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 the benefit of priority based on Korean Patent Application No. 10-2022-0176301, filed on December 15, 2022, and all the contents disclosed in the literature of the Korean patent application are incorporated herein by reference in their entirety.

[0002] The present invention relates to a positive electrode active material and a positive electrode including the same.

Background Art

[0003] With the development of technologies related to mobile devices and the increasing demand, the demand for secondary batteries as an energy source has been rapidly increasing. Among such secondary batteries, lithium secondary batteries having high energy density, high voltage, long cycle life, and low self-discharge rate have been commercialized and widely used. In addition, with the recent development of technologies such as electric vehicles, the demand for high-capacity secondary batteries has been increasing.

[0004] When a lithium secondary battery is driven to perform cycles, as the volume expansion and contraction are repeated, the positive electrode deteriorates and cracks occur, thereby reducing the capacity of the cell and increasing the resistance. In particular, when a high-nickel positive electrode active material having a Ni content of 80 atm% or more is used to increase the capacity of the secondary battery, the structural stability is poor and the occurrence of cracks is frequent, so the decrease in life with the progress of cycles is serious.

[0005] To improve such demerits, single particles or pseudo-single particles can be used. When a positive electrode active material in the form of single particles or pseudo-single particles is used, the contact interface with the electrolyte decreases, and compared with the conventional positive electrode active material in the form of secondary particles, there are problems such as a longer diffusion path of lithium ions and inferior output performance due to the formation of a surface rock salt structure by overfiring. Such deterioration of output performance tends to become more severe as the size of the single particles or pseudo-single particles increases.

[0006] Therefore, in order to complement the above problems of single particles, conventionally, small-sized single particles and secondary particles were mixed bimodally to manufacture a lithium secondary battery. However, when applying such a bimodal positive electrode active material, there is a problem that cracking of the relatively weak secondary particles further increases, and rather, side reactions with the electrolyte increase. Summary of the Invention Problems to be Solved by the Invention

[0007] Therefore, an object of the present invention is to provide a high-nickel positive electrode active material in the form of single particles or pseudo-single particles having excellent life characteristics and excellent characteristics such as capacity and output characteristics, and a secondary battery applying the same. Means for Solving the Problems

[0008] As a result of repeated experiments, the inventors of the present invention have found that the above object can be achieved by appropriately adjusting the D of the positive electrode active material, the average particle size of the nodules, and the content of Co contained in the coating layer formed on the surface of the positive electrode active material in an appropriate ratio in a high-nickel positive electrode active material in the form of single particles or pseudo-single particles. 50 Specifically, a positive electrode active material is provided that includes 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 in the form of single particles or pseudo-single particles, and a cobalt-containing coating layer located on the surface of the nickel-based lithium composite metal oxide, and satisfies the following formula 1.

[0009] [Formula 1] 1 ≤ XY / Z ≤ 3 In Formula 1, X is the number of moles (mol%) of Co in the coating layer with respect to 100 moles of the nickel-based lithium composite metal oxide, Y is the average particle size (μm) of the nodules of the nickel-based lithium composite metal oxide, and Z is the D of the positive electrode active material 50 (μm), and Z is 5 μm to 12 μm.

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

Advantages of the Invention

[0011] In the high-nickel positive electrode active material in the form of single particles or pseudo-single particles, by adjusting the D of the positive electrode active material, 50 the average particle size of nodules, and the content of Co contained in the coating layer formed on the surface of the positive electrode active material in an appropriate ratio, there is an effect that the surface resistance is small and the generation of cracks is reduced.

[0012] That is, the inventors of the present invention have found that when the number of internal nodules per positive electrode active material particle and the cobalt coating amount are adjusted within a range satisfying a specific formula, the interfacial resistance of the positive electrode active material can be minimized.

[0013] That is, a lithium secondary battery including a positive electrode to which the positive electrode active material of the present invention is applied has an effect that the life characteristics are improved, the resistance is low, and the output characteristics are excellent during cycle progress.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, the present invention will be described in more detail.

[0015] Terms and words used in this specification and claims should not be construed as being limited to their ordinary or dictionary meanings. The inventors should interpret them in accordance with the meaning and concept consistent with the technical idea of the present invention in accordance with the principle that they can appropriately define the concept of terms in order to explain their invention in the best way.

[0016] In the present invention, a "single particle" is a particle composed of one single nodule. In the present invention, a "pseudo-single particle" means a particle which is a composite formed of 10 or less nodules.

[0017] In the present invention, "nodule" means a particle unit body that constitutes a single particle and a pseudo-single particle, and the nodule is a single crystal lacking a crystalline grain boundary, or can be 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 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 a single particle, a pseudo-single particle, a primary particle, a nodule, and a secondary particle.

[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 powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (for example, Microtrac S3500), and 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" means the smallest particle unit that can be distinguished as a single mass when observing the cross-section of the positive electrode active material through a scanning electron microscope (SEM). It may consist of one crystal grain or a plurality of crystal grains. The average particle size of the nodule can be measured by measuring the respective particle sizes distinguished in the cross-section SEM image of the positive electrode active material particles and then obtaining the arithmetic mean value thereof.

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

[0023] In the present invention, "strain" means the twist of the lattice caused by a defect, that is, a minute deformation. The strain was measured by analyzing the XRD data obtained by X-ray diffraction analysis of the positive electrode active material powder by the Rietveld refinement method. Here, the X-ray diffraction analysis was performed using a Bruker D8 Endeavor equipped with a LynxEye XE-T-position sensitive detector (light source: Cu-Kα, λ = 1.54 Å). The sample was placed in the groove of a holder for general powder, and the surface of the sample was made uniform using a slide glass. After filling the sample so that the height of the sample matched the edge of the holder, the measurement was performed in the region of FDS 0.5°, 2θ = 15° to 90° under the conditions of step size = 0.02° and total scan time = about 20 minutes. For the measured data, Rietveld analysis was performed considering the charge at each site (the metal at the transition metal site is +3, and Ni at the Li site is +2) and cation mixing. Specifically, when analyzing the strain, the instrumental broadening uses the Fundamental Parameter Approach (FPA) realized by the Bruker TOPAS program, and the entire peak in the measurement range is used during fitting. The peak shape was fitted using only the Lorenzian contribution as FP (First Principle) among the peak types available in TOPAS.

[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, cobalt is known to reduce the resistance of the positive electrode active material when the cobalt content is high in order to smooth the formation of the layered structure. Also, when the positive electrode active material is composed of aggregates of a large number of primary particles, since the interface between the primary particles becomes a migration path for lithium ions, it is known that the higher the number of interfaces between the primary particles, the higher the lithium mobility and the lower the resistance. However, according to the research of the present inventors, in the case of a high-nickel positive electrode active material in the form of single particles or pseudo-single particles, it has been shown that there is a resistance improvement effect only when the cobalt content and the number of interfaces between nodules in the active material particles satisfy a specific relationship. Here, the number of interfaces between nodules in the particles is defined as the ratio of D 50 (Z) to the average particle diameter (Y) of the positive electrode active material. Specifically, in the case of a high-nickel positive electrode active material in the form of single particles or pseudo-single particles, when the Co content is high but the Z / Y value does not satisfy a specific range, the resistance increases, and when the Z / Y value increases but the Co content does not satisfy a specific range, the resistance increases.

[0027] In Formula 1, X is the number of moles (mol%) of Co in the coating layer with respect to 100 moles of the nickel-based lithium composite metal oxide. The 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 fine structure of the single particle and / or pseudo-single particle nickel-based lithium composite metal oxide is stabilized and the generation of cracks is reduced, so the disintegration of the positive electrode active material is suppressed even when cycling is performed.

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

[0029] In Formula 1, Z is D of the positive electrode active material 50 (μm). The Z can be 5 μm to 12 μm, preferably 6 to 10 μm, and most preferably 6.2 μm to 8 μm. Since the positive electrode active material of the present invention has a larger D 50 than conventional single particles or pseudo single particles, it is excellent in tap density and rolling density, and has a small BET, so there is an effect of improving slurry processability and thermal stability. Further, the positive electrode active material of the present invention has a D 50 within the above range, does not cause slurry aggregation problems, has excellent electrolyte impregnation properties, and has an effect of excellent output and life characteristics of a lithium secondary battery including the same.

[0030] In Formula 1, Z / Y has the meaning of substituting the number of nodules contained in one positive electrode active material particle or the number of interfaces between nodules in the active material particle.

[0031] In the positive electrode active material of the present invention, the Z / Y can be 1 to 3, preferably 1 to 2, and most preferably 1.1 to 1.5. When the average particle size of the nodules of the nickel-based lithium composite metal oxide and the D 50 of the positive electrode active material satisfy the above range, the particle strength is high, the rolling density is high, it is suitable for the composition of an electrode with a high energy density, and even when the rolling rate is high, there are few cracks in the particles, and the life characteristics and high-temperature storage characteristics are improved.

[0032] In the positive electrode active material of the present invention, the ratio of the positive electrode active material having a size of 5 μm to 7 μm in the entire positive electrode active material can be 80% by volume or more.

[0033] The positive electrode active material of the present invention can contain lithium by-products in an amount of 1 to 5 mol% with respect to the nickel-based lithium composite metal oxide, and preferably can contain them in an amount of 1 to 3 mol%. The positive electrode active material of the present invention is characterized by a small amount of lithium by-products in spite of overfiring to contain single particles.

[0034] The positive electrode active material of the present invention contains a nickel-based lithium composite metal oxide in which the content of Ni among transition metals other than lithium is 80 atm% or more, in a single particle or pseudo-single particle form, 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 can contain 80 atm% or more of nickel among transition metals other than lithium, preferably 85 atm% or more. When the nickel is less than 80 atm%, there is a problem that the capacity of the positive electrode active material decreases and it cannot be applied to an electrochemical element that requires high capacity.

[0036] Specifically, the nickel-based lithium composite metal oxide contained in the positive electrode active material of the present invention can 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 O 2

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

[0039] The 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, more preferably 1 ≦ a ≦ 1.08.

[0040] Said 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 realized.

[0041] Said c represents the molar ratio of cobalt among the metal elements other than lithium in the nickel-based lithium composite metal oxide, and can be 0 < c < 0.20, 0 < c ≦ 0.15, or 0.01 ≦ c ≦ 0.10.

[0042] Said d represents the molar ratio of M among the metal elements other than lithium in the nickel-based lithium composite metal oxide 1 and can be 0 < d < 0.20, 0 < d ≦ 0.15, or 0.01 ≦ d ≦ 0.10.

[0043] Said e represents the molar ratio of M among the metal elements other than lithium in the nickel-based lithium composite metal oxide 2 and can be 0 ≦ e ≦ 0.10, or 0 ≦ e ≦ 0.05.

[0044] Conventionally, as the positive electrode active material of a lithium secondary battery, it has been common to use spherical secondary particles in which dozens to hundreds of primary particles are aggregated. However, in the case of a positive electrode active material in the form of secondary particles in which many primary particles are aggregated like this, when manufacturing the positive electrode, particle cracking in which primary particles are detached occurs easily in the rolling process, and there is a problem that cracks occur inside the particles during the charge and discharge process. When particle cracking or cracks inside the particles of the positive electrode active material occur, since the contact area with the electrolyte increases, there is a problem that the generation of gas due to side reactions with the electrolyte increases.

[0045] In contrast, a single particle composed of one primary particle or a pseudo-single particle form in which 10 or fewer primary particles are aggregated has a higher particle strength than the existing secondary particle form of the positive electrode active material in which dozens to hundreds of primary particles are aggregated. Therefore, almost no particle cracking occurs during rolling. Further, in the case of a single particle or pseudo-single particle form of the positive electrode active material, since the number of primary particles constituting the particles is small, during charge and discharge, the change due to the expansion and contraction of the volume of the primary particles is small, and thus the generation of cracks inside the particles is also significantly reduced.

[0046] Therefore, when using a positive electrode active material composed of single particles and / or pseudo-single particles, it is possible to significantly suppress the reduction in life characteristics due to the occurrence of particle cracking and internal cracks.

[0047] The nickel-based lithium composite metal oxide can have an average crystallite size of 170 to 300 nm, preferably 170 to 250 nm, and most preferably 180 to 230 nm. When the average crystallite size is satisfied, firing is performed to an appropriate degree, and since the formation of the surface rock salt structure is small, there is an effect of excellent output performance.

[0048] The nickel-based lithium composite metal oxide has a strain value of 200×10 -6 ~380×10 -6 and preferably 210×10 -6 ~370×10 -6 It can be. When the range of the strain is satisfied, the degree of completion of the crystal structure is high, the positive electrode active material has a stable crystal structure, and the life performance is excellent.

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

[0050] Specifically, the coating layer can have a composition represented by the following Chemical Formula 3.

[0051] [Chemical Formula 3] Li x Co y O 2

[0052] Said 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] Said 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] By means of said coating layer, the contact between the positive electrode active material and the electrolyte contained in the lithium secondary battery is blocked to suppress the occurrence of side reactions, so that the life characteristics can be improved, and the packing density of the positive electrode active material can be increased.

[0055] Said coating layer may be formed on the entire surface of the positive electrode active material, or may be formed partially. Specifically, when the coating layer is formed partially on the surface of the positive electrode active material, it can be formed in an amount of 20% or more based on the total area of the positive electrode active material. When the area of the coating layer is less than 20%, the improvement effects of the life characteristics and the packing density due to the formation of the coating layer may be negligible.

[0056] Also, said coating layer can be formed at a thickness ratio of 1 / 10000 to 1 / 100 with respect to the average particle diameter of the positive electrode active material particles. When the thickness ratio of the coating layer with respect to the particles of the positive electrode active material is less than 1 / 10000, the improvement effects of the life characteristics and the packing density due to the formation of the coating layer are negligible, and when the thickness ratio exceeds 1 / 100, the battery characteristics may deteriorate.

[0057] Manufacturing method of positive electrode active material The method for manufacturing a positive electrode active material according to the present invention can include the step 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 the step of forming a coating layer on the surface of the nickel-based lithium composite metal oxide by mixing the nickel-based lithium composite metal oxide with a solution containing a cobalt raw material substance and then performing a first heat treatment.

[0058] First, a nickel-based lithium composite metal oxide in the form of single particles, pseudo-single particles, or a combination thereof, and having a nickel content of 80 atm% or more among metal elements other than lithium can be prepared.

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

[0060] The nickel-based lithium composite metal oxide precursor can be represented by, for example, the following [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 above Chemical Formula A and Chemical Formula B, M 1It can be at least one selected from Mn and Al, and preferably can be Mn or a combination of Mn and Al.

[0064] In the chemical formula A and the chemical formula B, M 2 can be at least one 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 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 q represents the molar ratio of cobalt among the metal elements in the precursor, and can be 0 < q ≦ 0.2, 0 < q ≦ 0.15, or 0.01 ≦ q ≦ 0.10.

[0067] The r represents the molar ratio of the M 1 element among the metal elements in the precursor, and can be 0 < r ≦ 0.2, 0 < r ≦ 0.15, or 0.01 ≦ r ≦ 0.1.

[0068] The s represents the molar ratio of the M 2 element among the metal elements in the precursor, and can be 0 ≦ s < 0.1, or 0 ≦ s ≦ 0.05.

[0069] The lithium raw material substance can be at least one selected from the group consisting of, for example, lithium carbonate (Li 2 CO 3 ), lithium hydroxide (LiOH·H 2 O), anhydrous lithium hydroxide (LiOH), LiNO 3 , CH 3 COOLi, and Li 2 (COO) 2 , and preferably, lithium carbonate (Li 2 CO 3 ), lithium hydroxide (LiOH·H 2(O) or combinations 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 so that the molar ratio of Li: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 content of the lithium raw material is too low, the crystal structure cannot develop properly. If it is too high, unreacted Li remains as a by-product, which can cause capacity reduction and gas generation.

[0071] When appropriately adjusting conditions such as the firing temperature and time, the nodule size and average particle size of the nickel-based lithium composite metal oxide can be adjusted 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, more preferably 700°C to 850°C. If the firing temperature is less than 700°C, raw materials may remain in the particles due to insufficient reaction, which may reduce the high-temperature stability of the battery, and the bulk density and crystallinity may decrease, and the structural stability may decrease. On the other hand, if the firing temperature exceeds 1000°C, non-uniform growth of particles may occur, it may be difficult to crush the particles, and capacity reduction may occur.

[0073] The 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 to obtain a high-crystallinity positive electrode active material. If it exceeds 24 hours, the particle size may become excessively large, and the production efficiency may decrease.

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

[0075] Specifically, it can be carried out by a method in which a nickel-based lithium composite metal oxide is mixed with a solution containing a cobalt raw material substance, then stirred, filtered and separated, and then heat-treated in an oxygen atmosphere.

[0076] The cobalt raw material substances can be mixed so as to be 0.8 to 5 parts by weight, preferably 1 to 4 parts by weight, and more preferably 1.5 to 3 parts by weight, respectively, based on 100 parts by weight of the nickel-based lithium composite metal oxide. When the content of the cobalt raw material substance satisfies the above range, the generation of cracks at the interface between nodules can be suppressed, and the stability and initial capacity can be improved.

[0077] As the cobalt raw material substance, for example, cobalt acetate, cobalt sulfate, cobalt chloride, cobalt nitrate, etc. can be used.

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

[0079] After adding and mixing the nickel-based lithium composite metal oxide into the solution containing the cobalt raw material substance and stirring, the cobalt contained in the solution reacts with the lithium by-product 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 this, it is heat-treated to obtain nickel-based lithium composite metal oxide powder with a coating layer formed.

[0081] Here, the filtration can be carried out by putting filter paper in a filter flask and performing vacuum decompression, 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 is performed to fix cobalt on the surface of the nickel-based lithium composite metal oxide to form a coating layer, and can be performed 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 substance reacts sufficiently with the lithium by-product on the surface, and the coating layer is well formed.

[0083] The heat treatment can be performed for 3 to 8 hours, preferably 4 to 7 hours. When the heat treatment time is within the above range, a coating layer with an appropriate thickness can be formed, and the 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 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, specific description is omitted, and only the remaining configuration will be specifically described below.

[0085] The positive electrode current collector of the present invention can include a metal with high conductivity, and is not particularly limited as long as the positive electrode active material layer can be easily adhered and there is no reactivity within the voltage range of the battery. The positive electrode current collector can be, for example, stainless steel, aluminum, nickel, titanium, heat-treated carbon, or a material obtained by surface-treating the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. Further, the positive electrode current collector can usually have a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the surface of the current collector to increase the adhesion force of the positive electrode active material. For example, it can be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, non-woven fabrics, etc.

[0086] The positive electrode active material contained in the positive electrode active material layer of the present invention can be contained 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 in the form of single particles or pseudo-single particles can be contained 100% alone. When the content of the positive electrode active material of the present invention satisfies the above range, sufficient life characteristics can be obtained. When the positive electrode active material in the form of secondary particles is contained in an amount exceeding 10% by weight of the total positive electrode active material, side reactions with the electrolyte increase due to the fine powder generated from the secondary particles during the manufacture and charge / discharge of the electrode, and the effect of suppressing gas generation decreases.

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

[0088] Here, the positive electrode active material can be contained in a content 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 when contained within the above content range, excellent capacity characteristics can be exhibited.

[0089] The conductive material is used to impart conductivity to the electrode, and in the battery to be configured, it can be used without particular limitation as long as it does not cause a chemical change and has electron conductivity. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based substances 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. Among these, one kind alone or a mixture of two or more kinds can be used. The conductive material can be contained in an amount of 0.1 to 15% by weight based on the total weight of the positive electrode active material layer.

[0090] The binder serves to improve the adhesion between the positive electrode active material particles and the adhesive force 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, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, 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, etc. Among these, one kind alone or a mixture of two or more kinds can be used. The binder can be contained in an amount of 0.1 to 15% by weight based on 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 if necessary, a composition for forming a positive electrode active material layer can be prepared by selectively dissolving or dispersing a binder, a conductive material, and a dispersant in a solvent. After applying the composition for forming the positive electrode active material layer, it can be dried and rolled to manufacture a positive electrode.

[0092] The solvent can be a solvent commonly used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water. Among these, one kind alone or a mixture of two or more kinds can be used. The usage amount of the solvent is determined by considering the coating thickness of the slurry and the production yield, so as to dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant, and then have a viscosity that can show excellent thickness uniformity during the coating for the production of the positive electrode.

[0093] As another method, the positive electrode can also be manufactured by casting the composition for forming the positive electrode active material on another support, and then laminating the film obtained by peeling from this support on the positive electrode current collector.

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

[0095] The lithium secondary battery specifically includes a positive electrode, a negative electrode located opposite to the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is as described above, a specific description thereof is omitted, and only the remaining components will be specifically described below.

[0096] In addition, the lithium secondary battery can selectively further include a battery container for housing the electrode assembly of 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 a chemical change in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, those obtained by surface treatment with carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, aluminum-cadmium alloy, etc. can be used. Further, 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 binding force of the negative electrode active material. For example, it can be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, non-woven fabrics.

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

[0100] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium can be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fibers, 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; SiO β (0 < β < 2), SnO 2Metal oxides that can be doped and undoped with lithium, such as vanadium oxides and lithium vanadium oxides; or composites containing the metal compound and a carbonaceous material, such as Si-C composites or Sn-C composites, etc. Any one or a mixture of two or more of these can be used. Also, a thin film of metallic lithium can be used as the negative electrode active material. Also, as the carbon material, both low-crystalline carbon and high-crystalline carbon can be used. Representative examples of low-crystalline carbon are soft carbon and hard carbon, and representative examples of high-crystalline carbon are amorphous, plate-like, flaky, spherical or fibrous natural graphite 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 negative electrode active material can be contained in an amount of 80% by weight to 99% by weight based on the total weight of the negative electrode active material layer.

[0102] The binder is a component that helps bind the conductive material, the active material, and the current collector, and is usually added in an amount of 0.1% by weight to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluorine rubber, 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, based on 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 has conductivity. For example, graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, 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; conductive materials such as polyphenylene derivatives can be used.

[0104] The negative electrode active material layer is produced by applying and drying a negative electrode active material forming composition prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material, in a solvent on a negative electrode current collector, or by casting the negative electrode active material forming composition on another support and then laminating a film obtained by peeling the support on the negative electrode current collector.

[0105] On the one hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a migration path for lithium ions. Generally, any separator that can be used in a lithium secondary battery can be used without particular limitation. In particular, a separator that has low resistance to the ion migration of the electrolyte and excellent electrolyte moisture retention ability is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as a polyethylene homopolymer, a polypropylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof can be used. Also, a normal porous non-woven fabric, for example, a non-woven fabric made of high-melting-point glass fibers, polyethylene terephthalate fibers, etc. can also be used. Further, in order to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer substance can also be used, and optionally, it can be used as a single-layer or multi-layer structure.

[0106] Also, examples of the electrolyte 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 can contain an organic solvent and a lithium salt.

[0108] As the organic solvent, any solvent can 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, examples of the organic solvent 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; carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol 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 may contain a double bond aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes. Among them, 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, which can enhance the charge and discharge performance of the battery, and a linear carbonate compound having low viscosity (e.g., ethylmethylcarbonate, dimethylcarbonate, or diethylcarbonate) is more preferred.

[0109] The lithium salt can be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, as the anion of the lithium salt, 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 - can be at least one or more selected from the group consisting of, and the lithium salt is LiPF 6 , LiClO 4 , LiAsF 6, LiBF 4 , LiSbF 6 , LiAlO 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 etc. can be used. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0110] In addition to the constituent components of the electrolyte, the electrolyte may further contain one or more additives for the purpose of improving the life characteristics of the battery, suppressing the capacity reduction of the battery, improving the discharge capacity of the battery, etc., such as haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethyl alcoholamine, cyclic ether, ethylenediamine, n-glyme, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethyl alcohol or aluminum trichloride. Here, the additive can be contained in an amount of 0.1 to 5% by weight based on the total weight of the electrolyte.

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

[0112] According to another embodiment of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell and a battery pack including the same.

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

[0114] The outer shape of the lithium secondary battery of the present invention is not particularly limited, and can be a cylindrical shape, a rectangular shape, a pouch type, a coin type, etc. using a can.

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

[0116] Examples of the 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 (OH) 2The precursor was mixed with LiOH such that the Li / Me (Ni, Co, Mn) molar ratio was 1.05, and heat-treated at 900 °C for 10 hours in an oxygen atmosphere to obtain LiNi 0.8 Co 0.1 Mn 0.1 O 2 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 5.69 μm.

[0118] To 100 moles of the produced nickel-based lithium composite metal oxide, 0.67 mole of cobalt raw material Co 3 O 4 was added and fired at 700 °C for 5 hours. The D 50 of the produced cathode active material was 6.25 μm, and the XY / Z value was 1.82.

[0119] The cathode active material, carbon nanotubes, and a PVdF binder were mixed in a weight ratio of 97.5:1.0:1.5 in an NMP solvent to produce a cathode slurry. The cathode slurry was applied to one side of an aluminum current collector (thickness 12 μm) and dried at 130 °C to form a cathode active material layer on the aluminum current collector, and then rolled to produce a cathode.

[0120] On the other hand, as the anode active material, graphite, a carbon conductive material (SuperC65), carboxymethyl cellulose (Daicell 2200), and a 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 an anode active material slurry. The composition for forming the anode was applied to a copper foil with a thickness of 8 μm, dried, and then roll-pressed to produce an anode.

[0121] The anode and cathode produced above were laminated together with a polyolefin separator to produce an electrode assembly, which was then placed in a battery case, and 1 M LiPF was added to 100 parts by weight of a mixed solvent obtained by mixing ethylene carbonate:diethyl carbonate at 3:7 6An electrolyte was dissolved and injected to manufacture a lithium secondary battery.

[0122] Example 2 Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 The precursor was mixed with LiOH so that the Li / Me (Ni, Co, Mn) molar ratio was 1.05, and heat-treated at 900 °C for 10 hours in an oxygen atmosphere to obtain LiNi 0.8 Co 0.1 Mn 0.1 O 2 A lithium composite transition metal oxide was manufactured. The manufactured nickel-based lithium composite metal oxide had a pseudo-single particle form consisting of 1 to 3 nodules, and the average particle size (μm) of the nodules was 5.56 μm.

[0123] 1 mol of cobalt raw material substance Co 3 O 4 was added to 100 mol of the manufactured nickel-based lithium composite metal oxide and fired at 700 °C for 5 hours. The D 50 of the manufactured positive electrode active material was 5.96 μm, and the XY / Z value was 2.80.

[0124] A positive electrode and a lithium secondary battery including 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 Co 0.1 Mn 0.1 (OH) 2 The precursor was mixed with LiOH so that the Li / Me (Ni, Co, Mn) molar ratio was 1.05, and heat-treated at 900 °C for 10 hours in an oxygen atmosphere to obtain LiNi 0.8 Co 0.1 Mn 0.1 O 2 A lithium composite transition metal oxide was manufactured. The manufactured nickel-based lithium composite metal oxide had 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] 0.5 mol of cobalt raw material Co was added to 100 mol 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 3 O 4 was 5.86 μm, and the XY / Z value was 1.07. 50

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

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

[0129] 0.67 mol of cobalt raw material Co was added to 100 mol 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 3 O 4 was 7.93 μm, and the XY / Z value was 0.54. 50

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

[0131] Comparative Example 2 Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 ​​The precursor was mixed with LiOH so that the Li / Me (Ni, Co, Mn) molar ratio was 1.05, and heat-treated at 920 °C for 10 hours in an oxygen atmosphere to obtain LiNi 0.8 Co 0.1 Mn 0.1 O 2 lithium composite transition metal oxide. The produced nickel-based lithium composite metal oxide was in a pseudo-single particle form composed of several nodules, and the average particle size (μm) of the nodules was 1.1 μm.

[0132] To 100 moles of the produced nickel-based lithium composite metal oxide, 1 mole of cobalt raw material Co 3 O 4 was added and fired at 700 °C for 5 hours. The D 50 of the produced positive electrode active material was 6.38 μm, and the XY / Z value was 0.52.

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

[0134] Comparative Example 3 Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 The precursor was mixed with LiOH so that the Li / Me (Ni, Co, Mn) molar ratio was 1.05, and heat-treated at 920 °C for 10 hours in an oxygen atmosphere to obtain LiNi 0.8 Co 0.1 Mn 0.1 O 2 lithium composite transition metal oxide. The produced nickel-based lithium composite metal oxide was in a pseudo-single particle form composed of several nodules, and the average particle size (μm) of the nodules was 1.1 μm.

[0135] To 100 moles of the produced nickel-based lithium composite metal oxide, 2 moles of cobalt raw material Co 3 O 4 was added and fired at 700 °C for 5 hours. The D 50 of the produced positive electrode active material was 3.15 μm, and the XY / Z value was 4.305.

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

[0137] Comparative Example 4 Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 The precursor was mixed with LiOH so that the Li / Me (Ni, Co, Mn) molar ratio was 1.05, and heat-treated at 900 °C for 10 hours in an oxygen atmosphere to obtain LiNi 0.8 Co 0.1 Mn 0.1 O 2 A lithium composite transition metal oxide was produced. The produced nickel-based lithium composite metal oxide had a pseudo-single particle form consisting of 1 to 3 nodules, and the average particle diameter (μm) of the nodules was 3.05 μm.

[0138] 0.67 mol of cobalt raw material Co 3 O 4 was added to 100 mol of the produced nickel-based lithium composite metal oxide and fired at 700 °C for 5 hours. The D 50 of the produced positive electrode active material was 3.50 μm, and the XY / Z value was 1.726.

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

[0140] Comparative Example 5 Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 The precursor was mixed with LiOH so that the Li / Me (Ni, Co, Mn) molar ratio was 1.05, and heat-treated at 900 °C for 10 hours in an oxygen atmosphere to obtain LiNi 0.8 Co 0.1 Mn 0.1 O 2A lithium composite transition metal oxide was produced. The produced nickel-based lithium composite metal oxide was in a pseudo-single particle form composed of 1 to 3 nodules, and the average particle size (μm) of the nodules was 1.69 μm.

[0141] To 100 moles of the produced nickel-based lithium composite metal oxide, 1 mole of cobalt raw material Co 3 O 4 was added and fired at 700 °C for 5 hours. The D 50 of the produced cathode active material was 5.76 μm, and the XY / Z value was 0.88.

[0142] 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.

[0143] Comparative Example 6 Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 The precursor was mixed with LiOH so that the Li / Me (Ni, Co, Mn) molar ratio was 1.05, and heat-treated at 900 °C for 10 hours in an oxygen atmosphere to obtain LiNi 0.8 Co 0.1 Mn 0.1 O 2 A lithium composite transition metal oxide was produced. The produced nickel-based lithium composite metal oxide was in a pseudo-single particle form composed of 1 to 3 nodules, and the average particle size (μm) of the nodules was 2.26 μm.

[0144] To 100 moles of the produced nickel-based lithium composite metal oxide, 1.5 moles of cobalt raw material Co 3 O 4 was added and fired at 700 °C for 5 hours. The D 50 of the produced cathode active material was 3.15 μm, and the XY / Z value was 3.22.

[0145] 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.

[0146] Experimental Example 1 - Evaluation of Life Characteristics Each of the lithium secondary batteries manufactured in Examples 1 to 3 and Comparative Examples 1 to 6 was charged to 4.25 V at a constant current of 0.5C at 45°C, and discharged to 2.5 V at a constant current of 0.5C. One cycle was defined as such, and after performing 50 cycles of charge and discharge, the capacity retention rate after 50 cycles was measured and shown in Table 1 below.

[0147] [Table 1]

[0148] As shown in Table 1 above, the lithium secondary batteries of Examples 1 to 3 manufactured including a positive electrode active material satisfying 1 ≦ XY / Z ≦ 3 in [Formula 1] and having a D 50 (μm) of 5 μm to 12 μm were confirmed to have excellent life characteristics compared to the lithium secondary batteries of Comparative Examples 1 to 6 manufactured including a positive electrode active material not satisfying 5 μm to 12 μm in the said formula 1 or D 50 (μm).

[0149] Experimental Example 2 - High Temperature Storage Characteristics Each of the positive electrode active materials, carbon black conductive materials, and PVDF binders manufactured in Examples 1 to 3 and Comparative Examples 1 to 6 was mixed in a weight ratio of 96:2:2 in an N-methylpyrrolidone solvent to produce a positive electrode mixture (viscosity: 5000 mPa·s). After applying this to one side of an aluminum current collector and drying at 130°C, it was rolled to produce a positive electrode. Lithium metal was used for the negative electrode.

[0150] An electrode assembly was manufactured with a porous polyethylene separator interposed between the positive electrode and the negative electrode manufactured as described above. After positioning the electrode assembly inside a case, an electrolyte was injected into the case to manufacture a lithium secondary battery. Here, the electrolyte is 1.0 M lithium hexafluorophosphate (LiPF 6) was manufactured by dissolution. For each lithium secondary battery half cell manufactured as described above, charging was performed in the CCCV mode at 0.2C until it reached 4.25V (end current 1 / 20C). After charging, two charged positive electrodes and two polyethylene separators obtained by disassembling the cell were alternately stacked on the lower plate of the coin cell, electrolyte was injected, and then the coin cell was assembled. Thereafter, the gas generated during storage at 70°C for two weeks was measured using a GC-MS (gas chromatograph-mass spectrometer). The results are shown in Table 2 below.

[0151]

Table 2

[0152] As shown in Table 2 above, the lithium secondary batteries of Examples 1 to 3 manufactured containing a positive electrode active material satisfying [Formula 1] 1 ≦ XY / Z ≦ 3 and having a D 50 (μm) of 5 μm to 12 μm were confirmed to be superior in high-temperature storage characteristics compared to the lithium secondary batteries of Comparative Examples 1 to 6 manufactured containing a positive electrode active material not satisfying 5 μm to 12 μm for the D 50 (μm).

Claims

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

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

1.

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

4. The positive electrode active material according to Claim 1, wherein the 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% with respect to the nickel-based lithium composite metal oxide.

7. The positive electrode active material according to Claim 1, wherein the nickel-based lithium composite metal oxide has an average crystal grain size (Crystallite size) of 170 nm to 300 nm.

8. The nickel-based lithium composite metal oxide has a strain value of 200×10 －６ to 380×10 －６ The positive electrode active material according to claim 1, wherein the positive electrode active material is as described above.

9. A positive electrode including a positive electrode active material layer containing the positive electrode active material according to Claim 1.

10. The positive electrode according to Claim 9, wherein the positive electrode active material is contained in an amount of 90 to 100% by weight based on the total weight of the positive electrode active material contained in the positive electrode.

11. The positive electrode according to Claim 9, wherein the ratio of the positive electrode active material having a size of 5 μm to 7 μm among the entire positive electrode active material is 80% by volume or more.

12. A lithium secondary battery including the positive electrode according to Claim 9, a negative electrode, and an electrolyte.

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