KR20150110318A - Positive active material for rechargeable lithium battery, method of preparing the same, and rechargeable lithium battery including the same - Google Patents

Abstract

The present invention relates to a positive electrode active material for a lithium secondary battery, a method for preparing the same, and a lithium secondary battery including the same. Provided is a positive electrode active material including a core including a compound presented by Li_aCo_(1-b-c-d)Mg_bM^1_cM^2_dO_(2-z)F_z; and a composite coating layer including a coating layer which is located on the surface of the core and includes a compound presented by M^3F_x and/or chemical formula M^4F_x, and a coating layer including Al. (In Li_aCo_(1-b-c-d)Mg_bM^1_cM^2_dO_(2-z)F_z, M^1 and M^2 are at least one metal selected among a group consisting of Zr, Ti, Ca, V, Zn, Mo, Ni, and Mn, and 0.90<a<1.10, 0<b<0.1, 0<c<0.1, 0<d<0.1, and 0<z<0.1. In M^3F_x, M^3 is at least one metal selected among a group consisting of Li, Ti, Ca, V, Zn, Mo, Ni, Co and Mn, and 0<x<=4. In M^4F_x, is at least one metal selected among a group consisting of Li, Ti, Ca, V, Zn, Mo, Ni, Co and Mn, and 0<x<=4)

Description

TECHNICAL FIELD The present invention relates to a cathode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery including the same. BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

A method for producing a positive electrode active material for a lithium secondary battery, and a positive electrode active material for a lithium secondary battery.

Recently, with regard to the tendency to miniaturize and lighten portable electronic devices, there is an increasing need for high performance and large capacity of batteries used as power sources for these devices.

Cells generate electricity by using materials that can electrochemically react to the positive and negative electrodes. A representative example of such a battery is a lithium secondary battery that generates electrical energy by a change in chemical potential when the lithium ions are intercalated / deintercalated in the positive electrode and the negative electrode.

The lithium secondary battery is manufactured by using a material capable of reversible intercalation / deintercalation of lithium ions as a positive electrode and a negative electrode active material, and filling an organic electrolytic solution or a polymer electrolyte between the positive electrode and the negative electrode.

As a cathode active material of a lithium secondary battery, a lithium composite metal compound is used. For example, composite metal oxides such as LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ and LiMnO ₂ have been studied.

Of the above cathode active materials, Mn-based cathode active materials such as LiMn ₂ O ₄ and LiMnO ₂ are easy to synthesize and are relatively inexpensive and have excellent thermal stability compared to other active materials in overcharging, However, it has a disadvantage of low capacity.

LiCoO ₂ is a typical cathode active material commercially available and commercially available since it has good electric conductivity, high battery voltage of about 3.7 V, excellent cycle life characteristics, stability and discharge capacity. However, since LiCoO ₂ is expensive, it accounts for more than 30% of the battery price, which causes the price competitiveness to deteriorate.

LiNiO ₂ also exhibits the highest discharge capacity of the battery among the above-mentioned cathode active materials, but it is difficult to synthesize LiNiO ₂ . Also, the high oxidation state of nickel causes degradation of battery life and electrode life, and there is a problem that self discharge is severe and reversibility is low. In addition, it is difficult to commercialize it because the stability is not completely secured.

The present invention also provides a lithium secondary battery comprising the positive electrode active material and the positive electrode active material.

In one embodiment of the present invention, a core comprising a compound represented by the following general formula (1); A coating layer positioned on the surface of the core and comprising a compound represented by the following Chemical Formula 2-1 and / or Chemical Formula 2-2; And a coating layer comprising Al. The present invention also provides a cathode active material for a lithium secondary battery comprising the composite coating layer.

[Chemical Formula 1]

Li _a Co _(1-bcd) Mg _b M ¹ _c M ² _d O _(2-z) F _z

(In the formula 1,

M ¹ and M ² are at least one or more metals selected from the group consisting of Zr, Ti, Ca, V, Zn, Mo, Ni and Mn; 0.90 <a <1.10, 0 <b < 0.1, 0 < d < 0.1, 0 < z <

[Formula 2-1]

M ³ F _x

(In the above formula (2-1)

M ³ is at least one metal selected from the group consisting of Li, Ti, Ca, V, Zn, Mo, Ni, Co and Mn and 0 &

[Formula 2-2]

M ⁴ F _x

(In the above formula (2-2)

M ⁴ is at least one metal selected from the group consisting of Li, Ti, Ca, V, Zn, Mo, Ni, Co and Mn and 0 &

The M ¹ may be Ca.

The M &lt; ² &gt; may be Ti, Zr or a combination thereof.

The molar doping ratios of Mg, M ¹ and M ² may be 0.001 to 0.01, independently of each other.

2-1 and / or 2-2 located on the surface of the positive electrode active material, wherein the formula (2-1) and / or (2-2) are independently of the doped M ¹ and / or M ² And may be a fluoride metal compound combined with at least one of them.

The compounds represented by the above formulas (2-1) and / or (2-2) may independently be CaF ₂ or TiF ₄ .

The coating layer may further include a metal fluoride compound derived from the core metal in the coating layer comprising the chemical formula 2-1 and / or 2-2 located on the surface of the cathode active material.

The coating layer comprising Al may include AlF ₃ , Al ₂ O ₃ , or a combination thereof.

A core comprising the compound represented by Formula 1; And a coating layer disposed on the surface of the core and including a compound represented by the general formula (2-1) and / or the general formula (2-2) and the coating layer comprising Al may be 0.02 to 0.2.

In another embodiment of the present invention, a core comprising a compound represented by the following general formula (3): ???????? A coating layer positioned on the surface of the core and comprising a compound represented by the following Formula 4-1 and / or Formula 4-2; And a coating layer comprising Al. The present invention also provides a cathode active material for a lithium secondary battery comprising the composite coating layer.

(3)

Li [Li _a A _(1-abcd) Mg _b M ¹ _c M ² _d ] O _{2 - z} F _z

(In the formula 3, A = Co, and Ni _{α β} Mn _γ, M ¹ and M ² are independently of each other, Zr, Ti, Ca, V, Zn, Mo, Ni, Mn, or a combination thereof, -0.05 0? D? 0.1, 0? B? 0.1, 0 <c <0.1, 0 <d <0.1, 0 <z <0.1, 0.6??? 0.81, 0.10?? 0.20 and 0.10?

[Formula 4-1]

M ³ F _x

(In the formula 4-1,

M ³ is derived from M ¹ or M ² of the above formula (3), and 0 <x? 4.

[Formula 4-2]

M ⁴ F _y

(In the formula 4-2,

M ⁴ is derived from Ni, Co, Mn or Mg of the above formula (3), 0 <y? 4,

The weight ratio of M ¹ / M ² in the cathode active material is 0.8 to 1.2.)

In another embodiment of the present invention, there is provided a process for preparing a lithium battery, comprising: dry-blending a lithium feed material, a transition metal precursor, a Mg feed material, an M ¹ feed material, an M ² feed material, and a fluorine feed material; Calcining the mixture; A core comprising a compound represented by the following formula (1); And a coating layer disposed on the surface of the core and comprising a compound represented by the following formula (2-1) and / or (2-2): (1) obtaining a cathode active material for a lithium secondary battery; Dry mixing the obtained positive electrode active material and a compound powder containing Al to uniformly adhere the compound powder containing Al to the surface of the obtained positive electrode active material; And a coating layer disposed on the surface of the core and comprising a compound represented by the following Chemical Formula 2-1 and / or Chemical Formula 2-2 by firing a cathode active material to which the Al-containing compound powder is adhered, And a coating layer comprising Al, and a step of obtaining a positive electrode active material comprising the composite coating layer.

[Chemical Formula 1]

Li _a Co _(1-bcd) Mg _b M ¹ _c M ² _d O _(2-z) F _z

(In the formula 1,

M ¹ and M ² are at least one or more metals selected from the group consisting of Zr, Ti, Ca, V, Zn, Mo, Ni and Mn; 0.90 <a <1.10, 0 <b < 0.1, 0 < d < 0.1, 0 < z <

[Formula 2-1]

M ³ F _x

(In the above formula (2-1)

M ³ is at least one metal selected from the group consisting of Li, Ti, Ca, V, Zn, Mo, Ni, Co and Mn and 0 &

[Formula 2-2]

M ⁴ F _x

(In the above formula (2-2)

M ⁴ is at least one metal selected from the group consisting of Li, Ti, Ca, V, Zn, Mo, Ni, Co and Mn and 0 &

The Mg, M ¹ , and M ² feed materials may independently be hydroxides, oxyhydroxides, nitrates, halides, carbonates, nitrates, oxalates, citrates, or combinations thereof.

The fluorine supplying material may be an ammonium salt, a lithium salt, a metal salt, or a combination thereof.

The Al-containing compound may be a hydroxide, an oxyhydroxide, a nitrate, a halide, a carbonate, a nitrate, a oxalate, a citrate, or a combination thereof.

Dry mixing the lithium supply material, the transition metal precursor, the Mg supply material, the M ¹ supply material, the M ² supply material, and the fluorine supply material; And firing the mixture, the firing temperature may be 800 to 1050 캜.

A coating layer disposed on the surface of the core and comprising a compound represented by the following Chemical Formula 2-1 and / or Chemical Formula 2-2 by firing a cathode active material to which the Al-containing compound powder is adhered; And a coating layer comprising Al. In the step of obtaining the cathode active material, the firing temperature may be 400 to 800 ° C.

According to another embodiment of the present invention, there is provided a positive electrode comprising a positive electrode active material for a lithium secondary battery according to any one of the above embodiments of the present invention; A negative electrode comprising a negative electrode active material; And an electrolyte.

A positive electrode active material having excellent battery characteristics and a lithium secondary battery including the same can be provided.

1 is a schematic view of a lithium secondary battery.
FIG. 2 is an X-ray photoelectron spectroscopic analysis graph of the cathode active material of Example 1. FIG.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

In one embodiment of the present invention, a core comprising a compound represented by the following general formula (1); A coating layer positioned on the surface of the core and comprising a compound represented by the following Chemical Formula 2-1 and / or Chemical Formula 2-2; And a coating layer comprising Al. The present invention also provides a cathode active material for a lithium secondary battery comprising the composite coating layer.

[Chemical Formula 1]

Li _a Co _(1-bcd) Mg _b M ¹ _c M ² _d O _(2-z) F _z

(In the formula 1,

M ¹ and M ² are at least one or more metals selected from the group consisting of Zr, Ti, Ca, V, Zn, Mo, Ni and Mn; 0.90 <a <1.10, 0 <b < 0.1, 0 < d < 0.1, 0 < z <

[Formula 2-1]

M ³ F _x

(In the above formula (2-1)

M ³ is at least one metal selected from the group consisting of Li, Ti, Ca, V, Zn, Mo, Ni, Co and Mn and 0 &

[Formula 2-2]

M ⁴ F _x

(In the above formula (2-2)

M ⁴ is at least one metal selected from the group consisting of Li, Ti, Ca, V, Zn, Mo, Ni, Co and Mn and 0 &

In general, lithium cobalt complex oxides are severely degraded in capacity and lifetime at high voltage. Further, the deterioration is further intensified under high temperature conditions.

To solve this problem, the present inventors have been able to improve this problem by improving the core part structure and / or surface modification of the surface part.

First, in order to improve the structure of the core portion it can be used for the M ¹ and / or the doping of M ² to stabilize the structure.

For example, M ¹ may be Ca.

For example, the M ² may be Ti, Zr or a combination thereof.

The molar doping ratios of Mg, M ¹ and M ² may be 0.001 to 0.01, independently of each other. If the above range is satisfied, the desired effect of the present invention can be obtained without excessively reducing the initial capacity and decreasing the efficiency characteristic.

When using a method for firing with a precursor for the doping of the Mg, M ¹ and / or M ^2, an effective firing temperature may be 800 to 1050 ℃. When firing at a temperature of less than 800 DEG C, rapid deterioration of the battery characteristics at room temperature and high temperature may occur. Also, when firing at a temperature higher than 1050 DEG C, a drastic decrease in capacity and capacity retention rate may occur. However, the present invention is not limited thereto.

The Mg, M ^1, and / or M ² may be doped into the core through the firing process.

However, the degree of doping of the doped elements varies depending on the ion radius. For example, in the case of Mg having a small ion radius, the doping is uniform in the core, but elements such as Ca, Ti, and Zr having a large ion radius cause a phenomenon that the ion radius is increased in the bulk of the core, Part of the doping is partially doped, but there is some tendency to exist on the surface.

For example, in the X-ray photoelectron spectroscopic analysis (XPS) graph of FIG. 2, in the active material according to an embodiment of the present invention, the doping element in the core reacts with the surface fluorine to form a metal fluoride compound, Can be confirmed.

When these fluorinated metal compounds are identified, it is possible to identify compounds bound to elements Ca and Ti, but Mg can not be confirmed on the surface. As a result, it can be confirmed that the ions tend to be partially doped or present on the surface depending on the ion radius.

By applying the tendency existing on such a surface, the surface of the metal fluoride compound of the formula (2-1) and / or the compound of the formula (2-2) is placed on the surface to improve the surface area. The fluorinated metal compound reduces the wettability with the electrolytic solution and plays a role of suppressing the side reaction, so that the surface can be stabilized.

As described above, the metal fluoride compound can be formed by the reaction of fluorine with M ¹ and / or M ² present on the surface.

For example, the fluorinated metal compound may be CaF ₂ , TiF ₄ , or a combination thereof.

Also, as described above, the cathode active material according to an embodiment of the present invention may include a coating layer containing Al. One example of such a compound containing Al is AlF ₃ , Al ₂ O ₃ , or a combination thereof.

A core comprising the compound represented by Formula 1; And a coating layer disposed on the surface of the core and including a compound represented by the general formula (2-1) and / or the general formula (2-2) and the coating layer comprising Al may be 0.02 to 0.2. If the weight ratio is less than 0.02, the role of the coating layer (electrolyte decomposition or crystal structure stabilization of the surface of the cathode active material) can not be expected. If the weight ratio is more than 0.2, initial capacity decrease and charge / discharge efficiency decrease may occur.

In order to improve the capacity and the service life deterioration at the high temperature and / or high voltage conditions, a composite coating layer which further includes a coating layer containing Al metal and a coating layer containing the metal fluoride compound in the surface modification of the surface portion may be effective .

For example, the coating layer containing Al can suppress the side reaction with the electrolyte on the surface, and can stabilize the structure. Further, the dissolution of Co can be suppressed at a high temperature and a high voltage, so that degradation of battery characteristics can be improved.

In the coating layer containing Al, for example, AlF ₃ may be a compound derived from the reaction with fluorine on the surface.

In one embodiment of the present invention, a coating layer positioned on the surface of the core and comprising a compound represented by the following Chemical Formula 4-1 and / or Chemical Formula 4-2; And a coating layer comprising Al. The cathode active material for a lithium secondary battery according to the present invention can be provided.

(3)

Li [Li _a A _(1-abcd) Mg _b M ¹ _c M ² _d ] O _{2 - z} F _z

(In the formula 3, A = Co, and Ni _{α β} Mn _γ, M ¹ and M ² are independently of each other, Zr, Ti, Ca, V, Zn, Mo, Ni, Mn, or a combination thereof, -0.05 0? D? 0.1, 0? B? 0.1, 0 <c <0.1, 0 <d <0.1, 0 <z <0.1, 0.6??? 0.81, 0.10?? 0.20 and 0.10?

[Formula 4-1]

M ³ F _x

(In the formula 4-1,

M ³ is derived from M ¹ or M ² of the above formula (3), and 0 <x? 4.

[Formula 4-2]

M ⁴ F _y

(In the formula 4-2,

M ⁴ is derived from Ni, Co, Mn or Mg of the above formula (3), 0 <y? 4,

The weight ratio of M ¹ / M ² in the cathode active material is 0.8 to 1.2.)

Since the composition is the same as that of the above-described embodiment of the present invention, detailed description thereof will be omitted.

In another embodiment of the present invention, there is provided a process for preparing a lithium battery, comprising: dry-blending a lithium feed material, a transition metal precursor, a Mg feed material, an M ¹ feed material, an M ² feed material, and a fluorine feed material; Calcining the mixture; A core comprising a compound represented by the following formula (1); And a coating layer disposed on the surface of the core and comprising a compound represented by the following formula (2-1) and / or (2-2): (1) obtaining a cathode active material for a lithium secondary battery; Dry mixing the obtained positive electrode active material and a compound powder containing Al to uniformly adhere the compound powder containing Al to the surface of the obtained positive electrode active material; And a coating layer disposed on the surface of the core and comprising a compound represented by the following Chemical Formula 2-1 and / or Chemical Formula 2-2 by firing a cathode active material to which the Al-containing compound powder is adhered, And a coating layer comprising Al, and a step of obtaining a positive electrode active material comprising the composite coating layer including the negative electrode active material and the coating layer containing Al.

[Chemical Formula 1]

Li _a Co _(1-bcd) Mg _b M ¹ _c M ² _d O _(2-z) F _z

(In the formula 1,

M ¹ and M ² are at least one or more metals selected from the group consisting of Zr, Ti, Ca, V, Zn, Mo, Ni and Mn; 0.90 <a <1.10, 0 <b < 0.1, 0 < d < 0.1, 0 < z <

[Formula 2-1]

M ³ F _x

(In the above formula (2-1)

M ³ is at least one metal selected from the group consisting of Li, Ti, Ca, V, Zn, Mo, Ni, Co and Mn and 0 &

[Formula 2-2]

M ⁴ F _x

(In the above formula (2-2)

M ⁴ is at least one metal selected from the group consisting of Li, Ti, Ca, V, Zn, Mo, Ni, Co and Mn and 0 &

The feed materials of Mg, M ¹ and M ² may independently be hydroxides, oxyhydroxides, nitrates, halides, carbonates, nitrates, oxalates, citrates, or combinations thereof.

The fluorine supplying material may be an ammonium salt, a lithium salt, a metal salt, or a combination thereof.

The Al feed material may be a hydroxide, oxyhydroxide, nitrate, halide, carbonate, acetate, oxalate citrate, or a combination thereof.

Dry mixing the lithium supply material, the transition metal precursor, the Mg supply material, the M ¹ supply material, the M ² supply material, and the fluorine supply material; And firing the mixture, the firing temperature may be 800 to 1050 캜. This may be an effective doping and / or range for coating layer compound formation.

A coating layer disposed on the surface of the core and comprising a compound represented by the following Chemical Formula 2-1 and / or Chemical Formula 2-2 by firing a cathode active material to which the Al-containing compound powder is adhered; And a coating layer comprising Al. In the step of obtaining the cathode active material, the firing temperature may be 400 to 800 ° C.

For example, when firing at a temperature of 400 ° C or less, the reactivity between the coating material and the cathode active material is low, and it is difficult to expect a coating effect such as free coating of the coating material. In addition, when baking is performed at a temperature higher than 800 ° C, Al is excessively doped, so that the initial capacity of the battery may be decreased and the lifetime characteristics at room temperature, high temperature and low temperature may be deteriorated.

In another embodiment of the present invention, there is provided a lithium secondary battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode includes a current collector and a positive electrode active material layer formed on the current collector, And a positive electrode active material.

The description related to the cathode active material is omitted since it is the same as the one embodiment of the present invention described above.

The cathode active material layer may include a binder and a conductive material.

The binder serves to adhere the positive electrode active material particles to each other and to adhere the positive electrode active material to the current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl Polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-acrylonitrile, styrene-butadiene rubber, Butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like, but not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any conductive material can be used without causing any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, Carbon-based materials such as black and carbon fiber; Metal powders such as copper, nickel, aluminum, and silver, or metal-based materials such as metal fibers; Conductive polymers such as polyphenylene derivatives; Or a mixture thereof may be used.

The negative electrode includes a current collector and a negative active material layer formed on the current collector, and the negative active material layer includes a negative active material.

The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

As a material capable of reversibly intercalating / deintercalating lithium ions, any carbonaceous anode active material commonly used in lithium ion secondary batteries can be used as the carbonaceous material. Typical examples thereof include crystalline carbon , Amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in the form of amorphous, plate-like, flake, spherical or fibrous type. Examples of the amorphous carbon include soft carbon (soft carbon) Or hard carbon, mesophase pitch carbide, fired coke, and the like.

As the lithium metal alloy, a lithium-metal alloy may be selected from the group consisting of lithium, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, An alloy of a selected metal may be used.

As the material capable of doping and dedoping lithium, Si, SiO _x (0 <x <2), Si-Y alloy (Y is an alkali metal, an alkali earth metal, a Group 13 element, a Group 14 element, Rare earth elements and combinations thereof, but not Si), Sn, SnO ₂ , Sn-Y (wherein Y is at least one element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Element and an element selected from the group consisting of combinations thereof, and not Sn), and at least one of them may be mixed with SiO ₂ . 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, Ti, Ge, P, As, Sb, Se, Te, Po, and combinations thereof.

Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, and the like.

The negative electrode active material layer also includes a binder, and may optionally further include a conductive material.

The binder serves to adhere the anode active material particles to each other and to adhere the anode active material to the current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, Such as polyvinyl chloride, polyvinyl fluoride, polymers comprising ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, Styrene-butadiene rubber, epoxy resin, nylon, and the like may be used, but the present invention is not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any conductive material can be used without causing any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, Carbon-based materials such as black and carbon fiber; Metal powders such as copper, nickel, aluminum, and silver, or metal-based materials such as metal fibers; Conductive polymers such as polyphenylene derivatives; Or a mixture thereof may be used.

The collector may be selected from the group consisting of a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foil, a polymer substrate coated with a conductive metal, and a combination thereof.

As the current collector, Al may be used, but the present invention is not limited thereto.

The negative electrode and the positive electrode are prepared by mixing an active material, a conductive material and a binder in a solvent to prepare an active material composition, and applying the composition to a current collector. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein. As the solvent, N-methylpyrrolidone or the like can be used, but it is not limited thereto.

The electrolyte includes a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

The non-aqueous organic solvent may be a carbonate, ester, ether, ketone, alcohol, or aprotic solvent. Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC) EC), propylene carbonate (PC), and butylene carbonate (BC) may be used. As the ester solvent, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate , gamma -butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone, and the like can be used. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran. As the ketone solvent, cyclohexanone may be used have. As the alcoholic solvent, ethyl alcohol, isopropyl alcohol and the like can be used. As the aprotic solvent, R-CN (R is a linear, branched or cyclic hydrocarbon group having 2 to 20 carbon atoms, , A double bond aromatic ring or an ether bond), and dioxolanes such as 1,3-dioxolane, sulfolanes, and the like can be used.

The non-aqueous organic solvent may be used alone or in admixture of one or more. If the non-aqueous organic solvent is used in combination, the mixing ratio may be appropriately adjusted according to the desired cell performance. .

In the case of the carbonate-based solvent, it is preferable to use a mixture of a cyclic carbonate and a chain carbonate. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of 1: 1 to 1: 9, the performance of the electrolytic solution may be excellent.

The non-aqueous organic solvent according to an embodiment of the present invention may further include an aromatic hydrocarbon-based organic solvent in the carbonate-based solvent. In this case, the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed in a volume ratio of 1: 1 to 30: 1.

The aromatic hydrocarbon-based organic solvent may be an aromatic hydrocarbon-based compound represented by the following formula (5).

[Chemical Formula 5]

(Wherein R ₁ to R ₆ are each independently hydrogen, halogen, a C1 to C10 alkyl group, a haloalkyl group, or a combination thereof)

The aromatic hydrocarbon-based organic solvent is selected from the group consisting of benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3- , 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4 - triiodobenzene, toluene, fluorotoluene, 1,2-difluorotoluene, 1,3-difluorotoluene, 1,4-difluorotoluene, 1,2,3-trifluorotoluene, 1,2,4-trifluorotoluene, chlorotoluene, 1,2-dichlorotoluene, 1,3-dichlorotoluene, 1,4-dichlorotoluene, 1,2,3-trichlorotoluene, 1,2,4 - trichlorotoluene, iodotoluene, 1,2-diiodotoluene, 1,3-diiodotoluene, 1,4-diiodotol Yen, it is 1,2,3-tree-iodo toluene, 1,2,4-iodo toluene, xylene, and selected from the group consisting of.

The non-aqueous electrolyte may further include vinylene carbonate or an ethylene carbonate-based compound represented by the following formula (6) to improve battery life.

[Chemical Formula 6]

(In Formula 6, R ₇ and R ₈ are each independently hydrogen, halogen, cyano (CN), nitro group (NO ₂₎ or a C1 to a to C5 fluoroalkyl group, at least one of the R ₇ and R ₈ Is a halogen group, a cyano group (CN), a nitro group (NO ₂ ) or a C1 to C5 fluoroalkyl group.

Representative examples of the ethylene carbonate-based compound include diethylene carbonate, diethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, fluoroethylene carbonate, and the like, such as difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, . When such a life improving additive is further used, its amount can be appropriately adjusted.

The lithium salt is dissolved in an organic solvent to act as a source of lithium ions in the cell to enable operation of a basic lithium secondary battery and to promote the movement of lithium ions between the anode and the cathode. The lithium salt Representative examples are _{LiPF 6, LiBF 4, LiSbF 6} , LiAsF 6, LiC 4 F 9 SO 3, LiClO 4, 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, and _{LiB (C 2 O 4) 2} ( lithium bis oxalate reyito borate (lithium bis (oxalato) borate; LiBOB) is selected from the group consisting of The concentration of the lithium salt is preferably in the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity Can exhibit excellent electrolyte performance, and lithium ions can effectively migrate.

Depending on the type of the lithium secondary battery, a separator may exist between the positive electrode and the negative electrode. The separator may be a polyethylene / polypropylene double layer separator, a polyethylene / polypropylene / polyethylene triple layer separator, a polypropylene / polyethylene / poly It is needless to say that a mixed multilayer film such as a propylene three-layer separator and the like can be used.

The lithium secondary battery can be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery depending on the type of the separator and electrolyte used. The lithium secondary battery can be classified into a cylindrical shape, a square shape, a coin shape, Depending on the size, it can be divided into bulk type and thin type. The structure and the manufacturing method of these cells are well known in the art, and detailed description thereof will be omitted.

FIG. 1 schematically shows a representative structure of the lithium secondary battery of the present invention. 1, the lithium secondary battery 1 includes a positive electrode 3, a negative electrode 2, and a battery 4 including an electrolyte solution impregnated in the separator 4 existing between the positive electrode 3 and the negative electrode 2, And a sealing member (6) for sealing the battery container (5).

Hereinafter, examples and comparative examples of the present invention will be described. However, the following examples are only illustrative of the present invention and are not intended to limit the scope of the present invention.

Example

Example  One

CaCO ₃ , CaF ₂ , and TiO ₂ based on the active material were dry mixed with the mixture so as to have the contents shown in the following Table 1, and then they were mixed at a stoichiometric ratio of Co ₃ O ₄ and Li ₂ CO ₃ at 1000 ° C. Followed by heat treatment for 10 hours to prepare a cathode active material.

The prepared cathode active material and Al (OH) ₃ powder were dry mixed with a weight ratio of 100: 0.2 (cathode active material: Al (OH) ₃ powder) to uniformly adhere the dispersed Al (OH) ₃ powder to the surface of the cathode active material .

The dry mixed powder was heat-treated at 600 ° C for 5 hours to prepare a lithium ion cathode active material.

Example  2

_{Ni 0 .60 Co 0 .20 Mn 0} .20 (OH) 2 and Li ₂ MgCO _3, to the CaF _2, and, TiO ₂ as the active material based on a mixture of a stoichiometric ratio of CO ₃ the amount shown in Table 1 And the mixture was heat-treated at 850 ° C for 10 hours to prepare a cathode active material.

The prepared cathode active material and Al (OH) ₃ powder were dry mixed with a weight ratio of 100: 0.2 (cathode active material: Al (OH) ₃ powder) to uniformly adhere the dispersed Al (OH) ₃ powder to the surface of the cathode active material .

The dry mixed powder was heat-treated at 400 ° C for 5 hours to prepare a lithium ion cathode active material.

Comparative Example  One

MgCO ₃ , CaF ₂ , and TiO ₂ were dry mixed with the mixture to the contents shown in the following Table 1 at a stoichiometric ratio of Co ₃ O ₄ and Li ₂ CO ₃ as transition metal precursors, For 10 hours to prepare a cathode active material.

Comparative Example  2

MgCO ₃ , CaCO 3, and TiO ₂ were dry mixed with the mixture to the contents shown in the following Table 1 as a transition metal precursor in a stoichiometric ratio of Co ₃ O ₄ and Li ₂ CO ₃ , Followed by heat treatment for 10 hours to prepare a cathode active material.

The prepared cathode active material and Al (OH) ₃ powder were dry mixed at a weight ratio of 100: 0.2 to uniformly adhere the dispersed Al (OH) ₃ powder to the surface of the cathode active material particle.

The dry mixed powder was heat-treated at 600 ° C for 5 hours to prepare a lithium ion cathode active material.

Comparative Example  3

MgCO ₃ , CaCO ₃ , and TiO ₂ were dry mixed with the mixture to the contents shown in the following Table 1 as a transition metal precursor in a stoichiometric ratio of Co ₃ O ₄ and Li ₂ CO ₃ , For 10 hours to prepare a cathode active material.

Comparative Example  4

As a transition metal precursor, a mixture of stoichiometric proportions of Co ₃ O ₄ and Li ₂ CO ₃ was heat-treated at 1000 ° C for 10 hours to prepare a cathode active material.

Comparative Example  5

A cathode active material was prepared by heat treating a mixture of stoichiometric proportions of Ni _{0 .60} Co _{0 .20} Mn _{0 .20} (OH) ₂ and Li ₂ CO ₃ as a transition metal precursor at 850 ° C. for 10 hours.

element Content (ppm) Mg 1000 Ca 500 Ti 500

Coin cell  Produce

N-methyl-2-pyrrolidone (NMP) as a solvent was mixed with 95 weight% of the cathode active material prepared in the above Examples and Comparative Examples, 2.5 weight% of carbon black as a conductive agent, and 2.5 weight% of PVDF as a binder. To 5.0 wt% to prepare a positive electrode slurry. The positive electrode slurry was coated on an aluminum (Al) thin film as a positive electrode current collector having a thickness of 20 to 40 mu m, followed by vacuum drying and roll pressing to produce a positive electrode.

Li-metal was used as the cathode.

A coin-cell type half-cell was fabricated by using the thus prepared positive electrode and Li-metal as a counter electrode and using 1.15M LiPF6EC: DMC (1: 1 vol%) as an electrolyte solution.

Charging and discharging was carried out in the range of 4.5-3.0V, and the lifetime was 1.0C

Experimental Example  1: Evaluation of battery characteristics

Table 2 below shows initial formations, 1 cycle, 30 cycle, 50 cycle capacity and life characteristic data at 4.5 V and high temperature and high voltage condition of the above Examples and Comparative Examples.

　
Discharge capacity (mAh / g) efficiency 1CY
Discharge capacity 30CY
Discharge capacity 50CY
Discharge capacity Life characteristics
(30CY /
1CY,%) Life characteristics
(50CY /
1CY,%) Rate characteristic
(1.0 / 0.1C,%) Example 1 180.14 95.92 170.21 161.47 146.43 94.87 86.03 94.49 Example 2 202.84 89.67 195.73 181.64 165.12 92.80 84.36 91.12 Comparative Example 1 180.37 95.77 168.31 157.79 142.62 93.75 84.74 94.11 Comparative Example 2 179.76 95.81 167.84 157.28 140.58 93.71 83.76 93.81 Comparative Example 3 179.15 96.13 167.17 155.37 135.91 92.94 81.30 93.06 Comparative Example 4 179.34 94.57 166.48 128.44 95.71 77.15 57.49 92.88 Comparative Example 5 203.49 88.67 196.21 148.67 118.27 75.77 60.28 90.17

And doped with M ¹ and / or M ² in the core portion in Table 2, including a formula 2-1 and / or formula 2-2 on at least a portion of the surface, combined with the M ¹ and / or M ² in which the doping And a coating layer containing Al and a fluoride metal compound derived from the metal of the core portion, and Al were found to be superior to those of Comparative Examples 1 to 4 which did not include the composite coating layer.

More specifically, excellent characteristics in life characteristics are confirmed. Especially, it is confirmed that the long life of more than 30cy is better. Example 1 including a composite coating layer of a coating layer containing a metal fluoride compound and Al was compared with Comparative Example 1 which included a fluorinated metal compound coating layer without forming a composite coating layer and Comparative Example 2 which included a coating layer containing Al A difference in life characteristic is confirmed.

Also in Example 2 and Comparative Example 5, which are cathode active materials having different compositions, the above-mentioned characteristic differences are confirmed.

Experimental Example  2: X-ray photoelectron spectroscopy (X- ray Photoelectron Spectroscopy ; XPS )

The positive electrode active material prepared in Example 1 was analyzed by XPS and the results are shown in FIG. 2 from the core portion is doped with the M ¹ and / or M ^2, and comprises a formula 2-1 and / or formula 2-2 on at least a portion of the surface, which combines the M ¹ and / or M ² in which the doping It was confirmed that an active material further comprising a fluoride metal compound, a fluoride metal compound derived from the metal of the core portion, and a coating layer containing Al was obtained.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (17)

A core comprising a compound represented by the following formula (1);
A coating layer positioned on the surface of the core and comprising a compound represented by the following Chemical Formula 2-1 and / or Chemical Formula 2-2; And a coating layer comprising Al;
And a positive electrode active material for a lithium secondary battery.
[Chemical Formula 1]
Li _a Co _(1-bcd) Mg _b M ¹ _c M ² _d O _(2-z) F _z
(In the formula 1,
M ¹ and M ² are at least one or more metals selected from the group consisting of Zr, Ti, Ca, V, Zn, Mo, Ni and Mn; 0.90 <a <1.10, 0 <b < 0.1, 0 < d < 0.1, 0 < z <
[Formula 2-1]
M ³ F _x
(In the above formula (2-1)
M ³ is at least one metal selected from the group consisting of Li, Ti, Ca, V, Zn, Mo, Ni, Co and Mn and 0 &
[Formula 2-2]
M ⁴ F _x
(In the above formula (2-2)
M ⁴ is at least one metal selected from the group consisting of Li, Ti, Ca, V, Zn, Mo, Ni, Co and Mn and 0 &
The method according to claim 1,
Wherein M &lt; ^{1 &gt;} is Ca.
The method according to claim 1,
And M ² is Ti, Zr or a combination thereof.
The method according to claim 1,
The molar doping ratio of Mg, M ¹ and M ² is independently 0.001 to 0.01.
The method according to claim 1,
In the coating layer comprising the chemical formula 2-1 and / or 2-2 located on the surface of the positive electrode active material,
The positive electrode active material for a lithium secondary battery according to any one of claims ¹ to 3, wherein the negative electrode active material is a metal fluoride compound bonded to at least one of the doped M ¹ and / or M ² .
6. The method of claim 5,
Wherein the compound represented by Formula 2-1 and / or 2-2 is independently CaF ₂ or TiF ₄ .
The method according to claim 1,
In the coating layer comprising the chemical formula 2-1 and / or 2-2 located on the surface of the positive electrode active material,
Wherein the coating layer further comprises a metal fluoride compound derived from the core metal.
The method according to claim 1,
Wherein the Al-containing coating layer comprises a compound that is AlF ₃ , Al ₂ O ₃ , or a combination thereof.
The method according to claim 1,
A core comprising the compound represented by Formula 1; And a coating layer disposed on the surface of the core and containing a compound represented by the general formula (2-1) and / or the general formula (2-2), and a coating layer comprising Al are 0.02 to 0.2. Cathode active material for secondary battery.
A core comprising a compound represented by the following formula (3);
A coating layer positioned on the surface of the core and comprising a compound represented by the following Formula 4-1 and / or Formula 4-2; And a coating layer comprising Al;
And a positive electrode active material for a lithium secondary battery.
(3)
Li [Li _a A _(1-abcd) Mg _b M ¹ _c M ² _d ] O _{2 - z} F _z
(In the formula 3, A = Co, and Ni _{α β} Mn _γ, M ¹ and M ² are independently of each other, Zr, Ti, Ca, V, Zn, Mo, Ni, Mn, or a combination thereof, -0.05 0? D? 0.1, 0? B? 0.1, 0 <c <0.1, 0 <d <0.1, 0 <z <0.1, 0.6??? 0.81, 0.10?? 0.20 and 0.10?
[Formula 4-1]
M ³ F _x
(In the formula 4-1,
M ³ is derived from M ¹ or M ² of the above formula (3), and 0 <x? 4.
[Formula 4-2]
M ⁴ F _y
(In the formula 4-2,
M ⁴ is derived from Ni, Co, Mn or Mg of the above formula (3), 0 <y? 4,
The weight ratio of M ¹ / M ² in the cathode active material is 0.8 to 1.2.)
Dry mixing the lithium feed material, the transition metal precursor, the Mg feed material, the M ¹ feed material, the M ² feed material, and the fluorine feed material;
Calcining the mixture;
A core comprising a compound represented by the following formula (1); And a coating layer disposed on the surface of the core and comprising a compound represented by the following formula (2-1) and / or (2-2): (1) obtaining a cathode active material for a lithium secondary battery;
Dry mixing the obtained positive electrode active material and a compound powder containing Al to uniformly adhere the compound powder containing Al to the surface of the obtained positive electrode active material; And
A coating layer disposed on the surface of the core and comprising a compound represented by the following Chemical Formula 2-1 and / or Chemical Formula 2-2 by firing a cathode active material to which the Al-containing compound powder is adhered; And a coating layer comprising Al; obtaining a cathode active material comprising a composite coating layer comprising:
Wherein the positive electrode active material is a lithium secondary battery.
[Chemical Formula 1]
Li _a Co _(1-bcd) Mg _b M ¹ _c M ² _d O _(2-z) F _z
(In the formula 1,
M ¹ and M ² are at least one or more metals selected from the group consisting of Zr, Ti, Ca, V, Zn, Mo, Ni and Mn; 0.90 <a <1.10, 0 <b < 0.1, 0 < d < 0.1, 0 < z <
[Formula 2-1]
M ³ F _x
(In the above formula (2-1)
M ³ is at least one metal selected from the group consisting of Li, Ti, Ca, V, Zn, Mo, Ni, Co and Mn and 0 &
[Formula 2-2]
M ⁴ F _x
(In the above formula (2-2)
M ⁴ is at least one metal selected from the group consisting of Li, Ti, Ca, V, Zn, Mo, Ni, Co and Mn and 0 &
12. The method of claim 11,
Wherein the Mg, M ¹ and M ² supply materials are in the form of hydroxides, oxyhydroxides, nitrates, halides, carbonates, nitrates, oxalates, citrates or combinations thereof. &Lt; / RTI &gt;
12. The method of claim 11,
Wherein the fluorine supplying material is an ammonium salt, a lithium salt, a metal salt, or a combination thereof.
12. The method of claim 11,
Wherein the Al-containing compound is a hydroxide, an oxyhydroxide, a nitrate, a halide, a carbonate, a nitrate, a oxalate, a citrate, or a combination thereof.
12. The method of claim 11,
Dry mixing the lithium supply material, the transition metal precursor, the Mg supply material, the M ¹ supply material, the M ² supply material, and the fluorine supply material; And firing the mixture,
Wherein the calcination temperature is 800 to 1050 占 폚.
12. The method of claim 11,
A coating layer disposed on the surface of the core and comprising a compound represented by the following Chemical Formula 2-1 and / or Chemical Formula 2-2 by firing a cathode active material to which the Al-containing compound powder is adhered; And a coating layer comprising Al, wherein the positive electrode active material comprises:
Wherein the calcination temperature is 400 to 800 ° C. 2. A method for producing a cathode active material for a lithium secondary battery according to claim 1,
A positive electrode comprising the positive electrode active material for a lithium secondary battery according to any one of claims 1 to 10;
A negative electrode comprising a negative electrode active material; And
Electrolyte;
&Lt; / RTI &gt;

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