Coated active material, electrode mixture and battery

Abstract

A coated active material (10) comprises: an electrode active material (1); and a coating layer (2) covering the electrode active material (1) and containing a coating material containing a B element, a P element, and an O element, wherein: a moisture amount X generated in the coated active material (10) in a temperature range of 120°C or more and 180°C or less is 10.0 ppm or less; and a coverage of the coating layer (2) with respect to the electrode active material (1) is greater than 67%.

Description

REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to Japanese Patent Application No. 2024-007478, filed on January 22, 2024, which is incorporated herein by reference in its entirety. BACKGROUND OF THE INVENTION 1. Field of the Invention

[0002] The present invention relates to a coated active material, an electrode mixture and a battery. 2. Description of the state of the art

[0003] Batteries have been actively developed in recent years. For example, the automotive industry is pushing ahead with the development of batteries for use in battery electric vehicles (BEVs), plug-in hybrid vehicles (PHEVs), or hybrid electric vehicles (HEVs). Furthermore, a technology is known in which the surface of an active electrode material to be used in the battery is coated with a phosphorus-based coating solution.

[0004] For example, Japanese Patent Application No. 2023-136753 discloses a composite particle comprising a positive electrode active material particle and a coating film covering at least a portion of the surface of the positive electrode active material particle and containing a phosphorus compound. Furthermore, JP 2023-136753 A discloses the preparation of a composite particle by mixing a positive electrode active material particle and a water-based coating solution containing phosphorus, and drying the mixture. SUMMARY OF THE INVENTION

[0005] In the coating process using a water-based coating solution containing phosphorus, moisture remains in a layer even after sufficient drying. This remaining moisture can decompose the active material of the electrode or an electrolyte present around the active material of the electrode, leading to an increase in resistance.

[0006] In view of the foregoing, the present inventors discussed coating the electrode active material with a coating material by a dry method. By using the dry method, the amount of moisture in the layer can be reduced. Meanwhile, the present inventors have discovered a new problem: it is difficult to increase the coverage of the layer with respect to the electrode active material in the case of the dry method. If the coverage of the layer with respect to the electrode active material is low, the electrode active material and the electrolyte may react to generate a high-resistance layer, which may cause an increase in resistance.

[0007] The present invention provides a coated active material that reduces an increase in resistance due to moisture and an increase in resistance due to a high resistance layer.

[0008] A coated active material according to a first aspect of the present invention comprises: an electrode active material; and a coating layer covering the electrode active material and containing a coating material containing a B element, a P element, and an O element, wherein: a moisture amount X generated in the coated active material in a temperature range of 120°C or more and 180°C or less is 10.0 ppm or less; and a coverage of the coating layer with respect to the electrode active material, or a coverage of the electrode active material with the coating layer, is greater than 67%.

[0009] In the coated active material according to the above aspect, the moisture amount X may be 8.0 ppm or less.

[0010] In the coated active material according to the above aspect, an amount of moisture Y generated in the coated active material in a temperature range of 180 °C or more and 300 °C or less may be 350 ppm or less.

[0011] In the coated active material according to the above aspect, the coverage may be 75% or more.

[0012] In the coated active material according to the above aspect, the coating material may further comprise a Li element.

[0013] In the coated active material according to the above aspect: the electrode active material may comprise a Li element, an M element, and an O element; M may be a metal other than Li and may comprise at least Ni; and a Ni / M molar ratio of Ni to M may be 50% or more.

[0014] In the coated active material according to the above aspect, Ni / M may be 80% or more.

[0015] In the coated active material according to the above aspect, a BET specific surface area may be 0.50 m 2 / g or more and less than 1.20 m 2 / g.

[0016] An electrode composition according to a second aspect of the present invention comprises: the coated active material according to the above aspect; and at least one of an electrically conductive material and a binder.

[0017] A battery according to a third aspect of the present invention comprises: a positive electrode layer; a negative electrode layer; and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer or the negative electrode layer comprises the electrode mixture of the above-mentioned aspect.

[0018] The coated active material of the present invention provides an effect of making it possible to reduce the resistance increase due to moisture and the resistance increase due to the high resistance layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Features, advantages and technical and industrial significance of exemplary embodiments of the invention are described below with reference to the accompanying drawings, in which like reference numerals designate like elements, and wherein: Fig. 1 is a schematic sectional view illustrating a coated active material of the present invention; Fig. 2 is a schematic sectional view illustrating a battery of the present invention; Fig. 3 is a flow chart illustrating a process for producing a coated active material of the present invention; and Fig. Figure 4 is a graph showing the resistances of the batteries manufactured in Examples 1 to 4 and Comparative Examples 1 to 7. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] Hereinafter, a coated active material, an electrode mixture, a battery and a method for producing a coated active material of the present invention will be described in detail. A. Coated active material

[0021] Fig. Figure 1 is a schematic sectional view illustrating the coated active material of the present invention. A coated active material 10, which is Fig.1, comprises an electrode active material 1 and a coating layer 2 covering the electrode active material 1 and containing a coating material containing a B element, a P element, and an O element. In the coated active material 10, a moisture amount X generated in a temperature range of 120°C or more and 180°C or less is typically 10.0 ppm or less. Furthermore, the coverage of the coating layer 2 with respect to the electrode active material 1 is typically greater than 67%.

[0022] According to the present invention, the moisture amount X is small and the coverage of the layer is high, and therefore, a coated active material is obtained that can reduce resistance increase due to moisture and resistance increase due to a high-resistance layer. As described above, JP 2023-136753 A discloses the production of a composite particle by mixing a positive electrode active material particle and a water-based coating solution containing phosphorus and drying the mixture. In the coating method using the water-based coating solution containing phosphorus, moisture remains in a coating layer even after sufficient drying. The remaining moisture may damage the electrode active material or an electrolyte present around the electrode active material and lead to an increase in resistance.

[0023] In view of the foregoing, the inventors of the present application have discussed covering the electrode active material with a coating material by a dry method. When using the dry method, it is not necessary to use a solvent such as water, and therefore the moisture content of the layer can be reduced. Meanwhile, the inventors of the present application have found a new problem, namely, that in the case of the dry method, it is difficult to increase the coverage of the layer with respect to the electrode active material. If the coverage of the coating layer with respect to the electrode active material is small, the electrode active material and the electrolyte may react to produce a high-resistance layer, which can increase the resistance.

[0024] The present inventors have intensively studied the solution to the above-mentioned new problem and found that the reason why it is difficult to increase the coverage is that the coating material containing phosphorus is hard, and the surface of the electrode active material is severely damaged by the coating material when the electrode active material is covered with the coating material. In view of the above, the present inventors found that the coverage of the coating material can be significantly improved by using a fine coating material to reduce damage to the surface of the electrode active material.This allows for the formation of a coated active material with a low moisture content and high coverage of the coating layer, simultaneously reducing the resistance increase caused by moisture and the resistance increase caused by the high-resistivity layer. Furthermore, the coating material contains the P element, which improves the chemical stability of the coating layer. Furthermore, the coating material contains the B element in addition to the P element, which can improve the ionic conduction of the coating layer while improving the chemical stability of the coating layer. 1. Coating layer

[0025] The coating layer in the present invention is a layer covering the active material of the electrode. Furthermore, the coating layer contains the coating material comprising the B element, the P element, and the O element. The coating material may further contain a Li element. Furthermore, the coating material preferably has a PO4 structure.

[0026] In the coating material, a molar ratio (B / P) of the B element to the P element is not particularly limited, but may be, for example, 0.5 or more and 2.0 or less, and may be 0.8 or more and 1.25 or less, or 0.9 or more and 1.11 or less. When the coating material further comprises the Li element, a molar ratio (Li / (P+B)) of the Li element to the sum of the P element and the B element is not particularly limited, but may be, for example, 0.3 or more and 1.2 or less, and may be 0.5 or more and 1.0 or less.

[0027] The coverage of the coating layer with respect to the electrode active material is usually greater than 67%, and may be 75% or more, or 80% or more. If the coverage is excessively low, it is difficult to sufficiently reduce the resistance increase due to the high-resistance layer. In fact, the coverage may be 100% or less than 100%. The coverage in the present invention is obtained by calculating an element ratio from intensity ratios of respective main elements based on X-ray photoelectron spectroscopy (XPS) measurement, and is obtained as a percentage of the elements contained in the coating layer with respect to a sum of the elements contained in the electrode active material and the elements contained in the coating layer.

[0028] The thickness of the coating layer is not particularly limited, but may be, for example, 1 nm or more and 100 nm or less, 5 nm or more and 50 nm or less, or 10 nm or more and 30 nm or less. The thickness of the coating layer is obtained, for example, as an average value of the thicknesses of a plurality of samples (for example, 100 or more samples) observed by a scanning electron microscope (SEM) or a transmission electron microscope (TEM). 2. Active electrode material

[0029] The active electrode material of the present invention is not particularly limited, but preferably includes a Li element, an M element, and an O element. M is a metal other than Li (including a metalloid). M may be a transition metal or a metal (including a metalloid) belonging to Group 13 to Group 16 in the periodic table. Further, M may be one metal or two or more kinds of metals. Of these, M is preferably at least one kind among Ni, Co, Mn, Al, V, and Fe.

[0030] In particular, M preferably comprises at least Ni. The electrode active material containing Ni may be affected by moisture, but the coated active material of the present invention has a small amount of moisture, and therefore, the deterioration of the electrode active material containing Ni can be reduced. A molar ratio (Ni / M) of Ni to M is not particularly limited, but may be, for example, 30% or more, 50% or more, 60% or more, 70% or more, or 80% or more. In fact, Ni / M may be 100% or less than 100%.

[0031] The active material of the electrode may include a non-metallic element such as an element P in addition to the element Li, the element M, and the element O. Furthermore, the crystal structure of the active material of the electrode is not particularly limited. Examples include a layered rock salt structure, a spinel structure, and an olivine structure.

[0032] As an example of the composition of the active material of the electrode, LiNi a Co y Mn z O2 (0.5 ≤ x, 0 ≤ y, 0 ≤ z, x + y + z = 1). The symbol x can be 0.6 or more, 0.7 or more, or 0.8 or more. The symbol y can be 0 or greater than 0. Furthermore, the symbol y is, for example, 0.3 or less. The symbol z can be 0 or greater than 0. Furthermore, the symbol z is, for example, 0.1 or less.

[0033] Another example of the composition of the active material of the electrode is LiNi a Cob Mn c O2 (0.5 ≤ a, 0 ≤ b, 0 ≤ c, a + b + c = 1). Symbol a can be 0.6 or more, 0.7 or more, or 0.8 or more. Symbol b can be 0 or greater than 0. Furthermore, symbol b is, for example, 0.3 or less. Symbol c can be 0 or greater than 0. Furthermore, symbol c is, for example, 0.3 or less.

[0034] The shape of the active material of the electrode is usually a particle shape. A particle size D 50 of the active material of the electrode is, for example, 100 nm or more and can be 1 µm or more or 5 µm or more. The particle size D 50 of the active material of the electrode is, for example, 50 µm or less and may be 20 µm or less. In the present invention, the particle size D 50 a particle size cumulatively corresponding to 50 vol%, measured using a laser diffraction particle size distribution measuring device. 3. Coated active material

[0035] In the coated active material of the present invention, a moisture amount X generated in a temperature range of 120°C or more and 180°C or less is normally 10.0 ppm or less. The moisture amount X may be 9.0 ppm or less, or 8.0 ppm or less. A small amount of moisture X can reduce the increase in resistance due to moisture. Further, in the coated active material, a moisture amount Y generated in a temperature range of 180°C or more and 300°C or less is, for example, 350 ppm or less, and may be 320 ppm or less. A small amount of moisture Y can reduce the increase in resistance due to moisture. The method for measuring the moisture amount X and the moisture amount Y is as described in the examples later.

[0036] The specific BET surface area of the coated active material is not particularly limited, but is, for example, 0.50 m 2 / g or more and can reach 0.70 m 2 / g or more. For example, the specific BET surface area of the coated active material is less than 1.20 m 2 / g and can reach 1.00 m 2 / g or less.

[0037] The coated active material of the present invention is typically used in a battery. The electrode active material in the coated active material can be a positive electrode active material or a negative electrode active material, with the former being preferable. Examples of the method for producing the coated active material include a method described later in "D. Method for Producing Coated Active Material." B. Electrode mixture

[0038] An electrode mixture according to the present invention comprises the above-mentioned coated active material and at least one of an electrically conductive material and a binder.

[0039] According to the present invention, the use of the above-mentioned coated active material makes it possible to obtain an electrode mixture which can reduce the increase in resistance due to moisture and the increase in resistance due to the high resistance layer.

[0040] The electrode mixture comprises the coated active material and at least one of the electrically conductive material and the binder. The coated active material is similar to the content described above under "A. Coated Active Material." The active electrode material in the coated active material can be a positive electrode active material or a negative electrode active material, with the former being preferable. That is, the electrode mixture can be a positive electrode mixture or a negative electrode mixture, with the former being preferable.

[0041] For example, the percentage of coated active material in the electrode mixture is 20 wt% or more, and may be 30 wt% or more, or 40 wt% or more. If the percentage of coated active material is too low, sufficient energy density may not be obtained. In fact, the percentage of coated active material is 80 wt% or less, for example, and may be 70 wt% or less, or 60 wt% or less. If the percentage of coated active material is excessively large, the ionic conduction and electronic conduction in the electrode mixture may be relatively reduced.

[0042] The electrode mixture comprises at least an electrically conductive material and a binder. Examples of electrically conductive materials include a carbon material, metal particles, and a conductive polymer. Examples of the carbon material include particulate carbon materials such as acetylene black (AB) and Ketjen black (KB), and fibrous carbon materials such as carbon fibers, carbon nanotubes (CNT), and carbon nanofibers (CNF). Further, examples of the binder include a rubber-based binder and a fluorine-based binder.

[0043] The electrode mixture may further comprise a solid electrolyte. The solid electrolyte may be an organic solid electrolyte such as a gel electrolyte or an inorganic solid electrolyte such as a sulfide solid electrolyte or an oxide solid electrolyte. Of these, the solid electrolyte is preferably a sulfide solid electrolyte. This is because the ionic conductivity is high.

[0044] The sulfide solid electrolyte typically contains at least one Li element and one S element. The sulfide solid electrolyte preferably also contains a Me element (Me is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In). Furthermore, the sulfide solid electrolyte may contain a halogen element such as F, Cl, Br, or I.

[0045] The sulfide solid electrolyte can be a glass-based (amorphous) sulfide solid electrolyte, a glass-ceramic-based sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. The sulfide solid electrolyte can have a crystal phase. Examples of the above-mentioned crystal phase include a thio-LISICON crystal phase, an argyrodite crystal phase, and an LGPS crystal phase.

[0046] The composition of the sulfide solid electrolyte is not particularly limited, but examples include xLi2S·(1-x)P2S5 (0.5 ≤ x < 1) and yLiI·z LiBr(100-yz)(xLi2S·(1-x)P2S5) (0.5 ≤ x < 1, 0 ≤ y ≤ 30, 0 ≤ z ≤ 30). In these compositions, the symbol x preferably satisfies 0.7 ≤ x ≤ 0.8. As another example of the composition of the sulfide solid electrolyte, Li 7-x-2y PS 6-x-y X y The symbol X represents at least one of F, Cl, Br, and I, and the symbols x and y satisfy 0 ≤ x and 0 ≤ y. Another example of the composition of the sulfidic solid electrolyte is Li 4-x Me 1-x P x S4 (0 < x < 1). Me is at least one type among Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi. C. Battery

[0047] Fig. Figure 2 is a schematic sectional view illustrating a battery of the present invention. Fig.The battery 20 shown in Figure 2 comprises a positive electrode layer 11, a negative electrode layer 12, an electrolyte layer 13 disposed between the positive electrode layer 11 and the negative electrode layer 12, a positive electrode current collector 14 that collects a current from the positive electrode layer 11, and a negative electrode current collector 15 that collects a current from the negative electrode layer 12. In the present invention, the positive electrode layer 11 or the negative electrode layer 12 comprises the electrode mixture described in "B. Electrode Mixture" above.

[0048] According to the present invention, the use of the above-mentioned electrode mixture enables a battery that exhibits reduced resistance increase due to moisture and reduced resistance increase due to the high-resistance layer. As described above, the electrode mixture can be a positive electrode mixture or a negative electrode mixture, with the former being preferable. Details of a battery in a case where the electrode mixture is a positive electrode mixture will be described below. 1. Layer of the positive electrode

[0049] The positive electrode layer in the present invention comprises the above-mentioned electrode mixture (positive electrode mixture). The electrode mixture is similar to the content described in "B. Electrode Mixture" above, so a description is omitted here. Further, the positive electrode layer may comprise an electrolyte if necessary. The electrolyte is similar to the content described in "3. Electrolyte Layer". The thickness of the positive electrode layer is, for example, 0.1 μm or more and 1000 μm or less, and may be 0.1 μm or more and 500 μm or less, or 0.1 μm or more and 100 μm or less. Further, examples of the method for forming the positive electrode layer include a method for applying the electrode mixture (positive electrode mixture) to the positive electrode current collector. 2. Layer of the negative electrode

[0050] The negative electrode layer is a layer comprising at least one negative electrode active material. Furthermore, the negative electrode layer may comprise at least one electrolyte, an electrically conductive material, and / or a binder, as needed.

[0051] Examples of negative electrode active materials include metal active materials such as Li and Sn, Si-based active materials, carbon active materials such as graphite, and oxide active materials such as Li4Ti5O 12 .

[0052] The negative electrode active material is preferably a Si-based active material. This is to increase the battery capacity. The Si-based active material is an active material containing Si as the main component. The Si-based active material may be Si alone, a Si alloy, or a Si oxide. In addition, the Si-based active material may include a diamond-like crystal phase, a Type I clathrate crystal phase, or a Type II clathrate crystal phase. In the Type I clathrate or Type II clathrate crystal phase, a plurality of Si elements form a polyhedron (cage) containing pentagons or hexagons. This polyhedron has a cavity that can enclose Li ions, thereby reducing the volume change during charging and discharging.

[0053] The active material of the negative electrode can, for example, be in the form of a particle. The particle size D 50 of the negative electrode active material is not particularly limited, but can be, for example, 10 nm or more and 100 nm or more. The particle size D 50 of the negative electrode active material is, for example, 50 µm or less and may be 20 µm or less.

[0054] The electrolyte used in the negative electrode layer is similar to that described in "3. Electrolyte Layer." Furthermore, the electrically conductive material and binder used in the negative electrode layer are similar to those described in "B. Electrode Mixture" above, so their description is omitted here. The thickness of the negative electrode layer is, for example, 0.1 μm or more and 1000 μm or less, and may be 0.1 μm or more and 500 μm or less, or 0.1 μm or more and 100 μm or less. 3. Electrolyte layer

[0055] The electrolyte layer is a layer formed between the positive electrode layer and the negative electrode layer and comprises at least one electrolyte. The electrolyte can be a solid electrolyte or a liquid electrolyte (electrolyte solution).

[0056] The solid electrolyte is similar to the contents described in "B. Electrode Mixture" above, so a description is omitted. The electrolytic solution preferably comprises a carrier salt and a solvent. Examples of the carrier salt (lithium salt) of the lithium ion conduction electrolytic solution include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, and LiAsF6, and organic lithium salts such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, and LiC(CF3SO2)3. Examples of the solvent used in the electrolytic solution include cyclic esters (cyclic carbonates) such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), and linear esters (linear carbonates) such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). The electrolytic solution preferably comprises two or more types of solvents.

[0057] The thickness of the electrolyte layer is, for example, 0.1 µm or more and 1000 µm or less, and may be 0.1 µm or more and 500 µm or less, or 0.1 µm or more and 100 µm or less. 4. Other configurations

[0058] The battery of the present invention preferably comprises a positive electrode current collector that collects current from the positive electrode layer and a negative electrode current collector that collects current from the negative electrode layer. Examples of the material of the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. Examples of the material of the negative electrode current collector include SUS, copper, nickel, and carbon.

[0059] The battery of the present invention may further comprise a retaining device that applies a retaining pressure to the positive electrode layer, the electrolyte layer, and the negative electrode layer along a direction of their thickness. Particularly when the electrolyte layer is a solid electrolyte layer, a retaining pressure is preferably applied to form a good ion conduction path and a good electronic conduction path. The retaining pressure is, for example, 0.1 MPa or more, and may be 1 MPa or more, or 5 MPa or more. The retaining pressure is, for example, 100 MPa or less, and may be 50 MPa or less, or 20 MPa or less. 5. Battery

[0060] The type of battery of the present invention is not particularly limited, but typically it is a lithium-ion battery. Further, the battery of the present invention may be a liquid battery comprising an electrolyte solution as the electrolyte layer, or a solid-state battery comprising a solid electrolyte layer as the electrolyte layer. The solid-state battery may be a semi-solid-state battery or a solid-state battery. Further, the battery of the present invention may be a primary battery or a secondary battery, of which the secondary battery is preferable. This is because the battery can be repeatedly charged and discharged and can be effectively used as, for example, a vehicle battery.

[0061] Examples of applications of the battery include a power supply for a vehicle such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), a battery electric vehicle (BEV), a gasoline vehicle, or a diesel vehicle. Specifically, the battery is preferably used for a power supply for driving the hybrid electric vehicle (HEV), the plug-in hybrid electric vehicle (PHEV), or the battery electric vehicle (BEV). Furthermore, the battery can be used as a power supply for a mobile object other than a vehicle (e.g., a train, a ship, or an aircraft) or as a power supply for an electrical product such as an information processing device. D. Method for producing the coated active material

[0062] Fig. Figure 3 is a flow chart illustrating the process for producing the coated active material of the present invention. Fig.3, the active electrode material and the coating material are prepared (preparation step and production step, respectively). Next, the active electrode material is covered with the coating material using a dry process to form the coating layer (coating layer formation step). In the present invention, the coating condition is adjusted to obtain the coated active material described above in "A. Coated Active Material." Specifically, a coating material having a particle size D 90 of 2 µm or less.

[0063] According to the present invention, the use of a fine coating material makes it possible to obtain a coated active material that can reduce the resistance increase due to moisture and the resistance increase due to the high resistance layer. 1. Preparation step or production step

[0064] The preparation step in the present invention is a step for preparing the above-mentioned active electrode material and the above-mentioned coating material. The active electrode material and the coating material are similar to those described above in "A. Coated Active Material."

[0065] The shape of the coating material in the preparation step is usually a particle shape. The particle size D 90The particle size of the coating material is typically 2 µm or less, and can be 1 µm or less, or 0.8 µm or less. Using a fine coating material can prevent the surface of the electrode's active material from being damaged by the coating material when the electrode's active material is or will be covered with the coating material. This can improve the coating coverage. The particle size D 90 of the coating material is not particularly limited, but is, for example, 0.2 µm or more. The particle size D 90 corresponds to a particle size cumulatively equal to 90 vol% from the smaller particle side, measured with the laser diffraction particle size distribution measuring device.

[0066] The particle size D 50of the coating material is, for example, 1 µm or less and can be 0.6 µm or less or 0.4 µm or less. The particle size D 50 of the coating material is not particularly limited, but can be, for example, 0.1 µm or more. Furthermore, the ratio of the particle size D 50 of the coating material to particle size D 50 of the active material of the electrode is not particularly limited, but is, for example, 1% or more and 25% or less, and may be 5% or more and 15% or less.

[0067] The method for producing the coating material is not particularly limited. Examples include a method comprising a synthesis step of synthesizing a coarse material of the coating material and a granulation step of granulating the above-mentioned coarse material. The synthesis step is, for example, a step of dissolving a solute comprising a B source and a P source in a solvent to prepare a coating solution, and then drying the coating solution.

[0068] The B source is not particularly limited as long as the B source is a simple substance or a compound containing the B element, and examples thereof include boric acid (H3BO3). The P source is not particularly limited as long as the P source is a simple substance or a compound containing the P element, and examples thereof include orthophosphoric acid (H3PO4) and metaphosphoric acid (HPO3). Further, the coating solution preferably comprises an O source. Examples of the O source include an O element contained in the above-mentioned B source or P source. Further, the above-mentioned solute may comprise a Li source. The Li source is not particularly limited as long as the Li source is a simple substance or a compound containing the Li element, and examples thereof include lithium hydroxide (LiOH). Further, examples of the solvent include water.

[0069] As a specific example of the method for preparing the coating solution, the following method for preparing the coating solution can be given. First, a first aqueous solution obtained by dissolving an orthophosphoric acid (H3PO4) or a metaphosphoric acid (HPO3) in water is prepared. Next, a second aqueous solution obtained by dissolving a boric acid (H3BO3) in the first aqueous solution is prepared. Next, lithium hydroxide monohydrate (LiOH·H2O) is dissolved in the second aqueous solution. Further, the coating solution is dried to obtain a coarse material. The method for drying the coating solution is not particularly limited, but examples include spray drying, an electric furnace, a vacuum drying furnace, and a spray pyrolysis device.

[0070] The granulation step is a step of granulating the above-mentioned coarse material. By granulating the coarse material, a coating material with a particle size D can be obtained. 90 of 2 µm or less. Examples of the method for granulating the coarse material include mechanical grinding, such as with a bead mill and a ball mill. The mechanical grinding can be carried out in a dry or wet state. When the mechanical grinding is carried out in a wet state, a solvent other than water is preferably used. The conditions of the mechanical grinding are not particularly limited and are adjusted so as to obtain the coating material with a particle size D 90 of 2 µm or less can be obtained. 2. Step to form the coating layer

[0071] The layer forming step in the present invention is a step of covering the above-mentioned electrode active material with the above-mentioned coating material by a dry method to form the above-mentioned layer.

[0072] Examples of the dry method include a method in which a mixture comprising the electrode active material and the coating material is subjected to shearing treatment. The above-mentioned mixture basically contains no water, but may contain a small amount of water as long as its influence is negligible. The shearing treatment is, for example, the treatment of rotating a chopper arranged in a container. Another example of the shearing treatment can be cited as a method of rotating a blade arranged in a container so that compressive shear energy is applied to the mixture existing between the blade and a wall surface of the container. Furthermore, the condition of the shearing treatment is not particularly limited and is adjusted as needed so that the coated active material described above in "A. Coated Active Material" can be obtained. 3. Coated active material

[0073] The coated active material obtained through the steps described above is similar to the content described in “A. Coating Material” above.

[0074] It should be noted that the present invention is not limited to the above-mentioned embodiment. The above-mentioned embodiment is exemplary, and anything having substantially the same configuration and producing similar actions and effects as a technical idea described in the claims of the present invention is included in the technical scope of the present invention. Comparative Example 1 Preparation of a coating solution or solution for coating

[0075] Metaphosphoric acid (manufactured by FUJIFILM Wako Pure Chemical Corporation) and deionized water were mixed in a weight ratio of 4.52:191.8 to obtain an aqueous solution. Boric acid (manufactured by NACALAI TESQUE, INC.) was added and dissolved in the resulting aqueous solution so that the molar ratio (B / P) of element B to element P was 1.0. Lithium hydroxide monohydrate (manufactured by FUJIFILM Wako Pure Chemical Corporation) was also added and dissolved so that the molar ratio (Li / (P+B)) of element Li to the sum of element P and element B was 0.9. Thus, the coating solution was obtained. Production of the coated active material

[0076] Particles of the active material (LiNi 0,81 Co 0,15 Al 0,04 O2, particle size D 50= 4.5 µm) were dispersed in the resulting coating solution to prepare a slurry. The solid concentration of the slurry was 69 wt%. The slurry was then dried using a spray dryer from BUCHI Corporation (product name: Mini Spray Dryer B-290) to form the layer on the surface of the active material particle. The drying air temperature of the spray dryer was 200 °C, and the drying air flowed at a speed of 0.45 m. 3 / min. Next, the active material particle with the layer formed on it was subjected to heat treatment in an air atmosphere to obtain the coated active material. The heat treatment temperature was 200 °C and the heat treatment time was 5 hours. Comparative Example 2Production of coating material A

[0077] A coating solution was obtained similarly to Comparative Example 1. The resulting coating solution was dried using a spray dryer manufactured by BUCHI Corporation, product name: Mini Spray Dryer B-290, to obtain powder. The drying air temperature of the spray dryer was 200 °C, and the drying air flow rate was 0.45 m³. 3 / min. Subsequently, an additional heat treatment was performed in an air atmosphere. The heat treatment temperature was 200 °C and the heat treatment time was 5 hours. This resulted in powder coating material A. Production of the coated active material

[0078] In a BALANCE GRAN BG-2L mixer-stirrer (manufactured by FREUND-TURBO CORPORATION), 1000 g of active material particles identical to those in Comparative Example 1 and 31.0 g of coating material A were added. Subsequently, stirring was performed for 1 hour at a chopper speed of 1,500 rpm to form the layer on the surface of the active material particles. Thus, the coated active material was obtained. Comparison example 3

[0079] The coated active material was obtained similarly to Comparative Example 2, except that when the layer was formed on the surface of the active material particle, stirring treatment was performed for 1 hour at each of the chopper speeds of 1,500 rpm and 2,000 rpm. Comparison example 4

[0080] The coated active material was obtained similarly to Comparative Example 2, except that when the layer was formed on the surface of the active material particle, a stirring treatment was performed for 1 hour at each of the chopper speeds of 1,500 rpm, 2,000 rpm, and 2,500 rpm. Comparison example 5

[0081] The coated active material was obtained similarly to Comparative Example 2, except that when the layer was formed on the surface of the active material particle, stirring treatment was performed for 1 hour at each of the chopper speeds of 1,500 rpm, 2,000 rpm, 2,500 rpm, and 3,000 rpm. Comparison example 6

[0082] The coated active material was obtained similarly to Comparative Example 2, except that when the layer was formed on the surface of the active material particle, a stirring treatment was performed for 1 hour at each of the chopper speeds of 1,500 rpm, 2,000 rpm, 2,500 rpm, 3,000 rpm, and 3,600 rpm. Comparative Example 7 Production of coating material B

[0083] Coating material A was obtained similarly to Comparative Example 2. Coating material A was dispersed in ethanol so that the solid concentration was 20 wt% to obtain a dispersion liquid. A LABSTAR Mini MGF015 wet bead mill (manufactured by Ashizawa Finetech Ltd.) was prepared, and the obtained dispersion liquid was placed in a grinding chamber together with zirconia beads (Ø 0.1 mm) to perform a grinding treatment for 90 minutes. The peripheral speed of the beads was 14 m / s and the circulation rate was 0.3 L / min. Subsequently, the material was air-dried for 24 hours to volatilize the ethanol. Furthermore, vacuum drying was performed at 100°C for 8 hours. Thus, coating material B was obtained. Production of the coated active material

[0084] In a BALANCE GRAN BG-2L mixer-stirrer (manufactured by FREUND-TURBO CORPORATION), 1,000 g of active material particles identical to those in Comparative Example 1 and 31.0 g of coating material B were added. Subsequently, stirring was performed for 1 hour at a chopper speed of 1,500 rpm to form the coating on the surface of the active material particles. Thus, the coated active material was obtained. Example 1

[0085] The coated active material was obtained similarly to Comparative Example 7, except that when the layer was formed on the surface of the active material particle, a stirring treatment was performed for 1 hour at each of the chopper speeds of 1,500 rpm and 2,000 rpm. Example 2

[0086] The coated active material was obtained similarly to Comparative Example 7, except that when the layer was formed on the surface of the active material particle, a stirring treatment was performed for 1 hour at each of the chopper speeds of 1,500 rpm, 2,000 rpm, and 2,500 rpm. Example 3

[0087] The coated active material was obtained similarly to Comparative Example 7, except that when the layer was formed on the surface of the active material particle, stirring treatment was carried out for 1 hour at each of the chopper speeds of 1,500 rpm, 2,000 rpm, 2,500 rpm, and 3,000 rpm. Example 4

[0088] The coated active material was obtained similarly to Comparative Example 7, except that when the layer was formed on the surface of the active material particle, a stirring treatment was performed for 1 hour at each of the chopper speeds of 1,500 rpm, 2,000 rpm, 2,500 rpm, 3,000 rpm, and 3,600 rpm. Table 1 shows the coating conditions of Examples 1 to 4 and Comparative Examples 1 to 7. Table 1 Coating conditions Type material Number of chopper revolutions Comparison example 1 wet Coating solution - Comparison example 2 dry Coating material A 1,5k Comparison example 3 dry Coating material A 1.5k, 2.0k Comparison example 4 dry Coating material A 1.5k, 2.0k, 2.5k Comparison example 5 dry Coating material A 1.5k, 2.0k, 2.5k, 3.0k Comparison example 6 dry Coating material A 1.5k, 2.0k, 2.5k, 3.0k, 3.6k Comparison example 7 dry Coating material B 1,5k Example 1 dry Coating material B 1.5k, 2.0k Example 2 dry Coating material B 1.5k, 2.0k, 2.5k Example 3 dry Coating material B 1.5k, 2.0k, 2.5k, 3.0k Example 4 dry Coating material B 1.5k, 2.0k, 2.5k, 3.0k, 3.6k EvaluationMeasurement of particle size distribution

[0089] The particle size distributions of coating material A and coating material B were measured using a laser diffraction particle size distribution measuring device. Coating material A had a particle size of D 50 of 2.3 µm and a particle size D 90 of 4.3 µm. The coating material B had a particle size D 50of 0.34 µm and a particle size D 90 of 0.75 µm. Measurement of coverage or degree of coverage

[0090] The coverage of the coated active material obtained in each of Examples 1 to 4 and Comparative Examples 1 to 7 was measured by X-ray photoelectron spectroscopy (XPS). Specifically, an X-ray photoelectron spectroscopy device (manufactured by ULVAC-PHI, Inc., PHIX-tool) was used to perform surface elemental analysis of the coated active material. A narrow-spectrum analysis was performed with a pass energy of 224 eV. Afterward, analysis software (MultiPak, manufactured by ULVAC-PHI, Inc.) was used to calculate an element ratio from the detected intensity values of C1s, O1s, P2p, Ni2p3, Co2p3, Al2p, and B1s, and the value of (P+B) / (P+B+Ni+Co+Al) [%] was obtained as the coverage. Table 2 shows the results. Measurement of the specific BET surface area

[0091] The BET specific surface area of the coated active material obtained in each of Examples 1 to 4 and Comparative Examples 1 to 7 was measured by a BET method. Specifically, Microtrac's BELSORP max II was used to measure the BET specific surface area of N2 adsorption. 5.0 g of the sample was weighed into a measuring tube under a nitrogen atmosphere and subjected to vacuum degassing at room temperature for 8 hours while connected to the measuring device. Afterward, measurements were performed at at least 10 points within a relative pressure P / P0 of 0.250 to 0.995 to calculate the BET specific surface area. Table 2 shows the results. Measuring the amount of moisture

[0092] The moisture content of the coated active material obtained in each of Examples 1 to 4 and Comparative Examples 1 and 7 was measured by the Karl Fischer method. Specifically, the MKC-710 series, manufactured by KYOTO ELECTRONICS MANUFACTURING CO., LTD., was used to measure a minute amount of moisture in the sample. 1.0 g of the coated active material was placed in a sample container under a nitrogen atmosphere, and then the sample container was inserted into the device. After a blank measurement at 120°C, the temperature was maintained at 120°C, and the moisture content was measured until the minimum electrolytic volume was 0.1 µg or less. Afterward, the temperature was raised to 180°C, and a similar procedure was performed. The moisture content was recorded until the minimum electrolytic volume was 0.1 µg or less. Next, the temperature was raised to 300°C, and a similar procedure was repeated.The amount of moisture formation was measured in each temperature range and divided by the sample weight to convert it into the amount of moisture (unit ppm). Table 2 shows the results. Resistance measurement

[0093] The coated active material obtained in each of Examples 1 to 4 and Comparative Examples 1 to 7 was used as a positive electrode active material for manufacturing a battery, and its resistance was measured.

[0094] First, a positive electrode active material (coated active material), a sulfide solid electrolyte (10LiI-15LiBr-75Li3PS4), an electrically conductive material (VGCF), a binder (SBR), and a dispersion medium (heptane) were mixed to prepare a positive electrode slurry. The mixing ratio of the positive electrode active material and the sulfide solid electrolyte was 6:4 (by volume). For 100 parts by weight of the positive electrode active material, 3 parts by mass of the electrically conductive material and 3 parts by mass of the binder were added. The positive electrode slurry was sufficiently stirred with an ultrasonic homogenizer, and the positive electrode slurry was coated onto the surface of the positive electrode current collector (aluminum foil) to form a coating film.The coating film was dried on a hot plate at 100 °C for 30 minutes. A mesh-like positive electrode was thus obtained. A disc-shaped positive electrode was cut from the mesh-like positive electrode. The positive electrode had an area of 1 cm. 2 .

[0095] Next, the negative electrode and the solid electrolyte layer were prepared. The active material of the positive electrode was graphite. The positive electrode, the solid electrolyte layer, and the negative electrode used the same type of sulfide solid electrolyte. In a cylindrical device, the positive electrode, the solid electrolyte layer, and the negative electrode were stacked in the specified order to form a stack. The stack was pressed to form a power-generating element. The power-generating element was connected to terminals to obtain a battery (solid-state battery). The open-circuit voltage (OCV) of the obtained solid-state battery was set to 2.03 V, and then a constant current discharge was performed. Furthermore, the voltage drop in 5 seconds was divided by the current to measure the battery resistance. The discharge current rate was 2.5 C.The resistance of the battery of Comparative Example 1 was used as a reference (1.0) to relatively evaluate the resistance of the battery of each example and each comparative example. Table 2 and . Fig. 4 shows the results. Table 2 Coverage [%] BET specific surface area [m 2 / G] Moisture content [ppm] Standardized resistance 120 °C-180 °C 180 °C-300 °C Comparison example 1 96 0,97 38,4 409,3 1,0 Comparison example 2 65 1,33 - - 2,1 Comparison example 3 56 1,43 - - 2,7 Comparison example 4 55 1,28 - - 2,7 Comparison example 5 42 1,27 - - 4,7 Comparison example 6 67 1,2 - - 5,2 Comparison example 7 53 1,53 8,8 319 1,8 Example 1 84 1,15 6,6 311 1,0 Example 2 80 0,99 7,8 282 0,9 Example 3 86 1 1,8 292 0,9 Example 4 93 0,95 9,8 229 0,9

[0096] As shown in Table 2, Comparative Example 1 used the wet method, and therefore, it was confirmed that the amount of moisture was relatively high even after drying. In contrast, Examples 1 to 4 used the dry method, and therefore, it was confirmed that the amount of moisture was low. As shown in Table 2 and Fig.As shown in Figure 4, when comparing Example 1 and Comparative Example 1, the coverage (84%) of Example 1 was lower than the coverage (96%) of Comparative Example 1, and Example 1 was in a situation where the increase in resistance was likely due to the high-resistance layer, but the amount of moisture in Example 1 was less than the amount of moisture in Comparative Example 1, and thus Example 1 was able to reduce the increase in resistance due to moisture. As a result, the resistance was at the same level. In addition, the resistance in Examples 2 to 4 was lower than that in Example 1. In Examples 1 to 4, no organic solvent was used, and therefore they were advantageous in terms of low cost and reducing environmental load.

[0097] As shown in Table 2, when comparing Comparative Examples 2 to 6 and Examples 1 to 4, it was confirmed that the coverage was greatly improved by using the granulated coating material B. As shown in Table 2 and Fig.As shown in Figure 4, Comparative Examples 2 to 6 used the dry method, so they had a small amount of moisture but also a small coverage. It is concluded that the increase in resistance was due to the high-resistance layer. Although Comparative Example 7 used the dry method, so it had a small amount of moisture, and also used granulated coating material B, the coverage was small because the coating treatment was insufficient. It is concluded that the increase in resistance occurred due to the high-resistance layer. In contrast, Examples 1 to 4 used the dry method, which generated a small amount of moisture, and also used granulated coating material B, and performed sufficient coating treatment. As a result, the coverage could be increased.It is assumed that this reduced the resistance increase due to moisture and the resistance increase due to the high resistance layer.

[0098] Furthermore, regarding the BET specific surface area, as shown in Table 2, in Comparative Examples 2 to 6 using Coating Material A, the BET specific surface areas of the coated active materials were substantially the same. This supports the fact that the coverage is not improved along with the stirring treatment. In Comparative Example 7 and Examples 1 to 4 using Coating Material B, the coverage improved with increasing stirring treatment time, and the value decreased to the BET specific surface area corresponding to Comparative Example 1 (wet process). This indicates that the coverage improved along with the stirring treatment by dispersing Coating Material B on the surface of the active material. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2024-007478

[0001] JP 2023-136753

[0004] JP 2023-136753 A [0004, 0022]

Claims

[1] Coated active material (10) comprising: an active material (1) of an electrode; and a coating layer (2) covering the active material (1) of the electrode and containing a coating material comprising a B element, a P element and an O element, wherein: a moisture amount X generated in the coated active material (10) in a temperature range of 120 °C or more and 180 °C or less is 10.0 ppm or less; and a coverage of the coating layer (2) with respect to the active material (1) of the electrode is greater than 67%. [2] The coated active material (10) according to claim 1, wherein the moisture amount X is 8.0 ppm or less. [3] The coated active material (10) according to claim 1, wherein an amount of moisture Y generated in the coated active material (10) in a temperature range of 180°C or more and 300°C or less is 350 ppm or less. [4] The coated active material (10) according to claim 1, wherein the coverage is 75% or more. [5] The coated active material (10) according to claim 1, wherein the coating material further comprises a Li element. [6] Coated active material (10) according to claim 1, wherein: the active material (1) of the electrode comprises a Li element, an M element and an O element; M is a metal other than Li and comprising at least Ni; and a molar ratio Ni / M of Ni to M is 50% or more. [7] The coated active material (10) according to claim 6, wherein Ni / M is 80% or more. [8] Coated active material (10) according to claim 1, wherein a BET specific surface area is 0.50 m 2 / g or more and less than 1.20 m 2 / g. [9] Electrode mixture comprising: the coated active material (10) according to any one of claims 1 to 8; and at least one of an electrically conductive material and a binder. [10] Battery (20), comprising: a layer (11) of a positive electrode; a layer (12) of a negative electrode; and an electrolyte layer (13) arranged between the positive electrode layer (11) and the negative electrode layer (12), wherein the positive electrode layer (11) or the negative electrode layer (12) comprises the electrode mixture according to claim 9.

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