Cathode active material, method for manufacturing same, and cathode and lithium secondary battery comprising same

Abstract

The present invention relates to: a cathode active material capable of improving the performance of a lithium secondary battery; a method for manufacturing same; and a cathode and a lithium secondary battery comprising same. The cathode active material includes a lithium composite transition metal oxide in the form of a single particle composed of at most 10 primary particles, wherein the lithium composite transition metal oxide has a nickel (Ni) content of at least 50 mol% of nickel (Ni) with respect to all metals other than lithium and contains yttrium (Y) and zirconium (Zr), and the average particle size (D'50) of the primary particles is 2.0-3.5 µm.

Description

Positive electrode active material, method for producing the same, and positive electrode and lithium secondary battery including the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0151119, filed November 3, 2023, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a positive electrode active material, a method for producing the same, and a positive electrode and a lithium secondary battery including the same.

[0005]

[0006] As technological development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which boast high energy density and voltage, long cycle life, and low self-discharge rates, are commercialized and widely used.

[0007] Lithium-cobalt composite metal oxides are commonly used as cathode active materials in lithium secondary batteries. Among these, lithium-cobalt composite metal oxides, such as LiCoO2, are primarily used due to their high operating voltage and superior capacity characteristics. However, LiCoO2 suffers from poor thermal properties due to crystal structure instability following delithiation. Furthermore, its high cost limits its widespread use as a power source in fields such as electric vehicles.

[0008] As materials to replace LiCoO2, lithium manganese composite metal oxides (such as LiMnO2 or LiMn2O4), lithium iron phosphate compounds (such as LiFePO4), or lithium nickel composite metal oxides (such as LiNiO2) have been developed. Among these, research and development is being more actively conducted on lithium nickel composite metal oxides, which have a high reversible capacity of approximately 200 mAh / g and can easily be used to implement large-capacity batteries. However, LiNiO2 has poor thermal stability compared to LiCoO2, and there is a problem that if an internal short circuit occurs due to external pressure while charged, the positive electrode active material itself decomposes, causing the battery to rupture and catch fire.

[0009] Accordingly, as a method to improve the low thermal stability while maintaining the excellent reversible capacity of LiNiO2, nickel-cobalt-manganese lithium composite transition metal oxides in which some of the Ni is replaced with Mn and Co, and nickel-manganese-aluminum lithium composite transition metal oxides in which some of the Ni is replaced with Mn and Al have been developed.

[0010] Conventional nickel-cobalt-manganese lithium composite transition metal oxides were generally in the form of spherical secondary particles formed by agglomeration of tens to hundreds of primary particles. However, in the case of nickel-cobalt-manganese lithium composite transition metal oxides formed by agglomeration of many primary particles into secondary particles, there is a problem in that the primary particles are easily broken during the rolling process during the manufacture of the positive electrode, and cracks occur inside the particles during the charge and discharge process. When the positive electrode active material is broken or cracked, the contact area with the electrolyte increases, which increases the problem of gas generation and active material degradation due to side reactions with the electrolyte.

[0011] Meanwhile, in the case of lithium composite transition metal oxides in which the nickel content is 50 mol% or more among all metals excluding lithium in the lithium composite transition metal oxide, structural stability and chemical stability are further reduced, it is more difficult to secure thermal stability, and there is also a cost issue due to the high heat treatment temperature.

[0012] Therefore, there is a need to develop a cathode active material that can implement a lithium secondary battery with improved capacity and life characteristics.

[0013]

[0014] [Prior Art Literature]

[0015] [Patent Document]

[0016] (Patent Document 1) Korean Patent Publication No. 10-2023-0013396

[0017]

[0018] The present invention is intended to solve the above problems, and to provide a positive electrode active material and a method for manufacturing the same that can improve the capacity and life characteristics of a battery.

[0019] In addition, the present invention seeks to provide a positive electrode and a lithium secondary battery having excellent capacity and lifespan characteristics, including the positive electrode active material as described above.

[0020]

[0021] (1) The present invention comprises a lithium composite transition metal oxide in the form of a single particle composed of 10 or fewer primary particles, wherein the lithium composite transition metal oxide has a nickel (Ni) content of 50 mol% or more among all metals excluding lithium, and includes yttrium (Y) and zirconium (Zr), and the average particle diameter (D') of the primary particles 50 ) provides a positive electrode active material having a diameter of 2.0㎛ or more and 3.5㎛ or less.

[0022] (2) The present invention provides a positive electrode active material in (1) above, wherein the lithium composite transition metal oxide has a nickel (Ni) content of 59 mol% or more and 70 mol% or less among all metals excluding lithium.

[0023] (3) The present invention provides a positive electrode active material in (1) or (2) above, wherein the lithium composite transition metal oxide has a composition represented by the following chemical formula 1.

[0024] [Chemical Formula 1]

[0025] Li 1+x Ni a Co b Mn c Y d Zr e M f O2

[0026] In the above chemical formula 1, M is at least one selected from B, Al, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S and La, and -0.1≤x≤0.1, 0.59≤a<1, 0 <b<0.41, 0<c<0.41, 0<d≤0.1, 0<e≤0.1, 0≤f≤0.1이다.

[0027] (4) The present invention provides a positive electrode active material in any one of the above (1) to (3), wherein the lithium composite transition metal oxide has a single particle magnetization degree (χ) of 0.4 or more according to the following formula 1.

[0028] [Formula 1]

[0029]

[0030] (5) The present invention provides a positive electrode active material having a single particle magnetization degree (χ) of 0.55 or more and 0.65 or less in the above (4).

[0031] (6) The present invention is characterized in that the average particle diameter (D) of the lithium composite transition metal oxide is in any one of the above (1) to (5). 50) provides a positive electrode active material having a diameter of 2.0㎛ or more and 5.0㎛ or less.

[0032] (7) The present invention provides a positive electrode active material in which the ratio of the area of ​​primary particles having a particle diameter of 1 ㎛ or less to the total area of ​​primary particles present in the positive electrode active material is 20% or less in any one of the above (1) to (6).

[0033] (8) The present invention provides a positive electrode active material in any one of the above (1) to (7), wherein the content of yttrium (Y) in the lithium composite transition metal oxide is 500 ppm or more and 4,000 ppm or less with respect to the total weight of the lithium composite transition metal oxide.

[0034] (9) The present invention provides a positive electrode active material in any one of the above (1) to (8), wherein the content of zirconium (Zr) in the lithium composite transition metal oxide is 500 ppm or more and 4,000 ppm or less with respect to the total weight of the lithium composite transition metal oxide.

[0035] (10) (A) a step of preparing a mixture by mixing a composite transition metal hydroxide containing nickel, a lithium (Li)-containing raw material, a yttrium (Y)-containing raw material, and a zirconium (Zr)-containing raw material; (B) a step of preparing a lithium composite transition metal oxide by calcining the mixture; and a method for preparing a positive electrode active material according to any one of (1) to (9), wherein the calcination is performed at a temperature of 920°C or higher and 980°C or lower.

[0036] (11) The present invention provides a method for producing a positive electrode active material, wherein, in the step (A), the yttrium (Y)-containing raw material is mixed so that the yttrium (Y) content is 500 ppm or more and 4,000 ppm or less based on the total weight of the composite transition metal hydroxide.

[0037] (12) The present invention provides a method for manufacturing a positive electrode active material, wherein in step (A), the zirconium (Zr)-containing raw material is mixed so that the zirconium (Zr) content is 500 ppm or more and 4,000 ppm or less based on the total weight of the composite transition metal hydroxide in (10) or (11).

[0038] (13) The present invention provides a positive electrode comprising a positive electrode active material according to any one of (1) to (9).

[0039] (14) The present invention provides a lithium secondary battery including a positive electrode according to (13) above.

[0040]

[0041] The cathode active material according to the present invention comprises zirconium (Zr) and yttrium (Y), and by controlling the particle size of the primary particles, the structural stability of the cathode active material is improved and the particle size and shape are made uniform. Accordingly, the capacity characteristics and life characteristics of the cathode and secondary battery including the cathode active material are improved.

[0042] In addition, according to the method for manufacturing a positive electrode active material of the present invention, the positive electrode active material described above can be effectively manufactured.

[0043]

[0044] Figure 1 is a SEM image of the positive electrode active material manufactured in Example 1.

[0045] Figure 2 is a SEM image of the positive electrode active material manufactured in Example 2.

[0046] Figure 3 is an SEM image of the positive electrode active material manufactured in Comparative Example 1.

[0047] Figure 4 is an SEM image of the positive electrode active material manufactured in Comparative Example 2.

[0048] Figure 5 is an SEM image of the positive electrode active material manufactured in Comparative Example 3.

[0049] Figure 6 is an SEM image of the positive electrode active material manufactured in Comparative Example 4.

[0050] Figure 7 is an SEM image of the positive electrode active material manufactured in Comparative Example 5.

[0051] Figure 8 is an SEM image of a positive electrode active material according to one embodiment of the present invention.

[0052] FIG. 9 is an image showing the boundaries of primary particles within a positive electrode active material divided using an SEM image of the positive electrode active material according to one embodiment of the present invention.

[0053] FIG. 10 is an image showing the boundaries of primary particles in a positive electrode active material divided and represented in random colors using an SEM image of a positive electrode active material according to one embodiment of the present invention.

[0054]

[0055] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0056] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0057] In this specification, it should be understood that terms such as “include,” “have,” or “have” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0058] In this specification, the term 'on' means not only when a configuration is formed directly on the top surface of another configuration, but also when a third configuration is interposed between these configurations.

[0059] In this specification, the term "single particle form" refers to a form composed of 10 or fewer primary particles, in contrast to the spherical secondary particle form formed by the agglomeration of tens to hundreds of primary particles manufactured by conventional methods. Specifically, the single particle form in the present invention may be a single particle composed of one primary particle, or may be a secondary particle form in which several primary particles are agglomerated.

[0060] In this specification, 'primary particle' means the smallest particle unit recognized when observing a positive electrode active material using a scanning electron microscope (SEM), and 'secondary particle' means a secondary structure formed by the aggregation of multiple primary particles.

[0061] In this specification, the content of each element in the lithium composite transition metal oxide may be measured through ICP (Inductive Coupled Plasma) analysis using an inductively coupled plasma optical emission spectrometer (ICP-OES; Aligent5110, Aligent Co.).

[0062] In this specification, the average particle diameter (D) of the lithium composite transition metal oxide 50 ) can be defined as the particle size corresponding to 50% of the volume cumulative distribution in the particle size distribution curve (graph curve of particle size distribution) of each particle. The average particle size of the lithium composite transition metal oxide 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., S3500 from Microtrac), measuring the difference in diffraction pattern according to particle size when the particles pass through the laser beam, calculating the particle size distribution, and calculating the particle diameter at the point where it becomes 50% of the volume cumulative distribution according to the particle size in the measuring device.

[0063] In this specification, the particle size of the primary particles may be calculated by calculating the area of ​​each primary particle through the number of pixels corresponding to each of n primary particles present in the SEM image, and calculating the particle size of each primary particle present in the SEM image using the radius of a circle having the same area as the area of ​​each primary particle. In addition, in this specification, the average particle size (D') of the primary particles 50 ) can be defined as the particle size corresponding to 50% of the volume cumulative distribution in the particle size distribution curve (graph curve of particle size distribution) of each particle. The average particle size (D') of the primary particles 50 ) can be measured by taking the volume of a sphere whose radius is half of the particle diameter of the primary particle as the volume of the primary particle, and then calculating the particle diameter at the point where 50% of the cumulative volume distribution according to the particle diameter in the result of calculating the volume of the primary particle is obtained.

[0064] In this specification, differentiation is a primary particle having a particle diameter of 1 ㎛ or less as a result of calculating the area of ​​each primary particle through the number of pixels corresponding to each of n primary particles present in the SEM image, and calculating the particle diameter of each primary particle present in the SEM image using the radius of a circle having the same area as the area of ​​each primary particle.

[0065]

[0066] positive electrode active material

[0067]

[0068] Hereinafter, the positive electrode active material according to the present invention will be described.

[0069]

[0070] The cathode active material according to the present invention comprises a lithium composite transition metal oxide in the form of a single particle composed of 10 or fewer primary particles, wherein the lithium composite transition metal oxide has a nickel (Ni) content of 50 mol% or more among all metals excluding lithium, and includes yttrium (Y) and zirconium (Zr), and has an average particle diameter (D') of the primary particles. 50 ) is 2.0㎛ or more and 3.5㎛ or less.

[0071] The lithium composite transition metal oxide is in the form of a single particle composed of 10 or fewer primary particles. That is, the lithium composite transition metal oxide is in the form of a single particle or a single particle in which 2 to 10 particles are aggregated. The single particle form is distinguished from a secondary particle in which more than 10 primary particles are aggregated. When the lithium composite transition metal oxide has a single particle form, the stability is excellent, so that even when a positive electrode active material including the same is rolled, the positive electrode active material does not break or crack, and thus side reactions between the positive electrode active material and the electrolyte can be reduced. As a result, the durability against volume changes during charge and discharge of the battery is improved, and the life characteristics can be improved. When the lithium composite transition metal oxide is in the form of a secondary particle, the positive electrode active material including the same is broken or cracked, and there is a problem of poor life characteristics due to a side reaction between the positive electrode active material and the electrolyte.

[0072] The primary particles forming the above single particles have an average particle diameter (D') 50 ) is 2.0㎛ or more and 3.5㎛ or less. Specifically, the primary particles have an average particle diameter (D' 50 ) may be 2.0㎛ or more, 2.1㎛ or more, 2.2㎛ or more, 2.3㎛ or more, 2.4㎛ or more, or 2.5㎛ or more, and may be 2.6㎛ or less, 2.7㎛ or less, 2.8㎛ or less, 2.9㎛ or less, 3.0㎛ or less, 3.1㎛ or less, 3.2㎛ or less, 3.3㎛ or less, 3.4㎛ or less, or 3.5㎛ or less. The average particle diameter (D') of the primary particles 50) is within the above range, the side reaction between the positive active material and the electrolyte is reduced, which can improve the life characteristics, and the lithium diffusion path inside the particle is shortened, which can improve the resistance characteristics. The average particle diameter of the primary particle (D' 50 ) is less than 2.0㎛, the grain boundary area in contact with the electrolyte is large, so there is a problem of poor life characteristics of the secondary battery due to gas generation caused by side reactions with the electrolyte, and the average particle diameter (D') of the primary particles 50 ) exceeds 3.5㎛, there is a problem of poor resistance characteristics due to the long lithium diffusion path inside the particle.

[0073] The above lithium composite transition metal oxide has a nickel (Ni) content of 50 mol% or more among all metals excluding lithium. When the nickel (Ni) content is within the above range, the capacity characteristics of the positive electrode active material can be improved. Specifically, when the Ni content is 59 mol% or more and 70 mol% or less, the capacity characteristics can be improved while maintaining the life characteristics. When the nickel (Ni) content is less than 50 mol% among all metals excluding lithium, there is a problem of poor charge / discharge capacity of the positive electrode active material.

[0074] The present inventors have found that when a lithium composite transition metal oxide having a nickel (Ni) content of 50 mol% or more among all metals excluding lithium includes yttrium (Y) and zirconium (Zr), specifically when yttrium (Y) is doped, yttrium (Y) ions in the positive electrode active material structure 3+ It exists in the form of Y 3+ - O has a bonding strength with oxygen of 512 kJ / mol, while Ni has a bonding strength with oxygen of 392 kJ / mol. 2+ -Co, which has a bonding strength with oxygen of 368 kJ / mol 3+ -O has a stronger bonding force with oxygen than Y, so it can improve structural stability. 3+ Ni at the tetrahedral site in the structure 2+It was found that the structural stability can be improved by suppressing cation mixing because it is more stable, and it can act as a flux to make the particle size and particle shape of the positive electrode active material uniform, and when zirconium (Zr) is doped, the zirconium (Zr) ions in the positive electrode active material structure are Zr 4+ It exists in the form of Ni 3+ Some of Ni 2+ The charge and discharge capacity can be increased by changing the zirconium (Zr) ion to occupy the lithium ion site, and the Ni 2+ It was found that the structural stability can be improved by suppressing the transformation from the layered structure to the spinel structure because it suppresses the diffusion into the lithium ion site. Accordingly, it was found that the life characteristics at high temperatures and high voltages can be improved, and the present invention was completed. Meanwhile, when the lithium composite transition metal oxide in which the content of nickel (Ni) among the total metals excluding lithium in the lithium composite transition metal oxide is 50 mol% or more and does not contain yttrium (Y) or zirconium (Zr), the particle shape of the lithium composite transition metal oxide is uneven and the particle size is non-uniform, and there are problems with the capacity characteristics and life characteristics.

[0075]

[0076] According to one embodiment of the present invention, the lithium composite transition metal oxide has a composition represented by the following chemical formula 1.

[0077] [Chemical Formula 1]

[0078] Li 1+x Ni a Co b Mn c Y d Zr e M f O2

[0079] In the above chemical formula 1,

[0080] M is at least one selected from B, Al, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, and La,

[0081] -0.1≤x≤0.1, 0.59≤a<1, 0 <b<0.41, 0<c<0.41, 0<d≤0.1, 0<e≤0.1, 0≤f≤0.1이다.

[0082] The above M is a doping element, and specifically, the above M may be at least one selected from B, Al, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, and La. The above M is not necessarily included, but when included in an appropriate amount, the particle shape of the positive electrode active material may be improved, and the stability of the crystal structure may be enhanced.

[0083] According to one embodiment of the present invention, the lithium composite transition metal oxide may include only one selected from among B, Al, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, and La. When the M includes only one selected from among B, Al, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, and La, the M is substituted to an appropriate degree in transition metal and lithium ion sites, thereby having the effect of improving capacity characteristics.

[0084]

[0085] Meanwhile, the above x may be -0.1 or more, -0.09 or more, -0.08 or more, -0.07 or more, -0.06 or more, -0.05 or more, -0.04 or more, -0.03 or more, -0.02 or more, -0.01 or more, 0 or more, 0.01 or more, or 0.02 or more, and may be 0.03 or less, 0.04 or less, 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, or 0.1 or less. When x satisfies the above range, high-capacity characteristics and high energy density per unit volume can be realized.

[0086] The above a is the molar fraction of nickel (Ni) among the total metals excluding lithium in the lithium composite transition metal oxide, and may be 0.59 or more, 0.60 or less, 0.61 or less, 0.62 or less, 0.63 or less, 0.64 or less, 0.65 or less, 0.66 or less, 0.67 or less, 0.68 or less, 0.69 or less, 0.7 or less, 0.8 or less, 0.9 or less, or less than 1. When a is within the above range, the capacity characteristics of the positive electrode active material can be improved. In particular, when a is 0.59 or more and 0.7 or less, the price competitiveness is excellent, and the structural stability and thermal stability of the positive electrode active material can be improved.

[0087] The above b is the mole fraction of cobalt (Co) among the total metals excluding lithium in the lithium composite transition metal oxide, and may be greater than 0, 0.01 or more, 0.02 or more, 0.03 or more, or 0.04 or more, and may be 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, 0.1 or less, 0.2 or less, 0.25 or less, 0.3 or less, 0.35 or less, or less than 0.41. When b satisfies the above range, the output characteristics can be improved during the charge and discharge process.

[0088] The above c is the mole fraction of manganese (Mn) among the total metals excluding lithium in the lithium composite transition metal oxide, and may be greater than 0, 0.1 or more, 0.15 or more, 0.2 or more, 0.25 or more, 0.3 or more, 0.31 or more, 0.32 or more, 0.33 or more, or 0.34 or more, and may be 0.35 or less, 0.36 or less, 0.37 or less, 0.38 or less, 0.39 or less, or less than 0.41. When c satisfies the above range, structural stability increases, and the decomposition reaction of the electrolyte may be relatively reduced.

[0089] The above d is the mole fraction of yttrium (Y) among the total metals excluding lithium in the lithium composite transition metal oxide, and may be greater than 0, 0.0001 or more, 0.0002 or more, 0.0003 or more, 0.0004 or more, 0.0005 or more, 0.0006 or more, 0.0007 or more, 0.0008 or more, 0.0009 or more, 0.001 or more, or 0.002 or more, and may be 0.003 or less, 0.004 or less, 0.005 or less, 0.006 or less, 0.007 or less, 0.008 or less, 0.009 or less, 0.01 or less, 0.02 or less, 0.03 or less, 0.04 or less, 0.05 or less, 0.06 or less, 0.07 or less, It may be 0.08 or less, 0.09 or less, or 0.1 or less. When d satisfies the above range, the structural stability of the positive electrode active material can be improved. Specifically, the yttrium (Y) ion in the positive electrode active material structure is Y 3+ It exists in the form of Y 3+ - O has a bonding strength with oxygen of 512 kJ / mol, while Ni has a bonding strength with oxygen of 392 kJ / mol. 2+ -Co, which has a bonding strength with oxygen of 368 kJ / mol 3+ -O has a stronger bonding force with oxygen than Ni, so it can improve structural stability, and Ni is present in the tetrahedral site within the structure. 2+Because it is more stable, cation mixing can be suppressed, thereby improving structural stability. In addition, it acts as a flux, allowing the particle size and shape of the positive electrode active material to be uniform.

[0090] The above e is the molar fraction of zirconium (Zr) among the total metals excluding lithium in the lithium composite transition metal oxide, and may be greater than 0, 0.0001 or more, 0.0002 or more, 0.0003 or more, 0.0004 or more, 0.0005 or more, 0.0006 or more, 0.0007 or more, 0.0008 or more, 0.0009 or more, or 0.001 or more, and 0.002 or less, 0.003 or less, 0.004 or less, 0.005 or less, 0.006 or less, 0.007 or less, 0.008 or less, 0.009 or less, 0.01 or less, 0.02 or less, 0.03 or less, 0.04 or less, 0.05 or less, 0.06 or less, 0.07 or less, It may be 0.08 or less, 0.09 or less, or 0.1 or less. When e satisfies the above range, the capacity characteristics and life characteristics of the positive electrode active material can be improved. Specifically, the zirconium (Zr) ion in the positive electrode active material structure is Zr 4+ It exists in the form of Ni 3+ Some of Ni 2+ can increase the charge and discharge capacity by changing into . In addition, zirconium (Zr) ions can occupy the lithium ion site, so Ni 2+ Since it inhibits the diffusion of lithium ions into the lithium ion site, the transformation from a layered structure to a spinel structure can be suppressed, thereby improving structural stability. In addition, it acts as a flux to uniformly adjust the particle size and shape of the positive active material. This can improve the life characteristics at high temperatures and high voltages.

[0091] The above f is the molar fraction of M among the total metals excluding lithium in the lithium composite transition metal oxide, and may be 0 or more, 0.001 or more, 0.002 or more, or 0.003 or more, and may be 0.004 or less, 0.005 or less, 0.006 or less, 0.007 or less, 0.008 or less, 0.009 or less, 0.01 or less, 0.02 or less, 0.03 or less, 0.04 or less, 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, or 0.1 or less. When f satisfies the above range, the stability of the crystal structure of the positive electrode active material can be improved and the grain shape can be improved.

[0092] The above a, b, c, d, e, and f can be a+b+c+d+e+f=1.

[0093]

[0094] In the present invention, the degree of single particle size is evaluated and expressed as a parameter represented by the following equation 1. The degree of single particle size in the present invention is the average particle diameter (D') of the primary particles forming the single particle. 50 ) and the average particle diameter (D) of single-particle lithium composite transition metal oxides 50 ) is the average particle diameter (D') of the primary particles present in the lithium composite transition metal oxide. 50 ) is the average particle diameter (D) of lithium composite transition metal oxides. 50 ) the closer it is to the particle size, the higher the degree of single particle magnetization.

[0095] For example, the maximum value of the single particle degree is 1, which means that one single particle is composed of one primary particle.

[0096] According to one embodiment of the present invention, the lithium composite transition metal oxide may have a single particle magnetization degree (χ) of 0.4 or more according to the following formula 1.

[0097] [Formula 1]

[0098]

[0099] The above single particle magnetization degree (χ) may be 0.4 or more, 0.45 or more, 0.5 or more, 0.55 or more, 0.56 or more, 0.57 or more, 0.58 or more, 0.59 or more, or 0.6 or more, and 0.61 or less, 0.62 or less, 0.63 or less, 0.64 or less, 0.65 or less, 0.66 or less, 0.67 or less, 0.68 or less, 0.69 or less, 0.7 or less, 0.71 or less, 0.72 or less, 0.73 or less, 0.74 or less, 0.75 or less, 0.76 or less, 0.77 or less, 0.78 or less, 0.79 or less, 0.8 or less, 0.81 or less, 0.82 or less, 0.83 or less, 0.84 or less, 0.85 or less, 0.86 or less, 0.87 or less, 0.88 or less, 0.89 or less, 0.9 or less, 0.91 or less, 0.92 or less, 0.93 or less, 0.94 or less, 0.95 or less, 0.96 or less, 0.97 or less, 0.98 or less, 0.99 or less, or 1 or less. When the above range is satisfied, it can be seen that the lithium composite transition metal oxide of the present invention has a single particle form in which agglomeration between particles is suppressed. Accordingly, the structural stability is improved, so that when rolling for electrode manufacture or operating a cell, particle breakage is suppressed, the grain boundary area in contact with the electrolyte is reduced, and gas generation due to side reactions with the electrolyte is reduced, so that the life characteristics of the secondary battery can be improved. In particular, when the single particle degree is 0.55 or more and 0.65 or less, the capacity characteristics and life characteristics can be improved.

[0100]

[0101] According to one embodiment of the present invention, the average particle diameter (D) of the lithium composite transition metal oxide 50 ) may be 2.0㎛ or more and 5.0㎛ or less. Specifically, the average particle diameter (D of the lithium composite transition metal oxide 50) may be 2.0 ㎛ or more, 2.1 ㎛ or more, 2.2 ㎛ or more, 2.3 ㎛ or more, 2.4 ㎛ or more, 2.5 ㎛ or more, 2.6 ㎛ or more, 2.7 ㎛ or more, 2.8 ㎛ or more, 2.9 ㎛ or more, 3.0 ㎛ or more, 3.1 ㎛ or more, 3.2 ㎛ or more, 3.3 ㎛ or more, 3.4 ㎛ or more, 3.5 ㎛ or more, 3.6 ㎛ or more, 3.7 ㎛ or more, 3.8 ㎛ or more, 3.9 ㎛ or more, 4.0 ㎛ or more, or 4.1 ㎛ or more, and may be 4.2 ㎛ or less, 4.3 ㎛ or less, 4.4 ㎛ or less, 4.5 ㎛ or less, 4.6 ㎛ or less, 4.7 ㎛ or less, 4.8 ㎛ or less, 4.9 ㎛ or less, or 5.0 ㎛ or less. The average particle diameter (D of the lithium composite transition metal oxide 50 ) is within the above range, electrode density can be implemented excellently and capacity characteristics can be improved.

[0102]

[0103] According to one embodiment of the present invention, the ratio of the area of ​​primary particles having a diameter of 1 μm or less to the total area of ​​primary particles present in the positive electrode active material may be 20% or less. Specifically, the ratio of the area of ​​primary particles having a diameter of 1 μm or less to the total area of ​​primary particles present in the positive electrode active material may be 10% or less, 11% or less, 12% or less, 13% or less, 14% or less, 15% or less, 16% or less, 17% or less, 18% or less, 19% or less, or 20% or less. The above ratio may be a measure of particle growth. The closer the ratio is to 0, the fewer primary particles that have not completed growth. The more particles that have not completed growth, that is, fine particles, there are, the lower the life characteristics due to side reactions with the electrolyte, and the more gas generation there is, the lower the stability. When the above ratio is within the above range, gas generation due to side reactions with the electrolyte is reduced, thereby suppressing degradation and improving stability.

[0104]

[0105] According to one embodiment of the present invention, the content of yttrium (Y) in the lithium composite transition metal oxide may be 500 ppm or more and 4,000 ppm or less with respect to the total weight of the lithium composite transition metal oxide. Specifically, the content of yttrium (Y) in the lithium composite transition metal oxide is 500 ppm or more, 600 ppm or more, 700 ppm or more, 800 ppm or more, 900 ppm or more, 1,000 ppm or more, 1,100 ppm or more, 1,200 ppm or more, 1,300 ppm or more, 1,400 ppm or more, 1,500 ppm or more, 1,600 ppm or more, 1,700 ppm or more, 1,800 ppm or more, 1,900 ppm or more, 2,000 ppm or more, 2,100 ppm or more, 2,200 ppm or more, 2,300 ppm or more, 2,400 ppm or more, 2,500 ppm or more, 2,600 ppm or more, or The yttrium (Y) content may be 2,700 ppm or more, 2,800 ppm or less, 2,900 ppm or less, 3,000 ppm or less, 3,100 ppm or less, 3,200 ppm or less, 3,300 ppm or less, 3,400 ppm or less, 3,500 ppm or less, 3,600 ppm or less, 3,700 ppm or less, 3,800 ppm or less, 3,900 ppm or less, or 4,000 ppm or less. When the content of the yttrium (Y) is within the above range, the structural stability of the positive electrode active material can be improved. Specifically, the yttrium (Y) ion in the positive electrode active material structure is Y 3+ It exists in the form of Y 3+ - O has a bonding strength with oxygen of 512 kJ / mol, while Ni has a bonding strength with oxygen of 392 kJ / mol. 2+ -Co, which has a bonding strength with oxygen of 368 kJ / mol 3+ -O has a stronger bonding force with oxygen than Ni, so it can improve structural stability. In addition, Ni is present in the tetrahedral site within the structure. 2+Because it is more stable, cation mixing can be suppressed, thereby improving structural stability. In addition, it acts as a flux, allowing the particle size and shape of the positive electrode active material to be uniform.

[0106]

[0107] According to one embodiment of the present invention, the content of zirconium (Zr) in the lithium composite transition metal oxide may be 500 ppm or more and 4,000 ppm or less with respect to the total weight of the lithium composite transition metal oxide. Specifically, the content of zirconium (Zr) in the lithium composite transition metal oxide may be 500 ppm or more, 600 ppm or more, 700 ppm or more, 800 ppm or more, 900 ppm or more, 1,000 ppm or more, 1,100 ppm or more, 1,200 ppm or more, or 1,300 ppm or more, and 1,400 ppm or less, 1,500 ppm or less, 1,600 ppm or less, 1,700 ppm or less, 1,800 ppm or less, 1,900 ppm or less, 2,000 ppm or less, 2,100 ppm or less, 2,200 ppm or less, 2,300 ppm or less, 2,400 ppm or less, 2,500 ppm or less, or 2,600 ppm based on the total weight of the lithium composite transition metal oxide. Below, 2,700 ppm or less, 2,800 ppm or less, 2,900 ppm or less, 3,000 ppm or less, 3,100 ppm or less, 3,200 ppm or less, 3,300 ppm or less, 3,400 ppm or less, 3,500 ppm or less, 3,600 ppm or less, 3,700 ppm or less, 3,800 ppm or less, 3,900 ppm or less, or 4,000 ppm or less. When the content of zirconium (Zr) is within the above range, the capacity characteristics and life characteristics of the positive electrode active material can be improved. Specifically, the zirconium (Zr) ion in the positive electrode active material structure is Zr 4+ It exists in the form of Ni 3+ Some of Ni 2+can increase the charge and discharge capacity by changing into . In addition, zirconium (Zr) ions can occupy the lithium ion site, so Ni 2+ Since it inhibits the diffusion of lithium ions into the lithium ion site, it can improve structural stability by suppressing the transformation from a layered structure to a spinel structure. In addition, it can act as a flux to uniformize the particle size and shape of the positive active material. This can improve the life characteristics at high temperatures and high voltages.

[0108]

[0109] Method for manufacturing positive electrode active material

[0110] Next, a method for manufacturing the positive electrode active material of the present invention will be described. The method for manufacturing the positive electrode active material of the present invention is a method for manufacturing the positive electrode active material according to the present invention.

[0111]

[0112] A method for producing a cathode active material according to the present invention comprises: (A) a step of mixing a composite transition metal hydroxide containing nickel, a lithium (Li)-containing raw material, a yttrium (Y)-containing raw material, and a zirconium (Zr)-containing raw material to produce a mixture; (B) a step of calcining the mixture to produce a lithium composite transition metal oxide.

[0113]

[0114] The cathode active material according to the present invention described above can be manufactured by appropriately controlling the type of raw material, the mixing ratio of raw materials, the sintering step, the sintering atmosphere, etc.

[0115]

[0116] Hereinafter, each step of the present invention will be described in detail.

[0117] (A) Step

[0118] A method for manufacturing a cathode active material according to the present invention includes step (A) of manufacturing a mixture by mixing a composite transition metal hydroxide containing nickel, a lithium (Li)-containing raw material, a yttrium (Y)-containing raw material, and a zirconium (Zr)-containing raw material.

[0119] Specifically, the mixing may be performed by dry mixing or wet mixing. When mixing each component through dry mixing, the firing process can be performed without a separate drying process. When mixing each component through wet mixing, the mixture may be prepared by adding it to a solvent, specifically water, or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water, or a solution containing each raw material, specifically an aqueous solution, is prepared, and then the mixed components are mixed and spray-dried before the firing process is performed. Each raw material and composite transition metal hydroxide may be used in an appropriate amount considering the content of each metal element in the lithium composite transition metal oxide to be finally manufactured.

[0120] The above complex transition metal hydroxide can be produced through a coprecipitation reaction by introducing a complex transition metal aqueous solution, an ammonium cation complex, and a basic compound into a reactor.

[0121] The above-mentioned composite transition metal aqueous solution can be prepared by dissolving a transition metal-containing raw material in a solvent such as water, and for example, can be prepared 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-mentioned 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. In addition, if necessary, the above-mentioned composite transition metal-containing solution can further include a metal-containing raw material containing a transition metal other than nickel (Ni), cobalt (Co), and manganese (Mn) (for example, at least one selected from Y, Zr, B, Al, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, and La).

[0122] The above nickel (Ni)-containing raw material may be at least one selected from the group consisting of NiO, Ni(OH)2, NiOㆍOH, NiCO3ㆍ2Ni(OH)2ㆍ4H2O, NiC2O4ㆍ2H2O, Ni(NO3)2ㆍ6H2O, fatty acid nickel, and nickel halides, and a mixture of one or two or more of these may be used.

[0123] The above cobalt (Co)-containing raw material may be at least one selected from the group consisting of Co(OH)2, Co3O4, CoOㆍOH, Co(OCOCH3)2ㆍ4H2O, Co(NO3)2ㆍ6H2O or Co(SO4)2ㆍ7H2O, fatty acid cobalt, and cobalt halides, and a mixture of one or two or more of these may be used.

[0124] 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 citrate, manganese salts of fatty acid manganese, oxyhydroxides, and halides of manganese chloride, and a mixture of one or two or more of these may be used.

[0125] 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 composite transition metal hydroxide being manufactured.

[0126] Meanwhile, the ammonium cation complex forming agent may include at least one compound selected from the group consisting of NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and NH4CO3, and may be introduced into the reactor in the form of a solution in which the compound is dissolved in a solvent. At this time, as the solvent, water or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water may be used.

[0127] The basic compound may be at least one compound selected from the group consisting of NaOH, KOH, and Ca(OH)2, and may be introduced into the reactor in the form of a solution in which the compound is dissolved in a solvent. At this time, the solvent may be water, or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water.

[0128] When a complex transition metal aqueous solution, an ammonium cation complex forming agent, and a basic compound are introduced into a reactor as described above, precursor particles in the form of a complex transition metal hydroxide are generated through a coprecipitation reaction of the transition metal in the complex transition metal aqueous solution.

[0129] At this time, the basic compound can be added in an amount such that the pH of the reaction solution becomes within the desired range.

[0130] Once precursor particles are formed by the above method, the particles are separated from the reaction solution to obtain a complex transition metal hydroxide. Specifically, the reaction solution is filtered to separate the precursor particles, and then the separated precursor particles are washed and dried to obtain a complex transition metal hydroxide. At this time, processes such as grinding and / or classification may also be performed, as needed.

[0131]

[0132] The above complex transition metal hydroxide is Ni p Co q Mn r M 1 s (OH)2(M above 1 is at least one selected from Y, Zr, B, Al, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S and La, and the p, q, r, s are 0.59≤p<1, 0 <q<0.41, 0<r<0.41, 0≤s≤0.1이다.)로 표시되는 조성을 가질 수 있다.

[0133]

[0134] The above lithium (Li)-containing raw material may be at least one selected from the group consisting of LiOH, Li2CO3, LiNO3, LiNO2, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li acetate, Li dicarboxylic acid, Li citrate, Li fatty acid, alkyl lithium, and lithium halides, and a mixture of one or two or more thereof may be used. Specifically, LiOH or Li2CO3 may be used.

[0135] The above yttrium (Y) containing raw material is Y2O3, It may be at least one selected from the group consisting of Y2(CO3)3·xH2O, Y(C5H7O2)3·xH2O, (CH3CO2)3Y·xH2O, Y(OH)3·xH2O, Y2(SO4)3·8H2O, Y(NO3)3·xH2O, and a mixture of one or two or more of these may be used. Specifically, when convenience in the process is taken into consideration, Y2O3 may be used.

[0136] The above zirconium (Zr)-containing raw material may be at least one selected from the group consisting of ZrO2, Zr(OH)4, Zr(OC2H5)4, Zr(SO4)2·xH2O, and Zr[OC(CH3)3]4, and a mixture of one or two or more of these may be used. Specifically, when convenience in the process is taken into consideration, ZrO2 may be used.

[0137]

[0138] According to one embodiment of the present invention, the yttrium (Y)-containing raw material may be mixed so that the yttrium (Y) content is 500 ppm or more and 4,000 ppm or less with respect to the total weight of the composite transition metal hydroxide. Specifically, the yttrium (Y)-containing raw material contains yttrium (Y) in an amount of 500 ppm or more, 600 ppm or more, 700 ppm or more, 800 ppm or more, 900 ppm or more, 1,000 ppm or more, 1,100 ppm or more, 1,200 ppm or more, 1,300 ppm or more, or 1,400 ppm or more, and 1,500 ppm or less, 1,600 ppm or less, 1,700 ppm or less, 1,800 ppm or less, 1,900 ppm or less, 2,000 ppm or less, 2,100 ppm or less, 2,200 ppm or less, 2,300 ppm or less, 2,400 ppm or less, 2,500 ppm or less, or 2,600 ppm, based on the total weight of the composite transition metal hydroxide. The yttrium (Y)-containing raw material may be mixed so that the content is 2,700 ppm or less, 2,800 ppm or less, 2,900 ppm or less, 3,000 ppm or less, 3,100 ppm or less, 3,200 ppm or less, 3,300 ppm or less, 3,400 ppm or less, 3,500 ppm or less, 3,600 ppm or less, 3,700 ppm or less, 3,800 ppm or less, 3,900 ppm or less, or 4,000 ppm or less. When the input amount of the yttrium (Y)-containing raw material is within the above range, the structural stability of the positive electrode active material can be improved. Specifically, the yttrium (Y) ion in the positive electrode active material structure is Y 3+ It exists in the form of Y 3+ - O has a bonding strength with oxygen of 512 kJ / mol, while Ni has a bonding strength with oxygen of 392 kJ / mol. 2+ -Co, which has a bonding strength with oxygen of 368 kJ / mol 3+ -O has a stronger bonding force with oxygen than Ni, so it can improve structural stability. Ni is located at the tetrahedral site within the structure.2+ Because it is more stable, cation mixing can be suppressed, thereby improving structural stability. In addition, it acts as a flux, allowing the particle size and shape of the positive electrode active material to be uniform.

[0139]

[0140] According to one embodiment of the present invention, the zirconium (Zr)-containing raw material may be mixed so that the zirconium (Zr) content is 500 ppm or more and 4,000 ppm or less based on the total weight of the composite transition metal hydroxide. Specifically, the zirconium (Zr)-containing raw material contains zirconium (Zr) in an amount of 500 ppm or more, 600 ppm or more, 700 ppm or more, 800 ppm or more, 900 ppm or more, 1,000 ppm or more, 1,100 ppm or more, 1,200 ppm or more, 1,300 ppm or more, 1,400 ppm or more, 1,500 ppm or more, 1,600 ppm or more, 1,700 ppm or more, 1,800 ppm or more, 1,900 ppm or more, 2,000 ppm or more, 2,100 ppm or more, 2,200 ppm or more, 2,300 ppm or more, 2,400 ppm or more, 2,500 ppm or more, 2,600 ppm based on the total weight of the composite transition metal hydroxide. The content may be mixed to be 2,700 ppm or more, 2,800 ppm or more, or 2,900 ppm or more, and 3,000 ppm or less, 3,100 ppm or less, 3,200 ppm or less, 3,300 ppm or less, 3,400 ppm or less, 3,500 ppm or less, 3,600 ppm or less, 3,700 ppm or less, 3,800 ppm or less, 3,900 ppm or less, or 4,000 ppm or less. When the mixing amount of the zirconium (Zr)-containing raw material is within the above range, the capacity characteristics and life characteristics of the positive electrode active material can be improved. Specifically, the zirconium (Zr) ions in the positive electrode active material structure are Zr 4+ It exists in the form of Ni 3+ Some of Ni2+ can increase the charge and discharge capacity by changing into . In addition, zirconium (Zr) ions can occupy the lithium ion site, so Ni 2+ Since it inhibits the diffusion of lithium ions into the lithium ion site, the transformation from a layered structure to a spinel structure can be suppressed, thereby improving structural stability. In addition, it acts as a flux to uniformly adjust the particle size and shape of the positive active material. This can improve the life characteristics at high temperatures and high voltages.

[0141]

[0142] According to one embodiment of the present invention, in step (A), a composite transition metal hydroxide containing nickel, a lithium (Li)-containing raw material, a yttrium (Y)-containing raw material, and a zirconium (Zr)-containing raw material can be mixed in an amount such that the composition is represented by the chemical formula 1.

[0143]

[0144] (B) Step

[0145] The method for manufacturing a positive electrode active material according to the present invention includes, after step (A), step (B) of calcining the mixture to manufacture a lithium composite transition metal oxide.

[0146] The above-mentioned sintering may be performed at a temperature of 920°C or higher and 980°C or lower. Specifically, the above-mentioned sintering may be performed at a temperature of 920°C or higher, 930°C or higher, 940°C or higher, and 950°C or lower, 960°C or lower, or 970°C or lower. By sintering in this manner, a lithium composite transition metal oxide in the form of single particles can be formed. When the lithium composite transition metal oxide is in the form of single particles, the particle interface is small, so that degradation due to insulation at the interface due to particle breakage during rolling or side reactions with the electrolyte can be suppressed. As a result, the life characteristics of the secondary battery can be improved, especially at high voltages. Meanwhile, when the above calcination is performed at a temperature lower than 920°C, sufficient heat energy is not supplied to form a lithium composite transition metal oxide in the form of a single particle, and sufficient heat energy required for primary particle growth is not supplied. When the calcination is performed at a temperature higher than 980°C, overcalcination occurs, a rock salt phase is generated, and there is a problem in that the primary particles grow excessively and form lumps.

[0147]

[0148] The above calcination may be performed for 6 hours or more and 20 hours or less. When the above range is satisfied, particles having high crystallinity and an appropriate size can be obtained, and production efficiency can be improved.

[0149] The above firing may be performed in an air atmosphere, an oxidizing atmosphere, or an inert atmosphere.

[0150]

[0151] anode

[0152] Next, the anode according to the present invention will be described.

[0153] The positive electrode according to the present invention comprises a positive electrode active material layer comprising the positive electrode active material according to the present invention. Specifically, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and comprising the positive electrode active material. Since the positive electrode active material has been described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0154]

[0155] The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change 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 positive electrode current collector may typically have a thickness of 3 µm to 500 µm, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesive strength of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0156]

[0157] The above-mentioned positive electrode active material layer may include a conductive material and a binder together with the positive electrode active material. At this time, the positive electrode active material may be included in an amount of 80 wt% to 99 wt%, more specifically 85 wt% to 98.5 wt%, based on the total weight of the positive electrode active material layer, and excellent capacity characteristics may be exhibited within this range.

[0158]

[0159] The conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. 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, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One type alone or a mixture of two or more types of these may be used. The conductive material may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0160]

[0161] The above binder serves to improve the adhesion between positive electrode active material particles and the adhesive strength 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, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The binder may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0162]

[0163] The positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material described above is used. Specifically, the positive electrode can be manufactured by coating a composition for forming a positive electrode active material layer, which is manufactured by dissolving or dispersing the positive electrode active material and optionally a binder and a conductive material in a solvent, on a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive material are as described above. Alternatively, the positive electrode can be manufactured by casting the composition for forming a positive electrode active material layer on a separate support, and then laminating the film obtained by peeling it from the support on a positive electrode current collector.

[0164]

[0165] The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0166]

[0167] lithium secondary battery

[0168] Next, a lithium secondary battery according to the present invention will be described.

[0169]

[0170] The present invention can manufacture an electrochemical device including the above-described positive electrode. The electrochemical device may be, specifically, a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

[0171]

[0172] The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is the same as described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0173]

[0174] In addition, the lithium secondary battery may optionally 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.

[0175]

[0176] In the above lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0177] The 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., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0178]

[0179] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0180]

[0181] As the 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 alloy, Sn alloy, or Al alloy; SiO β (0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fiber-like forms, 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.

[0182] The above negative electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of the negative electrode active material layer.

[0183]

[0184] The above binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1 wt% to 10 wt% 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, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0185]

[0186] The conductive agent 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 agent is not particularly limited as long as it has conductivity and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or 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 or metal fiber; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0187]

[0188] The negative electrode active material layer may be manufactured by applying and drying 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, on a negative electrode current collector, or by casting the composition for forming a negative electrode active material layer on a separate support, and then laminating the film obtained by peeling it off from the support on a negative electrode current collector.

[0189]

[0190] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without special restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure.

[0191]

[0192] In addition, examples of the electrolyte used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0193] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0194] As the organic solvent, any solvent that can serve as a medium through which ions involved in the electrochemical reaction of the battery can move may be used without particular limitation. Specifically, the organic solvent includes ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); Alcohol solvents such as ethyl alcohol, isopropyl alcohol, etc.; nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes, etc. can be used. Among these, carbonate solvents are preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of a battery and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferable.In this case, the performance of the electrolyte may be improved when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

[0195]

[0196] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably used within the range of 0.1 to 5.0 M, specifically, 0.1 to 3.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0197]

[0198] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additive may be included in an amount of 0.1 to 10 wt%, specifically, 0.1 to 5 wt%, based on the total weight of the electrolyte.

[0199]

[0200] As described above, a lithium secondary battery including a cathode active material according to the present invention exhibits excellent life characteristics and capacity characteristics, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0201] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0202] The above 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 a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0203] There is no particular limitation on the external shape of the lithium secondary battery of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0204] 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 be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

[0205]

[0206] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0207]

[0208] Hereinafter, the present invention will be described in detail with reference to examples. However, the examples according to the present invention may be modified in various ways, and the scope of the present invention should not be construed as being limited to the examples described below. The examples of the present invention are provided to more fully explain the present invention to those of ordinary skill in the art.

[0209]

[0210] Examples and Comparative Examples

[0211] Example 1

[0212] Ni 0.60 Co 0.05 Mn 0.35 A complex transition metal hydroxide having a composition represented by (OH)2 (product name: Nickel cobalt manganese hydroxide, D 50 : 3.5μm±0.2μm, secondary particles) and Li2CO3 were added so that the molar ratio of (Ni+Co+Mn):Li was 1:1.05, and Y2O3 was added to Ni 0.60 Co 0.05 Mn 0.35 ZrO2 is added to Ni so that the Y content is 1,500 ppm relative to the total weight of (OH)2. 0.60 Co 0.05 Mn 0.35 A mixture was prepared by adding and mixing Zr so that the content was 3,000 ppm based on the total weight of (OH)2.

[0213] The above mixture was heated from 25°C to 950°C at a rate of 3°C / min under an air atmosphere, and then calcined for 14 hours while maintaining the temperature at 950°C to produce a lithium composite transition metal oxide (positive electrode active material) in the form of single particles.

[0214]

[0215] Example 2

[0216] The mixture prepared in Example 1 was heated from 25°C to 960°C at a rate of 3°C / min in an air atmosphere, and then calcined for 14 hours while maintaining the temperature at 960°C to prepare a lithium composite transition metal oxide (positive electrode active material) in the form of single particles.

[0217]

[0218] Comparative Example 1

[0219] Ni 0.60 Co 0.05 Mn 0.35 A complex transition metal hydroxide having a composition represented by (OH)2 (product name: Nickel cobalt manganese hydroxide, D 50 : 3.5 μm ± 0.2 μm, secondary particles) and Li2CO3 were added and mixed so that the molar ratio of (Ni+Co+Mn):Li was 1:1.05 to prepare a mixture, and a positive electrode active material was prepared in the same manner as in Example 1.

[0220]

[0221] Comparative Example 2

[0222] Ni 0.60 Co 0.05 Mn 0.35 Complex transition metal hydroxides having a composition represented by (OH)2 (Product name: Nickel cobalt manganese hydroxide, D 50 : 3.5μm±0.2μm, secondary particles) and Li2CO3 were added so that the molar ratio of (Ni+Co+Mn):Li was 1:1.05, and ZrO2 was added to Ni 0.60 Co 0.05 Mn 0.35 A positive electrode active material was manufactured in the same manner as in Example 1, except that the mixture was manufactured by adding and mixing Zr so that the content was 3,000 ppm with respect to the total weight of (OH)2.

[0223]

[0224] Comparative Example 3

[0225] Ni0.60 Co 0.05 Mn 0.35 Complex transition metal hydroxides having a composition represented by (OH)2 (Product name: Nickel cobalt manganese hydroxide, D 50 : 3.5μm±0.2μm, secondary particles) and Li2CO3 were added so that the molar ratio of (Ni+Co+Mn):Li was 1:1.05, and Y2O3 was added to Ni 0.60 Co 0.05 Mn 0.35 A positive electrode active material was manufactured in the same manner as in Example 1, except that Y was added and mixed to make a mixture in an amount of 1,500 ppm relative to the total weight of (OH)2.

[0226]

[0227] Comparative Example 4

[0228] The mixture prepared in Example 1 was heated from 25°C to 900°C at a rate of 3°C / min in an air atmosphere, and then calcined for 14 hours while maintaining the temperature at 900°C to prepare a lithium composite transition metal oxide (positive electrode active material) in the form of single particles.

[0229]

[0230] Comparative Example 5

[0231] The mixture prepared in Example 1 was heated from 25°C to 995°C at a rate of 3°C / min in an air atmosphere, and then calcined for 14 hours while maintaining the temperature at 995°C to prepare a lithium composite transition metal oxide (positive electrode active material) in the form of a single particle.

[0232]

[0233] Experimental example

[0234] Experimental Example 1: Analysis of positive electrode active material

[0235] - Confirmation of the composition ratio and doping element content of positive electrode active material through ICP analysis

[0236] For the positive electrode active materials manufactured in Examples 1 and 2 and Comparative Examples 1 to 5, the composition and doping element content of the positive electrode active materials were confirmed by the following method, and are shown in Table 1 below.

[0237] To each of 0.1 g of the positive electrode active material particles manufactured in Examples 1 and 2 and Comparative Examples 1 to 5, 1 ml of hydrochloric acid was added, and the positive electrode active material was dissolved by heating. Thereafter, a small amount of hydrogen peroxide was added to promote the reaction, completely dissolving the positive electrode active material to prepare a solution. Next, the solution was diluted with deionized water to a total volume of 10 ml to prepare an analysis sample. Using ICP-OES (Aligent5100, Aligent Co.), the composition of the positive electrode active material and the weight (ppm) of the doping elements present in the analysis sample were confirmed, and these are shown in Table 1 below.

[0238]

[0239] - Morphological analysis of positive electrode active material

[0240] For the positive electrode active materials manufactured in Examples 1 and 2 and Comparative Examples 1 to 5, SEM images were obtained using a scanning electron microscope (SEM), and these images are shown in Figures 1 to 7.

[0241] Figure 1 is a SEM image of the positive electrode active material manufactured in Example 1.

[0242] Figure 2 is a SEM image of the positive electrode active material manufactured in Example 2.

[0243] Figure 3 is an SEM image of the positive electrode active material manufactured in Comparative Example 1.

[0244] Figure 4 is an SEM image of the positive electrode active material manufactured in Comparative Example 2.

[0245] Figure 5 is an SEM image of the positive electrode active material manufactured in Comparative Example 3.

[0246] Figure 6 is an SEM image of the positive electrode active material manufactured in Comparative Example 4.

[0247] Figure 7 is an SEM image of the positive electrode active material manufactured in Comparative Example 5.

[0248] As shown in Figures 1 to 7, it was confirmed that the positive electrode active material manufactured in Example 1 according to the present invention was in the form of a single particle. In addition, it was confirmed that the positive electrode active material manufactured in Example 1 had an excellent degree of single particle formation and an improved particle shape compared to Comparative Examples 1 to 3 in which Zr and / or Y were not doped, Comparative Example 4 manufactured by firing at a temperature of less than 920°C, and / or Comparative Example 5 manufactured by firing at a temperature of more than 980°C.

[0249] Doping element weight (ppm) Yttrium (Y) Zirconium (Zr) Example 1 Li 1.029 Ni 0.5995 Co 0.0498 Mn 0.3465 Y 0.0014 Zr 0.0028 O21,3602,790 Example 2Li 1.029 Ni 0.6006 Co 0.0488 Mn 0.3466 Y 0.0013 Zr 0.0027 O21,3402,650Comparative example 1Li 1.028 Ni 0.604 Co 0.049 Mn 0.347 O200 Comparison Example 2Li 1.022 Ni 0.6053 Co 0.0489 Mn 0.3431 Zr 0.0027 O202,710 Comparative Example 3Li 1.024 Ni 0.6042 Co 0.0489 Mn 0.3455 Y 0.0014 O21,3600 comparison example 4Li 1.040 Ni 0.6016 Co 0.0498 Mn 0.3446 Y 0.0014 Zr 0.0026 O21,3802,610 Comparative Example 5Li 1.030 Ni 0.6004 Co 0.0498 Mn 0.3455 Y 0.0014 Zr0.0029 O21,3802,880

[0250] Through Table 1, it was confirmed that the positive electrode active materials manufactured in Examples 1 and 2 had a composition represented by Chemical Formula 1, the content of nickel (Ni) among the total metals excluding lithium was 59 mol% or more and 70 mol% or less, the content of yttrium (Y) in the lithium composite transition metal oxide was 500 ppm or more and 4,000 ppm or less based on the total weight of the lithium composite transition metal oxide, and the content of zirconium (Zr) in the lithium composite transition metal oxide was 500 ppm or more and 4,000 ppm or less based on the total weight of the lithium composite transition metal oxide.

[0251] - Evaluation of single particle size and fine particle size of positive electrode active material

[0252] The average particle diameter (D) of the lithium composite transition metal oxides prepared in Examples 1 and 2 and Comparative Examples 1 to 5 was measured using PSA (S3500, Microtrac). 50 ) were measured and shown in Table 2 below.

[0253] In addition, using SEM (FEI, Inspect F), SEM images (5K magnification) of the lithium composite transition metal oxides manufactured in Examples 1 and 2 and Comparative Examples 1 to 5 were obtained, and using an image processing program (LG Chemical, DX program), the boundaries of the primary particles existing in the SEM images were divided and images were displayed in random colors. Using the images in which the boundaries of the primary particles were divided and displayed in random colors, the area of ​​each primary particle was calculated through the number of pixels corresponding to each of n primary particles (an average of 50,000 or more primary particles), and the average particle diameter (D') of the primary particles existing in the lithium composite transition metal oxides manufactured in Examples 1 and 2 and Comparative Examples 1 to 5 was calculated using the radius of a circle having the same area as the area of ​​each primary particle. 50) was measured and shown in Table 2 below. And, the average particle diameter (D) of lithium composite transition metal oxide 50 ) for the average particle diameter (D') of the primary particles 50 ) was calculated (the degree of single particle magnetization (χ)) and is shown in Table 2 below.

[0254] With respect to the fine particles present in the positive electrode active material, the area of ​​the fine particles relative to the total area of ​​the primary particles present in the positive electrode active material, i.e., the ratio (%) of the area of ​​the primary particles having a particle size of 1 μm or less, was calculated, and the results are shown in Table 2 below. Specifically, the area of ​​each primary particle was calculated through the number of pixels corresponding to each of n primary particles present in the SEM image, and the percentage of the area of ​​the fine particles relative to the total area of ​​the primary particles (the ratio (%) of the area of ​​the primary particles having a particle size of 1 μm or less) is shown in Table 2 below.

[0255] The steps of the above SEM image processing program (LG Chemical, DX program) are shown in Figures 8 to 10.

[0256] Figure 8 is an SEM image of a positive electrode active material according to one embodiment of the present invention.

[0257] FIG. 9 is an image showing the boundaries of primary particles within a positive electrode active material divided using an SEM image of the positive electrode active material according to one embodiment of the present invention.

[0258] FIG. 10 is an image showing the boundaries of primary particles in a positive electrode active material divided and represented in random colors using an SEM image of a positive electrode active material according to one embodiment of the present invention.

[0259] Average particle size (㎛) Degree of particle magnetization (χ) Proportion of the area of ​​primary particles with a particle size of 1 ㎛ or less (%) Primary particles (D') 50 )Lithium complex transition metal oxide (D 50) Example 12.54.10.610 Example 22.83.80.73 Comparative Example 11.74.30.430 Comparative Example 21.74.40.426 Comparative Example 32.03.90.516 Comparative Example 41.64.00.426 Comparative Example 53.84.30.92

[0260] Through Table 2, the positive electrode active materials manufactured in Examples 1 and 2, i.e., positive electrode active materials containing yttrium (Y) and zirconium (Zr), have an average particle diameter (D') of primary particles. 50 ) is 2.0㎛ or more and 3.5㎛ or less, and the average particle diameter (D) of the lithium composite transition metal oxide 50 ) is 2.0㎛ or more and 5.0㎛ or less, the particle size (χ) according to the formula 1 described in this specification is 0.4 or more, and the ratio of the area of ​​primary particles having a particle size of 1㎛ or less to the total area of ​​primary particles present in the positive electrode active material is 20% or less. On the other hand, the positive electrode active materials manufactured in Comparative Examples 1, 2, 4 and 5 had an average particle size (D') of primary particles 50 ) was confirmed to be less than 2.0 ㎛ or greater than 3.5 ㎛. In addition, it was confirmed that the positive electrode active materials manufactured in Comparative Examples 1, 2, and 4 had a ratio of the area of ​​primary particles having a particle diameter of 1 ㎛ or less to the total area of ​​primary particles present in the positive electrode active materials of more than 20%.

[0261]

[0262] Experimental Example 2: Battery Characteristics Evaluation

[0263] - Manufacturing pouch-type monocell batteries

[0264] A positive electrode slurry was prepared by mixing 95 wt% of the positive electrode active materials manufactured in Examples 1 and 2 and Comparative Examples 1 to 5, 2.0 wt% of Super P as a conductive agent, and 3.0 wt% of polyvinylidene fluoride (PVDF) as a binder in an N-methylpyrrolidone (NMP) solvent. The prepared positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to prepare a positive electrode.

[0265] A negative electrode slurry was prepared by mixing a negative electrode active material consisting of natural graphite and artificial graphite in a weight ratio of 5:5, a Super C conductive agent, an additive (Daicel, DAICEL2200), and a binder (ZEON, BML302) in water in a weight ratio of 95.6:1.0:2.3:1.1. The negative electrode slurry was applied to one surface of a copper current collector, dried at 130°C, and rolled to prepare a negative electrode.

[0266] An electrode assembly was manufactured by interposing a porous polyethylene separator between the positive and negative electrodes. This was placed inside a battery case, and an electrolyte solution containing 0.7 M LiPF6 and 0.3 M LiFSI dissolved in an organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7 was injected to manufacture a pouch-type monocell battery.

[0267]

[0268] - Evaluation of battery capacity characteristics and life characteristics

[0269] Using the pouch-type monocell manufactured as described above, the battery was charged (0.1C) in the CC-CV manner to 4.4 V at 25°C, and then discharged (0.1C) in the CC manner to 2.5 V. The discharge capacity at this time was measured and shown in Table 3.

[0270] After charging (0.1C) to 4.4 V in CC-CV mode at 25℃ and discharging (0.1C) to 2.5 V in CC mode, the SOC state was set based on the measured discharge capacity, and the initial SOC50 resistance (Ω) was measured at 25℃, and after charging (0.33C) to 4.4 V in CC-CV mode at 45℃ and discharging (0.33C) to 2.5 V in CC mode, one cycle was considered as 100 cycles of charging and discharging, and then the SOC50 resistance (Ω) was measured immediately after the 100th cycle at 25℃, and the percentage (resistance increase rate (%)) of the SOC50 resistance immediately after the 100th cycle with respect to the initial SOC50 resistance is shown in Table 3 below. The above SOC50 resistance is a value calculated by measuring the voltage drop by applying a 2.5C discharge current at SOC50 for 30 seconds at 25℃, and then dividing the voltage drop for the initial 10 seconds by the applied current.

[0271] After charging (0.33C) to 4.4 V at 45°C in the CC-CV manner, and then discharging (0.33C) to 2.5 V in the CC manner, one cycle was defined as a cycle, and a total of 100 cycles of charging and discharging were repeated. After measuring the discharge capacity in the first and 100th cycles, the percentage of the discharge capacity in the 100th cycle to the discharge capacity in the first cycle (capacity retention rate (%)) is shown in Table 3 below.

[0272] @25℃, 0.1C@45℃, 0.33C@25℃, 2.5CInitial discharge capacity (mAh / g)Discharge capacity (mAh / g)Capacity retention rate (%)SOC50 resistance (Ω)Resistance increase rate (%)First cycle100th cycleInitialImmediately after 100th cycleExample 1186189181961.492.9497Example 2186190182961.472.97102Comparative example 1185188171911.804.64158Comparative example 2183186173931.443.18121Comparative example 3183186175941.623.40110Comparative example 4190193172891.444.11186Comparative example 5184188171911.793.79112

[0273] Through Table 3, it was confirmed that the batteries including the positive electrode active materials manufactured in Examples 1 and 2, i.e., the positive electrode active materials including yttrium (Y) and zirconium (Zr), had high discharge capacities and capacity retention rates in the first and 100th cycles at 45°C, and low resistance increase rates at 25°C. On the other hand, the batteries including the positive electrode active materials manufactured in Comparative Examples 1 to 3, i.e., the positive electrode active materials not including yttrium (Y) and / or zirconium (Zr), and the positive electrode active materials manufactured in Comparative Examples 4 and 5, i.e., the average particle diameter (D') of the primary particles 50 ) It was confirmed that a battery including a positive electrode active material having a particle size of less than 2.0㎛ or greater than 3.5㎛ had low discharge capacity and capacity retention rate in the first and 100th cycles at 45℃ and a high resistance increase rate at 25℃.

[0274] In conclusion, it can be seen that the positive electrode active material according to the present invention is stable with little structural change even during charge and discharge cycles.

Claims

Contains a lithium composite transition metal oxide in the form of a single particle composed of 1.10 or less primary particles, The above lithium composite transition metal oxide has a nickel (Ni) content of 50 mol% or more among all metals excluding lithium, and includes yttrium (Y) and zirconium (Zr). The average particle diameter (D') of the above primary particles 50 ) is a positive electrode active material having a diameter of 2.0㎛ or more and 3.5㎛ or less.

2. In claim 1, The above lithium composite transition metal oxide is a cathode active material having a nickel (Ni) content of 59 mol% or more and 70 mol% or less among all metals excluding lithium.

3. In claim 1, The above lithium composite transition metal oxide is a positive electrode active material having a composition represented by the following chemical formula 1: [Chemical Formula 1] Li 1+x Ni a Co b Mr c Y d Zr e M f O2 In the above chemical formula 1, M is at least one selected from B, Al, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, and La, -0.1≤x≤0.1, 0.59≤a<1, 0 <b<0.41, 0<c<0.41, 0<d≤0.1, 0<e≤0.1, 0≤f≤0.1이다.

4. In claim 1, The above lithium composite transition metal oxide is a cathode active material having a single particle magnetization (χ) of 0.4 or more according to the following formula 1: [Formula 1] .

5. In claim 4, A cathode active material having a single particle magnetization (χ) of 0.55 or more and 0.65 or less.

6. In claim 1, The average particle diameter (D) of the above lithium composite transition metal oxide 50 ) is a positive electrode active material having a diameter of 2.0㎛ or more and 5.0㎛ or less.

7. In claim 1, A positive electrode active material in which the ratio of the area of ​​primary particles having a particle diameter of 1㎛ or less to the total area of ​​primary particles present in the positive electrode active material is 20% or less.

8. In claim 1, A cathode active material, wherein the content of yttrium (Y) in the lithium composite transition metal oxide is 500 ppm or more and 4,000 ppm or less based on the total weight of the lithium composite transition metal oxide.

9. In claim 1, A positive electrode active material, wherein the content of zirconium (Zr) in the lithium composite transition metal oxide is 500 ppm or more and 4,000 ppm or less based on the total weight of the lithium composite transition metal oxide. 10.(A) A step of preparing a mixture by mixing a composite transition metal hydroxide containing nickel, a lithium (Li)-containing raw material, a yttrium (Y)-containing raw material, and a zirconium (Zr)-containing raw material; (B) a step of producing a lithium composite transition metal oxide by calcining the mixture; A method for producing a positive electrode active material according to claim 1, wherein the above-mentioned sintering is performed at a temperature of 920°C or higher and 980°C or lower.

11. In claim 10, A method for producing a positive electrode active material, wherein in the step (A), the yttrium (Y)-containing raw material is mixed so that the yttrium (Y) content is 500 ppm or more and 4,000 ppm or less with respect to the total weight of the composite transition metal hydroxide.

12. In claim 10, A method for manufacturing a positive electrode active material, wherein in the step (A), the zirconium (Zr)-containing raw material is mixed so that the zirconium (Zr) content is 500 ppm or more and 4,000 ppm or less with respect to the total weight of the composite transition metal hydroxide.

13. A positive electrode comprising a positive electrode active material according to any one of claims 1 to 9.

14. A lithium secondary battery comprising a positive electrode according to claim 13.

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