Complex hydroxide, complex oxide, and production method

Abstract

To provide: a complex hydroxide which is a secondary particle obtained by aggregation of a plurality of primary particles and which prevents the secondary particles from being sintered in a state of the secondary particles being aggregated and a production method thereof; and a complex oxide produced by using the complex hydroxide and a production method thereof.SOLUTION: A production method of a complex hydroxide includes: a nucleation step of supplying an aqueous ammonia solution and sodium hydroxide to an aqueous solution containing a nickel-containing compound and a manganese-containing compound to thereby produce a nucleus while maintaining, based on a liquid temperature of 25°C, a pH of 12.0 to 13.5 and an ammonium ion concentration of 5.3 to 11.7 g / L; and a nucleus growth step of growing the nucleus while maintaining, based on the liquid temperature of 25°C, the pH of 9.7 to 10.8 and the ammonium ion concentration of 20.0 to 26.4 g / L.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a composite hydroxide, and further to a composite hydroxide, a method for producing a composite oxide, and a composite oxide. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2016-210674 (Patent Document 1) describes a nickel-cobalt composite hydroxide and a method for producing the same. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-210674 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to reduce durability due to particle cracking, the cathode active material used in non-aqueous electrolyte secondary batteries may undergo a calcination process of the precursor of the cathode active material at a relatively high temperature in the manufacturing process of the cathode active material to form secondary particles formed by agglomeration of a relatively small number of primary particles. However, when the nickel-cobalt composite hydroxide described in Patent Document 1 is calcined at a relatively high temperature, the secondary particles often end up being sintered in an agglomerated state. As a result, the packing property of the cathode active material layer may be reduced. To improve the packing property of the cathode active material layer, a crushing process for crushing the agglomerated secondary particles is required in the manufacturing process of the cathode active material, which increases the number of steps.

[0005] The present disclosure aims to provide a composite hydroxide containing nickel and manganese, which is a secondary particle formed by agglomeration of a plurality of primary particles, in which sintering of the secondary particles in the agglomerated state is suppressed, a method for producing the composite hydroxide, and a composite oxide produced using the composite hydroxide and a method for producing the composite oxide. [Means for solving the problem]

[0006] [1] A method for producing a composite hydroxide, comprising: The composite hydroxide contains nickel and manganese, a nucleation step of supplying an aqueous ammonia solution and sodium hydroxide to an aqueous solution containing a nickel-containing compound and a manganese-containing compound, thereby generating nuclei while maintaining the pH at a standard liquid temperature of 25°C at 12.0 to 13.5 and the ammonium ion concentration at 5.3 to 11.7 g / L; a nucleus growing step of growing the nuclei while maintaining a pH of 9.7 to 10.8 and an ammonium ion concentration of 20.0 to 26.4 g / L at a liquid temperature of 25°C; A method for producing a composite hydroxide, comprising: [2] The composite hydroxide has the following formula (i): Ni 1-x-y-z Co x Mn y M z (i) (In formula (i), 0 <x<0.5、0<y<0.5、0≦z<0.05であり、 M is one or more elements selected from the group consisting of Al, Ti, Zr, B, Mg, Fe, Cu, Zn, Sn, Na, K, Ba, Sr, Ca, W, Mo, Nb, Si, V, Cr, and Ge. The method for producing a composite hydroxide according to [1], wherein the composite hydroxide is a compound represented by the formula: [3] The method for producing a composite hydroxide according to [1] or [2], wherein the nucleation step and the nucleus growth step are both carried out in a non-oxidizing atmosphere. [4] A method for producing a composite oxide, comprising the method for producing a composite hydroxide according to any one of [1] to [3]. [5] The method for producing a composite oxide according to [4], which does not include a crushing step. [6] Secondary particles formed by agglomeration of multiple primary particles, The crystallite size Sp in the direction parallel to the (001) plane is 300 nm to 500 nm, The crystallite size Sv in the direction perpendicular to the (001) plane is 100 nm to 300 nm, the ratio (Lp / Lv) of the length Lp of the primary particle in a direction parallel to the (001) plane to the length Lv of the primary particle in a direction perpendicular to the (001) plane is 10 or more when observed with a scanning electron microscope; At least a portion of the plurality of primary particles are randomly aggregated, The average particle size of the secondary particles is 2.0 to 7.0 μm, A composite hydroxide containing nickel and manganese. [7] The BET specific surface area of ​​the secondary particles is 10 m 2 / g or less. [8] The composite hydroxide according to [6] or [7], wherein the ratio (I011 / I001) of the diffraction peak intensity I011 of the (011) plane to the diffraction peak intensity I001 of the (001) plane determined by X-ray diffraction of the secondary particles is 1.00 or more. [9] A composite oxide comprising a fired product of a mixture of the composite hydroxide according to any one of [6] to [8] and lithium. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide a composite hydroxide containing nickel and manganese, which is a secondary particle formed by agglomeration of a plurality of primary particles, in which sintering of the secondary particles in the agglomerated state is suppressed, a method for producing the composite hydroxide, and a composite oxide produced using the composite hydroxide and a method for producing the composite hydroxide. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a scanning electron microscope image of the composite hydroxide prepared in Example 1. [Figure 2] FIG. 2 is a diagram for explaining the direction perpendicular to the (001) plane of a primary particle and the direction parallel to the (001) plane. [Figure 3] 1 is a scanning electron microscope image of the composite oxide prepared in Example 1. [Figure 4] 1 is a scanning electron microscope image of the composite hydroxide prepared in Comparative Example 4. [Figure 5] 1 is a scanning electron microscope image of the composite hydroxide prepared in Comparative Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Method of producing composite hydroxide> The method for producing a composite hydroxide of the present disclosure comprises a nucleation step in which the composite hydroxide contains nickel (Ni) and manganese (Mn), and nuclei are generated by supplying an aqueous ammonia solution and sodium hydroxide to an aqueous solution containing a compound containing Ni and a compound containing Mn (hereinafter also referred to as raw metal hydroxide) while maintaining the pH at a standard liquid temperature of 12.0 to 13.5 and the ammonium ion concentration at 5.3 to 11.7 g / L at 25°C, and a nucleus growth step in which the nuclei are grown while maintaining the pH at 9.7 to 10.8 and the ammonia concentration at 20.0 to 26.4 g / L.

[0010] The composite hydroxide can be a precursor of a positive electrode active material used in an active material layer of a positive electrode of a non-aqueous electrolyte secondary battery (hereinafter also referred to as a secondary battery) such as a lithium ion battery. The positive electrode active material can be produced, for example, by mixing the composite hydroxide with lithium and subjecting the mixture to a firing treatment. The composite hydroxide may be in the form of particles, or may be secondary particles formed by agglomeration of primary particles.

[0011] In addition to Ni and Mn, the composite hydroxide may further contain at least one element (hereinafter also referred to as an additive element) selected from the group consisting of Co, Al, Ti, Zr, B, Mg, Fe, Cu, Zn, Sn, Na, K, Ba, Sr, Ca, W, Mo, Nb, Si, V, Cr, and Ge. The composite hydroxide is preferably a composite hydroxide containing Ni, Mn, and Co (hereinafter also referred to as an NCM composite hydroxide).

[0012] The NCM composite hydroxide may be, for example, a compound represented by the following formula (i): Ni 1-x-y-z Cox Mn y M z (i) (In formula (i), 0 <x<0.5、0<y<0.5、0≦z<0.05であり、 M is one or more elements selected from the group consisting of Al, Ti, Zr, B, Mg, Fe, Cu, Zn, Sn, Na, K, Ba, Sr, Ca, W, Mo, Nb, Si, V, Cr, and Ge. The composition of the composite hydroxide can be determined by, for example, ICP (inductively coupled plasma) emission spectrometry.

[0013] (Nucleation process) The nucleation step can be carried out, for example, by placing the raw metal aqueous solution in a reaction vessel and supplying an aqueous ammonia solution and sodium hydroxide to the reaction vessel while stirring, while maintaining the pH and ammonium ion concentration within predetermined ranges at a liquid temperature of 25° C. The raw metal aqueous solution can also be placed in the reaction vessel together with an aqueous ammonia solution, and then the pH and ammonium ion concentration at a liquid temperature of 25° C. can be adjusted by supplying the aqueous ammonia solution and sodium hydroxide to the reaction vessel.

[0014] The raw metal aqueous solution is prepared by adding a nickel-containing compound and a manganese-containing compound to water. The Ni-containing compound may be, for example, nickel sulfate (NiSO4), nickel nitrate [Ni(NO3)2], nickel carbonate (NiCO3), etc. The Mn-containing compound may be, for example, manganese sulfate (MnSO4), manganese nitrate [Mn(NO3)2], manganese carbonate (MnCO3), etc. The raw metal aqueous solution may further contain at least one element (hereinafter also referred to as an additive element) selected from the group consisting of Co, Al, Ti, Zr, B, Mg, Fe, Cu, Zn, Sn, Na, K, Ba, Sr, Ca, W, Mo, Nb, Si, V, Cr, and Ge. Co is particularly preferred. The additive element may be added to the raw metal aqueous solution as the element itself or in the form of a salt (e.g., sulfate, nitrate, carbonate, etc.). When the additive element is Co, the raw metal aqueous solution may contain a Co-containing compound. The Co-containing compound may be, for example, cobalt sulfate (CoSO4), cobalt nitrate [Co(NO3)2], cobalt carbonate (CoCO3), or the like.

[0015] The molar ratio of Ni and Mn in the raw metal solution (Ni:Mn) is, for example, 1-x:0 <x<0.5であってよく、1-x:0.1<x<0.5または1-x:0.2<x<0.4であってもよい。

[0016] When the raw metal aqueous solution contains Co, the molar ratio of Ni, Mn, and Co in the raw metal aqueous solution (Ni:Mn:Co) is, for example, 1-xy:0 <x<0.5:0<y<0.5であってよく、1-x-y:0.05<x<0.25:0.05<y<0.25または1-x-y:0.1<x<0.2:0.1<y<0.2であってもよい。

[0017] When the raw metal aqueous solution contains Co and other additive elements, the molar ratio of Ni, Mn, Co, and other additive elements in the raw metal aqueous solution (Ni:Co:Mn:other additive elements) is, for example, 1-xyz:0 <x<0.5:0<y<0.5:0<z<0.05であってよく、1-x-y-z:0.05<x<0.25:0.05<y<0.25:0.001<z<0.01または1-x-y-z:0.1<x<0.2:0.1<y<0.2:0.001<z<0.005であってもよい。

[0018] The metal content in the raw metal aqueous solution may be, for example, 0.5 to 2.0 mol / L.

[0019] The aqueous ammonia solution may have a pH of, for example, 11.5 to 13.5 at a standard liquid temperature of 25°C. The aqueous ammonia solution may have an ammonium ion concentration of, for example, 5 to 15 g / L. The aqueous ammonia solution can be prepared by adding aqueous sodium hydroxide solution and water to ammonium-containing water (to be distinguished from aqueous ammonia solution, hereinafter also referred to as ammonia water) so that the pH and ammonium ion concentration at a standard liquid temperature of 25°C are within the above-mentioned ranges. The aqueous ammonia solution can be prepared, for example, in a non-acidified atmosphere. The aqueous ammonia solution may be prepared while heating, for example, at a temperature of 25 to 50°C.

[0020] The nucleation step can be a step of supplying a raw metal aqueous solution and an ammonia aqueous solution to a reaction vessel and stirring them to cause crystallization while maintaining a pH of 12.0 to 13.5 and an ammonium ion concentration of 5.3 to 11.7 g / L at a liquid temperature of 25° C. Performing the nucleation step while maintaining the pH and ammonium ion concentration within the above ranges at a liquid temperature of 25° C. tends to make it easier to obtain a composite hydroxide in which sintering due to aggregation of secondary particles is suppressed.

[0021] In the nucleation step, the raw metal aqueous solution and the aqueous ammonia solution can be supplied to the reaction vessel so that the molar ratio of the raw metal aqueous solution to the aqueous ammonia solution is 1:1.

[0022] During stirring, while monitoring the pH and ammonium ion concentration at a liquid temperature of 25°C, the pH at a liquid temperature of 25°C can be adjusted to the above range by adding sodium hydroxide, and the ammonium ion concentration can be adjusted to the above range by adjusting the concentration of the aqueous ammonia solution being supplied. The pH can be adjusted by controlling the flow rate of sodium hydroxide using a pH controller.

[0023] In the nucleus growth step, the liquid temperature of the solution may be, for example, 10 to 60° C. The nucleus growth step may be carried out for, for example, 1 to 120 minutes. The nucleation step may be carried out in a non-acidified atmosphere, for example, while flowing nitrogen gas or the like into a reaction vessel.

[0024] (nucleus growth process) The nucleus growth step can be a step of crystallizing the solution after the nucleus generation step by adjusting the pH to 9.7 to 10.8 and the ammonium ion concentration to 20.0 to 26.4 g / L at a liquid temperature of 25° C. in a reaction tank, and then stirring the solution after the nucleus generation step while maintaining the pH at 9.7 to 10.8 and the ammonium ion concentration at 20.0 to 26.4 g / L at a liquid temperature of 25° C. Performing the nucleus growth step while maintaining the pH and ammonium ion concentration within the above ranges at a liquid temperature of 25° C. tends to make it easier to obtain a composite hydroxide in which sintering due to aggregation of secondary particles is suppressed.

[0025] In the nucleus growth step, the pH and ammonium ion concentration of the solution after the nucleation step at a standard liquid temperature of 25°C can be adjusted by simultaneously supplying sodium hydroxide and aqueous ammonia. The pH and ammonium ion concentration of the solution after the nucleation step at a standard liquid temperature of 25°C can also be adjusted by stopping the supply of the raw metal aqueous solution and the aqueous ammonia solution. After adjusting the pH and ammonium ion concentration at a standard liquid temperature of 25°C to the above ranges, nuclei can be grown by maintaining the pH at a standard liquid temperature of 9.7 to 10.8 and the ammonium ion concentration at a standard liquid temperature of 20.0 to 26.4 g / L while supplying the raw metal aqueous solution and the aqueous ammonia solution to the reaction vessel. The pH and ammonium ion concentration at a standard liquid temperature of 25°C can be adjusted in the same manner as in the nucleation step.

[0026] In the nucleus growth step, the liquid temperature of the solution may be, for example, 10 to 60° C. The nucleus growth step may be carried out for, for example, 1 to 24 hours. The nucleation step may be carried out in a non-acidified atmosphere, for example, while flowing nitrogen gas or the like into a reaction vessel.

[0027] The nucleus growth step can be terminated by stopping the supply of the aqueous solution of raw metals and the aqueous ammonia solution. The solution in the reaction vessel is filtered, and the filtrate is washed with water and then dried to obtain a composite hydroxide.

[0028] According to the method for producing a composite hydroxide, a composite hydroxide can be obtained in which sintering of the secondary particles in an agglomerated state is suppressed. Therefore, in the method for producing a composite oxide (positive electrode active material) described below, the crushing treatment for crushing the agglomerated composite oxide can be easily carried out or the crushing step for crushing the composite oxide can be eliminated.

[0029] <Composite hydroxide> The composite hydroxide of the present disclosure is a secondary particle formed by aggregation of a plurality of primary particles, and has a crystallite size Sp in a direction parallel to the (001) plane (hereinafter also referred to as crystallite size Sp) of 300 nm to 500 nm, and a crystallite size Sv in a direction perpendicular to the (001) plane (hereinafter also referred to as crystallite size Sv) of 100 nm to 300 nm. When observed with a scanning electron microscope (hereinafter also referred to as SEM), the ratio (Lp / Lv) of the length Lp in a direction parallel to the (001) plane (hereinafter also referred to as length Lp) to the length Lv in a direction perpendicular to the (001) plane of the primary particles (hereinafter also referred to as length Lv) [hereinafter also referred to as ratio (Lp / Lv)] is 10 or more. The primary particles are aggregated in a state where both the direction parallel to the (001) plane and the direction perpendicular to the (001) plane are randomly oriented. The composite hydroxide of the present disclosure has crystallite sizes Sp and Sv within the above ranges, and at least a portion of the multiple primary particles are randomly aggregated. Therefore, sintering in a state in which the secondary particles are aggregated together tends to be easily suppressed during the firing step (hereinafter also referred to as firing treatment) in the manufacturing process of the positive electrode active material.

[0030] The composite hydroxide may be one produced by the above-mentioned production method. The composite hydroxide is a composite hydroxide containing Ni and Mn, preferably a composite hydroxide containing Ni, Mn, and Co (NCM composite hydroxide), and more preferably a compound represented by the above formula (i).

[0031] The crystallite size Sp and crystallite size Sv can be calculated by applying the full width at half maximum values ​​of the intensities I001 and I100 of the diffraction peaks of the secondary particles determined by X-ray diffraction (XRD) to the Scherrer equation. When the crystallite size Sp and crystallite size Sv are within the above ranges, the growth of the primary particles during the firing process slows down, and the secondary particles are less likely to come into contact with each other due to rapid growth, which tends to make it easier to suppress sintering in a state where the secondary particles are agglomerated. The crystallite size Sp may be, for example, 350 to 450 nm. The crystallite size Sv may be, for example, 150 to 250 nm.

[0032] The ratio (Lp / Lv) can be calculated from the lengths Lv and Lp of the primary particles measured from SEM observation images of the surfaces of the secondary particles. The lengths Lv and Lp can be measured according to the method described in the Examples section below. When the ratio (Lp / Lv) is within the above range, the growth of the primary particles during the firing process slows down, and contact between secondary particles due to rapid growth is reduced, which tends to make it easier to suppress sintering in a state where the secondary particles are in an agglomerated state. The ratio (Lp / Lv) may be, for example, 10.3 or more or 10.4 or more.

[0033] A composite hydroxide is a secondary particle formed by randomly agglomerating at least a portion of a plurality of primary particles. "Randomly agglomerated" refers to a state in which the directions parallel to the (001) plane of a plurality of primary particles are not regularly aligned when the surfaces of the secondary particles are observed with an SEM. This does not include, for example, a state in which the directions parallel to the (001) plane of a plurality of primary particles are aligned in a fixed direction, or a state in which the directions parallel to the (001) plane of a plurality of primary particles extend radially from the center of the secondary particle. The composite hydroxide is preferably a secondary particle formed by randomly agglomerating at least 50% of a plurality of primary particles, more preferably a secondary particle formed by randomly agglomerating at least 70% of a plurality of primary particles, and even more preferably a secondary particle formed by randomly agglomerating all of the primary particles.

[0034] The number of primary particles constituting a secondary particle may be more than one, for example, 2 or more, or 50 or more, or 100 or more, or 1,000 or more, or 10,000 or more, or may be, for example, 1 million or less.

[0035] The average particle size of the secondary particles is 2.0 to 7.0 μm. Generally, composite hydroxides having an average particle size in the above range tend to have secondary particles that aggregate and are easily sintered during firing treatment, but the composite hydroxides of the present disclosure have secondary particles that do not easily aggregate and are easily sintered during firing treatment, despite having an average particle size in the above range. In this specification, the average particle size of the secondary particles may be the particle size D50 at which the cumulative frequency of particles with smaller particle sizes in the volume-based particle size distribution reaches 50%. The volume-based particle size distribution can be measured using a particle size distribution measuring device.

[0036] The BET specific surface area of ​​the secondary particles is, for example, 10 m 2 / g. The BET specific surface area can be measured using a flow gas adsorption specific surface area analyzer. When the BET specific surface area of ​​the secondary particles is within the above range, the reactivity with lithium tends to be reduced during the firing step in the production process of the positive electrode active material, and sintering in a state where the secondary particles are in an agglomerated state tends to be more easily suppressed.

[0037] The secondary particles can have a ratio (I011 / I001) of the diffraction peak intensity I011 of the (011) plane to the diffraction peak intensity I001 of the (001) plane determined by XRD of 1.00 or more. When the ratio (I011 / I001) is within the above range, the growth of the primary particles during firing is slowed, and rapid growth reduces contact between secondary particles, which tends to make it easier to suppress sintering in a state where the secondary particles are in an agglomerated state. The ratio (I011 / I001) may be, for example, 1.02 or more, 1.10 or less, or 1.05 or less.

[0038] Composite hydroxides are suitable as precursors for positive electrode active materials because they tend to suppress sintering in a state in which secondary particles aggregate together during the firing step in the manufacturing process of the positive electrode active material, which in turn tends to improve the filling properties of the positive electrode active material in the positive electrode.

[0039] <Method of manufacturing composite oxide> The method for producing a composite oxide according to the present disclosure includes the method for producing a composite hydroxide described above. The method for producing a composite oxide can further include a mixing step of mixing the composite hydroxide with Li to obtain a mixture, and a calcination step of calcining the mixture.

[0040] In the mixing step, the composite hydroxide and Li can be mixed so that the ratio of the number of Li atoms to the total number of metal elements other than Li in the composite oxide is, for example, 1.0 to 1.3.

[0041] In the firing step, the temperature at which the mixture is fired can be, for example, 700 to 1000° C. The time for which the mixture is fired can be, for example, 3 to 10 hours. The firing step can be carried out in an oxidizing atmosphere.

[0042] According to the method for producing an NCM composite oxide, including the method for producing a composite hydroxide described above, it becomes easier to obtain a positive electrode active material in which sintering of the secondary particles in an agglomerated state is suppressed, making it easier to perform a crushing process for crushing the agglomerated composite oxide, or making a crushing step for crushing the composite oxide unnecessary.

[0043] <Complex oxide> The composite oxide of the present disclosure includes a calcined mixture of the above-described composite hydroxide and lithium. The composite oxide of the present disclosure can be obtained by the above-described method for producing a composite oxide. The composite oxide may be a composite oxide containing Li, Ni, and Mn, and preferably a composite oxide containing Li, Ni, Mn, and Co.

[0044] The composite oxide may be a secondary particle formed by agglomeration of a plurality of primary particles.

[0045] The average particle size of the composite oxide is 2.0 to 7.0 μm.

[0046] The composite oxide may be, for example, a compound represented by the following formula (ii): Li 1-a1 Ni 1-x-y-z Co x Mny M z (ii) (In formula (ii), -0.3 <a1<0.3、0<x<0.5、0<y<0.5、0≦z<0.05であり、 M is one or more elements selected from the group consisting of Al, Ti, Zr, B, Mg, Fe, Cu, Zn, Sn, Na, K, Ba, Sr, Ca, W, Mo, Nb, Si, V, Cr, and Ge. The layered metal oxide may be represented by the following formula:

[0047] Since the sintering of the composite oxide particles in an aggregated state is suppressed, the composite oxide particles are easily packed in the positive electrode, making them suitable for use as a positive electrode active material in batteries. The proportion of the composite oxide particles that are sintered in an aggregated state may be, for example, 14% or less, 7% or less, or 5% or less. When the proportion of the composite oxide particles that are sintered in an aggregated state is within the above range, the packing property of the positive electrode active material tends to be easily improved. The proportion of the particles that are sintered in an aggregated state is measured according to the method described in the Examples section below.

[0048] The present disclosure will now be described in further detail with reference to examples. [Example]

[0049] [Measuring average particle size] The average particle size of the composite hydroxides prepared in the examples and comparative examples was measured using an integrated volume value measured with a commercially available laser light diffraction / scattering particle size analyzer.

[0050] [BET specific surface area measurement] The BET specific surface areas of the composite hydroxides prepared in the examples and comparative examples were measured using a commercially available flow-type gas adsorption specific surface area measuring device.

[0051] [Measurement of crystallite size and peak intensity ratio] Using a commercially available X-ray diffractometer, the crystallite size Sp in the direction parallel to the (001) plane and the crystallite size Sv in the direction perpendicular to the (001) plane of the composite hydroxides prepared in the examples and comparative examples were measured. In addition, the ratio of the peak intensity I011 of the (011) plane to the peak intensity I001 of the (001) plane (I011 / I001) was calculated.

[0052] [Method for measuring the length of primary particles] The composite hydroxides prepared in the examples and comparative examples were observed using a commercially available SEM. Primary particles were extracted from the measured SEM images using image analysis software, and the length Lp parallel to the (001) plane and the length Lv perpendicular to the (001) plane were calculated. Using the calculated lengths, the ratio (Lp / Lv) of the length Lp in the direction parallel to the (001) plane of the primary particles to the length Lv in the direction perpendicular to the (001) plane of the primary particles was calculated. In Figure 2, the X direction is parallel to the (001) plane, and the Y direction is perpendicular to the (001) plane.

[0053] [Evaluation of the proportion of sintered particles in an agglomerated state] A cross section of the composite oxide was extracted by ion milling. This cross section was observed using a commercially available SEM to obtain an SEM image. The average particle size of each particle was determined from the obtained image. Particles larger than 8 μm were considered to be particles sintered in a state where multiple particles were aggregated, and the proportion of particles larger than 8 μm out of 100 particles was calculated as the proportion (%) of particles sintered in a state where multiple particles were aggregated after firing (also referred to as the sintering proportion).

[0054] Example 1 [Preparation of composite hydroxides] (Preparation of aqueous ammonia solution) 2 L of aqueous ammonia solution with an ammonium ion concentration of 11.5 g / L was prepared using 28 wt% aqueous ammonia. The 2 L of aqueous ammonia solution was placed in a 5 L reactor, and nitrogen gas was introduced to maintain an oxygen concentration of 1.0% by volume or less within the reactor, followed by stirring at 800 rpm. After adjusting the solution temperature within the reactor to 40°C, an appropriate amount of 30 wt% aqueous sodium hydroxide solution was added, and the pH was adjusted to 13.0 at a liquid temperature of 25°C. (Preparation of raw metal aqueous solution) Next, nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in water in a molar ratio of 80:10:10 to prepare a 1.5 mol / L aqueous solution of raw metals.

[0055] (Nucleation process) The prepared raw metal aqueous solution and ammonia aqueous solution were supplied to the reaction vessel at an appropriate molar ratio of 1:1, and crystallization was carried out for 60 minutes with stirring while maintaining the pH at 13.0 at a liquid temperature of 25°C. The pH at 25°C was controlled by adjusting the flow rate of sodium hydroxide using a pH controller. The concentration of the supplied ammonia aqueous solution was adjusted so that the ammonium ion concentration in the reaction liquid was maintained at 11.5 g / L. Hereinafter, the pH at a liquid temperature of 25°C in the nucleation step is also referred to as the initial pH. The ammonium ion concentration in the reaction liquid in the nucleation step is also referred to as the initial NH3 concentration.

[0056] (nucleus growth process) After the nucleation step was completed, sulfuric acid was gradually supplied to the reaction vessel so that the pH of the solution in the reaction vessel was 10.7 at a base temperature of 25°C. At the same time, 28 wt% ammonia water was supplied, and the ammonium ion concentration in the reaction vessel was adjusted to 21.0 g / L. After this adjustment, the supply of the solution to the reaction vessel was resumed. At this time, the concentration of the 28 wt% ammonia water supplied was adjusted so that the ammonium ion concentration in the reaction vessel was maintained at 21.0 g / L. Crystallization was continued for 8 hours while maintaining the pH at a base temperature of 10.7 (post-pH) at a base temperature of 25°C. Thereafter, the supply of the solution was stopped, and crystallization was terminated. The product was then filtered, washed with water, and dried, in this order, to obtain the composite hydroxide of Example 1. Note that the atmosphere during the nucleation step and the nucleus growth step was a non-oxidizing atmosphere. Hereinafter, the pH at a base temperature of 25°C in the nucleus growth step is also referred to as the post-pH. The ammonium ion concentration in the reaction vessel in the nucleus growth step is also referred to as the final NH3 concentration. An SEM image of the composite hydroxide of Example 1 is shown in Figure 1. The composite hydroxide of Example 1 was a secondary particle in which all of the primary particles were randomly aggregated.

[0057] [Preparation of composite oxides] The composite hydroxide and the lithium compound were mixed so that the ratio of the number of lithium atoms to the total number of atoms of metal elements other than lithium was 1.10, and the mixture was fired in an oxidizing atmosphere at a temperature of 860°C for 7 hours to obtain the composite oxide of Example 1. The results are shown in Table 1. An SEM image of the composite oxide of Example 1 is shown in Figure 3.

[0058] <Example 2> In (preparation of aqueous ammonia solution), an aqueous ammonia solution with an ammonium ion concentration of 10.6 g / L and a pH of 13.2 at a liquid temperature of 25°C was prepared. In (preparation of raw metal solution), nickel sulfate, cobalt sulfate, manganese sulfate, and zirconium sulfate were dissolved in water in a molar ratio of 69.9:14.9:14.9:0.3 to prepare a 1.6 mol / L aqueous raw metal solution. In (nucleation step), the pH (pre-pH) of the solution in the reaction vessel was adjusted to 13.2 at a liquid temperature of 25°C. The composite hydroxide and composite oxide of Example 2 were prepared in the same manner as in Example 1, except that crystallization was carried out while maintaining the pH (post-pH) at 10.2 and the ammonium ion concentration (initial NH3 concentration) at 10.6 g / L, and that in the (nucleus growth step), the pH of the solution in the reaction vessel was adjusted to 10.1 (post-pH) at a liquid temperature of 25°C and the ammonium ion concentration (final NH3 concentration) to 24.1 g / L, and then crystallization was carried out while maintaining the pH (post-pH) at 10.1 and the ammonium ion concentration at 24.1 g / L at a liquid temperature of 25°C. The results are shown in Table 1.

[0059] <Comparative Example 1> The composite hydroxide and composite oxide were prepared in the same manner as in Example 1, except that in the (preparation of ammonia aqueous solution), an ammonia aqueous solution with an ammonium ion concentration of 10.6 g / L and a pH of 11.5 at a liquid temperature of 25°C was prepared; in the (nucleation step), crystallization was carried out while maintaining the solution in the reaction vessel at a pH (initial pH) of 11.5 at a liquid temperature of 25°C and an ammonium ion concentration (initial NH3 concentration) of 10.6 g / L; and in the (nucleus growth step), the solution in the reaction vessel was adjusted to a pH (final pH) of 10.6 at a liquid temperature of 25°C and an ammonium ion concentration (final NH3 concentration) of 21.0 g / L, and then crystallization was carried out while maintaining the pH (final pH) of 10.6 at a liquid temperature of 25°C and an ammonium ion concentration (final NH3 concentration) of 21.0 g / L. The results are shown in Table 1.

[0060] <Comparative Example 2> The composite hydroxide and composite oxide were prepared in the same manner as in Example 1, except that in the (preparation of ammonia aqueous solution), an ammonia aqueous solution with an ammonium ion concentration of 10.6 g / L and a pH of 13.0 at a liquid temperature of 25°C was prepared; in the (nucleation step), crystallization was carried out while maintaining the solution in the reaction vessel at a pH (initial pH) of 13.0 at a liquid temperature of 25°C and an ammonium ion concentration (initial NH3 concentration) of 10.6 g / L; and in the (nucleus growth step), the solution in the reaction vessel was adjusted to a pH (final pH) of 11.5 at a liquid temperature of 25°C and an ammonium ion concentration (final NH3 concentration) of 21.0 g / L, and then crystallization was carried out while maintaining the pH (final pH) of 11.5 at a liquid temperature of 25°C and an ammonium ion concentration (final NH3 concentration) of 21.0 g / L. The results are shown in Table 1.

[0061] <Comparative Example 3> In the (preparation of aqueous ammonia solution), an aqueous ammonia solution with an ammonium ion concentration of 10.6 g / L and a pH of 13.0 at a liquid temperature of 25 ° C was prepared; in the (nucleation step), crystallization was carried out while maintaining the solution in the reaction vessel at a pH (pre-pH) of 13.0 at a liquid temperature of 25 ° C and an ammonium ion concentration (initial NH3 concentration) of 10.6 g / L; and in the (nucleus growth step), the solution in the reaction vessel was adjusted to a pH (post-pH) of 9.3 at a liquid temperature of 25 ° C and an ammonium ion concentration (final NH3 concentration) of 21.0 g / L, and then crystallization was carried out while maintaining the pH (post-pH) of 9.3 at a liquid temperature of 25 ° C and an ammonium ion concentration (final NH3 concentration) of 21.0 g / L. A composite hydroxide was produced in the same manner as in Example 1. It was not possible to crystallize a composite hydroxide with a uniform particle size and shape.

[0062] <Comparative Example 4> The composite hydroxide and composite oxide were prepared in the same manner as in Example 1, except that in the (preparation of ammonia aqueous solution) an aqueous ammonia solution with an ammonium ion concentration of 9.6 g / L and a pH of 13.3 at a base temperature of 25°C was prepared; in the (nucleation step) the solution in the reaction vessel was crystallized while maintaining a pH (pre-pH) of 13.3 at a base temperature of 25°C and an ammonium ion concentration (initial NH3 concentration) of 9.6 g / L; and in the (nucleus growth step), the solution in the reaction vessel was adjusted to a pH (post-pH) of 10.6 at a base temperature of 25°C and an ammonium ion concentration (final NH3 concentration) of 13.3 g / L, and then crystallization was performed while maintaining a pH (post-pH) of 10.6 at a base temperature of 25°C and an ammonium ion concentration (final NH3 concentration) of 13.3 g / L. The results are shown in Table 1. SEM images of the composite hydroxide and composite oxide are shown in Figures 4 and 5, respectively.

[0063] <Comparative Example 5> The composite hydroxide and composite oxide were prepared in the same manner as in Example 1, except that in the (preparation of ammonia aqueous solution), an ammonia aqueous solution with an ammonium ion concentration of 4.7 g / L and a pH of 12.8 at a liquid temperature of 25°C was prepared; in the (nucleation step), crystallization was carried out while maintaining the solution in the reaction vessel at a pH (initial pH) of 12.8 at a liquid temperature of 25°C and an ammonium ion concentration (initial NH3 concentration) of 4.7 g / L; and in the (nucleus growth step), the solution in the reaction vessel was adjusted to a pH (final pH) of 10.8 at a liquid temperature of 25°C and an ammonium ion concentration (final NH3 concentration) of 21.0 g / L, and then crystallization was carried out while maintaining the pH (final pH) of 10.8 at a liquid temperature of 25°C and an ammonium ion concentration (final NH3 concentration) of 21.0 g / L. The results are shown in Table 1.

[0064] <Comparative Example 6> The composite hydroxide and composite oxide were prepared in the same manner as in Example 1, except that in the (preparation of ammonia aqueous solution), an ammonia aqueous solution with an ammonium ion concentration of 14.2 g / L and a pH of 12.8 at a liquid temperature of 25°C was prepared; in the (nucleation step), crystallization was carried out while maintaining the solution in the reaction vessel at a pH (initial pH) of 12.8 at a liquid temperature of 25°C and an ammonium ion concentration (initial NH3 concentration) of 14.2 g / L; and in the (nucleus growth step), the solution in the reaction vessel was adjusted to a pH (final pH) of 10.6 at a liquid temperature of 25°C and an ammonium ion concentration (final NH3 concentration) of 21.0 g / L, and then crystallization was carried out while maintaining the pH (final pH) of 10.6 at a liquid temperature of 25°C and an ammonium ion concentration (final NH3 concentration) of 21.0 g / L. The results are shown in Table 1.

[0065] <Comparative Example 7> In the (preparation of ammonia aqueous solution), an ammonia aqueous solution having an ammonium ion concentration of 9.6 g / L and a pH of 13.0 at a liquid temperature of 25 ° C was prepared; in the (nucleation step), crystallization was carried out while maintaining the solution in the reaction vessel at a pH (pre-pH) of 13.0 and an ammonium ion concentration (initial NH3 concentration) of 9.6 g / L at a liquid temperature of 25 ° C; and in the (nucleus growth step), the solution in the reaction vessel was adjusted to a pH (post-pH) of 10.6 and an ammonium ion concentration (final NH3 concentration) of 29.2 g / L at a liquid temperature of 25 ° C, and then crystallization was carried out while maintaining the pH (post-pH) of 10.6 and the ammonium ion concentration (final NH3 concentration) of 29.2 g / L at a liquid temperature of 25 ° C. A composite hydroxide was produced in the same manner as in Example 1, except that the composite hydroxide could not have the desired composition.

[0066] <Comparative Example 8> In the (preparation of ammonia aqueous solution), an ammonia aqueous solution with an ammonium ion concentration of 9.5 g / L and a pH of 13.0 at a liquid temperature of 25°C was prepared; in the (nucleation step), crystallization was carried out while maintaining the solution in the reaction vessel at a pH (pre-pH) of 13.0 at a liquid temperature of 25°C and an ammonium ion concentration (initial NH3 concentration) of 9.5 g / L; and in the (nucleus growth step), the solution in the reaction vessel was adjusted to a pH (post-pH) of 10.7 at a liquid temperature of 25°C and an ammonium ion concentration (final NH3 concentration) of 21.0 g / L, and then crystallization was carried out while maintaining the pH (post-pH) of 10.7 at a liquid temperature of 25°C and an ammonium ion concentration (final NH3 concentration) of 21.0 g / L; and the atmosphere in the nucleation step and nucleus growth step was an oxidizing atmosphere. A composite hydroxide was produced in the same manner as in Example 1. It was not possible to crystallize a composite hydroxide with a uniform particle size and shape.

[0067] [Table 1]

Claims

1. A method for producing a composite hydroxide, comprising: The composite hydroxide contains nickel and manganese, a nucleation step of supplying an aqueous ammonia solution and sodium hydroxide to an aqueous solution containing a nickel-containing compound and a manganese-containing compound, thereby generating nuclei while maintaining a pH of 12.0 to 13.5 and an ammonium ion concentration of 5.3 to 11.7 g / L at a liquid temperature of 25°C; a nucleus growing step of growing the nuclei while maintaining a pH of 9.7 to 10.8 and an ammonium ion concentration of 20.0 to 26.4 g / L at a liquid temperature of 25°C; A method for producing a composite hydroxide, comprising:

2. The composite hydroxide has the following formula (i): Ni １－ｘ－ｙ－ｚ Co ｘ Mn ｙ M ｚ (i) (In formula (i), 0<x<0.5, 0<y<0.5, 0≦z<0.05, M is one or more elements selected from the group consisting of Al, Ti, Zr, B, Mg, Fe, Cu, Zn, Sn, Na, K, Ba, Sr, Ca, W, Mo, Nb, Si, V, Cr, and Ge. The method for producing a composite hydroxide according to claim 1, wherein the compound is a compound represented by the formula:

3. The method for producing a composite hydroxide according to claim 1 or 2, wherein the nucleation step and the nucleus growth step are both carried out in a non-oxidizing atmosphere.

4. A method for producing a complex oxide, comprising the method for producing a complex hydroxide according to claim 1 or 2.

5. The method for producing a composite oxide according to claim 4, which does not include a crushing step.

6. Secondary particles formed by agglomeration of a plurality of primary particles, The crystallite size Sp in the direction parallel to the (001) plane is 300 nm to 500 nm, The crystallite size Sv in the direction perpendicular to the (001) plane is 100 nm to 300 nm, the ratio (Lp / Lv) of the length Lp of the primary particle in a direction parallel to the (001) plane to the length Lv of the primary particle in a direction perpendicular to the (001) plane is 10 or more when observed with a scanning electron microscope; At least a portion of the plurality of primary particles are randomly aggregated, the average particle size of the secondary particles is 2.0 to 7.0 μm; A composite hydroxide containing nickel and manganese.

7. The BET specific surface area of ​​the secondary particles is 10 m ２ The composite hydroxide according to claim 6, wherein the SiO 2 content is 1 / g or less.

8. The ratio (I011 / I001) of the diffraction peak intensity I011 of the (011) plane to the diffraction peak intensity I001 of the (001) plane obtained by X-ray diffraction of the secondary particles is 1.00 or more. The composite hydroxide according to claim 6 or 7.

9. A composite oxide comprising a calcined mixture of the composite hydroxide according to claim 6 or 7 and lithium.

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