Positive electrode for lithium-sulfur battery and manufacturing method therefor

Abstract

The present invention relates to a positive electrode for a lithium-sulfur battery and a manufacturing method therefor, the positive electrode comprising a positive electrode active material layer which includes: a positive electrode active material including a composite of a sulfur-based material, metal halide salts, and a carbon-based material; a sulfide-based solid electrolyte; a first binder comprising a rubber-based polymer; and a second binder including a vinyl polymer comprising a carbonyl group.

Description

Cathode for lithium-sulfur battery and method for manufacturing the same

[0001] The present invention relates to a positive electrode for a lithium-sulfur battery and a method for manufacturing the same.

[0002] Lithium-ion batteries are used in various fields due to their long lifespan, low self-discharge rate, and safety. However, because lithium-ion batteries utilize metal oxides such as lithium cobalt oxide (LCO) and lithium nickel cobalt aluminum oxide (NCA) as cathode materials, they are expensive and have limitations in improving energy density. Consequently, there is growing interest in batteries that can enhance energy density while ensuring stability and price competitiveness.

[0003] The problem that the present invention aims to solve is to provide a cathode for a lithium-sulfur battery capable of improving ion conductivity and electronic conductivity, and a method for manufacturing the same.

[0004] Another problem that the present invention aims to solve is to provide a lithium-sulfur battery comprising the positive electrode for the lithium-sulfur battery.

[0005] A positive electrode for a lithium-sulfur battery according to one embodiment of the present invention comprises a positive electrode current collector; and a positive electrode active material layer located on the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, a sulfide-based solid electrolyte, and a binder, wherein the positive electrode active material comprises a composite of a sulfur-based material, a metal halide salt, and a carbon-based material, and wherein the sulfur-based material comprises S8 and Li2S nIt includes at least one of (1 ≤ n ≤ 8, where n is an integer), and the metal halide salt includes a first metal halide salt including an alkali metal and a second metal halide salt including a boron group metal, and the binder includes a first binder including a rubber-based polymer and a second binder including a vinyl polymer including a carbonyl group.

[0006] A method for manufacturing a positive electrode for a lithium-sulfur battery according to another embodiment of the present invention comprises the steps of: manufacturing a positive electrode active material comprising a composite of a sulfur-based material, a metal halide salt, and a carbon-based material; mixing the positive electrode active material with a sulfide-based solid electrolyte and a binder to manufacture a positive electrode slurry; and applying the positive electrode slurry to one surface of a positive electrode current collector, wherein the binder comprises a first binder comprising a rubber-based polymer and a second binder comprising a vinyl polymer comprising carbonyl groups.

[0007] A lithium-sulfur battery according to another embodiment of the present invention comprises a positive electrode for the lithium-sulfur battery, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode.

[0008] A positive electrode for a lithium-sulfur battery according to one embodiment of the present invention comprises a positive electrode active material comprising a composite of a sulfur-based material, a metal halide salt, and a carbon-based material, a sulfide-based solid electrolyte, and a positive electrode active material layer comprising a first binder comprising a rubber-based polymer and a second binder comprising a vinyl polymer comprising carbonyl groups, thereby having excellent ionic conductivity and electronic conductivity.

[0009] In addition, a lithium-sulfur battery according to another embodiment of the present invention has excellent capacity and lifespan characteristics by including a positive active material with improved ion conductivity and electronic conductivity and a positive active material layer containing the same.

[0010] FIG. 1 is a cross-sectional view of a lithium-sulfur battery according to one embodiment of the present invention.

[0011] Figure 2 is a schematic diagram illustrating the ion conduction pathway of lithium ions in the positive active material layer.

[0012] FIG. 3 is a schematic diagram illustrating the ion conduction path of lithium ions in the positive active material layer of a lithium-sulfur battery according to one embodiment of the present invention.

[0013] Figure 4 is a schematic cross-sectional view showing an enlarged view of area A of Figure 1.

[0014] Figure 5 is a schematic cross-sectional view showing an enlarged view of area B of Figure 4.

[0015] FIG. 6 is a cross-sectional view of a lithium-sulfur battery according to another embodiment of the present invention.

[0016] FIG. 7 is a cross-sectional view of a lithium-sulfur battery according to another embodiment of the present invention.

[0017] <Explanation of Symbols>

[0018] 1: Lithium-sulfur battery

[0019] 100: Anode 110: Anode current collector

[0020] 120: Positive active material layer 121: Positive active material

[0021] 121a: Sulfur series substances 121b: First metal halide salts

[0022] 121c: Secondary metal halide salts 121d: Carbonaceous substances

[0023] 122: Sulfide-based solid electrolyte 123: Binder

[0024] 200: Cathode 210: Cathode current collector

[0025] 220: Coating layer 230: Lithium metal layer

[0026] 300: Solid electrolyte layer

[0027] In order to fully understand the structure and effects of the present invention, preferred embodiments of the present invention are described with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and various modifications can be made. The description of these embodiments is provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention.

[0028] In this specification, when a component is described as being on another component, it means that it may be formed directly on the other component or that a third component may be interposed between them. Additionally, in the drawings, the thicknesses of the components are exaggerated for the effective description of the technical content. Throughout the specification, parts indicated by the same reference numeral represent the same components.

[0029] The embodiments described herein will be explained with reference to cross-sectional and / or plan views, which are exemplary illustrations of the invention. In the drawings, the thicknesses of the films and regions are exaggerated for effective explanation of the technical content. Accordingly, the regions illustrated in the drawings are schematic in nature, and the shapes of the regions illustrated in the drawings are intended to illustrate specific forms of regions of the device and are not intended to limit the scope of the invention.

[0030] In the various embodiments of this specification, terms such as first, second, third, primary, secondary, tertiary, etc., have been used to describe various components, but these components should not be limited by such terms. These terms are used merely to distinguish one component from another. The embodiments described and illustrated herein also include their complementary embodiments.

[0031] All numbers and expressions indicating the amounts of components, reaction conditions, etc. described in this specification should be understood as being modified by the term "about" in all cases unless otherwise specified.

[0032] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, 'comprises' and / or 'comprising' do not exclude the presence or addition of one or more other components to the mentioned components.

[0033] In this specification, "combination of these" may mean a mixture of components, a laminate, a composite, a copolymer, an alloy, a blend, a reaction product, etc.

[0034] Unless otherwise defined in this specification, the particle diameter or size may be the average particle diameter. The average particle diameter refers to the average value of the diameter of the particles according to the cumulative volume in the particle size distribution. The particle size distribution may be measured by methods widely known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring from images obtained by a transmission electron microscope (TEM) or a scanning electron microscope (SEM). Alternatively, the average particle diameter may be calculated by measuring using a measuring device utilizing dynamic lightscattering, performing data analysis to count the number of particles for each particle size range, and then calculating the average particle diameter.

[0035] In addition, 'D10', 'D50', and 'D90' represent the particle size at the 10% point (D10), 50% point (D50), and 90% point (D90) of the volume cumulative distribution according to particle size, respectively. For example, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000, which irradiates ultrasound of approximately 28 kHz with an output of 60 W) to measure the difference in diffraction patterns according to particle size as the particles pass through the laser beam, thereby calculating the volume cumulative distribution according to particle size, and D10, D50, and D90 can be measured by calculating the particle diameter at the points that are 10%, 50%, and 90% of the volume cumulative distribution according to particle size in the measuring device.

[0036] In this specification, “metal” includes both metals and metalloids such as silicon and germanium in an elemental or ionic state, and “alloy” means a mixture of two or more metals.

[0037] In this specification, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation, and “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0038] In this specification, “lithiation” and “to lithiate” refer to the process of adding lithium to an electrode active material, and “delithiation” and “to delithiate” refer to the process of removing lithium from an electrode active material.

[0039] In this specification, “charge” and “to charge” refer to the process of providing electrochemical energy to a battery, and “discharge” and “to discharge” refer to the process of removing electrochemical energy from a battery.

[0040] In this specification, “anode” and “cathode” refer to electrodes where electrochemical reduction and lithiation occur during the discharge process, and “negative electrode” and “anode” refer to electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0041] Lithium-sulfur batteries are batteries that use sulfur-based materials as the cathode active material. Sulfur is non-toxic and abundant, offering excellent price competitiveness. Furthermore, compared to lithium-ion batteries that use metallic materials such as nickel and cobalt as cathode materials, lithium-sulfur batteries utilize the lighter sulfur, resulting in a higher gravitational energy density. Consequently, it is easier to achieve characteristics that are both lightweight and high-capacity.

[0042] Unlike lithium-ion batteries, which generate electrical energy through the redox reaction of electrons separated from lithium ions, lithium-sulfur batteries generate energy through the stepwise conversion of sulfur. Specifically, sulfur, which has a structure consisting of eight atoms in a ring form, undergoes a continuous reduction reaction during discharge and is converted into lithium polysulfide, which has a linear structure, and finally converted into lithium sulfide, thereby generating electrical energy.

[0043] These lithium-sulfur batteries offer the advantage of easily ensuring high capacity and stability; however, since sulfur, the main component of the cathode active material, is an insulator, it exhibits low ionic and electronic conductivity. Furthermore, there are issues such as volume changes in the cathode during charging and discharging, or the leaching of polysulfides—intermediates in the reduction reaction—which penetrate the separator through the electrolyte and migrate toward the anode. Consequently, research is ongoing to improve the performance and lifespan characteristics of lithium-sulfur batteries.

[0044] FIG. 1 is a cross-sectional view of a lithium-sulfur battery according to an embodiment of the present invention. Referring to FIG. 1, a lithium-sulfur battery (1) according to an embodiment of the present invention may include a positive electrode (100), a negative electrode (200), and a solid electrolyte layer (300) disposed between the positive electrode (100) and the negative electrode (200). More specifically, a lithium-sulfur battery (1) according to an embodiment of the present invention may have a structure in which a negative electrode (200), a solid electrolyte layer (300), a positive active material layer (120), and a positive current collector (110) are stacked in order. However, not limited thereto, the lithium-sulfur battery (1) may further include an additional functional layer, such as an adhesion enhancing layer, between the positive electrode (100) and the solid electrolyte layer (300), or between the negative electrode (200) and the solid electrolyte layer (300).

[0045]

[0046] cathode for lithium-sulfur batteries

[0047] A positive electrode for a lithium-sulfur battery according to one embodiment of the present invention comprises a positive electrode current collector; and a positive electrode active material layer located on the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, a sulfide-based solid electrolyte, and a binder, wherein the positive electrode active material comprises a composite of a sulfur-based material, a metal halide salt, and a carbon-based material, and wherein the sulfur-based material comprises S8 and Li2S n It includes at least one of (1 ≤ n ≤ 8, where n is an integer), and the metal halide salt includes a first metal halide salt including an alkali metal and a second metal halide salt including a boron group metal, and the binder includes a first binder including a rubber-based polymer and a second binder including a vinyl polymer including a carbonyl group.

[0048] A positive electrode for a lithium-sulfur battery according to one embodiment of the present invention comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. Specifically, the positive electrode (100) may comprise a positive electrode current collector (110) and a positive electrode active material layer (120) disposed on one or both surfaces of the positive electrode current collector (see FIG. 1).

[0049] <Blocked Household>

[0050] The positive current collector (110) can provide a reference surface on which the positive active material layer (120) is placed. For example, the positive current collector may include a plate or foil comprising indium (In), copper (Cu), magnesium (Mg), stainless steel (SUS), titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. As a specific example, the positive current collector may be an aluminum foil.

[0051] The thickness of the anode current collector may be, for example, 1 μm to 100 μm, 1 μm to 50 μm, 5 μm to 25 μm, or 10 μm to 20 μm.

[0052] According to another embodiment of the present invention, the anode may further include a carbon layer between the anode current collector (110) and the anode active material layer (120). For example, the carbon layer may include amorphous carbon, crystalline carbon, etc., and may have a thickness of 0.1 μm to 4 μm. By including the carbon layer, the bonding strength between the anode current collector (110) and the anode active material layer (120) can be improved.

[0053] <Anode Active Material Layer>

[0054] FIG. 4 is a schematic cross-sectional view showing an enlarged view of area A of FIG. 1. Referring to FIG. 4, a positive active material layer according to one embodiment of the present invention may include a positive active material (121), a sulfide-based solid electrolyte (122), and a binder (123).

[0055] The weight ratio of the positive active material to the binder in the positive active material layer may be 60:40 to 95:5, 75:25 to 95:5, or 85:15 to 95:5. By satisfying the above ranges for the weight ratio of the positive active material to the binder, ion conductivity can be further improved, and excellent capacity characteristics can be secured while maintaining the cycle characteristics of the battery at a certain level or higher.

[0056] The weight ratio of the positive active material and the sulfide-based solid electrolyte in the positive active material layer may be 40:60 to 90:10, 50:50 to 85:15, or 60:40 to 80:20. By satisfying the above ranges for the weight ratio of the positive active material and the sulfide-based solid electrolyte, the cycle characteristics of the battery can be maintained at a certain level or higher while securing excellent capacity characteristics.

[0057] positive electrode active material

[0058] A positive active material layer according to one embodiment of the present invention includes a positive active material.

[0059] According to one embodiment of the present invention, the positive active material (121) comprises a composite of a sulfur-based material (121a), a metal halide salt (121b and 121c), and a carbon-based material (121d). More specifically, the positive active material (121) according to one embodiment of the present invention may be a composite of a sulfur-based material (121a), a metal halide salt (121b and 121c), and a carbon-based material (121d).

[0060] FIG. 5 is a schematic cross-sectional view showing an enlarged view of region B of FIG. 4. FIG. 5 shows an enlarged view of the region corresponding to region B of FIG. 4 to explain in more detail the positive active material (121), specifically the composite of a sulfur-based material (121a), a metal halide salt (121b and 121c) and a carbon-based material (121d) within the positive active material (121). More specifically, the positive active material (121) according to one embodiment of the present invention may include a composite of a sulfur-based material (121a), a first metal halide salt (121b), a second metal halide salt (121c), and a carbon-based material (121d).

[0061] The above positive active material may have a particle form. For example, the above positive active material (121) may be a composite of the sulfur-based material (121a), metal halide salts (121b and 121c) and carbon-based material (121d), and the composite of the sulfur-based material (121a), metal halide salts (121b and 121c) and carbon-based material (121d) may have a particle form.

[0062] For example, the particle size of the positive electrode active material may be 50 μm or less, 30 μm or less, or 10 μm or less, and may be 0.1 μm to 50 μm or 1 μm to 10 μm. In addition, the composite of the sulfur-based material, metal halide salt, and carbon-based material in the positive electrode active material may be 50 μm or less, 30 μm or less, or 10 μm or less, and may have a particle size of 0.1 μm to 50 μm or 1 μm to 10 μm.

[0063] By satisfying the above range, the particle size of the positive electrode active material and / or the particle size of the composite of the sulfur-based material, metal halide salt, and carbon-based material can suppress volume change during charging and discharging, thereby effectively preventing degradation and improving lifespan characteristics. If the particle size of the positive electrode active material and / or the composite falls outside the above range, the volume change of the composite during charging and discharging increases, which may accelerate degradation and potentially degrade the cycle characteristics and lifespan characteristics of the battery.

[0064] The above particle size may be the average particle size measured using laser diffraction, scanning electron microscopy, etc. For example, the particle size of the composite may be the arithmetic mean of the particle sizes of a plurality of particles measured using software in a scanning electron microscopy image.

[0065] The above-mentioned positive electrode active material can have excellent ionic conductivity by comprising a complex of a sulfur-based material, a metal halide salt, and a carbon-based material. For example, the ionic conductivity of the above-mentioned positive electrode active material is 3 × 10⁻⁶ at 25°C. -6 S / cm or greater, 3.5 × 10 -6 S / cm or more, 4 × 10 -6 S / cm or more, 5 × 10 -6 S / cm or more, 6 × 10 -6 S / cm or greater or 6.75 × 10 -6 It may be greater than S / cm, and 1 × 10 -4 S / cm or less, 0.5 × 10 -4 S / cm or less or 1 × 10 -5 It may be less than S / cm. The above ionic conductivity may be measured using electrochemical impedance spectroscopy.

[0066] The content of the positive active material may be 40% to 90% by weight with respect to the total weight of the positive active material layer. For example, the content of the positive active material in the positive active material layer may be 50% to 85% by weight, 60% to 80% by weight, or 65% to 75% by weight with respect to the total weight of the positive active material layer. By satisfying the above ranges for the content of the positive active material, the capacity characteristics of the lithium-sulfur battery containing it can be improved.

[0067] According to one embodiment of the present invention, the sulfur-based material (121a) is S8 and Li2S n It includes at least one of (1 ≤ n ≤ 8, where n is an integer). Specifically, the positive active material of the present invention may include elemental sulfur (S), and the elemental sulfur may exist in the form of a sulfur-based material including at least one of S8 and Li2Sn (1 ≤ n ≤ 8, where n is an integer). For example, the content of the elemental sulfur in the positive active material layer may be 10% to 80% by weight, 10% to 65% by weight, or 15% to 60% by weight with respect to the total weight of the positive active material layer.

[0068] Sulfur is attracting attention as a next-generation cathode material because it has a high theoretical capacity (1,672 mAh / g), is abundant on Earth, and is relatively inexpensive. Since sulfur has relatively low ionic conductivity, the cathode active material may further include a solid electrolyte, binder, conductive material, etc., to form a smooth ionic conduction path for lithium ions.

[0069] The above sulfur-based material may undergo a continuous oxidation / reduction reaction of sulfur and / or lithium sulfide. For example, the above sulfur-based material (121a) may be converted to S8->Li2S8->Li2S6->Li2S4->Li2S2->Li2S by a continuous reduction reaction of sulfur. In this process, lithium ions move between the anode and cathode, and at the same time, electrons may move through an external circuit to generate an electric current.

[0070] The content of the sulfur-based material may be 20% to 80% by weight with respect to the total weight of the composite. For example, the content of the sulfur-based material may be 30% to 70% by weight, 35% to 60% by weight, 10% to 60% by weight, 20% to 50% by weight, or 25% to 45% by weight with respect to the total weight of the composite.

[0071] According to one embodiment of the present invention, the metal halide salt may include two different types of metal halide salts. Specifically, the metal halide salt may include a first metal halide salt (121b) containing an alkali metal and a second metal halide salt (121c) containing a boron group metal (see FIG. 5). Since the metal halide salt includes two different types of metal halide salts, a composite, more specifically a solid solution, can be formed, thereby improving ion conductivity while maintaining the overall shape, reducing interfacial resistance, and effectively suppressing the leaching of lithium polysulfide, which can improve the capacity and cycle characteristics of the battery.

[0072] The above solid solution is (1-xy)Li2S nIt may include -xAX-yBX3 or (1-xy)S8-xAX-yBX3. The x and the y are each 0.01 ≤ x ≤ 0.3 and 0.01 ≤ y ≤ 0.3, and the n is an integer 1 ≤ n ≤ 8, the A is an alkali metal, the B is a boron group metal, and the X is a halogen element.

[0073] The first metal halide salt may be a binary compound composed of an alkali metal and one element selected from Group 17 of the periodic table. Specifically, the first metal halide salt may be a lithium salt. For example, the first metal halide salt may include LiF, LiCl, LiBr, LiI, or a combination thereof.

[0074] The above first metal halide salt can improve the ion conductivity of the positive electrode active material by more easily forming a composite, more specifically a solid solution, with the above sulfur-based material.

[0075] The content of the first metal halide salt may be 2.5% to 15% by weight with respect to the total weight of the composite. For example, the content of the first metal halide salt may be 2.5% to 10% by weight, 3.3% to 6.6% by weight, 5% to 12.5% ​​by weight, or 7% to 10% by weight with respect to the total weight of the composite.

[0076] The weight ratio of the sulfur-based material and the first metal halide salt may be 30:1 to 1:1. For example, the weight ratio of the sulfur-based material and the first metal halide salt may be 20:1 to 2:1 or 10:1 to 3:1.

[0077] In addition, the second metal halide salt may be a binary compound composed of a boron group metal and one element selected from Group 17 of the periodic table. For example, the second metal halide salt may include AlF3, AlCl3, AlBr3, AlI3, GaF3, GaCl3, GaBr3, GaI3, InF3, InCl3, lnBr3, lnI3, TiF3, TiCl3, TiBr3, TiI3, or a combination thereof.

[0078] The second metal halide salt can more easily form a composite, more specifically a solid solution, with the sulfur-based material and the first metal halide salt, thereby suppressing the leaching of lithium polysulfide and improving the capacity and cycle characteristics of the battery.

[0079] In addition, the second metal halide salt can lower interfacial resistance while maintaining the overall shape of the composite. Specifically, the sulfur-based material undergoes oxidation / reduction to produce S8 and Li2S n Even if the shape is deformed between (1 ≤ n ≤ 8, where n is an integer), the shape deformation of the composite and / or the positive active material can be minimized by the second metal halide salt, thereby easily maintaining the overall shape and thus improving cycle characteristics.

[0080] The content of the second metal halide salt may be 7.5% to 45% by weight with respect to the total weight of the composite. For example, the content of the second metal halide salt may be 7.5% to 30% by weight, 10% to 20% by weight, 15% to 37.5% by weight, or 20% to 31% by weight with respect to the total weight of the composite.

[0081] The weight ratio of the sulfur-based material and the second metal halide salt may be 10:1 to 1:1. For example, the weight ratio of the sulfur-based material and the second metal halide salt may be 5:1 to 1:1 or 5:1 to 2:1.

[0082] In addition, the weight ratio of the first metal halide salt and the second metal halide salt may be 1:1 to 1:20. For example, the weight ratio of the first metal halide and the second metal halide salt may be 3:1 to 1:9, 1:1 to 1:9, or 1:3 to 1:9. By satisfying the above ranges for the weight ratio of the first and second metal halide salts, the effect of improving ion conductivity and capacitance characteristics can be maximized.

[0083] The content of the metal halide salt may be 10% to 60% by weight with respect to the total weight of the composite. For example, the total content of the metal halide salt may be 10% to 40% by weight, 15% to 30% by weight, 20% to 50% by weight, or 25% to 45% by weight with respect to the total weight of the composite.

[0084] The carbon-based material (121d) may form a complex with the sulfur-based material and the metal halide salt. The complex of the sulfur-based material, the metal halide salt, and the carbon-based material is distinguished from a simple mixture of the sulfur-based material, the metal halide salt, and the carbon-based material. A simple mixture of the sulfur-based material, the metal halide salt, and the carbon-based material may have high interfacial resistance because it fails to maintain a dense interface between the sulfur-based material, the metal halide salt, and the carbon-based material, which can degrade the lifespan characteristics of the battery.

[0085] The above carbon-based material (121d) is a material containing carbon atoms and is not particularly limited as long as it is used as a conductive material in the relevant technical field. In addition, the form of the above carbon-based material may be in the form of particles, sheets, flakes, etc., but is not limited thereto. For example, the carbon-based material may include crystalline carbon, amorphous carbon, or a combination thereof, and may include a calcined carbon precursor.

[0086] Additionally, the carbon-based material (121d) may be a carbon nanostructure and may include a one-dimensional carbon nanostructure, a two-dimensional carbon nanostructure, a three-dimensional carbon nanostructure, or a combination thereof. For example, the carbon nanostructure may include carbon nanotubes (CNT), carbon nanofibers (CNF), carbon nanobelts, carbon nanorods, graphene, or a combination thereof.

[0087] Additionally, the carbon-based material (121d) may be a porous carbon-based material or a non-porous carbon-based material and may include periodic and regular two-dimensional or three-dimensional pores. For example, the carbon-based material may include carbon black such as Ketjen black, acetylene black, Denka black, thermal black, channel black, graphite, activated carbon, or a combination thereof.

[0088] Additionally, the carbon-based material (121d) may include a fibrous carbon-based material. If the carbon-based material is a fibrous carbon-based material, electron and ion conduction can be performed more easily from the surface to the interior of the composite containing it, thereby further improving electron conductivity. As a result, the internal resistance of the positive active material containing the composite can be reduced, and the cycle characteristics of the battery containing it can be further improved.

[0089] The aspect ratio of the fibrous carbon-based material may be 2 or more, 3 or more, 4 or more, 5 or more, 10 or more, or 20 or more, and may be 2 to 30, 2 to 20, 2 to 10, 2 to 8, 2 to 5, 2 to 4, 3 to 30, 4 to 30, 5 to 30, 10 to 30, or 20 to 30. By satisfying the above ranges for the aspect ratio of the fibrous carbon-based material, the effect of enhancing the electronic conductivity of the composite containing it can be maximized, while also mitigating the imbalance of local electronic conductivity within the composite.

[0090] The diameter of the fibrous carbon-based material may be 0.01 μm to 10 μm, 0.05 μm to 10 μm, or 0.1 μm to 5 μm, and the length may be 1 μm to 50 μm or 1 μm to 20 μm. The diameter and length of the fibrous carbon-based material may be measured from scanning electron microscope (SEM) or transmission electron microscope (TEM) images, or may be measured by laser diffraction.

[0091] Additionally, the fibrous carbon-based material may include carbon nanostructures. For example, the carbon nanostructures may include carbon nanofibers (CNF), carbon nanotubes (CNT), carbon nanobelts, carbon nanorods, or a combination thereof. The carbon nanostructures may form a primary carbon nanostructure composed of a single carbon nanostructure and a secondary carbon nanostructure formed by the aggregation of multiple carbon nanostructures.

[0092] For example, the primary carbon nanostructure may have a diameter of 1 nm to 200 nm, 1 nm to 150 nm, 1 nm to 100 nm, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 20 nm, and a length of 10 nm to 2 µm, 10 nm to 1.5 µm, 10 nm to 1 µm, 10 nm to 500 nm, 10 nm to 400 nm, 10 nm to 300 nm, 10 nm to 200 nm, or 10 nm to 100 nm.

[0093] Additionally, the secondary carbon nanostructure may be a structure formed by assembling primary carbon nanostructures to form a bundle or rope type, either wholly or partially. For example, the secondary carbon nanostructure may include a bundle-type carbon nanostructure, a rope-type carbon nanostructure, or a combination thereof.

[0094] For example, the secondary carbon nanostructure may have a diameter of 2 nm to 200 nm, 3 nm to 150 nm, 5 nm to 100 nm, 5 nm to 50 nm, 5 nm to 30 nm, or 5 nm to 20 nm, and a length of 20 nm to 2 µm, 30 nm to 1.5 µm, 50 nm to 1 µm, 50 nm to 500 nm, 50 nm to 400 nm, 50 nm to 300 nm, 50 nm to 200 nm, or 50 nm to 100 nm.

[0095] The diameter and length of the above primary and secondary carbon nanostructures may be measured from scanning electron microscope (SEM) or transmission electron microscope (TEM) images, or may be measured by laser diffraction.

[0096] The content of the carbon-based material may be 1% to 30% by weight with respect to the total weight of the composite. For example, the content of the carbon-based material may be 1% to 20% by weight, 5% to 20% by weight, or 10% to 20% by weight with respect to the total weight of the composite. By satisfying the above range for the content of the carbon-based material, the cycle characteristics of the battery containing it can be further improved. Specifically, if the content of the carbon-based material is below the above range, the electronic conductivity of the composite containing it may be too low, which may increase the internal resistance of the positive active material, and if the content of the carbon-based material exceeds the above range, the energy density of the battery containing it may decrease.

[0097] In addition, the composite of the sulfur-based material, metal halide salt, and carbon-based material may possess ductility. Specifically, since the composite can function as a buffer material within the positive electrode active material layer, it can prevent defects caused by volume changes in the positive electrode active material layer.

[0098] The Mohs hardness of the composite of the sulfur-based material, metal halide salt, and carbon-based material may be less than 2. For example, the Mohs hardness of the composite may be smaller than the Mohs hardness of the lithium salt, and may be 1.5 or less or 0.7 or less.

[0099] The content of the composite of the sulfur-based material, metal halide salt, and carbon-based material may be 40% to 90% by weight with respect to the total weight of the positive electrode active material layer. For example, the content of the composite of the sulfur-based material, metal halide salt, and carbon-based material within the positive electrode active material layer may be 50% to 85% by weight, 60% to 80% by weight, or 65% to 75% by weight with respect to the total weight of the positive electrode active material layer. By satisfying the above ranges for the content of the composite of the sulfur-based material, metal halide salt, and carbon-based material, the capacity characteristics of the lithium-sulfur battery containing the same can be improved.

[0100] Sulfide-based solid electrolytes

[0101] A positive active material layer according to one embodiment of the present invention comprises a sulfide-based solid electrolyte. Specifically, the sulfide-based solid electrolyte can provide an ion transfer pathway within the positive active material layer. By including the aforementioned positive active material and the sulfide-based solid electrolyte, the positive active material layer according to one embodiment of the present invention can have a further reduced internal resistance, thereby further improving the cycle characteristics of a battery comprising the same.

[0102] The above sulfide-based solid electrolyte (122) may have a particle form and may be dispersed among the positive active materials (121) (see FIG. 4).

[0103] The above sulfide-based solid electrolyte may include a complex of Li2S and a solid electrolyte, and may be, for example, an inorganic solid electrolyte. Additionally, the above sulfide-based solid electrolyte (122) may include Li, S and / or P, and may optionally include a halogen element.

[0104] The above sulfide-based solid electrolyte may include an argyrodite-type compound.

[0105] For example, the above sulfide-based solid electrolyte 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 and n are positive, Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p and q are positive, respectively, M is one of P, Si, Ge, B, Al, Ga, or 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 It may include one or more selected from (0≤x≤2).

[0106] Alternatively, the above sulfide-based solid electrolyte is Li 7-a-c M a PS 6-c X c It may include an argyrodite-type compound represented by (0≤a≤2, 0≤c≤2). Specifically, the sulfide-based solid electrolyte is Li 7-a-c M a PS 6-c X c It may include an azirodite-type solid electrolyte represented by (0≤a≤2, 0≤c≤2).

[0107] The above X may be F, Br, Cl, I, or a combination thereof, and the above M is candium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), It may be antimony (Sb), bismuth (Bi), or a combination thereof.

[0108] As a specific example, the above sulfide-based solid electrolyte may include an argyrodite-type solid electrolyte and may include one or more selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0109] The density of the above-mentioned azyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. By satisfying the above range for the density of the azyrodite-type solid electrolyte, the internal resistance of the battery containing it can be reduced, and defects such as penetration or short-circuiting of the solid electrolyte film due to lithium dendrite formation can be prevented. In addition, the elastic modulus of the above-mentioned azyrodite-type solid electrolyte may be 15 GPa to 35 GPa or 15 GPa to 30 GPa.

[0110] In addition, the above sulfide-based solid electrolyte is 1 × 10⁻⁶ at room temperature -5 It can have an ionic conductivity of S / cm or greater. For example, the ionic conductivity of the sulfide-based solid electrolyte is 1.5 × 10⁻⁶ at room temperature. -5 S / cm or more, 2 × 10-5 S / cm or more, 4 × 10 -5 S / cm or more, 6 × 10 -5 S / cm or more, 8 × 10 -5 S / cm or more or 1 × 10 -4 It may be greater than S / cm.

[0111] According to another embodiment of the present invention, the positive active material layer (120) may further include a solid electrolyte in addition to the sulfide-based solid electrolyte (122). Specifically, the positive active material layer (120) may include, in addition to the aforementioned sulfide-based solid electrolyte (122), a sulfide-based solid electrolyte and / or an oxide-based solid electrolyte different therefrom.

[0112] For example, the above positive active material layer 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 one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are positive numbers, M is 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 It may include one or more sulfide-based solid electrolytes selected from , 0 ≤ x ≤ 2, and Li 1+x+y Al xThe 2-x Si y P.S 3-y O 12 (0 < x < 2, 0 ≤ y < 3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x The x Zr 1-y The y O3(PLZT)(0≤x<1, 0≤y<1), PB(Mg3Nb). 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, Nio, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x The y (PO4)3(0). <x<2, 0<y<3), Li x Al y The z (PO4)3(0). <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P.S 3-y O 12 (0≤x≤1 0≤y≤1), Li x The y TiO3(0). <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 (M=Te, Nb, Zr oxide, 0≤x≤10), Li7La3Zr2O 12 (LLZO) 및 Li 3+x La3Zr 2-a M a O 12 (M doped LLZO, M=Ga, W, Nb, Ta, oxide Al, 0 <a<2, 0≤x≤10) 중에서 선택된 가넷계(Garnet-type) 고체 전해질을 더 포함할 수 있으나, 이에 한정되는 것은 아니다.

[0113] In addition, the solid electrolyte in the positive active material layer (120) may be the same as or different from the solid electrolyte in the solid electrolyte layer (300).

[0114] The solid electrolyte in the positive active material layer (120) may have a smaller average particle size compared to the solid electrolyte in the solid electrolyte layer (300). For example, the average particle size of the solid electrolyte in the positive active material layer (120) may be 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less compared to the average particle size of the solid electrolyte in the solid electrolyte layer (300).

[0115] The content of the sulfide-based solid electrolyte may be 10% to 60% by weight with respect to the total weight of the positive electrode active material layer. For example, the content of the sulfide-based solid electrolyte in the positive electrode active material layer may be 15% to 50% by weight, 20% to 40% by weight, or 25% to 35% by weight with respect to the total weight of the positive electrode active material layer. By satisfying the above ranges for the content of the sulfide-based solid electrolyte, the capacity characteristics of the lithium-sulfur battery containing it can be improved.

[0116] bookbinder

[0117] A positive active material layer according to one embodiment of the present invention includes a binder.

[0118] FIG. 2 is a schematic diagram illustrating the ion conduction path of lithium ions in a positive active material layer. Specifically, FIG. 2 is an exemplary schematic diagram showing an enlarged view of a positive active material layer (120) including a positive active material (CAC) and a solid electrolyte (SEP), illustrating the ion conduction path (R1) of lithium ions.

[0119] Referring to FIG. 2, the solid electrolyte (SEP) can form an ion conduction path (R1) to move lithium ions. However, if there is insufficient solid electrolyte (SEP) within the positive active material layer (120) or if the solid electrolyte (SEP) is isolated by the positive active material (CAC), the movement of lithium ions may not proceed smoothly due to the blocked ion conduction path (R2). Additionally, if the ion conductivity of the positive active material (CAC) is low, ion contact between the positive active materials (CAC) may not proceed smoothly. As such, if the movement or contact of lithium ions does not proceed smoothly, there is a problem that the ion conductivity of the positive active material layer (120) may be reduced and the energy density may be lowered.

[0120] FIG. 3 is a schematic diagram illustrating the ion conduction path of lithium ions in a positive active material layer of a lithium-sulfur battery according to one embodiment of the present invention. Specifically, FIG. 3 is an exemplary schematic diagram showing an enlarged view of a positive active material layer comprising a positive active material (CAC), a solid electrolyte (SEP), and a binder (BID) according to one embodiment of the present invention, and illustrates the ion conduction path (R1) of lithium ions. Referring to FIG. 3, the positive active material layer (120) includes a binder (BID) having excellent ion conductivity and electron conductivity, thereby facilitating lithium ion contact between positive active materials (CAC) or the movement of lithium ions through the solid electrolyte (SEP) and the positive active material (CAC), thus improving the performance of the battery containing it.

[0121] More specifically, the binder comprises a first binder comprising a rubber-based polymer and a second binder comprising a vinyl polymer comprising carbonyl groups, thereby improving ionic conductivity and electronic conductivity while simultaneously reducing interfacial resistance, and effectively suppressing the leaching of lithium polysulfide to improve the capacity characteristics and cycle characteristics of the battery.

[0122] The above rubber-based polymer may include butadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), carboxylated nitrile-butadiene rubber (XNBR), silicone rubber (SR), or a combination thereof. NBR and XNBR may be preferred in that they exhibit uniformly excellent polarity, wettability, elasticity, electrochemical stability, and organic solvent resistance properties, but are not limited thereto.

[0123] The above rubber-based binder may have a weight-average molecular weight (Mw) of 20,000 g / mol to 250,000 g / mol. For example, the weight-average molecular weight of the above rubber-based binder may be 30,000 g / mol to 200,000 g / mol, 50,000 g / mol to 250,000 g / mol, or 100,000 g / mol to 200,000 g / mol.

[0124] The above rubber-based binder may have an elastic modulus of 1 MPa to 25 MPa. For example, the elastic modulus of the above rubber-based binder may be 1.5 MPa to 25 MPa, 2 MPa to 23 MPa, or 5 MPa to 20 MPa.

[0125] The above rubber-based binder may have an elongation of 300% to 1,000%. For example, the elongation of the above rubber-based binder may be 350% to 900%, 400% to 850%, or 500% to 700%.

[0126] The content of the first binder may be 0.1% to 10% by weight with respect to the total weight of the positive active material layer. For example, the content of the first binder may be 0.5% to 10% by weight, 1% to 10% by weight, or 1.5% to 5% by weight with respect to the total weight of the positive active material layer.

[0127] By satisfying the above range for the characteristics and / or content of the first binder, the affinity with lithium polysulfide can be maximized, thereby effectively suppressing the leaching of lithium polysulfide and improving the capacity characteristics and cycle characteristics of the battery.

[0128] In addition, the vinyl polymer comprises carbonyl groups, and the vinyl polymer comprising carbonyl groups may include polyvinylpyrrolidone, polyvinyl acetate, polyacrylate, polyacrylamide, or a combination thereof.

[0129] In addition, the vinyl polymer containing the carbonyl group may have a weight-average molecular weight (Mw) of 100,000 g / mol to 2,500,000 g / mol. For example, the weight-average molecular weight of the vinyl polymer may be 150,000 g / mol to 2,000,000 g / mol, 300,000 g / mol to 2,000,000 g / mol, or 500,000 g / mol to 1,500,000 g / mol.

[0130] The content of the second binder may be 0.1% to 10% by weight with respect to the total weight of the positive active material layer. For example, the content of the second binder may be 0.5% to 10% by weight, 1% to 10% by weight, or 2% to 5% by weight with respect to the total weight of the positive active material layer.

[0131] By satisfying the above range for the characteristics and / or content of the second binder, the affinity with the composite of the sulfur-based material, metal halide salt, and carbon-based material and the lithium polysulfide can be maximized, thereby improving ionic conductivity and electronic conductivity, while effectively suppressing the leaching of lithium polysulfide to improve the capacity characteristics and cycle characteristics of the battery.

[0132] The weight ratio of the first binder and the second binder may be 10:90 to 90:10. For example, the weight ratio of the first binder and the second binder may be 10:90 to 80:20, 15:85 to 60:40, or 20:80 to 50:50. By satisfying the above ranges for the weight ratio of the first binder and the second binder, the effect of improving ion conductivity and electronic conductivity and the effect of preventing the leaching of lithium polysulfide can be maximized.

[0133] A binder according to one embodiment of the present invention can maximize affinity with a composite of sulfur-based materials, metal halide salts, and carbon-based materials by including a first binder and a second binder having the above characteristics. That is, a binder according to one embodiment of the present invention, comprising a first and a second binder having the above characteristics, has the most suitable characteristics for the composite.

[0134] As a specific example, the first binder may include carboxylated nitrile-butadiene rubber (XNBR) and the second binder may include polyvinylpyrrolidone. In terms of maximizing affinity with lithium polysulfide and the effect of preventing the leaching of lithium polysulfide, it may be most preferable for the first binder to include carboxylated nitrile-butadiene and the second binder to include polyvinylpyrrolidone, but it is not limited thereto.

[0135] In the case where the binder according to one embodiment of the present invention includes a rubber-based binder that does not have the above characteristics as the first binder, the mechanical properties may be reduced and the affinity with the composite may be lowered, so the ion conductivity and electronic conductivity, as well as the effect of preventing the leaching of lithium polysulfide, may also be reduced.

[0136] In addition, if the binder according to one embodiment of the present invention includes a vinyl polymer that does not have the above characteristics as a second binder, the dispersibility may be reduced and the affinity with the composite may be lowered, so the ion conductivity and electronic conductivity, as well as the effect of preventing the leaching of lithium polysulfide, may also be reduced.

[0137] Accordingly, the positive electrode active material layer according to one embodiment of the present invention comprises a composite of a sulfur-based material, a metal halide salt, and a carbon-based material, and a binder having such characteristics that has excellent compatibility therewith, thereby improving ion conductivity and electronic conductivity while simultaneously reducing interfacial resistance, and effectively suppressing the leaching of lithium polysulfide to improve the capacity characteristics and cycle characteristics of the battery.

[0138] The total content of the binder may be 0.5% to 15% by weight with respect to the total weight of the positive active material layer. For example, the total content of the binder including the first and second binders may be 1% to 15% by weight, 2% to 13% by weight, or 3.5% to 10% by weight.

[0139] The weight ratio of the positive active material and the binder may be 99:1 to 80:20. For example, the weight ratio of the positive active material and the binder may be 98:2 to 80:20, 95:5 to 80:20, or 95:5 to 85:15.

[0140] According to another embodiment of the present invention, the positive active material layer (120) may further include a conductive material, etc.

[0141] The conductive material described above is conductive without causing chemical changes and can improve the electrical conductivity of the anode active material and the sulfide-based solid electrolyte. The conductive material may include a carbon-based material. For example, the conductive material may include one or more selected from graphite, carbon black, acetylene black, carbon nanofibers, and carbon nanotubes.

[0142] The content of the conductive material may be 0.5% to 5% by weight, 0.5% to 4% by weight, 0.5% to 3.5% by weight, or 0.5% to 2% by weight based on the total weight of the positive electrode active material layer.

[0143] According to another embodiment of the present invention, the positive active material layer may further include additives such as a filler, a coating agent, a dispersant, and an ion conductivity aid. Known materials generally used in electrodes of all-solid-state batteries may be used as the filler, coating agent, dispersant, ion conductivity aid, etc., and are not particularly limited.

[0144] For example, the filler may include organic fillers and / or inorganic fillers, and the filler may have an elastic modulus of 1 MPa to 2,000 MPa, 1 MPa to 500 MPa, or 5 MPa to 100 MPa, and an average particle size of 0.01 μm to 10 μm, 0.05 μm to 5 μm, or 0.1 μm to 5 μm. The elastic modulus of the filler may be measured using a tensile testing machine on a sample obtained by molding the organic filler at 150°C to 200°C for 10 minutes using a vacuum pressure press. The average particle size of the filler may be measured using a laser scattering particle size distribution analyzer.

[0145]

[0146] Method for manufacturing a positive electrode for a lithium-sulfur battery

[0147] A method for manufacturing a positive electrode for a lithium-sulfur battery according to another embodiment of the present invention comprises the steps of: manufacturing a positive electrode active material comprising a composite of a sulfur-based material, a metal halide salt, and a carbon-based material; mixing the positive electrode active material with a sulfide-based solid electrolyte and a binder to manufacture a positive electrode slurry; and applying the positive electrode slurry to one surface of a positive electrode current collector, wherein the binder comprises a first binder comprising a rubber-based polymer and a second binder comprising a vinyl polymer comprising carbonyl groups.

[0148] A method for manufacturing a positive electrode for a lithium-sulfur battery according to another embodiment of the present invention includes the step of manufacturing a positive electrode active material. The positive electrode active material comprises a complex of a sulfur-based material, a metal halide salt, and a carbon-based material.

[0149] The step of manufacturing the above-mentioned positive active material may be a dry method, a wet method, or a combination thereof. For example, the method of manufacturing the above-mentioned positive active material may be performed by milling, heat treatment, deposition, etc., but is not limited thereto.

[0150] The step of manufacturing the above-mentioned positive electrode active material may include a step of first milling a mixture of a sulfur-based material and a metal halide salt; and a step of secondarily milling a mixture of the first-milling product and a carbon-based material.

[0151] The description of the sulfur-based material, the metal halide salt, and the carbon-based material is as described above. The metal halide salt includes a first metal halide salt containing an alkali metal and a second metal halide salt containing a boron group metal.

[0152] The sulfur-based material, the first metal halide salt, and the second metal halide salt can be mixed in a weight ratio of 40:1 to 15:10 to 30. For example, the mixing weight ratio of the sulfur-based material, the first metal halide salt, and the second metal halide salt may be 40:2 to 10:15 to 30 or 40:5 to 10:15 to 20.

[0153] The above primary milling may refer to a grinding process as mechanical milling. For example, the above primary milling may be performed by a ball mill or a bead mill. Additionally, the above primary milling may be performed at 25°C and may be performed for 1 hour to 15 hours, 2 hours to 12 hours, or 5 hours to 10 hours at 100 rpm to 1,500 rpm, 150 rpm to 1,000 rpm, or 250 rpm to 800 rpm. At this time, the energy of the primary milling may be 10 G to 60 G, 10 G to 45 G, or 15 G to 40 G.

[0154] Subsequently, the primary milling product, that is, the complex of a sulfur-based material, a first metal halide salt, and a second metal halide salt obtained by the primary milling, can be mixed with the carbon-based material in a weight ratio of 3:1 to 15:1. For example, the mixing weight ratio of the primary milling product and the carbon-based material may be 3:1 to 12:1, 5:1 to 10:1, or 5:1 to 8:1.

[0155] The above secondary milling may refer to a grinding process as mechanical milling. For example, the above secondary milling may be performed by a ball mill or a bead mill. Additionally, the above secondary milling may be performed at 25°C and may be performed for 1 hour to 15 hours, 2 hours to 12 hours, or 5 hours to 10 hours at 100 rpm to 1,500 rpm, 150 rpm to 1,000 rpm, or 250 rpm to 800 rpm. At this time, the energy of the secondary milling may be 10 G to 60 G, 10 G to 45 G, or 15 G to 40 G. Furthermore, the process conditions of the above primary milling and the above secondary milling may be the same or different.

[0156] The description of the above sulfide-based solid electrolyte and the above binder is as previously described.

[0157] Subsequently, the anode active material can be mixed with a sulfide-based solid electrolyte and a binder to prepare an anode slurry, and then the anode slurry can be applied to at least one surface of an anode current collector, dried, and then pressed to form an anode active material layer.

[0158] The above drying can be performed at 85°C to 130°C or 90°C to 115°C.

[0159] The description of the above positive current collector is as previously stated.

[0160]

[0161] lithium-sulfur battery

[0162] A lithium-sulfur battery according to another embodiment of the present invention comprises a positive electrode for the lithium-sulfur battery, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode.

[0163] The description of the positive electrode for the lithium-sulfur battery above is as previously stated.

[0164] FIG. 6 is a cross-sectional view of a lithium-sulfur battery according to another embodiment of the present invention. Referring to FIG. 5, a lithium-sulfur battery (1) according to one embodiment of the present invention may include a positive electrode (100), a negative electrode (200), and a solid electrolyte layer (300) disposed between the positive electrode (100) and the negative electrode (200). More specifically, a lithium-sulfur battery (1) according to one embodiment of the present invention may have a structure in which a negative electrode current collector (210), a coating layer (220), a solid electrolyte layer (300), a positive electrode active material layer (120), and a positive electrode current collector (110) are stacked in order.

[0165] cathode

[0166] The above cathode (200) may include a cathode current collector (210) and a coating layer (220). The cathode current collector (210) may provide a reference surface on which the coating layer (220) is placed.

[0167] The above-mentioned negative electrode current collector may include a material that does not react with lithium, that is, does not form any alloys or compounds with lithium. For example, the above-mentioned negative electrode current collector may include at least one metal selected from the group consisting of copper (Cu), stainless steel (SUS), titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). The above-mentioned negative electrode current collector may be composed of one of the metals described above, or may include an alloy or coating material of two or more metals.

[0168] In addition, the above-mentioned cathode current collector may be in the form of a plate or a foil, and the thickness of the above-mentioned cathode current collector may be 1 μm to 20 μm, 5 μm to 15 μm, or 7 μm to 10 μm.

[0169] According to another embodiment of the present invention, the lithium-sulfur battery (1) may not include a negative electrode current collector (210). That is, the negative electrode current collector (210) may be omitted.

[0170] The coating layer (220) can be configured to allow lithium metal to grow between the solid electrolyte layer (300) and the negative current collector (210). The coating layer (220) can serve as a protective layer for the lithium metal and simultaneously suppress the precipitation and growth of lithium dendrites.

[0171] The coating layer may comprise a metal-carbon composite. More specifically, the coating layer may comprise a composite of metal particles and a carbon-based material.

[0172] The metal-carbon composite may have a particle form, and the average particle size of the metal-carbon composite may be 4 μm or less, 3 μm or less, 2 μm or less, 1 μm or less, or 900 nm or less, or 10 nm to 4 μm, 10 nm to 3 μm, 10 nm to 2 μm, 10 nm to 1 μm, or 10 nm to 900 nm. By satisfying the above ranges for the average particle size of the metal-carbon composite, reversible absorption and / or desorption of lithium during charging and discharging may be more facilitated.

[0173] The average particle size of the above metal-carbon composite is the median diameter measured using a laser particle size distribution meter.

[0174] The metal particles in the metal-carbon composite may comprise at least one metal or metalloid selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Additionally, the carbon-based material in the metal-carbon composite may comprise at least one selected from the group consisting of carbon black, acetylene black, furnace black, Kettjen black, and graphene. As a specific example, the carbon-based material in the metal-carbon composite may be amorphous carbon. The amorphous carbon may be carbon that does not have crystallinity or has very low crystallinity.

[0175] The weight ratio of the metal particles and the carbon-based material in the coating layer may be 10:1 to 1:2. For example, the mixing ratio of the metal particles and the carbon-based material may be 5:1 to 1:1 or 4:1 to 2:1.

[0176] In addition, the content of the metal particles may be 8% to 60% by weight, 10% to 50% by weight, 15% to 40% by weight, or 20% to 30% by weight with respect to the total weight of the metal-carbon composite. By satisfying the above ranges for the content of the metal particles, the cycle characteristics of the battery can be further improved.

[0177] According to another embodiment of the present invention, the coating layer (220) may further include other additives in addition to the metal-carbon composite. For example, the coating layer (220) may further include at least one additive selected from the group consisting of binders, fillers, coating agents, dispersants, and ion-conducting aids.

[0178] Additionally, the thickness of the coating layer (220) may be smaller than the thickness of the positive active material layer (120). For example, the thickness of the coating layer (220) may be 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less relative to the thickness of the positive active material layer (120), and may be 1 μm to 20 μm, 2 μm to 10 μm, or 3 μm to 7 μm. By satisfying the above ranges for the thickness of the coating layer, the cycle characteristics of the battery can be further improved. If the thickness of the coating layer exceeds the above ranges, the energy density of the battery containing it may decrease, and the internal resistance may increase, thereby degrading the cycle characteristics.

[0179] According to another embodiment of the present invention, the cathode may further include a carbon layer between the cathode current collector and the solid electrolyte layer. The description of the carbon layer is as described above.

[0180] According to another embodiment of the present invention, the cathode (200) may include a cathode active material layer corresponding to the coating layer (220).

[0181] The negative electrode active material in the above negative electrode active material layer may include a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0182] A material capable of reversibly intercalating / deintercalating the above lithium ions may be a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0183] As the above lithium metal alloy, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn may be used.

[0184] As a material capable of doping and undoping the above lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material may be used. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiOx (0 < x < 2), a Si-Q alloy (wherein Q is selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof), or a combination thereof. The Sn-based negative electrode active material may be Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0185] The silicon-carbon composite may be a composite of silicon and amorphous carbon. As a specific example, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, it may include a secondary particle (core) assembled from silicon primary particles and an amorphous carbon coating layer (shell) located on the surface of the secondary particle. The amorphous carbon may also be located between the silicon primary particles, for example, the silicon primary particles may be coated with the amorphous carbon. Additionally, the secondary particles may be dispersed within an amorphous carbon matrix.

[0186] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer located on the surface of the core.

[0187] The above Si-based or Sn-based negative electrode active material can be used in combination with a carbon-based negative electrode active material.

[0188] In addition, the content of the cathode active material in the cathode active material layer may be 90% to 99% by weight with respect to the total weight of the cathode active material layer. For example, the content of the cathode active material may be 93% to 99% by weight or 96% to 98.5% by weight with respect to the total weight of the cathode active material layer.

[0189] As a specific example, the above-mentioned negative electrode active material may include at least one of graphite and Si composites.

[0190] When the above-mentioned cathode active material includes a Si composite and graphite together, the Si composite and graphite may be included in the form of a mixture, in which case the weight ratio of the Si composite and graphite may be 1:99 to 50:50. For example, the weight ratio of the Si composite and graphite may be 3:97 to 20:80 or 5:95 to 20:80.

[0191] The above Si composite may include a core containing Si-based particles and an amorphous carbon coating layer, for example, the Si-based particles may be a Si-C composite, SiO x It may include one or more of (0 < x ≤ 2) and Si alloys. For example, the Si-C composite may include a core containing Si particles and crystalline carbon and an amorphous carbon coating layer located on the surface of the core.

[0192] The above crystalline carbon may include, for example, graphite, and more specifically, may include natural graphite, artificial graphite, or a mixture thereof.

[0193] The above-mentioned cathode may include a binder. The cathode binder can effectively bond the cathode active material particles to each other and can serve to effectively bond the cathode active material to the current collector. As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof may be used.

[0194] The above-mentioned non-aqueous binder may be polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide imide, polyimide, or a combination thereof.

[0195] The above-mentioned water-based binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0196] When a water-based binder is used as the above-mentioned cathode binder, a cellulose-based compound capable of imparting viscosity may be further included. As the cellulose-based compound, one or more types such as carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof may be mixed and used. The alkali metal salt may include Na, K, or Li.

[0197] The above dry binder is a polymer material capable of fiberization, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0198] In addition, the content of the binder may be 0.5% to 5% by weight with respect to the total weight of the cathode. For example, the content of the cathode binder may be 0.5% to 3.5% by weight or 0.5% to 2% by weight based on the total weight of the cathode.

[0199] The above-mentioned cathode may include a conductive material. The description of the conductive material is as previously stated.

[0200] solid electrolyte layer

[0201] The above solid electrolyte layer (300) may include a solid electrolyte.

[0202] The above solid electrolyte may include a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof. As a specific example, the solid electrolyte included in the solid electrolyte layer (300) may be the same as or different from the solid electrolyte included in the positive active material layer (110).

[0203] The description of the above solid electrolyte is as previously stated.

[0204] FIG. 7 is a cross-sectional view of a lithium-sulfur battery according to another embodiment of the present invention. Referring to FIG. 7, a lithium-sulfur battery (1) according to one embodiment of the present invention may include a positive electrode (100), a negative electrode current collector (210), a negative electrode (200), and a solid electrolyte layer (300) disposed between the positive electrode (100) and the negative electrode (200). More specifically, a lithium-sulfur battery (1) according to one embodiment of the present invention may have a structure in which a negative electrode current collector (210), a lithium metal layer (230), a coating layer (220), a solid electrolyte layer (300), a positive electrode active material layer (120), and a positive electrode current collector (110) are stacked in order.

[0205] The lithium metal layer (230) may include lithium or a lithium alloy. The lithium metal layer is a metal layer containing lithium and can function as a lithium reservoir. For example, the lithium alloy may be a Li-Al alloy, Li-Sn alloy, Li-In alloy, Li-Ag alloy, Li-Au alloy, Li-Zn alloy, Li-Ge alloy, Li-Si alloy, etc., but is not limited thereto. The lithium alloy may be composed of one of the metals described above or may include an alloy of two or more metals.

[0206] Additionally, the lithium metal layer (230) may be a plated layer formed by precipitation between the coating layer (220) and the negative current collector (210) during the charging process.

[0207] For example, the thickness of the lithium metal layer may be 1 μm to 500 μm, 1 μm to 200 μm, 1 μm to 150 μm, 1 μm to 100 μm, or 1 μm to 50 μm. By satisfying the above range for the thickness of the lithium metal layer, the cycle characteristics can be improved without degrading the performance of the battery containing it. If the thickness of the lithium metal layer is less than the above range, it cannot sufficiently perform the role of a lithium reservoir, and if it exceeds the above range, the mass and volume of the battery may increase, leading to a decrease in performance and a decrease in cycle characteristics.

[0208] According to another embodiment of the present invention, the lithium metal layer (230) may be provided between the negative electrode current collector (210) and the coating layer (220) before assembly of the battery. As a specific example, the lithium metal layer (230) may be placed as a lithium foil between the negative electrode current collector (210) and the coating layer (220) before assembly of the battery.

[0209] According to another embodiment of the present invention, the lithium metal layer (230) may be formed by precipitation through charging after the assembly of the battery. In this case, since the lithium metal layer is not included during the assembly of the battery, the energy density of the battery may be increased, and charging may be performed beyond the charging capacity of the coating layer (220). That is, the coating layer (220) may be overcharged. Specifically, lithium may be absorbed in the coating layer (220) at the beginning of charging, but when charged beyond the capacity of the coating layer (220), lithium may be precipitated between the coating layer (220) and the negative electrode current collector (210) to form the lithium metal layer (230).

[0210] Since the above lithium metal layer (230) can be composed mainly of lithium, the lithium in the lithium metal layer can be ionized and move to the positive electrode during discharge. That is, the lithium in the lithium metal layer can be used as a negative electrode active material.

[0211] In addition, since the coating layer (220) can be disposed on the lithium metal layer (230), the coating layer (220) can cover and protect the lithium metal layer (230) and suppress the precipitation growth of lithium dendrites. Therefore, short circuits and capacity degradation of the battery can be suppressed, and the cycle characteristics of the battery can be improved.

[0212] When a lithium metal layer (230) is formed by charging after assembly of the battery, the negative electrode current collector (210), the coating layer (220), and the region between them may be a Li-free region that does not contain lithium (Li) in the initial state or after complete discharge of the battery.

[0213] Examples and comparative examples of the present invention are described below. However, the following examples are merely one example of the present invention, and the present invention is not limited to the following examples.

[0214]

[0215] [Example]

[0216] Manufacturing of lithium-sulfur all-solid-state batteries

[0217] Example 1

[0218] (1) Preparation of positive electrode active material

[0219] Li2S, LiI, and AlI3 were mixed in a weight ratio of 40:5:15. The mixture was mechanically milled using a ball mill to produce a Li2S-LiI-AlI3 composite. At this time, the first milling was performed at 25°C and 450 rpm for 10 hours, and the milling energy applied to the sample during the first milling was 20 G.

[0220] Subsequently, the prepared Li2S-LiI-AlI3 composite and carbon nanofiber (CNF) were mixed in a weight ratio of 6:1. The mixture was mechanically milled a second time using a ball mill to prepare the Li2S-LiI-AlI3-CNF composite. At this time, the second milling was performed at 25°C and 450 rpm for 10 hours, and the milling energy applied to the sample during the second milling was 20 G.

[0221] (2) Manufacture of binder

[0222] Carboxylated nitrile-butadiene rubber (XNBR) as the first binder and polyvinylpyrrolidone (PVP) as the second binder were mixed in a weight ratio of 30:70.

[0223] (3) Preparation of the anode

[0224] Li6PS5Cl (D50 = 1.0 μm, crystalline), which is an argyrodite-type crystal, was prepared as a sulfide-based solid electrolyte. An anode slurry was prepared by mixing the anode active material prepared in step (1), the binder prepared in step (2), and the sulfide-based solid electrolyte in a weight ratio of 70:5:25. The anode slurry was coated onto an Al foil with a thickness of 15 μm, dried at 100°C, and then pressed to produce an anode.

[0225] (4) Preparation of the cathode

[0226] A stainless steel (SUS) foil with a thickness of 10 μm was prepared as a cathode current collector. As a metal-carbon composite, carbon black (CB) with a primary particle size of about 30 nm and silver (Ag) particles with an average particle diameter of about 60 nm were prepared.

[0227] 4 g of a mixed powder, prepared by mixing the carbon black (CB) and silver (Ag) particles in a weight ratio of 3:1, was placed in a container, and 4 g of a methylpyrrolidone (NMP) solution containing 7 wt% of a polyvinylidene fluoride (PVDF) binder (Kureha # 9300) was added to prepare a mixed solution. A cathode slurry was prepared by stirring while adding NMP little by little to the prepared mixed solution. The prepared cathode slurry was applied to the SUS foil using a bar coater, dried at 80°C in air for 10 minutes, and then vacuum dried at 40°C for 10 hours to produce a laminate. The surface of the prepared laminate was flattened by cold roll pressing to produce a cathode having a coating layer / cathode current collector structure. At this time, the thickness of the coating layer was approximately 15 μm, and the area of ​​the cathode coating layer and the cathode current collector were the same.

[0228] (5) Preparation of a solid electrolyte layer

[0229] 98.5 parts by weight of Li6PS5Cl solid electrolyte, which is an argyrodite-type crystal, and 1.5 parts by weight of an acrylic binder were mixed. Octyl acetate was added to the mixture while stirring to prepare a solid electrolyte slurry. The prepared solid electrolyte slurry was applied using a bar coater onto a 15 μm thick nonwoven fabric placed on a 75 μm thick PET substrate, dried at 80°C in air for 10 minutes, and then vacuum dried at 40°C for 2 hours to prepare a solid electrolyte layer.

[0230] (6) Manufacturing of lithium-sulfur all-solid-state batteries

[0231] A laminate was prepared by placing a solid electrolyte layer prepared in step (5) on the coating layer of the cathode prepared in step (4), and placing a positive electrode such that the positive active material layer of the positive electrode prepared in step (3) contacts the solid electrolyte layer (see FIG. 5). The laminate was subjected to plate press treatment at 85°C for 30 minutes at a pressure of 500 MPa. By this press treatment, the solid electrolyte layer is sintered, which can improve battery characteristics, and the thickness of the sintered solid electrolyte layer was approximately 45 μm. In addition, the density of the Li6PS5Cl solid electrolyte, which is an argyrodite-type crystal contained in the sintered solid electrolyte layer, was 1.6 g / cc, and the area of ​​the solid electrolyte layer was the same as the area of ​​the cathode.

[0232] Subsequently, a lithium-sulfur all-solid-state battery was manufactured by placing the pressurized laminate into a pouch and vacuum sealing it. Parts of the positive and negative current collectors were extended outside the sealed battery to serve as the positive and negative terminals.

[0233]

[0234] Example 2

[0235] A lithium-sulfur all-solid-state battery was manufactured in the same manner as Example 1, except that in step (2) above, the first binder and the second binder were mixed in a weight ratio of 10:90.

[0236]

[0237] Example 3

[0238] A lithium-sulfur all-solid-state battery was manufactured in the same manner as in Example 1, except that nitrile-butadiene rubber (NBR) was used instead of XNBR as the first binder in step (2) above.

[0239]

[0240] Example 4

[0241] A lithium-sulfur all-solid-state battery was manufactured in the same manner as in Example 1, except that polyvinyl acetate (PVA) was used instead of PVP as the second binder in step (2) above.

[0242]

[0243] Comparative Example 1

[0244] A lithium-sulfur all-solid-state battery was manufactured in the same manner as in Example 1, except that polyacrylonitrile (PAN) was used instead of the binder manufactured in step (2) above.

[0245]

[0246] Comparative Example 2

[0247] A lithium-sulfur all-solid-state battery was manufactured in the same manner as Example 1, except that the first binder was not used in step (2) above.

[0248]

[0249] Comparative Example 3

[0250] A lithium-sulfur all-solid-state battery was manufactured in the same manner as Example 1, except that the second binder was not used in step (2) above.

[0251]

[0252] Comparative Example 4

[0253] A lithium-sulfur all-solid-state battery was manufactured in the same manner as in Example 1, except that polyvinylidene fluoride (PVDF), a vinyl polymer that does not contain carbonyl groups, was used instead of the second binder in step (2) above.

[0254]

[0255] [Evaluation Example]

[0256] Evaluation Example 1: Electronic Conductivity and Ionic Conductivity

[0257] For the lithium-sulfur all-solid-state batteries prepared in Examples 1 to 4 and Comparative Examples 1 to 4 above, the electronic conductivity and ionic conductivity were measured using electrochemial impedance spectroscopy (EIS). At this time, the measurement conditions of EIS were an amplitude of 10 mV and a frequency of 10 mHz to 1 MHz.

[0258]

[0259] Classification Electron Conductivity (S / cm) Ionic Conductivity (S / cm) Example 11.69 × 10 -3 3.01 × 10 -5 Example 21.56 × 10 -3 2.87 × 10 -5 Example 31.59 × 10 -3 2.79 × 10 -5 Example 4 1.55 × 10 -3 2.48 × 10 -5 Comparative Example 11.07 × 10 -3 1.66 × 10 -5 Comparative Example 21.54 × 10 -3 2.45 × 10 -5 Comparative Example 31.50 × 10 -3 2.38 × 10 -5 Comparative Example 41.28 × 10 -3 1.78 × 10 -5

[0260]

[0261] Referring to Table 1 above, the lithium-sulfur all-solid-state batteries of Examples 1 to 4 had superior electronic conductivity and ion conductivity compared to the lithium-sulfur all-solid-state batteries of Comparative Examples 1 to 4.

[0262]

[0263] Evaluation Example 2: Charge / Discharge Test

[0264] The charge and discharge characteristics of the lithium-sulfur all-solid-state batteries prepared in Examples 1 to 4 and Comparative Examples 1 to 4 were evaluated as follows.

[0265] The all-solid-state battery was placed in a constant temperature bath at 45°C and charged and discharged in CC mode. The battery voltage was charged to 2.8 V at 0.05C and discharged to 1.0 V at 0.05C. The charge and discharge capacities of the first cycle were measured while performing one charge and discharge cycle under the above conditions. At this time, the discharge capacity of the first cycle was listed as the standard capacity in Table 2 below.

[0266] In addition, the discharge capacity of the second cycle was measured by performing the charge and discharge once more under the same conditions as above, and the discharge capacity of the third cycle was measured by performing the charge and discharge once more in CC mode at 0.1C. The capacity retention rate (%) at N=2 was calculated according to Equation A below and is listed in Table 2 below. At this time, the capacity retention rate could not be calculated for Comparative Examples 1 and 4 because the third cycle could not be performed.

[0267] [Essence A]

[0268] Capacity Retention Rate (%) = (Discharge Capacity of the N+1th Cycle / Discharge Capacity of the Nth Cycle) × 100 (%)

[0269]

[0270] Classification Standard Capacity (mAh / g) Capacity Retention Rate (%) Example 1 70 261 Example 2 67 955 Example 3 68 858 Example 4 66 549 Comparative Example 1 38 4- Comparative Example 2 66 134 Comparative Example 3 40 77 Comparative Example 4 39 2-

[0271]

[0272] Referring to Table 2 above, it can be confirmed that the lithium-sulfur all-solid-state batteries of Examples 1 to 4 have excellent cycle characteristics, as both the standard capacity and the capacity retention rate are superior compared to Comparative Examples 1 to 4.

[0273] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention.

Claims

positive current collector; and It includes a positive active material layer located on the positive current collector, and The above positive active material layer comprises a positive active material, a sulfide-based solid electrolyte, and a binder, and The above-mentioned positive active material comprises a composite of a sulfur-based material, a metal halide salt, and a carbon-based material, and The above sulfur-based materials are S8 and Li2S n Includes at least one of (1 ≤ n ≤ 8, n is an integer), and The above metal halide salt comprises a first metal halide salt comprising an alkali metal and a second metal halide salt comprising a boron group metal, and A positive electrode for a lithium-sulfur battery, wherein the binder comprises a first binder comprising a rubber-based polymer and a second binder comprising a vinyl polymer comprising a carbonyl group. In Article 1, The above rubber-based polymer comprises butadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), carboxylated nitrile-butadiene rubber (XNBR), silicon rubber (SR), or a combination thereof, for a positive electrode for a lithium-sulfur battery. In Article 1, A positive electrode for a lithium-sulfur battery, wherein the content of the first binder is 0.1% to 10% by weight with respect to the total weight of the positive electrode active material layer. In Article 1, The vinyl polymer containing the carbonyl group above comprises polyvinylpyrrolidone, polyvinyl acetate, polyacrylate, polyacrylamide, or a combination thereof, a positive electrode for a lithium-sulfur battery. In Article 1, A positive electrode for a lithium-sulfur battery, wherein the content of the second binder is 0.1% to 10% by weight with respect to the total weight of the positive electrode active material layer. In Article 1, A positive electrode for a lithium-sulfur battery, wherein the first binder comprises carboxylated nitrile-butadiene rubber (XNBR) and the second binder comprises polyvinylpyrrolidone. In Article 1, A positive electrode for a lithium-sulfur battery, wherein the weight ratio of the first binder and the second binder is 10:90 to 90:

10. In Article 1, A positive electrode for a lithium-sulfur battery, wherein the total content of the binder is 0.5% to 15% by weight with respect to the total weight of the positive electrode active material layer. In Article 1, A positive electrode for a lithium-sulfur battery, wherein the weight ratio of the positive electrode active material and the binder is 99:1 to 80:

20. In Article 1, The first metal halide salt comprises LiF, LiCl, LiBr, LiI, or a combination thereof, and The above second metal halide salt comprises AlF3, AlCl3, AlBr3, AlI3, GaF3, GaCl3, GaBr3, GaI3, InF3, InCl3, lnBr3, lnI3, TiF3, TiCl3, TiBr3, TiI3, or a combination thereof, for a cathode for a lithium-sulfur battery. In Article 1, The above carbon-based material comprises a carbon nanofiber (CNF), a carbon nanotube (CNT), a carbon nanobelt, a carbon nanorod, or a combination thereof, for a cathode for a lithium-sulfur battery. In Article 1, The above composite of the sulfur-based material, metal halide salt, and carbon-based material comprises 20% to 80% by weight of the sulfur-based material, 10% to 60% by weight of the metal halide salt, and 1% to 30% by weight of the carbon-based material, for a positive electrode for a lithium-sulfur battery. In Article 1, A cathode for a lithium-sulfur battery, wherein the content of the first metal halide salt is 2.5% to 15% by weight based on the total weight of the composite, and the content of the second metal halide salt is 7.5% to 45% by weight based on the total weight of the composite. In Article 1, A positive electrode for a lithium-sulfur battery, wherein the weight ratio of the first metal halide salt to the second metal halide salt is 1:1 to 1:

20. In Article 1, The above sulfide-based solid electrolytes are 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, and Li2S-P2S5-Z m S n (m and n are positive, Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p and q are positive, respectively, M is one of P, Si, Ge, B, Al, Ga, or 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 A positive electrode for a lithium-sulfur battery comprising one or more selected from (0≤x≤2). In Article 1, The above sulfide-based solid electrolyte includes an argyrodite-type solid electrolyte, and A positive electrode for a lithium-sulfur battery, wherein the above-mentioned argyrodite-type solid electrolyte comprises one or more selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I. In Article 1, A cathode for a lithium-sulfur battery, wherein the content of the sulfur-based material is 10% to 80% by weight based on the total weight of the cathode active material. A step of manufacturing an anode active material comprising a complex of a sulfur-based material, a metal halide salt, and a carbon-based material; A step of preparing an anode slurry by mixing the above anode active material with a sulfide-based solid electrolyte and a binder; and The method includes the step of applying the above anode slurry to one surface of an anode current collector, A method for manufacturing a positive electrode for a lithium-sulfur battery, wherein the binder comprises a first binder comprising a rubber-based polymer and a second binder comprising a vinyl polymer comprising carbonyl groups. In Article 18, The step of manufacturing the above positive active material is, A step of primary milling of the mixture of the sulfur-based material and the metal halide salt; and A method for manufacturing a positive electrode for a lithium-sulfur battery, comprising the step of secondarily milling a mixture of the first milling product and the carbon-based material. Anode for a lithium-sulfur battery according to Article 1; cathode; and A lithium-sulfur battery comprising a solid electrolyte layer disposed between the anode and the cathode.

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