KR20150069335A - Method for preparing Cathode active material, cathode active material prepared by the same, and lithium secondary batteries comprising the same - Google Patents

Abstract

The present invention relates to a method for preparing a positive electrode active material, comprising a step of mixing Li_α(NH_4)_βPO_4(α+β=3) to lithium metal composite oxide particles and treating the same by heat, wherein the a lithium metal phosphorus oxide is engraved and coated from surfaces of the lithium metal composite oxide particles to the inside by heat treatment, and to the positive electrode active material prepared by the method. According to the present invention, a lithium secondary battery using the positive electrode active material expresses high capacity due to the lithium metal phosphorus oxide having strong binding force with oxygen, and can highly improve lifespan properties since occurrence of oxygen gas is inhibited on surfaces of the positive electrode active material.

Description

FIELD OF THE INVENTION The present invention relates to a cathode active material, a cathode active material prepared by the method, and a lithium secondary battery comprising the cathode active material,

The present invention relates to a cathode active material, a method for producing the same, and a lithium secondary battery comprising the same, and more particularly, to a cathode active material for a lithium secondary battery having a high capacity and a long life, ≪ / RTI >

BACKGROUND ART [0002] A lithium secondary battery is a secondary battery having excellent performance such as a high capacity, a high output and a long life, and is widely used in small electronic products such as electronic devices, portable computers and mobile phones. Especially, as the interest in environmental problems grows, it is one of the main causes of air pollution. As a driving source of electric vehicles that can replace fossil fuel vehicles such as gasoline vehicles and diesel vehicles, lithium Research on secondary batteries is actively under way.

Lithium transition metal oxides containing lithium are mainly used as the positive electrode active material used in lithium secondary batteries, and layered lithium transition metal oxides such as cobalt based, nickel based, and cobalt-nickel- Of the total.

However, the layered lithium transition metal oxide, which is conventionally used as a cathode active material, has a limit in the energy density because the reversible capacity that can be used is 200 mAh / g or less. Therefore, as a means for solving the problem of the lithium secondary battery due to the limitation of the reversible capacity of the anode, a study on a lithium-excess layered oxide (OLO) containing an excess of lithium instead of the general layered lithium transition metal oxide .

The positive electrode active material containing a lithium-excess layered oxide has a structure in which a Li ₂ MnO ₃ phase is mixed with a layered lithium-transition metal oxide such as conventional LiMO ₂ (M is at least one selected from Co, Ni and Mn) When the battery is initially charged at 4.6 V, oxygen is desorbed from Li ₂ MnO ₃ , and lithium is extracted, thereby exhibiting a high capacity.

However, due to the decomposition of the electrolytic solution at high voltage and the generation of self-oxygen, the crystal structure is physically and chemically deformed at the time of repeated charging and discharging, and the rate characteristic is lowered, thereby deteriorating the performance and life characteristics of the battery.

In order to solve such a problem, Patent Document 1 discloses a method of modifying the surface of a lithium-excess metal composite oxide, specifically, a method of modifying the surface of a lithium-excess metal composite oxide, specifically Li _w Ni _x Co _y Mn _{1 -xy- z} M _z O ₂ M is at least one element selected from the group consisting of Al, Mg, Fe, Cu, Zn, Cr, Ag, Ca, Na, K, In, Ga, Ge, V, Mo, Nb, At least one metal selected from the group consisting of Si, Ti and Zr); And a coating layer containing a fluorine compound on the lithium-metal composite oxide core, and a cathode active material for a lithium secondary battery.

Further, Patent Document 2 _{XLi 2 MnO 3 · (1-} X) is composed of LiMO _2, the shell portion of the positive electrode active material having excellent thermal safety _δ Li [Ni _x Mn _(1- a core portion having high capacity properties of the positive electrode active material _{( x + y))} M ' _y ] O ₂ , wherein X is more than 0 and less than 0.9, and M is at least one element selected from the group consisting of nickel, Iron, manganese, cobalt or aluminum, 隆 is not less than 1.0 and not more than 1.5, x is not less than 0.01 and not more than 0.05, and M 'is cobalt, iron or aluminum.

In the case of the secondary battery manufactured using the cathode active material manufactured by the above prior art documents, the initial discharge capacity was 220 mAh / g The lithium transition metal oxide of the present invention has been improved as compared with the cathode active material using the conventional layered lithium transition metal oxide. However, there is a continuing need for research on a cathode active material for a lithium secondary battery having a higher discharge capacity and a longer lifetime.

KR 2013-0033155 A KR 2013-0080565 A

The present invention relates to a cathode active material having a high capacity and capable of exhibiting a high capacity by coating a lithium metal phosphide having a strong binding force with oxygen on the surface of a lithium-excess layered lithium metal composite oxide particle capable of high- The purpose is to provide.

Another object of the present invention is to provide a cathode active material having improved battery capacity by intentionally coating a lithium metal phosphate with the lithium metal complex oxide doped with fluorine (F).

It is another object of the present invention to provide a simple method for manufacturing the above-mentioned cathode active material and a secondary battery including the same.

According to an aspect of the present invention, there is provided a lithium metal composite oxide particle including Li _alpha (NH ₄ ) _β PO ₄ (α + β = 3) mixed with lithium metal composite oxide particles and heat- Wherein a lithium metal oxide is intaglio coated on the inner surface of the surface of the lithium metal composite oxide particle.

The mixing ratio of Li _alpha (NH ₄ ) _β PO ₄ (α + β = 3) is preferably from 1 to 10 mol% based on the total amount of lithium contained in the positive electrode active material, .

Also, the lithium metal composite oxide may be prepared by: synthesizing a transition metal compound precursor; And a step of mixing the precursor of the transition metal compound with a source of Li and then heat-treating the precursor at 600 to 1000 ° C., wherein the lithium source used is Li ₂ CO ₃ , LiOH, LiNO ₃ and LiCH ₃ COO Lt; / RTI >

The fluorine source may be added in the mixing process of the precursor and the Li source, and the fluorine source may be mixed such that the mole ratio of Li: F contained in the cathode active material is 1: 0.01-0.1 the fluorine source may be LiF, NaF, KF, CsF, RbF, TiF, AgF, AgF₂, BaF _2, CaF _2, CuF _2, CdF _2, FeF _2, HgF _2, Hg ₂ F _2, MnF _2, MgF _{2, NiF 2, PbF 2, SnF 2} , SrF 2, XeF 2, ZnF 2, AlF 3, BF 3, BiF 3, CeF 3, CrF 3, DyF 3, EuF 3, GaF 3, GdF 3, FeF 3, HoF 3 _{, InF 3, LaF 3, LuF} 3, MnF 3, NdF 3, VOF 3, PrF 3, SbF 3, ScF 3, SmF 3, TbF 3, TiF 3, TmF 3, YF 3, YbF 3, TIF 3, CeF _{4, GeF 4, HfF 4,} SiF 4, SnF 4, TiF 4, VF 4, ZrF 4, NbF 5, SbF 5, TaF 5, BiF 5, MoF 6, ReF 6, SF 6 , and from the group consisting of WF ₆ At least one selected may be used.

The present invention also provides a positive electrode active material characterized in that a lithium metal phosphate expressed by the following formula (2) is intaglio coated on the surface of a layered lithium metal composite oxide particle represented by the following formula (1).

Formula 1

Li _{1 + x} Ni _a Co _b Mn _c O _{2 + d}

(Where 0 <x <0.33, 0 <a <0.4, 0 <b <0.4, 0.4 <c <0.9, -0.5 <d <0.5, x + a + b + c = 1)

(2)

Li _{1 + y} Ni _a Co _b Mn _c PO _{4 + e}

0.4, 0 <b <0.4, 0.4 <c <0.9, -0.5 <e <0.5)

The content of the lithium metal phosphate is preferably 1 to 10 mol% based on the total amount of lithium contained in the cathode active material.

The lithium metal composite oxide may be doped with F, and the doping amount of F is preferably 1 to 10 mol% based on the total amount of Li contained in the cathode active material.

The present invention also provides a positive electrode comprising the positive electrode active material; A negative electrode comprising a negative electrode active material; And an electrolyte existing between the positive electrode and the negative electrode.

The lithium secondary battery using the cathode active material according to the present invention is capable of suppressing the generation of oxygen gas on the surface of the cathode active material and improving the lifetime characteristics while exhibiting a high capacity due to the lithium metal phosphorous having strong binding force with oxygen .

Further, when the positive electrode active material in which the lithium metal phosphate is intentionally coated on the lithium metal complex oxide doped with F further can be used, the battery capacity can be further improved.

According to the method for producing a cathode active material according to the present invention, a lithium metal phosphorous having a strong binding force with oxygen can be reliably coated on the surface of a lithium metal composite oxide by a simple process.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a positive electrode active material in which a lithium metal phosphate is intaglio coated.

&Lt; Method for producing positive electrode active material &

Invention to the inside on the surface of the _{Li α (NH 4) β PO} 4 (α + β = 3) were mixed, and comprising the step of heat-treating, the lithium-metal complex oxide by the heat-treated particles in the lithium-metal composite oxide particles And a method for producing a cathode active material in which a lithium metal phosphorus oxide is intaglio coated.

Here, the expression "intaglio coating" means that, in a state in which only some of the raw materials (the source of lithium and the source of phosphorous acid) in the raw material forming the coating layer are additionally supplied, Means that a lithium metal phosphate coating layer is formed by bonding with a transition metal. In the present specification, as described in Patent Document 1, there is a clear distinction between a general surface coating to which all the raw materials forming the coating layer are supplied, The expression "intaglio coating" is used.

That is, a Li _α (NH _{4) β} PO ₄ by heat-treating a mixture of (α + β = 3), the NH ₄ removed from the source is a lithium source and the source of phosphate in the lithium-metal composite oxide represented by the general formula (1) And Li and PO ₄ are diffused from the surface of the lithium metal composite oxide particle in an ionic form into the transition metal in the lithium metal complex oxide to form an oxide coating layer which is a lithium metal represented by the following Chemical Formula 2. Therefore, the cathode active material according to the present invention does not change the particle size due to the formation of the coating layer unlike the conventional surface coating.

By the heat treatment, a cathode active material having an intaglio coated lithium metal phosphate represented by the following formula (2) is produced inward from the surface of the lithium metal composite oxide particle represented by the following formula (1).

Formula 1

Li _{1 + x} Ni _a Co _b Mn _c O _{2 + d}

(Where 0 <x <0.33, 0 <a <0.4, 0 <b <0.4, 0.4 <c <0.9, -0.5 <d <0.5, x + a + b + c = 1)

(2)

Li _{1 + y} Ni _a Co _b Mn _c PO _{4 + e}

0.4, 0 <b <0.4, 0.4 <c <0.9, -0.5 <e <0.5)

The heat treatment is preferably performed at a temperature of 500 to 700 ° C for 1 to 10 hours. When the temperature is lower than 500 ° C, the reaction between the transition metal in the lithium metal complex oxide and Li _? (NH ₄ ) _? PO ₄ is not performed well It may be difficult to form an intaglio coating layer of a lithium metal phosphate. On the other hand, if it exceeds 700 ° C, there is a possibility that the inner center of the lithium metal composite oxide is converted to phosphoric acid.

In this heat treatment step to be mixed with the lithium metal oxide _{Li α (NH 4) β PO} 4 (α + β = 3) content of 1 to 10 mol, based on% the total amount of lithium contained in the positive electrode active material of If the content is less than 1 mol%, the intaglio coating ratio of the lithium metal phosphorus oxide is reduced, and it may be insufficient to inhibit the desorption of oxygen at the surface of the cathode active material under a high voltage, whereas when it exceeds 10 mol% The content of the lithium metal composite oxide is reduced, and the capacity of the secondary battery including the lithium metal composite oxide may be lowered.

Meanwhile, the lithium metal composite oxide may be prepared by: synthesizing a transition metal compound precursor; And mixing the precursor of the transition metal compound and a source of Li, followed by heat treatment at 600 to 1000 ° C.

Specifically, a method for producing the lithium metal composite oxide will be described below.

First, a transition metal hydroxide precursor in the hydroxide form is synthesized.

For the synthesis of a precursor in the form of a transition metal hydroxide, it is preferred to use one selected from the group consisting of nickel sulfate, nickel nitrate and nickel carbonate in the form of a salt dissolved in water; Cobalt sulfate, cobalt nitrate and cobalt carbonate; The aqueous solution is prepared by dissolving one selected from the group consisting of manganese sulfate, manganese nitrate, and manganese carbonate at a constant molar concentration, and then, by using at least one base selected from the group consisting of NaOH, NH ₄ OH, and KOH, 12 &lt; / RTI &gt; in the form of hydroxides.

At this time, when the pH is lower than 10, the particle aggregation rate is larger than the nucleation rate of the particles, and the particle size may grow to 3 μm or more. When the pH is higher than 12, The particles are not agglomerated and there may arise a problem that it is difficult to obtain a transition metal hydroxide in which each component of the transition metal such as Ni, Co, Mn is homogeneously mixed.

The SO ₄ ^{2 -} , NH ₄ ⁺ , NO ₃ ^- , Na ⁺ , K ⁺ adsorbed on the surface of the precipitated powder is washed several times with distilled water to synthesize a high purity transition metal hydroxide precursor. The thus-synthesized transition metal hydroxide precursor is dried in an oven at 150 ° C for at least 24 hours so that the water content is 0.1 wt% or less.

The transition metal compound precursor thus prepared is represented by the formula Ni _a Co _b Mn _c (OH) ₂ (0.1 ≤ a <0.5, 0 ≤ b <0.7, 0.2 ≤ c <0.9, a + b + c = 1) It is preferred that the transition metal hydroxide is in the form of a transition metal hydroxide.

After the dried transition metal hydroxide precursor and the Li source are homogeneously mixed, the lithium metal composite oxide is obtained by performing the first heat treatment at 600 to 1000 ° C for 5 to 30 hours. If the heat treatment temperature is less than 600 ° C, the reaction between the Li source and the transition metal hydroxide precursor may not be performed well. On the other hand, when the temperature exceeds 1000 ° C, the particle size of the active material is excessively increased, . As the lithium source, at least one selected from the group consisting of Li ₂ CO ₃ , LiOH, LiNO ₃ and LiCH ₃ COO can be used, and preferably Li ₂ CO ₃ And LiOH.

In addition, a fluorine source may be added to the precursor in the mixing process of the precursor and the Li source, and the mixture may be heat-treated at a mixing ratio of 1: 0.01 to 0.1 in terms of the molar ratio of Li: F contained in the cathode active material. . If the fluorine molar ratio is less than 0.01, the doping amount of fluorine in the cathode active material may be reduced, and the effect due to fluorine doping may not be sufficiently exhibited. On the other hand, if the fluorine molar ratio is more than 0.1, the doping amount of fluorine becomes too large, There is a concern. The fluorine source as LiF, NaF, KF, CsF, RbF, TiF, AgF, AgF₂, BaF 2, CaF 2, CuF 2, CdF 2, FeF 2, HgF 2, Hg 2 F 2, MnF 2, MgF 2, NiF ₂ , PbF ₂ , SnF ₂ , SrF ₂ , XeF ₂ , ZnF ₂ , AlF ₃ , BF ₃ , BiF ₃ , CeF ₃ , CrF ₃ , DyF ₃ , EuF ₃ , GaF ₃ , GdF ₃ , FeF ₃ , HoF ₃ , _{InF 3, LaF 3, LuF 3} , MnF 3, NdF 3, VOF 3, PrF 3, SbF 3, ScF 3, SmF 3, TbF 3, TiF 3, TmF 3, YF 3, YbF 3, TIF 3, CeF 4 _{, GeF 4, HfF 4, SiF} 4, SnF 4, TiF 4, VF 4, ZrF 4, NbF 5, SbF 5, TaF 5, BiF 5, MoF 6, ReF 6, SF 6 , and selected from the group consisting of WF ₆ It is preferable to use at least one of them, more preferably LiF.

<Cathode Active Material>

The cathode active material of the present invention is characterized in that a lithium metal phosphate expressed by the following formula (2) is intaglio coated on the surface of a layered lithium metal composite oxide particle represented by the following formula (1).

Formula 1

Li _{1 + x} Ni _a Co _b Mn _c O _{2 + d}

(Where 0 <x <0.33, 0 <a <0.4, 0 <b <0.4, 0.4 <c <0.9, -0.5 <d <0.5, x + a + b + c = 1)

(2)

Li _{1 + y} Ni _a Co _b Mn _c PO _{4 + e}

0.4, 0 <b <0.4, 0.4 <c <0.9, -0.5 <e <0.5)

1 is a schematic view of the positive electrode active material according to the present invention is a lithium metal phosphate coated with a negative, the formula Li _{1 + x} Ni _a Co _b Mn _c O _{2 + d} Formula on the surface of the lithium-metal composite oxide particle expressed by Li _{1 + y} Ni _a Co _b Mn _c PO _{4 + e} , the cathode active material is negatively coated.

First, the lithium-metal composite oxide has a layered crystal structure in which an excessive amount of lithium is mixed in the cationic layer of the transition metal corresponding to the range of x, and manganese in the metal other than lithium is excessive in comparison with other metals . However, when the excess lithium content is 0.33 mol or more, the resistance of the positive electrode active material increases and the output of the positive electrode active material decreases, which is not preferable.

Specifically, the lithium metal composite oxide is composed of two phases represented by a layered lithium-transition metal oxide LiMO ₂ (where M is Ni, Co and Mn) and a layered Li ₂ MnO ₃ due to excess lithium .

The layered LiMO ₂ Li ₂ MnO ₃ of the layered structure is an inactive region having Mn ^{4 +} at about 4.4 V or less, but when a voltage of about 4.4 V or more is applied, As shown in the reaction formula (2), oxygen is released from Li ₂ MnO ₃ and lithium is extracted to become electrochemically active, and a high capacity of 240 to 250 mAh / g or more can be expressed.

LiMO ₂ → MO ₂ + Li ⁺ + e ^- ... ... (One)

Li ₂ MnO ₃ ? MnO ₂ + 2Li ⁺ + 1 / 2O ₂ + 2e ^- ... ... (2)

However, in order to exhibit such a high capacity, the activation step through initial charging is necessarily required under a high voltage of 4.6 V or more. Therefore, the life of the secondary battery is degraded due to decomposition of the electrolyte at high voltage and generation of self-generated oxygen.

Therefore, the positive electrode active material of the present invention intentionally coating the lithium metal phosphorous having strong binding force with oxygen on the surface of the lithium metal composite oxide particle, thereby suppressing the desorption of oxygen from Li ₂ MnO _{3 on the} surface of the cathode active material under high voltage The life characteristics of the secondary battery can be improved.

The lithium metal oxide which is formed as a lithium metal composite oxide particles in _α Li (NH ₄₎ PO _{4 β} engraved coating layer on the surface of the composite oxide particles by heat treatment with a mixture of (α + β = 3).

The content of the lithium metal phosphate is preferably 1 to 10 mol% based on the total amount of lithium contained in the cathode active material. When the content of the lithium metal phosphorous is less than 1 mol%, Li ₂ If from MnO _3, and be out of the prevent desorption of oxygen, whereas exceeding 10 mol% is not preferred because it may be difficult to secure the capacity of the battery to a desired level, so relatively less the amount of the lithium-metal composite oxide.

Also, the lithium metal composite oxide may be doped with F. Such F doping stabilizes the crystal structure of the oxide and improves the mobility of lithium. The doping amount of F is preferably 1 to 10 mol% based on the total amount of Li contained in the cathode active material. If the doping amount is less than 1 mol%, the effect of fluorine addition may not be sufficiently exhibited. On the other hand, if the doping amount is more than 10 mol%, the lithium metal complex oxide can not maintain a stable structure, There is a concern.

&Lt; Lithium Secondary Battery Containing Cathode Active Material >

The positive electrode active material according to the present invention can be utilized as a positive electrode material of a lithium secondary battery and has the same structure as a known secondary battery except for the cathode active material composition and crystal structure and is manufactured by the same known manufacturing method .

Preferably, the lithium secondary battery can be manufactured by putting a porous separator between an anode and a cathode and introducing an electrolyte into the lithium secondary battery, which is a common method widely known in the art. The electrolyte was prepared using a mixed solution of 1.3 M LiPF ₆ EC (ethylene carbonate): DMC (dimethyl carbonate): EC in a weight ratio of 5: 3: 2 as a cathode, lithium metal as a separation membrane, do.

Hereinafter, a lithium secondary battery including a method for producing a cathode active material according to the present invention and a cathode active material produced thereby will be described in detail with reference to preferred embodiments and comparative examples. However, these embodiments are only a preferred embodiment of the present invention, and the present invention should not be interpreted as being limited by these embodiments.

Example  One

① Synthesis of transition metal hydroxide precursors

Nickel sulfate (NiSO ₄ ), cobalt sulfate (CoSO ₄ ) and manganese sulfate (MnSO ₄ ) were mixed at a molar ratio of 2: 2: 6 to prepare a 2M aqueous metal salt solution. The prepared metal salt aqueous solution was introduced into a 10 L continuous reactor at a rate of 0.5 L / h.

Ammonia water (NH ₄ OH) at a concentration of 2 M was fed through the ammonia supply unit of the reactor at a rate of 0.5 L / hr, and an aqueous solution of sodium hydroxide (NaOH) at a concentration of 2 M was automatically supplied through the sodium hydroxide aqueous solution supply unit , pH 10.8 was maintained through pH meter and control unit. The temperature of the reactor was adjusted to 50 캜, the residence time (RT) was adjusted to 10 hours, and the stirring was carried out at a speed of 500 rpm.

So then the resultant reaction solution was filtered through a filter and purified by distilled water, and dried for 24 hours in an oven of 120 ℃ to synthesize a transition metal hydroxide precursor _{Ni 0 .2 Co 0 .2 Mn 0} .6 (OH) 2.

② Cathode active material synthesis

1 molar equivalent of the transition metal hydroxide precursor synthesized in the above (1) and 0.58 molar equivalent of lithium carbonate (Li ₂ CO ₃ ) were mixed and then heat-treated at 700 ° C. for 10 hours to synthesize a lithium metal composite oxide.

The synthesized lithium metal composite oxide was mixed with 0.02 molar equivalent of Li (NH ₄ ) ₂ PO ₄ and then heat-treated at 600 ° C. for 3 hours to form a lithium metal composite oxide A positive electrode active material powder in which a lithium metal phosphorus oxide was intaglio coated was obtained.

Example  2

For the synthesis of the lithium metal complex oxide of Example 1, except for the addition of 0.04 molar equivalent of LiF to 1 molar equivalent of the transition metal hydroxide precursor synthesized in (1) and 0.58 molar equivalent of lithium carbonate (Li ₂ CO ₃ ) The cathode active material powder was obtained in the same manner as in Example 1.

Comparative Example  One

1 molar equivalent of a transition metal hydroxide precursor synthesized in Example 1 (1) and 0.58 molar equivalent of lithium carbonate (Li ₂ CO ₃ ) were mixed and heat-treated at 700 ° C. for 10 hours to synthesize a lithium metal composite oxide To obtain a positive electrode active material powder.

&Lt; Evaluation of battery capacity and service life characteristics &

Denka Black, a conductive material, and polyvinylidene fluoride (PVDF), a binder, were mixed at a weight ratio of 92: 4: 4 to prepare a slurry. The slurry was uniformly coated on an aluminum (Al) foil to prepare a positive electrode electrode plate.

A coin-cell type lithium secondary battery was fabricated using a mixture of lithium metal as a cathode, a separator of porous PE as a separator, and a mixture of 1.3M LiPF ₆ EC and DMC: EC as electrolytes in a weight ratio of 5: 3: 2 Respectively.

Battery capacity

The prepared coin cell was allowed to stand at a constant temperature of 25 ° C for 24 hours, and then a lithium secondary battery charge / discharge test apparatus (Toyo System) was used. The voltage range of the test cell was set to 3.0 to 4.6 V, / CV (Constant Voltage) mode, charging / discharging was carried out at a current of 0.2 C and the discharge capacity was obtained.

Life characteristics

After the first cycle, the voltage range of the test cell was set to 2.5 to 4.6 V, the current of 1 C was charged / discharged in the CC / CV mode, and the cycle was repeated for 50 cycles. The capacity retention rate was calculated by the following formula.

Capacity retention rate (%) = (discharge capacity after 50 charge / discharge / initial discharge capacity) * 100

The discharge capacity and capacity retention rate of the lithium secondary battery including the cathode active material prepared in Example 1, Example 2, and Comparative Example 1 according to the above evaluation method are shown in Table 1 below.

Discharge capacity (mAh / g) Capacity retention rate (%) Example 1 241 94 Example 2 242 94 Comparative Example 1 230 87

As can be seen from Table 1, in the case of the secondary battery including the cathode active material of Example 1 in which the lithium metal phosphate was intentionally coated on the lithium metal composite oxide according to the present invention, the battery capacity and lifetime characteristics It can be seen that it is greatly improved.

It can also be seen that the battery capacity of Example 2, in which the anion F is added to the positive electrode active material of Example 1, is more improved than that of Example 1.

Claims (13)

Lithium metal composite oxide particles in the _{Li α (NH 4) β PO} 4 were mixed with the (α + β = 3) comprises the step of heat treatment,
Wherein the lithium metal oxide is intaglio coated on the surface of the lithium metal composite oxide particle by heat treatment. The method according to claim 1,
Wherein the heat treatment temperature is 500 to 700 占 폚. The method according to claim 1,
The _{Li α (NH 4) β PO} 4 (α + β = 3) Amount of the method of producing a cathode active material characterized in that 1 to 10 mol%, based on the total amount of lithium contained in the positive electrode active material. The method according to claim 1,
The lithium metal composite oxide may be,
Synthesizing a transition metal compound precursor; And
Wherein the transition metal compound precursor is mixed with a Li source and then heat-treated at 600 to 1000 占 폚. 5. The method of claim 4,
Wherein the lithium source is at least one selected from the group consisting of Li ₂ CO ₃ , LiOH, LiNO ₃ and LiCH ₃ COO. 5. The method of claim 4,
Wherein a fluorine source is added in the mixing process of the precursor and the Li source, and the mixture is heat-treated together. The method according to claim 6,
Wherein the fluorine source is mixed such that the molar ratio of Li: F contained in the cathode active material is 1: 0.01 to 0.1. The method according to claim 6,
The fluorine source may be LiF, NaF, KF, CsF, RbF, TiF, AgF, AgF₂, BaF 2, CaF 2, CuF 2, CdF 2, FeF 2, HgF 2, Hg 2 F 2, MnF 2, MgF 2, NiF ₂ , PbF ₂ , SnF ₂ , SrF ₂ , XeF ₂ , ZnF ₂ , AlF ₃ , BF ₃ , BiF ₃ , CeF ₃ , CrF ₃ , DyF ₃ , EuF ₃ , GaF ₃ , GdF ₃ , FeF ₃ , HoF ₃ , _{InF 3, LaF 3, LuF 3} , MnF 3, NdF 3, VOF 3, PrF 3, SbF 3, ScF 3, SmF 3, TbF 3, TiF 3, TmF 3, YF 3, YbF 3, TIF 3, CeF 4 _{, GeF 4, HfF 4, SiF} 4, SnF 4, TiF 4, VF 4, ZrF 4, NbF 5, SbF 5, TaF 5, BiF 5, MoF 6, ReF 6, SF 6 , and selected from the group consisting of WF ₆ Wherein the positive electrode active material is at least one selected from the group consisting of lithium, A lithium metal phosphate represented by the following formula (2) is intaglio coated on the surface of a lithium metal complex oxide particle having a layered structure represented by the following formula (1)
Formula 1
Li _{1 + x} Ni _a Co _b Mn _c O _{2 + d}
(Where 0 <x <0.33, 0 <a <0.4, 0 <b <0.4, 0.4 <c <0.9, -0.5 <d <0.5, x + a + b + c = 1)
(2)
Li _{1 + y} Ni _a Co _b Mn _c PO _{4 + e}
0.4, 0 <b <0.4, 0.4 <c <0.9, -0.5 <e <0.5) 10. The method of claim 9,
Wherein the content of the lithium metal phosphate is 1 to 10 mol% based on the total amount of lithium contained in the positive electrode active material. 10. The method of claim 9,
Wherein the lithium metal composite oxide is doped with F. 12. The method of claim 11,
Wherein the doping amount of F is 1 to 10 mol% based on the total amount of Li contained in the cathode active material. A cathode comprising the cathode active material of any one of claims 9 to 12;
A negative electrode comprising a negative electrode active material; And
And an electrolyte existing between the positive electrode and the negative electrode.

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