KR20160082843A - Cathode active material for a lithium secondary battery, preparation method thereof, and a lithium secondary battery containing the same - Google Patents

Abstract

The present invention relates to a positive electrode active material for a lithium secondary battery including a nickel-based lithium transition metal oxide having a layered structure, represented by chemical formula 1. In the chemical formula 1, 1 < a < 1.14, b > c, b > d, 0.4 <= b <= 0.9, 0 < c < 0.4, 0 <= d < 0.4, wherein a peak having the highest point among peaks existing in a range of 20°-25° of the diffraction angle of 2θ during X-ray diffractometry of the lithium transition metal oxide is in a range of 21.8°-22.5°, to a preparation method thereof, and to a lithium secondary battery including the same. According to the present invention, by decreasing mobility of nickel around lithium in the nickel-based lithium transition metal oxide, it is possible to prevent nickel oxide-related heterogeneity, which can reduce performance of the active material, from being generated, and accordingly, to provide a lithium secondary battery having excellent initial efficiency, capacity, and life characteristics.

Description

TECHNICAL FIELD The present invention relates to a cathode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery including the cathode active material for a lithium secondary battery. BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to a positive electrode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery including the same. More particularly, the present invention relates to a nickel-based lithium transition metal oxide having reduced nickel mobility, And a lithium secondary battery including the same. BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a positive active material for a lithium secondary battery,

Electronic and information communication industries are showing rapid development through portable, miniaturized, lightweight and high performance of electronic devices, and demand for lithium secondary batteries capable of realizing high capacity and high performance as power sources of these electronic devices is increasing rapidly. Further, as electric vehicles (EV) and hybrid electric vehicles (HEV) have been put to practical use, studies on lithium secondary batteries having high capacity and high output and excellent stability have been actively conducted.

The lithium secondary battery is manufactured by using a material capable of intercalation and disintercalation of lithium ions as a cathode and an anode and filling an organic electrolyte or a polymer electrolyte between the cathode and the anode. And electrical energy is generated by an oxidation reaction and a reduction reaction when they are desorbed.

Among the components of the lithium secondary battery, the cathode material plays an important role in determining the capacity and performance of the battery in the battery.

Lithium cobalt oxide (LiCoO ₂ ) is a cathode material that has been commercialized for the first time, and is still used as a cathode material because of its relatively excellent structural stability and mass production ease compared to other lithium transition metal oxides. However, There is a problem that the price is expensive and harmful to the human body due to limitations.

Therefore, various studies have been made on a cathode material that can replace lithium cobalt oxide. Particularly, among the lithium metal oxides having a layered structure, the Ni-rich cathode active material containing a large amount of nickel (Ni) exhibits a high capacity of 200 mAh / g or more and is regarded as a cathode material for next-generation electric vehicles and electric power storage have. In addition, nickel (Ni) is less toxic to human body than cobalt (Co), and its price is low, and research has been carried out with a lot of interest (Non-Patent Document 1).

However, since nickel tends to prefer bivalent rather than trivalent valence, nickel vacancies having a bivalent valence similar to that of lithium ions and having a lithium ion deficiency in the lithium layer due to volatilization of the raw material lithium salt during high- As a result of the incorporation of ions (Ni ^{2 +} ), there is a problem that a lithium nickel oxide having a nonstoichiometric composition is produced. In the non-stoichiometric lithium-nickel oxide, Ni ^{2 +} incorporated in the lithium layer not only interferes with the diffusion of lithium ions, but also significantly increases the irreversible area, thereby reducing the reversible capacity.

The phenomenon in which Li ⁺ (0.76 Å) and Ni ^{2 +} (0.69 Å) having the same ionic radius as each other are crystallized by changing their positions is referred to as cation mixing. As a conventional method for solving such a problem, Patent Document 1 (Korean Patent Application Laid-Open Publication No. 2013-0084361) discloses a metal cation having a larger ionic radius than Ni cation so as to prevent Ni cation mixing in the Li layer Is contained in a Li cation site or in an empty space in a crystal lattice. According to this method, the migration path of Ni ²⁺ can be partially blocked, but the metal cation may interfere with the diffusion of lithium ions (Li ⁺ ), thereby deteriorating the electrochemical characteristics of the cathode active material.

Accordingly, the present inventors have found that diffraction peaks exist in a region where the diffraction angle 2 &amp;thetas; is 20 DEG to 25 DEG in X-ray diffraction analysis using a copper target, and the peak of the peak is located between 21.8 DEG and 22.5 DEG The inventors of the present invention have completed the present invention by confirming that the occurrence of nickel oxide-related dissociation phases which can deteriorate the performance of the active material due to the low mobility of nickel around lithium is suppressed.

KR 2013-0084361 A

 Lee, Sang-Yoon, A Study on the Substitution and Surface Modification of Heterogeneous Elements to Improve the Structural Stability of Ni-rich Cathode Active Materials for Lithium Secondary Batteries, Master's Thesis, Korea University, 2013.2

A problem to be solved by the present invention is that there is a diffraction peak in the region where the diffraction angle 2? Of 20 ° to 25 ° exists in the X-ray diffraction analysis using the copper target (Cu Target) and the peak has a peak at 22.8 And a nickel-based lithium transition metal oxide disposed between the nickel-based lithium transition metal oxide and the nickel-based lithium-transition metal oxide, thereby reducing the mobility of nickel around the lithium to improve the initial efficiency, capacity, and lifetime characteristics of the battery.

Another object of the present invention is to provide a lithium secondary battery including the cathode active material.

In order to solve the above-mentioned problems, the present invention provides a nickel-based lithium-transition metal oxide having a layered structure represented by the following Chemical Formula 1, wherein X-ray diffraction using the copper target of the lithium transition metal oxide Wherein a diffraction peak exists in a region where a diffraction angle 2? Of 20 to 25 ° is analyzed and a peak of the peak is located between 21.8 ° and 22.5 °.

[Chemical Formula 1]

Li _a Ni _b Co _c Mn _d O ₂

B? D, 0.4? B? 0.9, 0 <c <0.4, 0? D <0.4 in the formula (1).

Preferably, in Formula 1, 1 < a < 1.1 and 0.9 b + c + d 1.

Ray diffraction analysis of the nickel-based lithium-transition metal oxide preferably shows no peak in the region where the diffraction angle 2 &amp;thetas; is 20 DEG to 21.8 DEG, and the peak height appearing in the range of 21.8 DEG to 22.5 DEG is the lithium transition metal oxide Of the peak height appearing in the vicinity of the diffraction angle 2 &amp;thetas; 18 DEG in the X-ray diffraction analysis.

The present invention also provides a method for producing the cathode active material and a lithium secondary battery comprising the cathode active material.

The cathode active material may be prepared by mixing a precursor represented by the following general formula (2) and a lithium source in an equivalent ratio satisfying the following equation (1): And heat-treating the mixture at 800 to 1000 占 폚.

(2)

Ni _x Co _y Mn _z (OH) ₂

In the above formula (2), x> z, x> y, 0.4 ≦ x ≦ 0.9, 0 <y <0.4, 0 ≦ z <0.4.

 [Equation 1]

1.00 < Li moles / M < 1.14

In the above formula (1), M is an x + y + z value of the above formula (2).

According to the present invention, it is possible to suppress the occurrence of nickel oxide-related dissociation phases which can deteriorate the performance of the active material by lowering the mobility of nickel around nickel in the nickel-based lithium-transition metal oxide, The conductivity can be improved and the structural stability at the time of overcharging can be improved.

Therefore, by using the positive electrode active material containing the nickel-based lithium-transition metal oxide, it is possible to provide a lithium secondary battery excellent in initial efficiency, capacity and life characteristics.

1 shows the X-ray diffraction spectra of the cathode active material prepared according to Example 1 and Comparative Example 1 in comparison.
Fig. 2 shows the X-ray diffraction spectra of the cathode active materials prepared according to Examples 1 and 2 in comparison.
Fig. 3 shows X-ray diffraction spectra of the cathode active material prepared according to Example 1 and Comparative Example 2 in comparison.
4 is a graph showing the results of charge and discharge tests of a lithium secondary battery manufactured using the cathode active material of Example 1 and Comparative Example 1. FIG.
FIG. 5 is a graph showing lifetime characteristics of a lithium secondary battery manufactured using the cathode active material of Example 1 and Comparative Example 1 in comparison. FIG.
6 is a graph showing a comparison of the conductivities of the cathode active material prepared according to Example 1 and Comparative Example 1 according to the pressure.

The present invention relates to a nickel-based lithium-transition metal oxide having a layered structure represented by the following formula (1), wherein when the lithium transition metal oxide is subjected to X-ray diffraction analysis using a copper target, And a peak of the peak is located between 21.8 DEG and 22.5 DEG. The present invention also provides a cathode active material for a lithium secondary battery.

[Chemical Formula 1]

Li _a Ni _b Co _c Mn _d O ₂

B? D, 0.4? B? 0.9, 0 <c <0.4, 0? D <0.4 in the formula (1).

Preferably, in Formula 1, 1 < a < 1.1 and 0.9 b + c + d 1.

The lithium transition metal oxide according to the present invention is a nickel-rich lithium transition metal oxide containing nickel (Ni) more than cobalt (Co) and manganese (Mn). Such a nickel-rich lithium-transition metal oxide is capable of exhibiting a high capacity and is attracting attention as a material for next-generation electrode storage, but is fundamentally suffering from commercialization due to the structural instability in which Ni ^{3 +} is present .

However, since the nickel-based lithium transition metal oxide according to the present invention has a structure in which a part of lithium is partially and regularly arranged in a layered structure, the structural stability of nickel can be achieved.

The inventors of the present invention found that the peak of the nickel-based lithium transition metal oxide having the above structure among the peaks existing in the region where the diffraction angle 2 &amp;thetas; is 20 DEG to 25 DEG in the X-ray diffraction analysis is between 21.8 DEG and 22.5 DEG (Ni ^{2 +} incorporated in the lithium layer) which can deteriorate the performance of the active material due to a decrease in the mobility of nickel around the lithium is suppressed, thereby completing the present invention . When the generation of the nickel oxide-related dissimilar phases is suppressed in this manner, it is possible to provide a lithium secondary battery which can result in improving the conductivity of the active material by providing an additional migration site to lithium and improved initial efficiency, battery capacity and lifetime characteristics have.

It is preferable that the peak height appearing between 21.8 ° and 22.5 ° falls within the range of 0.05% to 2% of the peak height appearing when the diffraction angle 2θ of the nickel-based lithium-transition metal oxide is about 18 ° in the X-ray diffraction analysis. When the peak height appearing in the range of the diffraction angle 2? Of from 21.8 ° to 22.5 ° falls within the above range, the effect of lowering the mobility of nickel is most excellent, thereby maximizing the conductivity improving effect of the active material.

In the conventional art, LiMO ₂ (M = Co, Ni, Mn) single phase as a layered lithium transition metal oxide or an excess amount of lithium is additionally added to the LiMO ₂ (M = Co, Ni, Mn) (Li ₂ MnO ₃ ) crystals are mixed in the lithium manganese oxide. In the case of the lithium manganese oxide, lithium is surrounded by a metal element having a tetravalent valence such as manganese.

However, although the lithium transition metal oxide of the layered structure according to the present invention is produced by adding an excess amount of lithium, the metal element around lithium has an average valence of trivalent. That is, even if lithium is added at a ratio higher than the total amount of transition metals (Ni, Co, and Mn) in the production step, Li ₂ MnO ₃ , which is a heterogeneous phase composed of lithium and manganese, The metal elements around lithium are not tetravalent but have an average valence of trivalent.

1 and 3, in the X-ray diffraction analysis of the nickel-based lithium-transition metal oxide produced according to Example 1 of the present invention, no peaks were observed in the region where the diffraction angle 2θ was 20 ° to 21.8 ° Can be confirmed. When the Li ₂ MnO ₃ phase is present, a strong peak near 21 ° and a shoulder peak between 21 ° and 21.8 ° are observed in the region of 20 ° to 21.8 ° in which the diffraction peak originates from the Li ₂ MnO ₃ phase. . For example, in the lithium transition metal oxide of Comparative Example 2 containing a Li ₂ MnO ₃ phase, a peak was found in the range of 20 ° to 21.8 °.

The present invention also provides a method of producing a cathode active material comprising the nickel-based lithium-transition metal oxide. Specifically, the cathode active material is prepared by mixing a precursor represented by the following formula (2) and a lithium source in an equivalent ratio satisfying the following formula (1): And heat-treating the mixture at 800 to 1000 占 폚.

(2)

Ni _x Co _y Mn _z (OH) ₂

In the above formula (2), x> z, x> y, 0.4 ≦ x ≦ 0.9, 0 <y <0.4, 0 ≦ z <0.4.

 [Equation 1]

1.00 < Li moles / M < 1.14

 In the above formula (1), M is an x + y + z value of the above formula (2).

More preferably, the Li mole / M may be 1.01 to 1.05.

When the ratio (Li mole number / M) of lithium mole number to M calculated according to the above-mentioned formula (1) is 1 or less, LiMO ₂ in which no peak exists in the region where the diffraction angle 2? Ni, Mn) single phase positive electrode active material can be formed. On the other hand, when the ratio is 1.14 or more, a positive electrode active material including a Li ₂ MnO ₃ phase having a peak in a region where the diffraction angle 2θ is 20 ° to 21.8 ° is formed .

If the heat treatment temperature is less than 800 ° C, a cathode active material containing a Li ₂ MnO ₃ phase having a peak within a range of 20 ° to 21.8 ° may be formed. If the heat treatment temperature is higher than 1000 ° C, The particle size is excessively increased and the battery characteristics may be reduced.

Further, the present invention provides a lithium secondary battery including the cathode active material. The lithium secondary battery may include a cathode including the cathode active material, a cathode including the anode active material, a separator, and a non-aqueous electrolyte. The structure and manufacturing method of the lithium secondary battery are known in the technical field of the present invention and can be appropriately selected without departing from the scope of the present invention.

For example, the positive electrode is prepared by applying a composition for forming a positive electrode active material containing a positive electrode active material and a binder according to the present invention to a positive electrode collector, drying and then rolling.

The binder serves to bind the positive electrode active materials and to fix them to the current collector. Any binders used in the technical field can be used without limitation, and preferable examples include polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl And may be at least one selected from the group consisting of polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, polyethylene, polypropylene, styrene butylene rubber and fluorine rubber.

The composition for forming a positive electrode active material may further include a solvent such as NMP (N-methyl-2-pyrrolidone) and an oligomer such as polyethylene or polypropylene to the positive electrode active material and the binder; A filler made of a fibrous material such as glass fiber, carbon fiber, or the like. Further, it may further include conductive agents known in the art such as hard carbon, graphite, carbon fiber, and the like.

The cathode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and examples thereof include copper, stainless steel, aluminum, nickel, titanium, fired carbon; Surfaces of copper and stainless steel surface treated with carbon, nickel, titanium or silver; Aluminum-cadmium alloy, and the like, and various shapes such as a film, a sheet, a foil, a net, a porous body, a foaming agent, and a nonwoven fabric can be used.

The negative electrode may be prepared by applying a composition for forming an anode active material containing an anode active material on an anode current collector, drying and then rolling the anode active material, or may be lithium metal. The composition for forming the negative electrode active material may further include the binder and the conductive material.

The negative electrode active material may be selected from the group consisting of carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber and amorphous carbon, lithium and silicon, aluminum (Al), tin (Sn), lead (Pb) Metal alloys capable of alloying such as bismuth (Bi), indium (In), manganese (Mg), gallium (Ga), cadmium (Cd), silicon alloys, tin alloys, aluminum alloys and the like, And the like.

The negative electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery, and examples thereof include copper, stainless steel, aluminum, nickel, titanium, sintered carbon; Surfaces of copper and stainless steel surface treated with carbon, nickel, titanium or silver; Aluminum-cadmium alloy, and the like, and various shapes such as a film, a sheet, a foil, a net, a porous body, a foaming agent, and a nonwoven fabric can be used.

The separator is disposed between a cathode and an anode and is a conventional porous polymer film used as a conventional separator, for example, an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate A porous polymer film made of a polyolefin-based polymer such as a copolymer or the like may be used alone or in a laminated form. Further, a nonwoven fabric made of a conventional porous nonwoven fabric, for example, glass fiber of high melting point, polyethylene terephthalate fiber or the like can be used.

The non-aqueous electrolyte is composed of an electrolytic solution and a lithium salt. As the electrolytic solution, non-aqueous organic solvents, organic solid electrolytes, inorganic solid electrolytes, and the like may be used.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma -Butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane , Acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate Nonionic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyrophosphate, ethyl propionate and the like can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, A polymer containing an ionic dissociation group and the like may be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide.

The secondary battery can be divided into a coin type, a square type, a cylindrical type, a pouch type, and the like, and the structure and manufacturing method of the secondary battery are known in the art.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these embodiments.

Example  One

_{Ni 0 .6 Co 0 .2 Mn 0} .2 (OH) 1 ₂ precursor and LiOH: then a solution of an equivalent ratio (Li mole number / M = 1.01) of 1.01, and heat treated at a temperature of 850 ℃ LiNi _{0 .6} Co _{0 .2} Mn _{0 .2} O ₂ for the positive electrode active material was prepared having a composition.

Example  2

_{Ni 0 .5 Co 0 .2 Mn 0} .3 (OH) 2 precursor and a LiOH 1: then a solution of an equivalent ratio (Li mole number / M = 1.02) of 1.02, and heat treated at a temperature of 850 ℃ LiNi _{0 .5} Co _{0 .2} Mn _{0 .3} O ₂ for the positive electrode active material was prepared having a composition.

Comparative Example  One

_{Ni 0 .6 Co 0 .2 Mn 0} .2 (OH) 2 precursor and a LiOH 1: then a solution of an equivalent ratio (Li mole number / M = 1.00) in the first, heat-treated at a temperature of 850 ℃ LiNi _{0 .6} Co _{0 .2} Mn _{0 .2} O ₂ for the positive electrode active material was prepared having a composition.

Comparative Example  2

_{Ni 0 .2 Co 0 .2 Mn 0} .6 (OH) 2 precursor and LiOH to 1 equivalent ratio of 1.4 was mixed in (Li mole number / M = 1.40), heat treated at a temperature of 700 ℃ Li _{1 .17} Ni _{0 .17 Co 0 .17 Mn 0 .5} O 2 for the positive electrode active material was prepared having a composition.

<X-ray diffraction peak analysis of the positive electrode active material>

1 showing the X-ray diffraction spectrum of the cathode active material prepared according to Example 1 and Comparative Example 1 in comparison with FIG. 1, in the case of the cathode active material of Example 1, the diffraction peak And the highest peak of the peak is located between 21.8 ° and 22.5 °, whereas the cathode active material of Comparative Example 1 has the same composition as the cathode active material of Example 1, but the peak or peak of the peak is located in the region Do not.

2 showing a comparison of the X-ray diffraction spectra of the cathode active materials prepared according to Examples 1 and 2, as the content of nickel increases, the peaks appearing in the region where the diffraction angle 2? Is in the range of 21.8 ° to 22.5 ° It can be confirmed that the size is different from that of the cathode active material of Comparative Example 2 in terms of position and relative size.

That is, the X-ray diffraction spectrum of the cathode active material prepared in Example 1 and Comparative Example 2 was compared with that of Comparative Example 2. In the X-ray diffraction spectrum of the cathode active material according to Comparative Example 2, And a shoulder peak between 21 deg. And 21.8 deg., While the X-ray diffraction spectrum of Example 1 shows no peak at 20 deg. To 21.8 deg. This demonstrates that the positive electrode active material of Comparative Example 2 as a peak derived from the Li ₂ MnO ₃ is a does not include the cathode active material of Example 1 while containing Li ₂ MnO ₃ is a.

<Performance evaluation of lithium secondary battery>

1. Preparation of lithium secondary battery

The cathode active material, the conductive agent DenkaBlack, and the binder polyvinylidene fluoride (PVDF) prepared in Example 1 and Comparative Example 1 were mixed in a ratio (w / w) of 92: 4: 4, To prepare a positive electrode plate. A coin cell was fabricated using lithium metal as the cathode and 1.3M LiPF ₆ EC / DMC / EC = 3: 4: 3 solution as the electrolyte.

2. Cell Formation

The prepared coin cell was allowed to stand at a constant temperature of 25 DEG C for 24 hours and then subjected to a constant current of 0.1 C at a constant current of 4.3 V using a lithium secondary battery charge / discharge device (Toyo-System Co., LTD, TOSCAT- C was charged under a constant voltage condition with a termination current and discharged at 0.1 C to 2.8 V under a constant current condition to complete the cell formation process. The initial efficiency was determined according to the following formula (1) in the above-mentioned formation process.

The initial efficiency (%) = (discharge capacity / charge capacity at 1 ^st cycle of the 1 ^st cycle)

              × 100 ... (One)

3. Evaluation of life characteristics

After completion of the formation, the cells were charged and discharged at a current of 1.0 C to repeat 50 cycles. Capacity retention was obtained according to the following formula (2), and the lifetime characteristics were evaluated. The results are shown in Table 1.

Capacity retention rate (%) = (discharge capacity in 50 ^th cycle / discharge capacity in 1 ^st cycle)

                × 100 ... (2)

4. Conductivity measurement

The cathode active material prepared in Example 1 and Comparative Example 1 was measured for electronic conductivity while controlling the pressure applied to the powder using a powder resistance meter (LORESTA-GP, MITSHBISHI CHEMICAL ANALYTECH) equipped with a 4-pin probe, The results are shown in Fig.

1 ^hour Charging capacity (mAh / g) 1 ^st discharge capacity (mAh / g) Initial efficiency (%) 50 cycle capacity retention rate (%) Example 1 200.8 187.3 93.3 96.3 Comparative Example 1 202.2 178.5 88.3 91.0

In the case of the lithium secondary battery manufactured using the cathode active material of Example 1, the initial charge / discharge capacity, initial efficiency, and lifetime characteristics of the lithium secondary battery manufactured using the cathode active material of Comparative Example 1 It can be confirmed that it is excellent. 6, the conductivity of the cathode active material prepared according to Example 1 is improved compared to that of the cathode active material of Comparative Example 1. As shown in FIG.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed exemplary embodiments but is to be construed as being limited only by the appended claims. Should be construed as being included in the scope of the present invention.

Claims (7)

A nickel-based lithium-transition metal oxide having a layered structure represented by the following formula (1)
X-ray diffraction analysis of the lithium transition metal oxide using a copper target shows that diffraction peaks exist in the region where the diffraction angle 2 &amp;thetas; is in the range of 20 DEG to 25 DEG, and the peak of the peak exists between 21.8 DEG and 22.5 DEG A positive electrode active material for a lithium secondary battery,
[Chemical Formula 1]
Li _a Ni _b Co _c Mn _d O ₂
B? D, 0.4? B? 0.9, 0 <c <0.4, 0? D <0.4 in the formula (1). The method according to claim 1,
1 < a < 1.1 and 0.9 &lt; = b + c + d &lt; = 1 in the formula (1). The method according to claim 1,
X-ray diffraction analysis of the lithium transition metal oxide with a copper target (Cu Target) shows no peak in the region where the diffraction angle 2? Is 20 to 21.8 °. The method of claim 1, wherein
Wherein the peak height appearing between 21.8 DEG and 22.5 DEG falls within a range of 0.05% to 2% of a peak height appearing at a diffraction angle 2 &amp;thetas; near 18 DEG in the X-ray diffraction analysis of the lithium transition metal oxide. Cathode active material. A method for producing a cathode active material according to any one of claims 1 to 4,
Mixing a precursor represented by the following general formula (2) and a lithium source in an equivalent ratio satisfying the following equation (1); And
And heat-treating the mixture at 800 to 1000 占 폚.
(2)
Ni _x Co _y Mn _z (OH) ₂
In the above formula (2), x> z, x> y, 0.4 ≦ x ≦ 0.9, 0 <y <0.4, 0 ≦ z <0.4.
[Equation 1]
1.00 < Li moles / M < 1.14
In the above formula (1), M is an x + y + z value of the above formula (2). 6. The method of claim 5,
Wherein the number of Li moles / M is 1.01 to 1.05. A lithium secondary battery comprising a cathode active material for a lithium secondary battery according to any one of claims 1 to 4.

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