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

Abstract

The present invention relates to a positive electrode active material. More specifically, the positive electrode active material may comprise a first particle including lithium sulfide, a second particle including an ion-conductive material, and a third particle including a carbon-based material. The lithium sulfide may include at least one of Li2Sn (1≤n≤8, where n is an integer), and the ion-conductive material may include a halide-based first ion-conductive salt. Each of the first, second, and third particles has a primary particle form, and the first, second, and third particles are agglomerated to form a secondary particle, wherein the secondary particle may have a multi-contact structure in which the first, second, and third particles are interconnected.

Description

Positive active material, and lithium-sulfur battery including the same

[0001] This is about lithium-sulfur batteries.

[0002]

[0003] 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.

[0004] 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.

[0005] 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).

[0006]

[0007] The problem that the present invention aims to solve is to improve the ion and electron transport path through the interconnected structure of particles within the positive electrode active material.

[0008]

[0009] A positive electrode active material according to the concept of the present invention may comprise a first particle comprising lithium sulfide, a second particle comprising an ion-conducting material, and a third particle comprising 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 material may include a halide-based first lithium salt. Each of the first, second, and third particles has a primary particle shape, and the first, second, and third particles aggregate to form a secondary particle, and the secondary particle may include a multi-contact structure in which the first, second, and third particles are interconnected.

[0010] A positive electrode active material according to another concept of the present invention comprises a composite of a first particle that reversibly absorbs and releases lithium ions; a second particle having lithium ion conductivity; and a third particle having electron conductivity, wherein the composite comprises a plurality of plate-like structures, and the first, second, and third particles may constitute the plurality of plate-like structures.

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

[0012]

[0013] According to an embodiment of the present invention, the ionic conductivity and electronic conductivity of a sulfide-based cathode active material can be improved. Rate characteristics are improved and internal resistance is reduced, thereby improving lifespan characteristics and providing a high-capacity lithium-sulfur battery.

[0014]

[0015] FIG. 1 is a plan view of a lithium-sulfur battery according to embodiments of the present invention.

[0016] Figure 2 is a cross-sectional view along the line A-A' of Figure 1.

[0017] FIG. 3 is a cross-sectional view of a positive active material layer according to embodiments of the present invention.

[0018] Figures 4a and 4b show the multi-contact structure of the positive active material.

[0019] FIGS. 5a to 5d show positive active materials of one embodiment.

[0020] FIG. 6 is a cross-sectional view of a lithium-sulfur battery according to one embodiment of the present invention.

[0021] FIG. 7 is a cross-sectional view of a lithium-sulfur battery according to one embodiment of the present invention.

[0022] FIG. 8 is a cross-sectional view of a lithium-sulfur battery according to one embodiment of the present invention.

[0023] FIG. 9 is an SEM image of a positive electrode active material according to one embodiment of the present invention.

[0024] FIG. 10 is an SEM image of plate-shaped particles used in the manufacture of a positive electrode active material according to one embodiment of the present invention.

[0025] Figure 11 is an SEM image of a positive electrode active material according to a comparative example of the present invention.

[0026]

[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 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.

[0030] 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.

[0031] 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.

[0032] In this specification, “metal” includes both metals and metalloids such as silicon and germanium in an elemental or ionic state.

[0033] In this specification, “alloy” means a mixture of two or more metals.

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

[0035] In this specification, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0036] In this specification, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0037] In this specification, “lithiation” and “to lithiate” refer to the process of adding lithium to an electrode active material.

[0038] In this specification, “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.

[0040] In this specification, “discharge” and “discharge” refer to the process of removing electrochemical energy from a battery.

[0041] In this specification, “anode” and “cathode” refer to electrodes where electrochemical reduction and lithiation occur during the discharge process.

[0042] In this specification, “negative electrode” and “anode” refer to electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0043] In this specification, “lithium-sulfur battery” may be used interchangeably with “lithium-sulfur all-solid-state battery” or “all-solid-state battery.”

[0044]

[0045] lithium-sulfur battery (10)

[0046] 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.

[0047] 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).

[0048] positive electrode (100)

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] Cathode active material (CAC)

[0060] According to an embodiment of the present invention, the positive electrode active material (CAC) may include lithium sulfide, an ion-conducting material, and a carbon-based material. By including the above materials, the positive electrode 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 positive electrode active material (CAC) may include a composite of lithium sulfide, an ion-conducting material, and a carbon-based material.

[0061] 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 cathode active material (CAC), 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 cathode and the anode, while electrons simultaneously move through an external circuit to generate current. In a lithium-sulfur battery using a sulfide-based material as the cathode, since lithium sulfide can act as a lithium source, the provision of a lithium source at the anode can be omitted. That is, by including a lithium-containing sulfide in the cathode, a lithium-free structure can be introduced at the anode. Consequently, the energy density of the lithium-sulfur battery can be improved.

[0062] The ion-conducting material may improve the ion conductivity of the cathode active material (CAC). In the case of the aforementioned lithium sulfide, since its ion conductivity is very low in itself, the ion conductivity of the cathode active material (CAC) can be improved by including an ion-conducting material.

[0063] The ion-conducting material may include a first ion-conducting salt. The first ion-conducting salt may include a halide-based compound. The halide-based compound may include a compound of a metal element and a halogen group element. The first ion-conducting salt may include a lithium halide. In one embodiment, the first ion-conducting salt may include LiF, LiCl, LiBr, LiI, or a combination thereof. By including a halide-based lithium compound in the first ion-conducting salt, the ion conductivity of the cathode active material (CAC) can be improved.

[0064] The first ion-conducting salt may further include a metal halide. The metal of the metal halide may contain a metal other than lithium. 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 positive electrode active material. The metal halide may maintain the overall shape of the positive electrode active material and reduce interfacial resistance.

[0065] The ion-conducting material may include a chalcogenide-based second ion-conducting salt. The second ion-conducting salt may include a transition metal chalcogenide (TMC), which is a compound of a transition metal and a chalcogen group (Group 16) element. Additionally, the second ion-conducting salt may include a compound of a transition metal chalcogenide and lithium. In one embodiment, the second ion-conducting salt may include at least one selected from the group consisting of MoS2, VS2, LiMoS2, LiVS2, etc. By including a compound having a layered structure, the second ion-conducting salt can improve lithium ion conductivity. Furthermore, by having a crystalline form with a large contact area, connectivity with other particles can be improved during composite formation. As a result, the ion migration speed of the cathode active material (CAC) increases, thereby improving the performance of the electrode.

[0066] Carbon-based materials may mean having electronic conductivity. More specifically, carbon-based materials may include, without limitation, materials containing carbon atoms 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. The carbon-based precursor may include at least one selected from the group consisting of sucrose, glucose, pitch, chitosan, carbon black, carbon nanofibers, carbon nanotubes, graphite, polyvinyl alcohol, etc. By including a carbon-based material in the cathode active material (CAC), electronic conductivity can be improved and the cycle characteristics of the battery can be improved.

[0067] A positive active material (CAC) according to one embodiment of the present invention may comprise a composite of lithium sulfide, an ion-conducting material, and a carbon-based material. By forming the composite, the low ion conductivity and electron conductivity of lithium sulfide can be overcome, allowing it to be used as a positive active material for a lithium-sulfur battery. The composite according to these embodiments may have ductility. The composite may function as a buffer material within the positive active material layer (120). The composite may prevent the occurrence of defects due to volume changes in the positive active material layer (120).

[0068] The complex is Li2S-Li a X1 b -LiX3S2, Li2S-Li a X1 b -X3S2, Li2S-Li a X1 b -MX2 c -LiX3S2 or Li2S-Li a X1 b -MX2 c It may include a compound represented as -X3S2. a may be an integer between 1 and 5, b may be an integer between 1 and 5, and c may be an integer between 1 and 5. M may be selected from the group consisting of aluminum (Al), silver (Ag), gold (Au), platinum (Pt), palladium (Pd), bismuth (Bi), tin (Sn), and zinc (Zn). X1 and X2 may each be selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). X3 may be selected from the group consisting of molybdenum (Mo), vanadium (V), tungsten (W), titanium (Ti), iron (Fe), and niobium (Nb). A composite according to one embodiment may include a composite of Li2S, a lithium halide, and a metal halide. A composite according to one embodiment may include a composite of Li2S, a lithium halide, a metal halide, and a transition metal chalcogenide.

[0069] 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.

[0070] The content of the first ion-conducting salt in the positive electrode active material (CAC) may be 10 wt% to 50 wt%, 20 wt% to 50 wt%, or 30 wt% to 50 wt% of the total weight of the positive electrode active material (CAC). As an example, the first ion-conducting salt may include a lithium halide. The content of the lithium halide in the positive electrode active material (CAC) may be 5 wt% to 50 wt%, 10 wt% to 50 wt%, 20 wt% to 50 wt%, or 30 wt% to 50 wt% of the total weight of the positive electrode active material (CAC).

[0071] As another example, the first ion-conducting salt may further include a metal halide. The content of the metal halide in the positive electrode active material (CAC) may be 5 wt% to 30 wt%, or 5 wt% to 20 wt%, of the total weight of the positive electrode active material. When the metal halide is further included, the lithium halide and the metal halide may have a weight ratio of 1:3 to 3:1. By including an ion-conducting salt within the above range, excellent ion conductivity and ductility can be achieved.

[0072] The content of the second ion-conducting salt in the positive electrode active material (CAC) may be 5 wt% to 30 wt% or 5 wt% to 20 wt% of the total weight of the positive electrode active material. By including an ion-conducting salt within the above range, the electrochemical network can be improved.

[0073] 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.

[0074] Hereinafter, a positive electrode active material (CAC) according to an embodiment of the present invention will be described in more detail with reference to the drawings. Referring to FIGS. 4a and 4b, the positive electrode active material (CAC) of the present invention may include a multi-contact structure (MCS). A multi-contact structure (MCS) may mean that a plurality of particles constituting the positive electrode active material (CAC) are interconnected. For example, it may mean that a plurality of particles are in contact with one region.

[0075] In one embodiment, referring to FIGS. 4a and 4b, the positive active material (CAC) may include first, second, and third particles (SB1, SB2, SB3). The positive active material (CAC) may include a multi-contact structure (MCS) in which the first, second, and third particles (SB1, SB2, SB3) are interconnected. In this case, the multi-contact structure (MCS) may mean that the three particles form a network in which they are interconnected.

[0076] Individual particles do not exist individually but can be connected to other particles to form complex structures through interactions. In this context, the connection between particles can be understood as including physical contact, chemical bonding, or electrical connection. Multi-contact structures (MCS) can provide stability and functionality to cathode active materials (CAC) through interactions between particles. Multi-contact structures (MCS) can enhance the electrochemical and physical properties of cathode active materials (CAC).

[0077] For example, the first particle (SB1) may be connected to both the adjacent second particle (SB2) and the third particle (SB3). Alternatively, the case where the first particle (SB1) is connected to different first particles (SB1) and second particles (SB2) but not to the third particle (SB3) may not be included in the multi-contact structure.

[0078] Specifically, referring to FIG. 4a, the first particle (SB1) is connected to both the adjacent second particle (SB2) and the third particle (SB3). The second particle (SB2) is also connected to both the first particle (SB1) and the third particle (SB3). Likewise, it can be seen that the third particle (SB3) is also connected to the first particle (SB1) and the second particle (SB2).

[0079] In another embodiment, referring to FIG. 4b, the multi-contact structure (MCS) may be a structure in which particles of random shape are connected. For example, the cathode active material (CAC) may include a multi-contact structure (MCS) in which plate-like or rod-like particles are in contact. Plate-like particles have a large surface area, which allows for more contact with other particles through their surface. In the case of rod-like particles, their elongated shape in one direction allows for easy contact with other particles in various directions, making it easy to form a multi-contact structure (MCS).

[0080] The multi-contact structure (MCS) may include a structure in which particles of various shapes, such as spherical, elliptical, plate-like, or rod-like, come into contact, but is not limited to the shapes of the particles described above.

[0081] FIGS. 5a to 5d illustrate a positive electrode active material (CAC) according to embodiments of the present invention. The positive electrode active material (CAC) may be in the form of secondary particles in which a plurality of primary particles are aggregated. The average particle size of the secondary particles may be 3 μm to 15 μm. By including secondary particles, the composite density and stability of the positive electrode can be improved.

[0082] In one embodiment, the cathode active material (CAC) may comprise a complex of first, second, and third particles (SB1, SB2, SB3). Each of the first, second, and third particles (SB1, SB2, SB3) may have a primary particle form. The first, second, and third particles (SB1, SB2, SB3) in the form of primary particles may aggregate to form a secondary particle.

[0083] In this case, individual particles can interconnect to form a multi-contact structure (MCS). That is, the cathode active material (CAC) may be in the form of secondary particles configured such that primary particles form a multi-contact structure (MCS). Each primary particle can come into contact with other particles and aggregate to form a secondary particle.

[0084] Each primary particle can exist in various forms. For example, the cathode active material (CAC) may include primary particles such as spherical, elliptical, rod-shaped, plate-shaped, and needle-shaped, but this is merely illustrative.

[0085] In one embodiment, the primary particle may be plate-like. The positive electrode active material (CAC) may include a plate-like structure. That is, the plate-like structure may refer to a plate-like primary particle. By including a plate-like structure in the positive electrode active material (CAC), the number of contacts with other particles can be increased. Specifically, the plate-like structure can form the basic framework of the positive electrode active material (CAC) by having a relatively large contact area. Subsequently, other particles can be configured to contact adjacent to the plate-like structure to form a multi-contact structure.

[0086] The plate-shaped structure may be composed of different first, second, and third particles. The plate-shaped structure may include a first plate-shaped structure composed of a first particle (SB1), a second plate-shaped structure composed of a second particle (SB2), and / or a third plate-shaped structure composed of a third particle (SB3).

[0087] As shown in FIGS. 5a and 5b, the positive active material (CAC) may include a multi-contact structure (MCS) in which plate-like structures are interconnected. For example, in FIG. 5a, the plate-like structure may include a first particle (SB1). A plurality of plate-like structures may be interconnected with a second particle and a third particle to form a multi-contact structure (MCS).

[0088] The plate-shaped structure can form multiple contact structures (MCS). More specifically, referring to FIG. 5a, a plate-shaped third particle (SB3) can be configured so that one third particle (SB3) comes into contact with multiple first and second particles (SB1, SB2). As described above, the plate-shaped structure can serve to maximize inter-particle interactions and form a stable network within the composite.

[0089] Referring to FIGS. 5c and 5d, the positive active material (CAC) may be in the form of radial secondary particles. Specifically, a plurality of primary particles may be configured to extend in a radial direction from the center of the positive active material toward the surface. Each of the plurality of primary particles may be a plate-like structure. The plate-like structure may have a first length in the radial direction. The first length may be substantially equal to the radius of the positive active material. For example, the first length may be 1 μm to 8 μm. The plate-like structure may have a first width in a direction perpendicular to the radial direction. For example, the first width may be 100 nm to 300 nm, or 100 nm to 500 nm.

[0090] Some of the plate-like structures constituting the positive electrode active material (CAC) may be configured to extend in the radial direction to form radial secondary particles. As shown in FIG. 5c, the plate-like structures may generally form a radial structure, but may also include primary particles that are not arranged in the radial direction. As shown in FIG. 5d, it is also possible for all primary particles constituting the positive electrode active material (CAC) to be arranged in the radial direction.

[0091] By enabling the cathode active material (CAC) to contract and expand in the radial direction, the structural stability of the cathode active material (CAC) can be maintained even with volume changes resulting from repeated charging and discharging. Furthermore, as multiple particles constituting the cathode active material (CAC) are arranged to face outward, contact between each particle and the external environment can be maximized. In particular, the maximization of interaction with the external environment can improve the ionic and electronic conductivity of the cathode active material (CAC).

[0092] By including a multi-contact structure (MCS) of first, second, and third particles (SB1, SB2, SB3) in the positive electrode active material (CAC), the unique properties of each of the three particles can be combined to produce a synergistic effect. That is, the first, second, and third particles (SB1, SB2, SB3) do not each act independently within the positive electrode active material (CAC), but rather their respective properties can be optimized to improve the performance of the positive electrode active material (CAC).

[0093] The plurality of particles mentioned above may be exclusively selected from the lithium sulfide, ion-conducting material, and carbon-based material described above. This may mean that the plurality of particles are selected so as not to overlap with one another. For example, the first particle (SB1) may be composed of lithium sulfide, the second particle (SB2) may be composed of an ion-conducting material, and the third particle (SB3) may be composed of a carbon-based material.

[0094] Although the above description was based on three particles, namely the first, second, and third particles (SB1, SB2, SB3), it is not limited thereto, and it is obvious that any plurality of particles forming a multi-contact structure is included within the scope of the present invention. In one embodiment, the positive electrode active material may include a first particle composed of lithium sulfide, a second particle composed of a first ion-conducting salt, a third particle composed of a second ion-conducting salt, and a fourth particle composed of a carbon-based material.

[0095] The performance of the cathode active material (CAC) can be improved through a multi-contact structure (MCS). Lithium sulfide, which has low electronic and ionic conductivity, can be used as a cathode active material for high-capacity lithium-sulfur batteries by forming a multi-contact structure (MCS) in which it is interconnected with ion-conductive salts and / or carbon-based materials.

[0096] By including a multiple contact structure (MCS) in the positive electrode active material (CAC), the particles can be closely bonded to each other and formed uniformly. This prevents separation or aggregation between materials within the aforementioned composite, thereby improving consistency. The ionic conductivity and electronic conductivity of the positive electrode active material (CAC) can be improved. In this way, the electrochemical properties of the positive electrode active material (CAC) can be improved, while mechanical stability can be improved. Consequently, battery performance, such as performance characteristics and lifespan characteristics, can be improved.

[0097] Solid Electrolyte (SEP)

[0098] Referring again to FIG. 3, the positive active material layer (120) may further include a solid electrolyte (SEP) in addition to the positive active material (CAC). 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) to be described later.

[0099] 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).

[0100] 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).

[0101] 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).

[0102] 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.

[0103] Sulfide-based solid electrolytes may include, for example, an argyrodite-type solid electrolyte represented by the following chemical formula 1:

[0104] <Chemical Formula 1>

[0105] Li + 12-n-x A n+ X 2- 6-x Y - x

[0106] 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.

[0107] 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.

[0108] 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.

[0109] Challenge

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] Binder (BID)

[0120] 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.

[0121] 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).

[0122] cathode (200)

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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).

[0128] 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.

[0129] 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.

[0130] 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).

[0131] solid electrolyte layer (300)

[0132] 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).

[0133] 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).

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] 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.

[0140] 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).

[0141] 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).

[0142] 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).

[0143] 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).

[0144] 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).

[0145] 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).

[0146] 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).

[0147] 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).

[0148] 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).

[0149] 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.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] 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).

[0154] 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.

[0155] 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).

[0156] 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).

[0157] 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.

[0158] 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).

[0159] 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.

[0160] 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).

[0161] 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).

[0162] 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.

[0163] 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.

[0164] 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).

[0165] 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.

[0166] 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).

[0167] 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).

[0168] 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.

[0169] 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).

[0170] 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.

[0171] 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.

[0172] 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.

[0173] 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.

[0174] 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.

[0175] 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.

[0176] 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.

[0177] 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.

[0178]

[0179] 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.

[0180]

[0181] Preparation of positive electrode active material

[0182] Example 1

[0183] Lithium sulfate (Li2SO4) and the polysaccharide sucrose were mixed in distilled water and stirred at 200 rpm for 4 hours. Subsequently, the mixture was dried in an oven at 150°C for 8 hours to obtain a precipitate. The obtained precipitate was heat-treated to prepare Li2S particles having a plate-like crystal structure. Specifically, the heat treatment was performed by a carbon thermal reduction synthesis method at 800°C for 2 hours in an argon atmosphere. During heat treatment, the polysaccharide (sucrose) decomposes into monosaccharides, and acetic acid is produced through a dehydrogenation reaction. Pores are formed on the surface, and plate-like Li2S particles are formed upon high-temperature heat treatment. The shape of the Li2S can be controlled by the concentration of lithium sulfate, the drying temperature and speed, and the type and content of the carbon material. Along with the plate-like porous Li2S particles, a mixture of LiI and AlI3 as ion-conducting salts in a 1:1 weight ratio was prepared. Li2S, an ion-conducting salt, and carbon nanofibers (CNF) were mixed in a weight ratio of 4:2:1. The mixture was mechanically milled using a ball mill. The milling conditions were 500 rpm for 10 hours.

[0184] Example 2

[0185] LiMoS2 having a plate-like crystal structure was prepared. Li2S, LiI / AlI3, and carbon materials were mixed with plate-like LiMoS2, and then milled in a ball mill at 500 rpm for 10 hours to form a composite. The mixing weight ratio of the materials was Li2S: LiI / AlI3: LiMoS2: C = 4:1:1:1.

[0186] Example 3

[0187] Li2S particles having a plate-like crystal structure were prepared (see Example 1). A first ion-conducting salt was prepared by mixing LiI and AlI3 in a weight ratio of 1:1. A second ion-conducting salt, LiMoS2 having a plate-like crystal structure, was prepared. The plate-like Li2S, the first ion-conducting salt, the second ion-conducting salt, and carbon nanofibers (CNF) were mixed in a weight ratio of 4:1:1:1. The mixture was mechanically milled using a ball mill. The milling conditions were 500 rpm for 10 hours.

[0188] Comparative Example 1

[0189] Li2S and LiI / AlI3 were mixed in a weight ratio of 2:1. As an ion-conducting salt, a mixture of LiI and AlI3 in a weight ratio of 1:1 was used. Carbon nanofibers (CNF) were mixed into the above mixture.

[0190] The composition of the final mixture was Li2S: LiI / AlI3: C = 4: 2: 1. The mixture was mechanically milled using a ball mill. The first milling conditions were 25°C and 500 rpm for about 10 hours.

[0191] Li2S-LiI / AlI3-CNF was used as the positive active material.

[0192] Comparative Example 2

[0193] Li2S, LiI / AlI3, and LiMoS2 were mixed in a weight ratio of 4:1:1. A mixture of LiI and AlI3 in a weight ratio of 1:1 was used. Carbon nanofibers (CNF) were mixed into the above mixture.

[0194] The composition of the final mixture was Li2S: LiI / AlI3: LiMoS2: C = 4: 1: 1: 1. The mixture was mechanically milled using a ball mill. The first milling conditions were 25°C and 500 rpm for about 10 hours.

[0195] Li2S-LiI / AlI3-LiMoS2-CNF was used as the positive active material.

[0196] Comparative Example 3

[0197] A mixed solution was prepared by mixing Li2SO4, LiI / AlI3, and sucrose as a carbon-based additive with water. LiI and AlI3 were mixed in a weight ratio of 1:1. The weight ratio of the mixture in the solution was Li2SO4: LiI / AlI3: C = 4:2:1. The mixed solution was spray-dried to obtain a composite powder. The composite powder was heat-treated to obtain a spherical single-particle cathode active material.

[0198] The cathode active materials prepared according to the examples and comparative examples are shown in Table 1 below.

[0199] Active material composition (weight ratio) Plate-shaped particles Particle shape Example 1: Li2S: LiI / AlI3: C= 4: 2: 1 Li2S secondary particles Example 2: Li2S: LiI / AlI3: LiMoS2: C= 4: 1: 1: 1 LiMoS2 secondary particles Example 3: Li2S: LiI / AlI3: LiMoS2: C= 4: 1: 1: 1 Li2S / LiMoS2 secondary particles Comparative Example 1: Li2S: LiI / AlI3: C= 4: 2: 1 - Amorphous Comparative Example 2: Li2S: LiI / AlI3: LiMoS2: C= 4: 1: 1: 1 - Amorphous Comparative Example 3: Li2S: LiI / AlI3: C= 4: 2: 1 - Spherical single particles

[0200] Anode manufacturing

[0201] In addition to the positive electrode active material, a solid electrolyte of Li6PS5Cl, which is an azirodite-type crystal, was prepared, and PVDF-HFP was prepared as a binder. A positive electrode active material composition was prepared by mixing these materials in a weight ratio of positive electrode active material: solid electrolyte: binder = 80:19:1.

[0202] The above active material composition was coated on one side of an anode current collector made of aluminum foil with carbon coating on one side, and the anode was manufactured by applying pressure at 1 MPa and 130°C for about 10 minutes.

[0203] Cathode manufacturing

[0204] A SUS foil with a thickness of 10 μm was prepared as a negative electrode current collector. As negative electrode active materials, 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.

[0205] 4 g of a mixed powder, prepared by mixing carbon black (CB) and silver (Ag) 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, thereby preparing a cathode having a first cathode active material layer / cathode current collector structure. The thickness of the first cathode active material layer was approximately 15 μm. The area of ​​the first cathode active material layer and the cathode current collector were the same.

[0206] solid electrolyte layer fabrication

[0207] Li6PS5Cl solid electrolyte, an argyrodite-type crystal (D 50A mixture was prepared by adding 1.5 parts by weight of an acrylic binder to 98.5 parts by weight of a solid electrolyte (=3.0 μm, crystalline). 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. A solid electrolyte layer was prepared by vacuum drying the prepared laminate at 80 °C for 2 hours.

[0208] Manufacturing of lithium-sulfur batteries

[0209] A positive electrode, a solid electrolyte layer, and a negative electrode containing the positive active material according to the above examples and comparative examples were laminated. The prepared laminate was plate-pressed at approximately 85°C at a pressure of 500 MPa for 30 minutes. Through this pressurization treatment, the solid electrolyte layer is sintered, thereby improving battery characteristics.

[0210]

[0211] Evaluation Example 1: Analysis of Cathode Active Material Shape

[0212] After sampling the positive electrode active material, its morphology was analyzed by photographing it with a scanning electron microscope (SEM). Images of the positive electrode active materials of the examples are shown in Fig. 9. In addition, images of the plate-shaped Li2S particles used in the manufacture of the positive electrode active material are shown in Fig. 10. Furthermore, images of the positive electrode active material of the comparative example are shown in Fig. 11.

[0213] Referring to FIG. 9, it can be seen that plate-shaped structures exist within the anode in the case of the positive electrode active material according to the embodiments. In particular, as shown in FIG. 10, by having plate-shaped particles within the positive electrode active material, a structure that improves ion conductivity and electron conductivity can be formed.

[0214] In contrast, referring to FIG. 11, it can be seen that the positive active material according to the comparative example has an amorphous particle composition in a randomly dispersed form.

[0215]

[0216] Evaluation Example 2: Battery Performance Evaluation

[0217] 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.

[0218] 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.

[0219] For the second cycle discharge capacity, the specific capacity based on Li2S and the specific capacity based on the entire electrode were measured, respectively.

[0220] 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.

[0221] <Mathematical Formula 1>

[0222] Capacity Retention Rate[%] = [20th Cycle Discharge Capacity / 1st Cycle Discharge Capacity] × 100

[0223] The measurement results of the charge / discharge characteristics of the lithium-sulfur battery are shown in Table 2 below.

[0224] 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 189941198.297 Example 291942098.496 Example 391041698.195 Comparative Example 184938897.484 Comparative Example 283838397.286 Comparative Example 381837497.688

[0225] Referring to Table 2, it can be seen that the discharge capacity and capacity retention rate of the comparative examples are significantly lower than those of the examples. In the case of the comparative examples, it is determined that the performance was degraded because the particles constituting the positive electrode active material had a non-uniformly dispersed crystalline form, which accelerated the degradation of the particles due to repeated charging and discharging.

[0226] In contrast, the example shows high values ​​for both capacity retention rate and rate characteristics. This is because lithium ions and electrons can move smoothly through the formation of a uniform composite via a multi-contact structure.

[0227]

[0228] 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

1. A first particle comprising lithium sulfide, a second particle comprising an ion-conducting material, and a third particle comprising a carbon-based material, wherein The above lithium sulfide is Li2S n Includes at least one of (1≤n≤8, n is an integer), and The above ion-conducting material includes a halide-based first ion-conducting salt, and Each of the above first, second, and third particles has a primary particle form, and The first, second, and third particles aggregate to form secondary particles, and The above secondary particle comprises a multi-contact structure in which the first, second, and third particles are interconnected, Positive active material.

2. In Paragraph 1, The above ion-conducting material further comprises a second ion-conducting salt, and The above second ion-conducting salt comprises LiMoS2, Positive active material.

3. In Paragraph 2, The second particle containing the second ion-conducting salt has a plate-like structure, Positive active material.

4. In Paragraph 1, The first particle above has a plate-like structure, Positive active material.

5. In Paragraph 1, The above first ion-conducting salt comprises a lithium halide, and The above lithium halide comprises LiF, LiCl, LiBr, LiI, or a combination thereof, Positive active material.

6. In Paragraph 1, The above first 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.

7. A first particle that reversibly absorbs and releases lithium ions; A second particle having lithium ion conductivity; and It includes a complex of third particles having electronic conductivity, The above composite comprises a plurality of plate-like structures, and The first, second, and third particles above constitute the plurality of plate-like structures, Positive active material.

8. In Paragraph 7, The above positive active material is a secondary particle formed by the aggregation of the plurality of plate-like structures, Positive active material.

9. In Paragraph 8, Each of the above plurality of plate-like structures is configured to extend radially from its center toward its surface, Positive active material.

10. In Paragraph 8, The average particle size of the above secondary particles is 3 μm to 15 μm, Positive active material.

11. In Paragraph 7, The above plurality of plate-shaped structures are, A first plate-shaped structure comprising the first particle; and A second plate-shaped structure comprising the above second particle, Positive active material.

12. In Paragraph 7, The above plurality of plate-shaped structures are, The first, second, and third particles are configured to form a multi-contact structure in which they are interconnected. Positive active material.

13. In Paragraph 7, At least one of the plurality of plate-shaped structures comprises the first particle, and The first particle above contains Li2S, Positive active material.

14. In Paragraph 7, At least one of the plurality of plate-shaped structures includes the second particle, and The second particle above comprises LiMoS2, Positive active material.

15. Anode comprising a positive active material according to paragraph 1 or 8; Solid electrolyte layer; and including a cathode, Lithium-sulfur battery.

16. In Paragraph 15, 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.

17. In Paragraph 16, It further includes a lithium metal layer between the above-mentioned negative current collector and the above-mentioned coating layer, and The above lithium metal layer comprises lithium or a lithium alloy, Lithium-sulfur battery.

18. In Paragraph 15, 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 15, The above anode includes an anode current collector, and the anode current collector includes a base film and a metal layer disposed on at least one surface of the base film, and The above base film comprises a polymer, and the polymer comprises polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The metal layer comprises indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), or an alloy thereof. Lithium-sulfur battery.

20. In Paragraph 15, A further comprising an inert member disposed on one side of the above anode, Lithium-sulfur battery.

Images