Patent Description:
Metal-air cells typically include a fuel electrode at which metal fuel is oxidized, an oxidant electrode at which an oxidant (i.e., oxygen from the air) is reduced, and an ionically conductive medium therebetween for providing ion conductivity between the fuel and oxidant electrodes. In some embodiments of metal-air cells, or other cells utilizing an oxidant, a wound, rolled, folded, or otherwise compacted configuration may be utilized for enhancing cell space management and arrangement. In some such cells, multiple layers are formed that include the fuel electrode, the oxidant electrode, and the ionically conductive medium. Examples of such cells are disclosed in <CIT> and <CIT>. <CIT> discloses a fluid regulating microvalve assembly for use to control fluid flow to a fluid consuming electrode, such as an oxygen reduction electrode, in an electrochemical cell, the microvalve assembly includes a stationary valve body comprising a polymer, elastomer or rubber having an aperture and a microactuator movable from a first position where the microvalve body aperture is closed to fluid flow to at least a second position where fluid is able to pass through the microvalve body aperture.

In accordance with an aspect of the present invention, there is provided an electrochemical cell as set out in the first of the appending independent claims. There is also provided, in accordance with another aspect of the present invention, a system as set out in the second of the appending independent claims. Features of various embodiments are set out in the appending dependent claims.

There is also disclosed herein examples of an electrochemical cell including: an oxidant electrode for absorbing gaseous oxidant and a fuel electrode for receiving a metal fuel. The oxidant electrode has one or more active materials for reducing the gaseous oxidant. The cell also includes a liquid ionically conductive medium, that is contained by the oxidant electrode, for conducting ions for supporting electrochemical reactions at the fuel electrode and the oxidant electrode. The oxidant electrode and the fuel electrode are each configured in annular form, and the fuel electrode and the oxidant electrode are nested in the cell.

There is also disclosed herein examples of a system including a sealed container and a plurality of electrochemical cells. Each cell includes: an oxidant electrode for absorbing gaseous oxidant and a fuel electrode for oxidizing a metal fuel. The oxidant electrode has one or more active materials for reducing the gaseous oxidant. The oxidant electrode and the fuel electrode are each configured in annular form, and the oxidant electrode and the fuel electrode are nested. Also included in the system is a liquid ionically conductive medium for conducting ions for supporting electrochemical reactions at the fuel electrode and the oxidant electrode. The sealed container contains the plurality of electrochemical cells therein.

Other features and advantages of the present disclosure will become apparent from the following detailed description, the accompanying drawings, and the appended claims.

Generally described herein are electrochemical metal-air cells having nested electrodes provided in an annular or a cylindrical configuration. Systems that contain such cells in a container are also provided. Each cell may include an oxidant electrode (e.g., an air cathode) and a fuel electrode (e.g., an anode). A series of permeable bodies, screens, or current collectors may be provided as part of the fuel electrode. An oxygen evolution (or oxygen evolving) electrode may also be provided in the cells, e.g., to act as a charging electrode. The fuel electrode may be nested within the oxidant electrode, or vice versa. Optionally, in some embodiments, a second oxidant electrode may be included in the cell(s). An ionically conductive medium or electrolyte may be contained in the cell. Each cell may optionally have its own cell housing, formed by either the air cathode itself or an external housing. Optionally, an air space or pocket may be formed in a cell via an oxidant electrode. The container may contain the cells such that they are surrounded by air or a liquid ionically conductive medium/electrolyte. The container may include a compartment that is sealed (e.g., via a lid or a cover) to contain the cells therein. Additional features shall be understood by the Figures and description of embodiments provided below.

The term first electrode is used interchangeably with fuel electrode and/or anode in this disclosure. The term second electrode is used interchangeably with oxidant electrode. The term oxidant electrode is used interchangeably with oxidant electrode, oxidant reducing electrode, oxidant reduction electrode, air electrode, and/or air cathode. The first and second electrodes are electrodes of opposite polarity, e.g., the first electrode has an anodic potential to oxide its active reactant during standard discharge and a cathodic potential to reduce an oxidized species back to the active reactant during standard charge, and the second electrode does the opposite on its active reactant. The term ionically conductive medium may refer to an electrolyte, i.e., ionically conductive liquid electrolyte, liquid ionically conductive medium, and/or an aqueous ionically conductive medium, and such terms may be used interchangeably throughout this disclosure.

<FIG> is a schematic overhead view of an electrochemical metal-air cell <NUM> in accordance with an embodiment of this disclosure. Generally, the cell <NUM> includes at least a first electrode <NUM> and a second electrode <NUM>. In accordance with embodiments herein, the first electrode(s) is a fuel electrode <NUM> for receiving and oxidizing a metal fuel, and the second electrode <NUM> is an oxidant electrode <NUM> (or oxidant reduction electrode) that has one or more active materials for reducing a gas oxidant (e.g., oxygen in air). In an embodiment, e.g., during standard discharge, the fuel electrode <NUM> acts or functions as an anode where the fuel of the cell or system is oxidized so that electrons given off by the metal fuel, as the fuel is oxidized at the fuel electrode <NUM>, flows to an external load L, and the oxidant electrode <NUM> acts or functions as an air cathode for absorbing and reducing gaseous oxidant (e.g., oxygen in air) and is configured to receive electrons from the external load L. In accordance with an embodiment, the fuel electrode <NUM> of each cell <NUM> has fuel in the form of solid fuel electrodeposited on an electroconductive electrode body, but may be generally referred to as the anode, even when no fuel is present. Further, in the cell <NUM> of <FIG> an ionically conductive medium <NUM> is contained by the oxidant electrode <NUM>, for conducting ions for supporting electrochemical reactions at the fuel electrode(s) <NUM> and the oxidant electrode <NUM>.

The fuel electrode <NUM> includes an internal surface <NUM> that faces the ionically conductive medium <NUM> and an external surface <NUM> that faces the oxidant electrode <NUM>. The oxidant electrode <NUM> includes an internal surface <NUM> or cell side or face (e.g., facing and contacting electrolyte or ionically conductive medium <NUM> within the cell <NUM>) that faces the fuel electrode <NUM> and an external surface <NUM>, or air side or face, that is facing and exposed to oxidant (oxygen or air). In some embodiments, as illustrated in <FIG>, the external surface <NUM> of the oxidant electrode <NUM> may be an outermost surface of the cell <NUM>.

More specifically, as shown, the oxidant electrode <NUM> and the fuel electrode <NUM> are each configured in annular form in the cell <NUM>. In this disclosure, an "annular" configuration is meant to encompass shapes that are integral and continuous, such as a tubular cylinder or a shape with an ovular cross-section. An annular configuration excludes wound, spiral configurations with one or more open ends, but includes configurations having ends that are joined, e.g., by a seam, to form a continuous shape. For example, a square or rectangular shape of material may be rolled such that its ends may be bonded or sealed together, and thus provide an annular form.

In accordance with one embodiment, the fuel electrode <NUM> is nested within the oxidant electrode <NUM>. In another embodiment, the oxidant electrode <NUM> is nested within the fuel electrode <NUM>. Throughout this disclosure, the term "nested" refers to an electrode/object being placed or stored one inside the other; e.g., in <FIG>, the fuel electrode <NUM> is arranged in a hierarchical structure from a center C of the cell <NUM> such that it is provided inside the oxidant electrode <NUM>, i.e., the fuel electrode is nested within the oxidant electrode <NUM>. In this exemplary illustrated embodiment, an outer wall of the cell <NUM> is constituted by the oxidant electrode <NUM>. Accordingly, the oxidant electrode <NUM> forms the primary housing structure for the cell <NUM>. In this configuration, the cell <NUM> may function in ambient conditions, with no need for active air control. The oxidant electrode <NUM> and the fuel electrode <NUM> are spaced apart to form a gap or distance D1 therebetween.

In some embodiments, the first electrode or the second electrode of the electrochemical cell <NUM> may be provided by configurations other than a single electrode. In the non-limiting embodiment illustrated in cell <NUM>, for example, in some embodiments, the first or fuel electrode <NUM> for each cell may be provided by smaller, separate, and individual bodies instead of a larger, single electrode (single anode body). In an embodiment, the first or fuel electrode <NUM> may include a series of permeable bodies, e.g., bodies 12A, 12B, 12C. 12n, as shown in the detail of <FIG>. Each of the permeable bodies 12A, 12B, and 12C in the series are configured in annular form. In one embodiment, each of the permeable bodies 12A, 12B, and 12C are nested within the oxidant electrode <NUM>. Each permeable body 12A, 12B, 12C. 12n may be spaced apart relative to an adjacent permeable body. This enables fuel / metal growth on each permeable body and the metal growth may establish connections between the bodies 12A, 12B, 12C, etc. Further, using two or more anode bodies may help manage maintenance of the cell to avoid out of service time, for example. While three permeable bodies are illustrated in <FIG> as being part of the fuel electrode <NUM>, it should be understood to one of ordinary skill in the art that this number is not intended to be limiting. In accordance with embodiments, two or more permeable bodies may be provided in cell <NUM>. In accordance with one embodiment, the permeable bodies 12A. 12n may be current collectors or screens plated with a metal (e.g., zinc) and spaced apart from one another. The fuel electrode <NUM> or anode, and/or its permeable bodies 12A. 12n (if provided) may be a woven screen, a perforated metal sheet, or an expanded metal screen, for example, and may be corrugated or pleated. Thus, the use of a single fuel electrode/anode in the cell is not intended to be limiting.

In other embodiments, the oxidant electrode <NUM> for each cell may be provided by smaller, separate, and individual cathodes (or cathode bodies) instead of a larger, single cathode. That is, similar to the bodies described above with reference to fuel electrode <NUM>, the oxidant electrode <NUM> may include two or more bodies provided in series. Additionally and/or alternatively, in another embodiment, more than one oxidant electrode may be provided in a cell (an example of which is discussed later with reference to <FIG>). Thus, the use of a single oxidant electrode/air cathode in the cell is not intended to be limiting.

In addition to fuel electrode <NUM> and oxidant electrode <NUM>, cell <NUM> may include a charging electrode <NUM>. According to an embodiment, the charging electrode is an oxygen evolution electrode <NUM> (or oxygen evolving electrode), also referred to herein as OEE <NUM>. The OEE <NUM> may also have an annular shape or form geometrically similar to the fuel electrode <NUM> and the oxidant electrode <NUM>. The OEE <NUM> may be nested within the oxidant electrode <NUM>, in accordance with an embodiment. As shown in <FIG>, in one embodiment, the oxygen evolution electrode <NUM> is provided between the fuel electrode <NUM> and the oxidant electrode <NUM>. The fuel electrode <NUM> and OEE <NUM> may be immersed in the ionically conductive medium <NUM>. The OEE <NUM> includes an internal surface <NUM> that faces the fuel electrode <NUM> and an external surface <NUM> that faces the oxidant electrode <NUM>. The OEE <NUM> and the oxidant electrode <NUM> may be spaced apart by a distance D2.

The OEE <NUM> is configured to evolve oxygen for the purpose of creating mixing or circulation of the electrolyte due to convection driven by rising oxygen bubbles in the ionically conductive medium <NUM> / liquid electrolyte between the electrodes. By immersing the OEE <NUM> and positioning it between fuel electrode <NUM> and oxidant electrode <NUM>, oxygen in bubbles that are produced by the oxygen evolving electrode <NUM> rises up in the electrolyte <NUM> and in-between the surfaces <NUM> and <NUM> of the electrodes <NUM> and <NUM> (respectively) in the electrode assembly to circulate the electrolyte and prevent stratification. More specifically, oxygen bubbles are created on the OEE <NUM> by oxidation of hydroxide ions to oxygen gas, countered by the reduction of oxygen gas from air at the air cathode or oxidant reducing electrode <NUM> (which reduced oxygen may form, e.g., hydroxide ions in the electrolyte solution). That is, the electrodes <NUM> and <NUM> are electrically coupled together with an anodic potential at the electrode <NUM> and a cathodic potential at the electrode <NUM>.

Collectively, the fuel electrode <NUM>, OEE <NUM>, and oxidant electrode <NUM> may be referred to as an electrode assembly of the cell <NUM>.

Generally, a controller or circuit is used to control the modes and operation of the cell, as described in greater detail below. In the case of utilizing the oxygen evolving electrode <NUM>, for example, the controller is configured to apply an external voltage (potential) or current source between the oxidant electrode <NUM> and the OEE <NUM> to provide a driving force for oxygen reduction on the oxidant electrode <NUM> and oxygen evolution on the OEE <NUM>.

There are many permutations of OEE and anode electrode assemblies that can function within the annular air cathode "container" for specific cycling purposes. Accordingly, it should be understood by one of ordinary skill in the art that the features and illustrations as described herein are not intended to be limiting. Additional features regarding the electrodes of the cells are further described later.

When a cell <NUM> comprises a fuel electrode <NUM> with multiple permeable bodies (i.e., 12A, 12B. 12n), the oxygen evolution electrode <NUM> may be provided between the oxidant electrode <NUM> and a first permeable body in the series. The first permeable body of the fuel electrode <NUM> is defined as the permeable body that is closest to the oxidant electrode <NUM> in the series when the series of permeable bodies is nested within the oxidant electrode <NUM>. In this illustrative case of <FIG>, the first permeable body of the fuel electrode <NUM> is body 12A, and the OEE <NUM> is provided between permeable body 12A and the oxidant electrode <NUM>.

A top portion (or "top") <NUM> or cover and/or a bottom portion <NUM> (or "bottom") may be provided as part of the cell <NUM>, which are generally depicted in <FIG>. In accordance with an embodiment, the top <NUM> and/or bottom <NUM> may be provided in the form of a retainer or a cap. In one embodiment, the top <NUM> and/or bottom <NUM> may include a plastic or molded cap that is placed on either ends of the annular electrode assembly. In addition to holding the electrodes in place, the top <NUM> and/or bottom <NUM> of the cell <NUM> may be used to provide an electrical connection from the cell assembly to a power supply PS, a load L, or other cell assemblies, using electrical leads or terminals. In an embodiment, the top <NUM> and/or bottom <NUM> may include electrode terminals for connecting each first / fuel electrode <NUM>, OEE <NUM>, and each second / oxidant electrode <NUM>. The cell terminals may be referred to in conventional nomenclature as the negative and positive terminals, denoting their usage during standard discharging. However, it should be understood that the polarity may be reversed when current is applied thereto for charging operations, and thus reference to the negative and positive terminals is not intended to be limiting for all operational modes. In an embodiment, a negative terminal may be provided at one end of the cell and a positive terminal may be provided at an opposite end of the cell. In one embodiment, the bottom <NUM> of a cell <NUM> may be used to electrically connect the oxidant electrode <NUM> and the top <NUM> of the cell <NUM> may be used to electrically connect the fuel electrode <NUM> or anode and OEE <NUM>, or vice versa. In another embodiment, the anode <NUM> and cathode <NUM> may be connected to the top <NUM>. In an embodiment, one or more bus bars may be contained in the top <NUM> and/or bottom <NUM> to connect all the electrodes (<NUM>, <NUM>, <NUM>) together for collection or application of current from their respective terminals. For example, the fuel electrodes <NUM> (and optionally OEEs <NUM>) may be attached to a first bus bar and the oxidant electrodes <NUM> may be attached to a separate, second bus bar. The bus bar for the fuel electrodes <NUM> may be connected directly or indirectly to a negative terminal and the bus bar for the oxidant electrodes <NUM> may be connected directly or indirectly to a positive terminal.

The above noted embodiments and exemplary features are not intended to be limiting with regards to the top <NUM>, bottom <NUM>, and features of the cell <NUM>. In an embodiment, the top <NUM> and bottom <NUM> may be plastic caps which may be attached to the electrode assembly(ies), e.g., with potting epoxy. Plastic injection overmolding could also be used for any of the electrodes. In another embodiment, the anode <NUM> and OEE <NUM> could also be captured in a metal housing utilizing a rubber or thermoplastic insulator to prevent electrolyte transmission to the respective terminals.

<FIG> is a schematic overhead view of an electrochemical metal-air cell 10A in accordance with another embodiment; <FIG> shows a perspective view of this cell 10A. Cell 10A includes several features as previously described with respect to cell <NUM>. For purposes of clarity and brevity, like elements and components throughout all of the Figures are labeled with same designations and numbering as discussed with reference to <FIG>, for example. Thus, although not discussed entirely in detail herein, one of ordinary skill in the art should understand that various features associated with the cells and systems described throughout the Figures are similar to those features previously discussed. Additionally, it should be understood that the features shown in each of the individual figures is not meant to be limited solely to the illustrated embodiments. That is, the features described throughout this disclosure may be interchanged and/or used with other embodiments than those they are shown and/or described with reference to.

Cell 10A of <FIG> includes at least first and second electrodes, i.e., an oxidant electrode <NUM> and a fuel electrode <NUM>, both of annular configuration. The fuel electrode <NUM> is nested within the oxidant electrode <NUM>, much like the configuration of <FIG>. Also, ionically conductive medium <NUM> is contained by the oxidant electrode <NUM>, for conducting ions for supporting electrochemical reactions at the fuel electrode(s) <NUM> and the oxidant electrode <NUM>. Further, in an embodiment, cell 10A may include an oxygen evolution electrode <NUM>. The oxygen evolution electrode <NUM> may have an annular shape or form geometrically similar to the fuel electrode <NUM> and the oxidant electrode <NUM>. The OEE <NUM> may be nested within the oxidant electrode <NUM>, in accordance with an embodiment. The fuel electrode <NUM> and OEE <NUM> may be immersed in the ionically conductive medium <NUM>. As shown in <FIG>, in one embodiment, the oxygen evolution electrode <NUM> is provided between the fuel electrode <NUM> and the oxidant electrode <NUM>. The oxidant electrode <NUM> and the fuel electrode <NUM> may be spaced apart to form a gap or distance (D1) therebetween. The OEE <NUM> and the oxidant electrode <NUM> may be spaced apart by a distance (D2).

Optionally, the fuel electrode <NUM> of cell 10A may include multiple permeable bodies (i.e., 12A, 12B. 12n), in accordance with an embodiment.

In addition, cell 10A of <FIG>, <FIG> further includes a cell housing <NUM> configured to contain the oxidant electrode <NUM>, the fuel electrode <NUM>, and the ionically conductive medium <NUM> therein. In an embodiment, the cell housing <NUM> is an external container that is provided around the assembly of electrodes. The cell housing <NUM> may have any construction or configuration, and the illustrated housing <NUM> is not intended to be limiting. In an embodiment, the housing <NUM> has an annular or cylindrical configuration with an outer circumferential side wall, a top portion (not shown) and a bottom portion (not shown) to house the electrodes <NUM>, <NUM>, <NUM> therein. The side wall of the housing <NUM> has an internal diameter that is larger than an external diameter of the oxidant electrode <NUM>, so that the inner wall side of the external container / cell housing <NUM> is spaced apart from external surface <NUM> of the oxidant electrode <NUM> by a gap, a space, or distance D3 therebetween. This distance D3 or gap provides an air space <NUM> between the oxidant electrode <NUM> and external container <NUM>. The housing <NUM> may have an air flow receiving opening or channel at its top portion, bottom portion, or both, to allow air flow (ambient air) into the air space <NUM>.

Further, the top portion and/or bottom portion of housing <NUM> of cell 10A may be similar to top <NUM> and/or bottom <NUM> as described above with respect to <FIG>, and configured to provide an electrical connection from the cell assembly to a power supply PS, a load L, or other cell assemblies, using electrical leads or terminals. Optionally, the top <NUM> and/or bottom <NUM> in cell 10A may include the air flow receiving opening or channel for inputting and/or outputting air with respect to air space <NUM>.

<FIG> is a schematic overhead view of an electrochemical metal-air cell 10B in accordance with yet another embodiment of this disclosure. Cell 10B includes several features as previously described with respect to cell <NUM>. For purposes of clarity and brevity, like elements and components throughout all of the Figures are labeled with same designations and numbering as discussed with reference to <FIG>, for example. Thus, although not discussed entirely in detail herein, one of ordinary skill in the art should understand that various features associated with the cells and systems described throughout the Figures are similar to those features previously discussed.

Cell 10B of <FIG> includes at least first and second electrodes, i.e., an oxidant electrode <NUM> and a fuel electrode <NUM>, both of annular configuration. The fuel electrode <NUM> is nested within the oxidant electrode <NUM>, much like the configuration of <FIG>. Further, in an embodiment, cell 10A may include an oxygen evolution electrode <NUM>. The oxygen evolution electrode <NUM> may have an annular shape or form geometrically similar to the fuel electrode <NUM> and the oxidant electrode <NUM>. The OEE <NUM> may be nested within the oxidant electrode <NUM>, in accordance with an embodiment. As shown in <FIG>, in one embodiment, the oxygen evolution electrode <NUM> is provided between the fuel electrode <NUM> and the oxidant electrode <NUM>. The oxidant electrode <NUM> and the fuel electrode <NUM> may be spaced apart to form a gap or distance (D1) therebetween. The OEE <NUM> and the oxidant electrode <NUM> may be spaced apart by a distance (D2).

Optionally, the fuel electrode <NUM> of cell 10A may include multiple permeable bodies (i.e., 12A, 12B. 12n), in accordance with an embodiment. For example, <FIG> shows first and second anode / permeable bodies 12A and 12B provided as part of fuel electrode <NUM>, in accordance with one embodiment. These bodies 12A and 12B may be screens or sheets, for example, provided in an essentially cylindrical configuration. As noted previously, using two or more anode bodies may help manage maintenance of the cell to avoid out of service time, for example.

Cell 10B of <FIG> further includes an additional oxidant electrode <NUM>. More specifically, in the configuration of <FIG>, the oxidant electrode <NUM> is a first oxidant electrode, and a second oxidant electrode <NUM> is nested within the electrode assembly. The second oxidant electrode <NUM> may be provided as an "inner" electrode of the electrode assembly, such that it is arranged in hierarchical structure to be closer to a center C of the cell <NUM> relative to the other electrodes <NUM>, <NUM>, and <NUM>. The first oxidant electrode <NUM> acts as an "outer electrode" with respect to the inner, second oxidant electrode <NUM>, resulting in the donut-like configuration shown in <FIG>, when viewed from the top of the cell, for example. The second oxidant electrode <NUM> may be configured in annular form and nested within the fuel electrode <NUM>.

In an embodiment, the second oxidant electrode <NUM> forms an inner air space <NUM> of diameter D5 to contain and/or receive air therein. While the size of diameter D5 is not intended to be limiting, in one exemplary embodiment, D5 may be at least approximately fifty millimeters (<NUM>) smaller in diameter in relation to an inner diameter of the outer air cathode / oxidant electrode <NUM>. In an embodiment, the minimum diameter D5 of second oxidant electrode <NUM> is approximately seventy-five millimeters (<NUM>).

More specifically, the second oxidant electrode <NUM> includes an internal surface <NUM> that faces a center C of the cell 10B and is exposed to air within the air space <NUM>, as well as an external surface <NUM> that faces the ionically conductive medium <NUM> and fuel electrode <NUM>. The internal surface <NUM> may be configured to receive and/or contain air (e.g., atmospheric air) therein such that second oxidant electrode <NUM> functions as an air cathode for absorbing and reducing gaseous oxidant (e.g., oxygen in air).

In accordance with an embodiment, the second oxidant electrode <NUM> and the fuel electrode <NUM> are spaced apart to form a gap or distance D4 therebetween. Liquid ionically conductive medium <NUM> is contained between the first oxidant electrode <NUM> and the second oxidant electrode <NUM>, for conducting ions for supporting electrochemical reactions at the fuel electrode(s) <NUM> and the oxidant electrode <NUM> of the electrode assembly provided therebetween. The fuel electrode <NUM> and OEE <NUM> may be immersed in the ionically conductive medium <NUM>.

This second oxidant electrode <NUM> as added to the cell 10B further increases the air cathode surface area, while reducing the volume of ionically conductive medium <NUM> therein. This significantly increases the C-rate (i.e., the battery's current handling capability, or the constant current charge rate or discharge rate at which the battery / cell sustains for a particular period of time) of the cell 10B.

Although not shown, it is envisioned that, in some embodiments, cell 10B may include an external container, like housing <NUM> of <FIG>, around the assembly of electrodes (e.g., surrounding first oxidant electrode <NUM>).

Further, the top portion and/or bottom portion of cell 10B may be similar to top <NUM> and/or bottom <NUM> as described above with respect to <FIG>, and configured to provide an electrical connection from the cell assembly to a power supply PS, a load L, or other cell assemblies, using electrical leads or terminals. Optionally, the top <NUM> and/or bottom <NUM> in cell 10B may include the air flow receiving opening or channel for inputting and/or outputting air with respect to air space <NUM>.

Among other things, the cells <NUM>, 10A, and 10B as described with reference to <FIG> provide an oxidant electrode <NUM> as part of a nested set of electrodes, thereby making the air electrode <NUM> the largest electrode in the cell, which improves current density. Further, providing the electrodes (e.g., <NUM>, <NUM>, <NUM>) in annular form avoids issues with edge effects at corners that are typical of rectangular or planar electrodes.

The measurements and/or dimensions associated with the electrodes and cells is not meant to be limited in any way. In accordance with an embodiment, cells may be sized within a range of approximately <NUM> (Liters) to approximately <NUM> (both inclusive). In another embodiment, the size of the cells may be within a range of approximately <NUM> (Liters) to approximately <NUM> (both inclusive). As examples only, some cell dimension targets for <NUM> and <NUM> cells are summarized in the following table:.

Again, the above dimensions are illustrative only and not intended to be limiting in any way.

Similarly, the spacing (distances D1, D2, etc.) between parts and electrodes of the illustrative cells in <FIG>, <FIG>, and <FIG> are not limited. Merely as an example, the chart below provided exemplary distances for D1, D2, D3, D4, and D5 as shown in <FIG>, for a cell <NUM> of <NUM>:.

These dimensions are illustrative only and not intended to be limiting in any way.

<FIG> is a schematic overhead view of a system 100A containing multiple electrochemical metal-air cells (e.g., cells <NUM>) therein, in accordance with an embodiment of this disclosure. The system 100A includes a container <NUM> or housing for holding and containing multiple (i.e.,. more than two) electrochemical cells. The container <NUM> includes a cell chamber <NUM> and may be designed to be a sealed container (e.g., via a lid or cover and any optional seals, which are described later). A liquid ionically conductive medium <NUM> for conducting ions for supporting electrochemical reactions at the fuel electrode <NUM> and the oxidant electrode <NUM> of the cells therein is also part of system 100A; in particular, in this illustrative embodiment, the ionically conductive medium <NUM> is contained within each of the cells <NUM> (e.g., by oxidant electrode <NUM>). As described below, container <NUM> may help regulate the atmosphere and air flow to the cells <NUM>, and may include safety features.

A multi-cell container like container <NUM> (which may be sealed, as described below) can be tailored to deliver a range of power and voltage options. Examples of safety features for the system 100A and/or container <NUM> may include fire resistant plastics (v0), electronics logic on the cell controller to bypass and cells that are underperforming. This type of container design further allows a lot of flexibility in targeting many different power/voltage/energy combinations, depending on how the cells are sized and connected (series vs parallel). In certain cases, the battery system may be tailored to output a target range of power/voltage according to a customer request.

Referring back to <FIG>, for illustrative purposes, multiple cells <NUM> like those of <FIG> are shown in the cell chamber <NUM> of container <NUM> of system 100A. Alternatively, it should be understood that system 100A may include cells 10A or 10B in its container <NUM>. Although a total of four electrochemical cells are illustrated in this embodiment, more or less electrochemical cells may be included in the system. Indeed, in certain applications, a large two-dimensional array of parallel electrochemical cells can be created to provide for increased power output. In other embodiments, the cells may be in series. In some embodiments, the cells may be staggered. The illustrated embodiment is not intended to be limiting in any way and is merely an example.

As discussed previously, each cell <NUM> in system 100A includes an oxidant electrode <NUM> for absorbing gaseous oxidant and has one or more active materials for reducing the gaseous oxidant, a fuel electrode <NUM> for oxidizing a metal fuel, an OEE <NUM> nested therebetween the fuel electrode <NUM> and oxidant electrode <NUM> for charging the cell <NUM>. Further, the cells <NUM> of system 100A have a liquid ionically conductive medium <NUM> for conducting ions for supporting electrochemical reactions at the fuel electrode <NUM> and the oxidant electrode <NUM>. In this illustrated embodiment, the cells <NUM> have the liquid ionically conductive medium <NUM> contained by the oxidant electrode <NUM>. As shown in <FIG>, for example, each oxidant electrode <NUM> has its interior surface <NUM> facing and contacting the electrolyte or ionically conductive medium <NUM> within the cell <NUM>, and its exterior surface <NUM> facing and exposed to oxygen or air in cell chamber <NUM>. In other embodiments (such as shown in <FIG>), the ionically conductive medium <NUM> may be contained by the cell chamber <NUM> of container <NUM>. Again, the oxidant electrode <NUM>, OEE <NUM>, and the fuel electrode <NUM> of the cells <NUM> are configured in annular form. Further, each of the cells <NUM> have the fuel electrode <NUM> and OEE <NUM> nested within the oxidant electrode <NUM>. The container <NUM> contains all of the electrochemical cells <NUM> therein and supports the components of the electrochemical cell system 100A.

In accordance with an embodiment, the container <NUM> is a sealed container. That is, container <NUM> may include a lid <NUM> (see <FIG>), cover portion, or other device that connects to walls of a lower body of container <NUM>, to removably, releasably, and sealingly engage the container <NUM> to enclose the cells <NUM> therein. The configuration of the container <NUM> and lid <NUM> is not intended to be limiting or limited to the exemplary depiction as shown in the drawings, including that of <FIG>, and/or the number of cells <NUM> that may be contained in a container <NUM> and/or system 100A. Rather, the body of container <NUM> is designed to include at least one side wall and a bottom, like bottom <NUM> shown in <FIG>. Of course, reference to surface <NUM> being a "bottom" is not intended to be limiting; rather, it should be understood that the system 100A may be oriented in any way. Thus, any directional references are made with regard to the orientation as shown in the drawings, and are not intended to limit a working embodiment to any particular orientation. In an embodiment, the body of the container <NUM> may be annular, circular, rectangular, polygonal, cylindrical or other shapes configured to include an internal cell chamber <NUM> for receipt of multiple cells <NUM> therein. One or more seals or gaskets may be optionally provided between the lid and body of container <NUM> to further seal the cell chamber <NUM>. Optionally, the lid may also include one or more features, e.g., gaskets, designed to connect with and/or seal with the cells <NUM> such that any gases or fluids, such as an electrolyte or liquid ionically conductive medium <NUM> within cells <NUM>, are prevented from leaking out of the system 100A and/or into air space <NUM>.

In one embodiment, the cell chamber <NUM> of sealed container <NUM> contains air and forms an air space <NUM> therein to surround the cells <NUM>. The container <NUM> may have an air flow receiving opening or channel in one or more of its walls, including its lid, to allow flow of air (ambient air) into the air space <NUM> of cell chamber <NUM>. For example, the lid may include one or more openings therein to act as an oxidizer input for the electrochemical cells <NUM> contained therein.

The system 100A of <FIG> may further include an air flow generator <NUM> that is associated with the sealed container <NUM>, in accordance with an embodiment. The air flow generator <NUM> may be configured to force atmospheric air (from outside of the container <NUM>) into air space <NUM> of the sealed container <NUM>, to deliver atmospheric air into the sealed container such that said air is delivered to external surfaces of the oxidant electrodes <NUM> of each of the electrochemical cells <NUM> contained therein.

The positioning of the air flow generator <NUM> relative to the container <NUM> is not intended to be limiting, so as long as the air is at least periodically turned over in the air space <NUM>. In an embodiment, the generator <NUM> may be provided in a lid of sealed container <NUM>. In an embodiment, the air flow generator <NUM> is configured to force air flow into the nested assembly of the cells <NUM> (e.g., between surfaces of the fuel and oxidant electrodes <NUM>, <NUM>). The use of an air flow generator <NUM> facilitates delivery of air to the external surface of the oxidant electrode <NUM>. The air flow generator <NUM> may be a compressor, an electrically powered fan or impeller, a bellows, or any other device designed to generate airflow. For example, instead of generating positive pressure, a vacuum could generate negative pressure to force air flow through container <NUM> as well. The direction of air flow through the container <NUM> is also not intended to be limiting. In some embodiments, the direction of air flow may be axially through the cells <NUM>. In another embodiment, the air flow may flow longitudinally or horizontally through the container <NUM>.

The positioning of the cells <NUM> within the container <NUM> is also not intended to be limiting. According to one embodiment, the cells <NUM> may be spaced within the sealed container <NUM> such that centers of the cells <NUM> are substantially equidistantly spaced relative to one another therein. In an embodiment, spacing is provided between the cells <NUM>, and thus the oxidant electrodes <NUM>, to permit open air flow directly to the oxidant electrode external surface <NUM>. In another embodiment, the external surface <NUM> of each oxidant electrode is exposed to oxygen / oxidant by permitting permeation of the air through a porous portion of the oxidant electrode <NUM>.

In an embodiment, each of cells <NUM> in system 100A may have a fuel electrode <NUM> that may include a series of permeable bodies, such as previously described with reference to <FIG>. The series of permeable bodies in the cells <NUM> of system 100A may be configured in annular form, and each spaced apart relative to an adjacent permeable body. Additionally, in one embodiment, an oxygen evolution electrode <NUM> may be provided in the cells <NUM> of system 100A, such that the OEE <NUM> is between the oxidant electrode <NUM> and a first permeable body (e.g., 12A) in the series of bodies, as explained above.

<FIG> show another system 100B containing multiple electrochemical metal-air cells in accordance with another embodiment of this disclosure. Like system 100A, the system 100B includes a container <NUM> or housing that has a cell chamber <NUM> for holding and containing and multiple (i.e.,. more than two) electrochemical cells in the chamber <NUM>. The container <NUM> may be a sealed container (e.g., via a lid or cover and any optional seals). The container <NUM> contains all of the electrochemical cells therein and supports the components of the electrochemical cell system 100A. Again, the configuration of the container <NUM> is not intended to be limiting or limited to the exemplary depiction as shown in the drawings. The body of the container <NUM> may be annular, circular, rectangular, polygonal, or other shapes configured to receive multiple cells <NUM> therein. One or more seals or gaskets may be optionally provided between the lid and body of container <NUM> to further seal the cell chamber <NUM>. Optionally, the lid may also include one or more features, e.g., gaskets, designed to connect with and/or seal with the cells <NUM> such that any gases or fluids, including air in air spaces <NUM> of the cells 10C, are prevented from leaking out of the system 100A and/or into cell chamber <NUM>.

A liquid ionically conductive medium <NUM> for conducting ions for supporting electrochemical reactions at the fuel electrode <NUM> and the oxidant electrode <NUM> of the cells therein is also part of system 100A. In this system 100B, electrochemical cells 10C are provided and contained with a volume of ionically conductive medium <NUM> / electrolyte within the cell chamber <NUM> of container <NUM>. That is, in this illustrative embodiment, the ionically conductive medium <NUM> is contained within the cell chamber <NUM>, such that cells 10C are at least partially immersed in the ionically conductive medium <NUM>. In accordance with an embodiment, the container <NUM> is a sealed container. That is, container <NUM> may include a lid (like lid <NUM> shown <FIG>), cover portion, or other device that connects to walls of a lower body of container <NUM>, to removably, releasably, and sealingly engage the container <NUM> to enclose the cells <NUM> therein. In one embodiment, the sealed container <NUM> contains a pool or a volume <NUM> of liquid ionically conductive medium <NUM> in an internal space of cell chamber <NUM>, which surrounds and contacts the cells <NUM>. The liquid ionically conductive medium <NUM> conducts ions for supporting electrochemical reactions at the fuel electrode <NUM> and the oxidant electrode <NUM> of each cell. A level L (see <FIG>) of ionically conductive medium <NUM> in the cell chamber <NUM> may be adjusted based on the position of the cells 10C. For example, in some instances, the level L of ionically conductive medium is provided such that it is lower than the oxidant electrodes <NUM> of each cell 10C (that is, a portion of the air cathodes <NUM> of each cell 10C extends above the level L (out of) the ionically conductive medium), such as shown in <FIG>. In other cases, the level L of ionically conductive medium may be at a similar height as the cells 10C. In an embodiment, the cells 10C and the entire electrode assembly may be immersed in the chamber <NUM> and the electrolyte <NUM> is provided at a level L within the cell chamber <NUM> such that is above the tops of the electrodes <NUM>, <NUM>, and <NUM>.

Much like cells <NUM>, which were discussed previously, each cell 10C in system 100B includes an oxidant electrode <NUM> for absorbing gaseous oxidant that has one or more active materials for reducing the gaseous oxidant, a fuel electrode <NUM> for oxidizing a metal fuel, and an OEE <NUM> for charging the cell <NUM>. Again, the oxidant electrode <NUM>, OEE <NUM>, and the fuel electrode <NUM> are configured in annular form. However, in this case, the oxidant electrode <NUM> is arranged in a hierarchical structure from a center of the cell <NUM> such that it is provided inside the fuel electrode, i.e., the oxidant electrode <NUM> is nested within the fuel electrode <NUM> in each of electrochemical cells 10C. That is, the cells 10C include outward facing fuel electrodes <NUM> (outward facing relative to chamber <NUM> and/or inner walls of the container <NUM>). The fuel electrode <NUM> of each cell 10C has an internal surface 13A that faces the oxidant electrode <NUM> and an external surface 15A that faces the volume <NUM> of ionically conductive medium <NUM> as contained in cell chamber <NUM>. The OEE <NUM> of each cell 10C includes an internal surface 21A that faces the oxidant electrode <NUM> and an external surface 23A that faces the fuel electrode <NUM>. The fuel electrode <NUM> and OEE <NUM> may thus be immersed in the ionically conductive medium <NUM>. The OEE <NUM> and the oxidant electrode <NUM> may be spaced apart by a distance (D2). The fuel electrode <NUM> and the oxidant electrode <NUM> may be spaced apart by a distance (D1).

Further, in an embodiment, each oxidant electrode <NUM> forms an inner air space 28A, like air space <NUM>, to contain and/or receive air therein. The oxidant electrode <NUM> includes an internal surface 17A, or air side or face, that is facing and exposed to oxidant (oxygen or air) and an external surface 19A, or cell side or face, facing and contacting electrolyte or ionically conductive medium <NUM>. As similarly described above, exposure of the internal surface 17A to the air in air space 28A allows oxidant electrode <NUM> to function as an air cathode for absorbing and reducing gaseous oxidant (e.g., oxygen in air).

Furthermore, in one embodiment, each oxidant electrode <NUM> may be provided as a most internal layer of in the assembly of electrodes within each cell 10C.

Although a total of four electrochemical cells are illustrated in this embodiment of <FIG>, more or less electrochemical cells may be included in the system. Indeed, in certain applications, a large two-dimensional array of parallel electrochemical cells can be created to provide for increased power output. In other embodiments, the cells may be in series. In some embodiments, the cells may be staggered. The illustrated embodiment is not intended to be limiting in any way and is merely an example.

According to one embodiment, such as shown in <FIG>, the cells 10C themselves, and/or at least the oxidant electrodes <NUM> of the cells 10C, are at least partially suspended within the sealed container <NUM>, such that the oxidant electrodes <NUM> are configured to float within the ionically conductive medium <NUM>. In this case, float refers to positioning each of the cells 10C within the cell chamber <NUM> such that the electrode assembly of each cell 10C does not directly contact an inner surface of the bottom <NUM> of the container <NUM>. In some embodiments, a bottom <NUM> of each cell 10C does not directly contact an inner surface of the bottom <NUM> of the container <NUM>. Any number of structures may be utilized to position the cells 10C such that they float in the medium <NUM>. For example, in one embodiment, support tabs may extend from an exterior surface of the bottom <NUM> of each cell 10C, for placement against the inner surface of bottom <NUM>, in order to space the cells 10C therefrom and allow them to float within the ionically conductive medium <NUM>. In another embodiment, the lid (not shown) of the container <NUM> may include one or more structures that connect with the cells 10C in order to suspend them within the container <NUM>. In accordance with an embodiment, the electrode assembly <NUM> is configured to hang from a top (lid) of the sealed container <NUM> via external contacts provided by terminals. In yet another embodiment, a bracket, a barrier, a wall, or other structure may be provided in the container <NUM> for connecting with the cells 10C to removably secure them in place within the container <NUM>.

Because the container <NUM> in the system 100B of <FIG> holds (liquid) ionically conductive medium <NUM> within its walls, the collection of cells 10C in <FIG> as placed into the medium <NUM> will naturally want to float. That is, the cells 10C are naturally buoyant to the point of forcing the cells to possibly protrude more than may be desired above the electrolyte liquid level L. In an embodiment, a lid (such as lid <NUM>) may be used on/with the container <NUM> to set the proper or desired height of cells 10C in relation to the electrolyte level L. In one embodiment, the lid may contain nesting features to capture the lid/tops <NUM> of each cell; e.g., the lid may be include protrusions, divots, correspondingly shaped receiving openings, and/or other mechanical structures, for capturing and/or receiving the tops of the cells. These lid features could also incorporate a simple valve which may limit air access during idle periods, in some embodiments. The container may also be designed with a floating head lid, in yet another embodiment, which may allow the collection of cells 10C to float as a group up and down with the electrolyte level, e.g., as it may change over time due to evaporative losses.

In another embodiment, the bottom <NUM> of each of the cells 10C may be placed directly on a surface of the bottom <NUM> of the body of the container <NUM>. The level of ionically conductive medium <NUM> in the cell chamber <NUM> may be provided such that a portion of the air cathodes <NUM> of each cell 10C extends above the level and out of the ionically conductive medium.

As previously noted, air or oxidant in the inner air space 28A of each cell 10C is accessed from the inner exposed surface 13A of the oxidant electrodes <NUM>. Air may be provided to air space 28A in a number of ways. In one embodiment, the lid (not shown) may include an manifold assembly, in which air flows into the manifold assembly and then into the air spaces 28A of the cells 10C. In another embodiment, a head space may be provided above the fells 10C in the container <NUM>, wherein the head space is a shared air space above the cells 10C and the level of ionically conductive medium <NUM> contained therein. The container <NUM> and/or manifold assembly may include one or more inlets and outlets therein to circulate air into the air spaces 28A of the cells.

As previously described with respect to system 100A of <FIG>, in an embodiment, system 100B may include an air flow generator <NUM> that is associated with the sealed container <NUM> to force atmospheric air (from outside of the container <NUM>) into air spaces 28A of the cell 10C, to deliver air to internal surfaces 17A of the oxidant electrodes <NUM> of each of the electrochemical cells 10C contained therein. In an embodiment, the generator <NUM> may be a fan provided in the lid, for example.

In an embodiment, each of cells 10C may include a fuel electrode <NUM> that may have a series of permeable bodies, such as previously described with reference to <FIG>. The series of permeable bodies in the cells 10C of system 100B may be configured in annular form, and each spaced apart relative to an adjacent permeable body. Additionally, in one embodiment, an oxygen evolution electrode <NUM> may be provided in the cells 10C of system 100A, such that the OEE <NUM> is between the oxidant electrode <NUM> and a first permeable body (e.g., 12A) in the series of bodies, as explained above.

As shown, the systems 100A and 100B may be designed to include individual cell sub-assemblies, which allows for individual cells that could be easily changed (switched out with another cell) and thus is configured to facilitate a long duration installed system via intermittent maintenance.

In an embodiment, the container <NUM> of system 100A and/or 100B may be configured to provide an electrical connection from the cells contained therein to a power supply PS, a load L, or other cell assemblies, using electrical leads or terminals. In an embodiment, the fuel electrodes <NUM> (and optionally OEEs <NUM>) may be attached to a first bus bar and the oxidant electrodes <NUM> may be attached to a separate, second bus bar. A bus bar connects all the electrodes (<NUM>, <NUM>, <NUM>) together for collection or application of current from their respective terminals. The bus bar for the fuel electrodes <NUM> may be connected directly or indirectly to a negative terminal and the bus bar for the oxidant electrodes <NUM> may be connected directly or indirectly to a positive terminal. The bus bars may be contained in a cover or top part of the container <NUM>, for example. The use of bus bars is optional, and the electrodes can be connected by other connections, either collectively together or they can each be connected individually by switches or the like.

As previously noted, there are different types of permutations of OEE and anode electrode assemblies that may function within the annular air cathode "container" for specific cycling purposes. The following description relates to different features of the electrodes provided within a cell, that may apply to cells <NUM>, 10A, and/or 10B, as well as cells within systems 100A and/or 100B.

Fuel electrode <NUM> - Several features of fuel electrode <NUM> (or electrodes 12A, 12B,. 12n) have been previously described. As noted, fuel electrode <NUM> is of generally annular configuration. Fuel electrode <NUM> may have one or more electroconductive screens, meshes, or bodies on which the metal fuel may be deposited or otherwise collected. In some embodiments, the fuel electrode <NUM> may include a porous structure with a three-dimensional network of pores, a mesh screen, a plurality of mesh screens (permeable bodies) isolated from one another, or any other suitable electrode. The fuel electrode <NUM> may include a current collector, which may be a separate element, or the body on which the fuel is received may be electroconductive and thus also be the current collector. In embodiments, the fuel electrode <NUM> is laminated, bonded, or attached to a backing that provides the external surface <NUM> of the fuel electrode <NUM>. In some embodiments, this backing may be liquid impermeable or essentially impermeable to the ionic liquid <NUM> to prevent it from permeating outwardly through the fuel electrode <NUM> via its external surface <NUM>. More preferably, the backing is also impermeable to air, and particularly oxygen or other oxidant, to prevent any undesirable parasitic reaction, such as oxidant reduction in the presence of the fuel oxidation that occurs at the electrode during discharge.

The metal fuel may be of any type, and may be electrodeposited, absorbed, physically deposited, or otherwise provided on or constituting the fuel electrode <NUM>. The fuel may be of any metal, including alloys or hydrides thereof. For example, the fuel may comprise one or more of zinc, iron, aluminum, magnesium, gallium, manganese, vanadium, lithium or any other metal. As used herein, the term metal fuel refers broadly to any fuel comprising a metal, including elemental metal, metal bonded in a molecule, metal alloys, metal hydrides, etc..

The oxidant electrode <NUM> generally includes a porous body covered on the outer side by a gas permeable layer through which an oxidizer may diffuse, but the electrolyte may not pass through. That is, the layer is gas permeable, but not permeable by the electrolyte (i.e., it is gas permeable but not liquid permeable). As an option, the porous body may also be covered on the inner side by a liquid permeable layer through which the electrolyte may pass through so that the electrolyte may contact the porous body. The porous body of the oxidant electrode <NUM> has a high surface area and comprises a catalyst material that has a high activity for an oxidizer reduction reaction.

The oxidant electrode <NUM> may be a passive or "breathing" cathode that is passively exposed to an oxidizer source (typically oxygen present in ambient air) and absorbs the oxidizer for consumption in the electrochemical cell reactions. That is, the oxidizer, typically oxygen, will permeate from the ambient air into the oxidant electrode <NUM>. Thus, the oxidizer need not be actively pumped or otherwise directed to the cathode, such as via an inlet. Any part of the oxidant electrode <NUM> by which the oxidizer is absorbed or otherwise permeates or contacts the oxidant electrode <NUM> may be generically referred to as an "input. " The term input may broadly encompass all ways of delivering oxidizer to the cathode (and that term may similarly be used with reference to any way of delivering fuel to the anode).

The oxidant electrode <NUM> may be configured to absorb air or other gaseous oxidants exposed to its external surface <NUM> or another constituent portion thereof in a manner described below. While in some embodiments the oxidant electrode <NUM> is configured to receive ambient air, contained sources of oxidants may additionally or alternatively be utilized. Thus, where used herein, air refers to any gaseous oxidant source. When air is exposed to the external surface <NUM>, the oxidant electrode <NUM> is configured to absorb gaseous oxygen (or another oxidant) for reduction of the oxygen during discharge of the cell <NUM>. Some portions of the oxidant electrode <NUM> may be made porous to provide gaseous oxygen diffusion from the air side of the oxidant electrode <NUM> to reaction sites within the oxidant electrode <NUM> and to provide ionic conductivity for reactants and reaction products on the side of the oxidant electrode <NUM> facing the ionic liquid <NUM>. It may be appreciated that a number of configurations of the oxidant electrode <NUM> are possible.

The oxidant electrode <NUM> includes a catalyst material, such as manganese oxide, nickel, pyrolyzed cobalt, activated carbon, platinum, or any other catalyst material or mixture of materials with high oxygen reduction activity in the electrolyte for catalyzing reduction of the oxidizer. The porous body of the oxidant electrode <NUM> may comprise the catalyst material.

In various embodiments, any number of ionically conductive mediums may be utilized herein in the electrochemical cell <NUM>. In some embodiments wherein the ionically conductive medium <NUM> comprises an ionic liquid, the ionic liquid may be of any type, including room temperature ionic liquids, and including but not limited to the examples disclosed in <CIT>.

In some embodiments, the ionically conductive medium <NUM> may be an aqueous electrolyte, such as potassium hydroxide dissolved in water. Any such aqueous electrolyte may be used. For example, in an embodiment, the ionically conductive medium may include sodium hydroxide. The electrolytic solution <NUM> in any of the herein described systems or cells may be any of: potassium hydroxide, sodium hydroxide, zinc chloride, ammonium chloride, magnesium perchlorate, and magnesium bromide.

Spacers, such as non-conductive spacers, may be provided between the first and second electrodes <NUM> and <NUM>, the first and OEE electrodes <NUM> and <NUM>, and/or the second and OEE electrodes <NUM> and <NUM> (e.g., to provide and maintain the distance D1 and/or D2).

In accordance with an embodiment, a flow pump for pumping the ionically conductive medium <NUM> into and/or through the container <NUM> may be associated with the system (e.g., system 100A, 100B).

While the principles of the disclosure have been made clear in the illustrative embodiments set forth above, it will be apparent to those skilled in the art that various modifications may be made to the structure, arrangement, proportion, elements, materials, and components used in the practice of the disclosure.

The principles of the present invention may be broadly applied to any electrochemical cell and system where a fuel, such as a metal fuel, is electrodeposited on the anode. Such cells may include batteries, such as metal--air batteries, for example. The Figures illustrate embodiments of various aspects of the inventions claimed. These embodiments are in no way intended to be limiting, and are intended only as examples for facilitating an understanding of the principles of the claimed inventions.

Claim 1:
An electrochemical cell comprising:
a first oxidant electrode for absorbing gaseous oxidant and comprising one or more active materials for reducing the gaseous oxidant;
a fuel electrode for receiving a metal fuel; and
a liquid ionically conductive medium, that is contained by the first oxidant electrode, for conducting ions for supporting electrochemical reactions at the fuel electrode and the first oxidant electrode, wherein the first oxidant electrode and the fuel electrode are each configured in annular form, and wherein the fuel electrode and the oxidant electrode are nested;
characterized in that the cell further comprises a second oxidant electrode, the second oxidant electrode being in annular form and nested within the fuel electrode, and wherein the liquid ionically conductive medium is contained between the first oxidant electrode and the second oxidant electrode.