KR20110136689A - Positive active material for rechargeable lithium battery, method of preparing the same, and rechargeable lithium battery including the same - Google Patents

Abstract

PURPOSE: A positive electrode active material for producing a lithium secondary battery having high-capacity, a producing method thereof, and the lithium secondary battery are provided to prevent the cracking of the active material after a rolling process. CONSTITUTION: A positive electrode active material for producing a lithium secondary battery contains pores having the average diameter of 10-60nm, and has the porosity of 0.5-20%. A producing method of the positive electrode active material comprises the following steps: co-precipitation reacting materials containing nickel, cobalt, and manganese, with ammonium hydroxide or sodium hydroxide to obtain a precipitate; mixing the precipitate with a lithium source; and heat-processing the mixture for 8-10 hours at 800-950 deg C.

Description

A positive electrode active material for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery including the same TECHNICAL FIELD

The present disclosure relates to a cathode active material for a lithium secondary battery, a manufacturing method thereof, and a lithium secondary battery including the same.

A lithium secondary battery, which has recently been spotlighted as a power source for portable electronic devices, has a discharge voltage twice as high as that of a conventional battery using an alkaline aqueous solution, resulting in high energy density.

Such a lithium secondary battery includes a cathode including a cathode active material capable of intercalation and deintercalation of lithium, and an anode including a cathode active material capable of intercalating and deintercalating lithium. It is used to inject the electrolyte into the battery cell comprising a.

LiCoO ₂ is widely used as the cathode active material, and due to the scarcity of cobalt (Co), problems of increasing manufacturing cost and stable supply have emerged. Accordingly, development of a positive electrode active material using inexpensive Ni (nickel) or Mn (manganese) is in progress.

On the other hand, the positive electrode active material using Ni (nickel) is suitable for use in batteries for high capacity and high voltage, but the structure is unstable, causing capacity deterioration, and thermal stability is weak due to reaction with the electrolyte.

One aspect of the present invention is to provide a positive electrode active material having excellent thermal stability with an electrolyte solution by preventing particle breakage by increasing particle strength.

Another aspect of the present invention is to provide a method for producing the positive electrode active material.

Another aspect of the present invention is to provide a high capacity lithium secondary battery including the positive electrode active material.

One aspect of the invention provides a positive electrode active material for a lithium secondary battery comprising a pore of 10 to 60 nm average diameter, the porosity is 0.5 to 20%.

The pores may have an average diameter of 20 to 40 nm.

The cathode active material may include a lithium metal oxide represented by the following Chemical Formula 1, and specifically, may include a lithium metal oxide represented by the following Chemical Formula 2 or Chemical Formula 3.

[Formula 1]

Li _a Ni _x Co _y Mn _z M _k O ₂

(In the formula 1,

M is Al, Mg, Ti, Zr or a combination thereof, 0.95 ≦ a ≦ 1.2, 0.45 ≦ x ≦ 0.65, 0.15 ≦ y ≦ 0.25, 0.15 <z ≦ 0.35, 0 ≦ k ≦ 0.1, x + y + z + k = 1

[Formula 2]

Li _a Ni _x Co _y Mn _z O ₂

(In Formula 2, 0.95≤a≤1.10, 0.55≤x≤0.65, 0.15≤y≤0.25, 0.15 <z≤0.25, and x + y + z = 1.)

(3)

Li _a Ni _x Co _y Mn _z O ₂

(In Formula 3, 0.95≤a≤1.10, 0.45≤x≤0.55, 0.15≤y≤0.25, 0.25 <z≤0.35, and x + y + z = 1.)

In another aspect of the present invention, each metal raw material including nickel (Ni), cobalt (Co) and manganese (Mn); And coprecipitation reacting ammonium hydroxide (NH ₄ OH) or sodium hydroxide (NaOH) to prepare a precipitate. Mixing the precipitate with a lithium raw material to obtain a mixture; And heat-treating the mixture at a temperature of 800 to 950 ° C. for 8 to 10 hours, including a pore having an average diameter of 10 to 60 nm, and having a porosity of 0.5 to 20%. To provide.

The cathode active material may include a lithium metal oxide represented by Chemical Formula 1.

The heat treatment may be performed at a temperature of less than 800 to 900 ℃.

The coprecipitation reaction may be performed at a reaction rate of 600 to 800 rpm, may be performed at pH 10 to 12, may be performed for 8 to 10 hours, and may be performed at a temperature of 35 to 40 ° C.

The precipitate and the lithium raw material may be mixed in a weight ratio of 1: 1 to 1: 1.1.

Another aspect of the invention the positive electrode including the positive electrode active material; cathode; And it provides a lithium secondary battery comprising an electrolyte solution.

The lithium secondary battery may have a discharge capacity of 170 to 190 mAh / g.

Other details of aspects of the invention are included in the following detailed description.

Since the positive electrode active material has high particle strength, cracking is prevented after rolling, and thus, thermal stability with the electrolyte may be excellent, and a high capacity lithium secondary battery may be realized.

1 is a schematic view showing a rechargeable lithium battery according to one embodiment.
Figure 2 is a graph showing the average pore size distribution of the positive electrode active material according to Example 1 measured by the BET method.
Figure 3 is a graph showing the average pore size distribution of the positive electrode active material according to Example 1 measured by the mercury porosimetry.
Figure 4 is a FIB analysis of the positive electrode active material according to Example 1.
5 is a FIB analysis photograph of the positive electrode active material according to Example 2. FIG.
6 is a graph illustrating particle size analysis of the cathode active material according to Example 1;
7 is a graph illustrating particle size analysis of the cathode active material according to Example 2. FIG.
8 is a DSC graph of each cathode active material according to Example 1 and Comparative Example 1. FIG.

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

Hereinafter, a cathode active material according to an embodiment will be described.

The positive electrode active material includes fine pores, and the size of the pores may have an average diameter of 10 to 60 nm, and specifically, may have an average diameter of 20 to 40 nm. When the pore has a size in the above range, as the particle strength of the positive electrode active material is increased, cracking is prevented after rolling, thereby improving thermal stability with the electrolyte.

The cathode active material may have a porosity of 0.5 to 20%, and specifically, may have a porosity of 1 to 5%. When the porosity has the above range, as the particle strength of the cathode active material increases, cracking after rolling may be prevented, thereby improving thermal stability with the electrolyte.

The pore size and porosity are values obtained as a result of measurement by the BET method.

As the cathode active material having the voids, lithium metal oxides represented by the following Chemical Formula 1 may be used.

[Formula 1]

Li _a Ni _x Co _y Mn _z M _k O ₂

(In the formula 1,

M is Al, Mg, Ti, Zr or a combination thereof, 0.95 ≦ a ≦ 1.2, 0.45 ≦ x ≦ 0.65, 0.15 ≦ y ≦ 0.25, 0.15 <z ≦ 0.35, 0 ≦ k ≦ 0.1, x + y + z + k = 1

Specifically, the cathode active material may use a lithium metal oxide represented by the following Chemical Formula 2 or Chemical Formula 3.

[Formula 2]

Li _a Ni _x Co _y Mn _z O ₂

(In Formula 2, 0.95≤a≤1.10, 0.55≤x≤0.65, 0.15≤y≤0.25, 0.15 <z≤0.25, and x + y + z = 1.)

(3)

Li _a Ni _x Co _y Mn _z O ₂

(In Formula 3, 0.95≤a≤1.10, 0.45≤x≤0.55, 0.15≤y≤0.25, 0.25 <z≤0.35, and x + y + z = 1.)

The lithium metal oxide may implement a high capacity lithium secondary battery when the nickel (Ni) content is included in the above range.

The lithium metal oxide may be manufactured by a solid phase method of mixing a lithium raw material and a metal raw material such as nickel (Ni), cobalt (Co), and manganese (Mn) in a powder state to heat treatment.

In addition, the lithium metal oxide may be prepared by mixing metal raw materials such as nickel (Ni), cobalt (Co), and manganese (Mn) in a solvent, and adding ammonium hydroxide (NH ₄ OH) or sodium hydroxide (NaOH) thereto. It may be prepared by a coprecipitation method by continuously mixing in immersion to form a precipitate, and then mixing and heat treating a lithium raw material therein.

In this case, the coprecipitation reaction may be performed at a pH of 10 to 12, a reaction time of 8 to 10 hours, a reaction temperature of 35 to 40 ° C, and a reaction rate of 600 to 800 rpm. As described above, the coprecipitation reaction is performed at a rather low reaction rate to make fine pores, but when the reaction rate is too low, the particle size becomes too large, and thus the reaction rate range should be adjusted according to the composition of the positive electrode active material. When carried out in the conditions of the coprecipitation reaction it is easy to manufacture a positive electrode active material having a specific range of pore average size and porosity according to one embodiment, thereby obtaining a positive electrode active material having a high particle strength.

The precipitate and the lithium raw material may be mixed in a weight ratio of 1: 1 to 1: 1.1. When mixed in the above range can be obtained a positive electrode active material having a high particle strength.

Preferably among these manufacturing methods, it can manufacture by the said coprecipitation method. When prepared by the coprecipitation method, the metal raw material and the lithium raw material are better mixed, and the formation of fine pores is more advantageous.

Examples of the lithium raw material include lithium carbonate, lithium acetate, lithium hydroxide, and the like. Examples of the metal raw material include metal containing acetate, metal containing nitrate, metal containing hydroxide, metal containing oxide, and metal. Containing sulfates, and the like, but is not limited thereto. Among the metal raw materials, preferably metal-containing sulfates can be used. As the solvent, water, ethanol, methanol, acetone and the like can be used.

The heat treatment may be performed at both the solid phase method and the heat treatment after the coprecipitation method in a temperature range of 800 to 950 ° C., specifically, 800 to 900 ° C., and may be performed for 8 to 10 hours. As described above, the heat treatment is performed at a somewhat low temperature to make fine pores, but when the heat treatment temperature is too low, the unreacted material increases, and thus the temperature range must be adjusted according to the composition of the cathode active material. When the heat treatment is performed within the temperature and time range, the grain shape of the positive electrode active material is excellent, the surface is clean, and thermal stability with the electrolyte can be improved, and a lithium secondary battery having high capacity and excellent efficiency can be obtained. Can be.

Hereinafter, a lithium secondary battery including the cathode active material will be described with reference to FIG. 1.

1 is a schematic view showing a lithium secondary battery according to one embodiment.

Referring to FIG. 1, a lithium secondary battery 100 according to an embodiment includes a positive electrode 114, a negative electrode 112 facing the positive electrode 114, and a separator disposed between the positive electrode 114 and the negative electrode 112. (113) and a battery cell including an electrolyte solution (not shown) impregnating the positive electrode 114, the negative electrode 112, and the separator 113, the battery container 120 containing the battery cell, and the battery container And a sealing member 140 for sealing 120.

The positive electrode 114 includes a current collector and a positive electrode active material layer formed on the current collector. The positive electrode active material layer includes a positive electrode active material, a binder, and optionally a conductive material.

Al may be used as the current collector, but is not limited thereto.

As the cathode active material, a lithium metal oxide containing a void as described above may be used. When the lithium metal oxide is used as the positive electrode active material, a high capacity lithium secondary battery may be implemented, and as the particle strength of the positive electrode active material increases, cracking after rolling may be prevented, thereby improving thermal stability with the electrolyte.

The binder adheres positively to the positive electrode active material particles, and also adheres the positive electrode active material to the current collector, and specific examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, Carboxylated polyvinylchloride, polyvinylfluoride, polymers including ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber , Acrylated butadiene rubber, epoxy resin, nylon, and the like, but is not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any conductive material can be used without causing any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, Metal powders such as black, carbon fiber, copper, nickel, aluminum, and silver, metal fibers, and the like, and conductive materials such as polyphenylene derivatives may be used alone or in combination.

The negative electrode 112 includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector.

The negative electrode current collector may be a copper foil.

The negative electrode active material layer includes a negative electrode active material, a binder, and optionally a conductive material.

The anode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and undoping lithium, or a transition metal oxide.

As a material capable of reversibly intercalating / deintercalating the lithium ions, any carbon-based negative electrode active material generally used in a lithium secondary battery may be used, and representative examples thereof include crystalline carbon, Amorphous carbons or these may be used together. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in the form of amorphous, plate-like, flake, spherical or fibrous type. Examples of the amorphous carbon include soft carbon (soft carbon) Or hard carbon, mesophase pitch carbide, fired coke, and the like.

Examples of the alloy of the lithium metal include lithium and Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn. Alloys of the metals selected may be used.

Examples of the material capable of doping and undoping lithium include Si, SiO _x (0 <x <2), Si-Y alloys (wherein Y is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, Is an element selected from the group consisting of rare earth elements and combinations thereof, not Si), Sn, SnO ₂ , Sn-Y (Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth) element and an element selected from the group consisting of, Sn and the like are not), and may also use a mixture of at least one of these with SiO _2. As the element Y, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, and the like.

The binder adheres the anode active material particles to each other well, and also serves to adhere the anode active material to the current collector well, and representative examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, and carboxylation. Polyvinylchloride, polyvinylfluoride, polymers including ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic ray Tied styrene-butadiene rubber, epoxy resin, nylon, and the like may be used, but is not limited thereto.

The conductive material is used to impart conductivity to the electrode, and any battery can be used as long as it is an electronic conductive material without causing chemical change in the battery. For example, natural graphite, artificial graphite, carbon black, acetylene black, and ketjen. Carbon-based materials such as black and carbon fibers; Metal powders such as copper, nickel, aluminum, and silver, or metal-based materials such as metal fibers; Conductive polymers such as polyphenylene derivatives; Or a mixture thereof may be used.

The negative electrode 112 and the positive electrode 114 are each prepared by mixing an active material, a conductive material and a binder in a solvent to prepare an active material composition, and applying the composition to a current collector.

The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein. N-methylpyrrolidone may be used as the solvent, but is not limited thereto.

The electrolyte solution contains a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move. The non-aqueous organic solvent may be selected from carbonate, ester, ether, ketone, alcohol and aprotic solvents.

Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), and ethylpropyl carbonate ( ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate , BC) and the like can be used.

In particular, when a mixture of the chain carbonate compound and the cyclic carbonate compound is used, the dielectric constant may be increased, and the solvent may be prepared with a low viscosity solvent. In this case, the cyclic carbonate compound and the chain carbonate compound may be mixed and used in a volume ratio of about 1: 1 to 1: 9.

In addition, the ester solvent may be, for example, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, decanolide, valerolactone, and merol. Valonolactone, caprolactone, and the like may be used. As the ether solvent, for example, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc. may be used. As the ketone solvent, cyclohexanone may be used. have. In addition, ethyl alcohol, isopropyl alcohol, etc. may be used as the alcohol solvent.

The non-aqueous organic solvents may be used alone or in combination of one or more, and the mixing ratio in the case of mixing one or more may be appropriately adjusted according to the desired battery performance.

The non-aqueous electrolyte may further include an additive such as an overcharge inhibitor such as ethylene carbonate and pyrocarbonate.

The lithium salt is a substance that dissolves in an organic solvent and acts as a source of lithium ions in the battery to enable the operation of a basic lithium secondary battery and to promote the movement of lithium ions between the positive electrode and the negative electrode.

Specific examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiN (SO ₃ C ₂ F ₅ ) ₂ , LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO ₂ , LiAlCl ₄ , LiN (C _x F _{2x +1} SO ₂ ) (C _y F _{2y +1} SO ₂ ), where x and y are natural numbers, LiCl, LiI, LiB (C ₂ O ₄ ) ₂ (lithium bis (oxalato) ) borate; LiBOB), or a combination thereof.

The concentration of the lithium salt is preferably used within the range of about 0.1M to about 2.0M. When the concentration of the lithium salt is included in the above range, since the electrolyte has an appropriate conductivity and viscosity, it can exhibit excellent electrolyte performance, and lithium ions can move effectively.

The separator 113 may be a single film or a multilayer film, and may be made of, for example, polyethylene, polypropylene, polyvinylidene fluoride, or a combination thereof.

The lithium secondary battery may have a discharge capacity of 170 to 190 mAh / g under discharge conditions at 4.3V, CC / CV mode and 0.1C rate, specifically, may have a discharge capacity of 175 to 185 mAh / g. have. This improves the thermal stability and at the same time enables the implementation of a high capacity lithium secondary battery.

Hereinafter, specific embodiments of the present invention will be described. However, the embodiments described below are only intended to illustrate or explain the present invention, and thus the present invention should not be limited thereto.

In addition, the description is not described herein, so those skilled in the art that can be sufficiently technically inferred the description thereof will be omitted.

(Anode Active Material)

Example  One

Mix the NiSO ₄ , CoSO ₄ and MnSO ₄ aqueous solutions each having a concentration of about 3M in a molar ratio of 6: 2: 2, respectively, and add about 7M aqueous NaOH solution and about 1M aqueous NH ₄ OH solution in the coprecipitation unit. Mix continuously. The mixture was co-precipitated at pH 11 with a reaction time of 8 hours, a reaction temperature of 40 ° C., and a reaction rate of about 800 rpm to obtain a (NiCoMn) OH ₂ precursor. The precursor was washed with water, dried in an oven at 120 ° C., filtered, and then mixed with a simple mixer such that the precursor and Li ₂ CO ₃ had a weight ratio of about 1: 1.03. Put the mixture obtained from which the plastic containers to 10 hours and baked at a temperature of 860 ℃ at a rate of 2 ℃ / min, the lithium metal oxide LiNi _{0 .6} was prepared _{Co 0 .2 Mn 0 .2 O 2} .

Example  2

Mix the NiSO ₄ , CoSO ₄ and MnSO ₄ aqueous solutions each having a concentration of about 3M in a molar ratio of 6: 2: 2, respectively, and add about 7M aqueous NaOH solution and about 1M aqueous NH ₄ OH solution in the coprecipitation unit. Mix continuously. The mixture was co-precipitated at pH 11 with a reaction time of 8 hours, a reaction temperature of 40 ° C., and a reaction rate of about 800 rpm to obtain a (NiCoMn) OH ₂ precursor. The precursor was washed with water, dried in an oven at 120 ° C., filtered, and then mixed with a simple mixer such that the precursor and Li ₂ CO ₃ had a weight ratio of about 1: 1.03. Put the mixture obtained therefrom by the calcination vessel at a temperature of about 900 ℃ calcined for about 10 hours at a rate of 2 ℃ / min, the lithium metal oxide LiNi _{0 .6} was prepared _{Co 0 .2 Mn 0 .2 O 2} .

Example  3

Mix the NiSO ₄ , CoSO ₄ and MnSO ₄ aqueous solutions each having a concentration of about 3M in a molar ratio of 5: 2: 3, respectively, and add about 7M aqueous NaOH solution and about 1M aqueous NH ₄ OH solution in the coprecipitation unit. Mix continuously. The mixture was co-precipitated at pH 11 with a reaction time of 8 hours, a reaction temperature of 40 ° C., and a reaction rate of about 800 rpm to obtain a (NiCoMn) OH ₂ precursor. The precursor was washed with water, dried in an oven at 120 ° C., filtered, and then mixed with a simple mixer such that the precursor and Li ₂ CO ₃ had a weight ratio of about 1: 1.03. Put the mixture obtained from which the plastic containers to 10 hours and baked at a temperature of 860 ℃ at a rate of 2 ℃ / min, the lithium metal oxide LiNi _{0 .5} to prepare a _{Co 0 .2 Mn 0 .3 O 2} .

Example  4

Mix the NiSO ₄ , CoSO ₄ and MnSO ₄ aqueous solutions each having a concentration of about 3M in a molar ratio of 5: 2: 3, respectively, and add about 7M aqueous NaOH solution and about 1M aqueous NH ₄ OH solution in the coprecipitation unit. Mix continuously. The mixture was co-precipitated at pH 11 with a reaction time of 8 hours, a reaction temperature of 40 ° C., and a reaction rate of about 800 rpm to obtain a (NiCoMn) OH ₂ precursor. The precursor was washed with water, dried in an oven at 120 ° C., filtered, and then mixed with a simple mixer such that the precursor and Li ₂ CO ₃ had a weight ratio of about 1: 1.03. Put the mixture obtained therefrom by the calcination vessel at a temperature of about 900 ℃ calcined for about 10 hours at a rate of 2 ℃ / min, the lithium metal oxide LiNi _{0 .5} to prepare a _{Co 0 .2 Mn 0 .3 O 2} .

Comparative example  One

Mix the NiSO ₄ , CoSO ₄ and MnSO ₄ aqueous solutions each having a concentration of about 3M in a molar ratio of 5: 2: 3, respectively, and add about 7M aqueous NaOH solution and about 1M aqueous NH ₄ OH solution in the coprecipitation unit. Mix continuously. The mixture was co-precipitated at pH 11 with a reaction time of 8 hours, a reaction temperature of 40 ° C., and a reaction rate of about 1000 rpm to obtain a (NiCoMn) OH ₂ precursor. The precursor was washed with water, dried in an oven at 120 ° C., filtered, and then mixed with a simple mixer such that the precursor and Li ₂ CO ₃ had a weight ratio of about 1: 1.03. Put the mixture obtained therefrom by the calcination vessel at a temperature of about 970 ℃ calcined 15 hours at a rate of 2 ℃ / min, the lithium metal oxide LiNi _{0 .5} to prepare a _{Co 0 .2 Mn 0 .3 O 2} .

Comparative example  2

Mix the NiSO ₄ , CoSO ₄ and MnSO ₄ aqueous solutions each having a concentration of about 3M in a molar ratio of 5: 2: 3, respectively, and add about 7M aqueous NaOH solution and about 1M aqueous NH ₄ OH solution in the coprecipitation unit. Mix continuously. The mixture was co-precipitated at pH 11 with a reaction time of 8 hours, a reaction temperature of 40 ° C., and a reaction rate of about 1000 rpm to obtain a (NiCoMn) OH ₂ precursor. The precursor was washed with water, dried in an oven at 120 ° C., filtered, and then mixed with a simple mixer such that the precursor and Li ₂ CO ₃ had a weight ratio of about 1: 1.03. Put the mixture obtained therefrom by the calcination vessel at a temperature of about 1050 ℃ firing about 15 hours at a rate of 2 ℃ / min, the lithium metal oxide LiNi _{0 .5} to prepare a _{Co 0 .2 Mn 0 .3 O 2} .

Comparative example  3

Mix the NiSO ₄ , CoSO ₄ and MnSO ₄ aqueous solutions each having a concentration of about 3M in a molar ratio of 5: 2: 3, respectively, and add about 7M aqueous NaOH solution and about 1M aqueous NH ₄ OH solution in the coprecipitation unit. Mix continuously. The mixture was co-precipitated at pH 11 with a reaction time of 8 hours, a reaction temperature of 40 ° C., and a reaction rate of about 1000 rpm to obtain a (NiCoMn) OH ₂ precursor. The precursor was washed with water, dried in an oven at 120 ° C., filtered, and then mixed with a simple mixer such that the precursor and Li ₂ CO ₃ had a weight ratio of about 1: 1.03. Put the mixture obtained therefrom by the calcination vessel at a temperature of about 750 ℃ calcined 15 hours at a rate of 2 ℃ / min, the lithium metal oxide LiNi _{0 .5} to prepare a _{Co 0 .2 Mn 0 .3 O 2} .

Comparative example  4

Mix the NiSO ₄ , CoSO ₄ and MnSO ₄ aqueous solutions each having a concentration of about 3M in a molar ratio of 6: 2: 2, respectively, and add about 7M aqueous NaOH solution and about 1M aqueous NH ₄ OH solution in the coprecipitation unit. Mix continuously. The mixture was co-precipitated at pH 11 with a reaction time of 8 hours, a reaction temperature of 40 ° C., and a reaction rate of about 1000 rpm to obtain a (NiCoMn) OH ₂ precursor. The precursor was washed with water, dried in an oven at 120 ° C., filtered, and then mixed with a simple mixer such that the precursor and Li ₂ CO ₃ had a weight ratio of about 1: 1.03. Put the mixture obtained from which the plastic containers 2 ℃ / min at a temperature of about 1050 ℃ firing about 15 hours, the lithium metal oxide LiNi _{0 .6} was prepared _{Co 0 .2 Mn 0 .2 O 2} .

Comparative example  5

Mix the NiSO ₄ , CoSO ₄ and MnSO ₄ aqueous solutions each having a concentration of about 3M in a molar ratio of 6: 2: 2, respectively, and add about 7M aqueous NaOH solution and about 1M aqueous NH ₄ OH solution in the coprecipitation unit. Mix continuously. The mixture was co-precipitated at pH 11 with a reaction time of 8 hours, a reaction temperature of 40 ° C., and a reaction rate of about 1000 rpm to obtain a (NiCoMn) OH ₂ precursor. The precursor was washed with water, dried in an oven at 120 ° C., filtered, and then mixed with a simple mixer such that the precursor and Li ₂ CO ₃ had a weight ratio of about 1: 1.03. Put the mixture obtained from which the plastic containers 2 ℃ / min at a temperature of about 750 ℃ firing about 15 hours, the lithium metal oxide LiNi _{0 .6} was prepared _{Co 0 .2 Mn 0 .2 O 2} .

Experimental Example  1: Pore size and porosity evaluation of positive electrode active material

BET equipment was used to measure the pore size and porosity of the cathode active materials prepared in Examples 1 to 4 and Comparative Examples 1 to 5, respectively, and the results are shown in FIG. 2 and Table 1 below.

The pore size measurement range of the BET equipment is 1.7 to 300 nm.

Figure 2 is a graph showing the pore size distribution of the positive electrode active material according to Example 1 measured by the BET method. 2, it can be seen that the cathode active material according to Example 1 has a pore average diameter of 20 to 46 nm and a porosity of 2.53%.

Pore mean diameter (nm) Porosity (%) Example 1 35 2.53 Example 2 25 2.07 Example 3 45 2.91 Example 4 40 2.68 Comparative Example 1 75 29.9 Comparative Example 2 5 0.3 Comparative Example 3 120 39.2 Comparative Example 4 2 0.2 Comparative Example 5 100 32.4

3 is a graph showing the pore size distribution of the positive electrode active material according to Example 1 measured by a mercury porosimetry. Referring to FIG. 3, it can be seen that the cathode active material according to Example 1 has a pore size distribution similar to that of the graph of FIG. 2 measured by the BET method.

Experimental Example  2: of positive electrode active material Focused electron beam ( focus ion beam , FIB Analyze photo evaluation

The internal structures of the cathode active materials prepared in Example 1 and Comparative Example 1 were analyzed using FIB equipment, and the results are shown in FIGS. 4 and 5, respectively.

4 is a FIB analysis picture of the positive electrode active material according to Example 1, Figure 5 is a FIB analysis picture of the positive electrode active material according to Comparative Example 1. From FIG. 4, the size and porosity of the pores of the cathode active material according to the exemplary embodiment may be confirmed in cross-sectional area. Referring to Figure 5 it can be seen that the pore size and porosity of the positive electrode active material is large.

Experimental Example  3: Evaluation of particle size analysis graph of the positive electrode active material

In order to analyze the effect of preventing cracking after rolling of the positive electrode active materials prepared in Example 1 and Comparative Example 1, the particle size was measured using an analyzer, and the results are shown in FIGS. 6 and 7.

Measurement conditions of the particle size analyzer are shown in Table 2 below.

Item value Dispersion Water Radioisotopes of Particles 1.36 Residual <2% Data processing 5 measurements average Ultrasonic application X Dispersion Application X

6 is a particle size analysis graph of the positive electrode active material according to Example 1, Figure 7 is a particle size analysis graph of the positive electrode active material according to Comparative Example 1. Referring to FIG. 6, in the case of the positive electrode active material having a specific size of pore size and porosity according to one embodiment, the change in particle size distribution after rolling may not be large, and thus the breakage preventing effect may be large, according to one embodiment. It can be seen that the positive electrode active material has high particle strength. 7 shows that the change in the particle size distribution after rolling is large. From this, in the case of the positive electrode active material that is out of both the pore size range and the porosity range according to one embodiment, the particle strength is low and cracking occurs, thereby reacting with the electrolyte solution. Stability may be degraded.

Experimental Example  4: of positive electrode active material DSC  Graph evaluation

The thermal stability of the positive electrode active material prepared in Example 1 and Comparative Example 1 was measured using a DSC measuring instrument (DSC Q20), the results are shown in FIG.

8 is a DSC graph of each cathode active material according to Example 1 and Comparative Example 1. FIG.

Referring to FIG. 8, in the case of the positive electrode active material having a specific range of pore sizes and porosities, the main peak is moved to a higher temperature as compared to the case of the positive electrode active material which is out of both the pore size and the porosity range according to one embodiment. It can be seen that, from this it can be seen that the thermal stability is more excellent.

<Lithium secondary battery production>

96 wt% of the positive electrode active materials prepared in Examples 1 to 4 and Comparative Examples 1 to 5, 2 wt% of polyvinylidene fluoride (PVDF), and 2 wt% of acetylene black were mixed, followed by N-methyl-2. Slurry was prepared by dispersing in pyrrolidone. Next, the slurry was applied onto a glass plate to prepare a cathode active material layer. Next, the positive electrode active material layer was applied on an aluminum foil having a thickness of 60 μm, dried at 135 ° C. for 3 hours or more, and then rolled to prepare a positive electrode.

A coin-type half cell was manufactured using lithium metal as a counter electrode of the positive electrode. In this case, 1.3 M of LiPF ₆ was dissolved in a mixed solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) having a mixed volume ratio of 3: 7.

Experimental Example  5: of lithium secondary battery Charge and discharge  Property evaluation

The charge and discharge characteristics of each lithium secondary battery manufactured using the cathode active materials prepared in Examples 1 to 4 and Comparative Examples 1 to 5, respectively, were measured by the following method, and the results are shown in Table 3 below. .

After charging at 0.1C rate, the battery is discharged at 0.1C rate after 10 minutes of rest. After that, charge and discharge in the same way as 0.2C rate, 0.5C rate, 1.0C rate. Charging and discharging were carried out in CC / CV mode at 4.3V, respectively, and the results below show the initial charging and discharging capacity at 0.1C rate. Value.

Charge capacity (0.1C rate) (mAh / g) Discharge Capacity (0.1C rate) (mAh / g) Efficiency (0.1C rate) (%) Example 1 205.0 180.6 88.1 Example 2 199.9 175.7 87.9 Example 3 190.9 165.3 86.6 Example 4 191.6 166.9 87.1 Comparative Example 1 188.2 163.7 87.0 Comparative Example 2 186.3 158.7 85.2 Comparative Example 3 186.6 157.3 84.3 Comparative Example 4 202.4 169.8 83.9 Comparative Example 5 191.7 162.4 84.7

Through Table 3, in the case of the positive electrode active material having a specific pore size and porosity according to one embodiment, it can be confirmed that the implementation of a high capacity lithium secondary battery is excellent and the battery efficiency is excellent.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of the invention.

100: lithium secondary battery
112: cathode
113: separator
114: anode
120: battery container
140: sealing member

Claims (17)

Comprising pores of 10 to 60 nm average diameter,
A positive electrode active material for lithium secondary batteries having a porosity of 0.5 to 20%.
The method of claim 1,
The pore is a cathode active material for a lithium secondary battery having an average diameter of 20 to 40 nm.
The method of claim 1,
The cathode active material is a cathode active material for a lithium secondary battery containing a lithium metal oxide represented by the following formula (1).
[Formula 1]
Li _a Ni _x Co _y Mn _z M _k O ₂
(In Formula 1,
M is Al, Mg, Ti, Zr or a combination thereof, 0.95 ≦ a ≦ 1.2, 0.45 ≦ x ≦ 0.65, 0.15 ≦ y ≦ 0.25, 0.15 <z ≦ 0.35, 0 ≦ k ≦ 0.1, x + y + z + k = 1
The method of claim 1,
The cathode active material is a lithium secondary battery positive electrode active material containing a lithium metal oxide represented by the following formula (2) or (3).
(2)
Li _a Ni _x Co _y Mn _z O ₂
(In Formula 2, 0.95≤a≤1.10, 0.55≤x≤0.65, 0.15≤y≤0.25, 0.15 <z≤0.25, and x + y + z = 1.)
(3)
Li _a Ni _x Co _y Mn _z O ₂
(In Formula 3, 0.95≤a≤1.10, 0.45≤x≤0.55, 0.15≤y≤0.25, 0.25 <z≤0.35, and x + y + z = 1.)
Respective metal raw materials including nickel (Ni), cobalt (Co) and manganese (Mn); And coprecipitation reacting ammonium hydroxide (NH ₄ OH) or sodium hydroxide (NaOH) to prepare a precipitate.
Mixing the precipitate with a lithium raw material to obtain a mixture; And
Heat-treating the mixture at a temperature of 800-950 ° C. for 8-10 hours,
The manufacturing method of the positive electrode active material for lithium secondary batteries containing the void of 10-60 nm average diameter, and having a porosity of 0.5 to 20%.
The method of claim 5,
The cathode active material is a method for producing a cathode active material for a lithium secondary battery containing a lithium metal oxide represented by the formula (1).
[Formula 1]
Li _a Ni _x Co _y Mn _z M _k O ₂
(In Formula 1,
M is Al, Mg, Ti, Zr or a combination thereof, 0.95 ≦ a ≦ 1.2, 0.45 ≦ x ≦ 0.65, 0.15 ≦ y ≦ 0.25, 0.15 <z ≦ 0.35, 0 ≦ k ≦ 0.1, x + y + z + k = 1
The method of claim 5,
The heat treatment is a method of manufacturing a positive electrode active material for a lithium secondary battery that is carried out at a temperature of less than 800 to 900 ℃.
The method of claim 5,
The coprecipitation reaction is a method for producing a positive active material for a lithium secondary battery that is carried out at a reaction rate of 600 to 800 rpm.
The method of claim 5,
The coprecipitation reaction is a method of manufacturing a positive electrode active material for a lithium secondary battery that is carried out at pH 10 to 12.
The method of claim 5,
The coprecipitation reaction is a method for producing a positive active material for a lithium secondary battery will be carried out for 8 to 10 hours.
The method of claim 5,
The coprecipitation reaction is a method for producing a positive active material for a lithium secondary battery that is carried out at a temperature of 35 to 40 ℃.
The method of claim 5,
The precipitate and the lithium raw material is a method of producing a positive electrode active material for a lithium secondary battery is mixed in a weight ratio of 1: 1 to 1: 1.1.
A positive electrode comprising a positive electrode active material having a pore of 10 to 60 nm average diameter and having a porosity of 0.5 to 20%;
cathode; And
Electrolyte
&Lt; / RTI &gt;
The method of claim 13,
The pore is a lithium secondary battery having an average diameter of 20 to 40 nm.
The method of claim 13,
The positive electrode active material is a lithium secondary battery comprising a lithium metal oxide represented by the formula (1).
[Formula 1]
Li _a Ni _x Co _y Mn _z M _k O ₂
(In Formula 1,
M is Al, Mg, Ti, Zr or a combination thereof, 0.95 ≦ a ≦ 1.2, 0.45 ≦ x ≦ 0.65, 0.15 ≦ y ≦ 0.25, 0.15 <z ≦ 0.35, 0 ≦ k ≦ 0.1, x + y + z + k = 1
The method of claim 13,
The positive electrode active material is a lithium secondary battery comprising a lithium metal oxide represented by the following formula (2) or (3).
(2)
Li _a Ni _x Co _y Mn _z O ₂
(In Formula 2, 0.95≤a≤1.10, 0.55≤x≤0.65, 0.15≤y≤0.25, 0.15 <z≤0.25, and x + y + z = 1.)
(3)
Li _a Ni _x Co _y Mn _z O ₂
(In Formula 3, 0.95≤a≤1.10, 0.45≤x≤0.55, 0.15≤y≤0.25, 0.25 <z≤0.35, and x + y + z = 1.)
The method of claim 13,
The lithium secondary battery is a lithium secondary battery having a discharge capacity of 170 to 190 mAh / g.

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