Coated active material, electrode composite material, battery, and manufacturing method

Abstract

The invention relates to a coated active material, an electrode mixture, a battery and a manufacturing method. The coated active material includes: an electrode active material; and a coating layer that coats the electrode active material and contains a coating material having an element B, an element P, and an element O, in which a moisture content X generated by the coating active material in a temperature range of 120 DEG C to 180 DEG C is 10.0 ppm or less, and a coating rate of the coating layer with respect to the electrode active material is greater than 67%.

Description

Technical Field

[0001] The present disclosure relates to a coated active material, an electrode composite material, a battery, and a manufacturing method. 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) has been continuously advanced. 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 Unexamined Patent Application Publication No. 2023-136753 discloses a composite particle including a positive electrode active material particle and a coating film that coats at least a part of the surface of the positive electrode active material particle and contains a phosphorus compound. Further, Japanese Unexamined Patent Application Publication No. 2023-136753 discloses manufacturing the composite particle by mixing the positive electrode active material particle with an aqueous coating liquid (aqueous coating solution) containing phosphorus and drying. Summary of the Invention

[0004] In a coating method using an aqueous coating liquid containing phosphorus, moisture remains in the coating layer even after sufficient drying, and the remaining moisture deteriorates the electrode active material or deteriorates the electrolyte present around the electrode active material, sometimes causing an increase in resistance.

[0005] Therefore, the inventors of the present application studied coating the electrode active material with a coating material using a dry method. By using the dry method, the amount of moisture in the coating layer can be reduced. On the other hand, the inventors of the present application have learned the following new problem: in the case of the dry method, it is difficult to increase the coating rate of the coating layer with respect to the electrode active material. If the coating rate of the coating layer with respect to the electrode active material is low, sometimes the electrode active material and the electrolyte react to form a high-resistance layer, causing an increase in resistance.

[0006] The present disclosure provides a coated active material that suppresses an increase in resistance caused by moisture and an increase in resistance caused by a high-resistance layer.

[0007] The coated active material according to a first aspect of the present disclosure includes: 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 by the coated active material in a 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%.

[0008] The coated active material according to the above aspect, wherein the amount of moisture X is 8.0 ppm or less.

[0009] The coated active material involved in the above solution, wherein the amount of water Y generated by the coated active material in the temperature range of above 180°C and below 300°C is 350 ppm or less.

[0010] The coated active material involved in the above solution, wherein the coating rate is 75% or more.

[0011] The coated active material involved in the above solution, wherein the coating material further contains Li element.

[0012] The coated active material involved in the above solution, wherein the electrode active material contains Li element, M element, and O element, M is a metal other than Li and contains at least Ni, and the molar ratio of Ni to M is 50% or more.

[0013] The coated active material involved in the above solution, wherein Ni / M is 80% or more.

[0014] The coated active material involved in the above solution, wherein the BET specific surface area is 0.50 m 2 / g or more and less than 1.20 m 2 / g.

[0015] 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.

[0016] The electrode composite material involved in the above solution, wherein the electrode composite material contains a solid electrolyte.

[0017] The electrode composite material involved in the above solution, wherein the solid electrolyte is a sulfide solid electrolyte.

[0018] 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.

[0019] The battery involved in the above solution, wherein the positive electrode layer contains the electrode composite material.

[0020] The battery involved in the above solution, wherein the electrolyte layer contains a solid electrolyte.

[0021] The manufacturing method of the coated active material involved in the fourth solution of the present disclosure for manufacturing the coated active material involved in the above solution includes: preparing the electrode active material and the coating material; using a dry method to coat the electrode active material with the coating material to form the coating layer, wherein the particle size D of the coating material 90 is 2 μm or less.

[0022] The coated active material of the present disclosure achieves the following effects: it can inhibit the increase in resistance caused by moisture and the increase in resistance caused by the high-resistance layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Hereinafter, the features, advantages, and technical and industrial significance of the exemplary embodiments of the present invention will be described with reference to the drawings, in which the same reference numerals denote the same elements, and in which:

[0024] Figure 1 is a schematic cross-sectional view for illustrating the coated active material of the present disclosure.

[0025] Figure 2 is a schematic cross-sectional view for illustrating the battery of the present disclosure.

[0026] Figure 3 is a flowchart for illustrating the manufacturing method of the coated active material of the present disclosure.

[0027] Figure 4 is a coordinate diagram showing the resistances of the batteries fabricated in Examples 1 to 4 and Comparative Examples 1 to 7. DETAILED DESCRIPTION

[0028] Hereinafter, the coated active material, the electrode composite material, the battery, and the manufacturing method of the coated active material of the present disclosure will be described in detail.

[0029] A. Coated Active Material

[0030] Figure 1 is a schematic cross-sectional view for illustrating the coated active material of the present disclosure. Figure 1 The shown coated active material 10 has an electrode active material 1 and a coating layer 2. The coating layer 2 coats the electrode active material 1 and contains a coating material having B element, P element, and O element. The amount of moisture X generated by the coated active material 10 in the temperature range of 120°C or higher and 180°C or lower is usually 10.0 ppm or less. In addition, the coating rate of the coating layer 2 with respect to the electrode active material 1 is usually greater than 67%.

[0031] According to the present disclosure, since the amount of moisture X is small and the coating rate of the coating layer is high, a coated active material capable of inhibiting the increase in resistance caused by moisture and the increase in resistance caused by the high-resistance layer is obtained. As described above, Japanese Patent Application Laid-Open No. 2023-136753 discloses manufacturing composite particles by mixing positive electrode active material particles and an aqueous coating liquid containing phosphorus and drying. In the coating method using an aqueous coating liquid containing phosphorus, moisture remains in the coating layer even after sufficient drying, and the remaining moisture deteriorates the electrode active material or the electrolyte present around the electrode active material, sometimes causing an increase in resistance.

[0032] Therefore, the inventors of the present application studied the coating of electrode active materials with a coating material using a dry method. In the case of using the dry method, it is not necessary to use a solvent such as water, so the moisture content of the coating layer can be reduced. On the other hand, the inventors of the present application found a new problem that it is difficult to improve the coating rate of the coating layer relative to the electrode active material in the case of the dry method. If the coating rate of the coating layer relative to the electrode active material is low, sometimes the electrode active material reacts with the electrolyte to form a high-resistance layer, sometimes resulting in an increase in resistance.

[0033] The inventors of the present application repeatedly and deeply studied to solve the above new problems, and as a result, obtained the following understanding: The reason why it is difficult to improve 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, it was found that when using a fine coating material to suppress the damage of the surface of the electrode active material, the coating rate of the coating material can be greatly improved. As a result, a coated active material with a small moisture content and a high coating rate of the coating layer can be obtained, thereby simultaneously suppressing the increase in resistance caused by moisture and the increase in resistance caused by the high-resistance layer. In addition, since the coating material contains P element, the chemical stability of the coating layer is improved. Furthermore, since the coating material contains B element in addition to P element, the ionic conductivity of the coating layer can be improved while improving the chemical stability of the coating layer.

[0034] 1. Coating layer

[0035] The coating layer of the present disclosure is a layer that coats the electrode active material. In addition, the coating layer contains a coating material having B element, P element, and O element. The coating material may further contain Li element. In addition, the coating material preferably has a PO4 structure.

[0036] In the coating material, the molar ratio of B element to P element (B / P) is not particularly limited. For example, it is 0.5 or more and 2.0 or less, it can be 0.8 or more and 1.25 or less, and it can be 0.9 or more and 1.11 or less. In addition, when the coating material further contains 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 is 0.3 or more and 1.2 or less, and it can be 0.5 or more and 1.0 or less.

[0037] The coating rate of the coating layer relative to the electrode active material is usually greater than 67%, can be 75% or more, and can be 80% or more. If the coating rate is too low, it is difficult to sufficiently suppress the increase in resistance caused by the high-resistance layer. On the other hand, the coating rate can be 100%, or can be less than 100%. The coating rate of the present disclosure is measured based on X-ray photoelectron spectroscopy (XPS), and 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.

[0038] 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, can be 5 nm or more and 50 nm or less, and 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).

[0039] 2. Electrode active material

[0040] There is no particular limitation on the electrode active material of the present disclosure. Preferably, it contains Li element, M element, and O element. M is a metal (including a semi-metal) other than Li. M can be a transition metal or a metal (including a semi-metal) belonging to Group 13 to Group 16 of the periodic table. In addition, M can be one metal or two or more metals. Among them, M is preferably at least one of Ni, Co, Mn, Al, V, and Fe.

[0041] Particularly preferably, M contains at least Ni. The electrode active material containing Ni is liable to deteriorate due to moisture, but the coated active material of the present disclosure has a small amount of moisture, and thus can suppress the deterioration of the electrode active material containing Ni. There is no particular limitation on the molar ratio of Ni to M (Ni / M). For example, it is 30% or more, can be 50% or more, can be 60% or more, can be 70% or more, and can be 80% or more. On the other hand, Ni / M can be 100%, or can be less than 100%.

[0042] 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.

[0043] As an example of the composition of the electrode active material, LiNi x Co y Al zO2 (0.5 ≤ x, 0 ≤ y, 0 ≤ z, x + y + z = 1). x can be 0.6 or more, can be 0.7 or more, can be 0.8 or more. y can be 0, or can be greater than 0. Additionally, y is, for example, 0.3 or less. z can be 0, or can be greater than 0. Additionally, z is, for example, 0.1 or less.

[0044] As another example of the composition of the electrode active material, LiNi can be cited. a Co b Mn c O2 (0.5 ≤ a, 0 ≤ b, 0 ≤ c, a + b + c = 1). a can be 0.6 or more, can be 0.7 or more, can be 0.8 or more. b can be 0, or can be greater than 0. Additionally, b is, for example, 0.3 or less. c can be 0, or can be greater than 0. Additionally, c is, for example, 0.3 or less.

[0045] 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, can be 1 μm or more, can 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, can be 20 μm or less. In the present disclosure, the particle diameter D 50 corresponds to the particle diameter at the cumulative 50 volume % measured by a laser diffraction particle size distribution measuring device.

[0046] 3. Coated active material

[0047] The amount of moisture X generated by the coated active material of the present disclosure in the temperature range of 120 °C or more and 180 °C or less is usually 10.0 ppm or less. The amount of moisture X can be 9.0 ppm or less, can be 8.0 ppm or less. By having a smaller amount of moisture X, an increase in resistance due to moisture can be suppressed. Additionally, the amount of moisture Y generated by the coated active material in the temperature range of 180 °C or more and 300 °C or less is, for example, 350 ppm or less, can be 320 ppm or less. By having a smaller amount of moisture Y, an increase in resistance due to moisture can be suppressed. The measurement methods for the amount of moisture X and the amount of moisture Y are as described in the examples below.

[0048] There is no particular limitation on the BET specific surface area of the coated active material, and it is, for example, 0.50 m 2 / g or more, can be 0.70 m 2 / g or more. On the other hand, the BET specific surface area of the coated active material is, for example, less than 1.20 m 2 / g, can be 1.00 m 2 / g or less.

[0049] The coated active material of the present disclosure is generally used in batteries. The electrode active material in the coated active material can be a positive electrode active material or a negative electrode active material, preferably the former. As a method for manufacturing the coated active material, for example, the method described in "D. Method for Manufacturing Coated Active Material" described later can be cited.

[0050] B. Electrode composite

[0051] The electrode composite of the present disclosure contains the above-mentioned coated active material and at least one selected from a conductive material and a binder.

[0052] According to the present disclosure, by using the above-mentioned coated active material, an electrode composite capable of suppressing an increase in resistance caused by moisture and an increase in resistance caused by a high-resistance layer is obtained.

[0053] 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-mentioned "A. Coated Active Material". The electrode active material in the coated active material can be a positive electrode active material or a negative electrode active material, preferably the former. That is, the electrode composite can be a positive electrode composite or a negative electrode composite, preferably the former.

[0054] The proportion of the coated active material in the electrode composite 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 electron conductivity in the electrode composite may be reduced relatively.

[0055] The electrode composite 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 fibers, carbon nanotubes (CNT), and carbon nanofibers (CNF) can be cited. In addition, as the binder, for example, rubber-based binders and fluoride-based binders can be cited.

[0056] The electrode composite 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, it is preferable that the solid electrolyte is a sulfide solid electrolyte. This is because the ionic conductivity is high.

[0057] Sulfide solid electrolytes generally contain at least Li element and S element. The sulfide solid electrolyte preferably further contains 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, I.

[0058] 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, LGPS type crystal phase can be cited.

[0059] The composition of the sulfide solid electrolyte is not particularly limited. 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 can be cited. X is at least one of F, Cl, Br, I, and x and y satisfy 0≤x, 0≤y. In addition, as another example of the composition of the sulfide solid electrolyte, Li 4-x Me 1-x P x S4 (0<x<1) can be cited. Me is at least one of Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0060] C. Battery

[0061] Figure 2 is a schematic cross-sectional view of the battery of the present disclosure for illustration. 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".

[0062] According to the present disclosure, by using the above electrode composite material, a battery is obtained in which the increase in resistance caused by moisture and the increase in resistance caused by the high-resistance layer are suppressed. As described above, the electrode composite material can be a positive electrode composite material or a negative electrode composite material, and the former is preferred. Hereinafter, the detailed situation of the battery will be described for the case where the electrode composite material is a positive electrode composite material.

[0063] 1. Positive electrode layer

[0064] The positive electrode layer disclosed in the present invention contains the above-mentioned electrode composite (positive electrode composite). For the electrode composite, it is the same as the contents described in the above-mentioned "B. Electrode composite", so the description here is omitted. In addition, the positive electrode layer may contain an electrolyte as needed. For the electrolyte, it is the same as the contents described in "3. Electrolyte layer". The thickness of the positive electrode layer is, for example, greater than 0.1 μm and less than 1000 μm, can be greater than 0.1 μm and less than 500 μm, and can be greater than 0.1 μm and less than 100 μm. In addition, as a method for forming the positive electrode layer, for example, a method of applying the electrode composite (positive electrode composite) to the positive electrode collector can be listed.

[0065] 2. Negative electrode layer

[0066] The negative electrode layer is a layer containing at least a negative electrode active material. In addition, the negative electrode layer may contain at least one of an electrolyte, a conductive material, and a binder as required.

[0067] 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, Li4Ti5O 12 Oxidant active substances.

[0068] 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, the Si-based active material 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, a polyhedron (cage) containing pentagons or hexagons is formed using multiple Si elements. The polyhedron has a space inside that can accommodate Li ions, so that the volume change caused by charging and discharging can be suppressed.

[0069] 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.

[0070] For the electrolyte used in the negative electrode layer, it is the same as that described in "3. Electrolyte layer". In addition, for the conductive material and binder used in the negative electrode layer, they are the same as those described in "B. Electrode composite material", 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, 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] 3. Electrolyte layer

[0072] 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 can be a solid electrolyte or a liquid electrolyte (electrolyte solution).

[0073] For the solid electrolyte, it is the same as that described in the above "B. Electrode composite material", so the description here is omitted. On the other hand, the electrolyte solution preferably contains a supporting salt and a solvent. As the supporting salt (lithium salt) of the electrolyte solution having lithium ion conductivity, for example, inorganic lithium salts such as LiPF6, LiBF4, LiClO4, LiAsF6, etc.; organic lithium salts such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, LiC(CF3SO2)3, etc. As the solvent for the electrolyte solution, for example, cyclic esters (cyclic carbonates) such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC); chain-like esters (chain-like carbonates) such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC). The electrolyte solution preferably contains two or more solvents.

[0074] 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.

[0075] 4. Other components

[0076] The battery of 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. As the material of the positive electrode current collector, for example, SUS, aluminum, nickel, iron, titanium, and carbon can be cited. On the other hand, as the material of the negative electrode current collector, for example, SUS, copper, nickel, and carbon can be cited.

[0077] The battery of the present disclosure may further include a constraint jig that applies a constraint pressure to the positive electrode layer, the electrolyte layer, and the negative electrode layer in the thickness direction. In particular, when the electrolyte layer is a solid electrolyte layer, it is preferable to apply a constraint pressure in order to form good ion conduction paths and electron conduction paths. 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.

[0078] 5. Battery

[0079] There is no particular limitation on the type of the battery of the present disclosure. Typically, it is a lithium ion battery. In addition, the battery of 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 of the present disclosure may be a primary battery or a secondary battery, and a secondary battery is preferably used. This is because it can be repeatedly charged and discharged, and can be used, for example, as a vehicle-mounted battery.

[0080] Examples of the uses of the battery include 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. In particular, it is preferably used as a driving power source for a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or a battery electric vehicle (BEV). In addition, the battery can be used as a power source for mobile bodies other than vehicles (for example, railways, ships, and aircraft), and can also be used as a power source for electrical products such as information processing devices.

[0081] D. Method for manufacturing coated active material

[0082] Figure 3 is a flowchart illustrating the method for manufacturing the coated active material of the present disclosure. In the Figure 3 manufacturing method shown, 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 formation step). In the present disclosure, the coating conditions are adjusted so as to obtain the coated active material described in the above “A. Coated active material”. In particular, a coating material having a particle size D 90 of 2 μm or less is used.

[0083] According to the present disclosure, by using a fine coating material, a coated active material that can suppress an increase in resistance due to moisture and an increase in resistance due to a high-resistance layer can be obtained.

[0084] 1. Preparation step

[0085] The preparation process of the present disclosure is a process 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".

[0086] The shape of the coating material in the preparation process is usually particulate. The particle size D of the coating material 90 is usually 2 μm or less, can be 1 μm or less, and can be 0.8 μm or less. By using a fine coating material, when coating the electrode active material with the coating material, damage to the surface of the electrode active material by the coating material can be suppressed. As a result, the coating rate of the coating layer can be increased. On the other hand, there is no particular limitation on the particle size D of the coating material 90 , for example, it is 0.2 μm or more. The particle size D 90 corresponds to the particle size equivalent to 90% by volume in cumulative from the small particle side measured by a laser diffraction particle size distribution measuring device.

[0087] The particle size D of the coating material 50 , for example, is 1 μm or less, can be 0.6 μm or less, and can be 0.4 μm or less. On the other hand, there is no particular limitation on the particle size D of the coating material 50 , for example, it is 0.1 μm or more. In addition, there is no particular limitation on the particle size D of the coating material 50 with respect to the particle size D of the electrode active material 50 , and the ratio is not particularly limited, for example, it is 1% or more and 25% or less, and can be 5% or more and 15% or less.

[0088] There is no particular limitation on the production method of the coating material. For example, a method having a synthesis process of a coarse-grained material for synthesizing the coating material and a micronization process of micronizing the above coarse-grained material can be cited. The synthesis process is, for example, a process of dissolving a solute containing a B source and a P source in a solvent, preparing a coating solution, and then drying the coating solution.

[0089] As the B source, as long as it is a simple substance or compound containing B element, there is no particular limitation. For example, boric acid (H3BO3) can be cited. As the P source, as long as it is a simple substance or compound containing P element, there is no particular limitation. For example, orthophosphoric acid (H3PO4), metaphosphoric acid (HPO3) can be cited. In addition, the coating solution preferably contains an O source. As the O source, for example, the O element contained in the above 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 Li element, there is no particular limitation. For example, lithium hydroxide (LiOH) can be cited. In addition, as the solvent, for example, water can be cited.

[0090] As a specific example of the method for producing the coating liquid, the following method can be cited: First, a first aqueous solution in which orthophosphoric acid (H3PO4) or metaphosphoric acid (HPO3) is dissolved in water is prepared. Secondly, a second aqueous solution in which boric acid (H3BO3) is dissolved in the first aqueous solution is prepared. Secondly, lithium hydroxide monohydrate (LiOH·H2O) is dissolved in the second aqueous solution to prepare the coating liquid. Further, by drying the coating liquid, a coarse particle material is obtained. The method for drying the coating liquid is not particularly limited, and examples thereof include spray drying, an electric furnace, a vacuum drying furnace, and a spray pyrolysis device.

[0091] The fine particle step is a step of making the above-mentioned coarse particle material into fine particles. By making the coarse particle material into fine particles, a coating material having a particle diameter D 90 of 2 μm or less is obtained. As a method for making the coarse particle material into fine particles, for example, mechanical grinding such as bead milling and ball milling can be cited. Mechanical grinding can be carried out dry or wet. In the case of carrying out wet grinding, it is preferable to use a solvent other than water. The conditions for mechanical grinding are not particularly limited, and are appropriately adjusted in such a way as to obtain a coating material having a particle diameter D 90 of 2 μm or less.

[0092] 2. Coating layer formation step

[0093] The coating layer formation step of the present disclosure is a step of coating the above-mentioned electrode active material with the above-mentioned coating material by a dry method to form the above-mentioned coating layer.

[0094] As the dry method, for example, a method of applying a shear treatment to a mixture containing an electrode active material and a coating material can be cited. The above-mentioned mixture is substantially free of water and may contain a small amount of water to the extent that its influence can be ignored. The shear treatment is, for example, a treatment of rotating a chopper disposed in a container. As another example of the shear treatment, a method of rotating a scraper disposed in a container to give compressive shear energy to the mixture present between the scraper and the wall surface of the container can be cited. Further, the conditions for the shear treatment are not particularly limited, and are appropriately adjusted in such a way as to obtain the coated active material described in the above-mentioned "A. Coated active material".

[0095] 3. Coated active material

[0096] The coated active material obtained by the above-mentioned respective steps is the same as that described in the above-mentioned "A. Coating material".

[0097] Furthermore, the present disclosure is not limited to the above-mentioned embodiments. The above-mentioned embodiments are examples, and technical solutions having substantially the same constitution as the technical idea described in the claims of the present disclosure and achieving the same effects are all included in the technical scope of the present disclosure.

[0098] [Comparative Example 1]

[0099] (Preparation of Coating Liquid)

[0100] Metaphosphoric acid (manufactured by FUJIFILM Wako Pure Chemical Corporation) 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. In the obtained aqueous solution, boric acid (manufactured by NACALAI TESQUE) was added and dissolved so that the molar ratio of B element to P element (B / P) became 1.0. Further, lithium hydroxide monohydrate (manufactured by FUJIFILM Wako Pure Chemical Corporation) was added and dissolved so that the molar ratio of Li element to the total of P element and B element (Li / (P + B)) became 0.9. Thus, a coating liquid was obtained.

[0101] (Preparation of Coated Active Material)

[0102] 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, using a spray drying device "Product name: Mini Spray Dryer B-290" manufactured by BUCHI, the slurry was dried to form a coating layer on the surface of the active material particles. The air supply temperature of the spray drying device 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.

[0103] [Comparative Example 2]

[0104] (Preparation of Coating Material A)

[0105] In the same manner as in Comparative Example 1, a coating liquid was obtained. For the obtained coating liquid, using a spray drying device "Product name: Mini Spray Dryer B-290" manufactured by BUCHI, the coating liquid was dried to obtain a powder. The air supply temperature of the spray drying device was 200°C, and the air supply volume was 0.45 m 3 / min. Then, additional heat treatment was performed in an atmospheric atmosphere. The heat treatment temperature was 200°C. The heat treatment time was 5 hours. Thus, a powdery coating material A was obtained.

[0106] (Preparation of Coated Active Material)

[0107] In a mixing blender BALANCE GRAN BG-2L (manufactured by FREUND-TURBO), 1000 g of the same active substance particles as in Comparative Example 1 and 31.0 g of coating material A were charged. Next, stirring treatment was carried out at a chopper rotation speed of 1500 rpm for 1 hour to form a coating layer on the surface of the active substance particles, and the coated active substance was obtained.

[0108] [Comparative Example 3]

[0109] Except that when forming the coating layer on the surface of the active substance particles, stirring treatments were carried out at chopper rotation speeds of 1500 rpm and 2000 rpm for 1 hour each, the coated active substance was obtained in the same manner as in Comparative Example 2.

[0110] [Comparative Example 4]

[0111] Except that when forming the coating layer on the surface of the active substance particles, stirring treatments were carried out at chopper rotation speeds of 1500 rpm, 2000 rpm, and 2500 rpm for 1 hour each, the coated active substance was obtained in the same manner as in Comparative Example 2.

[0112] [Comparative Example 5]

[0113] Except that when forming the coating layer on the surface of the active substance particles, stirring treatments were carried out at chopper rotation speeds of 1500 rpm, 2000 rpm, 2500 rpm, and 3000 rpm for 1 hour each, the coated active substance was obtained in the same manner as in Comparative Example 2.

[0114] [Comparative Example 6]

[0115] Except that when forming the coating layer on the surface of the active substance particles, stirring treatments were carried out at chopper rotation speeds of 1500 rpm, 2000 rpm, 2500 rpm, 3000 rpm, and 3600 rpm for 1 hour each, the coated active substance was obtained in the same manner as in Comparative Example 2.

[0116] [Comparative Example 7]

[0117] (Production of Coating Material B)

[0118] 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, and a dispersion was obtained. A wet bead mill pulverization device LABSTAR Mini MGF015 (manufactured by Ashizawa Finetech Co., Ltd.) was prepared, and the obtained dispersion and zirconia beads (Φ0.1 mm) were put into the pulverization chamber, 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 atmospheric atmosphere to volatilize ethanol. Further, vacuum drying was performed at 100 °C for 8 hours. Thus, Coating Material B was obtained.

[0119] (Production of Coated Active Substance)

[0120] 1000 g of the same active substance particles as in Comparative Example 1 and 31.0 g of Coating Material B were put 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 substance particles, and a coated active substance was obtained.

[0121] [Example 1]

[0122] A coated active substance was obtained in the same manner as in Comparative Example 7, except that when forming the coating layer on the surface of the active substance particles, stirring treatment was performed at a chopper rotation speed of 1500 rpm and 2000 rpm for 1 hour each.

[0123] [Example 2]

[0124] A coated active substance was obtained in the same manner as in Comparative Example 7, except that when forming the coating layer on the surface of the active substance particles, stirring treatment was performed at a chopper rotation speed of 1500 rpm, 2000 rpm, and 2500 rpm for 1 hour each.

[0125] [Example 3]

[0126] A coated active substance was obtained in the same manner as in Comparative Example 7, except that when forming the coating layer on the surface of the active substance particles, stirring treatment was performed at a chopper rotation speed of 1500 rpm, 2000 rpm, 2500 rpm, and 3000 rpm for 1 hour each.

[0127] [Example 4]

[0128] Except when forming a coating layer on the surface of the active material particles, stirring treatments were carried out at shredder speeds of 1500 rpm, 2000 rpm, 2500 rpm, 3000 rpm, and 3600 rpm for 1 hour each, and the coated active material was obtained in the same manner as in Comparative Example 7. The coating conditions for Examples 1 to 4 and Comparative Examples 1 to 7 are shown in Table 1.

[0129]

Table 1

[0130]

[0131] [Evaluation]

[0132] (Particle size distribution measurement)

[0133] The particle size distributions of Coating Material A and Coating Material B were measured using a laser diffraction particle size distribution analyzer. As a result, the particle diameter D 50 of Coating Material A was 2.3 μm, and the particle diameter D 90 was 4.3 μm. On the other hand, the particle diameter D 50 of Coating Material B was 0.34 μm, and the particle diameter D 90 was 0.75 μm.

[0134] (Measurement of coating rate)

[0135] The coating rates of the coated active materials 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 active materials was performed using an X-ray photoelectron spectroscopy analyzer (manufactured by ULVAC-PHI, PHIX-tool). Narrow scan analysis was performed with the energy set to 224 eV. Then, using analysis software (MultiPak, manufactured by ULVAC-PHI), the element ratios were calculated from the intensity values of C1s, O1s, P2p, Ni2p3, Co2p3, Al2p, and B1s detected, and the value of (P + B) / (P + B + Ni + Co + Al) [%] was obtained as the coating rate. The results are shown in Table 2.

[0136] (Measurement of BET specific surface area)

[0137] 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 BELSORP max II manufactured by MICROTRAC. 5.0 g of the sample was weighed in a measurement tube under a nitrogen atmosphere, connected to the measurement device, and vacuum degassed at room temperature for 8 hours. Then, measurements were performed at at least 10 points between a relative pressure P / P0 = 0.250 and 0.995, and the BET specific surface area was calculated. The results are shown in Table 2.

[0138] (Measurement of moisture content)

[0139] The moisture content of the coated active materials obtained in Examples 1 to 4 and Comparative Examples 1 and 7 was measured by the Karl Fischer method. Specifically, a trace moisture content 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 installed in the apparatus. After a blank measurement at 120°C, temperature holding was carried out at 120°C, and moisture detection was performed until the minimum electrolysis amount became 0.1 μg or less. Then, the temperature was raised to 180°C, and the same operation was carried out, and moisture detection was performed 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, so that the amount of moisture generated in each temperature region was measured, and divided by the sample weight to be converted into a moisture content (in ppm units). The results are shown in Table 2.

[0140] (Resistance measurement)

[0141] Using the coated active materials obtained in Examples 1 to 4 and Comparative Examples 1 to 7 as the positive electrode active material, a battery was fabricated and resistance measurement was carried out.

[0142] 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 the 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. Thus, a raw positive electrode was obtained. A disc-shaped positive electrode was cut out from the raw positive electrode. The area of the positive electrode was 1 cm 2 .

[0143] 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. Inside a cylindrical jig, the positive electrode, the solid electrolyte layer, and the negative electrode were laminated in sequence, thereby forming 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 voltage drop during 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 (1.0), the resistances of the batteries of each Example and each Comparative Example were relativized and evaluated. The results are shown in Table 2 and Figure 4 。

[0144]

Table 2

[0145]

[0146] As shown in Table 2, in Comparative Example 1, the wet method was used, so it was confirmed that the water content was relatively high even after drying. In Examples 1 to 4, the dry method was used, so it was confirmed that the water content was low. In addition, as shown in Table 2 and Figure 4 shown, comparing Example 1 with Comparative Example 1, the coating rate of Example 1 (84%) was lower than that of Comparative Example 1 (96%), and it was a situation where an increase in resistance caused by a high-resistance layer was likely to occur. However, the water content of Example 1 was lower than that of Comparative Example 1, and an increase in resistance caused by water could be suppressed. As a result, the resistances were at the same level. In addition, in Examples 2 to 4, the resistance decreased compared with Example 1. In Examples 1 to 4, no organic solvent was used, so it was advantageous from the viewpoints of cost reduction and environmental load reduction.

[0147] On the other hand, as shown in Table 2, comparing Comparative Examples 2 to 6 with Examples 1 to 4, it was confirmed that by using the micronized coating material B, the coating rate was significantly increased. In addition, as shown in Table 2 and Figure 4 shown, in Comparative Examples 2 to 6, the dry method was used, so the water content was low, but due to the low coating rate, it was speculated that an increase in resistance caused by a high-resistance layer occurred. On the other hand, in Comparative Example 7, although the dry method was used, so the water content was low, and the micronized coating material B was used, but due to insufficient coating treatment, the coating rate decreased. Therefore, it was speculated that an increase in resistance caused by a high-resistance layer occurred. In Examples 1 to 4, the dry method was used, so the water content was low, and the micronized coating material B was used for sufficient coating treatment, so the coating rate could be increased. As a result, it was speculated that an increase in resistance caused by water and an increase in resistance caused by a high-resistance layer could be suppressed.

[0148] In addition, regarding the BET specific surface area, as shown in Table 2, in Comparative Examples 2 to 6 using Coating Material A, the BET specific surface area of the coated active material was substantially the same. This proves that the coating rate did not increase with the stirring treatment. On the other hand, in Comparative Example 7 and Examples 1 to 4 using Coating Material B, as the stirring treatment time was extended, the coating rate increased and the value decreased to a BET specific surface area equivalent to that of Comparative Example 1 (wet method). This indicates that by spreading Coating Material B on the surface of the active material, the coating rate increased with the stirring treatment.

Claims

1. A coated active material, characterized in that, Comprising: 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 by the coated active material in the temperature range of 120°C or higher and 180°C or lower is 10.0 ppm or less, the coating rate of the coating layer with respect to the electrode active material is greater than 67%; 2. The coated active material according to claim 1, characterized in that, the amount of moisture X is 8.0 ppm or less; 3. The coated active material according to claim 1, characterized in that, the amount of moisture Y generated by the coated active material in the temperature range of 180°C or higher and 300°C or lower is 350 ppm or less; 4. The coated active material according to claim 1, characterized in that, the coating rate is 75% or more; 5. The coated active material according to claim 1, characterized in that, the coating material further has Li element; 6. The coated active material according to claim 1, 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 50% or more; 7. The coated active material according to claim 6, wherein Ni / M is 80% or more; 8. The coated active material according to claim 1, characterized in that, The BET specific surface area is 0.50 m 2 / g or more and less than 1.20 m 2 / g.

9. An electrode composite material, characterized in that, Comprising: 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, characterized in that, The electrode composite material contains a solid electrolyte.

11. The electrode composite material according to claim 10, characterized in that, The solid electrolyte is a sulfide solid electrolyte.

12. 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 9.

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

14. The battery according to claim 12, characterized in that, The electrolyte layer contains a solid electrolyte.

15. A method for manufacturing a coated active material according to any one of claims 1 to 8, characterized in that, Comprising: Preparing the electrode active material and the coating material; Using a dry method, coating the electrode active material with the coating material to form the coating layer, Among them, the particle size D of the coating material 90 is 2 μm or less.

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