KR101673118B1 - Manufacturing method of precursor for cathode active material, and cathode active materials and lithium secondary battery using the same - Google Patents

Abstract

The positive electrode active material of the present invention has a uniform average particle size, and thus can realize high energy and high capacity, and can improve the capacity characteristics, lifetime characteristics, and rate characteristics of a lithium secondary battery in a voltage range of 3 V to 4.25 V Thereby providing a positive electrode active material.
In addition, the present invention can control the particle size of lithium transition metal oxide produced by controlling the pH and the reaction time according to progress of the reaction in the reactor, so that the lithium nickel co-manganese-based cathode active material Can be synthesized.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode active material precursor for a lithium secondary battery, and a cathode active material and a lithium secondary battery using the same. 2. Description of the Related Art A cathode active material precursor,

The present invention relates to a method for producing a cathode active material, and a cathode active material for a lithium secondary battery produced thereby.

As technology development and demand for mobile devices are increasing, the demand for secondary batteries as energy sources is rapidly increasing. Among such secondary batteries, lithium secondary batteries having high energy density and voltage, long cycle life and low self- It has been commercialized and widely used.

Lithium-containing cobalt oxide (LiCoO ₂ ) is mainly used as a positive electrode active material of a 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, (LiNiO ₂ ) is also being 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 and is expensive due to the resource limit of cobalt as a raw material. 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.

In addition, the lithium nickel oxide such as LiNiO ₂ has a lower discharge capacity than that of the cobalt oxide when it is charged at 4.25 V, and the reversible capacity of the doped LiNiO _{2 has} a capacity of LiCoO ₂ (about 153 mAh / g) < / RTI > to about 200 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. However, problems such as a high production cost of a LiNiO ₂ -based cathode active material, swelling due to gas generation in a battery, low chemical stability, and high pH are not sufficiently solved.

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

In the case of a lithium transition metal active material containing two or more of Ni, Co and Mn as described above, it is difficult to synthesize the lithium transition metal active material through a simple solid phase reaction. As a precursor for producing the lithium transition metal active material, Techniques using precursors are known.

Such transition metal precursors are being studied to produce lithium transition metal oxides for achieving desired performance through prevention of drop in tap density through control of particle size and optimization of particle shape such as sphering.

A problem to be solved by the present invention is to provide a lithium manganese-based cathode active material precursor having a uniform particle size.

The present invention also relates to a method for preparing a cathode active material of a lithium secondary battery having excellent capacity characteristics and output characteristics in a wide range of normal voltage as well as high voltage by controlling the pH of the cathode active material precursor by controlling the size of uniform powder particles .

In order to solve the above-mentioned problems, the present invention provides a method for producing an aqueous metal solution,

≪ Formula 1 >

M _{aa b} B _c

M is at least one element selected from the group consisting of Fe, Cr, Mg, Al, B, W, Ti, Zr, Cu, Zn, Yb and Y; PO ₄ , BO ₃ , CO ₃ , F and NO ₃ , and 0.95? A? 0.1, 0? B? 0.03, and 0? C? 0.02, wherein the metal aqueous solution and the precipitating agent And a co-precipitant are mixed in a reactor, and the mixture is reacted while stirring to obtain a precipitate. The pH of the reactor is adjusted by adjusting the pH at the time of mixing the coagulating agent with the precipitant in the aqueous metal solution Wherein the pH of the reaction in the reactor when the reaction reaches a steady state is different.

The present invention also provides a positive electrode active material precursor represented by the following formula (2)

(2)

Ni _a Co _b Mn _{c a 1-abc} (OH _1-x ) _2-y B _y

Wherein, A is at least one element selected from the group consisting of Fe, Cr, Mg, Al, B, W, Ti, Zr, Cu, Zn, Yb and Y, B is _{PO 4, BO 3, CO 3} , F and NO ₃ , and 0.45? A? 0.65, 0.1? B? 0.25, 0.1? C? 0.35, 0? X? 0.5, and 0? Y?

(D 3) of secondary particles represented by the following general formula (3), and the secondary particles have an average particle diameter (D ₅₀ ) of 2 to 6 μm.

(3)

Li _{1 + x} (Ni _a Co _b Mn _{c a d} ) O ₂

Wherein, A is at least one element selected from the group consisting of Fe, Cr, Mg, Al, B, W, Ti, Zr, Cu, Zn, Yb and Y, B is _{PO 4, BO 3, CO 3} , F, NO ₃ , 0.45? A? 0.65, 0.1? B? 0.25, 0.1? C? 0.35, 0? D? 0.1, -0.2? X? 0.2, and x + a + b + c + d = 1.

And the half-value width (I _1/2 ) of the maximum peak in the particle size distribution of the secondary particles is 0.1 탆 to 1 탆.

The positive electrode active material according to the present invention has a uniform average particle size and thus can realize high energy and high capacity as well as improve the capacity characteristics, lifetime characteristics and rate characteristics of the lithium secondary battery in a voltage range of 3 V to 4.25 V .

In addition, the method of the present invention can control the size of the produced lithium transition metal oxide particles by controlling the pH and the reaction time according to progress of the reaction in the reactor, so that lithium manganese Based cathode active material can be synthesized.

1 is an SEM photograph of a cathode active material precursor of Example 1. Fig.
2 is a SEM photograph of the cathode active material precursor of Comparative Example 1. Fig.
3 is a SEM photograph of the cathode active material of Example 2. Fig.
4 is a SEM photograph of the cathode active material of Comparative Example 2. Fig.
5 is a graph showing average particle distribution diagrams of Example 2 and Comparative Example 2. Fig.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

One embodiment of the present invention relates to a method for preparing a metal-containing aqueous solution, comprising the steps of: preparing an aqueous metal solution containing a compound represented by the following formula 1;

≪ Formula 1 >

M _{aa b} B _c

M is at least one element selected from the group consisting of Fe, Cr, Mg, Al, B, W, Ti, Zr, Cu, Zn, Yb and Y; PO ₄ , BO ₃ , CO ₃ , F and NO ₃ , and 0.95? A? 0.99, 0? B? 0.03, and 0? C? 0.02, and the metal aqueous solution and the precipitating agent And a co-precipitant are mixed in a reactor, and the mixture is reacted with stirring to obtain a precipitate. The pH of the reactor is adjusted by adjusting the pH of the aqueous solution mixed with the precipitant and the co- Wherein the pH of the reaction in the reactor when the reaction reaches a steady state is different.

The mixture is introduced into a reactor, and A _b B _c can be further added to the mixture when the mixture is stirred. A _b B _c In order to prevent precipitation from occurring in advance before the step of mixing into the reactor, since the precipitation reaction may occur beforehand according to the metal species A.

The above-mentioned production method is a method of producing two or more kinds of transition metal elements by simultaneous precipitation using a precipitation reaction in an aqueous solution. In a specific example, in the aqueous metal solution containing two or more transition metals, an aqueous solution is prepared by mixing the transition metal-containing salts in the respective molar ratios in consideration of the content of the transition metal, and then a strong base such as sodium hydroxide, Adding an additive such as an ammonia supply source, etc., and coprecipitating while maintaining the pH at a basic level. At this time, the average particle diameter, particle diameter distribution, and particle density can be controlled by controlling temperature, pH, reaction time, slurry concentration, ion concentration and the like.

The metal aqueous solution preferably has an anion which is easily decomposed and easily volatilized during firing, and may be at least one selected from the group consisting of PO ₄ , BO ₃ , CO ₃ , F and NO ₃ . Examples thereof include, but are not limited to, metal aqueous solutions such as nickel sulfate, cobalt sulfate, manganese sulfate, nickel nitrate, cobalt nitrate, and manganese nitrate.

The basic substance may be sodium hydroxide, potassium hydroxide, lithium hydroxide or the like, preferably sodium hydroxide, but is not limited thereto.

In the coprecipitation step, an additive capable of forming a complex with the metal aqueous solution or an alkali carbonate may be further added. The additive may be, for example, an ammonium ion supplier, an ethylenediamine compound, a citric acid compound or the like. Examples of the ammonium ion supplier include ammonia water, ammonium sulfate aqueous solution, ammonium nitrate aqueous solution and the like. The alkali carbonate may be selected from the group consisting of ammonium carbonate, sodium carbonate, potassium carbonate, and lithium carbonate. In some cases, two or more of these may be mixed and used.

The addition amount of the additive and the alkali carbonate may be used to control the amount of the transition metal-containing salt, the pH, and the like.

In particular, the pH in the reactor according to one embodiment of the present invention can be controlled by including a pH meter in the reactor. That is, the pH at the time of mixing the precipitant with the co-precipitant in the metal aqueous solution is 12 to 13.5, and the pH at the time when the reaction in the reactor reaches the steady state may be 9 to 11.

The reaction initiation step described above is a step for generating an initial precursor seed, and the size and amount of the seed can be controlled according to the reaction conditions at this step. The size and amount of this seed can vary greatly depending on the reaction pH, temperature and reaction time. The step of generating the seed is a nucleation reaction of the cathode active material precursor. Therefore, in one embodiment of the present invention, the reaction is carried out at a high pH, and the reaction at the start of the reaction varies depending on the reaction scale such as the area of the reactor. To 2 hours, and in one embodiment of the present invention, it may be 30 minutes to 1 hour.

The reaction holding step is a step of growing metal aqueous solution fine particles, and it is possible to control the primary inlet shape and the size of the secondary particle shape in the metal aqueous solution according to the pH of the reaction, the concentration of the complexing agent, the flow rate and the reaction time. The reaction time of this step varies from 2 hours to 17 hours, depending on the reaction scale such as the area of the reactor as in the reaction initiation step, and is from 5 hours to 15 hours in one embodiment of the present invention.

When the pH of the metal aqueous solution mixed with the precipitant and the co-precipitant is less than 12, it is difficult to secure a sufficient amount of seed because the precipitate in the initially generated metal aqueous solution grows more than necessary. There is a problem that the reaction solution is excessively gelated due to an excessive amount of seed, thereby adversely affecting the precipitation reaction. In addition, when the pH in the reactor reaches a steady state, when the pH is less than 9, there is a problem that the average particle diameter of produced particles is too large. When the pH is 11 or more, the average particle diameter of the produced particles becomes too small, There is a problem that it is difficult to form average particles.

As the pH controlling means, the adjustment of the concentration of OH ^- and NH ₃ ⁺ can be used.

As described above, the cathode active material precursor having a uniform average particle diameter, particle diameter distribution, and particle density can be prepared by adjusting the pH in the reaction step according to the reaction step.

The reaction time for obtaining the precipitate from the mixture is 4 to 20 hours, and the reaction temperature for reacting the mixture in the reactor may be 40 to 70 ° C. If the reaction time exceeds 20 hours, the reaction proceeds too much to obtain a precursor of a cathode active material having an average particle size distribution according to an embodiment of the present invention. If the reaction time is less than 4 hours, the reaction does not proceed sufficiently. It is difficult to obtain a uniform cathode active material precursor according to the examples.

The reactor may be a batch or continuous reactor, but is not limited thereto. In one embodiment of the present invention, the reactor may utilize a batch reactor.

The step of adding a mixture of the precipitant and the co-precipitant to the metal aqueous solution into the reactor and reacting the mixture with stirring to obtain a precipitate may further include filtering and washing the precipitate to prepare a precursor of the cathode active material . The precursor of the cathode active material generated at this time may be represented by the following formula (2).

(2)

Ni _a Co _b Mn _{c a 1-abc} (OH _1-x ) _2-y B _y

Wherein, A is at least one element selected from the group consisting of Fe, Cr, Mg, Al, B, W, Ti, Zr, Cu, Zn, Yb and Y, B is _{PO 4, BO 3, CO 3} , F and NO ₃ , and 0.45? A? 0.65, 0.1? B? 0.25, 0.1? C? 0.35, 0? X? 0.5, and 0? Y?

In another embodiment of the present invention, a cathode active material formed using the precursor of Formula 2 prepared by the method for producing a cathode active material precursor may be provided. Specifically, it includes a lithium transition metal oxide represented by the following formula (3)

And secondary particles in which primary particles represented by the following formula (3) are aggregated, and the average particle diameter (D ₅₀ ) of the secondary particles is in the range of 2 탆 to 6 탆.

(3)

Li _{1 + x} (Ni _a Co _b Mn _{c a d} ) O ₂

Wherein, A is at least one element selected from the group consisting of Fe, Cr, Mg, Al, B, W, Ti, Zr, Cu, Zn, Yb and Y, B is _{PO 4, BO 3, CO 3} , F, NO ₃ , 0.45? A? 0.65, 0.1? B? 0.25, 0.1? C? 0.35, 0? D? 0.1, -0.2? X? 0.2, and x + a + b + c + d = 1.

The cathode active material according to an embodiment of the present invention has a uniform average particle size, thereby not only realizing high energy and high capacity, but also capable of realizing a high capacity and a high capacity in a wide voltage range of 3 V to 4.25 V , Lifetime characteristics and rate characteristics can be improved.

According to an embodiment of the present invention, the cathode active material including the lithium transition metal oxide may have a spherical shape and may be formed of secondary particles having a micrometer-sized uniform size composed of primary particles of several tens of nanometers.

According to an embodiment of the present invention, the average particle size (D ₅₀ ) of the secondary particles may be 2 μm to 6 μm, preferably 4 μm to 6 μm, and the average particle size (D ₅₀ ) may be 100 nm to 900 nm, preferably 400 nm to 700 nm.

The average particle diameter (D ₅₀ ) of the primary and secondary particles of the lithium-transition metal oxide may be defined as a particle diameter at a standard of 50% of the particle diameter distribution.

The particle size distribution diagram and the average particle size of the cathode active material according to an embodiment of the present invention can be analyzed through, for example, a particle size analyzer (Cilas.1064). In the particle size analyzer, a lithium-transition can be used to calculate the average particle diameter (D ₅₀₎ of the metal oxide of 50% based on the primary particle diameter distribution in accordance with, the average particle diameter (D ₅₀₎ of from 50% based on the particle size distribution of secondary particles Can be calculated.

In addition, the cathode active material produced according to an embodiment of the present invention has a half width (I _1/2) of the maximum peak in the particle size distribution of the secondary particles on the graph analyzed through the particle size analyzer (Cilas.1064) ) May be a cathode active material having a thickness of 0.1 mu m to 1 mu m. When the half maximum width of the maximum peak is within the range of 0.1 탆 to 1 탆, the distribution of particles having an average particle size is large, and as a result, a more uniform cathode active material can be obtained.

When the average particle diameter of the secondary particles of the lithium transition metal oxide according to an embodiment of the present invention is less than 2 mu m, the amount of the binder for maintaining the desired electrode adhesion is increased due to the increase of the specific surface area of the cathode active material, There is a problem that the output may be lowered due to the decrease of the specific surface area when the thickness exceeds 7 mu m.

On the other hand, when the average particle diameter of the primary particles is less than 100 nm, there may be a problem that the porosity of the secondary particles formed by the agglomeration of the primary particles increases and the electrode adhesion force is lowered. When the average particle diameter exceeds 900 nm, There may be a problem that the moldability of the molded article is deteriorated.

The specific surface area (BET-SSA) of the cathode active material according to an exemplary embodiment of the present invention is preferably 0.6 m2 / g to 1.5 m2 / g, and more preferably 0.8 m2 / g to 1.2 m2 / g. If the specific surface area of the positive electrode active material is less than 0.6 m 2 / g, the adhesion between the electrodes may deteriorate. If the specific surface area exceeds 1.5 m 2 / g, the initial irreversible capacity at the time of charging and discharging may increase.

According to one embodiment of the present invention, the specific surface area of the cathode active material can be measured by a BET (Brunauer-Emmett-Teller; BET) method.

By controlling the size of particles synthesized according to pH and reaction time control by using the process for preparing a cathode active material precursor according to an embodiment of the present invention, it is possible to control the particle size of 2-6 mu m A secondary particle type cathode active material having a uniform size can be synthesized.

The present invention provides a positive electrode comprising the positive electrode active material and a lithium secondary battery including the same.

The positive electrode is prepared, for example, by applying a mixture of a positive electrode active material, a conductive material and a binder according to the present invention on a positive electrode current collector, followed by drying. If necessary, a filler may be further added to the mixture.

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. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The conductive material is usually added in an amount of 1 to 20 wt% 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 collector, and is usually added in an amount of 1 to 20% 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 lithium secondary battery generally comprises a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte containing a lithium salt, and other components of the lithium secondary battery according to the present invention will be described below.

The negative electrode is manufactured by applying a negative electrode material onto the negative electrode collector and drying it, and if necessary, may further include additional components.

The negative electrode material may be, for example, carbon such as non-graphitized carbon or 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 &lt; 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 negative electrode 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. In addition, like the positive electrode collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.

The separator is 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.

The lithium-containing non-aqueous electrolyte is composed of a nonaqueous electrolyte and lithium. As the non-aqueous electrolyte, a non-aqueous electrolyte, a solid electrolyte, an inorganic solid electrolyte and the like are used.

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.

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 charge / discharge characteristics, flame retardancy, etc., non-aqueous electrolytes may be used in the form of, 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.

Example

&Lt; Preparation of positive electrode active material precursor >

Example 1

A 5 L wet batch reactor was charged with 2 L of distilled water and nitrogen gas was continuously fed into the tank at a rate of 1 L / min to remove dissolved oxygen. At this time, the temperature of the distilled water in the tank was maintained at 60 캜 by using a temperature holding device. The distilled water in the tank was stirred at a speed of 1500 rpm using an impeller connected to a motor provided outside the tank.

A 2M concentration transition metal aqueous solution was prepared by mixing nickel sulfate, cobalt sulfate, and manganese sulfate at a ratio of 0.6: 0.2: 0.2 (molar ratio), and separately prepared 4M aqueous sodium hydroxide solution. The transition metal aqueous solution was continuously pumped into the tank for the wet reactor at a rate of 0.2 L / hr by a metering pump. The aqueous sodium hydroxide solution was variable pumped so that the pH of the transition metal aqueous solution in the wet reactor tank was kept at 13 by interlocking with the control equipment to adjust the pH of the transition metal aqueous solution in the tank. At this time, a 29% ammonia solution as an additive was pumped into the reactor continuously for 1 hour at a rate of 0.015 L / hr.

The average residence time in the wet reactor tank of the solution was adjusted to about 7 hours by controlling the flow rates of the transition metal aqueous solution, sodium hydroxide aqueous solution and ammonia solution. The reaction in the tank reached a steady state. 9.5. The lithium transition metal precursor was synthesized under the above-mentioned steady-state conditions with a duration of 10 hours.

After reaching the steady state, transition metal ions of the transition metal aqueous solution, hydroxide ions of sodium hydroxide, and ammonia ions of the ammonia solution were continuously reacted for 11 hours to obtain a nickel-cobalt-manganese complex transition metal precursor in the reactor .

The complex transition metal precursor thus obtained was washed several times with distilled water and dried in a constant temperature drier at 120 ° C for 24 hours to obtain a nickel-cobalt-manganese complex transition metal precursor. Scanning electron microscopy (SEM) photographs of the prepared nickel-cobalt-manganese complex transition metal precursor are shown in FIG.

Comparative Example 1

Similar to Example 1 except that the pH was maintained at 12.0 without adjustment

Nickel-cobalt-manganese complex transition metal precursor. A scanning electron microscope (SEM) photograph of the nickel-cobalt-manganese complex transition metal precursor thus prepared is shown in FIG.

&Lt; Preparation of positive electrode active material &

Example 2, Comparative Example 2

&Lt; Preparation of positive electrode active material &

The nickel cobalt manganese composite transition metal precursor obtained in Example 1 and Comparative Example 1 and lithium carbonate were mixed so that the atomic ratio of Li / Me (total of Ni, Co and Mn) was 1.01, and the mixture was heated to 900 캜 and fired. The resultant Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ The lithium-nickel-cobalt manganese composite oxide cathode active material was used as Example 2 and Comparative Example 2, and the particle size and the like were measured. Scanning Electron Microscopy (SEM) photographs of the cathode active materials of Example 2 and Comparative Example 2 are shown in FIGS. 3 and 4. FIG.

Example 3 and Comparative Example 3

&Lt; Production of lithium secondary battery >

A lithium secondary battery including the Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ prepared in Example 2 and Comparative Example 2 as a cathode active material was prepared.

&Lt; Preparation of positive electrode &

87.9% by weight of Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ as a positive electrode active material, 6.6% by weight of conductive black as a conductive material and 5.5% by weight of polyvinylidene fluoride as a binder were mixed in a solvent N-methylpyrrolidone (NMP) To prepare a cathode active material composition.

The positive electrode active material composition was applied to an aluminum (Al) thin film having a thickness of about 20 탆 and dried to prepare a positive electrode, followed by roll pressing to prepare a positive electrode.

&Lt; Preparation of negative electrode &

The negative electrode active material composition was prepared by adding carbon powder as a negative electrode active material, PVdF as a binder, and carbon black as a conductive material to 96 wt%, 3 wt% and 1 wt%, respectively, as a solvent. The negative electrode active material composition was applied to a copper (Cu) thin film having a thickness of 10 mu m as an anode current collector and dried to produce a negative electrode, followed by roll pressing to prepare a negative electrode.

&Lt; Preparation of lithium secondary battery &

Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 30:70, and LiPF ₆ was added to the non-aqueous electrolyte solvent to prepare a 1 M LiPF ₆ non-aqueous electrolyte.

Experimental Example  One

<Specific surface area, particle size distribution and average particle size measurement>

The cathode active materials synthesized in Example 2 and Comparative Example 2 were evaluated by nitrogen adsorption using BET. Particle size distribution and average particle size were analyzed by particle size analyzer (Cilas.1064). The results are shown in Table 1 and FIG.

D ₅₀
(um) D _min
(um) D _max
(um) Tap density
(g / cc) BET
(m ² / g) Example  2 5.5 3.33 13.1 1.63 0.84 Comparative Example  2 6.32 2.75 26.16 1.89 0.55

As can be seen from FIG. 1 and Table 1, in the case of Example 1 in which the pH in the reactor was different during the production of the precursor of the cathode active material, the average particle size (D ₅₀ ) was smaller than that of Comparative Example 1, there was.

Experimental Example  2

&Lt; Capacity characteristics test &

The lithium secondary batteries prepared in Example 3 and Comparative Example 3 were charged at a constant current / constant voltage of 4.3 V at a charge rate of 0.1 C and a discharge rate of 0.1 C, and then discharged at a constant current of 3.0 V. The results are shown in Table 2.

Example 3 Comparative Example 3 Charge 198.5 198.5 (mAh / g) Discharge (mAh / g) 186.6 182.4 Efficiency (%) 94.0 91.9

It was confirmed that the lithium secondary battery manufactured in Example 3 had an excellent charge / discharge efficiency as compared with Comparative Example 3.

Experimental Example  3

The discharge capacities of the secondary batteries of Example 3 and Comparative Example 3 were measured at 0.1 C, 1.0 C, and 2.0 C rates, respectively, and the results are shown in Table 3.

Example 3 Comparative Example 3 0.1 C 186.1 182.2 1.0 C 173.4
(93.2%) 169
(92.7%) 2.0C 168.2
(90.4%) 163.6
(89.8%)

Claims (5)

Preparing an aqueous metal solution comprising a compound represented by the following formula (1);
&Lt; Formula 1 >
M
Wherein M is Ni, Co, and Mn,
Adding the metal aqueous solution and a mixture of a precipitant and a co-agent to a reactor, and reacting the mixture with stirring to obtain a precipitate,
The pH in the reactor is adjusted such that pH is 12 to 13.5 when the precipitant and the co-precipitant are mixed in the aqueous metal solution and the pH is in the range of 9 to 11 when the reaction reaches the steady state. A method for manufacturing an active material precursor. The method according to claim 1,
After the step of adding a mixture of the precipitant and the co-precipitant to the metal aqueous solution into a reactor and reacting the mixture with stirring to obtain a precipitate,
Further comprising filtering and washing the precipitate and drying the precipitate to prepare a precursor. The method according to claim 1,
And the reaction time for obtaining the precipitate from the mixture is 1 to 2 hours. The method according to claim 1,
Wherein the reaction temperature at the time of reacting the mixture in the reactor is 40 占 폚 to 70 占 폚. The method according to claim 1,
Wherein the reactor is a batch or continuous reactor.

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