Solid electrolyte, method for preparing the same, protective layer, battery, and electrochemical device

Abstract

The present invention relates to a solid electrolyte, a method for preparing the same, a protective layer for a lithium battery, a metal-air battery, and an electrochemical device. The solid electrolyte includes: an oxide represented by Formula 1, wherein, in Formula 1, M is a divalent element, a trivalent element, or a combination thereof, and 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1. Formula 1 Li y M z HfO 3‑x .

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority and benefit of, and all rights arising from, U.S. Provisional Application No. 62 / 947,589, filed on December 13, 2019, with the United States Patent and Trademark Office, and Korean Patent Application No. 10 - 2019 - 0169185, filed on December 17, 2019, with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. Technical field

[0003] The present disclosure relates to a solid electrolyte, a method for preparing the same, a metal - air battery including the solid electrolyte, and an electrochemical device including the solid electrolyte. Background art

[0004] A lithium - air battery uses lithium metal as an anode, and since air is used as a cathode active material, there is no need to store air. Therefore, a lithium - air battery can serve as a high - capacity battery. The theoretical specific energy of a lithium - air battery is 3500 watt - hours per kilogram (Wh / kg) or greater, which is very high.

[0005] However, when lithium lanthanum titanium phosphate (LTAP) or the like is used as a solid electrolyte in a lithium - air battery, the solid electrolyte is unstable due to the presence of LiOH as a discharge product of the lithium - air battery. Therefore, there is a need for an improved solid electrolyte for use in a lithium - air battery. Summary of the invention

[0006] Provided is a solid electrolyte having improved stability in the presence of lithium, and a method for preparing the same.

[0007] Provided is a lithium - air battery including the solid electrolyte.

[0008] Provided is an electrochemical device including the solid electrolyte.

[0009] Additional aspects will be set forth in part in the description which follows and in part will be obvious from the description.

[0010] According to one aspect, the solid electrolyte includes:

[0011] an oxide represented by Formula 1,

[0012] Formula 1

[0013] Li y M z HfO 3-x

[0014] wherein, in Formula 1,

[0015] M is a divalent element, a trivalent element, or a combination thereof, and

[0016] 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1.

[0017] M is a cationic element.

[0018] According to one aspect, a metal-air battery includes: a positive electrode; a negative electrode; and an electrolyte between the positive electrode and the negative electrode, wherein at least one of the positive electrode, the negative electrode, or the electrolyte includes the solid electrolyte.

[0019] A protective layer including the solid electrolyte is also disclosed.

[0020] According to one aspect, an electrochemical device includes: a negative electrode; a positive electrode; and the solid electrolyte between the negative electrode and the positive electrode.

[0021] The electrochemical device may include a battery, an accumulator, a supercapacitor, a fuel cell, a sensor, or an electrochromic device.

[0022] A protective layer for a lithium battery is also disclosed, the protective layer including: the solid electrolyte, wherein the solid electrolyte is disposed on the positive electrode or the negative electrode.

[0023] According to one aspect, a method for preparing a solid electrolyte includes: providing a precursor mixture including a lithium precursor, a hafnium precursor, and an M precursor; and heat-treating the precursor mixture to prepare a solid electrolyte including an oxide represented by Formula 1,

[0024] Formula 1

[0025] Li y M z HfO 3-x

[0026] wherein, in Formula 1, M is a divalent element, a trivalent element, or a combination thereof, and 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1. Description of the Drawings

[0027] The above and other aspects, features, and advantages will become more apparent from the following description when considered in conjunction with the accompanying drawings, wherein:

[0028] Figure 1 Embodiments illustrating the crystal structure of the oxide;

[0029] Figure 2 A graph of intensity in arbitrary units (a.u.) versus diffraction angle (°, 2θ) and spectra of the solid electrolytes of Examples 1 to 11 and Comparative Example 1 analyzed by X-ray diffraction (XRD) using Cu Kα radiation;

[0030] Figure 3 A graph showing the logarithmic ionic conductivity (in Siemens per centimeter (S / cm)) of the solid electrolytes of Examples 1 to 11 and Comparative Example 1; and

[0031] Figure 4 A schematic diagram illustrating a lithium-air battery according to an embodiment.

[0032] Figure 5 A schematic diagram illustrating a lithium-air battery according to an embodiment. Detailed Description

[0033] The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which various embodiments are shown. However, the invention may 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.

[0034] 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.

[0035] 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 sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a “first element,” “component,” “region,” “layer” or “section” discussed below may be referred to as a second element, component, region, layer or section without departing from the teachings herein.

[0036] The terms used herein are for the purpose of describing particular embodiments only and are not intended to be limiting. As used herein, “a,” “an,” “the” and “at least one” do not denote a limitation of quantity and are intended to cover both the singular and the plural, unless the context clearly dictates otherwise. For example, “an element” has the same meaning as “at least one element” unless the context clearly dictates otherwise. “At least one” will not be construed as limiting “a.” “Or” means “and / or.” It will further be understood that the terms “comprises” or “comprising,” when used in this specification, specify the presence of the stated features, regions, wholes, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, regions, wholes, steps, operations, elements, components, and / or groups thereof.

[0037] In addition, relative terms such as "lower" or "bottom" and "upper" or "top" may be used herein to describe a relationship of one element to another element as shown in the figures. It will be understood that the relative terms are intended to include different orientations of the device in addition to the orientation shown in the figures. For example, if the device in one of the figures is turned over, an element described as on the "lower" side of another element will then be oriented on the "upper" side of the other element. Thus, depending on the specific orientation of the figure, the exemplary term "lower" can include both the "lower" and "upper" orientations. Similarly, if the device in one of the figures is turned over, an element described as "beneath" or "under" another element will then be oriented "above" the other element. Thus, the exemplary terms "beneath" or "under" can include both above and beneath.

[0038] As used herein, "about" or "approximately" includes the stated value and means within an acceptable deviation range for a particular value as determined by one of ordinary skill in the art in view of the measurements discussed and the error 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 of the stated value, or within ±30%, 20%, 10%, or 5%.

[0039] 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 that is 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.

[0040] Exemplary embodiments are described herein with reference to cross-sectional views that are schematic illustrations of idealized embodiments. Thus, deviations from the shapes of the figures as a result of, for example, manufacturing techniques and / or tolerances are to be expected. Accordingly, the embodiments described herein should not be construed as limited to the specific shapes of regions as illustrated herein, but include deviations in shapes that result, for example, from manufacturing. For example, regions illustrated or described as flat may typically have rough and / or non-linear features. Also, sharp corners illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the claims.

[0041] Hereinafter, embodiments will be described in detail, and examples thereof are illustrated in the accompanying drawings, in which the same reference numerals always refer to the same elements. In this regard, the present embodiments may have different forms and should not be construed as limited to the description set forth herein. Therefore, the embodiments are described below only by referring to the accompanying drawings to illustrate aspects. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. The expression such as "at least one (kind) of" modifies the entire list of elements when before or after the list of elements and does not modify the individual elements of the list.

[0042] Hereinafter, a solid electrolyte according to an embodiment, a method for preparing the same, a metal-air battery including the solid electrolyte, and an electrochemical device including the solid electrolyte will be described.

[0043] There is provided a solid electrolyte including an oxide represented by Formula 1:

[0044] Formula 1

[0045] Li y M z HfO 3-x

[0046] Wherein, in Formula 1, M is a divalent element, a trivalent element, or a combination thereof, and 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1.

[0047] M is a cationic element.

[0048] The oxide of Formula 1 satisfies charge balance to have a neutral state.

[0049] The oxide has a perovskite crystal structure or a perovskite-like crystal structure. As will be understood by those skilled in the art of solid state science and as used herein, "perovskite structure" or perovskite compound means that the compound is isostructural with perovskite, i.e., CaTiO3. The formula of the perovskite structure is generally referred to as "ABO3", which includes a divalent cation at the A-site 110 and a metal atom at the B-site 120, as Figure 1 shown. According to an embodiment, the oxide may have the following crystal structure: wherein Li, vacancies, and M are each present at the A-site in the perovskite crystal structure, and hafnium (Hf) is present at the B-site in the perovskite crystal structure. M may be, for example, a divalent element, and the crystal structure may have an oxygen-deficient structure based on charge balance.

[0050] The oxide of Formula 1 is an ion conductor having a thermodynamically stable composition. The compound of Formula 1 improves ionic conductivity by having an excess of lithium or oxygen vacancies.

[0051] When a commercially available perovskite solid electrolyte such as lithium lanthanum titanate oxide (LLTO) is used in a lithium-air battery having a lithium negative electrode, titanium (Ti) in the lithium lanthanum titanate oxide solid electrolyte is reduced (decreased). Although not wishing to be bound by theory, it is believed that the reduction of titanium results in mechanical deterioration of the solid electrolyte.

[0052] A solid electrolyte comprising an oxide of Formula 1 has been found to have improved stability and prevent mechanical deterioration of the solid electrolyte when used in a lithium-air battery having a lithium negative electrode.

[0053] Although not wishing to be bound by theory, when the oxide of Formula 1 contains hafnium, hafnium is understood to prevent mechanical deterioration of the solid electrolyte and is considered not to be reduced by lithium. Accordingly, a solid electrolyte containing an oxide of Formula 1 has improved stability in the presence of lithium metal and reduced mechanical degradation. When a lithium-air battery is fabricated using a solid electrolyte containing an oxide of Formula 1, the interface between the solid electrolyte and the lithium negative electrode is stabilized, and the reversibility of the lithium-air battery is stable under humid and / or atmospheric conditions. Although not wishing to be bound by theory, it is understood that the improved stability and reversibility are because the solid electrolyte is an excellent ionic conductor and is stable to moisture and strong bases. A lithium-air battery uses air as a positive electrode active material and lithium as a negative electrode active material.

[0054] A solid electrolyte containing an oxide of Formula 1 is stable to moisture and strong bases, which can be confirmed based on excellent ionic conductivity after exposure to a strong base such as lithium hydroxide and / or moisture.

[0055] In Formula 1, M is a divalent cation element, a trivalent cation element, or a combination thereof.

[0056] According to an embodiment, in Formula 1, x is 0 or from 0.1 to 0.9. x is 0, or from 0.1 to 0.9, from 0.1 to 0.8, from 0.1 to 0.7, from 0.1 to 0.6, from 0.1 to 0.5, or from 0.15 to 0.45, y is from 0.1 to 0.9, from 0.1 to 0.8, from 0.1 to 0.7, from 0.1 to 0.6, from 0.1 to 0.5, or from 0.1 to 0.4, z is from 0.1 to 0.9, from 0.1 to 0.8, from 0.2 to 0.8, or from 0.3 to 0.7, and y + z < 1 is satisfied.

[0057] In Formula 1, the atomic ratio of lithium to hafnium is from about 0.1:1 to less than 1:1, from 0.1:1 to 0.9:1, from 0.1:1 to 0.8:1, from 0.1:1 to 0.4:1, from 0.15:1 to 0.4:1, or from 0.15:1 to 0.3:1.

[0058] The divalent cation element is, for example, Sr, Ba, Ca, Mg, or a combination thereof.

[0059] The trivalent cation element is, for example, La, Ce, Pr, Gd, Y, Sc, or a combination thereof.

[0060] In Formula 1, M is Sr, Ba, Ca, Mg, La, Ce, Pr, Gd, Y, Sc, or a combination thereof.

[0061] In Formula 1, M can be Ba, Sr, Ca, La, Ce, Pr, Y, Sc, or a combination thereof, and x, y, and z are each independently 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1.

[0062] Figure 1 It is a schematic diagram for explaining an embodiment of the crystal structure of the oxide.

[0063] The oxide of Formula 1 has a perovskite crystal structure.

[0064] As Figure 1 shown, in the oxide of Formula 1, Li, vacancy 10, and M are in the A-site 110 of the perovskite crystal structure, and hafnium (Hf) as a tetravalent element is in the B-site 120 of the perovskite crystal structure. M can be, for example, a divalent element.

[0065] Since the oxide has such a structure, oxidation at the A-site is suppressed, and oxygen deficiency (defect) 12 is caused for the charge balance of the oxide. In Figure 1 , reference numeral 11 represents oxygen.

[0066] Different from prior art perovskite solid electrolytes, the oxide of Formula 1 does not include high oxidation state element ions such as tantalum or tungsten, which are not stable in the presence of lithium.

[0067] The oxide represented by Formula 1 can be an oxide represented by Formulas 2 to 9, or a combination thereof,

[0068] Formula 2

[0069] Li y Ba z HfO 3-x

[0070] In Formula 2, 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1,

[0071] Formula 3

[0072] Li y Sr z HfO 3-x

[0073] In Formula 3, 0 ≤ x < 3, 0 < y < 1, 0 < z < 1,

[0074] Formula 4

[0075] Li y Ca z HfO 3-x

[0076] In formula 4, 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1,

[0077] Formula 5

[0078] Li y La z HfO 3-x

[0079] In formula 5, 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1,

[0080] Formula 6

[0081] Li y Ce z HfO 3-x

[0082] In formula 6, 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1,

[0083] Formula 7

[0084] Li y Pr z HfO 3-x

[0085] In formula 7, 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1,

[0086] Formula 8

[0087] Li y Y z HfO 3-x

[0088] In formula 8, 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1, or

[0089] Formula 9

[0090] Li y Sc z HfO 3-x

[0091] wherein, in formula 9, 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1.

[0092] In Formulas 1 to 9, each x can be independently 0 or from 0.1 to 0.9. For example, each x can independently be 0, or from 0.1 to 0.9, from 0.1 to 0.8, from 0.1 to 0.7, from 0.1 to 0.6, from 0.1 to 0.5, or from 0.15 to 0.45, and each y can be independently from about 0.1 to about 0.9, and each z can be independently from 0.1 to 0.9, and y + z < 1.

[0093] In Formulas 1 to 9, each y can be independently from about 0.1 to about 0.9, from about 0.1 to about 0.8, from about 0.1 to about 0.7, from about 0.1 to about 0.6, from about 0.1 to about 0.5, or from about 0.1 to about 0.4, and each z can be from about 0.1 to about 0.9, from about 0.1 to about 0.8, from about 0.2 to about 0.8, or from about 0.3 to about 0.7, and y + z < 1.

[0094] According to an embodiment, in Formulas 1 to 9, each x can be independently 0, from about 0.1 to about 0.5, or from about 0.15 to about 0.45, y can be from about 0.1 to about 0.5 or from about 0.1 to about 0.4, and z can be from about 0.1 to about 0.8 or from about 0.2 to about 0.8.

[0095] Compared with available perovskite oxides, the oxide has improved stability in the presence of lithium. These properties can be confirmed by X-ray diffraction (XRD) analysis.

[0096] Analysis of the oxide of Formula 1 by X-ray diffraction (XRD) using Cu Kα radiation has a diffraction peak at a diffraction angle of 31.0° 2θ ± 1.0° 2θ having an intensity (IA) equal to or greater than the intensity (IB) of the diffraction peak at a diffraction angle of 21.8° 2θ ± 1.0° 2θ. IA / IB is represented by Equation 1.

[0097] Equation 1

[0098] IA / IB = {(intensity of the diffraction peak at a diffraction angle of 31.0° 2θ ± 1.0° 2θ) / (intensity of the diffraction peak at a diffraction angle of 21.8° 2θ ± 1.0° 2θ)}

[0099] IA / IB can be from about 1 to about 25, from about 1.5 to about 20, from about 3 to about 15, from about 5 to about 10, or from about 1.5 to about 21.5.

[0100] The oxide represented by Formula 1 is, for example, Li 0.3 Sr 0.6 HfO 2.75 、Li 0.3 Sr 0.4 HfO 2.55 、Li 0.3 Ba 0.6 HfO2.75 , Li 0.3 , Ba 0.4 , HfO 2.55 , Li 0.3 , Ca 0.6 , HfO 2.75 , Li 0.3 , Ca 0.4 , HfO 2.55 , Li 0.10 , Ca 0.80 , HfO 2.85 , Li 0.20 , Ca 0.60 , HfO 2.7 , Li 0.25 , Ca 0.50 , HfO 2.625 , Li 0.40 , Ca 0.20 , HfO 2.6 , Li 0.10 , Sr 0.80 , HfO 2.85 , Li 0.20 , Sr 0.60 , HfO 2.7 , Li 0.25 , Sr 0.50 , HfO 2.625 , Li 0.40 , Sr 0.20 , HfO 2.6 , Li 0.10 , Ba 0.80 , HfO 2.85 , Li 0.20 , Ba 0.60 , HfO 2.7 , Li 0.25 , Ba 0.50 , HfO 2.625 , Li 0.40 , Ba 0.20 , HfO 2.6 , Li 0.34 , La 0.55 , HfO3, Li 0.34 , Ce 0.55 , HfO3, Li 0.34 , Pr 0.55 , HfO3, Li 0.34 , Y 0.55 , HfO3, Li 0.34 , Sc 0.55 , HfO3, or a combination thereof.

[0101] According to an embodiment, the ionic conductivity of the solid electrolyte at 25 °C is, for example, about 1 × 10 -6 Siemens per centimeter (S / cm) or greater, about 3 × 10 -6S / cm or greater, or about 3×10 -6 S / cm to about 2×10 -5 S / cm, such as about 1×10 -6 S / cm to about 2×10 -5 S / cm. When the solid electrolyte has such a high ionic conductivity, the internal resistance of the lithium-air battery containing the solid electrolyte is further reduced.

[0102] The pellet (granule) density is determined as follows: dividing the mass by the volume, where the volume is determined, for example, by the Archimedes method or by measuring the height and diameter of a cylindrical pellet of the ion conductor (such as when compressed at 1000 kg / cm²). The pellet density of the solid electrolyte is about 4 grams per cubic centimeter (g / cc) to about 7.5 g / cc, about 4.5 g / cc to about 7.3 g / cc, about 4.8 g / cc to about 7.2 g / cc, about 5 g / cc to about 7.5 g / cc, or about 5.5 g / cc to about 7.0 g / cc. When the pellet density is within this range, the solid electrolyte is in a compact state and thus blocks moisture or air from entering the solid electrolyte, which allows for increased ionic conductivity.

[0103] The solid electrolyte can exist in the form of particles. The solid electrolyte particles can have an average particle diameter of about 5 nanometers (nm) to about 500 micrometers (μm), about 100 nm to about 15 μm, or about 300 nm to about 10 μm, and have a specific surface area of about 0.01 square meters per gram (m 2 / g) to about 1000 m 2 / g, about 0.5 m 2 / g to about 100 m 2 / g, about 1 m 2 / g to about 80 m 2 / g, about 2 m 2 / g to about 70 m 2 / g, or about 5 m 2 / g to about 50 m 2 / g. See E.P. Barrett, L.G. Joyner, P.P. 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 hereby incorporated by reference in their entirety.

[0104] When the average particle diameter of the solid electrolyte particles is within the above range, a solid electrolyte having a dense film state and a desired wafer density can be prepared.

[0105] According to an embodiment, a method for preparing a solid electrolyte is described herein.

[0106] A precursor mixture for preparing a solid electrolyte is provided. The precursor mixture can be prepared, pre-prepared, or purchased.

[0107] A lithium precursor, an M precursor, and a hafnium precursor can be mixed to provide the precursor mixture.

[0108] Subsequently, the precursor mixture is heat-treated to prepare a solid electrolyte including an oxide represented by Formula 1. M of the M precursor is the same as M defined in Formula 1.

[0109] If desired, a solvent can be added to the mixture.

[0110] Any suitable solvent can be used as long as it can appropriately dissolve or disperse the lithium precursor, the M precursor, and the hafnium precursor. The solvent can be, for example, ethanol, water, ethylene glycol, isopropyl alcohol, or a combination thereof.

[0111] Mixing can be carried out by methods such as grinding, blending, or stirring. Grinding can be performed by a ball mill, a mortar, a sieve, a roller mill, a disk mill, a jet mill, a jaw crusher, a crusher, or a combination thereof.

[0112] Subsequently, the mixture is heat-treated.

[0113] The heat treatment can include a primary heat treatment. In the primary heat treatment of the mixture, the temperature is increased at a rate of about 1 degree Celsius per minute (°C / min) to about 10 °C / min, and the primary heat treatment temperature is about 400 °C to about 950 °C or about 600 °C to about 950 °C. When the temperature increase rate in the primary heat treatment is within the above range, the heat treatment can be carried out sufficiently to obtain a solid electrolyte having a desired crystal structure after a secondary heat treatment process described later.

[0114] The primary heat treatment can be carried out in an inert gas, oxygen, or oxidizing gas atmosphere. Air is mentioned. The inert gas atmosphere can include argon, helium, nitrogen, or a combination thereof. The primary heat treatment time can be selected based on the primary heat treatment temperature and is, for example, about 1 hour to about 48 hours, about 1 hour to about 10 hours, or about 2 hours to about 7 hours.

[0115] The oxidizing gas atmosphere can be formed using air or oxygen.

[0116] The hafnium precursor and the M precursor are each an oxide containing hafnium or M, a carbonate containing hafnium or M, a chloride containing hafnium or M, a phosphate containing hafnium or M, a hydroxide containing hafnium or M, a nitrate containing hafnium or M, or a combination thereof, and are, for example, hafnium oxide, lanthanum oxide, barium oxide, calcium oxide, magnesium oxide, or a combination thereof.

[0117] The contents of the lithium precursor, hafnium precursor, and M precursor are stoichiometrically selected to obtain the oxide represented by Formula 1.

[0118] Subsequently, the heat-treated precursor mixture can be pulverized to obtain a pulverized product. The pulverized product can be, for example, a powder. The pulverized product (e.g., powder particles) obtained by pulverization can include particles having a size of 10 μm or less, for example, about 0.1 μm to about 10 μm. When the size of the particles is within the above range, pulverization and mixing can be carried out sufficiently because their size is small, making it easy to obtain the formation of a perovskite crystal phase. As used herein, "size" refers to the average diameter when the particles are spherical and the major axis length when the particles are non-spherical. For example, the size can be measured by using an electron scanning microscope or by a particle size analyzer utilizing light scattering.

[0119] An additive can be added to the heat-treated precursor mixture. As the additive, LiF, LiCl, Al2O3, Li3BO3, or a combination thereof can be used. The additive is used to control the grain size or the ionic conductivity at the grain boundaries. When the additive is added, the composition of the oxide is substantially unchanged, and its wafer density or ionic conduction characteristics can be improved. The content of the additive is about 0.1 parts by weight to about 10 parts by weight, about 0.5 parts by weight to about 10 parts by weight, or about 1 part by weight to about 5 parts by weight, based on 100 parts by weight of the heat-treated precursor mixture.

[0120] When the foregoing additives are added, Al, F, B, Cl, or a combination thereof may be present in the finally obtained oxide. Here, when Al2O3 is used as an additive, Al may be present in the finally obtained oxide, and when LiF is used as an additive, F may be present in the finally obtained oxide. When Li3BO3 is used as an additive, B may be present in the finally obtained oxide, and when LiCl is used as an additive, Cl may be present in the finally obtained oxide. According to an embodiment, the content of Al, F, B, Cl, or a combination thereof in the oxide is about 10 parts by weight or less, about 0.0001 parts by weight to about 8 parts by weight, about 0.001 parts by weight to about 5 parts by weight, about 0.001 parts by weight to about 3 parts by weight, about 0.001 parts by weight to about 2 parts by weight, about 0.001 parts by weight to about 1 part by weight, about 0.01 parts by weight to about 0.5 parts by weight, about 0.01 parts by weight to about 3 parts by weight, or about 0.1 parts by weight to about 2 parts by weight, based on the total weight of 100 parts by weight of the oxide.

[0121] The method may include a secondary heat treatment of the pulverized heat-treated precursor mixture, where the secondary heat treatment may include a heat treatment with a temperature increase of about 1 °C / min to about 10 °C / min. The secondary heat treatment may include a heat treatment at about 500 °C to about 1600 °C, about 600 °C to about 1500 °C, about 600 °C to about 1300 °C, or about 700 °C to about 1200 °C. The secondary heat treatment may include a heat treatment in a mixed gas that includes about 1 volume percent (vol%) to about 10 vol% of a reducing gas and about 90 vol% to about 99 vol% of an inert gas, based on the total amount of the mixed gas. For example, the secondary heat treatment may be carried out in a mixed gas that includes about 3 vol% to about 8 vol% of a reducing gas and about 92 vol% to about 97 vol% of an inert gas. When the secondary heat treatment is carried out in such a gas atmosphere, a solid electrolyte containing an oxygen-deficient oxide can be obtained.

[0122] The reducing gas is, for example, hydrogen.

[0123] According to an embodiment, the secondary heat treatment may be carried out at a temperature higher than the primary heat treatment temperature. Before the pulverized heat-treated precursor mixture is secondarily heat-treated as described above, the pulverized heat-treated precursor mixture may be pressed to form a wafer. When the wafer is secondarily heat-treated, the diffusion distance of the material being heat-treated is shortened, such that a desired solid electrolyte can be easily prepared. When the secondary heat treatment is carried out on powder or granules (i.e., not in the form of a wafer), an oxide of Formula 1 can be manufactured, but a longer heat treatment time and a higher temperature may be used because the diffusion distance in powder granules is increased compared to the diffusion distance in the wafer form.

[0124] The secondary heat treatment can be determined by the desired valence or oxidation value of M and can be carried out in an oxidizing gas atmosphere, a reducing gas atmosphere, or an inert gas atmosphere. The oxidizing gas atmosphere can be formed using air or oxygen, the reducing gas atmosphere can be formed using a reducing gas such as hydrogen, and the inert gas atmosphere can be formed using an inert gas such as nitrogen, argon, or helium.

[0125] The secondary heat treatment time can be selected depending on the secondary heat treatment temperature and is, for example, about 1 hour to about 50 hours or about 6 hours to about 48 hours.

[0126] After the secondary heat treatment, an oxide of Formula 1 is formed. When the rate of temperature increase during the primary heat treatment and the secondary heat treatment is within the above range, each heat treatment is carried out sufficiently so that not only the desired crystal structure is formed, but also the synthesis time is short and economical.

[0127] According to an embodiment, the solid electrolyte can be used in a metal-air battery, such as a lithium-air battery. In addition, the solid electrolyte can be used as an electrolyte of an all-solid-state battery. Moreover, the solid electrolyte can be used as an electrolyte of a lithium battery. The solid electrolyte can be used in the manufacture of the positive electrode and the negative electrode of a battery and can also be used in the surface coating of the positive electrode or the negative electrode.

[0128] The surface coating can be a protective layer. Refer to Figure 5 , the lithium-air battery 500 can include a protective layer 520. The protective layer 520 can include the solid electrolyte and can be disposed on the positive electrode 200. The lithium-air battery 500 can include a protective layer 510. The protective layer 510 includes the solid electrolyte and can be disposed on the negative electrode.

[0129] When applying the protective layer, other electrolytes can be used together with the solid electrolyte according to the embodiment. Other electrolytes include, for example, a liquid electrolyte, a gel electrolyte, a polymer electrolyte, a ceramic electrolyte, an organic / inorganic composite electrolyte, or a combination thereof.

[0130] According to another aspect, there is provided an electrochemical device including the solid electrolyte. Since the electrochemical device according to the embodiment includes the solid electrolyte that is chemically stable and conducts both ions and electrons, the stability against moisture and strong alkali is improved, and thus the deterioration of the electrochemical device can be effectively suppressed.

[0131] The electrochemical device is, but not limited to, a battery, a storage battery, a supercapacitor, a fuel cell, a sensor, or an electrochromic device. Any suitable electrochemical device can be used.

[0132] The battery is, for example, a primary battery or a secondary battery. Examples of the battery may include, but are not limited to, a lithium battery and a sodium battery. Any suitable battery may be used. Examples of the lithium battery may include, but are not limited to, a lithium ion battery and a lithium air battery. Any suitable lithium battery may be used. Examples of the electrochromic device may include, but are not limited to, an electrochromic mirror, an electrochromic window, and an electrochromic screen. Any electrochromic device may be used as long as it is used as an electrochromic device in the art.

[0133] The electrochemical device is, for example, a lithium metal battery using a metal such as lithium or zinc as the negative electrode, or a lithium air battery using lithium as the negative electrode. The life of such a lithium air battery is improved.

[0134] The positive electrode is porous. Since the positive electrode is porous, air, oxygen, or a combination thereof can easily diffuse into the positive electrode.

[0135] According to an embodiment, the lithium air battery includes: a positive electrode; a negative electrode; and an electrolyte between the positive electrode and the negative electrode.

[0136] According to an embodiment, at least one of the positive electrode, the negative electrode, or the electrolyte includes the solid electrolyte. The negative electrode may include lithium.

[0137] Since the lithium air battery includes the solid electrolyte, the lithium air battery has improved stability against moisture and strong bases, and improved reversibility under humid or air conditions, thereby enabling the lithium air battery to operate more effectively. Further, the structural stability of the lithium air battery is improved, and its deterioration is suppressed.

[0138] The lithium air battery includes a positive electrode, and the positive electrode is disposed on a positive electrode current collector.

[0139] The positive electrode may contain the solid electrolyte. The content of the solid electrolyte is about 2 parts by weight to about 70 parts by weight, about 3 parts by weight to about 70 parts by weight, about 3 parts by weight to about 60 parts by weight, about 10 parts by weight to about 60 parts by weight, based on 100 parts by weight of the positive electrode.

[0140] Holes may also be introduced into the positive electrode by introducing a pore-forming agent during the manufacture of the positive electrode. The positive electrode may be in the form of a porous wafer, a porous sheet, etc., but its form is not limited thereto, and it may be formed according to the desired battery form.

[0141] The positive electrode is permeable to gases such as oxygen or air. Therefore, the positive electrode is different from a positive electrode that is substantially impermeable to gases such as oxygen or air and only conducts ions. Since the positive electrode is porous and / or permeable to gases, oxygen and / or air can easily diffuse into the positive electrode, and lithium ions and / or electrons can easily move through the solid electrolyte included in the positive electrode. The electrochemical reaction of oxygen, lithium ions, and electrons easily proceeds in the positive electrode.

[0142] In the manufacture of the positive electrode, in addition to the solid electrolyte, a conductive material may be further added to further increase the electron conductivity and ion conductivity. The conductive material may be porous. The conductive material has porosity, thereby making the penetration of air easier. The conductive material may be any suitable material as a material having porosity and / or conductivity, and is, for example, a carbon-based material having porosity. Examples of the carbon-based material may include, but are not limited to, carbon black, graphite, graphene, activated carbon, carbon fiber, or a combination thereof. Any suitable carbon-based material may be used. The conductive material is, for example, a metal material. Examples of the metal material may include metal fibers, metal meshes, metal powders, or a combination thereof. Examples of the metal powder may include copper powder, silver powder, nickel powder, aluminum powder, or a combination thereof. The conductive material is, for example, an organic conductive material. Examples of the organic conductive material may include polyphenylene derivatives and polythiophene derivatives. The conductive materials are used alone or in combination. The positive electrode may include a composite conductor as the conductive material, and in addition to the composite conductor, the positive electrode may further include the conductive material.

[0143] The positive electrode further includes a catalyst for the oxidation / reduction of oxygen. Examples of the catalyst may include, but are not limited to, noble metal catalysts such as platinum, gold, silver, palladium, ruthenium, rhodium, and osmium; oxide catalysts such as manganese oxide, iron oxide, cobalt oxide, and nickel oxide; and organometallic catalysts such as cobalt phthalocyanine. Any suitable catalyst may be used.

[0144] The catalyst is supported on a carrier. Examples of the carrier may include an oxide carrier, a zeolite carrier, a clay-based mineral carrier, and a carbon carrier. The oxide carrier is an oxide carrier including Al, Si, Zr, Ti, Ce, Pr, Sm, Eu, Tb, Tm, Yb, Sb, Bi, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, W, or a combination thereof. Examples of the oxide carrier include alumina, silica, zirconium oxide, and titanium dioxide. Examples of the carbon carrier may include, but are not limited to, carbon black such as Ketjen black, acetylene black, channel black, and lamp black; graphite such as natural graphite, artificial graphite, and expanded graphite; activated carbon; and carbon fiber. Any suitable carbon carrier may be used.

[0145] The positive electrode further includes a binder. The binder includes a thermoplastic resin or a thermosetting resin. Examples of the binder may include, but are not limited to, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluorochloroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-trifluorochloroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, and ethylene-acrylic acid copolymer, which may be used alone or in combination. Any suitable binder may be used.

[0146] The positive electrode is manufactured as follows: mixing a conductive material, an oxidation / reduction catalyst for oxygen, and a binder to obtain a mixture, adding an appropriate solvent to the mixture to prepare a positive electrode slurry, and then applying the positive electrode slurry onto the surface of a substrate and drying the applied positive electrode slurry, or pressing the positive electrode slurry onto the substrate to improve the electrode density. The substrate is, for example, a positive electrode current collector, a separator, or a solid electrolyte membrane. The positive electrode current collector is, for example, a gas diffusion layer. The conductive material includes the solid electrolyte, and depending on the type of the desired positive electrode, the oxidation / reduction catalyst for oxygen and the binder in the positive electrode may be omitted.

[0147] The lithium-air battery includes a negative electrode. According to an embodiment, the negative electrode may include the solid electrolyte.

[0148] The negative electrode contains lithium.

[0149] The negative electrode is, for example, a lithium metal thin film or a lithium-based alloy thin film. The lithium-based alloy is, for example, an alloy of lithium with aluminum, tin, magnesium, indium, calcium, titanium, or vanadium.

[0150] The lithium-air battery includes an electrolyte disposed between the positive electrode and the negative electrode.

[0151] The electrolyte may be, for example, a solid electrolyte including an oxide represented by Formula 1.

[0152] According to an embodiment, in addition to the solid electrolyte, the electrolyte may further include another solid electrolyte, a gel electrolyte, or a liquid electrolyte. The other solid electrolyte, gel electrolyte, and liquid electrolyte are not particularly limited. Any suitable electrolyte may be used.

[0153] The other solid electrolyte includes, but is not limited to, a solid electrolyte including an ion-conducting inorganic material, a solid electrolyte including a polymer ionic liquid (PIL) and a lithium salt, a solid electrolyte including an ion-conducting polymer and a lithium salt, and a solid electrolyte including an electron-conducting polymer. Any suitable solid electrolyte may be used.

[0154] Ionic conductive inorganic materials include, but are not limited to, glass or amorphous metal ion conductors, ceramic active metal ion conductors, glass-ceramic active metal ion conductors, or combinations thereof. Any suitable ionic conductive inorganic material can be used. The ionic conductive inorganic material is in the form of, for example, particles or sheets.

[0155] Examples of ionic conductive inorganic materials can include BaTiO3, Pb(Zr a Ti 1-a )O3 (PZT) where 0 ≤ a ≤ 1, Pb 1-x La x Zr 1-y Ti y O3 (PLZT) (0 ≤ x < 1, 0 ≤ y < 1), Pb(Mg 1 / 3 Nb 2 / 3 )O3 - PbTiO3 (PMN - PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, SiC, lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3 where 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3 where 0 < x < 2, 0 < y < 1, 0 < z < 3), Li 1+x+y (Al a Ga 1-a ) x (Ti b Ge 1-b ) 2-x Si y P 3-y O 12 (0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ a ≤ 1, 0 ≤ b ≤ 1), lithium lanthanum titanate (Li x La y TiO3 where 0 < x < 2, 0 < y < 3), lithium germanium thiophosphate (Li x Ge y P z S w where 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride (Li x N y where 0 < x < 4, 0 < y < 2), SiS2-based glass (Li x Si y S z, where 0 < x < 3, 0 < y < 2, 0 < z < 4), glass based on P2S5 (Li x P y S z , where 0 < x < 3, 0 < y < 3, 0 < z < 7), Li2O, LiF, LiOH, Li2CO3, LiAlO2, ceramics based on Li2O - Al2O3 - SiO2 - P2O5 - TiO2 - GeO2, garnet - based ceramics (Li 3+x La3M2O 12 (M = Te, Nb, Zr, 0 ≤ x ≤ 5)), or a combination thereof.

[0156] Polymer ionic liquid (PIL) comprises i) ammonium - based ions, pyrrolidine - based ions, pyridine - based ions, pyrimidine - based ions, imidazole - based ions, piperidine - based ions, pyrazole - based ions, azole - based ions, pyridazine - based ions, - based ions, sulfonium - based ions, triazole - based ions, or a combination thereof, and ii) BF4 - , PF6 - , AsF6 - , SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , (CF3SO2)2N - , Cl - , Br - , I - , SO4 2- , CF3SO3 - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , NO3 - , Al2Cl7 - , CH3COO - , (CF3SO2)3C - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF- , (CF3)6P - , SF5CF2SO3 - , SF5CHFCF2SO3 - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (O(CF3)2C2(CF3)2O)2PO - , or a combination thereof. Examples of the polymeric ionic liquid (PIL) may include polyTFSI (diallyldimethylammonium), poly(bis(trifluoromethanesulfonyl)imide 1-allyl-3-methylimidazolium) ), or poly(bis(trifluoromethanesulfonyl)imide N-methyl-N-propylpiperidinium) ).

[0157] The ion-conducting polymer includes repeating units derived from: ether-based monomers, acrylic monomers, methacrylic monomers, siloxane-based monomers, or a combination thereof.

[0158] Examples of the ion-conducting polymer may include, but are not limited to, polyethylene oxide (PEO), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyvinyl sulfone, polypropylene oxide (PPO), polymethyl methacrylate, polyethyl methacrylate, polydimethylsiloxane, polyacrylic acid, polymethacrylic acid, poly(methyl acrylate), poly(ethyl acrylate), poly(2-ethylhexyl acrylate), poly(butyl methacrylate), poly(2-ethylhexyl methacrylate), poly(decyl acrylate), poly(ethylene vinyl acetate), phosphate ester polymers, polyester sulfides, polyvinylidene fluoride (PVF), or Li-substituted Nafion. Any suitable ion-conducting polymer can be used.

[0159] Examples of the electron-conducting polymer may include, but are not limited to, polyphenylene derivatives or polythiophene derivatives. Any suitable electron-conducting polymer can be used.

[0160] The gel electrolyte is obtained by adding a low molecular weight solvent to a solid electrolyte disposed between a positive electrode and a negative electrode. The gel electrolyte is obtained by adding a solvent, oligomer, or a combination thereof, which is a low molecular weight compound, to a polymer.

[0161] The liquid electrolyte includes a solvent and a lithium salt.

[0162] The solvent may include, but is not limited to, organic solvents, ionic liquids, oligomers, or a combination thereof. Any suitable solvent that is liquid at room temperature (25 °C) can be used.

[0163] The organic solvents include ether-based solvents, carbonate-based solvents, ester-based solvents, ketone-based solvents, or combinations of the foregoing. The organic solvents may include, but are not limited to, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, succinonitrile, diethylene glycol dimethyl ether (DEGDME), tetraethylene glycol dimethyl ether (TEGDME), polyethylene glycol dimethyl ether (PEGDME, Mn = ~500), dimethyl ether, diethyl ether, dibutyl ether, dimethoxyethane, or combinations thereof. Any suitable organic solvent may be used as long as it is a liquid at room temperature.

[0164] Ionic liquids (ILs) include i) ammonium-based ions, pyrrolidinium-based ions, pyridinium-based ions, pyrimidinium-based ions, imidazolium-based ions, piperidinium-based ions, pyrazolium-based ions, oxazolium-based ions, pyridazinium-based ions, thiazolium-based ions, sulfonium-based ions, triazolium-based ions, or combinations thereof, and ii) BF4, PF6, AsF6, SbF6, AlCl4, HSO4, ClO4, CH3SO3, CF3CO2, (CF3SO2)2N, Cl, Br, I, SO4, CF3SO3, (C2F5SO2)2N, (C2F5SO2)(CF3SO2)N, NO3, Al2Cl7, CH3COO -based ions, pyridinium -based ions, pyrimidinium -based ions, imidazolium -based ions, piperidinium -based ions, pyrazolium -based ions, oxazolium -based ions, pyridazinium -based ions, -based ions, thiazolium-based ions, sulfonium-based ions, triazolium-based ions, or combinations thereof, and ii) BF4, PF6, AsF6, SbF6, AlCl4, HSO4, ClO4, CH3SO3, CF3CO2, (CF3SO2)2N, Cl, Br, I, SO4, CF3SO3, (C2F5SO2)2N, (C2F5SO2)(CF3SO2)N, NO3, Al2Cl7, CH3COO -based ions, or combinations thereof, and ii) BF4 - 、PF6 - 、AsF6 - 、SbF6 - 、AlCl4 - 、HSO4 - 、ClO4 - 、CH3SO3 - 、CF3CO2 - 、(CF3SO2)2N - 、Cl - 、Br - 、I - 、SO4 2- 、CF3SO3 - 、(C2F5SO2)2N - 、(C2F5SO2)(CF3SO2)N - 、NO3 - 、Al2Cl7 - 、CH3COO- 、(CF3SO2)3C - 、(CF3)2PF4 - 、(CF3)3PF3 - 、(CF3)4PF2 - 、(CF3)5PF - 、(CF3)6P - 、SF5CF2SO3 - 、SF5CHFCF2SO3 - 、CF3CF2(CF3)2CO - 、(CF3SO2)2CH - 、(SF5)3C - 、(O(CF3)2C2(CF3)2O)2PO - 、or a combination thereof.

[0165] The lithium salt may include, but is not limited to, lithium bis(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2, LiTFSI), LiPF6, LiBF4, LiAsF6, LiClO4, LiNO3, lithium bis(oxalato)borate (LiBOB), LiCF3SO3, LiN(SO2C2F5)2, LiN(SO2F)2, LiC(SO2CF3)3, LiN(SO3CF3)2, LiC4F9SO3, LiAlCl4, or a combination thereof. Any suitable lithium salt may be used. The concentration of the lithium salt is, for example, about 0.01 M to about 5.0 M.

[0166] The lithium-air battery further includes a separator between the positive electrode and the negative electrode. The separator is not limited as long as it has a composition capable of withstanding the use range of the lithium-air battery. Examples of the separator may include a polymer nonwoven fabric such as a polypropylene nonwoven fabric or a polyphenylene sulfide nonwoven fabric, a porous membrane of an olefin resin such as polyethylene or polypropylene, glass fiber, or a combination thereof.

[0167] The electrolyte has a structure in which the separator is impregnated with a solid polymer electrolyte or a structure in which the separator is impregnated with a liquid electrolyte. The electrolyte having a structure in which the separator is impregnated with a solid polymer electrolyte is prepared by placing a solid polymer electrolyte membrane on one surface or a plurality of surfaces of the separator and rolling the solid polymer electrolyte membrane. The electrolyte having a structure in which the separator is impregnated with a liquid electrolyte is prepared by injecting a liquid electrolyte containing a lithium salt into the separator.

[0168] The lithium-air battery is prepared as follows: Place the negative electrode on one surface of the case, place the electrolyte layer on the negative electrode, place the positive electrode on the electrolyte layer, place the porous positive electrode current collector on the positive electrode, place the pushing member on the porous positive electrode current collector to transfer air to the air electrode, and push the pushing member to fix the unit cell. The case can be separated into an upper part that contacts the negative electrode and a lower part that contacts the air electrode, and an insulating resin can be provided between the upper part and the lower part to electrically insulate the positive electrode and the negative electrode from each other.

[0169] The lithium-air battery can be used in both primary and secondary batteries. The shape of the lithium-air battery is not particularly limited and is, for example, coin-shaped, button-shaped, sheet-shaped, laminated-shaped, cylindrical-shaped, flat-shaped, or angular-shaped. The lithium-air battery can be a large-sized battery or a medium-sized battery for an electric vehicle.

[0170] Figure 4 It is a schematic cross-sectional view for explaining the structure of the lithium-air battery according to an embodiment.

[0171] Reference Figure 4 , the lithium-air battery 500 has the following structure: in which a first electrolyte 400 is provided between a positive electrode 200 containing oxygen as an active material adjacent to a first current collector 210 and a negative electrode 300 containing lithium adjacent to a second current collector 310. The first electrolyte 400 is a separator impregnated with a liquid electrolyte.

[0172] A second electrolyte 450 can be provided between the positive electrode 200 and the first electrolyte 400. The second electrolyte 450 is a lithium-ion conducting solid electrolyte membrane, and a solid electrolyte according to an embodiment can be used. The first current collector 210 is porous and can also be used as a gas diffusion layer capable of diffusing air due to its porosity. A pushing member 220 capable of transferring air to the positive electrode 200 is provided on the first current collector 210.

[0173] Air is supplied to the air inlet 230a and discharged to the air outlet 230b. The lithium-air battery 500 can be accommodated in a stainless steel container. In Figure 4 , the reference numeral 320 denotes an insulating resin case 320.

[0174] The "air" of the lithium-air battery is not limited to atmospheric air, but can include a combination of gases containing oxygen, or pure oxygen. This broad definition of the term "air" applies to all applications such as air unit cells and air positive electrodes.

[0175] Hereinafter, the present disclosure will be described in detail with reference to examples and comparative examples. However, these examples are provided for illustrative purposes only, and the scope of the present disclosure is not limited thereto.

[0176] Examples

[0177] Preparation of a solid electrolyte including an oxide

[0178] Comparative Example 1: Li2HfO3

[0179] Mix Li2CO3 as a lithium precursor and HfO2 as a hafnium precursor according to the composition ratio of Li2HfO3, add ethanol thereto and mix to obtain a precursor mixture. Place the precursor mixture in a ball milling device, and pulverize and mix for 4 hours. Dry the resulting mixture, heat it to 650 °C at a temperature increasing rate of about 5 °C / minute, and then perform a primary heat treatment in an air atmosphere for 12 hours to obtain a powder.

[0180] Grind the powder obtained by the primary heat treatment, and then press it to prepare an ion conductor wafer having a diameter of about 1.3 cm and a height of about 0.5 cm. Perform a secondary heat treatment of the wafer at 700 °C for 12 hours in an air or oxygen atmosphere to obtain a solid electrolyte including an oxide. When raising the secondary heat treatment to 700 °C, increase the temperature at about 5 °C / minute.

[0181] Example 1

[0182] Mix Li2CO3 as a lithium precursor, HfO2 as a hafnium precursor, and strontium oxide (SrO) as an M precursor according to the composition ratio of Li 0.3 Sr 0.6 HfO 2.75 , add ethanol thereto and mix to obtain a precursor mixture. Place the precursor mixture in a ball milling device, and pulverize and mix for 4 hours. Dry the resulting mixture, heat it to 900 °C at a temperature increasing rate of about 5 °C / minute, and then perform a primary heat treatment in an argon atmosphere for 6 hours to obtain a powder.

[0183] Grind the powder obtained by the primary heat treatment, and then add LiF as an additive to the ground powder. The content of LiF is 2 parts by weight based on 100 parts by weight of the ground powder. Press this powder to prepare an ion conductor wafer having a diameter of about 1.3 cm and a height of about 0.5 cm. Perform a secondary heat treatment of the ion conductor wafer at 1000 °C for 6 hours in a mixed gas atmosphere including 3 vol% hydrogen and 97 vol% argon to obtain a solid electrolyte including an oxide. When heating to 1000 °C for the secondary heat treatment, increase the temperature at about 5 °C / minute.

[0184] Examples 2 to 11

[0185] A solid electrolyte was obtained in the same manner as in Example 1, except that: the types and contents of the precursors used were changed to obtain an oxide having the composition shown in Table 1. The additives added to the powder obtained by the primary heat treatment are also described in Table 1.

[0186]

[0187] Production Example 1: Production of a lithium-air battery

[0188] 40 parts by weight of carbon (Super-P), 10 parts by weight of polytetrafluoroethylene (PTFE), and 50 parts by weight of NMP (N-methylpyrrolidone) were mixed to prepare a positive electrode paste, and then the positive electrode paste was applied and roll-pressed to obtain a positive electrode composite sheet. The positive electrode composite sheet was pressed onto a stainless steel mesh and then vacuum-dried in an oven at 100 °C for 120 minutes to obtain a positive electrode.

[0189] The center of a 5 cm × 5 cm aluminum film (a polypropylene-coated aluminum film with a thickness of 200 μm) was perforated to form a hole, and the hole was plugged with the solid electrolyte of Example 1 using an adhesive to prepare a first aluminum film provided with the solid electrolyte of Example 1. The solid electrolyte of Example 1 had a size of 1.4 cm × 1.4 cm. Subsequently, a new second aluminum film having a size of 5 cm × 5 cm, a copper current collector (thickness: 20 μm), a lithium foil (1.4 cm × 1.4 cm, thickness: 100 μm), a separator (Celgard-3501, manufactured by Celgard Corporation) made of polypropylene with a thickness of 25 μm and impregnated with an electrolyte solution (including 1 M LiTFSI dissolved in propylene carbonate (PC)), and the prepared first aluminum film were laminated, heated in a vacuum, and adhered to obtain an aluminum pouch-type lithium negative electrode.

[0190] The lithium negative electrode was provided in a stainless steel case, and the positive electrode provided with a separator made of polypropylene with a thickness of 25 μm was arranged to face the negative electrode. Subsequently, a porous gas diffusion layer made of carbon fiber was placed on the positive electrode, a foam nickel plate was placed on the porous gas diffusion layer, and a pushing member for delivering air to the positive electrode was pressed onto the foam nickel plate to manufacture a lithium-air battery.

[0191] Production Examples 2 to 11: Production of a lithium-air battery

[0192] A lithium-air battery was manufactured in the same manner as in Production Example 1, except that: the solid electrolytes of Examples 2 to 11 were each used in place of the solid electrolyte of Example 1.

[0193] Comparative Example 1: Production of a lithium-air battery

[0194] A lithium-air battery was fabricated in the same manner as in Manufacturing Example 1, except that the solid electrolyte of Comparative Example 1 was used instead of the solid electrolyte of Example 1.

[0195] Evaluation Example 1: X-ray diffraction analysis

[0196] X-ray diffraction (XRD) analysis was performed on the solid electrolytes of Examples 1 to 11 and Comparative Example 1. The XRD analysis was carried out using a D8 Advance from Bruker Corporation and Cu Kα radiation.

[0197] By XRD analysis, the ratio (IA / IB) of the intensity (IA) of the first diffraction peak in the region where the diffraction angle 2θ is 31.0° 2θ ± 1.0° 2θ to the intensity (IB) of the second diffraction peak in the region where the diffraction angle 2θ is 21.8° 2θ ± 1.0° 2θ is represented by Equation 1, and the results are shown in Table 2 and Figure 2 in.

[0198] Equation 1

[0199] IA / IB = {(intensity of the diffraction peak in the region where the diffraction angle 2θ is 31.0° 2θ ± 1.0° 2θ) / (intensity of the diffraction peak in the region where the diffraction angle 2θ is 21.8° 2θ ± 1.0° 2θ)}

[0200] Table 2

[0201] Example IA / IB Example 1 5.2 Example 2 5.2 Example 3 21.3 Example 4 1.6 Example 5 4.1 Example 6 5.3 Example 7 4.9 Example 8 5.2 Example 9 5.0 Example 10 5.3 Example 11 5.3 Comparative Example 1 0.5

[0202] As Figure 2 and shown in Table 2, it was found that in the oxide-containing solid electrolytes of Examples 1 to 11, IA / IB was greater than 1, but in the oxide-containing solid electrolyte of Comparative Example 1, IA / IB was less than 1. As Figure 2 shown in, the oxide-containing solid electrolytes of Examples 1 to 11 contained HfO2, HfO2 was the minor phase, and the characteristic peak of HfO2 appeared in the region where the diffraction angle 2θ is 21.8° 2θ ± 1.0° 2θ.

[0203] Evaluation Example 2: Ionic conductivity

[0204] The upper and lower surfaces of each of the ion conductor wafers prepared in Examples 1 to 11 and Comparative Example 1 were coated (deposited) with gold (Au) by sputtering, and the impedance of the samples was measured by the two-probe method using an impedance analyzer. The frequency range was from 1 hertz (Hz) to 1 megahertz (MHz), and the amplitude voltage was 100 millivolts (mV). The impedance of the samples was measured at 30 °C in an air atmosphere. The resistance value was obtained from the arc of the Nyquist plot of the impedance measurement results, and the ionic conductivity was calculated from the resistance value.

[0205] As Figure 3 shown, it was found that the solid electrolytes of Examples 1 to 10 had improved ionic conductivity compared to the solid electrolyte of Comparative Example 1.

[0206] In addition, although the ion conductor wafer of Example 11 exhibited an almost identical level of ionic conductivity to the ion conductor wafer of Comparative Example 1, as shown in Table 3 of Evaluation Example 3, the wafer density increased in the ion conductor wafer of Example 11 compared to the wafer density of the ion conductor wafer of Comparative Example 1, whereby a more compact solid electrolyte was prepared using the ion conductor wafer of Example 11.

[0207] Evaluation Example 3: Wafer density

[0208] The wafer density of the ion conductor wafers was measured as follows: The diameters, heights, and weights of the ion conductor wafers obtained in Examples 1 to 11 and Comparative Example 1 were measured. The evaluation results of the wafer density are shown in Table 3.

[0209] Table 3

[0210] Example Wafer density (g / cc) Example 1 5.36 Example 2 5.39 Example 3 5.67 Example 4 5.08 Example 5 4.94 Example 6 5.11 Example 7 5.33 Example 8 5.14 Example 9 6.92 Example 10 7.34 Example 11 5.13 Comparative Example 1 3.97

[0211] As shown in Table 3, it was found that the wafer density of the wafers of Examples 1 to 11 was improved compared to the wafer density of the wafers of Comparative Example 1. Due to the improved wafer density, a more compact solid electrolyte could be obtained. As a result, the solid electrolytes prepared using the wafers of Examples 1 to 11 had improved moisture or air barrier properties compared to the solid electrolytes prepared using the wafers of Comparative Example 1.

[0212] Evaluation Example 4: Evaluation of electrochemical stability

[0213] After pulverizing the solid electrolyte of Example 1 to a size of about 1 μm, N-methyl-2-pyrrolidone was mixed with 85 weight percent (wt%) of the pulverized product, 10 wt% of carbon black as a conductive material, and 5 wt% of polyvinylidene fluoride (PVDF) as a binder to prepare a slurry. The slurry was applied on an aluminum foil and then dried to prepare a working electrode. A lithium metal foil was used as a counter electrode, and a separator impregnated with a liquid electrolyte (1 M LiTFSI in propylene carbonate (PC)) was disposed between the working electrode and the counter electrode to prepare a half-cell battery.

[0214] The electrochemical stability of the layered compound on lithium metal was evaluated by cyclic voltammetry at a scan rate of 0.1 millivolt per second (mV / sec) in a voltage range of 2 V to 4 V (versus Li).

[0215] As a result of the evaluation, during 1 scan, 80 scans, or 100 scans, the solid electrolyte of Example 1 was electrochemically stable without an overcurrent due to side reactions.

[0216] Evaluation Example 5: Evaluation of Charge and Discharge Characteristics of a Lithium-Air Battery

[0217] The lithium-air battery fabricated in Fabrication Example 1 was discharged at a constant current of 0.01 milliamperes per square centimeter (mA / cm 2 ) in an oxygen atmosphere at 60 °C and 1 atmosphere (atm) until 2.0 V (versus Li), and then charged at the same current until 4.25 V. The charge and discharge cycle was repeated. The charge and discharge test results of each lithium-air battery in the first cycle were examined.

[0218] As a result of the charge and discharge tests, it was confirmed that the lithium-air battery of Fabrication Example 1 employing the solid electrolyte of Example 1 was stably driven.

[0219] According to the embodiment, the solid electrolyte has improved stability in the presence of lithium, is stable to moisture in humid or atmospheric conditions, and maintains excellent ionic conductivity. When the solid electrolyte is used, an electrochemical device with suppressed deterioration can be fabricated.

[0220] It should be understood that the embodiments described herein should be considered only in a descriptive sense and not for purposes of limitation. The description of features, aspects, or advantages in each embodiment should be considered applicable to other similar features, aspects, or advantages in other embodiments. Although one or more embodiments have been described with reference to the accompanying drawings, those of ordinary skill in the art will understand that various changes in form and detail can be made therein without departing from the spirit and scope as defined by the appended claims.

Claims

1. Solid electrolyte, comprising: The oxide represented by Formula 1 Formula 1 Li y M z HfO 3-x wherein, in Formula 1 M is Sr, Ba, Ca, Mg, La, Ce, Pr, Gd, Y, Sc, or a combination thereof, and 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1, provided that the oxide is not any of the following compounds: Li 0.34 La 0.55 HfO3, Li 0.10 La 0.63 HfO3, Li 0.20 La 0.60 HfO3, Li 0.30 La 0.57 HfO3, Li 0.40 La 0.53 HfO3, Li 0.45 La 0.52 HfO3, Li 0.34 Ce 0.55 HfO3, Li 0.10 Ce 0.63 HfO3, Li 0.20 Ce 0.60 HfO3, Li 0.30 Ce 0.57 HfO3, Li 0.40 Ce 0.53 HfO3, Li 0.45 Ce 0.52 HfO3, Li 0.34 Pr 0.55 HfO3, Li 0.10 Pr 0.63 HfO3, Li 0.20 Pr 0.60 HfO3, Li 0.30 Pr 0.57 HfO3, Li 0.40 Pr 0.53 HfO3, Li 0.45 Pr 0.52 HfO3, Li 0.10 Ca 0.80 HfO3, Li 0.20 Ca 0.60 HfO3, Li 0.25 Ca 0.50 HfO3, Li 0.30 Ca 0.40 HfO3, Li 0.40 Ca 0.20 HfO3, Li 0.10 Sr 0.80 HfO3, Li 0.20 Sr 0.60 HfO3, Li 0.25 Sr 0.50 HfO3, Li 0.30 Sr 0.40 HfO3, Li 0.40 Sr 0.20 HfO3, Li 0.10 Ba 0.80 HfO3, Li 0.20 Ba 0.60 HfO3, Li 0.25 Ba 0.50 HfO3, Li 0.30 Ba 0.40 HfO3, Li 0.40 Ba 0.20 HfO3, and Li 0.25 La 0.50 HfO3.

2. The solid electrolyte according to claim 1, wherein, In Formula 1, x is from 0 to 0.

9.

3. The solid electrolyte according to claim 1, wherein, In Formula 1, y is from 0.1 to 0.

9.

4. The solid electrolyte according to claim 1, wherein, In Formula 1, z is from 0.1 to 0.

9.

5. The solid electrolyte according to claim 1, wherein the oxide represented by Formula 1 is at least one selected from the oxides represented by Formulas 2 to 9: [Formula 2] Li y Ba z HfO 3-x Wherein, In Formula 2, 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1 are satisfied; [Formula 3] Li y Sr z HfO 3-x wherein, in Formula 3, 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1 are satisfied; [Formula 4] Li y Ca z HfO 3-x wherein, in Formula 4, 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1 are satisfied; [Formula 5] Li y La z HfO 3-x wherein, in Formula 5, 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1 are satisfied; [Formula 6] Li y Ce z HfO 3-x wherein, in Formula 6, 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1 are satisfied; [Formula 7] Li y Pr z HfO 3-x wherein, in Formula 7, 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1 are satisfied; [Formula 8] Li y Y z HfO 3-x wherein, in Formula 8, 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1 are satisfied; and [Formula 9] Li y Sc z HfO 3-x wherein, in Formula 9, 0 ≤ x < 3, 0 < y < 1, and 0 < z < 1 are satisfied.

6. The solid electrolyte according to claim 5, wherein, x is from 0 to 0.9, y is from 0.1 to 0.9, z is from 0.1 to 0.9, and y + z < 1.

7. The solid electrolyte according to claim 1, wherein the oxide has a perovskite crystal structure.

8. The solid electrolyte according to claim 7, wherein the oxide has the following crystal structure: wherein Li, vacancies, and M each independently exist at the A-site in the ABO3 perovskite crystal structure, and hafnium exists at the B-site in the ABO3 perovskite crystal structure.

9. The solid electrolyte according to claim 7, wherein the oxide of formula 1 is Li 0.3 Sr 0.6 HfO 2.75 、Li 0.3 Sr 0.4 HfO 2.55 、Li 0.3 Ba 0.6 HfO 2.75 、Li 0.3 Ba 0.4 HfO 2.55 、Li 0.3 Ca 0.6 HfO 2.75 、Li 0.3 Ca 0.4 HfO 2.55 、Li 0.10 Ca 0.80 HfO 2.85 、Li 0.20 Ca 0.60 HfO 2.7 、Li 0.25 Ca 0.50 HfO 2.625 、Li 0.40 Ca 0.20 HfO 2.6 、Li 0.10 Sr 0.80 HfO 2.85 、Li 0.20 Sr 0.60 HfO 2.7 、Li 0.25 Sr 0.50 HfO 2.625 、Li 0.40 Sr 0.20 HfO 2.6 、Li 0.10 Ba 0.80 HfO 2.85 、Li0.20 Ba 0.60 HfO 2.7 、Li 0.25 Ba 0.50 HfO 2.625 、Li 0.40 Ba 0.20 HfO 2.6 、Li 0.34 La 0.55 HfO3、Li 0.34 Ce 0.55 HfO3Li 0.34 Pr 0.55 HfO3、Li 0.34 Y 0.55 HfO3、Li 0.34 Sc 0.55 HfO3, or a combination thereof.

10. The solid electrolyte according to claim 1, wherein the solid electrolyte has an ionic conductivity of 1×10 -6 S / cm or greater at 25 °C.

11. The solid electrolyte according to claim 1, wherein when analyzed by X-ray diffraction using Cu Kα radiation, the intensity of the first diffraction peak at a diffraction angle of 31.0 ± 1.0° 2θ is greater than the intensity of the second diffraction peak at a diffraction angle of 21.8 ± 1.0° 2θ.

12. The solid electrolyte according to claim 1, wherein when analyzed by X-ray diffraction using Cu Kα radiation, the first diffraction peak has an intensity in the region where the diffraction angle is 31.0 ± 1.0° 2θ and the second diffraction peak has an intensity in the region where the diffraction angle is 21.8 ± 1.0° 2θ, and wherein the intensity of the first diffraction peak is from the same as the intensity of the second diffraction peak to 25 times greater than the intensity of the second diffraction peak.

13. The solid electrolyte according to claim 1, wherein the solid electrolyte has a wafer density of 4 g / cm³ to 7.5 g / cm³.

14. A protective layer for a lithium battery, the protective layer comprising: The solid electrolyte according to any one of claims 1-13, wherein the solid electrolyte is disposed on a positive electrode or a negative electrode.

15. A metal-air battery, comprising: Positive electrode; Negative electrode; And An electrolyte between the positive electrode and the negative electrode, wherein at least one of the positive electrode, the negative electrode, or the electrolyte comprises the solid electrolyte according to any one of claims 1-13.

16. The metal-air battery according to claim 15, wherein the electrolyte comprises the solid electrolyte.

17. The metal-air battery according to claim 15, wherein the negative electrode comprises lithium.

18. An electrochemical device, comprising: Negative electrode; Positive electrode; And The solid electrolyte according to any one of claims 1-13 between the positive electrode and the negative electrode.

19. The electrochemical device according to claim 18, wherein the electrochemical device is a battery, a supercapacitor, a sensor, or an electrochromic device.

20. The electrochemical device according to claim 18, wherein the electrochemical device is a storage battery or a fuel cell.

21. A method for preparing a solid electrolyte according to any one of claims 1-13, the method comprising: Providing a precursor mixture comprising a lithium precursor, a hafnium precursor, and an M precursor; And Heat-treating the precursor mixture to prepare a solid electrolyte comprising the oxide represented by Formula 1.

22. The method according to claim 21, wherein the heat treatment comprises a primary heat treatment at 600 °C to 950 °C in an inert gas or in an oxidizing gas.

23. The method according to claim 22, further comprising: Crushing the initially heat-treated precursor mixture to obtain a crushed product; And secondarily heat-treating the crushed product.

24. The method according to claim 23, wherein the secondary heat treatment of the pulverized product comprises heat treatment at 900 °C to 1300 °C.

25. The method according to claim 24, wherein the secondary heat treatment comprises heat treatment in a mixed gas comprising 1 volume percent to 10 volume percent of a reducing gas and 90 volume percent to 99 volume percent of an inert gas, based on the total volume of the mixed gas.

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