Positive electrode active material for lithium-sulfur battery, and positive electrode comprising same

Abstract

The present invention relates to a positive electrode active material. More specifically, the positive electrode active material is provided as secondary particles, each having a plurality of primary particles agglomerated therein, and each of the plurality of primary particles may include a composite of lithium sulfide, an ion-conductive salt, and a carbon-based material. The lithium sulfide includes at least one of Li₂Sn (1≤n≤8, where n is an integer), and the ion-conductive salt may include a lithium salt.

Description

A positive electrode active material for a lithium-sulfur battery, and a positive electrode including the same

[0001] This is about lithium-sulfur batteries.

[0002] Lithium-sulfur batteries are batteries that use sulfur-based materials as the cathode active material. Sulfur, the main material, is abundant in resources and has a low weight per atom. Technological development is underway for lithium-sulfur batteries, which theoretically possess a higher energy density compared to lithium-ion batteries, which have a relatively low energy density relative to their weight.

[0003] In a lithium-sulfur battery, when discharged, lithium releases electrons and is oxidized as it ionizes into lithium cations, while the sulfur-based material, which is the positive electrode active material, is reduced as it accepts electrons. Meanwhile, the sulfur-based material is converted into a sulfur anion form through a reduction reaction.

[0004] Lithium cations generated by the oxidation reaction of lithium are transferred to the anode through the electrolyte, and sulfur-based compounds combine with sulfur anions generated by the reduction reaction to form salts. Before discharge, sulfur has a cyclic S8 structure, and through the reduction reaction, lithium polysulfide (Li2S) is formed. x The battery is driven through a shuttle mechanism that converts to , 1≤x≤8).

[0005]

[0006] The problem that the present invention aims to solve is to provide a high-capacity lithium-sulfur battery through a positive electrode active material in the form of secondary particles.

[0007] Another problem that the present invention aims to solve is to provide a lithium-sulfur battery with improved rate characteristics and lifespan characteristics through a positive electrode active material in the form of secondary particles.

[0008]

[0009] A positive electrode active material according to the concept of the present invention may include lithium sulfide; an ion-conducting salt; and a carbon-based material. The lithium sulfide is Li2S nIt includes at least one of (1 ≤ n ≤ 8, where n is an integer), and the ion-conducting salt may include a lithium salt. The positive electrode active material may be a secondary particle formed by the aggregation of a plurality of primary particles. Each of the plurality of primary particles may include a complex of the lithium sulfide, the ion-conducting salt, and the carbon-based material.

[0010] A positive electrode according to another concept of the present invention may include the positive electrode active material; and a solid electrolyte.

[0011] A lithium-sulfur battery according to another concept of the present invention may include the positive electrode; the negative electrode; and a solid electrolyte layer between the positive electrode and the negative electrode.

[0012]

[0013] According to one aspect, the capacity of a lithium-sulfur battery can be improved by increasing the composite density and energy density of the electrode.

[0014] According to another aspect, the rate characteristics and life characteristics of lithium-sulfur batteries can be improved through secondary particles of a uniform shape.

[0015]

[0016] FIG. 1 is a plan view of a lithium-sulfur battery according to embodiments of the present invention.

[0017] Figure 2 is a cross-sectional view along the line A-A' of Figure 1.

[0018] Figure 3 is a cross-sectional view of the positive active material layer of one embodiment.

[0019] Figure 4 illustrates a positive active material of one embodiment.

[0020] FIGS. 5a to 5e are SEM images of a positive electrode active material according to embodiments of the present invention.

[0021] FIG. 6 is a cross-sectional view of a lithium-sulfur battery according to one embodiment of the present invention.

[0022] FIG. 7 is a cross-sectional view of a lithium-sulfur battery according to one embodiment of the present invention.

[0023] FIG. 8 is a cross-sectional view of a lithium-sulfur battery according to one embodiment of the present invention.

[0024]

[0025] 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.

[0026] 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.

[0027] The embodiments described herein will be described with reference to cross-sectional and / or plan views, which are exemplary illustrations of the invention. In the drawings, the thicknesses of films and regions are exaggerated for effective description 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. Although terms such as first, second, third, etc., have been used to describe various components in the various embodiments of this specification, 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.

[0028] 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.

[0029] Unless otherwise defined in this specification, the particle size may be the average particle size. Additionally, the particle size refers to the average particle size (D50), which means the diameter of the particle whose cumulative volume in the particle size distribution is 50% by volume. The average particle size (D50) 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 with a transmission electron microscope (TEM) image or a scanning electron microscope (SEM) image. Alternatively, the average particle size (D50) value may be obtained by measuring using a measuring device utilizing dynamic light scattering, performing data analysis to count the number of particles for each particle size range, and then calculating from this. Alternatively, it may be measured using a laser diffraction method. When measuring by laser diffraction, more specifically, after dispersing the particles to be measured in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasound of about 28 kHz at an output of 60 W, and then the average particle size (D50) at 50% of the particle size distribution in the measuring device can be calculated.

[0030] In this specification, “metal” includes both metals and metalloids such as silicon and germanium in an elemental or ionic state.

[0031] In this specification, “alloy” means a mixture of two or more metals.

[0032] In this specification, “electrode active material” refers to an electrode material capable of undergoing lithiation and delithiation.

[0033] In this specification, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0034] In this specification, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0035] In this specification, “lithiation” and “to lithiate” refer to the process of adding lithium to an electrode active material.

[0036] In this specification, “delithiation” and “to delithiate” refer to the process of removing lithium from an electrode active material.

[0037] In this specification, “charge” and “to charge” refer to the process of providing electrochemical energy to a battery.

[0038] In this specification, “discharge” and “discharge” refer to the process of removing electrochemical energy from a battery.

[0039] In this specification, “anode” and “cathode” refer to electrodes where electrochemical reduction and lithiation occur during the discharge process.

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

[0041] In this specification, “lithium-sulfur battery” may be used interchangeably with “lithium-sulfur all-solid-state battery” or “all-solid-state battery.”

[0042]

[0043] lithium sulfur battery (10)

[0044] FIG. 1 is a plan view of a lithium-sulfur battery according to embodiments of the present invention. FIG. 2 is a cross-sectional view along line A-A' of FIG. 1. FIG. 3 is for illustrating a positive electrode active material layer of one embodiment of the present invention.

[0045] Referring to FIGS. 1 and 2, a lithium-sulfur battery (10) according to the present invention may include a positive electrode layer (100), a negative electrode layer (200) facing the positive electrode layer (100), and a solid electrolyte layer (300) disposed between the positive electrode layer (100) and the negative electrode layer (200). However, not limited thereto, the lithium-sulfur battery (10) may further include an additional functional layer, such as an adhesion-enhancing layer, disposed between the positive electrode layer (100) and the solid electrolyte layer (300) or between the negative electrode layer (200) and the solid electrolyte layer (300).

[0046] positive electrode (100)

[0047] An anode layer (100) according to one embodiment of the present invention may include an anode current collector (110) and an anode active material layer (120) disposed on the anode current collector (110). The anode active material layer (120) may include an anode active material, a solid electrolyte, a conductive material, and a binder.

[0048] The positive current collector (110) may provide a reference surface on which the positive active material layer (120) is disposed. The positive current collector (110) may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The positive current collector (110) may include a plate or a foil. In another embodiment of the present invention, the positive current collector (110) may be omitted. The thickness of the positive current collector (110) 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.

[0049] The positive current collector (110) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof.

[0050] The base film may be, for example, an insulator. Since the base film contains an insulating thermoplastic polymer, the base film may soften or liquefy upon the occurrence of a short circuit, thereby interrupting battery operation and suppressing a sudden increase in current.

[0051] The metal layer may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), or alloys thereof. The metal layer may act as an electrochemical fuse and cut off in the event of an overcurrent to perform a short-circuit prevention function. The limit current and maximum current can be controlled by adjusting the thickness of the metal layer. The metal layer may be plated or deposited on a base film. As the thickness of the metal layer decreases, the limit current and / or maximum current of the positive current collector (110) decreases, thereby improving the stability of the lithium battery in the event of a short circuit.

[0052] A lead tab may be added to the metal layer for external connection. The lead tab may be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or metal layer melt, allowing the metal layer to be electrically connected to the lead tab.

[0053] To make the weld between the metal layer and the lead tab more robust, a metal chip may be added between the metal layer and the lead tab. The metal chip may be a thin sheet of the same material as the metal of the metal layer. The metal chip may be, for example, metal foil, metal mesh, etc. The metal chip may be, for example, aluminum foil, copper foil, SUS foil, etc. The lead tab may be welded to a metal chip / metal layer laminate or a metal chip / metal layer / base film laminate by placing the metal chip on the metal layer and then welding it to the lead tab. During welding, as the base film, metal layer, and / or metal chip melt, the metal layer or the metal layer / metal chip laminate may be electrically connected to the lead tab. A metal chip and / or lead tab may be added to a portion of the metal layer.

[0054] The thickness of the base film may be, for example, 1 to 50 μm, 1.5 to 50 μm, 1.5 to 40 μm, or 1 to 30 μm. By having the base film within this thickness range, the weight of the electrode assembly can be reduced more effectively. The melting point of the base film may be, for example, 100 to 300 °C, 100 to 250 °C or lower, or 100 to 200 °C. By having the base film within this melting point range, the base film can melt during the welding process of the lead tab and be easily bonded to the lead tab. Surface treatments, such as corona treatment, may be performed on the base film to improve the adhesion between the base film and the metal layer.

[0055] The thickness of the metal layer may be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to μm. By having the metal layer within this range of thickness, the stability of the electrode assembly can be ensured while maintaining conductivity. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. By having the metal piece within this range of thickness, the connection between the metal layer and the lead tab can be performed more easily. Since the positive current collector (110) has a laminated structure of the base film and the metal layer described above, the weight of the positive layer (100) can be reduced, and consequently, the energy density of the all-solid-state battery (10) can be improved.

[0056] Referring to FIG. 3, the positive active material layer (120) according to embodiments of the present invention may include a positive active material (CAC), a solid electrolyte (SEP), and a binder (BID). The positive active material (CAC) within the positive active material layer may reversibly absorb and release lithium ions. The positive active material (CAC) may include a plurality of particles. The positive active material according to the present invention may include a sulfide-based positive active material. The sulfide-based positive active material may include a sulfur-based compound. The sulfide-based positive active material may include, for example, nickel sulfide, copper sulfide, lithium sulfide, lithium polysulfide, a lithium sulfide-containing composite, or a combination thereof.

[0057] The cathode active material (CAC) according to an embodiment of the present invention may include lithium sulfide, an ion-conducting salt, and a carbon-based material. By including the above materials, the cathode active material (CAC) can be used as an electrochemical energy source by possessing ion conductivity and electron conductivity while reversibly absorbing / releasing lithium ions. For example, the cathode active material may be a composite of lithium sulfide, an ion-conducting salt, and a carbon-based material.

[0058] Lithium sulfide is Li2S n It may include at least one of (1 ≤ n ≤ 8, where n is an integer). By including lithium sulfide in the positive electrode active material, capacity can be improved. Lithium sulfide can serve as the lithium source for the lithium-sulfur battery. Through the continuous oxidation / reduction reaction of lithium sulfide, lithium ions can move between the positive and negative electrodes, while electrons simultaneously move through an external circuit to generate current. In a lithium-sulfur battery using a sulfide-based material as the positive electrode, since lithium sulfide can act as a lithium source, the provision of a lithium source at the negative electrode can be omitted. That is, by including a lithium-containing sulfide in the positive electrode, a negative electrode structure can be introduced in which lithium is omitted at the negative electrode. Consequently, the energy density of the lithium-sulfur battery can be improved.

[0059] Ionic conductive salts can improve the ionic conductivity of the cathode active material (CAC). In the case of the aforementioned lithium sulfide, since its ionic conductivity is very low in itself, the ionic conductivity of the cathode active material (CAC) can be improved by including ionic conductive salts.

[0060] The ion-conducting salt may include a lithium salt. The lithium salt may include a lithium halide, which is a compound of lithium and a halogen element. In one embodiment, the lithium salt may include LiF, LiCl, LiBr, LiI, or a combination thereof. By including a lithium salt in the ion-conducting salt, the ion conductivity of the cathode active material (CAC) can be improved.

[0061] The ion-conducting salt may further include a metal halide. The metal halide may include a compound of a metal and a halogen element. The metal of the metal halide may include at least one selected from the group consisting of aluminum (Al), silver (Ag), gold (Au), platinum (Pt), palladium (Pd), bismuth (Bi), tin (Sn), and zinc (Zn). For example, the metal halide may include AlI3, AgI, SnI4, etc. The metal halide may include a lithium-affinity metal to improve the ion conductivity of the cathode active material. The metal halide may maintain the overall shape of the cathode active material and reduce interfacial resistance.

[0062] Carbon-based materials are materials containing carbon atoms and may include, without limitation, materials used as conductive materials in the relevant technical field. For example, carbon-based materials may include crystalline carbon, amorphous carbon, or a combination thereof. Carbon-based materials may include a calcined product of a carbon precursor. In one embodiment, the carbon-based precursor may include at least one selected from the group consisting of sucrose, glucose, RF (resorcinol-formaldehyde), pitch, chitosan, carbon black, carbon nanofibers, carbon nanotubes, graphite, polyvinyl alcohol, etc. By including a carbon-based material in the positive electrode active material, the electronic conductivity can be improved and the cycle characteristics of the battery can be improved.

[0063] The content of lithium sulfide in the cathode active material (CAC) may be 50 wt% to 95 wt%, 50 wt% to 90 wt%, 50 wt% to 80 wt%, or 50 wt% to 70 wt% of the total weight of the cathode active material (CAC). By including lithium sulfide within the above range, a high-capacity cathode active material can be provided.

[0064] The content of the ion-conducting salt in the positive electrode active material (CAC) may be 10 wt% to 50 wt%, 20 wt% to 40 wt%, 10 wt% to 30 wt%, or 20 wt% to 30 wt% of the total weight of the positive electrode active material (CAC). By including the ion-conducting salt within the above range, excellent ion conductivity and ductility can be achieved.

[0065] The ion-conducting salt may include a lithium salt and a metal halide. If the ion-conducting salt further includes a metal halide, the weight ratio of the lithium salt to the metal halide may be 1:27 to 3:1, 1:3 to 3:1, or about 1:1. Alternatively, the molar ratio of the lithium salt to the metal halide may be 1:9 to 9:1, 1:3 to 3:1, or about 1:1.

[0066] The content of carbon-based material in the positive electrode active material (CAC) may be 1 wt% to 20 wt%, 1 wt% to 10 wt%, 5 wt% to 10 wt%, 5 wt% to 20 wt%, 10 wt% to 20 wt%, or 10 wt% to 15 wt% with respect to the total weight of the positive electrode active material (CAC). By including carbon-based material within the above range, the electron conductivity of the positive electrode active material (CAC) can be improved.

[0067] Hereinafter, a positive active material (CAC) according to an embodiment of the present invention will be described in more detail. Referring to FIG. 4, the positive active material (CAC) may be in a polycrystalline form. Specifically, the positive active material (CAC) may include secondary particles (SAP) formed by the aggregation of a plurality of primary particles (PP). In one embodiment, the positive active material (CAC) may be spherical or elliptical, formed by the aggregation of a plurality of primary particles (PP). In this case, the positive active material (CAC) forms a spherical shape overall, but may have an uneven surface as the plurality of primary particles (PP) are aggregated. In another embodiment, the positive active material (CAC) may not have a spherical shape even if the plurality of primary particles (PP) are aggregated, but may have a random shape.

[0068] Referring to FIG. 4, each of the plurality of primary particles (PP) may be a composite of lithium sulfide (LPS), an ion-conducting salt (ICS), and a carbonaceous material (CMA). In one embodiment, each of the plurality of primary particles (PP) may comprise a solid solution of lithium sulfide (LPS), an ion-conducting salt (ICS), and a carbonaceous material (CMA). Specifically, each of the plurality of primary particles (PP) may comprise three particles of lithium sulfide (LPS), an ion-conducting salt (ICS), and a carbonaceous material (CMA) and exist as a single phase.

[0069] The ionic conductivity of the cathode active material (CAC) can be enhanced by including a solid solution of lithium sulfide (LPS), an ionic conductive salt (ICS), and a carbon-based material (CMA). For example, the ionic conductivity of the cathode active material (CAC) can be enhanced compared to the ionic conductivity of the lithium sulfide (LPS) itself by including lithium ions disposed within the lithium sulfide (LPS) crystallites in a plurality of primary particles (PP) existing as a solid solution.

[0070] The performance of the anode can be improved by the formation of secondary particles (SAP) from multiple composite primary particles (PP). By forming secondary particles (SAP), the particle size distribution can be easily controlled, thereby providing a uniform anode. Since it is uniform and structurally stable, it prevents the collapse or breakage of the anode active material particles, which can extend the electrode's lifespan. Furthermore, the energy density can be improved by increasing the composite density of the anode.

[0071] The average particle size (D50) of the positive active material (CAC) may be 3 μm to 15 μm. The average particle size of the positive active material (CAC) may refer to the average particle size of the secondary particle (SAP). The average particle size is measured by a particle size analyzer and may refer to the diameter (D50) of the particle whose cumulative volume in the particle size distribution is 50 volume%. As described above, by including secondary particles (SAP) with a large average particle size, mechanical stability can be increased and the uniformity of the electrode can be improved.

[0072] Referring to FIGS. 5a to 5e, the size of each of the plurality of primary particles constituting the secondary particle (SAP) may be 100 nm to 1 μm. The size of each of the plurality of primary particles may refer to the diameter measured through electron microscope images of the positive electrode active material. The size of each of the plurality of primary particles may be uniform.

[0073] In one embodiment, the sphericity of the positive active material (CAC) may be 0.7 to 0.9. The sphericity of the positive active material (CAC) may refer to the sphericity of the secondary particle (SAP). Sphericity is an evaluation of the degree to which the shape of the particle is close to an ideal sphere, and can be measured, for example, by analyzing 2D or 3D images taken with a scanning electron microscope. In this case, the sphericity can be calculated through the following Equation 1.

[0074] <Equation 1>

[0075] Sphericity = 4πA / P 2(A is the cross-sectional area of ​​the particle, P is the perimeter of the particle)

[0076] In one embodiment, the Span value analyzed by a particle size analyzer of the positive active material may be 3 to 6, 2 to 6, 2.5 to 3.5, or 2.6 to 3.4. The Span value of the positive active material may be the Span value of the secondary particle analyzed by a particle size analyzer. The Span value may be calculated by the following Equation 2.

[0077] <Equation 2>

[0078] Span = (D 90 -D 10 ) / D 50

[0079] In the above Equation 2, D n represents the size of the particles corresponding to the top n% in the particle size distribution. That is, D n represents the particle size when n% of the total particles are less than or equal to that size.

[0080] By providing a positive electrode active material with a uniform and consistent form as described above, the performance of the battery and the stability of the manufacturing process can be improved. For example, the structural stability of the positive electrode active material particles can be improved. In addition, the composite density of the positive electrode active material layer can be improved. As the uniformity within the positive electrode active material layer is improved and the electrode plate bonding strength is enhanced, the content of other additives such as binders or conductive materials can be minimized. In one embodiment, the composite density of the positive electrode may be 1.5 to 2.0, 1.6 to 1.9, or 1.7 to 1.9. The composite density of the positive electrode may refer to the composite density of the positive electrode active material layer.

[0081] In one embodiment, the specific surface area of ​​the cathode active material (CAC) is 0.3 m² 2 / g to 20 m 2It can be / g. The specific surface area can be measured, for example, through the BET (Braunauer-Emmett-Teller) adsorption method. By having a specific surface area within the above range, the performance of the anode can be improved by enhancing ionic and electronic conductivity while reducing side reactions. In addition, by increasing the contact area with the solid electrolyte (SEP) within the anode, the mobility of lithium ions can be increased, and a lithium-sulfur battery with improved rate characteristics can be provided.

[0082] As a result, by providing a positive electrode active material layer with a uniform and dense structure, the performance of the lithium-sulfur battery can be improved.

[0083] In one embodiment, the positive active material layer (120) may include a first particle of large diameter and a second particle of small diameter. The average particle size of the first particle may be larger than the average particle size of the second particle. The average particle size of the first particle may be 7 μm to 15 μm. The average particle size of the second particle may be 3 μm to 5 μm.

[0084] In one embodiment, the mixing weight ratio of the first and second particles may be 5:5 to 8:2, or 7:3 to 8:2. By including both large and small particle sizes, the composite density of the positive active material layer can be further improved. For example, the composite density of the positive active material layer may be 1.5 g / cc to 2.0 g / cc, 1.6 to 1.9, or 1.7 to 1.9.

[0085] Referring again to FIG. 3, the positive active material layer (120) may include not only the positive active material (CAC) but also a solid electrolyte (SEP). The solid electrolyte (SEP) in the positive active material layer may be the same as or different from the solid electrolyte in the solid electrolyte layer (300) described later.

[0086] The solid electrolyte (SEP) in the positive active material layer may have an average particle size (D50) smaller than the solid electrolyte in the solid electrolyte layer (300). For example, the average particle size of the solid electrolyte (SEP) 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 of the average particle size of the solid electrolyte in the solid electrolyte layer (300).

[0087] In one embodiment, the content of the positive active material (CAC) in the positive active material layer (120) may be 10% to 99% by weight, 40% to 90% by weight, 50% to 90% by weight, or 60% to 90% by weight of the total weight of the positive active material layer (120). This may be used in the same sense as the content of the positive active material (CAC) in the positive electrode (100) within this specification. It may mean a ratio calculated based on the weight excluding the positive current collector (110) in the positive electrode (100).

[0088] Among the components within the positive active material layer (120), the positive active material (CAC) may have the largest content. The content of the solid electrolyte (SEP) within the positive active material layer (120) may be 10% to 70% by weight, 10% to 60% by weight, or 10% to 40% by weight of the total weight of the positive active material layer (120). This may be used in the same sense as the content of the solid electrolyte (SEP) within the positive electrode (100) in this specification, and may mean a ratio calculated based on the weight excluding the positive current collector (110) within the positive electrode (100).

[0089] The solid electrolyte (SEP) may be, for example, a sulfide-based solid electrolyte. Sulfide-based solid electrolytes are, for example, 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, 0≤x≤2, and one or more selected from. Sulfide-based solid electrolytes are produced by processing starting materials, such as Li2S or P2S5, by methods such as melt quenching or mechanical milling. Additionally, heat treatment may be performed after such processing. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. Furthermore, the solid electrolyte may include sulfur (S), phosphorus (P), and lithium (Li) as at least constituent elements among the sulfide-based solid electrolyte materials described above. For example, the solid electrolyte may be a material containing Li2S-P2S5. When using a sulfide-based solid electrolyte material comprising Li2S-P2S5 to form a solid electrolyte, the molar ratio of Li2S and P2S5 is, for example, in the range of Li2S : P2S5 = 20 : 80 to 90 : 10, 25 : 75 to 90 : 10, 30 : 70 to 70 : 30, and 40 : 60 to 60 : 40.

[0090] Sulfide-based solid electrolytes may include, for example, an argyrodite-type solid electrolyte represented by the following chemical formula 1:

[0091] <Chemical Formula 1>

[0092] Li + 12-n-x A n+ X 2- 6-x Y - x

[0093] In the above formula, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta; X is S, Se, or Te; Y is Cl, Br, I, F, CN, OCN, SCN, or N3; and 1≤n≤5, 0≤x≤2. Sulfide-based solid electrolytes are, for example, Li 7-x PS 6-x Cl x , 0≤x≤2, Li7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x It may be an argyrodite-type compound containing one or more selected from 0≤x≤2. The sulfide-based solid electrolyte may be an argyrodite-type compound containing one or more selected from, for example, Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0094] Alternatively, sulfide-based solid electrolytes are Li 7-c M a PS 6-c X c It may be an argyrodite-type compound containing (0≤a≤2, (0≤c≤2)). Here, X may be F, Br, Cl, or a combination thereof. M may be 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), antimony (Sb), bismuth (Bi), or a combination thereof.

[0095] The density of the argyrodite-type solid electrolyte may be 1.5 to 2.0 g / cc. Since the argyrodite-type solid electrolyte has a density of 1.5 g / cc or higher, the internal resistance of the lithium-sulfur battery is reduced, and penetration of the solid electrolyte layer by Li can be effectively suppressed.

[0096] The positive active material layer (120) may further include a conductive material. The conductive material may be, for example, a carbon-based material, a metal-based material, or a combination thereof. The content of the conductive material in the positive active material layer (120) may be, for example, 1% to 30% by weight, 1% to 20% by weight, or 1% to 10% by weight of the total weight of the positive active material layer (120). This may be used in the same sense as the content of the conductive material in the positive, and may mean a ratio calculated based on the weight excluding the positive current collector in the positive.

[0097] Metallic materials may be metal powders, metal fibers, or combinations thereof, but are not limited to these; any metallic material used as a conductive material in the relevant technical field is acceptable.

[0098] The conductive material is a material containing carbon atoms and may include, without limitation, materials used as conductive materials in the relevant technical field. For example, the conductive material may include crystalline carbon, amorphous carbon, or a combination thereof.

[0099] The conductive material may include carbon nanostructures. The conductive material may include, for example, porous carbon or non-porous carbon. Porous carbon may include, for example, periodic and regular two-dimensional or three-dimensional pores. Porous carbon may be, for example, carbon black such as Ketjen black, acetylene black, Denka black, thermal black, channel black; graphite, activated carbon, or a combination thereof. The form of carbon within the conductive material may be, for example, particle form, sheet form, fibrous form, etc., but is not limited thereto, and any form used as carbon in the relevant technical field may be possible.

[0100] In one embodiment, the conductive material may include a fibrous carbon-based material. By including a fibrous carbon-based material in the conductive material, the electron conductivity of the positive active material layer (120) can be further improved. By including a fibrous carbon-based material in the conductive material, electron conduction from the surface to the interior of the positive active material layer (120) can be performed more easily. The internal resistance of the positive active material layer (120) is reduced by the conductive material, and the cycle characteristics of the secondary battery can be further improved.

[0101] The aspect ratio of the fibrous carbon-based material may be, for example, 2 or more, 3 or more, 4 or more, 5 or more, 10 or more, or 20 or more. The aspect ratio of the fibrous carbon-based material may be, for example, 2 to 30, 3 to 30, 4 to 30, 5 to 30, 10 to 30, or 20 to 30. The aspect ratio of the fibrous carbon-based material may be, for example, 2 to 30, 2 to 20, 2 to 10, 2 to 8, 2 to 5, or 2 to 4. By having the aspect ratio of the fibrous carbon-based material within this range, the overall electron conductivity of the positive active material layer (120) is improved, and the local imbalance of electron conductivity within the positive active material layer (120) can be further alleviated.

[0102] Fibrous carbon-based materials may include, for example, carbon nanostructures. Carbon nanostructures may include, for example, carbon nanofibers (CNF), carbon nanotubes (CNT), carbon nanobelts, carbon nanorods, or combinations thereof. 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.

[0103] The diameter of the primary carbon nanostructure may be, for example, 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. The length of the primary carbon nanostructure may be, for example, 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. The diameter and length of the primary carbon nanostructure may be measured from scanning electron microscope (SEM) or transmission electron microscope (TEM) images. Alternatively, the diameter and / or length of the primary carbon nanostructure may be measured by laser diffraction.

[0104] The secondary carbon nanostructure may be a structure formed by assembling primary carbon nanostructures, for example, to form a bundle or rope type, either wholly or partially. The secondary carbon nanostructure may include, for example, bundle-type carbon nanostructures, rope-type carbon nanostructures, or a combination thereof. The diameter of the secondary carbon nanostructure may be, for example, 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. The length of the secondary carbon nanotube structure may be, for example, 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 or more. The diameter and length of the secondary carbon nanostructure may be measured from scanning electron microscope (SEM) images or optical microscopes. Alternatively, the diameter and / or length of the secondary carbon nanostructure may be measured by laser diffraction.

[0105] The positive active material layer (120) may further include a binder (BID). The binder may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyethylene, etc., but is not limited to these and may be any binder used in the relevant technical field. The content of the binder (BID) in the positive active material layer (120) may be, for example, 0.1% to 10% by weight, 0.5% to 5% by weight, or 0.5% to 2% by weight of the total weight of the positive active material layer (120). The binder (BID) may be omitted. This may be used in the same sense as the content of the binder in the positive, and may mean a ratio calculated based on the weight excluding the positive current collector in the positive.

[0106] The positive active material layer (120) may further include additives such as a coating agent, a dispersant, and an ion conductivity aid in addition to the positive active material (CAC) and solid electrolyte (SEP) described above. Known materials generally used in electrodes of all-solid-state batteries or lithium-sulfur batteries may be used as coating agents, dispersants, and ion conductivity aids that may be included in the positive active material layer (120).

[0107] cathode (200)

[0108] The negative electrode layer (200) may include a negative electrode current collector (210) and a negative electrode coating layer (220) on the negative electrode current collector (210). The negative electrode current collector (210) may provide a reference surface on which the negative electrode coating layer (220) is placed. The negative electrode current collector (210) may include, for example, a material that does not react with lithium, that is, does not form any alloys or compounds with lithium. For example, the negative electrode current collector (210) may include at least one metal selected from the group consisting of copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). The thickness of the negative electrode current collector (210) may be 1 μm to 20 μm, more specifically 5 μm to 15 μm, and more specifically 7 μm to 10 μm.

[0109] The negative current collector (210) may be composed of one of the metals described above, or may include an alloy of two or more metals or a coating material. The negative current collector (210) may, for example, have a plate-like or foil-like shape. Meanwhile, in one embodiment, the negative current collector (210) may be omitted.

[0110] Although not illustrated, a negative current collector (210) according to one embodiment may include a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The polymer may be an insulating polymer. By including an insulating thermoplastic polymer in the base film, the base film may soften or liquefy upon a short circuit, thereby blocking battery operation and suppressing a sudden increase in current. The metal layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or an alloy thereof. The negative current collector (210) may additionally include a metal piece and / or a lead tab. For more specific details regarding the base film, metal layer, metal chip, and lead tab of the negative electrode current collector (210), refer to the positive electrode current collector (110) described above. By having the negative electrode current collector (210) have this structure, the weight of the negative electrode layer (200) can be reduced, and consequently, the energy density of the lithium-sulfur battery (10) can be improved.

[0111] The negative electrode coating layer (220) can be configured to allow lithium metal to grow between the lithium-sulfur battery (10) and the negative electrode current collector (210) during charging. The negative electrode coating layer (220) can serve as a protective layer for the lithium metal and simultaneously suppress the precipitation and growth of lithium dendrites.

[0112] The cathode coating layer (220) may include metal and carbon. For example, the cathode coating layer (220) may include at least one metal 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). The cathode coating layer (220) may include at least one carbon selected from the group consisting of carbon black, acetylene black, furnace black, ketjen black, and graphene. In one embodiment, the cathode coating layer (220) may include a mixture of carbon black and silver (Ag).

[0113] The cathode coating layer (220) may further include other additives in addition to metal and carbon. The cathode coating layer (220) may further include at least one additive selected from the group consisting of, for example, binders, fillers, coating agents, dispersants, and ion-conducting aids.

[0114] The negative electrode coating layer (220) may have a smaller thickness compared to the positive electrode active material layer (120). The thickness of the negative electrode coating layer (220) may be, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the thickness of the positive electrode active material layer (120). The thickness of the negative electrode coating layer (220) may be, for example, 1 µm to 20 µm, 2 µm to 10 µm, or 3 µm to 7 µm. If the thickness of the negative electrode coating layer (220) is excessively thin, lithium dendrites formed between the negative electrode coating layer (220) and the negative electrode current collector (210) may cause the negative electrode coating layer (220) to collapse, thereby degrading the cycle characteristics of the all-solid-state battery (10). If the thickness of the negative electrode coating layer (220) increases excessively, the energy density of the all-solid-state battery (10) decreases, and the internal resistance of the all-solid-state battery (10) due to the negative electrode coating layer (220) increases, which may degrade the cycle characteristics of the cell.

[0115] Meanwhile, although not illustrated, a carbon layer may be further included to improve adhesion between the cathode coating layer (220) and the solid electrolyte layer (300).

[0116] solid electrolyte layer (300)

[0117] A solid electrolyte layer (300) may be provided between the positive electrode layer (100) and the negative electrode layer (200). The solid electrolyte layer (300) may include a sulfide-based solid electrolyte with excellent lithium ion conductivity characteristics. The solid electrolyte in the solid electrolyte layer (300) may be the same as or different from any one of the materials included in the solid electrolyte (SEP, see FIG. 3) in the aforementioned positive electrode active material layer (120).

[0118] The solid electrolyte layer (300) may include a first solid electrolyte layer (310) and a second solid electrolyte layer (320). The first solid electrolyte layer (310) may be adjacent to the anode layer (100), and the second solid electrolyte layer (320) may be adjacent to the cathode layer (200).

[0119] Referring to FIG. 2, the first solid electrolyte layer (310) may include a first solid electrolyte. The first solid electrolyte may have a particle shape such as a sphere or an ellipsoid. The first solid electrolyte may include a sulfide-based solid electrolyte. The first solid electrolyte may be amorphous, crystalline, or a mixture thereof. Additionally, the solid electrolyte may include sulfur (S), phosphorus (P), and lithium (Li) as at least constituent elements among the sulfide-based solid electrolyte materials described above, for example. For example, the solid electrolyte may be a material containing Li2S-P2S5. When using a sulfide-based solid electrolyte material containing Li2S-P2S5 to form the solid electrolyte, the molar ratio of Li2S and P2S5 may be, for example, in the range of Li2S : P2S5 = 50 : 50 to 90 : 10.

[0120] In one embodiment, the first solid electrolyte is 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 an argyrodite-type compound comprising one or more selected from (0≤x≤2). The first solid electrolyte may include an argyrodite-type compound comprising one or more selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0121] In another embodiment, the first solid electrolyte is Li 7-c M a PS 6-c X c It may include an argyrodite-type compound comprising. Here, X may be Cl, Br, or a combination thereof. M may be Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn, or a combination thereof. a and c may each be a real number between 0 and 2.

[0122] The density of the azyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. Since the azyrodite-type solid electrolyte has a density of 1.5 g / cc or higher, the internal resistance of the all-solid-state battery is reduced, and defects such as penetration and short circuit of the solid electrolyte film due to lithium dendrite formation can be prevented. The elastic modulus of the first solid electrolyte is, for example, 15 GPa to 35 GPa.

[0123] The second solid electrolyte layer (320) may include a second solid electrolyte. The second solid electrolyte may have a particle shape such as a sphere or an ellipsoid. The second solid electrolyte may include a sulfide-based solid electrolyte. The description of the second solid electrolyte may be the same or similar as that described above for the first solid electrolyte. In one embodiment, the second solid electrolyte may have substantially the same composition as the first solid electrolyte. In another embodiment, the second solid electrolyte may have a composition similar to that of the first solid electrolyte.

[0124] The second solid electrolyte can come into direct contact with the negative electrode coating layer (220). By doing so, the second solid electrolyte can suppress lithium dendrites formed between the negative electrode coating layer (220) and the negative electrode current collector (210). The second solid electrolyte can effectively suppress negative side reactions. This can improve the cell performance of the lithium-sulfur battery (10) according to the present invention.

[0125] Each of the first and second solid electrolyte layers (310, 320) may further include a binder. The binder in the solid electrolyte layer (300) is, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited to these. The binder in the solid electrolyte layer (300) may be the same as or different from the binder in the positive active material layer (120) or the binder in the negative coating layer (220).

[0126] The content of the binder in the solid electrolyte layer (300) may be 0.1 to 10 wt%, 0.1 to 5 wt%, 0.1 to 3 wt%, 0.1 to 1 wt%, 0 to 0.5 wt%, or 0 to 0.1 wt% with respect to the total weight of the solid electrolyte layer (300).

[0127] In another embodiment of the present invention, the solid electrolyte layer (300) may be provided as a single layer structure rather than a double layer structure of the first solid electrolyte layer (310) and the second solid electrolyte layer (320).

[0128] Referring again to FIGS. 1 and FIGS. 2, the anode layer (100) and the first solid electrolyte layer (310) can form an anode composite layer (CSH). The cathode layer (200) and the second solid electrolyte layer (320) can form a cathode composite layer (ASH). An anode composite layer (CSH) can be laminated on the cathode composite layer (ASH).

[0129] The area of ​​the cathode composite layer (ASH) and the area of ​​the anode composite layer (CSH) may differ from each other. Specifically, the area of ​​the cathode composite layer (ASH) may be larger than the area of ​​the anode composite layer (CSH). The anode composite layer (CSH) may completely overlap within the cathode composite layer (ASH).

[0130] In one embodiment of the present invention, the first solid electrolyte layer (310) may have substantially the same area as the anode layer (100). The second solid electrolyte layer (320) may have substantially the same area as the cathode layer (200).

[0131] Specifically, the positive electrode composite layer (CSH) may have a first width (WI1) in a first direction (D1). The negative electrode composite layer (ASH) may have a second width (WI2) in a first direction (D1). The first width (WI1) may be smaller than the second width (WI2). The positive electrode composite layer (CSH) may have a third width (WI3) in a second direction (D2). The negative electrode composite layer (ASH) may have a fourth width (WI4) in a second direction (D2). The third width (WI3) may be smaller than the fourth width (WI4).

[0132] A lithium-sulfur battery (10) according to the present embodiment can be manufactured by forming a negative electrode composite layer (ASH) on a first carrier film and forming a positive electrode composite layer (CSH) on a second carrier film, and then laminating the negative electrode composite layer (ASH) and the positive electrode composite layer (CSH).

[0133] In one embodiment, as shown in FIG. 2, the positive active material layer (120) in a discharged state may have a first thickness (TK1). The lithium sulfur battery (10) may have a first height (HE1) in a third direction (D3). The first height (HE1) may be the sum of the thickness of the positive composite layer (CSH) and the thickness of the negative composite layer (ASH).

[0134] In the embodiments described below, detailed descriptions of technical features that overlap with those previously described with reference to FIGS. 1 to 3 are omitted, and the differences are described in detail.

[0135] FIG. 6 is a cross-sectional view along line A-A' of FIG. 1, illustrating a lithium-sulfur battery according to another embodiment of the present invention. Referring to FIG. 6, in one embodiment, a lithium-sulfur battery (10) in a charged state may further include a lithium metal layer (230) provided between a negative electrode current collector (210) and a negative electrode coating layer (220). The negative electrode layer (200) according to the present embodiment may include a negative electrode current collector (210), a negative electrode coating layer (220), and a lithium metal layer (230) between them.

[0136] The lithium metal layer (230) may include lithium or a lithium alloy. Since the lithium metal layer (230) is a metal layer containing lithium, it may function as, for example, a lithium reservoir. The lithium alloy may be, for example, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, but is not limited to these; any alloy used as a lithium alloy in the relevant technical field may be possible. The lithium metal layer (230) may be composed of one of these alloys or lithium, or may be composed of various types of alloys. The lithium metal layer (230) may be, for example, a plated layer. The lithium metal layer (230) may be deposited between the negative electrode coating layer (220) and the negative electrode current collector (210) during the charging process of the lithium-sulfur battery (10), for example.

[0137] The lithium metal layer (230) may have a third thickness (TK3). The third thickness (TK3) is not particularly limited, but may be, for example, 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. If the third thickness (TK3) of the lithium metal layer (230) is excessively thin, it may be difficult for the lithium metal layer (230) to perform the role of a lithium reservoir. If the third thickness (TK3) of the lithium metal layer (230) is excessively thick, the mass and volume of the lithium-sulfur battery (10) increase, and the cycle characteristics of the lithium-sulfur battery (10) may actually deteriorate.

[0138] In another embodiment of the present invention, a lithium metal layer (230) within the negative electrode layer (200) may be provided, for example, between the negative electrode current collector (210) and the negative electrode coating layer (220) before assembly of the lithium-sulfur battery (10). When the lithium metal layer (230) is placed between the negative electrode current collector (210) and the negative electrode coating layer (220) before assembly of the lithium-sulfur battery (10), the lithium metal layer (230) acts as a lithium reservoir because it is a metal layer containing lithium. For example, a lithium foil may be placed between the negative electrode current collector (210) and the negative electrode coating layer (220) before assembly of the lithium-sulfur battery (10).

[0139] When a lithium metal layer (230) is deposited by charging after the assembly of the lithium-sulfur battery (10), the energy density of the lithium-sulfur battery (10) can be increased because the lithium metal layer (230) is not included during the assembly of the lithium-sulfur battery (10). When charging the lithium-sulfur battery (10), it can be charged beyond the charging capacity of the negative electrode coating layer (220). That is, the negative electrode coating layer (220) is overcharged. At the beginning of charging, lithium can be absorbed in the negative electrode coating layer (220). When charging beyond the capacity of the negative electrode coating layer (220), lithium can be deposited, for example, between the negative electrode coating layer (220) and the negative electrode current collector (210). A lithium metal layer (230) can be formed by the deposited lithium.

[0140] The lithium metal layer (230) can be composed mainly of lithium (i.e., metallic lithium). During discharge, the lithium in the lithium metal layer (230) can be ionized and move to the positive electrode layer (100). In other words, lithium can be used as a negative electrode active material in the lithium-sulfur battery (10). In addition, since the negative electrode coating layer (220) covers the lithium metal layer (230), the negative electrode coating layer (220) can protect the lithium metal layer (230) and simultaneously suppress the precipitation growth of lithium dendrites. Therefore, the negative electrode coating layer (220) can suppress short circuits and capacity degradation of the lithium-sulfur battery (10) and improve the cycle characteristics of the lithium-sulfur battery (10).

[0141] When a lithium metal layer (230) is formed by charging after assembly of the lithium-sulfur battery (10), the negative electrode layer (200), that is, the negative electrode current collector (210) and the negative electrode 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 lithium-sulfur battery (10).

[0142] The positive active material layer (120) from which lithium ions are released by charging the lithium-sulfur battery (10) may have a second thickness (TK2). The second thickness (TK2) of the positive active material layer (120) may be smaller than the first thickness (TK1) of FIG. 2.

[0143] In one embodiment of the present invention, the difference between the first thickness (TK1) and the second thickness (TK2) may be substantially the same or similar to the third thickness (TK3) of the lithium metal layer (230). For example, the third thickness (TK3) may be 1.0 to 1.5 times, or 1.0 to 1.2 times, the difference between the first thickness (TK1) and the second thickness (TK2). According to the present invention, the thickness of the positive active material layer (120) may be reduced by the same amount as the thickness of the lithium metal layer (230) formed by charging the lithium-sulfur battery (10).

[0144] Although not illustrated, the lithium-sulfur battery (10) may operate (i.e., charge and / or discharge) while being pressurized by a pressurizing jig. In one embodiment, the lithium-sulfur battery (10) may be pressurized to 0.8 MPa to 2 MPa. For example, the lithium-sulfur battery (10) may have an internal pressure of about 1 MPa when discharged, and the lithium-sulfur battery (10) may have an internal pressure of about 1.5 MPa when charged. The ratio of the internal pressure of the lithium-sulfur battery (10) in the charged state of FIG. 7 to the internal pressure of the lithium-sulfur battery (10) in the discharged state of FIG. 2 may be 1.0 to 2.0, or 1.2 to 1.8.

[0145] The height (or thickness or volume) of the lithium-sulfur battery (10) may change according to charging and discharging under the aforementioned pressurized state. In the lithium-sulfur battery (10) according to the present embodiment, the thickness of the positive active material layer (120) may decrease in correspondence with the lithium metal layer (230) formed by charging. Accordingly, the second height (HE2) of the charged lithium-sulfur battery (10) shown in FIG. 6 may be similar to the first height (HE1) of the discharged lithium-sulfur battery (10) shown in FIG. 2. For example, the second height (HE2) may be 1 to 1.5 times, or 1 to 1.2 times, the first height (HE1).

[0146] FIG. 7 is a cross-sectional view along line A-A' of FIG. 1, illustrating a lithium-sulfur battery according to another embodiment of the present invention. Referring to FIG. 7, the lithium-sulfur battery (10) according to the present embodiment may further include a gasket (GSK). The gasket (GSK) may be provided to surround the positive electrode composite layer (CSH). The gasket (GSK) may fill the step difference on the side of the lithium-sulfur battery (10) caused by the difference in area between the negative electrode composite layer (ASH) and the positive electrode composite layer (CSH). The gasket (GSK) may surround the four sides of the positive electrode composite layer (CSH). For example, the thickness of the gasket (GSK) may be substantially the same as the thickness of the positive electrode composite layer (CSH).

[0147] The upper surface of the second solid electrolyte layer (320) may include a first region in contact with the first solid electrolyte layer (310) and a second region in contact with the gasket (GSK). The second region may be a peripheral region of the upper surface of the second solid electrolyte layer (320). The second region may surround the first region.

[0148] The gasket (GSK) can prevent cracking of the solid electrolyte layer (300) during the manufacture of the lithium-sulfur battery (10) and / or during the charging and discharging of the lithium-sulfur battery (10). This can improve the cycle characteristics of the lithium-sulfur battery (10). If the lithium-sulfur battery (10) does not include the gasket (GSK), uneven pressure is applied to the negative electrode composite layer (ASH) in contact with the positive electrode composite layer (CSH), causing cracking in the solid electrolyte layer (300), and the likelihood of a short circuit occurring due to the growth of lithium metal through this may increase.

[0149] The thickness of the gasket (GSK) may be greater than the thickness of the positive composite layer (CSH) or substantially equal to the thickness of the positive composite layer (CSH). Since the thickness of the gasket (GSK) is equal to the thickness of the positive composite layer (CSH), a uniform pressure is applied between the positive composite layer (CSH) and the negative composite layer (ASH), and the positive composite layer (CSH) and the negative composite layer (ASH) are sufficiently in contact, thereby reducing the interfacial resistance between the first solid electrolyte layer (310) and the second solid electrolyte layer (320). Additionally, the internal resistance of the solid electrolyte layer (300) may be reduced as the solid electrolyte layer (300) is sufficiently sintered during the pressurized manufacturing process of the lithium-sulfur battery (10).

[0150] The gasket (GSK) may have a single-layer structure, for example. Alternatively, although not shown in the drawings, the gasket (GSK) may have a multi-layer structure. In a gasket (GSK) having a multi-layer structure, each layer may have a different composition. A gasket (GSK) having a multi-layer structure may have, for example, a two-layer structure, a three-layer structure, a four-layer structure, or a five-layer structure. A gasket (GSK) having a multi-layer structure may include, for example, one or more adhesive layers and one or more support layers.

[0151] The gasket (GSK) may include, for example, a flame-retardant inert member. By providing flame retardancy, the flame-retardant inert member can prevent thermal runaway and the possibility of ignition of the lithium-sulfur battery (10). Consequently, the gasket (GSK) can further enhance the safety of the lithium-sulfur battery (10). By absorbing residual moisture within the lithium-sulfur battery (10), the flame-retardant inert member prevents the deterioration of the lithium-sulfur battery (10), thereby improving the lifespan characteristics of the lithium-sulfur battery (10).

[0152] FIG. 8 is a cross-sectional view along line A-A' of FIG. 1, illustrating a lithium-sulfur battery according to another embodiment of the present invention. Referring to FIG. 8, the positive electrode layer (100) may further include a coating layer (CTL) provided between the positive electrode current collector (110) and the positive electrode active material layer (120). The coating layer (CTL) may be placed directly, for example, on one or both sides of the positive electrode current collector (110). The coating layer (CTL) may be coated on one or both sides of the positive electrode current collector (110). No other layer may be placed between the positive electrode current collector (110) and the coating layer (CTL).

[0153] By placing the coating layer (CTL) directly on one or both sides of the positive current collector (110), the bonding strength between the positive current collector (110) and the positive active material layer (120) can be further improved. By placing the coating layer (CTL) between the positive current collector (110) and the positive active material layer (120), side reactions between the filler (FIL), solid electrolyte (SEP), or positive active material (CAC) and the positive current collector (110) can be more effectively suppressed. For example, the coating layer (CTL) can prevent corrosion of the sulfide-based positive active material (e.g., Li2S) by the positive current collector (110). Consequently, the coating layer (CTL) can suppress the degradation of the lithium-sulfur battery (10) during the charging and discharging process and improve cycle characteristics.

[0154] The thickness of the coating layer (CTL) is, for example, 0.01 to 20%, 0.1 to 20%, 0.5 to 20%, 1 to 20%, 1 to 15%, 1 to 10%, 2 to 8%, or 3 to 7% of the thickness of the positive current collector (110). The thickness of the coating layer (CTL) may be, for example, 10 nm to 5 µm, 50 nm to 5 µm, 200 nm to 4 µm, 500 nm to 3 µm, 500 nm to 2 µm, 500 nm to 1.5 µm, or 700 nm to 1.3 µm. By having the coating layer (CTL) have a thickness within this range, the bonding strength between the positive current collector (110) and the positive active material layer (120) is further improved, and the increase in interfacial resistance can be suppressed. The thickness of the coating layer (CTL) can be measured, for example, from a scanning electron microscope (SEM) image of a cross- section of the coating layer (CTL).

[0155] The coating layer (CTL) may include, for example, a carbon-based conductive material. The carbon-based conductive material included in the coating layer (CTL) may be selected from among the carbon-based conductive materials used in the positive active material layer (120). The coating layer (CTL) may include the same carbon-based conductive material as the carbon-based conductive material used in the positive active material layer (120). By including the carbon-based conductive material, the coating layer (CTL) may be, for example, a conductive layer.

[0156] The coating layer (CTL) may additionally include, for example, a binder. By additionally including a binder in the coating layer (CTL), the bonding strength between the positive current collector (110) and the positive active material layer (120) can be further improved. The binder included in the coating layer (CTL) is, for example, a conductive binder or a non-conductive binder. The conductive binder is, for example, an ion-conducting binder and / or an electron-conducting binder. A binder having both ion conductivity and electron conductivity may belong to both an ion-conducting binder and an electron-conducting binder.

[0157] The binder included in the coating layer (CTL) may be selected from among the binders used in the positive active material layer (120). The coating layer (CTL) may include the same binder as the binder used in the positive active material layer (120). The binder included in the coating layer (CTL) is, for example, a fluorine-based binder. The fluorine-based binder included in the coating layer (CTL) is, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), or a combination thereof. The coating layer (CTL) may be, for example, a binding layer containing a binder. The coating layer (CTL) may be, for example, a conductive layer containing a binder and a carbon-based conductive material.

[0158] The coating layer (CTL) can be disposed on the positive current collector (110) in a dry or wet manner, for example. The coating layer (CTL) can be disposed on the positive current collector (110) in a dry manner by deposition, for example, CVD, PVD, etc. The coating layer (CTL) can be disposed on the positive current collector (110) in a wet manner by, for example, spin coating, dip coating, etc. The coating layer (CTL) can be disposed on the positive current collector (110) by, for example, depositing a carbon-based conductive material onto a substrate by deposition. The dry-coated coating layer (CTL) may be made of a carbon-based conductive material and may not contain a binder. The coating layer (CTL) can be disposed on the positive current collector (110) by, for example, coating a composition comprising a carbon-based conductive material, a binder, and a solvent onto the surface of the electrode current collector and drying it. The coating layer (CTL) may have a single-layer structure or a multi-layer structure including multiple layers. The multi-story structure can be a 2-story structure, a 3-story structure, a 4-story structure, etc.

[0159] The negative electrode layer (200) may further include a thin film (TFL) provided between the negative electrode current collector (210) and the negative electrode coating layer (220). The thin film (TFL) may be provided on one side of the negative electrode current collector (210) to form an alloy with lithium.

[0160] The thin film (TFL) may include, for example, an element capable of forming an alloy with lithium. Elements capable of forming an alloy with lithium include, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., but are not necessarily limited to these, and any element capable of forming an alloy with lithium in the relevant technical field is possible. The thin film (TFL) may be composed of one of these metals or may be composed of an alloy of various types of metals.

[0161] By placing the thin film (TFL) on one side of the negative current collector (210), the deposition pattern of the lithium metal layer (230, see FIG. 4) deposited between, for example, the thin film (TFL) and the negative coating layer (220) is further flattened, and the cycle characteristics of the all-solid-state battery (10) can be further improved.

[0162] The thickness of the thin film (TFL) may be, for example, 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. If the thickness of the thin film (TFL) is less than 1 nm, it may be difficult to perform the function provided by the thin film (TFL). If the thickness of the thin film (TFL) is excessively thick, the thin film (TFL) itself absorbs lithium, and the amount of lithium precipitated in the negative electrode layer (200) decreases, which lowers the energy density of the all-solid-state battery (10) and may lower the cycle characteristics of the all-solid-state battery (10). The thin film (TFL) may be formed on the negative electrode current collector (210) by, for example, vacuum deposition, sputtering, plating, etc., but is not necessarily limited to these methods, and any method capable of forming a thin film in the relevant technical field may be possible.

[0163]

[0164] The present invention will be explained in more detail below through examples. However, these examples are intended to illustrate the present invention and the scope of the present invention is not limited to these examples.

[0165]

[0166] Preparation of positive electrode active material

[0167] (Example)

[0168] Step 1: Primary particle formation

[0169] A precursor solution was prepared by dissolving lithium sulfate (Li2SO4), lithium iodide (LiI), and resorcinol in water at a weight ratio of 73:15:12, and then adding 1 ml of a 38% ammonium hydroxide aqueous solution and 1.5 ml of a 30% formalin solution per 100 ml of water. Subsequently, the precursor solution was stirred at 200 rpm for more than 2 hours to prepare a precursor solution containing primary particle precipitates ranging from 100 nm to 1 µm. At this time, the primary particle size of the final cathode active material can be controlled by adjusting the concentration of the solution and the stirring time.

[0170]

[0171] Step 2: Secondary particle formation and drying

[0172] To the precursor solution formed in the first step, sucrose, a polysaccharide, was mixed as a carbon material at a ratio of 60 parts by weight per 100 parts by weight of a mixed solution of lithium sulfate (Li2SO4), lithium iodide (LiI), and resorcinol. The solution, stirred for at least 1 hour, was then fed into a spray dryer (B”U”CHI Mini Spray Dryer S-200) with an inlet temperature of 180°C, an outlet temperature of 100°C, a solution injection rate of 10 ml / min, a spray gas velocity of 1800 L / h, and a drying gas velocity of 35 m / h. 2 A composite powder in the shape of secondary particles, which are aggregates of primary particles, was obtained by drying at / h.

[0173]

[0174] Step 3: Heat Treatment

[0175] The manufactured secondary particles were subjected to reduction heat treatment at 800°C for 2 hours in an argon gas atmosphere to finally obtain a secondary particle-type cathode active material.

[0176] In the above manufacturing example, cathode active materials with different particle sizes and specific surface areas were prepared according to conditions such as the concentration of the precursor solution, the drying temperature and heat treatment temperature of the carbon-based organic material.

[0177]

[0178] (Comparative Example)

[0179] In contrast, Comparative Example 1 is an amorphous positive active material simply mixed through ball milling, and Comparative Example 2 is manufactured wet but has a single particle shape.

[0180] Specifically, in Comparative Example 1, Li2S as a sulfur compound and LiI as an ion-conducting material were mixed and mechanically milled using a ball mill to prepare a Li2S-LiI composite. Subsequently, the Li2S-LiI composite was mixed with carbon nanofiber (CNF), and the mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-CNF cathode active material.

[0181] In Comparative Example 2, a precursor solution was prepared by mixing lithium sulfate, lithium iodide, and Resorcinol in water at a ratio of 6:1.25:6. At this time, the precursor solution prepared by only one mixing step was used, without undergoing two mixing steps as in the example. The prepared precursor solution was spray-dried to obtain a dried powder, and heat-treated to obtain a single-particle cathode active material.

[0182] The cathode active materials according to the results of manufacturing are shown in Table 1 below as examples and comparative examples. In addition, the average particle size, specific surface area, and particle shape of the cathode active materials according to the examples and comparative examples are shown.

[0183] Average particle size (D50) Specific surface area (m²) 2 / g) Particle shape Example 1 11.6 4.4 Secondary particle Example 26.8 7.8 Secondary particle Example 3 10.5 5.4 Secondary particle Example 4 5.2 6.2 Secondary particle Comparative Example 17.0 14.6 Amorphous Comparative Example 26.5 3.1 Single particle

[0184]

[0185] Manufacturing of anodes

[0186] A cathode was prepared in the same manner, except that the cathode active material prepared according to the above examples and comparative examples was used, respectively. An azirodite-based solid electrolyte (Li6PS5Cl, D50 = 3.0 μm) was prepared as the solid electrolyte. PTFE was prepared as the binder. The cathode active material, solid electrolyte, and binder were mixed in a weight ratio of 80:19:1.

[0187] The positive electrode active material and the solid electrolyte were placed in a mixer and mixed for about 2 minutes. A binder was added to the mixed powder and mixed with a mixer for about 20 seconds. The mixed powder was further mixed using a kneader and then passed through calender rolls to produce a membrane-shaped positive electrode active material layer. During the additional mixing and calendering process using the kneader, the binder was fiberized.

[0188] An anode was manufactured by placing a prepared anode active material layer on an anode current collector made of carbon-coated aluminum foil.

[0189] Preparation of a solid electrolyte layer

[0190] A mixture was prepared by adding an acrylic binder to a solid electrolyte, Li6PS5Cl, which is an argyrodite-type crystal. The solid electrolyte and the binder were mixed in an amount of 98.5 parts by weight and 1.5 parts by weight, respectively. A slurry was prepared by stirring while adding octyl acetate to the prepared mixture. The prepared slurry was applied using a bar coater onto a 15 μm thick nonwoven fabric placed on a 75 μm thick PET substrate, and a laminate was prepared by drying in air at 80°C for 10 minutes. After vacuum drying the prepared laminate at 80°C for 2 hours, the solid electrolyte layer was separated from the PET substrate to produce a solid electrolyte layer.

[0191] Manufacturing of the cathode

[0192] A SUS foil with a thickness of about 10 μm was prepared as a cathode current collector. As cathode coating materials, carbon black (CB) with a primary particle size of about 30 nm and silver (Ag) particles with an average particle size of about 60 nm were prepared.

[0193] 4 g of a mixed powder, prepared by mixing carbon black (CB) and silver particles in a weight ratio of 3:1, was placed in a container, and 4 g of an NMP solution containing 7 wt% of a PVdF binder (Kureha # 9300) was added to prepare a mixed solution. A slurry was prepared by stirring the mixed solution while gradually adding NMP to it. The prepared slurry was applied to a SUS sheet using a bar coater, dried in air at 80°C for 10 minutes, and then vacuum dried at 40°C for 10 hours to prepare a laminate. The prepared laminate was cold-roll-pressed to flatten the surface to manufacture a cathode having a cathode coating layer / cathode current collector structure. The thickness of the cathode coating layer was approximately 15 μm. The surface areas of the cathode coating layer and the cathode current collector were the same.

[0194] Manufacturing of lithium-sulfur batteries

[0195] A solid electrolyte layer was positioned so that the cathode coating layer and the solid electrolyte layer were in contact, and an anode was placed on the solid electrolyte layer. The prepared laminate was subjected to plate pressing at approximately 85°C and a pressure of 500 MPa for 30 minutes. This pressing treatment sintered the solid electrolyte layer, thereby improving battery characteristics. The thickness of the sintered solid electrolyte layer was approximately 45 μm.

[0196] Lithium-sulfur batteries containing positive electrode active materials according to the examples and comparative examples are summarized in Table 2 below.

[0197] Anode (CAC: SEP: BID) Solid Electrolyte Layer Cathode Electrode Composite Density (g / cc) Example 1 80:19:1 Argyrodite SEAg / C1.72 Example 2 80:19:1 Argyrodite SEAg / C1.81 Example 3 80:19:1 Argyrodite SEAg / C1.84 Example 4 80:19:1 Argyrodite SEAg / C1.69 Comparative Example 180:19:1 Argyrodite SEAg / C1.52 Comparative Example 2 80:19:1 Argyrodite SEAg / C1.64

[0198]

[0199] Evaluation Example 1: Analysis of Cathode Active Material

[0200] FIGS. 5a to 5e are SEM images of a positive electrode active material according to an embodiment of the present invention. Referring to these figures, it can be seen that in the positive electrode active material according to an embodiment of the present invention, a plurality of primary particles aggregate to form secondary particles. It can be seen that the size of each of the plurality of primary particles forming the secondary particles is 1 μm or less.

[0201] The particle size distribution of the cathode active material was analyzed using a particle size analyzer. The particle size distribution was analyzed by calculating the Span value.

[0202] The crystal structure of the cathode active material was analyzed using X-ray diffraction (XRD). Specifically, the size and lattice constant of the Li2S crystallites were derived from the first peak corresponding to the (111) crystal plane appearing at a diffraction angle 2θ = 27° ± 2.0° in the XRD spectrum.

[0203] The analysis results of the cathode active materials according to the embodiments and comparative examples of the present invention are shown in Table 3 below.

[0204] Particle size (D50) Span rate (D90-D10) / (D50) Ionic conductivity (mS / cm) Electronic conductivity (mS / cm) Li2S crystallite size (nm) Lattice constant Example 1 1.6 3.3 5.2 X 10 -39.612.65.760 Example 26.83.14.2 X 10 -3 12.212.15.762 Example 310.52.76.7 X 10 -3 7.512.55.761 Example 45.22.95.2 X 10 -3 8.9 12.3 5.764 Comparative Example 174.1 3.2 X 10 -3 5.4 14.3 5.7 56 Comparative Example 26.5 3.6 3.6 X 10 -3 5.613.25.758

[0205] Referring to Table 3, the lattice constant of the positive electrode active material according to the embodiments of the present invention is 5.760 to 5.764, which is a large value compared to Comparative Example 1, which is amorphous and manufactured by ball milling, and Comparative Example 2, which is a single particle shape.

[0206] In addition, it can be seen that the positive electrode active material improves ion conductivity and electron conductivity by securing multiple pathways for the movement of lithium ions and electrons through the formation of secondary particles formed by the aggregation of primary particles with small particle sizes.

[0207] In addition, by referring to the span rate range, it can be seen that a positive electrode active material of uniform size can be provided.

[0208]

[0209] Evaluation Example 2: Battery Performance Evaluation

[0210] The performance of the lithium-sulfur battery manufactured according to the embodiments and comparative examples of the present invention was evaluated. The first cycle involved charging at a constant current of 0.05 C for 20 hours until the battery voltage reached 2.8 V. Subsequently, discharging was performed at a current of 0.05 C for 20 hours until the battery voltage reached 1.0 V.

[0211] The second cycle involved charging at a constant current of 0.1 C for 10 hours until the battery voltage reached 2.8 V. Subsequently, discharging was performed at a constant current of 0.1 C for 10 hours until the battery voltage reached 1.0 V.

[0212] For the second cycle discharge capacity, the specific capacity based on Li2S and the specific capacity based on the entire electrode were measured, respectively.

[0213] After the second cycle, charging and discharging were performed for up to 20 cycles under the same conditions as the second cycle. The capacity retention rate was evaluated as shown in Equation 1 below.

[0214] <Mathematical Formula 1>

[0215] Capacity Retention Rate[%] = [20th Cycle Discharge Capacity / 1st Cycle Discharge Capacity] × 100

[0216] The measurement results of the charge / discharge characteristics of the lithium-sulfur battery are shown in Table 4 below.

[0217] 2nd Cycle (0.1 C) Discharge Capacity [mAh / g, Li2S] 2nd Cycle (0.1 C) Discharge Capacity [mAh / g, Electrode] Rate Characteristic (%) (0.1C / 0.05C Discharge Capacity) Capacity Retention Rate [%] (Capacity retention rate after 20 cycles at 0.1C) Example 18 434229894 Example 28 5642898.293 Example 38 5142697.994 Example 48 6943598.192 Comparative Example 18 1040596.482 Comparative Example 28 2141196.989

[0218] Referring to the results in Table 4, it can be seen that the charge and discharge characteristics of the lithium-sulfur battery according to the embodiments of the present invention are further improved.

[0219] Specifically, referring to the results regarding the specific capacity (mAh / g, Li2S) based on Li2S, it can be seen that the specific capacity of Examples 1 to 4 is higher than that of the comparative examples. This means that the discharge capacity relative to the mass of Li2S, which acts as a lithium source within the cathode active material, is high. In addition, it can be seen that the values ​​of the examples are also high in terms of the discharge capacity based on the electrode.

[0220] In addition, looking at the results regarding rate characteristics and capacity retention rate, it can be seen that the characteristics of the lithium-sulfur battery according to the examples have been improved.

[0221] By introducing a cathode active material in the form of secondary particles, it is possible to provide a lithium-sulfur battery with overall improved rate characteristics, life characteristics, and energy density.

Claims

1. A positive electrode active material comprising lithium sulfide; an ion-conducting salt; and a carbon-based material: The above lithium sulfide is Li2S n Includes at least one of (1≤n≤8, n is an integer), and The above ion-conducting salt includes a lithium salt, and The above positive active material is a secondary particle formed by the aggregation of a plurality of primary particles, and Each of the plurality of primary particles comprises a complex of the lithium sulfide, the ion-conducting salt, and the carbon-based material.

2. In Paragraph 1, The size of the plurality of primary particles is 100 nm to 1 μm, Positive active material.

3. In Paragraph 1, The average particle size of the above secondary particles is 3 μm to 15 μm, Positive active material.

4. In Paragraph 1, The specific surface area of ​​the above secondary particle is 0.3 m 2 / g to 20 m 2 / g Positive active material.

5. In Paragraph 1, Each of the above plurality of primary particles comprises a solid solution of the lithium sulfide, the ion-conducting salt, and the carbon-based material. Positive active material.

6. In Paragraph 1, The span value of the secondary particle measured by a particle size analyzer is 2.6 to 3.4, Positive active material.

7. In Paragraph 1, The sphericity of the above secondary particles is 0.7 to 0.9, Positive active material.

8. In Paragraph 1, The above lithium salt comprises LiI, LiCl, LiBr, LiI, or a combination thereof. Positive active material.

9. In Paragraph 1, The above ion-conducting salt further comprises a metal halide, and The metal of the above metal halide comprises at least one selected from the group consisting of aluminum (Al), silver (Ag), gold (Au), platinum (Pt), palladium (Pd), bismuth (Bi), tin (Sn), and zinc (Zn). Positive active material.

10. In Paragraph 9, The above lithium salt is LiI, and the above metal halide is AlI3, Positive active material.

11. Anode active material according to paragraph 1; and containing solid electrolytes anode.

12. In Paragraph 11, The content of the positive electrode active material in the above positive electrode is 60% to 90% by weight, anode.

13. In Paragraph 11, The composite density of the above anode is 1.7 to 1.9, anode.

14. In Paragraph 11, The above solid electrolyte is Li 7-c M a PS 6-c X c It is an argyrodite-type sulfide-based solid electrolyte represented by (0≤a≤2, 0≤c≤2), and The above X is F, Br, Cl, 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), antimony (Sb), bismuth (Bi), or a combination thereof, anode.

15. In Paragraph 11, The above positive active material comprises a first particle and a second particle having an average particle size smaller than that of the first particle, and The average particle size of the first particle is 7 μm to 15 μm, and The average particle size of the second particle is 3 μm to 5 μm, anode.

16. In Paragraph 15, The mixing weight ratio of the first and second particles is 5:5 to 8:2, anode.

17. Anode pursuant to Paragraph 11; cathode; and A solid electrolyte layer between the anode and the cathode, Lithium-sulfur battery.

18. In Paragraph 17, The above solid electrolyte layer is Li 7-c M a PS 6-c X c It comprises an argyrodite-type sulfide-based solid electrolyte represented by (0≤a≤2, 0≤c≤2), and The above X is F, Br, Cl, 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), antimony (Sb), bismuth (Bi), or a combination thereof, Lithium-sulfur battery.

19. In Paragraph 17, The above cathode comprises a cathode current collector and a coating layer on the cathode current collector, and The above coating layer includes first and second particles, and The first particle above is amorphous carbon, crystalline carbon, porous carbon, or a combination thereof, and The second particle comprises gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, zinc, or a combination thereof. Lithium-sulfur battery.

20. In Paragraph 19, The above cathode further comprises a lithium metal layer between the cathode current collector and the coating layer, and The above lithium metal layer comprises lithium or a lithium alloy, Lithium-sulfur battery.

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