Coated active material, electrode mixture, battery, and producing method of coated active material

Abstract

To provide a coated active material capable of suppressing a resistance increase due to moisture and a resistance increase due to a high resistance layer.SOLUTION: In the present disclosure, there is provided a coated active material including an electrode active material and a coating layer that covers the electrode active material and contains a coating material including a B element, a P element, and an O element. In the coated active material, a moisture amount X generated 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 is larger than 67%.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a coated active material, an electrode composite material, a battery, and a method for manufacturing a coated active material.

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 used in battery electric vehicles (BEVs), plug-in hybrid vehicles (PHEVs), or hybrid electric vehicles (HEVs) has been promoted. Further, it is known to coat the surface of an electrode active material with a phosphorus-based coating liquid.

[0003] For example, Patent Document 1 discloses composite particles including positive electrode active material particles and a coating film that coats at least a part of the surface of the positive electrode active material particles and contains a phosphorus compound. Further, Patent Document 1 discloses that composite particles are manufactured by mixing positive electrode active material particles and an aqueous coating liquid (aqueous coating solution) containing phosphorus and drying the mixture.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a coating method using an aqueous coating liquid containing phosphorus, even after sufficient drying, moisture remains in the coating layer, and the remaining moisture may cause an increase in resistance by deteriorating the electrode active material or the electrolyte existing around the electrode active material.

[0006] Therefore, the inventor of the present application considered coating the electrode active material with a coating material by a dry method. By using the dry method, the moisture content of the coating layer can be reduced. On the other hand, the inventor of the present application found a new problem that it is difficult to increase the coating rate of the coating layer with respect to the electrode active material in the case of the dry method. If the coating rate of the coating layer with respect to the electrode active material is low, a high-resistance layer may be generated due to the reaction between the electrode active material and the electrolyte, causing an increase in resistance.

[0007] The present disclosure has been made in view of the above circumstances, and the main object thereof is to provide a coated active material capable of suppressing an increase in resistance due to moisture and an increase in resistance due to a high-resistance layer.

Means for Solving the Problems

[0008] [1] A coated active material having an electrode active material and a coating layer that coats the electrode active material and contains a coating material having B element, P element and O element, wherein the amount of moisture X generated in the temperature range of 120 ° C or higher and 180 ° C or lower is 10.0 ppm or less, and the coating rate of the coating layer with respect to the electrode active material is greater than 67%, the coated active material.

[0009] [2] The coated active material according to [1], wherein the amount of moisture X is 8.0 ppm or less.

[0010] [3] The coated active material according to [1] or [2], wherein the amount of moisture Y generated in the temperature range of 180 ° C or higher and 300 ° C or lower is 350 ppm or less.

[0011] [4] The coated active material according to any one of [1] to [3], wherein the coating rate is 75% or more.

[0012] [5] The coated active material according to any one of [1] to [4], wherein the coating material further has Li element.

[0013] [6] The above electrode active material has Li element, M element (M is a metal other than Li), and O element, wherein the above M contains at least Ni, The coating active material according to any one of [1] to [5], wherein the molar ratio of Ni to M (Ni / M) is 50% or more.

[0014] [7] The coating active material according to [6], wherein the Ni / M is 80% or more.

[0015] [8] The BET specific surface area is 0.50 m 2 / g or more and less than 1.20 m 2 / g. The coating active material according to any one of [1] to [7].

[0016] [9] An electrode mixture containing the coating active material according to any one of [1] to [8] and at least one of a conductive material and a binder.

[0017]

[10] The electrode mixture according to [9], wherein the above electrode mixture contains a solid electrolyte.

[0018]

[11] The electrode mixture according to

[10] , wherein the above solid electrolyte is a sulfide solid electrolyte.

[0019]

[12] A battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the above positive electrode layer and the above negative electrode layer, wherein the above positive electrode layer or the above negative electrode layer contains the electrode mixture according to any one of [9] to

[11] .

[0020]

[13] The battery according to

[12] , wherein the above positive electrode layer contains the above electrode mixture.

[0021]

[14] The battery according to

[12] or

[13] , wherein the electrolyte layer contains a solid electrolyte.

[0022]

[15] A method for producing a coated active material according to any one of [1] to [8], comprising: a preparation step of preparing the electrode active material and the coating material; a coating layer forming step of coating the electrode active material with the coating material by a dry method to form the coating layer. The particle diameter D of the coating material 90 is 2 μm or less. A method for producing a coated active material.

Advantages of the Invention

[0023] The coated active material in the present disclosure has the effect of suppressing an increase in resistance due to moisture and an increase in resistance due to a high-resistance layer.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0025] Hereinafter, the coated active material, the electrode mixture, the battery, and the method for producing the coated active material in the present disclosure will be described in detail.

[0026] A. Coated active material FIG. 1 is a schematic cross-sectional view illustrating a coated active material in the present disclosure. The coated active material 10 shown in FIG. 1 includes an electrode active material 1 and a coating layer 2 that covers the electrode active material 1 and includes a coating material having B element, P element, and O element. In the coated active material 10, the amount of moisture X generated in the temperature range of 120° C. or higher and 180° C. or lower is usually 10.0 ppm or less. Further, the coverage rate of the coating layer 2 with respect to the electrode active material 1 is usually greater than 67%.

[0027] According to the present disclosure, since the amount of moisture X is small and the coverage rate of the coating layer is high, it becomes a coated active material capable of suppressing an increase in resistance due to moisture and an increase in resistance due to a high-resistance layer. As described above, Patent Document 1 discloses that composite particles are produced by mixing and drying a positive electrode active material particle and an aqueous coating solution containing phosphorus. In the coating method using an aqueous coating solution containing phosphorus, even after sufficient drying, moisture remains in the coating layer, and the remaining moisture may cause an increase in resistance by deteriorating the electrode active material or the electrolyte present around the electrode active material.

[0028] Therefore, the inventor of the present application considered coating the electrode active material with a coating material by a dry method. When the dry method is used, since it is not necessary to use a solvent such as water, the amount of moisture in the coating layer can be reduced. On the other hand, the inventor of the present application found a new problem that it is difficult to increase the coverage rate of the coating layer with respect to the electrode active material in the case of the dry method. If the coverage rate of the coating layer with respect to the electrode active material is low, a high-resistance layer may be generated by the reaction of the electrode active material and the electrolyte, causing an increase in resistance.

[0029] In order to solve the above new problems, the inventors of the present application conducted intensive research. As a result, it was found that the reason why it is difficult to increase the coating rate is that the coating material containing phosphorus is hard, and when the electrode active material is coated with the coating material, the surface of the electrode active material is greatly damaged by the coating material. Therefore, when a fine coating material was used to suppress the damage to the surface of the electrode active material, it was found that the coating rate of the coating material could be significantly improved. As a result, a coated active material with a small amount of moisture and a high coating rate of the coating layer can be obtained, thereby making it possible to simultaneously suppress the increase in resistance due to moisture and the increase in resistance due to the high-resistance layer. In addition, since the coating material contains a P element, the chemical stability of the coating layer is improved. Furthermore, since the coating material contains a 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 The coating layer in the present disclosure is a layer that coats the electrode active material. The coating layer contains a coating material having B element, P element and O element. The coating material may further contain a Li element. Further, the coating material preferably has a PO4 structure.

[0031] In the coating material, the molar ratio of B element to P element (B / P) is not particularly limited. For example, it may be 0.5 or more and 2.0 or less, may be 0.8 or more and 1.25 or less, or may be 0.9 or more and 1.11 or less. When the coating material further contains a Li element, the molar ratio of Li element to the total of P element and B element (Li / (P+B)) is not particularly limited. For example, it may be 0.3 or more and 1.2 or less, or may be 0.5 or more and 1.0 or less.

[0032] The coverage rate of the coating layer on the electrode active material is usually greater than 67%, and may be 75% or more, or may be 80% or more. If the coverage rate is too low, it is difficult to sufficiently suppress the increase in resistance due to the high-resistance layer. On the other hand, the coverage rate may be 100% or may be less than 100%. In the present disclosure, the coverage rate is determined based on X-ray photoelectron spectroscopy (XPS) measurement, by calculating the elemental ratio from the intensity ratio of each main element, 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.

[0033] The thickness of the coating layer is not particularly limited, but for example, it is 1 nm or more and 100 nm or less, may be 5 nm or more and 50 nm or less, or may 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).

[0034] 2. Electrode active material The electrode active material in the present disclosure is not particularly limited, but preferably has Li element, M element, and O element. M is a metal other than Li (including semimetals). M may be a transition metal or may be a metal (including semimetals) belonging to Groups 13 to 16 of the periodic table. Also, M may be one kind of metal or may be two or more kinds of metals. Among them, M is preferably at least one of Ni, Co, Mn, Al, V, and Fe.

[0035] In particular, M preferably contains at least Ni. The electrode active material containing Ni is liable to deteriorate due to moisture, but the coating active material in the present disclosure has a small amount of moisture, so the deterioration of the electrode active material containing Ni can be suppressed. The molar ratio of Ni to M (Ni / M) is not particularly limited, but for example, it is 30% or more, may be 50% or more, may be 60% or more, may be 70% or more, or may be 80% or more. On the other hand, Ni / M may be 100% or may be less than 100%.

[0036] In addition to Li element, M element, and O element, the electrode active material may contain a non-metallic element such as P element. Also, the crystal structure of the electrode active material is not particularly limited, and examples thereof include a rock salt layered structure, a spinel structure, and an olivine structure.

[0037] As an example of the composition of the electrode active material, LiNi x Co y Al z O2 (0.5 ≦ x, 0 ≦ y, 0 ≦ z, x + y + z = 1) can be mentioned. x may be 0.6 or more, may be 0.7 or more, or may be 0.8 or more. y may be 0, or may be greater than 0. Also, y is, for example, 0.3 or less. z may be 0, or may be greater than 0. Also, z is, for example, 0.1 or less.

[0038] As another example of the composition of the electrode active material, LiNi a Co b Mn c O2 (0.5 ≦ a, 0 ≦ b, 0 ≦ c, a + b + c = 1) can be mentioned. a may be 0.6 or more, may be 0.7 or more, or may be 0.8 or more. b may be 0, or may be greater than 0. Also, b is, for example, 0.3 or less. c may be 0, or may be greater than 0. Also, c is, for example, 0.3 or less.

[0039] The shape of the electrode active material is usually particulate. The particle diameter D of the electrode active material 50 is, for example, 100 nm or more, may be 1 μm or more, or may be 5 μm or more. On the other hand, the particle diameter D of the electrode active material 50 is, for example, 50 μm or less, or may be 20 μm or less. In the present disclosure, the particle diameter D 50 corresponds to the particle diameter corresponding to the cumulative 50 volume% measured by a laser diffraction particle size distribution measuring device.

[0040] 3. Coating active material In the coating active material in the present disclosure, the amount of water X generated in the temperature range of 120°C or higher and 180°C or lower is usually 10.0 ppm or less. The amount of water X may be 9.0 ppm or less, or may be 8.0 ppm or less. By having a small amount of water X, an increase in resistance due to water can be suppressed. Further, in the coating active material, the amount of water Y generated in the temperature range of 180°C or higher and 300°C or lower is, for example, 350 ppm or less, and may be 320 ppm or less. By having a small amount of water Y, an increase in resistance due to water can be suppressed. The measuring methods of the amount of water X and the amount of water Y are as described in the examples described later.

[0041] The BET specific surface area of the coating active material is not particularly limited, but for example, it is 0.50 m 2 / g or more, and may be 0.70 m 2 / g or more. On the other hand, the BET specific surface area of the coating active material is, for example, less than 1.20 m 2 / g, and may be 1.00 m 2 / g or less.

[0042] The coating active material in the present disclosure is usually used in a battery. The electrode active material in the coating active material may be a positive electrode active material or a negative electrode active material, but the former is preferred. Examples of the manufacturing method of the coating active material include the methods described in "D. Manufacturing method of coating active material" described later.

[0043] B. Electrode mixture The electrode mixture in the present disclosure contains at least one of the above-described coating active material, a conductive material, and a binder.

[0044] According to the present disclosure, by using the above-described coating active material, an electrode mixture capable of suppressing an increase in resistance due to water and an increase in resistance due to a high-resistance layer can be obtained.

[0045] The electrode composite material contains a coated active material and at least one of a conductive material and a binder. The coated active material is the same as 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, but the former is preferred. That is, the electrode composite material may be a positive electrode composite material or a negative electrode composite material, but the former is preferred.

[0046] The proportion of the coated active material in the electrode composite material is, for example, 20% by weight or more, and may be 30% by weight or more, or may 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, and may be 70% by weight or less, or may 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.

[0047] The electrode composite material contains at least one of a conductive material and a binder. Examples of the conductive material include carbon materials, metal particles, and conductive polymers. Examples of the carbon materials include particulate carbon materials such as acetylene black (AB) and ketjen black (KB), fibrous carbon materials such as carbon fibers, carbon nanotubes (CNT), and carbon nanofibers (CNF). Examples of the binder include rubber-based binders and fluoride-based binders.

[0048] The electrode composite material may further contain 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. Among them, the solid electrolyte is preferably a sulfide solid electrolyte because of its high ionic conductivity.

[0049] Sulfide solid electrolytes usually contain 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). Also, the sulfide solid electrolyte may contain halogen elements such as F, Cl, Br, I.

[0050] The sulfide solid electrolyte may be a glass-based (amorphous) sulfide solid electrolyte, a glass-ceramics-based sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. The sulfide solid electrolyte may have a crystalline phase. Examples of the crystalline phase include, for example, Thio-LISICON type crystalline phase, argyrodite type crystalline phase, LGPS type crystalline phase.

[0051] The composition of the sulfide solid electrolyte is not particularly limited, and examples include, 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). In these compositions, x preferably satisfies 0.7≦x≦0.8. Also, as another example of the composition of the sulfide solid electrolyte, Li 7-x-2y PS 6-x-y X y is mentioned. X is at least one of F, Cl, Br, I, and x and y satisfy 0≦x, 0≦y. Also, as another example of the composition of the sulfide solid electrolyte, Li 4-x Me 1-x P x S4 (0<x<1) is mentioned. Me is at least one of Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0052] C. Battery Figure 2 is a schematic cross-sectional view illustrating a battery according to the present disclosure. The battery 20 shown in FIG. 2 includes 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 current from the positive electrode layer 11, and a negative electrode current collector 15 that collects 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".

[0053] According to the present disclosure, by using the above-described electrode composite material, a battery is obtained that suppresses an increase in resistance due to moisture and an increase in resistance due to a high-resistance layer. As described above, the electrode composite material may be a positive electrode composite material or a negative electrode composite material, but the former is preferred. Hereinafter, when the electrode composite material is a positive electrode composite material, the details of the battery will be described.

[0054] 1. Positive Electrode Layer The positive electrode layer in the present disclosure contains the above-described electrode composite material (positive electrode composite material). Since the electrode composite material is the same as that described in the above "B. Electrode Composite Material", the description here is omitted. Further, the positive electrode layer may contain an electrolyte as necessary. The electrolyte 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, may be 0.1 μm or more and 500 μm or less, or may be 0.1 μm or more and 100 μm or less. Further, as a method for forming the positive electrode layer, for example, a method of applying the electrode composite material (positive electrode composite material) to the positive electrode current collector can be mentioned.

[0055] 2. Negative Electrode Layer The negative electrode layer is a layer containing at least a negative electrode active material. Further, the negative electrode layer may contain at least one of an electrolyte, a conductive material, and a binder as necessary.

[0056] Examples of the negative electrode active material 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 and the like.

[0057] The negative electrode active material is preferably an Si-based active material because it can increase the battery capacity. The Si-based active material is an active material mainly composed of Si. The Si-based active material may be elemental Si, an Si alloy, or an Si oxide. Further, the Si-based active material may have a diamond-type crystal phase, a clathrate I-type crystal phase, or a clathrate II-type crystal phase. In the clathrate I-type or II-type crystal phase, polyhedra (cages) containing pentagons or hexagons are formed by a plurality of Si elements. Since this polyhedron has a space inside that can enclose Li ions, volume changes due to charge and discharge can be suppressed.

[0058] Examples of the shape of the negative electrode active material include particulate. The particle diameter D of the negative electrode active material 50 is not particularly limited, but is, for example, 10 nm or more, and may be 100 nm or more. On the other hand, the particle diameter D of the negative electrode active material 50 is, for example, 50 μm or less, and may be 20 μm or less.

[0059] The electrolyte used for the negative electrode layer is the same as the content described in "3. Electrolyte layer". Further, since the conductive material and the binder used for the negative electrode layer are the same as the content described in the above "B. Electrode composite material", 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, may be 0.1 μm or more and 500 μm or less, or may be 0.1 μm or more and 100 μm or less.

[0060] 3. Electrolyte layer 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 solution).

[0061] Regarding the solid electrolyte, since it is the same as the content described in the above "B. Electrode composite material", the description here is omitted. On the other hand, the electrolytic solution preferably contains a supporting salt and a solvent. Examples of the supporting salt (lithium salt) of the electrolytic solution having lithium ion conductivity include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, LiAsF6, etc., and organic lithium salts such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, 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), butylene carbonate (BC), and chain esters (chain carbonates) such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). The electrolytic solution preferably contains two or more solvents.

[0062] 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 may be 0.1 μm or more and 100 μm or less.

[0063] 4. Other configurations The battery in the present disclosure preferably has a positive electrode current collector for collecting current from the positive electrode layer and a negative electrode current collector for collecting current from the negative electrode layer. Examples of the material of the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. On the other hand, examples of the material of the negative electrode current collector include SUS, copper, nickel, and carbon.

[0064] The battery in the present disclosure may further include a restraining jig that applies a restraining pressure along 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, it is preferable to apply a restraining pressure to form good ion conduction paths and electron conduction paths. The restraining 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 restraining pressure is, for example, 100 MPa or less, may be 50 MPa or less, and may be 20 MPa or less.

[0065] 5. Battery The type of the battery in the present disclosure is not particularly limited, but is typically a lithium ion battery. Also, 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. Further, the battery in the present disclosure may be a primary battery or a secondary battery, but among them, a secondary battery is preferable. This is because it can be repeatedly charged and discharged and is useful as, for example, an in-vehicle battery.

[0066] Examples of the uses of the battery include power sources for vehicles such as hybrid vehicles (HEV), plug-in hybrid vehicles (PHEV), battery electric vehicles (BEV), gasoline vehicles, and diesel vehicles. In particular, it is preferably used as a driving power source for a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), or a battery electric vehicle (BEV). Also, the battery may be used as a power source for moving bodies other than vehicles (for example, railways, ships, and airplanes), and may be used as a power source for electrical products such as information processing devices.

[0067] D. Method for manufacturing a coated active material FIG. 3 is a flowchart illustrating a method for manufacturing a coated active material in the present disclosure. In the manufacturing method shown in FIG. 3, an electrode active material and a coating material are prepared (preparation step). Next, the electrode active material is coated with the coating material by a dry method to form a coating layer (coating layer forming step). In the present disclosure, the coating conditions are adjusted so that the coated active material described in the above "A. Coated Active Material" is obtained. In particular, the particle size D 90 of the coating material is 2 μm or less.

[0068] According to the present disclosure, by using a fine coating material, it is possible to obtain a coated active material capable of suppressing an increase in resistance due to moisture and an increase in resistance due to a high-resistance layer.

[0069] 1. Preparation step The preparation step in the present disclosure is a step of preparing the above electrode active material and the above coating material. The electrode active material and the coating material are the same as those described in the above "A. Coated Active Material".

[0070] The shape of the coating material in the preparation step is usually particulate. The particle size D 90 of the coating material is usually 2 μm or less, may be 1 μm or less, and may be 0.8 μm or less. By using a fine coating material, when the electrode active material is coated with the coating material, it is possible to suppress damage to the surface of the electrode active material by the coating material. As a result, the coating rate of the coating layer can be improved. On the other hand, 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 the particle size corresponding to 90% by volume cumulative from the small particle side measured by a laser diffraction particle size distribution measuring device.

[0071] The particle size D 50 of the coating material is, for example, 1 μm or less, may be 0.6 μm or less, and may be 0.4 μm or less. On the other hand, the particle size D 50 of the coating material is not particularly limited, but is, for example, 0.1 μm or more. Also, the particle size D 50 of the coating material with respect to the particle size D 50The ratio is not particularly limited, but for example, it may be 1% or more and 25% or less, or may be 5% or more and 15% or less.

[0072] The method for producing the coating material is not particularly limited. For example, a method having a synthesis step of synthesizing the coarse-grained material of the coating material and an atomization step of atomizing the coarse-grained material can be mentioned. The synthesis step is, for example, a step of dissolving a solute containing a B source and a P source in a solvent to prepare a coating solution, and then drying the coating solution.

[0073] The B source is not particularly limited as long as it is a simple substance or compound having a B element. For example, boric acid (H3BO3) can be mentioned. The P source is not particularly limited as long as it is a simple substance or compound having a P element. For example, orthophosphoric acid (H3PO4) and metaphosphoric acid (HPO3) can be mentioned. Further, it is preferable that the coating solution has an O source. As the O source, for example, the O element contained in the above-mentioned B source or P source can be mentioned. Further, the solute may contain a Li source. The Li source is not particularly limited as long as it is a simple substance or compound having a Li element. For example, lithium hydroxide (LiOH) can be mentioned. Further, as the solvent, for example, water can be mentioned.

[0074] As a specific example of the method for producing the coating solution, first, a first aqueous solution in which orthophosphoric acid (H3PO4) or metaphosphoric acid (HPO3) is dissolved in water is prepared. Next, a second aqueous solution in which boric acid (H3BO3) is dissolved in the first aqueous solution is prepared. Next, lithium hydroxide monohydrate (LiOH·H2O) is dissolved in the second aqueous solution to prepare a coating solution. Further, a coarse-grained material can be obtained by drying the coating solution. The method for drying the coating solution is not particularly limited. For example, spray drying, an electric furnace, a vacuum drying furnace, and a spray pyrolysis apparatus can be mentioned.

[0075] The atomization step is a step of atomizing the above-mentioned coarse-grained material. By atomizing the coarse-grained material, the particle diameter D 90A coating material with a particle size of 2 μm or less can be obtained. Examples of methods for atomizing coarse-grained materials include mechanical milling such as bead mills and ball mills. Mechanical milling may be performed dry or wet. When performed wet, it is preferable to use a solvent other than water. The conditions of mechanical milling are not particularly limited and are appropriately adjusted so that the coating material with a particle size D 90 is 2 μm or less.

[0076] 2. Coating layer formation step In the coating layer formation step in the present disclosure, the electrode active material is coated with the above coating material by a dry method to form the above coating layer.

[0077] Examples of the dry method include a method of applying shear treatment to a mixture containing an electrode active material and a coating material. The above mixture basically does not contain water, but may contain a small amount of water that can be ignored. The shear treatment is, for example, a treatment of rotating a chopper disposed in a container. Another example of the shear treatment is a method of applying compressive shear energy to the mixture existing between a blade and the wall surface of the container by rotating the blade disposed in the container. Further, the conditions of the shear treatment are not particularly limited and are appropriately adjusted so that the coated active material described in "A. Coating Material" above can be obtained.

[0078] 3. Coated active material Regarding the coated active material obtained by the above-described respective steps, it is the same as the content described in "A. Coating Material" above.

[0079] Note that the present disclosure is not limited to the above-described embodiments. The above-described embodiments are examples, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present disclosure and exhibits the same operational effects is included in the technical scope of the present disclosure.

Examples

[0080] [Comparative Example 1] (Preparation of Coating Liquid) 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. To the obtained aqueous solution, boric acid (manufactured by Nacalai Tesque, Inc.) was added and dissolved so that the molar ratio of B element to P element (B / P) was 1.0. Further, lithium hydroxide monohydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added and dissolved so that the molar ratio of Li element to the total of P element and B element (Li / (P + B)) was 0.9. Thereby, a coating liquid was obtained.

[0081] (Preparation of Coated Active Material) To the obtained coating liquid, active material particles (LiNi 0.81 Co 0.15 Al 0.04 O2, particle size D 50 = 4.5 μm) were dispersed 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 with the coating layer formed were heat-treated in an air atmosphere to obtain a coated active material. The heat treatment temperature was 200°C, and the heat treatment time was 5 hours.

[0082] [Comparative Example 2] (Preparation of Coating Material A) In the same manner as in Comparative Example 1, a coating liquid was obtained. The obtained coating liquid was dried using a spray dryer "Product Name: Mini Spray Dryer B-290" manufactured by BUCHI to obtain a powder. The air supply temperature of the spray dryer was 200°C, and the air supply volume was 0.45 m 3 / min. Thereafter, additionally, heat treatment was performed in an air atmosphere. The heat treatment temperature was 200°C. The heat treatment time was 5 hours. Thereby, a powdery coating material A was obtained.

[0083] (Production of Coated Active Material) 1000 g of the same active material particles as in Comparative Example 1 and 31.0 g of Coating Material A were charged into a mixing stirrer balance GRAN BG-2L (manufactured by Freund Turbo). Next, a stirring treatment was performed at a chopper rotation speed of 1500 rpm for 1 hour to form a coating layer on the surface of the active material particles, thereby obtaining a coated active material.

[0084] [Comparative Example 3] A coated active material was obtained in the same manner as in Comparative Example 2, except that when forming the coating layer on the surface of the active material particles, stirring treatments were performed at chopper rotation speeds of 1500 rpm and 2000 rpm for 1 hour each.

[0085] [Comparative Example 4] A coated active material was obtained in the same manner as in Comparative Example 2, except that when forming the coating layer on the surface of the active material particles, stirring treatments were performed at chopper rotation speeds of 1500 rpm, 2000 rpm, and 2500 rpm for 1 hour each.

[0086] [Comparative Example 5] A coated active material was obtained in the same manner as in Comparative Example 2, except that when forming the coating layer on the surface of the active material particles, stirring treatments were performed at chopper rotation speeds of 1500 rpm, 2000 rpm, 2500 rpm, and 3000 rpm for 1 hour each.

[0087] [Comparative Example 6] A coated active material was obtained in the same manner as in Comparative Example 2, except that when forming the coating layer on the surface of the active material particles, stirring treatments were performed at chopper rotation speeds of 1500 rpm, 2000 rpm, 2500 rpm, 3000 rpm, and 3600 rpm for 1 hour each.

[0088] [Comparative Example 7] (Production of Coating Material B) In the same manner as in Comparative Example 2, Coating Material A was obtained. Coating Material A was dispersed in ethanol so that the solid content concentration became 20% by weight to obtain a dispersion. A wet bead mill pulverization apparatus, Labo Star Mini MGF015 (manufactured by Asazawa Fine Tech Co., Ltd.), was prepared, and the obtained dispersion was charged into the pulverization chamber together with zirconia balls (Φ0.1 mm), and pulverization treatment was performed for 90 minutes. The peripheral speed of the beads was 14 m / s, and the circulation flow rate was 0.3 L / min. Next, natural drying was performed for 24 hours in an air atmosphere to volatilize ethanol. Further, vacuum drying was performed at 100 °C for 8 hours. Thereby, Coating Material B was obtained.

[0089] (Production of Coated Active Material) 1000 g of the same active material particles as in Comparative Example 1 and 31.0 g of Coating Material B were charged into a mixing stirrer, Balance Gran BG-2L (manufactured by Freund Turbo Co., Ltd.). Next, stirring treatment was performed at a chopper rotation speed of 1500 rpm for 1 hour to form a coating layer on the surface of the active material particles, and a coated active material was obtained.

[0090] [Example 1] A coated active material was obtained in the same manner as in Comparative Example 7, except that stirring treatment was performed at chopper rotation speeds of 1500 rpm and 2000 rpm for 1 hour each when forming a coating layer on the surface of the active material particles.

[0091] [Example 2] A coated active material was obtained in the same manner as in Comparative Example 7, except that stirring treatment was performed at chopper rotation speeds of 1500 rpm, 2000 rpm, and 2500 rpm for 1 hour each when forming a coating layer on the surface of the active material particles.

[0092] [Example 3] A coated active material was obtained in the same manner as in Comparative Example 7, except that stirring treatment was performed at chopper rotation speeds of 1500 rpm, 2000 rpm, 2500 rpm, and 3000 rpm for 1 hour each when forming a coating layer on the surface of the active material particles.

[0093] [Example 4] When forming a coating layer on the surface of the living matter particles, except that stirring treatments were performed at chopper rotation speeds of 1500 rpm, 2000 rpm, 2500 rpm, 3000 rpm, and 3600 rpm for 1 hour each, a coated living matter was obtained in the same manner as in Comparative Example 7. The coating conditions of Examples 1 to 4 and Comparative Examples 1 to 7 are shown in Table 1.

[0094] [Table 1]

[0095] [Evaluation] (Measurement of particle size distribution) The particle size distributions of Coating Material A and Coating Material B were measured using a laser diffraction particle size distribution measuring device. As a result, for Coating Material A, the particle diameter D 50 was 2.3 μm, and the particle diameter D 90 was 4.3 μm. On the other hand, for Coating Material B, the particle diameter D 50 was 0.34 μm, and the particle diameter D 90 was 0.75 μm.

[0096] (Measurement of coating rate) The coating rates of the coated living matters obtained in Examples 1 to 4 and Comparative Examples 1 to 7 were measured by X-ray photoelectron spectroscopy (XPS). Specifically, surface element analysis of the coated living matter was performed using an X-ray photoelectron spectroscopy analyzer (manufactured by ULVAC-PHI, PHI X-tool). The pass energy was set to 224 eV, and narrow scan analysis was performed. Thereafter, the element ratio was calculated from the intensity values of C1s, O1s, P2p, Ni2p3, Co2p3, Al2p, and B1s detected by analysis software (MultiPak, manufactured by ULVAC-PHI), and the value [%] of (P + B) / (P + B + Ni + Co + Al) was determined as the coating rate. The results are shown in Table 2.

[0097] (Measurement of BET specific surface area) The BET specific surface areas of the coated active materials obtained in Examples 1 to 4 and Comparative Examples 1 to 7 were measured by the BET method. Specifically, N2 adsorption BET specific surface area measurement was performed using a BELSORPmaxII manufactured by Microtrac. In a nitrogen atmosphere, 5.0 g of the sample was weighed into the measurement tube, connected to the measuring device, and degassed under vacuum at room temperature for 8 hours. Thereafter, measurements were carried out at at least 10 points between relative pressures P / P0 = 0.250 and 0.995, and the BET specific surface area was calculated. The results are shown in Table 2.

[0098] (Measurement of moisture content) The moisture contents of the coated active materials obtained in Examples 1 to 4 and Comparative Examples 1 and 7 were measured by the Karl Fischer method. Specifically, a trace amount of moisture in the sample was measured using an MKC-710 series manufactured by Kyoto Electronics Industry Co., Ltd. After putting 1.0 g of the coated active material into the sample container under a nitrogen atmosphere, it was set in the apparatus. After blank measurement at 120°C, the temperature was maintained at 120°C, and moisture was detected until the minimum electrolysis amount became 0.1 μg or less. Thereafter, the temperature was raised to 180°C and the same operation was performed, and moisture was detected until the minimum electrolysis amount became 0.1 μg or less. Next, the temperature was raised to 300°C, and the same operation was repeated to measure the amount of moisture generated in each temperature range, and it was converted to the moisture content (in ppm units) by dividing by the sample weight. The results are shown in Table 2.

[0099] (Resistance measurement) Using the coated active materials obtained in Examples 1 to 4 and Comparative Examples 1 to 7 as the positive electrode active material, batteries were fabricated and resistance measurements were performed.

[0100] First, a positive electrode slurry was prepared by mixing a positive electrode active material (coated active material), a sulfide solid electrolyte (10LiI - 15LiBr - 75Li3PS4), a conductive material (VGCF), a binder (SBR), and a dispersion medium (heptane). 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 slurry was sufficiently stirred by an ultrasonic homogenizer, and the positive electrode slurry was coated on the surface of a positive electrode current collector (Al foil) to form a coating film. The coating film was dried at 100°C for 30 minutes using a hot plate. Thereby, a positive electrode precursor was obtained. A disk-shaped positive electrode was cut out from the positive electrode precursor. The area of the positive electrode was 1 cm 2 was obtained.

[0101] Next, a negative electrode and a solid electrolyte layer were prepared. The negative electrode active material was graphite. The same kind of 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 this order 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-state battery). After adjusting the open circuit voltage (OCV) of the obtained all-solid-state battery to 2.03 V, constant current discharge was performed, and the voltage drop in 5 seconds was divided by the current amount to measure the battery resistance. The discharge current rate was 2.5C. Based on the resistance of the battery of Comparative Example 1 as a reference (1.0), the resistances of the batteries of each example and each example were relativized and evaluated. The results are shown in Table 2 and Figure 4.

[0102]

Table 2

[0103] As shown in Table 2, in Comparative Example 1, since the wet method was used, it was confirmed that the moisture content was relatively high even after drying. On the other hand, in Examples 1 to 4, since the dry method was used, it was confirmed that the moisture content was low. Also, as shown in Table 2 and FIG. 4, when comparing Example 1 and Comparative Example 1, the coating rate of Example 1 (84%) was lower than that of Comparative Example 1 (96%), and in a situation where an increase in resistance due to the high-resistance layer was likely to occur, the moisture content of Example 1 was lower than that of Comparative Example 1, and an increase in resistance due to moisture could be suppressed. As a result, the resistances were comparable. Also, in Examples 2 to 4, the resistance was lower than that of Example 1. In Examples 1 to 4, since no organic solvent was used, it was advantageous from the viewpoints of cost reduction and reduction of environmental load.

[0104] On the other hand, as shown in Table 2, when comparing Comparative Examples 2 to 6 and Examples 1 to 4, it was confirmed that the coating rate was significantly improved by using the atomized coating material B. Also, as shown in Table 2 and FIG. 4, in Comparative Examples 2 to 6, since the dry method was used, the moisture content was low, but since the coating rate was low, it is presumed that an increase in resistance due to the high-resistance layer occurred. On the other hand, in Comparative Example 7, since the dry method was used, the moisture content was low, and although the atomized coating material B was used, the coating treatment was not sufficiently performed, so the coating rate was low. Therefore, it is presumed that an increase in resistance due to the high-resistance layer occurred. In contrast, in Examples 1 to 4, since the dry method was used, the moisture content was low, and by sufficiently performing the coating treatment using the atomized coating material B, the coating rate could be increased. As a result, it is considered that an increase in resistance due to moisture and an increase in resistance due to the high-resistance layer could be suppressed.

[0105] Regarding the BET specific surface area, as shown in Table 2, in Comparative Examples 2 to 6 using the coating material A, the BET specific surface areas of the coating active materials were almost the same. This supports the fact that the coating rate does not improve with the stirring treatment. On the other hand, in Comparative Example 7 and Examples 1 to 4 using the coating material B, as the stirring treatment time increased, the coating rate improved, and the value decreased to a BET specific surface area equivalent to that of Comparative Example 1 (wet method). This indicates that the coating rate improved with the stirring treatment due to the coating material B spreading on the surface of the active material.

Explanation of Symbols

[0106] 1 … Electrode active material 2 … Coating layer 10 … Coated active material 11 … Positive electrode layer 12 … Negative electrode layer 13 … Electrolyte layer 14 … Positive electrode current collector 15 … Negative electrode current collector 20 … Battery

Claims

1. A coated active material comprising an electrode active material and a coating layer covering the electrode active material and containing a coating material having B element, P element and O element, wherein the amount of water X generated in the temperature range of 120 °C or more and 180 °C or less is 10.0 ppm or less, the coating rate of the coating layer with respect to the electrode active material is greater than 67%, the coated active material.

2. The coated active material according to claim 1, wherein the amount of water X is 8.0 ppm or less.

3. The coated active material according to claim 1, wherein the amount of water Y generated in the temperature range of 180 °C or more and 300 °C or less is 350 ppm or less.

4. The coated active material according to claim 1, wherein the coating rate is 75% or more.

5. The coated active material according to claim 1, wherein the coating material further has Li element.

6. The electrode active material has Li element, M element (M is a metal other than Li), and O element, the M contains at least Ni, The coated active material according to claim 1, wherein the molar ratio of Ni to M (Ni / M) is 50% or more.

7. The coated active material according to claim 6, wherein Ni / M is 80% or more.

8. The BET specific surface area is 0.50 m ２ / g or more and less than 1.20 m ２ / g, and the coated active material according to claim 1.

9. An electrode composite material containing the coated active material according to any one of claims 1 to 8 and at least one of a conductive material and a binder.

10. The electrode composite material according to claim 9, wherein the electrode composite material contains a solid electrolyte.

11. The electrode composite material according to claim 10, wherein the solid electrolyte is a sulfide solid electrolyte.

12. A battery having 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 9, the battery.

13. The battery according to claim 12, wherein the positive electrode layer contains the electrode composite material.

14. The battery according to claim 12, wherein the electrolyte layer contains a solid electrolyte.

15. A method for manufacturing a coated active material for manufacturing the coated active material according to any one of claims 1 to 8, comprising: a preparation step of preparing the electrode active material and the coating material; a coating layer forming step of coating the electrode active material with the coating material by a dry method to form the coating layer. The particle diameter D of the coating material ９０ is 2 μm or less, and a method for producing a coated active material.

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