KR20190024680A - Composite cathode active material, preparation method thereof, cathode and Lithium battery containing composite cathode active material - Google Patents

Abstract

A composite positive electrode active material, a positive electrode and a lithium battery comprising the same are provided. The composite positive electrode active material comprises secondary particles, wherein the secondary particles comprise: a plurality of primary particles comprising lithium transition metal oxides having a layered crystal structure; and a coating film disposed between a surface of the secondary particle and a primary particle of the plurality of primary particles. The coating film comprises a lithium cobalt composite 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.

Description

TECHNICAL FIELD The present invention relates to a composite cathode active material, a method for producing the same, a positive electrode and a lithium battery including the composite cathode active material, a preparation method thereof,

A composite cathode active material, a method of manufacturing the same, and a positive electrode and a lithium battery employing the same.

In order to meet the miniaturization and high performance of various devices, besides the miniaturization and weight reduction of lithium batteries, higher energy density is becoming important. A nickel-based cathode active material having a high capacity has been studied to realize a lithium battery that meets this importance.

The conventional nickel-based cathode active material is degraded in life characteristics due to high surface residual lithium content and side reaction by cationic mixing, and the thermal stability is not reached to 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 comprising the complex cathode active material.

Another aspect is to provide a lithium battery including the anode and having improved lifetime and cell capacity.

Another aspect of the present invention provides a method for producing the composite cathode active material.

On one side

Comprising secondary particles,

Wherein the secondary particles comprise a plurality of primary particles comprising a 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 comprises a lithium cobalt composite oxide having a spinel crystal structure,

The lithium-cobalt composite oxide is provided with a composite cathode active material containing cobalt (Co) and Group 2, Group 12, and Group 13 elements, or a combination thereof.

According to another aspect, there is provided a positive electrode comprising the aforementioned composite positive electrode active material.

According to yet another aspect, there is provided a lithium battery including the above-described anode.

According to another aspect

Preparing a lithium transition metal oxide having a layered crystal structure;

A lithium transition metal oxide having the layered crystal structure and a lithium cobalt complex having a spinel crystal structure and containing cobalt (Co) and a Group 2 element, a Group 12 element, a Group 13 element or a combination thereof, Oxide precursor to obtain a composite cathode active material composition; And

Drying the composite cathode active material composition, and heat treating the composite cathode active material composition in an oxidizing gas atmosphere at a temperature higher than 400 ° C. and lower than 1000 ° C. to produce the composite cathode active material.

According to one aspect, the composite cathode active material has reduced surface residual lithium content and improved thermal stability. This can improve the charging / discharging characteristics and life characteristics of the lithium battery.

FIG. 1A schematically shows a structure of a composite cathode active material according to one embodiment.
FIG. 1B shows a scanning electron microscopic analysis result of the composite cathode active material prepared according to Example 1. FIG.
2A to 2C are SEM micrographs of the composite cathode active material powder prepared according to Example 4a, Comparative Example 2 and Comparative Example 4, respectively.
FIG. 3 is an X-ray diffraction (XRD) spectrum of the composite cathode active material prepared according to Example 1. FIG.
FIG. 4 shows a structure of a lithium battery employing a positive electrode comprising a complex cathode active material according to an embodiment.
5 shows the high-temperature lifetime characteristics of a lithium battery (18650 minicell) produced according to Example 19 and Comparative Example 13.
6 shows high temperature lifetime characteristics of a lithium battery (18650 minicell) produced according to Examples 20-21 and Comparative Examples 14-15.

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

A plurality of primary particles comprising secondary particles, the secondary particles comprising a 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 a lithium cobalt composite oxide having a spinel crystal structure, and the lithium The cobalt composite oxide is provided with a composite cathode active material containing cobalt (Co), a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof.

The coating film may be present between the grain boundaries of the adjacent primary particles and on the surface of the secondary particles. And " between primary particles " can be interpreted to include both the grain boundary of primary particles and the surface of primary particles. The coating film containing the lithium-cobalt composite oxide is present between the surface of the secondary particles and the grain boundaries of the primary particles, so that the conductivity of lithium ions can be improved. Although not limited by theory, the content of residual lithium present on the surface of the composite cathode active material is reduced, deterioration of the composite cathode active material is suppressed, gas generation is reduced, and thermal stability of the lithium battery can be improved. The above-mentioned coating film disposed at the grain boundaries between adjacent primary particles exists to accommodate volume change due to charging and discharging of primary particles to suppress cracking of primary particles, thereby suppressing the mechanical strength deterioration of the composite cathode active material even after long- have. Further, the side reaction between the lithium transition metal oxide having a layered crystal structure and the electrolyte can be effectively suppressed, and the internal resistance of the lithium battery can be reduced, thereby improving the cycle characteristics of the lithium battery.

Herein, 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 a 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 .

[Chemical 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,

0 < a < 2, 0 < b <

In the formula (1), x is, for example, 1.0 to 1.09, a is 0.4 to 1.6, and b is 0.4 to 1.6. And the sum of a and b is 2, for example. In the formula 1, 0.1 <a + b? 2, for example 0.2 <a + b? 2, for example 0.5 <a + b? 1 < a + b? 2.

In Formula 1, M is Al, Ga, Mg, Ca, Ba, Zn, or a combination thereof.

Compounds of the formula I, for example, _{Li x Co a Al b O 4} + δ, Li x Co a Zn b O 4 + δ, Li x LiCo a Mg b O 4 + δ, Li x Co a Ga b O 4+ _? , Li _x Co _a Ca _b O _{4 +?,} or Li _x Co _a Ba _b O _{4 + ?} . In the above formula, 1.0? X? 1.1, 0 <a <2, 0 <b <2, 0 <a + b? 2, and -1.5? 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.

The compound of formula (1) is, for example, LiCo _{1 . 5} Al _{0 . 5} O _{4 +?} (-0.5??? ₀ ), LiCo _{1 . 5} Ga _{0 . 5} O _{4 +?} (-0.5??? ₀ ), LiCo _{1 . 33} Zn _{0 . 67} O _{4 +?} (-0.835??? ₀ ), LiCo _{1 . 33} Ca _{0 . 67} O _{4 +?} (-0.835??? ₀ ), LiCo _{1 . 33} Ba _{0 . 67} O _{4 +?} (-0.835??? ₀ ), LiCo _{1 . 33} Ga _{0 . 67} O _{4 +?} (-0.835??? ₀ ), LiCo _{1 . 2} Mg _{0 . 8} O _{4 +?} (-0.9??? ₀ ), LiCo _{1 . 2} Ga _{0 . 8} O _{4 +?} (-0.9??? 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 +?} (-0.9??? ₀ ), LiCo _{1 . 6} Mg _{0 . 4} O _{4 +?} (-0.7??? ₀ ), LiCo _{1 . 6} Ga _{0 . 4} O _{4 +?} (-0.7??? ₀ ), LiCo _{1 . 6} Ca _{0 . 4} O _{4 +?} (-0.7??? ₀ ), LiCo _{1 . 6} Ba _{0 . 4} O _{4 +?} (-0.7??? ₀ ), LiCo _{1 . 6} Zn _{0 . 4} O _{4 +?} (-0.7??? ₀ ), LiCo _{0 . 8} Mg _{1 . 2} O _{4 +?} (-1.1??? ₀ ), LiCo _0.8 Ga _1.2 O _{4 +?} (-1.1??? ₀ ), LiCo _{0 . 8} Ca _{1 . 2} O _{4 +?} (-1.1??? ₀ ), LiCo _{0 . 8} Ba _{1 . 2} O _{4 +?} (-1.1??? ₀ ), LiCo _{0 . 8} Zn _{1 . 2} O _{4 +?} (-1.1??? ₀ ), LiCo _{0 . 4} Mg _{1 . 6} O _{4 +?} (-1.3??? ₀ ), LiCo _{0 . 4} Ga _{1 . 6} O _{4 +?} (-1.3??? ₀ ), LiCo _{0 . 4} Ca _{1 . 6} O _{4 +?} (-1.3??? ₀ ), LiCo _{0 . 4} Ba _{1 . 6} O _{4 +?} (-1.3??? 0), LiCo _0.4 Zn _1.6 O _{4 +?} (-1.3 _?

The compound of formula (1) is, for example, LiCo _{1 . 5} Al _{0 . 5} O _{4 +?} (-0.5??? ₀ ), LiCo _{1 . 33} Zn _{0 . 67} O _{4 +?} (-0.835??? ₀ ), LiCo _{1 . 2} Mg _{0 . 8} O _{4 +?} (-0.9??? ₀ ), LiCo _{1 . 6} Mg _{0 .} There are _{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 a layered crystal structure belongs to a rock salt layered structure (R-3m space group), and the cobalt (Co) having the spinel crystal structure and a Group 2 element, Element, a Group 13 element or a combination thereof belong to the Fd-3m space group. By having the above-described crystal structure, the cycle characteristics and the thermal stability of the lithium battery including the 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 " cohere together to form secondary particles, wherein the primary particles can have various shapes ranging from rod to square, and the term " secondary particle " includes a plurality of primary particles, Refers to non-aggregate particles or particles that are no longer aggregated, and secondary particles may have a spherical shape. FIG. 1A is a cross-sectional view conceptually showing the microstructure of secondary particles in the composite cathode active material according to one embodiment. FIG.

Referring to this, it can be seen that primary particles 11 aggregate to form secondary particles 12 and form interstitial spaces 13 between primary particles 11, for example primary particles 14 and / 15).

The transition metal contained in the lithium transition metal oxide in the composite cathode active material may have a nickel content of 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 in the transition metal contained in the lithium transition metal oxide in the composite cathode active material is, for example, 70 to 99.9 mol%, for example, 80 to 95 mol% based on the total content of the transition metal of the lithium transition metal oxide . When the lithium transition range having a content of nickel above using the metal oxide can be prepared in high-capacity lithium battery.

A coating film comprising a cobalt (Co) having a spinel crystal structure and a lithium cobalt composite oxide containing a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof in a composite cathode active material is a composite cathode active material It can be arranged at a uniform concentration throughout. The composite cathode active material may have a concentration gradient from the center portion to the surface portion. For example, the concentration of the lithium-cobalt composite oxide in the center portion of the composite cathode active material may be low and the concentration of the coating layer including the lithium-cobalt composite oxide in the surface portion may be high. According to another embodiment, the concentration of the lithium cobalt composite oxide may be high in the center portion of the composite cathode active material, and the concentration of the lithium cobalt composite oxide may be low in the surface portion.

The content of the lithium cobalt complex 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 the 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.

The content of lithium cobalt in the coating film is 0.01 to 20 parts by weight, for example, 0.1 to 10 parts by weight, based on 100 parts by weight of the lithium transition metal oxide having a layered crystal structure, For example, 0.1 to 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 range, a composite cathode active material having excellent thermal stability and reduced surface residual lithium content can be obtained. By using this, a lithium battery improved in charge / discharge characteristics and life characteristics can be produced.

According to another embodiment, the total content of cobalt and metal (M) in the lithium cobalt complex 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, 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 layer. The mixed phase may mean a mixed structure of a layered crystal structure and a spinel crystal structure.

A compound having an amorphous structure between the primary particles, a compound having a layered crystal structure, or a combination thereof.

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

(2)

Li _x Co _{1 - y} M _y O _{2 - ?} X _?

(3)

Li _x Ni _{1 - y} Me _y O _{2 - ?} X _?

[Chemical Formula 4]

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

In the general formulas (2) to (4), 0.9? X? 1.1, 0? Y? 0.9, 0 <z? 0.2, 0?

Wherein M is at least one element selected from the group consisting of Co, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Fe, Wherein M is selected from the group consisting of Co, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Fe, Cu, B, , S, P, or a combination thereof.

In the general 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 selected from the compounds represented by the following formulas (5) to (7).

[Chemical Formula 5]

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

In formula (5), 0.8? A <1, 0? D?

Wherein Me is at least one metal selected from the group consisting of Ni, Co, Mn, Al, V, Cr, Fe, Zr, Re, B, Ge, Ru, Sn, Ti,

[Chemical Formula 6]

Li [Li _{1- xy z} Ma _x Mb _y Mc _z ] O _{2 + d}

X <y <1, 0 <x <1, 0 <y <1, 0 <z <1, 0? D?

Ma, Mb and Mc are at least one metal selected from the group consisting of Mn, Co, Ni and Al,

(7)

Li [Li _{1- xy z} Ni _x Co _y Mn _z ] O _{2 + d}

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).

[Chemical Formula 8]

aLi ₂ MnO _{3 -} (1-a) LiMO ₂

In formula (8), 0 < a < 1,

M is at least one element selected from the group consisting of Ni, Co, Mn, V, Cr, Fe, Zr, ), Ge, Ge, Ru, Sn, Ti, Nb, Mo and Pt.

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

[Chemical Formula 9]

Li _x Ni _{1 - y - z} M _y Co _z O ₂

In the formula (9), 0.9? X? 1.1, 0? Y? 0.2, 0 <z? 0.2, and 0.7? 1-y-z?

M is selected from the group consisting of Mn, Al, Ti and 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 formula (9a).

[Formula 9a]

Li _x Ni _{1- y- z} Mn _x Co _y O ₂

In the formula (9a), 0.80? X? 1.1, 0 = y? 0.2, 0 <z? 0.2, and 0.8? 1-y-z?

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

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

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

In the composite cathode active material, the average particle diameter of the secondary particles agglomerated by the primary particles may be about 1 탆 to about 30 탆, for example, 10 to 20 탆, for example, about 13 탆 to about 15 탆, And can be adjusted within a range that can provide improved charge / discharge characteristics of the lithium battery.

For example, the thickness of the coating film in the composite cathode active material may be 1 μm or less, for example, 500 nm or less, 200 nm or less, such as 100 nm or less, such as 50 nm or less such as 30 nm or less, For example, 30 nm to 200 nm, for example, 30 nm to 100 nm. The cycle characteristics and thermal stability of the lithium battery including the composite cathode active material in the thickness range of the coating film can be further improved.

According to one embodiment, in the composite cathode active material, the grain boundary has an average grain boundary length of from about 50 nm to about 1000 nm, an average grain boundary thickness of from about 1 nm to about 200 nm, the length direction parallel to the surface of the adjacent primary grain , The direction of thickness may be perpendicular to the surface of adjacent primary particles. 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. It is possible to provide further improved charge / discharge characteristics within the range of the average grain boundary length and the average grain boundary thickness.

According to another embodiment, a method of manufacturing a composite cathode active material includes the steps of: preparing a lithium transition metal oxide having a layered crystal structure; A lithium transition metal oxide having a layered crystal structure and cobalt (Co) having a spinel crystal structure and lithium containing a Group 2 element, a Group 12 element, a Group 13 element or a combination thereof, Cobalt composite oxide to obtain a composite cathode active material composition; And drying the composite cathode active material composition and subjecting the composite cathode active material composition to a heat treatment at 400 ° C or higher and 1000 ° C or lower under an oxidizing gas atmosphere.

A lithium transition metal oxide having a layered crystal structure and cobalt (Co) having a spinel crystal structure and lithium containing 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 may be carried out 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, and may be, for example, air having an increased oxygen content.

In the composite cathode active material composition, a precursor of a lithium-cobalt composite oxide containing cobalt (Co) having a spinel crystal structure and a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof, Is not more than 300 parts by weight based on 100 parts by weight of the lithium transition metal oxide having the layered crystal structure. The content of the precursor of the lithium cobalt composite oxide containing cobalt (Co) having the spinel crystal structure and the Group 2 element, the Group 12 element, the Group 13 element, or a combination thereof in the composite cathode active material composition is 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 heating rate during the heat treatment is, for example, 1 to 10 占 폚 / min. The rate of temperature rise is controlled in the range of 1 to 10 占 폚 / min, for example, about 2占 폚 / min so as to reach the heat treatment temperature. (Co) having a spinel crystal structure and a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof, between the surface of the secondary particles and the primary particles when the heat treatment temperature and the rate of temperature rise are in the above- A coating film containing a lithium-cobalt composite oxide containing water can be disposed.

The precursor of the lithium cobalt composite oxide is obtained by mixing the cobalt precursor and the M precursor and then mixing the solvent with the precursor mixture. Mixing the precursor mixture lamellar (layered) in the lithium transition metal oxide having a crystal structure is obtained, and a lithium transition metal oxide having a lamellar (layered) structure compound crystal coating film is arranged to be represented by the formula (10) by performing a precipitation reaction. Followed by heat treatment to obtain the desired composite cathode active material.

The cobalt precursors may be, for example, cobalt chloride, cobalt nitrate, cobalt sulfate, and the like, and the M precursor may be variously used in the same manner as the cobalt precursor except that the precursor is M instead of cobalt.

The composite cathode active material according to one embodiment may have a calorific value of 90% or less of the secondary particles including the lithium transition metal oxide having a layered crystal structure in the composite cathode active material. And the residual lithium of the composite cathode active material is 90% or less of the residual lithium of the secondary particles containing the lithium transition metal oxide having a layered crystal structure.

Prior to the surface treatment for residual lithium removal of the composite cathode active material, residual lithium can be effectively reduced to, for example, about 4,000 parts per million (ppm) and up to 2,000 ppm or less after surface treatment. The cell capacity of the composite cathode active material is 220 mAh / g and the lifetime is 50 times or more.

Also, the lithium cobalt composite oxide containing cobalt (Co) having a spinel crystal structure and a Group 2 element, a Group 12 element, a Group 13 element, or a combination thereof has at least 50% or more of the surface of the lithium transition metal oxide . With such a structure, the side reaction of the lithium transition metal oxide and the electrolyte can be substantially reduced and / or effectively minimized or effectively blocked.

The anode according to another embodiment may include the composite cathode active material described above.

The positive electrode is prepared, for example, by mixing the composite positive electrode active material, the conductive agent, the binder and the solvent described above. The positive electrode active material composition is directly coated on the aluminum current collector and dried to prepare a positive electrode having a positive electrode active material layer. Alternatively, the cathode active material composition may be cast on a separate support, and then a film obtained by peeling the support from the support may be laminated on the aluminum current collector to produce a cathode in which the cathode active material layer is formed.

Examples of the conductive agent include carbon black, graphite fine particles, natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fiber; Carbon nanotubes; Metal powder or metal fiber or metal tube such as copper, nickel, aluminum, or silver; Conductive polymers such as polyphenylene derivatives, and the like can be used, but the present invention is not limited thereto, and any conductive polymer may be used as the conductive polymer in the art.

Examples of the binder include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), a mixture of the above-mentioned polymers, a styrene butadiene rubber- Polymer, etc. may be used. As the solvent, N-methylpyrrolidone (NMP), acetone, water and the like may be used, but not limited thereto, and any of them can be used in the technical field.

The content of the composite cathode active material, the conductive agent, the binder, and the solvent is a level commonly used in a lithium battery. At least one of the conductive agent, the binder and the solvent may be omitted depending on the use and configuration of the lithium battery.

In addition, the anode may further include a general cathode active material other than the composite cathode active material described above.

The above general cathode active material is a lithium-containing metal oxide, and any of those commonly used in the art can be used without limitation. For example, at least one of complex oxides of metal and lithium selected from cobalt, manganese, nickel, and combinations thereof may be used. Specific examples thereof include Li _a A _{1 - b} B _b D ₂ 0.90? A? 1, and 0? B? 0.5); Li _a E _{1 - b} B _b O _{2 - c} D _{c where} 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05; LiE _{2 - b} B _b O _{4 - c} D _{c where} 0? B? 0.5, 0? C? 0.05; Li _a Ni _{1 -b- c} Co _b B _c D _{? Wherein} 0.90? A? 1, 0? B? 0.5, 0? C? 0.05, 0 <?? 2; Li _a Ni _{1 -b- c} Co _b B _c O _{2 - ?} F _{? Where} 0.90? A? 1, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _{1 -b- c} Co _b B _c O _{2 - ?} F ₂ wherein 0.90? A? 1, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _{1 -b- c} Mn _b B _c D _? Wherein, in the formula, 0.90? A? 1, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _{1 -b- c} Mn _b B _c O _{2 - ?} F _? Wherein? 0.90? A? 1, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _{1 -b- c} Mn _b B _c O _{2 - ?} F ₂ wherein 0.90? A? 1, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _b E _c G _d O ₂ wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, and 0.001 ≤ d ≤ 0.1; Li _a Ni _b Co _c Mn _d GeO ₂ wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, and 0.001 ≤ e ≤ 0.1; Li _a NiG _b O ₂ (in the above formula, 0.90? A? 1, and 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); LiFePO ₄ can be used. As a general cathode active material, a combination of the compounds listed above can be used.

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 combinations 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, those having a coating film on the surface of the positive electrode compound may be used, or a compound having a coating film and the above compound may be mixed and used. The coating film may contain, as a coating element, an oxide, a hydroxide, an oxyhydroxide, an oxycarbonate, a hydroxycarbonate or a combination thereof. The compound constituting these coating films may be amorphous or crystalline. As the coating element included in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof may be used. The coating film forming process may be any coating method as long as it can coat the above compound by a method that does not adversely affect physical properties of the cathode active material (for example, spray coating, dipping, etc.) by using these elements, It will be understood by those skilled in the art that a detailed description will be omitted.

According to another embodiment, the positive electrode may be manufactured by using the composite positive electrode active material according to one embodiment as a positive electrode active material and by using the positive electrode active material having a small particle size. Thus, the anode may contain a bimodal cathode active material.

A lithium battery according to another embodiment employs an anode, a cathode, and an electrolyte disposed therebetween including the complex cathode active material. The lithium battery can be produced by the following method.

First, a positive electrode is manufactured according to the above-described method of manufacturing the positive electrode.

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

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

In addition, the negative electrode active material can be used as the negative electrode active material of the lithium battery in the related art. For example, a lithium metal, an element capable of alloying with lithium, a transition metal oxide, a non-transition metal oxide, a carbon-based material, or a combination thereof.

For example, the lithium-alloying element may be an element selected from the group consisting of Si, Sn, Al, Ge, Pb, Bi, Sb Si-Y alloy (Y is an alkali metal, an alkaline earth metal, a Group 13 to 16 element, A combination element thereof and not Si), a Sn-Y alloy (Y is an alkali metal, an alkaline earth metal, a Group 13 to Group 16 element, a transition metal, a rare earth element or a combination element thereof, but not Sn) have. The element Y may be at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Se, Te, Po, or a combination thereof.

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

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

The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite such as natural graphite or artificial graphite in an amorphous, plate-like, flake, spherical or fibrous shape, and the amorphous carbon may be soft carbon or hard carbon carbon, mesophase pitch carbide, calcined coke, and the like.

The content of the negative electrode active material, the conductive agent, the binder and the solvent is a level commonly used in a lithium battery.

Next, a separator to be inserted between the positive electrode and the negative electrode is prepared. The separator is usable as long as it is commonly used in a lithium battery. A material having low resistance against the ion movement of the electrolyte and excellent in the ability to impregnate the electrolyte may be used. For example, selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be nonwoven fabric or woven fabric. For example, a rewindable separator such as polyethylene, polypropylene, or the like is used for the lithium ion battery, and a separator having excellent organic electrolyte impregnation capability can be used for the lithium ion polymer battery. For example, the separator may be produced according to the following method.

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

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

Next, the electrolyte is prepared.

For example, the electrolyte may be an organic electrolyte. In addition, the electrolyte may be a solid. For example, boron oxide, lithium oxynitride, and the like, but not limited thereto, and any of them can be used as long as they can be used as solid electrolytes in the art. The solid electrolyte may be formed on the cathode by a method such as sputtering.

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

The organic solvent may be any organic solvent which can be used in the art. Examples of the solvent include 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, , N, N-dimethylformamide, dimethylacetamide, dimethylsulfoxide, tetrahydrofuran, tetrahydrofuran, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, , Dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether or mixtures thereof.

The lithium salt may also be used as long as it can be used in the art as a lithium salt. For example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiAlO ₂ , LiAlCl ₄ , _{x F 2x + 1 SO 2)} (C y F 2y + 1 SO 2) ( stage x, y are natural numbers), LiCl, LiI or a lithium battery (1) as shown in these mixtures and the like. FIG. 4 Includes a positive electrode 3, a negative electrode 2, and a separator 4. The anode 3, the cathode 2 and the separator 4 described above are wound or folded and housed in the battery case 5. Then, the organic electrolyte is injected into the battery case 5 and sealed with a cap assembly 6, thereby completing the lithium battery 1. The battery case may have a cylindrical shape, a rectangular shape, a thin film shape, or the like. For example, the lithium battery may be a large-sized thin-film battery. The lithium battery may be a lithium ion battery. A separator may be disposed between the anode and the cathode to form a battery structure. The cell structure is laminated in a bi-cell structure, then impregnated with an organic electrolyte solution, and the obtained result is received in a pouch and sealed to complete a lithium ion polymer battery.

In addition, a plurality of battery assemblies may be stacked to form a battery pack, and such battery pack may be used for all devices requiring high capacity and high output. For example, a notebook, a smart phone, an electric vehicle, and the like.

Further, the lithium battery is excellent in life characteristics and high-rate characteristics, and thus can be used in an electric vehicle (EV). For example, a hybrid vehicle such as a plug-in hybrid electric vehicle (PHEV). It can also be used in applications where a large amount of power storage is required. For example, an electric bicycle, a power tool, and the like.

When the lithium battery is charged up to a voltage of 4.5 V or more with respect to the lithium metal at the time of the initial charging, the lithium secondary battery activates the spinel crystal structure belonging to the Fd-3m space group including the second lithium transition metal oxide of the shell, The discharge capacity can be utilized. Therefore, the initial charge / discharge capacity of the lithium battery can be improved.

The following Examples and Comparative Examples further illustrate the present invention in more detail and do not limit the scope of the present invention.

Comparative Example  One: Lithium transition metal  Manufacture of oxides

NiSO ₄ (H ₂ O) ₆ , CoSO ₄ and MnSO ₄ H ₂ O were added to water in a molar ratio of 91: 6: 3 to prepare a precursor aqueous solution. By stirring the aqueous solution neutralized with the precursor solution was slowly added dropwise an aqueous solution of sodium hydroxide Ni _{0. 91} Co _{0 . 06} to precipitate the Mn _{0 .03} (OH) _2. Drying the precipitate by filtration, washed with water and 120 ℃ to prepare a metal _{(Ni 0. 91 Co 0.} 06 Mn 0 .03) hydroxide powder.

The metal hydroxide powder and LiOH were mixed and then heat-treated at 765 ° C for 20 hours while flowing oxygen into a furnace to prepare a lithium transition metal oxide (Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ ) .

Comparative Example  2: Lithium transition metal  Manufacture 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 treatment was performed at 710 ° C. for 40 hours embodiment, and as in the Comparative example 1 except that the content of LiOH lithium transition metal oxide is controlled so as to obtain a _{(Li 1. 09 Ni 0.} 878 Co 0. 080 Mn 0. 040 Al 0. 002 O 2) for A lithium transition metal oxide (Li _1.09 Ni _0.878 Co _0.080 Mn _0.040 Al _0.002 O ₂ ) was prepared in the same manner.

Comparative Example  3: Composite cathode active material  Produce

CoCl ₂ · was then prepared H ₂ O 0.75 parts by weight of distilled water and added to 10 parts by weight to prepare an aqueous solution followed by stirring for one minute at room temperature.

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

The mixture was dried in an oven at 150 &lt; 0 &gt; C for 15 hours to prepare a dried product.

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

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

Comparative Example  3a: Composite cathode active material  Produce

MgCl ₂ · was then prepared H ₂ O 0.75 parts by weight of distilled water and added to 10 parts by weight to prepare an aqueous solution followed by stirring for one minute at room temperature.

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

The mixture was dried in an oven at 150 &lt; 0 &gt; C for 15 hours to prepare a dried product.

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

The composite cathode active material is Li _{1 . 05} Ni _{0 . 91} Co _{0 . 06} Mn _{0 . And a} coating film of LiMgO _{2 + delta} (-0.5??? 0) was disposed between the surface of the ₀₃ O ₂ secondary particles and the primary particles. The content of magnesium in the LiMgO _{2 +?} (-0.5??? 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  Produce

Li ₁ obtained according to Comparative Example 1 _{. 05} Ni _{0 . 91} Co _{0 . 06} Mn _{0 .} 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 in place of ₀₃ O ₂ , Was changed to be 0.5 part by weight based on 100 parts by weight of the composite cathode active material, a composite cathode active material was obtained in the same manner as in Comparative Example 3.

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

Example  One: Composite cathode active material  Produce

0.75 parts by weight of a mixed precursor of Co (NO ₃ ) ₂揃 6H ₂ O and Al (NO ₃ ) ₃揃 9H ₂ O at a molar ratio of 3: 1 was prepared and then added to 10 parts by weight of distilled water. And the mixture was stirred for 1 minute to prepare an aqueous solution.

The Li _{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 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 cathode active material precursor. The composite cathode active material precursor had a structure in which a cobalt aluminum hydroxide coating layer containing cobalt and aluminum in a molar ratio of 3: 1 was disposed on Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ .

The composite cathode active material precursor was charged into a furnace and heat-treated at 720 ° C for 5 hours in an oxygen atmosphere to obtain a composite cathode active material. Composite positive electrode active material is _{Li 1.05 Ni 0.91 Co 0.06 Mn 0.03} O LiCo 1 having a spinel crystal structure between the surface and the primary particles of the secondary particles of the _{two. 5} Al _{0 . 5} O _{4 +?} (-0.5??? 0) coating film was disposed. LiCo ₁ in composite cathode active material _{. 5} Al _{0 . 5} O _{4 + δ} (-0.5≤δ≤0) amount of cobalt and aluminum in the coating film is a lithium transition metal oxide _{(Li 1. 05 Ni 0.} 91 Co 0. 06 Mn 0. 03 O 2) 100 parts by weight based on the total weight 0.75 parts by weight.

Example  2: Composite cathode active material  Produce

Co (NO ₃ ) ₂ .6H ₂ O and Zn (NO ₃ ) ₂ .6H ₂ O were used instead of the mixed precursor of Co (NO ₃ ) ₂ .6H ₂ O and Al (NO ₃ ) ₃ .9H ₂ O in a molar ratio of 3: ₂ O in a mixed cathode precursor of LiCo _{1. 2} in a mixed cathode precursor in which the content of Co (NO ₃ ) ₂ .6H ₂ O and Al (NO ₃ ) ₃ .9H ₂ O was finally obtained _{. 33} Zn _{0 .} The content of cobalt zinc in the ₆₇ O _{4 +?} (-0.835??? 0) coating film was controlled to be 0.50 parts by weight based on 100 parts by weight of the lithium transition metal oxide, and the same procedure as in Example 1 was carried out Li _{1 . 05} Ni _{0 . 91} Co _{0 . 06} Mn _{0 . 03} LiCo ₁ having a spinel crystal structure between the surface of the secondary particles of O ₂ and the primary particles _{. 33} Zn _{0 . 67} O _{4 +?} (-0.5??? 0) coating film was formed.

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

LiCo ₁ in composite cathode active material _{. 33} Zn _{0 .} Except that the content of cobalt zinc in the ₆₇ O _{4 +?} (-0.835??? 0) 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 the lithium transition metal oxide, respectively The procedure of Example 2 was repeated to obtain a composite cathode active material.

Example  3: Composite cathode active material  Produce

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

Example  3a: Composite cathode active material  Produce

Except that a mixed precursor of Co (NO ₃ ) ₂ .6H ₂ O and Mg (NO ₃ ) ₂ .6H ₂ O in a molar ratio of 4: 1 was used as a precursor, Li _{1.05 Ni 0.91 Co 0.06 Mn 0.03 O} LiCo 1 having a spinel crystal structure between the surface and the primary particles of the secondary particles of the _{two. 6} Mg _{0 . 4} O _{4 +?} (-0.7??? 0) coating film was formed. LiCo ₁ in composite cathode active material _{. 6} Mg _{0 .} The content of cobalt magnesium in the ₄ O _{4 +?} (-0.7??? 0) coating film was 0.75 parts by weight based on 100 parts by weight of the lithium transition metal oxide.

Example  3b: Composite cathode active material  Produce

Except that a mixed precursor of Co (NO ₃ ) ₂ .6H ₂ O and Mg (NO ₃ ) ₂ .6H ₂ O in a molar ratio of 2: 3 was used as a precursor, Li _{1.05 Ni 0.91 Co 0.06 Mn 0.03 O} LiCo 0 having a spinel crystal structure between the surface and the primary particles of the secondary particles of the _{two. 8} Mg _{1 . 2} O _{4 +?} (-1.1??? 0) coating film was formed on the surface of the composite cathode active material. The content of cobalt magnesium in the _LiCoO.8 Mg _1.2 O ₄ coating film was 0.75 part by weight based on 100 parts by weight of the lithium transition metal oxide.

Example  3c: Composite cathode active material  Produce

Except that a mixed precursor of Co (NO ₃ ) ₂揃 6H ₂ O and Mg (NO ₃ ) ₂揃 6H ₂ O in a molar ratio of 1: 4 was used as a precursor, Li _1.05 LiCo ₀ having a spinel crystal structure between the surface of the secondary particles of Ni _0.91 Co _0.06 Mn _0.03 O ₂ and the primary particles _{. 4} Mg _{1 . 6} O _{4 +?} (-1.3??? 0) coating film was formed on the surface of the composite cathode active material. The content of cobalt magnesium in the _LiCoO.4 Mg _1.6 O _{4 +?} (-1.3??? 0) coating film was 0.75 parts by weight based on 100 parts by weight of the lithium transition metal oxide.

Example  4: Composite cathode active material  Produce

Li ₁ produced according to Comparative Example _{1 . 05} Ni _{0 . 91} Co _{0 . 06} Mn _{0 . 03} O ₂ Instead of using Li _1.09 Ni _0.88 Co _0.08 Mn _0.04 O ₂ prepared according to Comparative Example 2 and the content of Co (NO ₃ ) ₂ .6H ₂ O and Zn (NO ₃ ) ₂ .6H ₂ O in the composite cathode active material LiCo _{1 . 33} Zn _{0 .} The content of cobalt zinc in the ₆₇ O _{4 +?} (-0.835??? 0) coating film was controlled to be 0.25 parts by weight based on 100 parts by weight of the lithium transition metal oxide, and the same procedure as in Example 2 was carried out Li _{1 . 09} Ni _{0 . 88} Co _{0 . 08} Mn _{0 . 04} LiCo ₁ having a spinel crystal structure between the surface of primary particles of O ₂ and primary particles _{. 33} Zn _{0 . 67} O _{4 +?} (-0.835??? 0) coating film was prepared.

Example  4a: Composite cathode active material  Produce

Li ₁ produced according to Comparative Example _{1 . 05} Ni _{0 . 91} Co _{0 . 06} Mn _{0 . 03} O ₂ Prepared according to Comparative Example 2 instead of _{Li 1.09 Ni 0.88 Co 0.08 Mn 0.04} O 2 and prepared by the same procedure as in Example 3 except that Li _{1. 09} Ni _{0 . 88} Co _{0 . 08} Mn _{0 . 04} LiCo ₁ having a spinel crystal structure between the surface of primary particles of O ₂ and primary particles _{. 2} Mg _{0 . 8} O _{4 +?} (-0.9??? 0) coating film was prepared. LiCo ₁ in composite cathode active material _{. 2} Mg _{0 .} The content of cobalt magnesium in the ₈ O _{4 +?} (-0.9??? 0) coating film was 0.75 parts by weight based on 100 parts by weight of the lithium transition metal oxide.

Example  5: Composite cathode active material  Produce

LiCo ₁ in composite cathode active material _{. 33} Zn _{0 . The} procedure of Example 4 was repeated except that the content of cobalt zinc in the coating film of ₆₇ O _{4 +?} (-0.835??? 0) was changed to 0.50 parts by weight based on 100 parts by weight of the lithium transition metal oxide Thereby obtaining a composite cathode active material.

Example  5a: Composite cathode active material  Produce

Li ₁ produced according to Comparative Example _{1 . 05} Ni _{0 . 91} Co _{0 . 06} Mn _{0 . 03} O ₂ Prepared according to Comparative Example 2 instead of _{Li 1.09 Ni 0.88 Co 0.08 Mn 0.04} O 2 by the same manner as in Example 1, except that Li _{1. 09} Ni _{0 . 88} Co _{0 . 08} Mn _{0 . 04} LiCo ₁ having a spinel crystal structure between the surface of primary particles of O ₂ and primary particles _{. 5} Al _{0 . 5} O _{4 +?} (-0.5??? 0) coating film was prepared. LiCo ₁ in composite cathode active material _{. 5} Al _{0 .} The content of cobalt aluminum in the ₅ O _{4 +?} (-0.5??? 0) coating film was 0.75 parts by weight based on 100 parts by weight of the lithium transition metal oxide.

Example  6: Lithium battery ( Coin cell )

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

Using the positive electrode thus prepared, lithium metal was used as a counter electrode, and a PTFE separator and 1.15 M LiPF ₆ were mixed with EC (ethylene carbonate) + EMC (ethylmethyl carbonate) + DMC (dimethyl carbonate) : 4 volume ratio) was used as an electrolyte to prepare a coin cell.

Example  7 to 10: lithium batteries ( Coin cell )

Coin half cells were prepared in the same manner as in Example 6, except that the composite cathode active material prepared in Examples 2 to 5 was used in place of the composite cathode active material prepared in Example 1, respectively.

Example  11 to 13: lithium batteries ( Coin cell )

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

Example  14 to 16: lithium batteries ( Coin cell )

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

Example  17: Lithium battery ( Coin cell )

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

Comparative Example  5 to 8: lithium batteries ( Coin cell )

A coin cell was prepared in the same manner as in Example 6, except that the composite cathode active material prepared in Comparative Examples 1 to 4 was used in place of the composite cathode active material prepared in Example 1, respectively.

Comparative Example  8a: Lithium battery ( Coin cell )

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

Comparative Example  9: Composite cathode active material  Produce

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

Comparative Example  10: Composite cathode active material  Produce

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

Comparative Example  11-12: Lithium battery ( Coin cell )

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

Example  18: Lithium battery ( Coin cell )

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

Example  19: Lithium battery (18650 minicell )

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

The anode was wound in a cylindrical shape together with the graphite cathode. The positive electrode tab and negative electrode tab were welded to the cylindrical structure and inserted and sealed in a cylindrical can. Thereafter, an electrolyte is injected into the cylindrical can, and 18650 Minicell was prepared. At this time, α-Al ₂ O ₃ powder having an average particle diameter of 50 nm was coated on both surfaces of polyethylene (manufactured by Asahi Corporation) as a separator.

A solution in which 1.15 M LiPF ₆ was dissolved in EC (ethylene carbonate) + EMC (ethylmethyl carbonate) + DMC (dimethyl carbonate) (2: 4: 4 volume ratio) was used as the electrolyte.

Example  20-21: Lithium battery (18650 minicell )

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

Comparative Example  13: Lithium battery (18650 minicell )

Comparative Example 1 The lithium transition metal oxides obtained according to _{(Li 1 05 Ni 0 91 Co} 0 06 Mn 0 03 O 2....) And distilled water 1: a mixture of 2 weight ratio, and stirred at about 250rpm subjected to washing water Respectively. Thereafter, the resultant was dried at about 150 ° C for 15 hours to obtain a washed lithium transition metal oxide (Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ ).

Example 2 instead of the composite anode active material obtained according to the lithium transition metal oxide washing obtained according to the procedure _{(Li 1. 05 Ni 0.} 91 Co 0. 06 Mn 0. 03 O 2) in Example, except for using 19, a lithium battery (18650 minicell) was prepared.

Comparative Example  13a: Lithium battery (18650 minicell )

Comparative Example 1 The lithium transition metal oxides obtained according to _{(Li 1 05 Ni 0 91 Co} 0 06 Mn 0 03 O 2....) And distilled water 1: a mixture of 2 weight ratio, and stirred at about 250rpm subjected to washing water Respectively. Thereafter, the resultant was dried at about 150 ° C for 15 hours to obtain a washed lithium transition metal oxide (Li _1.05 Ni _0.91 Co _0.06 Mn _0.03 O ₂ ).

Conducted in Example except for using the example instead of the composite anode active material obtained according to one of the lithium-transition metal oxide, the cleaning obtained according to the procedure _{(Li 1. 05 Ni 0.} 91 Co 0. 06 Mn 0. 03 O 2) 6, a lithium battery (coin half cell) was produced.

Comparative Example  14: Lithium battery (18650 minicell )

Example 2 The lithium transition metal oxide obtained according to the composite positive electrode active material instead of the Comparative Example 2, obtained according to _{(Li 1. 09 Ni 0.} 88 Co 0. 08 Mn 0. 04 O 2) in Example 19, except for using To prepare a lithium battery (18650 minicell).

Comparative Example  15: Lithium battery ( Coin half cell )

Comparative Example 2 Lithium-transition metal oxides obtained according to _{(Li 1 09 Ni 0 88 Co} 0 08 Mn 0 04 O 2....) And distilled water 1: a mixture of a second mixing ratio and stirred at about 250rpm subjected to washing water Respectively. Thereafter, the resultant was dried at about 150 ° C for 15 hours to obtain a washed lithium transition metal oxide (Li _1.09 Ni _0.88 Co _0.08 Mn _0.04 O ₂ ).

Conducted in Example except for using the example instead of the composite anode active material obtained according to one of the lithium-transition metal oxide, the cleaning obtained according to the procedure _{(Li 1. 09 Ni 0.} 88 Co 0. 08 Mn 0. 04 O 2) 6, a lithium battery (coin half cell) was produced.

Evaluation example  One: SEM  Image analysis

1) Example 4a and Comparative Examples 2 and 4

The composite cathode active material powders prepared according to Example 4a and Comparative Examples 2 and 4 were analyzed by a scanning electron microscope and their results are shown in FIGS. 2a to 2c, respectively.

Referring to FIGS. 2A to 2C, the composite anode active material of Example 4a was larger in size than the composite cathode active materials of Comparative Examples 2 and 4. 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 microscopic analysis of the composite cathode active material prepared according to Example 1 was carried out, and the results are shown in FIG.

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

Evaluation example  2: X-ray diffraction analysis

XRD (X-ray diffraction) analysis of the composite cathode active material of Example 3 was performed. The results of the XRD analysis are shown in Fig.

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. Accordingly, it was confirmed that the composite cathode active material of Example 1 contains a lithium-transition metal oxide having a layered crystal structure and a coating film containing a lithium-cobalt composite oxide having a spinel crystal structure.

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

High-Angle Annular Dark-Field (HAADF) STEM and EDS analyzes were performed on the composite cathode active material prepared according to Example 3 to analyze the composition.

As a result, it was confirmed that Ni, Mn and Co were uniformly distributed throughout the composite cathode active material. Co and Mg were arranged between the primary particles and Co and Mg were arranged on the primary and secondary particle surfaces. Therefore, LiCo ₁ is formed on both the grain boundaries between the primary particles and on the surfaces of the primary and secondary particles _{. 2} Mg _{0 . 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 of the composite cathode active material prepared according to Examples 1-3, 2a, 3a-3c and Comparative Example 1 was measured 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 cathode active material by a wet method (or titration 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 reduced residual lithium content on the surface as compared with Comparative Example 1. Therefore, gas generation can be suppressed during charge and discharge of the lithium battery including the composite positive electrode active material of Examples 1-3, 2a, and 3a-3c, and deterioration in lifetime 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 residual lithium content on the surface of the composite cathode active material was measured by using Li ₂ CO ₃ And LiOH were evaluated by measurement by a wet method (or a titration 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 reduced residual lithium content on the surface as compared with Comparative Examples 2 and 4.

Evaluation example  5: Thermal stability test

Differential scanning calorimetry analysis of the composite cathode active material obtained in Examples 2 and 3 and Comparative Example 3 was carried out. The results of the analysis 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 calorific value of the composite cathode active material of Examples 2 and 3 was lower than that of Comparative Example 3. From this, it was found that the thermal stability of the composite cathode active material of Examples 2 and 3 was improved.

Evaluation example  6: Charging and discharging  characteristic

The lithium batteries prepared in Example 6, Example 8, and Comparative Example 5 and Comparative Example 7 were charged at a constant current of 0.1 C rate at 25 DEG C until the voltage reached 4.35 V (vs. Li) And discharged at a constant current of 0.1 C rate (1 ^st cycle, formation cycle) until reaching 2.8 V (vs. Li).

A lithium cell having passed through a 1- ^st cycle was charged at a constant current of 0.33 C rate at 25 캜 until the voltage reached 4.35 V (vs. Li), and then maintained at 4.35 V in the constant voltage mode, (cut-off). Then, at the time of discharge, the cell was discharged at a constant current of 0.2 C rate until the voltage reached 2.8 V (vs. Li) (2 ^nd cycle).

A lithium battery having passed through a 2 ^nd cycle was charged with a constant current until the voltage reached 4.35 V (vs. Li) at a current of 1 C at 25 ° C and then at a rate of 1 C until the voltage reached 2.8 V (vs. Li) And discharged at a constant current (3 ^rd cycle).

The lithium battery having passed through the 3 ^rd cycle was repeated under the same conditions up to the 53 ^th cycle.

In all the above charge / discharge cycles, there was a stop time of 20 minutes after one charge / discharge cycle.

Part of the above charge / discharge test results are shown in Table 4 below. The capacity retention rate in the 53 ^th cycle and the initial charge / discharge efficiency in the 1 ^st cycle are defined by the following equations (1) and (2).

[Formula 1]

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

[Formula 2]

The initial efficiency (%) = [discharge capacity / charge capacity at 1 ^st cycle at 1 ^st cycle] × 100%

1 ^st cycle charge capacity
(mAh / g) Initial efficiency
(%) 2 ^nd cycle
Discharge capacity
(mAh / g) Capacity retention 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 lithium battery of Examples 6 to 8 significantly improved the capacity retention rate as compared with the lithium battery of Comparative Example 5. The lithium battery of Comparative Example 5 had excellent initial efficiency, but the capacity retention ratio was much lower than that of Example 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 the capacity retention ratios were improved.

The charging / discharging characteristics (initial efficiency and capacity retention rate) of the lithium battery produced in Comparative Example 11-12 were measured and conducted in accordance with the same evaluation method as in the case of the lithium battery of Example 6 described above.

As a result, it was found that the initial efficiency and the capacity retention ratio of the lithium battery of Example 6 were improved compared with the lithium battery of Comparative Example 11-12.

Evaluation example  7: Charging and discharging  characteristic

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

A lithium cell having passed through a 1- ^st cycle was charged at a constant current of 0.33 C rate at 25 캜 until the voltage reached 4.35 V (vs. Li), and then maintained at 4.35 V in the constant voltage mode, (cut-off). Then, at the time of discharge, the cell was discharged at a constant current of 0.2 C rate until the voltage reached 2.8 V (vs. Li) (2 ^nd cycle).

A lithium battery having passed through a 2 ^nd cycle was charged with a constant current until the voltage reached 4.35 V (vs. Li) at a current of 1 C at 25 ° C and then at a rate of 1 C until the voltage reached 2.8 V (vs. Li) And discharged at a constant current (3 ^rd cycle).

The lithium battery having passed through the 3 ^rd cycle was repeated under the same conditions up to the 53 ^th cycle.

In all the above charge / discharge cycles, there was a stop time of 20 minutes after one charge / discharge cycle.

Part of the charge-discharge test results are shown in Table 5 below.

1 ^st cycle charge capacity
(mAh / g) Initial efficiency
(%) 2 ^nd cycle discharge capacity
(mAh / g) Capacity retention 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 improved the initial efficiency and capacity retention ratio as compared with the lithium batteries of Comparative Example 13a.

Evaluation example  8: Charging and discharging  characteristic

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

A lithium cell having passed through a 1- ^st cycle was charged at a constant current of 0.33 C rate at 25 캜 until the voltage reached 4.35 V (vs. Li), and then maintained at 4.35 V in the constant voltage mode, (cut-off). Then, at the time of discharge, the cell was discharged at a constant current of 0.2 C rate until the voltage reached 2.8 V (vs. Li) (2 ^nd cycle).

A lithium battery having passed through a 2 ^nd cycle was charged with a constant current until the voltage reached 4.35 V (vs. Li) at a current of 1 C at 25 ° C and then at a rate of 1 C until the voltage reached 2.8 V (vs. Li) And discharged at a constant current (3 ^rd cycle).

The lithium battery having passed through the 3 ^rd cycle was repeated under the same conditions up to the 53 ^th cycle.

In all the above charge / discharge cycles, there was a stop time of 20 minutes after one charge / discharge cycle.

Part of the charge-discharge test results are shown in Table 6 below.

Separately, high-rate characteristics were evaluated by 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 0.1 C rate at 25 DEG C until the voltage reached 4.35 V (vs. Li) And discharged at a constant current of 0.1 C rate (1 ^st cycle, formation cycle) until reaching 2.8 V (vs. Li).

A lithium cell having passed through a 1- ^st cycle was charged at a constant current of 0.33 C rate at 25 캜 until the voltage reached 4.35 V (vs. Li), and then maintained at 4.35 V in the constant voltage mode, (cut-off). Then, at the time of discharge, the cell was discharged at a constant current of 0.2 C rate until the voltage reached 2.8 V (vs. Li) (2 ^nd cycle).

2, while the voltage is constant-current charging up to the 4.35V (vs. Li) at a current rate of 0.5C to a rough ^nd cycle lithium batteries at 25 ℃, followed by keeping in the constant voltage mode, cut-off of 4.35V at a current of 0.05C rate (cut-off). The discharge was then discharged at a constant current of 0.33 C rate (3 ^rd cycles) until the voltage reached 2.8 V (vs. Li).

The lithium battery having passed through the 3 ^rd cycle was charged at a constant current of 0.5 C at a current of 25 C until the voltage reached 4.35 V (vs. Li), and then maintained at 4.35 V in the constant voltage mode, (cut-off). Then, at the time of discharging, the battery was discharged at a constant current of 1 C rate (4 ^th cycle) until the voltage reached 2.8 V (vs. Li).

A lithium cell through a 4 ^th cycle was charged with constant current until the voltage reached 4.35 V (vs. Li) at a current of 0.5 C rate at 25 ° C, followed by a cutoff at a current of 0.05 C rate while maintaining 4.35 V in constant voltage mode. (cut-off). Then, at the time of discharge, the cell was discharged at a constant current of 2 C rate (5 ^th cycle) until the voltage reached 2.8 V (vs. Li).

The lithium battery having passed through the 5 ^th cycle was charged with constant current until the voltage reached 4.35 V (vs. Li) at a current of 0.5 C rate at 25 ° C, and then maintained at 4.35 V in the constant voltage mode, (cut-off). Then, at discharge, the cell was discharged at a constant current of 3 C rate (6 ^th cycle) until the voltage reached 2.8 V (vs. Li).

A lithium cell through a 6 ^th cycle was charged at a constant current until the voltage reached 4.35 V (vs. Li) at a current of 1 C at 25 ° C. and then at a rate of 1 C until the voltage reached 2.8 V (vs. Li) Discharged at a constant current (7 ^th cycle), and this cycle was repeated under the same conditions up to 56 ^th cycle.

In all the above charge / discharge cycles, there was a stop time of 20 minutes after one charge / discharge cycle.

Part of the charge-discharge test results are shown in Table 6 below. The high-rate characteristics are defined by the following Equation 3, and the high-rate characteristics are shown in Table 6 below.

 [Formula 3]

High rate characteristic [%] = [Discharge capacity at 6 ^th cycle (3 C rate) / Discharge capacity at 3 ^rd cycle (0.33 C rate)] × 100

1 ^st cycle charge capacity
(mAh / g) Initial efficiency
(%) High rate characteristic
(%) 2 ^nd cycle
Discharge capacity
(mAh / g) Capacity retention 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 battery of Examples 8 and 14 to 16 shown in Table 6 has improved capacity retention and high rate characteristics as compared with the lithium battery of Comparative Example 5. [ In addition, the lithium batteries of Examples 8 and 16 had the same high rate characteristics as those of the lithium battery of Comparative Example 7, and their capacity retention ratios were improved. The lithium batteries of Examples 8 and 14 to 16 exhibited improved initial efficiency as compared with those of Comparative Example 8a.

Evaluation example  9: Charging and discharging  characteristic

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

A lithium cell having passed through a 1- ^st cycle was charged at a constant current of 0.33 C rate at 25 캜 until the voltage reached 4.35 V (vs. Li), and then maintained at 4.35 V in the constant voltage mode, (cut-off). Then, at the time of discharge, the cell was discharged at a constant current of 0.2 C rate until the voltage reached 2.8 V (vs. Li) (2 ^nd cycle).

2 ^nd cycle to the rough lithium batteries at 25 ℃ the voltage at a current of 1C rate and a constant current charging until the 4.35V (vs. Li), then up to the two 2.8V (vs. Li) voltage during discharge And discharged at a constant current of 1 C rate (3 ^rd cycle).

The lithium battery having passed through the 3 ^rd cycle was repeated under the same conditions up to the 53 ^th cycle.

In all the above charge / discharge cycles, there was a stop time of 20 minutes after one charge / discharge cycle.

Part of the above charge / discharge test results are shown in Table 7 below.

1 ^st cycle charge capacity
(mAh / g) Initial efficiency
(%) 2 ^nd cycle
Discharge capacity
(mAh / g) Capacity retention 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 lithium battery of Examples 9, 10, and 17 shown in Table 7 significantly improved the capacity retention rate as compared with the lithium batteries of Comparative Examples 8 and 15. In addition, the lithium battery of Example 9 had the same initial efficiency as that of the lithium battery of Comparative Example 8, and the capacity retention ratio was improved.

As shown in Table 7, the lithium battery of Example 18 showed the improved capacity retention ratio as compared with the lithium battery of Comparative Example 8, and the initial efficiency and capacity retention ratio of the lithium battery of Comparative Example 15 were improved.

Evaluation example  10: high temperature (45 캜) Charging and discharging  characteristic

1) Example 19 and Comparative Example 13

Each lithium cell (18650 Mini-CELL) was charged at constant current until the voltage reached 4.35 V (vs. Li) at a current of 0.1 C rate at 45 ° C, followed by 0.1 C (vs. Li) until the voltage reached 2.8 V (1 ^st cycle, formation cycle).

A lithium battery having passed through a 1 ^st cycle was charged at a constant current of 0.33 C rate at 45 캜 until the voltage reached 4.35 V (vs. Li), and then maintained at 4.35 V in a constant voltage mode, (cut-off). Then, at the time of discharge, the cell was discharged at a constant current of 0.2 C rate until the voltage reached 2.8 V (vs. Li) (2 ^nd cycle).

2 ^nd cycle to the rough lithium batteries at 45 ℃ the voltage at a current of 1C rate and a constant current charging until the 4.35V (vs. Li), then up to the two 2.8V (vs. Li) voltage during discharge And discharged at a constant current of 1 C rate (3 ^rd cycle).

The lithium battery having passed through the 3 ^rd cycle was repeated under the same conditions from 45 캜 to 302 ^th cycle.

In all the above charge / discharge cycles, there was a stop time of 20 minutes after one charge / discharge cycle.

The capacity retention rate according to the number of cycles was evaluated and shown in Fig.

Referring to FIG. 5, it was found that the capacity retention ratio of the lithium battery of Example 19 was improved as compared with that of Comparative Example 13.

The charging and discharging characteristics of the lithium batteries of Examples 20-21 and 14-15 were evaluated in the same manner as the charging and discharging characteristics evaluation methods of the lithium batteries of Example 19 and Comparative Example 12 to evaluate the charging and discharging characteristics. The results of the analysis are shown in Fig.

Referring to these results, it was found that the capacity retention characteristics at 45 ° C of the lithium batteries of Examples 20-21 were improved as compared with the lithium batteries of Comparative Examples 14-15.

1: Lithium battery 2: cathode
3: anode 4: separator
5: Battery case 6: Cap assembly

Claims (25)

Comprising secondary particles,
Wherein the secondary particles comprise a plurality of primary particles comprising a 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 comprises a lithium cobalt composite oxide having a spinel crystal structure,
Wherein 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 method according to claim 1,
The lithium cobalt complex oxide having the spinel crystal structure is LiCo _1.5 Al _0.5 O _{4 +?} (-0.5??? ₀ ), LiCo _{1 . 5} Ga _{0 . 5} O _{4 + ?} (-0.5??? ₀ ), LiCo _{1 . 33} Zn _{0 . 67} O _{4 +?} (-0.835??? ₀ ), LiCo _{1 . 33} Ca _{0 . 67} O _{4 +?} (-0.835??? ₀ ), LiCo _{1 . 33} Ba _{0 . 67} O _{4 +?} (-0.835??? 0), LiCo _1.33 Ga _0.67 O _{4 +?} (-0.835??? ₀ ), LiCo _{1 . 2} Mg _{0 . 8} O _{4 +?} (-0.9??? ₀ ), LiCo _{1 . 2} Ga _{0 . 8} O _{4 +?} (-0.9??? ₀ ), LiCo _{1 . 2} Ca _{0 . 8} O _{4 +?} (-0.9??? ₀ ), LiCo _{1 . 2} Ba _.8 O _{4 +?} (-0.9??? ₀ ), LiCo _{1 . 2} Zn _{0 . 8} O _{4 +?} (-0.9??? ₀ ), LiCo _{1 . 6} Mg _{0 . 4} O _{4 +?} (-0.7??? ₀ ), LiCo _{1 . 6} Ga _{0 . 4} O _{4 +?} (-0.7??? 0), LiCo _1.6 Ca _0.4 O _{4 +?} (-0.7??? ₀ ), LiCo _{1 . 6} Ba _{0 . 4} O _{4 +?} (-0.7??? ₀ ), LiCo _{1 . 6} Zn _{0 . 4} O _{4 +?} (-0.7??? ₀ ), LiCo _{0 . 8} Mg _{1 . 2} O _{4 +?} (-1.1??? ₀ ), LiCo _{0 . 8} Ga _{1 . 2} O _{4 +?} (-1.1??? ₀ ), LiCo _{0 . 8} Ca _{1 . 2} O _{4 +?} (-1.1??? ₀ ), LiCo _{0 . 8} Ba _{1 . 2} O _{4 +?} (-1.1??? ₀ ), LiCo _{0 . 8} Zn _{1 . 2} O _{4 +?} (-1.1?? ₀ ), LiCo _0.4 Mg _1.6 O _{4 +?} (-1.3??? ₀ ), LiCo _{0 . 4} Ga _{1 . 6} O _{4 +?} (-1.3??? ₀ ), LiCo _{0 . 4} Ca _{1 . 6} O _{4 +?} (-1.3??? ₀ ), LiCo _{0 . 4} Ba _{1 . 6} O _{4 +?} (-1.3??? ₀ ), or LiCo _{0 . 4} Zn _{1 . 6} O _{4 +?} (-1.3??? 0). The method according to claim 1,
The lithium cobalt composite oxide having a spinel crystal structure is a composite cathode active material represented by the following formula (1)
[Chemical 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,
0 < a < 2, 0 < b < The method of claim 3,
In Formula 1, Me is a composite cathode active material which is Al, Ga, Mg, Ca, Ba, Zn or a combination thereof. The method according to claim 1,
The lithium cobalt composite oxide having a spinel crystal structure may be 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 a _{Li x Co a Ba b O 4} + δ, 1.0≤x≤1.1, 0 <a <2, 0 <b <2, 0 < a + b? 2, and -1.5??? 0. The method according to claim 1,
The lithium cobalt complex oxide having the spinel crystal structure is LiCo _1.5 Al _0.5 O _{4 +?} (-0.5??? ₀ ), LiCo _{1 . 5} Ga _{0 . 5} O _{4 + ?} (-0.5??? ₀ ), LiCo _{1 . 33} Zn _{0 . 67} O _{4 +?} (-0.835??? ₀ ), LiCo _{1 . 33} Ca _{0 . 67} O _{4 +?} (-0.835??? ₀ ), LiCo _{1 . 33} Ba _{0 . 67} O _{4 +?} (-0.835??? 0), LiCo _1.33 Ga _0.67 O _{4 +?} (-0.835??? ₀ ), LiCo _{1 . 2} Mg _{0 . 8} O _{4 +?} (-0.9??? ₀ ), LiCo _{1 . 2} Ga _{0 . 8} O _{4 +?} (-0.9??? ₀ ), LiCo _{1 . 2} Ca _{0 . 8} O _{4 +?} (-0.9??? ₀ ), LiCo _{1 . 2} Ba _.8 O _{4 +?} (-0.9??? ₀ ), LiCo _{1 . 2} Zn _{0 . 8} O _{4 +?} (-0.9??? ₀ ), LiCo _{1 . 6} Mg _{0 . 4} O _{4 +?} (-0.7??? ₀ ), LiCo _{1 . 6} Ga _{0 . 4} O _{4 +?} (-0.7??? 0), LiCo _1.6 Ca _0.4 O _{4 +?} (-0.7??? ₀ ), LiCo _{1 . 6} Ba _{0 . 4} O _{4 +?} (-0.7??? ₀ ), LiCo _{1 . 6} Zn _{0 . 4} O _{4 +?} (-0.7??? ₀ ), LiCo _{0 . 8} Mg _{1 . 2} O _{4 +?} (-1.1??? ₀ ), LiCo _{0 . 8} Ga _{1 . 2} O _{4 +?} (-1.1??? ₀ ), LiCo _{0 . 8} Ca _{1 . 2} O _{4 +?} (-1.1??? ₀ ), LiCo _{0 . 8} Ba _{1 . 2} O _{4 +?} (-1.1??? ₀ ), LiCo _{0 . 8} Zn _{1 . 2} O _{4 +?} (-1.1?? ₀ ), LiCo _0.4 Mg _1.6 O _{4 +?} (-1.3??? ₀ ), LiCo _{0 . 4} Ga _{1 . 6} O _{4 +?} (-1.3??? ₀ ), LiCo _{0 . 4} Ca _{1 . 6} O _{4 +?} (-1.3??? ₀ ), LiCo _{0 . 4} Ba _{1 . 6} O _{4 +?} (-1.3??? ₀ ), or LiCo _{0 . 4} Zn _{1 . 6} O _{4 +?} (-1.3??? 0). The method according to claim 1,
The lithium transition metal oxide having a layered crystal structure has a salt salt layer structure and belongs to the R-3m space group, and the lithium cobalt complex oxide belongs to the Fd-3m space group. The method according to claim 1,
Wherein a mixed phase exists between the lithium transition metal oxide and the coating film, and the mixed phase includes a combination of a lithium transition metal oxide and a lithium cobalt complex oxide. The method according to claim 1,
A composite cathode active material further comprising a compound having an amorphous structure, a compound having a layered crystal structure, or a combination thereof between the primary particles. The method according to claim 1,
Wherein the lithium transition metal oxide having a layered crystal structure is one selected from the group consisting of compounds represented by Chemical Formulas 2 to 4:
(2)
Li _x Co _{1 - y} M _y O _{2 - ?} X _?
(3)
Li _x Ni _{1 - y} Me _y O _{2 - ?} X _?
[Chemical Formula 4]
Li _x Ni _{1 - y - z} Mn _y Ma _z O _{2 - α} X _α
In the general formulas (2) to (4), 0.9? X? 1.1, 0? Y? 0.9, 0 <z? 0.2, 0?
M is Ni, Mn, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Fe, Cu, B,
Wherein Me is at least one element selected from the group consisting of Co, Zr, Al, Mg, Ag, Mo, Ti, V, Cr, Mn, Fe, Cu, , Cr, Fe, Cu, B, or a combination thereof, and X is F, S, P, or a combination thereof. It is an element. The method according to claim 1,
Wherein the lithium transition metal oxide having a layered crystal structure is one selected from compounds represented by Chemical Formulas 5 to 7:
[Chemical Formula 5]
Li [Li _1-a Me _a ] O _{2 + d}
In formula (5), 0.8? A <1, 0? D?
Wherein Me is Ni, Co, Mn, Al, V, Cr, Fe, Zr, Re, B, Ge, Ru, Sn, Ti, Nb, Mo, Pt,
[Chemical Formula 6]
Li [Li _{1- xy z} Ma _x Mb _y Mc _z ] O _{2 + d}
X <y <1, 0 <x <1, 0 <y <1, 0 <z <1, 0? D?
Wherein said Ma, Mb and Mc are independently Mn, Co, Ni, Al or a combination thereof,
Li [Li _{1- xy z} Ni _x Co _y Mn _z ] O _{2 + d}
X + y + z &lt;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 nickel-based lithium transition metal oxide is represented by the following formula (8): < EMI ID =
[Chemical Formula 8]
aLi ₂ MnO _{3 -} (1-a) LiMO ₂
In formula (8), 0 < a &lt; 1,
M is at least one element selected from the group consisting of Ni, Co, Mn, V, Cr, Fe, Zr, Ge, Ru, Sn, Ti, Nb, Mo, Pt, or combinations thereof. The method according to claim 1,
Wherein the lithium transition metal oxide having a layered crystal structure is a composite cathode active material represented by the following formula (9): < EMI ID =
[Chemical Formula 9]
Li _x Ni _{1 - y - z} M _y Co _z O ₂
In the formula (9), 0.90? X? 1.1, 0? Y? 0.2, 0 <z? 0.2 and 0.7? 1-yz? 0.99.
M is manganese (Mn), aluminum (Al), titanium (Ti), calcium (Ca) or a combination thereof. The method according to claim 1,
Wherein the average particle diameter of the at least one secondary particle comprising the lithium transition metal oxide having the layered crystal structure is 10 to 20 占 퐉. The method according to claim 1,
Wherein the lithium transition metal oxide having a layered crystal structure is a composite cathode active material represented by the following formula (9a): < EMI ID =
[Formula 9a]
Li _x Ni _{1- y- z} Mn _x Co _y O ₂
In the formula (9a), 0.80? X? 1.1, 0 = y? 0.2, 0 <z? 0.2 and 0.8? The method according to claim 1,
The lithium transition metal oxide having a 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. The method according to claim 1,
Wherein the content of the lithium cobalt complex 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 the lithium transition metal oxide having a layered crystal structure. The method according to claim 1,
Wherein the content of residual lithium in the composite cathode active material is 90% or less of the content of residual lithium in the secondary particles containing a lithium transition metal oxide having a layered crystal structure. The method according to claim 1,
Wherein the coating film covers at least 50% of the surface of the lithium transition metal oxide having a layered crystal structure. The method according to claim 1,
Wherein the thickness of the coating film is 1 占 퐉 or less. An anode comprising the composite cathode active material of any one of claims 1 to 20. A positive electrode of claim 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 and a lithium cobalt complex having a spinel crystal structure and containing cobalt (Co) and a Group 2 element, a Group 12 element, a Group 13 element or a combination thereof, Oxide precursor to obtain a composite cathode active material composition; And
Drying the composite cathode active material composition and heat treating the composite cathode active material composition in an oxidizing gas atmosphere at a temperature in a range of more than 400 ° C and not more than 1000 ° C to manufacture a composite cathode active material of any one of claims 1 to 20 Way. 24. The method of claim 23,
A lithium transition metal oxide having the layered crystal structure and a lithium cobalt composite oxide containing a cobalt (Co) having a spinel crystal structure and a Group 2 element, a Group 12 element, a Group 13 element or a combination thereof, Wherein the mixing of the precursor of the first precursor and the precursor of the second precursor is carried out in a wet process in the presence of a solvent. 24. The method of claim 23,
Wherein the heat treatment is performed at 700 ° C in 700 and the rate of temperature increase during heat treatment is 1 to 10 ° C / min.

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