Positive electrode active material and positive electrode containing the same

Abstract

The present invention relates to a positive electrode active material comprising a nickel-based lithium composite metal oxide in which the content of Ni among transition metals other than lithium is 80 atm% or more and which is in a single particle or pseudo-single particle form, and a coating layer containing cobalt and located on the surface of the nickel-based lithium composite metal oxide, and satisfying the following formula 1. [Formula 1] 1 ≤ XY / Z ≤ 3 In the above formula 1, X is the number of moles of Co (mol%) in the coating layer with respect to 100 moles of the nickel-based lithium composite metal oxide, Y is the average particle diameter (μm) of the nodules of the nickel-based lithium composite metal oxide, and Z is the D 50 (μm) of the positive electrode active material, and Z is 5 μm to 12 μm.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2022-0176301 dated December 15, 2022, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] This invention relates to a positive electrode active material and a positive electrode containing the same. [Background technology]

[0003] With the technological development and increasing demand for mobile devices, the demand for rechargeable batteries as an energy source is rapidly increasing. Among these rechargeable batteries, lithium-ion batteries, which have high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used. Furthermore, with the recent advancements in technologies such as electric vehicles, the demand for high-capacity rechargeable batteries is increasing.

[0004] When lithium secondary batteries are driven and cycled, the positive electrode degenerates and cracks due to repeated expansion and contraction of volume, which reduces the cell capacity and increases resistance. In particular, when high-nickel positive electrode active materials with a Ni content of 80 atm% or more are used to increase the capacity of secondary batteries, structural stability is poor and crack formation is frequent, resulting in a serious decrease in lifespan as the cycle progresses.

[0005] To mitigate these disadvantages, single-particle or pseudo-single-particle cathode active materials can be used. When using single-particle or pseudo-single-particle cathode active materials, the contact interface with the electrolyte is reduced, resulting in longer lithium ion diffusion pathways and inferior power performance due to factors such as the formation of rock salt structures on the surface due to over-calcination, compared to conventional secondary-particle cathode active materials. This degradation of power performance tends to worsen as the size of the single-particle or pseudo-single-particle increases.

[0006] Therefore, to compensate for the above-mentioned problems with single particles, lithium secondary batteries have traditionally been manufactured by bimodally mixing small-diameter single particles and secondary particles. However, when applying bimodal cathode active materials in this way, there is a problem in that the cracking of the relatively weaker secondary particles increases, and side reactions with the electrolyte increase. [Overview of the project] [Problems that the invention aims to solve]

[0007] Therefore, the present invention aims to provide a high-nickel cathode active material in single-particle or pseudo-single-particle form that has excellent lifespan characteristics and other properties such as capacity and output characteristics, and a secondary battery to which the same is applied. [Means for solving the problem]

[0008] The inventors of this invention, through repeated experiments, have found that in single-particle or pseudo-single-particle high-nickel cathode active materials, the D content of the cathode active material is 50 We found that the above objective can be achieved by adjusting the average particle size of the nodules and the Co content in the coating layer formed on the surface of the positive electrode active material to an appropriate ratio.

[0009] Specifically, the present invention provides a positive electrode active material comprising a nickel-based lithium composite metal oxide in single-particle or pseudo-single-particle form, wherein the content of Ni among transition metals other than lithium is 80 atm% or more, and a coating layer containing cobalt located on the surface of the nickel-based lithium composite metal oxide, satisfying the following formula 1. [Formula 1] 1≦XY / Z≦3 In the above formula 1, X is the number of moles (mol%) of Co in the coating layer relative to 100 moles of the nickel-based lithium composite metal oxide, Y is the average particle size (μm) of the nickel-based lithium composite metal oxide nodules, and Z is the D of the positive electrode active material. 50 (μm) is such that Z is between 5μm and 12μm.

[0010] The present invention provides a positive electrode including a positive electrode active material layer containing the positive electrode active material. [Effects of the Invention]

[0011] The present invention relates to a high-nickel cathode active material in single-particle or pseudo-single-particle form, wherein the D of the cathode active material 50 By adjusting the average particle size of the nodules and the Co content in the coating layer formed on the surface of the positive electrode active material to an appropriate ratio, it is possible to reduce surface resistance and decrease crack occurrence.

[0012] In other words, the inventors of the present invention have found that the interfacial resistance of the positive electrode active material can be minimized when the number of internal nodules per positive electrode active material particle and the amount of cobalt coating are adjusted to satisfy a specific formula.

[0013] In other words, a lithium secondary battery containing a positive electrode to which the positive electrode active material of the present invention is applied exhibits improved lifespan characteristics, lower resistance, and superior output characteristics during the progression of cycles. [Modes for carrying out the invention]

[0014] The present invention will be described in more detail below.

[0015] The terms and words used herein and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may define the concepts of terms as appropriate to best describe their invention.

[0016] In this invention, "single particle" refers to a particle consisting of one single nodule. In this invention, "pseudo-single particle" refers to a particle that is a composite formed of 10 or fewer nodules.

[0017] In the present invention, "nodule" means a particle unit body that constitutes single particles and pseudo-single particles. The nodule may be a single crystal lacking a crystalline grain boundary, or a polycrystal that does not have a grain boundary in appearance when observed at a magnification of 5000 to 20000 times using a scanning electron microscope (SEM).

[0018] In the present invention, "secondary particle" means a particle formed by the aggregation of a plurality of primary particles in the range of several tens to several hundreds. More specifically, a secondary particle is an aggregate of 40 or more primary particles.

[0019] The expression "particle" used in the present invention can include any one or all of single particles, pseudo-single particles, primary particles, nodules, and secondary particles.

[0020] In the present invention, "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 the 50% point of the volume cumulative distribution according to the particle size, D 90 is the particle size at the 90% point of the volume cumulative distribution according to the particle size, and D 10 is the particle size at the 10% point of the volume cumulative distribution according to the particle size. The D n can be measured using the laser diffraction method. Specifically, after dispersing the measurement target powder in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (for example, Microtrac S3500). When the particles pass through the laser beam, the difference in the diffraction pattern according to the particle size is measured to calculate the particle size distribution. By calculating the particle sizes at the 10%, 50%, and 90% points of the volume cumulative distribution according to the particle size in the measuring device, D 10 、D 50 and D 90 can be measured.

[0021] In the present invention, "nodule" refers to the smallest particle unit that can be distinguished as a single mass when observing a cross-section of the positive electrode active material via a scanning electron microscope (SEM), and may consist of one crystal grain or multiple crystal grains. The average particle size of the nodule can be measured by measuring the individual particle diameters distinguishable in the cross-sectional SEM image of the positive electrode active material particles and then calculating the arithmetic mean of these measurements.

[0022] In this invention, the "average crystal grain size" was measured by analyzing XRD data obtained from X-ray diffraction analysis of the positive electrode active material powder using the Rietveld refinement method. Here, the X-ray diffraction analysis was performed using a Bruker D8 Endeavor (light source: Cu-Kα, λ=1.54Å) equipped with a LynxEye XE-T-position sensitive detector. The sample was placed in the groove of a general powder holder, the surface of the sample was made uniform using a slide glass, and the sample was filled so that its height matched the edge of the holder. Then, measurements were taken in the region of FDS 0.5°, 2θ=15°~90°, with a step size of 0.02° and a total scan time of approximately 20 minutes. Rietveld analysis was performed on the measured data, taking into account the charge at each site (metal at transition metal sites is +3, Ni at Li sites is +2) and cation mixing. Specifically, during the analysis of crystal grain size, instrumental broadening was performed using the Fundamental Parameter Approach (FPA) implemented in the Bruker TOPAS program, and the entire peak range was used during fitting. For peak shape, only the Lorenzian contribution (FP) was used as the First Principle (FP) among the peak types available in TOPAS for fitting, and strain was not considered.

[0023] In this invention, "strain" refers to the twisting of the lattice caused by defects, i.e., micro-deformation. The strain was measured by analyzing XRD data obtained by X-ray diffraction analysis of the positive electrode active material powder using the Rietveld refinement method. Here, the X-ray diffraction analysis was performed using a Bruker D8 Endeavor (light source: Cu-Kα, λ=1.54Å) equipped with a LynxEye XE-T-position sensitive detector. The sample was placed in the groove of a general powder holder, the surface of the sample was made uniform using a slide glass, and the sample was filled so that its height matched the edge of the holder. Then, measurements were taken in the region of FDS 0.5°, 2θ=15°~90°, with a step size of 0.02° and a total scan time of approximately 20 minutes. Rietveld analysis was performed on the measured data, taking into account the charge at each site (metal at transition metal sites is +3, and Ni at Li sites is +2) and cation mixing. Specifically, during strain analysis, instrumental broadening was performed using the Fundamental Parameter Approach (FPA) implemented in the Bruker TOPAS program, and the entire peak of the measurement range was used during fitting. For peak shape, only the Lorenzian contribution (FP) was used as the First Principle (FP) among the peak types available in TOPAS for fitting.

[0024] positive electrode active material The positive electrode active material of the present invention is characterized by satisfying the following formula 1.

[0025] [Formula 1] 1≦XY / Z≦3

[0026] Generally, it is known that cobalt facilitates the formation of layered structures, and therefore, a higher cobalt content reduces the resistance of the positive electrode active material. Furthermore, when the positive electrode active material is composed of aggregates of numerous primary particles, the interfaces between primary particles become pathways for lithium ion movement; therefore, a greater number of interfaces between primary particles leads to higher lithium mobility and reduced resistance. However, our research indicates that in the case of single-particle or pseudo-single-particle high-nickel positive electrode active materials, a resistance improvement effect is only observed when the cobalt content and the number of interfaces between nodules within the active material particles satisfy a specific relationship. Here, the number of interfaces between nodules within the particle is the ratio of the D of the positive electrode active material to the average particle size (Y) of the nodules. 50 It can be defined as the ratio of (Z). Specifically, in the case of high-nickel cathode active materials in single-particle or pseudo-single-particle form, it has been shown that resistance increases if the Z / Y value does not meet a certain range even with a high Co content, and that resistance increases if the Co content does not meet a certain range even with an increased Z / Y value.

[0027] In formula 1, X is the number of moles (mol%) of Co in the coating layer relative to 100 moles of the nickel-based lithium composite metal oxide. X can be 1 to 5 mol%, preferably 1 to 3 mol%. When the cobalt content in the coating layer satisfies the above range, the microstructure of the single-particle and / or pseudo-single-particle nickel-based lithium composite metal oxide is stabilized, reducing the occurrence of cracks, and thus suppressing the decay of the positive electrode active material even when cycling is performed.

[0028] In the above formula 1, Y is the average particle size (μm) of the nickel-based lithium composite metal oxide nodule. Y can be 1 μm to 10 μm, preferably 6 to 8 μm, and most preferably 2 to 7 μm. When the average particle size (μm) of the nickel-based lithium composite metal oxide nodule satisfies the above range, the specific surface area decreases, resulting in excellent high-temperature durability, reduced particle cracking, and reduced gas emissions during operation of the lithium secondary battery.

[0029] In the above formula 1, Z is the D of the positive electrode active material. 50 (μm). The above Z can be 5μm to 12μm, preferably 6 to 10μm, and most preferably 6.2μm to 8μm. The positive electrode active material of the present invention is D 50 Because it is larger than conventional single particles or pseudo-single particles, it exhibits superior tap density and rolling density, and because it has a small BET, it has the effect of improving slurry processability and thermal stability. Furthermore, the positive electrode active material of the present invention is within the range of D 50 Having this feature prevents slurry aggregation problems, provides excellent electrolyte impregnation, and results in superior output and lifespan characteristics for lithium secondary batteries containing it.

[0030] In Equation 1, Z / Y represents the number of nodules contained in one positive electrode active material particle or the number of interfaces between nodules within the active material particle.

[0031] In the positive electrode active material of the present invention, the ratio of Z / Y can be 1 to 3, preferably 1 to 2, and most preferably 1.1 to 1.5. The average particle size of the nickel-based lithium composite metal oxide nodule and the D of the positive electrode active material. 50 When the above range is met, the particle strength is high and the rolling density is high, making it suitable for the composition of high-energy-density electrodes. Even with a high rolling rate, there is less particle cracking, improving lifespan characteristics and high-temperature storage characteristics.

[0032] The positive electrode active material of the present invention may have a proportion of positive electrode active material having a size of 5 μm to 7 μm of 80 volume% or more of the total positive electrode active material.

[0033] The positive electrode active material of the present invention may contain lithium by-products in an amount of 1 to 5 mol%, preferably 1 to 3 mol%, relative to the nickel-based lithium composite metal oxide. The positive electrode active material of the present invention is characterized by having a low amount of lithium by-products despite undergoing over-calcination due to the presence of single particles.

[0034] The positive electrode active material of the present invention comprises a nickel-based lithium composite metal oxide in single-particle or pseudo-single-particle form, wherein the content of Ni among transition metals other than lithium is 80 atm% or more, and a coating layer containing cobalt located on the surface of the nickel-based lithium composite metal oxide.

[0035] The nickel-based lithium composite metal oxide contained in the positive electrode active material of the present invention may contain 80 atm% or more of nickel among the transition metals other than lithium, preferably 85 atm% or more. If the nickel content is less than 80 atm%, the capacity of the positive electrode active material decreases, which is a problem as it cannot be applied to electrochemical elements requiring high capacity.

[0036] Specifically, the nickel-based lithium composite metal oxide contained in the positive electrode active material of the present invention may have a composition represented by the following chemical formula 2.

[0037] [Chemical formula 2] Li a Ni b Co c M 1 d M 2 e O2

[0038] In the above chemical formula 2, M 1 M is Mn, Al, or a combination thereof. 2 This can be one or more elements selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb.

[0039] The above 'a' represents the molar ratio of lithium in the nickel-based lithium composite metal oxide, and can be 0.80 ≤ a ≤ 1.2, preferably 0.95 ≤ a ≤ 1.08, and more preferably 1 ≤ a ≤ 1.08.

[0040] The value b represents the molar ratio of nickel among the metal elements other than lithium in the nickel-based lithium composite metal oxide, and can be 0.8 ≤ b < 1, 0.80 ≤ b ≤ 0.95, or 0.83 ≤ b ≤ 0.93. When the nickel content satisfies the above range, high capacity characteristics can be achieved.

[0041] The aforementioned c represents the molar ratio of cobalt among the metal elements other than lithium in the nickel-based lithium composite metal oxide, and 0 <c<0.20、0<c≦0.15、または0.01≦c≦0.10であることができる。

[0042] The above d is M, which is a metal element other than lithium in the nickel-based lithium composite metal oxide. 1 The molar ratio is shown, 0 <d<0.20、0<d≦0.15、または0.01≦d≦0.10であることができる。

[0043] The aforementioned e is M, which is one of the metal elements other than lithium in the nickel-based lithium composite metal oxide. 2 This represents the molar ratio, and can be either 0 ≤ e ≤ 0.10 or 0 ≤ e ≤ 0.05.

[0044] Traditionally, spherical secondary particles, composed of tens to hundreds of primary particles aggregated together, have been commonly used as the positive electrode active material for lithium-ion batteries. However, with positive electrode active materials in this form of aggregated secondary particles, particle cracking is prone to occur during the rolling process in manufacturing the positive electrode, leading to cracks forming inside the particles during the charge-discharge process. When particle cracking or internal cracks occur in the positive electrode active material, the contact area with the electrolyte increases, leading to increased gas generation due to side reactions with the electrolyte.

[0045] In contrast, positive electrode active materials in the form of single particles or pseudo-single particles, where 10 or fewer primary particles are aggregated, have higher particle strength compared to existing positive electrode active materials in the form of secondary particles, where tens to hundreds of primary particles are aggregated. As a result, particle cracking during rolling is almost nonexistent. Furthermore, in the case of single-particle or pseudo-single-particle positive electrode active materials, the number of primary particles constituting the particle is small, so there is less change in volume due to expansion and contraction of the primary particles during charging and discharging. This significantly reduces the occurrence of cracks inside the particles.

[0046] Therefore, when using a cathode active material consisting of single particles and / or pseudo-single particles, the reduction in lifetime characteristics due to particle cracking and internal cracking can be significantly suppressed.

[0047] The nickel-based lithium composite metal oxide can have an average crystal grain size of 170 to 300 nm, preferably 170 to 250 nm, and most preferably 180 to 230 nm. When the average crystal grain size is met, firing is performed to an appropriate degree, and the formation of a rock salt structure on the surface is minimized, resulting in excellent output performance.

[0048] The aforementioned nickel-based lithium composite metal oxide has a strain value of 200 × 10⁻⁶. -6 ~380×10 -6 Preferably 210 × 10 -6 ~370×10 -6 This is possible. When the aforementioned strain range is satisfied, the crystal structure is highly complete, the positive electrode active material has a stable crystal structure, and it exhibits excellent lifetime performance.

[0049] The positive electrode active material of the present invention includes a coating layer located on the surface of a nickel-based lithium composite metal oxide. The coating layer is formed on the surface of the positive electrode active material and on some or all of the nodules, and may contain cobalt.

[0050] Specifically, the coating layer may have a composition represented by the following chemical formula 3.

[0051] [Chemical formula 3] Li x Co y O2

[0052] The aforementioned x represents the molar ratio of lithium in the coating layer, and can be 0.8 ≤ x ≤ 1.2, preferably 1.00 ≤ x ≤ 1.02.

[0053] The aforementioned y represents the molar ratio of Co in the coating layer, and can be 0.5 ≤ y ≤ 1.5, preferably 0.8 ≤ y ≤ 1.2.

[0054] The coating layer prevents contact between the positive electrode active material and the electrolyte contained in the lithium secondary battery, thereby suppressing the occurrence of side reactions, improving the lifespan characteristics, and increasing the packing density of the positive electrode active material.

[0055] The coating layer may be formed on the entire surface of the positive electrode active material or on a portion of it. Specifically, when the coating layer is formed on the surface of the positive electrode active material, it can cover 20% or more of the total surface area of ​​the positive electrode active material. If the area of ​​the coating layer is less than 20%, the effect of improving lifespan characteristics and packing density due to the formation of the coating layer may be minimal.

[0056] Furthermore, the coating layer can be formed with a thickness ratio of 1 / 10000 to 1 / 100 of the average particle diameter of the positive electrode active material particles. If the ratio of the thickness of the coating layer to the particles of the positive electrode active material is less than 1 / 10000, the effect of improving lifespan characteristics and packing density due to the formation of the coating layer is negligible, and if the thickness ratio exceeds 1 / 100, there is a risk that the battery characteristics will deteriorate.

[0057] Method for manufacturing positive electrode active material The method for producing a positive electrode active material according to the present invention may include the steps of: preparing a nickel-based lithium composite metal oxide in which the content of Ni among transition metals other than lithium is 80 atm% or more; and mixing the nickel-based lithium composite metal oxide with a solution containing a cobalt raw material, and then performing a first heat treatment to form a coating layer on the surface of the nickel-based lithium composite metal oxide.

[0058] First, nickel-based lithium composite metal oxides can be prepared in the form of single particles, pseudo-single particles, or combinations thereof, in which the nickel content among the metal elements other than lithium is 80 atm% or more.

[0059] The nickel-based lithium composite metal oxide may be purchased and used as a commercially available product, or it may be manufactured using a method for manufacturing nickel-based lithium composite metal oxides that is well known in the art. For example, the nickel-based lithium composite metal oxide can be manufactured by mixing a lithium raw material with a nickel-based lithium composite metal oxide precursor and then calcining it.

[0060] The nickel-based lithium composite metal oxide precursor can be represented, for example, by the following chemical formulas: [Chemical Formula A] or [Chemical Formula B].

[0061] [Chemical formula A] [Ni p Co q M 1 r M 2 s ](OH)2

[0062] [Chemical formula B] [Ni p Co q M 1 r M 2 s ]O.OH

[0063] In the aforementioned chemical formulas A and B, M 1This can be one or more selected from Mn and Al, preferably Mn or a combination of Mn and Al.

[0064] In the aforementioned chemical formulas A and B, M 2 This can be one or more elements selected from the group consisting of Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, and Y.

[0065] The aforementioned p represents the molar ratio of nickel among the metal elements in the precursor, and can be 0.80 ≤ p < 1.0, 0.80 ≤ p ≤ 0.98, or 0.80 ≤ p ≤ 0.95.

[0066] The aforementioned q represents the molar ratio of cobalt among the metal elements in the precursor, and 0 <q≦0.2、0<q≦0.15、または0.01≦q≦0.10であることができる。

[0067] The aforementioned r is M among the metal elements in the precursor. 1 It means the molar ratio of elements, 0 <r≦0.2、0<r≦0.15、または0.01≦r≦0.1であることができる。

[0068] The aforementioned s is M among the metal elements in the precursor. 2 This refers to the molar ratio of elements, and can be 0 ≤ s < 0.1 or 0 ≤ s ≤ 0.05.

[0069] The lithium raw material can be, for example, at least one selected from the group consisting of lithium carbonate (Li2CO3), lithium hydroxide (LiOH·H2O), anhydrous lithium hydroxide (LiOH), LiNO3, CH3COOLi, and Li2(COO)2, and preferably lithium carbonate (Li2CO3), lithium hydroxide (LiOH·H2O), or a combination thereof.

[0070] During the production of the positive electrode active material, the nickel-based lithium composite metal oxide precursor and the lithium raw material can be mixed such that the molar ratio of Li to transition metal is 1:1 to 1.3:1, preferably 1:1 to 1.1:1. When the mixing ratio of the nickel-based lithium composite metal oxide precursor and the lithium raw material satisfies the above range, the crystal structure of the positive electrode active material develops smoothly, and a positive electrode active material with excellent physical properties can be produced. If the lithium raw material content is too low, the crystal structure cannot develop properly, and if it is too high, unreacted Li remains as a by-product, which can lead to a decrease in capacity and gas generation.

[0071] By appropriately adjusting conditions such as firing temperature and time, the nodule size and average particle size of nickel-based lithium composite metal oxides can be controlled within an appropriate range.

[0072] The firing can be carried out at a temperature of 700°C to 1000°C, preferably 700°C to 900°C, and more preferably 700°C to 850°C. If the firing temperature is below 700°C, insufficient reaction may result in residual raw material in the particles, potentially reducing the high-temperature stability of the battery, decreasing volume density and crystallinity, and potentially reducing structural stability. On the other hand, if the firing temperature exceeds 1000°C, uneven particle growth may occur, making particle crushing difficult and potentially leading to a decrease in capacity.

[0073] The aforementioned firing can be carried out for 5 to 24 hours, preferably 10 to 24 hours. If the firing time is less than 5 hours, the reaction time is too short, making it difficult to obtain a highly crystalline positive electrode active material. If it exceeds 24 hours, the particle size may become excessively large, potentially reducing production efficiency.

[0074] Next, the prepared nickel-based lithium composite metal oxide can be mixed with a solution containing cobalt raw material, and then heat-treated to form a coating layer on the surface of the nickel-based lithium composite metal oxide.

[0075] Specifically, this can be carried out by mixing a nickel-based lithium composite metal oxide with a solution containing cobalt raw material, stirring the mixture, filtering and separating the contents, and then heat-treating it in an oxygen atmosphere.

[0076] The cobalt raw material can be mixed in an amount of 0.8 to 5 parts by weight, preferably 1 to 4 parts by weight, and more preferably 1.5 to 3 parts by weight, per 100 parts by weight of the nickel-based lithium composite metal oxide. When the cobalt raw material content satisfies the above range, the occurrence of cracks at the interfaces between nodules can be suppressed, and stability and initial capacity can be improved.

[0077] Examples of cobalt raw materials that can be used include cobalt acetate, cobalt sulfate, cobalt chloride, and cobalt nitrate.

[0078] On the other hand, the solution containing the cobalt raw material can be produced by dissolving the cobalt raw material in a solvent such as water or ethanol.

[0079] When a nickel-based lithium composite metal oxide is added to a solution containing the aforementioned cobalt raw material and mixed, and then stirred, the cobalt contained in the solution reacts with lithium by-products present on the surface of the nickel-based lithium composite metal oxide to form a coating layer on the surface.

[0080] After filtering and separating the material, it is heat-treated to obtain nickel-based lithium composite metal oxide powder with a coating layer formed on top.

[0081] Here, the filtration can be carried out by placing filter paper in a filtration flask and reducing the pressure under vacuum, and the drying can be carried out at 100 to 180°C, preferably 120 to 160°C, for 10 to 24 hours, preferably 12 to 22 hours.

[0082] The heat treatment described above is performed to fix cobalt to the surface of the nickel-based lithium composite metal oxide to form a coating layer, and can be carried out at a temperature of 630 to 800°C, preferably 650 to 750°C. When the heat treatment temperature is within the above range, the cobalt raw material reacts sufficiently with the lithium by-products on the surface, and the coating layer is well formed.

[0083] The heat treatment can be carried out for 3 to 8 hours, preferably 4 to 7 hours. When the heat treatment time is within this range, a coating layer of appropriate thickness can be formed, and production efficiency can be improved.

[0084] positive electrode The positive electrode according to the present invention includes the positive electrode active material of the present invention as described above. Specifically, the positive electrode includes 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 includes the positive electrode active material according to the present invention. Since the positive electrode active material has been described above, a detailed explanation will be omitted, and only the remaining components will be described in detail below.

[0085] The positive electrode current collector of the present invention is not particularly limited as long as it contains a highly conductive metal, allows for easy adhesion of the positive electrode active material layer, and is unreactive within the battery voltage range. The positive electrode current collector can be made of, for example, stainless steel, aluminum, nickel, titanium, heat-treated carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. The positive electrode current collector can also typically have a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the surface of the current collector to enhance the adhesion of the positive electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, nonwoven fabric, etc.

[0086] The positive electrode active material contained in the positive electrode active material layer of the present invention can be present in an amount of 90% to 100% by weight, 95% to 100% by weight, preferably 98% to 100% by weight, and more preferably 99% to 100% by weight, based on the total weight of the positive electrode active material contained in the positive electrode active material layer. Most preferably, the positive electrode active material can be present as 100% alone in the form of single particles or pseudo-single particles. When the content of the positive electrode active material of the present invention satisfies the above range, sufficient lifetime characteristics can be obtained. This is because if the positive electrode active material in the form of secondary particles is present in an amount exceeding 10% by weight of the total positive electrode active material, the fine powder generated from the secondary particles increases side reactions with the electrolyte during electrode manufacturing and charging / discharging, reducing the gas generation suppression effect.

[0087] The positive electrode active material layer of the present invention may optionally contain a conductive material and a binder together with the positive electrode active material.

[0088] Here, the positive electrode active material can be included in an amount of 80 to 99% by weight, more specifically 85 to 98.5% by weight, relative to the total weight of the positive electrode active material layer, and when included within this content range, it can exhibit excellent capacity characteristics.

[0089] The conductive material is used to impart conductivity to the electrodes and can be used without particular limitations in the battery it is configured in, as long as it does not cause chemical changes and has electronic conductivity. Specific examples include graphite such as natural graphite or 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. Of these, one or more can be used. The conductive material may be included in an amount of 0.1 to 15% by weight relative to the total weight of the positive electrode active material layer.

[0090] The binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, 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 the hydrogen atoms of these materials are substituted with Li, Na, or Ca, or various copolymers thereof. One of these materials alone or a mixture of two or more materials can be used. The binder can be present in an amount of 0.1 to 15% by weight relative to the total weight of the positive electrode active material layer.

[0091] The positive electrode can be manufactured by a conventional method for manufacturing a positive electrode. Specifically, a positive electrode active material can be prepared, and a composition for forming a positive electrode active material layer can be prepared by selectively dissolving or dispersing a binder, conductive material, and dispersant in a solvent as needed. After coating the composition for forming the positive electrode active material layer, the positive electrode can be manufactured by drying and rolling.

[0092] The solvent can be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, and one or more of these can be used individually or in mixtures of two or more. The amount of solvent used should be sufficient to dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant, taking into consideration the coating thickness of the slurry and the manufacturing yield, and to have a viscosity that allows for excellent thickness uniformity when applied for the manufacture of the positive electrode.

[0093] Alternatively, the positive electrode can also be manufactured by casting the positive electrode active material forming composition onto another support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0094] Electrochemical elements Next, the electrochemical element according to the present invention will be described. The electrochemical element according to the present invention includes the positive electrode of the present invention as described above, and the electrochemical element can be a battery, a capacitor, etc., and more specifically, a lithium secondary battery.

[0095] The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and electrolyte interposed between the positive and negative electrodes. As the positive electrode is as described above, a detailed explanation will be omitted, and only the remaining components will be described in detail below.

[0096] Furthermore, the lithium secondary battery may selectively further include a battery container for housing the electrode assembly comprising the positive electrode, negative electrode, and separator, and a sealing member for sealing the battery container.

[0097] In the lithium secondary battery, the negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0098] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy can be used. The negative electrode current collector can usually have a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, fine irregularities can 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 film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0099] The negative electrode active material layer may selectively include a binder and a conductive material together with the negative electrode active material.

[0100] As the negative electrode active material, compounds capable of reversible intercalation and deintercalation of lithium can be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO2. βExamples include metallic oxides that can be doped and dedoped with lithium, such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more mixtures thereof can be used. A metallic lithium thin film can also be used as the negative electrode active material. Furthermore, both low-crystallinity carbon and high-crystallinity carbon can be used as the carbon material. Typical examples of low-crystalline carbon include soft carbon and hard carbon, while typical examples of high-crystalline carbon include amorphous, plate-like, flaky, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature heat-treated carbon such as petroleum or coal tar pitch-derived cokes.

[0101] The anode active material can be present in an amount of 80% to 99% by weight relative to the total weight of the anode active material layer.

[0102] The binder is a component that helps to bond the conductive material, active material, and current collector, and is usually added in an amount of 0.1% to 10% by weight relative to the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0103] The conductive material is a component for further improving the conductivity of the negative electrode active material and can be added in an amount of 10% by weight or less, preferably 5% by weight or less, relative to the total weight of the negative electrode active material layer. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive, and 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; carbon fluoride; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can be used.

[0104] The negative electrode active material layer can be manufactured by coating a negative electrode active material forming composition, which is prepared by dissolving or dispersing a negative electrode active material and a binder and conductive material selectively in a solvent, onto a negative electrode current collector and then drying it, or by casting the negative electrode active material forming composition onto another support, peeling it off the support, and then laminating the resulting film onto the negative electrode current collector.

[0105] 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. Generally, any separator used in lithium secondary batteries can be used without particular limitations, but those with low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity are particularly preferred. Specifically, porous polymer films, such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures of two or more layers thereof can be used. Ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. Furthermore, coated separators containing ceramic components or polymeric substances can be used to ensure heat resistance or mechanical strength, and can be selectively used as single-layer or multi-layer structures.

[0106] Furthermore, the electrolytes used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0107] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0108] The aforementioned organic solvent can be used without particular limitations, as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the aforementioned organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcoholic solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and can include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred.

[0109] The lithium salt can be used without particular limitations as long as it is a compound that can provide lithium ions for use in lithium secondary batteries. Specifically, the anion of the lithium salt is F - Cl - , Br - , I - NO3 - , N(CN)2 - BF4 - CF3CF2SO3 - (CF3SO2)2N - , (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2) 2CH - (SF5)3C - , (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - and (CF3CF2SO2)2N - The lithium salt can be at least one selected from the group consisting of LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. The concentration of the lithium salt is preferably in the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within this range, the electrolyte can exhibit excellent electrolyte performance due to having appropriate conductivity and viscosity, and lithium ions can move effectively.

[0110] In addition to the components of the electrolyte, the electrolyte may also contain one or more additives for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity, such as haloalkylene carbonate compounds like difluoroethylene carbonate, pyridine, triethyl phosphite, triethyl alcoholamine, cyclic ether, ethylenediamine, n-glyme, hexamethyl phosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethyl alcohol, or aluminum trichloride. Here, the additive may be present in an amount of 0.1 to 5% by weight relative to the total weight of the electrolyte.

[0111] As described above, the lithium secondary battery containing the positive electrode according to the present invention exhibits excellent discharge capacity, output characteristics, and capacity retention rate stably, making it useful in portable devices such as mobile phones, notebook computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0112] Accordingly, according to another 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.

[0113] The aforementioned battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0114] The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be cylindrical, rectangular, pouch-type, or coin-type, using a can.

[0115] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for small devices, but also preferably as a unit battery in medium- and large-sized battery modules containing a large number of battery cells.

[0116] Examples of the aforementioned medium- and large-sized devices include, but are not limited to, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0117] Examples Example 1 Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor is mixed with LiOH and Li / Me(Ni, Co, Mn) in a molar ratio of 1.05, and then heat-treated at 900°C for 10 hours under an oxygen atmosphere to produce LiNi 0.8 Co 0.1 Mn 0.1 O2 lithium composite transition metal oxides were fabricated. The fabricated nickel-based lithium composite metal oxides were in a pseudo-single-particle morphology consisting of 1 to 3 nodules, with an average nodule particle size (μm) of 5.69 μm.

[0118] 100 moles of the manufactured nickel-based lithium composite metal oxide were mixed with 0.67 moles of the cobalt raw material Co3O4 and calcined at 700°C for 5 hours. The D of the manufactured cathode active material 50 The diameter was 6.25 μm, and the XY / Z value was 1.82.

[0119] A positive electrode slurry was prepared by mixing the positive electrode active material with carbon nanotubes and a PVdF binder in an NMP solvent in a weight ratio of 97.5:1.0:1.5. The positive electrode slurry was applied to one surface of an aluminum current collector (12 μm thick), dried at 130°C to form a positive electrode active material layer on the aluminum current collector, and then rolled to produce a positive electrode.

[0120] On the other hand, as a negative electrode active material, graphite, carbon conductive material (SuperC65), carboxymethylcellulose (Daicell 2200), and styrene-butadiene rubber binder (BM-L302) were mixed in a weight ratio of 96:20.5:21:2.5 and added to water as a solvent to produce a negative electrode active material slurry. The negative electrode forming composition was coated onto an 8 μm thick copper foil, dried, and then roll-pressed to produce a negative electrode.

[0121] After manufacturing an electrode assembly by stacking the positive and negative electrodes produced above together with a polyolefin separator, this assembly was placed in a battery case, and an electrolyte was injected by dissolving 1M LiPF6 in 100 parts by weight of a mixed solvent of ethylene carbonate and diethyl carbonate in a 3:7 ratio, thereby manufacturing a lithium secondary battery.

[0122] Example 2 Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor is mixed with LiOH and Li / Me(Ni, Co, Mn) in a molar ratio of 1.05, and then heat-treated at 900°C for 10 hours under an oxygen atmosphere to produce LiNi 0.8 Co 0.1 Mn 0.1 O2 lithium composite transition metal oxides were fabricated. The fabricated nickel-based lithium composite metal oxides were in a pseudo-single-particle morphology consisting of 1 to 3 nodules, with an average nodule particle size (μm) of 5.56 μm.

[0123] 100 moles of the manufactured nickel-based lithium composite metal oxide were mixed with 1 mole of the cobalt raw material Co3O4 and calcined at 700°C for 5 hours. The D of the manufactured cathode active material 50 The diameter was 5.96 μm, and the XY / Z value was 2.80.

[0124] A positive electrode and a lithium secondary battery containing the same were manufactured in the same manner as in Example 1, except that the positive electrode was manufactured using the positive electrode active material.

[0125] Example 3 Ni 0.8 Co0.1 Mn 0.1 Mix the (OH)2 precursor with LiOH so that the Li / Me (Ni, Co, Mn) molar ratio is 1.05, and heat-treat it at 900 °C for 10 hours in an oxygen atmosphere to obtain LiNi 0.8 Co 0.1 Mn 0.1 O2 lithium composite transition metal oxide. The produced nickel-based lithium composite metal oxide was in a pseudo-single particle form consisting of 1 to 3 nodules, and the average particle size (μm) of the nodules was 4.18 μm.

[0126] Add 0.5 mol of cobalt raw material Co3O4 to 100 mol of the produced nickel-based lithium composite metal oxide and calcine it at 700 °C for 5 hours. The D of the produced cathode active material 50 was 5.86 μm, and the XY / Z value was 1.07.

[0127] A cathode and a lithium secondary battery including the same were produced in the same manner as in Example 1, except that the cathode was produced using the above cathode active material.

[0128] Comparative Example 1 Ni 0.8 Co 0.1 Mn 0.1 Mix the (OH)2 precursor with LiOH so that the Li / Me (Ni, Co, Mn) molar ratio is 1.05, and heat-treat it at 920 °C for 10 hours in an oxygen atmosphere to obtain LiNi 0.8 Co 0.1 Mn 0.1 O2 lithium composite transition metal oxide. The produced nickel-based lithium composite metal oxide was in a pseudo-single particle form consisting of several nodules, and the average particle size (μm) of the nodules was 2.15 μm.

[0129] Add 0.67 mol of cobalt raw material Co3O4 to 100 mol of the produced nickel-based lithium composite metal oxide and calcine it at 700 °C for 5 hours. The D of the produced cathode active material 50 was 7.93 μm, and the XY / Z value was 0.54.

[0130] A positive electrode and a lithium secondary battery containing the same were manufactured in the same manner as in Example 1, except that the positive electrode was manufactured using the positive electrode active material.

[0131] Comparative Example 2 Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor is mixed with LiOH and Li / Me(Ni, Co, Mn) in a molar ratio of 1.05, and then heat-treated at 920°C for 10 hours under an oxygen atmosphere to produce LiNi 0.8 Co 0.1 Mn 0.1 O2 lithium composite transition metal oxides were fabricated. The fabricated nickel-based lithium composite metal oxides were in a pseudo-single-particle morphology consisting of several nodules, with an average nodule particle size (μm) of 1.1 μm.

[0132] 100 moles of the manufactured nickel-based lithium composite metal oxide were mixed with 1 mole of the cobalt raw material Co3O4 and calcined at 700°C for 5 hours. The D of the manufactured cathode active material 50 The diameter was 6.38 μm, and the XY / Z value was 0.52.

[0133] A positive electrode and a lithium secondary battery containing the same were manufactured in the same manner as in Example 1, except that the positive electrode was manufactured using the positive electrode active material.

[0134] Comparative Example 3 Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor is mixed with LiOH and Li / Me(Ni, Co, Mn) in a molar ratio of 1.05, and then heat-treated at 920°C for 10 hours under an oxygen atmosphere to produce LiNi 0.8 Co 0.1 Mn 0.1 O2 lithium composite transition metal oxides were fabricated. The fabricated nickel-based lithium composite metal oxides were in a pseudo-single-particle morphology consisting of several nodules, with an average nodule particle size (μm) of 1.1 μm.

[0135] 100 moles of the manufactured nickel-based lithium composite metal oxide were mixed with 2 moles of the cobalt raw material Co3O4 and calcined at 700°C for 5 hours. The D of the manufactured cathode active material 50 The diameter was 3.15 μm, and the XY / Z value was 4.305.

[0136] A positive electrode and a lithium secondary battery containing the same were manufactured in the same manner as in Example 1, except that the positive electrode was manufactured using the positive electrode active material.

[0137] Comparative Example 4 Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor is mixed with LiOH and Li / Me(Ni, Co, Mn) in a molar ratio of 1.05, and then heat-treated at 900°C for 10 hours under an oxygen atmosphere to produce LiNi 0.8 Co 0.1 Mn 0.1 O2 lithium composite transition metal oxides were fabricated. The fabricated nickel-based lithium composite metal oxides were in a pseudo-single-particle morphology consisting of 1 to 3 nodules, with an average nodule particle size (μm) of 3.05 μm.

[0138] 100 moles of the manufactured nickel-based lithium composite metal oxide were mixed with 0.67 moles of the cobalt raw material Co3O4 and calcined at 700°C for 5 hours. The D of the manufactured cathode active material 50 The diameter was 3.50 μm, and the XY / Z value was 1.726.

[0139] A positive electrode and a lithium secondary battery containing the same were manufactured in the same manner as in Example 1, except that the positive electrode was manufactured using the positive electrode active material.

[0140] Comparative Example 5 Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor is mixed with LiOH and Li / Me(Ni, Co, Mn) in a molar ratio of 1.05, and then heat-treated at 900°C for 10 hours under an oxygen atmosphere to produce LiNi 0.8 Co 0.1 Mn 0.1O2 lithium composite transition metal oxides were fabricated. The fabricated nickel-based lithium composite metal oxides were in a pseudo-single-particle morphology consisting of 1 to 3 nodules, with an average nodule particle size (μm) of 1.69 μm.

[0141] 100 moles of the manufactured nickel-based lithium composite metal oxide were mixed with 1 mole of the cobalt raw material Co3O4 and calcined at 700°C for 5 hours. The D of the manufactured cathode active material 50 The diameter was 5.76 μm, and the XY / Z value was 0.88.

[0142] A positive electrode and a lithium secondary battery containing the same were manufactured in the same manner as in Example 1, except that the positive electrode was manufactured using the positive electrode active material.

[0143] Comparative Example 6 Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor is mixed with LiOH and Li / Me(Ni, Co, Mn) in a molar ratio of 1.05, and then heat-treated at 900°C for 10 hours under an oxygen atmosphere to produce LiNi 0.8 Co 0.1 Mn 0.1 O2 lithium composite transition metal oxides were fabricated. The fabricated nickel-based lithium composite metal oxides were in a pseudo-single-particle morphology consisting of 1 to 3 nodules, with an average nodule particle size (μm) of 2.26 μm.

[0144] 1.5 moles of cobalt raw material Co3O4 were added to 100 moles of the manufactured nickel-based lithium composite metal oxide, and the mixture was calcined at 700°C for 5 hours. The D of the manufactured cathode active material 50 The diameter was 3.15 μm, and the XY / Z value was 3.22.

[0145] A positive electrode and a lithium secondary battery containing the same were manufactured in the same manner as in Example 1, except that the positive electrode was manufactured using the positive electrode active material.

[0146] Experimental Example 1 - Evaluation of Lifetime Characteristics Each of the lithium secondary batteries produced in Examples 1-3 and Comparative Examples 1-6 was charged to 4.25V at 45°C with a constant current of 0.5C and discharged to 2.5V with a constant current of 0.5C. This constituted one cycle, and after 50 charge-discharge cycles, the capacity retention rate after 50 cycles was measured and is shown in Table 1 below.

[0147] [Table 1]

[0148] As shown in Table 1 above, [Equation 1] satisfies 1 ≤ XY / Z ≤ 3, and the positive electrode active material D 50 The lithium secondary batteries of Examples 1 to 3, manufactured containing a positive electrode active material having a size of 5 μm to 12 μm, are based on the formula 1 or the D of the positive electrode active material. 50 Compared to the lithium secondary batteries of Comparative Examples 1-6, which were manufactured using positive electrode active materials that did not meet the (μm) requirement of 5μm-12μm, it was confirmed that this product exhibited superior lifespan characteristics.

[0149] Experimental Example 2 - High-Temperature Storage Characteristics The positive electrode active materials, carbon black conductive material, and PVDF binder produced in Examples 1-3 and Comparative Examples 1-6 were mixed in N-methylpyrrolidone solvent in a weight ratio of 96:2:2 to produce a positive electrode composite material (viscosity: 5000 mPa·s). This composite material was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to produce the positive electrode. Lithium metal was used for the negative electrode.

[0150] An electrode assembly was manufactured by interposing a porous polyethylene separator between the positive and negative electrodes produced as described above. After positioning the electrode assembly inside a case, an electrolyte was injected into the case to produce a lithium secondary battery. The electrolyte was prepared by dissolving 1.0 M lithium hexafluorophosphate (LiPF6) in an organic solvent consisting of ethylene carbonate / ethyl methyl carbonate / diethyl carbonate / (EC / EMC / DEC mixed volume ratio = 3 / 4 / 3). Each lithium secondary battery half cell produced as described above was charged in CCCV mode to 0.2C and 4.25V (end current 1 / 20C). After charging, the two charged positive electrodes and two polyethylene separators obtained by disassembling the cell were alternately stacked on the bottom plate of a coin cell, the electrolyte was injected, and then the coin cell was reassembled. Subsequently, the gas generated after storage at 70°C for two weeks was measured using GC-MS (gas chromatograph-mass spectrometer). The results are shown in Table 2 below.

[0151] [Table 2]

[0152] As shown in Table 2 above, [Equation 1] satisfies 1 ≤ XY / Z ≤ 3, and the positive electrode active material D 50 The lithium secondary batteries of Examples 1 to 3, manufactured containing a positive electrode active material having a size of 5 μm to 12 μm, are based on the formula 1 or the D of the positive electrode active material. 50 We were able to confirm that the lithium secondary batteries manufactured using comparative examples 1 to 6, which contained positive electrode active materials whose (μm) size did not meet the requirement of 5 μm to 12 μm, exhibited superior high-temperature storage characteristics.

Claims

1. The nickel-based lithium composite metal oxide comprises a single-particle or pseudo-single-particle form nickel-based lithium composite metal oxide having a Ni content of 80 atm% or more among transition metals other than lithium, and a coating layer containing cobalt located on the surface of the nickel-based lithium composite metal oxide. A positive electrode active material that satisfies the following equation 1. [Formula 1] 1≦XY / Z≦3 In formula 1, X is the number of moles (mol%) of Co in the coating layer relative to 100 moles of the nickel-based lithium composite metal oxide, Y is the average particle size (μm) of the nickel-based lithium composite metal oxide nodules, and Z is the D of the positive electrode active material. ５０ (μm) and Z is between 5μm and 12μm.

2. The nickel-based lithium composite metal oxide is represented by the following chemical formula 2, and is the positive electrode active material according to claim 1. [Chemical formula 2] Li ａ Ni ｂ Co ｃ M １ ｄ M ２ ｅ O ２ In the above chemical formula 2, M １ M is Mn, Al, or a combination thereof. ２ is one or more elements selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, and satisfies the following conditions: 0.8 ≤ a ≤ 1.2, 0.8 ≤ b < 1, 0 < c < 0.2, 0 < d < 0.2, and 0 ≤ e ≤ 0.

1.

3. The positive electrode active material according to claim 1, wherein X is 1 mol% to 5 mol%.

4. The positive electrode active material according to claim 1, wherein Y is 1 μm to 10 μm.

5. The positive electrode active material according to claim 1, wherein Z / Y is 1 to 3.

6. The positive electrode active material according to claim 1, wherein the positive electrode active material contains lithium by-products in an amount of 1 mol% to 5 mol% relative to the nickel-based lithium composite metal oxide.

7. The aforementioned nickel-based lithium composite metal oxide has a strain value of 200 × 10⁻⁶ －６ ~380 x 10 －６ The positive electrode active material according to claim 1.

8. A positive electrode comprising a positive electrode active material layer containing the positive electrode active material described in claim 1.

9. The positive electrode according to claim 8, wherein the positive electrode active material is present in an amount of 90 to 100% by weight relative to the total weight of the positive electrode active material contained in the positive electrode.

10. The positive electrode according to claim 8, wherein the proportion of positive electrode active material having a size of 5 μm to 7 μm in the total positive electrode active material is 80 volume% or more.

11. A lithium secondary battery comprising the positive electrode, negative electrode, and electrolyte described in claim 8.

12. The positive electrode active material according to any one of claims 1 to 7, wherein the positive electrode active material has a monomodal particle size distribution.

Images