Coated active material, electrode mixture, battery, and coating liquid

Abstract

The invention relates to a coated active material, an electrode mixture, a battery, and a coating liquid. The coated active material includes: an electrode active material; and a coating layer coating the electrode active material, wherein the electrode active material has Li element, M element, and O element; m is a metal other than Li and contains at least Ni; the molar ratio of Ni to M (Ni / M) is 80% or more, the coating layer contains element B, element P, element La, and element O, and the molar ratio of element La to element P (La / P) is 0.005-0.15 (inclusive).

Description

Technical Field

[0001] The present disclosure relates to a coated active material, an electrode composite material, a battery, and a coating liquid. Background Art

[0002] In recent years, the development of batteries has been actively carried out. For example, in the automotive industry, the development of batteries for battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), or hybrid electric vehicles (HEVs) is being promoted. In addition, it is known to coat the surface of an electrode active material for a battery with a phosphorus-based coating liquid.

[0003] For example, Japanese Patent Application Laid-Open No. 2023-136753 discloses a composite particle including a positive electrode active material particle and a coating film that covers at least a part of the surface of the positive electrode active material particle and contains a phosphorus compound. Further, Japanese Patent Application Laid-Open No. 2023-136753 discloses that the composite particle is manufactured by mixing a positive electrode active material particle and an aqueous coating liquid containing phosphorus (aqueous coating liquid) and drying the mixture. Summary of the Invention

[0004] From the viewpoint of increasing the capacity, an electrode active material having a high nickel ratio is promising. On the other hand, when an aqueous coating liquid containing phosphorus comes into contact with an electrode active material having a high nickel ratio, an exchange reaction of H + with Li + is presumed to occur, and NiO having a high resistance is generated. As a result, the resistance increases. This is a problem peculiar to the combination of an electrode active material having a high nickel ratio and an aqueous coating liquid containing phosphorus (coating layer containing phosphorus).

[0005] The present disclosure provides a coated active material that can suppress an increase in resistance even when an electrode active material having a high nickel ratio is combined with a coating layer containing phosphorus.

[0006] The coated active material according to the first aspect of the present disclosure includes: an electrode active material; and a coating layer that coats the electrode active material, where the electrode active material contains a Li element, an M element, and an O element; M is a metal other than Li and contains at least Ni; the molar ratio of Ni to M, Ni / M, is 80% or more, the coating layer contains a B element, a P element, a La element, and an O element, and the molar ratio of the La element to the P element, La / P, is 0.005 or more and 0.15 or less.

[0007] In the coated active material according to the above aspect, La / P may be 0.01 or more and 0.11 or less.

[0008] In the coated active material according to the above aspect, the molar ratio of the B element to the P element, B / P, may be 0.5 or more and 2.0 or less.

[0009] The coated active material involved in the above solution, wherein the coating rate of the coating layer relative to the electrode active material can be 75% or more.

[0010] The coated active material involved in the above solution, wherein M may further contain at least one of Co, Mn, and Al.

[0011] The electrode composite material involved in the second solution of the present disclosure includes: the coated active material involved in the above solution; and at least one of a conductive material and a binder.

[0012] The electrode composite material involved in the above solution, wherein the electrode composite material may contain a solid electrolyte.

[0013] The electrode composite material involved in the above solution, wherein the solid electrolyte may be a sulfide solid electrolyte.

[0014] The battery involved in the third solution of the present disclosure includes: 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 contains the electrode composite material involved in the above solution.

[0015] The battery involved in the above solution, wherein the positive electrode layer may contain the electrode composite material.

[0016] The battery involved in the above solution, wherein the electrolyte layer may contain a solid electrolyte.

[0017] The coating liquid for forming the coating layer in the coated active material involved in the fourth solution of the present disclosure includes: a solute containing B element, P element, and La element; and water as a solvent, wherein the molar ratio La / P of the La element to the P element is 0.001 or more and 0.100 or less, and the absorbance of the coating liquid is 0.1 or less.

[0018] The coated active material of the present disclosure achieves the following effect: even when a high-nickel ratio electrode active material is combined with a coating layer containing phosphorus, an increase in resistance can be suppressed. Brief Description of the Drawings

[0019] The features, advantages, and technical and industrial significance of the exemplary embodiments of the present invention will be described below with reference to the drawings, wherein the same reference numerals represent the same elements, and wherein:

[0020] Figure 1 It is a schematic cross-sectional view for illustrating the coated active material in the present disclosure.

[0021] Figure 2 It is a schematic cross-sectional view for illustrating the battery in the present disclosure.

[0022] Figure 3 A coordinate diagram showing the resistance of the batteries fabricated in Examples 1 to 5 and Comparative Example 1. Detailed Description

[0023] The following will explain in detail the coated active material, electrode composite material, battery, and coating liquid in the present disclosure.

[0024] A. Coated Active Material

[0025] Figure 1 A schematic cross-sectional view illustrating the coated active material in the present disclosure. Figure 1 The shown coated active material 10 has an electrode active material 1 and a coating layer 2 that coats the electrode active material 1. The electrode active material 1 contains Li element, M element (M is a metal other than Li and contains at least Ni), and O element. Additionally, the molar ratio of Ni to M (Ni / M) is 80% or more. On the other hand, the coating layer 2 contains B element, P element, La element, and O element, and the molar ratio of La element to P element (La / P) is 0.005 or more and 0.15 or less.

[0026] According to the present disclosure, by adding La element to the coating layer, a coated active material can be obtained that can suppress an increase in resistance even when an electrode active material with a high nickel ratio is combined with a coating layer containing phosphorus. As described above, Japanese Patent Application Laid-Open No. 2023-136753 discloses manufacturing composite particles by mixing and drying a positive electrode active material particle and an aqueous coating liquid containing phosphorus. On the other hand, from the perspective of increasing capacity, an electrode active material with a high nickel ratio is promising. It is presumed that if an aqueous coating liquid containing phosphorus comes into contact with an electrode active material with a high nickel ratio, an exchange reaction between H + and Li + occurs, generating high-resistance NiO. As a result, the resistance increases. For example, when the electrode active material is LiNiO2, the following reaction is speculated to occur.

[0027] LiNiO2 + H + → NiOOH + Li +

[0028] NiOOH → NiO + 0.5H2O + 0.25O2

[0029] In particular, in the case of using an aqueous coating liquid containing phosphorus, it is speculated that due to the presence of the P element, moisture easily stays in the coating layer, promoting the above-mentioned exchange reaction. In the present disclosure, by adding the La element having a high affinity for the P element, the retention of moisture in the coating layer is suppressed. As a result, it is speculated that the above-mentioned exchange reaction is suppressed. Therefore, an increase in resistance can be suppressed. In addition, since the coating layer contains the P element, the chemical stability of the coating layer is improved. Furthermore, since the coating layer contains the B element in addition to the P element, the ionic conductivity of the coating layer can be improved while improving the chemical stability of the coating layer.

[0030] 1. Coating layer

[0031] The coating layer in the present disclosure is a layer that coats the electrode active material. In addition, the coating layer contains the B element, the P element, and the O element. The coating layer may further contain the Li element. In addition, the coating layer preferably contains a PO4 structure.

[0032] In the coating layer, the molar ratio of the La element to the P element (La / P) is usually 0.005 or more and 0.15 or less, and may be 0.01 or more and 0.11 or less. If La / P is too small, it may not be possible to sufficiently obtain the resistance suppression effect caused by the La element. On the other hand, if La / P is too large, it may be difficult to manufacture.

[0033] There is no particular limitation on the molar ratio of the B element to the P element (B / P) in the coating layer. For example, it is 0.5 or more and 2.0 or less, may be 0.8 or more and 1.25 or less, and may be 0.9 or more and 1.11 or less. In addition, when the coating layer further contains the Li element, there is no particular limitation on the molar ratio of the Li element to the total of the P element and the B element (Li / (P + B)). For example, it may be 0.3 or more and 1.2 or less, and may be 0.5 or more and 1.0 or less.

[0034] There is no particular limitation on the coating rate of the coating layer of the electrode active material. For example, it is 75% or more, and may be 80% or more. If the coating rate is too low, it may not be possible to sufficiently suppress the increase in resistance caused by the high-resistance layer generated by the reaction between the electrode active material and the electrolyte. On the other hand, the coating rate may be 100%, or may be less than 100%. The coating rate in the present disclosure is obtained as follows: Based on the measurement by X-ray photoelectron spectroscopy (XPS), the element ratio is calculated from the intensity ratio of the main elements, and is obtained as the ratio of the elements contained in the coating layer to the total of the elements contained in the electrode active material and the elements contained in the coating layer.

[0035] There is no particular limitation on the thickness of the coating layer. For example, it is 1 nm or more and 100 nm or less, it can be 5 nm or more and 50 nm or less, and it can be 10 nm or more and 30 nm or less. The thickness of the coating layer is obtained, for example, as the 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).

[0036] 2. Electrode active material

[0037] The electrode active material in the present disclosure usually contains Li element, M element, and O element. M is a metal (including a semi-metal) other than Li, and contains at least Ni. M other than Ni can be a transition metal or a metal (including a semi-metal) belonging to Groups 13 to 16 of the periodic table. In addition, M other than Ni can be one metal or two or more metals. Among them, M other than Ni is preferably at least one of Co, Mn, Al, V, and Fe.

[0038] The molar ratio of Ni to M (Ni / M) is usually 80% or more, can be 85% or more, and can be 90% or more. On the other hand, Ni / M can be 100% or less than 100%.

[0039] In addition to the Li element, M element, and O element, the electrode active material can have a non-metal element such as a P element. In addition, there is no particular limitation on the crystal structure of the electrode active material. For example, a rock salt layered structure, a spinel structure, and an olivine structure can be cited.

[0040] As an example of the composition of the electrode active material, LiNi x Co y Al z O2 (0.80 ≤ x, 0 ≤ y, 0 ≤ z, x + y + z = 1). x is usually 0.80 or more, can be 0.85 or more, and can be 0.90 or more. y can be 0 or greater than 0. In addition, y is, for example, 0.20 or less. z can be 0 or greater than 0. In addition, z is, for example, 0.10 or less.

[0041] As another example of the composition of the electrode active material, LiNi a Co b Mn c O2 (0.80 ≤ a, 0 ≤ b, 0 ≤ c, a + b + c = 1). a is usually 0.80 or more, can be 0.85 or more, and can be 0.90 or more. b can be 0 or greater than 0. In addition, b is, for example, 0.20 or less. c can be 0 or greater than 0. In addition, c is, for example, 0.20 or less.

[0042] The shape of the electrode active material is usually particulate. The particle size D of the electrode active material 50is, for example, 100 nm or more, may be 1 μm or more, and may be 5 μm or more. On the other hand, the particle size D of the electrode active material 50 is, for example, 50 μm or less, and may be 20 μm or less. In the present disclosure, the particle size D 50 corresponds to the particle size at the cumulative 50 volume % measured by a laser diffraction particle size distribution measuring device.

[0043] 3. Coated active material

[0044] The coated active material in the present disclosure is generally used for a battery. The electrode active material in the coated active material may be a positive electrode active material or a negative electrode active material, and the former is preferred. In addition, there is no particular limitation on the manufacturing method of the coated active material. For example, a method having a preparation step of preparing an electrode active material and a coating liquid, and a coating layer formation step of coating the electrode active material with the coating liquid and drying to form a coating layer can be cited.

[0045] In the preparation step, an electrode active material and a coating liquid are prepared. For the electrode active material, it is the same as the content described in the above “A. Coated active material”. On the other hand, for the coating liquid, it will be described in the following “D. Coating liquid”. In addition, in the coating layer formation step, the electrode active material is coated with the coating liquid and dried to form a coating layer. As a method of coating the electrode active material with the coating liquid and drying, for example, a spray drying method can be cited. Furthermore, the present disclosure can also provide a manufacturing method of a coated active material having the above preparation step and coating layer formation step.

[0046] B. Electrode composite

[0047] The electrode composite in the present disclosure contains at least one of a conductive material and a binder, and the above-described coated active material.

[0048] According to the present disclosure, by using the above-described coated active material, an electrode composite can be obtained that can suppress an increase in resistance even when a high-nickel ratio electrode active material is combined with a coating layer containing phosphorus.

[0049] The electrode composite contains a coated active material and at least one selected from a conductive material and a binder. For the coated active material, it is the same as the content described in the above “A. Coated active material”. The electrode active material in the coated active material may be a positive electrode active material or a negative electrode active material, and the former is preferred. That is, the electrode composite may be a positive electrode composite or a negative electrode composite, and the former is preferred.

[0050] The proportion of the coated active material in the electrode composite material is, for example, 20% by weight or more, can be 30% by weight or more, and can be 40% by weight or more. If the proportion of the coated active material is too small, it may not be possible to obtain sufficient energy density. On the other hand, the proportion of the coated active material is, for example, 80% by weight or less, can be 70% by weight or less, and can be 60% by weight or less. If the proportion of the coated active material is too large, the ionic conductivity and electronic conductivity in the electrode composite material may relatively decrease.

[0051] The electrode composite material contains at least one of a conductive material and a binder. As the conductive material, for example, carbon materials, metal particles, and conductive polymers can be cited. As the carbon materials, for example, particulate carbon materials such as acetylene black (AB) and Ketjen black (KB); fibrous carbon materials such as carbon fiber, carbon nanotube (CNT), and carbon nanofiber (CNF). In addition, as the binder, for example, rubber-based binders and fluoride-based binders can be cited.

[0052] The electrode composite material may further contain a solid electrolyte. The solid electrolyte can 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. Among them, the solid electrolyte is preferably a sulfide solid electrolyte. This is because the ionic conductivity is high.

[0053] The sulfide solid electrolyte generally contains at least Li element and S element. The sulfide solid electrolyte preferably further contains a Me element (Me is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, In). In addition, the sulfide solid electrolyte may contain halogen elements such as F, Cl, Br, and I.

[0054] The sulfide solid electrolyte can be a glassy (amorphous) sulfide solid electrolyte, a glass-ceramic sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. The sulfide solid electrolyte may have a crystal phase. As the above crystal phase, for example, Thio-LISICON type crystal phase, argyrodite type crystal phase, and LGPS type crystal phase can be cited.

[0055] The composition of the sulfide solid electrolyte is not particularly limited, and for example, xLi2S·(1-x)P2S5 (0.5≤x<1), yLiI·zLiBr·(100-y-z)(xLi2S·(1-x)P2S5) (0.5≤x<1, 0≤y≤30, 0≤z≤30) can be cited. In these compositions, x preferably satisfies 0.7≤x≤0.8. In addition, as another example of the composition of the sulfide solid electrolyte, Li 7-x-2y PS 6-x-y X y. X is at least one of F, Cl, Br, and I, and 0 ≤ x and 0 ≤ y. Additionally, as another example of the composition of the sulfide solid electrolyte, Li can be cited. 4-x Me 1-x P x S4 (0 < x < 1). Me is at least one of Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0056] C. Battery

[0057] Figure 2 is a schematic cross-sectional view of the battery in the present disclosure. Figure 2 The battery 20 shown has: 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 for collecting current from the positive electrode layer 11, and a negative electrode current collector 15 for collecting current from the negative electrode layer 12. In the present disclosure, the positive electrode layer 11 or the negative electrode layer 12 contains the electrode composite material described in the above "B. Electrode Composite Material".

[0058] According to the present disclosure, by using the above electrode composite material, a battery is obtained that suppresses an increase in resistance even when an electrode active material with a high nickel ratio is combined with a coating layer containing phosphorus. As described above, the electrode composite material can be a positive electrode composite material or a negative electrode composite material, preferably the former. Hereinafter, for the case where the electrode composite material is a positive electrode composite material, the details of the battery will be described.

[0059] 1. Positive Electrode Layer

[0060] The positive electrode layer in the present disclosure contains the above electrode composite material (positive electrode composite material). Regarding the electrode composite material, it is the same as that described in the above "B. Electrode Composite Material", so the description here is omitted. Additionally, the positive electrode layer may contain an electrolyte as needed. Regarding the electrolyte, it is the same as that 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, can be 0.1 μm or more and 500 μm or less, and can be 0.1 μm or more and 100 μm or less. Additionally, as a method for forming the positive electrode layer, for example, a method of coating the electrode composite material (positive electrode composite material) on the positive electrode current collector can be cited.

[0061] 2. Negative Electrode Layer

[0062] The negative electrode layer is a layer containing at least a negative electrode active material. Additionally, the negative electrode layer may contain at least one of an electrolyte, a conductive material, and a binder as needed.

[0063] As the negative electrode active material, for example, metal active materials such as Li, Si-based active materials, carbon active materials such as graphite, and oxide active materials such as Li4Ti5O 12 etc.

[0064] The negative electrode active material is preferably a Si-based active material. This is because it can achieve a high capacity of the battery. Si-based active materials are active materials with Si as the main component. Si-based active materials can be Si single substance, Si alloy, or Si oxide. In addition, Si-based active materials can have a diamond-type crystal phase, an inclusion compound type I crystal phase, or an inclusion compound type II crystal phase. In the inclusion compound type I or type II crystal phase, multiple Si elements are used to form a polyhedron (cage) containing pentagons or hexagons. The polyhedron has a space inside that can accommodate Li ions, so the volume change caused by charging and discharging can be suppressed.

[0065] The shape of the negative electrode active material may be, for example, a particle shape. 50 There is no particular limitation, and it can be, for example, 10 nm or more, or 100 nm or more. 50 For example, it is 50 μm or less, or may be 20 μm or less.

[0066] The electrolyte used in the negative electrode layer is the same as that described in "3. Electrolyte layer". In addition, the conductive material and binder used in the negative electrode layer are the same as those described in "B. Electrode composite material" above, so the description here is omitted. The thickness of the negative electrode layer is, for example, 0.1 μm or more and 1000 μm or less, 0.1 μm or more and 500 μm or less, or 0.1 μm or more and 100 μm or less.

[0067] 3. Electrolyte layer

[0068] The electrolyte layer is a layer formed between the positive electrode layer and the negative electrode layer, and contains at least an electrolyte. The electrolyte may be a solid electrolyte or a liquid electrolyte (electrolyte).

[0069] For the solid electrolyte, the contents are the same as those described in the above-mentioned "B. Electrode composite materials", so the description here is omitted. On the other hand, the electrolyte preferably contains a supporting salt and a solvent. As supporting salts (lithium salts) of electrolytes having lithium ion conductivity, for example, inorganic lithium salts such as LiPF6, LiBF4, LiClO4, and LiAsF6 can be listed; organic lithium salts such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, and LiC(CF3SO2)3 can be listed. As solvents used in the electrolyte, for example, cyclic esters (cyclic carbonates) such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC) can be listed; chain esters (chain carbonates) such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) can be listed. The electrolyte preferably contains two or more solvents.

[0070] The thickness of the electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less, may be 0.1 μm or more and 500 μm or less, and may be 0.1 μm or more and 100 μm or less.

[0071] 4. Other components

[0072] The battery in the present disclosure preferably has a positive electrode current collector for collecting current of the positive electrode layer and a negative electrode current collector for collecting current of the negative electrode layer. As materials for the positive electrode current collector, for example, SUS, aluminum, nickel, iron, titanium, and carbon can be cited. On the other hand, as materials for the negative electrode current collector, for example, SUS, copper, nickel, and carbon can be cited.

[0073] The battery in the present disclosure may further have a constraint jig that applies a constraint pressure in the thickness direction to the positive electrode layer, the electrolyte layer, and the negative electrode layer. In particular, when the electrolyte layer is a solid electrolyte layer, in order to form good ion conduction paths and electron conduction paths, it is preferable to apply a constraint pressure. The constraint pressure is, for example, 0.1 MPa or more, may be 1 MPa or more, and may be 5 MPa or more. On the other hand, the constraint pressure is, for example, 100 MPa or less, may be 50 MPa or less, and may be 20 MPa or less.

[0074] 5. Battery

[0075] There is no particular limitation on the type of the battery in the present disclosure, and typically it is a lithium ion battery. In addition, the battery in the present disclosure may be a liquid battery containing an electrolytic solution as the electrolyte layer, or may be a solid battery having a solid electrolyte layer as the electrolyte layer. The solid battery may be a semi-solid battery or a all-solid battery. In addition, the battery in the present disclosure may be a primary battery or a secondary battery, and preferably a secondary battery. This is because it can be charged and discharged repeatedly and can be used, for example, as a vehicle-mounted battery.

[0076] As uses of the battery, for example, power sources for vehicles such as hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), battery electric vehicles (BEV), gasoline vehicles, and diesel vehicles can be cited. It is particularly preferably used as a driving power source for hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), or battery electric vehicles (BEV). In addition, the battery can be used as a power source for moving bodies other than vehicles (such as railways, ships, and aircraft) and as a power source for electrical products such as information processing devices.

[0077] D. Coating liquid

[0078] The coating liquid in the present disclosure is a coating liquid for forming the coating layer in the coated active material described in the above-mentioned "A. Coated active material". The coating liquid includes: a solute containing B element, P element and La element; and water as a solvent. The molar ratio (La / P) of the above La element to the above P element is 0.001 or more and 0.100 or less. In addition, the absorbance of the coating liquid is 0.1 or less.

[0079] According to the present disclosure, by adding the La element in such a manner as to obtain a specified absorbance, a coating liquid can be obtained that can suppress an increase in resistance even when combined with an electrode active material having a high nickel ratio.

[0080] The coating liquid includes: a solute containing B element, P element and La element; and water as a solvent. The solute may further contain O element. Among them, the solute preferably contains a PO4 structure. In addition, the coating liquid may further contain Li element.

[0081] In the coating liquid, the molar ratio (La / P) of the La element to the P element is generally 0.001 or more and 0.100 or less, and may be 0.003 or more and 0.080 or less. If La / P is too small, it may not be possible to sufficiently obtain the resistance suppression effect produced by the La element. On the other hand, if La / P is too large, it may become difficult to manufacture.

[0082] In the coating liquid, the molar ratio (B / P) of the B element to the P element is not particularly limited. For example, it is 0.5 or more and 2.0 or less, may be 0.8 or more and 1.25 or less, and may be 0.9 or more and 1.11 or less. In addition, when the coating liquid further contains Li element, the molar ratio (Li / (P + B)) of the Li element to the total of the P element and the B element is not particularly limited. For example, it is 0.3 or more and 1.2 or less, and may be 0.5 or more and 1.0 or less.

[0083] The absorbance of the coating liquid is generally 0.1 or less, may be 0.05 or less, and may be 0.001 or less. The method for measuring the absorbance is as described in the examples below.

[0084] The method for preparing the coating liquid is not particularly limited. For example, a method of dissolving a solute containing a B source, a P source, and a La source in water as a solvent can be cited. As the B source, as long as it is a simple substance or compound containing the B element, it is not particularly limited. For example, boric acid (H3BO3) can be cited. As the P source, as long as it is a simple substance or compound containing the P element, it is not particularly limited. For example, orthophosphoric acid (H3PO4), metaphosphoric acid (HPO3) can be cited. In addition, the coating liquid preferably contains an O source. As the O source, for example, the O element contained in the above-mentioned B source or P source can be cited. In addition, the above solute may contain a Li source. As the Li source, as long as it is a simple substance or compound containing the Li element, it is not particularly limited. For example, lithium hydroxide monohydrate (LiOH·H2O) can be cited.

[0085] Furthermore, the present disclosure is not limited to the above embodiments. The above embodiments are examples, and technical solutions having substantially the same constitution as the technical idea described in the patent claims of the present disclosure and achieving the same effects are included in the technical scope of the present disclosure.

[0086] [Comparative Example 1]

[0087] (Preparation of Coating Liquid)

[0088] Metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and ion-exchanged water were mixed at a ratio of metaphosphoric acid:ion-exchanged water = 4.52:191.8 (weight ratio) to obtain an aqueous solution. Boric acid (manufactured by Nacalai Tesque) was added to the obtained aqueous solution so that the molar ratio of B element to P element (B / P) became 1.0 and dissolved therein. Thus, a coating liquid was obtained.

[0089] (Preparation of Coated Active Material)

[0090] Active material particles (LiNi 0.81 Co 0.15 Al 0.04 O2, particle size D 50 = 4.5 μm) were dispersed in the obtained coating liquid to prepare a slurry. The solid content concentration of the slurry was 69% by weight. Next, the slurry was dried using a spray dryer "Product name: Mini Spray Dryer B-290" manufactured by BUCHI to form a coating layer on the surface of the active material particles. The air supply temperature of the spray dryer was 200 °C, and the air supply volume was 0.45 m 3 / min. Next, the active material particles having the coating layer formed thereon were heat-treated in an atmospheric atmosphere to obtain a coated active material. The heat treatment temperature was 200 °C, and the heat treatment time was 5 hours.

[0091] [Example 1]

[0092] Metaphosphoric acid (manufactured by FUJIFILM Wako Pure Chemical Corporation) and ion-exchanged water were mixed at a weight ratio of metaphosphoric acid:ion-exchanged water = 4.52:191.8 to obtain an aqueous solution. In the obtained aqueous solution, boric acid (manufactured by Nacalai Tesque) was added in such a manner that the molar ratio of B element to P element (B / P) became 1.0 and dissolved. Furthermore, lanthanum oxide (manufactured by FUJIFILM Wako Pure Chemical Corporation) was added in such a manner that the molar ratio of La element to P element (La / P) became 0.003 and dissolved. Thus, a coating solution was obtained. Except for using the obtained coating solution, a coated active material was obtained in the same manner as in Comparative Example 1.

[0093] [Examples 2 to 5]

[0094] Except that the molar ratio of La element to P element (La / P) was changed to 0.006, 0.01, 0.05, and 0.075, respectively, a coating solution was obtained in the same manner as in Example 1. Except for using the obtained coating solution, a coated active material was obtained in the same manner as in Comparative Example 1.

[0095] [Comparative Example 2]

[0096] Except that the molar ratio of La element to P element (La / P) was changed to 0.100, a coating solution was obtained in the same manner as in Example 1. Except for using the obtained coating solution, a coated active material was obtained in the same manner as in Comparative Example 1.

[0097] [Evaluation]

[0098] (Absorbance measurement)

[0099] The absorbances of the coating solutions obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were measured. Specifically, 3.5 mL of the coating solution was added to a quartz cell (10 mm × 10 mm × 45 mm), and the absorbance was measured using an ultraviolet-visible spectrophotometer (product name: UV-1280, manufactured by Shimadzu Corporation). The absorbance at a wavelength of 660 nm was measured, and as a result, in Examples 1 to 5 and Comparative Example 1, it was confirmed that the concentration of insoluble fine particles present in the coating solution was extremely low (for example, refer to JIS-K0101). On the other hand, in Comparative Example 2, the coating solution was visually observed to be turbid, so the absorbance measurement was not performed. The results are shown in Table 1.

[0100] (Measurement of coating rate and La / P)

[0101] The coating rates of the coated active materials obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were measured by X-ray photoelectron spectroscopy (XPS). Specifically, surface elemental analysis of the coated active materials was performed using an X-ray photoelectron analysis apparatus (PHIX-tool manufactured by ULVAC-PHI, Inc.). Narrow scan analysis was performed with the energy set to 224 eV. Then, using analysis software (MultiPak, manufactured by ULVAC-PHI, Inc.), the elemental ratio was calculated from the intensity values of C1s, O1s, P2p, Ni2p3, Co2p3, Al2p, B1s, and La3d3 detected, and the value of (La + P + B) / (La + P + B + Ni + Co + Al) [%] was obtained as the coating rate. In addition, the molar ratio of La element to P element (La / P) was also obtained from the above elemental ratio. These results are shown in Table 1.

[0102] (Measurement of resistance)

[0103] Using the coated active materials obtained in Examples 1 to 5 and Comparative Examples 1 and 2 as the positive electrode active material, a battery was fabricated and the resistance was measured.

[0104] First, the positive electrode active material (coated active material), sulfide solid electrolyte (10LiI - 15LiBr - 75Li3PS4), conductive material (VGCF), binder (SBR), and dispersion medium (heptane) were mixed to prepare a positive electrode paste. The mixing ratio of the positive electrode active material to the sulfide solid electrolyte was positive electrode active material:sulfide solid electrolyte = 6:4 (volume ratio). The compounding amounts of the conductive material and the binder were each 3 parts by weight with respect to 100 parts by weight of the positive electrode active material. The positive electrode paste was sufficiently stirred using an ultrasonic homogenizer, and the positive electrode paste was coated on the surface of a positive electrode current collector (Al foil) to form a coating film. The coating film was dried on a hot plate at 100 °C for 30 minutes. Thus, a raw positive electrode was obtained. A disk-shaped positive electrode was cut out from the raw positive electrode. The area of the positive electrode was 1 cm 2 .

[0105] Next, a negative electrode and a solid electrolyte layer were prepared. The negative electrode active material was graphite. The same sulfide solid electrolyte was used between the positive electrode, the solid electrolyte layer, and the negative electrode. In a cylindrical jig, the positive electrode, the solid electrolyte layer, and the negative electrode were laminated in sequence to form a laminate. The laminate was pressed to form a power generation element. Terminals were connected to the power generation element to obtain a battery (all-solid battery). After adjusting the open-circuit voltage (OCV) of the obtained all-solid battery to 2.03 V, constant current discharge was performed, and the battery resistance was measured by dividing the voltage drop during 5 seconds by the current amount. The discharge current rate was 2.5C. Based on the resistance of the battery of Comparative Example 1 (1.00), the resistances of the batteries of each Example and each Comparative Example were relativized and evaluated. The results are shown in Table 1 and Figure 3 .

[0106]

Table 1

[0107]

[0108] As shown in Table 1, in Examples 1 to 5 and Comparative Example 1, the value of La / P in the coating layer was larger than the value of La / P in the coating liquid. It is speculated that this is because La segregated. In addition, as shown in Table 1 and Figure 3 , compared with Comparative Example 1, a decrease in resistance was confirmed in Examples 1 to 5. Thus, it was confirmed that by adding La to the coating layer, even when a high-nickel ratio electrode active material was combined with a coating layer containing phosphorus, an increase in resistance could be suppressed. On the other hand, in Comparative Example 2, it was confirmed that the coating liquid became cloudy and was not a solution but a dispersion. Therefore, a compositional deviation occurred and the desired coated active material was not obtained.

Claims

1. A coated active material, characterized in that, Comprising: An electrode active material; and a coating layer covering the electrode active material, wherein the electrode active material has Li element, M element, and O element, M is a metal other than Li and contains at least Ni, The molar ratio of Ni to M, Ni / M, is 80% or more, The coating layer contains B element, P element, La element, and O element, The molar ratio of the La element to the P element, La / P, is 0.005 or more and 0.15 or less.

2. The coated active material according to claim 1, wherein La / P is 0.01 or more and 0.11 or less.

3. The coated active material according to claim 1, characterized in that, The molar ratio of the B element to the P element, B / P, is 0.5 or more and 2.0 or less.

4. The coated active material according to claim 1, characterized in that, The coating rate of the coating layer with respect to the electrode active material is 75% or more.

5. The coated active material according to claim 1, characterized in that, M further contains at least one of Co, Mn, and Al.

6. An electrode composite material, characterized in that, Comprising: The coated active material according to any one of claims 1 to 5; and At least one of a conductive material and a binder.

7. The electrode composite material according to claim 6, wherein The electrode composite material contains a solid electrolyte.

8. The electrode composite material according to claim 7, wherein The solid electrolyte is a sulfide solid electrolyte.

9. Battery, characterized in that, Comprising: 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 contains the electrode composite material according to claim 6.

10. The battery according to claim 9, characterized in that, The positive electrode layer contains the electrode composite material.

11. The battery according to claim 9, wherein The electrolyte layer contains a solid electrolyte.

12. A coating liquid for forming the coating layer in the coated active material according to any one of claims 1 to 5, characterized in that, Comprising: A solute containing B element, P element, and La element; and Water as a solvent, wherein the molar ratio of the La element to the P element, La / P, is 0.001 or more and 0.100 or less, The absorbance of the coating liquid is 0.1 or less.

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