Lithium-ion conductive sulfide-based compound and manufacturing method thereof

Abstract

The present specification relates to a lithium-ion conductive sulfide-based compound, a manufacturing method thereof, and a lithium secondary battery comprising same. More specifically, the present specification relates to a method for obtaining a sulfide-based compound having excellent electrochemical properties by regenerating defective products containing impurities in a sulfide-based solid electrolyte having an argyrodite-type crystal structure.

Description

Lithium ion conductive sulfide-based compound and method for manufacturing the same

[0001] This specification relates to a lithium ion-conducting sulfide-based compound, a method for manufacturing the same, and a lithium secondary battery containing the same. More specifically, this specification relates to a method for obtaining a sulfide-based compound having excellent electrochemical properties by regenerating a defective product containing impurities among a sulfide-based solid electrolyte having an azirodite-type crystal structure.

[0002]

[0003] A battery stores electrical power by using materials capable of electrochemical reactions at the positive and negative electrodes. A representative example of such a battery is the lithium secondary battery, which stores electrical energy based on the difference in chemical potential when lithium ions intercalate or deintercalate at the positive and negative electrodes.

[0004] The above lithium secondary battery is manufactured by using materials capable of reversible intercalation / deintercalation of lithium ions as positive and negative active materials, and by filling an organic electrolyte or a polymer electrolyte between the positive and negative electrodes.

[0005] However, these organic or polymer electrolytes typically use flammable organic solvents. Therefore, if abnormally high temperatures occur due to internal or external factors of the lithium secondary battery, a fire or explosion may occur due to the electrolyte.

[0006] Due to these safety concerns, solid-state batteries utilizing solid electrolytes are attracting attention as a substitute for liquid batteries. Solid-state batteries are expected to be commercialized as next-generation batteries with high energy density due to their high stability.

[0007] Among the solid electrolytes used in lithium-ion batteries, sulfide-based solid electrolytes are currently receiving significant attention. Various crystal structures of sulfide-based solid electrolytes are known, one of which is the argyrodite-type crystal structure.

[0008] However, sulfide-based solid electrolytes with an agitite-type crystal structure have problems such as high reactivity with moisture and oxygen, complex manufacturing processes, and significant variability in ionic conductivity performance. Furthermore, due to the nature of solid-phase materials, micronization is essential to maximize the contact surface area; however, this grinding process leads to degradation such as amorphization and impurity formation, resulting in reduced ionic conductivity. In particular, impurities can easily form in manufacturing methods utilizing dry bulk synthesis.

[0009]

[0010] According to the present specification, one objective is to provide a method for manufacturing a lithium ion-conducting sulfide-based compound with improved electrochemical performance and preventing performance degradation caused by impurities generated during the manufacture of a sulfide-based compound having an azirodite-type crystal structure.

[0011] In addition, the present specification has one objective of providing a lithium secondary battery using a sulfide-based solid electrolyte compound as defined herein.

[0012] The purposes of the present invention are not limited to those mentioned above, and other purposes and advantages of the present invention not mentioned may be understood from the following description and will be more clearly understood from the embodiments of this specification. Furthermore, it will be readily apparent that the purposes and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0013]

[0014] According to one aspect of the present specification, a method for manufacturing a lithium ion-conducting sulfide-based compound is provided, comprising: (a) preparing a sulfide-based compound containing impurities and having a crystal phase of an argyrodite-type crystal structure; (b) grinding the sulfide-based compound to obtain particles having a particle size of 100 μm or less; and (c) heat-treating the particles to obtain a regenerated sulfide-based compound.

[0015] Here, the crystalline phase of the azirodite-type crystal structure can be represented by the following chemical formula 1:

[0016] [Chemical Formula 1]

[0017] Li 7-x PS 6-x X x

[0018] In the above chemical formula 1, X is at least one selected from the group consisting of Cl, Br and I, and 0≤x≤2.

[0019] Meanwhile, the above impurity may have at least one peak selected from the group consisting of 2θ values ​​of 14.5°±1°, 27.1°±1°, 29.2°±1° and 33.9°±1° in Cu-Kα XRD analysis.

[0020] In addition, the sulfide-based compound of step (a) above may be prepared by a dry bulk synthesis method.

[0021] Here, the grinding in step (b) can be performed using at least one selected from the group consisting of a ball mill, a pebble mill, a rod mill, a roller mill, a colloid mill, an impact mill, a jet mill, a bead mill, a vibrating mill, a stirring mill, a disc mill, and a grinding classifier mill.

[0022] In addition, the heat treatment of step (c) above can be performed at 500 to 600°C for 5 to 10 hours.

[0023] Meanwhile, the wavenumber of the Raman analysis of the above-mentioned regenerated sulfide-based compound is 565–575 cm⁻¹ -1Peak intensity I3 observed in and wavenumber of Raman analysis of the sulfide compound of step (a) above 565–575 cm⁻¹ -1 The ratio of peak intensity I'3 observed in I3 / I'3 may be greater than 1.

[0024] According to another aspect of this specification, a sulfide-based compound comprising a crystalline phase having an argyrodite-type crystal structure, wherein the wavenumber of Raman analysis is 265–275 cm⁻¹ -1 Peak intensity I1 and 420–430 cm⁻¹ observed at -1 A lithium ion conductive sulfide-based compound is provided, wherein the ratio of I2 / I1, which is the peak intensity I2 observed in, is greater than 12.54.

[0025] Here, the sulfide-based compound may not show a peak in the regions where the 2θ values ​​of the Cu-Kα XRD analysis are 14.5°±1°, 27.1°±1°, 29.2°±1°, and 33.9°±1°.

[0026] In addition, Raman analysis wavenumber 265–275 cm -1 Peak intensity I1 and 565–575 cm⁻¹ observed at -1 The ratio of peak intensity I3 observed in I3 / I1, I3 / I1, may be greater than 2.22.

[0027] According to another aspect of the present specification, a lithium secondary battery comprising the above-described lithium ion-conducting sulfide-based compound is provided.

[0028]

[0029] According to the present specification, impurities that may occur during the manufacture of a azirodite-type sulfide-based compounds are treated, and a sulfide-based compound having excellent performance as a solid electrolyte is provided with further improved electrochemical properties.

[0030] In addition to the effects described above, the specific effects of the present invention are described together with the specific details of the specification below.

[0031]

[0032] FIG. 1 is the XRD analysis result of a sulfide-based compound according to one example of the present specification;

[0033] Figure 2 is the result of a Raman spectrum analysis of a sulfide-based compound according to one example of the present specification.

[0034]

[0035] For convenience, specific terms are defined herein to facilitate a better understanding of this specification. Unless otherwise defined herein, scientific and technical terms used in this invention shall have the meanings generally understood by those skilled in the art. Furthermore, unless specifically indicated in the context, terms in their singular form shall be understood to include their plural form, and terms in their plural form shall be understood to include their singular form.

[0036]

[0037] Method for manufacturing lithium ion conductive sulfide-based compounds

[0038] A method for manufacturing a lithium ion-conducting sulfide-based compound according to one aspect of the present specification may include: (a) a step of preparing a sulfide-based compound containing a crystalline phase having an argyrodite-type crystal structure and containing impurities; (b) a step of grinding the sulfide-based compound to obtain particles having a particle size of 100 μm or less; and (c) a step of heat-treating the particles to obtain a regenerated sulfide-based compound.

[0039] The above step (a) may be a step of preparing a defective product containing impurities that occurs in a conventional step of manufacturing a sulfide-based compound having a crystal phase of an azirodite-type crystal structure.

[0040] The above sulfide-based compound has lithium ion conductivity and can have a crystal phase with an azirodite-type crystal structure.

[0041] The term "azirodite-type crystal structure" refers to a structure identical to that of azirodite (Ag8GeS6), a silver-germanium-sulfur mineral. The azirodite-type crystal structure can possess orthorhombic (Pna21) and cubic (F-43m) phases, among which the cubic crystal structure exhibits high lithium ion conductivity. Typically, the azirodite-type crystal structure displays the cubic phase, which exhibits excellent lithium ion conductivity at high temperatures, and the orthorhombic phase at low temperatures.

[0042] For example, Li7PS6, Li6PS5X (where X is at least one of Cl, Br, and I) are known as lithium ion conductive solid electrolyte compounds having an azirodite-type crystal structure.

[0043] However, the azirodite crystal structure has the problem of easily degrading performance due to sensitivity to air and humidity. Therefore, compounds having an azirodite crystal structure may experience performance degradation or easily form impurities during the manufacturing process.

[0044] For example, the above sulfide-based compound is prepared by mixing lithium sulfide (Li2S) powder, phosphorus sulfide (P2S5) powder, and lithium halide (LiX) powder, and subjecting the mixture to an inert atmosphere at 350–500°C, for example, 350°C, 355°C, 360°C, 365°C, 370°C, 375°C, 380°C, 385°C, 390°C, 395°C, 400°C, 405°C, 410°C, 415°C, 420°C, 425°C, 430°C, 435°C, 440°C, 445°C, 450°C, 455°C, 460°C, 465°C, 470°C, 475°C, 480°C, 485°C, 490°C, 495°C. Calcined at 500°C or a range between two of these values, or at 350 to 650°C in an atmosphere containing hydrogen sulfide gas, e.g., 350°C, 355°C, 360°C, 365°C, 370°C, 375°C, 380°C, 385°C, 390°C, 395°C, 400°C, 405°C, 410°C, 415°C, 420°C, 425°C, 430°C, 435°C, 440°C, 445°C, 450°C, 455°C, 460°C, 465°C, 470°C, 475°C, 480°C, 485°C, 490°C, 495°C, 500°C, 505°C, 510°C, 515°C, It may be obtained by firing at a temperature of 520℃, 525℃, 530℃, 535℃, 540℃, 545℃, 550℃, 555℃, 560℃, 565℃, 570℃, 575℃, 580℃, 585℃, 590℃, 595℃, 600℃, 605℃, 610℃, 615℃, 620℃, 625℃, 630℃, 635℃, 640℃, 645℃, 650℃, or a range between two of these values, but is not limited thereto. Here, each component may be stoichiometrically calculated and mixed to have the desired composition.

[0045] If control is not properly managed in these processes, or if mass production occurs, sulfide compounds containing impurities may be included.

[0046] In one embodiment, the crystalline phase of the azirodite-type crystal structure can be represented by the following chemical formula 1:

[0047] [Chemical Formula 1]

[0048] Li 7-x PS 6-x X x

[0049] In the above chemical formula 1, X is at least one selected from the group consisting of Cl, Br and I, and 0≤x≤2.

[0050] Here, the molar ratio Li / P of lithium (Li) and phosphorus (P) elements in the crystal phase of the azirodite-type crystal structure may be 5.00 to 6.50, for example, 5.00, 5.05, 5.10, 5.15, 5.20, 5.25, 5.30, 5.35, 5.40, 5.45, 5.50, 5.55, 5.60, 5.65, 5.70, 5.75, 5.80, 5.85, 5.90, 5.95, 6.00, 6.05, 6.10, 6.15, 6.20, 6.25, 6.30, 6.35, 6.40, 6.45, 6.50, or a range between two of these values, but is limited thereto. It is not.

[0051] By adjusting the Li / P value, the arrangement and distribution ratio of lithium ions within the compound change, thereby preventing the phenomenon of reduced ion conductivity.

[0052] In addition, in the crystal phase of the azyrodite-type crystal structure, the molar ratio S / P of sulfur (S) and phosphorus (P) elements is 4.00 to 6.00, for example, 4.00, 4.05, 4.10, 4.15, 4.20, 4.25, 4.30, 4.35, 4.40, 4.45, 4.50, 4.55, 4.60, 4.65, 4.70, 4.75, 4.80, 4.85, 4.90, 4.95, 5.00, 5.05, 5.10, 5.15, 5.20, 5.25, 5.30, 5.35, 5.40, 5.45, 5.50, 5.55, 5.60, It may be 5.65, 5.70, 5.75, 5.80, 5.85, 5.90, 5.95, 6.00, or a range between two of these values, but is not limited thereto.

[0053] By adjusting the S / P value, the chemical stability and high ionic conductivity of the above compound can be secured in balance.

[0054] Replacing sulfur with a halogen anion in an azyrodite-type crystal structure stabilizes the cubic phase, allowing the structure to be maintained even at room temperature.

[0055] Substituted halogen elements can form vacancies at Li sites within the azirodite unit cell, thereby reducing activation energy and forming new lithium ion conduction pathways, which can consequently improve lithium ion conductivity.

[0056] Meanwhile, the crystal phase of the above-mentioned azyrodite-type crystal structure may contain two or more halogen elements. Halogen elements include F, Cl, Br, I, etc., but Cl, Br, I, etc. can typically be used in compounds having an azyrodite-type crystal structure.

[0057] Here, in the crystal phase of the azyrodite-type crystal structure, the molar ratio X / P of the halogen (X) element and the phosphorus (P) element is 1.00 to 2.00, for example, 1.00, 1.02, 1.04, 1.06, 1.08, 1.10, 1.12, 1.14, 1.16, 1.18, 1.20, 1.22, 1.24, 1.26, 1.28, 1.30, 1.32, 1.34, 1.36, 1.38, 1.40, 1.42, 1.44, 1.46, 1.48, 1.50, 1.52, 1.54, 1.56, 1.58, 1.60, 1.62, 1.64, 1.66, 1.68, 1.70, 1.72, 1.74, 1.76, 1.78, 1.80, 1.82, 1.84, 1.86, 1.88, 1.90, 1.92, 1.94, 1.96, 1.98, 2.00, or a range between two of these values, but is not limited thereto.

[0058] In one example, if the halogen (X) element contains Cl and Br, the content of Cl may be higher than the content of Br. In such cases, the content of the Br is 0.05 to 0.5 moles based on 1 mole of the phosphorus (P) element, for example, 0.05 moles, 0.06 moles, 0.07 moles, 0.08 moles, 0.09 moles, 0.1 moles, 0.11 moles, 0.12 moles, 0.13 moles, 0.14 moles, 0.15 moles, 0.16 moles, 0.17 moles, 0.18 moles, 0.19 moles, 0.2 moles, 0.21 moles, 0.22 moles, 0.23 moles, 0.24 moles, 0.25 moles, 0.26 moles, 0.27 moles, 0.28 moles, 0.29 moles, 0.3 moles, 0.31 moles, 0.32 moles, 0.33 moles, 0.34 moles, 0.35 moles, 0.36 moles, 0.37 moles, 0.38 moles, 0.39 moles, 0.4 moles, 0.41 moles, 0.42 moles, 0.43 moles, 0.44 moles, 0.45 moles, 0.46 moles, 0.47 moles, 0.48 moles, 0.49 moles, 0.5 moles, or a range between two of these values, but is not limited thereto.

[0059] Meanwhile, the above impurity may have at least one peak selected from the group consisting of 2θ values ​​of 14.5°±1°, 27.1°±1°, 29.2°±1°, and 33.9°±1° in Cu-Kα XRD analysis. Here, the XRD analysis is the result obtained by CuKα radiation (λ=1.540598Å).

[0060] In this XRD analysis, peaks observed in the region where the 2θ value satisfies the above range may be impurities that degrade the electrochemical performance of the sulfide-based compound.

[0061] In one example, the sulfide-based compound of step (a) above may be prepared by a dry bulk synthesis method. When preparing sulfide-based compounds by a dry bulk synthesis method, there is a high possibility that such impurity phases will occur. Therefore, the above manufacturing method can be applied in conjunction with the dry bulk synthesis method of sulfide-based compounds to increase process efficiency.

[0062] Here, the dry bulk synthesis method may refer to a process of mixing raw materials through a dry mixer. Sulfide compounds can be synthesized in large quantities by introducing and mixing raw materials that do not contain solvent into a mixer having a capacity of 10 kg or more, for example, 10 kg, 15 kg, 20 kg, 25 kg, 30 kg, 35 kg, 40 kg, 45 kg, 50 kg, or a range between two of these values, but is not limited thereto.

[0063] Meanwhile, the firing of the raw material here may be performed in a refractory crucible having a capacity of 0.5 kg or more, for example, 0.5 kg, 0.75 kg, 1 kg, 1.25 kg, 1.5 kg, 1.75 kg, 2 kg, 2.25 kg, 2.5 kg, 2.75 kg, 3 kg, 3.25 kg, 3.5 kg, or a range between two of these values, but is not limited thereto.

[0064] Step (b) above is a step of grinding sulfide-based compounds containing impurities, and without this grinding step, it is difficult to remove impurities even if heat treatment is performed.

[0065] The sulfide-based compound containing impurities has a particle size of 100 μm or less in step (b), for example, 100 μm, 97.5 μm, 95 μm, 92.5 μm, 90 μm, 87.5 μm, 85 μm, 82.5 μm, 80 μm, 77.5 μm, 75 μm, 72.5 μm, 70 μm, 67.5 μm, 65 μm, 62.5 μm, 60 μm, 57.5 μm, 55 μm, 52.5 μm, 50 μm, 47.5 μm, 45 μm, 42.5 μm, 40 μm, 37.5 μm, 35 μm, 32.5 μm, 30 μm, 27.5 μm, 25 μm, It may be ground to satisfy a range between two of these values, such as 22.5 µm, 20 µm, 17.5 µm, 15 µm, 12.5 µm, 10 µm, 7.5 µm, 5 µm, 4.5 µm, 4 µm, 3.5 µm, 3 µm, 2.5 µm, 2 µm, 1.5 µm, 1 µm, 0.5 µm, but is not limited thereto.

[0066] However, if the above sulfide-based compound has a particle size of more than 100 μm, impurities may not be removed normally.

[0067] Here, the grinding in step (b) may be performed using at least one selected from the group consisting of a ball mill, a pebble mill, a rod mill, a roller mill, a colloid mill, an impact mill, a jet mill, a bead mill, a vibrating mill, a stirring mill, a disc mill, and a grinding classifier mill, but is not limited thereto.

[0068] Step (c) above may be a step of removing impurity phases by reheat-treating a sulfide-based compound with controlled particle size.

[0069] In addition, the heat treatment of step (c) above may be performed at 500 to 600°C, for example, 500°C, 505°C, 510°C, 515°C, 520°C, 525°C, 530°C, 535°C, 540°C, 545°C, 550°C, 555°C, 560°C, 565°C, 570°C, 575°C, 580°C, 585°C, 590°C, 595°C, 600°C, or in a range between two of these values ​​for 5 to 10 hours, for example, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours.

[0070] Here, the heat treatment may be performed by increasing the temperature at a rate of 1 to 10℃ / min, for example, 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min, 5℃ / min, 5.5℃ / min, 6℃ / min, 6.5℃ / min, 7℃ / min, 7.5℃ / min, 8℃ / min, 8.5℃ / min, 9℃ / min, 9.5℃ / min, 10℃ / min, or a range between two of these values.

[0071] The heat treatment temperature of 500 to 600°C in step (c) above may refer to the maximum temperature maintained for 5 to 10 hours. If the heat treatment temperature falls outside the aforementioned range, impurities may not be removed. Meanwhile, if the heat treatment time falls outside the aforementioned range, impurities may not be sufficiently removed, or unnecessary energy may be consumed.

[0072] Meanwhile, the heat treatment of step (c) above can be performed by introducing an inert gas. For example, N2, Ar, etc. can be used as the inert gas.

[0073] In addition, the heat treatment of step (c) above can be performed using a crucible with the lid closed.

[0074] Meanwhile, the wavenumber of the Raman analysis of the above-mentioned regenerated sulfide-based compound is 565–575 cm⁻¹ -1Peak intensity I3 observed in and wavenumber of Raman analysis of the sulfide compound of step (a) above 565–575 cm⁻¹ -1 I3 / I'3, the ratio of the peak intensity I'3 observed in, is greater than 1, e.g., 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.2, 1.21, 1.22, 1.23, 1.24, 1.25, 1.26, 1.27, 1.28, 1.29, 1.3, 1.31, 1.32, 1.33, 1.34, 1.35, 1.36, 1.37, 1.38, 1.39, 1.4, 1.41, 1.42, 1.43, 1.44, 1.45, 1.46, 1.47, 1.48, 1.49, 1.5, or a range between two of these values.

[0075] Here, the wavenumber of the Raman analysis may vary depending on the composition of the azirodite-type sulfide compound. However, the wavenumber of the Raman analysis is 265–275 cm⁻¹ -1 , 420~430 cm -1 and 565~575 cm -1 It is known that all the peaks in the vicinity represent azirodite. For example, 420–430 cm⁻¹ -1 The peak is PS4 3- P2S6, which represents the PS bond, has low ionic conductivity. 4- to P2S7 4- It may be included, but is highly related to the PS4 structure having high ionic conductivity.

[0076] Therefore, with the above sulfide-based compound, 420–430 cm -1 In this case, the ionic conductivity may be superior as peak splitting does not occur.

[0077] According to the above manufacturing method for removing impurity phases, the wavenumber of Raman analysis is 265–275 cm⁻¹-1 The peak intensity may decrease. These sulfide compounds may actually have better ionic conductivity than normal products.

[0078]

[0079] lithium ion conductive sulfide compounds

[0080] A lithium ion-conducting sulfide-based compound according to another aspect of this specification is a sulfide-based compound comprising a crystalline phase having an azirodite-type crystal structure, with a wavenumber of 265–275 cm⁻¹ in Raman analysis. -1 Peak intensity I1 and 420–430 cm⁻¹ observed at -1 I2 / I1, the ratio of peak intensity I2 observed in, is greater than 12.54, e.g., 12.55, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, 20.5, 21, 21.5, 22, 22.5, 23, 23.5, 24, 24.5, 25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5, 29, 29.5, 30, 30.5, 31, 31.5, 32, 32.5, 33, 33.5, 34, 34.5, 35, 35.5, 36, 36.5, 37, 37.5, 38, 38.5, 39, 39.5, 40, 40.5, 41, 41.5, 42, 42.5, 43, 43.5, 44, 44.5, 45, 45.5, 46, 46.5, 47, 47.5, 48, 48.5, 49, 49.5, 50, or a range between two of these values.

[0081] The above sulfide compound has a Raman analysis wavenumber of 420–430 cm⁻¹, indicating azirodite. -1 and 265~275 cm -1 The ratio of peak intensity I2 / I1 observed in the above-described range may satisfy the above-described range, and may have excellent ionic conductivity without containing impurity phases.

[0082] In addition, the above sulfide-based compound has a Raman analysis wavenumber of 420–430 cm⁻¹ -1 The full width at half maximum of the peak observed in is 10.1 cm -1 Less than, for example, 10 cm -1 , 9.9 cm -1 , 9.8 cm -1 , 9.7 cm -1 , 9.6 cm -1 , 9.5 cm -1 , 9.4 cm -1 , 9.3 cm -1 , 9.2 cm -1 , 9.1 cm -1 , 9 cm -1 , 8.9 cm -1 , 8.8 cm -1 , 8.7 cm -1 , 8.6 cm -1 , 8.5 cm -1 , 8.4 cm -1 , 8.3 cm -1 , 8.2 cm -1 , 8.1 cm -1 , 8 cm -1 Or it may be a range between two of these values.

[0083] Meanwhile, the above-mentioned sulfide-based compound has a Raman analysis wavenumber of 420–430 cm⁻¹ -1 It may be that peak splitting does not occur.

[0084] For example, the wavenumber of the Raman analysis for the above sulfide-based compound is 420–430 cm⁻¹ -1 If the peak's full width at half maximum is wide or peak splitting occurs, it indicates P2S6 with low ionic conductivity. 4- to P2S7 4- Electrochemical properties may be degraded as a result.

[0085] Meanwhile, the above lithium ion conductive sulfide-based compound may be manufactured from a sulfide-based compound containing impurities by the manufacturing method described above.

[0086] Therefore, the above sulfide-based compound may not show peaks in the regions where the 2θ values ​​of the Cu-Kα XRD analysis are 14.5°±1°, 27.1°±1°, 29.2°±1°, and 33.9°±1°.

[0087] In addition, Raman analysis wavenumber 265–275 cm -1 Peak intensity I1 and 565–575 cm⁻¹ observed at -1 I3 / I1, the ratio of peak intensity I3 observed in, is greater than 2.22, e.g., 2.22, 2.25, 2.3, 2.35, 2.4, 2.45, 2.5, 2.55, 2.6, 2.65, 2.7, 2.75, 2.8, 2.85, 2.9, 2.95, 3, 3.05, 3.1, 3.15, 3.2, 3.25, 3.3, 3.35, 3.4, 3.45, 3.5, 3.55, 3.6, 3.65, 3.7, 3.75, 3.8, 3.85, 3.9, 3.95, 4, 4.05, 4.1, 4.15, 4.2, 4.25, 4.3, 4.35, 4.4, 4.45, 4.5, 4.55, 4.6, 4.65, 4.7, 4.75, 4.8, 4.85, 4.9, 4.95, 5, or a range between two of these values.

[0088] The above sulfide compound is argyrodite with a Raman analysis wavenumber of 565–575 cm⁻¹. -1 and 265~275 cm -1 The ratio of peak intensity I3 / I1 observed in the above range satisfies the above-mentioned range, so that excellent ionic conductivity can be achieved without containing impurity phases.

[0089]

[0090] lithium secondary battery

[0091] According to another aspect of the present specification, a lithium secondary battery comprising the above-described lithium ion-conducting sulfide-based compound is provided.

[0092] The above lithium ion conductive sulfide-based compound can be used to form a positive electrode by mixing it with a positive electrode active material, or it can be used as a solid electrolyte membrane to replace a separator.

[0093] The above lithium secondary battery may include a positive electrode, a negative electrode positioned opposite to the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode.

[0094] Meanwhile, the above lithium secondary battery may have the separator replaced with a solid electrolyte. The solid electrolyte may be disposed as a separate layer (solid electrolyte layer) between the positive electrode and the negative electrode. In such cases, an electrode slurry composition in which the solid electrolyte is further added during the manufacture of the negative electrode may be used.

[0095] That is, the lithium secondary battery may include a positive electrode, a negative electrode positioned opposite to the positive electrode, and a solid electrolyte membrane interposed between the positive electrode and the negative electrode.

[0096] In addition, the above-mentioned lithium secondary battery may be provided as an anode-free secondary battery. Here, since the anode is the same as previously described, a detailed description is omitted for convenience, and only the remaining components not described above will be explained in detail below. Furthermore, the description regarding the anode to be described later should be understood as being based on the premise that an anode is present in the above-mentioned lithium secondary battery.

[0097] In one example, the anode may include an anode current collector and an anode active material layer formed on the anode current collector. Here, the anode active material layer may include an anode active material and a lithium ion conductive sulfide-based compound according to the various embodiments described above.

[0098] The above positive current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and 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 above positive current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesion of the positive active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0099] The above-mentioned cathode active material may use a compound capable of reversible intercalation / deintercalation of lithium. Examples include, but are not limited to, cobalt oxide-based (LCO), nickel oxide-based (LNO), manganese oxide-based (LMO), nickel-cobalt-manganese oxide-based (NCM), nickel-cobalt-aluminum oxide-based (NCA), iron phosphate-based (LFP), and those doped with and / or coated therefrom.

[0100] The above positive active material layer can be manufactured by applying a positive slurry composition, which includes the sulfide-based compound and the positive active material, along with optionally a conductive material, a binder, etc., to the positive current collector as needed.

[0101] At this time, the sulfide-based compound may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0102] Meanwhile, the above-mentioned positive active material may be included in an amount of 80% to 99% by weight, more specifically 85% to 98.5% by weight, based on the total weight of the positive active material layer. Excellent capacity characteristics may be exhibited when included within the above-mentioned content range, but it is not necessarily limited thereto.

[0103] The above conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above conductive material may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0104] The above binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above binder may be included in an amount of 0.1% to 15% by weight based on the total weight of the positive active material layer.

[0105] The above anode can be manufactured according to a conventional anode manufacturing method. Specifically, it can be manufactured by applying an anode slurry composition, prepared by dissolving or dispersing a sulfide-based compound, an anode active material, a binder, and a conductive material in a solvent, onto an anode current collector, and then drying and rolling.

[0106] The above solvent may be a solvent commonly used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it has a viscosity that dissolves or disperses the anode active material, conductive material, and binder, taking into account the coating thickness of the slurry and the manufacturing yield, and subsequently provides excellent thickness uniformity when coated for anode manufacturing.

[0107] In addition, in another embodiment, the anode may be manufactured by casting the anode slurry composition onto a separate support and then laminating the film obtained by peeling off from the support onto an anode current collector.

[0108] The above cathode may include a cathode current collector and a cathode active material layer located on the cathode current collector.

[0109] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes 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., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 μm to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding force of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0110] The above-mentioned cathode active material layer can be manufactured by applying a cathode slurry composition, which includes a conductive material and optionally a binder together with the above-mentioned cathode active material, to the above-mentioned cathode current collector.

[0111] As the above-mentioned negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO₂ βExamples include metal oxides capable of doping and dedoping lithium, such as (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Furthermore, the carbon material may include low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0112] The above-mentioned negative electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of the negative electrode active material layer.

[0113] The above binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer.

[0114] Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0115] The above conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fiber or metal fiber; metal powder such as carbon fluoride, aluminum, or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxide such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0116] In one embodiment, the negative active material layer may be manufactured by applying a negative slurry composition, prepared by dissolving or dispersing a negative active material and optionally a binder and a conductive material in a solvent, onto a negative current collector and drying it, or by casting the negative slurry composition onto a separate support and then laminating the film obtained by peeling it off from the support onto a negative current collector.

[0117] Meanwhile, in the above-mentioned lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator typically used in lithium secondary batteries can be used without special limitations, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0118] In addition, the electrolytes used in the above lithium secondary battery may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which are usable when manufacturing lithium secondary batteries, but are not limited to these.

[0119] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0120] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.In this case, using a mixture of cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent performance of the electrolyte.

[0121] The above lithium salt can be used without special limitations as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable to use the lithium salt within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and allow lithium ions to move effectively.

[0122] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1 to 5 weight percent based on the total weight of the electrolyte.

[0123] In another example, the lithium secondary battery may be a type of all-solid-state battery that does not contain an electrolyte and includes a solid electrolyte layer made of a solid electrolyte membrane.

[0124] Here, the solid electrolyte membrane may refer to a sulfide-based solid electrolyte compound, which is a type of solid-phase material capable of ion conduction, formed in a membrane-like structure.

[0125] A solid electrolyte membrane can be manufactured according to conventional methods known in the art, for example, by press-molding a powder of a sulfide-based solid electrolyte compound and then processing it into the required shape.

[0126] However, since it is difficult to maintain a membrane-like structure with sulfide-based compounds alone, solid electrolyte membranes can be manufactured by mixing a binder.

[0127] Here, the binder should preferably have excellent binding strength to the sulfide-based compound, excellent flexibility without reducing ion conductivity, and be easily peelable from the release film typically used in the manufacture of solid electrolyte membranes.

[0128] Examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used.

[0129] This type of solid electrolyte membrane can be manufactured by applying a slurry containing a sulfide-based compound, a binder, and a solvent onto a release film, and then removing the solvent.

[0130] In addition, the above solid electrolyte membrane may further include a conductive material, an auxiliary binder, etc., as needed.

[0131] Conductive materials are used to impart conductivity so that electron movement accompanying ion movement is possible, and their types are not limited as long as they possess electronic conductivity without unnecessary chemical reactions. Examples include graphite, carbon black, acetylene black, Ketjen black, furnace black, lamp black, thermo black, carbon fiber, carbon nanotube, graphene, copper, aluminum, nickel, gold, silver, conductive polymers, etc.

[0132] The content of the sulfide-based solid electrolyte compound in the above solid electrolyte membrane is 80 to 99.9 wt%, for example, 80 wt%, 80.5 wt%, 81 wt%, 81.5 wt%, 82 wt%, 82.5 wt%, 83 wt%, 83.5 wt%, 84 wt%, 84.5 wt%, 85 wt%, 85.5 wt%, 86 wt%, 86.5 wt%, 87 wt%, 87.5 wt%, 88 wt%, 88.5 wt%, 89 wt%, 89.5 wt%, 90 wt%, 90.5 wt%, 91 wt%, 91.5 wt%, 92 wt%, 92.5 wt%, 93 wt%, 93.5 wt%, 94 wt%, 94.5 wt%, 95 wt%, 95.5 wt%, 96 wt%, 96.5 wt%, 97 wt%, 97.5 wt%, 98 wt%, 98.5 wt%, 99 wt%, 99.5 wt%, 99.9 wt%, or a range between two of these values, but is not limited thereto.

[0133] Here, the thickness of the solid electrolyte membrane is not limited and ranges from 5 to 300 µm, for example, 5 µm, 10 µm, 15 µm, 20 µm, 25 µm, 30 µm, 35 µm, 40 µm, 45 µm, 50 µm, 55 µm, 60 µm, 65 µm, 70 µm, 75 µm, 80 µm, 85 µm, 90 µm, 95 µm, 100 µm, 105 µm, 110 µm, 115 µm, 120 µm, 125 µm, 130 µm, 135 µm, 140 µm, 145 µm, 150 µm, 155 µm, 160 µm, 165 µm, 170 µm, 175 It may have a range between two of these values, such as µm, 180 µm, 185 µm, 190 µm, 195 µm, 200 µm, 205 µm, 210 µm, 215 µm, 220 µm, 225 µm, 230 µm, 235 µm, 240 µm, 245 µm, 250 µm, 255 µm, 260 µm, 265 µm, 270 µm, 275 µm, 280 µm, 285 µm, 290 µm, 295 µm, 300 µm.

[0134] Meanwhile, the above-mentioned solid electrolyte membrane may have free-standing characteristics that allow it to be used without a separate support, but is not limited thereto.

[0135] The above lithium secondary battery may optionally further include an electrode assembly of the positive electrode, the negative electrode, and the separator, or a battery container housing the electrode assembly of the positive electrode, the negative electrode, and the solid electrolyte membrane, and a sealing member for sealing the battery container.

[0136] As described above, since the lithium secondary battery containing the sulfide-based compound according to the present specification exhibits excellent electrochemical properties, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0137] The external shape of the lithium secondary battery according to the present specification is not subject to any particular limitations, but may be cylindrical, prismatic, pouch, or coin-shaped using a can. In addition, the lithium secondary battery may not only be used as a battery cell for powering small devices, but may also preferably be used as a unit cell in a medium-to-large battery module comprising a plurality of battery cells.

[0138] According to another aspect of the present specification, a battery module comprising the lithium secondary battery as a unit cell and / or a battery pack comprising the same may be provided.

[0139] The battery module or the battery pack may be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0140]

[0141] The present invention will be described in more detail below through examples. However, these examples are intended solely to illustrate the present invention and should not be interpreted as limiting the scope of the present invention.

[0142]

[0143] Preparation Example 1. Preparation of sulfide-based compounds

[0144] Comparative Example 1

[0145] In a drying chamber (DP-60℃), lithium precursor Li2S, phosphorus precursor P2S5, and chlorine precursor LiCl are prepared to form the desired composition Li. 5.6 PS 4.6 Cl 1.4It was prepared by weighing in stoichiometric ratios to obtain [the desired result]. After being fed into a 30 kg Henschel mixer (FM mixer), it was synthesized in large quantities using a dry method with uniform mixing at high rpm.

[0146] After loading more than 1.5 kg of the mixture into a large-capacity crucible containing Al2O3, it was placed in a large box furnace and calcined. To suppress the reaction with the gas present inside the box furnace, N2 gas was flowed as an inert gas while calcining.

[0147] The sulfide-based compound of Comparative Example 1 was prepared by heat treating the charged crucible using a box furnace by increasing the temperature from room temperature to 580°C at a rate of 6.0°C / min and maintaining it for 6 hours, and then naturally cooling it.

[0148]

[0149] Comparative Example 2

[0150] Among the sulfide-based compounds produced in the process of Comparative Example 1, those in which impurities occurred due to process equipment errors, etc., were separately classified as Comparative Example 2, excluding normal products.

[0151]

[0152] Comparative Example 3

[0153] A sulfide-based compound containing impurities of Comparative Example 2 was placed in a crucible containing Al2O3, the lid was closed, and the crucible was placed in a pipe to proceed with calcination again. To suppress the reaction with the gas present inside the pipe, N2 gas was flowed as an inert gas while calcination was carried out.

[0154] The sulfide-based compound of Comparative Example 3 was prepared by heating the charged crucible from room temperature to 500°C at a rate of 6.0°C / min using a pipe, maintaining it for 6 hours, and then naturally cooling it.

[0155]

[0156] Comparative Example 4

[0157] A sulfide compound of Comparative Example 4 was prepared in the same manner as Comparative Example 3, except that among sulfide compounds containing impurities, one with a particle size greater than 100 μm was used, and the crucible was heat-treated by raising the temperature from room temperature to 570°C at a rate of 6.0°C / min using a pipe and maintaining it for 6 hours.

[0158]

[0159] Comparative Example 5

[0160] The sulfide-based compound of Comparative Example 5 was prepared in the same manner as Comparative Example 3, except that the charged crucible was heated from room temperature to 600°C at a rate of 6.0°C / min using a pipe and then maintained for 6 hours for heat treatment.

[0161]

[0162] Examples

[0163] A sulfide-based compound containing impurities of Comparative Example 2 was fed into a colloid mill and ground, and a particle size of 100 μm or less was used.

[0164] The crushed sulfide-based compound was placed in a crucible containing Al2O3 and then placed in a pipe to proceed with calcination. To suppress the reaction with the gas present inside the pipe, N2 gas was flowed as an inert gas while calcination was carried out.

[0165] The sulfide-based compound of Comparative Example 3 was prepared by heating the charged crucible from room temperature to 570°C at a rate of 6.0°C / min using a pipe, maintaining it for 6 hours, and then naturally cooling it.

[0166]

[0167] Experimental Example 1. Characterization of Sulfide Compounds

[0168] The ionic conductivity of the sulfide-based compound prepared according to Preparation Example 1 at 25°C was measured and is shown in Table 1 below.

[0169] XRD analysis was performed using a Bruker D8 Advance diffractometer with Cu-Kα radiation (1.540598 Å), and the results are shown in Figure 1.

[0170] Classification Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Example Ion Conductivity (mS / cm) 3.2 1 2.9 4 2.7 5 3.0 3 2.2 3 3.6 7

[0171] Referring to Table 1, it can be seen that the example of reheat-treated defective sulfide-based compounds containing impurities in Comparative Example 2 has a higher ionic conductivity than Comparative Example 1, which consists of normal products. Meanwhile, referring to Fig. 1, it can be seen that no impurities are present in Comparative Example 1, which is a normal product, and the reheat-treated example.

[0172] To observe the structural characteristics of sulfide compounds, Raman spectrum analysis was performed, and the results are shown in Table 2 and Figure 2 below.

[0173] Classification Comparative Example 1 Comparative Example 2 Comparative Example 4 Example I 272 500352590240I 427 4,9374,4146,2867,905I 568 9557804541,028I 427 / I 272 9.8712.5410.6532.94I 568 / I 272 1.912.220.774.28I 568 / I' 568 -10.581.32FWHM 427 (cm -1 )10.810.112.19.5

[0174] (I 272 : 272 cm -1 Peak intensity in the vicinity, I 427 : 427 cm -1 Peak intensity in the vicinity, I 568 : 568 cm -1Peak intensity near, I'568: 568 cm⁻¹ of the compound before reheat treatment -1 Nearby peak intensity, FWHM 427 : 427 cm -1 Half width of nearby peaks)

[0175] Although embodiments of the present invention have been described above, those skilled in the art may modify and change the present invention in various ways by adding, changing, deleting, or adding components, etc., without departing from the spirit of the present invention as described in the claims, and such modifications and changes are also to be included within the scope of the rights of the present invention.

Claims

1. (a) A step of preparing a sulfide-based compound containing impurities and comprising a crystalline phase having an argyrodite-type crystal structure; (b) a step of grinding the above sulfide-based compound to obtain particles with a particle size of 100 μm or less; and (c) a step of heat-treating the above particles to obtain a regenerated sulfide-based compound; comprising, Method for manufacturing lithium ion conductive sulfide-based compounds.

2. In Paragraph 1, The crystalline phase of the above azirodite-type crystal structure is represented by the following chemical formula 1, Method for preparing lithium ion-conducting sulfide-based compounds: [Chemical Formula 1] Li 7-x PS 6-x X x In the above chemical formula 1, X is at least one selected from the group consisting of Cl, Br, and I, and 0≤x≤2.

3. In Paragraph 1, The above impurity has at least one peak selected from the group consisting of 2θ values ​​of 14.5°±1°, 27.1°±1°, 29.2°±1°, and 33.9°±1° in Cu-Kα XRD analysis, Method for manufacturing lithium ion conductive sulfide-based compounds.

4. In Paragraph 1, The sulfide compound of step (a) above is prepared by a dry bulk synthesis method, Method for manufacturing lithium ion conductive sulfide-based compounds.

5. In Paragraph 1, The grinding in step (b) above is performed using at least one selected from the group consisting of a ball mill, a pebble mill, a rod mill, a roller mill, a colloid mill, an impact mill, a jet mill, a bead mill, a vibrating mill, a stirring mill, a disc mill, and a grinding classifier mill. Method for manufacturing lithium ion conductive sulfide-based compounds.

6. In Paragraph 1, The heat treatment of step (c) above is performed at 500 to 600°C for 5 to 10 hours, Method for manufacturing lithium ion conductive sulfide-based compounds.

7. In Paragraph 1, Wavenumber of Raman analysis of the above-mentioned regenerated sulfide-based compound: 565–575 cm⁻¹ -1 Peak intensity I3 observed in and wavenumber of Raman analysis of the sulfide compound of step (a) above 565–575 cm⁻¹ -1 I3 / I'3, the ratio of peak intensity I'3 observed in, is greater than 1, Method for manufacturing lithium ion conductive sulfide-based compounds.

8. A sulfide compound comprising a crystalline phase of an argyrodite-type crystal structure, Raman analysis wavenumber 265–275 cm -1 Peak intensity I1 and 420–430 cm⁻¹ observed at -1 I2 / I1, the ratio of peak intensity I2 observed in, is greater than 12.54, Lithium ion conductive sulfide-based compounds.

9. In Paragraph 8, The above sulfide-based compound does not show peaks in regions where the 2θ values ​​of the Cu-Kα XRD analysis are 14.5°±1°, 27.1°±1°, 29.2°±1°, and 33.9°±1°, Lithium ion conductive sulfide-based compounds.

10. In Paragraph 8, Raman analysis wavenumber 265–275 cm -1 Peak intensity I1 and 565–575 cm⁻¹ observed at -1 I3 / I1, the ratio of peak intensity I3 observed in, is greater than 2.22, Lithium ion conductive sulfide-based compounds.

11. A lithium ion-conducting sulfide-based compound according to paragraph 8, Lithium secondary battery.

Images