Positive electrode active material for all-solid-state battery, positive electrode for all-solid-state battery comprising same, and all-solid-state battery

Abstract

The present invention relates to a positive electrode active material for an all-solid-state battery, a positive electrode for an all-solid-state battery comprising the same, and an all-solid-state battery. More specifically, since a coating layer comprising an oxysulfide-based solid electrolyte is formed on the positive electrode active material, a side reaction between the positive electrode active material and the solid electrolyte particles in the positive electrode is prevented, thereby exhibiting an effect of improving the output characteristics and the life characteristics of the all-solid-state battery.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2024-0149344, filed on October 29, 2024, and Korean Patent Application No. 10-2025-0159287, filed on October 29, 2025, and all disclosures in the documents of the Korean patent applications are incorporated herein by reference in their entirety. Technical Field

[0003] This invention relates to a positive electrode active material for all-solid-state batteries, a positive electrode for all-solid-state batteries containing the same, and an all-solid-state battery. Background Technology

[0004] From the perspectives of battery capacity, safety, output, miniaturization, and scaling, various batteries that can overcome the limitations of current lithium rechargeable batteries are being researched.

[0005] Representatively, academia and industry are conducting ongoing research on metal-air batteries, which have a much larger theoretical capacity than lithium-ion batteries; all-solid-state batteries, which do not pose an explosion risk; supercapacitors, which offer high output; NE batteries or RFB (redox flow batteries), which are miniaturized; and thin-film batteries, which are also miniaturized.

[0006] All-solid-state batteries refer to batteries that use a solid electrolyte instead of the liquid electrolyte used in existing lithium-ion batteries. Because no flammable solvents are used in the battery, there is no risk of fire or explosion due to the decomposition reaction of conventional electrolyte solutions, thus greatly improving safety. Furthermore, in the field of all-solid-state batteries, the development of sulfide-based all-solid-state batteries, which theoretically can achieve high energy densities of over 900 Wh / L while also possessing high ionic conductivity of the solid electrolyte, continues. At this point, sulfide-based all-solid-state batteries refer to all-solid-state batteries that contain a sulfide-based solid electrolyte.

[0007] In all-solid-state battery systems, lithium-ion conduction, which is achieved by the liquid electrolyte contained in existing lithium-ion batteries (LIBs), cannot be realized. Therefore, when manufacturing the cathode for sulfide-based all-solid-state batteries, it is necessary to add sulfide-based solid electrolyte particles with small particle sizes into the cathode to increase the contact interface between the cathode active material and the sulfide-based solid electrolyte particles, thereby increasing the ionic conductivity of lithium ions.

[0008] However, even when the positive electrode active material and sulfide-based solid electrolyte particles are only in physical contact with each other due to their energy level differences, chemical reactions occur at the interface. Resistive materials can be formed through chemical reactions. Due to these resistive materials, the initial capacity and long-life characteristics of all-solid-state batteries may be reduced during operation.

[0009] Furthermore, during the charging and discharging process, an electrochemical reaction occurs at the interface between the positive electrode active material and the sulfide solid electrolyte particles, which not only consumes the active lithium but may also increase the resistance.

[0010] Therefore, there is a need for technological development that can improve the output and lifespan characteristics of all-solid-state batteries by preventing side reactions at the interface between the positive electrode active material and sulfide-based solid electrolyte particles.

[0011] [Existing technical documents]

[0012] (Patent Document 1) Korean Patent Application Publication No. 10-2023-0031939 Summary of the Invention

[0013] [Technical Issues]

[0014] The inventors have conducted extensive research to address the aforementioned problems, and the results confirm that when a coating containing an oxysulfide-type solid electrolyte is formed on the surface of the positive electrode active material, side reactions between the positive electrode active material and the solid electrolyte particles in the positive electrode can be prevented.

[0015] Therefore, the object of the present invention is to provide a positive electrode active material for all-solid-state batteries having a coating thereon containing an oxysulfide-type solid electrolyte.

[0016] Another object of the present invention is to provide a positive electrode for an all-solid-state battery, comprising a positive electrode active material having a coating thereon containing an oxysulfide-based solid electrolyte.

[0017] Another object of the present invention is to provide an all-solid-state battery comprising a positive electrode containing a positive electrode active material having a coating thereon containing an oxysulfide-based solid electrolyte.

[0018] [Technical Solution]

[0019] To achieve the above objectives, the present invention provides a positive electrode active material for all-solid-state batteries, comprising: core particles; and a coating, the coating being located on the surface of the core particles. The coating contains an oxysulfide-based solid electrolyte.

[0020] In one embodiment of the present invention, there is provided a positive electrode active material for an all-solid-state battery, wherein the oxysulfide-based solid electrolyte comprises oxygen (O) and sulfur (S) in a weight ratio of 0.02:1 to 0.1:1.

[0021] In one embodiment of the present invention, there is provided a positive electrode active material for an all-solid-state battery, wherein the oxysulfide-based solid electrolyte is represented by the following Chemical Formula 1: <Chemical Formula 1> Li (7-x) PS (6-x-y) O y Ha x , wherein in Chemical Formula 1, Ha is Cl, Br or I, 0 < x < 1.6 and 0.1 < y < 1.

[0022] In one embodiment of the present invention, there is provided a positive electrode active material for an all-solid-state battery, wherein the oxysulfide-based solid electrolyte has an argyrodite-type crystal structure.

[0023] In one embodiment of the present invention, there is provided a positive electrode active material for an all-solid-state battery, wherein based on the total weight of the positive electrode active material, the content of the oxysulfide-based solid electrolyte is 0.1 wt% to 2 wt%.

[0024] In one embodiment of the present invention, there is provided a positive electrode active material for an all-solid-state battery, wherein the coating further comprises a lithium metal oxide.

[0025] In one embodiment of the present invention, there is provided a positive electrode active material for an all-solid-state battery, wherein the coating comprises a first coating containing a lithium metal oxide and a second coating containing an oxysulfide-based solid electrolyte.

[0026] In one embodiment of the present invention, there is provided a positive electrode active material for an all-solid-state battery, wherein the residual lithium content in the positive electrode active material is 3000 ppm or more.

[0027] In one embodiment of the present invention, there is provided a positive electrode active material for an all-solid-state battery, wherein the core particles are in the form of multi-particles formed by aggregation of a plurality of single particles of a positive electrode active material.

[0028] In one embodiment of the present invention, there is provided a positive electrode active material for an all-solid-state battery, wherein the plurality of single particles are aggregated in an oriented manner.

[0029] In one embodiment of the present invention, there is provided a positive electrode active material for an all-solid-state battery, wherein the aspect ratio of the single particles is 0.05:1 to 0.5:1.

[0030] In one embodiment of the present invention, a positive electrode active material for all-solid-state batteries is provided, wherein the particle size (D50) of the positive electrode active material is 3.3 μm to 6.3 μm.

[0031] In one embodiment of the present invention, a positive electrode for an all-solid-state battery is provided, comprising: the positive electrode active material, solid electrolyte particles, a binder, and a conductive material.

[0032] In one embodiment of the present invention, an all-solid-state battery is provided, which includes the positive electrode.

[0033] [Beneficial Effects]

[0034] According to the present invention, since a coating containing an oxysulfide-based solid electrolyte is formed on the surface of the positive electrode active material for all-solid-state batteries, side reactions at the interface between the positive electrode active material and the solid electrolyte particles in the positive electrode are prevented, thereby improving the output characteristics and lifespan characteristics of all-solid-state batteries. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of a positive electrode active material for an all-solid-state battery according to one embodiment of the present invention. Detailed Implementation

[0036] The invention will be described in more detail below to aid in understanding it.

[0037] The terms or words used in this specification and claims should not be construed as limited to their ordinary or dictionary meanings, but should be interpreted as meanings and concepts consistent with the technical concept of the invention, based on the principle that the inventor may appropriately define the concepts of the terms in order to best describe his or her invention.

[0038] As used in this specification, the term "positive electrode active material" refers to an active material that generates electrical energy at the positive electrode, and specifically to a material that contains lithium ions and provides lithium ions to the negative electrode during charging. That is, "positive electrode active material" refers to commonly used positive electrode active materials; however, in this specification, because positive electrode active materials have a structure including core particles and a coating formed on the surface of the core particles, the active material contained within the core particles is referred to as positive electrode active material to distinguish it from other positive electrode active materials.

[0039] Positive electrode active materials for all-solid-state batteries

[0040] This invention relates to a positive electrode active material for all-solid-state batteries.

[0041] The positive electrode active material for an all-solid-state battery of the present invention comprises: core particles; and a coating provided on the surface of the core particles, wherein the coating comprises an oxysulfide-based solid electrolyte.

[0042] In one embodiment, the core particles may comprise a positive electrode active material.

[0043] In one embodiment, a coating containing an oxysulfide-based solid electrolyte is formed on the surface of the core particle. Due to the coating, side reactions between the positive electrode active material and solid electrolyte particles in the positive electrode, particularly in the positive electrode active material layer, can be prevented. Specifically, at the interface between the positive electrode active material and the solid electrolyte particles, the solid electrolyte particles are in contact with the coating formed on the positive electrode active material. When the core particles containing the positive electrode active material and the solid electrolyte particles are in direct contact with each other, side reactions such as chemical and / or electrochemical reactions may occur due to the difference in energy levels. Interface deterioration may occur due to the side reactions, and battery performance may be reduced. However, when the coating containing the oxysulfide-based solid electrolyte and the solid electrolyte particles are in direct contact with each other, side reactions between the core particles containing the positive electrode active material and the solid electrolyte particles are prevented, thereby improving the output characteristics and life characteristics of the all-solid-state battery.

[0044] In one embodiment of the present invention, the oxysulfide-based solid electrolyte is a solid electrolyte containing oxygen (O) and sulfur (S), and may contain oxygen (O) and sulfur (S) in a weight ratio of 0.02:1 to 0.1:1.

[0045] When the weight ratio of oxygen to sulfur is less than 0.02:1 (=0.02 / 1), the content of oxygen becomes low and may be insufficient to function as an oxysulfide, and when the weight ratio of oxygen to sulfur exceeds 0.1:1 (=0.1 / 1), the content of oxygen becomes large and oxides may precipitate as impurities during the synthesis of the solid electrolyte. Specifically, the weight ratio of oxygen to sulfur may be 0.02:1 or more, 0.03:1 or more, 0.04:1 or more, 0.05:1 or more, 0.06:1 or more, or 0.07:1 or more, and may be 0.1:1 or less, 0.09:1 or less, or 0.08:1 or less.

[0046] In one embodiment of the present invention, the oxysulfide-based solid electrolyte may be represented by the following Chemical Formula 1: <Chemical Formula 1> Li (7-x) PS (6-x-y) O y Ha x , In Chemical Formula 1, Ha is Cl, Br or I, 0<x <1.6 and 0.1<y <1.

[0047] In one embodiment of the present invention, the oxysulfide solid electrolyte may have an argyrodite-type crystal structure.

[0048] The argyrodite-type crystal structure refers to a face-centered cubic (FCC) crystal structure. In the argyrodite-type crystal structure, lithium ions can move rapidly, thereby improving lithium ion conductivity.

[0049] In addition, the oxysulfide solid electrolyte having an argyrodite-type crystal structure has the properties of easy synthesis and good ionic conductivity, but the oxysulfide solid electrolyte is not limited thereto, and oxysulfide solid electrolytes with various crystal structures suitable for all-solid-state batteries may be used.

[0050] In one embodiment of the present invention, based on the total weight of the positive electrode active material, the content of the oxysulfide solid electrolyte may be 0.1 wt% to 2 wt%.

[0051] When the content of the oxysulfide solid electrolyte is less than 0.1 wt%, the effect of preventing side reactions between the positive electrode active material and solid electrolyte particles in the positive electrode active material layer may be reduced, while when it exceeds 2 wt%, it may act as a resistance in the battery. Specifically, the content of the oxysulfide solid electrolyte may be 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, 0.4 wt% or more, 0.5 wt% or more, 0.6 wt% or more, 0.7 wt% or more, 0.8 wt% or more, 0.9 wt% or more, or 1 wt% or more, and may be 2 wt% or less, 1.9 wt% or less, 1.8 wt% or less, 1.7 wt% or less, 1.6 wt% or less, 1.5 wt% or less, 1.4 wt% or less, 1.3 wt% or less, 1.2 wt% or less, or 1.1 wt% or less.

[0052] In one embodiment of the present invention, the coating layer may further comprise a lithium metal oxide.

[0053] The lithium metal oxide may be represented by the following chemical formula 2: <Chemical Formula 2> L x MO y In Chemical Formula 2, M is C, B, Zr, Nb, Ti, Al, W, P or Fe, 0 < x < 5 and 0 < y < 4.

[0054] When the coating layer contains a lithium metal oxide, the coating layer may have a double-layer structure, the double-layer structure comprising a first coating containing the lithium metal oxide and a second coating containing the oxysulfide solid electrolyte. Preferably, the lithium metal oxide may be LiNbO3.

[0055] In one embodiment of the present invention, the residual lithium content (Y) in the positive electrode active material can be 3000 ppm or more. The residual lithium comes from the core particles and can be a byproduct of the synthesis of the core particles. The residual lithium content is based on the total amount of positive electrode active material after removing the coating containing the oxysulfide-type solid electrolyte.

[0056] When the residual lithium content (Y) is less than 3000 ppm, the overvoltage during the initialization process may increase. Specifically, the lithium content (Y) can be above 3000 ppm, above 4000 ppm, above 5000 ppm, above 6000 ppm, above 7000 ppm, above 8000 ppm, above 9000 ppm, above 10000 ppm, above 11000 ppm, above 12000 ppm, above 13000 ppm, above 14000 ppm, or above 15000 ppm. There is no particular upper limit to the lithium content (Y), but considering the degree to which lithium conduction occurs at a suitable rate at the interface between the positive electrode active material and the solid electrolyte particles contained in the positive electrode active material layer, the content (Y) can be below 25,000 ppm, specifically, below 25,000 ppm, below 24,000 ppm, below 23,000 ppm, below 22,000 ppm, below 21,000 ppm, below 20,000 ppm, below 19,000 ppm, below 18,000 ppm, below 17,000 ppm, or below 16,000 ppm.

[0057] In one embodiment of the invention, the core particle can be in the form of a multi-particle aggregate formed by the aggregation of multiple single particles of the positive electrode active material. When the positive electrode active material is in the form of a multi-particle aggregate, the movement of lithium at the interface may be more stable because the specific surface area of ​​the same particle size is larger compared to the case of a single particle.

[0058] In one embodiment, the positive electrode active material may comprise a lithium composite metal oxide capable of reversibly inserting and de-intercalating lithium.

[0059] The lithium complex metal oxide may contain lithium with nickel, cobalt and metal element M (where M is at least one selected from the group consisting of Mn, Al, W, Cu, Fe, V, Cr, Ti, Zr, Zn, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B and Mo).

[0060] Specifically, lithium complex metal oxides can be represented by the following chemical formula 3: <Chemical Formula 3> Li α Ni x Coy M z O₂ In Chemical Formula 3, M is at least one selected from the group consisting of Mn, Al, W, Cu, Fe, V, Cr, Ti, Zr, Zn, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B and Mo, α, x, y and z are each independently the atomic fractions of the elements, and satisfy 0.9≤α≤1.05, 0<x<1, 0<y<1, 0<z<1, x+y+z=1, more specifically, 0.9≤α≤1.05, 0.6≤x<1, 0<y≤0.4, 0<z≤0.4, x+y+z=1, wherein α is a value in the uncharged state.

[0061] More specifically, the core particle may be a lithium composite metal oxide with high nickel content, such as LiNi 0.6 Co 0.2 Mn 0.2 O₂, LiNi 0.8 Mn 0.1 Co 0.1 O₂, LiNi 0.6 Co 0.2 Mn 0.2 W 0.02 O₂ or LiNi 0.85 Co 0.09 Mn 0.045 Al 0.015 O₂, and at least one or more of them may be used.

[0062] In one embodiment, based on the total weight of the positive electrode active material, the content of the core particles may be 97 to 99.9 wt%. When the content of the core particles is less than 97 wt%, the battery performance may be reduced; when the content of the core particles exceeds 99.9 wt%, the content of the coating layer is relatively reduced, and side reactions with the solid electrolyte may occur. Specifically, the content of the core particles may be 97 wt% or more, 97.5 wt% or more, 98 wt% or more, 98.5 wt% or more, or 99 wt% or more, and may be 99.9 wt% or less, 99.8 wt% or less, 99.7 wt% or less, 99.6 wt% or less, or 99.5 wt% or less.

[0063] In one embodiment of the present invention, a plurality of single particles may be aggregated in an orientation.

[0064] Orientation refers to an arrangement form in a certain direction. For example, a plurality of single particles may be aggregated in radial orientation, vertical orientation or horizontal orientation, but the present invention is not limited thereto, as long as the plurality of single particles are arranged in a certain direction.

[0065] Compared to multiparticles formed by random aggregation of single particles, multiparticles formed by oriented aggregation exhibit the following effect: the movement of lithium within the positive electrode active material is smooth.

[0066] The orientation of the core particles can be induced by adding dopant elements during synthesis. That is, orientation can be induced when synthesized by adding an appropriate amount of dopant element to the positive electrode active material constituting the core particles. Dopant elements can include one or more selected from the group consisting of B, Ta, and W. Dopant elements can be included to a degree capable of inducing core particle orientation. For example, the content of the dopant element can be from 0.01 to 3 wt% based on the total weight of the core particles. Specifically, the content of the dopant element can be 0.01 wt% or more, 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, 0.4 wt% or more, 0.5 wt% or more, or 1 wt% or more, and can be less than 3 wt%, less than 2.5 wt%, less than 2.0 wt%, or less than 1.5 wt%.

[0067] In one embodiment of the invention, a single particle may be in the form of a rod. However, the form of the single particle is not particularly limited, as long as it can be formed into a multi-particle form by aggregating the single particles together.

[0068] The aspect ratio of a single particle's cross-section, i.e., the ratio of its minor axis to its major axis, can be 0.5:1 or less. The longer the major axis of a single particle is relative to its minor axis, the more favorable it is for orientation formation. For example, the ratio of the minor axis to the major axis can be 0.5:1 or less, 0.4:1 or less, 0.3:1 or less, 0.2:1 or less, or 0.1:1 or less. Alternatively, the ratio of the minor axis to the major axis can be 0.05:1 or greater.

[0069] In one embodiment of the present invention, the particle size (D50) of the positive electrode active material can be from 3.3 μm to 6.3 μm.

[0070] When the particle size (D50) of the positive electrode active material is less than 3.3 μm, the positive electrode active material may aggregate during the positive electrode production process, or the electrode plate density may decrease. When it exceeds 6.3 μm, the lithium mobility may decrease. Specifically, the particle size (D50) of the positive electrode active material can be 3.3 μm or larger, 3.4 μm or larger, 3.5 μm or larger, 3.6 μm or larger, 3.7 μm or larger, 3.8 μm or larger, 3.9 μm or larger, or 4 μm or larger, and can be less than 6.3 μm, less than 6.2 μm, less than 6.1 μm, less than 6 μm, less than 5.9 μm, less than 5.8 μm, less than 5.7 μm, less than 5.6 μm, less than 5.5 μm, less than 5.4 μm, less than 5.3 μm, less than 5.2 μm, less than 5.1 μm, or less than 5 μm.

[0071] The particle size (D50) of the positive electrode active material can be defined as the particle size at 50% of the particle size distribution. The particle size (D50) of the positive electrode active material particles can be measured using, for example, laser diffraction methods. More specifically, after dispersing the positive electrode active material particles in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measurement device (e.g., Microtrac MT3000), irradiated with ultrasound at approximately 28 kHz with an output of 60 W, and the particle size (D50) at 50% of the particle size distribution in the measurement device is calculated.

[0072] In one embodiment of the present invention, the coating thickness can be from 1 nm to 50 nm. When the coating thickness is less than 1 nm, the effect of preventing side reactions between the core particles containing the positive electrode active material and the solid electrolyte particles may be reduced, while when the coating thickness exceeds 50 nm, the coating thickness becomes too thick and may act as a resistor. Specifically, the coating thickness can be 1 nm or more, 5 nm or more, 10 nm or more, 15 nm or more, 20 nm or more, or 25 nm or more, and can be less than 50 nm, less than 45 nm, less than 40 nm, less than 35 nm, or less than 30 nm.

[0073] In one embodiment of the present invention, the coating content can be from 0.1% to 3% by weight, based on the total weight of the positive electrode active material. When the coating content is less than 0.1% by weight, side reactions may occur between the positive electrode active material and the solid electrolyte particles. When the coating content exceeds 3% by weight, the coating content is too high and may act as a resistor. Specifically, the coating content can be 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, or 0.5% or more, and can be less than 3% by weight, less than 2.5% by weight, less than 2% by weight, less than 1.5% by weight, or less than 1% by weight.

[0074] Figure 1 This is a schematic diagram of a positive electrode active material for an all-solid-state battery according to one embodiment of the present invention.

[0075] Reference Figure 1 In the positive electrode active material 10, a coating 12 is formed on the surface of the core particle 11.

[0076] The core particle 11 can be formed into a multi-particle form by the oriented aggregation of single particles P1 of the positive electrode active material. For example, the single particle P1 can be in the form of a rod and can be radially oriented to form a multi-particle form.

[0077] In addition, the coating 12 contains an oxysulfide-type solid electrolyte, so that the surface of the core particle 11 containing the positive electrode active material can be coated with an oxysulfide-type solid electrolyte.

[0078] Additionally, when the coating 12 includes lithium metal oxide 12a, the lithium metal oxide 12a may be included adjacent to the core particle 11. The lithium metal oxide 12a may be included in a form that covers the entire surface of the core particle 11, or it may be included in a form that is adjacent to a portion of the surface of the core particle 11.

[0079] Manufacturing method of positive electrode active material for all-solid-state batteries

[0080] This invention also relates to a method for manufacturing a positive electrode active material for all-solid-state batteries. The types, physical properties, and contents of the core particles, oxysulfide-based solid electrolyte, and lithium metal oxide materials used in manufacturing the positive electrode active material for all-solid-state batteries are as described above. The orientation of the core particles can be induced by adding dopant elements during the synthesis of the positive electrode active material contained in the core particles. That is, orientation can be induced when synthesized by adding an appropriate amount of dopant elements to the positive electrode active material constituting the core particles. The dopant elements may include one or more selected from the group consisting of B, Ta, and W.

[0081] A method for manufacturing a positive electrode active material for an all-solid-state battery according to one embodiment of the present invention may include the step of coating a sulfide-based solid electrolyte onto the surface of a core particle. The manufactured positive electrode active material comprises a core particle and a coating, wherein the coating comprises a sulfide-based solid electrolyte.

[0082] In one embodiment of the invention, the coating containing an oxysulfide-based solid electrolyte can be formed by dry coating. Furthermore, a heat treatment can be performed after the dry coating process.

[0083] Dry coating is not particularly limited, as long as it is a coating method that does not use solvents. For example, dry coating can be a method of applying oxygen sulfide-based solid electrolytes to the surface of nuclear particles using mechanical force. Dry coating can be performed by mechanical grinding. Mechanical grinding is not particularly limited, as long as it is a grinding method commonly used in the art, such as ball milling, mechanical fusion grinding, vibratory grinding, planetary grinding, pulverized grinding, or disc grinding.

[0084] Furthermore, after dry coating, an additional heat treatment can be performed for firing. This heat treatment allows the coating containing the oxysulfide-based solid electrolyte to be more firmly retained. The heat treatment temperature can be appropriately selected within a certain temperature range to ensure a more robust coating and retention without denaturing the positive electrode active material contained in the core particles or the oxysulfide-based solid electrolyte contained in the coating. For example, the heat treatment temperature can be from 100°C to 300°C. When the heat treatment temperature is below 100°C, the bonding force between the core particles and the coating may be insufficient, while when the heat treatment temperature exceeds 300°C, the oxysulfide-based solid electrolyte components contained in the coating may diffuse into the core particles. Specifically, the heat treatment temperature can be above 100°C, above 110°C, above 120°C, above 130°C, above 140°C, above 150°C, above 160°C, above 170°C, above 180°C, or above 190°C, and can be below 300°C, below 290°C, below 280°C, below 270°C, below 260°C, below 250°C, below 240°C, below 230°C, below 220°C, or below 210°C.

[0085] Another embodiment of the present invention provides a method for manufacturing a positive electrode active material for an all-solid-state battery, comprising: (S1) mixing lithium metal oxide in an alcohol-based solvent to form a first mixed solution for forming a coating; (S2) mixing core particles with the first mixed solution to form a second mixed solution for forming a positive electrode active material; (S3) filtering and compressing the second mixed solution; (S4) calcining the product obtained in step (S3) to form a coating containing lithium metal oxide on the surface of the core particles; and (S5) mixing an oxysulfide-based solid electrolyte with the product obtained in step (S4) and calcining to form a coating containing an oxysulfide-based solid electrolyte.

[0086] In one embodiment of the invention, in step (S1), the first mixed solution for forming the coating can be formed by mixing lithium metal oxide in an alcohol-based solvent.

[0087] The raw materials used to synthesize lithium metal oxides can be mixed in an alcohol-based solvent, or the lithium metal oxides themselves can be mixed in an alcohol-based solvent.

[0088] Alcohol-based solvents may comprise one or more alcohol compounds having 1 to 4 carbon atoms. Specifically, alcohol-based solvents may include one or more selected from the group consisting of acetone, methanol, ethanol, isopropanol, butanol, octanol, and allyl alcohol. When considering processability during the manufacturing process of the positive electrode active material, the alcohol-based solvent may be ethanol.

[0089] In one embodiment of the present invention, in step (S2), the second mixed solution for forming the positive electrode active material can be formed by mixing the core particles with the first mixed solution.

[0090] The concentration of the second mixed solution, based on solids content, can be from 30% to 70% by weight. Here, solids content refers to the weight of lithium metal oxide and core particles excluding the solvent. The solids content can be appropriately adjusted to take into account the extent to which a coating containing lithium metal oxide can be formed. For example, the solids content can be 30% or more, 35% or more, 40% or more, or 45% or more, and can be less than 70% by weight, less than 65% by weight, less than 60% by weight, or less than 55% by weight.

[0091] In addition, the weight ratio of lithium metal oxide to core particles can be 0.1 to 1: 99 to 99.9, 0.2 to 0.8: 99.2 to 99.8, or 0.3 to 0.7: 99.3 to 99.7.

[0092] In one embodiment of the present invention, in step (S3), the second mixed solution may be filtered and compressed.

[0093] Filtration compression can be a process of removing alcohol-based solvents by pressurizing a second mixed solution used to form the positive electrode active material at 0.3 to 1 MPa. For example, pressurization can be performed by blowing air, and the alcohol-based solvent can be removed by pressurizing with blowing air for 5 to 15 minutes. Alternatively, filtration compression can use a pressurized filtration device to remove alcohol-based solvents from a second mixed solution containing coating raw materials and core particles. There are no particular limitations on the pressurized filtration device, as long as it is generally used in the relevant technical field and is a device capable of effectively removing alcohol-based solvents.

[0094] Due to filtration and compression, the alcohol solvent can be removed from the second mixed solution in a short time, thus minimizing the time the core particles are exposed to the liquid.

[0095] The filtered and compressed product obtained after filtration and compression is in the form of lithium metal oxide adsorbed on the surface of the core particles, and a small amount of alcohol-based solvent may be present in the filtered and compressed product. The filtered and compressed product can be referred to as a positive electrode active material having a coating formed on the surface of the core particles.

[0096] In one embodiment of the present invention, in step (S4), by firing the product obtained in step (S3), a coating containing lithium metal oxide can be formed on the surface of the core particles.

[0097] Alcohol-based solvents can be completely removed by drying.

[0098] There are no particular restrictions on the drying temperature, as long as it is sufficient to remove the alcohol-based solvent. For example, drying can be carried out at temperatures between 80°C and 120°C. When the drying temperature is below 80°C, the alcohol-based solvent may not be completely removed, while when it exceeds 120°C, the properties of the raw materials may be altered, and the performance of the manufactured positive electrode active material may deteriorate. Specifically, the drying temperature can be above 80°C, above 85°C, or above 90°C, and can be below 120°C, below 115°C, or below 110°C.

[0099] The dried product obtained after drying is in a state where lithium metal oxide is adsorbed on the surface of the core particles.

[0100] In one embodiment of the present invention, in step (S5), a coating containing an oxygen sulfide solid electrolyte can be formed by dry coating an oxygen sulfide solid electrolyte onto the product obtained in step (S4). The dry coating method is as described above.

[0101] Positive electrode for all-solid-state batteries

[0102] The present invention also relates to a positive electrode for an all-solid-state battery.

[0103] The positive electrode for an all-solid-state battery of the present invention comprises: a positive electrode current collector; and a positive electrode active material layer formed on one surface of the positive electrode current collector. The positive electrode active material layer comprises the positive electrode active material, solid electrolyte particles, binder, and conductive material as described above. The solid electrolyte particles may be sulfide-based solid electrolyte particles.

[0104] The positive electrode active material of one embodiment of the present invention is as described above.

[0105] Furthermore, based on the total weight of the positive electrode active material layer, the content of the positive electrode active material can range from 50% to 95% by weight. Specifically, the content of the positive electrode active material can be above 50% by weight, above 55% by weight, or above 60% by weight, and can be below 95% by weight, below 90% by weight, below 85% by weight, below 80% by weight, below 75% by weight, or below 70% by weight. When the content of the positive electrode active material is less than 50% by weight, the energy density may decrease, while when it exceeds 95% by weight, the mass transfer resistance may increase.

[0106] In one embodiment of the present invention, the sulfide-based solid electrolyte is a solid electrolyte containing sulfur and can improve ion conductivity.

[0107] Sulfide solid electrolytes may include one or more selected from the group consisting of LiPSX (X = Cl, Br, or I), LiGePS, and LiPS. However, sulfide solid electrolytes are not limited to this, and commonly used sulfide solid electrolytes in the art can be widely used.

[0108] Furthermore, the particle size (D50) of the sulfide-based solid electrolyte can be in the form of particles ranging from 0.1 μm to 1.5 μm. Specifically, the particle size (D50) of the sulfide-based solid electrolyte can be greater than 0.1 μm, greater than 0.3 μm, or greater than 0.5 μm, and can be less than 1.5 μm, less than 1.2 μm, less than 1.0 μm, or less than 0.9 μm. When the particle size (D50) of the sulfide-based solid electrolyte is less than 0.1 μm, the ultrafine sulfide-based solid electrolyte particles may not be sufficiently dispersed in the positive electrode active material layer and may aggregate. When it exceeds 1.5 μm, dispersion may be somewhat easier, but the contact area with the positive electrode active material particles may decrease and the positive electrode porosity may increase.

[0109] Furthermore, based on the total weight of the positive electrode active material layer, the content of sulfide-based solid electrolyte can range from 5% to 50% by weight. Specifically, the content of sulfide-based solid electrolyte can be 5% or more, 8% or more, 10% or more, 13% or more, 15% or more, 18% or more, or 20% or more, and can be less than 50% by weight, less than 45% by weight, less than 40% by weight, less than 35% by weight, less than 30% by weight, or less than 25% by weight. When the content of sulfide-based solid electrolyte is less than 10% by weight, ionic conductivity may decrease, while when it exceeds 50% by weight, the content of positive electrode active material and conductive material relatively decreases, and battery performance may decrease.

[0110] In one embodiment of the invention, an adhesive may be included to assist in the bonding between the materials contained in the positive electrode active material layer and the bonding between the positive electrode active material layer and the positive electrode current collector.

[0111] The adhesive may comprise one or more of the following groups: polytetrafluoroethylene (PTFE), polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepoxychloropropane, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropylene. Preferably, the adhesive may comprise polytetrafluoroethylene (PTFE).

[0112] Furthermore, based on the total weight of the positive electrode active material layer, the binder content can range from 0.1% to 3% by weight. Specifically, the binder content can be 0.1% or more, 0.5% or more, or 0.8% or more, and can be less than 1.5% by weight, less than 2% by weight, or less than 3% by weight. When the binder content is less than 0.1% by weight, the effect of improving the bonding force between the materials contained in the positive electrode active material layer is not significant, and the positive electrode active material layer may not form properly. Furthermore, when the binder content exceeds 3% by weight, ionic conductivity or electronic conductivity may decrease.

[0113] In one embodiment of the invention, the conductive material can form a path capable of conducting electrons to improve conductivity.

[0114] The conductive material can be a linear conductive material, and the linear conductive material can be one or more selected from the group consisting of carbon nanotubes (CNTs) and carbon nanofibers (CNFs). Linear conductive materials can improve conductivity due to their morphological characteristics. For example, the aspect ratio (length / diameter) of the linear conductive material can be 2 or more, and specifically, the aspect ratio can be 2 or more, 5 or more, 10 or more, 20 or more, 30 or more, 40 or more, 50 or more, or 100 or more. When the aspect ratio is less than 2, it may be difficult to form electronic conduction paths, and electronic conductivity may decrease. Furthermore, there is no particular upper limit to the aspect ratio, but considering the ease of forming electronic conduction paths, it can be less than 300, less than 400, less than 500, less than 600, or less than 700.

[0115] Furthermore, based on the total weight of the positive electrode active material layer, the content of conductive material can range from 1% to 10% by weight. Specifically, the content of conductive material can be more than 1% by weight, more than 2% by weight, or more than 3% by weight, and can be less than 6% by weight, less than 7% by weight, less than 8% by weight, less than 9% by weight, or less than 10% by weight. When the content of conductive material is less than 1% by weight, the electronic conductivity of the positive electrode may decrease. When the content of conductive material exceeds 10% by weight, the content of the positive electrode active material and the sulfide-based solid electrolyte decreases relatively, and the battery performance may deteriorate.

[0116] In one embodiment of the present invention, the thickness of the positive electrode active material layer can be from 100 μm to 300 μm, specifically, it can be 100 μm or more, 110 μm or more, or 120 μm or more, and it can be less than 200 μm, 250 μm or less, or 300 μm. However, the thickness of the positive electrode active material layer is not limited thereto.

[0117] In one embodiment of the present invention, the positive current collector supports the positive active material layer and is used to transfer electrons between the external wire and the positive active material layer.

[0118] There are no particular restrictions on the positive electrode current collector, as long as it has high conductivity and does not cause chemical changes in the all-solid-state battery. For example, stainless steel, aluminum, nickel, titanium, palladium, sintered carbon, stainless steel with surface treatments of carbon, nickel, silver, etc., and aluminum-cadmium alloys can be used as positive electrode current collectors.

[0119] The positive electrode current collector can have a finely textured surface or a three-dimensional porous structure to enhance its adhesion to the positive electrode active material layer. Therefore, the positive electrode current collector can take various forms, such as membranes, sheets, foils, meshes, nets, porous bodies, foams, non-woven fabrics, etc.

[0120] All-solid-state batteries

[0121] The present invention also relates to an all-solid-state battery including the positive electrode.

[0122] The all-solid-state battery of the present invention includes a positive electrode, a negative electrode, and a sulfide-based solid electrolyte membrane inserted therebetween. The positive electrode is as described above.

[0123] In one embodiment of the present invention, the negative electrode includes a negative electrode active material layer, and the negative electrode active material layer may be formed on one surface of the negative electrode current collector. The negative electrode active material layer may comprise a negative electrode active material and a conductive material.

[0124] The negative electrode active material can contain lithium (Li) that can be reversibly inserted or extracted. +Materials that can reversibly form lithium-containing compounds by reacting with lithium ions, such as lithium metal or lithium alloys.

[0125] Capable of reversibly inserting or de-inserting lithium ions (Li) + The material can be, for example, crystalline carbon, amorphous carbon, or mixtures thereof. It can be synthesized by reacting with lithium ions (Li... + Materials that reversibly form lithium-containing compounds can be, for example, tin oxide, titanium nitride, or silicon. Lithium alloys can be, for example, alloys of lithium (Li) and metals selected from the group consisting of indium (In), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn).

[0126] Preferably, the negative electrode active material can be lithium metal or lithium-indium alloy (Li-In), specifically, it can be in the form of lithium metal, lithium film, lithium-indium alloy film, or powder.

[0127] Based on the total weight of the negative electrode active material layer, the content of the negative electrode active material can be from 40% to 80% by weight. Specifically, the content of the negative electrode active material can be above 40% or 50% by weight, and below 70% or 80% by weight. When the content of the negative electrode active material is less than 40% by weight, the connectivity between the wet and dry negative electrode active material layers may be insufficient, while when it exceeds 80% by weight, the mass transfer resistance may increase.

[0128] Furthermore, there are no particular limitations on the conductive material, as long as it possesses excellent conductivity without causing side reactions in the internal environment of the all-solid-state battery and without causing chemical changes within the battery. Representatively, graphite or conductive carbon can be used, such as: graphite, including natural and artificial graphite; carbon black, including carbon black, acetylene black, Ketjen black, Denka black, thermally cracked carbon black, channel black, furnace black, lamp black, and summer black; carbon-based materials with a graphene or graphite crystal structure; conductive fibers such as carbon fibers and metal fibers; fluorinated carbon; metal powders, such as aluminum and nickel powders; conductive whiskers, such as zinc oxide and potassium titanate; conductive oxides, such as titanium oxide; and conductive polymers, such as polyphenylene derivatives. These can be used alone or in combination of two or more, but are not necessarily limited thereto. Preferably, the conductive material may include vapor-grown carbon fibers (VGCF).

[0129] Based on the total weight of the negative electrode active material layer, the content of conductive material can typically range from 1% to 5% by weight. Specifically, the content of conductive material can be above 1% by weight, above 1.5% by weight, or above 2% by weight, and can be below 4% by weight, below 4.5% by weight, or below 5% by weight. When the content of conductive material is too low, less than 1% by weight, it may be difficult to expect an improvement in conductivity, or the electrochemical characteristics of the battery may decrease. Conversely, when it is too high, exceeding 5% by weight, the amount of negative electrode active material is relatively reduced, and the capacity and energy density may decrease. There are no particular limitations on the method of including conductive material in the negative electrode; conventional methods known in the art can be used, such as mixing and coating with the negative electrode active material.

[0130] Furthermore, there are no particular restrictions on the negative electrode current collector, as long as it is conductive and does not cause chemical changes in the battery. For example, the negative electrode current collector can be made of copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloys. In addition, similar to the positive electrode current collector, the negative electrode current collector can be in various forms with fine irregularities formed on its surface, such as films, sheets, foils, meshes, porous materials, foams, non-woven fabrics, etc.

[0131] There are no particular limitations on the manufacturing method of the negative electrode, and it can be manufactured by forming a layer of negative electrode active material on the negative electrode current collector using layer or film forming methods commonly used in the art. For example, methods such as pressing, coating, and deposition can be used. In addition, the negative electrode of the present invention also includes a case in which a lithium metal film is formed on a metal plate after assembling a battery without a lithium film on the negative electrode current collector through initial charging.

[0132] In one embodiment of the present invention, the sulfide-based solid electrolyte membrane may include one or more selected from the group consisting of LiPSX (X = Cl, Br, or I), LiGePS, and LiPS. However, the sulfide-based solid electrolyte is not limited thereto, and commonly used sulfide-based solid electrolytes in the art can be widely used.

[0133] Battery Module

[0134] The present invention also relates to a battery module including an all-solid-state battery as a unit cell, a battery pack including the battery module, and an apparatus including the battery pack as a power source.

[0135] Specific examples of the device include, but are not limited to: power tools that move by receiving power from an electric motor; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc.; electric two-wheelers, including electric bicycles (E-bicycles) and electric scooters (E-scooters); electric golf carts; and energy storage systems.

[0136] [Example]

[0137] Preferred embodiments are given below to aid in understanding the invention; however, the following embodiments are merely examples of the invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and spirit of the invention, and such changes and modifications naturally fall within the scope of the appended claims.

[0138] In the following examples and comparative examples, a coated positive electrode active material was manufactured according to the requirements described in Table 1 below.

[0139] [Table 1]

[0140] Example 1

[0141] The manufacturing process is carried out as follows to manufacture a positive electrode active material, which comprises: a core particle, a first coating comprising lithium metal oxide formed on the surface of the core particle, and a second coating comprising an oxysulfide-based solid electrolyte formed on the surface of the first coating.

[0142] NMC811 was prepared as core particles, and NMC811 synthesized by adding B as a dopant element was prepared to induce orientation.

[0143] Lithium ethanol and niobium ethanol, which are raw materials for the first coating, are mixed in ethanol, which is an alcohol-based solvent, to obtain a first mixed solution for forming the first coating.

[0144] B-doped NCM811, used as the core particle, is mixed with a first mixed solution to obtain a second mixed solution for forming the positive electrode active material. The second mixed solution is prepared to have a solid content of 50% by weight; here, solid content refers to the weight of the raw materials used for the coating and core particles, excluding the alcohol solvent. Furthermore, the weight ratio of the first coating material to the core particles is 0.5:99.5.

[0145] The alcohol solvent is removed by filtering and compressing the second mixed solution.

[0146] Subsequently, a positive electrode active material precursor is obtained in the form of a first coating containing lithium metal oxide formed on the surface of the core particle. At this time, the lithium metal oxide contained in the first coating is LiNbO3.

[0147] The positive electrode active material precursor was dried in a vacuum oven at 100°C for 12 hours to completely remove the alcohol solvent. Afterward, the dried positive electrode active material precursor was calcined at 400°C for 9 hours and then ground.

[0148] Subsequently, the oxysulfide-based solid electrolyte is mixed with the positive electrode active material precursor, and the oxysulfide-based solid electrolyte is coated onto the surface of the first coating by mechanical milling to form a second coating containing the oxysulfide-based solid electrolyte, thereby manufacturing the positive electrode active material. Li6PS is used. 4.5 O 0.5 Cl is a solid electrolyte of the oxysulfide class.

[0149] The results, measured using a particle size analyzer (Mastersizer 3000+ pro), confirmed that the particle size (D50) of the manufactured cathode active material was 4 μm. Furthermore, images of the cross-section of the manufactured cathode active material obtained by scanning electron microscopy (SEM), analyzed using an image analysis program (Image J, NIH), confirmed that the core particles contained in the cathode active material were multi-particle in form and radially oriented.

[0150] Example 2

[0151] The positive electrode active material was prepared in the same manner as in Example 1, except that the NMC811 contained in the core particles was not oriented. In this case, the NMC811 is the NMC811 in which no B was added as a dopant element during synthesis.

[0152] Example 3

[0153] The positive electrode active material was manufactured in the same manner as in Example 1, except that a first coating containing lithium metal oxide was not formed.

[0154] Example 4

[0155] The positive electrode active material was manufactured in the same manner as in Example 2, except that a first coating containing lithium metal oxide was not formed.

[0156] Comparative Example 1

[0157] The positive electrode active material is manufactured in the same manner as in Example 1, except that a second coating containing an oxysulfide-type solid electrolyte is not formed.

[0158] Comparative Example 2

[0159] The positive electrode active material is manufactured in the same manner as in Example 2, except that a second coating containing an oxysulfide-type solid electrolyte is not formed.

[0160] Experimental Example 1: Coating Analysis

[0161] As confirmed by SEMEDS (JEOL, JSM-IT800), O, S, P and Nb were found in the coating of Example 1.

[0162] Furthermore, X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of oxysulfide-based solid electrolytes and LiNbO3 on the surface of the nuclei.

[0163] Experiment Example 2: Performance Evaluation

[0164] To evaluate the performance of the all-solid-state batteries using the positive electrode active materials manufactured in the application examples and comparative examples, charge / discharge experiments were conducted in pressurized cells. In the case of pressurized cells, the cells were configured such that the positive electrode, electrolyte, and negative electrode were stacked in corresponding molds. As a cell manufacturing method, a positive electrode active material, Super-P (manufacturer: Imerys) as a conductive material, and a sulfide electrolyte Li2S-P2S5 were mixed in a weight ratio of 70:25:5. Li-In was used as the counter electrode (negative electrode). The cells for all-solid-state batteries were manufactured as follows: A solid electrolyte layer was formed by placing a solid electrolyte in a corresponding mold and pressurizing it. Subsequently, a positive electrode active material composite was applied to one surface of the solid electrolyte layer, and a negative electrode was stacked on the other surface, followed by additional pressurization to manufacture the electrode assembly. The manufactured electrode assembly was placed in a battery case to manufacture an all-solid-state battery. After the all-solid-state battery was activated at 0.1C for 2 cycles in a charge / discharge device, the rate capacity was observed by discharging to the maximum 1C. Specifically, the rate capacity was observed using the following scheme: 0.1C CC / CV (constant current / constant voltage) charging, 0.05C CC (constant current) discharging for 2 cycles, followed by maintaining the 0.1C CC / CV charging process and CC discharging at 0.1C / 0.2C / 0.33C / 0.5C / 1C.

[0165] Table 2 below describes the results of the above experiments.

[0166] [Table 2]

[0167] Referring to Table 2, it can be seen that, compared with Examples 1 to 4, Comparative Examples 1 and 2, as positive electrode active materials that do not form a coating containing an oxygen sulfide-type solid electrolyte, have relatively poor capacity retention.

[0168] Furthermore, it can be seen that, compared with Examples 3 and 4 which only form a second coating, Examples 1 and 2, as positive electrode active materials that form a first coating containing lithium metal oxide and a second coating containing an oxysulfide-type solid electrolyte on the core particles, have slightly higher or similar overall performance.

[0169] Furthermore, it can be seen that when the nuclear particles are oriented, as in Examples 1 and 3, the overall performance is slightly higher or similar compared to Examples 2 and 4, which are not oriented.

[0170] [Explanation of reference numerals in the attached figures]

[0171] 10: Positive electrode active material

[0172] 11: Nuclear particles

[0173] 12: Coating

[0174] 12a: Lithium metal oxide

[0175] P1: Single particle

Claims

1. A positive electrode active material for an all-solid-state battery, comprising: core particles; and a coating layer, wherein the coating layer is located on a surface of the core particles, in, the coating layer comprises an oxysulfide solid electrolyte.

2. The positive electrode active material for an all-solid-state battery according to claim 1, in, the oxysulfide solid electrolyte comprises oxygen (O) and sulfur (S) in a weight ratio of 0.02:1 to 0.1:

1.

3. The positive electrode active material for an all-solid-state battery according to claim 1, in, the oxysulfide solid electrolyte is represented by the following Chemical Formula 1: <Chemical Formula 1> Li (7-x) P.S. (6-x-y) About y Yes x , wherein, in Chemical Formula 1, Ha is Cl, Br or I, 0<x <1.6 and 0.1<y <1.

4. The positive electrode active material for an all-solid-state battery according to claim 1, in, the oxysulfide solid electrolyte has an argyrodite-type crystal structure.

5. The positive electrode active material for an all-solid-state battery according to claim 1, in, based on a total weight of the positive electrode active material, a content of the oxysulfide solid electrolyte is 0.1 wt% to 2 wt%.

6. The positive electrode active material for an all-solid-state battery according to claim 1, in, the coating layer further comprises a lithium metal oxide.

7. The positive electrode active material for an all-solid-state battery according to claim 6, in, the coating layer comprises a first coating layer and a second coating layer, the first coating layer comprises a lithium metal oxide, and the second coating layer comprises an oxysulfide solid electrolyte.

8. The positive electrode active material for an all-solid-state battery according to claim 1, in, the core particles are in a form of multi-particles formed by aggregation of a plurality of primary particles of a positive electrode active material.

9. The positive electrode active material for an all-solid-state battery according to claim 8, in, the plurality of primary particles are aggregated with orientation.

10. The positive electrode active material for an all-solid-state battery according to claim 8, in, the primary particles have an aspect ratio of 0.05:1 to 0.5:

1.

11. The positive electrode active material for an all-solid-state battery according to claim 1, in, the positive electrode active material has a particle diameter D50 of 3.3 μm to 6.3 μm.

12. A positive electrode for an all-solid-state battery, comprising: the positive electrode active material according to any one of claims 1 to 11; solid electrolyte particles; a binder; and a conductive material.

13. An all-solid-state battery, comprising the positive electrode according to claim 12.

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