Metal composite hydroxides and methods for producing the same, as well as positive electrode active materials for non-aqueous electrolyte secondary batteries

Abstract

To provide a precursor for a positive electrode active material of a non-aqueous electrolyte secondary battery, in which variations in moisture content due to storage are improved, and a positive electrode active material using the same. [Solution] A metal composite hydroxide containing nickel and cobalt, which is a precursor for the positive electrode active material of a non-aqueous electrolyte secondary battery, wherein the drying rate DTG2 at 40°C when the water content of the metal composite hydroxide is 2% by mass is equal to the drying rate DTG at 40°C when the water content is 15% by mass. 15 Hydroxides that make up 70.0% or less of the total.

Description

[Technical Field]

[0001] This invention relates to metal composite hydroxides, methods for producing the same, and positive electrode active materials for non-aqueous electrolyte secondary batteries. [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] A positive electrode active material for a non-aqueous electrolyte secondary battery is known to contain nickel and cobalt. For example, Patent Document 1 discloses a positive electrode active material for a secondary battery which is a lithium composite transition metal oxide containing nickel and cobalt, and one or more elements selected from the group consisting of manganese and aluminum, wherein the nickel content of the total transition metal is 60 mol% or more, the lithium composite transition metal oxide is doped with one or more doping elements, and the weight loss rate at 600°C during thermogravimetric analysis (TGA) is 1.0% or less, and the weight loss rate at 900°C is 2.0% or less. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special Publication No. 2020-537298 [Overview of the project] [Problems that the invention aims to solve]

[0005] A precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery may be stored for a certain period of time before being mixed with a lithium compound and fired. During storage, the amount of moisture contained in the precursor may change, and variations in the moisture content of the precursor lead to deterioration in yield. Additionally, it may also affect the quality of the obtained positive electrode active material. The present invention relates to a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery in which variation in moisture content due to storage is improved, and to providing a positive electrode active material using the same. [Means for Solving the Problem]

[0006] The present invention provides, for example, a metal composite hydroxide containing nickel and cobalt that is a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the drying rate DTG2 at 40°C when the moisture content of the metal composite hydroxide is 2% by mass is the drying rate DTG at 40°C when the moisture content of the metal composite hydroxide is 15% by mass 15 of 70.0% or less, relating to the metal composite hydroxide.

[0007] The present invention also relates to a method for producing a metal composite hydroxide containing nickel and cobalt that is a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, the method comprising a reaction step of supplying a metal-containing aqueous solution containing nickel and cobalt, a complexing agent that is an ammonium ion supplier, and an alkaline aqueous solution to a reaction tank and causing a crystallization reaction to obtain a hydroxide, wherein in the reaction step, a value obtained by dividing a cobalt concentration (g / L) in the metal-containing aqueous solution supplied to the reaction tank by an ammonium ion concentration (g / L) in the reaction tank is adjusted to be 0.01 or more and 5.0 or less. [Effect 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 variation in moisture content due to storage is improved, and a positive electrode active material using the precursor. [Mode for Carrying Out the Invention]

[0009] Exemplary aspects of the present invention are listed below. [1] A metal composite hydroxide containing nickel and cobalt, which is a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein a drying rate DTG2 at 40°C when the moisture content of the metal composite hydroxide is 2% by mass is the drying rate DTG at 40°C when the moisture content of the metal composite hydroxide is 15% by mass 15 of 70.0% or less, a metal composite hydroxide. [2] The metal composite hydroxide according to [1], wherein a drying rate DTG4 at 40°C when the moisture content of the metal composite hydroxide is 4% by mass is 96.3% or less of the drying rate DTG at 40°C when the moisture content of the metal composite hydroxide is 15% by mass 15 . [3] The metal composite hydroxide according to [1] or [2], wherein a drying rate DTG6 at 40°C when the moisture content of the metal composite hydroxide is 6% by mass is 98.0% or less of the drying rate DTG at 40°C when the moisture content of the metal composite hydroxide is 15% by mass 15 . [4] The metal composite hydroxide according to any one of [1] to [3], which has a BET specific surface area of 5 m 2 / g or more and 55 m 2 / g or less. [5] The metal composite hydroxide according to any one of [1] to [4], which contains 60 mol% or more of nickel atoms based on the total amount of metal atoms contained therein. [6] The metal composite hydroxide according to any one of [1] to [5], which contains nickel (Ni), cobalt (Co), and optionally one or more additive elements (M) selected from the group consisting of Mn, Al, Fe, Ti, Mg, Ca, Sr, Ba, V, Nb, Cr, Mo, W, Ru, Cu, Zn, B, Ga, Si, Sn, P, Bi, and Zr, wherein the molar ratio of Ni:Co:M is 1-x-y:x:y (0 < x ≤ 0.2, 0 ≤ y ≤ 0.2). [7] A positive electrode active material for a non-aqueous electrolyte secondary battery, which is a fired product of the metal composite hydroxide according to any one of [1] to [6] and a lithium compound. [8] A method for producing a nickel- and cobalt-containing metal composite hydroxide that is a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising a reaction step of supplying a metal-containing aqueous solution containing nickel and cobalt, a complexing agent that is an ammonium ion supplier, and an alkaline aqueous solution to a reaction tank and causing a crystallization reaction to obtain a hydroxide, wherein in the reaction step, a value obtained by dividing a cobalt concentration (g / L) in the metal-containing aqueous solution supplied to the reaction tank by an ammonium ion concentration (g / L) in the reaction tank is adjusted to be 0.01 or more and 5.0 or less. [9] A drying rate DTG2 of the metal composite hydroxide at 40°C when a moisture content is 2% by mass is the drying rate DTG at 40°C when a moisture content is 15% by mass 15 of 70.0% or less. The production method according to [8].

[0010] [Metal composite hydroxide] Hereinafter, the metal composite hydroxide that is a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery will be described in detail. The metal composite hydroxide of the present invention contains nickel and cobalt, and a drying rate DTG2 of the metal composite hydroxide at 40°C when a moisture content is 2% by mass is the drying rate DTG at 40°C when a moisture content is 15% by mass 15 of 70.0% or less.

[0011] In the metal composite hydroxide of the present invention, a drying rate DTG2 at 40°C when the moisture content is 2% by mass (hereinafter also referred to as "DTG2") is the drying rate DTG at 40°C when the moisture content is 15% by mass 15 (hereinafter also referred to as "DTG 15 ") is preferably 60% or less, more preferably 50% or less, still more preferably 40% or less, and particularly preferably 30% or less. The smaller DTG2 is relative to DTG 15 , the more easily the adsorption of atmospheric moisture during storage of the metal composite hydroxide is suppressed. The lower limit of DTG2 is not particularly limited, and for example, it may be 1% or more, 5% or more, or 10% or more of DTG 15 .

[0012] The metal composite hydroxide of the present invention has a drying rate DTG4 (hereinafter also referred to as "DTG4") at 40°C when the water content is 4% by mass, which is DTG 15 It is preferable that it be 90% or less, more preferably 80% or less, even more preferably 70% or less, and particularly preferably 60% or less. DTG4 is DTG 15 The smaller the value relative to DTG4, the more likely it is that the adsorption of moisture from the atmosphere during storage of metal composite hydroxides will be suppressed for a longer period of time. The lower limit of DTG4 is not particularly limited, but for example, DTG 15 It may be 10% or more, 20% or more, or 30% or more.

[0013] The metal composite hydroxide of the present invention has a drying rate DTG6 (hereinafter also referred to as "DTG6") at 40°C when the water content is 6% by mass, which is DTG 15 It is preferable that it be 95% or less, more preferably 85% or less, even more preferably 80% or less, and particularly preferably 75% or less. DTG6 is DTG 15 The smaller the value relative to DTG6, the more likely it is that the adsorption of moisture from the atmosphere during storage of metal composite hydroxides will be suppressed for an even longer period. The lower limit of DTG6 is not particularly limited, but for example, DTG 15 It may be 10% or more, 20% or more, or 30% or more.

[0014] In one preferred embodiment, the metal composite hydroxide is such that DTG2 is DTG 15 It is less than 60% of and DTG4 is DTG 15 It is less than 90% of and DTG6 is DTG 15 It is 95% or less of the above. In a more preferred embodiment, the metal composite hydroxide is such that DTG2 is DTG 15 It is less than 50% of and DTG4 is DTG 15 It is less than 80% of and DTG6 is DTG 15 It is 85% or less of the above. In a more preferred embodiment, the metal composite hydroxide is such that DTG2 is DTG 15It is less than 40% of and DTG4 is DTG 15 It is 70% or less, and DTG6 is DTG 15 It is 80% or less of the above. In one particularly preferred embodiment, the metal composite hydroxide is such that DTG2 is DTG 15 It is less than 30% of and DTG4 is DTG 15 It is less than 60% of and DTG6 is DTG 15 It is less than 75% of that.

[0015] In the present invention, the water content and DTG2, DTG4, DTG6, and DTG 15 It shall be measured by the following method. • Method for measuring moisture content and drying speed A differential thermal-thermogravimetric (TG-DTA) analyzer is used as the apparatus. The gas flow rate (dry air) is set to 200 mL / min. A sample consisting of 10 mg of metal composite hydroxide, pre-dried in a shelf dryer at 100°C for 1 hour, and 10 mg of distilled water is added and placed in the measurement pan. The apparatus is programmed to start at a temperature of 30°C and to increase the temperature from the start to 40°C at a rate of 15°C / min, and drying is performed for 40 minutes from the start of heating (Period 1). During Period 1, the weight TG (μg) of the sample is measured, and the derivative with respect to time is taken as DTG (μg / min). After the end of Period 1, the temperature is increased to 110°C at a rate of 10°C / min, and an additional 40 minutes of drying is performed from the start of this heating (Period 2). The sample at the end of Period 2 is defined as being completely dry (0% moisture content). The moisture content at each time point is calculated using the formula {1 - (weight of sample in completely dry state / weight of sample at each time point in period 1)} × 100. From the DTG at the time points when the moisture content is 2 mass%, 4 mass%, 6 mass%, and 15 mass%, DTG2, DTG4, DTG6, and DTG 15 Calculate.

[0016] The metal composite hydroxide of the present invention preferably contains 60 mol% or more of nickel atoms, more preferably 70 mol% or more, even more preferably 75 mol% or more, and particularly preferably 80 mol% or more, based on the total amount of contained metal atoms. A higher content of nickel atoms in the metal composite hydroxide tends to be more advantageous in terms of initial charge-discharge efficiency, cycle characteristics, etc., and also facilitates reduction of raw material costs. Further, the content of nickel atoms in the metal composite hydroxide of the present invention is, for example, preferably less than 100 mol%, more preferably 98 mol% or less, even more preferably 97 mol% or less, and particularly preferably 96 mol% or less, based on the total amount of contained metal atoms. The lower limit and upper limit of the content of nickel atoms in the metal composite hydroxide of the present invention can be arbitrarily combined within the disclosed ranges. For example, the content of nickel atoms in the metal composite hydroxide of the present invention is preferably 60 mol% or more and less than 100 mol%, more preferably 70 mol% or more and 98 mol% or less, even more preferably 75 mol% or more and 97 mol% or less, and particularly preferably 80 mol% or more and 96 mol% or less, based on the total amount of contained metal atoms.

[0017] The metal composite hydroxide of the present invention contains nickel (Ni), cobalt (Co), and optionally one or more additive elements (M) selected from the group consisting of Mn, Al, Fe, Ti, Mg, Ca, Sr, Ba, V, Nb, Cr, Mo, W, Ru, Cu, Zn, B, Ga, Si, Sn, P, Bi, and Zr, and it is preferable that the molar ratio of Ni:Co:M is 1-x-y:x:y, where 0<x≤0.2 and 0≤y≤0.2. In particular, the metal composite hydroxide of the present invention preferably contains, as the additive element (M), one or more selected from the group consisting of Mn, Al, and Mg, and more preferably contains one or more selected from the group consisting of Mn and Al.

[0018] It is preferable that x is 0.01 ≤ x ≤ 0.15, more preferably 0.015 ≤ x ≤ 0.1, even more preferably 0.02 ≤ x ≤ 0.08, and particularly preferably 0.03 ≤ x ≤ 0.06. It is preferable that y is 0 ≤ y ≤ 0.15, more preferably 0 ≤ y ≤ 0.1, even more preferably 0 ≤ y ≤ 0.08, and particularly preferably 0 ≤ y ≤ 0.06.

[0019] The metal composite hydroxide of the present invention may contain secondary particles formed by the aggregation of multiple primary particles. The particle shape of the metal composite hydroxide of the present invention is not particularly limited and may be of a wide variety of shapes. Examples of primary particle shapes include needle-shaped, plate-shaped, columnar, etc. Examples of secondary particle shapes include approximately spherical, approximately elliptical, etc.

[0020] In the metal composite hydroxide 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 metal composite hydroxide of the present invention, the D50 of the secondary particles is preferably 3.0 μm or larger, more preferably 6.0 μm or larger, and even more preferably 10.0 μm or larger, from the viewpoint of improving the packing density of the positive electrode active material into the positive electrode. In the metal composite hydroxide of the present invention, the D50 of the secondary particles is preferably 20.0 μm or smaller, more preferably 18.0 μm or smaller, and even more preferably 15.0 μm or smaller, from the viewpoint of improving contactability with the electrolyte. The upper and lower limits of the D50 of the secondary particles in the metal composite hydroxide of the present invention can be arbitrarily combined within the disclosed range. For example, the D50 of the secondary particles in the metal composite hydroxide of the present invention is preferably 3.0 μm to 20.0 μm, more preferably 6.0 μm to 18.0 μm, and even more preferably 10.0 μm to 15.0 μm. Note that D50 is measured using a particle size distribution analyzer with laser diffraction / scattering method.

[0021] In the metal composite hydroxide of the present invention, the ratio (D90-D10) / D50 is preferably 1.2 or less, more preferably 0.9 or less, and even more preferably 0.5 or less, for the secondary particle D50, the particle size at which the cumulative volume percentage of the secondary particle is 10 vol% (D10), and the particle size at which the cumulative volume percentage of the secondary particle is 90 vol% (D90). Furthermore, (D90-D10) / D50 is preferably 0.2 or more, more preferably 0.3 or more, and even more preferably 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 0.2 or more and 1.2 or less, more preferably 0.3 or more and 0.9 or less, and even more preferably 0.4 or more and 0.5 or less. Note that D10 and D90 were measured using the laser diffraction / scattering method and a particle size distribution analyzer, similar to D50.

[0022] The BET specific surface area of ​​the metal composite hydroxide of the present invention is not particularly limited. For example, the BET specific surface area of ​​the metal composite hydroxide of the present invention is 5m, from the standpoint of improving the packing degree of the positive electrode active material into the positive electrode and the contact area with the non-aqueous electrolyte. 2 It is preferable that it is 10m or more per gram. 2 It is more preferable that it be 15m or more per gram. 2 It is even more preferable that the BET specific surface area of ​​the metal composite hydroxide of the present invention is 55 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 50m 2 It is more preferable that it be less than or equal to / g, 45m 2 It is even more preferable that the amount 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 metal composite hydroxide of the present invention is 5m². 2 / g or more 55m 2 It is preferable that the amount be less than or equal to / g, and 10m 2 / g or more 50m 2 It is more preferable that it be less than or equal to / g, 15m 2 / g or more 45m 2It is even more preferable that the amount be less than or equal to / g.

[0023] The tap density of the metal composite hydroxide of the present invention is not particularly limited. For example, from the viewpoint of improving the packing of the positive electrode active material into the positive electrode, the tap density of the metal composite hydroxide of the present invention is preferably 1.3 g / mL or more, and more preferably 1.5 g / mL or more. Also, from the viewpoint of improving the contact between the positive electrode active material and the non-aqueous electrolyte, the tap density of the metal composite hydroxide of the present invention may be 2.3 g / mL or less, or 2.2 g / mL or less. The lower and upper limits of the tap density can be arbitrarily combined within the disclosed range. For example, the tap density of the metal composite hydroxide of the present invention is preferably 1.3 g / mL or more and 2.3 g / mL or less, and more preferably 1.5 g / mL or more and 2.2 g / mL or less.

[0024] The reason why the present invention provides a precursor for the positive electrode active material of a non-aqueous electrolyte secondary battery with improved moisture content variation during storage is not entirely clear, but DTG2 is DTG 15 Metal composite hydroxides that are sufficiently small relative to the specific surface area (BET) may have a structure (such as pore size and quantity) that causes extremely low water adsorption and desorption rates in regions with low water content due to a combination of phenomena including capillary action for water movement to the particle surface, descent of water into the particle interior at the evaporation surface, and diffusion and evaporation of water within the pore space. Therefore, it is thought that variations in water content during storage are not simply affected by the size of the BET specific surface area, but are also influenced by the balance of various parameters such as pore size and arrangement.

[0025] [Method for producing metal composite hydroxides] Next, the method for producing the metal composite hydroxide of the present invention will be described. The metal composite hydroxide of the present invention can be produced by a method that includes a reaction step of supplying a metal-containing aqueous solution containing nickel and cobalt, a complexing agent which is an ammonium ion supplier, and an alkaline aqueous solution to a reaction vessel and causing a crystallization reaction to obtain a hydroxide.

[0026] In the reaction process, a metal-containing aqueous solution containing nickel and cobalt, a complexing agent, and an alkaline aqueous solution are added to the reaction vessel and mixed, and a coprecipitation reaction is carried out in the reaction solution to obtain hydroxide.

[0027] Specifically, by coprecipitation, a metal salt solution (hereinafter sometimes simply referred to as "metal-containing aqueous solution") containing nickel salt (e.g., sulfate), cobalt salt (e.g., sulfate), and a salt of an arbitrary 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 hydroxide. For example, water is used as the solvent for the suspension.

[0028] The complexing agent is capable of forming complexes with nickel, cobalt, and an additive element (M) in aqueous solution. In the present invention, an ammonium ion supplier is used as the complexing agent. Examples of ammonium ion suppliers include ammonium sulfate, ammonium chloride, ammonium carbonate, and ammonium fluoride.

[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, cobalt, and additive element (M) undergo a crystallization reaction to produce a metal composite hydroxide. During the crystallization reaction, the temperature inside the reaction vessel is controlled, for example, to 45°C or higher and 75°C or lower, preferably to 60°C or higher and 70°C or lower, and the pH value inside the reaction vessel is controlled, for example, to pH 10.0 or higher and 13.0 or lower, preferably to pH 10.3 or higher and 12.0 or lower, based on the liquid temperature of 40°C, while the substances inside the reaction vessel are stirred as appropriate.

[0031] The metal composite hydroxide of the present invention controls the cobalt concentration (g / L) in the metal-containing aqueous solution supplied to the reaction vessel, and the ammonium ion concentration (NH4) in the reaction vessel.+ It can be manufactured by carrying out the reaction process while maintaining the value obtained by dividing the concentration (g / L) of ) between 0.01 and 5.0, preferably between 0.02 and 4.0, more preferably between 0.03 and 3.5, even more preferably between 0.04 and 3.0, and particularly preferably between 0.05 and 2.0.

[0032] If the reaction process is continuous, the prepared hydroxide is continuously discharged from the reaction vessel by overflowing it through the overflow pipe. If it is a batch process, the reaction is stopped after a predetermined time, and the entire amount of metal composite compound in the reaction vessel is discharged from the system using a pump or the like.

[0033] In the reaction process, in the case of a continuous reaction, a portion of the slurry containing the obtained hydroxide is discharged from the reaction vessel by overflow. In the case of a batch reaction, a portion of the slurry containing the obtained hydroxide 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 the metal complex 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, in the reaction vessel, the reaction process is carried out while both the unreacted metal-containing aqueous solution and the slurry returned in the return process are supplied together. The slurry concentration (metal complex 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. After the reaction is complete, the hydroxide can be withdrawn from the reaction vessel using a pump or similar device, and the entire amount can be removed.

[0034] The slurry containing hydroxide obtained in this way can be filtered, 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 hydroxide. If necessary, the solid phase containing hydroxide may be dried to obtain hydroxide powder. If necessary, the solid phase may be washed with water or the like before drying. If necessary, the solid phase may be dried and the obtained hydroxide powder may be put back into the reaction vessel and used as seed crystal particles for batch reactions. The hydroxide obtained in this way may be further oxidized to an oxide. One method for obtaining an oxide from hydroxide is to perform an oxidation treatment in which the hydroxide is calcined at a temperature of 300°C to 800°C for 1 to 10 hours in an atmosphere in which oxygen gas is present.

[0035] [Cathode active material] Next, we will describe 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 metal composite hydroxide of the present invention and a lithium compound. The positive electrode active material of the present invention is obtained by calcining the metal composite hydroxide of the present invention with a lithium compound. By calcining the metal composite hydroxide of the present invention with a lithium compound, a positive electrode active material with stable quality can be obtained.

[0036] 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.

[0037] Next, the method for producing the positive electrode active material of the present invention will be described. For example, the method for producing the positive electrode active material of the present invention first involves adding a lithium compound to the metal composite hydroxide of the present invention or an oxide obtained by oxidizing it, in order to prepare a mixture. The lithium compound is not particularly limited as long as it is a compound containing lithium, and examples include lithium carbonate, lithium hydroxide, and the like.

[0038] When preparing the mixture, for example, the lithium compound and the precursor of the present invention may be mixed so that the molar ratio of lithium in the lithium compound to the total amount of metal atoms contained in the metal composite hydroxide of the present invention (total amount of nickel, cobalt, and additive elements) is within the range of 1.00 to 1.10.

[0039] 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.

[0040] [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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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 10Examples 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.

[0047] 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.

[0048] 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.

[0049] 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]

[0050] 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.

[0051] [Production of precursors (metal composite hydroxides)] (Example 1) Nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in a metal-containing aqueous solution with a nickel:cobalt:manganese molar ratio of 92:3:5. This solution, along with an aqueous solution of ammonium sulfate (complexing agent) and an aqueous solution of sodium hydroxide, were added dropwise to a reaction vessel of a predetermined volume. The reaction vessel was continuously stirred with a stirrer while maintaining the temperature at 70°C and the pH at 11.8 (based on a liquid temperature of 40°C). During the reaction, the cobalt concentration in the metal-containing aqueous solution added dropwise to the reaction vessel was controlled to 3.0 g / L, and the ammonium ion concentration in the reaction vessel was controlled to 1.0 g / L. The generated hydroxide was overflowed from the overflow pipe of the reaction vessel and introduced into a concentration tank. In the concentration tank, the generated hydroxide was separated into solid and liquid phases, and the supernatant was discharged to concentrate the hydroxide. The concentrated hydroxide was then returned to the reaction vessel. After 50 hours from the start of the reaction, the addition of each liquid was stopped, and the reaction was terminated. The particle size at that time (particle size at a cumulative volume percentage of 50% by volume (D50)) was 4 μm. After the reaction was completed, the hydroxide was withdrawn from the reaction vessel using a pump or the like, and the entire amount of hydroxide was subjected to washing with water, dehydration, and drying to obtain the metal composite hydroxide of Example 1.

[0052] (Example 2) Nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in a metal-containing aqueous solution with a nickel:cobalt:manganese molar ratio of 90:5:5. This solution, along with an aqueous solution of ammonium sulfate (complexing agent) and an aqueous solution of sodium hydroxide, was added dropwise to a reaction vessel of a predetermined volume. The mixture was continuously stirred with a stirrer while maintaining the temperature in the reaction vessel at 70°C and the pH at 11.5 relative to the liquid temperature of 40°C. 0.5 hours after the start of the reaction, the pH in the reaction vessel was changed to 10.5 relative to the liquid temperature of 40°C and maintained until the reaction was completed. During the reaction, the cobalt concentration in the metal-containing aqueous solution added dropwise to the reaction vessel was controlled to 5.0 g / L, and the ammonium ion concentration in the reaction vessel was controlled to 2.0 g / L. The generated hydroxide was overflowed from the overflow pipe of the reaction vessel and introduced into a concentration tank. In the concentration tank, the generated hydroxide was separated into solid and liquid phases, and the supernatant was discharged to concentrate the hydroxide. The concentrated hydroxide was then returned to the reaction vessel. Fifty hours after the start of the reaction, the addition of each liquid was stopped, and the reaction was terminated. The subsequent steps were carried out in the same manner as in Example 1 to obtain a metal composite hydroxide (Batch 1). A portion of the obtained metal composite hydroxide was returned to the reaction vessel along with warm water, and a metal-containing aqueous solution prepared by dissolving nickel sulfate, cobalt sulfate, and manganese sulfate in a nickel:cobalt:manganese molar ratio of 90:5:5, along with an aqueous solution of ammonium sulfate (complexing agent) and an aqueous solution of sodium hydroxide, was added dropwise to a reaction vessel of a predetermined volume. The reaction vessel was continuously stirred with a stirrer while maintaining the temperature at 70°C and the pH at 10.5 based on a liquid temperature of 40°C. The stirring power was set to a lower value than that used in the previously performed batch reaction. During the reaction, the cobalt concentration in the metal-containing aqueous solution added dropwise to the reaction vessel was controlled to 5.0 g / L, and the ammonium ion concentration in the reaction vessel was controlled to 2.0 g / L. The generated hydroxide was overflowed from the overflow pipe of the reaction vessel and introduced into a concentration tank. In the concentration tank, the generated hydroxide was separated into solid and liquid phases, and the supernatant was discharged to concentrate the hydroxide. The concentrated hydroxide was then returned to the reaction tank. Thirty hours after the start of the reaction, the input of each liquid was stopped, and the reaction was terminated. At that time, the particle size (particle size at which the cumulative volume percentage is 50% by volume (D50)) was 10 μm. The subsequent steps were carried out in the same manner as in Example 1 to obtain the metal composite hydroxide of Example 2 (Batch 2).

[0053] (Example 3) Nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in a metal-containing aqueous solution with a nickel:cobalt:manganese molar ratio of 90:5:5. This solution, along with an aqueous ammonium sulfate solution (complexing agent) and an aqueous sodium hydroxide solution, was added dropwise to a reaction vessel of a predetermined volume. The mixture was continuously stirred with a stirrer while maintaining the temperature in the reaction vessel at 70°C and the pH at 10.6 based on a liquid temperature of 40°C. During the reaction, the cobalt concentration in the metal-containing aqueous solution added dropwise to the reaction vessel was controlled to 5.0 g / L, and the ammonium ion concentration in the reaction vessel was controlled to 2.5 g / L. The generated hydroxide was discharged from the reaction vessel by overflowing it through the overflow pipe. The particle size at that time (particle size at a cumulative volume percentage of 50 vol% (D50)) was 13 μm. The subsequent steps were carried out in the same manner as in Example 1 to obtain the metal composite hydroxide of Example 3.

[0054] (Example 4) Nickel sulfate, cobalt sulfate, and aluminum sulfate were dissolved in a metal-containing aqueous solution with a nickel:cobalt:aluminum molar ratio of 94:4:2. This solution, along with an aqueous ammonium sulfate solution (complexing agent) and an aqueous sodium hydroxide solution, was added dropwise to a reaction vessel of a predetermined volume. The mixture was continuously stirred with a stirrer while maintaining the temperature in the reaction vessel at 50°C and the pH at 11.4 based on a liquid temperature of 40°C. During the reaction, the cobalt concentration in the metal-containing aqueous solution added dropwise to the reaction vessel was controlled to 4.5 g / L, and the ammonium ion concentration in the reaction vessel was controlled to 9.5 g / L. The generated hydroxide was discharged from the reaction vessel by overflowing it through the overflow pipe. The particle size at that time (particle size at a cumulative volume percentage of 50 vol% (D50)) was 11 μm. The subsequent steps were carried out in the same manner as in Example 1 to obtain the metal composite hydroxide of Example 4.

[0055] (Example 5) Nickel sulfate, cobalt sulfate, and magnesium sulfate were dissolved in a metal-containing aqueous solution with a nickel:cobalt:magnesium molar ratio of 95:2:3. This solution, along with an aqueous ammonium sulfate solution (complexing agent) and an aqueous sodium hydroxide solution, was added dropwise to a reaction vessel of a predetermined volume. The mixture was continuously stirred with a stirrer while maintaining the temperature in the reaction vessel at 48°C and the pH at 12.0 based on a liquid temperature of 40°C. During the reaction, the cobalt concentration in the metal-containing aqueous solution added dropwise to the reaction vessel was controlled to 1.9 g / L, and the ammonium ion concentration in the reaction vessel was controlled to 14.0 g / L. The generated hydroxide was discharged from the reaction vessel by overflowing it through the overflow pipe. The particle size at that time (particle size at a cumulative volume percentage of 50 vol% (D50)) was 10 μm. The subsequent steps were carried out in the same manner as in Example 1 to obtain the metal composite hydroxide of Example 5.

[0056] (Comparative Example 1) Nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in a metal-containing aqueous solution with a molar ratio of nickel:cobalt:manganese of 83:12:5. This solution, along with an aqueous solution of ammonium sulfate (complexing agent) and an aqueous solution of sodium hydroxide, was added dropwise to a reaction vessel of a predetermined volume. The mixture was continuously stirred with a stirrer while maintaining the temperature in the reaction vessel at 70°C and the pH at 11.2 based on a liquid temperature of 40°C. During the reaction, the cobalt concentration in the metal-containing aqueous solution added dropwise to the reaction vessel was controlled to 10.8 g / L, and the ammonium ion concentration in the reaction vessel was controlled to 2.1 g / L. The generated hydroxide was discharged from the reaction vessel by overflowing it through the overflow pipe. The particle size at that time (particle size at a cumulative volume percentage of 50 vol% (D50)) was 11 μm. The subsequent steps were carried out in the same manner as in Example 1 to obtain the metal composite hydroxide of Comparative Example 1.

[0057] The hydroxides in the examples and comparative examples were evaluated as follows.

[0058] (1) Compositional analysis of metal composite hydroxides Compositional analysis was performed by dissolving the obtained metal composite hydroxide in hydrochloric acid, followed by analysis using an inductively coupled plasma atomic emission spectrometer (Optima 8300, PerkinElmer Japan Co., Ltd.).

[0059] (2) Moisture content and drying rate Using a differential thermal-thermogravimetric analyzer (TG-DTA8122) manufactured by Rigaku Corporation, the drying rates DTG (DTG2, DTG4, DTG6, and DTG) at each water content were determined for the metal composite hydroxides obtained in each example and comparative example using the method described herein. 15 ) was calculated.

[0060] (3) Storage test 50 g of each metal composite hydroxide obtained in each example and comparative example was placed in an open polypropylene tube and stored for 20 hours in a constant temperature and humidity chamber (40°C, 85% humidity). The moisture content before and after storage was measured using an infrared moisture meter (FD-660, manufactured by Kett Scientific Research Institute Co., Ltd.).

[0061] (4) BET specific surface area One g of the metal composite hydroxide obtained in each example and comparative example was dried in a nitrogen atmosphere at 105°C for 30 minutes, and then measured by the single-point BET method using a specific surface area analyzer (Macsorb, manufactured by Mountec Co., Ltd.).

[0062] The evaluation results are shown in Tables 1 and 2.

[0063] [Table 1]

[0064] [Table 2]

[0065] In Examples 1-5, the reaction process was carried out so that the value obtained by dividing the cobalt concentration (g / L) in the metal-containing aqueous solution supplied to the reaction vessel by the ammonium ion concentration (g / L) in the reaction vessel was between 0.01 and 5.0. In Comparative Example 1, the reaction process was carried out so that this value was 5.1. The metal composite hydroxides obtained in Examples 1-5 were such that DTG2 was DTG 15 It was 70.0% or less. On the other hand, the metal composite hydroxide obtained in Comparative Example 1 had DTG2 as DTG 15 It was over 70.0%. By adjusting the cobalt concentration in the metal-containing aqueous solution and the ammonium ion concentration in the reaction vessel, cobalt, whose primary particle size changes greatly depending on the reaction conditions, crystallizes and accumulates appropriately, and DTG2 becomes DTG 15 We believe that the amount was 70.0% or less. In storage tests in high temperature and high humidity environments, the change in moisture content of the metal composite hydroxides obtained in Examples 1 to 5 was within an acceptable range. On the other hand, in storage tests in high temperature and high humidity environments, the moisture content of the metal composite hydroxide obtained in Comparative Example 1 changed significantly before and after storage. [Industrial applicability]

[0066] The secondary battery using the metal composite hydroxide 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 metal composite hydroxide containing nickel and cobalt, which is a precursor for the positive electrode active material of a non-aqueous electrolyte secondary battery, Drying rate DTG at 40°C when the water content of the metal composite hydroxide is 2% by mass. ２ However, the drying rate DTG at 40°C when the water content of the metal composite hydroxide is 15% by mass is １５ Metal composite hydroxides that are 70.0% or less of the total.

2. Drying rate DTG at 40°C when the water content of the metal composite hydroxide is 4% by mass. ４ However, the drying rate DTG at 40°C when the water content of the metal composite hydroxide is 15% by mass is １５ The metal composite hydroxide according to claim 1, wherein it is 96.3% or less of the above.

3. Drying rate DTG at 40°C when the water content of the metal composite hydroxide is 6% by mass. ６ However, the drying rate DTG at 40°C when the water content of the metal composite hydroxide is 15% by mass is １５ The metal composite hydroxide according to claim 1, wherein it is 98.0% or less of the above.

4. BET specific surface area is 5 m ２ / g or more 55m ２ A metal composite hydroxide according to any one of claims 1 to 3, wherein the amount is less than or equal to / g.

5. A metal composite hydroxide according to any one of claims 1 to 3, comprising 60 mol% or more of nickel atoms relative to the total amount of metal atoms contained.

6. Nickel (Ni) and Cobalt (Co) and, It optionally contains one or more additive elements (M) selected from the group consisting of Mn, Al, Fe, Ti, Mg, Ca, Sr, Ba, V, Nb, Cr, Mo, W, Ru, Cu, Zn, B, Ga, Si, Sn, P, Bi, and Zr, A metal composite hydroxide according to any one of claims 1 to 3, wherein the molar ratio of Ni:Co:M is 1-x-y:x:y (0 < x ≤ 0.2, 0 ≤ y ≤ 0.2).

7. A positive electrode active material for a non-aqueous electrolyte secondary battery, which is a calcined product of a metal composite hydroxide and a lithium compound as described in any one of claims 1 to 3.

8. A method for producing a metal composite hydroxide containing nickel and cobalt, which is a precursor for the positive electrode active material of a non-aqueous electrolyte secondary battery, The reaction includes a reaction step of supplying a metal-containing aqueous solution containing nickel and cobalt, a complexing agent which is an ammonium ion supplier, and an alkaline aqueous solution to a reaction vessel to carry out a crystallization reaction to obtain a hydroxide. A manufacturing method comprising the reaction step wherein the value obtained by dividing the cobalt concentration (g / L) in the metal-containing aqueous solution supplied to the reaction vessel by the ammonium ion concentration (g / L) in the reaction vessel is 0.01 or more and 5.0 or less.

9. The drying rate DTG at 40°C of said metal composite hydroxide when the water content is 2 mass% ２ is 70.0% or less of the drying rate DTG at 40°C when the water content is 15 mass% １５ according to claim 8.

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