KR20220109629A - Manufacturing method of positive electrode active material - Google Patents

Abstract

The present invention relates to a preparation method of a cathode active material which can reduce the preparation time of a cathode active material and control the surface properties of cathode active material particles. The preparation method of a cathode active material comprises the step of: (A) mixing a transition metal precursor including a transition metal hydroxide or a transition metal oxyhydroxide with a lithium-containing raw material and then firing the same to prepare a fired article; and (B) washing the fired article with a washing solution and then drying the same to prepare a lithium transition metal oxide, wherein the drying includes vacuum hot air drying and microwave drying.

Description

Manufacturing method of positive electrode active material {MANUFACTURING METHOD OF POSITIVE ELECTRODE ACTIVE MATERIAL}

The present invention relates to a method of manufacturing a positive electrode active material.

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, a lithium secondary battery having a high energy density and voltage, a long cycle life, and a low self-discharge rate has been commercialized and widely used.

A lithium transition metal composite oxide is used as a cathode active material for a lithium secondary battery, and among them, a lithium cobalt composite metal oxide of LiCoO ₂ having a high operating voltage and excellent capacity characteristics is mainly used. However, LiCoO ₂ has very poor thermal properties due to destabilization of the crystal structure due to lithium removal and is expensive, so there is a limit to its mass use as a power source in fields such as electric vehicles.

As a material for replacing LiCoO ₂ , a lithium manganese composite metal oxide (LiMnO ₂ or LiMn ₂ O ₄ etc.), a lithium iron phosphate compound (LiFePO ₄ etc.), or a lithium nickel composite metal oxide (LiNiO ₂ etc.) have been developed. Among them, research and development of lithium-nickel composite metal oxide, which has a high reversible capacity of about 200 mAh/g, and is easy to realize a large-capacity battery, is being actively studied. However, LiNiO ₂ has poor thermal stability compared to LiCoO ₂ , and when an internal short circuit occurs in a charged state due to external pressure, etc., the positive active material itself is decomposed to cause rupture and ignition of the battery.

Accordingly, as a method for improving the low thermal stability while maintaining the excellent reversible capacity of LiNiO ₂ , a nickel-cobalt-manganese-based lithium composite transition metal oxide in which a part of Ni is substituted with Mn and Co, and a part of Ni is substituted with Mn and Al. A nickel-cobalt-aluminum-based lithium composite transition metal oxide has been developed.

These lithium transition metal oxides are generally prepared by mixing a transition metal precursor in powder form with a lithium-containing raw material (ex. lithium hydroxide (LiOH), lithium carbonate (Li ₂ CO ₃ ), etc.), calcining, washing with water and drying. , As the drying method, a method such as vacuum drying or hot air drying is generally used. On the other hand, vacuum drying has a problem that it takes a long drying time, and hot air drying does not completely remove moisture, and consequently, there is a problem that adversely affects the particle surface properties of the produced positive active material.

Therefore, the development of a method for manufacturing a positive electrode active material capable of reducing the time and controlling the particle surface properties of the positive electrode active material is required.

An object of the present invention is to solve the above problems, and to provide a method of manufacturing a positive active material including a drying process capable of shortening the manufacturing time of the positive active material and controlling the particle surface of the positive active material.

The present invention comprises the steps of: (A) mixing a transition metal precursor containing a transition metal hydroxide or a transition metal oxyhydroxide and a lithium-containing raw material, followed by firing to prepare a fired product; and (B) washing the calcined product with water and then drying it to prepare a lithium transition metal oxide; wherein the drying includes vacuum hot air drying and microwave drying. to provide.

According to the method for manufacturing the positive active material of the present invention, when both the vacuum hot air drying method and the microwave drying method are applied in the drying process after washing with water, the manufacturing time of the positive electrode active material can be shortened, and the The surface properties can be controlled.

Accordingly, it is possible to improve the capacity, efficiency, lifespan, and output characteristics of the lithium secondary battery including the positive electrode active material manufactured according to the method for manufacturing the positive electrode active material of the present invention.

1 is a view showing the capacity retention rate characteristics of half-cells prepared by using the positive active materials prepared in Examples and Comparative Examples.
2 is a view showing the resistance increase rate characteristics of half-cells manufactured using the positive active materials prepared in Examples and Comparative Examples.

The terms or words used in the present specification and claims are not to be construed as being limited to their ordinary or dictionary meanings, and the inventor may properly define the concept of the term in order to best describe his invention. Based on the principle that there is, it should be interpreted as meaning and concept consistent with the technical idea of the present invention.

In this specification, terms such as "comprise", "comprising" or "have" are intended to designate the presence of an embodied feature, number, step, element, or a combination thereof, but one or more other features or numbers It is to be understood that it does not preclude in advance the possibility of the presence or addition of steps, components, or combinations thereof.

In the present specification, the 'average particle diameter (D ₅₀ )' may be defined as a particle diameter corresponding to 50% of the cumulative volume in the particle size distribution curve. The average particle diameter (D ₅₀ ) may be measured using, for example, a laser diffraction method. For example, in the method for measuring the average particle diameter (D ₅₀ ) of the positive active material, the particles of the positive active material are dispersed in a dispersion medium, and then introduced into a commercially available laser diffraction particle size measuring device (eg, HORIBA LA-960). Thus, after irradiating ultrasonic waves of about 28 kHz with an output of 60 W, the average particle diameter D ₅₀ corresponding to 50% of the volume accumulation amount in the measuring device can be calculated.

Hereinafter, the present invention will be described in more detail.

Method for manufacturing positive active material

The present inventors have found that when both the vacuum hot air drying method and the microwave drying method are applied in the drying process after washing with water, the manufacturing time of the positive electrode active material can be shortened, and the surface properties of the positive electrode active material particles can be controlled. , thereby completing the present invention by finding that a lithium secondary battery having excellent capacity, efficiency, lifespan and output characteristics can be realized.

The method for producing a cathode active material according to the present invention comprises the steps of: (A) mixing a transition metal precursor including a transition metal hydroxide or a transition metal oxyhydroxide and a lithium-containing raw material, followed by firing to prepare a fired product; and (B) washing the fired product with a water washing solution and drying it to prepare a lithium transition metal oxide. At this time, the drying is to include vacuum hot air drying and microwave drying.

The method for producing a cathode active material according to the present invention further comprises a step ((C) step) of mixing a raw material containing a coating element with a dried lithium transition metal oxide and heat-treating it to form a coating layer after performing the step (B). may include

Hereinafter, each step of the method for manufacturing the positive active material will be described in detail.

(A) step

The step (A) is a step of preparing a fired product by mixing a transition metal precursor including a transition metal hydroxide or transition metal oxyhydroxide and a lithium-containing raw material and then firing.

According to the present invention, the transition metal precursor may have a composition represented by the following Chemical Formula 1 or the following Chemical Formula 2.

[Formula 1]

[Ni _a Co _b M ¹ _c M ² _d ](OH) ₂

[Formula 2]

[Ni _a Co _b M ¹ _c M ² _d ]O OH

In Formula 1 and Formula 2,

Wherein M ¹ is at least one selected from Mn and Al,

The M ² is at least one selected from B, Mg, Ca, Ti, V, Cr, Fe, Zn, Ga, Y, Zr, Nb, Mo, Ta and W,

0.7≤a<1, 0<b<0.3, 0<c<0.3, 0≤d≤0.1, a+b+c+d=1.

The a denotes the atomic fraction of nickel among the metal elements in the precursor, and may be 0.7≤a<1, 0.8≤a<1, 0.8≤a≤0.95, or 0.82≤a≤0.95.

The b denotes the atomic fraction of cobalt among the metal elements in the precursor, and may be 0<b<0.3, 0<b≤0.2, 0.01≤b≤0.1, or 0.03≤b≤0.1.

The c denotes the atomic fraction of M ¹ element among the metal elements in the precursor, and may be 0<c<0.3, 0<c≤0.2, 0.01≤c≤0.1, or 0.02≤c≤0.08.

The d denotes the atomic fraction of the M ² element among the metal elements in the precursor, and may be 0≤d≤0.1 or 0≤d≤0.05.

The transition metal precursor may include two types of precursors having different average particle diameters (D ₅₀ ). For example, the transition metal precursor may include a small particle precursor having an average particle diameter (D ₅₀ ) of 3 μm to 6 μm and an allele precursor having an average particle diameter (D ₅₀ ) of 10 μm to 18 μm. In this case, the small particle precursor and the allele precursor may be included in a weight ratio of 1:9 to 3:7. In this case, the small particle precursor may be appropriately distributed between the antagonistic precursors, so that the filling rate may be excellent, and as a result, an anode having a high energy density may be realized.

The lithium-containing raw material is a lithium-containing carbonate (eg, lithium carbonate (Li ₂ CO ₃ , etc.), hydrate (eg, lithium hydroxide hydrate (LiOH·H ₂ O, etc.)), hydroxide (eg, lithium hydroxide etc.), nitrates (eg, lithium nitrate (LiNO ₃ ), etc.) and chlorides (eg, lithium chloride (LiCl), etc.) The lithium-containing raw material is specifically, Li ₂ CO ₃ and/or or LiOH.In this case, the reactivity of the precursor having a high atomic fraction of nickel among the metal elements in the precursor and the lithium-containing raw material may be improved. Considering the decomposition temperature, the lithium-containing raw material may be LiOH have.

The transition metal precursor and the lithium-containing raw material may be mixed in a molar ratio of 1:0.9 to 1:1.2, specifically, 1:0.95 to 1:1.15, and more specifically, 1:1 to 1:1.15. When the lithium-containing raw material is mixed below the above range, there is a risk that the capacity of the produced positive electrode active material may be lowered. , capacity reduction and separation of positive active material particles after firing (causing positive electrode active material impregnation phenomenon) may occur.

The firing may be performed in an oxygen atmosphere. Specifically, the firing may be performed in an oxygen atmosphere having an oxygen concentration of 90% by volume to 99.99% by volume. More specifically, the calcination may be performed in an oxygen atmosphere having an oxygen concentration of 97% by volume to 99.99% by volume. In this case, the sintering proceeds while maintaining a high-concentration oxygen state, so that insertion of lithium may occur well. Meanwhile, the gas other than oxygen may be an inert gas such as nitrogen, helium, or argon.

The calcination may be performed under 650°C to 800°C. When the sintering temperature is within the above range, the raw material is smoothly inserted into the particles due to a sufficient reaction to secure structural stability and at the same time secure optimal electrochemical properties.

The calcination may be performed for 5 to 30 hours. When the firing time is within the above range, there is no deviation for each firing position, that is, the crystal growth of the lithium transition metal oxide may sufficiently occur uniformly.

The fired product manufactured through step (A) of the present invention may include lithium transition metal oxide and impurities (eg, lithium by-product). Meanwhile, the impurities may be removed through a water washing process.

The fired product may be pulverized and/or classified before step (B), if necessary. The pulverization is a process of making a calcined product containing lithium transition metal oxide aggregated by the calcination of step (A) into a powder having a size suitable for use as a cathode active material. And, the classification is a process of separating only the powder having a size within a specific range suitable for use as a cathode active material.

(B) step

Step (B) is a step of preparing a lithium transition metal oxide by washing the fired product with a water washing solution and then drying, and the drying includes vacuum hot air drying and microwave drying.

Specifically, the step (B) may include washing the fired product by mixing the water washing solution, separating the fired product from the water washing solution, and drying the product.

The washing is a process of removing residual lithium, etc. as impurities with a washing solution.

The solvent of the washing solution may be deionized water and/or distilled water. In this case, it may be advantageous to remove the residual lithium present on the surface because the dissolution of lithium is easy.

The water washing is performed by adding the washing solution in an amount of 50 parts by weight to 200 parts by weight, specifically 60 parts by weight to 150 parts by weight, and more specifically 80 parts by weight to 120 parts by weight based on 100 parts by weight of the fired product. it could be When the content of the washing solution is within the above range, residual lithium as an impurity may be sufficiently washed without damage to the positive electrode active material, may be advantageous in terms of capacity improvement and initial resistance improvement, and productivity may be improved.

The water washing may be performed at 5°C to 40°C, specifically, at 20°C to 30°C. In addition, the washing with water may be performed for 3 minutes to 30 minutes, specifically 3 minutes to 20 minutes, and more specifically 5 minutes to 10 minutes. When the temperature and time of the water washing process are within the above ranges, only the residual lithium on the surface that did not participate in the reaction is removed, and dissolution of the lithium inserted therein can be suppressed as much as possible.

Separation of the fired product from the washing solution may be performed through filtration. For example, the fired product may be separated using a pressure reduction filter or the like.

The drying process is a process for removing moisture from the positive electrode active material including moisture through a water washing process. According to the present invention, the drying includes vacuum hot air drying and microwave drying. When both the vacuum hot air drying method and the microwave drying method are applied as in the present invention, the total drying time can be shortened, and consequently, the manufacturing time of the positive electrode active material can be shortened. In addition, since damage to the surface of the positive active material particles that may occur due to the applied heat can be reduced, the surface properties of the positive active material particles can be controlled. In addition, moisture inside and on the surface of the positive active material particles can be more completely removed.

According to the present invention, the drying may be microwave drying after vacuum hot air drying. That is, the drying may be drying using hot air under vacuum and then drying using microwaves. In this case, after microwave drying, it is possible to further improve the problem that the structural stability of the active material is lowered due to overdrying, etc. than vacuum hot air drying.

According to the present invention, the vacuum hot air drying may be performed at a temperature of 100°C to 200°C, specifically, 100°C to 150°C. When the temperature during vacuum hot air drying is within the above range, it is possible to shorten the time to remove moisture present in the positive electrode active material particles, and to prevent damage to the surface of the positive electrode active material by not drying excessively.

According to the present invention, the vacuum hot air drying may be performed under a pressure of 0.05 MPa to 0.15 MPa, specifically 0.06 Mpa to 0.12 MPa. When the pressure during vacuum hot air drying is within the above range, the drying time does not take long and there may be little residual moisture remaining, and the shape of the positive active material particles does not change because it does not dry excessively, so the sphericity of the positive active material particles is well maintained can be

According to the present invention, the vacuum hot air drying time may be 5 hours to 30 hours, specifically 10 hours to 20 hours, more specifically 10 hours to 17 hours. In this case, a cathode active material having excellent electrochemical performance can be realized, and a total drying time can be shortened, and consequently, a manufacturing time of the cathode active material can be shortened. The vacuum hot air drying time may be a time required to dry 100 g of the fired product.

According to the present invention, the microwave drying may be performed using a microwave having an output of 600W to 1,000W, specifically 600W to 800W, and more specifically 650W to 750W. When the output during microwave drying is within the above range, the total drying time may be shortened, and the problem of non-uniform particle phases of the positive electrode active material may be prevented.

According to the present invention, the microwave drying time may be 5 minutes to 30 minutes, specifically 5 minutes to 15 minutes, more specifically 5 minutes to 10 minutes. In this case, damage to the surface of the positive active material particles that may occur due to microwave drying may be prevented, and the sphericity of the positive active material particles may be well maintained. The microwave drying time may be a time required to dry 100 g of the fired product.

When the vacuum hot air drying temperature, pressure and time and the microwave drying output and time are adjusted as described above, there is little residual moisture in the resultantly produced positive active material particles, and the residual moisture reacts with the positive active material. The problem of loss of lithium inside the positive active material may not occur, and the total drying time may be shortened, thereby reducing the manufacturing time of the positive active material and reducing damage to the surface of the positive active material particle.

(C) step

The step (C) is a step of forming a coating layer by mixing the raw material containing the coating element with the dried lithium transition metal oxide as necessary after performing the step (B) and performing heat treatment. Accordingly, a cathode active material having a coating layer formed on the surface of the lithium transition metal oxide may be manufactured.

The metal element included in the raw material containing the coating element may be Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S and Y, etc. . The raw material containing the coating element may be an acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide or oxyhydroxide containing the metal element. For example, when the metal element is B, boric acid (B(OH) ₃ ) and the like may be used.

The raw material containing the coating element may be included in a weight of 200 ppm to 2000 ppm based on the dried lithium transition metal oxide. When the content of the raw material containing the coating element is within the above range, the capacity of the battery can be improved, and the resulting coating layer suppresses a direct reaction between the electrolyte and the lithium transition metal oxide, so that the long-term performance characteristics of the battery can be improved.

The heat treatment may be performed at a temperature of 200 °C to 400 °C. When the heat treatment temperature is within the above range, the coating layer may be formed while maintaining the structural stability of the lithium transition metal oxide.

The heat treatment may be performed for 1 hour to 10 hours. When the heat treatment time is within the above range, an appropriate coating layer may be formed and production efficiency may be improved.

cathode active material

The present invention may provide a positive electrode active material manufactured according to the above-described method for preparing a positive electrode active material.

The positive active material may have a composition represented by Formula 3 below.

[Formula 3]

Li _x [Ni _a' Co _b' M ¹ _c' M ² _d' ]O ₂

In Formula 3,

Wherein M ¹ is at least one selected from Mn and Al,

The M ² is at least one selected from B, Mg, Ca, Ti, V, Cr, Fe, Zn, Ga, Y, Zr, Nb, Mo, Ta and W,

0.9≤x≤1.1, 0.7≤a'<1, 0<b'<0.3, 0<c'<0.3, 0≤d'≤0.1, a'+b'+c'+d'=1.

The a' refers to the atomic fraction of nickel among metal elements other than lithium in the active material, and may be 0.7≤a'<1, 0.8≤a'<1,0.8≤a'≤0.95 or 0.82≤a'≤0.95. have.

The b' refers to the atomic fraction of cobalt among metal elements other than lithium in the active material, and may be 0<b'<0.3, 0<b'≤0.2, 0.01≤b'≤0.1 or 0.03≤b'≤0.1. have.

Wherein c' means the atomic fraction of M ¹ element among metal elements other than lithium in the active material, 0<c'<0.3, 0<c'≤0.2, 0.01≤c'≤0.1, 0.02≤c'≤0.08 can be

Wherein d' refers to the atomic fraction of M ² element among metal elements other than lithium in the active material, and may be 0≤d'≤0.1 or 0≤d'≤0.05.

The positive active material may include two types of positive active materials having different average particle diameters (D ₅₀ ). For example, the positive electrode active material may include a small particle positive active material having an average particle diameter (D ₅₀ ) of 3 μm to 6 μm and an opposite positive electrode active material having an average particle diameter (D ₅₀ ) of 10 μm to 18 μm. In this case, the small particle positive electrode active material and the opposite positive electrode active material may be included in a weight ratio of 1:9 to 3:7. In this case, the small particle positive electrode active material may be appropriately distributed between the opposite positive electrode active materials, and thus the filling rate may be excellent, and as a result, a positive electrode having a high energy density may be realized.

The positive active material may have a grain size of 100 nm to 200 nm, specifically 130 nm to 170 nm. In this case, even when charging and discharging under high temperature, particle breakage does not occur, so that high temperature lifespan characteristics can be improved.

anode

In addition, the present invention may provide a positive electrode including the above-described positive electrode active material.

Specifically, the positive electrode includes a positive electrode current collector, and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector and including the positive electrode active material.

The positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, fired carbon, or carbon, nickel, titanium on the surface of aluminum or stainless steel. , silver or the like surface-treated may be used. In addition, the positive electrode current collector may typically have a thickness of 3 μm to 500 μm, and may increase the adhesion of the positive electrode active material by forming fine irregularities on the surface of the current collector. For example, it may be used in various forms, such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven body.

The positive active material layer may include a conductive material and a binder together with the positive active material.

The positive active material may be included in an amount of 80% to 99% by weight, more specifically, 85% to 98% by weight based on the total weight of the positive active material layer. When included in the above content range, excellent capacity characteristics may be exhibited.

The conductive material is used to impart conductivity to the electrode, and in the configured battery, it can be used without any particular limitation as long as it has electronic conductivity without causing chemical change. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or a conductive polymer such as a polyphenylene derivative, and the like, and any one of them or a mixture of two or more thereof may be used. The conductive material may be included in an amount of 1 wt% to 30 wt% based on the total weight of the positive electrode active material layer.

The binder serves to improve adhesion between the positive active material particles and the adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC) ), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and any one of them or a mixture of two or more thereof may be used. The binder may be included in an amount of 1 wt% to 30 wt% based on the total weight of the positive electrode active material layer.

The positive electrode may be manufactured according to a conventional positive electrode manufacturing method except for using the above positive electrode active material. Specifically, it may be prepared by applying the above-described positive active material and optionally, a composition for forming a positive active material layer prepared by dissolving or dispersing a binder and a conductive material in a solvent on a positive electrode current collector, followed by drying and rolling. In this case, the types and contents of the positive electrode active material, the binder, and the conductive material are as described above.

The solvent may be a solvent generally used in the art, dimethyl sulfoxide (DMSO), isopropyl alcohol (isopropyl alcohol), N-methylpyrrolidone (NMP), acetone (acetone) or water and the like, and any one of them or a mixture of two or more thereof may be used. The amount of the solvent used is enough to dissolve or disperse the positive electrode active material, the conductive material and the binder in consideration of the application thickness of the slurry and the production yield, and to have a viscosity capable of exhibiting excellent thickness uniformity during application for the production of the positive electrode thereafter. do.

Alternatively, the positive electrode may be prepared by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating a film obtained by peeling from the support on the positive electrode current collector.

lithium secondary battery

In addition, the present invention may provide a lithium secondary battery including the positive electrode.

The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned to face the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode, and the positive electrode is the same as described above, so detailed description is omitted, Hereinafter, only the remaining components will be described in detail.

In addition, the lithium secondary battery may optionally further include a battery container for accommodating the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container.

In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface. Carbon, nickel, titanium, a surface treated with silver, etc., an aluminum-cadmium alloy, etc. may be used. In addition, the negative electrode current collector may have a thickness of typically 3 μm to 500 μm, and similarly to the positive electrode current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam body, a nonwoven body, and the like.

The anode active material layer optionally includes a binder and a conductive material together with the anode active material.

As the anode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metal compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; metal oxides capable of doping and dedoping lithium, such as SiO _β (0<β<2), SnO ₂ , vanadium oxide, and lithium vanadium oxide; Alternatively, a composite including the above-mentioned metallic compound and a carbonaceous material such as a Si-C composite or a Sn-C composite may be used, and any one or a mixture of two or more thereof may be used. In addition, a metal lithium thin film may be used as the negative electrode active material. In addition, as the carbon material, both low crystalline carbon and high crystalline carbon may be used. As low crystalline carbon, soft carbon and hard carbon are representative, and as high crystalline carbon, natural or artificial graphite of amorphous, plate-like, scale-like, spherical or fibrous shape, and Kish graphite (Kish) graphite), pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, liquid crystal pitches (Mesophase pitches), and petroleum and coal tar pitch (petroleum or coal tar pitch) High-temperature calcined carbon such as derived cokes) is a representative example.

The anode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the anode active material layer.

The binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and may be typically added in an amount of 0.1 wt% to 10 wt% based on the total weight of the anode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoro and roethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

The conductive material is a component for further improving the conductivity of the anode active material, and may be added in an amount of 10 wt% or less, specifically 5 wt% or less, based on the total weight of the anode active material layer. Such a conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The negative electrode active material layer is prepared by applying and drying a negative electrode mixture prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on the negative electrode current collector, or casting the negative electrode mixture on a separate support Then, it can be prepared by laminating the film obtained by peeling from the support on the negative electrode current collector.

On the other hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move, and if it is used as a separator in a lithium secondary battery, it can be used without any particular limitation, especially for the movement of ions in the electrolyte It is preferable to have a low resistance to and excellent electrolyte moisture content. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, and an ethylene/methacrylate copolymer, or these A laminated structure of two or more layers of may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, in order to secure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and may optionally be used in a single-layer or multi-layer structure.

In addition, examples of the electrolyte used in the present invention include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes, which can be used in the manufacture of lithium secondary batteries, and are limited to these. it's not going to be

Specifically, the electrolyte may include an organic solvent and a lithium salt.

The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, as the organic solvent, ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate, carbonate-based solvents such as PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and may contain a double bond aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; Or sulfolane may be used. Among these, a carbonate-based solvent is preferable, and a cyclic carbonate (eg, ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant capable of increasing the charge/discharge performance of the battery, and a low-viscosity linear carbonate-based compound ( For example, a mixture of ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) is more preferable. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the electrolyte may exhibit excellent performance.

The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN(C ₂ F ₅ SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ . LiCl, LiI, or LiB(C ₂ O ₄ ) ₂ and the like may be used. The concentration of the lithium salt is preferably used within the range of 0.1M to 2.0M. When the concentration of the lithium salt is included in the above range, since the electrolyte has appropriate conductivity and viscosity, excellent electrolyte performance may be exhibited, and lithium ions may move effectively.

In addition to the electrolyte components, the electrolyte includes, for example, haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, tri Ethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imida One or more additives such as jolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol or aluminum trichloride may be further included. In this case, the additive may be included in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrolyte.

As described above, since the lithium secondary battery including the positive active material according to the present invention exhibits excellent capacity, efficiency, lifespan and output characteristics, portable devices such as mobile phones, notebook computers, digital cameras, and hybrid electric vehicles (hybrid electric vehicles) It is useful in the field of electric vehicles such as vehicle and HEV).

Accordingly, according to the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same can be provided.

The battery module or battery pack is a power tool (Power Tool); electric vehicles, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); Alternatively, it may be used as a power source for any one or more medium and large-sized devices in a system for power storage.

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be a cylindrical shape using a can, a prismatic shape, a pouch type, or a coin type.

The lithium secondary battery according to the present invention may be used not only in a battery cell used as a power source for a small device, but may also be preferably used as a unit cell in a medium or large battery module including a plurality of battery cells.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

Examples and Comparative Examples

Example 1

A mixture was prepared by mixing a transition metal precursor having a composition represented by Ni _0.86 Co _0.1 Mn _0.02 Al _0.02 (OH) ₂ and LiOH in a molar ratio of 1:1.12. The mixture was fired under an oxygen atmosphere at 760° C. for 10 hours to prepare a fired product. 100 g of the fired product and deionized water were mixed in a weight ratio of 1:1, washed with water at 25° C. for 5 minutes, and then the washed fired product was separated using a reduced pressure filter, and was heated in a vacuum oven at 0.1 MPa and 130° C. After vacuum hot air drying for a period of time, the cathode active material having a composition represented by Li _1.0 Ni _0.86 Co _0.1 Mn _0.02 Al _0.02 O ₂ was prepared by microwave drying for 5 minutes using a microwave having an output of 650W.

Example 2

A positive active material was prepared in the same manner as in Example 1, except that the microwave drying time was adjusted to 10 minutes.

Example 3

A cathode active material was prepared in the same manner as in Example 1, except that a microwave having an output of 750 W was used.

Comparative Example 1

A mixture was prepared by mixing a transition metal precursor having a composition represented by Ni _0.86 Co _0.1 Mn _0.02 Al _0.02 (OH) ₂ and LiOH in a molar ratio of 1:1.12. The mixture was fired under an oxygen atmosphere at 760° C. for 10 hours to prepare a fired product. 100 g of the fired product and deionized water were mixed in a weight ratio of 1:1, washed with water at 25° C. for 5 minutes, and then the washed fired product was separated using a reduced pressure filter, and was placed in an oven at 130° C. under normal pressure for 12 hours. A positive active material having a composition represented by Li _1.0 Ni _0.86 Co _0.1 Mn _0.02 Al _0.02 O ₂ was prepared by hot air drying.

Comparative Example 2

A mixture was prepared by mixing a transition metal precursor having a composition represented by Ni _0.86 Co _0.1 Mn _0.02 Al _0.02 (OH) ₂ and LiOH in a molar ratio of 1:1.12. The mixture was fired under an oxygen atmosphere at 760° C. for 10 hours to prepare a fired product. 100 g of the fired product and deionized water were mixed in a weight ratio of 1:1, washed with water at 25° C. for 5 minutes, and then the washed fired product was separated using a reduced pressure filter, and was heated in a vacuum oven at 0.1 MPa and 130° C. A positive electrode active material having a composition represented by Li _1.0 Ni _0.86 Co _0.1 Mn _0.02 Al _0.02 O ₂ was prepared by vacuum hot air drying for a period of time.

Comparative Example 3

A mixture was prepared by mixing a transition metal precursor having a composition represented by Ni _0.86 Co _0.1 Mn _0.02 Al _0.02 (OH) ₂ and LiOH in a molar ratio of 1:1.12. The mixture was fired under an oxygen atmosphere at 760° C. for 10 hours to prepare a fired product. 100 g of the fired product and deionized water were mixed in a weight ratio of 1:1, washed with water at 25° C. for 5 minutes, and then the washed fired product was separated using a reduced pressure filter, and 10 using a microwave with an output of 650 W A cathode active material having a composition represented by Li _1.0 Ni _0.86 Co _0.1 Mn _0.02 Al _0.02 O ₂ was prepared by microwave drying for minutes.

Experimental example

Experimental Example 1: Evaluation of lithium by-products present in the positive electrode active material

5 g of each of the positive active materials of Examples 1 to 3 and Comparative Examples 1 to 3 were added to 100 g of distilled water and mixed for 5 minutes, followed by filtering. After filtering, the amounts of Li ₂ CO ₃ and LiOH dissolved in distilled water were measured by a titration method (using 0.1N HCl) using a pH meter, which is shown in Table 1.

LiOH (wt%) Li ₂ CO ₃ (wt%) Example 1 0.25 0.3 Example 2 0.16 0.2 Example 3 0.14 0.15 Comparative Example 1 0.4 0.6 Comparative Example 2 0.3 0.4 Comparative Example 3 0.28 0.36

Referring to Table 1, the positive electrode active materials of Examples 1 to 3 are manufactured through a drying process including both a vacuum hot air drying method and a microwave drying method, so that moisture in the surface and internal structure can be effectively removed, It can be seen that both Li ₂ CO ₃ and LiOH are present in small amounts compared to the cathode active materials of Comparative Examples 1 to 3.

Experimental Example 2: Evaluation of half-cell characteristics

Half cells were prepared using the positive active materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3, and initial charge/discharge capacity, initial efficiency, lifespan characteristics, resistance characteristics, and output characteristics were evaluated for each of the half cells.

First, each of the positive electrode active materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3, a carbon black conductive material and a PVdF binder were mixed in an NMP solvent in a weight ratio of 97.5:1.0:1.5 to prepare a positive electrode slurry. The positive electrode slurry was applied to one surface of an aluminum current collector (thickness: 12 μm), dried at 130° C., and then rolled to prepare a positive electrode. Meanwhile, a Li metal disk was used as the anode. An electrode assembly was prepared by interposing a separator between the positive electrode and the negative electrode prepared above, and then placed inside the battery case, and then the electrolyte was injected into the case to prepare a lithium secondary battery. At this time, an electrolytic solution obtained by dissolving 1M LiPF ₆ in an EC/EMC (5/5, vol%) organic solvent as an electrolytic solution was injected to prepare a half-cell.

The half-cell prepared as described above was charged at 25°C with a constant current of 0.2C until the voltage reached 4.25V, and then discharged at a constant current of 0.2C until the voltage reached 2.5V. The values of the initial charging capacity and the initial discharging capacity are shown in Table 2 below, and the ratio of the initial discharge capacity to the initial charging capacity is shown in Table 2 below as the initial efficiency (@0.2C). The initial efficiency (@1.0C) and the initial efficiency (@2.0C) were obtained in the same manner as described above, except that the C-rate was adjusted to 1.0C and 2.0C during charging and discharging, and it is shown in Table 2 below. .

Initial Charge Capacity (@0.2C)
(mAh/g) Initial discharge capacity (@0.2C)
(mAh/g) Initial Efficiency (@0.2C)
(%) Initial Efficiency (@1.0C)
(%) Initial Efficiency (@2.0C)
(%) Example 1 232.8 205.4 88.2 90.4 85.5 Example 2 232.6 209.6 90.1 92.8 88.1 Example 3 232.9 212.2 91.1 93.6 89.8 Comparative Example 1 226.4 192.4 85.0 85.2 78.6 Comparative Example 2 231.6 200.6 86.6 88.1 83.2 Comparative Example 3 231.8 202.2 87.2 89.0 84.1

In addition, the capacity of the half battery was measured by repeating the charge/discharge cycle 30 times with a constant current of 0.3C in the range of 45°C and 2.5 to 4.25V. Retention, %) as shown in FIG. 1 . And, the ratio of the DCIR obtained in the Nth discharge cycle to the DCIR obtained in the first discharge cycle is the resistance increase rate (ΔDCIR, %), and this is shown in FIG. 2 .

Finally, for the half-cell prepared as described above, ΔSOC 30 (SOC 35% to SOC 20%) was discharged at -10 °C (low temperature) and 25 °C (room temperature), respectively, and 0.4C IR drop for 1,350 seconds to confirm the change in the voltage value, and it is shown in Table 3 below.

IR drop (ΔV) at -10℃ at 25℃ Example 1 0.29 0.14 Example 2 0.22 0.11 Example 3 0.17 0.09 Comparative Example 1 0.53 0.3 Comparative Example 2 0.42 0.2 Comparative Example 3 0.34 0.18

Referring to Tables 2 and 3 and FIGS. 1 and 2, the positive active materials of Examples 1 to 3 were prepared according to the method for preparing the positive active material of the present invention, and the positive active materials of Comparative Examples 1 to 3 and residual moisture on the surface were There is a difference in that the surface structure is more stable because it is removed, and accordingly, it can be confirmed that the capacity, efficiency, capacity retention rate, and low temperature and room temperature output characteristics of the batteries including the positive active materials of Examples 1 to 3 are all excellent.

Claims (10)

(A) mixing a transition metal precursor including a transition metal hydroxide or a transition metal oxyhydroxide and a lithium-containing raw material, followed by firing to prepare a fired product; and
(B) washing the fired product with a water washing solution and drying it to prepare a lithium transition metal oxide;
The drying is a method of manufacturing a positive electrode active material comprising vacuum hot air drying and microwave drying.
The method according to claim 1,
The transition metal precursor is a method for producing a cathode active material having a composition represented by the following Chemical Formula 1 or the following Chemical Formula 2:
[Formula 1]
[Ni _a Co _b M ¹ _c M ² _d ](OH) ₂
[Formula 2]
[Ni _a Co _b M ¹ _c M ² _d ]O OH
In Formula 1 and Formula 2,
Wherein M ¹ is at least one selected from Mn and Al,
The M ² is at least one selected from B, Mg, Ca, Ti, V, Cr, Fe, Zn, Ga, Y, Zr, Nb, Mo, Ta and W,
0.7≤a<1, 0<b<0.3, 0<c<0.3, 0≤d≤0.1, a+b+c+d=1.
The method according to claim 1,
The drying is a method of producing a positive electrode active material that is vacuum dried after hot air drying, microwave drying.
The method according to claim 1,
The vacuum hot air drying method for producing a positive electrode active material is performed under a temperature of 100 ℃ to 200 ℃.
The method according to claim 1,
The vacuum hot air drying method for producing a positive electrode active material is performed under a pressure of 0.05 MPa to 0.15 MPa.
The method according to claim 1,
The vacuum hot air drying method for producing a positive electrode active material is performed under a pressure of 0.06 MPa to 0.12 MPa.
The method according to claim 1,
The vacuum hot air drying time is a method of manufacturing a positive electrode active material of 5 to 30 hours.
The method according to claim 1,
The microwave drying is a method of manufacturing a cathode active material that is performed using a microwave having an output of 600W to 1,000W.
The method according to claim 1,
The microwave drying is a method of manufacturing a cathode active material that is performed using a microwave having an output of 600W to 800W.
The method according to claim 1,
The microwave drying time is a method of producing a positive electrode active material of 5 minutes to 30 minutes.

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