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

Abstract

The present invention relates to a cathode active material for a lithium secondary battery, the cathode active material comprising a first lithium transition metal oxide and a second lithium transition metal oxide, wherein the first lithium transition metal oxide and the second lithium transition metal oxide each independently have a molar ratio (Li / Me) of lithium to transition metal of greater than 1, an average particle diameter (D50) of the first lithium transition metal oxide is greater than an average particle diameter (D50) of the second lithium transition metal oxide, the first lithium transition metal oxide and the second lithium transition metal oxide are included in a weight ratio of 60:40 to 80:20 (first lithium transition metal oxide:second lithium transition metal oxide), and the first lithium transition metal oxide and the second lithium transition metal oxide each independently have a BET specific surface area of 1.0-3.5 m2 / g.

Description

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

[0001] The present invention relates to a positive electrode active material for a lithium secondary battery and a lithium secondary battery including the same.

[0002]

[0003] As the scope of application of lithium secondary batteries expands from small electronic devices to electric vehicles and power storage devices, the demand for cathode materials with excellent high energy density and high output characteristics is increasing.

[0004] Accordingly, lithium-rich layered cathode active materials have very high charge / discharge capacities and are attracting attention as candidates for next-generation cathode materials, and research is actively underway recently.

[0005] However, lithium-rich layered cathode active materials inherently have lower true density of the active material itself than conventional cathode materials due to their high lithium content and relatively low transition metal ratio within the structure, and the crystal growth direction varies depending on the material composition, resulting in poor particle packing. This results in low tap density and electrode density, and even if the capacity characteristics of the active material itself are excellent, there is a problem that the energy density of the electrode is not significantly improved when applied to actual batteries.

[0006] Furthermore, since lithium-rich layered cathode active materials utilize oxygen redox reactions in addition to transition metals, oxygen on the surface or within the bulk can easily be generated as oxygen gas. Consequently, the active material particles can easily transform into a dense, non-reactive or less reactive spinel / rock salt structure, potentially degrading output characteristics compared to conventional cathode materials.

[0007]

[0008] Accordingly, one object of the present invention is to provide a positive electrode active material for a lithium secondary battery, which is a lithium transition metal oxide having a lithium-excess composition, and which can improve both electrode energy density and battery output characteristics, and a lithium secondary battery including the same.

[0009]

[0010] One embodiment of the present invention comprises a first lithium transition metal oxide and a second lithium transition metal oxide, wherein the first lithium transition metal oxide and the second lithium transition metal oxide each independently have a molar ratio of lithium to transition metal (Li / Me) greater than 1, an average particle diameter (D50) of the first lithium transition metal oxide is larger than an average particle diameter (D50) of the second lithium transition metal oxide, and the first lithium transition metal oxide and the second lithium transition metal oxide are included in a weight ratio of 60:40 to 80:20 (first lithium transition metal oxide: second lithium transition metal oxide), and the first lithium transition metal oxide and the second lithium transition metal oxide each independently have a BET specific surface area of ​​1.0 to 3.5 m 2 / g provides a cathode active material for a lithium secondary battery.

[0011] The ratio of the average particle diameter (D50) of the first lithium transition metal oxide to the average particle diameter (D50) of the second lithium transition metal oxide may be 3 to 4.

[0012] The first lithium transition metal oxide and the second lithium transition metal oxide may each independently have a molar ratio of nickel to transition metal (Ni / Me) of 0.2 to 0.4.

[0013] The above first lithium transition metal oxide and the above second lithium transition metal oxide may be secondary particles formed by agglomeration of a plurality of primary particles.

[0014] The average particle diameter (D50) of the above first lithium transition metal oxide may be 8 to 15 μm.

[0015] The average particle diameter (D50) of the second lithium transition metal oxide may be 2 to 5 μm.

[0016] D of the above first lithium transition metal oxide min can be 1 μm or more.

[0017] D of the above first lithium transition metal oxide max may be less than 60 μm.

[0018] D of the above second lithium transition metal oxide min can be 1 μm or more.

[0019] D of the above second lithium transition metal oxide max may be less than 30 μm.

[0020] The above-mentioned positive electrode active material for a lithium secondary battery may have a fine particle size increase rate of 1 μm or less of 4.5% or less when pressurized at a pressure of 6 tons.

[0021] The first lithium transition metal oxide and the second lithium transition metal oxide may each be independently represented by the following chemical formula 1.

[0022] [Chemical Formula 1]

[0023] Li 1+a (Ni x Co y Mn z M w ) 1-a O2

[0024] In the above chemical formula 1, 0 <a≤0.33, 0.2≤x≤0.4, 0≤y≤0.4, 0.3≤z≤0.8, 0≤w≤0.2이고, x+y+z+w=1이고, M은 Zr, Al, B, Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, Sn, Sb, Zn, Cu, Ge, Mo, Ru, Ir 또는 이들의 조합이며,

[0025]

[0026] Another embodiment of the present invention provides a positive electrode including the positive electrode active material described above and a lithium secondary battery including the positive electrode.

[0027]

[0028] A cathode active material for a lithium secondary battery according to one embodiment of the present invention can excellently implement both electrode energy density and battery output characteristics by including a lithium transition metal oxide having a small particle size and a large particle size with a lithium excess composition in an appropriate amount, and can improve the life characteristics of the battery by improving particle strength.

[0029]

[0030] Figures 1 and 2 are SEM images of the first lithium transition metal oxide of Example 1.

[0031] Figures 3 and 4 are SEM images of the second lithium transition metal oxide of Example 1.

[0032]

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0038] 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.

[0039] 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.

[0040]

[0041] One embodiment of the present invention comprises a first lithium transition metal oxide and a second lithium transition metal oxide, wherein the first lithium transition metal oxide and the second lithium transition metal oxide each independently have a molar ratio of lithium to transition metal (Li / Me) greater than 1, an average particle diameter (D50) of the first lithium transition metal oxide is larger than an average particle diameter (D50) of the second lithium transition metal oxide, and the first lithium transition metal oxide and the second lithium transition metal oxide are included in a weight ratio of 60:40 to 80:20 (first lithium transition metal oxide: second lithium transition metal oxide), and the first lithium transition metal oxide and the second lithium transition metal oxide each independently have a BET specific surface area of ​​1.0 to 3.5 m 2 / g provides a cathode active material for a lithium secondary battery.

[0042]

[0043] According to one embodiment of the present invention, a cathode active material for a lithium secondary battery includes a first lithium transition metal oxide and a second lithium transition metal oxide, and the first lithium transition metal oxide and the second lithium transition metal oxide each independently have a molar ratio of lithium to transition metal (Li / Me) greater than 1, and more specifically, 1.1, 1.2, or 1.3 or more, and 1.6 or 1.5 or less.

[0044] That is, the cathode active material for a lithium secondary battery according to one embodiment of the present invention contains lithium in excess compared to conventional cathode materials. Accordingly, the cathode active material according to one embodiment of the present invention can have a significantly improved initial charge / discharge capacity of 240 mAh / g or more compared to conventional cathode materials. At this time, the molar ratio of lithium to the transition metal of the first lithium transition metal oxide and the second lithium transition metal oxide is independently controlled, and may be the same or different.

[0045] However, since lithium-rich oxides typically grow into crystals in the form of flakes from primary particles, even when secondary particle formation occurs, the tap density and electrode density remain low. Consequently, even if the cathode material itself exhibits high-capacity characteristics, the actual electrode energy density does not significantly improve.

[0046] In addition, since lithium-excess oxide utilizes oxygen redox reactions in addition to transition metals, oxygen gas is likely to be generated on the surface or in the bulk, which may lead to the formation of a spinel / rock salt structure with little or no reactivity, resulting in a problem of deterioration in output characteristics compared to cathode materials of a typical composition.

[0047]

[0048] Accordingly, the cathode active material for a lithium secondary battery according to one embodiment of the present invention is a bimodal cathode active material in which the average particle diameter (D50) of the first lithium transition metal oxide is larger than the average particle diameter (D50) of the second lithium transition metal oxide. Accordingly, the tap density and electrode rolling density of the active material can be improved, thereby improving the electrode energy density. In addition, the particle strength of the active material can be improved, thereby improving structural stability and life characteristics.

[0049] At this time, the positive electrode active material for a lithium secondary battery according to one embodiment of the present invention may be a mixture of a first lithium transition metal oxide and a second lithium transition metal oxide.

[0050] More specifically, the first lithium transition metal oxide and the second lithium transition metal oxide may be included in a weight ratio of 60:40 to 80:20 (first lithium transition metal oxide: second lithium transition metal oxide), and more specifically, may be included in a weight ratio of 65:35 to 75:25 (first lithium transition metal oxide: second lithium transition metal oxide). When the weight ratio of the first lithium transition metal oxide and the second lithium transition metal oxide satisfies the above range, the limit rolling density of the electrode may be improved, so that the electrode energy density may be maximized, and the particle strength may be improved, so that the life characteristics of the battery may be improved.

[0051] In this specification, the average particle diameter (D50) can be defined as the particle diameter corresponding to 50% of the volume accumulation amount in the particle diameter distribution curve. The average particle diameter (D50) can be measured using, for example, the laser diffraction method. The laser diffraction method can generally measure particle diameters from the submicron range to several millimeters, and can obtain results with high reproducibility and high resolution.

[0052] In addition, the ratio of the average particle diameter (D50) of the first lithium transition metal oxide to the average particle diameter (D50) of the second lithium transition metal oxide may be 3 to 4, and more specifically, 3.1 to 3.7. When the ratio of the average particle diameter (D50) of the first lithium transition metal oxide to the average particle diameter (D50) of the second lithium transition metal oxide satisfies the above range, the aforementioned battery performance improvement effect can be more preferably implemented.

[0053] The average particle diameter (D50) of the first lithium transition metal oxide may be 8 to 15 μm. In addition, the average particle diameter (D50) of the second lithium transition metal oxide may be 2 to 5 μm. When the average particle diameters of the first lithium transition metal oxide and the second lithium transition metal oxide satisfy the above range, the aforementioned effects of improving electrode energy density and improving particle strength can be more preferably implemented.

[0054] D of the above first lithium transition metal oxide min may be 1 μm or more, and the D of the first lithium transition metal oxide max may be less than 60 μm. D of the first lithium transition metal oxide min and D max When the above range is satisfied, the aforementioned battery performance improvement effect can be more preferably implemented. More specifically, the D of the first lithium transition metal oxide min If this is too small, there may be slurry stability problems, and also, the D of the first lithium transition metal oxide max If it is too large, there may be a short circuit problem during electrode manufacturing.

[0055] D of the above second lithium transition metal oxide min may be 1 μm or more, and the D of the second lithium transition metal oxide max can be less than 30 μm. D of the second lithium transition metal oxide min and D max When the above range is satisfied, the aforementioned battery performance improvement effect can be more preferably implemented. More specifically, the D of the second lithium transition metal oxide min If this is too small, there may be a slurry stability problem. Also, the D of the second lithium transition metal oxide max If it is too large, there may be a short circuit problem during electrode manufacturing.

[0056] Meanwhile, the first lithium transition metal oxide and the second lithium transition metal oxide each independently have an average porosity and a BET specific surface area of ​​1.0 to 3.5 m 2 / g, and more specifically 1.3 to 3.2 m 2 / g may be. When the BET specific surface area of ​​the first lithium transition metal oxide and the second lithium transition metal oxide each satisfies the above range, the aforementioned battery performance improvement effect can be more preferably implemented. More specifically, if the BET specific surface area of ​​the first lithium transition metal oxide or the second lithium transition metal oxide is too small, there may be a problem that oxygen oxidation / reduction generation is suppressed, and if the BET specific surface area of ​​the first lithium transition metal oxide or the second lithium transition metal oxide is too large, there may be a problem that a significant amount of gas is generated at high voltage.

[0057] In this specification, the BET surface area of ​​a lithium transition metal oxide can be measured using the BET method (Surface area and Porosity analyzer) (Micromeritics, ASAP2020).

[0058] Meanwhile, the first lithium transition metal oxide and the second lithium transition metal oxide may each independently have a molar ratio of nickel to the transition metal (Ni / Me) of 0.2 to 0.4, more specifically, 0.3 to 0.4. When the molar ratio of nickel to the transition metal satisfies the above range, the capacity, initial efficiency, and output characteristics of the battery can be more preferably implemented. More specifically, if the molar ratio of nickel to the transition metal is too small, the amount of oxygen oxidation / reduction reaction may increase, which may cause a problem of reduced life characteristics, and if the molar ratio of nickel to the transition metal is too large, the amount of oxygen oxidation / reduction reaction may decrease, which may deteriorate the capacity and output characteristics of the battery. At this time, the molar ratio of nickel to the transition metal of each of the first lithium transition metal oxide and the second lithium transition metal oxide is independently controlled, and may be the same or different.

[0059] In addition, the first lithium transition metal oxide and the second lithium transition metal oxide may each independently have a molar ratio of manganese to the transition metal (Mn / Me) of 0.3 to 0.8, and more specifically, 0.4 to 0.7 or 0.4 to 0.6. If the molar ratio of manganese to the transition metal is too small, the manufacturing cost may increase, the safety of the active material may decrease, and there may be problems such as a decrease in capacity, and if the molar ratio of manganese to the transition metal is too large, the life characteristics may be deteriorated due to excessive use of oxygen oxidation / reduction reactions, and there may be problems such as manganese dissolution.

[0060]

[0061] The above-mentioned positive electrode active material for a lithium secondary battery may have a fine particle increase rate of 1 μm or less in particle size when pressed at a pressure of 6 tons, and more specifically, may have a fine particle increase rate of 4.5% or less, and more specifically, 4.2% or less. In this specification, the “fine particle increase rate” is a value converted into a percentage of the increase in the particle size distribution ratio of the fine particle after pressing with a specific pressure to the particle size distribution ratio of the fine particle before pressing. In this specification, the “fine particle size distribution ratio” can be obtained by measuring the particle size distribution using a laser diffraction method. When the fine particle increase rate of the active material satisfies the above range, the electrode rolling density can be increased, thereby improving the electrode energy density, and the battery life characteristics can be improved by preventing particle breakage, etc.

[0062]

[0063] More specifically, the first lithium transition metal oxide and the second lithium transition metal oxide can each be independently represented by the following chemical formula 1.

[0064] [Chemical Formula 1]

[0065] Li 1+a (Ni x Co y Mn z M w ) 1-a O2

[0066] In the above chemical formula 1, 0 <a≤0.33, 0.2≤x≤0.4, 0≤y≤0.4, 0.3≤z≤0.8, 0≤w≤0.2이고, x+y+z+w=1이고, M은 Zr, Al, B, Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, Sn, Sb, Zn, Cu, Ge, Mo, Ru, Ir 또는 이들의 조합이다.

[0067] In the lithium transition metal oxide of the above chemical formula 1, lithium may be included in an amount corresponding to 1+a, where a is 0. <a≤0.33일 수 있다. a가 0 초과로서 리튬 함량이 과잉임에 따라 용량 특성이 향상될 수 있다. 다만, a가 너무 크면 상안정성 저하 문제가 있을 수 있다.

[0068] In the lithium transition metal oxide of the above chemical formula 1, nickel may be included in an amount corresponding to x, i.e., 0.2≤x≤0.4. More specifically, if the nickel content is too low, the capacity, initial efficiency, and output characteristics may decrease. If the nickel content is too high, the manufacturing cost may increase, and the capacity, initial efficiency, and output characteristics may decrease.

[0069] In the lithium transition metal oxide of the above chemical formula 1, cobalt may be included in an amount corresponding to y, i.e., 0≤y≤0.4. If the cobalt content is too low, it may be difficult to simultaneously achieve sufficient rate characteristics and high powder density of the active material. If the cobalt content is too high, the overall cost of the raw material may increase and the reversible capacity may decrease.

[0070] In the lithium transition metal oxide of the above chemical formula 1, manganese may be included in a content corresponding to z, i.e., 0.3≤z≤0.8. If the manganese content is too low, the production cost may increase and the stability of the active material may decrease. If the manganese content is too high, the cycle life characteristics may be reduced due to excessive use of oxygen oxidation / reduction reactions, and manganese dissolution may occur.

[0071] In the lithium transition metal oxide of the above chemical formula 1, M may be included in a content corresponding to w, that is, 0≤w≤0.2. At this time, M is a doping element, and is Zr, Al, B, Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, Sn, Sb, Zn, Cu, Ge, Mo, Ru, Ir, or a combination thereof.

[0072] Meanwhile, the first lithium transition metal oxide and the second lithium transition metal oxide may be secondary particles formed by agglomeration of a plurality of primary particles. In this case, the primary particles may include plate-shaped primary particles.

[0073]

[0074] A positive electrode active material for a lithium secondary battery according to one embodiment of the present invention can be manufactured by manufacturing a first lithium transition metal oxide and a second lithium transition metal oxide according to a conventional active material manufacturing method, and then mixing them in the weight ratio described above.

[0075] For example, the first lithium transition metal oxide and the second lithium transition metal oxide can each be independently manufactured through a step of preparing a transition metal hydroxide; and a step of forming a mixture including the transition metal hydroxide and a lithium raw material, and then calcining the mixture at a temperature of 700 to 900°C to form a lithium transition metal oxide.

[0076] In the step of preparing the above transition metal hydroxide, the transition metal hydroxide may be prepared by a coprecipitation reaction by adding a complexing agent-containing solution and a pH adjusting agent-containing solution to a transition metal-containing solution including, for example, a nickel raw material and optionally a cobalt raw material or a manganese raw material, as a positive electrode active material precursor.

[0077] The above nickel raw material is not particularly limited as long as it is used in the art for manufacturing a positive electrode active material precursor. For example, the nickel raw material may be a nickel-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, may be NiSO4, NiSO4·6H2O, Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, fatty acid nickel salt, nickel halide, or a combination thereof, but is not limited thereto.

[0078] The above cobalt raw material is not particularly limited as long as it is used in the art for manufacturing a positive electrode active material precursor. For example, the cobalt raw material may be a cobalt-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, CoSO 4, It may be, but is not limited to, CoSO4ㆍ7H2O, Co(OH)2, CoOOH, Co(OCOCH3)2ㆍ4H2O, Co(NO3)2ㆍ6H2O or a combination thereof.

[0079] The manganese raw material is not particularly limited as long as it is used in the art for manufacturing a precursor of a cathode active material. For example, the manganese raw material may be a manganese-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof, and specifically, may be a manganese salt such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylic acid salt, manganese citrate, and manganese fatty acid salt, manganese oxide such as Mn2O3, MnO2, and Mn3O4, oxyhydroxide, manganese chloride, or a combination thereof, but is not limited thereto.

[0080] In the step of forming the lithium transition metal oxide, the lithium raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and is not particularly limited as long as it can be dissolved in water. Specifically, the lithium raw material may be, but is not limited to, Li2CO3, LiNO3, LiNO2, LiOH, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or a combination thereof.

[0081] The above firing is performed at a temperature of 800 to 900°C, and more specifically, can be performed at a temperature of 830 to 870°C.

[0082] The above firing can be performed under an oxygen or air atmosphere. When firing under the above atmosphere, the local oxygen partial pressure increases, which can improve the crystallinity of the positive electrode active material.

[0083]

[0084] Another embodiment of the present invention provides a positive electrode comprising the positive electrode active material described above.

[0085] More specifically, a positive electrode according to another embodiment of the present invention may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector and including the positive electrode active material described above.

[0086] The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 μm, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesion of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0087] The above-described positive electrode active material layer may include a binder and / or a conductive material together with the above-described positive electrode active material.

[0088] 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.

[0089] And, the conductive material is used to provide conductivity to the electrode, and in the battery to be constructed, 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094]

[0095] Another embodiment of the present invention provides a lithium secondary battery including the above-described positive electrode.

[0096] More specifically, a lithium secondary battery according to another embodiment of the present invention may include a positive electrode; a negative electrode; a separator; and an electrolyte.

[0097] The above lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0098] The above two poles are the same as described above.

[0099] The above negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0100] 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.

[0101] 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.

[0102] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples thereof 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, and Al alloy; metallic oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any 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.

[0103] The above binder and conductive material may be the same as those described above for the positive electrode.

[0104]

[0105] The above separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used as a separator in lithium secondary batteries can be used without any particular restrictions. In particular, a separator having low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure.

[0106]

[0107] The above electrolyte may include, but is 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.

[0108] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0109] 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.

[0110] 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.

[0111] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexamethylphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 to 5 wt% based on the total weight of the electrolyte.

[0112]

[0113] 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).

[0114] Accordingly, another embodiment of the present invention provides a battery module including the lithium secondary battery as a unit cell and a battery pack including the same.

[0115] The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0116]

[0117] Hereinafter, embodiments of the present invention will be described in more detail through examples. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0118]

[0119] Manufacturing Example 1: Manufacturing of first lithium transition metal oxide (large particle size for Examples 1 to 3 and Comparative Examples 1 to 5)

[0120] The transition metal solution, complexing solution and NaOH were placed in a co-precipitation reactor and stirred at 50°C, and the reaction time was adjusted to obtain a solution with an average particle size (D50) of 10 μm and a composition of Li. 1.13 Ni 0.3 Mn 0.57 A first transition metal oxide of O2 was prepared. At this time, the BET specific surface area of ​​the first lithium transition metal oxide was 1.5 m 2 / g was.

[0121]

[0122] Manufacturing Example 2: Manufacturing of a second lithium transition metal oxide (small particle size for Examples 1 to 3, Comparative Examples 1 to 5, and Reference Examples 3 and 4)

[0123] The transition metal solution, complexing solution and NaOH were placed in a co-precipitation reactor and stirred at 50°C, and the reaction time was adjusted to obtain a solution with an average particle size (D50) of 3 μm and a composition of Li. 1.13 Ni 0.3 Mn 0.57 A second transition metal oxide of O2 was prepared. At this time, the BET specific surface area of ​​the second lithium transition metal oxide was 3 m 2 / g was.

[0124]

[0125] Manufacturing Example 3: Manufacturing of the first lithium transition metal oxide (large particle size for comparative example 6)

[0126] The transition metal solution, complexing solution and NaOH were placed in a co-precipitation reactor and stirred at 70°C. The reaction time was adjusted to obtain a solution with an average particle size (D50) of 10 μm and a composition of Li. 1.13 Ni 0.3 Mn 0.57 A first transition metal oxide of O2 was prepared. At this time, the BET specific surface area of ​​the first lithium transition metal oxide was 0.8 m 2 / g was.

[0127]

[0128] Manufacturing Example 4: Manufacturing of a second lithium transition metal oxide (small particle size for Comparative Example 6)

[0129] The transition metal solution, complexing solution and NaOH were placed in a co-precipitation reactor and stirred at 70°C. The reaction time was adjusted to obtain a solution with an average particle size (D50) of 3 μm and a composition of Li. 1.13 Ni 0.3 Mn 0.57 A first transition metal oxide of O2 was prepared. At this time, the BET specific surface area of ​​the second lithium transition metal oxide was 0.9 m 2 / g was.

[0130]

[0131] Manufacturing Example 5: Manufacturing of the first lithium transition metal oxide (large particle size for comparative example 7)

[0132] The transition metal solution, complexing solution and NaOH were placed in a co-precipitation reactor and stirred at 30°C, and the reaction time was adjusted to obtain a solution with an average particle size (D50) of 10 μm and a composition of Li. 1.13 Ni 0.3 Mn 0.57 A first transition metal oxide of O2 was prepared. At this time, the BET specific surface area of ​​the first lithium transition metal oxide was 3.7 m 2 / g was.

[0133]

[0134] Manufacturing Example 6: Manufacturing of a second lithium transition metal oxide (small particle size for comparative example 7)

[0135] The transition metal solution, complexing solution and NaOH were placed in a co-precipitation reactor and stirred at 30°C, and the reaction time was adjusted to obtain a solution with an average particle size (D50) of 10 μm and a composition of Li. 1.13 Ni 0.3 Mn 0.57 A second transition metal oxide of O2 was prepared. At this time, the BET specific surface area of ​​the second lithium transition metal oxide was 4.8 m 2 / g was.

[0136]

[0137] Manufacturing Example 7: Manufacturing of the first lithium transition metal oxide (large particle size for Reference Example 1)

[0138] The transition metal solution was adjusted to a Ni / Me ratio of 0.1, and the complexing solution and NaOH were placed in a co-precipitation reactor, stirred at 50°C, and the reaction time was adjusted to obtain a solution with an average particle size (D50) of 10 μm and a composition of Li. 1.13 Ni 0.1 Mn 0.77 A first transition metal oxide of O2 was prepared. At this time, the BET specific surface area of ​​the first lithium transition metal oxide was 1.8 m 2 / g was.

[0139]

[0140] Manufacturing Example 8: Manufacturing of a second lithium transition metal oxide (small particle size for Reference Example 1)

[0141] The transition metal solution was adjusted to a Ni / Me ratio of 0.1, and the complexing solution and NaOH were placed in a co-precipitation reactor, stirred at 50°C, and the reaction time was adjusted to obtain a solution with an average particle size (D50) of 3 μm and a composition of Li. 1.13 Ni 0.1 Mn 0.77 A second transition metal oxide of O2 was prepared. At this time, the BET specific surface area of ​​the second lithium transition metal oxide was 2.9 m 2 / g was.

[0142]

[0143] Manufacturing Example 9: Manufacturing of the first lithium transition metal oxide (large particle size for Reference Example 2)

[0144] The transition metal solution was adjusted to a Ni / Me ratio of 0.5, and the complexing solution and NaOH were placed in a co-precipitation reactor, stirred at 50°C, and the reaction time was adjusted to obtain a solution with an average particle size (D50) of 10 μm and a composition of Li. 1.13 Ni 0.43 Mn 0.44 A first transition metal oxide of O2 was prepared. At this time, the BET specific surface area of ​​the first lithium transition metal oxide was 1.3 m 2 / g was.

[0145]

[0146] Manufacturing Example 10: Manufacturing of a second lithium transition metal oxide (small particle size for Reference Example 2)

[0147] The transition metal solution was adjusted to a Ni / Me ratio of 0.5, and the complexing solution and NaOH were placed in a co-precipitation reactor, stirred at 50°C, and the reaction time was adjusted to obtain a solution with an average particle size (D50) of 3 μm and a composition of Li. 1.13 Ni 0.43 Mn 0.44 A second transition metal oxide of O2 was prepared. At this time, the BET specific surface area of ​​the second lithium transition metal oxide was 3.2 m 2 / g was.

[0148]

[0149] Manufacturing Example 11: Manufacturing of the first lithium transition metal oxide (large particle size for Reference Example 3)

[0150] The transition metal solution, complexing solution and NaOH were placed in a co-precipitation reactor and stirred at 50°C, and the reaction time was adjusted to obtain a solution with an average particle size (D50) of 7.5 μm and a composition of Li. 1.13 Ni 0.3 Mn 0.57 A first transition metal oxide of O2 was prepared. At this time, the BET specific surface area of ​​the first lithium transition metal oxide was 2.3 m 2 / g was.

[0151]

[0152] Manufacturing Example 12: Manufacturing of a first lithium transition metal oxide (large particle size for Reference Example 4)

[0153] The transition metal solution, complexing solution and NaOH were placed in a co-precipitation reactor and stirred at 50°C. The reaction time was adjusted to obtain a solution with an average particle size (D50) of 13.5 μm and a composition of Li. 1.13 Ni 0.3 Mn 0.57 A first transition metal oxide of O2 was prepared. At this time, the BET specific surface area of ​​the first lithium transition metal oxide was 1.2 m 2 / g was.

[0154]

[0155] Examples, Comparative Examples, and Reference Examples

[0156] (1) Manufacturing of positive electrode active material

[0157] By using the first lithium transition metal oxide or the second lithium transition metal oxide as the manufacturing agent 1 to 12, a positive electrode active material was manufactured in which the composition, particle size, weight ratio, particle size ratio, and average porosity of the first lithium transition metal oxide with a large particle size and the second lithium transition metal oxide with a small particle size were controlled as shown in Table 1 below.

[0158] (2) Lithium secondary battery manufacturing

[0159] The slurry for manufacturing the electrode plate was mixed with the above-mentioned positive electrode active material: conductive material (acetylene black): binder (PVDF, KF1120) = 92.5:3.5:4 wt%, and additional NMP (N-Methyl-2-pyrrolidone) was added for solid content and slurry viscosity. The manufactured slurry was coated on Al foil using a doctor blade, and after drying, it was rolled to manufacture the electrode plate. At this time, the electrode loading amount was 15-16 mg / cm 2 and the composite density of the electrode was 2.9 g / cm 3 That was it.

[0160] The electrolyte used was 1M LiPF6 in EC:DMC:EMC = 3:4:3 (vol%) + VC 3.0 wt%, and a coin cell was manufactured using a PP separator and a lithium negative electrode (300 μm).

[0161]

[0162] First lithium transition metal oxide composition First lithium transition metal oxide average particle size (D50, μm) First lithium transition metal oxide BET specific surface area (m 2 / g) Second lithium transition metal oxide composition Second lithium transition metal oxide average particle size (D50, μm) Second lithium transition metal oxide BET specific surface area (m 2 / g) Example 1Li 1.13 Ni 0.3 Mn 0.57 O2101.5Li 1.13 Ni 0.3 Mn 0.57 O233 Example 2Li 1.13 Ni 0.3 Mn 0.57 O2101.5Li 1.13 Ni 0.3 Mn 0.57 O233 Example 3Li 1.13 Ni 0.3 Mn 0.57 O2101.5Li 1.13 Ni 0.3 Mn 0.57 O233 Comparative Example 1Li 1.13 Ni 0.3 Mn0.57 O2101.5Li 1.13 Ni 0.3 Mn 0.57 O233 Comparative Example 2Li 1.13 Ni 0.3 Mn 0.57 O2101.5Li 1.13 Ni 0.3 Mn 0.57 O233 Comparative Example 3Li 1.13 Ni 0.3 Mn 0.57 O2101.5Li 1.13 Ni 0.3 Mn 0.57 O233 Comparative Example 4Li 1.13 Ni 0.3 Mn 0.57 O2101.5Li 1.13 Ni 0.3 Mn 0.57 O233 Comparative Example 5Li 1.13 Ni 0.3 Mn 0.57 O2101.5Li 1.13 Ni 0.3 Mn 0.57 O233 Comparative Example 6Li 1.13 Ni 0.3 Mn 0.57 O2100.8Li 1.13 Ni 0.3 Mn 0.57 O230.9 Comparative Example 7Li 1.13 Ni 0.3 Mn 0.57 O2103.7Li 1.13 Ni 0.3 Mn 0.57 O234.8 Reference Example 1Li 1.13 Ni 0.1 Mn 0.77 O2101.8Li 1.13 Ni 0.1 Mn 0.77 O232.9 Reference Example 2Li 1.13 Ni 0.43 Mn 0.44 O2101.3Li 1.13 Ni 0.43 Mn 0.44 O233.2 Reference Example 3Li 1.13 Ni 0.3 Mn 0.57 O27.52.3Li 1.13 Ni0.3 Mn 0.57 O233 Reference Example 4Li 1.13 Ni 0.3 Mn 0.57 O213.51.2Li 1.13 Ni 0.3 Mn 0.57 O233

[0163] Large particle size: Small particle size weight ratio Large particle size to small particle size particle size ratio Ni / Me Non-example 180:203.330.35Example 270:303.330.35Example 360:403.330.35Comparative example 1100:03.330.35Comparative example 285:153.330.35Comparative example 350:503.330.35Comparative example 425:753.330.35Comparative example 50:1003.330.35Comparative example 670:303.330.35Comparative example 770:303.330.35Reference example 170:303.330.1Reference example 270:303.330.5Reference example 370:302.50.35 Reference example 470:304.50.35

[0164]

[0165] Experimental Example 1: SEM image of lithium transition metal oxide

[0166] SEM (scanning electron microscope) images of the first lithium transition metal oxide and the second lithium transition metal oxide of Example 1 were observed, and are shown in FIGS. 1 to 2 (first lithium transition metal oxide) and FIGS. 3 to 4 (second lithium transition metal oxide).

[0167] Referring to FIGS. 1 to 4, it was confirmed that the first and second lithium transition metal oxides of Example 1 were secondary particles formed by agglomeration of a plurality of primary particles, and that the primary particles had a plate-like shape and the secondary particles had a spherical shape.

[0168]

[0169] Experimental Example 2: Evaluation of the properties of positive electrode active materials

[0170] The properties of the positive electrode active materials manufactured according to Examples 1 to 3, Comparative Example 1, Comparative Example 5, Reference Example 1, and Reference Example 2 were evaluated, and the results are shown in Table 3 below. The specific experimental methods are as follows.

[0171] (1) Average particle size (D50) evaluation

[0172] For the active material powder, the particle size corresponding to 50% of the cumulative volume was measured using the laser diffraction method.

[0173] (2) Evaluation of differential increase rate (6 ton pressurization)

[0174] After applying pressure to 3 g of each active material contained in the mold using a hydraulic press, the fine particle increase rate of less than 1 μm was evaluated.

[0175] Average particle size (D50, μm) Differential increase rate (%) Example 17.97 4.1 Example 27.824 Example 37.764 Comparative example 19.655 Comparative example 53.45 4.8 Reference example 17.84 4.7 Reference example 28.19 5.6

[0176] Referring to Table 3, it was confirmed that the differential increase rate characteristics were very good in the case of examples in which the weight ratio of the first lithium transition metal oxide and the second lithium transition metal oxide, the BET specific surface area, the nickel content, etc. were appropriately controlled.

[0177] On the other hand, in the comparative examples and reference examples where the weight ratio of the first lithium transition metal oxide and the second lithium transition metal oxide or the nickel content was outside the appropriate range, it was confirmed that the differential increase rate characteristics were significantly deteriorated compared to the examples.

[0178]

[0179] Experimental Example 3: Evaluation of Battery Electrochemical Characteristics

[0180] The electrochemical characteristics of lithium secondary batteries manufactured according to Examples, Comparative Examples, and Reference Examples were evaluated, and the results are shown in Table 4 below. The specific experimental methods are as follows.

[0181] (1) Evaluation of initial discharge capacity and initial efficiency

[0182] After fabricating half-cells of lithium secondary batteries, they were aged at 25°C for 24 hours and then subjected to charge-discharge tests. To evaluate the initial capacity, 200 mAh / g was used as the reference capacity, and the cells were charged to 4.65 V at 45°C with a constant current of 0.1 C. After switching to constant voltage, the cells were charged until the end current reached 0.05 C. After a 10-minute rest period, the cells were discharged at a constant current of 0.1 C with a reference capacity of 200 mAh / g until the cells reached 2.5 V.

[0183] (2) Evaluation of limit rolling density

[0184] After setting the maximum pressure that the rolling mill can apply, rolling was repeated 3-5 times to evaluate the limit rolling density at which the thickness no longer decreases.

[0185] (3) Electrode energy density evaluation

[0186] The energy density of a secondary battery was evaluated based on the design of a secondary battery using a graphite cathode as the counter electrode.

[0187] (4) High-power characteristic evaluation (0.33C / 0.1C)

[0188] High-power characteristics were evaluated by dividing the initial discharge capacity at 0.33C by the initial discharge capacity at 0.1C and converting it into a percentage (%).

[0189] (5) Comprehensive performance index evaluation (corresponding to the Figure of merit in the invention description)

[0190] After setting the comprehensive performance index of Example 2 to 100 by making the square of the energy density and the weight of the output characteristics 1:1, the relative values ​​of other examples and comparative examples were derived.

[0191]

[0192] Discharge capacity (mAh / g) Initial efficiency (%) Limit rolling density (g / cc) Electrode energy density (Wh / L) Output characteristics (%) Comprehensive performance index Example 1 266.29 1.33.0 36 22.79 3.109 9.8 Example 2 268.59 1.53.0 46 22.99 3.22 100 Example 3 267.59 1.43.0 26 21.29 2.95 99.4 Comparative example 1 265.29 1.12.9 16 109 2.96 97.7 Comparative example 2 266.29 1.52.97 6 16.59 2.92 98.6 Comparative example 3 269.69 1.72.96 14.89 2.96 98.4 Comparative example 4274.591.92.85604.393.2897.1Comparative example 5279.791.92.65583.194.3294.7Comparative example 6262.493.73.05608.389.496.2Comparative example 7277.489.92.77598.395.396.1Reference example 1254.586.73.01574.390.8689.9Reference example 2251.288.43.01581.291.1291.2Reference example 3278.691.32.81596.693.395.3Reference example 4264.393.02.86588.386.692.3

[0193]

[0194] Referring to Table 4, in the case of an example in which the weight ratio of the first lithium transition metal oxide and the second lithium transition metal oxide, the BET specific surface area, the particle size ratio of the first lithium metal oxide and the second lithium metal oxide, the nickel content, etc. were appropriately adjusted to the range according to the present invention, it was confirmed that the discharge capacity, initial efficiency, limit rolling density, battery energy density, output characteristics, and comprehensive performance index were all very good overall.

[0195] On the other hand, in Comparative Examples 1 to 5 where the weight ratio of the first lithium transition metal oxide and the second lithium transition metal oxide was outside the appropriate range, the initial discharge capacity or initial efficiency of the positive electrode material itself was at a similar level to that of the example, but it was confirmed that the limit rolling density was reduced, and thus the battery energy density was deteriorated.

[0196] In addition, in the case of Comparative Examples 6 and 7 where the BET specific surface area of ​​the first and second lithium transition metal oxides was too small or too large, it was confirmed that the output characteristics were significantly reduced or the energy density was low.

[0197] In addition, for Reference Examples 1 and 2, where the nickel content was too low or too high, the limit rolling density was almost similar to that of the Example, but it was confirmed that the discharge capacity and initial efficiency were significantly reduced, and accordingly, it was confirmed that the electrode energy density was deteriorated. In addition, it was confirmed that the output characteristics were deteriorated.

[0198] In addition, in the case of Reference Examples 3 and 4 where the ratio of the large particle size to the small particle size was too small or too large, it was confirmed that the energy density and output characteristics were reduced.

[0199]

[0200] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

[0201] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Containing a first lithium transition metal oxide and a second lithium transition metal oxide, The first lithium transition metal oxide and the second lithium transition metal oxide each independently have a molar ratio of lithium to transition metal (Li / Me) greater than 1, The average particle diameter (D50) of the first lithium transition metal oxide is larger than the average particle diameter (D50) of the second lithium transition metal oxide, The first lithium transition metal oxide and the second lithium transition metal oxide are included in a weight ratio of 60:40 to 80:20 (first lithium transition metal oxide: second lithium transition metal oxide), The first lithium transition metal oxide and the second lithium transition metal oxide each independently have a BET surface area of ​​1.0 to 3.5 m 2 / g of a cathode active material for a lithium secondary battery.

2. In paragraph 1, A cathode active material for a lithium secondary battery, wherein a ratio of the average particle diameter (D50) of the first lithium transition metal oxide to the average particle diameter (D50) of the second lithium transition metal oxide is 3 to 4.

3. In paragraph 1, The first lithium transition metal oxide and the second lithium transition metal oxide are each independently a positive electrode active material for a lithium secondary battery, wherein the molar ratio of nickel to transition metal (Ni / Me) is 0.2 to 0.

4.

4. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the first lithium transition metal oxide and the second lithium transition metal oxide are secondary particles formed by agglomeration of a plurality of primary particles.

5. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the average particle diameter (D50) of the first lithium transition metal oxide is 8 to 15 μm.

6. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the average particle diameter (D50) of the second lithium transition metal oxide is 2 to 5 μm.

7. In paragraph 1, D of the above first lithium transition metal oxide min A cathode active material for a lithium secondary battery having a particle size of 1 μm or more.

8. In paragraph 1, D of the first lithium transition metal oxide max A cathode active material for a lithium secondary battery having a particle size of 60 μm or less.

9. In paragraph 1, D of the above second lithium transition metal oxide min A cathode active material for a lithium secondary battery having a particle size of 1 μm or more.

10. In paragraph 1, D of the above second lithium transition metal oxide max A cathode active material for a lithium secondary battery having a particle size of 30 μm or less.

11. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the increase rate of fine particles having a particle size of 1 μm or less is 4.5% or less when pressurized at a pressure of 6 tons.

12. In paragraph 1, The above first lithium transition metal oxide and the above second lithium transition metal oxide are each independently represented by the following chemical formula 1 as a positive electrode active material for a lithium secondary battery: [Chemical Formula 1] Li 1+a (Ni x Co y Mr z M w ) 1-a O2 In the above chemical formula 1, 0 <a≤0.33, 0.2≤x≤0.4, 0≤y≤0.4, 0.3≤z≤0.8, 0≤w≤0.2이고, x+y+z+w=1이고, M은 Zr, Al, B, Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, Sn, Sb, Zn, Cu, Ge, Mo, Ru, Ir 또는 이들의 조합이다.

13. A positive electrode comprising the positive electrode active material of any one of claims 1 to 12.

14. A lithium secondary battery comprising the positive electrode of clause 13.

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