Metal-air battery and method of manufacturing a metal-air battery

Abstract

The present invention relates to a metal-air battery and a method for manufacturing the metal-air battery. The metal-air battery includes: a negative electrode layer comprising a metal, a positive electrode layer comprising a conductive metal oxide, a solid electrolyte layer between the negative electrode layer and the positive electrode layer, and a bonding layer comprising a metal, wherein the bonding layer is disposed between the positive electrode layer and the solid electrolyte layer.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2019-0157677, filed on November 29, 2019, in the Korean Intellectual Property Office, and all rights arising therefrom, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure relates to secondary batteries, and more particularly, to metal-air batteries. Background Art

[0004] Metal-air batteries include a negative electrode that can absorb and release ions and a positive electrode that uses oxygen from the air as an active material. Oxygen reduction and oxidation reactions occur in the positive electrode, and metal oxidation and reduction reactions occur in the negative electrode. The chemical energy generated during the metal oxidation and reduction reactions is converted into electrical energy and then extracted. For example, metal-air batteries absorb oxygen during discharge and release oxygen during charging. When metal-air batteries use oxygen from the air, the specific energy of the battery can be greatly increased. For example, metal-air batteries can have a specific energy several times higher than existing lithium-ion batteries.

[0005] In metal-air batteries, the positive electrode has an electron transport path (channel) and an ion transport path, and the capacity or performance of the metal-air battery can be significantly affected by the positive electrode material and the structure of the positive electrode or air electrode. The positive electrode material may be porous, for example, having a void structure, and the bonding between the particles in the positive electrode may be weakened, resulting in deformation of the positive electrode. Deformation of the positive electrode can lead to reduced performance and shortened life of the metal-air battery. Therefore, there is still a need for improved metal-air battery materials. Summary of the Invention

[0006] Provided is a metal-air battery having excellent charge and discharge characteristics.

[0007] Provided is a metal-air battery capable of preventing deformation of a positive electrode.

[0008] Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description.

[0009] According to one aspect, a metal-air battery is provided, wherein the metal-air battery includes: a negative electrode layer including a metal; a positive electrode layer including a conductive metal oxide; a solid electrolyte layer between the negative electrode layer and the positive electrode layer; and a bonding layer including a metal, wherein the bonding layer bonds the positive electrode layer to the solid electrolyte layer.

[0010] The bonding layer may include at least one of Pt, Au, Mn, Co, Ni, Cr, V, Fe, Pb, or Sn.

[0011] The thickness of the bonding layer may be about 10 nanometers (nm) or less.

[0012] The conductive metal oxide may be RuO2, InSnO, IrO, OsO2, RhO2, Ce where 0≤x≤2 and 0≤y≤3 x O y , where W is 0≤x≤2 and 0≤y≤3 x O y , NbO, Eu2O3, Ti where 0≤x≤2 and 0≤y≤3 x O y , Mn2O3 or PbO2.

[0013] The positive electrode layer may be porous.

[0014] The positive electrode layer may have a porosity of about 90 volume percent (vol %) or less based on the total volume of the positive electrode layer.

[0015] The specific surface area of ​​the positive electrode layer can be about 1 square meter / gram (m 2 / g) or greater.

[0016] The solid electrolyte layer may include at least one compound having a NASICON structure, a garnet structure, or a perovskite structure.

[0017] The solid electrolyte layer may include Li wherein 0≤a≤1 1+a Al a Ti 2-a (PO4)3(LATP), Li with 5≤a≤9 a La3Zr2O 12 (LLZO), or La 0.55 Li 0.35 At least one of TiO3 (LLTO).

[0018] The metal-air battery may further include a gas diffusion layer on at least one surface of the positive electrode layer.

[0019] The positive electrode layer may not include an organic electrolyte.

[0020] According to another aspect, a method for manufacturing a metal-air battery is provided. The method includes: providing a solid electrolyte layer; coating (covering) a surface of the solid electrolyte layer with a bonding layer; disposing a metal oxide composite (composite) layer on the surface of the bonding layer; heat-treating the solid electrolyte layer, the bonding layer, and the metal oxide composite layer; and disposing a negative electrode layer on the surface of the solid electrolyte layer to manufacture the metal-air battery.

[0021] The metal oxide composite layer may be in the shape of a sheet (plate).

[0022] The metal oxide composite layer may include a conductive metal oxide and a binder.

[0023] The heat treatment may include heat treatment at a temperature of about 500°C to about 800°C.

[0024] The heat treatment may bond the conductive metal oxide to the bonding layer.

[0025] The melting point of the bonding layer may be between 230°C and about 1910°C.

[0026] The bonding layer may include at least one of Pt, Au, Mn, Co, Ni, Cr, V, Fe, Pb, or Sn.

[0027] The thickness of the bonding layer may be about 10 nanometers (nm) or less.

[0028] The conductive metal oxide may be RuO2, InSnO, IrO, OsO2, RhO2, Ce where 0≤x≤2 and 0≤y≤3 x O y , where W is 0≤x≤2 and 0≤y≤3 x O y , NbO, Eu2O3, Ti where 0≤x≤2 and 0≤y≤3 x O y , Mn2O3 or PbO2.

[0029] The solid electrolyte layer may have at least one compound having a NASICON structure, a garnet structure, or a perovskite structure.

[0030] The solid electrolyte layer may include Li wherein 0≤a≤1 1+a Al a Ti 2-a (PO4)3(LATP), Li with 5≤a≤9 a La3Zr2O 12 (LLZO), or La 0.55 Li 0.35 At least one of TiO3 (LLTO).

[0031] The method may further include providing a gas diffusion layer on at least one surface of the positive electrode layer.

[0032] According to one aspect, a metal-air battery is provided, wherein the metal-air battery comprises: a negative electrode layer comprising a metal; a positive electrode layer, wherein the porosity of the positive electrode layer is greater than 0 volume percent and less than or equal to about 90 volume percent, based on the total volume of the positive electrode layer; a solid electrolyte layer between the negative electrode layer and the positive electrode layer; and a binding layer disposed between the positive electrode layer and the solid electrolyte layer, wherein the binding layer comprises at least one of Pt, Au, Mn, Co, Ni, Cr, V, Fe, Pb, or Sn. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and other aspects, features and advantages of some embodiments of the present disclosure will become more apparent from the following description considered in conjunction with the accompanying drawings, in which:

[0034] Figure 1 A cross-sectional view schematically illustrating an embodiment of a metal-air battery;

[0035] Figure 2 SEM images of embodiments of the positive electrode layer, solid electrolyte layer, and bonding layer;

[0036] Figures 3A to 3E A cross-sectional view schematically illustrating an embodiment of a method for manufacturing a metal-air battery;

[0037] Figure 4 A cross-sectional view illustrating a comparative example of a metal-air battery;

[0038] Figure 5A is an SEM image of an embodiment of a positive electrode;

[0039] Figure 5B SEM image of the comparative example of the positive electrode;

[0040] Figure 6A is a cross-sectional view schematically illustrating an embodiment of the configuration of a metal-air battery;

[0041] Figure 6B A cross-sectional view of a comparative example schematically illustrating the configuration of a metal-air battery; and

[0042] Figure 7 、 8A 8B and 8B are each a graph of voltage (volts, V) versus capacity (milliampere-hours, mAh), illustrating charge and discharge simulation results for example and comparative example metal-air batteries.

[0043] Figure 9 is a graph of capacity (mAh) versus number of charge and discharge cycles for Examples and Comparative Examples. DETAILED DESCRIPTION

[0044] The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which various embodiments are shown. However, the present invention can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art.

[0045] It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.

[0046] It will be understood that although the terms "first," "second," "third," etc., may be used herein to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Therefore, without departing from the teachings herein, the "first element," "component," "region," "layer," or "part" discussed below may be referred to as a second element, component, region, layer, or part.

[0047] The terms used herein are only for the purpose of describing specific embodiments and are not intended to be restrictive. As used herein, "one (kind) (indefinite article) (a, an)", "said (the)" and "at least one (kind)" do not represent the limitation of quantity, and are intended to cover both the singular and the plural, unless the context clearly states otherwise. For example, "(an) element" has the same meaning as "at least one element", unless the context clearly states otherwise. "At least one (kind)" will not be interpreted as limiting "one (kind)". "Or" means "and / or". As used herein, the term "and / or" includes any and all combinations of one or more of the relevant enumerated items. It will be further understood that the term "comprising" or "including" when used in this specification indicates that there are stated features, regions, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, regions, wholes, steps, operations, elements, components, and / or their sets.

[0048] In addition, relative terms such as "lower" or "bottom" and "upper" or "top" may be used herein to describe the relationship of one element to another element as shown in the figures. It will be understood that relative terms are intended to include different orientations of the device in addition to the orientations shown in the figures. For example, if the device in one of the figures is turned over, an element described as being on the "lower" side of another element will be oriented on the "upper" side of the other element. Thus, depending on the specific orientation of the figure, the exemplary term "lower" may include both "lower" and "upper" orientations. Similarly, if the device in one of the figures is turned over, an element described as being "below" or "beneath" another element will be oriented "above" the other element. Thus, the exemplary terms "below" or "beneath" may include both "above" and "below" orientations.

[0049] As used herein, "about" or "approximately" is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art taking into account the measurements in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system). For example, "about" can mean within one or more standard deviations, or within ±30%, 20%, 10%, or 5% relative to the stated value.

[0050] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and this disclosure, and will not be interpreted in an idealized or overly formal sense unless clearly so defined herein.

[0051] Exemplary embodiments are described herein with reference to cross-sectional views that are schematic representations of idealized embodiments. As such, deviations from the shapes of the figures are to be expected as a result of, for example, manufacturing techniques and / or tolerances. Therefore, the embodiments described herein should not be construed as limited to the specific shapes of the regions as illustrated herein, but rather include deviations in shape resulting from, for example, manufacturing. For example, a region illustrated or described as flat may typically have rough and / or nonlinear features. Furthermore, illustrated sharp corners may be rounded. Therefore, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of the regions and are not intended to limit the scope of the claims.

[0052] Hereinafter, the metal-air battery according to the embodiment will be described in further detail with reference to the accompanying drawings. For clarity, the width and thickness of the layers or regions shown in the drawings may be exaggerated. The same reference numerals refer to the same elements throughout.

[0053] Figure 1 is a cross-sectional view schematically illustrating an embodiment of a metal-air battery. Figure 2 2 is an SEM image of an embodiment of a positive electrode layer, a solid electrolyte layer, and a bonding layer.

[0054] refer to Figure 1 The metal-air battery includes: a negative electrode layer 10 including a metal; and a positive electrode layer 30 spaced apart from the negative electrode layer 10. The positive electrode layer 30 includes a conductive metal oxide 31. The solid electrolyte layer 20 is disposed between the negative electrode layer 10 and the positive electrode layer 30. A bonding layer 50 that can bond the conductive metal oxide 31 to the solid electrolyte layer 20 is disposed between the solid electrolyte layer 20 and the positive electrode layer 30. The positive electrode layer 30 includes a conductive metal oxide 31. The metal-air battery may further include a gas diffusion layer 40 in contact with at least one surface of the positive electrode layer 30. The gas diffusion layer 40 can supply oxygen (O2) to the positive electrode layer 30. The positive electrode layer 30 may further include a positive electrode catalyst and may be a "positive electrode catalyst layer." A positive electrode layer further including a catalyst may be referred to as a "positive electrode." The positive electrode layer 30 and the gas diffusion layer 40 may be configured as a "positive electrode portion." In one aspect, the positive electrode portion of the metal-air battery includes the positive electrode layer 30 and, optionally, may further include the gas diffusion layer 40.

[0055] The negative electrode layer 10 may include a material capable of absorbing and releasing metal ions. The material may include, for example, lithium (Li), sodium (Na), zinc (Zn), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), aluminum (Al), or alloys thereof. For example, the negative electrode layer 10 may include lithium (Li). The negative electrode layer 10 may include at least one of lithium, a lithium-based alloy, or a lithium intercalation compound. When the negative electrode layer 10 includes lithium, the metal-air battery may be referred to as a "lithium-air battery."

[0056] The solid electrolyte layer 20 may include an inorganic material comprising lithium ion conductive glass, crystalline lithium ion conductive ceramic or glass-ceramic, or a combination thereof. For example, the solid electrolyte layer 20 may include a Li-ion conductive glass having a NASICON structure. 1+ a Al a Ti 2-a (PO4)3(LATP)(0≤a≤1), for example, with NASICON (i.e., Na 1+x Zr2Si x P 3-x O 12, materials isomorphic to (0 < x < 3). For example, in aspects where the solid electrolyte layer 20 comprises a material having a NASICON structure, although moisture may be present in the positive electrode layer 30 because the positive electrode layer 30 includes a hydrous electrolyte material 33, and although not wishing to be bound by theory, it is understood that the moisture does not pass through the solid electrolyte layer 20, and thus, the solid electrolyte layer 20 can be used as a protective film that prevents the moisture included in the hydrous electrolyte material 33 from directly reacting with the lithium included in the negative electrode layer 10. Additionally, and although not wishing to be bound by theory, it is understood that the ionic conductivity of the solid electrolyte layer 20 comprising a material having a NASICON structure is more improved compared to the ionic conductivity of a solid electrolyte layer 20 having another structure. When the solid electrolyte layer 20 comprises a compound having a garnet structure such as Li a La3Zr2O 12 (LLZO) (5 ≤ a ≤ 9), or a compound having a perovskite structure such as La 0.55 Li 0.35 TiO3 (LLTO), the ionic conductivity can also be improved. Additionally, the solid electrolyte layer 20 can also comprise a material having a layered rock salt crystal structure or a material having a thiogermanate crystal structure. Additionally, in addition to the glass-ceramic component, the solid electrolyte layer 20 can further comprise, for example, a polymer solid electrolyte component. The polymer solid electrolyte can be a lithium salt-doped poly(ethylene oxide). The lithium salt can include at least one of LiBF4, LiPF6, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiN(SO3CF3)2, LiC4F9SO3, or LiAlCl4. The positive electrode layer 30 can be an air electrode and can be configured to use oxygen (O2) in the air as an active material. For the electrochemical reaction of metal ions supplied from the negative electrode layer 10 and a gas (e.g., oxygen from the air) supplied to the positive electrode layer 30, the conductive metal oxide 31 can provide a path for the migration of electrons, such as electron transport, and the metal oxide 31 can comprise a material having suitable electronic conductivity. For example, the conductive metal oxide 31 can be RuO2, InSnO, IrO, OsO2, RhO2, Ce x O y where 0 ≤ x ≤ 2 and 0 ≤ y ≤ 3, W x O y where 0 ≤ x ≤ 2 and 0 ≤ y ≤ 3, NbO, Eu2O3, Ti x O y where 0 ≤ x ≤ 2 and 0 ≤ y ≤ 3, Mn2O3 or PbO2. The conductive metal oxide can include other suitable materials.

[0057] The conductive metal oxide may have a -6 Siemens / cm (S / cm) is about 1.0×10 1 S / cm, about 2.0×10 -6 S / cm is about 1.0×10 1 S / cm, about 2.0×10 -6 S / cm to about 5.0S / cm, about 4.0×10 -6 S / cm to about 5.0S / cm, about 4.0×10 -6 S / cm to about 1.0S / cm, about 5.0×10 -6 S / cm to about 1.0S / cm, about 1.0×10 -5 S / cm to about 1.0S / cm, about 2.0×10 -5 S / cm to about 1.0S / cm, about 4.0×10 -5 S / cm to about 1.0S / cm, about 5.0×10 -5 S / cm to about 1.0S / cm, about 1.0×10 -4 S / cm to about 1.0S / cm, about 2.0×10 -4 S / cm to about 1.0S / cm, about 2.0×10 -4 S / cm is about 5.0×10 -1 S / cm, or about 2.0×10 -4 S / cm is about 1.0×10 -1 The electronic conductivity is measured in s / cm. The electronic conductivity can be measured by the eddy current method or the Kelvin bridge method. The electronic conductivity can be measured by the eddy current method or the Kelvin bridge method. The electrical conductivity can be measured according to ASTM B-193, "Standard Test Method for Resistivity of Electrical Conductor Materials," for example at 20°C, or according to ASTM E-1004, "Standard Test Method for Determining Electrical Conductivity Using the Electromagnetic (Eddy-Current) Method," for example at 20°C. Additional details can be determined by those skilled in the art without undue experimentation.

[0058] For example, the positive electrode layer 30 may further include an aqueous electrolyte material 33 , which may provide suitable ion conductivity.

[0059] The electrolyte comprises a suitable salt and may include an alkali metal such as Li +or at least one of an alkaline earth metal. The alkali metal may be at least one of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), or francium (Fr). The alkaline earth metal may be at least one of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), or radium (Ra).

[0060] The aqueous electrolyte material may include at least one of the following: mono- or polyprotic (mono- or polybasic) organic acid salts, substituted carboxylic acids, carboxylic acid derivatives, lactones, esters of inorganic acids, sulfur-containing organic acids, phenols, inorganic neutral or acid salts, amphoteric hydroxides, A salt, halide, sulfide, sulfate, nitrate, or carbonate of an alkali metal or alkaline earth metal. For example, the salt may include at least one of LiBr, LiCl, NaBr, NaCl, zinc nitrate, magnesium nitrate, lithium dihydrogen phosphate, or lithium hydrogen selenite. The aqueous electrolyte material 33 may be an aqueous solution including water vapor (H2O) or water vapor (H2O) and at least one of Li2SO4, NH4Cl, LiCl, or lithium bis(pentafluoroethanesulfonyl)imide (LiBETI).

[0061] The concentration of the salt in the aqueous electrolyte material can be from about 0.01 molar (M) to about 1M, such as from about 0.02M to about 0.9M, or from about 0.04M to about 0.7M, or from about 0.08M to about 0.5M.

[0062] like Figure 1 As shown in , the aqueous electrolyte material 33 may be provided on the binding layer 50 and may be in the form of drops including water and salt. In one aspect, the positive electrode layer 30 may be an electrode that does not include an organic electrolyte, that is, it may be an electrode without an organic electrolyte. When the organic electrolyte cannot be detected when the electrolyte is analyzed by Fourier transform infrared spectroscopy (FT-IR), the electrode may be determined to be an electrode without an organic electrolyte.

[0063] When the metal-air battery according to the embodiment is a lithium-air battery, electrochemical reaction 1 occurs in the positive electrode portion during discharge.

[0064] Electrochemical reaction 1

[0065] 4Li + (放电) +O 2(放电) +2H2O (放电) +4e - →4LiOH (固体)

[0066] The lithium ions (Li + ) and oxygen (O2) provided from the atmosphere (air) can react with electrons (e -) combines (reacts) to produce LiOH, which is a solid. The conductive metal oxide 31 and the aqueous electrolyte material 33 included in the positive electrode layer 30 can provide electron transport, such as for electrons (e - ) migration pathways, and provide ion transport, such as for lithium ions (Li + ). LiOH may be produced and is an example of a reaction product. During charging, the discharge reaction may be reversed.

[0067] In order to make oxygen (O2) supplied from the atmosphere (air) and electrons (e - ) is combined (reacted) on the surface of the positive electrode layer 30, and the positive electrode layer 30 according to the example may be configured to include an empty space, such as a hole or a void. Therefore, the positive electrode layer 30 may include a void such as an air gap or a hole. A plurality of voids may be randomly arranged in the positive electrode layer 30. The positive electrode layer 30 according to the embodiment may include a conductive metal oxide 31, and the conductive metal oxide 31 may include a plurality of particles, such as Figure 1 As shown in , a plurality of voids may be randomly disposed between a plurality of particles of the conductive metal oxide 31 .

[0068] The voids in the positive electrode layer 30 may be spaces where reaction products are formed and, at the same time, may provide a path for gas (oxygen) to move through it. When the voids are not filled with electrolyte and are left empty or when the voids are only partially filled, gas (oxygen) may be supplied with improved uniformity.

[0069] Because as the porosity of the positive electrode layer 30 increases, the reaction area (area) of the battery increases, the capacity can be increased and the energy density can be increased. The porosity of the positive electrode layer 30 can be, for example, about 90 volume percent (volume %) or less, based on the total volume of the positive electrode layer. The porosity can be greater than 0 volume % to less than or equal to about 90 volume %, about 10 volume % to about 80 volume %, about 20 volume % to about 70 volume %, or about 30 volume % to about 60 volume %, based on the total volume of the positive electrode layer. In addition, as the specific surface area of ​​the positive electrode layer 30 increases, the reaction area of ​​the battery increases. When the reaction area of ​​the battery increases, the capacity can be increased and the energy density can be increased. The specific surface area of ​​the positive electrode layer 30 can be, for example, about 1 square meter / gram (m 2 / g) or more. The specific surface area may be about 1 square meter / gram (m 2 / g) to about 1000m 2 / g, about 1.5m 2 / g to about 500m 2 / g, about 2m 2 / g to about 100m 2 / g, about 5m 2 / g to about 50m 2 / g, or about 7m 2 / g to about 25m 2 / g. The specific surface area can be determined using a nitrogen isotherm. See, for example, EP Barrett, LG Joyner, PP Halenda, “The determination of pore volume and area distributions in porous substances. I. Computations from nitrogen isotherms”, J. Am. Chem. Soc. (1951), 73, 373–380, the contents of which are incorporated herein by reference in their entirety.

[0070] The positive electrode layer 30 may be porous, and the conductive metal oxide 31 included in the positive electrode layer 30 may include a plurality of particles to form voids. When the conductive metal oxide 31 is formed of a plurality of particles and the plurality of particles are combined together, the connection between the plurality of particles may be weak, and thus, the electrode form of the positive electrode layer 30 may be difficult to maintain during the charge and discharge process. Due to this weak connection, separation and peeling may occur between the positive electrode layer 30 and the solid electrolyte layer 20, which may weaken the charge and discharge characteristics of the metal-air battery.

[0071] The bonding layer 50 is a bonding member provided between the positive electrode layer 30 and the solid electrolyte layer 20 to bond the positive electrode layer 30 to the solid electrolyte layer 20. The bonding layer 50 may have a melting point lower than the melting point and / or sublimation point (e.g., at 1 atm) of the conductive metal oxide 31 included in the positive electrode layer 30. Therefore, during sintering of the bonding layer 50 provided between the solid electrolyte layer 20 and the conductive metal oxide 31, only the bonding layer 50 may be melted without any change in the conductive metal oxide 31, such as a change in shape or composition. During cooling of the melted bonding layer 50, the bonding layer 50 may bond the conductive metal oxide 31 to the solid electrolyte layer 20, as shown in FIG. Figure 2 As shown in . Figures 3A to 3E A more detailed process of bonding the conductive metal oxide 31 to the solid electrolyte layer 20 by using the bonding layer 50 is described.

[0072] The bonding layer 50 according to the example may include a material having electronic conductivity, for example, at least one of Pt, Au, Mn, Co, Ni, Cr, V, Fe, Pb, or Sn. Furthermore, the thickness of the bonding layer 50 according to the example may be approximately 10 nm or less, and thus, the specific surface area may be increased. As further described above, a portion of the conductive metal oxide 31 may be provided in contact with the bonding layer 50, and the gas diffusion layer 40 may be provided on the other surface of the positive electrode layer including the conductive metal oxide 31.

[0073] The gas diffusion layer 40 absorbs oxygen and carbon dioxide from the atmosphere and supplies them to the positive electrode layer 30. The gas diffusion layer 40 may have a porous structure to facilitate the smooth diffusion of oxygen and carbon dioxide. For example, the gas diffusion layer 40 may include at least one of carbon paper, carbon cloth, carbon felt (including carbon fibers), spongy metal foam, or metal fiber felt. Alternatively, the gas diffusion layer 40 may include a non-conductive, flexible, porous material, such as a nonwoven fabric. The positive electrode layer 30 may have a porous structure or other suitable structure and may function as both a gas diffusion layer and a positive electrode layer. In this case, the gas diffusion layer 40 may be omitted.

[0074] Despite Figure 1 Although not shown, a negative electrode current collector in contact with the negative electrode layer 10 may be further provided. The negative electrode current collector may be provided on the bottom surface of the negative electrode layer 10. Therefore, the negative electrode layer 10 may be disposed between the negative electrode current collector and the solid electrolyte layer 20. The negative electrode current collector may include, for example, copper (Cu), stainless steel (SUS), silver (Ag), magnesium (Mg), or other suitable conductors. In addition, a positive electrode current collector in contact with the gas diffusion layer 40 may be further provided. The positive electrode current collector may be provided on the upper surface of the gas diffusion layer 40. Therefore, the gas diffusion layer 40 may be disposed between the positive electrode current collector and the positive electrode layer 30. The positive electrode current collector may include, for example, stainless steel (SUS) or a porous carbon material. When the positive electrode current collector includes SUS, the SUS may have a mesh structure for the permeation of air (gas). The material of the positive electrode current collector is not limited to SUS, and may be other suitable materials such as aluminum. When the gas diffusion layer 40 is not used, the positive electrode current collector may be in contact with the positive electrode layer 30. The negative electrode portion may include a negative electrode current collector, and similarly, the positive electrode portion may include a positive electrode current collector.

[0075] Figures 3A to 3E A cross-sectional view schematically illustrating an embodiment of a method for manufacturing a metal-air battery.

[0076] refer to Figure 3A According to an embodiment, a solid electrolyte layer 20 may be provided. For example, the solid electrolyte layer 20 may be provided in a flat sheet shape, such as in the form of a film or layer. In addition, the solid electrolyte layer 20 may include a compound having a NASICON structure, such as Li 1+a Al a Ti 2-a (PO4)3(LATP)(0≤a≤1), compounds with garnet structure such as Li a La3Zr2O 12 (LLZO) (5≤a≤9), or compounds with a perovskite structure such as La 0.55 Li 0.35 At least one of TiO3 (LLTO).

[0077] refer to Figure 3B According to an embodiment, the upper surface of the solid electrolyte layer 20 may be coated with a bonding layer 50. For example, the upper surface of the solid electrolyte layer 20 may be coated with the bonding layer 50 by using a sputtering method. At this time, the bonding layer 50 may include at least one of Pt, Au, Mn, Co, Ni, Cr, V, Fe, Pb, or Sn.

[0078] refer to Figure 3C , a metal oxide composite layer 60 including the conductive metal oxide 31 may be provided on the upper surface of the bonding layer 50. For example, the conductive metal oxide composite layer 60 may be formed in a thin sheet shape, for example, as a layer, and include the conductive metal oxide 31 and a binder (not shown). For example, the metal oxide composite layer 60 may be a product of coating a mixture including the conductive metal oxide 31. The mixture including the conductive metal oxide may be formed by mixing and grinding the conductive metal oxide 31 and a binder (not shown), such as ruthenium oxide (RuO2) and 30 weight percent (wt%) polyvinyl butyral, using a mixer for approximately 1 hour, and thereafter, the conductive metal oxide 31 and binder slurry may be bar coated and dried to provide the metal oxide composite layer 60 having a thin sheet shape.

[0079] According to an embodiment, the metal oxide composite layer 60 may be provided on the upper surface of the bonding layer 50. The metal oxide composite layer 60 may be supported by the bonding layer 50 by using a material capable of applying a predetermined force, such as ethanol.

[0080] refer to Figure 3D , the solid electrolyte layer 20, the bonding layer 50, and the metal oxide composite layer 60 can be heat-treated at a predetermined temperature. For example, the composite of the solid electrolyte layer 20, the bonding layer 50, and the metal oxide composite layer 60 can be placed in a furnace 70 and heat-treated at a predetermined temperature. The composite of the solid electrolyte layer 20, the bonding layer 50, and the metal oxide composite layer 60 can have a temperature lower than a predetermined temperature, such as the melting point and / or sublimation point (at 1 atmosphere) of the conductive metal oxide 31 included in the metal oxide composite layer 60, and can be heated to a temperature higher than the melting point of the material included in the bonding layer 50. For example, the internal temperature of the furnace 70 can be about 500°C to about 800°C, and the temperature range is not limited thereto. The temperature of the heat treatment can be about 525°C to about 775°C, about 550°C to about 750°C, about 575°C to about 725°C, or about 600°C to about 700°C. The heat treatment can continue for a predetermined amount of time, such as from about 1 hour to about 24 hours, from about 2 hours to about 20 hours, from about 4 hours to about 16 hours, or from about 6 hours to about 12 hours.

[0081] When the composite of the solid electrolyte layer 20, the bonding layer 50, and the metal oxide composite layer 60 is heat-treated, the binder (not shown) included in the metal oxide composite layer 60 may be removed. In addition, the material included in the bonding layer 50 may be melted. In one aspect, because the melting point and / or sublimation point (at 1 atmosphere) of the conductive metal oxide 31 may be greater than the melting point of the bonding layer 50, the metal oxide 31 may not melt. Since the bonding layer 50 melts, a portion of the conductive metal oxide 31 included in the metal oxide composite layer 60 is buried in the bonding layer 50, and therefore, the bonding layer 50 may bond the conductive metal oxide 31 to the solid electrolyte layer 20.

[0082] refer to Figure 3E , a negative electrode layer 10 may be provided on the lower surface of the solid electrolyte layer 20. For example, the negative electrode layer 10 may be a lithium metal layer, but the negative electrode layer is not limited thereto, and any other suitable negative electrode material may be used.

[0083] Figure 4 A cross-sectional view illustrating a comparative example of a metal-air battery. Figure 5A is a SEM image of an embodiment of a positive electrode. Figure 5B The SEM image of the positive electrode of the comparative example.

[0084] refer to Figure 4 The metal-air battery according to the comparative example may include: a negative electrode layer 10 including a metal and a positive electrode layer 30 spaced apart from the negative electrode layer 10. The positive electrode layer 30 may include a conductive metal oxide 31. The solid electrolyte layer 20 may be provided between the negative electrode layer 10 and the positive electrode layer 30. The metal-air battery may further include a gas diffusion layer 40 in contact with at least one surface of the positive electrode layer 30. Figure 4 The metal-air battery according to the comparative example shown in does not include the bonding layer 50 capable of bonding the conductive metal oxide 31 to the solid electrolyte layer 20 .

[0085] In the metal-air battery according to the embodiment, the solid electrolyte layer 20 may include, for example, a LATP material, and a conductive metal oxide 31 such as ruthenium oxide (RuO2) (for example, in the form of nanopowder) may be provided on the upper portion of the solid electrolyte layer 20. When the conductive metal oxide 31 is ruthenium oxide (RuO2), the amount of electrode loading may be increased to about 0.8 mg / cm2 (mg / cm 2 ). Platinum (Pt) may be coated on the upper surface of the solid electrolyte layer 20 in a predetermined thickness, for example, a thickness of about 7 nanometers (nm) as a bonding layer 50. When the conductive metal oxide 31 and the bonding layer 50 described above are sintered at about 800° C. for about 4 hours, the electrode including the conductive metal oxide 31 may be maintained, as shown in FIG. Figure 5AIn a metal-air battery including this electrode, electrical conductivity can be increased, and charge and discharge characteristics can also be improved.

[0086] In the metal-air battery according to the comparative example, the solid electrolyte layer 20 may include, for example, a LATP material, and a conductive metal oxide 31, for example, ruthenium oxide (RuO2) in the form of a nanopowder, is provided on the upper portion of the solid electrolyte layer 20. When the conductive metal oxide 31 is ruthenium oxide (RuO2), the amount of electrode loading may be increased to about 0.8 mg / cm 2 However, when a separate bonding layer is not provided between the solid electrolyte layer 20 and the conductive metal oxide 31, the electrode formed by the conductive metal oxide 31 may be destroyed, as shown in FIG. Figure 5B In the comparative example, the metal-air battery including the electrode formed without a separate bonding layer had reduced electrical conductivity, and reduced charge and discharge capabilities.

[0087] Figure 6A A cross-sectional view illustrating an embodiment of the configuration of a metal-air battery. Figure 6B This is a cross-sectional view of a comparative example illustrating the configuration of a metal-air battery. The configuration can be a test structure for evaluating the performance of a metal-air battery.

[0088] refer to Figure 6A and 6B The metal-air battery according to the embodiment and the comparative example is in the form of a coin cell. The battery elements may be provided in a housing 180 having a plurality of open areas H1. A support structure 110 may be provided on the lower surface of the housing 180. The support structure 110 may include, for example, a spacer and a spring member. A negative electrode layer 10 including a metal may be provided on the support structure 110. A solid electrolyte layer 20 may be provided on the negative electrode layer 10.

[0089] In an embodiment, the bonding layer 50 may be provided on the upper portion of the solid electrolyte layer 20. The positive electrode layer 30 including the conductive metal oxide 31 may be provided on the upper portion of the bonding layer 50. Figure 6B As shown in FIG, the bonding layer 50 is not provided between the solid electrolyte layer 20 and the positive electrode layer 30 .

[0090] The positive electrode layer 30 in the embodiment and the comparative example may have a structure including a plurality of voids. A conductive material layer (hereinafter referred to as a "conductive layer") 160 may be provided on the positive electrode layer 30, and a gas diffusion layer 40 may be provided on the conductive layer 160. The gas diffusion layer 40 may be provided adjacent to the plurality of open areas H1 to supply external air to the positive electrode layer 30.

[0091] As an example, the negative electrode layer 10 may include Li, and the solid electrolyte layer 20 may include lithium aluminum titanium phosphate (LATP) as a solid electrolyte. LATP may be Li 1+x Al x Ti 2-x (PO4)3, where x may be approximately 0.3. The positive electrode layer 30 may include ruthenium oxide (RuO2) as the conductive metal oxide 31. For example, the conductive layer 160 may include at least one of Au, Ag, Pd, or Pt. A bonding layer including platinum (Pt) in the form of nanopowder may be provided between the positive electrode layer 30 and the solid electrolyte layer 20.

[0092] analyze Figure 6A and 6B The metal-air battery depicted in Figure 1 was tested to confirm whether atmospheric oxygen (O2) was reduced / oxidized on the surface of the positive electrode layer 30. In this analysis, characteristics were evaluated in an oxygen (O2) atmosphere and in a water vapor (H2O) atmosphere. Here, water vapor (H2O) may be an aqueous electrolyte material. The cycling characteristics of the metal-air batteries according to the embodiment and the comparative example were evaluated by repeatedly subjecting the metal-air batteries to charge and discharge cycles.

[0093] Figure 7 、 8A 8B are graphs illustrating voltage (V) versus charge capacity (milliampere-hour, mAh) of metal-air batteries according to Examples and Comparative Examples. Figure 9 Graphs illustrating capacity (mAh) versus number of charge and discharge cycles (-) according to Examples and Comparative Examples.

[0094] Figures 7 to 9 The figures are obtained using COMSOL analysis program according to the embodiment and comparative example. COMSOL Multiphysics is a cross-platform finite element analysis, solution and multi-physics simulation software. Figures 7 to 9 Analysis of the graphs shown in assumes that the bonding layer 50 is provided between the solid electrolyte layer 20 and the positive electrode layer 30 for the embodiment, and assumes that no bonding layer 50 is provided between the solid electrolyte layer 20 and the positive electrode layer 30 for the comparative example.

[0095] refer to Figure 7 The metal-air batteries according to the examples and comparative examples were tested at 0.02 mA / cm 2 The battery was charged and discharged once to 0.3 mAh. In the embodiment in which the bonding layer 50 was provided between the solid electrolyte layer 20 and the positive electrode layer 30, the discharge potential was 2.9 V, while in the comparative example in which the bonding layer 50 was not provided between the solid electrolyte layer 20 and the positive electrode layer 30, the discharge potential was reduced to 2.75 V.

[0096] refer to Figure 8A and8B , after multiple charge and discharge cycles, the capacities of the metal-air batteries according to the embodiment and the comparative example are shown. In the embodiment in which the bonding layer 50 is provided between the solid electrolyte layer 20 and the positive electrode layer 30, a uniform potential is provided throughout the charge and discharge cycles, while in the comparative example in which no bonding layer is provided between the solid electrolyte layer 20 and the positive electrode layer 30, the overvoltage continues to increase.

[0097] refer to Figure 9 , after multiple charge and discharge cycles up to a predetermined discharge voltage, the capacities of the metal-air batteries according to the embodiment and the comparative example are shown. In the embodiment in which the bonding layer 50 is provided between the solid electrolyte layer 20 and the positive electrode layer 30, it was confirmed that charging and discharging were performed up to a total of 89 times at a uniform discharge potential, while in the comparative example in which the bonding layer 50 is not provided between the solid electrolyte layer 20 and the positive electrode layer 30, it was confirmed that charging and discharging were performed up to 52 times.

[0098] In the embodiment in which the bonding layer 50 is provided between the solid electrolyte layer 20 and the positive electrode layer 30 , overvoltage can be reduced and reproducibility and charge capacity can be improved.

[0099] Example

[0100] Comparative Example: Metal-Air Battery Without Binding Layer

[0101] Will use Li 1.3 Al 0.3 Ti 1.7 A metal-air battery was prepared using (PO4)3 as a solid electrolyte layer and lithium metal as a negative electrode layer. The metal oxide composite layer was formed by mixing and grinding ruthenium oxide (RuO2) and polyvinyl butyral (30 wt%) using a mixer for approximately 1 hour, and then the slurry was bar coated and dried to form the metal oxide composite layer. The metal oxide composite layer will be disposed on the upper portion of the solid electrolyte layer to provide the positive electrode of the battery. The electrode loading will be approximately 0.8 mg / cm 2 The positive electrode in the battery is destroyed during the charge and discharge cycles.

[0102] Example: Metal-Air Battery Including a Bonding Layer

[0103] The metal air battery will be prepared in the same manner as the comparative example, except that a separate bonding layer will be provided between the solid electrolyte layer and the metal oxide composite layer. 7 nm of platinum will be coated on the upper surface of the solid electrolyte layer as a bonding layer. The metal oxide composite layer (RuO2) and the bonding layer will be sintered at 800°C for 4 hours. The electrode loading will be approximately 0.8 mg / cm 2 .

[0104] Without wishing to be bound by theory, it is understood that when the bonding layer 50 is provided between the solid electrolyte layer 20 and the positive electrode layer 30, the efficiency of the metal-air battery can be improved because the damage of the positive electrode layer 30 is reduced and the electrical conductivity between the conductive metal oxide 31 included in the positive electrode layer 30 is increased, which reduces the overpotential effect. Therefore, the positive electrode of the metal-air battery according to the embodiment in which the bonding layer 50 is provided between the solid electrolyte layer 20 and the positive electrode layer 30 can improve performance and extend the life of the battery.

[0105] Although many aspects have been described in detail in the foregoing description, these aspects should be interpreted as illustrations of specific embodiments, rather than as limitations on scope. For example, those skilled in the art will appreciate that the structure of the metal-air battery according to the embodiments may be modified. Therefore, the scope should not be limited by the disclosed embodiments.

[0106] According to embodiments, a metal-air battery has excellent performance. According to embodiments, a metal-air battery has excellent charge and discharge characteristics. According to embodiments, when a bonding layer is provided between a conductive metal oxide and a solid electrolyte, deformation of a positive electrode in a metal-air battery can be prevented.

[0107] It should be understood that the embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features, aspects, or advantages in various embodiments should be considered applicable to other similar features, aspects, or advantages in other embodiments. Although embodiments have been described with reference to the accompanying drawings, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the spirit and scope as defined by the appended claims.

Claims

1. Metal-air batteries, including: a negative electrode layer comprising a metal; a positive electrode layer comprising a conductive metal oxide; a solid electrolyte layer between the negative electrode layer and the positive electrode layer; as well as a bonding layer having a melting point lower than that of the positive electrode layer, which is provided between the positive electrode layer and the solid electrolyte layer and bonds the positive electrode layer to the solid electrolyte layer, where the conductive metal oxide is RuO2, indium tin oxide, IrO2, OsO2, RhO2, Ce where 0 < x ≤ 2 and 0 < y ≤ 3 x O y , W where 0 < x ≤ 2 and 0 < y ≤ 3 x O y , NbO, Eu2O3, Ti where 0 < x ≤ 2 and 0 < y ≤ 3 x O y , at least one of Mn2O3 or PbO2.

2. The metal-air battery of claim 1, wherein the bonding layer comprises at least one of Pt, Au, Mn, Co, Ni, Cr, V, Fe, Pb, or Sn. 3 . The metal-air battery according to claim 1 , wherein the thickness of the bonding layer is 10 nanometers or less. The metal-air battery of claim 1 , wherein the positive electrode layer is porous. 5 . The metal-air battery according to claim 4 , wherein the porosity of the positive electrode layer is 90 volume percent or less based on the total volume of the positive electrode layer. 6 . The metal-air battery according to claim 4 , wherein the positive electrode layer has a specific surface area of ​​1 m 2 / g or more. 7 . The metal-air battery according to claim 1 , wherein the solid electrolyte layer comprises at least one compound having a NASICON structure, a garnet structure, or a perovskite structure.

8. The metal-air battery according to claim 7, wherein the compound is Li wherein 0≤a≤1 1+a Al a Ti 2-a (PO4)3, where 5≤a≤9 Li a La3Zr2O 12 , or La 0.55 Li 0.35 At least one of TiO3.

9. The metal-air battery of claim 1, further comprising: A gas diffusion layer is provided on at least one surface of the positive electrode layer.

10. The metal-air battery of claim 1, wherein the positive electrode layer does not include an organic electrolyte.

11. A method for manufacturing a metal-air battery according to any one of claims 1 to 10, the method comprising: providing a solid electrolyte layer; coating the surface of the solid electrolyte layer with a bonding layer, providing a metal oxide composite layer on the surface of the bonding layer; heat-treating the solid electrolyte layer, the bonding layer, and the metal oxide composite layer; and A negative electrode layer is provided on the surface of the solid electrolyte layer to manufacture a metal-air battery.

12. The method of claim 11, wherein the metal oxide composite layer comprises a conductive metal oxide and a binder.

13. The method of claim 11, wherein the metal oxide composite layer is in the shape of a sheet.

14. The method of claim 12, wherein the heat treatment comprises heat treatment at a temperature of 500°C to 800°C.

15. The method of claim 14, wherein: The heat treatment bonds the conductive metal oxide to the bonding layer.

16. The method of claim 11, wherein the melting point of the bonding layer is lower than the melting point of the metal oxide.

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