KR102629461B1 - Composite cathode active material, preparation method thereof, cathode and Lithium battery containing composite cathode active material - Google Patents

Abstract

It includes secondary particles, wherein the secondary particles include a plurality of primary particles containing lithium transition metal oxide having a layered crystal structure; and a coating film disposed between the surface of the secondary particles and the primary particles of the plurality of primary particles, wherein the coating film includes lithium cobalt composite oxide having a spinel crystal structure, and the lithium Cobalt composite oxide provides a composite cathode active material containing cobalt (Co) and a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof, and a positive electrode and lithium battery containing the same.

Description

Composite cathode active material, preparation method thereof, cathode and lithium battery containing composite cathode active material}

It relates to composite cathode active materials, their manufacturing methods, and cathodes and lithium batteries employing them.

In order to meet the miniaturization and high performance of various devices, high energy density in addition to miniaturization and weight reduction of lithium batteries is becoming important. In order to implement lithium batteries that meet this importance, nickel-based positive electrode active materials with high capacity are being examined.

Conventional nickel-based positive electrode active materials have reduced lifespan characteristics due to high surface residual lithium content and side reactions caused by cation mixing, and thermal stability does not reach a satisfactory level.

One aspect is to provide a new composite cathode active material with reduced surface residual lithium content and improved thermal stability.

Another aspect is to provide a positive electrode containing the composite positive electrode active material.

Another aspect is to provide a lithium battery with improved lifespan and cell capacity including the positive electrode.

Another aspect is to provide a method for manufacturing the composite positive electrode active material.

according to one side

Contains secondary particles,

The secondary particles include a plurality of primary particles containing lithium transition metal oxide having a layered crystal structure; And a composite positive electrode active material containing a coating film disposed between the surface of the secondary particles and the primary particles of the plurality of primary particles,

The coating film includes lithium cobalt complex oxide having a spinel crystal structure,

The lithium cobalt composite oxide is provided as a composite positive electrode active material containing cobalt (Co) and a Group 2, Group 12, or Group 13 element, or a combination thereof.

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

According to another aspect, a lithium battery including the above-described positive electrode is provided.

According to another aspect
Preparing a lithium transition metal oxide having a layered crystal structure;

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A lithium transition metal oxide having the layered crystal structure, a lithium cobalt complex having a spinel crystal structure and containing cobalt (Co), a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof. Obtaining a composite positive electrode active material composition by mixing oxide precursors; and

A method for producing the composite cathode active material described above is provided, including the steps of drying the composite cathode active material composition and heat-treating the composite cathode active material composition in an oxidizing gas atmosphere at a temperature exceeding 400° C. and below 1000° C.

According to one aspect, the surface residual lithium content of the composite cathode active material is reduced and thermal stability is improved. Using this improves the charge/discharge characteristics and lifespan characteristics of lithium batteries.

Figure 1a schematically shows the structure of a composite positive electrode active material according to an embodiment.
Figure 1b shows the results of scanning electron microscopy analysis of the composite positive electrode active material prepared according to Example 1.
Figures 2a to 2c are scanning electron micrographs of composite positive electrode active material powders prepared according to Example 4a, Comparative Example 2, and Comparative Example 4, respectively.
Figure 3 is an XRD (X-ray Diffraction) spectrum for the composite positive electrode active material prepared according to Example 1.
Figure 4 shows the structure of a lithium battery employing a positive electrode containing a composite positive electrode active material according to an embodiment.
Figure 5 shows the high temperature lifespan characteristics of a lithium battery (18650 minicell) manufactured according to Example 19 and Comparative Example 13.
Figure 6 shows the high temperature lifespan characteristics of lithium batteries (18650 minicell) manufactured according to Examples 20-21 and Comparative Examples 14-15.

Hereinafter, the composite cathode active material according to example embodiments, its manufacturing method, and the cathode and lithium battery including the same will be described in more detail.

It includes secondary particles, wherein the secondary particles include a plurality of primary particles containing lithium transition metal oxide having a layered crystal structure; and a coating film disposed between the surface of the secondary particles and the primary particles of the plurality of primary particles, wherein the coating film includes lithium cobalt composite oxide having a spinel crystal structure, and the lithium Cobalt composite oxide is provided as a composite positive electrode active material containing cobalt (Co) and a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof.

The coating film may exist between grain boundaries of adjacent primary particles and on the surface of secondary particles. And in this specification, “between primary particles” can be interpreted to include both the grain boundaries of the primary particles and the surface of the primary particles. In this way, the conductivity of lithium ions can be improved by providing a coating film containing lithium cobalt complex oxide between the surface of the secondary particle and the grain boundary of the primary particle. Although not bound by theory, the content of residual lithium present on the surface of the composite cathode active material is reduced, thereby suppressing deterioration of the composite cathode active material, reducing gas generation, and improving the thermal stability of the lithium battery. The presence of the above-mentioned coating film disposed at the grain boundary between adjacent primary particles accommodates the volume change due to charging and discharging of the primary particles and suppresses cracking of the primary particles, thereby suppressing the decline in mechanical strength of the composite cathode active material even after long-term charging and discharging. there is. In addition, side reactions between the lithium transition metal oxide having a layered crystal structure and the electrolyte can be efficiently suppressed, and the internal resistance of the lithium battery can be reduced, thereby improving the cycle characteristics of the lithium battery.

In this specification, the coating film may be a continuous film or may have a discontinuous film state such as an island type.

The lithium cobalt composite oxide containing cobalt (Co) having the spinel crystal structure and a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof may be a compound represented by the following formula (1). .

[Formula 1]

Li _x Co _a Me _b O ₄

In Formula 1, Me is a group 2 element, a group 12 element, a group 13 element, or a combination thereof,

1.0≤x≤1.1, 0<a<2, 0<b<2, 0<a+b≤2, -1.5≤δ≤0.

In 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, for example, 2. In 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 aluminum (Al), gallium (Ga), magnesium (Mg), calcium (Ca), barium (Ba), zinc (Zn), or a combination thereof.

_{Compounds of formula 1 are , for example , Li _ _ _ _ _ _ _ _ _ δ} , Li _x Co _a Ca _b O _{4 + δ} , or Li _x Co _a Ba _b O _{4 + δ} . In the above formula, 1.0≤x≤1.1, 0<a<2, 0<b<2, 0<a+b≤2, -1.5≤δ≤0. In these 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.

Compounds of formula 1 are, 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 _.8 O _4+δ (-0.9≤δ≤0), LiCo _{1 . 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≤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≤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 . 6} O _{4 +δ} (-1.3≤δ≤0), LiCo _0.4 Zn _1.6 O _4+δ (-1.3≤δ≤0), etc.

Compounds of formula 1 are, 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 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 the layered crystal structure belongs to the rock salt layered structure (R-3m space group), and cobalt (Co) and Group 2 elements and Group 12 elements having the spinel crystal structure. Lithium cobalt complex oxide containing elements, group 13 elements, or combinations thereof belongs to the Fd-3m space group. By having the above-described crystal structure, the cycle characteristics and thermal stability of a lithium battery containing a composite cathode active material can be 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" refers to agglomerates together to form secondary particles, and the primary particles can have various shapes from rod-shaped to square, and the term "secondary particles" includes a plurality of primary particles and includes a plurality of primary particles and the It refers to particles that are not aggregates or particles that are no longer aggregated. Secondary particles may have a spherical shape.
Figure 1a is a cross-sectional view conceptually showing the microstructure of secondary particles in a composite positive electrode active material according to an embodiment.

With reference to this, the primary particles 11 are aggregated to form the secondary particles 12, and between the primary particles 11 (13), for example, the grain boundary 14 of the primary particle and/or the surface of the secondary particle ( 15) A coating film is formed.

In the composite cathode active material, the nickel content among the transition metals included 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, or 95 mol% or more. The content of nickel among the transition metals included in the lithium transition metal oxide in the composite positive electrode active material is, for example, 70 to 99.9 mol%, for example, 80 to 95 mol%, based on the total content of transition metals in the lithium transition metal oxide. . A high- capacity lithium battery can be manufactured by using a lithium transition metal oxide with a nickel content within the above-mentioned range.

In a composite cathode active material, a coating film containing cobalt (Co) having a spinel crystal structure and lithium cobalt composite oxide containing a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof is a composite cathode active material. It can be placed in a uniform concentration throughout. There may be a concentration gradient from the center of the composite cathode active material to the surface. For example, the concentration of lithium cobalt composite oxide in the center of the composite positive electrode active material may be low, and the concentration of the coating film containing lithium cobalt composite oxide in the surface portion may be high. According to another embodiment, the concentration of lithium cobalt composite oxide may be high in the center of the composite positive electrode active material, and the concentration of lithium cobalt composite oxide may be low in the surface portion.

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

The content of lithium cobalt in the coating film is small compared to the content of lithium cobalt composite oxide, and is 0.01 to 20 parts by weight, for example, 0.1 to 10 parts by weight, based on 100 parts by weight of lithium transition metal oxide having a layered crystal structure. , for example 0.1 to 2 parts by weight, for example 0.25 to 1.5 parts by weight. When the content of lithium cobalt composite oxide and lithium cobalt is within the above-mentioned range, a composite positive electrode active material with excellent thermal stability and reduced surface residual lithium content can be obtained. Using this, it is possible to manufacture lithium batteries with improved charge/discharge characteristics and lifespan characteristics.

According to another embodiment, the total content of cobalt and metal (M) in the lithium cobalt composite oxide of the coating film is 0.01 to 20 parts by weight based on 100 parts by weight of the lithium transition metal oxide having a layered crystal structure, e.g. 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 exist between the lithium transition metal oxide having the layered crystal structure and the coating film. A mixed phase may mean a mixed structure of a layered crystal structure and a spinel crystal structure.

It may further include a compound having an amorphous structure, a compound having a layered crystal structure, or a combination thereof between the primary particles.

The lithium transition metal oxide having a layered crystal structure may be one selected from compounds represented by the following formulas 2 to 4.

[Formula 2]

_{Li x} Co _{1 - y} M _y O _{2 - α}

[Formula 3]

Li _x Ni _{1 - y Me y} O _{2 - α}

[Formula 4]

Li _{x Ni 1 -y- z} Mn _y Ma _z O _{2 - α}

In formulas 2 to 4, 0.9≤x≤1.1, 0≤y≤0.9, 0<z≤0.2, 0≤α≤2,

M is Ni, Mn, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Fe, Cu, B or a combination thereof, and Me is Co, Zr, Al, Mg, Ag, Mo, Ti, V , Cr, Mn, Fe, Cu, B or a combination thereof, Ma is Co, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Fe, Cu, B or a combination thereof, and X is F , S, P or a combination thereof.

In 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 the layered crystal structure is one selected from compounds represented by the following formulas 5 to 7.

[Formula 5]

Li[Li _1-a Me _a ]O _{2 +d}

In Formula 5, 0.8≤a<1, 0≤d≤0.1,

wherein Me is one or more metals selected from the group consisting of Ni, Co, Mn, Al, V, Cr, Fe, Zr, Re, B, Ge, Ru, Sn, Ti, Nb, Mo and Pt,

[Formula 6]

Li[Li _1-xyz Ma _x Mb _y Mc _z ]O _2+d

In Formula 6, 0.8≤x+y+z<1, 0<x<1, 0<y<1, 0<z<1, 0≤d≤0.1,

Ma, Mb, and Mc are independently one or more metals selected from the group consisting of Mn, Co, Ni, and Al,

[Formula 7]

Li[Li _1-xyz Ni _x Co _y Mn _z ]O _2+d

In 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 the following formula (8).

[Formula 8]

aLi ₂ MnO _{3 -} (1-a)LiMO ₂

In 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), and boron (B ), germanium (Ge), ruthenium (Ru), tin (Sn), titanium (Ti), niobium (Nb), molybdenum (Mo), and platinum (Pt).

The lithium transition metal oxide having the layered crystal structure may be a compound represented by the following formula (9).

[Formula 9]

Li _x Ni _{1 -y- z} M _y Co _z O ₂

In 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 Formula 9, 1-y-z is, for example, 0.8 to 0.99.

The lithium transition metal oxide having the layered crystal structure may be a compound represented by the following Chemical Formula 9a.

[Formula 9a]

Li _x Ni _{1 -y- z} Mn _x Co _y O ₂

In Formula 9a, 0.80≤x≤1.1, 0≤y≤0.2, 0<z≤0.2, 0.8≤1-y-z≤0.99.

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

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 contain at least one of the substances listed above.

The average particle diameter of the primary particles in the composite positive electrode active material may be 0.1 to 5㎛, for example, 0.2 to 0.5㎛, but is not necessarily limited to this range and can be adjusted within a range that can provide improved charge and discharge characteristics.

The average particle diameter of the secondary particles in which the primary particles are aggregated in the composite cathode active material may be about 1㎛ to about 30㎛, for example, 10 to 20㎛, for example, about 13㎛ to about 15㎛, but is necessarily limited to this range. and can be adjusted within a range that can provide improved charge/discharge characteristics of the lithium battery.

The thickness of the coating film in the composite cathode active material is 1㎛ or less, for example 500nm or less, 200nm or less, for example 100nm or less, for example 50nm or less, for example 30nm or less, for example 10nm or less, for example 10nm or less. to 1 μm, for example 30 nm to 200 nm, for example 30 nm to 100 nm. Within this thickness range of the coating film, the cycle characteristics and thermal stability of a lithium battery containing a composite cathode active material can be further improved.

According to one embodiment, the grain boundaries in the composite cathode active material have an average grain boundary length of about 50 nm to about 1000 nm, an average grain boundary thickness of about 1 nm to about 200 nm, and the direction of the length is parallel to the surface of the adjacent primary particle. , the direction of thickness may be perpendicular to the surface of the adjacent primary particle. The average grain boundary length may be from about 50 nm to about 950 nm, from about 100 nm to about 900 nm, from about 150 nm to about 800 nm, or from about 200 nm to about 700 nm. For example, the average grain boundary thickness may be from about 2 nm to about 100 nm, from about 5 nm to about 100 nm, from about 10 nm to about 100 nm, or from about 20 nm to about 100 nm. Within this range of average grain boundary length and average grain boundary thickness, further improved charge and discharge characteristics can be provided.

According to another embodiment, a method of manufacturing a composite positive electrode active material includes manufacturing a lithium transition metal oxide having a layered crystal structure; Lithium containing the lithium transition metal oxide having the layered crystal structure, cobalt (Co) having a spinel crystal structure, a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof. Obtaining a composite positive electrode active material composition by mixing precursors of cobalt composite oxide; And drying the composite positive electrode active material composition and heat treating it in an oxidizing gas atmosphere at a temperature exceeding 400°C and below 1000°C.

Lithium containing the lithium transition metal oxide having the layered crystal structure, cobalt (Co) having a spinel crystal structure, a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof. Mixing of the precursors of the cobalt complex oxide can be performed wet in the presence of a solvent.

The oxidizing gas atmosphere is implemented using oxygen or air. The oxidizing gas atmosphere may contain oxygen, air or a combination thereof, for example air with an increased oxygen content.

In the composite positive electrode active material composition, the precursor and solvent of lithium cobalt composite oxide containing cobalt (Co) having the spinel crystal structure and a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof. The content is 300 parts by weight or less based on 100 parts by weight of the lithium transition metal oxide having the layered crystal structure. In the composite positive electrode active material composition, the content of the precursor of the lithium cobalt composite oxide containing cobalt (Co) having the spinel crystal structure and a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof is It is 100 parts by weight or less based on 100 parts by weight of the lithium transition metal oxide having the layered crystal structure. And the content of the solvent is 200 parts by weight or less based on 100 parts by weight of the lithium transition metal oxide having the layered crystal structure.

The heat treatment may be performed at, for example, 600 to 800°C, for example, 700 to 750°C. The temperature increase rate during heat treatment is, for example, 1 to 10°C/min. To reach this heat treatment temperature, the temperature increase rate is controlled in the range of 1 to 10°C/min, for example, about 2°C/min. When the heat treatment temperature and temperature increase rate are within the above-mentioned range, cobalt (Co) with a spinel crystal structure between the surface of the secondary particles and the primary particles and a group 2 element, a group 12 element, a group 13 element, or a combination thereof A coating film containing lithium cobalt complex oxide containing water may be disposed.

The precursor of lithium cobalt composite oxide is obtained by mixing a cobalt precursor and an M precursor and mixing them with a solvent to obtain a precursor mixture. This precursor mixture is mixed with a lithium transition metal oxide having a layered crystal structure and a precipitation reaction is performed to obtain a lithium transition metal oxide having a layered crystal structure on which a compound coating film represented by Chemical Formula 10 is disposed. This can then be heat treated to obtain the desired composite positive electrode active material.

Cobalt precursors include, for example, cobalt chloride, cobalt nitrate, cobalt sulfate, etc., and the M precursor can be used in the same variety as the cobalt precursor, except that M is used instead of cobalt.

In the composite cathode active material according to one embodiment, the calorific value of the composite cathode active material may be 90% or less of the secondary particles containing lithium transition metal oxide having a layered crystal structure. In addition, the residual lithium of the composite cathode active material is less than 90% of the residual lithium of the secondary particles containing lithium transition metal oxide having a layered crystal structure.

Before surface treatment to remove residual lithium of the composite cathode active material, residual lithium is, for example, about 4,000 parts per million (ppm), and after surface treatment, it can be effectively reduced to less than 2,000 ppm. And the cell capacity of the composite cathode active material is 220 mAh/g, and the lifespan is excellent at more than 50 times.

In addition, lithium cobalt composite oxide containing cobalt (Co) with a spinel crystal structure and Group 2 elements, Group 12 elements, Group 13 elements, or a combination thereof covers at least 50% of the surface of the lithium transition metal oxide. can cover When having this structure, side reactions between lithium transition metal oxide and electrolyte can be substantially reduced and/or effectively minimized or effectively blocked.

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

For example, a positive electrode active material composition is prepared by mixing the above-described composite positive electrode active material, a conductive agent, a binder, and a solvent. The positive electrode active material composition can be directly coated and dried on an aluminum current collector to manufacture a positive electrode with a positive electrode active material layer. Alternatively, the positive electrode active material composition may be cast on a separate support, and then the film obtained by peeling from the support may be laminated on the aluminum current collector to produce a positive electrode with a positive active material layer formed thereon.

Conductive agents include carbon black, graphite particles, natural graphite, artificial graphite, acetylene black, Ketjen black, and carbon fiber; carbon nanotubes; Metal powder or metal fiber or metal tube such as copper, nickel, aluminum, silver, etc.; Conductive polymers such as polyphenylene derivatives may be used, but are not limited to these, and any conductive agent that can be used in the relevant technical field can be used.

Binders include vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), mixtures of the above polymers, and styrene butadiene rubber. Polymers, etc. may be used, and solvents such as N-methylpyrrolidone (NMP), acetone, water, etc. may be used, but are not necessarily limited to these and any solvent that can be used in the art is possible.

The contents of the composite cathode active material, conductive agent, binder, and solvent are levels commonly used in lithium batteries. Depending on the use and configuration of the lithium battery, one or more of the conductive agent, binder, and solvent may be omitted.

Additionally, the positive electrode may additionally include other general positive electrode active materials in addition to the composite positive electrode active material described above.

The general positive electrode active material is a lithium-containing metal oxide, and any material commonly used in the industry can be used without limitation. For example, one or more types of complex oxides of lithium and a metal 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 (above where 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 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 (in the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li _a Ni _{1 -b- c} Co _b B _c D _α (wherein 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 (wherein 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 ₂ (wherein 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 (wherein 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 O _{2 - α} F _α (wherein 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 O _{2 - α} F ₂ (wherein 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 GeO 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 ; LiIO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); A compound represented by any one of the chemical formulas of LiFePO ₄ can be used: A combination of the compounds listed above can be used as a general positive electrode active material.

In the above formula, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, 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; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

Of course, a cathode compound having a coating film on the surface can be used, or a mixture of the above compound and a compound having a coating film can be used. This coating film may include oxide, hydroxide, oxyhydroxide, oxycarbonate, hydroxycarbonate, or a combination thereof as a coating element. The compounds that make up these coating films may be amorphous or crystalline. Coating elements included in the coating film may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. For the coating film formation process, any coating method may be used as long as the above compounds can be coated using these elements in a method that does not adversely affect the physical properties of the positive electrode active material (e.g., spray coating, dipping method, etc.). Since this is well-understood by people working in the field, detailed explanation will be omitted.

According to another embodiment, the positive electrode can be manufactured by using the composite positive electrode active material according to one embodiment as a large particle size positive electrode active material and using it together with a small particle size positive electrode active material. In this way, the positive electrode may contain a bimodal positive electrode active material.

A lithium battery according to another embodiment employs a positive electrode containing the composite positive electrode active material, a negative electrode, and an electrolyte disposed between them. Lithium batteries can be manufactured in the following way.

First, an anode is manufactured according to the anode manufacturing method described above.

Next, the cathode can be manufactured as follows. The negative electrode can be manufactured in the same manner as the positive electrode except that a negative electrode active material is used instead of the composite positive electrode active material. Additionally, the conductive agent, binder, and solvent in the negative electrode active material composition may be the same as those for the positive electrode.

For example, a negative electrode active material composition can be prepared by mixing a negative electrode active material, a conductive agent, a binder, and a solvent, and the negative electrode plate can be manufactured by coating the composition directly on a copper current collector. Alternatively, a negative electrode plate can be manufactured by casting the negative electrode active material composition on a separate support and laminating the negative electrode active material film peeled from the support to a copper current collector.

Additionally, the negative electrode active material may be any material that can be used as a negative electrode active material for a lithium battery in the art. For example, it may include lithium metal, an element alloyable with lithium, a transition metal oxide, a non-transition metal oxide, a carbon-based material, or a combination thereof.

For example, elements that can be alloyed with lithium include Si, Sn, Al, Ge, Pb, Bi, Sb Si-Y alloy (Y is an alkali metal, alkaline earth metal, group 13 to 16 element, transition metal, rare earth element or It may be a combination element thereof, but not Si), a Sn-Y alloy (where 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 element thereof, but not Sn), etc. there is. The element Y includes 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, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, It may be Se, Te, Po, or a combination thereof.

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

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

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

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

Next, a separator to be inserted between the anode and the cathode is prepared. Any separator commonly used in lithium batteries can be used. An electrolyte that has low resistance to ion movement and has excellent electrolyte moisturizing ability can be used. For example, it is selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be in the form of non-woven or woven fabric. For example, a rollable separator such as polyethylene or polypropylene may be used in a lithium ion battery, and a separator with excellent organic electrolyte impregnation ability may be used in a lithium ion polymer battery. For example, the separator can be manufactured according to the following method.

A separator composition is prepared by mixing polymer resin, filler, and solvent. The separator composition may be directly coated and dried on the top of the electrode to form a separator. Alternatively, after the separator composition is cast and dried on a support, a 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 materials used as a binder for electrode plates can be used. For example, vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, or mixtures thereof may be used.

Next, the electrolyte is prepared.

For example, the electrolyte may be an organic electrolyte. Additionally, the electrolyte may be solid. For example, it may be boron oxide, lithium oxynitride, etc., but it is not limited to these, and any solid electrolyte that can be used in the art can be used. The solid electrolyte may be formed on the cathode by a method such as sputtering.

Organic electrolytes can be prepared by dissolving lithium salt in an organic solvent.

The organic solvent may be any organic solvent that can be used 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, ethyl propyl carbonate. , benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide , dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or mixtures thereof.

Any lithium salt that can be used as a lithium salt in the art can be used. 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 ) (where x and y are natural numbers), LiCl, LiI, or mixtures thereof, etc. As shown in FIG. 4, the lithium battery (1) includes an anode (3), a cathode (2), and a separator (4). The above-described positive electrode (3), negative electrode (2), and separator (4) are wound or folded and accommodated in the battery case (5). Next, an organic electrolyte is injected into the battery case (5) and sealed with a cap assembly (6) to complete the lithium battery (1). The battery case may be cylindrical, prismatic, thin film, etc. For example, the lithium battery may be a large thin film type battery. The lithium battery may be a lithium ion battery. A separator may be disposed between the positive electrode and the negative electrode to form a battery structure. The battery structure is stacked in a bi-cell structure, then impregnated with an organic electrolyte solution, and the resulting product is placed in a pouch and sealed to complete the lithium ion polymer battery.

Additionally, a plurality of the battery structures are stacked to form a battery pack, and this battery pack can be used in all devices that require high capacity and high output. For example, it can be used in laptops, smartphones, electric vehicles, etc.

In addition, the lithium battery has excellent lifespan characteristics and high rate characteristics, so it can be used in electric vehicles (EV). For example, it can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEV). Additionally, it can be used in fields that require large amounts of power storage. For example, it can be used in electric bicycles, power tools, etc.

The lithium battery is charged to a voltage of 4.5V or higher with respect to lithium metal at the time of initial charging, thereby activating the spinel crystal structure belonging to the Fd-3m space group included in the second lithium transition metal oxide of the shell, which is a coating film, to provide additional charging capacity/ Discharge capacity can be utilized. Therefore, the initial charge/discharge capacity of the lithium battery can be improved.

It will be described in more detail through the following examples and comparative examples, but the scope of the invention is not limited to the following examples.

Comparative example One: Lithium transition metal Preparation of oxides

An aqueous precursor solution was prepared by adding NiSO ₄ (H ₂ O) ₆ , CoSO ₄ and MnSO ₄ H ₂ O to water at a molar ratio of 91:6:3. While stirring the aqueous solution, sodium hydroxide aqueous solution was slowly added dropwise to neutralize the precursor aqueous solution to Ni _{0 . 91} Co _{0 . 06 Mn 0.03} (OH) ₂ was precipitated. _This precipitate was filtered, washed with water, and dried at 120° _C to prepare metal ( _{Ni 0.91} Co _{0.06 Mn 0.03} ) hydroxide powder _.

After mixing the metal hydroxide powder and LiOH, it was placed in a furnace and heat treated at 765°C for 20 hours while oxygen was flowing to produce lithium transition metal oxide (Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ ). got it

Comparative example 2: Lithium transition metal Preparation of oxides

NiSO ₄ (H ₂ O) ₆ , CoSO ₄ , MnSO ₄ ·H ₂ O and Al(NO ₃ ) ₃ ·9H ₂ O were mixed at a molar ratio of 87.8:8:4:0.2 and heat treated at 710°C for 40 hours. Comparative _{Example 1} and _{Comparative Example} 1, except that the LiOH _content was controlled to obtain lithium transition metal oxide _{(Li 1.09 Ni 0.878 Co 0.080 Mn 0.040 Al 0.002 O 2 )} . Lithium transition metal oxide (Li _1.09 Ni _0.878 Co _0.080 Mn _0.040 Al _0.002 O ₂ ) was prepared according to the same method.

Comparative example 3: Composite cathode active material manufacturing

After preparing 0.75 parts by weight of CoCl ₂ ·H ₂ O, 10 parts by weight of distilled water was added and stirred for 1 minute at room temperature to prepare an aqueous solution.

Li ₁ prepared according to Comparative Example 1 _{. 05} Ni _{0 . 91} Co _{0 . 06} Mn _{0 .} 100 parts by weight of ₀₃ O ₂ powder was added to 90 parts by weight of distilled water and stirred at room temperature for 10 minutes. During stirring, the aqueous solution prepared according to the above process was added to prepare a mixture.

The mixture was dried in an oven at 150°C for 15 hours to prepare a dried product.

The dried material was put into a furnace and heat treated at 720°C for 5 hours while oxygen was flowing to prepare a composite positive electrode active material.

The composite cathode active material is Li _{1 . 05} Ni _{0 . 91} Co _{0 . 06} Mn _{0 . 03} O ₂ It had a structure in which a LiCoO ₂ coating film was disposed between the surface of the secondary particles and the primary particles. And the cobalt content of the LiCoO ₂ coating film was 0.75 parts by weight based on 100 parts by weight of the composite cathode active material.

Comparative example 3a: Composite cathode active material manufacturing

After preparing 0.75 parts by weight of MgCl ₂ ·H ₂ O, 10 parts by weight of distilled water was added and stirred at room temperature for 1 minute to prepare an aqueous solution.

Li ₁ prepared according to Comparative Example 1 _{. 05} Ni _{0 . 91} Co _{0 . 06} Mn _{0 .} 100 parts by weight of ₀₃ O ₂ powder was added to 90 parts by weight of distilled water and stirred at room temperature for 10 minutes. During stirring, the aqueous solution prepared according to the above process was added to prepare a mixture.

The dried product was prepared by drying the mixture in an oven at 150°C for 15 hours.

The dried material was put into a furnace and heat treated at 720°C for 5 hours while oxygen was flowing to prepare a composite positive electrode active material.

The composite cathode active material is Li _{1 . 05} Ni _{0 . 91} Co _{0 . 06} Mn _{0 . 03} O ₂ It had a structure in which a LiMgO _{2 +δ} (-0.5≤δ≤0) coating film was disposed between the surface of the secondary particles and the primary particles. And 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 cathode active material.

Comparative example 4: Composite cathode active material manufacturing

Li ₁ obtained according to Comparative Example 1 _{. 05} Ni _{0 . 91} Co _{0 . 06} Mn _{0 .} Instead of ₀₃ O ₂ , Li _1.09 Ni _0.878 Co _0.080 Mn _0.040 Al _0.002 O ₂ obtained according to Comparative Example 2 was used, and cobalt A composite cathode active material was obtained in the same manner as Comparative Example 3, except that the content was changed to 0.5 parts by weight based on 100 parts by weight of the composite cathode active material.

In Examples 1 to 3 and 3a-3c below, the lithium transition metal oxide (Ni91) of Comparative Example 1 was used.

Example One: Composite cathode active material manufacturing

After preparing 0.75 parts by weight of a mixed precursor of Co(NO ₃ ) ₂ ·6H ₂ O and Al(NO ₃ ) ₃ ·9H ₂ O at a molar ratio of 3:1, 10 parts by weight of distilled water was added and incubated at room temperature (25°C). An aqueous solution was prepared by stirring for 1 minute.

Li ₁ obtained according to Comparative Example 1 above _{. 05} Ni _{0 . 91} Co _{0 . 06} Mn _{0 .} 100 parts by weight of ₀₃ O ₂ powder was added to 90 parts by weight of distilled water, and the prepared aqueous solution was added while stirring at room temperature for 10 minutes to form a precipitate. The obtained precipitate was filtered and dried at 150°C for 15 hours to prepare a composite positive electrode active material precursor. The composite cathode active material precursor had a structure in which a cobalt aluminum hydroxide coating film containing cobalt and aluminum in a 3:1 molar ratio was placed on top of Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ .

The composite cathode 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 cathode active material. The composite positive electrode active material is LiCo ₁ , which has a spinel crystal structure between the surface of the secondary particles and the primary particles of Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O _{2 . 5} Al _{0 .} It had a structure in which _{a 5} O _{4 +δ} (-0.5≤δ≤0) coating film was arranged. LiCo ₁ in composite cathode active material _{. 5} Al _{0 . 5 O 4 +δ (} -0.5≤δ≤0) The content of cobalt and _aluminum in the _coating film is _{based on} 100 parts by weight of the total weight of lithium transition metal oxide (Li _{1.05 Ni 0.91 Co 0.06 Mn 0.03 O 2} ) It was 0.75 parts by weight.

Example 2: Composite cathode active material manufacturing

Co(NO ₃ ) ₂ ·6H ₂ O and Al(NO ₃ ) ₃ ·9H ₂ O were mixed at a molar ratio of 3:1 instead of Co(NO ₃ ) ₂ ·6H ₂ O and Zn(NO ₃ ) ₂ ·6H. A mixed precursor of ₂ O at a molar ratio of 2:1 was used, and the contents of Co(NO ₃ ) ₂ ·6H ₂ O and Al(NO ₃ ) ₃ ·9H ₂ O were finally obtained in the composite cathode active material, LiCo _{1 . 33} Zn _{0 . 67} O _{4 +δ} (-0.835≤δ≤0) Carried out in the same manner as Example 1, except that the content of cobalt zinc in the coating film was controlled to be 0.50 parts by weight based on 100 parts by weight of lithium transition metal oxide. So Li _{1 . 05} Ni _{0 . 91} Co _{0 . 06} Mn _{0 . 03} LiCo ₁ with a spinel crystal structure between the surface of the secondary particles of O ₂ and the primary particles _{. 33} Zn _{0 .} A composite positive electrode active material with _{a 67} O _{4 +δ} (-0.5≤δ≤0) coating film was prepared.

Example 2a-2c: Composite cathode active material manufacturing

LiCo ₁ in composite cathode active material _{. 33} Zn _{0 . 67} O _{4 +δ} (-0.835≤δ≤0) Except that the content of cobalt zinc in the coating film was changed to 0.25 parts by weight, 0.75 parts by weight, and 1.5 parts by weight based on 100 parts by weight of lithium transition metal oxide. A composite positive electrode active material was obtained by following the same method as Example 2.

Example 3: Composite cathode active material manufacturing

Li _1.05 was obtained in the same manner as in Example 1, except that a 3:2 molar ratio of Co(NO ₃ ) ₂ ·6H ₂ O and Mg(NO ₃ ) ₂ ·6H ₂ O was used as a precursor. Ni _0.91 Co _0.06 Mn _0.03 O ₂ LiCo ₁ having a spinel crystal structure between the surface of the secondary particles and the primary particles _{. 2} Mg _{0 . 8} O _{4 +δ} (-0.9≤δ≤0) A composite positive electrode active material with a coating film formed was prepared. LiCo ₁ in composite cathode active material _{. 2} Mg _{0 . 8} O _{4 +δ} (-0.9≤δ≤0) The content of cobalt magnesium in the coating film was 0.75 parts by weight based on 100 parts by weight of lithium transition metal oxide.

Example 3a: Composite cathode active material manufacturing

Li was carried out in the same manner as in Example 3, except that a mixed precursor of Co(NO ₃ ) ₂ ·6H ₂ O and Mg(NO ₃ ) ₂ ·6H ₂ O at a molar ratio of 4:1 was used as the precursor. LiCo ₁ has a spinel crystal structure between the surface of the secondary particles and the primary particles of _1.05 Ni _0.91 Co _0.06 Mn _0.03 O _{2 . 6} Mg _{0 .} A composite positive electrode active material with a ₄ O _{4 +δ} (-0.7≤δ≤0) coating film was prepared. LiCo ₁ in composite cathode active material _{. 6} Mg _{0 . 4} O _{4 +δ} (-0.7≤δ≤0) The content of cobalt magnesium in the coating film was 0.75 parts by weight based on 100 parts by weight of lithium transition metal oxide.

Example 3b: Composite cathode active material manufacturing

Li was carried out in the same manner as in Example 3, except that a mixed precursor of Co(NO ₃ ) ₂ ·6H ₂ O and Mg(NO ₃ ) ₂ ·6H ₂ O at a molar ratio of 2:3 was used as the precursor. LiCo ₀ has a spinel crystal structure between the surface of the secondary particles and the primary particles of _1.05 Ni _0.91 Co _0.06 Mn _0.03 O _{2 . 8} Mg _{1 .} A composite positive electrode active material with a ₂ O _{4 +δ} (-1.1≤δ≤0) coating film was prepared. The content of cobalt magnesium in the LiC _O0.8 Mg _1.2 O ₄ coating film was 0.75 parts by weight based on 100 parts by weight of lithium transition metal oxide.

Example 3c: Composite cathode active material manufacturing

Li _1.05 was obtained in the same manner as in Example 3, except that a mixed precursor of Co(NO ₃ ) ₂ ·6H ₂ O and Mg(NO ₃ ) ₂ ·6H ₂ O at a molar ratio of 1:4 was used as the precursor. Ni _0.91 Co _0.06 Mn _0.03 O ₂ LiCo ₀ having a spinel crystal structure between the surface of the secondary particles and the primary particles _{. 4} Mg _{1 .} A composite positive electrode active material with a ₆ O _{4 +δ} (-1.3≤δ≤0) coating film was prepared. LiC _O0.4 Mg _1.6 O _4+δ (-1.3≤δ≤0) The content of cobalt magnesium in the coating film was 0.75 parts by weight based on 100 parts by weight of lithium transition metal oxide.

Example 4: Composite cathode active material manufacturing

Li ₁ prepared according to Comparative Example 1 _{. 05} Ni _{0 . 91} Co _{0 . 06} Mn _{0 . 03} O ₂ Instead, Li _1.09 Ni _0.88 Co _0.08 Mn _0.04 O ₂ prepared according to Comparative Example 2 was used, and the contents of Co(NO ₃ ) ₂ ·6H ₂ O and Zn(NO ₃ ) ₂ ·6H ₂ O were found in the composite cathode active material. LiCo _{1 . 33} Zn _{0 . 67} O _{4 +δ} (-0.835≤δ≤0) Carried out in the same manner as in Example 2, except that the content of cobalt zinc in the coating film was controlled to be 0.25 parts by weight based on 100 parts by weight of lithium transition metal oxide. So Li _{1 . 09} Ni _{0 . 88} Co _{0 . 08} Mn _{0 . 04} LiCo ₁ with a spinel crystal structure between the surface of the secondary particles of O ₂ and the primary particles _{. 33} Zn _{0 .} A composite positive electrode active material with _{a 67} O _{4 +δ} (-0.835≤δ≤0) coating film was prepared.

Example 4a: Composite cathode active material manufacturing

Li ₁ prepared according to Comparative Example 1 _{. 05} Ni _{0 . 91} Co _{0 . 06} Mn _{0 . 03} O ₂ Instead, Li _1.09 Ni _0.88 Co _0.08 Mn _0.04 O ₂ prepared according to Comparative Example 2 was used, and the same method as Example ₃ was carried out _{. 09} Ni _{0 . 88} Co _{0 . 08} Mn _{0 . 04} LiCo ₁ with a spinel crystal structure between the surface of the secondary particles of O ₂ and the primary particles _{. 2} Mg _{0 . 8} O _{4 +δ} (-0.9≤δ≤0) A composite positive electrode active material with a coating film formed was prepared. LiCo ₁ in composite cathode active material _{. 2} Mg _{0 . 8} O _{4 +δ} (-0.9≤δ≤0) The content of cobalt magnesium in the coating film was 0.75 parts by weight based on 100 parts by weight of lithium transition metal oxide.

Example 5: Composite cathode active material manufacturing

LiCo ₁ in composite cathode active material _{. 33} Zn _{0 . 67} O _{4 +δ} (-0.835≤δ≤0) The same method as Example 4 was carried out, except that the content of cobalt zinc in the coating film was changed to 0.50 parts by weight based on 100 parts by weight of lithium transition metal oxide. A composite cathode active material was obtained.

Example 5a: Composite cathode active material manufacturing

Li ₁ prepared according to Comparative Example 1 _{. 05} Ni _{0 . 91} Co _{0 . 06} Mn _{0 . 03} O ₂ Instead, Li _1.09 Ni _0.88 Co _0.08 Mn _0.04 O ₂ prepared according to Comparative Example 2 was used, and the same method as Example ₁ was performed _{. 09} Ni _{0 . 88} Co _{0 . 08} Mn _{0 . 04} LiCo ₁ with a spinel crystal structure between the surface of the secondary particles of O ₂ and the primary particles _{. 5} Al _{0 .} A composite positive electrode active material with a ₅ O _{4 +δ} (-0.5≤δ≤0) coating film was prepared. LiCo ₁ in composite cathode active material _{. 5} Al _{0 . 5} O _{4 +δ} (-0.5≤δ≤0) The content of cobalt aluminum in the coating film was 0.75 parts by weight based on 100 parts by weight of lithium transition metal oxide.

Example 6: Lithium battery ( Coin cell )Manufacture of

A mixture of the composite cathode active material prepared in Example 1, a carbon conductive agent (Denka Black), and polyvinylidene fluoride (PVDF) at a weight ratio of 92:4:4 was mixed with N-methyl-pyrrolidone (NMP). A slurry was prepared by mixing in an agate mortar. The slurry was bar coated on a 15㎛ thick aluminum current collector, dried at room temperature, dried again under vacuum and 120°C, and rolled and punched to produce a 55㎛ thick positive electrode.

Using the positive electrode prepared above, lithium metal was used as the counter electrode, a PTFE separator and 1.15M LiPF ₆ were added to EC (ethylene carbonate) + EMC (ethylmethyl carbonate) + DMC (dimethyl carbonate) (2:4) Each coin cell was manufactured using a solution dissolved in (:4 volume ratio) as an electrolyte.

Example 7 to 10: Lithium battery ( Coin cell )Manufacture of

A coin half-cell was manufactured in the same manner as in Example 6, except that the composite cathode active materials prepared according to Examples 2 to 5 were used instead of the composite cathode active materials prepared in Example 1.

Example 11 to 13: Lithium battery ( Coin cell )Manufacture of

A coin cell was manufactured in the same manner as in Example 6, except that the composite cathode active materials prepared in Examples 2a to 2c were used instead of the composite cathode active materials prepared in Example 1.

Example 14 to 16: Lithium battery ( Coin cell )Manufacture of

A coin cell was manufactured in the same manner as in Example 6, except that the composite cathode active materials prepared in Examples 3a to 3c were used instead of the composite cathode active materials prepared in Example 1.

Example 17: Lithium battery ( Coin cell )Manufacture of

A coin cell was manufactured in the same manner as in Example 6, except that the composite cathode active material prepared according to Example 4a was used instead of the composite cathode active material prepared in Example 1.

Comparative example 5 to 8: Lithium battery ( Coin cell )Manufacture of

A coin cell was manufactured in the same manner as in Example 6, except that the composite cathode active materials prepared according to Comparative Examples 1 to 4 were used instead of the composite cathode active materials prepared in Example 1.

Comparative example 8a: Lithium battery ( Coin cell )Manufacture of

A coin cell was manufactured in the same manner as in Example 6, except that the composite cathode active material prepared according to Comparative Example 3a was used instead of the composite cathode active material prepared in Example 1.

Comparative example 9: Composite cathode active material manufacturing

A composite cathode active material was prepared in the same manner as in Example 1, except that the composite cathode active material precursor was put into a furnace and heat treated at 400° C. for 5 hours in an oxygen atmosphere.

Comparative example 10: Composite cathode active material manufacturing

A composite cathode active material was prepared in the same manner as in Example 1, except that the composite cathode active material precursor was put into a furnace and heat treated at 1050° C. for 5 hours in an oxygen atmosphere.

Comparative example 11-12: Lithium battery ( Coin cell )Manufacture of

A coin cell was manufactured in the same manner as in Example 6, except that the composite cathode active materials prepared according to Comparative Examples 9 and 10 were used instead of the composite cathode active materials prepared in Example 1.

Example 18: Lithium battery ( Coin cell )Manufacture of

A coin cell was manufactured in the same manner as in Example 6, except that the composite cathode active material prepared according to Example 5a was used instead of the composite cathode active material prepared in Example 1.

Example 19: Lithium battery (18650 minicell )Manufacture of

A mixture of the composite positive electrode active material prepared in Example 2, a carbon conductive agent (Denka Black), and polyvinylidene fluoride (PVDF) at a weight ratio of 92:4:4 was mixed with N-methyl-pyrrolidone (NMP). A slurry was prepared by mixing in an agate mortar. The slurry was bar coated on a 15㎛ thick aluminum current collector, dried at room temperature, dried again under vacuum and 120°C, and rolled and punched to produce a 55㎛ thick positive electrode.

The positive electrode was wound into a cylindrical shape together with the graphite negative electrode. An anode tab and a cathode tab were welded to the cylindrical structure and inserted into and sealed in a cylindrical can. Afterwards, electrolyte was injected into the cylindrical can and the cap was clipped to 18650. A minicell was prepared. At this time, the separator was used by coating both sides of α-Al ₂ O ₃ powder with an average particle diameter of 50 nm on a polyethylene (manufactured by Asahi) substrate.

As the electrolyte, a solution containing 1.15M LiPF ₆ dissolved in EC (ethylene carbonate) + EMC (ethylmethyl carbonate) + DMC (dimethyl carbonate) (2:4:4 volume ratio) was used.

Example 20-21: Lithium battery (18650 minicell )Manufacture of

A lithium battery (18650 minicell) was manufactured in the same manner as in Example 19, except that the composite cathode active materials of Examples 4 and 4a were used instead of the composite cathode active materials prepared in Example 2.

Comparative example 13: Lithium battery (18650 minicell )Manufacture of

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 was mixed with distilled water at a weight _{ratio of} 1:2 and stirred at about ₂₅₀ rpm for water washing _. did. The resulting product was then dried at about 150°C for 15 hours to obtain cleaned lithium transition metal oxide (Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ ).

Example, except that the cleaned lithium _transition metal oxide _{(Li 1.05 Ni 0.91 Co 0.06 Mn 0.03 O 2} ) obtained according to the above process was used instead _{of the} composite _cathode active material obtained according to Example 2 _. A lithium battery (18650 minicell) was manufactured following the same method as in 19.

Comparative example 13a: Lithium battery (18650 minicell )Manufacture of

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 was mixed with distilled water at a weight _{ratio of} 1:2 and stirred at about ₂₅₀ rpm for water washing _. did. The resulting product was then dried at about 150°C for 15 hours to obtain cleaned lithium transition metal oxide (Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ ).

Example _, except that the cleaned lithium _transition metal oxide _{(Li 1.05 Ni 0.91 Co 0.06 Mn 0.03 O 2} ) obtained according to the above process was used instead of _the composite _cathode active material obtained according to Example 1 _. A lithium battery (coin half cell) was manufactured following the same method as in 6.

Comparative example 14: Lithium battery (18650 minicell )Manufacture of

Example 19, except that lithium transition metal oxide (Li _{1.09 Ni 0.88} Co _{0.08 Mn 0.04} O ₂ ) obtained according to Comparative _Example 2 was used instead of _the composite cathode active _{material obtained} according to Example _{2 .} A lithium battery (18650 minicell) was manufactured according to the same method as above.

Comparative example 15: Lithium battery ( Coin Half Sell )Manufacture of

The lithium transition metal oxide _{(Li 1.09 Ni 0.88} Co _{0.08 Mn 0.04} O ₂ ) obtained according to Comparative Example ₂ was mixed with distilled water at _a 1:2 mixing _{ratio ,} and the mixture was stirred at about ₂₅₀ rpm to perform water washing _. did. The resulting product was then dried at about 150°C for 15 hours to obtain cleaned lithium transition metal oxide (Li _1.09 Ni _0.88 Co _0.08 Mn _0.04 O ₂ ).

Example _, except that the cleaned lithium transition metal oxide _{(Li 1.09 Ni 0.88 Co 0.08} Mn _0.04 O ₂ ) obtained according to the above process was used _instead of _the composite _cathode active _material obtained according to Example 1 _. A lithium battery (coin half cell) was manufactured following the same method as in 6.

Evaluation example One: S.E.M. image analysis

1) Example 4a and Comparative Examples 2 and 4

The surface of the composite positive electrode active material powder prepared according to Example 4a and Comparative Examples 2 and 4 was analyzed using a scanning electron microscope, and the results are shown in FIGS. 2A to 2C, respectively.

Referring to FIGS. 2A to 2C, the size of the primary particles of the composite cathode active material of Example 4a increased compared to the composite cathode active material of Comparative Examples 2 and 4. And the thickness of the layered double oxide (LDO) coating film in the composite cathode active material of Example 4a was about 100 nm.

2) Example 1

Scanning electron microscopy analysis was performed on the composite cathode active material prepared according to Example 1, and the results are shown in Figure 1b.

Referring to this, it was found that a coating film existed between the surface of the lithium transition metal oxide secondary particles and the primary particles and that the average particle diameter of the composite cathode active material was about 10 ㎛.

Evaluation example 2: X-ray diffraction analysis

XRD (X-ray Diffraction) analysis was performed on the composite cathode active material of Example 3. The XRD analysis results are as shown in Figure 3.

Referring to this, the layered crystal structure of the lithium transition metal oxide and the spinel crystal structure of the lithium cobalt composite oxide were observed from the XRD spectrum of the composite cathode active material of Example 1. Therefore, it was confirmed that the composite positive electrode active material of Example 1 contained a lithium transition metal oxide with a layered crystal structure and a coating film containing a lithium cobalt composite oxide with a spinel crystal structure.

Evaluation example 3: HAADF (High-Angle Annular Dark-Field) STEM and EDS (Energy-Dispersive X-ray Spectroscopy)

The composition of the composite cathode active material prepared according to Example 3 was analyzed by performing HAADF (High-Angle Annular Dark-Field) STEM and EDS analysis.

Referring to this, it was confirmed that Ni, Mn, and Co were uniformly distributed throughout the composite positive electrode active material. It was confirmed that Co and Mg were placed between the primary particles, and that Co and Mg were placed on the surfaces of the primary and secondary particles. Therefore, LiCo ₁ on both the grain boundaries and surfaces between primary particles and on the surfaces of secondary particles _{. 2} Mg _{0 .} It was confirmed that ₈ O ₄ was uniformly coated.

Evaluation example 4: Evaluation of residual lithium content

1) Examples 1-3, 2a, 3a-3c and Comparative Example 1

The surface residual lithium content was measured for the composite cathode active materials prepared according to Examples 1-3, 2a, 3a-3c and Comparative Example 1, and 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 using a wet method (or titrimetric method).

Residual lithium content (ppm) Example 1 374 Example 2 584 Example 2a 636 Example 3 394 Example 3a 494 Example 3b 384 Example 3c 491 Comparative Example 1 2807

Referring to Table 1, the composite cathode active materials of Examples 1-3, 2a, and 3a-3c showed a decrease in the residual lithium content on the surface compared to Comparative Example 1. Therefore, gas generation can be suppressed during charging and discharging of a lithium battery containing the composite positive electrode active material of Examples 1-3, 2a, and 3a-3c, and deterioration of life characteristics can be suppressed.

2) Examples 4, 5, 5a, Comparative Examples 2 and 4

The surface residual lithium content of the composite cathode active material prepared according to Examples 4, 5, 5a, and Comparative Examples 2 and 4 was measured, and some of the results are shown in Table 2 below.

The surface residual lithium content is the Li ₂ CO ₃ remaining on the surface of the composite cathode active material. and Li content in LiOH was evaluated by measurement using a wet method (or titrimetric method).

Residual lithium content (ppm) Example 4 545 Example 5 515 Example 5a 732 Comparative Example 2 5489 Comparative Example 4 2109

Referring to Table 2, the composite cathode active materials of Examples 4, 5, and 5a showed a decrease in the residual lithium content on the surface compared to Comparative Examples 2 and 4.

Evaluation example 5: Thermal stability test

Differential scanning calorimetry analysis was performed on the composite cathode active material obtained according to Examples 2 and 3 and Comparative Example 3. The analysis results are shown in Table 3 below.

division Calorific value (J/g) Example 2 1702 Example 3 1487 Comparative Example 3 1805

Referring to Table 3, the heat generation amount of the composite cathode active materials of Examples 2 and 3 was reduced compared to that of Comparative Example 3. From this, it was found that the thermal stability of the composite cathode active materials of Examples 2 and 3 was improved.

Evaluation example 6: charge/discharge characteristic

The lithium batteries manufactured in Example 6, Example 8, and Comparative Examples 5 and 7 were charged at a constant current of 0.1C rate at 25°C until the voltage reached 4.35V (vs. Li), and then the voltage was reduced. It was discharged at a constant current of 0.1C rate until it reached 2.8V (vs. Li) (1 ^st cycle, formation cycle).

A lithium battery that has undergone 1 ^st cycle is charged at a constant current of 0.33C rate at 25°C until the voltage reaches 4.35V (vs. Li), and then cut off at a current of 0.05C rate while maintaining 4.35V in constant voltage mode. (cut-off). Subsequently, the discharge was performed at a constant current of 0.2C rate until the voltage reached 2.8V (vs. Li) (2 ^nd cycle).

A lithium battery that has undergone 2 ^nd cycles is charged at a constant current at 25°C at a current of 1C until the voltage reaches 4.35V (vs. Li), and then charged at a 1C rate until the voltage reaches 2.8V (vs. Li). Discharged at constant current (3 ^rd cycle).

The same conditions were repeated for lithium batteries that had undergone 3 ^rd cycles up to 53 ^th cycles.

In all of the above charge/discharge cycles, a pause of 20 minutes was allowed after one charge/discharge cycle.

Some of the results of the charge and discharge experiment are shown in Table 4 below. The capacity maintenance rate at 53 ^th cycle and the initial charge/discharge efficiency at 1 ^st cycle are defined by Equations 1 and 2 below.

[Equation 1]

Capacity maintenance rate [%] = [Discharge capacity at 53 ^th cycle / Discharge capacity at 3 ^rd cycle] × 100%

[Equation 2]

Initial efficiency [%] = [Discharge capacity in 1 ^st cycle / Charge capacity in 1 ^st cycle] × 100%

1 ^st cycle charging capacity
(mAh/g) initial efficiency
(%) ^2nd cycle
Discharge capacity
(mAh/g) Capacity maintenance rate
(%) Example 6 246 90 216 85 Example 7 246 90 213 84.8 Example 8 246 90 215.2 87.6 Comparative Example 5 246 92 221 65.7 Comparative Example 7 246 90 213 84

As shown in Table 4, the capacity retention rate of the lithium batteries of Examples 6 to 8 was significantly improved compared to the lithium battery of Comparative Example 5. The lithium battery of Comparative Example 5 had excellent initial efficiency, but the capacity maintenance rate was very low compared to that of Examples 6-8.

In addition, the lithium batteries of Examples 6 to 8 showed the same initial efficiency as the lithium battery of Comparative Example 7, but showed improved capacity maintenance ratio.

Additionally, the charge/discharge characteristics (initial efficiency and capacity maintenance rate) of the lithium batteries manufactured according to Comparative Examples 11-12 were measured using the same evaluation method as for the lithium batteries of Example 6 described above.

As a result, it was found that the lithium battery of Example 6 had improved initial efficiency and capacity maintenance rate compared to the lithium battery of Comparative Examples 11-12.

Evaluation example 7: charge/discharge characteristic

The lithium batteries prepared in Examples 11-13 and Comparative Example 13a were charged at a constant current of 0.1C rate at 25°C until the voltage reached 4.35V (vs. Li), and then the voltage was reduced to 2.8V (vs. Li). ) was discharged at a constant current of 0.1C rate (1 ^st cycle, formation cycle).

A lithium battery that has undergone 1 ^st cycle is charged at a constant current of 0.33C rate at 25°C until the voltage reaches 4.35V (vs. Li), and then cut off at a current of 0.05C rate while maintaining 4.35V in constant voltage mode. (cut-off). Subsequently, the discharge was performed at a constant current of 0.2C rate until the voltage reached 2.8V (vs. Li) (2 ^nd cycle).

A lithium battery that has undergone 2 ^nd cycles is charged at a constant current at 25°C at a current of 1C until the voltage reaches 4.35V (vs. Li), and then charged at a 1C rate until the voltage reaches 2.8V (vs. Li). Discharged at constant current (3 ^rd cycle).

The same conditions were repeated for lithium batteries that had undergone 3 ^rd cycles up to 53 ^th cycles.

In all of the above charge/discharge cycles, a pause of 20 minutes was allowed after one charge/discharge cycle.

Some of the results of the charge and discharge experiment are shown in Table 5 below.

1 ^st cycle charging capacity
(mAh/g) initial efficiency
(%) 2 ^nd cycle discharge capacity
(mAh/g) Capacity maintenance rate
(%) Example 11 247 90 220 90.6 Example 12 243 90 216 90.0 Example 13 241 90 212 90.0 Comparative Example 13a 247 88 216 89.5

As shown in Table 5, the lithium batteries of Examples 11 to 13 had improved initial efficiency and capacity maintenance rate compared to the lithium battery of Comparative Example 13a.

Evaluation example 8: charge/discharge characteristic

The lithium batteries prepared in Examples 8, 14-16, and Comparative Examples 5, 7, and 8a were charged at a constant current of 0.1C rate at 25°C until the voltage reached 4.35V (vs. Li), and then the voltage was It was discharged at a constant current of 0.1C rate until it reached 2.8V (vs. Li) (1 ^st cycle, formation cycle).

A lithium battery that has undergone 1 ^st cycle is charged at a constant current of 0.33C rate at 25°C until the voltage reaches 4.35V (vs. Li), and then cut off at a current of 0.05C rate while maintaining 4.35V in constant voltage mode. (cut-off). Subsequently, the discharge was performed at a constant current of 0.2C rate until the voltage reached 2.8V (vs. Li) (2 ^nd cycle).

A lithium battery that has undergone 2 ^nd cycles is charged at a constant current at 25°C at a current of 1C until the voltage reaches 4.35V (vs. Li), and then charged at a 1C rate until the voltage reaches 2.8V (vs. Li). Discharged at constant current (3 ^rd cycle).

The same conditions were repeated for lithium batteries that had undergone 3 ^rd cycles up to 53 ^th cycles.

In all of the above charge/discharge cycles, a pause of 20 minutes was allowed after one charge/discharge cycle.

Some of the results of the charge and discharge experiment are shown in Table 6 below.

Separately, high rate characteristics were evaluated according to the following method.

The lithium batteries prepared in Examples 8, 14-16, and Comparative Examples 5, 7, and 8a were charged at a constant current of 0.1C rate at 25°C until the voltage reached 4.35V (vs. Li), and then the voltage was It was discharged at a constant current of 0.1C rate until it reached 2.8V (vs. Li) (1 ^st cycle, formation cycle).

A lithium battery that has undergone 1 ^st cycle is charged at a constant current of 0.33C rate at 25°C until the voltage reaches 4.35V (vs. Li), and then cut off at a current of 0.05C rate while maintaining 4.35V in constant voltage mode. (cut-off). Subsequently, the discharge was performed at a constant current of 0.2C rate until the voltage reached 2.8V (vs. Li) (2 ^nd cycle).

A lithium battery that has undergone 2 ^nd cycles is charged at a constant current of 0.5C rate at 25°C until the voltage reaches 4.35V (vs. Li), and then cut off at a current of 0.05C while maintaining 4.35V in constant voltage mode. (cut-off). Subsequently, the discharge was performed at a constant current of 0.33C rate until the voltage reached 2.8V (vs. Li) (3 ^rd cycle).

A lithium battery that has undergone 3 ^rd cycles is charged at a constant current of 0.5C rate at 25°C until the voltage reaches 4.35V (vs. Li), and then cut off at a current of 0.05C while maintaining 4.35V in constant voltage mode. (cut-off). Subsequently, the discharge was performed at a constant current of 1C rate until the voltage reached 2.8V (vs. Li) ( ^4th cycle).

A lithium battery that has undergone 4 ^th cycles is charged at a constant current of 0.5C rate at 25°C until the voltage reaches 4.35V (vs. Li), and then cut off at a current of 0.05C while maintaining 4.35V in constant voltage mode. (cut-off). Subsequently, the discharge was performed at a constant current of 2C rate until the voltage reached 2.8V (vs. Li) (5 ^th cycle).

A lithium battery that has undergone 5 ^th cycles is charged at a constant current of 0.5C rate at 25°C until the voltage reaches 4.35V (vs. Li), and then cut off at a current of 0.05C while maintaining 4.35V in constant voltage mode. (cut-off). Subsequently, the discharge was performed at a constant current of 3C rate until the voltage reached 2.8V (vs. Li) ( ^6th cycle).

A lithium battery that has undergone 6 ^th cycles is charged at a constant current at 25°C at a current of 1C until the voltage reaches 4.35V (vs. Li), and then at a rate of 1C until the voltage reaches 2.8V (vs. Li). Discharge was performed at constant current (7 ^th cycle), and this cycle was repeated under the same conditions up to 56 ^th cycle.

In all of the above charge/discharge cycles, a pause of 20 minutes was allowed after one charge/discharge cycle.

Some of the results of the charge and discharge experiment 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 6 ^th cycle (3C rate) / Discharge capacity at 3 ^rd cycle (0.33C rate)] × 100

1 ^st cycle charging capacity
(mAh/g) initial efficiency
(%) High rate characteristics
(%) ^2nd cycle
Discharge capacity
(mAh/g) Capacity maintenance rate
(%) Example 8 246 90 92 216 86.6 Example 14 246 90 93 215 87.6 Example 15 245 89 93 213 87.6 Example 16 245 89 92 213 87.3 Comparative Example 8a 241 87 - - - Comparative Example 5 246 92 87 221 65.7 Comparative Example 7 246 90 92 214 85.2

The lithium batteries of Examples 8 and 14 to 16 shown in Table 6 had improved capacity retention rate and high rate characteristics compared to the lithium battery of Comparative Example 5. In addition, the lithium batteries of Examples 8 and 16 had equally excellent high-rate characteristics and improved capacity retention compared to the lithium battery of Comparative Example 7. And the lithium batteries of Examples 8, 14 to 16 showed improved initial efficiency compared to Comparative Example 8a.

Evaluation example 9: charge/discharge characteristic

The lithium batteries manufactured in Examples 9, 10, 17, 18, and Comparative Examples 8 and 15 were charged at a constant current of 0.1C rate at 25°C until the voltage reached 4.35V (vs. Li), and then the voltage was It was discharged at a constant current of 0.1C rate until it reached 2.8V (vs. Li) (1 ^st cycle, formation cycle).

A lithium battery that has undergone 1 ^st cycle is charged at a constant current of 0.33C rate at 25°C until the voltage reaches 4.35V (vs. Li), and then cut off at a current of 0.05C rate while maintaining 4.35V in constant voltage mode. (cut-off). Subsequently, the discharge was performed at a constant current of 0.2C rate until the voltage reached 2.8V (vs. Li) (2 ^nd cycle).

A lithium battery that has undergone 2 ^nd cycles is charged at a constant current of 1C rate at 25°C until the voltage reaches 4.35V (vs. Li), and then discharged until the voltage reaches 2.8V (vs. Li). Discharge was performed at a constant current of 1C rate (3 ^rd cycle).

The same conditions were repeated for lithium batteries that had undergone 3 ^rd cycles up to 53 ^th cycles.

In all of the above charge/discharge cycles, a pause of 20 minutes was allowed after one charge/discharge cycle.

Some of the results of the charge and discharge experiment are shown in Table 7 below.

1 ^st cycle charging capacity
(mAh/g) initial efficiency
(%) ^2nd cycle
Discharge capacity
(mAh/g) Capacity maintenance rate
(%) Example 9 246 91 217 92 Example 10 246 90 214 92 Example 17 238 93 218 95.2 Example 18 241 90 213 91.3 Comparative Example 8 242 91 216 90 Comparative Example 15 243 89 216 90

The capacity retention rate of the lithium batteries of Examples 9, 10, and 17 shown in Table 7 was significantly improved compared to the lithium batteries of Comparative Examples 8 and 15. In addition, the lithium battery of Example 9 had the same excellent initial efficiency as the lithium battery of Comparative Example 8, and the capacity maintenance rate was improved.

In addition, as shown in Table 7, the lithium battery of Example 18 showed improved capacity maintenance rate compared to the lithium battery of Comparative Example 8, and both initial efficiency and capacity maintenance rate were improved compared to the lithium battery of Comparative Example 15.

Evaluation example 10: High temperature (45℃) charge/discharge characteristic

1) Example 19 and Comparative Example 13

Each lithium battery (18650 minicell) was charged at a constant current of 0.1C rate at 45°C until the voltage reached 4.35V (vs. Li), then 0.1C until the voltage reached 2.8V (vs. Li). Discharge was performed at a constant current rate (1 ^st cycle, formation cycle).

A lithium battery that has undergone 1 ^st cycle is charged at a constant current of 0.33C rate at 45℃ until the voltage reaches 4.35V (vs. Li), and then cut off at a current of 0.05C rate while maintaining 4.35V in constant voltage mode. (cut-off). Subsequently, the discharge was performed at a constant current of 0.2C rate until the voltage reached 2.8V (vs. Li) (2 ^nd cycle).

A lithium battery that has undergone 2 ^nd cycles is charged at a constant current of 1C rate at 45°C until the voltage reaches 4.35V (vs. Li), and then discharged until the voltage reaches 2.8V (vs. Li). Discharge was performed at a constant current of 1C rate (3 ^rd cycle).

The lithium battery that had gone through 3 ^rd cycles was repeated under the same conditions for 302 ^th cycles at 45°C.

In all of the above charge/discharge cycles, a pause of 20 minutes was allowed after one charge/discharge cycle.

The capacity maintenance rate according to the number of cycles was evaluated and is shown in Figure 5.

Referring to FIG. 5, it was found that the capacity maintenance rate of the lithium battery of Example 19 was improved compared to that of Comparative Example 13.

The charge/discharge characteristics of the lithium batteries of Examples 20-21 and Comparative Examples 14-15 were evaluated in the same manner as the method for evaluating the charge/discharge characteristics of the lithium batteries of Example 19 and Comparative Example 12. The analysis results are shown in Figure 6.

Referring to this, it was found that the capacity retention rate characteristics of the lithium battery of Example 20-21 at 45°C were improved compared to the lithium battery of Comparative Example 14-15.

1: Lithium battery 2: Cathode
3: Anode 4: Separator
5: Battery case 6: Cap assembly

Claims (25)

Contains secondary particles,
The secondary particles include a plurality of primary particles containing lithium transition metal oxide having a layered crystal structure; And a composite positive electrode active material containing a coating film disposed between the surface of the secondary particles and the primary particles of the plurality of primary particles,
The coating film includes lithium cobalt complex oxide having a spinel crystal structure,
The lithium cobalt composite oxide contains cobalt (Co) and a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof,
The lithium cobalt composite oxide having a spinel crystal structure is a composite positive electrode active material that is a compound represented by the following formula (1):
[Formula 1]
Li _x Co _a Me _b O _4+δ
Formula 1, Me is a group 2 element, a group 12 element, a group 13 element, or a combination thereof,
1.0≤x≤1.1, 0<a<2, 0<b<2, 0<a+b≤2, -1.5≤δ≤0. According to paragraph 1,
The lithium cobalt composite oxide having the spinel crystal structure is 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 _.8 O _{4 +δ} (-0.9≤δ≤0), LiCo _{1 . 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≤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≤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 . 6} O _{4 +δ} (-1.3≤δ≤0), or LiCo _{0 . 4} Zn _{1 . 6} O _{4 +δ} (-1.3≤δ≤0) composite anode active material. delete According to paragraph 1,
In Formula 1, Me is a composite positive electrode active material that is Al, Ga, Mg, Ca, Ba, Zn, or a combination thereof. According to paragraph 1,
The lithium cobalt complex oxide having the spinel crystal structure is 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, Composite cathode active material with 0<a+b≤2, -1.5≤δ≤0. delete According to paragraph 1,
The lithium transition metal oxide having the layered crystal structure has a rock salt layered structure and belongs to the R-3m space group, and the lithium cobalt composite oxide belongs to the Fd-3m space group. According to paragraph 1,
A mixed phase exists between the lithium transition metal oxide and the coating film, and the mixed phase includes a combination of lithium transition metal oxide and lithium cobalt composite oxide. According to paragraph 1,
A composite positive electrode active material further comprising a compound having an amorphous structure between the primary particles, a compound having a layered crystal structure, or a combination thereof. According to claim 1,
The lithium transition metal oxide having a layered crystal structure is a composite cathode active material selected from the compounds represented by the following formulas 2 to 4:
[Formula 2]
_{Li x} Co _{1 - y} M _y O _{2 - α}
[Formula 3]
Li _x Ni _{1 - y Me y} O _{2 - α}
[Formula 4]
Li _{x Ni 1 -y- z} Mn _y Ma _z O _{2 - α}
In formulas 2 to 4, 0.9≤x≤1.1, 0≤y≤0.9, 0<z≤0.2, 0≤α≤2,
M is Ni, Mn, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Fe, Cu, B or a combination thereof,
Me is Co, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Mn, Fe, Cu, B or a combination thereof, and Ma is Co, Zr, Al, Mg, Ag, Mo, Ti, V , Cr, Fe, Cu, B or a combination thereof, and X is F, S, P or a combination thereof. It is an element. According to claim 1,
The lithium transition metal oxide having a layered crystal structure is a composite cathode active material selected from the compounds represented by the following formulas 5 to 7:
[Formula 5]
Li[Li _1-a Me _a ]O _{2 +d}
In Formula 5, 0.8≤a<1, 0≤d≤0.1,
Wherein Me is Ni, Co, Mn, Al, V, Cr, Fe, Zr, Re, B, Ge, Ru, Sn, Ti, Nb, Mo, Pt or a combination thereof,
[Formula 6]
Li[Li _1-xyz Ma _x Mb _y Mc _z ]O _2+d
In 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 independently Mn, Co, Ni, Al, or a combination thereof, [Formula 7]
Li[Li _1-xyz Ni _x Co _y Mn _z ]O _2+d
In Formula 7, 0.8≤x+y+z<1;0<x<1,0<y<1,0<z<1, 0≤d≤0.1. The composite cathode active material according to claim 1, wherein the lithium transition metal oxide is represented by the following formula (8):
[Formula 8]
aLi ₂ MnO _3- (1-a)LiMO ₂
In 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), and boron (B ), germanium (Ge), ruthenium (Ru), tin (Sn), titanium (Ti), niobium (Nb), molybdenum (Mo), platinum (Pt), or a combination thereof. According to paragraph 1,
The lithium transition metal oxide having a layered crystal structure is a composite cathode active material that is a compound represented by the following formula (9):
[Formula 9]
Li _x Ni _{1 -y- z} M _y Co _z O ₂
In Formula 9, 0.90≤x≤1.1, 0≤y≤0.2, 0<z≤0.2, 0.7≤1-yz≤0.99.
M is manganese (Mn), aluminum (Al), titanium (Ti), calcium (Ca), or a combination thereof. According to paragraph 1,
A composite cathode active material wherein at least one secondary particle containing the lithium transition metal oxide having the layered crystal structure has an average particle diameter of 10 to 20 ㎛. According to paragraph 1,
The lithium transition metal oxide having a layered crystal structure is a composite cathode active material that is a compound represented by the following Chemical Formula 9a:
[Formula 9a]
Li _x Ni _1-yz Mn _x Co _y O ₂
In Formula 9a, 0.80≤x≤1.1, 0≤y≤0.2, 0<z≤0.2, 0.8≤1-yz≤0.99. According to paragraph 1,
The lithium transition metal oxide having the layered crystal structure is 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 Composite cathode active material. According to paragraph 1,
The content of lithium cobalt composite oxide or the total content of cobalt and metal (M) in the coating film is 0.01 to 20 parts by weight based on 100 parts by weight of lithium transition metal oxide having a layered crystal structure. According to paragraph 1,
A composite cathode active material in which the residual lithium content of the composite cathode 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. According to paragraph 1,
A composite cathode active material in which the coating film covers more than 50% of the surface of a lithium transition metal oxide having a layered crystal structure. According to paragraph 1,
A composite positive electrode active material wherein the coating film has a thickness of 1㎛ or less. A positive electrode comprising the composite positive electrode active material of any one of claims 1, 2, 4, 5, and 7 to 20. The anode of paragraph 21; cathode; and an electrolyte disposed between the anode and the cathode. Preparing a lithium transition metal oxide having a layered crystal structure;
A lithium transition metal oxide having the layered crystal structure, a lithium cobalt complex having a spinel crystal structure and containing cobalt (Co), a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof. Obtaining a composite positive electrode active material composition by mixing oxide precursors; and
Claims 1, 2, 4, 5, 7 to 20, including drying the composite positive active material composition and heat treating it in an oxidizing gas atmosphere in a range exceeding 400°C and below 1000°C. A method of manufacturing a composite cathode active material for producing the composite cathode active material of any one of the clauses. According to clause 23,
A lithium transition metal oxide having the layered crystal structure, a lithium cobalt composite oxide containing cobalt (Co) having a spinel crystal structure, a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof. A method for producing a composite positive electrode active material in which mixing of precursors is performed wet in the presence of a solvent. According to clause 23,
A method of producing a composite positive electrode active material in which the heat treatment is performed at 700 to 750°C and the temperature increase rate during heat treatment is 1 to 10°C/min.

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