KR20220026519A - Cobalt free positive active material for lithium secondary battery, and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a cobalt-free positive electrode active material having a cobalt-free layered structure and a lithium secondary battery including the same. The cobalt-free positive electrode active material and the lithium secondary battery including the same according to the present invention have high-efficiency electrochemical stability even at a high voltage, and exhibit excellent safety and long-term lifespan characteristics by improving high-temperature characteristics and particle strength.

Description

Cobalt free positive active material and lithium secondary battery comprising the same

The present invention relates to a cobalt-free positive electrode active material and a lithium secondary battery containing the same, and more particularly, to a cobalt-free positive electrode active material made of a metal element not containing cobalt and having a layered structure, and a lithium secondary battery including the same will be.

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, research and development for positive electrode active materials used in lithium secondary batteries is in progress. For example, in Korean Patent Laid-Open Publication No. 10-2014-0119621 (Application No. 10-2013-0150315), a precursor for manufacturing an excess lithium positive electrode active material is used to control the type and composition of the metal substituted in the precursor, and add A secondary battery having high voltage capacity and long life characteristics by controlling the type and amount of metal to be used is disclosed.

An object of the present invention is to provide a cobalt-free positive electrode active material having a layered structure that does not contain cobalt and having improved electrochemical properties and cycle performance at high voltage, and a lithium secondary battery including the same.

In addition, it is to provide a cobalt-free positive electrode active material having an improved effect by an additive metal other than nickel, manganese, and lithium of the present invention and a lithium secondary battery including the same.

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

In order to solve the above technical problem, the present invention provides a positive electrode active material and a positive electrode.

According to one embodiment, it includes a positive electrode active material for a lithium secondary battery that is composed of a layered structure represented by the following Chemical Formula 1.

[Formula 1]

Li _a1 Ni _x1 Mn _y1 O ₂

(In Formula 1, 0.95≤a1≤1.15, x1+y1=1, 0.5≤x1≤0.99, 0.01≤y1≤0.5)

According to an embodiment, it includes a positive electrode active material for a lithium secondary battery, which is formed of a layered structure represented by the following Chemical Formula 1 and is charged at a voltage of 4.4V or higher based on the positive electrode potential.

[Formula 1]

Li _a1 Ni _x1 Mn _y1 O ₂

(In Formula 1, 0.95≤a1≤1.15, x1+y1=1, 0.5≤x1≤0.99, 0.01≤y1≤0.5)

According to one embodiment, it includes a positive electrode active material for a lithium secondary battery, which is composed of a layered structure represented by the following Chemical Formula 2.

[Formula 2]

Li _a2 Ni _x2 Mn _y2 M _z2 O ₂

(In Formula 2, 0.95≤a2≤1.15, x2+y2+z2=1, 0.5≤x2≤0.99, 0.01≤y2≤0.5. 0.001≤z2≤0.05, M is tin (Sn), molybdenum ( Mo), tantalum (Ta), tungsten (W), magnesium (Mg), aluminum (Al), boron (B), niobium (Nb), titanium (Ti), antimony (Sb), tellurium (Te), any one or more of ruthenium (Ru), zirconium (Zr), rhodium (Rh), and ilithium (Ir))

According to one embodiment, in the positive electrode active material, the cation mixing ratio is the ratio of the transition metal present in the lithium layer, the cation mixing ratio is 1% to 12%, and the layered structure is only lithium (Li) A lithium layer including a lithium layer and a transition metal layer including only a transition metal are alternately and regularly arranged, wherein the cation mixture faces the lithium constituting the lithium layer and the lithium layer The transition metals constituting the transition metal layer may be formed by substituting with each other.

According to one embodiment, the positive electrode active material is made of the layered structure, the portion within 2㎛ in the direction from the outermost surface of the positive electrode active material toward the center further comprises a cation ordering (cation ordering), the layered structure is A lithium layer containing only lithium (Li) and a transition metal layer containing only a transition metal are alternately and regularly arranged, wherein the cation ordering includes lithium constituting the lithium layer and Transition metals constituting the transition metal layer facing the lithium layer may be substituted with each other.

According to an embodiment, the Full Width at Half-Maximum (FWHM) of the peak for the (104) plane obtained by X-ray diffraction (XRD) analysis using Cu-kα ray is 0.03V or more, and the anode The active material includes a region in which H2-H3 phase transition is performed during charging, and the voltage of the H2-H3 phase transition region may be in a range of 4.12V to 4.6V.

According to one embodiment, the lattice parameter of the c-axis of the unit lattice of the positive electrode active material expands and contracts during charging and discharging, and the amount of change in the lattice constant of the c-axis is 2% or less during expansion and may be 4.5% or less upon contraction.

According to an embodiment, the lattice constant of the c-axis may be 14.5 Å or less.

According to an embodiment, charging at a voltage of 4.4V or higher based on the positive potential may be performed in the formation step or several cycles or every cycle thereafter.

According to an embodiment, the positive electrode active material may be formed of secondary particles in which a plurality of primary particles are aggregated, and the secondary particles may have a particle strength of 120 MPa to 250 MPa. According to an embodiment, in a Nyquist plot obtained from impedance measurement, Rct (charge transfer resistance) may be 30Ω or less at 100 cycles.

According to an embodiment, the maximum exothermic peak temperature (T) measured according to a thermal stability evaluation method using a differential scanning calorimeter may be 195°C to 230°C.

According to one embodiment, the positive electrode active material is made of secondary particles in which a plurality of primary particles are aggregated, and the primary particles are provided on the surface of the secondary particles and include oriented particles having an a-axis and a c-axis, and the orientation The a-axis direction of the particles may include those corresponding to a lithium ion diffusion path.

An embodiment according to another aspect of the present invention is a positive electrode using a positive electrode active material; a negative electrode made of graphite or lithium metal facing the positive electrode; a separator interposed between the positive electrode and the negative electrode; and a lithium secondary battery comprising a; and an electrolyte or a solid electrolyte containing a lithium salt.

According to an embodiment, a charging cutoff voltage of the lithium secondary battery may be 4.4V or more.

According to the present invention as described above, it is possible to provide a cobalt-free positive electrode active material having improved high-temperature stability and high particle strength, and a lithium secondary battery including the same.

In addition, according to the present invention, it is a cathode active material that does not contain cobalt and is made of lithium, nickel, manganese, and an additive metal. It has a stable layered structure and has improved electrochemical performance at high voltage and thus long-term cycle performance is improved. and a lithium secondary battery including the same.

1 is a view schematically showing secondary particles according to an embodiment of the present invention.
2 is a schematic diagram of a cross-section of a cathode active material according to an embodiment of the present invention.
3 is a view schematically showing the movement of lithium ions in the positive electrode active material according to an embodiment of the present invention.
4 is an SEM photograph according to Preparation Example 3.
5 is an SEM photograph of the composite metal hydroxide (a, b, c) and the positive electrode active material (d, e, f) according to Preparation Examples 1 to 3;
6 and 7 are SEM photographs of the positive electrode active material particles charged with 4.3V and 4.4V of Preparation Examples 1 to 3.
8 is a view showing XRD spectra of Preparation Examples 1 to 3;
9 is a view analyzing XRD patterns of Preparation Examples 1 to 3;
10 is a view showing a dQ/dV curve in the first charge/discharge (2.7V-4.4V) of Preparation Examples 1 to 3;
11 is a diagram showing H2-H3 phase transition in the in-situ XRD analysis of Preparation Example 3;
12 is a graph showing a-axis and c-axis lattice parameters in the in-situ XRD analysis of Preparation Examples 1 to 3;
13 is a graph showing the DSC results of Preparation Example 2 and Preparation Example 3.
14 is a Nyquist plot showing the electrochemical resistance of Preparation Examples 1 to 3;
15 is an SEM photograph of the cathode active material discharged after 100 cycles of charging and discharging at each temperature of 30° C. and 60° C. of Preparation Examples 2 and 3;
16 is a graph showing the phase change of H2-H3 when the charging voltage cut-off of Preparation Examples 1 to 3 is charged to (a) 4.3V and (b) 4.4V, respectively.
17 is a graph showing a phase change when the charging voltages according to Preparation Example 3 were set to 4.23V and 4.4V, respectively, and then discharged to 4.04V.
18 is a graph confirming the rate characteristics while variously changing the cut-off of the charging voltage of Preparation Example 3;
19 and 20 are graphs showing the galvanostatic intermittent titration technique (GITT) analysis results for each of the charging voltages of Preparation Example 3 as 4.23V and 4.4V.
21 and 22 show the results of confirming the discharge rate characteristics of Preparation Examples 2 and 3 by setting the charging voltages to 4.23V and 4.4V, respectively.
23 is a result of confirming the charging characteristics of 2.7V-4.4V at -10 ℃ for Preparation Examples 2 and 3.
24 is an SEM photograph of the composite metal hydroxide according to Preparation Example 4.
25 is an SEM photograph of the positive electrode active material according to Preparation Example 4.
26 is an SEM photograph of the positive electrode active material according to Preparation Example 6.
27 is an SEM photograph of the positive electrode active material according to Preparation Example 9;
28 is a graph showing the phase change of H2-H3 according to the charging voltage according to Preparation Examples 4 to 7;
29 is a graph showing the H2-H3 phase change according to the charging voltage according to Preparation Example 4, Preparation Example 8, and Preparation Example 9;
30 is a graph showing the phase change of H2-H3 according to the charging voltage according to Preparation 4 and Preparation Example 10;
31 is a graph showing the phase change of H2-H3 according to the charging voltage according to Preparation 4 and Preparation Example 11;
32 is a graph showing the phase change of H2-H3 according to the charging voltage according to Preparation 4 and Preparation Example 12;
33 is a graph showing the phase change of H2-H3 according to the charging voltage according to Preparation 4 and Preparation Example 16;
34 is a graph showing the phase change of H2-H3 according to the charging voltage according to Preparation Examples 4 to 6, Preparation Example 8, Preparation Example 16.
35 is a graph showing the phase change of H2-H3 according to the charging voltage according to Preparation Example 4 and Preparation Examples 9 to 14.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the technical spirit of the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed subject matter may be thorough and complete, and the spirit of the present invention may be sufficiently conveyed to those skilled in the art.

In this specification, when a component is referred to as being on another component, it means that it may be directly formed on the other component or a third component may be interposed therebetween. In addition, in the drawings, thicknesses of films and regions are exaggerated for effective description of technical content.

Also, in various embodiments of the present specification, terms such as first, second, third, etc. are used to describe various components, but these components should not be limited by these terms. These terms are only used to distinguish one component from another. Accordingly, what is referred to as a first component in one embodiment may be referred to as a second component in another embodiment. Each embodiment described and illustrated herein also includes a complementary embodiment thereof. In addition, in this specification, 'and/or' is used in the sense of including at least one of the components listed before and after.

In the specification, the singular expression includes the plural expression unless the context clearly dictates otherwise. In addition, terms such as "comprise" or "have" are intended to designate that a feature, number, step, element, or a combination thereof described in the specification exists, but one or more other features, number, step, configuration It should not be construed as excluding the possibility of the presence or addition of elements or combinations thereof.

In addition, in the following description of the present invention, if it is determined that a detailed description of a related well-known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

In addition, in the present application, when the ratio of the first crystal structure in the specific portion is higher than the ratio of the second crystal structure, the specific portion includes both the first crystal structure and the second crystal structure, but the specific portion In , it is interpreted to mean that the ratio of the first crystal structure is higher than the ratio of the second crystal structure, and also means that the specific portion has only the first crystal structure.

In addition, in the present application, the crystal system (crystal system) is triclinic, monoclinic, orthorhombic, tetragonal, trigonal or rhombohedral, hexagonal. , and may be composed of 7 pieces of a cubic system.

In addition, in the present application, "mol%" is a positive electrode active material or composite metal hydroxide (positive electrode active material precursor), when the sum of the remaining metals except lithium and oxygen is assumed to be 100%, any included in the positive electrode active material or composite metal hydroxide It is interpreted as meaning indicating the content of metals in

1 is a view schematically showing secondary particles according to an embodiment of the present invention. 2 is a schematic diagram of a cross-section of a cathode active material according to an embodiment of the present invention. 3 is a view schematically showing the movement of lithium ions in the positive electrode active material according to an embodiment of the present invention.

1 to 3, the positive electrode active material according to the embodiment of the present invention may be made of secondary particles 100 having an approximately spherical shape, and the secondary particles 100 include a central portion 10 and a surface portion 20. and a plurality of primary particles 30 may be agglomerated and formed. The primary particles 30 may have a layered structure.

In the secondary particle 100, the primary particles 30 constituting the central portion 10 and the primary particles 30 constituting the surface portion 20 may have the same size or different sizes, and the surface portion 20 ) constituting the primary particles 30 are provided in a shape having a long axis and a short axis, and at least a portion of the primary particles 30 constituting the surface portion 20 is the central portion 10 of the secondary particles 100 It can be arranged in the direction facing. At least a portion of the primary particles 30 constituting the surface portion 20 may be provided in a radial form.

The secondary particle 100 has a hollow between the central portion 10 and the surface portion 20, or has a different crystal form between the central portion 10 and the surface portion 20, or the central portion 10 is manufactured. Then, by manufacturing the surface portion 20 to surround the central portion 10, a difference in image between the central portion 10 and the surface portion 20 may be formed, and thus the core and the shell It may be provided in a form separated by .

The primary particles 30 may extend in a direction radiated toward the surface 20 of the secondary particles in one region inside the secondary particles. One region inside the secondary particle may be the central portion 10 of the secondary particle. In other words, the primary particles 30 may be provided in a flake type, and the cross-section of the primary particles 30 is the surface 20 of the secondary particles in the one region inside the secondary particles. It may be in the form of a rod shape extending toward the

Between the primary particles 30 having the rod shape, that is, between the primary particles 30 extending from the central portion 10 of the secondary particles in the surface portion 20 direction (D). , metal ions (eg, lithium ions) and an electrolyte may be provided. Accordingly, in the positive electrode active material according to the embodiment of the present invention, the charging/discharging efficiency of the secondary battery may be improved.

For example, at least a portion of the primary particles may be provided to have a length in a c-axis direction, which is a minor axis, and a length in an a-axis direction, which is a major axis. For example, the primary particles may have a longer length in the a-axis direction with respect to the length in the c-axis direction, and thus may be provided in the form of a rod shape having an aspect ratio of 1 or more.

According to one embodiment, the primary particles 30 relatively adjacent to the surface portion 20 of the secondary particles rather than the primary particles 30 relatively adjacent to the central portion 10 inside the secondary particles, In a direction from the central portion 10 of the inner portion of the secondary particle toward the surface portion 20 of the secondary particle, the secondary particle may have a longer length. In other words, in at least a portion of the secondary particles extending from the central portion 10 of the secondary particles to the surface portion 20, the length of the primary particles 30 is equal to the length of the surface portion 20 of the secondary particles. The closer to , the more it can be increased.

According to one aspect of the present invention, an embodiment of the present invention may include a positive electrode active material for a lithium secondary battery, which is composed of a layered structure represented by the following formula (1).

[Formula 1]

Li _a1 Ni _x1 Mn _y1 O ₂

(In Formula 1, 0.95≤a1≤1.15, x1+y1=1, 0.5≤x1≤0.99, 0.01≤y1≤0.5)

In addition, it may include a cathode active material for a lithium secondary battery, which is represented by Chemical Formula 1, has a layered structure and is charged at a voltage of 4.4V or higher based on the cathode potential.

The positive electrode active material for a lithium secondary battery according to the present embodiment may be prepared as a sintered positive electrode active material by preparing a composite metal hydroxide containing nickel and manganese, mixing the composite metal hydroxide with a lithium compound and firing the composite metal hydroxide.

Among the composite metal hydroxides, the nickel and manganese may be provided to have a constant concentration in the entirety of the composite metal hydroxide in the form of bulk.

According to another aspect of the present invention, the positive electrode active material of the present invention may be formed of a layered structure represented by the following formula (2).

[Formula 2]

Li _a2 Ni _x2 Mn _y2 M _z2 O ₂

(In Formula 2, 0.95≤a2≤1.15, x2+y2+z2=1, 0.5≤x2≤0.99, 0.01≤y2≤0.5. 0.001≤z2≤0.05, M is tin (Sn), antimony (Sb) ), tellurium (Te), molybdenum (Mo), tantalum (Ta), tungsten (W), magnesium (Mg), aluminum (Al), boron (B), niobium (Nb), titanium (Ti), any one or more of ruthenium (Ru), zirconium (Zr), rhodium (Rh), and ilithium (Ir))

M may be an additive metal, and the average concentration of the additive metal in the positive electrode active material may be 0.01 mol% to 5 mol%, or 0.05 mol% to 2 mol%, specifically, 0.1 mol% to 2 mol%.

If the average concentration of the added metal in the total of the positive electrode active material is less than 0.1 mol%, the additive metal is not uniformly distributed throughout the primary particles constituting the secondary particles, and if it exceeds 2 mol%, the capacity may be reduced. do.

The additive metal may be prepared by being added together with the manganese and nickel (wet addition) in the process of preparing the composite metal hydroxide, or a composite metal hydroxide made of manganese and nickel may be added together with the lithium compound (dry type). adding).

In the cathode active material, a cation mixing ratio is a ratio of a transition metal present in the lithium layer, and a ratio of the transition metal in the lithium layer rather than the transition metal layer may be 1% to 12%. The layered structure includes that a lithium layer containing only lithium (Li) and a transition metal layer containing only a transition metal are alternately and regularly arranged, and the cation mixing is the lithium layer Lithium constituting the lithium and the transition metal constituting the transition metal layer facing the lithium layer may be formed by substituting each other.

The cathode active material includes lithium, a transition metal and oxygen, and the primary particles are layered in which a lithium layer containing only lithium and a transition metal layer containing only a transition metal are alternately and regularly arranged. Including a (layered) crystal structure, a cation ordering may be included in the surface portion of the secondary particle, for example, in a region within 2 μm in a direction from the outermost surface of the secondary particle to the center.

Specifically, in the positive electrode active material according to this embodiment, a lithium layer, an oxygen layer, and a transition metal layer (eg, a nickel layer, a manganese layer) are regularly formed with an oxygen layer interposed between a lithium layer made of only lithium and a manganese layer made of only manganese. It may be a layered structure in which they are alternately aligned with each other. On the other hand, the positive electrode active material according to this embodiment contains nickel and manganese, but does not contain cobalt, and thus, in the surface portion of the secondary particles of the positive electrode active material, lithium constituting the lithium layer and the transition facing the lithium layer Transition metals constituting the metal layer are substituted with each other to form a displacement, thereby forming a cation ordering ring.

In the cation ordering, only lithium exists in the lithium layer and only transition metals exist in the transition metal layer, but in the lithium layer and the transition metal layer facing each other, each lithium and transition metal are exchanged 1:1 to form an order in the form of a grid. When the lithium in the lithium layer is formed by exchanging the transition metal with the transition metal is called a lithium-transition metal layer, and the transition metal in the transition metal layer is formed by exchanging the lithium in the lithium layer is called the transition metal-lithium layer, the cation ordering structure is the lithium - It means a structure in which the transition metal layer and the transition metal-lithium layer are provided alternately and regularly.

The lattice formed by the lithium-transition metal layer and the transition metal-lithium layer may include a long range ordering lattice in which the a-axis is increased compared to the lattice formed by the lithium layer and the transition metal layer, for example, It may include a superlattice in which the a-axis is increased twice as much as the lattice formed by the lithium layer and the transition metal layer.

The cathode active material according to this embodiment has a full width at half-maximum (FWHM) of 0.03V or more for the (104) plane obtained by X-ray diffraction (XRD) analysis using Cu-kα rays, and , wherein the cathode active material includes a region in which H2-H3 phase transition is performed during charging, and a voltage of the H2-H3 phase transition region may be formed in a range of 4.12V to 4.6V.

In addition, the lattice parameter of the c-axis of the unit lattice of the positive electrode active material expands and contracts in the process of charging and discharging, and the amount of change in the lattice constant of the c-axis is 2% or less during expansion and contraction. 4.5% or less. Specifically, the lattice constant of the c-axis may be 14.5 Å or less.

In the positive electrode active material according to the present embodiment, charging at a voltage of 4.4V or higher based on the positive electrode potential may be performed in the formation step or several cycles or every cycle thereafter.

In addition, in a Nyquist plot obtained from impedance measurement, Rct (charge transfer resistance) may be 30 Ω or less at 100 cycles. The maximum exothermic peak temperature (T) measured according to a thermal stability evaluation method using a differential scanning calorimeter may be 195°C to 230°C.

The primary particles may include oriented particles provided on the surface of the secondary particles having an a-axis and a c-axis. The a-axis direction of the oriented particles may correspond to a lithium ion diffusion path.

The primary particles may further include oriented particles, and the oriented particles may be provided on a surface portion of the secondary particles. Specifically, the secondary particles may have a spherical shape having a central portion and a surface portion, and the oriented particles may be provided on a surface portion of the secondary particles, that is, a portion in contact with the electrolyte.

The oriented particles are arranged from the outermost surface of the secondary particles toward the center of the secondary particles, and thus may provide a movement path to facilitate lithium ion diffusion. In addition, since the outer surface of the secondary particles is structurally aligned by the oriented particles, the volume change of the primary particles occurring in the process of charging and discharging proceeds reversibly, thereby preventing microcracks, etc. from occurring can

The oriented particles, which are primary particles provided on the surface of the secondary particles with improved orientation, maintain an approximately constant distance between neighboring particles, and are caused by the volume change of contraction and expansion of the primary particles in the process of charging and discharging. It is possible to improve the life characteristics by suppressing the occurrence of micro-cracks.

The primary particles provided on the surface of the secondary particles may have a rod shape having a layered crystal structure having an a-axis and a c-axis, and the cathode active material includes a plurality of primary particles. It consists of agglomerated secondary particles, and the particle strength of the secondary particles may be 120 MPa to 250 MPa.

Since the positive electrode active material has a particle strength in the above-mentioned range, the electrode plate mixture density is not reduced in the process of using it for a secondary battery, and as a result, a lithium secondary battery having excellent safety and high rate characteristics can be implemented.

The positive electrode active material according to the present embodiment may include nickel-rich (Ni-rich), for example, 60 mol% or more, or 65 mol% or more, or 70 mol% or more, or 75 mol% or more, or 90 mol% or more of nickel.

According to another aspect of the present invention, a positive electrode using the above-described positive electrode active material; a negative electrode made of graphite or lithium metal facing the positive electrode; a separator interposed between the positive electrode and the negative electrode; and a lithium secondary battery comprising a; and an electrolyte or a solid electrolyte containing a lithium salt. A charging cutoff voltage of the lithium secondary battery may be 4.4V or more.

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 positive electrode active material

Production Example 1 (NC90)

After 10 liters of distilled water was put into the coprecipitation reactor (capacity 47L, 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. 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 composite metal hydroxide.

The prepared composite metal 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 mixing the composite metal hydroxide and lithium hydroxide (LiOH) prepared in powder form at a molar ratio of 1:1.01, heating was performed at a temperature increase rate of 2°C/min and maintained at 450°C for 5 hours to perform preliminary firing, followed by 730 It was calcined at ℃ for 10 hours to prepare a cathode active material powder, which is shown in Table 1.

Preparation 2 (NCM90)

After 10 liters of distilled water was put into the coprecipitation reactor (capacity 47L, 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 composite metal hydroxide.

The prepared composite metal 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 mixing the composite metal hydroxide and lithium hydroxide (LiOH) prepared in powder form at a molar ratio of 1:1.01, heating was performed at a temperature increase rate of 2°C/min and maintained at 450°C for 5 hours to perform preliminary firing, followed by 750 It was calcined at ℃ for 10 hours to prepare a cathode active material powder, which is shown in Table 1.

Preparation 3 (NM90)

After 10 liters of distilled water was put into the coprecipitation reactor (capacity 47L, 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 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 _0.9 Mn _0.1 (OH) ₂ composite metal hydroxide.

The prepared composite metal 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 mixing the composite metal hydroxide and lithium hydroxide (LiOH) prepared in powder form at a molar ratio of 1:1.01, heating was performed at a temperature increase rate of 2°C/min and maintained at 450°C for 5 hours to perform preliminary firing, followed by 770 It was calcined at ℃ for 10 hours to prepare a cathode active material powder, which is shown in Table 1.

division Ni (mol%) Co (mol%) Mn (Mol%) Preparation Example 1 NC90 90 10 0 Preparation 2 NCM90 90 5 5 Preparation 3 NM90 90 0 10

Preparation 4 (NM90)

After 10 liters of distilled water was put into the coprecipitation reactor (capacity 47L, 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 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 _0.9 Mn _0.1 (OH) ₂ composite metal hydroxide.

The prepared composite metal 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 mixing the composite metal hydroxide and lithium hydroxide (LiOH) prepared in powder form in a molar ratio of 1:1.01, heating was performed at a temperature increase rate of 2°C/min and maintained at 450°C for 5 hours to perform preliminary firing, followed by 770 By calcining at ℃ for 10 hours to prepare a cathode active material powder, which is shown in Table 2.

Preparation Example 5 (NM90-Sb0.3), Preparation Example 6 (NM90-Sb0.5), Preparation Example 7 (NM90-Sb1)

Ni _0.9 Mn _0.1 (OH) ₂ composite metal hydroxide prepared in powder form in Preparation Example 4, antimony trioxide (Sb ₂ O ₃ )[3+] as a dopant compound, and lithium hydroxide (LiOH) as described in Table 2 A cathode active material powder was prepared in the same manner as in Preparation Example 4, except for mixing in a content ratio.

Preparation 8 (NM90-Mo0.3), Preparation 9 (NM90-Mo1)

Ni _0.9 Mn _0.1 (OH) ₂ composite metal hydroxide prepared in powder form in Preparation Example 4, molybdenum trioxide (MoO ₃ ) as a dopant compound, and lithium hydroxide (LiOH) were mixed in the content ratio shown in Table 2 below. Except for that, each of the cathode active material powders was prepared in the same manner as in Preparation Example 4.

Preparation 10 (NM90-Ta1)

Ni _0.9 Mn _0.1 (OH) ₂ composite metal hydroxide prepared in powder form in Preparation Example 4, tantalum oxide (Ta ₂ O ₅ ) as a dopant compound, and lithium hydroxide (LiOH) were mixed in the content ratio shown in Table 2 below. Except for that, each of the cathode active material powders was prepared in the same manner as in Preparation Example 4.

Preparation 11 (NM90-W1)

Ni _0.9 Mn _0.1 (OH) ₂ composite metal hydroxide prepared in powder form in Preparation Example 4, tungsten trioxide (WO ₃ ) and lithium hydroxide (LiOH) as a dopant compound were mixed in the content ratio described in Table 2 below, except for mixing each prepared a cathode active material powder in the same manner as in Preparation Example 4.

Preparation 12 (NM90-Mg1)

Ni _0.9 Mn _0.1 (OH) ₂ composite metal hydroxide prepared in powder form in Preparation Example 4, magnesium oxide (MgO) and lithium hydroxide (LiOH) as a dopant compound were mixed in the content ratio shown in Table 2 below, except for mixing A cathode active material powder was prepared in the same manner as in Preparation Example 4, respectively.

Preparation 13 (NM90-Al1)

Ni _0.9 Mn _0.1 (OH) ₂ composite metal hydroxide prepared in powder form in Preparation Example 4, aluminum hydroxide (Al(OH) ₃ ) as a dopant compound, and lithium hydroxide (LiOH) were mixed in the content ratio described in Table 2 below. Except for that, a cathode active material powder was prepared in the same manner as in Preparation Example 4, respectively.

Preparation 14 (NM90-B1)

Ni _0.9 Mn _0.1 (OH) ₂ composite metal hydroxide prepared in powder form in Preparation Example 4, boron oxide (B ₂ O ₃ ) as a dopant compound, and lithium hydroxide (LiOH) were mixed in the content ratio shown in Table 2 below. Except for that, each of the cathode active material powders was prepared in the same manner as in Preparation Example 4.

Preparation 15 (NM90-Nb1)

Ni _0.9 Mn _0.1 (OH) ₂ composite metal hydroxide prepared in powder form in Preparation Example 4, niobium pentoxide (Nb ₂ O ₅ ) as a dopant compound, and lithium hydroxide (LiOH) were mixed at the content ratio shown in Table 2 below. Except for that, each of the cathode active material powders was prepared in the same manner as in Preparation Example 4.

Preparation 16 (NM90-Sn1)

Ni _0.9 Mn _0.1 (OH) ₂ composite metal hydroxide prepared in powder form in Preparation Example 4, tin dioxide (SnO ₂ ) as a dopant compound, and lithium hydroxide (LiOH) were mixed in the content ratio described in Table 2 below, except for mixing each prepared a cathode active material powder in the same manner as in Preparation Example 4.

Preparation 17 (NM90-Te1)

Ni _0.9 Mn _0.1 (OH) ₂ composite metal hydroxide prepared in powder form in Preparation Example 4, tellurium oxide (Te ₂ O ₅ ) and lithium hydroxide (LiOH) as a dopant compound were mixed in the content ratio described in Table 2 below. Except for that, a cathode active material powder was prepared in the same manner as in Preparation Example 4, respectively.

Preparation 18 (NM90-Ti0.5)

Ni _0.9 Mn _0.1 (OH) ₂ composite metal hydroxide prepared in powder form in Preparation Example 4, titanium dioxide (TiO ₂ ) and lithium hydroxide (LiOH) as a dopant compound were mixed in the content ratio described in Table 2 below, except for mixing each prepared a cathode active material powder in the same manner as in Preparation Example 4.

division Ni (mol%) Mn (Mol%) Metal Complex Hydroxide: Dopant:
Molar ratio of lithium hydroxide dopant dopant amount
(mol%) Preparation 4 NM90 90 10 1:0:1.01 - - Preparation 5 NM90-Sb0.3 90 10 0.997:0.003:1.01 Sb 0.3 Preparation 6 NM90-Sb0.5 90 10 0.995:0.005:1.01 Sb 0.5 Preparation 7 NM90-Sb1 90 10 0.99:0.01:1.01 Sb One Preparation 8 NM90-Mo0.3 90 10 0.997:0.003:1.01 Mo 0.3 Preparation 9 NM90-Mo1 90 10 0.99:0.01:1.01 Mo One Preparation 10 NM90-Ta1 90 10 0.99:0.01:1.01 Ta One Preparation 11 NM90-W1 90 10 0.99:0.01:1.01 W One Preparation 12 NM90-Mg1 90 10 0.99:0.01:1.01 Mg One Preparation 13 NM90-Al1 90 10 0.99:0.01:1.01 Al One Preparation 14 NM90-B1 90 10 0.99:0.01:1.01 B One Preparation 15 NM90-Nb1 90 10 0.99:0.01:1.01 Nb One Preparation 16 NM90-Sn1 90 10 0.99:0.01:1.01 Sn One Preparation 17 NM90-Te1 90 10 0.99:0.01:1.01 Te One Preparation 18 NM90-Ti0.5 90 10 0.995:0.005:1.01 Ti 0.5

2. Preparation of half-cell and full-cell using Preparation Example

A half-cell and a full-cell were manufactured using the positive electrode active material according to the above-described Preparation Example.

In order to prepare a half cell and a full cell, the positive electrode active material in the form of powder of Preparation Example (based on 1 g), poly(vinylidene fluoride), and carbon black were mixed with N-methyl in a weight ratio of 90:4.5:5.5, respectively. After adding in 0.4 g of pyrrolidine ( N -methyl pyrrolidone), the mixture was 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 with a half-cell, the positive electrode prepared as a slurry is coated on aluminum foil so that the loading level of the positive electrode active material is 5 mg/cm 2 means that the weight of only the positive active material in the positive electrode composition is 5 mg), and the electrolyte is ethylene carbonate and 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, the positive electrode is prepared by coating the positive electrode prepared as a slurry on aluminum foil so that the loading level of the positive electrode active material is 8.5 mg/cm 2 , and the graphite prepared in the slurry is applied to the copper foil with a loading level of 6.5 mg/cm 2 It was coated as much as possible, and after roll pressing, vacuum drying was performed 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 Production Examples

Each condition is individually described in each evaluation, and if there is no separate description, the following conditions were evaluated.

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

The prepared half-cell was charged at 4.3V and discharged at 2.7V with a constant current of 0.5C (1C is 180 mA/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, 2.7V-4.4V).

(2) Confirmation of capacity and cycle characteristics using full cell

Using the prepared full cell, the cycle was performed at 3.0V (discharge voltage) and 4.2V (charge voltage) at 0.5C (1C is 180 mA/g) constant current at 30°C, and the capacity and recovery capacity were checked.

(3) Confirmation of microstructure of composite metal hydroxide (positive electrode active material precursor) and positive electrode active material using SEM

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

Hereinafter, the microstructure, surface properties and electrochemical properties of the positive electrode active material according to Preparation Example were confirmed.

4 is an SEM photograph according to Preparation Example 3 (NM90). 5 is an SEM photograph of the composite metal hydroxide (a, b, c) and the positive electrode active material (d, e, f) according to Preparation Examples 1 to 3; 6 and 7 are SEM photographs of the positive electrode active material particles charged with 4.3V and 4.4V of Preparation Examples 1 to 3. 8 is a view showing XRD spectra of Preparation Examples 1 to 3; 9 is a view analyzing XRD patterns of Preparation Examples 1 to 3; 10 is a diagram illustrating a dQ/dV curve in the first charge/discharge (2.7V-4.4V) of Preparation Examples 1 to 3; 11 is a diagram showing H2-H3 phase transition in the in-situ XRD analysis of Preparation Example 3; 12 is a graph showing a-axis and c-axis lattice parameters in the in-situ XRD analysis of Preparation Examples 1 to 3; 13 is a graph showing the DSC results of Preparation Example 2 and Preparation Example 3. 14 is a Nyquist plot showing the electrochemical resistance of Preparation Examples 1 to 3; 15 is a SEM photograph of the cathode active material discharged after 100 cycles of charging and discharging at each temperature of 30° C. and 60° C. of Preparation Examples 2 and 3;

Table 3 below shows the results of confirming the residual lithium formed on the particle surface of Preparation Examples 1 to 3.

division Residual lithium (ppm) LiOH Li ₂ CO ₃ Total Preparation Example 1 NC90 6710 2721 9431 Preparation 2 NCM90 7886 2306 10172 Preparation 3 NM90 8890 1668 10558

Referring to Table 3, in Preparation Examples 1 to 3, it was confirmed that the residual lithium formed on each surface appeared almost the same.

4 is a SEM photograph of Preparation Example 3, (a) is a dark-field STEM photograph of the secondary particles of Preparation Example 3 (Dark-field STEM image), (b) is each indicated 1, 2, Areas 3 and 4 are SAED patterns of primary particles. Referring to FIG. 4 , in the positive electrode active material of Preparation Example 3, it was confirmed that lithium (Li) and manganese (Mn) had a cation ordering in which the positions of lithium (Li) and manganese (Mn) were regularly exchanged with each other on the surface of the secondary particles. For example, in the case of Preparation Example 3, in the case of cation ordering, it was confirmed that lithium and manganese were regularly replaced within 2 μm in the direction from the outermost surface of the secondary particle, which is the surface of the secondary particle, to the center of the secondary particle.

5 is an SEM photograph (a, b, c) of the composite metal hydroxide particles before the firing of Preparation Examples 1 to 3 to prepare a positive electrode active material, and SEM photographs (d, e, f) of the positive electrode active material particles after firing It is shown that the particle shape of Preparation Examples 1 to 3 in each of the composite metal hydroxide before firing and the positive electrode active material after firing is determined to be similar.

6 and 7 are SEM photographs showing the cross-sections of particles after primary charging with cut-off voltages of 4.3V (a) and 4.4V (b) for Preparation Example 1, Preparation Example 2, and Preparation Example 3, respectively. Referring to FIG. 6 , it was confirmed that microcracks occurring in the particle cross section were alleviated when charging in the order of Preparation Example 3, Preparation Example 2, and Preparation Example 1, which was further improved at 4.4V, a voltage higher than 4.3V. could be seen clearly.

8 and 9 are results of analysis of X-ray diffraction (XRD) patterns using Cu-Kα of Preparation Examples 1, 2, and 3; (a) of FIG. 8 shows the XRD pattern, (b) is an enlarged ratio of the intensity of the (104) plane peak to the (003) plane peak in the XRD spectrum, (c) is each a-axis and c-axis This is the result of calculating the lattice constant.

Table 4 below shows the results of confirming the cation mixing for each of Preparation Examples 1 to 3 analyzed based on the chemical composition of the positive electrode active material analyzed by ICP-OES and FIGS. 8 and 9 .

division Chemical composition (mol %) Cathode Li ⁺ /Ni ²⁺ cation mixing Ni Co Mn Preparation Example 1 NC90 90.5 9.5 0 Li[Ni _0.90 Co _0.10 ]O ₂ 0.70% Preparation 2 NCM90 90.2 4.9 4.9 Li[Ni _0.90 Co _0.05 Mn _0.05 ]O ₂ 1.80% Preparation 3 NM90 90.4 0 9.6 Li[Ni _0.90 Mn _0.10 ]O ₂ 3.30%

Cationic mixture refers to a form in which lithium and transition metal exchange positions. The cation mixing ratio was confirmed by comparing the intensity ratio of the peak corresponding to the (003) plane (the peak having 2θ approximately 18 to 19) and the peak corresponding to the (104) plane (the peak having 2θ approximately 44.5). Specifically, the cation mixture was a value obtained through an operation called Rietveld refinement, and was confirmed by calculating the value using a program. In the program, the crystal structure model was set, refined to have the same plot as the measured XRD spectra, and then the value was read and confirmed.

The peak corresponding to the (003) plane means a layered structure in the cathode active material, and the peak corresponding to the (104) plane has a structure different from the layered structure (eg, cubic structure, rock salt structure, etc.) It means a mixed structure, and as I ₍₀₀₃₎ /I ₍₁₀₄₎ increases, the cation mixing ratio decreases.

In FIG. 10, while performing the first charging and discharging of Preparation Examples 1 to 3 at 2.7V-4.4V, the dQ/dV curve was analyzed to compare the H2-H3 phase transition peak widths. In the dQ/dV curve, it was confirmed that the peak shape of the H2-H3 phase transition, which plays a major role in long-term lifespan characteristics, was formed in a broad range in the order of Preparation Example 3, Preparation Example 2, and Preparation Example 1. That is, as the manganese content of the positive electrode active material increases, the H2-H3 phase transition peak width increases, and it was confirmed that the stress within the particles caused by the anisotropic volume change was relieved.

11 is a result of confirming in-situ XRD for Preparation Example 3 prepared using a composite metal hydroxide composed of nickel and manganese as cobalt-free, and it was confirmed that the H2-H3 phase change was continued up to 4.3V or more. .

10 and 11 , the full width at half maximum (FWHM) refers to the width of the half point of the intensity height of the peak corresponding to the (003) plane (the peak having 2θ of about 44.5), and Preparation Example 1 is 0.021 V and Preparation Example 2 were 0.029V, and Preparation Example 3 was 0.035V, respectively, thereby confirming that the case of Cobalt-free as in Preparation Example 3 had a larger value. In the case of Preparation Example 3, it was confirmed that the H2-H3 phase change region was 4.12V to 4.4V, and continued up to a voltage of about 4.35V or higher.

12 is a result of confirming the change of the lattice constant of the a-axis and the c-axis according to Preparation Examples 1 to 3 in the process of charging and discharging at 4.4V. As the manganese content increases, the change in the lattice constant decreases, and cobalt-free manufacturing In the case of Example 3, it was confirmed that both the ratio of contraction and expansion of the c-axis decreased. In the case of Preparation Example 3, it was confirmed that the change rate of the c-axis lattice constant was within 2% during expansion and within 4.5% during contraction, and it was confirmed that the rate of change of the a-axis lattice constant was within 2.5% during contraction.

Table 5 below is a table showing the DSC results of Preparation Example 2 and Preparation Example 3.

division charged voltage Extracted
charge capacity peak temperature Enthalpy Preparation 2 NCM90 4.3V 225.6 191.2 ^o C 1243 J g ^-1 Preparation 3 NM90 4.3V 224.5 197.8 ^o C 754.6 J g ^-1

13 is a DSC result using an electrolyte (1.2 M LiPF ₆ , EC/EMC (3:7 (v:v)), 2wt% VC) by charging Preparation Examples 2 and 3 to 4.3V. Referring to Table 5 and FIG. 13, in Preparation Example 3, which contains a lot of manganese, the exothermic peak occurred at approximately 195°C to 230°C, and it was confirmed that it was thermally stable compared to Preparation Example 2.

Table 6 below shows the results showing the particle strength of Preparation Examples 1 to 3 and the resistance according to the number of cycles (1 time, 25 times, 50 times, 75 times, and 100 times).

division grain strength
(Mpa) Rct(Ω) 1st 25th 50th 75th 100th Δ(1st-100th) Preparation Example 1 NC90 99 15.24 27.07 40.37 62.42 89.65 74.41 Preparation 2 NCM90 138.6 10.89 16.28 26.11 36.31 45.73 34.84 Preparation 3 NM90 168.5 4.4 4.5 6 10.20 16.1 11.7

14 is a Nyquist plot showing the electrochemical resistance of Preparation Examples 1 to 3 after performing each 25 cycles while performing charging and discharging at 2.7V-4.3V. Rct is a value indicating charge transfer resistance on the surface of the anode during the reduction reaction of lithium ions (Li+). The resistance measurement method by EIS (electrochemical impedance spectroscopy, electrochemical spectroscopy) can be measured by flowing an alternating current using a VMP device in a charged state at 1st, 25th, 50th, 75th, and 100th time points. According to Preparation Example 3, Rct may be 30Ω or less. Comparing Rct at 100 times, it was confirmed that Preparation Example 3 had a very low value of -82% compared to Preparation Example 1.

The particle strength is measured by Equation 1 below.

(Equation 1) Grain strength (MPa) = ax (P/d ² )

In Equation 1, a is 2.8 (geometric factor), P is the test force (N), and d is the particle diameter (mm).

The particle strength was approximately 120 MPa to 200 MPa, and it was confirmed that Preparation Example 3 had the highest value, that is, when the manganese content was high and cobalt-free, the particle strength increased and the Rct value decreased.

15 is an SEM photograph of a discharged state after 100 cycles were performed at 30° C. and 60° C. with a charging voltage cutoff of 4.3 V for Preparation Examples 2 and 3; In the case of Preparation Example 3, it was confirmed that almost no microcracks occurred at both 30°C and 60°C.

16 is a graph showing the phase change of H2-H3 when the charging voltage cut-off of Preparation Examples 1 to 3 is charged to (a) 4.3V and (b) 4.4V, respectively. 17 is a graph showing a phase change when the charging voltages according to Preparation Example 3 were set to 4.23V and 4.4V, respectively, and then discharged to 4.04V. 18 is a graph illustrating rate characteristics while variously changing the cut-off of the charging voltage of Preparation Example 3; 19 and 20 are graphs showing the galvanostatic intermittent titration technique (GITT) analysis results for each of the charging voltages of Preparation Example 3 as 4.23V and 4.4V. 21 and 22 are results of confirming the discharge rate characteristics of Preparation Examples 2 and 3 by setting the charging voltages to 4.23V and 4.4V, respectively. 23 is a result of confirming the charging characteristics of 2.7V-4.4V at -10 ℃ for Preparation Examples 2 and 3.

Table 7 below shows the results of confirming the capacity micro-ratio characteristics for each charging voltage cutoff for Preparation Examples 1 to 3.

division 4.3V cut-off 4.4V cut-off 0.1C, 1st Dis-capa (mAh/g) 0.5C, 1st Dis-capa (mAh/g) 0.5C/0.1C 0.1C, 1st Dis-capa (mAh/g) 0.5C, 1st Dis-capa (mAh/g) 0.5C/0.1C Preparation Example 1 NC90 233 220.1 94.5% 235.7 221.7 94.1% Preparation 2 NCM90 231 216 93.5% 236.4 220.7 93.4% Preparation 3 NM90 226.5 207.2 91.5% 236.4 219.3 93.0%

In FIG. 16, with respect to Preparation Examples 1 to 3, (a) shows the result when the cut-off of the charging voltage is 4.3V and (b) is 4.4V. As the manganese content increased, it was confirmed that the reaction potential shifted to a high potential. In the case of 4.3V, it was confirmed that the H2-H3 phase transition was not completely completed and interrupted in the middle, and it was confirmed that the rate characteristic was low. On the other hand, in the case of charging at 4.4V, it was confirmed that the H2-H3 phase transition was completely completed and the rate characteristic was superior to that of 4.3V.

In Table 7, it was confirmed that the capacity decrease was large at 0.5C compared to 0.1C when charged to 4.3V, which confirmed that the rate characteristics worsened as the manganese content increased. On the other hand, in the case of charging at a high voltage of 4.4V, it was confirmed that the rate characteristics were similar even when the manganese content increased.

In general, the cobalt-free cathode active material has a disadvantage in that the rate characteristic is low, but as in Preparation Example 3, in the case of the cobalt-free cathode active material, when the charging voltage cutoff is performed at a high voltage of 4.4 V, the H2-H3 phase transition is completed, and the rate It was confirmed that the characteristics also had similar results to Preparation Examples 1 and 2 containing relatively little manganese.

Table 8 shows the results of confirming the rate characteristics for each charging voltage cutoff for Preparation Example 3.

division cut-off voltage 0.1C, 1st Dis-capa (mAh/g) 0.5C, 1st Dis-capa (mAh/g) 0.5C/0.1C Preparation 3 NM90 4.03 V 158.2 138.9 87.8% 4.13 V 176.2 159 90.2% 4.23 V 203.7 175.4 86.1% 4.30 V 227.9 206.1 90.4% 4.40 V 236.4 219.3 93.0%

17 is a graph showing the charging at 4.23V and 4.4V, respectively, and discharging to 4.04V at 5C for Preparation Example 3, respectively. In the case of charging and discharging only to 4.23V, where the H2-H3 phase transition is not completed, the phase could not be recovered quickly due to slow kinetics. could

18 and Table 8, the rate characteristics for each charging voltage were confirmed for Preparation Example 3, and as a result of evaluating the capacity for each rate of 0.5C/0.1C for each charging voltage cutoff, a plot reversed with respect to the peak of dQ/dV Appearance was confirmed, which was similar to the result of GITT (galvanostatic intermittent titration technique). That is, in the case of Preparation Example 3 having a high manganese content, since the H2-H3 phase transition is completed at 4.3V (half-cell basis) or higher, if the charge is not higher than 4.4V, the H2-H3 phase transition is not completed, so the rate characteristics during charging and discharging It was confirmed that this was lowered.

Referring to FIG. 19, when charging to 4.23V and 4.4V at 0.1C using Preparation Example 3, respectively, when analyzing the discharge GITT and the charging GITT, there is no significant change in the overall value, but when charging to 4.4V, the discharge H1 part when recharging, and H1 when recharging. It was confirmed that the resistance in the H3 part was reduced.

Referring to FIG. 20 , in Preparation Example 3, it was confirmed that the capacity was expressed more effectively than when charging at 4.3V at 4.4V even at dQ/dV. This is a result corresponding to a lower resistance value in the EIS result described above. In addition, a difference was confirmed in the XRD peak.

Table 9 shows the results of confirming the efficiency for each C-rate by charging 4.3V and 4.4V for Preparation Example 2 and Preparation Example 3, respectively.

4.3V 4.4V rate NCM90 NM90 Gap rate NCM90 NM90 Gap 0.2C 100.0% 100.0% 0.0% 0.2C 100.0% 100.0% 0.0% 0.5C 96.5% 95.7% 0.8% 0.5C 95.9% 95.9% 0.0% 1C 93.3% 91.9% 1.4% 1C 92.6% 92.5% 0.1% 2C 90.0% 87.7% 2.3% 2C 89.4% 89.2% 0.2% 5C 85.4% 82.0% 3.4% 5C 85.1% 84.4% 0.7%

Referring to FIG. 21 together with Table 9, comparing Preparation Example 2 and Preparation Example 3, NM90 of Preparation Example 3 has a relatively low rate characteristic at 4.3V, but when charged at 4.4V, the rate characteristic of Preparation Example 2 and It was confirmed that the characteristics were similar. In addition, as a result of dQ/dV, in Preparation Example 3, hysteresis of the H2-H3 peak was observed during discharging when charging at 4.3V.

Referring to FIG. 22 , as a result of charging Preparation Example 2 (NCM90) and Preparation Example 3 (NM90) to 4.3V and 4.4V, respectively, Preparation Example 3 in the process of evaluating the rate characteristics after 4.3V charging, charging H2- The H3 peak was not completed and was cut off in the middle, and hysteresis was severe in the discharge H2-H3 peak. That is, during reversible charging and discharging, since it acts as a resistance in the phase transition of discharge, irreversibility is increased, which is judged to act as a resistance in capacity expression during discharge. On the other hand, in the case of charging Preparation Example 3 to 4.4V, it was confirmed that, unlike charging at 4.3V, hysteresis did not appear at the peak of discharge H2-H3.

22, (a) is a result showing the position (position) of the discharge H2-H3 peak, Preparation Example 3 showed a lower potential compared to other results at 4.3V. Referring to (b) of FIG. 22, when the rate characteristics of 4.3V and 4.4V in Preparation Example 2 are evaluated, it can be confirmed that the position of the H2-H3 peak hardly occurs, but in Preparation Example 3, it is large. It is considered that the influence of the charging potential has a large effect. In (c) of FIG. 22, it was confirmed that the hysteresis of the H2-H3 peak was large during 4.3V charging and discharging in Preparation Example 3.

23 is a result of charging and discharging Preparation Example 2 and Preparation Example 3 at 2.7V-4.4V at a low temperature of -10°C. When the 0.5C capacity was confirmed for Preparation Example 2 and Preparation Example 3, respectively, by using 4.3V as the charging voltage cutoff at 0°C, it was confirmed that Preparation Example 3 showed approximately 27.8mA/h less. On the other hand, when charging and discharging was performed at -10°C at 2.7V-4.4V, Preparation Example 3 was lower by about 14.2mA/h. That is, when the charging voltage cut-off was performed at 4.4V at -10°C, which is lower than 0°C, it was confirmed that the capacity difference between Preparation Example 2 and Preparation 3 was reduced.

24 is an SEM photograph of the composite metal hydroxide according to Preparation Example 4. 25 is a SEM photograph of the positive electrode active material according to Preparation Example 4. 26 is an SEM photograph of the positive electrode active material according to Preparation Example 6. 27 is an SEM photograph of the positive electrode active material according to Preparation Example 9; 28 is a graph showing the phase change of H2-H3 according to the charging voltage according to Preparation Examples 4 to 7; 29 is a graph showing the H2-H3 phase change according to the charging voltage according to Preparation Example 4, Preparation Example 8, and Preparation Example 9; 30 is a graph showing the phase change of H2-H3 according to the charging voltage according to Preparation 4 and Preparation Example 10; 31 is a graph showing the phase change of H2-H3 according to the charging voltage according to Preparation 4 and Preparation Example 11; 32 is a graph showing the phase change of H2-H3 according to the charging voltage according to Preparation 4 and Preparation Example 12; 33 is a graph showing the H2-H3 phase change according to the charging voltage according to Preparation 4 and Preparation Example 16; 34 is a graph showing the H2-H3 phase change according to the charging voltage according to Preparation Examples 4 to 6, Preparation Example 8, Preparation Example 16. 35 is a graph showing the phase change of H2-H3 according to the charging voltage according to Preparation Example 4 and Preparation Examples 9 to 14.

In the following, the effect of the doping of the additive metal in the cobalt-free positive electrode active material was confirmed.

24 is an SEM photograph of NM90 composite metal hydroxide, mixed with a lithium compound and calcined. It is confirmed that a plurality of primary particles are composed of agglomerated secondary particles, and the primary particles have an a-axis and a c-axis, but develop into a rod shape in which the length in the c-axis direction is longer than the length in the a-axis direction. could It was confirmed that, when comparing the center and the surface portion, the primary particles developed in the direction from the center to the surface portion, but the rod shape in the surface portion was provided in a more developed form than the center portion.

25 is a SEM photograph of a positive electrode active material (sintered body) after mixing a lithium compound with NM90 composite metal hydroxide of Preparation Example 4 and sintering at a high temperature. 26 is a SEM photograph of a positive electrode active material (sintered body) after mixing and mixing 0.5 mol% of a lithium compound and an antimony (Sb) compound together with NM90 composite metal hydroxide of Preparation Example 6 and firing at a high temperature.

In Preparation Examples 4 and 6, NM90 composite metal hydroxide before firing is a material prepared by the same method, and has an approximately similar shape as shown in FIG. 24 . On the other hand, after firing, in Preparation Example 4, the primary particles were expanded or adjacent primary particles were agglomerated with each other so that the volume was increased, whereas in Preparation Example 6, the rod shape was developed differently from Preparation Example 4. could check

That is, in the process of firing, the volume of the primary particles expands, but it was confirmed that Preparation Example 6 produced less than Preparation Example 4, and in Preparation Example 6, the primary particles after firing were directed toward the center of the secondary particles. It can be confirmed that they are arranged to have . That is, in the case of the cobalt-free cathode active material, it was confirmed that by doping antimony, the expansion of the primary particles during the firing process was reduced and the shape and arrangement of the rod shape were controlled to be maintained.

In FIG. 27, as in Preparation Example 9, when molybdenum, not antimony, was added, similarly, it was confirmed that the expansion of the primary particles during the firing process was reduced and the rod shape shape/arrangement was maintained.

Table 10 below shows the results of confirming the electrochemical properties according to the addition of antimony (Sb).

division Dopant cut-off voltage 0.1C Dis-capa (mAh/g) 1st ^Efficiency 0.2C Capacity (mAh/g) 0.2/0.1C 0.5C Capacity (mAh/g) 0.5C/0.1C cycle NM90 Pristine 4.3 V 226.5 95.0% 220 97.1% 207.2 91.5% 100 4.4 V 236.4 99.0% 229.4 97.0% 219.3 92.8% 100 NM90-Sb0.3 Sb 0.3% 4.3 V 225.9 95.7% 214.7 95.0% 196.9 87.2% 18 4.4 V 234.8 101.1% 227.6 96.9% 216 92.0% 100 NM90-Sb0.5 Sb 0.5% 4.3 V 226 96.4% 216 95.6% 199.3 88.2% 8 4.4 V 238.3 100.5% 230.2 96.6% 216.5 90.8% 100 NM90-Sb1 Sb 1.0% 4.4 V 231.5 101.2% 222 95.9% 205.5 88.8% 9

Referring to FIG. 28 and Table 10, when antimony was added, it was confirmed that at 4.3 V, there was little difference between the case without the addition and the case of adding antimony, or exhibiting lower rate characteristics. On the other hand, when 4.4V is charged, it can be seen that the 0.5C/0.1C rate characteristics are improved by 1.3%, 4.8%, and 2.6%, respectively, higher than when 0 mol%, 0.3mol%, and 0.5mol% of antimony are not added. there was.

When antimony is added, the H2-H4 phase shift is shifted to a higher voltage range, so when charging up to 4.3 V, the effect of antimony doping is rather low in the rate characteristic, whereas the rate characteristic is improved at 4.4 V was able to confirm

In addition, both 4.3V and 4.4V showed that the long-term cycle performance was improved when antimony was added.

Table 11 below shows the results of confirming the electrochemical properties according to the addition of molybdenum (Mo).

division
Dopant
cut-off voltage
0.1C Dis-capa (mAh/g)
1st ^Efficiency
0.2C Capacity (mAh/g)
0.2/0.1C
0.5C Capacity (mAh/g)
0.5C/0.1C
cycle
capacity retention
Preparation 4
NM90
Pristine
4.3 V
226.5
95.00%
220
97.10%
207.2
91.50%
100
93.10%
4.4 V
236.4
99.00%
229.4
97.00%
219.3
92.80%
100
87.10%
Preparation 8
NM90-Mo0.3
Mo 0.3%
4.3 V
223.2
95.10%
212.2
95.10%
195.7
87.70%
31
98.50%
4.4 V
233.5
100.40%
225.7
96.70%
214.2
91.70%
100
91.40%
Preparation 9
NM90-Mo1
Mo 1%
4.3 V
222.2
94.40%
209.8
94.40%
191.6
86.20%
25
99.30%
4.4 V
234
100.10%
226.3
96.70%
214.5
91.60%
100
92.80%
4.45 V
236.5
99.90%
229.5
97.10%
219.5
92.80%
32
96.70%

Referring to FIG. 29 and Table 11, it was confirmed that even when molybdenum was added, the 0.5C/0.1C rate characteristic was low at 4.3V, which is a low voltage, as compared to Preparation Example 4, which was not added. It is judged that this is because the potential of the H2-H3 phase change has shifted to a high potential by the addition of ribdenium.

On the other hand, the 0.5C/0.1C rate characteristics confirmed by charging at 4.4V showed that the rate characteristics were 1.3%, 4% and 5.4% as the molybdenum content increased at 0 mol%, 0.3 mol%, and 1 mol% of molybdenum, respectively. It can be seen that there is a corresponding increase.

In terms of long lifespan, it was confirmed that the anode material to which molybdenum was added was superior to both 4.3V and 4.4V.

Table 12 below shows the results of confirming the electrochemical properties according to the addition of tantalum (Ta).

division
Dopant
cut-off voltage
0.1C Dis-capa (mAh/g)
1st ^Efficiency
0.2C Capacity (mAh/g)
0.2/0.1C
0.5C Capacity (mAh/g)
0.5C/0.1C
cycle
capacity retention
Preparation 4
NM90
Pristine
4.3 V
226.5
95.0%
220
97.1%
207.2
91.5%
100
93.1%
4.4 V
236.4
99.0%
229.4
97.0%
219.3
92.8%
100
87.1%
Preparation 10
NM90
-Ta1
Ta 1%
4.3 V
223.9
95.6%
210.5
94.0%
189.5
84.7%
3
100.4%
4.4 V
236.8
100.8%
228.3
96.4%
213.1
90.0%
100
92.9%

Referring to FIG. 30 and Table 12, comparing the case where tantalum was added and the case where it was not added, it was confirmed that the rate characteristic was more effective at 4.4V when tantalum was added. Comparing 4.3V and 4.4V, it was confirmed that 0.5C/0.1C increased by 1.3% in Preparation Example 4 without tantalum, but 0.5C/0.1C increased by 5.3% when 1 mol% of tantalum was added. could

In terms of long life, it was confirmed that the addition of tantalum was more effective.

Table 13 below shows the results of confirming the electrochemical properties according to the addition of tungsten (W).

division
Dopant
cut-off voltage
0.1C Dis-capa (mAh/g)
1st ^Efficiency
0.2C Capacity (mAh/g)
0.2/0.1C
0.5C Capacity (mAh/g)
0.5C/0.1C
cycle
capacity retention
Preparation 4
NM90
Pristine
4.3 V
226.5
95.0%
220
97.1%
207.2
91.5%
100
93.1%
4.4 V
236.4
99.0%
229.4
97.0%
219.3
92.8%
100
87.1%
Preparation 11
NM90-W1
W 1%
4.3 V
219.3
95.8%
207.8
94.8%
190.7
87.0%
3
100.2%
4.4 V
231.9
100.3%
224
96.6%
212.3
91.6%
100
92.4%

Referring to FIG. 31 and Table 13, it was confirmed that the voltage band of the H2-H3 phase transition peak shifted to a high voltage by adding tungsten. Accordingly, when the 4.3V charging case and the 4.4V charging case were compared, it was confirmed that the 4.4V charging case significantly improved the rate characteristics due to the addition of tungsten. In addition, it was confirmed that the lifespan characteristics were also improved by the addition of tungsten.

Table 14 below shows the results of confirming the electrochemical properties according to the addition of magnesium (Mg).

division
Dopant
cut-off voltage
0.1C Dis-capa (mAh/g)
1st ^Efficiency
0.2C Capacity (mAh/g)
0.2/0.1C
0.5C Capacity (mAh/g)
0.5C/0.1C
cycle
capacity retention
Preparation 4
NM90
Pristine
4.3 V
226.5
95.0%
220
97.1%
207.2
91.5%
100
93.1%
4.4 V
236.4
99.0%
229.4
97.0%
219.3
92.8%
100
87.1%
Preparation 12
NM90-Mg1
Mg 1%
4.3 V
220.1
94.3%
210
95.4%
195.4
88.7%
10
99.5%
4.4 V
231.9
100.0%
224.2
96.7%
213.5
92.1%
100
88.4%
4.45 V
233.6
99.7%
225.7
96.6%
214.8
92.0%
12
97.40%

Referring to FIG. 32 and Table 14, it was confirmed that the effect at 4.4V was greater than the effect at 4.3V by the addition of magnesium. This is considered to be because the H2-H3 phase transition voltage band shifted to a high potential during charging and discharging in the cobalt-free positive electrode active material by adding an additive metal, as described above.

On the other hand, it could be confirmed that even when magnesium was added, the lifespan characteristics were similar to those in which magnesium was not added. That is, it was confirmed that the effect of improving the rate characteristics obtained by doping the additive metal and the effect of improving the life characteristics did not show the same improvement.

Table 15 below shows the results of confirming the electrochemical properties according to the addition of titanium (Ti).

division
Dopant
cut-off voltage
0.1C Dis-capa (mAh/g)
1st ^Efficiency
0.2C Capacity (mAh/g)
0.2/0.1C
0.5C Capacity (mAh/g)
0.5C/0.1C
cycle
capacity retention
Preparation 4
NM90
Pristine
4.3 V
226.5
95.0%
220
97.1%
207.2
91.5%
100
93.1%
4.4 V
236.4
99.0%
229.4
97.0%
219.3
92.8%
100
87.1%
Preparation 18
NM90-Ti0.5
Ti 0.5%
4.3 V
220.1
93.8%
209.7
95.3%
196.3
89.2%
11
98.3%
4.4 V
232.2
99.6%
223.7
96.4%
213.2
91.8%
89
87.0%

Referring to FIG. 33 and Table 15, when comparing the cutoff of the charging voltage of 4.3V and 4.4V, it was confirmed that the effect of improving the rate characteristics obtained by adding titanium was greater when charging at 4.4V. In addition, it was confirmed that, while titanium also improved the rate characteristics similarly to magnesium, it did not significantly affect the lifespan characteristics.

Tables 16 and 17 below show the results of confirming the electrochemical characteristics of 4.4V charging according to various additive metals.

division
Dopant
cut-off voltage
0.1C Dis-capa (mAh/g)
1st ^Efficiency
0.2C Capacity (mAh/g)
0.2/0.1C
0.5C Capacity (mAh/g)
0.5C/0.1C
cycle
capacity retention
Preparation 4
NM90
Pristine
4.4 V
236.4
99.4%
227.6
96.3%
217.1
91.8%
100
86.5%
Preparation 5
NM90-Sb0.3
Sb 0.3%
234.8
101.1%
227.6
96.9%
216
92.0%
100
92.6%
Preparation 6
NM90-Sb0.5
Sb 0.5%
238.3
100.5%
230.2
96.6%
216.5
90.8%
100
91.9%
Preparation 8
NM90-Mo0.3
Mo 0.3%
233.5
100.4%
225.7
96.7%
214.2
91.7%
100
91.4%
Preparation 18
NM90-Ti0.5
Ti 0.5%
232.2
99.6%
223.7
96.4%
213.2
91.8%
89
87.0%

division
Dopant
cut-off voltage
1st ^Efficiency
0.2C Capacity (mAh/g)
0.2/0.1C
0.5C Capacity (mAh/g)
0.5C/0.1C
cycle
capacity retention
Preparation 4
NM90
Pristine
4.4 V
99.40%
227.6
96.30%
217.1
91.80%
100
86.50%
Preparation 9
NM90-Mo1
Mo 1%
100.10%
226.3
96.70%
214.5
91.60%
100
92.80%
Preparation 10
NM90-Ta1
Ta 1%
100.80%
228.3
96.40%
213.1
90.00%
100
92.90%
Preparation 11
NM90-W1
W 1%
100.30%
224
96.60%
212.3
91.60%
100
92.40%
Preparation 12
NM90-Mg1
Mg 1% (wet)
100.00%
224.2
96.70%
213.5
92.10%
100
88.40%
Preparation 13
NM90-Al1
Al 1%
100.60%
226.6
96.70%
216
92.20%
100
88.20%

Referring to FIG. 34 and Table 16, by doping the additive metal, the H2-H3 phase transition of the cobalt-free cathode active material is shifted to a higher potential, and thus it can be confirmed that the rate characteristic is more excellent at 4.4V than at 4.3V.

Referring to FIG. 35 and Table 17, it can be seen that, when the added metal is also added in the same amount of 1 mol%, the degree of voltage shift in the H2-H3 phase transition is different. On the other hand, it was found that the addition of an additive metal improved the rate characteristics at 4.4V.

As mentioned above, although the present invention has been described in detail using preferred embodiments, the scope of the present invention is not limited to specific embodiments and should be construed according to the appended claims. In addition, those skilled in the art should understand that many modifications and variations are possible without departing from the scope of the present invention.

10: central
20: surface portion
30: primary particle
100: secondary particle

Claims (15)

A cathode active material for a lithium secondary battery, which is composed of a layered structure represented by Formula 1 below:
[Formula 1]
Li _a1 Ni _x1 Mn _y1 O ₂
(In Formula 1, 0.95≤a1≤1.15, x1+y1=1, 0.5≤x1≤0.99, 0.01≤y1≤0.5) It consists of a layered structure represented by Formula 1 below,
A cathode active material for a lithium secondary battery that is charged at a voltage of 4.4V or higher based on the cathode potential:
[Formula 1]
Li _a1 Ni _x1 Mn _y1 O ₂
(In Formula 1, 0.95≤a1≤1.15, x1+y1=1, 0.5≤x1≤0.99, 0.01≤y1≤0.5) A cathode active material for a lithium secondary battery, which is composed of a layered structure represented by Formula 2 below:
[Formula 2]
Li _a2 Ni _x2 Mn _y2 M _z2 O ₂
(In Formula 2, 0.95≤a2≤1.15, x2+y2+z21, 0.5≤x2≤0.99, 0.01≤y2≤0.5. 0.001≤z2≤0.05, M is tin (Sn), antimony (Sb), Tellurium (Te), molybium (Mo), tantalum (Ta), tungsten (W), magnesium (Mg), aluminum (Al), boron (B), niobium (Nb), titanium (Ti), ruthenium ( Ru), zirconium (Zr), rhodium (Rh), and ilithium (Ir)) 4. The method according to any one of claims 1 to 3,
In the positive electrode active material, the cation mixing ratio is the ratio of the transition metal present in the lithium layer, and the cation mixing ratio is 1% to 12%,
The layered structure includes that a lithium layer containing only lithium (Li) and a transition metal layer containing only a transition metal are alternately and regularly arranged,
The positive ion mixture is a cathode active material for a lithium secondary battery formed by replacing lithium constituting the lithium layer and a transition metal constituting the transition metal layer facing the lithium layer. 4. The method according to any one of claims 1 to 3,
The positive electrode active material is made of the layered structure, and a portion within 2 μm in a direction from the outermost surface of the positive electrode active material toward the center further includes a cation ordering,
The layered structure includes that a lithium layer containing only lithium (Li) and a transition metal layer containing only a transition metal are alternately and regularly arranged,
The cation ordering is a positive electrode active material for a lithium secondary battery comprising lithium constituting the lithium layer and a transition metal constituting the transition metal layer facing the lithium layer are substituted with each other. 4. The method according to any one of claims 1 to 3,
The Full Width at Half-Maximum (FWHM) of the peak for the (104) plane obtained by X-ray diffraction (XRD) analysis using Cu-kα ray is 0.03V or more,
The cathode active material includes a region in which H2-H3 phase transition is performed during charging, wherein the voltage of the H2-H3 phase transition region is 4.12V to 4.6V. 4. The method according to any one of claims 1 to 3,
The lattice parameter of the c-axis of the unit lattice of the positive electrode active material expands and contracts during charging and discharging,
The amount of change of the lattice constant of the c-axis is 2% or less during expansion, and 4.5% or less during contraction, a cathode active material for a lithium secondary battery. 8. The method of claim 7,
The lattice constant of the c-axis is 14.5 Å or less, a cathode active material for a lithium secondary battery. 4. The method according to any one of claims 1 to 3,
Charging at a voltage of 4.4V or higher based on the positive electrode potential is a positive active material for a lithium secondary battery that is performed in the formation step or several cycles or every cycle thereafter. 4. The method according to any one of claims 1 to 3,
The positive electrode active material consists of secondary particles in which a plurality of primary particles are aggregated,
The secondary particles have a particle strength of 120 MPa to 250 MPa. 4. The method according to any one of claims 1 to 3,
In the Nyquist plot obtained from the impedance measurement, Rct (charge transfer resistance) is a cathode active material for a lithium secondary battery, including that of 30Ω or less in 100 cycles. 4. The method according to any one of claims 1 to 3,
A cathode active material for a lithium secondary battery having a maximum exothermic peak temperature (T) of 195°C to 230°C measured according to a thermal stability evaluation method using a differential scanning calorimeter. 4. The method according to any one of claims 1 to 3,
The positive electrode active material consists of secondary particles in which a plurality of primary particles are aggregated,
The primary particles are provided on the surface of the secondary particles and include oriented particles having an a-axis and a c-axis,
The a-axis direction of the oriented particles is a positive electrode active material for a lithium secondary battery comprising a corresponding to a lithium ion diffusion path (lithium ion diffusion path). A positive electrode using the positive electrode active material according to any one of claims 1 to 3;
a negative electrode made of graphite or lithium metal facing the positive electrode;
a separator interposed between the positive electrode and the negative electrode; and
A lithium secondary battery comprising; an electrolyte or a solid electrolyte containing a lithium salt. 15. The method of claim 14,
A lithium secondary battery having a charging cutoff voltage of 4.4V or more of the lithium secondary battery.

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