阅读说明：本技术 固体电解质、其制备方法、包括其的锂-空气电池及包括其的电化学装置 (Solid electrolyte, method of preparing the same, lithium-air battery including the same, and electrochemical device including the same ) 是由 马祥福 徐东和 李铉杓 于 2020-09-23 设计创作，主要内容包括：本发明涉及固体电解质、其制备方法、包括其的锂-空气电池及包括其的电化学装置。固体电解质包括：由式1表示的化合物,其中,在式1中,M1为四价元素,M2为单价元素、二价元素、三价元素、四价元素、五价元素、六价元素、或其组合,X为卤素原子、拟卤素、或其组合,0<x<8,0≤y<1,和0<z<4。式1Li-xM1-(2-y)M2-y(PO-(4-z)X-z)-3。(The present invention relates to a solid electrolyte, a method of preparing the same, a lithium-air battery including the same, and an electrochemical device including the same. The solid electrolyte includes: a compound represented by formula 1, wherein, in formula 1, M1 is a tetravalent element, M2 is a monovalent element, a divalent element, a trivalent element, a tetravalent element, a pentavalent element, a hexavalent element, or a combination thereof, X is a halogen atom, a pseudohalogen, or a combination thereof, 0<x<8，0≤y<1, and 0<z<4. Formula 1Li x M1 2‑y M2 y (PO 4‑z X z ) 3 。)

1. A solid electrolyte comprising:

a compound represented by the formula (1),

formula 1

Li_xM1_2-yM2_y(PO_4-zX_z)₃

Wherein, in the formula 1,

m1 is a tetravalent element (I),

m2 is a monovalent element, a divalent element, a trivalent element, a tetravalent element, a pentavalent element, a hexavalent element, or a combination thereof,

x is a halogen atom, a pseudohalogen, or a combination thereof,

0< x <8, 0 ≦ y <1, and 0< z < 4.

2. The solid electrolyte of claim 1, wherein M1 is hafnium, titanium, zirconium, or a combination thereof.

3. The solid electrolyte of claim 1, wherein M2 is aluminum, lanthanum, scandium, cerium, praseodymium, gadolinium, europium, or a combination thereof.

4. The solid electrolyte of claim 1, wherein X is chlorine, bromine, fluorine, cyanide, cyanate, thiocyanate, azide, or a combination thereof.

5. The solid electrolyte according to claim 1, wherein, in formula 1,

X_3zis F_n、Br_n、Cl_n、(F_aCl_1-a)_n、(F_aBr_1-a)_nOr (Cl)_aBr_1-a)_n，

n is 1 or less, and

a is 0.01 to 0.99.

6. The solid electrolyte of claim 1, wherein the solid electrolyte has a crystal structure isomorphic with NASICON.

7. The solid electrolyte according to claim 1, wherein, in formula 1, x is 0.5 to 1.5, y is 0 to 0.8, and z is greater than 0 and less than or equal to 1.

8. The solid electrolyte according to claim 1, wherein the compound represented by formula 1 is a compound represented by formula 2, a compound represented by formula 3, or a compound represented by formula 4:

formula 2

Li_1+y-3zHf_2-yM2_y(PO_4-zX_z)₃

Wherein, in formula 2, M2 is a monovalent element, a divalent element, a trivalent element, a tetravalent element, a pentavalent element, a hexavalent element, or a combination thereof,

x is a halogen atom, a pseudohalogen, or a combination thereof,

0< y <1, and 0< z <4, or

Formula 3

Li_1+y-3zTi_2-yM2_y(PO_4-zX_z)₃

Wherein, in formula 3, M2 is a monovalent element, a divalent element, a trivalent element, a tetravalent element, a pentavalent element, a hexavalent element, or a combination thereof,

x is a halogen atom, a pseudohalogen, or a combination thereof,

0< y <1, and 0< z <4, or

Formula 4

Li_1+y-3zZr_2-yM2_y(PO_4-zX_z)₃

Wherein, in formula 4, M2 is a monovalent element, a divalent element, a trivalent element, a tetravalent element, a pentavalent element, a hexavalent element, or a combination thereof,

x is a halogen atom, a pseudohalogen, or a combination thereof,

0< y <1, and 0< z < 4.

9. The solid electrolyte according to claim 8, wherein, in formulae 2 to 4, 1+ y-3z is 0.5 to 1.5, y is 0 to 0.8, and z is greater than 0 and less than or equal to 1.

10. The solid electrolyte according to claim 1, wherein the compound represented by formula 1 is Li_0.8Hf₂P₃O_11.8F_0.2、Li_0.8Hf₂P₃O_11.8Cl_0.2、LiHf_1.9Y_0.1P₃O_11.9F_0.1、LiHf_1.9Y_0.1P₃O_11.9Cl_0.1、Li_0.8Hf₂P₃O_11.8Br_0.2、Li_0.8Hf₂P₃O_11.8Br_0.1F_0.1、Li_0.8Hf₂P₃O_11.8Br_0.1Cl_0.1、LiHf_1.9Y_0.1P₃O_11.9Br_0.1、LiHf_1.9Y_0.1P₃O_11.9Br_0.05F_0.05、LiHf_1.9Y_0.1P₃O_11.9Br_0.05Cl_0.05、Li_0.8Ti₂P₃O_11.8F_0.2、Li_0.8Ti₂P₃O_11.8Cl_0.2、LiTi_1.9Y_0.1P₃O_11.9F_0.1、LiTi_1.9Y_0.1P₃O_11.9Cl_0.1、Li_0.8Ti₂P₃O_11.8Br_0.2、Li_0.8Ti₂P₃O_11.8Cl_0.2、LiTi_1.9Y_0.1P₃O_11.9F_0.1、LiTi_1.9Y_0.1P₃O_11.9Cl_0.1、Li_0.8Ti₂P₃O_11.8Br_0.1F_0.1、Li_0.8Ti₂P₃O_11.8Br_0.1Cl_0.1、LiTi_1.9Y_0.1P₃O_11.9Br_0.1、LiTi_1.9Y_0.1P₃O_11.9Br_0.05F_0.05、LiTi_1.9Y_0.1P₃O_11.9Br_0.05Cl_0.05、Li_0.8Zr₂P₃O_11.8F_0.2、Li_0.8Zr₂P₃O_11.8Cl_0.2、LiZr_1.9Y_0.1P₃O_11.9F_0.1、LiZr_1.9Y_0.1P₃O_11.9Cl_0.1、Li_0.8Zr₂P₃O_11.8Br_0.2、Li_0.8Zr₂P₃O_11.8Cl_0.2、LiZr_1.9Y_0.1P₃O_11.9F_0.1、LiZr_1.9Y_0.1P₃O_11.9Cl_0.1、Li_0.8Zr₂P₃O_11.8Br_0.1F_0.1、Li_0.8Zr₂P₃O_11.8Br_0.1Cl_0.1、LiZr_1.9Y_0.1P₃O_11.9Br_0.1、LiZr_1.9Y_0.1P₃O_11.9Br_0.05F_0.05、LiZr_1.9Y_0.1P₃O_11.9Br_0.05Cl_0.05、LiHf_1.9Al_0.1P₃O_11.9F_0.1、LiHf_1.9Al_0.1P₃O_11.9Br_0.1、LiHf_1.9Al_0.1P₃O_11.9F_0.05Br_0.05、LiHf_1.9Al_0.1P₃O_11.9Cl_0.1、LiHf_1.9Al_0.1P₃O_11.9Cl_0.05Br_0.05、LiHf_1.9La_0.1P₃O_11.9F_0.1、LiHf_1.9La_0.1P₃O_11.9Br_0.1、LiHf_1.9La_0.1P₃O_11.9F_0.05Br_0.05、LiHf_1.9La_0.1P₃O_11.9Cl_0.05Br_0.05、LiHf_1.9La_0.1P₃O_11.9Cl_0.1、LiHf_1.9Gd_0.1P₃O_11.9F_0.1、LiHf_1.9Gd_0.1P₃O_11.9F_0.05Br_0.05、LiHf_1.9Gd_0.1P₃O_11.9Cl_0.05Br_0.05、LiHf_1.9Gd_0.1P₃O_11.9Cl_0.1、LiZr_1.9Al_0.1P₃O_11.9F_0.1、LiHf_1.9Al_0.1P₃O_11.9F_0.05Br_0.05、LiHf_1.9Al_0.1P₃O_11.9Cl_0.05Br_0.05、LiZr_1.9Al_0.1P₃O_11.9Cl_0.1、LiZr_1.9La_0.1P₃O_11.9F_0.1、LiZr_1.9La_0.1P₃O_11.9Br_0.1、LiZr_1.9La_0.1P₃O_11.9Br_0.05F_0.05、LiZr_1.9La_0.1P₃O_11.9Br_0.05Cl_0.05、LiZr_1.9La_0.1P₃O_11.9Cl_0.1、LiZr_1.9Gd_0.1P₃O_11.9F_0.1、LiZr_1.9Gd_0.1P₃O_11.9Br_0.1、LiZr_1.9Gd_0.1P₃O_11.9Br_0.05F_0.05、LiZr_1.9Gd_0.1P₃O_11.9Br_0.05Cl_0.05、LiZr_1.9Gd_0.1P₃O_11.9Cl_0.1、LiTi_1.9Al_0.1P₃O_11.9F_0.1、LiTi_1.9Gd_0.1P₃O_11.9Br_0.1、LiTi_1.9Gd_0.1P₃O_11.9Br_0.05F_0.05、LiTi_1.9Gd_0.1P₃O_11.9Br_0.05Cl_0.05、LiTi_1.9Al_0.1P₃O_11.9Cl_0.1、LiTi_1.9La_0.1P₃O_11.9F_0.1、LiTi_1.9La_0.1P₃O_11.9Cl_0.1、LiTi_1.9Gd_0.1P₃O_11.9F_0.1、LiTi_1.9Gd_0.1P₃O_11.9Br_0.1、LiTi_1.9Gd_0.1P₃O_11.9Br_0.05F_0.05、LiTi_1.9Gd_0.1P₃O_11.9Br_0.05Cl_0.05、LiTi_1.9Gd_0.1P₃O_11.9Cl_0.1、Li_0.8Hf₂P₃O_11.8F_0.1Cl_0.1、LiHf_1.9Y_0.1P₃O_11.9F_0.05Cl_0.05、Li_0.8Ti₂P₃O_11.8F_0.1Cl_0.1、LiTi_1.9Y_0.1P₃O_11.9F_0.05Cl_0.05、Li_0.8Zr₂P₃O_11.8F_0.1Cl_0.1、LiZr_1.9Y_0.1P₃O_11.9F_0.05Cl_0.05Or a combination thereof.

11. The solid electrolyte of claim 1, wherein the solid electrolyte has a density of 1x10 after impregnation with a saturated lithium hydroxide solution^-5Siemens per centimeter or greater of ionic conductivity.

12. The solid electrolyte according to claim 1, wherein the solid electrolyte has an ionic conductivity retention of 50% or more in a saturated lithium hydroxide solution.

13. The solid electrolyte of claim 1, wherein the solid electrolyte exhibits when analyzed by X-ray diffraction using CuK α radiation

A first diffraction peak having a maximum point at 19.93 ° 2 θ to 19.99 ° 2 θ, and

a second diffraction peak having a maximum point at a diffraction angle of 20.17 ° 2 θ to 20.25 ° 2 θ.

14. The solid electrolyte of claim 13, wherein the intensity ratio of the second diffraction peak to the first diffraction peak is less than 1.

15. The solid electrolyte of claim 1, wherein the solid electrolyte exhibits when analyzed by X-ray diffraction using CuK α radiation

A first diffraction peak having a maximum point at a diffraction angle of 19.93 DEG 2 theta to 19.99 DEG 2 theta, and

a second diffraction peak having a doublet shape, and wherein the second diffraction peak comprises a peak having a first maximum point at 20.15 ° 2 θ to 20.25 ° 2 θ and a peak having a maximum point at 20.26 ° 2 θ to 20.32 ° 2 θ.

16. The solid electrolyte of claim 15, wherein the intensity ratio of the peak having the first maximum point at 20.15 ° 2 Θ to 20.25 ° 2 Θ to the first diffraction peak is greater than 1.

17. The solid electrolyte according to claim 15, wherein an intensity ratio of the peak having the maximum point of 20.26 ° 2 θ to 20.32 ° 2 θ to the first diffraction peak is greater than 1.

18. The solid electrolyte of claim 1, wherein the solid electrolyte has 1x10^-6Siemens/cm or greater, ion conductivity at 25 ℃.

19. The solid electrolyte according to claim 1, wherein M2 is a trivalent element, X is a halogen atom, 0 ≦ y <0.1, and 0< z < 0.2.

20. A lithium-air battery comprising:

a positive electrode; a negative electrode; and an electrolyte disposed between the positive electrode and the negative electrode,

the electrolyte comprises a solid electrolyte as claimed in any one of claims 1 to 19.

21. The lithium-air battery of claim 20, wherein at least one of the positive electrode and the negative electrode comprises a solid electrolyte comprising a compound of formula 1:

formula 1

Li_xM1_2-yM2_y(PO_4-zX_z)₃

Wherein, in the formula 1,

m1 is a tetravalent element (I),

m2 is a monovalent element, a divalent element, a trivalent element, a tetravalent element, a pentavalent element, a hexavalent element, or a combination thereof,

x is a halogen atom, a pseudohalogen, or a combination thereof,

0< x <8, 0 ≦ y <1, and 0< z < 4.

22. An electrochemical device comprising a solid electrolyte as claimed in any one of claims 1 to 19.

23. The electrochemical device of claim 22, comprising a battery, a supercapacitor, a fuel cell, a sensor, an electrochromic device, or a combination thereof.

24. A method of preparing the solid electrolyte of any one of claims 1-19, the method comprising:

providing a lithium precursor, an M1 precursor, an X precursor, a phosphorus precursor, and optionally an M2 precursor to prepare a precursor mixture; and

heat-treating the precursor mixture to prepare a solid electrolyte including the compound represented by formula 1

Formula 1

Li_xM1_2-yM2_y(PO_4-zX_z)₃

Wherein, in the formula 1,

m1 is a tetravalent element (I),

m2 is a monovalent element, a divalent element, a trivalent element, a tetravalent element, a pentavalent element, a hexavalent element, or a combination thereof,

x is a halogen atom, a pseudohalogen, or a combination thereof,

0< x <8, 0 ≦ y <1, and 0< z < 4.

25. The method of claim 24, wherein the precursor mixture comprises an M2 precursor.

26. The method of claim 24, wherein the heat treatment comprises a first heat treatment at 400 ℃ to 950 ℃.

27. The method of claim 26, further comprising pulverizing the product from the first heat treatment to obtain a pulverized product; and subjecting the pulverized product to a second heat treatment.

28. The method of claim 27, wherein the second heat treatment is performed at 500 ℃ to 1300 ℃.

Technical Field

The present disclosure relates to a solid electrolyte, a method of preparing the solid electrolyte, and a lithium-air battery and an electrochemical device each including the solid electrolyte.

Background

In the lithium-air battery, lithium metal is used as an anode active material, and there is no need to store air as a cathode active material in the battery, so the lithium-air battery can be implemented as a high-capacity battery. In addition, lithium-air batteries have a high theoretical specific energy of 3,500 watt-hours per kilogram (Wh/kg) or greater.

The solid electrolyte of a lithium-air battery is unsatisfactory in stability to lithium hydroxide, which is a discharge product of the lithium-air battery, and, for example, the ion conductivity under strongly alkaline conditions (as in lithium hydroxide) is lowered relative to that in acid. Accordingly, there is a need for improved battery materials.

Disclosure of Invention

Provided are a solid electrolyte that is stable against strong alkali and moisture, and a method of preparing the solid electrolyte.

A lithium-air battery including the solid electrolyte is provided.

An electrochemical device including the solid electrolyte is provided.

Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of embodiments of the disclosure presented.

According to one aspect, there is provided a solid electrolyte comprising: a compound represented by formula 1

Formula 1

Li_xM1_2-yM2_y(PO_4-zX_z)₃

Wherein, in formula 1, M1 is a tetravalent element, M2 is a monovalent element, a divalent element, a trivalent element, a tetravalent element, a pentavalent element, a hexavalent element, or a combination thereof, X is a halogen atom, a pseudohalogen, or a combination thereof, 0< X <8, 0 ≦ y <1, and 0< z < 4.

According to another aspect, there is provided a lithium-air battery including: a positive electrode; a negative electrode; and an electrolyte disposed between the positive electrode and the negative electrode, the electrolyte including the solid electrolyte.

In an embodiment, at least one of the positive electrode and the negative electrode may include the solid electrolyte including the compound of formula 1.

According to another aspect, an electrochemical device including the solid electrolyte is provided.

In embodiments, the electrochemical device may comprise a battery, a supercapacitor, a fuel cell, a sensor, an electrochromic device, or a combination thereof.

According to another aspect, there is provided a method of preparing a solid electrolyte, the method comprising: providing a lithium precursor, an M1 precursor, an X precursor, and a phosphorus precursor to prepare a precursor mixture; and heat-treating the precursor mixture to prepare a solid electrolyte including the compound represented by formula 1

Formula 1

Li_xM1_2-yM2_y(PO_4-zX_z)₃

Wherein, in formula 1, M1 is a tetravalent element, M2 is a monovalent element, a divalent element, a trivalent element, a tetravalent element, a pentavalent element, a hexavalent element, or a combination thereof, X is a halogen atom, a pseudohalogen, or a combination thereof, 0< X <8, 0 ≦ y <1, and 0< z < 4.

In embodiments, in the preparation of the precursor mixture, a M2 precursor may be further added.

Also disclosed is a solid electrolyte comprising: a compound represented by formula 1

Formula 1

Li_xM1_2-yM2_y(PO_4-zX_z)₃

Wherein, in formula 1, M1 is a tetravalent element, M2 is a trivalent element, X is a halogen atom, 0< X <8, 0. ltoreq. y <0.1, and 0< z < 0.2.

Drawings

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

fig. 1 is a graph of intensity (arbitrary unit, a.u.) versus diffraction angle (degrees, 2 θ) showing the results of X-ray diffraction analysis of the solid electrolytes of examples 1,2 and 4 and comparative example 1.

Fig. 2 is an enlarged view of a portion of the diagram shown in fig. 1.

Fig. 3 is a graph of the ionic conductivities (siemens/cm, S/cm) of the solid electrolytes of examples 1 to 4 and comparative example 1 before and after impregnation with lithium hydroxide.

Fig. 4 is a graph of conductivity retention (percentage after impregnation with lithium hydroxide) versus ionic conductivity (log (S/cm)), which illustrates changes in ionic conductivity in the solid electrolytes of example 3 and comparative example 1.

Fig. 5 is a schematic diagram of an embodiment of a lithium-air battery.

Detailed Description

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as limited to the descriptions set forth herein. Accordingly, the embodiments are described below to illustrate aspects only by referring to the figures. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. Expressions such as "at least one (of … …)" when preceding or succeeding a list of elements modify the entire list of elements and do not modify individual elements of the list.

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 "portion" discussed below could be termed a second element, component, region, layer or portion without departing from the teachings herein.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the terms "a", "an", "the" and "at least one" do not denote a limitation of quantity, and are intended to include both the singular and the plural, unless the context clearly dictates otherwise. For example, "an element(s)" has the same meaning as "at least one element" unless the context clearly dictates otherwise. "at least one" is not to be construed as limiting "a (an)". "or" means "and/or". As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

As used herein, "about" includes the stated value and is meant to be within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art in view of the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system). For example, "about" may mean within one or more standard deviations, or within ± 30%, 20%, 10%, or 5%, of the stated value.

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 present disclosure and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. For ease of description, spatially relative terms such as "below … …," "below … …," "lower," "above … …," "upper," and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below … …" can encompass both an orientation above … … and below … …. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

Exemplary embodiments are described herein with reference to cross-sectional views that are schematic illustrations of idealized embodiments. As such, deviations from the shapes of the figures as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to 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, the sharp corners shown 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 present claims.

Hereinafter, embodiments of a solid electrolyte, a method of preparing the solid electrolyte, a lithium-air battery including the solid electrolyte, and an electrochemical device including the solid electrolyte will be described in detail.

According to one aspect, a solid electrolyte including a compound represented by formula 1 is provided.

Formula 1

Li_xM1_2-yM2_y(PO_4-zX_z)₃

In formula 1, M1 may be a tetravalent element, M2 is a monovalent element, a divalent element, a trivalent element, a tetravalent element, a pentavalent element, a hexavalent element, or a combination thereof, and X is a halogen atom, a pseudohalogen, or a combination thereof,

0< x <8, 0 ≦ y <1, and 0< z < 4.

In formula 1, the element is a cationic element.

In formula 1, for example, when M2 is a trivalent element, x may be equal to 1+ y-3 z. When this condition is satisfied, the solid electrolyte including the compound of formula 1 may satisfy charge balance and be in a neutral state.

Desirably, the solid electrolyte of a lithium-air battery is reversibly stable to any changes that may occur under humid conditions or in air. For this reason, stability against lithium hydroxide (LiOH) and moisture as discharge products is required. However, the existing solid electrolyte has low stability against moisture and a strong base such as lithium hydroxide, and thus has very low conductivity. Accordingly, there is an increasing need for solid electrolytes with improved properties.

Disclosed is a solid electrolyte which maintains good ion conductivity even after exposure to a strong base such as lithium hydroxide, and maintains good ion conductivity after exposure to moisture. The solid electrolyte may be obtained by: anions from halogen atoms, pseudohalogens, or combinations thereof are introduced to the phosphate-based electrolyte.

Since the solid electrolyte includes the compound of formula 1 into which anions are introduced, the solid electrolyte may have improved phase stability. In particular, the solid electrolyte may have good stability under strongly alkaline conditions, for example, at a pH of about 12 to about 13, and thus may maintain good ionic conductivity.

In formula 1, M1 may be a tetravalent cationic element, such as hafnium (Hf), titanium (Ti), zirconium (Zr), or a combination thereof.

At some sites of M1 in the crystal structure of the compound, M2 may replace M1. M2 may be, for example, a divalent, trivalent, or tetravalent cationic element, such as aluminum (Al), lanthanum (La), scandium (Sc), cerium (Ce), praseodymium (Pr), gadolinium (Gd), europium (Eu), or combinations thereof. Aluminum (Al), lanthanum (La), scandium (Sc), and gadolinium (Gd) are all trivalent cationic elements, and cerium (Ce) and praseodymium (Pr) may be trivalent or tetravalent elements, and europium (Eu) may be divalent or trivalent elements.

While not wishing to be bound by theory, it is understood that the disclosed M2 element has a large lattice volume and the lithium ion conductivity of the solid electrolyte may be further improved by including M2 as compared to a solid electrolyte into which M2 is not incorporated.

As described above, X can be a halogen atom, a pseudohalogen, or a combination thereof.

As used herein, the term "pseudohalogen" is a halogen-like molecule that includes (e.g., consists of) two or more electronegative atoms that, in the free state (free state), produces an anion similar to a halide ion. Examples of pseudohalogens are Cyanide (CN), cyanate (OCN), thiocyanate (SCN), azide (N)₃) Or a combination thereof.

X may be, for example, at least one halogen atom, for example, two halogen atoms, and may replace oxygen and may remain on an oxygen site in the crystal structure of the compound of formula 1.

For example, X can be chlorine (Cl), bromine (Br), fluorine (F), cyanide, cyanate, thiocyanate, azide, or combinations thereof.

For example, X_3zCan be F_n、Br_n、Cl_n、(F_aCl_1-a)_n、(F_aBr_1-a)_nOr (Cl)_aBr_1-a)_nWherein n may be 1 or less, such as from about 0.1 to about 0.9, such as from about 0.1 to about 0.5, such as from about 0.1 to about 0.3, such as from about 0.1 to about 0.2. Also, a can be from about 0.01 to about 0.99, such as from about 0.2 to about 0.8, from about 0.3 to about 0.7, such as about 0.5.

In formula 1, x may be from about 0.5 to about 1.5, such as from about 0.7 to about 1.3, such as from about 0.8 to about 1.2. In formula 1, y may be 0 to about 0.8, such as 0 to about 0.5, such as about 0.05 to about 0.5, such as about 0.1 to about 0.3. In formula 1, when y is 0 or more and M2 is present, and although not wishing to be bound by theory, it is understood that, because the lattice volume of M2 may be greater than that of M1, a solid electrolyte having further improved ion conductivity may be prepared when a compound including M1 and M2 is used, compared to when M2 is not present in the compound (e.g., when a compound including only M1 is used).

In formula 1, z may be greater than 0 to about 1, such as about 0.01 to about 0.8, such as about 0.02 to about 0.7, such as about 0.03 to about 0.5, such as about 0.05 to about 0.2.

In embodiments, the solid electrolyte may have the following phases: it has a NASICON structure, i.e., a crystal structure that is isomorphic to NASICON. The structure of NASICON or the structure isomorphic with NASICON is shown as general formula A₁Q₂(PO₄)₃Wherein a is a monovalent cation and Q is a single trivalent, tetravalent, or pentavalent ion or a combination of trivalent, tetravalent, or pentavalent ions. The properties of these structures can be identified by X-ray diffraction (XRD) analysis. In an embodiment, in the XRD spectrum, the solid electrolyte including the compound of formula 1 may exhibit a peak at a diffraction angle (2 θ) of 14.1 ° ± 0.5 °, 19.9 ° ± 0.5 °, 20.2 ° ± 0.5 °, 23.5 ° ± 0.5 °, 28.5 ° ± 0.5 °, 31.7 ° ± 0.5 °, or 35.2 ° ± 0.5 °, when analyzed, for example, by X-ray diffraction spectroscopy using CuK α radiation.

The solid electrolyte including the compound of formula 1 may exhibit shifted X-ray diffraction peak characteristics compared to X-ray diffraction peak characteristics of the solid electrolyte including the compound of formula 1 (wherein z ═ 0). From such shifted X-ray diffraction peak characteristics, it can be understood that X replaces some of the oxygen in the compound. For example, X can replace oxygen and remain on the oxygen crystallographic site.

In an embodiment, the compound of formula 1 may exhibit two diffraction peaks in its XRD spectrum at diffraction angles (2 θ) of about 19.8 ° 2 θ to about 20.4 ° 2 θ. The two diffraction peaks may include a first diffraction peak and a second diffraction peak. The first diffraction peak may have a maximum point at a diffraction angle (2 θ) of about 19.93 ° 2 θ to about 19.99 ° 2 θ, and the second diffraction peak may have a maximum point at a diffraction angle (2 θ) of about 20.17 ° 2 θ to about 20.25 ° 2 θ. For example, the first diffraction peak may have a maximum point at a diffraction angle (2 θ) of about 19.95 ° 2 θ to about 19.97 ° 2 θ, and the second diffraction peak may have a maximum point at a diffraction angle (2 θ) of about 20.19 ° 2 θ to about 20.23 ° 2 θ or about 20.20 ° 2 θ to about 20.22 ° 2 θ.

While not wishing to be bound by theory, it is understood that the first diffraction peak is associated with, for example, the (104) crystal plane of a solid electrolyte comprising the compound of formula 1, and the second diffraction peak is associated with, for example, the (110) crystal plane thereof. The height of the second diffraction peak may be in the range of about 72% to about 99%, such as about 75% to about 82%, such as about 77% to about 81%, of the height of the first diffraction peak. The ratio of the intensity of the second diffraction peak (P2) to the intensity of the first diffraction peak (P1) can be less than about 1, from about 0.1 to less than about 1, from about 0.6 to less than about 1, or from about 0.77 to about 0.81.

The first diffraction peak may have a half width of about 0.7 ° 2 θ to about 1.3 ° 2 θ, and the second diffraction peak may have a half width of about 0.7 ° 2 θ to about 1.3 ° 2 θ.

In an embodiment, a solid electrolyte including the compound of formula 1 may exhibit two peaks at diffraction angles (2 θ) of about 19.8 ° 2 θ to about 20.4 ° 2 θ in its XRD spectrum. The two diffraction peaks may include a first diffraction peak and a second diffraction peak. The first diffraction peak may have a maximum at a diffraction angle (2 θ) of about 19.93 ° 2 θ to about 19.99 ° 2 θ, and the second diffraction peak may have a doublet peak shape.

The second diffraction peak having a doublet shape may include a second diffraction peak P2 having a first maximum point at a diffraction angle (2 θ) of about 20.15 ° 2 θ to about 20.25 ° 2 θ, and a second diffraction peak P3 having a second maximum point at a diffraction angle (2 θ) of about 20.26 ° 2 θ to about 20.32 ° 2 θ, for example, a second diffraction peak P2 having a first maximum point at a diffraction angle (2 θ) of about 20.16 ° 2 θ to about 20.24 ° 2 θ, about 20.17 ° 2 θ to about 20.20 ° 2 θ, or about 20.17 ° 2 θ to about 20.18 ° 2 θ, and a second diffraction peak P3 having a second maximum point at a diffraction angle (2 θ) of about 20.28 ° 2 θ to about 20.31 ° 2 θ, or about 20.29 ° 2 θ to about 20.30 ° 2 θ. The first diffraction peak may have a half width of about 0.7 ° 2 θ to about 1.3 ° 2 θ, and the second diffraction peak may have a half width of about 0.7 ° 2 θ to about 1.3 ° 2 θ.

In an embodiment, in an X-ray diffraction spectrum of the solid electrolyte, an intensity ratio of the second diffraction peak P2 to the first diffraction peak may be greater than 1, and an intensity ratio of the second diffraction peak P3 to the first diffraction peak may be greater than 1. X-ray diffraction can be performed with CuK α radiation.

As shown in fig. 2, the second diffraction peak may have a double peak shape including a second diffraction peak a1 having a first maximum point and a second diffraction peak a2 having a second maximum point.

While not wishing to be bound by theory, it is understood that the first diffraction peak is associated with, for example, the (104) crystal plane of the solid electrolyte comprising the compound of formula 1, and the second diffraction peak having the first maximum point is associated with, for example, the (110) crystal plane thereof. The second diffraction peak having the second maximum point is associated with, for example, the (210) crystal plane of the solid electrolyte including the compound of formula 1. The height of the second diffraction peak P2 having the first maximum point at 2 θ of about 20.15 ° 2 θ to about 20.25 ° 2 θ, and the height of the second diffraction peak P3 having the second maximum point at 2 θ of about 20.26 ° 2 θ to about 20.32 ° 2 θ may each exceed 100% of the height of the first diffraction peak. The intensity ratio of the second diffraction peak P2 to the first diffraction peak P1 (P2/P1), and the intensity ratio of the second diffraction peak P3 to the first diffraction peak P1 (P3/P1) can each be greater than 1, e.g., each independently greater than 1 to about 2, greater than 1 to about 1.5, or greater than 1 to about 1.26.

The first diffraction peak may have a half width of about 0.7 ° 2 θ to about 1.3 ° 2 θ, the second diffraction peak P2 having the first maximum point may have a half width of about 0.7 ° 2 θ to about 1.3 ° 2 θ, and the second diffraction peak P3 having the second maximum point may have a half width of about 0.7 ° 2 θ to about 1.3 ° 2 θ.

The compound represented by formula 1 may be a compound represented by formula 2, a compound represented by formula 3, or a compound represented by formula 4.

Formula 2

Li_1+y-3zHf_2-yM2_y(PO_4-zX_z)₃

In the formula 2, the first and second groups,

m2 may be a monovalent element, a divalent element, a trivalent element, a tetravalent element, a pentavalent element, a hexavalent element, or combinations thereof,

x may be a halogen atom, a pseudohalogen, or a combination thereof,

0< y <1, and 0< z < 4.

Formula 3

Li_1+y-3zTi_2-yM2_y(PO_4-zX_z)₃

In the formula 3, the first and second groups,

m2 may be a monovalent element, a divalent element, a trivalent element, a tetravalent element, a pentavalent element, a hexavalent element, or combinations thereof,

x may be a halogen atom, a pseudohalogen, or a combination thereof,

0< y <1, and 0< z < 4.

Formula 4

Li_1+y-3zZr_2-yM2_y(PO_4-zX_z)₃

In the formula 4, the first and second organic solvents are,

m2 may be a monovalent element, a divalent element, a trivalent element, a tetravalent element, a pentavalent element, a hexavalent element, or combinations thereof,

x may be a halogen atom, a pseudohalogen, or a combination thereof,

0< y <1, and 0< z < 4.

In formulas 2 to 4, 1+ y-3z may be from about 0.5 to about 1.5, y may be 0 or greater than 0 to about 0.8, and z may be greater than 0 to about 1.

In the solid electrolyte, the compound represented by formula 1 may be, for example, Li_0.8Hf₂P₃O_11.8F_0.2、Li_0.8Hf₂P₃O_11.8Cl_0.2、LiHf_1.9Y_0.1P₃O_11.9F_0.1、LiHf_1.9Y_0.1P₃O_11.9Cl_0.1、Li_0.8Hf₂P₃O_11.8Br_0.2、Li_0.8Hf₂P₃O_11.8Br_0.1F_0.1、Li_0.8Hf₂P₃O_11.8Br_0.1Cl_0.1、LiHf_1.9Y_0.1P₃O_11.9Br_0.1、LiHf_1.9Y_0.1P₃O_11.9Br_0.05F_0.05、LiHf_1.9Y_0.1P₃O_11.9Br_0.05Cl_0.05、Li_0.8Ti₂P₃O_11.8F_0.2、Li_0.8Ti₂P₃O_11.8Cl_0.2、LiTi_1.9Y_0.1P₃O_11.9F_0.1、LiTi_1.9Y_0.1P₃O_11.9Cl_0.1、Li_0.8Ti₂P₃O_11.8Br_0.2、Li_0.8Ti₂P₃O_11.8Cl_0.2、LiTi_1.9Y_0.1P₃O_11.9F_0.1、LiTi_1.9Y_0.1P₃O_11.9Cl_0.1、Li_0.8Ti₂P₃O_11.8Br_0.1F_0.1、Li_0.8Ti₂P₃O_11.8Br_0.1Cl_0.1、LiTi_1.9Y_0.1P₃O_11.9Br_0.1、LiTi_1.9Y_0.1P₃O_11.9Br_0.05F_0.05、LiTi_1.9Y_0.1P₃O_11.9Br_0.05Cl_0.05、Li_0.8Zr₂P₃O_11.8F_0.2、Li_0.8Zr₂P₃O_11.8Cl_0.2、LiZr_1.9Y_0.1P₃O_11.9F_0.1、LiZr_1.9Y_0.1P₃O_11.9Cl_0.1、Li_0.8Zr₂P₃O_11.8Br_0.2、Li_0.8Zr₂P₃O_11.8Cl_0.2、LiZr_1.9Y_0.1P₃O_11.9F_0.1、LiZr_1.9Y_0.1P₃O_11.9Cl_0.1、Li_0.8Zr₂P₃O_11.8Br_0.1F_0.1、Li_0.8Zr₂P₃O_11.8Br_0.1Cl_0.1、LiZr_1.9Y_0.1P₃O_11.9Br_0.1、LiZr_1.9Y_0.1P₃O_11.9Br_0.05F_0.05、LiZr_1.9Y_0.1P₃O_11.9Br_0.05Cl_0.05、LiHf_1.9Al_0.1P₃O_11.9F_0.1、LiHf_1.9Al_0.1P₃O_11.9Br_0.1、LiHf_1.9Al_0.1P₃O_11.9F_0.05Br_0.05、LiHf_1.9Al_0.1P₃O_11.9Cl_0.1、LiHf_1.9Al_0.1P₃O_11.9Cl_0.05Br_0.05、LiHf_1.9La_0.1P₃O_11.9F_0.1、LiHf_1.9La_0.1P₃O_11.9Br_0.1、LiHf_1.9La_0.1P₃O_11.9F_0.05Br_0.05、LiHf_1.9La_0.1P₃O_11.9Cl_0.05Br_0.05、LiHf_1.9La_0.1P₃O_11.9Cl_0.1、LiHf_1.9Gd_0.1P₃O_11.9F_0.1、LiHf_1.9Gd_0.1P₃O_11.9F_0.05Br_0.05、LiHf_1.9Gd_0.1P₃O_11.9Cl_0.05Br_0.05、LiHf_1.9Gd_0.1P₃O_11.9Cl_0.1、LiZr_1.9Al_0.1P₃O_11.9F_0.1、LiHf_1.9Al_0.1P₃O_11.9F_0.05Br_0.05、LiHf_1.9Al_0.1P₃O_11.9Cl_0.05Br_0.05、LiZr_1.9Al_0.1P₃O_11.9Cl_0.1、LiZr_1.9La_0.1P₃O_11.9F_0.1、LiZr_1.9La_0.1P₃O_11.9Br_0.1、LiZr_1.9La_0.1P₃O_11.9Br_0.05F_0.05、LiZr_1.9La_0.1P₃O_11.9Br_0.05Cl_0.05、LiZr_1.9La_0.1P₃O_11.9Cl_0.1、LiZr_1.9Gd_0.1P₃O_11.9F_0.1、LiZr_1.9Gd_0.1P₃O_11.9Br_0.1、LiZr_1.9Gd_0.1P₃O_11.9Br_0.05F_0.05、LiZr_1.9Gd_0.1P₃O_11.9Br_0.05Cl_0.05、LiZr_1.9Gd_0.1P₃O_11.9Cl_0.1、LiTi_1.9Al_0.1P₃O_11.9F_0.1、LiTi_1.9Gd_0.1P₃O_11.9Br_0.1、LiTi_1.9Gd_0.1P₃O_11.9Br_0.05F_0.05、LiTi_1.9Gd_0.1P₃O_11.9Br_0.05Cl_0.05、LiTi_1.9Al_0.1P₃O_11.9Cl_0.1、LiTi_1.9La_0.1P₃O_11.9F_0.1、LiTi_1.9La_0.1P₃O_11.9Cl_0.1、LiTi_1.9Gd_0.1P₃O_11.9F_0.1、LiTi_1.9Gd_0.1P₃O_11.9Br_0.1、LiTi_1.9Gd_0.1P₃O_11.9Br_0.05F_0.05、LiTi_1.9Gd_0.1P₃O_11.9Br_0.05Cl_0.05、LiTi_1.9Gd_0.1P₃O_11.9Cl_0.1、Li_0.8Hf₂P₃O_11.8F_0.1Cl_0.1、LiHf_1.9Y_0.1P₃O_11.9F_0.05Cl_0.05、Li_0.8Ti₂P₃O_11.8F_0.1Cl_0.1、LiTi_1.9Y_0.1P₃O_11.9F_0.05Cl_0.05、Li_0.8Zr₂P₃O_11.8F_0.1Cl_0.1、LiZr_1.9Y_0.1P₃O_11.9F_0.05Cl_0.05Or a combination thereof.

In embodiments, the solid electrolyte may have, for example, about 1x10 after impregnation with a saturated lithium hydroxide (LiOH) solution^-6Siemens per centimeter (S/cm) or greater, e.g., about 1.4X10^-5S/cm or greater, about 2x10^-5S/cm or greater, about 3x10^-5S/cm or greater, or about 5X10^-5S/cm or greater, e.g., about 1x10^-5S/cm to about 1x10^-3S/cm, about 5X10^-5S/cm to about 5x10^-4S/cm, about 1X10^-5S/cm to about 1x10^-4S/cm, and thus can be maintained even after exposure to strong bases. It is thus understood that the solid electrolyte according to the embodiment may have excellent stability against strong alkali.

As used herein, the term "ionic conductivity after impregnation with a saturated lithium hydroxide (LiOH) solution" means the ionic conductivity of a solid electrolyte after impregnating the solid electrolyte with a saturated lithium hydroxide solution and then maintaining at 40 ℃ for 6 days or 7 days.

In embodiments, the solid electrolyte may have an ionic conductivity retention of about 50% or greater, such as about 56% or greater, such as about 95% or greater, such as about 100% or greater, such as about 150% or greater, such as about 220% or greater, such as about 50% to about 400%, about 100% to about 350%, or about 100% to about 300%, in a saturated lithium hydroxide (LiOH) solution (e.g., after 6 or 7 days at 40 ℃).

Throughout the specification, "ionic conductivity retention rate for a saturated lithium hydroxide (LiOH) solution" can be calculated using equation 1.

Equation 1

The ionic conductivity retention (%) was (ionic conductivity after the electrolyte was impregnated with the saturated lithium hydroxide solution)/(ionic conductivity before the electrolyte was impregnated with the saturated lithium hydroxide solution) X100%

In embodiments, the solid electrolyte may have, for example, about 1x10^-6Siemens per centimeter (S/cm) or greater, e.g., about 1X10^-5S/cm or greater, e.g., about 3x10^-5S/cm or greater, e.g., about 1x10^-6S/cm to about 1x10^-3S/cm, about 5X10^-6S/cm to about 5x10^-4S/cm, about 1X10^-5S/cm to about 1x10^-4S/cm ion conductivity at 25 ℃. Since the solid electrolyte according to the embodiment has such high ion conductivity, the lithium-air battery including such a solid electrolyte may have further reduced internal resistance.

The solid electrolyte according to the embodiment may be in the form of particles. For example, the solid electrolyte may have an average particle size of about 5 nanometers (nm) to about 500 micrometers (μm), such as about 100nm to about 15 μm, such as about 300nm to about 10 μm, and about 0.01 square meters per gram (m)²Per g) to about 1000m²In g, e.g. about 0.1m²G to about 500m²In g, or about 0.5m²G to about 100m²Specific surface area in g. The specific surface area can be determined using a nitrogen isotherm. See, e.g., E.P. Barrett, L.G. Joyner, P.P. Halenda, The determination of pore volume and area distributions in pore substructures.I.computers from nitrogen isomers, J.Am.chem.Soc. (1951), 73, 373-type 380, The contents of which are incorporated herein by reference in their entirety.

Hereinafter, a method of preparing the solid electrolyte according to the embodiment will be further described.

The lithium precursor, M1 precursor, X precursor, phosphorus precursor, and optionally M2 precursor may be contacted, e.g., mixed together, to obtain a precursor mixture. In the preparation of the precursor mixture, a M2 precursor may be further added. M1 of the M1 precursor, X of the X precursor, and M2 of the M2 precursor may be as defined in formula 1.

A solvent may be added to the precursor mixture as needed. The solvent can be any suitable solvent, such as a solvent capable of dissolving or dispersing the lithium precursor, M1 precursor, X precursor, phosphorus precursor, and optionally M2 precursor. The solvent can be, for example, ethanol, water, ethylene glycol, isopropanol, or a combination thereof. Also, precursors including a plurality of M1, X, phosphorus, and optionally M2 may be used.

The mixing can be performed using methods known in the art, for example, milling, blending, or sputtering. The milling may be carried out using a ball mill, jet mill, bead mill or roller mill.

Subsequently, the precursor mixture may be subjected to a first thermal treatment.

In the first heat treatment of the precursor mixture, the ramp rate may be from about 1 degree celsius per minute (c/min) to about 10 c/min, and the first heat treatment temperature may be in the range of from about 400 c to about 950 c, such as in the range of from about 700 c to about 900 c. When the temperature increase rate in the first heat treatment is within this range, the first heat treatment may be sufficient to obtain a solid electrolyte according to an embodiment. A second heat treatment may be used, which will be further described later.

The first heat treatment may be performed under an oxidizing gas atmosphere. The oxidizing gas atmosphere may be generated using, for example, air or oxygen. The first heat treatment time may vary depending on the first heat treatment temperature, and the like. The first heat treatment time may be, for example, in the range of about 1 hour to about 20 hours, such as in the range of about 2 hours to about 12 hours, or such as in the range of about 5 hours to about 12 hours.

The M1 precursor and the M2 precursor may each independently be a M1 or M2 containing compound, such as an M1 or M2 containing oxide, an M1 or M2 containing carbonate, an M1 or M2 containing chloride, an M1 or M2 containing phosphate, an M1 or M2 containing hydroxide, an M1 or M2 containing nitrate, or a combination thereof. For example, the M1 precursor and the M2 precursor can each independently be hafnium oxide, zirconium oxide, titanium oxide, yttrium oxide, hafnium nitrate, hafnium sulfate, zirconium nitrate, zirconium sulfate, or a combination thereof.

The X precursor can be, for example, lithium chloride, lithium fluoride, lithium bromide, or a combination thereof. The lithium precursor can be, for example, lithium oxide, lithium carbonate, lithium chloride, lithium sulfide, lithium nitrate, lithium phosphate, lithium hydroxide, or combinations thereof.

The phosphorus precursor may be, for example, (NH)₄)₂HPO₄、(NH₄)H₂PO₄、Na₂HPO₄、Na₃PO₄Or a combination thereof.

The amounts of the lithium precursor, M1 precursor, M2 precursor, X precursor, and phosphorus precursor may be stoichiometrically controlled to obtain a compound represented by formula 1.

The product from the first heat treatment may then be comminuted to obtain a comminuted product. The comminuted product may be, for example, in the form of a powder comprising a plurality of particles. The pulverized product (particles) obtained by the pulverization may have a size of about 10 μm or less. When the pulverized particles have a size within this range, the particles may be small enough to be sufficiently pulverized and mixed, and may also promote the formation of a NASICON structure, for example, a compound having a structure isomorphic with NASICON. As used herein, the term "size" may refer to the average particle size when the particles are spherical, or may refer to the length of the major axis when the particles are non-spherical. The size of the particles can be measured using a scanning electron microscope or a particle size analyzer, for example by light scattering.

Next, the pulverized product may be subjected to a second heat treatment. In the second heat treatment of the pulverized product, the temperature rising rate may be about 1 ℃/minute to about 10 ℃/minute. The second heat treatment temperature may be in the range of about 500 ℃ to about 1300 ℃, for example in the range of about 800 ℃ to about 1200 ℃.

In an embodiment, the second heat treatment temperature may be higher than the first heat treatment temperature. The pulverized product may be pressed into a tablet before the second heat treatment is performed on the pulverized product. When the second heat treatment is performed on the pulverized product in the form of a sheet, it may become easier to obtain a target solid electrolyte due to a reduced diffusion distance in the material to be heat-treated. When the second heat treatment is performed on the pulverized product in the form of particles, a longer heat treatment time and a higher heat treatment temperature may be used, for example to accommodate a longer diffusion distance, than when the second heat treatment is performed on the pulverized product in the form of sheets.

The conditions of the second heat treatment may be determined according to the valence or oxidation values of M1 and M2. For example, the second heat treatment may be performed, for example, under an oxidizing gas atmosphere, a reducing gas atmosphere, or an inert gas atmosphere. The oxidizing gas atmosphere may be generated with, for example, air or oxygen. The reducing gas atmosphere may be generated with a reducing gas such as hydrogen. The inert gas atmosphere may be generated with an inert gas such as nitrogen, argon or helium.

The second heat treatment time may vary depending on the second heat treatment temperature. The second heat treatment time may be, for example, in the range of about 1 hour to about 50 hours, or, for example, in the range of about 4 hours to 48 hours.

By the second heat treatment, the compound of formula 1 may be obtained. When the rate of temperature rise in the first and second heat treatments is within the disclosed range, the heat treatment may be sufficient to form the desired crystal structure, and may also be economical due to reduced synthesis time.

In embodiments, the solid electrolyte may be used, for example, as an electrolyte for a metal-air battery such as a lithium-air battery. The solid electrolyte may be used as an electrolyte for an all-solid battery or an electrolyte for a lithium battery. The solid electrolyte can be used for preparing a positive electrode and a negative electrode of a battery. The solid electrolyte may be used to coat the surfaces of the positive and negative electrodes.

According to another aspect of the disclosure, an electrochemical device including the solid electrolyte is provided. By including the solid electrolyte, which may be chemically stable and may simultaneously conduct ions and electrons, stability against moisture and strong alkali may be improved, and thus deterioration of an electrochemical device may be effectively suppressed.

In embodiments, the electrochemical device may be, for example, a battery (accumulator), a supercapacitor, a fuel cell, a sensor, an electrochromic device, or a combination thereof. However, the disclosed embodiments are not limited thereto. Any suitable device that can be used as an electrochemical device in the art can be used.

The battery may be, for example, a primary battery or a secondary battery. The battery may be, for example, a lithium battery, a sodium battery, or the like. However, the disclosed embodiments are not limited thereto. The lithium battery may be, for example, a lithium ion battery or a lithium-air battery. However, the disclosed embodiments are not limited thereto. The electrochromic device may be an electrochemical mirror, a window, or a screen. However, the disclosed embodiments are not limited thereto.

The electrochemical device may be, for example, a lithium metal battery or a lithium-air battery. The battery includes a positive electrode, and a negative electrode, and an electrolyte therebetween.

The positive electrode may be porous. Since the positive electrode is porous, diffusion of air or oxygen into the positive electrode can be promoted.

According to another aspect of the disclosure, a lithium-air battery may include a positive electrode according to the disclosed embodiments, a negative electrode, and a solid electrolyte according to the disclosed embodiments, the solid electrolyte being interposed between the positive electrode and the negative electrode.

At least one of the anode and the cathode may include a solid electrolyte according to an embodiment. The negative electrode may include lithium.

Since the lithium-air battery uses the solid electrolyte as described above, the lithium-air battery can have improved stability against moisture and strong alkali and ensure its reversibility under humid or air conditions, allowing the battery to operate smoothly. The lithium-air battery may have improved structural stability and its deterioration may be suppressed.

In an embodiment, the lithium-air battery may include a positive electrode according to an embodiment. The positive electrode may be disposed on, for example, a positive current collector.

In embodiments, the positive electrode may include a solid electrolyte according to the disclosed embodiments. The amount of the solid electrolyte may be in the range of about 2 parts by weight to about 70 parts by weight, such as 3 parts by weight to about 60 parts by weight, such as about 10 parts by weight to about 60 parts by weight, each relative to 100 parts by weight of the positive electrode.

In fabricating the positive electrode, pores may be introduced into the positive electrode using a pore-forming agent. The positive electrode may be in the form of a porous disc, a porous sheet, or the like. However, the positive electrode is not limited thereto. The positive electrode may have any suitable form depending on the shape of the battery.

For example, the positive electrode may be permeable to a gas such as oxygen or air. Thus, the positive electrode is distinguished from a positive electrode that is substantially impermeable to gases such as oxygen or air, for example, a positive electrode that is only ionically conductive. The positive electrode may be porous and/or permeable to gases, and thus oxygen or air may readily diffuse into the positive electrode. In addition, lithium ions and/or electrons can also easily migrate through the solid electrolyte included in the positive electrode. Therefore, an electrochemical reaction involving oxygen, lithium ions, and electrons can be promoted in the positive electrode.

In an embodiment, in manufacturing the positive electrode, an electrically conductive (conductive) material may be further added in addition to the solid electrolyte to further improve electron conductivity and ion conductivity. For example, the conductive material may be porous. Due to the porosity of the conductive material, air permeation may be promoted. The conductive material may be any material having porosity and/or conductivity that is available in the art. For example, the conductive material may be a carbonaceous material having porosity. The carbonaceous material may be, for example, carbon black, graphite, graphene, activated carbon, carbon fiber, or a combination thereof. However, the embodiment is not limited thereto. Any suitable carbonaceous material available in the art may be used. The conductive material may be, for example, a metal material. For example, the metal material may be a metal fiber, a metal mesh, a metal powder, or a combination thereof. The metal powder may comprise, for example, copper, silver, nickel or aluminum in powder form. The conductive material may be, for example, an organic conductive material. The organic conductive material may be, for example, a polyphenylene derivative, a polythiophene derivative, or a combination thereof. For example, the conductive materials may be used alone or in combination thereof. The positive electrode may include a composite conductor as the conductive material. The positive electrode may further comprise any suitable conductive material in addition to the composite conductor.

In an embodiment, the positive electrode may further include a catalyst for oxidation/reduction of oxygen. Examples of the catalyst may include: metal-based catalysts such as catalysts comprising platinum, gold, silver, palladium, ruthenium, rhodium, osmium, or combinations thereof; oxide-based catalysts such as manganese oxide, iron oxide, cobalt oxide, nickel oxide, or combinations thereof; organometallic based catalysts such as cobalt phthalocyanine. Combinations comprising at least two of the foregoing may be used. However, the embodiment is not limited thereto. Any suitable catalyst for the oxidation/reduction of oxygen used in the art may be used.

In embodiments, the catalyst may be disposed on a catalyst support. The catalyst support may be an oxide support, a zeolite support, a clay-based mineral support, a carbon support, or a combination thereof. The oxide support may be a metal oxide support comprising: aluminum (Al), zirconium (Zr), titanium (Ti), cerium (Ce), praseodymium (Pr), samarium (Sm), europium (Eu), terbium (Tb), thulium (Tm), ytterbium (Yb), antimony (Sb), bismuth (Bi), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), niobium (Nb), molybdenum (Mo), tungsten (W), or a combination thereof. Examples of the oxide support may include alumina, silica, zirconia, titania, or a combination thereof. The oxide support may be a semimetal oxide support including silicon (Si). Examples of the carbon support may include: carbon black such as ketjen black, acetylene black, channel black, lamp black, or a combination thereof; graphite such as natural graphite, artificial graphite, expandable graphite, or combinations thereof; activated carbon; or carbon fibers. Combinations comprising at least two of the foregoing may be used. However, the embodiment is not limited thereto. Any suitable catalyst support available in the art may be used.

In an embodiment, the positive electrode may further include a binder. For example, the binder may include a thermoplastic resin or a heat curable resin. For example, the binder may include polyethylene, polypropylene, Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), styrene-butadiene rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, or ethylene-acrylic acid copolymer, which may be used alone or in combination thereof. However, the embodiment is not limited thereto. Any suitable adhesive available in the art may be used.

In an embodiment, the positive electrode may be manufactured by: mixing together a conductive material, a catalyst for oxidation/reduction of oxygen, and a binder and adding a suitable solvent thereto to prepare a positive electrode slurry, and coating the positive electrode slurry on the surface of a substrate and drying the coated resultant, and optionally compression-molding the dried product to improve electrode density. For example, the substrate may be a positive electrode current collector, a separator, or a solid electrolyte membrane. For example, the positive electrode current collector may be a gas diffusion layer. The conductive material may be, for example, a composite conductor.

For example, the catalyst and binder for oxidation/reduction of oxygen may be omitted depending on the type of the positive electrode.

In an embodiment, the lithium-air battery may include a negative electrode. The negative electrode may include the solid electrolyte.

The negative electrode may include lithium.

The negative electrode may be, for example, a lithium metal thin film or a lithium-based alloy thin film. For example, the lithium-based alloy may be a lithium alloy including, for example: aluminum, tin, magnesium, indium, calcium, titanium, vanadium, or combinations thereof.

The lithium-air battery according to the embodiment may include an electrolyte between the positive electrode and the negative electrode, as described above.

For example, the electrolyte may be a solid electrolyte including the compound represented by formula 1.

For example, the electrolyte may further include a second solid electrolyte, a gel electrolyte, a liquid electrolyte, or a combination thereof, in addition to the solid electrolyte. The second solid electrolyte, the gel electrolyte and the liquid electrolyte are not particularly limited. Any suitable electrolyte available in the art may be used.

In an embodiment, the second solid electrolyte may include: a solid electrolyte comprising an ion-conducting inorganic material, a solid electrolyte comprising a Polymeric Ionic Liquid (PIL) and a lithium salt, a solid electrolyte comprising an ion-conducting polymer and a lithium salt, a solid electrolyte comprising an electron-conducting polymer, or a combination thereof. However, the disclosed embodiments are not limited thereto. Any suitable solid electrolyte available in the art may be used.

For example, the ion-conducting inorganic material can include a glass or amorphous metal ion conductor, a ceramic active metal ion conductor, a glass-ceramic active metal ion conductor, or a combination thereof. However, the embodiment is not limited thereto. Any ion-conducting inorganic material available in the art may be used. For example, the ion-conductive inorganic material may be ion-conductive inorganic particles or a pulverized product thereof, for example, in a sheet form.

For example, the ion-conductive inorganic material may be BaTiO₃Pb (Zr) in which a is 0. ltoreq. a.ltoreq.1_1-aTi_a)O₃(PZT) wherein 0. ltoreq. x<1 and 0. ltoreq. y<Pb of 1_1-xLa_xZr_1-yTi_yO₃(PLZT)，Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃(PMN-PT)，HfO₂，SrTiO₃，SnO₂，CeO₂，Na₂O，MgO，NiO，CaO，BaO，ZnO，ZrO₂，Y₂O₃，Al₂O₃，TiO₂，SiO₂SiC, lithium phosphate (Li)₃PO₄) Lithium titanium phosphate(Li_xTi_y(PO₄)₃Wherein 0 is<x<2 and 0<y<3) Lithium aluminum titanium phosphate (Li)_xAl_yTi_z(PO₄)₃Wherein 0 is<x<2，0<y<1, and 0<z<3) Where x is 0. ltoreq. x.ltoreq.1, y is 0. ltoreq. y.ltoreq.1, a is 0. ltoreq. a.ltoreq.1, and b is 0. ltoreq. b.ltoreq.1_1+x+y(Al_aGa_1-a)_x(Ti_bGe_1-b)_2-xSi_yP_3-yO₁₂Lithium lanthanum titanate (Li)_xLa_yTiO₃Wherein 0 is<x<2, and 0<y<3) Lithium germanium thiophosphate (Li)_xGe_yP_zS_wWherein 0 is<x<4，0<y<1，0<z<1, and 0<w<5) Lithium nitride (Li)_xN_yWherein 0 is<x<4, and 0<y<2) Based on SiS₂Glass (Li)_xSi_yS_zWherein 0 is<x<3，0<y<2, and 0<z<4) Based on P₂S₅Glass (Li)_xP_yS_zWherein 0 is<x<3，0<y<3, and 0<z<7) Based on Li₂O, LiF-based, LiOH-based, Li-based₂CO₃Based on LiAlO₂Or based on Li₂O-Al₂O₃-SiO₂-P₂O₅-TiO₂-GeO₂Ceramics based on garnet (Li)_3+xLa₃M₂O₁₂Where 0 ≦ x ≦ 5, M ═ Te, Nb, or Zr), or a combination thereof.

For example, the Polymeric Ionic Liquid (PIL) may comprise: i) the following cations: ammonium-based cations, pyrrolidine-basedBased on pyridineBased on pyrimidinesBased on imidazoleBased on piperidineCationic pyrazole-based compounds ofBased on a cation ofAzoleBased on pyridazineBased on a cation ofOf (4) a cation, a sulfonium-based cation, a triazole-based cationA cation of (a), or a combination thereof; and ii) an anion selected from the group consisting of: BF (BF) generator₄ ^-、PF₆ ^-、AsF₆ ^-、SbF₆ ^-、AlCl₄ ^-、HSO₄ ^-、ClO₄ ^-、CH₃SO₃ ^-、CF₃CO₂ ^-、(CF₃SO₂)₂N^-、Cl^-、Br^-、I^-、SO₄ ^2-、CF₃SO₃ ^-、(C₂F₅SO₂)(CF₃SO₂)N^-、NO₃ ^-、Al₂Cl₇ ^-、CH₃COO^-、(CF₃SO₂)₃C^-、(CF₃CF₂SO₂)₂N^-、(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. For example, the Polymeric Ionic Liquid (PIL) may be poly (bis (trifluoromethanesulfonyl) imide (TFSI) (diallyldimethylammonium), poly (bis (trifluoromethanesulfonyl) imide 1-allyl-3-methylimidazole) Poly (bis (trifluoromethanesulfonyl) imide N-methyl-N-propylpiperidine)) Or a combination thereof.

The ionically conductive polymer may comprise at least one ionically conductive repeat unit. Examples are derived from ether-based monomers, acryl-based monomers, methacryl-based monomers, siloxane-based monomers, or combinations thereof.

The ionically conductive polymer may include, for example, polyethylene oxide (PEO), polyvinyl alcohol (PVA), polyvinyl pyrrolidone (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), polyvinyl acetate, phosphate polymers, polyester sulfides, polyvinylidene fluoride (PVdF), Li-substituted Nafion, or combinations thereof. However, the disclosed embodiments are not limited thereto. Any suitable ionically conductive polymer available in the art may be used.

The electron conducting polymer may be, for example, a polyphenylene derivative or a polythiophene derivative. However, the disclosed embodiments are not limited thereto. Any suitable electronically conductive polymer available in the art may be used.

In embodiments, the gel electrolyte may be obtained, for example, by: adding a low-molecular-weight solvent to the solid electrolyte interposed between the positive electrode and the negative electrode. The gel electrolyte may be a gel electrolyte obtained by: a low molecular weight organic compound such as a solvent or an oligomer is further added to the polymer. The gel electrolyte may be a gel electrolyte obtained by: a low molecular weight organic compound such as a solvent or oligomer is further added to any suitable polymer electrolyte.

In an embodiment, the liquid electrolyte may include a solvent and a lithium salt.

The solvent may include an organic solvent, an Ionic Liquid (IL), an oligomer, or a combination thereof. However, the disclosed embodiments are not limited thereto. Any suitable solvent available in the art that is in liquid form at room temperature (25 ℃) may be used.

The organic solvent may include, for example, an ether-based solvent, a carbonate-based solvent, an ester-based solvent, a ketone-based solvent, or a combination thereof. For example, the organic solvent may include propylene carbonate, ethylene carbonate, fluoroethylene carbonate, vinyl ethylene 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, gamma-butyrolactone, dioxolane, 4-methyldioxolane, dimethylacetamide, dimethyl sulfoxide, dimethylsulfoxide, and dibutyl carbonateAn alkane, 1, 2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, succinonitrile, diglyme (DEGDME), Tetraglyme (TEGDME), polyethylene glycol dimethyl ether (PEGDME, Mn ═ 500), dimethyl ether, diethyl ether, dibutyl ether, dimethoxyethane, or a combination thereof. However, the disclosed embodiments are not limited thereto. The organic solvent can be any suitable organic solvent available in the art that is in liquid form at room temperature.

The Ionic Liquid (IL) may comprise, for example: i) ammonium-based cations, pyrrolidine-basedBased on pyridineBased on pyrimidinesBased on imidazoleBased on piperidineCationic pyrazole-based compounds ofBased on a cation ofAzoleBased on pyridazineBased on a cation ofOf (4) a cation, a sulfonium-based cation, a triazole-based cationOr a combination thereof, and ii) an anion such as BF₄ ^-、PF₆ ^-、AsF₆ ^-、SbF₆ ^-、AlCl₄ ^-、HSO₄ ^-、ClO₄ ^-、CH₃SO₃ ^-、CF₃CO₂ ^-、(CF₃SO₂)₂N^-、Cl^-、Br^-、I^-、SO₄ ^2-、CF₃SO₃ ^-、(C₂F₅SO₂)(CF₃SO₂)N^-、NO₃ ^-、Al₂Cl₇ ^-、CH₃COO^-、(CF₃SO₂)₃C^-、(CF₃CF₂SO₂)₂N^-、(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.

The lithium salt may include lithium bis (trifluoromethanesulfonyl) imide (LiN (SO)₂CF₃)₂，LiTFSI)、LiPF₆、LiBF₄、LiAsF₆、LiClO₄、LiNO₃Lithium bis (oxalato) borate (LiBOB), LiCF₃SO₃、LiN(SO₂C₂F₅)₂、LiN(SO₂F)₂、LiC(SO₂CF₃)₃、LiN(SO₃CF₃)₂、LiC₄F₉SO₃、LiAlCl₄Or a combination thereof. However, the disclosed embodiments are not limited thereto. Any suitable material that is useful in the art as a lithium salt may be used. The concentration of the lithium salt may be, for example, about 0.01M to about 5.0M.

In an embodiment, the lithium-air battery may further include a separator between the positive electrode and the negative electrode. Any suitable separator may be used, such as a separator having suitable durability under the operating conditions of a lithium-air battery. For example, the separator may comprise a polymeric nonwoven fabric such as a nonwoven fabric of a polypropylene material or a nonwoven fabric of polyphenylene sulfide; porous films of olefin resins such as polyethylene or polypropylene; or glass fibers. The separator may be used in combination of at least two kinds thereof.

For example, the electrolyte may have a structure in which a solid polymer electrolyte is impregnated in a separator, or a structure in which a liquid electrolyte is impregnated in a separator. For example, the electrolyte in which the solid polymer electrolyte impregnates the separator may be prepared by: the solid polymer electrolyte membranes are disposed on opposite surfaces of the separator and simultaneously rolled. For example, when the electrolyte includes a liquid electrolyte impregnated in a separator, it may be prepared by: a liquid electrolyte including a lithium salt is injected into the separator.

In an embodiment, the lithium-air battery may be manufactured by: the negative electrode is mounted on the inside of a case, the electrolyte is sequentially disposed on the negative electrode, the positive electrode is disposed on the electrolyte, and a porous positive electrode current collector is disposed on the positive electrode, and then a pressing member is disposed on the porous positive electrode current collector to press the resulting unit cell structure with the pressing member, thereby allowing air to be transmitted to an air electrode (i.e., the positive electrode). The case may be divided into upper and lower portions contacting the negative electrode and the air electrode, respectively. An insulating resin may be disposed between the upper and lower portions of the case to electrically insulate the positive and negative electrodes from each other.

The lithium-air battery may be used as a lithium primary battery or a lithium secondary battery. The lithium-air cell can have any suitable shape, such as a coin, button, sheet, stack, cylinder, plane, or angular shape. However, the disclosed embodiments are not limited thereto. The lithium-air battery may be used in a large-sized battery for an electric vehicle.

Fig. 5 is a schematic diagram illustrating a structure of a lithium-air battery 500 according to an embodiment.

Referring to fig. 5, a lithium-air battery 500 according to an embodiment may include a positive electrode 200 adjacent to a first current collector 210 and using oxygen as an active material, a negative electrode 300 adjacent to a second current collector 310 and including lithium, and a first electrolyte 400 interposed between the positive electrode 200 and the negative electrode 300. The first electrolyte 400 may be a separator impregnated with a liquid electrolyte.

The second electrolyte 450 may be disposed between the positive electrode 200 and the first electrolyte 400. The second electrolyte 450, which is a lithium ion conductive solid electrolyte membrane, may be a solid electrolyte according to the disclosed embodiments. The first current collector 210 may be porous and function as a gas diffusion layer that allows diffusion of air. A pressing member 220 for transferring air to the positive electrode 200 may be disposed on the first current collector 210.

A case 320 made of insulating resin may be provided as shown in fig. 5. Air may be supplied into the lithium-air battery 500 through the air inlet 230a and may be discharged through the air outlet 230 b. The lithium-air battery 500 may be accommodated in a stainless steel container.

The term "air" as used herein is not limited to atmospheric air and, for convenience, may refer to a combination of gases including oxygen, or pure oxygen. This broad definition of the term "air" also applies to any other term used herein including "air cells" and "air electrodes".

Embodiments of the disclosure will now be described in further detail with reference to the following examples. However, these examples are for illustrative purposes only and are not intended to limit the scope of the disclosed embodiments.

Examples

Formation of solid electrolyte

Comparative example 1: LiHf (LiHf)₂P₃O₁₂

According to LiHf₂P₃O₁₂Composition ratio of (A) to Li as a lithium precursor₂CO₃HfO as a precursor of M1₂And (NH) as a phosphorus precursor₄)₂HPO₄Mixed in stoichiometric ratio, then ethanol was added thereto and mixed to obtain a precursor mixture. The precursor mixture was placed in a ball mill and then pulverized and mixed for about 4 hours. The resulting mixture was dried, heated to about 900 ℃ at a rate of about 5 ℃/minute, and then subjected to a first heat treatment under an air atmosphere for about 12 hours.

The powder obtained by the first heat treatment was pulverized and then pressed to form a tablet having a diameter of about 1.3cm and a height of about 0.5 cm. The sheet was subjected to a second heat treatment at about 1200 ℃ for about 4 hours under an air atmosphere to obtain a target product. For the second heat treatment, the temperature was raised to 1200 ℃ at a ramp rate of about 5 ℃/min.

Example 1: li_0.8Hf₂P₃O_11.8F_0.2

A solid electrolyte was prepared in the same manner as in comparative example 1, except that: further lithium fluoride (LiF) is added in the preparation of the precursor mixture, the amount of which is stoichiometrically controlled to obtain Li_0.8Hf₂P₃O_11.8F_0.2The first heat treatment is performed at about 800 deg.c, and the second heat treatment is performed at about 1200 deg.c.

Example 2: li_0.8Hf₂P₃O_11.8Cl_0.2

A solid electrolyte was prepared in the same manner as in comparative example 1, except that: further adding lithium chloride (LiCl) to the prepared precursor mixtureStoichiometrically controlling the amount of lithium chloride to obtain Li_0.8Hf₂P₃O_11.8Cl_0.2The first heat treatment is performed at about 800 c and the second heat treatment is performed at about 1250 c.

Example 3: LiHf (LiHf)_1.9Y_0.1P₃O_11.9F_0.1

A solid electrolyte was prepared in the same manner as in comparative example 1, except that: further lithium fluoride (LiF) and yttrium oxide (Y) were added to the preparation of the precursor mixture₂O₃) Stoichiometrically controlling the amounts of lithium fluoride and yttrium oxide to obtain LiHf_1.9Y_0.1P₃O_11.9F_0.1The first heat treatment is performed at about 850 deg.c, and the second heat treatment is performed at about 1300 deg.c.

Example 4: LiHf (LiHf)_1.9Y_0.1P₃O_11.9Cl_0.1

A solid electrolyte was prepared in the same manner as in comparative example 1, except that: further lithium chloride (LiCl) and yttrium oxide (Y) were added to the preparation of the precursor mixture₂O₃) Stoichiometrically controlling the amounts of lithium chloride and yttrium oxide to obtain LiHf_1.9Y_0.1P₃O_11.9Cl_0.1The first heat treatment is performed at about 850 deg.c and the second heat treatment is performed at about 1250 deg.c.

Examples 5 and 6

A solid electrolyte having a composition in table 1 was prepared in the same manner as in example 1, except that: in preparing the precursor mixture, zirconium oxide and titanium oxide were used instead of hafnium oxide (HfO), respectively₂) As M1 precursors, the amount of each precursor was stoichiometrically controlled to obtain the target product. In example 5, the first heat treatment and the second heat treatment were performed at about 900 ℃ and about 1300 ℃, respectively. In example 6, the first heat treatment and the second heat treatment were performed at about 900 ℃ and about 1250 ℃, respectively.

Example 7

A solid electrolyte was prepared in the same manner as in comparative example 1, except that: lithium chloride (LiCl) and lithium fluoride (LiF) were further added in preparing the precursor mixture, the amounts of lithium chloride and lithium fluoride were stoichiometrically controlled to obtain a solid electrolyte having the composition in table 1, the first heat treatment was performed at about 900 ℃, and the second heat treatment was performed at about 1300 ℃.

TABLE 1

Examples	Composition of
		Example 5	Li0.8Zr2P3O11.8F0.2
Example 6	Li0.8Ti2P3O11.8F0.2
		Example 7	Li0.8Hf2P3O11.8F0.1Cl0.1

Production example 1:

after 40 parts by weight of carbon (Super-P), 10 parts by weight of Polytetrafluoroethylene (PTFE) and 50 parts by weight of N-methylpyrrolidone (NMP) were mixed together to prepare a positive electrode slurry, the slurry was coated and rolled to obtain a positive electrode mixture sheet. The positive electrode mixture sheet was pressed on a stainless steel mesh, and then vacuum-dried in an oven at 100 ℃ for about 120 minutes to obtain a positive electrode.

A polypropylene coated aluminum film (200 μm) having a size of about 5cm × 5cm was perforated to form a hole of about 1cm × 1cm at the center thereof. The pores were plugged with the solid electrolyte of example 1 having a size of about 1.4cm × 1.4cm to thereby form a first aluminum film including the solid electrolyte of example 1 as a part thereof. Next, a second aluminum film having a size of about 5cm × 5cm, a copper current collector (having a thickness of about 20 μ M), a lithium foil (having a size of about 1.4cm × 1.4cm and a thickness of about 100 μ M), a Celgard-3501 polypropylene separator (having a thickness of about 25 μ M, available from Celgard) impregnated with an electrolyte solution that is a mixture of 1M lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) and Propylene Carbonate (PC), and the first aluminum film prepared as above were stacked on each other, and then vacuum-heated to be stuck together, thereby obtaining an aluminum pouch type protected lithium anode.

The protected lithium negative electrode was mounted in a stainless steel casing, and a positive electrode of Celgard-3501 polypropylene separator (available from Celgard) having a thickness of about 25 μm was placed on the side opposite the negative electrode. Subsequently, after the porous gas diffusion layer formed of carbon fibers was disposed on the positive electrode, a foamed nickel plate was disposed thereon, and then pressed with a pressing member, to thereby manufacture a lithium-air battery.

Production examples 2 to 4: manufacture of lithium-air battery

A lithium-air battery was manufactured in the same manner as in manufacturing example 1, except that: the solid electrolytes of examples 2 to 4 were used instead of the solid electrolyte of example 1, respectively.

Comparative example 1 was made: manufacture of lithium-air battery

A lithium-air battery was manufactured 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.

Evaluation example 1: evaluation by X-ray diffraction

The solid electrolytes of example 1, example 2, example 4 and comparative example 1 were evaluated for X-ray diffraction (XRD) spectra. The results are shown in FIGS. 1 and 2. The XRD spectra were obtained using a Bruker D8 Advance diffractometer with Cu ka radiation.

The analysis results of the XRD spectrum are shown in fig. 1 and 2. Fig. 2 illustrates an enlarged view of a portion at a diffraction angle (2 θ) of about 20 ° 2 θ in the XRD spectrum of fig. 1.

As shown in FIG. 1, comparative example 1 (LiHf)₂P₃O₁₂) Example 1 (Li)_0.8Hf₂P₃O_11.8F_0.2) Example 2 (Li)_0.8Hf₂P₃O_11.8Cl_0.2) And example 4 (LiHf)_1.9Y_0.1P₃O_11.9Cl_0.1) All exhibit very similar XRD patterns macroscopically and can be indexed as materials with a crystal structure isomorphic to NASICON.

Referring to fig. 2, it was found that the solid electrolytes of examples 1 and 2 had the first and second diffraction peaks all shifted to the right by about 0.1 ° 2 θ, as compared with the solid electrolyte of comparative example 1. It was found that the solid electrolyte of example 4 had the first diffraction peak and the second diffraction peak a1 all shifted rightward by about 0.05 ° 2 θ, as compared with the solid electrolyte of comparative example 1. In particular, the solid electrolyte of example 4 exhibited the second diffraction peak a2 at about 20.3 ° 2 θ.

In terms of peak intensity, when the intensity ratio (P2/P1) of the second diffraction peak (2 θ ═ 20.16 °) to the first diffraction peak (2 θ ═ 19.92 °) in the solid electrolyte of comparative example 1 was 0.58, the intensity ratio (P2/P1) of the second diffraction peak (2 θ ═ 20.16 °) to the first diffraction peak (2 θ ═ 19.92 °) in the solid electrolyte of example 1 was 0.77, the intensity ratio (P2/P1) of the second diffraction peak (2 θ ═ 20.16 °) to the first diffraction peak (2 θ ═ 19.92 °) in the solid electrolyte of example 2 was 0.81, and the intensity ratio (P385/P38964) of the second diffraction peak (2 θ ═ 20.16 °) to the first diffraction peak (2 θ ═ 19.92 °) in the solid electrolyte of example 4 was 1.26. In the solid electrolyte of example 4, the second diffraction peak has a higher intensity than that of the first diffraction peak.

Evaluation example 2: evaluation of ion conductivity

An electron blocking unit cell was manufactured by: a liquid electrolyte (1M LiTFSI in Propylene Carbonate (PC)) impregnated separator film was disposed on opposite surfaces of the sheet prepared in examples 1 to 4 (hereinafter, "sheet a") and the sheet prepared in comparative example 1 ("sheet B"), and then a lithium foil was disposed thereon. Then, the ionic conductivity of the electron-blocking unit cell was measured using a DC polarization method.

The time-dependent current of the unit cells was measured while a constant voltage of about 100mV was applied to each of the completed symmetrical unit cells for about 30 minutes. The ionic resistance was calculated from the measured current, and the ionic conductivity was calculated from the ionic resistance.

After the sheet a or the sheet B was immersed in a saturated aqueous lithium hydroxide solution at about 40 ℃ for about 6 days, the ion conductivity of the sheet a and the sheet B was evaluated in the same manner as that of the sheet a and the sheet B before the immersion. The results are shown in table 2 and fig. 3.

TABLE 2

Referring to table 2 and fig. 3, it was found that the solid electrolytes of examples 1 to 4 exhibited a larger ionic conductivity retention rate after impregnation with a lithium hydroxide solution, as compared to the solid electrolyte of comparative example 1. From these results, it was found that the solid electrolytes of examples 1 to 4 had significantly improved stability against moisture and strong alkali due to the introduction of anions such as fluoride ion and chloride ion and yttrium.

The ionic conductivity retention rates of the solid electrolytes of example 3 and comparative example 1 were evaluated. The results are shown in FIG. 4.

From the results in fig. 4, it was found that the solid electrolyte of example 3 had a greatly improved ionic conductivity retention ratio compared to the ionic conductivity retention ratio of the solid electrolyte of comparative example 1.

Evaluation example 3: evaluation of electrochemical stability

After the solid electrolyte of example 1 was pulverized to a size of about 1 μm to obtain a pulverized compound, about 85 weight percent (wt%) of the pulverized compound, about 10 wt% of carbon black as a conductive agent, and about 5 wt% of polyvinylidene fluoride (PVDF) as a binder were mixed with N-methyl-2-pyrrolidone, based on the total weight of the solid electrolyte, the carbon black, and the binder, to prepare a slurry. The prepared slurry was coated on an aluminum foil and then dried to thereby manufacture a working electrode. A separator impregnated with a liquid electrolyte (1M LiTFSI in Propylene Carbonate (PC)) was disposed between the working electrode and the lithium metal foil serving as the counter electrode to thereby complete the manufacture of a half cell.

Each half cell was analyzed by Cyclic Voltammetry (CV) at a scan rate of about 0.1 millivolts per second (mV/sec) over a voltage range of about 2 volts (V) to about 4V (vs Li) to evaluate the electrochemical stability of the solid electrolyte.

As a result, the solid electrolyte of example 1 was found to be electrochemically stable during 1 scan, 80 scans, or 100 scans without overcurrent caused by side reactions.

Evaluation example 5: evaluation of Charge-discharge characteristics of lithium-air Battery

The lithium-air battery manufactured in manufacturing example 1 was subjected to the following charge-discharge cycles: about 0.01mA/cm at about 60 ℃ under an oxygen atmosphere of about 1atm²Until the voltage reaches 2.0V (with respect to Li), and then charged with the same constant current until the voltage reaches 4.25V. The results of charge-discharge tests at the 1 st cycle of each lithium-air battery were evaluated.

As a result of the charge-discharge test, it was found that the lithium-air battery of manufacturing example 1 using the solid electrolyte of example 1 stably operated. It was found that the lithium-air batteries of production examples 2 to 4, which were respectively produced using the solid electrolytes of examples 2 to 4, also operated stably as the lithium-air battery of production example 1.

The lithium-air batteries of production examples 2 to 4 were evaluated for charge and discharge characteristics in the same manner as applied to the lithium-air battery of production example 1.

As a result of the charge and discharge characteristic analysis, it was found that the charge and discharge characteristics of the lithium-air batteries of manufacturing examples 2 to 4 were similar to those of the lithium-air battery of manufacturing example 1.

As described above, according to the disclosed embodiments, the solid electrolyte may be stable against strong alkali and moisture, and may have excellent ion conductivity even in contact with strong alkali. By using such a solid electrolyte, an electrochemical device in which deterioration is suppressed can be manufactured.

It is to be understood that the embodiments described herein are to be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features, aspects, or advantages within various embodiments should be considered as available for other similar features, aspects, or advantages in other embodiments. Although the embodiments have been described with reference to the accompanying drawings, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.