Solid electrolyte and all-solid-state battery containing the same

Abstract

The present invention aims to improve the atmospheric stability of conventional sulfide-based solid electrolytes. 2- The ionic radius (r s ) (unit: Å) to the ionic radius (r) (unit: Å) of the cation (r / r s The present invention relates to a solid electrolyte having an argyrodite-type crystal structure doped with a cation in which the cation ratio (R) is 0.20 to 0.30, and an all-solid-state battery including the same.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0106849, filed on August 25, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a solid electrolyte having an argyrodite-type crystal structure with improved atmospheric stability, and an all-solid-state battery including the same. [Background technology]

[0003] All-solid-state batteries replace the liquid electrolyte currently used between the positive and negative electrodes of lithium secondary batteries with a solid electrolyte. These batteries are safe and explosion-free, and have a higher energy density than conventional batteries, drawing attention as a next-generation battery. The solid electrolyte used in all-solid-state batteries is a solid-state material that allows lithium ions to be conducted within the battery, and has high ionic conductivity comparable to that of the liquid electrolytes currently used in lithium secondary batteries. Key materials for solid electrolytes include polymers, sulfides, and oxides. Among these, sulfide-based solid electrolytes, which are highly flexible and have high ionic conductivity, are considered suitable for the production of large-capacity batteries.

[0004] However, sulfide-based solid electrolytes are highly reactive to moisture, and react not only with moisture in the atmosphere but also with moisture under low humidity conditions, generating the toxic gas hydrogen sulfide (H2S). This not only poses a risk to worker safety, but also leads to the problem of deterioration of the performance of the sulfide-based solid electrolyte itself.

[0005] Therefore, there is a need to develop sulfide-based solid electrolytes that are highly stable in the atmosphere. Summary of the Invention [Problem to be solved by the invention]

[0006] It is an object of the present invention to provide a solid electrolyte with improved atmospheric stability, particularly improved water stability.

[0007] However, the problems that the present invention aims 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 following description. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides a solid electrolyte and an all-solid-state battery.

[0009] (1) The present invention is 2- The ionic radius (r s ) (unit: Å) to the ionic radius (r) (unit: Å) of the cation (r / r s The present invention provides a solid electrolyte having an argyrodite-type crystal structure doped with a cation in which the σ is 0.20 to 0.30.

[0010] (2) The present invention provides the solid electrolyte according to (1), wherein the cation has a ratio (c / r) of ion oxidation number (c) to ion radius (r) (unit: Å) of 7.00 to 14.00.

[0011] (3) The present invention provides a solid electrolyte having a composition represented by the following chemical formula 1 in the above (1) or (2). [Chemical formula 1] Li a (P 1-b M b )S c X d In the above Chemical Formula 1, M is one or more selected from Sn, Nb, Ni, Ge, Ga, and Al; X is one or more selected from F, Cl, Br and I; 5.0 <a<7.5、0<b≦0.7、3.5≦c≦7、0.8≦d≦1.7である。

[0012] (4) The present invention provides the solid electrolyte according to any one of (1) to (3) above, wherein M is at least one element selected from Sn, Nb, Ge, and Al.

[0013] (5) The present invention provides a solid electrolyte according to any one of (1) to (4), wherein the ratio of the number of moles of M to the sum of the number of moles of P (x) and the number of moles of M (y) (y / (x+y)) is 0.01 to 0.7.

[0014] (6) The present invention provides a solid electrolyte according to any one of the above items (1) to (5), wherein the ion conductivity retention rate determined by the following formula 1 is 55% or more:

number

[0015] (7) The present invention provides the solid electrolyte according to (6) above, wherein the initial ionic conductivity is 2.0 mS / cm to 20.0 mS / cm.

[0016] (8) The present invention provides the solid electrolyte according to (6) or (7), wherein the ionic conductivity after the exposure to water is 1.4 mS / cm to 18.0 mS / cm.

[0017] (9) In any one of the above (1) to (8), the present invention provides a compound having a wavelength of 5200 cm in the NIR spectrum. -1 ~4725cm -1 The present invention provides a solid electrolyte in which the area increase rate of the impurity peak according to the following formula 2 is 50% to 400% in relation to the impurity peak present in the region.

number

[0018] (10) The present invention provides the solid electrolyte according to (9), wherein the integral value of the impurity peak after the water exposure is 1 to 20.

[0019] (11) In any one of the above (1) to (10), the present invention provides a method for producing a granular material having an average particle size (D 50 ) is 0.5 μm to 4 μm.

[0020] (12) In any one of the above (1) to (11), the present invention provides a method for determining the span value ([D 90 -D 10 ] / D 50 ) is 4 or less.

[0021] (13) The present invention also provides an all-solid-state battery including the solid electrolyte according to any one of (1) to (12) above. [Effects of the Invention]

[0022] The solid electrolyte having an argyrodite-type crystal structure according to the present invention is 2- The ionic radius (r s ) (unit: Å) to the ionic radius (r) (unit: Å) of the cation (r / r s ) is doped with a cation having a valence of 0.20 to 0.30, and has the advantage of excellent atmospheric stability of the solid electrolyte itself. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 shows XRD graphs of the solid electrolytes of Examples 1, 4 and 5. [Figure 2] FIG. 1 is a diagram showing XRD graphs of the solid electrolytes of Comparative Examples 3, 4 and 5. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will now be described in more detail to facilitate understanding of the present invention.

[0025] The terms and words used in this specification should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as having meanings and concepts that are consistent with the technical idea of the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0026] The terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly indicates otherwise.

[0027] In this specification, the terms "comprises," "includes," "has," and the like are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but are not intended to preclude the possible presence or addition of one or more different features, numbers, steps, components, or combinations thereof.

[0028] In this specification, the ionic radius is the Shannon ionic radius.

[0029] In this specification, "D n " means the particle size at n% point of the volume cumulative distribution by particle size. That is, D 50 is the particle size at the 50% point of the volume cumulative distribution by particle size, and D 90 is the particle size at 90% of the volume cumulative distribution by particle size, and D 10 is the particle size at the 10% point of the volume cumulative distribution of particle size. ncan be measured using the laser diffraction method. Specifically, the powder to be measured is dispersed in a dispersion medium (xylene), and then introduced into a commercially available particle size analyzer (e.g., Malvern's Mastersizer 3000). When the particles pass through a laser beam, the difference in diffraction pattern due to particle size is measured to calculate the particle size distribution. By calculating the particle diameters at the 10%, 50%, and 90% points of the volume cumulative distribution due to particle size in the measuring device, D 10 , D 50 and D 90 can be measured.

[0030] solid electrolyte The solid electrolyte according to the present invention is S 2- The ionic radius (r s ) (unit: Å) to the ionic radius (r) (unit: Å) of the cation (r / r s ) has an argyrodite-type crystal structure doped with a cation in which the .gamma.

[0031] The present inventors have found that in the case of the solid electrolyte having an argyrodite-type crystal structure according to the present invention, S 2- The ionic radius (r s ) (unit: Å) to the ionic radius (r) (unit: Å) of the cation (r / r s ) is doped with a cation having a valence of 0.20 to 0.30, and the solid electrolyte itself has excellent atmospheric stability, and the chemical resistance can be improved in dry and wet processes when manufacturing a battery, which led to the completion of the present invention.

[0032] In the case of Li6PS5Cl, Li6PS5Br, etc., which are used in the industry as solid electrolytes with an argyrodite crystal structure, the S contained in the solid electrolyte 2- However, the solid electrolyte having an argyrodite-type crystal structure according to the present invention has a problem that S ions react with moisture in the atmosphere and are easily decomposed. 2- Cations that have strong bonding strength with ions, specifically, S2- The ionic radius (r s ) (unit: Å) to the ionic radius (r) (unit: Å) of the cation (r / r s The solid electrolyte particles are doped with a cation having a saturation ratio of 0.20 to 0.30, which can prevent the solid electrolyte particles from decomposing and deteriorating when exposed to moisture or oxygen. As a result, it is possible to prevent the generation of hydrogen sulfide, a toxic gas, and prevent the ionic conductivity of the solid electrolyte from decreasing. 2- The ionic radius (r s ) (unit: Å) to the ionic radius (r) (unit: Å) of the cation (r / r s ) can specifically be 0.20 or more, 0.21 or more, or 0.25 or more, and 0.30 or less.

[0033] On the other hand, S 2- The ionic radius (r s ) (unit: Å) to the ionic radius (r) (unit: Å) of the cation (r / r s ) is less than 0.20, the cation and S 2- The bond strength of S is low, so it is prone to decomposition reactions due to moisture. 2- The ionic radius (r s ) (unit: Å) to the ionic radius (r) (unit: Å) of the cation (r / r s ) exceeds 0.30, the size of the cation is too large to allow for doping within the argyrodite-type crystal structure, resulting in a problem that not only is there no improvement in water stability, but also impurities are generated, resulting in a decrease in ionic conductivity.

[0034] According to the present invention, the cation may have a ratio (c / r) of the ionic oxidation number (c) to the ionic radius (r) (unit: Å) of 7.00 to 14.00. In this case, the cation may be S 2- Since doping is easily performed at the P-site, which forms a bond with the cation, the initial ionic conductivity can be improved. 2- It has good bonding strength with the polymer, and moisture stability can be improved.

[0035] According to the present invention, the solid electrolyte may have a composition represented by the following Chemical Formula 1. In this case, the solid electrolyte may have high ionic conductivity and low reactivity with a lithium anode, and decomposition and degradation of the solid electrolyte particles when exposed to moisture or oxygen may be suppressed.

[0036] [Chemical formula 1] Li a (P 1-b M b )S c X d

[0037] In the above Chemical Formula 1, M is one or more selected from Sn, Nb, Ni, Ge, Ga, and Al; X is one or more selected from F, Cl, Br and I; 5.0 <a<7.5、0<b≦0.7、3.5≦c≦7、0.8≦d≦1.7である。

[0038] According to the present invention, M is a doping element to be doped in the solid electrolyte having an argyrodite-type crystal structure, and may be at least one element selected from Sn, Nb, Ni, Ge, Ga, and Al, specifically at least one element selected from Sn, Nb, Ge, and Al.

[0039] According to the present invention, the solid electrolyte may have a ratio (y / (x+y)) of the number of moles of M to the sum of the number of moles of P (x) and the number of moles of M (y) of 0.01 to 0.7, specifically, 0.01 or more and 0.5 or less, 0.6 or less, or 0.7 or less. In this case, the doping amount is appropriate, and the solid electrolyte may exist as an argyrodite phase with no or low impurity content, thereby improving ionic conductivity.

[0040] According to the present invention, the solid electrolyte may have an ionic conductivity retention rate of 55% or more, specifically 55% or more, and 70% or less, 75% or less, 80% or less, 85% or less, or 90% or less, as determined by the following formula 1:

[0041]

number

[0042] In the formula 1, The initial ionic conductivity is a value measured at 22°C immediately after the production of the solid electrolyte. The ionic conductivity after exposure to moisture was measured at 22°C immediately after the solid electrolyte was exposed to the atmosphere at a relative humidity of 1.91% for 5 hours.

[0043] According to the present invention, the solid electrolyte may have an initial ionic conductivity of 2.0 mS / cm to 20.0 mS / cm, specifically, 2.0 mS / cm or more, or 2.5 mS / cm or more, and 10.0 mS / cm or less, 15.0 mS / cm or less, or 20.0 mS / cm or less. The higher the ionic conductivity of the electrolyte, the better, but when the initial ionic conductivity satisfies the above range, an excellent effect of improving water stability can be achieved.

[0044] According to the present invention, the solid electrolyte may have an ionic conductivity of 1.4 mS / cm to 18.0 mS / cm after exposure to water, specifically, 1.4 mS / cm or more, or 1.5 mS / cm or more, and 9.0 mS / cm or less, 10.0 mS / cm or less, 11.0 mS / cm or less, 12.0 mS / cm or less, 13.0 mS / cm or less, 14.0 mS / cm or less, 15.0 mS / cm or less, 16.0 mS / cm or less, 17.0 mS / cm or less, or 18.0 mS / cm or less. In this case, there is an advantage that the electrolyte structure is maintained even when exposed to water during the battery manufacturing process.

[0045] According to the present invention, the solid electrolyte has a wavelength of 5200 cm in the NIR spectrum of the solid electrolyte. -1 ~4725cm -1With respect to the impurity peaks present in the region, the area increase rate of the impurity peaks according to the following formula 2 can be 50% to 400%, specifically, 50% or more, 100% or more, 150% or more, or 200% or more, and 350% or less, or 400% or less.

[0046]

number

[0047] In the formula 2, The integral value of the impurity peak before exposure to moisture is a value obtained from the NIR spectrum measured at room temperature immediately after the production of the solid electrolyte. The integral value of the impurity peak after exposure to moisture was obtained from the NIR spectrum measured at room temperature immediately after the solid electrolyte was exposed to the atmosphere at a relative humidity of 1.91% for 5 hours.

[0048] According to the present invention, the solid electrolyte may have an impurity peak integral value after the moisture exposure of 1.00 to 10.0, specifically 1.00 or more and 5.00 or less, or 10.0 or less. In this case, the electrolyte structure is maintained even after the moisture exposure, and therefore the ion conductivity performance can be maintained.

[0049] According to the present invention, the solid electrolyte has an average particle size (D 50 ) can be 0.5 μm to 4.0 μm, specifically 0.5 μm, 1.0 μm, or 2.0 μm or more, and 3.5 μm, 4.0 μm or less. When the average particle size of the solid electrolyte is within the above range, good contact with the electrode active material can be achieved, resulting in excellent battery life characteristics.

[0050] According to the present invention, the solid electrolyte has a span value ([D 90 -D 10 ] / D 50 ) can be 4.0 or less, specifically 1.0 or more and 4.0 or less. When the span value of the solid electrolyte is within the above range, there is an advantage that the particle size is uniform and it is possible to produce a uniform composite electrode.

[0051] The solid electrolyte of the present invention can be synthesized, for example, by mechanical milling and solid-phase synthesis. Specifically, one or more materials selected from LiCl, LiBr, and LiI, Li2S, P2S5, and a doping element-containing raw material (e.g., SnS2, GeS2, etc.) are stoichiometrically weighed and then mixed by ball milling. The resulting mixed precursor is heat-treated to crystallize it, and then pulverized by ball milling again. The mixing, heat treatment, and pulverization processes are carried out in an inert gas atmosphere.

[0052] all solid state battery The present invention provides an all-solid-state battery containing the solid electrolyte.

[0053] Specifically, the all-solid-state battery includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and a solid electrolyte layer containing the solid electrolyte according to the present invention disposed between the positive electrode and the negative electrode.

[0054] The all-solid-state battery according to the present invention has little decrease in ionic conductivity due to moisture, and can have excellent initial efficiency, life characteristics, and output characteristics.

[0055] The all-solid-state battery of the present invention can be manufactured by a conventional method known in the art, for example, by stacking a positive electrode and a negative electrode so that a solid electrolyte layer is present between them and applying pressure.

[0056] (1) Positive electrode The positive electrode may be prepared by coating a positive electrode current collector with a positive electrode slurry containing a positive electrode active material, a binder, a conductive material, and a solvent.

[0057] The positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has conductivity. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or those obtained by surface treatment of the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. can be used. Also, fine irregularities can be formed on the surface to strengthen the binding force of the positive electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven bodies, etc.

[0058] The positive electrode active material can include a compound capable of reversible intercalation and deintercalation of lithium, specifically, a lithium metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium. More specifically, the lithium metal oxide includes lithium-manganese-based oxides (e.g., LiMnO2, LiMn2O4, etc.), lithium-cobalt-based oxides (e.g., LiCoO2, etc.), lithium-nickel-based oxides (e.g., LiNiO2, etc.), lithium-nickel-manganese-based oxides (e.g., LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-z Ni z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt-based oxides (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), lithium-manganese-cobalt-based oxides (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-z1 Co z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt-based oxides (e.g., Li(Ni p Co q Mn r1 )O2 (where 0 < p < 1, 0 < q < 1, 0 < r1 < 1, p + q + r1 = 1) or Li(Ni p1 Co q1 Mn r2)O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r2 < 2, p1 + q1 + r2 = 2), etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 M S2 )O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r3, and s2 are the atomic fractions of the respective independent elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, and p2 + q2 + r3 + s2 = 1), etc.), and any one or two or more of these compounds can be included.

[0059] Among them, in terms of being able to enhance the capacity characteristics and stability of the battery, the lithium metal oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (e.g., Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), and considering the significance of the improvement effect by controlling the types and content ratios of the constituent elements forming the lithium composite metal oxide, the lithium composite metal oxide is Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15Co 0.15 )O2, and Li(Ni 0.8 Mn 0.1 Co 0.1 ) O2, etc., and any one or a mixture of two or more of these can be used.

[0060] The positive electrode active material may be contained in an amount of 60% by weight to 99% by weight, preferably 70% by weight to 99% by weight, and more preferably 80% by weight to 98% by weight, based on the total weight of solids other than the solvent in the positive electrode slurry.

[0061] The binder is a component that helps bind the conductive material, active material, and current collector together. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0062] Typically, the binder can be contained in an amount of 1 wt % to 20 wt %, preferably 1 wt % to 15 wt %, and more preferably 1 wt % to 10 wt %, based on the total weight of solids other than the solvent in the positive electrode slurry.

[0063] The conductive material is a component for further improving the conductivity of the positive electrode active material.

[0064] The conductive material is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, carbon-based materials such as graphite; carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber and metal fiber; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used.

[0065] Typically, the conductive material can be contained in an amount of 1 wt % to 20 wt %, preferably 1 wt % to 15 wt %, and more preferably 1 wt % to 10 wt %, based on the total weight of solids other than the solvent in the positive electrode slurry.

[0066] The solvent may include an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a desired viscosity when the positive electrode active material and, optionally, a binder and a conductive material are included. For example, the solvent may be included so that the concentration of the solids including the positive electrode active material and, optionally, a binder and a conductive material is 50 wt % to 95 wt %, preferably 70 wt % to 95 wt %, and more preferably 70 wt % to 90 wt %.

[0067] (2) Negative electrode The negative electrode can be prepared by, for example, coating a negative electrode current collector with a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, and a solvent, or a graphite electrode made of carbon (C) or a metal itself can be used as the negative electrode.

[0068] For example, when the negative electrode is manufactured by coating the negative electrode slurry onto the negative electrode current collector, the negative electrode current collector typically has a thickness of 3 to 500 μm. Such a negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. Examples of such a negative electrode current collector include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surfaces treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys. Furthermore, similar to the positive electrode current collector, the surface can be formed with fine irregularities to enhance the binding strength of the negative electrode active material, and the negative electrode current collector can be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0069] Examples of the negative electrode active material include natural graphite, artificial graphite, carbonaceous materials, lithium-containing titanium composite oxide (LTO), Si, SiO x , Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; alloys composed of the metals (Me); oxides of the metals (Me) (MeO x and composites of the metals (Me) with carbon. Specific examples of the negative electrode active material include silicon (Si), silicon oxide (SiO x Silicon-based negative electrode active materials, such as silicon dioxide, silicon nitride, silicon carbide ...

[0070] The negative electrode active material may be contained in an amount of 60% by weight to 99% by weight, preferably 70% by weight to 99% by weight, and more preferably 80% by weight to 98% by weight, based on the total weight of solids other than the solvent in the negative electrode slurry.

[0071] The binder is a component that helps bind the conductive material, active material, and current collector together. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0072] Typically, the binder can be contained in an amount of 1 wt % to 20 wt %, preferably 1 wt % to 15 wt %, and more preferably 1 wt % to 10 wt %, based on the total weight of solids other than the solvent in the negative electrode slurry.

[0073] The conductive material is a component for further improving the conductivity of the negative electrode active material. The conductive material is not particularly limited as long as it does not cause chemical changes in the battery and has conductivity, and examples thereof include graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber and metal fiber; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0074] The conductive material may be contained in an amount of 1 wt % to 20 wt %, preferably 1 wt % to 15 wt %, and more preferably 1 wt % to 10 wt %, based on the total weight of solids other than the solvent in the negative electrode slurry.

[0075] The solvent may include water or an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a desired viscosity when the negative electrode active material and, optionally, a binder and a conductive material are included. For example, the solvent may be included so that the concentration of the solids, including the negative electrode active material and, optionally, a binder and a conductive material, is 50 wt % to 95 wt %, preferably 70 wt % to 90 wt %.

[0076] When a metal is used as the anode, the anode can be fabricated by physically bonding, rolling, or depositing a metal thin film on the anode current collector or the metal thin film itself. The deposition method can be electrolytic deposition or chemical vapor deposition.

[0077] For example, the metal thin film itself or the metal bonded / rolled / deposited on the negative electrode current collector may include one metal or an alloy of two metals selected from the group consisting of lithium (Li), nickel (Ni), tin (Sn), copper (Cu), and indium (In).

[0078] (3) Solid electrolyte layer The solid electrolyte layer may further contain a binder in addition to the solid electrolyte according to the present invention.

[0079] The binder is a component that helps bind the conductive material, active material, and current collector together. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0080] Generally, the binder can be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, and more preferably 1 to 10% by weight, based on the total weight of the solid electrolyte layer.

[0081] The present invention provides a battery module including the all-solid-state battery as a unit cell, and a battery pack including the same. The battery module and battery pack include the secondary battery having high capacity, excellent rate-limiting characteristics, and excellent cycle characteristics, and can be used as a power source for medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0082] In the following, preferred embodiments will be presented to facilitate understanding of the present invention. However, the above embodiments are merely illustrative of the present description, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope of the scope and technical ideas of the present description. It goes without saying that such changes and modifications fall within the scope of the appended claims.

[0083] Examples and Comparative Examples Example 1 Four precursors, Li2S, P2S5, LiBr, and SnS2, were dry mixed (ball milled) in a molar ratio of 5.05:0.95:2:0.1. During the dry mixing, a planetary ball mill equipped with zirconia balls was used, and the ball mill was rotated at a speed of 300 rpm to 700 rpm to ensure uniform mixing. The mixed precursor was then heat-treated at 500°C to 600°C for 12 hours to crystallize it, and then pulverized again by ball milling to obtain Li2S with an argyrodite-type crystal structure. 6.05 P 0.95 Sn 0.05 A solid electrolyte having a composition represented by S5Br was prepared. All of the above processes were carried out under an inert Ar atmosphere.

[0084] Example 2 A solid electrolyte (having an argyrodite-type crystal structure, Li 6.02 P 0.98 Sn 0.02 S5Br) was produced.

[0085] Example 3 A solid electrolyte (having an argyrodite-type crystal structure, Li 6.01 P 0.99 Sn 0.01 S5Br) was produced.

[0086] Example 4 A solid electrolyte (having an argyrodite-type crystal structure, Li) was prepared in the same manner as in Example 1, except that four precursors, LiS, P2S5, LiI, and GeS2, were mixed in a molar ratio of 5.6:0.4:2:1.2. 6.6 P 0.4 Ge 0.6 S5I) was produced.

[0087] Example 5 A solid electrolyte (having an argyrodite-type crystal structure, Li) was prepared in the same manner as in Example 1, except that four precursors, Li2S, P2S5, LiBr, and Ga2S3, were mixed in a molar ratio of 2.25:0.45:1:0.05. 5.5 P 0.9 Ga 0.1 S 4.65 Br) was prepared.

[0088] Comparative Example 1 Three precursors, Li2S, P2S5, and LiBr, were dry mixed (ball milled) in a molar ratio of 5:1:2. A planetary ball mill equipped with zirconia balls was used for dry mixing, rotating at a speed of 300-700 rpm to ensure uniform mixing. The resulting mixed precursor was then heat-treated at 500-600°C for 12 hours to crystallize it, and then ball-milled again to produce Li6PS5Br with an argyrodite-type crystal structure. All of the above processes were carried out in an inert Ar atmosphere.

[0089] The Li6PS5Br having the argyrodite-type crystal structure was used as the solid electrolyte in Comparative Example 1.

[0090] Comparative Example 2 A solid electrolyte (having an argyrodite-type crystal structure and a composition represented by Li6PS5Cl) was produced in the same manner as in Example 1, except that three precursors, Li2S, P2S5, and LiCl, were mixed in a molar ratio of 5:1:2.

[0091] Comparative Example 3 A solid electrolyte (having an argyrodite-type crystal structure, Li 5.55 P 0.95 Hf 0.05 S 4.75 The compound (having the composition represented by Cl) was prepared.

[0092] Comparative Example 4 A solid electrolyte (having an argyrodite-type crystal structure, Li 5.6 P 0.9 Hf 0.1 S 4.75 The compound (having the composition represented by Cl) was prepared.

[0093] Comparative Example 5 A solid electrolyte (having an argyrodite-type crystal structure, Li 5.85 P 0.9 Hf 0.1 S 4.75 Cl 1.25 A compound having a composition represented by the formula:

[0094] Comparative Example 6 A solid electrolyte (having an argyrodite-type crystal structure, Li 5.6 P 0.9 Hf 0.1 S 4.5 Cl 0.5 Br) was prepared.

[0095] Comparative Example 7 A solid electrolyte (having an argyrodite-type crystal structure, Li 6.1 P 0.9 Si 0.1 S5Br) was produced.

[0096] Comparative Example 8 A solid electrolyte (having an argyrodite-type crystal structure, Li 6.2 P 0.8 Si 0.2 S5Br) was produced.

[0097] For each of the solid electrolytes produced in Examples 1 to 4 and Comparative Examples 3 to 8, S 2- The ionic radius (r s) (unit: Å) of the ionic radius (r) of the cation doped at the P-site to the ionic radius (r) (unit: Å) of the cation doped at the P-site (r / r s ) and the ratio (c / r) of the ionic oxidation number to the ionic radius (r) (unit: Å) of the cation doped at the P-site are shown in Table 1 below.

[0098] For reference, the solid electrolytes (not doped with cations) prepared in Comparative Examples 1 and 2 were 2- P for the ionic radius (unit: Å) of 5+ The ratio of the ionic radii (unit: Å) of P 5+ The ratio of the ionic oxidation number to the ionic radius (unit: Å) was calculated and shown in Table 1 below.

[0099] [Table 1]

[0100] Experimental Example 1: X-ray diffraction analysis, particle size analysis (Checking whether or not solid electrolyte is cation doped) The presence or absence of cation doping in the solid electrolytes produced in Examples 1, 4, and 5 and Comparative Examples 4 to 6 was confirmed by XRD analysis. XRD analysis was performed using a Bruker AXS D8 Endeavor XRD (voltage: 40 kV, current: 40 mA) using Cu Ka radiation (wavelength: 1.54 Å) at a scanning speed of 0.3 seconds per 0.02° angle from 2-Theta 10° to 60°. Graphs of the XRD analysis results for Examples 1, 4, and 5 and Comparative Examples 4 to 6 are shown in FIGS. 1 and 2.

[0101] Referring to FIG. 1, in the case of the solid electrolytes of Examples 1, 4, and 5, no unreacted impurity phase was detected, confirming that the solid electrolytes were 100% argyrodite phase and were doped with cations.

[0102] On the other hand, referring to FIG. 2, in the case of the solid electrolytes of Comparative Examples 4 to 6, excessive amounts of unreacted impurity phases presumably lithium halide (represented by diamonds) and unknown phases (represented by inverted triangles) were detected.

[0103] (Confirmation of the average particle size and span value of the solid electrolyte) The D of the solid electrolytes produced in Examples 1 to 5 and Comparative Examples 1 and 2 was measured using a particle size analyzer (Malvern, Mastersizer 3000). 10 , D 50 , D 90 The average particle size (D 50 ) and the span values calculated using the following formula 3 are shown in Table 2 below.

[0104] [Formula 3] span=[D 90 -D 10 ] / D 50

[0105] [Table 2]

[0106] Referring to Table 2, it can be seen that the solid electrolytes of Examples 1 to 5 have more uniform particle diameters than the solid electrolytes of Comparative Examples.

[0107] Experimental Example 2: Evaluation of ionic conductivity retention rate -Evaluation of initial ionic conductivity Immediately after production, 150 mg of each solid electrolyte powder produced in Examples 1 to 4 and Comparative Examples 1 to 8 was placed in a 13 mm diameter SUS mold. The mold, along with the insulating PEEK, was attached to a press, and a potentiostat was connected to the SUS mold. After applying a pressure of 370 MPa to sufficiently densify the electrolyte structure, the pressure was gradually reduced to maintain 100 MPa, and AC impedance measurements were performed at frequencies from 1 Hz to 7 MHz. The ionic conductivity was calculated from the measured resistance values using a Nyquist plot, and is shown in Table 3 below. All measurements were performed in a dry room at a temperature of 22°C and a relative humidity of 0.7%.

[0108] -Evaluation of ionic conductivity after exposure to moisture Immediately after 5 hours of exposure to an atmosphere with a relative humidity of 1.91% for each of the solid electrolyte powders prepared in Examples 1 to 4 and Comparative Examples 1 to 8, 150 mg of each was taken and placed in a 13 mm diameter SUS mold. The mold, along with the insulating PEEK, was attached to a press, and a potentiostat was connected to the SUS mold. After applying a pressure of 370 MPa to sufficiently densify the electrolyte structure, the pressure was gradually reduced to maintain 100 MPa, and AC impedance measurements were performed at frequencies from 1 Hz to 7 MHz. The ionic conductivity after moisture exposure was calculated from the measured resistance values using a Nyquist plot, and is shown in Table 3 below. All measurements were performed in a dry room at a temperature of 22°C and a relative humidity of 0.7%.

[0109] The ionic conductivity retention rate was calculated using the following formula 1 and is shown in Table 3 below.

[0110]

number

[0111] [Table 3]

[0112] Referring to Table 3, it can be seen that the solid electrolytes of Examples have superior water stability and a high ionic conductivity retention rate even after exposure to water compared to the solid electrolytes of Comparative Examples. It can also be seen that the solid electrolytes of Examples 1, 2, and 4, which are doped with cations having a ratio (c / r) of ionic oxidation number (c) to ionic radius (r) (unit: Å) of 7.00 to 14.00, have higher initial ionic conductivity compared to the solid electrolyte of Example 5, which is doped with a cation having a c / r value of less than 7.00. This is because the lower the c / r value, the greater the degree of interaction between the cation and S. 2- However, if the bonding strength is too low, P-site doping becomes difficult and the ionic conductivity performance decreases.

[0113] Experimental Example 3: Analysis of impurities after moisture exposure Immediately after the solid electrolyte powders in Examples 1, 2, and 5 and Comparative Examples 1 to 7 were produced, and immediately after the solid electrolyte powders were exposed to the atmosphere at a relative humidity of 1.91% for 5 hours, each powder was taken and placed in a glass vial. Then, the NIR reflectance spectrum of the solid electrolyte in the glass vial was measured using an FT-NIR spectrometer (manufactured by ABB, MB3600) equipped with a diffuse reflectance accessory (8 cm -1 resolution, 32 scans). 5300cm -1 , 4685cm -1 After baseline correction, 5200cm -1 ~4725cm -1 The integral values of the Li2CO3 impurity-related NIR peaks in the region were calculated and are shown in Table 4 below.

[0114] For reference, the analysis conditions are as follows:

[0115] -Covering Range: 3,700 to 14,885cm -1 range -Interferometer Mechanism: High-throughput double pivot Michelson -NIR source: Quartz-halogen (Electron Controlled) -Laser source: Solid-state laser (long lifetime) -Optical material: Completely non-Hygroscopic optics (ZnSe) -Detector: TE cooled InGaAs detector

[0116] The area increase rate of the impurity peak was calculated using the following formula 2 and shown in Table 4 below.

[0117]

number

[0118] [Table 4]

[0119] Referring to Table 4, it can be seen that the solid electrolytes of the Examples have a lower increase rate in the area of the impurity peaks even after exposure to moisture, and therefore have better moisture stability than the solid electrolytes of the Comparative Examples. In other words, it can be seen that the solid electrolytes of the Examples maintain their electrolyte structure even after exposure to moisture.

[0120] As a result, the solid electrolyte having an argyrodite-type crystal structure according to the present invention is 2- The ionic radius (r s ) (unit: Å) to the ionic radius (r) (unit: Å) of the cation (r / r s ) is 0.20 to 0.30, and when exposed to moisture, the sulfide-based solid electrolyte particles can be prevented from decomposing and deteriorating.

Claims

1. S ２－ The ionic radius (r ｓ The ratio of the ionic radius (r) (unit: Å) of the cation to the ionic radius (r) (unit: Å) of the cation (r / r ｓ A solid electrolyte having an argyrodite-type crystal structure doped with a cation in which the cation ratio (C) is 0.20 to 0.

30.

2. 2. The solid electrolyte according to claim 1, wherein the cation has a ratio (c / r) of ionic oxidation number (c) to ionic radius (r) (unit: Å) of 7.00 to 14.

00.

3. 2. The solid electrolyte according to claim 1, having a composition represented by the following chemical formula 1: [Chemical formula 1] Li ａ (P １－ｂ M ｂ )S ｃ X ｄ In the above Chemical Formula 1, M is one or more selected from Sn, Nb, Ni, Ge, Ga, and Al; X is one or more selected from F, Cl, Br and I; 5.0<a<7.5, 0<b≦0.7, 3.5≦c≦7, 0.8≦d≦1.

7.

4. 4. The solid electrolyte according to claim 3, wherein M is one or more elements selected from the group consisting of Sn, Nb, Ge, and Al.

5. The solid electrolyte according to claim 3, wherein a ratio (y / (x+y)) of the number of moles of M to the sum of the number of moles of P (x) and the number of moles of M (y) satisfies 0.01 to 0.

7.

6. 2. The solid electrolyte according to claim 1, wherein the ionic conductivity retention rate according to the following formula 1 is 55% or more: [Equation 1] In the formula 1, The initial ionic conductivity is a value measured at 22°C immediately after the production of the solid electrolyte. The ionic conductivity after exposure to moisture is a value measured at 22° C. immediately after the solid electrolyte is exposed to the atmosphere at a relative humidity of 1.91% for 5 hours.

7. 7. The solid electrolyte according to claim 6, wherein the initial ionic conductivity is 2.0 mS / cm to 20.0 mS / cm.

8. 7. The solid electrolyte according to claim 6, wherein the ionic conductivity after the exposure to water is 1.4 mS / cm to 18.0 mS / cm.

9. 5200 cm in the NIR spectrum －１ ~4725cm －１ 2. The solid electrolyte according to claim 1, wherein the area increase rate of the impurity peak according to the following formula 2 is 50% to 400% relative to the impurity peak present in the region. [Equation 2] In the formula 2, The integral value of the impurity peak before exposure to moisture is a value obtained from an NIR spectrum measured at room temperature immediately after the production of the solid electrolyte. The integral value of the impurity peak after exposure to moisture is a value obtained from an NIR spectrum measured at room temperature immediately after the solid electrolyte was exposed to the atmosphere at a relative humidity of 1.91% for 5 hours.

10. 10. The solid electrolyte according to claim 9, wherein an integral value of the impurity peak after the moisture exposure is 1 to 20.

11. Average particle size (D ５０ 2. The solid electrolyte according to claim 1, wherein the average particle size is 0.5 μm to 4 μm.

12. Span value ([D ９０ -D １０ ] / D ５０ 2. The solid electrolyte according to claim 1, wherein the σ is 4 or less.

13. An all-solid-state battery comprising the solid electrolyte according to any one of claims 1 to 12.

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