Positive electrode active material for lithium ion battery, positive electrode for lithium ion battery, lithium ion battery, positive electrode active material for all-solid-state lithium ion battery, positive electrode for all-solid-state lithium ion battery, all-solid-state lithium ion battery, method for producing positive electrode active material for lithium ion battery, and method for producing positive electrode active material for all-solid-state lithium ion battery

Abstract

A positive electrode active material for a lithium ion battery, wherein the composition represented by the following formula (1) is Li a Ni b Co c Mn d Ta e O f (1) (in formula (1), 1.0 ≤ a ≤ 1.07, 0.8 ≤ b ≤ 0.9, b + c + d + e = 1, 1.8 ≤ f ≤ 2.2, 0.001 ≤ e / (b + c + d + e) ≤ 0.005), the coefficient of variation CV1 is a value obtained by dividing the standard deviation of the average concentration of Ta element in the primary particles by the average concentration of Ta element obtained by transmission electron microscope (TEM) - energy dispersive X-ray spectroscopy (EDX) analysis, and the coefficient of variation CV2 is a value obtained by dividing the standard deviation of the average concentration of Ta element at the grain boundary of the primary particles by the average concentration of Ta element at the grain boundary of the primary particles obtained by TEM-EDX analysis, CV2 > CV1 in terms of the magnitude of both, and the average concentration of Ta element at the grain boundary obtained by TEM-EDX analysis is higher than the Ta element concentration of the positive electrode active material for a lithium ion battery obtained by ICP analysis.

Description

[0001] Positive electrode active material for lithium-ion batteries, positive electrode for lithium-ion batteries, lithium-ion battery, positive electrode active material for all-solid-state lithium-ion batteries, positive electrode for all-solid-state lithium-ion batteries, all-solid-state lithium-ion battery, manufacturing method of positive electrode active material for lithium-ion batteries, and manufacturing method of positive electrode active material for all-solid-state lithium-ion batteries. Technical Field

[0002] This invention relates to positive electrode active materials for lithium-ion batteries, positive electrodes for lithium-ion batteries, lithium-ion batteries, positive electrode active materials for all-solid-state lithium-ion batteries, positive electrodes for all-solid-state lithium-ion batteries, all-solid-state lithium-ion batteries, methods for manufacturing positive electrode active materials for lithium-ion batteries, and methods for manufacturing positive electrode active materials for all-solid-state lithium-ion batteries. Background Technology

[0003] With the rapid popularization of information and communication devices such as personal computers, camcorders, and portable phones in recent years, the development of batteries used as their power source has become increasingly important. Among these batteries, lithium-ion rechargeable batteries have attracted significant attention due to their high energy density. Besides liquid lithium-ion rechargeable batteries that use electrolytes, all-solid-state lithium-ion batteries, which use solid-state electrolytes, have also gained attention in recent years.

[0004] In the 1990s and 2000s, LiCoO2 was the most commonly used positive electrode active material for lithium-ion secondary batteries. However, to address the issues of increased power consumption due to the increasing functionality of electronic devices and the need for longer driving ranges due to the rise of electric vehicles (EVs), positive electrode active materials such as NCM523 and NCM622, with a Ni ratio of over 50%, were introduced after the 2010s, replacing LiCoO2. These positive electrode active materials exhibit excellent balance between output and durability, but further improvements in output and durability are needed for applications such as automotive. Previously, in particular, to overcome the issue of high durability, the following method was used: surface modification and doping of positive electrode active materials with elements that have a high affinity for oxygen, such as Zr, W, Nb, and Ta.

[0005] Patent documents 1 and 2 disclose that when elements such as W, Al, Ti, Zr, Nb, Ta, and Mo are added during the manufacturing process of the positive electrode active material, battery characteristics such as cycle characteristics, thermal stability, and rate characteristics are improved by homogenizing the concentration of the added elements at the grain boundaries and inside the grains.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 6378246

[0009] Patent Document 2: Japanese Patent Application Publication No. 2021-048070 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] In patent documents 1 and 2, dissimilar elements are added during the precursor preparation stage via crystallization in the manufacturing process of the positive electrode active material. Uneven concentrations of the added element at grain boundaries and within grains can affect the characteristics of batteries using the positive electrode active material. However, in existing manufacturing methods, the control of these uneven concentrations is determined by the precursor preparation stage, making control difficult in the subsequent firing process where the precursor is mixed with a Li source. Consequently, it is difficult to control the uneven concentrations of the added element at grain boundaries and within grains to the desired level, potentially leading to deterioration of battery characteristics.

[0012] Solution for solving the problem

[0013] This invention was made to solve the aforementioned problems, and its object is to provide a positive electrode active material for lithium-ion batteries with good battery characteristics, a positive electrode for lithium-ion batteries using the same positive electrode active material, a lithium-ion battery, and a method for manufacturing the positive electrode active material for lithium-ion batteries. Furthermore, its object is to provide a positive electrode active material for all-solid-state lithium-ion batteries with good battery characteristics, a positive electrode for all-solid-state lithium-ion batteries using the same positive electrode active material, an all-solid-state lithium-ion battery, and a method for manufacturing the positive electrode active material for all-solid-state lithium-ion batteries.

[0014] The present invention, based on the above insights, is defined as follows.

[0015] 1. A positive electrode active material for lithium-ion batteries, wherein the composition is represented by the following formula (1): Li a Ni b Co c Mn d Ta e O f(1) (In the formula (1), 1.0≤a≤1.07, 0.8≤b≤0.9, b+c+d+e=1, 1.8≤f≤2.2, 0.001≤e / (b+c+d+e)≤0.005.), the coefficient of variation CV1 is the value obtained by dividing the standard deviation of the average concentration of Ta element inside the primary particle obtained by transmission electron microscopy (TEM)-energy dispersive X-ray spectroscopy (EDX) by the average concentration of Ta element, and the coefficient of variation CV2 is the value obtained by dividing the standard deviation of the average concentration of Ta element at the grain boundary of the primary particle obtained by TEM-EDX by the average concentration of Ta element at the grain boundary of the primary particle. In terms of the magnitude of these two values, CV2>CV1, and the average concentration of Ta element at the grain boundary obtained by TEM-EDX is higher than the concentration of Ta element in the positive electrode active material for lithium-ion batteries obtained by ICP analysis.

[0016] 2. The positive electrode active material for lithium-ion batteries as described in 1, wherein the 50% cumulative volumetric particle size D50 is 5 to 8 μm.

[0017] 3. A positive electrode for a lithium-ion battery, comprising a positive electrode active material for a lithium-ion battery as described in 1 or 2.

[0018] 4. A lithium-ion battery comprising a positive electrode and a negative electrode as described in 3.

[0019] 5. A positive electrode active material for an all-solid-state lithium-ion battery, comprising: a positive electrode active material for a lithium-ion battery as described in 1 or 2; and a coating layer formed of oxides of Li and Nb disposed on the surface of the positive electrode active material particles of the positive electrode active material for the lithium-ion battery.

[0020] 6. The positive electrode active material for all-solid-state lithium-ion batteries as described in 5, wherein the Nb content in the positive electrode active material for all-solid-state lithium-ion batteries is 0.5 to 0.8% by mass.

[0021] 7. A positive electrode for an all-solid-state lithium-ion battery, comprising an all-solid-state lithium-ion battery positive electrode active material as described in 6.

[0022] 8. An all-solid-state lithium-ion battery comprising a positive electrode and a negative electrode as described in 7.

[0023] 9. A method for manufacturing a positive electrode active material for a lithium-ion battery, comprising: a step of preparing a precursor for the positive electrode active material for a lithium-ion battery, represented by the composition shown in formula (2) below, Ni b Coc Mn d (OH)2(2) (in the formula (2), 0.8≤b≤0.9, 0.07≤c≤0.15, and b+c+d=1.); a process of mixing Ta oxide with a cumulative volume particle size D50 of less than 1.0 μm in 50% of the precursor of the positive electrode active material for lithium-ion batteries to obtain a mixture; and a process of dry mixing the mixture with a lithium source and calcining it at a temperature of 700°C or higher for more than 4 hours.

[0024] 10. The method for manufacturing a positive electrode active material for a lithium-ion battery according to the method described in 9, wherein the D50 of the oxide of Ta is 0.3 to 1.0 μm.

[0025] 11. The method for manufacturing a positive electrode active material for a lithium-ion battery according to the method described in 9, wherein in the step of calcining the mixture, the mixture is dry-mixed with a lithium source and calcined at 700°C to 800°C for 4 to 12 hours.

[0026] 12. A method for manufacturing a positive electrode active material for an all-solid-state lithium-ion battery, comprising: a step of preparing a positive electrode active material for a lithium-ion battery manufactured by any one of the methods described in 9 to 11; and a step of forming a coating layer of oxides of Li and Nb on the surface of the positive electrode active material particles of the positive electrode active material for the lithium-ion battery using an aqueous solution containing Li and Nb and a rotating fluidized bed coating apparatus.

[0027] 13. The method for manufacturing a positive electrode active material for an all-solid-state lithium-ion battery as described in 12, wherein the aqueous solution containing Li and Nb comprises: (1) any one of lithium hydroxide monohydrate, lithium carbonate, and lithium nitrate as a lithium source; (2) any one of niobium hydroxide, niobium oxalate, and ammonium niobium oxalate as a niobium source; and (3) any one of pure water, hydrogen peroxide water, and ammonia water.

[0028] Invention Effects

[0029] According to the present invention, a positive electrode active material for lithium-ion batteries with good battery characteristics, a positive electrode for lithium-ion batteries using the positive electrode active material, a lithium-ion battery, and a method for manufacturing the positive electrode active material for lithium-ion batteries can be provided. Furthermore, a positive electrode active material for all-solid-state lithium-ion batteries with good battery characteristics, a positive electrode for all-solid-state lithium-ion batteries using the positive electrode active material, an all-solid-state lithium-ion battery, and a method for manufacturing the positive electrode active material for all-solid-state lithium-ion batteries can be provided. Attached Figure Description

[0030] Figure 1This is a schematic diagram of an all-solid-state lithium-ion battery according to an embodiment of the present invention.

[0031] Figure 2 This is a TEM image showing the location of the determination of Ta element concentration inside a primary particle obtained by TEM-EDX analysis of the positive electrode active material of Example 1.

[0032] Figure 3 This is a TEM image showing the location of the Ta element concentration at the grain boundaries of primary particles obtained by TEM-EDX analysis of the positive electrode active material of Example 1. Detailed Implementation

[0033] Next, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the present invention is not limited to the following embodiments, and appropriate design changes and improvements can be made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

[0034] (Positive electrode active material for lithium-ion batteries)

[0035] In this invention, when referred to as "positive electrode active material for lithium-ion batteries", it includes positive electrode active materials for liquid lithium-ion batteries that use electrolyte and positive electrode active materials for all-solid-state lithium-ion batteries where the electrolyte is solid.

[0036] The positive electrode active material for lithium-ion batteries according to embodiments of the present invention is represented by the composition shown in the following formula (1).

[0037] Li a Ni b Co c Mn d Ta e O f (1)

[0038] (In the formula (1), 1.0≤a≤1.07, 0.8≤b≤0.9, b+c+d+e=1, 1.8≤f≤2.2, 0.001≤e / (b+c+d+e)≤0.005.)

[0039] Regarding the positive electrode active material for lithium-ion batteries according to embodiments of the present invention, the lithium composition 'a' in formula (1) above is controlled to be 1.0 ≤ a ≤ 1.07. When the lithium composition 'a' is 1.0 or higher, nickel reduction due to lithium deficiency can be suppressed. Furthermore, when the lithium composition 'a' is 1.07 or lower, residual alkaline components such as lithium carbonate and lithium hydroxide, which may become resistive components during battery manufacturing, and which exist on the surface of the positive electrode active material particles, can be suppressed.

[0040] Regarding the positive electrode active material for lithium-ion batteries according to embodiments of the present invention, the sum of b (representing nickel composition), c (representing cobalt composition), d (representing manganese composition), and e (representing Ta composition) in the above formula (1) is controlled to be b+c+d+e=1, that is, controlled to be 0.1≤c+d+e≤0.2. Therefore, the cycle characteristics are improved, and the lattice expansion and contraction behavior caused by lithium insertion / extraction during charging and discharging can be reduced. When c+d+e is 0.1 or more, the above-mentioned cycle characteristics and expansion and contraction behavior effects are easily obtained, and when c+d+e is 0.2 or less, the reduction in initial discharge capacity is suppressed.

[0041] The positive electrode active material for lithium-ion batteries according to embodiments of the present invention has the morphology of secondary particles formed by the aggregation of multiple primary particles. The shape of the primary particles constituting the secondary particles is not particularly limited; for example, they can be various shapes such as approximately spherical, approximately elliptical, approximately plate-like, or approximately needle-like. Furthermore, the morphology of the aggregation of multiple primary particles is not particularly limited; for example, they can be condensed in random directions, or they can be condensed radially from a relatively uniform center to form approximately spherical or approximately elliptical secondary particles, etc. In embodiments of the present invention, a primary particle refers to a region in which grain boundaries can be observed, in part or all, when a cross-section of the positive electrode active material is observed using a transmission electron microscope (TEM).

[0042] Regarding the positive electrode active material for lithium-ion batteries according to embodiments of the present invention, in the above formula (1), 0.001 ≤ e / (b+c+d+e) ≤ 0.005. That is, the positive electrode active material for lithium-ion batteries contains Ta. By solid-dissolving this element into the positive electrode active material, it has the effect of reducing the lattice expansion and contraction behavior caused by lithium insertion / extraction during charging and discharging. Therefore, if e / (b+c+d+e), which is the composition ratio of Ta, is 0.001 or more, the cycle characteristics are improved. On the other hand, this element does not contribute to charge compensation during charging and discharging. Therefore, if e / (b+c+d+e), which is the composition ratio of Ta, is 0.005 or less, it has the effect of suppressing the decrease in discharge capacity. Furthermore, it is preferable that 0.004 ≤ e / (b+c+d+e) ≤ 0.005.

[0043] Regarding the positive electrode active material for lithium-ion batteries according to embodiments of the present invention, the coefficient of variation CV1 is a value obtained by dividing the standard deviation of the average concentration of Ta element inside the primary particle obtained by transmission electron microscopy (TEM)-energy dispersive X-ray spectroscopy (EDX) by the average concentration of Ta element inside the primary particle, and the coefficient of variation CV2 is a value obtained by dividing the standard deviation of the average concentration of Ta element at the grain boundaries of the primary particle obtained by the TEM-EDX analysis by the average concentration of Ta element at the grain boundaries of the primary particle. In terms of the magnitude of these two values, CV2 > CV1.

[0044] Here, the average concentration of Ta within the primary particles and at grain boundaries was determined and calculated as follows. First, as a sample pretreatment, the positive electrode active material particles were processed using an ion milling device and a focused ion beam (FIB) device to expose the cross-section of the secondary particles. Next, using an atomic resolution analytical electron microscope (JEM-ARM300F2) manufactured by JEOL Ltd., at a magnification of 100,000, electron beam irradiation was performed at five points within any one of the primary particles and at each of the grain boundaries, under an accelerating voltage of 300 kV and an irradiation current of 1.0 nA. Energy dispersive X-ray spectroscopy (EDX) analysis was then performed. Based on the count of the energies of the characteristic X-rays produced by Ni, Mn, Co, and Ta, which are components of the active material, the concentration of each element could be determined. When the total concentrations of Ni, Mn, Co, and Ta calculated in this way are set to 100, the average Ta concentration at five points inside the primary particle and at the grain boundary is defined as the average Ta concentration inside the primary particle and the average Ta concentration at the grain boundary of the primary particle, respectively. It should be noted that, regarding the "inside the primary particle" mentioned above, the measurement is taken at a position 20 nm or more above the nearest "grain boundary," which is the central part of the primary particle. Furthermore, when measuring the Ta concentration at the five points inside the primary particle and at the grain boundary obtained by the TEM-EDX method, if the Ta concentration is below the detection limit, the data below the detection limit is excluded, and the average concentration of the remaining measurement points is taken as the average Ta concentration inside the primary particle and the average Ta concentration at the grain boundary of the primary particle.

[0045] When the positive electrode active material for lithium-ion batteries in the embodiments of the present invention satisfies the above-mentioned CV2>CV1, Ta, as a heterogeneous element, segregates at the grain boundaries of primary particles, thereby improving the battery characteristics such as the discharge capacity and rate characteristics of the lithium-ion battery using this positive electrode active material for lithium-ion batteries.

[0046] The average Ta concentration at grain boundaries of the positive electrode active material for lithium-ion batteries according to the embodiments of the present invention, as obtained by TEM-EDX analysis, is higher than the Ta concentration of the positive electrode active material for lithium-ion batteries obtained by ICP analysis. Here, ICP analysis is a compositional analysis performed using an ICP (Inductively Coupled Plasma) emission spectrometer (ICP-OES), for example, an ICP (Inductively Coupled Plasma) emission spectrometer (ICP-OES) "PS7800" manufactured by Hitachi High-Tech Corporation.

[0047] The average Ta concentration at the grain boundaries of the positive electrode active material for lithium-ion batteries according to the embodiments of the present invention, as obtained by TEM-EDX analysis as described above, is higher than the Ta concentration of the positive electrode active material for lithium-ion batteries obtained by ICP analysis. Therefore, Ta, as a foreign element, segregates at the grain boundaries of primary particles, thereby improving the battery characteristics such as the discharge capacity and rate characteristics of the lithium-ion battery using this positive electrode active material.

[0048] In embodiments of the present invention, the 50% cumulative volumetric particle size D50 of the positive electrode active material for lithium-ion batteries is preferably 5 to 8 μm. Here, 50% cumulative volumetric particle size D50 refers to the volumetric particle size at which 50% of the cumulative particle size distribution curve is accumulated. If the 50% cumulative volumetric particle size D50 of the positive electrode active material for lithium-ion batteries is 5 μm or more, the specific surface area is suppressed, and the coating amount of Li and Nb oxides can be suppressed. If the 50% cumulative volumetric particle size D50 of the positive electrode active material for lithium-ion batteries is 8 μm or less, the specific surface area can be prevented from becoming too small. More preferably, the 50% cumulative volumetric particle size D50 of the positive electrode active material for lithium-ion batteries is 5 to 6 μm. The aforementioned 50% cumulative volumetric particle size D50 can be measured, for example, in the following manner. Specifically, firstly, for 100 mg of positive electrode active material powder, a Microtrac laser diffraction particle size distribution measuring device "MT3300EXII" was used. After dispersion with 40W ultrasonic irradiation for 60 seconds at a flow rate of 50%, the particle size distribution was measured to obtain a volume-based cumulative particle size distribution curve. Next, the volumetric particle size at which 50% of the cumulative particle size distribution curve was accumulated was taken as the 50% cumulative volumetric particle size D50 of the positive electrode active material powder. It should be noted that the water-soluble solvent was set to pass through a filter, and the solvent refractive index was set to 1.333, the particle transmittance condition was set to transmittance, the particle refractive index was set to 1.81, the shape was set to non-spherical, the measurement range was set to 0.021–2000 μm, and the measurement time was set to 30 seconds.

[0049] (Positive electrode active material for all-solid-state lithium-ion batteries)

[0050] The all-solid-state positive electrode active material for lithium-ion batteries according to embodiments of the present invention comprises a positive electrode active material for lithium-ion batteries and a coating layer formed of oxides of Li and Nb disposed on the surface of the positive electrode active material particles of the positive electrode active material for lithium-ion batteries. The oxides of Li and Nb constituting the coating layer may include lithium niobate (LiNbO3) or may be LiNbO3.

[0051] The positive electrode active material for lithium-ion batteries of the all-solid-state lithium-ion battery according to the embodiments of the present invention is represented by the composition shown in the following formula (1), similar to the positive electrode active material for lithium-ion batteries of the embodiments of the present invention described above.

[0052] Li a Ni b Co c Mn d Ta e O f (1)

[0053] (In the formula (1), 1.0≤a≤1.07, 0.8≤b≤0.9, b+c+d+e=1, 1.8≤f≤2.2, 0.001≤e / (b+c+d+e)≤0.005.)

[0054] Regarding the positive electrode active material for all-solid-state lithium-ion batteries according to embodiments of the present invention, the coefficient of variation CV1 is a value obtained by dividing the standard deviation of the average Ta concentration inside the primary particle obtained by transmission electron microscopy (TEM)-energy dispersive X-ray spectroscopy (EDX) by the average Ta concentration inside the primary particle, and the coefficient of variation CV2 is a value obtained by dividing the standard deviation of the average Ta concentration at the grain boundaries of the primary particle obtained by TEM-EDX analysis by the average Ta concentration at the grain boundaries of the primary particle. In terms of magnitude, CV2 > CV1, meaning the average Ta concentration at the grain boundaries obtained by TEM-EDX analysis is higher than the Ta concentration of the positive electrode active material for all-solid-state lithium-ion batteries obtained by ICP analysis. Similar to the positive electrode active material for lithium-ion batteries according to embodiments of the present invention described above, with this configuration, the battery characteristics of lithium-ion batteries, such as discharge capacity and rate characteristics, are improved.

[0055] The Nb content in the positive electrode active material for all-solid-state lithium-ion batteries is preferably 0.5 to 0.8% by mass. If the Nb content is 0.5% by mass or more, it will coat the entire surface of the active material, suppressing the increase in resistance caused by the interfacial reaction between the solid electrolyte and the positive electrode active material when exposed to high potential during charging. If the Nb content is less than 0.8% by mass, the coating layer can be formed as thin as possible, thus shortening the movement of Li ions within the coating layer during charging and discharging, reducing diffusion resistance. The Nb content in the positive electrode active material for all-solid-state lithium-ion batteries is more preferably 0.6 to 0.7% by mass.

[0056] The thickness of the coating layer is preferably less than 10 nm, more preferably less than 6 nm. A coating layer thickness of less than 6 nm can better avoid adverse effects such as hindering the movement of Li ions. There is no particular limitation on the lower limit of the coating layer thickness, but typically it is 4 nm or more, preferably 5 nm or more. It should be noted that the thickness of the coating layer can be determined by elemental mapping analysis and line analysis using a scanning transmission electron microscope (STEM).

[0057] (Manufacturing method of positive electrode active material for lithium-ion batteries)

[0058] Next, a detailed description of the method for manufacturing a positive electrode active material for a lithium-ion battery according to an embodiment of the present invention will be provided. The method for manufacturing a positive electrode active material for a lithium-ion battery according to an embodiment of the present invention first prepares a precursor for the positive electrode active material for a lithium-ion battery, represented by the composition shown in the following formula (2).

[0059] Ni b Co c Mn d (OH)2(2)

[0060] (In equation (2), 0.8≤b≤0.9, 0.07≤c≤0.15, and b+c+d=1.)

[0061] As a method for manufacturing a precursor for a positive electrode active material for lithium-ion batteries, firstly, an aqueous solution containing (a) a nickel salt, (b) a cobalt salt, (c) a manganese salt, and an alkaline aqueous solution containing ammonia (d) and an alkaline aqueous solution containing an alkali metal is prepared. Examples of (a) the nickel salt include nickel sulfate, nickel nitrate, or nickel hydrochloride. Examples of (b) the cobalt salt include cobalt sulfate, cobalt nitrate, or cobalt hydrochloride. Examples of (c) the manganese salt include manganese sulfate, manganese nitrate, or manganese hydrochloride. Examples of the alkaline aqueous solution containing ammonia (d) include aqueous solutions of ammonia, ammonium sulfate, ammonium carbonate, and ammonium hydrochloride. The alkaline aqueous solution containing the alkali metal can be an aqueous solution of sodium hydroxide, potassium hydroxide, or a carbonate. Furthermore, examples of aqueous solutions containing the carbonate include aqueous solutions of sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate, which utilize carbonate salts.

[0062] Furthermore, the composition of the aqueous solution can be appropriately adjusted according to the composition of the precursor used in the manufacturing process. Preferably, it is (a) an aqueous solution containing 45 to 110 g / L of nickel ions, (b) an aqueous solution containing 4 to 20 g / L of cobalt ions, (c) an aqueous solution containing 1 to 4 g / L of manganese ions, (d) 10 to 28% by mass of ammonia, and an alkaline aqueous solution with an alkali metal concentration of 10 to 30% by mass.

[0063] Next, the above-mentioned aqueous solution containing (a) nickel salt, (b) cobalt salt, (c) manganese salt, and alkaline aqueous solution containing ammonia (d) and alkali metal is used as the reaction solution. The pH of the reaction solution is controlled at 10.8–11.4, the ammonium ion concentration at 10–22 g / L, and the liquid temperature at 55–65°C, while a co-precipitation reaction is carried out. At this time, the reagent solution can also be transported to the reaction tank from three separate storage tanks: one containing a mixed aqueous solution of nickel salt, cobalt salt, and manganese salt; one containing an alkaline aqueous solution containing ammonia; and one containing an alkaline aqueous solution containing alkali metal. In this way, the precursor for the positive electrode active material of the lithium-ion battery shown in formula (2) can be manufactured.

[0064] Next, a mixture is obtained by mixing the hydroxide precursor of the positive electrode active material for lithium-ion batteries with 50% of Ta oxide with a cumulative volume particle size D50 of 1.0 μm or less using either a wet or dry method. The amount of Ta oxide mixed can be appropriately adjusted according to the composition of the target positive electrode active material for lithium-ion batteries. Ta₂O₅ or the like can be used as the Ta oxide. For the wet mixing method, the hydroxide precursor of the positive electrode active material for lithium-ion batteries and Ta oxide are added to an aqueous solvent and mixed mechanically to prepare a slurry. The slurry is then dried while remaining stationary. For the dry mixing method, a high-intensity mixer, such as the NOBILTA manufactured by Hosokawa Micron or an intensive mixer manufactured by Erich Corporation of Japan, can be used to mix the hydroxide precursor of the positive electrode active material for lithium-ion batteries and the added Ta oxide while applying shear force.

[0065] As described above, before mixing the precursor of the positive electrode active material for lithium-ion batteries with the lithium source, a slurry is prepared by mixing Ta oxide with 50% of its cumulative volumetric particle size D50 being 1.0 μm or less. This improves the adhesion rate of the oxide of the dissimilar element (Ta) to the surface of the precursor of the positive electrode active material for lithium-ion batteries. Furthermore, by adding a dissimilar element through this method, even a small amount of element addition can improve the cycle characteristics (capacity retention) of lithium-ion batteries using the manufactured positive electrode active material and reduce DC resistance. The 50% cumulative volumetric particle size D50 of the mixed Ta oxide particles is preferably 0.3 to 1.0 μm, more preferably 0.3 to 0.5 μm.

[0066] Next, the lithium source is dry-mixed into the mixture of the precursor of the positive electrode active material for lithium-ion batteries and the oxide of Ta obtained as described above, to form a lithium mixture. The amount of lithium source mixed can be appropriately adjusted according to the composition of the target positive electrode active material for lithium-ion batteries. Lithium hydroxide can be cited as an example of a lithium source. As a mixing method, the mixing ratio of each raw material is adjusted, and dry mixing is performed using a Henschel mixer, an automatic mortar, or a V-type mixer, etc.

[0067] Next, the lithium mixture obtained as described above is calcined at a temperature of 700°C or higher for at least 4 hours. By performing a single calcination of the lithium mixture at a temperature of 700°C or higher for at least 4 hours, the solid solubility of the foreign element (Ta) within the positive electrode active material for lithium-ion batteries is increased, and the strength of the positive electrode active material particles is improved. Therefore, particle breakage can be suppressed during the subsequent lithium composite oxide coating process, and oxides containing Li and Nb can be well coated, improving the output characteristics and durability of the all-solid-state lithium-ion battery. The preferred calcination temperature is 700–800°C, and the preferred calcination time is 4–12 hours. The preferred calcination atmosphere is an oxygen atmosphere.

[0068] Increasing the amount of Ta oxide added, and / or extending the firing time, and / or raising the firing temperature increases the solid solubility of the foreign element (Ta) in the cathode active material, enabling further diffusion of Ta into the primary particles of the cathode active material. Conversely, decreasing the amount of Ta oxide added, and / or shortening the firing time, and / or lowering the firing temperature suppresses the diffusion of Ta into the primary particles of the cathode active material, causing it to segregate at grain boundaries. This method allows for the control of concentration inhomogeneity at grain boundaries and within the primary particles. That is, the coefficient of variation CV1, obtained by dividing the standard deviation of the average concentration of Ta element inside the primary particle obtained by TEM-EDX analysis by the average concentration of Ta element, and the coefficient of variation CV2, obtained by dividing the standard deviation of the average concentration of Ta element at the grain boundary of the primary particle obtained by TEM-EDX analysis by the average concentration of Ta element at the grain boundary of the primary particle, can be controlled so that CV2 > CV1. Furthermore, the average concentration of Ta element at the grain boundary obtained by TEM-EDX analysis can be higher than the concentration of Ta element in the positive electrode active material for lithium-ion batteries obtained by ICP analysis.

[0069] Subsequently, if necessary, the sintered body can be pulverized using a pulverizer to obtain powder of the positive electrode active material for lithium-ion batteries.

[0070] (Manufacturing method of positive electrode active material for all-solid-state lithium-ion batteries)

[0071] Regarding the method for manufacturing the positive electrode active material for an all-solid-state lithium-ion battery according to an embodiment of the present invention, firstly, an aqueous solution (coating liquid) containing Li and Nb is coated onto the surface of the positive electrode active material particles of the positive electrode active material for a lithium-ion battery manufactured by the above-described method. Examples of coating liquids include: (1) any one of lithium hydroxide monohydrate, lithium carbonate, and lithium nitrate as a lithium source; (2) any one of niobium hydroxide, niobium oxalate, and ammonium niobium oxalate as a niobium source; and (3) an aqueous solution of any one of pure water, hydrogen peroxide solution, and ammonia solution. Furthermore, as a coating method, a coating apparatus having a rotating fluidized bed (rotating fluidized bed coating apparatus) can be used. By using a rotating fluidized bed coating apparatus, coating can be performed uniformly while controlling the thickness.

[0072] (Positive electrode for lithium-ion batteries and lithium-ion batteries)

[0073] The positive electrode for a lithium-ion battery according to embodiments of the present invention, for example, has a structure in which a positive electrode composite material prepared by mixing the above-described positive electrode active material, conductive auxiliary material, and binder is disposed on one or both sides of the current collector. Furthermore, the lithium-ion battery according to embodiments of the present invention includes a positive electrode for a lithium-ion battery with such a configuration and a known negative electrode for a lithium-ion battery.

[0074] Examples of conductive auxiliary materials include carbon-based conductive auxiliary materials (graphite and carbon black (acetylene black, Ketjen black, furnace black, channel black, and thermal lamp black), etc.) and mixtures thereof. These conductive auxiliary materials can be used individually or in combination of two or more. Furthermore, as these conductive auxiliary materials, conductive materials (preferably metallic materials from the aforementioned conductive auxiliary materials) can be coated around particle-based ceramic materials or resin materials using methods such as plating. The shape (morphology) of the conductive auxiliary material is not limited to a particle shape; it can also be a shape other than a particle shape, such as carbon nanofibers or carbon nanotubes, which are practically used as so-called filler-based conductive auxiliary materials.

[0075] As a binder, substances commonly used in positive electrode composite materials for lithium-ion batteries can be listed, preferably copolymers having a structure derived from vinylidene fluoride, copolymers or homopolymers having a structure derived from polyvinylidene fluoride (PVDF), tetrafluoroethylene (TEF), or copolymers or homopolymers having a structure derived from hexafluoropropylene (HFP). Specifically, PVDF-HFP, PVDF-HFP-TEF, PVDF-TEF, TEF-HFP, etc., can be listed.

[0076] Regarding positive electrode hybrid materials, a positive electrode hybrid material slurry is prepared by mixing positive electrode active material, conductive auxiliary material, and binder in a solvent. After being coated on one or both sides of the current collector, it is dried and then deposited on the current collector to form a positive electrode active material layer.

[0077] As a solvent for the cathode mixed material slurry, known organic solvents, such as hydrocarbon-based organic solvents, amide compounds, lactam compounds, urea compounds, organosulfur compounds, and cyclic organophosphorus compounds, can be used as individual solvents or as mixed solvents. As hydrocarbon-based organic solvents, saturated hydrocarbons, unsaturated hydrocarbons, or aromatic hydrocarbons can be used. Examples of saturated hydrocarbons include hexane, pentane, 2-ethylhexane, heptane, decane, and cyclohexane. Examples of unsaturated hydrocarbons include hexene, heptene, and cyclohexene. Examples of aromatic hydrocarbons include toluene, xylene, decahydronaphthalene, and 1,2,3,4-tetrahydronaphthalene. Toluene and xylene are particularly preferred.

[0078] Examples of materials constituting the current collector include metallic materials such as copper, aluminum, titanium, stainless steel, nickel, and their alloys, as well as sintered carbon, conductive polymers, and conductive glass. Among these, aluminum is more preferred from the viewpoints of lightweight, corrosion resistance, and high conductivity. Furthermore, the current collector is preferably a resin current collector made of a conductive polymer. The shape of the current collector is not particularly limited and can be a sheet-like current collector formed from the aforementioned materials, or a deposition layer composed of microparticles made from the aforementioned materials. The thickness of the current collector is not particularly limited, but is preferably 50–500 μm. For example, conductive polymers can be used, or materials for which conductive auxiliary materials are added to the resin as needed.

[0079] From the perspective of battery performance, the thickness of the positive electrode for lithium-ion batteries is preferably 150–600 μm, and more preferably 200–450 μm.

[0080] A lithium-ion battery using a positive electrode is obtained by: combining a negative electrode (which forms the counter electrode) with a separator and housing it together in a battery container, injecting electrolyte, and sealing the battery container. Alternatively, it can be obtained by: forming a positive electrode on one side of the current collector and a negative electrode on the other side to create a bipolar electrode; stacking the bipolar electrode with a separator and housing it in a battery container, injecting electrolyte, and sealing the battery container.

[0081] As a negative electrode, a negative electrode can include a negative electrode active material, a conductive auxiliary material, and a current collector. As a negative electrode active material, known lithium-ion battery negative electrode active materials can be used, including: carbon-based materials (graphite, non-graphitizable carbon, amorphous carbon). Materials containing carbon, sintered resins (e.g., materials formed by sintering and carbonizing phenolic resins and furan resins), cokes (e.g., pitch coke, needle coke, and petroleum coke), and carbon fibers, etc., silicon-based materials (silicon, silicon oxide (SiOx), silicon-carbon composites (materials formed by coating carbon particles with silicon and / or silicon carbide, materials formed by coating silicon particles or silicon oxide particles with carbon and / or silicon carbide, and silicon carbide, etc.), silicon alloys (silicon-aluminum alloys, silicon-lithium alloys, silicon-nickel alloys, silicon-iron alloys, silicon-titanium alloys, silicon-manganese alloys, silicon-copper alloys, and silicon-tin alloys, etc.), conductive polymers (e.g., polyacetylene and polypyrrole, etc.), metals (tin, aluminum, zirconium, and titanium, etc.), metal oxides (titanium oxides and lithium / titanium oxides, etc.), and metal alloys (e.g., lithium-tin alloys, lithium-aluminum alloys, and lithium-aluminum-manganese alloys, etc.), and mixtures thereof with carbon-based materials, etc. Furthermore, the conductive auxiliary material can preferably be the same conductive auxiliary material as the positive electrode described above.

[0082] As the current collector, the same current collector as the one constituting the positive electrode described above can be used. From the viewpoints of lightweight, corrosion resistance, and high conductivity, copper is preferred. Alternatively, a resin current collector can be used, and the same current collector as the one constituting the positive electrode described above is preferred. The thickness of the current collector is not particularly limited, but is preferably 10–60 μm.

[0083] Examples of separators for lithium-ion batteries include: porous membranes made of polyethylene or polypropylene, laminated membranes of porous polyethylene and porous polypropylene, nonwoven fabrics made of synthetic fibers (such as polyester fibers and aramid fibers) or glass fibers, and membranes with ceramic particles such as silica, alumina, and titanium oxide attached to their surfaces.

[0084] (Positive electrode for all-solid-state lithium-ion batteries and all-solid-state lithium-ion batteries)

[0085] The all-solid-state lithium-ion battery according to embodiments of the present invention uses a positive electrode active material to form a positive electrode, and uses this positive electrode as a positive electrode layer. An all-solid-state lithium-ion battery comprising this positive electrode layer, a solid electrolyte layer, and a negative electrode layer can be fabricated. The solid electrolyte layer and negative electrode layer constituting the all-solid-state lithium-ion battery of the embodiments of the present invention are not particularly limited and can be formed from known materials, such as... Figure 1 The known composition is shown.

[0086] The positive electrode layer of the all-solid-state lithium-ion battery can be formed into a layered positive electrode layer by mixing a positive electrode active material and a solid electrolyte according to embodiments of the present invention. The content of the positive electrode active material in the positive electrode layer is preferably 50% by mass or more and 99% by mass or less, more preferably 60% by mass or more and 90% by mass or less.

[0087] The positive electrode composite material may also include a conductive auxiliary material. This conductive auxiliary material can be a carbon-based material. Examples of carbon-based materials include Ketjen black, acetylene black, denka black, thermal black, channel black, graphite, carbon fiber, and activated carbon.

[0088] There is no particular limitation on the average thickness of the positive electrode layer in an all-solid-state lithium-ion battery; it can be designed appropriately according to the purpose. For example, the average thickness of the positive electrode layer in an all-solid-state lithium-ion battery can range from 1 μm to 100 μm, or from 1 μm to 10 μm.

[0089] There are no particular limitations on the method for forming the positive electrode layer of an all-solid-state lithium-ion battery; it can be selected appropriately depending on the purpose. Examples of methods for forming the positive electrode layer of an all-solid-state lithium-ion battery include, for instance, compressing an all-solid-state lithium-ion battery using a positive electrode active material.

[0090] The negative electrode layer of an all-solid-state lithium-ion battery can be a layered negative electrode layer formed from a known all-solid-state lithium-ion battery negative electrode active material. Alternatively, the negative electrode layer can be a layered negative electrode layer formed from a negative electrode hybrid material made by mixing a known all-solid-state lithium-ion battery negative electrode active material and a solid electrolyte. The content of the negative electrode active material in the negative electrode layer is preferably, for example, 10% by mass or more and 99% by mass or less, more preferably 20% by mass or more and 90% by mass or less.

[0091] The negative electrode layer may contain the same conductive auxiliary material as the positive electrode layer. This conductive auxiliary material may be the same as that described in the positive electrode layer. As the negative electrode active material, carbon-based materials may be used, specifically artificial graphite, graphite carbon fibers, resin-sintered carbon, pyrolytic vapor-grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin-sintered carbon, polyphenylene oxide, pitch-based carbon fibers, vapor-grown carbon fibers, natural graphite, and non-graphitizable carbon, or mixtures thereof. Furthermore, as the negative electrode material, metals such as lithium, indium, aluminum, and silicon, or alloys formed by combining them with other elements and compounds, may be used.

[0092] There is no particular limitation on the average thickness of the negative electrode layer in an all-solid-state lithium-ion battery; it can be selected appropriately depending on the purpose. For example, the average thickness of the negative electrode layer in an all-solid-state lithium-ion battery can range from 1 μm to 100 μm, or from 1 μm to 10 μm.

[0093] There are no particular limitations on the method for forming the negative electrode layer of an all-solid-state lithium-ion battery; it can be selected appropriately depending on the purpose. Examples of methods for forming the negative electrode layer in an all-solid-state lithium-ion battery include, for instance, compressing negative electrode active material particles into shape, and vapor-depositing the negative electrode active material.

[0094] Solid electrolytes can be well-known solid electrolytes used in all-solid-state lithium-ion batteries. Sulfide-based solid electrolytes, etc., can be used as solid electrolytes.

[0095] Examples of sulfide-based solid electrolytes include: LiI-Li2S-P2S5, LiI-Li2S-B2S3, Li3PO4-Li2S-Si2S, Li3PO4-Li2S-SiS2, LiPO4-Li2S-SiS, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li3PS4, and Li2S-P2S5.

[0096] There is no particular limitation on the average thickness of the solid electrolyte layer in an all-solid-state lithium-ion battery; it can be designed appropriately according to the purpose. For example, the average thickness of the solid electrolyte layer in an all-solid-state lithium-ion battery can be 50μm to 500μm, or it can be 50μm to 100μm.

[0097] There are no particular limitations on the method for forming the solid electrolyte layer in an all-solid-state lithium-ion battery; it can be selected appropriately depending on the purpose. Examples of methods for forming the solid electrolyte layer in an all-solid-state lithium-ion battery include sputtering of a target material using a solid electrolyte, or compressing the solid electrolyte into shape.

[0098] There are no particular limitations on other components that make up an all-solid-state lithium-ion battery. They can be selected appropriately according to the purpose. For example, positive current collector, negative current collector, and battery case can be listed.

[0099] There are no particular restrictions on the size and structure of the positive current collector; it can be selected appropriately according to the purpose.

[0100] Materials used as positive current collectors include, for example, mold steel, stainless steel, aluminum, aluminum alloy, titanium alloy, copper, gold, nickel, etc.

[0101] The shapes of positive current collectors can include, for example, foil, plate, and mesh.

[0102] The average thickness of the positive current collector can be, for example, 10 μm to 500 μm, or 50 μm to 100 μm.

[0103] There are no particular restrictions on the size and structure of the negative current collector; it can be selected appropriately according to the purpose.

[0104] Materials used as negative electrode current collectors include, for example, mold steel, gold, indium, nickel, copper, and stainless steel.

[0105] The shapes of negative current collectors can include, for example, foil, plate, and mesh.

[0106] The average thickness of the negative electrode current collector can be, for example, 10 μm to 500 μm, or 50 μm to 100 μm.

[0107] There are no particular limitations on the battery casing; it can be selected appropriately based on the purpose. For example, known laminates that can be used in existing all-solid-state lithium-ion batteries can be listed. Examples of laminates include resin-based laminates and films formed by vapor-depositing metal onto resin-based laminates.

[0108] There are no particular restrictions on the shape of the battery; it can be chosen appropriately according to the purpose. For example, cylindrical, square, button-shaped, coin-shaped, and flat shapes are all acceptable.

[0109] Example

[0110] The following are embodiments provided to better understand the present invention and its advantages, but the present invention is not limited to these embodiments.

[0111] (Example 1)

[0112] First, Ni was prepared. 0.82 Co 0.15 Mn 0.03 (OH)2 represents the precursor of the positive electrode active material for lithium-ion batteries.

[0113] Next, a precursor of a positive electrode active material for lithium-ion batteries with a cumulative volume particle size D50 of 5.6 μm was added to an aqueous solvent, and Ta2O5 with a cumulative volume particle size D50 of 0.32 μm was added as a heteroelement at a loading of 0.1 mol%. The mixture was then prepared by mechanical means (wet mixing), and the mixture was dried while the mixture was left to stand to obtain a mixture.

[0114] Next, lithium carbonate (lithium source) was added to the obtained mixture, and the mixture was mixed using a Henschel mixer (dry mixing) to form a lithium mixture.

[0115] Next, the lithium mixture obtained as described above was calcined at 700°C in an oxygen atmosphere for 12 hours to produce positive electrode active material particles.

[0116] Next, a coating layer is formed on the positive electrode active material particles in the following order.

[0117] First, an aqueous solution containing lithium hydroxide, niobium hydroxide, and pure water with a Li and Nb content of 0.15 mol / L was prepared as the coating solution. Next, using this coating solution, the surface of the prepared positive electrode active material particles was coated with an oxide precursor containing Li and Nb using a rotating fluidized bed coating apparatus. The mixture was then heat-treated at 250°C in an oxygen atmosphere to produce a fully solid-state lithium-ion battery positive electrode active material with a coating layer on its surface.

[0118] (Example 2)

[0119] First, Ni was prepared. 0.82 Co 0.15 Mn 0.03 (OH)2 represents the precursor of the positive electrode active material for lithium-ion batteries.

[0120] Next, a precursor of a positive electrode active material for lithium-ion batteries with a cumulative volume particle size D50 of 5.6 μm was added to an aqueous solvent, and Ta2O5 with a cumulative volume particle size D50 of 0.31 μm was added as a heteroelement at a loading of 0.2 mol%. The mixture was then prepared by mechanical means (wet mixing), and the mixture was dried while the mixture was left to stand to obtain a mixture.

[0121] Next, lithium carbonate (lithium source) was added to the obtained mixture, and the mixture was mixed using a Henschel mixer (dry mixing) to form a lithium mixture.

[0122] Next, the lithium mixture obtained as described above was calcined at 700°C in an oxygen atmosphere for 12 hours to produce positive electrode active material particles.

[0123] Next, a coating layer is formed on the positive electrode active material particles in the following order.

[0124] First, an aqueous solution containing lithium hydroxide, niobium hydroxide, and pure water with a Li and Nb content of 0.15 mol / L was prepared as the coating solution. Next, using this coating solution, the surface of the prepared positive electrode active material particles was coated with an oxide precursor containing Li and Nb using a rotating fluidized bed coating apparatus. The mixture was then heat-treated at 250°C in an oxygen atmosphere to produce a fully solid-state lithium-ion battery positive electrode active material with a coating layer on its surface.

[0125] (Example 3)

[0126] First, Ni was prepared. 0.82 Co 0.15 Mn 0.03 (OH)2 represents the precursor of the positive electrode active material for lithium-ion batteries.

[0127] Next, a precursor of a positive electrode active material for lithium-ion batteries with a cumulative volume particle size D50 of 5.6 μm was added to an aqueous solvent, and Ta2O5 with a cumulative volume particle size D50 of 0.32 μm was added as a heteroelement at a loading of 0.3 mol%. The mixture was then prepared by mechanical means (wet mixing), and the mixture was dried while the mixture was left to stand to obtain a mixture.

[0128] Next, lithium carbonate (lithium source) was added to the obtained mixture, and the mixture was mixed using a Henschel mixer (dry mixing) to form a lithium mixture.

[0129] Next, the lithium mixture obtained as described above was calcined at 700°C in an oxygen atmosphere for 12 hours to produce positive electrode active material particles.

[0130] Next, a coating layer is formed on the positive electrode active material particles in the following order.

[0131] First, an aqueous solution containing lithium hydroxide, niobium hydroxide, and pure water with a Li and Nb content of 0.15 mol / L was prepared as the coating solution. Next, using this coating solution, the surface of the prepared positive electrode active material particles was coated with an oxide precursor containing Li and Nb using a rotating fluidized bed coating apparatus. The mixture was then heat-treated at 250°C in an oxygen atmosphere to produce a fully solid-state lithium-ion battery positive electrode active material with a coating layer on its surface.

[0132] (Example 4)

[0133] First, Ni was prepared. 0.82 Co 0.15 Mn 0.03 (OH)2 represents the precursor of the positive electrode active material for lithium-ion batteries.

[0134] Next, a precursor of a positive electrode active material for lithium-ion batteries with a cumulative volume particle size D50 of 5.6 μm was added to an aqueous solvent, and Ta2O5 with a cumulative volume particle size D50 of 0.31 μm was added as a heteroelement at a loading of 0.4 mol%. The mixture was then prepared by mechanical means (wet mixing), and the mixture was dried while the mixture was left to stand to obtain a mixture.

[0135] Next, lithium carbonate (lithium source) was added to the obtained mixture, and the mixture was mixed using a Henschel mixer (dry mixing) to form a lithium mixture.

[0136] Next, the lithium mixture obtained as described above was calcined at 700°C in an oxygen atmosphere for 12 hours to produce positive electrode active material particles.

[0137] Next, a coating layer is formed on the positive electrode active material particles in the following order.

[0138] First, an aqueous solution containing lithium hydroxide, niobium hydroxide, and pure water with a Li and Nb content of 0.15 mol / L was prepared as the coating solution. Next, using this coating solution, the surface of the prepared positive electrode active material particles was coated with an oxide precursor containing Li and Nb using a rotating fluidized bed coating apparatus. The mixture was then heat-treated at 250°C in an oxygen atmosphere to produce a fully solid-state lithium-ion battery positive electrode active material with a coating layer on its surface.

[0139] (Example 5)

[0140] First, Ni was prepared. 0.82 Co 0.15 Mn 0.03 (OH)2 represents the precursor of the positive electrode active material for lithium-ion batteries.

[0141] Next, a precursor of a positive electrode active material for lithium-ion batteries with a cumulative volume particle size D50 of 5.6 μm was added to an aqueous solvent, and Ta2O5 with a cumulative volume particle size D50 of 0.30 μm was added as a heteroelement at a loading of 0.5 mol%. The mixture was then prepared by mechanical means (wet mixing), and the mixture was dried while the mixture was left to stand to obtain a mixture.

[0142] Next, lithium carbonate (lithium source) was added to the obtained mixture, and the mixture was mixed using a Henschel mixer (dry mixing) to form a lithium mixture.

[0143] Next, the lithium mixture obtained as described above was calcined at 700°C in an oxygen atmosphere for 12 hours to produce positive electrode active material particles.

[0144] Next, a coating layer is formed on the positive electrode active material particles in the following order.

[0145] First, an aqueous solution containing lithium hydroxide, niobium hydroxide, and pure water with a Li and Nb content of 0.15 mol / L was prepared as the coating solution. Next, using this coating solution, the surface of the prepared positive electrode active material particles was coated with an oxide precursor containing Li and Nb using a rotating fluidized bed coating apparatus. The mixture was then heat-treated at 250°C in an oxygen atmosphere to produce a fully solid-state lithium-ion battery positive electrode active material with a coating layer on its surface.

[0146] (Example 6)

[0147] First, Ni was prepared. 0.82 Co 0.15 Mn 0.03 (OH)2 represents the precursor of the positive electrode active material for lithium-ion batteries.

[0148] Next, a precursor of a positive electrode active material for lithium-ion batteries with a cumulative volume particle size D50 of 5.6 μm was added to an aqueous solvent, and Ta2O5 with a cumulative volume particle size D50 of 0.31 μm was added as a heteroelement at a loading of 0.2 mol%. The mixture was then prepared by mechanical means (wet mixing), and the mixture was dried while the mixture was left to stand to obtain a mixture.

[0149] Next, lithium carbonate (lithium source) was added to the obtained mixture, and the mixture was mixed using a Henschel mixer (dry mixing) to form a lithium mixture.

[0150] Next, the lithium mixture obtained as described above was calcined at 710°C in an oxygen atmosphere for 12 hours to produce positive electrode active material particles.

[0151] Next, a coating layer is formed on the positive electrode active material particles in the following order.

[0152] First, an aqueous solution containing lithium hydroxide, niobium hydroxide, and pure water with a Li and Nb content of 0.15 mol / L was prepared as the coating solution. Next, using this coating solution, the surface of the prepared positive electrode active material particles was coated with an oxide precursor containing Li and Nb using a rotating fluidized bed coating apparatus. The mixture was then heat-treated at 250°C in an oxygen atmosphere to produce a fully solid-state lithium-ion battery positive electrode active material with a coating layer on its surface.

[0153] (Example 7)

[0154] First, Ni was prepared. 0.82 Co 0.15 Mn 0.03 (OH)2 represents the precursor of the positive electrode active material for lithium-ion batteries.

[0155] Next, a precursor of a positive electrode active material for lithium-ion batteries with a cumulative volume particle size D50 of 5.6 μm was added to an aqueous solvent, and Ta2O5 with a cumulative volume particle size D50 of 0.31 μm was added as a heteroelement at a loading of 0.4 mol%. The mixture was then prepared by mechanical means (wet mixing), and the mixture was dried while the mixture was left to stand to obtain a mixture.

[0156] Next, lithium carbonate (lithium source) was added to the obtained mixture, and the mixture was mixed using a Henschel mixer (dry mixing) to form a lithium mixture.

[0157] Next, the lithium mixture obtained as described above was calcined at 710°C in an oxygen atmosphere for 12 hours to produce positive electrode active material particles.

[0158] Next, a coating layer is formed on the positive electrode active material particles in the following order.

[0159] First, an aqueous solution containing lithium hydroxide, niobium hydroxide, and pure water with a Li and Nb content of 0.15 mol / L was prepared as the coating solution. Next, using this coating solution, the surface of the prepared positive electrode active material particles was coated with an oxide precursor containing Li and Nb using a rotating fluidized bed coating apparatus. The mixture was then heat-treated at 250°C in an oxygen atmosphere to produce a fully solid-state lithium-ion battery positive electrode active material with a coating layer on its surface.

[0160] (Example 8)

[0161] First, Ni was prepared. 0.82 Co 0.15 Mn 0.03 (OH)2 represents the precursor of the positive electrode active material for lithium-ion batteries.

[0162] Next, a precursor of a positive electrode active material for lithium-ion batteries with a cumulative volume particle size D50 of 5.6 μm was added to an aqueous solvent, and Ta2O5 with a cumulative volume particle size D50 of 0.31 μm was added as a heteroelement at a loading of 0.2 mol%. The mixture was then prepared by mechanical means (wet mixing), and the mixture was dried while the mixture was left to stand to obtain a mixture.

[0163] Next, lithium carbonate (lithium source) was added to the obtained mixture, and the mixture was mixed using a Henschel mixer (dry mixing) to form a lithium mixture.

[0164] Next, the lithium mixture obtained as described above was calcined at 720°C in an oxygen atmosphere for 12 hours to produce positive electrode active material particles.

[0165] Next, a coating layer is formed on the positive electrode active material particles in the following order.

[0166] First, an aqueous solution containing lithium hydroxide, niobium hydroxide, and pure water with a Li and Nb content of 0.15 mol / L was prepared as the coating solution. Next, using this coating solution, the surface of the prepared positive electrode active material particles was coated with an oxide precursor containing Li and Nb using a rotating fluidized bed coating apparatus. The mixture was then heat-treated at 250°C in an oxygen atmosphere to produce a fully solid-state lithium-ion battery positive electrode active material with a coating layer on its surface.

[0167] (Example 9)

[0168] First, Ni was prepared. 0.82 Co 0.15 Mn 0.03 (OH)2 represents the precursor of the positive electrode active material for lithium-ion batteries.

[0169] Next, a precursor of a positive electrode active material for lithium-ion batteries with a cumulative volume particle size D50 of 5.6 μm was added to an aqueous solvent, and Ta2O5 with a cumulative volume particle size D50 of 0.32 μm was added as a heteroelement at a loading of 0.3 mol%. The mixture was then prepared by mechanical means (wet mixing), and the mixture was dried while the mixture was left to stand to obtain a mixture.

[0170] Next, lithium carbonate (lithium source) was added to the obtained mixture, and the mixture was mixed using a Henschel mixer (dry mixing) to form a lithium mixture.

[0171] Next, the lithium mixture obtained as described above was calcined at 720°C in an oxygen atmosphere for 12 hours to produce positive electrode active material particles.

[0172] Next, a coating layer is formed on the positive electrode active material particles in the following order.

[0173] First, an aqueous solution containing lithium hydroxide, niobium hydroxide, and pure water with a Li and Nb content of 0.15 mol / L was prepared as the coating solution. Next, using this coating solution, the surface of the prepared positive electrode active material particles was coated with an oxide precursor containing Li and Nb using a rotating fluidized bed coating apparatus. The mixture was then heat-treated at 250°C in an oxygen atmosphere to produce a fully solid-state lithium-ion battery positive electrode active material with a coating layer on its surface.

[0174] (Example 10)

[0175] First, Ni was prepared. 0.82 Co 0.15 Mn 0.03 (OH)2 represents the precursor of the positive electrode active material for lithium-ion batteries.

[0176] Next, a precursor of a positive electrode active material for lithium-ion batteries with a cumulative volume particle size D50 of 5.6 μm was added to an aqueous solvent, and Ta2O5 with a cumulative volume particle size D50 of 0.30 μm was added as a heteroelement at a loading of 0.5 mol%. The mixture was then prepared by mechanical means (wet mixing), and the mixture was dried while the mixture was left to stand to obtain a mixture.

[0177] Next, lithium carbonate (lithium source) was added to the obtained mixture, and the mixture was mixed using a Henschel mixer (dry mixing) to form a lithium mixture.

[0178] Next, the lithium mixture obtained as described above was calcined at 720°C in an oxygen atmosphere for 12 hours to produce positive electrode active material particles.

[0179] Next, a coating layer is formed on the positive electrode active material particles in the following order.

[0180] First, an aqueous solution containing lithium hydroxide, niobium hydroxide, and pure water with a Li and Nb content of 0.15 mol / L was prepared as the coating solution. Next, using this coating solution, the surface of the prepared positive electrode active material particles was coated with an oxide precursor containing Li and Nb using a rotating fluidized bed coating apparatus. The mixture was then heat-treated at 250°C in an oxygen atmosphere to produce a fully solid-state lithium-ion battery positive electrode active material with a coating layer on its surface.

[0181] (Comparative Example 1)

[0182] First, Ni was prepared. 0.82 Co 0.15 Mn 0.03 (OH)2 represents the precursor of the positive electrode active material for lithium-ion batteries.

[0183] Next, a precursor of a positive electrode active material for lithium-ion batteries with a cumulative volume particle size D50 of 5.6 μm was added to an aqueous solvent, and Ta2O5 with a cumulative volume particle size D50 of 0.32 μm was added as a heteroelement at a loading of 0.1 mol%. The mixture was then prepared by mechanical means (wet mixing), and the mixture was dried while the mixture was left to stand to obtain a mixture.

[0184] Next, lithium carbonate (lithium source) was added to the obtained mixture, and the mixture was mixed using a Henschel mixer (dry mixing) to form a lithium mixture.

[0185] Next, the lithium mixture obtained as described above was calcined at 710°C in an oxygen atmosphere for 12 hours to produce positive electrode active material particles.

[0186] Next, a coating layer is formed on the positive electrode active material particles in the following order.

[0187] First, an aqueous solution containing lithium hydroxide, niobium hydroxide, and pure water with a Li and Nb content of 0.15 mol / L was prepared as the coating solution. Next, using this coating solution, the surface of the prepared positive electrode active material particles was coated with an oxide precursor containing Li and Nb using a rotating fluidized bed coating apparatus. The mixture was then heat-treated at 250°C in an oxygen atmosphere to produce a fully solid-state lithium-ion battery positive electrode active material with a coating layer on its surface.

[0188] (Comparative Example 2)

[0189] First, Ni was prepared. 0.82 Co 0.15 Mn 0.03 (OH)2 represents the precursor of the positive electrode active material for lithium-ion batteries.

[0190] Next, a precursor of a positive electrode active material for lithium-ion batteries with a cumulative volume particle size D50 of 5.6 μm was added to an aqueous solvent, and Ta2O5 with a cumulative volume particle size D50 of 0.32 μm was added as a heteroelement at a loading of 0.3 mol%. The mixture was then prepared by mechanical means (wet mixing), and the mixture was dried while the mixture was left to stand to obtain a mixture.

[0191] Next, lithium carbonate (lithium source) was added to the obtained mixture, and the mixture was mixed using a Henschel mixer (dry mixing) to form a lithium mixture.

[0192] Next, the lithium mixture obtained as described above was calcined at 710°C in an oxygen atmosphere for 12 hours to produce positive electrode active material particles.

[0193] Next, a coating layer is formed on the positive electrode active material particles in the following order.

[0194] First, an aqueous solution containing lithium hydroxide, niobium hydroxide, and pure water with a Li and Nb content of 0.15 mol / L was prepared as the coating solution. Next, using this coating solution, the surface of the prepared positive electrode active material particles was coated with an oxide precursor containing Li and Nb using a rotating fluidized bed coating apparatus. The mixture was then heat-treated at 250°C in an oxygen atmosphere to produce a fully solid-state lithium-ion battery positive electrode active material with a coating layer on its surface.

[0195] (Comparative Example 3)

[0196] First, Ni was prepared. 0.82 Co 0.15 Mn 0.03 (OH)2 represents the precursor of the positive electrode active material for lithium-ion batteries.

[0197] Next, a precursor of a positive electrode active material for lithium-ion batteries with a cumulative volume particle size D50 of 5.6 μm was added to an aqueous solvent, and Ta2O5 with a cumulative volume particle size D50 of 0.30 μm was added as a heteroelement at a loading of 0.5 mol%. The mixture was then prepared by mechanical means (wet mixing), and the mixture was dried while the mixture was left to stand to obtain a mixture.

[0198] Next, lithium carbonate (lithium source) was added to the obtained mixture, and the mixture was mixed using a Henschel mixer (dry mixing) to form a lithium mixture.

[0199] Next, the lithium mixture obtained as described above was calcined at 710°C in an oxygen atmosphere for 12 hours to produce positive electrode active material particles.

[0200] Next, a coating layer is formed on the positive electrode active material particles in the following order.

[0201] First, an aqueous solution containing lithium hydroxide, niobium hydroxide, and pure water with a Li and Nb content of 0.15 mol / L was prepared as the coating solution. Next, using this coating solution, the surface of the prepared positive electrode active material particles was coated with an oxide precursor containing Li and Nb using a rotating fluidized bed coating apparatus. The mixture was then heat-treated at 250°C in an oxygen atmosphere to produce a fully solid-state lithium-ion battery positive electrode active material with a coating layer on its surface.

[0202] (Comparative Example 4)

[0203] First, Ni was prepared. 0.82 Co 0.15 Mn 0.03 (OH)2 represents the precursor of the positive electrode active material for lithium-ion batteries.

[0204] Next, a precursor of a positive electrode active material for lithium-ion batteries with a cumulative volume particle size D50 of 5.6 μm was added to an aqueous solvent, and Ta2O5 with a cumulative volume particle size D50 of 0.31 μm was added as a heteroelement at a loading of 0.4 mol%. The mixture was then prepared by mechanical means (wet mixing), and the mixture was dried while the mixture was left to stand to obtain a mixture.

[0205] Next, lithium carbonate (lithium source) was added to the obtained mixture, and the mixture was mixed using a Henschel mixer (dry mixing) to form a lithium mixture.

[0206] Next, the lithium mixture obtained as described above was calcined at 720°C in an oxygen atmosphere for 12 hours to produce positive electrode active material particles.

[0207] Next, a coating layer is formed on the positive electrode active material particles in the following order.

[0208] First, an aqueous solution containing lithium hydroxide, niobium hydroxide, and pure water with a Li and Nb content of 0.15 mol / L was prepared as the coating solution. Next, using this coating solution, the surface of the prepared positive electrode active material particles was coated with an oxide precursor containing Li and Nb using a rotating fluidized bed coating apparatus. The mixture was then heat-treated at 250°C in an oxygen atmosphere to produce a fully solid-state lithium-ion battery positive electrode active material with a coating layer on its surface.

[0209] The manufacturing conditions described above are shown in Table 1.

[0210] <Composition of Positive Electrode Active Materials for All-Solid-State Lithium-ion Batteries>

[0211] 0.2 g of each of the obtained positive electrode active materials for all-solid-state lithium-ion batteries (powder) was measured, decomposed by alkaline fusion, and then the composition was analyzed using an ICP (inductively coupled plasma) emission spectrometer (ICP-OES) "PS7800" manufactured by Hitachi High-Tech.

[0212] In addition to subtracting the analytical values ​​of Li and metal components from the total amount of the sample, the concentration of impurities and the amount of residual alkali are also subtracted to obtain the oxygen content, and thus the f of “Of” in formula (1) is calculated.

[0213] The evaluation results are shown in Table 2.

[0214] <TEM-EDX Analysis>

[0215] For the obtained samples (powders) of positive electrode active materials for all-solid-state lithium-ion batteries, the average concentration of Ta element within the primary particles and at grain boundaries was measured and calculated as follows. First, as a sample pretreatment, the sample particles were processed using a focused ion beam (FIB) device to expose the cross-section of the secondary particles. Next, using an atomic resolution analytical electron microscope (JEM-ARM300F2) manufactured by JEOL Ltd., at 100,000x magnification, electron beam irradiation was performed at five points each within the primary particle and at the grain boundary under an accelerating voltage of 300 kV and an irradiation current of 1.0 nA. Energy-dispersive X-ray spectroscopy (EDX) analysis was performed, and the concentration of each element was determined based on the count of characteristic X-rays generated in the active material components Ni, Mn, Co, and Ta at each energy. Here, regarding the "primary particle interior," the measurement was performed at a position 20 nm or more above the nearest "grain boundary," which is the central part of the primary particle. When the total concentrations of Ni, Mn, Co, and Ta calculated in this way are set to 100, the average Ta concentration at five points inside the primary particle and at the grain boundary is defined as the average Ta concentration inside the primary particle and the average Ta concentration at the grain boundary of the primary particle, respectively. Furthermore, when measuring the Ta concentration at five points inside the primary particle and at the grain boundary obtained by TEM-EDX as described above, if the Ta concentration is below the detection limit, the data below the detection limit is excluded, and the average concentration at the remaining measurement points (four or three points) is taken as the average Ta concentration inside the primary particle and the average Ta concentration at the grain boundary of the primary particle. Specifically, for the primary particle interior of Example 1, the primary particle interior of Example 2, and the grain boundary, the average Ta concentration at four points is taken respectively; for the grain boundary and the primary particle interior of Comparative Example 1, the average Ta concentration at three points is taken respectively.

[0216] The coefficient of variation (CV1) was calculated by dividing the standard deviation of the average Ta concentration within the primary particle obtained from TEM-EDX analysis by the average Ta concentration, and the coefficient of variation (CV2) was calculated by dividing the standard deviation of the average Ta concentration at the grain boundaries of the primary particle obtained from TEM-EDX analysis by the average Ta concentration at the grain boundaries of the primary particle. The magnitudes of CV1 and CV2 were then compared. Furthermore, the average Ta concentration at the grain boundaries obtained from TEM-EDX analysis was compared with the Ta concentration of the positive electrode active material for lithium-ion batteries obtained from ICP analysis.

[0217] The evaluation results are shown in Table 3. In Table 3, a value of "0" is recorded when CV2 > CV1, and "×" is recorded when the condition is not met. Furthermore, in Table 3, a value of "0" is recorded when the average Ta concentration at the grain boundaries obtained by TEM-EDX analysis is greater than the Ta concentration of the positive electrode active material for lithium-ion batteries obtained by ICP analysis, i.e., when "TEM-EDX average Ta concentration at grain boundaries" > "ICP Ta composition analysis concentration" is met, and "×" is recorded when the condition is not met.

[0218] Figure 2 This is a TEM image showing the location of the Ta element concentration determination within a primary particle, obtained by TEM-EDX analysis, of the positive electrode active material of Example 1. From Figure 2 As can be seen from this, the five measurement locations are set inside the primary particle.

[0219] Figure 3 This is a TEM image showing the location of the Ta element concentration at the grain boundaries of primary particles, obtained by TEM-EDX analysis, of the positive electrode active material of Example 1. From Figure 3 As can be seen from this, the five measurement locations are respectively set at the grain boundaries of the primary particles.

[0220] (Battery characteristics)

[0221] <Manufacturing Method of All-Solid-State Lithium-ion Batteries>

[0222] The all-solid-state lithium-ion battery positive electrode active material, sulfide-based solid electrolyte (75Li2S-25P2S5), acetylene black, and binder obtained in Examples 1-10 and Comparative Examples 1-4 were mixed sequentially in a mass ratio of 60:35:5:1.5. Anisole was added as a solvent so that the solid component of the slurry was 65% by mass. The mixture was stirred and degassed for 400 seconds using a Mazerustar to prepare a positive electrode mixed material slurry. This slurry was then coated onto the surface of an aluminum foil with a thickness of 0.03 mm, which served as the positive electrode current collector. At this time, the positive electrode mixed material slurry was coated onto the surface of the positive electrode current collector using an applicator with a gap of 400 μm and a moving speed of 15 mm / s.

[0223] Next, the positive electrode current collector coated with a positive electrode mixed material slurry is dried on a heating plate at 100°C for 30 minutes to remove the solvent, thereby forming a positive electrode mixed material layer on the surface of the positive electrode current collector.

[0224] Next, the aforementioned positive electrode mixed material layer is placed on a sulfide-based solid electrolyte with the same composition as the sulfide-based solid electrolyte used in the fabrication of the positive electrode mixed material layer, and pressed at 333 MPa to fabricate a laminate of solid electrolyte layer / positive electrode mixed material layer / positive electrode current collector.

[0225] Next, a Li-In alloy metal is pressed onto the negative electrode side of the solid electrolyte layer at 37 MPa to form a negative electrode layer. The resulting laminate is then placed in a SUS304 battery cell, and a confinement pressure is applied to create an all-solid-state secondary battery. Furthermore, the laminate used to create the all-solid-state secondary battery is placed in a sealed container to isolate it from the atmosphere.

[0226] <Evaluation of Initial Discharge Capacity>

[0227] Regarding the discharge capacity of the all-solid-state lithium-ion battery, the impedance was measured after an initial charge at 55°C and 0.1C, and the resistance was calculated. Then, the battery was discharged at 0.1C to evaluate the initial discharge capacity. The evaluation results are shown in Table 3.

[0228] <Evaluation of Rate Characteristics>

[0229] Regarding the rate characteristics (%) of the all-solid-state lithium-ion battery, the initial capacity (55°C, upper charging voltage limit: 3.7V, lower discharging voltage limit: 2.5V vs. Li-In) obtained at a discharge rate of 0.1C was measured, followed by the high-rate capacity (55°C, upper charging voltage limit: 3.7V, lower discharging voltage limit: 2.5V vs. Li-In) obtained at a discharge rate of 0.5C. The ratio of (high-rate capacity) to (initial capacity) was evaluated as a percentage. The evaluation results are shown in Table 3.

[0230] [Table 1]

[0231]

[0232] [Table 2]

[0233]

[0234] [Table 3]

[0235]

[0236] (Evaluation Results)

[0237] Based on the above experimental results, Examples 1 to 10 are all positive electrode active materials for lithium-ion batteries, represented by the composition shown in the following formula (1): Li a Ni b Co c Mn d Ta e O f(1) (In the formula (1), 1.0≤a≤1.07, 0.8≤b≤0.9, b+c+d+e=1, 1.8≤f≤2.2, 0.001≤e / (b+c+d+e)≤0.005), the coefficient of variation CV1 is the value obtained by dividing the standard deviation of the average concentration of Ta element inside the primary particles obtained by TEM-EDX analysis by the average concentration of Ta element, and the coefficient of variation CV2 is the value obtained by dividing the standard deviation of the average concentration of Ta element at the grain boundaries of the primary particles obtained by TEM-EDX analysis by the average concentration of Ta element at the grain boundaries of the primary particles. In terms of the magnitude of these two values, CV2>CV1, and the average concentration of Ta element at the grain boundaries obtained by TEM-EDX analysis is higher than the concentration of Ta element in the positive electrode active material for lithium-ion batteries obtained by ICP analysis. Therefore, the battery characteristics of Examples 1 to 10 are all good.

[0238] Comparative Examples 1 to 4 do not satisfy CV2 > CV1, therefore their battery characteristics are poor compared to Examples 1 to 10.

[0239] According to one embodiment of the present invention, it is possible to provide: a positive electrode active material for lithium-ion batteries with good battery characteristics, a positive electrode for lithium-ion batteries using the positive electrode active material, a lithium-ion battery, and a method for manufacturing the positive electrode active material for lithium-ion batteries; a positive electrode active material for all-solid-state lithium-ion batteries with good battery characteristics, a positive electrode for all-solid-state lithium-ion batteries using the positive electrode active material, an all-solid-state lithium-ion battery, and a method for manufacturing the positive electrode active material for all-solid-state lithium-ion batteries, thus contributing to the popularization of non-fossil energy, reducing the use of fossil fuels such as oil and natural gas that currently account for the majority of energy production, and potentially helping to curb global warming. Furthermore, since materials with low environmental impact, such as lithium, carbon, manganese, nickel, and cobalt, are used as the main materials, and harmful substances such as cadmium, lead, and mercury are not used, it is possible to reduce the environmental impact. Therefore, one embodiment of the present invention may contribute to the United Nations-led Sustainable Development Goals (SDGs) Goal 7, “Ensuring access to affordable, reliable, sustainable and modern energy for all,” Goal 9, “Seeking resilient infrastructure, promoting inclusive and sustainable industrialization and fostering innovation,” and Goal 12, “Ensuring sustainable consumption and production patterns.”

Claims

1. A positive electrode active material for lithium-ion batteries, wherein, The positive electrode active material for the lithium-ion battery is represented by the composition shown in the following formula (1): Li a Ni b Co c Mr d Dad e O f (1) In equation (1), 1.0≤a≤1.07, 0.8≤b≤0.9, b+c+d+e=1, 1.8≤f≤2.2, 0.001≤e / (b+c+d+e)≤0.

005. The coefficient of variation CV1 is obtained by dividing the standard deviation of the average Ta concentration inside a primary particle obtained from transmission electron microscopy (TEM)-energy dispersive X-ray spectroscopy (EDX) by the average Ta concentration inside that primary particle. The coefficient of variation CV2 is obtained by dividing the standard deviation of the average Ta concentration at the grain boundaries of the primary particle obtained from TEM-EDX analysis by the average Ta concentration at the grain boundaries of that primary particle. In terms of magnitude, CV2 > CV1. The average Ta concentration at the grain boundaries obtained by TEM-EDX analysis is higher than the Ta concentration of the positive electrode active material for lithium-ion batteries obtained by ICP analysis.

2. The positive electrode active material for lithium-ion batteries according to claim 1, wherein, The 50% cumulative volumetric particle size D50 is 5–8 μm.

3. A positive electrode for a lithium-ion battery, comprising the positive electrode active material for a lithium-ion battery as described in claim 1 or 2.

4. A lithium-ion battery comprising a positive electrode and a negative electrode as described in claim 3.

5. A positive electrode active material for all-solid-state lithium-ion batteries, wherein, Include: The positive electrode active material for lithium-ion batteries as described in claim 1 or 2; and A coating layer formed of Li and Nb oxides is provided on the surface of the positive electrode active material particles of the positive electrode active material for the lithium-ion battery.

6. The positive electrode active material for all-solid-state lithium-ion batteries according to claim 5, wherein, The Nb content in the positive electrode active material for the all-solid-state lithium-ion battery is 0.5-0.8% by mass.

7. A positive electrode for an all-solid-state lithium-ion battery, comprising the all-solid-state lithium-ion battery positive electrode active material as described in claim 6.

8. An all-solid-state lithium-ion battery comprising a positive electrode and a negative electrode as described in claim 7.

9. A method for manufacturing a positive electrode active material for lithium-ion batteries, wherein, include: The process of preparing a precursor for a positive electrode active material for a lithium-ion battery, represented by the composition shown in formula (2) below. Ni b What c Mn d (OH)2(2) In the above formula (2), 0.8≤b≤0.9, 0.07≤c≤0.15, and b+c+d=1; The process of mixing Ta oxides with a cumulative volume particle size D50 of less than 1.0 μm (50%) with the precursor of the positive electrode active material for lithium-ion batteries to obtain a mixture; as well as The process involves dry mixing the mixture with a lithium source and calcining it at a temperature above 700°C for more than 4 hours.

10. The method for manufacturing the positive electrode active material for lithium-ion batteries according to claim 9, wherein, The D50 of the Ta oxide is 0.3 to 1.0 μm.

11. The method for manufacturing the positive electrode active material for lithium-ion batteries according to claim 9, wherein, In the calcination process of the mixture, the mixture is dry-mixed with a lithium source and calcined at 700°C to 800°C for 4 to 12 hours.

12. A method for manufacturing a positive electrode active material for an all-solid-state lithium-ion battery, wherein, include: A process for preparing a positive electrode active material for a lithium-ion battery by the method described in any one of claims 9 to 11; as well as The process of forming a coating layer of Li and Nb oxides on the surface of the positive electrode active material particles of the positive electrode active material for lithium-ion batteries using an aqueous solution containing Li and Nb and a rotating fluidized bed coating apparatus.

13. The method for manufacturing the positive electrode active material for an all-solid-state lithium-ion battery according to claim 12, wherein, The aqueous solution containing Li and Nb is an aqueous solution containing the following i to iii: i: any one of lithium hydroxide monohydrate, lithium carbonate, and lithium nitrate can be used as the lithium source; ii: any one of niobium hydroxide, niobium oxalate, and ammonium niobium oxalate as the niobium source; and iii: Any one of pure water, hydrogen peroxide water, and ammonia water.

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