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

Abstract

The present invention provides a sulfide-based solid electrolyte with improved moisture stability, a sulfide-based solid electrolyte with improved ionic conductivity, a method for producing a sulfide-based solid electrolyte using low-cost raw materials, and a method for producing a sulfide-based solid electrolyte that is easily synthesized on a large scale. [Solution] The sulfide-based solid electrolyte has a content of at least one element A selected from the group consisting of Group 1 and Group 2 elements excluding Li, as determined by inductively coupled plasma spectroscopy (ICP) analysis, of 0.1 to 5 mol%.

Description

Technical Field

[0001] The present disclosure relates to a sulfide-based solid electrolyte, a method for manufacturing the same, and a all-solid-state battery including the same.

Background Art

[0002] In recent years, development of all-solid-state batteries including solid electrolytes has been continuously carried out. The above all-solid-state battery includes a solid electrolyte instead of an existing liquid electrolyte, is excellent in safety against explosion / fire, and can have an improved energy density. As solid electrolytes applicable to such all-solid-state batteries, there are polymer-based solid electrolytes, oxide-based solid electrolytes, sulfide-based solid electrolytes, and the like.

[0003] Among these, sulfide-based solid electrolytes have relatively high ionic conductivity and are attracting attention as electrolytes with high commercialization potential. Therefore, development of technologies capable of improving the performance of sulfide-based solid electrolytes is required.

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to one aspect of the present disclosure, a sulfide-based solid electrolyte with improved moisture stability is provided.

[0005] According to another aspect of the present disclosure, a sulfide-based solid electrolyte with improved ionic conductivity is provided. ​​​​​​​​​​​​​In one implementation example, the sulfide-based solid electrolyte has a content of at least one element A selected from the group consisting of Group 1 elements and Group 2 elements excluding Li of 0.1 to 5 mol% during inductively coupled plasma spectroscopy (ICP) analysis.

[0009] In some implementation examples, the sulfide-based solid electrolyte can be represented by the following Chemical Formula 1.

[0010] [Chemical Formula 1] Li a PS b (M1) c (M2) d A x B y

[0011] In Chemical Formula 1 above, 1 ≤ a ≤ 6, 1 ≤ b ≤ 5, 0 ≤ c ≤ 3, 0 ≤ d ≤ 3, 0 < x ≤ 1, 0 < y ≤ 2, Li is lithium, P is phosphorus, S is sulfur, M1 is a Group 17 element, M2 is a Group 17 element different from M1, A is at least one selected from the group consisting of Group 1 elements and Group 2 elements excluding Li, and B is a Group 17 element, NO3 - and BF4 - and is at least one selected from the group consisting of.

[0012] In some implementation examples, the element A can correspond to A in the compound represented by the following Formula 2.

[0013] [Formula 2] AB y

[0014] In Formula 2 above, A is at least one selected from the group consisting of Group 1 elements and Group 2 elements excluding Li, B is a Group 17 element, NO3 - and BF4 - and is at least one selected from the group consisting of, and y is 1 or 2.

[0015] In some implementation examples, when the above-mentioned sulfide-based solid electrolyte is subjected to SEM-EDS analysis using a scanning electron microscope (SEM) and an energy-dispersive X-ray spectrometer (EDS), the binding energy of the peak representing element A may be different from the binding energies of the peaks representing phosphorus (P) and sulfur (S).

[0016] In some implementations, the above-mentioned sulfide-based solid electrolyte may include regions in the EDS mapping image where the region representing element A differs from the regions representing phosphorus (P) and sulfur (S) when analyzed using a scanning electron microscope (SEM) and energy-dispersive X-ray spectrometer (EDS).

[0017] A method for producing a sulfide-based solid electrolyte according to one example includes the steps of: producing a first solution by mixing a sulfur compound represented by the following chemical formula 3 and a lithium compound represented by the following chemical formula 4 with a first solvent; obtaining a first mixture containing lithium sulfide (Li2S) and a compound represented by the following chemical formula 2 from the first solution; producing a second solution by i) mixing the first mixture with phosphorus pentasulfide (P2S5), a first lithium halide, and a second solvent, or ii) mixing it with phosphorus pentasulfide (P2S5), a first lithium halide, a second lithium halide, and a second solvent; and obtaining a sulfide-based solid electrolyte by heat treatment after obtaining a second mixture from the second solution, wherein the sulfide-based solid electrolyte may have a content of element A corresponding to A in the compound represented by the following chemical formula 2 of 0.1 to 5 mol% when analyzed by inductively coupled plasma spectroscopy (ICP).

[0018] [Chemical formula 2] AB y

[0019] In the above chemical formula 2, A is at least one selected from the group consisting of Group 1 and Group 2 elements excluding Li, and B is a Group 17 element, NO3 - and BF4 - At least one selected from the group consisting of the following, where y is 1 or 2.

[0020] [Chemical Formula 3] A x S

[0021] In the above Chemical Formula 3, A is at least one selected from the group consisting of Group 1 elements and Group 2 elements excluding Li, S is sulfur, and x is 1 or 2.

[0022] [Chemical Formula 4] LiB

[0023] In the above Chemical Formula 4, Li is lithium, and B is at least one selected from the group consisting of Group 17 elements, NO3 - and BF4 - from the group consisting of.

[0024] In some embodiments, the sulfide-based solid electrolyte can be represented by the following Chemical Formula 1.

[0025] [Chemical Formula 1] Li a PS b (M1) c (M2) d A x B y

[0026] In the above Chemical Formula 1, 1 ≦ a ≦ 6, 1 ≦ b ≦ 5, 0 ≦ c ≦ 3, 0 ≦ d ≦ 3, 0 < x ≦ 1, 0 < y ≦ 2, Li is lithium, P is phosphorus, S is sulfur, M1 is a Group 17 element, M2 is a Group 17 element different from M1, A is at least one selected from the group consisting of Group 1 elements and Group 2 elements excluding Li, and B is at least one selected from the group consisting of Group 17 elements, NO3 - and BF4 - from the group consisting of.

[0027] In some embodiments, the method for manufacturing the sulfide-based solid electrolyte may further include a step of removing a part of the compound represented by the above Chemical Formula 2 before the step of obtaining the first mixture from the above first solution.

[0028] In some implementations, the step of removing a portion of the compound represented by chemical formula 2 can be carried out by cooling the first solution to 15°C to 25°C.

[0029] In some implementations, the first solvent may include at least one selected from the group consisting of alcohol solvents, tetrahydrofuran solvents, and phosphoramide solvents.

[0030] In some implementations, the second solvent may include at least one selected from the group consisting of alcohol-based solvents, tetrahydrofuran-based solvents, cyanide-based solvents, and phosphoramide-based solvents.

[0031] In some implementation examples, the heat treatment of the second mixture can be carried out at a temperature of 250°C to 650°C.

[0032] An all-solid-state battery according to one of the implementation examples includes a sulfide-based solid electrolyte according to one of the implementation examples described above. [Effects of the Invention]

[0033] According to one implementation of this disclosure, the moisture stability of sulfide-based solid electrolytes can be improved.

[0034] According to another implementation of this disclosure, the ionic conductivity of sulfide-based solid electrolytes can be improved.

[0035] According to another implementation of this disclosure, sulfide-based solid electrolytes can be manufactured with excellent economic efficiency.

[0036] According to another implementation of this disclosure, large-scale synthesis may be facilitated during the production of sulfide-based solid electrolytes. [Brief explanation of the drawing]

[0037] [Figure 1] This figure shows the results of impedance analysis performed on the sulfide-based solid electrolyte in the example before and after exposure to air. [Figure 2] This figure shows the results of impedance analysis performed on the comparative example sulfide-based solid electrolyte before and after exposure to air. [Figure 3a] This figure shows the results of analyzing the peaks of each component corresponding to the binding energy of the sulfide-based solid electrolytes in the examples using a scanning electron microscope (SEM) and an energy-dispersive X-ray spectrometer (EDS). [Figure 3b] This figure shows the results of analyzing element A in the sulfide-based solid electrolytes of the examples using a scanning electron microscope (SEM) and an energy-dispersive X-ray spectrometer (EDS). [Figure 3c] This figure shows the results of phosphorus analysis of the sulfide-based solid electrolytes in the examples using a scanning electron microscope (SEM) and an energy-dispersive X-ray spectrometer (EDS). [Figure 3d] This figure shows the results of sulfur analysis of the sulfide-based solid electrolytes in the examples, performed using a scanning electron microscope (SEM) and an energy-dispersive X-ray spectrometer (EDS). [Figure 4a] This figure shows the results of analyzing the peaks of each component corresponding to the binding energy of the comparative example sulfide-based solid electrolyte using a scanning electron microscope (SEM) and energy-dispersive X-ray spectrometer (EDS). [Figure 4b] This figure shows the results of phosphorus analysis of the comparative sulfide-based solid electrolyte using a scanning electron microscope (SEM) and energy-dispersive X-ray spectrometer (EDS). [Figure 4c] This figure shows the results of sulfur analysis of the comparative example sulfide-based solid electrolyte using a scanning electron microscope (SEM) and energy-dispersive X-ray spectrometer (EDS). [Modes for carrying out the invention]

[0038] The technologies disclosed herein and their implementations will be described in detail below with reference to the accompanying drawings. However, the embodiments of the technologies described above can be modified into various different forms, and their scope is not limited to the implementations described below. Furthermore, the technologies disclosed herein may be applied not only to the configurations of the implementations described below, but may also be configured by selectively combining all or part of each implementation to allow for various modifications.

[0039] As mentioned above, there is a need for the development of technologies that can improve the performance of sulfide-based solid electrolytes. One example is that the ionic conductivity and / or water stability of sulfide-based solid electrolytes can be improved by doping them with different elements. For example, some of the phosphorus (P) and sulfur (S) in Li6PS5Cl, an argyrodite-structured sulfide-based solid electrolyte, can be replaced with other elements.

[0040] According to one implementation example of this disclosure, a sulfide-based solid electrolyte can be manufactured with improved performance, such as moisture stability, by substituting lithium (Li) with a different element. According to this implementation example, it becomes easy to synthesize sulfide-based solid electrolytes with improved performance in large quantities, and the manufacturing process is also economically efficient. Below, an implementation example of the technology disclosed in this disclosure will be specifically described with reference to Figures 1 to 4c.

[0041] Sulfide solid electrolyte In one example, the sulfide-based solid electrolyte has a content of at least one element A selected from the group consisting of Group 1 and Group 2 elements excluding Li, as determined by inductively coupled plasma spectroscopy (ICP) analysis, of 0.1 to 5 mol%. In the above sulfide-based solid electrolyte, a portion of the lithium (Li) is substituted (doped) with a different element, and it can have excellent water stability.

[0042] In some implementation examples, the above-mentioned sulfide-based solid electrolyte can be represented by the following chemical formula 1.

[0043] [Chemical formula 1] Li a PS b (M1) c (M2) d A x B y

[0044] In the above Chemical Formula 1, 1 ≤ a ≤ 6, 1 ≤ b ≤ 5, 0 ≤ c ≤ 3, 0 ≤ d ≤ 3, 0 < x ≤ 1, 0 < y ≤ 2, Li is lithium, P is phosphorus, S is sulfur, M1 is a Group 17 element, M2 is a Group 17 element different from M1, A is at least one selected from the group consisting of Group 1 elements and Group 2 elements excluding Li, and B is a Group 17 element, NO3 - and BF4 - and is at least one selected from the group consisting of. The above element A can correspond to A in the above Chemical Formula 1.

[0045] In some embodiments, the above element A can correspond to A in the compound represented by the following Chemical Formula 2.

[0046] [Chemical Formula 2] AB y

[0047] In the above Chemical Formula 2, A is at least one selected from the group consisting of Group 1 elements and Group 2 elements excluding Li, B is a Group 17 element, NO3 - and BF4 - and is at least one selected from the group consisting of, and y is 1 or 2.

[0048] The compound represented by the above Chemical Formula 2 can be generated in the process of manufacturing lithium sulfide (Li2S) by the reaction of the sulfur compound represented by the following Chemical Formula 3 and the lithium compound represented by the following Chemical Formula 4.

[0049] [Chemical Formula 3] A x S

[0050] In the above chemical formula 3, A is at least one selected from the group consisting of Group 1 and Group 2 elements excluding Li, S is sulfur, and x is 1 or 2.

[0051] [Chemical formula 4] LiB

[0052] In the above chemical formula 4, Li is lithium, B is a group 17 element, NO3 - and BF4 - It is at least one selected from the group consisting of the following:

[0053] In some implementations, the sulfide-based solid electrolyte represented by chemical formula 1 may be a sulfide-based solid electrolyte in which some of the lithium (Li) is replaced with sodium (Na) and the electrolyte is doped with sodium (Na). Specifically, the compound represented by chemical formula 2 may be sodium chloride (NaCl). When the sulfide-based solid electrolyte represented by chemical formula 1 is doped with sodium (Na), it may exhibit superior water stability and ionic conductivity.

[0054] In some implementation examples, the compound represented by chemical formula 3 may be sodium sulfide (Na2S), and the compound represented by chemical formula 4 may be lithium chloride (LiCl).

[0055] The above sulfide-based solid electrolyte has a content of at least one element A selected from the group consisting of Group 1 and Group 2 elements excluding Li, at a concentration of 0.1 to 5 mol% during inductively coupled plasma spectroscopy (ICP) analysis. The above inductively coupled plasma spectroscopy (ICP) analysis allows for the quantitative measurement of the cation content contained in the analyte. The above inductively coupled plasma spectroscopy (ICP) analysis equipment is not particularly limited. For example, the above inductively coupled plasma spectroscopy (ICP) analysis can be performed using an Agilent 5800.

[0056] In some implementation examples, the sulfide-based solid electrolyte may have a content of at least one element A selected from the group consisting of Group 1 and Group 2 elements excluding Li, which may be 3 mol% or less, 1.5 mol% or less, or 0.5 mol% or more, 1 mol% or more, or 1.4 mol% or more, as determined by inductively coupled plasma spectroscopy (ICP) analysis.

[0057] In some implementation examples, when the above-mentioned sulfide-based solid electrolyte is subjected to SEM-EDS analysis using a scanning electron microscope (SEM) and an energy-dispersive X-ray spectrometer (EDS), the binding energy of the peak representing element A may be different from the binding energies of the peaks representing phosphorus (P) and sulfur (S).

[0058] The peaks indicating phosphorus (P) and sulfur (S) may correspond to the phosphorus (P) and sulfur (S) contained in the sulfide-based solid electrolyte represented by chemical formula 1, and the peak indicating element A may correspond to the element A contained in the compound represented by chemical formula 2.

[0059] As shown in Figure 3a, in some implementation examples, the sulfide-based solid electrolyte can be clearly distinguished during SEM-EDS analysis because the peaks representing phosphorus (P) and sulfur (S) in chemical formula 1 are different from the peak corresponding to A in chemical formula 2.

[0060] In some implementations, the peak representing sulfur (S) in the above chemical formula 1 can appear with binding energies of 0.1–0.2 keV (exemplarily 0.15 keV) and 2.3–2.4 keV (exemplarily 2.31 keV) during SEM-EDS analysis, and the peak representing phosphorus (P) can appear with binding energies of 2.1–2.2 keV (exemplarily 2.013 keV) during SEM-EDS analysis.

[0061] In some implementation examples, the peak corresponding to A in the above chemical formula 2 can appear with a bond energy of 1.0 to 1.1 keV during SEM-EDS analysis.

[0062] In some implementations, the above-mentioned sulfide-based solid electrolyte may, when analyzed using a scanning electron microscope (SEM) and energy-dispersive X-ray spectrometer (EDS), include regions representing element A in the EDS mapping image that differ from regions representing phosphorus (P) and sulfur (S). For example, the regions representing phosphorus (P) and sulfur (S) may correspond to regions representing the sulfide-based solid electrolyte represented by chemical formula 1. Furthermore, the regions representing element A may correspond to regions representing the compound represented by chemical formula 2.

[0063] In the above EDS mapping image, the division of regions representing each component can be done by quantifying the points where each component is detected in the EDS mapping image, saving the image of the region where the target component is detected, and making a determination.

[0064] As shown in Figures 3b to 3d, in some implementation examples, the sulfide-based solid electrolyte may include a region in the EDS mapping image during SEM-EDS analysis where the region corresponding to A in chemical formula 2 is clearly different from the regions representing phosphorus (P) and sulfur (S) in chemical formula 1.

[0065] The above-mentioned SEM-EDS analysis equipment and conditions are not particularly limited. For example, the above SEM-EDS analysis can be performed using a Bruker FlatQuad equipped with an EDS system linked to the SEM, under the conditions of an acceleration voltage of 5kV, a pulse throughput of 130kcps, and a working distance of 15mm.

[0066] A sulfide-based solid electrolyte based on any one of the above-mentioned implementation examples can be manufactured by the method described below.

[0067] Method for producing sulfide-based solid electrolytes A method for producing a sulfide-based solid electrolyte according to one example includes the steps of: producing a first solution by mixing a sulfur compound represented by the following chemical formula 3 and a lithium compound represented by the following chemical formula 4 with a first solvent; obtaining a first mixture containing lithium sulfide (Li2S) and a compound represented by the following chemical formula 2 from the first solution; producing a second solution by i) mixing the first mixture with phosphorus pentasulfide (P2S5), a first lithium halide, and a second solvent, or ii) mixing it with phosphorus pentasulfide (P2S5), a first lithium halide, a second lithium halide, and a second solvent; and obtaining a sulfide-based solid electrolyte by heat treatment after obtaining a second mixture from the second solution, wherein the sulfide-based solid electrolyte has a content of 0.1 to 5 mol% of element A corresponding to A in the compound represented by the following chemical formula 2 when analyzed by inductively coupled plasma spectroscopy (ICP).

[0068] [Chemical formula 2] AB y

[0069] In the above chemical formula 2, A is at least one selected from the group consisting of Group 1 and Group 2 elements excluding Li, and B is a Group 17 element, NO3 - and BF4 - At least one selected from the group consisting of the following, where y is 1 or 2.

[0070] [Chemical formula 3] A x S

[0071] In the above chemical formula 3, A is at least one selected from the group consisting of Group 1 and Group 2 elements excluding Li, S is sulfur, and x is 1 or 2.

[0072] [Chemical formula 4] LiB

[0073] In the above chemical formula 4, Li is lithium, B is a group 17 element, NO3 - and BF4 - It is at least one selected from the group consisting of the following:

[0074] The above-described method for producing sulfide-based solid electrolytes allows for the production of sulfide-based solid electrolytes with high economic efficiency using inexpensive raw materials. Furthermore, by employing a liquid-phase synthesis reaction, this method can facilitate large-scale synthesis. The following sections will describe each step of the above-described method for producing sulfide-based solid electrolytes in detail.

[0075] <Manufacturing stage of the first solution> The manufacturing step of the above first solution involves the sulfur compound (A) represented by the above chemical formula 3. x The step may also involve reacting S) with the lithium compound (LiB) represented by the above chemical formula 4 to synthesize lithium sulfide (Li2S). The above first solution is lithium sulfide (Li2S) synthesized by the reaction of the compounds represented by chemical formulas 3 and 4 and the compound (AB) represented by chemical formula 2. y ) may include the sulfur compound represented by the above chemical formula 3 (A x S) and the lithium compound (LiB) represented by the above chemical formula 4 can be prepared in a 1:2 molar ratio for the synthesis of lithium sulfide (Li2S).

[0076] In some implementations, the manufacturing step of the first solution may be carried out at a temperature above room temperature. For example, the manufacturing step of the first solution may be carried out at a temperature of 25°C or higher, or at a temperature below the boiling point of the solvent (for example, 70°C or lower).

[0077] In some implementations, the method for producing the sulfide-based solid electrolyte may further include a step of removing a portion of the compound represented by chemical formula 2 before the step of obtaining the first mixture from the first solution. The compound represented by chemical formula 2 may be a compound used to dope the sulfide-based solid electrolyte with a different element, but if its content is too high, it may actually degrade the performance of the sulfide-based solid electrolyte. Therefore, by removing a portion of the compound represented by chemical formula 2 before obtaining the first mixture from the first solution, a sulfide-based solid electrolyte with superior performance can be produced.

[0078] In some implementations, the step of removing a portion of the compound represented by chemical formula 2 can be performed by cooling the first solution to 15°C to 25°C. When the temperature of the first solution is lowered to room temperature (25°C or below), the solubility of the compound represented by chemical formula 2 contained in the first solution is reduced, allowing it to precipitate. If the temperature of the first solution exceeds 25°C, the compound represented by chemical formula 2 may not precipitate easily. On the other hand, if the temperature of the first solution is below 15°C, the solubility of lithium sulfide (Li2S) will also decrease, potentially reducing the amount of lithium sulfide (Li2S) obtained, and the compound represented by chemical formula 2 may precipitate excessively, preventing doping with the sulfide-based solid electrolyte.

[0079] In some implementations, the first solvent may be a polar solvent. For example, the first solvent may include at least one selected from the group consisting of alcohol solvents, tetrahydrofuran solvents, and phosphoramide solvents.

[0080] The above alcoholic solvent is not particularly limited as long as it is an alcohol compound having a hydroxyl group (-OH). For example, the above alcoholic solvent may be methanol, ethanol, isopropanol, etc.

[0081] The above-mentioned tetrahydrofuran solvent is not particularly limited as long as it is a compound having a pentagonal heterocycle in which four carbon atoms and an oxygen atom are linked by a single bond. For example, the above-mentioned tetrahydrofuran solvent may be one or more selected from tetrahydrofuran and compounds in which at least one functional group is bonded to the second or third carbon position of the above-mentioned tetrahydrofuran. For example, compounds in which at least one functional group is bonded to the second or third carbon position of the above-mentioned tetrahydrofuran may be 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 2-(isocyanomethyl)tetrahydrofuran, 3-(aminomethyl)tetrahydrofuran, etc.

[0082] The above-mentioned phosphoramide solvent is not particularly limited as long as it is a compound having a structure in which a phosphorus atom, double-bonded to an oxygen atom, is connected to an oxygen atom or a nitrogen atom by three single bonds. For example, the above-mentioned phosphoramide solvent may be phosphoramide, diethyl phosphoramidate, hexamethyl phosphoramide, etc.

[0083] In some implementation examples, the concentration of the first solution may be 0.1 to 0.5 M. If the concentration of the first solution is less than 0.1 M, the amount of solvent used may increase, potentially raising the cost per process. If the concentration of the first solution exceeds 0.5 M, the yield of the sulfide-based solid electrolyte may decrease.

[0084] <Steps for obtaining the first mixture> The step of obtaining the first mixture described above means obtaining the first mixture containing lithium sulfide (Li2S) and the compound represented by chemical formula 2 described above from the first solution produced as described above. Substances precipitated in the first solution can be removed by filtration. The filtration of the first solution can be carried out in an inert gas environment such as argon (Ar).

[0085] In some implementations, if the method for producing the sulfide-based solid electrolyte further includes a step of removing a portion of the compound represented by chemical formula 2 before the step of obtaining the first mixture from the first solution, the portion of the compound represented by chemical formula 2 can be precipitated in the first solution by a cooling process and then removed by filtration.

[0086] The first mixture can be obtained by removing the first solvent by drying the first solution after it has undergone a filtration process. The first mixture is dissolved in the first solution after the filtration process, and the first mixture can be obtained in high purity when the first solvent is removed through the drying process.

[0087] The drying process of the first solution described above can be carried out at a temperature above the boiling point of the first solvent used, so as to be able to remove the first solvent. In some implementations, the drying process of the first solution described above can be carried out at a temperature of 70°C or higher and 900°C or lower under a vacuum or inert gas environment such as argon (Ar).

[0088] <Manufacturing stage of the second solution> The above-mentioned step for producing the second solution may be a step of producing a second mixture for the production of a sulfide-based solid electrolyte and a second solution containing the first mixture obtained as described above. Specifically, the above-mentioned step for producing the second solution may be a step of i) mixing the first mixture with phosphorus pentasulfide (P2S5), a first lithium halide, and a second solvent, or ii) mixing the first mixture with phosphorus pentasulfide (P2S5), a first lithium halide, a second lithium halide, and a second solvent.

[0089] The first lithium halide mentioned above refers to the lithium halide represented by the chemical formula LiM1, where M1 is a group 17 element and has the same meaning as M1 in chemical formula 1.

[0090] The above-mentioned second lithium halide is represented by the chemical formula LiM2, and means a lithium halide different from the above-mentioned first lithium halide. The above-mentioned M2 is a group 17 element different from M1 and has the same meaning as M2 in chemical formula 1.

[0091] In some implementation examples, the content of the first mixture contained in the second solution may be 34 to 44% by weight.

[0092] In some implementation examples, the content of phosphorus pentasulfide (P2S5) in the second solution may be 41-42% by weight.

[0093] In some implementations, if the manufacturing step of the second solution involves mixing the first mixture with phosphorus pentasulfide (P2S5), a first lithium halide, and a second solvent, the content of the first lithium halide in the second solution may be 15 to 24% by weight.

[0094] In some implementations, if the manufacturing step of the second solution involves mixing the first mixture with phosphorus pentasulfide (P2S5), a first lithium halide, a second lithium halide, and a second solvent, the total content of the first lithium halide and the second lithium halide in the second solution may be 22 to 28% by weight. The weight ratio of the first lithium halide and the second lithium halide in the second solution may be 0.18 to 22.

[0095] In some implementations, the second solvent may be a polar solvent. For example, the second solvent may include at least one selected from the group consisting of alcohol-based solvents, tetrahydrofuran-based solvents, cyanide-based solvents, and phosphoramide-based solvents.

[0096] The above-mentioned cyanide solvent is not particularly limited as long as it is a cyanide compound having a cyano group (C≡N). For example, the above-mentioned cyanide solvent may be benzyl cyanide, 4-methylbenzyl cyanide, allyl cyanide, acetonitrile, etc.

[0097] Detailed explanations of the above-mentioned alcohol-based solvents, tetrahydrofuran-based solvents, and phosphoramide-based solvents are omitted as they would be redundant with the information provided above.

[0098] <Acquisition steps for sulfide-based solid electrolytes> The step of obtaining the above-mentioned sulfide-based solid electrolyte can mean the step of obtaining a second mixture from the second solution produced as described above, and then heat-treating it to obtain the sulfide-based solid electrolyte represented by the above-mentioned chemical formula 1.

[0099] The second mixture can be obtained by removing the second solvent by drying the second solution prepared as described above. The second mixture is dissolved in the second solution, and the second mixture can be obtained in high purity when the second solvent is removed during the drying process.

[0100] The second mixture described above may be i) a substance obtained by mixing the first mixture, phosphorus pentasulfide (P2S5), and the first lithium halide, or ii) a substance obtained by mixing the first mixture, phosphorus pentasulfide (P2S5), the first lithium halide, and the second lithium halide.

[0101] The drying process of the second solution described above can be carried out at a temperature above the boiling point of the second solvent used, so as to be able to remove the second solvent. In some implementations, the drying process of the second solution described above can be carried out in a vacuum at a temperature of 70°C or higher, and at a temperature of 200°C or lower.

[0102] The second mixture obtained from the above second solution can be heat-treated to form a sulfide-based solid electrolyte represented by the above chemical formula 1. In some implementations, the heat treatment of the second mixture can be carried out at 250°C to 650°C. Exemplarily, the heat treatment of the second mixture can be carried out at 350°C or above, or 450°C or above, and at 600°C or below, or 550°C or below. The heat treatment of the second mixture can be carried out in an inert gas environment such as argon (Ar).

[0103] All solid state battery An all-solid-state battery according to one implementation example includes a sulfide-based solid electrolyte according to one of the implementation examples described above. Exemplarily, the all-solid-state battery may include a sulfide-based solid electrolyte according to one of the implementation examples described above between the negative electrode and the positive electrode.

[0104] The structure, components, etc., of the positive and negative electrodes described above are not particularly limited. For example, the positive and negative electrodes may each have a structure comprising an electrode current collector and an electrode mixture layer on at least one surface of the electrode current collector.

[0105] The composition of the electrode current collector described above is not particularly limited. For example, the electrode current collector may be a plate or foil made of one or more of the following: indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), and alloys thereof. Furthermore, the thickness of the electrode current collector is not particularly limited. For example, the thickness of the negative electrode current collector may be 0.1 to 50 μm.

[0106] The electrode mixture layer described above may contain a positive electrode active material or a negative electrode active material. The positive electrode active material and the negative electrode active material are not particularly limited and may include compounds that can reversibly intercalate and deintercalate lithium ions.

[0107] The above-mentioned positive electrode active material is not particularly limited. For example, the positive electrode active material may include a lithium-nickel metal oxide. The lithium-nickel metal oxide may further include at least one of cobalt (Co), manganese (Mn), and aluminum (Al).

[0108] In some implementations, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or crystalline structure represented by the following chemical formula 5.

[0109] [Chemical formula 5] Li x Ni a M b O 2+z

[0110] In the above chemical formula 5, 0.9 ≤ x ≤ 1.2, 0.6 ≤ a ≤ 0.99, 0.01 ≤ b ≤ 0.4, and -0.5 ≤ z ≤ 0.1 may also be applicable. As stated above, M may include Co, Mn, and / or Al.

[0111] The chemical structure represented by chemical formula 5 above indicates the bonding relationships contained within the layered or crystalline structure of the positive electrode active material and does not exclude other further elements. Exemplarily, M may include Co and / or Mn, and Co and / or Mn may be provided together with Ni as the main active element of the positive electrode active material. Chemical formula 5 above is provided to represent the bonding relationships of the main active element and should be understood as a formula that encompasses the introduction and substitution of further elements.

[0112] In some implementations, auxiliary elements may be included in addition to the main active element to enhance the chemical stability of the positive electrode active material or the layered / crystalline structure. These auxiliary elements may be mixed together with the layered / crystalline structure to form bonds, and in this case, they should also be understood as being within the range of the chemical structure represented by chemical formula 5.

[0113] The above auxiliary elements may include, for example, at least one of Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, and Zr. The above auxiliary elements may also act as auxiliary active elements that contribute to the capacity / power activity of the positive electrode active material together with Co or Mn, such as Al.

[0114] For example, the above-mentioned positive electrode active material or lithium-nickel metal oxide may include a layered structure or crystalline structure represented by the following chemical formula 5-1.

[0115] [Chemical formula 5-1] Li x Ni a M1 b1 M2 b2 O 2+z

[0116] In chemical formula 5-1, M1 may include Co, Mn, and / or Al. M2 may include the aforementioned auxiliary elements. In chemical formula 5-1, 0.9 ≤ x ≤ 1.2, 0.6 ≤ a ≤ 0.99, 0.01 ≤ b1 + b2 ≤ 0.4, and -0.5 ≤ z ≤ 0.1 may also be true.

[0117] The above-mentioned positive electrode active material may further contain coating elements or doping elements. For example, elements substantially identical or similar to the auxiliary elements described above can be used as coating elements or doping elements. Exemplaryly, one or more of the above-mentioned elements can be used as coating elements or doping elements.

[0118] The above-mentioned coating element or doping element may be present on the surface of the lithium-nickel metal oxide particles, or may penetrate through the surface of the lithium-nickel metal oxide particles and be contained within the bonding structure represented by chemical formula 5 or chemical formula 5-1.

[0119] The above-mentioned positive electrode active material can include nickel-cobalt-manganese (NCM)-based lithium oxide. In this case, an NCM-based lithium oxide with an increased nickel content may be used.

[0120] The content of Ni in the above NCM-based lithium oxide (for example, the molar fraction of nickel in the total number of moles of nickel, cobalt, and manganese) may be 0.6 or more, 0.7 or more, or 0.8 or more. In some embodiments, the content of Ni may be 0.8 to 0.95, 0.82 to 0.95, 0.83 to 0.95, 0.84 to 0.95, 0.85 to 0.95, or 0.88 to 0.95.

[0121] In some embodiments, the above positive electrode active material may also include a lithium cobalt oxide-based active material, a lithium manganese oxide-based active material, a lithium nickel oxide-based active material, or a lithium iron phosphate-based (LFP) active material (for example, LiFePO4).

[0122] In some embodiments, the above positive electrode active material can include an Mn-rich-based active material, an LLO (Li rich layered oxide) / OLO (Over Lithiated Oxide)-based active material, or a Co-less-based active material having a chemical structure or crystal structure represented by Chemical Formula 6.

[0123] [Chemical Formula 6] p[Li2MnO3]·(1-p)[Li q JO2]

[0124] In Chemical Formula 6, 0 < p < 1, 0.9 ≤ q ≤ 1.2, and J can include at least one element among Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg, and B.

[0125] The above negative electrode active material is not particularly limited. Exemplarily, the above negative electrode active material may be one or more selected from the group consisting of carbon-based materials such as crystalline carbon, amorphous carbon, carbon composites, and carbon fibers; lithium metal; lithium alloys; silicon-containing substances, and tin-containing substances.

[0126] The crystalline carbon may, for example, be a graphite-based carbon such as natural graphite, artificial graphite, graphitized coke, graphitized mesocarbon microbeads (MCMB), graphitized mesophase pitch-based carbon fiber (MPCF), or the like.

[0127] The amorphous carbon may, for example, be hard carbon, soft carbon, coke, mesocarbon microbeads (MCMB), or mesophase pitch-based carbon fiber (MPCF).

[0128] The elements contained in the lithium alloy may, for example, be aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium.

[0129] The silicon-containing substance is not particularly limited as long as it contains silicon, and may be an active material capable of alloying with lithium (Li). For example, the silicon-containing substance may be one or more selected from the group consisting of silicon (Si), silicon oxide (SiOx; 0 < x < 2), metal-doped silicon oxide (SiOx; 0 < x < 2), carbon-coated silicon oxide (SiOx; 0 < x < 2), silicon-carbon composite (Si-C), and silicon alloy.

[0130] The electrode mixture layer may further contain a binder. The binder is not particularly limited. For example, the positive electrode mixture layer may contain one or more of the following as a binder: polyvinylidene fluoride, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0131] Furthermore, the negative electrode mixture layer may contain, as a binder, any one selected from rubber-based binders such as styrene-butadiene rubber (SBR), fluoropolymer rubber, ethylene propylene rubber, butadiene rubber, isoprene rubber, and silane rubber; cellulose-based binders such as carboxymethylcellulose (CMC), hydroxypropylmethylcellulose, methylcellulose, or alkali metal salts thereof; and combinations thereof.

[0132] The electrode mixture layer described above may further contain a conductive material. The conductive material is not particularly limited. For example, the conductive material may include one or more types of materials such as graphite, including natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotubes (CNTs); metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives.

[0133] Examples 1. Manufacturing of sulfide-based solid electrolytes 1) Example Sodium sulfide (Na2S) and lithium chloride (LiCl), weighed in a 1:2 molar ratio, were prepared as a sulfur compound and a lithium compound. The above sodium sulfide (Na2S) and lithium chloride (LiCl) were mixed with ethanol, the first solvent, at a temperature of 25°C or higher (55°C) to produce a 0.3 M first solution. After mixing the above first solution with a magnetic stirrer, the precipitated substance in the first solution was filtered under an argon (Ar) environment. At this time, the temperature of the first solution was 15°C to 25°C. Subsequently, the filtered first solution was dried at 70°C or higher to remove the first solvent, and the first mixture containing lithium sulfide (Li2S) and sodium chloride (NaCl) was recovered.

[0134] The recovered first mixture was mixed with phosphorus pentasulfide (P2S5) and lithium chloride (LiCl) with acetonitrile, the second solvent, to produce a second solution. At this time, the first mixture, phosphorus pentasulfide (P2S5), and lithium chloride (LiCl) were added in proportions of 42.7% by weight, 41.4% by weight, and 15.9% by weight, respectively, and the second solvent was added so that the concentration of the solution was 1 L per 100 g of the raw material mixture (100 g / L).

[0135] After mixing the second solution with a magnetic stirrer, the second solution was dried at 70°C or higher to remove the second solvent and obtain the second mixture. Subsequently, the second mixture was heat-treated at 550°C in an argon (Ar) environment to obtain a sodium (Na)-doped sulfide-based solid electrolyte.

[0136] 2) Comparative Example A sulfide-based solid electrolyte was obtained in the same manner as in the above example, except that the first solution was cooled to 0°C to maximize the precipitation of sodium chloride (NaCl) before filtering the substance precipitated in the first solution under an argon (Ar) environment.

[0137] 2. Evaluation of sulfide-based solid electrolytes 1) Inductively coupled plasma spectroscopy (ICP) analysis After measuring a certain weight of sulfide-based solid electrolytes that would not cause safety problems for workers due to hydrogen sulfide generated by the electrolytes, the sulfide-based solid electrolytes of the examples and comparative examples with this content were dissolved in tertiary distilled water that contained no ions and reacted thoroughly, and then analyzed by ICP. At this time, the reaction of dissolving the sulfide-based solid electrolytes in distilled water was carried out by the following method.

[0138] Mix 1.20 mg of the sample with 15 mL of distilled water by shaking thoroughly. If any suspended particles are present, remove them using a 0.45 μm Syringe Filter.

[0139] 2. Add 5 drops of nitric acid and mix thoroughly. Subsequently, in order to determine the concentration of element A, ICP analysis was performed using an inductively coupled plasma (ICP) spectrometer, and the results are shown in Table 1 below. At this time, the ICP analysis was performed using an Agilent 700s under the following conditions.

[0140] - RF Power (W): 1200 - Coolant gas (L / min): 15 - Auxiliary gas (L / min): 1.5 - Carrier gas (L / min): 0.75

[0141] 2) SEM-EDS analysis To prevent contact with the atmosphere, sulfide-based solid electrolyte samples of the examples and comparative examples for SEM-EDS analysis were prepared in powder form inside a glove box. The results of SEM-EDS analysis of the sulfide-based solid electrolytes of the examples and comparative examples were then performed using a scanning electron microscope (SEM) and an energy-dispersive X-ray spectrometer (EDS), as shown in Figures 3a to 4c. The SEM-EDS analysis was performed using a Bruker FlatQuad equipped with an EDS system linked to the SEM, under conditions of an acceleration voltage of 5kV, a pulse throughput of 130kcps, and a working distance of 15mm.

[0142] 3) Evaluation of ionic conductivity and moisture stability (1) Ionic conductivity Table 1 below shows the results of AC impedance analysis performed at room temperature to confirm the lithium ion conductivity of the manufactured sulfide-based solid electrolytes in the examples and comparative examples. Specifically, 100 mg of solid electrolyte was placed in a pressure mold, and a pressure of 370 MPa was applied to produce pellets. The solid electrolyte in pellet form was then placed in a lithium ion conductivity measurement jig. After that, the jig was placed in a constant temperature and humidity chamber and left at room temperature for 3 hours. Then, an AC potential of 100 mV was applied, and the ion conductivity was measured based on the impedance obtained by a frequency sweep from 1000 Hz to 1 MHz.

[0143] (2) Moisture stability The water stability of the manufactured sulfide-based solid electrolytes in the examples and comparative examples was evaluated by measuring the degree of decrease in ionic conductivity after exposure to air. Specifically, 100 mg of the solid electrolyte was exposed to air at room temperature (23±5°C) with a dew point of -40°C for 1 hour, and then the ionic conductivity of the solid electrolyte was measured using the same method as described above. Subsequently, the measured ionic conductivity value was compared with the ionic conductivity value before exposure to air, and the decrease rate was calculated. The results are shown in Table 1 below.

[0144] [Table 1]

[0145] Referring to Table 1, Figure 1, and Figure 2, it can be seen that the sulfide-based solid electrolyte of the comparative example, in which element A is not detected during ICP analysis, not only has relatively lower ionic conductivity values ​​before and after exposure to air compared to the sulfide-based solid electrolyte of the example, but also exhibits a relatively larger decrease in ionic conductivity before and after exposure to air.

[0146] On the other hand, referring to Figure 3a, in the sulfide-based solid electrolyte of the example, a peak representing element A can be clearly identified as a peak with a different binding energy from the peaks representing phosphorus (P) and sulfur (S). Furthermore, referring to Figures 3b to 3d, it can be confirmed that in the EDS mapping image, the sulfide-based solid electrolyte of the example includes a region representing element A (Figure 3b) that is different from the regions representing phosphorus (P) and sulfur (S) (Figures 3c and 3d).

[0147] In contrast, referring to Figure 4a, it can be seen that in the comparative example's sulfide-based solid electrolyte, only peaks indicating phosphorus (P) and sulfur (S) are observed, and no peak indicating element A is detected. Furthermore, referring to Figures 4b and 4c, it can be seen that in the EDS mapping image of the comparative example's sulfide-based solid electrolyte, regions indicating phosphorus (P) and sulfur (S) (Figures 4b and 4c) are observed, respectively, but no region indicating element A is observed.

Claims

1. A sulfide-based solid electrolyte in which, during inductively coupled plasma spectroscopy (ICP) analysis, the content of at least one element A selected from the group consisting of Group 1 and Group 2 elements excluding Li is 0.1 to 5 mol%.

2. The sulfide-based solid electrolyte according to claim 1, wherein the sulfide-based solid electrolyte is represented by the following chemical formula 1. [Chemical formula 1] Li ａ PS ｂ (71) ｃ (72) ｄ A ｘ B ｙ In the chemical formula (1), 1 ≤ a ≤ 6, 1 ≤ b ≤ 5, 0 ≤ c ≤ 3, 0 ≤ d ≤ 3, 0 < x ≤ 1, 0 < y ≤ 2, Li is lithium, P is phosphorus, S is sulfur, M1 is a Group 17 element, M2 is a Group 17 element different from M1, A is at least one selected from the group consisting of Group 1 elements and Group 2 elements excluding Li, and B is a Group 17 element, NO ３ － and BF ４ － and is at least one selected from the group consisting of.

3. The element A is the sulfide-based solid electrolyte according to claim 1, which corresponds to A in the compound represented by the following chemical formula 2. [Chemical formula 2] AB ｙ In the above chemical formula 2, A is at least one selected from the group consisting of Group 1 and Group 2 elements excluding Li, and B is a Group 17 element, NO ３ － and BF ４ － It is at least one selected from the group consisting of the following, and y is 1 or 2.

4. The sulfide-based solid electrolyte according to claim 1, wherein, during SEM-EDS analysis using a scanning electron microscope (SEM) and an energy-dispersive X-ray spectrometer (EDS), the binding energy of the peak representing element A is different from the binding energies of the peaks representing phosphorus (P) and sulfur (S).

5. The sulfide-based solid electrolyte according to claim 1, wherein, during SEM-EDS analysis using a scanning electron microscope (SEM) and an energy-dispersive X-ray spectrometer (EDS), the EDS mapping image includes regions where the region representing element A is different from the regions representing phosphorus (P) and sulfur (S).

6. A step of preparing a first solution by mixing a sulfur compound represented by the following chemical formula 3 and a lithium compound represented by the following chemical formula 4 with a first solvent, From the first solution, lithium sulfide (Li ２ A step of obtaining a first mixture containing S and the compound represented by the following chemical formula 2, i) phosphorus pentasulfide (P) of the first mixture ２ S ５ ), mixed with the first lithium halide and the second solvent, or ii) phosphorus pentasulfide (P ２ S ５ The steps include: mixing the first lithium halide, the second lithium halide, and the second solvent to produce a second solution; The process includes the step of obtaining a second mixture from the second solution, and then heat-treating it to obtain a sulfide-based solid electrolyte, The method for producing a sulfide-based solid electrolyte, wherein, during inductively coupled plasma spectroscopy (ICP) analysis, the content of element A, corresponding to A in the compound represented by the following chemical formula 2, is 0.1 to 5 mol%. [Chemical formula 2] AB ｙ In the above chemical formula 2, A is at least one selected from the group consisting of Group 1 and Group 2 elements excluding Li, and B is a Group 17 element, NO ３ － and BF ４ － It is at least one selected from the group consisting of the following, and y is 1 or 2. [Chemical formula 3] A ｘ S In the above chemical formula 3, A is at least one selected from the group consisting of Group 1 and Group 2 elements excluding Li, S is sulfur, and x is 1 or 2. [Chemical formula 4] LiB In the above chemical formula 4, Li is lithium, B is a group 17 element, NO ３ － and BF ４ － It is at least one selected from the group consisting of the following:

7. The method for producing a sulfide-based solid electrolyte according to claim 6, wherein the sulfide-based solid electrolyte is represented by the following chemical formula 1. [Chemical formula 1] Li ａ PS ｂ (71) ｃ (72) ｄ A ｘ B ｙ In the above chemical formula 1, 1 ≤ a ≤ 6, 1 ≤ b ≤ 5, 0 ≤ c ≤ 3, 0 ≤ d ≤ 3, 0 < x ≤ 1, 0 < y ≤ 2, Li is lithium, P is phosphorus, S is sulfur, M1 is a group 17 element, M2 is a group 17 element different from M1, A is at least one selected from the group consisting of group 1 and group 2 elements excluding Li, B is a group 17 element, NO ３ － and BF ４ － It is at least one selected from the group consisting of the following:

8. A method for producing a sulfide-based solid electrolyte according to claim 6, further comprising the step of removing a portion of the compound represented by chemical formula 2 before the step of obtaining a first mixture from the first solution.

9. The method for producing a sulfide-based solid electrolyte according to claim 8, wherein the step of removing a portion of the compound represented by the chemical formula 2 is carried out by cooling the first solution to 15°C to 25°C.

10. The method for producing a sulfide-based solid electrolyte according to claim 6, wherein the first solvent comprises at least one selected from the group consisting of alcohol-based solvents, tetrahydrofuran-based solvents, and phosphoramide-based solvents.

11. The method for producing a sulfide-based solid electrolyte according to claim 6, wherein the second solvent comprises at least one selected from the group consisting of alcohol-based solvents, tetrahydrofuran-based solvents, cyanide-based solvents, and phosphoramide-based solvents.

12. The method for producing a sulfide-based solid electrolyte according to claim 6, wherein the heat treatment of the second mixture is carried out at 250°C to 650°C.

13. An all-solid-state battery comprising a sulfide-based solid electrolyte according to any one of claims 1 to 5.

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