Solid-state electrolyte, method for preparing the same, and lithium secondary battery comprising the same

Abstract

This invention relates to solid electrolytes, methods for preparing the same, and lithium secondary batteries containing the same. Specifically, this invention relates to a sulfide solid electrolyte comprising one or more of Li₂O, Li₂SO₄, and P₂O₅, methods for preparing the same, and lithium secondary batteries containing the same.

Description

Technical Field

[0001] This invention relates to solid electrolytes, methods for preparing the same, and lithium secondary batteries containing the same. Specifically, this invention relates to a sulfide solid electrolyte comprising one or more of Li₂O, Li₂SO₄, and P₂O₅, methods for preparing the same, and lithium secondary batteries containing the same. Background Technology

[0002] In recent years, with the surge in demand for small power-driven devices such as IT mobile devices, electric bicycles, and small electric vehicles, attention to high-capacity batteries has continued to grow. Furthermore, improving the safety and energy density of high-capacity batteries has become a major issue. Therefore, to improve the safety and energy density of traditional secondary batteries, there is increasing interest in all-solid-state batteries, and related research is actively underway. All-solid-state batteries replace the liquid electrolyte used in traditional lithium secondary batteries with a solid electrolyte. Because no flammable solvents are used, fires or explosions caused by the decomposition reactions of traditional electrolytes are eliminated, thus improving battery safety. In addition, lithium metal or lithium alloys can be used as the negative electrode material, thereby increasing the energy density of the battery's mass and volume. In all-solid-state batteries, inorganic solid electrolytes are commonly used, with extensive research conducted on solid electrolytes such as Li6PS5Cl with an argyrodite structure. However, sulfide-based solid electrolytes are difficult to handle in normal atmospheric environments due to side reactions with moisture, and improving this issue has become an important research topic. Summary of the Invention

[0003] (a) Technical problems to be solved The technical problem to be solved by the present invention is to provide a solid electrolyte with improved moisture stability and initial capacity.

[0004] Another technical problem to be solved by the present invention is to provide a method for preparing a solid electrolyte with the aforementioned advantages.

[0005] Another technical problem to be solved by the present invention is to provide a lithium secondary battery comprising a solid electrolyte having the aforementioned advantages.

[0006] (II) Technical Solution According to one embodiment of the present invention, the solid electrolyte can be represented by the following chemical formula 1.

[0007] [Chemical Formula 1] Li x PS y O z Cl w Among them, 4 <x≤6,4<y<5,0<z<0.1,0.7<w≤1。

[0008] A method for preparing a solid electrolyte according to another embodiment of the present invention may include: preparing a lithium compound, a sulfur compound, and a halogen compound as raw materials; mixing the raw materials; pressing the mixture to form a pellet; and heat-treating the pellet to form a solid electrolyte represented by the following chemical formula 1.

[0009] [Chemical Formula 1] Li x PS y O z Cl w Among them, 4 <x≤6,4<y<5,0<z<0.1,0.7<w≤1。

[0010] According to another embodiment of the present invention, a lithium secondary battery may include: a positive electrode comprising a positive electrode active material; a negative electrode comprising a negative electrode active material; and a solid electrolyte located between the positive electrode and the negative electrode, the solid electrolyte comprising one or more of Li2O, Li2SO4 and P2O5, and represented by the following chemical formula 1.

[0011] [Chemical Formula 1] Li x PS y O z Cl w Among them, 4 <x≤6,4<y<5,0<z<0.1,0.7<w≤1。

[0012] (III) Beneficial Effects According to one embodiment of the present invention, a solid electrolyte comprising one or more of Li2O, Li2SO4 and P2O5 can provide a solid electrolyte with higher water stability and initial capacity compared to conventional sulfide solid electrolytes.

[0013] According to another embodiment of the present invention, a method for preparing a solid electrolyte can be provided that has the aforementioned advantages.

[0014] According to yet another embodiment of the present invention, a lithium secondary battery comprising a solid electrolyte having the aforementioned advantages can be provided. Best practice

[0015] The terms "first," "second," "third," etc., are used to describe various parts, components, regions, layers, and / or segments, but these parts, components, regions, layers, and / or segments should not be limited by these terms. These terms are only used to distinguish one part, component, region, layer, and / or segment from another. Therefore, without departing from the scope of the invention, the first part, component, region, layer, and / or segment described below can also be described as a second part, component, region, layer, and / or segment.

[0016] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. Unless the context clearly indicates otherwise, the singular forms used are intended to include the plural forms as well. It should also be understood that the term "comprising" as used in the specification can specifically refer to a particular feature, domain, integer, step, action, element, and / or component, and does not exclude the presence or addition of other features, domains, integers, steps, actions, elements, and / or components.

[0017] If one part is described as being on top of another part, then other parts can exist directly on top of or in between the other part. When one part is described as being directly on top of another part, there are no other parts in between.

[0018] Although not otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in dictionaries should be interpreted as having the same meaning as disclosed in relevant technical literature and herein, and should not be interpreted in an idealized or overly formal sense.

[0019] Furthermore, unless otherwise specified, % means weight, 1 ppm is 0.0001 wt%.

[0020] In the following, a solid electrolyte according to an embodiment of the present invention will be described.

[0021] According to one embodiment, the solid electrolyte can be represented by the following chemical formula 1.

[0022] [Chemical Formula 1] Li x PS y O z Cl w Among them, 4 <x≤6,4<y<5,0<z<0.1,0.7<w≤1。

[0023] Regarding the chemical formula 1, preferably, 5 < x ≤ 6, 4.5 < y < 5, 0 < z < 0.1, 0.8 < w ≤ 1. More preferably, 5.5 < x ≤ 6, 4.6 < y < 5, 0 < z < 0.1, 0.9 < w ≤ 1.

[0024] The solid electrolyte according to an embodiment may contain Li2O.

[0025] In order to improve the moisture stability of the solid electrolyte, Li2O may be included.

[0026] In the solid electrolyte according to an embodiment, based on 100 mol% of the total amount of the solid electrolyte, the content of the Li2O may be greater than 0 and less than 2 mol%. Preferably, the content of the Li2O may be greater than 0 and less than 1 mol%. More preferably, the content of the Li2O may be greater than 0 and less than 0.6 mol%.

[0027] When the content of the Li2O is within the foregoing range, the moisture stability and discharge capacity of the solid electrolyte can be improved. On the other hand, when the content of the Li2O is not within the foregoing range, the moisture stability of the solid electrolyte may be reduced. In addition, as the content of Li2O as an impurity increases, the incidence rate of side reactions becomes higher, and the structural stability of the solid electrolyte may be reduced.

[0028] The solid electrolyte according to an embodiment may further contain one or more of Li2SO4 and P2O5.

[0029] In order to improve the moisture stability of the solid electrolyte, one or more selected from Li2SO4 and P2O5 may be further included.

[0030] In the solid electrolyte according to an embodiment, based on 100 mol% of the total amount of the solid electrolyte, the content of the Li2SO4 may be greater than 0 and less than 3 mol%. Preferably, the content of the Li2SO4 may be greater than 0 and less than 2 mol%. More preferably, the content of the Li2SO4 may be greater than 0 and less than 1 mol%.

[0031] When the content of the Li2SO4 is within the foregoing range, the moisture stability and discharge capacity of the solid electrolyte can be improved. On the other hand, when the content of the LiSO4 is not within the foregoing range, the moisture stability of the solid electrolyte may be reduced. In addition, if the content of Li2SO4 as an impurity increases, as the amount of Li2SO4 that cannot be included in the structure of the solid electrolyte increases, the structure of the solid electrolyte may become unstable.

[0032] In a solid electrolyte according to one embodiment, based on a total solid electrolyte content of 100 mol%, the content of P2O5 can be greater than 0 and less than 20 mol%. Preferably, the content of P2O5 can be greater than 0 and less than 10 mol%. More preferably, the content of P2O5 can be greater than 0 and less than 5 mol.

[0033] When the P2O5 content is within the aforementioned range, the moisture stability and discharge capacity of the solid electrolyte can be improved. On the other hand, when the P2O5 content is not within the aforementioned range, the moisture stability of the solid electrolyte may decrease. Furthermore, if the P2O5 content increases, the Li concentration relative to the P concentration in the solid electrolyte decreases, and therefore the discharge capacity may decrease.

[0034] According to one embodiment, the solid electrolyte can satisfy the following formula 1.

[0035] [Equation 1] 0≤[C Li2O ] 2 [C Li2SO4 ] 2 [C P2O5 <2.25 In Equation 1, [C Li2O [C] Li2SO4 [C] P2O5 Each of these represents the molar percentage (mol%) concentration of Li₂O, Li₂SO₄, and P₂O₅ in the solid electrolyte, and [C Li2O [C] Li2SO4 [C] P2O5 At least one of them is greater than 0.

[0036] Preferably, in Equation 1, 0 ≤ [C] Li2O ] 2 [C Li2SO4 ] 2 [C P2O5 <1.60. More preferably, in Equation 1, it can be 0 ≤ [C Li2O ] 2 [C Li2SO4 ] 2 [C P2O5 <0.80. More preferably, in Equation 1, 0 ≤ [C] Li2O ] 2 [C Li2SO4 ] 2 [C P2O5 ≤0.40。

[0037] In the formula 1, when Li2O 2 [C Li2SO4 2 [C P2O5 is within the aforementioned range, the moisture stability and discharge capacity of the solid electrolyte can be improved. On the other hand, when Li2O 2 [C Li2SO4 2 [C P2O5 is not within the aforementioned range, problems such as a decrease in the moisture stability and discharge capacity of the solid electrolyte may occur.

[0038] Hereinafter, a method for preparing a solid electrolyte according to another embodiment of the present invention will be described.

[0039] The method for preparing a solid electrolyte according to another embodiment may include: a step of preparing a lithium compound, a sulfur compound, and a halogen compound as raw material substances; a step of mixing the raw material substances; a step of pressure-molding the mixture to form a tablet; and a step of heat-treating the tablet, and forming a solid electrolyte represented by the following Chemical Formula ˚

[0040] [Chemical Formula 1] Li x PS y O z Cl w Where 4 < x ≤ 6, 4 < y < 5, 0 < z < 0.1, 0.7 < w ≤ 1.

[0041] Regarding the Chemical Formula 1, preferably, 5 < x ≤ 6, 4.5 < y < 5, 0 < z < 0.1, 0.8 < w ≤ 1. More preferably, 5.5 < x ≤ 6, 4.6 < y < 5, 0 < z < 0.1, 0.9 < w ≤ 1.

[0042] In the method for preparing a solid electrolyte according to another embodiment, the lithium compound may be Li2S containing at least one of Li2O and Li2SO4 as an impurity.

[0043] As described above, when the lithium compound contains at least one of Li2O and Li2SO4 as an impurity, the moisture stability can be improved compared to the conventional argyrodite-type solid electrolyte Li6PS5Cl prepared without impurities. ​​​​

[0044] In a method for preparing a solid electrolyte according to another embodiment, the raw material preparation step may include further mixing at least one of Li2O, Li2SO4, and P2O5.

[0045] In addition to Li2O and Li2SO4, which are impurities contained in the aforementioned lithium compounds, at least one of Li2O, Li2SO4, and P2O5 can be further mixed in to improve moisture stability.

[0046] In a method for preparing a solid electrolyte according to another embodiment, based on a total raw material content of 100 mol%, the amount of Li2O added in the further mixed form can be greater than 0 and less than 2 mol%. Preferably, the content of Li2O can be greater than 0 and less than 1 mol%. More preferably, the content of Li2O can be greater than 0 and less than 0.6 mol.

[0047] When the amount of Li₂O added is within the aforementioned range, the moisture stability and discharge capacity of the solid electrolyte can be improved. On the other hand, when the amount of Li₂O added is not within the aforementioned range, the moisture stability of the solid electrolyte may decrease. In particular, when the amount of Li₂O added is excessively increased, the residual Li₂O that is not included in the structure may trigger side reactions, potentially leading to a decrease in the structural stability of the solid electrolyte.

[0048] In a method for preparing a solid electrolyte according to another embodiment, based on a total raw material content of 100 mol%, the amount of Li₂SO₄ further mixed can be greater than 0 and less than 3 mol%. Preferably, the content of Li₂SO₄ can be greater than 0 and less than 2 mol%. More preferably, the content of Li₂SO₄ can be greater than 0 and less than 1 mol.

[0049] When the amount of Li₂SO₄ added is within the aforementioned range, the moisture stability and discharge capacity of the solid electrolyte can be improved. On the other hand, when the amount of Li₂SO₄ added is not within the aforementioned range, the moisture stability of the solid electrolyte may decrease. Furthermore, if the amount of Li₂SO₄ added increases, the structure of the solid electrolyte may become unstable as the amount of Li₂SO₄ that cannot be included in the solid electrolyte structure increases.

[0050] In a method for preparing a solid electrolyte according to another embodiment, based on a total raw material content of 100 mol%, the amount of P2O5 added in the further mixed form can be greater than 0 and less than 20 mol%. Preferably, the content of P2O5 can be greater than 0 and less than 10 mol%. More preferably, the content of P2O5 can be greater than 0 and less than 5 mol%.

[0051] When the addition amount of the P2O5 is within the aforementioned range, the moisture stability and discharge capacity of the solid electrolyte can be improved. On the other hand, when the addition amount of the P2O5 is not within the aforementioned range, the moisture stability of the solid electrolyte may be reduced. In addition, if the addition amount of P2O5 increases, the Li concentration in the solid electrolyte decreases relative to the P concentration, and thus the discharge capacity may decrease.

[0052] Hereinafter, a lithium secondary battery according to another embodiment of the present invention will be described.

[0053] A lithium secondary battery according to another embodiment may include: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and a solid electrolyte located between the positive electrode and the negative electrode, the solid electrolyte including one or more of Li2O, Li2SO4, and P2O5, and being represented by the following Chemical Formula 1.

[0054] [Chemical Formula 1] Li x PS y O z Cl w where 4 < x ≤ 6, < y < 5, 0 < z < 0.1, 0 < w ≤ 1.

[0055] Regarding the Chemical Formula 1, preferably, 5 < x ≤ 6, 4.5 < y < 5, 0 < z < 0.1, 0.8 < w ≤ 1. More preferably, 5.5 < x ≤ 6, 4.6 < y < 5, 0 < z < 0.1, 0.9 < w ≤ 1.

[0056] In the lithium secondary battery according to another embodiment, the solid electrolyte may satisfy the following Formula 1.

[0057] [Formula 1] 0 ≤ [C Li2O 2 [C Li2SO4 2 [C P2O5 < 2.25 In the Formula 1, [C Li2O , [C Li2SO4 , [C P2O5 each represent the molar percentage (mol%) concentration of Li2O, Li2SO4, and P2O5 contained in the solid electrolyte, and at least one of [C Li2O , [C Li2SO4 , [C P2O5 is greater than 0.

[0058] ​​Preferably, in Equation 1, 0 ≤ [C] Li2O ] 2 [C Li2SO4 ] 2 [C P2O5 <1.60. More preferably, in Equation 1, it can be 0 ≤ [C Li2O ] 2 [C Li2SO4 ] 2 [C P2O5 <0.80. More preferably, in Equation 1, 0 ≤ [C] Li2O ] 2 [C Li2SO4 ] 2 [C P2O5 ≤0.40.

[0059] In Equation 1, when [C Li2O ] 2 [C Li2SO4 ] 2 [C P2O5 When the value of [C] is within the aforementioned range, the moisture stability and discharge capacity of the solid electrolyte can be improved. On the other hand, when [C] is within the range of [C], the moisture stability and discharge capacity of the solid electrolyte can be improved. Li2O ] 2 [C Li2SO4 ] 2 [C P2O5 When the value is not within the aforementioned range, problems such as reduced moisture stability and discharge capacity of the solid electrolyte may occur. Detailed Implementation

[0060] The following describes embodiments, comparative examples, and experimental examples of the present invention. However, the following embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to the following embodiments. Furthermore, various modifications can be made within the scope of the claims, specification, and drawings, and these modifications also fall within the scope of the present invention.

[0061] <Example 1> Li6PS 4.99 O 0.01 Preparation of Cl (including Li₂O: 0.5 mol%; Li₂SO₄: 0 mol%; P₂O₅: 0 mol%) The raw materials were mixed in stoichiometric proportions to contain 0.5 mol% Li₂O based on 100 mol% of the total solid electrolyte. The mixture was then blended using a planetary mill at 300 rpm for approximately 8 hours. Subsequently, a pressure of 300 MPa was applied to form a tablet, which was then heat-treated at 550 °C in an Ar atmosphere to prepare Li₆PS. 4.99 O 0.01 Cl.

[0062] <Example 2> Li 5.88 PS 4.89 O 0.01 Cl 0.98 Preparation of (containing Li₂O: 0.5 mol%; Li₂SO₄: 0 mol%; P₂O₅: 1 mol%) A compound with the composition Li was prepared by using 0.5 mol% Li₂O and 1 mol% P₂O₅. 5.88 PS 4.89 O 0.01 Cl 0.98 The solid electrolyte is prepared by the same method as in Example 1.

[0063] <Example 3> Li 5.88 PS 4.89 O 0.09 Cl 0.98 Preparation of (containing Li₂O: 0.5 mol%; Li₂SO₄: 0.8 mol%; P₂O₅: 1 mol%) A compound with the composition Li was prepared by comprising 0.5 mol% Li₂O, 0.8 mol% Li₂SO₄, and 1 mol% P₂O₅. 5.88 PS 4.89 O 0.09 Cl 0.98 The solid electrolyte is prepared by the same method as in Example 1.

[0064] <Example 4> Li 5.71 PS 4.74 O 0.09 Cl 0.95 Preparation of (containing Li₂O: 0.5 mol%; Li₂SO₄: 0.8 mol%; P₂O₅: 2.5 mol%) A compound with the composition Li was prepared by comprising 0.5 mol% Li₂O, 0.8 mol% Li₂SO₄, and 2.5 mol% P₂O₅. 5.71 PS 4.74 O 0.09 Cl 0.95The solid electrolyte is prepared by the same method as in Example 1.

[0065] <Example 5> Li 5.43 PS 4.51 O 0.08 Cl 0.9 Preparation of (containing Li₂O: 0.5 mol%; Li₂SO₄: 0.8 mol%; P₂O₅: 5 mol%) A compound with the composition Li was prepared by comprising 0.5 mol% Li₂O, 0.8 mol% Li₂SO₄, and 5 mol% P₂O₅. 5.43 PS 4.51 O 0.08 Cl 0.9 The solid electrolyte is prepared by the same method as in Example 1.

[0066] <Example 6> Li 4.91 PS 4.08 O 0.08 Cl 0.82 Preparation of (containing Li₂O: 0.5 mol%; Li₂SO₄: 0.8 mol%; P₂O₅: 10 mol%) A compound with the composition Li was prepared by comprising 0.5 mol% Li₂O, 0.8 mol% Li₂SO₄, and 10 mol% P₂O₅. 4.91 PS 4.08 O 0.08 Cl 0.82 The solid electrolyte is prepared by the same method as in Example 1.

[0067] <Comparative Example 1> Li4PS 3.33 O 0.06 Cl 0.67 Preparation of (containing Li₂O: 0.5 mol%; Li₂SO₄: 0.8 mol%; P₂O₅: 20 mol%) A compound with the composition Li4PS was prepared by comprising 0.5 mol% Li2O, 0.8 mol% Li2SO4, and 20 mol% P2O5. 3.33 O 0.06 Cl 0.67 The solid electrolyte is prepared by the same method as in Example 1.

[0068] <Comparative Example 2> Li 5.88 PS 4.89 O 0.31 Cl 0.98Preparation of (containing Li₂O: 0.5 mol%; Li₂SO₄: 3 mol%; P₂O₅: 1 mol%) A compound with the composition Li was prepared by comprising 0.5 mol% Li₂O, 3 mol% Li₂SO₄, and 1 mol% P₂O₅. 5.88 PS 4.89 O 0.31 Cl 0.98 The solid electrolyte is prepared by the same method as in Example 1.

[0069] <Comparative Example 3> Li 5.71 PS 4.74 O 0.3 Cl 0.95 Preparation of (containing Li₂O: 0.5 mol%; Li₂SO₄: 3 mol%; P₂O₅: 2.5 mol%) A compound with the composition Li was prepared by comprising 0.5 mol% Li₂O, 3 mol% Li₂SO₄, and 2.5 mol% P₂O₅. 5.71 PS 4.74 O 0.3 Cl 0.95 The solid electrolyte is prepared by the same method as in Example 1.

[0070] <Comparative Example 4> Li 5.43 PS 4.51 O 0.28 Cl 0.9 Preparation of (containing Li₂O: 0.5 mol%; Li₂SO₄: 3 mol%; P₂O₅: 5 mol%) A compound with the composition Li was prepared by comprising 0.5 mol% Li₂O, 3 mol% Li₂SO₄, and 5 mol% P₂O₅. 5.43 PS 4.51 O 0.28 Cl 0.9 The solid electrolyte is prepared by the same method as in Example 1.

[0071] <Comparative Example 5> Li 4.91 PS 4.08 O 0.26 Cl 0.82 Preparation of (containing Li₂O: 0.5 mol%; Li₂SO₄: 3 mol%; P₂O₅: 10 mol%) A compound with the composition Li was prepared by comprising 0.5 mol% Li₂O, 3 mol% Li₂SO₄, and 10 mol% P₂O₅. 4.91 PS 4.08 O0.26 Cl 0.82 The solid electrolyte is prepared by the same method as in Example 1.

[0072] <Comparative Example 6> Li 5.71 PS 4.74 O 0.96 Cl 0.95 Preparation of (containing Li₂O: 0.5 mol%; Li₂SO₄: 10 mol%; P₂O₅: 2.5 mol%) A compound with the composition Li was prepared by comprising 0.5 mol% Li₂O, 10 mol% Li₂SO₄, and 2.5 mol% P₂O₅. 5.71 PS 4.74 O 0.96 Cl 0.95 The solid electrolyte is prepared by the same method as in Example 1.

[0073] <Comparative Example 7> Li 4.91 PS 4.08 O 0.83 Cl 0.82 Preparation of (containing Li₂O: 0.5 mol%; Li₂SO₄: 10 mol%; P₂O₅: 10 mol%) A compound with the composition Li was prepared by comprising 0.5 mol% Li₂O, 10 mol% Li₂SO₄, and 10 mol% P₂O₅. 4.91 PS 4.08 O 0.83 Cl 0.82 The solid electrolyte is prepared by the same method as in Example 1.

[0074] <Comparative Example 8> Li 5.29 PS 4.26 O 0.13 Cl 1.57 Preparation of (containing Li₂O: 2 mol%; Li₂SO₄: 0.8 mol%; P₂O₅: 1 mol%) A compound with the composition Li was prepared by comprising 2 mol% Li₂O, 0.8 mol% Li₂SO₄, and 1 mol% P₂O₅. 5.29 PS 4.26 O 0.13 Cl 1.57 The solid electrolyte is prepared by the same method as in Example 1.

[0075] <Comparative Example 9> Li 5.14 PS 4.14 O 0.12 Cl1.52 Preparation of (containing Li₂O: 2 mol%; Li₂SO₄: 0.8 mol%; P₂O₅: 2.5 mol%) A compound with the composition Li was prepared by using 2 mol% Li₂O, 0.8 mol% Li₂SO₄, and 2.5 mol% P₂O₅. 5.14 PS 4.14 O 0.12 Cl 1.52 The solid electrolyte is prepared by the same method as in Example 1.

[0076] <Comparative Example 10> Li 4.89 PS 3.94 O 0.12 Cl 1.45 Preparation of (containing Li₂O: 2 mol%; Li₂SO₄: 0.8 mol%; P₂O₅: 5 mol%) A compound with the composition Li was prepared by comprising 2 mol% Li₂O, 0.8 mol% Li₂SO₄, and 5 mol% P₂O₅. 4.89 PS 3.94 O 0.12 Cl 1.45 The solid electrolyte is prepared by the same method as in Example 1.

[0077] <Comparative Example 11> Li 4.42 PS 3.56 O 0.11 Cl 1.31 Preparation of (containing Li₂O: 2 mol%; Li₂SO₄: 0.8 mol%; P₂O₅: 10 mol%) A compound with the composition Li was prepared by comprising 2 mol% Li₂O, 0.8 mol% Li₂SO₄, and 10 mol% P₂O₅. 4.42 PS 3.56 O 0.11 Cl 1.31 The solid electrolyte is prepared by the same method as in Example 1.

[0078] <Experimental Example 1> Evaluation of ionic conductivity at 30℃ and 0.1C Electrochemical evaluations were performed on the solid electrolytes of Comparative Examples 1 and 2, and Examples 1 to 3, using a powder-pressed battery. After adding the electrolyte, it was densified at a pressure of 300 MPa. Subsequently, the battery cells were assembled using an SUS electrode at a pressure of 70 MPa, and the impedance was measured by applying a voltage of 10 mV at 25 degrees Celsius.

[0079] <Experimental Example 2> Evaluating Moisture Stability 0.5 g of solid electrolyte was coated on a petri dish and exposed in a dry room with a dew point of -45 °C for 8 hours. The ionic conductivity before and after exposure was compared and evaluated.

[0080] <Experimental Example 3> Evaluation of Electrochemical Properties After fabricating the solid electrolyte pellet, the positive electrode was bonded to the top and the counter electrode (In) to the bottom, and then it was densified under a pressure of 500 MPa. After assembling the all-solid-state battery cell, it was formed and cycled at 0.1C in a 30-degree chamber, and its lifetime characteristics were evaluated at 0.5C.

[0081] According to Table 1 below, it can be confirmed that the solid electrolyte of the present invention has better moisture stability and discharge capacity than Comparative Examples 1 to 11. In particular, it can be confirmed that the ionic conductivity of the solid electrolyte of Examples 1 to 4 is also better than that of Comparative Examples 1 to 11.

[0082] Table 1

Claims

1. A solid electrolyte, The solid electrolyte is represented by the following chemical formula 1: [Chemical Formula 1] Li x PS y O z Cl w in, 4 <x≤6,4<y<5,0<z<0.1,0.7<w≤1。 2. The solid electrolyte according to claim 1, wherein, The solid electrolyte contains Li2O.

3. The solid electrolyte according to claim 2, wherein, Based on a total solid electrolyte content of 100 mol%, the content of Li2O is greater than 0 and less than 2 mol.

4. The solid electrolyte according to claim 2, wherein, The solid electrolyte further comprises one or more of Li2SO4 and P2O5.

5. The solid electrolyte according to claim 4, wherein, Based on a total solid electrolyte content of 100 mol%, the content of Li2SO4 is greater than 0 and less than 3 mol.

6. The solid electrolyte according to claim 4, wherein, Based on a total solid electrolyte content of 100 mol%, the content of P2O5 is greater than 0 and less than 20 mol.

7. The solid electrolyte according to claim 1, wherein, The solid electrolyte satisfies the following equation: [Equation 1] 0≤[C Li2O ] 2 [C Li2SO4 ] 2 [C P2O5 <2.25 In Equation 1, [C Li2O [C] Li2SO4 [C] P2O5 Each of these represents the molar percentage (mol%) concentration of Li₂O, Li₂SO₄, and P₂O₅ in the solid electrolyte, and [C Li2O [C] Li2SO4 [C] P2O5 At least one of them is greater than 0.

8. A method for preparing a solid electrolyte, comprising: The steps for preparing lithium compounds, sulfur compounds, and halogen compounds as raw materials; The step of mixing the raw materials; The step of compressing the mixture to form a tablet; and The step of heat-treating the tablet. And form a solid electrolyte represented by the following chemical formula 1, [Chemical Formula 1] Li x PS y O z Cl w in, 4 <x≤6,4<y<5,0<z<0.1,0.7<w≤1。 9. The method for preparing a solid electrolyte according to claim 8, wherein, The lithium compound is Li2S containing at least one of Li2O and Li2SO4 as an impurity.

10. The method for preparing a solid electrolyte according to claim 8, wherein, In the raw material preparation step, at least one of Li2O, Li2SO4, and P2O5 is further mixed.

11. The method for preparing a solid electrolyte according to claim 10, wherein, Based on a total raw material content of 100 mol%, the amount of Li2O added in the further mixed mixture is greater than 0 and less than 2 mol.

12. The method for preparing a solid electrolyte according to claim 10, wherein, Based on a total raw material content of 100 mol%, the amount of Li2SO4 added in the further mixed mixture is greater than 0 and less than 3 mol.

13. The method for preparing a solid electrolyte according to claim 10, wherein, Based on a total raw material content of 100 mol%, the amount of P2O5 added in the further mixed step is greater than 0 and less than 20 mol.

14. A lithium secondary battery, comprising: The positive electrode, which includes the positive electrode active material; Anode, comprising anode active material; and A solid electrolyte, located between the positive and negative electrodes. The solid electrolyte comprises one or more of Li₂O, Li₂SO₄, and P₂O₅, and is represented by the following chemical formula 1: [Chemical Formula 1] Li x PS y O z Cl w in, 4 <x≤6,4<y<5,0<z<0.1,0.7<w≤1。 15. The lithium secondary battery according to claim 14, wherein, The solid electrolyte satisfies the following equation: [Equation 1] 0≤[C Li2O ] 2 [C Li2SO4 ] 2 [C P2O5 <2.25 In Equation 1, [C Li2O [C] Li2SO4 [C] P2O5 Each of these represents the molar percentage (mol%) concentration of Li₂O, Li₂SO₄, and P₂O₅ in the solid electrolyte, and [C Li2O [C] Li2SO4 [C] P2O5 At least one of them is greater than 0.

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