Superionic conductor and electrochemical cell comprising same

Abstract

The present application relates to a superionic conductor having excellent ionic conductivity and being stable at room temperature, a method of preparing same, and an electrochemical cell including same. A first aspect of the present application provides an acid-hydride-based superionic conductor, which is a composite comprising: a complex hydride including a hydride-based complex ion and a cation containing an alkali metal or an alkaline earth metal; and a metal oxide. When the superionic conductor of the present invention is applied to an all-solid state battery and used as a solid electrolyte of a secondary battery, an all-solid state battery having significantly improved high energy density, high output, and stability can be provided.

Description

Superionic conductor and electrochemical cell containing the same

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

[0002] Electrochemical cells using solid electrolytes are one of the most promising candidates to address the inherent shortcomings of lithium-ion batteries using conventional liquid 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 both ionic conductivity and electrochemical stability with the electrodes as key performance characteristics. Materials being considered for solid electrolytes include oxide-based, sulfide-based, and polymer-based solid ionic conductors. Sulfide-based solid electrolytes have attracted attention for their relatively high ionic conductivity. However, they react with water, generating toxic hydrogen sulfide and degrading ionic conductivity. Furthermore, their weak reducibility leads to poor electrochemical stability at low potentials. Therefore, there is a need to develop new solid ionic conductors that do not generate toxic gases, exhibit excellent electrochemical stability at room temperature, and exhibit superior ionic conductivity.

[0003] (Patent Document 001) Republic of Korea Patent Publication No. 10-2020-0053099

[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 producing the same, and an electrochemical cell including the same.

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

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

[0007] The second aspect of the present invention provides a method for producing an acid-hydride system superionic conductor which is a composite of a hydride and a metal oxide, the method comprising the steps of: a) mixing a cation including an alkali metal or alkaline earth metal and a hydride-based complex anion and a metal oxide at a desired molar ratio; and b) inducing a reaction of the hydride 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 positive electrode; a negative electrode; and a solid electrolyte comprising a superionic conductor according to the first aspect positioned between the positive electrode and the negative electrode.

[0009] According to one embodiment of the present invention, a superionic conductor is an acid-hydride ion conductor which is a composite formed by a reaction between a hydride and a metal oxide, and can stably maintain a superionic conductive high-temperature phase of the hydride even at room temperature, thereby exhibiting excellent ionic conductivity characteristics even at room temperature and having the characteristic of not generating toxic substances. In addition, since it has excellent stability to metals such as Li or Na, thermal stability, and processability, when the superionic conductor of the present invention is grafted onto an all-solid state battery and used as a solid electrolyte of a secondary battery, an all-solid state battery having significantly improved high energy density, high output, and stability can be provided.

[0010] Furthermore, the superionic conductor of the present invention can be manufactured by a simple process of mixing a starting material and a metal oxide and then mechanical milling, so it is not only economical in terms of manufacturing method but also advantageous in mass production.

[0011] FIG. 1a, FIG. 1b, FIG. 1c, FIG. 1d and FIG. 1e are drawings showing the results of changes in ionic conductivity characteristics according to temperature for the ionic conductors of Examples 4 and 14, Examples 6 and 16, Examples 7 and 17, Examples 8 and 18 and Comparative Examples 2 and 4, respectively, compared with Comparative Examples 1 and 3.

[0012] FIG. 2 is a diagram showing the results of changes in ionic conductivity characteristics according to temperature for an ionic conductor depending on the mixing ratio of metal oxides according to one embodiment.

[0013] Figures 3a, 3b and 3c show the superionic conductors of Examples 4, 2 and 1, respectively, and Comparative Example 1 (LiCB 11 H 12 ) is a drawing comparing the XRD measurement results.

[0014] Below, with reference to the attached drawings, embodiments of the present invention are described in detail to facilitate easy implementation by those skilled in the art. However, the present invention can be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, irrelevant parts have been omitted for clarity, and similar reference numerals have been used throughout the specification to indicate similar elements.

[0015] Throughout this specification, when it is said that an element is “on” another element, this includes not only cases where the element is in contact with the other element, but also cases where another element exists between the two elements.

[0016] Throughout this specification, when a part is said to “include” a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated. The terms “about,” “substantially,” etc., used throughout this specification, are used in a sense of numerical value or approximation when manufacturing and material tolerances inherent to the meanings referred to are presented, and are used to prevent unscrupulous infringers from unfairly exploiting disclosures that contain precise or absolute values ​​to aid understanding of this specification. The terms “step of doing” or “step of” used throughout this specification do not mean “step for.”

[0017] Throughout this specification, the term “combination(s) thereof” included in the expressions in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expressions in the Makushi format, and means including one or more selected from the group consisting of said components.

[0018] Throughout this specification, references to “A and / or B” mean “A or B, or A and B.”

[0019] Hereinafter, implementation examples and embodiments 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 implementation examples and embodiments and drawings.

[0020] The first aspect of the present invention is an acid-hydride system superionic conductor comprising a cation including an alkali metal or alkaline earth metal and a hydride-based complex anion; and a metal oxide, wherein the cation is a complex of the hydride and the metal oxide.

[0021] Here, the complex hydride may be an ionic conductor having ionic conductivity by including a complex ion containing hydrogen, and the term "complex hydride" may be referred to as "complex hydride" or "composite metal hydride".

[0022] Specifically, the superionic conductor of the oxide-hydride system, which is a complex of a metal oxide and a metal oxide synthesized by the reaction of the metal oxide and the oxide, is a superionic conductor that is formed by the reaction of the two substances, the metal oxide and the oxide, by defects in the crystal structure of the metal oxide. + A space charge layer can be formed due to the formation of defects in the crystal structure of the hydride, and this increases the disorder of the crystal, so that the phase at high temperatures is stably maintained even at room temperature, and the superionic conductor of the present invention can exhibit significantly superior ionic conductivity characteristics even at room temperature compared to conventional hydride.

[0023] Conventional superionic conductors, such as LiBH4, have been reported to have high lithium ion conductivity at high temperatures. However, their practical use as solid electrolytes is limited due to the problem of rapid deterioration of ion conductivity characteristics at room temperature. However, as described above, the superionic conductor of the present invention can have excellent ion conductivity characteristics even at room temperature, and thus has the advantage of being usable as a solid electrolyte in electrochemical cells.

[0024] According to one embodiment of the present invention, the composite, i.e., the superionic conductor, increases the degree of crystal disorder by forming defects in the metal cations within the crystal structure of the superionic conductor through the reaction of the superionic conductor and the metal oxide. As a result, the superionic conductor of the present invention can exhibit superior ionic conductivity characteristics by maintaining a stable high-temperature phase even at room temperature compared to conventional superionic conductors.

[0025] In one embodiment of the present invention, the composite may be heat-treated. The acid-hydride superionic conductor synthesized by the reaction of the starting hydride and the metal oxide can be manufactured by a simple process such as a grinding process such as mechanical milling. The acid-hydride superionic conductor that has undergone the heat treatment can exhibit higher ionic conductivity characteristics than when not heat-treated. The mechanical milling and heat treatment will be described in more detail in the manufacturing method aspect described below.

[0026] In one embodiment of the present invention, the molar ratio of the initiator: metal oxide included in the complex 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.

[0027] When the molar ratio of the metal oxide to the initiating compound is less than 1:0.01, the effect of maintaining the structural disorder of the initiating compound is minimal, so there is a limit to improving the ionic conductivity characteristics at room temperature. When the molar ratio of the metal oxide to the initiating compound exceeds 1:20, the ionic conductivity characteristics of the composite, i.e., the superionic conductor, may deteriorate. Therefore, it is advantageous for the molar ratio of the metal oxide to the initiating compound to satisfy the above-mentioned range.

[0028] Specifically, the above acid-hydride superionic conductor is (1-α)M x (M' y H z ) can be expressed as -αK, and at this time, M x (M' y H z ) is a starting material, K is a metal oxide, α is 0.1 to 0.9, x is 1 or 2, y may be 1 ≤ y ≤ 15, and z may be 1 ≤ z ≤ 15.

[0029] The above α is a factor indicating the molar ratio, and can provide a complex having different ionic conductivity characteristics depending on the molar ratio of the starting material and the metal oxide. The present invention has the characteristic of providing an optimal ratio that exhibits stable and excellent ionic conductivity at room temperature.

[0030] As an example of the present invention, the above-mentioned metal oxide can be used without limitation as long as it can increase the degree of structural disorder due to defects induced within the lattice of the initiating hydride through reaction with the initiating hydride compared to before the reaction, as described above.

[0031] As a non-limiting example, the metal oxide may be at least one selected from TiO2, ZnO, CuO, CaO, SiO2, Al2O3, MgO, and ZrO2, and specifically may be at least one selected from SiO2, Al2O3, MgO, and ZrO2, but the present invention is not limited by the type of the metal oxide.

[0032] In one embodiment of the present invention, the anion included in the starting material 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 - One or more of the following may be selected, specifically CB9H 10 - , CB 11 H 12 - and B 12 H 12 2-There may be one or more selected from among, more specifically CB 11 H 12 - It could be.

[0033] For example, as described above, the hydride complex includes a cation including an alkali metal or alkaline earth metal in addition to the hydride complex anion described above, and the cation may be at least one selected from among Na, Li, Mg, Ca, K, and Cs, and may be specifically Li or Na, and may be more specifically Li.

[0034] In one embodiment of the present invention, the superionic conductor described above may include a first peak located in a diffraction angle 2θ range of 15.9 ± 0.5˚ and a second peak located in a diffraction angle 2θ 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.

[0035] Specifically, the first peak may be derived from the hydride 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 diffraction angle 2θ value of the hydride before reaction with the metal oxide (located in the range of 15.9 ± 0.5˚), and the upper limit value is not limited, but the first peak may be located at a 2θ value that is 0.5˚ or less, specifically 0.3˚ or less, and more specifically 0.12˚ or less, based on the diffraction angle 2θ value of the hydride before reaction with the metal oxide.

[0036] More specifically, since the first peak in the X-ray diffraction pattern is located at a 2θ value that satisfies the aforementioned conditions, the superionic conductor can have excellent ionic conductivity characteristics even at room temperature. As described above, the reaction between the hydride and the metal oxide can induce lattice expansion of the hydride before the reaction, and through this, it can be seen that cationic defects included in the hydride are formed in the hydride structure before the reaction, and the formation of these cationic defects increases the structural disorder of the hydride. In this way, the increased structural disorder increases entropy, which reduces the phase transition temperature of the hydride with excellent ionic conductivity to a high-temperature phase, thereby exhibiting excellent ionic conductivity characteristics even at room temperature.

[0037] In addition, since the metal oxide included in the superionic conductor not only increases the structural disorder of the initiating compound but also effectively maintains the increased structural disorder, the superionic conductor of the present invention has the advantage of being able to stably exhibit excellent ionic conductivity characteristics at room temperature.

[0038] In one embodiment of the present invention, the cationic defect formed inside the initiating agent included in the superionic conductor is, for example, Li + It could be a defect.

[0039] In addition, the superionic conductor of the present invention may further include a third peak having a diffraction angle 2θ of 18.2 ± 0.5˚ in addition to the first peak described above in the X-ray diffraction pattern. At this time, the third peak may be located at a smaller 2θ value than the diffraction angle 2θ value of the metal oxide and the hydride before reaction (located in the range of 18.2 ± 0.5˚). At this time, the difference between the diffraction angle 2θ values ​​of the third peak of the superionic conductor of the present invention and the metal oxide and the hydride before reaction 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 hydride before reaction described above.

[0040] In one embodiment of the present invention, the second peak located in the aforementioned 45 ± 5˚ range may be derived from a metal oxide.

[0041] 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 intensities of the first peak and the second peak may be values ​​calculated based on the lowest intensity in an X-ray diffraction pattern having a diffraction angle 2θ value within a range of 10 to 80˚.

[0042] In this way, as 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.

[0043] In addition, the superionic conductor may further include peaks other than the second peak derived from the metal oxide. For example, the peaks other than the second peak may be located at different diffraction angle 2θ values ​​depending on the type of the metal oxide, and may independently include multiple peaks that are different from each other. As a non-limiting example, the peaks other than the second peak may be any one or more peaks located in the diffraction angle 2θ range of 25 ± 5˚, 35 ± 4.99˚, 55 ± 4.99˚, and 70 ± 10˚, but the present invention is not limited thereto, and it goes without saying that other peaks may be located in addition to the above-described diffraction angle ranges.

[0044] As described above, the acid-hydride superionic conductor of the present invention is a complex of a hydride and a metal oxide, and can exhibit the above-described characteristics by being synthesized through a reaction between the two substances, the hydride and the metal oxide. Therefore, it should be understood as a different substance from a simple mixture of the hydride and the metal oxide. In other words, the effect of the acid-hydride superionic conductor of the present invention having excellent ionic conductivity characteristics at room temperature is an effect that cannot be exhibited simply in the form of a mixture of the hydride and the metal oxide.

[0045] Hereinafter, a manufacturing method capable of manufacturing an acid-hydride type superionic conductor, which is a composite of the aforementioned initiator and metal oxide of the present invention, will be described in detail.

[0046] The second aspect of the present invention relates to a method for producing a superionic conductor of an acid-hydride system, which is a composite of a hydride and a metal oxide, and may include the steps of: a) mixing a cation including an alkali metal or alkaline earth metal and a hydride-based complex anion, and a metal oxide, at a desired molar ratio; and b) inducing a reaction of the hydride and the metal oxide through a first milling process of mechanically milling the mixed mixture.

[0047] Specifically, the acid-hydride superionic conductor of the present invention is manufactured by inducing a reaction of the hydride and the metal oxide through mechanical milling of a mixture in which a cation including an alkali metal or alkaline earth metal and a hydride-based complex anion including a hydride complex anion are mixed at a desired molar ratio, thereby making the manufacturing process extremely simple and economically advantageous, and also having the advantage of being advantageous for mass production.

[0048] At this time, the starting material and metal oxide mixed in step a) are the same as those described above, and a detailed description thereof is omitted.

[0049] In the above-described step a), the complex hydride and the metal oxide can be mixed so as to satisfy the molar ratio described above.

[0050] As an example of the present invention, the first milling process of step b) can be performed without limitation using any method known in the art.

[0051] By way of non-limiting example, the first milling process may be performed using, but is not limited to, a bead mill, a ball mill, a high energy ball mill, a planetary mill, a stirred ball mill, or a vibration mill.

[0052] For example, the first milling process can be performed for 0.1 to 20 hours or 0.5 to 10 hours under conditions of 100 to 500 rpm using a high-energy ball mill in an inert atmosphere. If the first milling process is performed for less than 0.1 hour, the reaction between the mixed starting material and the metal oxide does not occur, which may limit the improvement of the ionic conductivity characteristics at room temperature. In addition, if the first milling process exceeds 20 hours, it is not economical in terms of the manufacturing process compared to the effect of improving the ionic conductivity characteristics. Therefore, it may be advantageous to perform the first milling process within the aforementioned time range.

[0053] In addition, the first milling process can be performed as a dry or wet process, and when performed through a wet process, the milling process can be performed by adding a solvent to the mixture, performing the milling process, and then removing the solvent. At this time, 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.

[0054] In one embodiment of the present invention, a second milling process step of mechanically milling the starting material may be further included before performing the mixing step of step a) described above.

[0055] By performing the second milling process, not only can the structural disorder of the starting material be further increased, but also the starting material can be pulverized into nano-size, which can be more advantageous in inducing a reaction with the metal oxide in the first milling process described above. That is, the specific surface area of ​​the starting material pulverized into nano-size can be increased, thereby increasing the reaction area with the metal oxide in the first milling process step, and thus, there is an advantage in that the ionic conductivity characteristics of the acid-hydride system superionic conductor finally obtained at room temperature can be further improved.

[0056] For example, the size of the starting material 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.

[0057] In one embodiment of the present invention, the second milling process may be performed in a similar manner to the first milling process described above. However, the second milling process may be performed under high-speed rotation conditions compared to the first milling process for 1 to 100 hours, 5 to 80 hours, or 10 to 50 hours. For example, the second milling process may be performed under conditions of 200 to 800 rpm for the time within the aforementioned range.

[0058] In one embodiment of the present invention, after the step b) described above, a step of heat treating the obtained complex may be further included.

[0059] By including more heat treatment steps, there is an advantage in that the ionic conductivity characteristics of the superionic conductor can be further improved.

[0060] At this time, the heat treatment can be performed on the obtained complex itself after step b), and of course, the heat treatment can be performed on the pelletized complex formed by pressing the obtained complex.

[0061] In one embodiment of the present invention, the heat treatment may be performed at a temperature range of 60 to 300°C, specifically 100 to 250°C, and more specifically 150 to 250°C for 0.01 to 50 hours.

[0062] The present invention also provides a solid electrolyte for an electrochemical cell comprising the aforementioned superionic conductor according to a third aspect. Here, the solid electrolyte may be a solid electrolyte for an all-solid-state battery.

[0063] As a non-limiting example, the solid electrolyte may be composed solely of the superionic conductor described above, and may further include a binding material. In addition, the solid electrolyte may further include, in addition to the superionic conductor of the present invention, at least one solid electrolyte selected from oxide-based solid electrolytes, sulfide-based solid electrolytes, polymer-based solid electrolytes, and phosphate compound solid electrolytes known in the art.

[0064] A fourth aspect of the present invention provides an electrochemical cell comprising a positive electrode; a negative electrode; and a solid electrolyte comprising a superionic conductor according to the first aspect positioned between the positive electrode and the negative electrode. 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 output, and improved stability.

[0065] In one embodiment of the present invention, the positive electrode includes a positive electrode current collector and a positive electrode mixture containing a positive electrode active material, and the positive electrode mixture may be coated on the positive electrode current collector. In this case, the coating of the positive electrode mixture may be coated on one side or both sides of the positive electrode current collector.

[0066] For example, the positive electrode current collector coated with the positive electrode mixture is not particularly limited as long as it does not cause a chemical change 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. can be used. In addition, the positive electrode current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc., and the present invention is not limited according to the form of the positive electrode current collector.

[0067] In one embodiment of the present invention, the positive electrode active material included in the positive electrode mixture may include at least one selected from a sulfide-based active material and an oxide-based active material.

[0068] 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 , 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).

[0069] In addition, oxide active materials include LiCoO2, LiMnO2, LiNiO2, LiVO2, and Li 1+x Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc. rock salt layer type active material, LiMn2O4, Li(Ni 0.5 Mn 1.5 )O4, etc., spinel-type active materials, reverse spinel-type active materials, such as LiNiVO4, LiCoVO4, etc., olivine-type active materials, such as LiFePO4, LiMnPO4, LiCoPO4, LiNiPO4, etc., silicon-containing active materials, such as Li2FeSiO4, 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 of Al, Mg, Co, Fe, Ni, Zn, and 0 <x+y<2)와 같이 천이 금속의 일부를 이종 금속으로 치환한 스피넬형 활물질일 수 있으나, 이에 제한되지는 않는다.

[0070] For example, a positive electrode mixture including a positive electrode active material may further include an ion conductor, and the ion conductor may be a hydride-based ion conductor including a cation including an alkali metal or an alkaline earth metal and a hydride-based complex ion, specifically, CB 11 H 12 - , B 12 H 12 2- and CB9H 10 - It may be a hydride-based ion conductor containing at least one anion selected from the group consisting of, and of course, it may be the superionic conductor described above.

[0071] In addition, the positive electrode composite may further include a conductive material, a binder, etc., in addition to the positive electrode active material and ion conductor described above.

[0072] The conductive material may be any material known in the art that can form an electronic conduction path within the electrode, and may be used without limitation. The conductive material may be sp, such as carbon black, conducting graphite, ethylene black, carbon nanotube, etc. 2 It may be, but is not limited to, carbon material or graphene.

[0073] The above binder is selected from the group consisting of 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, phenol resin, epoxy resin, carboxymethylcellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, It may be selected from the group consisting of cyanoethyl cellulose, 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.

[0074] In one embodiment of the present invention, the negative electrode may include lithium metal. For example, the negative electrode may include lithium metal positioned on the negative electrode current collector, and at this time, the lithium metal may be positioned in the form of a thin film on the negative electrode current collector. For example, the thin film form of lithium metal may be formed by physically or chemically depositing lithium metal on the negative electrode current collector, or by positioning lithium foil or lithium metal powder on the negative electrode current collector and then rolling, but is not limited thereto, and the thin film form of lithium metal may be positioned on one or both sides of the negative electrode current collector.

[0075] For example, the negative electrode current collector may be any one metal selected from the group consisting of, but not limited to, copper, aluminum, stainless steel, zinc, titanium, silver, palladium, nickel, iron, chromium, alloys thereof, and combinations thereof.

[0076] Additionally, the negative electrode may include a negative electrode active material commonly used in the art.

[0077] For example, the negative active material may include, but is not limited to, one or more selected from carbon-based materials, silicon, silicon oxide, silicon-based alloys, silicon-carbon composites, tin, tin-based alloys, tin-carbon composites, metal oxides, or combinations thereof.

[0078] By way of non-limiting example, the carbonaceous material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite, such as natural graphite or artificial graphite in the form of an amorphous, plate-like, flake-like, spherical, or fiber-like form, 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.

[0079] In addition, the negative electrode may further include a binder and a conductive material in addition to the above-described negative electrode active material, and may be similar or identical to the above-described binder and conductive material, and a detailed description thereof is omitted.

[0080] 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 liquid as needed.

[0081] Here, the liquid may mean 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.

[0082] In addition, the electrolyte layer may further include at least one selected from the group consisting of a sulfide-based electrolyte, an oxide-based electrolyte, and a polymer-based electrolyte. However, when the electrolyte layer is provided in a multi-layer configuration, the solid electrolyte layer including the aforementioned superionic conductor may be positioned in contact with the aforementioned cathode.

[0083] Hereinafter, the present invention will be described in more detail through examples of the present invention. However, the following examples are provided only to help understanding of the present invention, and the contents of the present invention are not limited to the following examples.

[0084] [Example]

[0085] (Example 1)

[0086] Li[CB, a raw material 11 H 12 ]1 / 2H2O was heat-treated under high vacuum at a temperature of 100 to 200°C in an Ar atmosphere, and then subjected to primary ball milling at 200 to 800 rpm for 10 to 50 hours to produce Li[CB of nanometer size (1 to 500 nm) 11 H 12 ] The hydrocarbon cargo was recovered.

[0087] Afterwards, the recovered starting material and Al2O3 as metal oxide were added to Li[CB 11 H 12 ] : Al2O3 = 9:1 molar ratio was measured and secondary ball milling was performed at 100 to 500 rpm for 0.5 to 10 hours to manufacture a superionic conductor of an acid-hydride system, which is a complex of a starting material and a metal oxide.

[0088] (Example 2)

[0089] The same procedure as in Example 1 was performed, but Li[CB 11 H 12 ] : A superionic conductor was manufactured in the same manner as described above, except that a mixture was used so that the molar ratio was Al2O3 = 6:4.

[0090] (Example 3)

[0091] The same procedure as in Example 1 was performed, but Li[CB 11 H 12 ] : A superionic conductor was manufactured in the same manner as described above, except that a mixture was used so that the molar ratio was Al2O3 = 4:6.

[0092] (Example 4)

[0093] The same procedure as in Example 1 was performed, but Li[CB 11 H 12 ] : A superionic conductor was manufactured in the same manner as described above, except that a mixture was used so that the molar ratio was Al2O3 = 2:8.

[0094] (Example 5)

[0095] The same procedure as in Example 1 was performed, but Li[CB 11 H 12 ] : A superionic conductor was manufactured in the same manner as described above, except that a mixture was used so that the molar ratio of Al2O3 = 1:9.

[0096] (Example 6)

[0097] The same procedure as in Example 1 was followed, but SiO2 was added as the recovered starting material and metal oxide, Li[CB 11 H 12 ] : A superionic conductor was manufactured in the same manner as described above, except that a mixture was used so that the molar ratio of SiO2 = 2:8.

[0098] (Example 7)

[0099] The same procedure as in Example 1 was followed, but MgO was added as the recovered starting material and metal oxide, Li[CB 11 H12 ] : A superionic conductor was manufactured in the same manner as described above, except that a mixture was used so that the molar ratio of MgO = 1:9.

[0100] (Example 8)

[0101] The same procedure as in Example 1 was followed, but ZrO2 was added as the recovered starting material and metal oxide, Li[CB 11 H 12 ] : A superionic conductor was manufactured in the same manner as described above, except that a mixture was used so that the molar ratio of ZrO2 = 3:7.

[0102] (Example 9)

[0103] The same procedure as Example 2 was carried out, but Li[CB9H 10 ]·1 / 2H2O was used to manufacture a superionic conductor.

[0104] (Example 10)

[0105] The same procedure as Example 2 was carried out, but Li2B was used as the raw material. 12 H 12 An ionic conductor was manufactured by performing the same procedure except that .

[0106] (Examples 11 to 20)

[0107] Each of the manufactured superionic conductors of Examples 1 to 10 was heat-treated at 100 to 200°C for 1 hour in an Ar atmosphere. At this time, the heat-treated examples 1 to 10 are sequentially the superionic conductors of Examples 11 to 20.

[0108] (Comparative Example 1)

[0109] Li[CB before the first ball milling in Example 1 without mixing with metal oxide 11 H 12 ] The cargo was recovered.

[0110] (Comparative Example 2)

[0111] Li[CB] obtained by performing the first ball milling of Example 1 without mixing with metal oxide 11 H 12 ] The cargo was recovered.

[0112] (Comparative Examples 3 and 4)

[0113] Each of the manufactured Comparative Examples 1 and 2 was heat-treated in the same manner as in Example 11, and the heat-treated Comparative Examples 1 and 2 are the starting materials of Comparative Examples 3 and 4, respectively.

[0114] (Experimental Example 1) Comparative Analysis of Ionic Conductivity Characteristics of Superionic Conductors

[0115] 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 and forming it into a pellet shape with a diameter of 10 mm and a thickness of 100 to 500 μm.

[0116] First, the change in ionic conductivity characteristics according to the type of metal oxide was compared and analyzed (Figs. 1a to 1e and Table 1).

[0117] FIG. 1a, FIG. 1b, FIG. 1c, FIG. 1d and FIG. 1e are drawings showing Arrhenius plots comparing 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 with Comparative Examples 1 and 3, respectively, and the ionic conductivity characteristics at 25°C are summarized in Table 1 below.

[0118]

[0119] Ionic conductivity at 25℃before heat treatment (S / cm)Ionic conductivity at 25℃after heat treatment (S / cm)Example 44.49 x 10 -5Example 143.86 x 10 -4 Example 62.24 x 10 -5 Example 161.26 x 10 -4 Example 75.64 x 10 -5 Example 173.11 x 10 -4 Example 82.05 x 10 -4 Example 181.32 x 10 -3 Comparative example 15.38 x 10 -7 Comparative example 31.52 x 10 -6 Comparative example 21.01 x 10 -4 Comparative example 41.44 x 10 -6

[0120] Referring to FIGS. 1A to 1E, as is known, one of the starting materials is Li[CB 11 H 12 ] The ionic conductors, that is, Comparative Examples 1 and 3, exhibit ionic conductivity characteristics suitable as electrolytes for electrochemical cells at high temperatures of about 120°C or higher, but it can be seen that the ionic conductivity characteristics rapidly decrease 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 hydride and a metal oxide, relatively gradually decrease in ionic conductivity characteristics as the temperature decreases.

[0121] Additionally, when examining the appearance before and after heat treatment at 25℃, it was observed that the ionic conductivity characteristics were 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 ionic conductivity increased by about 183% compared to Comparative Example 1 before heat treatment, but in the cases of Examples 14, 16, 17 and 18, it was found that the ionic conductivity was significantly improved by about 760%, 463%, 451% and 544% compared to before heat treatment, respectively.

[0122] On the other hand, in the case of Comparative Example 2, excellent ionic conductivity characteristics were observed compared to Comparative Example 1, but it was confirmed that the ionic conductivity characteristics of Comparative Example 4, in which Comparative Example 2 was heat-treated, decreased by about 99% compared to before heat treatment.

[0123] From this, it can be seen that the superionic conductor, which is a composite of a hydride and a metal oxide, exhibits significantly superior ionic conductivity characteristics at room temperature compared to conventional hydrides, and it can be seen that these ionic conductivity characteristics can be further improved through a heat treatment process.

[0124] In addition, in the case of Comparative Example 2, which does not include a metal oxide, it was confirmed that although the ionic conductivity characteristics could be temporarily improved at room temperature simply through a ball milling process, 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 initiator and the metal oxide of the present invention, stably maintains the improved ionic conductivity characteristics.

[0125] 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 in the same manner as in Experimental Example 1 and compared and analyzed (Table 2 and Fig. 2).

[0126] Ionic conductivity at 25℃before heat treatment (S / cm)Ionic conductivity at 25℃after heat treatment (S / cm)Example 17.04 x 10 -5 Example 115.74 x 10 -5 Example 21.35 x 10 -4 Example 121.73 x 10 -3 Example 35.65 x 10 -5 Example 137.04 x 10 -4 Example 44.49 x 10 -5 Example 143.86 x 10 -4Example 53.24 x 10 -5 Example 153.04 x 10 -5

[0127] Referring to FIG. 2 and Table 2, it was confirmed that the superionic conductors of Comparative Examples 1 and 3 all exhibited significantly superior ionic conductivity characteristics compared to the superionic conductors of Comparative Examples 1 and 3 at all molar ratios of the hydride and the metal oxide, similar to the ionic conductivity characteristics according to the type of metal oxide described above. However, it was confirmed that the ionic conductivity improvement effect after heat treatment was reduced compared to before heat treatment when the molar ratio of the metal oxide to the superionic conductor was 0.1 mol or less or 15 mol or more based on 1 mol of the hydride. Through this, it was reconfirmed that the metal oxide included in the superionic conductor can improve the ionic conductivity characteristics at room temperature, as described above. In other words, it was confirmed that the ionic conductivity characteristics can be significantly improved after heat treatment compared to the comparative example as long as the content of the metal oxide included in the superionic conductor was not too small or too large.

[0128] Although not shown in the drawing, it was confirmed that in the case of Examples 9, 10, 19, and 20 using different starting materials as raw materials, the ionic conductivity characteristics were improved compared to the conventional starting materials, similar to Examples 2 and 12.

[0129] Experimental Example 2: Analysis of the crystal structure of a superionic conductor

[0130] The crystal structure of each manufactured superionic conductor was confirmed through X-ray diffraction (XRD, 45 kV, 200 mA, 1° min -1, Cu-Kα radiation, λ = 0.15406 nm) analysis.

[0131] Figures 3a, 3b and 3c show the superionic conductors of Examples 4, 2 and 1, respectively, and Comparative Example 1 (LiCB 11 H 12 ) is a drawing comparing the XRD measurement results.

[0132] Looking at the enlarged peak on the right in FIGS. 3a to 3c, Comparative Example 1 is LiCB at a diffraction angle of 2θ = 15.9°. 11 H 12 It can be seen that a peak corresponding to the (111) surface appears.

[0133] On the other hand, in the case of Example 4, Example 2 and Example 1, all LiCB 11 H 12 It can be seen that the peak corresponding to the (111) plane is located at a 2θ value that is 0.05˚ or smaller than the diffraction angle 2θ at which it appears. From this, 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 initiating agent and the metal oxide Al2O3.

[0134] That is, the superionic conductor of the present invention is not a simple mixture of a hydride and a metal oxide, but a composite of a hydride and a metal oxide.

[0135] Looking more specifically, in the case of Example 4, Example 2 and Example 1, LiCB 11 H 12 It was observed that the peak corresponding to the (111) plane (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 (15.9˚), respectively, and although not shown in the drawing, it was confirmed that Examples 3 and 5 were also located at a diffraction angle 2θ value that was 0.09˚ smaller.

[0136] Also, LiCB located at a diffraction angle of about 18.2˚ 11 H 12 The peak of was also observed to be located at a smaller diffraction angle as the aforementioned peak shifted.

[0137] Additionally, it was confirmed that an additional peak originated from the metal oxide included in the superionic conductor appeared. At this time, when comparing the intensity ratio (I1 / I2) between the maximum intensity (I1) of the first peak and the maximum intensity (I2) of the peak (hereinafter referred to as the second peak) at a diffraction angle 2θ value of 45° originated from the metal oxide based on the lowest intensity among the XRD patterns within the range of diffraction angle 2θ of 10˚ to 80˚, it was confirmed that Example 4 was about 4.5, Example 2 was about 19.8, and Example 1 was about 49.9.

[0138] (Example 21) Manufacturing of an all-solid-state battery

[0139] The superionic conductor of Example 2 was pressurized to produce an electrolyte layer of an electrochemical cell, and the superionic conductor powder, a cathode active material (Sulfur), and a conductive agent (Super P, Carbon nanotube) were mixed and pressurized to produce a cathode layer, and an all-solid-state battery using lithium metal as a cathode layer was produced, and it was confirmed that the electrochemical cell operated through a charge-discharge experiment at room temperature.

[0140] The above description of the present invention is for illustrative purposes only, and those skilled in the art will readily appreciate that the present invention can be readily modified into other specific forms without altering the technical spirit or essential characteristics 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 entity may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0141] The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

[0142] When the superionic conductor of the present invention is grafted onto an all-solid-state battery and used as a solid electrolyte for a secondary battery, an all-solid-state battery with significantly improved high energy density, high output, and stability can be provided.

Claims

1. A complex hydride comprising a cation containing an alkali metal or alkaline earth metal and a hydride complex anion; and Including metal oxides, An acid-hydride superionic conductor which is a composite of the above-mentioned hydride and metal oxide.

2. In paragraph 1, The above complex is a superionic conductor characterized in that it is synthesized by reaction with the metal oxide to form a defect in the crystal structure of the above-described hydride.

3. In paragraph 1, A superionic conductor, wherein the molar ratio of the initiating agent included in the above complex: metal oxide is 1:0.01 to 20.

4. In paragraph 1, The above complex is a superionic conductor comprising at least one metal oxide selected from MgO, Al2O3, SiO2, and ZrO2.

5. In paragraph 1, The above complex 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 - A superionic conductor comprising one or more hydride-based anions selected from:

6. In paragraph 2, The above superionic conductor is a superionic conductor, wherein the X-ray diffraction pattern using CuKα rays includes a first peak located in the range of 15.9 ± 0.5˚ of diffraction angle 2θ and a second peak located in the range of 45 ± 5˚.

7. In paragraph 6, A superionic conductor, wherein the first peak is derived from the initiating oxidant, but is located at a 2θ value that is at least 0.05° smaller than that of the initiating oxidant before the reaction.

8. In paragraph 6, A superionic conductor wherein the second peak is derived from the metal oxide. 9.a) A step of mixing a complex hydride containing a cation including 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 starting material and the metal oxide through a first milling process of mechanically milling the mixed mixture. A method for manufacturing an acid-hydride system superionic conductor which is a composite of a metal oxide and a starting material including .

10. In paragraph 9, A method for manufacturing a superionic conductor, further comprising a second milling process step of mechanically milling the starting material before performing the mixing step of step a).

11. In paragraph 9, A method for manufacturing a superionic conductor, further comprising a step of heat treating the complex after step b).

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

13. Bipolar; cathode; and A solid electrolyte comprising a superionic conductor according to any one of claims 1 to 8 positioned between the positive electrode and the negative electrode. An electrochemical cell comprising:

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