Patent Publication Number: US-11652252-B2

Title: Zinc-air battery systems and methods

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a non-provisional of and claims the benefit of U.S. Provisional Application No. 63/020,655, filed May 6, 2020, entitled “ZINC-AIR BATTERY SYSTEMS AND METHODS”. This application is hereby incorporated herein by reference in its entirety and for all purposes. 
     This application is a non-provisional of and claims the benefit of U.S. Provisional Application No. 63/020,670, filed May 6, 2020, entitled “ZINC-AIR BATTERY COMPOSITIONS AND METHODS”. This application is hereby incorporated herein by reference in its entirety and for all purposes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG.  1    illustrates an example of a zinc-air battery cell assembly having an anode and cathode can that define a cavity with anode and cathode materials disposed within the cavity. 
       FIG.  2    illustrates a cross-sectional view of an example of an air cathode assembly in accordance with one embodiment, which includes a first conductive layer, a grid disposed in a second air cathode layer and a third separator layer. 
       FIG.  3    illustrates a bottom perspective view of a cathode can of one embodiment. 
       FIG.  4    illustrates a top internal perspective view of a cathode can of one embodiment. 
       FIG.  5    illustrates an example cross-sectional view of a side portion of a zinc-air battery cell assembly. 
       FIG.  6    illustrates an example method of making a zinc-air battery assembly in accordance with an embodiment. 
       FIG.  7   a    illustrates a method where a separator is inserted into the cavity of a cathode can. 
       FIG.  7   b    illustrates a method where a cathode disc is inserted into the cavity of a cathode can over the separator to generate a cathode can assembly. 
       FIG.  8   a    illustrates a method where a grommet is inserted into an anode can. 
       FIG.  8   b    illustrates a method where anode material is inserted into the assembly of the anode can and grommet to generate an anode can assembly. 
       FIG.  9   a    illustrates a method where a cathode can assembly is placed into an anode can assembly. 
       FIG.  9   b    illustrates a method where the terminal end of the cathode is crimped to a curved configuration such that the end of the cathode sidewall curls over the ridge and slot of the anode can to generate zinc-air battery cell assembly. 
       FIG.  10   a    illustrates a top view of a zinc-air battery assembly of one embodiment. 
       FIG.  10   b    illustrates an example cross section of the embodiment of  FIG.  10     a.    
       FIG.  10   c    illustrates example dimensions on one specific example embodiment of a zinc-air battery assembly. 
       FIG.  11   a    illustrates a top view of a grommet in accordance with an embodiment. 
       FIG.  11   b    illustrates a cross section of the grommet of  FIG.  11     a.    
       FIG.  11   c    illustrates a detail view of a portion of the grommet of  FIG.  11     b.    
       FIG.  12   a    illustrates an example embodiment of a cathode can. 
       FIG.  12   b    illustrates a cross-section of the embodiment of  FIG.  12     a.    
       FIG.  13   a    illustrates a close-up detail view of a portion of a cathode can. 
       FIG.  13   b    illustrates a close-up detail view of the cathode can of  FIGS.  12   a    and  12   b.    
       FIG.  13   c    illustrates a close-up detail view of the cathode can of  FIGS.  12   a    and  12   b.    
       FIG.  14   a    illustrates and example embodiment of an anode can. 
       FIG.  14   b    illustrates a cross section of the example embodiment of the anode can of  FIG.  14     a.    
       FIG.  14   c    illustrates a close-up detail view of a portion of the anode can of  FIG.  14     b.    
       FIG.  15   a    illustrates an example of air diffusion into the cavity of a zinc-air battery assembly via a hole defined by a cathode can. 
       FIG.  15   b    illustrates a perspective view of an example embodiment of a cathode can. 
       FIG.  15   c    illustrates a top view of the cathode can of  FIG.  15     b.    
       FIG.  16    illustrates a close-up cross sectional view of a portion of a zinc-air battery assembly. 
       FIG.  17   a    illustrates a top view of an embodiment of a zinc-air battery assembly. 
       FIG.  17   b    illustrates an embodiment of a grommet. 
       FIG.  17   c    illustrates an embodiment of a cathode can. 
       FIG.  17   d    illustrates a side view of an embodiment of a zinc-air battery assembly. 
       FIG.  18   a    illustrates an example embodiment of an anode can 
       FIG.  18   b    illustrates an example embodiment of a grommet. 
       FIG.  18   c    illustrates an example embodiment of a cathode can. 
    
    
     It should be noted that the figures are not drawn to scale and that elements of similar structures or functions are generally represented by like reference numerals for illustrative purposes throughout the figures. It also should be noted that the figures are only intended to facilitate the description of the preferred embodiments. The figures do not illustrate every aspect of the described embodiments and do not limit the scope of the present disclosure. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Some zinc-air batteries can include the use of a welded woven or expanded metal grid outside of the cathode material being connected to the cathode can by a metal grid welded to the cathode can being pressed between the cathode can and the cathode disk. However, in some examples, such a method over time can have a decrease in electrical connection as there is not a permanent and constant constraining force to keep the two members in contact because the cathode layer in contact with metal is expanding and contracting during use, which can lead to separation of the two. An elastic and compressive conductive layer like carbon felt/foam/pliable paper can provide a permanent and secure contact because this conductive layer can expand and retract with the cathode as needed. These materials can be very conductive. 
     Additional zinc-air batteries can include the use of an annular ring in the cathode can which presses into the cathode material but still makes use of an external welded woven or expanded metal grid for electrical contact between the cathode can and the cathode material. As with the previous case, the electrical connection can, over time, decrease due to a loss of constraining pressure in some examples. In addition, this embodiment can cause, in some examples, the cathode to bow away from the wire mesh grid resulting in a decreased anode cavity which provides a decreased cell capacity. 
     In view of the foregoing, a need exists for an improved sealing system and method for improving the electrical connection between the cathode can and cathode material in an effort to overcome the aforementioned obstacles and deficiencies of conventional zinc-air battery systems. 
     In some aspects, the present disclosure relates to a zinc-air battery cell assembly having a cathode assembly that includes the following layers in the following order: separator-cathode active layer-cathode conductive layer-conductive diffusion pad. The cathode active layer can comprise PTFE, carbon and manganese dioxide (or transitional metal oxides). A nickel mesh can be embedded in the cathode layer and in some examples, the mesh is preferably positioned away from the separator. The purpose of the cathode active layer can be to enable an Oxygen Reduction Reaction (ORR), which generates electrical energy. The cathode active layer can have a mix of both hydrophobic and hydrophilic properties. The cathode active layer can allow air diffusion and can be electrically conductive. The cathode conductive layer, in some examples, contains no transition metal oxide and/or only contains PTFE and carbon. PTFE content in various embodiments can be higher in the cathode conductive layer than the cathode active layer. In various examples, the cathode conductive layer can be totally or substantially hydrophobic and enables electronic conduction and air diffusion. The conductive diffusion pad can sit between a cathode can and the cathode conductive layer. In some examples, the conductive diffusion pad can comprise carbon foam, felt or paper. In some examples, the conductive diffusion pad can comprise a nickel mesh grid, foam or expanded metal welded to the cathode can, or the like. 
     In some aspects, the present disclosure relates to the achievement of high-power performance and the reduction of performance variability that can exist in some zinc-air batteries. Various embodiments relate to high-power single use zinc-air batteries. “High Power” in various embodiments and for portable applications that utilize a Zinc Air Battery can be a battery product that achieves continuous areal power capability of equal or greater than 50 mW/cm 2 . Various examples can define a reaction area of a battery product as the interfacial area between the zinc anode and air cathode. 
     In one aspect, presence of a mesh in the cathode is combined with the use of a conductive diffusion layer. The role of the mesh embedded in the cathode can change from its traditional role of cathode conductor in the radial plane to more that of a structural support that allows that cathode to be made with more consistency and more cohesion. 
     In a further aspect, the number of holes in a zinc-air battery can be over 5 per cm 2  and the hole diameter can be equal or greater than 0.5 mm. The holes can be arranged in a pattern so that no hole is further than 5 mm from the hole closest to it or from the edge of the air cathode. 
     In yet another aspect, the cell can be permitted to bulge by between 5-25%, which can be as a result of a high power (e.g., 50-135 mW/cm 2 ) discharge reaction. This can allow a reduction of the void volume in a cell and can promote better anode consistency, connectivity with the anode current collector and an increase in the overall anode capacity. 
     In various embodiments, such aspects separately and/or together, can improve the high-power performance of primary zinc air cells. Such a battery in some examples can provide performance benefits to small (portable) rechargeable devices such as a cell phone. 
     Various embodiments can lead to a higher more consistent cathode running voltage and a zinc anode that is less susceptible to passivation and premature failure. In some examples of a zinc air product these can be experienced in a device as either: More power (W) capability for a given run time; more run time for a given power drain; or combinations thereof. 
     Turning to  FIG.  1   , various embodiments can include zinc-air battery cell assembly  100  that comprises a cathode can  120  made of a metallic material compatible with the electrochemistry of the cell assembly  100  as discussed in more detail herein. The material of the cathode can  120  can comprise nickel-plated steel in some embodiments. The cathode can  120  can comprise a plurality of holes  160  defined by a bottom planar base  121  of the cathode can  120  which can allow air passage into the zinc-air battery cell assembly  100  at a calculated rate, which can produce a redox reaction that generates an electrical circuit within the zinc-air battery cell assembly  100 . 
     The zinc-air battery cell assembly  100  can also comprise an anode can  110 , which can be made of a metallic material. The anode can  110  in some examples can comprise, consist essentially of or consist of a tri-layer material containing a copper layer, a steel layer and a nickel layer. In another embodiment, the anode can  110  can comprise, consist essentially of or consist of a bi-layer material having a copper layer and a stainless steel layer with the copper layer being an internal surface and in contact with or facing an anode material  140  disposed within a cavity  180  defined by the anode can  110  and cathode can  120 . 
     A grommet  130  can surround the anode can  110  that can be made of a thermoplastic material coated with styrene-butylene-styrene block copolymer (SBS) or styrene-butadiene copolymer (SBR) compatible with the electrochemistry of the zinc-air battery cell assembly  100 . In one embodiment, the grommet  130  can comprise, consist essentially of or consist of a polypropylene homo-polymer. Polyamide materials can also be used for the grommet  130  in some embodiments, and in other sealant applications, the material of the grommet  130  can also be a polyamide-based material such as Versamid (Huntsman Advanced Materials, The Woodlands, Tex.). In various embodiments, the mechanical design of a zinc-air battery cell assembly  100  can specify the style of sealant that is desirable for ensuring appropriate compatibility with an electrolyte of the anode material  140 , the gasket material and the manufacturing methods used for application of the sealant. 
     The anode material  140  can be contained within the cavity  180  defined by the anode can  110  and cathode can  120 , which in some examples can comprise, consist of, or consist essentially of zinc, aqueous potassium hydroxide, zinc oxide and gelling agents in an aqueous slurry. While a slurry anode material  140  is desirable in some embodiments, zinc-air battery cell assemblies  100  of some examples can be made using a poured anode process. Even distribution of the anode material  140  within the cavity  180  can be desirable in various embodiments. 
     In some embodiments, if a zinc-air battery cell assembly  100  is discharged at a low rate, high utilization may be required by the zinc-air battery cell assembly  100 . In such embodiments, providing a significant void volume in the cavity  180  of the zinc-air battery cell assembly  100  can be desirable (e.g., 30% utilized). For example,  FIG.  1    illustrates an example of a zinc-air battery cell assembly  100  having a void volume  181  in the cavity  180  of the zinc-air battery cell assembly  100  between the anode material  140  and a top end  111  of the anode can  110 . In some embodiments, current density on the anode material  140  can be &gt;60 mA/cm 2  for a high power drain, which in some examples can cause the zinc-air battery cell assembly  100  to achieve a zinc utilization of 50% or less. 
     In some embodiments, a 15% void volume  181  can be desirable, with the void volume  181  being defined as the amount of space remaining in the cavity  180  of the zinc-air battery cell assembly  100  aside from components such as the anode material  140 , cathode material  150 , and the like disposed within the cavity  180  in the assembled zinc-air battery cell assembly  100 . In some embodiments, a desirable high-power capability is enabled in a zinc-air battery cell assembly  100  with a void volume  181  between 15-30% that generates a zinc utilization between 30% and 80%. In further embodiments, the void volume can be 5-40%, 10-35%, 20-25%, 10-20%, 5-25%, and the like. 
     In yet another aspect, the zinc-air battery cell assembly  100  can be configured to bulge, which can be as a result of expansion of the anode material  140  and/or cathode material  150  during a discharge reaction of the zinc-air battery cell assembly  100 . For example, such bulging can occur in some embodiments during a high-power discharge reaction, which may include a power discharge of 50-135 mW/cm 2 , 50-100 mW/cm 2 , 50-75 mW/cm 2 , 50-150 mW/cm 2 , 75-135 mW/cm 2 , 100-135 mW/cm 2 , and the like. 
     Various embodiments relate to single use zinc-air battery cell assembly  100 , where “single use” can be defined as a zinc-air battery cell assembly  100  configured for only being discharged once without the ability to re-charge the zinc-air battery cell assembly  100  after being discharged. For example, in various embodiments, a reaction that generates power can be a one-way reaction such that the reaction cannot be suitably reversed such that the zinc-air battery cell assembly  100  can be recharged. In various embodiments, this can be distinguished from a rechargeable battery that only has a limited recharging lifespan and the specific situation where such a battery is discharged for a final time and becomes inoperable. 
     In various embodiments, the zinc-air battery cell assembly  100  can be configured to bulge (e.g., increase its thickness at a maximum point) to at least between 5-25%, which in some examples can be defined as a volume displacement of the zinc-air battery cell assembly  100  from a normal configuration (e.g., as shown in  FIG.  1   , where the anode and cathode cans  110 ,  120  are generally planar on the top and bottom of the zinc-air battery cell assembly  100 ). For example, bulging of the zinc-air battery cell assembly  100  can include outward bulging of the top end  111  of the anode can  110  and/or outward bulging of the base  121 . 
     In some examples, having the zinc-air battery cell assembly  100  configured to bulge to at least a certain amount can be defined as an amount of bulge that the zinc-air battery cell assembly  100  is able to sustain without being damaged, breaking, or the like, (e.g., where seals are broken, the anode and cathode cans  110 ,  120  break apart, contents within the zinc-air battery cell assembly  100  come out of the cavity  180 , etc.). In some examples, having the zinc-air battery cell assembly  100  configured to bulge to at least a certain amount can be defined as an amount of bulge that the zinc-air battery cell assembly  100  is able to sustain while still being capable of returning to an original shape, (e.g., the anode and/or cathode cans  110 ,  120  can deform while bulging, but can return to an original configuration when bulging is not present). In further embodiments, the zinc-air battery cell assembly  100  can be configured to bulge an amount from 0-5%, 0-10%, 0-15%, 0-20%, 0-25%, 0-30%, 0-35%, 0-40%, 0-45%, 0-50%, and the like. 
     In some embodiments, expansion of contents within the cavity  180  (e.g., anode material  140  and/or cathode material  150 ), can result in a reduction of the void volume  181  in a zinc-air battery cell assembly  100 , which in some examples can promote better anode consistency, connectivity with an anode current collector and an increase in overall anode capacity. Additionally, a void volume  181  in the cavity  180  can be desirable because it can allow for expansion of the contents within the cavity  180  (e.g., anode material  140  and/or cathode material  150 ), which in some examples may remove or reduce the amount of bulge that the zinc-air battery cell assembly  100  needs to accommodate. Accordingly, the volume of the void volume  181  can be configured based at least in part on an anticipated expansion of contents within the cavity  180  (e.g., anode material  140  and/or cathode material  150 ). 
     In various embodiments, a volume of anode material  140  to be present in the cavity  180  of the zinc-air battery cell assembly  100 , and therefore the total weight of the anode material  140 , can be determined initially based at least in part on the volume of the cavity  180  that will be generated in an assembled zinc-air battery cell assembly  100 . Such a volume of the cavity  180  can be selected based at least in part on the mechanical design of the zinc-air battery cell assembly  100 , and components thereof, and making appropriate allowances for the separator and its electrolyte absorption. In some specific embodiments, the anode material  140  can have a volume of 2.96 cc, or a volume between 3.0 and 2.9 cc, 3.5-2.5 cc, and the like. 
     The anode material  140  can be wet (e.g., have a high weight ratio of electrolyte:Zinc) in various examples, and in some examples, wetter than embodiments that run between 75-80% Zinc Weight %. Sealing can accommodate this in some embodiments. For example, in some embodiments the Zinc weight % can be between 60-70%, 60-66%, 55%-75%, 58%-%72%, or the like. Use of a zinc-air developed zinc powder from EverZinc (EverZinc Canada, Quebec, Canada) or Grillo (Grillo-Werke AG, Duisburg, Germany) is preferred in some embodiments, using zinc material used by Alkaline Button or Cylindrical Cell Company may be desirable in some examples. A caustic electrolyte containing potassium hydroxide can be used in some embodiments (e.g., 35% KOH and 2% ZnO, or a range of 33%-37%, 30-40% or 25-45% KOH and 1%-5%, 1%-4% or 1%-3% ZnO). 
     In some embodiments the anode material  140  can comprise a slurry or gelled composition using sodium polyacrylate of polyacrylic acid as the gellant (e.g., Carbopol 940 NF Polymer, Lubrizol Corporation, Wickliffe, Ohio). The zinc weight % in the slurry can, in some such embodiments, be 64% to 74% or 62% to 74% for best results in some examples and the KOH concentration of the electrolyte can be between 33%-37%, 30-40% or 25-45%. The electrolyte of the anode material  140  may also contain zinc oxide and organic inhibitors in some embodiments, such as Polyethylene Glycol (PEG), Crown 18-6 or inorganic inhibitors such as indium hydroxide. 
     Carboxymethyl cellulose (CMC) can be used as an anode expander (e.g., in a poured anode process). High molecular weight, cross-linked polyacrylic acid polymers (e.g., Carbopol) can be used as an anode expander (e.g., in a slurry anode process). High (e.g., up to 2%) CMC content in the anode material  140  can help with cell wetness in some embodiments and the balance between the separator and CMC absorption of electrolyte can be tuned. In some embodiments, the type of zinc used in the anode material  140  can be an appropriate alloy with small amounts of zinc gassing inhibitors. For example, in some embodiments, individual alloying components can be less than 500 ppm and can include Indium, Bismuth calcium, aluminum, mercury, lead, or the like. 
     Packing density (e.g., particle-particle contact) can be an important variable in various embodiments. In some examples, a large diameter (e.g., greater than 500 microns) can produce problems such that a small cone of zinc becomes unreacted in the center of the zinc-air battery cell assembly  100 . Distribution of the anode material  140  can be important in some embodiments, and if a poured anode material  140  is used, multiple pouring holes may be required in some examples. Alternatively, a method of manufacturing a zinc-air battery cell assembly  100  may employ a rotating fixture to ensure even filling of anode material  140  within the cavity  180  of the zinc-air battery cell assembly  100 . 
     It can be desirable for gassing rates of the anode material  140  to be low in some embodiments (e.g., less than 0.5 cm 3  after 1 week at 60° C.). In various embodiments, contaminants can be managed in some or all components to current zero added mercury (Hg) zinc-air cells. Corrosion inhibitors can be dissolved in an electrolyte of the anode material  140  to reduce zinc gassing. Polyethylene Glycol (PEG) can be used for this purpose in some examples. Crown 18-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) can be effective for reducing zinc gassing and can be added in some examples at a level of between 200-2500 ppm, 100-3500 ppm, 250-2000 ppm, 300-1500 ppm by weight of electrolyte, and the like. Note that as discussed herein, the terms “zinc corrosion” and “gassing,” or the like, can be synonymous in various examples. 
     In various embodiments, zinc corrosion can be maintained at a low level. A corrosion rate at 60° C. of less than 0.2%/g/week or gas evolution rate of less than 0.04 micro-liter/g/week can be desirable in some examples. Higher corrosion/gassing rates in some embodiments can lead to leakage, cathode flooding, gas collection between the cathode and separator, gas collection between the separator and anode and/or ion impeding gas bubbles trapped in the zinc gel/slurry. 
     Various examples of aqueous alkaline batteries that have zinc anodes (e.g., anode material  140 ) can be configured to manage and control the corrosion of zinc that results in the production of hydrogen gas within the battery. While this can be undesirable in various types of batteries, a zinc-air battery cell assembly  100  in various embodiments can be particularly sensitive in some examples that have an open design and access to air. Problems that can result in some examples can include leakage, cathode flooding, separation of components and particularly deleterious for high power performance in some examples, the collection of gas bubbles within the anode material  140  that can lead to impedance and uniform zinc discharge issues. 
     Gassing management can be achieved in various embodiments by the use of alloying components in the zinc of anode material  140 , a focus on material purity and/or by plating of an anode conductor. In addition, the use of an organic inhibitor can be added to an electrolyte of the anode material  140 , and in some embodiments this can reduce the gassing reaction while at the same time not interfering with the battery discharge reaction. Many suitable types of inhibitors can be used in embodiments of aqueous alkaline batteries including Polyethylene Glycol, Non-ionic Alkyl and/or Aryl Phosphate surfactants, for example, RA-600, Sodium dodecylbenzenesulfonate, for example, Witconate and different Polyamines. Each of these chemicals in various examples may be able to dissolve in an alkaline electrolyte, may be chemically stable in a zinc-air battery cell assembly  100 , may adsorb onto the zinc surface, but may not impede the electrochemical oxidation of the zinc or the distribution of oxy-zinc products. 
     This disclosure in one aspect relates to a series of organic ring molecules called, Crown Ethers that can act as complexing agents in various embodiments and may be able, depending on their structure, to trap different cations. In one preferred embodiment, 0.2 weight percent of 18-Crown-6 is added to an alkaline electrolyte, while further embodiments can include 0.15-0.25 or 0.1-0.3 weight percent of 18-Crown-6. Tests of an implementation having 0.2 weight percent of 18-Crown-6 show that at this level, zinc corrosion of the zinc-air battery cell assembly  100  can be reduced versus other inhibitors and that the high-power performance is improved. 18-Crown-6 can be best for potassium-based alkaline electrolytes in some examples, but other Crown-style inhibitors can have efficacy and moreover can, in some examples, be better suited for sodium or lithium hydroxide systems or electro-chemistries that have a different anode than zinc. 
     The following Crown Ethers can be used in some embodiments and an electrolyte concentration of between 0.05 weight % and 0.5 weight % can be desirable in various examples: 18-Crown-6, 15-Crown-5, 12-Crown-4, Diaza-18-Crown-6, Di-Benzo-18 Crown-6, Diazacrowns, Cryptands, Azo-Crowns, Lariats, and the like. Some embodiments can have an electrolyte concentration of between 0.05-0.5 weight %, 0.05-1.0 weight %, 0.05-1.5 weight %, 0.1-0.45 weight %, 0.15-0.40 weight %, 0.2-0.35 weight %, 0.25-0.30 weight %, and the like. 
     Located between the anode material  140  and the cathode material  150  can be a separator  190 , which in some examples can act as both an electronic insulator and an ion conductive path. In various embodiments, a separator  190  in a zinc-air battery cell assembly  100  (e.g., a high-power single-use zinc-air battery) can provide electronic insulation between the anode material  140  and the cathode material  150 , but at the same time, provide for low resistance ionic conduction. The balancing act between the two may not be easy to achieve in various examples, and for a zinc-air battery cell assembly  100 , in various embodiments it can be desirable for the separator to have the added property of reducing and managing the transfer of Oxygen (O 2 ), Water vapor (H 2 O) and/or Carbon Dioxide (CO 2 ). This can be important for some example applications of a zinc-air battery cell assembly  100  that can have run times measured in days, weeks or even months as both O 2  and CO 2  may pass through the separator  190  and may degrade the zinc and electrolyte of the anode material  110  given enough time. 
     Separators for high power and/or low power batteries may not need low wet ionic resistance to deliver the required level of performance and such separators may be characterized by small pore size to minimize gas transfer. For example, a zinc-air battery cell assembly  100  in some examples can comprise one or more separators having pore sizes less than 1 micron and wet ionic resistances of higher than 50 mohm.cm 2 . In some embodiments, a separator can have a pore size of less than 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.75, 0.5, 0.25 microns, or the like. In some embodiments, a separator can have wet ionic resistances of higher than 100 mohm.cm 2 , 75 mohm.cm 2 , 50 mohm.cm 2 , 25 mohm.cm 2 , and the like. 
     In some examples of a high-power zinc-air battery cell assembly  100 , such as a cell phone charger, the zinc-air battery cell assembly  100  can deliver practical energy between 1-10 hours which may be insufficient time for deleterious gas transfer across the separator  190  to cause an unacceptable decrease in the performance of the zinc-air battery cell assembly  100 . It is therefore possible, in some embodiments, for such an application to open up the pore size and/or increase the overall porosity of the separator  190 , which can generate a benefit from a reduced wet ionic resistance without causing an unacceptable decrease in the performance of the zinc-air battery cell assembly  100  due to gas transfer across the separator  190  given expected operation time and/or one-use nature of such a zinc-air battery cell assembly  100 . 
     An implementation of one example embodiment of a zinc-air battery cell assembly  100  a separator  190  included two layers of a PVA-Cellulosic separator supplied by SWM (Schweitzer-Maudit International). This material had the following properties: Basis Weight: 20.5 g/m 2 ; Thickness: 60-70 microns; Absorption: 115 g/m 2 ; Mean Pore Size: 2.20 microns; and Maximum Pore Size: 9.80 microns. When this configuration was tested in a zinc-air battery cell assembly  100  at a rate of 70 mW/cm 2 , the example separator  190  in this example embodiment outperformed separators  190  with smaller pore size and higher wet ionic resistance. 
     One preferred embodiment can include a separator  190  comprising PVA fibers blended with synthetic or natural cellulose using the dry-laid or wet-laid process. Surfactants can also be added to improve the properties of the separator. Other separator compositions can include: Polyolefin, Polyamide, Polyester, Polysulfone and Wood Pulp. 
     In various embodiments, high power can be maximized for a zinc-air battery cell assembly  100  without deleterious gas transfer across the separator  190  when the mean pore size is between 1 and 10 microns and when the wet ionic resistance for the separator system (e.g., one or more layers) is less than 50 mohm.cm 2 . Some embodiments can have a mean pore size between 1 and 20 microns, between 1 and 15 microns, between 1 and 5 microns, and the like. In some embodiments, wet ionic resistance can be less than or equal to 100 mohm.cm 2 , 75 mohm.cm 2 , 50 mohm.cm 2 , 25 mohm.cm 2 , and the like. 
     The cathode material  150  can be in direct contact with the cathode can  120  and can be comprised of a carbon-polymer composite in some examples. In some examples, a metal oxide catalyst can be added to the cathode material  150  to aid an oxygen reduction reaction. Located within the area between the planar base  121  of the cathode can  120  containing the air access holes  160  and a planar rim  122  in contact with the cathode material  150  can be an air diffusion member  170 . This air diffusion member  170  can be a primary means of conduction of electrical charge between the cathode material  150  and the cathode can  120  in various embodiments. The air diffusion member  170  in some examples can be made of various suitable materials such as a carbon foam, carbon felt, carbon paper material, or the like. In some embodiments, the conductive diffusion member  170  can have a porosity of greater than 60% and an electronic resistivity of less than 20 mohm-cm. In some embodiments, the conductive diffusion member  170  can have a porosity or open area of greater than 40%, 45%, 50%, 55%, 60%, 65%, 70%, the like. 
     While some examples can include non-woven diffusion member  170 , some embodiments can comprise a diffusion member  170 , a nickel mesh diffusion pad  170  (e.g., a nickel mesh diffusion pad is used instead of a non-woven diffusion pad). Such embodiments can provide desirable contact between the cathode material  150  and the cathode can  120  across the entire or a large portion of the surface area of the cathode material  150 . Some embodiments can comprise several (e.g., 4, 6, 8, 10, or the like) spot welds or laser welds to ensure good electrical contact with the cathode can  120 . In various examples, it can be desirable for a nickel diffusion pad to not interfere with air flow and/or be chemically reactive with composition of the zinc-air battery cell assembly  100 . 
     In various examples, it can be desirable for the anode can  110  to not promote excessive zinc gassing when in contact with zinc and electrolyte that may comprise the anode material  140 . Accordingly, in some embodiments, it can be desirable for metal components such as the anode can  110  and/or cathode can  120  to comprise pure copper, brass, tin or indium plating, or the like. For example, tin plating the whole of the anode can  110  can be present in some embodiments. Various examples can include welding to or cladding with tin plate. 
     One aspect of the present disclosure includes an air cathode assembly that can comprise, consist of, or consist essentially of a multiple layer assembly (e.g., 0.4 mm+/−0.04 mm thick), which can be circular in shape with a diameter corresponding to the size of a cathode can  120  as discussed herein. 
       FIG.  2    illustrates a cross-sectional view of an example of an air cathode assembly  200  in accordance with one embodiment, which can comprise, consist of, or consist essentially of a first conductive cathode diffusion layer  210 , a grid  220  disposed in a second active air cathode layer  230  and a third separator layer  240 . In the example of  FIG.  2   , the second active air cathode layer  230  is sandwiched between, directly adjacent to and bonded to the first conductive cathode diffusion layer  210  and the third separator layer  240 , without any intervening layers. 
     In various examples, first conductive cathode diffusion layer  210  can comprise, consist of, or consist essentially of a conductive microporous polymer layer bonded to the second active air cathode layer  230 . In some embodiments, the first conductive cathode diffusion layer  210  can comprise a carbon containing polytetrafluoroethylene (PTFE). Electronic conduction in both layer  210  and layer  230  can be into and out of the plane. In some embodiments, the thickness of the conductive cathode diffusion layer  210  can be between 0.1 and 0.3 mm. In some embodiments the thickness of the active air cathode layer  230  can be between 0.2 and 0.6 mm. 
     In various examples, the grid  220  can comprise, consist of, or consist essentially of a nickel mesh that may or may not be coated with carbon or graphite paint (e.g., coated with Timrex Graphite and/or Dispersions, Imerys Graphite &amp; Carbon Switzerland SA or coated with Acheson graphite paint, or the like). In some embodiments, the grid  220  may or may not be coated with carbon or graphite paint and fixed to the inside of a cathode can  120  with a conductive glue such as MG Chemicals Super Silver Epoxy adhesive, spot welding, laser welding, or the like. 
     The grid  220  can be embedded into the second active air cathode layer  230  and can provide stability and high-power performance consistency in some examples. In various embodiments, the grid  220  can be defined by a plurality of elongated grid elements  221  disposed in a plurality of parallel rows and parallel columns, with the rows and columns being perpendicular to each other and engaging at a plurality of intersections. For example,  FIG.  2    illustrates a cross-section with a plurality of grid elements  221  disposed in parallel and embedded in the second active air cathode layer  230 . As shown in  FIG.  2   , the grid  220  can be planar with a plane of the grid  220  being parallel to respective planes of contact between the active air cathode layer  230  and the conductive cathode diffusion layer  210  and the separator  240 . In some embodiments, the grid elements  221  can comprise nickel, nickel alloys, nickel plated steel, and the like. In some embodiments, thickness of grid elements can be 0.05-0.25 mm. Distance between grid elements can be expressed as % open area and can be 60% to 90% in some examples. 
     Additionally, as shown in the example of  FIG.  2   , the grid  220  can be disposed within the second active air cathode layer  230  proximate to the conductive cathode diffusion layer  210  or disposed closer to the conductive cathode diffusion layer  210  compared to the separator layer  240 . In other words, the second active air cathode layer  230  can have a central plane and the grid  220  can be disposed within the second active air cathode layer  230  on one side of the central plane closer to the conductive cathode diffusion layer  210 . In some embodiments, the grid  220  can be flush with the conductive cathode diffusion layer  210 . For example, the grid  220  can be disposed at an external edge of the second active air cathode layer  230  such that the grid  220  can engage with or directly abut the conductive cathode diffusion layer  210   
     The size, position and configuration of the grid  220  illustrated in  FIG.  2    is provided as one example; however, in further embodiments the grid  220  can have any suitable size, configuration or position relative to layers  210  and  240 . For example, in some embodiments, the grid  220  can comprise a plurality of circular rings of various diameters with a plurality of radial grid elements extending radially from a central location of the grid. Also, while an example of a grid  220  defining square or rectangular spaces between rows and columns of grid elements  221 , further embodiments can include a grid  220  including spaces of one or more suitable shape, including triangular, pentagonal, hexagonal, heptagonal, octagonal, or the like. Additionally, grid elements  221  may not be linear or elongated in various embodiments. 
     In some embodiments, the grid  220  may or may not provide an electric conduction and connection through its circumference to the cathode can  120  of the zinc-air battery cell assembly  100  (see, e.g.,  FIG.  1   ) that the cathode assembly  200  is disposed in. For example, in some embodiments, one or more ends of grid elements  221  can engage the cathode can  120  of a zinc-air battery cell assembly  100  to generate an electrical connection between the grid  220  and the cathode can  120  of the zinc-air battery cell assembly  100 . In further examples, the grid  220  can comprise a peripheral rim or other suitable element that allows the grid  220  to engage with and have an electrical connection with the cathode can  120  of the zinc-air battery cell assembly  100 . However, it should be clear that in various embodiments, electrical and/or physical contact (e.g., radially) between the grid  220  and cathode can  120  is specifically absent. 
     In some embodiments an electrical connection between the active air cathode layer  230  and the cathode can  120  can be provided by a conductive carbon disk (e.g., conductive diffusion member  170 ). In some embodiments, such a conductive disc can comprise a felt, a foam or a paper. Such a conductive disc in some examples can have a thickness between 0.1 mm and 0.25 mm and can have a resistivity of less than 20 mohm.cm 2 . Preferably, in some embodiments, the thickness of the conductive disc can be between 0.1 and 0.25 mm and the conductivity can be between 5 and 15 mohm.cm 2 . The conductive disk may be held in place by pressure between the cathode assembly  200  or the cathode material  150  and the cathode can  120 , by adhesive, or the like. 
     In various embodiments, the second active air cathode layer  230  can be pressed together to form a contiguous cathode strip and can then be pressed onto a grid  220  such that the grid  220  is embedded in the second active air cathode layer  230 . In some examples, the second active air cathode layer  230  can comprise high-conductivity carbons and/or high-surface-area carbons, and finely dispersed manganese dioxide all mixed together with a dispersion of polytetrafluoroethylene (PTFE) in water. Other methods may use the permanganate method where the carbon is washed with a permanganate solution and then dried in an oven to produce the manganese oxide catalyst. 
     In various embodiments, the third separator layer  240  can comprise a 25 μm microporous monolayer polypropylene membrane that is laminated to a polypropylene nonwoven fabric and surfactant coated to a total thickness of about 110 μm. For example, some embodiments of the third separator layer  240  can comprise Celgard 5550 (Celgard, LLC, Charlotte, N.C.). In some examples, the separator layer  240  can be glued onto the second active air cathode layer  230  using various suitable adhesives such as a polyvinyl alcohol (PVA) or polyacrylic acid (PAA) based glue, or the like. Carboxymethyl cellulose (CMC) may be included as a component of the separator layer  240 . In some embodiments, pre-wetting of the separator  240  can be desirable. 
     In various embodiments, the separator layer  240  serves to maximize ionic conduction (e.g., and minimize ionic resistance) and can provide electronic insulation between the anode and the cathode. Ionic conduction in aqueous batteries can be enabled by separator porosity and the presence of conducting electrolyte within the separator pores. In some embodiments, porosity of the separator layer  240  can be between 75% and 90%. Shorting or puncture resistance can also be important in some examples. In various embodiments, it can be important that the anode and cathode never touch; even when the cell is fresh or during discharge when the anode and cathode expand and the separator is squeezed between them and when semi-conducting solids can deposit in the pores of the separator layer  240 . Factors that can be important in some examples can be the separator thickness, separator tortuosity and separator mechanical integrity. 
     In some examples, a cathode assembly  200  can have a total thicknesses T of between 0.3 mm and 0.7 mm, and in some embodiments preferably less than 0.45 mm. Further embodiments can include a cathode assembly  200  having a thickness between 0.1 mm and 0.9 mm, 0.2 mm and 0.8 mm, 0.4 mm and 0.6 mm, 0.5 mm and 0.2 mm, 0.5 mm and 0.3 mm, 0.5 mm and 0.4 mm, or the like. 
     In some examples, such an air cathode assembly  200  embodied in a zinc-air battery cell assembly  100  (or other embodiments of a zinc-air battery cell assembly  100  discussed herein) can have a minimum continuous power capability of 60 mW/cm 2 , 70 mW/cm 2 , 80 mW/cm 2 , 90 mW/cm 2 , 100 mW/cm 2 , 110 mW/cm 2 , 120 mW/cm 2 , 130 mW/cm 2 , 135 mW/cm 2  140 mW/cm 2 , 150 mW/cm 2 , and the like. 
     It should be noted that the examples of  FIGS.  1  and  2    can be suitably combined in various ways and that the elements of one given example should not be considered to be exclusive to that illustrative embodiment. For example, in on embodiment, the cathode material  150  of  FIG.  1    can comprise, consist of or consist essentially of an active air cathode layer  230  and the conductive cathode diffusion layer  210  of  FIG.  2   . Accordingly, various suitable elements of  FIGS.  1  and  2    should be considered interchangeable, or may be specifically absent in some embodiments. For example, the cathode material  150  of  FIG.  1    can be interchangeable with the combined active air cathode layer  230  and conductive cathode diffusion layer  210  of  FIG.  2   . In another example, the third separator layer  240  of  FIG.  2    can be interchangeable with the separator  190  of  FIG.  1   . In a further example the cathode assembly  200  of  FIG.  2    (having an air cathode layer  230 , conductive cathode diffusion layer  210  and separator layer  240 ), can be interchangeable with the cathode material  150  and separator  190  of  FIG.  1   . 
     Turning to  FIGS.  3 - 5   , various embodiments can make use of a series of protrusions  310  formed into the planar rim  122  of the cathode can  120  that can be in contact with the cathode material  150  such as shown in  FIG.  5   . As shown in the example of  FIGS.  3  and  4   , these protrusions  310  can be formed in a circular pattern about the central axis of the cathode can  120  with the protrusions  310  located on the planar rim  122  and extending into the cavity  180  of the cathode can  120 . For example, in some embodiments, the protrusions  310  can be formed in a cathode can  120  by stamping the protrusions into the planar rim  122  such that the protrusions  310  extend into the cavity  180  of the cathode can  120  as shown in  FIG.  4   , and leave a protrusion slot on the external side of the planar rim  122  of the cathode can  120  as shown in  FIG.  3   . 
     The size, shape and count of these protrusions  310  are not restricted by the present disclosure and the specific example embodiments shown and described should not be construed to be limiting. In some examples, such as shown in  FIGS.  3  and  4   , the cathode can  120  can comprise 18 protrusions  310  with a protrusion height between 0.05-0.15 mm and a protrusion width between 0.5 and 1.50 mm and a length between 3.0 and 5.0 mm, having a generally rectangular cross-section and stepping up to a maximum protrusion height from opposing ends of the protrusion. In some embodiments, protrusions  310  can be spaced apart by 1.5 mm +/−0.2 mm). 
     Further embodiments can have a protrusion height from the face of the planar rim  122  of 0.05-0.25, 0.05-0.20, 0.05-0.15, 0.05-0.10, 0.10-0.15 mm and the like. Some embodiments can have a protrusion width between 0.5 and 2.00 mm, 0.5 and 1.50 mm, 0.5 and 1.00 mm, 1.0 and 1.50 mm, and the like. Some embodiments can have a protrusion length between 1.0 and 7.0 mm, 2.0 and 6.0 mm, 3.0 and 5.0 mm, 4.0 and 6.0 mm, 2.0 and 4.0 mm, and the like. Protrusions  310  can be spaced apart by 1.4-1.6 mm, 1.3-1.7 mm, 1.2-1.8 mm, 1.1-1.9 mm, 1-2 mm, and the like. Various embodiments can include any suitable number of protrusions, including 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 45, 50, 75, 100, 125, 150, 200, and the like. Also, while the examples of  FIGS.  3  and  4    illustrate protrusions  310  that are the same size and shape and spaced apart the same amount, further embodiments can including protrusions  310  that are different shapes and/or sizes, which may or may not be spaced apart different amounts. 
     The dimensions and configuration of protrusions  310  in further embodiments can be based upon the size, shape and configuration of the zinc-air battery cell assembly  100 . In various embodiments, upon closure of the zinc-air battery cell assembly  100  as discussed herein, the protrusions  310  penetrate the cathode material  150  and make contact with a metal screen mesh (e.g., grid  220 ) embedded inside the cathode material  150 , which can generate a permanent and secure contact between the metal screen mesh and the cathode can  120 . The penetration of the protrusions  310  into the cathode material  150  can, in various examples, place the cathode material  150  under increased compression, which can provide for better sealing between the cathode can  120  and cathode material  150 . In some embodiments, a portion of the cathode material  150  compressed by the protrusions  310  flows into the areas  315  between the protrusions  310 , which can increase the volumetric amount of cathode material  150  in those areas  315  which can increase the pressure on the cathode material  150  to an amount similar to the pressure on the cathode material  150  in areas of the cathode material  150  compressed by protrusions  310 . Another aspect of the protrusions  310  can be to put increased pressure on the cathode material  150  which can provide for better sealing between a grommet  130  (see  FIGS.  1  and  5   ) and the cathode material  150 . 
     As shown in  FIG.  5   , anode can  110  can comprise a planar top end  111  (see  FIG.  1   ) that peripherally curves downward to define a slot  112  with a ridge  113 , that extends to an elongated anode sidewall  114 , which extends perpendicular to the planar top end  111  of the anode can  110 . The cathode can  120  can comprise an elongated cathode sidewall  123  that extends perpendicular to the planar base  121  and planar rim  122  of the cathode can  120 . The anode can  110  can be configured to be disposed within the cathode can  120  with the anode and cathode sidewalls  114 ,  123  being disposed in parallel and adjacent as shown in the example of  FIG.  5   . 
     In various embodiments, the zinc-air battery cell assembly  100  can comprise a grommet  130  that provides a seal between the anode can  110  and the cathode can  120  while also keeping the anode can  110  and cathode can  120  physically and electrically separate. For example, as shown in the example of  FIG.  5   , the grommet  130  can surround an end  115  of the anode sidewall  114  with a first elongated portion  131  of the grommet  130  being disposed between the anode and cathode sidewalls  114 ,  123 . The end  115  of the anode sidewall  114  can be disposed within a grommet slot  132 , with a second elongated portion  133  of the grommet  130  extending along an internal portion of the anode sidewall  114  with the first and second elongated portions  131 ,  133  being coupled via bridge portion  136  that defines a portion of the grommet slot  132 . 
     An end  134  of the first elongated portion  131  can be configured to extend over the ridge  113  and into the slot  112  of the anode can  110 . For example, as discussed in more detail herein, an end  124  of the cathode sidewall  123  can be crimped to the configuration shown in  FIG.  5   , where the end  124  of the cathode sidewall  123  curls over the ridge  113  and slot  112  (compared to the configuration of the end  124  of the cathode sidewall  123  shown in  FIG.  4   ). As discussed in more detail herein, such crimping of the end  124  of the cathode sidewall  123  can create a seal between the anode can  110  and cathode can  120  via the grommet  130 . 
     In various embodiments, the grommet  130  can further comprise feet  135 A,  135 B, that can compress against the cathode material  150  and/or separator  190 , which can provide increased leakage protection for the zinc-air battery cell assembly  100 . For example, the feet  135 A,  135 B can provide an improved seal between the anode can  110  and cathode can  120  such that contents within the cavity  180  of the zinc-air battery cell assembly  100  such as the anode material  140  and/or cathode material  150  is prevented from leaking out from between the anode can  110  and cathode can  120 , even where anode material  140  and/or cathode material  150  expands within the cavity  180  as discussed herein. 
     As shown in the example of  FIG.  5   , a first foot  135 A can be present at a peripheral edge of the bridge portion  136  of the grommet  130  proximate to the second elongated portion  133  and the second foot  135 B can be present on an opposing peripheral edge of the bridge portion  136  proximate to the first elongated portion  131 . The feet  135 A,  135 B can be various suitable sizes and shapes. For example, in some embodiments, the feet  135 A,  135 B can be generally the same width as the first and second elongated portions  131 ,  133  and spaced apart the thickness of the anode sidewall  114 . 
     In various embodiments, compression of the grommet  130  and the feet  135 A,  135 B into the cathode material  150  and/or separator  190  can be generated by the application of a downward force of the anode can  110  into the grommet  130 , which in some examples can be caused by a closure process of the zinc-air battery cell assembly  100  such as crimping of the end  124  of the cathode sidewall  123  to create a seal between the anode can  110  and cathode can  120  via the grommet  130  as discussed herein. 
     The feet  135 A,  135 B can provide an increased compressive force between the grommet  130  and the cathode material  150  and/or separator  190 . A first area of higher compression generated by the first foot  135 A can, for example, act as a dam blocking the movement of electrolyte from the anode material  140  area across the interface between the cathode material  150  and/or separator  190  and grommet  130 . The area of the bridge portion  136  between the feet  135 A,  135 B can be under compression, which can provide an additional tortuous path blocking the flow of electrolyte from the anode material  140  area across the interface between the cathode material  150  and/or separator  190  and grommet  130 . A second area of higher compression generated by the second foot  135 B can act as a sealing surface, which can further block the movement of any electrolyte from the anode material  140  across the interface between the cathode material  150  and/or separator  190  and grommet  130 . The use of two or more higher-pressure areas can ensure that electrolyte contained within the cavity  180  is not allowed to leak from the zinc air battery cell assembly  100 . Accordingly, the novel configuration of the feet  135 A,  135 B of the grommet  130  in various embodiments cannot be considered a mere design choice given the improved sealing that can be generated by specific configurations of the feet  135 A,  135 B. 
     In some embodiments, a crimped zinc-air battery assembly  100  can tolerate at least 50 psi internal pressure (e.g., generated by expansion of the anode material  140  and/or cathode material  150 ) without opening of a crimping of the end  124  of the cathode sidewall  123  that creates a seal between the anode can  110  and cathode can  120  via the grommet  130  and/or pressure that will force the force electrolyte into the cathode and cause failure of the zinc-air battery assembly  100 . Further embodiments can be configured to tolerate at least 10 psi, 20 psi, 30 psi, 40 psi, 50 psi, 60 psi, 70 psi, 80 psi, 90 psi, 100 psi, 110 psi, 120 psi, 130 psi, 140 psi, 150 psi, and the like. Various examples of a zinc-air battery assembly  100  do not have any pressure build up under normal temperature of use and storage up to 45° C. because, in some embodiments, hydrogen can permeate through the cathode material  150  easily. In some embodiments, a zinc-air battery assembly  100  does not have any pressure build up under normal temperature of use and storage up to 30° C., 35° C., 40° C., 45° C., 50° C., 55° C., 60° C., 65° C., 70° C., and the like. 
     For many applications, the zinc-air battery assembly  100  of various embodiments offers the longest run time of any primary aqueous battery system with flat discharge voltage, safety and low cost. However, when in use in various examples, a zinc-air battery assembly  100  can be open to the ambient atmosphere; therefore, the zinc-air battery assembly  100  may not be independent of environmental conditions. Drying out in low humidity conditions in some examples can limit life once opened to the air. 
     Flooding of a zinc-air battery assembly  100  in a high humidity environment can limit power output and activated life of the zinc-air battery assembly  100  in some examples. Air access management can therefore be an important feature for zinc-air battery assemblies  100  in some embodiments. Therefore, air holes  160  in some examples can be designed to meet a minimum 50 mW/cm 2  discharge and activated life requirement of 24 hours. For example, in one embodiment, the number of holes  160  defined by the cathode can  120  of a zinc-air battery assembly  100  can be over 5 per cm 2  and the hole diameter can be equal or greater than 0.5 mm and the holes  160  can be arranged in a pattern so that no hole  160  is further than 5 mm from the hole  160  closest to it or from the edge of the air cathode. 
     In some embodiments, the number of holes  160  defined by the cathode can  120  of a zinc-air battery assembly  100  can be over 1 per cm 2 , 2 per cm 2 , 3 per cm 2 , 4 per cm 2 , 5 per cm 2 , 6 per cm 2 , 7 per cm 2 , 8 per cm 2 , 9 per cm 2 , 10 per cm 2 , 15 per cm 2 , 20 per cm 2 , and the like. In some embodiments, hole diameter can be greater than 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, and the like. In some embodiments, hole diameter can be between 0.1 mm and 1.0 mm, 0.2 mm and 0.9 mm, 0.3 mm and 0.8 mm, 0.4 mm and 0.7 mm, 0.5 mm and 0.6 mm, and the like. In some embodiments, holes  160  can be arranged in a pattern so that no hole  160  is further than, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, or the like, from the hole  160  closest to it and/or from the edge of the air cathode can  120 . 
     Regulation can be desirable in various embodiments because other gases, like hydrogen, water vapor and carbon dioxide can enter or leave the cavity  180  of the zinc-air battery assembly  100 . If not properly controlled, in some examples, undesirable gas transfer can cause performance degradation including degradation of service life of the zinc-air battery assembly  100 . Water vapor transfer can be the dominant form of gas transfer that can result in performance degradation in some examples. This transfer of water vapor can occur in various examples when electrolyte and the ambient relative humidity are not equal. 
     In some embodiments, the electrolyte of a zinc-air battery assembly  100  can be in equilibrium with the ambient room temperature when relative humidity is approximately 55%. Accordingly, in some conditions such a zinc-air battery assembly  100  can lose water on drier days and gain water on more humid days. In some examples, water gain or water loss can cause the zinc-air battery assembly  100  to fail before delivering the intended performance. Smaller and more evenly distributed holes  160  in the zinc-air battery assembly  100  can slow down the exchange in some examples. Another measure to increase tolerance can be making sure that the tortuous path in the cathode diffusion layer is adequate. 
     In some examples, a zinc anode material  140  can be a porous structure of granulated powder in mix with electrolyte and a gelling agent. Metal cathode and anode cans  110 ,  120  for housing cathode and anode active materials  140 ,  150  can also act as the terminals with a plastic gasket (e.g., grommet  130 ) in between to insulate. 
     In various embodiments, a portion of the total volume of the cavity  180  of a zinc-air battery assembly  100  can be a void volume  181  reserved to accommodate the expansion that occurs when zinc is converted to zinc oxide during power discharge of the zinc-air battery assembly  100 . This void volume  181 , (e.g., 15% to 25% of the total volume of the cavity  180 ), can provide additional tolerance to sustained water gain during high humidity operating conditions. For example, some embodiments can include an initial void volume  181  within the available volume of the cavity  180  of 15%, 18%, 21%, 23%, 25%, or the like, to accommodate this. In further embodiments, the void volume  181  can be 14-16%, 17-19%, 20-22%, 22-24%, 24-26%, 5-40%, 10-35%, 20-25%, 10-20%, 5-25%, and the like. In some embodiments, the void volume  181  can be 0.5-5.5 cc, 1.0-5.0 cc, 1.5-4.5 cc, 2.0-4.0 cc, 2.5-3.5 cc, 2.0-3.0 cc, and the like. 
     In some embodiments, mechanisms that degrade a zinc-air battery assembly  100  during storage and use can be (1) corrosion of the zinc with hydrogen gas evolution and/or (2) gas transfer. Gas transfer can include direct oxidation of the zinc anode material  140 , carbonation of an electrolyte, and electrolyte water gain or loss. During storage, air access holes  160  of the cell can be sealed to minimize degradation by gas transfer. Adhesive tape containing a polyester layer can be used in some examples to cover the vent holes  160  when the zinc-air battery assembly  100  is not in use. 
     A zinc-air battery assembly  100  and components thereof can be configured in any suitable way. For example,  FIGS.  10   a   - 18  illustrate example embodiments of a zinc-air battery assembly  100  and/or components thereof. For example,  FIG.  10   a    illustrates a top view of a zinc-air battery assembly  100  of one embodiment,  FIG.  10   b    illustrates an example cross section of the embodiment of  FIG.  10   a   , and  FIG.  10   c    illustrates example dimensions on one specific example embodiment of a zinc-air battery assembly  100  in millimeters.  FIG.  11   a    illustrates a top view of a grommet  130  in accordance with an embodiment,  FIG.  11   b    illustrates a cross section of the example embodiment of  FIG.  11   a    with example dimensions in millimeters, and  FIG.  11   c    illustrates a detail view of a portion of  FIG.  11     b.    
       FIG.  12   a    illustrates an example embodiment of a cathode can  120  and  FIG.  12   b    illustrates a cross-section of the embodiment of  FIG.  12   a    with example dimensions in millimeters.  FIG.  13   a    illustrates a close-up detail view of a portion of a cathode can  120 ,  FIG.  13   b    illustrates a close-up detail view of the cathode can  120  of  FIGS.  12   a  and  12   b    with example dimensions in millimeters, and  FIG.  13   c    illustrates a close-up detail view of the cathode can  120  of  FIGS.  12   a  and  12   b    with example dimensions in millimeters. 
       FIG.  14   a    illustrates an example embodiment of an anode can  110 ,  FIG.  14   b    illustrates a cross section of the example embodiment of the anode can  110  of  FIG.  14   a    with example dimensions in millimeters, and  FIG.  14   c    illustrates a close-up detail view of a portion of  FIG.  14   b    with example dimensions in millimeters.  FIG.  15   a    illustrates an example of air diffusion into the cavity  180  of a zinc-air battery assembly  100  via a hole  160  defined by a cathode can  120 ,  FIG.  15   b    illustrates a perspective view of an example embodiment of a cathode can  120  and  FIG.  15   c    illustrates a top view of the cathode can  120  of  FIG.  15     b.    
       FIG.  16    illustrates a close-up cross sectional view of a portion of a zinc-air battery assembly  100  with example and non-limiting dimensions in millimeters.  FIG.  17   a    illustrates a top view of an embodiment of a zinc-air battery assembly  100 ,  FIG.  17   b    illustrates an embodiment of a grommet  130 ,  FIG.  17   c    illustrates an embodiment of a cathode can  120 , and  FIG.  17   d    illustrates a side view of an embodiment of a zinc-air battery assembly  100  with example dimensions in millimeters.  FIG.  18   a    illustrates an example embodiment of an anode can  110 ,  FIG.  18   b    illustrates an example embodiment of a grommet  130 , and  FIG.  18   c    illustrates an example embodiment of a cathode can  120 , with example dimensions in millimeters. 
       FIG.  6    illustrates an example method  600  of making a zinc-air battery assembly  100  in accordance with an embodiment. The method  600  begins at  605  where a diffusion pad (e.g., diffusion member  170 ) is inserted into the cavity  180  of a cathode can  120  (see, e.g.,  FIG.  7   a   ), and at  610 , a cathode disc (e.g., cathode material  150 , cathode assembly  200 , or the like) is inserted into the cavity  180  of a cathode can  120  over the separator to generate a cathode can assembly (see, e.g.,  FIG.  7   b   ). 
     At  620 , a separator (e.g., separator  190 ) is inserted into the cavity  180  of the cathode can  120  over the cathode disc. However, note that in some embodiments, the cathode disc can comprise a separator, so the step of  620  can be absent and a separator (e.g., separator  190  or  240 ) can be introduced via the cathode disc. Similarly, in some embodiments, the cathode disc can include a diffusion pad, so the step  605  can be absent and the diffusion pad (e.g., diffusion member  170 ,  210 ) can be introduced via the cathode disc. 
     At  630 , a grommet  130  is inserted into an anode can  110  (see, e.g.,  FIG.  8   a   ) and at  640 , anode material  140  is inserted into the assembly of the anode can  110  and grommet  130  assembled at  630  to generate an anode can assembly (see e.g.,  FIG.  8   b   ). At  650 , the cathode can assembly generated at  620  is placed into the anode can assembly generated at  640 , and at  660 , the assembly generated at  650  is crimped to generate a zinc-air battery assembly  100 . For example, the terminal end  124  of the cathode can sidewall  123  can initially be in a straight configuration as shown in  FIGS.  4  and  9     a  and can be crimped to a curved configuration as shown in  FIG.  5  or  9     b  such that the end  124  of the cathode sidewall  123  curls over the ridge  113  and slot  112  of the anode can  110 , which can create a seal between the anode can  110  and cathode can  120  via the grommet  130  as discussed herein. 
     In some embodiments, a cathode assembly  200 , including the separator layer  240  can be shipped to a button cell manufacturer to generate a zinc-air battery cell assembly  100  having the air cathode assembly  200  and an anode material  140  disposed in the cavity  180  defined by anode can  110  and cathode can  120  as discussed herein. 
     The described embodiments are susceptible to various modifications and alternative forms, and specific examples thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the described embodiments are not to be limited to the particular forms or methods disclosed, but to the contrary, the present disclosure is to cover all modifications, equivalents, and alternatives. Additionally, elements of a given embodiment should not be construed to be applicable to only that example embodiment and therefore elements of one example embodiment can be applicable to other embodiments. Additionally, elements that are specifically shown in example embodiments should be construed to cover embodiments that comprise, consist essentially of, or consist of such elements, or such elements can be explicitly absent from further embodiments. Accordingly, the recitation of an element being present in one example should be construed to support some embodiments where such an element is explicitly absent.