Cathode active material for lithium secondary battery and lithium secondary battery comprising same

Abstract

The present embodiments relate to a cathode active material for a lithium secondary battery, and a lithium secondary battery comprising same. The cathode active material for a lithium secondary battery, according to an embodiment, comprises: a metal oxide in the form of a single particle, including 0.8 mol or more of nickel based on 1 mol of the total metals excluding lithium; and a coating layer positioned on the surface of the metal oxide and including cobalt, wherein the metal oxide having formed thereon the coating layer may have a particle diameter (Dn10), which corresponds to 10% of the cumulative distribution of the number of particles, of 1.1 ㎛ or more.

Description

Cathode active material for lithium secondary batteries and lithium secondary batteries containing the same

[0001] These examples relate to a positive electrode active material for a lithium secondary battery and a lithium secondary battery including the same.

[0002] Driven by the recent explosive demand for electric vehicles and the need to increase driving range, the development of high-capacity, high-energy-density secondary batteries to meet these demands is actively underway worldwide.

[0003] To meet these requirements, a technology using a high-nickel NCM cathode material with a high Ni content and a secondary particle form has been proposed.

[0004] However, as the nickel content increases, particle strength decreases, causing microcracks to occur during charge and discharge, which increases the specific surface area of ​​the cathode material, leading to increased gas generation due to increased reaction with the electrolyte. Furthermore, the secondary particle strength is weak, which can cause secondary particles to break during the electrode rolling process, increasing the amount of fine particles generated, thereby deteriorating the battery's lifespan characteristics.

[0005] To solve this problem, a method was proposed to reduce the specific surface area and increase the strength of the particles by manufacturing the cathode material in the form of single particles by increasing the size of the primary particles as much as possible.

[0006]

[0007] However, in general, in order to manufacture a cathode material in the form of a single particle, firing must be performed at a higher temperature than that of a secondary particle, and at this time, over-firing often occurs, causing crystal defects in the layered structure, which causes a problem of reduced output and life characteristics.

[0008] In this embodiment, an object is to provide a positive electrode active material for a lithium secondary battery having excellent output and life characteristics and a lithium secondary battery including the same.

[0009] According to one embodiment, a cathode active material for a lithium secondary battery comprises a metal oxide in the form of a single particle containing 0.8 mol or more of nickel based on 1 mol of total metal excluding lithium; and a coating layer located on the surface of the metal oxide and containing cobalt; wherein the metal oxide on which the coating layer is formed may have a particle diameter (Dn10) of 1.1 μm or more corresponding to 10% of the cumulative distribution of the number of particles.

[0010] A positive electrode for a lithium secondary battery according to another embodiment may include a positive electrode active material according to one embodiment.

[0011] A lithium secondary battery according to another embodiment may include the positive electrode for a lithium secondary battery according to one embodiment.

[0012] According to the present embodiment, by controlling the degree of differentiation to a certain level or higher based on the cumulative distribution of the number of particles for a single-particle metal oxide, the high-temperature life of the battery can be significantly improved. More specifically, when the particle diameter (Dn10) of a particle corresponding to 10% of the cumulative distribution of the number of particles for a single-particle metal oxide having a coating layer formed thereon is 1.1 ㎛ or more, excellent high-temperature life and resistance characteristics of a lithium secondary battery can be secured.

[0013] Figure 1 shows the particle size according to the cumulative distribution of the number of particles for the positive electrode active materials manufactured in Examples 1 to 4 and Comparative Examples 1 to 2.

[0014] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0015] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0016] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0017] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0018] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0019] In this specification, the term "combination(s) thereof" described in the expression in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression in the Makushi format, and means including any one or more selected from the group consisting of said components.

[0020] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0021]

[0022] Cathode active material for lithium secondary batteries

[0023] As described above, the positive electrode active material in the form of a single particle has a problem in that oversintering occurs, causing defects in the layered crystal structure, resulting in a decrease in output and high-temperature life characteristics.

[0024] However, in this embodiment, this problem was solved by controlling the particle diameter (Dn10) of the particle corresponding to 10% of the cumulative distribution of the number of particles for the single particle-shaped metal oxide on which the coating layer is formed to be 1.1 ㎛ or more.

[0025] Specifically, a cathode active material for a lithium secondary battery according to one embodiment comprises a metal oxide in the form of a single particle containing 0.8 mol or more of nickel based on 1 mol of the total metal excluding lithium; and a coating layer located on the surface of the metal oxide and containing cobalt; wherein the metal oxide on which the coating layer is formed may have a particle diameter (Dn10) of 1.1 μm or more corresponding to 10% of the cumulative distribution of the number of particles.

[0026] In this specification, a single particle may include at least one of a single crystal structure composed of a single particle and a structure in which 2 to 20 or 2 to 10 particles are clumped together and can be distinguished as a single lump when observing a cross-section of the powder through a scanning electron microscope (SEM). Here, one particle means one grain or crystallite.

[0027] As in this example, the single particle-type active material has a smaller specific surface area than the conventional secondary particle-type positive electrode active material formed by the agglomeration of tens to hundreds of primary particles, thereby reducing the amount of gas generated by side reactions with the electrolyte. In addition, the particle strength is large, which can suppress particle breakage during rolling and reduce the occurrence of cracks due to repeated charging and discharging. Accordingly, it has superior lifespan and safety compared to secondary particles, and has the advantage of being able to realize high energy density of the electrode.

[0028] However, in general, the lithium ion movement distance of single particle active materials may increase as the crystal grain size increases, and in this case, there is a problem of reduced capacity and high-temperature life characteristics.

[0029] However, in the present invention, by controlling the fine powder content so that the particle diameter (Dn10) corresponding to 10% of the cumulative distribution of the number of particles for the metal oxide on which the coating layer is formed is 1.1 ㎛ or more, more specifically, in the range of 1.1 ㎛ to 2.0 ㎛, a positive electrode active material having excellent high-temperature life characteristics can be implemented.

[0030] In this embodiment, the metal oxide on which the coating layer is formed may satisfy the following equation 1.

[0031] [Formula 1]

[0032] 1.1 ≤ Dv10 / Dn10 ≤ 2.2

[0033] In this embodiment, the metal oxide on which the coating layer is formed may satisfy the following equation 2.

[0034] [Formula 2]

[0035] 0.5㎛ ≤ Dv10 - Dn10 ≤ 1.2㎛

[0036] In the above equations 1 and 2, Dv10 is the average particle diameter of the particles corresponding to 10% of the volume cumulative percentage in the particle size distribution obtained from the volume of the metal oxide on which the coating layer is formed, and Dn10 is the average particle diameter of the particles at a point corresponding to 10% of the cumulative distribution of the number of particles when the metal oxide on which the coating layer is formed is accumulated from the smallest particle.

[0037] The above average particle diameter by volume (Dv10) and average particle diameter by number (Dn10) can be measured using, for example, the laser diffraction method.

[0038] Next, the metal oxide on which the coating layer is formed may have a particle diameter (Dnmin) corresponding to the minimum cumulative distribution of the number of particles of 1.0 ㎛ or more, more specifically, in the range of 1.0 ㎛ to 1.4 ㎛.

[0039] The cathode active material of the present embodiment can dramatically improve the high-temperature life characteristics of a lithium secondary battery by controlling the particle size (Dnmin) corresponding to the minimum cumulative distribution of the number of particles and the fine particle content to satisfy Equation 1 and / or Equation 2.

[0040] In addition, the average particle diameter (Dv50) of the metal oxide on which the coating layer is formed may be 5 ㎛ or less, more specifically, in the range of 2 ㎛ to 5 ㎛.

[0041] Meanwhile, the metal oxide in the form of a single particle may contain nickel in an amount of 0.8 mol or more, based on 1 mol of the total metal excluding lithium. The content of nickel may be 0.8 mol or more, more specifically, in the range of 0.8 mol to 0.99 mol, 0.82 mol to 0.95 mol, or 0.82 mol to 0.93 mol, based on 1 mol of the total metal excluding lithium. When the nickel content satisfies the above range, a high-capacity battery can be realized.

[0042] As described above, since the single particle type positive electrode active material is manufactured by firing at a high temperature compared to the conventional secondary particle type positive electrode active material, crystal defects in the layered structure may occur. In the present embodiment, by forming a coating layer including cobalt as described above on the surface of a metal oxide, crystal defects such as an increase in the cation mixing ratio due to high-temperature firing can be prevented, and the crystal grain size within the single particle and the average particle diameter of the single particle can be efficiently increased during the firing process.

[0043] The content of cobalt included in the coating layer may be in the range of 0.035 mol to 0.08 mol, more specifically, in the range of 0.05 mol to 0.07 mol, based on the total metal excluding lithium in the single particle metal oxide. When the content of cobalt included in the coating layer satisfies the above range, crystal grains can be grown to an appropriate size, and the production cost can be appropriately controlled, resulting in excellent economic efficiency.

[0044] Next, the coating layer may further include aluminum. When aluminum is included together with cobalt in the coating layer, the output characteristics can be further improved.

[0045] Meanwhile, in the positive electrode active material of the present embodiment, the metal oxide may further include cobalt and manganese. Here, the content of cobalt included in the metal oxide may be 0.05 mol or less, more specifically, greater than 0 and 0.05 mol or less, based on 1 mol of the total metal excluding lithium.

[0046] In addition, the content of the manganese may be 0.1 mol or less, more specifically, in the range of 0.05 mol to 0.1 mol, based on 1 mol of the total metal excluding lithium.

[0047] The above metal oxide may further contain a doping element.

[0048] Here, the doping element may include, for example, at least one of Y, Al, Zr, Nb, Mo, W, Ti, Ce, Mg, B, P, V, Sr, and B. In the present embodiment, the doping element may include, for example, Y, Al, and Zr.

[0049] At this time, the content of the doping element may be 0 or more and 0.2 mol or less, more specifically, 0.0005 mol to 0.1 mol, 0.0005 mol to 0.08 mol, 0.0005 mol to 0.04 mol, or 0.001 mol to 0.03 mol, based on 1 mol of the total metal excluding lithium. Specifically, the content of Y may be in the range of 400 ppm to 2,000 ppm, the content of Al may be in the range of 200 ppm to 1,800 ppm, and the content of Zr may be in the range of 1,200 ppm to 2,800 ppm, based on 1 mol of the total metal excluding lithium.

[0050] In this embodiment, the content of the doping element refers to the doping amount of the doping element included in the final obtained positive electrode active material.

[0051]

[0052] anode

[0053] In another embodiment, a positive electrode is provided, comprising a current collector and a positive electrode active material layer positioned on one surface of the current collector and comprising a positive electrode active material manufactured according to one embodiment described above.

[0054] The characteristics of the positive electrode active material constituting the positive electrode active material layer are the same as described above. Therefore, a detailed description of the positive electrode active material will be omitted.

[0055] The above-mentioned collector may be, for example, made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc.

[0056] Meanwhile, the positive electrode active material layer may include a binder and a conductive material.

[0057] At this time, the binder plays a role of improving the adhesion between the positive electrode active material particles and the adhesive strength between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one kind alone or a mixture of two or more kinds thereof may be used, but is not limited thereto. The binder may be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

[0058] And, the conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. 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, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One type alone or a mixture of two or more types among these may be used, but the present invention is not limited thereto. The conductive material may typically be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

[0059] The above positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the above positive electrode active material is used.

[0060] Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, including the positive electrode active material described above and optionally a binder, a conductive agent, or a solvent, on a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive agent are as described above.

[0061] The solvent may be a solvent generally used in the relevant technical field, such as dimethylsulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0062] Alternatively, the positive electrode may be manufactured by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating the resulting film on a positive electrode current collector by peeling it off from the support.

[0063]

[0064] lithium secondary battery

[0065] In another embodiment, a lithium secondary battery including the positive electrode is provided.

[0066] The lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as described above. In addition, the lithium secondary battery may optionally further include a battery container that houses an electrode assembly including the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0067] In the above lithium secondary battery, the negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0068] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0069] The negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material. As an example, the negative electrode active material layer may be manufactured by applying a composition for forming a negative electrode active material layer comprising the negative electrode active material and optionally a binder and a conductive material onto a negative electrode current collector and drying the composition, or by casting the negative electrode forming composition onto a separate support and then laminating the resulting film onto a negative electrode current collector by peeling the film off from the support.

[0070] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β(0 < β < 2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fiber-like forms, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0071] The above binder and conductive material may be the same as those described above for the positive electrode.

[0072] Next, depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators may include polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof, and mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0073] In addition, in the lithium secondary battery, examples of the electrolyte 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.

[0074] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0075] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may 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 (wherein R is a C2 to C20 linear, branched, or cyclic hydrocarbon group, and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.In this case, the performance of the electrolyte may be improved when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

[0076] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. It is preferable that the concentration of the lithium salt be 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.

[0077]

[0078] As described above, a lithium secondary battery including a cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0079]

[0080] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and the present invention is not limited thereto, and the present invention is defined only by the scope of the claims set forth below.

[0081]

[0082] Example 1

[0083] (1) Manufacturing of positive electrode active material

[0084] Ni0.87 Co 0.03 Mn 0.10 After preparing a precursor of (OH)2 composition, a mixture was prepared by uniformly mixing LiOH·H2O (Samsung Chemical, battery grade) as a lithium raw material and Y2O3, ZrO2 and Al(OH)3 as doping raw materials into the precursor.

[0085] At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.05, and doping raw materials were added so that Zr was 2000 ppm, Y was 1200 ppm, and Al was 1000 ppm based on the above precursor.

[0086] The above mixture was placed in a kiln with an oxygen atmosphere and pre-fired at 680°C for 6.5 hours to obtain a pre-fired product. Afterwards, the obtained pre-fired product was placed in a kiln with an oxygen atmosphere and heated to 880°C for 3 hours (1 st After step), it was fired at 940℃ for 1 hour (2 nd step) and then fired at 780℃ for 11 hours (3 rd The sintered product was obtained by sintering using a 3-step method.

[0087] The above-mentioned sintered material was crushed to obtain a single particle metal oxide doped with Al, Y, and Zr.

[0088] Co(OH)2 and Al(OH)3 were dry mixed with the obtained single particle metal oxide as coating raw materials, and then heat treated at 700°C for 5 hours in an oxygen atmosphere to manufacture a cathode active material having a coating layer formed thereon. At this time, Co(OH)2 and Al(OH)3 were mixed in a content corresponding to 2.5 mol% of Co and a content corresponding to 1000 ppm of Al based on the single particle metal oxide.

[0089] Example 2

[0090] Firing at 885℃ for 3 hours (1 stA single-particle type positive electrode active material was manufactured in the same manner as in Example 1, except that step (step) was used.

[0091] Example 3

[0092] Firing at 890℃ for 3 hours (1 st A single-particle type positive electrode active material was manufactured in the same manner as in Example 1, except that step (step) was used.

[0093] Example 4

[0094] Firing at 895℃ for 3 hours (1 st A single-particle type positive electrode active material was manufactured in the same manner as in Example 1, except that step (step) was used.

[0095] Comparative Example 1

[0096] After preliminary firing at 680℃ for 6.5 hours to obtain a preliminary fired product, the obtained preliminary fired product was put into a kiln in an oxygen atmosphere and then heated up to be fired at 900℃ for 4 hours (1 st After step), it was fired at 780℃ for 11 hours (2 nd A single-particle type positive electrode active material was manufactured in the same manner as in Example 1, except that the sintering process was performed in the step (step).

[0097] Comparative Example 2

[0098] Firing at 910℃ for 4 hours (1 st A single-particle type positive electrode active material was manufactured in the same manner as in Comparative Example 1, except that step (a) was used.

[0099]

[0100] The firing process conditions of the examples and comparative examples are summarized in Table 1 below.

[0101] ClassificationPreliminary firing temperature (℃) / time (hr)Main firing 1st temperature (℃) / time (hr)Main firing 2nd temperature (℃) / time (hr)Example 1880 / 3940 / 1780 / 11Example 2885 / 3940 / 1780 / 11Example 3890 / 3940 / 1780 / 11Example 4895 / 3940 / 1780 / 11Comparative example 1900 / 4-780 / 11Comparative example 2910 / 4-780 / 11

[0102] Experimental Example 1 - Measurement of Dn and Dv Values ​​The Dv and Dn values ​​of the positive electrode active materials manufactured in Examples 1 to 4 and Comparative Examples 1 to 2 were measured using the laser diffraction method. The results are shown in Tables 2 and 3 below.

[0103] In addition, Fig. 1 shows a particle size graph according to the cumulative number distribution for the positive electrode active materials manufactured in Examples 1 to 4 and Comparative Examples 1 to 2.

[0104] DvminDv05Dv10Dv50Dv90Dv95DvmaxExample 11.2611.9472.2553.635.716.4811Example 21.2612.1112.4243.795.796.5311Example 31.2612.1032.4033.685.616.3411Example 41.2612.1112.4083.695.636.3611Comparative Example 11.0602.0072.3523.735.866.7513.08Comparative Example 21.2612.0852.4243.826.016.9413.08

[0105] DnminDn05Dn10Dn50Dn90Dn95DnmaxExample 11.1921.2971.4122.3483.834.379.19Example 21.2171.3771.5572.6024.124.669.4Example 31.2181.3831.5672.59144.519.16Example 41.2211.3941.5822.5994.014.529.19Comparative Example 10.8410.9110.9962.13.614.119.15Comparative Example 20.8410.9110.9962.0963.614.119.17

[0106] (Unit: ㎛) Referring to Figure 1, Table 2 and Table 3, the positive electrode active materials manufactured in Examples 1 to 4 all have particle diameters (Dn10) corresponding to 10% of the cumulative distribution of the number of particles of 1.1 ㎛ or more, but in the case of Comparative Examples 1 and 2, it can be seen that the fine powder content is high, with a particle diameter of 1.0 ㎛ or less.

[0107]

[0108] Experimental Example 2: Coin Cell Manufacturing and High-Temperature Lifespan Evaluation

[0109] (1) Manufacturing of coin cells

[0110] A CR2032 coin cell was manufactured using the positive electrode active material manufactured in the examples and comparative examples using the following method.

[0111] Specifically, a positive electrode active material, a conductive agent (acetylene black FX35, Denka), and a polyvinylidene fluoride binder (trade name: KF9709) were mixed in a weight ratio of 96.5:1.5:2 95:2.2:2.8, and the mixture was added to an N-methyl-2-pyrrolidone solvent so that the solid content was about 65 to 69 wt% to prepare a positive electrode active material slurry.

[0112] The above slurry was coated on an aluminum foil (Al foil, thickness: 20 μm), which is a positive electrode collector, using a doctor blade, dried, and rolled to manufacture a positive electrode. The loading amount of the positive electrode was about 15-16 mg / cm2, and the rolling density was about 3.5 g / cm 3 It was.

[0113] A 2032 coin-type half-cell was manufactured using the above positive electrode, lithium metal negative electrode (400 μm thick, NEBA), electrolyte, and polypropylene polyethylene separator in a conventional manner. The electrolyte was manufactured by dissolving 1 M LiPF6 in a mixed solvent of ethylene carbonate, dimethyl carbonate, and diethyl carbonate (mixing ratio EC:DMC:DEC=1:2:1 vol%) to prepare a mixed solution, to which 2 wt% of vinylene carbonate (VC) was added.

[0114] (2) Measurement of capacity retention rate and resistance increase rate

[0115] After aging the coin-shaped half-cell manufactured in the above (1) at room temperature (25°C) for 10 hours, a charge / discharge test was conducted.

[0116] After a formation cycle of 0.1C / 0.1C constant current charge / discharge within a voltage range of 2.5 to 4.25 V at 45°C, a constant current charge / discharge test was performed at 0.5C / 1C, and the capacity retention rate and DCIR increase rate at the 50th cycle were calculated compared to the capacity of the first cycle.

[0117] DCIR = (V0-V1 / )I

[0118] 1 st , 50 th In each cycle, measurements are taken at the beginning of the discharge phase from the charged state.

[0119] (V0: voltage before current application, V1: voltage after current application (10 seconds), I: applied current)

[0120] The results are shown in Table 4 below.

[0121] Classification Dv10-Dn10 (unit: ㎛) Dv10 / Dn10 Capacity retention rate (%) DCIR increase rate (%) Example 10.8431.59793.156.2 Example 20.8671.55793.555.2 Example 30.8361.53493.454.2 Example 40.8261.52293.156.0 Comparative example 11.3562.36191.382.4 Comparative example 21.4282.43491.878.0

[0122] Referring to Table 4, it can be seen that the positive electrode active materials of Examples 1 to 4, whose Dv10 / Dn10 values ​​and Dv10-Dn10 values ​​satisfy the range of the present invention, have excellent high-temperature capacity retention rates of 93% or more and resistance increase rates of 56.2% or less. In contrast, the positive electrode active materials of Comparative Examples 1 and 2, whose Dv10 / Dn10 values ​​and Dv10-Dn10 values ​​are outside the range of the present invention, show deteriorated high-temperature capacity retention rates and resistance increase rates compared to the Examples.

[0123] The present invention is not limited to the above-described embodiments, but can be manufactured in a variety of different forms. Those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. A metal oxide in the form of a single particle containing 0.8 mole or more of nickel based on 1 mole of the total metal excluding lithium; and A coating layer located on the surface of the metal oxide and containing cobalt; Including, A cathode active material for a lithium secondary battery, wherein the metal oxide on which the coating layer is formed has a particle diameter (Dn10) of 1.1㎛ or more corresponding to 10% of the cumulative distribution of the number of particles.

2. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the metal oxide on which the coating layer is formed has a particle diameter (Dn10) corresponding to 10% of the cumulative distribution of the number of particles in the range of 1.1 ㎛ to 2.0 ㎛.

3. In paragraph 1, The metal oxide on which the above coating layer is formed is a positive electrode active material for a lithium secondary battery, which satisfies the following formula 1. [Formula 1] 1.1 ≤ Dv10 / Dn10 ≤ 2.2 (In the above formula 1, Dv10 is the average particle diameter of the particles corresponding to 10% of the volume cumulative percentage in the particle size distribution obtained from the volume of the metal oxide on which the coating layer is formed, and Dn10 is the average particle diameter of the particles at the point corresponding to 10% of the cumulative distribution of the number of particles when the metal oxide on which the coating layer is formed is accumulated from the smallest particle.) 4. In paragraph 1, The metal oxide on which the above coating layer is formed is a positive electrode active material for a lithium secondary battery, which satisfies the following formula 2. [Formula 2] 0.5㎛ ≤ Dv10 - Dn10 ≤ 1.2㎛ (In the above formula 2, Dv10 is the average particle diameter of the particles corresponding to 10% of the volume cumulative percentage in the particle size distribution obtained from the volume of the metal oxide on which the coating layer is formed, and Dn10 is the average particle diameter of the particles at the point corresponding to 10% of the cumulative distribution of the number of particles when the metal oxide on which the coating layer is formed is accumulated from the smallest particle.) 5. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the metal oxide on which the coating layer is formed has a particle diameter (Dnmin) corresponding to the minimum cumulative distribution of the number of particles of 1.0㎛ or more.

6. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the metal oxide on which the coating layer is formed has a particle diameter (Dnmin) corresponding to the minimum cumulative distribution of the number of particles in the range of 1.0 ㎛ to 1.4 ㎛.

7. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the average particle diameter (Dv50) of the metal oxide on which the coating layer is formed is 5㎛ or less.

8. In paragraph 1, A positive electrode active material for a lithium secondary battery, wherein the coating layer further comprises aluminum.

9. In paragraph 1, A positive electrode active material for a lithium secondary battery, wherein the content of cobalt included in the coating layer is in the range of 0.035 mol to 0.08 mol based on the total metal excluding lithium in the metal oxide in the form of a single particle.

10. In paragraph 1, The above metal oxide further contains cobalt and manganese, A positive electrode active material for a lithium secondary battery, wherein the content of the above cobalt is 0.05 mol or less based on 1 mol of the total metal excluding lithium.

11. In paragraph 10, The above metal oxide further contains a doping element, A cathode active material for a lithium secondary battery, wherein the doping element comprises at least one of Y, Al, Zr, Nb, Mo, W, Ti, Ce, Mg, B, P, V, Sr, and B.

12. A positive electrode for a lithium secondary battery, comprising the positive electrode active material of any one of claims 1 to 11.

13. A lithium secondary battery comprising the positive electrode for a lithium secondary battery of Article 12.

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