Positive electrode active material precursor and method for producing positive electrode active material using the same

Abstract

The positive electrode active material precursor according to the present invention comprises composite hydroxide particles, wherein the composite hydroxide particles contain a plurality of pores, wherein the volume of a first pore with a diameter of less than 2 nm is 0.1 vol% to 5 vol% of the total volume of the plurality of pores. According to the method for preparing the positive electrode active material of the present invention, a mixture of the positive electrode active material precursor and a lithium precursor is subjected to a first heat treatment and a second heat treatment, wherein the positive electrode active material precursor comprises composite hydroxide particles, wherein the composite hydroxide particles contain a plurality of pores, wherein the volume of a first pore with a diameter of less than 2 nm is 0.1 vol% to 5 vol% of the total volume of the plurality of pores.

Description

Technical Field

[0001] This invention relates to a positive electrode active material precursor and a method for preparing a positive electrode active material using the positive electrode active material precursor. Background Technology

[0002] Rechargeable batteries are batteries that can be recharged and discharged repeatedly. With the development of the information communication and display industries, rechargeable batteries are widely used as power sources for portable electronic communication devices such as portable cameras, mobile phones, and laptops. In addition, in recent years, battery packs that include rechargeable batteries have been developed for use as power sources in environmentally friendly vehicles such as hybrid electric vehicles.

[0003] Secondary batteries can be categorized into, for example, lithium secondary batteries, nickel-cadmium batteries, and nickel-metal hydride batteries. Among them, lithium secondary batteries have high operating voltage and energy density per unit weight, and are advantageous for charging speed and lightweight design, so they are being actively developed and applied.

[0004] For example, a lithium secondary battery may include an electrode assembly and an electrolyte impregnating the electrode assembly, the electrode assembly including a positive electrode, a negative electrode, and a separator (separation membrane). The lithium secondary battery may further include an outer packaging material housing the electrode assembly and the electrolyte, such as an outer packaging material in the form of a pouch.

[0005] The positive electrode active material can exist as secondary particles, which are aggregates of small primary particles, or as single particles. Depending on the particle form of the positive electrode active material, the electrochemical characteristics and lifespan characteristics of the secondary battery can change.

[0006] For example, in the case of positive electrode active materials in the form of secondary particles, cracks may occur during the charging and discharging process of the secondary battery, which may lead to a reduction in the battery's lifespan characteristics. In the case of positive electrode active materials in the form of single particles, residual lithium or changes in surface structure during the manufacturing process may lead to a reduction in the electrical characteristics of the secondary battery. Summary of the Invention

[0007] (a) Technical problems to be solved One technical problem of the present invention is to provide a positive electrode active material precursor for a secondary battery that can achieve improved electrical properties.

[0008] One technical problem of the present invention is to provide a method for preparing a positive electrode active material using the aforementioned positive electrode active material precursor.

[0009] (II) Technical Solution The positive electrode active material precursor according to the present invention comprises composite hydroxide particles, the composite hydroxide particles comprising a plurality of pores, wherein the volume of a first pore with a diameter of less than 2 nm is 0.1% to 5% of the total volume of the plurality of pores.

[0010] According to an exemplary embodiment, the composite hydroxide particles may include a second pore with a diameter greater than 2 nm and less than 50 nm, the volume of the second pore being 70% to 97% of the total volume of the plurality of pores.

[0011] According to an exemplary embodiment, the composite hydroxide particles may include a third pore with a diameter of 50 nm or more, the volume of which is 2% to 25% of the total volume of the plurality of pores.

[0012] According to the method for preparing the positive electrode active material of the present invention, a mixture of a positive electrode active material precursor and a lithium precursor is subjected to a first heat treatment and a second heat treatment. The positive electrode active material precursor comprises composite hydroxide particles, which contain a plurality of pores, wherein the volume of a first pore with a diameter of less than 2 nm is 0.1 vol% to 5 vol% of the total volume of the plurality of pores. The heat treatment distribution value according to Formula 1 below is 0.5 to 8.

[0013] [Formula 1] Heat treatment distribution = (T2) t2) / (T1 t1) In Equation 1, T1 is the temperature of the first heat treatment, t1 is the time of the first heat treatment, T2 is the temperature of the second heat treatment, and t2 is the time of the second heat treatment.

[0014] According to an exemplary implementation, the heat treatment distribution value can be from 1 to 4.

[0015] According to an exemplary embodiment, the temperature of the second heat treatment may be lower than the temperature of the first heat treatment.

[0016] According to an exemplary embodiment, the composite hydroxide particles may include a second pore with a diameter greater than 2 nm and less than 50 nm, the volume of the second pore being 70% to 97% of the total volume of the plurality of pores.

[0017] According to an exemplary embodiment, the composite hydroxide particles may include a third pore with a diameter of 50 nm or more, the volume of which is 2% to 25% of the total volume of the plurality of pores.

[0018] According to an exemplary embodiment, the BET specific surface area of ​​the composite hydroxide particles can be 1.0 m². 2 / g to 7.0m 2 / g.

[0019] According to an exemplary embodiment, the total volume of the plurality of pores in the composite hydroxide particles can be 0.001 cm³. 3 / g to 0.04cm 3 / g.

[0020] According to an exemplary embodiment, the aspect ratio of the composite hydroxide particles can be from 1.0 to 6.0.

[0021] According to an exemplary implementation, the temperature of the first heat treatment can be from 700°C to 1000°C.

[0022] According to an exemplary embodiment, the temperature of the second heat treatment can be from 600°C to 800°C.

[0023] According to an exemplary embodiment, the composite hydroxide particles may contain nickel, cobalt, and manganese, and the nickel content in the total metal content of the composite hydroxide particles may be 80 mol% or more.

[0024] According to an exemplary embodiment, the composite hydroxide particles may have a flake structure.

[0025] According to an exemplary implementation, a positive electrode active material can be formed in the form of single particles.

[0026] (III) Beneficial Effects According to embodiments of the present invention, the positive electrode active material precursor can contain pores with diameters within a specified volume ratio. Therefore, the electrical characteristics of the secondary battery can be improved.

[0027] The method for preparing the positive electrode active material according to an embodiment of the present invention involves a two-step heat treatment of the positive electrode active material precursor. Therefore, a particle-grown and crystallized positive electrode active material can be prepared, and the electrical characteristics of a secondary battery containing the positive electrode active material can be improved. Attached Figure Description

[0028] Figure 1 and Figure 2 These are schematic plan views and schematic cross-sectional views of a lithium secondary battery according to an exemplary embodiment.

[0029] Figure 3a , Figure 3b , Figure 4a and Figure 4bThese are figures showing SEM images of a positive electrode active material precursor according to an exemplary embodiment.

[0030] Figure 5a and Figure 5b These are SEM images showing the positive electrode active material precursors according to the comparative examples.

[0031] Figure 6 This is a diagram showing SEM images of the positive electrode active material according to an embodiment.

[0032] Figure 7 This is a graph showing SEM images of the positive electrode active material according to the comparative example. Detailed Implementation

[0033] This invention provides a positive electrode active material precursor comprising composite hydroxide particles having multiple pores with controlled pore size. Furthermore, this invention provides a method for preparing a positive electrode active material using the aforementioned positive electrode active material precursor.

[0034] The method for preparing the positive electrode active material precursor and the positive electrode active material of this invention can be widely applied in green technology fields such as electric vehicles, battery charging stations, and other battery-powered solar and wind power generation. Furthermore, the method for preparing the positive electrode active material precursor and the positive electrode active material of this invention can be used in eco-friendly electric vehicles and hybrid vehicles, which prevent climate change by suppressing air pollution and greenhouse gas emissions.

[0035] The present invention will now be described in detail with reference to the accompanying drawings. However, this is merely an exemplary description, and the present invention is not limited to the specific embodiments described herein.

[0036] The term "single-particle form" as used in this invention is used to exclude secondary particles, for example, those formed by the aggregation of multiple primary particles. For example, in the context of lithium metal oxide particles described below, it can refer to secondary particles that are substantially formed by the assembly or aggregation of primary particles (e.g., more than 10, 20, 30, 40, 50, etc.) into a single particle. However, the term "single-particle form" does not exclude cases where two to ten single particles are attached or closely adhered to each other and substantially have a monolithic form (e.g., transforming into a single-particle structure).

[0037] For example, in the case of the single particle, unlike the secondary particle, the boundary of the primary particle may not be observable in the SEM cross-sectional image.

[0038] For example, the secondary particle can refer to a particle that is an aggregate of multiple primary particles and is substantially regarded or observed as a single particle. For example, in the case of the secondary particle, the boundary of the primary particle can be observed in the SEM cross-sectional image.

[0039] For example, the secondary particles may contain more than 10, 30, 50, or 100 primary particles.

[0040] The positive electrode active material precursor according to the present invention comprises composite hydroxide particles having controlled pores.

[0041] According to an exemplary embodiment, the composite hydroxide particles contain a plurality of pores.

[0042] The multiple pores can be distinguished based on their diameter.

[0043] According to an exemplary embodiment, the plurality of pores may include a first pore with a diameter of less than 2 nm, a second pore with a diameter greater than 2 nm and less than 50 nm, and a third pore with a diameter of more than 50 nm.

[0044] The lower limit of the diameter of the first pore is not limited, but for example, it can be greater than 0.01 nm, greater than 0.05 nm, or greater than 0.1 nm. For example, measurable pores with a diameter of less than 2 nm can be classified as the first pore.

[0045] There is no upper limit to the diameter of the third pore, but it can be, for example, less than 500 nm, less than 300 nm, or less than 200 nm. For example, a measurable pore with a diameter of 50 nm or more can be classified as the third pore.

[0046] According to an exemplary embodiment, the volume of the first pore can be from 0.1% to 5% of the total volume of the plurality of pores.

[0047] In some embodiments, the volume of the first pore can be 0.3% to 4.5%, 0.5% to 4.2%, 0.6% to 4.0%, 0.7% to 3.8%, or 0.8% to 3.5% of the total volume of the plurality of pores.

[0048] Within the aforementioned range, the positive electrode active material formed by the reaction of composite hydroxide particles with the lithium precursor can be fully grown and crystallized. Therefore, the internal porosity of the positive electrode active material can be reduced, and its packing properties can be improved, thereby increasing the energy density of the secondary battery.

[0049] For example, when the volume of the first pore exceeds the above range, fine voids may remain inside the composite hydroxide particles. During the charging and discharging process of the secondary battery, as these fine voids expand, cracks may form in the positive electrode active material, potentially reducing its lifespan. Conversely, when the volume of the first pore is smaller than the above range, the composite hydroxide particles and the lithium precursor may not react uniformly, potentially reducing the electrical properties of the positive electrode active material.

[0050] According to an exemplary embodiment, the volume of the second pore can be 70% to 97% of the total volume of the plurality of pores.

[0051] In some embodiments, the volume of the second pore can be 72% to 96%, 75% to 95%, 77% to 94.5%, or 78% to 94% of the total volume of the plurality of pores.

[0052] Within the aforementioned range, lithium diffusion during the preparation of the positive electrode active material can be promoted, thereby reducing residual lithium on the positive electrode active material. Furthermore, the cation mixing ratio during the crystallization process of the positive electrode active material can be reduced, thereby improving the electrical characteristics of the secondary battery.

[0053] According to an exemplary embodiment, the volume of the third pore can be 2% to 25% of the total volume of the plurality of pores.

[0054] In some embodiments, the volume of the third pore can be 2% to 20% of the total volume of the plurality of pores, 2.2% to 22% of the total volume, 2.5% to 21% of the total volume, 2.8% to 20.5% of the total volume, or 3.0% to 20.0% of the total volume of the plurality of pores.

[0055] Within the aforementioned range, the reaction between the composite hydroxide particles and the lithium precursor can be promoted, thus increasing the particle growth time and consequently increasing the particle size of the positive electrode active material.

[0056] According to an exemplary embodiment, the total volume of the plurality of pores can be 0.001 cm³. 3 / g to 0.04cm 3 / g.

[0057] In some embodiments, the total volume of the plurality of pores can be 0.002 cm³. 3 / g to 0.038cm 3 / g, 0.003cm 3 / g to 0.035cm 3 / g, 0.005cm3 / g to 0.033cm 3 / g or 0.007cm 3 / g to 0.031cm 3 / g.

[0058] Within the aforementioned range, lithium can enter the interior of composite hydroxide particles and reduce the size of pores or block pores, thereby forming a positive electrode active material in the form of single particles.

[0059] According to an exemplary embodiment, the total volume of the plurality of pores can represent the sum of the volumes of the first pore, the second pore, and the third pore.

[0060] The diameter and volume of the pores can be measured or calculated by Brunauer-Emmett-Teller (BET) analysis of the composite hydroxide particles. For example, by combining BET analysis with known analytical methods (e.g., Barrett-Joyner-Halenda (BJH), Horvath-Kawazoe (HK), Density Functional Theory (DFT), etc.), the diameter and volume of the pores can be analyzed based on adsorption-desorption data. For example, by measuring the amount of gas, relative pressure, temperature, etc., during the adsorption / desorption of the composite hydroxide particles in a gas (e.g., nitrogen), and using the measured values ​​and formulas according to the above methods, the diameter and volume of the pores of the composite hydroxide particles can be measured.

[0061] In some embodiments, the BET specific surface area of ​​the composite hydroxide particles can be 1.0 m². 2 / g to 7.0m 2 / g, 1.5m 2 / g to 6.5m 2 / g, 2.0m 2 / g to 6.0m 2 / g, 2.5m 2 / g to 5.8m 2 / g, 2.7m 2 / g to 5.5m 2 / g or 2.8m 2 / g to 5.0m 2 / g.

[0062] Within the aforementioned range, aggregation can occur during the reaction of composite hydroxide particles with lithium precursors, thereby forming positive electrode active materials in the form of single particles with increased particle size.

[0063] The BET specific surface area can be measured according to a well-known method. For example, by adsorbing a gas onto the composite hydroxide particles, the BET specific surface area can be determined based on the amount of the adsorbed gas.

[0064] According to an exemplary embodiment, the composite hydroxide particles may contain one or more metals among nickel, cobalt, and manganese. For example, the composite hydroxide particles may contain nickel, cobalt, and manganese. For example, the composite hydroxide particles may contain oxides of one or more metals among nickel, cobalt, and manganese.

[0065] According to an exemplary embodiment, in the total content of the metals in the composite hydroxide particles, the content of nickel may be 80 mol% or more. For example, in the total content of the metals in the composite hydroxide particles, the content of nickel may be 82 mol% or more, 85 mol% or more, 88 mol% or more, or 90 mol% or more.

[0066] Within the above range, a secondary battery having an improved energy density can be achieved.

[0067] According to an exemplary embodiment, the composite hydroxide particles may include a crystal structure of a compound represented by the following Chemical Formula 1.

[0068] [Chemical Formula 1] Ni 1-x-y-z Co x Mn y M z (OH) 2+a In Chemical Formula 1, 0 < x ≤ 0.2, 0 < y ≤ 0.2, 0 ≤ z ≤ 0.1, 0.7 ≤ 1 - x - y - z < 1, -0.1 ≤ a ≤ 0.1, and M may include at least one selected from Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga, La, W, and B.

[0069] For example, 0 < x ≤ 0.15 or 0 < x ≤ 0.1.

[0070] For example, 0 < y ≤

此处原文有误,推测为0&lt;y≤0.15或者0&lt;y≤0.1

[0071] For example, 0.8 ≤ 1 - x - y - z < 1 or 0.9 ≤ 1 - x - y - z < 1.

[0072] In some embodiments, the composite hydroxide particles may include a crystal structure of a compound represented by the following Chemical Formula 1-1.

[0073] [Chemical Formula 1-1] Ni 1-x1-y1 Co x1 Mn y1 (OH)2 In Chemical Formula 1-1, 0 < x1 ≤ 0.2, 0 < y1 ≤ 0.2, 0.6 ≤ 1 - x1 - y1 < 1, and M may include at least one selected from Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga, La, W, and B.

[0074] The structure of the composite hydroxide particles may be a flaky structure, a needle-like structure, or an amorphous structure.

[0075] In one embodiment, the composite hydroxide particles may consist essentially of oxides of nickel, cobalt, and manganese. However, other metals are not excluded from the positive electrode active material containing the composite hydroxide particles. For example, composite hydroxide particles with controlled pores can be formed by nickel, cobalt, and manganese, thereby promoting the growth of the particles.

[0076] According to an exemplary embodiment, the structure of the composite hydroxide particles may be a flaky structure.

[0077] The flaky composite hydroxide particles can induce the aggregation and growth of lithium precursors and composite hydroxide particles into a morphology, thereby increasing the particle size of the positive electrode active material in the form of single particles. For example, when the structure of the composite hydroxide particles is a needle-like structure or amorphous, the particles are not easily aggregated, which may reduce the particle size of the positive electrode active material in the form of single particles.

[0078] In some embodiments, the aspect ratio of the composite hydroxide particles may be 1.0 to 6.0, 1.1 to 5.8, 1.15 to 5.5, 1.2 to 5.2, or 1.3 to 5.0.

[0079] Within the above range, the formation of the orientation of the composite hydroxide particles can be suppressed, thereby quickly forming the seeds of the positive electrode active material in the form of single particles, and thus increasing the particle size of the positive electrode active material.

[0080] In some embodiments, the average particle size (D 50 ) of the composite hydroxide particles may be 0.1 nm to 5 nm, 0.3 nm to 4 nm, or 0.5 nm to 3 nm.

[0081] The "average particle size (D 50 )" may represent the particle size value corresponding to when the volume cumulative distribution of the particles reaches 50%. The volume cumulative distribution of the particles can be obtained based on the laser diffraction scattering method.

[0082] According to the method for preparing the positive electrode active material precursor of the present invention, a mixed solution of a metal source comprising a nickel source, a cobalt source, and a manganese source and a solvent can be prepared. The mixed solution can be reacted to prepare a positive electrode active material precursor containing the composite hydroxide particles.

[0083] The nickel source, cobalt source, and / or manganese source may each comprise a metal nitrate, sulfate, carbonate, etc. For example, the nickel source may be nickel sulfate, the cobalt source may be cobalt sulfate, and the manganese source may be manganese sulfate.

[0084] The contents of the nickel source, cobalt source, and manganese source can be adjusted to satisfy the composition of the chemical formula 1. For example, the number of moles of nickel source in the total number of moles of metal source can be 80 mol% or more, 85 mol% or more, or 95 mol% or more.

[0085] According to an exemplary embodiment, the total concentration of the metal source in the mixed solution can be from 0.5 M to 4 M. According to some embodiments, the total concentration of the metal source in the mixed solution can be from 1 M to 3 M.

[0086] The solvent may include a water-based solvent. For example, in the water-based solvent, the water content may be 70% or more, 90% or more, 95% or more, or 99% or more of the total volume of the water-based solvent.

[0087] According to an exemplary embodiment, the mixed solution may further contain a chelating agent or a basic compound.

[0088] The chelating agent may include, for example, ammonia (NH3·H2O), ammonium sulfate ((NH4)2SO4), ammonium nitrate (NH4NO3), ammonium chloride (NH4Cl), ammonium acetate (CH3COONH4), ammonium carbonate, etc.

[0089] The chelating agent may also include, for example, organic compounds having a carboxyl group. For example, the organic compounds having a carboxyl group may include oxalic acid, ethylenediaminetetraacetic acid, citric acid, acetic acid, succinic acid, malonic acid, malic acid, propionic acid, tartaric acid, lactic acid, pyruvic acid, fumaric acid, etc. These can be used alone or in combination of two or more. The content of the chelating agent may be from 0.01% to 3% by weight or from 0.05% to 1% by weight of the total weight of the mixed solution.

[0090] According to an exemplary embodiment, the concentration of the chelating agent in the mixed solution can be from 0.5M to 4M or from 1M to 3M. In some embodiments, the ratio of the concentration of the chelating agent to the total concentration of the metal source can be from 0.5 to 1.5 or from 0.7 to 1.2. Within these ranges, porosity can be more easily controlled.

[0091] The alkaline compound can be added as a precipitant. For example, the alkaline compound may include sodium hydroxide (NaOH), sodium carbonate (Na2CO3), ammonium chloride (NH4Cl), etc. These can be used alone or in combination of two or more.

[0092] The content of the alkaline compound may be from 0.01% to 3% by weight or from 0.05% to 1% by weight of the total weight of the mixed solution.

[0093] According to an exemplary embodiment, the alkaline compound can be added together with the chelating agent described above to bring the pH of the mixed solution to 11 or higher. For example, the pH of the mixed solution can be 11.5 or higher or 12 or higher. Therefore, the proportion of the positive electrode active material precursor with a sheet-like structure can be increased.

[0094] According to an exemplary embodiment, the mixed solution can be reacted and dried to form the aforementioned composite hydroxide particles.

[0095] For example, complex hydroxide particles can be formed through a co-precipitation reaction.

[0096] For example, the temperature of the coprecipitation reaction can be 20°C to 100°C, 40°C to 80°C, or 50°C to 75°C. The time of the coprecipitation reaction can be 1 hour to 100 hours, 10 hours to 90 hours, or 20 hours to 80 hours.

[0097] For example, the solvent present in the formed reactants can be removed by a single drying process, and the porosity can be controlled by a second drying process.

[0098] For example, porosity can be controlled by adjusting the reaction time, metal source, chelating agent, basic compound, and reaction temperature. For instance, increasing the reaction time increases particle growth, thereby reducing internal porosity. For instance, increasing the content of the metal source, chelating agent, and / or basic compound causes the metal source, etc., to adhere to the internal voids of the formed particles, thereby reducing internal porosity. For instance, increasing the reaction temperature allows particles to grow in the direction that reduces internal porosity, thereby reducing internal porosity.

[0099] According to the method for preparing the positive electrode active material of the present invention, a mixture of a positive electrode active material precursor containing the above-mentioned composite hydroxide particles and a lithium precursor is subjected to a first heat treatment, followed by a second heat treatment. The first heat treatment and the second heat treatment can be distinguished according to temperature.

[0100] The mixing can be performed considering the total number of moles of metal in the positive electrode active material precursor and the total number of moles of lithium in the lithium precursor.

[0101] According to an exemplary embodiment, the positive electrode active material precursor and the lithium precursor can be mixed such that the ratio of the molar number of lithium in the lithium precursor to the total molar number of metals contained in the positive electrode active material precursor is 0.8 to 1.5. In some embodiments, the ratio of the molar number of lithium in the lithium precursor to the total molar number of metals contained in the positive electrode active material precursor may be 0.85 to 1.3 or 0.9 to 1.2.

[0102] The lithium precursor may include, for example, lithium carbonate, lithium nitrate, lithium acetate, lithium oxide, lithium hydroxide, etc. These may be used alone or in combination of two or more.

[0103] The positive electrode active material can be prepared by heat treatment of a mixture of the positive electrode active material precursor and the lithium precursor. The positive electrode active material may comprise lithium metal oxide particles formed by the reaction of the composite hydroxide particles and the lithium precursor.

[0104] According to an exemplary embodiment, the lithium metal oxide particles may include a single-particle form. The single-particle form does not exclude the possibility that two to ten individual particles are attached or closely adhered to each other, thus substantially having a monolithic form (e.g., transforming into a single-particle structure).

[0105] For example, the aforementioned composite hydroxide particles with controlled pore volume aggregate with the lithium precursor, and during heat treatment, the voids between the composite hydroxide particles, the lithium precursor, and / or combinations thereof are eliminated, thereby forming lithium metal oxide particles in the form of single particles.

[0106] By adjusting the steps, temperature, and time of the heat treatment, a positive electrode active material for a secondary battery with improved electrical properties can be prepared. For example, by performing two or more heat treatment steps, particle damage can be reduced. Furthermore, by ensuring that the temperature and time of the first heat treatment and the temperature and time of the second heat treatment meet a predetermined relationship, lithium metal oxide particles with reduced residual lithium on the particle surface and sufficiently increased particle size and crystallinity can be prepared.

[0107] The temperature and time of the first heat treatment and the second heat treatment can be expressed as the following heat treatment distribution values.

[0108] According to an exemplary embodiment, the heat treatment distribution value calculated from the respective time and temperature of the first heat treatment and the second heat treatment can be from 0.5 to 8.

[0109] [Formula 1] Heat treatment distribution = (T2) t2) / (T1 t1) In Equation 1, T1 is the temperature of the first heat treatment, t1 is the time of the first heat treatment, T2 is the temperature of the second heat treatment, and t2 is the time of the second heat treatment.

[0110] The temperatures of the first heat treatment and the second heat treatment can remain constant, or they can be increased and / or decreased. When the temperature increases or decreases, the average temperature over time can correspond to the temperatures of the first heat treatment and the second heat treatment.

[0111] In some implementations, the heat treatment distribution value may be 0.5 to 8, 0.6 to 6, 0.7 to 5, 0.8 to 4.5, 0.9 to 4, 1 to 4, 1.1 to 3.8, 1.2 to 3.5, 1.3 to 3.2, 1.5 to 3.0, or 1.7 to 2.5.

[0112] Within the aforementioned range, the growth of lithium metal oxide particles in single-particle form can be promoted. For example, when the heat treatment distribution values ​​are not within the aforementioned range, the particle size may not grow sufficiently, or crystallization may not proceed adequately.

[0113] Furthermore, by using a positive electrode active material precursor containing composite hydroxide particles with controlled pore volume and satisfying the aforementioned heat treatment distribution values, it is possible to simultaneously reduce residual lithium on the surface of lithium metal oxide particles, increase the energy density of the positive electrode active material, and improve mechanical stability.

[0114] According to an exemplary embodiment, the temperature of the second heat treatment may be lower than the temperature of the first heat treatment.

[0115] Therefore, the particles can be grown and crystallized at a relatively high temperature, thereby increasing the particle size of lithium metal oxide particles.

[0116] According to an exemplary embodiment, the temperature of the first heat treatment can be from 700°C to 1000°C. In some embodiments, the temperature of the first heat treatment can be from 720°C to 980°C, 750°C to 950°C, 780°C to 920°C, 800°C to 900°C, or 820°C to 870°C.

[0117] Within the aforementioned temperature range, the particle size of the composite hydroxide particles can be sufficiently increased, thereby reducing the voids between particles. This allows a relatively large number of composite hydroxide particles to exist in an aggregated state. With reduced voids, subsequent second heat treatment crystallizes the particles, thereby increasing the size of the individual lithium metal oxide particles.

[0118] According to an exemplary embodiment, the temperature of the second heat treatment can be from 600°C to 800°C. In some embodiments, the temperature of the second heat treatment can be from 620°C to 780°C, 640°C to 770°C, 660°C to 760°C, 680°C to 750°C, or 700°C to 740°C.

[0119] Within the above temperature range, particle damage can be reduced, and the formation of residual lithium can be reduced.

[0120] According to an exemplary implementation, the temperature difference between the first heat treatment and the second heat treatment can be above 50°C, above 70°C, above 80°C, above 90°C, or above 100°C.

[0121] By utilizing the aforementioned temperature differences, particle growth and particle crystallization can be carried out separately, thereby improving the uniformity of the prepared lithium metal oxide particles.

[0122] According to an exemplary embodiment, the lithium metal oxide particles may include a crystal structure of a compound represented by Chemical Formula 2 below.

[0123] [Chemical Formula 2] Li 1+b Ni 1-x-y-z Co x Mn y M z O 2+a In Chemical Formula 2, 0 < x ≤ 0.1, 0 < y ≤ 0.2, 0 ≤ z ≤ 0.1, 0.7 ≤ 1 - x - y - z < 1, -0.1 ≤ a ≤ 0.1, -0.5 ≤ b ≤ 0.5, and M may include at least one selected from Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga, La, W, and B.

[0124] In Chemical Formula 2, M may act as an auxiliary element. The auxiliary element may be mixed into the layered structure / crystal structure together and form a bond. In addition, the auxiliary element may be attached to main active elements such as nickel, cobalt, and manganese to enhance the chemical stability of the positive electrode active material or the layered structure / crystal structure.

[0125] Figure 1 and Figure 2 are a schematic plan view and a schematic cross-sectional view showing a lithium secondary battery according to an exemplary embodiment, respectively. Figure 2 is a cross-sectional view taken along the I-I' line of Figure 1 .

[0126] Referring to Figure 1 and Figure 2 , the lithium secondary battery may include an electrode assembly 150 accommodated in a case 160. As shown in Figure 2 , the electrode assembly 150 may include a positive electrode 100, a negative electrode 130, and a separator 140 that are repeatedly stacked.

[0127] ]The positive electrode 100 includes a positive electrode current collector 105 and a positive electrode active material layer 110 disposed on at least one surface of the positive electrode current collector 105.

[0128] The positive electrode current collector 105 may include stainless steel, nickel, aluminum, titanium, or an alloy thereof. The positive electrode current collector 105 may also include aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver. The thickness of the positive electrode current collector 105 is not particularly limited, but for example, it may be 10 μm to 50 μm.

[0129] The positive electrode active material layer 110 can also be disposed on both sides of the positive electrode current collector 105.

[0130] The positive electrode active material layer 110 may contain a positive electrode active material. The positive electrode active material may contain the aforementioned lithium metal oxide.

[0131] In addition to the lithium metal oxide, the positive electrode active material may further include other positive electrode active materials. For example, the positive electrode active material may further include lithium cobalt oxide-based active materials, lithium manganese oxide-based active materials, or lithium iron phosphate (LFP)-based active materials (e.g., LiFePO4), and may further include lithium metal oxides that do not have a single-particle structure (e.g., a secondary particle structure).

[0132] The positive electrode active material layer may further comprise a conductive material. The conductive material can enhance the conductivity of the positive electrode active material layer that has been reduced due to the binder.

[0133] The conductive material may include, for example, carbon-based conductive materials such as graphite, carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes, vapor-grown carbon fiber (VGCF), and carbon fibers, and / or metal-based conductive materials including perovskite materials such as tin, tin oxide, titanium oxide, LaSrCoO3, and LaSrMnO3. For example, the conductive material may include carbon nanotubes.

[0134] The content of the conductive material in the total weight of the positive electrode active material layer can be from 0.01% by weight to 3% by weight. In some embodiments, the content of the conductive material in the total weight of the positive electrode active material layer can be from 0.1% by weight to 1% by weight.

[0135] The positive electrode active material layer may further include an adhesive. The adhesive can bond the positive electrode active material and the conductive material together, and can increase the bonding force between the positive electrode active material layer and the positive electrode current collector.

[0136] The adhesive can be an organic adhesive such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or a water-based adhesive such as styrene-butadiene rubber (SBR), and can be used with a thickener such as carboxymethyl cellulose (CMC).

[0137] For example, PVDF-based adhesives can be used as binders for forming the positive electrode. In this case, the amount of adhesive used to form the positive electrode active material layer can be reduced, and the amount of positive electrode active material particles can be relatively increased, thereby improving the power and capacity of the secondary battery.

[0138] The adhesive content can be from 0.5% to 5% of the total weight of the positive electrode active material layer. In some embodiments, the adhesive content can be from 1% to 3% of the total weight of the positive electrode active material layer.

[0139] The positive electrode active material layer may further contain thickeners and / or dispersants. For example, the positive electrode active material layer may contain thickeners such as carboxymethyl cellulose (CMC).

[0140] The positive electrode active material layer 110 can be formed from a positive electrode slurry composition comprising a positive electrode active material and a binder. For example, the positive electrode active material layer 110 can be manufactured by coating a positive electrode slurry composition comprising a positive electrode active material and a binder onto one side of the positive electrode current collector 105 and then drying and calendering it.

[0141] According to an exemplary embodiment, the positive electrode slurry composition may include a solvent. The solvent may be N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc.

[0142] The coating of the positive electrode slurry composition can be performed by methods such as gravure coating, slot extrusion coating, multi-layer simultaneous die coating, embossing, doctor blade coating, dip coating, bar coating, and casting, and is not limited to these methods.

[0143] According to an exemplary embodiment, the thickness of the positive electrode active material layer is not particularly limited, but for example, it can be from 10 μm to 200 μm.

[0144] According to some embodiments, the positive electrode active material layer may include two or more layers, wherein the two or more layers contain different positive electrode active materials, conductive materials, and / or binders. For example, the positive electrode active material layer may include a first positive electrode active material layer and a second positive electrode active material layer, wherein the types and / or contents of the active materials, conductive materials, and / or binders in the first positive electrode active material layer may be different from those in the second positive electrode active material layer.

[0145] The negative electrode 130 may include a negative electrode current collector 125 and a negative electrode active material layer 120, which is formed by coating the negative electrode active material onto the negative electrode current collector 125.

[0146] The negative electrode active material can be any material known in the art that enables lithium ion insertion and extraction, without particular restriction. For example, the negative electrode active material can be carbon-based materials such as crystalline carbon, amorphous carbon, carbon composites, and carbon fibers; lithium alloys; silicon or tin, etc.

[0147] Examples of amorphous carbon include hard carbon, coke, mesocarbon microbeads (MCMB) calcined below 1500°C, and mesophase pitch-based carbon fiber (MPCF). Examples of crystalline carbon include graphite-based carbon such as natural graphite, graphitized coke, graphitized mesophase carbon microbeads (MCMB), and graphitized mesophase pitch-based carbon fiber (MPCF). Elements included in the lithium alloy include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium.

[0148] The negative electrode current collector 125 may include, for example, gold, stainless steel, nickel, aluminum, titanium, copper or alloys thereof, preferably copper or copper alloys.

[0149] In some embodiments, the negative electrode active material can be mixed with a binder, conductive material, and / or dispersant in a solvent and stirred to prepare a slurry. The slurry can be coated on at least one side of the negative electrode current collector 125 and then calendered and dried to manufacture the negative electrode 130.

[0150] The adhesive and conductive material may be substantially the same as or similar to the substances used in the positive electrode active material layer 110. In some embodiments, for example, for compatibility with carbon-based active materials, the adhesive used to form the negative electrode may include a water-based adhesive such as styrene-butadiene rubber (SBR) and may be used with a thickener such as carboxymethyl cellulose (CMC).

[0151] A separator 140 can be disposed between the positive electrode 100 and the negative electrode 130. The separator 140 may comprise a porous polymer membrane made of polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer. The separator 140 may also comprise a nonwoven fabric formed from high-melting-point glass fibers, polyethylene terephthalate fibers, etc.

[0152] In some embodiments, the area (e.g., the area in contact with the separator 140) and / or volume of the negative electrode 130 can be larger than that of the positive electrode 100. Therefore, for example, lithium ions generated from the positive electrode 100 can migrate smoothly to the negative electrode 130 without precipitation in between. Thus, it is easier to achieve the effect of simultaneously improving power and stability through the combination of the first and second positive electrode active material layers described above.

[0153] According to an exemplary embodiment, the battery cell can be defined by a positive electrode 100, a negative electrode 130, and a separator 140, and an electrode assembly 150 can be formed, for example, in the form of a jelly roll, by stacking multiple battery cells. For example, the electrode assembly 150 can be formed by winding, lamination, folding, etc. of the separator 140.

[0154] The electrode assembly 150 can be housed together with the electrolyte within the housing 160, thereby defining a lithium secondary battery. According to an exemplary embodiment, the electrolyte can be a non-aqueous electrolyte.

[0155] Non-aqueous electrolytes may contain lithium salts and organic solvents, wherein the lithium salts may be, for example, derived from Li. + X - This indicates that the anion (X) of the lithium salt is... - ), can be exemplified by F - Cl - ,Br - I - NO3 - N(CN)2 - BF4 - ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - CF3SO3 - CF3CF2SO3 - (CF3SO2)2N - (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2- CH3CO2 - SCN - and (CF3CF2SO2)2N - wait.

[0156] The organic solvents may include, for example, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, γ-butyrolactone, propylene sulfite, and tetrahydrofuran. These may be used alone or in combination of two or more.

[0157] like Figure 1 As shown, the tabs (positive tab and negative tab) can protrude from the positive current collector 105 and negative current collector 125 belonging to each cell and extend to one end of the housing 160. The tabs can be fused to said end of the housing 160 to form electrode leads (positive lead 107 and negative lead 127) extending to or exposed outside the housing 160.

[0158] Figure 1 The diagram shows the positive electrode lead 107 and the negative electrode lead 127 protruding from the upper side of the housing 160 in a planar direction, but the position of the electrode leads is not limited thereto. For example, the electrode leads may protrude from at least one of the two sides of the housing 160, or from the lower side of the housing 160. Alternatively, the positive electrode lead 107 and the negative electrode lead 127 may be formed to protrude from different sides of the housing 160, respectively.

[0159] The lithium secondary battery can be manufactured in shapes such as cylindrical, prismatic, pouch, or coin, for example, using a can.

[0160] The embodiments of the present invention will be further described below with reference to specific experimental examples. The embodiments and comparative examples included in the experimental examples are only for illustrating the present invention and are not intended to limit the scope of the claims. Various changes and modifications can be made to the embodiments within the scope of the present invention and its technical concept, which is obvious to those skilled in the art, and such variations and modifications naturally fall within the scope of the claims.

[0161] Example 1 (1) Preparation of positive electrode active material precursor Distilled water, bubbled with nitrogen (N2) for 24 hours to remove dissolved oxygen, was used to mix nickel sulfate (NiSO4), cobalt sulfate (CoSO4), and manganese sulfate (MnSO4) in a ratio of 0.8:0.1:0.1. The mixed solution was added to a reactor at 70°C, along with sodium hydroxide (NaOH) as a precipitant and ammonium hydroxide (NH3·H2O) as a chelating agent, to bring the pH to 12.0. At this point, the transition metals and ammonium hydroxide (NH3·H2O) were added in a 1:1 concentration ratio. A co-precipitation reaction was then carried out for 72 hours to obtain Ni as a transition metal precursor. 0.8 Co 0.1 Mn 0.1 (OH)2. The obtained transition metal precursor is dried at 100°C for 12 hours and then dried again at 120°C for 10 hours to obtain a positive electrode active material precursor containing transition metal precursor particles.

[0162] (2) Characteristics of positive electrode active material precursor The specific surface area, pore volume, and aspect ratio of the transition metal precursor particles were measured.

[0163] Specific surface area and pore volume were measured using a BET measuring instrument (Micromeritics, ASAP2420) according to the gas adsorption-desorption method. Pores were classified by diameter into micropores (below 2 nm), mesopores (greater than 2 nm and less than 50 nm), and macropores (greater than 50 nm).

[0164] For aspect ratio, a scanning electron microscope (SEM) (Helios Nanolab 650 manufactured by Thermo Fisher Scientific) was used to photograph the precursor particles of the positive electrode active material, and the aspect ratio was measured based on the photographs.

[0165] (3) Preparation of positive electrode active material Lithium hydroxide (LiOH) and the aforementioned positive electrode active material precursor were added to a dry high-speed mixer at a ratio of 1.01:1 and mixed uniformly for 20 minutes. The mixture was then placed in a calcining furnace and heated to 830°C at a rate of 2°C / min for a first heat treatment, which was maintained for 5 hours. Subsequently, the temperature was lowered to 720°C and maintained for 10 hours for a second heat treatment.

[0166] Oxygen was continuously introduced at a flow rate of 10 mL / min during the heating and holding period. After calcination, the mixture was naturally cooled to room temperature and then pulverized and graded to obtain a product containing LiNi. 0.8 Co0.1 Mn 0.1 O2 is a positive electrode active material in the form of single-particle lithium metal oxide particles.

[0167] The specific surface area, aspect ratio, and pore volume of the transition metal precursor particles are shown in Table 1 below.

[0168] Examples 2 to 8 The positive electrode active material precursor and positive electrode active material were prepared by the same method as in Example 1. The difference was that the specific surface area, aspect ratio and pore volume of the transition metal precursor were changed by adjusting the reactor temperature and reaction time, the amount and ratio of the added transition metal, sodium hydroxide (NaOH) and ammonium hydroxide (NH3·H2O), as shown in Table 1 below.

[0169] Examples 9 to 13 The positive electrode active material was prepared by the same method as in Examples 1 to 5, except that in the preparation of the positive electrode active material, the temperature was raised to 720°C and held for 10 hours for a first heat treatment, and the temperature was raised to 830°C and held for 5 hours for a second heat treatment.

[0170] Comparative Example 1 and Comparative Example 2 The positive electrode active material precursor and positive electrode active material were prepared by the same method as in Example 1. The difference was that the specific surface area, aspect ratio and pore volume of the transition metal precursor were changed by adjusting the reactor temperature and reaction time, the amount and ratio of the added transition metal, sodium hydroxide (NaOH) and ammonium hydroxide (NH3·H2O), as shown in Table 1 below.

[0171] Comparative Examples 3 to 7 The positive electrode active material was prepared by the same method as in Examples 1 to 5, except that in the preparation of the positive electrode active material, the temperature was raised to 830°C and held for 10 hours for heat treatment.

[0172] [Table 1] Manufacturing of secondary batteries The above-mentioned positive electrode active material, carbon black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder were mixed in a weight ratio of 93:5:2 and dispersed in N-methylpyrrolidone to prepare a slurry. The slurry was coated on one side of an aluminum current collector (20 μm thick) and then dried and calendered to obtain the positive electrode.

[0173] The negative electrode uses 1.2T of lithium metal.

[0174] The positive and negative electrodes are cut (notching) into predetermined sizes and stacked. A separator (polyethylene, 13 μm thick) is placed between the positive and negative electrodes, and then an electrolyte is injected to obtain a 2032 coin-shaped battery.

[0175] The electrolyte used is a solution containing 1 M LiPF6 dissolved in a solvent comprising ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1:2.

[0176] Experimental Example (1) Evaluation of positive electrode active material precursor Evaluation of SEM images Figure 3a and Figure 3b The image shows a SEM image of the positive electrode active material precursor according to Example 1. Figure 4a and Figure 4b The image shows a SEM image of the positive electrode active material precursor according to Example 3. Figure 5a and Figure 5b The image shown is a SEM image of the positive electrode active material precursor according to Comparative Example 2.

[0177] Reference Figure 3a , Figure 3b , Figure 4a and Figure 4b It was confirmed that even if the positive electrode active material precursors have the same lamellar structure and similar BET values, the pore volume may be different.

[0178] Reference Figure 5a and Figure 5b In the positive electrode active material precursor with needle-like structure, there are a large number of pores with large pore sizes.

[0179] (2) Evaluation of positive electrode active material Evaluation of SEM images Figure 6 The image shows a SEM image of the positive electrode active material prepared using the positive electrode active material precursor according to Example 1. Figure 7 The image shows an SEM image of a positive electrode active material prepared using the positive electrode active material precursor according to Comparative Example 2.

[0180] Reference Figure 6 and Figure 7 Compared with the positive electrode active material according to the comparative example, the positive electrode active material according to the embodiment exhibits a larger average particle size and higher uniformity.

[0181] Measurement of residual lithium Add 2.5 g of each positive electrode active material according to the examples and comparative examples to a 250 mL beaker, add 100 g of deionized water, then place a magnetic rod in the beaker and stir at 300 rpm for 10 minutes. Afterwards, filter using a vacuum flask, and then aliquot 100 g. Add the aliquoted solution to the container of an automatic titrator, and perform automatic titration with 0.1 N HCl according to the Wader method to measure the content of Li₂CO₃ and LiOH in the solution.

[0182] Particle size measurement The volumetric particle size distribution of the positive electrode active material was measured using laser diffraction (Microtrac MT3000). The D0.05 of the positive electrode active material was... 50 The particle size is calculated as the particle size at the 50% position in the volumetric particle size distribution.

[0183] (3) Evaluation of secondary batteries Measurement of initial charge / discharge capacity The secondary batteries manufactured according to the examples and comparative examples were charged in a chamber at 25°C (CC-CV 0.1C 4.3V 0.005C cut-off), and the battery capacity (initial charge capacity) was measured. Then, they were discharged (CC 0.1C 3.0V cut-off), and the battery capacity (initial discharge capacity) was measured.

[0184] Evaluation of rate capability The secondary batteries manufactured according to the examples and comparative examples were charged (CC / CV 0.1C 4.3V 0.005C cutoff) and discharged (CC 0.1C 3.0V cutoff) twice, and then charged (CC / CV 0.5C 4.3V 0.005C cutoff) and discharged (CC 4.0C 3.0V cutoff) once more. The rate performance was evaluated by converting the 4.0C discharge capacity divided by the 0.1C discharge capacity into a percentage (%).

[0185] The evaluation results of the positive electrode active material and the secondary battery are shown in Table 2 below.

[0186] [Table 2] Referring to Table 2, the content of residual lithium on the surface of the positive electrode active material according to the embodiment is reduced. Furthermore, the discharge capacity of the secondary battery according to the embodiment is increased, and the rate performance is improved.

[0187] In Example 6, where the micropore volume is relatively large, Example 7, where the mesopore volume is relatively small, and Example 8, where the mesopore volume is relatively large, the discharge capacity and rate characteristics of the secondary battery are relatively reduced.

[0188] The comparative example showed an increase in the residual lithium content on the surface of the positive electrode active material. Furthermore, the discharge capacity of the secondary battery according to the comparative example decreased, and its rate performance was significantly reduced.

Claims

1. A positive electrode active material precursor, the positive electrode active material precursor comprising composite hydroxide particles, the composite hydroxide particles comprising a plurality of pores, wherein the volume of a first pore with a diameter of less than 2 nm is 0.1% to 5% of the total volume of the plurality of pores.

2. The positive electrode active material precursor according to claim 1, wherein, The composite hydroxide particles contain a second pore with a diameter greater than 2 nm and less than 50 nm, and the volume of the second pore is 70% to 97% of the total volume of the plurality of pores.

3. The positive electrode active material precursor according to claim 2, wherein, The composite hydroxide particles contain a third pore with a diameter of 50 nm or more, and the volume of the third pore is 2% to 25% of the total volume of the plurality of pores.

4. The positive electrode active material precursor according to claim 1, wherein, The composite hydroxide particles have a BET specific surface area of ​​1.0 m². 2 / g to 7.0m 2 / g.

5. The positive electrode active material precursor according to claim 1, wherein, The total volume of the plurality of pores in the composite hydroxide particles is 0.001 cm³. 3 / g to 0.04cm 3 / g.

6. The positive electrode active material precursor according to claim 1, wherein, The aspect ratio of the composite hydroxide particles is 1.0 to 6.

0.

7. A method for preparing a positive electrode active material, comprising the following steps: A mixture of a positive electrode active material precursor and a lithium precursor is subjected to a first heat treatment. The positive electrode active material precursor comprises composite hydroxide particles, which contain multiple pores, wherein the volume of a first pore with a diameter of less than 2 nm is 0.1% to 5% of the total volume of the multiple pores. Perform a second heat treatment. Wherein, the heat treatment distribution value according to Equation 1 below is 0.5 to 8. [Formula 1] Heat treatment distribution = (T2) t2) / (T1 t1) In Equation 1, T1 is the temperature of the first heat treatment, t1 is the time of the first heat treatment, T2 is the temperature of the second heat treatment, and t2 is the time of the second heat treatment.

8. The method for preparing the positive electrode active material according to claim 7, wherein, The temperature of the second heat treatment is lower than the temperature of the first heat treatment.

9. The method for preparing the positive electrode active material according to claim 7, wherein, The composite hydroxide particles contain a second pore with a diameter greater than 2 nm and less than 50 nm, and the volume of the second pore is 70% to 97% of the total volume of the plurality of pores.

10. The method for preparing the positive electrode active material according to claim 7, wherein, The composite hydroxide particles contain a third pore with a diameter of 50 nm or more, and the volume of the third pore is 2% to 25% of the total volume of the plurality of pores.

11. The method for preparing the positive electrode active material according to claim 7, wherein, The temperature of the first heat treatment is 700°C to 1000°C.

12. The method for preparing the positive electrode active material according to claim 7, wherein, The temperature of the second heat treatment is 600°C to 800°C.

13. The method for preparing the positive electrode active material according to claim 7, wherein, The composite hydroxide particles contain nickel, cobalt, and manganese, and the nickel content in the total metal content of the composite hydroxide particles is more than 80 mol%.

14. The method for preparing the positive electrode active material according to claim 7, wherein, The composite hydroxide particles have a plate-like structure.

15. The method for preparing the positive electrode active material according to claim 7, wherein, The positive electrode active material is formed in the form of single particles.

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