Transition metal hydroxide, its manufacturing method, and manufacturing method of positive electrode active material using the same

Abstract

The present invention relates to a transition metal hydroxide capable of providing a positive electrode active material with excellent capacity characteristics, a method for producing the same, and a method for producing a positive electrode active material using the same. The transition metal hydroxide contains polycrystalline particles composed of spherical secondary particles formed by agglomeration of acicular primary particles, and has a specific surface area of ​​23 m2 measured by a nitrogen adsorption BET method. 2 / g~43m 2 The present invention provides a transition metal hydroxide represented by Chemical Formula 1, having a particle size distribution curve diffusion index of less than 0.7 and a particle size distribution curve diffusion index of less than 0.7, a method for producing the same, and a method for producing a positive electrode active material using the same.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0015174, filed February 3, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a transition metal hydroxide capable of providing a positive electrode active material having excellent capacity characteristics, a method for producing the same, and a method for producing a positive electrode active material using the same. [Background technology]

[0003] With the technological development and increasing demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which have high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0004] Lithium-transition metal composite oxides are used as the positive electrode active material for lithium secondary batteries, and the lithium-cobalt composite metal oxide LiCoO2 is the most commonly used, due to its high operating voltage and excellent capacity characteristics. However, LiCoO2 has very poor thermal properties due to the destabilization of its crystal structure caused by lithium removal, and is also expensive, which limits its use in large quantities as a power source in fields such as electric vehicles.

[0005] Materials being developed as alternatives to LiCoO2 include lithium manganese composite metal oxides (such as LiMnO2 or LiMn2O4), lithium iron phosphate compounds (such as LiFePO4), and lithium nickel composite metal oxides (such as LiNiO2). Among these, active research and development has been conducted on lithium nickel composite metal oxides, which have a high reversible capacity of approximately 250 mAh / g and are easy to use in large-capacity batteries. However, LiNiO2 has poorer thermal stability than LiCoO2, and if an internal short circuit occurs due to external pressure while the battery is charged, the positive electrode active material itself decomposes, resulting in the battery exploding and catching fire.

[0006] Therefore, as a way to improve the low thermal stability of LiNiO2 while maintaining the excellent reversible capacity, nickel-cobalt-manganese-based lithium composite metal oxides (hereinafter simply referred to as "NCM-based lithium oxides") were developed, in which part of the Ni was replaced with Mn and Co or Al.

[0007] However, due to the recent rise in the price of cobalt (Co), development is underway for lithium-rich (Li-rich) NCM-based positive electrode active materials that contain relatively low or no cobalt (Co) content but can still provide high capacity.

[0008] The primary particles of the precursor of a typical NCM-based positive electrode active material are flake-shaped and have a low specific surface area. The positive electrode active material produced from the precursor also has a flake-shaped primary particle with a specific surface area of ​​1 m. 2 / g and exhibits suitable capacitance characteristics.

[0009] On the other hand, cobalt-free, Li- and Mn-rich positive electrode active materials require more Li than typical NCM-based positive electrode active materials, which necessitates a positive electrode active material precursor with a large specific surface area that can come into contact with Li.

[0010] Therefore, when the primary particles have a plate-like shape and a low specific surface area, as with a typical NCM-based positive electrode active material precursor, the reaction with an excess amount of Li does not proceed smoothly, making it difficult to achieve sufficient capacity characteristics, resulting in problems such as poor initial capacity, life characteristics, and resistance characteristics.

[0011] Therefore, there is a need for the development of a positive electrode active material precursor for developing a cobalt-reduced or cobalt-free Li- and Mn-rich positive electrode active material that has excellent capacity, life, and resistance characteristics. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] CN109970106A (2019.07.05.) Summary of the Invention [Problem to be solved by the invention]

[0013] The present invention has been made to solve the above-mentioned problems, and aims to provide a transition metal hydroxide containing polycrystalline particles composed of secondary particles formed by agglomeration of acicular primary particles, and having a specific specific surface area and particle size distribution curve diffusion index.

[0014] An object of the present invention is to provide a method for producing the transition metal hydroxide, which comprises a coprecipitation reaction carried out under conditions in which the amount of dissolved oxygen is adjusted.

[0015] It is another object of the present invention to provide a method for producing a positive electrode active material using the positive electrode active material precursor. [Means for solving the problem]

[0016] In order to solve the above problems, the present invention provides a transition metal hydroxide, a method for producing the same, and a method for producing a positive electrode active material.

[0017] (1) The present invention includes polycrystalline particles composed of spherical secondary particles formed by agglomeration of acicular primary particles, and has a specific surface area of ​​23 m2 measured by a nitrogen adsorption BET method. 2 / g~43m 2 / g, and a particle size distribution curve diffusion index defined by the following mathematical formula 1 is less than 0.7, and is represented by the following chemical formula 1.

[0018] [Mathematical formula 1] Particle size distribution curve diffusion index=[(D 90 -D 10 ) / D 50 ]

[0019] In the above mathematical formula 1, D 10 D means the particle size at which the volume cumulative from the smaller particle size side corresponds to 10% in the volume-based particle size distribution curve measured by the laser diffraction scattering particle size distribution measurement method. 90 means the particle size at which the cumulative volume from the smallest particle size in the particle size distribution is 90%, and D 50 means the particle size at which the cumulative volume from the smaller particle size side in the particle size distribution is 50%.

[0020] [Chemical formula 1] [Mn a Ni b M 1 c1 M 2 c2 ](OH)2

[0021] In the above Chemical Formula 1, M 1 is Co, M 2 is one selected from Zr, Al, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, and Pt; 0.50 <a≦0.80、0.10≦b≦0.40、0≦c1≦0.02、0≦c2≦0.10、a+b+c1+c2=1である。

[0022] (2) The present invention provides the transition metal hydroxide according to (1) above, which does not contain Co.

[0023] (3) The present invention provides the transition metal hydroxide according to (1) or (2) above, which is represented by the following chemical formula 1-1:

[0024] [Chemical formula 1-1] [Mn a Ni b M 2 c2 ](OH)2

[0025] In the above chemical formula 1-1, M 2 is one selected from Zr, Al, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, and Pt; 0.6≦a≦0.8, 0.1≦b≦0.4, 0≦c2≦0.1, and a+b+c2=1.

[0026] (4) The present invention provides the transition metal hydroxide according to any one of (1) to (3) above, wherein the particle size distribution curve diffusion index is 0.4 or more and less than 0.7.

[0027] (5) The present invention provides the average particle size (D 50 ) is 3 μm to 12 μm.

[0028] (6) The present invention provides a method for producing a transition metal hydroxide according to any one of (1) to (5), comprising a step of co-precipitation of a transition metal solution containing Ni and Mn in the presence of a basic solution, the co-precipitation being carried out under conditions of a dissolved oxygen concentration of 0.0054 mg / L to 0.075 mg / L.

[0029] (7) The present invention provides a method for producing a transition metal hydroxide according to (6) above, wherein the coprecipitation reaction is carried out by step (S1-1) of adding a transition metal solution containing Ni and Mn and a basic solution to a reactor in which an inert atmosphere is created at a pH of 12.0 or less, and initiating the reaction at a pH of 11.0 or less to generate particle nuclei, and step (S1-2) of continuing the reaction while maintaining the pH at 11.0 or less to grow the particle nuclei, wherein nitrogen and air are introduced into the reactor simultaneously with the initiation of the reaction in step (S1-1) to create the dissolved oxygen condition, and the dissolved oxygen condition is maintained throughout the entire reaction of steps (S1-1) and (S1-2).

[0030] (8) The present invention provides the method for producing a transition metal hydroxide according to (6) or (7) above, wherein the coprecipitation reaction is carried out further using an ammonium cation complex-forming agent.

[0031] (9) The present invention provides the method for producing a transition metal hydroxide according to any one of (6) to (8) above, wherein the transition metal solution further contains one or more elements selected from Zr, Al, Co, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, and Pt.

[0032] (10) The present invention provides the method for producing a transition metal hydroxide according to any one of (6) to (9) above, wherein the transition metal solution contains 50 mol % or more of Mn among the transition metals.

[0033] (11) The present invention provides a method for producing a positive electrode active material, the method comprising the steps of mixing the transition metal hydroxide according to any one of (1) to (5) above with a lithium source material, and calcining the mixture.

[0034] (12) The present invention provides the method for producing a positive electrode active material according to (11) above, wherein the transition metal hydroxide and the lithium source material are mixed so that the molar ratio of the transition metal hydroxide to the lithium element in the lithium source material is 1:1.2 to 1:1.6. [Effects of the Invention]

[0035] The transition metal hydroxide according to the present invention has the characteristics of a large specific surface area and a particle size distribution curve diffusion index of less than 0.7, and therefore exhibits high reactivity with lithium when fired with a lithium raw material, thereby making it possible to provide a positive electrode active material with excellent capacity characteristics.

[0036] Furthermore, the method for producing a transition metal hydroxide according to the present invention can produce a transition metal hydroxide having a high specific surface area and particle size distribution curve diffusion index within a specific range by carrying out a coprecipitation reaction under conditions in which the amount of dissolved oxygen is adjusted. [Brief explanation of the drawings]

[0037] The following drawings attached to this specification are intended to illustrate preferred embodiments of the present invention and, together with the above-described content of the invention, serve to further understand the technical concept of the present invention. Therefore, the present invention should not be interpreted as being limited only to the matters shown in these drawings. [Figure 1] 1 is an SEM image (magnification 10K) of the transition metal hydroxide produced in Example 1. [Figure 2] 1 is an SEM image (magnification 10K) of the transition metal hydroxide produced in Example 2. [Figure 3] 1 is an SEM image (magnification 10K) of the transition metal hydroxide produced in Comparative Example 1. [Figure 4] 1 is an SEM image (magnification 10K) of the transition metal hydroxide produced in Comparative Example 2. [Figure 5] 1 is an SEM image (magnification 10K) of the positive electrode active material of Example 1. [Figure 6] 1 is an SEM image (magnification 10K) of the positive electrode active material of Example 2. [Figure 7] 1 is an SEM image (magnification 10K) of the positive electrode active material of Comparative Example 1. [Figure 8] 1 is an SEM image (magnification 10K) of the positive electrode active material of Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0038] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0039] Definition of Terms As used herein, the term "primary particle" refers to a single particle in a form in which particles are not morphologically aggregated with each other and exist separated and / or dispersed from each other as independent phases.

[0040] As used herein, the term "secondary particles" generally refers to a particle structure in contrast to a primary particle (single particle), and refers to a structure in which small primary particles are physically and / or chemically aggregated to form a relatively large particle.

[0041] As used herein, the term "polycrystalline particle" refers to a particle having such a shape that, in the case of a secondary particle formed by the aggregation of a number of primary particles, the crystal lattice structure is not regularly maintained throughout the particle but has multiple orientations.

[0042] As used herein, the term "average particle size (D 50 )" means the particle size at which the cumulative volume is 50% in the volume-based particle size distribution curve measured by a laser diffraction / scattering particle size distribution measurement method.

[0043] Measurement method In the present invention, the "average particle size (D 50 , D 90 , D 10) is measured using a laser diffraction scattering particle size distribution measurement method. Specifically, particles are dispersed in a dispersion medium, then introduced into a laser diffraction measurement device (Microtrac S3500), and irradiated with 28 kHz ultrasound at an output of 60 W. The particle sizes corresponding to 50%, 10%, and 90% of the cumulative volume in the measurement device are calculated and measured.

[0044] In the present invention, the "specific surface area" is calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) after pretreating 3.00 g of a sample under vacuum conditions at 200°C using a surface area analyzer TriStar 2 plus (Micromeritics).

[0045] transition metal hydroxide The present invention provides a transition metal hydroxide that can provide a low-cobalt or cobalt-free perlithium-manganese nickel-based positive electrode active material that has high reactivity with lithium source materials and excellent capacity characteristics.

[0046] According to one embodiment of the present invention, the transition metal hydroxide is a positive electrode active material precursor, particularly a positive electrode active material precursor useful for preparing a cobalt-free perlithium-manganese nickel-based positive electrode active material, and includes polycrystalline particles composed of spherical secondary particles formed by agglomeration of acicular primary particles, and has a specific surface area of ​​23 m2 as measured by a nitrogen adsorption BET method. 2 / g~43m 2 / g, and the particle size distribution curve diffusion index defined by the following mathematical formula 1 is less than 0.7, and is characterized by being represented by the following chemical formula 1.

[0047] [Mathematical formula 1] Particle size distribution curve diffusion index=[(D 90 -D 10 ) / D 50 ]

[0048] In the above mathematical formula 1, D 10D means the particle size at which the cumulative volume from the smaller particle size side is 10% in the volume-based particle size distribution measured by the laser diffraction scattering particle size distribution measurement method. 90 means the particle size at which the cumulative volume from the smallest particle size in the particle size distribution is 90%, and D 50 means the particle size at which the cumulative volume from the smaller particle size side in the particle size distribution is 50%.

[0049] [Chemical formula 1] [Mn a Ni b M 1 c1 M 2 c2 ](OH)2

[0050] In the above Chemical Formula 1, M 1 is Co, M 2 is one selected from Zr, Al, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, and Pt; 0.50 <a≦0.80、0.10≦b≦0.40、0≦c1≦0.02、0≦c2≦0.10、a+b+c1+c2=1である。

[0051] A typical NCM-based positive electrode active material is a single phase, manufactured from a precursor with a rhombohedral lattice structure, and has a structure in which a transition metal layer and a Li layer are repeated.

[0052] In contrast, Li- and Mn-rich positive electrode active materials that contain little or no cobalt are manufactured from Mn-rich precursors with two layers, namely, monoclinic lattice and rhombohedral lattice crystal structures, and have a structure in which transition metal layers and Li layers are repeated, and additionally, Li atoms are contained in the transition metal layer. This requires more Li than typical NCM-based positive electrode active materials, which requires a positive electrode active material precursor with a high specific surface area that can come into contact with Li.

[0053] Therefore, precursors with a plate-like primary particle shape and a low specific surface area, like common NCM-based positive electrode active material precursors, do not react smoothly with excess Li, making it difficult for the resulting positive electrode active material to exhibit sufficient capacity characteristics, resulting in problems such as poor initial capacity, life characteristics, and resistance characteristics of the battery.

[0054] However, the transition metal hydroxide according to the present invention contains polycrystalline particles composed of secondary particles formed by agglomeration of acicular primary particles, and has a high specific surface area within a specific range and a particle size distribution curve diffusion index of less than 0.7. As a result, the transition metal hydroxide has high reactivity with Li, and therefore reacts smoothly with excess Li, making it possible to provide a positive electrode active material with excellent capacity characteristics, life characteristics, and resistance characteristics.

[0055] A transition metal hydroxide according to one embodiment of the present invention may contain Ni and Mn, and may contain 50 mol % or more of Mn among the transition metals, which makes it easy to ensure a high capacity of the positive electrode active material obtained therefrom.

[0056] As another example, in order to achieve a well-balanced initial charge / discharge capacity, the content of Mn among the transition metals may be 55 mol % or more and 80 mol % or less, specifically 60 mol % or more and 80 mol % or less.

[0057] As another example, the transition metal hydroxide according to one embodiment of the present invention may have other metal components (M 1 and M2 ) may be coated or doped. In this case, the metal component M 1 is Co and M 2 may be one selected from Zr, Al, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, and Pt.

[0058] As yet another example, the transition metal hydroxide according to an embodiment of the present invention may be represented by the following Chemical Formula 1:

[0059] [Mn a Ni b M 1 c1 M 2 c2 ](OH)2

[0060] In the above Chemical Formula 1, M 1 is Co, M 2 is one selected from Zr, Al, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, and Pt; 0.50 <a≦0.80、0.10≦b≦0.40、0≦c1≦0.02、0≦c2≦0.10、a+b+c1+c2=1である。

[0061] In Formula 1, Mn may be included in an amount corresponding to a, and when a is in the above range, excellent charge capacity can be obtained.

[0062] In addition, in Formula 1, Ni may be contained in an amount corresponding to b, and when b is in the above range, excellent charge capacity can be obtained.

[0063] In addition, in the above-mentioned chemical formula 1, M 1 and M 2 are metal elements coated or doped on the surface of the transition metal hydroxide, and may be contained in amounts corresponding to c1 and c2, respectively.

[0064] More specifically, the transition metal hydroxide may be represented by the following chemical formula 1-1.

[0065] [Chemical formula 1-1] [Mn a Ni b M 2 c2 ](OH)2

[0066] In the above chemical formula 1-1, M 2 is one selected from Zr, Al, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, and Pt; 0.6≦a≦0.8, 0.1≦b≦0.4, 0≦c2≦0.1, and a+b+c2=1.

[0067] More specifically, in the above chemical formula 1-1, 0.6≦a≦0.8, 0.2≦b≦0.4, c2=0, and a+b+c=1.

[0068] The transition metal hydroxide has a specific surface area of ​​23 m as measured by the nitrogen adsorption BET method. 2 / g~43m 2 / g, and the particle size distribution curve diffusion index defined by Mathematical Formula 1 is less than 0.7. Specifically, the particle size distribution curve diffusion index may be 0.4 or more and less than 0.7. The transition metal hydroxide according to the present invention satisfies the above-mentioned specific surface area and particle size distribution curve diffusion index, and therefore has excellent particle uniformity and high reactivity with Li, making it possible to provide a positive electrode active material with excellent capacity characteristics.

[0069] The transition metal hydroxide contains polycrystalline particles composed of spherical secondary particles formed by agglomeration of needle-like primary particles.

[0070] As another example, the transition metal hydroxide may be polycrystalline particles composed of secondary particles formed by agglomeration of needle-like primary particles.

[0071] Meanwhile, the transition metal hydroxide according to one embodiment of the present invention has a particle morphology including spherical secondary particles formed by agglomeration of needle-shaped primary particles, and thus voids may be developed within the particles, resulting in a high specific surface area.

[0072] As yet another example, the specific surface area and particle size distribution curve diffusion index of the transition metal hydroxide are affected by the shape and size of the primary particles constituting the transition metal hydroxide. A transition metal hydroxide according to one embodiment of the present invention is produced by a co-precipitation reaction under conditions in which the amount of dissolved oxygen described below is adjusted to a specific range, and the aspect ratio and average particle size of the primary particles, as well as the average particle size of the secondary particles, are appropriately adjusted, thereby making it possible to satisfy the above-mentioned specific surface area and particle size distribution curve diffusion index.

[0073] Specifically, when the primary particles are formed too thin or too thick, the specific surface area of ​​the resulting transition metal hydroxide may be too low or too high. If the specific surface area is too low, the reactivity with Li may be low, resulting in a problem of poor capacity characteristics of the resulting positive electrode active material. Conversely, if the specific surface area is too high, the particles may become more non-uniform, resulting in significant variation in the capacity characteristics of the resulting positive electrode active material, resulting in poor reproducibility.

[0074] From this point of view, the transition metal hydroxide of the present invention, by satisfying both the specific surface area and particle distribution diffusion index described above, can provide a positive electrode active material excellent in capacity characteristics and reproducibility.

[0075] In addition, in order to more easily satisfy both the specific surface area and the particle distribution diffusion index, the secondary particles are preferably formed to have an average particle size (D 50 ) may be 3 μm to 12 μm.

[0076] Method for producing transition metal hydroxide The present invention provides a method for producing the transition metal hydroxide.

[0077] The method for producing the transition metal hydroxide according to one embodiment of the present invention includes a step of co-precipitation of a transition metal solution containing Ni and Mn in the presence of a basic solution, and the co-precipitation reaction is carried out under conditions where the dissolved oxygen content is 0.0054 mg / L to 0.075 mg / L.

[0078] Specifically, the coprecipitation reaction may be carried out by step (S1-1) of adding a transition metal solution containing Ni and Mn and a basic solution to a reactor in which an inert atmosphere is created at a pH of 12.0 or less, and initiating the reaction at a pH of 11.0 or less to generate particle nuclei, and step (S1-2) of continuing the reaction while maintaining the pH at 11.0 or less to grow the particle nuclei. Simultaneously with the initiation of the reaction in step (S1-1), nitrogen and air may be introduced into the reactor to create the dissolved oxygen condition, and the dissolved oxygen condition may be maintained throughout the entire reaction of steps (S1-1) and (S1-2).

[0079] The method for producing the transition metal hydroxide according to the present invention allows a coprecipitation reaction to proceed in an atmosphere controlled to satisfy the above-mentioned dissolved oxygen content conditions, thereby forming the above-mentioned primary particles and allowing them to grow into secondary particles, thereby producing a transition metal hydroxide that satisfies a specific specific surface area and particle distribution diffusion index.

[0080] Meanwhile, the amount of dissolved oxygen can be controlled by adjusting the amounts of nitrogen and air added. For example, nitrogen and air may be added in a volume ratio of 99.5:0.5 to 95:5.

[0081] The transition metal solution may be prepared by adding a transition metal source material to a solvent, specifically, deionized water or a mixed solvent of deionized water and an organic solvent (e.g., alcohol) that is uniformly miscible with deionized water, and then mixing the two together. Alternatively, the transition metal solution may be prepared by mixing an aqueous solution of the transition metal source material.

[0082] The transition metal source material may be a transition metal sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide.

[0083] Specific examples of the Ni source material include, but are not limited to, nickel-containing acetates, nitrates, sulfates, halides, sulfides, hydroxides, oxides, or oxyhydroxides, and more specific examples include, but are not limited to, Ni(OH), NiO, NiOOH, NiCO·2Ni(OH)·4H2O, NiCO·2H2O, Ni(NO)·6H2O, NiSO·6H2O, fatty acid nickel salts, nickel halides, and combinations thereof.

[0084] Furthermore, the Mn source material may be, for example, a manganese-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or oxyhydroxide. More specific examples include, but are not limited to, manganese oxides such as MnO, MnO, and MnO; manganese salts such as MnCO, Mn(NO), MnSO, ​​manganese acetate, manganese dicarboxylate, manganese citrate, and manganese fatty acid salt; manganese oxyhydroxide, manganese chloride, or combinations thereof.

[0085] As yet another example, the transition metal solution may further include one or more selected from Zr, Al, Co, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, and Pt. In this case, the transition metal solution may further include a source material containing Zr, Al, Co, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, or Pt, and the source material may be acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or the like containing each of the metals.

[0086] The transition metal solution may contain 50 mol % or more of Mn among the transition metals in the solution.

[0087] As another example, the transition metal solution does not contain Co.

[0088] The basic solution may also be a precipitant, which may be an alkali metal or alkaline earth metal hydroxide, such as NaOH, KOH, or Ca(OH)2, a hydrate thereof, or a combination thereof.

[0089] Alternatively, the basic solution may be used in the form of an aqueous solution, and the solvent may be deionized water or a mixture of deionized water and an organic solvent (e.g., alcohol) that is uniformly miscible with deionized water.

[0090] The basic solution may also serve to adjust the pH in the reactor during the coprecipitation reaction, and by adjusting the amount of the basic solution added, the pH in the reactor can be controlled to a desired condition.

[0091] The coprecipitation reaction may be carried out using an ammonium cation complexing agent, if necessary. The ammonium cation complexing agent may include at least one selected from the group consisting of NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and NH4CO3. The ammonium cation complexing agent may be used in the form of an aqueous solution, which may be prepared by mixing the ammonium cation complexing agent with deionized water or a mixture of deionized water and an organic solvent (e.g., alcohol) that is uniformly miscible with deionized water.

[0092] On the other hand, the coprecipitation reaction may be carried out at a temperature of 40°C to 70°C with stirring. The stirring speed is not particularly limited, but stirring may be carried out at 100 rpm to 2,000 rpm, as this facilitates an increase in the reaction rate.

[0093] In addition, in the method for preparing the transition metal hydroxide according to the embodiment of the present invention, after the co-precipitation reaction, one or more steps selected from washing with water and drying may be further performed, and in this case, the washing with water and drying may be performed by a conventional method known in the art.

[0094] For example, the water washing may be carried out by adding the precursor to ultrapure water and stirring it, and the water washing temperature may be 70°C or less, specifically 40°C to 70°C, and the water washing time may be 10 minutes to 1 hour.

[0095] The drying method is not particularly limited as long as it can dry the produced precursor without causing any chemical change. For example, a drying method using a spray dryer or a rotary evaporator, a vacuum drying method, or an air drying method may be used.

[0096] positive electrode active material The present invention provides a positive electrode active material prepared using the transition metal hydroxide.

[0097] The positive electrode active material according to one embodiment of the present invention includes polycrystalline particles composed of secondary particles formed by agglomeration of acicular primary particles, and has a specific surface area of ​​1.00 m as measured by a nitrogen adsorption BET method. 2 / g~1.90m 2 / g.

[0098] The positive electrode active material may be a compound represented by the following chemical formula 2:

[0099] [Chemical formula 2] x[Li(Mn d Ni e M 1 f1 M 2 f2 )O2]·1-x[Li2MnO3]

[0100] In the above Chemical Formula 2, M 1 is Co, M 2 is one selected from Zr, Al, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, and Pt; 0.600≦x≦0.800, 0.570≦d≦0.720, 0.140≦e≦0.290, 0≦f1<0.034, 0≦f2≦0.140, d+e+f1+f2<1.200.

[0101] Method for producing positive electrode active material The present invention provides a method for producing a positive electrode active material using the transition metal hydroxide.

[0102] The method for producing the positive electrode active material may include mixing the transition metal hydroxide and a lithium source material, and firing the mixture.

[0103] Specifically, the method for producing a positive electrode active material according to the present invention may be carried out by a method for producing a positive electrode active material known in the art, except that the transition metal hydroxide according to the present invention is used as a precursor, and the method is not particularly limited.

[0104] Examples of the lithium source material include lithium-containing carbonates (e.g., lithium carbonate), hydrates (e.g., lithium hydroxide hydrate (LiOH·H2O)), hydroxides (e.g., lithium hydroxide), nitrates (e.g., lithium nitrate (LiNO3)), and chlorides (e.g., lithium chloride (LiCl)). One of these may be used alone, or two or more may be used in combination.

[0105] Meanwhile, the transition metal hydroxide and the lithium source material may be mixed by solid-phase mixing using a jet mill or the like, and the mixing ratio of the transition metal hydroxide and the lithium source material may be determined within a range that satisfies the molar fraction of each component in the final cathode active material. More specifically, the transition metal hydroxide and the lithium source material may be mixed so that the molar ratio of the transition metal hydroxide to the lithium element in the lithium source material is 1:1.2 to 1:1.6.

[0106] Furthermore, although not required, during the mixing, in addition to the transition metal hydroxide and lithium source material, a source material for doping a portion of the transition metal and / or oxygen of the positive electrode active material may be further included. For example, during the mixing, the above-mentioned M-containing source material and / or the below-described X-containing source material may be further mixed. In this case, examples of the X-containing source material include, but are not limited to, Na3PO4, K3PO4, Mg3(PO4)2, AlF3, NHF, and LiF. When a portion of the oxygen is replaced by the X element as described above, the effect of suppressing oxygen desorption and reaction with the electrolyte during charge and discharge of the secondary battery can be obtained.

[0107] On the other hand, the firing may be carried out at 800°C to 1,000°C, specifically 850°C to 950°C, and the firing time may be 5 hours to 30 hours, specifically 8 hours to 15 hours, but is not limited to these.

[0108] Positive electrodes and secondary batteries The present invention provides a positive electrode including the positive electrode active material, and a lithium secondary battery including the positive electrode.

[0109] The positive electrode according to an embodiment of the present invention includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, wherein the positive electrode active material layer includes the positive electrode active material.

[0110] The positive electrode may be manufactured by a conventional method for manufacturing a positive electrode, except for using the positive electrode active material. For example, the positive electrode may be manufactured by dissolving or dispersing components constituting the positive electrode active material layer, i.e., the positive electrode active material, and a conductive material and / or a binder, in a solvent to manufacture a positive electrode composite, applying the positive electrode composite to at least one surface of a positive electrode current collector, and then drying and rolling the applied material. Alternatively, the positive electrode may be manufactured by casting the positive electrode composite on a separate support, peeling it from the support, and laminating the resulting film on the positive electrode current collector.

[0111] The positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like may be used. The positive electrode current collector typically has a thickness of 3 μm to 500 μm, and the adhesion of the positive electrode active material may be enhanced by forming fine irregularities on the surface of the current collector. Various forms are possible, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0112] A positive electrode active material layer containing the positive electrode active material according to the present invention and optionally further containing at least one of a conductive material and a binder is located on at least one surface of the current collector.

[0113] The positive electrode active material may be contained in an amount of 80 to 99 wt %, more specifically 85 to 98 wt %, based on the total weight of the positive electrode active material layer. When contained in this range, excellent capacity characteristics can be exhibited.

[0114] The conductive material is used to impart conductivity to the electrode and can be any material that does not cause chemical changes in the resulting battery and has electronic conductivity. Specific examples include graphite, such as natural graphite or artificial graphite; carbon-based materials, such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber, such as copper, nickel, aluminum, and silver; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and conductive polymers, such as polyphenylene derivatives. One of these may be used alone, or two or more may be used in combination. The conductive material may be contained in an amount of 1 wt % to 30 wt % based on the total weight of the positive electrode active material layer.

[0115] The binder also serves to improve adhesion between positive electrode active material particles and between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. One of these may be used alone, or two or more may be used in combination. The binder may be contained in an amount of 1 wt% to 30 wt% based on the total weight of the positive electrode active material layer.

[0116] Meanwhile, the solvent used in preparing the cathode composite may be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, either alone or in combination. The amount of the solvent used may be adjusted appropriately in consideration of the coating thickness, production yield, viscosity, etc. of the slurry.

[0117] In addition, the lithium secondary battery according to the present invention includes a positive electrode, a negative electrode facing the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is the positive electrode according to the present invention.

[0118] Meanwhile, the lithium secondary battery may optionally further include a battery container that houses an electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0119] In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector.

[0120] The negative electrode may be manufactured by a conventional method for manufacturing a negative electrode generally known in the art. For example, the negative electrode may be manufactured by dissolving or dispersing components constituting the negative electrode active material layer, i.e., the negative electrode active material, and a conductive material and / or a binder, in a solvent to prepare a negative electrode mixture, applying the negative electrode mixture to at least one surface of a negative electrode current collector, drying, and rolling the mixture, or by casting the negative electrode mixture on a separate support, peeling it from the support, and laminating the resulting film on the negative electrode current collector.

[0121] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surfaces treated with carbon, nickel, titanium, silver, or the like, and aluminum-cadmium alloys may be used. The negative electrode current collector typically has a thickness of 3 μm to 500 μm, and, like the positive electrode current collector, the surface of the current collector may be formed with fine irregularities to strengthen the binding force of the negative electrode active material. Various forms are possible, such as films, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0122] The negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, and Al alloys; and SiO. v(0 < v < 2), metal oxides such as SnO2, vanadium oxides, and lithium vanadium oxides that can be doped and undoped with lithium; or composites containing the above metal compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, etc. may be mentioned, and one or a mixture of two or more of these may be used. Further, a thin film of metallic lithium may be used as the negative electrode active material. Also, as the carbon material, both low-crystalline carbon and high-crystalline carbon can be used. Representative examples of low-crystalline carbon are soft carbon and hard carbon, and representative examples of high-crystalline carbon are amorphous, plate-like, scaly, spherical, or fibrous natural graphite or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbons such as petroleum and coal tar pitch-derived cokes.

[0123] Further, the binder and the conductive material are the same as those described above for the positive electrode.

[0124] Meanwhile, in the secondary battery, the separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator commonly used in secondary batteries can be used without particular limitations. In particular, separators with low resistance to electrolyte ion movement and excellent electrolyte impregnation ability are preferred. Specifically, porous polymer films, such as those made of polyolefin-based polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminate structures of two or more layers thereof can be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. To ensure heat resistance or mechanical strength, coated separators containing ceramic components or polymeric materials can also be used, and they can be selectively used in single-layer or multi-layer structures.

[0125] On the other hand, the electrolyte may be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, or the like that can be used in manufacturing a secondary battery, but is not limited thereto.

[0126] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0127] The organic solvent may be any solvent capable of acting as a medium for the movement of ions involved in the electrochemical reaction of the battery. Specific examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether and tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate. Examples of suitable electrolytes include carbonate-based solvents such as ethylene carbonate (PC), alcohol-based solvents such as ethyl alcohol and isopropyl alcohol, nitriles such as Ra-CN (Ra is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double-bonded aromatic ring or an ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, and sulfolanes. Among these, carbonate-based solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with low viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) are more preferred, as they have high ionic conductivity and a high dielectric constant, which can improve the charge / discharge performance of batteries. In this case, a mixture of the cyclic carbonate and the linear carbonate at a volume ratio of approximately 1:1 to 9:9 provides excellent electrolyte performance.

[0128] The lithium salt can be any compound capable of providing lithium ions used in lithium secondary batteries. Specifically, examples of the lithium salt include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, and LiB(C2O4)2. The lithium salt concentration is preferably in the range of 0.1M to 2.0M. When the lithium salt concentration is within the above range, the electrolyte has appropriate conductivity and viscosity, resulting in excellent electrolyte performance and efficient lithium ion migration.

[0129] In addition to the electrolyte components, the electrolyte may further contain one or more additives, such as haloalkylene carbonate compounds (e.g., difluoroethylene carbonate), pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving battery life characteristics, suppressing battery capacity loss, and improving battery discharge capacity. In this case, the additives may be contained in an amount of 0.1 wt % to 5 wt % based on the total weight of the electrolyte.

[0130] As described above, the secondary battery including the cathode active material according to the present invention has excellent capacity characteristics and high-temperature stability, and is therefore useful in the fields of portable devices such as mobile phones, notebook computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0131] The secondary battery according to the present invention may be used as a unit cell of a battery module, and the battery module may be applied to a battery pack. The battery module or the battery pack may be used as a power source for one or more medium- to large-sized devices, including power tools, electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs), and power storage systems.

[0132] Example Although the present invention may be embodied in various different forms, it is not intended to be limited to the embodiments set forth herein, and the present invention is not limited to the embodiments set forth herein.

[0133] Example 1 NiSO4 and MnSO4 were mixed in deionized water in amounts that gave a molar ratio of Ni:Mn of 35:65 to prepare a 2.4 M aqueous transition metal solution.

[0134] A 10-L continuous stirred tank reactor was charged with 2.6 L of deionized water and purged with nitrogen gas at 2 L / min to remove dissolved oxygen and create a non-oxidizing atmosphere. While continuing to flow nitrogen gas at 2 L / min, 3.87 mL of a 25 wt% NaOH aqueous solution was then charged. The mixture was stirred at 150 rpm at 50°C until the pH in the reactor reached approximately 12.0.

[0135] Then, while stirring at 1000 rpm, the reactor was continuously charged with a transition metal aqueous solution at 0.83 L / hr and a NaOH aqueous solution at 0.29 L / hr. At the same time, nitrogen and air were charged at a volume ratio of 99.5:0.5 to control the dissolved oxygen content at 0.0054 mg / L. Coprecipitation was carried out so that the pH in the reactor reached approximately 11.0 within 2 hours, and then the coprecipitation reaction was continued for 48 hours at a pH of approximately 11.0. After the coprecipitation reaction was completed, the generated particles were separated and washed, and then dried at 120°C for 12 hours to obtain Mn. 0.65 Ni 0.35 Transition metal hydroxides of (OH)2 were prepared.

[0136] Example 2 The same procedure as in Example 1 was carried out to obtain Mn, except that the coprecipitation reaction was carried out under the condition that nitrogen and air were introduced at a volume ratio of 95:5 at the same time as the introduction of the aqueous transition metal solution, and the dissolved oxygen content was controlled to 0.079 mg / L. 0.65 Ni 0.35 Transition metal hydroxides of (OH)2 were prepared.

[0137] Comparative Example 1 The same procedure as in Example 1 was carried out to obtain Mn, except that the coprecipitation reaction was carried out under the condition that nitrogen and air were introduced at a volume ratio of 99.8:0.2 at the same time as the introduction of the aqueous transition metal solution, and the dissolved oxygen content was controlled to 0.0049 mg / L. 0.65 Ni 0.35 Transition metal hydroxides of (OH)2 were prepared.

[0138] Comparative Example 2 The same procedure as in Example 1 was carried out to obtain Mn, except that the coprecipitation reaction was carried out under the condition that nitrogen and air were introduced at a volume ratio of 90:10 at the same time as the introduction of the aqueous transition metal solution, and the dissolved oxygen content was controlled to 0.092 mg / L. 0.65 Ni 0.35 Transition metal hydroxides of (OH)2 were prepared.

[0139] Experimental Example 1 The particle surfaces of the transition metal hydroxides produced in the examples and comparative examples were analyzed, and the specific surface area and particle size distribution diffusion index were analyzed. The results are shown in Table 1 below and in FIGS.

[0140] (1) Analysis of particle surfaces The surface state of the particles was confirmed by SEM analysis, and the SEM analysis was performed using an SEM (QUANTA FEG 250, Thermo Fischer) under the following conditions. 1) High voltage: 10,000kV 2) Chamber pressure: 9.0 × 10 -5 mbar 3) Gun pressure: 6.85 x 10 -10 mbar 4) Emission current: 165μA 5) Working Distance: 10mm 6) Beam spot size: 3.0 7) Stage bias: 4000V 8) Magnification: 10K

[0141] (2) Specific surface area (m 2 / g) The specific surface area was measured by the BET method and calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77 K) using a Tristar II (Micromeritics).

[0142] (3) Particle size distribution curve diffusion index The particle size distribution was measured by a laser diffraction scattering particle size distribution measurement method. Specifically, particles were dispersed in a dispersion medium, and then introduced into a laser diffraction measurement device (Microtrac S3500). Ultrasound of 28 kHz was irradiated at an output of 60 W, and the particle sizes corresponding to 50%, 10%, and 90% of the cumulative volume in the measurement device were calculated and calculated using the following mathematical formula 1.

[0143] [Mathematical formula 1] Particle size distribution curve diffusion index=[(D 90 -D 10 ) / D 50 ]

[0144] In the above mathematical formula 1, D 10 D means the particle size at which the volume cumulative from the smaller particle size side corresponds to 10% in the volume-based particle size distribution curve measured by the laser diffraction scattering particle size distribution measurement method. 90 means the particle size at which the cumulative volume from the smallest particle size in the particle size distribution is 90%, and D 50 means the particle size at which the cumulative volume from the smaller particle size side in the particle size distribution is 50%.

[0145] [Table 1]

[0146] As shown in Table 1, it was confirmed that the transition metal hydroxides of Examples 1 and 2 satisfy the specific surface area and particle size distribution curve diffusion index proposed in the present invention. Furthermore, it can be seen from Figures 1 and 2 that the transition metal hydroxides of Examples 1 and 2 are composed of uniformly aggregated needle-shaped primary particles of uniform size.

[0147] Experimental Example 2 Positive electrode active materials were produced using the positive electrode active material precursors produced in the Examples and Comparative Examples, and batteries were produced using the positive electrode active materials, after which the battery performance was evaluated.

[0148] (1) Manufacturing of positive electrode active material Each positive electrode active material precursor was mixed with LiOH so that the molar ratio of Li in the precursor and LiOH was 1:1.35, and then calcined at 900°C for 15 hours in an air atmosphere to produce each positive electrode active material.

[0149] The produced positive electrode active material was measured for specific surface area using an SEM (QUANTA FEG 250, Thermo Fisher Scientific) in the same manner as in Experimental Example 1, and the results are shown in Table 2 below and FIGS.

[0150] (2) Manufacturing of the positive electrode The prepared positive electrode active materials, carbon black conductive material, and PVdF binder were mixed in a weight ratio of 92.5:3.0:4.5 in N-methylpyrrolidone solvent to prepare a positive electrode mixture (viscosity: 5000 mPa s). The mixture was applied to one side of an aluminum current collector, dried at 130°C, and rolled to prepare a positive electrode.

[0151] (3) Battery manufacturing Lithium metal was used as the negative electrode.

[0152] An electrode assembly was fabricated by interposing a porous polyethylene separator between the cathode and anode, and the electrode assembly was placed inside a case. An electrolyte solution was then injected into the case to fabricate a lithium secondary battery. The electrolyte solution was prepared by dissolving 1.0 M lithium hexafluorophosphate (LiPF6) in an organic solvent consisting of ethylene carbonate / ethyl methyl carbonate (EC / EMC volume ratio = 3 / 7).

[0153] Half cells of each lithium secondary battery prepared as described above were charged at 0.1 C in CCCV mode at 25°C to 4.70 V, and then discharged at a constant current of 0.1 C to 2.0 V to activate them. They were then charged at 0.1 C and 0.33 C in CCCV mode to 4.4 V, and discharged at constant currents of 0.1 C and 0.33 C to 2.5 V to measure the initial charge / discharge capacity and efficiency. The ratio of the capacity when charged at 0.1 C and discharged at 0.1 C to the capacity when discharged at 0.33 C (0.33 C / 0.1 C, %) was also measured.

[0154] In addition, 60 seconds after the start of discharge, the discharge resistance was confirmed by calculating the voltage / current, and the increase rate of the discharge resistance value at the 30th cycle relative to the discharge resistance value at the first cycle was calculated and shown as the resistance increase rate (%).

[0155] [Table 2]

[0156] Figures 5 and 6 show that the particles of the positive electrode active materials of Examples 1 and 2 are uniform and have developed voids. In contrast, Figures 7 and 8 show that the particles of the positive electrode active materials of Comparative Examples 1 and 2 are not uniform or lack voids, and irregular oversized particles are formed due to aggregation. Table 2 also shows that the positive electrode active materials of Examples 1 and 2 generally have improved initial charge / discharge capacity, resistance, and resistance increase rate characteristics compared to Comparative Examples 1 and 2.

Claims

1. The polycrystalline particles are composed of spherical secondary particles formed by agglomeration of needle-like primary particles, The specific surface area measured by the nitrogen adsorption BET method is 23 m ２ / g~43m ２ / g, The particle size distribution curve diffusion index defined by the following mathematical formula 1 is less than 0.7, A transition metal hydroxide represented by the following chemical formula 1. [Mathematical formula 1] Particle size distribution curve dispersion index = [(D)] ９０ -D １０ ) / D ５０ ] (In the above mathematical formula 1, D １０ means the particle size at which the volume cumulative amount from the smaller particle size side is 10% in the volume-based particle size distribution curve measured by a laser diffraction scattering particle size distribution measurement method, and D ９０ means a particle size corresponding to 90% of the cumulative volume from the small particle size side in the particle size distribution, and D ５０ means a particle size corresponding to 50% of the cumulative volume from the smaller particle size side in the particle size distribution. [Chemical formula 1] [Mn ａ Ni ｂ M １ ｃ１ M ２ ｃ２ ](OH) ２ (In the above Chemical Formula 1, M １ is Co, M ２ is one selected from Zr, Al, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, and Pt; 0.50<a≦0.80, 0.10≦b≦0.40, 0≦c １ ≦0.02, 0≦c ２ ≦0.10, a+b+c １ +c ２ = 1.)

2. The transition metal hydroxide according to claim 1 , which does not contain Co.

3. The transition metal hydroxide according to claim 1, which is represented by the following chemical formula 1-1. [Chemical formula 1-1] [Mn ａ Ni ｂ M ２ ｃ２ ](OH) ２ (In the above chemical formula 1-1, M ２ is one selected from Zr, Al, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, and Pt; 0.6≦a≦0.8, 0.1≦b≦0.4, 0≦c ２ ≦0.1, a+b+c ２ = 1.)

4. 2. The transition metal hydroxide according to claim 1, wherein the particle size distribution curve diffusion index is 0.4 or more and less than 0.

7.

5. The average particle size of the secondary particles (D ５０ 2. The transition metal hydroxide according to claim 1, wherein the average particle size is 3 μm to 12 μm.

6. Co-precipitation of a transition metal solution containing Ni and Mn in the presence of a basic solution; The method for producing a transition metal hydroxide, wherein the coprecipitation reaction is carried out under conditions where the amount of dissolved oxygen is 0.0054 mg / L to 0.075 mg / L.

7. The coprecipitation reaction is A step (S1-1) of adding a transition metal solution containing Ni and Mn and a basic solution to a reactor in which an inert atmosphere is created at a pH of 12.0 or less, and initiating a reaction under conditions of a pH of 11.0 or less to generate particle nuclei; and a step (S1-2) of continuing the reaction while maintaining the pH at 11.0 or less to grow particle nuclei.

7. The method for producing a transition metal hydroxide according to claim 6, wherein nitrogen and air are introduced into the reactor simultaneously with the start of the reaction in step (S1-1) to form the dissolved oxygen amount condition, and the dissolved oxygen amount condition is maintained throughout the entire reaction in steps (S1-1) and (S1-2).

8. The method for producing a transition metal hydroxide according to claim 6 , wherein the coprecipitation reaction is carried out further using an ammonium cation complex-forming agent.

9. 7. The method for producing a transition metal hydroxide according to claim 6, wherein the transition metal solution further contains one or more selected from Zr, Al, Co, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, and Pt.

10. The method for producing a transition metal hydroxide according to claim 6 , wherein the transition metal solution contains 50 mol % or more of Mn among the transition metals.

11. mixing the transition metal hydroxide according to any one of claims 1 to 5 with a lithium source material; and firing the mixture.

12. 12. The method for producing a positive electrode active material according to claim 11, wherein the transition metal hydroxide and the lithium source material are mixed so that the molar ratio of the transition metal hydroxide to the lithium element in the lithium source material is 1:1.2 to 1:1.6.

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