Precursor for positive electrode active material of non-aqueous electrolyte secondary battery and positive electrode active material of non-aqueous electrolyte secondary battery

Abstract

To provide a precursor for a positive electrode active material that can improve the discharge rate characteristics of a non-aqueous electrolyte secondary battery. [Solution] A precursor for a positive electrode active material of a non-aqueous electrolyte secondary battery, comprising secondary particles formed by the aggregation of a plurality of primary particles, containing 50 mol% or more nickel atoms relative to the total amount of contained metal atoms, having a coefficient of variation (CV) of the particle diameter of the primary particles of 0.50 or less, and having a ratio of D50 / PS1 of 15.00 or less between the average particle diameter (PS1) of the primary particles and the particle diameter (D50) at which the cumulative volume percentage of the secondary particles is 50% by volume.

Description

[Technical Field]

[0001] This invention relates to a precursor for a positive electrode active material of a non-aqueous electrolyte secondary battery and to a positive electrode active material of a non-aqueous electrolyte secondary battery. [Background technology]

[0002] In recent years, secondary batteries have been used in a wide range of fields, including portable devices such as mobile phones and portable personal computers, as well as vehicles that use or use electricity as a power source, from the perspective of reducing environmental impact. 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 miniaturization and weight reduction and are excellent in various battery characteristics.

[0003] As positive electrode active materials for non-aqueous electrolyte secondary batteries, those containing secondary particles formed by the aggregation of primary particles are known. For example, Patent Document 1 discloses a lithium transition metal compound powder for a specific lithium secondary battery positive electrode material in which the ratio A / B of the median diameter A to the average diameter (average primary particle diameter B) of the secondary particles is in the range of 8 to 100. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2009-081130 [Overview of the project] [Problems that the invention aims to solve]

[0005] As the application fields of non-aqueous electrolyte secondary batteries expand, there is a need to improve the discharge rate characteristics of these batteries. This invention relates to a positive electrode active material and its precursor that can improve the discharge rate characteristics of a non-aqueous electrolyte secondary battery. [Means for solving the problem]

[0006] The present invention relates to a precursor for a positive electrode active material of a non-aqueous electrolyte secondary battery, which includes, for example, secondary particles formed by the aggregation of a plurality of primary particles, contains 50 mol% or more nickel atoms relative to the total amount of contained metal atoms, has a coefficient of variation (CV) of particle diameter of the primary particles of 0.50 or less, and has a ratio of D50 / PS1 of 15.00 or less between the average particle diameter (PS1) of the primary particles and the particle diameter (D50) at which the cumulative volume percentage of the secondary particles is 50% by volume. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a positive electrode active material and its precursor that can improve the discharge rate characteristics of a non-aqueous electrolyte secondary battery. [Modes for carrying out the invention]

[0008] The following are exemplary embodiments of the present invention. [1] A precursor of the positive electrode active material for a non-aqueous electrolyte secondary battery, It contains secondary particles formed by the aggregation of multiple primary particles, It contains 50 mol% or more nickel atoms relative to the total amount of metal atoms contained, The coefficient of variation (CV) of the particle size of the primary particles is 0.50 or less. A precursor wherein the ratio D50 / PS1 is 15.00 or less, where D50 is the average particle diameter (PS1) of the primary particles and D50 is the particle diameter at which the cumulative volume percentage of the secondary particles is 50% by volume. [2] The particle size (D10) of the secondary particles such that the cumulative volume percentage of the secondary particles is 10 volume%, A precursor of [1], wherein (D90-D10) / D50 is 1.0 or less for particle size (D50) with a cumulative volume percentage of 50 vol%, and particle size (D90) with a cumulative volume percentage of 90 vol%, of the secondary particles. [3] A metal composite compound represented by the following chemical formula (I), which is a precursor of [1] or [2]. Ni 1-x-y-w Co x Mn y M w O z (OH) 2-α Equation (I) (where 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.) The precursor according to any one of [1] to [3], wherein D50 is 1 μm or more and 15 μm or less. The positive electrode active material of 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.

[0009] [Precursor of positive electrode active material] Hereinafter, the precursor of the positive electrode active material of the 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 the primary particles include needle-like, plate-like, columnar, etc. Examples of the shape of the secondary particles include substantially spherical shape, substantially elliptical shape, etc.

[0010] The precursor of the present invention contains 50 mol% or more of nickel atoms relative to the total amount of contained metal atoms. In the precursor of the present invention, the content of nickel atoms relative to the total amount of contained metal atoms is preferably, for example, 55 mol% or more, more preferably 60 mol% or more, and particularly preferably 80 mol% or more. Typically, the higher the content of nickel atoms in the precursor, the more likely it is to be advantageous in terms of initial charge-discharge efficiency, utilization rate, cycle characteristics, etc., and it is also easier to reduce raw material costs. Further, in the precursor of the present invention, the content of nickel atoms relative to the total amount of contained metal atoms is preferably, for example, less than 100 mol%, more preferably 98 mol% or less, still more preferably 97 mol% or less, and particularly preferably 96 mol% or less. The lower limit and upper limit of the content of nickel atoms in the precursor of the present invention can be arbitrarily combined within the disclosed range. For example, in the precursor of the present invention, the content of nickel atoms relative to the total amount of contained metal atoms is preferably 50 mol% or more and less than 100 mol%, more preferably 55 mol% or more and 98 mol% or less, still more preferably 60 mol% or more and 97 mol% or less, and particularly preferably 80 mol% or more and 96 mol% or less.

[0011] 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 Formula (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.)

[0012] In the compositional formula (I), x is preferably 0.01 ≦ x ≦ 0.4, more preferably 0.015 ≦ x ≦ 0.3, still more preferably 0.02 ≦ x ≦ 0.2, and particularly preferably 0.025 ≦ x ≦ 0.1.

[0013] In the compositional formula (I), y is preferably 0.01 ≦ y ≦ 0.4, more preferably 0.02 ≦ y ≦ 0.3, still more preferably 0.03 ≦ y ≦ 0.2, and particularly preferably 0.04 ≦ y ≦ 0.1.

[0014] In the compositional formula (I), w is preferably 0 ≦ w ≦ 0.05, more preferably 0 ≦ w ≦ 0.04, still more preferably 0 ≦ w ≦ 0.03, and particularly preferably 0 ≦ w ≦ 0.02.

[0015] The precursor of the present invention has a coefficient of variation (CV) of the particle diameter of the primary particles of 0.50 or less. Here, the particle diameter of the primary particles shall be measured by the following method. Note that the image processing software "ImageJ" can be used for image analysis.

[0016] (Measurement method of the average particle diameter (PS1) of primary particles) ·Measurement range In the SEM (scanning electron microscope) image of the secondary particles, on the perpendicular bisector of the long axis of the figure surrounded by the outer edge of the secondary particles, let the length of the line segment connecting the two intersections of the perpendicular bisector and the outer edge be A. The portion surrounded by a virtual circle centered on the midpoint of the line segment and with a radius r calculated by the following formula shall be the measurement range. r = A × 3 / 8

[0017] ·Measurement method For all the primary particles whose entire length is surrounded by the virtual circle and can be visually recognized in the SEM image, measure the major axis (the dimension of the long axis). However, for the primary particles partially hidden by other primary particles, measure the length within the range observable in the SEM image. For example, when one primary particle is hidden and bisected by another primary particle crossing it, it shall be treated as two primary particles. The number average value of all the major axes measured in this way shall be the average particle diameter (PS1) of the primary particles.

[0018] The coefficient of variation (CV) of the particle size of primary particles is obtained by dividing the standard deviation (σ) of the particle size of primary particles by the number mean value (PS1). A small coefficient of variation (CV) means that there is little variation in the particle size of primary particles. In the precursor of the present invention, the coefficient of variation (CV) of the particle size of primary particles is preferably 0.49 or less, more preferably 0.48 or less, even more preferably 0.47 or less, and particularly preferably 0.46 or less. The lower limit of the coefficient of variation (CV) of the particle size of primary particles is not particularly limited, but may be, for example, 0.1 or more. In the precursor of the present invention, having a coefficient of variation (CV) of the particle size of primary particles within an appropriate range is advantageous in the discharge rate characteristics of a non-aqueous electrolyte secondary battery.

[0019] In the precursor of the present invention, the average particle size (PS1) of the primary particles is not particularly limited. The average particle size (PS1) of the primary particles in the precursor of the present invention is preferably 0.2 μm or more and 0.8 μm or less, more preferably 0.3 μm or more and 0.5 μm or less, and even more preferably 0.4 μm or more and 0.45 μm or less.

[0020] In the precursor of the present invention, the particle size (D50) at which the cumulative volume percentage of secondary particles is 50% by volume (hereinafter sometimes simply referred to as "D50") is not particularly limited. In the precursor of the present invention, the D50 of the secondary particles may be 1 μm or more, 1.5 μm or more, 2 μm or more, 2.5 μm or more, or 3 μm or more, from the viewpoint of improving the packing density of the positive electrode active material into the positive electrode. In the precursor of the present invention, the D50 of the secondary particles may be 15 μm or less, 10 μm or less, 8 μm or less, 6 μm or less, or 4.5 μm or less, from the viewpoint of improving contactability with the electrolyte. The upper and lower 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 secondary particle D50 in the precursor of the present invention may be 1 μm or more and 15 μm or less, 1.5 μm or more and 10 μm or less, 2 μm or more and 8 μm or less, 2.5 μm or more and 6 μm or less, or 3 μm or more and 4.5 μm or less. This was measured using a laser diffraction / scattering method and a particle size distribution analyzer.

[0021] The precursor of the present invention has a value (D50 / PS1) obtained by dividing D50 by the average particle diameter (PS1) of the primary particles of 15.00 or less. A small value of D50 / PS1 means that the particle diameter of the primary particles is large relative to the particle diameter of the secondary particles. D50 / PS1 may be 14.00 or less, 13.00 or less, 12.00 or less, 11.00 or less, or 10.00 or less. The lower limit of D50 / PS1 is not particularly limited, but may be, for example, 4.00 or more. The precursor of the present invention is advantageous in the discharge rate characteristics of non-aqueous electrolyte secondary batteries because the value of D50 / PS1 is within an appropriate range.

[0022] The precursor of the present invention may have a ratio of (D90-D10) / D50 of 1.0 or less for secondary particles D50, particle size (D10) at which the cumulative volume percentage of secondary particles is 10 vol%, and particle size (D90) at which the cumulative volume percentage of secondary particles is 90 vol%. (D90-D10) / D50 may be, for example, 0.8 or less, or 0.6 or less. Also, (D90-D10) / D50 may be, for example, 0.3 or more, 0.35 or more, or 0.4 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 0.3 or more and 1.0 or less, more preferably 0.35 or more and 0.8 or less, and even more preferably 0.4 or more and 0.6 or less. When the value of (D90-D10) / D50 is within an appropriate range, the resulting positive electrode active material tends to have excellent discharge rate characteristics. Note that D10 and D90, like D50, were measured using the laser diffraction / scattering method with a particle size distribution analyzer.

[0023] The tap density (TD) of the precursor of the present invention is not particularly limited. For example, the tap density (TD) of the precursor of the present invention may be 0.7 g / ml or more, 1 g / ml or more, or 1.2 g / ml or more, from the viewpoint of improving the manufacturing efficiency when producing the positive electrode active material. On the other hand, the tap density (TD) of the precursor of the present invention may be 1.9 g / ml or less, or 1.8 g / ml or less, from the viewpoint of improving the contactability between the positive electrode active material and the non-aqueous electrolyte. The above-mentioned lower and upper limits can be arbitrarily combined within the disclosed range.

[0024] [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 by a method comprising: a reaction step of supplying a metal-containing aqueous solution containing nickel, a complexing agent, and an alkaline aqueous solution to a reaction vessel and causing a crystallization reaction to obtain nickel-containing hydroxide; a slurry extraction step of overflowing and removing the slurry containing nickel-containing hydroxide from the reaction vessel; a concentration step of concentrating the slurry extracted in the slurry extraction step in a concentration tank; and a return step of returning the concentrated slurry to the reaction vessel.

[0025] The reaction process involves adding a metal-containing aqueous solution containing nickel, an alkaline aqueous solution, and a complexing agent to a reaction vessel, mixing them, and allowing a coprecipitation reaction to occur in the reaction solution to obtain nickel-containing hydroxide.

[0026] 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.

[0027] In the reaction process, it is preferable that the metal concentration of the metal-containing aqueous solution supplied to the reaction vessel be adjusted to 70-120 g / L.

[0028] 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.

[0029] 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).

[0030] When the above-mentioned metal-containing aqueous solution, alkaline aqueous solution, and complexing agent are supplied to the reaction vessel, nickel, optional components such as cobalt, manganese, and additive element M undergo a crystallization reaction to produce nickel-containing hydroxide. During the crystallization reaction, the temperature in the reaction vessel is controlled, for example, within the range of 20°C to 70°C, preferably 30°C to 60°C, and the pH value in the reaction vessel is controlled, for example, within the range of pH 10 to pH 13, preferably pH 10.5 to pH 12.5, based on a liquid temperature of 40°C, while the substances in the reaction vessel are stirred as appropriate. It is more preferable to initially set the pH value in the reaction vessel to within the range of pH 11.4 to pH 13, based on a liquid temperature of 40°C, and then change it to within the range of pH 10 to pH 11.2 after a predetermined time has elapsed since the start of the reaction.

[0031] A portion of the slurry containing nickel-containing hydroxide obtained in the reaction process can be withdrawn by overflow from the reaction vessel (slurry withdrawal process). The withdrawn slurry is concentrated in a concentration tank (concentration process). The concentration process is a process to increase the concentration of nickel-containing hydroxide in the slurry. The concentration process may be carried out by any solid-liquid separation method (e.g., filtration, sedimentation, extraction, etc.). The slurry concentrated in the concentration process is returned to the reaction vessel (return process). Therefore, the reaction process is carried out in the reaction vessel while both the unreacted metal-containing aqueous solution and the slurry returned in the return process are supplied together. The slurry concentration (nickel-containing hydroxide concentration) in the reaction vessel increases over time as the reaction progresses. The reaction can be stopped after a predetermined time has elapsed following the addition of predetermined amounts of the metal-containing aqueous solution, alkaline aqueous solution, and complexing agent.

[0032] In the method described above, the precursor of the present invention can be produced by adjusting the ratio of the flow rate of the unreacted metal-containing aqueous solution supplied to the reaction vessel (flow rate X) to the flow rate of the slurry returned to the reaction vessel (flow rate Y), thereby controlling the rate at which the slurry concentration in the reaction vessel increases. For example, the flow rate X / flow rate Y may be in the range of 0.001 to 1, preferably in the range of 0.005 to 0.5, and more preferably in the range of 0.007 to 0.3. Alternatively, by adjusting the flow rate X / flow rate Y, the rate at which the slurry concentration in the reaction vessel increases may be 4 g / (L·h) to 10 g / (L·h), preferably 5 g / (L·h) to 8 g / (L·h).

[0033] 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 the 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, in the presence of oxygen gas... An example of an oxidation treatment is firing at a temperature of 300°C to 800°C for 1 to 10 hours under certain conditions.

[0034] [Cathode active material] Next, the positive electrode active material for a non-aqueous electrolyte secondary battery (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, will be described. 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 discharge rate characteristics can be obtained.

[0035] 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 be 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.

[0036] 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, a lithium compound is first 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.

[0037] 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.

[0038] 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.

[0039] [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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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 of lithium salts include 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.

[0046] 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.

[0047] 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 within 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. stomach.

[0048] 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]

[0049] 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.

[0050] [Precursor production] (Example 1) After filling a reaction vessel equipped with a rotary stirring device having a stirring blade and an overflow pipe with water, the temperature inside the reaction vessel was heated to 40°C. A nickel-containing metal aqueous solution was prepared by mixing nickel sulfate aqueous solution, cobalt sulfate aqueous solution, and manganese sulfate aqueous solution in a molar ratio of nickel:cobalt:manganese of 92:3:5. Next, the metal-containing aqueous solution, along with ammonium sulfate aqueous solution and sodium hydroxide aqueous solution as complexing agents, 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 11.6 relative to the liquid temperature of 40°C. After 0.5 hours from the start of the reaction, the pH inside the vessel was changed to 11.0 relative to the liquid temperature of 40°C and maintained there until the reaction was completed. The slurry containing the generated nickel-containing hydroxide particles was introduced into a concentration tank by overflowing it through the overflow pipe of the reaction vessel. In the concentration tank, the nickel-containing hydroxide particles were separated into solid and liquid phases, and the supernatant liquid was discharged to concentrate the slurry. The concentrated slurry was then returned to the reaction vessel. The ratio (flow rate X / flow rate Y) of the flow rate of the metal-containing aqueous solution added dropwise to the reaction vessel (flow rate X) to the flow rate of the concentrated slurry returned to the reaction vessel (flow rate Y) was adjusted to 0.009. The rate of increase in slurry concentration in the reaction vessel was 6.96 g / (L·h). 67 hours after the start of the reaction, the addition of each liquid was stopped, and the reaction was terminated. After the reaction was complete, 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 removed slurry containing the 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 the positive electrode active material) of Example 1.

[0051] (Example 2) After filling a reaction vessel equipped with a rotary stirring device having a stirring blade and an overflow pipe with water, the temperature inside the reaction vessel was heated to 60°C. A nickel-containing metal aqueous solution was prepared by mixing nickel sulfate aqueous solution, cobalt sulfate aqueous solution, and manganese sulfate aqueous solution in a molar ratio of nickel:cobalt:manganese of 60:20:20. Next, the metal-containing aqueous solution, along with ammonium sulfate aqueous solution and sodium hydroxide aqueous solution as complexing agents, 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 11.9 relative to a liquid temperature of 40°C. Two hours after the start of the reaction, the pH inside the vessel was changed to 10.6 relative to a liquid temperature of 40°C and maintained there until the reaction was completed. The slurry containing the generated nickel-containing hydroxide particles flows out of the overflow pipe of the reaction vessel. The slurry was introduced into a concentration tank by overflowing. In the concentration tank, nickel-containing hydroxide particles were separated into solid and liquid phases, and the supernatant liquid was discharged to concentrate the slurry. The concentrated slurry was then returned to the reaction tank. The ratio (flow rate X / flow rate Y) of the flow rate of the metal-containing aqueous solution added dropwise to the reaction vessel (flow rate X) to the flow rate of the concentrated slurry returned to the reaction vessel (flow rate Y) was adjusted to 0.367. The rate of increase in slurry concentration in the reaction vessel was 6.15 g / (L·h). The addition of each liquid was stopped 45 hours after the start of the reaction, and the reaction was terminated. The subsequent steps were carried out in the same manner as in Example 1 to obtain the nickel-containing hydroxide (precursor for the positive electrode active material) of Example 2.

[0052] (Comparative Example 1) After filling a reaction vessel equipped with a rotary stirring device having a stirring blade and an overflow pipe with water, 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 85:10:5. Next, the metal-containing aqueous solution, along with ammonium sulfate aqueous solution and sodium hydroxide aqueous solution as complexing agents, 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 12.1 based on a liquid temperature of 40°C. The slurry containing the generated nickel-containing hydroxide particles was removed from the reaction vessel by overflowing it through the overflow pipe. The removed slurry containing the 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 the positive electrode active material) of Comparative Example 1.

[0053] (Comparative Example 2) After filling a reaction vessel equipped with a rotary stirring device having a stirring blade and an overflow pipe with water, 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 in a molar ratio of nickel:cobalt:manganese of 94:4:2. Next, the metal-containing aqueous solution, along with ammonium sulfate aqueous solution and sodium hydroxide aqueous solution as complexing agents, 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 and pH of the reaction vessel at 11.6 based on a liquid temperature of 40°C. The subsequent steps were carried out in the same manner as in Comparative Example 1 to obtain the nickel-containing hydroxide (precursor for positive electrode active material) of Comparative Example 2.

[0054] (Comparative Example 3) After filling a reaction vessel equipped with a rotary stirring device having a stirring blade and an overflow pipe with water, 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 90:5:5. Next, the metal-containing aqueous solution, along with ammonium sulfate aqueous solution and sodium hydroxide aqueous solution as complexing agents, 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 and pH of the reaction vessel at 11.6 based on a liquid temperature of 40°C. The subsequent steps were carried out in the same manner as in Comparative Example 1 to obtain the nickel-containing hydroxide (precursor of the positive electrode active material) of Comparative Example 3.

[0055] (Comparative Example 4) A reaction vessel equipped with a rotary stirring device having a stirring blade and an overflow pipe is filled with water. Next, the temperature inside the reaction vessel was raised to 60°C. A nickel-containing metal aqueous solution was prepared by mixing nickel sulfate aqueous solution, cobalt sulfate aqueous solution, and manganese sulfate aqueous solution in a molar ratio of nickel:cobalt:manganese of 60:20:20. Next, the metal-containing aqueous solution, along with ammonium sulfate aqueous solution and sodium hydroxide aqueous solution as complexing agents, 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 and pH of the reaction vessel at 11.8 based on a liquid temperature of 40°C. The subsequent steps were carried out in the same manner as in Comparative Example 1 to obtain the nickel-containing hydroxide (precursor for positive electrode active material) of Comparative Example 4.

[0056] The precursors of the examples and comparative examples, and the positive electrode active materials obtained therefrom, were evaluated as follows.

[0057] (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.).

[0058] (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, the particle size at the point where the cumulative volume from the smallest particle side reached 10% was defined as D10 (μm), the particle size at the point where it reached 50% was defined as D50 (μm), and the particle size at the point where it reached 90% was defined as D90 (μm).

[0059] (3) The average particle diameter (PS1) of the primary particles and the coefficient of variation (CV) of that particle diameter. For each of the nickel-containing hydroxide particles in the examples and comparative examples, secondary particle images were obtained by SEM observation at a magnification of 20,000x. In the obtained SEM images, the length of the line segment connecting the two intersection points of the perpendicular bisector of the major axis of the figure enclosed by the outer edge of the secondary particles and the perpendicular bisector was defined as A. The measurement range was defined as the area enclosed by a virtual circle centered at the midpoint of the line segment and with radius r calculated by the following formula. r = A × 3 / 8 For all primary particles whose entire length was included in the aforementioned virtual circle and which were visible in the SEM image, the major axis (dimension of the longest axis) was measured. However, for primary particles whose portions were partially hidden by other primary particles, the length of the area observed in the SEM image was measured. The image processing software "ImageJ" was used for image analysis. The numerical average of all the major axes measured in this way was taken as the average particle diameter (PS1) of the primary particles. The coefficient of variation (CV) of the particle diameter of the primary particles was taken as the value obtained by dividing the standard deviation (σ) of the particle diameter of the primary particles by the numerical average.

[0060] (4) D50 / PS1 The D50 of the secondary particles obtained in (2) above was divided by the average particle diameter (PS1) of the primary particles obtained in (3) above to obtain the value of D50 / PS1.

[0061] (5) Tap density (TD) Tap density was measured using a tap denser (Seishin Co., Ltd., KYT-4000) by constant mass measurement. The measurement conditions for tap density were as follows: cell volume: 20 ml, stroke length: 10 mm, number of taps: 200.

[0062] (6) Discharge rate characteristics • Manufacturing of positive electrode active material To the nickel-containing hydroxides of the examples and comparative examples, lithium hydroxide powder was added and mixed so that the molar ratio of Li / (Ni+Co+Mn) was 1.01, respectively, to obtain a mixture of nickel-containing hydroxide and lithium hydroxide. The obtained mixtures were subjected to calcination treatment to obtain a lithium metal composite oxide, which was used as the positive electrode active material. The calcination conditions were an oxygen atmosphere, a heating rate of 120°C / h, a calcination temperature of 750°C, and a calcination time of 10 hours.

[0063] • Manufacturing of positive electrodes A positive electrode was fabricated using the positive electrode active material obtained as described above, and an evaluation battery was assembled using the fabricated positive electrode. Specifically, the obtained positive electrode active material, a conductive additive (acetylene black), and a binder (PVdF) were mixed in a weight ratio of 92:5:3, the resulting mixture was applied to a positive electrode current collector (aluminum foil), dried, and pressed to fix it to the positive electrode current collector, thus forming the positive electrode.

[0064] • Manufacturing of lithium-ion rechargeable batteries A lithium secondary battery was fabricated using the positive electrode obtained as described above, a negative electrode (metallic lithium), an electrolyte solution containing an electrolyte (LiPF6) (a mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 30:35:35), and a separator (made of polypropylene).

[0065] • Discharge rate test The discharge rate characteristics were evaluated using the fabricated lithium secondary battery under the following conditions. Test temperature: 25℃ Maximum charging voltage 4.3V, charging current 1CA, constant current constant voltage charging Minimum discharge voltage 2.5V, discharge current 0.5CA, 1CA, or 5CA, constant current discharge. The discharge capacity (0.5C) at 0.5CA was used as an indicator for evaluating the discharge rate characteristics. A discharge capacity of 183mAh / g or higher at 0.5C was considered good. Furthermore, the discharge capacity obtained by constant current discharge at 1CA and the discharge capacity obtained by constant current discharge at 5CA, and calculated using the following formula (5C / 1C), were also used as an indicator of the discharge rate characteristics. Discharge capacity at 5CA / Discharge capacity at 1CA ... (Formula) For 5C / 1C, a value of 0.55 or higher was considered good.

[0066] The evaluation results are shown in Table 1.

[0067] [Table 1]

[0068] In Examples 1 and 2, the precursor was produced by a method comprising a concentration step in which the slurry was concentrated in a concentration tank, and a return step in which the concentrated slurry was returned to the reaction tank. Comparative Examples 1-4 Next, precursors were produced by a method that did not involve such a process. The precursors obtained in Examples 1 and 2 had a coefficient of variation (CV) of primary particle size of 0.50 or less, and a secondary particle D50 / primary particle PS1 of 15.00 or less. This means that the primary particle sizes of the precursors obtained in Examples 1 and 2 were uniform, and the primary particle size was large relative to the secondary particle size. Secondary batteries equipped with positive electrode active material obtained from such precursors had superior discharge rate characteristics compared to secondary batteries equipped with positive electrode active material obtained from the precursors of the comparative examples. In particular, secondary batteries equipped with positive electrode active material obtained from the precursors of the examples achieved high values ​​at both 5C / 1C and 0.5C. [Industrial applicability]

[0069] The secondary battery using the precursor and 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 the positive electrode active material of a non-aqueous electrolyte secondary battery, It contains secondary particles formed by the aggregation of multiple primary particles, It contains 50 mol% or more nickel atoms relative to the total amount of metal atoms contained, The coefficient of variation (CV) of the particle size of the primary particles is 0.50 or less. A precursor wherein the ratio of D50 / PS1 to the average particle diameter (PS1) of the primary particles and the particle diameter (D50) of the secondary particles at which the cumulative volume percentage is 50% is 15.00 or less.

2. The precursor according to claim 1, wherein (D90 - D10) / D50 is 1.0 or less for particle sizes (D10) where the cumulative volume percentage of the secondary particles is 10 vol%, particle sizes (D50) where the cumulative volume percentage of the secondary particles is 50 vol%, and particle sizes (D90) where the cumulative volume percentage of the secondary particles is 90 vol%.

3. The precursor according to claim 1 or 2, 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 Formula (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.)

4. The precursor according to claim 1 or 2, wherein D50 is 1 μm or more and 15 μm or less.

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.

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