Electrolyte surfactant composition for metal-air and alkaline batteries

Abstract

A metal-air battery can include an air cathode, a metal anode, and an electrolyte including a surface-modified surfactant. The electrolyte for a metal-air battery can include a surface-modified surfactant, and the surface-modified surfactant can include polyethylene glycol (PEG), monoalkyl polyethylene glycol, or a combination thereof.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 423,953, filed November 9, 2022, the entire disclosure of which is incorporated herein by reference.

[0002] The present technology relates generally to the field of electrochemical cells. In particular, the present technology relates to electrolytes for electrochemical cells that contain surface-modifying surfactants that enhance cell discharge capacity. Summary of the Invention

[0003] In one aspect, an electrolyte for an electrochemical cell is provided, the electrolyte comprising a surface-modified surfactant, wherein the surface-modified surfactant comprises polyethylene glycol (PEG), monoalkyl polyethylene glycol (m-PEG), or a combination thereof. In at least one embodiment, the electrochemical cell comprises a metal-air battery. In at least one embodiment, the metal-air battery comprises a zinc-air battery. In at least one embodiment, the electrochemical cell comprises an alkaline electrochemical cell.

[0004] In another aspect, a metal-air battery is provided that includes an air cathode, a metal anode, and an electrolyte, wherein the electrolyte includes a surface-modified surfactant. In at least one embodiment, the surfactant includes polyethylene glycol (PEG), monoalkyl polyethylene glycol, or a combination thereof. In any embodiment, the metal-air battery further includes a separator between the air cathode and the metal anode.

[0005] In some embodiments that can be combined with other aspects and embodiments, the surfactant comprises a monoalkyl polyethylene glycol. In at least one embodiment, the alkyl of the monoalkyl polyethylene glycol is methyl, ethyl, propyl, n-butyl, or hexyl. In at least one embodiment, the surfactant comprises a methyl polyethylene glycol. In at least one embodiment, the surfactant comprises polyethylene glycol.

[0006] In any of the above embodiments, which may be combined with other aspects and embodiments, the electrolyte comprises from about 10 ppm to about 15,000 ppm of a surface-modifying surfactant. In at least one embodiment, the electrolyte comprises from about 10 ppm to about 2,000 ppm of methyl polyethylene glycol. In at least one embodiment, the electrolyte comprises from about 1,000 to about 10,000 ppm of polyethylene glycol.

[0007] In some embodiments that can be combined with other aspects and embodiments, the electrolyte further comprises a gas suppressing additive. In at least one embodiment, the gas suppressing additive comprises lithium hydroxide, calcium hydroxide, aluminum hydroxide, zinc oxide, lead acetate, bismuth oxide, or a combination of any two or more thereof. In at least one embodiment, the gas suppressing additive comprises lithium hydroxide. In at least one embodiment, the electrolyte comprises from about 1,000 to about 30,000 ppm of the gas suppressing additive. In at least one embodiment, the electrolyte comprises from about 15,000 to about 20,000 ppm of lithium hydroxide.

[0008] In some embodiments that may be combined with other aspects and embodiments, the electrolyte further comprises an amphoteric fluorosurfactant. In some embodiments, the amphoteric fluorosurfactant comprises a partially fluorinated surfactant having betaine functionality. In at least one embodiment, the amphoteric fluorosurfactant is selected from the group consisting of CHEMGUARD® S-111, CHEMGUARD® S-500, CAPSTONE® FS-50, CAPSTONE® FS-51, APFS-14, DYNAX DX3001, Zonyl® FSK, Zonyl® FS-500, or a combination of any two or more thereof.

[0009] In any of the above embodiments, which may be combined with other aspects and embodiments, the electrolyte comprises from about 10 ppm to about 30,000 ppm of amphoteric fluorosurfactant. In any of the above embodiments, the electrolyte comprises from about 100 ppm to about 10,000 ppm of amphoteric fluorosurfactant.

[0010] In some embodiments that can be combined with other aspects and embodiments, the electrolyte can further include an additional surfactant, including, but not limited to, cetyltrimethylammonium bromide (CTAB), sodium dodecylbenzenesulfonate (SDBS), sodium dodecyl sulfate (SDS), sodium hexametaphosphate (SHMP), lauryltrimethylammonium bromide, dodecyltrimethylammonium bromide, octyltrimethylammonium bromide, or a combination of any two or more thereof.

[0011] In any of the above embodiments, which may be combined with other aspects and embodiments, the electrolyte comprises from about 10 ppm to about 30,000 ppm of an additional surfactant. In any of the above embodiments, the electrolyte comprises from about 100 ppm to about 10,000 ppm of an additional surfactant.

[0012] In any of the above embodiments that can be combined with other aspects and embodiments, the electrolyte further comprises a corrosion inhibitor, a gelling agent, zinc oxide, potassium hydroxide, sodium hydroxide, a polyacrylate polymer, or a combination of any two or more thereof.

[0013] In any of the above embodiments, which can be combined with other aspects and embodiments, the anode can include a surfactant system, a corrosion inhibitor, a gelling agent, a gas suppressing additive, potassium hydroxide, sodium hydroxide, cesium hydroxide, other functional additives, or a combination of any two or more thereof.

[0014] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the exemplary aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the following drawings and detailed description. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional schematic diagram depicting an exemplary electrochemical cell according to an embodiment of the present disclosure. [Figure 2] 1 is a graph showing a comparison of various electrolyte surfactants in ANSI size 13 hearing aid standard testing, according to an embodiment of the present disclosure. [Figure 3] 10 is a graph showing a comparison of various electrolyte surfactants in the ANSI size 13 hearing aid standard test, according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0016] Various embodiments are described below. It should be noted that the specific embodiments are not intended as an exhaustive description or as a limitation to the broader aspects discussed herein. An aspect described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced with any other embodiment(s).

[0017] As used herein, "about" will be understood by one of ordinary skill in the art and will vary to some extent depending on the context in which it is used. If there are uses of the term that are not clear to persons of ordinary skill in the art given the context in which it is used, "about" will mean up to plus or minus 10% of the particular term.

[0018] The use of the terms "a," "an," and "the," and similar referents in the context of describing elements (particularly in the context of the claims below) should be construed to cover both the singular and the plural unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values ​​herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated herein as if it were individually referred to herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "etc.") provided herein is intended merely to further clarify embodiments and does not present a limitation on the scope of the claims unless otherwise stated. No language in the specification should be construed as indicating any non-claimed element as required.

[0019] As used herein in the specification and claims, the term "and / or" should be understood to mean "either or both" of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Other elements other than the elements specifically identified by the term "and / or" may optionally be present, whether related or unrelated to those elements specifically identified. As a non-limiting example, a reference to "X and / or Y" can refer in one embodiment to X only (optionally including elements other than Y), in another embodiment to Y only (optionally including elements other than X), and in yet another embodiment to both X and Y (optionally including other elements).

[0020] Ratios, concentrations, amounts, and other numerical data may be expressed herein in a range format. It should be understood that such range formats are used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values ​​explicitly stated as the limits of the ranges, but also all individual numerical values ​​or subranges subsumed within that range, as if expressly recited. For example, 5 to 40 wt% should be interpreted to include not only the explicitly stated limits of 5 to 40 wt%, but also subranges such as 10 wt% to 30 wt%, 7 wt% to 25 wt%, and individual amounts including fractions within the specified range, such as 15.5 wt%, 29.1 wt%, and 12.9 wt%.

[0021] As used herein, the term "cationic fluorosurfactant" refers to a fluorosurfactant that contains a cationic group and / or a group that can be protonated to a cationic group. In some embodiments, the cationic fluorosurfactant contains primary, secondary, tertiary, and / or quaternary amine groups.

[0022] As used herein, the term "anionic fluorosurfactant" refers to a fluorosurfactant that contains an anionic group and / or a group that can be deprotonated to an anionic group. In some embodiments, the anionic fluorosurfactant contains carboxy group(s), sulfonic acid group(s), phosphate group(s), phosphonic acid group(s), or their corresponding salts.

[0023] As used herein, the term "amphoteric fluorosurfactant" refers to a fluorosurfactant that contains at least one cationic group and at least one anionic group as defined above for cationic fluorosurfactants and anionic fluorosurfactants. Examples of amphoteric fluorosurfactants include, but are not limited to, CHEMGUARD® S-111 (a short-chain perfluoro-based amphoteric fluorosurfactant of the alkylamine oxide type), CHEMGUARD® S-500 (a short-chain perfluoro-based amphoteric fluorosurfactant), CAPSTONE® FS-50 (a betaine partially fluorinated surfactant), CAPSTONE® FS-51 (an amine oxide partially fluorinated surfactant), APFS-14 (an amphoteric polyfluoroalkyl betaine surfactant), DYNAX DX3001 (a perfluoroalkyl betaine amphoteric fluorochemical surfactant), ZONYL® FSK (a sparingly water-soluble ethoxylated nonionic fluorosurfactant), ZONYL® FS-500 (a betaine fluorinated amphoteric surfactant), or a combination of any two or more thereof. As used herein, the term "betaine-functional" refers to a neutral compound having a positively charged cationic functional group and a negatively charged functional group. In some embodiments, the cationic functional group can be a quaternary ammonium or phosphonium cation that lacks a hydrogen atom, hi some embodiments, the negatively charged functional group can be a carboxyl group.

[0024] As used herein, the term "metal anode" refers to an anode that includes a metal or metal alloy as the active anode material. For example, the term "zinc anode" refers to an anode that includes zinc or a zinc alloy as the active anode material.

[0025] As used herein, the term "ppm" means parts per million by weight unless expressly stated otherwise.

[0026] The present disclosure relates to improving the performance of electrochemical cells, such as metal-air electrochemical cells or alkaline electrochemical cells. Metal-air electrochemical cells or batteries operate by capturing oxygen from ambient air, reducing it at the cathode, and oxidizing a metal at the anode, thereby generating a current in an external circuit connected between the anode and cathode. Metal-air batteries, such as zinc-air batteries, are considered one of the most promising candidates for next-generation energy storage batteries due to their safety, high energy density, and low cost. However, metal anodes use metal or metal alloy powders that can corrode in the presence of air and alkaline electrolytes. One cause of corrosion of metal anodes is the hydrogen evolution reaction (HER), also known as self-corrosion of metal anodes. Metals, such as zinc, have a more negative reduction potential than hydrogen, making them thermodynamically unstable in alkaline solutions, resulting in the evolution of hydrogen gas. In addition to causing corrosion, HER consumes electrolyte and reduces metal utilization efficiency. Therefore, hydrogen evolution contributes to a decrease in coulombic efficiency during both the charging and discharging processes. Corrosion significantly shortens the shelf life and reduces the capacity and usable current production of metal-air batteries.

[0027] In the present invention, we have newly discovered that a specific type of surfactant, e.g., a surface-modifying surfactant, can be added to an electrolyte to modify the surface of an anode active material, such as a metal-based particle. The electrolyte composition and surface-modifying surfactant disclosed herein also improve discharge capacity over current and conventional surfactants used in metal-air batteries. Without being bound by theory, we believe this effect is achieved by the facile migration of reactants and reaction products and a reduction in the hydrogen evolution reaction, thereby allowing the metal to remain unconsumed until later in the discharge.

[0028] In one aspect, an electrochemical cell is provided that includes an anode, a cathode, and an electrolyte. Suitable electrochemical cells include, but are not limited to, metal-air electrochemical cells and alkaline electrochemical cells. Examples of metals in metal-air electrochemical cells include, but are not limited to, zinc, lithium, aluminum, iron, magnesium, and alloys thereof. Examples of metal-air cells may include, for example, 675 cells (PR44), 13 cells (PR48), 312 cells (PR41), and 10 cells (PR70). Examples of alkaline cells are commonly known as LR6 (AA), LR03 (AAA), LR14 (C), and LR20 (D). In certain embodiments, the electrochemical cell includes a metal-air battery and an alkali metal battery. In certain embodiments, the electrochemical cell includes a metal-air battery. In certain embodiments, the electrochemical cell includes a zinc-air battery.

[0029] In one aspect, a metal-air battery includes a cathode, an anode active material, an electrolyte, and optionally a separator disposed between the anode and the cathode, the electrolyte including a surface-modifying surfactant. The metal-air battery is typically filled with an electrolyte solution including an aqueous alkaline solution between the cathode and the metal anode, and optionally includes an insulating porous separator to prevent direct short-circuiting between the air electrode and the metal anode.

[0030] The electrochemical cell may include an electrolyte. The electrolyte may have high ionic conductivity. The electrolyte may be an alkaline electrolyte, such as an aqueous solution of an alkali metal hydroxide, or a quaternary ammonium electrolyte. Examples of alkali metal hydroxides include potassium hydroxide, lithium hydroxide, or sodium hydroxide solution, or the like, or a combination of any two or more thereof. In some embodiments, the alkali metal hydroxide may be potassium hydroxide, sodium hydroxide, indium hydroxide, or a mixture of any two or more thereof. In some embodiments, the alkali metal hydroxide may include potassium hydroxide. In some embodiments, the alkali metal hydroxide may include sodium hydroxide.

[0031] The alkali metal hydroxide may be present in the electrolyte at about 10% to about 50% by weight of the electrolyte. This may include about 15% to about 45%, about 20% to about 40%, about 25% to about 35%, or about 25% to about 30% by weight of the electrolyte, as well as ranges between any two of these values ​​or less than any one of these values. In any embodiment, the alkali metal hydroxide may be present in an amount between about 30% to about 40% by weight of the electrolyte. For example, the concentration or content of the hydroxide in the electrolyte may be about 1 wt% to about 60 wt%. This may include about 5 wt% to about 50 wt%, about 10 wt% to about 45 wt%, about 15 wt% to about 40 wt%, about 20 wt% to about 35 wt%, and about 25 wt% to about 30 wt%, as well as ranges between any two of these values ​​or less than any one of these values. In some embodiments, the electrolyte can have a hydroxide content of 20 wt% to 34 wt%. In some embodiments, the electrolyte can have a hydroxide content of less than about 60 wt%, including hydroxide contents of less than about 50 wt%, less than about 40 wt%, less than about 30 wt%, less than about 20 wt%, and less than about 10 wt%.

[0032] The electrolyte includes a surface-modifying surfactant. The surface-modifying surfactant modifies the surface of the anode active material, such as metal-based particles, to reduce self-corrosion due to the hydrogen evolution reaction and improve discharge capacity. Suitable surface-modifying surfactants include, but are not limited to, polyalkylene glycols, alkyl polyalkylene glycols, polyethylene glycol methyl ether, polypropylene methyl ether, and polypropylene ethyl ether, and derivatives thereof. Suitable polyalkylene glycols and derivatives thereof may include, but are not limited to, polymethylene glycol (PMG), polyethylene glycol (PEG), polypropylene glycol (PPG), polybutylene glycol (PBG), or a combination of any two or more thereof. The alkyl polyalkylene glycols and derivatives thereof may include monoalkyl polyalkylene glycols or dialkyl polyalkylene glycols. The alkyl of the alkyl polyethylene glycol may be a C1-C2 group, such as a methyl group, an ethyl group, a propyl group, an n-butyl group, a hexyl group, a heptyl group, or an octyl group. 12 It may include alkyl or C1-C6 alkyl groups. Suitable alkyl polyalkylene glycols and derivatives thereof may include, but are not limited to, methyl polymethylene glycol (mPMG), methyl polyethylene glycol (mPEG), methyl polypropylene glycol (mPPG), ethyl polymethylene glycol (ePMG), ethyl polyethylene glycol (ePEG), ethyl polypropylene glycol (ePPG), or a combination of any two or more thereof. In some embodiments, the surface-modifying surfactant comprises polyethylene glycol (PEG), methyl polyethylene glycol (mPEG), or a combination thereof.

[0033] Polyalkylene glycols and alkylpolyalkylene glycols having a molecular weight (weight average) of about 100 to about 30,000 may be useful in the electrolyte compositions, with some embodiments having a molecular weight of about 300 to about 20,000. Suitable molecular weights of glycol surfactants include, but are not limited to, about 100 to about 30,000, about 200 to about 25,000, about 300 to about 20,000, about 400 to about 15,000, about 500 to about 10,000, or about 550 to about 5,000, and ranges between any two of these values ​​or less than any one of these values. In some embodiments, the surface-modifying surfactant comprises polyethylene glycol (PEG) having a molecular weight of 300. In other embodiments, the surface-modifying surfactant comprises polyethylene glycol (PEG) having a molecular weight of 20,000. In some embodiments, the surface-modifying surfactant comprises methylpolyethylene glycol (mPEG) having a molecular weight of 550.

[0034] The amount of surface-modifying surfactant in the electrolyte can vary depending on the type of surfactant and other components in the electrolyte. For example, the concentration of the surface-modifying surfactant in the electrolyte can range from about 1 ppm to about 20,000 ppm, including about 10 ppm to about 15,000 ppm, about 50 ppm to about 10,000 ppm, about 100 ppm to about 5,000 ppm, or about 500 ppm to about 3,000 ppm, about 1,000 ppm to about 2,000 ppm, and ranges between any two of these values ​​or less than any one of these values. In some embodiments, the electrolyte comprises about 10 ppm to about 15,000 ppm of surface-modifying surfactant. In any of the above embodiments, which can be combined with other aspects and embodiments, the electrolyte comprises about 1,000 ppm to about 10,000 ppm of surface-modifying surfactant. In any of the above embodiments, the electrolyte comprises from about 100 ppm to about 5,000 ppm of a surface-modifying surfactant. In any of the above embodiments, the electrolyte comprises from about 100 ppm to about 3,000 ppm of a surface-modifying surfactant.

[0035] In addition to the use of surface-modifying surfactants, suppression of gassing in electrochemical cells, such as the production of hydrogen or carbon dioxide from HER, can be further achieved by adding one or more additives to the electrolyte or the cell itself. Suitable gas-suppressing additives may include, but are not limited to, lithium hydroxide, calcium hydroxide, aluminum hydroxide, zinc oxide, lead acetate, bismuth oxide, or a combination of any two or more thereof. When present, the gas-suppressing additive may be present in an amount of about 1% to about 10% by weight of the electrolyte. This may include about 1% to about 8%, 1% to about 5%, about 1.5% to about 5%, or about 2% to about 5% by weight of the electrolyte. In one embodiment, the gas-suppressing additive is present in an amount of about 1%, about 1.5%, about 2%, about 2.5%, about 3%, about 3.5%, or about 4% by weight of the electrolyte, or a range between and including any two of these values. The gas-suppressing additive not only functions as a gas-suppressing additive but also provides other benefits. Therefore, the term "gas suppressing additive" does not necessarily mean that a component is limited to a specific function. For example, in the case of a zinc-air battery, zinc oxide can adjust the passivation of the zinc surface, and lithium hydroxide can form a porous deposit on the zinc oxide anode, thereby allowing the electrolyte mixture to access the anode for a longer period of time.

[0036] In addition to the surface-modifying surfactant, the electrolyte may optionally contain an amphoteric fluorosurfactant. Suitable amphoteric fluorosurfactants are described in U.S. Pat. No. 10,320,041, the contents of which are incorporated herein by reference. In some embodiments, the amphoteric fluorosurfactant comprises a partially fluorinated surfactant having betaine functionality. For example, the amphoteric surfactant may include, but is not limited to, CHEMGUARD® S-111, CHEMGUARD® S-500, CAPSTONE® FS-50, CAPSTONE® FS-51, APFS-14, DYNAX DX3001, ZONYL® FSK, ZONYL® FS-500, or a combination of any two or more thereof. When present, the amphoteric fluorosurfactant may be present in the electrolyte at about 10 ppm to about 20,000 ppm. For example, the concentration of the amphoteric fluorosurfactant in the electrolyte can range from about 1 ppm to about 20,000 ppm, including about 10 ppm to about 15,000 ppm, about 50 ppm to about 10,000 ppm, about 100 ppm to about 5,000 ppm, or about 500 ppm to about 3,000 ppm, about 1,000 ppm to about 2,000 ppm, and ranges between any two of these values ​​or less than any one of these values. In some embodiments, the amphoteric fluorosurfactant is present in the electrolyte at about 100 ppm to about 10,000 ppm. In other embodiments, the concentration of the amphoteric fluorosurfactant in the electrolyte is about 500 ppm to about 5,000 ppm.

[0037] The electrolyte may further comprise one or more additional surfactants. Suitable surfactants include, but are not limited to, cetyltrimethylammonium bromide (CTAB), sodium dodecylbenzenesulfonate (SDBS), sodium dodecyl sulfate (SDS), sodium hexametaphosphate (SHMP), lauryltrimethylammonium bromide, dodecyltrimethylammonium bromide, octyltrimethylammonium bromide, polyethylene glycol methyl ether, polypropylene methyl ether, and polypropylene ethyl ether, or a combination of any two or more thereof. The electrolyte may comprise from about 10 ppm to about 15,000 ppm of the additional surfactant. In some embodiments, the electrolyte comprises from about 50 ppm to about 10,000 ppm of the additional surfactant. In other embodiments, the electrolyte comprises from about 100 ppm to about 5,000 ppm of the additional surfactant.

[0038] The electrolyte may further comprise water and / or a solvent. The water content of the electrolyte may range from about 25% to about 99% by volume of the solvent component of the electrolyte.

[0039] The anode active material may include a metal, and the anode may be referred to as a "metal anode." In this regard, as used herein, anode "active material" may refer to a single chemical compound that is part of the discharge reaction at the cell's anode and contributes to the cell's discharge capacity, including impurities and trace amounts of other components that may be present therein. Anode "active material" does not include current collectors, electrode leads, etc., which may contain or support the metal active material. Examples of anode active materials include, but are not limited to, metals such as zinc, lithium, aluminum, iron, and magnesium, and / or their alloys. In certain embodiments, the anode active material includes alloys of the above metals with other metals. For example, in the case of zinc-air batteries, zinc alloys may include alloying elements intended to increase the overpotential for hydrogen evolution and minimize hydrogen evolution within the anode. In some embodiments, zinc may be alloyed with one or more metals selected from lead (Pb), indium (In), bismuth (Bi), calcium (Ca), magnesium (Mg), and aluminum (Al). The specific alloying agent may be selected based on the desired properties and performance. Some combinations of alloying materials may be more compatible with zinc than others. In some embodiments, the alloying metal is bismuth. In some embodiments, the zinc alloy includes zinc, bismuth, and indium. In some embodiments, the zinc alloy includes zinc, bismuth, indium, and aluminum. In some embodiments, the zinc alloy includes zinc, lead, indium, and aluminum. In certain embodiments, the anode active material includes zinc particles. In certain embodiments, the anode active material includes zinc alloy particles.

[0040] The amounts of various alloying agents can vary depending on the desired properties. For example, the concentration of the alloying agents can range from about 20 ppm to about 750 ppm, including about 50 ppm to about 100 ppm, about 100 ppm to about 300 ppm, about 300 ppm to about 400 ppm, or about 400 ppm to about 600 ppm, and ranges between any two of these values ​​or less than any one of these values. In some embodiments, the alloying agents are present in concentrations from about 50 ppm to 550 ppm. In some embodiments, the alloy material can include about 0.01% to about 0.5% by weight of an activator, alone or in combination with about 0.005% to about 0.2% by weight of one or more alloying agents. In some embodiments, the alloy may include about 400 ppm to about 600 ppm lead, about 100 ppm to about 300 ppm indium, and about 50 ppm to about 100 ppm aluminum. In some embodiments, the alloy may include about 0 ppm to about 200 ppm lead, about 100 ppm to about 300 ppm indium, and about 50 ppm to about 100 ppm aluminum. In some embodiments, the alloy may include about 50 ppm to about 450 ppm bismuth and about 50 ppm to about 450 ppm indium. The concentrations of the components are specified based on the total weight of the metals in the anode.

[0041] The performance of the anodes and metal-air cells of the present technology can be further improved by using metal anode materials with a defined particle size distribution to provide a narrow distribution of similar metal particle sizes within the anode, thereby enhancing the diffusion pathways for hydroxide ions. In addition to improving diffusion characteristics, the particle size distribution also provides porous sites for metal oxide deposition, thereby delaying anode passivation. This approach is effective for use in metal-air battery cell anodes and can be used in combination with the other improvements disclosed herein. A suitable metal particle size distribution may be such that about 0% to about 1% by weight of the anode active material, based on the total amount of the anode active material, has a particle size less than about 75 microns; about 15% to about 35% by weight of the total amount of the metal or metal alloy has a particle size of about 75 microns to about 125 microns; about 15% to about 35% by weight of the total amount of the metal or metal alloy has a particle size of about 125 microns to about 150 microns; about 15% to about 35% by weight of the total amount of the anode active material has a particle size of about 150 microns to about 180 microns; about 15% to about 35% by weight of the total amount of the anode active material has a particle size of about 180 microns to about 250 microns; and about 0% to about 1% by weight of the total amount of the anode active material has a particle size greater than about 250 microns.

[0042] The electrolyte and / or anode may optionally include a surfactant system, a corrosion inhibitor, a gelling agent, a gas suppressing additive, an ionic conductivity enhancer, potassium hydroxide, sodium hydroxide, cesium hydroxide, other functional additives, or a combination of any two or more thereof. In some embodiments, the electrolyte and / or anode may include a corrosion inhibitor, a gelling agent, zinc oxide, potassium hydroxide, sodium hydroxide, a polyacrylate polymer, or a combination of any two or more thereof. For example, the electrolyte and / or anode may further include a surfactant system (e.g., hexyldiphenyloxide disulfonic acid, diethylenetriamine, octylphenoxypolyethoxyethanol, Igepal® CA-630, Triton® X-100), a corrosion inhibitor (e.g., indium hydroxide, polyaniline, clay, polyethylene glycol, polypropylene glycol, or lithium hydroxide), a gelling agent (e.g., polyacrylate polymer), a gas-inhibiting additive (e.g., zinc oxide, aluminum hydroxide, or calcium bromide), a functional additive (e.g., boric acid, sodium borate, potassium borate, sodium stannate, potassium stannate), a clay additive (e.g., laponite, montmorillonite, bentonite, kaolinite, smectite, and), a flow aid (e.g., polytetrafluoroethylene (PTFE) and an acrylate polymer), or a combination of any two or more thereof. When these additives are included, their concentration can range from about 0.01 wt % to about 20 wt %, based on the total weight of the electrolyte and / or anode.

[0043] Metal-air batteries include an air cathode. The air cathode is not particularly limited as long as the electrode functions as a positive electrode in a metal-air battery. Various air electrodes that can use oxides as the positive electrode active material can be used. Suitable air cathodes include metals with redox catalytic properties, such as platinum and nickel; catalytic materials including carbon-based materials with redox catalytic properties, such as graphite; and inorganic oxides with redox catalytic properties, such as perovskite-type oxides, manganese dioxide, nickel oxide, cobalt oxide, and spinel-type oxides. In some embodiments, the cathode can can be formed entirely of a metal or alloy with a hydrogen overvoltage similar to that of the cathode (rather than plating or cladding the can), as long as sufficient strength and ductility are obtained from the selected material. In addition to nickel, materials with such hydrogen overvoltage properties include, but are not limited to, cobalt and gold. In some embodiments, such materials can be coated as one or more coating layers on a core layer, for example, by plating, cladding, or other application processes. Materials that provide sufficient strength and ductility can also be used as a single layer material instead of a composite structure, which includes CRS or other suitable material as the core layer.

[0044] In some embodiments, nickel and nickel alloy plated steel strip may be used, as pre-plated steel strip is commercially available that generally does not require post-plating treatment due to cost considerations. The metal in the can is preferably both ductile enough to withstand drawing, and strong and rigid enough to withstand the cell crimping and sealing process and otherwise be durable, and provide the primary overall structural strength for the cell.

[0045] In some embodiments, the cathode can may be made of nickel-plated stainless steel. In other embodiments, materials for the cathode can include nickel-coated stainless steel, nickel-plated cold-rolled steel, INCONEL® (a non-magnetic nickel alloy), pure nickel with minor alloying elements (e.g., Nickel 200 and related families of Nickel 200 alloys such as Nickel 201), all available from Huntington Alloys, or DURANICKEL® 301, available from Special Metals. In some embodiments, some precious metals may also be used to plate, clad, or otherwise coat can metals, including nickel-plated steel strip and nickel-plated mild steel strip after can production.

[0046] In some embodiments, when a double-sided nickel-coated multilayer (e.g., CRS) is used, the present disclosure contemplates either an additional layer (e.g., a fourth layer, a fifth layer, etc.) between the nickel and the CRS, or an additional layer (e.g., a fourth layer, a fifth layer, etc.) with the nickel layer between the CRS and the additional layer(s). For example, gold, cobalt, or other good electrical conductors can be deposited on some or all of the exterior surface of the cathode can (outside the nickel layer) after the can is drawn or drawn and ironed. Alternatively, such a layer, such as a fourth layer, can be, for example, an adhesion-promoting layer between the CRS and the nickel.

[0047] Cans can be manufactured using a typical raw material structure of Ni / SST / Ni as the sheet structure, with such sheet structures having a thickness of about 0.002 inches to about 0.012 inches. This may include about 0.003 inches to about 0.010 inches, or about 0.004 inches to about 0.006 inches. In some embodiments, the thickness is about 0.002 inches, about 0.003 inches, about 0.004 inches, about 0.005 inches, or about 0.006 inches. In some embodiments, the thickness is about 0.005 inches. In some embodiments, each of the nickel layers comprises about 1% to about 10% of the overall thickness of such a three-layered metal sheet. This may include about 1.5% to about 9%, about 2% to about 8%, about 2.5% to about 7%, or about 3% to about 6.5% of the overall thickness of such a three-layered metal sheet. In some embodiments, each of the nickel layers comprises about 2% to about 4% of the overall thickness of such a three-layer metal sheet, hi some embodiments, each of the nickel layers comprises about 2% of the overall thickness of such a three-layer metal sheet.

[0048] Metal-air batteries may include a grommet / gasket between the air cathode and the metal anode.

[0049] An insulating gasket is typically disposed between the cathode can and the anode can. The insulating gasket may serve at least two primary functions. First, the insulating gasket serves as a closure for the cell, preventing anode material and / or electrolyte from leaking from the cell between the outer surface of the anode can sidewall and the inner surface of the cathode can sidewall. Therefore, the insulating gasket must have sufficient liquid-tightness to prevent such leakage. Generally, such properties are available in a variety of elastically deformable thermoplastic polymer materials.

[0050] It should be noted that the electrochemical cells of the present disclosure can be configured according to or consistent with the designs of metal-air cells known in the art, such as zinc / silver oxide batteries and zinc / manganese dioxide batteries, except for design modifications provided in detail herein below. For example, in various embodiments, the electrochemical cells of the present disclosure can be designed to specifications suitable for button-sized batteries. In particular, the electrochemical cell can be a metal-air cell, such as a zinc-air button cell. In some embodiments, the shape of the cell is such that the anode is held in a somewhat flat or pan-shaped position. Thus, generally speaking, an exemplary embodiment of a cell of the present disclosure can be as illustrated in FIG. 1.

[0051] As shown in FIG. 1 and with specific reference to cell 10, the negative electrode includes an anode can assembly 22, with an anode can 24 having an electrochemically reactive anode 26 contained therein and an insulating gasket 60. Anode can 24 has a bottom wall 28 and a circumferentially downwardly depending side wall 30. Side wall 30 terminates in a circumferential can leg 36. The bottom wall and side wall 30 generally define an anode cavity 38 within anode can 24, which contains anode 26.

[0052] The positive electrode includes a cathode can assembly 40, which includes a cathode can 44 and a cathode 42. The cathode 42 includes the area below the separator 74 and up to the cathode can 44. This area of ​​the cathode 42 includes a porous diffusion layer 57, a cellulose air diffusion layer, and a cathode active layer 72. The active layer 72 preferably ranges in thickness from about 50 microns to about 1,250 microns and promotes the reaction between hydroxide ions in the electrolyte and cathode oxygen from the air. The separator 74 may include or consist of one or both of a microporous plastic membrane and a microporous cellulose paper. The microporous plastic membrane is about 25 microns thick and is typically made of polypropylene. The paper material is 70 to 90 microns thick, has a basis weight of 20 to 25 g / m², and is typically made of polyvinyl alcohol and a cellulose-based material. The separator's primary function is to prevent physical contact between the anode metal particles and the remaining elements of the cathode 42. However, the separator 74 allows hydroxide ions and water to pass therethrough to the cathode assembly. Here, the cathode is an air cathode, and the cathode active layer comprises carbon. The cathode can 44 has a bottom 46 and a circumferentially upstanding sidewall 47. The bottom 46 has a generally flat inner surface 48, a generally flat outer surface 50, and an outer periphery 52 defined on the flat outer surface 50. A plurality of air ports 54 extend through the bottom 46 of the cathode can 44, providing a path for oxygen to enter the adjacent cathode can assembly 40 through the bottom 46. An air reservoir 55 separates the cathode can assembly 40 from the bottom 46 and the corresponding air port 54. A porous diffusion layer 57 and a cellulose air diffusion layer 32 fill the air reservoir 55. The cathode can sidewall 47 has an inner surface 56 and an outer surface 58.

[0053] The anode can assembly 22 is electrically insulated from the cathode can assembly 40 by an insulating gasket 60. The insulating gasket 60 includes a circumferential side wall 62 that is disposed between the upright side wall 47 of the cathode can and the downwardly depending side wall 30 of the anode can. An insulating gasket leg 64 is disposed generally between the can leg 36 of the anode can and the cathode can assembly 40. An insulating gasket top 66 is disposed where the side wall 62 of the insulating gasket 60 extends from between the side wall 30 and the side wall 47 adjacent the top of the cell.

[0054] Thus, the outer surface 68 of the cell 10 is defined by the outer surface of the top of the anode can 24 , the outer surface 58 of the sidewall 47 of the cathode can 44 , the outer surface 50 of the bottom of the cathode can 44 , and the top 66 of the insulating gasket 60 .

[0055] The insulating gasket also provides electrical insulation, preventing all effective direct electrical contact between the anode can 24 and the cathode can 44. Therefore, the insulating gasket side wall 62 must surround and provide electrical insulation around the entire circumference of the cell between the exterior and interior surfaces 56, generally from the top of side wall 47 to the bottom of side wall 30. Similarly, the insulating gasket legs 64 must surround and provide electrical insulation around the entire circumference of the cell between the legs 36 of side wall 30, the bottom of side wall 47, and the outer periphery of the cathode can assembly 40. The combination of good liquid-tightness and good electrical insulation is typically achieved by molding known battery-grade nylon polymer materials into the desired configuration.

[0056] To meet electrical insulation requirements, the insulating gasket may have good dielectric insulation properties and a minimal thickness around the perimeter of sidewall 62, free of any pinholes or other imperfections that may allow current transmission between sidewall 30 and sidewall 47. Thicknesses of insulating gasket sidewall 62 of about 200 to about 250 microns are common in conventional electrochemical cells. By using the same elastically deformable thermoplastic nylon material as the thicker insulating gaskets of the prior art, thicknesses as thin as 100 microns are acceptable in the cells of the present disclosure.

[0057] Depending on the battery configuration to which the insulating gasket is applied, intermediate thicknesses such as 150 microns, 140 microns, 127 microns, etc. may be selected for some cells. However, when cell volumetric efficiency is an important consideration, preferred thicknesses are thinner, e.g., 120 microns or 110 microns, and as thin as 100 microns. Thus, the preferred range of thicknesses for insulating gasket 60 for use in cells 10 of the present disclosure has a lower limit of about 100 microns.

[0058] In some embodiments, the porous diffusion layer 57 is a microporous hydrophobic polymeric material, such as a polytetrafluoroethylene (PTFE) membrane about 25 to about 100 microns thick, which allows air to pass through and is generally impermeable to the battery electrolyte. In some embodiments, the porous diffusion layer 57 is Teflon™. In some embodiments, the porous diffusion layer 57 is used in combination with the air port 54 to efficiently transport oxygen to the active reaction surface area of ​​the cathode assembly.

[0059] In some embodiments, the cellulose air diffusion layer 32 is positioned below the porous diffusion layer 57 and serves as a protective side air diffusion layer. Specifically, when the cell is activated, the anode can assembly 22 presses downward on the separator 74, and the cellulose air diffusion layer 32 helps prevent the air ports 54 from being completely covered.

[0060] In some embodiments, the active layer 72 further includes a connecting base layer, i.e., a conductive braided nickel wire layer (not shown), that can be interconnected with the cathode can as a current collector. In some embodiments, carbon forms a matrix surrounding the nickel wire conductive layer. In some embodiments, nickel is used for the conductive layer because it exhibits little or no corrosion in the metal-air cell environment and is an excellent electrical conductor. In some embodiments, the thickness of the cathode assembly between the separator 74 and the porous diffusion layer 57 is minimized.

[0061] With the exceptions detailed in this disclosure, the various components of the electrochemical cell may generally be fabricated using materials and techniques commonly known in the art.

[0062] In another embodiment, the metal-air battery may be manufactured by any means known in the art so long as the resulting battery is not inconsistent with the disclosure provided herein. Accordingly, the present disclosure includes methods of manufacturing a metal-air battery comprising the components and their respective concentrations as discussed throughout this disclosure.

[0063] The invention thus generally described will be more readily understood with reference to the following examples, which are provided by way of illustration and are not intended to limit the invention. [Example]

[0064] In the following examples, zinc-air battery cells were fabricated and tested.

[0065] Example 1: Preparation of Control Electrolyte. To prepare the control electrolyte, 100 lbs of KOH was diluted with deionized water to adjust the KOH concentration to approximately 40%. 1000 ppm of cross-linked polyacrylic acid gelling agent (ETD) and 15,000 ppm of lithium hydroxide monohydrate were added to the KOH and mixed to obtain the control electrolyte.

[0066] Example 2: Preparation of surfactant-containing electrolyte. To prepare the surface-modified surfactant-containing electrolyte in this example, 100 g of KOH was diluted with deionized water to adjust the KOH concentration to approximately 32%. The appropriate amount of surface-modified electrolyte, 1000 ppm of cross-linked polyacrylic acid-based gelling agent (ETD), and 15,000 ppm of lithium hydroxide monohydrate were added to the KOH and mixed to complete the process. Various surface-modified surfactants and conventional surfactants were tested, as summarized in Table 1 below. [Table 1]

[0067] Example 3: Fabrication of a Control Battery Cell. A control cell with a control electrolyte was fabricated as described in Example 1. In the anode preparation step, Zn-Pb-In-Al alloy (98 wt%), cross-linked polyacrylic acid gelling agent (0.3 wt%), clay additive (0.2 wt%), and indium / lithium hydroxide (0.3 wt%) were mixed in an Elweka. Deionized water was added during the zinc mixing to coat the additive powder onto the zinc powder. The coated zinc was dried at room temperature (20°C) for 24 hours. The dried additive-coated zinc was then mixed in equal amounts with uncoated zinc containing Teflon™ powder (0.02 wt%). The final zinc was sieved. The concentration is specified based on the total weight of zinc in the anode. During cell assembly, the mixed zinc was dispensed into the cavity of the anode can, followed by the electrolyte, at a ratio that varied depending on the cell size.

[0068] Example 4: Battery cell fabrication using electrolytes containing surface-modified surfactants. Cells with electrolytes of each of the surface-modified surfactants described in Example 2 were fabricated using the anode formulation described in Example 3. During cell assembly, mixed zinc was dispensed into the cavity of the anode can, followed by the electrolyte in proportions that varied depending on the cell size.

[0069] Example 5: Battery Testing In the examples presented below, zinc-air cells made according to the present technology were tested under hearing aid standards and wireless streaming discharge tests using the following test protocols.

[0070] Measuring Battery Performance Under Hearing Aid Standard Test Protocols. Electrochemical cells can be tested according to several methods under the American National Standards Institute (ANSI) test standards. For primary hearing aid batteries using aqueous electrolytes, a pair of ANSI tests, known as the Hearing Aid Standard Test and the Wireless Streaming Test, determine the cell's performance and service life. The Hearing Aid Standard Test involves applying a 5 mA constant current load for 15 minutes, followed by a 3 mA load for 45 minutes, followed by a 12-hour rest period. The daily cycle consists of 12 hours of on-load followed by a 12-hour off-load (or rest period). This cycle is repeated until the cell operating voltage falls below 1.05 V. A second test alternates between applying a 12 mA load for two hours and a 3 mA load for two hours for a total of 12 hours, followed by a 12-hour rest period. The (12-hour on / 12-hour off) load cycle continues until the cell operating voltage falls below 1.1 V. Both studies were performed after 4 months at room temperature to test long-term stability.

[0071] For each surfactant tested, a plot of the capacity (mAh) interval to reach the end-point voltage (EPV) was recorded, and the results are shown in Figures 2 and 3. These figures compare the performance of electrolytes containing surface-modified surfactants with conventional electrolytes containing commonly used surfactants in hearing aid benchmark tests and wireless streaming pulse tests, respectively. The cells with the surface-modified surfactants clearly show superior discharge capacity.

[0072] While particular embodiments have been shown and described, it will be understood that changes and modifications thereof can be made by those skilled in the art without departing from the technology in its broader aspects as defined in the following claims.

[0073] The embodiments illustratively described herein may suitably be practiced in the absence of any element(s) or limitation(ies) not specifically disclosed herein. Thus, for example, terms such as "comprising," "including," and "containing" are intended to be broadly understood and not limiting. Furthermore, the terms and expressions used herein are used as terms of description rather than limitation, and the use of such terms and expressions is not intended to exclude any equivalents of the shown and described features or portions thereof, recognizing that various modifications are possible within the scope of the claimed technology. Additionally, the phrase "consisting essentially of" will be understood to include the elements specifically mentioned and additional elements that do not materially affect the basic and novel characteristics of the claimed technology. The phrase "consisting of" excludes any elements not specified.

[0074] The present disclosure should not be limited in terms of the specific embodiments described in this application. Many modifications and variations are possible without departing from the spirit and scope of the present disclosure, as will be apparent to those skilled in the art. Functionally equivalent methods and compositions within the scope of the present disclosure, in addition to those recited herein, will be apparent to those skilled in the art from the foregoing description. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is to be understood that the present disclosure is not limited to particular methods, reagents, compounds, compositions, or biological systems, which can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

[0075] As will be understood by those skilled in the art, for any purpose, particularly in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations thereof. Any recited range can be readily understood as fully describing and allowing for the same range to be divided into at least one half, one third, one quarter, one fifth, one tenth, etc. As a non-limiting example, each range discussed herein can be readily divided into a lower third, middle third, and upper third, etc. As will be understood by those skilled in the art, all terms such as "maximum," "at least," "greater than," and "less than" are inclusive of the stated numerical value and refer to ranges that can be subsequently divided into subranges as described above. Finally, as will be understood by those skilled in the art, a range includes each individual numerical value.

[0076] All publications, patent applications, issued patents, and other references mentioned herein are herein incorporated by reference to the same extent as if each individual publication, patent application, issued patent, or other reference was specifically and individually indicated to be incorporated by reference in its entirety. Definitions contained within text incorporated by reference are excluded to the extent they conflict with definitions in this disclosure.

[0077] Other embodiments are set forth in the following claims.

Claims

1. A metal-air battery, an air cathode; a metal anode; an electrolyte comprising a surface-modifying surfactant; The surface-modifying surfactant comprises polyethylene glycol (PEG), monoalkyl polyethylene glycol, or a combination thereof; Metal-air battery.

2. 2. The metal-air battery of claim 1, wherein the surface-modifying surfactant comprises polyethylene glycol.

3. 3. The metal-air battery according to claim 1, wherein the alkyl of the monoalkyl polyethylene glycol is methyl, ethyl, propyl, n-butyl, or hexyl.

4. 2. The metal-air battery of claim 1, wherein the surface-modifying surfactant comprises methyl polyethylene glycol (mPEG).

5. 5. The metal-air battery according to claim 1, wherein the electrolyte comprises about 10 ppm to about 15,000 ppm of the surface-modifying surfactant.

6. The metal-air battery according to any one of claims 1 to 5, wherein the electrolyte further comprises a gas-suppressing additive.

7. 7. The metal-air battery of claim 6, wherein the gas-suppressing additive comprises lithium hydroxide, calcium hydroxide, aluminum hydroxide, zinc oxide, lead acetate, bismuth oxide, or a combination of any two or more thereof.

8. 8. The metal-air battery of claim 7, wherein the gas-suppressing additive comprises the lithium hydroxide.

9. 7. The metal-air battery of claim 6, wherein the electrolyte comprises about 1,000 ppm to about 30,000 ppm of the gas-suppressing additive.

10. 10. The metal-air battery according to any one of claims 1 to 9, wherein the electrolyte further comprises an amphoteric fluorosurfactant selected from CHEMGUARD (registered trademark) S-111, CHEMGUARD (registered trademark) S-500, CAPSTONE (registered trademark) FS-50, CAPSTONE (registered trademark) FS-51, APFS-14, DYNAX DX3001, ZONYL (registered trademark) FSK, ZONYL (registered trademark) FS-500, or a combination of any two or more thereof.

11. 11. The metal-air battery of claim 10, wherein the electrolyte comprises about 10 ppm to about 30,000 ppm of the amphoteric fluorosurfactant.

12. 12. The metal-air battery according to claim 1, wherein the electrolyte further comprises an additional surfactant comprising cetyltrimethylammonium bromide (CTAB), sodium dodecylbenzenesulfonate (SDBS), sodium dodecyl sulfate (SDS), sodium hexametaphosphate (SHMP), lauryltrimethylammonium bromide, dodecyltrimethylammonium bromide, octyltrimethylammonium bromide, polyethylene glycol methyl ether, polypropylene methyl ether, and polypropylene ethyl ether, or a combination of any two or more thereof.

13. 13. The metal-air battery of claim 12, wherein the electrolyte comprises about 10 ppm to about 15,000 ppm of the additional surfactant.

14. The metal-air battery according to any one of claims 1 to 13, wherein the electrolyte further comprises a corrosion inhibitor, a gelling agent, zinc oxide, potassium hydroxide, sodium hydroxide, a polyacrylate polymer, or a combination of any two or more thereof.

15. The metal-air battery according to any one of claims 1 to 14, further comprising a separator between the air cathode and the metal anode.

16. The metal-air battery according to any one of claims 1 to 15, wherein the metal of the metal anode comprises zinc, lithium, aluminum, iron, magnesium, or an alloy thereof.

17. An electrolyte comprising a surface-modifying surfactant and a gas-suppressing additive.

18. 18. The electrolyte of claim 17, wherein the surface-modifying surfactant comprises polyethylene glycol (PEG) or a monoalkyl polyethylene glycol.

19. 19. The electrolyte of claim 17 or claim 18, wherein the electrolyte comprises from about 10 ppm to about 15,000 ppm of the surface-modifying surfactant.

20. 20. The electrolyte of any one of claims 17 to 19, wherein the gas suppressing additive comprises lithium hydroxide, calcium hydroxide, aluminum hydroxide, zinc oxide, lead acetate, bismuth oxide, or a combination of any two or more thereof.

21. 21. The electrolyte of claim 20, wherein the electrolyte comprises from about 1,000 ppm to about 30,000 ppm of the gas suppressing additive.

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