JP2019046795A - Composite cathode active material, method of preparing the same, and cathode and lithium battery including the composite cathode active material - Google Patents

Abstract

To provide a composite cathode active material, a method of preparing the same, and a cathode and a lithium battery including the composite cathode active material.SOLUTION: There are provided a composite cathode active material, and a cathode and a lithium battery including the composite cathode active material. The composite cathode active material includes at least one secondary particle including an agglomerate of a plurality of primary particles. The secondary particle contains a plurality of primary particles including a lithium transition metal oxide having a layered crystal structure, and a coating layer disposed on a surface of the secondary particle and between adjacent primary particles of the plurality of primary particles. The coating layer includes a lithium cobalt composite oxide having a spinel crystal structure, and the lithium cobalt composite oxide includes cobalt (Co) and a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof.SELECTED DRAWING: Figure 1A

Description

  The present invention relates to a composite positive electrode active material, a method for producing the same, a positive electrode employing the same, and a lithium battery.

  In order to conform to the miniaturization and high performance of various devices, in addition to the miniaturization and weight reduction of lithium batteries, high energy density formation is important. In order to realize a lithium battery meeting such importance, a nickel-based positive electrode active material having a high capacity has been considered.

  Conventional nickel-based positive electrode active materials have poor life characteristics due to high surface residual lithium content and side reactions due to cation mixing, and thermal stability can not reach a satisfactory level.

  The problem to be solved by the present invention is to provide a new composite positive electrode active material with reduced surface residual lithium content and improved thermal stability.

  The problem to be solved by the present invention is also to provide a positive electrode comprising the composite positive electrode active material.

  The problem to be solved by the present invention is also to provide a lithium battery including the above-mentioned positive electrode and having improved life and cell capacity.

  The problem to be solved by the present invention is also to provide a method for producing the composite positive electrode active material.

According to one side,
A plurality of primary particles comprising at least one secondary particle comprising an aggregate of a plurality of primary particles, the secondary particles comprising a plurality of primary particles comprising a lithium transition metal oxide having a layered crystal structure, and a surface of the secondary particles And a coating film disposed between a plurality of primary particles, and a composite positive electrode active material,
The coating film includes lithium cobalt composite oxide having a spinel crystal structure,
The lithium cobalt composite oxide provides a composite positive electrode active material including cobalt (Co) and a group 2, 12, or 13 element or a combination thereof.

  According to another aspect, a positive electrode including the composite positive electrode active material described above is provided.

  According to yet another aspect, a lithium battery is provided that includes the positive electrode described above.

According to yet another aspect,
Producing a lithium transition metal oxide having a layered crystal structure;
The lithium transition metal oxide having the layered crystal structure, cobalt (Co) having a spinel crystal structure, and one or more selected from Group 2, Group 12, Group 13 elements Mixing a lithium cobalt composite oxide precursor to obtain a composite positive electrode active material composition;
Drying the composite positive electrode active material composition and heat-treating the composite positive electrode active material composition in an oxidizing gas atmosphere at a temperature of more than 400 ° C. and 1,000 ° C. or less; and producing the composite positive electrode active material described above A method of producing a positive electrode active material is provided.

  According to the present invention, the composite positive electrode active material has a reduced surface residual lithium content to improve the thermal stability. If it is used, the charge / discharge characteristics and the life characteristics of the lithium battery will be improved.

1 schematically shows a structure of a composite positive electrode active material according to an embodiment of the present invention. 5 is an image showing the results of scanning electron microscopy analysis of the composite positive electrode active material manufactured according to Example 1. FIG. It is a scanning electron micrograph with respect to the composite positive electrode active material powder manufactured by Example 4a. 7 is a scanning electron micrograph of the composite positive electrode active material powder produced according to Comparative Example 2; 7 is a scanning electron micrograph of the composite positive electrode active material powder produced according to Comparative Example 4; FIG. 1 is an XRD (X-ray diffraction) spectrum of a composite positive electrode active material produced according to Example 1. FIG. 1 is a view showing a structure of a lithium battery employing a positive electrode including a composite positive electrode active material according to an embodiment; It is the graph which showed the high temperature life characteristic of the lithium battery (18650minicell) manufactured by Example 19 and Comparative Example 13. It is the figure which showed the high temperature life characteristic of the lithium battery (18650minicell) manufactured by Examples 20 and 21 and Comparative Examples 14 and 15.

  Hereinafter, a composite positive electrode active material according to an exemplary embodiment, a method of manufacturing the same, a positive electrode including the same, and a lithium battery will be described in more detail.

  At least one secondary particle comprising an aggregate of a plurality of primary particles, wherein the secondary particle comprises a lithium transition metal oxide having a layered crystal structure, the surface of the secondary particle, and a primary A coating film comprising a lithium cobalt composite oxide containing cobalt (Co) having a spinel crystal structure and one or more selected from group 2, group 12 and group 13 elements among particles. A composite positive electrode active material is provided.

  The coating film can be present between the grain boundaries of adjacent primary particles and on the surface of secondary particles. And, in the present specification, “between primary particles” is interpreted to include both the particle diameter of the primary particles and the surface of the primary particles. Thus, the coating film containing the lithium-cobalt composite oxide is present between the surface of the secondary particles and the particle size of the primary particles, and the conductivity of lithium ions is improved. Then, the content of residual lithium present on the surface of the composite positive electrode active material is reduced, deterioration of the composite positive electrode active material is suppressed, gas generation is reduced, and the thermal stability of the lithium battery is improved. The above-mentioned coating film arranged in the particle size between adjacent primary particles is present, accepts the volume change due to charge and discharge of the primary particles, and suppresses cracks of the primary particles, even after long-term charge and discharge, A reduction in mechanical strength of the composite positive electrode active material can be suppressed. Then, the side reaction between the lithium transition metal oxide having a layered crystal structure and the electrolytic solution can be efficiently suppressed, the internal resistance of the lithium battery is reduced, and the cycle characteristics of the lithium battery are improved.

  In the present specification, the coating film may be a continuous film or may be a discontinuous film such as an Irish type.

The lithium cobalt composite oxide having the spinel crystal structure and containing cobalt (Co) and one or more elements selected from group 2, group 12 and group 13 elements is a compound represented by the following chemical formula 1 It may be.
[Chemical formula 1]
Li _x Co _a Me _b O _{4 + δ}
In Chemical Formula 1, Me is one or more selected from the group 2 elements, the group 12 elements, and the group 13 elements,
1.0 ≦ x ≦ 1.1, 0 <a <2, 0 <b <2, 0 <a + b ≦ 2, −1.5 ≦ δ ≦ 0.

  In Chemical Formula 1, x is, for example, 1.0 to 1.09, a is 0.4 to 1.6, and b is 0.4 to 1.6. And the sum of a and b is 2, for example. In Chemical Formula 1, 0.1 <a + b ≦ 2, for example, 0.2 <a + b ≦ 2, for example, 0.5 <a + b ≦ 2, for example, 1 <a + b ≦ 2.

  In Formula 1, M is at least one selected from aluminum (Al), gallium (Ga), magnesium (Mg), calcium (Ca), barium (Ba), and zinc (Zn).

The compounds of the formula 1 are, for example, Li _x Co _a Al _b O _{4 + δ} , Li _x Co _a Zn _b O _{4 + δ} , Li _x Co _a Mg _b O _{4 + δ} , Li _x Co _a Ga _b O _{4+ δ} , Li _x Co _a Ca _b It may be O _{4 + δ} or Li _x Co _a Ba _b O _{4 + δ} . In the above chemical formula, 1.0 ≦ x ≦ 1.1, 0 <a <2, 0 <b <2, 0 <a + b ≦ 2, −1.5 ≦ δ ≦ 0. In such compounds, x is, for example, 1.0 to 1.09, a is 0.4 to 1.6, and b is 0.4 to 1.6.

The compound of Chemical Formula 1 is, for example, LiCo _1.5 Al _0.5 O _{4 + δ} (−0.5 ≦ δ ≦ 0), LiCo _1.5 Ga _0.5 O 4+ _δ (−0.5 ≦ δ ≦ 0), LiCo _1.33 Zn _0.67 O _{4 + δ} (−0.835 ≦ δ ≦ 0), LiCo _1.33 Ca _0.67 O _{4 + δ} (−0.835 ≦ δ ≦ 0), LiCo _1.33 Ba _0.67 O _{4 + δ} (−0.835 ≦ δ ≦ 0), LiCo _1.33 Ga _0.67 O _{4 + δ} (−0.835 ≦ δ ≦ 0), LiCo _1.2 Mg _0.8 O _{4 + δ} (−0.9 ≦ _{δ ≦ 0), LiCo 1.2 Ga} 0.8 O 4 + δ (-0.9 ≦ δ ≦ 0), LiCo 1.2 Ca 0.8 O 4 + δ (-0.9 ≦ δ ≦ 0), LiCo 1. _{2 Ba 0.8 O 4 + δ (} -0.9 ≦ δ ≦ 0), LiCo 1.2 Zn 0.8 O 4 + δ (- _{.9 ≦ δ ≦ 0), LiCo} 1.6 Mg 0.4 O 4 + δ (-0.7 ≦ δ ≦ 0), LiCo 1.6 Ga 0.4 O 4 + δ (-0.7 ≦ δ ≦ 0), LiCo _1.6 Ca _0.4 O _{4 + δ} (−0.7 ≦ δ ≦ 0), LiCo _1.6 Ba _0.4 O 4+ _δ (−0.7 ≦ δ ≦ 0), LiCo _1.6 Zn _0.4 O _{4 + δ} (−0.7 ≦ δ ≦ 0), LiCo _0.8 Mg _1.2 O _{4 + δ} (−1.1 ≦ δ ≦ 0), LiCo _0.8 Ga _1.2 O _{4 + δ} (−1.1 ≦ δ ≦ 0), LiCo _0.8 Ca _1.2 O _{4 + δ} (−1.1 ≦ δ ≦ 0), LiCo _0.8 Ba _1.2 O _{4 + δ} (−1.1 ≦ δ ≦ 0), LiCo _{0. 8} Zn _1.2 O _{4 + δ} (-1.1 δ δ 0 0), LiCo _0.4 Mg _1.6 O _{4 + δ} (-1.3 δ δ 0 0), LiCo _0.4 Ga _1.6 O _{4 + δ} (−1.3 ≦ δ ≦ 0), LiCo _0.4 Ca _1.6 O _{4 + δ} (−1.3 ≦ δ ≦ 0), LiCo _0.4 Ba _1.6 O 4+ _δ (−1.3 ≦ There are δ ≦ 0), LiCo _0.4 Zn _1.6 O _{4 + δ} (−1.3 ≦ δ ≦ 0), and the like.

Compounds of Formula 1 may, for _{example, LiCo 1.5 Al 0.5 O 4 +} δ (-0.5 ≦ δ ≦ 0), LiCo 1.33 Zn 0.67 O 4 + δ (-0.835 ≦ δ ≦ 0), LiCo _1.2 Mg _0.8 O _{4 + δ} (−0.9 ≦ δ ≦ 0), LiCo _1.6 Mg _0.4 O 4+ _δ (−0.7 ≦ δ ≦ 0), LiCo _0.8 Mg _1.2 There is O _{4 + δ} (−1.1 ≦ δ ≦ 0) or LiCo _0.4 Mg _1.6 O _{4 + δ} (−1.3 ≦ δ ≦ 0).

  The lithium transition metal oxide having a layered crystal structure belongs to a rock salt layered structure (R-3 m space group), has a spinel crystal structure, and has cobalt (Co), and a group 2, group 12, group 13 element The lithium cobalt composite oxide including one or more selected from the above belongs to the Fd-3m space group. By having the above-described crystal structure, the cycle characteristics and thermal stability of the lithium battery containing the composite positive electrode active material are further improved.

  The term "grain boundary" refers to the interface of two adjacent primary particles. At this time, the interface between the primary particles exists inside the secondary particles. The term "primary particles" may co-aggregate with one another to form secondary particles, wherein the primary particles may have a variety of morphologies from rod shape to square shape, and the term "secondary particles" refers to Refers to particles that are not aggregates of other particles, or particles that are not further aggregated, including primary particles, and secondary particles may have spherical morphology.

  FIG. 1A is a cross-sectional view conceptually showing the fine structure of secondary particles in a composite positive electrode active material according to one embodiment.

  In reference thereto, primary particles 11 aggregate to form secondary particles 12, and 13 between primary particles 11 such as on the grain boundaries (14) of primary particles and / or on the surface (15) of secondary particles. , The coating film is formed.

  In the composite positive electrode active material, the content of nickel in the transition metal contained in the lithium transition metal oxide may be 70 mol% or more, for example, 80 mol% or more, for example, 90 mol% or more, for example, 95 mol% or more. Among transition metals contained in lithium transition metal oxide in the composite positive electrode active material, the content of nickel is, for example, 70 to 99.9 mol%, for example, 80 to 99 mol% based on the total content of transition metals of lithium transition metal oxide. It is 95 mol%. By using a lithium transition metal oxide having a nickel content in the above-mentioned range, a high capacity lithium battery can be manufactured.

  A coating film comprising a lithium cobalt composite oxide having a spinel crystal structure and containing cobalt (Co) and one or more selected from Group 2, 12 and 13 elements in the composite positive electrode active material Are disposed at uniform concentrations throughout the composite positive electrode active material. A concentration gradient can be provided from the central portion to the surface portion of the composite positive electrode active material. For example, in the central part of the composite positive electrode active material, the concentration of the lithium cobalt composite oxide is low, and in the surface part, the concentration of the coating film containing the lithium cobalt composite oxide is high. According to another embodiment, the concentration of the lithium cobalt composite oxide is high in the central portion of the composite positive electrode active material, and the concentration of the lithium cobalt composite oxide is low in the surface portion.

  In the coating film, the content of the lithium cobalt composite oxide is 0.05 to 30 parts by weight, for example, 0.1 to 20 parts by weight, based on 100 parts by weight of the lithium transition metal oxide having a layered crystal structure. For example, 0.1 to 10 parts by weight, such as 0.1 to 2 parts by weight, such as 0.25 to 1.5 parts by weight.

  The content of lithium cobalt in the coating film is less than the content of lithium cobalt composite oxide, and is 0.01 to 20 parts by weight, for example, based on 100 parts by weight of lithium transition metal oxide having a layered crystal structure. 0.1 to 10 parts by weight, such as 0.1 to 2 parts by weight, such as 0.25 to 1.5 parts by weight. When the content of lithium cobalt composite oxide and lithium cobalt is within the above range, it is possible to obtain a composite positive electrode active material excellent in thermal stability and having a reduced content of surface residual lithium. By using it, it is possible to manufacture a lithium battery with improved charge and discharge characteristics and life characteristics.

  According to another embodiment, the total content of cobalt and metal (M) in the lithium-cobalt composite oxide of the coating film is 100 parts by weight of lithium transition metal oxide having a layered crystal structure. 0.01 to 20 parts by weight, for example, 0.1 to 10 parts by weight, for example, 0.1 to 2 parts by weight, for example, 0.25 to 1.5 parts by weight.

  A mixed phase may be present between the lithium transition metal oxide having the layered crystal structure and the coating film, and the mixed phase may be a lithium transition metal oxide and a lithium cobalt complex oxide. Including combinations with The mixed phase means a mixed structure of a layered crystal structure and a spinel crystal structure.

  The composition may further include a compound having an amorphous structure or a compound having a layered crystal structure or a combination thereof among the primary particles.

The lithium transition metal oxide having a layered crystal structure may be one selected from the compounds represented by the following chemical formulas 2 to 4.
[Chemical formula 2]
Li _x Co _1-y M _y O _2-α X _α
[Chemical formula 3]
Li _x Ni _1-y Me _y O _2-α X _α
[Chemical formula 4]
_{Li x Ni 1-y-z} Mn y Ma z O 2-α X α
In the chemical formulas 2 to 4, 0.9 ≦ x ≦ 1.1, 0 ≦ y ≦ 0.9, 0 <z ≦ 0.2, 0 ≦ α ≦ 2,
M is one or more metals selected from the group consisting of Ni, Mn, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Fe, Cu and B, Me is Co, Zr At least one metal selected from the group consisting of Al, Mg, Ag, Mo, Ti, V, Cr, Mn, Fe, Cu and B, and Ma is Co, Zr, Al, Mg, Ag And one metal selected from the group consisting of Mo, Ti, V, Cr, Fe, Cu and B, and X is an element selected from the group consisting of F, S and P.
In the chemical formulas 2 to 4, x is 1.03 to 1.09, for example, 1.03, 1.06 or 1.09.

The lithium transition metal oxide having a layered crystal structure is one selected from the compounds represented by the following Chemical Formulas 5 to 7.
[Chemical formula 5]
_{Li [Li 1-a Me a} ] O 2 + d
In Chemical Formula 5, 0.8 ≦ a <1, 0 ≦ d ≦ 0.1,
The Me is at least one metal selected from the group consisting of Ni, Co, Mn, Al, V, Cr, Fe, Zr, Re, B, Ge, Ru, Sn, Ti, Nb, Mo and Pt. And
[Chemical formula 6]
_{Li [Li 1-x-y} -z Ma x Mb y Mc z] O 2 + d
In Chemical Formula 6, 0.8 ≦ x + y + z <1, 0 <x <1, 0 <y <1, 0 <z <1, 0 ≦ d ≦ 0.1,
The Ma, Mb and Mc are each independently one or more metals selected from the group consisting of Mn, Co, Ni and Al,
[Chemical formula 7]
_{Li [Li 1-x-y} -z Ni x Co y Mn z] O 2 + d
In Chemical Formula 7, 0.8 ≦ x + y + z <1, 0 <x <1, 0 <y <1, 0 <z <1, 0 ≦ d ≦ 0.1.

The lithium transition metal oxide may be a compound represented by Formula 8 below.
[Chemical formula 8]
aLi ₂ MnO _3- (1-a) LiMO ₂
In the chemical formula 8, 0 <a <1,
M is nickel (Ni), cobalt (Co), manganese (Mn), vanadium (V), chromium (Cr), iron (Fe), zirconium (Zr), rhenium (Re), aluminum (Al), boron ( B) Two or more elements selected from germanium (Ge), ruthenium (Ru), tin (Sn), titanium (Ti), niobiome (Nb), molybdenum (Mo) and platinum (Pt).

The lithium transition metal oxide having a layered crystal structure may be a compound represented by Formula 9 below.
[Chemical formula 9]
Li _x Ni _1-y-z M _y Co _z O ₂
In Chemical Formula 9, 0.9 ≦ x ≦ 1.1, 0 ≦ y ≦ 0.2, 0 <z ≦ 0.2, 0.7 ≦ 1-y-z ≦ 0.99.
M is selected from the group consisting of manganese (Mn), aluminum (Al), titanium (Ti) and calcium (Ca).
In Chemical formula 9, 1-y-z is, for example, 0.8 to 0.99.

The lithium transition metal oxide having a layered crystal structure may be a compound represented by the following chemical formula 9a.
[Chemical formula 9a]
_{Li x Ni 1-y-z} Mn x Co y O 2
In the chemical formula 9a, 0.80 ≦ x ≦ 1.1, 0 = y ≦ 0.2, 0 <z ≦ 0.2, 0.8 ≦ 1-y-z ≦ 0.99.

  In the chemical formulas 5 to 9, x is 1.03 to 1.09, for example, 1.03, 1.06 or 1.09.

The lithium transition metal oxide is, for example, Li _1.03 [Ni _0.91 Co _0.06 Mn _0.03 ] O ₂ , Li _1.03 [Ni _0.88 Co _0.08 Mn _0.04 ] O ₂ , Li _1.03 [Ni _0.8 Co _0.15 Mn _0.05 ] O ₂ , Li _1.03 [Ni _0.85 Co _0.10 Mn _0.05 ] O ₂ , Li _1.03 [Ni _{0 .91} Co _0.05 Mn _0.04 ] O ₂ , Li _1.05 [Ni _0.91 Co _0.06 Mn _0.03 ] O ₂ , Li _1.06 [Ni _0.91 Co _0.06 Mn _{0 .03} ] O ₂ , Li _1.06 [Ni _0.88 Co _0.08 Mn _0.04 ] O ₂ , Li _1.06 [Ni _0.8 Co _0.15 Mn _0.05 ] O ₂ , Li _{1 .06} [Ni _0.85 Co _0.10 Mn _0.05 ] O ₂ , Li _1.06 [Ni _0.91 Co _0.05 Mn _0.04 ] O ₂ , Li _1.09 [Ni _0.91 Co _0.06 Mn _0.03 ] O ₂ , Li _1.09 [Ni _0.88 Co _0.08 Mn _0.04 ] O ₂ , Li _1.09 [Ni _0.8 Co _0.15 Mn _0.05 ] O ₂ , Li _1.09 [Ni _0.85 Co _{0. 10} Mn _0.05 ] O ₂ or Li _1.09 [Ni _0.91 Co _0.05 Mn _0.04 ] O ₂ . The lithium transition metal oxide may comprise at least one of the above mentioned substances.

  In the composite positive electrode active material, the average particle diameter of the primary particles may be 0.1 to 5 μm, for example, 0.2 to 0.5 μm, but not necessarily limited to such a range, and lithium It is adjusted in the range which can provide the improved charge and discharge characteristic of a battery.

  In the composite positive electrode active material, the average particle diameter of the secondary particles in which the primary particles are aggregated may be about 1 μm to about 30 μm, for example, 10 to 20 μm, for example about 13 μm to about 15 μm. The range is not limited to the above range, but is adjusted within the range capable of providing improved charge and discharge characteristics.

  In the composite positive electrode active material, the thickness of the coating film is 1 μm or less, for example, 500 nm or less, 200 nm or less, for example, 100 nm or less, for example, 50 nm or less, for example, 30 nm or less, for example, 10 nm or less, for example, 10 nm to 1 μm, for example , 30 nm to 200 nm, for example, 30 nm to 100 nm. In the thickness range of such a coating film, the cycle characteristics and thermal stability of the lithium battery containing the composite positive electrode active material are further improved.

  According to one embodiment, the composite positive electrode active material has an average particle size length of about 50 nm to about 1,000 nm, an average particle size thickness of about 1 nm to about 200 nm, and a length of The direction may be parallel to the surface of the adjacent primary particle, and the direction of thickness may be perpendicular to the surface of the adjacent primary particle. The average particle size length may be about 50 nm to about 950 nm, about 100 nm to about 900 nm, about 150 nm to about 800 nm, or about 200 nm to about 700 nm. For example, the average particle size thickness may be about 2 nm to about 100 nm, about 5 nm to about 100 nm, about 10 nm to about 100 nm, or about 20 nm to about 100 nm. Within such a range of average particle diameter length and average particle diameter thickness, further improved charge and discharge characteristics can be provided.

  According to another embodiment, a method of manufacturing the composite positive electrode active material includes: manufacturing a lithium transition metal oxide having a layered crystal structure; a lithium transition metal oxide having the layered crystal structure; and a spinel crystal structure. A composite positive electrode active material composition by mixing a lithium cobalt composite oxide precursor having cobalt (Co) and one or more selected from the group 2, group 12 and group 13 elements; Obtaining the composite positive electrode active material composition, and heat treating the composite positive electrode active material composition at a temperature higher than 400 ° C. and lower than 1,000 ° C. in an oxidizing gas atmosphere.

  A lithium cobalt composite comprising a lithium transition metal oxide having a layered crystal structure, and a spinel crystal structure having cobalt (Co) and one or more elements selected from Group 2, Group 12 and Group 13 elements. The mixing of the oxide with the precursor is also carried out wet in the presence of a solvent.

  The oxidizing gas atmosphere may be implemented using oxygen or air. The oxidizing gas atmosphere may include oxygen, air, or a combination thereof, such as air with an increased oxygen content.

  In the composite positive electrode active material composition, a lithium cobalt composite oxide having the spinel crystal structure and containing cobalt (Co) and one or more elements selected from Group 2, Group 12, Group 13 elements The content of the precursor and the solvent is 300 parts by weight or less with respect to 100 parts by weight of the lithium transition metal oxide having the layered crystal structure. In the composite positive electrode active material composition, a lithium cobalt composite oxide having the spinel crystal structure and containing cobalt (Co) and one or more elements selected from Group 2, Group 12, Group 13 elements The content of the precursor is 100 parts by weight or less based on 100 parts by weight of the lithium transition metal oxide having the layered crystal structure. The content of the solvent is 200 parts by weight or less with respect to 100 parts by weight of the lithium transition metal oxide having the layered crystal structure.

  The heat treatment may be performed, for example, at 600 to 800 ° C., for example, 700 to 750 ° C. At the time of heat treatment, the temperature rising rate is, for example, 1 to 10 ° C./min. The heating rate is controlled in the range of 1 to 10 ° C./min, for example, about 2 ° C./min, to reach such a heat treatment temperature. When the heat treatment temperature and the temperature raising rate are within the above-mentioned range, they have a spinel crystal structure between the secondary particle surface and the primary particles, and cobalt (Co) and the groups 2, 12 and 13 A coating film including a lithium cobalt composite oxide including one or more selected from elements is disposed.

  The lithium cobalt composite oxide precursor is obtained by mixing a cobalt precursor and an M precursor, and mixing a solvent therein to obtain a precursor mixture. The precursor mixture is mixed with a lithium transition metal oxide having a layered crystal structure, a precipitation reaction is performed, and a lithium transition metal oxide having a layered crystal structure in which a compound coating film represented by Formula 10 is disposed. obtain. Next, it can be heat-treated to obtain a desired composite positive electrode active material.

  Examples of the cobalt precursor include cobalt chloride, cobalt nitrate, cobalt sulfate and the like, and the M precursor is the same as the cobalt precursor except that it is M instead of cobalt. Also used.

  In the composite positive electrode active material according to one embodiment, the calorific value of the composite positive electrode active material may be 90% or less of secondary particles including a lithium transition metal oxide having a layered crystal structure. The content of residual lithium in the composite positive electrode active material is 90% or less of the residual lithium content of secondary particles including a lithium transition metal oxide having a layered crystal structure.

  The residual lithium is, for example, about 4,000 parts per million (ppm) before surface treatment for removing residual lithium of the composite positive electrode active material, and effectively not more than 2,000 ppm after surface treatment. It can be reduced. And, the cell capacity of the composite positive electrode active material is 220 mAh / g, and the life is very excellent at 50 times or more.

  Further, a lithium cobalt composite oxide having a spinel crystal structure and containing cobalt (Co) and one or more selected from the group 2, group 12 and group 13 elements has a lithium transition metal oxide surface. Cover at least 50% or more. When having such a structure, side reactions between the lithium transition metal oxide and the electrolyte can be substantially reduced and / or efficiently minimized or blocked efficiently.

  The positive electrode according to another embodiment may include the composite positive electrode active material described above.

  The positive electrode mixes, for example, the composite positive electrode active material described above, a conductive agent, a binder and a solvent to prepare a positive electrode active material composition. The positive electrode active material composition may be directly coated on an aluminum current collector and dried to manufacture a positive electrode having a positive electrode active material layer formed thereon. As an alternative, after the positive electrode active material composition is cast on a separate support, a film obtained by peeling from the support is laminated on the aluminum current collector to form a positive electrode active material layer. Can be manufactured.

  As the conductive agent, carbon black, graphite fine particles, natural graphite, artificial graphite, acetylene black, ketjen black, carbon fiber; carbon nanotube; metal powder such as copper, nickel, aluminum, silver, metal fiber or metal tube; polyphenylene derivative Conductive polymers and the like are used, but the present invention is not limited thereto, and any of those used as a conductive agent in the art can be used.

  As the binder, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), a mixture of the aforementioned polymers, a styrene butadiene rubber polymer, etc. are used, As the solvent, N-methyl pyrrolidone (NMP), acetone, water and the like may be used, but the present invention is not necessarily limited thereto, and any of those used in the art can be used. .

  The contents of the composite positive electrode active material, the conductive agent, the binder and the solvent are at levels generally used in lithium batteries. Depending on the application and configuration of the lithium battery, one or more of the conductive agent, the binder and the solvent may be omitted.

  Moreover, the said positive electrode may add and contain another general positive electrode active material other than the above-mentioned composite positive electrode active material.

The common positive electrode active material may be used without limitation as long as it is commonly used in the art as a lithium-containing metal oxide. For example, one or more of complex oxides of lithium and metals selected from cobalt, manganese, nickel, and combinations thereof can be used, and specific examples thereof include Li _a A _{1- b} B ' _b D ₂ (in the above formula, 0.90 a a 1 1 and 0 b b 0.5 0.5); Li _a E _{1- b} B' _b O _2-c D _c In the above formula, 0.90 ≦ a ≦ 1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); LiE _2-b B ′ _b O _4-c D _c (wherein 0) ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); Li _a Ni _1-b-c Co _b B ′ _c D _α (in the above formula, 0.90 ≦ a ≦ 1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, 0 <α ≦ 2); Li _a Ni _1-b-c Co _{b B} ′ _c O _2-α F ′ _α (in the above formula, 0.90 ≦ a ≦ 1, 0 ≦ b 0.5,0 ≦ c ≦ 0.05,0 <α <a _{2); Li a Ni 1-} b-c Co b B 'c O 2-α F' 2 ( in the formula, 0.90 ≦ a ≦ 1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, 0 <α <2); Li _a Ni _1-b-c Mn _b B ′ _c D _α (in the above formula, 0 90 ≦ a ≦ 1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α ≦ 2); Li _a Ni _1-b-c Mn _b B ′ _c O _2-α F _'alpha (in the formula, 0.90 ≦ a ≦ 1,0 ≦ b ≦ 0.5,0 ≦ c ≦ 0.05,0 <α < a _{2); Li a Ni 1-} b-c Mn b B ' _c O _2-α F' ₂ (in the above formula, 0.90 ≦ a ≦ 1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, 0 <α <2); Li _a Ni _b E _c G _d O ₂ (In the above formula, 0.90 ≦ a ≦ 1, 0 ≦ b ≦ 0.9, 0 ≦ c ≦ 0.5, 0 .001 ≦ d ≦ 0.1); Li _a Ni _b Co _c Mn _d G _e O ₂ (in the above formula, 0.90 ≦ a ≦ 1, 0 ≦ b ≦ 0.9, 0 ≦ c ≦ 0 .5, 0 ≦ d ≦ 0.5, 0.001 ≦ e ≦ 0.1); Li _a NiG _b O ₂ (in the above formula, 0.90 ≦ a ≦ 1, 0.001 ≦ b ≦ 0 .1); Li _a CoG _b O ₂ (in the above formula, 0.90 ≦ a ≦ 1, 0.001 ≦ b ≦ 0.1); Li _a MnG _b O ₂ (in the above formula, 0) .90 ≦ a ≦ 1, 0.001 ≦ b ≦ 0.1); Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90 ≦ a ≦ 1, 0.001 ≦ b ≦ 0.1) QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiI′O ₂ ; LiNiVO ₄ ; Li _3-f J ₂ (PO ₄ ) ₃ (0 ≦ f ≦ 2); Li ₃ It can be used LiFePO compound represented by any one of the _{four formulas; f Fe 2 (PO 4)} 3 (0 ≦ f ≦ 2).

  In the above chemical formula, A is Ni, Co, Mn, or a combination thereof, and B ′ is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, a rare earth element, or a combination thereof, D is O, F, S, P, or a combination thereof, E is Co, Mn, or a combination thereof, F ′ is F, S, P, or a combination thereof, G Is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof, Q is Ti, Mo, Mn, or a combination thereof, I ′ is Cr, V , Fe, Sc, Y, or a combination thereof, and J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

  Here, it goes without saying that one having a coating film on the surface of the positive electrode compound can also be used, or the above-mentioned compound and a compound having a coating film can be mixed and used. The coating film may contain a coating element compound of oxide of coating element, hydroxide, oxyhydroxide of coating element, oxycarbonate of coating element, or hydroxycarbonate of coating element. The compounds forming the coating film may be amorphous or crystalline. As the coating element contained in the coating film, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof may be used. it can. In the coating film forming step, any element can be used for the compound and any coating method can be used as long as it does not adversely affect the physical properties of the positive electrode active material (for example, spray coating method, immersion method, etc.) A coating method may be used, as it is well understood by those skilled in the art, so a detailed description is omitted.

  According to another embodiment, the positive electrode may be manufactured using the composite positive electrode active material according to an embodiment as a large particle size positive electrode active material and using it with a small particle size positive electrode active material . Thus, the positive electrode may comprise a bimodal positive electrode active material.

  A lithium battery according to still another embodiment employs a positive electrode including the composite positive electrode active material, a negative electrode, and an electrolyte disposed therebetween. The lithium battery is also manufactured by the following method.

  First, a positive electrode is manufactured by the above-mentioned positive electrode manufacturing method.

  Next, the negative electrode is manufactured as follows. The negative electrode is manufactured by the same method as the positive electrode except that the negative electrode active material is used instead of the composite positive electrode active material. Further, as the negative electrode active material composition, the conductive agent, the binder and the solvent may be the same as in the case of the positive electrode.

  For example, a negative electrode active material, a conductive agent, a binder and a solvent may be mixed to produce a negative electrode active material composition, which may be directly coated on a copper current collector to produce a negative electrode plate. Alternatively, the negative electrode active material composition can be cast on a separate support, and the negative electrode active material film peeled off from the support can be laminated on a copper current collector to produce a negative electrode plate. .

  In addition, the negative electrode active material can be any as long as it is used as a negative electrode active material of a lithium battery in the relevant technical field. For example, it may include one or more selected from the group consisting of lithium metal, an element capable of alloying with lithium, a transition metal oxide, a non-transition metal oxide, and a carbon-based material.

  For example, the element which can be alloyed with the lithium is Si, Sn, Al, Ge, Pb, Bi, SbSi-Y alloy (the Y is an alkali metal, an alkaline earth metal, a group 13 to 16 element, a transition metal, a rare earth Element or a combination thereof, not Si, Sn—Y alloy (wherein Y is an alkali metal, an alkaline earth metal, a group 13 to 16 element, a transition metal, a rare earth element, or a combination thereof) And not Sn) or the like. As the element Y, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, It may be S, Se, Te, Po, or a combination thereof.

  For example, the transition metal oxide may be lithium titanium oxide, vanadium oxide, lithium vanadium oxide or the like.

For example, the non-transition metal oxide may be SnO ₂ , SiO _x (0 <x <2), and the like.

  The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite such as amorphous, plate-like, flake-like, spherical or fiber type natural graphite or artificial graphite, and the amorphous carbon may be soft carbon (soft carbon). It may be low temperature calcined carbon) or hard carbon, mesophase pitch carbide, calcined coke and the like.

  The contents of the negative electrode active material, the conductive agent, the binder and the solvent are at levels generally used in lithium batteries.

  Next, a separator to be inserted between the positive electrode and the negative electrode is prepared. Any separator may be used as long as it is commonly used in lithium batteries. An electrolyte which has a low resistance to ion migration and which is excellent in the ability to wet the electrolyte is used. For example, it is selected from glass fiber, polyester, Teflon (registered trademark), polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be in a non-woven form or a woven form. For example, in lithium ion batteries, rollable separators such as polyethylene and polypropylene are used, and in lithium ion polymer batteries, separators excellent in organic electrolyte impregnation ability are used. For example, the separator is also manufactured by the following method.

  The polymer resin, the filler and the solvent are mixed to prepare a separator composition. The separator composition is directly coated on the electrode and dried to form a separator. Alternatively, after the separator composition is cast on a support and dried, the separator film peeled from the support is laminated on the electrode to form a separator.

  The polymer resin used to manufacture the separator is not particularly limited, and any material used for the binder of the electrode plate may be used. For example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, or a mixture thereof is used.

  Next, an electrolyte is prepared.

  For example, the electrolyte may be an organic electrolyte. Also, the electrolyte may be solid. For example, it may be, but is not limited to, boron oxide, lithium oxynitride and the like, and any one may be used in the art if it is used as a solid electrolyte. The solid electrolyte is formed on the negative electrode by a method such as sputtering.

  The organic electrolyte can also be produced by dissolving a lithium salt in an organic solvent.

  Any organic solvent may be used as long as it is used as an organic solvent in the art. For example, ethylene carbonate, fluoroethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, methyl isopropyl carbonate, ethyl propyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran , 2-methyltetrahydrofuran, γ-buterolactone, dioxolane, 4-methyldioxolane, N, N-dimethylformamide, dimethylacetamide, dimethylsulfoxide, dimethylsulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethylether ,Also Mixtures thereof, and the like.

The lithium salt is also used if it is used in the art as a lithium salt. For _{example, 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, LiAlO 2, LiAlCl 4, LiN (C x F _{2x + 1 SO 2) (C} y F 2y + 1 SO 2) ( however, x, y are natural numbers), LiCl, LiI, or mixtures thereof, and the like.

  As can be seen from FIG. 4, the lithium battery 1 includes a positive electrode 3, a negative electrode 2 and a separator 4. The positive electrode 3, the negative electrode 2 and the separator 4 described above are taken up and folded, and stored in the battery case 5. Next, an organic electrolyte is injected into the battery case 5 and sealed in a cap assembly 6 to complete the lithium battery 1. The battery case may be cylindrical, square, thin film type, or the like. For example, the lithium battery may be a large thin film battery. The lithium battery may be a lithium ion battery.

  A separator is disposed between the positive electrode and the negative electrode to form a battery structure. After the battery assembly is stacked in a bicell structure, the battery assembly is impregnated with an organic electrolyte, and the resultant is accommodated in a pouch and sealed to complete a lithium ion polymer battery.

  Further, a plurality of the battery structures are stacked to form a battery pack, and such a battery pack is used for all devices that require high capacity and high output. For example, it is used also for a laptop computer, a smart phone, an electric vehicle, etc.

  The lithium battery is also used in electric vehicles (EVs) because of its excellent life characteristics and high rate characteristics. For example, it is also used for hybrid vehicles such as plug-in hybrid vehicles (PHEV: plug-in hybrid electric vehicle). It is also used in fields where large amounts of power storage are required. For example, it is used also for an electric bicycle, a power tool, etc.

  The lithium battery belongs to the Fd-3m space group including the second lithium transition metal oxide of the shell which is a coating film by charging the lithium metal to a high voltage of 4.5 V or more with respect to lithium metal at the time of initial charge. The spinel crystal structure can be activated to take advantage of the additional charge / discharge capacity. Therefore, the initial charge / discharge capacity of the lithium battery can be improved.

  The present invention will be described in more detail through the following examples and comparative examples, but the following examples do not mean that the scope of the invention is limited.

Comparative Example 1: Production of lithium transition metal oxide
NiSO ₄ (H ₂ O) ₆ , CoSO ₄ and MnSO ₄ H ₂ O were added to water at a molar ratio of 91: 6: 3 to prepare an aqueous precursor solution. While stirring the aqueous solution, the aqueous sodium hydroxide solution was gradually added dropwise to neutralize the aqueous precursor solution, thereby precipitating Ni _0.91 Co _0.06 Mn _0.03 (OH) ₂ . The precipitate was filtered, washed with water and dried at 120 ° C. to produce metal (Ni _0.91 Co _0.06 Mn _0.03 ) hydroxide powder.
After mixing the metal hydroxide powder and LiOH, the mixture is placed in a furnace and heat-treated at 765 ° C. for 20 hours while flowing oxygen, and lithium transition metal oxide (Li _1.05 Ni _0.91 Co _{0 .06} Mn _0.03 O ₂ ) was obtained.

Comparative Example 2 Production of Lithium Transition Metal Oxide
Heat treatment by mixing NiSO ₄ (H ₂ O) ₆ , CoSO ₄ , MnSO ₄ · H ₂ O and Al (NO ₃ ) ₃ · 9H ₂ O at a molar ratio of 87.8: 8: 4: 0.2 _Is carried out at 710 ° C. for 40 hours, and the content of LiOH is controlled to obtain lithium transition metal oxide (Li _1.09 Ni _0.878 Co _0.080 Mn _0.040 Al _0.002 O ₂ ) A lithium transition metal oxide (Li _1.09 Ni _0.878 Co _0.080 Mn _0.040 Al _0.002 O ₂ ) was manufactured in the same manner as Comparative Example 1 except for the above.

Comparative Example 3 Production of Composite Positive Electrode Active Material
After preparing 0.75 parts by weight of CoCl ₂ · H ₂ O, it was poured into 10 parts by weight of distilled water and stirred at room temperature for 1 minute to prepare an aqueous solution.
100 parts by weight of Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ powder prepared according to Comparative Example 1 is added to 90 parts by weight of distilled water, stirred at room temperature for 10 minutes, and The aqueous solution prepared by the above process was charged to prepare a mixture.
The mixture was dried in a 150 ° C. oven for 15 hours to prepare a dry matter.
The dried product was put into a furnace, and heat treated at 720 ° C. for 5 hours while flowing oxygen to produce a composite positive electrode active material.
The composite positive electrode active material had a structure in which a LiCoO ₂ coating film was disposed on the surface of Li _1.05 Ni _0.91 Co _0.061 Mn _0.03 O ₂ secondary particles and between primary particles. The cobalt content of the LiCoO ₂ coating film was 0.75 parts by weight based on 100 parts by weight of the composite positive electrode active material.

Comparative Example 3a Production of Composite Positive Electrode Active Material
After preparing 0.75 parts by weight of MgCl ₂ · H ₂ O, it was poured into 10 parts by weight of distilled water and stirred at room temperature for 1 minute to prepare an aqueous solution.
100 parts by weight of Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ powder prepared according to Comparative Example 1 is added to 90 parts by weight of distilled water, stirred at room temperature for 10 minutes, and The aqueous solution prepared by the above process was charged to prepare a mixture.
The mixture was dried in a 150 ° C. oven for 15 hours to prepare a dry matter.
The dried product was put into a furnace, and heat treated at 720 ° C. for 5 hours while flowing oxygen to produce a composite positive electrode active material.
The composite positive electrode active material is coated with LiMgO _{2 + δ} (−0.5 ≦ δ ≦ 0) coating on the surface of Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ secondary particles and between primary particles. It had a structure in which the membrane was arranged. The content of magnesium in the LiMgO _{2 + δ} (−0.5 ≦ δ ≦ 0) coating film was 0.75 parts by weight based on 100 parts by weight of the composite positive electrode active material.

Comparative Example 4 Production of Composite Positive Electrode Active Material
Instead of Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ obtained by Comparative Example 1, Li _1.09 Ni _0.878 Co _0.080 Mn ₀ obtained by Comparative Example 2 Comparative Example 3 and Comparative Example 3 except using _.040 Al _0.002 O ₂ and changing the content of cobalt to 0.5 parts by weight based on 100 parts by weight of the composite positive electrode active material It implemented by the same method and obtained the composite positive electrode active material.
In the following Examples 1 to 3, 3a to 3c, the lithium transition metal oxide (Ni 91) of Comparative Example 1 was used.

Example 1 Production of Composite Positive Electrode Active Material
After preparing 0.75 parts by weight of a 3: 1 molar ratio mixed precursor of Co (NO ₃ ) ₂ · 6H ₂ O and Al (NO ₃ ) ₃ · 9H ₂ O, it is put into 10 parts by weight of distilled water, The aqueous solution was prepared by stirring at (25 ° C.) for 1 minute.
100 parts by weight of Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ powder obtained according to Comparative Example 1 was added to 90 parts by weight of distilled water and prepared while stirring at normal temperature for 10 minutes. The aqueous solution was added to form a precipitate. The resulting precipitate was filtered and dried at 150 ° C. for 15 hours to prepare a composite positive electrode active material precursor. The composite positive electrode active material precursor is a cobalt aluminum hydroxide coating film containing cobalt and aluminum in a 3: 1 molar ratio on top of Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ Have a arranged structure.
The composite positive electrode active material precursor was put into a furnace, and heat treated at 720 ° C. for 5 hours in an oxygen atmosphere to obtain a composite positive electrode active material. The composite positive electrode active material is a surface of secondary particles of Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ and LiCo _1.5 Al _0.5 having a spinel crystal structure between primary particles. It had the structure where the O _{4 + δ} (−0.5 ≦ δ ≦ 0) coating film was disposed. In the composite positive electrode active material, the content of cobalt and aluminum in the LiCo _1.5 Al _0.5 O _{4 + δ} (−0.5 ≦ δ ≦ 0) coating film is lithium transition metal oxide (Li _1.05 Ni) It was 0.75 parts by weight based on 100 parts by weight of _0.91 Co _0.06 Mn _0.03 O ₂ ).

Example 2 Production of Composite Positive Electrode Active Material
_{Co (NO 3) 2 · 6H} 2 O and _{Al (NO 3) 3 · 9H} 2 O 3: 1 instead of mixing the precursor of the molar _{ratio, Co (NO 3) 2 ·} 6H 2 O and Zn _(NO 3) Using the mixed precursor of ₂ · 6H ₂ O 2: 1 molar ratio, the content of Co (NO ₃ ) ₂ · 6H ₂ O and Al (NO ₃ ) ₃ · 9H ₂ O was finally obtained composite In the positive electrode active material, in the coating film of LiCo _1.33 Zn _0.67 O _{4 + δ} (−0.835 ≦ δ ≦ 0), the content of cobalt zinc is 0. 0 based on 100 parts by weight of lithium transition metal oxide. The process is carried out by the same method as in Example 1 except that it is controlled to be 50 parts by weight, and the surface of the secondary particle of Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ And spinel crystal structure between primary particles That _{LiCo 1.33 Zn 0.67 O 4 + δ} (-0.5 ≦ δ ≦ 0) the coating film to produce a composite positive electrode active material formed.

[Examples 2a to 2c: Production of Composite Positive Electrode Active Material]
In the composite positive electrode active material, in the LiCo _1.33 Zn _0.67 O _{4 + δ} (−0.835 ≦ δ ≦ 0) coating film, the content of cobalt zinc is 0 based on 100 parts by weight of lithium transition metal oxide. A composite positive electrode active material was obtained in the same manner as in Example 2 except that the amounts were changed to 25 parts by weight, 0.75 parts by weight, and 1.5 parts by weight, respectively.

Example 3 Production of Composite Positive Electrode Active Material
As a _{precursor, Co (NO 3) 2 ·} 6H 2 O and _{Mg (NO 3) 2 · 6H} 2 O 3: except for using a mixed precursor of 2 molar ratio, the same method as in Example 1 LiCo _1.2 Mg _0.8 O _{4 + δ} with a spinel crystal structure on the surface of the secondary particles of Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ and between the primary particles. A composite positive electrode active material having a coating film formed thereon was produced. In the composite positive electrode active material, the content of cobalt magnesium in a LiCo _1.2 Mg _0.8 O _{4 + δ} (−0.9 ≦ δ ≦ 0) coating film is based on 100 parts by weight of lithium transition metal oxide, It was 0.75 parts by weight.

[Example 3a: Production of Composite Positive Electrode Active Material]
As a _{precursor, Co (NO 3) 2 ·} 6H 2 O and _{Mg (NO 3) 2 · 6H} 2 O 4: except for using a mixed precursor 1 molar ratio, Example 3 in the same way LiCo _1.6 Mg _0.4 O _{4 + δ} with a spinel crystal structure on the surface of the secondary particles of Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ and between the primary particles. A composite positive electrode active material having a coating film formed thereon was produced (-0.7 ≦ δ ≦ 0). In the composite positive electrode active material, the content of cobalt magnesium in a LiCo _1.6 Mg _0.4 O _{4 + δ} (−0.7 ≦ δ ≦ 0) coating film is based on 100 parts by weight of lithium transition metal oxide, It was 0.75 parts by weight.

Example 3b Production of Composite Positive Electrode Active Material
As a _{precursor, Co (NO 3) 2 ·} 6H 2 O and _{Mg (NO 3) 2 · 6H} 2 O 2: except for using a mixed precursors of 3 molar ratio, Example 3 in the same way LiCo _0.8 Mg _1.2 O _{4 + δ} with a spinel crystal structure on the surface of the secondary particles of Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ and between the primary particles. A composite positive electrode active material in which a coating film was formed was manufactured. In the LiCO _0.8 Mg _1.2 O ₄ coating film, the content of cobalt magnesium was 0.75 parts by weight based on 100 parts by weight of lithium transition metal oxide.

[Example 3c: Production of Composite Positive Electrode Active Material]
As a _{precursor, Co (NO 3) 2 ·} 6H 2 O and _{Mg (NO 3) 2 · 6H} 2 O 1: except for using a mixed precursor of 4 molar ratio, by the same method as in Example 3 LiCo _0.4 Mg _1.6 O _{4 + δ} (with spinel crystal structure) between the surface of the secondary particles of Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ and between the primary particles -1.3 <= (delta) <= 0) The composite positive electrode active material in which the coating film was formed was manufactured. The content of cobalt magnesium in the coating film of LiCO _0.4 Mg _1.6 O _{4 + δ} (-1.3 δ δ 0 0) is 0.75 parts by weight based on 100 parts by weight of lithium transition metal oxide. The

Example 4 Production of Composite Positive Electrode Active Material
Instead of Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ prepared according to Comparative Example 1, Li _1.09 Ni _0.88 Co _0.08 Mn ₀ prepared according to Comparative Example 2 _.04 O ₂ , and the contents of Co (NO ₃ ) ₂ .6H ₂ O and Zn (NO ₃ ) ₂ .6H ₂ O in the composite positive electrode active material are LiCo _1.33 Zn _0.67 O _{4 + δ} ( In the coating film, the content of cobalt zinc is controlled to be 0.25 parts by weight based on 100 parts by weight of lithium transition metal oxide, Conducted by the same method as Example 2, LiCo _1.33 having a spinel crystal structure on the surface of secondary particles of Li _1.09 Ni _0.88 Co _0.08 Mn _0.04 O ₂ and between primary particles. Z A composite positive electrode active material in which a coating film of n _0.67 O _{4 + δ} (−0.835 ≦ δ ≦ 0) was formed was manufactured.

[Example 4a: Production of Composite Positive Electrode Active Material]
Instead of Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ prepared according to Comparative Example 1, Li _1.09 Ni _0.88 Co _0.08 Mn ₀ prepared according to Comparative Example 2 The surface of the secondary particles of Li _1.09 Ni _0.88 Co _0.08 Mn _0.04 O _{2 and} the primary were carried out in the same manner as in Example 3, except that _.04 O ₂ was used. A composite positive electrode active material was manufactured, in which a LiCo _1.2 Mg _0.8 O _{4 + δ} (−0.9 ≦ δ ≦ 0) coating film having a spinel crystal structure was formed between particles. In the composite positive electrode active material, the content of cobalt magnesium in a LiCo _1.2 Mg _0.8 O _{4 + δ} (−0.9 ≦ δ ≦ 0) coating film is based on 100 parts by weight of lithium transition metal oxide, It was 0.75 parts by weight.

Example 5 Production of Composite Positive Electrode Active Material
In the composite positive electrode active material, in the coating film of LiCo _1.33 Zn _0.67 O _{4 + δ} (−0.835 ≦ δ ≦ 0), the content of cobalt zinc is 0. 0 based on 100 parts by weight of lithium transition metal oxide. A composite positive electrode active material was obtained in the same manner as in Example 4 except that the amount was changed to 50 parts by weight.

[Example 5a: Production of Composite Positive Electrode Active Material]
Instead of Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ prepared according to Comparative Example 1, Li _1.09 Ni _0.88 Co _0.08 Mn ₀ prepared according to Comparative Example 2 except for using the _.04 O _2, carried out by the same method as in example _{1, Li 1.09 Ni 0.88 Co 0.08} Mn 0.04 surface of O ₂ in the secondary particles, and the primary between the particles, to produce a composite positive electrode active material _LiCo 1.5 _Al 0.5 _{O 4 + δ} where (-0.5 ≦ δ ≦ 0) the coating film is formed having a spinel crystal structure. In the composite positive electrode active material, in the LiCo _1.5 Al _0.5 O _{4 + δ} (−0.5 ≦ δ ≦ 0) coating film, the content of cobalt aluminum is based on 100 parts by weight of lithium transition metal oxide, It was 0.75 parts by weight.

Example 6 Production of Lithium Battery (Coin Cell)
A mixture of the composite positive electrode active material produced in Example 1, carbon conductive agent (Denka Black) and polyvinylidene fluoride (PVDF) in a weight ratio of 92: 4: 4 is mixed with N-methylpyrrolidone (NMP) The slurry was prepared by mixing in an agate mortar. The slurry is bar coated on a 15 μm thick aluminum current collector, dried at room temperature, dried once again at 120 ° C. under vacuum, rolled and punched to obtain a 55 μm thick positive electrode. Manufactured.
Using the positive electrode manufactured as described above, using lithium metal as a counter electrode, using a PTFE separator, using 1.15 M LiPF ₆ as ethylene carbonate (EC) + ethyl methyl carbonate (EMC) + dimethyl carbonate The coin cell was manufactured using the solution dissolved in DMC) (2: 4: 4 volume ratio) as an electrolyte.

Examples 7 to 10: Production of Lithium Battery (Coin Cell)
A coin cell was manufactured in the same manner as in Example 6, except that the composite positive electrode active materials manufactured in Examples 2 to 5 were used instead of the composite positive electrode active material manufactured in Example 1. .

[Examples 11 to 13: Production of lithium battery (coin cell)]
A coin cell was manufactured in the same manner as in Example 6, except that the composite positive electrode active materials prepared in Examples 2a to 2c were used instead of the composite positive electrode active material prepared in Example 1. .

Examples 14 to 16: Production of Lithium Battery (Coin Cell)
A coin cell was manufactured in the same manner as in Example 6, except that the composite positive electrode active materials prepared in Examples 3a to 3c were used instead of the composite positive electrode active material prepared in Example 1. .

Example 17 Production of Lithium Battery (Coin Cell)
A coin cell was manufactured in the same manner as in Example 6, except that the composite positive electrode active material manufactured in Example 4a was used instead of the composite positive electrode active material manufactured in Example 1.

Comparative Examples 5 to 8: Production of Lithium Battery (Coin Cell)
A coin cell was manufactured in the same manner as in Example 6, except that the composite positive electrode active materials manufactured in Comparative Examples 1 to 4 were used instead of the composite positive electrode active material manufactured in Example 1. .

Comparative Example 8a Production of Lithium Battery (Coin Cell)
A coin cell was manufactured in the same manner as in Example 6, except that the composite positive electrode active material manufactured in Comparative Example 3a was used instead of the composite positive electrode active material manufactured in Example 1.

Comparative Example 9 Production of Composite Positive Electrode Active Material
A composite positive electrode active material was manufactured in the same manner as in Example 1 except that the composite positive electrode active material precursor was introduced into a furnace and heat treated at 400 ° C. for 5 hours in an oxygen atmosphere.

Comparative Example 10 Production of Composite Positive Electrode Active Material
A composite positive electrode active material was manufactured in the same manner as in Example 1 except that the composite positive electrode active material precursor was introduced into a furnace and heat treated at 1050 ° C. for 5 hours in an oxygen atmosphere.

Comparative Examples 11 and 12 Production of Lithium Battery (Coin Cell)
A coin cell was manufactured in the same manner as in Example 6, except that the composite positive electrode active materials manufactured according to Comparative Examples 9 and 10 were used instead of the composite positive electrode active material manufactured in Example 1. .

Example 18 Production of Lithium Battery (Coin Cell)
A coin cell was manufactured in the same manner as in Example 6, except that the composite positive electrode active material manufactured in Example 5a was used instead of the composite positive electrode active material manufactured in Example 1.

[Example 19: Production of lithium battery (18650 minicell)]
A mixture of the composite positive electrode active material prepared in Example 2, carbon conductive agent (Denka Black), and polyvinylidene fluoride (PVDF) in a weight ratio of 92: 4: 4 is mixed with N-methylpyrrolidone (NMP). The slurry was prepared by mixing in an agate mortar. The slurry is bar coated on a 15 μm thick aluminum current collector, dried at room temperature, dried once again at 120 ° C. under vacuum, rolled and punched to obtain a 55 μm thick positive electrode. Manufactured.
The positive electrode was cylindrically wound together with a graphite negative electrode. The positive electrode tab and the negative electrode tab were welded to the cylindrical structure, inserted into a cylindrical can and sealed. Thereafter, an electrolyte was poured into the cylindrical can, and an 18650 minicell was manufactured through cap clipping. At this time, the separator was used by coating an α-Al ₂ O ₃ powder having an average particle diameter of 50 nm on both sides of a polyethylene (manufactured by Asahi) base material.
As the electrolyte, a solution in which 1.15M LiPF ₆ was dissolved in ethylene carbonate (EC) + ethyl methyl carbonate (EMC) + dimethyl carbonate (DMC) (2: 4: 4 volume ratio) was used.

[Examples 20 and 21: Production of lithium battery (18650 minicell)]
A lithium battery was prepared in the same manner as in Example 19 except that the composite positive electrode active materials of Examples 4 and 4a were used instead of the composite positive electrode active material manufactured according to Example 2, and a lithium battery (18650 minicell). Manufactured.

Comparative Example 13 Production of Lithium Battery (18650 minicell)
The lithium transition metal oxide (Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ ) obtained by Comparative Example 1 and distilled water are mixed at a weight ratio of 1: 2, which is about 250 rpm The solution was stirred and water washing was carried out. Thereafter, the resultant was dried at about 150 ° C. for 15 hours to obtain a washed lithium transition metal oxide (Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ ).
Instead of the composite positive electrode active material obtained by Example 2, the washed lithium transition metal oxide (Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ ) obtained by the above process is used. A lithium battery (18650 minicell) was manufactured in the same manner as in Example 19 except that it was used.

Comparative Example 13a: Manufacture of Lithium Battery (Coin Half Cell)
The lithium transition metal oxide (Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ ) obtained according to Comparative Example 1 and distilled water are mixed in a 1: 2 weight ratio, which is about 250 rpm Stir and wash with water. Thereafter, the resultant was dried at about 150 ° C. for 15 hours to obtain a washed lithium transition metal oxide (Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ ).
Instead of the composite positive electrode active material obtained in Example 1, the washed lithium transition metal oxide (Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ ) obtained by the above process was used. A lithium battery (coin half cell) was manufactured by the same method as in Example 6 except for the above.

Comparative Example 14 Production of Lithium Battery (18650 minicell)
The lithium transition metal oxide (Li _1.09 Ni _0.88 Co _0.08 Mn _0.04 O ₂ ) obtained by Comparative Example 2 was used instead of the composite positive electrode active material obtained by Example 2. A lithium battery (18650 minicell) was manufactured according to the same method as Example 19 except for the above.

Comparative Example 15 Production of Lithium Battery (Coin Half Cell)
The lithium transition metal oxide (Li _1.09 Ni _0.88 Co _0.08 Mn _0.04 O ₂ ) obtained by Comparative Example 2 and distilled water are mixed in a 1: 2 mixing ratio, which is about 250 rpm The solution was stirred and water washing was carried out. Thereafter, the resultant was dried at about 150 ° C. for 15 hours to obtain a washed lithium transition metal oxide (Li _1.09 Ni _0.88 Co _0.08 Mn _0.04 O ₂ ).
Instead of the composite positive electrode active material obtained by Example 2, the washed lithium transition metal oxide (Li _1.09 Ni _0.88 Co _0.08 Mn _0.04 O ₂ ) obtained by the above process is used. A lithium battery (coin half cell) was manufactured by the same method as in Example 6 except that it was used.

[Evaluation example 1: SEM (scanning electron microscope) image analysis]
1) Example 4a and Comparative Examples 2 and 4
The surfaces of the composite positive electrode active material powders produced according to Example 4a and Comparative Examples 2 and 4 were analyzed with a scanning electron microscope, and the results are shown in FIGS. 2A to 2C, respectively.
Referring to FIGS. 2A to 2C, the size of primary particles of the composite positive electrode active material of Example 4a is increased as compared to the composite positive electrode active materials of Comparative Examples 2 and 4. And, in the composite positive electrode active material of Example 4a, the thickness of the layered double oxide (LDO) coating film was about 100 nm.

2) Example 1
Scanning electron microscopy analysis was performed on the composite positive electrode active material manufactured according to Example 1, and the result is shown in FIG. 1B.
Referring to that, it was found that a coating film was present on the surface of the lithium transition metal oxide secondary particles and between the primary particles, and the average particle diameter of the composite positive electrode active material was about 10 μm.

Evaluation Example 2: X-ray Diffraction Analysis
An XRD (X-ray diffraction) analysis was performed on the composite positive electrode active material of Example 3. The XRD analysis results are as shown in FIG.
In reference to it, from the XRD spectrum of the composite positive electrode active material of Example 1, the layered crystal structure of lithium transition metal oxide and the spinel crystal structure of lithium cobalt composite oxide were observed. Therefore, it was confirmed that the composite positive electrode active material of Example 1 includes a lithium transition metal oxide having a layered crystal structure and a coating film including a lithium cobalt composite oxide having a spinel crystal structure.

[Evaluation Example 3: HAADF (high-angle annular dark-field) STEM and EDS (energy-dispersive X-ray spectroscopy)]
The composition was analyzed by performing high-angle annular dark-field (HAADF) STEM and EDS analysis on the composite positive electrode active material manufactured according to Example 3.
Referring to that, it was confirmed that Ni, Mn and Co were uniformly distributed throughout the composite positive electrode active material. Then, it was confirmed that Co and Mg were disposed between the primary particles, and Co and Mg were disposed on the surfaces of the primary particles and the secondary particles. Therefore, it was confirmed that LiCo _1.2 Mg _0.8 O ₄ was uniformly coated on both the particle size and the surface between the primary particles and the surface of the secondary particles.

Evaluation Example 4: Evaluation of residual lithium content
1) Examples 1 to 3, 2a, 3a to 3c and Comparative Example 1
The surface residual lithium content of the composite positive electrode active materials manufactured according to Examples 1 to 3, 2a, 3a to 3c, and Comparative Example 1 was measured. The results are shown in Table 1 below.
The surface residual lithium content was evaluated by measuring the Li content in Li ₂ CO ₃ and LiOH remaining on the surface of the composite positive electrode active material by a wet method (or a titration method).

  Referring to Table 1, the composite positive electrode active materials of Examples 1 to 3, 2a and 3a to 3c show that the residual lithium content on the surface was reduced as compared with Comparative Example 1. Therefore, at the time of charge and discharge of the lithium battery containing the composite positive electrode active material of Examples 1 to 3, 2a and 3a to 3c, the generation of gas can be suppressed and the deterioration of the life characteristics can be suppressed.

2) Examples 4, 5, 5a and Comparative Examples 2 and 4
The surface residual lithium content of the composite positive electrode active materials manufactured according to Examples 4, 5, 5a and Comparative Examples 2 and 4 was measured, and a part of the results is shown in Table 2 below.
The surface residual lithium content was evaluated by measuring the Li content in Li ₂ CO ₃ and LiOH remaining on the surface of the composite positive electrode active material by a wet method (or a titration method).

  Referring to Table 2, the composite positive electrode active materials of Examples 4, 5 and 5a show that the residual lithium content on the surface was reduced as compared with Comparative Examples 2 and 4.

Evaluation Example 5: Thermal Stability Test
Differential scanning calorimetry analysis was performed on the composite positive electrode active materials obtained by Examples 2 and 3 and Comparative Example 3. The analysis results are as shown in Table 3 below.

  Referring to Table 3, in the composite positive electrode active materials of Examples 2 and 3, the calorific value was reduced compared to the case of Comparative Example 3. Thereby, it turned out that the thermal stability of the composite positive electrode active material of Example 2 and 3 improves.

Evaluation Example 6: Charge and Discharge Characteristics
For the lithium batteries manufactured in Example 6, Example 8, and Comparative Examples 5 and 7, constant current up to a voltage of 4.35 V (vs Li) at a current of 0.1 C rate at 25 ° C. The battery was charged and then discharged at a constant current of 0.1 C rate until the voltage reached 2.8 V (vs. Li) (first cycle, formation cycle).
For the first cycle lithium battery, constant current charge up to 4.35V (vs. Li) at 25 ° C at a current of 0.33C rate, and then maintain 4.35V in constant voltage mode. While cut off at a current of 0.05 C rate. Next, at the time of discharge, the voltage was discharged at a constant current of 0.2 C rate until the voltage reached 2.8 V (vs. Li) (second cycle).
For a lithium battery that has undergone a second cycle, constant current charge at a current of 1 C rate at 25 ° C and a voltage of 4.35 V (vs Li), and then a voltage of 2.8 V (vs Li) Discharged at a constant current of 1 C rate up to the third cycle.
The cycle was repeated under the same conditions up to the 53rd cycle for lithium batteries that had undergone the 3rd cycle.
In all the charge and discharge cycles, a rest time of 20 minutes was allowed after one charge / discharge cycle.
Some of the results of the charge and discharge test are shown in Table 4 below. The capacity retention rate at the 53rd cycle and the initial charge / discharge efficiency at the first cycle are defined by the following formulas 1 and 2.
[Equation 1]
Capacity retention rate [%] = [Discharge capacity at 53rd cycle / Discharge capacity at third cycle] × 100%
[Equation 2]
Initial efficiency [%] = [Discharge capacity at first cycle / Charge capacity at first cycle] x 100%

As shown in Table 4, the lithium batteries of Examples 6 to 8 significantly improved the capacity retention rate as compared with the lithium battery of Comparative Example 5. The lithium battery of Comparative Example 5 showed excellent initial efficiency, but the capacity retention rate showed a very low result as compared with Examples 6-8.
In addition, the lithium batteries of Examples 6 to 8 showed equivalent results as compared with the lithium battery of Comparative Example 7, but showed that the capacity retention rate was improved.
Moreover, the charge / discharge characteristics (initial efficiency and capacity maintenance ratio) of the lithium battery manufactured by Comparative Examples 11 and 12 were measured by the same evaluation method as the lithium battery of Example 6 described above.
As a result, it was found that in the lithium battery of Example 6, the initial efficiency and the capacity retention ratio were improved as compared with the lithium batteries of Comparative Examples 11 and 12.

Evaluation Example 7: Charge and Discharge Characteristics
The lithium batteries manufactured in Examples 11 to 13 and Comparative Example 13 are constant current charged at a temperature of 25 ° C. and a current of 0.1 C rate up to 4.35 V (vs. Li), and then the voltage Were discharged at a constant current of 0.1 C rate (first cycle, formation cycle) until the voltage reached 2.8 V (vs. Li).
For the first cycle lithium battery, constant current charge at 25 ° C at a current of 0.33C rate to 4.35V (vs. Li) at a current of 0.33C rate, then maintain 4.35V in constant voltage mode , Cut off at a current of 0.05 C rate. Next, at the time of discharge, discharge was performed at a constant current of 0.2 C rate until the voltage reached 2.8 V (vs. Li) (second cycle).
For a lithium battery that has undergone a second cycle, constant current charge at a current of 1 C rate at 25 ° C and a voltage of 4.35 V (vs Li), and then a voltage of 2.8 V (vs Li) Discharged at a constant current of 1 C rate up to the third cycle.
The cycle was repeated under the same conditions up to the 53rd cycle for lithium batteries that had undergone the 3rd cycle.
In all the charge and discharge cycles, a rest time of 20 minutes was allowed after one charge / discharge cycle.
The results of the charge and discharge test are shown in Table 5 below.

  As shown in Table 5, the lithium batteries of Examples 11 to 13 have improved initial efficiency and capacity retention as compared with the lithium battery of Comparative Example 13a.

Evaluation Example 8 Charge / Discharge Characteristics
For the lithium batteries manufactured in Examples 8, 14 to 16 and Comparative Examples 5, 7 and 8a, constant current charging up to a voltage of 4.35 V (vs Li) at a current of 0.1 C rate at 25 ° C. Then, it was discharged at a constant current of 0.1 C rate (first cycle, formation cycle) until the voltage reached 2.8 V (vs. Li).
For the first cycle lithium battery, constant current charge up to 4.35V (vs. Li) at 25 ° C at a current of 0.33C rate, and then maintain 4.35V in constant voltage mode. While it was cut off at a current of 0.05 C rate. Next, at the time of discharge, discharge was performed at a constant current of 0.2 C rate until the voltage reached 2.8 V (vs. Li) (second cycle).
Charge the lithium battery that has undergone the second cycle at 25 ° C. at a current of 1 C rate to a voltage of 4.35 V (vs. Li), and then apply a voltage of 2.8 C (vs. Li) to 1 C It discharged by the constant current of rate (3rd cycle).
The lithium battery that had undergone the third cycle was repeated under the same conditions up to the 53rd cycle.
After one charge / discharge cycle for all the charge / discharge cycles, a 20 minute down time was placed.
The results of the charge and discharge test are shown in Table 6 below.
Separately, the high rate characteristics were evaluated by the following method.
The lithium batteries produced in Examples 8, 14 to 16 and Comparative Examples 5, 7 and 8a are constant current charged at 25 ° C. at a current of 0.1 C rate until the voltage reaches 4.35 V (vs. Li), Then, it was discharged at a constant current of 0.1 C rate until the voltage reached 2.8 V (vs. Li) (first cycle, formation cycle).
The first cycle lithium battery is constant current charged at 25 ° C. at a current of 0.33 C rate until the voltage reaches 4.35 V (vs. Li), and then 0 while maintaining 4.35 V in constant voltage mode The cut-off was performed at a current of .05 C rate. Next, it was discharged at a constant current of 0.2 C rate until the voltage reached 2.8 V (vs. Li) during discharge (second cycle).
Charge the lithium battery that has undergone the second cycle constant current charging at 25 ° C. at a current of 0.5 C rate to 4.35 V (vs. Li), then hold 4.35 V in constant voltage mode, It was cut off at a current of 0.05 C rate. Next, it was discharged at a constant current of 0.33 C rate until the voltage reached 2.8 V (vs. Li) during discharge (third cycle).
For a lithium battery that has undergone a third cycle, constant current charge at a current of 0.5C at 25 ° C and a voltage of 4.35V (vs. Li), and then maintain 4.35V in a constant voltage mode While cutting off at a current of 0.05 C rate. Next, at the time of discharge, discharge was performed at a constant current of 1 C rate until the voltage reached 2.8 V (vs. Li) (fourth cycle).
For a lithium battery that has undergone the fourth cycle, constant current charge at a current of 0.5C at 25 ° C to a voltage of 4.35V (vs. Li), and then maintain 4.35V in a constant voltage mode While cutting off at a current of 0.05 C rate. Next, at the time of discharge, discharge was performed at a constant current of 2 C rate until the voltage reached 2.8 V (vs. Li) (fifth cycle).
For a lithium battery that has undergone the fifth cycle, constant current charge at a current of 0.5C at 25 ° C and a voltage of 4.35V (vs. Li), and then maintain 4.35V in a constant voltage mode While cutting off at a current of 0.05 C rate. Next, at the time of discharge, discharge was performed at a constant current of 3 C rate until the voltage reached 2.8 V (vs. Li) (sixth cycle).
For a lithium battery that has undergone a sixth cycle, constant current charge at a current of 1 C rate at 25 ° C. to a voltage of 4.35 V (vs Li) and then a voltage of 2.8 V (vs Li) Discharge was performed at a constant current of 1 C rate (7th cycle), and such cycle was repeated under the same conditions up to 56th cycle.
In all the charge and discharge cycles, a rest time of 20 minutes was allowed after one charge / discharge cycle.
The results of the charge and discharge test are shown in Table 6 below. The high rate characteristics are defined by Equation 3 below, and the high rate characteristics are shown in Table 6 below.
[Equation 3]
High rate characteristics [%] = [Discharge capacity at 3rd cycle (3C rate) / 3 discharge capacity at 3rd cycle (0.33C rate)] × 100

  The lithium batteries of Examples 8 and 14 to 16 shown in Table 6 have improved capacity retention and high rate characteristics as compared with the lithium battery of Comparative Example 5. In addition, the lithium batteries of Examples 8 and 16 have the same high-rate characteristics as the lithium battery of Comparative Example 7, and have improved the capacity retention rate. And, the lithium batteries of Examples 8, 14 to 16 show the result that the initial efficiency is improved as compared with the case of Comparative Example 8a.

Evaluation Example 9: Charge and Discharge Characteristics
With respect to the lithium batteries manufactured in Examples 9, 10, 17, 18 and Comparative Examples 8 and 15, constant current charging up to a voltage of 4.35 V (vs Li) at a current of 0.1 C rate at 25 ° C. Then, it was discharged at a constant current of 0.1 C rate (first cycle, formation cycle) until the voltage reached 2.8 V (vs. Li).
For the first cycle lithium battery, constant current charge up to 4.35V (vs. Li) at 25 ° C at a current of 0.33C rate, and then maintain 4.35V in constant voltage mode. While it was cut off at a current of 0.05 C rate. Next, at the time of discharge, discharge was performed at a constant current of 0.2 C rate until the voltage reached 2.8 V (vs. Li) (second cycle).
For a lithium battery that has undergone the second cycle, constant current charge is performed at a current of 1 C rate at 25 ° C and a voltage of 4.35 V (vs Li), and then, when discharging, the voltage is 2.8 V (vs Li It was discharged at a constant current of 1 C rate (the third cycle) until reaching.
The cycle was repeated under the same conditions up to the 53rd cycle for lithium batteries that had undergone the 3rd cycle.
In all the charge and discharge cycles, a rest time of 20 minutes was allowed after one charge / discharge cycle.
The results of the charge and discharge test are shown in Table 7 below.

As can be seen from Table 7, in the lithium batteries of Examples 9, 10 and 17, the capacity retention rate was remarkably improved as compared with the lithium batteries of Comparative Examples 8 and 15. In addition, the lithium battery of Example 9 has the same initial efficiency as the lithium battery of Comparative Example 8, and the capacity retention rate is improved.
Further, as shown in Table 7, the lithium battery of Example 18 shows a result that the capacity retention rate is improved as compared with the lithium battery of Comparative Example 8, and compared with the lithium battery of Comparative Example 15, the initial efficiency and Both capacity maintenance rates have improved.

Evaluation Example 10: High Temperature (45 ° C.) Charge and Discharge Characteristics
1) Example 19 and Comparative Example 13
For each lithium battery (18650 minicell), constant current charge to a voltage of 4.35V (vs Li) at a current of 0.1C rate at 45 ° C, and then a voltage of 2.8V (vs Li) Discharge was performed at a constant current of 0.1 C rate (first cycle, formation cycle).
For a lithium battery that has undergone the first cycle, charge at a current of 0.33C at 45 ° C and constant current charge to 4.35V (vs. Li), and then maintain 4.35V in constant voltage mode. While it was cut off at a current of 0.05 C rate. Next, at the time of discharge, discharge was performed at a constant current of 0.2 C rate until the voltage reached 2.8 V (vs. Li) (second cycle).
For a lithium battery that has undergone the second cycle, constant current charge at a temperature of 1 ° C at 45 ° C to a voltage of 4.35V (vs Li), and then, when discharging, the voltage is 2.8V (vs Li It was discharged at a constant current of 1 C rate (the third cycle) until reaching.
The cycle was repeated under the same conditions up to the 302nd cycle at 45 ° C. for a lithium battery that had undergone the third cycle.
For all the charge and discharge cycles, a rest time of 20 minutes was placed after one charge / discharge cycle.
The capacity retention rate according to the number of cycles was evaluated and is shown in FIG.
Referring to FIG. 5, it was found that the capacity retention ratio of the lithium battery of Example 19 is improved as compared to that of Comparative Example 13.
The charge and discharge characteristics of the lithium batteries of Examples 20 and 21 and Comparative Examples 14 and 15 were evaluated in the same manner as the method of evaluating the charge and discharge characteristics of the lithium batteries of Example 19 and Comparative Example 12. The analysis results are shown in FIG.
Referring to it, it was found that the lithium batteries of Examples 20 and 21 have improved capacity retention ratio characteristics at 45 ° C. as compared with the lithium batteries of Comparative Examples 14 and 15.

  The composite positive electrode active material, the method for producing the same, the positive electrode including the same, and the lithium battery of the present invention are effectively applicable to, for example, the technical fields related to power supply.

REFERENCE SIGNS LIST 1 lithium battery 2 negative electrode 3 positive electrode 4 separator 5 battery case 6 cap assembly 11 primary particles 12 secondary particles 13 between primary particles

Claims (25)

A plurality of primary particles comprising at least one secondary particle comprising an aggregate of a plurality of primary particles, the secondary particles comprising a plurality of primary particles comprising a lithium transition metal oxide having a layered crystal structure, and a surface of the secondary particles And a coating film disposed between a plurality of primary particles, and a composite positive electrode active material,
The coating film includes lithium cobalt composite oxide having a spinel crystal structure,
The composite positive electrode active material, wherein the lithium cobalt composite oxide contains cobalt (Co) and a group 2, 12, or 13 element or a combination thereof.   The composite positive electrode active material according to claim 1, wherein the coating film is present on the surfaces of the grain boundaries of the adjacent primary particles of the plurality of primary particles and the surface of the secondary particles. The composite positive electrode active material according to claim 1, wherein the lithium cobalt composite oxide having a spinel crystal structure is a compound represented by the following chemical formula 1:
[Chemical formula 1]
Li _x Co _a Me _b O _{4 + δ}
In Chemical Formula 1, Me is one or more selected from the group 2 elements, the group 12 elements, and the group 13 elements,
1.0 ≦ x ≦ 1.1, 0 <a <2, 0 <b <2, 0 <a + b ≦ 2, −1.5 ≦ δ ≦ 0.   The composite positive electrode active material according to claim 3, wherein Me in the chemical formula 1 is one or more selected from Al, Ga, Mg, Ca, Ba and Zn. Lithium cobalt composite oxides having a spinel crystal _{structure, Li x Co a Al b O} 4 + δ, Li x Co a Zn b O 4 + δ, Li x Co a Mg b O 4 + δ, Li x Co a Ga b O 4 + δ, Li _x Co _a Ca _b O _{4 + δ} or Li _x Co _a Ba _b O _{4 + δ} , 1.0 ≦ x ≦ 1.1, 0 <a <2, 0 <b <2, 0 <a + b ≦ 2, −1. The composite positive electrode active material according to claim 1, wherein 5 ≦ δ ≦ 0. The lithium-cobalt composite oxide having the above spinel crystal structure can be prepared as follows: LiCo _1.5 Al _0.5 O _{4 + δ} (−0.5 ≦ δ ≦ 0), LiCo _1.5 Ga _0.5 O _{4 + δ} (−0.5 ≦ δ ≦ 0), LiCo _1.33 Zn _0.67 O _{4 + δ} (−0.835 ≦ δ ≦ 0), LiCo _1.33 Ca _0.67 O _{4 + δ} (−0.835 ≦ δ ≦ 0), LiCo _{1. 33} Ba _0.67 O _{4 + δ} (−0.835 ≦ δ ≦ 0), LiCo _1.33 Ga _0.67 O _{4 + δ} (−0.835 ≦ δ ≦ 0), LiCo _1.2 Mg _0.8 O 4+ _δ ( −0.9 ≦ δ ≦ 0), LiCo _1.2 Ga _0.8 O _{4 + δ} (−0.9 ≦ δ ≦ 0), LiCo _1.2 Ca _0.8 O _{4 + δ} (−0.9 ≦ δ ≦ 0) _{), LiCo 1.2 Ba 0.8 O 4} + δ (-0.9 ≦ δ ≦ 0), LiCo _{.2 Zn 0.8 O 4 + δ (} -0.9 ≦ δ ≦ 0), LiCo 1.6 Mg 0.4 O 4 + δ (-0.7 ≦ δ ≦ 0), LiCo 1.6 Ga 0.4 O 4 + δ (−0.7 ≦ δ ≦ 0), LiCo _1.6 Ca _0.4 O _{4 + δ} (−0.7 ≦ δ ≦ 0), LiCo _1.6 Ba _0.4 O _{4 + δ} (−0.7 ≦ δ ≦ 0), LiCo _1.6 Zn _0.4 O _{4 + δ} (−0.7 ≦ δ ≦ 0), LiCo _0.8 Mg _1.2 O _{4 + δ} (−1.1 ≦ δ ≦ 0), LiCo _0.8 Ga _1.2 O _{4 + δ} (-1.1 δ δ 0 0), LiCo _0.8 Ca _1.2 O _{4 + δ} (-1.1 δ δ 0 0), LiCo _0.8 Ba _1.2 O _{4 + δ} (-1 _{.1 ≦ δ ≦ 0), LiCo} 0.8 Zn 1.2 O 4 + δ (-1.1 ≦ δ ≦ 0), LiCo 0.4 Mg 1.6 O 4 + δ (-1.3 ≦ δ ≦ 0 _{, LiCo 0.4 Ga 1.6 O 4 +} δ (-1.3 ≦ δ ≦ 0), LiCo 0.4 Ca 1.6 O 4 + δ (-1.3 ≦ δ ≦ 0), LiCo 0.4 Ba 1. _{It is 6} O _{4 + δ} (-1.3 ≦ δ ≦ 0) or LiCo _0.4 Zn _1.6 O _{4 + δ} (−1.3 ≦ δ ≦ 0), The composite positive electrode active according to claim 1. material.   The lithium transition metal oxide having a layered crystal structure belongs to a rock salt layered structure (R-3m space group), and the lithium cobalt composite oxide belongs to an Fd-3m space group. Composite positive electrode active material as described.   A mixed phase exists between the lithium transition metal oxide and the coating film, and the mixed phase includes a combination of a lithium transition metal oxide and a lithium cobalt composite oxide. The composite positive electrode active material described in 4.   The composite positive electrode active material according to claim 1, further comprising a compound having an amorphous structure, a compound having a layered crystal structure, or a combination thereof among the primary particles. The composite positive electrode active material according to claim 1, wherein the lithium transition metal oxide having a layered crystal structure is one selected from compounds represented by the following chemical formulas 2 to 4.
[Chemical formula 2]
Li _x Co _1-y M _y O _2-α X _α
[Chemical formula 3]
Li _x Ni _1-y Me _y O _2-α X _α
[Chemical formula 4]
_{Li x Ni 1-y-z} Mn y Ma z O 2-α X α
In the chemical formulas 2 to 4, 0.9 ≦ x ≦ 1.1, 0 ≦ y ≦ 0.9, 0 <z ≦ 0.2, 0 ≦ α ≦ 2,
M is one or more metals selected from the group consisting of Ni, Mn, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Fe, Cu and B,
Me is one or more metals selected from the group consisting of Co, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Mn, Fe, Cu and B,
Ma is one metal selected from the group consisting of Co, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Fe, Cu and B,
X is an element selected from the group consisting of F, S and P. The composite positive electrode active material according to claim 1, wherein the lithium transition metal oxide having a layered crystal structure is one selected from compounds represented by the following Chemical Formulas 5 to 7.
[Chemical formula 5]
_{Li [Li 1-a Me a} ] O 2 + d
In Chemical Formula 5, 0.8 ≦ a <1, 0 ≦ d ≦ 0.1,
Me is at least one metal selected from the group consisting of Ni, Co, Mn, Al, V, Cr, Fe, Zr, Re, B, Ge, Ru, Sn, Ti, Nb, Mo and Pt Yes,
[Chemical formula 6]
_{Li [Li 1-x-y} -z Ma x Mb y Mc z] O 2 + d
In Chemical Formula 6, 0.8 ≦ x + y + z <1, 0 <x <1, 0 <y <1, 0 <z <1, 0 ≦ d ≦ 0.1,
The Ma, Mb and Mc independently of one another are at least one metal selected from the group consisting of Mn, Co, Ni and Al,
[Chemical formula 7]
_{Li [Li 1-x-y} -z Ni x Co y Mn z] O 2 + d
In Chemical Formula 7, 0.8 ≦ x + y + z <1, 0 <x <1, 0 <y <1, 0 <z <1, 0 ≦ d ≦ 0.1. The composite positive electrode active material according to claim 1, wherein the lithium transition metal oxide is represented by the following chemical formula 8.
[Chemical formula 8]
aLi ₂ MnO _3- (1-a) LiMO ₂
In the chemical formula 8, 0 <a <1,
M is nickel (Ni), cobalt (Co), manganese (Mn), vanadium (V), chromium (Cr), iron (Fe), zirconium (Zr), rhenium (Re), aluminum (Al), boron ( B) Two or more elements selected from germanium (Ge), ruthenium (Ru), tin (Sn), titanium (Ti), niobium (Nb), molybdenum (Mo) and platinum (Pt). The composite positive electrode active material according to claim 1, wherein the lithium transition metal oxide having a layered crystal structure is a compound represented by the following chemical formula 9.
[Chemical formula 9]
Li _x Ni _1-y-z M _y Co _z O ₂
In the chemical formula 9, 0.90 ≦ x ≦ 1.1, 0 ≦ y ≦ 0.2, 0 <z ≦ 0.2, 0.7 ≦ 1-y-z ≦ 0.99,
M is selected from the group consisting of manganese (Mn), aluminum (Al), titanium (Ti) and calcium (Ca).   The composite positive electrode active material according to claim 1, wherein an average particle diameter of at least one secondary particle containing a lithium transition metal oxide having a layered crystal structure is 10 to 20 m. The composite positive electrode active material according to claim 1, wherein the lithium transition metal oxide having a layered crystal structure is a compound represented by the following chemical formula 9a:
[Chemical formula 9a]
_{Li x Ni 1-y-z} Mn x Co y O 2
In the chemical formula 9a, 0.80 ≦ x ≦ 1.1, 0 = y ≦ 0.2, 0 <z ≦ 0.2, 0.8 ≦ 1-y-z ≦ 0.99. The lithium transition metal oxide having the layered crystal structure may be formed of Li _1.03 [Ni _0.91 Co _0.06 Mn _0.03 ] O ₂ , Li _1.03 [Ni _0.88 Co _0.08 Mn _{0. 04} ] O ₂ , Li _1.03 [Ni _0.8 Co _0.15 Mn _0.05 ] O ₂ , Li _1.03 [Ni _0.85 Co _0.10 Mn _0.05 ] O ₂ , Li _{1. 03} [Ni _0.91 Co _0.05 Mn _0.04 ] O ₂ , Li _1.05 [Ni _0.91 Co _0.06 Mn _0.03 ] O ₂ , Li _1.06 [Ni _0.91 Co _{0 .06} Mn _0.03 ] O ₂ , Li _1.06 [Ni _0.88 Co _0.08 Mn _0.04 ] O ₂ , Li _1.06 [Ni _0.8 Co _0.15 Mn _0.05 ] O _{2, Li 1.06 [Ni 0.85 Co} 0. _{0 Mn 0.05] O 2, Li} 1.06 [Ni 0.91 Co 0.05 Mn 0.04] O 2, Li 1.09 [Ni 0.91 Co 0.06 Mn 0.03] O 2 , Li _1.09 [Ni _0.88 Co _0.08 Mn _0.04 ] O ₂ , Li _1.09 [Ni _0.8 Co _0.15 Mn _0.05 ] O ₂ , Li _1.09 [Ni _0] The composite positive electrode active material according to claim 1, characterized in that _.85 Co _0.10 Mn _0.05 ] O ₂ or Li _1.09 [Ni _0.91 Co _0.05 Mn _0.04 ] O _2. material.   In the coating film, the content of the lithium-cobalt composite oxide, or the total content of cobalt and metal (M) is 0.01 to 20 weight based on 100 parts by weight of lithium transition metal oxide having a layered crystal structure. The composite positive electrode active material according to claim 1, which is a part.   The composite positive electrode according to claim 1, wherein the content of residual lithium in the composite positive electrode active material is 90% or less of the residual lithium content of secondary particles containing a lithium transition metal oxide having a layered crystal structure. Active material.   The composite positive electrode active material according to claim 1, wherein the coating film covers 50% or more of the surface of the lithium transition metal oxide having a layered crystal structure.   The thickness of the said coating film is 1 micrometer or less, The composite positive electrode active material of Claim 1 characterized by the above-mentioned.   A positive electrode comprising the composite positive electrode active material according to any one of claims 1 to 20.   A lithium battery comprising the positive electrode according to claim 21, a negative electrode, and an electrolyte disposed between the positive electrode and the negative electrode. Producing a lithium transition metal oxide having a layered crystal structure;
A lithium cobalt composite comprising a lithium transition metal oxide having a layered crystal structure, and a spinel crystal structure having cobalt (Co) and one or more elements selected from Group 2, Group 12 and Group 13 elements. Mixing an oxide precursor to obtain a composite positive electrode active material composition;
And drying the composite positive electrode active material composition and heat-treating the composite positive electrode active material composition in an oxidizing gas atmosphere at a temperature of more than 400 ° C. and 1,000 ° C. or less. Method of producing a composite positive electrode active material for producing   The lithium transition metal oxide having a layered crystal structure, a lithium cobalt composite having a spinel crystal structure, cobalt (Co), and one or more elements selected from Group 2, Group 12, Group 13 elements The method for producing a composite positive electrode active material according to claim 23, wherein the mixing of the oxide with the precursor is performed wet in the presence of a solvent.   24. The method of claim 23, wherein the heat treatment is performed at 700 to 750 ° C., and the temperature rising rate is 1 to 10 ° C./min during the heat treatment.