Precursor for positive electrode active material for non-aqueous electrolyte secondary battery and method for producing the precursor for positive electrode active material for non-aqueous electrolyte secondary battery

Abstract

To provide a precursor for a positive electrode active material for a non-aqueous electrolyte secondary battery in which particle fracture of secondary particles is suppressed, and a method for producing the same. [Solution] A precursor for a positive electrode active material for a non-aqueous electrolyte secondary battery containing at least nickel, comprising secondary particles formed by the aggregation of a plurality of primary particles, wherein the secondary particles have a nucleus particle inside, and among the secondary particles, a particle P corresponding to a particle diameter D50 where the cumulative volume percentage is 50% 50 Let A (μm) be the average secondary particle diameter of the particle P 50 Let a (μm) be the average core particle diameter of the secondary particles, and P corresponds to particle diameter D90, where the cumulative volume percentage is 90%. 90 Let B (μm) be the average secondary particle diameter of the particle P 90 A precursor for a positive electrode active material for a non-aqueous electrolyte secondary battery, satisfying 1.25 ≤ (b / B) / (a / A), where b (μm) is the average core particle diameter.

Description

Technical Field

[0001] The present invention relates to a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery and a method for producing the precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery.

Background Art

[0002] In recent years, from the viewpoint of reducing environmental load, secondary batteries have been used in a wide range of fields including portable devices such as mobile phones and portable personal computers, and vehicles that use or combine electricity as a power source. Examples of secondary batteries include non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries. These non-aqueous electrolyte secondary batteries are suitable for size and weight reduction, and are excellent in various battery characteristics.

[0003] As precursors of positive electrode active materials for non-aqueous electrolyte secondary batteries, those containing secondary particles formed by aggregation of a plurality of primary particles are known. As such secondary particles, core-shell type secondary particles composed of a central part (core particle) formed by aggregation of primary particles and an outer shell part formed by aggregation of primary particles are known. Such core-shell type secondary particles can be produced by a production method including a nucleation step and a particle growth step. For example, Patent Document 1 discloses secondary particles having a two-layer structure in which the average ratio of the outer diameter of the central part to the particle diameter is in the range of 10% to 50%.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] In core-shell secondary particles, cracks may occur on the surface. When a positive electrode active material is produced from a precursor containing such secondary particles, there is a possibility that it may adversely affect the battery characteristics of a non-aqueous electrolyte secondary battery. The present invention relates to a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery in which particle cracking of secondary particles is suppressed, and a method for producing the same. [Means for Solving the Problem]

[0006] The present invention includes, for example, secondary particles formed by aggregation of a plurality of primary particles, the secondary particles have core particles inside, and among the secondary particles, the particle P corresponding to the particle diameter D50 at which the cumulative volume percentage is 50% 50 has an average secondary particle diameter A (μm), and the particle P 50 has an average core particle diameter a (μm), and among the secondary particles, the particle P corresponding to the particle diameter D90 at which the cumulative volume percentage is 90% 90 has an average secondary particle diameter B (μm), and the particle P 90 has an average core particle diameter b (μm), the present invention relates to a nickel-containing precursor for a positive electrode active material for a non-aqueous electrolyte secondary battery that satisfies 1.25≦(b / B) / (a / A).

[0007] The present invention also relates to a method for producing a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, the method comprising: a nucleation step of supplying a nickel-containing metal-containing aqueous solution, a complexing agent, and an alkaline aqueous solution to a reaction tank to obtain core particles; and a particle growth step of supplying a metal-containing aqueous solution, a complexing agent, and an alkaline aqueous solution to a reaction tank containing the core particles obtained in the nucleation step and water to obtain secondary particles, wherein concentration of the slurry is performed in the particle growth step, and when the slurry concentration at the start of the reaction in the particle growth step is S1 (g / L) and the slurry concentration at the end of the reaction is S2 (g / L), the method satisfies 0<S1≦100, 100≦S2≦400, and 0<S1 / S2≦0.30. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery in which particle cracking of secondary particles is suppressed, and a method for producing the same. MODES FOR CARRYING OUT THE INVENTION

[0009] Exemplary embodiments of the present invention are listed below. [1] A precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery containing at least nickel, comprising secondary particles formed by aggregation of a plurality of primary particles, the secondary particles have core particles inside, among the secondary particles, among the particles P corresponding to the particle diameter D50 at which the cumulative volume percentage is 50% 50 let the average secondary particle diameter be A (μm), and the average particle diameter of the particles P 50 let the average core particle diameter be a (μm), and among the secondary particles, among the particles P corresponding to the particle diameter D90 at which the cumulative volume percentage is 90% 90 let the average secondary particle diameter be B (μm), and the average particle diameter of the particles P 90 let the average core particle diameter be b (μm), then 1.25≦(b / B) / (a / A) A precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery that satisfies the above condition. [2] The precursor according to [1], which is a metal composite compound represented by the following compositional formula (I). Ni 1-x-y-w Co x Mn y M w O z (OH) 2-α (I) (wherein x, y, w, z, and α satisfy 0≦x≦0.5, 0≦y≦0.5, 0≦w≦0.1, 0<x+y+w≦0.5, 0≦z≦3, -0.5≦α≦2, and α-z<2, and M is one or more additional elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si.) [3] The precursor according to [1] or [2], wherein (D90-D10) / D50 is 0.7 or less, where D10 is a particle diameter at which the cumulative volume percentage of the secondary particles is 10%, D50 is said particle diameter, and D90 is a particle diameter at which the cumulative volume percentage of the secondary particles is 90%. [4] The precursor according to any one of [1] to [3], which satisfies (b / B) / (a / A)≦3.00. [5] A positive electrode active material for a non-aqueous electrolyte secondary battery, which is a fired product of the precursor according to any one of [1] to [4] and a lithium compound. [6] A nucleation step of obtaining core particles by supplying a nickel-containing metal-containing aqueous solution, a complexing agent, and an alkaline aqueous solution into a reaction tank; a particle growth step of obtaining secondary particles by supplying a metal-containing aqueous solution, a complexing agent, and an alkaline aqueous solution to a reaction tank containing the core particles obtained in the nucleation step and water; in the particle growth step, the slurry is concentrated; when the slurry concentration at the start of the reaction in the particle growth step is defined as S1 (g / L) and the slurry concentration at the end of the reaction is defined as S2 (g / L), the method satisfies 0 < S1 ≦ 100, 100 ≦ S2 ≦ 400, and 0 < S1 / S2 ≦ 0.30, which is a method for producing a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery. [7] The production method according to [6], which satisfies 30≦S1≦100. [8] The production method according to [6] or [7], wherein the particle growth step is repeated by using the slurry obtained in the immediately preceding step instead of the core particles until D50, which is a particle diameter at which the cumulative volume percentage is 50%, becomes 10 µm or more.

[0010] [Precursor of Positive Electrode Active Material] Hereinafter, the precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery will be described in detail. The precursor of the present invention includes secondary particles formed by aggregation of a plurality of primary particles. The particle shape of the precursor of the present invention is not particularly limited, and may be various shapes. Examples of the shape of primary particles include acicular, plate-like, and columnar shapes. Examples of the shape of secondary particles include substantially spherical shape, substantially elliptical shape, and the like.

[0011] A precursor according to one embodiment of the present invention includes core-shell type secondary particles having a nucleus particle inside. Among the secondary particles having a nucleus particle inside in the precursor, particles P corresponding to particle diameter D50 where the cumulative volume percentage is 50% 50 Let A (μm) be the average secondary particle diameter of the particle P 50 Let a (μm) be the average nuclear particle diameter. Furthermore, among the secondary particles in the precursor that contain nuclear particles, particle P corresponds to particle diameter D90, where the cumulative volume percentage is 90%. 90 Let B (μm) be the average secondary particle diameter of the particle P 90 Let b (μm) be the average nucleus particle diameter. In one embodiment of the present invention, the precursor A, a, B, and b satisfy the following relationship. 1.25 ≤ (b / B) / (a / A)

[0012] (a / A) represents particle P, which corresponds to the size of D50. 50 This is the ratio of the average nucleus particle diameter to the average secondary particle diameter. (b / B) represents the size of particle P corresponding to D90. 90 This is the ratio of the average nucleus particle diameter to the average secondary particle diameter. If (b / B) / (a / A) is equal to 1, it suggests that the ratio of the nucleus particle diameter to the secondary particle diameter is constant regardless of the size of the secondary particle. On the other hand, if (b / B) / (a / A) is greater than 1, it suggests that a particle P of the size corresponding to D90 exists. 90 In this case, the ratio of the core particle diameter to the secondary particle diameter is large (in other words, the thickness of the outer shell is thin relative to the core particle diameter), or particles P corresponding to the size of D50. 50 This suggests that the ratio of the core particle diameter to the secondary particle diameter is small (in other words, the thickness of the outer shell is thick relative to the core particle diameter).

[0013] The inventors have found that particle fracture in core-shell type secondary particles is more likely to occur in larger particles. They have also found that in larger particles, if there is a difference in the ratio of the thickness of the outer shell to the thickness of the core particle, particle fracture is more likely to occur due to the difference in density between the core particle and the outer shell. The setting of 1.25 ≤ (b / B) / (a / A) was derived from these novel findings by the inventors. By setting (b / B) / (a / A) within an appropriate range, particle fracture in core-shell type secondary particles can be suppressed.

[0014] (b / B) / (a / A) is 1.25 or greater, preferably 1.40 or greater, more preferably 1.50 or greater, even more preferably 1.60 or greater, and particularly preferably 1.70 or greater. (b / B) / (a / A) may be 3.00 or less. (b / B) / (a / A) is preferably 2.80 or less, more preferably 2.60 or less, even more preferably 2.40 or less, and particularly preferably 2.20 or less.

[0015] The lower and upper limits of (b / B) / (a / A) can be any combination within the disclosed range. For example, (b / B) / (a / A) is preferably 1.25 or more and 3.00 or less, more preferably 1.40 or more and 2.80 or less, even more preferably 1.50 or more and 2.60 or less, particularly preferably 1.60 or more and 2.40 or less, and most preferably 1.70 or more and 2.20 or less.

[0016] particle P 50 The average secondary particle diameter A of particle P is not particularly limited. 50 The average secondary particle diameter A is preferably 10 μm or more and 30 μm or less, more preferably 12 μm or more and 25 μm or less, and even more preferably 14 μm or more and 20 μm or less.

[0017] particle P 90 The average secondary particle diameter B of particle P is not particularly limited. 90The average secondary particle diameter B is preferably 15 μm or more and 40 μm or less, more preferably 17 μm or more and 30 μm or less, and even more preferably 18 μm or more and 25 μm or less.

[0018] particle P 50 The average nuclear particle diameter a is not particularly limited. 50 The average nuclear particle diameter a is preferably 0.5 μm or more and 10 μm or less, more preferably 1 μm or more and 9 μm or less, even more preferably 2 μm or more and 8 μm or less, and particularly preferably 3 μm or more and 7 μm or less.

[0019] particle P 90 The average nuclear particle diameter b is not particularly limited. 90 The average nuclear particle diameter b is preferably 1 μm or more and 13 μm or less, more preferably 2 μm or more and 12 μm or less, even more preferably 3 μm or more and 11 μm or less, and particularly preferably 4 μm or more and 10 μm or less.

[0020] In this specification, particle P 50 Average secondary particle diameter A, particle P 50 Average nuclear particle diameter a, particle P 90 The average secondary particle diameter B and particle P 90 The average nuclear particle diameter b shall be measured by the following method. The image processing software "ImageJ" may be used for image analysis.

[0021] (Measurement method) In cross-sectional SEM images at magnifications of 3,000x to 10,000x, secondary particles are selected in which the boundary between the core particle and the outer shell can be observed. For these secondary particles, the distance between the two points on the outer circumference of the outer shell is defined as the secondary particle diameter (μm). For these secondary particles, the distance between the two points on the outer circumference of the core particle is defined as the core particle diameter (μm). Ten secondary particles are selected in which the secondary particle diameter is ±5% of D50, and particle P is selected. 50 This group consists of 10 secondary particles whose secondary particle diameter is ±5% of D90, and particle P 90 Let this be the group. Particle P50 In the group, the number-averaged secondary particle diameter is defined as average secondary particle diameter A, and the number-averaged core particle diameter is defined as average core particle diameter a. Particles P 90 In the group, the number-averaged secondary particle diameter is defined as average secondary particle diameter B, and the number-averaged core particle diameter is defined as average core particle diameter b.

[0022] The precursor of the present invention may be a metal composite compound represented by the following compositional formula (I). Ni 1-x-y-w Co x Mn y M w O z (OH) 2-α (I) (wherein x, y, w, z, and α satisfy 0≦x≦0.5, 0≦y≦0.5, 0≦w≦0.1, 0<x+y+w≦0.5, 0≦z≦3, -0.5≦α≦2, and α-z<2, and M is one or more additional elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si.)

[0023] In the compositional formula (I), x preferably satisfies 0.01≦x≦0.4, more preferably 0.015≦x≦0.2, still more preferably 0.02≦x≦0.1, and particularly preferably 0.025≦x≦0.07.

[0024] In the compositional formula (I), y preferably satisfies 0.01≦y≦0.4, more preferably 0.03≦y≦0.3, still more preferably 0.04≦y≦0.2, and particularly preferably 0.05≦y≦0.15.

[0025] In the compositional formula (I), w preferably satisfies 0≦w≦0.05, more preferably 0≦w≦0.04, still more preferably 0≦w≦0.03, and particularly preferably 0≦w≦0.02.

[0026] In the compositional formula (I), x+y+w preferably satisfies 0.01≦x+y+w≦0.4, more preferably 0.02≦x+y+w≦0.3, and still more preferably 0.03≦x+y+w≦0.2.

[0027] In the precursor of the present invention, the particle size D50 at which the cumulative volume percentage of secondary particles reaches 50% is not particularly limited. The D50 of the secondary particles affects the packing density of the positive electrode active material into the positive electrode and the contactability with the electrolyte. The D50 of the secondary particles in the precursor of the present invention may be 10 μm or more, 12 μm or more, or 14 μm or more. The D50 of the secondary particles in the precursor of the present invention may be 30 μm or less, 25 μm or less, or 20 μm or less. The lower and upper limits of the D50 of the secondary particles in the precursor of the present invention can be arbitrarily combined within the disclosed range. For example, the D50 of the secondary particles in the precursor of the present invention may be 10 μm or more and 30 μm or less, 12 μm or more and 25 μm or less, or 14 μm or more and 20 μm or less. Note that D50 is measured using a particle size distribution analyzer with laser diffraction and scattering method.

[0028] From the viewpoint of battery characteristics, the precursor of the present invention preferably has a particle diameter D10 at which the cumulative volume percentage of secondary particles is 10%, a particle diameter D50 at which the cumulative volume percentage of secondary particles is 50%, and a particle diameter D90 at which the cumulative volume percentage of secondary particles is 90%, such that (D90-D10) / D50 is 0.70 or less, more preferably 0.60 or less, and even more preferably 0.50 or less. Furthermore, (D90-D10) / D50 is preferably 0.05 or more, more preferably 0.10 or more, and even more preferably 0.15 or more. The upper and lower limits of (D90-D10) / D50 can be arbitrarily combined within the disclosed range. For example, (D90-D10) / D50 is preferably 0.05 or more and 0.70 or less, more preferably 0.10 or more and 0.60 or less, and even more preferably 0.15 or more and 0.50 or less. Note that D10 and D90 were measured using the laser diffraction / scattering method and a particle size distribution analyzer, similar to D50.

[0029] The BET specific surface area of ​​the precursor of the present invention is not particularly limited. For example, the BET specific surface area of ​​the precursor of the present invention is 5.0 m², from the viewpoint of improving the contact area with non-aqueous electrolytes.2 It is preferable that it be 7.0m or more. 2 It is more preferable that it be 9.0m or more per gram. 2 Furthermore, it is even more preferable that the BET specific surface area of ​​the precursor of the present invention is 30.0 m², from the viewpoint of improving the crushing strength of the positive electrode active material. 2 It is preferable that the amount be less than or equal to 28.0m 2 It is more preferable that it be less than or equal to / g, and 26.0m 2 It is even more preferable that the BET specific surface area is less than or equal to / g. The lower and upper limits of the BET specific surface area can be arbitrarily combined within the disclosed range. For example, the BET specific surface area of ​​the precursor of the present invention is 5.0 m². 2 / g or more 30.0m 2 It is preferable that the amount be less than or equal to 7.0m 2 / g or more 28.0m 2 It is more preferable that it be less than or equal to 9.0m 2 / g or more 26.0m 2 It is even more preferable that the amount be less than or equal to / g.

[0030] The tap density (TD) of the precursor of the present invention is not particularly limited. For example, from the viewpoint of improving the packing density of the positive electrode active material into the positive electrode, the tap density (TD) of the precursor of the present invention is preferably 1.2 g / mL or more, and more preferably 1.4 g / mL or more. Also, from the viewpoint of improving the contactability between the positive electrode active material and the non-aqueous electrolyte, the tap density (TD) of the precursor of the present invention may be 2.4 g / mL or less, or 2.2 g / mL or less. The lower and upper limits of the tap density (TD) can be arbitrarily combined within the disclosed range. For example, the tap density (TD) of the precursor of the present invention is preferably 1.2 g / mL or more and 2.4 g / mL or less, and more preferably 1.4 g / mL or more and 2.2 g / mL or less.

[0031] [Method for producing precursors] Next, a method for producing the precursor of the present invention will be described. The precursor of the present invention can be produced, for example, by the following method, which includes a nucleation step and a particle growth step.

[0032] (Nucleation process) In the nucleation process, a metal-containing aqueous solution including nickel, a complexing agent, and an alkaline aqueous solution are supplied to the reaction vessel to obtain nucleus particles. Specifically, water, a complexing agent, and an alkaline aqueous solution are supplied to the reaction vessel to prepare a mother liquor, and then a metal-containing aqueous solution including nickel, a complexing agent, and an alkaline aqueous solution are supplied to the reaction vessel to undergo a crystallization reaction to obtain nucleus particles.

[0033] Specifically, by coprecipitation, a metal salt solution (hereinafter sometimes simply referred to as "metal-containing aqueous solution") containing a nickel salt (e.g., sulfate), an optional cobalt salt (e.g., sulfate), a manganese salt (e.g., sulfate), and a salt of additive element M (e.g., sulfate), along with an alkaline aqueous solution and a complexing agent, is appropriately added to the reaction vessel. A neutralization reaction occurs in the reaction vessel, causing crystallization and obtaining a slurry-like suspension containing nickel-containing hydroxide. For example, water is used as the solvent for the suspension.

[0034] The complexing agent is not particularly limited as long as it can form a complex with nickel, an optional component such as cobalt or manganese, and an additive element M in an aqueous solution. Examples include ammonium ion suppliers (ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, etc.), hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracildiacetic acid, glycine, and the like.

[0035] The alkaline aqueous solution is not particularly limited as long as it adjusts the pH value of the solution during coprecipitation, and examples include aqueous solutions of alkali metal hydroxides (for example, sodium hydroxide and potassium hydroxide).

[0036] When the above-mentioned metal-containing aqueous solution, complexing agent, and alkaline aqueous solution are supplied to the reaction vessel, nickel, optional components such as cobalt, manganese, and additive element M undergo a crystallization reaction to produce nucleation particles. In the nucleation process, the temperature in the reaction vessel is controlled, for example, within the range of 30°C to 80°C, preferably 40°C to 70°C, and the pH value in the reaction vessel is controlled, for example, within the range of pH 10.0 to pH 13.0, preferably pH 10.5 to pH 12.5, based on the liquid temperature of 40°C, while the substances in the reaction vessel are stirred as appropriate.

[0037] (Particle growth process) In the particle growth step, secondary particles are obtained by supplying a metal-containing aqueous solution, a complexing agent, and an alkaline aqueous solution to a reaction vessel containing the nucleation particles obtained in the nucleation step, water, a complexing agent, and an alkaline aqueous solution. Specifically, the nucleation particles obtained in the nucleation step, the complexing agent, and the alkaline aqueous solution are supplied to the reaction vessel to prepare a mother liquor, and then a metal-containing aqueous solution containing nickel, a complexing agent, and an alkaline aqueous solution are supplied to the reaction vessel to grow particles by crystallization. The metal-containing aqueous solution, complexing agent, and alkaline aqueous solution can be the same as those used in the nucleation step. Alternatively, the particle growth step may be repeated using the particles produced in the particle growth step as nucleation particles.

[0038] In the particle growth process, the temperature inside the reaction vessel is controlled, for example, within a range of 30°C to 80°C, preferably 40°C to 70°C, and the pH value inside the reaction vessel is controlled, for example, within a range of pH 10.0 to pH 13.0, preferably pH 10.5 to pH 12.5, based on a liquid temperature of 40°C, while the substances inside the reaction vessel are stirred as appropriate.

[0039] In the particle growth process, the slurry is concentrated. By controlling the slurry concentration conditions as described below, a precursor satisfying 1.25 ≤ (b / B) / (a / A) can be produced.

[0040] In the particle growth step, part of the slurry containing the nickel-containing hydroxide can be overflowed and extracted from the reaction tank. The extracted slurry is concentrated in a concentration tank, and the concentration of the nickel-containing hydroxide in the slurry increases. The concentration may be performed by any solid-liquid separation method (for example, filtration, sedimentation, extraction, etc.). The concentrated slurry is returned to the reaction tank. Accordingly, the reaction proceeds in the reaction tank while both the unreacted metal-containing aqueous solution and the returned slurry are supplied. The slurry concentration (nickel-containing hydroxide concentration) in the reaction tank increases over time as the reaction proceeds.

[0041] In the particle growth step, when the slurry concentration at the start of the reaction is defined as S1 (g / L) and the slurry concentration at the end of the reaction is defined as S2 (g / L), the conditions 0 < S1 ≤ 100, 100 ≤ S2 ≤ 400, and 0 < S1 / S2 ≤ 0.30 are satisfied. When S1 falls within the range of 0 < S1 ≤ 100, since seed particles necessary for particle growth are present, uniform particle growth can be achieved. Further, S1 preferably satisfies 30 ≤ S1 ≤ 100, more preferably 40 ≤ S1 ≤ 90, and particularly preferably 50 ≤ S1 ≤ 80. When S2 falls within the range of 100 ≤ S2 ≤ 400, particles that have sufficiently grown can be easily obtained, and furthermore, uniform particle growth can be achieved. Further, S2 preferably satisfies 150 ≤ S2 ≤ 350, and more preferably 180 ≤ S2 ≤ 320. S1 / S2 preferably satisfies 0.10 ≤ S1 / S2 ≤ 0.29, and more preferably 0.15 ≤ S1 / S2 ≤ 0.28.

[0042] The particle growth step may be repeated a plurality of times in accordance with the content described above. That is, a plurality of batches may be performed by supplying part of the slurry obtained in the immediately preceding batch to the next batch instead of seed particles such that S1 and S2 satisfy the above conditions in each batch. In particular, the particle growth step is preferably repeated until the particle diameter D50 of secondary particles becomes 10 µm or more, preferably 12 µm or more, more preferably 14 µm or more.

[0043] After filtering the slurry containing the nickel-containing hydroxide obtained in this way, the nickel-containing hydroxide can be washed with an alkaline aqueous solution and separated into a solid phase and a liquid phase by solid-liquid separation to obtain a solid phase containing nickel-containing hydroxide. If necessary, the solid phase containing nickel-containing hydroxide may be dried to obtain nickel-containing hydroxide powder. If necessary, the solid phase may be washed with water or the like before drying. The precursor of the present invention may be the nickel-containing hydroxide obtained in this way, or it may be a nickel-containing oxide obtained by further oxidizing the nickel-containing hydroxide obtained in this way. As a method for preparing a nickel-containing oxide from nickel-containing hydroxide, for example, an oxidation treatment can be given in which the material is calcined in an atmosphere containing oxygen gas at a temperature of 300°C to 800°C for 1 to 10 hours.

[0044] [Cathode active material] Next, we will describe the positive electrode active material for non-aqueous electrolyte secondary batteries (hereinafter sometimes simply referred to as "the positive electrode active material of the present invention"), which is a calcined product of the precursor of the present invention and a lithium compound. The positive electrode active material of the present invention is obtained by calcining the precursor of the present invention with a lithium compound. By calcining the precursor of the present invention with a lithium compound, a non-aqueous electrolyte secondary battery with excellent battery characteristics can be obtained.

[0045] The crystal structure of the positive electrode active material of the present invention is a layered structure, and from the viewpoint of obtaining a secondary battery with high discharge capacity, it is preferable that it has a trigonal crystal structure, a hexagonal crystal structure, or a monoclinic crystal structure. The positive electrode active material of the present invention can be used, for example, as a positive electrode active material for non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries.

[0046] Next, a method for producing the positive electrode active material of the present invention will be described. For example, in the method for producing the positive electrode active material of the present invention, first, a lithium compound is added to the precursor of the present invention to prepare a mixture of the precursor and the lithium compound. The lithium compound is not particularly limited as long as it is a compound containing lithium, and examples include lithium carbonate and lithium hydroxide.

[0047] When preparing the mixture, for example, the lithium compound and the precursor of the present invention may be mixed such that the molar ratio of lithium in the lithium compound to the total amount of metal contained in the precursor of the present invention (total amount of nickel, and optional components such as cobalt, manganese, and additive element M) is within the range of 1.00 to 1.10.

[0048] The positive electrode active material can be produced by calcining the above mixture. Examples of calcination conditions include a calcination temperature of 600°C to 1000°C, a heating rate of 50°C / h to 300°C / h, and a calcination time of 5 hours to 20 hours. The calcination may be carried out, for example, in an atmospheric or oxygen atmosphere. The calcination furnace used is not particularly limited, but examples include a stationary box furnace and a roller hearth continuous furnace.

[0049] [Nonaqueous electrolyte secondary battery] A non-aqueous electrolyte secondary battery can be assembled by preparing a positive electrode using the positive electrode active material of the present invention, a negative electrode, an electrolyte containing a predetermined electrolyte, and a separator using a known method.

[0050] The positive electrode comprises a positive electrode current collector and a positive electrode active material layer formed on the surface of the positive electrode current collector, using the positive electrode active material of the present invention. The positive electrode active material layer comprises the positive electrode active material of the present invention, a binder, and optionally a conductive additive. The conductive additive is not particularly limited as long as it can be used for non-aqueous electrolyte secondary batteries, and for example, carbon-based materials can be used. Examples of carbon-based materials include graphite powder, carbon black (e.g., acetylene black), and fibrous carbon materials. The binder is not particularly limited, but for example, a thermoplastic resin can be used. Examples of thermoplastic resins include polyvinylidene fluoride (PVdF), butadiene rubber (BR), polyvinyl alcohol (PVA), carboxymethylcellulose (CMC), and polytetrafluoroethylene (PTFE), as well as combinations thereof. The positive electrode current collector is not particularly limited, but for example, conductive metal materials such as aluminum foil, nickel foil, and stainless steel can be used.

[0051] The positive electrode can be obtained, for example, by mixing a positive electrode active material, a conductive additive, and a binder to prepare a positive electrode active material slurry, filling the positive electrode active material slurry into a positive electrode current collector using a known filling method, drying it, and then rolling and fixing it using a press or the like.

[0052] The negative electrode can be an electrode in which a negative electrode active material layer is supported on a negative electrode current collector, or an electrode consisting of the negative electrode active material alone. The negative electrode active material is not particularly limited as long as it is commonly used, and for example, graphite such as natural graphite and artificial graphite, coke, carbon black, pyrolytic carbons, carbon fibers, and sintered organic polymer compounds can be used. The negative electrode current collector is not particularly limited, but for example, metal materials such as copper foil, nickel foil, and stainless steel can be used. The negative electrode may also be metallic lithium.

[0053] The negative electrode active material layer may contain additional conductive additives, binders, etc., as needed. Examples of conductive additives and binders are the same as those used in the positive electrode active material layer.

[0054] The negative electrode can be obtained, for example, by preparing a negative electrode active material slurry by mixing a negative electrode active material with a conductive additive, binder, and water as needed, filling the negative electrode active material slurry into a negative electrode current collector using a known filling method, drying it, and then rolling and fixing it using a press or the like.

[0055] Electrolytes included in non-aqueous electrolytes include LiClO4, LiPF6, LiAsF6, LiSbF6, LiBF4, LiCF3SO3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(COCF3), Li(C4F9SO3), LiC(SO2CF3)3, and Li2B 10 Cl 10 Examples include lithium salts such as LiBOB (where BOB is bis(oxalato)borate), LiFSI (where FSI is bis(fluorosulfonyl)imide), lithium salts of lower aliphatic carboxylates, and LiAlCl4. These may be used individually or in combination of two or more.

[0056] Furthermore, as dispersion media for electrolytes, examples include carbonates such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, and 1,2-di(methoxycarbonyloxy)ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, and 2-methyltetrahydrofurethane. Ethers such as lanes; esters such as methyl formate, methyl acetate, and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; carbamates such as 3-methyl-2-oxazolidone; sulfur-containing compounds such as sulfolane, dimethyl sulfoxide, and 1,3-propanesaltone; or these organic solvents to which a fluoro group has been further introduced (one or more hydrogen atoms in the organic solvent have been replaced with a fluorine atom). These may be used alone or in combination of two or more.

[0057] Furthermore, a solid electrolyte may be used instead of an electrolyte solution containing an electrolyte. As a solid electrolyte, for example, an organic polymer electrolyte such as a polyethylene oxide-based polymer compound, a polymer compound containing at least one of a polyorganosiloxane chain or a polyoxyalkylene chain can be used. Alternatively, a so-called gel type, in which a non-aqueous electrolyte is held in a polymer compound, can also be used. Other examples include inorganic solid electrolytes containing sulfides such as Li2S-SiS2, Li2S-GeS2, Li2S-P2S5, Li2S-B2S3, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li2SO4, and Li2S-GeS2-P2S5. These may be used individually or in combination of two or more.

[0058] The separator is not particularly limited, but for example, materials such as polyethylene, polyolefin resins such as polypropylene, fluororesins, and nitrogen-containing aromatic polymers, which have the form of porous membranes, nonwoven fabrics, woven fabrics, etc., can be used. These may be used alone or two or more in combination. [Examples]

[0059] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0060] [Precursor production] (Example 1) ·Nucleation process After adding water to a reaction vessel equipped with a rotary stirring device having a stirring blade and an overflow pipe, an aqueous solution of ammonium sulfate and an aqueous solution of sodium hydroxide were added as complexing agents to prepare a mother liquor, and the temperature inside the reaction vessel was heated to 70°C. A nickel-containing metal aqueous solution was prepared by mixing nickel sulfate aqueous solution, cobalt sulfate aqueous solution, and manganese sulfate aqueous solution so that the molar ratio of nickel:cobalt:manganese was 85:5:10. Next, the above-mentioned metal-containing aqueous solution, ammonium sulfate aqueous solution as a complexing agent, and sodium hydroxide aqueous solution were continuously added to the reaction vessel under stirring to obtain a slurry containing nickel-containing hydroxide particles. During this time, the reaction vessel was continuously stirred with a stirrer while maintaining the temperature inside the vessel and the pH inside the vessel at 11.5 based on a liquid temperature of 40°C.

[0061] ·Particle growth process After adding water to a reaction vessel equipped with a rotary stirring device having a stirring blade and an overflow pipe, an aqueous solution of ammonium sulfate and an aqueous solution of sodium hydroxide were added as complexing agents to prepare a mother liquor. A portion of the slurry remaining after the nucleation process was supplied, and the temperature inside the reaction vessel was heated to 70°C. Next, while stirring, the above-mentioned metal-containing aqueous solution, an ammonium sulfate aqueous solution as a complexing agent, and a sodium hydroxide aqueous solution were continuously added into the reaction tank, and a particle growth step was performed. At this time, while maintaining the temperature inside the reaction tank and maintaining the pH inside the reaction tank at 10.5 based on a liquid temperature of 40° C., continuous stirring was performed with a stirrer. The slurry containing the produced nickel-containing hydroxide particles was caused to overflow from the overflow pipe of the reaction tank and introduced into a concentration tank. In the concentration tank, the nickel-containing hydroxide particles were subjected to solid-liquid separation, the slurry was concentrated by discharging the supernatant, and the concentrated slurry was returned into the reaction tank. After completion of the reaction, the slurry was drawn out from the reaction tank using a pump or the like, and the slurry containing nickel-containing hydroxide particles was taken out of the system. The above operation in the particle growth step was regarded as one batch, and the same operation was repeated to perform a total of 3 batches (provided that from the second batch onward, the phrase "supplying a part of the slurry after completion of the nucleation step" above shall be read as "supplying a part of the slurry after completion of the previous batch"). In all batches, the slurry concentration S1 at the start of the reaction and the slurry concentration S2 at the end of the reaction satisfied 0 < S1 ≤ 100, 100 ≤ S2 ≤ 400, and 0 < S1 / S2 ≤ 0.30. In the final batch, the slurry concentration S1 at the start of the reaction was 71 g / L, and the slurry concentration S2 at the end of the reaction was 266 g / L. The slurry containing the taken-out metal composite compound was subjected to solid-liquid separation, the solid phase was washed with an alkaline aqueous solution, and then the solid phase was dried to obtain the nickel-containing hydroxide (precursor of positive electrode active material) of Example 1.

[0062] (Example 2) · Nucleation step A nucleation step was performed in the same manner as in Example 1, except that the pH in the reaction tank was maintained at 11.4 based on a liquid temperature of 40°C.

[0063] · Particle growth step After water was put into a reaction tank equipped with a rotary stirring device having a stirring blade and an overflow pipe, an ammonium sulfate aqueous solution as a complexing agent and a sodium hydroxide aqueous solution were added to prepare a mother liquor, a part of the slurry after completion of the nucleation step was supplied, and the temperature in the reaction tank was heated to 70°C. Next, while stirring, the above-mentioned metal-containing aqueous solution, an aqueous ammonium sulfate solution as a complexing agent, and an aqueous sodium hydroxide solution were continuously added into the reaction tank to carry out a particle growth step. At this time, while maintaining the temperature inside the reaction tank, and maintaining the pH in the reaction tank at 10.5 based on a liquid temperature of 40°C, continuous stirring was performed with a stirrer. The slurry containing the produced nickel-containing hydroxide particles was overflowed from the overflow pipe of the reaction tank and introduced into a concentration tank. In the concentration tank, the nickel-containing hydroxide particles were subjected to solid-liquid separation, the supernatant was discharged to concentrate the slurry, and the concentrated slurry was returned to the reaction tank. After the completion of the reaction, the slurry was drawn out from the reaction tank using a pump or the like, and the slurry containing the nickel-containing hydroxide particles was taken out of the system. The above operation in the particle growth step was defined as one batch, and the same operation was repeated for a total of 2 batches (provided that in the second batch, the phrase "supply a part of the slurry after completion of the nucleation step" shall be read as "supply a part of the slurry after completion of the previous batch"). In all batches, the slurry concentration S1 at the start of the reaction and the slurry concentration S2 at the end of the reaction satisfied 0<S1≦100, 100≦S2≦400, and 0<S1 / S2≦0.30. In the final batch, the slurry concentration S1 at the start of the reaction was 71 g / L, and the slurry concentration S2 at the end of the reaction was 311 g / L. The subsequent steps were carried out in the same manner as in Example 1 to obtain the nickel-containing hydroxide (precursor of the positive electrode active material) of Example 2.

[0064] (Comparative Example 1) ·Nucleation step The nucleation step was performed in the same manner as in Example 1, except that the pH in the reaction tank was maintained at 11.2 based on a liquid temperature of 40°C.

[0065] ·Particle growth step After water was put into a reaction tank equipped with a rotary stirring device having a stirring blade and an overflow pipe, an aqueous ammonium sulfate solution as a complexing agent and an aqueous sodium hydroxide solution were added to prepare a mother liquor, a part of the slurry after completion of the nucleation step was supplied, and the temperature in the reaction tank was heated to 70°C. Next, the above-mentioned metal-containing aqueous solution, ammonium sulfate aqueous solution as a complexing agent, and sodium hydroxide aqueous solution were continuously added to the reaction vessel under stirring to carry out the particle growth process. During this time, the temperature inside the reaction vessel was maintained, and the pH inside the reaction vessel was maintained at 10.5 based on a liquid temperature of 40°C, while the mixture was continuously stirred with a stirrer. The slurry containing the generated nickel-containing hydroxide particles was overflowed from the overflow pipe of the reaction vessel and introduced into a concentration tank. In the concentration tank, the nickel-containing hydroxide particles were separated into solid and liquid components, and the slurry was concentrated by discharging the supernatant liquid, and the concentrated slurry was returned to the reaction vessel. After the reaction was completed, the slurry was withdrawn from the reaction vessel using a pump or the like, and the slurry containing nickel-containing hydroxide particles was removed from the system. The slurry concentration S1 at the start of the reaction was 71 g / L, and the slurry concentration S2 at the end of the reaction was 161 g / L. The subsequent steps were carried out in the same manner as in Example 1 to obtain the nickel-containing hydroxide (precursor of the positive electrode active material) of Comparative Example 1.

[0066] The precursors of the examples and comparative examples were evaluated as follows.

[0067] (1) Compositional analysis of nickel-containing hydroxides Compositional analysis was performed by dissolving the obtained nickel-containing hydroxide in hydrochloric acid, followed by analysis using an inductively coupled plasma atomic emission spectrometer (Optima 8300, PerkinElmer Japan Co., Ltd.).

[0068] (2) D10, D50, D90 D10, D50, and D90 were measured using a particle size distribution analyzer (Microtrac-Bell Co., Ltd., MT3300EXII) (principle: laser diffraction / scattering method). Measurement conditions included using water as the solvent, adding 1 mL of sodium hexametaphosphate as a dispersant, maintaining a transmittance of 80±2% after sample addition, and not generating ultrasound. The solvent refractive index used for analysis was 1.333, the refractive index of water. In the obtained cumulative particle size distribution curve, D10 (μm) was defined as the particle size at which the cumulative volume percentage from the smallest particle side reached 10%, D50 (μm) as the value at which it reached 50%, and D90 (μm) as the value at which it reached 90%.

[0069] (3) Particle P 50 Average secondary particle diameter A, particle P 50 Average nuclear particle diameter a, particle P 90 The average secondary particle diameter B and particle P 90 Average nuclear particle diameter b Cross-sectional SEM images of secondary particles were obtained for each of the nickel-containing hydroxide particles in the examples and comparative examples by cross-sectional SEM observation at magnifications of 3,000x to 10,000x. Secondary particles in which the boundary between the core particle and the outer shell could be observed in the cross-sectional SEM image were selected. For these secondary particles, the distance between the two points on the outer circumference of the outer shell that was the maximum distance was defined as the secondary particle diameter (μm). For these secondary particles, the distance between the two points on the outer circumference of the core particle that was the maximum distance was defined as the core particle diameter (μm). Ten secondary particles with a secondary particle diameter of ±5% of D50 were selected, and particle P 50 This was the group. Ten secondary particles were selected whose secondary particle diameter was ±5% of D90, and particle P 90 This was defined as the group. Particle P 50 In this group, the number average of the secondary particle diameters was defined as the average secondary particle diameter A, and the number average of the nuclear particle diameters was defined as the average nuclear particle diameter a. Particle P 90 In this group, the number-averaged secondary particle diameter was defined as the average secondary particle diameter B, and the number-averaged nuclear particle diameter was defined as the average nuclear particle diameter b. The image processing software "ImageJ" was used for image analysis.

[0070] (4) Particle fracture of secondary particles Three fields of view were selected from SEM images at an arbitrary magnification of 500x, and the number of particles and the equivalent circle diameter of each particle were evaluated using image analysis software (SEM Supporter, manufactured by System Infiltrator Co., Ltd.). The number of fractured secondary particles was counted from the three SEM images from which the number of particles was counted. The counting of fractured secondary particles was performed as follows: First, secondary particles in which fracture was visually confirmed from the SEM image were selected. Next, the length of the fracture was measured using the image processing software "ImageJ". Secondary particles with fractures longer than 5% of the equivalent circle diameter were counted as fractured secondary particles. The percentage of fractured secondary particles was calculated from the number of particles and the number of fractured secondary particles.

[0071] (5) BET specific surface area 1 g of nickel-containing hydroxide was dried at 105°C for 30 minutes in a nitrogen atmosphere, and then measured by the one-point BET method using a specific surface area analyzer (Macsorb, manufactured by Mountech Co., Ltd.).

[0072] (6) Tap density (g / mL) Measurement was carried out by the constant mass measurement method among the methods described in JIS R1628 using a tap denser (KYT-4000, manufactured by Seishin Enterprise Co., Ltd.).

[0073] The above evaluation results are shown in Table 1. In the examples where multiple batches were carried out, S1 and S2 in the table are values from the final batch.

[0074]

Table 1

[0075] In Examples 1 and 2, the particle growth step was performed to satisfy 0 < S1 ≤ 100, 100 ≤ S2 ≤ 400, and 0 < S1 / S2 ≤ 0.30, thereby producing the precursors. In Comparative Example 1, the condition 0 < S1 / S2 ≤ 0.30 was not satisfied in the particle growth step. The (b / B) / (a / A) of the precursors obtained in Examples 1 and 2 was 1.25 or more, whereas the (b / B) / (a / A) of the precursor obtained in Comparative Example 1 was less than 1.25. As shown in Table 1, cracking of secondary particles was significantly suppressed in the precursors obtained in Examples 1 and 2 compared to the precursor obtained in Comparative Example 1.

Industrial Applicability

[0076] The secondary battery using the precursor and the positive electrode active material of the present invention can be suitably used in a wide range of fields such as portable devices and vehicles.

Claims

1. A precursor for a positive electrode active material for a non-aqueous electrolyte secondary battery containing at least nickel, comprising secondary particles formed by the aggregation of a plurality of primary particles, The aforementioned secondary particle has a nuclear particle inside, Among the secondary particles, particle P corresponds to particle size D50 where the cumulative volume percentage is 50%. ５０ Let A (μm) be the average secondary particle diameter of the particle P ５０ Let a (μm) be the average core particle diameter of the secondary particles, and P corresponds to particle diameter D90, where the cumulative volume percentage is 90%. ９０ Let B (μm) be the average secondary particle diameter of the particle P ９０ If the average nuclear particle diameter is b (μm), 1.25≦(b / B) / (a / A) A precursor for positive electrode active material for non-aqueous electrolyte secondary batteries that satisfies the following conditions.

2. The precursor according to claim 1, which is a metal composite compound represented by the following compositional formula (I). Ni １－ｘ－ｙ－ｗ Co ｘ Mn ｙ M ｗ O ｚ (OH) ２－α (I) (In the formula, x, y, w, z, and α satisfy 0 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.5, 0 ≤ w ≤ 0.1, 0 < x + y + w ≤ 0.5, 0 ≤ z ≤ 3, -0.5 ≤ α ≤ 2, and α - z < 2, and M is one or more additive elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si.)

3. The precursor according to claim 1 or 2, wherein (D90 - D10) / D50 is 0.7 or less for particle diameter D10, particle diameter D50, and particle diameter D90, where the cumulative volume percentage of the secondary particles is 10%.

4. A precursor according to claim 1 or 2, satisfying (b / B) / (a / A) ≤ 3.

00.

5. A positive electrode active material for a non-aqueous electrolyte secondary battery, which is a calcined product of the precursor described in claim 1 or 2 and a lithium compound.

6. A nucleation process to obtain nucleus particles by supplying a metal-containing aqueous solution containing nickel, a complexing agent, and an alkaline aqueous solution to a reaction vessel, The particle growth step includes supplying a metal-containing aqueous solution, a complexing agent, and an alkaline aqueous solution to a reaction vessel containing the nucleation particles obtained in the nucleation step and water, thereby obtaining secondary particles. In the particle growth process, the slurry is concentrated, A method for producing a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein, when the slurry concentration at the start of the particle growth step is S1 (g / L) and the slurry concentration at the end of the reaction is S2 (g / L), the following conditions are met: 0 < S1 ≤ 100, 100 ≤ S2 ≤ 400, and 0 < S1 / S2 ≤ 0.

30.

7. The manufacturing method according to claim 6, satisfying 30 ≤ S1 ≤ 100.

8. The manufacturing method according to claim 6 or 7, wherein the particle growth step is repeated using the slurry obtained in the immediately preceding step instead of the nucleus particles until the particle diameter D50 at which the cumulative volume percentage is 50% is 10 μm or more.

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