Composite sulfide-based solid electrolyte and method for producing the same

Abstract

The present invention relates to a composite sulfide-based solid electrolyte, which is a secondary particle including a plurality of primary particles and a lithium halide represented by the following Chemical Formula 1, the primary particles including a sulfide-based solid electrolyte, and the lithium halide being located between the primary particles, and a method for manufacturing the same. [Chemical formula 1] LiX In the above formula 1, X is any one selected from F, Cl, Br and I.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0176307 filed on December 15, 2022, and includes all the contents disclosed in the document of the Korean Patent Application as part of this specification.

[0002] The present invention relates to a composite sulfide-based solid electrolyte and a method for manufacturing the same.

Background Art

[0003] As the demand for electric vehicles and large-capacity power storage devices increases, various secondary batteries have been developed to meet this demand.

[0004] Among various secondary batteries, lithium secondary batteries have the most excellent energy density and output characteristics and have been widely commercialized. As lithium secondary batteries, lithium secondary batteries containing a liquid-type electrolyte containing an organic solvent (hereinafter referred to as "liquid-type secondary batteries") are mainly used.

[0005] However, it has been pointed out that in liquid-type secondary batteries, the liquid electrolyte is decomposed by an electrode reaction, causing battery expansion, and there is a risk of ignition due to leakage of the liquid electrolyte. To solve such problems of liquid-type secondary batteries, lithium secondary batteries (hereinafter referred to as "all-solid-state batteries") applying a solid electrolyte with excellent stability have attracted attention.

[0006] Solid electrolytes can be broadly classified into polymer-based electrolytes, oxide-based solid electrolytes, and sulfide-based solid electrolytes. Sulfide-based solid electrolytes exhibit soft characteristics compared to oxide-based solid electrolytes, and thus can impart excellent inter-particle contact characteristics even with only room-temperature pressing without a separate sintering process. As a result, sulfide-based solid electrolytes have attracted attention because they have lower contact resistance and can exhibit high ionic conductivity compared to oxide-based solid electrolytes.

[0007] However, sulfide-based solid electrolytes have a disadvantage in that their chemical stability is relatively lower than oxide-based solid electrolytes, resulting in reduced stability when applied to all-solid-state batteries. Specifically, sulfide-based solid electrolytes are prone to reacting with moisture in the atmosphere or moisture introduced during the manufacturing process due to various factors such as residual L2S and P2S7-bridged sulfur within the electrolyte. As a result, sulfide-based solid electrolytes may generate hydrogen sulfide (H2S) gas when reacting with moisture, and are therefore handled in environments such as glove boxes with an argon gas atmosphere or dry rooms from which moisture has been removed. Furthermore, sulfide-based solid electrolytes have manufacturing process problems, such as a decrease in ionic conductivity due to the effects of hydrogen sulfide gas generated by reaction with moisture.

[0008] Thus, conventional sulfide-based solid electrolytes require stringent handling conditions, making it difficult to manufacture all-solid-state batteries using them, particularly in terms of large-area production and mass production. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Korean Published Patent Publication No. 2019-0079135 [Overview of the project] [Problems that the invention aims to solve]

[0010] The object of the present invention is to provide a composite sulfide-based solid electrolyte that can improve the water resistance of the solid electrolyte due to prolonged exposure to moisture during the manufacture of all-solid-state batteries and prevent a decrease in ionic conductivity by forming a composite sulfide-based solid electrolyte in the form of secondary particles by mixing lithium halide with a sulfide-based solid electrolyte.

[0011] Another object of the present invention is to provide a method for producing the composite sulfide-based solid electrolyte. [Means for solving the problem]

[0012] One embodiment of the present invention provides a composite sulfide-based solid electrolyte comprising a plurality of primary particles and secondary particles containing a lithium halide represented by the following chemical formula 1, wherein the primary particles contain a sulfide-based solid electrolyte, and the lithium halide is located between the primary particles. [Chemical formula 1] LiX In the above chemical formula 1, X is one of the following selected from F, Cl, Br, and I.

[0013] The average particle size (D50) of the lithium halide can be 0.01 to 3 μm.

[0014] The average particle size (D50) of the secondary particles of the composite sulfide-based solid electrolyte can be 0.11 to 100 μm.

[0015] Based on a total of 100 parts by weight of the composite sulfide-based solid electrolyte, the content ratio of the sulfide-based solid electrolyte to lithium halide in the primary particles can be 99.9 parts by weight:0.1 parts by weight to 80 parts by weight:20 parts by weight.

[0016] The sulfide-based solid electrolyte may include an argyrodite-type crystal structure.

[0017] The average particle size (D50) of the primary particles can be 0.1 to 15 μm.

[0018] In the composite sulfide-based solid electrolyte of the secondary particles, the lithium halide may not be formed as a coating layer for the primary particles.

[0019] The sulfide-based solid electrolyte of the primary particles may be represented by the following chemical formula 2. [Chemical formula 2] Li k M 1 l S m X 1 n In the aforementioned chemical formula 2, M 1is Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, or La, and X 1 is F, Cl, Br, I, Se, Te, or O, where 0 < k ≦ 6, 0 < l ≦ 6, 0 < m ≦ 6, and 0 ≦ n ≦ 6.

[0020] Another embodiment of the present invention provides a all-solid-state battery including the composite sulfide-based solid electrolyte.

[0021] Another embodiment of the present invention provides a method for manufacturing a composite sulfide-based solid electrolyte, including the steps of preparing a sulfide-based solid electrolyte and lithium halide represented by the following Chemical Formula 1; grinding the lithium halide; and mixing the ground lithium halide and the sulfide-based solid electrolyte. [Chemical Formula 1] LiX In Chemical Formula 1, X is any one selected from F, Cl, Br, and I.

[0022] Before grinding the lithium halide, the method may further include a step of vacuum drying to remove moisture of the lithium halide.

[0023] The lithium halide may be formed by grinding through ball-milling at 100 - 2,000 rpm for 5 - 30 minutes as one cycle, and repeating the ball-milling 5 - 20 cycles.

[0024] The average particle size (D50) of the ground lithium halide may be 0.01 - 3 μm.

[0025] The ground lithium halide and the sulfide-based solid electrolyte may be mixed at a content ratio of 99.9 parts by weight: 0.1 part by weight to 80 parts by weight: 20 parts by weight based on 100 parts by weight of the total composite sulfide-based solid electrolyte. [Effects of the Invention]

[0026] According to the present invention, by forming a composite sulfide-based solid electrolyte in the form of secondary particles such that lithium halide particles having a relatively small size are located in the empty space between the primary particles of the sulfide-based solid electrolyte, it is possible to improve the water resistance of the solid electrolyte and prevent a decrease in the ionic conductivity of the all-solid-state battery. [Brief explanation of the drawing]

[0027] [Figure 1] This is a schematic diagram of a composite sulfide-based solid electrolyte according to one embodiment of the present invention. [Figure 2] This is a schematic diagram of a lithium halide-free sulfide-based solid electrolyte according to a comparative example of the present invention. [Figure 3] This is a scanning electron microscope (SEM) image of a composite sulfide-based solid electrolyte according to one embodiment of the present invention. [Figure 4] This image shows the results of energy dispersive X-ray spectroscopy (EDX) analysis of a composite sulfide-based solid electrolyte according to one embodiment of the present invention. [Figure 5] This image shows the results of energy dispersive X-ray spectroscopy (EDX) analysis of a composite sulfide-based solid electrolyte according to one embodiment of the present invention. [Figure 6] This graph shows the change in ionic conductivity over time of a composite sulfide-based solid electrolyte according to one embodiment of the present invention. [Figure 7] This graph shows the normalized change in ionic conductivity over time for a composite sulfide-based solid electrolyte according to one embodiment of the present invention. [Figure 8]This graph shows the EIS (Electrochemical Impedance Spectroscopy) analysis of lithium halide (LiBr). [Figure 9] This graph shows the EIS (Electrochemical Impedance Spectroscopy) analysis of Li6PS5Cl, a sulfide-based solid electrolyte with an argyrodite crystal structure. [Modes for carrying out the invention]

[0028] Embodiments of the present invention will now be described in detail. Prior to this, terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical idea of ​​the present invention, based on the principle that inventors may appropriately define the concepts of terms in order to best describe their invention. Therefore, it should be understood that the configurations described in the embodiments described herein represent only one of the most preferred embodiments of the present invention and do not represent the entire technical idea of ​​the present invention, and that at the time of filing, there may be various equivalents and modifications that can substitute for them.

[0029] Whenever a part of this specification is said to "include" a certain component, unless otherwise stated, this means that it may include other components rather than excluding them.

[0030] Furthermore, explanations that specify or add components can be applied to all inventions unless otherwise specified, and are not limited to any particular invention.

[0031] Furthermore, throughout the description of the invention and the claims of this application, any singular nouns include plural nouns unless otherwise specified.

[0032] Furthermore, throughout the description of the invention and the claims of this application, "or" includes "and" unless otherwise specified. Therefore, "including A or B" means including A, including B, or including both A and B—all three of the aforementioned cases.

[0033] Furthermore, all numerical ranges include the values ​​at both ends and all intermediate values ​​between them, unless otherwise explicitly stated.

[0034] Throughout this specification, the average particle size may be, for example, the median diameter (D50) measured using a laser particle size analyzer.

[0035] The following describes a composite sulfide-based solid electrolyte according to one embodiment of the present invention.

[0036] The present invention relates to a composite sulfide-based solid electrolyte and a method for producing the same, which can improve the water resistance of the solid electrolyte, prevent a decrease in the ionic conductivity of an all-solid-state battery due to the influence of external moisture during the manufacturing of the all-solid-state battery, and improve its electrochemical and lifespan characteristics.

[0037] Typically, sulfide-based solid electrolytes have the advantage of excellent inter-particle contact, low contact resistance, and high ionic conductivity achieved solely through room temperature pressurization without a separate sintering process. However, they are prone to reacting with moisture in the atmosphere or moisture introduced during the manufacturing process to generate hydrogen sulfide (H2S) gas, which reduces the ionic conductivity, a core characteristic of solid electrolytes.

[0038] To address these issues, attempts were made to form a coating layer on the surface of sulfide-based solid electrolyte particles to block their reaction with moisture. However, this resulted in the substances in the coating layer acting as a resistive layer, further reducing the ionic conductivity of the solid electrolyte.

[0039] In response to the above-mentioned problems, the present invention, instead of forming a separate coating layer on sulfide-based solid electrolyte particles, mixes primary particles of sulfide-based solid electrolyte with lithium halide to form a secondary particle-type solid electrolyte. In particular, by positioning the lithium halide in the empty spaces between the primary particles of the sulfide-based solid electrolyte, the lithium halide performs the function of adsorbing external moisture, improving the water resistance of the sulfide-based solid electrolyte, reducing the generation of hydrogen sulfide, and exhibiting high ionic conductivity. This has been confirmed, and the present invention has been completed.

[0040] Figure 1 is a schematic diagram showing a composite sulfide-based solid electrolyte according to one embodiment of the present invention.

[0041] Referring to Figure 1, a composite sulfide-based solid electrolyte according to one embodiment of the present invention comprises a plurality of primary particles and secondary particles containing a lithium halide represented by the following chemical formula 1, wherein the primary particles contain the sulfide-based solid electrolyte, and the lithium halide may be located between the primary particles. [Chemical formula 1] LiX In the above chemical formula 1, X is one of the following selected from F, Cl, Br, and I.

[0042] In other words, the lithium halide is not formed as a coating layer on the primary particles of the sulfide-based solid electrolyte, but is located between the primary particles of the sulfide-based solid electrolyte, thereby adsorbing external moisture and improving the water resistance of the sulfide-based solid electrolyte. For example, the lithium halide represented by chemical formula 1 may be LiF, LiCl, LiBr, or LiI, and preferably LiBr.

[0043] Figures 8 and 9 are graphs showing the EIS (Electrochemical Impedance Spectroscopy) analysis of lithium halide (LiBr) and sulfide-based solid electrolytes with argyrodite crystal structures, respectively.

[0044] Referring to FIGS. 8 and 9, in the case of a sulfide-based solid electrolyte having an argyrodite crystal structure, it exhibits a high ionic conductivity of 0.1 mS / cm or more. In the case of LiBr, which is a kind of lithium halide, as can be confirmed by the EIS measurement results at 25° C. in FIG. 8, the self-ion conductivity (9.62×10 -6 mS / cm) is very low, so it can be seen that when applied to a sulfide-based solid electrolyte, it can act as a very large resistance layer.

[0045] Therefore, in the unlikely event that lithium halide is formed as a surface coating layer on the surface of the sulfide-based solid electrolyte as shown in FIG. 2, regardless of the moisture adsorption performance of lithium halide, due to the excessively large resistance at the grain boundary of lithium halide, there is a problem that it is difficult for ion conduction between sulfide-based solid electrolyte particles.

[0046] In contrast, the composite sulfide-based solid electrolyte according to an embodiment of the present invention does not separately form a coating layer of lithium halide on the sulfide-based solid electrolyte particles. Therefore, while preventing an increase in internal resistance, lithium halide is arranged between the primary particles of the sulfide-based solid electrolyte, and there is an advantage that sufficient moisture resistance can be imparted. Further, by including lithium halide as fine particles with an average particle size of 0.01 to 3 μm, the conduction of lithium ions (Li + ) inside the secondary particles of the sulfide-based solid electrolyte is not significantly hindered.

[0047] Referring to the manufacturing method of the composite sulfide-based solid electrolyte of the present application described later, lithium halide according to an embodiment of the present application can undergo a micronization process through a ball mill or the like before being mixed with the sulfide-based solid electrolyte. In an embodiment of the present invention, the average particle size (D50) of the lithium halide may be 0.01 to 3 μm, for example, 0.01 to 1 μm, 0.01 to 0.5 μm, preferably 0.01 to 0.1 μm.

[0048] If the average particle size of lithium halide is less than 0.01 μm, it may be difficult to maintain the small particle size, potentially complicating the manufacturing process of the composite sulfide-based solid electrolyte in secondary particle form. If it exceeds 3 μm, the specific surface area of ​​the lithium halide particles will relatively decrease, potentially reducing the effectiveness of improving the water resistance of the composite sulfide-based solid electrolyte.

[0049] The lithium halide has no limitations on its form; for example, it can be spherical, plate-shaped, pyramidal, cylindrical, or any other shape, but is not limited to these. The average particle size of the lithium halide may have different meanings depending on its form; for example, in the case of a spherical shape, it refers to the diameter of the sphere, and in the case of an elliptical shape, it may refer to the diameter of the major axis or the diameter of the minor axis.

[0050] In one embodiment of the present invention, the average particle size (D50) of the secondary particles of the composite sulfide-based solid electrolyte may be 0.11 to 100 μm, for example, 0.2 to 80 μm, 0.3 to 70 μm, 0.4 to 60 μm, 0.5 to 50 μm, 0.6 to 40 μm, 0.7 to 40 μm, 0.8 to 30 μm, 0.9 to 25 μm, or 1 to 20 μm.

[0051] If the average particle size of the secondary particles of the composite sulfide-based solid electrolyte is less than 0.11 μm, the lithium ion conductivity and water resistance of the solid electrolyte may decrease significantly. If it exceeds 100 μm, there may be problems in the process of forming the solid electrolyte film when manufacturing an all-solid-state battery using the solid electrolyte.

[0052] In one embodiment of the present invention, the content ratio of the sulfide-based solid electrolyte to lithium halide in the primary particles may be 99.9 parts by weight:0.1 parts by weight to 80 parts by weight:20 parts by weight, based on a total of 100 parts by weight of the composite sulfide-based solid electrolyte. For example, it may be 99.5 parts by weight:0.5 parts by weight to 85 parts by weight:15 parts by weight, 99 parts by weight:1 part by weight to 90 parts by weight:10 parts by weight, and preferably 99 parts by weight:1 part by weight to 92.5 parts by weight:7.5 parts by weight.

[0053] If the lithium halide content is less than 0.1 parts by weight relative to 100 parts by weight of the total composite sulfide solid electrolyte, the adsorption capacity to external moisture, i.e., the water resistance of the composite sulfide solid electrolyte will decrease, and the ionic conductivity of the solid electrolyte may decrease due to causes such as hydrogen sulfide gas generation. If it exceeds 20 parts by weight, the content of primary particles of the sulfide solid electrolyte within the composite sulfide solid electrolyte will relatively decrease, which may lead to a decrease in the lithium ion conductivity of the electrolyte.

[0054] In one embodiment of the present invention, the average particle size (D50) of the primary particles of the composite sulfide-based solid electrolyte may be 0.1 to 15 μm, for example, 0.2 to 15 μm, 0.3 to 10 μm, and preferably 0.5 to 5 μm.

[0055] If the average particle size of the primary particles of the composite sulfide-based solid electrolyte is less than 0.1 μm, the lithium ion conductivity and water resistance of the solid electrolyte may decrease significantly. If it exceeds 15 μm, the relative size of the secondary particles of the composite sulfide-based solid electrolyte containing these particles may increase, potentially causing problems in the process of forming the solid electrolyte film when manufacturing all-solid-state batteries using the solid electrolyte.

[0056] In one embodiment of the present invention, the sulfide-based solid electrolyte of the primary particles may be represented by the following chemical formula 2. [Chemical formula 2]

[0057] Li k M 1 l S m X 1 n In the aforementioned chemical formula 2, M 1 is Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, or La; 1is F, Cl, Br, I, Se, Te, or O, where 0 < k ≦ 6, 0 < l ≦ 6, 0 < m ≦ 6, and 0 ≦ n ≦ 6.

[0058] For example, in Chemical Formula 2, M 1 can be B, Si, Ge, P, or N.

[0059] For example, in Chemical Formula 2, X 1 can be F, Cl, Br, I, or O.

[0060] For example, the sulfide-based solid electrolyte represented by Chemical Formula 2 is Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n , m, n are positive numbers, Z is any one of Ge, Zn, or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is any one of P, Si, Ge, B, Al, Ga, In, Li 7-x PS 6-x Cl x , 0 ≦ x ≦ 2, Li 7-x PS 6-x Br x , 0 ≦ x ≦ 2, and Li 7-x PS 6-x I x may be one or more selected from 0 ≦ x ≦ 2.

[0061] Also, preferably, the sulfide-based solid electrolyte may be a solid electrolyte having an argyrodite crystal structure containing one or more selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0062] The composite sulfide-based solid electrolyte according to the present invention can be manufactured by the following manufacturing method. The steps of the manufacturing method for the sulfide-based solid electrolyte according to the present invention will be described in detail below.

[0063] First, in order to produce the composite sulfide-based solid electrolyte according to the present invention, a sulfide-based solid electrolyte and a lithium halide represented by the following chemical formula 1 are prepared. [Chemical formula 1] LiX (In the above chemical formula 1, X is one of the following selected from F, Cl, Br, and I).

[0064] The sulfide-based solid electrolyte and the lithium halide represented by chemical formula 1 are the same as those described above, so a detailed explanation will be omitted below.

[0065] Next, the lithium halide is crushed to form fine particles.

[0066] The step of grinding the lithium halide is not limited to a specific method. For example, one cycle may consist of ball milling at 100 to 2,000 rpm for 5 to 30 minutes, and the grinding can be carried out through 5 to 20 cycles of ball milling. If the grinding speed and grinding time of the ball mill are below the aforementioned numerical range, the spaces between the primary particles of the sulfide-based solid electrolyte, which are the primary particles, cannot be properly filled, and the effect of improving the water resistance of the sulfide-based solid electrolyte may be minimal. If the numerical range is exceeded, the manufacturing process time and cost of the solid electrolyte will increase, and there will be problems of excessive heat generation.

[0067] To further enhance the moisture adsorption capacity of the lithium halide, preferably, the process may include vacuum drying to remove moisture from the lithium halide before grinding, and although not limited to a particular method, the lithium halide before grinding may be placed in a vacuum oven and dried at a temperature of 25-80°C for 24-48 hours.

[0068] As described above, lithium halide that has been pulverized through a ball mill or the like can have an average particle size (D50) of 0.01 to 3 μm.

[0069] Finally, the sulfide-based solid electrolyte and the pulverized lithium halide are mixed to form a composite sulfide-based solid electrolyte in the form of secondary particles, in which the lithium halide is positioned in particulate form between the primary particles of the sulfide-based solid electrolyte.

[0070] In one embodiment of the present invention, the sulfide-based solid electrolyte of the primary particles and the lithium halide may be mixed in an amount of 99.9 parts by weight:0.1 parts by weight to 80 parts by weight to 20 parts by weight, based on 100 parts by weight of the total composite sulfide-based solid electrolyte. For example, they may be mixed in an amount of 99.5 parts by weight:0.5 parts by weight to 85 parts by weight to 15 parts by weight, 99 parts by weight:1 part by weight to 90 parts by weight to 10 parts by weight, preferably 99 parts by weight:1 part by weight to 92.5 parts by weight to 7.5 parts by weight.

[0071] Furthermore, the present invention provides an all-solid-state battery comprising the aforementioned composite sulfide-based solid electrolyte. The all-solid-state battery comprises a positive electrode, a negative electrode, and a solid electrolyte membrane, and one or more of the positive electrode, negative electrode, and solid electrolyte membrane may contain a composite sulfide-based solid electrolyte having the aforementioned properties.

[0072] In one embodiment of the present invention, the solid electrolyte membrane is an ion-conducting sheet interposed between the positive and negative electrodes in an all-solid-state battery, acting as an insulating and ion-conducting channel, and is preferably 1.0 × 10⁻⁶. -5 It has an ionic conductivity of S / cm or higher. The solid electrolyte membrane may contain a composite sulfide-based solid electrolyte according to the present invention, and may further contain other electrolyte materials described below.

[0073] In the present invention, the positive electrode and the negative electrode each have a current collector and an electrode active material layer formed on at least one surface of the current collector, and the active material layer contains a plurality of electrode active material particles and an electrolyte material. The positive electrode and the negative electrode can contain the composite sulfide-based solid electrolyte according to the present invention as the electrolyte material, and can further contain, in addition, other electrolyte materials to be described later.

[0074] In addition, each of the electrodes can further contain one or more of a conductive material and a binder resin, as necessary. Further, the electrode can further contain various additives for the purpose of complementing or improving the physical and chemical properties of the electrode.

[0075] In the present invention, as the negative electrode active material, lithium metal can be included as the negative electrode active material of a lithium-ion secondary battery, and any other material that can be used as the negative electrode active material can also be used. For example, the negative electrode active material includes carbon such as non-graphitizable carbon and graphite-based carbon; Li x Fe2O3 (0 ≦ x ≦ 1), Li x WO2 (0 ≦ x ≦ 1), Sn x Me 1-x Me′ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8) and other metal composite oxides; lithium alloys; silicon-based alloys; tin-based alloys; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; titanium oxides; lithium titanium oxides, etc., and can further contain one or more selected therefrom.

[0076] When the electrode is the positive electrode, the electrode active material can be used without limitation as long as it is suitable for use as a positive electrode active material in a lithium-ion secondary battery. For example, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3); chemical formula LiMn 1-x M x Lithium manganese composite oxide represented by O2 (where M = Co, Ni, Fe, Cr, Zn, or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu, or Zn); LiNi x Mn 2-x This can include, but is not limited to, lithium manganese complex oxides with a spinel structure represented by O4; LiMn2O4 in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion; disulfide compounds; Fe2(MoO4)3, etc.

[0077] In the present invention, the current collector is made of a metal plate or the like, which is electrically conductive, and an appropriate one can be used depending on the polarity of the current collector electrode known in the field of secondary batteries.

[0078] In the present invention, the conductive material is usually added in an amount of 1% to 30% by weight based on the total weight of the mixture containing the electrode active material. Such a conductive material is not particularly limited as long as it does not induce a chemical change in the battery and is conductive, and may include, for example, one or more types of conductive materials selected from graphite such as natural graphite or artificial graphite; carbon black-based carbon materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0079] In the present invention, the binder resin is not particularly limited as long as it is a component that assists in the bonding of the active material to the conductive material and to the current collector. Examples include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers. The binder resin may typically be present in an amount of 1% to 30% by weight, or 1% to 10% by weight, based on 100% by weight of the electrode layer.

[0080] On the other hand, in the present invention, each electrode active material layer may optionally contain one or more additives such as oxidation stabilizing additives, reduction stabilizing additives, flame retardants, heat stabilizers, and antifogging agents.

[0081] In the present invention, the all-solid-state battery may include the composite sulfide-based solid electrolyte according to the present invention as the solid electrolyte material. In addition, it may further include one or more of the polymer-based solid electrolyte, oxide-based solid electrolyte, and sulfide-based solid electrolyte.

[0082] The aforementioned polymer solid electrolyte is a composite of a lithium salt and a polymer resin, that is, a polymer electrolyte material formed by adding a polymer resin to a solventized lithium salt, and is approximately 1 × 10⁻⁶ -7 S / cm or more, preferably about 1 × 10 -5 It can exhibit ionic conductivity of S / cm or higher.

[0083] Non-limiting examples of the polymer resin include polyether polymers, polycarbonate polymers, acrylate polymers, polysiloxane polymers, phosphazene polymers, polyethylene derivatives, alkylene oxide derivatives such as polyethylene oxide, phosphate ester polymers, agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ionic dissociation groups, and may contain one or more of these. Furthermore, as the polymer electrolyte, examples of polymer resins include branched copolymers obtained by copolymerizing a PEO (polyethylene oxide) main chain with amorphous polymers such as PMMA, polycarbonate, polysiloxane (pdms) and / or phosphazene as copolymerizers, comb-like polymers, and crosslinked polymers, and may contain one or more of these.

[0084] In the electrolyte of the present invention, the aforementioned lithium salt is an ionizable lithium salt, Li + X - This can be shown as follows. There are no particular limitations on the anion of such a lithium salt, but F - Cl - , Br - , I - NO3 - , N(CN)2 - BF4 - ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF -, (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , (CF3CF2SO2)2N - Examples thereof include the following.

[0085] The oxide-based solid electrolyte material contains oxygen (O) and has ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table. Non-limiting examples thereof include LLTO-based compounds, Li6La2CaTa2O 12 , Li6La2ANb2O 12 (A is Ca or Sr), Li2Nd3TeSbO 12 , Li3BO 2.5 N 0.5 , Li9SiAlO8, LAGP-based compounds, LATP-based compounds, Li 1+x Ti 2-x Al x Si y (PO4) 3-y (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1), LiAl x Zr 2-x (PO4)3 (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1), LiTi x Zr 2-x (PO4)3 (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1), LISICON-based compounds, LIPON-based compounds, perovskite-based compounds, NASICON-based compounds, LLZO-based compounds, and may contain one or more selected therefrom. However, it is not particularly limited thereto.

[0086] The sulfide-based solid electrolyte material may be the sulfide-based solid electrolyte represented by Chemical Formula 2 described above, but is not particularly limited thereto.

[0087] The present invention also provides a secondary battery having the structure described above. Furthermore, the present invention provides a battery module including the secondary battery as a unit battery, a battery pack including the battery module, and a device including the battery pack as a power source. Specific examples of the device include, but are not limited to, power tools powered by electric motors; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc.; electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters; electric golf carts; and power storage systems.

[0088] The following are specific embodiments of the present invention. However, the embodiments described below are merely for illustrative or explanatory purposes and do not limit the present invention. Furthermore, matters not described herein can be sufficiently inferred by technical analogy to those skilled in the art, and their explanations are omitted.

[0089] Example 1: Production of a composite sulfide-based solid electrolyte (1) LiBr was prepared using lithium halide, and it was placed in a vacuum oven to remove internal moisture and vacuum dried at 80°C for 24 hours.

[0090] (2) 5 g of LiBr from which moisture has been removed was placed in a ball mill device containing 20 zirconia balls (diameter: 10 mm), and high-energy ball milling was performed at a rotation speed of 750 rpm for 15 minutes, which constituted one cycle. A total of 16 cycles of ball milling were performed to obtain pulverized LiBr.

[0091] (3) In a glove box, the pulverized LiBr and Li6PS5Cl, a sulfide-based solid electrolyte with an argyrodite crystal structure, were mixed in a content ratio of 5 parts by weight to 95 parts by weight, and a composite sulfide-based solid electrolyte was produced by mixing these together.

[0092] Example 2: Production of a composite sulfide-based solid electrolyte A composite sulfide-based solid electrolyte was prepared in the same manner as in Example 1, except that pulverized LiBr and Li6PS5Cl, a sulfide-based solid electrolyte with an argyrodite crystal structure, were mixed in a content ratio of 10 parts by weight to 90 parts by weight.

[0093] Example 3: Production of a composite sulfide-based solid electrolyte A composite sulfide-based solid electrolyte was prepared in the same manner as in Example 1, except that pulverized LiBr and Li6PS5Cl, a sulfide-based solid electrolyte with an argyrodite crystal structure, were mixed in a content ratio of 15 parts by weight to 85 parts by weight.

[0094] Comparative Example 1: Production of a sulfide-based solid electrolyte that does not contain lithium halide Unlike Examples 1-3, the solid electrolyte was prepared using only Li6PS5Cl, a sulfide-based solid electrolyte with an argyrodite crystal structure that does not contain lithium halide.

[0095] [Experimental Example 1: EDX (Energy dispersive X-ray spectroscopy) analysis of a complex sulfide-based solid electrolyte] Energy dispersive X-ray spectroscopy (EDX) experiments were performed to measure the sulfur (S) and brin (Br) elemental components in the composite sulfide solid electrolyte produced by Example 1, and the results are shown in Figures 4 and 5. The EDX measurement instrument used was the JSM7900F from JEOL.

[0096] Referring to Figures 4 and 5, it was found that in the case of the composite sulfide-based solid electrolyte according to Example 1 of the present invention, LiBr is not formed as a coating layer of the sulfide-based solid electrolyte, and fine-particle LiBr is located between the primary particles of the sulfide-based solid electrolyte.

[0097] [Experimental Example 2: Measurement of ionic conductivity of a complex sulfide-based solid electrolyte and analysis of the rate of decrease in ionic conductivity] The ionic conductivity and the rate of decrease in ionic conductivity due to moisture exposure were measured and analyzed for each of the composite sulfide-based solid electrolytes from Examples 1-3 and the sulfide-based solid electrolyte from Comparative Example 1.

[0098] (1) Measurement of ionic conductivity The composite sulfide-based solid electrolytes from Examples 1-3 and the sulfide-based solid electrolyte from Comparative Example 1 were each prepared as specimens with a diameter of 6 mm and a thickness of 1 mm. These specimens were interposed between Al-C current collectors, and an aluminum pouch was vacuum-sealed to produce an all-solid-state battery.

[0099] The all-solid-state battery was fastened to a jig and a pressure of 250 MPa was applied. The ionic conductivity was measured using impedance spectroscopy, and the results are shown in Table 1 below.

[0100] Referring to Table 1, it was confirmed that in the case of the composite sulfide-based solid electrolytes of Examples 1 to 3, even if LiBr is further included between the primary particles of the sulfide-based solid electrolyte, the overall ionic conductivity of the composite sulfide-based solid electrolyte does not decrease significantly.

[0101] This is achieved by micronizing lithium halides such as LiBr and mixing them with a sulfide-based solid electrolyte, which allows the LiBr to form lithium ions (Li) within the complex sulfide-based solid electrolyte. + It can be predicted that this is because the movement path of the lithium ions was not obstructed, resulting in no significant impact on lithium ion conduction.

[0102] (2) Measurement of ionic conductivity reduction rate Two g each of the composite sulfide-based solid electrolytes from Examples 1-3 and the sulfide-based solid electrolyte from Comparative Example 1 were spread evenly on a plate and exposed to a dry room environment with a dew point of -45°C (21°C, 0.46% humidity) for a total of 5 hours. The rate of decrease in ionic conductivity of the solid electrolyte over time was measured, and the results are shown in Table 1, Figures 6 and 7 below. Figure 7 is a normalized ionic conductivity graph of only the pure sulfide-based solid electrolyte, with the rate of change in ionic conductivity due to LiBr excluded from the ionic conductivity measurement results from Figure 6.

[0103] The ionic conductivity was measured at each time point in the same manner as described in "(1) Measurement of Ionic Conductivity" above.

[0104] Referring to Table 1, Figures 6 and 7, it can be seen that, compared to the solid electrolyte of Comparative Example 1, the composite sulfide-based solid electrolytes of Examples 1 to 3 have improved water resistance and a smaller rate of decrease in ionic conductivity over time due to the inclusion of lithium halide in particulate form, which can adsorb moisture within the solid electrolyte.

[0105] [Table 1]

[0106] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto. Various modifications and improvements by those skilled in the art, using the basic concepts of the present invention as defined in the following claims, also fall within the scope of the present invention. [Explanation of symbols]

[0107] 10: Primary particles of sulfide-based solid electrolytes 20: Lithium halogenate 30: Secondary particles of composite sulfide-based solid electrolytes 40: Sulfide solid electrolyte 100: Composite sulfide solid electrolyte 200: Sulfide solid electrolyte

Claims

1. It consists of multiple primary particles and secondary particles containing lithium halide represented by the following chemical formula 1. The primary particles contain a sulfide-based solid electrolyte, The lithium halogen is located between the primary particles, The lithium halide has an average particle size (D50) that is relatively small compared to the primary particles of the sulfide-based solid electrolyte. Composite sulfide solid electrolyte: [Chemical formula 1] LiX (In the above chemical formula 1, X is one selected from F, Cl, Br, and I).

2. The average particle size (D50) of the lithium halide is 0.01 to 3 μm. The composite sulfide-based solid electrolyte according to claim 1.

3. The average particle size (D50) of the secondary particles of the composite sulfide-based solid electrolyte is 0.11 to 100 μm. The composite sulfide-based solid electrolyte according to claim 1.

4. Based on a total of 100 parts by weight of the aforementioned composite sulfide-based solid electrolyte, The content ratio of the sulfide-based solid electrolyte and lithium halide in the primary particles is 99.9 parts by weight:0.1 parts by weight to 80 parts by weight:20 parts by weight. The composite sulfide-based solid electrolyte according to claim 1.

5. The aforementioned sulfide-based solid electrolyte includes an argyrodite-type crystal structure. The composite sulfide-based solid electrolyte according to claim 1.

6. The average particle size (D50) of the primary particles is 0.1 to 15 μm. The composite sulfide-based solid electrolyte according to claim 1.

7. In the aforementioned composite sulfide-based solid electrolyte of secondary particles, The lithium halide is not formed as a coating layer for the primary particles. The composite sulfide-based solid electrolyte according to claim 1.

8. The sulfide-based solid electrolyte of the primary particles is represented by the following chemical formula 2: The composite sulfide-based solid electrolyte according to claim 1: [Chemical formula 2] Li ｋ M １ ｌ S ｍ X １ ｎ (In the above chemical formula 2, M １ is Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, or La; １ (where is F, Cl, Br, I, Se, Te, or O, and 0 < k ≤ 6, 0 < l ≤ 6, 0 < m ≤ 6, and 0 ≤ n ≤ 6).

9. An all-solid-state battery comprising a composite sulfide-based solid electrolyte according to any one of claims 1 to 8.

10. The steps include: preparing a sulfide-based solid electrolyte and a lithium halide represented by the following chemical formula 1; The steps include: grinding the lithium halide; The steps include: mixing the pulverized lithium halide with the sulfide-based solid electrolyte; The pulverized lithium halide has an average particle size (D50) that is relatively small compared to the primary particles of the sulfide-based solid electrolyte, a method for producing a composite sulfide-based solid electrolyte: [Chemical formula 1] LiX (In the above chemical formula 1, X is one selected from F, Cl, Br, and I).

11. The process further includes a step of vacuum drying the lithium halide to remove moisture before grinding it. A method for producing a composite sulfide-based solid electrolyte according to claim 10.

12. The lithium halide is crushed and formed by ball milling at 100 to 2,000 rpm for 5 to 30 minutes, with one cycle consisting of 5 to 20 cycles. A method for producing a composite sulfide-based solid electrolyte according to claim 10.

13. The average particle size (D50) of the pulverized lithium halide is 0.01 to 3 μm. A method for producing a composite sulfide-based solid electrolyte according to claim 10.

14. The pulverized lithium halide and the sulfide-based solid electrolyte are mixed in a content ratio of 99.9 parts by weight:0.1 parts by weight to 80 parts by weight:20 parts by weight, based on 100 parts by weight of the total amount of the composite sulfide-based solid electrolyte. A method for producing a composite sulfide-based solid electrolyte according to claim 10.

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