Lithium secondary battery cathode material and method for manufacturing the same

Abstract

The present invention relates to a lithium secondary battery cathode material, and the lithium secondary battery cathode material of the present invention includes a cathode active material, and the cathode active material includes lithium metal oxide particles containing lithium, nickel, cobalt, and manganese, and the average roughness (Ra) of the surface of the cathode material can be 1.0 μm or less in a first roughness measured by the average value of the active material within a randomly selected 40 μm x 40 μm range.

Description

Technical Field

[0001] This invention relates to lithium secondary batteries. More specifically, this invention relates to a positive electrode material for lithium secondary batteries. Background Technology

[0002] With the technological development and increasing demand for mobile devices, the demand for secondary batteries as an energy source is increasing dramatically. Among various types of secondary batteries, lithium secondary batteries have taken the lead in achieving large-scale commercial application due to their high energy density, high operating voltage, long cycle life, and low self-discharge rate.

[0003] In addition, with increasing attention to environmental issues, electric vehicles and hybrid electric vehicles, which can replace fossil fuel vehicles such as gasoline and diesel vehicles, which are one of the sources of air pollution, have attracted much attention. As the power source for the electric vehicles and hybrid electric vehicles, the technological development of lithium secondary batteries has become a current research hotspot.

[0004] Lithium-ion rechargeable batteries typically consist of a positive electrode containing a positive electrode material, a negative electrode containing a negative electrode material, a separator, and an electrolyte. They are charged and discharged through the intercalation-decalation of lithium ions. These batteries possess advantages such as high energy density, large electromotive force, and high capacity, making them suitable for various applications.

[0005] Specifically, to improve the performance of cathode active materials, a technology using high-nickel NCM (nickel-cobalt-manganese) cathode materials with high nickel content has been proposed. However, traditional high-nickel NCM cathode materials are secondary particles formed by the agglomeration of primary particles. Due to the large specific surface area of ​​the powder, the contact area with the electrolyte is large, leading to increased gas production. Furthermore, because the secondary particles are relatively weak, they break back into primary particles during the electrode pressing process, resulting in a deterioration in lifespan characteristics.

[0006] Therefore, by increasing the primary particle size to reduce the specific surface area and increase the particle strength, a single-particle-shaped cathode material can be designed, which can suppress the degradation of lifetime characteristics in high-nickel NCM cathode materials.

[0007] However, when preparing single-particle cathode materials using traditional methods, the deagglomeration process is quite challenging, resulting in some particles remaining as secondary particles formed from the aggregation of primary particles. This leads to an increase in residual lithium content.

[0008] This residual lithium can degrade the electrochemical properties of the battery, so it must be removed through further heat treatment.

[0009] Therefore, there is a need for a method to prepare positive electrode active material for lithium secondary batteries that can suppress the generation of residual lithium and can be prepared into single particles through a simple process. Summary of the Invention

[0010] Technical problems to be solved According to an embodiment of the present invention, a lithium secondary battery cathode material is provided, which includes a lithium secondary battery cathode active material. Since the active material has less residual lithium, it can impart excellent electrochemical properties when applied to a lithium secondary battery, and the cathode material has excellent uniformity when the electrode is prepared.

[0011] Technical solution According to an embodiment of the present invention, a lithium secondary battery cathode material comprises a cathode active material, wherein the cathode active material comprises lithium metal oxide particles containing lithium, nickel, cobalt and manganese, wherein the average roughness (Ra: Average Roughness) of the cathode material surface can be less than 1.0 μm in a first roughness measured by the average value of the active material in a randomly selected range of 40 μm × 40 μm.

[0012] In one embodiment, the peak-to-valley ratio (Rpv) of the first roughness may be less than 9.0 μm. In another embodiment, the root-mean-square roughness (Rq) of the first roughness may be less than 1.20 μm.

[0013] In one embodiment, in the second roughness obtained from a single particle under the electrode state, the average roughness (Ra) of the positive electrode material surface may be less than 0.20 μm. In one embodiment, in the second roughness obtained from a single particle under the electrode state, the peak-to-valley ratio (Rpv) may be less than 0.90 μm.

[0014] In one embodiment, the root-mean-square roughness (Rq) in the second roughness obtained from a single particle under the electrode condition can be less than 0.25 μm. In one embodiment, the positive electrode active material can satisfy the following equation 1.

[0015] <Formula 1> AB≤1.30 In Formula 1, when a 3g positive electrode active material sample is placed in a mold with a diameter of 1.3cm and pressurized under a pressure of 9 tons, A represents the sum of micro powder values ​​below 1μm after pressurization, and B represents the sum of micro powder values ​​below 1μm before pressurization.

[0016] In one embodiment, the average particle size (D50) may be 4.0 to 5.0 μm. In one embodiment, the specific surface area may be 0.40 to 0.55 m². 2 / g. In one embodiment, the positive electrode active material may be a single particle. In one embodiment, the nickel content may be 0.85 moles or more, based on 1 mole of the total amount of nickel, manganese, and doping elements.

[0017] Beneficial effects According to an embodiment of the present invention, the lithium secondary battery cathode material includes a cathode active material and has excellent particle uniformity. The average roughness (Ra) of the cathode material surface is less than 1.0 μm, thereby providing a cathode material capable of producing batteries with excellent electrochemical characteristics and high energy density. Attached Figure Description

[0018] Figures 1 to 6 These are SEM images of the calcined products prepared according to the preparation example.

[0019] Figure 7 and Figure 8 These are SEM images of the positive electrode active materials for lithium secondary batteries prepared according to the examples and comparative examples.

[0020] Figure 9 This is a graph showing the particle size of the positive electrode active material for lithium secondary batteries prepared according to the examples and comparative examples.

[0021] Figures 10a to 10d The first roughness is shown as the electrode surface roughness obtained by random measurement of a 40 μm × 40 μm range of the electrode of the embodiment using AFM (atomic force microscopy). Figures 10e to 10h The first roughness is shown as the electrode surface roughness obtained by AFM (atomic force microscopy) measurement over a random 40 μm × 40 μm range on the electrode of the comparative example.

[0022] Figure 11a and Figure 11b , Figure 11c and Figure 11d , Figure 11e and Figure 11f , Figure 11g and Figure 11h , Figure 11i and Figure 11j , Figure 11k and Figure 11l , Figure 11m and Figure 11n as well as Figure 11o and Figure 11pThe roughness of a single particle on the electrode surface, i.e., the second roughness, is shown by AFM (atomic force microscopy) measured on lines 1 to 4 according to the embodiment and lines 1 to 4 of the comparative example, respectively. Detailed Implementation

[0023] The terms first, second, and third are used to describe various parts, components, regions, layers, and / or segments, but are not limited thereto. These terms are used only to distinguish a particular part, component, region, layer, or segment from other parts, components, regions, layers, or segments. Therefore, without departing from the scope of this invention, the first part, component, region, layer, or segment described below may be referred to as the second part, component, region, layer, or segment.

[0024] The technical terms used herein are for reference only to specific embodiments and are not intended to limit the invention. The singular forms used herein also include the plural forms unless the opposite is expressly stated herein. The word "comprising" as used in the specification means to embody specific features, regions, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other features, regions, integers, steps, actions, elements, and / or components.

[0025] When describing one part as "above" or "on top of" another part, it can be directly on top of or on the other part, or there can be other parts in between. Conversely, when describing one part as "directly above" another part, there are no other parts in between.

[0026] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms as defined in commonly used dictionaries are further interpreted as having meanings consistent with relevant technical literature and the present disclosure, and are not to be construed as having idealized or highly formal meanings unless otherwise defined.

[0027] Embodiments of the present invention will be described in detail below. However, the following embodiments are merely illustrative, and the present invention is not limited to these embodiments; rather, it is defined only by the scope of the claims.

[0028] According to an embodiment of the present invention, the positive electrode material of a lithium secondary battery may include a positive electrode active material, wherein the positive electrode active material comprises lithium metal oxide particles containing lithium, nickel, cobalt, and manganese. Specifically, the positive electrode material of the lithium secondary battery may include a positive electrode active material containing lithium metal oxide particles.

[0029] In one embodiment, for a lithium secondary battery cathode material, the surface roughness of a randomly selected 40μm × 40μm area on the electrode, i.e., the first roughness, can have the following characteristics. Specifically, the first roughness can be an index used to characterize the uniform filling state of the cathode active material in the electrode.

[0030] In one embodiment, in the first roughness, the average roughness (Ra) of the electrode surface may be less than 1.0 μm. Specifically, Ra represents the area between the actual surface and the centerline, i.e., the sum of the absolute values ​​of the heights of the surface profiles within the measurement interval. Ra may be less than 1.0 μm, specifically from 0.3 to 0.9 μm, more specifically from 0.4 to 0.8 μm.

[0031] In one embodiment, in the first roughness, the height difference (Rpv: peak-to-valley ratio) between the highest and lowest points on the electrode surface can be less than 9.0 μm. Specifically, Rpv represents the difference between the Max (μm) and Min (μm) values, where Max (μm) represents the highest measured value and Min (μm) represents the lowest measured value. The Rpv can be less than 9.0 μm, specifically from 2.0 to 8.0 μm, more specifically from 3.0 to 7.0 μm.

[0032] In one embodiment, in the first roughness, the root-mean-square roughness (Rq) of the electrode surface may be less than 1.20 μm. The root-mean-square roughness refers to the square root of the sum of all squared height values ​​divided by the line length. The root-mean-square roughness may be less than 1.20 μm, specifically from 0.5 to 1.10 μm, more specifically from 0.7 to 1.00 μm.

[0033] In the first roughness setting, exceeding the upper limit of the aforementioned roughness index range indicates reduced particle uniformity, leading to decreased electrode loading and additive density, as well as the induction of voids. This can potentially cause electrochemical degradation and reduced energy density during battery fabrication. Conversely, exceeding the lower limit of the aforementioned roughness index range indicates reduced particle growth, resulting in smaller particle sizes or more microparticles. Furthermore, increased NMP absorption during electrode fabrication leads to reduced solids content, problems in slurry preparation, and decreased additive density, resulting in electrochemical degradation and reduced energy density.

[0034] In one embodiment, the second roughness may have the following characteristics: the second roughness refers to the surface roughness of the positive electrode material relative to the particle surface of an active material in the electrode state. Specifically, the second roughness refers to the surface roughness of the active material relative to the particle surface in the electrode state, and refers to the roughness measured within a range excluding other particles.

[0035] In one embodiment, in the second roughness, the average roughness (Ra) of the cathode material surface may be less than 0.20 μm. The Ra may be less than 0.20 μm, specifically less than 0.18 μm, and more specifically less than 0.16 μm.

[0036] In one embodiment, in the second roughness, the height difference (Rpv: peak-to-valley ratio) between the highest and lowest points on the surface of the cathode material can be less than 0.8 μm. The Rpv can be less than 0.80 μm, specifically less than 0.70 μm, and more specifically less than 0.60 μm.

[0037] In one embodiment, in the second roughness, the root-mean-square roughness (Rq) of the cathode material surface can be below 0.25 μm. Specifically, Rq can be below 0.25 μm, more specifically, below 0.2 μm, and even more specifically, below 0.18 μm.

[0038] In the second roughness, if the roughness index meets the aforementioned range, it can be determined that the growth and uniformity of the particles are excellent. Therefore, the filling degree is high and the surface roughness is low when preparing the electrode, resulting in high loading and agent density when preparing the battery, which has the advantage of being able to prepare high energy density batteries.

[0039] According to one embodiment of the present invention, the positive electrode active material of a lithium secondary battery may comprise lithium metal oxide particles. Specifically, the positive electrode active material of a lithium secondary battery may comprise metal oxides such as lithium, nickel, cobalt, and manganese.

[0040] In one embodiment, the positive electrode active material of a lithium secondary battery can have a layered crystal structure. Specifically, the crystal structure of the lithium metal oxide can contain a lithium layer.

[0041] In one embodiment, the cation mixing ratio of nickel cations in the lithium layer within the crystal structure of the lithium metal oxide can be from 1.0% to 1.8%, specifically from 1.2% to 1.6%.

[0042] For lithium-ion battery cathode active materials, by ensuring the nickel cation mixing ratio in the lithium layer meets the aforementioned range, the phenomenon of lithium layer collapse leading to reduced lifetime characteristics can be suppressed. Furthermore, the following phenomenon can be suppressed: the irreversible sites in the bulk portion of the lithium-ion battery cathode active material increase in size, leading to a decrease in lithium-ion mobility, thereby causing a decline in resistance and output characteristics.

[0043] In one embodiment, the positive electrode active material of a lithium secondary battery can be in the form of a single particle. The term "single particle" is used to distinguish it from the secondary particle form of positive electrode active material particles, which are formed by the aggregation of dozens to hundreds of primary particles as commonly used in the past. It can be the concept of a single particle consisting of one primary particle and an aggregate of particles with fewer than 30 primary particles.

[0044] The primary particle refers to the smallest unit of particle that can be classified as a block when the cross-section of the positive electrode active material is observed using a scanning electron microscope (SEM). It can consist of a single grain or multiple grains. Here, a grain refers to the region within a primary particle where atoms form a lattice structure with a specific orientation, thus distinguishing it from other particles. Furthermore, secondary particles refer to aggregates of dozens to hundreds of primary particles that are bound together through physical or chemical bonding without deliberate agglomeration or granulation processes; these are secondary structures.

[0045] In one embodiment, the positive electrode active material of a lithium secondary battery may contain doping elements. For example, the doping elements may include at least one of zirconium (Zr) and yttrium (Y).

[0046] As a dopant element, the presence of zirconium suppresses the diffusion of Ni²⁺ to Li⁺ sites, preventing deformation from the layered structure to a spinel structure, thereby reducing cation mixing and improving structural stability. Furthermore, it has the advantage of improving charge / discharge capacity and thermal stability by reducing the concentration of Ni⁺ ions.

[0047] The zirconium doping amount in the lithium metal oxide particles can be 1,000 to 4,000 ppm, preferably 1,500 to 3,500 ppm, and more preferably 2,000 to 3,000 ppm.

[0048] If the zirconium is included within the specified range, the contraction of the lithium-ion pathway can be mitigated during battery charging and discharging, thereby stabilizing the layered structure. Accordingly, the cation mixing ratio can be reduced, ultimately improving resistivity and lifetime characteristics.

[0049] When the yttrium is contained as the doping element, the structure is stabilized during the discharge process of the lithium secondary battery, thereby alleviating the voltage hysteresis phenomenon, and ultimately having the advantage of improving the life characteristics.

[0050] The doping amount of yttrium in the lithium metal oxide particles may be 500 to 2000 ppm, preferably 700 to 1800 ppm, and more preferably 1000 to 1500 ppm. If yttrium is included within this range, grain growth is promoted, thereby effectively increasing the grain size within a single particle and the average particle size of the single particle.

[0051] In one embodiment, the doping element may further include one or more selected from the group consisting of B, Al, Mg, Ti, Nb, W, Sc, Si, V, Fe, Mo, Ce, Hf, Ta, La, and Sr, but is not limited thereto.

[0052] In one embodiment, the positive electrode active material of the lithium secondary battery may satisfy the following Chemical Formula 1.

[0053] [Chemical Formula 1] Li a [Ni x Co y Mn z M w O2 In Chemical Formula 1, M is at least one of Zr and Y, 0.8 ≤ a ≤ 1.3, 0.8 ≤ x < 1, 0 < y < 0.08, 0 < z < 0.08, 0 < w ≤ 0.04, and x + y + z + w = 1. Specifically, it may be 0.001 ≤ w ≤ 0.01, and more specifically, it may be 0.002 ≤ w ≤ 0.008.

[0054] In one embodiment, for the positive electrode active material of the lithium secondary battery, based on 1 mole of the total of the nickel, cobalt, manganese, and doping element, the nickel content may be 0.85 mole or more. Specifically, the nickel content may be 0.90 mole or more.

[0055] According to the positive electrode active material of the lithium secondary battery of the present invention, by including the aforementioned nickel content, a high-nickel positive electrode active material can be achieved. Specifically, the positive electrode active material of the lithium secondary battery may be a high-nickel positive electrode active material containing nickel and manganese.

[0056] In one embodiment, the average particle size (D50) of the positive electrode active material for a lithium-ion battery can be 3.0 to 5.0 μm. Specifically, it can be 3.5 to 4.5 μm. The average particle size (D50) refers to the particle size corresponding to 50% of the volumetric cumulative amount in the particle size distribution curve. The average particle size (D50) can be measured, for example, using laser diffraction.

[0057] In one embodiment, the specific surface area of ​​the positive electrode active material for a lithium secondary battery can be from 0.40 to 0.55 m². 2 / g. Specifically, it can be 0.42 to 0.53m. 2 / g. The specific surface area is the BET specific surface area, which can be measured using the BET method (specific surface area and porosity analyzer) (Micromeritics, ASAP2020).

[0058] By ensuring the specific surface area meets the aforementioned range, the degradation of lifespan characteristics can be suppressed as the particle strength of the positive electrode active material in lithium-ion batteries increases. Conversely, if the specific surface area exceeds the aforementioned range, the electrochemical properties of the positive electrode active material will deteriorate.

[0059] In one embodiment, for the positive electrode active material of a lithium secondary battery, the residual lithium content, based on 100 wt% of the total positive electrode active material, can be less than 0.80 wt%. Specifically, the residual lithium content can be less than 0.50 wt%, more specifically less than 0.45 wt%, and even more specifically less than 0.4 wt%. The residual lithium content can be measured using an automatic titrator.

[0060] By ensuring the residual lithium content meets the aforementioned range, a lithium-ion battery cathode active material with excellent electrochemical properties can be provided. If the residual lithium content exceeds the aforementioned range, the electrochemical properties of the lithium-ion battery cathode active material will deteriorate.

[0061] In one embodiment, the positive electrode active material of a lithium secondary battery can satisfy the following formula 1.

[0062] <Formula 1> AB≤1.30 In Formula 1, when a 3g positive electrode active material sample is placed in a mold with a diameter of 1.3cm and pressurized under a pressure of 9 tons, A represents the sum of micro powder values ​​below 1μm after pressurization, and B represents the sum of micro powder values ​​below 1μm before pressurization.

[0063] Formula 1 can be an indicator representing the increase in micronized active material powder. Formula 1 can be from 0.80 to 1.30, specifically from 0.85 to 1.20, more specifically from 0.90 to 1.10, and even more specifically from 0.95 to 1.05. By satisfying Formula 1, there is an advantage in improving the single-particle density of the positive electrode active material in lithium-ion batteries. When Formula 1 exceeds the aforementioned range, there is a problem of decreased single-particle density of the active material leading to an increase in micronized powder.

[0064] In one embodiment, when a 3g sample of positive electrode active material is placed in a mold with a diameter of 1.3cm and pressurized under a pressure of 9 tons, the sum of the microparticle values ​​A below 1μm after pressurization can be 1.20 to 2.50. Specifically, the value of A can be 1.40 to 1.90, more specifically 1.50 to 1.80.

[0065] In one embodiment, when a 3g sample of positive electrode active material is placed in a mold with a diameter of 1.3cm and pressurized under a pressure of 9 tons, the sum of the microparticle values ​​B below 1μm before pressurization can be 0.5 to 0.9. Specifically, the B value can be 0.6 to 0.8, more specifically 0.65 to 0.75.

[0066] The A and B values ​​can be characteristics of the positive electrode active material, which is obtained in the preparation method of positive electrode active material for lithium secondary batteries through the following steps: a primary calcination temperature in the range of 840 to 860°C, followed by a secondary calcination through a depolymerization process. When the A and B values ​​exceed the aforementioned range, there is a problem of decreased single-particle density of the active material leading to an increase in microparticles.

[0067] In one embodiment, the positive electrode active material of a lithium secondary battery may include LiOH and Li2CO3. Accordingly, the positive electrode active material of a lithium secondary battery may include a predetermined amount of residual lithium.

[0068] A method for preparing a lithium-ion battery cathode active material according to another embodiment of the present invention may include: forming a mixture comprising a metal hydroxide precursor and a lithium raw material; calcining the mixture once to obtain a calcined product; depolymerizing the calcined product to obtain a metal oxide; and calcining the metal oxide a second time to obtain lithium metal oxide particles. In the method for preparing the lithium-ion battery cathode active material of the present invention, after the first calcination, the secondary particles formed by the agglomeration of the primary particles are depolymerized, and then single particles are grown in the second calcination. This method has the following advantages compared to conventional single-particle preparation methods: it simplifies the process, and because there is less residual lithium, no additional heat treatment process is required.

[0069] For the preparation method of positive electrode active material for lithium secondary batteries, the step of forming a mixture comprising a metal hydroxide precursor and lithium raw material can be a step of mixing the raw material before the calcination step.

[0070] In one embodiment, the metal hydroxide precursor may be a plate-like precursor. The plate-like precursor is defined as a primary particle having two relatively flat surfaces, referring to a precursor that comprises a complete plate-like shape as well as flake-like shapes similar to plates.

[0071] In one embodiment, the metal hydroxide precursor may contain one or more elements selected from the group consisting of Ni, Co, and Mn. Specifically, the metal hydroxide precursor may be purchased directly or prepared directly using conventional methods in the art.

[0072] For example, the metal hydroxide precursor may be prepared by co-precipitation reaction of adding a complexing agent solution and a pH adjusting agent solution to a metal-containing solution containing nickel, manganese or cobalt raw materials. However, it is not limited to this.

[0073] There are no particular limitations on the nickel raw material used in the preparation of precursors for positive electrode active materials. For example, the nickel raw material can be a nickel-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or hydroxyoxide, specifically NiSO4, NiSO4•6H2O, Ni(OH)2, NiO, NiOOH, NiCO3•2Ni(OH)2•4H2O, NiC2O2•2H2O, Ni(NO3)2•6H2O, nickel salts of fatty acids, nickel halides, or combinations thereof, but is not limited thereto.

[0074] There are no particular limitations on the cobalt raw material, as long as it is used in the preparation of precursors for positive electrode active materials in this art. For example, the cobalt raw material can be a cobalt-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or hydroxyoxide, etc. Specifically, it can be CoSO4, CoSO4•7H2O, Co(OH)2, CoOOH, Co(OCOCH3)2•4H2O, Co(NO3)2•6H2O, or combinations thereof, but is not limited thereto.

[0075] There are no particular limitations on the manganese raw material used in the preparation of precursors for positive electrode active materials. For example, the manganese raw material can be a manganese-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, hydroxy oxide, or a combination thereof. Specifically, it can be manganese salts such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylate, manganese citrate and fatty acid manganese salts, manganese oxides such as Mn2O3, MnO2 and Mn3O4, hydroxy oxides, manganese chloride, or a combination thereof, but is not limited thereto.

[0076] The metal-containing solution may be prepared by adding nickel, manganese, or cobalt raw materials to a solvent, specifically water or a mixture of water and an organic solvent (e.g., ethanol) that can be uniformly mixed with water.

[0077] The complexing agent-containing solution serves to form a complex. The complexing agent may include, for example, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or combinations thereof, but is not limited thereto. Alternatively, the complexing agent-containing solution may be used in the form of an aqueous solution, in which case water, or a mixture of water and an organic solvent (e.g., ethanol) that is homogeneous with water, may be used as the solvent.

[0078] The pH-adjusting solution acts as a precipitant or pH adjuster and may contain basic compounds such as hydroxides of alkali metals or alkaline earth metals, hydrates of these metals, or combinations thereof, such as NaOH, KOH, or Ca(OH)₂. Alternatively, the pH-adjusting solution may also be used in aqueous solution form, in which case water, or a mixture of water and an organic solvent (e.g., ethanol) that is homogeneous with water, can be used as the solvent. In this case, the pH-adjusting solution can be added to the reaction solution to achieve a pH of 10 to 13.

[0079] The coprecipitation reaction can be carried out under an inert atmosphere such as nitrogen or argon, at a temperature of 30 to 70°C, and at a pH of 10 to 13.

[0080] Nickel (or manganese-cobalt) hydroxide particles are generated through the aforementioned process and precipitated in the reaction solution. The precipitated precursor particles are then separated, washed, and dried using conventional methods to obtain the precursor.

[0081] At this point, the molar ratio of nickel, cobalt, or manganese in the precursor can be adjusted by regulating the concentration of the nickel, cobalt, or manganese raw materials. In other words, the concentrations of the nickel, cobalt, and manganese raw materials can be adjusted so that the molar ratio of nickel, cobalt, or manganese in the final lithium metal oxide product is within the range specified according to the invention.

[0082] The lithium raw material can be any lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or hydroxyl oxide, as long as it is soluble in water, there are no particular restrictions. Specifically, the lithium raw material can be Li₂CO₃, LiNO₃, LiNO₂, LiOH, LiOH•H₂O, LiH, LiF, LiCl, LiBr, LiI, CH₃COOLi, Li₂O, Li₂SO₄, CH₃COOLi, Li₃C₆H₅O₇ or a combination thereof, but is not limited thereto.

[0083] The lithium raw material can be added to achieve a total metal (Li / Me) molar ratio of lithium to the metal hydroxide precursor and dopant elements of 1.02 to 1.08, preferably 1.02 to 1.05.

[0084] While it is undesirable to be limited by theory, some lithium raw material may be lost during the oxidation process. When the amount of lithium raw material added meets the aforementioned range, a lithium secondary battery positive electrode active material with the target composition can be obtained, which is therefore preferred.

[0085] In one embodiment, during the step of forming the mixture, the mixture may contain a dopant element. The dopant element may contain at least one selected from the group consisting of zirconium and yttrium.

[0086] In one embodiment, in addition to zirconium and yttrium, the doping element may further include one or more elements selected from the group consisting of B, Al, Mg, Ti, Nb, W, Sc, Si, V, Fe, Mo, Ce, Hf, Ta, La, and Sr, but is not limited thereto. A detailed description of the doping element can be found in the foregoing section on lithium-ion secondary battery cathode active materials.

[0087] The step of calcining the mixture once to obtain the calcined product can be carried out at 830 to 870°C. Specifically, the first calcination step can be carried out at 840 to 860°C.

[0088] When the calcination is carried out within the specified temperature range, the formation of overgrown particles or unagrown particles can be suppressed, and the cation mixing ratio of nickel cations in the lithium layer within the crystal structure of the lithium metal oxide particles can be easily controlled.

[0089] If the initial calcination temperature exceeds the upper limit of the aforementioned range, there is a problem of excessive particle growth, making proper crushing and deagglomeration impossible. If the initial calcination temperature exceeds the lower limit of the aforementioned range, there is a problem of insufficient particle growth, making proper crushing and deagglomeration impossible.

[0090] In one embodiment, the calcination can last for 2 to 6 hours. Specifically, the calcination can last for 3 to 5 hours.

[0091] With the calcination performed within the aforementioned time range, positive electrode active materials with grain sizes suitable for crushing and deagglomeration can be easily obtained. If the time exceeds the upper limit of the aforementioned range, there is a problem of over-growth of particles, making proper crushing and deagglomeration impossible. If the time exceeds the lower limit of the aforementioned range, there is a problem of insufficient particle growth, making proper crushing and deagglomeration impossible.

[0092] In one embodiment, in the step of obtaining the calcined product by a single calcination, the calcined product can satisfy the following formula 2.

[0093] <Formula 2> 1.00≤CD≤5.00 In Formula 2, when a 3g sample of a single calcination product is placed in a mold with a diameter of 1.3cm and pressurized under a pressure of 9 tons, C represents the sum of micro-powder values ​​below 1μm after pressurization, and B represents the sum of micro-powder values ​​below 1μm before pressurization.

[0094] Formula 2 can be an indicator of particle growth during primary calcination. Formula 2 can be from 1.00 to 5.00, specifically from 1.20 to 4.80, and more specifically from 1.50 to 4.50. By satisfying Formula 2, the following advantages are available: it is suitable for pulverization and depolymerization after primary calcination of the positive electrode active material for lithium-ion batteries.

[0095] If Equation 2 exceeds the upper limit of the aforementioned range, there is a problem that the particles do not grow properly and cannot be properly crushed and deagglomerated. If Equation 2 exceeds the lower limit of the aforementioned range, there is a problem that the particles grow excessively and cannot be properly crushed and deagglomerated.

[0096] In one embodiment, the Li / Ni cation mixing degree of the calcined product obtained in the step of obtaining the calcined product by one calcination can satisfy 1.3 to 2.1%. Specifically, the mixing degree can be 1.4 to 2.1, more specifically 1.5 to 2.0.

[0097] By ensuring the mixing degree of the primary calcination product meets the aforementioned range, it has the advantage of reducing lithium layer collapse and thus minimizing battery life characteristics. Furthermore, meeting the aforementioned mixing degree suppresses the phenomenon of decreased lithium-ion mobility, which leads to deterioration of resistance and output characteristics, making it a preferred option.

[0098] The step of depolymerizing the calcined product to obtain the metal oxide can be a step of pulverizing and depolymerizing the calcined product using an air jet mill at a pressure of 2.0 to 5.0 bar to obtain the metal oxide. Specifically, the pressure can be [insert pressure here].

[0099] When the pulverization and depolymerization are carried out under pressure within the specified range, the single-particle positive electrode active material grown by the secondary calcination described later has an appropriate particle size, which can impart excellent lifespan characteristics when applied to lithium secondary batteries.

[0100] Compared to equipment such as rotor mills, ball mills, pin mills, bead mills, and roller mills, the air jet mill described above can pulverize a variety of materials, offering the advantages of pollution-free dry pulverization and deagglomeration. In particular, it allows for various particle size adjustments, ensuring consistent particle size during repeated production and facilitating quality management.

[0101] Before the step of pulverizing and depolymerizing the calcined product using an air jet mill at a pressure of 2.0 to 5.0 bar to obtain metal oxides, the process may include a step of depolymerization using equipment such as a rotor mill, ball mill, pin mill, bead mill, roller mill, etc., but is not limited thereto.

[0102] The depolymerization step using equipment such as rotor mills, ball mills, pin mills, bead mills, and roller mills can be appropriately set under depolymerization conditions without compromising the purpose of this invention, and this invention does not impose any particular restrictions on this.

[0103] Depolymerization is usually carried out after calcination, but according to the preparation method of the positive electrode active material of lithium secondary battery of the present invention, depolymerization is carried out between the first calcination and the second calcination, specifically, it involves the steps of crushing and depolymerization.

[0104] In one embodiment, the pulverization and depolymerization can be performed by cooling the calcined product to 50 to 200°C, specifically to 50 to 100°C. Cooling to this temperature can be done at room temperature. Cooling to this temperature can suppress the reaction between external moisture and the calcined product, and can also suppress the increase of residual lithium.

[0105] The step of secondary calcination of the metal oxide to obtain lithium metal oxide particles can be carried out at a temperature of 750 to 830°C. Specifically, the secondary calcination can be carried out at a temperature of 760 to 820°C, and more specifically, at a temperature of 770 to 810°C. When the secondary calcination is carried out within the calcination temperature range, the crystal structure of the obtained lithium metal oxide particles tends to be stable.

[0106] Specifically, the lithium byproducts remaining on the surface of the lithium metal oxide particles decompose upon heating and diffuse into the interior of the lithium metal oxide particles, thereby reducing the amount of lithium remaining on the surface. The lithium ions react with the surface of the lithium metal oxide particles to form a stable layered structure, which makes the surface structure of the lithium metal oxide particles more stable. Therefore, it has the advantage of improving the side reactions with the electrolyte and the resistance and lifespan characteristics.

[0107] The secondary calcination can be carried out for 8 to 12 hours, but is not limited to this. When the secondary calcination is carried out within the specified time range, the lithium byproducts remaining on the surface of the lithium metal oxide particles are thermally decomposed and fully diffuse into the interior of the lithium metal oxide particles, which is therefore preferred.

[0108] In one embodiment, based on 100wt% of the total positive electrode active material, the LiOH content may be less than 0.40wt%. Specifically, the LiOH content may be less than 0.35wt%.

[0109] The lithium metal oxide particles after the secondary calcination can further undergo a depolymerization step, but are not limited to this. Depolymerization can be carried out using equipment such as rotor mills, ball mills, pin mills, bead mills, and roller mills, as long as the depolymerization conditions do not impair the purpose of this invention.

[0110] As described above, the lithium secondary battery positive electrode active material prepared according to the preparation method of lithium secondary battery positive electrode active material has the following significant advantages: due to the low residual lithium, it does not need to undergo additional heat treatment process, and it does not need to undergo additional water washing and drying process.

[0111] According to another embodiment of the present invention, a lithium secondary battery is provided, comprising: a positive electrode comprising the aforementioned positive electrode active material; a negative electrode; and a non-aqueous electrolyte.

[0112] The negative electrode includes a current collector and a positive electrode active material layer located on the current collector. The positive electrode active material layer includes a positive electrode active material, which may include a lithium secondary battery positive electrode active material according to one of the foregoing embodiments. In the positive electrode active material layer, the content of the positive electrode active material relative to the total weight of the positive electrode active material layer may be from 90% to 99% by weight.

[0113] The positive electrode active material layer may further include a binder and / or a conductive material. In this case, the content of the binder and the conductive material may be from 1% to 5% by weight, respectively, relative to the total weight of the positive electrode active material layer.

[0114] The binder functions to enable the positive electrode active material particles to adhere well to each other and to adhere well to the current collector. As representative examples of the binder, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc. can be used, but are not limited thereto.

[0115] The conductive material is used to impart conductivity to the electrode. In the battery constituted, any substance can be used as long as it is an electron conductive material that does not cause a chemical change. As examples of the conductive material, carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc. can be cited; metal-based materials such as metal powders or metal fibers of copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or conductive materials containing mixtures thereof.

[0116] As the positive electrode current collector, aluminum foil, nickel foil, or a combination thereof can be used, but is not limited thereto.

[0117] The negative electrode includes a current collector and a negative electrode active material layer formed on the current collector, and the negative electrode active material layer includes a negative electrode active material.

[0118] As the negative electrode active material, a substance into which lithium ions can be reversibly intercalated / deintercalated, lithium metal, a lithium metal alloy, a substance into which lithium can be doped and dedoped, or a transition metal oxide is included.

[0119] For the substance into which lithium ions can be reversibly intercalated / deintercalated, as a carbon material, any carbon-based negative electrode active material commonly used in a lithium ion secondary battery can be used, and representative examples thereof can include crystalline carbon, amorphous carbon, or a mixture thereof.

[0120] As the alloy of the lithium metal, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0121] As the substance into which lithium can be doped and dedoped, Si, SiOx (0 < x < 2), Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof and is not Si), Sn, SnO2, Sn-Y (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof and is not Sn), etc. can be cited.

[0122] Examples of transition metal oxides include vanadium oxide and lithium vanadium oxide. The negative electrode active material layer also includes a binder and may optionally further include a conductive material.

[0123] The binder serves to ensure that the negative electrode active material particles adhere well to each other and that the negative electrode active material adheres well to the current collector.

[0124] The conductive material is used to impart conductivity to the electrodes. In the constructed battery, any substance can be used as long as it is an electronically conductive material that does not cause chemical changes.

[0125] As the current collector, one selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, and combinations thereof can be used.

[0126] For the negative and positive electrodes, an active material composition is prepared by mixing an active material, a conductive material, and a binder in a solvent, and then coating this composition onto a current collector. Since such electrode preparation methods are well known in the art, detailed descriptions are omitted here. N-methylpyrrolidone and the like can be used as the solvent, but are not limited to these.

[0127] The electrolyte contains a non-aqueous organic solvent and a lithium salt.

[0128] The non-aqueous organic solvent acts as a medium that allows ions participating in the battery's electrochemical reactions to move.

[0129] The lithium salt is dissolved in an organic solvent and acts as a source of lithium ions within the battery, enabling the basic lithium secondary battery to operate and promoting the movement of lithium ions between the positive and negative electrodes.

[0130] Depending on the type of lithium-ion secondary battery, a separator can also be present between the positive and negative electrodes. Such a separator can be made of polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof. Hybrid multilayer films such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polypropylene three-layer separators, and polypropylene / polypropylene / polypropylene three-layer separators can also be used.

[0131] Based on the type of separator and electrolyte used, lithium secondary batteries can be classified into lithium-ion batteries, lithium-ion polymer batteries, and lithium polymer batteries. Based on shape, they can be classified into cylindrical, prismatic, button, and pouch types, etc. Based on size, they can be classified into bulk and thin-film types. Since the structure and manufacturing methods of these batteries are well-known in this field, detailed descriptions are omitted.

[0132] Preferred embodiments and comparative examples of the present invention are described below. However, the following embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to the following embodiments.

[0133] Experimental Example <Comparative Example 1> 1. Preparation of precursors The precursors for the positive electrode active material were prepared by a conventional co-precipitation method. The nickel raw material was NiSO4•6H2O, the cobalt raw material was CoSO4•7H2O, and the manganese raw material was MnSO4•H2O. These raw materials were dissolved in distilled water to prepare an aqueous solution of the metal salt.

[0134] After preparing the coprecipitation reactor, N2 was introduced for purging to prevent oxidation of metal ions during the coprecipitation reaction. The reactor temperature was maintained at 50℃. NH4(OH) was added to the coprecipitation reactor as a chelating agent, and NaOH was used to adjust the pH. The precipitate obtained according to the coprecipitation process was filtered, washed with distilled water, and dried in a filter cake dryer at 180℃ to prepare the precursor of the positive electrode active material.

[0135] The precursor prepared has the following composition: (Ni 0.90 Co 0.05 Mn 0.05 (OH)2, the primary particles are plate-shaped.

[0136] 2. Preparation of positive electrode active materials Preparation of positive electrode active material for lithium secondary batteries: one-time calcination <Preparation Example 1-1> 79.07 g of LiOH•H2O and ZrO2 and Y2O3 as doping raw materials were weighed and added to 170.93 g of the positive electrode active material precursor prepared in step 1. The mixture was then uniformly mixed using a mixer and calcined in a box furnace under an O2 atmosphere.

[0137] At this point, the molar ratio (Li / Me) of lithium added to the lithium metal precursor reaches 1.02, the Zr doping amount of ZrO2 added to the lithium metal oxide particles reaches 2500ppm, and the Y doping amount of Y2O3 added to the lithium metal oxide particles reaches 1200ppm.

[0138] Subsequently, the product was prepared by calcining at 900℃ for 4 hours.

[0139] <Preparation Examples 1-2> Except for the first calcination temperature of 880°C, the positive electrode active material precursor and the first calcination product were prepared using the same method as in Comparative Example 1.

[0140] <Preparation Examples 1-3> Except for the first calcination temperature of 860°C, the positive electrode active material precursor and the first calcination product were prepared using the same method as in Comparative Example 1.

[0141] <Preparation Examples 1-4> Except for the first calcination temperature of 840°C, the positive electrode active material precursor and the first calcination product were prepared using the same method as in Comparative Example 1.

[0142] <Preparation Examples 1-5> Except for the first calcination temperature of 820°C, the positive electrode active material precursor and the first calcination product were prepared using the same method as in Comparative Example 1.

[0143] <Preparation Examples 1-6> Except for the first calcination temperature of 800°C, the positive electrode active material precursor and the first calcination product were prepared using the same method as in Comparative Example 1.

[0144] Table 1 below shows the average particle size (D50), specific surface area (BET), Li / Ni (%), and micron powder values ​​below 1 μm before and after 9-ton pressing of the first calcination product. The average particle size (D50), specific surface area (BET), Li / Ni (%), and micron powder values ​​below 1 μm before and after 9-ton pressing were measured using the following method.

[0145] Average particle size (D50): The average particle size (D50) was measured using a Microtrac (S3000) instrument employing the laser diffraction method. The volume-based average particle size (Dv50) can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve.

[0146] BET specific surface area: The BET specific surface area was measured using the Brunauer-Emmett-Teller Analysis method based on nitrogen adsorption. By using the BET formula to adsorb and desorb nitrogen on the surface of a solid sample, and measuring the amount of adsorption at each partial pressure, the specific surface area of ​​the material was determined.

[0147] Li / Ni cation mixing ratio: The cation mixing ratio of nickel cations in the lithium layer within the crystal structure of the obtained calcined metal oxide was measured by XRD. Specifically, the raw data measured by XRD was applied to the details for Rietveld refinement, and calculations were performed using the calculated Ni1(3b) occupancy value.

[0148] 9-ton press: A 3g sample is placed in a mold with a diameter of 1.3cm and pressed under a pressure of 9 tons. The particle size of the sample before and after pressing is analyzed by a Malvern (MS3000) instrument using the laser diffraction method, and the sum of the proportions smaller than 1μm is calculated.

[0149] Table 1

[0150] The results observed using SEM are shown below Figures 1 to 6 (See also) Figures 1 to 6 As shown in Table 1 above, when the primary calcination step was carried out at temperatures of 840 and 860 °C as described in Preparation Examples 1-3 and 1-4, single particles exhibiting a Li / Ni mixing degree of 1.5 to 2.0% were generated, and primary calcination products with an average particle size (D50) that was neither too large nor too small were obtained.

[0151] On the other hand, for Preparation Examples 1-1 and 1-2, where the primary calcination temperature was too high (above 860°C), there was a problem of generating overgrown particles. For Preparation Examples 1-5 and 1-6, where the primary calcination temperature was too low (below 840°C), there was a problem of generating ungrown particles.

[0152] Preparation of positive electrode active materials for lithium secondary batteries: pulverization and depolymerization <Preparation Example 2-1> Subsequently, the calcined products prepared according to Preparation Examples 1-4 were cooled to 80°C at room temperature and then pulverized and depolymerized using an air jet mill at 3.0 Bar.

[0153] <Preparation Example 2-2> Subsequently, the calcined products prepared according to Preparation Examples 1-4 were cooled to 80°C at room temperature and then pulverized and depolymerized using an air jet mill at 3.5 Bar.

[0154] <Preparation Examples 2-3> Subsequently, the calcined products prepared according to Preparation Examples 1-4 were cooled to 80°C at room temperature and then pulverized and depolymerized using an air jet mill at 4.0 Bar.

[0155] Table 2 below shows the average particle size (D50) and specific surface area (BET) of the depolymers when the airflow mill conditions were controlled according to Preparation Examples 2-1 to 2-3.

[0156] Table 2

[0157] Referring to Table 2 above, when the air jet mill is operated in a range above 4.0 Bar, the average particle size of the depolymer is controlled between 2.5 and 3.0 μm, and the specific surface area is high, promoting particle growth during secondary calcination. On the other hand, as shown in Preparation Examples 2-1 and 2-2, when the air jet mill is operated in a range below 4.0 Bar, the average particle size and specific surface area of ​​the depolymer exceed the scope of the present invention.

[0158] Preparation of positive electrode active materials for lithium secondary batteries: Examples The metal oxides prepared according to Preparation Examples 2-3 were calcined a second time at a calcination temperature of 770°C for 9 hours to prepare lithium secondary battery positive electrode active materials according to Examples 1 to 3.

[0159] Preparation of positive electrode active materials for lithium secondary batteries: Comparative example The plate-shaped metal hydroxide precursor prepared according to the preparation example, LiOH•H2O, and ZrO2 and Y2O3 as dopants are placed in a mixer and mechanically mixed to form a mixture. The method of adding LiOH•H2O, ZrO2, and Y2O3 is the same as in the first calcination step described above.

[0160] Specifically, the single calcination process lasted 13 hours, including 4 hours at 840°C and 9 hours at 770°C. After cooling to 50°C at room temperature, the material was then pulverized and depolymerized using an air jet mill at a pressure of 3.0 bar to obtain the positive electrode active material for lithium secondary batteries.

[0161] Preparation of lithium secondary batteries To understand the electrochemical properties of the positive electrode active materials for lithium secondary batteries prepared according to the examples and comparative examples, lithium secondary batteries were prepared using them.

[0162] The positive electrode active material was prepared by mixing a slurry with a conductive material (carbon black, Super C) and a binder (polyvinylidene fluoride, KF1120) in a ratio of 96.5:1.5:2wt%. NMP (N-methyl-2-pyrrolidone) was added, and the viscosity was adjusted to achieve a solids content of approximately 70%. The prepared slurry was coated onto a 20 μm thick aluminum foil using a doctor blade, followed by drying and pressing. The electrode loading was 16.7 mg / cm³. 2 The compressed density (at 25℃) is 3.5 g / cm³. 3 .

[0163] The electrolyte used was 1M LiPF6 dissolved in EC:DMC:EMC=3:4:3 (vol%), and 3.0wt% VC, 0.5wt% PS and 1.0wt% ESA were added relative to the total weight of the electrolyte. Coin cells were fabricated using a PP separator and a lithium anode (200μm, Welcos).

[0164] <Evaluation Example 1> Table 3 below shows the particle size (volume and number), PD (bulk density), specific surface area (BET), compressive density, and micron powder values ​​below 1 μm before and after 9-ton pressing of the positive electrode active materials of the examples and comparative examples. The average particle size, residual lithium content, and electrochemical characteristics were measured using the methods described below.

[0165] Particle size (Dmin, D50, Dmax): Dmin, D50, and Dmax were measured using a Microtrac (S3000) instrument employing the laser diffraction method. Specifically, based on volume and number, Dmin, D50, and Dmax were defined as the particle sizes corresponding to the minimum, 50%, and maximum values ​​in the particle size distribution curve, according to the cumulative volume (%) and cumulative number (%).

[0166] BET specific surface area: The BET specific surface area was measured using the Brunauer-Emmett-Teller method based on nitrogen adsorption. By using the BET formula to adsorb and desorb nitrogen on the surface of a solid sample, and measuring the amount of adsorption at each partial pressure, the specific surface area of ​​the material was determined.

[0167] Compressive density (PD, Press Density) (g / cc): The compressive density was measured by weighing 10g of the obtained calcined product and pressing it twice with a pressure of 108N.

[0168] 9-ton press: A 3g sample is placed in a mold with a diameter of 1.3cm and pressed under a pressure of 9 tons. The particle size of the sample before and after pressing is analyzed by a Malvern (MS3000) instrument using the laser diffraction method, and the sum of the proportions smaller than 1μm is calculated.

[0169] Table 3

[0170] Furthermore, the results of SEM observation of the positive electrode active materials for lithium secondary batteries prepared according to the examples and comparative examples are shown in the figures. Figure 7and Figure 8 , Figure 9 The particle size distribution of the positive electrode active materials prepared according to the examples and comparative examples is shown.

[0171] Reference Figure 7 , Figure 8 , Figure 9 As shown in Table 3 above, compared with the comparative example, under the same conditions, the examples also exhibit excellent particle growth properties, with fewer aggregated particles and improved particle uniformity. Furthermore, due to the lower proportion of micropowder below 1 μm, the increase in micropowder size and its relative proportion after 9 tons of pressing are also lower, resulting in improved single-particle formation.

[0172] Preparation of positive electrode sheet for lithium secondary batteries To understand the surface roughness characteristics of the positive electrode active materials for lithium secondary batteries prepared according to the examples and comparative examples, positive electrode sheets for lithium secondary batteries were prepared as follows.

[0173] The positive electrode active material was prepared by mixing a slurry with the following components: conductive material (carbon black, Super C): binder (polyvinylidene fluoride, KF1120) = 96.5:1.5:2wt%. NMP (N-methyl-2-pyrrolidone) was added, and the viscosity was adjusted to achieve a solid content of approximately 70%. The prepared slurry was then applied to a 20μm thick aluminum foil using a doctor blade and subsequently dried.

[0174] <Evaluation Example 2-1>: First Roughness Table 4 below shows the first roughness measurement results of the positive electrode active materials of the Examples and Comparative Examples. The first roughness was measured using the following method.

[0175] First roughness (μm): refers to the measured roughness of the electrode surface within a randomly selected range of 40μm × 40μm.

[0176] Specifically, Table 4 below shows the Min(μm), Max(μm), Mid(μm), Mean(μm), Rpv(μm), Rq(μm), Ra(μm) and Rz(μm) of the first roughness, each defined as follows.

[0177] Min(μm): Min(μm) refers to the minimum height, indicating the highest value among the measured values.

[0178] Max(μm): Max(μm) refers to the maximum height, indicating the lowest value among the measured values.

[0179] Mid(μm): refers to the average of Min(μm) and Max(μm).

[0180] Mean(μm): This is the value obtained by summing the heights of all points in the measurement and dividing by the number of points.

[0181] Rpv(μm): refers to the difference between Max(μm) and Min(μm).

[0182] Rq(μm): Rq(μm) refers to the root mean square roughness, which is the square root of the sum of all the squared height values ​​and the result divided by the line length.

[0183] Ra(μm): Ra refers to the average roughness, which represents the area between the actual surface and the centerline, that is, the sum of the absolute values ​​of the height of the surface profile in the measurement interval.

[0184] Rz(μm): Rz refers to the ten-point average roughness, which is the average of the sum of the heights of the five highest peaks and the depths of the five lowest valleys measured over the entire measurement range.

[0185] Table 4

[0186] Figures 10a to 10d The first roughness is shown as the electrode surface roughness obtained by random measurement of a 40 μm × 40 μm range using AFM (atomic force microscopy). Figures 10e to 10h The image shows the electrode surface roughness of a comparative example measured randomly over a 40 μm × 40 μm area using AFM (atomic force microscopy), i.e., the first roughness. (Refer to...) Figures 10a to 10h As shown in Table 4, regarding electrode surface roughness, compared to the comparative example, the surface roughness index value of the embodiment is lower, thus exhibiting excellent particle uniformity, electrode active material filling degree, and density.

[0187] <Evaluation Example 2-2>: Second Roughness Table 5 below shows the measurement results of the second roughness of the positive electrode active materials of the Examples and Comparative Examples. The second roughness was measured using the method described below.

[0188] Second roughness (μm): The roughness of a single particle under electrode conditions was measured.

[0189] Table 5

[0190] Figure 11a and Figure 11b , Figure 11c and Figure 11d , Figure 11e and Figure 11f , Figure 11g and Figure 11h , Figure 11i and Figure 11j , Figure 11k and Figure 11l , Figure 11m and Figure 11n as well as Figure 11o and Figure 11p The roughness of the active material, measured by AFM (atomic force microscopy), is shown for lines 1 to 4 according to the embodiments and lines 1 to 4 of the comparative examples, respectively. Lines 1 to 4 show the roughness of an active material particle of the embodiments and the comparative examples, respectively.

[0191] Reference Figures 11a to 11p As shown in Table 5 above, regarding the particles of the active material (specifically, a single particle in the electrode state), compared with the comparative example, the particle roughness index value of the example is lower, which confirms the growth of the particles and can increase the loading and compound density when preparing the electrode.

[0192] Preparation of lithium secondary batteries To understand the electrochemical properties of the positive electrode active materials for lithium secondary batteries prepared according to the examples and comparative examples, lithium secondary batteries were prepared using them.

[0193] In the lithium secondary battery, the electrode used was the one prepared in Evaluation Example 2, and the electrolyte used was 1M LiPF6 dissolved in EC:DMC:EMC=3:4:3 (vol%), with 3.0wt% VC, 0.5wt% PS, and 1.0wt% ESA added relative to the total weight of the electrolyte; and a coin cell was prepared using a PP separator and a lithium anode (200μm, Welcos).

[0194] (1) Evaluation of initial capacity and initial efficiency After fabricating the lithium secondary battery half-cells, they were aged at 25°C for 12 hours, followed by charge-discharge tests at 25°C. To evaluate the initial capacity, a baseline capacity of 200 mAh / g was used, and the cells were charged at a constant current of 0.1C to 4.3V, then switched to constant voltage charging until the cutoff current reached 0.05C. After charging, the cells were allowed to stand for 10 minutes, and then discharged at a constant current of 0.1C using the baseline capacity of 200 mAh / g until reaching 3.0V.

[0195] (2) Evaluation of high-temperature life characteristics After fabricating the lithium secondary battery half-cell, it was charged at 45°C with a constant current of 0.5C to 4.3V, then switched to constant voltage charging until the cutoff current reached 0.05C. After charging, it was allowed to rest for 10 minutes, and then discharged with a constant current of 1.0C until it reached 3.0V. This charge-discharge cycle was performed 30 times, and the capacity retention rate of the 30th cycle relative to the first cycle was calculated.

[0196] Table 6

[0197] Refer to Tables 3, 4 and 5. Figure 9 , Figures 10a to 10g , Figures 11a to 11p The uniformity and roughness of the active material, the surface roughness of the electrode, and Table 6 above show that, compared with the comparative example, the loading and agent density of the example are high, which can prepare high energy density batteries, and the charge / discharge capacity, initial efficiency and lifetime characteristics are excellent.

[0198] As described above, the difference between the comparative example and the embodiment is that the comparative example uses an existing process to form the final product from single particles that are crushed and deagglomerated after a single calcination, while the embodiment involves a second calcination after a single calcination, which is a crushing and deagglomeration process, allowing the crushed single particles to grow further during the second calcination.

[0199] Due to this process difference, the particle growth and uniformity of the comparative example may be worse than those of the example. Therefore, when preparing the electrode, the roughness of the example is lower than that of the comparative example. When the final product is made into a battery, the loading and flux density are higher, thus enabling the preparation of a high-energy-density battery with excellent charge / discharge capacity, initial efficiency, and lifetime characteristics.

[0200] While the preferred embodiments have been described in detail above, the scope of the present invention is not limited to the above embodiments. Various modifications and improvements made by those skilled in the art using the basic concepts defined in the claims also fall within the scope of the present invention.

Claims

1. A positive electrode material for a lithium secondary battery, comprising a positive electrode active material, wherein the positive electrode active material comprises lithium metal oxide particles containing lithium, nickel, cobalt, and manganese, wherein, In the first roughness measured by the average value of the active material within a randomly selected range of 40 μm × 40 μm, the average roughness of the surface of the cathode material is less than 1.0 μm.

2. The lithium secondary battery cathode material according to claim 1, wherein, In the first roughness, Rpv (peak-to-valley ratio) is below 9.0 μm.

3. The lithium secondary battery cathode material according to claim 1, wherein, In the first roughness, the root mean square roughness (Rq) is less than 1.20 μm.

4. The lithium secondary battery cathode material according to claim 1, wherein, In the second roughness obtained from a single particle under the measurement electrode condition The average surface roughness (Ra) of the cathode material is below 0.20 μm.

5. The lithium secondary battery cathode material according to claim 1, wherein, In the second roughness obtained from a single particle under the measurement electrode condition Rpv (peak-to-valley ratio) is below 0.90 μm.

6. The lithium secondary battery cathode material according to claim 1, wherein, In the second roughness obtained from a single particle under the measurement electrode condition The root mean square roughness (Rq) is below 0.25 μm.

7. The lithium secondary battery cathode material according to claim 1, wherein, The positive electrode material satisfies the following formula 1. <Formula 1> AB≤1.30 In Formula 1, when a 3g positive electrode active material sample is placed in a mold with a diameter of 1.3cm and pressurized under a pressure of 9 tons, A represents the sum of micro powder values ​​below 1μm after pressurization, and B represents the sum of micro powder values ​​below 1μm before pressurization.

8. The lithium secondary battery cathode material according to claim 1, wherein, The average particle size (D50) of the cathode material is 4.0 to 5.0 μm.

9. The lithium secondary battery cathode material according to claim 1, wherein, The specific surface area of ​​the cathode material is 0.40 to 0.55 m². 2 / g.

10. The lithium secondary battery cathode material according to claim 1, wherein, The cathode material is a single particle.

11. The lithium secondary battery cathode material according to claim 1, wherein, The nickel content is 0.85 moles or more, based on a total of 1 mole of nickel, manganese and doping elements.

Images