Superionic conductor and Electrochemical Cell comprising the Same

Abstract

The present invention relates to a superionic conductor having stable and excellent ionic conductivity characteristics at room temperature, a method for manufacturing the same, and an electrochemical cell including the same.

Description

Technology Field

[0001] The present invention relates to a superionic conductor and an electrochemical cell comprising the same. Background Technology

[0002] Electrochemical cells using solid electrolytes are one of the most promising candidates to address the inherent drawbacks of conventional lithium-ion batteries using liquid-based electrolytes, such as electrolyte leakage, flammability, and limited energy density. As one of the three major components of an electrochemical cell, the electrolyte must possess ion conductivity and electrochemical stability with the electrodes as core performance characteristics. Solid-phase ion 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 due to the development of materials with relatively high ion conductivity; however, they have a reactive nature with water, which leads to the generation of hydrogen sulfide, a toxic substance, and a degradation of ion conductivity characteristics. Additionally, the issue of low electrochemical stability at low potentials due to weak reducing properties is also emerging as a problem. Therefore, there is a need to develop new solid ion conductors that do not generate toxic substances (gases), possess excellent electrochemical stability, are stable at room temperature, and exhibit superior ion conductivity characteristics. Prior art literature

[0003] (Patent Document 001) Republic of Korea Published Patent Application No. 10-2020-0053099 The problem to be solved

[0004] To solve the above problems, the present invention aims to provide a superionic conductor having stable and excellent ionic conductivity characteristics at room temperature, a method for manufacturing the same, and an electrochemical cell including the same.

[0005] However, the problems that this invention seeks to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0006] The first aspect of the present invention provides an acid-hydride superionic conductor that is a complex comprising a cation comprising an alkali metal or alkaline earth metal and a hydride-based complex anion; and a metal oxide.

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

[0008] A third aspect of the present invention provides an electrochemical cell comprising a solid electrolyte comprising an anode; a cathode; and a superionic conductor according to a first aspect located between the anode and the cathode. Effects of the invention

[0009] A superionic conductor according to one embodiment of the present invention is an acid-hydride-based ionic conductor that is a composite formed by a reaction between a starter compound and a metal oxide. It is characterized by stably maintaining the superionic conductive high-temperature phase of the starter compound even at room temperature, thereby exhibiting excellent ionic conductivity characteristics even at room temperature, and not generating toxic substances. Furthermore, it exhibits excellent stability with respect to metals such as Li or Na, thermal stability, and processability. Therefore, when the superionic conductor of the present invention is incorporated into an all-solid-state battery and used as a solid electrolyte for a secondary battery, it is possible to provide an all-solid-state battery with significantly improved high energy density, high power output, and stability.

[0010] Furthermore, since the superionic conductor of the present invention can be manufactured through a simple process of mechanical milling after mixing a starter compound and a metal oxide, it not only possesses economic feasibility in terms of manufacturing method but also has the advantage of being favorable for mass production. Brief explanation of the drawing

[0011] FIGS. 1A, 1B, 1C, 1D, and 1E are drawings illustrating the results of changes in ionic conductivity characteristics according to 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, respectively, compared with Comparative Example 1 and Comparative Example 3. FIG. 2 is a diagram illustrating the results of the change in ionic conductivity characteristics according to temperature for an ionic conductor according to the metal oxide mixing ratio according to one embodiment. FIGS. 3A, 3B, and 3C are, respectively, the superionic conductors of Example 4, Example 2, and Example 1 and Comparative Example 1 (LiCB 11 H 12 This is a diagram comparing the XRD measurement results of ). Specific details for implementing the invention

[0012] Embodiments of the present invention are described below with reference to the attached drawings to enable those skilled in the art to easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. Furthermore, in order to clearly explain the present invention in the drawings, parts unrelated to the explanation have been omitted, and similar parts throughout the specification are denoted by similar reference numerals.

[0013] Throughout this specification, when a component is described as being located “on” another component, this includes not only cases where a component is in contact with another component, but also cases where another component exists between the two components.

[0014] Throughout this specification, when a part is described as “comprising” a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. Throughout this specification, terms of degree such as “about,” “substantially,” etc., are used to mean at or near the stated value when inherent manufacturing and material tolerances are presented in the said meaning, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosure in which precise or absolute values ​​are mentioned to aid in understanding this specification. Throughout this specification, terms of degree such as “step” or “step of” do not mean “step for”.

[0015] Throughout this specification, the term “combination(s) of these” included in the Markush-form expression means one or more mixtures or combinations selected from the group consisting of the components described in the Markush-form expression, and means including one or more selected from the group consisting of said components.

[0016] Throughout this specification, the description “A and / or B” means “A or B, or A and B”.

[0017] Hereinafter, embodiments and examples of the present invention will be described in detail with reference to the attached drawings. However, the present invention may not be limited to these embodiments and examples and drawings.

[0018] The first aspect of the present invention is an acid-hydride superionic conductor comprising a cation comprising an alkali metal or alkaline earth metal and a hydride-based complex anion; and a metal oxide, wherein the cation comprises an alkali metal or alkaline earth metal and a hydride-based complex anion, and the metal oxide is a complex of the hydride-based complex and the metal oxide.

[0019] Here, the initiation hydride may be an ion conductor having ion conductivity containing a hydrogen complex ion, and the term "initiation hydride" may be named as "complex hydride" or "complex metal hydride."

[0020] Specifically, the acid-hydride superionic conductor, which is a complex of a starter compound and a metal oxide synthesized by the reaction of the starter compound and the metal oxide, is a defect within the crystal structure of the starter compound (for example, Li) resulting from the reaction between the two materials. + A defect may be formed. A space charge layer may be formed due to the formation of defects within the crystal structure of the initiation compound, and as a result, the disorder of the crystal increases, so that the phase at high temperature is stably maintained even at room temperature, and thus the superionic conductor of the present invention can exhibit significantly superior ionic conductivity characteristics even at room temperature compared to conventional initiation compounds.

[0021] Although conventional initiation compounds such as LiBH4 have been reported to possess high lithium ion conductivity at high temperatures, there are practical limitations to their use as solid electrolytes due to the problem of rapidly degrading ion conductivity characteristics at room temperature. However, as mentioned above, the superionic conductor of the present invention can possess excellent ion conductivity characteristics even at room temperature, thus offering the advantage of being usable as a solid electrolyte for electrochemical cells.

[0022] In a composite according to one embodiment of the present invention, namely a superionic conductor, the disorder of the crystal is increased by the formation of defects of metal cations within the crystal structure of the initiator compound through the reaction of the initiator compound and the metal oxide. As a result, the superionic conductor of the present invention can exhibit excellent ionic conductivity characteristics, as the high-temperature phase is stably maintained even at room temperature compared to conventional initiator compounds.

[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 starter compound and a metal oxide can be manufactured through a simple process such as a grinding process like mechanical milling, and the acid-hydride superionic conductor subsequently subjected to heat treatment may exhibit higher ionic conductivity characteristics than when not subjected to heat treatment. The mechanical milling and heat treatment will be described in more detail in terms of the manufacturing method described later.

[0024] In one embodiment of the present invention, the molar ratio of the initiator compound to the metal oxide included 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 initiator compound to the metal oxide is less than 1:0.01, the effect of maintaining the structural disorder of the initiator compound is negligible, so there is a limit to improving the ionic conductivity characteristics at room temperature, and when the molar ratio of the initiator compound to the metal oxide exceeds 1:20, the ionic conductivity characteristics of the composite, i.e., the superionic conductor, may be degraded, so it is advantageous for the molar ratio of the metal oxide to the initiator compound to satisfy the aforementioned range.

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

[0027] The above α is a factor representing the molar ratio, and can provide a composite with different ionic conductivity characteristics depending on the molar ratio of the initiator compound and the metal oxide, and the present invention is characterized by providing an optimal ratio that exhibits stable and excellent ionic conductivity at room temperature.

[0028] In one embodiment of the present invention, the aforementioned metal oxide may be used without limitation if it is capable of increasing the degree of structural disorder caused by defects induced within the lattice of the initiator through reaction with the initiator, as described above.

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

[0030] In one embodiment of the present invention, the complex anion included in the initiation compound 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 - It may be one or more selected from among, specifically CB9H 10 - , CB 11 H 12 - and B 12 H 12 2- It may be one or more selected from among, more specifically CB 11 H 12 - It could be.

[0031] For example, as described above, the initiation compound comprises a cation including an alkali metal or an alkaline earth metal in addition to the aforementioned hydride-based complex anion, and the cation may be one or more selected from Na, Li, Mg, Ca, K, and Cs, specifically may be Li or Na, and more specifically may be Li.

[0032] In one embodiment of the present invention, the superionic conductor described above may include 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. In this case, the X-ray diffraction pattern may be measured at 25°C.

[0033] Specifically, the first peak is derived from a starter compound included in the superionic conductor, and may be located at a 2θ value that is 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 smaller than the 2θ value of the starter compound before reaction with the metal oxide located in the range of 15.9 ± 0.5° (located in the range of 15.9 ± 0.5°), and although the upper limit is not restricted, the first peak may be located at a 2θ value that is 0.5° or less, specifically 0.3° or less, more specifically 0.12° or less, smaller than the 2θ value of the starter compound before reaction with the metal oxide.

[0034] More specifically, as the first peak in the X-ray diffraction pattern is located at a 2θ value satisfying the aforementioned conditions, the superionic conductor can possess excellent ionic conductivity characteristics even at room temperature. As previously described, the reaction between the initiator compound and the metal oxide can induce lattice expansion of the initiator compound prior to the reaction. Through this, it can be seen that cation defects contained in the initiator compound are formed in the structure of the initiator compound prior to the reaction, and the formation of these cation defects increases the structural disorder of the initiator compound. In this way, the entropy increases due to the increased structural disorder, thereby reducing the phase transition temperature to the high-temperature phase of the initiator compound with excellent ionic conductivity characteristics, so that excellent ionic conductivity characteristics appear even at room temperature.

[0035] In addition, since the metal oxide included in the superionic conductor not only increases the structural disorder of the initiator but can also effectively maintain the increased structural disorder, the superionic conductor of the present invention has the advantage of stably exhibiting excellent ionic conductivity characteristics at room temperature.

[0036] In one embodiment of the present invention, the cation defect formed inside the initiator included in the superionic conductor is, as an example, Li +It could be a defect.

[0037] In addition, the superionic conductor of the present invention may further include a third peak in the X-ray diffraction pattern in addition to the first peak described above, wherein 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 smaller 2θ value compared to the diffraction angle 2θ value of the metal oxide and the initial compound before reaction (located in the range of 18.2 ± 0.5˚) which is located in the range of 18.2 ± 0.5˚. In this case, the difference in the diffraction angle 2θ value at which the third peak of the superionic conductor of the present invention and the metal oxide and the initial compound before reaction is located may be similar to or identical to the range in which the first peak of the superionic conductor is shifted and located based on the metal oxide and the initial compound before reaction described above.

[0038] In one embodiment of the present invention, the second peak located in the aforementioned range of 45 ± 5˚ may be of origin from a metal oxide.

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

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

[0041] In addition, the superionic conductor may include additional peaks other than the second peak derived from the metal oxide. For example, the additional peak other than the second peak may be located at different diffraction angle 2θ values ​​depending on the type of metal oxide and may include multiple peaks that are independently different from each other. As a non-limiting example, the additional peak other than the second peak may be one or more of the peaks located in the range of diffraction angle 2θ of 25 ± 5˚, 35 ± 4.99˚, 55 ± 4.99˚, and 70 ± 10˚, but the present invention is not limited thereto, and it is obvious that other peaks may be located outside the aforementioned diffraction angle ranges.

[0042] As described above, the acid-hydride-based superionic conductor of the present invention is a complex of a starter hydride and a metal oxide, and the aforementioned characteristics can be exhibited by synthesizing the two materials through the reaction of the starter hydride and the metal oxide. Therefore, it should be understood as a material distinct from a simple mixture of a starter hydride and a metal oxide. In other words, the effect of the acid-hydride-based superionic conductor of the present invention having excellent ionic conductivity characteristics at room temperature is an effect that cannot be achieved in the form of a simple mixture of a starter hydride and a metal oxide.

[0043] Hereinafter, a method for manufacturing an acid-hydride-based superionic conductor, which is a composite of the initiator compound and metal oxide of the present invention described above, will be explained in detail.

[0044] The second aspect of the present invention relates to a method for manufacturing an acid-hydride-based superionic conductor, which is a composite of a starter compound and a metal oxide, comprising: a) a step of mixing a starter compound and a metal oxide, which include a cation comprising an alkali metal or an alkaline earth metal and a hydride-based complex anion, in a desired molar ratio; and b) a step of inducing a reaction between the starter compound and the metal oxide through a first milling process of mechanically milling the mixed mixture.

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

[0046] At this time, the initiator compound and metal oxide mixed in step a) above are the same as those previously described, so a detailed description is omitted.

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

[0048] In one embodiment of the present invention, the first milling process of step b) above may be performed using any method known in the art without limitation.

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

[0050] For example, the first milling process can be performed using a high-energy ball mill under an inert atmosphere at a speed of 100 to 500 rpm for 0.1 to 20 hours or 0.5 to 10 hours. If the first milling process is performed for less than 0.1 hours, the reaction between the mixed initiator and the metal oxide does not occur, which may limit the improvement of ion conductivity characteristics at room temperature; and if it exceeds 20 hours, it is not economically viable in terms of the manufacturing process compared to the effect of improving ion conductivity characteristics. Therefore, it may be advantageous to perform the first milling process within the aforementioned time range.

[0051] In addition, the first milling process can be performed as a dry or wet process, and if performed as a wet process, the milling process can be performed by adding a solvent to the mixture and then removing the solvent. At this time, acetonitrile, tetrahydrofuran, diethyl ether, N,N-dimethylformamide, N,N-dimethylacetamide, methanol, ethanol, or a mixture thereof may be used as the added solvent, but is not limited thereto.

[0052] In one embodiment of the present invention, a second milling process step of mechanically milling the starter material before performing the mixing step of step a) described above may be further included.

[0053] By performing the second milling process, not only can the structural disorder of the initiator compound be further increased, but the initiator compound can also be ground to a nano-size, which is more advantageous for inducing a reaction with the metal oxide in the aforementioned first milling process. In other words, the specific surface area of ​​the initiator compound ground to a nano-size increases, thereby increasing the reaction surface area with the metal oxide during the first milling process. Consequently, there is an advantage in that the ionic conductivity characteristics of the oxyhydride-based superionic conductor finally obtained at room temperature can be further improved.

[0054] For example, the size of the starter hydrate after performing the second milling process step may be 1 to 1000 nm, 1 to 800 nm, 1 to 700 nm, 1 to 600 nm, or 1 to 500 nm.

[0055] In one embodiment of the present invention, the second milling process may be performed as a process similar to the first milling process described above. However, the second milling process may be performed for 1 to 100 hours, 5 to 80 hours, or 10 to 50 hours under high-speed rotation conditions compared to the first milling process. As an example, the second milling process may be performed under conditions of 200 to 800 rpm for the time range described above.

[0056] In one embodiment of the present invention, after the aforementioned step b), a step of heat-treating the obtained composite may be further included.

[0057] Including an additional heat treatment step has the advantage of further improving the ionic conductivity characteristics of the superionic conductor.

[0058] At this time, it goes without saying that heat treatment can be performed on the obtained composite itself after step b), or on the pelletized composite formed by applying pressure to the obtained composite.

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

[0060] The present invention also provides, according to a third aspect, a solid electrolyte for an electrochemical cell comprising the aforementioned superionic conductor. 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. Furthermore, in addition to the superionic conductor of the present invention, 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] The fourth aspect of the present invention provides an electrochemical cell comprising a solid electrolyte comprising an anode; a cathode; and a superionic conductor according to the first aspect located between the anode and the cathode. An electrochemical cell comprising a solid electrolyte comprising a superionic conductor having excellent ionic conductivity characteristics at room temperature can realize an all-solid-state battery with high energy density, high power output, and improved stability.

[0063] In one embodiment of the present invention, the anode comprises an anode current collector and an anode composite containing an anode active material, and the anode composite may be coated on the anode current collector, wherein the coating of the anode composite may be coated on one or both sides of the anode current collector.

[0064] For example, the positive current collector coated with the positive composite is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity, and for example, stainless steel, aluminum, nickel, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive current collector may be used in various forms such as film, sheet, foil, net, porous body, foam, nonwoven fabric, etc., and the present invention is not limited according to the form of the positive current collector.

[0065] In one embodiment of the present invention, the positive active material included in the positive composite may include one or more selected from sulfide-based active materials and oxide-based active materials.

[0066] For example, the sulfide-based active material may be inorganic sulfur (S8), a sulfur-based compound, or a mixture thereof, and the sulfur-based compound may be a metal sulfide (M x S y It may be one or more selected from the group consisting of , M=Li, Ni, Co, Cu, Fe, Mo, Ti, Nb, 1≤x≤4, 1≤y≤8), organic sulfur compounds and carbon-sulfur polymers ((C2Sx)n: x=2.5~50, n≥2).

[0067] In addition, oxide-based active materials include LiCoO2, LiMnO2, LiNiO2, LiVO2, Li 1+x Ni 1 / 3 Co 1 / 3 Mn 1 / 3 Rock salt layer type active materials such as O2, LiMn2O4, Li(Ni 0.5 Mn 1.5 Spinel-type active materials such as )O4, inverse spinel-type active materials such as LiNiVO4 and LiCoVO4, olivine-type active materials such as LiFePO4, LiMnPO4, LiCoPO4, and LiNiPO4, silicon-containing active materials such as Li2FeSiO4 and Li2MnSiO4, LiNi 0.8 Co (0.2-x) Al x O2(0 <x<0.2)과 같이 천이 금속의 일부를 이종 금속으로 치환한 암염층형형 활물질, Li 1+x Mn 2-x-y M y O4(M is at least one species among Al, Mg, Co, Fe, Ni, and Zn, and 0 <x+y<2)와 같이 천이 금속의 일부를 이종 금속으로 치환한 스피넬형 활물질일 수 있으나, 이에 제한되지는 않는다.

[0068] For example, a positive electrode composite comprising a positive electrode active material may further comprise an ion conductor, and said ion conductor may be a hydride-based ion conductor comprising a cation comprising an alkali metal or alkaline earth metal and a hydride-based complex anion, specifically CB 11 H 12 - , B 12 H 12 2- and CB9H 10 - It may be a hydride-based ion conductor comprising one or more selected from the group consisting of, as a complex anion, and of course, it may be a superion conductor as described above.

[0069] In addition, the anode composite may further include a conductive material, a binder, etc., in addition to the aforementioned anode active material and ion conductor.

[0070] The above conductive material may be used without limitation as long as it is a material known in the art capable of forming an electron conduction path within the electrode, and the above conductive material may be sp such as carbon black, conducting graphite, ethylene black, carbon nanotubes, etc. 2 It may be a carbon material or graphene, but is not limited thereto.

[0071] The above binder is styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluorine rubber, 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, epoxy resin, carboxymethylcellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, It may be selected from the group consisting of cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, fluorinated polymer, chlorinated polymer, alginate, polyvinylidene fluoride, poly(vinylidene fluoride)-hexafluoropropene, and combinations thereof.

[0072] In one embodiment of the present invention, the cathode may comprise lithium metal. For example, the cathode may comprise lithium metal located on a cathode current collector, wherein the lithium metal may be located in the form of a thin film on the cathode current collector. For example, the lithium metal in the form of a thin film may be formed by depositing lithium metal on the cathode current collector by a physical or chemical method, or by placing a lithium foil or lithium metal powder on the cathode current collector and then rolling it, but is not limited thereto, and the lithium metal in the form of a thin film may be located on one or both sides of the cathode current collector.

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

[0074] In addition, the cathode may include a cathode active material commonly used in the industry.

[0075] For example, the negative electrode active material may include, but is not limited to, one or more selected from carbon-based materials, silicon, silicon oxide, silicon-based alloy, silicon-carbon composite, tin, tin-based alloy, tin-carbon composite, metal oxide, or combinations thereof.

[0076] As a non-limiting example, the carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite, and the amorphous carbon may be soft carbon (low-temperature calcined carbon) or hard carbon, mesophase pitch carbide, calcined coke, graphene, carbon black, fullerene soot, carbon nanotubes, and carbon fibers, etc.

[0077] In addition, the cathode may further include a binder and a conductive material in addition to the aforementioned cathode active material, and may be similar to or identical to the aforementioned binder and conductive material, and a detailed description is omitted.

[0078] In one embodiment of the present invention, the superionic conductor described above may be positioned between the anode and the cathode to form an electrolyte layer, and the electrolyte layer may additionally include a binder or a liquid as needed.

[0079] Here, the liquid may refer to a liquid electrolyte containing a lithium salt widely used in the field of lithium-ion batteries, and the present invention is not limited by the type of lithium salt contained in the liquid electrolyte and / or the composition of the liquid electrolyte.

[0080] In addition, 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 as a multilayer, the solid electrolyte layer including the aforementioned superionic conductor may be located in contact with the aforementioned cathode.

[0081] The present invention will be explained in more detail below through embodiments thereof; however, the following embodiments are merely illustrative to aid in understanding the present invention, and the content of the present invention is not limited to the following embodiments.

[0082] [Example]

[0083] (Example 1)

[0084] The raw material Li[CB 11 H 12 ]1 / 2H2O was heat-treated under high vacuum at a temperature of 100–200°C in an Ar atmosphere, followed by primary ball milling at 200–800 rpm for 10–50 hours to produce nanometer-sized (1–500 nm) Li[CB 11 H 12 ] The immersion product was recovered.

[0085] Subsequently, the recovered initiator and Al2O3 as a metal oxide were Li[CB 11 H 12 An acid-hydride-based superionic conductor, which is a complex of a starter hydrate and a metal oxide, was prepared by weighing the material to a molar ratio of ] : Al2O3 = 9 : 1 and performing secondary ball milling at 100 to 500 rpm for 0.5 to 10 hours.

[0086] (Example 2)

[0087] The procedure is carried out in the same manner as Example 1, except that Li[CB 11 H 12 A superionic conductor was prepared by carrying out the same procedure, except that a mixture was used in a molar ratio of ] : Al2O3 = 6 : 4.

[0088] (Example 3)

[0089] The procedure is carried out in the same manner as Example 1, except that Li[CB 11 H 12 A superionic conductor was prepared by carrying out the same procedure, except that a mixture was used in a molar ratio of ] : Al2O3 = 4 : 6.

[0090] (Example 4)

[0091] The procedure is carried out in the same manner as Example 1, except that Li[CB 11 H 12 A superionic conductor was prepared by carrying out the same procedure, except that a mixture was used in a molar ratio of ] : Al2O3 = 2 : 8.

[0092] (Example 5)

[0093] The procedure is carried out in the same manner as Example 1, except that Li[CB 11 H 12 A superionic conductor was prepared by carrying out the same procedure, except that a mixture was used in a molar ratio of ] : Al2O3 = 1 : 9.

[0094] (Example 6)

[0095] The procedure was carried out in the same manner as in Example 1, except that the recovered initiator hydrate and SiO2 as the metal oxide were Li[CB 11 H 12 A superionic conductor was prepared by carrying out the same procedure, except that a mixture was used in a molar ratio of ] : SiO2 = 2 : 8.

[0096] (Example 7)

[0097] The procedure was carried out in the same manner as in Example 1, except that the recovered initiator hydrate and MgO as the metal oxide were Li[CB 11 H12 A superionic conductor was prepared by carrying out the same procedure, except that a mixture was used in a molar ratio of ] : MgO = 1 : 9.

[0098] (Example 8)

[0099] The procedure was carried out in the same manner as in Example 1, except that the recovered initiator hydrate and ZrO2 as the metal oxide were Li[CB 11 H 12 A superionic conductor was prepared by carrying out the same procedure, except that a mixture was used in a molar ratio of ] : ZrO2 = 3 : 7.

[0100] (Example 9)

[0101] The procedure was carried out in the same manner as Example 2, except that the raw material was Li[CB9H 10 A superionic conductor was prepared by carrying out the same procedure, except that ]·1 / 2H2O was used.

[0102] (Example 10)

[0103] The procedure is carried out in the same manner as Example 2, except that Li2B is used as the raw material. 12 H 12 A superionic conductor was manufactured by carrying out the same procedure except for using [the appropriate method].

[0104] (Examples 11 to 20)

[0105] Each of the manufactured superionic conductors of Examples 1 to 10 was subjected to heat treatment at 100 to 200°C for 1 hour under an Ar atmosphere. At this time, the heat-treated Examples 1 to 10 are sequentially the superionic conductors of Examples 11 to 20.

[0106] (Comparative Example 1)

[0107] Li[CB before performing the first ball milling in Example 1, which was not mixed with metal oxide 11 H 12 ] The incoming cargo was recovered.

[0108] (Comparative Example 2)

[0109] Li[CB that underwent primary ball milling of Example 1 without mixing with metal oxide 11 H 12 ] The incoming cargo was recovered.

[0110] (Comparative Examples 3 and 4)

[0111] Each of the manufactured Comparative Example 1 and Comparative Example 2 was heat-treated in the same manner as Example 11, and the heat-treated Comparative Example 1 and Comparative Example 2 are the starter products of Comparative Example 3 and Comparative Example 4, respectively.

[0112] (Experimental Example 1) Comparative Analysis of Ionic Conductivity Characteristics of Superionic Conductors

[0113] The ionic conductivity characteristics of each manufactured superionic conductor were compared and analyzed. At this time, the ionic conductivity was measured by compressing each manufactured superionic conductor under 100 to 400 MPa to form a pellet with a diameter of 10 mm and a thickness of 100 to 500 μm.

[0114] First, changes in ionic conductivity characteristics according to the type of metal oxide were compared and analyzed (Figs. 1a to 1e and Table 1).

[0115] FIGS. 1a, 1b, 1c, 1d, and 1e are drawings showing Arrhenius plots comparing the change in ionic conductivity characteristics according to temperature with Comparative Example 1 and Comparative Example 3 for 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, respectively, and the ionic conductivity characteristics at 25°C are summarized in Table 1 below.

[0117] Ionic conductivity at 25℃before heat treatment (S / cm) Ionic conductivity at 25℃after heat treatment (S / cm) Example 4 4.49 x 10 -5 Example 14 3.86 x 10 -4 Example 6 2.24 x 10 -5 Example 16 1.26 x 10 -4 Example 7 5.64 x 10 -5 Example 17 3.11 x 10 -4 Example 8 2.05 x 10 -4 Example 18 1.32 x 10 -3 Comparative Example 1 5.38 x 10 -7 Comparative Example 3 1.52 x 10 -6 Comparative Example 2 1.01 x 10 -4 Comparative Example 4 1.44 x 10 -6

[0118] Referring to FIGS. 1a through 1e, Li[CB, which is one of the initiation compounds as is known. 11 H 12It can be seen that the ionic conductors, namely Comparative Examples 1 and 3, exhibit ionic conductivity characteristics suitable as electrolytes for electrochemical cells at high temperatures of approximately 120°C or higher, but the ionic conductivity characteristics deteriorate rapidly as the temperature decreases. On the other hand, it was confirmed that the superionic conductors of Examples 4, 6 to 8, 14, and 16 to 18, which are complexes of a precipitate and a metal oxide, exhibit a relatively gradual decrease in ionic conductivity characteristics as the temperature decreases.

[0119] Additionally, when examining the characteristics before and after heat treatment at 25°C, it was observed that the ion conductivity characteristics improved compared to before heat treatment in Examples 14, 16 to 18, and Comparative Example 3. Specifically, in the case of Comparative Example 3, it was confirmed that the ion conductivity increased by approximately 183% compared to Comparative Example 1 before heat treatment, whereas in the case of Examples 14, 16, 17, and 18, it was found that the ion conductivity was significantly improved by approximately 760%, 463%, 451%, and 544%, respectively, compared to before heat treatment.

[0120] On the other hand, Comparative Example 2 showed superior ion conductivity characteristics compared to Comparative Example 1, but it was confirmed that the ion conductivity characteristics of Comparative Example 4, which was heat-treated from Comparative Example 2, actually decreased by about 99% compared to before heat treatment.

[0121] From this, it can be seen that the superionic conductor, which is a complex of a starter compound and a metal oxide, exhibits significantly superior ionic conductivity characteristics at room temperature compared to conventional starter compounds, and that these ionic conductivity characteristics can be further improved through a heat treatment process.

[0122] In addition, in the case of Comparative Example 2, which does not contain a metal oxide, it was confirmed that although the ionic conductivity characteristics can be temporarily improved at room temperature through a simple ball milling process, the improved ionic conductivity characteristics can rapidly deteriorate due to the external environment. That is, it can be seen that the superionic conductor, which is a composite of the initiator compound and the metal oxide of the present invention, maintains the improved ionic conductivity characteristics stably.

[0123] Next, in Experimental Example 1, the rate of increase in ionic conductivity after heat treatment was the greatest. Using Example 4, the ionic conductivity according to the metal oxide mixing ratio was measured and compared in the same way as in Experimental Example 1 (Table 2 and Figure 2).

[0124] Ionic conductivity at 25℃before heat treatment (S / cm) Ionic conductivity at 25℃after heat treatment (S / cm) Example 1 7.04 x 10 -5 Example 11 5.74 x 10 -5 Example 2 1.35 x 10 -4 Example 12 1.73 x 10 -3 Example 3 5.65 x 10 -5 Example 13 7.04 x 10 -4 Example 4 4.49 x 10 -5 Example 14 3.86 x 10 -4 Example 5 3.24 x 10 -5 Example 15 3.04 x 10 -5

[0125] Referring to Figure 2 and Table 2, it was confirmed that, similar to the ionic conductivity characteristics according to the type of metal oxide described above, all molar ratios of the initiator and the metal oxide exhibited significantly superior ionic conductivity characteristics compared to the initiator of Comparative Example 1 and Comparative Example 3. However, it was confirmed that when the molar ratio of the metal oxide to the initiator is 0.1 mole or less or 15 moles or more based on 1 mole of the initiator, the effect of improving ionic conductivity after heat treatment compared to before heat treatment is reduced. Through this, it was reconfirmed that, as previously described, the metal oxide included in the superionic conductor can improve ionic conductivity characteristics at room temperature. In other words, it was confirmed that ionic conductivity characteristics can be significantly improved after heat treatment compared to the comparative examples, provided that the content of the metal oxide included in the superionic conductor is not excessively small or large.

[0126] Although not illustrated in the drawings, in the case of Examples 9 and 10 and Examples 19 and 20 using different starter digests as raw materials, it was confirmed that the ion conductivity characteristics were improved compared to the conventional starter digest, similar to Examples 2 and 12.

[0127] Experimental Example 2: Analysis of the Crystal Structure of a Superionic Conductor

[0128] The crystal structure of each fabricated superionic conductor was confirmed through X-ray diffraction (XRD, 45 kV, 200 mA, 1° min -1, Cu-Kα radiation, λ= 0.15406 nm) analysis.

[0129] FIGS. 3A, 3B, and 3C are, respectively, the superionic conductors of Example 4, Example 2, and Example 1 and Comparative Example 1 (LiCB 11 H 12 This is a diagram comparing the XRD measurement results of ).

[0130] Looking at the magnified peak on the right in Figs. 3a to 3c, at a diffraction angle 2θ = 15.9°, Comparative Example 1 is LiCB 11 H 12 It can be seen that a peak corresponding to the (111) plane appears.

[0131] On the other hand, in the case of Examples 4, 2, and 1, all are LiCB 11 H 12 It can be seen that the peak corresponding to the (111) plane is located at a diffraction angle 2θ value that is at least 0.05˚ smaller than the 2θ value at which the peak appears. From this, it can be seen that the superionic conductor of the present invention is LiCB 11 H 12 It can be seen that the lattice constant increased in all compositions due to the reaction between the phosphorus initiation compound and the metal oxide Al2O3.

[0132] In other words, the superionic conductor of the present invention is not in the form of a simple mixture of a starter compound and a metal oxide, but is a composite of a starter compound and a metal oxide.

[0133] Looking more specifically, in the case of Examples 4, 2, and 1, LiCB 11 H 12It was observed that the peak corresponding to the plane (111) of the (111) (hereinafter referred to as the first peak) was located at a diffraction angle 2θ value that was 0.09˚, 0.07˚, and 0.10˚ smaller than the diffraction angle 2θ value, respectively, and although not illustrated in the drawing, it was confirmed that Example 3 and Example 5 were also similarly located at a diffraction angle 2θ value that was 0.09˚ smaller.

[0134] In addition, a LiCB located at a diffraction angle of approximately 18.2˚ 11 H 12 Likewise, it was observed that the peak of was located at a smaller diffraction angle as the aforementioned peak shifted to a different position.

[0135] Additionally, it was confirmed that an additional peak originating from the metal oxide contained in the superionic conductor appeared. At this time, when comparing the intensity ratio (I1 / I2) between the maximum intensity of the first peak (I1) and the maximum intensity of the peak (hereinafter referred to as the second peak) located at a diffraction angle 2θ value of 45˚ originating from the metal oxide, based on the lowest intensity of the XRD pattern within the range where the diffraction angle 2θ is 10˚ to 80˚, it was confirmed that in the case of Example 4, it was about 4.5, in Example 2, about 19.8, and in Example 1, about 49.9.

[0136] (Example 21) Preparation of an all-solid-state battery

[0137] An electrolyte layer of an electrochemical cell was prepared by pressurizing the superionic conductor of Example 2, and a positive electrode layer was prepared by mixing and pressurizing the superionic conductor powder, a positive electrode active material (Sulfur), and a conductive agent (Super P, Carbon nanotube). An all-solid-state battery was prepared using lithium metal as the negative electrode layer, and it was confirmed that the electrochemical cell operated by conducting charge-discharge experiments at room temperature.

[0138] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will understand that other specific forms can be easily modified without altering the technical concept or essential features of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single unit may be implemented in a distributed manner, and components described as distributed may likewise be implemented in a combined form.

[0139] The scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the meaning and scope of the claims and the concept of equivalents thereof should be interpreted as being included within the scope of the present invention.

Claims

Claim 1 An acid-hydride superionic conductor comprising a complex hydride comprising a cation comprising an alkali metal or alkaline earth metal and a hydride-based complex anion; and a metal oxide, wherein the complex hydride and the metal oxide are a composite synthesized by reaction with the metal oxide to form defects in the crystal structure of the complex hydride, and the composite is 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 - A superionic conductor comprising one or more hydride-based complex anions selected from among. Claim 2 delete Claim 3 A superionic conductor according to claim 1, wherein the molar ratio of the initiator compound to the metal oxide included in the complex is 1:0.01 to 20. Claim 4 In claim 1, the composite is a superionic conductor comprising one or more metal oxides selected from MgO, Al2O3, SiO2, and ZrO2. Claim 5 delete Claim 6 The superion conductor according to claim 1, wherein the superion conductor comprises a first peak located in the range of 15.9 ± 0.5˚ and a second peak located in the range of 45 ± 5˚ in the X-ray diffraction pattern using CuKα rays. Claim 7 A superionic conductor according to claim 6, wherein the first peak is derived from the starter digest and is located at a 2θ value that is at least 0.05˚ smaller than the starter digest prior to the reaction. Claim 8 In claim 6, the superionic conductor, wherein the second peak is derived from the metal oxide. Claim 9 a) a step of mixing a complex hydride comprising a cation comprising an alkali metal or alkaline earth metal and a hydride-based complex anion and 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 process of mechanically milling the mixed mixture, wherein the hydride-based complex anion is 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 - A method for manufacturing a superionic conductor selected from among. Claim 10 A method for manufacturing a superionic conductor according to claim 9, further comprising a second milling process step of mechanically milling the starter material before performing the mixing step of step a). Claim 11 A method for manufacturing a superionic conductor according to claim 9, further comprising the step of heat-treating the composite after step b) above. Claim 12 A solid electrolyte for an electrochemical cell comprising a superionic conductor according to any one of claims 1, 3, 4, 6 through 8. Claim 13 An electrochemical cell comprising a solid electrolyte comprising an anode; a cathode; and a superionic conductor according to any one of claims 1, 3, 4, 6 to 8 located between the anode and the cathode.

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