KR101841113B1 - Cathode Active Material for Lithium Secondary Battery Which Ionized Metal Is Coated on Surface Thereof and Method for Preparation of the Same - Google Patents

Abstract

The present invention relates to a positive electrode for a lithium secondary battery, characterized in that _a metal dissolved and ionized by a solvent is bonded to an opposite charge on the surface of a lithium transition metal oxide having a composition represented by the formula (Li _a MO ₂ ) Thereby providing an active material.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode active material for a lithium secondary battery having a surface coated with an ionized metal and a method for manufacturing the cathode active material,

The present invention relates to a cathode active material for a lithium secondary battery having a surface coated with an ionized metal and a method for producing the same.

In recent years, the demand for environmentally friendly alternative energy sources has become an indispensable factor for the future, as the increase in the price of energy sources due to depletion of fossil fuels and the interest in environmental pollution are amplified. Various researches on power generation technologies such as nuclear power, solar power, wind power, and tidal power have been continuing, and electric power storage devices for more efficient use of such generated energy have also been attracting much attention.

In particular, as technology development and demand for mobile devices increase, the demand for secondary batteries as energy sources is rapidly increasing. In recent years, the use of secondary batteries as power sources for electric vehicles (EV) and hybrid electric vehicles And it has been widely used for applications such as grid assisted power supply and the like. The lithium secondary battery has high energy density and operating potential among such secondary batteries, has a long cycle life, has a low self- Batteries have been commercialized and widely used.

Of the above cathode active materials, LiCoO ₂ has excellent properties such as excellent cycle characteristics and is widely used at present. However, LiCoO ₂ has low safety, is expensive due to the resource limit of cobalt as a raw material, and is used as a power source for fields such as electric vehicles There is a limit.

Lithium manganese oxides such as LiMnO ₂ and LiMn ₂ O ₄ have attracted much attention as a cathode active material capable of replacing LiCoO ₂ because they have the advantage of using manganese rich in resources and environment friendly as a raw material. However, these lithium manganese oxides have disadvantages such as small capacity and poor cycle characteristics.

On the other hand, LiNiO _2, such as a lithium nickel based oxide is time, the reversible capacity of the bar, the doped LiNiO ₂ having a high discharge capacity when charged to 4.3 V, while the cost is cheaper than the cobalt oxide is the capacity of LiCoO ₂ (about 165 lt; / RTI > (mAh / g). Therefore, in spite of a slightly low average discharge voltage and volumetric density, the compatibilized battery including LiNiO ₂ cathode active material has an improved energy density. Therefore, in order to develop a high capacity battery, Research is actively under way.

Therefore, many prior arts focus on improving the characteristics of the LiNiO ₂ based cathode active material and the manufacturing process of LiNiO ₂ , and suggest that a lithium transition metal oxide in which a part of nickel is substituted with another transition metal such as Co or Mn is proposed .

However, since the LiNiO ₂ -based cathode active material is subjected to additional steps such as washing or coating to remove impurities during production, the washing process lowers the capacity of the cathode active material, damages the surface thereof, Can be reduced.

In addition, the coating process of a general active material is performed by a dry coating method such as a mechanical coating method such as hybridization, a mechanofusion method or a ball mill method, and a desired material is coated on the surface of the cathode active material, There is a problem that it is difficult to uniformly disperse the coating.

Furthermore, in general, the cleaning process and the coating process are performed stepwise as a separate process, thereby increasing the cost and time for production of the cathode active material.

Therefore, there is a high need for a technique capable of fundamentally solving such problems.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted intensive research and various experiments, and as described later, in a process of washing a cathode active material through a solvent, the ionized metal dissolved in the solvent is simultaneously coated, It has been found that metal can be uniformly applied to the entire surface, and the cost and time required for the production of the cathode active material can be saved, thereby improving productivity. The present invention has been accomplished based on this finding.

According to an aspect of the present invention, there is provided a positive active material for a lithium secondary battery,

A metal dissolved and ionized by a solvent is bonded to an opposite charge on the surface of a lithium transition metal oxide having a composition represented by the following formula (1).

Li _a MO ₂ (1)

In this formula,

Wherein M is represented by Ni _b M ' _1-b and M' is one or two or more selected from the group consisting of Al, Mg, Mn, Co, Cr, V, Fe, Cu, Zn,

0.95? A? 1.5, and 0.5? B? 1.

Accordingly, in the process of washing the cathode active material through the solvent, the cathode active material for a lithium secondary battery according to the present invention is coated with the metal in the ionized state dissolved in the solvent so that the metal coating on the surface of the cathode active material is uniformly formed , And the cost and time required for the production of the cathode active material can be saved.

In one specific example, the metal is selected from the group consisting of Fe, Ni, Co, Mn, Cr, Zr, Nb, Cu, V, Ti, Zn, Al, Ga, Mg, B, Or more.

More specifically, the lithium nickel-based positive electrode active material has a low cost and can be used at a high capacity and a high voltage, but has a disadvantage that high-rate characteristics and life characteristics at high temperatures are poor. In order to overcome this disadvantage, the electrochemical characteristics of the cathode active material can be improved by coating the metal with good conductivity on the surface of the cathode active material.

Accordingly, the metal may be applied in an amount of 0.01 wt% to 5.00 wt% based on the weight of the lithium-transition metal oxide, and more specifically, 0.05 wt% to 2.00 wt% .

The metal may be coated on the surface of the lithium-transition metal oxide to a thickness of 5 nm to 15 nm, more specifically, a thickness of 8 nm to 12 nm, more specifically, a thickness of about 10 nm .

If the metal is coated in a content of less than 0.01% by weight or in a thickness of less than 5 nm, the amount of the metal active material coated on the surface of the cathode active material is too small to improve the desired electrochemical characteristics On the other hand, when the metal is applied in a content exceeding 5.00 wt% or in a thickness exceeding 15 nm, the amount of the metal to be applied is excessively large, and the entire surface of the positive electrode active material Uniform coating may not be achieved.

On the other hand, the solvent may be water or ethanol.

That is, the metal coated on the surface of the cathode active material for a lithium secondary battery according to the present invention is dissolved in a solvent and is applied in an ionized state. The metal source containing the metal is dissolved in water or ethanol to be ionized Can be formed.

In this case, the metal may have a positive charge (+) in the ionized state.

In addition, the metal having the positive electric charge (+) is bonded and applied to the opposite electric charge at the surface of the lithium transition metal oxide, so that the lithium transition metal oxide has negative charge (-) before the metal is applied Lt; / RTI >

At this time, the negative charge of the lithium transition metal oxide can be formed through pH control, and the pH can be adjusted in the range of 9 to 12, in particular, in the range of 10 to 11.

If the pH is adjusted to an excessively low or high range beyond the above range, a desired negative charge can not be formed on the lithium transition metal oxide, or a lithium transition metal oxide may be added to the lithium transition metal oxide, By reacting with the materials, unnecessary by-products can be formed.

The pH may be adjusted by adding a pH adjusting agent in the state that the lithium transition metal oxide is supported on the solvent, and the pH adjusting agent may be added to the lithium transition metal oxide The kind of the substance which can control the pH to such a range as to have a negative charge is not limited in its kind, and in particular, it is possible to use an aqueous ammonia solution, a carbonic acid gas, a compound containing an OH group, , And more particularly, it may be sodium hydroxide (NaOH).

Meanwhile, the cathode active material may have a surface roughness ( _Rmax ) of 0.001 mu m to 10 mu m.

In one specific example, the lithium transition metal oxide may have a composition represented by the following formula (2).

Li _c Ni _d Mn _e Co _f O ₂ (2)

In this formula,

0.95? C? 1.5, 0.5? D? 1, and d + e + f = 1.

In another specific example, the lithium transition metal oxide may have the following formula (3).

Li _g Ni _h Co _i Al _j O ₂ (3)

In this formula,

0.95? G? 1.5, 0.5? H? 1, and h + i + j = 1.

In other words, the lithium transition metal oxide contains an excessive amount of nickel, and in particular, may be lithium nickel-manganese-cobalt oxide or lithium nickel-cobalt-aluminum oxide.

The present invention also provides a method of producing the cathode active material for a lithium secondary battery,

A transition metal precursor and a lithium precursor to produce a lithium transition metal oxide;

Adding the lithium transition metal oxide prepared in the step (a) to the solvent and washing the lithium transition metal oxide while stirring;

Introducing a metal source into the solvent to be stirred in the step (b);

A step of adding a pH adjusting agent to the solvent to be stirred in the step (c);

A process for preparing a cathode active material by drying the lithium transition metal oxide through the steps (a) to (e) to remove the solvent;

. ≪ / RTI >

As described above, the solvent may be water or ethanol, and thus the lithium transition metal oxide prepared in the step (a) may be added to a solvent composed of water or ethanol and stirred and washed.

In addition, in the washing process, the metal source and the pH adjuster may be added in a state dissolved in the same solvent as the solvent to which the lithium transition metal oxide is added.

Therefore, the metal source is dissolved in the solvent and ionized, and the metal ionized in the solvent is introduced into the solvent in which the lithium transition metal oxide is washed, so that it can be easily applied to the surface of the lithium transition metal oxide have.

In this case, the metal source is not limited in its kind as long as it can be dissolved in a solvent composed of water or ethanol to form an ionized metal. Specifically, metal sources such as ZINC NITRATE HEXAHYDRATE, / ≪ / RTI > or metal nitrates.

In addition, since the pH adjuster is also added in a state dissolved in a solvent, the lithium transition metal oxide being washed in the solvent can have a negative charge more easily and quickly.

At this time, the pH adjusting agent plays a role of making the lithium transition metal oxide have a negative charge and promoting the coating of the metal ion on the surface of the lithium transition metal oxide.

Specifically, a metal dissolved and ionized in a solvent is attached to the surface of the lithium-transition metal oxide by the difference in charge with the lithium-transition metal oxide in the form of a metal ion, and the metal ion maintains its ionic state It is difficult to form a stable coating layer on the surface of the lithium transition metal oxide.

However, since the OH group contained in the pH adjusting agent changes the metal ion into an oxide state, the metal ion may form a metal oxide layer, and a more stable metal coating layer may be formed on the surface of the lithium transition metal oxide.

Meanwhile, the steps (b) and (e) may be performed within a temperature range of 60 to 80 degrees Celsius within one hour.

As described above, the cathode active material for a lithium secondary battery according to the present invention is washed and coated with a metal at the same time while being supported on a solvent. If the process is performed at a temperature of less than 60 degrees Celsius, And the pH adjuster can not be sufficiently dissolved in the solvent.

In addition, since the solvent is composed of water or ethanol, if the solvent is carried out at an excessively high temperature for a long period of time beyond the above range, the solvent evaporates and the lithium transition metal oxide can not be washed and coated.

Accordingly, the steps (b) and (e) may be performed within a temperature range of 60 to 80 degrees Celsius within one hour.

In one specific example, after the step (d), the solvent may be further added with the surfactant and / or the reaction initiator dissolved in the same kind of solvent as the solvent.

Specifically, the surfactant exists in the form of nanoparticles in a solvent, and plays a role of uniformly applying a metal in an ionized state over the entire surface of the lithium transition metal oxide, and the reaction initiator is in an ionized state The time required for the entire process can be shortened and the productivity can be improved.

In this case, the surfactant is not limited to a specific type as long as it can exhibit a desired effect without changing the electrochemical performance of the cathode active material. Specifically, the surfactant is not limited to sodium borohydride (sodium borohydride) .

The type of the reaction initiator is not limited as long as it can promote the coating of the ionized metal with respect to the surface of the lithium transition metal oxide without changing the electrochemical performance of the cathode active material, In particular, it may be sodium thiosulfate.

The present invention also provides a secondary battery comprising the cathode active material.

Generally, a lithium secondary battery is composed of a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte containing a lithium salt.

The positive electrode is prepared, for example, by coating a mixture of a positive electrode active material, a conductive material and a binder on a positive electrode current collector, and then drying the mixture. Optionally, a filler may be further added to the mixture.

The conductive material is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The binder is a component which assists in bonding of the active material and the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

The filler is optionally used as a component for suppressing the expansion of the anode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

The negative electrode is manufactured by applying and drying a negative electrode active material on a negative electrode collector, and if necessary, the above-described components may be selectively included.

Examples of the negative electrode active material include carbon such as non-graphitized carbon and graphite carbon; _{Li x Fe 2 O 3 (0≤x≤1} ), Li x WO 2 (0≤x≤1), Sn x Me 1-x Me 'y O z (Me: Mn, Fe, Pb, Ge; Me' : Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, Halogen, 0 < x < Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, and Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

The separation membrane and the separation film are interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 mu m and the thickness is generally 5 to 300 mu m. Such separation membranes include, for example, olefinic polymers such as polypropylene, which are chemically resistant and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

Further, in one specific example, in order to improve the safety of the battery, the separation membrane and / or the separation film may be an organic / inorganic composite porous SRS (Safety-Reinforcing Separators) separation membrane.

The SRS separator is manufactured by using inorganic particles and a binder polymer on the polyolefin-based separator substrate as an active layer component. In addition to the pore structure contained in the separator substrate itself, the SRS separator is formed by interstitial volume between inorganic particles And has a uniform pore structure.

The use of such an organic / inorganic composite porous separator has the advantage of suppressing an increase in thickness of the cell due to swelling at the time of chemical conversion compared with the case of using a conventional separator, When a gelable polymer is used when liquid electrolyte is impregnated, it can also be used as an electrolyte.

In addition, the organic / inorganic composite porous separator can exhibit excellent adhesion characteristics by controlling the contents of the inorganic particles and the binder polymer in the separator, so that the cell assembly process can be easily performed.

The inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles usable in the present invention are not particularly limited as long as the oxidation and / or reduction reaction does not occur in the operating voltage range of the applied battery (for example, 0 to 5 V based on Li / Li +). Particularly, when inorganic particles having an ion-transporting ability are used, the ion conductivity in the electrochemical device can be increased and the performance can be improved. Therefore, it is preferable that the ionic conductivity is as high as possible. In addition, when the inorganic particles have a high density, it is difficult to disperse the particles at the time of coating, and there is a problem of an increase in weight during the production of the battery. In the case of an inorganic substance having a high dielectric constant, dissociation of an electrolyte salt, for example, a lithium salt, in the liquid electrolyte also contributes to increase ionic conductivity of the electrolyte.

The nonaqueous electrolyte solution containing a lithium salt is composed of a polar organic electrolyte and a lithium salt. As the electrolytic solution, a non-aqueous liquid electrolytic solution, an organic solid electrolyte, an inorganic solid electrolyte and the like are used.

Examples of the nonaqueous liquid electrolytic solution include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma -Butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane , Acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate Nonionic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyrophosphate, ethyl propionate and the like can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, Polymers containing ionic dissociation groups, and the like can be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide have.

For the purpose of improving the charge-discharge characteristics and the flame retardancy, the non-aqueous liquid electrolyte may contain, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride and the like are added It is possible. In some cases, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further added to impart nonflammability, or a carbon dioxide gas may be further added to improve high-temperature storage characteristics.

The present invention also provides a device comprising at least one of the above mentioned arch cells, wherein the device is a mobile phone, a tablet computer, a notebook computer, a power tool, a wearable electronic device, an electric vehicle, a hybrid electric vehicle, a plug- , And a power storage device.

Since the devices are well known in the art, a detailed description thereof will be omitted herein.

As described above, in the cathode active material for a lithium secondary battery according to the present invention, in the course of washing the cathode active material through the solvent, the metal in the ionized state dissolved in the solvent is simultaneously coated, Can be applied uniformly, and the cost and time required for the production of the cathode active material can be saved, so that the productivity can be improved.

1 is a schematic view schematically showing a method of manufacturing a cathode active material according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings according to the embodiments of the present invention, but the scope of the present invention is not limited thereto.

FIG. 1 is a schematic view schematically showing a method of manufacturing a cathode active material according to an embodiment of the present invention.

Referring to FIG. 1, the lithium transition metal oxide is stirred and washed while being supported on a solvent.

The lithium transition metal oxide 110 is adjusted to have a pH of from 9 to 12, specifically from 10 to 11, by the pH adjusting agent introduced into the solvent, and thus has a negative charge.

The metal source is metal acetate and / or metal nitrate, which is dissolved and ionized by the solvent, so that the metal ion 120 has a positive charge.

That is, the lithium transition metal oxide 110 and the metal ion 120 have opposite charges, and the metal ion 120 is applied to the surface of the lithium transition metal oxide 110 by the difference in charge .

Therefore, the cathode active material 130 according to the present invention is characterized in that the coating 131 of the metal ions 120 on the surface of the lithium-transition metal oxide 110 has a higher electrical conductivity than that of the lithium transition metal oxide 110). ≪ / RTI >

In addition, since the stirring and washing processes in the solvent and the coating process of the metal are performed simultaneously in the solvent, compared with the conventional cathode active material separately performing the cleaning process and the coating process, the cost and time required for the production of the cathode active material The productivity can be improved.

≪ Example 1 >

A lithium nickel manganese composite oxide containing excessive nickel as a cathode active material was prepared and washed with stirring while the lithium nickel manganese composite oxide was supported on ethanol at 80 ° C. While the ZINC NITRATE HEXAHYDRATE as a metal source, NaOH as a pH adjusting agent, sodium borohydride as a surfactant, and sodium thiosulfate as a reaction initiator were sequentially added to the solvent in the washing process of the lithium nickel manganese composite oxide, The mixture was stirred for 60 minutes, and the solvent was evaporated in an oven at 120 DEG C for 24 hours to obtain a cathode active material.

≪ Comparative Example 1 &

The same lithium nickel manganese composite oxide as in Example 1 was washed with stirring in an 80 ° C ethanol for 60 minutes, and the solvent was evaporated for 24 hours in an oven at 120 ° C. to obtain a lithium nickel manganese composite oxide powder . Zinc (Zn) was coated on the surface of the lithium nickel manganese composite oxide powder by a mechanofusion method to prepare a positive electrode active material.

<Experimental Example 1>

A positive electrode containing each of the positive electrode active materials according to Example 1 and Comparative Example 1 was prepared and batteries having a laminated structure facing the negative electrode were prepared through a separator. Capacity characteristics and cycle performance of each battery including the active material were evaluated. Specifically, after the CC mode was charged to 5 mV at a current density of 0.1 C at the time of charging, it was kept constant at 5 mV in the CV mode to complete the charging when the current density reached 0.01 C. Discharge was accomplished in CC mode up to 1.5V with a current density of 0.1C at discharge, and the first cycle charge / discharge capacity and efficiency were obtained. Thereafter, the current density was changed to 0.5 C, and the remaining charge and discharge cycles were repeated 50 times, and the capacity retention rate was measured. The results are shown in Table 1.

Example 1 Comparative Example 1 Charging capacity 191.1 mAh / g 187.4 mAh / g Discharge capacity 177.3 mAh / g 174.8 mAh / g efficiency 92.8% 93.3% Capacity retention after 50 cycles 96% 92.8%

As shown in Table 1, when the lithium transition metal oxide was washed and coated at the same time as in Example 1 of the present invention and the coating due to the difference in charge between the lithium transition metal oxide and the metal ion, It can be confirmed that there is generally no change in the capacity as compared with the battery, and excellent life characteristics are exhibited after 50 charge / discharge cycles.

This is because the cathode active material of Example 1 can improve the electrochemical performance of the battery by more uniformly and stably coating the ionized metal on the surface of the lithium transition metal oxide in the solvent.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (26)

delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete 1. A method for producing a cathode active material for a lithium secondary battery in which a metal dissolved and ionized by a solvent is bonded to an opposite charge on the surface of a lithium transition metal oxide having a composition represented by the following Chemical Formula 1,
(a) preparing a lithium transition metal oxide by reacting a transition metal precursor and a lithium precursor;
(b) washing the lithium transition metal oxide prepared in the step (a) with a solvent while stirring;
(c) injecting a metal source into the solvent to be stirred in the step (b);
(d) adding a pH adjusting agent to the solvent to be stirred in the step (c);
(e) drying the lithium transition metal oxide through the steps (a) to (d) at a temperature in the range of 60 to 80 캜 to remove the solvent, thereby producing a cathode active material;
Wherein the positive electrode active material is a positive electrode active material.

Li _a MO ₂ (1)
In this formula,
Wherein M is represented by Ni _b M ' _1-b and M' is one or two or more selected from the group consisting of Al, Mg, Mn, Co, Cr, V, Fe, Cu, Zn,
0.95? A? 1.5, and 0.5? B? 1. 18. The method of claim 16, wherein the metal source and the pH adjuster are added in the same solvent as that of the lithium-transition metal oxide-added solvent. 17. The method of claim 16, wherein the metal source is dissolved and ionized by a solvent. 19. The method of claim 18, wherein the metal source is a metal acetate and / or a metal nitrate. 17. The method of claim 16, wherein the steps (b) and (e) are performed within a temperature range of 60 to 80 degrees Celsius within one hour. The method according to claim 16, wherein after the step (d), the surfactant and / or the reaction initiator is further added to the solvent in a state that the surfactant and / or the reaction initiator are dissolved in the same solvent as the solvent. Gt; 22. The method of claim 21, wherein the surfactant is sodium borohydride. 22. The method of claim 21, wherein the reaction initiator is sodium thiosulfate. A secondary battery comprising a cathode active material produced according to the method of claim 16. A device comprising at least one secondary battery according to claim 24. 26. The device of claim 25, wherein the device is selected from the group consisting of a cell phone, a tablet computer, a notebook computer, a power tool, a wearable electronic device, an electric vehicle, a hybrid electric vehicle, a plug- . &Lt; / RTI &gt;

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