Coated active material, electrode mixture, battery and coating solution

Abstract

A coated active material (10) includes: an electrode active material (1); and a coating layer (2) covering the electrode active material (1), wherein: the electrode active material (1) includes a Li element, an M element, and an O element; M is a metal other than Li and includes at least Ni; a molar ratio (Ni / M) of Ni to M is 80% or more; the coating layer (2) includes a B element, a P element, a La element, and an O element; and a molar ratio (La / P) of the La element to the P element is 0.005 or more and 0.15 or less.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The present disclosure relates to a coated active material, an electrode mixture, a battery and a coating solution. 2. Description of the related art

[0002] Batteries have been actively developed in recent years. For example, the automotive industry is promoting the development of batteries for battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and hybrid electric vehicles (HEVs). Furthermore, a technology is known in which the surface of an electrode active material to be used in the battery is coated with a phosphorus-based coating solution.

[0003] For example, Japanese Unexamined Patent Application Laid-Open No. 2023-136753 discloses a composite particle containing a positive electrode active material particle and a coating film covering at least a portion of a surface of the positive electrode active material particle and containing a phosphorus compound. Furthermore, JP 2023-136753 A discloses the production of a composite particle by mixing a positive electrode active material particle and a phosphorus-containing water-based coating solution (water-based coating solution) and drying the mixture. SUMMARY OF THE INVENTION

[0004] An electrode active material with a high nickel content is promising from the point of view of capacity enhancement. However, when the phosphorus-containing water-based coating solution comes into contact with the electrode active material with a high nickel content, an exchange reaction between H+ and Li + to produce high-resistance NiO. As a result, an increase in resistance occurs. This is a specific problem when an electrode active material with a high nickel content and a water-based phosphorus-containing coating solution (phosphorus coating) are combined.

[0005] The present disclosure provides a coated active material that can reduce resistance increase even when an electrode active material with a high nickel content and a phosphorus-containing coating layer are combined.

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

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

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

[0009] In the coated active material according to the above aspect, the coverage of the coating layer with respect to the electrode active material may be 75% or more.

[0010] In the coated active material according to the above-mentioned aspect, M may further include at least one kind of Co, Mn and Al.

[0011] An electrode composition according to a second aspect of the present disclosure includes: the coated active material according to the aforementioned aspect; and at least one of an electrically conductive material and a binder.

[0012] In the electrode mixture according to the above-mentioned aspect, the electrode mixture may contain a solid electrolyte.

[0013] In the electrode composition according to the above aspect, the solid electrolyte may be a sulfide solid electrolyte.

[0014] A battery according to a third aspect 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 includes the electrode mixture of the above-mentioned aspect.

[0015] A coating solution for forming the coating layer in the coated active material of the above-mentioned aspect according to a fourth aspect of the present disclosure includes: a solute including a B element, a P element, and a La element; and water, which is a solvent, wherein: a molar ratio (La / P) of the La element to the P element is 0.001 or more and 0.100 or less; and an absorbance of the coating solution is 0.1 or less.

[0016] The coated active material in the present disclosure provides the effect that the resistance increase can be reduced even when the electrode active material with a high nickel content and the phosphorus-containing coating layer are combined. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Features, advantages and technical and industrial significance of embodiments of the invention are described below with reference to the accompanying drawings, in which like characters designate like elements and in which: Fig. 1 is a schematic sectional view showing a coated active material according to the present disclosure; Fig. 2 is a schematic sectional view showing a battery according to the present disclosure; and Fig.3 is a graph showing the resistances of the batteries manufactured in Examples 1 to 5 and Comparative Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] Hereinafter, a coated active material, an electrode mixture, a battery, and a coating solution are described in detail in the present disclosure. A. Coated active material

[0019] Fig. 1 is a schematic sectional view illustrating the coated active material in the present disclosure. Fig.The coated active material 10 shown in FIG. 1 includes an electrode active material 1 and a coating layer 2 covering the electrode active material 1. The electrode active material 1 includes a Li element, an M element (M is a metal other than Li and includes at least Ni), and an O element. Furthermore, the molar ratio (Ni / M) of Ni to M is 80% or more. Meanwhile, the coating layer 2 includes a B element, a P element, a La element, and an O element, and the molar ratio (La / P) of the La element to the P element is 0.005 or more and 0.15 or less.

[0020] According to the present disclosure, a coated active material is obtained that can reduce resistance increase when the La element is added to the coating layer, even when an electrode active material with a high nickel content and a phosphorus-containing coating layer are combined. As described above, JP 2023-136753 A discloses the preparation of a composite particle by mixing a positive electrode active material particle and a phosphorus-containing water-based coating solution and drying the mixture. An electrode active material with a high nickel content is promising from the viewpoint of capacity increase. When the phosphorus-containing water-based coating solution comes into contact with the electrode active material with a high nickel content, an exchange reaction between H + and Li +to produce high-resistance NiO. As a result, the resistance increases. For example, if the electrode active material is LiNiO2, the following reaction appears to occur. LiNiO2 + H + → NiOOH + Li + NiOOH → NiO + 0.5H2O + 0.25O2

[0021] Particularly when using a water-based phosphorus-containing coating solution, the presence of the P element appears to cause moisture to remain in the coating layer, thereby promoting the above-mentioned exchange reaction. In contrast, in the present disclosure, the addition of the La element, which has a high affinity for the P element, appears to prevent moisture from remaining in the coating layer, thus reducing the above-mentioned exchange reaction. Accordingly, the increase in resistance can be reduced. In addition, the coating layer includes the P element, thereby improving the chemical stability of the coating layer. Furthermore, the coating layer includes the B element in addition to the P element, so that the ionic conduction of the coating layer can be improved while improving the chemical stability of the coating layer. 1. Coating layer

[0022] The coating layer in the present disclosure is a layer covering the electrode active material. Furthermore, the coating layer contains the B element, the P element, and the O element. The coating layer may further contain a Li element. Furthermore, the coating layer preferably has a PO4 structure.

[0023] In the coating layer, the molar ratio (La / P) of the La element to the P element is usually 0.005 or more and 0.15 or less, and can be 0.01 or more and 0.11 or less. If the La / P ratio is too small, the resistance-reducing effect of the La element may not be sufficiently achieved. Conversely, if the La / P ratio is too large, manufacturing may be difficult.

[0024] In the coating layer, the molar ratio (B / P) of the B element to the P element is not particularly limited, but is, for example, 0.5 or more and 2.0 or less, and may be 0.8 or more and 1.25 or less, or 0.9 or more and 1.11 or less. When the coating layer further contains a Li element, the molar ratio (Li / (P+B)) of the Li element to the sum of the P element and the B element is not particularly limited, but is, for example, 0.3 or more and 1.2 or less, and may be 0.5 or more and 1.0 or less.

[0025] The coverage of the coating layer with respect to the electrode active material is not particularly limited, but is, for example, 75% or more, and may be 80% or more. If the coverage is too low, the resistance increase caused by the high-resistance layer formed by the reaction between the electrode active material and the electrolyte may not be sufficiently reduced. Meanwhile, the coverage may be 100% or less than 100%. The coverage in the present disclosure is determined by calculating an element ratio from the intensity ratios of the respective main elements based on X-ray photoelectron spectroscopy (XPS) measurements, and is expressed as a percentage of the elements contained in the coating layer with respect to the sum of the elements contained in the electrode active material and the coating layer.

[0026] The thickness of the coating layer is not particularly limited, but is, for example, 1 nm or more and 100 nm or less, and may be 5 nm or more and 50 nm or less, or 10 nm or more and 30 nm or less. The thickness of the coating layer is determined, for example, as the average value of the thicknesses of multiple samples (e.g., 100 or more samples) examined with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). 2. Electrode active material

[0027] The electrode active material in the present disclosure typically includes a Li element, an M element, and an O element. M is a metal other than Li (including a metalloid) and includes at least Ni. M other than Ni may be a transition metal or a metal (including a metalloid) belonging to Group 13 to Group 16 of the periodic table. Furthermore, M may be one type of metal other than Ni or two or more types of metals. Of these, M other than Ni is preferably at least one type of Co, Mn, Al, V, and Fe.

[0028] The molar ratio (Ni / M) of Ni to M is usually 80% or more, and can be 85% or more, or 90% or more. Meanwhile, Ni / M can be 100% or less than 100%.

[0029] In addition to the Li element, the M element, and the O element, the electrode active material can also contain a non-metallic element such as a P element. Furthermore, the crystal structure of the electrode active material is not particularly limited. Examples include a layered rock salt structure, a spinel structure, and an olivine structure.

[0030] As an example of the composition of the electrode active material, LiNi x Co y Al-O2 (0.80 ≤ x, 0 ≤ y, 0 ≤ z, x + y + z = 1). The symbol x is usually 0.80 or more and can be 0.85 or more or 0.90 or more. The symbol y can be 0 or greater than 0. In addition, the symbol y is, for example, 0.20 or less. The symbol z can be 0 or greater than 0. For example, z is 0.10 or less.

[0031] As another example of the composition of the electrode active material, LiNi a Co b Mn cO2 (0.80 ≤ a, 0 ≤ b, 0 ≤ c, a + b + c = 1). Symbol a is usually 0.80 or more and can be 0.85 or more or 0.90 or more. Symbol b can be 0 or greater than 0. Also, symbol b is, for example, 0.20 or less. Symbol c can be 0 or greater than 0. For example, c is 0.20 or less.

[0032] The shape of the electrode active material is usually particulate. The particle size D 50 of the electrode active material is, for example, 100 nm or more and can be 1 µm or more or 5 µm or more. The particle size D 50 of the electrode active material is, for example, 50 µm or less and may be 20 µm or less. In the present disclosure, the particle size D 50 a particle size corresponding to a cumulative 50 percent by volume, measured using a laser diffraction particle size distribution measuring device. 3. Coated active material

[0033] The coated active material in the present disclosure is typically used in a battery. The electrode active material in the coated active material may be a positive electrode active material or a negative electrode active material, with the former being preferred. Furthermore, the method for producing the coated active material is not particularly limited, but examples of the method include a method including a preparatory step of preparing the electrode active material and the coating solution, and a coating layer formation step of covering the electrode active material with the coating solution and drying the electrode active material to form the coating layer.

[0034] In the preparation phase, the electrode active material and the coating solution are prepared. The electrode active material corresponds to the content described in "A. Coated Active Material." The coating solution will be described later in "D. Coating Solution." In the formation of the coating layer, the electrode active material is covered with the coating solution and dried to form the coating layer. Examples of the method for covering the electrode active material with the coating solution and drying the electrode active material include a spray-drying method. Note that the present disclosure can also provide a method for producing a coated active material that includes the above-mentioned preparation step and the coating layer formation step. B. Electrode mixture

[0035] An electrode mixture in the sense of the present disclosure comprises the above-mentioned coated active material and at least one of an electrically conductive material and a binder.

[0036] According to the present disclosure, by using the above-mentioned coated active material, even when an electrode active material having a high nickel content and a phosphorus-containing coating layer are combined, an electrode mixture capable of reducing an increase in resistance is obtained.

[0037] The electrode mixture includes the coated active material and at least one of the two materials, namely the electrically conductive material and the binder. The coated active material corresponds to the content described above under "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, with the former being preferable. That is, the electrode mixture can be a positive electrode mixture or a negative electrode mixture, with the former being preferable.

[0038] For example, the percentage of coated active material in the electrode mixture is 20% by weight or more, and can be 30% by weight or more, or 40% by weight or more. If the percentage of coated active material is too low, sufficient energy density may not be achieved. For example, the percentage of coated active material is 80% by weight or less, but can also be 70% by weight or less, or 60% by weight or less. If the percentage of coated active material is too high, the ionic conduction and electronic conduction in the electrode mixture may be relatively reduced.

[0039] The electrode mixture contains at least one of two materials: the electrically conductive material and the binder. Examples of the electrically conductive material include a carbon material, metal particles, and a conductive polymer. Examples of the carbon material include particulate carbon materials such as acetylene black (AB) and Ketjen black (KB), and fibrous carbon materials such as carbon fibers, carbon nanotubes (CNTs), and carbon nanofibers (CNFs). Other examples of the binder include a rubber-based binder and a fluorine-based binder.

[0040] The electrode mixture may further include 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. The solid electrolyte is preferably a sulfide solid electrolyte. This is because the ionic conductivity is high.

[0041] The sulfide solid electrolyte typically contains at least one Li element and one S element. The sulfide solid electrolyte preferably also contains a Me element (Me is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In). Furthermore, the solid electrolyte may contain a halogen element such as F, Cl, Br, or I.

[0042] The sulfide solid electrolyte can be a glass-based (amorphous) sulfide solid electrolyte, a glass-ceramic-based sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. The sulfide solid electrolyte can have a crystal phase. Examples of the above-mentioned crystal phase include a thio-LISICON-type crystal phase, an argyrodite-type crystal phase, and an LGPS-type crystal phase.

[0043] The composition of the sulfide solid electrolyte is not particularly limited, but examples include xLi2S-(1-x)P2S5 (0.5 ≤ x < 1) and yLiI zLiBr(100-yz)(xLi2S (1-x)P2S5) (0.5 ≤ x < 1, 0 ≤ y ≤ 30, 0 ≤ z ≤ 30). In these compositions, the symbol x preferably satisfies the condition 0.7 ≤ x ≤ 0.8. As another example of the composition of the sulfide solid electrolyte, Li 7-x-2y PS 6-x-y X yThe symbol X denotes at least one of F, Cl, Br and I, and the symbols x and y satisfy 0 ≤ x and 0 ≤ y. Another example of the composition of the solid electrolyte is Li 4-x Me 1-x P x S4 (0 < x < 1). Me is at least one of Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi. C. Battery

[0044] Fig. 2 is a schematic sectional view showing a battery according to the present disclosure. Fig.The battery 20 shown in Figure 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 a current from the positive electrode layer 11, and a negative electrode current collector 15 that collects a current from the negative electrode layer 12. In the present disclosure, the positive electrode layer 11 or the negative electrode layer 12 includes the electrode mixture described under "B. Electrode Mixture."

[0045] According to the present disclosure, by using the above-mentioned electrode mixture, even when an electrode active material with a high nickel content and a phosphorus-containing coating layer are combined, a battery with a lower resistance increase is obtained. As described above, the electrode mixture may be a positive electrode mixture or a negative electrode mixture, with the former being preferable. Details of a battery in which the electrode mixture is a positive electrode mixture will be described below. 1. Positive electrode layer

[0046] The positive electrode layer in the present disclosure includes the above-mentioned electrode mixture (positive electrode mixture). The electrode mixture is similar to the content described in "B. Electrode Mixture" above, and therefore, the description thereof is omitted here. Further, the positive electrode layer may include an electrolyte as needed. The electrolyte corresponds to the content described in "3. Electrolyte Layer." The thickness of the positive electrode layer is, for example, 0.1 μm or more and 1,000 μm or less, and may be 0.1 μm or more and 500 μm or less, or 0.1 μm or more and 100 μm or less. Other examples of the method for forming the positive electrode layer include a method for applying the electrode mixture (positive electrode mixture) to the positive electrode current collector. 2. Negative electrode layer

[0047] The negative electrode layer is a layer containing at least one negative electrode active material. Furthermore, the negative electrode layer may contain at least one electrolyte, an electrically conductive material, or a binder, as required.

[0048] Examples of the electrode active material include metallic active materials such as Li, a Si-based active material, a carbon active material such as graphite, and an oxide active material such as Li4Ti5O 12 .

[0049] The negative electrode active material is preferably a Si-based active material. This is because it can increase the capacity of the battery. The Si-based active material is one that contains Si as the main component. The Si-based active material can be Si alone, a Si alloy, or a Si oxide. Furthermore, the Si-based active material can include a diamond-like crystal phase, a type I clathrate crystal phase, or a type II clathrate crystal phase. In the type I clathrate or type II clathrate crystal phase, a plurality of Si elements form a polyhedron (cage) containing pentagons or hexagons. This polyhedron has a space for enclosing Li ions, so that the volume change during charging and discharging can be reduced.

[0050] The negative electrode active material can be in the form of a particle, for example. The particle size D 50of the negative electrode active material is not particularly limited, but is, for example, 10 nm or more and can be 100 nm or more. The particle size D 50 of the negative electrode active material is, for example, 50 µm or less and may be 20 µm or less.

[0051] The electrolyte used in the negative electrode layer is comparable to the contents described in "3. Electrolyte Layer." The electrically conductive material and binder used in the negative electrode layer are the same as those described in "B. Electrode Mixture," so their description is omitted here. The thickness of the negative electrode layer is, for example, 0.1 µm or more and 1,000 µm or less, and can be 0.1 µm or more and 500 µm or less, or 0.1 µm or more and 100 µm or less. 3. Electrolyte layer

[0052] The electrolyte layer is a layer formed between the positive electrode layer and the negative electrode layer and contains at least one electrolyte. The electrolyte can be a solid electrolyte or a liquid electrolyte (electrolyte solution).

[0053] The solid electrolyte is similar to the contents described above in "B. Electrode Mixture," so its description is omitted here. Meanwhile, the electrolytic solution preferably includes an auxiliary salt and a solvent. Examples of the auxiliary salt (lithium salt) of the electrolytic solution that exhibits lithium ion conduction include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, and LiAsF6, and organic lithium salts such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, and LiC(CF3SO2)3. Examples of the solvent used in the electrolytic solution include cyclic esters (cyclic carbonates) such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), and linear esters (linear carbonates) such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). The electrolyte solution preferably contains two or more types of solvents.

[0054] The thickness of the electrolyte layer is, for example, 0.1 µm or more and 1,000 µm or less, and may be 0.1 µm or more and 500 µm or less, or 0.1 µm or more and 100 µm or less. 4. Other configurations

[0055] The battery in the present disclosure preferably includes the positive electrode current collector that collects current from the positive electrode layer and the negative electrode current collector that collects current from the negative electrode layer. Examples of the material of the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. Examples of the material of the negative electrode current collector include SUS, copper, nickel, and carbon.

[0056] The battery in the present disclosure may further include a holding device that applies a holding pressure to the positive electrode layer, the electrolyte layer, and the negative electrode layer along a direction of their thickness. Particularly, when the electrolyte layer is a solid electrolyte layer, a holding pressure is preferably applied to form a good ion conduction path and an electronic conduction path. The holding pressure is, for example, 0.1 MPa or more, and may be 1 MPa or more, or 5 MPa or more. Meanwhile, the holding pressure is, for example, 100 MPa or less, and may be 50 MPa or less, or 20 MPa or less. 5. Battery

[0057] The type of battery in the present disclosure is not particularly limited, but is typically a lithium-ion battery. Further, the battery in the present disclosure may be a liquid battery including an electrolyte solution as the electrolyte layer, or may be a solid-state battery including a solid electrolyte layer as the electrolyte layer. The solid-state battery may be a semi-solid-state battery or an all-solid-state battery. Further, the battery in the present disclosure may be a primary battery or a secondary battery, but the secondary battery is preferable. This is because the battery can be repeatedly charged and discharged and can be effectively used, for example, as a vehicle battery.

[0058] Examples of applications of the battery include a power supply for a vehicle such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), a battery electric vehicle (BEV), a gasoline vehicle, or a diesel vehicle. Specifically, the battery is preferably used to supply energy for propulsion of the hybrid electric vehicle (HEV), the plug-in hybrid electric vehicle (PHEV), or the battery electric vehicle (BEV). Furthermore, the battery can be used as a power supply for a mobile object other than a vehicle (e.g., a train, a ship, or an aircraft) or as a power supply for an electrical product such as an information processing device. D. Coating solution

[0059] The coating solution in the present disclosure is a coating solution for forming the coating layer in the coated active material described above under "A. Coated Active Material." The coating solution includes a solute containing a B element, a P element, and a La element, as well as water as a solvent. The molar ratio (La / P) of the La element to the P element is 0.001 or more and 0.100 or less. Furthermore, the absorbance of the coating solution is 0.1 or less.

[0060] According to the present disclosure, with the La element added so that a predetermined absorption can be obtained even when an electrode active material having a high nickel content is combined, a plating solution capable of reducing a resistance increase is obtained.

[0061] The coating solution contains the solute containing the B element, the P element, and the La element, as well as water as a solvent. The solute may also contain an O element. Of these, the solute preferably has a PO4 structure. Furthermore, the coating solution may also contain a Li element.

[0062] In the coating solution, the molar ratio (La / P) of the La element to the P element is usually 0.001 or more and 0.100 or less, and can be 0.003 or more and 0.080 or less. If the La / P ratio is too small, the resistance-reducing effect of the La element may not be sufficiently achieved. Conversely, if the La / P ratio is too large, manufacturing may be difficult.

[0063] In the plating solution, the molar ratio (B / P) of the B element to the P element is not particularly limited, but is, for example, 0.5 or more and 2.0 or less, and may be 0.8 or more and 1.25 or less, or 0.9 or more and 1.11 or less. When the plating solution further contains a Li element, the molar ratio (Li / (P+B)) of the Li element to the sum of the P element and the B element is not particularly limited, but is, for example, 0.3 or more and 1.2 or less, and may be 0.5 or more and 1.0 or less.

[0064] The absorbance of the coating solution is usually 0.1 or less, but can also be 0.05 or less or 0.001 or less. The method for measuring absorbance is as described in the examples described later.

[0065] The method for preparing the coating solution is not particularly limited, but examples of the method include a method of dissolving a solute containing a B source, a P source, and a La source in water as the solvent. The B source is not particularly limited as long as the B source is a simple substance or a compound containing the B element, and examples thereof include boric acid (H3BO3). The P source is not particularly limited as long as the P source is a simple substance or a compound containing the P element, and examples thereof include orthophosphoric acid (H3PO4) and metaphosphoric acid (HPO3). Further, the coating solution preferably contains an O source. Examples of the O source include an O element contained in the above-mentioned B source or P source. Further, the above-mentioned solution may contain a Li source.The Li source is not particularly limited as long as the Li source is a simple substance or a compound containing the Li element, and examples include lithium hydroxide monohydrate (LiOH·H2O).

[0066] Note that the present disclosure is not limited to the above-mentioned embodiment. The above-mentioned embodiment is exemplary, and anything that has substantially the same configuration and produces similar actions and effects as a technical idea described in the claims of the present disclosure is included in the technical scope of the present disclosure. Comparative Example 1 Preparation of the coating solution

[0067] Metaphosphoric acid (manufactured by FUJIFILM Wako Pure Chemical Corporation) and deionized water were mixed in a ratio of metaphosphoric acid to ion-exchanged water = 4.52:191.8 (weight ratio) to obtain an aqueous solution. Boric acid (manufactured by NACALAI TESQUE, INC.) was added to the resulting aqueous solution and dissolved so that the molar ratio (B / P) of the B element to the P element became 1.0. Thus, the coating solution was obtained. Production of coated active material

[0068] Active material particles (LiNi 0,81 Co 0,15 Al 0,04 O2, particle size D 50= 4.5 µm) were dispersed in the resulting coating solution to prepare a slurry. The solid concentration of the slurry was 69 wt%. The slurry was then dried using a spray-drying device manufactured by BUCHI Corporation (product name: Mini Spray Dryer B-290) to form the coating layer on the surface of the active material. The drying air temperature in the device was 20°C, and the drying air flow rate was 0.45 m³. 3 / min. Subsequently, the active material particle with the coating formed on it was subjected to heat treatment in an air atmosphere to obtain the coated active material. The heat treatment temperature was 200°C and the heat treatment time was 5 hours. Example 1

[0069] Metaphosphoric acid (manufactured by FUJIFILM Wako Pure Chemical Corporation) and deionized water were mixed in a ratio of metaphosphoric acid:ion-exchanged water = 4.52:191.8 (weight ratio) to obtain an aqueous solution. Boric acid (manufactured by NACALAI TESQUE, INC.) was added to the resulting aqueous solution and dissolved so that the molar ratio (B / P) of the B element to the P element became 1.0. Furthermore, lanthanum oxide (manufactured by FUJIFILM Wako Pure Chemical Corporation) was added and dissolved so that the molar ratio (La / P) of the La element to the P element became 0.003. Thus, the coating solution was obtained. The coated active material was prepared in a similar manner to Comparative Example 1, except that the obtained coating solution was used. Examples 2 to 5

[0070] The coating solution was obtained similarly to Example 1, except that the molar ratio (La / P) of the La element to the P element was changed to 0.006, 0.01, 0.05, and 0.075, respectively. The coated active material was prepared in a similar manner to Comparative Example 1, except that the obtained coating solution was used. Comparison example 2

[0071] The coating solution was prepared similarly to Example 1, except that the molar ratio (La / P) of the La element to the P element was changed to 0.100. The coated active material was prepared similarly to Comparative Example 1, except that the obtained coating solution was used. EvaluationAbsorption measurement

[0072] The absorbance of the coating solution obtained in Examples 1 to 5 and Comparative Examples 1 and 2 was measured. Specifically, 3.5 mL of the coating solution was placed in a quartz cuvette (10 mm × 10 mm × 45 mm), and the absorbance was measured using an ultraviolet-visible spectrophotometer (product name UV-1280, manufactured by SHIMADZU CORPORATION). When measuring the absorbance at a wavelength of 660 nm, it was confirmed that the concentration of insoluble particulate matter in the coating solution in Examples 1 to 5 and Comparative Example 1 was extremely low (see, for example, JIS-K0101). In Comparative Example 2, however, the coating solution was visually opaque, so the absorbance measurement was not performed. Table 1 shows the results. Measurement of coverage and La / P

[0073] The coverage of the coated active material obtained in Examples 1 to 5 and Comparative Examples 1 and 2 was measured using X-ray photoelectron spectroscopy (XPS). Specifically, an X-ray photoelectron spectroscopy device (manufactured by ULVAC-PHI, Inc., PHIX-tool) was used to perform elemental analysis of the surface of the coated active material. Narrow-scan analysis was performed with a pass energy of 224 eV. Analysis software (MultiPak, manufactured by ULVAC-PHI) was then used to calculate an elemental ratio from the obtained intensity values of C1s, O1s, P2p, Ni2p3, Co2p3, Al2p, B1s, and La3d3, and the value of (La + P + B) / (La + P + B + Ni + Co + Al) [%] was determined as the coverage. In addition, the molar ratio (La / P) of the La element to the P element was determined based on the element ratio. Table 1 shows the results. Resistance measurement

[0074] The coated active material obtained in Examples 1 to 5 and Comparative Examples 1 and 2 was used as a positive electrode active material for manufacturing a battery, and its resistance was measured.

[0075] First, a positive electrode active material (coated active material), a sulfide solid electrolyte (10LiI-15LiBr-75Li3PS4), an electrically conductive material (VGCF), a binder (SBR), and a dispersion medium (heptane) were mixed to prepare a positive electrode slurry. The mixing ratio of the electrode active material and the solid electrolyte was 6:4 (by volume). For 100 parts by weight of the electrode active material, 3 parts by mass of the electrically conductive material and 3 parts by mass of the binder were added. The positive electrode slurry was sufficiently stirred with an ultrasonic homogenizer, and the positive electrode slurry was coated onto the surface of the positive electrode current collector (Al foil) to form a coating film. The coating film was dried on a hot plate at 100°C for 30 minutes.In this way, a positive electrode sheet was obtained. A disc-shaped positive electrode was cut out of the positive electrode sheet. The positive electrode had an area of 1 cm. 2 .

[0076] Next, the negative electrode and the solid electrolyte layer were prepared. Graphite was used as the active material for the negative electrode. The same type of sulfide solid electrolyte was used between the positive electrode, the solid electrolyte layer, and the negative electrode. The positive electrode, the solid electrode layer, and the negative electrode were stacked in the specified order in a cylindrical device to form a stack. The stack was pressed to form a power generation element. The power generation element was connected to the terminals to obtain a battery (solid-state battery). The open-circuit voltage (OCV) of the resulting solid-state battery was set to 2.03 V, and then a constant-current discharge was performed. The voltage drop in 5 seconds was then divided by the current to measure the battery resistance. The discharge current was 2.5 C.The resistance of the battery of Comparative Example 1 was used as a reference (1.00) to relatively evaluate the resistance of the battery of each example and each comparative example. Table 1 and . Fig. 3 shows the results. [Table 1] Coating solution Coated active material Standardized resistance Contain ne element e P / B La / P Absorption degree Detection rate [%] La / P Comparison example 1 P, B, O 1, 0 0,00 0 < 0,001 91 0 1,00 Example 1 P, B, La, O 1, 0 0,00 3 < 0,001 90 0,0 1 0,90 Example 2 P, B, La, O 1, 0 0,00 6 < 0,001 92 0,0 2 0,82 Example 3 P, B, La, O 1, 0 0,01 0 < 0,001 92 0,0 3 0,80 Example 4 P, B, La, O 1, 0 0,05 0 < 0,001 92 0,0 9 0,66 Example 5 P, B, La, O 1, 0 0,07 5 < 0,001 92 0,1 1 0,65 Comparison example 2 P, B, La, O 1, 0 0,10 0 Opaque - 0,0 2 Not measured

[0077] As shown in Table 1, in Examples 1 to 5 and Comparative Example 1, the value of La / P in the coating layer was larger than the value of La / P in the coating solution. The reason for this seems to be the precipitation of La. As shown in Table 1 and Fig.As shown in Figure 3, it was confirmed that Examples 1 to 5 had lower resistance than Comparative Example 1. As described above, it was confirmed that by adding La to the coating layer, even when an electrode active material with a high nickel content and a phosphorus-containing coating layer were combined, the increase in resistance could be reduced. In Comparative Example 2, on the other hand, the coating solution was opaque, and it was confirmed that the coating solution was not a solution but a dispersion liquid. Accordingly, a deviation in composition occurred, and the desired coated active material could not be obtained. QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] JP 2023-136753

[0003] JP 2023-136753 A [0003, 0020]

Claims

[1] Coated active material (10) comprising: an electrode active material (1); and a coating layer (2) covering the electrode active material (1), wherein: the electrode active material (1) includes a Li element, an M element and an O element; M is a metal other than Li and contains at least Ni; a molar ratio (Ni / M) of Ni to M is 80% or more; the coating layer (2) contains a B element, a P element, a La element and an O element; and a molar ratio (La / P) of the La element to the P element is 0.005 or more and 0.15 or less. [2] The coated active material (10) according to claim 1, wherein La / P is 0.01 or more and 0.11 or less. [3] The coated active material (10) according to claim 1, wherein a molar ratio (B / P) of the B element to the P element is 0.5 or more and 2.0 or less. [4] The coated active material (10) according to claim 1, wherein a coverage of the coating layer (2) with respect to the electrode active material (1) is 75% or more. [5] The coated active material (10) according to claim 1, wherein M further includes at least one of Co, Mn and Al. [6] Electrode mixture comprising: the coated active material (10) according to any one of claims 1 to 5; and at least one of an electrically conductive material and a binder. [7] Electrode mixture according to claim 6, wherein the electrode mixture includes a solid electrolyte. [8] Electrode mixture according to claim 7, wherein the solid electrolyte is a sulfide solid electrolyte. [9] Battery (20), comprising: a positive electrode layer (11); a negative electrode layer (12); and an electrolyte layer (13) arranged between the positive electrode layer (11) and the negative electrode layer (12), wherein the positive electrode layer (11) or the negative electrode layer (12) contains the electrode mixture according to claim 6. [10] Coating solution for forming the coating layer (2) in the coated active material (10) according to any one of claims 1 to 5, the coating solution comprising: a solute containing a B element, a P element and a La element; and Water, which is a solvent, where: a molar ratio (La / P) of the La element to the P element is 0.001 or more and 0.100 or less; and an absorption of the coating solution is 0.1 or less.

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