Cathode active material for lithium secondary battery, manufacturing method of same, 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 lithium transition metal oxide in the form of a single particle that contains 50-70 mol% of nickel on the basis of the total number of moles of transition metals, and satisfying the following expression 1: [Expression 1] Dv50 / Dn50 ≥ 3.0 In expression 1, Dv50 is a volume-based average particle diameter of the cathode active material, and Dn50 is a number-based average particle diameter of the cathode active material.

Description

Positive electrode active material for lithium secondary batteries, method for producing the same, and lithium secondary batteries comprising the same

[0001] The present invention relates to a positive electrode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery comprising the same, and more specifically, to a method for producing a positive electrode active material for a lithium secondary battery in the form of a single particle, a positive electrode active material produced therefrom, and a lithium secondary battery comprising the same.

[0002]

[0003] Lithium secondary batteries produce electrical energy through oxidation and reduction reactions when lithium ions are inserted / deintercalated from the positive and negative electrodes, while an organic electrolyte or polymer electrolyte is charged between the positive and negative electrodes, which are made of active materials capable of intercalating and deintercalating lithium ions.

[0004] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMn2O4, etc.), and lithium iron phosphate compound (LiFePO4) have been used as cathode active materials for lithium secondary batteries. Among these, lithium cobalt oxide (LiCoO2) is widely used due to its high operating voltage and excellent capacity characteristics, and is applied as a cathode active material for high voltage. However, due to the rising price of cobalt (Co) and unstable supply, it is difficult to use it in large quantities as a power source in fields such as electric vehicles, and the need for the development of a cathode active material that can replace it has arisen.

[0005] Accordingly, nickel-cobalt-manganese lithium composite transition metal oxides (hereinafter simply referred to as 'NCM-based lithium composite transition metal oxides') in which some of the cobalt (Co) is replaced with nickel (Ni) and manganese (Mn) have been developed. However, the NCM-based lithium composite transition metal oxides developed previously are generally in the form of secondary particles in which primary particles are aggregated, and have a large specific surface area, low particle strength, and a high content of lithium byproducts, which causes a lot of gas generation during cell operation, and thus, there were problems with reduced lifespan and stability.

[0006] Accordingly, development is underway on a cathode active material in the form of a single particle rather than the existing secondary particle form.

[0007]

[0008] Accordingly, one object of the present invention is to provide a lithium secondary battery cathode active material having improved capacity and high-temperature lifespan characteristics as a lithium transition metal oxide in the form of a single particle, a method for producing the same, and a lithium secondary battery including the same.

[0009]

[0010] One embodiment of the present invention provides a cathode active material for a lithium secondary battery, comprising a lithium transition metal oxide in the form of single particles containing 50 to 70 mol% of nickel based on the total mole number of transition metals, and satisfying the following formula 1.

[0011] [Formula 1]

[0012] Dv50 / Dn50 ≥ 3.0

[0013] In the above equation 1, Dv50 is the average particle diameter based on the volume of lithium transition metal oxide, and Dn50 is the average particle diameter based on the number of lithium transition metal oxide.

[0014]

[0015] The above positive electrode active material for a lithium secondary battery can satisfy the following equation 2.

[0016] [Formula 2]

[0017] Dv50 - Dn50 ≥ 2.5 nm

[0018] In the above equation 2, Dv50 is the average particle size based on the volume of lithium transition metal oxide, and Dn50 is the average particle size based on the number of lithium transition metal oxide.

[0019] The average particle diameter (Dv50) based on volume of the lithium transition metal oxide may be 3.5 to 4.5 μm.

[0020] The average particle diameter (Dn50) based on the number of the above lithium transition metal oxides may be 1 μm or less.

[0021] The crystallite size of the above lithium transition metal oxide may be 190 nm or less.

[0022] The ratio of the c-axis lattice constant to the a-axis lattice constant of the above lithium transition metal oxide (Lc / La) may be 4.955 or more.

[0023] The c-axis lattice constant (Lc) of the above lithium transition metal oxide may be 14.2472 nm or more.

[0024] The a-axis lattice constant (La) of the above lithium transition metal oxide may be 2.8752 nm or less.

[0025] The above lithium transition metal oxide can be represented by the following chemical formula 1.

[0026] [Chemical Formula 1]

[0027] Li a [Ni x Co y Mn z M w ]O2

[0028] In the above chemical formula 1, 0.8≤a≤1.2, 0.5≤x≤0.7, 0≤y≤0.2, 0≤z≤0.4, 0≤w≤0.2, x+y+z+w=1, and M is Zr, Al, B, Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

[0029]

[0030] Another embodiment of the present invention provides a method for producing a cathode active material for a lithium secondary battery, comprising the steps of: preparing a transition metal precursor containing 50 to 70 mol% of nickel based on the total mole number of transition metals; mixing the transition metal precursor and a lithium raw material, and then performing a first calcination and a second calcination to form a lithium transition metal oxide; and performing a first pulverization and a second pulverization of the lithium transition metal oxide to form a lithium transition metal oxide in the form of single particles, wherein the second sintering is performed in an oxygen (O2) atmosphere.

[0031] The above secondary disintegration can be performed so that the volume-based average particle diameter (Dv50) of the lithium transition metal oxide becomes 3.5 to 4.5 μm.

[0032] The above primary disintegration can be performed at a stirring speed of 15,000 to 20,000 rpm.

[0033] The above secondary crushing can be performed at a crushing pressure of 3.5 to 4.5 bar.

[0034] The above primary firing can be performed in an air atmosphere.

[0035] The above first firing and the above second firing can each be independently performed at a temperature of 900 to 960°C.

[0036]

[0037] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery comprising the positive electrode active material described above.

[0038] Another embodiment of the present invention provides a lithium secondary battery including the positive electrode for the lithium secondary battery.

[0039]

[0040] According to one embodiment of the present invention, a positive electrode active material for a lithium secondary battery is in the form of a single particle, and by appropriately controlling the ratio of the average particle diameter based on volume to the average particle diameter based on number, not only can the capacity and electrode energy density be improved, but also the high-temperature life characteristics can be improved.

[0041]

[0042] Figure 1 is a SEM image of a positive electrode active material manufactured according to Example 1.

[0043] Figure 2 is an SEM image of a positive electrode active material manufactured according to Comparative Example 1.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0049] 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.

[0050] 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.

[0051]

[0052] 1. Positive active material

[0053] According to one embodiment of the present invention, a cathode active material for a lithium secondary battery comprises a lithium transition metal oxide in the form of a single particle. Compared to conventional secondary particles, the single particle active material has a smaller specific surface area, which reduces the amount of gas generated by side reactions with the electrolyte. Furthermore, the single particle active material has a higher particle strength, which suppresses particle breakage during rolling, and reduces the occurrence of cracks during repeated charging and discharging. Accordingly, the single particle active material has superior lifespan and safety compared to secondary particles, and has the advantage of being able to realize a high energy density of the electrode.

[0054] In this specification, the term “single particle” is used to distinguish it from the secondary particle type positive electrode active material particle formed by the agglomeration of tens to hundreds of primary particles, which has been commonly used in the past, and is a concept that includes a single particle composed of one primary particle and an aggregate particle of 30 or fewer primary particles. In addition, “secondary particle” means an aggregate, i.e., a secondary structure, formed by the physical or chemical bonding between tens to hundreds of primary particles without an intentional agglomeration or assembly process for the primary particles.

[0055] Meanwhile, the lithium transition metal oxide according to one embodiment of the present invention contains 50 to 70 mol% of nickel based on the total mole number of transition metals. Conventional NCM (nickel-cobalt-manganese ternary) cathode active materials have attempted to implement high capacity of batteries by increasing the nickel content, but if the nickel content is too high, there may be a thermal propagation issue, i.e., a thermal safety problem, and the high nickel price may increase the manufacturing cost. Therefore, the lithium transition metal oxide according to the present invention has the nickel content adjusted to the above range in order to secure appropriate capacity and thermal safety characteristics while implementing economic feasibility.

[0056] However, in order to manufacture lithium transition metal oxide in the form of single particles, the sintering temperature is higher than that in the case of secondary particles, so there is a problem that the capacity characteristics are inherently lower than those of secondary particles.

[0057] The inventors of the present invention have conducted repeated research to address the above-mentioned capacity characteristic degradation problem and have discovered that capacity characteristics can be improved by appropriately adjusting the ratio of the volume average particle diameter (Dv50) to the number average particle diameter (Dn50) of lithium transition metal oxides. Furthermore, they have also discovered that high-temperature life characteristics are simultaneously enhanced. This will be described in more detail below.

[0058]

[0059] A positive electrode active material for a lithium secondary battery according to one embodiment of the present invention satisfies the following equation 1.

[0060] [Formula 1]

[0061] Dv50 / Dn50 ≥ 3.0

[0062] In the above equation 1, Dv50 is the volume-based average particle diameter of the lithium transition metal oxide, and Dn50 is the number-based average particle diameter of the lithium transition metal oxide. More specifically, the volume-based average particle diameter (Dv50) can be defined as a particle diameter corresponding to 50% of the volume accumulation amount in the particle diameter distribution curve of the particles. The number-based average particle diameter (Dn50) can be defined as a particle diameter corresponding to 50% of the number accumulation amount in the particle diameter distribution curve of the particles. The volume-based average particle diameter (Dv50) and the number-based average particle diameter (Dn50) can be measured using, for example, a laser diffraction method.

[0063] The Dv50 / Dn50 value of the above lithium transition metal oxide may be, more specifically, 3.5, 4.0 or 4.3 or more, and 5.0 or 4.8 or less.

[0064] In addition, the positive electrode active material for the lithium secondary battery can further satisfy the following equation 2.

[0065] [Formula 2]

[0066] Dv50 - Dn50 ≥ 2.5 nm

[0067] In the above equation 2, Dv50 is the average particle size based on the volume of lithium transition metal oxide, and Dn50 is the average particle size based on the number of lithium transition metal oxide.

[0068] The Dv50 - Dn50 value of the above lithium transition metal oxide may be, more specifically, 2.7 nm or 3.0 nm or more, and 3.5 nm or 3.2 nm or less.

[0069] By satisfying Equation 1 or Equation 2, the positive electrode active material for a lithium secondary battery according to one embodiment of the present invention can not only improve capacity and electrode energy density, but also improve high-temperature life characteristics.

[0070] More specifically, the fact that the positive electrode active material satisfies Equation 1 or Equation 2 may mean that the number of small-diameter particles is relatively greater than the number of medium-diameter or large-diameter particles in the overall particle size distribution. Accordingly, when actually implementing the positive electrode, the small-diameter particles can exist between the medium-diameter or large-diameter particles, which may improve the electrode rolling density. In addition, as the pores within the electrode are reduced, the diffusion path length of lithium ions is reduced, which may improve the diffusion rate of lithium ions. As a result, the electrode energy density, capacity, and initial efficiency can be excellently implemented.

[0071] Furthermore, the inventors of the present invention confirmed that when the positive electrode active material satisfies Equation 1 or Equation 2, high-temperature life characteristics are improved in addition to the electrochemical characteristics. This is believed to be due to the reduction of pores within the electrode, thereby increasing the diffusion rate of lithium ions, thereby promoting the electrochemical reaction and reducing the irreversible characteristics.

[0072] However, if the Dv50 / Dn50 value or Dv50 - Dn50 value is too large, it means that the number of small-sized particles is too large, which may cause the problem of increased gas generation due to side reactions by excessively increasing the surface area of ​​the active material in contact with the electrolyte.

[0073]

[0074] More specifically, the volume-based average particle diameter (Dv50) of the lithium transition metal oxide may be 3.5 to 4.5 μm. If the volume-based average particle diameter (Dv50) is too small, the electrode rolling density may decrease, which may deteriorate the electrode energy density. If the volume-based average particle diameter (Dn50) is too large, the crystal grain and particle size may become too large, which may cause the lithium ion migration length to become too long, which may deteriorate the capacity and output characteristics. In addition, as described in the manufacturing method described below, the particle size distribution of the lithium transition metal oxide may be ultimately determined by controlling the process conditions of the disintegration step. When the volume-based average particle diameter (Dv50) is controlled within the above range during the disintegration process, the properties of the aforementioned Equations 1 and 2 can be more easily satisfied.

[0075] In addition, the average particle diameter (Dn50) based on the number of lithium transition metal oxides may be 1 μm or less. When the average particle diameter (Dn50) based on the number of lithium transition metal oxides satisfies the above range, not only can the electrode energy density and capacity be improved, but also the high-temperature life characteristics can be improved.

[0076]

[0077] Meanwhile, the crystallite size of the lithium transition metal oxide may be 190 nm or less, and more specifically, 185 nm or less.

[0078] In this specification, “crystal grain” means a distinct region in which atoms in a primary particle form a lattice structure with a certain direction, and “crystal grain size” can be estimated using peak broadening of XRD data and can be quantitatively calculated using the Scherr equation.

[0079] In general, as the crystal grain size of a lithium transition metal oxide increases, the cycle life characteristics improve, but the capacity characteristics deteriorate. On the other hand, the cathode active material according to the present invention can have improved high-temperature cycle characteristics even when the crystal grain size is reduced in this way. Consequently, when the crystal grain size of the lithium transition metal oxide satisfies the above range, not only the effect of improving the capacity characteristics due to the reduction in the crystal grain size but also the effect of improving the high-temperature cycle characteristics can be realized simultaneously. This is believed to be because, as described below, the c-axis lattice constant of the lithium transition metal oxide according to the present invention is sufficiently large to facilitate the intercalation of lithium ions and reduce the irreversible reaction.

[0080]

[0081] Meanwhile, the ratio of the c-axis lattice constant to the a-axis lattice constant of the lithium transition metal oxide (Lc / La) may be 4.955 or more, and more specifically, 4.9553 or more. The ratio of the c-axis lattice constant to the a-axis lattice constant of the lithium transition metal oxide (Lc / La) satisfying the above range may mean that the c-axis lattice constant is sufficiently larger than the a-axis lattice constant. Accordingly, a layered structure within the lithium transition metal oxide may be well formed to promote the intercalation of lithium ions. As a result, the capacity and initial efficiency of the battery may be improved.

[0082] More specifically, the c-axis lattice constant (Lc) of the lithium transition metal oxide may be 14.2472 nm or more. In addition, the a-axis lattice constant (La) of the lithium transition metal oxide may be 2.8752 nm or less.

[0083]

[0084] The above lithium transition metal oxide can be more specifically represented by the following chemical formula 1.

[0085] [Chemical Formula 1]

[0086] Li a [Ni x Co y Mn z M w ]O2

[0087] In the above chemical formula 1, 0.8≤a≤1.2, 0.5≤x≤0.7, 0≤y≤0.2, 0≤z≤0.4, 0≤w≤0.2, x+y+z+w=1, and M is Zr, Al, B, Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

[0088] In the lithium transition metal oxide of the above chemical formula 1, lithium may be included in a content corresponding to a, that is, 0.8≤a≤1.2. If a is too small, the capacity may be reduced, and if a is too large, the strength of the sintered positive electrode active material may be increased, making pulverization difficult, and the amount of gas generated may increase due to an increase in lithium byproducts. Considering the effect of improving the capacity characteristics of the positive electrode active material according to the control of the lithium content and the sinterability balance during the production of the active material, the lithium may be included in a content of 0.9≤a≤1.1 more preferably.

[0089] In the lithium transition metal oxide of the above chemical formula 1, nickel may be included in an amount corresponding to x, i.e., 0.5≤x≤0.7. If the nickel content is too low, it may be difficult to achieve high capacity of the battery, and if the nickel content is too high, the battery life and thermal safety may be reduced due to a decrease in the structural stability of the active material, and the manufacturing cost may increase.

[0090] 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≤0.2 or 0.05≤y≤0.2. 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.

[0091] 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≤z≤0.4 or 0.1≤z≤0.4. If the manganese content is too low, the production cost may increase and the stability of the active material may deteriorate. If the manganese content is too high, the capacity and output characteristics of the battery may deteriorate.

[0092] 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 may be Zr, Al, B, Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

[0093]

[0094] 2. Method for manufacturing positive electrode active material

[0095] Another embodiment of the present invention provides a method for producing a cathode active material for a lithium secondary battery, comprising the steps of: preparing a transition metal precursor containing 50 to 70 mol% of nickel based on the total mole number of transition metals; mixing the transition metal precursor and a lithium raw material, and then performing a first calcination and a second calcination to form a lithium transition metal oxide; and performing a first disintegration and a second disintegration of the lithium transition metal oxide to form a lithium transition metal oxide in the form of single particles, wherein the second disintegration is performed in an oxygen (O2) atmosphere.

[0096] Hereinafter, a method for manufacturing a positive electrode active material for a lithium secondary battery according to another embodiment of the present invention will be described step by step.

[0097]

[0098] First, a transition metal precursor containing 50 to 70 mol% of nickel based on the total mole number of transition metals is prepared.

[0099] The above transition metal precursor may be a transition metal hydroxide.

[0100] The above transition metal hydroxide may be manufactured by, for example, adding a complexing agent-containing solution and a pH adjusting agent-containing solution to a transition metal-containing solution including a nickel raw material and optionally a cobalt raw material or a manganese raw material, and performing a co-precipitation reaction.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] The above transition metal-containing solution may be prepared by adding a nickel raw material and optionally a cobalt raw material or a manganese raw material to a solvent, specifically, water, or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water.

[0105] The above complexing agent-containing solution performs the function of forming a complex, and may include, but is not limited to, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3 or a combination thereof as the complexing agent. Meanwhile, the complexing agent-containing solution may be used in the form of an aqueous solution, and at this time, water or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water may be used as the solvent.

[0106] The above pH adjusting agent-containing solution acts as a precipitant or pH adjusting agent, and may include an alkaline compound such as a hydroxide of an alkali metal or alkaline earth metal, such as NaOH, KOH, or Ca(OH)2, a hydrate thereof, or a combination thereof. Meanwhile, the pH adjusting agent-containing solution may also be used in the form of an aqueous solution, and at this time, water or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water may be used as the solvent. At this time, the pH adjusting agent-containing solution may be added in an amount such that the pH of the reaction solution becomes 11 to 13.

[0107] The above coprecipitation reaction can be performed under an inert atmosphere such as nitrogen or argon, can be performed at a temperature of 30 to 70°C, and can be performed at a pH of 11 to 13.

[0108] Through the above process, nickel-cobalt-manganese (doped element) hydroxide particles are generated and precipitated within the reaction solution. The precipitated precursor particles can be separated, washed, and dried using conventional methods to obtain the precursor. The precursor may be a secondary particle formed by the agglomeration of primary particles.

[0109] At this time, the molar ratio of nickel, cobalt, and manganese in the precursor can be controlled by controlling the concentration of nickel raw material, cobalt raw material, and manganese raw material.

[0110] Accordingly, the content of nickel in the transition metal precursor may be 50 to 70 mol% based on the total mole number of transition metals. The technical significance of controlling the content of nickel in the transition metal precursor is as described above and therefore is omitted.

[0111]

[0112] Next, the above transition metal precursor and lithium raw material are mixed, and then subjected to primary and secondary calcination to form a lithium transition metal oxide.

[0113] In the past, the formation of lithium transition metal oxides in the form of single particles was achieved by only performing a primary calcination at high temperatures for a long time. However, this method had problems such as a decrease in the electrochemical properties of the active material due to nickel cation mixing and the formation of rock salt impurities caused by over-calcination. On the other hand, the manufacturing method according to the present invention can prevent the above problems by performing the calcination in two stages, thereby improving the particle strength of the active material and increasing the production volume.

[0114] At this time, the atmosphere during the first firing is not particularly limited. For example, it can be performed in an air or oxygen (O2) atmosphere, but more specifically, it can be performed in an air atmosphere. Since the layered crystal structure of a high-nickel cathode active material does not form well when performed in an air atmosphere, a significant deterioration in electrochemical characteristics occurs, so it is generally performed in an oxygen atmosphere. On the other hand, when the nickel content is relatively low as in the present invention, even if the firing is performed in an air atmosphere, a significant deterioration in electrochemical characteristics does not occur, and the process cost can be reduced.

[0115] In particular, the secondary firing is performed in an oxygen (O2) atmosphere. More specifically, the oxygen atmosphere may have an oxygen partial pressure of 90%, 95%, 97%, or 99% or higher. Through the secondary firing in an oxygen atmosphere, the ratio of particles with a small particle size, that is, fine particles, can be appropriately increased during the disintegration process described later, so that the obtained positive electrode active material can satisfy the properties of the aforementioned Equation 1, etc. This is because the particle strength of the lithium transition metal oxide obtained when the secondary firing is performed in an oxygen atmosphere is weaker than when the secondary firing is performed in an air atmosphere. In particular, unlike the prior art that arbitrarily increased the particle strength of the lithium transition metal oxide in order to improve the life characteristics, the present invention forms a lithium transition metal oxide having a somewhat weak particle strength and then appropriately forms the ratio of fine particles through disintegration, thereby making it possible to implement simultaneous improvements in capacity and life characteristics.

[0116] The above first calcination and the above second calcination can be independently performed at a temperature of 900 to 960°C. If the first calcination and the second calcination temperatures are too low, lithium transition metal oxides in the form of single particles may not be easily formed. If the first calcination and the second calcination temperatures are too high, overcalcination may occur, which may deteriorate electrochemical characteristics such as capacity.

[0117] The above first firing can be performed for 2 to 6 hours. If the first firing time is too short, there may be a problem in which lithium ions are not fully inserted into the precursor, and if the first firing time is too long, there may be a problem in which the production speed is reduced due to difficulty in disintegration due to over-firing.

[0118] The above secondary firing can be performed for 7 to 14 hours. If the secondary firing time is too short, the shape of single particles will not be achieved completely, and there will not be enough annealing time to form a layered structure, which may result in poor electrochemical performance. If the secondary firing time is too long, the problem of capacity reduction due to over-firing may occur.

[0119]

[0120] Next, the lithium transition metal oxide is first and secondly crushed to form a lithium transition metal oxide in the form of single particles.

[0121] By performing the disintegration by dividing it into primary disintegration and secondary disintegration, the aggregated secondary particles can be efficiently released into the form of single particles, and the ratio of particles with a small particle size, i.e., fine particles, can be increased, so that the obtained positive electrode active material can satisfy the properties of the aforementioned equation 1 or equation 2, etc.

[0122] The above primary disintegration can be performed using disintegration equipment commonly used in the art. For example, the above primary disintegration can be performed using a rotor mill, but is not necessarily limited thereto.

[0123] At this time, the first disintegration can be performed at a stirring speed of 15,000 to 20,000 rpm. When the stirring speed during the first disintegration satisfies the above range, the first disintegration is performed with an appropriate force, so that the particle size, i.e., the fine particle ratio, can be appropriately controlled, and thus the obtained positive electrode active material can satisfy the properties of the above-described formula 1, etc.

[0124] The secondary disintegration described above can be performed using disintegration equipment commonly used in the art. For example, the secondary disintegration can be performed using a jet mill, but is not necessarily limited thereto.

[0125] At this time, the secondary disintegration can be performed so that the average particle diameter (Dv50) based on volume of the lithium transition metal oxide becomes 3.5 to 4.5 μm. As the secondary disintegration is controlled so that the average particle diameter (Dv50) based on volume of the lithium transition metal oxide becomes within the above range, the obtained positive electrode active material can more easily satisfy the properties of the above-described formula 1, etc.

[0126] The above secondary disintegration can be performed at a crushing pressure of 3.5 to 4.5 bar, and more specifically, at a crushing pressure of 3.5 to 3.9 bar. When the crushing pressure satisfies the above range during the secondary disintegration, since the secondary disintegration is performed with an appropriate force, the particle size, i.e., the fine powder ratio, can be appropriately controlled, so that the obtained positive electrode active material can satisfy the properties of the above-described formula 1, etc.

[0127]

[0128] Through the above series of manufacturing methods, a lithium transition metal oxide in the form of a single particle according to the present invention can be formed, and the obtained lithium transition metal oxide can satisfy the properties of Equation 1, etc. Accordingly, the electrode energy density can be improved, and the capacity and high-temperature life characteristics of the battery can be improved.

[0129]

[0130] 3. Cathode ray and lithium secondary battery

[0131] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery comprising the positive electrode active material described above.

[0132] More specifically, the positive electrode 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] 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.

[0140] 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.

[0141]

[0142] Another embodiment of the present invention provides a lithium secondary battery including the positive electrode for a lithium secondary battery as described above.

[0143] The above lithium secondary battery may more specifically include a positive electrode; a negative electrode; a separator; and an electrolyte.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] The above binder and conductive material may be the same as those described above for the positive electrode.

[0150]

[0151] 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.

[0152]

[0153] 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.

[0154] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0155] 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.

[0156] 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.

[0157] 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.

[0158] 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).

[0159] 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.

[0160] 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.

[0161]

[0162] 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.

[0163]

[0164] Example 1

[0165] (1) Manufacturing of positive electrode active material

[0166] (Mixed) Ni 0.6 Co 0.1 Mn 0.3 (OH)2 composition precursor and LiOH·H2O were introduced into a mixer and mechanically mixed to form a mixture so that the molar ratio (Li / M) of lithium to the transition metal of the precursor was 1.07.

[0167] (1st firing) After that, the mixture was heated to 940℃ through heat treatment in an air atmosphere, and then 1st firing was performed at a constant temperature of 940℃ for 4 hours, and then naturally cooled. Thereafter, the 1st fired material was crushed using a rotor mill.

[0168] (Secondary firing) Afterwards, the above-mentioned crushed primary fired material was subjected to secondary firing at a constant temperature of 940°C for 10 hours in an oxygen atmosphere with an oxygen partial pressure of 99%, and then naturally cooled to form a lithium transition metal oxide.

[0169] (1st disintegration) After that, the lithium transition metal oxide was disintegrated for the first time using a rotor mill at a stirring speed of 17,000 rpm.

[0170] (Secondary disintegration) After secondary disintegration using a jet mill at a crushing pressure of 3.7 bar, lithium transition metal oxide in the form of single particles was formed.

[0171] The composition of the final obtained lithium transition metal oxide is Li 1.07 Ni 0.6 Co 0.1 Mn 0.3 It was O2.

[0172] (2) Lithium secondary battery manufacturing

[0173] The slurry for manufacturing the electrode plate was mixed with the above-mentioned positive electrode active material: conductive material (carbon black, Denka black): binder (PVDF, KF9700) = 95.0:2.0:3.0 wt%, and the viscosity was adjusted so that the solid content was approximately 60% by adding NMP (N-Methyl-2-pyrrolidone). The manufactured slurry was coated on a 20 μm thick Al foil using a doctor blade, and then dried and rolled. The electrode loading was 16.0 mg / cm 2 and the rolling density (25 ℃, 20 kN) was 3.5 g / cm 3 It was.

[0174] The electrolyte was 1M LiPF6in EC:DMC:DEC=1:2:1 (vol%), with 2.0 vol% VC added to the total amount of the electrolyte, and a coin cell was manufactured using a PP separator and a lithium negative electrode (400 μm, Niba metal).

[0175]

[0176] Example 2

[0177] In the second firing step, a positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the second firing was performed for 11 hours.

[0178]

[0179] Comparative Example 1

[0180] In the second firing step, a cathode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the second firing was performed in an air atmosphere with an oxygen partial pressure of 21% and then the second crushing was performed using a jet mill at a crushing pressure of 4.1 bar.

[0181]

[0182] Comparative Example 2

[0183] In the second firing step, a cathode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the second firing was performed for 9 hours in an air atmosphere with an oxygen partial pressure of 21%, and then secondary crushing was performed using a jet mill at a crushing pressure of 4.1 bar.

[0184]

[0185] Comparative Example 3

[0186] In the second firing step, a cathode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the second firing was performed for 8 hours in an air atmosphere with an oxygen partial pressure of 21%, and then secondary crushing was performed using a jet mill at a crushing pressure of 4.0 bar.

[0187]

[0188] Experimental Example 1: SEM image of positive electrode active material

[0189] SEM images of the positive electrode active materials manufactured according to Example 1 and Comparative Example 1 were observed and are shown in FIGS. 1 and 2, respectively.

[0190] Referring to FIGS. 1 and 2, it was confirmed that the positive electrode active materials of the examples and comparative examples had a single particle form.

[0191]

[0192] Experimental Example 2: Evaluation of the properties of positive electrode active materials

[0193] The properties of the positive electrode active materials of the examples and comparative examples were evaluated using the methods below, and are shown in Table 2.

[0194] (1) Dv50 and Dn50, Dv50 / Dn50, Dv50 - Dn50 evaluation

[0195] The volume-based average particle diameter (Dv50) was measured by measuring the particle diameter corresponding to 50% of the volume accumulation amount using the laser diffraction method, and the number-based average particle diameter (Dn50) was measured by measuring the particle diameter corresponding to 50% of the number accumulation amount. Afterwards, Dv50 / Dn50 and Dv50 - Dn50 were calculated using these.

[0196] (2) Evaluation of crystal grain size, a-axis lattice constant (La), c-axis lattice constant (Lc), and Lc / La

[0197] XRD data of the active material were measured using Bruker's D8 Discover with GADDS XRD equipment, and the crystal size, a-axis lattice constant (La), and c-axis lattice constant (Lc) were obtained through the Reitveld refinement method built into Bruker's DIFFRAC.TOPAS program. Lc / La was obtained by dividing the c-axis lattice constant (Lc) by the a-axis lattice constant (La).

[0198] Process conditions 1st firing 2nd firing 2nd firing Atmosphere 1st disintegration 2nd disintegration Comparative example 1940℃, 4h, air 940℃, 10hair (oxygen partial pressure 21%) Rotor mill 17000rpm Jet mill 4.1bar Comparative example 2940℃, 9hair (oxygen partial pressure 21%) Rotor mill 17000rpm Jet mill 4.1bar Comparative example 3940℃, 8hair (oxygen partial pressure 21%) Rotor mill 17000rpm Jet mill 4.0bar Example 1940℃, 10hO2 (oxygen partial pressure 99%) Rotor mill 17000rpm Jet mill 3.7bar Example 2940℃, 11hO2 (oxygen partial pressure 99%) Rotor mill 17000rpm Jet mill 3.7bar

[0199] Particle size Dv50 (um) Dn50 (um) Dv50 / Dn50 Dv50 - Dn50 (um) Comparative example 13.99 2.8 1.4 2 1.19 Comparative example 23.98 2.79 1.4 2 1.19 Comparative example 33.86 2.5 2 1.5 3 1.34 Example 14.0 3 0.8 9 4.5 4 3.14 Example 23.99 0.9 4.4 3 3.09

[0200] XRDCrystal Size(nm)a-aixs(Å)c-aixs(Å)Lc / LaComparative Example 12102.875314.24564.9545Comparative Example 22082.875514.24634.9544Comparative Example 32002.875514.2474.9546Example 11812.875114.24754.9555Example 21832.87514.24734.9556

[0201] Referring to Tables 1 to 3, in the case of Examples 1 and 2, in which the conditions of the active material manufacturing process were appropriately controlled, such as performing the secondary firing in an oxygen atmosphere and performing the secondary disintegration, it was confirmed that Dv50 / Dn50, Dv50 - Dn50, and other XRD properties were appropriately obtained within the range according to the present invention. On the other hand, in the case of Comparative Examples 1 to 3, in which the secondary firing was performed in an air atmosphere, it was confirmed that Dv50 / Dn50, Dv50 - Dn50, and other XRD properties were outside the range according to the present invention.

[0202]

[0203] Experimental Example 3: Evaluation of Electrochemical Characteristics of Lithium Secondary Battery

[0204] The electrochemical characteristics of lithium secondary batteries of examples and comparative examples were evaluated using the following methods, and are shown in Table 4.

[0205] (1) Initial capacity and initial efficiency evaluation

[0206] After fabricating a lithium secondary battery half-cell, it was aged at 25°C for 12 hours and then subjected to a charge-discharge test at 25°C. To evaluate the initial capacity, the battery was charged to 4.4 V at a constant current of 0.1 C with a reference capacity of 200 mAh / g, then switched to a constant voltage and charged until the end current reached 0.05 C. After a 10-minute rest time after charging, the battery was discharged to 2.5 V at a constant current of 0.1 C with a reference capacity of 200 mAh / g.

[0207] (2) Evaluation of high-temperature life characteristics (high-temperature capacity retention rate) (45℃, 50 cycles)

[0208] After fabricating a lithium secondary battery half-cell, it was charged to 4.4 V at a constant current of 0.5 C at 45°C, then switched to a constant voltage and charged until the end current reached 0.05 C. After a rest time of 10 minutes after charging, it was discharged at a constant current of 1.0 C until it reached 2.5 V. Under these charge-discharge cycle conditions, 50 charge-discharge cycles were performed, and the capacity retention rate of the 50th cycle was calculated compared to the first cycle.

[0209] (3) Evaluation of high temperature resistance increase rate (45℃, 50 cycles)

[0210] After fabricating a lithium secondary battery half-cell, it was charged to 4.4 V at a constant current of 0.5 C at 45°C, then switched to a constant voltage and charged until the end current reached 0.05 C. After a rest time of 10 minutes after charging, it was discharged at a constant current of 1.0 C until it reached 2.5 V. Under these charge-discharge cycle conditions, 50 charge-discharge cycles were performed, and the resistance increase rate of the 50th cycle compared to the first cycle was calculated.

[0211] 0.1C / 0.1C Initial Cycle High Temperature TestCharge(mAh / g)Discharge(mAh / g)Efficiency(%)Retention @50thΔDCIR @50thComparative Example 1213.6191.889.80%94.20%154.30%Comparative Example 2213.4191.589.70%94.10%154.20%Comparative Example 3213.6191.789.70%94.30%155.70%Example 1214193.790.50%94.90%134.20%Example 2213.7193.790.70%94.90%135.10%

[0212] Referring to Table 4, in the case of Examples 1 and 2, where the properties of the positive electrode active material, such as Equation 1, satisfy the range according to the present invention, it was confirmed that the initial charge capacity, discharge capacity, initial efficiency, high-temperature life characteristics, and high-temperature resistance characteristics were all excellent. On the other hand, in the case of Comparative Examples 1 to 3, where the properties of the positive electrode active material, such as Equation 1, are outside the range according to the present invention, it was confirmed that the initial charge capacity, discharge capacity, initial efficiency, high-temperature life characteristics, and high-temperature resistance characteristics were inferior to those of the examples.

[0213]

[0214] 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.

[0215] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Contains a lithium transition metal oxide in the form of a single particle containing 50 to 70 mol% of nickel based on the total mole number of transition metals, A cathode active material for a lithium secondary battery satisfying the following equation 1: [Formula 1] Dv50 / Dn50 ≥ 3.0 In the above equation 1, Dv50 is the average particle diameter based on the volume of the positive electrode active material, and Dn50 is the average particle diameter based on the number of positive electrode active materials.

2. In paragraph 1, A cathode active material for a lithium secondary battery satisfying the following equation 2: [Formula 2] Dv50 - Dn50 ≥ 2.5 nm In the above equation 2, Dv50 is the average particle diameter based on the volume of the positive electrode active material, and Dn50 is the average particle diameter based on the number of positive electrode active materials.

3. In paragraph 1, A positive electrode active material for a lithium secondary battery, wherein the volume-based average particle diameter (Dv50) of the lithium transition metal oxide is 3.5 to 4.5 μm.

4. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the average particle diameter (Dn50) based on the number of lithium transition metal oxides is 1 μm or less.

5. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the crystallite size of the lithium transition metal oxide is 190 nm or less.

6. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the ratio of the c-axis lattice constant to the a-axis lattice constant (Lc / La) of the lithium transition metal oxide is 4.955 or more.

7. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the c-axis lattice constant (Lc) of the lithium transition metal oxide is 14.2472 nm or more.

8. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the a-axis lattice constant (La) of the lithium transition metal oxide is 2.8752 nm or less.

9. In paragraph 1, The above lithium transition metal oxide is a positive electrode active material for a lithium secondary battery represented by the following chemical formula 1: [Chemical Formula 1] Li a [Ni x Co y Mr z M w ]O2 In the above chemical formula 1, 0.8≤a≤1.2, 0.5≤x≤0.7, 0≤y≤0.2, 0≤z≤0.4, 0≤w≤0.2, x+y+z+w=1, and M is Zr, Al, B, Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

10. A step of preparing a transition metal precursor containing 50 to 70 mol% of nickel based on the total mole number of transition metals; A step of forming a lithium transition metal oxide by mixing the above transition metal precursor and lithium raw material, and then performing a first calcination and a second calcination; and It includes a step of first and second disintegrating the lithium transition metal oxide to form a lithium transition metal oxide in the form of single particles, The above secondary firing is performed in an oxygen (O2) atmosphere. A method for manufacturing a cathode active material for a lithium secondary battery.

11. In paragraph 10, A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein the above secondary disintegration is performed so that the average particle diameter (Dv50) based on volume of the lithium transition metal oxide becomes 3.5 to 4.5 μm.

12. In paragraph 10, A method for producing a positive electrode active material for a lithium secondary battery, wherein the above primary disintegration is performed at a stirring speed of 15,000 to 20,000 rpm.

13. In paragraph 10, A method for producing a positive electrode active material for a lithium secondary battery, wherein the above secondary crushing is performed at a crushing pressure of 3.5 to 4.5 bar.

14. In paragraph 10, A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein the above primary firing is performed in an air atmosphere.

15. In paragraph 10, A method for producing a positive electrode active material for a lithium secondary battery, wherein the first firing and the second firing are each independently performed at a temperature of 900 to 960°C.

16. A positive electrode for a lithium secondary battery comprising the positive electrode active material of any one of claims 1 to 9.

17. A lithium secondary battery comprising the positive electrode for a lithium secondary battery of Article 16.

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