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

Abstract

The present invention relates to a positive electrode active material precursor capable of realizing a uniform single particle positive electrode active material, and specifically, the present invention relates to a positive electrode active material precursor comprising a single particle lithium transition metal oxide having a lithium to total transition metal molar ratio (Li / Me) of 0.01 to 0.7, and having a pellet density of 3.0 g / cm. 3 ~4.0g / cm 3 The present invention relates to a positive electrode active material precursor, a method for producing the same, a method for producing a positive electrode active material using the same, and the positive electrode active material.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0111520, filed September 2, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a positive electrode active material precursor, a method for producing the same, a method for producing a positive electrode active material using the same, and the positive electrode active material. [Background technology]

[0003] Recently, with the technological development and increasing demand for mobile devices and electric vehicles, the demand for secondary batteries as energy sources has been rapidly increasing. Among these secondary batteries, lithium secondary batteries, which have high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0004] Lithium transition metal oxides such as lithium cobalt oxides (LiCoO2), lithium nickel oxides (LiNiO2), lithium manganese oxides (LiMnO2 or LiMn2O4), and lithium iron phosphate oxides (LiFePO4) have been developed as positive electrode active materials for lithium secondary batteries. 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.

[0005] Lithium transition metal oxides developed to date are typically prepared by mixing a transition metal hydroxide with a lithium-containing raw material and then subjecting the mixture to high-temperature heat treatment. To prepare lithium transition metal oxide in the form of a single particle, which has better strength and thermal stability than secondary particle-type materials, the temperature during the high-temperature heat treatment is increased slightly.

[0006] However, when a lithium transition metal oxide in the form of secondary particles is prepared by mixing a conventional transition metal hydroxide with a lithium-containing raw material and then firing (over-firing) the mixture at a higher temperature to prepare a lithium transition metal oxide in the form of single particles, there is a limit to the growth of the large single particles. As a result, the average particle size of the prepared single particle positive electrode active material is not large, and the capacity retention rate of a battery containing the same is not significantly improved. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention is intended to solve the above-mentioned problems, and has an object to provide a positive electrode active material precursor that can realize a single-particle positive electrode active material that can improve the capacity retention rate of a battery.

[0008] Another object of the present invention is to provide a method for producing a positive electrode active material precursor.

[0009] Another object of the present invention is to provide a method for producing a positive electrode active material using the positive electrode active material precursor.

[0010] Finally, an object of the present invention is to provide a positive electrode active material in a single particle form that can improve the capacity retention rate of a battery. [Means for solving the problem]

[0011] The present invention provides a positive electrode active material precursor, a method for producing the same, a method for producing a positive electrode active material using the same, and the positive electrode active material.

[0012] (1) The present invention provides a lithium transition metal composite oxide in the form of a single particle, in which the molar ratio of lithium to all transition metals (Li / Me) is 0.01 to 0.7, and the pellet density is 3.0 g / cm 3 ~4.0g / cm 3 The present invention provides a positive electrode active material precursor comprising:

[0013] (2) In the present invention, in the above (1), the pellet density is 3.4 g / cm 3 ~4.0g / cm 3 The present invention provides a positive electrode active material precursor comprising:

[0014] (3) In the present invention, in the above (1) or (2), the lithium composite transition metal oxide in the form of a single particle, in which the molar ratio of lithium to the total transition metals is 0.01 to 0.7, has an average particle size (D 50 ) is 5.0 μm to 15.0 μm.

[0015] (4) The present invention provides a positive electrode active material precursor according to any one of (1) to (3), wherein the lithium composite transition metal oxide in a single particle form, in which the molar ratio of lithium to all transition metals is 0.01 to 0.7, contains 60 mol % or more of nickel relative to all transition metals other than lithium.

[0016] (5) The present invention provides a positive electrode active material precursor according to any one of (1) to (4), wherein the lithium composite transition metal oxide in a single particle form, in which the molar ratio of lithium to all transition metals is 0.01 to 0.7, has a composition represented by the following chemical formula 1: [Chemical formula 1] Li x Ni a M1 b M2 c O y In the above Chemical Formula 1, M1 is one or more selected from Co, Mn, and Al; M2 is one or more selected from B, Mg, Ca, Ti, V, Cr, Fe, Zn, Ga, Y, Zr, Nb, Mo, Ta, W, Na, and La; 0.01≦x≦0.7, 0.60≦a<1.0, 0 <b≦0.40、0≦c≦0.1、1≦y≦2、a+b+c=1である。

[0017] (6) The present invention also provides a method for producing a positive electrode active material precursor, including the steps of: (A) mixing one or more selected from composite transition metal hydroxides and composite transition metal oxyhydroxides with a lithium-containing doping material so that the molar ratio of lithium contained in the lithium-containing doping material to all transition metals contained in the one or more selected from composite transition metal hydroxides and composite transition metal oxyhydroxides is 0.01 to 0.7, to produce a mixture; and (B) firing the mixture at a temperature of 800°C to 1,200°C to produce a lithium composite transition metal oxide in the form of a single particle, in which the molar ratio of lithium to all transition metals is 0.01 to 0.7.

[0018] (7) The present invention provides a method for producing a positive electrode active material precursor according to (6), wherein the composite transition metal hydroxide and composite transition metal oxyhydroxide contain 60 mol % or more of nickel relative to the total transition metals.

[0019] (8) The present invention provides the method for producing a positive electrode active material precursor according to (6) or (7), wherein the lithium-containing doping substance is at least one selected from the group consisting of lithium carbonate, lithium hydroxide, lithium oxide, lithium sulfate, lithium chloride, lithium nitrate, lithium acetate, and lithium phosphate.

[0020] (9) The present invention provides the method for producing a positive electrode active material precursor according to any one of the above (6) to (8), wherein the firing in the step (B) is carried out in air or an oxygen atmosphere.

[0021] (10) The present invention also provides a method for producing a positive electrode active material, comprising the steps of: mixing a positive electrode active material precursor according to any one of (1) to (5) above with a lithium-containing raw material; and calcining the mixture at a temperature of 700°C to 1,100°C to produce a lithium composite transition metal oxide in a single particle form, the lithium composite transition metal oxide having a molar ratio of lithium to all transition metals of 0.9 to 1.1; and the lithium-containing raw material is mixed so that the molar ratio of total lithium contained in the positive electrode active material precursor and the lithium-containing raw material to all transition metals other than lithium contained in the positive electrode active material precursor is 0.9 to 1.1.

[0022] (11) The present invention provides the method for producing a positive electrode active material according to (10), wherein the firing is performed by primary firing at a temperature of 700°C to 1,100°C, followed by secondary firing at a temperature of 650°C to 900°C.

[0023] (12) The present invention also provides a lithium composite transition metal oxide in the form of a single particle, in which the molar ratio of lithium to all transition metals is 0.9 to 1.1, and the span value ([D 90 -D 10 ] / D 50 ) is 0.800 to 1.00, and the absolute value of the negative skewness is 0.3000 to 0.7000.

[0024] (13) The present invention provides, in the above (12), that the lithium composite transition metal oxide in which the molar ratio of lithium to the total transition metals is 0.9 to 1.1 has an average particle size (D 50 ) is 5.0 μm to 15.0 μm.

[0025] (14) The present invention provides a positive electrode active material according to (12) or (13), wherein the lithium composite transition metal oxide having a molar ratio of lithium to all transition metals of 0.9 to 1.1 contains 60 mol % or more of nickel relative to all transition metals other than lithium.

[0026] (15) The present invention provides a positive electrode active material according to any one of the above (12) to (14), wherein the lithium composite transition metal oxide in which the molar ratio of lithium to all transition metals is 0.9 to 1.1 has a composition represented by the following chemical formula 4: [Chemical formula 4] Li x’ [Ni a’ M1 b’ M2 c’ ]O2 In the above Chemical Formula 4, M1 is one or more selected from Co, Mn, and Al; M2 is one or more selected from B, Mg, Ca, Ti, V, Cr, Fe, Zn, Ga, Y, Zr, Nb, Mo, Ta, W, Na, and La; 0.9≦x'≦1.1, 0.6≦a'<1.0, 0 <b’≦0.4、0<c’≦0.1、a’+b’+c’=1である。 [Effects of the Invention]

[0027] The cathode active material produced using the cathode active material precursor according to the present invention has a single particle form, a narrow particle size distribution, and a high degree of single particle formation, and therefore can improve the capacity retention rate of a battery. [Brief explanation of the drawings]

[0028] [Figure 1] 1A is an SEM image of the positive electrode active material precursor of Example 1, and FIG. 1B is an SEM image of the positive electrode active material of Example 1. FIG. [Figure 2] 1A is an SEM image of the positive electrode active material precursor of Example 2, and FIG. 1B is an SEM image of the positive electrode active material of Example 2. [Figure 3] 1A is an SEM image of the positive electrode active material precursor of Example 3, and FIG. 1B is an SEM image of the positive electrode active material of Example 3. [Figure 4] 1A is an SEM image of the positive electrode active material precursor of Comparative Example 1, and FIG. 1B is an SEM image of the positive electrode active material of Comparative Example 1. FIG. [Figure 5]1A is an SEM image of the positive electrode active material precursor of Comparative Example 2, and FIG. 1B is an SEM image of the positive electrode active material of Comparative Example 2. FIG. [Figure 6] 1A is an SEM image of the positive electrode active material precursor of Comparative Example 3, and FIG. 1B is an SEM image of the positive electrode active material of Comparative Example 3. FIG. [Figure 7] 1A is an SEM image of the positive electrode active material precursor of Comparative Example 4, and FIG. 1B is an SEM image of the positive electrode active material of Comparative Example 4. FIG. [Figure 8] 1 shows an SEM image of a composite transition metal hydroxide having a D50 of 9 μm used in Examples 1 and 2 and Comparative Examples 1, 3, and 4. DETAILED DESCRIPTION OF THE INVENTION

[0029] The 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 as having meanings and concepts that are consistent with the technical idea of ​​the present invention, based on the principle that inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0030] In this specification, the terms "comprises," "includes," "has," and the like are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but are not intended to preclude the possible presence or addition of one or more different features, numbers, steps, components, or combinations thereof.

[0031] In this specification, D 10 , average particle size (D 50 ), D 90 can be defined as the particle diameters corresponding to 10%, 50%, and 90% of the cumulative volume in the particle size distribution curve (graph curve of particle size distribution degree), respectively. 10 , average particle size (D 50 ), D 90can be measured using, for example, the laser diffraction method. The laser diffraction method generally allows measurement of particle sizes from the submicron range to several mm, and can obtain results with high reproducibility and high resolution. 10 , average particle size (D 50 ), D 90 Specifically, it can be measured using PSA (Microtrac, S3500).

[0032] In this specification, the term "on" refers not only to a case where one structure is formed immediately on top of another structure, but also to a case where a third structure is interposed between the structures.

[0033] In this specification, the term "single particle form" refers to a concept that contrasts with the spherical secondary particle form formed by the aggregation of tens to hundreds of primary particles produced by conventional methods, and can include a form in which particles are separated and / or dispersed to form independent and / or distinct phases, or a form in which 2 to 10 particles are attached to each other, etc. That is, the single particle form can be a form consisting of only one particle or a form consisting of 2 to 10 primary particles.

[0034] In this specification, the term "primary particle" refers to the smallest unit particle observed in scanning electron microscope (SEM) measurements, and the term "secondary particle" refers to an aggregate formed by physical or chemical bonding between primary particles, i.e., a secondary structure, without any intentional aggregation or granulation process of the primary particles that make up the secondary particle.

[0035] In this specification, in a lithium transition metal composite oxide or a positive electrode active material in a single particle form, a high degree of single particle size means that, from the viewpoint of shape, the number of primary particles constituting one particle is small, and therefore the primary particles are large.

[0036] In this specification, the pellet density is a value obtained by placing 3 g of a sample in a pellet holder having a diameter of 13 mm using an Auto Pellet Press (Carver, 3887.4), adjusting the zero point, applying a force corresponding to 2000 kgf, measuring the thickness of the pellet at this point, obtaining the pellet volume, and then calculating the pellet density according to the following equation 1:

[0037] [Formula 1] Pellet density (g / cm 3 ) = Weight of positive electrode active material precursor (g) / Volume of pellet (cm 3 )

[0038] In this specification, the negative skewness of the positive electrode active material can be determined by a method of determining Pearson's asymmetry coefficient using the median, and specifically, can be determined according to the following formula 2.

[0039] [Formula 2] Negative skewness = [3 × (median − mean particle size (D 50 ))] / (standard deviation)

[0040] In the above formula 2, the median is the data value corresponding to the center (middle) of all the data of the particle size distribution, the average particle size is as described above, and the standard deviation indicates the degree of dispersion in the particle size distribution, and means the degree of dispersion based on the mode. 50 ) and the standard deviation can be measured or calculated using PSA (Microtrac, S3500).

[0041] Positive electrode active material precursor The positive electrode active material precursor according to the present invention includes a lithium composite transition metal oxide in the form of a single particle, in which the molar ratio of lithium to the total transition metals (Li / Me) is 0.01 to 0.7, and the pellet density is 3.0 g / cm. 3 ~4.0g / cm 3 is.

[0042] The present inventors have conducted extensive research to develop a positive electrode active material in a single particle form that has a narrow particle size distribution and a high degree of single particle formation. As a result, they have discovered a positive electrode active material precursor that contains a single particle form lithium composite transition metal oxide having a lithium to total transition metal molar ratio (Li / Me) of 0.01 to 0.7, and has a pellet density of 3.0 g / cm. 3 ~4.0g / cm 3 When a positive electrode active material precursor having a narrow particle size distribution and a high degree of mono-particle size is used, the average particle size (D 50 ) can produce various single particle shaped positive electrode active materials, and have completed the present invention.

[0043] The lithium composite transition metal oxide contained in the positive electrode active material precursor of the present invention has a molar ratio of lithium to all transition metals (Li / Me) of 0.01 to 0.7, and has a single particle form due to the resulting flux effect. Specifically, the lithium composite transition metal oxide contained in the positive electrode active material precursor in a single particle form may have a molar ratio of lithium to all transition metals (Li / Me) of 0.01 or more, 0.03 or more, 0.3 or less, 0.5 or less, or 0.7 or less.

[0044] On the other hand, in the case of a lithium composite transition metal oxide in which the molar ratio of lithium to the total transition metal (Li / Me) is less than 0.01, the flux effect does not occur, so it does not have a single particle form, and its volume is about 20% smaller than that of the composite transition metal hydroxide positive electrode active material precursor, and its average particle size (D 50 Furthermore, in the case of a lithium composite transition metal oxide in which the molar ratio of lithium to all transition metals (Li / Me) is greater than 0.7, the oxide has a single particle form, but in this case, the amount of lithium-containing raw material that can be used in the process of stoichiometrically mixing a cathode active material precursor with a lithium-containing raw material and then calcining the mixture to produce a cathode active material is reduced, making it difficult to form a structurally stable cathode active material, resulting in a problem of reduced electrochemical performance.

[0045] The positive electrode active material precursor according to the present invention has a pellet density of 3.0 g / cm 3 ~4.0g / cm 3 In this case, the density of the cathode active material produced using the cathode active material precursor is high, and thus particle cracking does not occur even when high pressure is applied in the rolling process during electrode fabrication, thereby achieving high energy density. Specifically, the cathode active material precursor has a pellet density of 3 g / cm. 3 More than 3.1g / cm 3 More than 3.2g / cm 3 More than 3.3g / cm 3 More than 3.4g / cm 3 More than 3.8g / cm 3 Below, 3.9g / cm 3 Below, 4.0g / cm 3 It can be:

[0046] On the other hand, the pellet density of the positive electrode active material precursor is 3.0 g / cm 3 If the density is less than 4.0 g / cm, the density of the positive electrode active material prepared using the positive electrode active material precursor is low, particle cracking is likely to occur during the rolling process when preparing the electrode, and a high energy density cannot be achieved. 3 In the case of a cathode active material precursor exceeding 1000 kJ / cm 2 , the density of the cathode active material produced using the cathode active material precursor is too high, and the cathode active material is not mixed with the conductive material during electrode production, resulting in the problem of agglomeration of the cathode active material particles.

[0047] According to the present invention, the lithium composite transition metal oxide in the form of a single particle, in which the molar ratio of lithium to the total transition metals (Li / Me) is 0.01 to 0.7, has an average particle size (D 50 Specifically, the average particle diameter (D) of the lithium composite transition metal oxide in the form of a single particle, in which the molar ratio of lithium to the total transition metals (Li / Me) is 0.01 to 0.7, may be 5.0 μm to 15.0 μm. 50) may be 5.0 μm or more, 6.0 μm or more, 7.0 μm or more, 8.0 μm or more, 12.0 μm or less, 13.0 μm or less, 14.0 μm or less, or 15.0 μm or less. In this case, an electrode including a cathode active material prepared using the cathode active material precursor according to the present invention has a high density and can achieve a high energy density.

[0048] According to the present invention, the lithium transition metal composite oxide in the form of single particles, having a lithium to total transition metal molar ratio (Li / Me) of 0.01 to 0.7, may contain 60 mol % or more of nickel relative to the total transition metals other than lithium, and specifically, may have a composition represented by the following Chemical Formula 1. In this case, the high nickel content reduces the potential of the positive electrode active material within the same voltage, thereby enabling high capacity to be achieved.

[0049] [Chemical formula 1] Li x Ni a M1 b M2 c O y

[0050] In the above Chemical Formula 1, M1 is one or more selected from Co, Mn, and Al; M2 is one or more selected from B, Mg, Ca, Ti, V, Cr, Fe, Zn, Ga, Y, Zr, Nb, Mo, Ta, W, Na, and La; 0.01≦x≦0.7, 0.60≦a<1.0, 0 <b≦0.40、0≦c≦0.1、1≦y≦2、a+b+c=1である。

[0051] Method for producing a positive electrode active material precursor The method for producing a positive electrode active material precursor according to the present invention includes the steps of: (A) mixing one or more selected from composite transition metal hydroxides and composite transition metal oxyhydroxides with a lithium-containing doping material so that the molar ratio (Li / Me) of lithium contained in the lithium-containing doping material to all transition metals contained in the one or more selected from composite transition metal hydroxides and composite transition metal oxyhydroxides is 0.01 to 0.7, thereby producing a mixture; and (B) firing the mixture at a temperature of 800°C to 1200°C, thereby producing a lithium composite transition metal oxide in the form of a single particle, in which the molar ratio (Li / Me) of lithium to all transition metals is 0.01 to 0.7.

[0052] The cathode active material precursor prepared by the method for preparing a cathode active material precursor may be the cathode active material precursor according to the present invention, that is, the cathode active material precursor includes a lithium composite transition metal oxide in the form of a single particle having a lithium to total transition metal molar ratio (Li / Me) of 0.01 to 0.7 and a pellet density of 3.0 g / cm. 3 ~4.0g / cm 3 The positive electrode active material precursor may be

[0053] The present inventors have found that an oxide precursor prepared by adding a specific amount of a lithium-containing doping material has a higher density than a conventional cathode active material precursor, and that a cathode active material prepared using the cathode active material precursor prepared according to the present invention has a narrow particle size distribution and a single-particle morphology with a high degree of single particle size, thereby completing the present invention.

[0054] Hereinafter, the method for producing the positive electrode active material precursor will be specifically described step by step.

[0055] (A) Step The step (A) is a step of producing a mixture by mixing one or more selected from composite transition metal hydroxides and composite transition metal oxyhydroxides with a lithium-containing doping material so that the molar ratio (Li / Me) of lithium contained in the lithium-containing doping material to all transition metals contained in the one or more selected from composite transition metal hydroxides and composite transition metal oxyhydroxides is 0.01 to 0.7.

[0056] The present invention is characterized in that one or more selected from composite transition metal hydroxides and composite transition metal oxyhydroxides are mixed with a lithium-containing doping material so that the molar ratio (Li / Me) of lithium contained in the lithium-containing doping material to all transition metals contained in the one or more selected from the composite transition metal hydroxides and composite transition metal oxyhydroxides is 0.01 to 0.7, so that the resulting positive electrode active material precursor contains a lithium composite transition metal oxide in the form of a single particle having a molar ratio (Li / Me) of lithium to all transition metals contained in the one or more selected from the composite transition metal hydroxides and composite transition metal oxyhydroxides of 0.01 to 0.7.

[0057] On the other hand, when one or more selected from composite transition metal hydroxides and composite transition metal oxyhydroxides are mixed with a lithium-containing doping material so that the molar ratio (Li / Me) of lithium contained in the lithium-containing doping material to the total transition metals contained in the one or more selected from composite transition metal hydroxides and composite transition metal oxyhydroxides is less than 0.01, the primary particles do not grow much during the firing in step (B), and an oxide (precursor) in the form of a single particle is not formed, resulting in a problem that the boundaries of the primary particles remain (remain). Furthermore, when one or more selected from composite transition metal hydroxides and composite transition metal oxyhydroxides are mixed with a lithium-containing doping material so that the molar ratio (Li / Me) of lithium contained in the lithium-containing doping material to the total transition metals contained in the one or more selected from the composite transition metal hydroxides and composite transition metal oxyhydroxides is greater than 0.7, for example, 0.9, an oxide (precursor) in the form of a single particle is produced after the firing in step (B). However, in this case, the amount of lithium-containing raw material that can be used in the process of producing a positive electrode active material by mixing the positive electrode active material precursor and the lithium-containing raw material according to stoichiometry and then firing the mixture is reduced. As a result, it is difficult to form a structurally stable positive electrode active material, resulting in a problem of reduced electrochemical performance.

[0058] According to the present invention, in order to achieve a high energy density, the composite transition metal hydroxide and composite transition metal oxyhydroxide can contain 60 mol % or more of nickel relative to the total transition metals.

[0059] The composite transition metal hydroxide may have a composition represented by the following Chemical Formula 2, and the composite transition metal oxyhydroxide may have a composition represented by the following Chemical Formula 3.

[0060] [Chemical formula 2] Ni a2 M1 b2 M2 c2 (OH)2

[0061] In the above Chemical Formula 2, M1 is at least one selected from Co, Mn, and Al, M2 is at least one selected from B, Mg, Ca, Ti, V, Cr, Fe, Zn, Ga, Y, Zr, Nb, Mo, Ta, W, Na, and La, and 0.60≦a2<1.0, 0 <b2≦0.40、0≦c2≦0.1、a2+b2+c2=1である。

[0062] [Chemical formula 3] Ni a2 M1 b2 M2 c2 O.O.H.

[0063] In the above Chemical Formula 3, M1 is at least one selected from Co, Mn, and Al, M2 is at least one selected from B, Mg, Ca, Ti, V, Cr, Fe, Zn, Ga, Y, Zr, Nb, Mo, Ta, W, Na, and La, and 0.60≦a2<1.0, 0 <b2≦0.40、0≦c2≦0.1、a2+b2+c2=1である。

[0064] According to the present invention, the lithium-containing doping material may be at least one selected from the group consisting of lithium carbonate, lithium hydroxide, lithium oxide, lithium sulfate, lithium chloride, lithium nitrate, lithium acetate, and lithium phosphate. Specifically, the lithium-containing doping material may be Li2CO3, LiOH, or a combination thereof.

[0065] (B) Step Step (B) is a step of calcining the mixture at a temperature of 800°C to 1,200°C to produce a lithium composite transition metal oxide in the form of a single particle having a lithium to total transition metal molar ratio (Li / Me) of 0.01 to 0.7. By calcining the mixture at a temperature of 800°C to 1,200°C, a lithium composite transition metal oxide in the form of a single particle having a lithium to total transition metal molar ratio (Li / Me) of 0.01 to 0.7 can be obtained. Specifically, the calcination in step (B) can be carried out at a temperature of 800°C or higher, 850°C or higher, 900°C or higher, 950°C or higher, 1,000°C or lower, 1,050°C or lower, 1,100°C or lower, 1,150°C or lower, or 1,200°C or lower.

[0066] On the other hand, if the mixture is fired at a temperature below 800°C, the lithium-containing doping material remains on the surface without dissolving, preventing particle growth (expansion), while if fired at a temperature above 1,200°C, the mixture is overfired, forming the lithium composite transition metal oxide phase as the energetically most stable NiO-phase, but it is difficult to recrystallize the NiO-phase into an ideal layered structure. Furthermore, the commonly used alumina crucible may be degraded, resulting in the formation of undesired substances.

[0067] According to the present invention, the firing in step (B) can be carried out in air or an oxygen atmosphere.

[0068] The firing in step (B) may be carried out for 1 hour to 20 hours.

[0069] Method for producing positive electrode active material A method for producing a cathode active material according to the present invention includes the steps of: mixing a cathode active material precursor according to the present invention with a lithium-containing raw material such that the molar ratio of the total lithium contained in the cathode active material precursor and the lithium-containing raw material to the total transition metals other than lithium contained in the cathode active material precursor is 0.9 to 1.1; and calcining the mixture at a temperature of 700°C to 1,100°C to produce a lithium composite transition metal oxide in the form of a single particle having a lithium to total transition metal molar ratio (Li / Me) of 0.9 to 1.1. When the calcination temperature is 700°C to 1,100°C, the NiO-phase can be recrystallized stably into a layered structure. On the other hand, when the calcination temperature in the cathode active material production step is less than 700°C, there is a problem that recrystallization does not occur due to insufficient thermal energy; when the calcination temperature is more than 1,100°C, there is a problem that a stable layered structure cannot be formed.

[0070] The lithium-containing raw material may be at least one selected from lithium carbonate, lithium hydroxide, lithium oxide, lithium sulfate, lithium chloride, lithium nitrate, lithium acetate, lithium phosphate, and hydrates thereof. Specifically, the lithium-containing raw material may be at least one selected from lithium carbonate, lithium hydroxide, lithium oxide, and hydrates thereof, more specifically, at least one selected from lithium carbonate, lithium hydroxide, and hydrates thereof. In this case, the reactivity between the lithium-containing raw material and a precursor having a high atomic fraction of nickel among the metal elements in the precursor may be improved. Furthermore, since the gases generated during the calcination process are CO2 and HO, they are non-toxic and can be easily removed.

[0071] According to the present invention, the lithium-containing raw material is mixed so that the molar ratio of the total lithium contained in the cathode active material precursor and the lithium-containing raw material to the total transition metals other than lithium contained in the cathode active material precursor is 0.9 to 1.1. In this case, the resulting cathode active material has an ideal layered structure, which can provide excellent electrochemical performance.

[0072] On the other hand, if the lithium-containing raw material is mixed so that the molar ratio of the total lithium contained in the cathode active material precursor and the lithium-containing raw material to the total transition metals other than lithium contained in the cathode active material precursor is less than 0.9, the resulting cathode active material will have insufficient lithium in its structure, resulting in a reduced amount of reversibly movable lithium and therefore problems with electrochemical performance. Also, if the lithium-containing raw material is mixed so that the molar ratio of the total lithium contained in the cathode active material precursor and the lithium-containing raw material to the total transition metals other than lithium contained in the cathode active material precursor is greater than 1.1, the lithium-containing raw material that remains unreacted with the precursor will be present on the surface of the cathode active material and interact with lithium by-products, resulting in gelation of the electrode slurry during electrode fabrication and increased gas generation in the battery.

[0073] According to the present invention, the firing in the method for producing the positive electrode active material may include primary firing at a temperature of 800°C to 1,100°C, followed by secondary firing at a temperature of 700°C to 900°C. Specifically, the firing may be performed in one of the following ways: i) primary firing at a temperature of 800°C to 1,100°C, followed immediately by adjusting the temperature to 700°C to 900°C and secondary firing at 700°C to 900°C; or ii) primary firing at a temperature of 800°C to 1,100°C, followed by lowering the temperature to room temperature and then raising the temperature to 700°C to 900°C. Here, the secondary firing temperature may be lower than the primary firing temperature. Meanwhile, when the firing is performed as in ii), more specifically, the firing may be performed by primary firing at a temperature of 800°C to 1,000°C, pulverizing the primary fired product, and then secondary firing at a temperature of 750°C to 850°C.

[0074] In the method for preparing the positive electrode active material, the firing may be performed in air or an oxygen atmosphere, and thus the primary firing and secondary firing may also be performed in air or an oxygen atmosphere.

[0075] The calcination in the method for producing the positive electrode active material may be performed for a time sufficient to form a stable layer structure, specifically, for 3 to 20 hours. The primary calcination may be performed for 3 to 20 hours, and the secondary calcination may be performed for 3 to 20 hours.

[0076] The cathode active material prepared by the method for preparing the cathode active material includes a lithium transition metal oxide in a single particle form having a lithium to total transition metal molar ratio (Li / Me) of 0.9 to 1.1, and can have a narrow particle size distribution and a high degree of single particle formation.

[0077] The positive electrode active material manufactured by the method for manufacturing the positive electrode active material has a span value ([D 90 -D 10 ] / D 50 ) may be 0.800 to 1.00. The cathode active material produced by the method for producing a cathode active material may have an absolute value of negative skewness of 0.3000 to 0.7000. The cathode active material produced by the method for producing a cathode active material may have a composition represented by the following chemical formula 4:

[0078] [Chemical formula 4] Li x’ [Ni a’ M1 b’ M2 c’ ]O2

[0079] In the above Chemical Formula 4, M1 is at least one selected from Co, Mn, and Al, M2 is at least one selected from B, Mg, Ca, Ti, V, Cr, Fe, Zn, Ga, Y, Zr, Nb, Mo, Ta, W, Na, and La, and 0.9≦x′≦1.1, 0.6≦a′<1.0, 0 <b’≦0.4、0<c’≦0.1、a’+b’+c’=1である。

[0080] positive electrode active material The positive electrode active material according to the present invention includes a lithium composite transition metal oxide in the form of a single particle, in which the molar ratio of lithium to the total transition metals (Li / Me) is 0.9 to 1.1, and has a span value ([D 90 -D 10 ] / D 50 ) is 0.800 to 1.00, and the absolute value of the negative skewness is 0.3000 to 0.7000. The positive electrode active material has a narrow particle size distribution and a high degree of monoparticulation, which can improve the performance of a battery when applied to the battery. In particular, the capacity retention rate can be further improved.

[0081] The cathode active material according to the present invention is a cathode active material prepared using the cathode active material precursor according to the present invention, and may be prepared by the method for preparing the cathode active material according to the present invention.

[0082] According to the present invention, the lithium composite transition metal oxide in the form of a single particle, in which the molar ratio of lithium to the total transition metals (Li / Me) is 0.9 to 1.1, has an average particle size (D 50 Specifically, the average particle diameter (D) of the lithium composite transition metal oxide in the form of a single particle, in which the molar ratio of lithium to the total transition metals (Li / Me) is 0.9 to 1.1, may be 7.0 μm to 13.0 μm. 50 ) may be 7.0 μm or more, 7.1 μm or more, 7.2 μm or more, 10.0 μm or less, 11.0 μm or less, 12.0 μm or less, or 13.0 μm or less. In this case, the density of the electrode including the positive electrode active material is high, and a high energy density can be achieved.

[0083] According to the present invention, the lithium transition metal composite oxide in the form of single particles, having a lithium to total transition metal molar ratio (Li / Me) of 0.9 to 1.1, may contain 60 mol % or more of nickel relative to the total transition metals other than lithium, and specifically, may have a composition represented by the following chemical formula 4. In this case, the high nickel content reduces the potential of the positive electrode active material at the same voltage, thereby enabling high capacity to be achieved.

[0084] [Chemical formula 4] Lix’ [Ni a’ M1 b’ M2 c’ ]O2

[0085] In the above Chemical Formula 4, M1 is one or more selected from Co, Mn, and Al; M2 is one or more selected from B, Mg, Ca, Ti, V, Cr, Fe, Zn, Ga, Y, Zr, Nb, Mo, Ta, W, Na, and La; 0.9≦x'≦1.1, 0.6≦a'<1.0, 0 <b’≦0.4、0<c’≦0.1、a’+b’+c’=1である。

[0086] positive electrode The present invention also provides a positive electrode for a lithium secondary battery, which contains the positive electrode active material produced by the above-described method.

[0087] Specifically, the positive electrode includes 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 including the positive electrode active material.

[0088] The positive electrode current collector may be any conductive material that does not cause chemical changes in the battery, and may be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like. The positive electrode 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 enhance adhesion of the positive electrode active material. The positive electrode current collector may be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0089] The positive electrode active material layer may contain a conductive material and a binder in addition to the positive electrode active material.

[0090] The positive electrode active material may be included in an amount of 80 wt % to 99 wt %, more specifically 85 wt % to 98 wt %, based on the total weight of the positive electrode active material layer, and excellent capacity characteristics can be exhibited when included in this range.

[0091] The conductive material is used to impart conductivity to the electrode. Any material that does not cause chemical changes in the resulting battery and has electronic conductivity can be used without particular limitations. 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 fiber; metal powder or metal fiber, such as copper, nickel, aluminum, and silver; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and conductive polymers, such as polyphenylene derivatives. These materials may be used alone or in combination. The conductive material may be present in an amount of 1 wt % to 30 wt % based on the total weight of the positive electrode active material layer.

[0092] The binder serves to improve adhesion between positive electrode active material particles and between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. One or more of these may be used alone or in combination. The binder may be included in an amount of 1 wt% to 30 wt% based on the total weight of the positive electrode active material layer.

[0093] The positive electrode can be manufactured by a conventional method for manufacturing a positive electrode, except for using the positive electrode active material described above. Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, which is prepared by dissolving or dispersing the positive electrode active material described above and, optionally, a binder and a conductive material in a solvent, onto a positive electrode current collector, followed by drying and rolling. In this case, the types and contents of the positive electrode active material, binder, and conductive material are as described above.

[0094] The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and may be used alone or in combination. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, and to provide a viscosity that allows excellent thickness uniformity during subsequent application to fabricate a positive electrode, taking into consideration the coating thickness of the slurry and manufacturing yield.

[0095] Alternatively, the positive electrode can be produced by casting the composition for forming a positive electrode active material layer on a separate support, peeling the composition from the support, and laminating the resulting film on a positive electrode current collector.

[0096] Lithium secondary battery The present invention also provides an electrochemical device including the positive electrode. The electrochemical device may be, for example, a battery or a capacitor, and more specifically, a lithium secondary battery.

[0097] Specifically, the lithium secondary battery includes a positive electrode, a negative electrode facing the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is as described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0098] The lithium secondary battery may further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0099] In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0100] The negative electrode current collector may be any material that does not cause chemical changes in the battery and has high conductivity, and examples of such materials include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surfaces treated with carbon, nickel, titanium, silver, or the like, and aluminum-cadmium alloys. The negative electrode current collector typically has a thickness of 3 μm to 500 μm. As with the positive electrode current collector, the current collector may have fine irregularities on its surface to enhance the binding strength of the negative electrode active material. The negative electrode current collector may be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0101] The negative electrode active material layer includes a negative electrode active material, and optionally a binder and a conductive material.

[0102] The negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium. Specific examples thereof 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, and Al alloys; and SiO. βExamples of the negative electrode active material include metal oxides capable of doping and dedoping lithium, such as SnO2, vanadium oxide, and lithium vanadium oxide (0<β<2); and composites containing the metallic compounds and carbonaceous materials, such as Si-C composites and Sn-C composites. These may be used alone or in combination. A thin film of metallic lithium may also be used as the negative electrode active material. The carbon material may be either low-crystalline carbon or high-crystalline carbon. Typical low-crystalline carbons are soft carbon and hard carbon, while typical high-crystalline carbons are amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature-fired carbons such as petroleum or coal tar pitch-derived cokes.

[0103] The negative electrode active material may be contained in an amount of 80 wt % to 99 wt % based on the total weight of the negative electrode active material layer.

[0104] The binder is a component that facilitates bonding between the conductive material, active material, and current collector, and is typically added in an amount of 0.1 to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0105] The 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 wt % or less, specifically 5 wt % or less, based on the total weight of the negative electrode active material layer. The conductive material is not particularly limited as long as it does not cause chemical changes in the battery and has conductivity. Examples of the conductive material include graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber and metal fiber; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0106] The negative electrode active material layer can be produced by coating a negative electrode composite, which is prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material, in a solvent, on a negative electrode current collector and drying the coating. Alternatively, the negative electrode composite can be produced by casting the negative electrode composite on a separate support, peeling it off from the support, and laminating the resulting film on the negative electrode current collector.

[0107] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without particular limitation. In particular, a separator that exhibits low resistance to ion movement of the electrolyte and excellent electrolyte impregnation ability is preferred. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof can be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. To ensure heat resistance or mechanical strength, a separator coated with a ceramic component or a polymer material can also be used, and can be selectively used in a single-layer or multi-layer structure.

[0108] Furthermore, examples of the electrolyte used in the present invention include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the production of lithium secondary batteries, but are not limited to these.

[0109] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0110] The organic solvent may be any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether and tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate. Examples of suitable solvents include carbonate-based solvents such as ethylene carbonate (PC), alcohol-based solvents such as ethyl alcohol and isopropyl alcohol, nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may contain a double-bonded aromatic ring or an ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, and sulfolanes. Among these, carbonate-based solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with low viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) are more preferred, as they have high ionic conductivity and a high dielectric constant, which can enhance the charge / discharge performance of batteries. In this case, the cyclic carbonate and linear carbonate are mixed in a volume ratio of about 1:1 to about 1:9, which allows the electrolyte to exhibit excellent performance.

[0111] The lithium salt can be any compound capable of providing lithium ions used in lithium secondary batteries. Specifically, examples of the lithium salt include LiPF, LiClO, LiAsF, LiBF, LiSbF, LiAlO, LiAlCl, LiCF, SO, LiCF, SO, LiN(CF, SO), LiN(CF, SO), LiN(CF, SO), LiCl, LiI, and LiB(C, O) . The lithium salt is preferably used in a concentration range of 0.1 M to 2.0 M. When the lithium salt concentration falls within this range, the electrolyte has appropriate conductivity and viscosity, resulting in excellent electrolyte performance and efficient lithium ion migration.

[0112] In addition to the electrolyte components, the electrolyte may further contain one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, to improve battery life characteristics, suppress battery capacity reduction, and improve battery discharge capacity. In this case, the additives may be contained in an amount of 0.1 wt % to 5 wt % based on the total weight of the electrolyte.

[0113] As described above, the lithium secondary battery including the cathode active material according to the present invention stably exhibits excellent cycle characteristics and is therefore useful in portable devices such as mobile phones, notebook computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0114] Therefore, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0115] The battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and an electric vehicle (PHEV), including a plug-in hybrid electric vehicle; or a power storage system.

[0116] The external shape of the lithium secondary battery of the present invention is not particularly limited, and may be a cylindrical shape using a can, a square shape, a pouch shape, a coin shape, or the like.

[0117] 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 also as a unit battery for a medium- to large-sized battery module including a large number of battery cells.

[0118] While the present invention may be embodied in various different forms, it is to be understood that the invention is not limited to the specific embodiments set forth herein, and that the invention may be embodied in various different forms without departing from the spirit or scope of the present invention.

[0119] Examples and Comparative Examples Example 1 Ni 0.96 Co 0.03 Mn 0.01 Complex transition metal hydroxide (D 50 :9μm) and LiOH, a lithium-containing doping material, were mixed using an acoustic mixer so that the molar ratio (Li / Me) of lithium (Li) contained in the LiOH to the total transition metals (Me) contained in the composite transition metal hydroxide was 0.3, to prepare a mixture.

[0120] The mixture was baked at 1,020°C for 9 hours in an air atmosphere to form Li 0.3 Ni 0.96 Co 0.03 Mn 0.01 O 1.3 A lithium composite transition metal oxide in the form of a single particle having a composition represented by the following formula (hereinafter referred to as positive electrode active material precursor A) was produced.

[0121] The positive electrode active material precursor A and LiOH were mixed so that the molar ratio (Li' / Me') of the total lithium contained in the positive electrode active material precursor and the LiOH to the total transition metals (Me') other than lithium contained in the positive electrode active material precursor was 1.0, and the mixture was subjected to primary firing at 830°C for 12 hours in an oxygen atmosphere, followed by pulverization using a jet mill and secondary firing at 770°C for 12 hours in an oxygen atmosphere to obtain LiNi 0.96 Co 0.03 Mn 0.01 A positive electrode active material A was prepared, which was a lithium composite transition metal oxide in the form of a single particle and having a composition represented by O2.

[0122] For reference, the total number of moles of lithium contained in the positive electrode active material precursor and the LiOH is the sum of the number of moles of lithium contained in the positive electrode active material precursor and the number of moles of lithium contained in the LiOH.

[0123] Example 2 Ni 0.96 Co 0.03 Mn 0.01 Complex transition metal hydroxide (D 50 The same procedure as in Example 1 was used to prepare a mixture, except that Li was mixed with LiOH as a lithium-containing dopant using an acoustic mixer so that the molar ratio (Li / Me) of lithium contained in the LiOH to the total transition metals contained in the composite transition metal hydroxide was 0.5. 0.5 Ni 0.96 Co 0.03 Mn 0.01 O 1.5A lithium transition metal composite oxide in the form of a single particle having a composition represented by the following formula (hereinafter referred to as positive electrode active material precursor B) was produced.

[0124] The same method as in Example 1 was used except that the positive electrode active material precursor B was used. 0.96 Co 0.03 Mn 0.01 A positive electrode active material B was prepared, which was a single particle lithium composite transition metal oxide having a composition represented by O2.

[0125] Example 3 Ni 0.96 Co 0.03 Mn 0.01 Complex transition metal hydroxide (D 50 The same procedure as in Example 1 was used to prepare a mixture, except that Li was mixed with LiOH as a lithium-containing dopant using an acoustic mixer so that the molar ratio (Li / Me) of lithium contained in the LiOH to the total transition metals contained in the composite transition metal hydroxide was 0.3. 0.3 Ni 0.96 Co 0.03 Mn 0.01 O 1.3 A lithium composite transition metal oxide in the form of a single particle having a composition represented by the following formula (hereinafter referred to as positive electrode active material precursor C) was produced.

[0126] The same method as in Example 1 was used except that the positive electrode active material precursor C was used. 0.96 Co 0.03 Mn 0.01 A positive electrode active material C was prepared, which was a single particle lithium composite transition metal oxide having a composition represented by O2.

[0127] Comparative Example 1 Ni 0.96 Co 0.03 Mn 0.01 Complex transition metal hydroxide (D 50 : 9μm) was baked at 1,020℃ for 9 hours in an air atmosphere, 0.96 Co 0.03 Mn 0.01A composite transition metal oxide having a composition represented by O (hereinafter referred to as positive electrode active material precursor D) was produced.

[0128] The positive electrode active material precursor D and LiOH were mixed so that the molar ratio (Li' / Me') of lithium contained in the LiOH to all transition metals other than lithium contained in the positive electrode active material precursor was 1.0, and the mixture was subjected to primary firing at 830°C for 12 hours in an oxygen atmosphere, followed by pulverization using a jet mill and secondary firing at 770°C for 12 hours in an oxygen atmosphere to obtain LiNi 0.96 Co 0.03 Mn 0.01 A positive electrode active material D was prepared, which was a lithium composite transition metal oxide in the form of a single particle and having a composition represented by O2.

[0129] Comparative Example 2 Ni 0.96 Co 0.03 Mn 0.01 Complex transition metal hydroxide (D 50 : 6μm) was baked at 1,020℃ for 9 hours in an air atmosphere, 0.96 Co 0.03 Mn 0.01 A composite transition metal oxide having a composition represented by O (hereinafter referred to as positive electrode active material precursor E) was produced.

[0130] The positive electrode active material precursor E and LiOH were mixed so that the molar ratio (Li' / Me') of lithium contained in the LiOH to all transition metals other than lithium contained in the positive electrode active material precursor was 1.0, and the mixture was subjected to primary firing at 830°C for 12 hours in an oxygen atmosphere, followed by pulverization using a jet mill and secondary firing at 770°C for 12 hours in an oxygen atmosphere to obtain LiNi 0.96 Co 0.03 Mn 0.01 A positive electrode active material E was prepared, which was a single particle lithium transition metal composite oxide having a composition represented by O2.

[0131] Comparative Example 3 Ni 0.96 Co 0.03 Mn 0.01Complex transition metal hydroxide (D 50 The same procedure as in Example 1 was used to prepare a mixture, except that Li was mixed with LiOH as a lithium-containing dopant using an acoustic mixer so that the molar ratio (Li / Me) of lithium contained in the LiOH to the total transition metals contained in the composite transition metal hydroxide was 0.005. 0.005 Ni 0.96 Co 0.03 Mn 0.01 O 1.005 A lithium transition metal composite oxide in the form of a single particle having a composition represented by the following formula (hereinafter referred to as positive electrode active material precursor F) was produced.

[0132] The same method as in Example 1 was used except that the positive electrode active material precursor F was used. 0.96 Co 0.03 Mn 0.01 A positive electrode active material F was prepared, which was a lithium composite transition metal oxide in the form of a single particle and had a composition represented by O2.

[0133] Comparative Example 4 Ni 0.96 Co 0.03 Mn 0.01 Complex transition metal hydroxide (D 50 The same procedure as in Example 1 was used to prepare a mixture, except that Li was mixed with LiOH as a lithium-containing dopant using an acoustic mixer so that the molar ratio (Li / Me) of lithium contained in the LiOH to the total transition metals contained in the composite transition metal hydroxide was 0.9. 0.9 Ni 0.96 Co 0.03 Mn 0.01 O 1.9 A lithium composite transition metal oxide in the form of a single particle having a composition represented by the following formula (hereinafter referred to as positive electrode active material precursor G) was produced.

[0134] The same method as in Example 1 was used except that the positive electrode active material precursor G was used. 0.96 Co 0.03 Mn 0.01A positive electrode active material G was prepared, which was a single particle lithium composite transition metal oxide having a composition represented by O2.

[0135] Experimental Example Experimental Example 1 Using an SEM (Inspect F manufactured by FEI), SEM images of the positive electrode active material precursors and positive electrode active materials of Examples 1 to 3 and Comparative Examples 1 to 4 were measured and are shown in FIGS. 1 to 7. 50 The SEM image of the composite transition metal hydroxide with a particle size of 9 μm was measured and is shown in FIG.

[0136] Experimental Example 2 Using an Auto Pellet Press (Carver, 3887.4), 3 g of each of the positive electrode active material precursors of Examples 1 to 3 and Comparative Examples 1 to 4 was taken and placed in a pellet holder having a diameter of 13 mm. After adjusting the zero point, a force corresponding to 2000 kgf was applied, and the thickness at this point was measured to obtain the pellet volume. The pellet density was then calculated according to the following Equation 1, and is shown in Table 1 below.

[0137] [Formula 1] Pellet density (g / cm 3 ) = Weight of positive electrode active material precursor (g) / Volume of pellet (cm 3 )

[0138] Experimental Example 3 The average particle size (D 50 ) were obtained and are shown in Table 1 below.

[0139] In addition, the D of each of the positive electrode active materials of Examples 1 to 3 and Comparative Examples 1 to 4 10 , average particle size (D 50 ), D 90 , we obtain a negative skewness and the average particle size (D 50 ), the span value and the absolute value of the negative skewness are shown in Table 1 below.

[0140] [Table 1]

[0141] Experimental Example 4 Positive electrode slurries were prepared by mixing the positive electrode active materials prepared in Examples 1 to 3 and Comparative Examples 1 to 4, carbon black conductive material, and polyvinylidene fluoride (PVDF) binder in a ratio of 96:2:2 in N-methylpyrrolidone (NMP) solvent. The positive electrode slurries were applied to one side of an aluminum current collector, dried at 130°C, and rolled to prepare positive electrodes.

[0142] A lithium metal electrode was used as the negative electrode, and a porous polyethylene separator was interposed between the positive and negative electrodes to prepare an electrode assembly. The electrode assembly was then placed inside a battery case, and an electrolyte solution was injected into the case to prepare a half-cell. The electrolyte solution was prepared by dissolving 1.0 m LiPF6 in an organic solvent containing ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a volume ratio of 3:4:3.

[0143] Each half-cell thus prepared was charged to 4.25 V at 0.1 C-rate in CC-CV mode at 25°C, and discharged to 2.5 V at 0.1 C-rate, while measuring the initial charge capacity and initial discharge capacity, and calculating the initial efficiency, which is shown in Table 2 below. For reference, the initial efficiency value is the percentage of the initial discharge capacity to the initial charge capacity.

[0144] Furthermore, the capacity of the lithium secondary battery was measured by repeating 50 charge-discharge cycles at 45°C in the range of 2.5 to 4.25 V, with charging at a 0.5 C-rate and discharging at a 1.0 C-rate. The capacity retention rate was calculated as the percentage of the 50th cycle discharge capacity relative to the 1st cycle discharge capacity, and is shown in Table 2 below.

[0145] [Table 2]

[0146] Referring to the SEM images and Tables 1 and 2, the positive electrode active material precursor contains a lithium composite transition metal oxide in the form of a single particle, in which the molar ratio of lithium to the total transition metals (Li / Me) is 0.01 to 0.7, and the pellet density is 3.0 g / cm. 3 ~4.0g / cm 3 When a positive electrode active material precursor having a narrow particle size distribution and a high degree of mono-particle size is used, the average particle size (D 50 ) can produce positive electrode active materials with various single particle forms. In addition, the positive electrode active materials of Examples 1 to 3 have narrow particle size distributions and high degrees of single particle formation, and when applied to a battery, they can improve the performance of the battery, particularly the capacity retention rate.

[0147] Specifically, the lithium composite transition metal oxide has a single particle form and a lithium to total transition metal molar ratio (Li / Me) in the range of 0.01 or 0.7, and has a pellet density of 3.0 g / cm 3 ~4.0g / cm 3 It can be seen that the positive electrode active materials of Examples 1 and 2 prepared using the positive electrode active material precursor having a molar ratio of lithium to the total transition metals (Li / Me) in the range of 0.01 or 0.7 have excellent capacity retention rates due to an increased degree of single particle formation, compared to the positive electrode active material of Comparative Example 1. In addition, the positive electrode active materials of Examples 1 and 2 contain a single particle lithium composite transition metal oxide having a molar ratio of lithium to the total transition metals (Li / Me) in the range of 0.01 or 0.7, and have a pellet density of 3.0 g / cm. 3 ~4.0g / cm 3 It can be confirmed that the positive electrode active material of Example 3, which was produced using a positive electrode active material precursor within this range, has a superior capacity retention rate due to an increased degree of monoparticulation compared to the positive electrode active material of Comparative Example 2.

[0148] It can also be seen that the positive electrode active materials of Examples 1 and 2 have a superior degree of single particle size and are significantly superior in both initial efficiency and capacity retention compared to the positive electrode active material of Comparative Example 3, which was produced using a lithium composite transition metal oxide in which the molar ratio of lithium to all transition metals (Li / Me) was 0.005.It can also be seen that the positive electrode active materials of Examples 1 and 2 have higher structural stability, a superior degree of single particle size, and are significantly superior in both initial efficiency and capacity retention compared to the positive electrode active material of Comparative Example 4, which was produced using a lithium composite transition metal oxide in which the molar ratio of lithium to all transition metals (Li / Me) was 0.005.

Claims

1. The lithium composite transition metal oxide has a single particle form and a lithium to total transition metal molar ratio (Li / Me) of 0.01 to 0.7; Pellet density is 3.0 g / cm ３ ~4.0 g / cm ３ A positive electrode active material precursor.

2. The pellet density is 3.4 g / cm ３ ~4.0 g / cm ３ The positive electrode active material precursor according to claim 1 ,

3. The lithium composite transition metal oxide in the form of a single particle, in which the molar ratio of lithium to the total transition metals is 0.01 to 0.7, has an average particle size (D ５０ 2. The positive electrode active material precursor according to claim 1, wherein the average particle size is 5.0 μm to 15.0 μm.

4. 2. The positive electrode active material precursor according to claim 1, wherein the lithium composite transition metal oxide in single particle form, having a molar ratio of lithium to all transition metals of 0.01 to 0.7, contains 60 mol % or more of nickel relative to all transition metals other than lithium.

5. 2. The positive electrode active material precursor of claim 1, wherein the lithium composite transition metal oxide in the form of a single particle, in which the molar ratio of lithium to the total transition metals is 0.01 to 0.7, has a composition represented by the following Chemical Formula 1: [Chemical formula 1] Li ｘ Ni ａ M1 ｂ M2 ｃ O ｙ In the above Chemical Formula 1, M1 is one or more selected from Co, Mn, and Al; M2 is one or more selected from B, Mg, Ca, Ti, V, Cr, Fe, Zn, Ga, Y, Zr, Nb, Mo, Ta, W, Na, and La; 0.01≦x≦0.7, 0.60≦a<1.0, 0<b≦0.40, 0≦c≦0.1, 1≦y≦2, and a+b+c=1.

6. (A) mixing one or more selected from composite transition metal hydroxides and composite transition metal oxyhydroxides with a lithium-containing doping material so that the molar ratio of lithium contained in the lithium-containing doping material to all transition metals contained in the one or more selected from composite transition metal hydroxides and composite transition metal oxyhydroxides is 0.01 to 0.7, thereby producing a mixture; (B) firing the mixture at a temperature of 800°C to 1,200°C to produce a lithium composite transition metal oxide in a single particle form, the lithium to total transition metal molar ratio being 0.01 to 0.

7.

7. The method for producing a positive electrode active material precursor according to claim 6 , wherein the composite transition metal hydroxide and composite transition metal oxyhydroxide contain 60 mol % or more of nickel relative to the total transition metals.

8. 7. The method for producing a positive electrode active material precursor according to claim 6, wherein the lithium-containing doping material is at least one selected from the group consisting of lithium carbonate, lithium hydroxide, lithium oxide, lithium sulfate, lithium chloride, lithium nitrate, lithium acetate, and lithium phosphate.

9. The method for producing a cathode active material precursor according to claim 6 , wherein the firing in step (B) is performed in air or an oxygen atmosphere.

10. a step of mixing the cathode active material precursor according to any one of claims 1 to 5 with a lithium-containing raw material, and calcining the mixture at a temperature of 700°C to 1,100°C to prepare a lithium composite transition metal oxide in a single particle form, the lithium composite transition metal oxide having a molar ratio of lithium to all transition metals of 0.9 to 1.1; the lithium-containing raw material is mixed so that a molar ratio of total lithium contained in the positive electrode active material precursor and the lithium-containing raw material to all transition metals other than lithium contained in the positive electrode active material precursor is 0.9 to 1.

1.

11. The method for producing a positive electrode active material according to claim 10, wherein the firing comprises primary firing at a temperature of 800°C to 1,100°C and secondary firing at a temperature of 700°C to 900°C.

12. The lithium composite transition metal oxide has a single particle form and a lithium to total transition metal molar ratio of 0.9 to 1.1, Span value ([D ９０ -D １０ ] / D ５０ ) is 0.800 to 1.00, A positive electrode active material having an absolute value of negative skewness of 0.3000 to 0.7000.

13. The lithium composite transition metal oxide having a molar ratio of lithium to all transition metals of 0.9 to 1.1 has an average particle size (D ５０ 13. The positive electrode active material according to claim 12, wherein the average particle size is 5.0 μm to 15.0 μm.

14. 13. The positive electrode active material according to claim 12, wherein the lithium composite transition metal oxide having a molar ratio of lithium to all transition metals of 0.9 to 1.1 contains 60 mol% or more of nickel relative to all transition metals other than lithium.

15. The positive electrode active material according to claim 12, wherein the lithium composite transition metal oxide having a lithium to total transition metal molar ratio of 0.9 to 1.1 has a composition represented by the following chemical formula 4: [Chemical formula 4] Li ｘ’ [Ni ａ’ M1 ｂ’ M2 ｃ’ ]O ２ In the above Chemical Formula 4, M1 is one or more selected from Co, Mn, and Al; M2 is one or more selected from B, Mg, Ca, Ti, V, Cr, Fe, Zn, Ga, Y, Zr, Nb, Mo, Ta, W, Na, and La; 0.9≦x′≦1.1, 0.6≦a′<1.0, 0<b′≦0.4, 0<c′≦0.1, and a′+b′+c′=1.

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