KR102334909B1 - Positive active material for lithium secondary battery, preparing method thereof, and lithium secondary battery comprising positive electrode including positive active material - Google Patents

Abstract

In the present invention, in a positive electrode active material including secondary particles made of a group of a plurality of primary particles, at least some of the primary particles provided on the surface of the secondary particles are in the form of flakes having a pair of first crystal planes facing each other phosphorus, wherein the first primary particles have the first crystal planes arranged in a radial direction, and one end of the pair of first crystal planes is provided with a plurality of crystal planes different from the first crystal planes. One end of the first crystal plane is connected, and the longitudinal cross-section of the first primary particle includes a pair of first crystal planes spaced apart from each other, and a second crystal plane and a third crystal plane connecting one end of the pair of first crystal planes; The second and third crystal planes relate to a positive electrode active material that is provided on the outermost surface of the secondary particles and connected to have an angle.

Description

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

The present invention relates to a cathode active material, a method for manufacturing the same, and a lithium secondary battery including the same, and more particularly, to a cathode active material having a high capacity and improved lifespan characteristics, a manufacturing method thereof, and a lithium secondary battery including the same .

With the development of portable mobile electronic devices such as smart phones, MP3 players, and tablet PCs, the demand for secondary batteries capable of storing electrical energy is increasing explosively. In particular, with the advent of electric vehicles, medium and large energy storage systems, and portable devices requiring high energy density, the demand for lithium secondary batteries is increasing.

With such an increase in demand for lithium secondary batteries, various research and development for improving the characteristics of positive electrode active materials used in lithium secondary batteries are being conducted. For example, in Korean Patent Publication No. 10-2014-0119621 (Application No. 10-2013-0150315), the type and composition of a metal substituted in the precursor is controlled by using a precursor for preparing an excess lithium positive electrode active material, and the type of metal added and a secondary battery having high voltage capacity and long lifespan characteristics by controlling the addition amount.

One technical problem to be solved by the present application is to provide a high-capacity cathode active material, a method for manufacturing the same, and a lithium secondary battery including the same.

Another technical problem to be solved by the present application is to provide a long-life positive electrode active material, a manufacturing method thereof, and a lithium secondary battery including the same.

Another technical problem to be solved by the present application is to provide a positive electrode active material having high stability, a method for manufacturing the same, and a lithium secondary battery including the same.

Another technical problem to be solved by the present application is to provide a positive electrode active material having a high discharge capacity and at the same time having a minimized lifespan deterioration according to the number of charge/discharge, a method for manufacturing the same, and a lithium secondary battery including the same.

The technical problem to be solved by the present application is not limited to the above.

According to one aspect of the present invention, embodiments of the present invention provide a positive electrode active material including secondary particles composed of a plurality of primary particles, wherein at least some of the primary particles provided on the surface of the secondary particles are a pair of facing each other It includes first primary particles in the form of flakes having a first crystal plane, wherein the first primary particles have the first crystal planes arranged in a radial direction, and one end of the pair of first crystal planes is the first crystal plane A plurality of different crystal planes are provided to connect one end of a pair of first crystal planes, and a longitudinal cross-section of the first primary particle is a first crystal plane connecting a pair of first crystal planes spaced apart from each other, and one end of the pair of first crystal planes It includes a second crystal plane and a third crystal plane, and the second and third crystal planes may include a positive electrode active material that is provided on the outermost surface of the secondary particle and connected to have an angle.

In one embodiment, the first primary particles have a first length that is a long axis of the first crystal plane, a second length that is a short axis of the first crystal plane perpendicular to the first length, and between the pair of first crystal planes. and a third length that is an interval of , and the third length may be 10 nm to 400 nm.

In an embodiment, the ratio of the first length to the third length may be 2 to 100, and the ratio of the second length to the third length may be 1.5 to 80.

In an embodiment, the cathode active material is a layered rhombohedral system compound, and the first crystal plane is (hkℓ, where h=0, k=0, ℓ=3n, and n is an integer). and the first crystal plane, the second crystal plane, and the third crystal plane may be provided to be different from each other.

In an embodiment, the angle between the second crystal plane and the third crystal plane may be 30° to 170°.

In one embodiment, the positive electrode active material is used as the positive electrode and lithium metal is used as the negative electrode in a 2032 coin-type half-cell, charged to 4.3 V at 0.5 C constant current, and discharged to 2.7 V at 0.5 C constant current After 100 cycles, the intensity of the peak corresponding to the phase transition of H2-H3 in the dQ/dV curve may be 40% or more compared to 1 cycle.

In one embodiment, the primary particles include nickel (Ni), M1 and M2, wherein M1 is made of at least any one or more of manganese (Mn), cobalt (Co) and aluminum (Al), the Nickel (Ni) may be 65 mol% or more, and M2 may be composed of 0.05 mol% to 5 mol% as a doping element.

In one embodiment, the M2, boron (B); Alternatively, boron (B) and tungsten (W), molybdenum (Mo), tantalum (Ta), niobium (Nb), hafnium (Hf), silicon (Si), tin (Sn), zirconium (Zr), calcium (Ca) ), germanium (Ge), gallium (Ga), indium (In), ruthenium (Ru), tellurium (Te), antimony (Sb), iron (Fe), chromium (Cr), vanadium (V) and titanium (Ti) any one or more; may consist of.

In an embodiment, a coating layer including boron (B) covering at least a portion of the second and third crystal planes may be provided on the second and third crystal planes.

In one embodiment, the concentration of boron (B) is provided uniformly in the secondary particles, and is provided to have a concentration gradient in the coating layer, and the average concentration of boron (B) in the coating layer is in the secondary particles may be provided higher than the average concentration of boron (B).

In one embodiment, the coating layer is LiBO ₂ , LiB ₃ O ₅ , LiB ₅ O ₈ , α-LiBO _{2 ,} Li ₂ B ₂ O ₄ , Li ₂ B ₂ O ₇ , Li ₂ B ₄ O ₇ , Li ₂ B ₆ O ₇ , Li ₂ B ₆ O ₁₀ , Li ₂ B ₈ O ₁₃ , Li ₃ BO ₃ , Li ₃ B ₇ O ₁₂ , Li ₄ B ₂ O ₅ , α-Li ₄ B ₂ O ₅ , β-Li _{At least one of 4} B ₂ O _5, Li ₄ B ₁₀ O _17, and Li ₆ B ₄ O ₉ may be included.

In one embodiment, in the cross section of secondary particles charged up to 4.3 V at 0.5 C constant current with a half-cell using lithium metal as a negative electrode as a positive electrode using the positive electrode active material, neighboring primary particle boundaries ), which is a space formed between the microcracks, may have an area of less than 15% of the area of the cross section of the secondary particles.

In one embodiment, the secondary particle is a device having a 45 kV, 40 mA output. In the X-ray diffraction analysis obtained by measuring at a scan rate of 1 degree per minute at an interval of 0.0131 step size using a Cu Ka beam source, the intensity of the 003 peak The ratio of intensities of the to 104 peaks may be between 1.6 and 2.3.

In an embodiment, as the content of the doping element increases, the ratio of the intensity of the 003 peak to the intensity of the 104 peak may decrease.

In one embodiment, the secondary particles are provided in a spherical shape having a center portion and a surface portion, and the first primary particles are provided in a direction in which the first crystal plane is directed from the center portion toward the surface portion, and in the first primary particles, the The second and third crystal planes may be provided on the surface portion of the secondary particle, and the outermost surface of the surface portion of the secondary particle may form a concave-convex structure by the second and third crystal planes.

In one embodiment, the secondary particles, represented by the following <Formula 1>, the surface portion of the secondary particles may further include a coating layer covering at least a portion of the second and third crystal planes.

<Formula 1>

Li _a M _x D _y O ₂

(M is at least any one of Ni, Co, Mn, or Al, and D is a doping element consisting of B alone or co-doping with any one of W, Mo, Nb, Ta, and Sb. , 0.9<a<1.1, x+y = 1, 0.95<x<1, 0<y<0.05)

In one embodiment, the first primary particles have a first length that is a long axis of the first crystal plane, a second length that is a short axis of the first crystal plane perpendicular to the first length, and between the pair of first crystal planes. and a third length that is an interval of , wherein the doping element is provided in an amount of 0.05 mol% to 5 mol%, and as the concentration of the doping element increases, the first length of the first primary particles increases, and the third length can be reduced.

According to another aspect of the present invention, embodiments of the present invention include a positive electrode for a secondary battery including the above-described positive electrode active material.

According to another aspect of the present invention, embodiments of the present invention include a lithium secondary battery including the positive electrode.

According to another aspect of the present invention, embodiments of the present invention include a battery module including the lithium secondary battery as a unit cell.

According to another aspect of the present invention, embodiments of the present invention are battery packs including the above-described G module, wherein the battery pack is used as a power source for a medium or large device, and the medium or large device is an electric vehicle, a hybrid electric vehicle, and a plug-in. It includes a battery pack that is selected from the group consisting of hybrid electric vehicles and systems for power storage.

According to the present invention as described above, the positive electrode active material according to the present invention includes secondary particles formed by aggregation of a plurality of primary particles, and the secondary particles may contain a doping element together with a high Ni content.

The doping element can control the flake shape of the first primary particles, thereby providing a positive electrode active material that can be used stably for a long period with high discharge capacity.

1a is an SEM photograph showing secondary particles according to an embodiment of the present invention.
Figure 1b is a view for showing the radial shape of the secondary particles of Figure 1b.
1c is a view schematically showing a cross-section of a secondary particle according to an embodiment of the present invention.
2 is a flowchart illustrating a method of manufacturing a cathode active material according to another embodiment of the present invention.
3 is an SEM image of the metal composite hydroxide according to Examples 1 and 2.
4 is an SEM image of the positive electrode active material according to Examples 1 and 2;
5 is an SEM image of the metal composite hydroxide according to Examples 4 to 7;
6 is an SEM image of the positive electrode active material according to Examples 4 and 7.
7 is an SEM image of the metal composite hydroxide according to Examples 9 to 12.
8 is an SEM image of the positive electrode active material according to Examples 9 and 12.
9 is an SEM image of measuring the thickness of the primary particles located on the surface of the secondary particles according to the boron (B) doping amount in the NCO-based positive electrode active material using a metal composite hydroxide containing 90 mol% of Ni.
10 is a SEM image of the positive electrode active material not doped with boron (B) in FIG. 9 .
11 is a SEM image of the positive electrode active material doped with boron (B) in 0.5 mol% in FIG. 9 .
12 is a SEM image of the positive electrode active material doped with boron (B) 1 mol% in FIG. 9 .
13 is a SEM image of the positive electrode active material doped with boron (B) 1.5 mol% in FIG. 9 .
14 is a SEM image of the positive electrode active material doped with boron (B) 2 mol% in FIG. 9 .
15a shows the third length of the primary particles (003) and ( 003) is a graph showing the result of measuring the spacing between the planes.
15B is a graph of the length of the (003) plane according to boron (B) doping.
16A is a graph illustrating a first length, a second length, and a third length according to boron (B) doping.
16B is a graph illustrating a ratio of a first length to a second length with respect to a third length according to boron (B) doping.
17 is an SEM image of the positive electrode active material according to Example 24 and Comparative Example 7.
18 is a FIB TEM image of the positive electrode active material according to Example 24 and Comparative Example 7.
19 is a FIB TEM image of the positive electrode active material according to Example 24 and Comparative Example 7 before the first cycle.
20 is an FIB TEM image before the first cycle of Example 24 of FIG. 19 .
21 is a FIB TEM image after 100 cycles of Example 24.
22 to 24 are results of analyzing the coating layer formed on the primary particles provided on the surface of the secondary particles in Example 24.
25 is a TEM image of the primary particles of Example 24.
26 to 28 are XRD analysis results before and after heat treatment of boron oxide and lithium hydroxide.
29 is a cycle graph of a full cell using the positive electrode active material according to Example 24 and Comparative Example 7.
30 is an SEM image illustrating a cross section of secondary particles by charging the positive electrode active materials according to Example 24 and Comparative Example 7 for each charging voltage.
31 is an SEM image of a half-cell and a full-cell using the cathode active materials of Example 24 and Comparative Example 7 after cycling.
32 and 33 are in-situ XRD data of Example 24 and Comparative Example 7.

The details of other embodiments are included in the detailed description and drawings.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in a variety of different forms, and unless otherwise specified in the following description, the components, reaction conditions, and content of components are expressed in the present invention. It is to be understood that all numbers, values and/or expressions are modified in all instances by the term "about," as these numbers are inherently approximations reflecting the various uncertainties of measurement arising out of obtaining such values, among other things. . Also, when numerical ranges are disclosed in this description, such ranges are continuous and inclusive of all values from the minimum to the maximum inclusive of the range, unless otherwise indicated. Furthermore, when such ranges refer to integers, all integers inclusive from the minimum to the maximum inclusive are included, unless otherwise indicated.

Also, when a range is recited for a variable in the present invention, it will be understood that the variable includes all values within the recited range, including the recited endpoints of the range. For example, a range of “5 to 10” includes the values of 5, 6, 7, 8, 9, and 10, as well as any subranges such as 6 to 10, 7 to 10, 6 to 9, 7 to 9, etc. It will be understood to include any value between integers that are appropriate for the scope of the recited range, such as 5.5, 6.5, 7.5, 5.5 to 8.5 and 6.5 to 9, and the like. For example, a range of “10% to 30%” includes values such as 10%, 11%, 12%, 13%, and all integers up to and including 30%, as well as 10% to 15%, 12% to 18%. It will be understood to include any subranges such as %, 20% to 30%, and the like, and also include any value between reasonable integers within the scope of the recited range, such as 10.5%, 15.5%, 25.5%, and the like.

In one embodiment, regarding the size and particle diameter of various particles such as primary particles and secondary particles, there is a method of expressing the average size of a group by quantifying it by a measurement method, but it is universally used and all There are diameters, median diameters corresponding to the median of the integral distribution curve, various average diameters (number average, length average, area average, mass average, volume average, etc.), and unless otherwise specified in the present invention, average size and average particle diameter is the number average size and diameter, and means that D50 (particle diameter at the point where the distribution rate is 50%) is measured.

1a is a SEM photograph showing secondary particles according to an embodiment of the present invention, FIG. 1b is a view for showing the radial shape of the secondary particle of FIG. 1b, and FIG. 1c is a cross-section of the secondary particle according to an embodiment of the present invention It is a schematic drawing.

1A to 1C , the positive electrode active material according to this embodiment is made of secondary particles 200 including a plurality of primary particles, and may be used as a positive electrode active material of a lithium secondary battery.

At least a portion of the primary particles provided on the surface of the secondary particles 200 may include the first primary particles 100 in the form of flakes having a pair of first crystal surfaces 110 facing each other.

The secondary particles 200 may be formed by aggregation of a plurality of primary particles, and among the primary particles, the first primary particles 100 having the pair of first crystal planes 110 have the first crystal planes 110 . The secondary particles 200 may be arranged in a radial direction from the center (c) to the surface portion. For example, one end of the pair of first crystal planes 110 provided in a portion forming the outermost surface of the secondary particle 200 may be connected by a plurality of crystal planes. More specifically, the pair of first crystal planes 110 are provided to be spaced apart from each other, and one end of the pair of first crystal planes 110 has a plurality of crystal planes different from the first crystal planes 110 from each other. It may be provided to cover one end of a pair of spaced apart first crystal planes 110 .

The first primary particles 100 provided in the form of flakes are directed toward the center of the secondary particles 200, and the longitudinal cross-sections perpendicular to the direction of the pair of crystal planes 110 are parallel to each other. and one or more second crystal planes 120 and one or more third crystal planes 130 connecting one end of the pair of first crystal planes 110 to each other. In addition, the second and third crystal planes 120 and 130 may be connected to have an angle θ at the outermost surface of the secondary particle 200 .

The radial direction means that the first primary particles 100 are aligned in a direction (R) from the central portion (c) of the secondary particles 200 to the surface portion of the secondary particles 200 as shown in FIG. 1B .

In the positive electrode active material according to the present embodiment, the first primary particles 100 having a pair of first crystal planes 110 may be radially aligned on the surface of the secondary particles 200 . The first primary particles 100 may be provided in the form of flakes extending from one end to the other end. One end of the first primary particles 100 faces the surface of the secondary particles 200, and the first primary particles The other end of (100) may be provided to face the center (c) of the secondary particles (200).

For example, in the first primary particle 100 , the direction of the first crystal plane 110 is aligned parallel to the radial direction, thereby promoting diffusion of lithium ions from the surface portion of the secondary particle 200 to the inside. can do. In addition, the first primary particles 100 are provided to be side by side in the movement direction of lithium ions, and the spacing between the pair of first crystal planes 110 is controlled and aligned. Therefore, it relieves the volume change even during expansion and contraction caused by repeated reversible charging and discharging, and cracks that may occur between the primary particles, for example, the primary particles according to the shape change of the primary particles due to the volume change accompanying the electrochemical reaction. The separation distance between them is reduced, so that the lifespan characteristics of the secondary battery can be improved.

In the flake shape of the first primary particles 100, as shown in FIG. 1c, a pair of first crystal planes 110 are provided on the outermost surface, and the pair of first crystal planes 110 are provided to have a thickness. means to be provided. In addition, the longitudinal cross-section of the first primary particle 100 may consist of a pair of first crystal planes 110 and second and third crystal planes 120 and 130 connecting one end of the pair of first crystal planes 110 . have.

The first primary particles 100 have a first length f1 that is a long axis of the first crystal plane 110 and a second length that is a short axis of the first crystal plane 110 perpendicular to the first length f1. (f2), and a third length f3 that is an interval between the pair of first crystal planes 110 may be included.

The first length f1 may be the longest length in a radially parallel direction from the first crystal plane 110 , and the second length f2 is one end of the pair of first crystal planes 110 , that is, the first The shortest length of the portion facing the surface of the secondary particles 200 in the crystal plane 110 may be the length of the short axis. The third length f3 may be a thickness between the pair of first crystal planes 110 . The first length f1 may be longer than the second and third lengths f2 and f3 , and the second length f2 may be longer than the third length f3 .

The third length f3 may be 10 nm to 400 nm. When the third length f3 is less than 10 nm, the surface area of the secondary particles 200 is increased to increase the contact area with the electrolyte. can be significantly lowered. In addition, if the third length f3 is greater than 400 nm, cracks may be formed due to volume change due to repeated contraction and expansion of primary particles during charging and discharging of the secondary battery, thereby reducing the lifespan. Preferably, the third length f3 is an average value, and may be 30 nm to 300 nm, and more preferably 50 nm to 150 nm.

A ratio of the first length f1 to the third length f3 may be 2 to 100, and a ratio of the second length f2 to the third length f3 may be 1.5 to 80.

In the first primary particle 100, the first length f1, the second length f2, and the third length f3 affect each other, and the first length f1 and the second length f2 and the third length f3 is provided in the above-described range, so that the secondary particles including the first primary particles 100 are stably maintained in high discharge capacity due to high-capacity nickel (Ni), while performing in a number of cycles. The lifespan characteristics are improved by maintaining structurally constant.

The positive electrode active material is a layered rhombohedral system compound, and the first crystal plane 110, the second crystal plane 120, and the third crystal plane 130 are Miller index (Miller index) (hkℓ), The first crystal plane 110 , the second crystal plane 120 , and the third crystal plane 130 may be provided as different crystal planes. For example, in the case of the first crystal plane, (hkℓ), where h=0, k=0, ℓ=3n, n may be an integer, and the second and third crystal planes are different crystal planes from the first crystal plane can be provided as

The first crystal plane 110 , the second crystal plane 120 , and the third crystal plane 130 may be made of crystal planes forming a layered trigonal compound, for example, the first crystal plane 110 (hkℓ) may be any one or more of (003), (006), (009), (0012), and (0015), and the second crystal plane 120 and the third crystal plane 130 are ( hkl) except for the first crystal plane 110 of (hkl). The second and third crystal planes 120 and 130 may be formed of crystal planes provided to connect one end of a pair of first crystal planes 110 spaced apart from each other at one end of the first crystal plane 110 .

The first primary particles 100 according to the present embodiment may be provided in the form of flakes including at least four or more crystal faces. The crystal plane is a plane representing the outer shape of the crystal and means a plane parallel to the lattice plane.

The first crystal plane 110 constituting the first primary particle 100 is a pair of wide planes facing each other in the flake shape, and the second and third crystal planes 120 and 130 are the pair of first crystal planes One end of the flake shape connected to one side and the other side of 110 may be provided so that the cross section becomes a triangle by the second and third crystal planes 120 and 130 .

In the first primary particle 100, the first crystal plane 110 is made of a (003) plane, and one end of the pair of first crystal planes 110 in the first primary particle 100, that is, the secondary particle ( Both ends of the portion provided on the outer surface of 200 , the second crystal plane 120 and the third crystal plane 130 may be connected to each other at an angle.

For example, a second crystal plane 120 is connected to one end of the pair of first crystal planes 110 to have an angle of 90° or more, and the third crystal plane is connected to the other end of the pair of second crystal planes 110 . 130 may be connected to have an angle of 90° or more. The second crystal plane 120 and the third crystal plane 130 connecting both ends of the pair of first crystal planes 110, respectively, are connected to have a predetermined angle, and are connected to the ends of the first primary particles 100. Thus, the outer surface of the secondary particles 200 may be provided to have sharp irregularities. In addition, in the direction from the surface portion of the secondary particle 200 toward the center (c), with respect to a cross section perpendicular to the pair of first crystal planes 110, between the second crystal plane and the third crystal plane The angle θ may be 30° to 170°. If the angle (θ) between the second crystal plane and the third crystal plane is less than 30°, the surface area of the secondary particles increases to increase the contact area with the electrolyte, thereby causing the electrolyte to pass through the secondary particles 200 in the charging and discharging process. It may flow into the center and cause the formation of microcracks in secondary particles. When the angle θ between the second crystal plane and the third crystal plane exceeds 170°, the efficiency of lithium ions moving into the secondary particles 200 may be reduced. Specifically, the angle θ between the second crystal plane and the third crystal plane may be 90° to 170°, more specifically 110° to 170°, and even more specifically 120° to 160°. .

100 cycles of 2.7V discharge at 0.5C constant current and 4.3V charge at 0.5C constant current in a 2032 coin-type half-cell using the positive electrode active material as the positive electrode and lithium metal as the negative electrode, after charging and discharging In the dQ/dV curve, which is a graph in which the curve is differentiated by one degree, the intensity of the peak corresponding to the phase transition of H2-H3 may be 40% or more compared to one cycle, preferably 60% to 98%, more preferably It may be 70% to 90%.

The primary particles include Ni and M1 and M2, wherein M1 consists of at least any one of Mn, Co, and Al, the Ni is 65 mol% or more, and M2 is a doping element in an amount of 0.05 mol% to 5 mol % can be made.

The primary particles according to the present embodiment may include nickel (Ni) in a high content of 65 mol% or more, and may further include a doping element. The doping element may be made of a material other than lithium (Li), nickel (Ni), manganese (Mn), cobalt (Co) and aluminum (Al), and the doping element may be included in an amount of 0.05 mol% to 5 mol% have.

The doping element may control the shape of the first primary particle 100 among the primary particles, and control the shape of contraction and expansion occurring during insertion or desorption of lithium ions, thereby improving the lifespan characteristics of the secondary battery. If the content of the doping element is less than 0.05 mol%, it is difficult for the first primary particles to be radially arranged, so that the lithium ion movement efficiency is lowered. The gap between 110 is too narrow, and cracks may occur in the course of the cycle.

Preferably, the doping element M2 may include boron (B).

In the present invention, in the first primary particle 100, the second and third crystal planes 120 and 130 provided on the outer surface of the secondary particle 200, the second and third crystal planes 120, A coating layer including boron (B) covering at least a portion of 130 may be provided. The boron (B) may be provided by being doped in the secondary particles 200, wherein the boron (B) controls the shape of the first primary particles and at the same time forms a coating layer covering at least a part of the outer surface of the secondary particles. can be

The first primary particle 100 according to the present embodiment may include boron (B), and a coating layer including boron (B) may be provided on the outer surface of the secondary particle 200 . The concentration of boron (B) may be uniformly provided in the secondary particles 200 and may be provided to have a concentration gradient in the coating layer. Preferably, the average concentration of boron (B) in the coating layer may be higher than the average concentration of boron (B) in the secondary particles 200 .

The coating layer is LiBO ₂ , LiB ₃ O ₅ , LiB ₅ O ₈ , α-LiBO _{2 ,} Li ₂ B ₂ O ₄ , Li ₂ B ₂ O ₇ , Li ₂ B ₄ O ₇ , Li ₂ B ₆ O ₇ , Li ₂ B ₆ O ₁₀ , Li ₂ B ₈ O ₁₃ , Li ₃ BO ₃ , Li ₃ B ₇ O ₁₂ , Li ₄ B ₂ O ₅ , α-Li ₄ B ₂ O ₅ , β-Li ₄ B ₂ O _{5 ,} Li ₄ B ₁₀ O ₁₇ and Li ₆ B ₄ O ₉ It may include a lithium boron oxide consisting of at least one.

The coating layer may be formed by reacting a lithium compound and boron oxide, for example, according to the following reaction formula.

Li ₂ CO ₃ + B ₂ O ₃ → Li ₂ B ₂ O ₄ + CO ₂

LiOH + B ₂ O ₃ → Li ₂ B ₂ O ₄ + H ₂ O

Li ₂ CO ₃ + 2B ₂ O ₃ → Li ₂ B ₄ O ₇ + CO ₂

2LiOH + B ₂ O ₃ → Li ₂ B ₄ O ₇ + H ₂ O

For example, using nickel (Ni), manganese (Mn), cobalt (Co), and aluminum (Al) at least one metal compound and boron (B) as a doping element to prepare secondary particles consisting of a group of primary particles can do. Then, the secondary particles may be mixed with a lithium compound and fired to prepare a cathode active material, and boron oxide may be provided in a controlled concentration in the secondary particles. The boron oxide may react with a lithium compound as shown in the above reaction formula to form a coating layer on the outer surface of the secondary particles. The above-described reaction formula for forming the coating layer is an example, and lithium boron oxide constituting the coating layer may be formed by various reaction formulas.

In the secondary particles 200 according to the present embodiment, the secondary particles 200 are composed of a group of a plurality of primary particles including the first primary particles 100, and the first primary particles 100 are secondary particles ( 200) may be provided so that the first crystal surface 110 of the first primary particle 100 is radially aligned in the secondary particle 200. In addition, the first primary particle 100 may be provided so that the second and third crystal surfaces 120 and 130 of the first primary particle 100 are located on the outer surface of the secondary particle 200 . The doping element may include boron (B), and the boron (B) is provided in a uniform concentration inside the first primary particle 100 to determine the shape and position of the first primary particle 100 . controllable, provided in the coating layer covering at least a portion of the second and third crystal planes 120 and 130 of the first primary particle 100, the first crystal plane 110 of the first primary particle 100 Directional growth can be controlled.

In addition, in another embodiment of the present invention, the doping element M2 is boron (B); and tungsten (W), molybdenum (Mo), tantalum (Ta), niobium (Nb), hafnium (Hf), silicon (Si), tin (Sn), zirconium (Zr), calcium (Ca), germanium (Ge) any one of , gallium (Ga), indium (In), ruthenium (Ru), tellurium (Te), antimony (Sb), iron (Fe), chromium (Cr), vanadium (V) and titanium (Ti) It can be made of; More preferably, the doping element M2 may be formed by co-doping two doping elements, boron (B) and tungsten (W), boron (B) and molybdenum (Mo) , boron (B) and niobium (Nb), boron (B) and tantalum (Ta), and boron (B) and antimony (Sb) may be formed of any one or more.

In an embodiment of the present invention, in a cross section of secondary particles 200 charged with 4.3V at 0.5C constant current with a half-cell using lithium metal as a negative electrode as a positive electrode using the positive electrode active material, neighboring primary particle boundaries The area of the microcrack, which is a space formed between (boundary), may be provided to be less than 15% of the area of the cross-section of the secondary particle.

The microcrack may be formed in the form of a space formed between the primary particle and the primary particle when the spherical secondary particle is cut in a cross section, and approximately from the center of the secondary particle toward the surface of the secondary particle can be connected The microcracks start at the center of the secondary particles, and may be formed by a sudden change in volume when charging and discharging proceed, which may extend from the center to the surface during the charging/discharging cycle. Microcracks extending to the surface portion act as an inflow path of the electrolyte, and the electrolyte is introduced through the microcracks and a passivation layer is formed inside the secondary particles to act as a resistance to reduce electrical efficiency. can In severe cases, the passivation layer increases the area of microcracks in the secondary particles, whereby the secondary particles may be almost separated.

On the other hand, in the secondary particles according to the present embodiment, when a plurality of cycles are performed, microcracks are hardly formed. For example, in a cross section of a secondary particle 200 charged with 4.3V at 0.5C constant current with a 2032 coin-type half-cell, the area of microcracks, which is a space formed between neighboring primary particle boundaries, is It may be provided in less than 15% of the area of the cross-section of the secondary particles. Preferably, the area of the microcracks may be provided in less than 10%, more preferably less than 7%.

The secondary particle 200 is a device (Empyrean, Panalytical) having an output of 45 kV and 40 mA. , the ratio of the intensity of the 003 peak to the intensity of the 104 peak excluding the background may be 1.6 to 2.15. Also, as the content of the doping element increases, a ratio of the intensity of the 003 peak to the intensity of the 104 peak may decrease.

According to another aspect of the present invention, the secondary particles 200 are provided in a spherical shape having a central portion (c) and a surface portion, and the first primary particles 100 have the first crystal plane 110 in the central portion (c). may be provided in a direction toward the surface portion. In the first primary particle 100, the second and third crystal planes 120 and 130 are provided on the surface portion of the secondary particle 200, and the outermost surface of the surface portion of the secondary particle 200 is the second and A concave-convex structure may be formed by the third crystal planes 120 and 130 .

The secondary particle 200 is represented by the following <Formula 1>, and the surface portion of the secondary particle 200 may further include a coating layer covering at least a portion of the second and third crystal planes 120 and 130. can

<Formula 1>

Li _a M _x D _y O ₂

In the <Formula 1>, M is at least any one of Ni, Co, Mn, or Al, D is B or a doping element consisting of B and W, 0.9<a<1.1, x + y = 1, 0.95<x<1, 0<y<0.05.

The first primary particles 100 have a first length f1 that is a long axis of the first crystal plane 110 and a second length that is a short axis of the first crystal plane 110 perpendicular to the first length f1. (f2), and a third length f3 that is an interval between the pair of first crystal planes 110 may be provided in the form of flakes. The first primary particles 100 in the form of flakes may be aligned so that the long axis faces the center (c) of the secondary particles 200 .

The doping element is provided in an amount of 0.05 mol% to 5 mol%, and as the concentration of the doping element increases, the first length f1 of the first primary particles 100 increases, and the third length f3 is can be reduced. Preferably, the doping element may be 0.05 mol% to 2 mol%, and more preferably, the doping element may be 0.5 mol% to 2 mol%.

According to another aspect of the present invention, the present invention provides a spherical secondary particle formed of a layered trigonal system (Rhombohedral system) compound containing metal, lithium, a doping element, and oxygen; and a coating layer provided on the surface of the secondary particles, formed of a compound containing lithium, the doping element, and oxygen, and having a crystal structure different from that of the secondary particles; (Ni); and any one or more of cobalt (Co), manganese (Mn), and aluminum (Al).

The average concentration of the doping element in the coating layer is higher than the average concentration of the doping element in the secondary particles, and the coating layer is, LiBO ₂ , LiB ₃ O ₅ , LiB ₅ O ₈ , α-LiBO _{2 ,} Li ₂ B ₂ O ₄ , Li ₂ B ₂ O ₇ , Li ₂ B ₄ O ₇ , Li ₂ B ₆ O ₇ , Li ₂ B ₆ O ₁₀ , Li ₂ B ₈ O ₁₃ , Li ₃ BO ₃ , Li ₃ B ₇ O ₁₂ , Li ₄ B ₂ O ₅ , α-Li ₄ B ₂ O ₅ , β-Li ₄ B ₂ O _{5 ,} Li ₄ B ₁₀ O ₁₇ and Li ₆ B ₄ O ₉ Lithium boron oxide comprising at least one of can

The thickness of the coating layer may be 1 nm to 10 nm. When the thickness of the coating layer is less than 1 nm, it is difficult to effectively protect the surface portion of the secondary particles, and thus the lifespan characteristics of the secondary battery are deteriorated.

The first primary particle may have a crystal structure, and an a-axis of the crystal structure may be arranged parallel to a direction from the central portion of the secondary particle toward the surface portion. For this reason, it can act as a movement path of lithium ions and electrolyte between the first primary particles having the flake shape, and thus the charging and discharging efficiency of the secondary battery including the present positive electrode active material can be improved.

According to one embodiment, the metal may be provided to have a concentration gradient in the secondary particles. For example, at least one of nickel, cobalt, manganese, and aluminum may have a continuous or discontinuous concentration gradient in at least one region of the secondary battery.

According to an embodiment of the present invention, the cathode active material may be prepared by calcining a cathode active material precursor prepared using a metal and a doping element and a lithium compound.

Alternatively, according to another embodiment, the method for manufacturing the positive electrode active material includes supplying the transition metal aqueous solution, the chelating agent, and the doping source into a reactor to prepare the positive electrode active material precursor doped with the doping element; and sintering the cathode active material precursor and the lithium salt.

According to another aspect of the present invention, an embodiment of the present invention includes a positive electrode for a secondary battery including the above-described positive electrode active material.

In addition, it may include a lithium secondary battery including the positive electrode.

An embodiment of the present invention may include a battery module including the lithium secondary battery as a unit cell.

In addition, a battery pack including the battery module, wherein the battery pack is used as a power source for a medium or large device, and the medium or large device is selected from the group consisting of an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a system for power storage It may include a battery pack that will.

2 is a flowchart illustrating a method for manufacturing a cathode active material according to another embodiment of the present invention.

Referring to FIG. 2 , the method for manufacturing a cathode active material according to the present embodiment includes preparing a metal solution (S210); preparing a metal complex hydroxide by coprecipitating the metal solution with an ammonia solution and sodium hydroxide solution (S220); Preparing boron oxide by pulverizing to a first particle size (S230); mixing the metal complex hydroxide, lithium hydroxide, and boron oxide of the first particle size and then pre-firing for a first temperature range and a first time (S240); and calcining for a second temperature range and a second time after the preliminary firing is completed (S250), wherein the boron oxide is provided in a powder form, and the first particle size of the boron oxide is 0.1 μm to It may be 500 μm.

In the method for manufacturing the positive electrode active material according to the present embodiment, in the step of preparing the metal solution ( S210 ), a metal solution including any one or more of cobalt, manganese, and aluminum along with nickel may be prepared. In this case, the metal solution may be provided to have one or more concentration ranges. For example, the metal solution includes a first metal solution having a first concentration and a second metal solution having a second concentration different from the first concentration as a metal combination using any one or more of nickel, cobalt, manganese, and aluminum. may include By using the first metal solution and the second metal solution, any one or more of nickel, cobalt, manganese, and aluminum can be prepared as a metal complex hydroxide having a concentration gradient therein.

In the step of preparing the metal complex hydroxide by the co-precipitation reaction (S220), the metal complex hydroxide may be prepared using the metal solution. The co-precipitation reaction may be performed by continuously introducing a metal solution, an ammonia solution, and a sodium hydroxide solution to the co-precipitation reactor at different rates, respectively, in which case the input rate and concentration of the metal solution, the ammonia solution and the sodium hydroxide solution are controlled. By doing so, it is possible to control the microstructure, shape, etc. of the primary and secondary particles constituting the metal complex hydroxide. The co-precipitation reaction may be carried out at 20 °C to 60 °C, preferably at 22 °C to 47 °C. In addition, the pH may be maintained at 10 to 12 during the coprecipitation reaction in the coprecipitation reactor.

Subsequently, the prepared metal complex hydroxide is filtered to remove the liquid phase, washed several times using distilled water, and then dried in a vacuum dryer to prepare a powder form. The temperature of the vacuum dryer may be 100 °C to 160 °C, preferably 100 °C to 135 °C.

In the preparing step (S230) by pulverizing boron oxide to a first particle size, solid boron oxide (B ₂ O ₃ ) may be used to prepare. The particle size of the boron oxide may be controlled using a ball-mill or the like, for example, the first particle size of boron oxide may be 0.1 μm to 500 μm. When the first particle size is less than 0.1 μm, the boron oxide is agglomerated and it is difficult to be uniformly mixed with the metal complex hydroxide, and when it exceeds 500 μm, there may be a problem in that it does not adhere to the metal complex hydroxide. Preferably, the first particle size may be 1㎛ to 50㎛, more preferably 2㎛ to 10㎛.

In the pre-firing step (S240) after mixing the metal composite hydroxide, lithium hydroxide and boron oxide, the metal composite hydroxide, lithium hydroxide and boron oxide are first mixed, and then heated for a first temperature range and a first time Thus, preliminary firing can be performed. The preliminary firing may further improve the electrochemical performance of the positive electrode active material manufactured by firing by preliminarily applying heat at a relatively low temperature before firing at a high temperature. The first temperature range may be 350°C to 500°C, and the first time period may be 3 hours to 8 hours. Since the preliminary firing is performed within the first temperature range and the first time, the microstructure of the positive electrode active material is controlled by subsequent firing, and electrical properties can be further improved. In addition, boron controls the crystallinity of the primary particles in the surface portion of the positive electrode active material, so that the movement path of lithium ions can be formed more efficiently. Preferably, the first temperature range may be 400 °C to 500 °C, more preferably 410 °C to 480 °C. Also, preferably, the first time period may be 3 hours to 7 hours, more preferably 4 hours to 6 hours.

Subsequently, the step of sintering for a second temperature range and a second time (S250) may be performed. The boron-doped final positive electrode active material may be prepared by the firing, wherein the second temperature range is 700° C. to 1000° C., and the second time period may be 8 hours to 15 hours. If it is less than 700°C in the second temperature range of the firing step (S250), the primary particles constituting the secondary particles of the positive electrode active material are not uniformly aligned as a whole, and when it exceeds 1000°C, the process efficiency is lowered, such as some materials are evaporated become a problem Preferably, the second temperature range may be 1.8 times to 2.2 times the first temperature range.

Hereinafter, Examples and Comparative Examples of the present invention will be described. However, the following examples are only preferred examples of the present invention, and the scope of the present invention is not limited by the following examples.

1. Preparation of Examples and Comparative Examples

(1) Preparation of NCM-based positive electrode active material

Example 1 (NCM65-B1)

After 10 liters of distilled water was put into the coprecipitation reactor (capacity 40L, output of the rotary motor 750W or more), N ₂ gas was supplied to the reactor at a rate of 6 liters/minute, and the temperature of the reactor was maintained at 45° C. and stirred at 350 rpm. . Nickel sulfate aqueous solution (NiSO ₄ 6H ₂ O, Samjeon Chemical), cobalt sulfate aqueous solution (CoSO ₄ 7H ₂ O, Samjeon Chemical), and manganese sulfate aqueous solution (MnSO ₄ H ₂ O, Samjeon Chemical) were mixed with nickel (Ni), cobalt (Co ) and manganese (Mn) were mixed in an amount such that the molar ratio was 65:15:20 to prepare a metal solution having a concentration of 2M. The prepared metal solution was 0.561 liters/hour, 16M ammonia solution (NH ₄ OH, JUNSEI) was 0.08 liters/hour, and 4M sodium hydroxide solution (NaOH, Samchun Chemical) was 0.60 liters/hour, respectively. was continuously added for 24 hours. The coprecipitation reaction was performed while maintaining the pH in the reactor in the range of 10 to 12 to prepare Ni _0.65 Co _0.15 Mn _0.2 (OH) ₂ metal composite hydroxide.

The prepared Ni _0.65 Co _0.15 Mn _0.2 (OH) ₂ metal complex hydroxide was filtered, washed several times using distilled water, and dried in a vacuum dryer at 110° C. for 12 hours to prepare a powder form. After preparing boron oxide (B ₂ O ₃ ) by pulverizing it using a ball mill to have an average particle size of 50 μm, Ni _0.65 Co _0.15 Mn _0.2 (OH) ₂ metal composite hydroxide, boron oxide (B _{2 ) prepared in powder form} O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.99:0.005:1.01, heated at a temperature increase rate of 2°C/min, and maintained at 450°C for 5 hours to perform preliminary calcination. Subsequently, it was calcined at 820° C. for 10 hours to prepare a cathode active material powder (NCM65-B1) doped with boron (B) by 1 mol%. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 1 that the B doping amount of the doping element, in the process of preparing the metal complex hydroxide, Molar ratios and firing temperatures of metals (nickel (Ni), cobalt (Co) and manganese (Mn)) are shown.

Example 2 (NCM65-B1)

_{Boron in the same manner as in Example 1, except that 16M concentration of ammonia solution (NH 4} OH, JUNSEI) was continuously added into the co-precipitation reactor at 0.213 liters/hour in the process of preparing the metal complex oxide to perform the co-precipitation reaction. (B) 1 mol% doped positive electrode active material powder (NCM65-B1) was prepared. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 1.

Comparative Example 1 (NCM65)

_{Ni 0.65} Co _0.15 Mn _0.2 (OH) ₂ metal composite hydroxide prepared in powder form and lithium hydroxide (LiOH) were mixed in a molar ratio of 1:1.01 and pre-calcined in the same manner as in Example 1, except that boron (B) was An undoped cathode active material powder (NCM65) was prepared. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 1.

Example 3 (NCM90-B0.4)

After 10 liters of distilled water was put into the coprecipitation reactor (capacity 40L, output of the rotary motor 750W or more), N ₂ gas was supplied to the reactor at a rate of 6 liters/minute, and the temperature of the reactor was maintained at 45° C. and stirred at 350 rpm. . Nickel sulfate aqueous solution (NiSO ₄ 6H ₂ O, Samjeon Chemical), cobalt sulfate aqueous solution (CoSO ₄ 7H ₂ O, Samjeon Chemical), and manganese sulfate aqueous solution (MnSO ₄ H ₂ O, Samjeon Chemical) were mixed with nickel (Ni), cobalt (Co ) and manganese (Mn) were mixed in an amount such that the molar ratio was 90:5:5 to prepare a metal solution having a concentration of 2M. The prepared metal solution was 0.561 liters/hour, 16M ammonia solution (NH ₄ OH, JUNSEI) was 0.08 liters/hour, and 4M sodium hydroxide solution (NaOH, Samchun Chemical) was 0.60 liters/hour, respectively. was continuously added for 24 hours. The co-precipitation reaction was performed while maintaining the pH in the reactor in the range of 10 to 12 to prepare Ni _0.9 Co _0.05 Mn _0.05 (OH) ₂ metal composite hydroxide.

The prepared Ni _0.9 Co _0.05 Mn _0.05 (OH) ₂ metal complex hydroxide was filtered, washed several times using distilled water, and dried in a vacuum dryer at 110° C. for 12 hours to prepare a powder form. After preparing boron oxide (B ₂ O ₃ ) by pulverizing it using a ball mill to have an average particle size of 50 μm, Ni _0.9 Co _0.05 Mn _0.05 (OH) ₂ metal composite hydroxide, boron oxide (B ₂ O) prepared in powder form ₃ ), and lithium hydroxide (LiOH) in a molar ratio of 0.996:0.002:1.01, heated at a temperature increase rate of 2°C/min, and maintained at 450°C for 5 hours to perform preliminary firing, followed by 10 at 750°C The time calcination was performed to prepare a cathode active material powder (NCM90-B0.4) doped with boron (B) in 0.4 mol%. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 1 that the B doping amount of the doping element, in the process of preparing the metal complex hydroxide, Molar ratios and firing temperatures of metals (nickel (Ni), cobalt (Co) and manganese (Mn)) are shown.

Example 4 (NCM90-B1)

_{Example 3 except that Ni 0.9} Co _0.05 Mn _0.05 (OH) ₂ metal composite hydroxide prepared in powder form, boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.99:0.005:1.01 A cathode active material powder (NCM90-B1) doped with boron (B) in 1 mol% was prepared in the same manner as described above. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 1.

Example 5 (NCM90-B1)

In the process of preparing the metal complex oxide, a 16M concentration of ammonia solution (NH ₄ OH, JUNSEI) was continuously added into the coprecipitation reactor at 0.113 liters/hour to perform the coprecipitation reaction, and Ni _0.9 Co prepared in powder form _{Boron (B) in the same manner as in Example 3 except that 0.05} Mn _0.05 (OH) ₂ metal composite hydroxide, boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.99:0.005:1.01. This 1 mol% doped positive electrode active material powder (NCM90-B1) was prepared. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 1.

Example 6 (NCM90-B1)

In the process of preparing the metal complex oxide, a 16M concentration of ammonia solution (NH ₄ OH, JUNSEI) was continuously added into the coprecipitation reactor at 0.146 liters/hour to perform the coprecipitation reaction, and Ni _0.9 Co prepared in powder form _{Boron (B) in the same manner as in Example 3 except that 0.05} Mn _0.05 (OH) ₂ metal composite hydroxide, boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.99:0.005:1.01. This 1 mol% doped positive electrode active material powder (NCM90-B1) was prepared. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 1.

Example 7 (NCM90-B1)

In the process of preparing the metal complex oxide, a 16M concentration of ammonia solution (NH ₄ OH, JUNSEI) was continuously added into the coprecipitation reactor at 0.267 liters/hour to perform the coprecipitation reaction, and Ni _0.9 Co prepared in powder form _{Boron (B) in the same manner as in Example 3 except that 0.05} Mn _0.05 (OH) ₂ metal composite hydroxide, boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.99:0.005:1.01. This 1 mol% doped positive electrode active material powder (NCM90-B1) was prepared. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 1.

Comparative Example 2 (NCM90)

In the same manner as in Example 3, boron (B) was prepared in the same manner as in Example 3, except _{that Ni 0.9} Co _0.05 Mn _0.05 (OH) ₂ metal composite hydroxide prepared in powder form and lithium hydroxide (LiOH) were mixed in a molar ratio of 1:1.01 and pre-calcined. An undoped cathode active material powder (NCM90) was prepared. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 1.

Example 8 (NCM92-B1)

After 10 liters of distilled water was put into the coprecipitation reactor (capacity 40L, output of the rotary motor 750W or more), N ₂ gas was supplied to the reactor at a rate of 6 liters/minute, and the temperature of the reactor was maintained at 45° C. and stirred at 350 rpm. . Nickel sulfate aqueous solution (NiSO ₄ 6H ₂ O, Samjeon Chemical), cobalt sulfate aqueous solution (CoSO ₄ 7H ₂ O, Samjeon Chemical), and manganese sulfate aqueous solution (MnSO ₄ H ₂ O, Samjeon Chemical) were mixed with nickel (Ni), cobalt (Co ) and manganese (Mn) were mixed in an amount such that the molar ratio was 92:4:4 to prepare a metal solution having a concentration of 2M. The prepared metal solution was 0.561 liters/hour, 16M ammonia solution (NH ₄ OH, JUNSEI) was 0.08 liters/hour, and 4M sodium hydroxide solution (NaOH, Samchun Chemical) was 0.60 liters/hour, respectively. was continuously added for 24 hours. The co-precipitation reaction was performed while maintaining the pH in the reactor in the range of 10 to 12 to prepare Ni _0.92 Co _0.04 Mn _0.04 (OH) ₂ metal composite hydroxide.

The prepared Ni _0.92 Co _0.04 Mn _0.04 (OH) ₂ metal complex hydroxide was filtered, washed several times using distilled water, and dried in a vacuum dryer at 110° C. for 12 hours to prepare a powder. After preparing boron oxide (B ₂ O ₃ ) by pulverizing it using a ball mill to have an average particle size of 50 μm, Ni _0.92 Co _0.04 Mn _0.04 (OH) ₂ metal composite hydroxide, boron oxide (B _{2 ) prepared in powder form} O ₃ ), and lithium hydroxide (LiOH) were mixed at a molar ratio of 0.99:0.005:1.01, heated at a temperature increase rate of 2°C/min, and maintained at 450°C for 5 hours to perform preliminary firing, followed by pre-calcination at 730°C By calcining for 10 hours, a cathode active material powder (NCM92-B1) doped with boron (B) in 1 mol% was prepared. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 1 that the B doping amount of the doping element, in the process of preparing the metal complex hydroxide, Molar ratios and firing temperatures of metals (nickel (Ni), cobalt (Co) and manganese (Mn)) are shown.

Comparative Example 3 (NCM92)

_{Ni 0.0.92} Co _0.04 Mn _0.04 (OH) ₂ metal composite hydroxide and lithium hydroxide (LiOH) prepared in powder form in a molar ratio of 1:1.01 (the total number of moles of nickel (Ni), cobalt (Co) and manganese (Mn)) : A positive electrode active material powder (NCM92) not doped with boron (B) was prepared in the same manner as in Example 8, except that the mixture was mixed with lithium (Li) and pre-fired. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 1.

division Cathode active material powder chemical formula Chemical composition analyzed by ICP-OES B doping [mol%] Ammonia Molar Ratio to Metal Firing temperature [℃] Comparative Example 1 Li _1.01 Ni _0.65 Co _0.13 Mn _0.22 O ₂ Ni _0.649 Co _0.127 Mn _0.224 0 1.2 820 Example 1 Li _1.01 B _0.01 Ni _0.65 Co _0.13 Mn _0.22 O ₂ Ni _0.642 Co _0.128 Mn _0.221 B _0.009 1.0 1.2 820 Example 2 Li _1.01 B _0.01 Ni _0.65 Co _0.13 Mn _0.22 O ₂ Ni _0.645 Co _0.131 Mn _0.214 B _0.01 1.0 3.2 820 Comparative Example 2 Li _1.01 Ni _0.90 Co _0.05 Mn _0.05 O ₂ Ni _0.903 Co _0.047 Mn _0.05 0 1.2 750 Example 3 Li _1.01 B _0.004 Ni _0.90 Co _0.05 Mn _0.05 O ₂ Ni _0.90 Co _0.048 Mn _0.048 B _0.004 0.4 1.2 750 Example 4 Li _1.01 B _0.01 Ni _0.90 Co _0.05 Mn _0.05 O ₂ Ni _0.8905 Co _0.055 Mn _0.054 B _0.0105 1.0 1.2 750 Example 5 Li _1.01 B _0.01 Ni _0.90 Co _0.05 Mn _0.05 O ₂ Ni _0.90 Co _0.05 Mn _0.05 B _0.01 1.0 1.7 750 Example 6 Li _1.01 B _0.01 Ni _0.90 Co _0.05 Mn _0.05 O ₂ Ni _0.889 Co _0.05 Mn _0.05 B _0.011 1.0 2.2 750 Example 7 Li _1.01 B _0.01 Ni _0.90 Co _0.05 Mn _0.05 O ₂ Ni _0.90 Co _0.05 Mn _0.05 B _0.01 1.0 4.0 750 Comparative Example 3 Li _1.01 Ni _0.92 Co _0.04 Mn _0.04 O ₂ Ni _0.921 Co _0.039 Mn _0.04 0 1.2 730 Example 8 Li _1.01 B _0.01 Ni _0.92 Co _0.04 Mn _0.04 O ₂ Ni _0.91 Co _0.041 Mn _0.039 B _0.01 1.0 1.2 730

(2) Preparation of LNO-based positive electrode active material

Example 9 (LNO-B1)

After 10 liters of distilled water was put into the coprecipitation reactor (capacity 40L, output of the rotary motor 750W or more), N ₂ gas was supplied to the reactor at a rate of 6 liters/minute, and the temperature of the reactor was maintained at 45° C. and stirred at 350 rpm. . A metal solution having a concentration of 2M was prepared by mixing an aqueous nickel sulfate solution (NiSO ₄ 6H _{2 O, Samjeon Chemical) with distilled water.} The prepared metal solution was 0.561 liters/hour, 16M ammonia solution (NH ₄ OH, JUNSEI) was 0.067 liters/hour, and 4M sodium hydroxide solution (NaOH, Samjeon Chemical) was 0.60 liters/hour, respectively. was continuously added for 24 hours. The co-precipitation reaction was performed while maintaining the pH in the reactor in the range of 10 to 12 to prepare a Ni(OH) ₂ metal composite hydroxide.

The prepared Ni(OH) ₂ metal composite hydroxide was filtered, washed several times with distilled water, and dried in a vacuum dryer at 110° C. for 12 hours to prepare a powder. After preparing boron oxide (B ₂ O ₃ ) by pulverizing it using a ball mill to have an average particle size of 50 μm, Ni(OH) ₂ metal composite hydroxide prepared in powder form, boron oxide (B ₂ O ₃ ), and Lithium hydroxide (LiOH) was mixed at a molar ratio of 0.99:0.005:1.01, heated at a temperature increase rate of 2°C/min, and maintained at 450°C for 5 hours to perform preliminary firing, followed by firing at 650°C for 10 hours, A cathode active material powder (LNO-B1) doped with boron (B) in 1 mol% was prepared. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 2 that the B doping amount of the doping element, in the process of preparing the metal complex hydroxide, Molar ratio of metal (nickel (Ni)) and firing temperature are shown.

Example 10 (LNO-B1)

_{Boron in the same manner as in Example 9 except that 16M ammonia solution (NH 4} OH, JUNSEI) was continuously added into the co-precipitation reactor at 0.13 liters/hour in the process of preparing the metal complex oxide to perform the co-precipitation reaction. (B) 1 mol% doped positive electrode active material powder (LNO-B1) was prepared. The content of each element was confirmed in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 2.

Example 11 (LNO-B1)

_{Boron in the same manner as in Example 9, except that 16M ammonia solution (NH 4} OH, JUNSEI) was continuously added into the co-precipitation reactor at 0.2 liters/hour in the process of preparing the metal complex oxide to perform the co-precipitation reaction. (B) 1 mol% doped positive electrode active material powder (LNO-B1) was prepared. The content of each element was confirmed in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 2.

Example 12 (LNO-B1)

_{Boron in the same manner as in Example 9, except that 16M ammonia solution (NH 4} OH, JUNSEI) was continuously added into the coprecipitation reactor at 0.26 liters/hour in the process of preparing the metal complex oxide to perform the coprecipitation reaction. (B) 1 mol% doped positive electrode active material powder (LNO-B1) was prepared. The content of each element was confirmed in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 2.

Comparative Example 4 (LNO)

In the process of preparing the metal complex oxide, a 16M concentration of ammonia solution (NH ₄ OH, JUNSEI) was continuously added into the coprecipitation reactor at 0.067 liters/hour to perform the coprecipitation reaction, and Ni(OH) prepared in powder form ) _{2 A} cathode active material powder (LNO) not doped with boron (B) was prepared in the same manner as in Example 9 except for mixing the 2 metal composite hydroxide and lithium hydroxide (LiOH) in a molar ratio of 1:1.01. The content of each element was checked in the prepared cathode active material powder using ICP-OES, and it is shown in Table 2.

division Cathode active material powder chemical formula Chemical composition analyzed by ICP-OES B doping [mol%] Ammonia Molar Ratio to Metal Firing temperature [℃] Comparative Example 4 Li _1.01 NiO ₂ Ni _1.00 0 1.0 650 Example 9 Li _1.01 B _0.01 NiO ₂ Ni _0.991 B _0.009 1.0 1.0 650 Example 10 Li _1.01 B _0.01 NiO ₂ Ni _0.99 B _0.01 1.0 2.0 650 Example 11 Li _1.01 B _0.01 NiO ₂ Ni _0.991 B _0.009 1.0 3.0 650 Example 12 Li _1.01 B _0.01 NiO ₂ Ni _0.991 B _0.009 1.0 4.0 650

(3) Preparation of NCO-based positive electrode active material

Example 13 (NCO90-B0.05)

After 10 liters of distilled water was put into the coprecipitation reactor (capacity 40L, output of the rotary motor 750W or more), N ₂ gas was supplied to the reactor at a rate of 6 liters/minute, and the temperature of the reactor was maintained at 45° C. and stirred at 350 rpm. . Nickel sulfate aqueous solution (NiSO ₄ 6H ₂ O, Samjeon Chemical) and cobalt sulfate aqueous solution (CoSO ₄ 7H ₂ O, Samjeon Chemical) are mixed in an amount such that the molar ratio of nickel (Ni) and cobalt (Co) is 9:1. A metal solution having a concentration of 2M was prepared. The prepared metal solution was 0.561 liters/hour, 16M ammonia solution (NH ₄ OH, JUNSEI) was 0.11 liters/hour, and 4M sodium hydroxide solution (NaOH, Samjeon Chemical) was 0.60 liters/hour, respectively. It was continuously introduced into the reactor for 24 hours. The co-precipitation reaction was performed while maintaining the pH in the reactor in the range of 10 to 12 to prepare Ni _0.9 Co _0.1 (OH) ₂ metal composite hydroxide.

The prepared Ni _0.9 Co _0.1 (OH) ₂ metal composite hydroxide was filtered, washed several times with distilled water, and dried in a vacuum dryer at 110° C. for 12 hours to prepare a powder. After preparing boron oxide (B ₂ O ₃ ) by pulverizing it using a ball mill to have an average particle size of 50 μm, Ni _0.9 Co _0.1 (OH) ₂ metal composite hydroxide prepared in powder form, boron oxide (B ₂ O _{3 )} ), and lithium hydroxide (LiOH) in a molar ratio of 0.9995:0.00025:1.01, heated at a temperature increase rate of 2°C/min, maintained at 450°C for 5 hours, followed by pre-calcination at 730°C for 10 hours By calcination, a cathode active material powder (NCO90-B0.05) doped with boron (B) at 0.05 mol% was prepared. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and the B doping amount of the doping element, in the process of preparing the metal composite hydroxide, Molar ratios and firing temperatures of metals (nickel (Ni) and cobalt (Co)) are shown.

Example 14 (NCO90-B0.1)

_{Ni 0.9} Co _0.1 (OH) ₂ metal composite hydroxide prepared in powder form, boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.999:0.0005:1.01, except for mixing the same as in Example 13. A cathode active material powder (NCO90-B0.1) doped with boron (B) in 0.1 mol% was prepared by the method. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 3.

Example 15 (NCO90-B0.5)

_{Ni 0.9} Co _0.1 (OH) ₂ metal composite hydroxide prepared in powder form, boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.995:0.0025:1.01, except for mixing the same as in Example 13. A cathode active material powder (NCO90-B0.5) doped with boron (B) in 0.5 mol% was prepared by this method. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 3.

Example 16 (NCO90-B1)

_{Ni 0.9} Co _0.1 (OH) ₂ metal composite hydroxide prepared in powder form, boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.99:0.005:1.01, except for mixing the same as in Example 13. A cathode active material powder (NCO90-B1) doped with boron (B) in 1 mol% was prepared by the method. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 3.

Example 17 (NCO90-B1.5)

_{Ni 0.9} Co _0.1 (OH) ₂ metal composite hydroxide prepared in powder form, boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.985:0.0075:1.01, except for mixing the same as in Example 13. A positive electrode active material powder (NCO90-B1.5) doped with boron (B) in 1.5 mol% was prepared by the method. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 3.

Example 18 (NCO90-B2)

_{Ni 0.9} Co _0.1 (OH) ₂ metal composite hydroxide prepared in powder form, boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.98:0.01:1.01, except for mixing the same as in Example 13. A cathode active material powder (NCO90-B2) doped with 2 mol% boron (B) was prepared by the method. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 3.

Example 19 (NCO90-B3)

_{Ni 0.9} Co _0.1 (OH) ₂ metal composite hydroxide prepared in powder form, boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.97:0.015:1.01, except for mixing the same as in Example 13. A cathode active material powder (NCO90-B3) doped with boron (B) in 3 mol% was prepared by the method. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 3.

Example 20 (NCO90-B4)

_{Ni 0.9} Co _0.1 (OH) ₂ metal composite hydroxide prepared in powder form, boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.96:0.02:1.01, except for mixing the same as in Example 13. A cathode active material powder (NCO90-B4) doped with boron (B) in 4 mol% was prepared by this method. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 3.

Example 21 (NCO90-B5)

_{Ni 0.9} Co _0.1 (OH) ₂ metal composite hydroxide prepared in powder form, boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.95:0.025:1.01, except for mixing the same as in Example 13. A cathode active material powder (NCO90-B5) doped with boron (B) in 5 mol% was prepared by this method. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 3.

Example 22 (NCO90-B0.5,Mo0.5)

_{Ni 0.9} Co _0.1 (OH) ₂ metal composite hydroxide prepared in powder form, molybdenum trioxide (MoO ₃ ), boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) in a molar ratio of 0.99:0.005:0.0025:1.01 A cathode active material powder (NCO90-B0.5, Mo0.5) doped with molybdenum (Mo) and boron (B) by 0.5 mol% each was prepared in the same manner as in Example 13 except for mixing. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 3.

Comparative Example 5 (NCO90)

A cathode active material not doped with boron (B) in the same manner as in Example 13, except _{that Ni 0.9} Co _0.1 (OH) ₂ metal composite hydroxide prepared in powder form and lithium hydroxide (LiOH) were mixed in a molar ratio of 1:1.01. A powder (NCO90) was prepared. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 3.

Comparative Example 6 (NCO90-B7)

_{Ni 0.9} Co _0.1 (OH) ₂ metal composite hydroxide prepared in powder form, boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.93:0.035:1.01, except for mixing the same as in Example 13. A cathode active material powder (NCO90-B7) doped with boron (B) in 7 mol% was prepared by the method. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 3.

division Cathode active material powder chemical formula Chemical composition analyzed by ICP-OES B doping [mol%] Ammonia Molar Ratio to Metal Firing temperature [℃] Comparative Example 5 Li _1.01 Ni _0.9 Co _0.10 O ₂ Ni _0.902 Co _0.098 0 1.7 730 Example 13 Li _1.01 B _0.0005 Ni _0.9 Co _0.10 O ₂ Ni _0.899 Co _0.1 B _0.0006 0.05 1.7 730 Example 14 Li _1.01 B _0.001 Ni _0.9 Co _0.10 O ₂ Ni _0.90 Co _0.1 B _0.001 0.1 1.7 730 Example 15 Li _1.01 B _0.005 Ni _0.9 Co _0.10 O ₂ Ni _0.90 Co _0.1 B _0.005 0.5 1.7 730 Example 16 Li _1.01 B _0.01 Ni _0.9 Co _0.10 O ₂ Ni _0.90 Co _0.1 B _0.01 One 1.7 730 Example 17 Li _1.01 B _0.015 Ni _0.9 Co _0.10 O ₂ Ni _0.90 Co _0.1 B _0.015 1.5 1.7 730 Example 18 Li _1.01 B _0.02 Ni _0.9 Co _0.10 O ₂ Ni _0.90 Co _0.1 B _0.02 2 1.7 730 Example 19 Li _1.01 B _0.03 Ni _0.9 Co _0.10 O ₂ Ni _0.90 Co _0.1 B _0.03 3 1.7 730 Example 20 Li _1.01 B _0.04 Ni _0.9 Co _0.10 O ₂ Ni _0.90 Co _0.1 B _0.04 4 1.7 730 Example 21 Li _1.01 B _0.05 Ni _0.9 Co _0.10 O ₂ Ni _0.90 Co _0.1 B _0.051 5 1.7 730 Comparative Example 6 Li _1.01 B _0.07 Ni _0.9 Co _0.10 O ₂ Ni _0.902 Co _0.998 B _0.073 7 1.7 730 Example 22 Li _1.01 B _0.005 Ni _0.895 Co _0.10 Mo _0.005 O ₂ Ni _0.894 Co _0.101 B _0.005 Mo _0.005 0.5 (+Mo 0.5) 1.7 730

(4) Preparation of NCA-based positive electrode active material

Example 23 (NCA88.5-B0.5)

After 10 liters of distilled water was put into the coprecipitation reactor (capacity 40L, output of the rotary motor 750W or more), N ₂ gas was supplied to the reactor at a rate of 6 liters/minute, and the temperature of the reactor was maintained at 45° C. and stirred at 350 rpm. . Nickel sulfate aqueous solution (NiSO ₄ 6H ₂ O, Samjeon Chemical) and cobalt sulfate aqueous solution (CoSO ₄ 7H ₂ O, Samjeon Chemical) are mixed in an amount such that the molar ratio of nickel (Ni) and cobalt (Co) is 9:1. A metal solution having a concentration of 2M was prepared. The prepared metal solution was 0.561 liter/hour, the ammonia solution (NH ₄ OH, JUNSEI) of 16M concentration was 0.08 liters/hour, and the sodium hydroxide solution (NaOH, Samjeon Chemical) of 4M concentration was 0.60 liters/hour, respectively. It was continuously introduced into the reactor for 24 hours. The co-precipitation reaction was performed while maintaining the pH in the reactor in the range of 10 to 12 to prepare Ni _0.9 Co _0.1 (OH) ₂ metal composite hydroxide.

The prepared Ni _0.9 Co _0.1 (OH) ₂ metal composite hydroxide was filtered, washed several times with distilled water, and dried in a vacuum dryer at 110° C. for 12 hours to prepare a powder. After preparing boron oxide (B ₂ O ₃ ) by pulverizing it using a ball mill to have an average particle size of 50 μm, Ni _0.9 Co _0.1 (OH) ₂ metal composite hydroxide, aluminum hydroxide (Al(OH) ₃ ), boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.98:0.015:0.0025:1.01, heated at a temperature increase rate of 2°C/min, and maintained at 450°C for 5 hours. Preliminary firing was performed, followed by firing at 730° C. for 10 hours to prepare a cathode active material powder (NCA88.5-B0.5) doped with boron (B) in 0.5 mol%. In the prepared cathode active material powder, the content of each element was checked using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 4 that the B doping amount of the doping element, in the process of preparing the metal complex hydroxide, Molar ratios and firing temperatures of metals (nickel (Ni) and cobalt (Co)) are shown.

Example 24 (NCA88.5-B1)

_{Ni 0.9} Co _0.1 (OH) ₂ metal composite hydroxide prepared in powder form, aluminum hydroxide (Al(OH) ₃ ), boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) 0.975:0.015:0.005:1.01 A cathode active material powder (NCA88.5-B1) doped with boron (B) 1 mol% was prepared in the same manner as in Example 23 except for mixing in a molar ratio of . The content of each element was confirmed in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 4.

Comparative Example 6 (NCA88.5)

_{Ni 0.9} Co _0.1 (OH) ₂ metal composite hydroxide prepared in powder form, aluminum hydroxide (Al(OH) ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.985:0.015:1.01, except that Example 23 and A cathode active material powder (NCA88.5) not doped with boron (B) was prepared in the same manner. The content of each element was confirmed in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 4.

Example 25 (NCA80-B1)

After 10 liters of distilled water was put into the coprecipitation reactor (capacity 40L, output of the rotary motor 750W or more), N ₂ gas was supplied to the reactor at a rate of 6 liters/minute, and the temperature of the reactor was maintained at 45° C. and stirred at 350 rpm. . Nickel sulfate aqueous solution (NiSO ₄ 6H ₂ O, Samjeon Chemical) and cobalt sulfate aqueous solution (CoSO ₄ 7H ₂ O, Samjeon Chemical) are mixed in an amount such that the molar ratio of nickel (Ni) and cobalt (Co) is 83:17. A metal solution having a concentration of 2M was prepared. The prepared metal solution was 0.561 liter/hour, the ammonia solution (NH ₄ OH, JUNSEI) of 16M concentration was 0.08 liters/hour, and the sodium hydroxide solution (NaOH, Samjeon Chemical) of 4M concentration was 0.60 liters/hour, respectively. It was continuously introduced into the reactor for 24 hours. The co-precipitation reaction was performed while maintaining the pH in the reactor in the range of 10 to 12 to prepare Ni _0.83 Co _0.17 (OH) ₂ metal composite hydroxide.

The prepared Ni _0.83 Co _0.17 (OH) ₂ metal complex hydroxide was filtered, washed several times with distilled water, and dried in a vacuum dryer at 110° C. for 12 hours to prepare a powder. After preparing boron oxide (B ₂ O ₃ ) by pulverizing it using a ball mill to have an average particle size of 50 μm, Ni _0.83 Co _0.17 (OH) ₂ metal composite hydroxide, aluminum hydroxide (Al(OH) ₃ ), boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.95:0.04:0.005:1.01, heated at a temperature increase rate of 2°C/min, and maintained at 450°C for 5 hours. Preliminary calcination was performed, followed by calcination at 750° C. for 10 hours to prepare a cathode active material powder (NCA80-B1) doped with boron (B) 1 mol%. In the prepared cathode active material powder, the content of each element was checked using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 4 that the B doping amount of the doping element, in the process of preparing the metal complex hydroxide, Molar ratios and firing temperatures of metals (nickel (Ni) and cobalt (Co)) are shown.

Comparative Example 8 (NCA80)

_{Ni 0.83} Co _0.17 (OH) ₂ metal composite hydroxide prepared in powder form, aluminum hydroxide (Al(OH) ₃ ), and lithium hydroxide (LiOH) in a molar ratio of 0.96:0.04:1.01 were mixed in Example 25 and A cathode active material powder (NCA88.5) not doped with boron (B) was prepared in the same manner. The content of each element was confirmed in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 4.

division Cathode active material powder chemical formula Chemical composition analyzed by ICP-OES B doping [mol%] Ammonia Molar Ratio to Metal Firing temperature [℃] Comparative Example 7 Li _1.01 Ni _0.885 Co _0.10 Al _0.015 O ₂ Ni _0.885 Co _0.1 Al _0.015 0 1.2 730 Example 23 Li _1.01 B _0.005 Ni _0.885 Co _0.10 Al _0.015 O ₂ Ni _0.883 Co _0.098 Al _0.015 B _0.004 0.5 1.2 730 Example 24 Li _1.01 B _0.01 Ni _0.885 Co _0.10 Al _0.015 O ₂ Ni _0.876 Co _0.099 Al _0.015 B _0.01 One 1.2 730 Comparative Example 8 Li _1.01 Ni _0.80 Co _0.16 Al _0.04 O ₂ Ni _0.795 Co _0.165 Al _0.04 0 1.2 750 Example 25 Li _1.01 B _0.01 Ni _0.80 Co _0.16 Al _0.04 O ₂ Ni _0.79 Co _0.157 Al _0.04 3B _0.01 One 1.2 750

(5) Preparation of NMO-based positive electrode active material

Example 26 (NMO90-B0.5)

After 10 liters of distilled water was put into the coprecipitation reactor (capacity 40L, output of the rotary motor 750W or more), N ₂ gas was supplied to the reactor at a rate of 6 liters/minute, and the temperature of the reactor was maintained at 45° C. and stirred at 350 rpm. . Nickel sulfate aqueous solution (NiSO ₄ 6H ₂ O, Samjeon Chemical) and manganese sulfate aqueous solution (MnSO ₄ H ₂ O, Samjeon Chemical) are mixed in an amount such that the molar ratio of nickel (Ni) and manganese (Mn) is 9:1. A metal solution having a concentration of 2M was prepared. The prepared metal solution was 0.561 liter/hour, the 16wt% concentration of ammonia solution (NH ₄ OH, JUNSEI) was 0.08 liters/hour, and the 4M sodium hydroxide solution (NaOH, Samjeon Chemical) was 0.60 liters/hour, respectively. It was continuously introduced into the reactor for 24 hours. The co-precipitation reaction was performed while maintaining the pH in the reactor in the range of 10 to 12 to prepare Ni _0.9 Mn _0.1 (OH) ₂ metal composite hydroxide.

The prepared Ni _0.9 Mn _0.1 (OH) ₂ metal composite hydroxide was filtered, washed several times with distilled water, and dried in a vacuum dryer at 110° C. for 12 hours to prepare a powder form. After preparing boron oxide (B ₂ O ₃ ) by pulverizing it using a ball mill to have an average particle size of 50 μm, Ni _0.9 Mn _0.1 (OH) ₂ metal composite hydroxide prepared in powder form, boron oxide (B ₂ O _{3 )} ), and lithium hydroxide (LiOH) in a molar ratio of 0.995:0.0025:1.01, heated at a temperature increase rate of 2°C/min, maintained at 450°C for 5 hours, followed by pre-calcination at 770°C for 10 hours By calcination, a cathode active material powder (NMO90-B0.5) doped with boron (B) in 0.5 mol% was prepared. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 5. Molar ratios and firing temperatures of metals (nickel (Ni) and manganese (Mn)) are shown.

Example 27 (NMO90-B1)

_{Ni 0.9} Mn _0.1 (OH) ₂ metal composite hydroxide prepared in powder form, boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.99:0.005:1.01, except for mixing the same as in Example 26. A cathode active material powder (NMO90-B1) doped with boron (B) in 1 mol% was prepared by this method. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 5.

Comparative Example 9 (NMO90)

An anode not doped with boron (B) in the same manner as in Example 26, except _{that Ni 0.9} Mn _0.1 (OH) ₂ metal composite hydroxide prepared in powder form, and lithium hydroxide (LiOH) were mixed in a molar ratio of 1:1.01. An active material powder (NMO90) was prepared. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 5.

division Cathode active material powder chemical formula Chemical composition analyzed by ICP-OES B doping [mol%] Ammonia Molar Ratio to Metal Firing temperature [℃] Comparative Example 9 Li _1.01 Ni _0.9 Mn _0.10 O ₂ Ni _0.90 Mn _0.1 0 1.2 770 Example 26 Li _1.01 B _0.005 Ni _0.9 Mn _0.10 O ₂ Ni _0.895 Mn _0.1 B _0.005 0.5 1.2 770 Example 27 Li _1.01 B _0.01 Ni _0.9 Mn _0.10 O ₂ Ni _0.895 Mn _0.095 B _0.01 1.0 1.2 770

(6) Preparation of concentration gradient type positive electrode active material

Example 28 (gradient NCM89-B1)

After 10 liters of distilled water was put into the coprecipitation reactor (capacity 40L, output of the rotary motor 750W or more), N ₂ gas was supplied to the reactor at a rate of 6 liters/minute, and the temperature of the reactor was maintained at 45° C. and stirred at 350 rpm. . Nickel sulfate aqueous solution (NiSO ₄ 6H ₂ O, Samjeon Chemical), cobalt sulfate aqueous solution (CoSO ₄ 7H ₂ O, Samjeon Chemical), and manganese sulfate aqueous solution (MnSO ₄ H ₂ O, Samjeon Chemical) were mixed with nickel (Ni), cobalt (Co ) and manganese (Mn) are mixed in an amount such that the molar ratio is 100:0:0, and the first metal solution having a 2M concentration is mixed in an amount such that the molar ratio is 80:16:04 to prepare a second metal solution having a 2M concentration did The prepared first metal solution was 0.561 liters/hour, 16M ammonia solution (NH ₄ OH, JUNSEI) was 0.08 liters/hour, and 4M sodium hydroxide solution (NaOH, Samjeon Chemical) was 0.60 liters/hour Each reactor was continuously introduced for 14 hours to form a first concentration maintaining part. Thereafter, the second metal solution was added to the first metal solution tank at 0.561 liters/hour, continuously changing the concentration of the metal solution fed into the reactor for 10 hours while constantly changing the second concentration outside the first concentration maintaining unit. A gradient was formed. Thereafter, after stopping the input of the second metal solution into the first metal solution, only the first metal solution with a changed concentration was introduced into the reactor at 0.561 liters/hour to form a third concentration maintaining part outside the second concentration gradient part . The coprecipitation reaction was performed while maintaining the pH in the reactor in the range of 10 to 12 to prepare a concentration gradient-type metal composite hydroxide having _{an average composition of Ni 0.90} Co _0.08 Mn _0.02 (OH) _{2 .}

The prepared Ni _0.90 Co _0.08 Mn _0.02 (OH) ₂ concentration gradient type metal complex hydroxide was filtered, washed several times with distilled water, and dried in a vacuum dryer at 110° C. for 12 hours to prepare a powder. After preparing boron oxide (B ₂ O ₃ ) by pulverizing it using a ball mill to have an average particle size of 50 μm, Ni _0.90 Co _0.08 Mn _0.02 (OH) ₂ metal composite hydroxide, boron oxide (B _{2 ) prepared in powder form} O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.99:0.005:1.01, heated at a temperature increase rate of 2°C/min, and maintained at 450°C for 5 hours to perform preliminary firing, followed by pre-calcination at 820°C After calcination for 10 hours, a cathode active material powder (gradient NCM89-B1) doped with 1 mol% boron (B) was prepared. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and the B doping amount of the doping element, the amount of B doping of the doping element, in the process of preparing the metal composite hydroxide, Molar ratios and firing temperatures of metals (nickel (Ni), cobalt (Co) and manganese (Mn)) are shown.

Comparative Example 10 (NCM90)

After 10 liters of distilled water was put into the coprecipitation reactor (capacity 40L, output of the rotary motor 750W or more), N ₂ gas was supplied to the reactor at a rate of 6 liters/minute, and the temperature of the reactor was maintained at 45° C. and stirred at 350 rpm. . Nickel sulfate aqueous solution (NiSO ₄ 6H ₂ O, Samjeon Chemical), cobalt sulfate aqueous solution (CoSO ₄ 7H ₂ O, Samjeon Chemical), and manganese sulfate aqueous solution (MnSO ₄ H ₂ O, Samjeon Chemical) were mixed with nickel (Ni), cobalt (Co ) and manganese (Mn) were mixed in an amount such that the molar ratio was 90:8:2 to prepare a metal solution having a concentration of 2M. The prepared metal solution was 0.561 liters/hour, 16M% ammonia solution (NH ₄ OH, JUNSEI) was 0.08 liters/hour, and 4M sodium hydroxide solution (NaOH, Samchun Chemical) was 0.60 liters/hour, respectively. It was continuously introduced into the reactor for 24 hours. The co-precipitation reaction was performed while maintaining the pH in the reactor in the range of 10 to 12 to prepare Ni _0.90 Co _0.08 Mn _0.02 (OH) ₂ metal composite hydroxide.

_{In the same manner as in Example 28, except that Ni 0.90} Co _0.08 Mn _0.02 (OH) ₂ metal composite hydroxide prepared in powder form, and lithium hydroxide (LiOH) were mixed in a molar ratio of 1:1.01, boron (B) was not doped. A positive electrode active material powder (NCM90) was prepared. The content of each element was confirmed in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 6.

Example 29 (gradient NCA88.5-B1)

After 10 liters of distilled water was put into the coprecipitation reactor (capacity 40L, output of the rotary motor 750W or more), N ₂ gas was supplied to the reactor at a rate of 6 liters/minute, and the temperature of the reactor was maintained at 45° C. and stirred at 350 rpm. . Nickel sulfate aqueous solution (NiSO ₄ 6H ₂ O, Samjeon Chemical) and cobalt sulfate aqueous solution (CoSO ₄ 7H ₂ O, Samjeon Chemical) are mixed in an amount such that the molar ratio of nickel (Ni) and cobalt (Co) is 100:0. A second metal solution having a concentration of 2M was prepared by mixing the first metal solution having a concentration of 2M and an amount to be 80:20. The prepared first metal solution was 0.561 liters/hour, 16M ammonia solution (NH ₄ OH, JUNSEI) was 0.08 liters/hour, and 4M sodium hydroxide solution (NaOH, Samjeon Chemical) was 0.60 liters/hour Each reactor was continuously introduced for 14 hours to form a first concentration maintaining part. Thereafter, the second metal solution was added to the first metal solution tank at 0.561 liters/hour, continuously changing the concentration of the metal solution fed into the reactor for 10 hours while constantly changing the second concentration outside the first concentration maintaining unit. A gradient was formed. Thereafter, after stopping the input of the second metal solution into the first metal solution, only the first metal solution with a changed concentration was introduced into the reactor at 0.561 liters/hour to form a third concentration maintenance part outside the second concentration gradient part . The co-precipitation reaction was performed while maintaining the pH in the reactor in the range of 10 to 12 to prepare a concentration gradient-type metal composite hydroxide having _{an average composition of Ni 0.90} Co _0.10 (OH) _{2 .}

The prepared Ni _0.90 Co _0.1 (OH) ₂ concentration gradient-type metal complex hydroxide was filtered, washed several times using distilled water, and dried in a vacuum dryer at 110° C. for 12 hours to prepare a powder. After preparing boron oxide (B ₂ O ₃ ) by pulverizing it using a ball mill to have an average particle size of 50 μm, Ni _0.90 Co _0.1 (OH) ₂ Metal composite hydroxide, aluminum hydroxide (Al(OH) ₃ ), boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.975:0.015:0.005:1.01, heated at a temperature increase rate of 2°C/min, and maintained at 450°C for 5 hours to prepare The calcination was performed, followed by calcination at 700° C. for 10 hours to prepare a cathode active material powder (gradient NCA88.5-B1) doped with boron (B) by 1 mol%. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and the B doping amount of the doping element, the amount of B doping of the doping element, in the process of preparing the metal composite hydroxide, Molar ratios and firing temperatures of metals (nickel (Ni) and cobalt (Co)) are shown.

Comparative Example 11 (NCA88.5)

After 10 liters of distilled water was put into the coprecipitation reactor (capacity 40L, output of the rotary motor 750W or more), N ₂ gas was supplied to the reactor at a rate of 6 liters/minute, and the temperature of the reactor was maintained at 45° C. and stirred at 350 rpm. . Nickel sulfate aqueous solution (NiSO ₄ 6H ₂ O, Samjeon Chemical) and cobalt sulfate aqueous solution (CoSO ₄ 7H ₂ O, Samjeon Chemical) are mixed in an amount such that the molar ratio of nickel (Ni) and cobalt (Co) is 90:10 Thus, a metal solution having a concentration of 2M was prepared. The prepared metal solution was 0.561 liters/hour, 16M% ammonia solution (NH ₄ OH, JUNSEI) was 0.08 liters/hour, and 4M sodium hydroxide solution (NaOH, Samchun Chemical) was 0.60 liters/hour, respectively. It was continuously introduced into the reactor for 24 hours. The coprecipitation reaction was performed while maintaining the pH in the reactor in the range of 10 to 12 to prepare Ni _0.90 Co _0.10 (OH) ₂ metal composite hydroxide.

_{Ni 0.90} Co _0.1 (OH) ₂ concentration gradient metal composite hydroxide prepared in powder form, aluminum hydroxide (Al(OH ₃ )), and lithium hydroxide (LiOH) were mixed in a molar ratio of 0.985:0.015:1.01 except for mixing A cathode active material powder (NCA88.5) not doped with boron (B) was prepared in the same manner as in Example 29. The content of each element was confirmed in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 6.

Comparative Example 12 (gradient NCA88.5)

_{Ni 0.90} Co _0.1 (OH) ₂ concentration gradient type prepared in powder form Metal complex hydroxide, aluminum hydroxide (Al (OH _3), and lithium hydroxide (LiOH) 0.985: boron in the same manner as in Example 29 as mixture in a molar ratio of 1.01, to the sintering temperature to 730 ℃ other than (0.015 B) was prepared undoped cathode active material powder (gradient NCM89) The content of each element was checked for the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 6.

division Cathode active material powder chemical formula Chemical composition analyzed by ICP-OES B doping [mol%] Ammonia Molar Ratio to Metal Firing temperature [℃] Comparative Example 10 Li _1.01 Ni _0.90 Co _0.08 Mn _0.02 O ₂ Ni _0.90 Co _0.08 Mn _0.02 0 1.2 720 Example 28 Li _1.01 B _0.01 Ni _0.90 Co _0.08 Mn _0.02 O ₂ Ni _0.891 Co _0.079 Mn _0.021 B _0.09 1.0 1.2 720 Comparative Example 11 Li _1.01 Ni _0.885 Co _0.10 Al _0.015 O ₂ Ni _0.885 Co _0.10 Al _0.015 0 1.2 730 Comparative Example 12 Li _1.01 Ni _0.885 Co _0.10 Al _0.015 O ₂ Ni _0.885 Co _0.10 Al _0.015 0 1.2 700 Example 29 Li _1.01 B _0.01 Ni _0.885 Co _0.10 Al _0.015 O ₂ Ni _0.876 Co _0.10 Al _0.014 B _0.01 1.0 1.2 700

(7) Preparation of co-doping type positive electrode active material

Example 30 (NCO96-B0.5, Ta0.5)

After 10 liters of distilled water was put into the coprecipitation reactor (capacity 40L, output of the rotary motor 750W or more), N ₂ gas was supplied to the reactor at a rate of 6 liters/minute, and the temperature of the reactor was maintained at 45° C. and stirred at 350 rpm. . Nickel sulfate aqueous solution (NiSO ₄ 6H ₂ O, Samjeon Chemical) and cobalt sulfate aqueous solution (CoSO ₄ 7H ₂ O, Samjeon Chemical) are mixed in an amount such that the molar ratio of nickel (Ni) and cobalt (Co) is 96:4. A metal solution of 2M concentration was prepared. The prepared 2M metal solution was 0.561 liters/hour, the 16M ammonia solution (NH ₄ OH, JUNSEI) was 0.11 liters/hour, and the 4M sodium hydroxide solution (NaOH, Samjeon Chemical) was 0.60 liters/hour. Each time was continuously added to the reactor for 24 hours. The co-precipitation reaction was performed while maintaining the pH in the reactor in the range of 10 to 12 to prepare Ni _0.96 Co _0.04 (OH) ₂ metal composite hydroxide.

The prepared Ni _0.96 Co _0.04 (OH) ₂ metal composite hydroxide was filtered, washed several times using distilled water, and dried in a vacuum dryer at 110° C. for 12 hours to prepare a powder. _{Ni 0.96} Co _0.04 (OH) ₂ metal composite hydroxide prepared in powder form, tantalum pentoxide (Ta ₂ O ₅ ), boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) 0.99:0.0025:0.0025:1.01 After mixing at a molar ratio of A cathode active material powder (NCO96-B0.5, Ta0.5) doped by 0.5 mol%, respectively, was prepared. The content of each element was checked in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and the doping amount of the doping element, the doping amount of the doping element, and the metal to ammonia in the process of preparing the metal complex hydroxide Molar ratios of (nickel (Ni) and cobalt (Co)) and sintering temperature are shown.

Example 31 (NCO96-B0.5,Mo0.5)

_{Ni 0.96} Co _0.04 (OH) ₂ metal composite hydroxide prepared in powder form, molybdenum trioxide (MoO3), boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) in a molar ratio of 0.99:0.005:0.0025:1.01 A cathode active material powder (NCO96-B0.5, Mo0.5) doped with molybdenum (Mo) and boron (B) by 0.5 mol%, respectively, was prepared in the same manner as in Example 30 except for mixing. The content of each element was confirmed in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 7.

Example 32 (NCO96-B0.5,Nb0.5)

_{Ni 0.96} Co _0.04 (OH) ₂ metal composite hydroxide prepared in powder form, niobium pentoxide (Nb ₂ O ₅ ), boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) in 0.99:0.0025:0.0025:1.01 A cathode active material powder (NCO96-B0.5, Nb0.5) doped with niobium (Nb) and boron (B) by 0.5 mol% each was prepared in the same manner as in Example 30 except for mixing in a molar ratio. The content of each element was confirmed in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 7.

Example 33 (NCO96-B0.5, Sb0.5)

_{Ni 0.96} Co _0.04 (OH) ₂ metal composite hydroxide prepared in powder form, antimony trioxide (Sb ₂ O ₃ ), boron oxide (B ₂ O ₃ ), and lithium hydroxide (LiOH) 0.99:0.0025:0.0025:1.01 A cathode active material powder (NCO96-B0.5, Ta0.5) doped with antimony (Sb) and boron (B) by 0.5 mol% each was prepared in the same manner as in Example 30 except for mixing in a molar ratio of . The content of each element was confirmed in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 7.

Comparative Example 13 (NCO96)

A cathode active material powder (NCO96) was prepared in the same manner as in Example 31, except _{that Ni 0.96} Co _0.04 (OH) ₂ metal composite hydroxide prepared in powder form, and lithium hydroxide (LiOH) were mixed in a molar ratio of 1:1.01. . The content of each element was confirmed in the prepared cathode active material powder using ICP-OES (OPTIMA 8300, Perkin Elmer), and it is shown in Table 7.

2. Preparation of half-cell and full-cell using Examples and Comparative Examples

Half-cells and full-cells were prepared using Examples 1 to 33 and Comparative Examples 1 to 13, respectively.

In order to prepare a half cell and a full cell, the positive electrode active material in powder form prepared according to Examples 1 to 33 and Comparative Examples 1 to 13 (based on 1 g), poly(vinylidene fluoride) (poly(vinylidene fluoride) )) and carbon black were added in 0.4 g of N -methyl pyrrolidone in a weight ratio of 90:4.5:5.5, respectively, and then uniformly mixed to prepare a positive electrode slurry. The prepared positive electrode slurry was coated on aluminum foil and vacuum dried after roll pressing to prepare a positive electrode.

In the case of manufacturing a half cell using the prepared positive electrode active material, the positive electrode is prepared by coating the prepared positive electrode as a slurry on aluminum foil so that the loading level of the positive electrode active material is 5 mg/cm2 (a positive electrode active material coated aluminum foil) (meaning that the weight of only the positive active material in the positive electrode composition is 5 mg) when sampled in a square of 1 cm2, and the electrolyte is ethylene carbonate, ethyl methyl carbonate (EC:EMC) = 3:7 v/v) as a solvent, and as an additive, 2 wt% of vinylene carbonate (VC) and 1.2 mol/L LiPF ₆ of lithium salt were uniformly dissolved and used. The half-cell was prepared as a 2032-coin-type half-cell (hereinafter, coin cell) using _{Li o as an anode.}

In the case of manufacturing a full cell using the prepared positive electrode active material, the positive electrode prepared as a slurry is coated on aluminum foil so that the loading level of the positive electrode active material is 8.5 mg/cm2 to prepare the positive electrode, and the graphite prepared as the slurry is applied to the copper foil. The coating was made so that the loading level was 6.5 mg/cm 2 , followed by roll pressing and vacuum drying to prepare a negative electrode. The electrolyte is ethylene carbonate, ethyl methyl carbonate (EC:EMC = 3:7 v/v) as a solvent, and vinylene carbonate (VC) as an additive 2-wt% and lithium salt 1.2 mol/L LiPF ₆ were uniformly dissolved and used. In a pouch-type battery case, a positive electrode, a separator (Celgard, model 2320) and a negative electrode were stacked and sealed together with the prepared electrolyte to prepare a pouch-type full cell.

3. Evaluation of Examples, Comparative Examples and Preparation Examples

(1) Confirmation of capacity and cycle characteristics using half cell

The manufactured half-cell was charged at 4.3V and discharged at 2.7V with a constant current of 0.5C (100mA/g) at 30°C, and 100 cycles were performed under the same conditions as the charge/discharge test to confirm the recovery capacity (hereinafter, 2.7V). -4.3V), which is shown in Table 7 below.

division Type of cathode active material Cathode active material powder chemical formula doping element doping [mol%] Refined
Structure 0.1C discharge capacity
[mAh g-1] Initial Coulombic Efficiency
[%] 0.5 C discharge capacity
[mAh g-1] 0.5C discharge capacity after 100 cycles Capacity retention after 100 cycles [%] Comparative Example 1 NCM system Li _1.01 Ni _0.65 Co _0.13 Mn _0.22 O ₂ B 0 X 198.6 95.2 188.8 180.9 95.8 Example 1 NCM system Li _1.01 B _0.01 Ni _0.65 Co _0.13 Mn _0.22 O ₂ B 1.0 O 200.7 95.5 190.8 185.8 97.4 Example 2 NCM system Li _1.01 B _0.01 Ni _0.65 Co _0.13 Mn _0.22 O ₂ B 1.0 X 183.2 93.5 173.4 156.1 90 Comparative Example 2 NCM system Li _1.01 Ni _0.90 Co _0.05 Mn _0.05 O ₂ B 0 X 229.3 95.6 215.2 179.5 83.4 Example 3 NCM system Li _1.01 B _0.004 Ni _0.90 Co _0.05 Mn _0.05 O ₂ B 0.4 O 232.6 94.6 214.9 191.7 89.2 Example 4 NCM system Li _1.01 B _0.01 Ni _0.90 Co _0.05 Mn _0.05 O ₂ B 1.0 O 230.7 94 209.4 191.4 91.4 Example 5 NCM system Li _1.01 B _0.01 Ni _0.90 Co _0.05 Mn _0.05 O ₂ B 1.0 O 229.3 95.6 215.2 190.5 88.5 Example 6 NCM system Li _1.01 B _0.01 Ni _0.90 Co _0.05 Mn _0.05 O ₂ B 1.0 O 225.4 95 208.9 188.4 90.2 Example 7 NCM system Li _1.01 B _0.01 Ni _0.90 Co _0.05 Mn _0.05 O ₂ B 1.0 X 214.1 93.7 186.5 159.8 85.7 Comparative Example 3 NCM system Li _1.01 Ni _0.92 Co _0.04 Mn _0.04 O ₂ B 0 X 233.7 94.9 217.4 186.7 85.9 Example 8 NCM system Li _1.01 B _0.01 Ni _0.92 Co _0.04 Mn _0.04 O ₂ B 1.0 O 237.4 95.5 218.9 199.0 90.9 Comparative Example 4 LNO system Li _1.01 NiO ₂ B 0 X 250.0 95.8 231.7 166.8 72.0 Example 9 LNO system Li _1.01 B _0.01 NiO ₂ B 1.0 O 247.3 97 235.5 184.6 78.4 Example 10 LNO system Li _1.01 B _0.01 NiO ₂ B 1.0 O 248.2 96.8 230.2 179.1 77.8 Example 11 LNO system Li _1.01 B _0.01 NiO ₂ B 1.0 X 247.5 96.5 231.5 169.0 73 Example 12 LNO system Li _1.01 B _0.01 NiO ₂ B 1.0 X 244.7 96.4 228.4 141.8 62.1 Comparative Example 5 NCO system Li _1.01 Ni _0.9 Co _0.10 O ₂ B 0 X 225.3 95.1 209.8 141.0 67.2 Example 13 NCO system Li _1.01 B _0.0005 Ni _0.9 Co _0.10 O ₂ B 0.05 X 224.8 94.1 209.5 161.9 77.3 Example 14 NCO system Li _1.01 B _0.001 Ni _0.9 Co _0.10 O ₂ B 0.1 O 224.3 93.5 208 169.1 81.3 Example 15 NCO system Li _1.01 B _0.005 Ni _0.9 Co _0.10 O ₂ B 0.5 O 234.2 96.1 218.2 181.8 83.3 Example 16 NCO system Li _1.01 B _0.01 Ni _0.9 Co _0.10 O ₂ B One O 236.2 96.7 222.8 198.1 88.9 Example 17 NCO system Li _1.01 B _0.015 Ni _0.9 Co _0.10 O ₂ B 1.5 O 232.7 95.6 221.7 202.2 91.2 Example 18 NCO system Li _1.01 B _0.02 Ni _0.9 Co _0.10 O ₂ B 2 O 232.3 96.4 220 201.5 91.6 Example 19 NCO system Li _1.01 B _0.03 Ni _0.9 Co _0.10 O ₂ B 3 O 226.7 94.2 216.1 197.3 91.3 Example 20 NCO system Li _1.01 B _0.04 Ni _0.9 Co _0.10 O ₂ B 4 O 229.1 95.6 213.2 184.6 86.6 Example 21 NCO system Li _1.01 B _0.05 Ni _0.9 Co _0.10 O ₂ B 5 O 218.8 94.5 198.2 170.3 85.9 Comparative Example 6 NCO system Li _1.01 B _0.07 Ni _0.9 Co _0.10 O ₂ B 7 O 186.7 91.2 165.7 142.2 85.8 Example 22 NCO system Li _1.01 B _0.005 Ni _0.895 Co _0.10 Mo _0.005 O ₂ B/Mo 0.5/0.5 O 232.2 94.9 217.2 205.7 94.7 Comparative Example 7 NCA system Li _1.01 Ni _0.885 Co _0.10 Al _0.015 O ₂ B 0 X 225.1 95.1 210.6 176.3 83.7 Example 23 NCA system Li _1.01 B _0.005 Ni _0.885 Co _0.10 Al _0.015 O ₂ B 0.5 O 224 94.2 208 191.8 92.2 Example 24 NCA system Li _1.01 B _0.01 Ni _0.885 Co _0.10 Al _0.015 O ₂ B One O 229.8 95.2 207.6 199.7 96.2 Comparative Example 8 NCA system Li _1.01 Ni _0.80 Co _0.16 Al _0.04 O ₂ B 0 X 203.2 93.2 190.7 174.3 91.4 Example 25 NCA system Li _1.01 B _0.01 Ni _0.80 Co _0.16 Al _0.04 O ₂ B One O 204.3 94.8 191.6 177.2 92.5 Comparative Example 9 NMO system Li _1.01 Ni _0.9 Mn _0.10 O ₂ B 0 O 226.6 93.9 212.4 185.6 87.4 Example 26 NMO system Li _1.01 B _0.005 Ni _0.9 Mn _0.10 O ₂ B 0.5 O 228.5 96.1 207.7 191.3 92.1 Example 27 NMO system Li _1.01 B _0.01 Ni _0.9 Mn _0.10 O ₂ B 1.0 O 228.4 96 207.2 192.9 93.1 Comparative Example 10 gradient NCM system Li _1.01 Ni _0.90 Co _0.08 Mn _0.02 O ₂ B 0 X 233.6 96.7 22.7 20.7 91.3 Example 28 NCM system Li _1.01 B _0.01 Ni _0.90 Co _0.08 Mn _0.02 O ₂ B 1.0 O 232.8 96.1 219.9 208.5 94.8 Comparative Example 11 gradient NCA system Li _1.01 Ni _0.885 Co _0.10 Al _0.015 O ₂ B 0 X 222.4 94.5 206.1 191.1 92.7 Comparative Example 12 NCM system Li _1.01 Ni _0.885 Co _0.10 Al _0.015 O ₂ B 0 X 221.3 94.3 209.4 190.8 91.1 Example 29 gradient NCM system Li _1.01 B _0.01 Ni _0.885 Co _0.10 Al _0.015 O ₂ B 1.0 O 228.1 96.1 216.9 204.3 94.2 Comparative Example 13 NCO system Li _1.01 Ni _0.96 Co _0.04 O ₂ B 0 X 237.2 95.1 216.0 169.3 78.4 Example 30 NCO system Li _1.01 B _0.005 Ta _0.005 Ni _0.95 Co _0.10 O ₂ B/Ta 0.5/0.5 O 239.4 94.4 216.2 193.3 89.4 Example 31 NCO system Li _1.01 B _0.005 Nb _0.005 Ni _0.95 Co _0.10 O ₂ B/Nb 0.5/0.5 O 242.8 95.5 230.5 201.0 87.2 Example 32 NCO system Li _1.01 B _0.005 Mo _0.005 Ni _0.95 Co _0.10 O ₂ B/Mo 0.5/0.5 O 242.2 94.9 224.8 199.4 88.7 Example 33 NCO system Li _1.01 B _0.005 Sb _0.005 Ni _0.95 Co _0.10 O ₂ B/Sb 0.5/0.5 O 239.4 95.1 219.4 201.0 91.6

(2) Confirmation of microstructure of precursor and positive electrode active material using SEM

In the following, the microstructure of the positive electrode active material according to Examples and Comparative Examples and the metal composite hydroxide (precursor) before the preliminary firing of the positive electrode active material was confirmed by SEM (Nova Nano SEM 450, FEI).

3 is an SEM image of the metal composite hydroxide according to Examples 1 and 2, and FIG. 4 is an SEM image of the cathode active material according to Examples 1 and 2.

3 and 4, when comparing (a) Example 1 and (b) Example 2 with an NCM-based cathode active material having an Ni content of about 65 mol%, the same content of metals (nickel, cobalt, manganese) When used, when the molar ratio of ammonia to metal increased from 1.2 to 3.2, it was confirmed that the shape of the primary particles in the metal composite hydroxide before preliminary firing was different from each other.

3, in the case of the metal complex hydroxide, in Example 1, the primary particles are separated from each other and provided in the form of thin flakes, whereas in Example 2, it is confirmed that a plurality of primary particles are bonded to each other and formed in an aggregated form. could 4, the positive electrode active material calcined at a high temperature together with lithium hydroxide while doping with boron (B) in Examples 1 and 2 was obtained by doping with boron (B) in both Examples 1 and 2 It was confirmed that the primary particles were provided to have an approximate angle to the corner side in the view from the top of the primary particles. In addition, in Example 1, the primary particles exist separated from each other, but in Example 2, it was confirmed that the aggregated form of the primary particles observed in the metal composite hydroxide was also observed in the cathode active material after firing.

In Table 7, when it is confirmed that the 0.1C discharge capacity of Examples 1 and 2 is 200.7 mAh/g and 183.2 mAh/g, and the capacity retention after 100 cycles is 97.4% and 90%, the primary particles are agglomerated In the case of Example 2, which is present in the form of It was confirmed that the capacity retention rate was low.

5 is an SEM image of the metal composite hydroxide according to Examples 4 to 7, and FIG. 6 is an SEM image of the cathode active material according to Examples 4 and 7.

In FIG. 5, the metal composite hydroxides according to (a) Example 4, (b) Example 5, (c) Example 6 and (d) Example 7 were prepared as an NCM-based positive electrode active material having a Ni content of approximately 90 mol%. In comparison, as the molar ratio of ammonia to metal (A/M) increased from 1.2 to 4, it was confirmed that the size of the primary particles in the metal composite hydroxide was relatively increased in an aggregated form.

Referring to FIG. 6 , when (a) Example 4 and (b) Example 7 were compared, it was confirmed that the trend shown in the metal composite hydroxide was reflected as it is even after doping with 1 mol% of boron (B) and firing. Referring to Table 7, each 0.1C discharge capacity of Examples 4, 5, 6 and 7 was 230.7 mAh/g, 229.3 mAh/g, 225.4 mAh/g, and 214.1 mAh/g, and It was confirmed that the capacity retention rates after 100 cycles were 91.4%, 88.5%, 90.2%, and 85.7%. In the case of an NCM-based positive electrode active material of 90 mol%, the 0.1C discharge capacity is slightly reduced only when the ammonia molar ratio to the metal is 4, and the capacity retention rate is slightly reduced after 100 cycles, and the ammonia molar ratio to the metal is less than 4, such as 2.2 or less was found to be almost similar.

When the metal composite hydroxide is prepared from the NCM-based positive electrode active material, Comparative Examples 1 and 1 containing 65 mol% of nickel (Ni) and Comparative Examples 2 and 4 containing 90 mol% of nickel (Ni) In comparison, it was confirmed that Comparative Examples 2 and 4 having a high nickel content had relatively high discharge capacity, which are summarized in Table 8 below. On the other hand, it was confirmed that Comparative Example 1 and Example 1 were higher in the capacity retention rate of 100 cycles. That is, it was confirmed that when the content of nickel (Ni) in the NCM-based positive electrode active material was increased, the discharge capacity was increased but the cycle characteristics were decreased.

Comparing Comparative Examples 1 and 1, and comparing Comparative Examples 2 and 4, respectively, it can be seen that boron (B) is doped by 1 mlo%, so that the 100-cycle capacity retention rate is improved even though there is no significant difference in the discharge capacity. It was also confirmed that even when the content of nickel was 90 mol%, it appeared more significantly. In Examples 1 and 4, the primary particles were clearly identified with the refined structure shown in the cathode active material after firing, and in Comparative Examples 1 and 2, irregular lumps appeared only as aggregated spherical particles. , it was not possible to clearly identify straight particles having the same microstructure as those observed in Examples 1 and 4.

That is, the cycle characteristics of the NCM-based positive electrode active material containing nickel (Ni) are improved by doping with boron (B), and it was confirmed that the effect increases as the content of nickel (Ni) increases. In addition, it is determined that the microstructure of the positive electrode active material is improved by doping with boron (B).

division Type of cathode active material doping element doping [mol%] Refined
Structure Initial discharge capacity
[mAh g-1] Initial Coulombic Efficiency
[%] 0.5 C discharge capacity
[mAh g-1] Capacity retention after 100 cycles [%] Comparative Example 1 NCM system B 0 X 198.6 95.2 188.8 95.8 Example 1 NCM system B 1.0 O 200.7 95.5 190.8 97.4 Comparative Example 2 NCM system B 0 X 229.3 95.6 215.2 83.4 Example 4 NCM system B 1.0 O 230.7 94 209.4 91.4

7 is an SEM image of the metal composite hydroxide according to Examples 9 to 12, and FIG. 8 is an SEM image of the positive electrode active material according to Examples 9 and 12.

Referring to FIG. 7 , when the metal composite hydroxide is made of 100 mol% of Ni, the molar ratio of ammonia to metal is increased ((a) Example 9, (b) Example 10, (c) Example 11, (d) Example Example 12), it was confirmed that the primary particles agglomerate and shorten with each other. On the other hand, as shown in FIG. 8, (a) Example 9 maintains the thickness of the primary particles thin even after firing, but (b) Example 12 is formed in a form in which the primary particles are melted and a plurality of primary particles are combined, and inside It was confirmed that microcracks were formed.

Referring to Table 7, 0.1C discharge capacities of Examples 9 to 12 were similarly shown as 247.3 mAh/g, 248.2 mAh/g, 247.5 mAh/g, and 244.7 mAh/g, respectively, but 100-cycle capacity retention rate It was confirmed that Example 12, in which the ammonia-to-metal molar ratio was 4, was relatively inferior.

That is, as the ammonia content of the metal in the LNO-based positive electrode active material increases, the primary particles of the metal composite hydroxide tend to agglomerate with each other. It was confirmed that the thickness of the particles increased and the capacity retention rate characteristics decreased after 100 cycles. In the case of Example 12, microcracks were generated in the center of the secondary particles during the firing process, and it was determined that cycle characteristics were deteriorated thereby.

9 is a SEM image of measuring the thickness of the primary particles located on the surface of the secondary particles according to the boron (B) doping amount in the NCO-based positive electrode active material using a metal composite hydroxide containing 90 mol% Ni. FIG. 10 is an SEM image of the positive electrode active material not doped with boron (B) in FIG. 9, FIG. 11 is an SEM image of the positive electrode active material doped with boron (B) 0.5 mol% in FIG. 9, and FIG. boron (B) is an SEM image of the positive electrode active material doped with 1 mol%, FIG. 13 is a SEM image of the positive electrode active material doped with 1.5 mol% boron (B) in FIG. 9, and FIG. 14 is boron (B) in FIG. This is an SEM image of the positive electrode active material doped with 2 mol%.

In Table 9 below, the thickness (third length) of the primary particles located on the surface of the secondary particles according to the boron (B) doping amount in the NCO-based positive electrode active material using a metal composite hydroxide containing 90 mol% Ni as shown in FIG. The measured value ((003) plane Avg. Width [nm]), the value calculated by applying Scherrer's equation using (003) reflection based on the XRD data, the presence or absence of a refined structure, and I(003) ) / I(104) ratio is shown.

division Type of cathode active material B doping [mol%] Firing temperature [℃] (003) plane
Avg. Width
[nm] (003) plane
Crystallite size
[nm] Refined
Structure I(003) / I(104) ratio Comparative Example 5 NCO system 0.0 730 351 294 X 2.19 Example 13 NCO system 0.05 730 288 221.4 X 2.15 Example 15 NCO system 0.5 730 147 198 O 2.01 Example 16 NCO system One 730 59.8 138 O 1.99 Example 17 NCO system 1.5 730 41.9 115.0 O 1.85 Example 18 NCO system 2.0 730 29.8 103.6 O 1.8 Comparative Example 7 NCA system 0.0 730 374 271.0 O 2.33

Referring to FIGS. 9 to 14 together with Table 9, it was confirmed that as the doping of boron (B) increased, in the NCO-based positive electrode active material using a metal composite hydroxide containing 90 mol% of Ni, it was confirmed that the doping gradually decreased. In Table 9, the third length, which is the interval between a pair of (003) planes and (003) planes of the primary particles provided on the outermost surface of the primary particles constituting the secondary particles, is measured and the value ((003) plane Avg. Width [nm]) was shown.

15a shows the third length of the primary particles (003) and ( 003) is a graph showing the results of measuring the spacing between the planes, and Table 10 is a table showing the average, deviation, maximum, and minimum values of the values of FIG. 15A. 15B is a graph of the length of the (003) plane according to boron (B) doping. In the following, the unit of the length of the primary particles of the positive electrode active material is all nm.

division Type of cathode active material B doping [mol%] medium maximum minimum Standard Deviation Comparative Example 5 NCO system B 0 mol% 351.3 551.5 194.0 98.1 Example 13 NCO system B 0.05 mol% 288.1 403.2 129.6 59.4 Example 15 NCO system B 0.5 mol% 145.8 246.0 35.3 39.2 Example 16 NCO system B 1 mol% 55.5 111.1 23.7 18.2 Example 17 NCO system B 1.5 mol% 40.6 91.3 17.4 14.0 Example 18 NCO system B 2 mol% 30.0 63.6 3.5 9.7 Comparative Example 7 NCA system B 0 mol% 383.6 569.6 231.3 90.9

Referring to FIG. 15A together with Table 10, as the doping content of boron (B) in the NCO-based positive electrode active material using a metal composite hydroxide containing 90 mol% of Ni increases, the average value of the third length decreases and at the same time the third length It was confirmed that the standard deviation of That is, it was confirmed that the third length of the primary particles positioned on the surface of the secondary particles among the primary particles was gradually decreased by the doping of boron (B), and was provided with a thickness within a controlled range at the same time. That is, it was confirmed that the doping of boron (B) can control the third length within a predetermined range while reducing the third length.

Referring to Table 10, it was confirmed that the NCA-based Comparative Example 7 not doped with boron (B) showed similar average and standard deviation to the NCO-based Comparative Example 5. That is, it was confirmed that the average value and standard deviation of the third length of the primary particles positioned on the surface of the secondary particles among the primary particles were controlled by the content of doped boron (B), regardless of the type of the positive electrode active material.

In addition, in Table 10, the crystal size of the (003) plane ((003) plane Crystallite size [nm]) was described, which is based on the XRD data and Scherrer's equation using (003) reflection It is a calculated value by applying In FIG. 15b, the value measured using the SEM image ((003) plane Avg. Width [nm]) and the value calculated using the Scherrer equation ((003) plane Crystallite size [nm]) are compared and shown as a graph it was

Table 11 below shows the first length (f1), which is the long axis of the (003) plane of the primary particles provided on the surface of the secondary particles among the primary particles, using the SEM image, and the primary particles in the direction perpendicular to the first length (f1) The results of measuring the second length (f2), which is the short axis of the (003) plane, and the third length (f3), which is the interval between the (003) plane and the (003) plane are shown, and in Table 12, the first length (f1) ), the ratio of the first length f1 to the third length f3 using the average values of each of the second length f2 and the third length f, and the second length f3 The ratio of the length (f2) is shown. 16A is a graph showing a first length, a second length, and a third length according to boron (B) doping, and FIG. 16B is a ratio of the first length to the second length with respect to the third length according to boron (B) doping. is a graph showing

division Comparative Example 5 Example 15 Example 16 Example 17 Example 18 B doping B 0 mol% B 0.5 mol% B 1 mol% B 1.5 mol% B 2 mol% f1 medium 665.2 1230.3 1045.9 991.9 1102.4 maximum 1212.0 1839.0 1676.0 1509.0 1721.9 minimum 259.0 546.0 359.0 401.0 529.1 Standard Deviation 249.1 346.1 319.5 319.5 327.8 f2 medium 519.0 446.2 437.2 477.8 588.2 maximum 978.0 860.0 1087.0 803.0 1045.0 minimum 224.0 185.0 210.0 264.0 287.0 Standard Deviation 187.5 129.5 152.5 136.4 190.3 f3 medium 351.3 145.8 55.5 40.6 30.0 maximum 551.5 246.0 111.1 91.3 63.6 minimum 194.0 35.3 23.7 17.4 3.5 Standard Deviation 98.1 39.2 18.2 14.0 9.7

division Comparative Example 5 Example 15 Example 16 Example 17 Example 18 B doping B 0 mol% B 0.5 mol% B 1 mol% B 1.5 mol% B 2 mol% f1 665.2 1230.3 1045.9 991.9 1102.4 f2 519.0 446.2 437.2 477.8 588.2 f3 351.3 145.8 55.5 40.6 30.0 f1/f3 1.894 8.437 18.850 24.425 36.71 f2/f3 1.478 3.060 7.881 11.764 19.583

Referring to Table 9 and Figure 15b, the value based on the XDR data corresponds to the overall average value of the primary particles constituting the secondary particles (dotted line, hereinafter XRD-based value), and the value measured using the SEM image is the secondary particle It means a value measured by the third length of the primary particles located on the surface of the middle (solid line, hereinafter measured value). When 0 mol% of boron (B) was not doped and 0.05 mol% of boron (B) was doped, the measured values showed larger values than the XRD-based values, but when boron (B) was 0.5 mol%, 1 mol%, In the case of doping with 1.5 mol% and 2 mol%, it was confirmed that the measured value showed a smaller value than the XRD-based value. Referring to the ratio of I(003)/I(104) obtained using XRD data in Table 9, it was confirmed that the value decreased as the doping of boron (B) increased. This is considered to be because the size of the primary particles is reduced by doping of boron (B), and thus the I(003) peak of the peak is relatively reduced.

10 to 14 , as the doping of boron (B) increased, it was confirmed that the third length of the primary particles gradually decreased. It can be confirmed that it is available. That is, when boron (B) doping is 0 mol%, when viewed from the top, the edges of the primary particles are not clear and are provided in the form of some curved surfaces, whereas as boron (B) doping increases, the edges of the primary particles It can be confirmed that the angular shape of is provided in a rectangular shape with a gradually decreasing third length.

Referring to Table 11 and FIG. 16A, the second length f2 is not significantly different by boron (B) doping in the NCO-based positive electrode active material, but the first length f1 has a boron (B) concentration of up to 0.5 mol%. It increased, but from that point on, it was confirmed that it did not change any more and maintained a certain level. In addition, it was confirmed that the third length decreased as boron (B) doping increased, but did not decrease any more after the addition of about 1.5 mol%. That is, it was confirmed that the first length f1, the second length f2, and the third length f3 were all affected by boron (B) doping.

Referring to Table 12 and FIG. 16B, it was confirmed that both the first length f1 for the third length f3 and the second length f2 for the third length f3 increased, and the increased As for the degree, it was confirmed that the slope of the first length f1 with respect to the third length f3 was larger.

In Table 13 below, when boron (B) is not doped in the NCO-based positive electrode active material (Comparative Example 5), when boron (B) is doped by 0.5 mol% (Example 15), boron (B) is doped by 1 mol% Case (Example 16) and boron (B) and molybdenum (Mo) were each doped together by 0.5 mol% (co-doping) was reviewed.

In Table 13 below, it was confirmed that the 0.1C discharge capacity of Comparative Example 5, Example 15, Example 16, and Example 22 were all similar. On the other hand, it was confirmed that Comparative Example 5 not doped with boron (B) had a capacity retention rate of 67.2% after 100 cycles, which was lower than Examples 15, 16 and 22.

Comparing Example 15 doped with 0.5 mol% of boron (B) and Example 22 doped with 0.5 mol% of boron (B) and 0.5 mol% of molybdenum (Mo), Example 22 is 100 cycles rather than Example 15 After that, it was confirmed that the capacity retention rate was improved. In addition, even when comparing Example 16 and Example 22 in which boron (B) was doped at 1 mol%, when both sides were doped at 1 mol%, even when the doped amount was the same, Example 22 had a higher capacity retention rate after 100 cycles improvement could be confirmed. That is, by doping with molybdenum (Mo) together with boron (B) doping, it is determined that the effect of boron (B) is improved.

division Type of cathode active material doping element doping [mol%] Refined
Structure 0.1C discharge capacity
[mAh g-1] Initial Coulombic Efficiency
[%] 0.5 C discharge capacity
[mAh g-1] Capacity retention after 100 cycles [%] Comparative Example 5 NCO system B 0 X 225.3 95.1 209.8 67.2 Example 15 NCO system B 0.5 O 234.2 96.1 218.2 83.3 Example 16 NCO system B One O 236.2 96.7 222.8 88.9 Example 22 NCO system B/Mo 0.5/0.5 O 232.2 94.9 217.2 94.7

17 is an SEM image of the positive electrode active material according to Example 24 and Comparative Example 7, and FIG. 18 is a FIB TEM image of the positive electrode active material according to Example 24 and Comparative Example 7. 19 is a FIB TEM image before the first cycle of the cathode active material according to Example 24 and Comparative Example 7, FIG. 20 is a FIB TEM image before the first cycle of Example 24 of FIG. 19, FIG. 21 is It is a FIB TEM image after 100 cycles of Example 24. 22 to 24 are results of analyzing the coating layer formed on the primary particles provided on the surface of the secondary particles in Example 24. 25 is a TEM image of the primary particles of Example 24. 26 to 28 are XRD analysis results before and after heat treatment of boron oxide and lithium hydroxide.

Referring to Table 9, when an NCA-based positive electrode active material was prepared using a metal composite hydroxide containing 88.5 mol% nickel (Ni), in Comparative Example 7 in which boron (B) was not doped, a refined structure was found. The microstructure was found only in Examples 23 and 24 in which boron (B) was doped with 0.5 mol% and 1 mol%, respectively. In addition, 0.1C discharge capacity was similar in Comparative Examples 7, 23 and 24 at 225.1 mAh/h, 224 mAh/g, and 229.8 mAh/g, respectively, but the capacity retention rate after 100 cycles was 83.7%, 92.2%, and It was confirmed that it increased as boron (B) doping increased to 96.2%.

Referring to Table 9 and FIGS. 17 and 18 , in Comparative Example 7, the third length of the primary particles was relatively thick, whereas in Example 24, the third length of the primary particles was thin and the upper side of the primary particles. It was confirmed that the corners were provided to have an angle, so that the cross-section was provided in the form of a rectangle. In the case of Example 24, it is determined that the distal end of the primary particle provided on the surface of the secondary particle is connected to the crystal plane from the primary particle provided on the surface of the secondary particle among the primary particles due to boron (B) doping. .

19 is an enlarged FIB TEM image of the surface of Comparative Example 7 and Example 24. In the case of Comparative Example 7, the end is provided to be rounded smoothly, whereas Example 24 has two crystal planes, such as (012) plane and It was confirmed that the (014) surfaces were provided in a form connected to each other.

Referring to FIGS. 20 and 21 , in Example 24, the primary particles located on the surface of the secondary particles are provided so that (003) planes and (003) planes face each other, and a pair of (003) planes and (003) planes It can be seen that the vertical section perpendicular to the crystal planes on both sides of is connected so that the (012) plane and the (014) plane are angled to each other.

20, in the case of Example 24, before the first cycle, the primary particles provided on the surface of the secondary particles among the primary particles are provided side by side so that a pair of (003) faces face each other, the pair (003) planes are connected by two or more crystal planes. Here, when the pair of (003) planes are cut perpendicularly, it can be seen that the pair of (003) planes are connected by two different crystal planes. As described above, Example 24 is composed of a pair of (003) planes and a plurality of crystal planes connecting the pair of (003) planes, whereby the surface portion of the secondary particles is uneven.

21 shows secondary particles after 100 cycles of Example 24. It was confirmed that Example 24 still had a crystal plane even after 100 cycles.

The positive electrode active material according to the present embodiment is doped with boron (B), whereby the third length, which is the thickness of the primary particles provided on the surface of the secondary particles among the primary particles, may be thin. In addition, in the positive electrode active material according to the present embodiment, the primary particles provided on the surface of the secondary particles among the primary particles have an angle formed at at least a portion of the corner in a direction viewed from the upper surface of the secondary particles, and the secondary particles It can be seen that the surface of the primary particle provided on the surface of the secondary particle cut in the direction from the surface of the secondary particle toward the center is provided with two different crystal planes at an angle.

In the positive electrode active material according to the present embodiment, it was confirmed that the surface portion of the secondary particle was connected to two or more crystal planes at the ends, and this was maintained even after a plurality of cycles. As a result, the positive electrode active material according to the present embodiment has crystal planes connected to each other at the surface of the secondary particles, thereby preventing the electrolyte from easily penetrating into the secondary particles, thereby improving lifespan characteristics. In addition, along with the alignment of the crystal planes, the primary particles are aligned in a direction toward the center of the secondary particles, whereby lithium ions are easily moved to the center of the secondary particles along the direction in which the primary particles are aligned, and the charging and discharging process By suppressing the formation of microcracks during the process, the electrochemical efficiency is increased and the lifespan characteristics are improved.

Referring to FIGS. 22 to 25 together with FIG. 19 , it was confirmed that, although not shown in Comparative Example 7, a coating layer was further provided on the outer surface of the surface portion in Example 24. When the coating layer formed in Example 24 was analyzed, it could be confirmed that boron oxide was included.

22, it can be seen that the concentration of boron (B) is provided to have a concentration gradient in the coating layer, and is uniformly provided in the secondary particles. In addition, the average concentration of boron (B) in the secondary particles may be provided in an error range of 1 mol%, which is the concentration of boron (B) added to the composite metal hydroxide, to 0.05 mol%.

For example, when the concentration of boron (B) is Y1 as the concentration of boron (B) added to the composite metal hydroxide, the average concentration of boron (B) in the secondary particles is Y2, and boron (B) in the coating layer The average concentration of can be expressed by Equations 1 and 2 below when Y3.

(Formula 1) Y1-0.005 ≤ Y2 ≤ Y1+0.005

(Equation 2) Y2 < Y3

23 to 25, as a result of confirming the surface portion of the secondary particles by TEM, it was confirmed that the coating layer was provided to cover the second and third crystal surfaces of the first primary particles. Referring to FIGS. 23 and 24 , it can be seen that the distances of crystal planes that do not occur in the secondary particles, ˜0.30 nm, 0.28 nm, and 0.22˜0.24 nm, are heat-treated in a state in which boron oxide and lithium hydroxide are mixed as follows. It can be confirmed that it corresponds to the XRD result that occurs when performing (refer to FIGS. 26 and 28).

That is, in the process of pre-calcining the metal composite hydroxide, boron oxide, and lithium hydroxide at 450°C, boron oxide is uniformly included in the secondary particles, and at the same time, some of them chemically react with lithium hydroxide on the surface of the secondary particles to form a coating layer. is formed In the coating layer, the second and third crystal planes formed on the surface of the secondary particles, the concentration of each material constituting the positive electrode active material, the heat treatment process thereof, and the controlled pH during the coprecipitation reaction are complexly related. is considered to be formed.

29 is a cycle graph of a full cell using the positive electrode active material according to Example 24 and Comparative Example 7. 30 is an SEM image illustrating a cross section of secondary particles by charging the positive electrode active materials according to Example 24 and Comparative Example 7 for each charging voltage. 31 is an SEM image after cycling of a half cell and a full cell using the cathode active materials of Example 24 and Comparative Example 7. FIG. 32 and 33 are in-situ XRD data of Example 24 and Comparative Example 7.

Using the full cell using Example 24 and Comparative Example 7, the cycle was carried out at 1C constant current at 25°C at 3.0V (discharge voltage) and 4.2V (charge voltage) (see FIG. 29 ), Example 24 is 1000 cycles On the other hand, in Comparative Example 7, the capacity was decreased from 200 cycles, and at 1000 cycles, Example 24 showed a capacity retention rate of 83.4%, whereas Comparative Example 7 showed a capacity retention rate of 49%. It was confirmed that there was a difference in the lifespan characteristics.

30, as a result of charging while increasing the state of charge (SOC) to 3.9V, 4.0V, 4.1V, 4.2V, and 4.2V, Comparative Example 7 showed a weakly visible hairline at 4.1V, At 4.2V, it was confirmed that microcracks were formed from the center of the secondary particles, and at 4.3V, it was confirmed that they extended to the surface of the secondary particles. On the other hand, in Example 24, a weak hairline appeared at 4.3V, but was confirmed less than that seen at 4.1V of Comparative Example 7, and it was also confirmed that microcracks were not formed.

For Comparative Example 7 and Example 24, the cross-sections of secondary particles discharged to 4.1V after charging to 4.3V and secondary particles discharged to 2.7V after charging to 4.3V were compared. It was confirmed that microcracks formed at 4.3V were also generated in the secondary particles discharged to 4.1V after charging to 4.3V only in Comparative Example 7.

The cathode active material undergoes a continuous phase change such as H1 (hexagonal 1) -> M (monoclinic) -> H2 (hexagonal 2) -> H3 (hexagonal 3) during the charging process, and the last H2 -> H3 is abruptly anisotropic. volume change occurs. Here, the volume change proceeds gently up to 4.15V, which is the voltage before the H2 -> H3 phase transition starts, and then the cell volume rapidly decreases at 4.2V where the H2 -> H3 phase transition starts.

After charging to 4.3V, which is the part where such a rapid volume change begins, it was confirmed that microcracks were formed in the microstructure of the secondary particles in Comparative Example 7 at 4.1V, whereas in Example 24, such a structure did not appear. That is, in Example 24, even during the H2 -> H3 phase change as described above, it is determined that the primary particles are arranged in the secondary particles so that microcracks are not formed in the microstructure due to the anisotropic volume change. . In the case of Comparative Example 7, during the cycle, the volume change occurring in the H2 -> H3 phase change process was not fully recovered reversibly, and the remaining irreversible part was accumulated, causing the secondary particles to crack after the cycle progressed. is determined to be formed (refer to FIGS. 32 and 33).

In FIG. 31, for the half cell and the full cell prepared according to Comparative Example 7 and Example 24, 100 cycles were performed for the half cell, respectively, and 1000 cycles were performed for the full cell, respectively, and are SEM images of secondary particles confirmed. As shown in FIG. 31 , in Comparative Example 7, it can be seen that microcracks are formed in the secondary particles as a whole, and in severe cases, it can be confirmed that the secondary particles are almost decomposed. On the other hand, in Example 24, it could be confirmed that the initial particle shape was almost maintained in both the half-cell and the full-cell.

That is, in the case of Example 24, along with boron (B) doping, the primary particles formed in the manufacturing process of the metal complex hydroxide are aligned to form secondary particles, and among the primary particles, the primary particles located on the surface of the secondary particles. , a coating layer is provided on the surface, and the volume change is performed reversibly in the charging/discharging process by forming a plurality of crystal planes, and thereby, it is judged that cycle characteristics are improved because microcracks and the like do not occur.

In Table 14 below, 100 cycles of 2.7 V discharge at 0.5 C constant current and 4.3 V charge at 0.5 C constant current were performed in a half cell using a positive electrode active material according to Examples and Comparative Examples as a positive electrode, followed by 100 cycles of 1 cycle. The intensity of the peak corresponding to the phase transition of H2-H3 is shown. The intensity of the peak corresponding to the phase transition of H2-H3 was confirmed using the dQ/dV curve, which is a graph obtained by differentiating the charge/discharge curve by one degree.

division Types of cathode active materials doping element Doping [mol%] Capacity retention after 100 cycles [%] H2/H3 peak retention after 100 cycles [%] Example 3 NCM system B 0.4 89.2 73.4 Example 4 NCM system B One 91.4 82.7 Comparative Example 5 NCO system B 0 67.2 38.1 Example 13 NCO system B 0.05 77.3 48.8 Example 14 NCO system B 0.1 81.3 52.6 Example 15 NCO system B 0.5 83.3 61.4 Example 16 NCO system B One 88.9 70.3 Example 17 NCO system B 1.5 91.2 83.5 Example 18 NCO system B 2 91.6 82.6 Example 19 NCO system B 3 91.3 80.1 Example 20 NCO system B 4 86.6 75.6 Example 21 NCO system B 5 85.9 77.5 Comparative Example 6 NCO system B 7 85.8 50.4 Comparative Example 7 NCA system B 0 83.7 63.7 Example 23 NCA system B 0.5 92.2 90.6 Example 24 NCA system B One 96.2 94

Referring to Table 14, in Examples 3 and 4, the intensity of the peak corresponding to the phase transition of H2-H3 after 100 cycles compared to 1 cycle (H2/H3 peak retention after 100 cycles [%]) was 73.4%, respectively, 73.4%, 82.7% was confirmed. Comparing Comparative Example 5, Comparative Example 6, and Examples 13 to 21, Examples 13 to 21 were 40% or more, whereas Comparative Example 5 had a low value of 38.1%. Comparing Examples 13 to 19, it was confirmed that the value increased as the doping amount of boron increased. That is, as the doping amount of boron increased, it was confirmed that the structure similar to that of 1 cycle could be maintained even after 100 cycles. In addition, it was confirmed that Comparative Example 7, Example 23, and Example 24 showed a similar tendency.

Table 15 below shows co-doping in which other doping elements are further added along with boron.

division Types of cathode active materials Cathode active material powder chemical formula two Doping [mol%] Refined Structure 0.1C discharge capacity [mAh g-1] Capacity retention after 100 cycles [%] Comparative Example 5 NCO system Li _1.01 Ni _0.9 Co _0.10 O ₂ B 0 X 225.3 67.2 Example 15 NCO system Li _1.01 B _0.005 Ni _0.9 Co _0.10 O ₂ B 0.5 O 234.2 83.3 Example 16 NCO system Li _1.01 B _0.01 Ni _0.9 Co _0.10 O ₂ B One O 236.2 88.9 Example 22 NCO system Li _1.01 B _0.005 Ni _0.895 Co _0.10 Mo _0.005 O ₂ B/Mo 0.5/0.5 O 232.2 94.7 Comparative Example 13 NCO system Li _1.01 [Ni _0.96 Co _0.04 ]O ₂ B 0 X 237.2 78.4 Example 30 NCO system Li _1.01 B _0.005 Ta _0.005 Ni _0.95 Co _0.10 O ₂ B/Ta 0.5/0.5 O 239.4 89.4 Example 31 NCO system Li _1.01 B _0.005 Nb _0.005 Ni _0.95 Co _0.10 O ₂ B/Nb 0.5/0.5 O 242.8 87.2 Example 32 NCO system Li _1.01 B _0.005 Mo _0.005 Ni _0.95 Co _0.10 O ₂ B/Mo 0.5/0.5 O 242.2 88.7 Example 33 NCO system Li _1.01 B _0.005 Sb _0.005 Ni _0.95 Co _0.10 O ₂ B/Sb 0.5/0.5 O 239.4 91.6

Referring to Table 15, when co-doping with boron and molybdenum (Example 22), boron and tantalum (Example 30, Example 32), boron and niobium (Example 31), and boron and antimony (Example 33) It could be confirmed that the microstructure was also present, and the capacity retention rate after 100 cycles was also more than 80%, which was superior to the case in which boron was not doped.

Comparing Comparative Example 5, Example 15, Example 16, and Example 22, in the case of 90 mol% of Ni, the capacity retention rate was excellent as the content of boron increased, and when comparing Example 16 and Example 22, the total doping amount In the same case, it was confirmed that Example 22 co-doped with boron and molybdenum had better capacity retention than Example 16 doped with boron alone.

Comparing Comparative Example 13 and Examples 30 to 33, when co-doped with boron, they all exhibited a refined structure regardless of the type of co-doped dopant, and exhibited excellent capacity retention rate even after 100 cycles. could check

Those of ordinary skill in the art to which the present invention pertains will understand that the present invention may be embodied in other specific forms without changing the technical spirit or essential features thereof. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the following claims rather than the above detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts are included in the scope of the present invention. should be interpreted

100: first primary particle
110: first crystal plane
120: second crystal plane
130: third crystal plane
200: secondary particle

Claims (21)

In a positive electrode active material comprising secondary particles consisting of a group of a plurality of primary particles,
At least some of the primary particles provided on the surface of the secondary particles include first primary particles in the form of flakes having a pair of first crystal faces facing each other,
In the first primary particles, the first crystal planes are arranged in a radial direction, and one end of the pair of first crystal planes is provided with a plurality of crystal planes different from the first crystal planes to connect one end of the pair of first crystal planes,
The longitudinal cross-section of the first primary particle includes a pair of first crystal planes spaced apart from each other, and a second crystal plane and a third crystal plane connecting one end of the pair of first crystal planes,
The second and third crystal planes are provided on the outermost surface of the secondary particles, and the positive electrode active material is connected to have an angle. According to claim 1,
The first primary particles have a first length that is a long axis of the first crystal plane, a second length that is a short axis of the first crystal plane perpendicular to the first length, and a third length that is an interval between the pair of first crystal planes. including,
The third length of the cathode active material is 10nm to 400nm. 3. The method of claim 2,
The ratio of the first length to the third length is 2 to 100, and the ratio of the second length to the third length is 1.5 to 80. 3. The method of claim 2,
The cathode active material is a layered trigonal system (Rhombohedral system) compound,
The first crystal plane is (hkℓ, where h=0, k=0, ℓ=3n, and n is an integer),
The first crystal plane, the second crystal plane, and the third crystal plane are provided differently from each other. 3. The method of claim 2,
An angle between the second crystal plane and the third crystal plane is 30° to 170°. According to claim 1,
A 2032 coin-type half cell using the positive electrode active material as a positive electrode and lithium metal as a negative electrode,
After 100 cycles of charging to 4.3 V at 0.5 C constant current and discharging to 2.7 V at 0.5 C constant current, the peak intensity corresponding to the phase transition of H2-H3 in the dQ/dV curve is 40% or more compared to 1 cycle. According to claim 1,
The primary particles include nickel (Ni) and M1 and M2,
M1 is made of at least one of manganese (Mn), cobalt (Co) and aluminum (Al),
The nickel (Ni) is 65 mol% or more,
The M2 is a doping element, and the positive electrode active material consists of 0.05 mol% to 5 mol%. 8. The method of claim 7,
The M2 is,
boron (B); or,
boron (B) and tungsten (W), molybdenum (Mo), tantalum (Ta), niobium (Nb), hafnium (Hf), silicon (Si), tin (Sn), zirconium (Zr), calcium (Ca), Germanium (Ge), gallium (Ga), indium (In), ruthenium (Ru), tellurium (Te), antimony (Sb), iron (Fe), chromium (Cr), vanadium (V) and titanium (Ti) ) of any one or more; cathode active material consisting of. 9. The method of claim 8,
A cathode active material provided with a coating layer including boron (B) covering at least a portion of the second and third crystal planes on the second and third crystal planes. 10. The method of claim 9,
The concentration of boron (B) is,
It is provided uniformly in the secondary particles, and is provided to have a concentration gradient in the coating layer,
The positive electrode active material having an average concentration of boron (B) in the coating layer is higher than the average concentration of boron (B) in the secondary particles. 11. The method of claim 10,
The coating layer is LiBO ₂ , LiB ₃ O ₅ , LiB ₅ O ₈ , α-LiBO _{2 ,} Li ₂ B ₂ O ₄ , Li ₂ B ₂ O ₇ , Li ₂ B ₄ O ₇ , Li ₂ B ₆ O ₇ , Li ₂ B ₆ O ₁₀ , Li ₂ B ₈ O ₁₃ , Li ₃ BO ₃ , Li ₃ B ₇ O ₁₂ , Li ₄ B ₂ O ₅ , α-Li ₄ B ₂ O ₅ , β-Li ₄ B ₂ O _{5 ,} A cathode active material comprising at least one of Li ₄ B ₁₀ O ₁₇ and Li ₆ B ₄ O _9. According to claim 1,
In a cross-section of secondary particles charged to 4.3 V at a constant current of 0.5 C with a half-cell using lithium metal as a negative electrode as a positive electrode using the positive electrode active material,
A positive electrode active material in which an area of microcracks, which is a space formed between neighboring primary particle boundaries, is less than 15% of an area of a cross-section of the secondary particles. 8. The method of claim 7,
The secondary particle is a device with 45 kV, 40 mA output, and in X-ray diffraction analysis obtained by measuring at a scan rate of 1 degree per minute at 0.0131 step size intervals using a Cu Ka beam source, the intensity of the 003 peak versus the intensity of the 104 peak A positive electrode active material having a ratio of 1.6 to 2.3. 14. The method of claim 13,
As the content of the doping element increases, the ratio of the intensity of the 003 peak to the intensity of the 104 peak decreases. According to claim 1,
The secondary particles are provided in a spherical shape having a central portion and a surface portion,
The first primary particles are provided in a direction in which the first crystal plane faces the surface portion from the central portion,
In the first primary particle, the second and third crystal planes are provided on a surface portion of the secondary particle, and an outermost surface of the surface portion of the secondary particle forms a concave-convex structure by the second and third crystal planes. 16. The method of claim 15,
The secondary particles are represented by the following <Formula 1>,
The positive electrode active material further comprising a coating layer covering at least a portion of the second and third crystal planes on the surface of the secondary particles.
<Formula 1>
Li _a M _x D _y O ₂
(M is at least any one of Ni, Co, Mn, or Al, and D is B alone, or B and any one of W, Mo, Nb, Ta, and Sb is co-doped. element, 0.9<a<1.1, x+y = 1, 0.95<x<1, 0<y<0.05) 17. The method of claim 16,
The first primary particles have a first length that is a long axis of the first crystal plane, a second length that is a short axis of the first crystal plane perpendicular to the first length, and a third length that is an interval between the pair of first crystal planes. including,
The doped element is provided in an amount of 0.05 mol% to 5 mol%, and as the concentration of the doping element increases, the first length of the first primary particles increases and the third length decreases. A positive electrode for a secondary battery comprising the positive electrode active material according to any one of claims 1 to 17. A lithium secondary battery comprising the positive electrode according to claim 18. A battery module comprising the lithium secondary battery according to claim 19 as a unit cell. A battery pack comprising the battery module according to claim 20,
The battery pack is used as a power source for medium and large devices,
The medium and large device is a battery pack selected from the group consisting of an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a system for power storage.

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