JP7191039B2 - metal air fuel cell - Google Patents

Description

The present invention relates to metal-air fuel cells and their uses, including use as long-life, mechanically rechargeable DC power sources for devices and products.

Any reference in this specification to any prior publication or to information derived therefrom or to any matter known to the public is part of the common general knowledge in the subject matter to which this specification pertains. It is not and should not be construed as an affirmation or admission or any form of suggestion that the information derived or known matters forms.

Many products, especially home and portable devices, are designed to be powered by batteries such as AA, C and D batteries. Disadvantages when using such traditional batteries are the relatively short operating life and limited shelf life, i.e. the internal (closed system) configuration over time even when not in use. Includes expiration due to element degradation. Therefore, these devices are alternatively powered by other power sources including solar power or kerosene.

Disadvantages of using kerosene as an alternative power source include high monthly costs, environmental pollutants (millions of tons of _CO2 and black carbon released into the atmosphere contributing to global warming). ), adverse health effects (e.g., lungs, eyes, skin, and general health), potential fire hazards (due to flammability), safe storage and subscription issues, and some Unsuitability for powering products and equipment (emergency beacons, radios, communication equipment, charging docks for USB devices, etc.) and even possible poisoning caused by accidental ingestion by mixing it with a beverage mentioned.

Disadvantages of using solar energy as an alternative power source include variability in the amount and duration of sunshine (particularly in winter), the effects of rain (during the tropical wet/monsoon season, which reduces the sun's potential to almost zero). possible), cloudy conditions and fog can reduce power production (about 10-80%), shadows and haze can also reduce the effectiveness of solar power, solar latitude (sun angle) The need to adjust the position of the sun capture device for influence and effective capture, damage from external elements and the need to install outdoors to capture the escaping sunlight at the risk of theft. and limitations of the solar system itself in that it is not rechargeable and must be disposed of at the end of its life.

Metal-air fuel cells, such as magnesium-air fuel cells, can also be used as an alternative to traditional batteries. Metal-air fuel cells are believed to offer certain advantages, including: high energy density, low cost, and potential for long-term storage.

Generally speaking, metal-air fuel cells operate by suspending them in an ionic aqueous solution, such as seawater or other saline solution, which acts as the electrolyte between the air cathode and the anode. The air cathode is exposed to oxygen to allow electrochemical reactions to occur. As a by-product of this electrochemical reaction,
a) release of hydrogen gas (and traces of chlorine gas), and
b) Waste from anode degradation (e.g. metal hydroxides)
is mentioned.

Metal-air fuel cell technology suffers from electrolyte leakage from the cell, degraded performance from exposing the electrodes to excess electrolyte, sealing problems, gas (e.g. hydrogen and chlorine) accumulation and exhaust problems, and runaway exothermic oxidation. Dangerous temperature and pressure rises caused by reduction reactions, waste management issues related to anode degradation (e.g. reduced cathode life caused by waste material build-up within the fuel cell in the absence of regular cleaning and electrolyte replacement) is not without its drawbacks.

Magnesium air fuel cells have a typical life of 50-100 hours before requiring replacement of the anode. Also, the performance of air cathodes often degrades very quickly after only 100-200 hours of use or even during storage after the first use. Some metal-air fuel cells require rigorous regular maintenance and cleaning actions by the user to maximize air cathode life.

A typical metal-air fuel cell configuration is described by Huebscher, R.; G et al., U.S. Pat. No. 3,519,486 (July 7, 1970) and Louie, H.; P. U.S. Pat. No. 3,963,519 (June 15, 1976).

US Pat. No. 3,519,486 describes a trapped electrolyte fuel cell that includes an internal reservoir/chamber at the bottom of the cell to trap excess electrolyte. The trapped excess electrolyte forms an electrolyte pool in which the electrodes and matrix are located. The matrix is formed from a material that is resistant to potassium hydroxide, such as fibrous asbestos mat (column 2, lines 4-5). The battery must be sealed to prevent electrolyte leakage. Furthermore, since the reservoir is located at the bottom of the battery, the battery must be positioned in an upright orientation to ensure electrolyte storage and battery operation.

US Pat. No. 3,963,519 describes another trapped electrolyte fuel cell with a protective shield spacer. The spacers provide structural strength to the cell and protect the cathode while allowing air to pass over all surfaces of the cathode. This configuration is an advance over earlier heavy-framed metal/air battery designs that were considered unsuitable for use as primary and secondary lightweight metal-air batteries in the AA, C, and D formats. It was considered. A liquid-tight configuration is described for sealing the electrolyte internally.

Both U.S. Pat. Nos. 3,519,486 and 3,963,519 remove or isolate accumulated anode degradation waste and/or by-products to alleviate pressure buildup. does not describe the process for discharging the

Development of metal-air fuel cell technology is underway. For example, Japan's Aqua Power System is currently advancing metal-air fuel cell technology as described in at least three PCT patent applications, and their "realistic magnesium-air fuel" (RMAF ) as system technology (http://aquapowersystems.com/technology/how-aqua-powers-technology-works/, website accessed Dec. 19, 2016).

WO2014/097909 (Aqua Power System, Japan; also published as U.S. Patent Application Publication No. 2015/0340704) discloses a metal-air fuel cell having a layered cathode body comprising a water-repellent and conductive carbon material. Disclose. The resulting fuel cells are described as being highly water-repellent, breathable, and leak-proof.

WO2014/115880 (Aqua Power System, Japan; also published as U.S. Patent Application Publication No. 2015/0364800) discloses that the distance between the anode and cathode is relatively large to improve the electrochemical reaction. A short magnesium air fuel cell is provided. The height and width of the fuel cell, the relative positions of the anode and cathode, and the use of water supply pipes, which further include the reaction gas discharge pipe, are said to produce a stable power supply over relatively long periods of time. However, since the inlet to the reactant gas exhaust pipe may be located within the cell, the reactant gas exhaust pipe may leak electrolyte and/or gas, which is undesirable.

WO2014/115879 (Aqua Power System, Japan; also published as U.S. Patent Application Publication No. 2015/0380693) describes a magnesium air fuel cell that can be turned ON/OFF by a lid that is tightened A magnesium-air fuel cell is disclosed in which the power is turned on when the terminals are in contact with each other and turned off when the terminals are loosened.

It is understood that RMAF technology is incorporated into many commercial products, including water powered 1.5V AA batteries. (http://aquapowersystems.com/products/batteries/, website accessed December 19, 2016). Configured as a closed system of a given size that requires installation.

Fluidic, Inc. , (USA) is another company that is currently advancing metal-air fuel cell technology. Fluidic, Inc. platform technology is believed to be incorporated into the first commercialized rechargeable zinc-air battery (http://fluidicenergy.com/technology/, website accessed December 19, 2016 ).

Fluidic, Inc. , for example, the use of dopants to enhance the electrical conductivity of metal fuel oxidation products, i.e., the anode is degenerately doped (WO2014/062385, Fluidic, Inc.); the use of additives in ion-conducting media to reduce and/or extend the capacity of batteries (WO2014/160144, Fluidic, Inc.); the use of heteroionic aromatic additives (WO2014/ 160087, Fluidic, Inc.); use of additives comprising poly(ethylene glycol) tetrahydrofurfuryl; /030723, Fluidic, Inc.), various advances in metal-air fuel cell technology are described. Other claimed advances brought about by the design change include housing a gaseous oxidant receiving space (WO2013/066828, Fluidic. Inc), which catalyzes the oxidation of waste particulates. (WO2012/012364, Fluidic, Inc.), an anode with a scaffold structure (WO2011/163553, Fluidic), a fuel cell with multiple electrodes (each WO2011/130178 and WO2012/037026, Fluidic, Inc.) and multiple fuel cell systems (WO2011/035176, WO2012/106369 and WO2012/106369, respectively) 2010/065890, Fluidic, Inc.).

Generally, Fluidic, Inc. metal-air fuel cell technology differs from conventional rechargeable batteries in that the process is reversible because the anode is not consumed, and in that the anode is "doped" or coated to prevent it from degrading. It's similar to.

U.S. Pat. No. 3,519,486 U.S. Pat. No. 3,963,519 WO2014/097909 WO2014/115880 WO2014/115879 WO2014/062385 WO2014/160144 WO2014/160087 WO2016/123113 WO2012/030723 WO2013/066828 WO2012/012364 WO2011/163553 WO2011/130178 WO2012/037026 WO2011/035176 WO2012/106369 WO2010/065890

Affordable, environmentally friendly (reusable, recyclable), long-lived (shelf-life and/or operating-life) and reliable despite numerous advances in metal-air fuel cell technology There remains a need to overcome certain disadvantages associated with that technology and to provide a new source of DC power, particularly in the form of batteries, for use in devices and products that are safe and secure.

The present invention
(a) an anode;
(b) a positionable air cathode;
(c) a layer of absorbent material configured to hold an electrolyte, said layer of absorbent material being positioned intermediate an anode and an air cathode such that it is in contact with said anode;
(d) resilient air cathode positioning means adapted to position the air cathode so that it remains in contact with the layer of absorbent material while accommodating any changes in the volume of the layer of absorbent material;
with
The absorbent material layer provides a metal-air fuel cell that functions as an ion transfer bridge between the anode and cathode by retaining the electrolyte.

The present invention
(a) an anode;
(b) a positionable air cathode;
(c) a layer of absorbent material configured to hold an electrolyte, said layer of absorbent material being positioned intermediate an anode and an air cathode such that it is in contact with said anode;
(d) resilient air cathode positioning means adapted to accommodate any changes in the volume of the absorbent material layer while allowing the air cathode to remain in contact with the absorbent material layer;
with
The absorbent material layer provides a metal-air fuel cell that functions as an ion transfer bridge between the anode and cathode by retaining the electrolyte.

Preferably, the anode, the layer of absorbent material and the air cathode are coaxially arranged such that the air cathode substantially surrounds the layer of absorbent material and the layer of absorbent material substantially surrounds the anode.

Preferably, the anode, the layer of absorbent material and the air cathode are provided in a stacked or "sandwich layered" arrangement, for example with the air cathode overlying the layer of absorbing material and the layer of absorbing material overlying the anode.

Preferably, the resilient air cathode positioning means are positioned around the cross-sectional perimeter of the metal-air fuel cell.

Preferably, the resilient air cathode positioning means are incorporated within or separate from the air cathode and are comprised of O-rings, deformable polymeric material, elastic (or rubber) bands or expandable mesh. is selected from

Preferably, the metal-air fuel cell is contained within an open housing unit.

Preferably, the metal-air fuel cell is activated or reactivated for use by allowing the layer of absorbent material to retain the electrolyte (eg, by immersing the metal-air fuel cell in a liquid).

Preferably, the absorbent material layer is pre-impregnated with ions to form an electrolyte when the absorbent material layer retains moisture.

Preferably, the layer of absorbent material comprises a sub-layer of absorbent material pre-impregnated with ions and a sub-layer of absorbent material not pre-impregnated with ions.

Preferably, the layer of absorbent material changes volume upon adsorption or depletion of retained electrolyte and/or upon capture of anode waste.

Preferably, the absorbent material layer comprises woven or non-woven fibrous material or a combination thereof. It is further preferred that the absorbent material layer comprises fibrous cellulose, bamboo fibres, or a combination thereof.

Preferably, the anode comprises a magnesium alloy.

Preferably, the air cathode comprises a sheet layer. More preferably, the air cathode is hydrophobic, breathable and comprises a layered Teflon material.

Preferably, the metal-air fuel cell has a paper separator layer positioned between the layer of absorbent material and the air cathode to support and contain the layer of absorbent material and/or to further separate and protect the cathode from anode waste deposits. Further prepare.

In one embodiment, a metal-air fuel cell is adapted and/or used to provide a DC power source used to power the operation of a product or device. Preferably, the products or devices are torches (including flashlights, maglites, penlights), lights and lighting products or devices (including globe lights, LED lights, strobe lights and Christmas lights), safety or temporary lighting applications (including road construction), lanterns (including camping lanterns and paper lanterns), combination products (including flashlight-lantern combinations convertible between operating as flashlights and as lanterns), household products (including electric toothbrushes and shavers) emergency beacons (including EPIRB and directional finders), radios (analog and digital), communications equipment (including radios, CB radios and small audio equipment), toys (i.e. , battery powered), power banks for rechargeable products and charging docks for USB devices (small electronic products including mobile phones, i-pods, i-pads).

Definitions Unless otherwise specified herein, the following terms are understood to have the following general meanings.

"Air permeable" means, with respect to a material, allowing or having the ability to allow air to flow, diffuse, or otherwise pass therethrough.

"Absorptive" means, with respect to a material, capable of, having such an ability or having a tendency to wick or absorb a fluid (liquid or gas), especially a liquid.

"Activate", with respect to the metal-air fuel cell of the present invention, means to prepare (activate or operate) for use, i.e. to generate electricity through the oxidation-reduction reaction of the metal-air fuel cell.

"Shrinkable" means, with respect to a material or object, capable or adapted to decrease in size and/or volume by shrinking or shrinking.

"Immersion" means the process of placing or immersing something in a liquid for a short period of time.

"Dry storage" means a process of storage in a dry state, ie, in a low humidity environment and in the absence of atmospheric moisture.

"Elastic" means, with respect to a material or object, capable of or having the ability to spontaneously recover its original size and shape after being stretched or compressed or otherwise deformed.

"Electrolyte" means a solution (liquid or gel, preferably liquid) that contains ions and is capable or capable of conducting electricity.

"Expandable" means, in reference to a material or object, capable of or adapted to increase in size and/or volume by expansion.

By "hydrophobic" is meant, for a material, capable of or having the ability to repel (as opposed to attract or absorb) water.

"Mechanically rechargeable", in relation to a fuel cell or battery, means replacement of a consumed anode, e.g. in the case of a magnesium anode, the magnesium material is a storage medium for electrons released during chemical reactions. and magnesium material is consumed in the process.

"Pressure increase", with respect to a gas, means the increase in pressure caused by the gas within a sealed system or within a closed system.

"Shelf-life", with respect to a product, means the period, length or duration during which the product remains usable including suitability for its intended purpose.

"Vent" means with respect to gas, the process of releasing gas from a seal or containment system, including, for example, through an outlet.

"Waste" means undesired materials or by-products resulting from the process, magnesium hydroxide and/or hydrogen and/or means a gas such as chlorine.

"Wicking" means the process of absorbing or drawing liquid into or through a material by capillary action.

The present invention will be further described in connection with the accompanying figures which illustrate preferred embodiments of metal-air fuel cells according to the present invention. Other embodiments of the invention are possible, and thus the details of the accompanying drawings should not be taken as superseding the generality of the foregoing description of the invention.

1 shows a cross-sectional cutaway side view of a conventional magnesium air (MgO ₂ ) fuel cell as known in the art. FIG. 1 shows a cross-sectional partial cut-away side view of a magnesium-air fuel cell according to one embodiment of the present invention; FIG. FIG. 1B shows a cross-sectional cutaway side view of the magnesium-air fuel cell of FIG. FIG. 1B shows a cross-sectional cutaway side view of the conventional MgO ₂ cell of FIG. FIG. 1B shows a cross-sectional cutaway side view of the metal-air fuel cell of FIG. FIG. 1B shows a cross-sectional cutaway side view of the MgO ₂ cell of FIG. 1B shows a cross-sectional cutaway side view of the metal-air fuel cell of FIG. 1B to illustrate the prevention or reduction of corrosive magnesium anode waste deposits (fuel cell reaction by-products) on the cathode from use. FIG. FIG. 1B shows a cross-sectional cutaway side view of the MgO ₂ cell of FIG. 1B shows a cross-sectional cutaway side view of the metal-air fuel cell of FIG. 1B to illustrate the capture or containment of magnesium anode waste by the absorbent material within the cell during use. FIG. (elastic O-rings or mesh A book for describing a concentric layered (coaxial arrangement) structure of an inner anode rod, an intermediate absorbent material layer, a paper separator layer and an outer air cathode layer held or positioned in place using resilient air cathode positioning means such as 1 shows a perspective view of a metal-air fuel cell according to the invention; FIG. Figure 6B shows a cross-sectional cutaway front view of the fuel cell of Figure 6A to illustrate the concentric layered (coaxial) structure prior to expansion of the absorbent material layer; 6B shows a cross-sectional cutaway front view of the fuel cell of FIG. 6A to illustrate the concentric layered (coaxial) structure after expansion of the absorbent material layer; FIG. An exploded view of a magnesium-air fuel cell according to one embodiment of the invention is shown to illustrate the various components of the cell. 1 shows a cross-sectional cutaway front view of a magnesium-air fuel cell to illustrate an absorbent material layer according to one embodiment of the present invention; FIG. Durability (milliampere) test results for prototype batteries 1, 2, 3 according to one embodiment of the present invention over approximately 750 hours are given (Example 1, Experiment 1). Comparative power (milliampere) test results for a conventional _MgO2 battery and a prototype battery according to one embodiment of the present invention over about 500 hours of operation are given (Example 1, Experiment 2). Performance test results (in milliamps) for prototype cells 1, 2, 3 according to one embodiment of the present invention over about 500 hours are given (Example 1, Experiment 3).

FIG. 1A shows a traditional MgO ₂ battery known in the art. The MgO ₂ cell comprises a Mg anode (1) centrally located within a closed container (2) containing an aqueous electrolyte (3), the anode suspended into the aqueous electrolyte (3). An air cathode (4) is incorporated into the outer wall of the vessel such that redox reactions with the external atmosphere take place to effect ion exchange between the anode and cathode via the electrolyte.

As shown in FIG. 3A, the gas by-products produced by the MgO ₂ cell of FIG. 1A accumulate within the air gap (12) within the closed system. These gaseous by-products must be vented to the atmosphere (13) through a vent (14) that allows the gas to escape but prevents leakage of the electrolyte (3).

FIG. 4A shows the degradation of the anode (16) of the MgO ₂ cell of FIG. 1A and the corresponding accumulation (17) of anode waste deposits (eg magnesium hydroxide) on the cathode (4).

In contrast to FIG. 1A, FIG. 1B shows the present invention in which a magnesium anode (5) is positioned in an open container (6) with one or more vents (7) and surrounded by an absorbent material layer (8). shows a metal-air fuel cell according to an embodiment of , wherein the absorbent material layer (8) is surrounded by an air cathode (9).

FIG. 2 shows the uptake of liquid electrolyte (10) by the metal-air fuel cell of FIG. 1B. The electrolyte (10) is absorbed by the absorbent material layer (8) via a wicking action in the direction of arrow (11) when the absorbent material is immersed in the electrolyte.

As shown in FIG. 3B, the metal-air fuel cell of FIG. It comprises an open housing unit (6) having a .

Anode (5) is described as a magnesium anode, but alternative metals, alloys or combinations of alloys are generally known to those skilled in the art to provide suitable anodes. Suitable alternative metals include Li, Ca, Al, Zn and Fe. Preferably, the anode comprises a magnesium alloy such as "AZ31 B" having the following composition.
Aluminum: 2.5-3.5
Copper: max 0.05
Iron: max 0.005
Magnesium: Balance Manganese: 0.2 minutes Nickel: Maximum 0.005
Silicon: max 0.1
Zinc: 0.6-1.4

Since the anode (5) may be adapted to be located internally, preferably centrally, within the metal-air fuel cell, the anode may generally be formed in the shape of a rod or cylinder and may be extruded. It can be formed by molding. If the metal-air fuel cell is alternatively constructed in a sandwich layered (i.e., laminate) arrangement, the anode, absorbent material layer, and air cathode may each be provided as substantially planar layers. . This configuration may be particularly desirable when replacing certain rectangular battery shapes, such as existing 9V batteries.

Air cathodes (9) that may be suitable for use in the metal-air fuel cell of the present invention are generally known to those skilled in the art. Suitable properties of the air cathode (9) include hydrophobicity and air permeability. Preferably, the air cathode (9) is in the form of a sheet layer adapted to accommodate changes in volume of the layer of absorbent material (8) upon expansion and contraction. Preferably, the air cathode (9) is hydrophobic and air permeable and comprises a layered Teflon material. Even more preferably, the air cathode (9) may comprise layered Teflon material, carbon and nickel plated wire.

The absorbent material layer (8) may be a material having properties that make it suitable for absorbing electrolyte and retaining an absorbed amount of electrolyte. The absorbent material layer (8) essentially functions to transport ions in the electrolyte in an absorbent amount between the air cathode and the anode. Thus, the absorbent material layer is believed to act as the ionic cross-linking system (or ionic transfer bridge) required for battery operation.

The absorbent material layer (8) may be formed from an absorbent material capable of absorbing and retaining or retaining electrolytes by processes such as wicking, entrainment, capillary action. The absorbent material may be selected based on it having one or more, preferably all, of the following properties.
- wicking and electrolyte retention capacity;
- Ability to expand to accommodate increased volume due to absorption of liquid electrolyte and/or retention of anode waste;
- Ability to encapsulate solid particles to capture and/or retain solid waste;
- the ability to function as an "ionic bridge"; and/or
• Ability to allow gas exchange or diffusion (ie, for the oxygen gas diffusion process and release of gas by-products during cell operation).

The absorbent material layer (8) may be formed from a combination of breathable water-absorbing, hydrophilic and/or hydrophobic materials and may be conductive or non-conductive. Suitable materials are made from microfiber, rayon, cotton, cotton wool, hemp, wool, hessian, natural fiber wood pulp, airgel composites, bamboo fiber pulp, and/or any suitable combination thereof. Woven or nonwoven materials or any suitable combination thereof may be included. Preferably, the absorbent material layer comprises fibrous cellulose, bamboo fiber pulp, or a combination thereof.

The performance of the absorbent material layer (8) is enhanced using additives, such as the addition of sphagnum moss and polyacrylates, as well as other petroleum-derived superabsorbent gels well known to those skilled in the art. may

The battery may be activated or reactivated for use when the absorbent material layer comprises an absorbent amount of electrolyte. The absorbent material layer (8) may comprise an electrolyte (if the absorbent material layer is pre-impregnated with ions) or an absorbent amount of electrolyte after absorption of water. A preferred alternative arrangement of the layers of absorbent material is presented and described in connection with FIG. 8 described in more detail below.

The types of electrolytes that may be suitable for use in the metal-air fuel cells of the invention are generally known to those skilled in the art. Suitable examples include aqueous solutions containing ions such as NaCl (e.g., salt water, seawater, and saline), electrolytes (e.g., sports drinks), urine, and alkaline solutions (e.g., KOH), and water (e.g., , when the absorbing material is pre-impregnated with ions).

As shown in FIG. 4B, the anode waste precipitate (18) is trapped within the absorbent material layer (8) of the metal-air fuel cell of FIG. 1B and prevented from direct contact with the air cathode (9). . This process is also illustrated in FIGS. 5A and 5B, respectively, where FIG. 5A shows the accumulation of anode waste precipitate (17) on the cathode (4) of the _MgO2 cell of FIG. 1A, FIG. 5B, on the other hand, shows the capture of the anode waste precipitate (18) within the absorbent material layer (8) of the metal-air fuel cell of FIG. 1B.

Figure 6A provides a metal-air fuel cell according to the invention providing a coaxial arrangement of the internal anode rods (19) substantially surrounded by a layer of absorbent material (20), the layer of absorbent material (20) comprising a paper separator layer (20A). ). The paper separator layer (20A) is also substantially surrounded by an air cathode layer (21). The air cathode layer (21) is positioned by a resilient air cathode positioning means (22) such as a resilient O-ring or mesh to maintain contact with the absorbent material layer (20). Thus, the metal-air fuel cell can accommodate expansion (and contraction) of the absorbent material layer upon uptake (or depletion) of liquid electrolyte and/or upon collection of anode waste deposits over time. In another configuration, the elastic air cathode positioning means can be incorporated into the air cathode layer, such as by weaving an elastic material into the air cathode.

A cross-sectional view of the fuel cell of Figure 6A is also provided to show the absorbent material layer (20) before (Figure 6B) and after (Figure 6C) expansion. As shown in Figures 6B and 6C, the air cathode layer (21) remains positioned in contact with the absorbent material layer (20) and the paper separator layer (20A) by the resilient air cathode positioning means.

FIG. 7 shows an exploded view of a metal-air fuel cell according to the invention to illustrate some of its various components. a magnesium anode (28), an absorbent material layer (29), a paper separator layer (29A) and an air cathode (30) are coaxially arranged such that the air cathode (30) surrounds the paper separator layer (29A); A paper separator layer (29A) surrounds the absorbent material layer (29), which surrounds the magnesium anode (28). A resilient air cathode positioning means (27), formed in this embodiment by an O-ring, ensures contact between the air cathode (30) and the absorbent material layer (29). A coaxial array of electrodes is located within a vented housing (32). The vented housing (32) is closed at each end by a top lid (25) and a bottom lid (33) held in place by screws (24) each fixed to the anode (28). A contact ring (23) located outside the top lid (25) carries terminals from the air cathode (30) and is connected to the air cathode (30) by contact tabs (31). Rubber or plastic O-rings (27A) and plastic washers (26) are retained at and within each end of the electrode array to seal the electrolyte from other components and protect it from corrosion.

As demonstrated by FIG. 7, the metal-air fuel cell components consist of screws (24) that hold either the top lid (25) or the bottom lid (33) in place to access the electrode array. They can be easily replaced by loosening one of them. Thus, the magnesium anode (28) (and air cathode (30)) can be easily replaced, thereby providing an energy source that can be mechanically recharged in a simple manner.

FIG. 8 shows a cross-sectional view of the metal-air fuel cell of the present invention to illustrate the preferred embodiment of the absorbent material layer. The metal-air fuel cell comprises, in order from the perimeter inwards, an air cathode positioning means 35, an air cathode 34, and an air cathode locating means 35, an air cathode 34, and a liner for supporting and containing a layer of absorbent material and for isolating and protecting the cathode from anode waste deposits. A paper separator layer 36, a pre-impregnated sub-layer 37 of the absorbent material layer (pre-impregnated with ions), a non-impregnated sub-layer 38 of the absorbent material layer (not pre-impregnated with ions), and the anode. 39.

According to the illustrated preferred embodiment, the morphology of the absorbent material allows for controlled dissolution of ions into the retained electrolyte. This allows for control of events such as dissipation or concentration of solution heat that occurs when ions are dissolved in solution. This morphology may also allow control of the composition of the electrolyte within the sub-layers of the absorbent material layer, particularly if, for example, the pre-impregnated ions have a slow dissolution rate. This allows control of reaction rates and temperatures within the absorbent material layer and within the metal-air fuel cell, keeping in mind that redox reactions between the cathode and anode are typically exothermic. In this way, the higher temperature caused by the runaway redox reaction will allow for greater evaporative cooling and concomitant reduction of the electrolyte content in specific regions of the absorbent material layer to limit the runaway redox reaction. It may be included within or within a sublayer (eg, sublayer 37 provided in the embodiment shown in FIG. 8).

As suggested by the drawings and the foregoing description, the metal-air fuel cell of the present invention preferably allows expansion and contraction of the absorbent material layer upon absorption/desorption of electrolyte and/or upon capture of anode waste. do. Further potential advantages of the present invention include:
• Metal-air fuel cells can be simply and conveniently activated and reactivated on demand by soaking the absorbent material in the electrolyte, and deactivated by allowing it to dry between uses. This gives metal-air fuel cells the associated potential in a "dormant" mode in which no components are consumed, and a long shelf life without significant or appreciable loss of performance output of the cell.
By providing a novel wicking and retention system for the electrolyte, avoiding bulky water baths and allowing configurations requiring less electrolyte, thereby eliminating the possibility of electrolyte leakage due to, for example, tipping over Fuel cells from an upright position which reduces the weight of the battery.
By providing the metal-air fuel cell in an open housing unit, the present invention overcomes the drawbacks present in closed metal-air fuel cell systems such as gas pressure build-up and effective sealing of the electrolyte, while oxygen Intake and by-product emissions can also be improved.
• Convenient replacement and recycling of components. The anode, absorbent material layer and air cathode can be easily and conveniently replaced and reused to provide an environmentally friendly mechanically rechargeable device and/or
• A novel wicking and retention system for the electrolyte may enable improved thermal control to prevent runaway exothermic reactions. Metal-air fuel cells function by producing an exothermic redox reaction between an anode and a cathode. In traditional metal-air fuel cells, this creates the potential for a runaway exothermic reaction, which can build pressure and heat within the cell to dangerous levels. The absorbent material layer of the present invention allows for improved electrolyte evaporation and drainage as the temperature within the battery increases. This can control runaway reactions by reducing available electrolyte by evaporation, thereby slowing down the reaction. Any redox reaction in the battery can stop completely when the electrolyte is completely evaporated.

The metal-air fuel cells of the present application are believed to potentially provide a power source equivalent to using 90-100 traditional AA batteries, depending on their size. Based on the known storage capacity of the material compared to dry cell batteries. AA standard carbon batteries have an energy storage capacity of less than 1 Watt-hour (Wh) (eg, website http://www.allaboutbatteries.com/Energy-tables.html, accessed December 19, 2016). reference).
Table: Energy storage of AA batteries (Table reproduced from website http://www.allaboutbatteries.com/Energy-tables.html, accessed December 19, 2016).

The magnesium alloy used has a storage capacity of 1 Watt-hour (Wh) per gram weight of material. Thus, a 50 g magnesium alloy rod provides 50 watt hours of potential storage, while a heavier or larger magnesium rod, eg, 150 grams, provides 150 watt hours of storage. The criteria for magnesium galvanic energy density are:

EXAMPLES To test the performance of metal-air fuel cells according to the present invention, a series of experiments were conducted using prototype cells constructed in accordance with the present invention. In Experiment 1, the prototype cell was tested alone. Experiments 2 and 3 tested prototype cells against traditional MgO ₂ fuel cells constructed substantially according to FIGS. 1A, 3A and 4A.

Experimental Parameters Identical anode and cathode materials were used in all tests.

Magnesium Anode An extruded magnesium AZ31 B rod (anode) with the following composition yields a magnesium anode composition of approximately (typically) 96% pure magnesium.
Aluminum: 2.5-3.5
Copper: max 0.05
Iron: max 0.005
Magnesium: Balance Manganese: 0.2 minutes Nickel: Maximum 0.005
Silicon: max 0.1
Zinc: 0.6-1.4

Air Cathode Sufficiently hydrophobic air cathode consisting of layered Teflon material, carbon, and nickel-plated wire

Conventional _MgO2 Fuel Cell Morphology A conventional _MgO2 cell is generally understood as having a magnesium anode housed within a container of 5% saline solution electrolyte and an air cathode forming part of the container wall structure. It was a configuration that

Prototype Cell Morphology The prototype cell consisted of a 45 gram magnesium anode and an air cathode consisting of layered Teflon material, carbon and nickel plated wire. The anode was encapsulated in an absorbent material (wool-like woven material rolled and woven into a mat-like substance). An air cathode was wrapped around the absorbent material and secured with an elastic O-ring to allow expansion.

Test Methodology Electronic measurements were made using hand-held multimeters of known voltage and amperage measurement accuracy (generally within 1%) stored in a climate-controlled environment. The instrument was allowed to warm up before starting measurements.

The tests were conducted on a 24 hour basis in a climate-controlled laboratory with a constant air temperature of typically 65% humidity and 25°C. Traditional _MgO2 cells were maintained by carefully emptying and replacing the saline electrolyte every 24 h, while prototype cells were immersed in the same saline solution for about 10 s every 24 h.

An electronic load in the form of a high efficiency DC-DC converter circuit was used to feed three LEDs. This circuit was specifically designed to maximize the load on the battery at all times while maximizing the brightness of the LEDs.

Experiment 1: Improvement of Life and Performance of Metal-Air Fuel Cells (or Endurance Test)
Experiments were conducted with three identically configured prototype batteries, labeled Battery 1, Battery 2, and Battery 3. The goal was to exceed 1.2 volts (under constant electrical load) and produce at least 250 milliamps for 250 hours (running time required by the product).

Cells 1 and 2 had a continuous electrical load (ie 24 hours a day), while Control Cell 3 operated under electrical load for 4 hours a day.

The voltage of each cell was not recorded daily, but randomly recorded at regular intervals. All cells remained above 1.2V for the duration of the test, typically between 1.3V and 1.65V.

Results Results are given in Table 1 below and in FIG.
Table 1: Endurance test results (milliamps) for batteries 1, 2, 3 according to embodiments of the present invention over about 750 hours.

As follows, the results show that the prototype cell exceeded the 250 milliamp target threshold after 264 hours.
Battery 1: 440mA
Battery 2: 360mA
Battery 3: 350mA

The test duration was extended and the 250 mA threshold was crossed again after 504 hours as follows.
Battery 1: 280mA
Battery 2: 490mA
Battery 3: 580mA

Cells 2 and 3 continued to show improved performance.

At 740 hours, two of the three cells still exceeded the 250 mA target output threshold, as follows.
Battery 1: 180mA
Battery 2: 340mA
Battery 3: 280mA

After several repeated experiments with similar observations and results, it was concluded that the battery exceeded the life cycle endurance prediction (ie, 250 mA target) by a factor of 3.

Based on these results, it is expected that the cell will perform satisfactorily or at target outputs above 250 mA and 1.2 volts for at least 250 hours and often over 500 hours in most applications.

Experiment 2: Improving Cathode Life and Performance Identically configured prototype cells (labeled as prototype cell 1 and prototype cell 2) and identically configured traditional cells were used to test cathode life and performance. Comparative experiments were performed using conventional MgO ₂ batteries (labeled as Traditional Battery 1 and Traditional Battery 2).

Results Results are given in Table 2 below and in FIG.
Table 2: Comparative power output (in milliamps) of a traditional _MgO2 battery and a prototype battery according to one embodiment of the present invention over about 500 hours of operation.

_The results show that after the commonly observed initial initial activation power peak, MgO traditional batteries continued to degrade at a steady pace after rapidly declining electrical performance. After 500 hours of continuous operation, the traditional _MgO2 battery could not generate more than 10% of the original initial power output.

In contrast, after 500 hours of continuous operation, the prototype battery can maintain more than 70% of its original power output in some cases, and more than 100% of its output in other cases. We were able to - clearly showing an improvement in power output far beyond the initial first activation power.

It is well known that the air cathode pores of Mg-Air cells become increasingly clogged with precipitates (eg, magnesium hydroxide precipitates) that form during discharge and consumption of magnesium. This, in turn, adversely affects oxygen gas diffusion, thereby degrading reaction and degrading air-cathode performance over time. Therefore, the microstructure and air permeability of carbon-based air-cathode materials are important factors affecting the electrochemical performance of MgO ₂ cells.

Upon examination, it was observed that the air-cathode of a traditional _MgO2 cell was completely degraded, covered with a solid white material (solidified magnesium hydroxide), and severely corroded and thus no longer usable. .

In contrast, the air cathode of the prototype cell appeared normal and was reused for future experiments with little or no loss of performance.

After several repeated experiments with identical observations and identical results, it was concluded that the prototype cell demonstrated improved lifetime and cathode performance in contrast to the traditional _MgO2 cell morphology.

Experiment 3: Improving Metal-Air Fuel Cell Performance with Waste Accumulation in Absorbent Layer A series of experiments and tests were conducted to characterize the benefits and effectiveness of the waste management system incorporated into the cell of the present application. rice field.

The absorbent material layer for each battery tested according to embodiments of the present invention was composed of a fibrous cellulose/bamboo material with a similar consistency to feminine hygiene products. The expandable layer of anode-encapsulated absorbent material provides an "ionic bridge" between the anode and cathode after immersion in an electrolyte solution (brine) to initiate and sustain ionic reactions that can last up to several days. It worked like The ion exchange process was observed to improve in the cell over time with the accumulation of anode waste (magnesium hydroxide) produced as a by-product of the reaction, as demonstrated by the results below.

Results Results are given in Table 3 below and in FIG.
Table 3: Performance test results (in milliamps) for batteries 1, 2, 3 according to one embodiment of the invention over about 500 hours.

The results show that as the magnesium hydroxide "waste" accumulates, the electrical performance (electrical output) of the cell actually improves until the magnesium anode material is completely consumed. This is evident from all tests over 100 hours that have been performed. That is, once the initial drop in power stabilizes, the results show improved electrical performance (power output) as a result of subsequent gradual improvement in battery output.

Without wishing to be bound by theory, the inventors believe that this unexpected phenomenon may result from any or all of the following.
- Anode waste trapped over time in the absorbent material layer provides better conductive or ionic pathways to facilitate the reaction;
- As the battery expands during waste accumulation, more electrolyte becomes available for reaction, adsorbed by the absorbent material;
- the surface area of the cell over which the reaction is taking place is increased, which can increase the reaction; and/or - the pores of the air cathode are protected from magnesium hydroxide precipitation, thereby allowing oxygen gas diffusion is not significantly damaged.

Based on the results of experiments and observations, the unique configuration, engineering, and operation of the metal-air fuel cell according to the present invention allows the anode waste precipitate to be filtered and/or captured within the absorbent material, thereby
- Protects the pores found within the air cathode from blockage by waste particulates, thus allowing significant oxygen gas diffusion across the air cathode;
- effective prevention of waste deposits that would otherwise degrade the air cathode, salt migration due to salt ingress or corrosion (e.g. salt creep, i.e. salt ingress and/or corrosion); crystal migration) also potentially improves the life of the cathode and other battery components such as contacts, wiring and/or electronics;
Eliminates the need for periodic internal cleaning of the battery to remove accumulated waste and/or
• The performance of the battery can actually increase as the waste sediment collects or becomes trapped within the absorbent material.
It was considered.

A metal-air fuel cell according to the present invention can provide an affordable, low-cost power source for use in developing countries. It is expected that such metal air fuels can provide about 5 hours of light usage per day for less than the first year cost of $0.05/day (including the initial cost of the equipment). . This could decrease to 0.01 USD/day in subsequent years. The entire battery is intrinsically safe as all components are replaceable and interchangeable (ideal for third world applications) and short circuits have no detrimental effect other than consumption of anode metal Note further that .

Therefore, the metal-air fuel cell according to the present invention is portable, lightweight (i.e. lightweight and robust unit construction avoiding large water tanks and/or vessels), environmentally friendly, replaceable and powerful (i.e. Certain known metal-air fuel cells can be powerful enough to power a myriad of electrical applications heretofore not possible), scalable and miniaturized direct current generators (i.e. D cell and other form factors such as batteries, which can be miniaturized for use in areas previously dominated by "classic" batteries, and/or for products and devices It provides the potential for environmentally friendly or "pollution free" power sources (eg, when compared to traditional batteries, solar cells and kerosene as components). This is because the components are environmentally friendly and commonly available, which provides excellent recyclability of the entire device, and the cathode itself is removable and suitable for recycling.

Such modifications and variations as would be obvious to a person skilled in the art are included within the scope of the invention as claimed in the appended claims.

Unless the context requires otherwise, "locate", when used as a verb, means to place or put something into a new location or shape, and "locate" and "positionable" accordingly. should be interpreted.

Claims (19)

(a) an anode;
(b) a positionable air cathode;
(c ) a layer of absorbent material, said layer of absorbent material configured to retain aqueous electrolyte and anode waste sediments without submerging said layer of absorbent material in the electrolyte during use, said layer of absorbent material a layer of absorbent material positioned intermediate the anode and the air cathode such that a is in contact with the anode;
(d) the air cathode to remain in contact with the absorbent material layer while accommodating any changes in the volume of the absorbent material layer due to retention of the electrolyte and anode waste deposits ; a resilient air cathode positioning means configured to position;
with
A metal-air fuel cell, wherein the absorbent material layer acts as an ion transfer bridge between the anode and the cathode by retaining the electrolyte. 3. The anode, the layer of absorbent material and the air cathode are coaxially arranged such that the air cathode substantially surrounds the layer of absorbent material and the layer of absorbent material substantially surrounds the anode. 2. The metal-air fuel cell according to 1. 2. The metal-air fuel cell of claim 1, wherein said anode, said layer of absorbent material, and said air cathode are provided in a stacked arrangement. 4. A metal-air fuel cell according to any one of claims 1 to 3, wherein said resilient air cathode positioning means are positioned around the cross-sectional perimeter of said cell. The resilient air cathode positioning means may be incorporated within the air cathode or provided separately from the air cathode and may be an O-ring, a deformable polymeric material, an elastic (or rubber) band, or an expandable mesh. 5. The metal-air fuel cell of any one of claims 1-4, selected from: 6. A metal-air fuel cell according to any preceding claim, wherein the metal-air fuel cell is housed within an open housing unit. 7. The metal-air fuel cell of any one of claims 1-6, wherein the metal-air fuel cell is activated or reactivated for use by allowing the layer of absorbent material to retain electrolyte. . 8. A metal-air fuel cell according to any one of the preceding claims, wherein the absorbent material layer is pre-impregnated with ions to form an electrolyte when the absorbent material layer retains moisture. 9. A layer of absorbent material according to any one of the preceding claims, wherein the layer of absorbent material comprises a first sublayer of absorbent material pre-impregnated with ions and a second sublayer of absorbent material not pre-impregnated with ions. metal-air fuel cell. 10. The metal-air fuel cell of any one of claims 1-9, wherein the metal-air fuel cell is activated or reactivated for use by immersing the metal-air fuel cell in a liquid to retain the electrolyte. Metal air fuel cell. 11. A metal-air fuel cell according to any one of the preceding claims, wherein the layer of absorbent material changes volume upon adsorption or depletion of retained electrolyte or water and/or capture of anode waste. 12. A metal-air fuel cell according to any one of the preceding claims, wherein the layer of absorbent material comprises a woven or non-woven fibrous material or a combination thereof. 13. The metal-air fuel cell of any one of claims 1-12, wherein the absorbent material layer comprises fibrous cellulose, bamboo fibers, or a combination thereof. 14. The metal-air fuel cell of any one of claims 1-13, wherein the anode comprises a magnesium alloy. 15. The metal-air fuel cell of any one of claims 1-14, wherein the air cathode comprises a sheet layer. 16. The metal-air fuel cell of any one of claims 1-15, wherein the air cathode is hydrophobic, breathable and comprises a layered Teflon material. The metal-air fuel cell is positioned between the layer of absorbent material and the air cathode to support and contain the layer of absorbent material and/or remove anode waste deposits trapped in the layer of absorbent material from the cathode. 17. The metal-air fuel cell of any one of claims 1-16, further comprising a paper separator layer to further separate and protect the . 18. A metal-air fuel cell according to any one of the preceding claims, which in use provides a DC power source used to power the operation of a product or device. Said product or device:
torches, including flashlights, maglites, and penlights;
Lights and lighting products or devices, including globe lights, LED lights, strobe lights and Christmas lights;
safety or temporary lighting applications, including road construction;
lanterns, including camping lanterns and paper lanterns;
combination products, including flashlight-lantern combinations convertible between operating as flashlights and operating as lanterns;
household products, including electric toothbrushes and shavers;
emergency beacons, including EPIRBs and directional finders;
radio, both analog and digital
communication equipment, including radios, CB radios and small audio equipment;
Power banks for toys and rechargeable products, including battery-powered, charging docks for USB devices, and charging docks for small electronic products, including mobile phones, tablets and audio equipment. 19. The metal-air fuel cell of claim 18.

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