Cathode active material, 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; and a cathode and a lithium secondary battery which comprise the cathode active material. The cathode active material comprises: a lithium composite transition metal oxide in the form of a single particle composed of 50 or less primary particles; and a coating layer containing a coating element and formed on the lithium composite transition metal oxide, wherein the coating element is at least one selected from the group consisting of Zn, Co, Ti, Nb, V, Mo, W, Al, Zr, and B, the dibutylphthalate (DBP) oil absorption per 100 g of the cathode active material is 25.0 ml or less, and the circularity according to Equation 1 described in the present specification is 0.70 or more.

Description

Positive electrode active material, and positive electrode and lithium secondary battery containing the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0042077, filed March 27, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a positive electrode active material, 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 expected to be commercialized and widely used.

[0007] First, lithium composite transition metal oxides are 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 excellent capacity characteristics. However, LiCoO2 suffers from extremely poor thermal properties due to crystal structure instability following delithiation, and 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 in the form of secondary particles formed by agglomeration of many primary 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 order to manufacture a lithium secondary battery with high energy density and voltage, long cycle life, and low self-discharge rate among secondary batteries, not only the cathode active material described above but also the electrode's coating properties are important issues. Generally, the cathode is manufactured by mixing the cathode active material, binder, conductive material, etc., applying it on a current collector, drying it, and then press forming. The purpose of press forming is to improve the electrode density, and the press forming is repeated until a certain density is reached. At this time, if the amount of binder is insufficient, the bonding strength between the cathode active materials or between the cathode active material and the current collector is reduced, which may cause the electrode to crack or the cathode mixture layer to peel off from the current collector. On the other hand, if the amount of binder is excessive, the proportion of the cathode active material in the electrode decreases, which may cause the energy density of the electrode to be low.

[0012] Therefore, there is a need to develop a cathode active material that can realize a lithium secondary battery with improved conductivity and energy density.

[0013]

[0014] [Prior Art Literature]

[0015] [Patent Document]

[0016] Korean Patent Publication No. 10-2021-0097528

[0017]

[0018] The present invention is intended to solve the above problems, and to provide a positive electrode active material having excellent conductivity and energy density and a method for manufacturing the same.

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

[0020]

[0021] (1) The present invention provides a positive electrode active material comprising a lithium composite transition metal oxide in the form of a single particle composed of 50 or fewer primary particles; and a coating layer formed on the lithium composite transition metal oxide, wherein the coating layer comprises at least one coating element selected from the group consisting of Zn, Co, Ti, Nb, V, Mo, W, Al, Zr, and B, and has an absorption amount of DBP (dibutyl phthalate) of 25.0 ml or less per 100 g of the positive electrode active material, and a circularity according to the following formula 1 of 0.70 or more.

[0022] [Formula 1]

[0023] Circularity =

[0024] In the above equation 1, A is the area of ​​the primary particle measured in the SEM image, and P is the perimeter of the primary particle measured in the SEM image.

[0025] (2) The present invention provides a positive electrode active material in (1) above, wherein the lithium composite transition metal oxide has a nickel content of 50 mol% or more among the total transition metals.

[0026] (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.

[0027] [Chemical Formula 1]

[0028] Li 1+x Ni a Co b M 1 c M 2 d O2

[0029] In the above chemical formula 1, the M 1 is at least one selected from the group consisting of Al and Mn, and the M 2is at least one selected from the group consisting of B, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P and Sr, and -0.10≤x≤0.30, 0.5000≤a<1.0000, 0.0000 <b<0.5000, 0.0000<c<0.5000, 0.0000≤d≤0.3000이다.

[0030] (4) The present invention is characterized in that the average particle diameter (Dv) of the primary particles is in any one of the above (1) to (3). 50 ) provides a positive electrode active material having a diameter of 2.00 ㎛ or more and 6.00 ㎛ or less.

[0031] (5) The present invention provides a positive electrode active material in which the ratio of the area of ​​primary particles having a particle diameter of less than 1 ㎛ to the total area of ​​primary particles present in the positive electrode active material is 10% or less in any one of the above (1) to (4).

[0032] (6) The present invention provides a positive electrode active material in any one of the above (1) to (5), wherein the coating layer includes at least one selected from the group consisting of M'-O compounds and Li-M'-O compounds, and M' is at least one selected from the group consisting of Zn, Co, Ti, Nb, V, Mo, W, Al, Zr, and B.

[0033] (7) The present invention has a tap density of 2.00 g / cm in any one of the above (1) to (6). 3 More than 2.50 g / cm 3 A positive electrode active material is provided as follows.

[0034] (8) The present invention relates to any one of the above (1) to (7), wherein the average particle diameter (D 50 ) provides a positive electrode active material having a diameter of 3.0 ㎛ or more and 6.0 ㎛ or less.

[0035] (9) The present invention provides a positive electrode active material having an absorption amount of DBP (dibutyl phthalate) of 10.0 ml or more and 25.0 ml or less per 100 g of the positive electrode active material in any one of the above (1) to (8).

[0036] (10) The present invention provides a positive electrode active material having a circularity of 0.70 or more and 0.80 or less in any one of the above (1) to (9).

[0037] (11) The present invention provides a positive electrode comprising a positive electrode active material according to any one of (1) to (10).

[0038] (12) The present invention provides a lithium secondary battery including a positive electrode according to (11) above.

[0039]

[0040] The positive electrode active material of the present invention comprises a lithium composite transition metal oxide in the form of a single particle composed of 50 or fewer primary particles; and a coating layer formed on the lithium composite transition metal oxide, wherein the coating element is at least one selected from the group consisting of Zn, Co, Ti, Nb, V, Mo, W, Al, Zr, and B, and the positive electrode active material has an absorption amount of DBP (dibutyl phthalate) of 25.0 ml or less per 100 g of the positive electrode active material, and a circularity according to Equation 1 described in the present specification is 0.70 or more, thereby preventing an increase in the viscosity of the positive electrode slurry, thereby improving the electrode porosity, and has an effect of increasing the electrode density by reducing the voids between positive electrode active material particles.

[0041] Accordingly, there is an effect of improving the capacity characteristics of the positive electrode and secondary battery including the positive electrode active material.

[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 a SEM image of the positive electrode active material manufactured in Example 3.

[0047] Figure 4 is an SEM image of the positive electrode active material manufactured in Comparative Example 1.

[0048] Figure 5 is an SEM image of the positive electrode active material manufactured in Comparative Example 2.

[0049] Figure 6 is an SEM image of the positive electrode active material manufactured in Comparative Example 3.

[0050] Figure 7 is an SEM image of the positive electrode active material manufactured in Comparative Example 4.

[0051] Figure 8 is an SEM image of the positive electrode active material manufactured in Comparative Example 5.

[0052] Figure 9 is an SEM image of the positive electrode active material manufactured in Comparative Example 6.

[0053] Figure 10 is an SEM image of the positive electrode active material manufactured in Comparative Example 7.

[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 spirit 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 possible manner.

[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 50 or fewer primary particles, in contrast to the spherical secondary particle form formed by 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 50 or fewer 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, 'DBP adsorption (dibutylpthalate adsorption)' is a measure of how much liquid (particularly, non-aqueous electrolyte) can enter the gaps between particles and the internal pores of the particles. The DBP adsorption is related to the amount of binder required for electrode manufacturing, and thus serves as an indicator of the electrode's porosity.

[0062] The DBP uptake can be measured by calculating the change in torque generated when DBP is mixed with a certain amount of the positive electrode active material using an uptake measuring instrument (for example, Asahi absorption tester S-500, manufactured by Asahi).

[0063] In this specification, the number of pixels corresponding to each of the n primary particles present in the SEM image and the length of the boundary surface can be confirmed using a scanning electron microscope (SEM) image and an image processing program (refer to LG Chem, DX program, KR Patent No. 2022-0175986). Specifically, it can be measured from a two-dimensional segmentation image segmented by primary particle units obtained by image processing using an artificial intelligence model. The segmentation image can be obtained by acquiring a scanning electron microscope (SEM) image of the positive electrode active material powder to be measured, inputting the acquired SEM image into a U-NET structure or the like to generate a boundary image, generating a boundary removal image by removing the boundary in the SEM image based on the boundary image, identifying a plurality of objects included in the boundary removal image, and segmenting the SEM image into primary particle units based on the plurality of objects.

[0064] In the present specification, the area of ​​a primary particle may be calculated through the number of pixels corresponding to each of n primary particles existing in the SEM image. Specifically, the area of ​​the primary particle may be calculated through the number of pixels of the surface area corresponding to each primary particle when the scanning electron microscope (SEM) image is converted into a segmentation image, which is an image projected onto a two-dimensional plane. In addition, the perimeter of the primary particle may be the length of the boundary surface corresponding to each of n primary particles existing in the SEM image. Specifically, the perimeter of the primary particle means the length of the outer boundary surface forming the outermost surface of each primary particle when the scanning electron microscope (SEM) image is converted into a segmentation image, which is an image projected onto a two-dimensional plane.

[0065] In this specification, circularity is an indicator of the degree to which the cross-sectional shape of a particle is close to a circle, and can be defined as the relationship between the area of ​​a primary particle measured in an SEM image and the circumference of the primary particle.

[0066] In this specification, the particle size of the primary particle 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.

[0067] In this specification, the average particle diameter (Dv) of the primary particles 50) may be measured using a scanning electron microscope (SEM) (FEI, Inspect F). Specifically, it can be defined as a 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 obtained using a scanning electron microscope (SEM). The volume of a sphere having a radius equal to half of the particle size of the primary particle obtained using a scanning electron microscope (SEM) is the volume of the primary particle, and then the particle diameter at the point where the volume cumulative distribution according to the particle size in the result of calculating the volume of the primary particle is 50% can be measured.

[0068] In this specification, the differential is a positive electrode active material particle having a particle diameter of 1 μm or less, which is 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 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.

[0069] In this specification, the content of each element in the positive electrode active material may be measured through ICP (Inductive Coupled Plasma) analysis using an inductively coupled plasma optical emission spectrometer (ICP-OES; Avio 220 Max, Perkin Elmer).

[0070] In this specification, tap density is measured at a distance of about 20 cm using a conventional tap density meter (e.g., GEOPYC-1365 from Micromeritics). 3 It can be measured by filling 10g of powder into a container, applying pressure of 108N, measuring the density of the particles twice, and calculating the average of the measured values.

[0071] In this specification, the average particle diameter (D 50) may be measured using a laser diffraction particle size measuring device (e.g., S3500 from Microtrac). Specifically, it 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 obtained using a laser diffraction particle size measuring device. After dispersing the powder to be measured in a dispersion medium, the particle size distribution is calculated by measuring the difference in diffraction pattern according to particle size when the particles pass through the laser beam, and calculating the particle diameter at the point where the volume cumulative distribution according to the particle size in the measuring device is 50%, thereby measuring.

[0072] In this specification, the specific surface area is measured by the BET method, and can be calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77 K) using, for example, TriStar II Plus from Micromeritics.

[0073]

[0074] positive electrode active material

[0075] Hereinafter, the positive electrode active material according to the present invention will be described.

[0076]

[0077] The cathode active material according to the present invention is a cathode active material comprising a lithium composite transition metal oxide in the form of a single particle composed of 50 or fewer primary particles; and a coating layer formed on the lithium composite transition metal oxide; wherein the coating layer comprises at least one coating element selected from the group consisting of Zn, Co, Ti, Nb, V, Mo, W, Al, Zr, and B, and has an absorption amount of DBP (dibutyl phthalate) of 25.0 ml or less per 100 g of the cathode active material, and a circularity according to the following formula 1 of 0.70 or more.

[0078] [Formula 1]

[0079] Circularity =

[0080] In the above equation 1, A is the area of ​​the primary particle measured in the SEM image, and P is the perimeter of the primary particle measured in the SEM image.

[0081]

[0082] The lithium composite transition metal oxide is in the form of a single particle composed of 50 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 or more but 50 or fewer particles are aggregated. The single particle form is distinguished from a secondary particle in which more than 50 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.

[0083]

[0084] The above-described positive electrode active material includes a coating layer formed on a lithium composite transition metal oxide, and the coating layer includes at least one coating element selected from the group consisting of Zn, Co, Ti, Nb, V, Mo, W, Al, Zr, and B. By including the coating layer including the above-described coating element, deterioration of the positive electrode surface due to a side reaction of the electrolyte can be suppressed, and electrical conductivity can be improved, thereby improving output characteristics. In the case where the coating layer including the above-described coating element is not included, there is a problem that the life characteristics are inferior due to a side reaction between the positive electrode active material and the electrolyte, and the electrical conductivity is low, resulting in inferior output characteristics.

[0085]

[0086] In the present invention, circularity is evaluated and expressed as a parameter represented by the following equation 1. The circularity referred to in the present invention is a value that is adjusted according to the area of ​​the primary particle forming the single particle and the perimeter of the primary particle forming the single particle, and the closer the square of the perimeter of the primary particle is to a value 4π times the area of ​​the primary particle, the higher the circularity appears.

[0087] For example, the maximum value of the circularity is 1.00, which means that the cross-sectional shape of one primary particle is close to an ideal circle.

[0088] [Formula 1]

[0089] Circularity =

[0090] In the above equation 1, A is the area of ​​the primary particle measured in the SEM image, and P is the perimeter of the primary particle measured in the SEM image.

[0091] The above positive electrode active material has a circularity of 0.70 or more. Specifically, the circularity may be 0.70 or more, or 0.71 or more, and may be 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, 0.80 or less, 0.90 or less, or 1.00 or less. When the circularity satisfies the above range, the coating property of the positive electrode slurry is excellent even when a small amount of binder is used. In particular, when the circularity is 0.70 or more and 0.80 or less, there is an effect of further improving the energy density of the electrode.

[0092]

[0093] The present inventors have found that when a positive electrode active material including a lithium composite transition metal oxide in the form of a single particle composed of 50 or fewer primary particles; and a coating layer formed on the lithium composite transition metal oxide and including at least one coating element selected from the group consisting of Zn, Co, Ti, Nb, V, Mo, W, Al, Zr, and B; has an absorption amount of DBP (dibutyl phthalate) of 25.0 ml or less per 100 g of the positive electrode active material, a positive electrode slurry having an appropriate viscosity required for electrode production can be produced when mixed with a binder or the like, and specifically, when the absorption amount of DBP (dibutyl phthalate) per 100 g of the positive electrode active material of the positive electrode active material is 10.0 ml or more and 25.0 ml or less, the porosity of the slurry including the positive electrode active material can be improved while maintaining the energy density. For reference, DBP absorption is a parameter related to the absolute input of DBP into the pores between positive electrode active material particles and is not related to the absorption rate.

[0094] In addition, when the circularity according to Equation 1 in this specification is 0.70 or more, the pores of the positive electrode mixture layer are reduced, so that the amount of binder required for electrode manufacture can be reduced, and when the absorption amount of DBP (dibutyl phthalate) per 100 g of positive electrode active material is 25.0 ml or less and the circularity according to Equation 1 described in this specification is 0.70 or more, the coating property of the positive electrode slurry is excellent even when a small amount of binder is used, and the energy density of the electrode is improved by using a small amount of binder, thereby completing the present invention.

[0095]

[0096] Meanwhile, lithium composite transition metal oxides in the form of single particles consisting of 50 or fewer primary particles; And a coating layer formed on the lithium composite transition metal oxide; a positive electrode active material including a positive electrode active material, wherein the coating layer comprises at least one coating element selected from the group consisting of Zn, Co, Ti, Nb, V, Mo, W, Al, Zr and B, and when the positive electrode active material includes DBP (dibutyl phthalate) per 100 g of the positive electrode active material exceeds 25 ml, the viscosity of the slurry containing the positive electrode active material increases when mixed with a binder, which causes a problem of poor coating properties, and when an excessive amount of binder is used to produce a slurry having an appropriate viscosity required for electrode production, there is a problem of poor energy density, and when the circularity according to the formula 1 described in the present specification is less than 0.70, there is a problem of excessive pores in the positive electrode mixture layer, which causes a low energy density, and a relatively excessive amount of binder content is required, and when the circularity according to the formula 1 described in the present specification is less than 0.70, there is a problem of excessive pores in the positive electrode mixture layer, which causes a low energy density, and a problem of requiring a relatively excessive amount of binder, and when the absorption of DBP (dibutyl phthalate) per 100 g of the positive electrode active material exceeds 25.0 ml and ... according to the formula described in the present specification When the circularity according to 1 is less than 0.70, there is a problem of using an excessive amount of binder for the porosity of the positive electrode slurry, and there is a problem of the energy density of the electrode being lowered due to the excessive use of binder.

[0097]

[0098] According to one embodiment of the present invention, the lithium composite transition metal oxide has a nickel content of 50 mol% or more among the total transition metals. Specifically, the lithium composite transition metal oxide may have a nickel content of 50 mol% or more, or 60 mol% or more among the total transition metals, and may have a nickel content of 70 mol% or less, 80 mol% or less, 95 mol% or less, or 99 mol% or less among the total transition metals. When the nickel content among the total transition metals in the lithium composite transition metal oxide is within the above range, the capacity characteristics of the positive electrode active material can be improved.

[0099]

[0100] According to one embodiment of the present invention, the lithium composite transition metal oxide has a composition represented by the following chemical formula 1.

[0101] [Chemical Formula 1]

[0102] Li 1+x Ni a Co b M 1 c M 2 d O2

[0103] In the above chemical formula 1,

[0104] Above M 1 is at least one selected from the group consisting of Al, Mn,

[0105] Above M 2 is at least one selected from the group consisting of B, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P and Sr,

[0106] -0.10≤x≤0.30, 0.5000≤a<1.0000, 0.0000 <b<0.5000, 0.0000<c<0.5000, 0.0000≤d≤0.3000이다.

[0107] Above M 1 M may be at least one selected from the group consisting of Al and Mn. 1 is included as a must.

[0108] Above M 2 is a doping element, specifically the above M 2 It may be at least one selected from the group consisting of B, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P and Sr. The above M 2 Although it is not essential to include, if included in an appropriate amount, the particle shape of the positive electrode active material can be improved and the stability of the crystal structure can be enhanced. In particular, M 2When Zr is used, there is an effect of improving high temperature life.

[0109] Meanwhile, the above x may be -0.10 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, 0.00 or more, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, or 0.05 or more, and may be 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, 0.10 or less, 0.20 or less, or 0.30 or less. When x satisfies the above range, high-capacity characteristics and high energy density per unit volume can be realized.

[0110] 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 0.5000 or more, or 0.6000 or more, and may be 0.6100 or less, 0.6200 or less, 0.6300 or less, 0.6400 or less, 0.6500 or less, 0.6600 or less, 0.6700 or less, 0.6800 or less, 0.6900 or less, 0.7000 or less, 0.8000 or less, 0.9000 or less, or less than 1.0000. When a is within the above range, the capacity characteristics of the positive electrode active material can be improved. In particular, when a is 0.6000 or more and 0.6500 or less, the structural stability and thermal stability of the positive electrode active material can be improved.

[0111] 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 0.0000, 0.0500 or more, 0.1000 or more, or 0.1500 or more, and may be 0.2000 or less, 0.2500 or less, 0.3000 or less, 0.3500 or less, 0.4000 or less, 0.4500 or less, or less than 0.5000. When b satisfies the above range, the output characteristics can be improved during the charge and discharge process.

[0112] The above c is M of all metals except lithium in the lithium complex transition metal oxide. 1 , that is, the mole fraction of at least one selected from the group consisting of manganese (Mn) and aluminum (Al) may be greater than 0.0000, 0.0500 or more, 0.1000 or more, or 0.1500 or more, and may be 0.2000 or less, 0.2500 or less, 0.3000 or less, 0.3500 or less, 0.4000 or less, 0.4500 or less, or less than 0.5000. When c satisfies the above range, structural stability may increase, and the decomposition reaction of the electrolyte may be relatively reduced.

[0113] The above d is M of all metals except lithium in the lithium composite transition metal oxide. 2 The mole fraction of d may be 0.0000 or more, 0.0100 or less, 0.0200 or less, 0.0300 or less, 0.0400 or less, 0.0500 or less, 0.0600 or less, 0.0700 or less, 0.0800 or less, 0.0900 or less, 0.1000 or less, 0.2000 or less, or 0.3000 or less. When d satisfies the above range, the structural stability of the positive electrode active material can be improved.

[0114] The above a, b, c, d can be a+b+c+d=1.0000.

[0115]

[0116] According to one embodiment of the present invention, the primary particles have an average particle diameter (Dv 50 ) may be 2.00 ㎛ or more and 6.00 ㎛ or less. Specifically, the primary particles may have an average particle diameter (Dv 50 ) may be 2.00 ㎛ or more, 2.50 ㎛ or more, or 3.00 ㎛ or more, and may be 4.00 ㎛ or less, 4.50 ㎛ or less, 5.00 ㎛ or less, 5.50 ㎛ or less, or 6.00 ㎛ or less. The average particle diameter (Dv) of the primary particles 50) is within the above range, the output characteristics and charge / discharge efficiency can be improved.

[0117]

[0118] According to one embodiment of the present invention, the ratio of the area of ​​particles having a particle diameter of less than 1 μm to the total area of ​​primary particles present in the positive electrode active material may be 10% or less. Specifically, the ratio may be 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, or 4% or less. When the area ratio of primary particles having a particle diameter of less than 1 μm is within the above range, the resistance characteristics may be improved, and the energy density of the electrode may be improved.

[0119]

[0120] According to one embodiment of the present invention, the shape of the coating layer may be a film type, an island type, or a combination thereof. The film type may be a continuous shape, and the island type may be a discontinuous shape. When the coating layer satisfies the above shapes, the mobility of lithium ions may be enhanced, thereby improving capacity characteristics.

[0121]

[0122] According to one embodiment of the present invention, the coating layer includes at least one selected from the group consisting of M'-O compounds and Li-M'-O compounds, wherein M' may include at least one selected from the group consisting of Zn, Co, Ti, Nb, V, Mo, W, Al, Zr and B. Specifically, Li-Al-O compounds, Li-BO compounds or BO compounds, more specifically, LiAlO2, LiBO3, LiB2O3, When at least one selected from the group consisting of LiB2O4, B3O5 and Li2B3O6 is used, side reactions with the electrolyte can be reduced, thereby improving life characteristics, especially at high temperatures.

[0123]

[0124] According to one embodiment of the present invention, the content of the coating layer may be 0.01 part by weight or more and 0.50 part by weight or less based on 100 parts by weight of the lithium composite transition metal oxide. Specifically, the content of the coating layer may be 0.01 part by weight or more, 0.02 part by weight or more, 0.03 part by weight or more, 0.04 part by weight or more, 0.05 part by weight or more, 0.06 part by weight or more, 0.07 part by weight or more, 0.08 part by weight or more, 0.09 part by weight or more, 0.10 part by weight or more, or 0.20 part by weight or more, and may be 0.30 part by weight or less, 0.40 part by weight or less, or 0.50 part by weight or less. When the content of the coating layer is within the above range, the structural stability and electrical conductivity of the positive electrode active material are improved without acting as a resistor, so that the capacity characteristics can be improved.

[0125]

[0126] According to one embodiment of the present invention, the total content of the coating elements included in the coating layer may be 300 ppm or more and 3,000 ppm or less with respect to the total weight of the lithium composite transition metal oxide. Specifically, the total content of the coating element included in the coating layer may be 300 ppm or more, 400 ppm or more, 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 less, 1,300 ppm or less, 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, It may be 2,600 ppm or less, 2,700 ppm or less, 2,800 ppm or less, 2,900 ppm or less, or 3,000 ppm or less. When the content of the coating element is within the above range, the structural stability and electrical conductivity of the positive electrode active material are improved without acting as a resistor, so that the capacity characteristics can be improved.

[0127]

[0128] According to one embodiment of the present invention, the positive electrode active material has a tap density of 2.00 g / cm 3 More than 2.50 g / cm 3 It may be less than or equal to 2.00 g / cm2. Specifically, the tap density is 2.00 g / cm2. 3 Above, 2.10 g / cm 3 or 2.20 g / cm 3 It may be more than 2.30 g / cm 3 Below, 2.40 g / cm3 or less, or 2.50 g / cm 3 It may be as follows. When the tap density is within the above range, there is an effect of further improving the energy density of the electrode.

[0129]

[0130] According to one embodiment of the present invention, the positive electrode active material has an average particle diameter (D 50 ) may be 3.0 ㎛ or more and 6.0 ㎛ or less. Specifically, the average particle diameter (D 50 ) may be 3.0 ㎛ or more, 3.5 ㎛ or more, or 4.0 ㎛ or more, and may be 4.5 ㎛ or less, 5.0 ㎛ or less, 5.5 ㎛ or less, or 6.0 ㎛ or less. The average particle diameter (D of the positive electrode active material 50 ) is within the above range, the output characteristics and charge / discharge efficiency can be improved.

[0131]

[0132] Method for manufacturing positive electrode active material

[0133] 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.

[0134]

[0135] A method for manufacturing a cathode active material according to the present invention comprises the steps of (A) mixing a composite transition metal hydroxide and a lithium (Li)-containing raw material, and then calcining to manufacture a lithium composite transition metal oxide; (B) mixing the lithium composite transition metal oxide and a coating element-containing raw material, and then heat-treating to form a coating layer on the lithium composite transition metal oxide; wherein the calcination is performed at a temperature of 960°C or higher and 1,100°C or lower, the coating element is at least one selected from the group consisting of Zn, Co, Ti, Nb, V, Mo, W, Al, Zr, and B, and the heat treatment is performed at a temperature of 300°C or higher and 400°C or lower.

[0136]

[0137] 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 firing and heat treatment time, the firing amount, etc.

[0138]

[0139] Hereinafter, each step of the present invention will be described in detail.

[0140]

[0141] (A) Step

[0142] The method for manufacturing a cathode active material according to the present invention includes the step (A) of mixing a composite transition metal hydroxide and a lithium (Li)-containing raw material and then calcining to manufacture a lithium composite transition metal oxide.

[0143] 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.

[0144] 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, for example, by dissolving a nickel (Ni)-containing raw material, a cobalt (Co)-containing raw material in water, and by dissolving a manganese (Mn)-containing raw material or an aluminum (Al)-containing raw material in water. That is, the above-mentioned composite transition metal-containing solution includes at least one selected from the group consisting of a nickel (Ni)-containing raw material, a cobalt (Co)-containing raw material, a manganese (Mn)-containing raw material, and an aluminum (Al)-containing raw material. In addition, if necessary, the complex transition metal-containing solution may further include a metal-containing raw material containing a transition metal other than nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al) (for example, at least one selected from the group consisting of B, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, and Sr).

[0145] 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.

[0146] 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.

[0147] 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.

[0148] The above aluminum (Al)-containing raw material may be at least one selected from the group consisting of oxides, carbonates, nitrates, hydroxides, oxyhydroxides, and halides containing aluminum (Al), and a mixture of one or two or more of these may be used.

[0149]

[0150] Raw materials containing nickel (Ni), cobalt (Co), manganese (Mn), aluminum (Al), etc. can be used in appropriate amounts considering the content of each metal element in the composite transition metal hydroxide being manufactured.

[0151]

[0152] 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.

[0153] 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.

[0154] 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, 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.

[0155] 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.

[0156]

[0157] Once particles in the form of a complex transition metal hydroxide are formed using the above method, the particles are separated from the reaction solution to obtain the complex transition metal hydroxide. Specifically, the reaction solution is filtered to separate the particles, and then the separated particles are washed and dried to obtain the complex transition metal hydroxide. At this time, processes such as grinding and / or classification may also be performed, as needed.

[0158]

[0159] The above complex transition metal hydroxide is Ni p Co q M 3 r M 4 s (OH)2(M above 3 is at least one selected from the group consisting of Al and Mn, and the M 4is at least one selected from the group consisting of B, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P and Sr, and the p, q, r, s are 0.5000≤p<1.0000, 0.0000 <q<0.5000, 0.0000<r<0.5000, 0.0000≤s≤0.3000, p+q+r+s=1.0000이다.)로 표시되는 조성을 가질 수 있다.

[0160]

[0161] 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 may be used for convenience in the process due to its low melting point.

[0162]

[0163] According to one embodiment of the present invention, in step (A), the composite transition metal hydroxide and the lithium (Li)-containing raw material can be mixed in an amount such that the raw material has a composition represented by the chemical formula 1.

[0164]

[0165] According to one embodiment of the present invention, the composite transition metal hydroxide may have a nickel content of 50 mol% or more among the total transition metals. Specifically, the composite transition metal hydroxide may have a nickel content of 50 mol% or more among the total transition metals, or 60 mol% or more among the total transition metals, and may have a nickel content of 70 mol% or less, 80 mol% or less, 95 mol% or less, or 99 mol% or less among the total transition metals. When the nickel content among the total transition metals in the composite transition metal hydroxide is within the above range, the capacity characteristics of a cathode active material manufactured from the composite transition metal hydroxide can be improved.

[0166]

[0167] According to one embodiment of the present invention, the composite transition metal hydroxide has a tap density of 1.50 g / cm 3 More than 2.00 g / cm 3 It may be as follows. Specifically, the complex transition metal hydroxide has a tap density of 1.50 g / cm 3 or 1.60 g / cm 3 It may be more than 1.80 g / cm 3 Below, 1.90 g / cm 3 or less, or 2.00 g / cm 3 It may be as follows. When the tap density is within the above range, the energy density of the electrode can be improved.

[0168]

[0169] According to one embodiment of the present invention, the composite transition metal hydroxide has a BET specific surface area of ​​4 m 2 / g or more than 15 m 2 / g or less. Specifically, the complex transition metal hydroxide has a BET specific surface area of ​​4 m 2 / g or more, 5 m 2 / g or more, 6 m 2 / g or more, 7 m 2 / g or more, 8 m 2 / g or more, 9 m 2 / g or more, 10 m 2 / g or more, 11 m 2 / g or more, or 12 m 2 / g may be more than 13 m 2 / g or less, 14 m 2 / g or less, 15 m 2 / g or less, 16 m 2 / g or less, 17 m 2 / g or less, 18 m 2 / g or less, 19 m 2 / g or less, or 20 m 2 / g or less. When the BET specific surface area is within the above range, the absorption amount of the final positive electrode active material can be controlled to improve the electrode porosity.

[0170]

[0171] According to one embodiment of the present invention, the composite transition metal hydroxide and the lithium (Li)-containing raw material may be mixed so that the molar ratio of lithium (Li) to the transition metal (M) (Li / M) is 0.95 or more and 1.10 or less. Specifically, the molar ratio of lithium (Li) to the transition metal (M) (Li / M) may be 0.95 or more, 1.00 or more, 1.01 or more, 1.02 or more, 1.03 or more, 1.04 or more, or 1.05 or more, and 1.06 or less, 1.07 or less, 1.08 or less, 1.09 or less, or 1.10 or less. When the molar ratio of mixing (Li / M) is within the above range, the capacity characteristics and resistance characteristics may be improved.

[0172]

[0173] According to one embodiment of the present invention, in the step (A), a raw material containing a doping element is further mixed, and the doping element is at least one selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, and Sr. Specifically, when the doping element is Zr, there is an effect of improving the high-temperature lifespan. In particular, when ZrO2 is used, the interface reaction is reduced by suppressing cation mixing and NiO secondary phase formation, and the lifespan characteristics can be improved by improving the structural stability through surface modification.

[0174]

[0175] According to one embodiment of the present invention, the doping element-containing raw material may be mixed so that the doping element content is 1,000 ppm or more and 4,000 ppm or less with respect to the total weight of the positive electrode active material. Specifically, the doping element-containing raw material contains the doping element in an amount of 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, or 2,300 ppm or more, and 2,500 ppm or less, 2,600 ppm or less, 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, based on the total weight of the positive electrode active material. It may be mixed so that the content is 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 amount of doping element mixed is within the above range, the interfacial reaction is reduced by suppressing cation mixing and NiO secondary phase formation, and the life characteristics can be improved by improving structural stability through surface modification.

[0176]

[0177] According to the present invention, the sintering is performed at a temperature of 960°C or more and 1,100°C or less. Specifically, the sintering is performed at a temperature of 960°C or more, and 970°C or less, 980°C or less, 990°C or less, 1,000°C or less, 1,010°C or less, 1,020°C or less, 1,030°C or less, 1,040°C or less, 1,050°C or less, 1,060°C or less, 1,070°C or less, 1,080°C or less, 1,090°C or less, or 1,100°C or less. When the sintering temperature is within the above range, a lithium composite transition metal oxide in the form of a single particle can be formed. When the lithium composite transition metal oxide is in the form of a single particle, since the particle interface is small, degradation due to insulation at the interface due to particle breakage during rolling or side reactions with the electrolyte can be suppressed. This can improve the lifespan characteristics of secondary batteries, especially at high voltages. However, when performed at temperatures below 960°C, there is a problem in that sufficient thermal energy is not supplied to form lithium composite transition metal oxides in the form of single particles. Furthermore, when performed at temperatures exceeding 1,100°C, oversintering occurs, resulting in the formation of a rock salt phase.

[0178]

[0179] According to one embodiment of the present invention, the calcination may be performed under an air atmosphere or an oxygen atmosphere. When the calcination is performed under the atmosphere, the atmosphere can be easily maintained and sufficient oxygen required for the reaction can be supplied.

[0180]

[0181] According to one embodiment of the present invention, the method may further include a step of crushing the lithium composite transition metal oxide. If the crushing step is further included, the particle size of the lithium composite transition metal oxide can be controlled.

[0182]

[0183] (B) Step

[0184] The method for manufacturing a cathode active material according to the present invention includes, after step (A), step (B) of mixing the lithium composite transition metal oxide and a raw material containing a coating element, and then performing heat treatment to form a coating layer on the lithium composite transition metal oxide.

[0185] The above coating element is at least one selected from the group consisting of Zn, Co, Ti, Nb, V, Mo, W, Al, Zr, and B. In particular, in the case of Al, the coating layer formed by heat treatment contains Al, and the coating layer containing Al can suppress deterioration of the positive electrode surface due to a side reaction between hydrogen fluoride and the electrolyte by removing hydrogen fluoride, and in the case of B, by forming a lithium boron oxide phase, it can suppress deterioration of the positive electrode surface and improve the capacity characteristics and life characteristics at high temperatures. In the case where the coating layer contains both Al and B, due to the property of aluminum (Al) to form a coating layer in a nanoparticle size, the coating layer containing aluminum (Al) and boron (B) is uniformly formed, thereby suppressing the elution of metal ions of the positive electrode active material while improving the electrical conductivity. On the other hand, in the case where the raw material containing the coating element is not mixed, the final positive electrode active material has poor life characteristics due to a side reaction between the positive electrode active material and the electrolyte, and has low electrical conductivity, resulting in poor output characteristics.

[0186]

[0187] According to one embodiment of the present invention, the coating element-containing raw material may be at least one selected from the group consisting of oxides, carbonates, nitrates, hydroxides, oxyhydroxides, and halides containing the coating element. Specifically, considering economic efficiency and process convenience, it may be Al(OH)3 and HBO3.

[0188]

[0189] According to one embodiment of the present invention, the coating element-containing raw material may be mixed so that the total coating element content is 500 ppm or more and 3,000 ppm or less based on the total weight of the lithium composite transition metal oxide. Specifically, the coating element-containing raw material has a total coating element content of 500 ppm or more, 600 ppm or more, 700 ppm or more, 800 ppm or more, 900 ppm or more, or 1,000 ppm or more, and 1,200 ppm or less, 1,300 ppm or less, 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, 2,600 ppm or less, 2,700 ppm or less, based on the total weight of the lithium composite transition metal oxide. It may be mixed so that the content is 2,800 ppm or less, 2,900 ppm or less, or 3,000 ppm or less. When the mixing amount of the raw material containing the coating element is within the above range, the life characteristics of the battery can be improved by suppressing the deterioration of the positive electrode surface due to the side reaction of the electrolyte, and the output characteristics of the battery can be improved by improving the electrical conductivity.

[0190]

[0191] According to the present invention, the heat treatment is performed at a temperature of 300°C or higher and 400°C or lower. Specifically, the heat treatment may be performed at a temperature of 300°C or higher, 310°C or higher, 320°C or higher, 330°C or higher, or 340°C or higher, and 350°C or lower, 360°C or lower, 370°C or lower, 380°C or lower, 390°C or lower, or 400°C or lower. When the heat treatment is within the above temperature range, the thermal energy required for coating can be sufficiently supplied. On the other hand, when the heat treatment is less than 300°C, there is a problem that sufficient energy required for forming a coating layer is not supplied, and when it is 400°C or higher, there is a problem that the life characteristics are poor due to deterioration of the surface of the positive electrode active material.

[0192] Meanwhile, when the calcination and heat treatment are performed within the ranges described in the present specification during the manufacture of the positive electrode active material, specifically, when the calcination in step (A) is performed at a temperature of 960°C or more and 1,100°C or less, and the heat treatment in step (B) is performed at a temperature of 300°C or more and 400°C or less, the DBP absorption and circularity of the positive electrode active material can be controlled, thereby manufacturing a positive electrode active material with improved porosity while maintaining energy density.

[0193]

[0194] When a mixture prepared by mixing the lithium composite transition metal oxide and a raw material containing a coating element is heat-treated in the above temperature range, a coating layer containing a coating element can be formed on the lithium composite transition metal oxide. The coating layer includes at least one selected from the group consisting of M'-O compounds and Li-M'-O compounds, and M' can include at least one selected from the group consisting of Zn, Co, Ti, Nb, V, Mo, W, Al, Zr, and B. In addition, the coating layer containing the coating element can be in the form of partially covering (discontinuously) at least a portion of the lithium composite transition metal oxide, that is, a region of the lithium composite transition metal oxide, or covering (continuously) the entire region. The coating layer can be in the form of a film type, an island type, or a combination thereof.

[0195]

[0196] According to one embodiment of the present invention, the heat treatment may be performed in an air atmosphere or an oxygen atmosphere. When the heat treatment is performed in the atmosphere, the atmosphere can be easily maintained and sufficient oxygen required for the reaction can be supplied.

[0197]

[0198] According to one embodiment of the present invention, the heat treatment may be performed for a period of 3 hours or more and 7 hours or less. When the heat treatment time is within the above range, the thermal energy required for coating can be sufficiently supplied.

[0199]

[0200] anode

[0201] Next, the anode according to the present invention will be described.

[0202] 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.

[0203]

[0204] 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.

[0205]

[0206] The above-mentioned positive electrode active material layer may include a conductive material and a binder together with the positive electrode active material. In this case, 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.

[0207]

[0208] 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.

[0209]

[0210] 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.

[0211]

[0212] 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.

[0213]

[0214] 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.

[0215]

[0216] lithium secondary battery

[0217] Next, a lithium secondary battery according to the present invention will be described.

[0218]

[0219] 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.

[0220]

[0221] 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.

[0222]

[0223] 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.

[0224]

[0225] 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.

[0226] 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.

[0227]

[0228] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0229]

[0230] 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.

[0231] The above negative electrode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0232]

[0233] 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.

[0234]

[0235] 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.

[0236]

[0237] 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.

[0238]

[0239] 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, can 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. can also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength can be used, and can optionally be used in a single-layer or multi-layer structure.

[0240]

[0241] 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.

[0242] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0243] 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.

[0244]

[0245] 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.

[0246]

[0247] 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.

[0248]

[0249] 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).

[0250] 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.

[0251] 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.

[0252] 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.

[0253] 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.

[0254]

[0255] 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.

[0256]

[0257] Example 1

[0258] Ni 0.605 Co 0.198 Mn 0.197 Complex transition metal hydroxides (D) having a composition represented by (OH)2 50 : 3.5㎛~4.5㎛, tap density: 1.6g / cm 2 ~1.8g / cm 2 , BET surface area: 12m 2 / g, secondary particle form) and LiOH were mixed so that the molar ratio of (Ni+Co+Mn):Li was 1:1.06, and ZrO2 was added to Ni 0.605 Co 0.198 Mn 0.197 (OH)2 A mixture was prepared by mixing Zr to a content of 2,400 ppm with respect to the total weight, and 1.5 kg of the mixture was calcined at 960°C in an air atmosphere for 12.5 hours to obtain a single particle form, and Li 1.06 Ni 0.6041 Co 0.1977 Mn 0.1967 Zr 0.0015 A lithium composite transition metal oxide having a composition represented by O2 was prepared.

[0259] The above lithium composite transition metal oxide was jet-milled to a particle size of 4.1 μm to 4.7 μm.

[0260] The above-mentioned pulverized lithium composite transition metal oxide Li 1.06 Ni 0.6041 Co 0.1977 Mn 0.1967 Zr 0.0015 After mixing O2, Al(OH)3 and H3BO3, heat treatment was performed for 5 hours at a temperature of 340°C in an air atmosphere to produce a positive electrode active material in which a coating layer containing aluminum (Al) and boron (B) was formed on the lithium composite transition metal oxide. At this time, the Al(OH)3 is the Li 1.06 Ni 0.6041 Co 0.1977 Mn 0.1967 Zr 0.0015Aluminum (Al) is mixed so that the content is 600 ppm with respect to the total weight of O2, and H3BO3 is mixed so that the content is 600 ppm with respect to the total weight of Li. 1.06 Ni 0.6041 Co 0.1977 Mn 0.1967 Zr 0.0015 Boron (B) was mixed to a content of 500 ppm with respect to the total weight of O2. The coating layer includes Li-Al-O, Li-BO, and BO compounds, and has a form of a film type, an island type, or a combination thereof.

[0261]

[0262] Example 2

[0263] A positive electrode active material including a coating layer containing aluminum (Al) and boron (B) on the lithium composite transition metal oxide was manufactured in the same manner as in Example 1, except that the heat treatment was performed at 360°C instead of 340°C.

[0264]

[0265] Example 3

[0266] A positive electrode active material including a coating layer containing aluminum (Al) and boron (B) on the lithium composite transition metal oxide was manufactured in the same manner as in Example 1, except that the heat treatment was performed at 350°C instead of 340°C.

[0267]

[0268] Comparative Example 1

[0269] A positive electrode active material including a coating layer containing aluminum (Al) and boron (B) on the lithium composite transition metal oxide was manufactured in the same manner as in Example 2, except that the firing was performed at 940°C instead of 960°C.

[0270]

[0271] Comparative Example 2

[0272] A positive electrode active material including a coating layer containing aluminum (Al) and boron (B) on the lithium composite transition metal oxide was manufactured in the same manner as in Example 2, except that the firing was performed at 950°C instead of 960°C.

[0273]

[0274] Comparative Example 3

[0275] A positive electrode active material including a coating layer containing aluminum (Al) and boron (B) on the lithium composite transition metal oxide was manufactured in the same manner as in Example 1, except that the firing was performed at 940°C instead of 960°C.

[0276]

[0277] Comparative Example 4

[0278] A positive electrode active material including a coating layer containing aluminum (Al) and boron (B) on the lithium composite transition metal oxide was manufactured in the same manner as in Example 1, except that the firing was performed at 950°C instead of 960°C.

[0279]

[0280] Comparative Example 5

[0281] Ni 0.605 Co 0.198 Mn 0.197 The BET surface area of ​​a complex transition metal hydroxide having a composition represented by (OH)2 is 12 m 2 6m not / g 2 A positive electrode active material including a coating layer containing aluminum (Al) and boron (B) on the lithium composite transition metal oxide was manufactured in the same manner as in Example 1, except that the temperature was / g, the firing was performed at 950°C instead of 960°C, and 2.0 kg instead of 1.5 kg of the mixture was fired.

[0282]

[0283] Comparative Example 6

[0284] A positive electrode active material including a coating layer containing aluminum (Al) and boron (B) on the lithium composite transition metal oxide was manufactured in the same manner as in Example 2, except that the firing was performed at 950°C instead of 960°C and that 2.0 kg instead of 1.5 kg of the mixture was fired.

[0285]

[0286] Comparative Example 7

[0287] Ni 0.605 Co 0.198 Mn 0.197 The BET surface area of ​​a complex transition metal hydroxide having a composition represented by (OH)2 is 12 m 2 6m not / g 2 A positive electrode active material including a coating layer containing aluminum (Al) and boron (B) on the lithium composite transition metal oxide was manufactured in the same manner as in Example 2, except that the / g point was used, the firing was performed at 950°C instead of 960°C, and 2.0 kg instead of 1.5 kg of the mixture was fired.

[0288]

[0289] BET surface area (m) of complex transition metal hydroxides 2 / g) Firing weight (kg) Firing temperature (℃) Heat treatment temperature (℃) Example 1 121.5960 340 Example 2 121.5960 360 Example 3 121.5960 350 Comparative example 1 121.5940 360 Comparative example 2 121.5950 360 Comparative example 3 121.5940 340 Comparative example 4 121.5950 340 Comparative example 5 62.0950 340 Comparative example 6 122.0950 360 Comparative example 7 62.0950 360

[0290] Experimental example

[0291] Experimental Example 1: SEM Analysis

[0292] -Particle shape analysis

[0293] For each of the positive electrode active materials manufactured in the above examples and comparative examples, SEM images were obtained using a scanning electron microscope (SEM) (FEI, Inspect F), and these are shown in FIGS. 1 to 10.

[0294] Figure 1 is a SEM image of the positive electrode active material manufactured in Example 1.

[0295] Figure 2 is a SEM image of the positive electrode active material manufactured in Example 2.

[0296] Figure 3 is a SEM image of the positive electrode active material manufactured in Example 3.

[0297] Figure 4 is an SEM image of the positive electrode active material manufactured in Comparative Example 1.

[0298] Figure 5 is an SEM image of the positive electrode active material manufactured in Comparative Example 2.

[0299] Figure 6 is an SEM image of the positive electrode active material manufactured in Comparative Example 3.

[0300] Figure 7 is an SEM image of the positive electrode active material manufactured in Comparative Example 4.

[0301] Figure 8 is an SEM image of the positive electrode active material manufactured in Comparative Example 5.

[0302] Figure 9 is an SEM image of the positive electrode active material manufactured in Comparative Example 6.

[0303] Figure 10 is an SEM image of the positive electrode active material manufactured in Comparative Example 7.

[0304]

[0305] Through Figures 1 to 3, it was confirmed that the positive electrode active materials manufactured in Examples 1 to 3 according to the present invention were in the form of single particles and had a relatively uniform particle size without fine particles or agglomerates of multiple particles.

[0306] Through Figures 4 to 10, it was confirmed that the positive electrode active materials manufactured in Comparative Examples 1 to 7 according to the present invention were in the form of fine particles or large particles agglomerated together.

[0307]

[0308] -Circular analysis

[0309] Circularity is an indicator of the degree to which the cross-sectional shape of a particle is close to a circle, and can be calculated according to Equation 1 below.

[0310] [Formula 1]

[0311] Circularity =

[0312] In the above equation 1, A is the area of ​​the primary particle measured in the SEM image, and P is the perimeter of the primary particle measured in the SEM image.

[0313] Specifically, using SEM (FEI, Inspect F), SEM images (5K magnification) of the positive electrode active materials manufactured in the Examples and Comparative Examples were obtained, and using an image processing program (LG Chemical, DX program), a two-dimensional segmentation image was obtained in which the boundaries of the primary particles existing in the SEM image were divided and displayed in random colors. Using the segmentation image, the area of ​​each primary particle can be measured through the number of pixels corresponding to each of n primary particles (an average of 100 or more primary particles). In addition, the perimeter of the primary particle can be measured through the length of the boundary corresponding to each of n primary particles existing in the SEM image. The perimeter of the primary particles of the positive electrode active materials manufactured in the Examples and Comparative Examples and the area of ​​each primary particle were measured, and the circularity was calculated, and the results are shown in Table 2 below.

[0314]

[0315] -Analysis of average particle diameter of primary particles

[0316] Using SEM (FEI, Inspect F), SEM images (5K magnification) of the positive electrode active materials manufactured in the examples and comparative examples were obtained, and using an image processing program (LG Chemical, DX program), the average particle diameter (Dv) of the primary particles manufactured in the examples and comparative examples was obtained. 50 ) was measured, and the results are shown in Table 2 below.

[0317]

[0318] -Analysis of the area ratio of particles with a diameter of less than 1㎛

[0319] With regard 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, i.e., the ratio (%) of the area of ​​particles having a particle diameter of 1 μm or less, was calculated, and the results are shown in Table 2 below.

[0320] Specifically, SEM images (5K magnification) of the positive electrode active materials manufactured in the examples and comparative examples were obtained using an SEM (FEI, Inspect F), and the area of ​​each primary particle was calculated through the number of pixels corresponding to each of n primary particles using an image processing program (LG Chemical, DX program), and the results are shown in Table 2 below as a percentage of the area of ​​the differential particles to the total area of ​​the primary particles (the ratio (%) of the area of ​​primary particles having a particle diameter of 1 ㎛ or less).

[0321]

[0322] Circularity Dv 50 (㎛) The ratio of the area of ​​primary particles having a particle size of 1㎛ or less (%) Example 10.71 3.543 Example 20.72 3.404 Example 30.72 3.474 Comparative Example 10.67 2.429 Comparative Example 20.71 2.955 Comparative Example 30.66 2.349 Comparative Example 40.69 2.886 Comparative Example 50.64 3.54 Comparative Example 60.68 2.887 Comparative Example 70.67 3.395

[0323] Through Table 2, the positive electrode active materials of Examples 1 to 3 have a circularity of 0.70 or more and Dv as described herein 50It was confirmed that the ratio of the area of ​​primary particles having a particle size of less than 1 ㎛ to the total area of ​​primary particles present in the positive electrode active material was 10% or less, and that the size was 2.00 ㎛ or more and 6.00 ㎛ or less.

[0324] In comparison, it was confirmed that the positive electrode active materials of Comparative Example 1 and Comparative Examples 3 to 7 had a circularity of 0.70 or less.

[0325]

[0326] Experimental Example 2: DBP Absorption Analysis

[0327] The DBP (dibutyl phthalate) absorption amount of each of the positive electrode active materials manufactured in the above examples and comparative examples can be calculated by measuring the DBP absorption amount in accordance with JIS K5101-13-1. Specifically, using an absorption tester (Asahi absorption tester S-500, Asahi Corporation), DBP is titrated with a burette at a constant speed (2 ml / min) into a sample stirred by a rotor. As DBP is added, the mixture changes from a freely flowing powder to a slightly viscous mass. The point at which a certain percentage (70% of the maximum value) of the maximum torque obtained from the torque curve generated by the change in viscosity characteristics is reached is set as the end point of this measurement. The DBP absorption amount (ml / 100g) is calculated by dividing the volume (ml) of DBP at the end point by the sample mass of 100g, and is shown in Table 3 below.

[0328]

[0329] DBP absorption (ml / 100g) Example 122.1 Example 222.8 Example 322.5 Comparative Example 129.8 Comparative Example 227.1 Comparative Example 327.2 Comparative Example 426.0 Comparative Example 524.9 Comparative Example 624.6 Comparative Example 725.7

[0330] Through Table 3, it was confirmed that the positive electrode active materials of Examples 1 to 3 had an absorption amount of DBP (dibutyl phthalate) of 25.0 ml or less per 100 g.

[0331] In comparison, it was confirmed that the positive electrode active materials of Comparative Examples 1 to 4 and 7 had an absorption amount of DBP (dibutyl phthalate) of more than 25.0 ml per 100 g.

[0332]

[0333] Experimental Example 3: Tap Density Analysis

[0334] 10g of each of the positive electrode active materials manufactured in the above examples and comparative examples was measured at a density of about 20cm using a tap density meter (e.g., GEOPYC-1365 from Micromeritics) 3 By filling the container with 108 N and measuring the density of the particles twice, and calculating the average of the measured values, the tap density (g / cm) is obtained. 3 ) was measured, and the results are shown in Table 4 below.

[0335]

[0336] Experimental Example 4: PSA Analysis

[0337] Using PSA (S3500, Microtrac), the average particle diameter (D) of each positive electrode active material manufactured in the examples and comparative examples 50 ) were measured and shown in Table 4 below.

[0338]

[0339] Tap density (g / cm) 3 )Average particle diameter (D) 50 )(㎛)Example 12.214.2Example 22.214.1Example 32.214.2Comparative Example 12.004.2Comparative Example 22.054.3Comparative Example 32.074.4Comparative Example 42.134.4Comparative Example 52.074.4Comparative Example 61.974.3Comparative Example 71.974.2

[0340] Through Table 4, the tap density of Examples 1 to 3 is 2.00 g / cm 3 More than 2.5 g / cm 3 It was confirmed that the average particle size was 3.0 ㎛ or more and 6.0 ㎛ or less.

[0341] In comparison, the tap density of Comparative Examples 6 and 7 was 2.00 g / cm 3 It was confirmed that it was less than .

[0342]

[0343] Experimental Example 5: TOF-SIMS Analysis

[0344] Using TOF-SIMS (TOF-SIMS 5-100, IonTOF (Germany) Co.), surface analysis of each positive electrode active material manufactured in the examples and comparative examples was performed to confirm the form of the compound included in the coating layer within the positive electrode active material.

[0345] Specifically, the surface of the positive electrode active material was analyzed using secondary ion mass spectrometry (SIMS), and the conditions under which the analysis was performed are shown in Table 5 below.

[0346] Through secondary ion mass spectrometry, in the case of the positive electrode active material manufactured in the practice, at least one selected from the group consisting of BO compounds and Li-BO compounds, specifically LiBO3, is present in the coating layer. LiB2O3, It was confirmed that it contains LiB2O4, B3O5 and Li2B3O6.

[0347]

[0348] Spectra acquisition condition2D ion mapping (imaging) conditionAnalysis modespectrometry modeDelayed extraction modePrimary IonBi 3+ Polaritynegative & positiveFlood gunOnOn, Ar floodingCycle time100㎲ (mass range 1~880u)50(mass range 1~214Analysis area (pixel)500㎛×500㎛ (128×128)500㎛×500㎛ (512×512)

[0349] Experimental Example 6: Analysis of pottery properties

[0350] A positive electrode slurry was prepared by mixing 96.5 wt% of each of the positive electrode active materials manufactured in the above examples and comparative examples, 1.5 wt% of Super C as a conductive agent, and 2 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 a positive electrode was manufactured with a porosity of 20%.

[0351] After visually checking the state of the anode after pressurization, if the coating surface is smooth and free of defects such as peeling and tearing, it is judged as good (○), if there are some defects but battery production is possible, it is judged as insufficient (△), and if battery production is impossible due to the above defects, it is judged as unacceptable (X). The coating workability is shown in Table 6 below.

[0352]

[0353] DBP Absorption (ml / 100g) 25.0ml or less Circularity 0.70 or more Porosity Example 1○○○ Example 2○○○ Example 3○○○ Comparative Example 1XXX Comparative Example 2XXX Comparative Example 3XXX Comparative Example 4XXX Comparative Example 5○Xβ Comparative Example 6○X△ Comparative Example 7XXX

[0354] Through Table 6, it was confirmed that in the case of the positive electrode active materials of Examples 1 to 3, that is, the positive electrode active materials having an absorption amount of DBP (dibutyl phthalate) of 25.0 ml or less per 100 g of the positive electrode active material and a circularity of 0.70 or more according to the formula 1 described herein, a positive electrode having a smooth coating surface and no defects such as peeling and tearing can be manufactured. In contrast, in the case of the positive electrode active materials of Comparative Examples 1 to 4 and 7, that is, the absorption amount of DBP (dibutyl phthalate) per 100 g of the positive electrode active material exceeds 25.0 ml, it was confirmed that battery manufacturing was impossible due to defects, and in the case of the positive electrode active materials of Comparative Examples 5 and 6, that is, the absorption amount of DBP (dibutyl phthalate) per 100 g of the positive electrode active material is 25.0 ml or less and the circularity according to the formula 1 described herein is less than 0.70, battery manufacturing was possible but some defects existed. It was confirmed. In conclusion, in the case of the positive electrode active material according to the present invention, it was confirmed that when a binder was used under the same conditions, a positive electrode slurry with excellent processability could be manufactured, and thus a positive electrode with excellent quality and improved energy density could be manufactured.

Claims

A cathode active material comprising a lithium composite transition metal oxide in the form of a single particle consisting of 1.50 or fewer primary particles; and a coating layer formed on the lithium composite transition metal oxide; The above coating layer comprises at least one coating element selected from the group consisting of Zn, Co, Ti, Nb, V, Mo, W, Al, Zr and B, The absorption amount of DBP (dibutyl phthalate) per 100g of the above positive electrode active material is 25.0ml or less, A positive electrode active material having a circularity of 0.70 or more according to the following formula 1: [Formula 1] Circularity = In the above equation 1, A is the area of ​​the primary particle measured in the SEM image, and P is the perimeter of the primary particle measured in the SEM image.

2. In claim 1, The above lithium composite transition metal oxide is a positive electrode active material in which the proportion of nickel among the total transition metal is 50 mol% or more.

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 M 1 c M 2 d O2 In the above chemical formula 1, Above M 1 is at least one selected from the group consisting of Al and Mn, Above M 2 is at least one selected from the group consisting of B, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P and Sr, -0.10≤x≤0.30, 0.5000≤a<1.0000, 0.0000 <b<0.5000, 0.0000<c<0.5000, 0.0000≤d≤0.3000이다.

4. In claim 1, The above primary particles have an average particle diameter (Dv 50 ) is a positive electrode active material having a particle size of 2.00 ㎛ or more and 6.00 ㎛ or less.

5. In claim 1, A positive electrode active material, wherein the ratio of the area of ​​primary particles having a particle diameter of less than 1㎛ to the total area of ​​primary particles present in the positive electrode active material is 10% or less.

6. In claim 1, A positive electrode active material, wherein the coating layer comprises at least one selected from the group consisting of M'-O compounds and Li-M'-O compounds, wherein M' is at least one selected from the group consisting of Zn, Co, Ti, Nb, V, Mo, W, Al, Zr, and B.

7. In claim 1, Tap density is 2.00 g / cm 3 More than 2.50 g / cm 3 The positive electrode active material is as follows.

8. In claim 1, Average particle diameter (D 50 ) is a positive electrode active material having a particle size of 3.0 ㎛ or more and 6.0 ㎛ or less.

9. In claim 1, A cathode active material having an absorption amount of DBP (dibutyl phthalate) of 10.0 ml or more and 25.0 ml or less per 100 g of cathode active material.

10. In claim 1, A positive electrode active material having a circularity of 0.70 or more and 0.80 or less.

11. A positive electrode comprising a positive electrode active material according to any one of claims 1 to 10.

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

Images