KR20210015707A - Cathode active material, and method of fabricating of the same - Google Patents

Abstract

A method for manufacturing a positive electrode active material is provided. The method for manufacturing a positive electrode active material includes the steps of: manufacturing a positive electrode active material precursor; and mixing and calcining the positive electrode active material precursor and a lithium salt, and controlling the calcination temperature to manufacture a positive electrode active material with controlled crystallinity and grain size. Accordingly, charge/discharge characteristics and lifespan characteristics of a lithium secondary battery including the positive electrode active material may be improved.

Description

Cathode active material, and method of fabricating of the same}

The present application relates to a positive electrode active material and a method of manufacturing the same, and more particularly, to a positive electrode active material in which crystallinity and grain size are controlled through controlling a firing temperature, and a method of manufacturing the same.

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

As the demand for lithium secondary batteries increases, research and development on positive electrode active materials used in lithium secondary batteries are in progress. For example, Korean Patent Laid-Open Publication No. 10-2014-0119621 (application number 10-2013-0150315) uses a precursor for manufacturing an excess lithium cathode active material, controls the type and composition of the metal substituted in the precursor, and the type of metal added. And by controlling the amount of addition, a secondary battery having a high voltage capacity and long life characteristics is disclosed.

One technical problem to be solved by the present application is to provide a high-capacity positive electrode active material, a method of 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 cathode active material having a long life, a method of 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 high stability, a method of 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, a method of manufacturing the same, and a lithium secondary battery including the same, in which life-deterioration characteristics are minimized according to the number of charge and discharge times.

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

In order to solve the above technical problem, the present application provides a method of manufacturing a positive electrode active material.

According to an embodiment, the method of manufacturing the positive electrode active material includes preparing a positive electrode active material precursor, and mixing and sintering the positive electrode active material precursor and a lithium salt, but controlling the sintering temperature to control crystallinity and grain size. It may include the step of preparing the positive electrode active material.

According to an embodiment, the cathode active material precursor may include Ni(OH) ₂ .

According to an embodiment, the firing of the cathode active material precursor and the lithium salt may include primary firing at a first temperature, and secondary firing at a second temperature higher than the first temperature. have.

According to an embodiment, the second temperature may include a temperature greater than 600°C and less than 650°C.

According to an embodiment, the second firing may be longer than the first firing time.

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

According to an embodiment, the positive electrode active material may include an average grain size of more than 26.282 nm and less than 68.249 nm, and 100 mol% of Ni.

According to an embodiment, the positive electrode active material has a lattice constant a value greater than 2.8749 Å and less than 2.8752 Å, a lattice constant b value greater than 2.8749 Å and less than 2.8752 Å, and a lattice constant c value greater than 14.1907 Å and less than 14.1187 Å. It may include.

According to an embodiment, the d spacing value for the (003) crystal plane of the unit lattice may be greater than 4.73024 Å and less than 4.72955 Å.

According to an embodiment, the positive electrode active'U reel may be represented by the following <Chemical Formula 1>.

<Formula 1>

LiNiO ₂

In order to solve the above technical problem, the present application provides a lithium secondary battery.

According to an embodiment, the lithium secondary battery may include a positive electrode including a positive electrode active material according to the above-described exemplary embodiment, a negative electrode on the positive electrode, and an electrolyte between the positive electrode and the negative electrode.

In the method of manufacturing a positive electrode active material according to an embodiment of the present application, a positive electrode active material is prepared by mixing and firing a positive electrode active material precursor and a lithium salt, and by controlling the firing temperature, crystallinity, grain size, and the above The size of the primary particles constituting the positive electrode active material may be controlled. Accordingly, charge/discharge characteristics and life characteristics of a lithium secondary battery including the positive electrode active material may be improved.

For example, the cathode active material precursor may be Ni(OH) ₂ , and the cathode active material may be LiNiO ₂ in which the cathode active material precursor and the lithium salt are fired at a temperature of more than 600°C and less than 650°C. In this case, the LiNiO ₂ positive electrode active material may have an average grain size of more than 26.282 nm and less than 68.249 nm, and a decrease in capacity according to the number of charging and discharging times of the secondary battery having the positive electrode active material may be minimized.

1 is a view for explaining a precursor of a positive electrode active material according to an embodiment of the present invention.
2 are SEM images of a cathode active material precursor prepared according to an embodiment of the present invention.
3 is an XRD graph of a positive electrode active material prepared according to an embodiment of the present invention.
4 and 5 are SEM photographs of positive electrode active materials prepared according to Examples 1 to 6 of the present invention.
6 is an XRD graph of positive electrode active materials prepared according to Examples 1 to 6 of the present invention.
7 is Rietveld Refinement XRD graphs of cathode active materials according to Examples 1 to 6 of the present invention.
8 is a graph measuring a grain size and a ratio of (003)/(104) of a positive electrode active material according to Examples 1 to 6 of the present invention.
9 is a graph showing BET measurement results of positive electrode active materials of Examples 1 to 6 according to an exemplary embodiment of the present invention.
10 is a TEM photograph and ED pattern of a positive electrode active material according to Example 2 of the present invention.
11 is a TEM photograph and an ED pattern of a cathode active material according to Example 4 of the present invention.
12 is a TEM photograph and ED pattern of a positive electrode active material according to Example 6 of the present invention.
13 are graphs for explaining life characteristics according to the number of charge/discharge times of the secondary battery according to Examples 1 to 6 of the present invention.
14 are graphs for explaining a change in charge/discharge capacity of a secondary battery according to Examples 1 to 6 of the present invention.
15 are graphs measuring differential capacity of secondary batteries according to Examples 1 to 6 of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the technical idea 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 content may be thorough and complete, and the spirit of the present invention may be sufficiently conveyed to those skilled in the art.

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

In addition, in various embodiments of the present specification, terms such as first, second, and third 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 component. 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 its complementary embodiment. In addition, in the present specification,'and/or' is used to mean including at least one of the elements listed before and after.

In the specification, expressions in the singular include plural expressions unless the context clearly indicates otherwise. In addition, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, elements, or a combination of the features described in the specification, and one or more other features, numbers, steps, and configurations It is not to be understood as excluding the possibility of the presence or addition of elements or combinations thereof.

Further, in the following description of the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

1 is a view for explaining a precursor of a positive electrode active material according to an embodiment of the present invention.

Referring to FIG. 1, a cathode active material precursor is prepared (S110).

The cathode active material precursor may be a transition metal hydroxide. For example, the cathode active material precursor may be nickel hydroxide (Ni(OH) ₂ ). Alternatively, as another example, the cathode active material precursor may be a hydroxide including at least one of nickel, cobalt, manganese, and aluminum.

According to an embodiment, the cathode active material precursor may be prepared by a co-precipitation method. Specifically, the cathode active material precursor may be prepared by reacting while supplying a transition metal aqueous solution, sodium hydroxide, and ammonium hydroxide into a reactor. As described above, when the cathode active material precursor is nickel hydroxide, the transition metal aqueous solution may be an aqueous nickel sulfate solution (NiSO ₄ ·H ₂ O).

The cathode active material precursor and the lithium salt may be mixed and fired to prepare a cathode active material (S120).

As described above, the cathode active material precursor may be a transition metal hydroxide, and the cathode active material may be a lithium transition metal hydroxide. For example, as described above, when the cathode active material precursor is nickel hydroxide, the cathode active material may be lithium nickel oxide, and may be represented by the following <Chemical Formula 1>. That is, the proportion of nickel excluding lithium in the composition of the positive electrode active material may be 100 mol%.

<Formula 1>

LiNiO ₂

In addition, according to an embodiment, the positive electrode active material precursor and the lithium salt may be mixed using a mechanical mixing method, and the molar ratio of lithium in the lithium salt may be relatively high compared to the transition metal of the positive electrode active material precursor. I can. For example, the molar ratio of transition metal and lithium may be 1:1.05.

After mixing the cathode active material precursor and the lithium salt, primary firing and secondary firing may be sequentially performed. The first firing is performed at a first temperature, and the second firing is performed at a second temperature higher than the first temperature, but may be performed for a longer time than the first firing time. For example, the first firing may be performed at 500° C. for 5 hours, and the second firing may be performed at a temperature greater than 600° C. and less than 650° C. for 10 hours. The first firing and the second firing may be performed in an oxygen atmosphere.

The positive electrode active material may have a form in which a plurality of primary particles are aggregated. The plurality of primary particles may be arranged in a form radiating from the center of the positive electrode active material toward the outside.

By controlling the firing temperature of the secondary firing of the cathode active material precursor and the lithium salt, crystallinity and grain size of the cathode active material may be controlled. Specifically, as the sintering temperature increases, the crystallinity of the positive electrode active material is improved, so that the grain size may increase.

According to an embodiment, the firing temperature may be greater than 600°C and less than 650°C. Accordingly, the average grain size of the positive electrode active material may be more than 26.282 nm and less than 68.249 nm, the lattice constant a value of the positive electrode active material is more than 2.8749 Å and less than 2.8752 Å, and the lattice constant b value is more than 2.8749 Å and less than 2.8752 Å, The lattice constant c value may be greater than 14.1907 Å and less than 14.1187 Å. Accordingly, charge/discharge characteristics and life characteristics of a secondary battery including the positive electrode active material may be improved.

In addition, the length of the plurality of primary particles constituting the positive electrode active material may be controlled according to the firing temperature. Unlike the above, when the firing temperature is 600° C. or less, or 650° C. or more, the grain size of the positive electrode active material and the size of the plurality of primary particles constituting the positive electrode active material may be remarkably small or large. When the size of the plurality of primary particles is remarkably small, the surface in contact with the electrolyte is widened, and the charge/discharge characteristics and life characteristics may be deteriorated due to an increase in side reactions. In addition, when the size of the plurality of primary particles is remarkably large, the length of the passage through which lithium ions move inside the plurality of primary particles is lengthened, thereby increasing the resistance to lithium ions, and thereby charging/discharging characteristics and lifespan characteristics. This can be degraded.

As described above, according to an embodiment of the present invention, the firing temperature may be greater than 600° C. and less than 650° C., and thus, charge/discharge characteristics and lifespan of a secondary battery including the positive electrode active material according to an embodiment of the present invention Characteristics can be improved.

Hereinafter, a result of evaluating the characteristics of the positive electrode active material manufactured according to a specific experimental example of the present invention will be described.

Manufacture of cathode active material and secondary battery according to Example 1

Using a co-precipitation reactor, Ni(OH) ₂ was prepared as a cathode active material precursor, and LiOH·H ₂ O was prepared as a lithium salt. Specifically, a pH of 11.00 and H ₂ O 1.6 L and NH ₄ OH 80 ml solution was added to NH ₄ OH 2 L of 2 mol of NiSO ₄ · H ₂ O 2 L and 3 moles of the addition of NaOH 5 moles of Adjusted and stirred at 800 rpm, a co-precipitation reaction was performed for 96 hours to prepare Ni(OH) ₂ .

0.2 g of the positive electrode active material precursor and 0.0952 g of the lithium salt were mixed for 10 minutes using a mortar so that the molar ratio of nickel and lithium was 1:1.05.

Thereafter, the mixture of the cathode active material precursor and the lithium salt was put into a furnace in an oxygen atmosphere, and the mixture was raised to 500°C at a rate of 3°C/min, followed by primary firing at 500°C for 5 hours. Thereafter, after raising it to 550°C at a rate of 3°C/min, secondary firing at 550°C for 10 hours, lowering the temperature to 25°C, and then putting it into a BET preprocessor to remove residual O ₂ , According to the cathode active material (LiNiO ₂ ) was prepared.

As conductive materials, 0.006 g of Super P and 0.0015 g of KS-6 were prepared, and mixed with 0.085 g of the positive electrode active material according to Example 1 using a mortar for 10 minutes. Thereafter, 0.0952 g of PVDF was mixed as a binder, mixed using a Thinky mixer, applied to an aluminum foil with a thickness of 6 μm using a doctor-blade, and dried at 100° C. for 1 hour using a vacuum oven, and 60° C. After taking out the slurry from, it was compressed using a roll presser, and dried using a vacuum oven at 100° C. for 5 hours to prepare a positive electrode.

A coin-type half-cell was prepared using an electrolyte containing 1.13 M LiPF ₆ (EC: DMC: DEC = 3: 4: 3), a positive electrode prepared by the above-described method, a lithium negative electrode, and a separator. I did.

Preparation of cathode active material and secondary battery according to Example 2

A positive electrode active material and a secondary battery according to Example 2 were manufactured by performing the same method as in Example 1, but performing secondary firing at 575°C.

Preparation of cathode active material and secondary battery according to Example 3

The same method as in Example 1 was performed, but the secondary firing was performed at 600° C. to prepare a positive electrode active material and a secondary battery according to Example 3.

Preparation of cathode active material and secondary battery according to Example 4

A positive electrode active material and a secondary battery according to Example 4 were manufactured by performing the same method as in Example 1, but performing secondary firing at 625°C.

Preparation of cathode active material and secondary battery according to Example 5

A positive electrode active material and a secondary battery according to Example 5 were manufactured by performing the same method as in Example 1, but performing secondary firing at 650°C.

Preparation of cathode active material and secondary battery according to Example 6

The same method as in Example 1 was performed, but secondary firing was performed at 700° C. to prepare a positive electrode active material and a secondary battery according to Example 6.

division Firing temperature Example 1 550℃ Example 2 575℃ Example 3 600℃ Example 4 625℃ Example 5 650℃ Example 6 700℃

2 is an SEM photograph of a cathode active material precursor manufactured according to an embodiment of the present invention, and FIG. 3 is an XRD graph of a cathode active material manufactured according to an embodiment of the present invention.

2 and 3, a Ni(OH) ₂ positive electrode active material precursor was prepared according to the above-described embodiment of the present invention, and SEM photographs were taken, and XRD measurement was performed.

As shown in Figure 2, it can be confirmed that the positive electrode active material precursor in the form of particles is generated, and as shown in Figure 3, it can be confirmed that the positive electrode active material precursor prepared according to the embodiment has a composition of Ni (OH) ₂ have.

4 and 5 are SEM pictures of positive electrode active materials prepared according to Examples 1 to 6 of the present invention, and FIG. 6 is an XRD graph of positive electrode active materials prepared according to Examples 1 to 6 of the present invention. .

4 to 6, FIGS. 4A and 4B are photographs of a positive electrode active material according to Example 1, and FIGS. 4C and 4D are a positive electrode active material according to Example 2 4 (E) and (F) are photographed of the positive electrode active material according to Example 3, Figure 4 (G) and (H) are photographed of the positive electrode active material according to Example 4 4(I) and (J) are photographs of the positive electrode active material according to Example 5, and FIGS. 4 (K) and (L) are photographs of the positive electrode active material according to Example 6.

As shown in FIGS. 4 and 5, it can be seen that the positive electrode active materials manufactured according to Examples 1 to 6 of the present invention have a form in which a plurality of primary particles are aggregated. In addition, when the firing temperature is 550℃, the shape of the primary particles is relatively non-uniform and not clearly distinguished, but as the firing temperature increases, the shape of the primary particles can be more clearly identified, and the size of the primary particles You can see that is increasing.

In addition, as shown in FIG. 6, it can be seen that all of the positive electrode active materials prepared according to Examples 1 to 6 have the same chemical composition of LiNiO ₂ .

In conclusion, it can be seen that the chemical composition of the positive electrode active materials prepared according to Examples 1 to 6 does not substantially change depending on the firing temperature, but the size of the primary particles constituting the positive electrode active material changes.

7 is a Rietveld Refinement XRD graph of cathode active materials according to Embodiments 1 to 6 of the present invention, and FIG. 8 is a grain size and (003)/() of cathode active materials according to Embodiments 1 to 6 of the present invention. 104) This is a graph measuring the ratio.

7 to 8, the Rietveld Refinement XRD of the cathode active materials according to Examples 1 to 6 was measured, the grain size was measured, and the ratio of the (003) crystal plane to the (104) crystal plane was calculated. I did.

The lattice constant, grain size, and d spacing values for the (003) plane of the unit lattice of the cathode active materials according to Examples 1 to 6 are summarized as shown in Table 2 below.

division Grid constant
a (Å) Grid constant
b (Å) Grid constant
c (Å) Grain size (nm) d spacing
(003) Example 1 2.8805 2.880 14.193 13.348 4.73092 Example 2 2.8751 2.8751 14.1835 18.067 4.72782 Example 3 2.8749 2.8749 14.1907 26.282 4.73024 Example 4 2.8766 2.8766 14.1945 45.081 4.73151 Example 5 2.8752 2.8752 14.1887 68.249 4.72955 Example 6 2.8769 2.8769 14.1905 102.362 4.73018

As can be seen in FIGS. 7, 8 and <Table 2>, it can be seen that the grain size increases as the firing temperature increases. In particular, from 550℃ to 600℃, the grain size increased to 0.25868 nm/℃ on average, increasing the grain size of 12.934 nm while increasing 50℃, but after 600℃, the grain size increased to 0.7608 nm/℃. It can be seen that the size increases significantly. In other words, it can be confirmed that the grain size of the positive electrode active material can be efficiently controlled through the firing temperature control.

In addition, it can be seen that as the firing temperature increases up to 650 °C, the ratio of (003)/(104) increases, and the ratio of (003)/(104) gradually decreases after 650 °C. That is, as the firing temperature increases to 650° C., the degree of mixing of cations (Li ions and Ni ions) in the positive electrode active material gradually decreases, and after 650° C., the mixing of cations increases.

In addition, as can be seen in <Table 2>, the amount of change in the lattice constant value of the unit lattice of the cathode active materials according to Examples 1 to 6 according to the change of the firing temperature is relatively small compared to the change amount of the grain size. I can confirm. Accordingly, it can be seen that the grain size and crystallization degree of the positive electrode active material can be controlled through the firing temperature control without changing the actual crystal structure.

9 is a graph showing BET measurement results of positive electrode active materials of Examples 1 to 6 according to an exemplary embodiment of the present invention.

Referring to FIG. 9, BET measurements of cathode active materials according to Examples 1 to 6 were performed, and specific surface area, average pore size, and total pore volume were measured as shown in Table 3 below.

division BET specific surface area
(m ² g ^-1 ) Average pore diameter
(nm) Total pore volume
(cm ³ g ^-1 ) Example 1 0.6422 42.4 0.0068 Example 2 0.0052 38.0 0.0052 Example 3 0.3907 57.1 0.0056 Example 4 0.3492 27.5 0.0024 Example 5 0.2742 31.2 0.0021 Example 6 0.3071 33.1 0.0025

10 is a TEM photograph and ED pattern of the positive electrode active material according to Example 2 of the present invention, FIG. 11 is a TEM photograph and ED pattern of the positive electrode active material according to Example 4 of the present invention, and FIG. 12 is an exemplary embodiment of the present invention. This is the TEM photo and ED pattern of the positive electrode active material according to 6.

10 to 12, TEM photographs of the positive electrode active material according to Examples 2, 4, and 6 of the present invention were taken to analyze the ED pattern. Specifically, TEM photographs were enlarged for regions I, II and III of FIGS. 10 to 12 (A) and (B), and ED patterns were analyzed for regions IV, V, and VI.

As can be seen from FIGS. 10 to 12, it can be seen that as the firing temperature increases, the grain size of the positive electrode active material increases and the size of the primary particles increases. In addition, compared to the central portion of the positive electrode active material, it can be seen that the aspect ratio of the primary particles is relatively long in the outer portion of the positive electrode active material.

13 are graphs for explaining life characteristics according to the number of charge/discharge times of secondary batteries according to Examples 1 to 6 of the present invention, and FIG. 14 is a diagram of secondary batteries according to Examples 1 to 6 of the present invention. These are graphs for explaining the change in charge/discharge capacity, and FIG. 15 is graphs measuring differential capacity of secondary batteries according to Examples 1 to 6 of the present invention.

13 to 15, the discharge capacity characteristics according to the number of charge/discharge times of the secondary batteries according to Examples 1 to 6 were evaluated, and change in charge/discharge capacity under various charge and discharge conditions (0.1C to 5C). It was measured and the differential capacity was measured.

In FIG. 15, H1 phase indicates a crystal structure in which the positive electrode active material according to the embodiments has a specific lattice constant in the c-axis direction, and H2 phase indicates that the positive electrode active material according to the embodiments has a lattice constant longer than the inherent lattice constant in the c-axis direction. The H3 phase represents a crystal structure having a lattice constant shorter than the inherent lattice constant in the c-axis direction of the positive electrode active material according to the embodiments, and the M phase represents a monoclinic crystal structure.

As can be seen from FIGS. 13 to 15, it was confirmed that the initial capacity of the secondary battery including the positive electrode active material according to Example 5 fired at 650° C. was the largest. However, regardless of the firing temperature, it can be seen that the capacity decreases as the number of charging and discharging increases. Specifically, after performing charging and discharging 300 times, the capacity of the secondary battery including the positive electrode active material fired at 550°C according to Example 1 was greatly reduced, and the positive electrode active material fired at 625°C according to Example 4 It can be seen that the capacity of the included secondary battery is reduced to the least.

In particular, in the case of a secondary battery including the positive electrode active material fired at 625°C according to Example 4, the secondary battery including the positive electrode active material according to Example 3 fired at 600°C, and Example 5 fired at 650°C. It can be seen that the secondary battery including the cathode active material according to the above, of course, has a significantly smaller capacity reduction compared to the secondary battery including the cathode active material fired at different temperatures.

In other words, when controlling the sintering temperature of the lithium salt and the cathode active material precursor, the crystallization degree and grain size of the cathode active material as well as the size of the primary particles can be controlled, and the sintering temperature of the lithium salt and the cathode active material precursor is 600°C. It can be seen that controlling the temperature above and below 650°C is an efficient method of improving the charge/discharge characteristics and life characteristics of the secondary battery.

In the above, the present invention has been described in detail using preferred embodiments, but the scope of the present invention is not limited to specific embodiments, and should be interpreted by the appended claims. In addition, those who have acquired ordinary knowledge in this technical field should understand that many modifications and variations can be made without departing from the scope of the present invention.

Claims (10)

Preparing a cathode active material precursor; And
Mixing and sintering the positive electrode active material precursor and the lithium salt, and controlling a firing temperature to prepare a positive electrode active material having crystallinity and grain size controlled.
The method of claim 1,
The cathode active material precursor is a method of manufacturing a cathode active material comprising Ni(OH) ₂ .
The method of claim 1,
The step of sintering the cathode active material precursor, and the lithium salt,
First firing at a first temperature; And
A method of manufacturing a positive electrode active material comprising the step of secondary firing at a second temperature higher than the first temperature.
The method of claim 3,
The second temperature is a method of manufacturing a positive electrode active material comprising that of less than 600 ℃ 650 ℃.
The method of claim 3,
A method for producing a positive electrode active material comprising the second firing longer than the first firing time.
The average grain size is greater than 26.282 nm and less than 68.249 nm,
A positive electrode active material containing 100 mol% Ni.
The method of claim 6,
A positive electrode active material comprising a unit lattice having a lattice constant a value of more than 2.8749 Å and less than 2.8752 Å, a lattice constant b value of more than 2.8749 Å and less than 2.8752 Å, and a lattice constant c value of more than 14.1907 Å and less than 14.1187 Å.
The method of claim 7,
A positive electrode active material comprising a d spacing value of the unit grid with respect to the (003) crystal plane is greater than 4.73024 Å and less than 4.72955 Å.
The method of claim 1,
The positive electrode active material represented by <Chemical Formula 1> below.
<Formula 1>
LiNiO ₂
A positive electrode comprising the positive electrode active material according to claim 6;
A cathode on the anode; And
Lithium secondary battery including an electrolyte between the positive electrode and the negative electrode

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