KR20170106810A - 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 rechargeable lithium battery, a method for preparing the same and a rechargeable lithium battery including the same. The positive electrode active material for a rechargeable lithium battery comprises a compound capable of reversible intercalation and deintercalation of lithium. The compound comprises Al, and is doped with M1 and M2. The M1 and M2 are independently at least one of metals selected from the group consisting of Zr, Ti, Mg, Ca, V, Zn, Mo, Ni, Co and Mn. M1 and M2 are different.

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]

One embodiment of 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.

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 typical example of such a battery is a lithium secondary battery that generates electrical energy by a change in chemical potential when intercalation-deintercalation of lithium ions occurs 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 electrolyte 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 a problem of poor price competitiveness.

LiCoO ₂ has the highest discharge capacity of the battery among the above-mentioned cathode active materials, but it has a disadvantage that it is difficult to synthesize. In addition, the high oxidation state of nickel causes a decrease in 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.

One embodiment of the present invention provides a cathode active material for a lithium secondary battery having excellent life characteristics, a method for producing the same, and a lithium secondary battery including the same.

An embodiment of the present invention includes a compound capable of reversible intercalation and deintercalation of lithium, wherein the compound is doped with M1 and M2, and contains Al. The cathode active material for a lithium secondary battery includes to provide.

(M1 and M2 are at least any one selected from the group consisting of Zr, Ti, Mg, Ca, V, Zn, Mo, Ni, Co and Mn and M1 and M2 are different from each other.

The compound may be a cathode active material for a lithium secondary battery comprising a lithium composite oxide represented by the following general formula (1).

[Chemical Formula 1]

Li [Li _z A _(1-ZaBc) M _{1 a} M _{2 b} Al _c ] O ₂

In Formula 1,

A = _α Ni and Co _β Mn _γ, wherein M1 and M2 are independently selected from Zr, Ti, Mg, Ca, V, Zn, Mo, Ni, and at least one element selected from the group consisting of Co and Mn, -0.05 each other ? Z? 0.1 and 0.001? A + b + c? 0.03, 0.7??? 0.9, 0.05?? 0.2 and 0.01?? 0.15.

At this time, the M may be Zr, Ti, or a combination thereof.

Also, Al in the compound may be doped.

In addition, Al of the compound may be present inside and on the surface of the cathode active material.

In addition, the compound may further comprise a coating layer comprising Al and / or B.

The weight ratio of the coating layer to the total weight may be 0.05 to 0.5.

Another embodiment of the present invention is a method for preparing a lithium composite material, comprising: dry-mixing a lithium supply material, a transition metal precursor, and an M supply material, an Al supply material, and then firing the first mixture to form a lithium composite compound; Depositing a second mixture on the surface of the lithium composite compound by mixing the lithium composite compound with an Al supply material or a B supply material; Heat treating the compound to which the second mixture is attached; And a core doped with M and Al; And a coating layer disposed on the surface of the core and containing Al or B, to obtain a cathode active material for a lithium secondary battery.

(M is Zr, Ti, Mg, Ca, V, Zn, Mo, Ni, Co, Mn or a combination thereof)

At this time, in the step of firing the first mixture to form the lithium composite compound, the firing temperature may be 700 to 1,050 캜.

Further, in the step of heat-treating the compound to which the second mixture is attached, the heat treatment temperature may be 300 to 500 ° C.

Another embodiment of the present invention is a negative electrode comprising a positive electrode and a negative electrode active material including the above-described positive electrode active material for a lithium secondary battery; And an electrolyte. ≪ IMAGE >

According to one embodiment of the present invention, a cathode active material for a lithium secondary battery having excellent battery characteristics, a method for producing the same, and a lithium secondary battery including the same are provided.

1 is a schematic view of a lithium secondary battery.
FIG. 2 shows electrochemical impedance spectroscopy (EIS) results.

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

First, in one embodiment of the present invention, there is provided a compound capable of reversible intercalation and deintercalation of lithium, wherein the compound is doped with M1 and M2 and contains Al. Thereby providing a cathode active material.

(M1 and M2 are at least any one selected from the group consisting of Zr, Ti, Mg, Ca, V, Zn, Mo, Ni, Co and Mn and M1 and M2 are different from each other.

More specifically, the cathode active material can improve the battery characteristics of the lithium secondary battery. More specifically, according to one embodiment of the present invention, a cathode active material including composite doping can provide a cathode active material having improved lifetime characteristics than a cathode active material not containing doping.

The compound may be a cathode active material for a lithium secondary battery comprising a lithium composite oxide represented by the following general formula (1).

[Chemical Formula 1]

Li [Li _z A _(1-ZaBc) M _{1 a} M _{2 b} Al _c ] O ₂

In Formula 1,

A = _α Ni and Co _β Mn _γ, wherein M1 and M2 are independently selected from Zr, Ti, Mg, Ca, V, Zn, Mo, Ni, and at least one element selected from the group consisting of Co and Mn, -0.05 each other ? Z? 0.1 and 0.005? A + b + c? 0.05, 0.7??? 0.9, 0.05?? 0.2 and 0.01?? 0.15.

First, a compound capable of reversible intercalation and deintercalation of lithium is doped with M, and M is at least one element selected from the group consisting of Zr, Ti, Mg, Ca, V, Zn, Mo, Ni, It can be a metal in combination.

For example, the M may be Zr, Ti, or a combination thereof, but is not limited thereto.

The cathode active material may have a high Ni content and a high Ni content. There is a disadvantage in that the lifetime is deteriorated. Accordingly, the structure can be improved by doping to improve lifetime characteristics.

Also, Al in the compound may be doped.

The cathode active material may include Al, and Al may be a dopant cathode active material. Al doping suppresses the phase transition, which is a disadvantage of Ni-rich, and suppresses NiO by doping the inner and surface portions.

In addition, Al of the compound may be present inside and on the surface of the cathode active material.

Since the Al exists in the inside and on the surface of the cathode active material, Al is distributed on the surface as well as the internal structure, so that the side reaction with the electrolyte can be suppressed and the battery characteristics can be improved.

In addition, the compound may further comprise a coating layer comprising Al and / or B.

In addition, the coating layer may be further included to enhance the surface area, thereby further improving battery characteristics.

The weight ratio of the coating layer to the total weight may be 0.05 to 0.5.

According to another embodiment of the present invention, there is provided a method of manufacturing a lithium secondary battery, comprising the steps of: dry mixing a lithium supply material, a transition metal precursor, and an M supply material, and an Al supply material; Depositing a second mixture on the surface of the lithium composite compound by mixing the lithium composite compound with an Al supply material or a B supply material; Heat treating the compound to which the second mixture is attached; And a core doped with M and Al; And a coating layer disposed on the surface of the core and containing Al or B, to obtain a cathode active material for a lithium secondary battery.

The M may be Zr, Ti, Mg, Ca, V, Zn, Mo, Ni, Co, Mn, or combinations thereof.

At this time, the effective firing temperature for firing the first mixture to form the lithium composite compound may be 700 to 1,050 ° C.

Here, when the firing temperature is lower than 700 캜, rapid deterioration of the battery characteristics at normal temperature and high temperature may occur. If the firing temperature is higher than 1,050 占 폚, the capacity and capacity retention rate may be drastically lowered.

In addition, the effective firing temperature for heat-treating the compound to which the second mixture is attached may be 300 to 500. [

Here, when the firing temperature is less than 300 ° C, 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. If the firing temperature is higher than 500 ° C, the Al and B supply materials are excessively adhered to the compound, so that the initial capacity of the battery may be decreased and the life characteristics may be deteriorated at room temperature, high temperature and low temperature.

The description of the manufactured positive electrode active material is the same as that of the embodiment of the present invention described above, so a detailed description thereof will be omitted.

In still 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, A lithium secondary battery comprising a positive electrode active material.

The description related to the cathode active material is the same as that of the above-described embodiment of the present invention, and thus will not be described.

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, SiOx (0 <x <2), Si-Y alloy (Y is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, Sn, 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, transition metals, rare earth elements, and combinations thereof) Or an element selected from the group consisting of combinations thereof, but not Sn), and at least one of them may be mixed with SiO2. 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 ,? -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 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 hydrogen, a halogen group, a cyano group (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 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 batteries are well known in the art, and a 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 an anode 3, a cathode 2, and an electrolyte impregnated in the separator 4 existing between the anode 3 and the cathode 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 1

The mixture of NCM complex transition metal hydroxide (Ni: Co: Mn = 80:10:10), dispersed ZrO ₂ powder, TiO ₂ powder and Al (OH) ₃ were mixed in a mixer at a weight ratio of 100: 0.2: 0.3: 0.15 After dry mixing and firing, ZrO ₂ powder and TiO ₂ Powder and Al (OH) ₃ were allowed to uniformly adhere to the surface of the particles of the composite transition metal hydroxide, and then 1 mole of the complex transition metal hydroxide in which the ZrO ₂ powder, TiO ₂ powder and Al (OH) ₃ were uniformly adhered to the surface (Li / Metal = 1.025) in which LiOH was 1.025 mol based on the amount of LiOH. Then, the dry mixed powder was heat-treated at 750 ° C for 10 hours to prepare a lithium composite compound.

Example 2

The mixture of NCM complex transition metal hydroxide (Ni: Co: Mn = 80:10:10), dispersed ZrO ₂ powder, TiO ₂ powder and Al (OH) ₃ were mixed in a mixer at a weight ratio of 100: 0.2: 0.3: 0.15 After dry mixing and firing, ZrO ₂ powder and TiO ₂ Powder and Al (OH) ₃ were allowed to uniformly adhere to the surface of the particles of the composite transition metal hydroxide, and then 1 mole of the complex transition metal hydroxide in which the ZrO ₂ powder, TiO ₂ powder and Al (OH) ₃ were uniformly adhered to the surface (Li / Metal = 1.025) in which LiOH was 1.025 mol based on the amount of LiOH. Then, the dry mixed powder was heat-treated at 750 ° C for 10 hours to prepare a lithium composite compound.

The lithium composite compound thus prepared was dry mixed at a weight ratio of the lithium composite compound: B ₂ O ₃ powder = 100: 0.2 and then calcined to uniformly adhere the dispersed B ₂ O ₃ powder to the surface of the lithium composite compound Respectively. Then, the dry mixed powder was heat-treated at 400 ° C for 6 hours to prepare a cathode active material.

Comparative Example 1

LiOH was added to the mixer at a ratio (Li / Metal = 1.025) of 1.0 mol of LiOH to 1 mol of NCM complex transition metal hydroxide (molar ratio Ni: Co: Mn = 80:10:10) and dry mixed. Then, the dry mixed powder was heat-treated at 750 ° C for 10 hours to prepare a lithium composite compound.

Comparative Example 2

The NCM composite transition metal hydroxide (Ni: Co: Mn = 80: 10: 10), the dispersed ZrO ₂ powder and the TiO ₂ powder were dry mixed at a weight ratio of 100: 0.2: 0.3, ₂ powder and TiO ₂ The powder was uniformly adhered to the surface of the particles of the composite transition metal hydroxide and then the ratio of LiOH to LiO 2 / Li (metal / TiO ₂₎ / TiO ₂ powder was set such that the molar ratio of LiOH to one mole of the complex transition metal hydroxide to which the ZrO ₂ powder and TiO ₂ powder were uniformly adhered to the surface = 1.025) and dry mixed. Then, the dry mixed powder was heat-treated at 750 ° C for 10 hours to prepare a lithium composite compound.

Manufacture of Coin Cell

(Solvent) N-methyl-2-pyrrolidone (NMP) was added to 95% by weight of the positive electrode active material prepared in the above Examples and Comparative Examples, 2.5% by weight of carbon black as a conductive agent and 2.5% ) 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.

Experimental Example

Experimental Example 1: Evaluation of Battery Characteristics

Table 1 below shows the capacity and life characteristic data of 4.3 V initial mold, 45 DEG C, 4.5 V 1 cycle, 20 cycle, 30 cycle, and 23 DEG C of the above 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,%) Example 1 202.46 88.86 216.27 195.06 177.54 90.2 82.1 Example 2 202.75 89.22 216.34 195.12 178.10 90.2 82.3 Comparative Example 1 204.12 88.42 218.02 188.21 160.24 86.3 73.5 Comparative Example 2 203.55 89.14 217.91 194.04 174.16 89.0 79.9

As can be seen from the above Table 1, Examples 1 and 2 which were doped with M1 and M2 and contained Al exhibited excellent battery characteristics in terms of life characteristics as compared with Comparative Examples 1 and 2.

More specifically, the example including Al shows good lifetime characteristics at high temperature and high voltage as compared with Comparative Example 2 doped with M1 and M2.

In addition, better cell characteristics were confirmed in Example 2 further comprising a coating layer.

Experimental Example 2: Electrochemical Impedance Spectroscopy (EIS) Analysis

FIGS. 2 and 3 are electrochemical impedance spectroscopy (EIS) analysis results of Example 1 and Comparative Example 2, respectively. As the cycle progresses, it is confirmed that the resistance value of Comparative Example 2 is higher than that of Example 1 including Al and being doped with M1 and M2.

Experimental Example  3: Electrochemical Impedance Spectrocopy (EIS) analysis

Table 2 below shows XRD spectrum analysis data of Example 1 and Comparative Example 2 described above. XRD measurements were carried out by X-ray diffraction (Ultima IV, Rigaku) at 25 ° C in room temperature, CuKa, voltage of 40 kV, current of 3 mA, 10 to 90 deg, step width of 0.01 deg and step scan.

a axis c axis Example 1 2.8716 14.2112 Comparative Example 2 2.8724 14,192

Comparing Comparative Example 2 and Example 1 in Table 2, it is confirmed that the a axis decreases and the c axis increases. This is the result of Al doping.

Thereby increasing the structural stability and ease of Li migration.

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.

1: lithium secondary battery 2: negative electrode
3: anode 4: separator
5: Battery container 6: Sealing member

Claims (11)

A compound capable of reversible intercalation and deintercalation of lithium,
Said compound comprising Al,
Wherein the compound is doped with M &lt; 1 &gt; and M &lt; 2 &gt;. 2. A cathode active material for a lithium secondary battery,
M1 and M2 are independently at least one selected from the group consisting of Zr, Ti, Mg, Ca, V, Zn, Mo, Ni, Co, and Mn, and M1 and M2 are different from each other.
The method according to claim 1,
The present invention provides a lithium secondary battery comprising a lithium composite oxide represented by the following general formula (1): &lt; EMI ID =
[Chemical Formula 1]
Li [Li _z A _(1-ZaBc) M _{1 a} M _{2 b} Al _c ] O ₂
In Formula 1,
A = _α Ni and Co _β Mn _γ, wherein M1 and M2 are independently selected from Zr, Ti, Mg, Ca, V, Zn, Mo, Ni, and at least one element selected from the group consisting of Co and Mn, -0.05 each other ? Z? 0.1 and 0.001? A + b + c? 0.03, 0.5??? 0.9, 0.05?? 0.2 and 0.01?? 0.3.
The method according to claim 1,
And M is Zr, Ti or a combination thereof.
The method according to claim 1,
Wherein Al in said compound is a doping element.
The method according to claim 1,
Wherein the Al of the compound is present inside and on the surface of the cathode active material.
The method according to claim 1,
Wherein said compound further comprises a coating layer comprising Al and / or B. &lt; Desc / Clms Page number 24 &gt;
The method according to claim 6,
With respect to the total weight of the whole cathode active material,
Wherein the coating layer comprises 0.05 to 0.5% by weight of the coating layer.
Preparing a first mixture by dry mixing of a lithium supply material, a transition metal precursor, an M supply material, and an Al supply material, and then firing the mixture to form a lithium composite compound;
Preparing a second mixture by mixing the lithium composite compound with an Al supply material and / or a B supply material, and then attaching the second mixture to the surface of the lithium composite compound;
Heat treating the compound to which the second mixture is attached; And
A core doped with M and Al; And a coating layer disposed on the surface of the core and including Al and / or B, the method comprising: obtaining a cathode active material for a lithium secondary battery;
Wherein the positive electrode active material is a positive electrode active material.
(M is Zr, Ti, Mg, Ca, V, Zn, Mo, Ni, Co, Mn or a combination thereof)
9. The method of claim 8,
Preparing a first mixture by dry mixing of a lithium supply material, a transition metal precursor, an M supply material, and an Al supply material, and firing the mixture to form a lithium composite compound;
And the firing temperature is 700 to 1,050 占 폚.
9. The method of claim 8,
Heat treating the compound to which the second mixture is attached,
Wherein the heat treatment temperature is 300 to 500 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
And a lithium secondary battery.

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