KR101627847B1 - Positive active material for rechargeable lithium battery, and method for manufacturing the same - Google Patents

Abstract

A positive electrode active material for a lithium secondary battery, and a method of manufacturing the same, comprising: a core including a flake type primary particle compound; And a first coating layer of NiO on the core, wherein the primary particles have a particle diameter of 100 nm to 3 占 퐉, and the cathode active material of the secondary particle type has the following formula 1 < / RTI &gt; for a lithium secondary battery.
[Chemical Formula 1]
_{(1-xy) Li 2 MnO} 3 -xLiM 1 O 2
(Wherein 0 < x < 1 and 0 &lt; y &lt; 1 and M ¹ is a transition metal)

Description

[0001] The present invention relates to a cathode active material for a lithium secondary battery, and a cathode active material for a lithium secondary battery,

A cathode active material for a lithium secondary battery, and a process for producing the same.

Recently, with regard to the tendency to miniaturize and lighten portable electronic devices, there is an increasing need for high performance and large capacity of batteries used as power sources for these devices.

Cells generate electricity by using materials that can electrochemically react to the positive and negative electrodes. A representative example of such a battery is a lithium secondary battery that generates electrical energy by a change in chemical potential when the lithium ions are intercalated / deintercalated in 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 filling an organic electrolytic solution or a polymer electrolyte between the positive electrode and the negative electrode.

As a cathode active material of the lithium secondary battery, a lithium composite metal compound is used. Examples of the lithium composite metal compound include LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _{1 -x} Co _x O ₂ (0 <x <1), LiMnO ₂ Metal oxides are being studied.

Of the above cathode active materials, Mn-based cathode active materials such as LiMn ₂ O ₄ and LiMnO ₂ are easy to synthesize and are relatively inexpensive and have excellent thermal stability compared to other active materials in overcharging, However, it has a disadvantage of low capacity.

LiNiO ₂ also exhibits the highest discharge capacity of the battery among the above-mentioned cathode active materials, but it is difficult to synthesize LiNiO ₂ . Also, the high oxidation state of nickel causes degradation of battery life and electrode life, and there is a problem that self discharge is severe and reversibility is low. In addition, it is difficult to commercialize it because the stability is not completely secured.

LiCoO ₂ is currently popularized as an active material with a particle size of about 10 μm, but it does not guarantee a sufficient energy density.

It is possible to provide a cathode active material having improved characteristics. More particularly, the present invention relates to a cathode active material for a lithium secondary battery excellent in lifetime characteristics and excellent in output characteristics, with high initial coulombic efficiency, a method for producing the same, and a lithium secondary battery manufactured using the same.

In one embodiment of the invention, a core comprising a primary particle compound in the form of a flake; And a first coating layer of NiO on the core, wherein the primary particles have a particle diameter of 100 nm to 3 占 퐉, and the cathode active material of the secondary particle type has the following formula 1 &lt; / RTI &gt; for a lithium secondary battery.

[Chemical Formula 1]

_{(1-xy) Li 2 MnO} 3 -xLiM 1 O 2

(Wherein 0 < x < 1 and 0 < y < 1 and M ¹ is a transition metal)

The thickness of the first coating layer may be 1 to 15 nm.

And a second coating layer between the core and the first coating layer, and the second coating layer may be a mixture of the NiO phase and the spinel phase.

The thickness of the second coating layer may be 1 to 100 nm.

The thickness ratio of the first coating layer to the second coating layer may be 1/1 to 13/100.

The molar ratio of lithium / (other metals except lithium) in the total positive electrode active material including the core, the first coating layer and the second coating layer may be 1.05 to 1.4.

M ¹ in Formula 1 may include at least one metal selected from the group consisting of Ni, Co, and Mn.

In another embodiment of the present invention, there is provided a lithium secondary battery comprising: a lithium composite oxide having a flake shape and having a primary particle diameter of 100 nm to 3 占 퐉; And a basic solution; Introducing, mixing and heating the lithium composite oxide into the basic solution to activate the surface of the lithium composite oxide; And heat treating the surface of the activated lithium complex oxide. The present invention also provides a method for producing a cathode active material for a lithium secondary battery.

Preparing a lithium composite oxide having a flake form and having a primary particle diameter of 100 nm to 3 占 퐉 and a basic solution, wherein the primary particle has a particle size of 100 nm to 3 占 퐉, 탆 is obtained by mixing a metal composite oxide precursor and a lithium raw material; Wherein the step of obtaining a lithium composite oxide by heat treating the mixed metal complex oxide precursor and the lithium source material comprises the steps of preparing a mixed metal oxide precursor and a lithium source material by heat treatment, A first heat treatment step at 200 to 600 ° C; And a second heat treatment step at 700 to 1000 &lt; 0 &gt; C.

Mixing the metal complex oxide precursor and the lithium source material, wherein the metal complex oxide precursor is a mixture of a metal raw material, an aqueous ammonia solution or an ammonium aqueous solution, and an aqueous sodium hydroxide solution; And maintaining the temperature of the reactor at 20 to &lt; RTI ID = 0.0 &gt; 90 C &lt; / RTI &gt; and stirring.

Stirring the mixture while maintaining the temperature of the reactor at 20 to 90 DEG C; and stirring speed may be 700 to 1500 rpm.

Mixing the lithium complex oxide with the basic solution and activating the surface of the lithium complex oxide by heating the basic solution to 30 to 120 ° C; And charging the lithium complex oxide into the heated basic solution, followed by stirring.

The step of charging the lithium complex oxide into the heated basic solution followed by stirring may be performed for 1 to 240 hours.

Heat treating the surface of the activated lithium complex oxide; The method may further include drying the lithium composite oxide on which the surface is activated.

The step of drying the surface-activated lithium composite oxide may be performed at 80 to 160 ° C.

The step of heat-treating the surface-activated lithium composite oxide may be performed at 150 to 900 ° C.

The basic solution may be a solution having hydrogen ions and capable of causing exchange with lithium ions.

The basic solution may be a hydrazine solution, an ammonia solution, or a combination thereof.

The cathode active material according to the above production method comprises: a core comprising a flake-form primary particle compound; And a first coating layer of NiO on the core, wherein the primary particles have a particle diameter of 100 nm to 3 占 퐉, and the cathode active material of the secondary particle type has the following formula 1 &lt; / RTI &gt;

[Chemical Formula 1]

_{(1-xy) Li 2 MnO} 3 -xLiM 1 O 2

(Wherein 0 < x < 1 and 0 < y < 1 and M ¹ is a transition metal)

The thickness of the first coating layer may be 1 to 15 nm.

And a second coating layer between the core and the first coating layer, and the second coating layer may be a mixture of the NiO phase and the spinel phase.

The thickness of the second coating layer may be 1 to 100 nm.

According to another embodiment of the present invention, there is provided a positive electrode comprising a positive electrode active material for a lithium secondary battery according to an embodiment of the present invention; A negative electrode comprising a negative electrode active material; And an electrolyte.

A cathode active material for a lithium secondary battery excellent in lifetime characteristics and excellent in output characteristics as well as a high initial coulombic efficiency, a method for producing the same, and a lithium secondary battery manufactured using the same can be provided.

More specifically, it is possible to provide a method for synthesizing a cathode active material for a lithium secondary battery having a high energy density per unit volume and a chemical treatment method for implementing the method.

1 is an SEM photograph of an active material according to Examples and Comparative Examples.
2 is a TEM photograph of the active material according to Example 3. Fig.
3 is a high magnification TEM image corresponding to the green square of FIG.
4 is a graph showing the output characteristic of the battery according to Example 4 and Comparative Example 2. Fig.
FIG. 5 is a graph showing output characteristics of the battery according to Example 4 and Comparative Example 4. FIG.
6 is a graph showing the life characteristics of the capacity per unit volume of the battery according to Example 4 and Comparative Example 4. Fig.
7 is a graph showing lifetime characteristics of the energy density per unit volume of the battery according to Example 4 and Comparative Example 4. 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.

In one embodiment of the present invention, there is provided a cathode active material for a lithium secondary battery, which has excellent energy per unit volume, high initial coulombic efficiency, excellent lifetime characteristics and excellent output characteristics, a method for producing the same, and a lithium secondary battery manufactured using the same .

One embodiment of the present invention can more specifically provide a cathode active material having an energy density per volume of (1200 WhL- ¹ ) or more. More specifically (1280 WhL- ¹ ) or more.

The positive electrode active material according to an embodiment of the present invention may be prepared by chemically activating a Li ₂ MnO ₃ phase on the active material surface using an aqueous solution (e.g., a basic solution) containing hydrogen ions, and then heat- An electrochemically stable coating layer (or surface layer) can be formed.

More specifically, in one embodiment of the present invention, a core comprising a primary particle compound in the form of a flake; And a first coating layer of NiO on the core, wherein the primary particles have a particle diameter of 100 nm to 3 占 퐉, and the cathode active material of the secondary particle type has the following formula 1 &lt; / RTI &gt; for a lithium secondary battery.

[Chemical Formula 1]

_{(1-xy) Li 2 MnO} 3 -xLiM 1 O 2

(Wherein 0 < x < 1 and 0 < y < 1 and M ¹ is a transition metal)

In the present specification, the primary particle means the first lithium composite oxide obtained from the precursor, and the secondary particle means the particle in which such primary particles are aggregated. Thus, the particle size of the secondary particles can be controlled by the particle diameter of the primary particles, the number of aggregates, and the like.

The first coating layer is a structure in which lithium is removed by a production method using a basic solution to be described later. Such a structure can improve the lifetime characteristics and the output characteristics of the battery with a structural and electrochemically stable structure. The thickness of the first coating layer may be 1 to 15 nm, more specifically, 1 to 10 nm. The lifetime characteristics and the output characteristics may be slightly changed depending on the thickness range, and the stirring time to be described later can be controlled according to the desired thickness.

More specifically, y may be 0 < y? 0.8 or 0 < y? 0.5. It can be seen that a coating layer in which lithium is removed by the y value is formed.

More specifically, a second coating layer may be further disposed between the core and the first coating layer. The second coating layer may be a mixture of a NiO phase and a spinel phase.

More specifically, the thickness of the second coating layer may be 1 to 100 nm.

This second coating layer is evidence that an aqueous solution containing hydrogen chemically activated the Li ₂ MnO ₃ phase on the surface of the active material.

For example, the thickness ratio of the first coating layer to the second coating layer may be 1/1 to 13/100. However, the present invention is not limited thereto.

The Li / M molar ratio in the whole cathode active material including the core and the coating layer may be 1.05 to 1.6, more specifically 1.1 to 1.35. This is the rate at which Li is removed from the raw material to be initially introduced, and can be changed depending on the thickness of the coating layer.

Here, M represents all of the metals other than lithium in the entire cathode active material.

M ¹ in Formula 1 may include at least one metal selected from the group consisting of Ni, Co, and Mn. Any transition metal that is already known in the art can be used, but is not limited thereto.

According to another embodiment of the present invention, there is provided a method of manufacturing a lithium secondary battery, comprising the steps of: preparing a lithium composite oxide having a flake form and having a primary particle diameter of 100 nm to 3 占 퐉; and a basic solution; Introducing, mixing and heating the lithium composite oxide into the basic solution to activate the surface of the lithium composite oxide; And heat treating the surface of the activated lithium complex oxide. The present invention also provides a method for producing a cathode active material for a lithium secondary battery.

More specifically, in the step of preparing the lithium composite oxide having the flake form and having a primary particle diameter of 100 nm to 3 占 퐉 and a basic solution, the primary particle has a particle diameter of 100 nm to 3 占 퐉 lithium The composite oxide comprises: mixing a metal composite oxide precursor and a lithium raw material; Wherein the step of obtaining a lithium composite oxide by heat treating the mixed metal complex oxide precursor and the lithium source material comprises the steps of preparing a mixed metal oxide precursor and a lithium source material by heat treatment, A first heat treatment step at 200 to 600 ° C; And a second heat treatment step at 700 to 1000 &lt; 0 &gt; C.

These two stages of heat treatment can control the size of the primary particle size. Independently of each of the two steps above, the temperature raising rate may be between 1 and 10 ° C. However, the present invention is not limited thereto.

Mixing the metal complex oxide precursor and the lithium source material, wherein the metal complex oxide precursor is a mixture of a metal raw material, an aqueous ammonia solution or an ammonium aqueous solution, and an aqueous sodium hydroxide solution; And maintaining the temperature of the reactor at 20 to &lt; RTI ID = 0.0 &gt; 90 C &lt; / RTI &gt; and stirring.

Stirring the mixture while maintaining the temperature of the reactor at 20 to 90 DEG C; and stirring speed may be 700 to 1500 rpm. However, the present invention is not limited thereto.

Mixing the lithium complex oxide with the basic solution and activating the surface of the lithium complex oxide by heating the basic solution to 30 to 120 ° C; And charging the lithium complex oxide into the heated basic solution, followed by stirring.

The step of charging the lithium complex oxide into the heated basic solution and stirring the lithium complex oxide may be performed for 1 to 240 hours and more specifically for 1 to 20 hours. The thickness of the coating layer may be controlled according to the agitation time.

Heat treating the surface of the activated lithium complex oxide; The method may further include drying the lithium composite oxide on which the surface is activated.

The step of drying the surface-activated lithium composite oxide may be performed at 80 to 160 ° C. However, the present invention is not limited thereto.

The step of heat-treating the surface-activated lithium complex oxide may be performed at 150 to 900 ° C, more specifically at 180 to 220 ° C. However, the present invention is not limited thereto.

The basic solution may be a solution having hydrogen ions and capable of causing exchange with lithium ions.

More specifically, the basic solution may be a hydrazine solution, an ammonia solution, or a combination thereof. However, the present invention is not limited thereto.

The cathode active material according to the above production method comprises: a core comprising a flake-form primary particle compound; And a first coating layer of NiO on the core, wherein the primary particles have a particle diameter of 100 nm to 3 占 퐉, and the cathode active material of the secondary particle type has the following formula 1 &lt; / RTI &gt; for lithium secondary batteries.

[Chemical Formula 1]

_{(1-xy) Li 2 MnO} 3 -xLiM 1 O 2

(Wherein 0 < x < 1 and 0 < y < 1 and M ¹ is a transition metal)

The detailed description of the structure of the cathode active material is the same as that of the embodiment of the present invention described above, so that a description thereof will be omitted.

The positive electrode active material according to one embodiment of the present invention can be usefully used as a positive electrode of a lithium secondary battery. The lithium secondary battery includes a cathode and an electrolyte including an anode active material together with a cathode.

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

The conductive material may be carbon black, graphite, metal powder, and the binder may include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene And mixtures thereof. Further, N-methylpyrrolidone, acetone, tetrahydrofuran, decane and the like are used as the solvent. At this time, the content of the cathode active material, the conductive material, the binder and the solvent is used at a level normally used in a lithium secondary battery.

The negative electrode is prepared by mixing an anode active material, a binder and a solvent in the same manner as in the case of the anode. The anode active material composition is directly coated on the copper current collector or cast on a separate support, and the anode active material film, Laminated. 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, lithium alloy, coke, artificial graphite, natural graphite, organic polymeric compound combustion material, . The conductive material, the binder and the solvent are used in the same manner as in the case of the above-mentioned anode.

The separator may be polyethylene, polypropylene, polyvinylidene fluoride or a multilayer film of two or more thereof. The separator may be a polyethylene / polypropylene double-layer separator, It is needless to say that a mixed multilayer film such as a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator and the like can be used.

As the electrolyte to be charged into the lithium secondary battery, a non-aqueous electrolyte or a known solid electrolyte may be used, and a lithium salt dissolved therein may be 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? -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 and the like can be used. These may be used singly or in combination. Particularly, a mixed solvent of cyclic carbonate and chain carbonate can be preferably used.

As the electrolyte, a gelated polymer electrolyte in which an electrolyte solution is impregnated with a polymer electrolyte such as polyethylene oxide or polyacrylonitrile, or an inorganic solid electrolyte such as LiI or Li ₃ N can be used.

Wherein the lithium salt is selected from the group consisting of 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 , LiCl, and LiI.

Hereinafter, preferred embodiments and comparative examples 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

Synthesis of metal complex oxide precursor

In deionized water (deionized water) of _{NiSO 4 · 6H 2 O, MnSO} 4 · 5H 2 O 1: was added at a rate of 3 to prepare a metal solution of 2M. A 2M metal solution, 15.3 M ammonia water and 4 M aqueous sodium hydroxide solution were continuously added to a 7 L continuous reactor (CSTR) filled with 3 L of deionized water. While the internal temperature of the reactor was maintained at 50 캜 at the same time as the addition, the internal solution was stirred at a speed of 900 rpm with a stirrer.

As the reaction time becomes longer, the amount of metal solution, ammonia water and aqueous sodium hydroxide solution is increased, and thus, an outflowing solution is obtained to synthesize a metal complex oxide precursor Ni _{0 .25} Mn _{0 .75} (OH) ₂ Respectively.

Synthesis of lithium complex oxide

Metal complex oxide precursor _{Ni 0 .25 Mn 0 .75 (OH} ) ₂ obtained for LiOH · H ₂ O and 1: After stirring a solid phase in a weight ratio of 0.72, was subjected to heat treatment.

The heat treatment conditions were as follows: the temperature was increased from 5 ° C / min to 450 ° C / min in the first stage, and then heat-treated for 5 hours. In the second step of the heat treatment, the temperature was raised to 900 ° C. at a rate of 5 ° C. per minute, and then heat-treated for 10 hours to prepare a lithium complex oxide 0.5Li ₂ MnO ₃ -0.5 LiNi _0.5 Mn _0.5 O ₂ .

At this time, the primary particles had a plate-like particle size of 500 nm to 1 탆 and a height of 100 to 600 nm. The secondary particles had a particle diameter of about 10 탆.

Synthesis of surface-treated lithium composite oxide

After adding 40 하 of hydrazine monohydrate to 10 mg of deionized water, the aqueous solution was heated to 90 캜 and maintained at the temperature.

Then, the obtained 0.5Li ₂ MnO ₃ -0.5LiNi _{0 .5} then mixed into 2g Mn _{0 .5} O _2, and the mixture was stirred for 3 hours. Then, it was dried at a temperature of 120 DEG C for 12 hours and then heat-treated at a temperature of 200 DEG C for 3 hours.

Thus, a positive electrode active material for a lithium secondary battery was produced. The composition of the above-prepared cathode active material for a lithium secondary battery is _{0.45Li 2 MnO 3 -0.5LiNi 0 .5 Mn} 0 .5 O 2 to be.

Manufacture of lithium secondary battery

Super-P as a conductive material and polyvinylidene fluoride (PVdF) as a binder were mixed at a weight ratio of 8: 1: 1, respectively, to the obtained positive electrode active material for a lithium secondary battery to prepare a slurry. The slurry was uniformly applied to an aluminum foil having a thickness of 15 탆, and vacuum dried at a temperature of 120 캜 to prepare a positive electrode.

The prepared positive electrode and lithium foil were used as a counter electrode, and a liquid electrolyte in which LiPF ₆ was dissolved at a concentration of 1.0 M was used in a solvent in which porous polyethylene membrane carbonate, ethylmethyl carbonate and dimethyl carbonate were mixed at a volume ratio of 3: 4: 3 To prepare a half cell according to a conventionally known manufacturing process.

Comparative Example  One

Example 0.5Li ₂ MnO ₃ obtained in -0.5LiNi _{0 .5 0 .5} O ₂ was used as the Mn compound to a cathode active material for a lithium secondary battery.

A coin half cell was produced in the same manner as in the above example, except that the kind of the cathode active material was changed.

Comparative Example  2

_{0.5Li 2 MnO 3 -0.5LiNi 0 .5 Mn} 0 .5 O 2 A cathode active material having been subjected to surface treatment was used.

The difference from the active material of the embodiment is that a compound having a primary particle size (particle diameter of spherical primary particles having a similar aspect ratio) of 20 to 100 nm was used as a cathode active material for a lithium secondary battery. Specifically, secondary particles having a particle size of 5 占 퐉 were used.

Specifically, except that the ammonia concentration was set to 3M in the examples, and the internal temperature of the reactor was set to 60 캜, the remainder was carried out in the same manner.

A coin half cell was produced in the same manner as in the above example, except that the kind of the cathode active material was changed.

Experimental Example

Experimental Example  One: IPC  analysis

Table 1 below shows the results of analyzing the components of the cathode active material prepared in Examples and Comparative Example 1.

Li Mn Ni Li / M ratio (molar ratio) Comparative Example 1 6.01 3.01 1.00 1.5 Example 5.56 2.99 1.00 1.4

(M means a metal other than lithium).

As a result of the analysis, it can be confirmed that the ratio of Li / M was changed by the hydrazine treatment in the examples. It is believed that this is due to the chemical desorption of Li.

Experimental Example  2: SEM  analysis

1 is an SEM photograph of an active material according to Examples and Comparative Examples. The positive electrode active material for a lithium secondary battery of the above example and the comparative example 2 was sampled on a carbon tape, and platinum (Pt) plasma coating was performed to take an SEM photograph. More specifically, the description of each photograph in Fig. 1 is as follows.

a. In the example  0.5 Li ₂ MnO ₃ -0.5 LiNi _{0 .5} Mn _{0 .5} O ₂

b. Comparative Example  0.5 used in 2 Li ₂ MnO ₃ -0.5 LiNi _{0 .5} Mn _{0 .5} O ₂

c. Example  Active material electronic conduction concept diagram

d. Comparative Example  2 active material electronic conductivity concept diagram

It can be seen that the active material according to the embodiment of the present invention has a larger primary particle diameter as compared with Comparative Example 2. [

Experimental Example  3: TEM  analysis

2 is a TEM photograph of the active material according to the embodiment. 2, it can be confirmed that a surface layer of about 50 nm is formed on the surface of the active material.

It can also be seen that this surface layer consists of a first coating layer having a surface of 2-5 nm and a second coating layer of 10-40 nm.

FIG. 3 is a high magnification TEM image corresponding to the green square of FIG. 2, which shows the atomic structure and crystal structure of the surface layer of 10-20 nm.

From FIG. 3, it can be seen that this layer is a mixture of NiO and spinel phases.

Experimental Example  4: Battery characteristic data

4 is a graph showing the output characteristic of the battery according to Example and Comparative Example 1. Fig. More specifically, the output characteristic was measured (1C-rate) at room temperature / 2.0-4.6V after the first cycle. Also, in order to know the influence of the initial charging / discharging voltage, Comparative Example 1 was charged / discharged once to the initial 4.8V voltage, and then a comparative experiment was performed.

The coin cell of the embodiment shows better output characteristics than the coin cell of the comparative example 1 and the coin cell of the comparative example 1 which was initially charged and discharged at 4.8 V. That is, it can be seen that the hydrazine-treated active material shows higher discharge capacity and output characteristics than the active material before the treatment and the active material after the initial charge and discharge at 4.8 V.

5 is a graph showing output characteristics of the battery according to the example and the comparative example 2. Fig.

It can be seen that the coin cell using the active material according to the embodiment exhibits high energy density per unit volume and high output characteristics. The reason for this is that in the case of small primary particles, the surface side reaction with the electrolyte is increased due to the increase of the specific surface area, and the SEI (solid-electrolyte interface) layer having low conductivity is formed on the surface.

6 and 7 are graphs showing lifetime characteristics of the capacity and the energy density per unit volume of the battery according to the example and the comparative example 2. FIG. The deterioration of the life characteristics is also caused by the reason as shown in FIG.

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.

Claims (10)

A core comprising a primary particle compound in flake form; And
A first coating layer disposed on the core, the first coating layer including a NiO phase,
The primary particles have a particle size of 100 nm to 3 탆,
Wherein the cathode active material of the secondary particle type is represented by the following general formula (1).
[Chemical Formula 1]
_{(1-xy) Li 2 MnO} 3 -xLiM 1 O 2
(Wherein 0 <x <1, 0 <y <0.8, M ¹ is a transition metal, and Ni and Mn).
The method according to claim 1,
Wherein the first coating layer has a thickness of 1 to 15 nm.
The method according to claim 1,
Further comprising a second coating layer between the core and the first coating layer,
Wherein the second coating layer is a mixture of a NiO phase and a spinel phase.
The method of claim 3,
Wherein the thickness of the second coating layer is 1 to 100 nm.
The method of claim 3,
Wherein the thickness ratio of the first coating layer to the second coating layer is 1/1 to 13/100.
The method according to claim 1,
Wherein the molar ratio of lithium / (other metals other than lithium) in the total positive electrode active material including the core, the first coating layer, and the second coating layer is 1.05 to 1.4.
The method according to claim 1,
A lithium secondary battery positive electrode active material M ¹ in the formula (1) further comprises a Co.
A lithium composite oxide having a flake shape and having a primary particle diameter of 100 nm to 3 占 퐉; And a basic solution;
Introducing, mixing and heating the lithium composite oxide into the basic solution to activate the surface of the lithium composite oxide; And
Heat treating the surface of the activated lithium complex oxide;
A cathode active material for a lithium secondary battery,
The prepared positive electrode active material for a lithium secondary battery,
A core comprising a primary particle compound in flake form; And
A first coating layer disposed on the core, the first coating layer including a NiO phase,
The primary particles have a particle size of 100 nm to 3 탆,
Wherein the cathode active material of the secondary particle type is represented by the following general formula (1).
[Chemical Formula 1]
_{(1-xy) Li 2 MnO} 3 -xLiM 1 O 2
(Wherein 0 <x <1, 0 <y <0.8, M ¹ is a transition metal, and Ni and Mn).
9. The method of claim 8,
Preparing a lithium composite oxide in the flake form and having a primary particle diameter of 100 nm to 3 占 퐉 and a basic solution,
The lithium composite oxide, which is in the flake form and has a primary particle diameter of 100 nm to 3 占 퐉,
Metal composite oxide precursor and a lithium source material;
Heat-treating the mixed metal composite oxide precursor and the lithium source material to obtain a lithium composite oxide,
The step of obtaining the lithium composite oxide by heat-treating the mixed metal composite oxide precursor and the lithium raw material may include:
A first heat treatment step at 200 to 600 ° C; And a second heat treatment step at 700 to 1000 占 폚.
10. The method of claim 9,
Mixing the metal complex oxide precursor and the lithium source material,
The metal composite oxide precursor may include,
Introducing a metal raw material, an aqueous ammonia solution or an aqueous ammonium solution, and an aqueous sodium hydroxide solution into a reactor; And
And maintaining the temperature of the reactor at 20 to 90 DEG C and stirring the mixture. The method for producing a cathode active material for a lithium secondary battery according to claim 1,

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