492 awarded by the Department of Energy. The government has certain rights in the invention.BACKGROUND

[0003] Metal-air batteries refer to the class of secondary batteries where the positive electrode, or cathode, is exposed to air and can reduce oxygen to hydroxides or peroxides during discharging of the battery and can oxidize the hydroxides or peroxides back to oxygen during charging of the battery. By replacing the metal cathode with functionally weightless ambient air along with an entirely metal anode (or negative electrode), metal-air batteries can theoretically reach higher specific capacities and higher energy densities than conventional battery chemistries having a metal (oxide) cathode. Metal-air batteries are still undergoing research and development to overcome various issues including degradation and lifespan concerns for various components, achieving sufficient safety margins due to the caustic chemicals, and realizing performance closer to their theoretical values.SUMMARY

[0004] According to one embodiment, an anode-less metal-air battery includes a solid electrolyte surrounding an anode, a polymer border surrounding the solid electrolyte, and dual oxygenevolution reaction (“OER”) and oxy gen-reduction reaction (“ORR”) cathodes. The metal-airbattery further includes one or more of: a reinforcing mesh contacting the polymer border; the polymer border formed of an impermeable material OER including a nickel iron oxyhydroxide coating; or the ORR including an iron nitride or manganese oxide coating.

[0005] According to another embodiment, a method of improving a metal-air battery including a solid electrolyte on top of an anode, a polymer border surrounding the solid electrolyte’s and anode’s edges, and dual oxygen-evolution reaction (“OER”) and oxy gen-reduction reaction (“ORR”) cathodes can be improved by one or more of providing a reinforcing mesh contacting the polymer border; placing a porous polymer between the reinforcing mesh and solid electrolyte to mechanically protect the solid electrolyte from scratches while trapping H2 bubbles on the solid electrolyte surface to limit degradation from dendrites; forming a nickel iron oxyhydroxide coating on the OER cathode; or forming an iron nitride coating on the ORR cathode.BRIEF DESCRIPTION OF DRAWINGS

[0006] FIGS. 1A to 1C depict a comparative schematic view of a current collector, anode, solid electrolyte, and polymer border of a known metal-air battery. FIG. 1 A depicts the side view of an uncharged metal-air battery negative electrode; FIG. IB depicts the same side view of a charged metal-air battery negative electrode, and FIG. 1C depicts a front view of the metal-air battery negative electrode.

[0007] FIGS. 2A to 2C depict an inventive schematic view of a current collector, anode, and polymer border of an improved metal-air battery design. FIG. 2A depicts the side view of an uncharged metal-air battery negative electrode with the OER electrode embedded in the polymer border; FIG. 2B depicts the same side view of a charged metal-air battery negative electrode with the OER electrode embedded in the polymer border, and FIG. 2C depicts a front view of the metal - air battery negative electrode with the OER electrode embedded in the polymer border.

[0008] FIG. 3 depicts a cross-sectional view of a metal-air battery cell having a reinforced polymer border.

[0009] FIG. 4 depicts a portion of the core of a comparative metal-air battery. FIGS. 4B to 4D depict enlarged sections of FIG. 4A showing growth of a dendrite leading to reaction of aqueous electrolyte and the anode.

[0010] FIG. 5 depicts a portion of the core of an inventive metal-air battery including a porous polymer sheet on top of the solid electrolyte. FIGS. 5B and 5C depict enlarged sections of FIG. 5A showing how growth of a dendrite does not lead to ingress of aqueous electrolyte to the anode.DETAILED DESCRIPTION OF THE BACKGROUND

[0011] As will be described herein, durability and performance improvements to metal-air batteries are disclosed as well as metal-air batteries incorporating such durability and performance improvements. The improvements described herein include advances to the structure of a metalair battery cell to improve the safety and efficiency of the cells as well as to durability and efficiency improvements for the air cathode. Specifically described improvements include a resilient design for the battery cell that improves both safety and efficiency, a new design for a polymer border that mitigates undesired reaction of the aqueous electrolyte with the anode, and improvements to both the oxygen evolution reaction cathode and the oxygen reduction reaction cathode.

[0012] Although the improvements described herein are described with respect to metal-air batteries, it should be appreciated that such improvements can also have utility in other applications. For example, improvements described herein relating to the oxygen evolution and oxygen reduction cathodes can be useful for fuel cells, the chlor-alkali process, and other electrolytic processes. Similarly, improvements to the polymer border have wide utility in applications subject to highly corrosive conditions including various protective coatings, desalination films, sensors, containers, and the like. Such further applications are expressed contemplated herein and are considered within the scope of this application.

[0013] Generally, the improvements to metal-air batteries and to metal-air batteries thereof described herein can be widely applied to all known metal-air battery chemistries. For example, the improvements described herein can be applied to alkali metal-air batteries, alkaline earth metalair batteries, and first-row transition metal-air batteries. More specifically, but without limitation, the improvements described herein can apply to sodium air batteries, lithium air batteries, iron air batteries, potassium air batteries, zinc air batteries, magnesium air batteries, calcium air batteries, aluminum air batteries, tin air batteries, or germanium air batteries. Additionally, the improvements described herein can be applicable to single cell batteries, multi-cell batteries, andflow batteries. In certain embodiments, the improvements can be particularly applicable to aqueous metal-air batteries having an alkali metal anode such as sodium-air batteries.Cell Design Improvements

[0014] To increase energy density and improve manufacturing ease, it is known to form what are termed “anode-less batteries.” In anode-less batteries, the battery cell includes a negative current collector, a cathode, and a solid electrolyte and / or an electrolyte solution including salts of the anode metal. During charging of the battery cell, the cations in the electrolyte are reduced at the current collector to form a solid metal anode. For example, a sodium-air battery can include an electrolyte solution (sometimes referred to as a catholyte solution) including sodium hydroxide as a sodium salt. Charging of such a sodium-air battery reduces the sodium hydroxide to metallic sodium on the current collector to thereby form the anode. Anode-less batteries negate the need to work with highly-reactive metal anodes and minimizes nucleation sites for dendrites to form on the anode during charging.

[0015] As can be appreciated however, various additional structures are commonly required to make such battery cells operate. For instance, when the anode is formed from a reactive metal, such as a Column 1 alkali metal, the electrolyte must be kept separated from the anode to prevent exothermic reaction of the anode with the aqueous electrolyte. To prevent such reactions, a solid electrolyte can be included in the battery to allow the metal ions from the electrolyte to transit to the current collector to form the anode while preventing aqueous electrolyte from contacting the anode. While a solid electrolyte is effective to prevent most electrolyte ingress, electrolyte solution can still ingress around the edges of the solid electrolyte necessitating the inclusion of a border around the solid electrolyte such as a polymer border.

[0016] Generally, such polymer border can be made of an impervious material impermeable to water. For example, the polymer border can be made of an impervious elastomer or can be a composite structure including one or more polymer layers and one or more metallic layers. For example, in certain embodiments, the polymer border can be formed of a layer of aluminum foil sandwiched between plastic materials such as polypropylene and polyamide.

[0017] Resilient designs for this polymer border have faced challenges. For example, charging of the battery, and consequently formation of the anode, causes an increase in the thickness of the anode. As can be appreciated, as the thickness of the anode increases during charging of the battery cell, the border must accommodate for this expansion while still adhering to the solid electrolyte and maintaining a good seal. Such expansion can cause failure of the border either immediately due to stress or over time due to loss of elastic properties as the anode cycles in size with each charge and discharge cycle.

[0018] FIG. 1 illustrates the issue of known polymer borders. In FIG. 1, a metal-air battery core 100 includes a current collector 110, a solid electrolyte 130, and a polymer border 140 surrounding the edges of the solid electrolyte 130 to prevent ingress of electrolyte (not depicted) to contact the anode 120. FIG. 1 A specifically depicts the metal-air battery core 100 in an uncharged state with no anode yet formed. FIG. IB depicts the same metal-air battery core 100 after charging of the cell which forms metal anode 120. As can be seen comparing FIGS. 1A and IB, the polymer border 140 must stretch considerably to prevent intrusion of aqueous electrolyte from touching the reactive metal anode 120. This stretch creates tensile forces pulling outward that could lead to the polymer border slipping off the edges and allowing the aqueous catholyte to make contact with the negative electrode or anode. FIG. 1C depicts a top view of the same battery cell as FIGS. 1A and IB.PER Embedded in Polymer Border

[0019] To overcome such failure modes of the polymer border, improved metal-air battery cell designs are disclosed which provide a reinforcing mesh to the polymer border. The reinforcing mesh can provide inward tensile forces to the polymer border and can allow the polymer border to maintain constriction around the anode through multiple charging and discharging cycles.

[0020] Generally, the reinforcing mesh can be formed of any material that provides reinforcement to the polymer border. For example, the reinforcing mesh can be formed of a strong plastic, rubber, fiber, or a metal in various embodiments. In certain embodiments, it can be particularly advantageous to form the reinforcing mesh out of a metal as metals can maintain their strength through indefinite cycles as long as the stretching stays within the metal’s elastic deformation region. The reinforcing material can be in the form of a fiber, wire, or rod with the thickness orgauge depending on factor such as the size of the battery. In certain embodiments, the thickness can range from about 0.001mm to about 1mm including, for example, a thickness of about 0.025mm.

[0021] The reinforcing mesh can be formed by interleaving fibers or strands of the reinforcing material in two or more directions to form a weave or cross-hatch. The angle and spacing between the strands can vary. For example, in certain embodiments, the fibers can be at an about 90° angle to one another. In certain embodiments, the number of strands can be expressed by a unit area. For example, there can be about 100 strands per centimeter or about 10,000 cross-hatched fibers per square centimeter.

[0022] In certain embodiments, the reinforcing mesh can be embedded in the polymer border by, for example, providing a reinforcing mesh, then providing molten or uncured polymer around the reinforcing mesh, and then cooling or curing the polymer. In yet other embodiments, a polymer border formed of a thermoplastic material can be heated and then a reinforcing mesh can be embedded into the softened material using force applied by, for example, a roller. In yet other embodiments, the reinforcing mesh can alternatively surround the polymer border and be attached through either friction alone or by a suitable adhesive. In each such embodiment, the polymer border is reinforced by the stronger reinforcing mesh enabling the polymer border to maintain constriction around the solid electrolyte and prevent intrusion of the electrolyte through multiple charging and discharging cycles.

[0023] In certain embodiments, when the reinforcing material is metal, the reinforcing mesh can further operate as the oxygen evolution reaction (“OER”) electrodefor the metal-air battery. As can be appreciated, such a design not only improves the lifespan and mechanical integrity of the battery cell but also improves the efficiency of the battery cell by placing the OER nearer to the anode decreasing the internal resistance of the battery during charging. In such embodiments, the reinforcing mesh can be formed of a suitable metal for the OER such as stainless steel or copper and / or a material that can be coated with a suitable conductor.

[0024] An inventive metal-air battery core is depicted in side view in FIGS. 2A and 2B. In FIGS. 2A and 2B, the metal-air battery core 200 includes a current collector 210, an anode 220, a solid electrolyte 230, and a polymer border 240 including a reinforcing mesh 250. As depicted in thefront view FIG. 2C, the reinforcing mesh 250 can act as the OER electrode and can extend in a tab protruding from the battery cell to facilitate oxygen evolution reactions with oxygen in the atmosphere outside of the cell.

[0025] FIG. 3 depicts a schematic of a complete metal-air battery 300. The metal air battery 300 includes a current collector 310, an anode 320, a solid electrolyte 330, a polymer border 340, a reinforcing mesh 350, an electrolyte 360, and an oxygen reduction reaction cathode 370. An optional porous separator 380 is included between the solid electrolyte 330 and the reinforcing mesh 350. The reinforcing mesh 350 of the metal-air battery 300 can further operate as the oxygen evolution reaction cathode for the battery.Porous Separator

[0026] There is a risk of damage to the battery cell if the solid electrolyte or polymer border develops damage. To prevent potentially dangerous interaction of the anode with the aqueous electrolyte, an improved battery cell design is disclosed that includes a porous separator between the solid electrolyte and the OER electrode. The porous separator provides for an added layer of inherent safety of the battery.

[0027] The porous separator is formed of a polymer having a plurality of micro holes, or pores, which can allow catholyte transfer but which traps hydrogen bubbles on the solid electrolyte surface in the event of a leak preventing further aqueous catholyte ingress to the anode. Each of the plurality of the micro holes can be about 0.01 micrometer to about 200 micrometers in diameter.

[0028] FIG. 4 depicts an example of a comparative metal-air battery which does not include the presently disclosed porous separator. As depicted in FIG. 4A, a partially depicted metal-air battery core 400 includes anode 420, solid electrolyte 430, a polymer border 440, and an electrolyte 460. FIGS. 4B to 4D depict an enlarged section of FIG. 4A showing growth of a dendrite 425 from the anode 420. As the dendrite 425 grows, the dendrite punctures the solid electrolyte 430 leading to ingress of the electrolyte 460 to the anode 420. Reaction of the electrolyte 460 with the anode 420 exothermically produces hydrogen gas 490 leading to potentially catastrophic failure of the battery.

[0029] FIG. 5 depicts an example of an improved metal-air battery incorporating the presently disclosed porous separator. As depicted in FIG. 5A, a partially depicted metal-air battery core 500 includes anode 520, a solid electrolyte 530, an impermeable polymer border 540, a porous polymer separator 580 extending over the face of the solid electrolyte, an electrolyte 560, and an OER 550. FIGS. 5B to 5C depict an enlarged section of FIG. 5 A showing growth of a dendrite 525 from the anode 520. As the dendrite 525 grows, the dendrite punctures the solid electrolyte 530 and the porous polymer separator 580. While there is ingress of some electrolyte 560, the hydrogen bubbles 590 are entrapped in the micro-pores of the porous polymer separator 580 drastically limiting the ingress of further electrolyte 560. The slow ingress of additional electrolyte 560 prevents catastrophic failure of the battery.

[0030] Cathode Improvements

[0031] As can be appreciated, the lifetime and efficiency of a metal-air battery depends, in part, on the lifetime and efficiency of the positive electrode, or air cathode, which must reduce dissolved oxygen gas from the air (oxygen reduction reactions (“ORR”)) during discharge of the battery and oxidize hydroxide from the catholyte to oxygen gas (oxygen evolution reactions (“OER”) during charging of the battery. However, cycling between ORR and OER can be detrimental to the lifespan of the cathode catalysts with the oxygen reduction electrode being particularly susceptible to damage due to the high oxidizing potentials of the OER. As previously described in U.S. Patent App. Pub. No. 2023 / 0068006 Al, hereby incorporated herein by reference, metal-air batteries can separate the air cathode into dual oxygen reduction electrodes and oxygen evolution electrodes (sometimes referred to as dual oxygen reduction and evolution electrodes). In certain such embodiments, the dual oxygen reduction electrodes and oxygen evolution electrodes can further be formed as a mesh to increase surface area of the electrodes to air.

[0032] Although dual oxygen revolution and evolution electrodes improves the design of a metalair battery by enabling each of the OER and ORR to be optimized for oxygen evolution and oxygen reduction reactions respectively, both the OER and ORR are still susceptible to degradation over time. To further improve the lifespan and efficiency of the OER and ORR, it would be desirable to further improve the electrodes by offering improved coatings for the respective electrodes.

[0033] Oxygen Evolution Reaction Improvements

[0034] In certain embodiments described herein, an OER electrode, such as an OER electrode mesh, can be improved by forming a nickel iron oxyhydroxide layer, such as NixFei-xOOH, on the surface of the electrode. Nickel iron oxyhydroxides are known to be among the best performing electrocatalysts but have not been previously known to be used in metal air batteries where their durability can further enhance the desirability of their electrocatalytic potential.

[0035] In addition to incorporating a nickel iron oxyhydroxide coating on the OER electrode, methods of forming such nickel iron oxyhydroxide layers have presently been discovered. Such methods include depositing the nickel iron oxyhydroxide layer on the OER electrode and by modifying the OER electrode itself to form a nickel iron oxyhydroxide layer in-situ.

[0036] For deposition methods, it has been discovered that a nickel iron oxyhydroxide layer can advantageously be formed by depositing a nickel layer followed by deposition of the nickel iron oxyhydroxide layer. Generally, each such layer can be deposited through any suitable means. In certain embodiments however, it has been found that electroless deposition (e.g., chemical deposition, vapor deposition, plasma deposition, sputtering, spin coating, etc.) for formation of the nickel layer can be particularly suitable while electrodeposition methods can be particularly suitable for formation of the nickel iron oxyhydroxide layer. Generally, each of the nickel layer and the nickel iron oxyhydroxide layer can be of any suitable thickness such as about 0.1 microns to about 1,000 microns in thickness.

[0037] In alternative embodiments, the nickel iron oxyhydroxide layer can alternatively be formed by oxidizing stainless steel. In such embodiments, the OER can be entirely formed of stainless steel or can include a deposited layer of stainless steel. The nickel iron oxyhydroxide layer can then be formed by leeching chromium from the stainless steel through application of an oxidizing potential. As can be appreciated, this method can facilitate formation of the nickel iron oxyhydroxide layer in-situ without the use of complicated deposition steps.

[0038] In certain embodiments, the OER in the metal-air batteries described herein can further act as the reinforcing mesh for the polymer border.

[0039] Oxygen Reduction Reaction Improvements

[0040] In certain embodiments described herein, an ORR electrode can be improved by forming a stable, highly active, iron nitride or manganese oxide coating on the surface of the electrode. Iron nitrides and manganese oxide coatings are desirable as they have high electrical conductivity, high catalytic activity for oxygen redox reactions, and are highly stable under standard operating conditions. These properties can enable ORR electrodes to be highly efficient and have a long lifespan compared to comparative ORR electrodes without an iron nitride coating.

[0041] Although iron nitrides generally exhibit improved stability and catalytic activity, certain iron nitrides have been found to be particularly suitable for the metal-air batteries disclosed herein including (Fe2N) which exhibits higher conductivity and higher catalytic activity than other iron nitrides. In certain embodiments however, suitable iron nitrides can comprise other iron nitrides or can comprise a mixture of many iron nitrides.

[0042] Prior to the present disclosure, it was not known to use iron nitride or manganese oxide as an electrocatalyst coating for metal-air batteries. However, the contemplated metal-air batteries having dual oxygen evolution and reduction cathodes which enables the presently contemplated batteries to include an ORR electrode having an iron nitride or manganese oxide coating.

[0043] Generally, the iron nitride coatings described herein can be formed on an iron-containing ORR electrode by treatment in an ammonia atmosphere at temperatures of about 450 °C to about 500 °C. At such temperatures, iron rapidly reacts to form iron nitride. Manganese oxide coatings can be formed as known in the art using techniques such as chemical co-precipitation processes, hydrothermal / sonothermal processes, sol-gel and solution combustion processes, and electrodeposition processes. In certain embodiments, electrodeposition processes can be preferred.

[0044] As can be appreciated, the ORR electrode coated with iron nitride can also be formed of other materials if an iron containing layer is first formed. For example, copper or another conductive material can be coated with iron or an iron oxide or hydroxide layer via electroless deposition, slot die coating, blade coating, chemical vapor deposition, plasma vapor deposition, or any other coating method to form an iron containing coating. Once the iron layer is formed, treatment with ammonia can form an iron nitride coating layer. For an ORR electrode coated with manganese oxide, the ORR electrode can be formed of any conductive material followed by formation of the manganese oxide layer.

[0045] In certain embodiments, it can be further advantageous to additionally include an anticorrosion layer beneath the iron nitride or manganese oxide layer. In such embodiments, the ORR electrode can first be coated with a corrosion resistant material such as nickel or ultra-pure copper immediately before formation of an iron layer or manganese layer that is subsequently converted to iron nitride or coated with manganese oxide. The anti-corrosion layer can also be useful to prevent intermixing of the iron nitride or manganese oxide with the underlying material of the electrode.

[0046] In certain embodiments, the anti-corrosion layer can alternatively be a layer of glassy carbon. Generally, glassy carbon coatings can be formed by applying a layer of carbon to the electrode and then carbonizing the carbon using high temperatures in the absence of oxygen to form a high surface area glass with high chemical resistance. The layer of carbon can be graphite, carbon fiber paper, or a polymeric resin. Further details of glassy carbon coatings are disclosed in PCT Patent App. No. PCT / US2024 / 10603, which is hereby incorporated herein by reference.Improved Metal-Air Batteries

[0047] Improved metal-air batteries can incorporate one or more of the improvements described herein. Generally, the metal-air batteries described herein can include one or more of the improvements described herein. For example, the improvements to the polymer border can be used in combination with the improved OER coating. In certain embodiments, an improved metal-air battery can include one or more of a reinforcing mesh in the polymer border, a porous polymer separator, a nickel iron oxyhydroxide coating on the OER, and an iron nitride coating on the ORR.

[0048] Generally, the improved metal-air batteries can be formed as known in the art. For example, each of the components can be assembled together and sealed, filled with catholyte, and then charged to form the anode. Additional details of how to form an improved metal-air battery are disclosed in in U.S. Patent App. Pub. No. 2023 / 0068006 Al.

[0049] The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value.

[0050] It should be understood that every maximum numerical limitation given throughout this specification includes every lower numerical limitation, as if such lower numerical limitations were expressly written herein. Every minimum numerical limitation given throughout this specification will include every higher numerical limitation, as if such higher numerical limitations were expressly written herein. Every numerical range given throughout this specification will include every narrower numerical range that falls within such broader numerical range, as if such narrower numerical ranges were all expressly written herein.

[0051] Every document cited herein, including any cross-referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests, or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in the document shall govern.

[0052] The foregoing description of embodiments and examples has been presented for purposes of description. It is not intended to be exhaustive or limiting to the forms described. Numerous modifications are possible in light of the above teachings. Some of those modifications have been discussed and others will be understood by those skilled in the art. The embodiments were chosen and described for illustration of various embodiments. The scope is, of course, not limited to the examples or embodiments set forth herein, but can be employed in any number of applications and equivalent articles by those of ordinary skill in the art. Rather it is hereby intended the scope be defined by the claims appended hereto.

[0053] It should be understood that certain aspects, features, structures, or characteristics of the various embodiments can be interchanged in whole or in part. Reference to certain embodiments mean that a particular aspect, feature, structure, or characteristic described in connection with certain embodiments can be included in at least one embodiment and may be interchanged with certain other embodiments. The appearances of the phrase “in certain embodiments” in various places in specification are not necessarily all referring to the same embodiment, nor are certainembodiments necessarily mutually exclusive of other certain embodiments. It should also be understood that the steps of the methods set forth herein are not necessarily required to be performed in the orders described, and the order of the steps of such methods should be understood to be merely exemplary. Likewise, additional steps can be included in such methods, and certain steps may be omitted or combined, in methods consistent with certain embodiments.

Claims

WHAT IS CLAIMED IS:

1. An anode-less metal-air battery comprising a solid electrolyte surrounding an anode, a polymer border formed of an impervious material surrounding the borders of the solid electrolyte, and dual oxygen-evolution reaction (“OER”) and oxygen-reduction reaction (“ORR”) cathodes, the metal-air battery further comprising one or more of a reinforcing mesh contacting the polymer border; a porous polymer separator between the reinforcing mesh and the solid electrolyte the OER comprising a nickel iron oxyhydroxide coating; or the ORR comprising an iron nitride coating or manganese oxide coating.

2. The metal -air battery of claim 1, wherein the reinforcing mesh is formed of copper or stainless steel.

3. The metal -air battery of claim 2, wherein the reinforcing mesh comprises about 1,000 strands to about 100,000 strands per square centimeter.

4. The metal-air battery of claim 2, wherein the reinforcing mesh is embedded into the polymer border.

5. The metal-air battery of claim 2, wherein the reinforcing mesh acts as the OER for the metal-air battery.

6. The metal-air battery of claim 5, wherein the reinforcing mesh comprises a tab that extends outside of the metal-air battery.

7. The metal-air battery of claim 1, wherein the porous polymer separator comprises a plurality of micro-holes.

8. The metal-air battery of claim 7, wherein each of the plurality of micro-holes have a diameter of about 0.01 micrometer to about 200 micrometers.

9. The metal-air battery of claim 1, wherein the nickel iron oxyhydroxide coating comprises NixFei-xOOH.

10. The metal-air battery of claim 1, wherein the nickel iron oxyhydroxide coating is about 0.1 microns to about 1,000 microns in thickness.

11. The metal-air battery of claim 1, wherein the iron nitride coating comprises Fe2N.

12. The metal-air battery of claim 11, wherein the iron nitride coating is about 0.01 micrometers to about 5 micrometers in thickness.

13. The metal-air battery of claim 1 comprises each of: the reinforcing mesh contacting the polymer border; the porous polymer separator between the reinforcing mesh and the solid electrolyte; the OER comprising the nickel iron oxyhydroxide coating; and the ORR comprising the iron nitride coating or the manganese oxide coating.

14. The metal-air battery of claim 1 is a sodium-air battery.

15. A method of improving a metal-air battery comprising a solid electrolyte on top of an anode, a polymer border surrounding the solid electrolyte edges and anode edges, and dual oxygenevolution reaction (“OER”) and oxygen-reduction reaction (“ORR”) cathodes, the method comprising one or more of: providing a reinforcing mesh contacting the polymer border; forming the polymer separator of a porous material comprising a plurality of micro-holes; forming a nickel iron oxyhydroxide coating on the OER cathode; or forming an iron nitride coating or manganese oxide coating on the ORR cathode.

16. The method of claim 15, wherein the reinforcing mesh is embedded into the polymer border by heating the polymer border and then using pressure to force the reinforcing mesh into the polymer border.

17. The method of claim 15, wherein the reinforcing mesh further acts as the OER cathode for the metal-air battery.

18. The method of claim 15, wherein the nickel iron oxyhydroxide coating is formed by electroless deposition of a nickel layer followed by electrodeposition of the nickel iron oxyhydroxide.

19. The method of claim 15, wherein the nickel iron oxyhydroxide layer is formed by oxidation of stainless steel.

20. The method of claim 15, wherein the iron nitride coating is formed by placing the ORR cathode in a heated ammonia atmosphere.

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