KR101860367B1 - Cathode active material for lithium secondary battery and preparing method of the same - Google Patents

Abstract

A cathode active material for a lithium secondary battery comprising the aluminum-modified precursor, a method for producing the cathode active material for the lithium secondary battery, and a lithium secondary battery including the cathode active material.

Description

Technical Field [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,

The present invention relates to a cathode active material for a lithium secondary battery comprising an aluminum-modified precursor, a method for producing the cathode active material for the lithium secondary battery, and a lithium secondary battery including the cathode active material.

As the electric, electronic, communication and computer industries rapidly develop, the demand for high performance and high stability secondary batteries is gradually increasing. Especially, due to the thin and simple miniaturization and portability of precision electric appliances, The battery is also required to be thinned and miniaturized.

In response to this demand, a lithium secondary battery is one of the batteries that has been most popular in recent years.

The lithium secondary battery generally includes a positive electrode, an organic electrolyte, a separator, and a negative electrode. These materials are selected in consideration of battery life, charge / discharge capacity, temperature characteristics, stability and the like.

Accordingly, the anode uses a lithium metal oxide, and the separation membrane uses a solvent free polymer electrolyte or a plasticized polymer electrolyte.

In recent years, a lithium secondary battery using lithium titanium oxide (LTO), which has a higher Li intercalation desorption potential than a carbonaceous material, as a negative electrode active material has been used as the negative electrode in recent years, such as graphite or cokes. Has been put to practical use.

However, there is a problem in that the lifetime of the lithium secondary battery rapidly decreases as the charge and discharge are repeated. In addition, the problem of high temperature characteristics is also serious. For this reason, the electrolyte is decomposed due to moisture or other influences inside the battery, the active material is deteriorated, and the internal resistance of the battery is increased.

A lot of efforts are being made to solve these problems. Among them, as a cathode active material property modifying method for a cathode, a manufacturing method of adding a transition metal oxide to suppress additional side reaction and improve the performance of a battery is generally accepted.

Korean Patent No. 10-0277796 discloses a technique of coating a metal oxide by coating a metal such as Mg, Al, Co, K, Na, or Ca on a surface of a cathode active material and heat-treating the surface of the cathode active material in an oxidizing atmosphere. However, the problem of deterioration of lifetime and the problem of generation of gas due to decomposition of electrolyte during charging and discharging are not completely solved yet.

In Korean Patent Laid-Open Publication No. 2003-0032363, there is disclosed a positive electrode active material containing a metal of Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, Oxides, hydroxides, hydroxides, hydroxycarbonates, and the like. However, this technique also fails to solve the problem of lifetime reduction at high voltage of the cathode active material.

The present invention provides a cathode active material for a lithium secondary battery comprising an aluminum-modified precursor, a method for producing the cathode active material for the lithium secondary battery, and a lithium secondary battery comprising the cathode active material.

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

According to a first aspect of the present invention, there is provided a cathode active material for a lithium secondary battery, which comprises a precursor including aluminum-modified Ni and Mn, and is represented by the following Chemical Formula 1:

[Chemical Formula 1]

Li _a Ni _x Mn _y M ' _z O _b M'';

Wherein M 'is selected from the group consisting of Mg, Al, Sr, Co, Ni, P, Cr, Ti, V, Sr, Ga, In, Sn, Ge, Bi, Pb, And M is at least one element selected from the group consisting of B, Al, Co, Ga, Mg, Ca, Ti, V, Cr, Fe, Zn, Si, Y, Zr, Nb, In, Sn, Mo, A is 0.9 to 2.0, b is 1.5 to 3.0, x is 0.1 to 0.9, y is 0.1 to 0.9, z is 0.9 or less, and x + y + z = 1.

The second aspect of the present invention relates to a method of forming a precursor comprising the steps of: mixing a precursor including Ni and Mn and an aluminum-containing material, followed by heat treatment to form a precursor including Al-modified Ni and Mn; And a step of heat treating the precursor containing the aluminum-modified Ni and Mn and the lithium-containing compound to prepare a positive electrode active material represented by the following formula 1:

[Chemical Formula 1]

Li _a Ni _x Mn _y M ' _z O _b M'';

Wherein M 'is selected from the group consisting of Mg, Al, Sr, Co, Ni, P, Cr, Ti, V, Sr, Ga, In, Sn, Ge, Bi, Pb, And M is at least one element selected from the group consisting of B, Al, Co, Ga, Mg, Ca, Ti, V, Cr, Fe, Zn, Si, Y, Zr, Nb, In, Sn, Mo, A is 0.9 to 2.0, b is 1.5 to 3.0, x is 0.1 to 0.9, y is 0.1 to 0.9, z is 0.9 or less, and x + y + z = 1.

A third aspect of the present invention provides a lithium secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode includes a positive electrode active material for a lithium secondary battery according to the first aspect of the present invention as a positive electrode active material.

The present invention relates to a process for preparing an aluminum-modified precursor by mixing a precursor comprising Ni and Mn with an aluminum-containing material followed by heat treatment and using the aluminum-modified precursor as a precursor of a cathode active material of a lithium secondary battery, A cathode active material and a method for producing the cathode active material are provided.

In one embodiment of the present invention, the improvement of the battery characteristics by improving the aluminum of the cathode active material precursor including Ni and Mn to suppress the reaction between the cathode active material and the electrolytic solution can reduce the capacity of the battery, It is also possible to provide a lithium secondary battery improved in charge / discharge characteristics, lifetime characteristics, high voltage characteristics, high rate characteristics, and thermal stability.

FIG. 1 is a graph showing a discharge capacity according to a cycle of a lithium secondary battery including a cathode active material according to a comparative example and an embodiment of the present invention. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, the same reference numbers are used throughout the specification to refer to the same or like parts.

Throughout this specification, when a part is referred to as being "connected" to another part, it is not limited to a case where it is "directly connected" but also includes the case where it is "electrically connected" do.

Throughout this specification, when a member is " on " another member, it includes not only when the member is in contact with the other member, but also when there is another member between the two members.

Throughout this specification, when an element is referred to as " including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise.

The terms " about ", " substantially ", etc. used to the extent that they are used throughout the specification are intended to be taken to mean the approximation of the manufacturing and material tolerances inherent in the stated sense, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure.

The word " step (or step) " or " step " used to the extent that it is used throughout the specification does not mean " step for.

Throughout this specification, the term " combination (s) thereof " included in the expression of the machine form means a mixture or combination of one or more elements selected from the group consisting of the constituents described in the expression of the form of a marker, Quot; means at least one selected from the group consisting of the above-mentioned elements.

Throughout this specification, the description of "A and / or B" means "A or B, or A and B".

Hereinafter, embodiments and examples of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to these embodiments and examples and drawings.

According to a first aspect of the present invention, there is provided a cathode active material for a lithium secondary battery, which comprises a precursor including aluminum-modified Ni and Mn, and is represented by the following Chemical Formula 1:

[Chemical Formula 1]

Li _a Ni _x Mn _y M ' _z O _b M'';

Wherein M 'is selected from the group consisting of Mg, Al, Sr, Co, Ni, P, Cr, Ti, V, Sr, Ga, In, Sn, Ge, Bi, Pb, And M is at least one element selected from the group consisting of B, Al, Co, Ga, Mg, Ca, Ti, V, Cr, Fe, Zn, Si, Y, Zr, Nb, In, Sn, Mo, A is 0.9 to 2.0, b is 1.5 to 3.0, x is 0.1 to 0.9, y is 0.1 to 0.9, z is 0.9 or less, and x + y + z = 1.

In one embodiment of the present invention, M " in the above formula (1) means a substance for modifying a precursor, and may be aluminum, but it may not be limited thereto.

In one embodiment of the present invention, the structural stability is improved through the aluminum modification of the cathode active material precursor including Ni and Mn to improve the battery characteristics to suppress the reaction between the cathode active material and the electrolytic solution, Can be improved, and a lithium secondary battery improved in charge / discharge characteristics, life characteristics, high voltage characteristics, high rate characteristics, and thermal stability can be provided.

In one embodiment of the invention, the aluminum is _{Al (OH) 3, Al 2} O 3, Al (C 3 H 7 O) 3, AlPO 4, AlBr 3, Al 2 (SO 4) 3, and combinations thereof Aluminum-containing materials selected from the group consisting of aluminum-containing materials.

In one embodiment of the invention, the particle size of the precursor including the aluminum-modified Ni and Mn may be from about 5 nm to about 20 탆, but may not be limited thereto. For example, the particle size of the precursor including the aluminum-modified Ni and Mn may be about 5 nm to about 20 탆, about 100 nm to about 20 탆, about 200 nm to about 20 탆, about 400 nm to about 20 탆 From about 5 nm to about 800 nm, from about 5 nm to about 600 nm, from about 1 nm to about 20 nm, from about 5 nm to about 1 nm, from about 600 nm to about 20 nm, from about 800 nm to about 20 nm, From about 5 nm to about 400 nm, from about 5 nm to about 200 nm, or from about 5 nm to about 100 nm.

The second aspect of the present invention relates to a method of forming a precursor comprising the steps of: mixing a precursor including Ni and Mn and an aluminum-containing material, followed by heat treatment to form a precursor including Al-modified Ni and Mn; And a step of heat treating the precursor containing the aluminum-modified Ni and Mn and the lithium-containing compound to prepare a positive electrode active material represented by the following formula 1:

[Chemical Formula 1]

Li _a Ni _x Mn _y M ' _z O _b M'';

Wherein M 'is selected from the group consisting of Mg, Al, Sr, Co, Ni, P, Cr, Ti, V, Sr, Ga, In, Sn, Ge, Bi, Pb, And M is at least one element selected from the group consisting of B, Al, Co, Ga, Mg, Ca, Ti, V, Cr, Fe, Zn, Si, Y, Zr, Nb, In, Sn, Mo, A is 0.9 to 2.0, b is 1.5 to 3.0, x is 0.1 to 0.9, y is 0.1 to 0.9, z is 0.9 or less, and x + y + z = 1.

In one embodiment of the present invention, an aluminum-modified precursor is prepared by mixing a precursor comprising Ni and Mn with an aluminum-containing material and then heat-treating the precursor, and using the aluminum-modified precursor as a precursor of the cathode active material of the lithium secondary battery A cathode active material having improved capacity and a method for producing the cathode active material are provided.

In one embodiment herein, the precursor comprising Ni and Mn may be, but not limited to, performed by co-precipitation.

In one embodiment, the precursor containing Ni and Mn and the aluminum-containing material are mixed and heat-treated may be performed at about 400 ° C to about 900 ° C, but the present invention is not limited thereto. For example, the heat treatment may be performed at a temperature of from about 400 ° C to about 900 ° C, from about 400 ° C to about 800 ° C, from about 400 ° C to about 700 ° C, from about 400 ° C to about 600 ° C, To about 900 캜, from about 600 캜 to about 900 캜, from about 700 캜 to about 900 캜, or from about 800 캜 to about 900 캜.

In one embodiment of the present invention, the precursor containing Ni and Mn and the aluminum-containing material may be mixed and heat-treated may be performed in an air atmosphere, and the precursor may be oxidized But may not be limited thereto.

In one embodiment herein, the precursor comprising Ni and Mn and the aluminum-containing material may be mixed in a molar ratio of about 1: 1, but the present invention is not limited thereto.

In one embodiment of the invention, the heat treatment of the precursor containing the aluminum-modified Ni and Mn and the lithium-containing compound is performed at a rate of about 1 ° C / min to about 5 ° C / But may be, but not limited to, heating to about 1000 < 0 > C. Further, in one embodiment of the present invention, it may include, but is not limited to, maintaining the heating at the heating temperature for about 4 hours to about 10 hours after the heating.

A third aspect of the present invention provides a lithium secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode includes a positive electrode active material for a lithium secondary battery according to the first aspect of the present invention as a positive electrode active material.

According to one embodiment of the present invention, the positive electrode is obtained by, for example, suspending a positive electrode active material, a positive electrode conductive agent, and a binder in a suitable solvent, applying the slurry prepared by suspending the positive electrode current collector to a positive electrode current collector, Containing layer and then pressing it. As the conductive agent, it is preferable to use carbon black. Examples of the binder include polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyacrylonitrile, nitrile rubber, polybutadiene, polystyrene, styrene butadiene rubber, Rubber, butyl rubber, hydrogenated styrene-butadiene rubber, nitrocellulose, carboxymethylcellulose or a mixture thereof is preferably used. At this time, the content of the cathode active material, the conductive agent, the binder and the solvent is a level commonly used in a lithium secondary battery.

According to one embodiment of the present invention, the organic electrolyte may include, but is not limited to, an organic solvent and a lithium salt.

The solvent may be a material known in the art and may be one having a high permittivity (polarity) and a low viscosity and a low reactivity with lithium metal in order to increase the degree of dissociation of ions and smooth the conduction of ions And may be, for example, a mixture of chain-like hydrocarbons and cyclic hydrocarbons. The chain hydrocarbon may be, for example, polyethylene carbonate, ethylene carbonate, or propylene carbonate, and the cyclic hydrocarbon may be, for example, dimethyl carbonate or diethyl carbonate, but may not be limited thereto

As the lithium salt, materials known in the art can be used, and it is preferable to use one having good lattice energy and high dissociation degree, excellent ion conductivity, and good thermal safety and oxidation resistance. The lithium salt may be selected from the group consisting of LiPF ₆ , LiBF ₄ , LiClO ₄ , LiN (CF ₃ SO ₂ ) ₂ , LiCF ₃ SO ₃ , LiC (CF ₃ SO ₃ ) ₃ , LiAsF ₆ , But are not limited thereto.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto.

[ Example ]

[ The lithium secondary battery  Produce( Example  One)]

≪ Preparation of positive electrode active material &

NiSO ₄ -xH ₂ O (≥99%) of Norilsk nickel as Ni-containing compound, MnSO ₄ - x H ₂ O (≥99%) of Mechema as a Mn-containing compound as the Li-containing compound, Li ₂ CO ₃ H ₂ O (≥98%) was used.

First, Ni-containing compounds and Mn-containing compounds were prepared in the form of hydrates using co-precipitation. 0.2 M and 0.75 M of each of the Ni-containing compound and Mn-containing compound were dissolved in distilled water to prepare a 2.3 M lithium nickel composite oxide precursor solution. A proper amount of 2 M to 4 M sodium carbonate aqueous solution and ammonia water were mixed at 55 ° C At a speed of 700 rpm. The pH of the coprecipitation reaction was maintained at pH 7.5 and the average residence time of the solution in the reaction tank was 10 hours. The co-precipitate thus obtained was washed and rinsed, and then dissolved in ethanol at a temperature of about 60 ° C with an aluminum isopropoxide [Al (C ₃ H ₇ O) ₃ ] powder (3 wt% based on the precursor) And then heat-treated at 600 ° C. for 10 hours. The powder formed by the heat treatment was mixed with Li ₂ CO _{3 at} a molar ratio of 1: 1, and then heated at a rate of 5 ° C./min to 850 ° C. After heating, it was heat-treated at the above temperature for 10 hours to obtain LiNi _{0 . 5} Mn _{1 . 5} O ₄ / Al ₂ O ₃ .

< Lithium secondary battery  Manufacturing>

In order to produce a lithium secondary battery according to one embodiment of the present invention, the positive electrode is prepared by suspending a positive electrode active material, a positive electrode conductive agent, and a binder in a suitable solvent, applying the slurry prepared by suspending the positive electrode current collector, A cathode active material-containing layer was produced, followed by pressing.

As the positive active material LiNi ₀ manufactured by this _{embodiment. 5} Mn _{1 . 5} O ₄ / Al ₂ O ₃ was used, and Super-p of Timcal was used as a conductive agent. The weight ratio of the cathode active material, the conductive agent, and the binder was 84: 8: 8, and the slurry was prepared and applied to an aluminum foil to prepare a positive electrode.

On the other hand, a separation membrane of Asahi was used as a separation membrane, and the separation membrane was an electrochemically stable insulating film having a porosity of 30% by volume to 60% by volume in a lithium secondary battery.

The above-prepared anode forming composition was coated on an aluminum foil to a thickness of 25 탆 to prepare a thin electrode plate, dried at 135 캜 for 6 hours, and then rolled at a rolling rate of 40% Respectively.

As the organic electrolytic solution, a solution obtained by mixing 1.2 M LiPF ₆ of lithium salt of Panaxitec with an organic solvent (EC: EMC = 1: 1) was used. The lithium salt may be used alone or as an optional mixture, and the ionic conductivity of the lithium salt in the organic electrolytic solution is preferably in the range of , The concentration of the lithium salt is preferably 0.4 M to 1.5 M.

The negative electrode was used as a metal lithium having a thickness of 500 ㎛ punching a 16.5 mmφ, the positive electrode active material is applied to the electrode plate sheet and then punching a 16.5 mmφ, by laminating the above material in CR2032-type coin cell kit compressed into 1.7 t / cm ² To prepare a coin cell (lithium secondary battery).

[ Example  2]

After washing with coprecipitate prepared in Example 1 and drying, the mixture was mixed with a solution of Alumina (Al ₂ O ₃ ) powder (3 wt% based on the precursor) of Topmet and dissolved in ethanol at a temperature of about 60 ° C. , A coin cell (lithium secondary battery) was fabricated through the manufacturing process of a LiNi _0.5 Mn _1.5 O ₄ / Al ₂ O ₃ cathode active material and an electrode, in the same manner as in Example 1.

[ Comparative Example  1]

After washing and co-drying in the co-precipitate prepared in Example 1, Li ₂ CO ₃ and Li ₂ CO ₃ were mixed at a molar ratio of 1: 1, followed by heating at 850 ° C at a heating rate of 5 ° C / min in an air atmosphere. Heat treatment was performed for 10 hours to obtain Li (Ni _0.5 Mn _1.5 ) O ₄ Lt; / RTI &gt; The obtained cathode active material was mixed with a solution of alumina isopropoxide [Al (C ₃ H ₇ O) ₃ ] powder (3 wt% based on the precursor) same as that of Example 1 and dissolved in ethanol at a temperature of about 60 ° C Thereafter, the resultant was heated up to 600 ° C at a heating rate of 5 ° C / min in an air atmosphere, and then heat-treated at the above temperature for 10 hours. A coin cell was fabricated in the same manner as in Example 1 using the prepared positive electrode active material.

[ Comparative Example  2]

After washing with water and drying in the co-precipitate prepared in Example 1, the mixture was mixed with Li ₂ CO ₃ in a molar ratio of 1: 1, and then heated to 850 ° C. at a temperature raising rate of 5 ° C./min in an air atmosphere. For 10 hours to obtain Li (Ni _0.5 Mn _1.5 ) O ₄ Lt; / RTI &gt; The obtained cathode active material was mixed with the same alumina (Al ₂ O ₃ ) powder (3 wt% based on the precursor) and the solution dissolved in ethanol at a temperature of about 60 ° C. in the same manner as in Example 2, Min, and then heat-treated at the above-mentioned temperature for 10 hours. A coin cell was fabricated in the same manner as in Example 1 using the prepared positive electrode active material.

[ Comparative Example  3]

After washing with water and drying in the co-precipitate prepared in Example 1, the mixture was mixed with Li ₂ CO ₃ in a molar ratio of 1: 1, and then heated to 850 ° C. at a temperature raising rate of 5 ° C./min in an air atmosphere. Gt _; LiNi &lt; / RTI &gt; _{0 . 5} Mn _{1 . 5} O ₄ Lt; / RTI &gt; A coin cell was fabricated in the same manner as in Example 1 using the prepared positive electrode active material.

The results of the measurement of the discharge capacity of the lithium secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 3 were shown in Table 1 and FIG. 1, respectively, for 1 to 30 cycles.

[Table 1]

As shown in Table 1 and FIG. 1, Examples 1 and 2, in which aluminum was modified to co-precipitate before production of the positive electrode active material, were prepared by mixing the positive electrode active material with aluminum treatment (Comparative Examples 1 and 2) Example 3), and it was confirmed that the discharge capacity was maintained even though the cycle number was increased.

It will be understood by those of ordinary skill in the art that the foregoing description of the embodiments is for illustrative purposes and that those skilled in the art can easily modify the invention without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims (8)

delete delete 1. A lithium secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte containing a positive electrode active material,
The positive electrode active material,
Mixing a precursor containing Ni and Mn and an aluminum-containing material and then heat-treating to form a precursor containing aluminum-modified Ni and Mn; And
Treating the precursor containing the aluminum-modified Ni and Mn and the lithium-containing compound in an air atmosphere to prepare a cathode active material represented by the following Formula 1
&Lt; RTI ID = 0.0 &gt;
Wherein the aluminum-containing material is selected from the group consisting of Al (OH) ₃ , Al ₂ O ₃ , Al (C ₃ H ₇ O) ₃ , AlPO ₄ , AlBr ₃ , Al ₂ (SO ₄ ) ₃ , Selected &lt; / RTI &gt;
The precursor containing Ni and Mn and the aluminum-containing material are mixed and then heat-treated is performed at 400 ° C to 800 ° C,
Wherein said lithium secondary battery exhibits a discharge capacity of 185 mAh / g to 195 mAh / g.
[Chemical Formula 1]
LiNi _0.5 Mn _1.5 O ₄ / Al ₂ O ₃ .
The method of claim 3,
Wherein the precursor containing Ni and Mn is carried out by coprecipitation.
delete The method of claim 3,
Wherein the precursor containing Ni and Mn and the aluminum-containing material are mixed at a molar ratio of 1: 1.
The method of claim 3,
Wherein the precursor containing the aluminum-modified Ni and Mn and the lithium-containing compound are mixed and heat-treated is heated at a temperature raising rate of 1 ° C / minute to 5 ° C / minute to 800 ° C to 1,000 ° C. .

delete

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