Sulfide-based solid electrolyte for lithium secondary battery excellent in mechanical physical property and manufacturing method thereof

Abstract

To provide a sulfide-based solid electrolyte for a lithium secondary battery with improved mechanical physical properties, and a method for manufacturing the same.SOLUTION: A sulfide-based solid electrolyte for a lithium secondary battery includes a lithium element, a phosphorus element, a sulfur element, and a halogen element, and includes an Argyrodite crystal structure, and contains an antimony (Sb) element in at least a part of a Wyckoff position 48h.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sulfide-based solid electrolyte for a lithium secondary battery, which has excellent mechanical properties such as fracture strength, and a method for producing the same. [Background technology]

[0002] Rechargeable lithium secondary batteries are used in small electronic devices such as mobile phones and laptops, as well as large transportation vehicles such as hybrid cars and electric cars. Therefore, there is a need to develop secondary batteries with higher stability and energy density.

[0003] Existing lithium secondary batteries generally have a cell structure based on a liquid electrolyte, which limits improvements in stability and energy density.

[0004] On the other hand, all-solid-state batteries using solid electrolytes are based on technology that does not use organic solvents, and as such, cells can be produced in a safe and simple manner, and have been attracting a great deal of attention in recent years.

[0005] Solid electrolytes are non-flammable or flame-retardant, and therefore are safer than liquid electrolytes.

[0006] Solid electrolytes are divided into oxide-based and sulfide-based types. Sulfide-based solid electrolytes are primarily used because they have higher lithium ion conductivity and are stable over a wide voltage range compared to oxide-based solid electrolytes.

[0007] However, sulfide-based solid electrolytes have lower chemical stability than oxide-based solid electrolytes, leading to unstable battery operation. Therefore, most research on sulfide-based solid electrolytes has been limited to improving lithium ion conductivity and electrochemical stability. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to provide a sulfide-based solid electrolyte for a lithium secondary battery with improved mechanical physical properties that have a significant impact on the actual driving of the battery.

[0009] The object of the present invention is not limited to the object mentioned above. The object of the present invention will become more apparent from the following description and will be realized by the means described in the claims and their combinations.

Means for Solving the Problems

[0010] The sulfide-based solid electrolyte for a lithium secondary battery according to an embodiment of the present invention contains a lithium element, a phosphorus element, a sulfur element, and a halogen element, includes an argyrodite crystal structure, and may contain an antimony (Sb) element in at least a part of the Wyckoff position 48h.

[0011] The sulfide-based solid electrolyte may be such that the molar ratio ((Li+Sb) / P) of the sum of the lithium element and the antimony element to the phosphorus element is 4.9 or more and less than 5.5.

[0012] The sulfide-based solid electrolyte may be represented by the following formula 1.

Chemical formula

[0013] The sulfide-based solid electrolyte may be represented by the following formula 2.

Chemical formula

[0014] The sulfide-based solid electrolyte has a Raman spectrum of 400 cm compared to a sulfide-based solid electrolyte that does not contain antimony. -1 ~450cm -1 The peaks seen in the graph may be shifted downward.

[0015] The sulfide-based solid electrolyte may have a fracture strength of 60 kPa or more according to the ASTM C773 measurement method.

[0016] The sulfide-based solid electrolyte has a pellet density of 1.8 g / cm 3 ~2.0g / cm 3 It may be.

[0017] A sulfide-based solid electrolyte for a lithium secondary battery according to an embodiment of the present invention may include the steps of: reacting lithium sulfide, phosphorus sulfide, lithium halide, and antimony sulfide to obtain a product; and heat-treating the product to obtain a sulfide-based solid electrolyte.

[0018] The heat treatment may be performed at a temperature of 450°C to 500°C.

[0019] The heat treatment may be performed for 10 to 30 minutes.

[0020] A lithium secondary battery according to an embodiment of the present invention includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer sandwiched between the positive electrode layer and the negative electrode layer, and at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer may include the sulfide-based solid electrolyte. [Effects of the Invention]

[0021] According to the present invention, a sulfide-based solid electrolyte for a lithium secondary battery having excellent mechanical properties can be obtained.

[0022] According to the present invention, it is possible to obtain a sulfide-based solid electrolyte for a lithium secondary battery which is excellent in flexibility and toughness as well as high in fracture strength.

[0023] According to the present invention, it is possible to obtain a sulfide-based solid electrolyte for a lithium secondary battery that exhibits excellent performance when applied to an all-solid-state battery that involves large volume expansion.

[0024] The effects of the present invention are not limited to those mentioned above, and should be understood to include all effects that can be inferred from the following description. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a diagram showing a lithium secondary battery according to the present invention. [Figure 2] FIG. 1 is a diagram showing the compositions of a sulfide-based solid electrolyte according to the present invention and a conventional sulfide-based solid electrolyte in a ternary system. [Figure 3] FIG. 1 shows the argyrodite crystal structure. [Figure 4] 1 shows Raman spectra of sulfide-based solid electrolytes according to Comparative Example 2, Example 2, and Comparative Example 4. [Figure 5] FIG. 5 is an enlarged view of the peak in the range of 400 cm −1 to 450 cm −1 in FIG. [Figure 6] 1 shows Raman spectra of sulfide-based solid electrolytes according to Comparative Example 2, Example 2, Example 3, and Comparative Example 3. [Figure 7] FIG. 7 is an enlarged view of the peak in the range of 400 cm −1 to 450 cm −1 in FIG. 6. [Figure 8] 1 shows the results of X-ray diffraction analysis of sulfide-based solid electrolytes according to Comparative Example 2, Example 2, and Comparative Example 4. [Figure 9] FIG. 9 is an enlarged view of a specific portion of FIG. 8. [Figure 10] 1 shows the results of X-ray diffraction analysis of sulfide-based solid electrolytes according to Comparative Example 2, Example 2, Example 3, and Comparative Example 3. [Figure 11] FIG. 11 is an enlarged view of a specific portion of FIG. 10. [Figure 12] 1 shows the results of X-ray diffraction analysis of sulfide-based solid electrolytes according to Comparative Examples 2 and 11 to 13. [Figure 13] The cell performance of each lithium secondary battery containing a sulfide-based solid electrolyte according to Comparative Example 2, Example 2, and Comparative Example 10 was evaluated. DETAILED DESCRIPTION OF THE INVENTION

[0026] The above and other objects, features, and advantages of the present invention will be readily understood from the following preferred embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content will be thorough and complete, and so that the concept of the present invention will be fully conveyed to those skilled in the art.

[0027] In the accompanying drawings, the dimensions of structures are exaggerated for clarity of the present invention, and like reference numerals have been used to refer to like elements throughout the description of the various figures.

[0028] As used herein, terms such as "comprise" or "have" are intended to specify the presence of a stated feature, numeral, step, operation, component, part, or combination thereof, and should be understood not to preclude the possibility of the presence or addition of one or more other features, numerals, steps, operations, components, parts, or combinations thereof. Furthermore, when a layer, film, region, plate, or other part is described as being "on" another part, this includes not only the case where it is "directly on" the other part, but also the case where there is another part between them. Similarly, when a layer, film, region, plate, or other part is described as being "under" another part, this includes not only the case where it is "directly under" the other part, but also the case where there is another part between them.

[0029] Unless otherwise indicated, all numbers, values, and / or expressions representing amounts of components, reaction conditions, polymer compositions, and formulations used herein are to be understood as being modified in all instances by the term "about" in that such numbers reflect approximations that take into account various uncertainties of measurements that inherently occur in obtaining such values from different substances. Also, when a numerical range is disclosed herein, such range is continuous and, unless otherwise specified, includes all values from the minimum value to the maximum value including the maximum value. Further, when such range indicates integers, unless otherwise specified, all integers from the minimum value to the maximum value including the maximum value are included.

[0030] FIG. 1 is a diagram showing a lithium secondary battery according to the present invention. The lithium secondary battery may include a all-solid-state battery.

[0031] The lithium secondary battery may include a positive electrode layer 10, a negative electrode layer 20, and a solid electrolyte layer 30 located between the positive electrode layer 10 and the negative electrode layer 20. At least one of the positive electrode layer 10, the negative electrode layer 20, and the solid electrolyte layer 30 may include a sulfide-based solid electrolyte according to the present invention.

[0032] The sulfide-based solid electrolyte may include a lithium (Li) element, a phosphorus (P) element, a sulfur (S) element, and a halogen element. Further, the sulfide-based solid electrolyte may include an antimony (Sb) element that substitutes at least a part of the lithium element. Specifically, the sulfide-based solid electrolyte may include a compound represented by the following formula 1 and / or a compound represented by the following formula 2.

Chemical formula

Chemical formula

[0033] Conventionally, various studies have been actively conducted to introduce various substitution elements in order to improve the lithium ion conductivity, electrochemical stability, etc. of sulfide-based solid electrolytes. However, conventionally, mainly the phosphorus (P) element has been substituted, whereas the present invention is characterized in that the lithium (Li) element is substituted to improve the mechanical physical properties of the sulfide-based solid electrolyte.

[0034] The sulfide-based solid electrolyte is one in which the lithium (Li) element is substituted with the antimony (Sb) element. Therefore, the molar ratio ((Li + Sb) / P) of the sum of the lithium (Li) element and the antimony (Sb) element to the phosphorus (P) element may be 4.9 or more and less than 5.5. If the phosphorus (P) element is replaced with a substitution element as in the prior art, the molar ratio is 5.5 or more. FIG. 2 is a diagram showing a ternary system of the sulfide-based solid electrolyte according to the present invention and a solid electrolyte in which the phosphorus (P) element is replaced with the antimony (Sb) element as in the prior art. Referring to this, it can be seen that the composition ratios of the two sulfide-based solid electrolytes are completely different.

[0035] The sulfide-based solid electrolyte according to the present invention may include an argyrodite crystal structure. FIG. 3 is a diagram showing the argyrodite crystal structure. A compound represented as Li6PS5Cl and having an argyrodite crystal structure has a PS4 3- tetrahedron at the Wyckoff position 4b, S at 4a and 4c 2- ions, and Li + ions at 48h. The present invention is characterized in that the antimony (Sb) element is introduced into at least a part of the Wyckoff position 48h.

[0036] The substitution elements for the lithium (Li) element may include, in addition to antimony (Sb), trivalent cations resulting from bismuth (Bi), niobium (Nb), scandium (Sc), tantalum (Ta), titanium (Ti), vanadium (V), etc.; and / or divalent cations resulting from calcium (Ca), chromium (Cr), iron (Fe), germanium (Ge), magnesium (Mg), titanium (Ti), vanadium (V), etc.

[0037] The method for manufacturing the sulfide-based solid electrolyte may include preparing starting materials including lithium sulfide, phosphorus sulfide, lithium halide, and antimony sulfide; reacting the starting materials to obtain a product; and heat-treating the product.

[0038] The type of the lithium sulfide is not particularly limited and may include Li2S, Li2S2, Li2S4, Li2S8, etc. The type of the phosphorus sulfide is not particularly limited and may include P2S3, Sb2S3, etc. The type of the lithium halide is not particularly limited and may include LiCl, LiBr, LiI, etc. The type of the antimony sulfide is not particularly limited and may include Sb2S3, etc.

[0039] The starting material may further include elemental lithium, elemental sulfur, elemental phosphorus, and the like.

[0040] The content of the starting materials may be appropriately adjusted according to the final composition of the desired sulfide-based solid electrolyte, so that the antimony (Sb) element substitutes for the lithium (Li) element instead of the phosphorus (P) element.

[0041] The step of reacting the starting materials to obtain a product can be carried out by a wet method or a dry method. For example, the starting materials can be added to a solvent and stirred to cause collisions between the starting materials, and the collision energy generated during the process can cause the reaction of the starting materials. Alternatively, the starting materials can be added to equipment such as a ball mill and pulverized, and energy can be directly applied to cause the reaction of the starting materials.

[0042] The product obtained by the above method can be heat-treated and crystallized to obtain a crystalline sulfide-based solid electrolyte having an argyrodite crystal structure. Because antimony (Sb) is introduced as a substitution element in the present invention, if the heat treatment is performed at too high a temperature for too long, secondary phase impurities such as LiSbS2 may be generated. Therefore, the present invention is characterized in that the product is heat-treated at 450°C to 500°C for 10 to 30 minutes to prevent the generation of impurities.

[0043] Other aspects of the present invention will be described in more detail below using examples. The following examples are merely illustrative examples to aid in understanding the present invention, and are not intended to limit the scope of the present invention.

[0044] Examples 1 to 4 Starting materials were prepared by weighing out Li2S, Sb2S3, LiCl, and Sb2S3 according to the composition of each compound below. The starting materials were pulverized in a ball mill, and the resulting product was heat-treated at about 500°C for about 25 minutes to obtain a sulfide-based solid electrolyte.

[0045] Example 1: Li 5.35 Sb 0.05 PS 4.5 Cl 1.5 Example 2: Li 5.2 Sb 0.1 PS 4.5 Cl 1.5 Example 3: Li 4.9 Sb 0.2 PS 4.5 Cl 1.5 Example 4: Li 4.6 Sb 0.3 PS 4.5 Cl 1.5

[0046] Comparative Examples 1 and 2 Starting materials were prepared by weighing LiS, SbS, and LiCl according to the composition of each compound below. The starting materials were pulverized in a ball mill, and the resulting product was heat-treated at about 550°C for about 300 minutes to obtain a sulfide-based solid electrolyte.

[0047] - Comparative example 1: Li6PS5Cl - Comparative example 2: Li 5.5 PS 4.5 Cl 1.5 Comparative Example 3 Li4Sb 0.5 PS 4.5 Cl 1.5 The starting materials were prepared by weighing out Li2S, Sb2S3, LiCl, and Sb2S3 according to the composition of the starting materials. The starting materials were pulverized in a ball mill, and the resulting product was heat-treated at about 450°C for about 25 minutes to obtain a sulfide-based solid electrolyte.

[0048] Comparative Examples 4 to 6 Starting materials were prepared by weighing out LiS, SbS, LiCl, and SbS according to the composition of each compound below. The starting materials were pulverized in a ball mill, and the resulting products were heat-treated at about 550°C (Comparative Examples 4 and 5) or about 450°C (Comparative Example 6) for about 25 minutes to obtain sulfide-based solid electrolytes.

[0049] - Comparative example 4: Li 5.5 P 0.9 Sb 0.1 S 4.4 Cl 1.5 - Comparative example 5: Li 5.5 S 4.3 Sb 0.2 S 4.3 Cl 1.5 - Comparative example 6: Li 5.5 P 0.5 Sb 0.5 S4Cl 1.5

[0050] Comparative Examples 7 to 10 Starting materials were prepared by weighing LiS, SbS, LiCl, and LiBr according to the composition of each compound below. The starting materials were pulverized in a ball mill, and the resulting product was heat-treated at about 550°C for about 25 minutes to obtain a sulfide-based solid electrolyte.

[0051] - Comparative example 7: Li 5.5 PS 4.5 Cl 1.4 Br 0.1 - Comparative example 8: Li 5.5 PS 4.5 Cl 1.2 Br 0.3 - Comparative example 9: Li 5.5 PS 4.5 Cl 1.0 Br 0.5 - Comparative Example 10: Li 5.5 PS 4.5 Cl 0.7 Br 0.8

[0052] Comparative Example 11 A sulfide-based solid electrolyte was produced in the same manner as in Example 2, but the heat treatment conditions were changed to a temperature of about 550° C. and a time of about 300 minutes.

[0053] Comparative Example 12 A sulfide-based solid electrolyte was produced in the same manner as in Example 3, but the heat treatment conditions were changed to a temperature of about 550° C. and a time of about 300 minutes.

[0054] Comparative Example 13 A sulfide-based solid electrolyte was produced in the same manner as in Comparative Example 3, but the heat treatment conditions were changed to a temperature of about 550° C. and a time of about 300 minutes.

[0055] Measurement of lithium ion conductivity, pellet density, and fracture strength The lithium ion conductivity of each sulfide-based solid electrolyte was measured. Specifically, each sulfide-based solid electrolyte was compression-molded to prepare a measurement molded body (diameter 13 mm, thickness 1 to 1.5 mm). After applying an AC potential of 10 mV to the molded body, a 1×10 6A frequency sweep of ~1 Hz was applied to measure the impedance values, which were used to calculate the lithium ion conductivity.

[0056] The pellet density of each sulfide-based solid electrolyte was measured using a pellet density tester. Approximately 3 g of each sulfide-based solid electrolyte was placed in a container of a specified diameter, and the pellet density was measured at approximately 1,000 kgf / cm. 2 The pellet density was measured by pressing at 1000 kJ / cm2.

[0057] The fracture strength of each sulfide-based solid electrolyte was measured based on the ASTM C773 measurement method.

[0058] The composition, heat treatment conditions, lithium ion conductivity, pellet density, and breaking strength of each sulfide-based solid electrolyte are shown in Table 1 below.

[0059] [Table 1] Comparative Examples 1 and 2 are general sulfide-based solid electrolytes. The breaking strength of Comparative Examples 1 and 2 is very low, at about 25 kPa to 27 kPa. Therefore, when applied to a lithium secondary battery with large volume expansion, the cell performance deteriorates due to low resistance to stress.

[0060] In Examples 1 to 4 and Comparative Example 3, lithium (Li) element was replaced with antimony (Sb). Comparative Example 3 introduced antimony (Sb) element beyond the range proposed in the present invention. Examples 1 to 4 have much higher fracture strength than Comparative Examples 1 and 2. Furthermore, when the number of moles of antimony (Sb) is 0.05 to 0.1, the lithium ion conductivity is also very high. This is presumably because vacancies are formed at the lithium (Li) element sites, allowing lithium ions to move more easily. When an excessive amount of antimony (Sb) is substituted, as in Comparative Example 3, both the lithium ion conductivity and fracture strength decrease. As will be described later, when the number of moles of antimony (Sb) element is large, a completely different crystalline phase is formed, and the material is unable to function as a solid electrolyte. Furthermore, Examples 1 to 4 have higher pellet densities than Comparative Examples 1 and 2.

[0061] In short, the sulfide-based solid electrolyte according to the present invention has a pellet density of 1.8 g / cm 3 ~2.0g / cm 3 When the pellet density of the sulfide-based solid electrolyte falls within the above range, the density of the positive electrode layer, the negative electrode layer, and / or the solid electrolyte layer containing the sulfide-based solid electrolyte can be increased, thereby improving the rate-limiting characteristics.

[0062] Furthermore, the sulfide-based solid electrolyte according to the present invention may have a breaking strength of 60 kPa or more as measured by ASTM C773. The upper limit of the breaking strength is not particularly limited. For example, the breaking strength of the sulfide-based solid electrolyte may be 300 kPa or less, 250 kPa or less, or 200 kPa or less. When the breaking strength of the sulfide-based solid electrolyte falls within the above range, the sulfide-based solid electrolyte can maintain its original shape without being affected by volume expansion during charging and discharging of a lithium secondary battery.

[0063] In Comparative Examples 4 to 6, the phosphorus (P) element is substituted with antimony (Sb). When compared with Examples 1 to 4, the lithium ion conductivity and breaking strength are at somewhat lower levels.

[0064] Comparative Examples 7 to 10 are Li 5.5 PS 4.5 Cl 1.5 The basic composition of Example 1 was replaced with Cl and Br in a ratio of 1:1. Compared with Examples 1 to 4, the pellet density and breaking strength were very low.

[0065] Raman spectrum FIG. 4 shows Comparative Example 2 (Li 5.5 PS 4.5 Cl 1.5 ), Example 2 (Li 5.2 Sb 0.1 PS 4.5 Cl 1.5 ), and Comparative Example 4 (Li 5.5 P 0.9 Sb 0.1 S 4.4 Cl 1.5 ) of the sulfide-based solid electrolyte. -1 ~450cm -1 This is an enlarged view of the peak in the range.

[0066] In Comparative Example 2 and Example 2, the Raman spectrum at 400 cm -1 ~450cm -1 It can be seen that the peaks seen in Comparative Example 2 and Comparative Example 4 have shifted downward. In contrast, the peak shapes are substantially the same in Comparative Example 2 and Comparative Example 4. Furthermore, Comparative Example 4 has a very large number of impurity peaks.

[0067] FIG. 6 shows Comparative Example 2 (Li 5.5 PS 4.5 Cl 1.5 ), Example 2 (Li 5.2 Sb 0.1 PS 4.5 Cl 1.5 ), Example 3 (Li 4.9 Sb 0.2 PS 4.5 Cl 1.5 ), and Comparative Example 3 (Li4Sb 0.5 PS 4.5 Cl 1.5) of the sulfide-based solid electrolyte. -1 ~450cm -1 This is an enlarged view of the peak in the range.

[0068] 6 and 7, Examples 2 and 3, in which antimony (Sb) element is present, show a difference in the 400 cm of the Raman spectrum compared to Comparative Example 2, in which antimony (Sb) element is not present. -1 ~450cm -1 It can be seen that the peaks seen in the antimony ion (Sb 3+ ) and lithium ion (Li + ) have similar effective ionic radii of about 76 pm, but the difference in atomic weight causes the peak to shift downward as shown above. -1 ~450cm -1 The downward shift of the peak observed at about 390 cm is evidence that antimony (Sb) has been substituted for lithium (Li). -1 Below, a completely different vibration mode of the bond occurs, which is consistent with the sudden decrease in lithium ion conductivity and fracture strength shown in Table 1.

[0069] X-ray diffraction analysis FIG. 8 shows Comparative Example 2 (Li 5.5 PS 4.5 Cl 1.5 ), Example 2 (Li 5.2 Sb 0.1 PS 4.5 Cl 1.5 ), and Comparative Example 4 (Li 5.5 P 0.9 Sb 0.1 S 4.4 Cl 1.5 9 shows the results of X-ray diffraction analysis of the sulfide-based solid electrolyte by NMR.

[0070] Similar to the Raman spectra, the peak shapes are substantially the same in Comparative Examples 2 and 4. This is presumably because antimony (Sb) element cannot substitute for phosphorus (P) element in Comparative Example 4 and is not dissolved.

[0071] Comparing Comparative Example 2 with Example 2, although there is a shift in the peak, it is within the error range, which shows that the sulfide-based solid electrolyte according to the present invention maintains the argyrodite crystal structure.

[0072] FIG. 10 shows Comparative Example 2 (Li 5.5 PS 4.5 Cl 1.5 ), Example 2 (Li 5.2 Sb 0.1 PS 4.5 Cl 1.5 ), Example 3 (Li 4.9 Sb 0.2 PS 4.5 Cl 1.5 ), and Comparative Example 3 (Li4Sb 0.5 PS 4.5 Cl 1.5 11 is an enlarged view of a specific portion of FIG. 10. FIG. 12 is a graph showing the results of X-ray diffraction analysis of the sulfide-based solid electrolyte obtained by Comparative Example 2 (Li 5.5 PS 4.5 Cl 1.5 11) and 13) show the results of X-ray diffraction analysis of the sulfide-based solid electrolytes of Comparative Examples 11 to 13. Comparative Examples 11 to 13 have the same compositions as Example 2, Example 3, and Comparative Example 3, respectively, but the heat treatment conditions were increased to 550°C and 300 minutes.

[0073] Raman spectroscopy and X-ray diffraction analysis confirmed that lithium (Li) element was present in PS4 3- We confirmed that stress is applied to the anion, and that this causes substitution.

[0074] Referring to Figure 12, it can be seen that as the heat treatment temperature and time increase, a significant amount of impurities are generated. In contrast, in Examples 2 and 3 of Figure 10, heat treatment was performed at a relatively low temperature for a short time, and no impurities were generated. On the other hand, Comparative Example 3 shows a peak of a completely different crystalline phase. This result is consistent with the rapid decrease in lithium ion conductivity and fracture strength of Comparative Example 3 in Table 1.

[0075] Cell performance evaluation Comparative example 2 (Li 5.5 PS 4.5 Cl 1.5 ), Example 2 (Li 5.2 Sb 0.1 PS 4.5 Cl 1.5 ), and Comparative Example 10 (Li 5.5 PS 4.5 Cl 0.7 Br 0.8 A lithium secondary battery was manufactured using the sulfide-based solid electrolyte obtained by the method described below.

[0076] A cathode powder containing a nickel-cobalt-manganese-based cathode active material, a solid electrolyte represented by Li6PS5Cl, a conductive material, and a binder was prepared. The cathode powder was placed in a mold, followed by the sulfide-based solid electrolytes of Comparative Example 2, Example 2, and Comparative Example 10, respectively, and a pressure of approximately 54 kPa was applied to obtain a laminate of a cathode layer and a solid electrolyte layer. Lithium metal was deposited on the solid electrolyte layer to obtain a lithium secondary battery.

[0077] The capacity of each lithium secondary battery was measured while charging and discharging under the following conditions, and the results are shown in Figure 13.

[0078] - Charging conditions: CC(~3.7V)-C / 20&CV(3.7V) - limiting current of C / 10 - Discharge condition: CC(~2.2V) - C / 20 Referring to Table 1, Comparative Example 10 has higher lithium ion conductivity than Example 2. However, referring to FIG. 13, Example 2 has superior cell performance than Comparative Example 10. This is because Example 2 has superior mechanical properties, which enable it to effectively form and maintain interfaces with the positive and negative electrode layers, thereby improving the durability of the solid electrolyte layer. It can be seen that the performance of a lithium secondary battery is significantly affected not only by lithium ion conductivity but also by mechanical properties.

[0079] Although the experimental examples and examples of the present invention have been described in detail above, the scope of the present invention is not limited to the above-mentioned experimental examples and examples, and various modifications and improvements made by those skilled in the art based on the basic concept of the present invention as defined in the appended claims are also included in the scope of the present invention. [Explanation of symbols]

[0080] 10: Positive electrode layer 20: Negative electrode layer 30: Solid electrolyte layer

Claims

1. containing lithium, phosphorus, sulfur, and a halogen element; It contains an argyrodite crystal structure, A sulfide-based solid electrolyte for a lithium secondary battery, which contains antimony (Sb) elements at least in part at the Wyckoff position 48h.

2. 2. The sulfide-based solid electrolyte for lithium secondary batteries according to claim 1, wherein the molar ratio of the sum of lithium and antimony to phosphorus ((Li+Sb) / P) is 4.9 or more and less than 5.

5.

3. The sulfide-based solid electrolyte for a lithium secondary battery according to claim 1, which is represented by the following formula 1: 【Chemical 1】 Ha includes fluorine (F), chlorine (Cl), bromine (Br), or iodine (I); The relationship 1.0≦x≦1.7 and 0<y≦0.3 are satisfied.

4. The sulfide-based solid electrolyte for a lithium secondary battery according to claim 1, which is represented by the following formula 2: 【Chemistry 2】 Ha1 and Ha2 contain different elements, Ha1 and Ha2 each independently contain fluorine (F), chlorine (Cl), bromine (Br), or iodine (I); The following conditions are satisfied: 1.0≦x≦1.7, 0<y≦0.3, and 0<a<1.

0.

5. Compared with sulfide-based solid electrolytes that do not contain antimony, the sulfide-based solid electrolyte has a Raman spectrum of 400 cm －１ ~450cm －１ 2. The sulfide-based solid electrolyte for a lithium secondary battery according to claim 1, wherein the peak observed in

6. 2. The sulfide-based solid electrolyte for a lithium secondary battery according to claim 1, which has a fracture strength of 60 kPa or more as measured by ASTM C773.

7. Pellet density is 1.8 g / cm ３ ~2.0 g / cm ３ 2. The sulfide-based solid electrolyte for a lithium secondary battery according to claim 1, wherein

8. reacting lithium sulfide, phosphorus sulfide, lithium halide, and antimony sulfide to obtain a product; and heat-treating the product to obtain a sulfide-based solid electrolyte. The sulfide-based solid electrolyte contains lithium, phosphorus, sulfur, and a halogen, has an argyrodite crystal structure, and contains antimony (Sb) at at least a portion of the 48h Wyckoff position.

9. 9. The method of claim 8, wherein the heat-treating step comprises heat-treating the product at 450°C to 500°C.

10. 9. The method of claim 8, wherein the heat treatment comprises heat treating the product for 10 to 30 minutes.

11. 9. The method for producing a sulfide-based solid electrolyte for a lithium secondary battery according to claim 8, wherein the molar ratio of the sum of lithium and antimony to phosphorus ((Li+Sb) / P) is 4.9 or more and less than 5.

5.

12. The method for producing a sulfide-based solid electrolyte for a lithium secondary battery according to claim 8, which is represented by the following formula 1: 【Chemistry 3】 Ha includes fluorine (F), chlorine (Cl), bromine (Br), or iodine (I); The relationship 1.0≦x≦1.7 and 0<y≦0.3 are satisfied.

13. The method for producing a sulfide-based solid electrolyte for a lithium secondary battery according to claim 8, which is represented by the following formula 2: 【Chemistry 4】 Ha1 and Ha2 contain different elements, Ha1 and Ha2 each independently contain fluorine (F), chlorine (Cl), bromine (Br), or iodine (I); The following conditions are satisfied: 1.0≦x≦1.7, 0<y≦0.3, and 0<a<1.

0.

14. As the antimony content increases, the 400 cm －１ ~450cm －１ The method for producing a sulfide-based solid electrolyte for a lithium secondary battery according to claim 8, wherein the peak observed in

15. 9. The method for producing a sulfide-based solid electrolyte for a lithium secondary battery according to claim 8, wherein the fracture strength measured by ASTM C773 is 60 kPa or more.

16. Pellet density is 1.8 g / cm ３ ~2.0 g / cm ３ The method for producing a sulfide-based solid electrolyte for a lithium secondary battery according to claim 8, wherein

17. a positive electrode layer; a negative electrode layer; a solid electrolyte layer sandwiched between the positive electrode layer and the negative electrode layer, A lithium secondary battery, wherein at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer comprises the sulfide-based solid electrolyte according to any one of claims 1 to 7.

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