Positive electrode active material, and positive electrode and lithium secondary battery comprising same

Abstract

The present invention relates to a positive electrode active material which comprises a polycrystalline lithium transition metal oxide having a nickel (Ni) content of 40-70 mol% with respect to the total content of transition metals, the positive electrode active material having an average particle diameter (D50) of 15 µm or more, having a particle size distribution (K90) of 0.3 or more and less than 0.7, and having a grain size of 95-130 nm as measured by X-ray diffraction (XRD) analysis, and the positive electrode active material can have excellent levels of charge / discharge capacity and rate characteristics.

Description

Cathode active material, a cathode including the same, and a lithium secondary battery

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0133698 filed on October 2, 2024, and all contents disclosed in the document of said Korean Patent Application are incorporated herein as part of this specification.

[0003]

[0004] Technology field

[0005] The present invention relates to a positive electrode active material, a positive electrode containing the same, and a lithium secondary battery.

[0006]

[0007] With the recent increase in technological development and demand for mobile devices and electric vehicles, the demand for rechargeable batteries as an energy source is rapidly rising. Among these rechargeable batteries, lithium-ion batteries, which possess high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0008] Lithium transition metal oxides, such as lithium cobalt oxide like LiCoO2, lithium nickel oxide like LiNiO2, lithium manganese oxide like LiMnO2 or LiMn2O4, and lithium iron phosphate oxide like LiFePO4, have been developed as cathode active materials for lithium secondary batteries, and recently, Li[Ni a Co b Mn c ]O2, Li[Ni a Co b Al c ]O2, Li[Ni a Co b Mn c Al d Lithium composite transition metal oxides containing two or more transition metals, such as O2, have been developed and are widely used.

[0009] Meanwhile, as the demand for high-capacity batteries for electric vehicles and the like has recently increased, there has been active development of high-nickel (High-Ni) cathode active materials with improved capacity characteristics by increasing the nickel content in lithium composite transition metal oxides to 70 mol% or more.

[0010] However, in order to properly express the capacity of lithium-rich NCM-based cathode active materials, a higher voltage range than the conventional voltage range must be used. However, in the high voltage range, there are stability issues such as oxygen desorption of the cathode active material and phase changes at the interface, which lead to a rapid degradation of the lifespan. In addition, although the average particle size (D50) is increased to improve high energy density and lifespan performance, a problem has arisen where output performance deteriorates as the size of the secondary particles increases.

[0011] (Patent Document 1) JP 2021-051880 A

[0012]

[0013] The problem to be solved by the present invention is to provide a positive active material with excellent charge / discharge capacity and rate characteristics by controlling the particle size distribution (K90) of the positive active material, a positive electrode including the same, and a lithium secondary battery.

[0014]

[0015] The present invention provides a positive electrode active material, a positive electrode including the same, and a lithium secondary battery.

[0016] (1) The present invention provides a positive electrode active material comprising a polycrystalline lithium transition metal oxide having a nickel (Ni) content of 40 mol% or more and 70 mol% or less of the total transition metal content, an average particle size (D50) of 15 μm or more, a particle size distribution (K90) of 0.3 or more and less than 0.7, and a crystal grain size of 95 nm or more and 130 nm or less as measured by XRD (X-ray diffraction) analysis.

[0017] (2) The present invention provides a positive electrode active material according to (1), wherein the positive electrode further comprises a coating portion on the surface of the particles of the lithium transition metal oxide, and the coating portion comprises one or more elements selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, V, Ti, Fe, Zr, Si, Y, Nb, Ga, Sn, Mo, W, P, S and combinations thereof.

[0018] (3) The present invention provides a positive electrode active material in which, in (1) or (2), the particle size distribution (K90) is 0.5 or more and 0.6 or less.

[0019] (4) The present invention provides a positive electrode active material in any one of (1) to (3), wherein the lithium transition metal oxide contains 50 mol% or more and 60 mol% or less of Ni among the total transition metals.

[0020] (5) The present invention provides a positive electrode active material in any one of (1) to (4), wherein the lithium transition metal oxide comprises one or more transition metals selected from the group consisting of Ni, Co and Mn.

[0021] (6) The present invention provides a positive electrode active material in any one of (1) to (5), wherein the lithium transition metal oxide is in the form of a secondary particle formed by the aggregation of a plurality of primary particles.

[0022] (7) The present invention provides a positive electrode active material represented by the following chemical formula 1, wherein in any one of (1) to (6) the lithium transition metal oxide is a positive electrode active material.

[0023] [Chemical Formula 1]

[0024] Li a Ni x Co y M 1z M 2(1-x-y-z) O2

[0025] In the above chemical formula 1

[0026] 0.9≤a≤1.1, 0.5≤x≤0.6, 0.1≤y≤0.3, 0.1≤z≤0.3, 0≤1-xyz≤0.4,

[0027] M1 includes at least one of Mn and Al, and

[0028] M2 includes one or more selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, V, Ti, Fe, Zr, Si, Y, Nb, Ga, Sn, Mo, W, P, S, and combinations thereof.

[0029] (8) The present invention provides a positive electrode active material in any one of (1) to (7), wherein the average particle size is 15 μm or more and 20 μm or less.

[0030] (9) The present invention provides a positive electrode active material in any one of (1) to (8), wherein the crystal grain size is greater than 100 nm and less than or equal to 125 nm.

[0031] (10) The present invention provides a positive electrode for a secondary battery comprising a positive electrode active material according to any one of (1) to (9) above.

[0032] (11) The present invention provides a lithium secondary battery comprising a positive electrode according to (10) above.

[0033]

[0034] The positive active material of the present invention is in the form of large particles, and by controlling the particle size distribution and crystal grain size, it can have excellent levels of charge / discharge capacity and rate characteristics.

[0035]

[0036] Figure 1 shows a graph of the particle size distribution of the examples and comparative examples.

[0037] Figure 2 is an SEM image showing the lithium transition metal oxide of Example 1.

[0038] Figure 3 is an SEM image showing the lithium transition metal oxide of Example 2.

[0039] Figure 4 is an SEM image showing the lithium transition metal oxide of Example 3.

[0040] Figure 5 is an SEM image showing the lithium transition metal oxide of Comparative Example 1.

[0041] Figure 6 is an SEM image showing the lithium transition metal oxide of Comparative Example 2.

[0042]

[0043] Hereinafter, the present invention will be described in more detail to aid in understanding the invention. In this case, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0044] The terms used in this specification are used merely to describe exemplary embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0045] In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0046] In the present invention, the term 'primary particle' refers to a minimum particle unit that is distinguished as a single mass when the cross-section of the positive active material is observed through a scanning electron microscope (SEM), and may consist of multiple crystal grains.

[0047] In the present invention, the term 'single particle form' includes both cases where the particles of the positive electrode active material and / or lithium transition metal composite oxide are single particles, and cases where they are in a similar single particle form in which two or more and 100 or fewer particles are aggregated. That is, the single particle form positive electrode active material and / or single particle form lithium transition metal composite oxide of the present invention may comprise one or more selected from the group consisting of single particles and particles in which two or more and 100 or fewer primary particles are aggregated.

[0048] In the present invention, the term 'polycrystal grain' refers to a type of particle in which a crystal lattice structure is assembled in an irregular orientation throughout the particle, and may be composed of secondary particles formed by the aggregation of primary particles. Here, the secondary particles are typically particle structures contrasting with primary particles, and are structures in which small-sized primary particles are physically and / or chemically aggregated to form relatively large particle shapes.

[0049] In the present invention, the term 'secondary particle' refers to a secondary structure formed by the aggregation of a plurality of primary particles. Specifically, it refers to a form in which a number of primary particles exceeding the number of primary particles included in the single particle form are aggregated. The average particle size of the secondary particles can be measured using a particle size analyzer.

[0050] In the present invention, the term 'average particle size (D 50)' refers to the particle size at the 50% point of the cumulative volume distribution according to particle size. The above average particle size is determined by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Malvern's Mastersizer 3000), measuring the difference in diffraction patterns according to particle size as the particles pass through a laser beam to calculate the particle size distribution, and calculating the particle diameter at the point where the cumulative volume distribution according to particle size in the measuring device reaches 50%, thereby D 50 It can measure.

[0051]

[0052] positive electrode active material

[0053] The present invention provides a positive electrode active material comprising a polycrystalline lithium transition metal oxide having a nickel (Ni) content of 40 mol% or more and 70 mol% or less of the total transition metal content, an average particle size (D50) of 15 μm or more, a particle size distribution (K90) of 0.3 or more and less than 0.7, and a crystal grain size measured by XRD (X-ray diffraction) analysis of 95 nm or more and 130 nm or less. Specifically, the positive electrode active material of the present invention is mid-nickel (Mid-Ni) and has the characteristics of maintaining a large particle size while simultaneously controlling the particle size distribution and crystal grains within a specific range to improve high energy density and lifespan characteristics and improve rate characteristics.

[0054] The nickel content is 40 mol% or more and 70 mol% or less of the total transition metal content. For example, based on the total transition metal content, it may be 40 mol% or more, 45 mol% or more, 50 mol% or more, 55 mol% or more, 70 mol% or less, 65 mol% or less, or 60 mol% or less. By including nickel within the above ranges, the cathode active material of the present invention can have high capacity characteristics, while simultaneously reducing cation mixing and improving rate characteristics. Furthermore, the cathode active material of the present invention can maintain energy density while relatively lowering the proportion of cobalt, thereby reducing the amount of cobalt used and lowering battery costs, and can improve the structural stability, thermal stability, and cycle life characteristics of the electrode through the manganese ratio.

[0055] The above average particle size (D50) is 15 μm or more, and, for example, may be 15 μm or more, 15.5 μm or more, 16 μm or more, 16.5 μm or more, 16.6 μm or more, 17 μm or more, 17.5 μm or more, 18 μm or more, 18.5 μm or more, 19 μm or more, 23 μm or less, 21 μm or less, or 20 μm or less. Specifically, the lithium transition metal oxide may be in the form of secondary particles formed by the aggregation of a plurality of primary particles, and may have a polycrystalline structure, and the average particle size of the secondary particles may be 15 μm or more. If the average particle size does not satisfy the above range, output performance, capacity and lifespan characteristics may be degraded, and problems such as having a low composite density may occur. Since the coating portion formed on the lithium transition metal oxide according to the present invention is formed with a thickness in the nano range, the difference in average particle size between the lithium transition metal oxide and the positive electrode active material may not be large.

[0056] The above particle size distribution (K90) can be named as a span. From the above particle size distribution, i.e., the span, it is possible to determine how much difference there is between large and small particles relative to the average particle size. The above particle size distribution (K90) can be derived from Equation 1 below.

[0057] [Equation 1]

[0058]

[0059] In the above Equation 1, 'D10', 'D50', and 'D90' represent the particle size at the 10% point (D10), 50% point (D50), and 90% point (D90) of the volume cumulative distribution according to particle size, respectively. The above D10, D50, and D90 can be measured by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Malvern’s Mastersizer 3000), measuring the difference in diffraction patterns according to particle size as the particles pass through a laser beam to calculate the volume cumulative distribution according to particle size, and calculating the particle diameter at the points that are 10%, 50%, and 90% of the volume cumulative distribution according to particle size in the measuring device.

[0060] The above particle size distribution (K90) is 0.3 or more and less than 0.7, and, for example, may be 0.30 or more, 0.31 or more, 0.33 or more, 0.35 or more, 0.37 or more, 0.39 or more, 0.4 or more, 0.41 or more, 0.43 or more, 0.45 or more, 0.47 or more, 0.49 or more, 0.5 or more, 0.51 or more, 0.51 or more, 0.53 or more, 0.54 or more, 0.55 or more, less than 0.7, 0.69 or less, 0.67 or less, 0.65 or less, 0.63 or less, 0.61 or less, 0.6 or less, 0.59 or less, 0.57 or less. If the particle size distribution falls outside the above range, the particle size distribution becomes very wide, resulting in differences in electrochemical characteristics and physical properties between small and large particles, which may lead to a decrease in rate characteristics.

[0061] The crystalline size measured through the above XRD (X-ray diffraction) analysis is 95 nm or larger and 130 nm or smaller. The crystalline size can be measured through X-ray diffraction analysis. The crystalline size can be calculated using the Scherrer equation of Equation 2, which uses the full width at half maximum (FWHM) obtained through XRD analysis.

[0062] [Equation 2]

[0063]

[0064] In Equation 2, L represents the grain size, λ represents the X-ray wavelength, β represents the full width at half maximum of the corresponding peak, and θ represents the diffraction angle. For example, the full width at half maximum in XRD analysis for grain size measurement can be measured from the peak of the (003) plane. The XRD analysis is performed on dried powder of lithium-metal oxide particles using a Cu Kα ray as a diffraction light source, at a scan rate of 0.0065° / s in a diffraction angle (2θ) range of 10° to 120°. Additionally, in Equation 2, β can be a full width at half maximum corrected from a value derived from the equipment. In one embodiment, Si can be used as a standard material to reflect the value derived from the equipment. In this case, the full width at half maximum profile of Si over the entire 2θ range can be fitted to express the full width at half maximum derived from the equipment as a function of 2θ. Subsequently, the value obtained by subtracting the equipment-derived half-width value at the corresponding 2θ from the above function can be used as β.

[0065] The grain size of the present invention may be 95 nm or more, 97 nm or more, 99 nm or more, 100 nm or more, 101 nm or more, 102 nm or more, 103 nm or more, 105 nm or more, 107 nm or more, 109 nm or more, 110 nm or more, 111 nm or more, 113 nm or more, 115 nm or more, 130 nm or less, 129 nm or less, 127 nm or less, 125 nm or less, 123 nm or less, 121 nm or less, 120 nm or less, 119 nm or less, and 117 nm or less. If the grain size deviates from the lower limit of the above range, charge / discharge capacity, efficiency, and rate characteristics may be degraded, and if the grain size deviates from the upper limit of the above range, a problem may occur in which high-temperature life characteristics are degraded.

[0066] According to one embodiment of the present invention, the lithium transition metal oxide may have a ratio of the number of moles of lithium to the total number of moles of transition metal (Li / Me) of 0.9 or more and 1.3 or less. For example, the ratio of the number of moles of lithium may be 0.9 or more, 0.93 or more, 0.95 or more, 0.97 or more, 1.0 or more, 1.01 or more, 1.02 or more, 1.03 or more, 1.04 or more, 1.05 or more, 1.06 or more, 1.07 or more, 1.3 or less, 1.27 or less, 1.25 or less, 1.2 or less, 1.17 or less, 1.15 or less, 1.13 or less, and 1.1 or less. Specifically, the Li / Me may be 1.0 or more and 1.1 or less. By having a Li / Me within the above range, the lithium transition metal oxide may have excellent charge / discharge capacity.

[0067]

[0068] According to one embodiment of the present invention, the lithium transition metal oxide of the present invention may have a composition represented by the following chemical formula 1.

[0069] [Chemical Formula 1]

[0070] Li a Ni x Co y M1 z M2 (1-x-y-z) O2

[0071] In the above chemical formula 1, 0.9≤a≤1.1, 0.5≤x≤0.6, 0.1≤y≤0.3, 0.1≤z≤0.3, 0≤1-xyz≤0.4, M1 includes at least one of Mn and Al, and M2 includes one or more selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, V, Ti, Fe, Zr, Si, Y, Nb, Ga, Sn, Mo, W, P, S and combinations thereof.

[0072] According to one embodiment of the present invention, a is a molar ratio of lithium to transition metal in a lithium transition metal composite oxide, which may be 0.9 or more, 0.91 or more, 0.93 or more, 0.95 or more, 0.97 or more, 1.0 or more, 1.01 or more, 1.03 or more, and may also be 1.1 or less, 1.07 or less, 1.05 or less.

[0073] According to one embodiment of the present invention, x may be a molar ratio of nickel (Ni) and may be 0.5 or more, 0.51 or more, 0.53 or more, 0.55 or more, 0.6 or less, 0.59 or less, or 0.57 or less.

[0074] According to one embodiment of the present invention, the y may be a molar ratio of cobalt (Co) and may be 0.1 or more, 0.13 or more, 0.15 or more, 0.17 or more, 0.2 or more, 0.3 or less, 0.27 or less, 0.25 or more, 0.23 or less, and 0.21 or less.

[0075] According to one embodiment of the present invention, z may be a molar ratio of manganese (Mn) or aluminum (Al), and may be 0.1 or more, 0.13 or more, 0.15 or more, 0.17 or more, 0.2 or more, 0.3 or less, 0.27 or less, 0.25 or more, 0.23 or less, or 0.21 or less.

[0076] According to one embodiment of the present invention, the 1-xyz may be a molar ratio of an element included in a coating portion on the particle surface of a lithium transition metal oxide, and may be 0.1 or more, 0.13 or more, 0.15 or more, 0.17 or more, 0.2 or more, 0.4 or less, 0.37 or less, 0.35 or less, 0.33 or less, 0.31 or less, 0.3 or less, 0.27 or less, 0.25 or more, 0.23 or less, 0.21 or less.

[0077] According to one embodiment of the present invention, the positive electrode active material of the present invention may further include a coating portion on the particle surface of the lithium transition metal oxide. In addition, the coating portion may include one or more elements selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, V, Ti, Fe, Zr, Si, Y, Nb, Ga, Sn, Mo, W, P, S, and combinations thereof, and specifically, may include boron (B). The lithium coating portion may be a film type, an island type, or a combination thereof. The film type may be a continuous form, and the island type may be a discontinuous form. If the coating portion satisfies the above forms, the degradation of the positive electrode surface and the electrical conductivity can be improved, thereby improving the lifespan characteristics and output characteristics of the battery.

[0078] According to the present invention, the lithium transition metal oxide may be in the form of secondary particles in which a plurality of primary particles are aggregated. That is, the lithium transition metal oxide may have a polycrystalline structure.

[0079]

[0080] Method for manufacturing positive electrode active material

[0081] The method for manufacturing a positive electrode active material according to the present invention is one example of several methods for manufacturing a positive electrode active material having high charge / discharge capacity and rate characteristics by controlling the particle size distribution to a specific range with a large particle size.

[0082] The present invention provides a method for manufacturing an anode active material comprising the steps of mixing a lithium compound and a transition metal precursor to prepare a mixture, and calcining the mixture to produce a lithium transition metal oxide. Herein, the transition metal precursor may contain Ni in an amount of 40 mol% or more and 70 mol% or less of the total transition metal. For example, the transition metal oxide may contain nickel in an amount of 40 mol% or more, 45 mol% or more, 50 mol% or more, 55 mol% or more, 70 mol% or less, 65 mol% or less, and 60 mol% or less of the total transition metal, and specifically, may contain 50 mol% or more and 60 mol% or less.

[0083] Specifically, the above mixing may be performed by dry mixing or wet mixing. If the components are mixed through dry mixing, the calcination process can be performed without a separate drying process. If the components are mixed through wet mixing, they may be prepared by adding them to a solvent, specifically water, or a mixture of water and an organic solvent that is uniformly miscible with water (specifically alcohol, etc.), or by preparing a solution containing each raw material, specifically an aqueous solution, mixing them, spray-drying the mixed components, and then proceeding with the calcination process. Each raw material and transition metal hydroxide may be used in appropriate amounts considering the content of each metal element in the final lithium transition metal oxide produced.

[0084] The above transition metal precursor can be prepared through a co-precipitation reaction by introducing an aqueous transition metal solution, an ammonium cation complex, and a basic compound into a reactor.

[0085] The above transition metal aqueous solution can be prepared by dissolving a transition metal-containing raw material in a solvent such as water, for example, by dissolving a nickel (Ni)-containing raw material, a cobalt (Co)-containing raw material, and a manganese (Mn)-containing raw material in water. That is, the above composite transition metal-containing solution includes a nickel (Ni)-containing raw material, a cobalt (Co)-containing raw material, and a manganese (Mn)-containing raw material. Additionally, if necessary, the above composite transition metal-containing solution may further include a metal-containing raw material containing a transition metal other than nickel (Ni), cobalt (Co), and manganese (Mn) (for example, one or more selected from Y, Zr, B, Al, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, and La).

[0086] The above nickel (Ni)-containing raw material may be at least one selected from the group consisting of NiO, Ni(OH)2, NiO·OH, NiCO3·2Ni(OH)2·4H2O, NiC2O4·2H2O, Ni(NO3)2·6H2O, nickel fatty acids, and nickel halides, and one or more of these may be used.

[0087] The above cobalt (Co)-containing raw material may be at least one selected from the group consisting of Co(OH)2, Co3O4, CoO·OH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O or Co(SO4)2·7H2O, fatty acid cobalt, and cobalt halides, and one or more of these may be used.

[0088] The above manganese (Mn)-containing raw material may be at least one selected from the group consisting of MnCO3, Mn2O3, MnO2, Mn3O4, Mn(NO3)2, manganese acetate, manganese dicarboxylate, manganese citric acid, manganese fatty acid salts, oxyhydroxides, and manganese chloride halides, and one or more of these may be used.

[0089] Nickel (Ni)-containing raw materials, cobalt (Co)-containing raw materials, manganese (Mn)-containing raw materials, etc., can be used in appropriate amounts considering the content of each metal element in the manufactured complex transition metal hydroxide.

[0090] The lithium compound is a reactant for forming a lithium transition metal oxide by reacting with the transition metal precursor. For example, the lithium compound is a compound containing lithium and is not particularly limited as long as it can be used as a lithium source. For example, the lithium compound may be at least one selected from the group consisting of lithium carbonate (Li2CO3), lithium hydroxide (LiOH), lithium nitrate (LiNO3), and lithium hydrate (LiOH·H2O).

[0091] In the above mixing step, the ratio of the lithium compound to the transition metal precursor may be 0.9 or more and 1.3 or less. For example, the ratio of the number of moles of lithium may be 0.9 or more, 0.93 or more, 0.95 or more, 0.97 or more, 1.01 or more, 1.02 or more, 1.03 or more, 1.04 or more, 1.05 or more, 1.06 or more, 1.07 or more, 1.3 or less, 1.27 or less, 1.25 or less, 1.2 or less, 1.17 or less, 1.15 or less, 1.13 or less, 1.1 or less, 1.09 or less, and 1.08 or less. Specifically, the ratio of the number of moles of lithium may be 1.0 or more and 1.1 or less. Since the lithium compound has the characteristic of volatilizing at high temperatures, a relatively excess amount must be added relative to the transition metal oxide for the reaction to occur sufficiently. Therefore, it is preferable that the lithium compound be mixed with the transition metal oxide within the above ratio range.

[0092] According to one embodiment of the present invention, the span value of the mixture of the transition metal precursor may be 0.3 or more and less than 0.7. For example, it may be 0.30 or more, 0.31 or more, 0.33 or more, 0.35 or more, 0.37 or more, 0.39 or more, greater than 0.4, 0.41 or more, 0.43 or more, 0.45 or more, 0.47 or more, 0.49 or more, 0.5 or more, 0.51 or more, 0.51 or more, 0.53 or more, 0.54 or more, 0.55 or more, less than 0.7, 0.69 or less, 0.67 or less, 0.65 or less, 0.63 or less, 0.61 or less, 0.6 or less, 0.59 or less, 0.57 or less. If the particle size distribution of the above mixture falls outside the above range, the particle size distribution becomes very wide, resulting in differences in electrochemical characteristics and physical properties between small and large particles, which may lead to a decrease in rate characteristics. The particle size distribution of the mixture of the lithium compound and the transition metal precursor, i.e., the span, can be controlled to achieve a desired particle size distribution of the positive electrode active material.

[0093] The above mixing can be performed in a Continuous Stirring Tank Reactor (CSTR). The CSTR refers to a method in which raw materials are introduced to co-precipitate while simultaneously discharging precursors formed into particles. The method for manufacturing an anode active material according to the present invention can improve the productivity of the anode active material precursor by introducing raw materials to co-precipitate and simultaneously discharging the precursors produced using the CSTR.

[0094] The above calcination can be performed under temperature conditions exceeding 860 ℃ and not exceeding 900 ℃. For example, the temperature conditions may be exceeding 860 ℃, 865 ℃ or higher, 870 ℃ or higher, 900 ℃ or lower, 895 ℃ or lower, 890 ℃ or lower, 885 ℃ or lower, and 880 ℃ or lower. When calcination is performed under the above temperature conditions, a positive electrode active material that satisfies both excellent levels of charge / discharge capacity and rate characteristics can be manufactured.

[0095] According to one embodiment of the present invention, the calcination step may be performed in an atmosphere of oxygen, anhydrous air, nitrogen (N2), or argon (Ar).

[0096] According to one embodiment of the present invention, the method may further include the step of mixing the lithium transition metal oxide and the coating raw material after the calcination, and then calcining to form a coating portion on the particle surface of the lithium transition metal oxide. The coating raw material may include one or more elements selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, V, Ti, Fe, Zr, Si, Y, Nb, Ga, Sn, Mo, W, P, S, and combinations thereof, and specifically, may include boron (B). The coating raw material may be mixed in an amount of 100 ppm or more and 2000 ppm or less based on the total moles of the positive electrode active material, and, for example, may be included in an amount of 800 ppm or more and 1200 ppm or less.

[0097] In addition, the firing temperature for forming the coating portion may be 350 ℃ or higher and 400 ℃ or lower. For example, the firing temperature may be 350 ℃ or higher, 360 ℃ or higher, 370 ℃ or higher, 400 ℃ or lower, 390 ℃ or lower, or 380 ℃ or lower. When the above firing temperature conditions are satisfied, the coating can be evenly applied to the surface of the positive active material particles, and charge / discharge capacity and lifespan characteristics can be improved.

[0098]

[0099] anode

[0100] The present invention may provide a positive electrode for a lithium secondary battery comprising a positive electrode active material manufactured by the method described above. Specifically, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer located on at least one surface of the positive electrode current collector and comprising the positive electrode active material described above.

[0101] The above positive current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the above positive current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesion of the positive active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0102] The above positive active material layer may include a conductive material and a binder together with the positive active material.

[0103] The above-mentioned positive active material may be included in an amount of 80% to 99% by weight, more specifically 85% to 98% by weight, based on the total weight of the positive active material layer. Excellent capacity characteristics can be exhibited when included within the above-mentioned content range.

[0104] The above conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fibers; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above conductive material may be included in an amount of 1% to 30% by weight relative to the total weight of the positive electrode active material layer.

[0105] The above binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above binder may be included in an amount of 1% to 30% by weight based on the total weight of the positive active material layer.

[0106] The above-described anode may be manufactured according to a conventional anode manufacturing method, except for using the above-described anode active material. Specifically, it may be manufactured by applying a composition for forming an anode active material layer, prepared by dissolving or dispersing the above-described anode active material and, optionally, a binder and a conductive material in a solvent, onto an anode current collector, followed by drying and rolling. At this time, the types and contents of the above-described anode active material, binder, and conductive material are as described above.

[0107] The above solvent may be a solvent commonly used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it has a viscosity that dissolves or disperses the anode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the composition for forming the active material layer, and subsequently provides excellent thickness uniformity when coated for anode manufacturing.

[0108] In addition, the anode may also be manufactured by casting the composition for forming the anode active material layer onto a separate support and then laminating the film obtained by peeling from the support onto an anode current collector.

[0109]

[0110] lithium secondary battery

[0111] In addition, the present invention can manufacture an electrochemical device including the anode. Specifically, the electrochemical device may be a battery, a capacitor, etc., and more specifically, a lithium secondary battery.

[0112] Specifically, the above lithium secondary battery comprises a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is identical to the one described above, a detailed description is omitted, and only the remaining components are described in detail below.

[0113] Additionally, the lithium secondary battery may optionally further include a battery container that accommodates the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

[0114] In the above lithium secondary battery, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0115] The above-mentioned negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative electrode current collector may typically have a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0116] The above-mentioned cathode active material layer optionally includes a binder and a conductive material together with the cathode active material.

[0117] As the above-mentioned negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO₂ β Examples include metal oxides capable of doping and dedoping lithium, such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Furthermore, the carbon material may include low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0118] The above-mentioned negative electrode active material may be included in an amount of 80% to 99% by weight relative to the total weight of the negative electrode active material layer.

[0119] The above binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1% to 10% by weight relative to the total weight of the negative active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0120] The above conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, specifically 5% by weight or less, based on the total weight of the negative electrode active material layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fiber or metal fiber; metal powder such as carbon fluoride, aluminum, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0121] The above-mentioned negative electrode active material layer may be manufactured by applying a composition for forming a negative electrode active material layer, prepared by dissolving or dispersing a negative electrode active material and optionally a binder and a conductive material in a solvent, onto a negative electrode current collector and drying it, or by casting the composition for forming a negative electrode active material layer onto a separate support and then laminating the film obtained by peeling from the support onto a negative electrode current collector.

[0122] Meanwhile, in the above-mentioned lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator typically used in lithium secondary batteries may be used without special limitations, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0123] In addition, the electrolytes used in the present invention may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which are usable when manufacturing lithium secondary batteries, but are not limited to these.

[0124] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0125] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; aromatic hydrocarbon-based solvents such as benzene and fluorobenzene; and carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC). Alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond-directing ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, carbonate-based solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.In this case, using a mixture of cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent performance of the electrolyte.

[0126] The above lithium salt may be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the above lithium salt is LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4). 2　 The above may be used. It is preferable to use the lithium salt within the range of 0.1M to 2.0M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0127] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, haloalkylene carbonate-based compounds like difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the above additive may be included in an amount of 0.1% to 5% by weight based on the total weight of the electrolyte.

[0128] As described above, since the lithium secondary battery containing the positive electrode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and lifespan characteristics, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0129] Accordingly, a battery module including the above-mentioned lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0130] The above battery module or battery pack can be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0131] The external shape of the lithium secondary battery of the present invention is not particularly limited, but can be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape.

[0132] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also preferably be used as a unit cell in a medium-to-large battery module comprising a plurality of battery cells.

[0133]

[0134] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0135]

[0136] Example 1

[0137] Ni in a continuous stirred reactor 0.55 Co 0.20 Mn 0.25 Transition metal precursor having a composition represented by (OH)2 (Product name: Nickel cobalt manganese hydroxide, D 50 : 16.9 μm, K90=0.39) and Li2CO3 as a lithium compound were added so that the molar ratio of (Ni+Co+Mn):Li was 1:1.07, mixed, and then calcined at 870 ℃ for 12 hours under an atmospheric environment to Li 1.06 Ni 0.55 Co 0.20 Mn 0.25 A lithium transition metal oxide having a composition represented by O2 was prepared.

[0138] Subsequently, the above lithium composite transition metal oxide Li 1.07 Ni 0.55 Co 0.20 Mn 0.25 After mixing O2 with H3BO3 as a coating raw material, the mixture was heat-treated at a temperature of 380 °C for 5 hours in an atmospheric environment to produce a positive electrode active material containing a coating portion containing boron (B) on the lithium transition metal oxide. The average particle size of the produced positive electrode active material was 16.1 μm, span (K90) = 0.39, and the crystal grain size was 100 nm.

[0139]

[0140] Example 2

[0141] In the above Example 1, a positive electrode active material was prepared by carrying out the same procedure as in Example 1, except that a transition metal precursor with K90=0.54 was used. The average particle size of the prepared positive electrode active material was 15.7 μm, span(K90)=0.57, and the crystal grain size was 102 nm.

[0142]

[0143] Example 3

[0144] A positive electrode active material was prepared in the same manner as in Example 2, except that the calcination temperature was changed to 880 ℃. The average particle size of the prepared positive electrode active material was 16.2 μm, the span (K90) was 0.54, and the crystal grain size was 123 nm.

[0145]

[0146] Comparative Example 1

[0147] A positive electrode active material was prepared in the same manner as in Example 2, except that the calcination temperature was changed to 860 ℃. The average particle size of the prepared positive electrode active material was 15.8 μm, the span (K90) was 0.57, and the crystal grain size was 91 nm.

[0148]

[0149] Comparative Example 2

[0150] A positive electrode active material was prepared in the same manner as in Example 1, except that a transition metal precursor with K90=0.73 was used in Example 1. The average particle size of the prepared positive electrode active material was 16.5 μm, the span=0.70, and the crystal grain size was 102 nm.

[0151]

[0152] Experimental Example 1 - Analysis of Cathode Active Material Particle Size Distribution

[0153] 0.02 g each of the cathode active material prepared in the examples and comparative examples was taken, and each was placed in a vial containing 5 ml of ultrapure water and 5 ml of dispersant. After dispersing the cathode active material with a sonicator for 2 minutes, it was placed in a particle size analyzer (PSA) (Malvern Mastersizer 3000) to determine the D of each cathode active material prepared in the examples and comparative examples. 10 , D 50 , D 90 Obtain the value, and D 50 Value and span value((D 90 -D 10 ) / D 50 ) is shown in Table 1 and Figure 1 below.

[0154]

[0155] Experimental Example 2 - Evaluation of Charge / Discharge Characteristics

[0156] A lithium secondary battery was manufactured using the positive active material prepared in the above examples and comparative examples, respectively.

[0157] Specifically, the positive active material, carbon black conductive material, and PVDF binder prepared in the above examples and comparative examples were mixed in a weight ratio of 96.5:1.5:2 in an N-methylpyrrolidone solvent to prepare a positive composite material, which was then coated on one side of an aluminum current collector, dried at 100°C, and rolled to produce a positive electrode.

[0158] The cathode used lithium metal.

[0159] An electrode assembly was manufactured by interposing a porous polyethylene separator between the anode and cathode manufactured as described above, and after placing the electrode assembly inside a case, a liquid electrolyte was injected into the case to manufacture a lithium secondary battery. At this time, the liquid electrolyte was prepared by dissolving 1.0 M concentration lithium hexafluorophosphate (LiPF6) in an organic solvent composed of ethylene carbonate / dimethyl carbonate / ethylmethyl carbonate (mixed volume ratio of EC / DMC / EMC = 3 / 4 / 3).

[0160] Each lithium secondary battery half cell manufactured as described above was charged at 25°C in CCCV mode at 0.2 C until it reached 4.35 V, and discharged at a constant current of 0.05 C to 2.5 V. The charge / discharge capacity and resistance were measured through the voltage change over 60 seconds. Additionally, the rate capability was measured by charging at 0.2 C until it reached 4.35 V, and discharging at constant currents of 0.2 C, 0.5 C, and 1.0 C to 2.5 V.

[0161]

[0162] Experimental Example 3 - Confirmation of SEM image of cathode active material

[0163] The positive electrode active materials prepared in the examples and comparative examples were each photographed using a Scanning Electron Microscope (SEM), and each SEM image is shown in Figures 2 to 6.

[0164]

[0165] Classification Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 PSD span (D90-D10) / D500 0.39 0.57 0.54 0.57 0.7 Grain size (nm) 100 102 1239 110 2CHC Evaluation Charge capacity (mAh / g) 201.52 01.82 02.71 99.52 01 Discharge capacity (mAh / g) 186.41 88.51 88.81 82.91 85.11 st , Cycle efficiency92.593.493.291.792.160s DCIR16.917.117.417.218.40.5 C / 0.2 C96.396.596.795.996.11.0 C / 0.2 C92.693.293.491.992.3

[0166] Referring to Table 1 above, it can be seen that the positive electrode active materials of Examples 1 to 3, which satisfy all ranges of nickel content, particle size distribution (PSD span), and crystal grain size of the present invention, exhibit excellent charge / discharge capacity, resistance characteristics, and rate capability. On the other hand, in the case of Comparative Examples 1 and 2, which do not satisfy either the particle size distribution or crystal grain size, it can be seen that the charge / discharge capacity, resistance characteristics, and rate capability are reduced compared to the Examples.

Claims

1. It comprises a polycrystalline lithium transition metal oxide having a nickel (Ni) content of 40 mol% or more and 70 mol% or less of the total transition metal content, and The average particle size (D50) is 15 μm or larger, and The particle size distribution (K90) is 0.3 or greater and less than 0.7, and A positive electrode active material having a grain size of 95 nm or more and 130 nm or less as measured by XRD (X-ray diffraction) analysis.

2. In Claim 1, The above lithium transition metal oxide particle surface further includes a coating portion, The above coating portion comprises one or more elements selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, V, Ti, Fe, Zr, Si, Y, Nb, Ga, Sn, Mo, W, P, S and combinations thereof, in a positive active material.

3. In Claim 1, The above particle size distribution (K90) is 0.5 or more and 0.6 or less, and is an anode active material.

4. In Claim 1, The above lithium transition metal oxide is a positive electrode active material containing 50 mol% or more and 60 mol% or less of Ni among the total transition metals.

5. In Claim 1, The above lithium transition metal oxide is a positive electrode active material comprising one or more transition metals selected from the group consisting of Ni, Co, and Mn.

6. In Claim 1, The above lithium transition metal oxide is a positive electrode active material in the form of secondary particles formed by the aggregation of multiple primary particles.

7. In Claim 1, The above lithium transition metal oxide is an anode active material represented by the following chemical formula 1: [Chemical Formula 1] The a Nor x Co y M1 z M2 (1-x-y-z) O2 In the above chemical formula 1 0.9≤a≤1.1, 0.5≤x≤0.6, 0.1≤y≤0.3, 0.1≤z≤0.3, 0≤1-xyz≤0.4, M1 includes at least one of Mn and Al, and M2 includes one or more selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, V, Ti, Fe, Zr, Si, Y, Nb, Ga, Sn, Mo, W, P, S, and combinations thereof.

8. In Claim 1, A positive active material having an average particle size of 15 μm or more and 20 μm or less.

9. In Claim 1, A positive active material having a crystal grain size greater than 100 nm and less than or equal to 125 nm.

10. A positive electrode for a secondary battery comprising a positive electrode active material according to Claim 1.

11. A lithium secondary battery comprising a positive electrode according to claim 10.

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