Transition metal hydroxide, method for preparing same, and method for preparing positive electrode active material using same

Abstract

The present invention relates to a transition metal hydroxide capable of providing a positive electrode active material having excellent capacity characteristics, a method for preparing the same, and a method for preparing a positive electrode active material using the same. The present invention provides a transition metal hydroxide represented by chemical formula 1 and containing polycrystalline particles composed of spherical secondary particles in which needle-like primary particles are agglomerated, a method for preparing the same, and a method for preparing a positive electrode active material using the same, wherein the specific surface area measured by a nitrogen adsorption BET method is 23 m2 / g to 43 m2 / g, and the particle size distribution curve diffusion index defined by mathematical formula 1 is less than 0.7.

Description

Technical Field

[0001] [Cross - Reference to Related Applications]

[0002] This application claims the benefit of priority of Korean Patent Application No. 10 - 2023 - 0015174, filed with the Korean Intellectual Property Office on February 3, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates to a transition metal hydroxide, a method for preparing the same, and a method for preparing a positive electrode active material using the same, and the transition metal hydroxide can provide a positive electrode active material having excellent capacity characteristics. Background Art

[0004] With the technological development and increasing demand of mobile devices, the demand for secondary batteries as an energy source has increased significantly. Among these secondary batteries, lithium secondary batteries having high energy density, high voltage, long cycle life, and low self - discharge rate have been commercialized and widely used.

[0005] Lithium transition metal oxides have been used as positive electrode active materials for lithium secondary batteries, and among these oxides, lithium cobalt composite metal oxide LiCoO2 having a high working voltage and excellent capacity characteristics has been mainly used. However, due to the instability of the crystal structure caused by de - lithiumation, the thermal performance of LiCoO2 is very poor, and it is expensive. Thus, there are limitations in using a large amount of LiCoO2 as a power source for applications such as electric vehicles.

[0006] Lithium manganese composite metal oxides (LiMnO2 or LiMn2O4), lithium iron phosphate compounds (LiFePO4, etc.), or lithium nickel composite metal oxides (LiNiO2, etc.) have been developed as materials to replace LiCoO2. Among these materials, lithium nickel composite metal oxides have been actively studied and developed, and a large - capacity battery can be easily realized due to a high reversible capacity of about 250 mAh / g. However, the limitation of LiNiO2 is that its thermal stability is worse than that of LiCoO2, and when an internal short - circuit occurs due to external pressure in a charged state, the positive electrode active material itself decomposes, resulting in battery rupture and fire.

[0007] Therefore, as a method for improving low thermal stability while maintaining the excellent reversible capacity of LiNiO2, nickel - cobalt - manganese - based lithium composite transition metal oxides (hereinafter, simply referred to as "NCM - type lithium oxides") in which a part of Ni is replaced by Mn and Co or Al have been developed.

[0008] However, due to the recent increase in the price of cobalt (Co), a lithium-rich (Li-rich) NCM-based cathode active material has been developed that can meet the capacity requirements while containing or not containing a relatively low amount of cobalt (Co).

[0009] Conventional NCM-based cathode active material precursors have flaky primary particles and a low specific surface area, and the cathode active materials prepared therefrom also have flaky primary particles and a specific surface area of less than 1 m 2 / g and exhibit suitable capacity characteristics.

[0010] On the other hand, in the case of a cobalt-free, Li-rich, and Mn-rich cathode active material, a large amount of Li is required compared to conventional NCM-based cathode active materials, and thus a cathode active material precursor with a high specific surface area capable of contacting Li is needed.

[0011] Therefore, similar to conventional NCM-based cathode active material precursors, when the precursor has flaky primary particles and a low specific surface area, the reaction with excessive Li cannot proceed properly, making it difficult to exhibit sufficient capacity characteristics, and thus there are limitations in terms of initial capacity, life characteristics, and resistance characteristics.

[0012] Therefore, there is a need to develop a cathode active material precursor for developing a cobalt-free or cobalt-reduced, Li-rich, and Mn-rich cathode active material with excellent capacity characteristics, life characteristics, and resistance characteristics.

[0013] [Prior Art Documents]

[0014] [Patent Documents]

[0015] (Patent Document 1) CN 109970106 A (July 5, 2019) Summary of the Invention

[0016] Technical Problem

[0017] To solve the above problems, one aspect of the present invention provides a transition metal hydroxide, which comprises polycrystalline particles and has a specific surface area and a particle size distribution curve diffusion index, and the polycrystalline particles are composed of secondary particles in which acicular primary particles are aggregated.

[0018] Another aspect of the present invention provides a method for preparing a transition metal hydroxide, which includes a coprecipitation reaction carried out under conditions where dissolved oxygen is controlled.

[0019] In addition, another aspect of the present invention provides a method for preparing a cathode active material by using a cathode active material precursor.

[0020] Technical Solution

[0021] To solve the above problems, the present invention provides a transition metal hydroxide, a method for preparing the same, and a method for preparing a positive electrode active material.

[0022] (1) According to one aspect of the present invention, there is provided a transition metal hydroxide represented by the following Chemical Formula 1 and including polycrystalline particles composed of spherical secondary particles in which acicular primary particles are aggregated, wherein the specific surface area measured by the nitrogen adsorption BET method is 23 m 2 / g to 43 m 2 / g, and the particle size distribution curve diffusion index defined by the following Mathematical Formula 1 is less than 0.7:

[0023] [Mathematical Formula 1]

[0024] Particle size distribution curve diffusion index = [(D 90 -D 10 ) / D 50

[0025] Wherein, in the above Mathematical Formula 1,

[0026] D 10 represents the particle size corresponding to 10% cumulative volume from the smaller particle size side in the volume-based particle size distribution curve obtained by measurement through the laser diffraction scattering type particle size distribution measurement method,

[0027] D 90 represents the particle size corresponding to 90% cumulative volume from the smaller particle size side in the particle size distribution,

[0028] D 50 represents the particle size corresponding to 50% cumulative volume from the smaller particle size side in the particle size distribution,

[0029] [Chemical Formula 1]

[0030] [Mn a Ni b M 1 c1 M 2 c2 (OH)2

[0031] Wherein, in the above Chemical Formula 1,

[0032] M 1 is Co,

[0033] M 2 is one selected from Zr, Al, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, and Pt, and

[0034] ​0.50 < a ≤ 0.80, 0.10 ≤ b ≤ 0.40, 0 ≤ c1 ≤ 0.02, 0 ≤ c2 ≤ 0.10, a + b + c1 + c2 = 1.

[0035] (2) In the above (1) of the present invention, a transition metal hydroxide not containing Co is provided.

[0036] (3) In the above (1) or (2) of the present invention, a transition metal hydroxide represented by the following Chemical Formula 1-1 is provided:

[0037] [Chemical Formula 1-1]

[0038] [Mn a Ni b M 2 c2 (OH)2

[0039] Wherein, in the above Chemical Formula 1-1,

[0040] M 2 is one selected from Zr, Al, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, and Pt, and

[0041] 0.6 ≤ a ≤ 0.8, 0.1 ≤ b ≤ 0.4, 0 ≤ c2 ≤ 0.1, a + b + c2 = 1.

[0042] (4) In any one of the above (1) to (3) of the present invention, a transition metal hydroxide is provided, wherein the diffusion index of the particle size distribution curve is 0.4 or more and less than 0.7.

[0043] (5) In any one of the above (1) to (4) of the present invention, a transition metal hydroxide is provided, wherein the average particle diameter (D 50 ) of the secondary particles is 3 μm to 12 μm.

[0044] (6) According to another aspect of the present invention, a method for preparing a transition metal hydroxide according to any one of the above (1) to (5) is provided, the method comprising: in the presence of an alkaline solution, subjecting a transition metal solution containing Ni and Mn to a coprecipitation reaction,

[0045] wherein the coprecipitation reaction is carried out under the condition that the dissolved oxygen is 0.0054 mg / L to 0.075 mg / L.

[0046] (7) In the above (6) of the present invention, a method for preparing a transition metal hydroxide is provided, wherein the coprecipitation reaction is carried out through the following steps:

[0047] Step (S1-1): Add a transition metal solution containing Ni and Mn and an alkaline solution to a reactor in which the pH is below 12.0 and an inert atmosphere is formed, and start the reaction under the condition that the pH is below 11.0 to generate particle nuclei; and

[0048] Step (S1-2): While maintaining the pH below 11.0, continuously grow the particle nuclei, and

[0049] While starting the reaction in step (S1-1), introduce nitrogen and air into the reactor to form a dissolved oxygen condition, and

[0050] Maintain the dissolved oxygen condition during the entire reaction in steps (S1-1) and (S1-2).

[0051] (8) In the above (6) or (7) of the present invention, there is provided a method for preparing a transition metal hydroxide, wherein the coprecipitation reaction is carried out by further using an ammonium cation complexing agent.

[0052] (9) In any one of (6) to (8) of the present invention, there is provided a method for preparing a transition metal hydroxide, 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.

[0053] (10) In any one of (6) to (9) of the present invention, there is provided a method for preparing a transition metal hydroxide, wherein the transition metal solution contains at least 50 mol% of Mn in the transition metal.

[0054] (11) According to still another aspect of the present invention, there is provided a method for preparing a positive electrode active material, the method comprising:

[0055] Mix a transition metal hydroxide according to any one of (1) to (5) with a lithium raw material; and

[0056] Fire the mixture.

[0057] (12) In the above (11) of the present invention, there is provided a method for preparing a positive electrode active material, wherein the transition metal hydroxide is mixed with the lithium raw material such that the molar ratio of the transition metal hydroxide to the lithium element in the lithium raw material is 1:1.2 to 1:1.6.

[0058] Advantageous effects

[0059] The transition metal hydroxide according to the present invention has a large specific surface area and a spread index of the particle size distribution curve less than 0.7, and thus can exhibit high reactivity to lithium during firing with a lithium raw material, thereby providing a cathode active material having excellent capacity characteristics.

[0060] In addition, the method for preparing a transition metal hydroxide according to the present invention can prepare a transition metal hydroxide having a high specific surface area and a spread index of the particle size distribution curve within a specific range by performing a coprecipitation reaction under conditions where dissolved oxygen is controlled therein. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The above and other aspects, features, and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0062] Figure 1 SEM image (magnification of 10 K) of the transition metal hydroxide prepared in Example 1.

[0063] Figure 2 SEM image (magnification of 10 K) of the transition metal hydroxide prepared in Example 2.

[0064] Figure 3 SEM image (magnification of 10 K) of the transition metal hydroxide prepared in Comparative Example 1.

[0065] Figure 4 SEM image (magnification of 10 K) of the transition metal hydroxide prepared in Comparative Example 2.

[0066] Figure 5 SEM image (magnification of 10 K) of the cathode active material of Example 1.

[0067] Figure 6 SEM image (magnification of 10 K) of the cathode active material of Example 2.

[0068] Figure 7 SEM image (magnification of 10 K) of the cathode active material of Comparative Example 1.

[0069] Figure 8 SEM image (magnification of 10 K) of the cathode active material of Comparative Example 2. DETAILED DESCRIPTION

[0070] The terms or words used in this specification and the claims should not be construed as limited to the conventional or dictionary meanings, and should be construed as meanings and concepts consistent with the technical gist based on the principle that the inventor can appropriately define the terms in order to best explain the present invention.

[0071] Definition of terms

[0072] As used herein, the term "primary particle" refers to a single particle as an independent phase in which the particles are not agglomerated morphologically with each other, and the single particle is in a form in which the particles are separated and / or dispersed from each other.

[0073] As used herein, the term "secondary particle" refers to a particle structure that is generally contrasted with primary particles (single particles), and refers to a structure in which small-sized primary particles are physically and / or chemically agglomerated to form a relatively large particle shape.

[0074] As used herein, the term "polycrystalline particle" refers to a secondary particle formed by the agglomeration of a plurality of primary particles, in which the crystal lattice structure is not regularly maintained throughout the particle but has various orientations.

[0075] As used herein, the term "average particle diameter (D 50 )" refers to the particle diameter corresponding to a cumulative volume of 50% in the volume-based particle size distribution curve measured by laser diffraction scattering particle size distribution measurement.

[0076] Measurement method

[0077] In the present invention, the "average particle diameter (D 50 , D 90 , D 10 )" is measured by laser diffraction scattering particle size distribution measurement, and is measured by the following method: The particles are dispersed in a dispersion medium, and then the particles are introduced into a laser diffraction measurement device (Microtrac S3500), ultrasonic waves of 28 kHz are emitted at an output of 60 W, and then the particle diameters corresponding to cumulative volumes of 50%, 10%, and 90% are respectively calculated in the measurement device.

[0078] In the present invention, the "specific surface area" is calculated based on the amount of nitrogen adsorbed at liquid nitrogen temperature (77 K) by pretreating 3.00 g of the sample at 200 °C under vacuum conditions using a surface area analyzer TriStar 2 plus (Micromeritics).

[0079] Transition metal hydroxide

[0080] The present invention provides a transition metal hydroxide, which can provide a low-cobalt or cobalt-free lithium-rich and manganese-rich nickel-based cathode active material, and has excellent capacity characteristics due to its high reactivity with lithium raw materials.

[0081] According to one embodiment of the present invention, the transition metal hydroxide is a precursor of a positive electrode active material, particularly a precursor of a positive electrode active material that can be usefully applied to the preparation of a cobalt-free lithium-rich and manganese-containing nickel-based positive electrode active material, and comprises polycrystalline particles composed of spherical secondary particles in which acicular primary particles are aggregated, wherein the specific surface area measured by the nitrogen adsorption BET method is 23 m 2 / g to 43 m 2 / g, and the particle size distribution curve diffusion index defined by the following Mathematical Formula 1 is less than 0.7. The transition metal hydroxide is represented by the following Chemical Formula 1:

[0082] [Mathematical Formula 1]

[0083] Particle size distribution curve diffusion index = [(D 90 - D 10 ) / D 50

[0084] wherein, in the above Mathematical Formula 1,

[0085] D 10 represents the particle size corresponding to 10% volume accumulation from the smaller particle size side in the volume-based particle size distribution obtained through measurement by the laser diffraction scattering method for particle size distribution measurement,

[0086] D 90 represents the particle size corresponding to 90% volume accumulation from the smaller particle size side in the particle size distribution,

[0087] D 50 represents the particle size corresponding to 50% volume accumulation from the smaller particle size side in the particle size distribution,

[0088] [Chemical Formula 1]

[0089] [Mn a Ni b M 1 c1 M 2 c2 (OH)2

[0090] wherein, in the above Chemical Formula 1,

[0091] M 1 is Co,

[0092] M 2 is one selected from Zr, Al, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, and Pt, and

[0093] ​0.50 < a ≤ 0.80, 0.10 ≤ b ≤ 0.40, 0 ≤ c1 ≤ 0.02, 0 ≤ c2 ≤ 0.10, a + b + c1 + c2 = 1.

[0094] Typical NCM-based cathode active materials are prepared from a single-phase precursor having a rhombohedral lattice structure and have a structure in which transition metal layers and Li layers are repeated.

[0095] On the other hand, low-cobalt or cobalt-free Li- and Mn-rich cathode active materials are prepared from an Mn-rich precursor, which is in two phases and has a crystal structure of monoclinic lattice and rhombohedral lattice, and in addition to the repeated structure of transition metal layers and Li layers, also has a structure in which Li atoms are additionally included in the transition metal layer, thereby requiring more Li compared to conventional NCM-based cathode active materials, and thus requiring a cathode active material precursor having a high specific surface area and capable of contacting Li.

[0096] Therefore, similar to the precursor of conventional NCM-based cathode active materials, it is difficult for a precursor having flaky primary particles and a low specific surface area to react properly with excessive Li, and thus the prepared cathode active material is difficult to exhibit sufficient capacity characteristics. As a result, there are limitations in that the initial capacity, life characteristics, and resistance characteristics of the battery are poor.

[0097] However, the transition metal hydroxide according to the present invention includes polycrystalline particles, which are composed of secondary particles in which needle-like primary particles are aggregated, and have a high specific surface area within a specific range, and the diffusion index of the particle size distribution curve is less than 0.7, so that the reactivity with Li is high and it reacts smoothly with excessive Li, thereby providing a cathode active material having excellent capacity characteristics, life characteristics, and resistance characteristics.

[0098] The transition metal hydroxide according to an embodiment of the present invention may include Ni and Mn, and may include at least 50 mol% of Mn in the transition metal. In this case, it is easy to ensure the high capacity of the obtained cathode active material.

[0099] As another example, in terms of an excellently balanced initial charge / discharge capacity, the content of Mn in the transition metal may be 55 mol% to 80 mol%, specifically 60 mol% to 80 mol%.

[0100] As another example, in the transition metal hydroxide according to an embodiment of the present invention, a metal component (M 1 and M 2 ) other than Ni and Mn may be coated or doped on its surface. In this case, the metal component M 1may be 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.

[0101] As another example, the transition metal hydroxide according to an embodiment of the present invention may be represented by Chemical Formula 1 below:

[0102] [Mn a Ni b M 1 c1 M 2 c2 (OH)2

[0103] Wherein, in Chemical Formula 1 above,

[0104] M 1 is Co,

[0105] M 2 is one selected from Zr, Al, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, and Pt, and

[0106] 0.50 < a ≤ 0.80, 0.10 ≤ b ≤ 0.40, 0 ≤ c1 ≤ 0.02, 0 ≤ c2 ≤ 0.10, and a + b + c1 + c2 = 1.

[0107] In Chemical Formula 1 above, Mn may be included in an amount corresponding to a, and when a is within the above range, the charge capacity may be excellent.

[0108] In addition, in Chemical Formula 1 above, Ni may be included in an amount corresponding to b, and when b is within the above range, the charge capacity may be excellent.

[0109] In addition, in Chemical Formula 1 above, M 1 and M 2 are metal elements coated or doped on the surface of the transition metal hydroxide, respectively, and may be included in amounts corresponding to c1 and c2, respectively.

[0110] More specifically, the transition metal hydroxide may be represented by Chemical Formula 1-1 below:

[0111] [Chemical Formula 1-1]

[0112] [Mn a Ni b M 2 c2 (OH)2

[0113] Wherein, in Chemical Formula 1-1 above,

[0114] M 2 is one selected from Zr, Al, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, and Pt, and

[0115] 0.6 ≤ a ≤ 0.8, 0.1 ≤ b ≤ 0.4, 0 ≤ c2 ≤ 0.1, and a + b + c2 = 1.

[0116] More specifically, in the above Chemical Formula 1-1, 0.6 ≤ a ≤ 0.8, 0.2 ≤ b ≤ 0.4, c2 = 0, and a + b + c2 = 1 can be satisfied.

[0117] In addition, the specific surface area of the transition metal hydroxide measured by the nitrogen adsorption BET method is 23 m 2 / g to 43 m 2 / g, and the spread index of the particle size distribution curve defined by Mathematical Formula 1 is less than 0.7. Specifically, the spread index of the particle size distribution curve can be 0.4 to 0.7 (excluding 0.7). The transition metal hydroxide according to the present invention satisfies the specific surface area and the spread index of the particle size distribution curve, thereby providing a positive electrode active material having excellent particle uniformity and high reactivity with Li, and thus having excellent capacity characteristics.

[0118] In addition, the transition metal hydroxide includes polycrystalline particles, and the polycrystalline particles are composed of spherical secondary particles in which needle-like primary particles are agglomerated.

[0119] As another example, the transition metal hydroxide can be polycrystalline particles composed of secondary particles in which needle-like primary particles are agglomerated.

[0120] On the other hand, the transition metal hydroxide according to an embodiment of the present invention has a particle shape including spherical secondary particles in which needle-like primary particles are agglomerated, whereby pores in the particles can be developed and can have a high specific surface area.

[0121] As another example, in the transition metal hydroxide, the specific surface area and the spread index of the particle size distribution curve may be affected by the shape and size of the primary particles constituting the transition metal hydroxide. The transition metal hydroxide according to an embodiment of the present invention can be prepared by a coprecipitation reaction under conditions in which dissolved oxygen to be described later is controlled within a specific range, whereby the aspect ratio and the average particle diameter of the primary particles and the average particle diameter of the secondary particles can be appropriately controlled, so as to satisfy the above specific surface area and the spread index of the particle size distribution curve.

[0122] Specifically, when the primary particles are formed very thin or very thick, the specific surface area of the resulting transition metal hydroxide may be too low or too high. When the specific surface area is too low, the reactivity with Li is low, and the capacity characteristics of the positive electrode active material prepared therefrom are poor. On the contrary, when the specific surface area is too high, the non-uniformity of the particles increases, and the capacity characteristics of the positive electrode active material prepared therefrom are significantly increased, resulting in poor reproducibility.

[0123] In this regard, the transition metal hydroxide of the present invention satisfies both the above specific surface area and the particle size distribution curve diffusion index, thereby providing a positive electrode active material having excellent capacity characteristics and reproducibility.

[0124] In addition, in terms of more easily satisfying both the specific surface area and the particle size distribution curve diffusion index, the average particle diameter (D 50 ) of the secondary particles may be 3 μm to 12 μm.

[0125] Method for preparing transition metal hydroxide

[0126] The present invention provides a method for preparing a transition metal hydroxide.

[0127] The method for preparing a transition metal hydroxide according to an embodiment of the present invention includes the following steps: in the presence of an alkaline solution, a co-precipitation reaction is carried out on a transition metal solution containing Ni and Mn, and the co-precipitation reaction is carried out under the condition that the dissolved oxygen is 0.0054 mg / L to 0.075 mg / L.

[0128] Specifically, the co-precipitation reaction can be carried out through the following steps:

[0129] Step (S1-1): Add a transition metal solution containing Ni and Mn and an alkaline solution to a reactor in which the pH is below 12.0 and an inert atmosphere is formed, and start the reaction under the condition that the pH is below 11.0, thereby generating particle nuclei; and

[0130] Step (S1-2): While maintaining the pH below 11.0, continuously grow the particle nuclei, and

[0131] While starting the reaction of step (S1-1), introduce nitrogen and air into the reactor to form a dissolved oxygen condition, and

[0132] Maintain the dissolved oxygen condition during the entire reaction of steps (S1-1) and (S1-2).

[0133] In the method for preparing a transition metal hydroxide according to the present invention, the above primary particles are formed by carrying out a coprecipitation reaction in an atmosphere controlled by dissolved oxygen conditions and grown into secondary particles, thereby preparing a transition metal hydroxide that satisfies a specific specific surface area and a particle size distribution curve diffusion index.

[0134] On the other hand, the dissolved oxygen can be controlled here by injecting nitrogen and air and adjusting these inputs. For example, nitrogen and air can be injected in a volume ratio of 99.5:0.5 to 95:5.

[0135] The transition metal solution can be prepared by adding a transition metal raw material to a solvent, specifically deionized water or a mixed solvent of deionized water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with deionized water and mixing them, or can be prepared by mixing aqueous solutions of transition metal raw materials.

[0136] The transition metal raw material can be a sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or hydroxyoxide of a transition metal.

[0137] As a specific example, for instance, the Ni raw material can be a nickel-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or hydroxyoxide, and more specific examples thereof can include: Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, NiSO4·6H2O, nickel fatty acid salts, nickel halides, or combinations thereof, but are not limited thereto.

[0138] In addition, for example, the Mn raw material can be a manganese-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or hydroxyoxide, and specific examples thereof can include: manganese oxides, such as Mn2O3, MnO2, or Mn3O4; manganese salts, such as MnCO3, Mn(NO3)2, MnSO4, manganese acetate, manganese dicarboxylate, manganese citrate, or manganese fatty acid salts; manganese hydroxyoxides; manganese chlorides, or combinations thereof, but are not limited thereto.

[0139] As another example, the transition metal solution can further contain at least one 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 can further contain raw materials containing Zr, Al, Co, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, or Pt, and the raw materials can be acetates, nitrates, sulfates, halides, sulfides, hydroxides, oxides, or hydroxyoxides containing each of the above metals.

[0140] In addition, the transition metal solution may contain at least 50 mol% of Mn among the transition metals in the solution.

[0141] As another example, the transition metal solution does not contain Co.

[0142] In addition, the alkaline solution may be a precipitating agent and may contain hydroxides of alkali metals or alkaline earth metals, such as NaOH, KOH, or Ca(OH)2, hydrates thereof, or combinations thereof.

[0143] As another example, the alkaline solution may be used in the form of, for example, an aqueous solution. In this case, as the solvent, deionized water or a mixture of deionized water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with deionized water may be used.

[0144] In addition, the alkaline solution can be used to control the pH in the reactor during the coprecipitation reaction, and the addition amount thereof can be adjusted to control the pH in the reactor under the desired conditions.

[0145] In addition, the coprecipitation reaction can be further carried out by using an ammonium cation complex former as needed. The ammonium cation complex former may include any one or more selected from NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and (NH4)2CO3, and the ammonium cation complex former can be used in the form of an aqueous solution. In this case, the ammonium cation complex former can be prepared by mixing deionized water or a mixed solvent of deionized water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with deionized water.

[0146] On the other hand, the coprecipitation reaction can be carried out while stirring at a temperature of 40°C to 70°C, and the stirring speed is not particularly limited, but in terms of facilitating the increase in the reaction rate, it can be stirred at 100 rpm to 2,000 rpm.

[0147] In addition, the method for preparing a transition metal hydroxide according to an embodiment of the present invention may further perform one or more processes selected from washing and drying after the coprecipitation reaction. In this case, washing and drying can be carried out in a conventional manner in the art.

[0148] For example, washing can be carried out by adding a precursor to ultrapure water and stirring the mixture, and the washing temperature can be 70°C or lower, specifically 40°C to 70°C, and the washing time can be 10 minutes to 1 hour.

[0149] In addition, there is no particular limitation on drying, as long as it is a method capable of drying the prepared precursor without causing adverse chemical changes in the prepared precursor. For example, the following drying methods can be used: drying methods using a spray dryer or a rotary evaporator, vacuum drying method, or natural drying method.

[0150] Positive electrode active material

[0151] The present invention provides a positive electrode active material prepared using a transition metal hydroxide.

[0152] The positive electrode active material according to one embodiment of the present invention includes polycrystalline particles, the polycrystalline particles are composed of secondary particles in which acicular primary particles are aggregated, and the specific surface area measured by the nitrogen adsorption BET method may be 1.00 m 2 / g to 1.90 m 2 / g.

[0153] In addition, the positive electrode active material may be a compound represented by the following Chemical Formula 2:

[0154] [Chemical Formula 2]

[0155] x[Li(Mn d Ni e M 1 f1 M 2 f2 )O2]·1-x[Li2MnO3]

[0156] Wherein, in the above Chemical Formula 2,

[0157] M 1 is Co,

[0158] M 2 is one selected from Zr, Al, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, and Pt, and

[0159] 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.

[0160] Method for preparing positive electrode active material

[0161] The present invention provides a method for preparing a positive electrode active material using a transition metal hydroxide.

[0162] The method for preparing the positive electrode active material may include:

[0163] A step of mixing a transition metal hydroxide with a lithium raw material; and

[0164] A step of firing the mixture.

[0165] Specifically, the method for preparing a positive electrode active material according to the present invention can be carried out by a method for preparing a positive electrode active material known in the art, except that, as a precursor, the transition metal hydroxide according to the present invention is used, and there is no particular limitation on the method.

[0166] Examples of the lithium raw material may include: lithium-containing carbonates (e.g., lithium carbonate, etc.), hydrates (e.g., lithium hydroxide hydrate (LiOH·H2O), etc.), hydroxides (e.g., lithium hydroxide, etc.), nitrates (e.g., lithium nitrate (LiNO3), etc.), chlorides (e.g., lithium chloride (LiCl), etc.), etc., and any one of them or a mixture of two or more thereof can be used alone.

[0167] On the other hand, the mixing of the transition metal hydroxide and the lithium raw material can be carried out by solid-phase mixing such as jet milling, and the mixing ratio of the transition metal hydroxide and the lithium raw material can be determined within a range that satisfies the molar fractions of the respective components in the finally prepared positive electrode active material. More specifically, the transition metal hydroxide and the lithium raw material can be mixed so that the molar ratio of the transition metal hydroxide to the lithium element in the lithium raw material becomes 1:1.2 to 1:1.6.

[0168] In addition, although not essential, during mixing, in addition to the transition metal hydroxide and the lithium raw material, a raw material for doping a part of the transition metal and / or oxygen of the positive electrode active material can be additionally included. For example, during mixing, the above-mentioned raw material containing M or the raw material containing X to be described below can be additionally mixed. In this case, the raw material containing X can be, for example, Na3PO4, K3PO4, Mg3(PO4)2, AlF3, NH4F, LiF, etc., but is not limited thereto. When a part of oxygen is replaced with the X element as described above, the effect of suppressing oxygen deintercalation and reaction with the electrolyte during charging and discharging of the secondary battery can be obtained.

[0169] On the other hand, the firing can be carried out at 800°C to 1,000°C, specifically at 850°C to 950°C, and the firing time can be 5 hours to 30 hours, specifically 8 hours to 15 hours, but is not limited thereto.

[0170] Positive electrode and secondary battery

[0171] The present invention provides a positive electrode including the positive electrode active material, and a lithium secondary battery including the positive electrode.

[0172] The positive electrode according to one 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. In this case, the positive electrode active material layer contains the positive electrode active material as described above.

[0173] The positive electrode can be prepared according to a typical method for preparing a positive electrode, except that the above positive electrode active material is used. For example, the positive electrode can be prepared by the following steps: dissolving or dispersing the components constituting the positive electrode active material layer, that is, the positive electrode active material, the conductive material, and / or the binder in a solvent to prepare a positive electrode material mixture, coating at least one surface of the positive electrode current collector with the positive electrode material mixture, and then drying and rolling the coated positive electrode current collector, or it can be prepared by casting the positive electrode material mixture on a separate support and then peeling off the support to obtain a film and laminating the obtained film on the positive electrode current collector.

[0174] In this case, there is no particular limitation on the positive electrode current collector as long as it has conductivity and does not cause adverse chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc. can be used. In addition, the positive electrode current collector generally can have a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the surface of the current collector to improve the adhesion of the positive electrode active material. For example, the positive electrode current collector can be used in various shapes such as a film, a sheet, a foil, a net, a porous body, a foam body, and a non-woven fabric body.

[0175] The 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.

[0176] Relative to the total weight of the positive electrode active material layer, the content of the positive electrode active material can be 80% by weight to 99% by weight, for example, 85% by weight to 98% by weight. When the content of the positive electrode active material is within the above range, excellent capacity characteristics can be obtained.

[0177] The conductive material is used to provide conductivity to the electrode. Any conductive material can be used without particular limitation as long as it has appropriate electron conductivity and does not cause adverse chemical changes in the battery. Specific examples of the conductive material can be: 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 cracking carbon black, and carbon fiber; powders or fibers of metals such as copper, nickel, aluminum, and silver; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxides; or conductive polymers, such as polyphenylene derivatives, and any one of them or a mixture of two or more of them can be used. Relative to the total weight of the positive electrode active material layer, the content of the conductive material is generally 1% by weight to 30% by weight.

[0178] In addition, the binder is used to improve the binding between the positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples of the binder may include: polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber or various copolymers thereof, and any one of them or a mixture of two or more thereof may be used. The content of the binder may be 1% by weight to 30% by weight based on the total weight of the positive electrode active material layer.

[0179] On the other hand, the solvent used in the preparation of the positive electrode may be a solvent commonly used in the art. For example, the following substances may be used alone or in a mixture thereof: dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone or water. The amount of the solvent may be appropriately adjusted in consideration of the coating thickness of the slurry, the manufacturing yield, the viscosity, etc.

[0180] In addition, the lithium secondary battery according to the present invention includes a positive electrode, a negative electrode disposed to face 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 as described above.

[0181] On the other hand, the lithium secondary battery may also optionally include a battery container for accommodating the electrode assembly including the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container.

[0182] In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector.

[0183] The negative electrode can be prepared by a typical method for preparing a negative electrode known in the art. For example, the negative electrode can be prepared by the following steps: dissolving or dispersing the components constituting the negative electrode active material layer, i.e., the negative electrode active material, the conductive material, and / or the binder in a solvent to prepare a negative electrode material mixture, coating at least one surface of the negative electrode current collector with the negative electrode material mixture, and then drying and calendering the coated negative electrode current collector, or it can be prepared by casting the negative electrode material mixture on a separate support and then peeling off the support to obtain a film and laminating the obtained film on the negative electrode current collector.

[0184] There is no particular limitation on the negative electrode current collector as long as it has high electrical conductivity without causing adverse chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc., and aluminum cadmium alloy can be used. In addition, the negative electrode current collector usually can have a thickness of 3 μm to 500 μm, and like the case of the positive electrode current collector, fine irregularities can be formed on the surface of the negative electrode current collector to enhance the adhesion of the negative electrode active material. For example, the negative electrode current collector can be used in various shapes such as films, sheets, foils, meshes, porous bodies, foams, and non-woven fabric bodies.

[0185] Compounds capable of reversibly inserting and extracting lithium can be used as the negative electrode active material. Specific examples of the negative electrode active material can include: carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; (semi) metallic materials that can alloy with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; (semi) metal oxides that can be doped and de-doped with lithium such as SiO x (0 < x < 2), SnO2, vanadium oxides, and lithium vanadium oxides; or composite materials containing (semi) metallic materials and carbonaceous materials such as Si-C composite materials or Sn-C composite materials, and any one or a mixture of two or more thereof can be used. In addition, as the negative electrode active material, a thin film of metallic lithium can be used. In addition, as the carbon material, both low-crystalline carbon and high-crystalline carbon can be used. Typical examples of low-crystalline carbon can be soft carbon and hard carbon, and typical examples of high-crystalline carbon can be irregular-shaped, planar, sheet-like, spherical, or fibrous natural graphite or artificial graphite, condensated graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesophase carbon microbeads, mesophase pitch, and high-temperature sintered carbon such as coke derived from petroleum or coal tar pitch.

[0186] In addition, the binder and the conductive material can be the same as those previously described in the positive electrode.

[0187] On the other hand, in a secondary battery, a separator separates the negative electrode and the positive electrode and provides a movement path for lithium ions. Any separator can be used as the separator without particular limitation as long as it is generally used in a secondary battery. In particular, a separator having a high moisture retention ability for an electrolytic solution and a low resistance to the movement of electrolyte ions can be preferably used. Specifically, a porous polymer film can be used, for example, a porous polymer film prepared from an olefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure having two or more layers thereof. In addition, a typical porous non-woven fabric can be used, for example, a non-woven fabric formed from high melting point glass fibers or polyethylene terephthalate fibers. In addition, in order to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material can be used, and a separator having a single-layer or multi-layer structure can be optionally used.

[0188] On the other hand, the electrolyte may include, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a molten-type inorganic electrolyte that can be used to prepare a secondary battery.

[0189] Specifically, the electrolyte may contain an organic solvent and a lithium salt.

[0190] Any organic solvent can be used as the organic solvent without particular limitation as long as it can be used as a medium through which ions participating in the electrochemical reaction of the battery can move. Specifically, as the organic solvent, the following can be used: ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic solvents such as benzene and fluorobenzene; or carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethanol and isopropanol; nitriles such as Ra-CN (where Ra is a linear, branched, or cyclic C2-C20 hydrocarbon group that may contain a double bond, an aromatic ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolane. Among these solvents, carbonate solvents are preferred. For example, a mixture of a cyclic carbonate having a high ionic conductivity and a high dielectric constant (e.g., ethylene carbonate or propylene carbonate) that can improve the charge / discharge performance of the battery and a linear carbonate compound having a low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred. In this case, when the cyclic carbonate and the chain carbonate are mixed at a volume ratio of about 1:1 to 9, the performance of the electrolytic solution can be excellent.

[0191] The lithium salt can be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, as the lithium salt, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO 4、 LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, LiB(C2O4)2, etc. can be used. The lithium salt can be used in a concentration range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within the above range, since the electrolyte can have appropriate conductivity and viscosity, excellent electrolyte performance can be obtained, and lithium ions can move effectively.

[0192] In order to improve the life characteristics of the battery, suppress the decrease in battery capacity, and improve the discharge capacity of the battery, in addition to the electrolyte components, the electrolyte may further contain at least one additive, such as: halogenated alkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, (poly)glycol dimethyl ethers, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, based on the total weight of the electrolyte, the content of the additive can be 0.1 wt% to 5 wt%.

[0193] The secondary battery including the positive electrode active material according to the present invention as described above has excellent capacity characteristics and high-temperature stability, and thus can be usefully applied to fields of portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0194] In addition, the secondary battery according to the present invention can be used as a unit cell of a battery module, and the battery module can be applied to a battery pack. The battery module or the battery pack can be used as a power source for at least one of the following medium and large-sized devices: power tools; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0195] Examples

[0196] Hereinafter, examples of the present invention will be described in detail in such a way that those skilled in the art to which the present invention pertains can easily implement the present invention. However, the present invention can be implemented in various different forms and should not be construed as being limited to the embodiments described herein.

[0197] Example 1

[0198] Mix NiSO4 and MnSO4 in deionized water in an amount such that the molar ratio of Ni:Mn is 35:65 to prepare a 2.4 M aqueous transition metal solution.

[0199] Add 2.6 L of deionized water to a 10 L continuous stirred tank reactor, and introduce nitrogen at 2 L / min to remove dissolved oxygen in the water, thereby establishing a non-oxidizing atmosphere in the reactor. Thereafter, while nitrogen is flowing continuously at 2 L / min, add 3.87 mL of a 25 wt% aqueous NaOH solution thereto, and stir the resulting mixture at a rate of 150 rpm at 50 °C, so that the pH in the reactor is formed to be about 12.0.

[0200] Thereafter, while stirring the mixture at 1,000 rpm, continuously introduce the aqueous transition metal solution into the reactor at 0.83 L / h and continuously introduce the aqueous NaOH solution into the reactor at 0.29 L / h, and at the same time introduce nitrogen and air at a volume ratio of 99.5:0.5 to control the amount of dissolved oxygen to 0.0054 mg / L, and carry out a coprecipitation reaction such that the pH in the reactor becomes about 11.0 within a reaction time of 2 hours, and then continue the coprecipitation reaction at a pH of about 11.0 for 48 hours. After the coprecipitation reaction is completed, the resulting particles are separated, washed and dried at 120 °C for 12 hours to prepare the transition metal hydroxide Mn 0.65 Ni 0.35 (OH)2.

[0201] Example 2

[0202] Prepare the transition metal hydroxide Mn 0.65 Ni 0.35 (OH)2 in the same manner as in Example 1, except that the coprecipitation reaction is carried out under the condition that the dissolved oxygen is controlled to 0.079 mg / L therein by adding the aqueous transition metal solution and simultaneously adding nitrogen and air at a volume ratio of 95:5.

[0203] Comparative Example 1

[0204] Prepare the transition metal hydroxide Mn 0.65 Ni 0.35 (OH)2 in the same manner as in Example 1, except that the coprecipitation reaction is carried out under the condition that the dissolved oxygen is controlled to 0.0049 mg / L therein by adding the aqueous transition metal solution and simultaneously adding nitrogen and air at a volume ratio of 99.8:0.2.

[0205] Comparative Example 2

[0206] Prepare the transition metal hydroxide Mn0.65 Ni 0.35 (OH)2, except that a co-precipitation reaction is carried out under the condition of controlling the dissolved oxygen to 0.092 mg / L therein by adding an aqueous solution of a transition metal and simultaneously adding nitrogen and air with a volume ratio of 90:10.

[0207] Experimental example 1

[0208] Analyze the particle surface analysis, specific surface area, and particle size distribution curve diffusion index of each transition metal hydroxide prepared in the examples and comparative examples. The results are shown in Table 1 below and Figures 1 to 4 in.

[0209] (1) Particle surface analysis

[0210] The particle surface state is confirmed by SEM analysis. SEM analysis (QUANTA FEG 250 manufactured by Thermo Fischer) is carried out under the following conditions.

[0211] 1) High voltage: 10,000 kV

[0212] 2) Chamber pressure: 9.0×10 -5 mbar

[0213] 3) Gun pressure: 6.85×10 -10 mbar

[0214] 4) Emission current: 165 μA

[0215] 5) WD: 10 mm

[0216] 6) Beam spot size: 3.0

[0217] 7) Stage bias voltage: 4000 V

[0218] 8) Magnification: 10 K

[0219] (2) Specific surface area (m 2 / g)

[0220] The specific surface area is measured by the BET method using Tristar II (Micromeritics) and calculated based on the amount of nitrogen adsorbed at liquid nitrogen temperature (77 K).

[0221] (3) Particle size distribution curve diffusion index

[0222] Measurement was carried out by laser diffraction scattering particle size distribution measurement method. The particles were dispersed in a dispersion medium and then introduced into a laser diffraction measurement device (Microtrac S3500). Ultrasonic waves of 28 kHz were emitted at an output of 60 W, and then the particle diameters corresponding to 50%, 10%, and 90% of the volume cumulative amount in the measuring instrument were calculated according to the following mathematical formula 1:

[0223] [Mathematical formula 1]

[0224] Diffusion index of particle size distribution curve = [(D 90 - D 10 ) / D 50

[0225] Wherein, in the above mathematical formula 1,

[0226] D 10 represents the particle diameter corresponding to 10% of the volume cumulative amount from the smaller particle diameter side in the volume-based particle size distribution obtained by measurement through the laser diffraction scattering particle size distribution measurement method,

[0227] D 90 represents the particle diameter corresponding to 90% of the volume cumulative amount from the smaller particle diameter side in the particle size distribution,

[0228] D 50 represents the particle diameter corresponding to 50% of the volume cumulative amount from the smaller particle diameter side in the particle size distribution.

[0229]

[0230] As shown in Table 1 above, it was confirmed that the transition metal hydroxides of Examples 1 and 2 satisfy the specific surface area and the diffusion index of the particle size distribution curve proposed in the present invention. In addition, through Figure 1 and 2 it can be confirmed that the transition metal hydroxides of Examples 1 and 2 have needle-like primary particles with uniform agglomeration, and the needle-like primary particles have uniform sizes.

[0231] Experimental example 2

[0232] The positive electrode active materials were prepared by using the positive electrode active material precursors prepared in the examples and comparative examples, and the batteries were manufactured by using the positive electrode active materials, and then the battery performance was evaluated.

[0233] (1) Preparation of positive electrode active material

[0234] Each positive electrode active material precursor and LiOH were mixed so that the molar ratio of Li in the precursor and LiOH became 1:1.35, and then fired in an air atmosphere at 900 °C for 15 hours to prepare each positive electrode active material. ​

[0235] For the SEM (QUANTA FEG 250, Thermo Fisher) and specific surface area, the prepared positive electrode active material was measured by the same method as in Experimental Example 1, and the results are shown in Table 2 below and Figures 5 to 8 .

[0236] (2) Preparation of positive electrode

[0237] Each of the prepared positive electrode active materials, carbon black conductive material, and PVdF binder were mixed at a weight ratio of 92.5:3.0:4.5 in an N-methylpyrrolidone solvent to prepare a positive electrode material mixture (viscosity: 5,000 mPa·s). One surface of an aluminum current collector was coated with the positive electrode material mixture, dried at 130 °C, and then calendered to prepare a positive electrode.

[0238] (3) Manufacture of battery

[0239] Lithium metal was used as the negative electrode.

[0240] An electrode assembly was prepared by inserting a porous polyethylene separator between the positive electrode and the negative electrode. The electrode assembly was positioned inside a battery case, and an electrolytic solution was injected into the battery case to manufacture a lithium secondary battery. In this case, the electrolytic solution was prepared by dissolving 1.0 M of lithium hexafluorophosphate (LiPF6) in an organic solvent composed of ethylene carbonate / ethyl methyl carbonate (EC / EMC mixed volume ratio = 3 / 7).

[0241] For each half-cell of the lithium secondary battery prepared as described above, the half-cell was charged at 0.1C in the CCTV mode until it reached 4.70 V at 25 °C, discharged at a constant current of 0.1C to 2.0 V, and activated. Then, it was charged at 0.1C and 0.33C in the CCTV mode until it reached 4.4 V, and discharged at a constant current of 0.1C and 0.33C to 2.5 V to measure the initial charge / discharge capacity and efficiency. In addition, the ratio of the capacity when charged at 0.1C and discharged at 0.1C to the capacity when discharged at 0.33C (0.33C / 0.1C, %) was measured.

[0242] In addition, the discharge resistance was confirmed by calculating the voltage / current 60 seconds after the start of discharge, and the increase rate of the discharge resistance value in the 30th cycle compared to the discharge resistance value in the 1st cycle was calculated to represent the resistance increase rate (%).

[0243]

[0244] Reference Figure 5 and 6 It was confirmed that the particles of the positive electrode active materials in Examples 1 and 2 were uniform and the pores were well-developed. On the other hand, referenceFigure 7 and 8 It was confirmed that the positive electrode active materials of Comparative Examples 1 and 2 formed irregular large particles due to aggregation, without uniform particles or pores. In addition, referring to Table 2, it was confirmed that the positive electrode active materials of Examples 1 and 2 had overall improved initial charge / discharge capacity, resistance, and resistance increase rate characteristics compared to Comparative Examples 1 and 2.

Claims

1. A transition metal hydroxide, represented by the following chemical formula 1 and comprising polycrystalline particles, wherein the polycrystalline particles are composed of spherical secondary particles in which needle-shaped primary particles are aggregated, The specific surface area measured by nitrogen adsorption BET method is 23 m 2 / g to 43 m 2 / g, and the particle size distribution curve diffusion index defined by the following mathematical formula 1 is less than 0.7: [Mathematical formula 1] Diffusion index of particle size distribution curve = [(D 90 -D 10 ) / D 50 ] in, In the above mathematical formula 1, D 10 Indicates the particle size corresponding to 10% volume accumulation from the smaller particle size side in the volume-based particle size distribution curve obtained by measurement using the laser diffraction scattering particle size distribution measurement method. D 90 It represents the particle size corresponding to 90% of the volume accumulation from the smaller particle size side in the particle size distribution. D 50 It represents the particle size corresponding to 50% volume accumulation from the side with the smallest particle size in the particle size distribution. [Chemical formula 1] [Mn a Ni b M 1 c1 M 2 c2 ](OH)2 Wherein, in the above chemical formula 1, M 1 For Co, M 2 is one selected from the group consisting of Zr, Al, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W and Pt, and 0.50 <a≤0.80,0.10≤b≤0.40,0≤c1≤0.02,0≤c2≤0.10,a+b+c1+c2=1。 2. The transition metal hydroxide according to claim 1, wherein the transition metal hydroxide does not contain Co.

3. The transition metal hydroxide according to claim 1, wherein the transition metal hydroxide is represented by the following chemical formula 1-1: [Chemical formula 1-1] [Mn a No b M 2 c2 ](OH)2 in, In the above chemical formula 1-1, M 2 is one selected from the group consisting of Zr, Al, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W and Pt, and 0.6≤a≤0.8, 0.1≤b≤0.4, 0≤c2≤0.1, a+b+c2=1. The transition metal hydroxide according to claim 1 , wherein the particle size distribution curve diffusion index is greater than or equal to 0.4 and less than 0.

7.

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

6. A method for preparing a transition metal hydroxide, the method comprising the steps of: subjecting a transition metal solution containing Ni and Mn to a coprecipitation reaction in the presence of an alkaline solution, The coprecipitation reaction is carried out under the condition that the dissolved oxygen is 0.0054 mg / L to 0.075 mg / L.

7. The method according to claim 6, wherein the coprecipitation reaction is carried out by the following steps: Step (S1-1): adding a transition metal solution containing Ni and Mn and an alkaline solution to a reactor in which the pH is 12.0 or less and an inert atmosphere is formed, and starting a reaction under the condition of a pH of 11.0 or less, thereby generating particle cores; and Step (S1-2): while maintaining the pH below 11.0, allowing the particle core to continue to grow, in, At the same time as starting the reaction of step (S1-1), nitrogen and air are introduced into the reactor to form the dissolved oxygen condition, and The dissolved oxygen conditions are maintained throughout the reaction period of step (S1-1) and step (S1-2).

8. The method according to claim 6, wherein the coprecipitation reaction is performed by further using an ammonium cation complex forming agent.

9. The method according to claim 6, wherein the transition metal solution further comprises one or more selected from the group consisting of Zr, Al, Co, Cu, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W and Pt.

10. The method of claim 6, wherein the transition metal solution comprises at least 50 mol % Mn in the transition metal.

11. A method for preparing a positive electrode active material, the method comprising the following steps: mixing the transition metal hydroxide according to claim 1 with a lithium raw material; and The mixture is sintered. 12 . The method according to claim 11 , wherein the transition metal hydroxide is mixed with the lithium raw material so that a molar ratio of the transition metal hydroxide to the lithium element in the lithium raw material becomes 1:1.2 to 1:1.6.

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