KR20240059476A - Positive electrode active material, manufacturing method of the same and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a positive electrode active material, which includes a lithium composite transition metal oxide in the form of a single particle with an average particle diameter (D ₅₀ ) of 5㎛ to 8㎛, and a span value ((D ₉₀ -D ₁₀ )/D ₅₀ ). It relates to a positive electrode active material having a pellet density of 0.8 or more and a pellet density of 3.60 g/cm ³ or more, a method of manufacturing the same, and a lithium secondary battery containing the same.

Description

Cathode active material, manufacturing method thereof, and lithium secondary battery comprising the same {POSITIVE ELECTRODE ACTIVE MATERIAL, MANUFACTURING METHOD OF THE SAME AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME}

The present invention relates to a positive electrode active material capable of improving the energy density of a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery containing the same.

Recently, with technological developments such as electric vehicles, the demand for secondary batteries with high energy density is increasing, and accordingly, research on high-nickel (High-Ni)-based cathode active materials with excellent capacity characteristics is being actively conducted.

However, there is a limit to continuously increasing the nickel content of the positive electrode active material, and when the nickel content is high, there is a problem that battery performance rapidly deteriorates as the battery cycle progresses. On the other hand, the positive electrode active material in the form of secondary particles formed by agglomerating tens to hundreds of primary particles has a problem of side reactions occurring due to cracks occurring due to rolling strength or battery cycle progress, and as a result, single particle high-nickel ( Research on high-Ni cathode active materials is in progress.

However, after mixing the composite transition metal hydroxide prepared through coprecipitation, which is a generally known method, and lithium-containing raw materials, the positive electrode active material in the form of single particles is produced at a higher temperature than when producing the positive active material in the form of secondary particles. In the case of the positive electrode active material manufactured by the manufacturing method, there is a problem of low energy density due to the small average particle diameter.

The present invention is an invention to solve the above problems, and the positive electrode active material not only has a large average particle diameter (D ₅₀ ) in the form of a large particle of 5㎛ to 8㎛, but also has a span value ((D ₉₀ -D ₁₀ )/D ₅₀ ) is greater than 0.8, and the pellet density is greater than 3.60 g/cm ³ The purpose is to provide a positive electrode active material.

In addition, the present invention involves dry mixing raw materials containing nickel, cobalt, manganese, aluminum, etc. with lithium-containing raw materials, performing primary calcination, pulverizing, additionally adding lithium-containing raw materials, and then performing secondary calcination. The purpose is to provide a method for manufacturing the above-described positive electrode active material.

Additionally, the present invention aims to provide a lithium secondary battery with increased energy density, including the positive electrode active material.

In order to solve the above problems, the present invention provides a positive electrode active material, a method for manufacturing the same, and a positive electrode and lithium secondary battery including the same.

(1) The present invention includes a lithium composite transition metal oxide in the form of a single particle with an average particle diameter (D ₅₀ ) of 5㎛ to 8㎛, and a span value ((D ₉₀ -D ₁₀ )/D ₅₀ ) of 0.8 or more. , providing a positive electrode active material having a pellet density of 3.60 g/cm ³ or more.

(2) The present invention provides the positive electrode active material according to (1) above, wherein the single particle lithium composite transition metal oxide contains 60 mol% or more of nickel based on the total number of moles of metals excluding lithium.

(3) The present invention provides the positive electrode active material according to (1) or (2) above, wherein the single particle lithium composite transition metal oxide has a composition represented by the following formula (1).

[Formula 1]

Li _x [Ni _a Co _b Mn _c M1 _d ]O _2-y A _y

In Formula 1,

M1 is one or more selected from Y, Zr, Al, B, Ti, W, Nb, Sr, Mo and Mg,

A is one or more selected from F, Cl, Br, I and S,

0.9≤x≤1.2, 0.6≤a<1, 0≤b≤0.4, 0≤c≤0.4, 0≤d≤0.2, a+b+c+d=1, 0≤y≤0.2.

(4) In any one of (1) to (3) above of the present invention, the single particle form is a single particle form or has two to two primary particles having an average particle diameter of 2 μm to 5 μm derived from an SEM image. A positive electrode active material in the form of 10 aggregates is provided.

(5) In addition, the present invention (A) (i) nickel-containing raw materials, (ii) cobalt-containing raw materials, manganese-containing raw materials, and M1-containing raw materials (M1 is Y, Zr, Al, B, Ti, W , Nb, Sr, Mo and Mg) and (iii) dry mixing a first lithium-containing raw material to prepare a mixture; (B) producing a first fired product by first firing the mixture at a temperature of 760°C to 850°C; and (C) pulverizing the first fired product; and (D) mixing the first sintered product obtained in step (C) above with a second lithium-containing raw material and performing a second sintering at a temperature of 700°C to 900°C to produce a lithium composite transition metal oxide. A method for producing a positive electrode active material according to any one of (1) to (4) above is provided.

(6) The present invention provides a method for producing a positive electrode active material according to (5) above, wherein the nickel-containing raw material is at least one selected from nickel hydroxide, nickel oxide, nickel carbonate, nickel sulfide, and nickel nitrate.

(7) The present invention provides a method for producing a positive electrode active material according to (5) or (6) above, wherein the cobalt-containing raw material is at least one selected from cobalt hydroxide, cobalt oxide, cobalt carbonate, cobalt sulfide, and cobalt nitrate. do.

(8) The present invention provides a method for producing a positive electrode active material according to any one of (5) to (7) above, wherein the manganese-containing raw material is at least one selected from manganese oxide, manganese carbonate, manganese nitrate, and manganese sulfide. do.

(9) The present invention provides a method for producing a positive electrode active material according to any one of (5) to (8) above, wherein the first calcination is performed in an oxygen atmosphere.

(10) The present invention provides a method for producing a positive electrode active material according to any one of (5) to (9) above, wherein the first firing is performed for 5 to 20 hours.

(11) The present invention provides a method for producing a positive electrode active material according to any one of (5) to (10) above, wherein the secondary firing is performed in an oxygen atmosphere.

(12) The present invention provides a method for producing a positive electrode active material according to any one of (5) to (11) above, wherein the secondary firing is performed for 5 to 15 hours.

(13) Additionally, the present invention provides a positive electrode containing the positive electrode active material according to any one of (1) to (4) above.

(14) Additionally, the present invention provides an anode according to (13) above; cathode; a separator disposed between the anode and the cathode; It provides a lithium secondary battery including; and an electrolyte.

The positive electrode active material of the present invention not only has a single baryonic particle form with a large average particle diameter (D ₅₀ ) of 5㎛ to 8㎛, but also has a large span value ((D ₉₀ -D ₁₀ )/D ₅₀ ) of 0.8 or more, and is a pellet The density is greater than 3.60 g/cm ³ , which can improve the rolling density and energy density of lithium secondary batteries.

In addition, according to the method for producing a positive electrode active material of the present invention, the above-described positive active material can be effectively produced.

1 is a scanning electron microscope (SEM) image of the positive electrode active material of Example 1.
Figure 2 is an SEM image of the positive electrode active material of Comparative Example 1.

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

Terms or words used in this specification and claims should not be construed as limited to their common or dictionary meanings, and the inventor may appropriately define the concept of terms in order to explain his or her invention in the best way. It should be interpreted with meaning and concept consistent with the technical idea of the present invention based on the principle that it is.

In this specification, terms such as 'comprise', 'provide', or 'have' are intended to designate the presence of implemented features, numbers, steps, components, or a combination thereof, but are not intended to indicate the presence of one or more other features or numbers. It should be understood that this does not exclude in advance the possibility of the presence or addition of steps, components, or combinations thereof.

In this specification, the term 'on' means not only the case where a certain component is formed directly on top of another component, but also the case where a third component is interposed between these components.

In this specification, 'single particle type positive electrode active material' is a concept in contrast to the positive electrode active material in the form of spherical secondary particles formed by agglomerating tens to hundreds of primary particles manufactured by conventional methods, and is composed of 10 or less particles. It refers to a positive electrode active material composed of primary particles. Specifically, in the present invention, the positive electrode active material in the form of a single particle may be a single particle composed of one primary particle, or may be a secondary particle in which several primary particles are aggregated.

'Primary particle' refers to the minimum unit of particle recognized when observing a positive electrode active material through a scanning electron microscope, and 'secondary particle' refers to a secondary structure formed by aggregating a plurality of primary particles.

In this specification, the 'particle size D _n ' of the positive electrode active material means the particle size at the n% point of the volume cumulative distribution according to the particle size. That is, D ₅₀ is the particle size at 50% of the volume cumulative distribution according to particle size, D ₉₀ is the particle size at 90% of the volume cumulative distribution according to particle size, and D ₁₀ is 10% of the volume cumulative distribution according to particle size. It means the entrance diameter at the point. And, D _min refers to the minimum particle size of the positive electrode active material, and D _max refers to the maximum value of the particle size of the positive electrode active material. On the other hand, D _n is calculated by dispersing the powder to be measured in a dispersion medium and then introducing it into a commercially available laser diffraction particle size measurement device (for example, Microtrac's S3500) to determine the difference in diffraction patterns depending on the particle size when the particles pass through the laser beam. Measure and calculate the particle size distribution, and measure D ₁₀ , D ₅₀ and D ₉₀ by calculating the particle diameters at points that are 10%, 50% and 90% of the volume cumulative distribution according to the particle size in the measuring device. can do.

In this specification, 'pellet density (D _p )' is the density measured after pressing the positive electrode active material at a pressure of 6784 kgf/cm ² . Specifically, the pellet density (D _p ) was calculated by putting 3 g of the positive electrode active material into a pelletizer circular mold with a diameter of 13 mm, pressing it at 9000 kgf for 3 seconds to make a pellet, measuring the height of the pellet, and using the following relationship: It is a value.

D _p (g/cm ³ ) = W / [(π×(D/2) ² )×H/1000]

(W is the input amount of positive electrode active material (g), D is the diameter of the pelletizer circular mold (mm), and H is the height of the pellet (mm).)

positive electrode active material

The present invention includes a lithium composite transition metal oxide in the form of a single particle having an average particle diameter (D ₅₀ ) of 5㎛ to 8㎛, a span value ((D ₉₀ -D ₁₀ )/D ₅₀ ) of 0.8 or more, and a pellet density of A positive electrode active material having a value of 3.60 g/cm ³ or more is provided.

The present inventors found that the positive electrode active material not only has a baryonic single particle form with an average particle diameter (D ₅₀ ) of 5㎛ to 8㎛, but also has a span value ((D ₉₀ -D ₁₀ )/D ₅₀ ) of 0.8 or more, and a pellet density. When is greater than 3.60 g/cm ³ , it was found that the rolling density and energy density of the lithium secondary battery were greatly improved, and the present invention was completed. Specifically, the present invention was completed by finding that the energy density of the battery could be improved by increasing the pellet density by broadening the particle size distribution of the single-particle type positive active material paper.

The single particle lithium composite transition metal oxide included in the positive electrode active material of the present invention may have an average particle diameter (D ₅₀ ) of 5 ㎛ or more, 6 ㎛ or less, 7 ㎛ or less, and 8 ㎛ or less. If the average particle diameter (D ₅₀ ) of the lithium composite transition metal oxide in the form of a single particle is less than 5㎛, there is a problem of reduced capacity due to low rolling density, and if it is more than 8㎛, the single particle form is not formed well, so the battery There is a problem with gas generation when applied to .

The positive electrode active material according to the present invention may have a span value ((D ₉₀ -D ₁₀ )/D ₅₀ ) of 0.80 or more, 0.90 or more, or 1.00 or more. If the span value ((D ₉₀ -D ₁₀ )/D ₅₀ ) of the positive electrode active material is less than 0.8, there is a problem of reduced capacity due to low rolling density.

The positive electrode active material according to the present invention may have a pellet density of 3.60 g/cm ³ or more, 3.61 g/cm ³ or more, 3.62 g/cm ³ or more, and 3.63 g/cm ³ or more. If the pellet density of the positive electrode active material is less than 3.60 g/cm ³ , there is a problem of reduced capacity due to low rolling density.

According to the present invention, the positive electrode active material may have D _min of 1 ㎛ or more and D _max of 22 ㎛ or less in order to suppress side reactions caused by an increase in surface area and prevent degradation of battery performance due to air pollution. In this case, the formation of cracks is prevented, improving the structural stability of the positive electrode active material itself, and the generation of fine powder due to cracking during rolling for manufacturing the positive electrode can be prevented.

According to the present invention, the single particle lithium composite transition metal oxide contains 60 mol% or more, specifically, 80 mol% or more, and more specifically, 85 mol% or more of nickel relative to the total number of moles of metals excluding lithium. You can. That is, the single particle lithium composite transition metal oxide may be a high-nickel (High Ni)-based lithium composite transition metal oxide. In this case, the energy density of the lithium secondary battery can be further improved.

According to the present invention, the single particle lithium composite transition metal oxide may have a composition represented by the following formula (1).

[Formula 1]

Li _x [Ni _a Co _b Mn _c M1 _d ]O _2-y A _y

In Formula 1,

M1 is one or more selected from Y, Zr, Al, B, Ti, W, Nb, Sr, Mo and Mg,

A is one or more selected from F, Cl, Br, I and S,

0.9≤x≤1.2, 0.6≤a<1, 0≤b≤0.4, 0≤c≤0.4, 0≤d≤0.2, a+b+c+d=1, 0≤y≤0.2.

Specifically, M1 may be one or more selected from Y, Zr, and Al.

The a refers to the atomic fraction of nickel among the metal elements in the lithium composite transition metal oxide, and may be 0.6≤a<1, 0.8≤a≤0.98, or 0.85≤a≤0.95.

The b refers to the atomic fraction of cobalt among the metal elements in the lithium composite transition metal oxide, and may be 0≤b≤0.4, 0.01≤b≤0.2, or 0.01≤b≤0.15.

The c refers to the atomic fraction of manganese among the metal elements in the lithium composite transition metal oxide, and may be 0≤b≤0.4, 0.01≤b≤0.2, or 0.01≤b≤0.15.

The d refers to the atomic fraction of the M1 element among the metal elements in the lithium composite transition metal oxide, and may be 0≤d≤0.2, 0≤d≤0.1, or 0≤d≤0.05.

According to the present invention, the single particle form may be a single particle form or an agglomerated form of 2 to 10 primary particles having an average particle diameter of 2 ㎛ to 5 ㎛ derived from SEM images. In this case, side reactions due to increased surface area can be suppressed. The average particle size of the primary particles derived from the SEM image is measured using a scale bar to measure the particle size of tens to hundreds of primary particles present in the SEM image of the positive electrode active material taken using a SEM (Scanning Electron Microscope). This is the average value.

Cathode active material manufacturing method

The present invention relates to (A) (i) nickel-containing raw materials, (ii) cobalt-containing raw materials, manganese-containing raw materials, and M1-containing raw materials (M1 is Y, Zr, Al, B, Ti, W, Nb, Sr, preparing a mixture by dry mixing at least one selected from Mo and Mg) with (iii) a first lithium-containing raw material; (B) producing a first fired product by first firing the mixture at a temperature of 760°C to 850°C; (C) pulverizing the first fired product; and (D) mixing the first sintered product obtained in step (C) above with a second lithium-containing raw material and performing a second sintering at a temperature of 700°C to 900°C to produce a lithium composite transition metal oxide. A method for manufacturing a positive electrode active material according to the present invention described above is provided. That is, the positive electrode active material according to the present invention described above is manufactured by the method for manufacturing the positive electrode active material according to the present invention.

As in the present invention, when a dry mixture of raw materials containing nickel, cobalt, manganese, aluminum, etc. and lithium-containing raw materials is used, the specific surface area of the mixed materials is large, so the product manufactured through coprecipitation method Compared to the method of overheating using a complex transition metal hydroxide precursor, the sintering temperature is lower and it has the advantage of producing a single particle positive electrode active material. For reference, when using a mixture of composite transition metal hydroxide prepared through coprecipitation, which is a generally known method, and lithium-containing raw materials, there is a problem that washing with water is essential due to the high content of lithium impurities. There is a problem that the manufacturing process is complicated because the positive electrode active material is manufactured through a needle method.

According to the present invention, the nickel-containing raw material may be one or more selected from nickel hydroxide, nickel oxide, nickel carbonate, nickel sulfide, and nickel nitrate.

According to the present invention, the cobalt-containing raw material may be one or more selected from cobalt hydroxide, cobalt oxide, cobalt carbonate, cobalt sulfide, and cobalt nitrate.

According to the present invention, the manganese-containing raw material may be one or more selected from manganese oxide, manganese carbonate, manganese nitrate, and manganese sulfide.

The M1-containing raw material (M1 is one or more selected from Y, Zr, Al, B, Ti, W, Nb, Sr, Mo, and Mg) may be an M1-containing hydroxide, oxide, etc., for example, M1 is Al(OH) ₃ in the case of Al, ZrO ₂ in the case of Zr, Y ₂ O ₃ in the case of Y, WO ₄ in the case of W, TiO ₂ in the case of Ti, and B(OH) ₃ in the case of B. You can.

The first lithium-containing raw material and the second lithium-containing raw material may include lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide. For example, the first lithium-containing raw material and the second lithium-containing raw material are each independently Li ₂ CO ₃ , LiNO ₃ , LiNO ₂ , LiOH, LiOH·H ₂ O, LiH, LiF, LiCl, LiBr , LiI, CH ₃ COOLi, Li ₂ O, Li ₂ SO ₄ , CH ₃ COOLi, Li ₃ C ₆ H ₅ O ₇ or a mixture thereof.

(i) nickel-containing raw materials, (ii) cobalt-containing raw materials, manganese-containing raw materials and M1-containing raw materials (M1 is selected from Y, Zr, Al, B, Ti, W, Nb, Sr, Mo and Mg) and (iii) the first lithium-containing raw material is the total number of moles of Ni, Co, Mn, and M1 included in (i) and (ii) above and the first lithium-containing raw material. It may be mixed so that the molar ratio of lithium contained in the material is 1:0.97 to 1:1.02, specifically 1:0.97 or more and less than 1:1.00.

In addition, the second lithium-containing raw material has a molar ratio of the total number of moles of Ni, Co, Mn, and M1 excluding lithium contained in the first fired product to the lithium contained in the second lithium-containing raw material of 1: It may be mixed to 0.03 to 1:0.07.

As in the present invention, when the calcination is carried out in two stages, primary calcination and secondary calcination, and the lithium-containing raw material is added in two steps, there is an advantage that it is easy to remove fine powder (fine particles) generated during the process. In contrast, when firing is carried out in one step, particle growth progresses less and performance deteriorates, and when lithium-containing raw materials are added at once rather than dividedly, there is a problem of side reactions due to fine powder. there is.

As in the present invention, when the first firing is performed at a temperature of 760°C to 850°C, the growth of the positive electrode active material proceeds well as the raw material containing nickel, cobalt, manganese, aluminum, etc. reacts with the lithium-containing raw material. When the secondary calcination is carried out at a temperature of 700℃ to 900℃, the fine powder generated during the process participates in the reaction, causing the positive active material to grow additionally, which has the advantage of growing well in the form of single particles. there is.

The first calcination may be performed at a temperature of preferably 760°C to 850°C, more preferably 790°C to 830°C, to form single particles.

According to the present invention, the first calcination may be performed under an oxygen atmosphere for a smooth reaction. Specifically, the oxygen atmosphere may be an atmosphere in which the oxygen concentration is 90% by volume or more.

According to the present invention, the first firing may be performed for 5 to 20 hours, specifically 5 to 15 hours.

The step (C) is a step of pulverizing the primary fired product, and may be performed to crush necking between particles and ensure that the particle size satisfies the scope of the present invention.

The pulverization may be performed under conditions such that the average particle diameter (D ₅₀ ) of the primary fired product is 5㎛ to 8㎛ and the span value ((D ₉₀ -D ₁₀ )/D ₅₀ ) is 0.8 or more, Preferably, the grinding is performed under conditions such that the average particle diameter (D ₅₀ ) of the resulting positive electrode active material is 5㎛ to 8㎛ and the span value ((D ₉₀ -D ₁₀ )/D ₅₀ ) is 0.8 or more. It may be possible. Specifically, the grinding may be performed under a pressure of 3 bar using Jet-mill equipment so that the average particle diameter (D ₅₀ ) of the resulting positive electrode active material is 5㎛ to 8㎛, and the primary fired product is 3.5 It may be performed while supplying at a feeding rate of more than kg/h and less than 4.5 kg/h.

The secondary calcination may be performed at a temperature of preferably 700°C to 900°C, more preferably 750°C to 800°C for single particle growth.

According to the present invention, the secondary calcination may be performed under an oxygen atmosphere for a smooth reaction. Specifically, the oxygen atmosphere may be an atmosphere in which the oxygen concentration is 90% by volume or more.

According to the present invention, the secondary firing may be performed for 5 to 15 hours, specifically 5 to 10 hours.

anode

The present invention provides a positive electrode containing the above positive electrode active material.

According to one embodiment of the present invention, the positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer may include the positive electrode active material.

According to one embodiment of the present invention, the positive electrode current collector may include a highly conductive metal, and the positive electrode active material layer is easily adhered, but is not particularly limited as long as it is not reactive within the voltage range of the battery. The positive electrode current collector may be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or an aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. Additionally, the positive electrode current collector may typically have a thickness of 3 ㎛ to 500 ㎛, and fine irregularities may be formed on the surface of the current collector to increase the adhesion of the positive electrode active material. For example, it can be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven materials.

According to one embodiment of the present invention, the positive electrode active material layer may optionally include a conductive material and a binder along with the positive electrode active material. At this time, the positive electrode active material may be included in an amount of 80% to 99% by weight, more specifically 85% to 98.5% by weight, based on the total weight of the positive electrode active material layer, and can exhibit excellent capacity characteristics within this range. .

According to one embodiment of the present invention, the conductive material is used to provide conductivity to the electrode, and can be used without particular limitation as long as it does not cause chemical change and has electronic conductivity in the battery being constructed. 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, thermal black, and carbon fiber; Metal powders or metal fibers such as copper, nickel, aluminum, and silver; Conductive tubes such as carbon nanotubes; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Or conductive polymers such as polyphenylene derivatives, etc., of which one type alone or a mixture of two or more types may be used. The conductive material may be included in an amount of 0.1% to 15% by weight based on the total weight of the positive electrode active material layer.

According to one embodiment of the present invention, the binder serves to improve adhesion between positive electrode active material particles and adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylalcohol, polyacrylonitrile, and polymethylmethane. Crylate (polymethymethaxrylate), carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene- Diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and polymers in which hydrogen thereof is substituted with Li, Na, or Ca, or various copolymers thereof Combinations, etc. may be mentioned, and one type of these may be used alone or a mixture of two or more types may be used. The binder may be included in an amount of 0.1% by weight to 15% by weight based on the total weight of the positive electrode active material layer.

According to one embodiment of the present invention, the positive electrode can be manufactured according to a conventional positive electrode manufacturing method except for using the positive electrode active material described above. Specifically, the positive electrode is prepared by dissolving or dispersing the positive electrode active material and optionally a binder, a conductive material, and a dispersant in a solvent, and the composition for forming a positive active material layer is applied to the positive electrode current collector and then dried. and rolling, or by casting the composition for forming the positive electrode active material layer on a separate support and then peeling from this support and laminating the film obtained on the positive electrode current collector.

According to an embodiment of the present invention, the solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, and N-methylpyrrolidone. (NMP), dimethylformamide (DMF), acetone, or water, among which one type alone or a mixture of two or more types may be used. The amount of the solvent used is to dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant in consideration of the application thickness and manufacturing yield of the slurry, and to have a viscosity capable of exhibiting excellent thickness uniformity when applied for subsequent positive electrode production. That's enough.

Lithium secondary battery

The present invention provides a lithium secondary battery including the positive electrode.

According to one embodiment of the present invention, the lithium secondary battery includes the positive electrode; cathode; It may include a separator and an electrolyte interposed between the anode and the cathode. Additionally, the lithium secondary battery may optionally further include a battery container that accommodates the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

According to one embodiment of the present invention, the negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

According to one embodiment of the present invention, the negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, for example, copper, stainless steel, aluminum, nickel, titanium, plastic. Surface treatment of carbon, copper or stainless steel with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector may typically have a thickness of 3 ㎛ to 500 ㎛, and like 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 can be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven materials.

According to one embodiment of the present invention, the negative electrode active material layer may optionally include a binder and a conductive material along with the negative electrode active material.

According to one embodiment of the present invention, a compound capable of reversible intercalation and deintercalation of lithium may be used as the negative electrode active material. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; Metallic compounds that can be alloyed with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; Metal oxides that can dope and undope lithium, such as SiO _β (0<β<2), SnO ₂ , vanadium oxide, and lithium vanadium oxide; Alternatively, a composite containing the above-described metallic compound and a carbonaceous material, such as a Si-C composite or Sn-C composite, may be used, and any one or a mixture of two or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Additionally, the carbon material may include both low-crystalline carbon and high-crystalline carbon. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and high-crystalline carbon includes amorphous, plate-shaped, flaky, spherical, or fibrous natural graphite, artificial graphite, and Kish graphite. graphite, pyrolytic carbon, mesophase pitch based carbonfiber, meso-carbon microbeads, mesophase pitches, and petroleum or coal tar pitch derived High-temperature fired carbon such as cokes is a representative example. The negative electrode active material may be included in an amount of 80% by weight to 99% by weight based on the total weight of the negative electrode active material layer.

According to one embodiment of the present invention, the binder of the negative electrode active material layer is a component that assists the bonding between the conductive material, the active material, and the current collector, and is typically contained in the amount of 0.1% by weight to 10% by weight based on the total weight of the negative electrode active material layer. is added. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, and polytetra. Examples include fluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluorine rubber, and various copolymers thereof.

According to one embodiment of the present invention, the conductive material of the negative electrode active material layer is a component to further improve the conductivity of the negative electrode active material, and is contained in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. may be added. These conductive materials are not particularly limited as long as they have conductivity without causing chemical changes in the battery, and examples include 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 fiber and metal fiber; fluorinated carbon; Metal powders such as 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.

According to one embodiment of the present invention, the negative electrode is manufactured by applying and drying a composition for forming a negative electrode active material layer prepared by dissolving or dispersing the negative electrode active material and optionally the binder and the conductive material in a solvent on the negative electrode current collector, or Alternatively, it can be manufactured by casting the composition for forming the negative electrode active material layer on a separate support, and then lamination of the film obtained by peeling from this support onto the negative electrode current collector.

According to one embodiment of the present invention, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. It can be used without particular restrictions as long as it is normally used as a separator in a lithium secondary battery, and in particular, it can be used for ion movement in the electrolyte. It is desirable to have low resistance and excellent electrolyte moisturizing ability. Specifically, porous polymer films, for example, porous polymer films made of polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer, or these. A laminated structure of two or more layers may be used. In addition, conventional porous nonwoven fabrics, for example, nonwoven fabrics made of high melting point glass fibers, polyethylene terephthalate fibers, etc., may be used. Additionally, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

According to an embodiment of the present invention, the electrolyte may include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, and a molten inorganic electrolyte that can be used when manufacturing a lithium secondary battery. It is not limited to these. As a specific example, the electrolyte may include an organic solvent and a lithium salt.

According to one embodiment of the present invention, the organic solvent may be used without 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, the organic solvent includes ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; Ether-based solvents such as dibutyl ether or tetrahydrofuran; Ketone-based 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 (PC) ), carbonate-based solvents such as; Alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a straight-chain, branched or ring-structured hydrocarbon group having 2 to 20 carbon atoms and may include a double bond aromatic ring or an ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; Alternatively, sulfolane, etc. may be used. Among these, carbonate-based solvents are preferable, and cyclic carbonates (e.g., ethylene carbonate or propylene carbonate, etc.) with high ionic conductivity and high dielectric constant that can improve the charge/discharge performance of the battery, and low-viscosity linear carbonate-based compounds ( For example, ethylmethyl carbonate, dimethyl carbonate, diethyl carbonate, etc.) are more preferable.

According to one embodiment of the present invention, the lithium salt can be used without particular limitation as long as it is a compound that can provide lithium ions used in lithium secondary batteries. Specifically, the anions of the lithium salt include F ^- , Cl ^- , Br ^- , I ^- , NO ₃ ^- , N(CN) ₂ ^- , BF ₄ ^- , CF ₃ CF ₂ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , (SF ₅ ) ₃ C ^- , (CF ₃ SO ₂ ) ₃ C ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- , and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- It may be at least one selected from the group consisting of, 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 may be used. The concentration of the lithium salt is preferably used within the range of 0.1 M to 2.0 M. When the concentration of lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, so excellent electrolyte performance can be achieved and lithium ions can move effectively.

According to one embodiment of the present invention, in addition to the electrolyte components, the electrolyte contains halo such as difluoroethylene carbonate for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. Alkylene carbonate compounds, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexanoic acid triamide, nitrobenzene derivatives, sulfur, quinone imine dye, N-substituted oxazoli One or more additives such as dinon, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, or aluminum trichloride may be further included. At this time, the additive may be included in an amount of 0.1% to 5% by weight based on the total weight of the electrolyte.

Since the lithium secondary battery containing the positive electrode active material according to the present invention stably exhibits excellent capacity characteristics, output characteristics, and lifespan characteristics, it is used in portable devices such as mobile phones, laptop computers, and digital cameras, and hybrid electric vehicles. It is useful in the field of electric vehicles such as HEV) and electric vehicles (EV).

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

The lithium secondary battery according to the present invention can not only be used in battery cells used as a power source for small devices, but can also be preferably used as a unit cell in medium to large-sized battery modules containing a plurality of battery cells.

Accordingly, according to one embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

According to one embodiment of the present invention, the battery module or battery pack includes a power tool; Electric vehicles, including electric vehicles (EV), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEV); Alternatively, it can be used as a power source for one or more mid- to large-sized devices among power storage systems.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement it. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein.

Examples and Comparative Examples

Example 1

Ni(OH) ₂ , Co ₃ O ₄ , MnO ₂ , Al(OH) ₃ , LiOH·H ₂ O so that the molar ratio of Ni:Co:Mn:Al:Li is 93:5:1:1:0.97. The mixture was prepared by dry mixing.

The mixture was first fired at a temperature of 820°C for 15 hours in an oxygen atmosphere (oxygen concentration: 90% by volume or more) to prepare a first fired product. In order to break necking between particles, the first fired product was ground under a pressure of 3 bar while being supplied at a feeding rate of 4.0 kg/h using a jet mill.

Thereafter, the pulverized first sintered product and the second lithium-containing raw material are mixed with the total number of moles of transition metals (Ni, Co, Mn, Al) excluding lithium contained in the first sintered product and the second lithium-containing raw material. was mixed so that the molar ratio of lithium contained in was 1:0.03, and secondary calcination was performed for 10 hours at a temperature of 700°C to 900°C under an oxygen atmosphere (oxygen concentration: 90% by volume or more) to produce lithium composite transition metal oxide (positive electrode active material). ) (Composition: Li(Ni _0.93 Co _0.05 Mn _0.01 Al _0.01 )O ₂ ) was prepared.

Comparative Example 1

When pulverizing the first fired product in Example 1, lithium complex transition metal oxide (anode active material) (composition) was prepared in the same manner as Example 1, except that the feeding rate was 3.0 kg/h. : Li(Ni _0.93 Co _0.05 Mn _0.01 Al _0.01 )O ₂ ) was prepared.

Comparative Example 2

Lithium complex transition metal oxide was prepared in the same manner as in Example 1, except that Ni _0.93 Co _0.05 Mn _0.01 Al _0.01 (OH) ₂ was used instead of Ni(OH) ₂ , Co ₃ O ₄ , MnO ₂ , and Al(OH) ₃ . (Cathode active material) (composition: Li(Ni _0.93 Co _0.05 Mn _0.01 Al _0.01 )O ₂ ) was prepared.

Experiment example

Experimental Example 1: Analysis of positive electrode active material particle size

After taking 0.02 g of the positive electrode active material prepared in Example 1 and Comparative Examples 1 to 2, each was placed in a vial containing 5 ml of ultrapure water and 5 ml of dispersant, and the positive active material was dispersed with a sonicator for 2 minutes, and then analyzed with a particle size analyzer. (PSA) (Microtrac, S3500) to obtain the D _min , D ₁₀ , D ₅₀ , D ₉₀ , and D _max values of each positive electrode active material prepared in Example 1 and Comparative Examples 1 to 2, and D _min , D ₅₀ , D _max values and span values ((D ₉₀ -D ₁₀ )/D ₅₀ ) are shown in Table 1 below.

Experimental Example 2: Evaluation of positive electrode active material pellet density

After taking 3g each of the positive electrode active materials prepared in Example 1 and Comparative Examples 1 to 2, each was put into a circular pelletizer mold with a diameter of 13mm, and pressed at 900kgf for 3 seconds to make pellets, and then the height of the pellets was measured. . Then, the pellet density (D _p ) was calculated using the following relationship, and it is shown in Table 1 below.

D _p (g/cm ³ ) = W / [(π×(D/2) ² )×H/1000]

(W is the input amount of positive electrode active material (g), D is the diameter of the pelletizer circular mold (mm), and H is the height of the pellet (mm).)

D _min (㎛) D ₅₀ (㎛) D _max (㎛) span value pellet density Example 1 2.0 5.7 21.8 1.04 3.63 Comparative Example 1 2.8 6.0 15.5 0.70 3.58 Comparative Example 2 - - 8.0 0.71 3.35

Experimental Example 3: Confirmation of SEM image of positive electrode active material

The positive electrode active materials prepared in Example 1 and Comparative Examples 1 to 2 were each photographed using a Scanning Electron Microscope (SEM), and the SEM image of the positive electrode active material of Example 1 is shown in Figure 1 and the SEM image of the positive active material of Comparative Example 1 is shown in Figure 1. is shown in Figure 1.

Experimental Example 4: Battery characteristic evaluation

Each of the positive electrode active materials, carbon black conductive material, and polyvinylidene fluoride (PVDF) binder prepared in Example 1 and Comparative Examples 1 to 2 were mixed in N-methylpyrrolidone (NMP) solvent at a ratio of 95:2:3. A positive electrode slurry was prepared by mixing. The positive electrode slurry was applied to one side of an aluminum current collector, dried at 150°C, and rolled to prepare a positive electrode.

A lithium metal electrode was used as the negative electrode, an electrode assembly was manufactured with a porous polyethylene separator between the positive electrode and the negative electrode, the electrode assembly was placed inside the battery case, and the electrolyte solution was injected into the case to form a half battery ( half-cell) was prepared. At this time, the electrolyte solution was prepared by dissolving 1.0M LiPF ₆ in an organic solvent mixed with ethylene carbonate (EC): dimethyl carbonate (DMC): diethyl carbonate (DEC) in a volume ratio of 2:1:2.

For each half cell manufactured in this way, the initial charge capacity and initial discharge capacity were measured while charging at 0.1C until 4.3V in CC-CV mode at 25°C and discharging to 3.0V at a constant current of 0.1C. And the direct current internal resistance (DCIR) was calculated and shown in Table 2 below. For reference, the DCIR value is a value calculated by dividing the difference between the voltage at 60 seconds and the initial voltage while discharging with a constant current of 0.1C by the applied current.

Initial charge capacity (mAh/g) Initial discharge capacity (mAh/g) Example 1 245.3 217.4 Comparative Example 1 244.9 216.3 Comparative Example 2 228.7 210.6

Referring to Table 1 and Figures 1 to 2, the positive electrode active material of Example 1 not only has a baryon single particle form with a large average particle diameter (D ₅₀ ) of 5 μm to 8 μm, but also has a span value ((D ₉₀ It can be seen that -D ₁₀ )/D ₅₀ ) is greater than 0.8, and the pellet density is greater than 3.60 g/cm ³ . In comparison, the positive electrode active materials of Comparative Examples 1 and 2 had an average particle diameter (D ₅₀ ) of 6.0 ㎛ and 8 ㎛, but it could be confirmed that the span value was small and the pellet density was low.

Additionally, referring to Table 2, it can be seen that the battery using the positive electrode active material of Example 1 had superior initial charge capacity and initial discharge capacity compared to the battery using the positive electrode active material of Comparative Examples 1 and 2. This is because the positive electrode active material of Example 1 has a higher rolling density than the positive active material of Comparative Example 1.

As a result, the positive electrode active material according to the present invention not only has a large average particle diameter (D ₅₀ ) of 5㎛ to 8㎛, but also has a span value ((D ₉₀ -D ₁₀ )/D ₅₀ ) of 0.8 or more. It is large, and the pellet density is high at more than 3.60 g/cm ³ , indicating that the energy density is high.

Claims (14)

Contains a lithium complex transition metal oxide in the form of a single particle having an average particle diameter (D ₅₀ ) of 5㎛ to 8㎛,
The span value ((D ₉₀ -D ₁₀ )/D ₅₀ ) is greater than 0.8,
A positive electrode active material with a pellet density of 3.60 g/cm ³ or more. In claim 1,
The single particle lithium composite transition metal oxide is a positive electrode active material containing 60 mol% or more of nickel based on the total number of moles of metals excluding lithium. In claim 1,
The single particle lithium composite transition metal oxide is a positive electrode active material having a composition represented by the following formula (1):
[Formula 1]
Li _x [Ni _a Co _b Mn _c M1 _d ]O _2-y A _y
In Formula 1,
M1 is one or more selected from Y, Zr, Al, B, Ti, W, Nb, Sr, Mo and Mg,
A is one or more selected from F, Cl, Br, I and S,
0.9≤x≤1.2, 0.6≤a<1, 0≤b≤0.4, 0≤c≤0.4, 0≤d≤0.2, a+b+c+d=1, 0≤y≤0.2. In claim 1,
The single particle form is a positive electrode active material in the form of a single particle or an agglomeration of 2 to 10 primary particles with an average particle diameter of 2㎛ to 5㎛ derived from SEM images. (A) (i) nickel-containing raw materials, (ii) cobalt-containing raw materials, manganese-containing raw materials and M1-containing raw materials (M1 is Y, Zr, Al, B, Ti, W, Nb, Sr, Mo and Mg) preparing a mixture by dry mixing at least one selected from among) and (iii) a first lithium-containing raw material;
(B) producing a first fired product by first firing the mixture at a temperature of 760°C to 850°C;
(C) pulverizing the first fired product; and
(D) mixing the first sintered product that has undergone step (C) above with the second lithium-containing raw material and performing secondary sintering at a temperature of 700°C to 900°C to produce a lithium composite transition metal oxide; comprising Method for producing a positive electrode active material according to claim 1. In claim 5,
A method of producing a positive electrode active material, wherein the nickel-containing raw material is at least one selected from nickel hydroxide, nickel oxide, nickel carbonate, nickel sulfide, and nickel nitrate. In claim 5,
A method of producing a positive electrode active material, wherein the cobalt-containing raw material is at least one selected from cobalt hydroxide, cobalt oxide, cobalt carbonate, cobalt sulfide, and cobalt nitrate. In claim 5,
A method for producing a positive electrode active material, wherein the manganese-containing raw material is at least one selected from manganese oxide, manganese carbonate, manganese nitrate, and manganese sulfide. In claim 5,
A method for producing a positive electrode active material, wherein the first firing is performed under an oxygen atmosphere. In claim 5,
A method of producing a positive electrode active material, wherein the first firing is performed for 5 to 20 hours. In claim 5,
A method for producing a positive electrode active material, wherein the secondary firing is performed under an oxygen atmosphere. In claim 5,
A method of producing a positive electrode active material, wherein the secondary firing is performed for 5 to 15 hours. A positive electrode comprising the positive electrode active material according to any one of claims 1 to 4. An anode according to claim 13;
cathode;
a separator disposed between the anode and the cathode; and
A lithium secondary battery containing an electrolyte.