Solid electrolyte, Preparation method thereof, and electrochemical device including the solid electrolyte

Abstract

A solid electrolyte comprising a crystalline complex, wherein the complex is a compound represented by the following chemical formula 1, a compound represented by the following chemical formula 2, or a combination thereof, a method for manufacturing the solid electrolyte, and an electrochemical device comprising the same are provided. 3LiF-M12O3 In Chemical Formula 1, M1 is an element or combination thereof with an oxidation number of +3, provided that aluminum (Al) and yttrium (Y) are excluded, 3LiF-M2(OH)3 In Chemical Formula 2, M2 is an element or combination thereof with an oxidation number of +3, provided that aluminum (Al) and yttrium (Y) are excluded.

Description

Technology Field

[0001] The invention relates to a solid electrolyte, a method for manufacturing the same, a solid electrolyte containing the same, and an electrochemical device. Background Technology

[0002] Solid-state secondary batteries consist of a positive electrode, a solid electrolyte, and a negative electrode, and among these, the solid electrolyte requires high ionic conductivity.

[0003] Sulfide-based or oxide-based solid electrolytes are used as solid electrolytes. To utilize these solid electrolytes in solid-state secondary batteries, it is necessary to minimize grain boundaries between crystal particles within the solid electrolyte.

[0004] When using sulfide-based solid electrolytes, cell fabrication is possible through pressurization; however, toxic sulfur gases may be generated upon exposure to air. Therefore, to manufacture solid secondary batteries with excellent safety, it is necessary to develop oxide-based solid secondary batteries that are stable in air. However, when using oxide-based solid electrolytes, improvements are required due to the non-uniform interfacial adhesion between the anode and the solid electrolyte caused by the rigid physical properties of the electrolytes. The problem to be solved

[0005] One aspect is to provide a novel solid electrolyte and a method for manufacturing the same.

[0006] Another aspect is to provide an electrochemical device comprising the above-mentioned solid electrolyte.

[0007] Another aspect is to provide an electrochemical cell containing the above-mentioned solid electrolyte. means of solving the problem

[0008] According to one aspect, a solid electrolyte is provided comprising a complex in a crystalline state, wherein the complex is a compound represented by the following chemical formula 1, a compound represented by the following chemical formula 2, or a combination thereof.

[0009] <Chemical Formula 1>

[0010] 3LiF-M12O3

[0011] In Chemical Formula 1, M1 is an element or combination thereof with an oxidation number of +3, provided that aluminum (Al) and yttrium (Y) are excluded,

[0012] <Chemical Formula 2>

[0013] 3LiF-M2(OH)3

[0014] In Chemical Formula 2, M2 is an element or combination thereof with an oxidation number of +3, provided that aluminum (Al) and yttrium (Y) are excluded.

[0015] An electrochemical device comprising the solid electrolyte described above is provided according to other aspects.

[0016] The above electrochemical device is one selected from electrochemical cells, capacitors, supercapacitors, fuel cells, sensors, and color-changing devices.

[0017] According to another aspect, an electrochemical cell containing a solid electrolyte is provided.

[0018] The above electrochemical cell is a secondary battery comprising a positive electrode, a negative electrode, and a solid electrolyte interposed between them, wherein one or more selected from the positive electrode, the negative electrode, and the solid electrolyte comprises the solid electrolyte of claim 1.

[0019] According to another aspect, a method for manufacturing a solid electrolyte is provided, comprising the steps of: providing a mixture of LiOH and MF3 in a 3:1 molar ratio; and performing mechanical and / or chemical mixing of the mixture. Effects of the invention

[0020] The solid electrolyte according to the first embodiment exhibits improved ionic conductivity at room temperature.

[0021] It can be used as an excellent lithium-ion conductor. Additionally, the solid electrolyte has improved lithium stability and a high oxidation potential, making it suitable for use as an anode electrolyte. Brief explanation of the drawing

[0022] Figure 1a shows the X-ray diffraction (XRD) spectra for the complex of Example 1 and the complexes of Comparative Examples 1 to 3. Figure 1b shows the X-ray diffraction (XRD) spectra for the complex of Examples 1-2 and the complex of Comparative Example 4. Figure 2a is a graph showing the conductivity of the composite-containing solid electrolyte of Example 1 and the composite-containing solid electrolyte of Comparative Examples 1-2. FIG. 2b is a graph showing the conductivity of the composite-containing solid electrolyte of Examples 1-2 and the composite-containing solid electrolyte of Comparative Example 4. FIG. 3a is a cross-sectional view showing the schematic configuration of a solid secondary battery according to one embodiment. FIG. 3b is a cross-sectional view showing the schematic configuration of a solid secondary battery according to another embodiment. FIG. 4 is a cross-sectional view showing the schematic configuration of a solid secondary battery according to one embodiment. FIG. 5 is a cross-sectional view showing the schematic configuration of a solid secondary battery according to another embodiment. FIG. 6 is a cross-sectional view showing the schematic configuration of a solid secondary battery according to another embodiment. Specific details for implementing the invention

[0023] A solid electrolyte according to one embodiment, a method for manufacturing the same, an electrochemical device including the solid electrolyte, and an electrochemical cell will be described in more detail below.

[0024] A solid electrolyte is provided comprising a complex in a crystalline state, wherein the complex is a compound represented by the following chemical formula 1, a compound represented by the following chemical formula 2, or a combination thereof.

[0025] <Chemical Formula 1>

[0026] 3LiF-M12O3

[0027] In Chemical Formula 1, M1 is an element or combination thereof with an oxidation number of +3, provided that aluminum (Al) and yttrium (Y) are excluded,

[0028] <Chemical Formula 2>

[0029] 3LiF-M2(OH)3

[0030] In Chemical Formula 2, M2 is an element or combination thereof with an oxidation number of +3, provided that aluminum (Al) and yttrium (Y) are excluded.

[0031] In chemical formulas 1 and 2, M1 and M2 are Ga, Sc, In, lanthanide elements, or combinations thereof. Examples of lanthanide elements include the 15 rare earth elements from lanthanum (atomic number 57) to lutetium (atomic number 71). Examples of lanthanide elements include Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, or combinations thereof.

[0032] In order to manufacture solid-state secondary batteries with excellent safety, research on all-solid-state secondary batteries employing air-stable oxide-based solid electrolytes is active.

[0033] However, due to the rigid physical properties of oxide-based solid electrolytes, the interface between the anode and the solid electrolyte may come into non-uniform contact. To address this non-uniform contact between the anode and the oxide-based solid electrolyte, a high-temperature sintering process has been proposed. Nevertheless, this high-temperature sintering process fails to achieve satisfactory overall battery characteristics while satisfying the requirements for complete solidification, thus requiring improvement.

[0034] Solid electrolytes include crystalline solid electrolytes such as garnet, azirodite, and perovskite, as well as solid electrolytes or composite solid electrolytes having a single-phase crystal structure that transports lithium within an open framework. As for general composite solid electrolytes, research is being conducted on matrix-dispersed-phase crystal solid electrolytes that form complexes with metal compounds to improve the ionic conductivity of lithium compounds such as lithium fluoride, lithium chloride, and lithium iodide, which are difficult to utilize as electrolytes due to their low ionic conductivity.

[0035] Lithium fluoride, lithium chloride, lithium iodide, etc. are used as the matrix, and alumina, silica, etc. can be used as the dispersed phase. However, since the ionic conductivity of these solid electrolytes does not reach a satisfactory level at room temperature, there is room for improvement.

[0036] Accordingly, the inventors provide a solid electrolyte with improved ion conductivity through the composite formation of a crystalline material with almost no lithium conductivity.

[0037] A composite of solid electrolytes according to one embodiment may contain, for example, a compound represented by Chemical Formula 1, a compound represented by Chemical Formula 2, or a combination thereof.

[0038] <Chemical Formula 1>

[0039] 3LiF-M12O3

[0040] In Chemical Formula 1, M1 is an element or combination thereof with an oxidation number of +3, provided that aluminum (Al) and yttrium (Y) are excluded,

[0041] <Chemical Formula 2>

[0042] 3LiF-M(OH)3

[0043] In Chemical Formula 2, M2 is an element or combination thereof with an oxidation number of +3, provided that aluminum (Al) and yttrium (Y) are excluded.

[0044] In Chemical Formula 1, M1 is Ga, Sc, a lanthanide element, or a combination thereof, and in Chemical Formula 2, M2 comprises i) In or ii) In and one or more selected from Ga, Sc, and a lanthanide element.

[0045] In a composite according to one embodiment, a new phase can be formed at the interface between each material forming it, or lithium ion conductivity can be improved through a space charge layer.

[0046] In one embodiment, the complex is a product obtained through the mechanochemical mixing of lithium hydroxide (LiOH) and a metal fluoride, wherein the molar ratio of LiOH to MF3 is 3:1. The reaction product varies depending on the molar ratio of LiOH to the metal fluoride. Here, the metal fluoride reacts with lithium hydroxide to form a crystalline complex and can be selected to obtain a compound represented by Chemical Formula 1, a compound represented by Chemical Formula 2, or a combination thereof.

[0047] <Chemical Formula 1>

[0048] 3LiF-M12O3

[0049] In Chemical Formula 1, M1 is an element or combination thereof with an oxidation number of +3, provided that aluminum (Al) and yttrium (Y) are excluded,

[0050] <Chemical Formula 2>

[0051] 3LiF-M2(OH)3

[0052] In Chemical Formula 2, M2 is an element or combination thereof with an oxidation number of +3, provided that aluminum (Al) and yttrium (Y) are excluded.

[0053] The metal fluoride is, for example, M1F3, M2F3, or a combination thereof. Here, M1 and M2 are as defined in chemical formulas 1 and 2.

[0054] When preparing the compound of Formula 1, a fluoride containing Ga, Sc, a lanthanide element, or a combination thereof may be used as the fluoride metal. And when preparing the compound of Formula 2, a fluoride containing i) indium (In) and ii) one or more selected from Ga, Sc, and a lanthanide element, or a combination thereof may be used as the fluoride metal.

[0055] Fluoride metals may include, but are not limited to, examples such as GaF3, InF3, ScF3, LaF3, CeF3, PrF3, EuF3, NdF3, TbF3, GdF3, SmF3, HoF3, TmF3, or combinations thereof.

[0056] In this specification, "mechanochemical mixing" refers to mechanical, chemical milling and / or grinding processes. Examples of mechanical and / or chemical mixing include mechanical milling, etc.

[0057] The complex according to one embodiment is not bound by a specific theory, but can be obtained according to the following reaction scheme 1 or the following reaction scheme 2.

[0058] [Reaction Equation 1]

[0059] 3LiF + M12O3→ 3LiF + 1 / 2M12O3 + 3 / 2H2O

[0060] In reaction scheme 1, M1 is as defined in chemical formula 1, for example, Ga.

[0061] <Reaction Equation 2>

[0062] 3LiF + M2F3 → 3LiF + M2(OH)3

[0063] In reaction equation 2, M2 is as defined in chemical formula 2, and is, for example, In.

[0064] The above reaction equation 1 proceeds by a dehydration reaction, and reaction equation 2 can proceed by a substitution reaction.

[0065] The complex is, for example, 3LiF-Ga2O3, 3LiF-In(OH)3, 3LiF-Sc2O3, 3LiF-La2O3, 3LiF-Ce2O3, 3LiF-Pr2O3, 3LiOH-EuF3, 3LiF-Eu2O3, 3LiF-Nd2O3, 3LiF-Tb2O3, 3LiF-Gd2O3, 3LiF-Sm2O3, 3LiF-Ho2O3, 3LiF-Tm2O3, or a combination thereof.

[0066] The ionic conductivity of the solid electrolyte at room temperature (25℃) is 10 -5 S / cm or more, 10 -4 S / cm or more, 2X10 -4 S / cm or more, or 3X10 -4 to 9X10 -4 It is S / cm.

[0067] The solid electrolyte according to one embodiment has high ionic conductivity, so the internal resistance of the electrochemical cell containing such a solid electrolyte is further reduced.

[0068] The above solid electrolyte has an activation energy of 200 to 445 meV at 25°C.

[0069] M1 of Chemical Formula 1 and M2 of Chemical Formula 2 are elements with an oxidation number of +3, such as Ga, Sc, lanthanide elements, or combinations thereof. In this specification, "oxidation number" may mean average oxidation number.

[0070] In Chemical Formula 2, M2 comprises i) In or ii) In and one or more selected from Ga, Sc, and lanthanide elements.

[0071] Lanthanide elements are, for example, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, or combinations thereof.

[0072] According to one embodiment, a main peak appears in the region where the diffraction angle 2θ is 35 to 38°, and minor peaks appear in the regions where the diffraction angle 2θ is 30 to 32°, 57 to 60°, and 63 to 65°. Here, the main peak has a maximum intensity, and the main peak and minor peak are associated with crystalline characteristics such as LiCl, and the minor peak has a smaller intensity compared to the main peak.

[0073] No peak appears at a diffraction angle 2θ of 23 to 27°, as obtained by XRD analysis using Cu Kα rays of the above complex.

[0074] The intensity ratio of the main peak (peak A) in the region where the diffraction angle 2θ is 35 to 38° and the volume peak (peak B) appearing in the region where the diffraction angle 2θ is 30 to 32°, obtained by XRD analysis of the above complex using Cu Kα rays, is 1:0.25 to 1:0.35 or 1:0.35 to 1:0.45. The intensity ratio of the main peak and the volume peak (peak C) appearing in the region of 57 to 60° is 1:0.25 to 1:0.35, 1:0.27 to 1:0.33, or 1:0.29 to 0.31, and the intensity ratio of the volume peak (minor peak) (peak D) appearing at 63 to 65° to the main peak (peak A) is 1:0.3 to 1:0.5, or 1:0.35 to 1:0.45.

[0075] According to another embodiment, a main peak (peak A-1) appears in the region where the diffraction angle 2θ is 22 to 23° and a region where the diffraction angle 2θ is 31 to 33° (peak B-1) is obtained by XRD analysis using Cu Kα rays for a solid electrolyte. A solid electrolyte having these characteristics is, for example, 3LiF-Ga2O3.

[0076] The intensity ratio of main peak A-1 and bulk peak B-1 is 1:0.5 to 1:0.6, 1:0.52 to 1:0.58, or 1:0.55 to 1:0.57.

[0077] According to another embodiment, a main peak (peak A-2) appears in the region where the diffraction angle 2θ is 22 to 23°, obtained by XRD analysis of a solid electrolyte using Cu Kα rays, and a volume peak appears in the region where the diffraction angle 2θ is 31 to 33° (peak B-2), the region where it is 50 to 52° (peak B-3), and the region where it is 55 to 57° (peak B-4). A solid electrolyte exhibiting these characteristics contains, for example, In(OH)3.

[0078] The intensity ratio of main peak A-2 and puffy peak B-2 is 1:0.5 to 1:0.6, 1:0.52 to 1:0.58, or 1:0.55 to 1:0.57, and the intensity ratio of main peak A-2 and puffy peak B-3 is 1:0.4 to 1:0.45, 1:0.41 to 1:0.44, or 1:0.42 to 1:0.43. And the intensity ratio of main peak A-2 and puffy peak B-4 is 1:0.15 to 1:0.18, or 1:0.16 to 1:0.17.

[0079] The solid electrolyte according to one embodiment can be formed into a thin film with a thickness of 100 μm or less. The thickness of the solid electrolyte is, for example, 1 to 100 μm, or for example, 1 to 50 μm. In addition, the composition of the solid electrolyte can be verified through an Inductively Coupled Plasma Spectrometer (ICP).

[0080] The solid electrolyte according to one embodiment is electrochemically stable with respect to lithium metal at 2.0 to 4.6 V, for example, 2.4 to 4.1 V. In addition, the complex of Formula 1 may exist in a particulate state. The average particle size of the particles is 5 nm to 500 µm, for example, 100 nm to 100 µm, for example, 1 µm to 50 µm, and the specific surface area is 0.01 to 1000 m² 2 / g, e.g. 0.5 to 100m 2 / g is.

[0081] The method for manufacturing a solid electrolyte according to one embodiment is described as follows.

[0082] First, a mixture of lithium hydroxide (LiOH) and a metal fluoride in a 3:1 molar ratio is provided. A solid electrolyte can be obtained by performing mechanochemical mixing of the above mixture.

[0083] Fluoride metals may include, but are not limited to, examples such as GaF3, InF3, ScF3, LaF3, CeF3, PrF3, EuF3, NdF3, TbF3, GdF3, SmF3, HoF3, TmF3, or combinations thereof.

[0084] Mechanochemical mixing refers to the process by which dehydration or substitution reactions proceed through the contact of LiOH with metal fluoride. An example of mechanochemical mixing is mechanical milling.

[0085] Mechanical milling utilizes the principle that surface energy is generated by mechanical energy, and that coating is achieved by bonding and / or fusing interfaces with high surface energy. Mechanical milling can be performed by mechanically frictionalizing the components of a mixture, and, for example, compressive stress can be applied by rotating at a rotational speed of 100 rpm to 3,000 rpm, 300 rpm to 1,000 rpm, or 500 to 800 rpm. Mechanical milling may be performed by any one of the following methods, but is not limited to: a ball mill, an airjet mill, a bead mill, a roll mill, a planetary mill, a hand mill, a high energy ball mill, a planetary ball mill, a stirred ball mill, a vibrating mill, a mechanofusion milling, a shaker milling, an atritor milling, a disk milling, a shape milling, a nata milling, a nobilta milling, a high speed mix, or a combination thereof.

[0086] Mechanical milling can be performed using, for example, ball mills, air jet mills, bead mills, roll mills, planetary mills, hand mills, etc.

[0087] Mechanical milling can be performed, for example, under an inert gas atmosphere. An inert gas atmosphere can be created using nitrogen, argon, helium, etc.

[0088] According to one embodiment, the temperature of the reaction mixture can be controlled to be suitable for a dehydration reaction through mechanical milling.

[0089] After the above mechanical milling, a resting step may be further included if necessary. By undergoing such a resting step, the temperature of the product that has undergone mechanical milling can be cooled. By undergoing the resting step, the temperature of the product that has undergone mechanical milling can be controlled, for example, to 120°C or lower, for example, to 20°C to 60°C.

[0090] Unlike the manufacturing process of general solid electrolytes, the solid electrolyte according to one embodiment does not require a separate heat treatment process. After mechanically milling the mixture to obtain the solid electrolyte, a separate heat treatment process is not performed. If a heat treatment process is further performed, it becomes difficult to obtain the solid electrolyte according to one embodiment.

[0091] As described above, by performing mechanical milling of the mixture, the particle size of the product obtained through mechanical milling can be controlled. The particle size of the product obtained through mechanical milling can be controlled to 1 μm or less, 0.01 μm to 0.9 μm, 0.01 μm to 0.7 μm, for example, 0.01 to 0.5 μm. By controlling the particle size in this way, a solid electrolyte with improved density can be obtained as a final product. In this specification, “particle size” refers to the particle diameter when the particle is spherical, and may refer to the major axis length when the particle is not spherical.

[0092] The mechanical milling mentioned above is, for example, high energy milling. For such high energy milling, equipment such as the Pulverisette 7 Premium line can be utilized. By undergoing high energy milling in this way, the size of the components of the mixture can be refined, allowing these reactions to proceed smoothly and enabling the solid electrolyte to be manufactured in a short period of time.

[0093] After the above resting step, the mechanical milling step and the resting step can be repeated. One cycle consisting of the mechanical milling step and the resting step can be repeated, for example, for a total of 50 to 100 cycles.

[0094] The mechanical milling time and resting time described above are variable, but, for example, the resting time can be controlled to be smaller than the mechanical milling time. The mechanical milling time is, for example, 5 minutes to 20 hours, for example, 5 hours to 15 hours, and the resting time is 1 minute to 15 minutes, 2 minutes to 10 minutes, or 5 minutes.

[0095] According to another aspect, an electrochemical device comprising a solid electrolyte according to one embodiment is provided.

[0096] The above electrochemical device is one selected from, for example, an electrochemical cell, a capacitor, a supercapacitor, a fuel cell, a sensor, and a color-changing device. The sensor may be, for example, a moisture sensor.

[0097] According to another aspect, an electrochemical cell comprising a solid electrolyte according to one embodiment is provided.

[0098] The electrochemical device may be a secondary battery containing a positive electrode, a negative electrode, and a solid electrolyte according to one embodiment interposed between them.

[0099] The above secondary battery may be a secondary battery comprising a positive electrode; a negative electrode containing lithium; and a solid electrolyte disposed between the positive electrode and the negative electrode and containing a solid electrolyte according to one embodiment. The secondary battery may be, for example, a lithium secondary battery, a lithium-air battery, a solid secondary battery, etc., and among these, a solid secondary battery.

[0100] The electrochemical battery can be used in both primary and secondary batteries, and the shape of the electrochemical battery is not particularly limited, such as coin type, button type, sheet type, stacked type, cylindrical type, flat type, horn type, etc. The electrochemical battery according to one embodiment can also be applied to medium and large batteries for electric vehicles.

[0101] The electrochemical cell may be, for example, a solid-state secondary battery utilizing a precipitation-type anode. A precipitation-type anode refers to an anode that has a non-anode coating layer without anode active material during the assembly of the electrochemical cell, but in which an anode material such as lithium metal is precipitated after the electrochemical cell is charged.

[0102] The above solid electrolyte may be an anode electrolyte, an electrolyte protective film, an anode protective film, a cathode protective film, or a combination thereof.

[0103] The solid electrolyte according to one embodiment has an oxidation stability potential of 3.5 V vs. Li / Li+ or higher, for example, 4.6 to 5.0 V vs. Li / Li+ It is high enough to be used as a catholyte, for example, as a catholyte for all-solid-state secondary batteries.

[0104] The solid electrolyte according to one embodiment can replace the ionic liquid-containing electrolyte in a solid secondary battery employing a conventional oxide-based solid electrolyte or a sulfide-based solid electrolyte.

[0105] In addition, the solid electrolyte of one embodiment can be manufactured without a sintering process by using the composite according to one embodiment.

[0106] A solid secondary battery according to one embodiment may further include an oxide-based solid electrolyte, a sulfide-based solid electrolyte, or a combination thereof that is stable in air.

[0107] The above solid secondary battery may have a structure comprising a positive electrode / solid electrolyte according to one embodiment / oxide-based solid electrolyte / lithium anode or a structure comprising a positive electrode / solid electrolyte according to one embodiment / sulfide-based solid electrolyte / lithium anode.

[0108] A solid secondary battery according to one embodiment may further include an ionic liquid-containing electrolyte and an oxide-based solid electrolyte, and may have a structure comprising a positive electrode / ionic liquid-containing electrolyte / oxide-based solid electrolyte / solid electrolyte according to one embodiment / oxide-based solid electrolyte / lithium negative electrode.

[0109] According to another embodiment, the solid secondary battery may further include an ionic liquid-containing electrolyte and a sulfide-based solid electrolyte, and may have a structure comprising a positive electrode / ionic liquid-containing electrolyte / sulfide-based solid electrolyte / solid electrolyte according to one embodiment / sulfide-based solid electrolyte / lithium negative electrode.

[0110] The lithium anode can be a lithium metal electrode or a lithium alloy electrode. By employing a lithium anode in this way, a high energy density per unit volume of the solid-state secondary battery can be achieved.

[0111] Garnet-based ceramics Li are used as oxide-based solid electrolytes. 3+x La3M2O 12 (M = Te, Nb, or Zr)(x is an integer from 1 to 10) Lithium phosphorus oxynitride (LixPOyNz)(0 <x<1, 0<y<1, 0<z<1)(LiPON: Lithium Phosphorus Oxynitride), Li X P Y O Z N K (2.7≤x≤3.3, 0.8≤y≤1.2, 3.5≤z≤3.9, 0.1≤k≤0.5), Li w PO x N y S z (0 <w<1, 0<x<1, 0<y<1, 0<z<1). Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, O≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr1-y Ti y O3(PLZT)(O≤x<1, O≤y<1),Pb(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, SiC, Lithium Phosphate (Li3PO4), Lithium Titanium Phosphate (Li x Ti y (PO4)3,0 <x<2,0<y<3), 리튬알루미늄티타늄포스페이트 (Li x Al y Ti z (PO4)3, 0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (O≤x≤1, O≤y≤1), lithium lanthanum titanate (Li x La y TiO3, 0 <x<2, 0<y<3), 리튬게르마늄티오포스페이트(LixGeyPzSw, 0<x<4, 0<y<1, 0<z<1, 0<w<5), 리튬나이트라이드계열 글래스(Li x N y , 0 <x<4, 0<y<2), SiS2(Li x Si y S z , 0 <x<3,0<y<2, 0<z<4), P2S5계열 글래스(Li x P y S z , 0 <x<3, 0<y<3, 0<z<7), Li2O, LiF, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2계 세라믹스, 가넷(Garnet)계 세라믹스 Li 3+x La3M2O 12 (M = Te, Nb, or Zr)(x is an integer from 1 to 10) or a combination thereof is used.

[0112] As for oxide-based solid electrolytes, for example, garnet-based oxide-based solid electrolytes with excellent reduction stability when in contact with a lithium anode can be used. Garnet-based ceramics Li 3+x La3M2O 12 (M = Te, Nb, or Zr), for example LLZO(Li 6.5 La3Zr 1.5 Ta 0.5 O 12 ) can be used.

[0113] Sulfide-based solid electrolytes may include, for example, an argyrodite-type solid electrolyte represented by the following chemical formula 3:

[0114] <Chemical Formula 3>

[0115] Li + 12-n-x A n+ X 2- 6-x Y - x

[0116] In Chemical Formula 3, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta, X is S, Se, or Te, Y is Cl, Br, I, F, CN, OCN, SCN, or N3, and 1≤n≤5, 0≤x≤2.

[0117] Sulfide-based solid electrolytes are, for example, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I xIt may be an argyrodite-type compound containing one or more selected from 0≤x≤2. The sulfide-based solid electrolyte may be an argyrodite-type compound containing one or more selected from, for example, Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0118] Sulfide-based solid electrolytes are, for example, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n , m, n are positive numbers, Z is one of Ge, Zn, or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga, In, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x , 0≤x≤2, one or more selected from.

[0119] The solid electrolyte according to one embodiment can be used as a positive electrode protective film in a solid secondary battery that uses an oxide-based solid electrolyte or a sulfide-based solid electrolyte that is stable in air, and can effectively reduce the reaction between the solid electrolyte and the positive electrode. In addition, the solid electrolyte according to one embodiment can be used as a positive electrode coating material and can be used as a positive electrode protective film.

[0120] FIG. 3a is a cross-sectional view schematically showing the structure of a solid secondary battery according to another embodiment.

[0121] Referring to this, a first oxide-based solid electrolyte (93) and a solid electrolyte (92) according to one embodiment are sequentially arranged on the upper surface of the cathode (91), and an anode (90) is arranged adjacent to the solid electrolyte (93). In this way, the solid electrolyte (93) is arranged between the first oxide-based solid electrolyte (93) and the anode (90), so that the interface between the solid electrolyte and the anode can be uniformly contacted without an ionic liquid-containing electrolyte. Furthermore, the solid electrolyte (93) has excellent compatibility with the first oxide-based solid electrolyte (93) and can be used as an anode electrolyte to replace the existing ionic liquid-containing electrolyte. The ionic liquid-containing electrolyte may be, for example, a liquid electrolyte containing an ionic liquid.

[0122] Ionic liquids may include, for example, one or more selected from the group consisting of N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidinium bis(3-trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazoliium bis(trifluoromethylsulfonyl)imide, and 1-ethyl-3-methylimidazoliium bis(trifluoromethylsulfonyl)imide.

[0123] Figure 3b shows the structure of a solid secondary battery according to one embodiment.

[0124] An ionic liquid-containing electrolyte (94) is disposed on top of the anode (90), and a first oxide-based solid electrolyte (93), a solid electrolyte (92) according to one embodiment, and a second oxide-based solid electrolyte (93') are sequentially disposed on top of it. A cathode (91) is disposed adjacent to the first oxide-based solid electrolyte (93), and the cathode (91) may be a lithium cathode.

[0125] Due to the presence of the solid electrolyte (92) according to the first embodiment, not only is it not necessary to apply high pressure for complete solidification of the battery, but the interface between the positive electrode and the solid electrolyte can also be in very uniform contact.

[0126] Referring to FIG. 4, the configuration of a solid secondary battery (1) according to another embodiment will be described.

[0127] As shown in FIG. 4, the solid secondary battery (1) may be equipped with a positive electrode (10), a negative electrode (20), and a solid electrolyte (30) according to one embodiment.

[0128] The positive electrode (10) may include a positive electrode current collector (11) and a positive electrode active material layer (12).

[0129] For the positive current collector (11), for example, a plate or foil body made of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof can be used. The positive current collector (11) may be omitted.

[0130] The positive active material layer (12) may include a positive active material and a solid electrolyte. Additionally, the solid electrolyte included in the positive (10) may be similar to or different from the solid electrolyte included in the solid electrolyte (30).

[0131] The positive electrode active material may be any positive electrode active material capable of reversibly absorbing and releasing lithium ions. For example, the positive electrode active material may be formed using lithium cobalt oxide (hereinafter referred to as LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (hereinafter referred to as NCA), lithium nickel cobalt manganese oxide (hereinafter referred to as NCM), lithium manganese oxide, lithium iron phosphate, nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide. Each of these positive electrode active materials may be used individually, or two or more may be used in combination.

[0132] In addition, the positive active material is, for example, LiNi x Co y Al z O2(NCA) or LiNi x Co y Mn z Examples include lithium salts of ternary transition metal oxides such as O2(NCM) (where 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1).

[0133] The positive electrode active material may be covered by a coating layer. Here, any coating layer known as a coating layer for a positive electrode active material of a solid-state secondary battery can be used as the coating layer of this embodiment. Examples of coating layers include, for instance, Li2O-ZrO2.

[0134] In addition, if the positive active material is formed as a lithium salt of a ternary transition metal oxide such as NCA or NCM and includes nickel (Ni) as the positive active material, the capacity density of the solid secondary battery (1) can be increased, thereby reducing the metal leaching of the positive active material in the charged state. Accordingly, the long-term reliability and cycle characteristics of the solid secondary battery (1) according to the present embodiment can be improved in the charged state.

[0135] Here, the shape of the positive active material may be, for example, an elliptical or spherical particle shape. In addition, the particle size of the positive active material is not particularly limited and must be within a range applicable to the positive active material of a conventional solid secondary battery. In addition, the content of the positive active material of the positive (10) is not particularly limited and must be within a range applicable to the positive of a conventional solid secondary battery.

[0136] In addition, the anode (10) may appropriately incorporate additives such as, for example, a conductive agent, a binder, a filler, a dispersant, and an ion-conducting aid, in addition to the anode active material and solid electrolyte described above.

[0137] Examples of conductive agents that can be incorporated into the anode (10) include graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder, etc. Also, examples of binders that can be incorporated into the anode (10) include styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc. Additionally, known materials generally used in electrodes of solid secondary batteries can be used as coating agents, dispersants, ion conductivity aids, etc. that can be incorporated into the anode (10).

[0138] The cathode (20) may include a cathode current collector (21) and a non-cathode coating layer (22).

[0139] Although a non-cathode coating layer (22) is shown in FIG. 4, it may be a general cathode active material layer. For example, it may be a lithium cathode, such as the cathode in FIG. 3a and FIG. 3b.

[0140] The non-cathode coating layer (22) may have a structure containing a metal such as silicon and carbon, and a conductive binder disposed around the metal and carbon.

[0141] The thickness of the non-cathode coating layer (22) is 1 μm to 20 μm. The cathode current collector (21) may be composed of a material that does not react with lithium, that is, does not form either an alloy or a compound. Examples of materials constituting the cathode current collector (21) include copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). The cathode current collector (21) may be composed of one type of metal, or an alloy or coating material of two or more types of metals. The cathode current collector (21) may be formed, for example, in a plate shape or a thin film shape.

[0142] Here, as shown in FIG. 5, a thin film (24) may be formed on the surface of the negative current collector (21). The thin film (24) may contain an element capable of forming an alloy with lithium. Elements capable of forming an alloy with lithium may include, for example, gold, silver, zinc, tin, indium, silicon, aluminum, and bismuth. The thin film (24) may be composed of one of these metals or may be composed of several types of alloys. By having the thin film (24), the precipitation pattern of the metal layer (23) shown in FIG. 19 may be further flattened, and the characteristics of the solid secondary battery (1) may be further improved.

[0143] Here, the thickness of the thin film (24) is not particularly limited, but may be 1 nm to 500 nm. When the thickness of the thin film (24) is within the above range, the function of the thin film (24) is fully exerted, and the amount of lithium precipitated at the negative electrode is appropriate, so the characteristics of the solid secondary battery (1) are excellent. The thin film (24) can be formed on the negative electrode current collector (21) by, for example, vacuum deposition, sputtering, plating, etc.

[0144] The non-cathode coating layer (22) may include a negative electrode active material that forms an alloy or compound with lithium.

[0145] Examples of cathode active materials include amorphous carbon, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Here, examples of amorphous carbon include carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), and graphene.

[0146] The non-cathode coating layer (22) may include only one of these negative active materials or may include two or more negative active materials. For example, the non-cathode coating layer (22) may include only amorphous carbon as the negative active material, or it may include one or more selected from the group consisting of gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, and zinc. Additionally, the non-cathode coating layer (22) may include a mixture of amorphous carbon and one or more selected from the group consisting of gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, and zinc. The mixing weight ratio of the mixture of amorphous carbon and gold, etc., may be, for example, about 10:1 to 1:2. By composing the negative active material with such materials, the characteristics of the solid secondary battery (1) can be further improved.

[0147] The binder included in the solid electrolyte (30) may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc. The binder of the solid electrolyte (30) may be of the same type as or different from the binder of the positive active material layer (12) and the negative coating layer (22).

[0148] Additionally, the negative electrode active material may comprise a mixture of first particles formed of amorphous carbon and second particles formed of a metal or semiconductor. The metal or semiconductor may include, for example, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, zinc, etc. Here, the content of the second particles may be about 8 to 60 weight % or about 10 to 50 weight % based on the total weight of the mixture. In this case, the characteristics of the solid secondary battery (1) may be further improved.

[0149] The thickness of the non-cathode coating layer (22) is not particularly limited as long as it satisfies the requirements of Equation 1 above, but it may be approximately 1 μm to 20 μm. When the thickness of the non-cathode coating layer (22) is within the above range, the characteristics of the solid secondary battery (1) are sufficiently improved. By using the aforementioned binder, the thickness of the non-cathode coating layer (22) can be easily secured to an appropriate level.

[0150] The non-cathode coating layer (22) may have additives used in general solid-state batteries, such as fillers, dispersants, ion conductive agents, etc., appropriately mixed in it.

[0151] The solid electrolyte may be a solid electrolyte according to one embodiment, and a general solid electrolyte may be used together.

[0152] General solid electrolytes may consist of, for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, or a combination thereof.

[0153] Examples 10 and 11

[0154] In addition, among the above sulfide-based solid electrolyte materials, a solid electrolyte comprising at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements may be used, and for example, a material comprising Li2S-P2S5 may be used. Here, when a sulfide-based solid electrolyte material comprising Li2S-P2S5 is used to form the solid electrolyte, the molar ratio of Li2S and P2S5 may be selected in a range of, for example, Li2S:P2S5 = 50:50 to 90:10.

[0155] Comparative Examples 1 to 3

[0156] The binder included in the solid electrolyte (30) may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc. The binder of the solid electrolyte (30) may be of the same type as or different from the binder of the positive active material layer (12) and the negative coating layer (22).

[0157] Comparative Examples 4 and 5

[0158] Example 1

[0159] A mixture was obtained by mixing LiOH and GaF3 in a 3:1 molar ratio, and this mixture was subjected to high-energy milling for 10 minutes using ball milling at 700 rpm for a total of 18 hours with a Pulverisette 7 Premium line machine. After high-energy milling, the mixture was allowed to stand for 5 minutes to undergo a cooling process (1 cycle). This high-energy milling and standing step was repeated for a total of 72 cycles to obtain a composite in a crystalline state having the composition shown in Table 1 below.

[0160] Examples 2-9

[0161] A composite having the composition shown in Table 1 below was obtained in a crystalline state by following the same method as in Example 1, except that InF3, CeF3, LaF3, ScF3, TbF3, GdF3, NdF3, and TmF3 were used instead of GaF3, respectively.

[0162] Example 10

[0163] The composite was prepared in a crystalline state according to the same method as in Example 1, except that the 700 rpm was changed to 300 rpm and 1000 rpm, respectively.

[0164] Comparative Examples 1-3

[0165] A composite was obtained by following the same method as in Example 1, except that the molar ratio of Li and GaF3 was changed to 2:1, 4:1, and 1:1, respectively, instead of 3:1.

[0166] Comparative Example 4-5

[0167] A composite having the composition shown in Table 1 below was obtained by carrying out the same method as in Example 1, except that AlF3 and YF3 were used instead of GaF3, respectively.

[0168] division Composition of starting materials Composition of the complex Example 1 A mixture of LiOH and GaF3 in a 3:1 molar ratio 3LiF-Ga2O3 Example 2 A mixture of LiOH and InF3 in a 3:1 molar ratio 3LiF-In(OH)3 Example 3 A mixture of LiOH and CeF3 in a 3:1 molar ratio 3LiF-Ce2O3 Example 4 A mixture of LiOH and LaF3 in a 3:1 molar ratio 3LiF-La2O3 Example 5 A mixture of LiOH and ScF3 in a 3:1 molar ratio 3LiF-Sc2O3 Example 6 A mixture of LiOH and TbF3 in a 3:1 molar ratio 3LiF-Tb2O3 Example 7 A mixture of LiOH and GdF3 in a 3:1 molar ratio 3LiF-Gd2O3 Example 8 A mixture of LiOH and NdF3 in a 3:1 molar ratio 3LiF-Nd2O3 Example 9 A mixture of LiOH and TmF3 in a 3:1 molar ratio 3LiF-Tm2O3 Example 10 A mixture of LiOH and GaF3 in a 3:1 molar ratio 3LiF-Ga2O3 Example 11 A mixture of LiOH and GaF3 in a 3:1 molar ratio 3LiF-Ga2O3 Comparative Example 1 A mixture of LiOH and GaF3 in a 2:1 molar ratio xLiF-yGa2O3(1.8≤x≤2.2, 0.8≤y≤1.2) Comparative Example 2 A mixture of LiOH and GaF3 in a 4:1 molar ratio 3LiF-LiGaO2 Comparative Example 3 A mixture of LiOH and GaF3 in a 1:1 molar ratio Ga(OH, F)3·xH2O(x=0 or 0<x≤1.5) Comparative Example 4 A mixture of LiOH and AlF3 in a 3:1 molar ratio 3LiF-Al2O3 Comparative Example 5 A mixture of LiOH and YF3 in a 3:1 molar ratio 3LiF-Y(OH)3)

[0169] Preparation Example 1

[0170] A cathode active material having an aLi2O-ZrO2 coating film was prepared according to the method disclosed in Korean Patent Publication No. 10-2016-0064942, and the one prepared according to the following method was used.

[0171] The composite powder prepared in Example 1 was prepared as the solid electrolyte. Carbon nanofibers (CNF) were prepared as the conductive agent. These materials were mixed in a weight ratio of positive active material:solid electrolyte:conductive agent = 60:35:5, and the mixture was formed into a large sheet to produce a positive sheet. The prepared positive sheet was pressed onto a positive current collector made of carbon-coated aluminum foil with a thickness of 18 μm to produce a positive layer. The thickness of the positive active material layer was approximately 100 μm.

[0172] Next, the above aLi2O-ZrO2 coating solution is applied to the positive electrode active material LiNi 0.8 Co 0.15 Mn 0.05 O2(NCM) fine powder was mixed, and the mixed solution was heated to about 40°C while stirring to evaporate and dry the solvent, such as alcohol. At this time, ultrasound was applied to the mixed solution.

[0173] By carrying out the above process, it was possible to support an aLi2O-ZrO2 precursor on the particle surface of the anode active material fine powder.

[0174] In addition, a precursor of aLi2O-ZrO2 (a=1) supported on the particle surface of the positive electrode active material was heat-treated at approximately 350°C for 1 hour under an oxygen atmosphere. During this heat treatment process, the precursor of aLi2O-ZrO2 (a=1) present on the upper surface of the positive electrode active material was transformed into aLi2O-ZrO2 (a=1). The content of Li2O-ZrO2 (LZO) is approximately 0.4 parts by weight based on 100 parts by weight of NCM.

[0175] According to the manufacturing process described above, LiNi having an aLi2O-ZrO2 coating film 0.8 Co 0.15 Mn 0.05 O2(NCM) could be obtained. In aLi2O-ZrO2, a is 1.

[0176] (Manufacturing of all-solid-state secondary batteries)

[0177] Production Examples 2 to 11

[0178] (Bipolar layer)

[0179] Comparative Examples 1 to 5

[0180] The composite powder prepared in Example 1 was prepared as the solid electrolyte. Carbon nanofibers (CNF) were prepared as the conductive agent. These materials were mixed in a weight ratio of positive active material:solid electrolyte:conductive agent = 60:35:5, and the mixture was formed into a large sheet to prepare a positive sheet. The prepared positive sheet was pressed onto a positive current collector made of carbon-coated aluminum foil with a thickness of 18 μm to prepare a positive layer. The thickness of the positive active material layer was approximately 100 μm.

[0181] (Cathode layer)

[0182] A lithium metal with a thickness of about 30 μm was used as the cathode layer.

[0183] (Solid electrolyte layer)

[0184] Referring to FIG. 1a, for the composite of Example 1, main peak A was observed in the region where the diffraction angle 2θ is 35 to 38°, and peak B was observed in the region where the diffraction angle 2θ is 30 to 32°, peak C in the region where the diffraction angle 2θ is 57 to 60°, and peak D in the region where the diffraction angle 2θ is 63 to 65°. Also, as shown in FIG. 1, no peaks associated with LiGaO2, GaF3, and LiOH were observed in the compound of Example 1. The peak appearing in the region where the diffraction angle 2θ is 63 to 65° is a peak associated with a metal oxide such as Ga2O3, as shown in FIG. 1b.

[0185] As shown in FIG. 1a, the composites of Comparative Examples 1 to 3 yielded a product mixed with LiGaO2 or other by-products, exhibiting diffraction angle characteristics very different from those of the composite of Example 1.

[0186] Production Example 2-11

[0187] A solid secondary battery was manufactured by following the same method as in Example 1, except that the composites of Examples 2 to 11 were used instead of the composite of Example 1.

[0188] Comparative Production Examples 1-5

[0189] A solid secondary battery was manufactured by following the same method as in Example 1, except that the composites of Comparative Examples 1 to 5 were used instead of the composite of Example 1.

[0190] XRD spectra were measured for the composites obtained according to Examples 1-2 and Comparative Example 4, and the results are shown in Fig. 1b. Cu Kα radiation was used for the XRD spectrum measurement, and X-ray diffraction analysis was performed using a Bruker D8 Advance.

[0191] delete

[0192] XRD spectra of the composites obtained according to Example 1 and Comparative Examples 1 to 3 were measured, and the results are shown in Fig. 1a. Cu Kα radiation was used for the XRD spectrum measurement, and X-ray diffraction analysis was performed using a Bruker D8 Advance.

[0193] Referring to FIG. 1a, for the composite of Example 1, main peak A was observed in the region where the diffraction angle 2θ is 35 to 38°, and peak B was observed in the region where the diffraction angle 2θ is 30 to 32°, peak C in the region where the diffraction angle 2θ is 57 to 60°, and peak D in the region where the diffraction angle 2θ is 63 to 65°. Also, as shown in FIG. 1, no peaks associated with LiGaO2, GaF3, and LiOH were observed in the compound of Example 1. The peak appearing in the region where the diffraction angle 2θ is 63 to 65° is a peak associated with a metal oxide such as Ga2O3, as shown in FIG. 1b.

[0194] As shown in FIG. 1a, the composites of Comparative Examples 1 to 3 yielded a product mixed with LiGaO2 or other by-products, exhibiting diffraction angle characteristics very different from those of the composite of Example 1.

[0195] The intensity ratio of the main peak A and the volumetric peaks B, C, or D of the above complex was measured and is shown in Table 2 below.

[0196] 0.2 g of each sample of the composites of Examples 1 to 9 and the composites of Comparative Examples 1 to 5 were placed between SUS plates with a diameter of 16 mm and a thickness of 500 μm to form a SUS / compound / SUS structure, and then 100 to 200 kg was applied for 10 seconds using uniaxial pressure to produce a circular SUS / composite / SUS structure.

[0197] The main peak and volumetric intensity ratios of Comparative Examples 1 to 3 are compared for any peak corresponding to the diffraction angles of main peak A and volumetrics B, C, and D shown in Example 1. That is, the comparison values ​​between the peaks shown in Comparative Examples 1 to 3 are shown for the diffraction angle range of the main peak and volumetrics corresponding to Example 1.

[0198] (1) Examples 1-2 and Comparative Example 4

[0199] XRD spectra for the composites obtained according to Examples 1-2 and Comparative Example 4

[0200] Measurements were taken and the results are shown in Fig. 1b. Cu Kα radiation was used for XRD spectrum measurement, and X-ray diffraction analysis was performed using Bruker's D8 Advance.

[0201] Referring to Fig. 1b, a peak corresponding to In(OH)3 was observed in the composite of Example 2 compared to the composite of Example 1. In the composite of Example 2, a main peak A-1 (2θ: 22–23°) and a volume peak B-1 (2θ: 31–33°) (56.7%) were observed, and no diffraction peak corresponding to In2O3 appeared. From this, the composition of the composite of Example 2 could be confirmed.

[0202] The intensity ratio of main peak A-1 and bulk peak B-1 was measured and is shown in Table 3 below.

[0203] division Intensity ratio of main peak A-1 and bufiq B-1 Example 1 1:0.567 Example 2 1:0.567

[0204] The complex obtained according to Comparative Example 4 did not show the peak described above.

[0205] Evaluation Example 2: Measurement of Ion Conductivity and Activation Energy

[0206] 0.2 g of each sample of the composites of Examples 1-9 and Comparative Examples 1-5 were placed between SUS plates with a diameter of 16 mm and a thickness of 500 μm to form a SUS / composite / SUS structure, and then 100 to 200 kg was applied for 10 seconds using uniaxial pressure to produce a circular SUS / solid electrolyte / SUS structure.

[0207] For the above S structure, a potentiostatic impedance measurement method was introduced, and resistance was measured in the range of -20 to 80 ℃ while varying the open circuit voltage of 10 mV AC from 1 MHz to 0.01 Hz. The impedance evaluation was performed, and the results are shown in Fig. 2a.

[0208] The total resistance (Rtotal) value is obtained from the impedance results, and the conductivity value is calculated by correcting the electrode area and pellet thickness from this value. In addition, during EIS measurement, the activation energy (Ea) for Li ion conduction was calculated from the results obtained by varying the chamber temperature in which each oxide sample was loaded. Ea can be calculated from the slope value by converting the conductivity values ​​measured at different temperatures in the range of 298–378 K into the Arrhenius plot (Ln (σT) vs. 1 / T) of Equation 1 below.

[0209] [Equation 1]

[0210] σT = A exp(Ea / RT)

[0211] In Equation 1, Ea is the activation energy, T is the absolute temperature, A is the pre-exponential factor, R is the gas constant, and σ is the conductivity.

[0212] The activation energy obtained according to the above process is shown in Table 4 below, and the ionic conductivity of some solid electrolytes among the solid electrolytes is shown in Figures 2a and 2b. Figure 2a shows the ionic conductivity of the composite-containing solid electrolytes of Example 1, Comparative Example 1, and Comparative Example 2, and Figure 2b shows the ionic conductivity of the composite-containing solid electrolytes of Examples 1-2 and Comparative Example 4.

[0213]

[0214] It was found that the composite-containing solid electrolytes of Examples 1 and 2 exhibited excellent conductivity over various temperature ranges, as shown in Figures 2a and 2b. The composite-containing solid electrolyte of Example 1 had 2.049 x 10⁻⁶ at room temperature. -4 It exhibited excellent ionic conductivity with S / cm. In addition, the compound of Example 2 showed 8.9 x 10⁻⁶ at room temperature (25 °C), as shown in Fig. 4a. -4 It exhibited excellent ionic conductivity of S / cm and an activation energy of approximately 424.4 meV.

[0215] In addition, the ionic conductivity of the composite-containing solid electrolytes of Examples 3 to 9 showed excellent results at a level equivalent to that of Example 1. From these results, it was confirmed that the conductivity of the composite-containing solid electrolytes of Examples 1 to 9 was significantly improved compared to that of Comparative Examples 1 to 5. The conductivity of the compound of Comparative Example 3 and the composite-containing solid electrolyte of Comparative Example 5 was too low, so it fell outside the measurement range of ionic conductivity and could not be measured.

[0216] In addition, the composite-containing solid electrolytes of Examples 1 to 9 exhibited a smaller activation energy, specifically less than 425 meV / atom, compared to the composite-containing solid electrolytes of Comparative Examples 1 to 3. Thus, a decrease in activation energy results in improved ionic conductivity at low temperatures.

[0217] Evaluation Example 3: Charge and Discharge Profile

[0218] The solid secondary battery of Preparation Example 1 at 60°C and in the voltage range of 2.85 to 4.2 V at 0.2 mA / cm² 2 Charging and discharging were performed at a current rate. The battery was charged at a constant current of 0.067C for 15 hours until the battery voltage reached 4.2V, and then discharged at a constant current of 0.067C for 15 hours until the battery voltage reached 2.85V.

[0219] After performing charge and discharge, the voltage profile was examined.

[0220] Based on this, it was confirmed that the composite-containing solid electrolyte of Example 1 has excellent compatibility with the garnet solid electrolyte. Furthermore, approximately 3 mAh / cm², which is close to the design capacity of the anode of 3.2 mAh / cm². 2 It was found that the capacity was reversibly expressed. It was found that the solid secondary battery of Fabrication Example 1 has excellent compatibility with LLZO garnet and can be used as a solid electrolyte inside the secondary battery.

[0221] In addition, the charge and discharge profiles of the batteries of Comparative Examples 1 to 5 were evaluated. As a result of the evaluation, the characteristics were degraded compared to the case of Example 1.

[0222] Evaluation Example 4: Charge / Discharge Profile and Cycle Characteristics

[0223] The solid secondary battery of Production Example 1-1 and the solid secondary battery of Comparative Production Example 6 were charged and discharged at a current rate of 0.3 mA / cm2 at 60℃ and a voltage range of 2.85 to 4.2 V, which are the same conditions as the evaluation method of Evaluation Example 8, and

[0224] The cycle characteristics were performed by placing the above-mentioned all-solid-state secondary battery in a constant temperature bath at 60°C.

[0225] The battery was charged at a constant current of 0.1C for 10 hours until the battery voltage reached 4.2V, and then discharged at a constant current of 0.1C for 20 hours until the battery voltage reached 2.85V (1st cycle).

[0226] After performing one cycle of charge and discharge, the voltage profile and cycle characteristics were investigated.

[0227] As a result of the evaluation, as a solid electrolyte for the positive electrode in the solid secondary battery of Production Example 1-1

[0228] It was found that battery operation is possible by utilizing it. In addition, it was found that the solid secondary battery of Fabrication Example 1-1 exhibited improved cycle characteristics compared to the case of Comparative Fabrication Example 6.

[0229] Although one embodiment has been described above with reference to the drawings and examples, this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the scope of protection of this application should be determined by the appended claims. Explanation of the symbols

[0230] 1, 1a: Solid-state secondary battery 10: Positive electrode 11: Positive current collector 12: Positive active material layer 20: Cathode 21: Cathode current collector 22: Cathode-free coating layer 23: Metal layer 24: Thin film 30: Solid electrolyte

Claims

Claim 1 A solid electrolyte comprising a crystalline complex, wherein the complex is a compound represented by the following chemical formula 1, a compound represented by the following chemical formula 2, or a combination thereof. <Chemical Formula 1> 3LiF-M12O3 In Chemical Formula 1, M1 is an element or combination thereof with an oxidation number of +3, provided that aluminum (Al) and yttrium (Y) are excluded; <Chemical Formula 2> 3LiF-M2(OH)3 In Chemical Formula 2, M2 is an element or combination thereof with an oxidation number of +3, provided that aluminum (Al) and yttrium (Y) are excluded. Claim 2 In claim 1, the solid electrolyte in which M1 in Chemical Formula 1 is Ga, Sc, a lanthanide element, or a combination thereof. Claim 3 In claim 1, M2 in the above chemical formula 2 is a solid electrolyte comprising i) In or ii) In and one or more selected from Ga, Sc, and lanthanide elements. Claim 4 In claim 1, the composite is a product obtained through mechanochemical mixing of lithium hydroxide (LiOH) and a metal fluoride, and the molar ratio of the lithium hydroxide (LiOH) and the metal fluoride is 3:1, and the solid electrolyte. Claim 5 A solid electrolyte according to claim 1, wherein the composite is 3LiF-Ga2O3, 3LiF-In(OH)3, 3LiF-Sc2O3, 3LiF-La2O3, 3LiF-Ce2O3, 3LiF-Pr2O3, 3LiOH-EuF3, 3LiF-Eu2O3, 3LiF-Nd2O3, 3LiF-Tb2O3, 3LiF-Gd2O3, 3LiF-Sm2O3, 3LiF-Ho2O3, 3LiF-Tm2O3, or a combination thereof. Claim 6 A solid electrolyte according to claim 1, wherein a main peak appears in the region where the diffraction angle 2θ obtained by XRD analysis using Cu Kα rays of the composite is 35 to 38°, and minor peaks appear in the region where the diffraction angle 2θ is 30 to 32°, the region where it is 57 to 60°, and the region where it is 63 to 65°. Claim 7 A solid electrolyte according to claim 1, wherein no peak appears in the region where the diffraction angle 2θ obtained by XRD analysis using Cu Kα rays of the composite is 23 to 27°. Claim 8 A solid electrolyte according to claim 6, wherein the intensity ratio of a main peak (peak A) in a region where the diffraction angle 2θ is 35 to 38° and a minor peak (peak B) appearing in a region where the diffraction angle 2θ is 30 to 32°, obtained by XRD analysis using Cu Kα rays of the composite, is 1:0.25 to 1:0.35, the intensity ratio of the main peak (peak A) and the minor peak (peak C) appearing in a region where the diffraction angle 2θ is 57 to 60° is 1:0.25 to 1:0.35, and the intensity ratio of the minor peak (peak D) appearing at 63 to 65° relative to the main peak (peak A) is 1:0.3 to 1:0.

5. Claim 9 A solid electrolyte according to claim 1, wherein a main peak (peak A-1) appears in a region where the diffraction angle 2θ obtained by XRD analysis using Cu Kα rays of the composite is 22 to 23°, a minor peak (peak C-1) appears in a region where the diffraction angle 2θ is 31 to 33° (peak B-1), and the intensity ratio of the main peak A-1 and the minor peak B-1 is 1:0.5 to 1:0.

6. Claim 10 A solid electrolyte according to claim 1, wherein a main peak (peak A-2) appears in a region where the diffraction angle 2θ obtained by XRD analysis using Cu Kα rays of the composite is 22 to 23°, and a volumetric peak appears in a region where the diffraction angle 2θ is 31 to 33° (peak B-2), a region where it is 50 to 52° (peak B-3), and a region where it is 55 to 57° (peak B-4), and the intensity ratio of the main peak A-2 to the volumetric peak B-2 is 1:0.5 to 1:0.6, the intensity ratio of the main peak A-2 to the volumetric peak B-3 is 1:0.4 to 1:0.45, and the intensity ratio of the main peak A-2 to the volumetric peak B-4 is 1:0.15 to 1:0.

18. Claim 11 In claim 1, the ionic conductivity of the solid electrolyte at room temperature (25℃) is 10 -4 Solid electrolyte with a S / cm or higher. Claim 12 An electrochemical device comprising a solid electrolyte according to any one of claims 1 to 11. Claim 13 In claim 12, the electrochemical element is an electrochemical element selected from an electrochemical cell, a capacitor, a supercapacitor, a fuel cell, a sensor, and a color-changing element. Claim 14 An electrochemical cell comprising a solid electrolyte according to any one of claims 1 to 11. Claim 15 In claim 14, the electrochemical cell is a secondary battery comprising a positive electrode, a negative electrode, and a solid electrolyte interposed between them, and at least one selected from the positive electrode, the negative electrode, and the solid electrolyte comprises a solid electrolyte. Claim 16 In claim 15, an electrochemical cell in which the negative electrode comprises a lithium metal or a lithium alloy. Claim 17 In paragraph 15, an electrochemical cell in which the solid electrolyte is an electrolyte protective film, an anode protective film, a cathode protective film, an anode electrolyte, or a combination thereof. Claim 18 In Clause 14, the electrochemical cell is a solid-state secondary battery. Claim 19 In paragraph 18, the above-mentioned solid secondary battery is an electrochemical cell further comprising an oxide-based solid electrolyte, a sulfide-based solid electrolyte, or a combination thereof. Claim 20 In paragraph 19, the oxide-based solid electrolyte is Garnet-based ceramics Li 3+x La3M2O 12 (M = Te, Nb, or Zr)(x is an integer from 1 to 10) Lithium phosphorus oxynitride (LixPOyNz)(0 <x<1, 0<y<1, 0<z<1)(LiPON: Lithium Phosphorus Oxynitride), Li X P Y O Z N K (2.7≤x≤3.3, 0.8≤y≤1.2, 3.5≤z≤3.9, 0.1≤k≤0.5), Li w PO x N y S z (0 <w<1, 0<x<1, 0<y<1, 0<z<1). Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, O≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(O≤x<1, O≤y<1),Pb(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, SiC, Lithium Phosphate (Li3PO4), Lithium Titanium Phosphate (Li x Ti y (PO4)3,0 <x<2,0<y<3), 리튬알루미늄티타늄포스페이트 (Li x Al y Ti z (PO4)3, 0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (O≤x≤1, O≤y≤1), lithium lanthanum titanate (Li x La y TiO3, 0 <x<2, 0<y<3), 리튬게르마늄티오포스페이트(LixGeyPzSw, 0<x<4, 0<y<1, 0<z<1, 0<w<5), 리튬나이트라이드계열 글래스(Li x N y , 0 <x<4, 0<y<2), SiS2(Li x Si y S z , 0 <x<3,0<y<2, 0<z<4), P2S5계열 글래스(Li x P y S z , 0 <x<3, 0<y<3, 0<z<7), Li2O, LiF, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2계 세라믹스, 또는 이들의 조합물인 전기화학전지. Claim 21 In claim 19, the above sulfide-based solid electrolyte is Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n , m, n are positive numbers, Z is one of Ge, Zn, or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga, In, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x One or more electrochemical cells selected from , 0≤x≤2. Claim 22 A method for manufacturing a solid electrolyte according to any one of claims 1 to 11, comprising the steps of: providing a mixture of lithium hydroxide (LiOH) and a metal fluoride in a 3:1 molar ratio; and performing mechanochemical mixing of the mixture. Claim 23 A method for manufacturing a solid electrolyte according to claim 22, further comprising a standing step after the above-mentioned mechanochemical mixing. Claim 24 A method for manufacturing a solid electrolyte according to claim 22, wherein the temperature of the reaction mixture obtained by the above mechanochemical mixing is controlled to 20 to 60°C. Claim 25 A method for manufacturing a solid electrolyte according to claim 22, wherein the mechanochemical mixing is mechanical milling, and the mechanical milling is a ball mill, air jet mill, bead mill, roll mill, planetary mill, hand milling, high-energy ball mill, planetary mill ball mill, stirred ball mill, vibratory mill, mechanofusion milling, shaker milling, attitter milling, disc milling, safe milling, nauta milling, nobilta milling, high-speed mixing, or a combination thereof. Claim 26 A method for manufacturing a solid electrolyte according to claim 25, wherein the mechanical milling is high energy milling. Claim 27 A method for manufacturing a solid electrolyte according to claim 22, wherein the fluoride metal is a fluoride containing Ga, Sc, a lanthanide element or a combination thereof, indium fluoride (InF3), i) indium (In) and ii) a fluoride containing one or more selected from Ga, Sc, and a lanthanide element or a combination thereof. Claim 28 A method for manufacturing a solid electrolyte according to claim 22, wherein the fluoride metal is GaF3, InF3, ScF3, LaF3, CeF3, PrF3, EuF3, NdF3, TbF3, GdF3, SmF3, HoF3, TmF3, or a combination thereof.

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