Positive electrode active material for secondary battery, positive electrode for secondary battery, and lithium secondary battery

Abstract

The positive electrode active material for a secondary battery according to the present invention contains lithium metal oxide particles. The difference between the maximum particle diameter (Dmaximum) and the average particle diameter (D50) of the lithium metal oxide particles is 5 [mu] m to 12 [mu] m. The D10 of the lithium metal oxide particles is greater than 1.8 [mu] m and less than 3 [mu] m. D10 and D50 are particle diameter values at 10% and 50% cumulative volumes, respectively, in the results of analyzing the volume cumulative particle size distribution of the lithium metal oxide particles by laser diffraction.

Description

Technical Field

[0001] This invention relates to a positive electrode active material for secondary batteries, a positive electrode for secondary batteries, and a lithium secondary battery. Background Technology

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

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

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

[0005] Lithium-ion rechargeable batteries are preferably characterized by high capacity, high stability, and long lifespan. Therefore, methods have been proposed to introduce single-particle structured positive electrode active materials or to adjust the composition of the positive electrode active material layer. However, as the battery is charged and discharged, the structure of the positive electrode active material deforms, resulting in a significant reduction in battery capacity. Therefore, a high-capacity positive electrode with sufficient long lifespan is needed. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] One technical problem of the present invention is to provide a positive electrode active material for secondary batteries with improved electrochemical and physical properties.

[0008] One technical problem of the present invention is to provide a positive electrode for a secondary battery comprising the aforementioned positive electrode active material for a secondary battery.

[0009] One technical problem of the present invention is to provide a lithium secondary battery including the positive electrode for the secondary battery.

[0010] (II) Technical Solution

[0011] The positive electrode active material for secondary batteries according to the present invention comprises lithium metal oxide particles. The maximum particle size (D) of the lithium metal oxide particles is... 最大(max)The difference between the average particle size (D50) and the average particle size is 5 μm to 12 μm. The D10 of the lithium metal oxide particles is greater than 1.8 μm and less than 3 μm. D10 and D50 are the particle size values ​​at 10% and 50% of the cumulative volume in the results of volumetric particle size distribution analysis of the lithium metal oxide particles by laser diffraction.

[0012] According to an exemplary embodiment, the D of the lithium metal oxide particles 最大 The difference from D50 can be 6μm to 8μm.

[0013] According to an exemplary embodiment, the D10 of the lithium metal oxide particles can be from 2 μm to 2.6 μm.

[0014] According to an exemplary embodiment, the D of the lithium metal oxide particles 最大 It can range from 8μm to 13μm.

[0015] According to an exemplary embodiment, the D50 of the lithium metal oxide particles can be 3 μm to 5 μm.

[0016] According to an exemplary embodiment, the D90 of the lithium metal oxide particles can be from 5 μm to 10 μm. D90 can be the particle size value at 90% of the cumulative volume in the result of analyzing the volume cumulative particle size distribution of the lithium metal oxide particles by laser diffraction.

[0017] According to an exemplary embodiment, the lithium metal oxide particles may contain nickel, and the nickel content in the lithium metal oxide particles, excluding lithium and oxygen, may be 60 mol% or more.

[0018] According to an exemplary embodiment, the lithium metal oxide particles may further contain cobalt, and among the elements other than lithium and oxygen contained in the lithium metal oxide particles, the content of nickel may be more than 60 mol% and less than 100 mol%, and the content of cobalt may be greater than 0 mol% and less than 10 mol%.

[0019] According to an exemplary embodiment, the tap density of the lithium metal oxide particles can be 2.1 g / cm³. 3 Up to 3g / cm 3 .

[0020] According to an exemplary embodiment, the powder compaction density of the lithium metal oxide particles can be 3.15 g / cm³. 3 Up to 4g / cm 3 .

[0021] According to an exemplary embodiment, the lithium metal oxide particles may have a single-particle structure.

[0022] The positive electrode for a secondary battery according to the present invention comprises: a positive electrode current collector; and a positive electrode active material layer, the positive electrode active material layer being disposed on one or both sides of the positive electrode current collector, and the positive electrode active material layer comprising the positive electrode active material for a secondary battery.

[0023] The lithium secondary battery according to the present invention includes: a positive electrode for the secondary battery; and a negative electrode, wherein the negative electrode is disposed opposite to the positive electrode.

[0024] (III) Beneficial Effects

[0025] Using the positive electrode active material for secondary batteries according to an exemplary embodiment of the present invention, a positive electrode with improved capacity and energy density can be achieved.

[0026] The positive electrode for a secondary battery according to the exemplary embodiment and the battery including the positive electrode can have high capacity and improved charge and discharge efficiency. Attached Figure Description

[0027] 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. Detailed Implementation

[0028] This invention provides a positive electrode active material with a suitable particle size. This invention also provides a positive electrode for a secondary battery comprising the aforementioned positive electrode active material, and a lithium secondary battery comprising the aforementioned positive electrode.

[0029] The present invention will now be described in detail with reference to the accompanying drawings. However, this is merely an exemplary description, and the present invention is not limited to the specific embodiments described herein.

[0030] The positive electrode active material for secondary batteries according to the present invention comprises lithium metal oxide particles. The lithium metal oxide particles may have a particle size suitable for improving the capacity and energy density of the positive electrode.

[0031] As used in this specification, the term "D##" can refer to the particle size value at ##% of the cumulative volume in the volumetric cumulative particle size distribution of multiple particles. For example, D10 and D50 are the particle size values ​​at 10% and 50% of the cumulative volume in the results of laser diffraction analysis of the volumetric cumulative particle size distribution of the lithium metal oxide particles, respectively. For example, D90 and D100 are the particle size values ​​at 90% and 100% of the cumulative volume in the results of laser diffraction analysis of the volumetric cumulative particle size distribution of the lithium metal oxide particles, respectively.

[0032] The method for analyzing the volumetric cumulative particle size distribution of the particles is not particularly limited, but measurements can be performed using a laser diffraction particle size analyzer, for example, using an S3500 (Microtrac) or MASTERSIZER3000 (Malvern) device.

[0033] For example, the laser diffraction particle size analyzer can measure particle sizes in the range of 0.005 μm to 3000 μm.

[0034] For example, the laser diffraction particle size analyzer can analyze the particle size of particles with shapes such as spherical, near-spherical, non-spherical, and irregular.

[0035] There are no particular restrictions on the lasers used in particle size analysis, but three red lasers with a wavelength of about 780 nm can be used.

[0036] For example, particle size can be analyzed by measuring the laser diffraction pattern of a dispersion containing lithium metal oxide particles and a solvent by irradiating it with a laser.

[0037] For example, the solvent may contain deionized water, and a dispersant may be used to uniformly disperse the lithium metal oxide particles. The dispersant is not particularly limited, but may contain, for example, (NaPO3)6.

[0038] The content of the dispersant in the total weight of the dispersion may be from about 0.2% by weight to 0.5% by weight.

[0039] For example, the dispersant and lithium metal oxide particles can be added to the solvent and ultrasonically treated for about 1 to 2 minutes to prepare a dispersion.

[0040] The refractive index of the dispersion can be about 1 to 2, for example, 1.3 to 1.4.

[0041] The laser diffraction particle size analyzer may include a sample circulator. The sample circulator can uniformly disperse and transport various types of samples to the measuring unit, thus improving the reliability of particle size analysis results.

[0042] The sample circulator can operate under the following conditions.

[0043] - Number of Rinses: 1 to 5

[0044] - Number of deaerate cycles: 1 to 5

[0045] - Background measurement duration: 10 to 30 seconds

[0046] - Sample measurement duration: 5 to 30 seconds.

[0047] In an exemplary embodiment, the lithium metal oxide particles have a D10 greater than 1.8 μm and less than 3 μm. In some embodiments, the D10 of the lithium metal oxide particles can be from 2 μm to 2.6 μm.

[0048] Within the aforementioned range, appropriate pores can be formed between lithium metal oxide particles, enabling the realization of batteries with high energy density.

[0049] When the D10 of the lithium metal oxide particles is less than 1.8 μm, the porosity between the lithium metal oxide particles is reduced, which may hinder the impregnation of the electrolyte.

[0050] When the D10 of the lithium metal oxide particles is greater than 3 μm, the increased porosity between the lithium metal oxide particles during the rolling process may lead to a decrease in electrode density, which may in turn lead to a decrease in battery energy density.

[0051] According to an exemplary embodiment, the D50 of the lithium metal oxide particles can be from 3 μm to 5 μm. According to some embodiments, the D50 of the lithium metal oxide particles can be from 3.5 μm to 4.5 μm or from 3.7 μm to 4 μm.

[0052] According to an exemplary embodiment, the D90 of the lithium metal oxide particles can be from 5 μm to 10 μm. According to some embodiments, the D90 of the lithium metal oxide particles can be from 6 μm to 8 μm or from 6.3 μm to 7.5 μm.

[0053] According to an exemplary embodiment, the D of the lithium metal oxide particles 最大 The diameter can range from 8 μm to 13 μm. According to some embodiments, the D0 of the lithium metal oxide particles... 最大 It can be 9μm to 12μm or 9.5μm to 11.7μm.

[0054] D 最大 It is the particle size of the particle with the largest particle size in the particle, which can be the particle size at D100 in the volumetric cumulative particle size distribution.

[0055] The maximum particle size (D) of the lithium metal oxide particles 最大The difference between the maximum particle size (D50) and the average particle size (D50) is 5 μm to 12 μm. According to some embodiments, the maximum particle size (D50) of the lithium metal oxide particles is... 最大 The difference between the average particle size (D50) and the average particle size can be 6 μm to 8 μm.

[0056] Within the aforementioned range, the energy density of the positive electrode can be increased, and a battery with improved charge-discharge efficiency can be achieved.

[0057] When the maximum particle size of the lithium metal oxide particles (D) 最大 When the difference between the particle size and the average particle size (D50) is less than 5 μm, the particle size is not uniform, which may prevent the electrode from achieving uniform power.

[0058] When the maximum particle size of the lithium metal oxide particles (D) 最大 When the difference between the positive electrode active material and the average particle size (D50) is greater than 12 μm, the porosity between the positive electrode active materials increases excessively, which may lead to a decrease in the energy density of the positive electrode.

[0059] According to an exemplary embodiment, the lithium metal oxide particles may contain nickel, and may further contain at least one of cobalt, manganese and aluminum.

[0060] Nickel can serve as a transition metal relevant to the power and capacity of lithium-ion secondary batteries. Therefore, increasing the nickel content can provide both high-capacity cathodes and high-capacity lithium-ion secondary batteries.

[0061] However, with increasing nickel content, the long-term storage stability and lifetime stability of the cathode or secondary battery may relatively decrease, and side reactions with the electrolyte may also increase. However, according to an exemplary embodiment, conductivity can be maintained by including cobalt, while lifetime stability and capacity retention characteristics can be improved by including manganese.

[0062] In the lithium metal oxide particles, the nickel content, excluding lithium and oxygen, may be 60 mol% or more. In some embodiments, the nickel content, excluding lithium and oxygen, may be 60 mol% or more but less than 100 mol%, 60 mol% to 99 mol%, or 60 mol% to 80 mol%.

[0063] According to some implementation schemes, the lithium metal oxide may contain nickel, cobalt, and manganese, and nickel, cobalt, and manganese may be provided as the main active element of the positive electrode active material.

[0064] In one embodiment, in addition to the primary active element, auxiliary elements may be included to enhance the chemical stability of the positive electrode active material or the layered / crystal structure. These auxiliary elements may be incorporated into the layered / crystal structure of the lithium metal oxide and form a bond.

[0065] The auxiliary element may include at least one of, for example, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, or Zr. The auxiliary element can function as an auxiliary active element that contributes to the capacity and power activity of the positive electrode active material.

[0066] According to an exemplary embodiment, the lithium metal oxide particles may further comprise cobalt, wherein the cobalt content among the elements other than lithium and oxygen contained in the lithium metal oxide particles may be greater than 0 mol% and less than 10 mol%. According to some embodiments, the cobalt content among the elements other than lithium and oxygen contained in the lithium metal oxide particles may be from 5 mol% to 10 mol%.

[0067] The lithium metal oxide may include a layered structure or a crystal structure represented by the following chemical formula 1.

[0068] [Chemical Formula 1]

[0069] Li x Ni a M b O 2+z

[0070] In chemical formula 1, the values ​​can be 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b≤0.4, and -0.5≤z≤0.1. As mentioned above, M can contain Co, Mn, and / or Al.

[0071] The chemical structure represented by Formula 1 indicates the bonding relationships contained in the layered or crystalline structure of the positive electrode active material, and does not exclude other additional elements. For example, M may contain Co and / or Mn, and Co and / or Mn may be provided together with Ni as the main active elements of the positive electrode active material. Formula 1 is provided to represent the bonding relationships of the main active elements, and it should be understood that Formula 1 includes the introduction and substitution of additional elements.

[0072] According to some embodiments, the lithium metal oxide may include a layered structure or a crystal structure represented by the following chemical formula 1-1.

[0073] [Chemical Formula 1-1]

[0074] Lix Ni a M1 b1 M2 b2 O 2+z

[0075] In chemical formula 1-1, M1 may contain Co, Mn, and / or Al. M2 may contain the aforementioned auxiliary elements. In chemical formula 1-1, the elements can be 0.9≤x≤1.2, 0.6≤a≤1, 0≤b1≤0.1, 0≤b2≤0.3, and -0.5≤z≤0.1.

[0076] According to some embodiments, the lithium metal oxide may further comprise coating elements or doping elements. For example, elements substantially the same as or similar to the aforementioned auxiliary elements may be used as coating elements or doping elements. For example, one or more combinations of the aforementioned elements may be used as coating elements or doping elements.

[0077] The coating element or doping element may exist on the surface of the lithium metal oxide particles, or may penetrate through the surface of the lithium metal oxide particles and be contained in the bonding structure represented by chemical formula 1 or chemical formula 1-1.

[0078] According to an exemplary embodiment, the tap density of the lithium metal oxide particles can be 2.1 g / cm³. 3 Up to 3g / cm 3 According to some embodiments, the tap density of the lithium metal oxide particles can be 2.2 g / cm³. 3 Up to 2.5g / cm 3 According to an exemplary embodiment, the powder compaction density of the lithium metal oxide particles can be 3.15 g / cm³. 3 Up to 4g / cm 3 According to some embodiments, the compacted density of the lithium metal oxide particles can be 3.17 g / cm³. 3 Up to 3.5g / cm 3 Within the aforementioned range, it is possible to achieve a lighter cathode and improve the energy density of the battery.

[0079] According to an exemplary embodiment, the lithium metal oxide particles may have a single-particle structure. The term "single-particle structure" as used herein refers to a secondary particle that substantially forms a single particle, excluding, for example, the aggregation of multiple primary particles (e.g., more than 10).

[0080] For example, the lithium metal oxide particles may consist substantially of particles in the form of single particles, and secondary particle structures assembled or aggregated from primary particles may be excluded. Furthermore, the term "single-particle structure" as used in this specification does not exclude, for example, two to ten single particles attached or closely adhered to each other in a monolithic form.

[0081] The single-particle structure may also include a structure in which multiple primary particles merge together to form a single particle.

[0082] For example, the lithium metal oxide particles may have a single-particle structure containing fewer than 10 grains.

[0083] For example, the lithium metal oxide particles may have a single-crystal structure. The single-crystal structure may include a structure where the particle consists of a single crystal. For example, the single-crystal structure can be distinguished based on ion images of the particle cross-section analyzed by focused ion beam (FIB) analysis. For example, if the particle has a single-crystal structure, a crystal can be observed in the FIB analysis image based on differences in crystal orientation.

[0084] According to an exemplary embodiment, the positive electrode for a secondary battery includes a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer being disposed on one or both sides of the positive electrode current collector.

[0085] The positive current collector may include, for example, stainless steel, nickel, aluminum, titanium, copper, or alloys thereof; for example, it may include aluminum or aluminum alloys.

[0086] The positive electrode active material layer can be disposed on one or both sides of the positive electrode current collector, and the positive electrode active material layer contains the aforementioned positive electrode active material for secondary batteries.

[0087] The positive electrode active material of the secondary battery can be mixed with binders, conductive materials and / or dispersing materials in a solvent and stirred to prepare a slurry. The slurry can be coated on a positive electrode current collector and then dried and calendered to manufacture the positive electrode.

[0088] The adhesive may include, for example, organic adhesives such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or water-based adhesives such as styrene-butadiene rubber (SBR), and may be used with thickeners such as carboxymethyl cellulose (CMC).

[0089] For example, PVDF-based binders can be used as positive electrode binders. In this case, the amount of binder used to form the positive electrode active material layer can be reduced, and the amount of positive electrode active material can be relatively increased, thereby improving the power and capacity of the secondary battery.

[0090] The conductive material may be included to facilitate electron migration between active material particles. For example, the conductive material may include carbon-based conductive materials such as graphite, carbon black, graphene, and carbon nanotubes, and / or metal-based conductive materials including perovskite materials such as tin, tin oxide, titanium oxide, LaSrCoO3, and LaSrMnO3.

[0091] The solvent may include, for example, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc.

[0092] A lithium secondary battery according to an exemplary embodiment includes: the aforementioned positive electrode; and a negative electrode, the negative electrode being disposed opposite to the positive electrode. The lithium secondary battery may further include a separator and an electrolyte disposed between the positive electrode and the negative electrode.

[0093] Hereinafter, with reference to the accompanying drawings, a lithium secondary battery according to an exemplary embodiment will be described in more detail. Figure 1 and Figure 2 These are schematic plan views and schematic cross-sectional views illustrating a lithium secondary battery according to an exemplary embodiment. For example, Figure 2 It is along Figure 1 A cross-sectional view taken from the I-I' line.

[0094] Reference Figure 1 and Figure 2 The lithium secondary battery may include an electrode assembly comprising a positive electrode 100, a negative electrode 130, and a separator 140 disposed between the positive and negative electrodes. The electrode assembly may be housed together with an electrolyte within a housing 160 and immersed in the electrolyte.

[0095] The positive electrode 100 includes a positive electrode current collector 105 and a positive electrode active material layer 110, the positive electrode active material layer 110 containing the aforementioned positive electrode active material for secondary batteries. The positive electrode 100 may be the same as the aforementioned positive electrode.

[0096] 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. If necessary, it may include a negative electrode binder and a conductive material.

[0097] For example, the negative electrode active material can be any material known in the art capable of adsorbing and desorbing lithium ions, without particular limitation. 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 (Si)-based compounds; or tin, etc. Examples of amorphous carbon include hard carbon, coke, mesocarbon microbeads (MCMB), and mesophase pitch-based carbon fiber (MPCF).

[0098] Examples of crystalline carbon include natural graphite, artificial graphite, graphitized coke, graphitized mesophase carbon microspheres (MCMB), and graphitized mesophase pitch-based carbon fibers (MPCF). Elements included in the lithium alloy include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium.

[0099] The silicon-based compound may include, for example, silicon, silicon oxide, or silicon carbide (SiC) and other silicon-carbon composite compounds.

[0100] In some embodiments, the content of silicon-based compounds in the total weight of the negative electrode active material can be from 1% to 20% by weight, from 1% to 15% by weight, or from 1% to 10% by weight.

[0101] The negative electrode active material can be mixed with binders, conductive materials, thickeners, and / or dispersants in a solvent and stirred to prepare a negative electrode slurry. The slurry can be coated onto the negative electrode current collector 125 and then dried and calendered to prepare the negative electrode active material layer 120.

[0102] The coating process 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.

[0103] Non-limiting examples of the solvent include water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, tert-butanol, etc.

[0104] The adhesive, conductive material, and thickener may be any of the aforementioned substances that can be used in the manufacture of the positive electrode.

[0105] In some implementations, the negative electrode adhesive may be a styrene-butadiene rubber (SBR) based adhesive, carboxymethyl cellulose (CMC), polyacrylic acid based adhesive, or poly(3,4-ethylenedioxythiophene) (PEDOT) based adhesive, etc.

[0106] A separator 140 may be disposed between the positive electrode 100 and the negative electrode 130. The separator 140 may comprise a porous polymer membrane made of polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer. The separator 140 may also comprise a nonwoven fabric formed from high-melting-point glass fibers, polyethylene terephthalate fibers, etc.

[0107] 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 migrate smoothly to the negative electrode 130 without being deposited in the middle.

[0108] 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.

[0109] The electrode assembly 150 can be housed together with the electrolyte within the housing 160, thereby defining a lithium secondary battery. According to an exemplary embodiment, a non-aqueous electrolyte can be used.

[0110] 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.

[0111] 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.

[0112] 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 side of the housing 160. The tabs can be fused to said side of the housing 160 to form electrode leads (positive lead 107 and negative lead 127) extending to or exposed outside the housing 160.

[0113] The lithium secondary battery can be manufactured in shapes such as cylindrical, prismatic, pouch, or coin, for example, using a can.

[0114] 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.

[0115] Examples and Comparative Examples

[0116] Example 1

[0117] Using distilled water that had been bubbled with N2 for 24 hours to remove dissolved oxygen, NiSO4, CoSO4, and MnSO4 were mixed in a ratio of 0.60:0.10:0.30. The solution was added to a reactor at 50°C, and a co-precipitation reaction was carried out for 72 hours using NaOH and NH3·H2O as precipitating and chelating agents, respectively, to obtain Ni as a transition metal precursor. 0.6 Co 0.1 Mn 0.3 (OH)2. The obtained precursor was dried at 100°C for 12 hours, and then dried again at 120°C for 10 hours.

[0118] Lithium hydroxide and the transition metal precursor were added to a dry high-speed mixer at a lithium:transition metal (nickel, cobalt, and manganese) molar ratio of 1.03:1 and mixed uniformly for 5 minutes. The mixture was then placed in a calcination furnace and heated to 800-1000°C at a rate of 2°C / min, and held at 800-1000°C for 10 hours. Oxygen was continuously introduced at a flow rate of 20 L / min during the heating and holding process. After calcination, the mixture was allowed to cool naturally to room temperature and then pulverized and classified using a jet mill to obtain LiNi. 0.6 Co 0.1 Mn 0.3 O2 is composed of lithium-nickel-based metal oxide particles.

[0119] Examples 2 to 4

[0120] Lithium metal oxide particles were prepared using the same method as in Example 1, except that the molar ratio of nickel, cobalt, and manganese was adjusted to be as shown in Table 1 below.

[0121] Example 5 and Comparative Examples 1 to 4

[0122] Lithium metal oxide particles were prepared using the same method as in Example 1, except that the molar ratio of nickel, cobalt, and manganese was adjusted to that shown in Table 1 below, and the pulverizing pressure of the pulverizing process was changed.

[0123] Measurement example

[0124] (1) Analysis of particle size distribution

[0125] The volumetric particle size distribution of lithium metal oxide particles was analyzed using an S3500 (McChic) / MASTERSIZER3000 (Malvin) laser diffraction method. The particle size values ​​(μm) at the cumulative volume of 10%, 50%, 90%, or 100% are shown in Table 1 below.

[0126] Laser diffraction analysis was performed under the following conditions.

[0127] - Laser: Three red lasers (3x Red), wavelength 780nm

[0128] Solvent: Deionized water

[0129] - Dispersant: (NaPO3)6 0.3% by weight

[0130] - Ultrasonic treatment: 1 to 2 minutes

[0131] - Refractive index of the dispersion: 1.333

[0132] - Number of rinses: 1 to 5

[0133] - Number of degassing cycles: 1 to 5

[0134] - Background measurement duration: 10 to 30 seconds

[0135] - Sample measurement duration: 5 to 30 seconds

[0136] (2) Measurement of powder compaction density

[0137] 1g of lithium metal oxide particles were filled into a cylindrical mold (granulator) with a diameter of 13mm, and a pressure of 8kN was applied for 10 seconds. The height of the granulator was then measured. The compacted powder density (g / cm³) was calculated by using the difference between the measured height of the granulator and the initial height of the empty granulator. 3 ).

[0138] (3) Measurement of tap density

[0139] 10g of lithium metal oxide particles were filled into a 25ml graduated cylinder. The cylinder was then fixed on a tapping device and tapped 3000 times at an amplitude of 10mm. The tapped density (g / cm³) was then measured. 3 ).

[0140] [Table 1]

[0141]

[0142] Battery manufacturing

[0143] A positive electrode slurry was prepared using acetylene black (Denka Black) as the conductive material and polyvinylidene fluoride (PVDF) as the binder, with a mass ratio of lithium metal oxide particles: conductive material: binder of 97:2:1. The positive electrode slurry was then coated onto an aluminum substrate and dried and calendered to obtain the positive electrode.

[0144] A negative electrode slurry is coated onto a copper substrate. The negative electrode slurry contains 93% by weight of natural graphite as the negative electrode active material, 5% by weight of flake-type conductive material KS6 as the conductive material, 1% by weight of styrene-butadiene rubber (SBR) as the binder, and 1% by weight of carboxymethyl cellulose (CMC) as the thickener. The slurry is then dried and calendered to obtain the negative electrode.

[0145] The positive and negative electrodes are notched to appropriate sizes and then stacked with a 12μm thick polyethylene diaphragm between them. The tabs of the positive and negative electrodes are then welded together. The welded positive / diaphragm / negative electrode assembly is placed in a soft case, and three sides, including the side with the tabs, are sealed.

[0146] After injecting the electrolyte through the unsealed surface, seal it and immerse it for at least 12 hours. The electrolyte used was a 1M LiPF6 solution prepared using a mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) (20 / 80; volume ratio).

[0147] Pre-charge at 0.24C (5A) for 50 minutes. After approximately 12 hours, degassing is performed, followed by aging for at least 24 hours, and then formation charge-discharge (charging conditions: CC-CV 0.24C 4.3V 0.05C cut-off; discharging conditions: CC 0.24C 2.5V cut-off). Subsequently, the secondary battery undergoes further transport charging (charging conditions: CC-CV 0.24C 4.3V SOC 30% cut-off).

[0148] Experimental Example

[0149] The batteries of the embodiments and comparative examples were evaluated using the following methods, and the results are shown in Table 2.

[0150] (1) Measurement of discharge capacity

[0151] The batteries, after formation and subsequent transport charging, were charged and discharged at 25°C under the following conditions (charging conditions: CC-CV 0.1C to 1C 4.25V 0.05C cutoff; discharging conditions: CC 0.1C to 1C 2.5V cutoff), and the discharge capacity (mAh / g) was measured.

[0152] (2) Evaluation of charge and discharge efficiency

[0153] The charging capacity and discharging capacity are measured using the same method as described in (1) above, and the ratio of the discharging capacity to the charging capacity, expressed as a percentage (%), is calculated.

[0154] [Table 2]

[0155]

[0156] Referring to Table 2 above, with the same ratio of nickel moles to cobalt moles, the discharge capacity and charge / discharge efficiency of the batteries in the examples are improved compared to those in the comparative examples.

[0157] The above description is merely an example of applying the principles of this invention, and other configurations may be further included without departing from the scope of this invention.

Claims

1. A positive electrode active material for secondary batteries, comprising lithium metal oxide particles, The maximum particle size D of the lithium metal oxide particles 最大 The difference from the average particle size D50 is 5 μm to 12 μm. The lithium metal oxide particles have a D10 greater than 1.8 μm and less than 3 μm. D10 and D50 are the particle size values ​​at 10% and 50% of the cumulative volume, respectively, in the results of the volumetric cumulative particle size distribution analysis of the lithium metal oxide particles by laser diffraction.

2. The positive electrode active material for secondary batteries according to claim 1, wherein, The lithium metal oxide particles D 最大 The difference from D50 is 6μm to 8μm.

3. The positive electrode active material for secondary batteries according to claim 1, wherein, The lithium metal oxide particles have a D10 of 2 μm to 2.6 μm.

4. The positive electrode active material for secondary batteries according to claim 1, wherein, The lithium metal oxide particles D 最大 The size ranges from 8μm to 13μm.

5. The positive electrode active material for secondary batteries according to claim 1, wherein, The D50 of the lithium metal oxide particles is 3 μm to 5 μm.

6. The positive electrode active material for secondary batteries according to claim 1, wherein, The D90 of the lithium metal oxide particles is 5 μm to 10 μm. D90 is the particle size value at 90% of the cumulative volume in the result of the volume cumulative particle size distribution analysis of the lithium metal oxide particles by laser diffraction.

7. The positive electrode active material for secondary batteries according to claim 1, wherein, The lithium metal oxide particles contain nickel, and the nickel content in the lithium metal oxide particles, excluding lithium and oxygen, is 60 mol% or more.

8. The positive electrode active material for secondary batteries according to claim 7, wherein, The lithium metal oxide particles further comprise cobalt, and among the elements other than lithium and oxygen contained in the lithium metal oxide particles, the content of nickel is more than 60 mol% and less than 100 mol%, and the content of cobalt is more than 0 mol% and less than 10 mol%.

9. The positive electrode active material for secondary batteries according to claim 1, wherein, The tap density of the lithium metal oxide particles is 2.1 g / cm³. 3 Up to 3g / cm 3 .

10. The positive electrode active material for secondary batteries according to claim 1, wherein, The compacted density of the lithium metal oxide particles is 3.15 g / cm³. 3 Up to 4g / cm 3 .

11. The positive electrode active material for secondary batteries according to claim 1, wherein, The lithium metal oxide particles have a single-particle structure.

12. A positive electrode for a secondary battery, comprising: Positive current collector; as well as A positive electrode active material layer is disposed on one or both sides of the positive electrode current collector, and the positive electrode active material layer comprises the positive electrode active material for secondary batteries as described in claim 1.

13. A lithium secondary battery, comprising: The positive electrode for a secondary battery as described in claim 12; as well as The negative electrode is positioned opposite to the positive electrode.

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