Method for producing composite hydroxide and composite hydroxide

Abstract

The present invention provides a method for producing a composite hydroxide that contains nickel (Ni) and cobalt (Co), said method being capable of adequately controlling the BET specific surface area without deteriorating the tap density, while being also capable of reducing the production cost.　A method for producing a composite hydroxide that contains at least nickel (Ni) and cobalt (Co), wherein: a first metal-containing aqueous solution that contains A mol% of nickel (Ni) and B mol% of cobalt (Co), a second metal-containing aqueous solution that contains C mol% of nickel (Ni) and D mol% of cobalt (Co) (provided that A > C, B < D, (A + B) = 100 and (C + D) = 100), an aqueous alkali metal solution, and an aqueous solution containing an ammonium ion donor are separately supplied into a reaction tank; and the solution within the reaction tank is maintained so that the pH value thereof is within the range of from 10.0 to 13.0 as determined at a reference solution temperature of 25˚C and the ammonium ion concentration thereof is within the range of from 1.0 g / L to 10.0 g / L.

Description

Technical Field

[0001] The present invention relates to a method for producing a composite hydroxide containing nickel (Ni) and cobalt (Co), and more particularly to a method for producing a composite hydroxide capable of appropriately controlling the BET specific surface area while reducing the production cost of the composite hydroxide. The present invention also relates to a composite hydroxide containing nickel (Ni) and cobalt (Co), which homogenizes the reactivity between the composite hydroxide and a lithium compound by suppressing the change in the BET specific surface area due to the difference in particle size.

Background Art

[0002] In recent years, from the viewpoint of reducing environmental load, secondary batteries have been used in a wide range of fields such as power sources for portable devices and power sources for vehicles that use or combine electricity. Examples of secondary batteries include secondary batteries using non-aqueous electrolytes such as lithium-ion secondary batteries. Secondary batteries using non-aqueous electrolytes such as lithium-ion secondary batteries are suitable for miniaturization and weight reduction, and have battery characteristics such as high utilization rate, high cycle characteristics, and large charge-discharge capacity.

[0003] A composite hydroxide is used as a precursor for the positive electrode active material of non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries. As the composite hydroxide which is a precursor of the positive electrode active material, a composite hydroxide containing nickel (Ni) and cobalt (Co) may be used.

[0004] In addition, with the increasing sophistication of devices equipped with secondary batteries, further improvements in battery characteristics, such as higher capacity, are required. Therefore, a method for producing a composite hydroxide containing nickel (Ni) and cobalt (Co) has been studied to obtain a cathode active material that can impart even better battery characteristics. In the method for producing the composite hydroxide, it has been studied that excellent battery characteristics can be imparted by devising the method of adding the raw material solution. As the method for producing the composite hydroxide related to the method of adding the raw material solution, for example, an aqueous solution of a metal compound containing at least one element selected from Ni and Co or Mn, an aqueous solution of sodium aluminate, an aqueous solution of sodium hydroxide, and an aqueous solution containing an ammonium ion donor are individually and simultaneously supplied into the same reaction vessel and reacted (Patent Document 1).

[0005] In Patent Document 1, the particle shape of the composite hydroxide containing nickel (Ni) and cobalt (Co) becomes spherical, and the cathode active material obtained from the composite hydroxide can be densely loaded on the cathode, and a high-capacity cathode material with good safety such as thermal stability and charge-discharge cycle characteristics can be obtained.

[0006] On the other hand, since secondary batteries are used in a wide range of fields, it is also required to reduce the production cost of the composite hydroxide containing nickel (Ni) and cobalt (Co). Further, when the composite hydroxide containing nickel (Ni) and cobalt (Co) is used as a precursor of the cathode active material of a lithium-ion secondary battery, the composite hydroxide as the precursor may need to appropriately control the reactivity with lithium in order to impart excellent battery characteristics such as cycle characteristics and high capacity according to its use conditions and the like. The composite hydroxide as the precursor can appropriately control the reactivity with lithium by appropriately controlling the BET specific surface area. Further, regardless of the particle size of the composite hydroxide as the precursor, by equalizing the BET specific surface area and equalizing the reactivity between the composite hydroxide and lithium, the composite hydroxide can impart excellent battery characteristics such as cycle characteristics and high capacity.

[0007] However, in Patent Document 1, there was room for improvement in terms of reducing the production cost of the composite hydroxide and appropriately controlling the BET specific surface area. Also, in Patent Document 1, there was room for improvement in terms of equalizing the BET specific surface area regardless of the particle size of the composite hydroxide.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] In view of the above circumstances, an object of the present invention is to provide a method for producing a composite hydroxide containing nickel (Ni) and cobalt (Co) that can appropriately control the BET specific surface area without impairing the tap density and can reduce the production cost, and a composite hydroxide that can equalize the reactivity between the composite hydroxide and the metal compound and improve the battery characteristics by suppressing the change in the BET specific surface area due to the difference in particle size.

Means for Solving the Problems

[0010] In the present invention, as a raw material solution for a composite hydroxide containing nickel (Ni) and cobalt (Co), a first raw material solution mainly containing nickel (Ni) and a second raw material solution mainly containing cobalt (Co) among nickel (Ni) and cobalt (Co) are prepared, and the first raw material solution and the second raw material solution are separately added into a reaction tank to produce a composite hydroxide containing nickel (Ni) and cobalt (Co).

[0011] The gist of the configuration of the present invention is as follows. [1]A method for producing a composite hydroxide containing at least nickel (Ni) and cobalt (Co), comprising: a first metal-containing aqueous solution containing A mol% of nickel (Ni) and B mol% of cobalt (Co); a second metal-containing aqueous solution containing C mol% of nickel (Ni) and D mol% of cobalt (Co) (where A > C, B < D, A + B = 100, C + D = 100); an alkali metal aqueous solution; and an aqueous solution containing an ammonium ion donor, which are separately supplied to a reaction vessel, and maintaining the solution in the reaction vessel within a range where the pH value based on a liquid temperature of 25 °C is 10.0 or more and 13.0 or less, and the ammonium ion concentration is 1.0 g / L or more and 10.0 g / L or less. [2]The method for producing a composite hydroxide according to [1], wherein the ratio of A to C is 5 or more, and the ratio of D to B is 5 or more. [3]The method for producing a composite hydroxide according to [1] or [2], wherein the first metal-containing aqueous solution does not contain cobalt (Co), and the second metal-containing aqueous solution does not contain nickel (Ni). [4]The method for producing a composite hydroxide according to any one of [1] to [3], wherein the first metal-containing aqueous solution and the second metal-containing aqueous solution are simultaneously supplied to the reaction vessel. [5]The composite hydroxide is represented by Ni 1-x-y Co x M y O z (OH) 2-α (0 < x ≤ 0.3, 0 ≤ y ≤ 0.3, 0 ≤ z ≤ 3.00, -0.50 ≤ α < 2.00, and M represents one or more additive metal elements selected from the group consisting of Mn, Mg, Zr, Al, Ca, Ti, Nb, V, Cr, Mo, and W). The method for producing a composite hydroxide according to any one of [1] to [4]. [6]The method for producing a composite hydroxide according to any one of [1] to [5], wherein the first metal-containing aqueous solution is supplied to the reaction vessel from a first raw material liquid supply unit, and the second metal-containing aqueous solution is supplied to the reaction vessel from a second raw material liquid supply unit different from the first raw material liquid supply unit. [7]The method for producing a composite hydroxide according to any one of [1] to [6], wherein the reaction vessel is a continuous reaction vessel that overflows the produced composite hydroxide. [8] The method for producing a composite hydroxide according to any one of [1] to [7], wherein the ammonium ion concentration in the reaction tank is maintained in the range of 1.0 g / L or more and 5.0 g / L or less. [9] The method for producing a composite hydroxide according to any one of [1] to [8], wherein the reaction temperature in the reaction tank is 20°C or more and 80°C or less.

[10] The method for producing a composite hydroxide according to any one of [1] to [9], wherein the composite hydroxide is a precursor of a positive electrode active material of a secondary battery.

[11] A composite hydroxide containing at least nickel (Ni) and cobalt (Co), wherein the composite hydroxide has a first particle in the range of the secondary particle diameter (D10) ± 1.0 μm with a cumulative volume percentage of 10% by volume, a second particle in the range of the secondary particle diameter (D50) ± 1.0 μm with a cumulative volume percentage of 50% by volume, and a third particle in the range of the secondary particle diameter (D90) ± 1.0 μm with a cumulative volume percentage of 90% by volume, and the absolute value of the ratio of the change calculated by the following formula (1) from the BET specific surface area of the first particle and the secondary particle diameter (D50) with a cumulative volume percentage of 50% by volume and the BET specific surface area of the third particle and the secondary particle diameter (D50) with a cumulative volume percentage of 50% by volume, and the molar percentage of cobalt (Co) with respect to the metal elements (where the metal elements are Ni, Co, Mn, Mg, Zr, Al, Ca, Ti, Nb, V, Cr, Mo, and W) contained in the composite hydroxide, the product of which is 0 or more and 0.015 or less. |(BET specific surface area of the third particle - BET specific surface area of the first particle) / (D50 of the third particle - D50 of the first particle)| = absolute value of the ratio of change ··· formula (1)

[12] Ni 1-x-y Co x M y O z (OH) 2-α (0 < x + y < 0.20, 0 ≤ z ≤ 3.00, -0.50 ≤ α < 2.00, M represents one or more additive metal elements selected from the group consisting of Mn, Mg, Zr, Al, Ca, Ti, Nb, V, Cr, Mo, and W.) The composite hydroxide according to

[11] .

[13] The Ni 1-x-yCo x M y O z (OH) 2-α In the formula, the composite hydroxide described in

[12] where 0.02 < x < 0.20.

[14] The composite hydroxide according to any one of

[11] to

[13] , wherein the value of (D90 of the composite hydroxide - D10 of the composite hydroxide) / D50 of the composite hydroxide is 0.50 or more and 1.40 or less.

Advantages of the Invention

[0012] According to an aspect of the method for producing a composite hydroxide of the present invention, a first metal-containing aqueous solution containing nickel (Ni) at A mol% and cobalt (Co) at B mol% and a second metal-containing aqueous solution containing nickel (Ni) at C mol% and cobalt (Co) at D mol% (where A > C, B < D, A + B = 100, C + D = 100) are separately supplied to a reaction vessel, whereby a composite hydroxide with an appropriately controlled BET specific surface area can be produced while suppressing the reaction temperature and / or the ammonium ion concentration and without impairing the tap density. Thus, according to an aspect of the present invention, in the production of a composite hydroxide with an appropriately controlled BET specific surface area, the reaction temperature and / or the ammonium ion concentration can be suppressed, so that the production cost of the composite hydroxide can be reduced.

[0013] According to an aspect of the method for producing a composite hydroxide of the present invention, when the ratio of the nickel (Ni) content of the first metal-containing aqueous solution to the nickel (Ni) content of the second metal-containing aqueous solution is 5 or more, and the ratio of the cobalt (Co) content of the first metal-containing aqueous solution to the cobalt (Co) content of the second metal-containing aqueous solution is 5 or more, a composite hydroxide with a more appropriately controlled BET specific surface area can be produced without impairing the tap density even when the reaction temperature and / or the ammonium ion concentration are further suppressed.

[0014] According to an aspect of the method for producing a composite hydroxide of the present invention, since the first metal-containing aqueous solution does not contain cobalt (Co) and the second metal-containing aqueous solution does not contain nickel (Ni), even if the reaction temperature and / or the ammonium ion concentration are more suppressed, a composite hydroxide with a BET specific surface area more reliably and appropriately controlled without impairing the tap density can be produced.

[0015] According to an aspect of the method for producing a composite hydroxide of the present invention, the composite hydroxide is Ni 1-x-y Co x M y O z (OH) 2-α (0 < x ≤ 0.3, 0 ≤ y ≤ 0.3, 0 ≤ z ≤ 3.00, -0.50 ≤ α < 2.00, M represents one or more additive metal elements selected from the group consisting of Mn, Mg, Zr, Al, Ca, Ti, Nb, V, Cr, Mo, and W.) By being represented in this way, it can contribute to imparting high-capacity battery characteristics to a secondary battery using the obtained composite hydroxide as a precursor of a positive electrode active material.

[0016] According to an aspect of the method for producing a composite hydroxide of the present invention, since the reaction tank is a continuous reaction tank that overflows the produced composite hydroxide, the production efficiency of the composite hydroxide can be improved.

[0017] According to an aspect of the composite hydroxide of the present invention, the composite hydroxide has a first particle with a secondary particle diameter (D10) in the range of ±1.0 μm of the cumulative volume percentage of 10% by volume, a second particle with a secondary particle diameter (D50) in the range of ±1.0 μm of the cumulative volume percentage of 50% by volume, and a third particle with a secondary particle diameter (D90) in the range of ±1.0 μm of the cumulative volume percentage of 90% by volume. The absolute value of the rate of change calculated by the above formula (1) from the BET specific surface area in the first particle and the secondary particle diameter (D50) with a cumulative volume percentage of 50% by volume, the BET specific surface area in the third particle, and the secondary particle diameter (D50) with a cumulative volume percentage of 50% by volume, and the molar percentage of cobalt (Co) with respect to the metal elements (however, the metal elements are Ni, Co, Mn, Mg, Zr, Al, Ca, Ti, Nb, V, Cr, Mo, and W) contained in the composite hydroxide, the product of which is 0 or more and 0.015 or less, suppresses the change in the BET specific surface area due to the difference in particle diameter, thereby making the reactivity between the composite hydroxide and a metal compound such as a lithium compound uniform and improving the battery characteristics.

Brief Description of the Drawings

[0018]

Figure 1

Embodiments for Carrying Out the Invention

[0019] Next, the method for producing the composite hydroxide of the present invention will be described in detail. The method for producing the composite hydroxide of the present invention includes a first metal-containing aqueous solution containing nickel (Ni) at A mol% and cobalt (Co) at B mol%, and a second metal-containing aqueous solution containing nickel (Ni) at C mol% and cobalt (Co) at D mol% (however, A > C, B > D, A + B = 100, C + D = 100), an alkali metal aqueous solution, and an aqueous solution containing an ammonium ion donor are separately supplied to a reaction tank, and the solution in the reaction tank is maintained in a range where the pH value based on a liquid temperature of 25°C is 10.0 or more and 13.0 or less, and the ammonium ion concentration is 1.0 g / L or more and 10.0 g / L or less. In the present invention, a composite hydroxide containing nickel (Ni) and cobalt (Co) is produced.

[0020] In the present invention, a first metal-containing aqueous solution, which is a first raw material solution mainly containing nickel (Ni), and a second metal-containing aqueous solution, which is a second raw material solution mainly containing cobalt (Co), are respectively prepared, and the first metal-containing aqueous solution and the second metal-containing aqueous solution are added into a reaction tank through separate paths. When adding the first metal-containing aqueous solution and the second metal-containing aqueous solution into the reaction tank, the solution in the reaction tank is maintained in a range where the pH value based on a liquid temperature of 25°C is 10.0 or more and 13.0 or less, and the ammonium ion concentration is 1.0 g / L or more and 10.0 g / L or less.

[0021] In order to produce a composite hydroxide with an appropriately controlled BET specific surface area, it is necessary to increase the reaction temperature and the ammonium ion concentration in order to promote the particle growth of the composite hydroxide. On the other hand, in the present invention, by separately adding the first metal-containing aqueous solution and the second metal-containing aqueous solution into the reaction tank, a composite hydroxide with an appropriately controlled BET specific surface area can be produced while suppressing the reaction temperature and / or the ammonium ion concentration without impairing the tap density. Thus, when producing a composite hydroxide with an appropriately controlled BET specific surface area, the reaction temperature and / or the ammonium ion concentration can be suppressed, that is, the energy consumption can be reduced and the amount of ammonium ion used can be suppressed, so that the production cost of the composite hydroxide can be reduced.

[0022] <The first metal-containing aqueous solution and the second metal-containing aqueous solution> In the present invention, as raw material solutions, a plurality of raw material solutions with different components, that is, a first metal-containing aqueous solution and a second metal-containing aqueous solution, are prepared.

[0023] The first metal-containing aqueous solution is a metal-containing aqueous solution mainly containing nickel (Ni) among nickel (Ni) and cobalt (Co). The second metal-containing aqueous solution is a metal-containing aqueous solution mainly containing cobalt (Co) among nickel (Ni) and cobalt (Co). Therefore, the molar concentration (A mol%) of nickel (Ni) and the molar concentration (B mol%) of cobalt (Co) in the first metal-containing aqueous solution are different from the molar concentration (C mol%) of nickel (Ni) and the molar concentration (D mol%) of cobalt (Co) in the second metal-containing aqueous solution. Also, the molar concentration of nickel (Ni) has a relationship of A > C, and the molar concentration of cobalt (Co) has a relationship of B < D. Furthermore, it has a relationship of A + B = 100 and C + D = 100. Therefore, nickel (Ni) and cobalt (Co) are mainly supplied to the reaction tank in different raw material liquids.

[0024] Regarding the molar concentration of nickel (Ni), as long as the relationship of A > C is satisfied, the ratio of the molar concentration of nickel (Ni) in the first metal-containing aqueous solution to the molar concentration of nickel (Ni) in the second metal-containing aqueous solution is not particularly limited. From the viewpoint of producing a composite hydroxide in which the BET specific surface area is more appropriately controlled without impairing the tap density even when the reaction temperature and / or the ammonium ion concentration are further suppressed, the ratio of the molar concentration of nickel (Ni) in the first metal-containing aqueous solution to the molar concentration of nickel (Ni) in the second metal-containing aqueous solution is preferably 5 or more, more preferably 10 or more, and even more preferably 20 or more. From the viewpoint of producing a composite hydroxide in which the BET specific surface area is more reliably and appropriately controlled without impairing the tap density even when the reaction temperature and / or the ammonium ion concentration are further suppressed, it is particularly preferable that the second metal-containing aqueous solution does not contain nickel (Ni). That is, the lower the molar concentration of nickel (Ni) in the second metal-containing aqueous solution, the more preferable.

[0025] Regarding the molar concentration of cobalt (Co), if the relationship B < D is satisfied, the ratio of the molar concentration of cobalt (Co) in the first metal-containing aqueous solution to the molar concentration of cobalt (Co) in the second metal-containing aqueous solution is not particularly limited. From the viewpoint of producing a composite hydroxide in which the BET specific surface area is more appropriately controlled without impairing the tap density even when the reaction temperature and / or the ammonium ion concentration are further suppressed, the ratio of the molar concentration of cobalt (Co) in the second metal-containing aqueous solution to the molar concentration of cobalt (Co) in the first metal-containing aqueous solution is preferably 5 or more, more preferably 10 or more, and even more preferably 20 or more. From the viewpoint of producing a composite hydroxide in which the BET specific surface area is more surely and appropriately controlled without impairing the tap density even when the reaction temperature and / or the ammonium ion concentration are further suppressed, it is particularly preferable that the first metal-containing aqueous solution does not contain cobalt (Co). That is, the lower the molar concentration of cobalt (Co) in the first metal-containing aqueous solution, the more preferable.

[0026] From the above, it is particularly preferable that in the composite hydroxide containing nickel (Ni) and cobalt (Co) produced by the method of the present invention, nickel (Ni) and cobalt (Co) are derived from different raw material solutions.

[0027] The first metal-containing aqueous solution and the second metal-containing aqueous solution are, for example, supplied to the reaction tank simultaneously and individually. Therefore, since the supply of the first metal-containing aqueous solution to the reaction tank and the supply of the second metal-containing aqueous solution to the reaction tank are carried out in parallel, the supply of nickel (Ni) and cobalt (Co) to the reaction tank is carried out in parallel. Depending on the composition of nickel (Ni) and cobalt (Co) in the composite hydroxide and the residence time in the reaction tank, the molar concentration of nickel (Ni) in the first metal-containing aqueous solution, the molar concentration of cobalt (Co) in the second metal-containing aqueous solution, and the flow rates of the first metal-containing aqueous solution and the second metal-containing aqueous solution are appropriately adjusted.

[0028] The supply amount of nickel (Ni) relative to the supply amount of cobalt (Co) per unit time to the reaction tank is not particularly limited and can be appropriately selected according to the desired composition ratio of nickel (Ni) and cobalt (Co) in the composite hydroxide. For example, the supply amount of nickel (Ni) relative to the supply amount of cobalt (Co) per unit time to the reaction tank is preferably in the range of 2.5 or more and 50.0 or less, and particularly preferably in the range of 6.0 or more and 30.0 or less, from the viewpoint of imparting high-capacity battery characteristics to a secondary battery using the obtained composite hydroxide as a precursor of a positive electrode active material.

[0029] The composite hydroxide containing nickel (Ni) and cobalt (Co) may further contain an additive metal element M other than nickel (Ni) and cobalt (Co), if necessary. Examples of the additive metal element M include manganese (Mn), magnesium (Mg), aluminum (Al), calcium (Ca), titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), niobium (Nb), molybdenum (Mo), and tungsten (W). These additive metal elements M may be used alone or in combination of two or more.

[0030] Examples of the composite hydroxide containing nickel (Ni) and cobalt (Co) include 1-x-y Co x M y O z (OH) 2-α (0 < x ≤ 0.3, 0 ≤ y ≤ 0.3, 0 ≤ z ≤ 3.00, -0.50 ≤ α < 2.00, and M represents one or more additive metal elements selected from the group consisting of Mn, Mg, Zr, Al, Ca, Ti, Nb, V, Cr, Mo, and W).

[0031] Further, the added metal element M may be contained only in the first metal-containing aqueous solution, may be contained only in the second metal-containing aqueous solution, or may be contained in both the first metal-containing aqueous solution and the second metal-containing aqueous solution. Therefore, the added metal element M may be supplied to the reaction tank only in a raw material solution containing nickel (Ni), may be supplied to the reaction tank only in a raw material solution containing cobalt (Co), or may be supplied to the reaction tank in a state of being contained in both a raw material solution containing nickel (Ni) and a raw material solution containing cobalt (Co).

[0032] In the method for producing the composite hydroxide of the present invention, by the coprecipitation method, a first metal-containing aqueous solution containing a salt of nickel (Ni) (for example, sulfate), a second metal-containing aqueous solution containing a salt of cobalt (Co) (for example, sulfate), an aqueous solution containing an ammonium ion donor, and an alkali metal aqueous solution are individually added into the reaction tank, respectively, and a neutralization reaction is carried out in the reaction tank to produce particles of a composite hydroxide containing nickel (Ni) and cobalt (Co), thereby obtaining a slurry-like suspension containing the composite hydroxide containing nickel (Ni) and cobalt (Co).

[0033] <Alkali metal aqueous solution> The alkali metal aqueous solution is a pH adjuster. Examples of the alkali metal aqueous solution include sodium hydroxide and potassium hydroxide. In the method for producing the composite hydroxide of the present invention, by adding the alkali metal aqueous solution into the reaction tank, the pH value of the mother liquor in the reaction tank based on a liquid temperature of 25 °C is adjusted to a range of 10.0 or more and 13.0 or less. The pH value of the mother liquor in the reaction tank based on a liquid temperature of 25 °C is not particularly limited as long as it is in the range of 10.0 or more and 13.0 or less, but a range of 10.5 or more and 12.0 or less is preferable.

[0034] <Ammonium ion donor> The ammonium ion donor is a complexing agent. Ammonium ions can form complexes with nickel (Ni) ions, cobalt (Co) ions, and ions of the added metal element M. Examples of the ammonium ion donor include aqueous ammonia, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, and the like. In the method for producing the composite hydroxide of the present invention, a composite hydroxide with an appropriately controlled BET specific surface area can be produced even if the amount of ammonium ions in the mother liquor in the reaction tank is suppressed. Specifically, the ammonium ion concentration in the mother liquor in the reaction tank may be adjusted to a range of 1.0 g / L or more and 10.0 g / L or less. In the method for producing the composite hydroxide of the present invention, the amount of the ammonium ion donor used can be suppressed, so the production cost can be reduced. From the above, it is preferable to adjust the ammonium ion concentration in the mother liquor in the reaction tank to a range of 1.0 g / L or more and 5.0 g / L or less.

[0035] Further, in the method for producing the composite hydroxide of the present invention, a composite hydroxide with an appropriately controlled BET specific surface area can be produced even if the reaction temperature of the mother liquor in the reaction tank is suppressed. Specifically, even if it is controlled to 20°C or higher and 80°C or lower, a composite hydroxide with an appropriately controlled BET specific surface area can be produced.

[0036] Next, an example of the reaction apparatus used in the method for producing the composite hydroxide of the present invention will be described. FIG. 1 is a side cross-sectional view for explaining the outline of an example of the reaction apparatus used in the method for producing the composite hydroxide of the present invention.

[0037] As shown in FIG. 1, the reaction apparatus 1 used in the method for producing the composite hydroxide of the present invention includes a reaction tank 10 for storing the mother liquor 20, a first raw material liquid supply section 11 for supplying the first metal-containing aqueous solution 21 to the mother liquor 20 in the reaction tank 10, a second raw material liquid supply section 12 for supplying the second metal-containing aqueous solution 22 to the mother liquor 20 in the reaction tank 10, an alkali metal supply section 13 for supplying the alkali metal aqueous solution 23 to the reaction tank 10, and an ammonium ion supply section 14 for supplying the aqueous solution 24 containing the ammonium ion donor to the mother liquor 20 in the reaction tank 10.

[0038] The first raw material liquid supply section 11 is a tubular body having one end communicating with the reaction tank 10 and the other end communicating with a storage tank (not shown) storing the first metal-containing aqueous solution 21. The second raw material liquid supply section 12 is a tubular body having one end communicating with the reaction tank 10 and the other end communicating with a storage tank (not shown) storing the second metal-containing aqueous solution 22. The alkali metal supply section 13 is a tubular body having one end communicating with the reaction tank 10 and the other end communicating with a storage tank (not shown) storing the alkali metal aqueous solution 23. The ammonium ion supply section 14 is a tubular body having one end communicating with the reaction tank 10 and the other end communicating with a storage tank (not shown) storing the aqueous solution 24 containing the ammonium ion supply body.

[0039] In the reaction apparatus 1, the first raw material liquid supply section 11 is arranged at a different position from the second raw material liquid supply section 12. Further, the storage tank storing the first metal-containing aqueous solution 21 is a different storage tank from the storage tank storing the second metal-containing aqueous solution 22. Therefore, the first metal-containing aqueous solution 21 and the second metal-containing aqueous solution 22 are added into the reaction tank 10 through different paths, respectively.

[0040] Further, a stirrer 17 is provided inside the reaction tank 10. The stirrer 17 mixes the first metal-containing aqueous solution 21 and the second metal-containing aqueous solution 22 contained in the mother liquor 20 stored in the reaction tank 10, the alkali metal aqueous solution 23 supplied from the alkali metal supply section 13, and the aqueous solution 24 containing the ammonium ion supply body supplied from the ammonium ion supply section 14 to equalize the raw material concentration of the entire mother liquor 14 stored in the reaction tank 10.

[0041] Examples of the stirrer 17 include a stirring device having stirring blades with a plurality of propeller blades at the tip of a stirring shaft. Further, the stirring rotation speed of the stirrer 17 can be appropriately selected according to the volume of the reaction tank 10, the type of the stirring blades, and the residence time. For example, when using three propeller blades and carrying out a coprecipitation reaction with a residence time of 10 to 25 hours, the stirring power is 0.3 kW / m 3 above 4.0 kW / m 3 below is preferable, and 1.8 kW / m3 2.6 kW / m or less is particularly preferred. 3

[0042] From the reaction tank 10 in which the raw material concentration is homogenized and the mother liquor 20 containing metal components derived from the first metal-containing aqueous solution 21 and the second metal-containing aqueous solution 22 is stored, a slurry 25 containing a composite hydroxide, which is a reaction product that has been generated and grown (a composite hydroxide containing nickel (Ni) and cobalt (Co)), is obtained. An overflow pipe 18 communicating with the inside of the reaction tank 10 is provided on the side surface portion on the top side of the reaction tank 10, and the slurry 25 containing the target composite hydroxide is taken out from the reaction tank 10 to the outside through the overflow pipe 18.

[0043] From the above, the reaction apparatus 1 is a reaction apparatus including a continuous reaction tank 10 that recovers the slurry 25 containing the target composite hydroxide by overflowing it. Since the reaction tank 10 is of a continuous type that overflows the slurry 25 containing the generated composite hydroxide, the production efficiency of the slurry 25 containing the composite hydroxide can be improved.

[0044] Note that the reaction apparatus 1 shown in FIG. 1 illustrates an outline of an example of a continuous reaction apparatus, and the reaction apparatus used in the method for producing a composite hydroxide of the present invention is not limited to the reaction apparatus 1 shown in FIG. 1, and it is sufficient that the first metal-containing aqueous solution and the second metal-containing aqueous solution have a structure in which they are individually added to the reaction tank. Further, the reaction apparatus used in the method for producing a composite hydroxide of the present invention may be a batch-type reaction tank that does not discharge to the outside of the system until the reaction in the reaction tank is completed, instead of the continuous reaction tank, as long as the first metal-containing aqueous solution and the second metal-containing aqueous solution have a structure in which they are individually added to the reaction tank.

[0045] The composite hydroxide produced by the production method of the present invention can be used as a precursor of a positive electrode active material for a secondary battery. Next, a method for producing a positive electrode active material using the composite hydroxide produced by the production method of the present invention as a precursor will be described. For example, the method for producing a positive electrode active material using the composite hydroxide produced by the production method of the present invention as a precursor first involves adding a lithium compound to the composite hydroxide produced by the production method of the present invention to prepare a mixture of the composite hydroxide and the lithium compound. The lithium compound is not particularly limited as long as it is a compound containing lithium, and examples thereof include lithium carbonate and lithium hydroxide.

[0046] Next, the positive electrode active material can be produced by firing the mixture obtained as described above. Examples of the firing conditions include a firing temperature of 700°C or higher and 1000°C or lower, a heating rate of 50°C / h or higher and 300°C / h or lower, and a firing time of 5 hours or longer and 20 hours or shorter. The firing atmosphere is not particularly limited, and examples thereof include air and oxygen. Also, the firing furnace used for firing is not particularly limited, and examples thereof include a stationary box furnace and a roller hearth continuous furnace.

[0047] Examples of the secondary battery using the composite hydroxide produced by the production method of the present invention include a lithium ion secondary battery.

[0048] Next, the composite hydroxide produced by the production method of the present invention will be described in detail. The composite hydroxide of the present invention is a composite hydroxide containing at least nickel (Ni) and cobalt (Co), and the composite hydroxide has a first particle with a secondary particle diameter (D10) in the range of ±1.0 μm with a cumulative volume percentage of 10% by volume, a second particle with a secondary particle diameter (D50) in the range of ±1.0 μm with a cumulative volume percentage of 50% by volume, and a third particle with a secondary particle diameter (D90) in the range of ±1.0 μm with a cumulative volume percentage of 90% by volume. The absolute value of the rate of change calculated by the following formula (1) from the BET specific surface area of the first particle, the secondary particle diameter (D50) with a cumulative volume percentage of 50% by volume, the BET specific surface area of the third particle, and the secondary particle diameter (D50) with a cumulative volume percentage of 50% by volume, and the molar percentage of cobalt (Co) with respect to the metal elements contained in the composite hydroxide (however, the metal elements are Ni, Co, Mn, Mg, Zr, Al, Ca, Ti, Nb, V, Cr, Mo, and W.) is 0 or more and 0.015 or less. |(BET specific surface area of the third particle - BET specific surface area of the first particle) / (D50 of the third particle - D50 of the first particle)| = absolute value of the rate of change ··· Formula (1)

[0049] In the composite hydroxide having a conventional particle size distribution, the BET specific surface area of the smaller particle diameter is larger than that of the larger particle diameter. When firing the composite hydroxide and the lithium compound, the smaller particle diameter has an increased contact area with the lithium compound per unit volume, and the reaction with the lithium compound is promoted compared to the larger particle diameter. Therefore, in the conventional composite hydroxide, there is a large difference in the reactivity with the lithium compound between the larger particle diameter and the smaller particle diameter, and as a whole, the reaction with the lithium compound becomes non-uniform. When the reaction with the lithium compound becomes non-uniform as a whole, the battery characteristics and battery life may be impaired.

[0050] On the other hand, due to having the above configuration, the composite hydroxide of the present invention suppresses the change in BET specific surface area due to the difference in particle size, that is, the difference in BET specific surface area between the first particle, the second particle, and the third particle is reduced. As a result, the reactivity of the entire composite hydroxide with a metal compound such as a lithium compound is made uniform, and the battery characteristics can be improved.

[0051] When the composite hydroxide of the present invention is classified into a first particle which is a small particle having a secondary particle size in the range of D10 ± 1.0 μm, a second particle which is a medium particle having a secondary particle size in the range of D50 ± 1.0 μm, and a third particle which is a large particle having a secondary particle size in the range of D90 ± 1.0 μm, the absolute value of the ratio of the difference in BET specific surface area between the third particle and the first particle to the difference in D50 between the third particle and the first particle (hereinafter, the absolute value may be referred to as "BET slope") is reduced. As a result, the product of the BET slope and the molar percentage of cobalt (Co) with respect to the metal element contained in the composite hydroxide (where the metal element is Ni, Co, Mn, Mg, Zr, Al, Ca, Ti, Nb, V, Cr, Mo, and W) (hereinafter, may be simply referred to as "cobalt molar percentage") is suppressed to 0.015 or less. Since the composition of the composite hydroxide also affects the BET specific surface area and battery characteristics of the composite hydroxide, as a characteristic of the composite hydroxide of the present invention, the configuration of the BET slope and the cobalt molar percentage is used. Note that, as a method for classifying the composite hydroxide of the present invention into the first particle, the second particle, and the third particle, air classification can be mentioned.

[0052] The value of the product of the BET slope and the cobalt molar percentage is not particularly limited as long as it is 0 or more and 0.015 or less. However, from the viewpoint that the reactivity of the entire composite hydroxide with the lithium compound is further made uniform and the battery characteristics can be further improved, 0.013 or less is preferable, and 0.011 or less is particularly preferable.

[0053] Examples of the composite hydroxide of the present invention include Ni 1-x-y Co x M y Oz (OH) 2-α (0 < x + y < 0.20, 0 ≤ z ≤ 3.00, -0.50 ≤ α < 2.00, where M represents one or more additive metal elements selected from the group consisting of Mn, Mg, Zr, Al, Ca, Ti, Nb, V, Cr, Mo, and W.) Composite hydroxides represented by the general formula are exemplified. In the composite hydroxide of the above general formula, nickel (Ni) is contained in an amount exceeding 80 mol% based on the total of nickel (Ni), cobalt (Co), and the additive metal element (M).

[0054] Also, in the general formula Ni 1-x-y Co x M y O z (OH) 2-α In the composite hydroxide represented by, it is preferable that 0.02 < x < 0.20, that is, cobalt (Co) is contained in a range exceeding 2 mol% and less than 20 mol% based on the total of nickel (Ni), cobalt (Co), and the additive metal element (M).

[0055] The composite hydroxide of the present invention has a spread of a predetermined particle size distribution. For example, the value of (D90 of the composite hydroxide - D10 of the composite hydroxide) / D50 of the composite hydroxide, which is an index of the particle size distribution, is in the range of 0.50 or more and 1.40 or less. By the value of (D90 of the composite hydroxide - D10 of the composite hydroxide) / D50 of the composite hydroxide being 0.50 or more and 1.40 or less, the loading density of the positive electrode active material using the composite hydroxide of the present invention as a precursor on the positive electrode is improved, and more excellent battery characteristics can be exhibited. The value of (D90 of the composite hydroxide - D10 of the composite hydroxide) / D50 of the composite hydroxide is not particularly limited, but from the viewpoint of improving the loading density of the positive electrode, the lower limit value of the value of (D90 of the composite hydroxide - D10 of the composite hydroxide) / D50 of the composite hydroxide is preferably 0.65 or more, and particularly preferably 0.80 or more. Also, the BET specific surface area of the composite hydroxide of the present invention is not particularly limited, but from the viewpoint of controlling the reactivity with metal compounds such as lithium compounds, the upper limit value is preferably 50.0 or less, more preferably 25.0 or less, and particularly preferably 15.0 or less. Also, the lower limit value of the BET specific surface area is preferably 3.0 or more, more preferably 4.5 or more, and particularly preferably 6.0 or more.

Example

[0056] Next, the method for producing the composite hydroxide of the present invention and examples of the composite hydroxide of the present invention will be described. However, the present invention is not limited to these examples as long as the gist thereof is not exceeded.

[0057] Production of Composite Hydroxides in Examples and Comparative Examples Production of Composite Hydroxide of Example 1 An aqueous nickel sulfate solution, an aqueous manganese sulfate solution, and an aqueous magnesium sulfate solution were mixed in predetermined amounts so that the composition of the composite hydroxide was as shown in Table 1 below, and an aqueous solution not containing cobalt (corresponding to the first metal-containing aqueous solution), an aqueous cobalt sulfate solution not containing nickel (corresponding to the second metal-containing aqueous solution), an aqueous ammonium sulfate solution (corresponding to the aqueous solution containing an ammonium ion donor), and an aqueous sodium hydroxide solution (corresponding to the alkali metal aqueous solution) were separately and simultaneously dropped into the reaction tank, and the pH of the mixed solution in the reaction tank was maintained at 11.7 based on a liquid temperature of 25 °C, and the ammonia concentration was maintained at 4.4 g / L while continuously stirring with a stirrer. Also, the liquid temperature (reaction temperature) of the mixed solution in the reaction tank was maintained at 70 °C. The slurry containing the generated composite hydroxide particles was taken out by overflowing from the overflow pipe of the reaction tank. The slurry of the composite hydroxide particles collected after 41.7 hours or more had elapsed since the start of the reaction was washed in the order of an alkaline aqueous solution and water, and each treatment of dehydration and drying was performed to obtain a composite hydroxide. The composition and production conditions of the composite hydroxide of Example 1 are shown in Table 1 below.

[0058] Production of Composite Hydroxide of Example 2 An aqueous cobalt sulfate solution, an aqueous manganese sulfate solution, and an aqueous magnesium sulfate solution were mixed in predetermined amounts so that the composition of the composite hydroxide would be as shown in Table 1 below, and an aqueous solution containing no nickel (corresponding to the second metal-containing aqueous solution), an aqueous nickel sulfate solution containing no cobalt (corresponding to the first metal-containing aqueous solution), an aqueous ammonium sulfate solution (corresponding to the aqueous solution containing an ammonium ion donor), and an aqueous sodium hydroxide solution (corresponding to the alkali metal aqueous solution) were each separately and simultaneously dropped into a reaction vessel, and while maintaining the pH of the mixed solution in the reaction vessel at 11.2 based on a liquid temperature of 25°C and the ammonia concentration at 3.7 g / L, it was continuously stirred with a stirrer. Also, the liquid temperature (reaction temperature) of the mixed solution in the reaction vessel was maintained at 70°C. The slurry containing the produced composite hydroxide particles was overflowed from the overflow pipe of the reaction vessel and taken out. The slurry of the composite hydroxide particles collected after 42.0 hours or more had elapsed since the start of the reaction was washed in the order of an alkaline aqueous solution and water, and subjected to dehydration and drying treatments to obtain a composite hydroxide. The composition and production conditions of the composite hydroxide of Example 2 above are shown in Table 1 below.

[0059] Production of the composite hydroxide of Comparative Example 1 A metal salt aqueous solution in which an aqueous nickel sulfate solution, an aqueous cobalt sulfate solution, an aqueous manganese sulfate solution, and an aqueous magnesium sulfate solution were mixed in predetermined amounts so that the composition of the composite hydroxide would be as shown in Table 1 below, an aqueous ammonium sulfate solution (ammonium ion donor), and an aqueous sodium hydroxide solution were each separately and simultaneously dropped into a reaction vessel, and while maintaining the pH of the mixed solution in the reaction vessel at 11.5 based on a liquid temperature of 25°C and the ammonia concentration at 3.7 g / L, it was continuously stirred with a stirrer. Also, the liquid temperature of the mixed solution in the reaction vessel was maintained at 70°C. The slurry containing the produced composite hydroxide particles was overflowed from the overflow pipe of the reaction vessel and taken out. The slurry of the composite hydroxide particles collected after 41.7 hours or more had elapsed since the start of the reaction was washed in the order of an alkaline aqueous solution and water, and subjected to dehydration and drying treatments to obtain a composite hydroxide. The composition and production conditions of the composite hydroxide of Comparative Example 1 above are shown in Table 1 below.

[0060] Production of the composite hydroxide of Comparative Example 2 A composite hydroxide was obtained in the same manner as in Comparative Example 1, except that the pH was 11.9 based on a liquid temperature of 25°C and the ammonia concentration was 6.0 g / L. The composition and production conditions of the composite hydroxide of Comparative Example 2 are shown in Table 1 below.

[0061] Production of the composite hydroxide of Example 3 A nickel sulfate aqueous solution and a manganese sulfate aqueous solution were mixed in predetermined amounts so that the composition of the composite hydroxide would be as shown in Table 2 below, and an aqueous solution containing no cobalt (corresponding to the first metal-containing aqueous solution), a cobalt sulfate aqueous solution containing no nickel (corresponding to the second metal-containing aqueous solution), an ammonium sulfate aqueous solution (ammonium ion donor), and a sodium hydroxide aqueous solution were each individually and simultaneously dropped into a reaction vessel, and while maintaining the pH of the mixed solution in the reaction vessel at 10.9 based on a liquid temperature of 25°C and the ammonia concentration at 4.7 g / L, the mixture was continuously stirred with a stirrer. Also, the liquid temperature of the mixed solution in the reaction vessel was maintained at 70°C. The slurry containing the produced composite hydroxide particles was overflowed from the overflow pipe of the reaction vessel and taken out. The slurry of the composite hydroxide particles collected after 41.7 hours or more had elapsed since the start of the reaction was washed in the order of an alkaline aqueous solution and water, and subjected to dehydration and drying treatments to obtain a composite hydroxide. The composition and production conditions of the composite hydroxide of Example 3 are shown in Table 2 below.

[0062] Production of the composite hydroxide of Comparative Example 3 A metal salt aqueous solution prepared by mixing a nickel sulfate aqueous solution, a cobalt sulfate aqueous solution, and a manganese sulfate aqueous solution in predetermined amounts so that the composition of the composite hydroxide becomes as shown in Table 2 below, an ammonium sulfate aqueous solution (ammonium ion donor), and a sodium hydroxide aqueous solution were each individually and simultaneously dropped into a reaction vessel, and while maintaining the pH of the mixed solution in the reaction vessel at 11.4 based on a liquid temperature of 25°C and the ammonia concentration at 4.4 g / L, it was continuously stirred with a stirrer. Also, the liquid temperature of the mixed solution in the reaction vessel was maintained at 50°C. The slurry containing the generated composite hydroxide particles was overflowed from the overflow pipe of the reaction vessel and taken out. The slurry of the composite hydroxide particles collected after 41.7 hours or more had elapsed since the start of the reaction was washed in the order of an alkaline aqueous solution and water, and subjected to dehydration and drying treatments to obtain a composite hydroxide. The composition and production conditions of the composite hydroxide of Comparative Example 3 above are shown in Table 2 below.

[0063] Production of Composite Hydroxide of Comparative Example 4 A composite hydroxide was obtained in the same manner as in Comparative Example 3, except that the pH was maintained at 11.1 based on a liquid temperature of 25°C, the ammonia concentration was 4.7 g / L, and the liquid temperature of the mixed solution in the reaction vessel was maintained at 70°C. The composition and production conditions of the composite hydroxide of Comparative Example 4 above are shown in Table 2 below.

[0064] Production of Composite Hydroxide of Example 4 An aqueous solution in which a nickel sulfate aqueous solution and a manganese sulfate aqueous solution were dissolved in predetermined amounts and which did not contain cobalt (corresponding to the first metal-containing aqueous solution) and a cobalt sulfate aqueous solution that did not contain nickel (corresponding to the second metal-containing aqueous solution) were used so that the composition of the composite hydroxide became as shown in Table 3 below. Except that the pH was maintained at 11.4 based on a liquid temperature of 25°C, the ammonia concentration was 2.1 g / L, the liquid temperature of the mixed solution in the reaction vessel was maintained at 71°C, and the slurry of the composite hydroxide particles collected after 51.0 hours or more had elapsed since the start of the reaction was washed in the order of an alkaline aqueous solution and water, and subjected to dehydration and drying treatments to obtain a composite hydroxide, a composite hydroxide was obtained in the same manner as in Example 3. The composition and production conditions of the composite hydroxide of Example 4 above are shown in Table 3 below.

[0065] Production of Composite Hydroxide of Example 5 A cobalt sulfate aqueous solution and a manganese sulfate aqueous solution were dissolved in predetermined amounts so that the composition of the composite hydroxide would be as shown in Table 3 below, and an aqueous solution containing no nickel (corresponding to the second metal-containing aqueous solution) and a nickel sulfate aqueous solution containing no cobalt (corresponding to the first metal-containing aqueous solution) were used. The pH was 11.0 based on a liquid temperature of 25 °C, the ammonia concentration was 2.3 g / L, and after 48.6 hours or more had elapsed since the start of the reaction, the slurry of the composite hydroxide particles collected was washed in the order of an alkaline aqueous solution and water, and subjected to dehydration and drying treatments to obtain a composite hydroxide, except that the composite hydroxide was obtained in the same manner as in Example 4. The composition and production conditions of the composite hydroxide of Example 5 above are shown in Table 3 below.

[0066] Production of the composite hydroxide of Comparative Example 5 Instead of the first metal-containing aqueous solution and the second metal-containing aqueous solution, a metal salt aqueous solution obtained by mixing a nickel sulfate aqueous solution, a cobalt sulfate aqueous solution, and a manganese sulfate aqueous solution was used. The liquid temperature of the mixed solution in the reaction tank was set to 60 °C, the pH was 11.7 based on a liquid temperature of 25 °C, the ammonia concentration was 2.0 g / L, and after 49.2 hours or more had elapsed since the start of the reaction, the slurry of the composite hydroxide particles collected was washed in the order of an alkaline aqueous solution and water, and subjected to dehydration and drying treatments to obtain a composite hydroxide, except that the composite hydroxide was obtained in the same manner as in Example 4. The composition and production conditions of the composite hydroxide of Comparative Example 5 above are shown in Table 3 below.

[0067] Production of the composite hydroxide of Comparative Example 6 Instead of the first metal-containing aqueous solution and the second metal-containing aqueous solution, a metal salt aqueous solution obtained by mixing a nickel sulfate aqueous solution, a cobalt sulfate aqueous solution, and a manganese sulfate aqueous solution was used. The pH was 11.0 based on a liquid temperature of 25 °C, the ammonia concentration was 1.7 g / L, and after 50.1 hours or more had elapsed since the start of the reaction, the slurry of the composite hydroxide particles collected was washed in the order of an alkaline aqueous solution and water, and subjected to dehydration and drying treatments to obtain a composite hydroxide, except that the composite hydroxide was obtained in the same manner as in Example 4. The composition and production conditions of the composite hydroxide of Comparative Example 6 above are shown in Table 3 below.

[0068] Production of the composite hydroxide of Example 6 The nickel sulfate aqueous solution and the manganese sulfate aqueous solution were mixed in predetermined amounts so that the composition of the composite hydroxide was as shown in Table 4 below, and an aqueous solution containing no cobalt (corresponding to the first metal-containing aqueous solution) and a cobalt sulfate aqueous solution containing no nickel (corresponding to the second metal-containing aqueous solution) were used. The pH was maintained at 11.3 based on a liquid temperature of 25 °C, the ammonia concentration was 3.1 g / L, and the liquid temperature of the mixed solution in the reaction tank was maintained at 75 °C. After 32.7 hours or more had elapsed since the start of the reaction, the slurry of the composite hydroxide particles collected was washed with an alkaline aqueous solution and then water in that order, and subjected to dehydration and drying treatments to obtain a composite hydroxide, in the same manner as in Example 3 except for the above. The composition and production conditions of the composite hydroxide of Example 6 above are shown in Table 4 below.

[0069] Production of the composite hydroxide of Comparative Example 7 Instead of the first metal-containing aqueous solution and the second metal-containing aqueous solution, a metal salt aqueous solution obtained by mixing a nickel sulfate aqueous solution, a cobalt sulfate aqueous solution, and a manganese sulfate aqueous solution was used. A composite hydroxide was obtained in the same manner as in Example 6 except that the pH was maintained at 11.0 based on a liquid temperature of 25 °C, the ammonia concentration was 2.6 g / L, and the liquid temperature of the mixed solution in the reaction tank was maintained at 70 °C. The composition and production conditions of the composite hydroxide of Comparative Example 7 above are shown in Table 4 below.

[0070] Production of the composite hydroxide of Comparative Example 8 Instead of the first metal-containing aqueous solution and the second metal-containing aqueous solution, a metal salt aqueous solution obtained by mixing a nickel sulfate aqueous solution, a cobalt sulfate aqueous solution, and a manganese sulfate aqueous solution was used. A composite hydroxide was obtained in the same manner as in Example 6 except that the ammonia concentration was 3.7 g / L and the liquid temperature of the mixed solution in the reaction tank was maintained at 80 °C. The composition and production conditions of the composite hydroxide of Comparative Example 8 above are shown in Table 4 below.

[0071] Evaluation of the produced composite hydroxide (1) Secondary particle diameter (D50) at a cumulative volume percentage of 50% by volume The obtained composite hydroxide was measured using a particle size distribution analyzer (in Examples 1, 2, 4 to 6 and Comparative Examples 1, 2, 5 to 8, MT3300EX II manufactured by Nikkiso Co., Ltd.; in Example 3 and Comparative Examples 3 and 4, LA-950 manufactured by Horiba, Ltd.). The principle of both analyzers is the laser diffraction / scattering method. The measurement conditions of the particle size distribution analyzer are as follows. Solvent: water, solvent refractive index: 1.33, particle refractive index: 1.55, transmittance 80 ± 5%, dispersion medium: 10.0 mass% aqueous sodium hexametaphosphate solution

[0072] (2) Tap density (TD) For the obtained composite hydroxide, the tap density was measured by the constant volume measurement method using a tap densitometer (KYT-4000 manufactured by Seishin Enterprise Co., Ltd.). The measurement conditions of TD are as follows. Cell volume: 20 cc, stroke length: 10 mm, number of tapping times: 200 times (500 times in Example 3 and Comparative Examples 3 and 4).

[0073] (3) BET specific surface area After drying 0.3 g of the obtained composite hydroxide at 105°C for 30 minutes in a nitrogen atmosphere, the specific surface area was measured by the one-point BET method using a specific surface area analyzer (Macsorb manufactured by Mountech Co., Ltd.).

[0074] The evaluation results of the physical properties of the composite hydroxides of the examples and comparative examples are shown in Tables 1 to 4 below.

[0075]

Table 1

[0076]

Table 2

[0077]

Table 3

[0078]

Table 4

[0079] From Table 1 above, in the composite hydroxides of Examples 1 and 2, a first metal-containing aqueous solution containing nickel (Ni) and not containing cobalt (Co) and a second metal-containing aqueous solution containing cobalt (Co) and not containing nickel (Ni) were separately and simultaneously added to the reaction vessel. The ammonia concentrations were 4.4 g / L and 3.7 g / L respectively, and with a small amount of addition, the BET specific surface areas were suppressed to 15.1 m 2 / g and 10.7 m 2 / g respectively. Also, excellent tap densities of 2.11 g / ml and 2.01 g / ml were obtained respectively. The compositions of the composite hydroxides of Examples 1 and 2 were Ni:Co:Mn:Mg = 94.8:4.7:0.26:0.26, and the D50s were 11.2 μm and 10.6 μm respectively.

[0080] In contrast, for the composite hydroxide with Ni:Co:Mn:Mg = 94.8:4.7:0.26:0.26 from Table 1 above, under the same reaction conditions as in Examples 1 and 2 and with the same D50, in Comparative Example 1 where nickel (Ni) and cobalt (Co) were added using the same raw material solution, the BET specific surface area was 24.8 m 2 / g and the BET specific surface area could not be suppressed. Also, in Comparative Example 2 where nickel (Ni) and cobalt (Co) were added using the same raw material solution and having the same D50 as in Examples 1 and 2, by setting the ammonia concentration to 6.0 g / L, the BET specific surface area could be suppressed to some extent. Therefore, in Comparative Example 2, the usage amount of the ammonium ion donor increased and the production cost of the composite hydroxide could not be reduced.

[0081] From Table 2 above, in Example 3 where a first metal-containing aqueous solution containing nickel (Ni) and not containing cobalt (Co) and a second metal-containing aqueous solution containing cobalt (Co) and not containing nickel (Ni) were separately and simultaneously added to the reaction vessel, the ammonia concentration was 4.7 g / L, and with a small amount of addition, the BET specific surface area was 5.1 m 2It could be suppressed to / g. Also, an excellent tap density of 2.26 g / ml was obtained. The composition of the composite hydroxide in Example 3 was Ni:Co:Mn = 55:20:25, and the D50 was 12.5 μm.

[0082] In contrast, from Table 2 above, for the composite hydroxide with Ni:Co:Mn = 55:20:25, in Comparative Example 3 where the reaction temperature was as low as 50 °C and nickel (Ni) and cobalt (Co) were added from the same raw material solution, the BET specific surface area increased to 9.4 m 2 / g and the BET specific surface area could not be suppressed. Also, under the same reaction conditions as in Example 3 and with the same D50, in Comparative Example 4 where nickel (Ni) and cobalt (Co) were added from the same raw material solution, the BET specific surface area was 6.2 m 2 / g and still the BET specific surface area could not be suppressed.

[0083] From Table 3 above, in the composite hydroxides of Examples 4 and 5 where the first metal-containing aqueous solution containing nickel (Ni) and not containing cobalt (Co) and the second metal-containing aqueous solution containing cobalt (Co) and not containing nickel (Ni) were separately and simultaneously added to the reaction tank, the ammonia concentrations were 2.1 g / L and 2.3 g / L respectively, and with a small addition, the BET specific surface areas were 6.6 m 2 / g and 6.0 m 2 / g respectively, and could be suppressed. Also, excellent tap densities of 2.04 g / ml and 2.00 g / ml were obtained respectively. The compositions of the composite hydroxides in Examples 4 and 5 were Ni:Co:Mn = 83.1:12.1:4.9, and the D50s were 10.4 μm and 10.1 μm respectively.

[0084] In contrast, from Table 3 above, for the composite hydroxide with Ni:Co:Mn = 83.1:12.1:4.9, in Comparative Example 5 where the reaction temperature was as low as 60 °C and nickel (Ni) and cobalt (Co) were added from the same raw material solution, the BET specific surface area was 11.1 m 2It increased up to / g and the BET specific surface area could not be suppressed. Also, in Comparative Example 6 where the reaction conditions were the same as those in Examples 4 and 5 and the D50 was the same, but nickel (Ni) and cobalt (Co) were added from the same raw material solution, the BET specific surface area was 10.8 m 2 / g, and still the BET specific surface area could not be suppressed.

[0085] From Table 4 above, in Example 6 where the first metal-containing aqueous solution containing nickel (Ni) and not containing cobalt (Co) and the second metal-containing aqueous solution containing cobalt (Co) and not containing nickel (Ni) were individually and simultaneously added to the reaction tank, the reaction temperature was suppressed to 75°C, and with an ammonia concentration of 3.1 g / L and a small addition, the BET specific surface area was reduced to 8.4 m 2 / g. Also, a tapped density of 2.05 g / ml, an excellent tapped density, was obtained. The composition of the composite hydroxide in Example 6 was Ni:Co:Mn = 83.1:12.1:4.9, and the D50 was 10.8 μm.

[0086] In contrast, from Table 4 above, for the composite hydroxide with Ni:Co:Mn = 83.1:12.1:4.9, in Comparative Example 7 where the reaction temperature was 70°C and the ammonia concentration was 2.6 g / L, with both the reaction temperature and the ammonia concentration being low, and nickel (Ni) and cobalt (Co) were added from the same raw material solution, the BET specific surface area increased up to 14.2 m 2 / g and the BET specific surface area could not be suppressed. Also, in Comparative Example 8 where the reaction temperature was 80°C and the ammonia concentration was 3.7 g / L, with the reaction temperature and the ammonia concentration increased compared to Example 6, and nickel (Ni) and cobalt (Co) were added from the same raw material solution, the BET specific surface area could be suppressed to the same level as in Example 6. Therefore, in Comparative Example 8, the energy consumption could not be reduced and the usage amount of ammonium ions could not be suppressed, so the production cost of the composite hydroxide could not be suppressed.

[0087] Among the composite metal hydroxides of Examples 1 to 6 and Comparative Examples 1 to 8, for the composite metal hydroxides of Examples 1, 2, 4 to 6 and Comparative Examples 1, 2, 6, and 7, in the same manner as the evaluation method for the secondary particle diameter (D50) with a cumulative volume percentage of 50% by volume, the secondary particle diameter (D10) with a cumulative volume percentage of 10% by volume and the secondary particle diameter (D90) with a cumulative volume percentage of 90% by volume were measured. From D10, D50, and D90 of the composite metal hydroxide, the value of (D90 - D10) / D50, which is an index of the particle size distribution, was calculated.

[0088] Furthermore, for the composite metal hydroxides of Examples 1, 2, 4 to 6 and Comparative Examples 1, 2, 6, and 7, by air classification, the composite metal hydroxide was classified into a first particle with a secondary particle diameter D50 after classification in the range of D10 ± 1.0 μm of the composite metal hydroxide, a second particle with a secondary particle diameter D50 after classification in the range of D50 ± 1.0 μm of the composite metal hydroxide, and a third particle with a secondary particle diameter D50 after classification in the range of D90 ± 1.0 μm of the composite metal hydroxide. For the first particle and the third particle obtained by classifying the composite metal hydroxide, in the same manner as the evaluation method for the secondary particle diameter (D50) with a cumulative volume percentage of 50% by volume, the secondary particle diameter (D50) with a cumulative volume percentage of 50% by volume was measured. Also, for the first particle and the third particle, the BET specific surface area was measured in the same manner as the evaluation method for the BET specific surface area. The BET slope was calculated from D50 and the BET specific surface area of the first particle and the third particle, and the product of the calculated BET slope and the cobalt molar percentage was calculated from the composition.

[0089] The results of the above items are shown in Table 5 below.

[0090]

Table 5

[0091] (4) Thermogravimetric measurement (TG measurement) Among the composite hydroxides of Examples 1, 2, 4 to 6 and Comparative Examples 1, 2, 6, and 7, for the first particles and the third particles of the composite hydroxides of Examples 1, 2, and 6 and Comparative Examples 1, 2, and 7, lithium hydroxide monohydrate was mixed with lithium hydroxide so that the molar ratio of lithium / total metal elements was 1.05, and TG measurement was carried out under the conditions of a temperature increase rate of 10 °C / min, an oxygen supply amount of 200 ml / min, and a sampling frequency of 1 time / 1 second. Further, DTG was calculated by differentiating the TG data. From the relationship between DTG and temperature, for the first particles and the third particles, the temperature of the peak top near 300 °C considered to be derived from the reaction between the composite hydroxide and lithium was obtained, and further, the difference between the temperature of the peak top of the first particles and the temperature of the peak top of the third particles was obtained.

[0092] The evaluation results of the TG measurement are shown in Table 6 below.

[0093]

Table 6

[0094] From Tables 5 and 6 above, in Examples 1, 2, and 6 where the product of the BET slope and the cobalt molar percentage was 0.015 or less, the difference between the first particles and the third particles in the temperature of the peak top near 300 °C considered to be derived from the reaction between the composite hydroxide and lithium was reduced to 11.3 °C or less. Therefore, it was found that in Examples 1 to 6 including Examples 1, 2, and 6 where the product of the BET slope and the cobalt molar percentage was 0.015 or less, the reactivity with the lithium compound was made uniform as a whole for the composite hydroxide, and battery characteristics such as cycle characteristics could be improved. In addition, the composite hydroxides of Examples 1, 2, 4 to 6 had a spread in particle size distribution equivalent to that of conventional composite hydroxides, with the value of (D90 - D10) / D50 in the range of 1.07 to 1.15.

[0095] On the other hand, in Comparative Examples 1, 2, and 7 where the product of the BET slope and the cobalt molar percentage exceeds 0.015, the difference between the first particles and the third particles regarding the temperature at the peak top near 300°C was 14.8°C or more. Therefore, in Comparative Examples 1 to 8 including Comparative Examples 1, 2, and 7 where the product of the BET slope and the cobalt molar percentage exceeds 0.015, the reactivity with the lithium compound is non-uniform as a whole for the composite hydroxide, and it has been found that the battery characteristics such as cycle characteristics cannot be sufficiently improved.

Industrial Applicability

[0096] The method for producing a composite hydroxide containing nickel (Ni) and cobalt (Co) according to the present invention can appropriately adjust the reactivity with lithium by appropriately controlling the BET specific surface area without impairing the tap density, and can also reduce the production cost. Therefore, it has high utility value in the field of positive electrode active materials for lithium-ion secondary batteries. Further, the composite hydroxide containing nickel (Ni) and cobalt (Co) according to the present invention has a uniform reactivity with lithium regardless of the particle size, and can improve battery characteristics such as cycle characteristics. Therefore, it has high utility value in the field of positive electrode active materials for lithium-ion secondary batteries.

Explanation of Reference Numerals

[0097] 1 Reaction apparatus 10 Reaction tank 21 First metal-containing aqueous solution 22 Second metal-containing aqueous solution

Claims

1. A method for producing a composite hydroxide containing at least nickel (Ni), cobalt (Co), and an additive metal element M, comprising: a first metal-containing aqueous solution containing A mol% of nickel (Ni) and B mol% of cobalt (Co); a second metal-containing aqueous solution containing C mol% of nickel (Ni) and D mol% of cobalt (Co) (where A > C, B < D, A + B = 100, C + D = 100); an alkali metal aqueous solution; and an aqueous solution containing an ammonium ion donor, which are separately supplied to a reaction tank. The solution in the reaction tank is maintained within a range where the pH value based on a liquid temperature of 25 °C is 10.0 or more and 13.0 or less, and the ammonium ion concentration is 1.0 g / L or more and 10.0 g / L or less. The additive metal element M is one or more elements selected from the group consisting of Mn, Mg, Zr, Al, Ca, Ti, Nb, V, Cr, Mo, and W. The additive metal element M is contained in the first metal-containing aqueous solution, the second metal-containing aqueous solution, or both. The first metal-containing aqueous solution and the second metal-containing aqueous solution are simultaneously supplied to the reaction tank. A method for producing a composite hydroxide, wherein the first metal-containing aqueous solution is supplied to the reaction tank from a first raw material liquid supply section, and the second metal-containing aqueous solution is supplied to the reaction tank from a second raw material liquid supply section different from the first raw material liquid supply section.

2. The method for producing a composite hydroxide according to Claim 1, wherein the ratio of A to C is 5 or more, and the ratio of D to B is 5 or more.

3. The method for producing a composite hydroxide according to Claim 1 or 2, wherein the first metal-containing aqueous solution does not contain cobalt (Co), and the second metal-containing aqueous solution does not contain nickel (Ni).

4. The composite hydroxide is Ni １－ｘ－ｙ Co ｘ M ｙ O ｚ (OH) ２－α The method for producing a composite hydroxide according to any one of claims 1 to 3, represented by (0 < x ≤ 0.3, 0 ≤ y ≤ 0.3, 0 ≤ z ≤ 3.00, -0.50 ≤ α < 2.00).

5. The method for producing a composite hydroxide according to any one of Claims 1 to 4, wherein the reaction tank is a continuous reaction tank that overflows the produced composite hydroxide.

6. The method for producing a composite hydroxide according to any one of Claims 1 to 5, wherein the ammonium ion concentration in the reaction tank is maintained within a range of 1.0 g / L or more and 5.0 g / L or less.

7. The method for producing a composite hydroxide according to any one of Claims 1 to 6, wherein the reaction temperature in the reaction tank is 20 °C or more and 80 °C or less.

8. The method for producing a composite hydroxide according to any one of Claims 1 to 7, wherein the composite hydroxide is a precursor of a positive electrode active material of a secondary battery. **Claim 9**: A composite hydroxide represented by Ni₁₋ₓ₋ᵧCoxMyOz(OH)₂₋α (0.02 < x < 0.20, 0 < x + y < 0.20, 0 ≤ z ≤ 3.00, -0.50 ≤ α < 2.00, where M represents one or more additive metal elements selected from the group consisting of Mn, Mg, Zr, Al, Ca, Ti, Nb, V, Cr, Mo, and W). The composite hydroxide has a first particle in the range of the secondary particle diameter (D10) ± 1.0 μm with a cumulative volume percentage of 10% by volume, a second particle in the range of the secondary particle diameter (D50) ± 1.0 μm with a cumulative volume percentage of 50% by volume, and a third particle in the range of the secondary particle diameter (D90) ± 1.0 μm with a cumulative volume percentage of 90% by volume. The absolute value of the rate of change calculated by the following formula (1) from the BET specific surface area of the first particle and the secondary particle diameter (D50) with a cumulative volume percentage of 50% by volume and the BET specific surface area of the third particle and the secondary particle diameter (D50) with a cumulative volume percentage of 50% by volume, and the molar percentage of cobalt (Co) with respect to the metal elements (where the metal elements are Ni, Co, Mn, Mg, Zr, Al, Ca, Ti, Nb, V, Cr, Mo, and W) contained in the composite hydroxide, the product of which is 0 or more and 0.015 or less. |(BET specific surface area of the third particle - BET specific surface area of the first particle) / (D50 of the third particle - D50 of the first particle)| = absolute value of the rate of change... Formula (1) **Claim 10** The composite hydroxide according to Claim 9, wherein the value of (D90 of the composite hydroxide - D10 of the composite hydroxide) / D50 of the composite hydroxide is 0.50 or more and 1.40 or less.

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