KR20100079535A - Cathode active material for lithium secondary batteries - Google Patents

Abstract

PURPOSE: A lithium transition metal oxide for a non-aqueous lithium secondary battery is provided to facilitate the growth of particles by passing a calcinations process after inserting a crushing transition metal compound. CONSTITUTION: A lithium transition metal oxide for a non-aqueous lithium secondary battery is produced with the following steps: inserting a crushing transition metal oxide into a transition metal oxide with a fixed content rate; mixing the result with a lithium compound; plasticizing the mixture; and crushing the plasticized mixture. The crushing transition metal oxide is marked with chemical formula 1: Li_aNi_(1-x-y)Co_xM_yO_2. In the chemical formula 1, M is a metal selected from the group consisting of Mn, Mg, Fe, Al and their combination.

Description

Lithium transition metal oxide for a non-aqueous secondary battery prepared by adding a pulverized transition metal compound {CATHODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERIES}

The present invention relates to a cathode active material for a non-aqueous electrolyte secondary battery, and relates to a cathode active material made of a transition metal compound and a lithium compound.

Specifically, the present invention is characterized by providing a positive electrode active material that can improve the stability and reliability by reducing the fine powder generated in the embodiment for lithium cobalt oxide (LiCoO ₂ ) for the grinding.

The positive electrode active material that determines the capacity of a lithium secondary battery should be capable of intercalation and deintercalation of lithium ions (Li ⁺ ) continuously, and the crystal structure should remain unchanged in the process. Representative materials meeting these conditions include oxides based on lithium cobalt oxide (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ) and lithium manganate (LiMn ₂ O ₄ ). Since the oxides have a layered or spinel structure, lithium is easily occluded and desorbed. In addition, in the process, since lithium moves between layers without changing the crystal structure, excellent cycle characteristics can be obtained.

Among these cathode active materials, lithium cobalt oxide (LiCoO ₂ ) having a layered structure is known to be the best in terms of charge and discharge characteristics, reversibility, charge and discharge efficiency, flatness of the discharge voltage and cycle characteristics. Therefore, most of the LIB (lithium ion battery) systems currently in use use lithium cobalt oxide (LiCoO ₂ ) as a cathode active material.

In general, lithium cobalt oxide (LiCoO ₂ ) is synthesized using the solid phase method. The solid phase method is a method of producing a desired compound by mixing a raw material powder in a solid state, firing and pulverizing. For example, LiNi _1-x CoO ₂ electrode material is pulverized after heat treatment using Ni (OH) ₂ and Co (OH) ₂ or hydroxides containing Ni and Co in Japanese Patent Application Laid-Open No. 8-103513. A method of synthesizing an electrode material through a particle size fractionation process is described. The solid phase method can simplify the manufacturing process and provide a cathode active material having more improved voltage characteristics.

However, in the solid phase method, fine powder is generated in the pulverization process, and the fine powder is present on the surface of the positive electrode active material, thereby degrading the stability and reliability of the battery. Accordingly, the present applicant has devised a method for controlling the generation of fine powder and securing the disadvantages of the conventional solid phase method in the cathode active material providing method.

The present invention has been proposed to solve the above problems, to provide a method for producing a lithium transition metal oxide which is a cathode active material for a non-aqueous electrolyte secondary battery that controlled the generation of fine powder.

Specifically, an embodiment of manufacturing a lithium cobalt oxide (LiCoO ₂ ) having an average particle diameter of 15㎛ or more, for example, by adding a constant ratio of the pulverized cobalt compound to the cobalt compound and the lithium compound to undergo a calcination and grinding process, It is characterized in that to provide a lithium cobalt oxide (LiCoO ₂ ) to reduce the occurrence of improved reliability and stability.

Lithium transition metal oxide for a non-aqueous secondary battery prepared by adding a pulverized transition metal compound to solve the problems described above is added to the transition metal compound in a certain ratio, and then mixed with a lithium compound for the firing process and By going through the grinding process, to reduce the occurrence of fine powder to improve the reliability and stability, the transition metal compound is selected from any one of the compounds based on the cobalt compound, nickel-cobalt-manganese complex compound, manganese compound, The cobalt compound is selected from cobalt hydroxide, oxy cobalt hydroxide, and cobalt carbonate.

In the lithium transition metal oxide according to the present invention, the lithium compound is selected from the group consisting of lithium carbonate, lithium nitrate, lithium sulfate, lithium acetate, lithium chloride, lithium hydroxide, and lithium oxide, and the pulverized transition metal compound is a cobalt compound, nickel A cobalt-manganese complex compound or a transition metal compound based on a manganese compound may be obtained through a crushing process, and the pulverized cobalt compound may be selected from two or more selected from cobalt hydroxide, oxy cobalt hydroxide, cobalt oxide, and cobalt carbonate. It is characterized by obtaining cobalt compound by mixing and grinding.

The lithium transition metal oxide according to the present invention has an average particle diameter of 15 μm or more prepared by adding a predetermined ratio of a pulverized transition metal compound to the transition metal compound, mixed with a lithium compound, and subjected to a calcination process and a pulverization process, and the pulverized transition metal The compound is characterized by having two or more particle size distribution peaks.

In addition, the transition metal compound is crushed to separate the smaller-diameter lapse assignment based on the average particle size (D ₅₀₎ of 1㎛, the small particle size and the ratio (D ₅₀ in respect substituted average particle size (D ₅₀₎ substituting light / D ₅₀ small particle diameter) is 5 to 30, and the pulverized transition metal compound has a volume ratio of large particle size and small particle size of 4: 1 to 13: 7, and the transition metal compound and the pulverized transition metal compound are 10: 1 to 1 Mixing is carried out in a weight ratio (%) of 4: 1, and the transition metal compound and the lithium compound (Li / Metal) in a molar ratio of 1.04 to 1.06, characterized in that the manufacturing through the calcination and grinding process.

      In addition, the firing process of the lithium transition metal oxide according to the present invention is baked for 12 to 24 hours at a firing temperature of 600 ℃ to 1050 ℃.

In another method, the firing process is the first firing for 4 to 10 hours at a firing temperature of 400 ℃ to 650 ℃, and the second firing for 12 to 24 hours at a firing temperature of 800 ℃ to 1050 ℃.

The transition metal compound and the pulverized transition metal compound in the addition of a predetermined ratio of the pulverized transition metal compound to the transition metal compound of the lithium transition metal oxide according to the present invention is characterized in that the same kind or different hetero transition metal compound.

As described above, when the pulverized cobalt compound is added and calcined, the cobalt compound particles and the lithium compound particles having different particle diameters may be well packed and thus may be tightly adhered to promote grain growth.

In addition, by controlling the fine powder generated during the grinding process, it is possible to reduce the fine powder adhering to the surface of the lithium cobalt oxide (LiCoO ₂ ) to improve the stability and reliability of the battery.

The object of the present invention described above will become more apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings, by those skilled in the art. Hereinafter, the present invention will be described with reference to the accompanying drawings.

Referring to the present invention for achieving the above object is as follows.

The present invention is added to the transition metal compound and the lithium compound by a certain ratio of the pulverized transition metal compound to undergo a calcination process and a pulverization process, by adding a pulverized transition metal compound, characterized in that to reduce the generation of fine powder to improve the reliability and stability An object of the present invention is to provide a prepared lithium transition metal oxide for a non-aqueous secondary battery.

The transition metal compound may include a cobalt compound, a nickel-cobalt-manganese complex compound, and a manganese compound.

The transition metal compound may be represented by the following Chemical Formula 1 or Chemical Formula 2.

[Formula 1]

Li _a Ni _{1 -x- y} Co _x M _y O ₂

     (In Formula 1, M is one metal selected from the group consisting of Mn, Mg, Fe, Al, and a combination thereof, 1.0 ≦ a ≦ 1.1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y≤1)

[Formula 2]

Li _a Mn _{2 -x- y} Ni _x Co _y O ₄

   (In Formula 2, 1.0 ≦ a ≦ 1.1, 0 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.5, and 0 ≦ x + y ≦ 0.5)

The lithium compound may be selected from the group consisting of lithium carbonate, lithium nitrate, lithium sulfate, lithium acetate, lithium chloride, lithium hydroxide and lithium oxide.

The pulverized transition metal compound may be selected from any one of a cobalt compound, a nickel-cobalt-manganese composite compound, and a transition metal compound based on a manganese compound.

In particular, the pulverized cobalt compound may be obtained by mixing and pulverizing two or more kinds of cobalt compounds selected from cobalt hydroxide, oxy cobalt hydroxide, cobalt oxide, and cobalt carbonate.

Thus, the present invention will be described for the production method using a pulverized cobalt compound.

Lithium cobalt oxide (LiCoO ₂ ) according to the present invention includes a cobalt compound, a lithium compound and a ground cobalt compound.

The cobalt compound is one or more compounds selected from cobalt hydroxide, oxy cobalt hydroxide, cobalt oxide, and cobalt carbonate.

The lithium compound is not limited and may be selected from the group consisting of lithium carbonate, lithium nitrate, lithium sulfate, lithium acetate, lithium chloride, lithium hydroxide, and lithium oxide.

The ground cobalt compound is prepared by grinding the cobalt compound in a ball mill.

The pulverized cobalt compound has two or more peaks in the particle size distribution within an average particle diameter of 0.01 μm to 10 μm, and is divided into large particle sizes and small particle sizes based on an average particle size size (D ₅₀ ) of 1 μm. In this case, the volume ratio versus the particle size: small particle size on the particle size distribution is characterized in that 4: 1 to 13: 7.

In addition, the mean particle diameter size of 1㎛ (D ₅₀₎ ratio (D ₅₀ substituting diameter / small particle diameter D ₅₀₎ is from 5 to 30. The average particle size (D ₅₀ ) of the small particle size is preferably 0.2 μm or less, and the weight ratio of the cobalt compound and the ground cobalt compound is preferably mixed in a 10: 1 to 4: 1 weight ratio (%).

Meanwhile, the pulverized cobalt compound according to the present invention is prepared by pulverizing one cobalt compound, by mixing and grinding two different cobalt compounds selected from cobalt hydroxide, oxy cobalt hydroxide, cobalt oxide, and cobalt carbonate. It is also possible to make.

On the other hand, looking at the manufacturing method of the lithium cobalt oxide according to the present invention.

Forming the ground cobalt compound and mixing the cobalt compound in a predetermined ratio; Mixing a lithium compound in a proportion to the mixed and prepared cobalt compound; Cooling after the firing process; And obtaining lithium cobalt oxide (LiCoO ₂ ) of a desired size through a grinding process.

The forming of the pulverized cobalt compound may be performed by pulverizing the ratio of the large particle size and the small particle to a volume ratio of 4: 1 to 13: 7 and then weighting the cobalt compound and the pulverized cobalt compound in a weight ratio of 10: 1 to 4: 1. To mix.

In the step of mixing the lithium compound in a predetermined ratio to the mixed cobalt compound prepared to mix the lithium compound to the mixed cobalt compound. At this time, the magnification of the cobalt compound and the lithium compound is mixed in a molar ratio (Li / Co) of Co atoms and Li atoms in 1.04 to 1.06.

After the calcination process, cooling is performed to obtain lithium cobalt oxide (LiCoO ₂ ). When pulverized cobalt compounds are added to the cobalt compound and the lithium compound, the voids between the particles are reduced, and when a high temperature heat is applied to the cobalt compound, the particles move in a direction in which the surface area decreases and the particles grow in a state where grain boundaries are separated. This is facilitated.

In the present invention, two firing conditions are presented. First, one-step firing is performed at 800 ° C. to 1050 ° C. for 12 hours to 24 hours. This is not preferable because the lithium cobalt composite oxide (LiCoO ₂ ) cannot be sufficiently synthesized when the firing temperature is lower than 800 ° C., and lithium compound particles remain, and when the firing temperature is higher than 1050 ° C., the target lithium cobalt oxide ( LiCoO ₂ ) is not preferable because it decomposes and degrades the cycle characteristics of the lithium secondary battery.

Secondly, the firing conditions suggested are the first firing of 4 to 10 hours at a firing temperature of 400 ℃ to 650 ℃, and the second firing of 12 to 24 hours at a firing temperature of 800 ℃ to 1050 ℃. As described above, more uniform lithium cobalt oxide may be obtained through the multi-step firing.

The firing step can be performed either in the air or in an oxygen atmosphere, and is not particularly limited. In addition, these baking can be performed several times as needed.

After cooling through the calcination process, in the pulverization process, lithium cobalt oxide (LiCoO ₂ ) of a desired size is obtained in the pulverization of the lithium cobalt oxide using a ball mill, a cutter mill, a hammer mill, a jet mill, or the like. Grinding process.

When the grinding process is performed without adding the grinding compound as in the conventional method, fine powder is generated during grinding, and the generated fine powder adheres to the surface of lithium cobalt oxide (LiCoO ₂ ) to reduce the stability and performance of the battery.

However, lithium cobalt oxide prepared by the addition of the crushing compound according to the present invention improves the stability and performance of the battery because the grain growth is made by the grain growth is separated during the calcination process to reduce the fine powder generated during crushing Can be.

Hereinafter, an embodiment according to the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to these examples.

FIG. 1 shows a particle size distribution of cobalt oxide having an average particle diameter of 4 μm, and FIG. 2 shows pulverized cobalt oxide having different particle size distribution peaks by grinding cobalt oxide having an average particle diameter of 4 μm.

Figure 3a is a SEM photo showing the particle shape of lithium cobalt oxide (LiCoO ₂₎ obtained in Example, Fig. 3b illustrates the state of the surface of the particles on a SEM picture by expanding the lithium cobalt oxide (LiCoO ₂₎ obtained in Example do.

4A is a SEM photograph showing the particle shape of lithium cobalt oxide (LiCoO ₂ ) obtained in the comparative example, and FIG. 4B is an enlarged view of the particle surface state on the SEM with the enlarged lithium cobalt oxide (LiCoO ₂ ) as a comparative example.

Cobalt oxide having an average particle diameter of 4 mu m is formed using a planatary ball mill to form pulverized cobalt oxide. The pulverized cobalt oxide is pulverized into a large particle diameter of 3 μm, a small particle size of 1 μm or less, and has two different particle size distribution peaks. Grinding is carried out so that the volume ratio of the large particle size to the small particle size is 4: 1.

Thereafter, the cobalt oxide and the ground cobalt oxide are mixed in a weight ratio (%) of 4: 1, and lithium carbonate is mixed. The cobalt oxide mixed with lithium carbonate with a 1.05 molar ratio (Li / Co) of Co atoms and Li atoms, cooled and then maintained for 6 hours at 1000 ℃, crushed to produce a mean particle diameter of the Li 20㎛ _{1 .01} CoO ₂ do.

(Comparative example)

Then a solution of the cobalt oxide and lithium carbonate in a 1.05 molar ratio (Li / Co) of Co atoms and Li atom, a cooling after maintained for 6 hours at 1000 ℃, pulverized to prepare a Li _{1 .01} CoO ₂ having an average particle diameter of 17㎛ do. That is, to prepare a Li _{1 .01} CoO ₂ in the same manner as in Example except for not adding the grinding of cobalt oxide.

3 to 4, it can be seen that the lithium cobalt oxide (LiCoO ₂ ) obtained as an example has a clean surface and less fine powder than the lithium cobalt oxide (LiCoO ₂ ) obtained as a comparative example.

5 is a comparison of DSC (Differential Scanning Calorimetry) of the above Example and Comparative Example, in the case of the exothermic peak (peak) is moved from 216.02 ℃ to 227.92 ℃, the calorific value also from 281.5 J / g to 106.6 J / g It can be seen that the thermal stability is improved by decreasing.

D ₅ D ₅₀ D ₉₅ Example 9.91 19.87 36.16 Comparative example 7.73 16.87 31.88

In addition, Table 1 compares the average particle diameter size of the lithium cobalt oxide (LiCoO ₂ ) obtained in Examples and Comparative Examples. As shown in the above table, in the case of the embodiment in which the pulverized cobalt oxide is added, it can be seen that the average grain size increased at the same firing temperature.

As described above, the lithium cobalt oxide prepared by adding the pulverizing compound according to the present invention has a technical advantage in that it provides a stable cathode active material for a non-aqueous electrolyte secondary battery by improving the stability and reliability by reducing the generation of fine powder during the grinding process. Will do.

The foregoing description relates to specific embodiments and can be easily understood by those of ordinary skill in the art that various modifications and changes can be made without departing from the spirit and scope of the invention as indicated by the claims. Could be.

1 is a particle size distribution of cobalt oxide.

2 is a particle size distribution of pulverized cobalt oxide.

FIG. 3A is a SEM photograph showing the particle shape of lithium cobalt oxide (LiCoO ₂ ) obtained in the example. FIG.

FIG. 3B is a SEM photograph showing the particle surface of lithium cobalt oxide (LiCoO ₂ ) obtained in the example. FIG.

4A is a SEM photograph showing the particle shape of lithium cobalt oxide (LiCoO ₂ ) as a comparative example.

4B is a SEM photograph showing the particle surface of lithium cobalt oxide (LiCoO ₂ ) obtained in a comparative example.

Figure 5 is a DSC (Differential Scanning Calorimetry) comparison graph of the comparative example and the example.

Claims (15)

In the positive electrode active material for a non-aqueous electrolyte secondary battery, After adding a predetermined ratio of the pulverized transition metal compound to the transition metal compound, the mixture is mixed with a lithium compound to undergo a calcination process and a pulverization process, thereby reducing the generation of fine powder and improving reliability and stability. A lithium transition metal oxide for a non-aqueous secondary battery prepared by adding a pulverized transition metal compound.      [Formula 1] Li _a Ni _1-xy Co _x M _y O ₂      (In Formula 1, M is one metal selected from the group consisting of Mn, Mg, Fe, Al, and a combination thereof, 1.0 ≦ a ≦ 1.1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y≤1) In the positive electrode active material for a non-aqueous electrolyte secondary battery, After adding a predetermined ratio of the pulverized transition metal compound to the transition metal compound, the mixture is mixed with a lithium compound to undergo a calcination process and a pulverization process, thereby reducing the generation of fine powder and improving reliability and stability. A lithium transition metal oxide for a non-aqueous secondary battery prepared by adding a pulverized transition metal compound.     [Formula 2] Li _a Mn _2-xy Ni _x Co _y O ₄    (In Formula 2, 1.0 ≦ a ≦ 1.1, 0 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.5, and 0 ≦ x + y ≦ 0.5) The method according to claim 1 or 2, The transition metal compound is a cobalt compound, a nickel-cobalt-manganese composite compound, a lithium transition metal oxide for a non-aqueous secondary battery prepared by adding a pulverized transition metal compound, characterized in that any one of a compound based on the manganese compound. The method of claim 3, wherein The cobalt compound is a lithium transition metal oxide for a non-aqueous secondary battery prepared by adding a pulverized transition metal compound, characterized in that any one selected from cobalt hydroxide, oxy cobalt hydroxide, cobalt carbonate. The method according to claim 1 or 2, The lithium compound is a lithium transition metal oxide for a non-aqueous secondary battery prepared by adding a grinding transition metal compound, characterized in that selected from the group consisting of lithium carbonate, lithium nitrate, lithium sulfate, lithium acetate, lithium chloride, lithium hydroxide, lithium oxide . The method according to claim 1 or 2, The grinding transition metal compound is a non-aqueous system prepared by adding a grinding transition metal compound, characterized in that any one of a cobalt compound, a nickel-cobalt-manganese composite compound, and a transition metal compound based on a manganese compound is obtained through a grinding step. Lithium transition metal oxide for secondary batteries. The method of claim 6, The pulverized cobalt compound is a lithium transition metal oxide prepared by adding a pulverized transition metal compound, characterized in that obtained by mixing and pulverizing two or more cobalt compounds selected from cobalt hydroxide, oxy cobalt hydroxide, cobalt oxide, cobalt carbonate. The method according to claim 1 or 2, Non-aqueous system prepared by adding a pulverized transition metal compound, characterized in that the average particle diameter is 15㎛ or more after adding a predetermined ratio of the pulverized transition metal compound to the transition metal compound, mixed with the lithium compound and subjected to the calcination process and pulverization process Lithium transition metal oxide for secondary batteries. The method according to claim 1 or 2, The pulverized transition metal compound is a lithium transition metal oxide for a non-aqueous secondary battery prepared by adding a pulverized transition metal compound, characterized in that there are two or more particle size distribution peak (peak). The method according to claim 1 or 6, The ratio of the small particle size and assignment respect average particle size (D ₅₀₎ when the cutting transition metal compound is classified into a smaller-diameter lapse assignment based on the average particle size (D ₅₀₎ of 1㎛ (D ₅₀ substituting light / D ₅₀ Small particle diameter) is a lithium transition metal oxide for a non-aqueous secondary battery prepared by adding a grinding transition metal compound, characterized in that 5 to 30. The method according to claim 1 or 2, The pulverized transition metal compound is a lithium transition metal oxide for a non-aqueous secondary battery prepared by adding a pulverized transition metal compound, characterized in that the volume ratio of 4: 1 to 13: 7 large particle size and small particle size. The method according to claim 1 or 7, The transition metal compound and the pulverized transition metal compound is mixed in a weight ratio (%) of 10: 1 to 4: 1, and the transition metal compound and the lithium compound (Li / Metal) in a molar ratio of 1.04 to 1.06, firing and grinding Lithium transition metal oxide for a non-aqueous secondary battery prepared by adding a pulverized transition metal compound characterized in that it is prepared through.         The method according to claim 1 or 2,        The firing process is a lithium transition metal oxide for a non-aqueous secondary battery prepared by the addition of a pulverized transition metal compound, characterized in that 12 to 24 hours firing at a firing temperature of 600 ℃ to 1050 ℃. The method according to claim 1 or 2, The firing step is a pulverized transition metal compound characterized in that the primary firing at a firing temperature of 400 ℃ to 650 ℃ 4 to 10 hours, and the secondary firing 12 to 24 hours at a firing temperature of 800 ℃ to 1050 ℃. Lithium transition metal oxide for a non-aqueous secondary battery prepared by addition. The method according to claim 1 or 2, In adding a predetermined ratio of a pulverized transition metal compound to the transition metal compound, the transition metal compound and the pulverized transition metal compound are non-aqueous systems prepared by adding a pulverized transition metal compound, characterized in that the same or different hetero transition metal compounds. Lithium transition metal oxide for secondary batteries.

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