Superionic conductors and electrochemical cells containing them

Abstract

This application relates to a superionic conductor that is stable at room temperature and has excellent ionic conductivity characteristics, a method for producing the same, and an electrochemical cell containing the same. The first aspect of this application provides an acid-hydride system superionic conductor which is a complex hydride containing a cation containing an alkali metal or alkaline earth metal and a complex negative ion of the hydride system, and a composite containing a metal oxide. When the superionic conductor of this application is incorporated into an all-solid-state battery and used as a solid electrolyte in a secondary battery, it is possible to provide an all-solid-state battery with significantly improved energy density, high output, and stability.

Description

[Technical Field]

[0001] This application relates to a superionic conductor and an electrochemical cell containing the same. [Background technology]

[0002] Electrochemical cells using solid electrolytes are one of the most promising candidates for solving the fundamental problems inherent in lithium-ion batteries using existing liquid-based electrolytes, such as electrolyte leakage, flammability, and limited energy density. The electrolyte, one of the three main components of an electrochemical cell, must possess ionic conductivity and electrochemical stability with the electrodes as core performance characteristics. Solid-phase ionic conductors such as oxide-based, sulfide-based, and polymer-based materials are being considered for use as solid electrolytes. Among these, sulfide-based solid electrolytes are attracting attention because materials with relatively high ionic conductivity have been developed. However, they have the property of reacting with water, which generates hydrogen sulfide, a toxic substance, and reduces their ionic conductivity characteristics. Furthermore, their weak reducing ability has been pointed out as a problem, resulting in low electrochemical stability at low potentials. Therefore, there is a need to develop new solid ionic conductors that do not generate toxic substances (gases), have excellent electrochemical stability, are stable at room temperature, and possess excellent ionic conductivity characteristics. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Korean Published Patent No. 10-2020-0053099 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] To solve the above-mentioned problems of this invention, we provide a superionic conductor that is stable at room temperature and has excellent ionic conductivity, a method for producing the same, and an electrochemical cell containing the same.

[0005] However, the problems that this application seeks to solve are not limited to those described above, and other problems not mentioned should be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0006] The first aspect of the present invention provides an acid-hydride superionic conductor which is a composite comprising a complex hydride containing a cation including an alkali metal or alkaline earth metal and a complex negative ion of the hydride system, and a metal oxide.

[0007] A second aspect of the present invention provides a method for producing an acid-hydride superionic conductor, which is a composite of a complex hydride and a metal oxide, comprising: a) a step of mixing a complex hydride containing a cation containing an alkali metal or alkaline earth metal and a complex negative ion of the hydride system with a metal oxide in a desired molar ratio; and b) a step of inducing a reaction between the complex hydride and the metal oxide through a first milling step of mechanically milling the mixed mixture.

[0008] A third aspect of the present invention provides an electrochemical cell comprising a positive electrode, a negative electrode, and a solid electrolyte comprising a superionic conductor by a first aspect located between the positive electrode and the negative electrode. [Effects of the Invention]

[0009] The superionic conductor according to one embodiment of the present invention is an acid-hydride system ionic conductor which is a composite formed by the reaction of a complex hydride and a metal oxide. It has the characteristic of stably maintaining the superionic high-temperature phase of the complex hydride even at room temperature, having excellent ionic conductivity characteristics even at room temperature, and not generating toxic substances. Furthermore, it has excellent stability with respect to metals such as Li or Na, thermal stability, and processability. When the superionic conductor of the present invention is incorporated into an all-solid-state battery and used as a solid electrolyte in a secondary battery, it is possible to provide an all-solid-state battery with significantly improved energy density, high output, and stability.

[0010] Furthermore, the superionic conductor of this invention can be manufactured by a simple process of mechanical milling after mixing a complex hydride and a metal oxide, thus offering economic advantages in terms of manufacturing and suitability for mass production. [Brief explanation of the drawing]

[0011] [Figure 1a] This figure shows the results of the change in ionic conductivity characteristics with temperature for the ionic conductors of Example 4 and Example 14, Example 6 and Example 16, Example 7 and Example 17, Example 8 and Example 18, and Comparative Example 2 and Comparative Example 4, in comparison with Comparative Example 1 and Comparative Example 3. [Figure 1b] This figure shows the results of the change in ionic conductivity characteristics with temperature for the ionic conductors of Example 4 and Example 14, Example 6 and Example 16, Example 7 and Example 17, Example 8 and Example 18, and Comparative Example 2 and Comparative Example 4, in comparison with Comparative Example 1 and Comparative Example 3. [Figure 1c] This figure shows the results of the change in ionic conductivity characteristics with temperature for the ionic conductors of Example 4 and Example 14, Example 6 and Example 16, Example 7 and Example 17, Example 8 and Example 18, and Comparative Example 2 and Comparative Example 4, in comparison with Comparative Example 1 and Comparative Example 3. [Figure 1d]This figure shows the results of the change in ionic conductivity characteristics with temperature for the ionic conductors of Example 4 and Example 14, Example 6 and Example 16, Example 7 and Example 17, Example 8 and Example 18, and Comparative Example 2 and Comparative Example 4, in comparison with Comparative Example 1 and Comparative Example 3. [Figure 1e] This figure shows the results of the change in ionic conductivity characteristics with temperature for the ionic conductors of Example 4 and Example 14, Example 6 and Example 16, Example 7 and Example 17, Example 8 and Example 18, and Comparative Example 2 and Comparative Example 4, in comparison with Comparative Example 1 and Comparative Example 3. [Figure 2] This figure shows the results of the change in ionic conductivity characteristics with temperature for an ionic conductor based on the mixing ratio of metal oxides, according to one embodiment. [Figure 3a] This figure shows a comparison of the XRD measurement results of the superionic conductors of Example 4, Example 2, and Example 1 and Comparative Example 1 (LiCB11H12). [Figure 3b] This figure shows a comparison of the XRD measurement results of the superionic conductors of Example 4, Example 2, and Example 1 and Comparative Example 1 (LiCB11H12). [Figure 3c] This figure shows a comparison of the XRD measurement results of the superionic conductors of Example 4, Example 2, and Example 1 and Comparative Example 1 (LiCB11H12). [Modes for carrying out the invention]

[0012] Hereinafter, embodiments of the present application will be described in detail with reference to the attached drawings, so that they can be easily implemented by a person with ordinary skill in the art to which the present application pertains. However, the present application can be embodied in a variety of different forms and is not limited to the embodiments described herein. Furthermore, in order to clearly illustrate the present application, parts unrelated to the description have been omitted from the drawings, and similar parts throughout the specification are denoted by similar reference numerals.

[0013] Throughout the specification of this application, when a member is described as being "on top of" another member, this includes not only cases where one member is in contact with another member, but also cases where another member exists between the two members.

[0014] Throughout the specification of this application, when a part "includes" a component, this means, unless otherwise stated, that it may include other components rather than excluding them. Throughout the specification of this application, terms of degree such as "about" and "substantially" are used in the sense of, or close to, the numerical values ​​of the manufacturing and material tolerances inherent to the meaning referred to, and are used to prevent unscrupulous infringers from unfairly using disclosures that refer to precise or absolute numerical values ​​to aid in understanding the application. Throughout the specification of this application, terms of degree such as "stage ~" or "stage ~" do not mean "stage for ~".

[0015] Throughout the specification of this application, the term “these combinations” as used in the Markush expression means one or more mixtures or combinations selected from the group of components described in the Markush expression, and means including one or more selected from the group of components.

[0016] Throughout the specification of this application, the phrase "A and / or B" means "A or B, or A and B."

[0017] The following describes in detail the embodiment and examples of the present application with reference to the attached drawings. However, the present application is not limited to these embodiment and examples and drawings.

[0018] The first aspect of the present invention is an acid-hydride superionic conductor comprising a complex hydride containing a cation including an alkali metal or alkaline earth metal and a complex negative ion of the hydride system, and a metal oxide, wherein the complex hydride and the metal oxide are composites.

[0019] Here, a complex hydride is an ionic conductor that contains a complex ion including hydrogen and possesses ionic conductivity. The term "complex hydride" is sometimes also referred to as a "complex hydride" or "complex metal hydride."

[0020] Specifically, acid-hydride superionic conductors, which are complex hydrides synthesized by the reaction of complex hydrides with metal oxides, have defects in the crystal structure of the complex hydride due to the reaction of both the complex hydride and the metal oxide (for example, Li + A defect can be formed. The formation of a space charge layer can be created by the formation of a defect in the crystal structure of the complex hydride, which increases the degree of disorder in the crystal and allows the high-temperature phase to be stably maintained even at room temperature. As a result, the superionic conductor of this application can have significantly superior ionic conductivity characteristics even at room temperature compared to conventional complex hydrides.

[0021] Conventional complex hydrides such as LiBH4 have been reported to exhibit high lithium-ion conductivity at high temperatures, but they suffer from a rapid decrease in ionic conductivity at room temperature, which imposes many limitations on their practical use as solid electrolytes. However, as mentioned above, the superionic conductor of this invention has the advantage of being able to exhibit excellent ionic conductivity even at room temperature, making it suitable for use as a solid electrolyte in electrochemical cells.

[0022] In one embodiment of the present invention, the composite, namely the superionic conductor, undergoes a reaction between a complex hydride and a metal oxide, which leads to the formation of metal cation defects within the crystal structure of the complex hydride, thereby increasing the degree of crystalline disorder. As a result, the superionic conductor of the present invention maintains a more stable high-temperature phase at room temperature than conventional complex hydrides, and can exhibit superior ionic conductivity characteristics.

[0023] In one embodiment of the present invention, the composite may be heat-treated. An acid-hydride superionic conductor synthesized by the reaction of a complex hydride with a metal oxide can be manufactured by a simple process such as mechanical milling or other grinding steps, and thereafter, a heat-treated acid-hydride superionic conductor can have higher ionic conductivity characteristics than one that has not been heat-treated. The mechanical milling and heat treatment will be explained in more detail later from the perspective of manufacturing methods.

[0024] In one embodiment of the present application, the molar ratio of the complex hydride to the metal oxide contained in the composite may be 1:0.01 to 20, 1:0.05 to 10, 1:0.1 to 10, 1:0.1 to 7, 1:0.1 to 5, 1:0.1 to 3, 1:0.1 to 2, or 1:0.1 to 1.

[0025] When the molar ratio of the complex hydride to the metal oxide is less than 1:0.01, the effect of maintaining the structural disorder of the complex hydride is significantly reduced, and there is a limit to the improvement of the ionic conductivity characteristics at room temperature. When the molar ratio of the complex hydride to the metal oxide exceeds 1:20, the ionic conductivity characteristics of the composite, i.e., the superionic conductor, may decrease. Therefore, it is preferable that the molar ratio of the metal oxide to the complex hydride satisfies the aforementioned range.

[0026] Specifically, the acid-hydride superionic conductor is (1-α)Mx(M' y H z )-αK can be expressed as M x (M' y H z ) is a complex hydride, K is a metal oxide, α is 0.1 to 0.9, x is 1 or 2, y is 1 ≤ y ≤ 15, and z can be 1 ≤ z ≤ 15.

[0027] The aforementioned α is a factor indicating the molar ratio, and it is possible to provide composites with different ionic conductivity characteristics depending on the molar ratio of the complex hydride to the metal oxide. The present invention is characterized by providing an optimal ratio that is stable at room temperature and exhibits excellent ionic conductivity.

[0028] As an embodiment of the present application, as described above, the metal oxide can be used without particular limitation as long as it can increase the degree of structural disorder due to defects induced inside the lattice of the complex hydride through reaction with the complex hydride, compared to before the reaction.

[0029] As a non-limiting example, the metal oxide is any one or more selected from TiO2, ZnO, CuO, CaO, SiO2, Al2O3, MgO, and ZrO2, and specifically, it can be any one or more selected from SiO2, Al2O3, MgO, and ZrO2, but the present application is not limited by the type of metal oxide.

[0030] In one embodiment of the present application, the complex anion contained in the complex hydride is BH4 - , B6H6 2- , B 10 H 10 2- , B 11 H 11 2- , B 12 H 12 2- , CB9H 10 - , CB 10 H 11 - , and CB 11 H 12 - is any one or more selected from, specifically, CB9H 10 - , CB 11 H 12 - , and B 12 H 12 2- is any one or more selected from, more specifically, it can be CB 11 H 12 - .

[0031] As an example, as mentioned above, the complex hydride contains a cation containing an alkali metal or alkaline earth metal along with the complex negative ion of the hydride system described above, and the cation is one or more selected from Na, Li, Mg, Ca, K, and Cs, specifically Li or Na, and more specifically Li.

[0032] In one embodiment of the present invention, the superionic conductor described above may have an X-ray diffraction pattern using CuKα rays that includes a first peak located in the diffraction angle 2θ range of 15.9 ± 0.5° and a second peak located in the 45 ± 5° range. In this case, the X-ray diffraction pattern may have been measured at 25°C.

[0033] Specifically, the first peak is caused by a complex hydride contained in the superionic conductor and may be located at a 2θ value of 0.01° or more, 0.02° or more, 0.03° or more, 0.04° or more, 0.05° or more, or 0.06° or more, or even smaller, relative to the diffraction angle 2θ value of the metal oxide located in the 15.9±0.5° range and the complex hydride before the reaction (located in the 15.9±0.5° range). Although there is no upper limit, the first peak may be located at a 2θ value of 0.5° or less, specifically 0.3° or less, or more specifically, 0.12° or less, relative to the diffraction angle 2θ value of the metal oxide and the complex hydride before the reaction.

[0034] More specifically, in the X-ray diffraction pattern, the first peak is located at a 2θ value that satisfies the aforementioned conditions, allowing the superionic conductor to exhibit excellent ionic conductivity even at room temperature. As previously mentioned, the reaction between the complex hydride and the metal oxide induces lattice expansion of the complex hydride before the reaction, which indicates that cation defects were formed in the complex hydride structure before the reaction. The formation of such cation defects increases the degree of structural disorder of the complex hydride. Thus, the increased degree of structural disorder increases entropy, reducing the phase transition temperature to the high-temperature phase of the complex hydride with excellent ionic conductivity, resulting in excellent ionic conductivity even at room temperature.

[0035] Furthermore, the metal oxide contained in the superionic conductor increases the degree of structural disorder of the complex hydride and effectively maintains the increased degree of structural disorder. Therefore, the superionic conductor of this invention has the advantage of being able to stably exhibit excellent ionic conductivity characteristics at room temperature.

[0036] In one embodiment of the present invention, the cation vacancies formed within the complex hydride contained in the superionic conductor are, for example, Li + It could be a defect.

[0037] Furthermore, the superionic conductor of the present invention may include, in addition to the first peak described above, a third peak in its X-ray diffraction pattern, where the diffraction angle 2θ is located in the range of 18.2 ± 0.5°. In this case, the third peak may be located at a 2θ value even smaller than the diffraction angle 2θ value of the metal oxide and the complex hydride before reaction (located in the range of 18.2 ± 0.5°). In this case, the difference in the diffraction angle 2θ value where the third peak of the superionic conductor of the present invention and the metal oxide and the complex hydride before reaction are located may be similar to, or identical to, the range in which the first peak of the superionic conductor shifts and is located relative to the metal oxide and the complex hydride before reaction described above.

[0038] As an example of the present invention, the second peak located in the aforementioned 45±5° range may originate from a metal oxide.

[0039] For example, the intensity ratio (I1 / I2) between the maximum intensity of the first peak (I1) and the maximum intensity of the second peak (I2) can be 1-100, 1-80, 1-60, 1-50, 1-40, 1-30, 1-20, 2-20, 3-20, 4-20, or 4-10. In this case, the maximum intensities of the first and second peaks may be values ​​calculated based on the lowest intensity in an X-ray diffraction pattern with a diffraction angle 2θ value in the range of 10-80°.

[0040] Thus, by ensuring that the intensity ratio (I1 / I2) between the maximum intensity of the first peak (I1) and the maximum intensity of the second peak (I2) satisfies the aforementioned range, the superionic conductor can exhibit excellent ionic conductivity characteristics even at room temperature.

[0041] Furthermore, superionic conductors may contain other peaks in addition to the second peak originating from the metal oxide. For example, the other peaks besides the second peak can be located at different diffraction angle 2θ values ​​depending on the type of metal oxide, and may include multiple independently distinct peaks. As a non-limiting example, the other peaks besides the second peak may be one or more peaks located in the diffraction angle 2θ range of 25±5°, 35±4.99°, 55±4.99°, and 70±10°, but this application is not limited thereto, and it goes without saying that other peaks may be located outside the diffraction angle ranges mentioned above.

[0042] As mentioned above, the acid-hydride superionic conductor of this application is a composite of a complex hydride and a metal oxide, synthesized by the reaction of both the complex hydride and the metal oxide, and can possess the properties described above. Therefore, it should be understood as a substance different from a mixture of a complex hydride and a metal oxide. In other words, the effect of the acid-hydride superionic conductor of this application having excellent ionic conductivity characteristics at room temperature cannot be shown simply as a mixture of a complex hydride and a metal oxide.

[0043] The following describes in detail a manufacturing method for producing an acid-hydride system superionic conductor, which is a composite of the complex hydride and metal oxide described above.

[0044] A second aspect of the present application relates to a method for producing an acid-hydride superionic conductor which is a composite of a complex hydride and a metal oxide, and may include: a) a step of mixing a complex hydride containing a cation containing an alkali metal or alkaline earth metal and a complex negative ion of the hydride system with a metal oxide in a desired molar ratio; and b) a step of inducing a reaction between the complex hydride and the metal oxide through a first milling step of mechanically milling the mixed mixture.

[0045] Specifically, the acid-hydride superionic conductor of the present invention is manufactured by inducing a reaction between the complex hydride and the metal oxide through mechanical milling of a mixture in which a complex hydride containing a cation containing an alkali metal or alkaline earth metal and a complex negative ion of the hydride system and a metal oxide are mixed in a desired molar ratio. This has the advantage of being extremely simple and economically advantageous, as well as suitable for mass production.

[0046] In this case, the complex hydride and metal oxide mixed in step a) above are as described above, and a detailed explanation is omitted.

[0047] In step a) described above, the complex hydride and the metal oxide can be mixed to satisfy the aforementioned molar ratio.

[0048] As an embodiment of the present invention, the first milling step in step b) above can be carried out by any method known in the art, without any particular limitations.

[0049] As a non-limiting example, the first milling process may be carried out using a bead mill, ball mill, high-energy ball mill, planetary mill, stirred ball mill, or vibration mill, but is not limited to these.

[0050] For example, the first milling process can be performed in an inactive atmosphere using a high-energy ball mill at 100-500 rpm for 0.1-20 hours or 0.5-10 hours. If the first milling process is performed in less than 0.1 hours, the reaction between the mixed complex hydride and the metal oxide does not occur, limiting the improvement of the ionic conductivity characteristics at room temperature. If it exceeds 20 hours, the effect on improving the ionic conductivity characteristics is not economical from a manufacturing perspective. Therefore, it is preferable to perform the first milling process within the aforementioned time ranges.

[0051] The first milling step can be carried out by a dry or wet process. When carried out by a wet process, the process can be carried out by adding a solvent to the mixture, performing the milling step, and then removing the solvent. In this case, the solvent to be added may be, but is not limited to, acetonitrile, tetrahydrofuran, diethyl ether, N,N-dimethylformamide, N,N-dimethylacetamide, methanol, ethanol, or mixtures thereof.

[0052] As an embodiment of the present invention, a second milling step may be included in which the complex hydride is mechanically milled before the mixing step in step a) described above.

[0053] Performing a second milling step can further increase the degree of structural disorder of the complex hydride and may be more advantageous in pulverizing the complex hydride to nanoscale size, thereby inducing a reaction with the metal oxide in the first milling step described above. In other words, the non-surface area of ​​the complex hydride pulverized to nanoscale size increases, which can increase the reaction area with the metal oxide at the stage of the first milling step, and this has the advantage of further improving the ionic conductivity characteristics of the acid-hydride superionic conductor finally obtained at room temperature.

[0054] For example, the size of the complex hydride after the second milling step may be 1-1000 nm, 1-800 nm, 1-700 nm, 1-600 nm, or 1-500 nm.

[0055] As an embodiment of the present invention, the second milling process can be carried out in a manner similar to the first milling process described above. However, the second milling process can be carried out under high-speed rotation conditions for 1 to 100 hours, 5 to 80 hours, or 10 to 50 hours compared to the first milling process. For example, the second milling process can be carried out at a speed of 200 to 800 rpm within the aforementioned time range.

[0056] In one embodiment of the present invention, the step of heat-treating the resulting composite can be further included after step b) described above.

[0057] The addition of a heat treatment step offers the advantage of further improving the ionic conductivity characteristics of the superionic conductor.

[0058] In this case, it goes without saying that the heat treatment can be applied to the resulting composite itself after step b), or to the pelletized composite formed by pressurizing the resulting composite.

[0059] In one embodiment of the present invention, the heat treatment may be carried out at a temperature range of 60 to 300°C, specifically 100 to 250°C, and more specifically 150 to 250°C, for a period of 0.01 to 50 hours.

[0060] Furthermore, in a third aspect, this application provides a solid electrolyte for an electrochemical cell containing the superionic conductor described above. Here, the solid electrolyte may be a solid electrolyte for an all-solid-state battery.

[0061] As a non-limiting example, the solid electrolyte may consist solely of the superionic conductor described above and may further include a binding material. It goes without saying that, in addition to the superionic conductor of this application, the solid electrolyte may further include one or more solid electrolytes selected from oxide-based solid electrolytes, sulfide-based solid electrolytes, polymer-based solid electrolytes, and phosphate compound solid electrolytes known in the art.

[0062] A fourth aspect of the present invention provides an electrochemical cell comprising a positive electrode, a negative electrode, and a solid electrolyte containing a superionic conductor on a first aspect located between the positive and negative electrodes. An electrochemical cell comprising a solid electrolyte containing a superionic conductor having excellent ionic conductivity characteristics at room temperature can embody an all-solid-state battery with high energy density, high output, and improved stability.

[0063] In one embodiment of the present invention, the positive electrode comprises a positive electrode current collector and a positive electrode mixture containing a positive electrode active material, wherein the positive electrode mixture is coated on the positive electrode current collector, and in this case, the coating of the positive electrode mixture may be coated on one or both sides of the positive electrode current collector.

[0064] As an example, the positive electrode current collector coated with the positive electrode active material is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery. For example, stainless steel, aluminum, nickel, plastic carbon, or those obtained by surface treatment with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel can be used. Note that the positive electrode current collector can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven fabric bodies, etc., and the present application is not limited according to the form of the positive electrode current collector.

[0065] In one embodiment of the present application, the positive electrode active material contained in the positive electrode active material may contain any one or more selected from sulfide-based active materials and oxide-based active materials.

[0066] As an example, the sulfide-based active material is inorganic sulfur (S8), a sulfur-based compound, or a mixture thereof, and the sulfur-based compound is a metal sulfide (M x S y , M = Li, Ni, Co, Cu, Fe, Mo, Ti, Nb, 1 ≦ x ≦ 4, 1 ≦ y ≦ 8), an inorganic sulfur compound, and a carbon-sulfur polymer ((C2Sx)n: x = 2.5 to 50, n ≧ 2), and may be any one or more selected from the group consisting of them.

[0067] Note that the oxide-based active material includes rock salt layer type active materials such as LiCoO2, LiMnO2, LiNiO2, LiVO2, Li 1+x Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2, spinel type active materials such as LiMn2O4, Li(Ni 0.5 Mn 1.5 )O4, inverse spinel type active materials such as LiNiVO4, LiCoVO4, olivine type active materials such as LiFePO4, LiMnPO4, LiCoPO4, LiNiPO4, silicon-containing active materials such as Li2FeSiO4, Li2MnSiO4, and rock salt layer type active materials in which a part of the transition metal is switched to a different metal such as LiNi 0.8 Co( 0.2-x )Al x O2 (0 < x < 0.2), and Li 1+x Mn2-x-y MyO4 (where M is at least one of Al, Mg, Co, Fe, Ni, Zn, and 0 < x + y < 2) can be a spinel-type active material in which some of the transition metals are switched to different metals, but is not limited thereto.

[0068] As an example, the positive electrode mixture containing the positive electrode active material can further contain an ion conductor, and the ion conductor is a hydride-based ion conductor containing a cation containing an alkali metal or an alkaline earth metal and a hydride-based complex anion. Specifically, CB 11 H 12 - , B 12 H 12 2- and CB9H 10 - is a hydride-based ion conductor containing any one or more selected from the group consisting of as a complex anion, and it is needless to say that it can be the above-mentioned superionic conductor.

[0069] In addition, the positive electrode mixture can further contain a conductive material, a binder, etc. together with the above-mentioned positive electrode active material and ion conductor.

[0070] The conductive material can form an electron conduction path in the electrode, and can be used without limitation as long as it is a substance known in the art. The conductive material can be an sp2 carbon material such as carbon black, conducting graphite, ethylene black, carbon nanotube, or graphene, but is not limited thereto.

[0071] The binder is styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin This may be selected from the group consisting of lipids, epoxy resins, carboxymethylcellulose, hydroxypropylcellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, polyesters, polyamides, polyethers, polyimides, polycarboxylates, polycarboxylic acids, polyacrylic acids, polyacrylates, polymethacrylic acids, polymethacrylates, polyacrylamides, polyurethanes, fluorinated polymers, chlorinated polymers, alginates, polyvinylidene fluoride, poly(vinylidene fluoride)-hexafluoropropene, and combinations thereof.

[0072] In one embodiment of the present invention, the negative electrode may contain lithium metal. For example, the negative electrode may contain lithium metal located on the negative electrode current collector, in which case the lithium metal may be located on the negative electrode current collector in the form of a thin film. For example, the lithium metal in the form of a thin film may be formed by depositing lithium metal onto the negative electrode current collector by physical or chemical means, or by placing lithium foil or lithium metal powder on the negative electrode current collector and then rolling it, but is not limited to these, and the lithium metal in the form of a thin film may be located on one or both sides of the negative electrode current collector.

[0073] As an example, the negative electrode current collector may be, but is not limited to, any one metal selected from the group consisting of copper, aluminum, stainless steel, zinc, titanium, silver, palladium, nickel, iron, chromium, alloys thereof, and combinations thereof.

[0074] The negative electrode may contain negative electrode active material commonly used in this industry.

[0075] As an example, the negative electrode active material may include, but is not limited to, one or more of the following selected from carbon-based materials, silicon, silicon oxides, silicon-based alloys, silicon-carbon composites, tin, tin-based alloys, tin-carbon composites, metal oxides, or combinations thereof.

[0076] As a non-limiting example, carbon-based materials may be crystalline carbon, amorphous carbon, or mixtures thereof. The crystalline carbon may be amorphous, plate-like, flake-like, spherical, or fibrous soot, such as natural or artificial soot, while the amorphous carbon may be soft carbon (low-temperature plastic carbon) or hard carbon, mesophase pitch carbides, plasticized coke, graphene, carbon black, fullerene soot, carbon nanotubes, and carbon fiber furnaces, etc.

[0077] The negative electrode may further contain a binder and a conductive material in addition to the negative electrode active material described above. These materials may be similar to or identical to the binder and conductive material described above, and a detailed explanation is omitted.

[0078] In one embodiment of the present invention, the superionic conductor described above can be positioned between the positive electrode and the negative electrode to form an electrolyte layer, and the electrolyte layer may further contain a binder or liquid as needed.

[0079] Here, the liquid can mean a liquid electrolyte containing a lithium salt widely used in the field of lithium-ion batteries, and the present application is not limited by the type of lithium salt contained in the liquid electrolyte and / or the preparation of the liquid electrolyte.

[0080] The electrolyte layer may further include one or more selected from the group consisting of sulfide-based electrolytes, oxide-based electrolytes, and polymer-based electrolytes. However, if the electrolyte layer is provided in a multi-layer structure, the solid electrolyte layer containing the superionic conductor described above may be located in contact with the negative electrode described above.

[0081] The present application will be described in more detail below through embodiments thereof. However, these embodiments are merely examples to facilitate understanding of the present application, and the content of the present application is not limited to these embodiments.

[0082] [Examples] (Example 1) The raw material is Li[CB] 11 H 12 ]1 / 2H2O is heat-treated in a high vacuum under an Ar atmosphere at a temperature of 100-200°C, followed by primary ball milling at 200-800 rpm for 10-50 hours to obtain Li[CB] particles of nanometer size (1-500 nm). 11 H 12 The complex hydride was recovered.

[0083] Subsequently, the recovered complex hydride and metal oxide were used to convert Al2O3 to Li[CB]. 11 H 12 Weighed out Al2O3 in a molar ratio of 9:1 and performed secondary ball milling at 100-500 rpm for 0.5-10 hours to produce an acid-hydride system superionic conductor, which is a composite of a complex hydride and a metal oxide.

[0084] (Example 2) The procedure was carried out in the same manner as in Example 1, and Li[CB 11 H 12A superionic conductor was fabricated in the same manner, except that a mixture was used with a molar ratio of 6:4 between Al2O3 and Al2O3.

[0085] (Example 3) The procedure was carried out in the same manner as in Example 1, and Li[CB 11 H 12 A superionic conductor was fabricated in the same manner, except that a mixture was used with a molar ratio of 4:6 between Al2O3 and Al2O3.

[0086] (Example 4) The procedure was carried out in the same manner as in Example 1, and Li[CB 11 H 12 A superionic conductor was fabricated in the same manner, except that a mixture was used with a molar ratio of 2:8 between Al2O3 and Al2O3.

[0087] (Example 5) The procedure was carried out in the same manner as in Example 1, and Li[CB 11 H 12 A superionic conductor was fabricated in the same manner, except that a mixture was used that was prepared with a molar ratio of 1:9 between Al2O3 and Al2O3.

[0088] (Example 6) The procedure was carried out in the same manner as in Example 1, and the recovered complex hydride and SiO2 as a metal oxide were converted to Li[CB]. 11 H 12 A superionic conductor was fabricated in the same manner, except that a mixture was used that was prepared with a molar ratio of SiO2 = 2:8.

[0089] (Example 7) The procedure was carried out in the same manner as in Example 1, and the recovered complex hydride and MgO as a metal oxide were converted to Li[CB]. 11 H 12 A superionic conductor was fabricated in the same manner, except that a mixture was used that was prepared with a molar ratio of 1:9 for MgO.

[0090] (Example 8) The procedure was carried out in the same manner as in Example 1, and the recovered complex hydride and ZrO2 as a metal oxide were converted to Li[CB]. 11 H 12 A superionic conductor was fabricated in the same manner, except that a mixture was used that was prepared with a molar ratio of 3:7 for ZrO2.

[0091] (Example 9) The procedure was carried out in the same manner as in Example 2, with Li[CB9H 10 Except for the use of 1 / 2H2O, the same procedure was followed to produce a superionic conductor.

[0092] (Example 10) The procedure was carried out in the same manner as in Example 2, using Li2B as the raw material. 12 H 12 Aside from the use of [specific material], a superionic conductor was manufactured in the same manner.

[0093] (Examples 11-20) Each of the superionic conductors manufactured in Examples 1 to 10 was heat-treated at 100-200°C for 1 hour under an Ar atmosphere. In this process, the heat-treated Examples 1 to 10 are sequentially the superionic conductors of Examples 11 to 20.

[0094] (Comparative Example 1) In Example 1, which is not mixed with metal oxides, Li[CB] before primary ball milling. 11 H 12 The complex hydride was recovered.

[0095] (Comparative Example 2) Li[CB] from Example 1, which was not mixed with metal oxides, underwent primary ball milling. 11 H 12 The complex hydride was recovered.

[0096] (Comparative Example 3 and Comparative Example 4) Each of the manufactured Comparative Example 1 and Comparative Example 2 was heat-treated in the same manner as in Example 11, and each of the heat-treated Comparative Example 1 and Comparative Example 2 is the complex hydride of Comparative Example 3 and Comparative Example 4.

[0097] (Experimental Example 1) Comparative Analysis of Ionic Conductivity Characteristics of Superionic Conductors The ionic conductivity characteristics of each manufactured superionic conductor were compared and analyzed. For this analysis, the ionic conductivity of each manufactured superionic conductor was measured after compressing it under 100-400 MPa and forming it into pellets with a diameter of 10 mm and a thickness of 100-500 μm.

[0098] First, we compared and analyzed the changes in ionic conductivity characteristics depending on the type of metal oxide (Figures 1a to 1e, and Table 1).

[0099] Figures 1a, 1b, 1c, 1d, and 1e are Arrhenius plots showing the change in ionic conductivity characteristics with temperature for Examples 4 and 14, Examples 6 and 16, Examples 7 and 17, Examples 8 and 18, and Comparative Examples 2 and 4, compared with Comparative Examples 1 and 3. The ionic conductivity characteristics at 25°C are shown in Table 1 below.

[0100] [Table 1]

[0101] As shown in Figures 1a to 1e, as is well known, Li[CB] is one of the complex hydrides. 11 H 12 The ionic conductors, specifically Comparative Examples 1 and 3, exhibit ionic conductivity characteristics suitable for use as electrolytes in electrochemical cells at high temperatures of approximately 120°C or higher, but it can be seen that their ionic conductivity characteristics decrease rapidly as the temperature decreases. On the other hand, the superionic conductors of Examples 4, 6-8, 14, and 16-18, which are composites of complex hydrides and metal oxides, were found to exhibit a relatively gradual decrease in ionic conductivity characteristics as the temperature decreases.

[0102] Additionally, examining the characteristics before and after heat treatment at 25°C, it was observed that the ionic conductivity characteristics improved in Examples 14, 16-18, and Comparative Example 3 compared to before heat treatment. Specifically, in Comparative Example 3, the ionic conductivity increased by approximately 183% compared to Comparative Example 1 before heat treatment, while in Examples 14, 16, 17, and 18, the ionic conductivity significantly improved by approximately 760%, 463%, 451%, and 544%, respectively, compared to before heat treatment.

[0103] On the other hand, while Comparative Example 2 exhibited superior ionic conductivity compared to Comparative Example 1, it was confirmed that the ionic conductivity of Comparative Example 4, which was obtained by heat treatment of Comparative Example 2, actually decreased by approximately 99% compared to before heat treatment.

[0104] Furthermore, it was found that superionic conductors, which are composites of complex hydrides and metal oxides, have significantly superior ionic conductivity characteristics at room temperature compared to conventional complex hydrides, and that these ionic conductivity characteristics can be further improved through heat treatment processes.

[0105] In the case of Comparative Example 2, which does not contain metal oxides, it was confirmed that the ionic conductivity characteristics could be temporarily improved at room temperature simply through the ball milling process, but that the improved ionic conductivity characteristics could be rapidly reduced by the external environment. In other words, it can be seen that the superionic conductor, which is a composite of the complex hydride and metal oxide of the present invention, maintains improved ionic conductivity characteristics stably.

[0106] Next, using Example 4, which showed the largest increase in ionic conductivity after heat treatment in Experimental Example 1, the ionic conductivity based on the mixing ratio of metal oxides was measured and compared in the same manner as in Experimental Example 1 (Table 2 and Figure 2).

[0107] [Table 2]

[0108] As shown in FIG. 2 and Table 2, similar to the ionic conductivity characteristics depending on the types of the above-described metal oxides, it was confirmed that both had significantly superior ionic conductivity characteristics compared to the complex hydrides of Comparative Example 1 and Comparative Example 3 in terms of the molar ratios of both the complex hydride and the metal oxide. However, when the molar ratio of the metal oxide to the complex hydride is 0.1 mol or less or 15 mol or more based on 1 mol of the complex hydride, it was confirmed that the effect of improving the ionic conductivity after heat treatment is reduced compared to before heat treatment. Through this, as described above, it was reconfirmed that the metal oxide contained in the superionic conductor can improve the ionic conductivity characteristics at room temperature. That is, it was confirmed that in the range where the content of the metal oxide contained in the superionic conductor is too small or not contained much, the ionic conductivity characteristics can be significantly improved after heat treatment compared to the comparative examples.

[0109] Although not shown, in the cases of Example 9, Example 10, Example 19, and Example 20 using other complex hydrides as raw material substances, it was confirmed that the ionic conductivity characteristics were improved compared to the conventional complex hydrides, similar to Example 2 and Example 12.

[0110] Experimental Example 2: Analysis of Crystal Structure of Superionic Conductor The crystal structures of the respective produced superionic conductors were confirmed through X-ray diffraction (XRD, 45 kV, 200 mA, 1° min-1, Cu-Kα radiation, λ = 0.15406 nm) analysis.

[0111] Each of FIGS. 3a, 3b, and 3c is a diagram showing a comparison of the XRD measurement results of the superionic conductors of Example 4, Example 2, and Example 1 with Comparative Example 1 (LiCB 11 H 12 ).

[0112] In FIGS. 3a to 3c, when examining the enlarged peaks on the right side, it can be seen that at a diffraction angle 2θ = 15.9°, Comparative Example 1 shows a peak corresponding to the (111) plane of LiCB 11 H 12 .

[0113] In the cases of Example 4, Example 2, and Example 1, in all cases, LiCB 11 H 12 It can be seen that the diffraction angle 2θ corresponding to the peak corresponding to the (111) plane is located at a 2θ value that is 0.05° or more and further smaller than that. Then, the superionic conductor of the present application is composed of a complex hydride LiCB 11 H 12 and a metal oxide Al2O3. It can be seen that the lattice constant increased in all formations.

[0114] That is, the superionic conductor of the present application is a composite of a complex hydride and a metal oxide, not in a form where the complex hydride and the metal oxide are simply mixed.

[0115] More specifically, in the cases of Example 4, Example 2, and Example 1, based on the diffraction angle 2θ (15.9°) value of the peak corresponding to the (111) plane of LiCB 11 H 12 (hereinafter referred to as the first peak), it is observed that they are located at diffraction angle 2θ values that are 0.09°, 0.07°, and 0.10° smaller, respectively. Although not shown in the figure, it was also confirmed that in the cases of Example 3 and Example 5, they are located at diffraction angle 2θ values that are 0.09° smaller.

[0116] In addition, the peak of LiCB 11 H 12 located at a diffraction angle of about 18.2° was also observed to be located at a smaller diffraction angle, just by the movement of the aforementioned peak.

[0117] Additionally, it was confirmed that additional peaks appeared due to the metal oxide contained in the superionic conductor. At this time, among the XRD patterns within the range where the diffraction angle 2θ is 10° to 80°, when comparing the maximum intensity (I1) of the first peak and the maximum intensity (I2) of the peak (hereinafter referred to as the second peak) whose diffraction angle 2θ value due to the metal oxide is located at 45° based on the minimum intensity, it was confirmed that in the case of Example 4, it is about 4.5, in Example 2 it is about 19.8, and in Example 1 it is about 49.9.

[0118] (Example 21) Manufacturing of all-solid-state batteries In Example 2, the superionic conductor was pressurized to produce the electrolyte layer of an electrochemical cell. The superionic conductor powder was then mixed with a positive electrode active material (Sulfur) and a conductive agent (Super P, Carbon nanotube) and pressurized to produce the positive electrode layer. A solid-state battery was then manufactured with lithium metal as the negative electrode layer. Charge and discharge experiments were conducted at room temperature to confirm that the electrochemical cell was operational.

[0119] The above description of the present application is illustrative, and a person with ordinary skill in the art to which the present application belongs will understand that it can be easily modified into other specific forms without changing the technical idea or essential features of the present application. Therefore, the above-described embodiments should be understood in all respects as illustrative and not limiting. For example, each component described as a single type can be implemented in a distributed manner, and similarly, components described as distributed can be implemented in a combined form.

[0120] The scope of this application is indicated by the claims, which are set forth below, rather than by the detailed description above, and all modified or altered forms derived from the meaning and scope of the claims, as well as the concept of equivalents thereof, should be interpreted as being included within the scope of this application. [Industrial applicability]

[0121] When the superionic conductor of this invention is incorporated into an all-solid-state battery and used as the solid electrolyte of a secondary battery, it is possible to provide an all-solid-state battery with significantly improved energy density, high output, and stability.

Claims

1. A complex hydride containing a cation containing an alkali metal or alkaline earth metal and a complex negative ion of the hydride system, It contains metal oxides, An acid-hydride superionic conductor which is a composite of the complex hydride and the metal oxide.

2. The superionic conductor according to claim 1, characterized in that the composite is synthesized by reaction with the metal oxide in order to form defects in the crystal structure of the complex hydride.

3. The superionic conductor according to claim 1, wherein the molar ratio of the complex hydride to the metal oxide contained in the composite is 1:0.01 to 20.

4. The aforementioned complex is MgO, Al ２ O ３ SiO ２ and ZrO ２ The superionic conductor according to claim 1, comprising one or more metal oxides selected from the following.

5. The complex is BH ４ － , B ６ H ６ ２－ , B １０ H １０ ２－ , B １１ H １１ ２－ , B １２ H １２ ２－ , CB ９ H １０ － , CB １０ H １１ － , and CB １１ H １２ － The superionic conductor according to claim 1, comprising any one or more hydride-based complex anions selected from these.

6. The superionic conductor according to claim 2, wherein the superionic conductor includes a first peak located in the range of 15.9 ± 0.5° and a second peak located in the range of 45 ± 5° in an X-ray diffraction pattern using CuKα rays.

7. The superionic conductor according to claim 6, wherein the first peak is attributable to the complex hydride and is located at a 2θ value at least 0.05° smaller than that of the complex hydride before the reaction.

8. The superionic conductor according to claim 6, wherein the second peak is due to the metal oxide.

9. a) A step of mixing a complex hydride containing cations containing alkali metals or alkaline earth metals and complex negative ions of the hydride system with a metal oxide in a desired molar ratio, b) A step of inducing a reaction between the complex hydride and the metal oxide through a first milling step of mechanically milling the mixed mixture, A method for producing an acid-hydride system superionic conductor, which is a composite of a complex hydride containing a metal oxide.

10. A method for producing a superionic conductor according to claim 9, further comprising a second milling step of mechanically milling the complex hydride before performing the mixing step in step a) above.

11. A method for producing a superionic conductor according to claim 9, further comprising the step of heat-treating the composite after step b) above.

12. A solid electrolyte for an electrochemical cell comprising a superionic conductor according to any one of claims 1 to 8.

13. Positive electrode and, The negative electrode and, An electrochemical cell comprising a solid electrolyte containing a superionic conductor according to any one of claims 1 to 8, positioned between the positive electrode and the negative electrode.

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