Sulfide-based solid electrolyte, method for producing same, and all-solid-state battery comprising same

Abstract

The present specification provides a sulfide-based solid electrolyte, a method for producing same, and an all-solid-state battery comprising same, the sulfide-based solid electrolyte having an average crystal grain size of 200 nm or more and represented by chemical formula 1.

Description

Sulfide-based solid electrolyte, method for producing the same, and all-solid-state battery comprising the same

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0030860, filed March 4, 2024, Korean Patent Application No. 10-2024-0030861, filed March 4, 2024, and Korean Patent Application No. 10-2024-0030862, filed March 4, 2024, the entire disclosure of which is incorporated herein by reference.

[0003] The present invention relates to a sulfide-based solid electrolyte, a method for producing the same, and an all-solid-state battery including the same.

[0004] All-solid-state batteries replace the liquid electrolyte that fills the space between the anode and cathode of conventional lithium secondary batteries with a solid electrolyte. These all-solid-state batteries are safe because they do not use flammable solvents, eliminating the risk of explosion. Furthermore, because they allow the use of lithium metal or lithium alloys as a cathode material, they offer higher energy density than conventional batteries, attracting attention as next-generation batteries.

[0005] The core materials that make up solid electrolytes include polymers, sulfides, and oxides, but among them, sulfide-based solid electrolytes with high ductility and high ionic conductivity are considered suitable for manufacturing high-capacity, large-scale batteries.

[0006] The lithium ion conductivity of sulfide-based solid electrolytes with an argyrodite-type crystal structure, represented by Li6PS5Cl, is approximately 2 mS / cm, which is somewhat superior to existing materials, but has limitations in application to next-generation technologies that require high lithium ion conductivity of 5 mS / cm or more.

[0007] In order to further increase the ionic conductivity of a sulfide-based solid electrolyte having an argyrodite crystal structure, a method is known in which Cl and Br are doped together as halogen elements into the sulfide-based solid electrolyte, and Cl and Br are doped in an excess of 1 or more. However, when such a sulfide-based solid electrolyte uses lithium metal as the negative electrode of an all-solid-state battery, the excessively doped halogen element may cause a side reaction with the lithium metal or the positive electrode, which may cause a deterioration in battery performance.

[0008] Accordingly, there is a continuous demand for the development of argyrodite-type sulfide-based solid electrolytes with high ionic conductivity that can be applied to next-generation technologies.

[0009] The present invention relates to a sulfide-based solid electrolyte with improved ionic conductivity, a method for producing the same, and an all-solid-state battery including the same.

[0010] The present invention has an average crystal grain size of 200 nm or more,

[0011] A sulfide-based solid electrolyte represented by the following chemical formula 1 is provided.

[0012] [Chemical Formula 1]

[0013] Li a P 1-b M b S c Cl d Br e

[0014] In chemical formula 1,

[0015] M is at least one selected from the group consisting of Sb, Si, Ge, Sn, Cu, Ag, Mg, Ca, Al, As, Na, K and Ga,

[0016] 5≤a≤7.5, 0≤b≤0.3, 0.5≤ac≤1.5, 0 <d≤1.5, 0<e≤1.5이다.

[0017] The present invention comprises the steps of preparing a mixture by mixing a lithium-containing compound, a phosphorus-containing compound, a sulfur-containing compound, a chlorine-containing compound, and a bromine-containing compound; and

[0018] A method for producing the above-described sulfide-based solid electrolyte is provided, including a step of heat-treating the above mixture.

[0019] The present invention provides an all-solid-state battery comprising a positive electrode; a negative electrode; and a solid electrolyte layer provided between the positive electrode and the negative electrode, wherein the positive electrode or the solid electrolyte layer includes the above-described sulfide-based solid electrolyte.

[0020] The sulfide-based solid electrolyte according to the present invention has an optimized crystal grain size, can have high ionic conductivity by doping a halogen element at a high level and appropriately controlling the molar ratio with the lithium element, and at the same time has high-quality characteristics without impurity phases.

[0021] In addition, the sulfide-based solid electrolyte according to the present invention has a wide heat treatment temperature range for crystallization, so that the process window, such as heat treatment conditions in a mass production process, can be improved, and thus, excellent quality and high yield can be secured when applied to a mass production process.

[0022] Figures 1 to 3 are X-ray diffraction patterns of the sulfide-based solid electrolytes manufactured in Examples 1 to 3.

[0023] Figures 4 and 5 are X-ray diffraction patterns of the sulfide-based solid electrolytes manufactured in Comparative Examples 1 and 2.

[0024] Hereinafter, a sulfide-based solid electrolyte, its manufacturing method, and its use according to a specific embodiment of the invention will be described in more detail.

[0025] Unless otherwise defined herein, all technical and scientific terms used herein are used merely to describe exemplary embodiments and are not intended to be limiting of the present invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, it should be understood that the terms "comprises," "includes," or "has" indicate the presence of a feature, number, step, component, or combination thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0026] The present invention is susceptible to various modifications and takes various forms. Specific embodiments are illustrated and described in detail below. However, this is not intended to limit the present invention to specific disclosed forms, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

[0027] In the present invention, 'y is greater than or equal to x1' can be expressed as 'x1≤y', and 'y is less than or equal to x2' can be expressed as 'y≤x2'. For example, 'x1≤y≤x2' means that 'y has a value greater than or equal to x1 and less than or equal to x2'.

[0028] The present invention provides a sulfide-based solid electrolyte having an average crystal grain size of 200 nm or more and represented by the following chemical formula 1.

[0029] [Chemical Formula 1]

[0030] Li a P 1-b M b S c Cl d Br e

[0031] In chemical formula 1,

[0032] M is at least one selected from the group consisting of Sb, Si, Ge, Sn, Cu, Ag, Mg, Ca, Al, As, Na, K and Ga,

[0033] 5≤a≤7.5, 0≤b≤0.3, 0.5≤ac≤1.5, 0 <d≤1.5, 0<e≤1.5이다.

[0034] In the present invention, the average crystal grain size of the sulfide-based solid electrolyte may be 200 nm or more. Preferably, it may be 210 nm or more, 220 nm or more, 230 nm or more, 240 nm or more, 250 nm or more, or 300 nm or more, and may be 1,000 nm or less, 500 nm or less, 450 nm or less, or 400 nm or less. In the above numerical range, the elements and vacancies within the unit cell have a well-ordered structure, so that Li ion hopping is facilitated, and lithium ion conductivity can be maintained excellently.

[0035] A solid electrolyte of the basic composition of Li6PS5Cl having a conventional argyrodite-type crystal structure is PS4 3- It has a structure in which the main unit structure of the skeleton is occupied by S and halogen surrounded by Li at the sites around it, and has low ionic conductivity.

[0036] However, the sulfide-based solid electrolyte of the present invention has the effect of improving ionic conductivity by controlling the average crystal grain size to 200 nm or more.

[0037] The above average grain size can be calculated through Rietveld refinement calculation of X-ray diffraction patterns. The Rietveld refinement calculation was performed using TOPAS, a Bruker XRD-specific analysis program, and the lower factor was reflected to consider the instrumental peak broadening caused by the Bruker D8-Endeavor (Cu source), the measuring device.

[0038] 1.X-ray beam divergence (0.5 degrees),

[0039] 2. Detector type and size (1-D PSD, measurement area: 4.1 degrees),

[0040] 3.Full axial method among axial convolutions

[0041] The whole powder pattern decomposition method, which considers only the space group and lattice constant of the crystal phase, was used for the fit related to peak position and intensity. The final calculated value was obtained by considering only 'Cry Size L' of the 'Double-Voigt Approach' for the grain size-related terms.

[0042] The average grain size tends to increase with increasing heat treatment temperature. However, if the heat treatment temperature exceeds a certain level, impurity phases are formed, which lowers ionic conductivity and adversely affects the quality and yield of the solid electrolyte. Therefore, controlling ionic conductivity through grain size must also consider the heat treatment temperature.

[0043] Another method for increasing the ionic conductivity of a sulfide-based solid electrolyte having an argyrodite-type crystal structure is to limit the composition.

[0044] In the present invention, the sulfide-based solid electrolyte can be represented by the following chemical formula 1.

[0045] [Chemical Formula 1]

[0046] Li a P 1-b M b S c Cl d Br e

[0047] In chemical formula 1,

[0048] M is at least one selected from the group consisting of Sb, Si, Ge, Sn, Cu, Ag, Mg, Ca, Al, As, Na, K and Ga,

[0049] 5≤a≤7.5, 0≤b≤0.3, 0.5≤ac≤1.5, 0 <d≤1.5, 0<e≤1.5이다.

[0050] In the above chemical formula 1, the composition ratio of lithium, phosphorus, sulfur, and M, i.e., the numerical ranges of a, b, and c, may be 5≤a≤7.5, 0≤b≤0.3, and 0.5≤ac≤1.5. When the composition ratio of each element is adjusted within this range, an argyrodite-type crystal structure is easily formed.

[0051] The molar ratio of lithium and halogen elements among the above lithium, phosphorus, sulfur, and M is related to ionic conductivity.

[0052] From a crystal structure perspective, when halogens occupy the 4a and 4d sites of the argyrodite crystal structure instead of S, a new Li ion migration path is created. When two or more halogens with different ionic radii are used, the site disorder of the 4a and 4d anions increases, shortening the Li ion migration path. In addition, when the Li ion concentration in the composition is lowered to match the stoichiometry, Li vacancy sites are created, facilitating hopping, and consequently improving ionic conductivity.

[0053] In the present invention, a may be 5≤a≤7.5. Preferably, it may satisfy 5.1≤a≤7, 5.2≤a≤6.5, 5.3≤a≤6.2, 5.4≤a≤5.9, 5.5≤a≤5.8, or 5.5≤a≤5.6.

[0054] In the present invention, the above b may be 0≤b≤0.3. Preferably, it may be 0≤b≤0.2, 0≤b≤0.1, 0≤b≤0.05, 0≤b≤0.02, 0≤b≤0.01 or 0.

[0055] In the present invention, c may be 5.5≤c≤9. Preferably, it may be 5.3≤c≤8.15, 5.1≤c≤7.3, 4.9≤c≤6.4, 4.7≤c≤5.5, or 4.45≤c≤4.65.

[0056] In the present invention, d is 0 <d≤1.5일 수 있다. 바람직하게는, 0.15≤d≤1.4, 0.3≤d≤1.3, 0.45≤d≤1.2, 0.6≤d≤1.1 또는 0.75≤d≤1일 수 있다.

[0057] In the present invention, e is 0 <e≤1.5일 수 있다. 바람직하게는, 0.2≤e≤1.2, 0.35≤e≤1.1, 0.45≤e≤0.9, 0.55≤e≤0.85 또는 0.65≤e≤0.75일 수 있다.

[0058] In the present invention, the ac may be 0.5≤ac≤1.5. Preferably, it may satisfy 0.6≤a≤1.4, 0.7≤a≤1.3, 0.8≤a≤1.2, and 0.9≤a≤1.1.

[0059] In the present invention, the sulfide-based solid electrolyte can satisfy 1.32≤d+e≤1.58. Preferably, the value calculated as d+e can be 1.336 or more, 1.352 or more, 1.368 or more, 1.384 or more, 1.4 or more, 1.416 or more, 1.432 or more, 1.448 or more, 1.464 or more, or 1.48 or more. In addition, the value calculated as d+e can be 1.57 or less, 1.56 or less, 1.54 or less, 1.53 or less, or 1.52 or less. At this time, when the substitution rate of halogen in the 4a site and the 4d site existing in the unit cell of the argyrodite-type crystal structure is increased, there is an effect of increasing the ionic conductivity of the solid electrolyte. In the above numerical range, the lattice structure is stabilized by the halogen element, and the ionic conductivity of the solid electrolyte can be improved by promoting lithium ion movement.

[0060] In the present invention, the sulfide-based solid electrolyte can satisfy 0.23≤(d+e) / a≤0.29. Preferably, the value calculated as (d+e) / a can be 0.234 or more, 0.238 or more, 0.242 or more, 0.246 or more, 0.25 or more, 0.254 or more, 0.258 or more, 0.262 or more, 0.266 or more, or 0.27 or more. In addition, the value calculated as (d+e) / a can be 0.288 or less, 0.286 or less, 0.284 or less, 0.282 or less, or 0.28 or less. In the above numerical range, the lattice structure is stabilized by the halogen element, and lithium ion movement is promoted, thereby improving the ionic conductivity of the solid electrolyte.

[0061] In the present invention, the sulfide-based solid electrolyte can satisfy 0.1≤e / d<0.99. Preferably, the value calculated as e / d can be 0.18 or more, 0.25 or more, 0.33 or more, 0.4 or more, 0.48 or more, 0.56 or more, 0.63 or more, 0.71 or more, 0.78 or more, or 0.86 or more. In addition, the value calculated as e / d can be 0.97 or less, 0.95 or less, 0.93 or less, 0.91 or less, or 0.89 or less. In the above numerical range, the contents of Cl and Br can be balanced. Specifically, the lattice structure stabilizing action by Cl and the lithium ion path providing action by Br are mutually balanced, so that the ionic conductivity of the solid electrolyte can be further improved.

[0062] In the present invention, the sulfide-based solid electrolyte is Li 5.6 PS 4.6 ClBr 0.4 , Li 5.5 PS 4.5 ClBr 0.5 , Li 5.5 PS 4.5 Cl 0.8 Br 0.7 or Li 5.6 PS 4.6 Cl 0.8 Br 0.6 , Li 5.5 PS 4.5 Cl 1.2 Br 0.3 It can be. Preferably, Li 5.5 PS 4.5 Cl 0.8 Br 0.7 , Li 5.5 PS 4.5 ClBr 0.5 or Li 5.5 PS 4.5 Cl 1.2 Br 0.3 It can be. The above compound can obtain high ionic conductivity by optimally controlling the sum of the composition ratios of halogen elements Cl and Br, the composition ratios thereof, and the molar ratio of lithium element and halogen element.

[0063] In the present invention, the sulfide-based solid electrolyte may have an argyrodite-type crystal structure. The argyrodite-type crystal structure can be confirmed using X-ray diffraction pattern analysis.

[0064] The sulfide-based solid electrolyte of the present invention may have a first peak that appears at any one or more positions selected from the group consisting of diffraction angles (2θ) of 14° to 16°, 17° to 19°, 24° to 25.65°, 29.5° to 31°, 31° to 32°, and 44° to 46° when analyzing an X-ray diffraction pattern. The X-ray diffraction pattern may be a powder X-ray diffraction pattern according to Cu Kα radiation, wavelength 1.5406 Å. The first peak means that an argyrodite phase has been formed. When the first peak appears, ionic conductivity may be improved.

[0065] In the present invention, the first peak may not have a peak split. In the process of manufacturing a sulfide-based solid electrolyte, an argyrodite decomposition phase, i.e., an impurity phase, may be generated during high-temperature heat treatment, which appears as a peak split in which the argyrodite peak is separated into doublets or triplets. However, in the present invention, peak splitting does not occur in the argyrodite peak range.

[0066] In the present invention, the sulfide-based solid electrolyte may not include an impurity phase. Generally, as the size of crystal grains in a sulfide-based solid electrolyte increases, the ratio of crystal grains / crystal grain boundaries increases, impurity segregation that blocks the conduction of lithium ions decreases, and the overall resistance decreases due to the decrease in grain boundary resistance, thereby increasing the overall ionic conductivity. However, the sulfide-based solid electrolyte of the present invention does not include an impurity phase, and even if it does include an impurity phase, it exists at a negligible level that does not affect the quality. In the present invention, by appropriately controlling the sum of the composition ratio of Cl and Br, which are halogen elements of the sulfide-based solid electrolyte, and the composition ratio thereof, a sulfide-based solid electrolyte that does not include an impurity phase can be obtained.

[0067] Impurities present in sulfide-based solid electrolytes cause a decrease in ionic conductivity, and the presence of impurities also causes problems in terms of the quality and yield of sulfide-based solid electrolytes.

[0068] The presence of an impurity phase in the present invention can be confirmed through powder X-ray diffraction pattern measurement using CuKα rays. That is, a sulfide-based solid electrolyte that does not include an impurity phase does not show a peak related to the impurity phase when a powder X-ray diffraction pattern is measured using CuKα rays.

[0069] The peaks associated with the impurity phase are related to the heat treatment temperature, and can be identified through peak splitting associated with the argyrodite decomposition phase at high temperature heat treatment, while the peaks associated with the low temperature heat treatment or unreacted impurity phase can be identified through identification of a peak in a specific range.

[0070] In the present invention, the impurity phase can be identified from the second peak appearing at one or more positions selected from the group consisting of 25.65° to 26.5°, 26.5° to 27.5°, 28.5° to 29.5°, and 33° to 35°. The impurities detected in the corresponding region are Li2S, LiCl, LiBr, LiCl. a Br b (LiCl / Br mixed phase) may be present.

[0071] In the present invention, the sulfide-based solid electrolyte may have a value calculated by the following mathematical formula 1 of 0.9 or more.

[0072] [Mathematical Formula 1]

[0073] I O / (I O +I A )

[0074] In the above mathematical formula 1,

[0075] I O is the peak intensity that appears at a diffraction angle (2θ) of 24° to 25.65° when analyzing an X-ray diffraction pattern.

[0076] I A is the peak intensity that appears at a diffraction angle (2θ) of 25.65° to 26.5°.

[0077] The value calculated by the above mathematical formula 1 is the intensity of the argyrodite peak (I O ) and impurity peak (I A ) shows the relationship with the century. When the argyrodite peak exists and the impurity peak does not exist, the value calculated by mathematical expression 1 becomes 1.

[0078] In the present invention, the value calculated by the above mathematical formula 1 may be 0.95 or more, 0.96 or more, 0.97 or more, 0.99 or more, 0.999 or more, or 1. The upper limit of the value calculated by the above mathematical formula 1 may be 1. In the above numerical range, an argyrodite peak may be present, but an impurity corresponding to a diffraction angle (2θ) of 25.65° to 26.5° may not be present.

[0079] In the present invention, the sulfide-based solid electrolyte may have a value calculated by the following mathematical formula 2 of 0.994 or more.

[0080] [Equation 2]

[0081] I O / (I O +I B )

[0082] In the above mathematical formula 2,

[0083] I O is the peak intensity that appears at a diffraction angle (2θ) of 24° to 25.65° when analyzing an X-ray diffraction pattern.

[0084] I B is the peak intensity that appears at a diffraction angle (2θ) of 28.5° to 29.5°.

[0085] The value calculated by the above mathematical formula 2 is the intensity of the argyrodite peak (I O ) and impurity peak (I B ) shows the relationship with the century. When the argyrodite peak exists and the impurity peak does not exist, the value calculated by mathematical expression 2 becomes 1.

[0086] In the present invention, the value calculated by the above mathematical formula 2 may be 0.995 or more, 0.996 or more, 0.997 or more, 0.998 or more, 0.999 or more, or 1. The upper limit of the value calculated by the above mathematical formula 1 may be 1. In the above numerical range, an argyrodite peak may be present, but an impurity corresponding to a diffraction angle (2θ) of 28.5° to 29.5° may not be present.

[0087] In the present invention, the sulfide-based solid electrolyte may have a value calculated by the following mathematical formula 3 of 0.99 or more.

[0088] [Equation 3]

[0089] I O / (I O +I C )

[0090] In the above mathematical formula 3,

[0091] I O is the peak intensity that appears at a diffraction angle (2θ) of 24° to 25.65° when analyzing an X-ray diffraction pattern.

[0092] I C is the peak intensity that appears at a diffraction angle (2θ) of 33° to 35°.

[0093] The value calculated by the above mathematical formula 3 is the intensity of the argyrodite peak (I O ) and impurity peak (I C ) shows the relationship with the century. When the argyrodite peak exists and the impurity peak does not exist, the value calculated by mathematical expression 3 becomes 1.

[0094] In the present invention, the value calculated by the above mathematical formula 3 may be 0.992 or more, 0.994 or more, 0.996 or more, 0.998 or more, 0.999 or more, or 1. The upper limit of the value calculated by the above mathematical formula 3 may be 1. In the above numerical range, an argyrodite peak may be present, but an impurity corresponding to a diffraction angle (2θ) of 33° to 35° may not be present.

[0095] The sulfide-based solid electrolyte of the present invention may have a process window parameter calculated by the following mathematical expression 4 of 100°C or higher.

[0096] [Equation 4]

[0097] △T=T H -T L

[0098] In mathematical formula 4,

[0099] T H is the heat treatment process temperature of the sulfide-based solid electrolyte, and is the maximum value of the heat treatment temperature that satisfies at least one of the first to third properties.

[0100] T L is the heat treatment process temperature of a sulfide-based solid electrolyte, and is the minimum value of the heat treatment temperature that satisfies at least one of the first to third properties.

[0101] First property: Condition where the ionic conductivity at 22℃ is 6 mS / cm or more

[0102] Second property: Condition where the average crystal grain size is 200 nm or more

[0103] Third property: Condition not containing impurities

[0104] In the present invention, the process window parameter calculated by the above mathematical expression 4 is obtained by manufacturing a solid electrolyte by changing the heat treatment temperature of the sulfide-based solid electrolyte, measuring and comparing the properties of the manufactured solid electrolyte, and T at the boundary temperature satisfying the property parameters. H Wow T L It can be calculated from . The detailed method will be described later.

[0105] As the above process window parameters satisfy the numerical range, the solid electrolyte exhibits excellent ionic conductivity and a wider heat treatment temperature range than other solid electrolytes, preventing the formation of impurity phases. The wide heat treatment temperature range for producing high-quality solid electrolytes facilitates heat treatment temperature control during mass production, and reduces the possibility of producing low-quality solid electrolytes outside the heat treatment temperature range. This can be advantageous in terms of quality and yield during mass production.

[0106] In the present invention, the process window parameter calculated by the above mathematical formula 4 may be 100°C or higher. Preferably, it may be more than 100°C, 110°C or higher, 120°C or higher, 130°C or higher, or 140°C or higher. The larger the process window parameter, the wider the heat treatment temperature range for excellent physical properties, so the upper limit is not particularly limited, but may be 200°C or lower or 180°C or lower.

[0107] In the present invention, the T H satisfies the above first property.

[0108] In the present invention, the T H satisfies the above second property.

[0109] In the present invention, the T H satisfies the above third property.

[0110] In the present invention, the T H Satisfies the first to third properties above.

[0111] In the present invention, the T L satisfies the above first property.

[0112] In the present invention, the T L satisfies the above second property.

[0113] In the present invention, the T L satisfies the above third property.

[0114] In the present invention, the T L Satisfies the first to third properties above.

[0115] The conventional heat treatment temperature range varies depending on the doping concentration of the halogen element, and the higher the doping concentration, the smaller the value tends to be. However, in the present invention, by appropriately controlling the composition ratio (doping concentration) of the halogen elements Cl and Br and the molar ratio of lithium and the halogen element, a high-quality sulfide-based solid electrolyte having high ionic conductivity and containing no impurities can be obtained even under a wide range of heat treatment temperature conditions.

[0116] In the present invention, the sulfide-based solid electrolyte may have an ionic conductivity of 6 mS / cm or more at 22°C. Preferably, it may be 7 mS / cm or more, 8 mS / cm or more, 8.7 mS / cm or more, 9 mS / cm or more, 10 mS / cm or more, 10.5 mS / cm or more, 11 mS / cm or more, or 12 mS / cm or more. The upper limit is not particularly limited, but may be 50 mS / cm or less. Within the above numerical range, the solid electrolyte may have a lithium ion conductivity sufficient for the operation of the lithium battery. The measurement temperature of 22°C may refer to the ambient temperature in the measurement environment. Meanwhile, the ionic conductivity may be measured under a relative humidity of 0.7%.

[0117] In the present invention, the sulfide-based solid electrolyte has a lithium ion conductivity sufficient for the operation of a lithium battery at room temperature, i.e., 22°C, and specifically, has an ion conductivity of 6.0 mS / cm or more and 15.0 mS / cm or less. According to one embodiment, the sulfide-based solid electrolyte of the present invention has an ion conductivity of 6 mS / cm or more, and when the heat treatment temperature is 500°C, has an ion conductivity of 8.0 mS / cm or more and 8.5 mS / cm or more. In addition, it has an ion conductivity of 6 mS / cm or more in a wide heat treatment temperature range of 300°C to 600°C. In this case, the ion conductivity refers to the ion conductivity after induction grinding of the heat-treated powder, and may refer to the ion conductivity of the solid electrolyte before performing an ultra-fine grinding process for particle size control.

[0118] The above ionic conductivity is derived from the resistance value of the Nyquist plot obtained by measuring the AC impedance from 1 Hz to 7 MHz with an amplitude of 10 mV while pressurizing 370 MPa to sufficiently densify the electrolyte structure by injecting 0.15 g of a sulfide-based solid electrolyte into a 13ф SUS mold and then slowly lowering the pressure to maintain it at 100 MPa. All measurements are performed in a drying room at a temperature of 22°C and a relative humidity of 0.7%.

[0119] The present invention comprises the steps of preparing a mixture by mixing a lithium-containing compound, a phosphorus-containing compound, a sulfur-containing compound, a chlorine-containing compound, and a bromine-containing compound; and

[0120] A method for producing the above-described sulfide-based solid electrolyte is provided, including a step of heat-treating the above mixture.

[0121] In the present invention, the step of heat treating the mixture is performed at a maximum heat treatment temperature (T H ) and minimum heat treatment temperature (T L ) is composed of the process window parameter (△T = T H -T L ) is performed within the heat treatment temperature range, and the process window parameter may be 100°C or higher.

[0122] The method for manufacturing a sulfide-based solid electrolyte of the present invention has a wide process window. A wide process window means that the range of process variable combinations that can maintain excellent physical properties of the manufactured sulfide-based solid electrolyte is wide.

[0123] The method for manufacturing a sulfide-based solid electrolyte of the present invention is characterized by a wide process window corresponding to the heat treatment temperature, and the process window is a maximum heat treatment temperature (T H ) and minimum heat treatment temperature (T L ) difference value (△T=T H -T L) can be expressed as a process window parameter.

[0124] As will be described later, the maximum heat treatment temperature refers to the highest heat treatment temperature within the range where the properties of the sulfide-based solid electrolyte being manufactured are maintained, and the minimum heat treatment temperature refers to the lowest heat treatment temperature within the range where the properties of the sulfide-based solid electrolyte being manufactured are maintained. Heat treatment temperature is an important factor affecting the crystallization of the sulfide-based solid electrolyte, and is a factor that is difficult to control during large-scale processing.

[0125] The conventional method for manufacturing a sulfide-based solid electrolyte had a narrow process window, which required excessive effort and trial and error to maintain the temperature within a narrow range during the heat treatment process. In addition, there was a problem in that the properties of the manufactured sulfide-based solid electrolyte deteriorated when the process window was exceeded.

[0126] In the present invention, the range of process window parameters in which excellent physical properties are maintained is wide, and by setting the maximum and minimum heat treatment temperatures known in advance, there is an effect of minimizing trial and error that may require changing the temperature during a large-scale process.

[0127] In the present invention, the process window parameter may be 100°C or higher. Preferably, it may be more than 100°C, 110°C or higher, 120°C or higher, 130°C or higher, or 140°C or higher. The larger the process window parameter, the wider the heat treatment temperature range with excellent physical properties, so the upper limit is not particularly limited, but may be 300°C or lower or 200°C or lower. In the above numerical range, it is possible to manufacture a sulfide-based solid electrolyte with excellent physical properties even in a wide temperature range, which has an advantageous effect for large-scale processes.

[0128] In the present invention, the method for manufacturing the sulfide-based solid electrolyte is the maximum heat treatment temperature (T H ) is determined in advance; the minimum heat treatment temperature (T L) step of pre-determining the temperature; and a step of pre-setting the maximum heat treatment temperature and the minimum heat treatment temperature in the step of heat-treating the mixture. In this case, the maximum heat treatment temperature (T) may be set in advance before a large-scale process for manufacturing the final sulfide-based solid electrolyte. H ) and minimum heat treatment temperature (T L ) and by setting each heat treatment temperature to the process equipment, unnecessary repetitive work can be minimized and the preparatory work required for a large-scale process can be completed at low cost and high efficiency. At this time, the step of pre-setting the maximum heat treatment temperature and the minimum heat treatment temperature may be pre-setting the operating temperature of the heat treatment equipment used in the step of heat-treating the mixture.

[0129] The above maximum heat treatment temperature (T H ) and the step of pre-determining the minimum heat treatment temperature (T L ) Each step of pre-determining can use a sample mixture.

[0130] In the present invention, the sample mixture is distinct from the mixture used in the heat treatment step described above, and is used to determine the maximum and minimum heat treatment temperatures. That is, the sample mixture may be present in a smaller amount than the original mixture. For example, the amount may be 10% or less or 1% or less.

[0131] In the present invention, the maximum heat treatment temperature (T H ) is a step of preparing a sample mixture by mixing a lithium-containing compound, a phosphorus-containing compound, a sulfur-containing compound, a chlorine-containing compound and a bromine-containing compound; starting from the initial heat treatment temperature (T0), the heat treatment temperature is set to T X A step of repeating increasing the temperature by n times; a step of determining whether the property parameters are satisfied for each round (n1); a temperature (T) when the property parameters are not satisfied for the first time F) measuring step; and the T F In T X The value minus the maximum heat treatment temperature (T H ) includes a step of determining the temperature. For example, the initial heat treatment temperature (T0) is 400℃ to 20℃ (T X ) was repeatedly increased in steps of 520℃ to determine whether the parameters were satisfied. As a result, the maximum heat treatment temperature (T) was set to 520℃ for the 6th time (n1) when the physical property parameters were not satisfied for the first time. H ) becomes 520℃-20℃=500℃.

[0132] In the present invention, the minimum heat treatment temperature (T L ) is a step of preparing a sample mixture by mixing a lithium-containing compound, a phosphorus-containing compound, a sulfur-containing compound, a chlorine-containing compound and a bromine-containing compound; starting from the initial heat treatment temperature (T0), the heat treatment temperature is set to T X A step of repeating the process of reducing the temperature by n2 times; a step of determining whether the property parameters are satisfied for each round (n2); a temperature (T) when the property parameters are not satisfied for the first time I ) measuring step; and the T I In T X The minimum heat treatment temperature (T) is the value added L ) includes a step of determining the temperature. For example, the initial heat treatment temperature (T0) is 400℃ to 20℃ (T X ) and determine whether the parameters are satisfied by repeatedly reducing the temperature by 340℃. If the physical property parameters are not satisfied for the first time at the third time (n2), the minimum heat treatment temperature (T L ) becomes 340℃+20℃=360℃.

[0133] In the present invention, the initial heat treatment temperature (T0) may be any process starting temperature, and may refer to a heat treatment temperature that satisfies at least one of the first to third properties described below. The initial heat treatment temperature (T0) may be selected from a temperature range of 300°C to 600°C. For example, it may be 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, or 520°C.

[0134] In the present invention, T X is the heat treatment temperature interval between each round (n), and can be selected considering the number of processes. Preferably, it can be 10°C, 15°C, or 20°C.

[0135] In the present invention, n1 and n2 each represent the number of times the heat treatment temperature is changed, and may be 1 to 20 times.

[0136] In the present invention, the step of heat-treating the mixture includes a step of pre-setting the maximum heat-treatment temperature and the minimum heat-treatment temperature. In this case, the heat-treatment temperature is the maximum heat-treatment temperature (T H ) and minimum heat treatment temperature (T L ) can be maintained within the range. The above step may be to preset the maximum heat treatment temperature value and the minimum heat treatment temperature value in the equipment used for heat treatment.

[0137] In the present invention, the manufactured sulfide-based solid electrolyte can satisfy at least one of the following first to third properties under all heat treatment temperature conditions corresponding to the process window parameters.

[0138] First property: Condition where the ionic conductivity at 22℃ is 6 mS / cm or more

[0139] Second property: Condition where the average crystal grain size is 200 nm or more

[0140] Third property: Condition not containing impurities

[0141] In the present invention, satisfying a specific property under all heat treatment temperature conditions corresponding to the process window parameter means the maximum heat treatment temperature (T H ) and minimum heat treatment temperature (T L ) means that a sulfide-based solid electrolyte manufactured under any heat treatment temperature condition selected within the range satisfies the above properties, and that a sulfide-based solid electrolyte that does not satisfy the properties does not exist.

[0142] In the present invention, the process window parameter may be a value calculated by the following mathematical expression 4.

[0143] [Equation 4]

[0144] △T=T H -T L

[0145] In mathematical formula 4,

[0146] T H is the maximum value of the heat treatment temperature at which the sulfide-based solid electrolyte manufactured during the heat treatment step of the above mixture satisfies at least one of the first to third properties below,

[0147] T L is the minimum value of the heat treatment temperature at which the sulfide-based solid electrolyte manufactured during the heat treatment step of the above mixture satisfies at least one of the first to third properties below.

[0148] First property: Condition where the ionic conductivity at 22℃ is 6 mS / cm or more

[0149] Second property: Condition where the average crystal grain size is 200 nm or more

[0150] Third property: Condition not containing impurities

[0151] In the present invention, the first to third properties may each be named as property parameters.

[0152] In the present invention, the maximum heat treatment temperature (T H ) and minimum heat treatment temperature (T L ) is a boundary condition for configuring the above process window parameters, and can satisfy any one of the first to third properties, respectively.

[0153] In the present invention, the T H satisfies the above first property.

[0154] In the present invention, the T H satisfies the above second property.

[0155] In the present invention, the T H satisfies the above third property.

[0156] In the present invention, the T H satisfies the first and second properties above.

[0157] In the present invention, the T H Satisfies the first to third properties above.

[0158] In the present invention, the T L satisfies the above first property.

[0159] In the present invention, the T L satisfies the above second property.

[0160] In the present invention, the T L satisfies the above third property.

[0161] In the present invention, the T L satisfies the first and second properties above.

[0162] In the present invention, the T L Satisfies the first to third properties above.

[0163] In the present invention, the process window parameter satisfying the first property may be 110°C or higher. Preferably, it may be 120°C or higher, 130°C or higher, 130°C or higher, or 140°C or higher.

[0164] In the present invention, the process window parameter (△T=T) satisfying the second property H -T L ) may be 110°C or higher. Preferably, it may be 120°C or higher, 130°C or higher, 130°C or higher, or 140°C or higher.

[0165] In the present invention, the first physical property may be applied to the ionic conductivity described below. Specifically, the ionic conductivity at 22°C may be 6 mS / cm or more. Preferably, it may be 7 mS / cm or more, 8 mS / cm or more, 8.7 mS / cm or more, 9 mS / cm or more, 10 mS / cm or more, 10.5 mS / cm or more, 11 mS / cm or more, or 12 mS / cm or more. The upper limit is not particularly limited, but may be 50.0 mS / cm or less. Within the above numerical range, the lithium ion conductivity sufficient for the operation of the lithium battery may be provided. The measurement temperature of 22°C may refer to the ambient temperature in the measurement environment. Meanwhile, the ionic conductivity may be measured under a relative humidity of 0.7%.

[0166] In the present invention, the second property may be applied to the average crystal grain size described below.

[0167] In the present invention, the third property may be applied to the impurities described below. Specifically, the contents of mathematical formulas 1 to 3 may be applied.

[0168] In the present invention, the maximum heat treatment temperature (T H ) can be 580℃, 570℃, 560℃, 550℃, 540℃, 530℃, 520℃, 510℃ or 500℃.

[0169] In the present invention, the minimum heat treatment temperature (T L ) can be 300°C, 320°C, 340°C, 360°C, 380°C, 420°C, 460°C or 480°C. The heat treatment temperature can be the temperature of the atmosphere inside the heat treatment equipment where the process is performed or the temperature of the surface of the mixture to which the heat treatment is applied, and can be identified through the numerical value displayed on the temperature controller attached to the heat treatment equipment.

[0170] In the present invention, the step of heat-treating the mixture is a step of heat-treating the mixture to have an argyrodite-type crystal structure. The step of heat-treating the mixture can be performed within a temperature range in which the sulfide-based solid electrolyte has an argyrodite-type crystal structure.

[0171] In the present invention, the heat treatment step of the mixture may be performed for 1 to 20 hours. Preferably, it may be performed for 3 to 16 hours or 5 to 13 hours. Within the above numerical range, the material is not damaged and the argyrodite crystal structure can be easily formed.

[0172] In the present invention, the step of heat-treating the mixture may be performed in an inert atmosphere. Specifically, the inert atmosphere may be an Ar atmosphere, an N2 atmosphere, an H2S atmosphere, a vacuum atmosphere, or a combination thereof.

[0173] The method for producing a sulfide-based solid electrolyte of the present invention includes a step of producing a mixture by mixing a lithium-containing compound, a phosphorus-containing compound, a sulfur-containing compound, a chlorine-containing compound, and a bromine-containing compound.

[0174] In the present invention, the lithium-containing compound may include lithium compounds such as lithium sulfide (Li2S), lithium oxide (Li2O), lithium carbonate (Li2CO3), or lithium metal compounds.

[0175] In the present invention, the phosphorus-containing compound may include, for example, phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5), phosphorus compounds such as sodium phosphate (Na3PO4), and phosphorus single particles.

[0176] In the present invention, the sulfur-containing compound may include sulfur (S8), lithium sulfide or phosphorus sulfide.

[0177] In the present invention, each of the chlorine-containing compound and the bromine-containing compound may be a compound represented by QX. At this time, Q may be Li, P, S, Sb, Si, Ge, Sn, Cu, Ag, Mg, Ca, Al, As, Na, K, and Ga, or an oxygen element or sulfur element combined with these elements, and X is Cl or Br.

[0178] In the present invention, the chlorine-containing compound may include LiCl, PCl3, PCl5, POCl3, P2Cl4, SCl2, S2Cl2, SbCl3, SbCl5, SiCl4, SiCl3, Si2Cl6, SiBrCl3, SiBr2Cl2, GeCl4, GeCl2, SnCl4, SnCl2, CuCl2, CuCl3, AgCl, MgCl, MgCl2, MgCl3, CaCl2, AlCl, AlCl2, AlCl3, AsCl3, NaCl, NaCl2, NaCl3, Na3Cl2, KCl, KCl2, KCl3, GaCl2, GaCl3, GaCl5, etc. Preferably, it is LiCl, PCl5, PCl3, etc., and more preferably, it is LiCl.

[0179] In the present invention, the bromine-containing compound may include LiBr, PBr3, POBr3, S2Br2, SbBr3, SiBr4, SiBrCl3, SiBr2Cl2, GeBr4, GeBr2, SnBr4, SnBr2, CuBr2, AgBr, MgBr, MgBr2, MgBr3, CaBr2, AlBr3, AsBr3, NaBr, KBr, KBr2, KBr3, GaBr3, etc. Preferably, it is LiBr, PBr5 and PBr3, and more preferably, it is LiBr and PBr3.

[0180] In the present invention, the mixture may further include an M-containing compound. At this time, M may be at least one selected from Sb, Si, Ge, Sn, Cu, Ag, Mg, Ca, Al, As, Na, K, and Ga.

[0181] In the present invention, the M-containing compound may be a compound in which oxygen element, sulfur element, or halogen element (Cl, Br) is combined with Sb, Si, Ge, Sn, Cu, Ag, Mg, Ca, Al, As, Na, K, and Ga or these elements.

[0182] In the present invention, the M-containing compound may be a sulfide containing one or more elements selected from the group consisting of Sb, Si, Ge, Sn, Cu, Ag, Mg, Ca, Al, As, Na, K, and Ga. For example, it may be one of Sb2S3, SiS2, GeS2, SnS2, CuS2, AgS2, MgS, CaS, Al2S3, As2S3, Na2S, K2S, and Ga2S3.

[0183] In the present invention, the content ratio of the lithium-containing compound, phosphorus-containing compound, sulfur-containing compound, chlorine-containing compound, and bromine-containing compound can be variously adjusted depending on the molar ratio of the sulfide-based solid electrolyte to be finally manufactured, and is not particularly limited in the present invention.

[0184] In the present invention, the step of preparing a mixture by mixing the lithium-containing compound, the phosphorus-containing compound, the sulfur-containing compound, the chlorine-containing compound, and the bromine-containing compound may be performed by a grinding and mixing process. Specifically, the grinding and mixing may be performed while applying mechanical energy, such as by a bead mill, a planetary ball mill, a planetary mill, a mechanofusion mill, a mortar, or an auto grinder. If necessary, a non-polar organic solvent, such as toluene, xylene, heptane, octane, or anisole, may be added. The material of the ball used for the grinding and mixing is not particularly limited, and examples thereof include alumina balls, zirconia balls, stainless steel balls, silicon nitride balls, and tungsten carbide balls.

[0185] In the present invention, when a planetary ball mill is used as a pulverizing device, the rotation speed may be 100 rpm to 2,000 rpm for 1 to 50 hours, but is not limited thereto. Preferably, 10 mm zirconia balls are placed in the planetary ball mill, pulverized at a speed of 400 rpm to 700 rpm, and then further pulverized using a mortar or auto grinder.

[0186] In the present invention, the step of heat-treating the mixture is a step of heat-treating the mixture to have an argyrodite-type crystal structure. The step of heat-treating the mixture can be performed within a temperature range in which the sulfide-based solid electrolyte has an argyrodite-type crystal structure.

[0187] In the present invention, the step of heat treating the mixture is performed at a maximum heat treatment temperature (T H ) and minimum heat treatment temperature (T L) is performed under the conditions, and the maximum heat treatment temperature may be 600°C or less, and the minimum heat treatment temperature may be 300°C or more. Specifically, the minimum heat treatment temperature and the maximum heat treatment temperature are preset temperatures during the process, and the heat treatment temperature may be performed while maintaining a temperature included in the range of the minimum heat treatment temperature and the maximum heat treatment temperature. The T H Wow T L is as described above.

[0188] In the present invention, the heat treatment temperature of the step of heat treating the mixture is the maximum heat treatment temperature (T H ) and the minimum heat treatment temperature (T L ) can be performed within the range. For example, the maximum heat treatment temperature (T H ) is 580°C, and when the minimum heat treatment temperature is 300°C, it can be performed within a temperature range of 300°C to 580°C.

[0189] The heat treatment temperature in the step of heat treating the above mixture is the maximum heat treatment temperature (T H ) and minimum heat treatment temperature (T L ) If maintained within the range, a high-quality sulfide-based solid electrolyte with excellent ionic conductivity and no impurities can be obtained.

[0190] The method for manufacturing a sulfide-based solid electrolyte according to the present invention has a wide heat treatment temperature range for manufacturing a high-quality solid electrolyte, so that the heat treatment temperature can be easily controlled during mass production, thereby improving the process window and ensuring excellent quality and yield.

[0191] In the present invention, the heat treatment step of the mixture may be performed for 1 to 20 hours. Preferably, it may be performed for 3 to 16 hours or 5 to 13 hours. Within the above numerical range, the material is not damaged and the argyrodite crystal structure can be easily formed.

[0192] In the present invention, the step of heat-treating the mixture may be performed in an inert atmosphere. Specifically, the inert atmosphere may be an Ar atmosphere, an N2 atmosphere, an H2S atmosphere, a vacuum atmosphere, or a combination thereof.

[0193] The method for producing a sulfide-based solid electrolyte of the present invention may include, after the step of heat-treating the mixture, a step of crushing the heat-treated product, a step of classifying the heat-treated product, or a combination thereof. The sulfide-based solid electrolyte produced through the heat treatment is further subjected to subsequent processes of crushing and / or classifying.

[0194] In the present invention, the step of grinding the heat-treated material may be performed using either a dry grinding method or a wet grinding method. Specifically, more than one of them may be used, and they may be mixed and used, or the process may be performed two or more times.

[0195] In the present invention, the device used for the pulverization is not particularly limited as long as the purpose of the present invention is achieved. For example, media-type pulverization such as a bead mill or a planetary ball mill, jet pulverization, cavitation pulverization, etc. can be used. Among these, a bead mill or a planetary ball mill is preferred. The pulverization conditions can be set so as to pulverize the solid electrolyte into a desired particle size.

[0196] In the present invention, the dry grinding is performed by introducing the sulfide-based solid electrolyte particles to be ground in a dry state into a device such as a ball mill as described above. Wet grinding is performed by dispersing the sulfide-based solid electrolyte particles in an organic solvent and grinding them in a slurry state.

[0197] In the present invention, the organic solvent usable for the wet grinding is at least one of aliphatic organic solvents such as heptane, decane, hexane, and cyclohexane; and aromatic organic solvents such as toluene, xylene, 1,2,4-trimethylbenzene, anisole, dimethoxybenzene, chlorobenzene, ethyl benzoate, and benzyl acetate. At this time, the slurry concentration for wet grinding is preferably in the range of 2 to 60 wt% in terms of solid content, and more preferably in the range of 10 to 50 wt%.

[0198] In the present invention, the step of classifying the heat-treated material can be performed after the step of crushing the heat-treated material.

[0199] In the present invention, if the pulverizing step is wet pulverization, the organic solvent is removed through a drying process before the pulverized material is classified, and if necessary, a solid-liquid separation process such as filtration, centrifugation, pressure filtration, or reduced pressure filtration may be further performed before the drying to separate the solid electrolyte particles and the organic solvent.

[0200] The present invention provides an all-solid-state battery comprising a positive electrode; a negative electrode; and a solid electrolyte layer provided between the positive electrode and the negative electrode, wherein the positive electrode or the solid electrolyte layer includes the above-described sulfide-based solid electrolyte.

[0201] Specifically, the all-solid-state battery comprises a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and a solid electrolyte layer disposed between the positive electrode and the negative electrode. In this case, the sulfide-based solid electrolyte according to the present invention can be introduced into at least one layer of the positive electrode or the solid electrolyte layer.

[0202] In the present invention, by controlling the composition of the halogen element of the sulfide-based solid electrolyte and the molar ratio with the lithium element, the solid electrolyte can have high ionic conductivity, so that when an all-solid-state battery is manufactured using the solid electrolyte, battery performance can be improved.

[0203] The all-solid-state battery of the present invention can be manufactured according to conventional methods known in the art. For example, it can be manufactured by laminating and pressurizing a solid electrolyte layer so that it exists between the positive and negative electrodes. At this time, the solid electrolyte layer can be adjusted to various thicknesses by controlling the performance of the all-solid-state battery and various process variables. Preferably, the thickness can be 1 to 10 mm, and more preferably, it can have a thickness of 3 to 4 mm.

[0204] In the present invention, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector.

[0205] The above-mentioned positive electrode active material layer includes a positive electrode active material, a binder, a conductive material, and a solid electrolyte. The positive electrode can be manufactured by coating a positive electrode slurry including a positive electrode active material, a binder, a conductive material, a solid electrolyte, and a solvent on a positive electrode current collector, or in the form of a dry electrode that does not include a solvent.

[0206] The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the bonding strength of the positive electrode active material may be strengthened by forming fine irregularities on the surface, and may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0207] The above positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically may include a lithium metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, or aluminum.

[0208] More specifically, the lithium metal oxide is a lithium-manganese oxide (e.g., LiMnO2, LiMn2O4, etc., LMO), a lithium-cobalt oxide (e.g., LiCoO2, etc., LCO), a lithium-nickel oxide (e.g., LiNiO2, etc., LNO), a lithium-nickel-manganese oxide (e.g., LiNi 1-Y Mn Y O2 (here, 0 <Y<1), LiMn 2-z NizO4 (where 0<Z<2), LNMO), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y 1O2(here, 0 <Y1<1) 등, NC), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2 (here, 0 <Y2<1), LiMn 2-z1 Co z1 O4 (wherein, 0<Z1<2), etc., NCM), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r1 )O2(wherein, 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) or Li(Ni p1 Co q1 Mn r2 )O4 (wherein, 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2), etc., NCM), or lithium-nickel-cobalt-transition metal (M) oxides (e.g., Li(Ni p2 Co q2 Mn r3 M S2 )O2 (wherein, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r3 and s2 are atomic fractions of independent elements, respectively, 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, p2+q2+r3+s2=1), etc.), and lithium-phosphate-iron oxide (e.g., Li (3-t) Fe2(PO4)3(0≤t≤2), Liw Examples include FePO4(0.90≤w≤1.8), LFP, etc.

[0209] The above 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 Mn02Co02)O2, Li(Ni 0.5 Mn 0.3 Co02)O2, Li(Ni07Mn0 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.) are more preferable in that they can increase the capacity characteristics and stability of the battery.

[0210] The above lithium composite metal oxide is Li(Ni 0.6 Mn 0.2 Co02)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. is more preferable in that the improvement effect is excellent according to the control of the type and content ratio of the constituent elements forming the lithium composite metal oxide.

[0211] The above positive electrode active material may be included in an amount of 60 wt% to 99 wt%, preferably 65 wt% to 99 wt%, and more preferably 70 wt% to 98 wt%, based on the total weight of the solid content excluding the solvent in the positive electrode slurry.

[0212] The above solid electrolyte may use at least one selected from a polymer-based solid electrolyte, a sulfide-based solid electrolyte, and an oxide-based solid electrolyte. According to one specific example of the present invention, the solid electrolyte uses a sulfide-based solid electrolyte.

[0213] When the sulfide-based solid electrolyte of the present invention is used in the positive electrode, side reactions between the positive electrode active material and the solid electrolyte can be suppressed, thereby preventing a decrease in ionic conductivity due to the side reactions.

[0214] The solid electrolyte may be included in an amount of 1 wt% to 45 wt%, preferably 1 wt% to 40 wt%, and more preferably 5 wt% to 30 wt%, based on the total weight of the solid content excluding the solvent in the positive electrode slurry.

[0215] The above binder is a component that helps bond between the conductive material, the active material, and the current collector. 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.

[0216] Typically, the binder may be included 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 the solid content excluding the solvent in the positive electrode slurry.

[0217] The above-mentioned conductive agent is a component for further improving the conductivity of the positive electrode active material.

[0218] The conductive material is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and 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 fibers or metal fibers; metal powders such as fluorinated carbon, aluminum, and nickel powders; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can be used.

[0219] Typically, the conductive agent may be included 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 excluding the solvent in the positive electrode slurry.

[0220] The solvent may be at least one of aliphatic organic solvents such as heptane, decane, hexane, and cyclohexane; aromatic organic solvents such as toluene, xylene, 1,2,4-trimethylbenzene, anisole, dimethoxybenzene, chlorobenzene, ethyl benzoate, and benzyl acetate; and ester solvents such as isobutyl propionate, isoamyl propionate, isobutyl butyrate, and ethyl 2-methylbutyrate. In addition, the solvent may be used in an amount that provides a desirable viscosity when including the positive electrode active material and optionally a binder and a conductive material. For example, the solvent may be included so that the concentration of the solid content 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%.

[0221] The negative electrode can be manufactured, for example, by coating a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, and a solvent on a negative electrode current collector, or a graphite electrode made of carbon (C), an electrode containing silver nanoparticles and carbon black, or lithium metal itself can be used as the negative electrode.

[0222] For example, when manufacturing a negative electrode by coating a negative electrode slurry on the negative electrode current collector, the negative electrode current collector generally has a thickness of 3 to 500 μm. The negative electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, like the positive electrode current collector, the bonding strength of the negative electrode active material can be strengthened by forming fine unevenness on the surface, and can be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc.

[0223] The negative electrode active material may include one or more negative electrode active materials selected from the group consisting of silver nanoparticles; natural graphite, artificial graphite, carbonaceous materials; lithium-containing titanium composite oxide (LTO); Si, SiOx, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe metals (Me); alloys composed of the metals (Me); oxides (MeOx) of the metals (Me); and complexes of the metals (Me) and carbon. Specifically, the negative electrode active material may be a silicon-based negative electrode active material including silicon (Si), silicon oxide (SiOx) or a silicon alloy. Preferably, the negative electrode active material may be a mixture containing silver nanoparticles and carbon black.

[0224] The above negative electrode active material may be included in an amount of 60 wt% to 99 wt%, preferably 70 wt% to 99 wt%, and more preferably 80 wt% to 98 wt%, based on the total weight of solids excluding the solvent in the negative electrode slurry.

[0225] The above binder is a component that helps bond between the conductive material, the active material, and the current collector. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof. Polyvinylidene fluoride is preferably used.

[0226] Typically, the binder may be included 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 excluding the solvent in the slurry for the negative electrode.

[0227] The above conductive agent is a component for further improving the conductivity of the negative electrode active material. The conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite or 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 or metal fiber; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0228] The above-mentioned conductive agent may be included 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 excluding the solvent in the negative electrode slurry.

[0229] The solvent may include an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a desirable viscosity when including the negative electrode active material and optionally a binder and a conductive material. For example, the solvent may be included so that the concentration of the solid content 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%.

[0230] When using the metal itself as the above-mentioned cathode, it can be manufactured by physically bonding, rolling, or depositing the metal onto the metal thin film itself or the cathode current collector. The deposition method can use an electrical deposition method or a chemical vapor deposition method.

[0231] For example, the metal to be bonded / rolled / deposited on the metal thin film itself or the negative electrode current collector may include one metal selected from the group consisting of lithium (Li), nickel (Ni), tin (Sn), copper (Cu), and indium (In), or an alloy of two metals.

[0232] The manufacture of an all-solid-state battery having the above-described configuration is not particularly limited in the present invention, and a known method can be used.

[0233] When manufacturing the all-solid-state battery of the present invention, electrodes including a positive electrode and a negative electrode are placed and then pressure-molded to assemble the battery.

[0234] The assembled battery is then installed in an outer packaging material and sealed by heat pressing, etc. As the outer packaging material, a laminate pack made of aluminum, stainless steel, etc., or a cylindrical or square metal container is highly suitable.

[0235] As described above, the all-solid-state battery according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0236] Hereinafter, the present invention will be described in more detail by way of examples. However, the scope of the present invention is not limited to these examples.

[0237] <Examples and Comparative Examples>

[0238] <Example 1>

[0239] As raw material powders, Li2S, P2S5, LiCl, and LiBr were prepared in a molar ratio of 2.1:0.5:1:0.4 according to the composition, placed in a ZrO2 container together with 10 mm ZrO2 balls (5 times the total amount of precursors), and mixed 24 times at 600 rpm for 20 minutes each using a planetary ball mill, and then the resultant was obtained from the container and coarsely ground for 10 minutes using an autogrinder.

[0240] Next, the solid electrolyte was placed in an Ar atmosphere furnace and heat treated at 500°C for 12 hours to obtain an argyrodite-type sulfide-based solid electrolyte.

[0241] <Examples 2 to 5 and Comparative Examples 1 to 3>

[0242] A sulfide-based solid electrolyte was manufactured using the same method as Example 1, except that the content of raw material powder and the heat treatment temperature were changed as shown in Table 1 below.

[0243] Comparative Example 4

[0244] As raw material powders, Li2S, P2S5, LiCl, and LiBr were prepared in a molar ratio of 2.1:0.5:1:0.4 according to the composition, placed in a ZrO2 container together with 3 mm ZrO2 balls, and mixed 24 times at 300 rpm for 20 minutes each using a planetary ball mill, and then the resultant was obtained from the container and coarsely ground for 10 minutes using an autogrinder.

[0245] Next, the solid electrolyte was placed in an Ar atmosphere furnace and heat treated at 400°C for 1 hour to obtain an argyrodite-type sulfide-based solid electrolyte.

[0246] Molar ratio Chemical formula Heat treatment temperature (℃) Li2SP2S5LiClLiBr(d+e) / ae / dExample 1Li 5.6 PS 4.6 ClBr 0.4 5002.10.51.00.40.250.4 Example 2Li 5.5 PS 4.5 ClBr 0.5 5002.00.51.00.50.2730.5 Example 3Li 5.5 PS 4.5 Cl 0.8 Br 0.7 5002.00.50.80.70.2730.875 Example 4Li 5.6 PS 4.6 Cl 0.8 Br 0.6 5002.10.50.80.60.250.75 Example 5Li 5.5 PS 4.5 Cl 1.2 Br 0.3 5002.00.51.20.30.2730.25 Comparative Example 1Li 5.4 PS 4.4 Cl 0.8 Br 0.8 5002.10.50.80.80.2961 Comparative Example 2Li 5.4 PS 4.4 Cl 1.0 Br 0.6 5202.10.51.00.60.2960.6 Comparative Example 3Li 5.4 PS 4.4 Cl 0.6 Br 1.05202.10.50.61.00.2961.667 Comparative Example 4Li 5.6 PS 4.6 ClBr 0.4 4002.10.510.40.250.4

[0247] <Experimental Example 1: Measurement of average grain size>

[0248] X-ray diffraction pattern: The sample was filled into a non-atmospheric holder for X-ray powder diffraction, and a Bruker D8 Endeavor XRD was used. X-rays were measured by scanning at a scanning speed of 0.3 s per 0.02° with Cu Kα (λ = 1.5406 Å), an applied voltage of 40 kV, and an applied current of 40 mA.

[0249] Average grain size: Estimated by Rietveld refinement calculation of X-ray diffraction patterns. Rietveld refinement calculations were performed using TOPAS, a Bruker XRD analysis program, and a lower factor was reflected to account for instrumental peak broadening caused by the Bruker D8-Endeavor (Cu source), the measuring instrument.

[0250] 1. X-ray beam divergence (0.5 degrees)

[0251] 2. Detector type and size (1-D PSD, measurement area: 4.1 degrees)

[0252] 3. Full axial method among axial convolutions

[0253] <Experimental Example 2: X-ray Diffraction Pattern Analysis>

[0254] An X-ray diffraction pattern diagram was derived in the same manner as Experimental Example 1, and the presence and intensity of peaks corresponding to specific values ​​of 2θ were observed, and values ​​calculated using the following mathematical equations 1 to 3 were calculated.

[0255] FIGS. 1 to 3 are X-ray diffraction patterns of sulfide-based solid electrolytes manufactured in Examples 1 to 3, and FIGS. 4 and 5 are X-ray diffraction patterns of sulfide-based solid electrolytes manufactured in Comparative Examples 1 and 2.

[0256] The solid electrolytes manufactured in Examples 1 to 3 exhibited peaks at positions of the argyrodite-type crystal structure at diffraction angles (2θ) of 14° to 16°, 17° to 19°, 24° to 25.65°, 29.5° to 31°, 31° to 32°, and 44° to 46°.

[0257] In the solid electrolytes manufactured in Examples 1 to 3, no split peaks were found at diffraction angles (2θ) of 25.65° to 26.5° and 28.5° to 29.5° related to the impurity phase and peaks related to the argyrodite crystal structure.

[0258] On the other hand, the solid electrolytes manufactured in Comparative Examples 1 and 2 showed peak splitting such as doublets and triplets at 2θ = 24° to 25.65°, 29.5° to 31°, 31° to 32°, and 44° to 46°, which are argyrodite crystal peaks. That is, it was found that the sulfide-based solid electrolytes of Comparative Examples 1 and 2 included an impurity phase.

[0259] [Mathematical Formula 1]

[0260] I O / (I O +I A )

[0261] [Equation 2]

[0262] I O / (I O +I B )

[0263] [Equation 3]

[0264] I O / (I O +I C )

[0265] In the above mathematical equations 1 to 3,

[0266] I O is the peak intensity that appears at a diffraction angle (2θ) of 24° to 25.65° when analyzing an X-ray diffraction pattern.

[0267] I A is the peak intensity that appears at a diffraction angle (2θ) of 25.65° to 26.5°,

[0268] I B is the peak intensity that appears at a diffraction angle (2θ) of 28.5° to 29.5°,

[0269] I C is the peak intensity that appears at a diffraction angle (2θ) of 33° to 35°.

[0270] <Experimental Example 3: Ionic Conductivity Measurement>

[0271] In the Examples and Comparative Examples, 0.15 g of the sulfide-based solid electrolyte manufactured was injected into a 13ф SUS mold, pressurized to 370 MPa to sufficiently densify the electrolyte structure, and then the pressure was slowly lowered to maintain it at 100 MPa, and the AC impedance was measured at a measurement frequency of 1 Hz to 7 MHz with an amplitude of 10 mV, and the resistance value of the resulting Nyquist plot was derived. All measurements were performed in a drying room at a temperature of 22℃ and a relative humidity of 0.7%. At this time, the ionic conductivity refers to the ionic conductivity after induction grinding of the heat-treated powder, and means the ionic conductivity of the solid electrolyte before performing the ultra-fine grinding process for particle size control.

[0272] Classification Experimental Example 1 Experimental Example 2 Experimental Example 3 Examples and Comparative Examples Chemical Formula Unit: nm Mathematical Formula 1 Mathematical Formula 2 Mathematical Formula 3 Unit: mS / cm Example 1 Li 5.6 PS 4.6 ClBr 0.4 >300nm1118.5Example 2Li 5.5 PS 4.5 ClBr 0.5 >300nm11110.4Example 3Li 5.5 PS 4.5 Cl 0.8 Br0.7 230nm11112.5Example 4Li 5.6 PS 4.6 Cl 0.8 Br 0.6 >300nmNot measuredNot measuredNot measured9.5Example 5Li 5.5 PS 4.5 Cl 1.2 Br 0.3 >300nmNot measuredNot measuredNot measured10.1Comparative example 1Li 5.4 PS 4.4 Cl 0.8 Br 0.8 130nm0.8820.99215.8Comparative example 2Li 5.4 PS 4.4 Cl 1.0 Br 0.6 160 nm or less 0.89 2 0.99 0.98 8 5.4 Comparative example 3 Li 5.4 PS 4.4 Cl 0.6 Br 1.0 100 nm or less, not measured, not measured, not measured, 4.9, comparative example 4Li 5.6 PS 4.6 ClBr 0.4 180nm or less not measured not measured not measured 6.9

[0273] In Table 2 above, '>' means exceeding the corresponding value. For example, >300nm means exceeding 300nm.

[0274] From the above results, the sulfide-based solid electrolytes of Examples 1 to 5 having an average grain size of 200 nm or more exhibited excellent ionic conductivity. On the other hand, it was confirmed that the sulfide-based solid electrolytes of the comparative examples having an average grain size of less than 200 nm had low ionic conductivity.

[0275] In particular, it was confirmed that the sulfide-based solid electrolytes of Examples 1 to 3 did not contain impurities, and the sulfide-based solid electrolytes of Comparative Examples 1 and 2 contained impurities.

[0276] In addition, it was confirmed that the sulfide-based solid electrolyte of Example 3 had the largest average crystal grain size, no impurities, and the best ionic conductivity.

[0277] <Experimental Example 4: Experiment on changes in average grain size according to heat treatment temperature>

[0278] The optimization of the process for producing sulfide-based solid electrolytes is designed through modifications of various conditions. For example, the optimal heat treatment temperature for high ionic conductivity is influenced by the composition of the sulfide-based solid electrolyte. Furthermore, the heat treatment temperature changes grain size and influences the formation of impurity phases during the heat treatment process. Therefore, Experimental Examples 4 to 6 investigated the correlation between heat treatment temperature, ionic conductivity, grain size, and impurity phases.

[0279] Sulfide-based solid electrolytes of Examples 1 to 3 and Comparative Examples 1 to 3 were manufactured, and the heat treatment temperature was changed at intervals of 20°C. The average grain size of the manufactured sulfide-based solid electrolytes was measured, and the results are shown in Table 3 below. For example, the sulfide-based solid electrolyte according to Example 1 was manufactured, the average grain size was measured, and the same process was repeated by changing only the heat treatment temperature, and the results were recorded.

[0280] Classification Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 360℃~190nm~250nm~200nm~180nm--380℃~220nm~270nm~210nm~250nm~120nm~100nm 400℃~250nm~300nm~200nm>300nm~300nm250nm 420℃>300nm>300nm>300nm>300nm>300nm>300nm>300nm 440℃>300nm>300nm>300nm>300nm>300nm>300nm>30 0nm460℃>300nm>300nm~260nm>300nm>300nm>300nm480℃>300nm>300nm>300nm~120nm>300nm>300nm500℃>300nm >300nm~230nm~130nm~210nm~190nm520℃~290nm~280nm~110nm~80nm~160nm~100nm540℃>300nm~130nm--~190nm-

[0281] As shown in Table 3 above, the average crystal grain size of the sulfide-based solid electrolyte tends to increase as the heat treatment temperature increases, and rather tends to decrease above a certain temperature.

[0282] The sulfide-based solid electrolytes of Examples 1 to 3 exhibited a size of 200 nm or more, preferably 300 nm or more, in the range of 380°C to 540°C, or 360°C to 500°C. In comparison, the sulfide-based solid electrolytes of Comparative Examples 1 to 3 exhibited values ​​of less than 300 nm or less than 200 nm at a heat treatment temperature of 380°C. The sulfide-based solid electrolytes of Comparative Examples 1 to 3 exhibited a tendency for the heat treatment temperature to increase as the heat treatment temperature increased, but a rapid decrease in the crystal grain size was observed around 500°C.

[0283] <Experimental Example 5: Experiment on Changes in Ionic Conductivity According to Heat Treatment Temperature>

[0284] In the same manner as Experimental Example 4, the ionic conductivity (unit: mS / cm) according to the heat treatment temperature was measured and recorded in Table 4 below. Specifically, the temperature at which the ionic conductivity was maintained at 6 mS / cm or more was measured, and the maximum heat treatment temperature (T H ), minimum heat treatment temperature (T L ) and its difference (△T=T H -T L ) was recorded.

[0285] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3360℃5.76.16.54.9--380℃6.57.79.19.45.95.4400℃6.49.111.413.29.58.8420℃8.49.611.512.811.210.9440℃7.910.112.113.011.11 2460℃7.29.612.413.111.411.5480℃7.810.211.513.012.212.3500℃ 8.510.412.55.89.410520℃8.07.93.91.65.44.9540℃6.95.6--3.2-T H 540℃520℃500℃480℃500℃500℃T L 380℃360℃360℃380℃400℃400℃△T160℃160℃140℃100℃100℃100℃

[0286] Specifically, the sulfide-based solid electrolyte of Example 1 has a maximum heat treatment temperature (T) at which an ionic conductivity of 6 mS / cm or more is maintained. H ) is 540℃, and the minimum heat treatment temperature (T L ) is 380℃, so it was confirmed that the difference was 160℃.

[0287] On the other hand, the sulfide-based solid electrolyte of Comparative Example 1 has a maximum heat treatment temperature (T) at which an ionic conductivity of 6 mS / cm or more is maintained. H ) is 480℃, and the minimum heat treatment temperature (T L) was 380℃, it was confirmed that the difference was 100℃. The temperature was measured and recorded in the same way in the sulfide-based solid electrolytes of the remaining examples and comparative examples.

[0288] From the above results, it was confirmed that the sulfide-based solid electrolyte of the example according to the present invention was able to secure high ionic conductivity over a wide heat treatment temperature range. In particular, it was confirmed that the heat treatment temperature range having an ionic conductivity of 6 mS / cm or more was identical to the heat treatment temperature range having an average grain size of 200 nm or more in Experimental Example 4.

[0289] Through the above results, it was found that the sulfide-based solid electrolyte of the present invention has a wide heat treatment temperature range capable of securing the average grain size and ionic conductivity, and consequently, the process window can be widened.

[0290] <Experimental Example 6: Experiment to Confirm Impurity Phase According to Heat Treatment Temperature>

[0291] In the same manner as Experimental Example 4, the presence or absence of impurities according to the heat treatment temperature was confirmed and recorded in Table 5 below. Specifically, the temperature at which impurities began to be generated was measured, and the temperature immediately before that was the maximum heat treatment temperature (T H ) and minimum heat treatment temperature (T L ) was recorded, and the difference value (△=T H -T L ) was calculated and recorded.

[0292] At this time, the impurity phase was confirmed through the impurity peak. The impurity peak was confirmed as a split peak at the diffraction angle (2θ) of the argyrodite crystal structure, peaks at 25.65° to 26.5°, 26.5° to 27.5°, 28.5° to 29.5°, and 33° to 35°. At this time, if any one or more of the above peaks was detected, it was indicated as 'detected', and if not detected, it was indicated as 'not detected'.

[0293] Classification Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 360℃ Detected Detected Detected Detected--380℃ Detected Detected Detected Detected Detected 400℃ Detected Not Detected Not Detected Detected Detected 420℃ Not Detected Not Detected Not Detected Not Detected Not Detected Not Detected 440℃ Not Detected Not Detected Not Detected Not Detected Not Detected Not Detected 460℃ Not Detected Not Detected Not Detected Not Detected Not Detected Not Detected 480℃ Not Detected Not Detected Not Detected Not Detected Not Detected 500℃ Not Detected Not Detected Not Detected Not Detected Not Detected 520℃ Not Detected Detected Detected Detected 540℃ Detected Detected--Detected-

[0294] Looking at the results in Table 5 above, both the sulfide-based solid electrolytes of the examples and comparative examples showed a tendency for impurity phases to form more easily when the heat treatment temperature range was exceeded.

[0295] Specifically, it can be seen that the sulfide-based solid electrolytes of Examples 1 to 3 do not contain impurity phases at a wider heat treatment temperature than the solid electrolytes of Comparative Examples 1 to 3. The results of Tables 3 to 5 are summarized and the maximum heat treatment temperature (T H ) and minimum heat treatment temperature (T L ) was recorded, and the difference value (△=T H -T L ) was calculated and summarized in Table 6 below.

[0296] Distinctive ion conductivity 6 mS / cm or moreAverage grain size 200 nm or moreImpurity phase not detectedExample 1380℃~540℃ (△160℃)380℃~540℃ (△160℃)420℃~520℃ (△100℃)Example 2360℃~520℃ (△160℃)360℃~520℃ (△160℃)400℃~500℃ (△100℃)Example 3360℃~500℃ (△140℃)360℃~500℃ (△140℃)400℃~500℃ (△100℃)Comparative example 1380℃~480℃ (△100℃)380℃~460℃ (△80℃)400℃~180℃ (△80℃)Comparative example 2400℃~500℃ (△100℃)400℃~500℃ (△100℃)420℃~500℃ (△80℃)Comparative example 3400℃~500℃ (△100℃)400℃~180℃ (△80℃)420℃~500℃ (△80℃)

[0297] Accordingly, as shown in Table 6 above, it can be seen that the temperature range in which the sulfide-based solid electrolytes of Examples 1 to 3 satisfy each property is wider than that of the sulfide-based solid electrolytes of Comparative Examples 1 to 3, thereby improving the process window. In addition, the process window for producing a high-quality sulfide-based solid electrolyte without impurities also showed wider results.

Claims

1. The average crystal grain size is 200 nm or more, A sulfide-based solid electrolyte represented by the following chemical formula 1: [Chemical Formula 1] Li a P 1-b M b S c Cl d Br e In chemical formula 1, M is at least one selected from the group consisting of Sb, Si, Ge, Sn, Cu, Ag, Mg, Ca, Al, As, Na, K and Ga, 5≤a≤7.5, 0≤b≤0.3, 0.5≤ac≤1.5, 0 <d≤1.5, 0<e≤1.5이다.

2. In claim 1, A sulfide-based solid electrolyte satisfying 0.23≤(d+e) / a≤0.

29.

3. In claim 1, A sulfide-based solid electrolyte satisfying 0.1≤e / d<0.

99.

4. In claim 1, A sulfide-based solid electrolyte having an argyrodite-type crystal structure.

5. In claim 1, A sulfide-based solid electrolyte having a first peak appearing at any one or more positions selected from the group consisting of diffraction angles (2θ) of 14° to 16°, 17° to 19°, 24° to 25.65°, 29.5° to 31°, 31° to 32°, and 44° to 46° when analyzing an X-ray diffraction pattern.

6. In claim 5, The above first peak is a sulfide-based solid electrolyte without peak splitting.

7. In claim 1, The above sulfide-based solid electrolyte is a sulfide-based solid electrolyte that does not contain an impurity phase.

8. In claim 1, A sulfide-based solid electrolyte having a value of 0.9 or greater calculated by the following mathematical formula 1: [Mathematical Formula 1] I O / (I O +I A ) In the above mathematical formula 1, I O is the peak intensity that appears at a diffraction angle (2θ) of 24° to 25.65° when analyzing an X-ray diffraction pattern. I A is the peak intensity that appears at a diffraction angle (2θ) of 25.65° to 26.5°.

9. In claim 1, A sulfide-based solid electrolyte having a value calculated by the following mathematical formula 2 of 0.994 or greater: [Equation 2] I O / (I O +I B ) In the above mathematical formula 2, I O is the peak intensity that appears at a diffraction angle (2θ) of 24° to 25.65° when analyzing an X-ray diffraction pattern. I B is the peak intensity that appears at a diffraction angle (2θ) of 28.5° to 29.5°.

10. In claim 1, A sulfide-based solid electrolyte having a value calculated by the following mathematical formula 3 of 0.99 or greater: [Equation 3] I O / (I O +I C ) In the above mathematical formula 3, I O is the peak intensity that appears at a diffraction angle (2θ) of 24° to 25.65° when analyzing an X-ray diffraction pattern. I C is the peak intensity that appears at a diffraction angle (2θ) of 33° to 35°.

11. In claim 1, A sulfide-based solid electrolyte having a process window parameter of 100°C or higher calculated by the following mathematical formula 4: [Equation 4] △T=T H -T L In mathematical formula 4, T H is the heat treatment process temperature of the sulfide-based solid electrolyte, and is the maximum value of the heat treatment temperature that satisfies at least one of the first to third properties. T L is the heat treatment process temperature of a sulfide-based solid electrolyte, and is the minimum value of the heat treatment temperature that satisfies at least one of the first to third properties. First property: Condition where the ionic conductivity at 22℃ is 6 mS / cm or more Second property: Condition where the average crystal grain size is 200 nm or more Third property: Condition not containing impurities 12. In claim 1, A sulfide-based solid electrolyte having an ionic conductivity of 6 mS / cm or more at 22°C.

13. A step of preparing a mixture by mixing a lithium-containing compound, a phosphorus-containing compound, a sulfur-containing compound, a chlorine-containing compound, and a bromine-containing compound; and A method for producing a sulfide-based solid electrolyte according to any one of claims 1 to 12, comprising a step of heat treating the mixture.

14. Including a positive electrode; a negative electrode; and a solid electrolyte layer provided between the positive electrode and the negative electrode, An all-solid-state battery, wherein the positive electrode or solid electrolyte layer comprises a sulfide-based solid electrolyte according to any one of claims 1 to 12.

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