KR20160094338A - 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 having high capacity, high efficiency, and an excellent life characteristic, and also relates to a lithium secondary battery having a positive electrode comprising the positive active material. Provided is the positive active material for a lithium secondary battery, comprising: a compound which enables reversible intercalation and deintercalation of lithium, wherein the compound is represented by chemical formula 1; and a coating layer which is disposed on at least part of a surface of the compound represented by chemical formula 1, wherein the coating layer comprises Li_3PO_4 and further comprises a composite coating layer further comprising a lithium metal oxide, a metal oxide, or a combination thereof. The chemical formula 1 is represented by Li_aM_(1-b)M_bO_2, wherein M is at least one element selected from the group consisting of Ni, Co, and Mn; M is at least one element selected from the group consisting of Zr, Ti, Mg, Ca, V, Zn, W, Mo, Sn, Ga, B and Al; and 0.90 < a < 1.10, and 0.09 < b < 0.15.

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 cathode active material for a lithium secondary battery, a method for producing the same, and a cathode 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, in a compound capable of reversible intercalation and deintercalation of lithium,

The compound is represented by the following general formula (1)

[Chemical Formula 1]

Li _a M _{1 - b} M ^` _b O ₂

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, Ga, 0.90 < a < 1.10, 0.09 < b &lt; 0.15,

A coating layer disposed on at least a part of the surface of the compound of Formula 1,

Wherein the coating layer comprises Li ₃ PO ₄ and the coating layer comprises a composite coating layer further comprising a lithium metal oxide, a metal oxide, or a combination thereof.

In Formula 1,

The metal M 'may be at least one element selected from Mg, Ti, Zr, Al,

In Formula 1,

The metal M 'may be Mg.

The compound capable of reversible intercalation and deintercalation of lithium may be a Li rich (Li / M ratio> 1.0) composition.

The Li ₃ PO ₄ contained in the composite coating layer or lithium of the lithium metal oxide may be derived from Li contained in a compound capable of reversible intercalation and deintercalation of lithium, .

In the lithium metal oxide or metal oxide contained in the composite coating layer, the metal may be Na, K, Ca, Ni, Co, Ti, Al, Si, Sn, Mn, Cr, Fe, V, Zr, have.

The content of the composite coating layer with respect to the total weight of the cathode active material may be 0.2 to 2.0 wt%

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, and an M &

Calcining the mixture; And

Comprising: obtaining a compound represented by the following formula (1);

Preparing a compound capable of reversible intercalation and deintercalation of lithium represented by Formula 1 below;

Phosphorus source; And a metal source;

Said phosphorus source to a compound capable of reversible intercalation and deintercalation of said lithium; And / or a metal source to provide a phosphorous source on the surface of the compound capable of reversible intercalation and deintercalation of lithium; 0.0 &gt; and / or &lt; / RTI &gt; And

The phosphorus source; Or a compound capable of reversible intercalation and deintercalation of lithium to which a metal source is attached is heat treated to include Li ₃ PO ₄ , and the coating layer further comprises a lithium metal oxide, a metal oxide, or a combination thereof And a compound capable of reversible intercalation and deintercalation of lithium including a composite coating layer formed on the surface of the lithium secondary battery.

[Chemical Formula 1]

Li _a M _{1 - b} M ^` _b O ₂

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, Ga, And 0.90 < a < 1.10 and 0.09 < b &lt; 0.15.

In the step of firing the mixture, the firing temperature may be 750 to 1,050 캜.

The phosphorus source; And / or a compound capable of reversible intercalation and deintercalation of lithium to which a metal source is attached is heat treated to form Li ₃ PO ₄ , said coating layer comprising a lithium metal oxide, a metal oxide, A compound capable of reversible intercalation and deintercalation of lithium, including a composite coating layer that further comprises a composite coating layer, wherein the heat treatment temperature may be 650 to 950 캜.

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.

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, in a compound capable of reversible intercalation and deintercalation of lithium,

The compound is represented by the following general formula (1)

[Chemical Formula 1]

Li _a M _{1 - b} M ^` _b O ₂

In Formula 1,

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, 0.90 < a < 1.10, 0.09 < b &lt; 0.15,

A coating layer disposed on at least a part of the surface of the compound of Formula 1,

Wherein the coating layer comprises Li ₃ PO ₄ and the coating layer comprises a composite coating layer further comprising a lithium metal oxide, a metal oxide, or a combination thereof.

In Formula 1,

The metal M 'may be at least one element selected from Mg, Ti, Zr, Al,

In Formula 1,

The metal M 'may be Mg.

In the case of excessive doping in a general cathode active material, capacity drop and battery characteristics may be deteriorated. However, due to the excessive doping at the high voltage, the structure is stabilized to provide a cathode active material suitable for a high voltage.

In addition, when the metal M 'is Mg, Co4 + elution is inhibited at a high voltage, thereby suppressing battery characteristics deterioration due to elution.

The compound capable of reversible intercalation and deintercalation of lithium may be a Li rich (Li / M ratio> 1.0) composition.

Li3PO4 contained in the composite coating layer, or lithium of the lithium metal oxide, may originate from Li contained in a compound capable of reversible intercalation and deintercalation of the lithium, or may originate from a separate Li supply material .

In the lithium metal oxide or metal oxide contained in the composite coating layer, the metal may be Na, K, Ca, Ni, Co, Ti, Al, Si, Sn, Mn, Cr, Fe, V, Zr, have.

The content of the composite coating layer with respect to the total weight of the cathode active material may be 0.2 to 2.0 wt%

The positive electrode active material including the composite coating layer containing Li ₃ PO ₄ and further including a lithium metal oxide, a metal oxide, or a combination thereof can improve the battery characteristics of the lithium secondary battery. More specifically, it is possible to provide a cathode active material having an initial capacity higher than that of the conventional cathode active material, an improved efficiency characteristic, and an excellent rate characteristic.

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.

If the above-described reversible intercalation and deintercalation of lithium is doped with a particular doping element excessively, it may be particularly preferable to realize the battery characteristics by the coating layer. In the LiMO ₂ (M, Ni, Co, or Mn) composition system, a rock-salt structure can be formed on the surface of the anode material under conventional manufacturing conditions. In the chemical reaction process in which Li 3 PO 4 is formed as in the present invention, Rocksalt -> layered) occurs to control the structure defects and impurities formed on the surface. The general LiMO ₂ (M is Ni, Co, or Mn) when applying the composition Li ₃ PO ₄ is a Li shortage is generated in the course of formation to be characteristic, some degradation battery and also Li ₃ in the composition that is not doped When PO ₄ coating is carried out, structural defects may occur due to the reduction reaction occurring between P and the surface of the cathode material. In conclusion, Li ₃ PO ₄ is formed when a coating is applied to a compound having a Li rich (Li / M ratio> 1.0) composition and capable of reversible intercalation and deintercalation of lithium doped with a specific element It is possible to further provide a surface capable of maximizing the effect of the coating layer by suppressing the surface defects due to the lack of Li and the reduction reaction occurring in the process.

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, and an M &

Calcining the mixture; And

Comprising: obtaining a compound represented by the following formula (1);

Preparing a compound capable of reversible intercalation and deintercalation of lithium represented by Formula 1 below;

Phosphorus source; And / or a metal source;

Said phosphorus source to a compound capable of reversible intercalation and deintercalation of said lithium; And / or a metal source to provide a phosphorous source on the surface of the compound capable of reversible intercalation and deintercalation of lithium; 0.0 &gt; and / or &lt; / RTI &gt; And

The phosphorus source; And / or a compound capable of reversible intercalation and deintercalation of lithium to which a metal source is attached is heat treated to form Li ₃ PO ₄ , said coating layer comprising a lithium metal oxide, a metal oxide, And a compound capable of reversible intercalation and deintercalation of lithium including a composite coating layer that further comprises a composite coating layer on the surface of the lithium secondary battery.

[Chemical Formula 1]

Li _a M _{1 - b} M ^` _b O ₂

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, Ga, And 0.90 < a < 1.10 and 0.09 < b &lt; 0.15.

Firing the mixture,

The firing temperature may be 750 to 1,050 캜.

The phosphorus source; Or a compound capable of reversible intercalation and deintercalation of lithium to which a metal source is attached, comprising Li3PO4, wherein the coating layer is a composite coating layer further comprising a lithium metal oxide, a metal oxide, To obtain a compound capable of reversible intercalation and deintercalation of lithium,

The heat treatment temperature may be 650 to 950 캜.

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 (2).

(2)

(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 (3) to improve battery life.

(3)

(In Formula 3, 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

Co ₃ O _{4 ,} Li ₂ CO ₃ And MgCO ₃ mixture were dry mixed and then the mixture was heat-treated at 1000 ° C. for 10 hours to prepare a cathode active material Li _{1 .02} Co _{0 .9} Mg _{0 .1} O ₂ .

100 g of the prepared cathode active material, 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 mixed to prepare a mixture adhered to the surface of the cathode active material body The mixture was heat-treated at 800 ° C for 6 hours to prepare a cathode active material.

Example  2

Co ₃ O _{4 ,} Li ₂ CO ₃ And ZrO ₂ were dry mixed, and then the mixture was heat-treated at 1000 ° C. for 10 hours to prepare a cathode active material Li _{1 .02} Co _{0 .9} Zr _{0 .1} O ₂ .

100 g of the prepared cathode active material, 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 mixed to prepare a mixture adhered to the surface of the cathode active material body The mixture was heat-treated at 800 ° C for 6 hours to prepare a cathode active material.

Example  3

_{Ni 0 .6 Co 0 .2 Mn 0} .2 (OH) 2, Li 2 CO 3 And MgCO ₃ were dry mixed and then the mixture was heat-treated at 800 ° C. for 12 hours to prepare a cathode active material such that Li _{1 .01} (Ni _{0 .6} Co _{0 .2} Mn _{0 .2} ) _0.99 Mg _{0 .1} O ₂ Respectively.

100 g of the prepared cathode active material, 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 mixed to prepare a mixture adhered to the surface of the cathode active material body The mixture was heat-treated at 650 ° C. for 6 hours to prepare a cathode active material.

Comparative Example  One

Co ₃ O _{4 ,} Li ₂ CO ₃ And MgCO ₃ mixture were dry mixed and then the mixture was heat-treated at 1000 ° C. for 10 hours to prepare a cathode active material Li _{1 .02} Co _{0 .8} Mg _{0 .2} O ₂ .

100 g of the prepared cathode active material, 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 mixed to prepare a mixture adhered to the surface of the cathode active material body The mixture was heat-treated at 800 ° C for 6 hours to prepare a cathode active material.

Comparative Example  2

LiCoO _2, 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 mixed to prepare a mixture in which the powder was adhered to the surface of the cathode active material body, The mixture was heat-treated at 800 DEG C for 6 hours to prepare a cathode active material.

Comparative Example  3

LiCoO ₂ was used.

Comparative Example  4

LiNi _{0 .60} Co _{0 .20} Mn _{0 .20} O ₂ was used.

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 LiPF ₆ EC: 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.

Discharge capacity
(mAh / g) efficiency 1CY
Discharge capacity 20CY
Discharge capacity 30CY
Discharge capacity Life characteristics
(20CY /
1CY,%) Life characteristics
(30CY /
1CY,%) Rate characteristic
(1.0 / 0.2C,%) Example 1 192.47 97.79 186.10 181.13 177.23 97.33 95.23 96.66 Example 2 191.72 97.43 184.91 180.09 176.34 97.39 95.37 96.71 Example 3 202.47 91.07 196.22 183.74 180.11 93.64 91.79 91.14 Comparative Example 1 190.31 95.92 184.69 175.19 173.22 94.86 93.79 93.92 Comparative Example 2 191.75 96.57 186.12 179.14 174.12 96.25 93.55 95.61 Comparative Example 3 189.74 95.11 185.22 160.81 147.54 86.82 79.66 92.81 Comparative Example 4 204.11 87.91 195.68 177.54 166.17 90.73 84.92 88.89

In Table 1, the battery characteristics of Examples 1 to 3 are superior to those of Comparative Examples 1 to 4.

It is confirmed that the cathode active material including the complex coating layer excessively doped in Examples 1 and 2 contains a composite coating layer but the battery of Comparative Example 2 in which the doping is not doped has a difference in battery characteristics. It is confirmed that excessive doping is useful for high voltage.

Compared with Comparative Example 1, which is much overdoped, it is confirmed that the excessive doping is less effective on the battery characteristics.

Also, the improvement of the characteristics of the cathode active materials having different compositions is confirmed.

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 (11)

For compounds capable of reversible intercalation and deintercalation of lithium,
The compound is represented by the following general formula (1)
[Chemical Formula 1]
Li _a M _{1 - b} M ^{`</sup> <sub>b</sub> O <sub>2</sub>
In Formula 1,
The metal M is at least one element selected from the group consisting of Ni, Co and Mn, and M <sup>'</sup> is at least one element selected from the group consisting of Zr, Ti, Mg, Ca, V, Zn, W, Mo, Sn, Ga, 0.90 < a < 1.10, 0.09 < b &lt; 0.15,
A coating layer disposed on at least a part of the surface of the compound of Formula 1,
Wherein the coating layer comprises Li <sub>3</sub> PO <sub>4</sub> , and the coating layer comprises a composite coating layer further comprising a lithium metal oxide, a metal oxide, or a combination thereof.
The method according to claim 1,
In Formula 1,
And the metal M <sup>'</sup> is at least one element selected from Mg, Ti, Zr, Al, and B. The positive electrode active material for a lithium secondary battery according to claim 1,
The method according to claim 1,
In Formula 1,
And the metal M <sup>`} is Mg.
The method according to claim 1,
Wherein the compound capable of reversible intercalation and deintercalation of lithium has a composition of Li rich (Li / M ratio> 1.0).
The method according to claim 1,
The Li ₃ PO ₄ contained in the composite coating layer or lithium of the lithium metal oxide may be derived from Li contained in a compound capable of reversible intercalation and deintercalation of lithium, And a positive electrode active material for a lithium secondary battery.
The method according to claim 1,
In the lithium metal oxide or metal oxide contained in the composite coating layer, the metal is Na, K, Ca, Ni, Co, Ti, Al, Si, Sn, Mn, Cr, Fe, V, Zr, 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 0.2 to 2.0 wt%.
Dry mixing the lithium feed material, the transition metal precursor, and the M ^' feed material;
Calcining the mixture; And
Comprising: obtaining a compound represented by the following formula (1);
Preparing a compound capable of reversible intercalation and deintercalation of lithium represented by Formula 1 below;
Phosphorus source; And / or a metal source;
Said phosphorus source to a compound capable of reversible intercalation and deintercalation of said lithium; And / or a metal source to provide a phosphorous source on the surface of the compound capable of reversible intercalation and deintercalation of lithium; 0.0 &gt; and / or < / RTI &gt; And
The phosphorus source; And / or a compound capable of reversible intercalation and deintercalation of lithium to which a metal source is attached is heat treated to form Li ₃ PO ₄ , said coating layer comprising a lithium metal oxide, a metal oxide, A compound capable of reversible intercalation and deintercalation of lithium comprising a composite coating layer further comprising:
: &Lt; / RTI &gt; a method for producing a cathode active material for a lithium secondary battery comprising:
[Chemical Formula 1]
Li _a M _{1 - b} M ^` _b O ₂
(In the 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, Ga, And 0.90 &lt; a &lt; 1.10 and 0.09 &lt; b &lt; 0.15.
9. The method of claim 8,
Firing the mixture,
And the firing temperature is 750 to 1,050 ° C.
9. The method of claim 8,
The lithium source; Phosphorus source; And / or a material capable of reversible intercalation and deintercalation of lithium to which a metal source is attached is heat treated to form Li3PO4, wherein the coating layer further comprises a lithium metal oxide, a metal oxide, and / A compound capable of reversible intercalation and deintercalation of lithium, including a composite coating comprising lithium,
And the heat treatment temperature is 650 to 950 占 폚.
A positive electrode comprising the positive electrode active material for a lithium secondary battery according to any one of claims 1 to 7;
A negative electrode comprising a negative electrode active material; And
Electrolyte;
&Lt; / RTI &gt;

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