Metal oxide precursor particles, method for producing same, and method for producing positive electrode active material

Abstract

The metal oxide precursor particles according to the present invention have a hollow structure, contain nickel, cobalt, and manganese, and have an average particle diameter of 20 [mu] m to 40 [mu] m. According to the preparation method of the metal oxide precursor particles, a mixed solution containing water and metal sources is prepared, and the metal sources comprise a nickel source, a cobalt source and a manganese source. And spraying the mixed solution into a quartz tube. The interior of the quartz tube includes a particle formation region, and the temperature of the particle formation region is 750 DEG C to 1100 DEG C. According to the method for preparing the positive electrode active material of the present invention, the metal oxide precursor particles are pulverized to prepare small-particle-size metal oxide precursor particles. A mixture comprising the small particle size metal oxide precursor particles and a lithium source is calcined to produce lithium metal oxide particles.

Description

Technical Field

[0001] This invention provides a metal oxide precursor particle, its preparation method, and a method for preparing a positive electrode active material. Background Technology

[0002] Rechargeable batteries are batteries that can be repeatedly charged and discharged. 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 including 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 (membrane). The lithium secondary battery may further include an outer packaging material containing the electrode assembly and the electrolyte, such as a pouch-type outer packaging material.

[0005] Lithium-ion rechargeable batteries ideally possess high capacity while maintaining driving and storage stability in extreme high or low temperature environments. Therefore, there is a need to develop a cathode material for lithium-ion rechargeable batteries that achieves both high capacity and high stability. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] One technical problem of the present invention is to provide metal oxide precursor particles that enable batteries to have improved electrochemical performance.

[0008] One technical problem of the present invention is to provide a method for preparing the metal oxide precursor particles.

[0009] One technical problem of the present invention is to provide a method for preparing positive electrode active material using the metal oxide precursor particles.

[0010] (II) Technical Solution

[0011] The metal oxide precursor particles according to the present invention have a hollow structure, contain nickel, cobalt and manganese, and have an average particle size of 20 μm to 40 μm.

[0012] According to an exemplary embodiment, the metal oxide precursor particles may have an average particle size of 25 μm to 35 μm.

[0013] According to an exemplary embodiment, the hollow structure may include a core as a cavity and a shell that wraps the outside of the core. The average thickness of the shell may be 1 μm to 5 μm.

[0014] According to an exemplary embodiment, the shell may wrap more than 90% of the area of the outer surface of the core.

[0015] According to an exemplary embodiment, the metal oxide precursor particles may include a crystal structure represented by Chemical Formula 1 below.

[0016] [Chemical Formula 1]

[0017] Ni 1-x-y-z Co x Mn y M z O 2+a

[0018] In Chemical Formula 1, 0 < x ≤ 0.1, 0 < y ≤ 0.2, 0 ≤ z ≤ 0.1, 0.5 ≤ 1 - x - y - z < 1, -0.1 ≤ a ≤ 0.1, and M may include at least one selected from B, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Ag, Ba, Zr, Nb, Mo, Al, W, Ru, Sn, Ta, La, and Ce.

[0019] According to an exemplary embodiment, the metal oxide precursor particles may further include lithium.

[0020] According to an exemplary embodiment, the metal oxide precursor particles may include a crystal structure represented by Chemical Formula 2 below.

[0021] [Chemical Formula 2]

[0022] Li 1+b Ni 1-x-y-z Co x Mn y M z O 2+a

[0023] In Chemical Formula 2, 0 < x ≤ 0.1, 0 < y ≤ 0.2, 0 ≤ z ≤ 0.1, 0.5 ≤ 1 - x - y - z < 1, -0.1 ≤ a ≤ 0.1, -0.5 ≤ b ≤ 0.5, and M may include at least one selected from B, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Ag, Ba, Zr, Nb, Mo, Al, W, Ru, Sn, Ta, La, and Ce.

[0024] According to the method for preparing metal oxide precursor particles of the present invention, a mixed solution comprising water and a metal source, wherein the metal source includes a nickel source, a cobalt source, and a manganese source, is prepared. The mixed solution is then sprayed into the interior of a quartz tube. The interior of the quartz tube includes a particle-forming region, the temperature of which is between 750°C and 1100°C.

[0025] According to an exemplary embodiment, the concentration of the metal source in the mixed solution can be from 0.5M to 4M.

[0026] According to an exemplary implementation, the temperature of the particle forming region can be from 800°C to 1000°C.

[0027] According to an exemplary embodiment, the spraying can be performed such that the flow rate of the mixed solution is from 30 ml / min to 150 ml / min.

[0028] According to an exemplary embodiment, the metal source in the mixed solution may further include a lithium source.

[0029] According to an exemplary embodiment, the mixed solution may further contain a chelating agent or a basic compound.

[0030] According to the method for preparing the positive electrode active material of the present invention, metal oxide precursor particles are pulverized to prepare small-particle-size metal oxide precursor particles. These metal oxide precursor particles have a hollow structure, contain nickel, cobalt, and manganese, and have an average particle size of 20 μm to 40 μm. A mixture comprising the small-particle-size metal oxide precursor particles and a lithium source is calcined to prepare lithium metal oxide particles.

[0031] According to an exemplary embodiment, the average particle size of the small-diameter metal oxide precursor particles can be from 1 μm to 10 μm.

[0032] According to an exemplary embodiment, the calcination can be carried out at 700°C to 1000°C.

[0033] According to an exemplary embodiment, the positive electrode active material may have a single-particle structure.

[0034] (III) Beneficial Effects

[0035] Using metal oxide precursor particles according to exemplary embodiments of the present invention, positive electrode active materials with high capacity and high charge-discharge efficiency can be realized.

[0036] The method for preparing metal oxide precursor particles according to an exemplary embodiment of the present invention can rapidly and efficiently prepare the metal oxide precursor particles.

[0037] The method for preparing a positive electrode active material according to an exemplary embodiment of the present invention can provide a positive electrode active material having a stable single-particle structure.

[0038] The metal oxide precursor particles, their preparation method, and the method for preparing 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 metal oxide precursor particles, their preparation method, and the method for preparing the positive electrode active material of this invention can be used in eco-friendly electric vehicles and hybrid vehicles that prevent climate change by suppressing air pollution and greenhouse gas emissions. Attached Figure Description

[0039] 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.

[0040] Figure 3 This is a scanning electron microscope (SEM) image of the metal oxide precursor particles from Example 1.

[0041] Figure 4 This is a SEM image of the cross-section of the metal oxide precursor particles in Example 4.

[0042] Figures 5 to 7 The images are SEM images of the pulverized small-diameter metal oxide precursor particles from Examples 4, 7, and Comparative Example 1, respectively. Detailed Implementation

[0043] This invention provides hollow metal oxide precursor particles. Furthermore, this invention provides a method for preparing the metal oxide precursor particles and a method for preparing positive electrode active materials using the metal oxide precursor particles.

[0044] The present invention will now be described in detail with reference to the accompanying drawings. However, these are merely exemplary embodiments, and the present invention is not limited to the specific embodiments described herein.

[0045] The metal oxide precursor particles (hereinafter, simply referred to as precursor particles) according to the present invention have a hollow structure. The hollow structure can be formed by the preparation process of the metal oxide precursor particles described below.

[0046] According to an exemplary embodiment, the hollow structure may include a core as a cavity and a shell surrounding the core. For example, the shell may completely surround the core.

[0047] According to an exemplary embodiment, the shell may cover more than 90% of the area of ​​the outer surface of the core. According to some embodiments, the shell may cover more than 95% of the area of ​​the outer surface of the core. For example, the shell may include a hole connecting the core and the exterior of the precursor particle. The hole may be an area on the outside of the core that is not covered by the shell.

[0048] According to an exemplary embodiment, the average thickness of the shell can be from 1 μm to 5 μm. According to some embodiments, the average thickness of the shell can be from 1.5 μm to 4.5 μm or from 1.6 μm to 4 μm.

[0049] Within the aforementioned range, the productivity of the metal oxide precursor particles can be improved, and the following pulverization process for preparing positive electrode active materials can be carried out quickly.

[0050] According to an exemplary embodiment, the average thickness of the shell can be measured using a cross-sectional image of the metal oxide precursor particles. For example, a scanning electron microscope (SEM) image of the cross-section of the metal oxide precursor particles can be acquired using a Hitachi S4800 device. The shell thickness can be measured using the obtained SEM image. From the SEM image of the cross-section of the metal oxide precursor particles, the thickness at four locations on the shell cross-section can be measured, and their average value can be used to calculate the average thickness of the shell of the metal oxide precursor particles.

[0051] The average thickness of the shell can be the average shell thickness of a metal oxide precursor particle.

[0052] According to an exemplary embodiment, the average thickness of the shell can be 10% to 30% of the radius of the metal oxide precursor particles. According to some embodiments, the average thickness of the shell can be 12% to 27% of the radius of the metal oxide precursor particles.

[0053] The metal oxide precursor particles have an average particle size of 20 μm to 40 μm. According to an exemplary embodiment, the metal oxide precursor particles may have an average particle size of 25 μm to 35 μm.

[0054] Within the aforementioned range, positive electrode active materials with high capacity and improved lifetime characteristics can be achieved.

[0055] When the average particle size of the metal oxide precursor particles is less than 20 μm, the charge-discharge efficiency of the positive electrode containing the positive electrode active material prepared from the metal oxide precursor particles may decrease.

[0056] When the average particle size of the metal oxide precursor particles exceeds 40 μm, the conductivity may decrease, which may result in poor life.

[0057] The "average particle size (D50)" may be the particle size value when the volume cumulative distribution of the particles reaches 50%. The volume cumulative distribution of the particles may be obtained based on the laser diffraction scattering method.

[0058] The metal oxide precursor particles contain nickel, cobalt, and manganese. In an exemplary embodiment, the metal oxide precursor particles may further contain other metals in addition to nickel, cobalt, and manganese.

[0059] The content of nickel in the total moles of nickel, cobalt, and manganese of the metal oxide precursor particles may be 50 mol% or more. In some embodiments, the content of nickel in the total moles of nickel, cobalt, and manganese of the metal oxide precursor particles may be 60 mol% or more, 70 mol% or more, 80 mol% or more, or 90 mol% or more.

[0060] Within the above range, the capacity of the positive electrode active material prepared from the metal oxide precursor particles can be further increased.

[0061] According to an exemplary embodiment, the metal oxide precursor particles may include a crystal structure represented by the following Chemical Formula 1. For example, the metal oxide precursor particles may be represented by the following Chemical Formula 1.

[0062] [Chemical Formula 1]

[0063] Ni 1-x-y-z Co x Mn y M z O 2+a <For example, it can be 0.6 ≤ 1 - x - y - z < 1, 0.7 ≤ 1 - x - y - z < 1, 0.8 ≤ 1 - x - y - z < 1, or 0.9 ≤ 1 - x - y - z < 1.

[0068] According to an exemplary embodiment, the metal oxide precursor particles may further contain lithium.

[0069] According to an exemplary embodiment, the metal oxide precursor particles may include a crystal structure represented by Chemical Formula 2 below. For example, the metal oxide precursor particles may be represented by Chemical Formula 2 below.

[0070] [Chemical Formula 2]

[0071] Li 1+b Ni 1-x-y-z Co x Mn y M z O 2+a

[0072] In Chemical Formula 2, it can be 0 < x ≤ 0.1, 0 < y ≤ 0.2, 0 ≤ z ≤ 0.1, 0.5 ≤ 1 - x - y - z < 1, -0.1 ≤ a ≤ 0.1, -0.5 ≤ b ≤ 0.5, and M may include at least one selected from B, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Ag, Ba, Zr, Nb, Mo, Al, W, Ru, Sn, Ta, La, and Ce.

[0073] According to the method for preparing metal oxide precursor particles of the present invention, a mixed solution containing water and a metal source is prepared, and the metal source includes a nickel source, a cobalt source, and a manganese source. The mixed solution is a solution in which the metal source is dissolved in water, and it can be a precursor solution for preparing the precursor particles.

[0074] The metal source may further include a lithium source. When the metal source further includes a lithium source, a separate lithium source may not be added during the calcination of the precursor particles.

[0075] The lithium source, the nickel source, the cobalt source, and / or the manganese source may respectively include metal nitrates, sulfates, carbonates, etc. For example, the lithium source may be lithium nitrate, the nickel source may be nickel nitrate, the cobalt source may be cobalt nitrate, and the manganese source may be manganese nitrate.

[0076] The lithium source, the nickel source, the cobalt source, and the manganese source may adjust the molar ratio to meet the composition of Chemical Formula 1 and be included in the mixed solution. For example, among the total molar amount of the metal source, the molar amount of the nickel source may be 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, or 90 mol% or more.

[0077] According to an exemplary embodiment, the concentration of the metal source in the mixed solution can be from 0.5 M to 4 M. According to some embodiments, the concentration of the metal source in the mixed solution can be from 1 M to 3 M.

[0078] Within the aforementioned range, the mixed solution can have a suitable viscosity and can be sprayed in a uniform shape as droplets in the spraying process described below.

[0079] According to an exemplary embodiment, the mixed solution may further contain a chelating agent or a basic compound.

[0080] The chelating agent is, for example, an organic compound having a carboxyl group. Examples include carboxylic acids, oxalic acid, ethylenediaminetetraacetic acid, citric acid, acetic acid, succinic acid, malonic acid, malic acid, propionic acid, tartaric acid, lactic acid, pyruvic acid, and fumaric acid. These can be used alone or in combination of two or more.

[0081] The content of the chelating agent can be from 0.01% to 3% by weight or from 0.05% to 1% by weight of the total weight of the mixed solution.

[0082] The alkaline compounds may include, for example, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, NaOH, KOH, Ca(OH)2, etc. These may be used alone or in combination of two or more.

[0083] 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.

[0084] Next, the mixed solution is sprayed into the interior of a quartz tube. A heat source can be placed on the outside of the quartz tube to heat its interior. During the evaporation of the solvent in the mixed solution sprayed into the interior of the quartz tube, hollow metal oxide precursor particles can be formed.

[0085] The interior of the quartz tube can contain two or more regions with different temperatures. For example, regions with different temperatures can be arranged along the length of the interior of the quartz tube. For example, the mixed solution can be sprayed from one end of the interior of the quartz tube, and metal oxide precursor particles can be obtained from the other end.

[0086] According to some embodiments, the interior of the quartz tube may contain three or more regions with different temperatures. At least one of the regions located between a region adjacent to one end and a region adjacent to another end can be a particle-forming region. The interior of the quartz tube may include a particle-forming region, and the metal oxide precursor particles can be formed within this particle-forming region.

[0087] The temperature of the particle-forming region can be higher than that of other regions. Therefore, the solvent can evaporate rapidly at the highest temperature, thereby forming hollow metal oxide precursor particles.

[0088] The temperature of the particle-forming region is between 750°C and 1100°C. According to some embodiments, the temperature of the particle-forming region can be between 800°C and 1000°C.

[0089] Within the above range, metal oxide precursor particles with appropriate particle size and shell thickness can be prepared.

[0090] When the temperature of the particle formation region is below 750°C, the size of the prepared metal oxide precursor particles may be too small.

[0091] When the temperature in the particle formation region exceeds 1100°C, the size of the prepared metal oxide precursor particles may be too large.

[0092] According to an exemplary embodiment, the spraying can be performed using an ultrasonic sprayer (atomizer), but is not limited thereto.

[0093] According to an exemplary embodiment, the spraying can be performed at a flow rate of 30 ml / min to 150 ml / min for the mixed solution. According to some embodiments, the spraying can be performed at a flow rate of 50 ml / min to 100 ml / min for the mixed solution.

[0094] Within the aforementioned range, metal oxide precursor particles can be prepared at an appropriate production rate while preventing particle aggregation inside the quartz tube.

[0095] When the mixed solution is sprayed, it can be atomized into tiny droplets. In this case, inside the high-temperature quartz tube, water can rapidly evaporate from the outer surface of the droplets, thus dramatically increasing the concentration of the metal source on the outer surface. Through the principle of osmotic pressure, the mixed solution in the center of the droplet can move to the outer surface, thereby forming a void (cavity) in the center. The water in the mixed solution that has moved to the outer surface also evaporates, and at high temperatures, the metal source on the outer surface of the droplet reacts to form metal oxides, thereby forming hollow metal oxide precursor particles.

[0096] While the mixed solution is being sprayed, a carrier gas can be injected. The carrier gas can transport the metal oxide precursor particles formed inside the quartz tube to the other end of the quartz tube for collection of the metal oxide precursor particles.

[0097] The carrier gas can be an inert gas, such as nitrogen (N2), argon (Ar), or helium (He).

[0098] According to the method for preparing the positive electrode active material of the present invention, the metal oxide precursor particles are pulverized to prepare small-particle-size metal oxide precursor particles.

[0099] The pulverization can be, for example, dry pulverization or wet pulverization. For instance, the metal oxide precursor particles can be pulverized by ball milling or pulverized together with water.

[0100] According to an exemplary embodiment, the average particle size of the small-diameter metal oxide precursor particles can be from 1 μm to 10 μm. According to some embodiments, the average particle size of the small-diameter metal oxide precursor particles can be from 2 μm to 5 μm.

[0101] Within the above range, the grain size of the prepared positive electrode active material can be relatively large, and a single-particle structure positive electrode active material can be obtained.

[0102] Lithium metal oxide particles are prepared by calcining a mixture containing the small-diameter metal oxide precursor particles and a lithium source.

[0103] A mixture can be prepared by mixing the total molar number of metals contained in the small-diameter metal oxide precursor particles with the molar number of lithium hydroxide in a molar ratio of 1:0.5 to 1:1.8. In some embodiments, the mixture can be prepared by mixing the total molar number of metals contained in the small-diameter metal oxide precursor particles with the molar number of lithium hydroxide in a molar ratio of 1:0.8 to 1:1.5. In some embodiments, the mixture can be prepared by mixing the total molar number of metals contained in the small-diameter metal oxide precursor particles with the molar number of lithium hydroxide in a molar ratio of 1:0.5 to 1:1.5. In some embodiments, the mixture can be prepared by mixing the total molar number of metals contained in the small-diameter metal oxide precursor particles with the molar number of lithium hydroxide in a molar ratio of 1:0.8 to 1:1.8.

[0104] The mixture can be calcined to prepare lithium metal oxide particles. According to an exemplary embodiment, the calcination can be carried out at 700°C to 1000°C. According to some embodiments, the calcination can be carried out at 800°C to 900°C. Within these ranges, a positive electrode active material with a highly stable single-particle structure can be prepared.

[0105] According to an exemplary embodiment, the lithium metal oxide particles may have a single-particle structure. The term "single-particle structure" as used herein is used to refer to secondary particles, excluding those substantially formed by the aggregation of multiple primary particles (e.g., more than 10).

[0106] For example, the lithium metal oxide particles may be substantially composed of particles in the form of single particles, excluding secondary particle structures assembled or aggregated from primary particles. Furthermore, the term "single-particle structure" as used in this specification does not exclude, for example, a monolithic form consisting of 2-10 single particles attached or adhered to each other.

[0107] In some embodiments, the lithium metal oxide particles may also include a structure in which multiple primary particles are merged into one, substantially transforming into a single particle.

[0108] For example, the lithium metal oxide particles may have a single-particle structure comprising fewer than 10 grains.

[0109] For example, the lithium metal oxide particles may have a single crystal structure. The single crystal structure may include a structure in which one particle is composed of one crystal grain. For example, the single crystal structure may be distinguished based on an ion image of a particle cross-section analyzed by a Focused Ion Beam (FIB). For example, if the particle has a single crystal structure, one crystal may be observed in the FIB analysis image according to the difference in crystal orientation.

[0110] According to an exemplary embodiment, the lithium metal oxide particles may include a crystal structure represented by Chemical Formula 3 below.

[0111] [Chemical Formula 3]

[0112] Li 1+b Ni 1-x-y-z Co x Mn y M z O 2+a

[0113] In Chemical Formula 3, 0 < x ≤ 0.1, 0 < y ≤ 0.2, 0 ≤ z ≤ 0.1, 0.5 ≤ 1 - x - y - z < 1, -0.1 ≤ a ≤ 0.1, -0.5 ≤ b ≤ 0.5, and M may include at least one selected from B, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Ag, Ba, Zr, Nb, Mo, Al, W, Ru, Sn, Ta, La, and Ce.

[0114] In Chemical Formula 3, 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, in addition to containing main active elements such as nickel, cobalt, and manganese, the auxiliary element may be added to enhance the chemical stability of the positive electrode active material or the layered structure / crystal structure.

[0115] Figure 1 and Figure 2 are a schematic plan view and a schematic cross-sectional view of a lithium secondary battery according to an exemplary embodiment. Specifically, Figure 2 is a cross-sectional view taken along the I - I' line of Figure 1 in the thickness direction of the lithium secondary battery.

[0116] 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.

[0117] The positive electrode 100 includes a positive electrode current collector 105 and a positive electrode active material layer 110 disposed on at least one side of the positive electrode current collector 105.

[0118] The positive electrode current collector 105 may include stainless steel, nickel, aluminum, titanium, or alloys thereof. The positive electrode current collector 105 may also include aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver. There is no particular limitation on the thickness of the positive electrode current collector 105, but for example, the thickness may be from 10 µm to 50 µm.

[0119] The positive electrode active material layer 110 can also be disposed on both sides of the positive electrode current collector 105.

[0120] 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.

[0121] 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 also further include lithium metal oxides that do not have a single-particle structure (e.g., a secondary particle structure).

[0122] 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.

[0123] 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 fiber, 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.

[0124] 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.

[0125] The positive electrode active material layer may further include an adhesive. The adhesive can bond the positive electrode active material to the conductive material and increase the bonding force between the positive electrode active material layer and the positive electrode current collector.

[0126] 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).

[0127] 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, thus improving the power and capacity of the secondary battery.

[0128] 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.

[0129] 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).

[0130] The positive electrode active material layer 110 can be formed from a positive electrode slurry containing a positive electrode active material and a binder. For example, the positive electrode active material layer 110 can be prepared by coating a positive electrode slurry containing a positive electrode active material and a binder onto one side of the positive electrode current collector 105 and then drying and calendering it.

[0131] According to an exemplary embodiment, the positive electrode slurry may contain a solvent. The solvent may be N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc.

[0132] The coating of the positive electrode slurry can be carried out 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.

[0133] According to an exemplary embodiment, the thickness of the positive electrode active material layer is not particularly limited, but for example, the thickness of the positive electrode active material layer can be from 10 μm to 200 μm.

[0134] According to some embodiments, the positive electrode active material layer may include two or more layers comprising 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 differ from those in the second positive electrode active material layer.

[0135] 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.

[0136] 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. 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 MCMB, and graphitized MPCF. Elements included in the lithium alloy can include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium, etc.

[0137] 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.

[0138] In some embodiments, the negative electrode active material can be mixed and stirred with a binder, conductive material and / or dispersant in a solvent to prepare a slurry. The slurry can be coated on at least one side of the negative electrode current collector 125 and then dried and calendered to manufacture the negative electrode 130.

[0139] The adhesive and the 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).

[0140] 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 prepared from 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.

[0141] 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, lithium ions generated from the positive electrode 100 can, for example, move smoothly to the negative electrode 130 without depositing in the middle. Thus, by combining the first and second positive electrode active material layers described above, it is easier to simultaneously improve power and stability.

[0142] 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.

[0143] The electrode assembly 150 can be housed together with the electrolyte in the housing 160, thereby defining a lithium secondary battery. According to an exemplary embodiment, the electrolyte can be a non-aqueous electrolyte.

[0144] Non-aqueous electrolytes may contain a lithium salt as the electrolyte and an organic solvent, wherein the lithium salt may be, for example, 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.

[0145] 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.

[0146] 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.

[0147] 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 to this. For example, the electrode leads may protrude from at least one side 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.

[0148] The lithium secondary battery can be manufactured in shapes such as cylindrical, prismatic, pouch, or coin, for example, using a can.

[0149] 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.

[0150] Example 1

[0151] A metal source comprising nickel nitrate, cobalt nitrate, and manganese nitrate in a molar ratio of 90:5:5 was mixed with water to achieve a metal source concentration of 1M, thereby preparing a mixed solution. The mixed solution was sprayed into the interior of a quartz tube at a flow rate of 50 ml / min using an ultrasonic nebulizer. Simultaneously, argon gas, as a carrier gas, was injected into the interior of the quartz tube at a flow rate of 6 L / min. The interior of the quartz tube, starting from the ultrasonic nebulizer and extending along its length, comprises five regions: a first region (50°C to 100°C), a second and fourth region (200°C to 600°C), and a third region (800°C). Metal oxide precursor particles were formed in the third region and at the end of the fifth region.

[0152] Figure 3 The image shows a scanning electron microscope (SEM) image of the metal oxide precursor particles of Example 1.

[0153] See Figure 3 The metal oxide precursor particles of Example 1 have a hollow structure and contain a shell that completely encloses the core as a cavity.

[0154] Example 2

[0155] Metal oxide precursor particles were prepared using the same method as in Example 1, except that the temperature of the third region of the quartz tube was changed to 900°C.

[0156] Example 3

[0157] Metal oxide precursor particles were prepared using the same method as in Example 1, except that the temperature of the third region of the quartz tube was changed to 1000°C.

[0158] Example 4

[0159] Metal oxide precursor particles were prepared using the same method as in Example 3, except that the concentration of the metal source in the mixed solution was changed to 2M.

[0160] Example 5

[0161] The metal oxide precursor particles were prepared using the same method as in Example 3, except that the mixture was sprayed at a flow rate of 100 ml / min.

[0162] Example 6

[0163] The metal oxide precursor particles were prepared using the same method as in Example 4, except that the mixture was sprayed at a flow rate of 100 ml / min.

[0164] Example 7

[0165] Metal oxide precursor particles were prepared using the same method as in Example 4, except that the concentration of the metal source in the mixed solution was changed to 3M.

[0166] Example 8

[0167] Metal oxide precursor particles were prepared using the same method as in Example 1, except that a metal source containing nickel nitrate, cobalt nitrate, and manganese nitrate in a molar ratio of 60:10:30 was used.

[0168] Example 9

[0169] Metal oxide precursor particles were prepared using the same method as in Example 1, except that a metal source containing lithium nitrate, nickel nitrate, cobalt nitrate, and manganese nitrate in a molar ratio of 103:90:5:5 was used.

[0170] Comparative Example 1

[0171] Metal oxide precursor particles were prepared using the same method as in Example 1, except that the temperature of the third region of the quartz tube was changed to 700°C.

[0172] Comparative Example 2

[0173] Metal oxide precursor particles were prepared using the same method as in Example 1, except that the concentration of the metal source in the mixed solution was changed to 3M and the temperature of the third region of the quartz tube was changed to 1200°C.

[0174] Measurement Example: Measurement of the size of metal oxide precursor particles

[0175] The average particle size and average shell thickness of the metal oxide precursor particles in the examples and comparative examples were measured using the following methods.

[0176] (1) Average particle size

[0177] Using a Microtrac S3500 bluewave laser diffraction-scattering particle size distribution measurement device, the volumetric cumulative distribution based on particle size was analyzed within the range of 0.01 μm to 2800 μm using a 1x red (780 nm) / 2x blue (405 nm) laser at 100% transmittance (transparent). The average particle size (D50) was determined from the volumetric cumulative distribution of the metal oxide precursor particles in the examples and comparative examples.

[0178] (2) Average thickness of the shell

[0179] Using Hitachi's S4800 equipment, SEM images of the particle cross-section were taken. The thickness of the shell of the metal oxide precursor particles of the examples and comparative examples was measured at four locations, and the average value of the measured values ​​was calculated as the average thickness of the shell.

[0180] Figure 4 The image shows a cross-sectional SEM image of the metal oxide precursor particles of Example 4.

[0181] like Figure 4 As shown, the thickness of the shell at four locations is measured from the SEM image of the particle cross-section, and the average of these values ​​is used to calculate the average thickness of the shell.

[0182] The concentration and flow rate of the mixed solution, the temperature of the third region inside the quartz tube, the average particle size of the metal oxide precursor particles, and the average thickness of the shell during the preparation of metal oxide precursor particles in the examples and comparative examples are shown in Table 1 below.

[0183] [Table 1]

[0184]

[0185] Preparation of positive electrode active material

[0186] The metal oxide precursor particles of the examples and comparative examples were pulverized by ball milling to prepare small-diameter metal oxide precursor particles with an average particle size of 3.5 μm. These small-diameter metal oxide precursor particles were mixed with lithium hydroxide such that the molar ratio of lithium hydroxide to metal in the small-diameter metal oxide precursor particles was 1.03, thus preparing a mixture. The mixture was calcined at 850°C for 10 hours to prepare lithium metal oxide. In Example 9, lithium hydroxide was not added, and the mixture was calcined at 850°C for 10 hours to prepare lithium metal oxide.

[0187] Figures 5 to 7The images show SEM images of the pulverized small-diameter metal oxide precursor particles of Examples 4, 7 and Comparative Example 1, respectively.

[0188] See Figure 5 and Figure 6 Compared to the primary particles of lithium metal oxide in Example 4, the primary particles of lithium metal oxide in Example 7 have a smaller size. On the other hand, see... Figure 7 In Comparative Example 1, excessive aggregation of primary particles in the lithium metal oxide may lead to deterioration of the interaction with lithium ions during battery charging and discharging, and may result in reduced battery performance.

[0189] Manufacturing of secondary batteries

[0190] A slurry is prepared by mixing and dispersing the lithium metal oxide, carbon black as a conductive material, and PVDF as a binder in an N-methylpyrrolidone mixture at a weight ratio of 93:5:2. The slurry is then coated onto one side of an aluminum current collector (20 μm thick) and dried and calendered to produce the positive electrode.

[0191] The negative electrode uses 1.2T of lithium metal.

[0192] The positive and negative electrodes are cut (notching) and stacked according to predetermined dimensions. A separator (polyethylene with a thickness of 13 μm) is placed between the positive and negative electrodes, and then an electrolyte is injected to manufacture the 2016 coin-shaped battery.

[0193] 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 1:1.

[0194] Experimental Example

[0195] The physical properties of the battery were evaluated using the following methods, and are shown in Table 2 below.

[0196] (1) Evaluation of charge and discharge efficiency

[0197] The batteries of the examples and comparative examples were subjected to formation charging and discharging (charging conditions: CC-CV 0.1C 4.3V 0.005C cut-off, discharging conditions: CC 0.1C 3.0V cut-off). During this process, the charging capacity and discharging capacity were measured, and the ratio of the discharging capacity to the charging capacity was calculated as the efficiency.

[0198] (2) Evaluation of lifespan characteristics

[0199] The charge-discharge cycle under the same conditions as described in (1) was considered as one cycle, and the batteries of the examples and comparative examples were repeated 100 times. After repeated cycles, the discharge capacity of the battery was measured, and the ratio of this discharge capacity to the discharge capacity measured in (1) was measured as the capacity retention rate.

[0200] [Table 2]

[0201]

[0202] Referring to Tables 1 and 2, the metal oxide precursor particles of the embodiments enable the realization of a secondary battery with improved charge-discharge efficiency.

[0203] On the other hand, the secondary battery implemented using the metal oxide precursor particles of Comparative Example 1, which have an average particle size of less than 20 μm, has reduced efficiency.

[0204] The secondary battery implemented using metal oxide precursor particles of Comparative Example 2 with an average particle size of over 40 μm exhibited reduced conductivity, resulting in deterioration of battery life characteristics.

[0205] The above description is merely an example of applying the principles of this invention, and other configurations may be included without departing from the scope of this invention.

Claims

1. A metal oxide precursor particle having a hollow structure, containing nickel, cobalt, and manganese, and having an average particle size of 20 μm to 40 μm.

2. The metal oxide precursor particles according to claim 1, wherein, The metal oxide precursor particle has an average particle size of 25 μm to 35 μm.

3. The metal oxide precursor particles according to claim 1, wherein, The hollow structure includes a core as a cavity and a shell wrapping the outside of the core, and the average thickness of the shell is 1 μm to 5 μm.

4. The metal oxide precursor particles according to claim 3, wherein, The shell wraps more than 90% of the outer surface area of the core.

5. The metal oxide precursor particles according to claim 1, wherein, The metal oxide precursor particle includes a crystal structure represented by the following Chemical Formula 1: [Chemical Formula 1] Ni 1-x-y-z Co x Mr y M z O 2+a In Chemical Formula 1, 0 < x ≤ 0.1, 0 < y ≤ 0.2, 0 ≤ z ≤ 0.1, 0.5 ≤ 1 - x - y - z < 1, -0.1 ≤ a ≤ 0.1, M includes at least one selected from B, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Ag, Ba, Zr, Nb, Mo, Al, W, Ru, Sn, Ta, La, and Ce.

6. The metal oxide precursor particles according to claim 1, wherein, The metal oxide precursor particle further contains lithium.

7. The metal oxide precursor particles according to claim 6, wherein, The metal oxide precursor particle includes a crystal structure represented by the following Chemical Formula 2: [Chemical Formula 2] Li 1+b Ni 1-x-y-z Co x Mr y M z O 2+a In Chemical Formula 2, 0 < x ≤ 0.1, 0 < y ≤ 0.2, 0 ≤ z ≤ 0.1, 0.5 ≤ 1 - x - y - z < 1, -0.1 ≤ a ≤ 0.1, -0.5 ≤ b ≤ 0.5, M includes at least one selected from B, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Ag, Ba, Zr, Nb, Mo, Al, W, Ru, Sn, Ta, La, and Ce.

8. A method for preparing a metal oxide precursor particle, comprising the following steps: Preparing a mixed solution containing water and a metal source, the metal source including a nickel source, a cobalt source, and a manganese source; and Injecting the mixed solution into the interior of a quartz tube, wherein the interior of the quartz tube includes a particle formation region, and the temperature of the particle formation region is 750 °C to 1100 °C.

9. The method for preparing metal oxide precursor particles according to claim 8, wherein, The concentration of the metal source in the mixed solution is 0.5 M to 4 M.

10. The method for preparing metal oxide precursor particles according to claim 8, wherein, The temperature of the particle formation region is 800 °C to 1000 °C.

11. The method for preparing metal oxide precursor particles according to claim 8, wherein, The injection is performed in such a manner that the flow rate of the mixed solution is 30 ml / min to 150 ml / min.

12. The method for preparing metal oxide precursor particles according to claim 8, wherein, The metal source in the mixed solution further includes a lithium source.

13. The method for preparing metal oxide precursor particles according to claim 8, wherein, The mixed solution further contains a chelating agent or an alkaline compound.

14. A method for preparing a positive electrode active material, comprising the following steps: Crushing metal oxide precursor particles to prepare small particle size metal oxide precursor particles, the metal oxide precursor particles having a hollow structure, containing nickel, cobalt, and manganese, and having an average particle size of 20 μm to 40 μm; and Calcinating a mixture containing the small particle size metal oxide precursor particles and a lithium source to prepare lithium metal oxide particles.

15. The method for preparing the positive electrode active material according to claim 14, wherein, The average particle size of the small particle size metal oxide precursor particles is 1 μm to 10 μm.

16. The method for preparing the positive electrode active material according to claim 14, wherein, The calcination is performed at 700 °C to 1000 °C.

17. The method for preparing the positive electrode active material according to claim 14, wherein, The lithium metal oxide particles have a single particle structure.

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