KR20160066227A - Method for Preparing Cathode Active Material for Secondary Battery and Cathode Active Material Using the Same - Google Patents

Abstract

In the present invention, provided are a manufacturing method of a positive electrode active material, and a positive electrode active material manufactured therefrom. The manufacturing method of the present invention has improved manufacturing processability while minimizing manufacturing costs. The manufacturing method comprises the following processes of: (a) forming a transition metal precursor represented by chemical formula of Li_(1+x)M_(1-y)B_yO_(2-z)L_z*B′_wA_v by mixing an aqueous transition metal solution including nickel-containing salt, with an alkaline substance; (b) manufacturing a coating solution by dissolving salts containing heterogeneous metal elements in a solvent; (c) coating the transition metal precursor with the heterogeneous metal elements by adding and mixing the coating solution to the transition metal precursor, filtering the resultant mixture, and primarily sintering the same; and (d) mixing the transition metal precursor which is coated with the heterogeneous metal elements with a lithium compound, and secondarily sintering the same under an oxidizing atmosphere.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preparing a cathode active material and a cathode active material prepared from the cathode active material,

The present invention relates to a method for producing a cathode active material and a cathode active material produced therefrom, and more particularly, to a method for manufacturing a cathode active material having improved manufacturing processability by simultaneously performing washing and coating of a dissimilar metal element at a precursor stage of a cathode active material To a cathode active material to be produced.

2. Description of the Related Art In recent years, portable electronic devices such as portable computers, portable telephones, and camcorders have been continuously developed for miniaturization and weight reduction. In addition, secondary batteries used as power sources for these electronic devices are required to have higher capacity, smaller size, and lighter weight. In particular, lithium ion secondary batteries have been actively studied for their advantages such as high voltage, long life and high energy density, .

Lithium-containing cobalt oxide (LiCoO ₂ ) is mainly used as a positive electrode active material of a conventional lithium secondary battery, and a lithium-containing manganese oxide such as LiMnO _{2 having a} layered crystal structure and LiMn ₂ O _{4 having a} spinel crystal structure, The use of nickel oxide (LiNiO ₂ ) is also considered.

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 the advantage of using manganese which is abundant in resources and environmentally friendly as a raw material. However, these lithium manganese oxides have a disadvantage of small capacity and poor cycle characteristics Have.

On the other hand, LiNiO _2, etc. of the lithium nickel oxide when charging with 4.3 V, while the cost is cheaper than the cobalt oxide, the reversible capacity of the bar, the doped LiNiO ₂ having a high discharge capacity of LiCoO ₂ capacity (about 165 mAh / in g) < / RTI > to about 200 mAh / g. Therefore, in spite of a slightly low average discharge voltage and a volumetric density, a commercial battery including a LiNiO ₂ based cathode active material has an improved energy density. Therefore, in order to develop a high capacity battery, Research is actively under way.

However, the LiNiO ₂ -based cathode active material causes a large amount of by-products as reaction residues, and when they are charged, they are decomposed or reacted with an electrolyte to cause a swelling phenomenon, which seriously affects the life characteristics and output characteristics of the battery.

To solve this problem, a method of washing or coating LiNiO ₂ has been proposed.

However, in the conventional washing process of LiNiO ₂ , adverse effects such as the damage of the surface of the active material during the washing and the deceleration of the capacity are observed.

In addition, the coating process is also generally difficult to uniformly coat the surface of the active material by coating with a dry process after synthesis of LiNiO ₂ , which is caused by a rise in process ratio and a decrease in capacity, Stability and other problems are not sufficiently solved.

Accordingly, there is a high need for a technique capable of improving the manufacturing processability while using lithium-nickel-based positive electrode active material suitable for high capacity.

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.

Accordingly, an object of the present invention is to provide a method for manufacturing a cathode active material, which is capable of simultaneously performing cleaning and coating of a dissimilar metal element at the precursor stage of the cathode active material, thereby minimizing the manufacturing cost and improving the manufacturing processability.

Another object of the present invention is to provide a cathode active material capable of high capacity and high performance by the production method of the present invention.

Accordingly, the present invention provides a method for producing a positive electrode active material comprising a lithium transition metal oxide,

(a) mixing a transition metal aqueous solution containing a nickel-containing salt and a basic material to produce a transition metal precursor represented by the following formula (1);

(b) dissolving a salt containing a dissimilar metal element in a solvent to prepare a coating solution;

(c) coating the transition metal precursor with the dissimilar metal element by adding and stirring the coating solution to the transition metal precursor of Formula 1, followed by filtering and first firing; And

(d) mixing the transition metal precursor coated with the dissimilar metal element and the lithium compound and then performing a second calcination in an oxidizing atmosphere;

The present invention also provides a method for producing a cathode active material.

_{Ni a M (1-a)} (OH 1-b) 2 (1) wherein, M represents at least one selected from the group consisting of Co, Mn, Cu and Fe; And

0.4? A? 0.9; 0 < b < 0.5.

As described above, the by-products generated in the process of manufacturing the cathode active material are one of factors that degrade the electrochemical performance of the secondary battery including the cathode active material.

The inventors of the present application have repeatedly carried out various experiments. When the washing and coating are simultaneously carried out at the precursor stage of the cathode active material, the generation of by-products of the cathode active material can be minimized and high capacity can be achieved. By using such a cathode active material It has been confirmed that a lithium secondary battery exhibiting excellent lifetime characteristics and output characteristics can be produced.

In the present invention, the step (a) is a step of forming a transition metal precursor represented by the following formula (2) by coprecipitation in the state of a transition metal aqueous solution containing a nickel-containing salt, an aqueous ammonia solution as a complexing agent and an aqueous alkali solution as a pH regulator .

Ni _a M _(1-a) (OH _1-b ) ₂ (2) wherein M is at least one selected from the group consisting of Co and Mn; And

0.4? A? 0.9; 0 < b < 0.5.

The transition metal precursor of the present invention is a hydrate form of a transition metal oxide precursor containing a predetermined metal element (M) in addition to nickel, and is a higher capacity than a transition metal oxide precursor composed of one kind of element and superior in structural stability. And can be particularly preferably used for producing the cathode active material.

In the transition metal precursor, nickel is an excess nickel composition having a higher content than the other metal element (M). When the nickel content is less than 0.4, it is difficult to expect a high capacity. Conversely, when the nickel content exceeds 0.9 There is a problem that the safety is greatly deteriorated. Specifically, the content of nickel may be 0.5 or more and 0.8 or less.

In the process (a), the nickel-containing salt preferably has an anion which is easily decomposed and easily volatilized during firing, and may be one or more selected from the group consisting of nickel-containing sulfate, nickel-containing nitrate, In particular, a nickel-containing sulfate. Such a nickel-containing salt may contain at least one predetermined metal element (M).

As the pH adjusting agent, an aqueous alkali solution such as lithium hydroxide (LiOH), sodium hydroxide (NaOH) and potassium hydroxide (KOH) can be used. The pH adjusting agent acts as a precipitating agent and functions to maintain a pH suitable for coprecipitation in the mixed aqueous solution.

A method of preparing a transition metal precursor using a coprecipitation method is a method of simultaneously precipitating various different ions described above in an aqueous solution or a nonaqueous solution, which is well known in the art, and a detailed description thereof will be omitted.

The dissimilar metal element may be selected from the group consisting of Mg, Al, Ti, Sr, Zn, B, Ca, Cr, Si, Ga, Sn, P, V, Sb, Nb, Ta, Mo, W, Zr, Lt; / RTI &gt;

In the process (b), the salt containing the dissimilar metal element may be at least one selected from the group consisting of a halide, a carbonate, an alkoxide salt, a nitrate, a nitrate, and a mixture thereof. Specifically, the salt may be a nitrate and / have.

If the amount of the dissimilar metal element is less than 0.01 mass% based on the total mass of the lithium transition metal oxide as the cathode active material, the desired effect can not be attained. If the amount exceeds 5 mass%, the internal resistance of the battery increases, Which may deteriorate battery performance.

Therefore, in the step (b), the molar concentration of the coating liquid may be adjusted so that the amount of the dissimilar metal element is 0.01 mass% to 5.00 mass%, more specifically 0.03 mass% to 3.00 mass%, based on the total mass of the cathode active material .

The solvent of the process (b) may be at least one selected from the group consisting of water, ethanol, propanol and butanol, and may be water and / or ethanol in view of economy.

As described above, when the transition metal precursor is washed with water in order to remove the byproducts generated in the production process of the cathode active material, the surface of the transition metal precursor is damaged and the electrochemical performance may be deteriorated. Cleaning and coating of the transition metal precursor can be performed simultaneously using the coating solution containing the dissimilar metal element ions.

Specifically, in the case where the coating liquid containing the dissimilar metal element is added to the transition metal precursor in the step (c), the transition metal precursor is formed by the electric force acting between the surface of the transition metal precursor and the dissimilar metal element ions dissolved in the coating liquid. Cleaning and coating can be performed simultaneously.

The coating liquid may further comprise a surfactant and / or a reaction initiator for controlling pH.

When the coating liquid contains a surfactant, the surfactant is a sulfonate (RSO ₃ ^-), sulfate (RSO ₄ ^-), carboxylates (RCOO ^-), phosphate (RPO ₄ ^-), ammonium (R _x H _y N ^+: x is 1-3 and y is 3-1), quaternary ammonium (R ₄ N ^+), betaine _{^{(betaines; RN + (CH 3}} ) 2 CH 2 COO -), sulfonic Phoebe others (Sulfobetaines; RN ^{_{+ (CH 3) 2 CH 2}} SO 3 -), polyethylene oxide _{(R-OCH 2 CH 2 (} OCH 2 CH 2) n OH) (1≤n≤200), an amine compound, and gelatin (in which R is a saturated Or an unsaturated C ₁ -C ₂₀ hydrocarbon group).

When the coating liquid contains a reaction initiator for controlling pH, the reaction initiator for controlling pH may be at least one aqueous solution selected from the group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide, and ammonium hydroxide.

If the content of the surfactant and / or the reaction initiator is less than 1 wt%, the desired effect can not be exhibited. On the other hand, if the content is more than 10 wt%, the content of the coating liquid is relatively decreased, The content of the surfactant and / or the reaction initiator may be 1 wt% to 10 wt%, and more specifically 2 wt% to 5 wt%, based on the total weight of the coating solution.

After the addition of the coating solution, the mixture is stirred at a speed of 200 to 1000 rpm, and the transition metal precursor is filtered with a filter before the first firing, whereby the firing process can be effectively performed.

The first sintering may be performed at a temperature of 100 to 500 degrees centigrade and the second sintering may be performed at a temperature of 400 to 1000 degrees centigrade. More specifically, the first sintering may be performed at a temperature of 100 to 400 degrees centigrade Temperature, and the second firing can be performed at a temperature of 500 to 800 degrees centigrade.

The dissimilar metal element can be introduced into the transition metal precursor through the first sintering, and the lithium transition metal oxide including the dissimilar metal element can be produced through the second sintering. The firing temperature is not optimal when it is lower or higher than the optimum range for performing such a process.

The lithium compound of step (d) may be at least one selected from the group consisting of lithium hydroxide, oxyhydroxide, oxide, carbonate, nitrate, and halide, and more specifically lithium carbonate.

The present invention also provides a cathode active material represented by the following general formula (3).

Li _{1 + x} Ni _y M _{(1- y z )} L _z O _{2-w a w} * L '_z' (3)

In this formula,

-0.3? X? 0.3; 0.4? Y? 0.9; 0 < y + z? 1, and 0? W? 0.3;

M is at least one member selected from the group consisting of Co, Mn, Cu, and Fe;

L is a dissimilar metal element and is composed of Mg, Al, Ti, Sr, Zn, B, Ca, Cr, Si, Ga, Sn, P, V, Sb, Nb, Ta, Mo, W, Zr, &Lt; / RTI &gt;

A is a monovalent or divalent anion;

L 'means L coated on the lithium transition metal oxide particle;

z means the amount of L doped inside the lithium transition metal oxide particle;

z 'means the amount of L' coated on the lithium transition metal oxide particle; And

The sum of z and z 'is 0.01% by mass to 5% by mass based on the total mass of the lithium transition metal oxide.

That is, in the cathode active material according to the present invention, the dissimilar metal element is introduced at the precursor stage of the cathode active material, and thus may be doped or coated inside the cathode active material.

Specifically, the amount of the dissimilar metal element may be 0.03 mass% to 3.00 mass% based on the total mass of the lithium transition metal oxide. If the amount of the dissimilar metal element is less than 0.01 mass% based on the total mass of the lithium transition metal oxide, the desired effect can not be attained. If the amount of the dissimilar metal element exceeds 5 mass%, the internal resistance of the battery increases, Is undesirably deteriorated.

Since the cathode active material is simultaneously coated and cleaned at the precursor stage, it is not necessary to separately wash the cathode active material at the stage of the cathode active material, thereby minimizing the generation of byproducts while preventing surface damage of the cathode active material.

The cathode active material may include an oxide of a dissimilar metal element and a lithium oxide of a dissimilar metal element.

The present invention provides a positive electrode comprising a positive electrode active material and a lithium secondary battery including the positive electrode. The lithium secondary battery is composed of the above-described positive electrode, negative electrode, separator, non-aqueous electrolyte containing lithium salt, and the like.

The positive electrode is prepared, for example, by applying a mixture of a positive electrode active material, a conductive material and a binder on a positive electrode current collector, followed by drying, and if necessary, a filler is further added. The negative electrode is also manufactured by applying and drying the negative electrode material on the negative electrode collector, and if necessary, may further include the above-described components.

Examples of the negative electrode active material include carbon and graphite materials such as natural graphite, artificial graphite, expanded graphite, carbon fiber, non-graphitizable carbon, carbon black, carbon nanotube, fullerene and activated carbon; Metals such as Al, Si, Sn, Ag, Bi, Mg, Zn, In, Ge, Pb, Pd, Pt and Ti which can be alloyed with lithium and compounds containing these elements; Complexes of metals and their compounds and carbon and graphite materials; Lithium-containing nitrides, and the like. Among them, a carbon-based active material, a silicon-based active material, a tin-based active material, or a silicon-carbon based active material is more preferable, and these may be used singly or in combination of two or more.

The separator is an insulating thin film interposed between the anode and the cathode and having high ion permeability and mechanical strength. The pore diameter of the separator is generally 0.01 to 10 mu m, and the thickness is generally 5 to 300 mu m. As such a separation membrane, for example, a sheet or a nonwoven fabric made of an olefin-based polymer such as polypropylene which is chemically resistant and hydrophobic, 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.

Examples of the binder 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 high molecular weight polyvinyl alcohol.

The conductive material is a component for further improving the conductivity of the electrode active material and may be added in an amount of 1 to 30% by weight based on the total weight of the electrode mixture. 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; Carbon fibers such as carbon nanotubes and fullerene; conductive fibers such as carbon fibers and metal fibers; 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 viscosity adjusting agent may be added up to 30% by weight based on the total weight of the electrode mixture, so as to control the viscosity of the electrode mixture so that the mixing process of the electrode mixture and the coating process on the collector may be easy. Examples of such viscosity modifiers include carboxymethylcellulose, polyvinylidene fluoride and the like, but are not limited thereto. In some cases, the above-described solvent may play a role as a viscosity adjusting agent.

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

The coupling agent is an auxiliary component for increasing the adhesive force between the electrode active material and the binder. The coupling agent has two or more functional groups and can be used up to 30% by weight based on the weight of the binder. Such a coupling agent can be obtained by, for example, a method in which one functional group reacts with a hydroxyl group or a carboxyl group on the surface of a silicon, a tin, or a graphite active material to form a chemical bond and the other functional group reacts with a polymeric binder to form a chemical bond Lt; / RTI &gt; Specific examples of the coupling agent include triethoxysilylpropyl tetrasulfide, mercaptopropyl triethoxysilane, aminopropyl triethoxysilane, and chloropropyltriethoxysilane ( chloropropyl triethoxysilane, vinyl triethoxysilane, methacryloxypropyl triethoxysilane, glycidoxypropyl triethoxysilane, isocyanatopropyl triethoxysilane, And silane-based coupling agents such as cyanopropyl triethoxysilane, but are not limited thereto.

The adhesion promoter may be added in an amount of 10% by weight or less based on the binder, for example, oxalic acid, adipic acid, Formic acid, acrylic acid derivatives, itaconic acid derivatives, and the like.

As the molecular weight modifier, t-dodecylmercaptan, n-dodecylmercaptan, n-octylmercaptan and the like can be used. As the crosslinking agent, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, aryl acrylate, aryl methacrylate, trimethylolpropane triacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, Divinylbenzene and the like can be used.

The current collector in the electrode is a portion where electrons move in the electrochemical reaction of the active material, and an anode current collector and a cathode current collector exist depending on the type of the electrode.

The negative electrode current collector is generally made to have a thickness of 3 to 500 mu m. Such an anode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and may be formed of a material such as copper, stainless steel, aluminum, nickel, titanium, fired carbon, surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used.

The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery, and may be formed of a material such as stainless steel, aluminum, nickel, titanium, sintered carbon, or a surface of aluminum or stainless steel Treated with carbon, nickel, titanium, silver or the like may be used.

These current collectors may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, or the like, by forming fine irregularities on the surface of the current collectors to enhance the binding force of the electrode active material.

The lithium-containing non-aqueous electrolyte is composed of a non-aqueous electrolyte and a lithium salt.

Examples of the nonaqueous electrolytic solution include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, But are not limited to, lactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, Nitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives , Tetrahydrofuran derivatives, ether, methyl pyrophosphate, ethyl propionate and the like can be used.

The lithium salt is a material which is soluble in the non-aqueous liquid electrolyte and includes, 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.

In some cases, organic solid electrolytes, inorganic solid electrolytes, etc. may 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.

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, , Nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxyethanol, . 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 lithium secondary battery according to the present invention can provide a battery module included as a unit cell, and can provide a battery pack including the battery module.

The battery pack can be used as a power source for a device requiring a high capacity, excellent output characteristics, and battery safety. Specific examples of the battery pack include a compact device such as a computer, a mobile phone, a power tool, A power tool powered and moved by the power tool; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like; An electric motorcycle including an electric bike (E-bike) and an electric scooter (E-scooter); An electric golf cart; Power storage systems, and the like, but are not limited thereto.

As described above, since the cleaning and the coating of the dissimilar metal element can be simultaneously performed at the precursor stage of the cathode active material by using the manufacturing method according to the present invention, the manufacturing cost of the cathode active material can be minimized and the process yield can be improved.

In addition, not only is it possible to provide a cathode active material capable of high capacity and high performance by the above method, but also can exhibit excellent safety.

&Lt; Example 1 >

Nickel cobalt manganese sulfate hydrate, 28% ammonia water as a complexing agent and 25% sodium hydroxide solution as a pH adjusting agent were used. A continuous reactor having an internal volume of 90 L filled with a 1 M aqueous ammonia solution was used and the pH of the initial solution was in the range of 11 to 12. The prepared 2.0 M nickel cobalt manganese metal mixed solution, 28% ammonia water, and 25% sodium hydroxide solution were simultaneously and continuously injected at a speed of 600 rpm using a metering pump while stirring. At this time, while the temperature in the reactor was maintained at 50 ° C., the metal mixture solution was fed at a rate of 7 L / hr and the ammonia water was fed at a rate of 0.5 L / hr. While sodium hydroxide was continuously supplied, Respectively. The residence time of the reactor was 8 hours. The slurry as a reaction product discharged through a reactor overflow in a continuous reaction was collected to prepare a hydrate of Ni _0.6 Co _0.2 Mn _0.2 .

The aluminum acetate solution of Ni _0.6 Co _0.2 Mn _0.2 was added to the hydrate and the temperature was maintained at 50 캜 and the rotation speed was maintained at 600 rpm while the concentration of the aluminum acetate solution was adjusted so that Al was 0.1% by mass based on the total mass of the cathode active material Respectively. At this time, the feed rate of the aluminum acetate solution was 2 L / hr, and the sodium hydroxide was reacted for 1 hour while adjusting the feed amount so that the pH in the reactor was maintained at 8 to 10. The slurry solution in the reactor was filtered and washed with distilled water of high purity and then dried in a vacuum oven at 110 ° C for 12 hours to prepare aluminum-coated nickel cobalt manganese hydroxide.

To 850 ℃, calcined 20 hours under an oxygen atmosphere, the aluminum coated with nickel cobalt manganese hydroxide was mixed with lithium carbonate, aluminum is Li (Ni _0.6 Co _0.2 in the lithium-transition is 2.00 mass% coating, based on the total mass of the metal oxide Mn _0.2 ) O ₂ .

&Lt; Comparative Example 1 &

In the same manner as in Example 1, except that aluminum precursor was prepared in the same manner as in Example 1 and then the active material was calcined, aluminum was coated with 2.00% by mass of Li (Ni _0.6 Co _0.2 Mn _0.2 ) O ₂

<Experimental Example>

The cathode active material prepared in Example 1 and Comparative Example 1: conductive material: binder = 95: 2.5: 2.5 was mixed and mixed with NMP to prepare a positive electrode mixture, which was applied to an aluminum electrode, And a coin half cell made of lithium metal as the negative electrode. Capacity and cycle characteristics were evaluated.

The coin half cell was charged to 4.25 V in the CC mode at 0.1 C and maintained in the CV mode at 4.25 V. When the voltage was 0.05 C, the charge was completed. When the voltage was 3.0 V after the CC mode discharge at 0.1 C, the first charge discharge capacity was obtained , And the cycle characteristics are shown in the following Table 1 for 30 cycles after charging and discharging at 0.5C.

Example 1 Comparative Example 1 Charging capacity 188.7 mAh / g 187.8 mAh / g Discharge capacity 166.6 mAh / g 164.8 mAh / g efficiency 88.3%  87.8% Capacity retention after 30 charge / discharge cycles 97.5% 95.1%

According to the above Table 1, in Comparative Example 1 prepared using the cathode active material coated with aluminum in the active material stage in the case of Example 1 produced using the cathode active material coated with aluminum on the precursor by the production method according to the present invention And thus it can be confirmed that it exhibits excellent electrochemical characteristics.

Claims (19)

A method for producing a positive electrode active material comprising a lithium transition metal oxide,
(a) mixing a transition metal aqueous solution containing a nickel-containing salt and a basic material to produce a transition metal precursor represented by the following formula (1);
(b) dissolving a salt containing a dissimilar metal element in a solvent to prepare a coating solution;
(c) coating the transition metal precursor with the dissimilar metal element by adding and stirring the coating solution to the transition metal precursor of Formula 1, followed by filtering and first firing; And
(d) mixing the transition metal precursor coated with the dissimilar metal element and the lithium compound and then performing a second calcination in an oxidizing atmosphere;
Wherein the positive electrode active material comprises:
_{Ni a M (1-a)} (OH 1-b) 2 (1) wherein, M represents at least one selected from the group consisting of Co, Mn, Cu and Fe; And
0.4? A? 0.9; 0 < b < 0.5. The method according to claim 1, wherein the step (a) comprises the steps of: preparing a transition metal precursor represented by the following formula (2) by coprecipitation in a state that an aqueous solution of a transition metal containing a nickel-containing salt, an aqueous ammonia solution as a complexing agent, Wherein the positive electrode active material is produced by:
Ni _a M _(1-a) (OH _1-b ) ₂ (2) wherein M is at least one selected from the group consisting of Co and Mn; And
0.4? A? 0.9; 0 < b < 0.5. The method of claim 1, wherein the nickel-containing salt is one selected from the group consisting of a nickel-containing sulfate, a nickel-containing nitrate, a nickel-containing acetate, and a mixture thereof. The method of claim 1, wherein the dissimilar metal element is at least one element selected from the group consisting of Mg, Al, Ti, Sr, Zn, B, Ca, Cr, Si, Ga, Sn, P, V, Sb, Nb, Ta, Mo, And Y is at least one selected from the group consisting of Y and Y. The method of claim 1, wherein the salt containing the dissimilar metal element is one selected from the group consisting of halides, carbonates, alkoxide salts, nitrates, nitrates, and mixtures thereof. The method for producing a cathode active material according to claim 1, wherein the molar concentration of the coating liquid in the step (b) is adjusted so that the amount of the dissimilar metal element is 0.01% by mass to 5.00% by mass based on the total mass of the cathode active material . The method for producing a cathode active material according to claim 1, wherein the molar concentration of the coating liquid in the step (b) is adjusted so that the amount of the dissimilar metal element is 0.03 mass% to 3.00 mass% based on the total mass of the cathode active material . The method of claim 1, wherein the solvent of step (b) is at least one selected from the group consisting of water, ethanol, propanol, and butanol. The method according to claim 1, wherein the transition metal precursor is simultaneously washed and coated by an electric force acting between the surface of the transition metal precursor and the dissimilar metal element ions dissolved in the coating liquid in the step (c) &Lt; / RTI &gt; The method for producing a cathode active material according to claim 1, wherein the step (c) comprises filtering the transition metal precursor with a filter before the first firing after stirring. The method of claim 1, wherein the coating liquid of step (c) further comprises a surfactant and / or a reaction initiator for pH control. 12. The method of claim 11, wherein, when the coating liquid contains a surfactant, the surfactant is a sulfonate (RSO ₃ ^-), sulfate (RSO ₄ ^-), carboxylates (RCOO ^-), phosphate (RPO ₄ ^-), ammonium (R _x H _y N ^+: x is 1-3 and y is 3-1), quaternary ammonium (R ₄ N ^+), betaine _{^{(betaines; RN + (CH 3}} ) 2 CH 2 COO -), sulfonic Phoebe others _{^{(Sulfobetaines; RN + (CH 3}} ) 2 CH 2 SO 3 -), polyethylene oxide _{(R-OCH 2 CH 2 (} OCH 2 CH 2) n OH) (1≤n≤200), an amine compound, and gelatin Wherein R is at least one selected from the group consisting of saturated or unsaturated C ₁ -C ₂₀ hydrocarbon groups. 12. The method according to claim 11, wherein when the coating liquid comprises a reaction initiator for controlling pH, the reaction initiator for pH adjustment is at least one aqueous solution selected from the group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide, and ammonium hydroxide. A method for producing an active material. 12. The method of claim 11, wherein the content of the surfactant and / or the reaction initiator is 1 wt% to 10 wt% based on the total weight of the coating liquid. The method of claim 1, wherein the first sintering is performed at a temperature of 300 to 700 degrees Celsius and the second sintering is performed at a temperature of 600 to 1000 degrees Celsius. The method of claim 1, wherein the lithium compound in step (d) is at least one selected from the group consisting of lithium hydroxide, oxyhydroxide, oxide, carbonate, nitrate, and halide. A positive electrode active material according to claim 1, which is represented by the following formula (3)
Li _{1 + x} Ni _y M _{(1- y z )} L _z O _{2-w a w} * L '_z' (3)
In this formula,
-0.3? X? 0.3; 0.4? Y? 0.9; 0 &lt; y + z? 1, and 0? W? 0.3;
M is at least one member selected from the group consisting of Co, Mn, Cu, and Fe;
L is a dissimilar metal element and is composed of Mg, Al, Ti, Sr, Zn, B, Ca, Cr, Si, Ga, Sn, P, V, Sb, Nb, Ta, Mo, W, Zr, &Lt; / RTI &gt;
A is a monovalent or divalent anion;
L 'means L coated on the lithium transition metal oxide particle;
z means the amount of L doped inside the lithium transition metal oxide particle;
z 'represents the amount of L' coated on the lithium transition metal oxide particle
The sum of z and z 'is 0.01% by mass to 5% by mass based on the total mass of the lithium transition metal oxide. 18. The cathode active material according to claim 17, wherein the cathode active material comprises an oxide of a dissimilar metal element and a lithium oxide of a dissimilar metal element. A lithium secondary battery comprising the cathode active material according to claim 17.