KR101810574B1 - Positive electrode active material for rechargable lithium battery, method for manufacturing the same, and rechargable lithium battery including the same - Google Patents

Abstract

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 comprising the same, wherein a plurality of nickel-based lithium metal oxide particles are aggregated into secondary particles; And a first coating layer disposed on the voids inside the secondary particles and containing a compound having a spinel structure to cover the surface of a part or the whole of the plurality of nickel-based lithium metal oxide particles, wherein the first coating layer The present invention provides a cathode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery comprising the same, wherein the compound having a spinel structure is represented by the following formula (1).
[Formula 1] Li _x CoO ₂
(In the above formula (1), 0.95 < x &lt; = 1.05.

Description

TECHNICAL FIELD 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. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive active material for a lithium secondary battery,

A cathode active material for a lithium secondary battery, a production method thereof, and a lithium secondary battery comprising the same.

BACKGROUND ART [0002] Lithium secondary batteries are now widely used as power sources for driving various electronic apparatuses.

In connection with this, studies have been made to improve the energy density while reducing the size and weight of the battery in small-sized fields such as portable apparatuses. On the other hand, in large fields such as electric vehicles, Researches for developing a battery which can secure such a large number of cells have been recognized as important.

Various cathode active materials have been studied in order to realize batteries conforming to the applications of each of these fields.

Specifically, the most widely studied cathode active material is LiCoO _2, but nickel-based lithium metal oxides having a high discharge capacity per unit weight have recently attracted attention.

However, in the case of the nickel-based lithium metal oxide, there is a problem that the structural and thermal stability are deteriorated by the continuous charging and discharging of the battery.

In order to solve the above-mentioned problems, in one embodiment of the present invention, secondary particles in which a plurality of nickel-based lithium metal oxide particles are aggregated; And a first coating layer disposed on the pores inside the secondary particles and covering the surface of a part or all of the plurality of nickel-based lithium metal oxide particles, the first coating layer including a compound having a spinel structure, .

In another embodiment of the present invention, there is provided a method for preparing a nickel-based lithium metal oxide powder, comprising: preparing a nickel-based lithium metal oxide powder; Preparing a coating composition comprising a lithium raw material, a cobalt raw material, and a solvent; Reacting the lithium raw material and the cobalt raw material in the coating composition by mixing the nickel-based lithium metal oxide powder and the coating composition, reacting the reaction product of the lithium raw material and the cobalt raw material with the nickel-based lithium metal oxide powder Distributing the particles on the surface of some or all of the plurality of particles to obtain a cathode active material precursor; And heat-treating the cathode active material precursor to obtain a cathode active material. The method for producing a cathode active material for a lithium secondary battery according to the present invention includes the steps of:

In another embodiment of the present invention, a lithium secondary battery including any one of the above-mentioned cathode active materials can be provided.

In one embodiment of the present invention, secondary particles in which a plurality of nickel-based lithium metal oxide particles are aggregated; And a first coating layer disposed on the voids inside the secondary particles and including a spinel structure compound covering a surface of a part or all of the plurality of nickel-based lithium metal oxide particles, wherein the first coating layer Wherein the spinel structure compound is represented by the following formula (1).

[Formula 1] Li _x CoO ₂

(In the above formula (1), 0.95 < x &lt; = 1.05.

Specifically, the first coating layer will be described below.

The first coating layer may continuously coat the entire surfaces of the plurality of lithium metal composite oxide particles.

The spinel structure compound included in the first coating layer may be a compound containing cobalt. At this time, the content of cobalt in the first coating layer may be 5 to 50 mol% based on 100 mol% of the entire first coating layer.

Specifically, the spinel structure compound included in the first coating layer may be LiCoO ₂ .

The thickness of the first coating layer may be 0.001 to 20 nm.

The content of the first coating layer in the cathode active material may be 0.5 to 2 parts by weight based on 100 parts by weight of the secondary particles aggregated with the plurality of nickel-based lithium metal oxide particles.

On the other hand, a second coating layer covering the surface of the secondary particles and containing a compound having a spinel structure may be further included.

The spinel structure compound contained in the second coating layer may be represented by the following formula (2).

[Formula 2] Li _x CoO ₂

(In the above formula (2), 0.95 < x &lt; 1.05.

The thickness of the second coating layer may be 5 to 20 nm.

The content of the second coating layer in the cathode active material may be 0.5 to 2 parts by weight based on 100 parts by weight of the secondary particles of the nickel-based lithium metal oxide particles aggregated.

Specifically, the secondary particles may be contained in an amount of 98 to 99.5% by weight based on 100% by weight of the total of the cathode active material, 0.5 to 2% by weight of the first coating layer, and the remainder of the second coating layer may be included .

The plurality of nickel-based lithium metal oxide particles may each be represented by the following formula (3).

???????? Li _a Ni _{1 -x- y} Co _x M _y O _{2 +?}

Wherein M is at least one element selected from the group consisting of Mg, Ti, Zr, Nb, Mo, Al, Mn, Mg, V and a rare earth element.)

The average particle diameter of the plurality of nickel-based lithium metal oxide particles may be 200 nm to 15 탆.

The average particle diameter of the secondary particles may be 5 to 15 占 퐉.

In another embodiment of the present invention, there is provided a method of preparing a lithium secondary battery, comprising: preparing a nickel-based lithium metal oxide powder in the form of a secondary particle comprising a plurality of primary particles; Preparing a coating composition comprising a lithium raw material, a cobalt raw material, and a solvent; Mixing the nickel-based lithium metal oxide powder of the secondary particle type and the coating composition to obtain a nickel-based lithium metal oxide coated with the coating composition; And firing the nickel-based lithium metal oxide coated with the coating composition, wherein the nickel-based lithium metal oxide powder of the secondary particle type and the coating composition are mixed so that the nickel-based lithium metal oxide Wherein the nickel-based lithium-metal oxide secondary particles are injected into the internal void of the nickel-based lithium-metal oxide secondary particles, and the nickel-based lithium metal oxide to which the coating composition is applied is calcined, Wherein the first coating layer containing a compound having a spinel structure is formed in the pores of the metal oxide secondary particles and the spinel structure compound included in the first coating layer is represented by the following formula 4: &Lt; / RTI &gt;

[Formula 4] Li _x CoO ₂

(In the formula (4), 0.95 < x &lt; = 1.05).

The nickel-based lithium metal oxide powder of the secondary particle type and the coating composition are mixed to obtain a nickel-based lithium metal oxide coated with the coating composition.

The mixing may be performed in a temperature range of 60 to 80 캜.

Specifically, the nickel-based lithium metal oxide powder of the secondary particle type and the coating composition are mixed to obtain a nickel-based lithium metal oxide coated with the coating composition. The lithium-based lithium metal oxide powder and the cobalt raw material The material reacting to form a reaction product of the spinel structure; And injecting the reaction product of the spinel structure into the internal void of the nickel-based lithium metal oxide secondary particle.

Independently, the lithium source material and the cobalt source material in the coating composition react to form a reaction product of a spinel structure; And a reaction product of the spinel structure is injected into the inner pores of the nickel-based lithium metal oxide secondary particles and is applied to the outside of the nickel-based lithium metal oxide secondary particles.

In this case, the nickel-based lithium metal oxide coated with the coating composition is fired to form a first coating layer containing a compound having a spinel structure on the inside of the nickel-based lithium metal oxide secondary particle, And a second coating film containing a compound having a spinel structure is formed on the surface of the lithium metal oxide secondary particles.

Meanwhile, a detailed description of the step of firing the nickel-based lithium metal oxide coated with the coating composition is as follows.

The calcination may be performed at a temperature ranging from 400 to 600 ° C.

The calcination may be performed for 3 to 5 hours.

The firing may be performed in an oxidizing atmosphere.

Calcining the nickel-based lithium metal oxide to which the coating composition is applied; Drying the nickel-based lithium metal oxide to which the coating composition has previously been applied.

Preparing a coating composition comprising a lithium raw material, a cobalt raw material, and a solvent, wherein the lithium raw material is contained in an amount of 1 to 2 wt% based on 100 wt% of the entire coating composition, The raw material may be contained in an amount of 90 to 93% by weight, and the solvent may be prepared to be contained in the remainder.

In another embodiment of the present invention, cathode; And an electrolyte, wherein the anode comprises a cathode active material according to any one of the above-mentioned aspects.

According to one embodiment and another embodiment of the present invention, there is provided a secondary battery comprising: i) a secondary battery comprising: i) A cathode active material for a lithium secondary battery having improved mechanical and thermal stability by coating a surface of a part or all of particles constituting secondary particles and containing a spinel structure compound and a method for producing the same.

According to another embodiment of the present invention, it is possible to provide a lithium secondary battery having improved charge / discharge efficiency, high-rate characteristics and lifetime characteristics at high temperature by including the cathode active material for the lithium secondary battery. In particular, a lithium secondary battery including a generally known cathode active material has a deterioration in life characteristics at a temperature higher than room temperature, while a lithium secondary battery including the cathode active material for a lithium secondary battery can exhibit lifetime characteristics equivalent to room temperature.

FIG. 1 schematically illustrates a lithium secondary battery according to an embodiment of the present invention. Referring to FIG.
2 schematically shows a lithium secondary battery according to an embodiment of the present invention.
3 is a scanning electron microscope (SEM) image of the surface of the cathode active material secondary particle of Example 1. Fig.
4 is a photograph of a pellet formed by measuring the pressure density of the cathode active material of Example 1 and a scanning electron microscope (SEM) image of the sample surface.
FIG. 5 is a scanning electron microscopic photograph of a scanning electron microscope photograph shown in FIG.
6 is a SEM photograph of the surface of the cathode active material secondary particle of Comparative Example 1. Fig.
7 is a photograph of a pellet formed by measuring the pressure density of the cathode active material of Comparative Example 1 and a scanning electron microscope (SEM) image of the sample surface.
Fig. 8 is a scanning electron microscopic photograph of a scanning electron microscope photograph shown in Fig. 7, which is magnified twice.
9 is a transmission electron microscope photograph of two primary particles inside the cathode active material secondary particle of Example 1. Fig.
10 and 11 are respectively a transmission electron microscope photograph showing an enlarged area of the area shown in FIG.
12 is a high-speed Fourier transform image showing structural information on a coating film inside the cathode active material secondary particle of Example 1. Fig.
13 is a transmission electron microscope photograph of the two primary particles inside the cathode active material secondary particle of Comparative Example 1. FIG.
FIGS. 14 and 15 are respectively a transmission electron microscope photograph showing an enlarged view of the area shown in FIG.
16 is a high-speed Fourier transform image showing the structure information of the primary particles in the cathode active material secondary particle of Comparative Example 1. Fig.
17 is a graph showing initial charging / discharging characteristics of each lithium secondary battery of Production Example 1 and Comparative Production Example 1
18 is a graph showing the charge-discharge characteristics of each lithium secondary battery of Production Example 1 and Comparative Production Example 1 at a rate.
19 is a graph showing the high-temperature lifetime characteristics of each lithium secondary battery of Production Example 1 and Comparative Production Example 1. Fig.
20 to 22 are graphs showing the characteristics at room temperature and high temperature life of each lithium secondary battery of Production Examples 1 and 2 and Comparative Production Examples 1 to 3.
23 is a transmission electron microscope photograph of the positive electrode active material recovered in the lithium secondary battery of Production Example 1. Fig.
Fig. 24 is an enlarged transmission electron microscope photograph of Fig. 23. Fig.
25 is a transmission electron microscope analysis photograph of the positive electrode active material recovered in the lithium secondary battery of Comparative Production Example 1. Fig.
Fig. 26 is an enlarged transmission electron microscope photograph of Fig. 25. Fig.
27 is an EDXS analysis image showing chemical information on the positive electrode active material recovered in the lithium secondary battery of Production Example 1. Fig.
28 is an EDXS analysis image showing chemical information on the positive electrode active material recovered in the lithium secondary battery of Comparative Production Example 1. Fig.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

Here, "primary particles" means one grain (grain or crystallite). And "secondary particle" means an aggregate obtained by agglomeration of the primary particles, and may include pores and boundaries between different primary particles.

In one embodiment of the present invention, secondary particles in which a plurality of nickel-based lithium metal oxide particles are aggregated; And a first coating layer disposed on the pores of the secondary particles and covering a surface of a part or all of the plurality of nickel-based lithium metal oxide particles, wherein the first coating layer includes a compound having a spinel structure, Wherein the spinel structure compound represented by the formula (1) is represented by the following formula (1).

[Formula 1] Li _x CoO ₂

(In the above formula (1), 0.95 < x &lt; = 1.05.

The positive electrode active material for a lithium secondary battery is characterized in that i) a secondary battery including a secondary battery including a secondary battery including a secondary battery including a secondary battery including: i) Is a cathode active material for a lithium secondary battery improved in mechanical and thermal stability by coating a surface of some or all of particles (i.e., primary particles) with a first coating layer comprising a compound having a spinel structure represented by Formula 1 .

FIG. 1 schematically shows a cathode active material for a lithium secondary battery.

Generally, a nickel-based lithium metal oxide is a material which exhibits a high discharge capacity per unit weight. However, the battery, which is used as a cathode active material, is degraded in performance under high temperature or high-rate conditions and is difficult to be commercialized.

Specifically, the nickel-based lithium metal oxide is not firmly adhered to each other with respect to the primary particles, and the agglomerated secondary particles have a weak mechanical strength such that they are easily broken by physical pressing.

Further, when the secondary particles are applied to the battery as a cathode active material, micro-cracks are generated on the surfaces of the secondary particles as the volume expansion of the primary particles is different from each other, The electrolyte penetrates into the inside of the particles to induce a side reaction with the primary particles. As a result, the electrochemical characteristics of the battery shortens its service life.

These problems can be solved by the first coating film.

Specifically, the first coating layer enhances the mechanical strength of the secondary particles by adhering the primary particles to each other, and prevents penetration of the electrolyte by being located in the voids inside the secondary particles, By including the compound of formula (1), the volume expansion can be suppressed even when it is reacted with lithium. As a result, it is possible to improve the charging / discharging efficiency of the battery and the life characteristic at high temperature.

Further, the first coating layer may serve as a bridge of electron mobility between the primary particles, thereby contributing to improvement of the high-rate characteristics of the battery.

Hereinafter, the cathode active material for a lithium secondary battery provided in one embodiment of the present invention will be described in detail.

First, the first coating layer will be described as follows.

The spinel structure compound included in the first coating layer may be a compound containing lithium and cobalt. Accordingly, the first coating layer can maintain structural stability even in various oxidation states.

Specifically, as mentioned above, the spinel structure compound included in the first coating layer may be represented by the following formula (1).

[Formula 1] Li _x CoO ₂ (In the above formula (1), 0.95 < x &lt; = 1.05.

The spinel structure compound represented by the formula (1) has no reactivity with the primary particles, so that the capacity can be prevented from being lowered even when the battery is continuously driven.

More specifically, the spinel structure compound represented by Formula 1 may be a product obtained by inducing a sol-gel reaction of a coating composition comprising a lithium source material, a cobalt source material, and a solvent.

Unlike the coating film formed by wet coating or mechanically milling the lithium cobalt oxide itself, it may be a coating film having a dense state while completely covering the primary particles. Accordingly, generation of micro-cracks on the surface of the secondary particles due to the volume expansion of the primary particles can be effectively suppressed.

At this time, the first coating layer may continuously coat the entire surfaces of the plurality of lithium metal composite oxide particles. Here, "continuously" means that it is not a discontinuous coating film of the island type but a single continuous coating film. Further, by covering the surface of the "all" of the plurality of lithium metal composite oxide particles, the mechanical strength of the secondary particles can be further improved.

At this time, the content of cobalt in the first coating layer may be 5 to 50 mol%, for example, 10 to 25 mol%, based on 100 mol% of the entire first coating layer. Within this concentration range, adequate mechanical strength can be ensured by the first coating film.

More specifically, the compound having the spinel structure represented by Formula 1 may be LiCoO ₂ .

The thickness of the first coating film may be 0.001 to 20 nm, for example, 0.001 to 10 nm. When the thickness satisfies this range, the lithium secondary battery can be realized which does not lower the discharge capacity of the positive electrode active material and consequently has excellent capacity and life characteristics.

The content of the first coating layer in the cathode active material may be 0.5 to 2 parts by weight based on 100 parts by weight of the secondary particles aggregated with the plurality of nickel-based lithium metal oxide particles. If the amount is more than 2 parts by weight, the discharge capacity of the cathode active material may be excessively reduced. If the amount is less than 0.5 parts by weight, the content thereof is excessively low and it is not effective to introduce the first coating film.

On the other hand, a second coating layer covering the surface of the secondary particles and containing a compound having a spinel structure may be further included.

The spinel structure compound contained in the second coating layer may be represented by the following formula (2).

[Formula 2] Li _x CoO ₂

(In the above formula (2), 0.95 < x &lt; 1.05.

The thickness of the second coating layer may be 5 to 20 nm.

The content of the second coating layer in the cathode active material may be 0.5 to 2 parts by weight based on 100 parts by weight of the secondary particles of the nickel-based lithium metal oxide particles aggregated. If the amount is more than 2 parts by weight, the discharge capacity of the cathode active material may be excessively reduced. If the amount is less than 0.5 parts by weight, the content thereof is excessively low and it is not effective to introduce the first coating film.

Specifically, the secondary particles may be contained in an amount of 98 to 99.5% by weight based on 100% by weight of the total of the cathode active material, 0.5 to 2% by weight of the first coating layer, and the remainder of the second coating layer may be included This is based on the content of the first coating layer and the second coating layer, which are defined on the basis of 100 parts by weight of the secondary particles.

Each of the cathode active materials of Examples 1 to 4 described below satisfies the respective content ranges of the respective components, and in particular, the content of the secondary particles in 100 wt% of the cathode active material of Example 3 is 99.5 wt% Of the total. Further, the content of the secondary particles in the 100 wt% of the cathode active material of Example 4 is 98 wt%, which supports the lower limit of the secondary particle content.

The plurality of nickel-based lithium metal oxide particles may each be represented by the following formula (3).

???????? Li _a Ni _{1 -x- y} Co _x M _y O _{2 +?}

Wherein M is at least one element selected from the group consisting of Mg, Ti, Zr, Nb, Mo, Al, Mn, Mg, V And a rare earth element.

Specifically, in Formula 3, 0.9 <x <1.1, 0 <x <0.5, 0 <y <0.5, and a range of 1-x-y may be 0.4 to 1. For example, the range of 1-x-y may be 0.5 to 0.6. As such, the nickel-rich lithium metal oxide rich in nickel has a high energy density.

For example, the Formula _{3 NCA (LiNi 0 .8 Co 0} .15 Al 0 .05 O 2), 811 NCM (LiNi 0.8 Co 0.1 Mn 0.1 O 2), and LiNi _{0 .5} Co _{0 .2} Mn _{0 .3} O ₂ can be used. In the embodiments of the present invention described later, each of the nickel-based lithium metal oxides in which M is Al or Mn in Formula 3 is used.

The average particle diameter of the plurality of nickel-based lithium metal oxide particles may be 200 nm to 15 탆.

The average particle diameter of the secondary particles may be 5 to 15 占 퐉. When the average particle diameter is within this range, the density of the electrode plate mixture is not reduced, and as a result, a lithium secondary battery having superior safety and high-rate characteristics can be realized. In this case, when the secondary particles are not spherical, the average particle diameter indicates the major axis length.

In another embodiment of the present invention, there is provided a method of preparing a lithium secondary battery, comprising: preparing a nickel-based lithium metal oxide powder in the form of a secondary particle comprising a plurality of primary particles; Preparing a coating composition comprising a lithium raw material, a cobalt raw material, and a solvent; Mixing the nickel-based lithium metal oxide powder of the secondary particle type and the coating composition to obtain a nickel-based lithium metal oxide coated with the coating composition; And firing the nickel-based lithium metal oxide coated with the coating composition, wherein the nickel-based lithium metal oxide powder of the secondary particle type and the coating composition are mixed so that the nickel-based lithium metal oxide Wherein the nickel-based lithium-metal oxide secondary particles are injected into the internal void of the nickel-based lithium-metal oxide secondary particles, and the nickel-based lithium metal oxide to which the coating composition is applied is calcined, Wherein the first coating layer containing a compound having a spinel structure is formed in the pores of the metal oxide secondary particles and the spinel structure compound included in the first coating layer is represented by the following formula 4: &Lt; / RTI &gt;

[Formula 4] Li _x CoO ₂

(In the formula (4), 0.95 < x &lt; = 1.05).

The method for producing the cathode active material for a lithium secondary battery corresponds to a method for producing a cathode active material for a lithium secondary battery having the above-described characteristics.

Specifically, in order to form a first coating film containing a compound having a spinel structure on the internal pores of the nickel-based lithium metal oxide secondary particles, lithium cobalt oxide itself is not wet-coated or mechanically milled, Gel reaction of a coating composition comprising a starting material, a solvent, and a solvent.

In this case, the first coating layer formed through the sol-gel reaction includes a spinel structure compound represented by Formula 4, and may be a coating layer having a dense state while completely covering the primary particles.

Hereinafter, the description of the above-described steps will be omitted.

First, the nickel-based lithium metal oxide powder of the secondary particle type and the coating composition are mixed to obtain a nickel-based lithium metal oxide coated with the coating composition.

The mixing may be performed in a temperature range of 60 to 80 캜. Further, depending on the amount of the nickel-based lithium metal oxide powder, the mixing time may be 30 minutes to 1 hour.

In this temperature range, a sol-gel reaction of the coating composition is induced, and a first coating layer having a spinel structure represented by the general formula (1) can be formed.

Specifically, the nickel-based lithium metal oxide powder of the secondary particle type and the coating composition are mixed to obtain a nickel-based lithium metal oxide coated with the coating composition. The lithium-based lithium metal oxide powder and the cobalt raw material The material reacting to form a reaction product of the spinel structure; And injecting the reaction product of the spinel structure into the internal void of the nickel-based lithium metal oxide secondary particle.

Independently, the lithium source material and the cobalt source material in the coating composition react to form a reaction product of a spinel structure; And a reaction product of the spinel structure is injected into the inner pores of the nickel-based lithium metal oxide secondary particles and is applied to the outside of the nickel-based lithium metal oxide secondary particles.

In this case, the nickel-based lithium metal oxide coated with the coating composition is fired to form a first coating layer containing a compound having a spinel structure on the inside of the nickel-based lithium metal oxide secondary particle, And a second coating film containing a compound having a spinel structure is formed on the surface of the lithium metal oxide secondary particles.

Meanwhile, a detailed description of the step of firing the nickel-based lithium metal oxide coated with the coating composition is as follows.

The calcination may be performed at a temperature ranging from 400 to 600 ° C. If the calcination temperature is less than 400 ° C, the first coating layer may not be continuously formed on the surfaces of the plurality of primary particles, and a compound having a spinel structure represented by the following Formula 4 may not be formed have. Alternatively, if the calcination temperature exceeds 600 ° C., the cobalt raw material may be diffused into the primary particles, so that a concentration gradient in which the concentration of cobalt increases toward the center of the primary particles may be formed have.

The calcination may be performed for 3 to 5 hours. When the calcination is performed for more than 5 hours for a long time, the coating composition reacts with the primary particles and is difficult to form into the first coating layer. On the contrary, when the calcination is performed for less than 3 hours for a short time, the spinel structure compound represented by Formula 4 is hardly formed.

The firing may be performed in an oxidizing atmosphere. In this oxidizing atmosphere, the sol-gel reaction of the coating composition can be induced.

Calcining the nickel-based lithium metal oxide to which the coating composition is applied; Drying the nickel-based lithium metal oxide to which the coating composition has previously been applied.

Specifically, the drying may be performed at a temperature ranging from 120 to 160 ° C.

In addition, the coating composition and the nickel-based lithium metal oxide powder of the secondary particle type may be prepared as follows.

Preparing a coating composition comprising a lithium raw material, a cobalt raw material, and a solvent, wherein the lithium raw material is contained in an amount of 1 to 2 wt% based on 100 wt% of the entire coating composition, 90 to 93% by weight, and the solvent may be prepared to be included in the remainder.

When a coating composition satisfying the concentration range of each of these materials is prepared, the first coating layer and the second coating layer of the spinel structure represented by the above formulas (1) and (2) are respectively formed by the sol- .

Preparing a nickel-based lithium metal oxide powder in the form of a secondary particle containing the plurality of primary particles, the method comprising: mixing a precursor of the nickel-based lithium metal oxide and a lithium precursor; And heat-treating the mixture of the precursor of the nickel-based lithium metal oxide and the lithium precursor in an air atmosphere at 800 ° C to 1000 ° C for 10 to 20 hours.

At this time, the precursor of the nickel-based lithium metal oxide may be prepared by coprecipitation of a nickel precursor and a precursor of another transition metal. For example, the precursor of the nickel-based lithium metal oxide may be a hydroxide comprising nickel and other metals.

More specifically, examples of the other metal include cobalt and nickel. In this regard, cobalt acetate, cobalt sulfate, cobalt nitrate, etc. may be used as precursors of the cobalt. As the precursor of nickel, nickel acetate, nickel sulfate, nickel nitrate and the like can be used.

The lithium precursor may be lithium carbonate (Li ₂ CO ₃ ), lithium hydroxide (LiOH), or the like, but is not limited thereto, and any lithium precursor that can be used in the art can be used.

In another embodiment of the present invention, cathode; And an electrolyte, wherein the anode comprises a cathode active material according to any one of the above-mentioned aspects.

Specifically, the anode includes a current collector; And a cathode active material layer disposed on the current collector.

The positive electrode may be formed, for example, by forming the positive electrode active material composition containing the positive electrode active material and the binder in a predetermined shape, or applying the positive electrode active material composition to a current collector such as copper foil or aluminum foil .

Specifically, a cathode active material composition in which the cathode active material, the conductive material, the binder, and the solvent are mixed is prepared. The positive electrode active material composition is directly coated on the metal current collector to produce a positive electrode plate. Alternatively, the cathode active material composition may be cast on a separate support, and then the film peeled from the support may be laminated on the metal current collector to produce a cathode plate. The anode is not limited to those described above, but may be in a form other than the above.

As the conductive material, carbon black, graphite fine particles, or the like may be used, but not limited thereto, and any material that can be used as a conductive material in the related art can be used. For example, graphite such as natural graphite or artificial graphite; Conductive materials such as carbon black, acetylene black, and Ketjen black may be used.

Examples of the binder include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene and mixtures thereof, styrene butadiene rubber-based polymers, etc. May be used, but are not limited thereto and can be used as long as they can be used as bonding agents in the art.

As the solvent, N-methylpyrrolidone, acetone, water or the like may be used, but not limited thereto, and any solvent which can be used in the technical field can be used.

The content of the cathode active material, the conductive material, the binder, and the solvent is a level commonly used in a lithium secondary battery. Depending on the application and configuration of the lithium secondary battery, one or more of the conductive material, the binder, and the solvent may be omitted.

Next, the negative electrode active material composition is prepared by mixing the negative electrode active material, the conductive material, the binder and the solvent. The negative electrode active material composition is directly coated on the metal current collector and dried to produce a negative electrode plate. Alternatively, the negative electrode active material composition may be cast on a separate support, and then the film peeled off from the support may be laminated on the metal current collector to produce a negative electrode plate.

The negative electrode active material is not particularly limited and is generally used in the art. More specifically, it may be a lithium metal, a metal capable of alloying with lithium, a transition metal oxide, a transition metal sulfide, a material capable of doping and dedoping lithium, A material capable of reversibly intercalating and deintercalating lithium ions, a conductive polymer, and the like can be used.

As the conductive material, binder and solvent in the negative electrode active material composition, the same materials as those of the positive electrode active material composition may be used. It is also possible to add a plasticizer to the cathode active material composition and / or the anode active material composition to form pores inside the electrode plate.

The content of the negative electrode active material, the conductive material, the binder and the solvent is also a level commonly used in a lithium secondary battery. Depending on the application and configuration of the lithium secondary battery, one or more of the conductive material, the binder, and the solvent may be omitted.

2 schematically shows a typical structure of the lithium secondary battery. Specifically, the lithium secondary battery 1 includes a battery container 5 (including a positive electrode 3, a negative electrode 2, and an electrolyte solution impregnated in the separator 4 existing between the positive electrode 3 and the negative electrode 2) , And a sealing member (6) for sealing the battery container (5).

Hereinafter, preferred embodiments of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

Example  One: Li [ Ni _{0 .8} Co _{0 .15} Al _{0 .05} ] O ₂ The inner pores of the secondary particles and the outer LiCoO ₂ The coating film  The formed cathode active material

(One) Li [ Ni _{0 .8} Co _{0 .15} Al _{0 .05} ] O ₂ &Lt; / RTI &gt;

First, the _{Li [Ni 0 .8 Co 0 .15} Al 0 .05] of Ni _{0 .80} Co _{0 .15} precursor of _{O 2 Al 0 .05 (OH)} 2 was prepared by the following process.

Nickel precursor NiSO ₄ (H ₂ O) ₆ and cobalt precursor CoSO ₄ were added to water at a molar ratio of 90:10 (nickel precursor: cobalt precursor) to prepare a precursor aqueous solution.

While stirring the aqueous solution, an aqueous solution of sodium hydroxide was slowly dropped to neutralize the aqueous solution of the precursor. As a result, the precipitated precipitate is _{2 Ni 0 .89 Co 0 .11 (} OH), was filtered, the process proceeds to the process of drying in the washing with water, and 80 ℃ sequentially, to afford the Ni _0.89 Co _0.11 (OH) ₂ powder Respectively.

Al (OH) (C ₂ H ₃ O ₂ ) ₂ powder and ethanol were added to the Ni _{0 .89} Co _{0 .11} (OH) ₂ powder, and the mixture was dried in a vacuum oven at 80 ° C., _{Al 0 .05 (OH) 0 .80} Co 0 .15 to give the _second powder. In this case, the Al (OH) Loading of _{(C 2 H 3 O 2)} 2 powder, Ni _{1 -} x was determined to be 0.05 moles in formula of _{x Co 0 .1 Al x (OH} ) 2.

(2) Li [ Ni _{0 .8} Co _{0 .15} Al _{0 .05} ] O ₂  Preparation of secondary particles

The Li precursor is LiOH the _{Ni 0 .80 Co 0 .15 Al 0} .05 (OH) 2 powder 1: 1.03: then a solution by introducing a molar ratio of _{(Ni 0.80 Co 0.15 Al 0.05 (} OH) 2 LiOH), The mixture was calcined at 450 ° C. for 5 hours while flowing dry air into the furnace and then calcined at 750 ° C. for 18 hours to obtain the target Li [Ni _{0 .8} Co _{0 .15} Al _{0 .05} ] O ₂ secondary Particles (average particle diameter: about 7 mu m) were obtained.

(3) Li [ Ni _{0 .8} Co _{0 .15} Al _{0 .05} ] O ₂ The inner pores of the secondary particles and the outer LiCoO ₂ The coating film  Preparation of the formed cathode active material

0.546 g of lithium acetate and 2.665 g of cobalt acetate were added to 50 ml of ethanol and mixed to prepare a coating composition.

The _{Li [Ni 0 .8 Co 0 .15} Al 0 .05] O 2 (NCA) for the secondary particles of 100 parts by weight, the coating composition was added 1 part by weight, and mixed at about 60 ℃ for 30 min, and a sol-gel The reaction was induced and the solvent was completely removed.

The resultant was vacuum-dried at about 150 ° C and then calcined at about 600 ° C for 4 hours to finally obtain a cathode active material (average particle diameter: about 7 μm).

At this time, the obtained positive electrode active material is the _{Li [Ni 0 .8 Co 0 .15} Al 0 .05] O 2 (NCA) includes secondary particles, the crystal structure of the primary particles constituting them have a layered structure (R-3m) Respectively.

In addition, LiCoO ₂ A coating film is formed on the inner pores (first coating film) and the outside (second coating film) of the secondary particles, and the LiCoO ₂ The crystal structure of the coating film was confirmed to be a spinel-like structure (Fd-3m).

The crystal structure of the primary particles constituting the secondary particles, the crystal structure of the first coating layer and the crystal structure of the second coating layer are confirmed through the following evaluation examples.

The Li [Ni _0.8 Co _0.15 Al _0.05 ] O ₂ secondary particles in an amount of 100 wt% of the entire cathode active material were 99 wt% and LiCoO ₂ The coating film was confirmed to be 1% by weight.

At this time, the LiCoO ₂ The content of the coating film is 1% by weight, which means the total content of the first coating film located on the inner space of the Li [Ni _0.8 Co _0.15 Al _0.05 ] O ₂ secondary particle and the entire second coating film located on the outside thereof .

Example  2: Li [ Ni _{0 .8} Co _{0 .One} Mn _{0 .One} ] O ₂ The inner pores of the secondary particles and the outer LiCoO ₂ The coating film  The formed cathode active material

Exemplary _{Li [Ni 0 .8 Co 0 .15} Al 0 .05] O 2 secondary particle instead of Li [Ni Mn _{0 .8} Co _{.1 0 .1 0]} O ₂ was prepared in the secondary particle, except that, for example, 1 and by performing the same procedure, Li [Ni Mn _{0 .8} Co _{.1 0 .1 0]} O LiCoO ₂ inside and outside the pores of the secondary particle ₂ Thereby preparing a cathode active material having a coating film.

In addition, the Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ secondary particles were contained in an amount of 99% by weight and LiCoO ₂ The coating was found to be 1 wt.

At this time, the LiCoO ₂ The content of the coating film of 1 wt% means the total content of the first coating layer located on the inner pore of the Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ secondary particle and the entire second coating layer located on the outside of the Li [Ni _0.8 Co _0.1 Mn _0.1 ] do.

Specifically, the process for producing the Li [Ni Mn _{0 .8} Co _{.1 0 .1 0]} O ₂ secondary particle is as follows.

(One) Li [ Ni _{0 .8} Co _{0 .One} Mn _{0 .One} ] O ₂ &Lt; / RTI &gt;

First, the Li [Ni Mn _{0 .8} Co _{.1 0 .1 0]} O ₂ in the precursor of _{Ni 0 .80 Co 0 .10 Mn 0} .10 (OH) 2 was prepared by the following process.

Nickel precursor NiSO ₄ (H ₂ O) ₆ , cobalt precursor CoSO ₄ (H ₂ O) ₆ and manganese precursor MnSO ₄ (H ₂ O) ₆ were mixed at a ratio of 80:10:10 (nickel precursor: cobalt precursor: manganese precursor) To prepare a precursor aqueous solution.

While stirring the aqueous solution, an aqueous solution of sodium hydroxide was slowly dropped to neutralize the aqueous solution of the precursor. As a result, the precipitated precipitate is _{Mn 0 .10 (OH) Ni 0} .80 Co 0 .10 2, the process proceeds was filtered, dried in the process of washing with water, and 80 ℃ sequentially, the Ni _0.80 Co _0.10 Mn _0.10 ( OH) &lt; / RTI &gt; ₂ powder.

(2) Li [ Ni _{0 .8} Co _{0 .One} Mn _{0 .One} ] O ₂ Preparation of secondary particles

The _{Ni 0 .80 Co 0 .10 Mn 0} .10 (OH) ₂ LiOH lithium precursor powder 1: 1.03: then a solution by introducing a molar ratio of _{(Ni 0.80 Co 0.10 Mn 0.10 (} OH) 2 LiOH), And calcined at 450 ° C. for 5 hours and then calcined at 750 ° C. for 18 hours to obtain the desired Li [Ni _{0 .8} Co _{0 .1} Mn _{0 .1} ] O ₂ quasicide (Average particle diameter: about 10 mu m).

Example  3: Li [ Ni _{0 .8} Co _{0 .15} Al _{0 .05} ] O ₂  The inner pores of the secondary particles and the outer LiCoO ₂ The coating film  The formed cathode active material

The _{Li [Ni 0 .8 Co 0 .15} Al 0 .05] O 2 (NCA) for the secondary particles of 100 parts by weight, the coating composition was added 1 part by weight, and mixed at about 60 ℃ for 30 min, and a sol-gel and except that the reaction was induced, and, in example 1, a procedure is the _{same, Li [Ni 0 .8 Co 0} .15 Al 0 .05] O LiCoO 2 inside the gap and outside the _second secondary particle Thereby preparing a cathode active material having a coating film.

In addition, it was confirmed that the Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ secondary particles were 99.5 wt% and the LiCoO ₂ coating film was 0.5 wt% in 100 wt% of the entire cathode active material.

In this case, the content of the LiCoO ₂ coating layer is 0.5% by weight. The first coating layer located in the inner void of the Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ secondary particles and the entire second coating layer Means one content.

Example  4: Li [ Ni _{0 .8} Co _{0 .15} Al _{0 .05} ] O ₂  The inner pores of the secondary particles and the outer LiCoO ₂ The coating film  The formed cathode active material

The _{Li [Ni 0 .8 Co 0 .15} Al 0 .05] O 2 (NCA) for the secondary particles of 100 parts by weight, the coating composition was added 1 part by weight, and mixed at about 60 ℃ for 30 min, and a sol-gel and except that the reaction was induced, and, in example 1, a procedure is the _{same, Li [Ni 0 .8 Co 0} .15 Al 0 .05] O LiCoO 2 inside the gap and outside the _second secondary particle Thereby preparing a cathode active material having a coating film.

In addition, the Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ secondary particles at 98 wt% and LiCoO ₂ The coating film was found to be 2% by weight.

At this time, the LiCoO ₂ coating layer having a content of 2 wt% is composed of the first coating layer located in the inner voids of the Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ secondary particles and the entire second coating layer It means the total content.

Comparative Example  One: Li [ Ni _{0 .8} Co _{0 .15} Al _{0 .05} ] O ₂  Secondary particle

Subjected to a _{Li [Ni 0 .8 Co 0 .15} Al 0 .05] O 2 secondary particles prepared in Example 1 was used as a positive electrode active material.

Comparative Example  2: Li [ Ni _{0 .8} Co _{0 .15} Al _{0 .05} ] O ₂  Only on the outside of secondary particles The coating film  The formed cathode active material

Carrying out the _{Li [Ni 0 .8 Co 0 .15} Al 0 .05] coating the outside of the O ₂ only the secondary particles prepared in Example 1 was formed.

Specifically, 0.3 g of ammonium vanadate was added to 35 ml of ethanol and mixed to prepare a coating composition.

The _{Li [Ni 0 .8 Co 0 .15} Al 0 .05] O 2 (NCA) for the secondary particles of 100 parts by weight, the coating composition was added 1 part by weight, and mixed at about 60 ℃ for 30 min, and a sol-gel The reaction was induced,

The resultant was vacuum-dried at about 150 ° C. and then calcined at about 600 ° C. for 4 hours. Finally, the above-mentioned Li [Ni _{0 .8} Co _{0 .15} Al _{0 .05} ] O ₂ (NCA) (Average particle diameter: about 7 mu m) having a vanadate coating film was obtained.

Comparative Example  3: Li [ Ni _{0 .8} Co _{0 .10} Mn _{0 .10} ] O ₂  Secondary particle

Example  2 Li [ Ni _{0 .8} Co _{0 .10} Mn _{0 .10} ] O ₂  Secondary particles were used as the cathode active material.

Production Example  1: anode and lithium secondary battery (coin Half cell )

The cathode active material powder obtained in Example 1 and a carbon conductive material (Super P) were uniformly mixed in a weight ratio of 92: 4 (cathode active material powder: carbon conductive material), and then a PVDF (polyvinylidene fluoride) A cathode active material slurry was prepared so that the weight ratio of active material powder: carbon conductive material: binder = 92: 4: 4.

Using the doctor blade, the cathode active material slurry was coated on the aluminum current collector having a thickness of 15 占 퐉 to a thickness of 200 占 퐉, dried at 110 占 폚 for 3 hours or more and rolled to produce a positive electrode plate having a thickness of 50 占 퐉.

Using the above-mentioned positive electrode plate, lithium metal was used as a counter electrode and a polyethylene separator (STAR 20, Asahi) and 1.15M LiPF ₆ were mixed with EC (ethylene carbonate) + EMC (ethylmethyl carbonate) + DMC (dimethyl carbonate) : 3: 4 by volume) was used as an electrolyte to prepare a 2032R coin cell.

Production Example  2 to 4: positive electrode and lithium secondary battery (coin Half cell )

A positive electrode and a lithium secondary battery (coin half cell) were respectively prepared in the same manner as in Production Example 1, except that the positive electrode active materials of Examples 2 to 4 were used in place of the positive electrode active material of Example 1, respectively.

Comparative Production Example  1 to 3: positive electrode and lithium secondary battery (coin Half cell )

A positive electrode and a lithium secondary battery (coin half cell) were respectively prepared in the same manner as in Production Example 1, except that the positive electrode active materials of Comparative Examples 1 to 3 were used instead of the positive electrode active material of Example 1.

Evaluation example  1: Pressure density measurement

Each of the cathode active materials of Example 1 and Comparative Example 1 was made into pellets, and the pressure densities thereof were measured. Specifically, a pressure of about 25 MPa (= 254.93 kgf / cm ² ) was applied to each of the cathode active material powders of Example 1 and Comparative Example 1 for 30 seconds to prepare pellets, and the pressure density was measured.

The pressure density of each pellet was measured to be 3.34 g / cc for Comparative Example 1 and 3.41 g / cc for Example 1.

It is thus the pressure density of Example 1 higher than in Comparative Example _{1, Li [Ni 0.8 Co 0.15} Al 0.05] O 2 as compared to the positive electrode active material of Comparative Example 1 comprising only the secondary particles, the Li [Ni _{0 .8} Co _{0. 15} Al _{0 .05} ] O ₂ secondary particles (first coating layer) and the outer (second coating layer) of LiCoO ₂ Means that the mechanical strength is improved by the coating film.

Evaluation example  2: scanning electron microscope SEM ) Experiment

SEM photographs of each cathode active material of Example 1 and Comparative Example 1 were taken before and after measurement of the pressure density in Evaluation Example 1, and the results are shown in Figs. 3 to 8. Fig.

3 to 5 are for the cathode active material of Example 1. Specifically, SEM photographs of the cathode active material powder before measurement of the pressure density in Evaluation Example 1 are shown in Fig. 3, and after the pressure density was measured, 4 and 5 are SEM photographs taken. 4 is a photograph of the outside of the pellet after measuring the pressure density.

6 to 8 are for the cathode active material of Comparative Example 1. Specifically, an SEM photograph of the cathode active material powder for measuring the pressure density in Evaluation Example 1 is shown in Fig. 6, and the pressure density was measured, The SEM photographs taken are FIGS. 6 and 7. 6 is a photograph of the outside of the pellet after measuring the pressure density.

Referring to FIGS. 4 and 5, it is confirmed that even when mechanical pressure is applied to the cathode active material of Example 1, the secondary particles retain their spherical shape. On the other hand, referring to FIGS. 7 and 8, it was confirmed that the cathode active material of Comparative Example 1 collapsed to such an extent that the secondary particles could not be recognized by mechanical pressure.

_{This, Li [Ni 0 .8 Co 0} .15 Al 0 .05] O 2, compared with the positive electrode active material of Comparative Example 1 comprising only the secondary particles _{Li [Ni 0 .8 Co 0 .15} Al 0 .05] O ₂ LiCoO ₂ formed in the inner pores (first coating film) of the secondary particles and the outer (second coating film) It was once again confirmed that the mechanical strength was improved by the coating film.

Evaluation example  3: Scanning transmission electron microscope ( Scanning Transmission Electron  Microscopy: STEM ) analysis

Scanning transmission electron microscopy (STEM) photographs were taken of each of the cathode active materials of Example 1 and Comparative Example 1, and the results are shown in FIGS. 9 to 16. By doing so, different secondary particles We tried to obtain structural information about the interface between primary particles.

9 to 12 are for the cathode active material of Example 1. Specifically, FIG. 9 is an STEM photograph of a boundary between primary particles located inside Li [Ni _0.8 Co _0.15 Al _0.05 ] O ₂ secondary particles, 10 and 11 are STEM photographs obtained by enlarging and photographing an area indicated by a rectangle in Fig.

13 to 16 are for the cathode active material of Comparative Example 1. More specifically, FIG. 13 is a STEM photograph of a boundary between primary particles located inside Li [Ni _0.8 Co _0.15 Al _0.05 ] O ₂ secondary particles, 14 and 15 are STEM photographs obtained by enlarging and photographing a region indicated by a rectangle in Fig.

Referring to FIGS. 14 and 15, it can be seen that the cathode active material of Comparative Example 1 has a void space of several nanometers (nm) between different primary particles. Further, referring to FIG. 16, it can be seen that the crystal structure of the primary particles is a layered structure (triangular system, space group R3m).

On the other hand, referring to FIGS. 10 and 11, it can be seen that the cathode active material of Example 1 has no void space between different primary particles. Further, referring to FIG. 12, it can be seen that the crystal structure of the coating film (first coating film) filling between the different primary particles is a spinel structure (cubic system, space group Fd-3m).

Evaluation example  3: Lithium secondary battery Charging and discharging  characteristic

Each lithium secondary battery of Production Example 1 and Comparative Production Example 1 was subjected to constant current charging at a current of 0.1 C rate at 25 DEG C until the voltage reached 4.3 V (vs. Li), and the voltage was 3.0 V RTI ID = 0.0 &gt; of Li). &lt; / RTI &gt; The first cycle characteristic is shown in Fig.

Subsequently, each lithium secondary battery of Production Example 1 and Comparative Production Example 1 was charged at a constant current of 0.5 C under the same conditions as those of the first cycle, and then 0.2 C and 0.5 C , 1C, 3C, 5C, 7C, and 10C, respectively. The cycle characteristics at this time are shown in Fig.

The charge-discharge efficiency and the high-rate characteristic obtained through the above charge-discharge experiment are expressed by the following formula 1.

[Formula 1]

High rate characteristic [%] = [1 C (second cycle) discharge capacity / 0.2 C (first cycle) discharge capacity] × 100

Referring to FIG. 18, it can be seen that the lithium secondary battery manufactured according to Production Example 1 exhibits improved high-rate characteristics as compared with Comparative Production Example 1.

Evaluation example  4: Life characteristics evaluation of lithium secondary battery

(One) Production Example  1 and Comparative Production Example  Comparison of high temperature lifetime characteristics

In order to compare lifetime characteristics at high temperature, each lithium secondary battery of Production Example 1 and Comparative Production Example 1 was subjected to constant current charging at a current of 0.5 C rate at 60 DEG C until the voltage reached 4.3 V, The cycle of discharging at a constant current of 1cc until the voltage reached 3.0 V was repeated 300 times.

The results of such charging and discharging tests are shown in FIG. 19. Referring to these results, the lithium secondary battery of Production Example 1 has a reduced capacity even when the battery is repeatedly charged and discharged at a high temperature, Can be seen.

(2) Production Example  1 and Comparative Production Example  1 at a high rate of room temperature Life characteristics comparison

To compare lifetime characteristics at the time of high rate discharge, each lithium secondary battery of Production Example 1 and Comparative Production Example 1 was subjected to constant current charging at a current of 0.5 C rate at room temperature until the voltage reached 4.3 V, The cycle of discharging at a constant current of 1 C until the voltage reached 3.0 V was repeated 100 times.

The results of such charge-discharge tests are shown in FIG. 20. Referring to these results, the lithium secondary battery of Production Example 1 has a reduced capacity even when the battery is repeatedly charged and discharged at a high rate as compared with Comparative Production Example 1, Can be seen.

(3) Production Example  1 and 2, Comparative Production Example  High temperature and high rate of 1 to 3 Life characteristics comparison

In order to compare lifetime characteristics at high rate and high temperature discharge, each of the lithium secondary batteries of Production Examples 1 and 2 and Comparative Production Examples 1 to 3 was charged at 60 ° C. with a current of 0.5 C rate until the voltage reached 4.3 V The cycle of constant current charging and discharging at a constant current of 1 C until the voltage reached 3.0 V at the time of discharging was repeated 100 times.

The results of such charge-discharge tests are shown in FIGS. 20 to 22, and it is understood that each lithium secondary battery of Production Examples 1 and 2 has a higher capacity than the Comparative Production Examples 1 to 3 even if the battery is repeatedly charged and discharged at high temperature and high rate. Is not lowered, and an improved life characteristic is exhibited.

(4) Scanning transmission electron microscope ( Scanning Transmission Electron Microscopy : STEM) analysis

After evaluating the high-temperature and high-rate lifespan characteristics, Scanning Transmission Electron Microscopy (STEM) photographs of each of the cathode active materials recovered in each lithium secondary battery of Production Example 1 and Comparative Production Example 1 were taken, Are shown in Figs. 23 to 26.

23 and 24 are for the positive electrode active material recovered in the lithium secondary battery of Production Example 1. It can be confirmed that the internal shape of the secondary particles is maintained even though charging and discharging were performed at a high temperature of 60 캜 for 300 cycles.

25 and 26 are for the positive electrode active material recovered in the lithium secondary battery of Comparative Production Example 1 and 300 cycles of charging and discharging at a high temperature of 60 캜 show that significant collapse progressed inside the secondary particles.

27 and 28, the positive electrode active material recovered in the lithium secondary battery of Comparative Production Example 1 has a more severe electrolyte side reaction than Production Example 1, and P and F ions are generated between the different primary particles constituting the secondary particles And it is distributed.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

1: lithium secondary battery 2: negative electrode
3: anode 4: separator
5: Battery container 6: Sealing member

Claims (23)

Secondary particles in which a plurality of nickel-based lithium metal oxide particles are aggregated;
Based lithium metal oxide particles, which are located in the voids in the secondary particles and are in a dense state while completely covering the surface of a part or all of the plurality of nickel-based lithium metal oxide particles constituting the secondary particles, A first coating layer for applying a coating solution; And
And a second coating film covering the surface of the secondary particle,
Wherein the first coating layer and the second coating layer comprise a spinel structure Li _x CoO ₂ (where 0.95 < _x &lt; = 1.05)
Cathode active material for lithium secondary battery.
delete The method according to claim 1,
The content of cobalt in the first coating layer may be,
Wherein the first coating layer comprises 5 to 50% by mole,
Cathode active material for lithium secondary battery.
The method according to claim 1,
The spinel structure compound contained in the first coating layer is a compound having a spinel structure,
LiCoO ₂ ,
Cathode active material for lithium secondary battery.
The method according to claim 1,
The thickness of the first coating layer may be,
0.001 to 20 nm,
Cathode active material for lithium secondary battery.
The method according to claim 1,
The content of the first coating film in the positive electrode active material is,
Wherein the first coating layer is included in an amount of 0.5 to 2 parts by weight based on 100 parts by weight of the secondary particles.
Cathode active material for lithium secondary battery.
delete delete The method according to claim 1,
The thickness of the second coating film may be,
5-20 nm,
Cathode active material for lithium secondary battery.
The method according to claim 1,
The content of the second coating film in the cathode active material is,
Wherein the second coating layer is included in an amount of 0.5 to 2 parts by weight based on 100 parts by weight of the secondary particles.
Cathode active material for lithium secondary battery.
The method according to claim 1,
Wherein the secondary particles are contained in an amount of 98 to 99.5% by weight based on 100% by weight of the total of the cathode active material, and the first coating layer and the second coating layer are collectively contained in a range of 0.5% by weight to 2%
Cathode active material for lithium secondary battery.
The method according to claim 1,
Wherein the plurality of nickel-based lithium metal oxide particles each comprise
Wherein R < 1 &gt;
Cathode active material for lithium secondary battery.
(3)
Li _a Ni _{1 -x- y} Co _x M _y O _{2 + alpha}
Wherein M is at least one element selected from the group consisting of Mg, Ti, Zr, Nb, Mo, Al, Mn, Mg, V and a rare earth element.)
The method according to claim 1,
The average particle diameter of the secondary particles is,
5 to 15 [micro] m,
Cathode active material for lithium secondary battery.
Preparing a nickel-based lithium metal oxide powder in the form of a secondary particle comprising a plurality of primary particles;
Preparing a coating composition comprising a lithium raw material, a cobalt raw material, and a solvent;
Mixing the nickel-based lithium metal oxide powder of the secondary particle type and the coating composition to obtain a nickel-based lithium metal oxide coated with the coating composition; And
Calcining the nickel-based lithium metal oxide to which the coating composition is applied;
, &Lt; / RTI &
Mixing the nickel-based lithium metal oxide powder of the secondary particle type and the coating composition to obtain a nickel-based lithium metal oxide coated with the coating composition, wherein the lithium raw material and the cobalt raw material in the coating composition are reacted To form a reaction product of a spinel structure; And applying the reaction product of the spinel structure to the outside of the nickel-based lithium metal oxide secondary particle while being injected into the internal void of the nickel-based lithium metal oxide secondary particle,
A nickel-based lithium metal oxide having the coating composition applied thereon is fired, and a coating film containing a compound having a spinel structure is formed as the coating is performed in a temperature range of 400 to 600 ° C,
The coating film has a dense state while completely covering the surface of a part or all of a plurality of nickel-based lithium metal oxide particles which are located in the voids in the secondary particles and constitute the secondary particles, and the plurality of nickel- A first coating film which adheres each other to each other; And a second coating film covering the surface of the secondary particle,
Wherein the first coating layer and the second coating layer comprise a spinel structure Li _x CoO ₂ (wherein 0.95 &lt; _x &lt; = 1.05)
(Method for producing positive electrode active material for lithium secondary battery).
delete delete delete delete 15. The method of claim 14,
Firing the nickel-based lithium metal oxide to which the coating composition is applied,
RTI ID = 0.0 &gt; 3-5 &lt; / RTI &gt;
(Method for producing positive electrode active material for lithium secondary battery).
15. The method of claim 14,
Firing the nickel-based lithium metal oxide to which the coating composition is applied,
Lt; RTI ID = 0.0 &gt;
(Method for producing positive electrode active material for lithium secondary battery).
15. The method of claim 14,
Calcining the nickel-based lithium metal oxide to which the coating composition is applied; Before,
And drying the nickel-based lithium metal oxide coated with the coating composition.
(Method for producing positive electrode active material for lithium secondary battery).
15. The method of claim 14,
Preparing a coating composition comprising a lithium raw material, a cobalt raw material, and a solvent,
Wherein the lithium raw material is contained in an amount of 1 to 2 wt% based on 100 wt% of the entire coating composition, the cobalt raw material is contained in an amount of 90 to 93 wt%, and the solvent is prepared to be included in the remainder.
(Method for producing positive electrode active material for lithium secondary battery).
anode;
cathode; And
An electrolyte;
Wherein the anode comprises the cathode active material according to any one of claims 1 to 7 and 13 to 13.
Lithium secondary battery.

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