KR20160083818A - 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 active material for a rechargeable lithium battery, which has high capacity, high efficiency and an excellent life characteristic, and also relates to a method of preparing the same, and a rechargeable lithium battery including the same. According to the present invention, provided is the positive active material for a rechargeable lithium battery, comprising: a compound configured to reversibly intercalate/deintercalate lithium, wherein the compound is represented by chemical formula 1: Li_aM_(1-b)M_bO_(2-z); and a coating layer located on at least part of a surface of the compound represented by chemical formula 1, wherein the coating layer is a composite coating layer comprising a lithium metal oxide, a metal oxide, and/or a combination thereof.

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.

As described above, there have been provided cathode active materials for lithium secondary batteries including various coating layers for improving battery characteristics in the prior art.

The present invention provides a positive electrode active material for lithium secondary batteries excellent in high capacity, high efficiency, and long life characteristics, and a lithium secondary battery including the positive electrode active material.

In one embodiment of the present invention, there is provided a compound capable of reversible intercalation and deintercalation of lithium, wherein the compound is represented by the following formula (1), wherein at least a part of the surface of the compound of formula Wherein the coating layer is a composite coating layer further comprising a lithium metal oxide, a metal oxide, and / or a combination thereof.

[Chemical Formula 1]

Li _a M _{1 - b} M ^' _b O _{2 -z}

In Formula 1,

The metal M is at least one element selected from the group consisting of Ni, Co and Mn, and M ^' is at least one element selected from the group consisting of Zr, Ti, Mg, Ca, V, Zn, W, Mo, Sn, Ni, And 0.90 < a < 1.10, 0 < b < 0.1 and 0 &lt; z &lt;

More specifically, 0 < b < 0.1.

The compound of Formula 1 may be supplemented with oxygen deficiency due to the complex coating layer.

The composite coating layer may be formed through heat treatment.

The composite coating layer may comprise Li ₃ PO ₄ and / or LiF.

P and / or F of Li ₃ PO ₄ and / or LiF contained in the composite coating layer may be derived from a compound capable of reversible intercalation and deintercalation of lithium, or may be derived from P and / Or F compound.

The composite coating layer may further comprise S.

The lithium metal oxide included in the composite coating layer may be LiAlO ₂ , Li ₂ MgO ₂ , Li ₂ TiO ₃ , Li ₂ ZrO ₃ , Li ₂ SiO ₃ , Li ₄ SiO _4, or a combination thereof.

The metal oxide contained in the composite coating layer may be _{Al 2 O 3, MgO, TiO} 2, ZrO 2, SiO 2, or combinations thereof.

The content of the composite coating layer with respect to the total weight of the cathode active material may be 0.05 to 1.0 wt%.

In another embodiment of the present invention, there is provided a method of preparing a compound capable of reversible intercalation and deintercalation of lithium; Heat treating the compound capable of reversible intercalation and deintercalation of lithium in a hydrogen atmosphere to obtain a compound represented by Formula 1; A lithium source; A phosphorus and / or fluorine source; And a metal source; ; To the obtained compound of the formula (1), the lithium source; A phosphorus and / or fluorine source; And a metal source; and a lithium source on the surface of the obtained compound of the formula (1); A phosphorus and / or fluorine source; And a metal source; And the lithium source; A phosphorus and / or fluorine source; And a metal source; and heat-treating the compound of Formula 1, wherein the lithium source; A phosphorus and / or fluorine source; And a heat treatment of the compound of Formula 1 to which a metal source is attached, a coating layer is formed on at least a part of the surface of the compound of Formula 1, and the coating layer is formed of a lithium metal oxide, a metal oxide, and / Wherein the positive electrode active material is a composite coating layer further comprising a combination of these.

[Chemical Formula 1]

Li _a M _{1 - b} M ^' _b O _{2 -z}

In Formula 1,

The metal M is at least one element selected from the group consisting of Ni, Co and Mn, and M ^' is at least one element selected from the group consisting of Zr, Ti, Mg, Ca, V, Zn, W, Mo, Sn, Ni, And 0.90 < a < 1.10, 0 < b < 0.1 and 0 &lt; z &lt;

In the step of heat-treating the compound capable of reversible intercalation and deintercalation of lithium in a hydrogen atmosphere to obtain a compound of Formula 1, the heat treatment temperature may be 600 to 850 ° C.

The lithium source; A phosphorus and / or fluorine source; And a metal source; wherein the heat treatment temperature may be 600 to 850 ° 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 an embodiment 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 shows the results of 7Li MAS NMR analysis of Example 2. Fig.
3 shows the results of 7Li MAS NMR analysis of Comparative Example 2. 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, there is provided a compound capable of reversible intercalation and deintercalation of lithium, wherein the compound is represented by the following formula (1), wherein at least a part of the surface of the compound of formula Wherein the coating layer is a composite coating layer further comprising a lithium metal oxide, a metal oxide, and / or a combination thereof.

[Chemical Formula 1]

Li _a M _{1 - b} M ^' _b O _{2 -z}

In Formula 1,

The metal M is at least one element selected from the group consisting of Ni, Co and Mn, and M ^' is at least one element selected from the group consisting of Zr, Ti, Mg, Ca, V, Zn, W, Mo, Sn, Ni, And 0.90 < a < 1.10, 0 < b < 0.1 and 0 &lt; z &lt;

The compound of formula (1) may be supplemented with an oxygen deficiency by including the composite coating layer through heat treatment.

The compound of Formula 1 is generated by reduction treatment in an oxygen deficiency state and crystal structure change may occur on the surface. By containing the complex coating layer through heat treatment of the oxygen deficient compound, the deficiency of the surface structure can be suppressed through rearrangement of the surface crystal structure while the oxygen deficiency disappears. Thereby improving battery characteristics.

The composite coating layer may include Li ₃ PO ₄ and / or LiF to improve the battery characteristics of the lithium secondary battery. More specifically, it is possible to provide a cathode active material having improved efficiency characteristics and excellent lifetime characteristics over existing cathode active materials.

The above-mentioned Li ₃ PO ₄ also improves the ion conductivity and is effective for improving the efficiency characteristic. Further, when LiF is further contained, it is more advantageous to improve the battery characteristics by contributing to the stabilization of the surface structure by suppressing the side reaction with the electrolyte

P and / or F of Li ₃ PO ₄ and / or LiF contained in the composite coating layer may be derived from a compound capable of reversible intercalation and deintercalation of lithium, or P and / / RTI &gt; and / or F compounds.

The composite coating layer may further comprise S,

Similar to the above P and / or F, the S compound is also easily doped with anions in the oxygen deficient portion, thereby restricting defects in the surface structure through rearrangement of the crystal structure.

The composite coating layer of lithium metal contained in the oxide is _{LiAlO 2, Li 2 MgO 2,} Li 2 TiO 3, Li 2 ZrO 3, Li 2 SiO 3, the Al ₂ Li ₄ SiO _4, or may be a combination thereof, metal oxides O ₃ , MgO, TiO ₂ , ZrO ₂ , SiO ₂ , or a combination thereof.

The Li-containing metal compound of the composite coating layer facilitates the diffusion of Li ions in the cathode active material, thereby facilitating the movement of Li ions, thereby contributing to the improvement of battery characteristics.

In addition, the cathode active material according to one embodiment of the present invention can improve the battery characteristics of the lithium secondary battery. Examples of improved battery characteristics include improved efficiency characteristics of the battery at high voltage characteristics and excellent lifetime characteristics.

The content of the composite coating layer with respect to the total weight of the cathode active material may be 0.05 to 1.0 wt%. If the weight ratio is less than 0.05, the role of the coating layer may decrease. If the weight ratio is more than 1.0, the initial capacity decrease and the charge / discharge efficiency may decrease. However, the present invention is not limited thereto.

In another embodiment of the present invention, there is provided a method of preparing a compound capable of reversible intercalation and deintercalation of lithium; Heat treating the compound capable of reversible intercalation and deintercalation of lithium in a hydrogen atmosphere to obtain a compound represented by Formula 1; A lithium source; A phosphorus and / or fluorine source; And a metal source; ; To the obtained compound of the formula (1), the lithium source; A phosphorus and / or fluorine source; And a metal source; and a lithium source on the surface of the obtained compound of the formula (1); A phosphorus and / or fluorine source; And a metal source; And the lithium source; A phosphorus and / or fluorine source; And heat treating the compound of Formula 1 to which the metal source is attached,

The lithium source; A phosphorus and / or fluorine source; And a heat treatment of the compound of Formula 1 to which a metal source is attached, a coating layer is formed on at least a part of the surface of the compound of Formula 1, and the coating layer is formed of a lithium metal oxide, a metal oxide, and / Wherein the positive electrode active material is a composite coating layer further comprising a combination of these.

[Chemical Formula 1]

Li _a M _{1 - b} M ^' _b O _{2 -z}

In Formula 1,

The metal M is at least one element selected from the group consisting of Ni, Co and Mn, and M ^' is at least one element selected from the group consisting of Zr, Ti, Mg, Ca, V, Zn, W, Mo, Sn, Ni, And 0.90 < a < 1.10, 0 < b < 0.1 and 0 &lt; z &lt;

Treating the compound in the hydrogen atmosphere to obtain a compound of Formula 1, wherein the heat treatment temperature may be 600 to 850 ° C. If the temperature is within the above range, oxygen deficiency may occur in the cathode active material.

The lithium source; A phosphorus and / or fluorine source; And a metal source; And a coating layer disposed on at least a part of a surface of the compound of Formula 1 by heat treatment of the compound of Formula 1 attached thereto, wherein the coating layer is a composite comprising a lithium metal oxide, a metal oxide, and / In the step of obtaining the cathode active material including the coating layer, the heat treatment temperature may be 600 to 850 캜. In the case of the temperature range, the coating layer formed on the surface of the cathode active material can play a stable role.

The description of the remaining configuration is the same as that of the above-described embodiment of the present invention, so that the description thereof will be omitted.

According to another embodiment of the present invention, there is provided a lithium secondary battery including 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 lithium secondary battery comprising the above-described cathode 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 (1).

[Chemical Formula 1]

(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 (2) to improve battery life.

(2)

(In Formula 2, 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

LiCoO ₂ was heat-treated at 800 ° C under an atmosphere of 2% H2 for 1.5 hours to prepare a cathode active material deficient in oxygen. The oxygen deficient LiCoO ₂ and Al (OH) ₃ powders were dry mixed with a weight ratio of 100: 0.2 (cathode active material: Al (OH) ₃ powder) to uniformly adhere 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.

Example  2

100 g of the oxygen-deficient LiCoO ₂ prepared in Example 1, 0.054 g of LiOH powder, 0.172 g of Zr (OH) ₄ powder, 0.054 g of SiO ₂ powder and 0.387 g of (NH ₄ ) ₂ HPO ₄ powder were dry- after the powder is to prepare a mixture adhering to the surface of the oxygen-deficient LiCoO ₂ positive active material was prepared in a body by heat-treating the mixture 6 hours at 800 ℃.

Example  3

100 g of the oxygen deficient LiCoO ₂ prepared in Example 1, 0.032 g of LiOH powder, 0.172 g of Zr (OH) ₄ powder, 0.054 g of SiO ₂ powder, 0.387 g of (NH ₄ ) ₂ HPO ₄ powder and 0.029 g of LiF powder To prepare a mixture in which the powder adhered to the surface of the oxygen-deficient LiCoO ₂ body, and then the mixture was heat-treated at 800 ° C for 6 hours to prepare a cathode active material.

Example  4

The lack of oxygen prepared in Example 1, the mixer LiCoO ₂ 100g and 0.054g LiOH powder and Zr (OH) ₄ powder and SiO ₂ powder, 0.172g and 0.054g (NH _{4) 2} HPO ₄ powder, and 0.387g (NH _{4) 2} SO ₄ powder was dry mixed to prepare a mixture in which the powder was attached to the surface of the oxygen-deficient LiCoO ₂ body, and the mixture was heat-treated at 800 ° C for 6 hours to prepare a cathode active material.

Example  5

LiNi _{0 .60} Co _{0 .20} Mn _{0 .20} O ₂ was heat-treated at 600 ° C under an atmosphere of H ₂ 2% for 1.5 hours to prepare a cathode active material deficient in oxygen. The oxygen deficient LiNi _{0 .60} Co _{0 .20} Mn _{0 .20} O ₂ and Al (OH) ₃ powder were dry mixed with a weight ratio of 100: 0.2 (cathode active material: Al (OH) ₃ powder) ) ₃ powder was uniformly adhered to the surface of the positive electrode active material particles.

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

Comparative Example  One

LiCoO ₂ and Al (OH) ₃ powder were dry mixed with a mixer at 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 particle .

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

Comparative Example  2

100 g of LiCoO _2, 0.054 g of LiOH powder, 0.172 g of Zr (OH) 4 powder, 0.054 g of SiO 2 powder and 0.387 g of (NH ₄ ) ₂ HPO ₄ powder were mixed in a mixer so that the powder was attached to the surface of the LiCoO ₂ body After the mixture was prepared, the mixture was heat-treated at 800 ° C for 6 hours to prepare a cathode active material.

Comparative Example  3

General LiCoO ₂ free from oxygen deficiency was heat treated at 800 ° C for 6 hours to prepare a cathode active material.

Comparative Example  4

The oxygen deficient LiCoO ₂ prepared in Example 1 was heat-treated at 800 ° C for 6 hours to prepare a cathode active material.

Comparative Example  5

A general LiCoO ₂ cathode active material free from oxygen deficiency was prepared.

Comparative Example  6

The weight ratio of 0.2 (the positive electrode active material:: Al (OH) ₃ powder) LiNi _{0 .60} to mixer Co _{0 .20} Mn _{0 .20} O ₂ and Al (OH) ₃ powder 100 of Al (OH) dispersed in a mixture of dry ₃ powder was uniformly adhered to the surface of the positive electrode active material particles.

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

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 were performed in the range of 4.5-3.0V.

Experimental Example  1: Evaluation of battery characteristics

Table 1 below shows the 4.5 V initial formations, rate characteristics, 1 cycle, 20 cycle, 30 cycle capacity and life characteristic data of the examples and comparative examples.

Formation
Discharge capacity (mAh / g) efficiency 1CY
Discharge capacity 20CY
Discharge capacity 30CY
Discharge capacity Life characteristics
(20CY /
1CY,%) Life characteristics
(30CY /
1CY,%) Rate characteristic
(2.0 / 0.1C,%) Example 1 187.27 96.34 179.93 175.42 173.36 97.49 96.35 92.17 Example 2 193.32 97.71 191.22 187.68 185.25 98.15 96.88 94.72 Example 3 192.87 97.68 191.17 188.33 186.67 98.51 97.65 94.91 Example 4 193.94 97.49 190.87 187.25 185.22 98.10 97.04 94.62 Example 5 202.24 91.07 196.47 184.51 180.33 93.91 91.79 91.45 Comparative Example 1 187.81 96.12 180.20 173.42 170.80 96.24 94.78 90.51 Comparative Example 2 193.27 97.35 191.25 185.27 180.94 96.87 94.61 93.22 Comparative Example 3 188.47 95.11 181.28 157.22 144.68 86.73 79.81 88.79 Comparative Example 4 187.68 95.21 180.54 156.97 145.97 86.94 80.85 89.55 Comparative Example 5 187.69 94.62 180.23 156.11 142.87 86.62 79.27 87.94 Comparative Example 6 202.47 90.94 196.17 182.15 176.11 92.85 89.77 91.24

In Table 1, the battery characteristics of Examples 1 to 4 are superior to those of Comparative Examples 1 to 5.

More specifically, the cathode active material further comprises a coating layer positioned on at least a part of the surface of the oxygen-deficient compound, wherein the coating layer further comprises a lithium metal oxide, a metal oxide, and / Excellent characteristics are observed in the characteristic and life characteristic parts than the cathode active materials 1 to 2.

Oxygen Deficient Cathode Active Material Containing No Coating Layer Comparing Example 4 with the oxygen deficient cathode active material containing the coating layer in Example 2, it was found that the oxygen deficient cathode active material could not provide sufficient cell characteristics, It is confirmed that excellent cell characteristics are realized by surface rearrangement through crystal structure change. Comparing Example 2 and Comparative Example 2, the same coating layer was included but the difference in cell characteristics was confirmed by the presence or absence of oxygen deficiency.

Also in Example 5 and Comparative Example 6 having different compositions, the above-mentioned characteristic difference was confirmed.

Experimental Example  2: 7 Li MAS  NMR analysis

Example 2 and Comparative Example 2 were subjected to 7Li MAS NMR analysis. The analysis was performed at NMR frequency: 194.2676 MHz, Delay time: 10 sec, Number of scan: 400, π / 2 pulse: 9 μs, Reference: LiCl = 0 ppm. The results are shown in Figs. Unlike the comparative example, it can be confirmed that the impurity peak does not appear in the examples. It is confirmed that the impurity control is more improved in Example 2 than in Comparative Example 2 by changing the surface crystal structure by coating the oxygen deficient cathode active material.

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 (13)

A compound capable of reversible intercalation and deintercalation of lithium,
The compound is represented by the following general formula (1)
And a coating layer disposed on at least a part of a surface of the compound of Formula 1, wherein the coating layer is a composite coating layer further comprising a lithium metal oxide, a metal oxide, and / or a combination thereof.
[Chemical Formula 1]
Li _a M _{1 - b} M ^' _b O _{2 -z}
In Formula 1,
The metal M is at least one element selected from the group consisting of Ni, Co and Mn, and M ^' is at least one element selected from the group consisting of Zr, Ti, Mg, Ca, V, Zn, W, Mo, Sn, Ni, And 0.90 < a < 1.10, 0 < b &lt; 0.1 and 0 &lt; z &lt;
The method according to claim 1,
Wherein the compound of Formula 1 is supplemented with an oxygen deficiency due to the composite coating layer.
3. The method of claim 2,
Wherein the composite coating layer is formed through heat treatment.
The method according to claim 1,
Wherein the composite coating layer comprises Li ₃ PO ₄ and / or LiF.
5. The method of claim 4,
P and / or F of Li ₃ PO ₄ and / or LiF contained in the composite coating layer may be derived from a compound capable of reversible intercalation and deintercalation of lithium, or may be derived from P and / Or F compound. &Lt; RTI ID = 0.0 &gt; A &lt; / RTI &gt;
5. The method of claim 4,
Wherein the composite coating layer further comprises S as a cathode active material.
The method according to claim 1,
Wherein the lithium metal oxide contained in the composite coating layer is LiAlO ₂ , Li ₂ MgO ₂ , Li ₂ TiO ₃ , Li ₂ ZrO ₃ , Li ₂ SiO ₃ , Li ₄ SiO _4, or a combination thereof.
The method according to claim 1,
Contained in the composite coating layer of metal oxide is _{Al 2 O 3, MgO, TiO} 2, ZrO 2, SiO 2, or combinations thereof would a cathode active material for a lithium secondary battery.
The method according to claim 1,
Wherein the content of the composite coating layer with respect to the total weight of the cathode active material is 0.05 to 1.0 wt%.
Preparing a compound capable of reversible intercalation and deintercalation of lithium;
Heat treating the compound capable of reversible intercalation and deintercalation of lithium in a hydrogen atmosphere to obtain a compound represented by Formula 1;
A lithium source; A phosphorus and / or fluorine source; And a metal source; ;
To the obtained compound of the formula (1), the lithium source; A phosphorus and / or fluorine source; And a metal source; and a lithium source on the surface of the obtained compound of the formula (1); A phosphorus and / or fluorine source; And a metal source; And
The lithium source; A phosphorus and / or fluorine source; And heat treating the compound of Formula 1 to which the metal source is attached,
The lithium source; A phosphorus and / or fluorine source; And a heat treatment of the compound of Formula 1 to which a metal source is attached, a coating layer is formed on at least a part of the surface of the compound of Formula 1, and the coating layer is formed of a lithium metal oxide, a metal oxide, and / Lt; RTI ID = 0.0 &gt; a < / RTI &gt; combination of these
(Method for producing positive electrode active material for lithium secondary battery).
[Chemical Formula 1]
Li _a M _{1 - b} M ^' _b O _{2 -z}
In Formula 1,
The metal M is at least one element selected from the group consisting of Ni, Co and Mn, and M ^' is at least one element selected from the group consisting of Zr, Ti, Mg, Ca, V, Zn, W, Mo, Sn, Ni, And 0.90 &lt; a &lt; 1.10, 0 &lt; b &lt; 0.1 and 0 &lt; z &lt;
11. The method of claim 10,
Heat treating the compound capable of reversible intercalation and deintercalation of lithium in a hydrogen atmosphere to obtain a compound represented by the following formula 1,
And the heat treatment temperature is 600 to 850 占 폚.
11. The method of claim 10,
The lithium source; A phosphorus and / or fluorine source; And heat treating the compound of Formula 1 to which the metal source is attached,
And the heat treatment temperature is 600 to 850 占 폚.
A positive electrode comprising the positive electrode active material for a lithium secondary battery according to any one of claims 1 to 9;
A negative electrode comprising a negative electrode active material; And
Electrolyte;
&Lt; / RTI &gt;

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