KR20200090727A - Positive active material for rechargeable lithium battery, method of preparing the same, and rechargeable lithium battery including the same - Google Patents

Abstract

The present invention relates to a cathode active material for a lithium secondary battery, a method of producing the same, and a lithium secondary battery comprising the same. According to one example of the present invention, the cathode active material for a lithium secondary battery is represented by chemical formula 1, Li_a[Ni_bCo_cMn_dM_e]O_2, and has an I(003)/(104) value of 1.13-1.27 as a result of X-ray diffraction analysis. In chemical formula 1, 1.0<=a<=1.1, 0.8<=b<1.0, 0<=c<=0.2, 0<=d<=0.2, 0<=e<=0.05 and b+c+d+e=1.0 are satisfied, and a doping element M includes Zr, Al, Mg, Ti, B, Si, P, or a combination thereof.

Description

A cathode active material for a lithium secondary battery, a manufacturing method thereof, and a lithium secondary battery comprising the same {POSITIVE ACTIVE MATERIAL FOR RECHARGEABLE LITHIUM BATTERY, METHOD OF PREPARING THE SAME, AND RECHARGEABLE LITHIUM BATTERY INCLUDING THE SAME}

The present invention relates to a positive electrode active material for a lithium secondary battery, a method for manufacturing the lithium secondary battery including the same. More specifically, the present invention relates to a positive electrode active material for a lithium secondary battery having improved structural stability and thermal stability, a method for manufacturing the same, and a lithium secondary battery including the same.

In recent years, in connection with the development of electric vehicles such as HEV, PHEV, EV, the need for high performance and high capacity of batteries used as power sources for automobile electric motors has increased.

The battery generates electricity by using a material capable of electrochemical reaction on the positive electrode and the negative electrode. A typical example of such a battery is a lithium secondary battery that generates electrical energy by changing the chemical potential when lithium ions are intercalated/deintercalated at the positive electrode and the negative electrode.

The lithium secondary battery is manufactured by using a material capable of reversible intercalation/deintercalation of lithium ions as a positive electrode and a negative electrode active material, and charging an organic electrolyte solution or a polymer electrolyte solution between the positive electrode and the negative electrode.

A lithium composite metal compound is used as a cathode active material of a lithium secondary battery, and examples thereof include composite metal oxides such as LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , and LiMnO ₂ .

Among the positive electrode active materials, Mn-based positive electrode active materials such as LiMn ₂ O ₄ and LiMnO ₂ are also easy to synthesize, relatively inexpensive, have the best thermal stability compared to other active materials when overcharged, and have low environmental pollution and are attractive materials. Wins, but has the disadvantage of low capacity.

On the other hand, LiCoO ₂ has good electrical conductivity and a high battery voltage of about 3.7V, excellent cycle life characteristics and stability, and also excellent discharge capacity, and thus is a representative positive electrode active material commercially available and commercially available. However, because LiCoO ₂ is expensive, it occupies more than 30% of the battery price, and the actual capacity is only about 50% of the theoretical capacity (270mAh/g), which does not meet the requirements of the positive electrode active material for large batteries.

To solve this, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ was developed, and recently, a High Ni-based (Ni=60%) active material has been studied to increase energy density.

The High-Ni-based NCM positive electrode active material exhibits high discharge capacity battery characteristics, but has a disadvantage in that it is difficult to synthesize due to its high Ni content, and is difficult to secure in stability, and thus has difficulty in applying electric vehicles.

Accordingly, research is needed to improve the structural stability and thermal stability of the High-Ni positive electrode active material.

The present invention is to provide a positive electrode active material for a lithium secondary battery, a manufacturing method thereof and a lithium secondary battery comprising the same. More specifically, to provide a positive electrode active material for a lithium secondary battery having improved structural stability and thermal stability, a manufacturing method thereof, and a lithium secondary battery including the same.

In one embodiment of the present invention, it is represented by the following Chemical Formula 1, and provides a positive electrode active material for a lithium secondary battery having an I(003)/(104) value of 1.13 to 1.27 according to X-ray diffraction analysis results.

[Formula 1]

Li _a [Ni _b Co _c Mn _d M _e ]O ₂

In Formula 1, 1.0≤a≤1.1, 0.8≤b<1.0, 0≤c≤0.2, 0≤d≤0.2, 0≤e≤0.05, b+c+d+e=1.0 , The doping element M may include Zr, Al, Mg, Ti, B, Si, P, or a combination thereof.

In Formula 1, e may be 0<e≤0.05.

In Formula 1, M may be Al.

I (003) / (104) according to the X-ray diffraction analysis results of the positive electrode active material may be 1.13 to 1.17.

I(006+102)/(101) according to the X-ray diffraction analysis result of the positive electrode active material may be 0.53 to 0.63.

More specifically, I(006+102)/(101) may be 0.55 to 0.60.

The positive electrode active material may satisfy Equation 1 below.

[Equation 1]

0.42 ≤ [I(006+102)/(101)]/[I(003)/(104)]

The particle diameter of the positive electrode active material may be 3 to 20 μm.

The positive electrode active material may further include a coating layer.

More specifically, the coating layer may include boron, boron oxide, lithium boron oxide, or a combination thereof.

In another embodiment of the present invention, the step of preparing the metal hydroxide precursor particles; Preparing a mixture by mixing precursor particles, a lithium raw material, and optionally a doped raw material; And calcining the mixture to obtain a lithium metal oxide; provides a method for producing a positive electrode active material for a lithium secondary battery comprising a.

The firing may be a first firing of the mixture at a temperature of 300 to 500 °C, followed by a second firing at a temperature of 700 to 800 °C.

The precursor particles may be represented by Formula 2 below.

[Formula 2]

[Ni _x Co _y Mn _z ](OH) ₂

In Chemical Formula 2, 0.8≤x<1.0, 0≤y≤0.2, 0≤z≤0.2, and x+y+z=1.0.

The lithium raw material is one or more selected from the group consisting of Li ₂ CO ₃ , LiOH, C ₂ H ₃ LiO ₂ , LiNO ₃ , Li ₂ SO ₄ , Li ₂ SO ₃ , Li ₂ O, Li ₂ O ₂ , LiCl. Can.

The doping raw material may be Zr, Al, Mg, Ti, B, Si, P or a combination thereof.

The primary firing time may be 1 hour to 2 hours.

The second firing time may be 9 hours to 13 hours.

Secondary firing may be made in the range of 760 to 780 ℃.

The obtained lithium metal oxide may be represented by Formula 1 below.

[Formula 1]

Li _a [Ni _b Co _c Mn _d M _e ]O ₂

In Formula 1, 1.0≤a≤1.1, 0.8≤b<1.0, 0≤c≤0.2, 0≤d≤0.2, 0≤e≤0.05, b+c+d+e=1.0 , The doping element M may include Zr, Al, Mg, Ti, B, Si, P, or a combination thereof.

The obtained lithium metal oxide may have an I(003)/(104) value of 1.13 to 1.27 according to X-ray diffraction analysis results.

More specifically, obtaining a lithium metal oxide; Subsequently, mixing the raw material for coating on the lithium metal oxide and then firing to form a coating layer; may further include.

In another embodiment of the present invention, a positive electrode for a lithium secondary battery including the positive electrode active material according to the above-described embodiment of the present invention is provided.

In another embodiment of the present invention, the anode; cathode; And an electrolyte positioned between the positive electrode and the negative electrode, and the positive electrode provides a lithium secondary battery including a positive electrode active material according to an embodiment of the present invention described above.

According to an embodiment of the present invention, by effectively distributing the doping element evenly inside the positive electrode active material of a lithium secondary battery, it is possible to provide a positive electrode active material for a lithium secondary battery having excellent structural stability and thermal stability characteristics.

1 is a graph showing the total elution amount of transition metal according to the ratio of I(003)/(104) after high temperature storage of Examples 1 to 9 and Comparative Example 1 of the present invention.
2 is a graph showing the elution amount of transition metal after high temperature storage of Examples 1 to 9 and Comparative Example 1 of the present invention.

In this specification, terms such as first, second, and third are used to describe various parts, components, regions, layers, and/or sections, but are not limited thereto. These terms are only used to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, a first portion, component, region, layer or section described below may be referred to as a second portion, component, region, layer or section without departing from the scope of the present invention.

In the present specification, when a part “includes” a certain component, it means that the component may further include other components, not to exclude other components, unless otherwise stated.

In this specification, the terminology used is only for referring to a specific embodiment, and is not intended to limit the present invention. The singular forms used herein include plural forms unless the phrases clearly indicate the opposite. As used herein, the meaning of “comprising” embodies a particular property, region, integer, step, action, element, and/or component, and the presence or presence of another property, region, integer, step, action, element, and/or component. It does not exclude addition.

In the present specification, the term "combination of these" included in the expression of the marki form means one or more mixtures or combinations selected from the group consisting of the elements described in the expression of the marki form, the components It means to include one or more selected from the group consisting of.

In this specification, when it is said that a part is "on" or "on" another part, it may be directly on or on another part, or another part may be involved therebetween. In contrast, if one part is referred to as being “just above” another part, no other part is interposed therebetween.

Although not defined differently, all terms including technical terms and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present invention pertains. Commonly used dictionary-defined terms are additionally interpreted as having meanings consistent with related technical documents and currently disclosed contents, and are not interpreted in an ideal or very formal meaning unless defined.

In addition, unless otherwise specified,% means weight%, and 1 ppm is 0.0001% by weight.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art to which the present invention pertains can easily practice. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

Advantages and features of the present invention, and methods for achieving them will be clarified with reference to embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only the embodiments allow the disclosure of the present invention to be complete, and are conventional in the art to which the present invention pertains. It is provided to fully inform the knowledgeable person of the scope of the invention, and the invention is only defined by the scope of the claims. The same reference numerals refer to the same components throughout the specification.

Thus, in some embodiments, well-known techniques are not specifically described to avoid obscuring the present invention. Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used as meanings commonly understood by a person having ordinary skill in the art to which the present invention pertains.

The positive electrode active material for a lithium secondary battery according to an embodiment of the present invention provides a lithium composite oxide represented by the following Chemical Formula 1.

[Formula 1]

Li _a [Ni _b Co _c Mn _d M _e ]O ₂

In this case, 1.0≤a≤1.1, 0.8≤b<1.0, 0≤c≤0.2, 0≤d≤0.2, 0≤e≤0.05, and b+c+d+e=1.0 . Further, the doping element M may be Zr, Al, Mg, Ti, B, Si, P, or a combination thereof.

In this case, 0≤e≤0.05 means that the doping element may or may not be included. Specifically, e may be 0<e≤0.05, that is, it may necessarily include a doping element. The doping element at this time may be Al. When the doping element is Al, the initial discharge capacity and efficiency of the coin battery made of the active material decreases due to the doping of Al, but the elution of the transition metal at high temperature storage can be reduced, thereby improving the high temperature stability.

I(003)/(104) obtained from the X-ray diffraction analysis results of the positive electrode active material for a lithium secondary battery according to an embodiment of the present invention generally indicates the positive electrode active material crystallinity. The larger the number, the more stable the hexagonal structure is developed, but the size of the (003) plane of the transition metal layer decreases as a doping element with a smaller atomic number than Ni, Co, Mn, which is a transition metal material, decreases. It can be used as a measure of the distribution of doping elements inside the positive electrode active material with a reduction width of (003)/(104). However, at this time, the change in the value of I(006+102)/(101) used as a similar indicator should be small.

At this time, I (003) / (104) of the positive electrode active material may be 1.13 to 1.27. More specifically, it may be 1.13 to 1.20. More specifically, it may be 1.13 to 1.17. In addition, I (006+102)/(101) of the positive electrode active material may be 0.53 to 0.63. More specifically, it may be 0.55 to 0.60. When I(003)/(104) and I(006+102)/(101), which are the results of X-ray diffraction analysis of the positive electrode active material, satisfy the above range, high temperature stability and thermal stability may be improved.

In addition, the positive electrode active material may satisfy Equation 1 below.

[Equation 1]

0.42 ≤ [I(006+102)/(101)]/[I(003)/(104)]

More specifically, the [I(006+102)/(101)]/[I(003)/(104)] value may be 0.425 or more. More specifically, the [I(006+102)/(101)]/[I(003)/(104)] value may be 0.43 or more. More specifically, the value of [I(006+102)/(101)]/[I(003)/(104)] may be 0.434 or more.

The particle diameter of the positive electrode active material may be 3 to 20 μm. More specifically, it may be 5 to 18 μm. When the particle diameter of the positive electrode active material satisfies the above range, density, life characteristics, and output characteristics may be excellent. However, one embodiment of the present invention is not limited to the particle size range, and the particle size range may be adjusted according to required battery characteristics.

The positive electrode active material may further include a coating layer. The coating layer may include boron, boron oxide, lithium boron oxide, or a combination thereof. When the coating layer is used, there is an effect of improving life characteristics and improving high temperature stability.

A method of manufacturing a positive electrode active material for a lithium secondary battery according to an embodiment of the present invention comprises the steps of preparing metal hydroxide precursor particles; Preparing a mixture by mixing precursor particles, a lithium raw material, and optionally a doped raw material; And calcining the mixture to obtain a lithium metal oxide.

More specifically, a method of manufacturing a positive electrode active material for a lithium secondary battery according to an embodiment of the present invention comprises the steps of preparing metal hydroxide precursor particles; Preparing a mixture by mixing the precursor particles and the lithium raw material; And calcining the mixture to obtain a lithium metal oxide.

Or, a method of manufacturing a positive electrode active material for a lithium secondary battery according to an embodiment of the present invention comprises the steps of preparing metal hydroxide precursor particles; Preparing a mixture by mixing the precursor particles, the lithium raw material, and the doped raw material; And calcining the mixture to obtain a lithium metal oxide.

The precursor particles may be represented by Formula 2 below.

[Formula 2]

[Ni _x Co _y Mn _z ](OH) ₂

In Chemical Formula 2, 0.8≤x<1.0, 0≤y≤0.2, 0≤z≤0.2, x+y+z=1.0, and the metal hydroxide precursor may be directly manufactured or a commercially available product may be used. . The doping raw material may be Zr, Al, Mg, Ti, B, Si, P, or a combination thereof, particularly Al. The effect in the case of doping Al is as described above.

At this time, the firing may be a primary firing of the mixture at a temperature of 300 to 500 °C, followed by secondary firing at a temperature of 700 to 800 °C. The temperature of the secondary firing may be more specifically in the range of 760 to 780 °C. In addition, the first firing time may be 1 hour to 2 hours, more specifically 1 hour 20 minutes to 1 hour 40 minutes. In addition, the second firing time may be 9 hours to 13 hours, more specifically 10 hours to 12 hours. When performing the heat treatment step, the lithium salt may be melted/decomposed to facilitate reaction with the transition metal precursor.

Meanwhile, the lithium raw material is one selected from the group consisting of Li ₂ CO ₃ , LiOH, C ₂ H ₃ LiO ₂ , LiNO ₃ , Li ₂ SO ₄ , Li ₂ SO ₃ , Li ₂ O, Li ₂ O ₂ , LiCl. It may include the above.

Meanwhile, the obtained lithium metal oxide may be represented by Formula 1 below.

[Formula 1]

Li _a [Ni _b Co _c Mn _d M _e ]O ₂

In Formula 1, 1.0≤a≤1.1, 0.8≤b<1.0, 0≤c≤0.2, 0≤d≤0.2, 0≤e≤0.05, b+c+d+e=1.0 days Can.

On the other hand, obtaining a lithium metal oxide; Subsequently, mixing the raw material for coating on the lithium metal oxide and then firing to form a coating layer may be further included, and the coating layer may include boron, boron oxide, lithium boron oxide, or a combination thereof.

The positive electrode active material according to an embodiment of the present invention can be usefully used for the positive electrode of a lithium secondary battery. The lithium secondary battery may include a negative electrode and an electrolyte including a negative electrode active material together with a positive electrode.

The positive electrode is prepared by mixing a positive electrode active material, a conductive material, a binder, and a solvent according to an embodiment of the present invention to prepare a positive electrode active material composition, and then directly coating and drying the aluminum current collector. Alternatively, the positive electrode active material composition can be produced by casting on a separate support and then laminating the film obtained by peeling from the support on an aluminum current collector.

At this time, carbon black, graphite, and metal powder are used as the conductive material, and the binder is vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene And mixtures thereof. Also, N-methylpyrrolidone, acetone, tetrahydrofuran, and decane are used as the solvent. At this time, the content of the positive electrode active material, the conductive material, the binder, and the solvent is used at a level commonly used in lithium secondary batteries.

The anode is prepared by mixing an anode active material, a binder, and a solvent, as in the anode, to prepare an anode active material composition, which is coated directly on a copper current collector or cast on a separate support and a negative electrode active material film peeled from the support is applied to the copper current collector. It is manufactured by lamination. At this time, the negative electrode active material composition may further contain a conductive material, if necessary.

As the negative electrode active material, a material capable of intercalating/deintercalating lithium is used, for example, lithium metal or lithium alloy, coke, artificial graphite, natural graphite, organic polymer compound burner, carbon fiber, etc. . Further, the conductive material, the binder and the solvent are used in the same manner as in the case of the positive electrode described above.

All of the separators can be used as long as they are commonly used in lithium secondary batteries. For example, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof can be used, and a polyethylene/polypropylene two-layer separator, It goes without saying that a mixed multilayer film such as a polyethylene/polypropylene/polyethylene three-layer separator, a polypropylene/polyethylene/polypropylene three-layer separator, or the like can be used.

As the electrolyte charged in the lithium secondary battery, a non-aqueous electrolyte or a known solid electrolyte can be used, and a lithium salt is used.

The solvent of the non-aqueous electrolyte is not particularly limited, but cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate; Chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate; Esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone; Ethers such as 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane and 2-methyltetrahydrofuran; Nitriles such as acetonitrile; Amides such as dimethylformamide can be used. These may be used alone or in combination of a plurality. In particular, a mixed solvent of cyclic carbonate and chain carbonate can be preferably used.

Further, as the electrolyte, a gel polymer electrolyte impregnated with a polymer electrolyte such as polyethylene oxide or polyacrylonitrile or an inorganic solid electrolyte such as LiI or Li ₃ N is possible.

At this time, the lithium salt is LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , One selected from the group consisting of LiCl and LiI is possible.

In addition, the existing prior art focused on improving the performance of the cathode material by minimizing the cation mixing effect. On the other hand, the present invention uses a cation mixing effect to improve stability. That is, it is possible to maximize the stability of the cathode material by using cation mixing in a reasonable range.

Hereinafter, the present invention will be described in more detail through examples. However, it is necessary to note that the following examples are only intended to illustrate the present invention in more detail and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the items described in the claims and the items reasonably inferred therefrom.

[Example 1]

The metal hydroxide precursor was mixed with lithium hydroxide and aluminum hydroxide. At this time, Li/M was mixed at a ratio of 1.03, and aluminum hydroxide was mixed with 2 mol% of M, that is, 0.02 mol. Thereafter, the mixture was put in an alumina crucible and calcined at 400°C for 1 hour 30 minutes and at 760°C for 10 hours in an oxygen atmosphere. Thereafter, the lithium composite oxide and distilled water were mixed at a weight ratio of 1:1, followed by washing, filtering, and drying, followed by adding H ₃ BO ₃ at a weight ratio of 0.01 wt% compared to the active material. The mixed material was maintained at 300° C. for 6 hours and 30 minutes to conduct heat treatment to prepare a positive electrode active material for a lithium secondary battery.

The prepared positive electrode active material for a lithium secondary battery, a conductive agent (Denka black), and a binder (PVDF) were uniformly mixed in a N-methyl-2-pyrrolidone solvent such that the weight ratio was 96.5:1.5:2.0.

The mixture was evenly applied to an aluminum foil, compressed in a roll press, dried for 1 hour, and then dried in a vacuum oven at 100° C. for 1 hour to prepare an anode.

2032 half cell (half) according to a conventional manufacturing method using Li-metal as a counter electrode and 1 mol of LiPF ₆ solution as a liquid electrolyte in a mixed solvent of EC:DMC:EMC = 30:40:30 as the electrolyte. coin cell).

[Example 2]

The firing conditions were prepared in the same manner as in Example 1, except that the firing conditions were fired at 400°C for 1 hour and 30 minutes, and at 760°C for 11 hours.

[Example 3]

It was prepared in the same manner as in Example 1, except that the firing conditions were fired at 400°C for 1 hour and 30 minutes, and at 760°C for 12 hours.

[Example 4]

The firing conditions were prepared in the same manner as in Example 1, except that the firing conditions were fired at 400°C for 1 hour and 30 minutes, and at 770°C for 10 hours.

[Example 5]

It was prepared in the same manner as in Example 1, except that the firing conditions were fired at 400°C for 1 hour and 30 minutes, and at 770°C for 11 hours.

[Example 6]

The firing conditions were prepared in the same manner as in Example 1, except that the firing conditions were fired at 400°C for 1 hour and 30 minutes, and at 770°C for 12 hours.

[Example 7]

It was prepared in the same manner as in Example 1, except that the firing conditions were fired at 400°C for 1 hour and 30 minutes, and at 780°C for 10 hours.

[Example 8]

The firing conditions were prepared in the same manner as in Example 1, except that the firing conditions were fired at 400°C for 1 hour and 30 minutes, and at 780°C for 11 hours.

[Example 9]

It was prepared in the same manner as in Example 1, except that the firing conditions were fired at 400°C for 1 hour and 30 minutes, and at 780°C for 12 hours.

[Comparative Example 1]

A positive electrode active material and a coin battery were manufactured in the same manner as in Example 1, except that Al(OH) ₃ was not added during mixing.

[Comparative Example 2]

It was prepared in the same manner as in Example 1, except that the firing conditions were fired at 760°C for 10 hours.

[Experimental Example]

Experimental Example 1: X-ray diffraction analysis

X-ray diffraction analysis of the positive electrode active material powders prepared in Examples 1 to 9 and Comparative Examples 1 to 2 and the results are shown in Table 1 below.

division I(003)/(104) I(006+102)/(101) [I(006+102)/(101)]/[I(003)/(104)] Example 1 1.26 0.55 0.437 Example 2 1.24 0.54 0.435 Example 3 1.21 0.55 0.455 Example 4 1.22 0.55 0.451 Example 5 1.20 0.55 0.458 Example 6 1.18 0.56 0.475 Example 7 1.17 0.55 0.470 Example 8 1.15 0.56 0.487 Example 9 1.13 0.56 0.496 Comparative Example 1 1.32 0.51 0.386 Comparative Example 2 1.28 0.53 0.414

Experimental Example 2: Battery characteristics evaluation

The coin cells of Examples 1 to 9 and Comparative Examples 1 to 2 were charged with a constant current of 0.2C at 25°C to 4.25V, respectively, and charged at a constant voltage of 4.25V until 1/200C to measure the charging capacity. After the rest time was given for 10 minutes, the discharge capacity was measured by discharging a constant current of 0.2C to 2.5V and shown in Table 2.

division Charging capacity (mAh/g) Discharge capacity (mAh/g) Charge/discharge efficiency (%) Example 1 233.5 212.1 90.8 Example 2 234.5 213.3 91.0 Example 3 231.8 209.9 90.5 Example 4 234.6 211.1 90.0 Example 5 232.8 211.6 90.9 Example 6 235.7 212.1 90.0 Example 7 235.2 211.3 89.8 Example 8 234.6 210.5 89.7 Example 9 234.7 210.9 89.8 Comparative Example 1 236.9 217.3 91.7 Comparative Example 2 233.6 212.3 90.9

Experimental Example 3: High temperature stability evaluation 1 (DSC)

The coin cells of Examples 1 to 9 and Comparative Examples 1 to 2 were charged with a constant current of 0.2C at 25°C to 4.25V, and charged at a constant voltage of 4.25V until 1/200C. After 10 minutes of rest time, 0.2C of constant current was discharged to 2.5V, and then charged to 0.225 of constant current up to 4.25V, and charged until 1/200C at a constant voltage of 4.25V. Thereafter, the coin cell is disassembled to recover the positive electrode plate, and then the recovered positive electrode plate is punched with 3Φ to be injected into the cell for DSC measurement together with the electrolyte, and then combined. At this time, the positive electrode plate and the electrolyte are added at a weight ratio of 0.75%.

The assembled cell was heated to 10°C per minute in a nitrogen atmosphere in DSC measurement equipment and measured to 30~350°C, and the results are shown in Table 3.

division 1 ^st Main Peak (℃) Calorific value (J/g) Example 1 237.3 967 Example 2 237.7 926 Example 3 238.4 870 Example 4 238.1 909 Example 5 238.7 854 Example 6 240.8 791 Example 7 241.5 775 Example 8 243.2 751 Example 9 244.8 652 Comparative Example 1 227.8 1092 Comparative Example 2 233.9 1097

Experimental Example 4: High temperature stability evaluation 2 (transition metal elution)

The coin cells for Examples 1 to 9 and Comparative Examples 1 to 2 were charged at a constant current of 0.2C at 25°C to 4.25V, and charged at a constant voltage of 4.25V until 1/200C. After 10 minutes of rest time, 0.2C of constant current was discharged to 2.5V, and then charged to 0.2V of constant current up to 4.7V, and charged at a constant voltage of 4.7V until 1/200C. After that, the coin cell was disassembled to recover the positive electrode plate, sealed with 20 ml of electrolyte in the Al-Pouch, stored in an oven at 50°C for 1 to 4 weeks, and then recovered to recover the amount of transition metal eluted through ICP analysis. It was measured. And the results are shown in FIG. 1.

[result]

Referring to Tables 1 to 3 and FIGS. 1 to 2, in the case of Example 9 and Example 7 according to the present invention, the positive electrode active material has an X-ray diffraction analysis result I(003)/(104) of 1.13 and 1.17. It can be seen that I(006+102)/(101) is 0.56 and 0.55, respectively.

The initial discharge capacity and efficiency of the coin cells made of the active materials of Examples 1 to 9 and Comparative Examples 1 to 2 decrease due to the doping of Al, but as a result of high temperature stability evaluation, I(003)/(104) increased. Accordingly, it can be seen that DSC 1 ^St Main Peak increases and elution of transition metal at high temperature decreases.

On the other hand, in the active material of Comparative Example 1, the result of X-ray diffraction analysis was I(006+102)/(101) of 0.51, and I(003)/(104) was 1.32, which is I(003)/(104) compared to Example 7. It can be seen that is higher and the value of I(006+102)/(101) is lowered. In this situation, it can be seen that the DSC obtained in Table 3 increases. It can be understood that the DSC increases when the cation mixing is made better by changing the process conditions.

Looking at Example 4 and Example 9, as the cation mixing index increases, it can be seen that the DSC value increases, but it can be seen that the charge/discharge efficiency decreases. However, between Examples 2 and 5, a decrease in charge/discharge capacity was minimized, and a sharp increase in DSC was found, indicating that the stability of I(003)/(104) in this region was significantly increased between 1.13 and 1.20. .

The present invention is not limited to the above embodiments, but may be manufactured in various different forms, and a person having ordinary skill in the art to which the present invention pertains may have other specific forms without changing the technical spirit or essential features of the present invention. It will be understood that can be carried out as. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (13)

It is represented by the following formula (1),
The I(003)/(104) values according to the X-ray diffraction analysis results are 1.13 to 1.27,
The value of I(006+102)/(101) is 0.53 to 0.63,
The positive electrode active material further includes a coating layer,
The coating layer is a positive electrode active material for a lithium secondary battery comprising boron, boron oxide, lithium boron oxide or a combination thereof:
[Formula 1]
Li _a [Ni _b Co _c Mn _d M _e ]O ₂
In Formula 1, 1.0≤a≤1.1, 0.8≤b<1.0, 0<c≤0.2, 0<d≤0.2, 0<e≤0.05, b+c+d+e=1.0 , The doping element M is Al.
According to claim 1,
The I (003) / (104) is a positive electrode active material for a lithium secondary battery of 1.13 to 1.17.
According to claim 1,
The I (006 + 102) / (101) is a positive electrode active material for a lithium secondary battery of 0.55 to 0.60.
According to claim 1,
The positive electrode active material is a positive electrode active material for a lithium secondary battery that satisfies Expression 1 below.
[Equation 1]
0.42 ≤ [I(006+102)/(101)]/[I(003)/(104)] ≤ 0.56
According to claim 1,
The positive electrode active material for a lithium secondary battery having a particle diameter of 3 to 20 μm.
Preparing metal hydroxide precursor particles;
Preparing a mixture by mixing the precursor particles, a lithium raw material, and a doped raw material;
Calcining the mixture to obtain lithium metal oxide; And
Mixing the lithium metal oxide with a coating raw material and firing to form a coating layer;
Including,
The firing is a first firing of the mixture at a temperature of 300 to 500 °C, followed by a second firing at a temperature of 700 to 800 °C,
The obtained lithium metal oxide is a positive electrode active material for a lithium secondary battery having an I(003)/(104) value of 1.13 to 1.27 and an I(006+102)/(101) value of 0.53 to 0.63 according to X-ray diffraction analysis results. Become a manufacturing method,
The obtained lithium metal oxide is represented by the following formula (1),
The coating layer is a method for producing a positive electrode active material for a lithium secondary battery that includes boron, boron oxide, lithium boron oxide, or a combination thereof:
[Formula 1]
Li _a [Ni _b Co _c Mn _d M _e ]O ₂
In Formula 1, 1.0≤a≤1.1, 0.8≤b<1.0, 0<c≤0.2, 0<d≤0.2, 0<e≤0.05, b+c+d+e=1.0 , The doping element M is Al.
The method of claim 6,
The precursor particles are represented by the following formula (2) Method for producing a positive electrode active material for a lithium secondary battery:
[Formula 2]
[Ni _x Co _y Mn _z ](OH) ₂
In Formula 2, 0.8≤x<1.0, 0≤y≤0.2, 0≤z≤0.2, and x+y+z=1.0.
The method of claim 6,
The lithium raw material is at least one selected from the group consisting of Li ₂ CO ₃ , LiOH, C ₂ H ₃ LiO ₂ , LiNO ₃ , Li ₂ SO ₄ , Li ₂ SO ₃ , Li ₂ O, Li ₂ O ₂ , LiCl A method of manufacturing a positive electrode active material for a lithium secondary battery.
The method of claim 6,
The doping raw material is a method of manufacturing a positive electrode active material for a lithium secondary battery is Al.
The method of claim 6,
The primary firing time is 1 hour to 2 hours, the method for producing a positive electrode active material for a lithium secondary battery.
The method of claim 6,
The secondary firing time is 9 hours to 13 hours, the method for producing a positive electrode active material for a lithium secondary battery.
The method of claim 6,
The secondary firing is a method for producing a positive electrode active material for a lithium secondary battery that is made in the range of 760 to 780 ℃.
anode;
cathode; And
It includes an electrolyte located between the positive electrode and the negative electrode,
The positive electrode is a lithium secondary battery comprising the positive electrode active material according to claim 1.

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