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

Abstract

The present invention relates to a positive electrode active material for a full solid-state battery, and a positive electrode and a full solid-state battery comprising the same. More specifically, the positive electrode active material for a full solid-state battery is in a form comprising core particles and an amorphous coating layer formed on the surface of the core particles, the core particles comprising a positive electrode core active material in a secondary particle form, such that the porosity of the positive electrode active material for a full solid-state battery itself is minimized, which reduces the porosity of the positive electrode when applied to the positive electrode, and improves the output of the full solid-state battery.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2024-0112108, filed on August 21, 2024, and Korean Patent Application No. 10-2025-0115634, filed on August 20, 2025, the disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0003] This invention relates to positive electrode active materials for all-solid-state batteries, as well as positive electrodes and all-solid-state batteries containing the same. Background Technology

[0004] Various batteries are being researched to overcome the current limitations of lithium-ion batteries in terms of capacity, safety, output, large-scale application, and miniaturization.

[0005] Representative examples include metal-air batteries, which have a very high theoretical capacity compared to lithium-ion batteries; all-solid-state batteries, which have no risk of explosion; supercapacitors for output; NaS batteries or redox flow batteries (RFB) for large-scale applications; and thin-film batteries for miniaturization. These technologies are under continuous research in both academia and industry.

[0006] All-solid-state batteries use a solid electrolyte instead of the liquid electrolyte found in conventional lithium-ion batteries. Because no flammable solvents are used, there is no risk of fire or explosion due to the decomposition of conventional electrolytes, significantly improving safety. Furthermore, development of sulfide-based all-solid-state batteries is ongoing. Sulfide-based all-solid-state batteries utilize solid electrolytes with high ionic conductivity and can theoretically achieve energy densities of at least 900 Wh / L. Sulfide-based all-solid-state batteries refer to all-solid-state batteries that contain sulfide-based solid electrolytes.

[0007] In all-solid-state battery systems, lithium ions are not conducted by the liquid electrolyte found in conventional lithium-ion batteries (LIBs). Therefore, when manufacturing the cathode for sulfide-based all-solid-state batteries, it is necessary to increase the contact interface between the cathode active material and the sulfide solid electrolyte particles by adding small-diameter sulfide solid electrolyte particles within the cathode, thereby increasing lithium-ion conductivity. Furthermore, to improve energy density, the physical contact between the cathode active material, sulfide solid electrolyte particles, and other battery components must be improved, and the porosity of the cathode after rolling must be reduced, which must be maintained during charging and discharging.

[0008] Unlike liquid electrolytes, solid electrolytes are not fluid and cannot penetrate between the positive electrode active material particles, thus leaving pores between the positive electrode active material particles as dead zones, thereby reducing the output of all-solid-state batteries.

[0009] Therefore, there is a continued need to develop technologies that can further reduce the porosity at the cathode of all-solid-state batteries to improve their performance.

[0010] [Existing Technical Documents]

[0011] [Patent Literature]

[0012] (Patent Document 1) Chinese Patent Publication No. 117613259 Summary of the Invention

[0013] [Technical Issues]

[0014] The inventors of this invention have conducted extensive research to address the aforementioned problems and have confirmed that when a positive electrode active material comprising core particles and an amorphous coating on the surface of the core particles is applied to the positive electrode, the porosity of the positive electrode can be reduced and the output of the all-solid-state battery can be improved, wherein the core particles comprise secondary particles (polyparticles) formed by the agglomeration of multiple primary particles of positive electrode core active material.

[0015] Therefore, one object of the present invention is to provide a positive electrode active material for all-solid-state batteries, which has a form that can reduce the porosity of the positive electrode.

[0016] Another object of the present invention is to provide a positive electrode for all-solid-state batteries, which comprises a positive electrode active material for all-solid-state batteries having a form that can reduce the porosity of the positive electrode.

[0017] Another object of the present invention is to provide an all-solid-state battery comprising a positive electrode active material having a form capable of reducing the porosity of the positive electrode.

[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 an amorphous coating on the surface of the core particles. The core particles are secondary particles formed by the aggregation of multiple primary particle-form positive electrode nuclear active materials. The amorphous coating comprises a compound containing at least two of the following: Li, M, and O, wherein M contains at least one of the following: B, Zr, Nb, Ti, Al, W, P, Fe, C, N, Si, P, S, Co, Ge, Ga, Y, and In.

[0020] In one embodiment of the present invention, a positive electrode active material for all-solid-state batteries is provided, wherein the compound comprises at least one selected from the group consisting of LiO, MO, LiM and LiMO.

[0021] In one embodiment of the present invention, a positive electrode active material for all-solid-state batteries is provided, wherein the thickness of the amorphous coating is from 5 nm to 200 nm.

[0022] 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 for all-solid-state batteries is 3 μm to 5 μm.

[0023] In one embodiment of the present invention, a positive electrode active material for all-solid-state batteries is provided, wherein the span ((D90-D10) / D50) of the positive electrode active material for all-solid-state batteries is 0.7 or less.

[0024] In one embodiment of the present invention, a positive electrode active material for all-solid-state batteries is provided, wherein the positive electrode core active material comprises a lithium composite metal oxide.

[0025] In one embodiment of the present invention, a positive electrode active material for all-solid-state batteries is provided, wherein the porosity of the positive electrode active material for all-solid-state batteries is less than 7%.

[0026] The present invention also provides a positive electrode for an all-solid-state battery, comprising the above-mentioned positive electrode active material.

[0027] In one embodiment of the present invention, a positive electrode for an all-solid-state battery is provided, wherein the positive electrode comprises the above-mentioned positive electrode active material, a sulfide-based solid electrolyte, a binder, and a conductive material.

[0028] The present invention also provides an all-solid-state battery, which includes a positive electrode, a negative electrode and a sulfide-based solid electrolyte membrane disposed therebetween.

[0029] [Beneficial Effects]

[0030] The positive electrode active material for all-solid-state batteries of the present invention includes core particles and an amorphous coating formed on the surface of the core particles. The core particles are in the form of secondary particles formed by the agglomeration of multiple primary positive electrode active material particles. The positive electrode active material has the effect of reducing the porosity of the positive electrode and improving the output characteristics of the all-solid-state battery. Attached Figure Description

[0031] Figure 1 This is a schematic cross-sectional view illustrating the interface between the positive electrode active material and the sulfide-based solid electrolyte, as an example of the present invention.

[0032] Figure 2This is the X-ray diffraction (XRD) pattern of the positive electrode active material of Example 1 of the present invention. Detailed Implementation

[0033] The invention will be described in more detail below to provide a better understanding.

[0034] The terms and words used in this specification and claims should not be interpreted in their ordinary or dictionary sense, but rather should be interpreted in a sense and in a sense consistent with the technical concept of the invention, based on the principle that the inventor can appropriately define the terms to best interpret the invention.

[0035] As used herein, the term "positive electrode core active material" refers to a substance that generates electrical energy through a chemical reaction at the positive electrode of a battery, and it has the same concept as "positive electrode active material." To distinguish between materials contained in core particles and materials containing core particles and amorphous coatings, the former are called positive electrode core active materials, and the latter are called positive electrode active materials.

[0036] As used herein, the term "primary particle" refers to a single particle. A primary particle is a primary particle of the cathode nuclear active material.

[0037] As used in this article, the term "secondary particle" refers to a polyparticle formed by the aggregation of multiple primary particles. Secondary particles are secondary particles in cathode core active materials.

[0038] Positive electrode active materials for all-solid-state batteries

[0039] This invention relates to a positive electrode active material for all-solid-state batteries.

[0040] The positive electrode active material for all-solid-state batteries of the present invention comprises: core particles; and an amorphous coating on the surface of the core particles. The core particles are secondary particles formed by the aggregation of multiple primary particle-form positive electrode nuclear active materials. The amorphous coating comprises a compound containing at least two of the following: Li, M, and O, wherein M contains at least one of the following: B, Zr, Nb, Ti, Al, W, P, Fe, C, N, Si, S, Co, Ge, Ga, Y, and In.

[0041] Figure 1 This is a schematic cross-sectional view illustrating the interface between a positive electrode active material and a sulfide-based solid electrolyte, as an example of the present invention.

[0042] Reference Figure 1The positive electrode active material contained in the core particles (11) of the positive electrode active material (10) is in the form of secondary particles (11b) formed by the aggregation of multiple primary particles (11a). Compared with a positive electrode containing only primary particles, this can reduce the porosity of the positive electrode, thereby improving the output characteristics of the all-solid-state battery. In addition, since an amorphous coating (12) is formed on the surface of the core particles (11) containing secondary particles (11b), side reactions between the positive electrode active material contained in the core particles (11) and the sulfide-based solid electrolyte (20) are prevented, which can improve the output and lifetime characteristics of the all-solid-state battery. Furthermore, pores (P) are formed inside the secondary particles (11b), but the secondary particles (11b) are in the form of aggregates of primary particles (11a), so that the porosity of the positive electrode active material (10) in the form of secondary particles (11b) is kept below a certain level.

[0043] In one embodiment of the invention, the amorphous coating may comprise a compound containing at least two selected from the group consisting of Li, M, and O, wherein M comprises at least one selected from the group consisting of B, Zr, Nb, Ti, Al, W, P, Fe, C, N, Si, S, Co, Ge, Ga, Y, and In.

[0044] The positive electrode for all-solid-state batteries can consist of a sulfide-based solid electrolyte and a positive electrode active material. The amorphous coating is the part that is in direct contact with the sulfide-based solid electrolyte. It can prevent side reactions at the interface between the positive electrode active material and the sulfide-based solid electrolyte, thereby suppressing the generation of resistance and ultimately improving the output of the all-solid-state battery.

[0045] Furthermore, amorphous coatings can form a uniform coating compared to crystalline coatings. A uniformly formed amorphous coating can further improve the output and lifespan of all-solid-state batteries. Because crystalline coatings form as islands on the core particles rather than forming a complete coating, it is impossible to form a uniform coating.

[0046] Furthermore, the compound may contain at least one selected from the group consisting of LiO, MO, LiM, and LiMO. M may include at least one selected from the group consisting of B, Zr, Nb, Ti, Al, W, P, Fe, C, N, Si, S, Co, Ge, Ga, Y, and In.

[0047] Furthermore, the thickness of the amorphous coating can range from 5 nm to 200 nm. If the thickness of the amorphous coating is less than 5 nm, side reactions may occur between the positive electrode active material and the sulfide-based solid electrolyte; if its thickness exceeds 200 nm, the excessively thick layer may act as a resistive component. Specifically, the thickness of the amorphous coating can be greater than 5 nm, greater than 10 nm, greater than 15 nm, greater than 20 nm, greater than 25 nm, greater than 30 nm, greater than 35 nm, greater than 40 nm, or greater than 45 nm, less than 200 nm, less than 190 nm, less than 180 nm, less than 170 nm, less than 160 nm, less than 150 nm, less than 140 nm, less than 130 nm, less than 120 nm, less than 110 nm, less than 100 nm, less than 90 nm, less than 80 nm, less than 70 nm, less than 60 nm, or less than 50 nm.

[0048] Furthermore, based on the total weight of the positive electrode active material, the content of the amorphous coating can be from 0.1% to 3% by weight. If the content of the amorphous coating is less than 0.1% by weight, side reactions may occur between the positive electrode active material and the sulfide-based solid electrolyte; if its content is greater than 3% by weight, the excess content may act as a resistive component. Specifically, the content of the amorphous coating can be more than 0.1% by weight, more than 0.2% by weight, more than 0.3% by weight, more than 0.4% by weight, or more than 0.5% by weight, 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.

[0049] In one embodiment of the present invention, the particle size (D50) of the positive electrode active material can be from 3 μm to 5 μm.

[0050] If the particle size (D50) of the positive electrode active material is less than 3 μm, the positive electrode active material may agglomerate during the positive electrode manufacturing process, or the electrode plate density may decrease. If its particle size exceeds 5 μm, the lithium mobility may decrease. Specifically, the particle size (D50) of the positive electrode active material can be greater than 3 μm, greater than 3.1 μm, greater than 3.2 μm, greater than 3.3 μm, greater than 3.4 μm, or greater than 3.5 μm, and can be less than 5 μm, less than 4.9 μm, less than 4.8 μm, less than 4.7 μm, less than 4.6 μm, less than 4.5 μm, less than 4.4 μm, less than 4.3 μm, less than 4.2 μm, less than 4.1 μm, less than 4 μm, less than 3.9 μm, less than 3.8 μm, less than 3.7 μm, or less than 3.6 μm.

[0051] Furthermore, the span ((D90-D10) / D50) of the positive electrode active material can be less than 0.7. The term "span" refers to the width of the particle size distribution and is a dimensionless value without units, simply indicating whether the distribution is narrow or wide.

[0052] If the span exceeds 0.7, lithium mobility may be reduced due to coarse or fine-particle cathode active materials. Specifically, the span can be below 0.7, below 0.6, below 0.5, or below 0.4. The lower limit of the span is not particularly limited, but can be, for example, above 0.1 or above 0.2.

[0053] The particle size (D50) of the positive electrode active material can be measured, for example, using laser diffraction. More specifically, the particle size (D50) of the positive electrode active material can be determined by dispersing the positive electrode active material in a dispersant, introducing it into a commercially available laser diffraction particle size measurement device (e.g., Microtrac MT 3000), irradiating it with 28 kHz ultrasound at a power of 60 W, and calculating the average particle size (D50) corresponding to 50% of the particle size distribution in the measurement device.

[0054] In one embodiment of the invention, the positive electrode nuclear active material contained in the core particles, in the form of primary and secondary particles, comprises a lithium composite metal oxide capable of reversibly inserting and de-inserting lithium.

[0055] In addition to lithium, lithium complex metal oxides may also contain nickel, cobalt, and a metallic element M', wherein 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.

[0056] Specifically, lithium composite metal oxides can be represented by the following formula 1: <Formula 1> Li α Ni x Co y M' z O2 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. Where α, x, y, and z each represent the atomic fractions of independent elements, and can be 0.9 ≤ α ≤ 1.05, 0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1, or more specifically, 0.9 ≤ α ≤ 1.05, 0.6 ≤ x < 1, 0 < y ≤ 0.4, 0 < z ≤ 0.4, x + y + z = 1, where α is the value before charging, and the composition of Formula 1 represents an average value.

[0057] More specifically, the core particles can be lithium composite metal oxides with a 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 of them can be used.

[0058] In addition, based on the total weight of the positive electrode active material, the content of the core particles can be 97 wt% to 99.9 wt%. If the content of the core particles is less than 97 wt%, the battery performance may deteriorate, while if the content of the core particles exceeds 99.9 wt%, the content of the amorphous coating is relatively reduced, which may cause side reactions with the solid electrolyte. Specifically, the content of the core particles can be more than 97 wt%, more than 97.5 wt%, more than 98 wt%, more than 98.5 wt% or more than 99 wt%, and less than 99.9 wt%, less than 99.8 wt%, less than 99.7 wt%, less than 99.6 wt% or less than 99.5 wt%.

[0059] In the present invention, the porosity of the positive electrode active material can be 7% or less. The core particles contained in the positive electrode active material include secondary particles aggregated from primary particles, so that pores can be formed between the aggregated primary particles. The porosity of the positive electrode active material refers to the volume of pores (%(v / v)) relative to the total volume of the positive electrode active material.

[0060] If the porosity of the positive electrode active material exceeds 7%, the porosity of the positive electrode active material layer and the positive electrode may increase, resulting in a reduction in the output of the all-solid-state battery. Specifically, the porosity of the positive electrode active material can be 7% or less, 6% or less, 5% or less, 4% or less, or 3% or less. The lower limit of this porosity is not particularly limited, but can be, for example, 1% or more or 2% or more.

[0061] Method for preparing positive electrode active materials for all-solid-state batteries

[0062] This invention also relates to a method for preparing positive electrode active materials for all-solid-state batteries.

[0063] The method for preparing a positive electrode active material for all-solid-state batteries according to the present invention includes the following steps: (S1) mixing and stirring a transition metal salt, a chelating agent, and a pH adjuster to form a precursor of the positive electrode core active material; (S2) adding a lithium raw material to the precursor of the positive electrode core active material and calcining it to form secondary particles of the positive electrode core active material; and (S3) forming an amorphous coating on the surface of the core particles including the secondary particles. The amorphous coating may contain a compound containing at least two selected from Li, M, and O, wherein M contains at least one selected from the group consisting of B, Zr, Nb, Ti, Al, W, P, Fe, C, N, Si, S, Co, Ge, Ga, Y, and In.

[0064] The method for preparing the positive electrode active material for all-solid-state batteries according to the present invention will be described in more detail below, step by step.

[0065] In one embodiment of the present invention, in step (S1), a transition metal salt, a chelating agent and a pH adjuster may be mixed and stirred to form a precursor of a positive electrode active material.

[0066] Transition metals may include at least one selected from the group consisting of nickel, cobalt, and manganese.

[0067] In addition, transition metal salts may include at least one selected from the group consisting of nitrates, sulfates, and chlorides of transition metals. For example, transition metal salts may include nickel nitrate, cobalt nitrate, and manganese nitrate.

[0068] In addition, chelating agents can be added to promote the deintercalation and extraction of transition metals from transition metal salts, allowing them to bind well with the lithium source. Chelating agents may include at least one selected from the group consisting of aqueous solutions of ammonia and ammonium sulfate.

[0069] In addition, the pH adjuster may contain one or more of the following: fumaric acid, glutaric acid, oxalic acid, malonic acid, succinic acid, maleic acid, palmitic acid, tartaric acid, formic acid, acetic acid, glycolic acid, sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, sulfonic acid, aminosulfonic acid, lithium hydroxide, and sodium hydroxide.

[0070] Furthermore, the porosity of the prepared positive electrode active material can be adjusted according to the stirring time. For example, a shorter stirring time can increase the porosity of the positive electrode active material. Therefore, the stirring time can be appropriately adjusted to ensure that the porosity of the positive electrode active material is within an appropriate range.

[0071] In one embodiment of the present invention, in step (S2), lithium raw material can be added to the precursor of positive electrode active material and calcined to form secondary particles of positive electrode active material.

[0072] Lithium raw materials may include at least one selected from the group consisting of lithium carbonate, lithium nitrate, lithium sulfate, lithium hydroxide, and lithium oxide.

[0073] In one embodiment of the present invention, in step (S3), an amorphous coating may be formed on the surface of the core particles containing secondary particles. The coating may be performed by wet coating or dry coating.

[0074] In one embodiment of the present invention, the wet coating method for forming an amorphous coating includes the following steps: (a1) mixing a raw material containing at least one element (M) selected from the group consisting of B, Zr, Nb, Ti, Al, W, P and Fe and / or a lithium raw material in an alcohol solvent to obtain a first mixed solution for forming an amorphous coating; (a2) mixing a core particle containing secondary particles into the first mixed solution for forming an amorphous coating obtained in step (a1) to obtain a second mixed solution for forming a positive electrode active material; (a3) ​​pressure filtering the second mixed solution for forming a positive electrode active material obtained in step (a2); (a4) drying the filter cake obtained in step (a3); and (a5) calcining the dried product obtained in step (a4).

[0075] In one example of the present invention, in step (a1), a raw material containing at least one element (M) selected from the group consisting of B, Zr, Nb, Ti, Al, W, P and Fe and / or a lithium raw material may be mixed in an alcohol solvent to obtain a first mixed solution for forming an amorphous coating.

[0076] The raw material for element (M) may include at least one selected from the group consisting of oxides, hydroxides, chlorides, fluorides, carbides, and alkoxides of element (M). For example, the raw material for B mentioned above may include B₂O₃, H₃BO₃, and C. 13 H 19 The raw materials for Zr may include at least one selected from the group consisting of ZrO2, Zr alkoxides, and Zr hydroxides. The raw materials for Nb may include at least one selected from the group consisting of niobium fluoride, niobium chloride, and niobium carbide. The raw materials for Ti may include at least one selected from the group consisting of TiO2, titanium ethoxide, and tetrabutyl titanate.

[0077] In addition, lithium feedstocks may include at least one selected from the group consisting of lithium carbonate, lithium nitrate, lithium sulfate, lithium hydroxide, and lithium oxide. For example, lithium feedstocks may include LiOH or Li₂CO₃.

[0078] The alcohol solvent may contain at least one alcohol compound having 1 to 4 carbon atoms. Specifically, the alcohol solvent may include one or more selected from the group consisting of acetone, methanol, ethanol, isopropanol, butanol, octanol, and allyl alcohol. Considering the processability during the manufacturing process of the positive electrode active material and the formability of the amorphous coating on the final manufactured positive electrode active material, the alcohol solvent may be ethanol.

[0079] In one example of the present invention, in step (a2), the core particles containing secondary particles can be mixed in the first mixed solution obtained in step (a1) above for forming an amorphous coating, thereby obtaining a second mixed solution for forming a positive electrode active material.

[0080] The types and amounts of nuclear particles are as described above.

[0081] In one embodiment of the present invention, in step (a3), the second mixed solution obtained in step (a2) above for forming the positive electrode active material can be pressure filtered.

[0082] Pressure filtration can be a process of removing alcohol solvents by pressurizing a second mixed solution used to form the positive electrode active material to 0.3 MPa to 1 MPa. For example, pressurization can be performed by blowing air, and alcohol solvents can be removed by pressurizing with air for 5 to 15 minutes. Furthermore, pressure filtration using a pressure filtration device can remove alcohol solvents from a second mixed solution containing coating material and core particles. There are no particular limitations on the pressure filtration device, as long as it is commonly used in the art and capable of effectively removing alcohol solvents.

[0083] By using pressure filtration, alcohol solvents can be removed from the second mixed solution in a short time, thereby minimizing the time that the nuclei are exposed to the liquid.

[0084] The filter cake obtained after pressure filtration is in the form of element (M) and / or lithium raw materials adsorbed on the surface of the core particles, and may contain trace amounts of alcohol solvents. The filter cake may also be in the form of a positive electrode active material with an amorphous coating formed on the surface of the core particles.

[0085] Furthermore, the removed alcohol solvent can be recycled by recovering it and adding it to a second mixed solution used to form the positive electrode active material. The alcohol solvent removed from the second mixed solution also contains residues of element (M), lithium raw materials, and / or core particles, thereby improving the yield during recycling.

[0086] Furthermore, the process of recovering the removed alcohol solvent into the second mixed solution used to form the positive electrode active material can be performed more than twice, and the uniformity of the amorphous coating can be improved with increasing number of repetitions. There is no specific upper limit to the number of repetitions, but for processability, the process can be performed no more than three, four, or five times.

[0087] In one example of the content of this invention, in step (a4), the filter cake obtained in step (a3) ​​above can be dried.

[0088] Alcohol solvents can be completely removed by drying.

[0089] There are no particular restrictions on the drying temperature, as long as it is sufficient to remove the alcohol solvent. For example, drying can be carried out at temperatures between 80°C and 120°C. If the drying temperature is below 80°C, the alcohol solvent may not be completely removed; if it is above 120°C, the properties of the raw material may be altered, and the performance of the prepared positive electrode active material may be reduced. Specifically, the drying temperature can be above 80°C, above 85°C, or above 90°C, or below 120°C, below 115°C, or below 110°C.

[0090] The dried product obtained after drying is in a state where the raw material of element (M) and lithium raw material are adsorbed on the surface of the core particles.

[0091] In one embodiment of the present invention, in step (a5), the dried product obtained in step (a4) above may be calcined.

[0092] The calcination temperature can be adjusted according to the type of raw material (M), for example, from 200°C to 650°C. If the calcination temperature is below 200°C, the raw material may react incompletely and may maintain a weak bond with the positive electrode active material; if the calcination temperature exceeds 650°C, Li may deintercalate from the structure of the positive electrode active material due to the high calcination temperature, leading to deterioration of structural stability and crystallinity. Specifically, the calcination temperature can be above 200°C, above 250°C, above 300°C, above 350°C, or above 400°C, or it can be below 650°C, below 600°C, below 550°C, or below 500°C.

[0093] Next, the calcined positive electrode active material can be ground. Grinding allows for adjustment of the particle size of the positive electrode active material. For example, the particle size can increase as the grinding time decreases.

[0094] In one embodiment of the invention, the dry coating method for forming an amorphous coating can be performed by atomic layer deposition (ALD) or by heat treatment following mechanical mixing.

[0095] Atomic layer deposition is a process in which raw materials for forming an amorphous coating on the surface of a nucleus particle are deposited on the nucleus particle surface to form an amorphous coating.

[0096] In addition, the heat treatment following mechanical mixing is a process in which the nuclei and raw materials used to form the amorphous coating are mixed and then heat-treated to form the amorphous coating.

[0097] The raw materials used to form the amorphous coating may include raw materials of element (M) and / or lithium raw materials, wherein the raw materials of element (M) include at least one selected from the group consisting of B, Zr, Nb, Ti, Al, W, P and Fe.

[0098] Positive electrode for all-solid-state batteries

[0099] The present invention also relates to a positive electrode for an all-solid-state battery comprising the above-mentioned positive electrode active material.

[0100] 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 side of the positive electrode current collector. The positive electrode active material layer comprises the positive electrode active material, a sulfide-based solid electrolyte, a binder, and a conductive material as described above.

[0101] In one embodiment of the present invention, since the porosity of the positive electrode active material is limited to 7% or less, the porosity of the positive electrode can be 18% or less.

[0102] The positive electrode active material of one example of the present invention is as described above.

[0103] 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 90% 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 below 90% by weight, below 85% by weight, below 80% by weight, below 75% by weight, or below 70% by weight. If the content of the positive electrode active material is less than 50% by weight, the battery performance may decrease; if the content exceeds 90% by weight, the mass transfer resistance may increase.

[0104] In one embodiment of the present invention, the sulfide solid electrolyte is a sulfur-containing solid electrolyte that can improve ion conductivity.

[0105] Sulfide solid electrolytes may contain at least one selected from the group consisting of LiPSX (where X is Cl, Br, or I), LiGePS, and LiPS. However, sulfide solid electrolytes are not limited to these compounds, and a wide range of sulfide solid electrolytes conventionally used in the art can be used.

[0106] Furthermore, sulfide-based solid electrolytes can be in the form of particles with a particle size (D50) of 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 less than 0.9 μm, less than 1.0 μm, less than 1.2 μm, or less than 1.5 μm. If 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 agglomerate; if it exceeds 1.5 μm, dispersion may be slightly easier, but the contact surface with the positive electrode active material particles may be reduced, and the positive electrode porosity may increase.

[0107] 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 30% 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, or 18% or more, or it can be less than 30% by weight, less than 28% by weight, less than 25% by weight, or less than 22% by weight. If the content of sulfide-based solid electrolyte is less than 5% by weight, the ionic conductivity may decrease; if it exceeds 30% by weight, the content of positive electrode active material and conductive material may decrease relatively, leading to a reduction in battery performance.

[0108] In one embodiment of the invention, an adhesive may be included to promote cohesion between the materials contained within the positive electrode active material layer and adhesion between the positive electrode active material layer and the positive electrode current collector.

[0109] The adhesive may contain at least one selected from the following: polytetrafluoroethylene (PTFE), polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepoxychloropropane, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resins, phenolic resins, epoxy resins, 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-co-hexafluoropropylene). Preferably, the adhesive may include polytetrafluoroethylene (PTFE).

[0110] 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, 0.8% or more, or less than 3% by weight, less than 2% by weight, or less than 1.5% by weight. If the binder content is less than 0.1% by weight, the effect of improving the cohesive force between the various materials contained in the positive electrode active material layer may be insufficient, and the positive electrode active material layer may not form properly. If its content exceeds 3% by weight, the ionic conductivity or electronic conductivity may decrease.

[0111] In one embodiment of the invention, the conductive material can form a path for conducting electrons, thereby improving electronic conductivity.

[0112] The conductive material can be a linearly conductive material, wherein the linearly conductive material can be at least one selected from the group consisting of carbon nanotubes (CNTs) and carbon nanofibers (CNFs). Due to their morphological characteristics, linearly conductive materials can improve conductivity. For example, the aspect ratio (length / diameter) of a linearly conductive material can be 2 or higher, specifically 2 or higher, 5 or higher, 10 or higher, 20 or higher, 30 or higher, 40 or higher, 50 or higher, or 100 or higher. If the aspect ratio is less than 2, it is difficult to form electronic conduction paths, which may lead to a decrease in electronic conductivity. Furthermore, there is no particular upper limit to the aspect ratio, but it can be below 300, below 400, below 500, below 600, or below 700, thereby facilitating the formation of electronic conduction paths.

[0113] 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%, more than 2%, or more than 3% by weight, or it can be less than 6%, less than 7%, less than 8%, less than 9%, or less than 10% by weight. If the content of conductive material is less than 1% by weight, the conductivity of the positive electrode may decrease; if it exceeds 10% by weight, the content of the positive electrode active material and the sulfide-based solid electrolyte may decrease relatively, leading to a deterioration in battery performance.

[0114] In one embodiment of the present invention, the thickness of the positive electrode active material layer can be from 100 μm to 300 μm, more specifically, it can be 100 μm or more, 110 μm or more, 120 μm or more, or it can be less than 200 μm, 250 μm or less, or 300 μm or less. However, the thickness of the positive electrode active material layer is not limited thereto, and depending on the composition of the positive electrode active material layer, the thickness can be adjusted to have a positive electrode load in which the ratio of ionic conductivity to electronic conductivity is 0.8 and 1.2.

[0115] In one embodiment of the 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.

[0116] There are no particular restrictions on the positive electrode current collector, as long as it has high electronic conductivity and does not cause chemical changes in the all-solid-state battery. For example, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, stainless steel with a surface treated with carbon, nickel or silver, aluminum-cadmium alloys, etc., can be used as positive electrode current collectors.

[0117] The positive electrode current collector can have a microscopically uneven structure on its surface or adopt a three-dimensional porous structure to enhance its bonding with the positive electrode active material layer. Therefore, the positive electrode current collector can come in various forms, such as membranes, sheets, foils, screens, meshes, porous materials, foams, nonwoven materials, etc.

[0118] All-solid-state batteries

[0119] The present invention also relates to an all-solid-state battery including the positive electrode.

[0120] The all-solid-state battery of the present invention includes a positive electrode, a negative electrode, and a sulfide-based solid electrolyte membrane disposed between them. The positive electrode is as described above.

[0121] In one embodiment of the present invention, the negative electrode includes a negative electrode active material layer, wherein the negative electrode active material layer may be formed on one side of the negative electrode current collector. The negative electrode active material layer may include a negative electrode active material and a conductive material.

[0122] The negative electrode active material can contain lithium (Li) that can be reversibly inserted or extracted. + Materials that can react with lithium ions to reversibly form lithium-containing compounds, lithium metal, or lithium alloys.

[0123] Capable of reversibly inserting or removing lithium ions (Li) + The material can be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. It is capable of reacting with lithium ions (Li... + The materials that can reversibly form lithium-containing compounds through the reaction can be, for example, tin oxide, titanium nitrate, or silicon. Lithium alloys can be, for example, alloys of lithium (Li) with 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).

[0124] Preferably, the negative electrode active material can be lithium metal or lithium-indium alloy (Li-In), and more specifically, it can be in the form of lithium metal, lithium film, or lithium-indium alloy film or powder.

[0125] 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 more than 40% by weight, more than 50% by weight, or less than 70% by weight, or less than 80% by weight. If the content of the negative electrode active material is less than 40% by weight, the connection between the wet and dry negative electrode active material layers may be insufficient; if the content exceeds 80% by weight, the mass transfer resistance may increase.

[0126] Furthermore, the conductive material is not particularly limited, as long as it prevents side reactions in the internal environment of the all-solid-state battery, provides excellent conductivity, and does not cause chemical changes within the battery. Representative examples may include: graphite or conductive carbon, such as natural or artificial graphite; carbon black, such as acetylene black, Ketjen black, Denka black, thermally cracked carbon black, channel black, furnace black, lamp black, etc.; carbon-based materials having a graphene or graphite crystal structure; conductive fibers, such as carbon fibers or metal fibers; fluorides; metal powders, such as aluminum powder or nickel powder; conductive whiskers, such as zinc oxide, potassium titanate, etc.; conductive oxides, such as titanium oxide; and conductive polymers, such as polyphenylene derivatives. These materials may be used alone or in mixtures of two or more, but are not limited thereto. Preferably, the conductive material may include vapor-grown carbon fibers (VGCF).

[0127] Furthermore, based on the total weight of the negative electrode active material layer, the content of conductive material can range from 1% to 5% by weight, more specifically, it can be more than 1% by weight, more than 1.5% by weight, more than 2% by weight, or less than 4% by weight, less than 4.5% by weight, or less than 5% by weight. If the content of conductive material is too low, i.e., less than 1% by weight, it may be difficult to obtain improved conductivity, or the electrochemical properties of the battery may deteriorate. Conversely, if the content of conductive material is too high, i.e., greater than 5% by weight, the relative amount of negative electrode active material decreases, leading to a reduction in capacity and energy density. The method of incorporating conductive material into the negative electrode is essentially unrestricted, and any conventional method known in the art can be used, such as mixing with or coating the negative electrode active material.

[0128] 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, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with a surface treated with carbon, nickel, or silver, aluminum-cadmium alloys, etc., can be used. In addition, like 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 materials, etc.

[0129] There are no particular limitations on the manufacturing method of the negative electrode. Conventional methods in the art for forming layers or films can be used to form a layer of negative electrode active material on the negative electrode current collector, thereby manufacturing the negative electrode. For example, methods such as pressing, coating, or deposition can be used. The negative electrode of the present invention also includes the case where, after assembling a battery without a lithium film on the negative electrode current collector, a thin film of metallic lithium is formed on a metal plate through initial charging.

[0130] In one embodiment of the invention, the sulfide-based solid electrolyte membrane may contain at least one selected from the group consisting of LiPSX (where X is Cl, Br, or I), LiGePS, and LiPS. However, the sulfide-based solid electrolyte is not limited to these compounds, and a wide range of sulfide-based solid electrolytes conventionally used in the art can be used.

[0131] Battery Module

[0132] The present invention also relates to a battery module including the 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.

[0133] Specific examples of this device may include, but are not limited to: power tools powered by electric motors; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc.; electric two-wheelers, including electric bicycles (E-bikes) and electric scooters (E-scooters); electric golf carts; energy storage systems; and so on.

[0134] [Example]

[0135] In the following description, preferred embodiments of the invention are presented for the purpose of illustrating the invention. However, it will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the invention and its technical concept, and such changes and modifications fall within the scope of the appended claims.

[0136] In the following examples and comparative examples, positive electrode active materials with amorphous coatings were prepared according to the requirements listed in Table 1 below.

[0137] [Table 1]

[0138] Example 1

[0139] (1) Precursor for forming positive polarity active materials

[0140] The mixture and stirring consist of transition metal salts of nickel nitrate, cobalt nitrate, and manganese nitrate, an aqueous ammonia solution as a chelating agent, and fumaric acid as a pH adjuster, thereby preparing a precursor for the positive electrode active material.

[0141] (2) Formation of nuclei containing secondary particles

[0142] Lithium carbonate, used as a lithium feedstock, is added to the precursor of the positive electrode active material and calcined to prepare core particles containing NCM811 in the form of secondary particles.

[0143] (3) Forming an amorphous coating

[0144] H3BO3 and Li2CO3, which are raw materials for amorphous coating, are mixed in ethanol, which is an alcohol solvent, to obtain a first mixed solution for forming an amorphous coating.

[0145] The core particles are mixed in a first mixed solution to obtain a second mixed solution for forming the positive electrode active material. Furthermore, the solid content in the second mixed solution is 50% by weight, where solids refer to the weight of the raw materials for the amorphous coating (excluding alcohol solvents) and the core particles. Additionally, the weight ratio of the raw materials for the amorphous coating to the core particles is 0.5:99.5.

[0146] The second mixed solution was pressure filtered to remove the alcohol solvent, resulting in a positive electrode active material with an amorphous coating formed on the surface of the core particles.

[0147] The positive electrode active material was dried in a vacuum oven at 100°C for 12 hours to completely remove the alcohol solvent.

[0148] The dried positive electrode active material was then calcined at 400°C for 9 hours. The positive electrode active material was then ground.

[0149] The particle size (D50) of the prepared positive electrode active material was confirmed to be 3.72 μm with a span of 0.5 mm using a particle size analyzer (Mastersizer 3000+ pro). Furthermore, the porosity of the prepared positive electrode active material was determined to be 2.4% by analyzing cross-sectional images taken with a scanning electron microscope (SEM) using Image J (NIH).

[0150] Example 2

[0151] The same method as in Example 1 was performed, except that the stirring time of the first mixed solution and the core particles was relatively shorter compared to Example 1.

[0152] Measured in the same manner as in Example 1, the porosity of the positive electrode active material was found to be 7%, and the particle size (D50) of the positive electrode active material was found to be 3.63 μm.

[0153] Example 3

[0154] The same method as in Example 1 was performed, except that the stirring time of the first mixed solution and the core particles was relatively shorter compared to Example 2.

[0155] Measured in the same manner as in Example 1, the porosity of the positive electrode active material was found to be 11%, and the particle size (D50) of the positive electrode active material was found to be 3.61 μm.

[0156] Example 4

[0157] The same method as in Example 1 was performed, except that the stirring time of the first mixed solution and the core particles was relatively longer and the grinding time was shorter compared to Example 1.

[0158] Measured in the same manner as in Example 1, the porosity of the positive electrode active material was found to be 2.4%, and the particle size (D50) of the positive electrode active material was found to be 7.52 μm.

[0159] Comparative Example 1

[0160] Perform the same method as in Example 1, except that no coating is formed.

[0161] Measured in the same manner as in Example 1, the porosity of the positive electrode active material was found to be 6%, and the particle size (D50) of the positive electrode active material was found to be 3.84 μm.

[0162] Comparative Example 2

[0163] The same method as in Example 1 was used, except that TiO2 was used instead of H3BO3 as the coating material to form a crystalline coating, and the dried positive electrode active material was calcined at 700°C for 6 hours.

[0164] Experiment Example 1: Performance Evaluation

[0165] To evaluate the performance of all-solid-state batteries using the positive electrode active materials prepared in the examples and comparative examples, charge and discharge experiments were conducted in pressed cells. The pressed cells consisted of a positive electrode, an electrolyte, and a negative electrode stacked within a mold. As a method for manufacturing the cells, a positive electrode active material, Super-P (manufacturer: Imerys) as a conductive material, and a sulfide-based solid electrolyte Li2S-P2S5 were mixed in a weight ratio of 70:25:5 to prepare a positive electrode composite material. The counter electrode (negative electrode) was Li-In. The cells for the all-solid-state batteries were manufactured as follows: The sulfide-based solid electrolyte Li2S-P2S5 was placed in a mold and pressurized to form a solid electrolyte layer. Then, the positive electrode active material composite was applied to one side of the solid electrolyte layer, and the negative electrode was stacked on the other side, followed by further pressurization to manufacture an electrode assembly. The manufactured electrode assembly was placed in a battery case to manufacture an all-solid-state battery. The initial capacity and rate characteristics of the manufactured all-solid-state batteries were measured as follows.

[0166] (1) Measure the initial capacity

[0167] The fabricated all-solid-state battery was charged (CC / CV) to 4.25 V using a charger / discharger at a current density of 0.1C, and charging was terminated when the current density reached 0.05C. It was then discharged (CV) to 3.0 V at a current density of 0.1C, and the initial capacity was measured.

[0168] (2) Measurement of magnification performance

[0169] The battery was charged at 0.1C under CC / CV conditions and discharged at 0.33C / 0.5C / 1.0C to obtain rate performance.

[0170] Table 2 below shows the results of the above experiments.

[0171] [Table 2]

[0172] As shown in Table 2 above, Examples 1 and 2 both exhibited good charge / discharge capacity, initial coulombic efficiency, and 1C output characteristics. It can be seen that Example 3 has a slightly higher porosity of the positive electrode active material compared to Examples 1 and 2, resulting in poorer 1C output characteristics. Furthermore, Example 4 exhibits a slightly larger particle size (D50) of the positive electrode active material compared to Examples 1 and 2, leading to poorer 1C output characteristics.

[0173] Furthermore, it was confirmed that the positive electrode active material of Comparative Example 1 contained core particles but no coating. It exhibited a higher charging capacity due to the side reaction between the core particles of the positive electrode active material and the solid electrolyte, a decrease in coulombic efficiency due to the slight decrease in discharge capacity, and poor 1C output characteristics due to the low conductivity of the interfacial side reaction layer formed by the side reaction.

[0174] Furthermore, it was confirmed that the positive electrode active material of Comparative Example 2 contained a crystalline coating formed on the surface of the core particles, exhibiting poor 1C output characteristics. This crystalline coating was formed due to the relatively high calcination temperature.

[0175] Experiment Example 2: Confirming whether an amorphous coating has been formed

[0176] To confirm the formation of the amorphous coating, the positive electrode active material prepared in Example 1 was subjected to X-ray diffraction (XRD) analysis.

[0177] Figure 2 This is the X-ray diffraction (XRD) pattern of the positive electrode active material of Example 1 of the present invention.

[0178] refer to Figure 2 A coating containing lithium titanate oxide (LTO) was formed on the NCM core particles, and no LTO peak was detected, indicating that the coating is amorphous.

[0179] [Figure Labels]

[0180] 10: Positive electrode active material

[0181] 11: Nuclear particles

[0182] 11a: Primary particles, 11b: Secondary particles

[0183] 12: Amorphous coating

[0184] 20: Solid electrolytes

Claims

1. A positive electrode active material for all-solid-state batteries, comprising: core particles; and an amorphous coating on the surface of the core particles. in, The core particles are secondary particles formed by the aggregation of multiple primary particle-form positive electrode nuclear active materials. The amorphous coating comprises a compound containing at least two of the following: Li, M, and O, wherein M contains at least one of the following: B, Zr, Nb, Ti, Al, W, P, Fe, C, N, Si, S, Co, Ge, Ga, Y, and In.

2. The positive electrode active material for all-solid-state batteries as described in claim 1, wherein, The compound comprises at least one selected from the group consisting of LiO, MO, LiM and LiMO.

3. The positive electrode active material for all-solid-state batteries as described in claim 1, wherein, The thickness of the amorphous coating is from 5 nm to 200 nm.

4. The positive electrode active material for all-solid-state batteries as described in claim 1, wherein, The particle size D50 of the positive electrode active material used in the all-solid-state battery is 3 μm to 5 μm.

5. The positive electrode active material for all-solid-state batteries as described in claim 1, wherein, The span (D90-D10) / D50 of the positive electrode active material used in the all-solid-state battery is less than 0.

7.

6. The positive electrode active material for all-solid-state batteries as described in claim 1, wherein, The positive electrode active material comprises lithium composite metal oxide.

7. The positive electrode active material for all-solid-state batteries as described in claim 1, wherein, The porosity of the positive electrode active material used in the all-solid-state battery is less than 7%.

8. A positive electrode for an all-solid-state battery, comprising the positive electrode active material for an all-solid-state battery as described in any one of claims 1 to 7.

9. The positive electrode for an all-solid-state battery as described in claim 8, wherein, The positive electrode comprises the positive electrode active material, a sulfide solid electrolyte, a binder, and a conductive material.

10. An all-solid-state battery comprising a positive electrode, a negative electrode, and a sulfide-based solid electrolyte membrane disposed therebetween, as described in claim 8.

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