Positive electrode active material for lithium secondary battery and lithium secondary battery comprising same

Abstract

The present invention relates to a positive electrode active material for a lithium secondary battery, comprising lithium metal oxide particles containing nickel (Ni), wherein the lithium metal oxide particles contain aluminum (Al) as a doping element, the lithium metal oxide particles have a concentration gradient region in which the concentration of aluminum gradually increases and then decreases from the center toward the surface of the particles, and a point at which the concentration of aluminum in the concentration gradient region is maximum is located within a distance of 0.755 R from the center of the particles when the distance from the center to the surface of the particles is R.

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] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMnO4, etc.), and lithium iron phosphate compound (LiFePO4) have been used as cathode active materials for lithium secondary batteries. Among these, lithium cobalt oxide has the advantages of high operating voltage and excellent capacity characteristics, but the high price of cobalt, which is the raw material, and its supply are unstable, making it difficult to commercially apply it to large-capacity batteries. Lithium nickel oxide has poor structural stability, making it difficult to achieve sufficient cycle life characteristics. Meanwhile, lithium manganese oxide has excellent stability but has the problem of poor capacity characteristics. Therefore, lithium composite transition metal oxides containing two or more transition metals have been developed to complement the problems of lithium transition metal oxides containing only Ni, Co, or Mn. Among these, lithium nickel cobalt manganese oxide containing Ni, Co, and Mn is widely used in the field of electric vehicle batteries.

[0004] In addition, the demand for high-output, high-capacity batteries, such as those for electric vehicles, is increasing, and accordingly, the nickel content in the cathode active material is gradually increasing (so-called “high nickel”).

[0005] However, when the nickel content in the positive electrode active material increases, the initial capacity characteristics are improved, but when charge and discharge are repeated, the highly reactive Ni +4 There is a problem that a large amount of ions are generated, causing structural collapse of the positive electrode active material, which increases the rate of deterioration of the positive electrode active material and reduces the life characteristics.

[0006]

[0007] Accordingly, one object of the present invention is to provide a positive electrode active material for a lithium secondary battery having improved life characteristics.

[0008]

[0009] One embodiment of the present invention provides a cathode active material for a lithium secondary battery, comprising lithium metal oxide particles containing nickel (Ni), wherein the lithium metal oxide particles contain aluminum (Al) as a doping element, wherein the lithium metal oxide particles have a concentration gradient region in which the concentration of aluminum gradually increases and then decreases from the center of the particle toward the surface, and wherein a point in the concentration gradient region in which the concentration of aluminum is maximum is located within a distance of 0 to 0.755 R from the center of the particle, where R is the distance from the center of the particle to the surface.

[0010] The above concentration gradient region can exist throughout the entire region within the particle from the center to the surface of the lithium metal oxide particle.

[0011] The point where the concentration of aluminum within the above concentration gradient region is maximum may be located within a distance of 0 to 0.45 R from the center of the particle.

[0012] 80% of the aluminum in the lithium metal oxide particles may be located within a distance of 0 to 0.3 R from the center of the particle.

[0013] The content of aluminum in the lithium metal oxide particles may be 0.8 to 3.0 mol% based on the total mole number of metals excluding lithium.

[0014] The content of nickel in the lithium metal oxide particles may be 80 mol% or more based on the total mole number of metals excluding lithium.

[0015] The lithium metal oxide particles may have a ratio of the c-axis lattice constant (Lc) to the a-axis lattice constant (La) (Lc / La) of 4.9423 to 4.9435.

[0016] The above lithium metal oxide particles may have an a-axis lattice constant (La) of 2.8725 to 2.8745.

[0017] The above lithium metal oxide particles may have a c-axis lattice constant (Lc) of 14.2000 to 14.2045.

[0018] The above lithium metal oxide particles may have a crystallite size of 100 to 120 nm.

[0019] The above lithium metal oxide particles may have an average particle diameter (D50) of 10.0 to 18.0 μm.

[0020] The above positive electrode active material is positioned on lithium metal oxide particles and may further include a coating layer containing boron (B).

[0021] The content of boron in the above positive electrode active material may be 400 to 1000 ppm based on the total mole number of lithium metal oxide.

[0022] The above lithium metal oxide particles can be represented by the following chemical formula 1.

[0023] [Chemical Formula 1]

[0024] Li a [Ni x Co y Mn z Al w1 M W2 ]O2

[0025] In the above chemical formula 1, 0.8≤a≤1.2, 0.8≤x<1, 0≤y≤0.2, 0≤z≤0.2, 0.008≤w1≤0.03, 0≤w2≤0.1, x+y+z+w1+w2=1, and M is another doping element such as Zr, Y, B, Mg, Ti, Nb, W, Sc, Si, V, Fe, Mo, Ce, Hf, Ta, La, Sr, Sn, Sb, Zn, Cu, Ge, Mo, Ru, Ir, or a combination thereof.

[0026]

[0027] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery comprising the positive electrode active material described above.

[0028]

[0029] Another embodiment of the present invention provides a lithium secondary battery including the positive electrode for the lithium secondary battery.

[0030]

[0031] A cathode active material for a lithium secondary battery according to one embodiment of the present invention contains aluminum as a doping element, and since the aluminum has a specific concentration gradient tendency, the life characteristics can be improved.

[0032]

[0033] Figure 1 is a graph showing the results of EDS (Energy Dispersive Spectroscopy) line scan analysis for Al element after CP (Cross section Polisher) of positive electrode active materials manufactured according to Examples 1 to 4 and Comparative Example 2.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0039] 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.

[0040] 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.

[0041]

[0042] 1. Positive active material

[0043] A cathode active material for a lithium secondary battery according to one embodiment of the present invention includes lithium metal oxide particles containing nickel (Ni). The lithium metal oxide particles may more specifically have a layered crystal structure containing nickel.

[0044] The above lithium metal oxide particles may be secondary particles formed by agglomeration of multiple primary particles.

[0045] In this specification, “secondary particle” means an aggregate, i.e., a secondary structure, in which tens to hundreds of primary particles are aggregated together by physical or chemical bonding between the primary particles without any intentional aggregation or assembly process for the primary particles.

[0046] The above “primary particle” refers to the smallest particle unit that can be distinguished as a single lump when observing the cross-section of the positive electrode active material through a scanning electron microscope (SEM), and may be composed of a single crystal grain or multiple crystal grains.

[0047] Meanwhile, the content of nickel in the lithium metal oxide particles may be high nickel containing a high nickel content of 80 mol% or more, more specifically, 85 mol% or more, based on the total mole number of metals excluding lithium. Accordingly, the capacity and output characteristics may be improved.

[0048] However, when the nickel content in lithium metal oxide increases, the initial capacity characteristics are improved, but when charge and discharge are repeated, the highly reactive Ni+4 There is a problem that a large amount of ions are generated, causing structural collapse of the positive electrode active material, which increases the rate of deterioration of the positive electrode active material and reduces the life characteristics.

[0049] Accordingly, the inventors of the present invention have conducted repeated research on a positive electrode active material with improved life characteristics, and as a result, have completed the present invention by doping lithium metal oxide with aluminum (Al) and controlling the concentration gradient of aluminum within the particles in a specific manner, thereby effectively improving the structural stability of the positive electrode active material and consequently improving the high-temperature life characteristics of the battery.

[0050]

[0051] Specifically, the lithium metal oxide particles according to the present invention contain aluminum (Al) as a doping element. Aluminum doped in transition metal sites, such as nickel, cobalt, or manganese, within the lithium metal oxide has a relatively strong bonding force with oxygen, thereby enhancing the structural stability of the layered structure within the active material, thereby improving the high-temperature life characteristics of the battery.

[0052] In particular, the lithium metal oxide particles according to the present invention have a concentration gradient region in which the concentration of aluminum gradually increases and then decreases from the center of the particle toward the surface.

[0053] At this time, the concentration gradient region may exist in the entire region within the particle from the center to the surface of the lithium metal oxide particle. That is, the lithium metal oxide particle according to the present invention may have a concentration gradient in the above manner throughout the entire region of the particle, rather than having a partial concentration gradient only in a region where aluminum is limited to the center or surface of the particle.

[0054] In addition, the point where the concentration of aluminum within the above concentration gradient region is maximum is located within a distance of 0 to 0.755 R from the center of the particle, when the distance from the center of the particle to the surface is R. When aluminum has the above-described concentration gradient and is concentratedly doped within the distance from the particle center, more bonds can be formed within the particle. In addition, the particle growth in the center is suppressed by the Al element, so that relatively thin and small particles are formed in the center and relatively thick and large particles are formed in the periphery, thereby minimizing the stress within the particle during lithium insertion / de-insertion due to charge / discharge. Accordingly, the structural stability of the active material can be more desirably improved, and as a result, the high-temperature life characteristics can be more desirably improved.

[0055] More specifically, the point where the concentration of aluminum within the concentration gradient region is maximum may be located within a distance of 0 to 0.45 R or within a distance of 0.25 R to 0.45 R from the center of the particle. When the point where the concentration of aluminum within the concentration gradient region is maximum is more appropriately controlled within the above range, the capacity characteristics and high-temperature life characteristics can be comprehensively and more preferably implemented. More specifically, when the point where the concentration of aluminum within the concentration gradient region is maximum is too close to the center of the particle, the life characteristics may be good, but the capacity characteristics may be deteriorated. When the point where the concentration of aluminum within the concentration gradient region is maximum is too close to the particle surface, the capacity characteristics may be good, but the effect of improving the life characteristics may be minimal.

[0056] In addition, 80% of aluminum, which is a doping element in the lithium metal oxide particles according to the present invention, may be located within a distance of 0 to 0.3 R from the center of the particle, and more specifically, may be located within a distance of 0.22 R to 0.3 R. When the content distribution of aluminum in the lithium metal oxide particles satisfies the above range, capacity characteristics and high-temperature life characteristics may be preferably implemented.

[0057] In addition, the content of aluminum, which is a doping element in the lithium metal oxide particles according to the present invention, may be 0.8 to 3.0 mol%, and more specifically, 0.8 to 2.0 mol% or 0.8 to 1.5 mol%, based on the total mole number of metals excluding lithium. If the content of aluminum is too low, the effect of improving the life characteristics due to the improvement in the structural stability of the active material may be minimal. If the content of aluminum is too high, the capacity characteristics may deteriorate.

[0058] In addition, the lithium metal oxide particles according to the present invention may have a ratio of the c-axis lattice constant (Lc) to the a-axis lattice constant (La) (Lc / La) of 4.9423 to 4.9435. When the ratio of the c-axis lattice constant (Lc) to the a-axis lattice constant (La) of the lithium metal oxide particles (Lc / La) is controlled within the above range, the lifespan characteristics may be improved. The ratio of the c-axis lattice constant (Lc) to the a-axis lattice constant (La) within the above range (Lc / La) may be a range that is realized when the concentration gradient aspect of aluminum is appropriately controlled within the range according to the present invention.

[0059] In addition, the lithium metal oxide particles according to the present invention may have an a-axis lattice constant (La) of 2.8725 to 2.8745 Å, more specifically, 2.8725 to 2.8740 Å or 2.8733 to 2.8738. When the a-axis lattice constant (La) of the lithium metal oxide particles satisfies the above range, the life-cycle characteristics are improved, and the capacity characteristics can also be excellently implemented. The a-axis lattice constant (La) within the above range may be a range implemented when the concentration gradient aspect of aluminum is appropriately controlled within the range according to the present invention.

[0060] In addition, the lithium metal oxide particles according to the present invention may have a c-axis lattice constant (Lc) of 14.2000 to 14.2045 Å, more specifically, 14.2005 to 14.20435 Å or 14.2020 to 14.2040 Å. When the c-axis lattice constant (Lc) of the lithium metal oxide particles satisfies the above range, the life-cycle characteristics are improved, and the capacity characteristics can also be excellently implemented. The c-axis lattice constant (Lc) within the above range may be a range implemented when the concentration gradient aspect of aluminum is appropriately controlled within the range according to the present invention.

[0061] In addition, the lithium metal oxide particles according to the present invention may have a crystallite size of 100 to 120 nm, more specifically, 104 to 120 nm or 107 to 112 nm. When the crystallite size of the lithium metal oxide particles satisfies the above range, the life characteristics are improved, and the capacity characteristics can also be excellently implemented. The crystallite size in the above range may be a range implemented when the concentration gradient aspect of aluminum is appropriately controlled within the range according to the present invention.

[0062] In this specification, the a-axis lattice constant, c-axis lattice constant, and crystal grain size of lithium metal oxide can be estimated using peak broadening of XRD data, and can be quantitatively calculated using the Scherrer equation.

[0063] In addition, the positive electrode active material particles according to the present invention may have an average particle diameter (D50) of 10.0 to 18.0 μm. If the average particle diameter (D50) of the positive electrode active material particles is too small, the contact area with the electrolyte may increase, which may cause rapid deterioration and a decrease in life characteristics. If the average particle diameter (D50) of the positive electrode active material particles is too large, the energy density may decrease, which may cause a decrease in capacity.

[0064] 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.

[0065]

[0066] Meanwhile, the positive electrode active material according to the present invention is positioned on lithium metal oxide particles and may further include a coating layer containing boron (B). As the positive electrode active material further includes a coating layer containing boron, the effect of improving life characteristics can be more preferably implemented.

[0067] At this time, the content of boron in the positive electrode active material may be 400 to 1000 ppm based on the total mole number of lithium metal oxide. Accordingly, by coating an appropriate amount of boron, both life and capacity characteristics can be excellently implemented.

[0068]

[0069] Meanwhile, although Al is mainly mentioned as a doping element in this specification, the effect of providing a doping element concentration gradient according to the present invention can be implemented in the same manner as any doping element that is doped into a transition metal layer position in the layered structure of lithium metal oxide during doping and has a strong bonding force with oxygen and can implement an effect of improving structural stability.

[0070] Accordingly, the present invention can be extended to doping elements such as Al, Mn, Fe, Co, Ni or a combination thereof.

[0071] At this time, the ratio of the input amount of the doping raw material in the manufacturing method, the total input amount (total doping amount), and the concentration gradient pattern in the positive electrode active material according to this can be applied in the same way as Al.

[0072]

[0073] The lithium metal oxide particles according to the present invention can be more specifically represented by the following chemical formula 1.

[0074] [Chemical Formula 1]

[0075] Li a [Ni x Co y Mn z Al w1 M W2 ]O2

[0076] In the above chemical formula 1, 0.8≤a≤1.2, 0.8≤x<1, 0≤y≤0.2, 0≤z≤0.2, 0.008≤w1≤0.03, 0≤w2≤0.1, x+y+z+w1+w2=1, and M is another doping element such as Zr, Y, B, Mg, Ti, Nb, W, Sc, Si, V, Fe, Mo, Ce, Hf, Ta, La, Sr, Sn, Sb, Zn, Cu, Ge, Mo, Ru, Ir, or a combination thereof.

[0077] In the lithium metal oxide of the above chemical formula 1, lithium may be included in an amount 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 an amount of 0.9≤a≤1.1 more preferably.

[0078] In the lithium metal oxide of the above chemical formula 1, nickel may be included in an amount corresponding to x, i.e., 0.8≤x<1 or 0.85≤x≤0.97. If the nickel content is too low, the capacity and output characteristics may deteriorate. If the nickel content is too high, the lifespan and thermal safety may deteriorate due to a decrease in the structural stability of the active material, and the manufacturing cost may increase.

[0079] In the lithium metal oxide of the above chemical formula 1, cobalt may be included in a content corresponding to y, i.e., 0≤y≤0.2 or 0.03≤y≤0.15. If the cobalt content is too low, grain size growth may be inhibited and output characteristics may be reduced. If the cobalt content is too high, manufacturing costs may increase and reversible capacity may be reduced.

[0080] In the lithium metal oxide of the above chemical formula 1, manganese may be included in a content corresponding to z, i.e., 0≤z≤0.2 or 0.01≤z≤0.10. If the manganese content is too low, the production cost may increase, and the lifespan and stability of the active material may decrease. If the manganese content is too high, the capacity and output characteristics of the battery may decrease.

[0081] In the lithium metal oxide of the above chemical formula 1, aluminum as a doping element may be included in a content corresponding to w1, i.e., 0.008≤w1≤0.03. If the aluminum content is too low, the effect of improving the life characteristics may be minimal. If the aluminum content is too high, the capacity characteristics may deteriorate.

[0082] In the lithium metal oxide of the above chemical formula 1, M, which is another doping element, may be included in a content corresponding to w2, that is, 0≤w2≤0.1, and may be appropriately added and used within a range that does not deteriorate battery performance.

[0083] Alternatively, the lithium metal oxide may be represented by the following chemical formula 2.

[0084] [Chemical Formula 2]

[0085] Li a [Ni x Co y Mn z D w1 M W2 ]O2

[0086] In the above chemical formula 1, 0.8≤a≤1.2, 0.8≤x<1, 0≤y≤0.2, 0≤z≤0.2, 0.008≤w1≤0.03, 0≤w2≤0.1, x+y+z+w1+w2=1, D is a transition metal layer site doping element such as Al, Mn, Fe, Co, Ni or a combination thereof, and M is another doping element such as Zr, Y, B, Mg, Ti, Nb, W, Sc, Si, V, Fe, Mo, Ce, Hf, Ta, La, Sr, Sn, Sb, Zn, Cu, Ge, Mo, Ru, Ir or a combination thereof.

[0087]

[0088] The concentration gradient tendency of aluminum according to the present invention, the maximum concentration point of aluminum, and other various properties can be obtained by dividing the sintering into first and second sintering during the sintering process in the manufacturing method and introducing and doping the Al raw material at an appropriate content ratio.

[0089] Specifically, another embodiment of the present invention provides a method for manufacturing a cathode active material for a lithium secondary battery, comprising the steps of: preparing a metal precursor containing nickel; mixing the metal precursor, a lithium raw material, and a first Al raw material, and then performing a first firing to form a first fired product; and mixing the first fired product and a second Al raw material, and then performing a second firing to form a lithium metal oxide.

[0090] 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 in detail.

[0091]

[0092] First, a metal precursor containing nickel is prepared.

[0093] The nickel content in the above metal precursor may be 80 mol% or more based on the total molar number of the metal. Accordingly, the capacity and output characteristics of the battery can be more preferably implemented.

[0094] The above metal precursor may more specifically be a metal hydroxide.

[0095] The above metal hydroxide may be produced by a coprecipitation reaction by adding a complexing agent-containing solution and a pH adjusting agent-containing solution to a metal-containing solution including, for example, a nickel raw material and optionally a cobalt raw material or a manganese raw material.

[0096] 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.

[0097] The above cobalt raw material is not particularly limited as long as it is used in the manufacture of a cathode active material precursor in the art. 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.

[0098] 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.

[0099] The above metal-containing solution may be prepared by adding nickel raw material and optionally cobalt raw material or 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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 a precursor. The precursor may be a secondary particle formed by the agglomeration of primary particles.

[0104] 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.

[0105] Accordingly, the content of nickel in the metal precursor can be controlled to 80 mol% or more 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.

[0106]

[0107] Next, the metal precursor, lithium raw material, and first Al raw material are mixed and then fired for the first time to form a first fired product.

[0108] Next, the first calcined material and the second Al raw material are mixed and then calcined a second time to form lithium metal oxide.

[0109] In this way, the present invention dopes by dividing and introducing the first Al raw material and the second Al raw material as Al raw materials at an appropriate input ratio through the first and second firings. At this time, the first Al raw material and the second Al raw material are conceptualized expressions to represent the Al raw material introduced during the first and second firings, and the Al raw material does not necessarily have to be introduced during each of the first and second firing steps. That is, the first Al raw material and the second Al raw material that can be introduced during the first or second firing need only be controlled within the following range.

[0110] That is, the ratio of the input amounts of the first Al raw material and the second Al raw material (first Al raw material: second Al raw material) may be 100:0 to 15:85, and more specifically, may be 100:0 to 60:40 or 80:20 to 60:40. When the ratio of the input amounts of the first Al raw material and the second Al raw material satisfies the above range, Al has a concentration gradient tendency according to the present invention, so that the life characteristics can be improved, and further, the capacity characteristics can be excellently implemented. More specifically, if the input amount of the first Al raw material is too large, the maximum concentration point of Al may be too close to the center of the particle, so that the life characteristics may be excellent, but the capacity characteristics may deteriorate. If the input amount of the second Al raw material is too large, the maximum concentration point of Al may be too close to the particle surface, so that the effect of improving the life characteristics may be minimal.

[0111] In addition, the sum of the input amounts of the first Al raw material and the second Al raw material can be controlled so that the Al content in the lithium metal oxide is 0.8 to 3.0 mol% based on the total mole number of metals excluding lithium, and more specifically, can be controlled so that it is 0.8 to 2.0 mol% or 0.8 to 1.5 mol%. As the sum of the input amounts of the first Al raw material and the second Al raw material is adjusted within the above range, the Al content doped in the lithium metal oxide can be controlled within the range according to the present invention. The technical significance thereof is omitted as it has been described above.

[0112] The first Al raw material and the second Al raw material may each independently be Al(OH)3, Al2O3, Al2(SO4)3, Al(NO)3, AlCl3, or a combination thereof, but are not necessarily limited thereto.

[0113] The above first firing temperature may be 650 to 750°C, and more specifically, 670 to 730°C. When the first firing temperature satisfies the above range, there may be an advantage in that some lithium is diffused while removing moisture from the metal precursor and lithium raw material to form lithium metal oxide.

[0114] The above secondary firing temperature may be 680 to 780°C. When the secondary firing temperature satisfies the above range, there may be advantages in that the capacity and life characteristics are improved due to an increase in the layered structure and an improvement in structural stability.

[0115] At this time, the first firing temperature may be lower than the second firing temperature. In this way, since the second firing temperature is higher than the first firing temperature, higher structural stability can be secured, which may have the advantage of improving capacity and life characteristics.

[0116] The above first and second firing times can be independently performed for 2 to 12 hours, and more specifically, for 3 to 8 hours. When the first and second firing times satisfy the above ranges, there may be an advantage of preventing underfiring and underfiring and improving capacity and life characteristics through an appropriate firing effect. The above firing time may refer to the firing temperature maintenance time.

[0117] Optionally, if necessary, after the step of forming the lithium metal oxide, a step of mixing the lithium metal oxide and the B raw material and then performing a coating heat treatment to form a B-containing coating layer may be further included.

[0118] By further forming a B-containing coating layer on the lithium metal oxide, the effect of improving the life characteristics can be more preferably implemented.

[0119]

[0120] At this time, the input amount of the above B raw material can be controlled so that the content of B based on the total mole number of lithium metal oxide is 400 to 1000 ppm. The technical significance thereof is omitted as it has been described above.

[0121] The above B raw material may be B(OH)3, but is not necessarily limited thereto.

[0122] The above coating heat treatment can be performed at a temperature of 250 to 350°C. When the temperature satisfies the above range during the coating heat treatment, the B coating is efficiently performed, and the effect of improving the life characteristics of the battery can be more preferably implemented.

[0123]

[0124] 2. Cathode ray and lithium secondary battery

[0125] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery comprising the positive electrode active material described above.

[0126] 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.

[0127] 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, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135]

[0136] Another embodiment of the present invention provides a lithium secondary battery including the positive electrode for a lithium secondary battery as described above.

[0137] The above lithium secondary battery may more specifically include a positive electrode; a negative electrode; a separator; and an electrolyte.

[0138] The above lithium secondary battery may optionally further include a battery container that houses an electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β (0 < β < 2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fiber-like forms, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0143] The above binder and conductive material may be the same as those described above for the positive electrode.

[0144]

[0145] 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.

[0146]

[0147] 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.

[0148] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] 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).

[0153] 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.

[0154] 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.

[0155]

[0156] 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.

[0157]

[0158]

[0159] Example 1

[0160] (1) Manufacturing of positive electrode active material

[0161] (1st firing) Ni 0.9 Co 0.07 Mn 0.03 After mixing the metal precursor of (OH)2 composition, the lithium raw material of LiOH·H2O, and the first Al raw material of Al(OH)3, the first calcination was performed at a temperature of 700℃ for 5.5 hours in an oxygen atmosphere to form the first calcined product, and then it was naturally cooled.

[0162] (Secondary calcination) After mixing the first calcined material and the second Al raw material of Al(OH)3, secondary calcination was performed at a temperature of 730℃ for 5.5 hours in an oxygen atmosphere to form secondary particles of lithium metal oxide. At this time, the ratio of the input amounts of the first Al raw material and the second Al raw material was 100:0, and the total input amounts of the first Al raw material and the second Al raw material were such that the doping content of Al based on the total mole number of metals excluding lithium in the lithium metal oxide was 1 mol%. In addition, the total input amount of the lithium raw material was controlled so that the molar ratio of lithium to metal in the metal precursor (Li / Me) was 1.06.

[0163] (Coating) After that, the lithium metal oxide and B raw material B(OH)3 were mixed, and then a coating heat treatment was performed at a temperature of 280℃ for about 8 hours to form a B-containing coating layer, thereby manufacturing the final positive electrode active material. At this time, the amount of B(OH)3 added was controlled so that the B content based on the total mole number of lithium metal oxide was 600 ppm. As a result, a positive electrode active material having an average particle diameter (D50) of 13.4 μm was manufactured.

[0164] (2) Lithium secondary battery manufacturing

[0165] The slurry for manufacturing the electrode plate was mixed with the above-mentioned positive electrode active material: conductive material (carbon black, Super-C): binder (PVDF, KF1120) = 96.5:1.5:2.0 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 16.5 mg / cm 2 and the rolling density (25 ℃, 20 kN) was 3.6 g / cm 3 It was.

[0166] 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 (200 μm, Niba metal).

[0167]

[0168] Example 2

[0169] In the first and second firing stages, a positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the ratio of the input amounts of the first Al raw material and the second Al raw material was set to 70:30.

[0170]

[0171] Example 3

[0172] In the first and second firing stages, a positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the ratio of the input amounts of the first Al raw material and the second Al raw material was set to 50:50.

[0173]

[0174] Example 4

[0175] In the first and second firing stages, a positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the ratio of the input amounts of the first Al raw material and the second Al raw material was set to 30:70.

[0176]

[0177] Comparative Example 1 (Al continuous firing doping)

[0178] Ni 0.9 Co 0.07 Mn 0.03A cathode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a lithium metal oxide was formed by mixing a metal precursor of (OH)2 composition with LiOH·H2O and Al(OH)3 as an Al raw material, and then performing a first continuous firing at a temperature of 740°C for about 10 hours in an oxygen atmosphere. At this time, the amount of Al raw material added was such that the doping content of Al was 1 mol% based on the total mole number of metals excluding lithium in the lithium metal oxide.

[0179]

[0180] Comparative Example 2

[0181] In the first and second firing stages, a positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the ratio of the input amounts of the first Al raw material and the second Al raw material was set to 0:100.

[0182]

[0183] Table 1 below is a table summarizing the process conditions of examples and comparative examples, and Tables 2 and 3 below are tables summarizing the results of evaluating the properties of positive electrode active materials and the electrochemical characteristics of lithium secondary batteries according to Experimental Examples 2 and 3 described below.

[0184] In Table 1 below, the amount of Al raw material input during continuous firing, the amount of first Al raw material input during second firing, and the amount of second Al raw material input are relative amounts when the amount of Al raw material input that makes the Al doping content 1 mol% based on the total mole number of metals excluding lithium in the lithium metal oxide is assumed to be 100.

[0185] Process conditionsContinuous firingSecondary firingAl raw material inputAmount of first Al raw material inputAmount of second Al raw material inputComparative example 1100--Example 1-1000Example 2-7030Example 3-5050Example 4-3070Comparative example 2-0100

[0186] Active material properties Distance from particle center at point of maximum Al concentration (μm) Distance from particle center at point of maximum Al concentration (relative to particle radius) a-axis lattice constant (Å) c-axis lattice constant (Å) c-axis / a-axis lattice constant Amorphous grain size (nm) Average particle diameter (D50) (μm) Comparative example 1--2.874214.20474.942112213.4 Example 11.4430.2142.872914.20084.943011613.4 Example 22.0440.3032.873614.20274.942510913.4 Example 33.3660.4992.873114.20174.943011313.4 Example Comparative Example 25.170.7662.874114.20444.942210313.4

[0187] Electrochemical characteristics Initial charge capacity (mAh / g) Initial discharge capacity (mAh / g) Initial efficiency (%) Life cycle characteristics (45℃, 30 cycles) (%) Comparative example 1241.6222.892.291.3 Exemplary example 1237.922092.594.7 Exemplary example 2239.822292.694.3 Exemplary example 3239.4220.892.293.8 Exemplary example 4240.8221.792.193.6 Comparative example 2241.2222.692.392.5

[0188] Experimental Example 1: Evaluation of the Al concentration gradient of the cathode active material and other properties.

[0189] (1) Evaluation of Al concentration gradient pattern

[0190] After CP (Cross-section Polisher) was performed on the positive electrode active materials manufactured according to Examples 1 to 4 and Comparative Example 2, EDS (Energy-Dispersive Spectroscopy) line scan analysis for Al element was performed, and the results are shown in Fig. 1. In Fig. 1, Distance, which is the horizontal axis, means the distance from the center of the particle to the concentration measurement point in the direction of the surface. In Fig. 1, Normalized Intensity of Al, which is the vertical axis, means the Al concentration calculated by selectively detecting the Al element.

[0191] At this time, the distance from the particle center at the point where the Al concentration is maximum was evaluated, and this is shown in Table 2. The radius (distance from the particle center to the surface) of the positive electrode active material particles of Examples 1 to 4 and Comparative Example 2 used in the above analysis was 6.75 μm, and the distance based on this was also calculated.

[0192] (2) Average particle size (D50) evaluation

[0193] For the positive electrode active materials manufactured according to the examples and comparative examples, the particle size corresponding to 50% of the volume accumulation amount was measured using the laser diffraction method.

[0194] (3) Evaluation of a-axis lattice constant, c-axis lattice constant, and crystallite size

[0195] For the positive electrode active materials manufactured according to the examples and comparative examples, the a-axis lattice constant, c-axis lattice constant, and crystal grain size were evaluated by quantitative calculation using the Scherrer equation using the peak broadening of XRD data.

[0196]

[0197] Experimental Example 2: Evaluation of Electrochemical Characteristics of Lithium Secondary Battery

[0198] (1) Initial capacity and initial efficiency evaluation

[0199] 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 a reference capacity of 200 mAh / g at a constant current of 0.1C to 4.3 V, then switched to a constant voltage and charged until the end current reached 0.05 C. After a 10-minute rest period after charging, the battery was discharged to a reference capacity of 200 mAh / g at a constant current of 0.1 C until the voltage reached 3.0 V.

[0200] (2) Evaluation of high temperature life characteristics (45℃, 30 cycles)

[0201] After fabricating a lithium secondary battery half-cell, it was charged to 4.3 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 10-minute rest period after charging, it was discharged at a constant current of 1.0 C until it reached 3.0 V. Under these charge-discharge cycle conditions, 30 charge-discharge cycles were performed, and the capacity retention rate of the 30th cycle was calculated compared to the first cycle.

[0202]

[0203] Referring to Tables 1 to 3 and FIG. 1, in the case of Examples 1 to 4 in which the Al raw material was doped by adding an appropriate amount within the range according to the present invention during the first and second firings, it was confirmed that the Al concentration in the lithium metal oxide particles had a concentration gradient in which it gradually increased from the center of the particle toward the surface and then decreased. In addition, it was confirmed that this concentration gradient region was formed over the entire area of ​​the particle. In addition, it was confirmed that the point where the Al concentration was maximum satisfied the range according to the present invention. As a result, it was confirmed that the structural stability of the active material was effectively improved, and the life characteristics were excellently implemented.

[0204] In Comparative Example 1, Al was doped using a continuous firing method, and it was predicted that Al would be doped evenly and uniformly within the particles, without any particular concentration gradient. In addition, it was confirmed that the effect of Al doping on improving life characteristics was minimal compared to the examples.

[0205] In Comparative Example 2, the amount of Al raw material added during the second firing was too high, resulting in the maximum Al concentration point being formed too close to the particle surface. Furthermore, it was confirmed that the lifespan improvement effect due to Al doping was minimal compared to the examples.

[0206] A more detailed comparison of Examples 1 to 4 revealed that in Examples 1 to 2, where the point of maximum Al concentration expression was formed closer to the particle center, the life characteristics were more desirably implemented. However, in Example 1, where the point of maximum Al concentration expression was closest to the particle center, the capacity characteristics were somewhat deteriorated. Through this, it was confirmed that when the point of maximum Al concentration expression was more appropriately controlled, the life characteristics could be desirably improved while the capacity characteristics could also be implemented excellently.

[0207]

[0208] 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.

[0209] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Contains lithium metal oxide particles containing nickel (Ni), The above lithium metal oxide particles contain aluminum (Al) as a doping element, The lithium metal oxide particles have a concentration gradient region in which the concentration of aluminum gradually increases from the center of the particle toward the surface and then decreases after reaching the maximum concentration. The point where the concentration of aluminum is maximum within the above concentration gradient region is located within a distance of 0 to 0.755 R from the center of the particle, where R is the distance from the center of the particle to the surface. Cathode active material for lithium secondary batteries.

2. In paragraph 1, The above concentration gradient region is a positive electrode active material for a lithium secondary battery that exists in the entire region within the particle from the center of the lithium metal oxide particle to the surface.

3. In paragraph 1, A positive electrode active material for a lithium secondary battery, wherein the point at which the concentration of aluminum is maximum within the above concentration gradient region is located within a distance of 0 to 0.45 R from the center of the particle.

4. In paragraph 1, A cathode active material for a lithium secondary battery, wherein 80% of the aluminum in the lithium metal oxide particles is located within a distance of 0 to 0.3 R from the center of the particles.

5. In paragraph 1, A positive electrode active material for a lithium secondary battery, wherein the content of aluminum in the lithium metal oxide particles is 0.8 to 3.0 mol% based on the total mole number of metals excluding lithium.

6. In paragraph 1, A positive electrode active material for a lithium secondary battery, wherein the content of nickel in the lithium metal oxide particles is 80 mol% or more based on the total mole number of metals excluding lithium.

7. In paragraph 1, The above lithium metal oxide particles are a cathode active material for a lithium secondary battery, wherein the ratio of the c-axis lattice constant (Lc) to the a-axis lattice constant (La) (Lc / La) is 4.9423 to 4.9435.

8. In paragraph 1, The above lithium metal oxide particles are a cathode active material for a lithium secondary battery having an a-axis lattice constant (La) of 2.8725 to 2.8745.

9. In paragraph 1, The above lithium metal oxide particles are a cathode active material for a lithium secondary battery having a c-axis lattice constant (Lc) of 14.2000 to 14.2045.

10. In paragraph 1, The above lithium metal oxide particles are a cathode active material for a lithium secondary battery having a crystallite size of 100 to 120 nm.

11. In paragraph 1, The above lithium metal oxide particles are a positive electrode active material for a lithium secondary battery having an average particle diameter (D50) of 10.0 to 18.0 μm.

12. In paragraph 1, A positive electrode active material for a lithium secondary battery further comprising a coating layer containing boron (B) positioned on the lithium metal oxide particles.

13. In paragraph 12, A positive electrode active material for a lithium secondary battery, wherein the content of boron in the positive electrode active material is 400 to 1000 ppm based on the total mole number of lithium metal oxide.

14. In paragraph 1, The above lithium metal oxide particles are 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 Al w1 M W2 ]O2 In the above chemical formula 1, 0.8≤a≤1.2, 0.8≤x<1, 0≤y≤0.2, 0≤z≤0.2, 0.008≤w1≤0.03, 0≤w2≤0.1, x+y+z+w1+w2=1, and M is another doping element such as Zr, Y, B, Mg, Ti, Nb, W, Sc, Si, V, Fe, Mo, Ce, Hf, Ta, La, Sr, Sn, Sb, Zn, Cu, Ge, Mo, Ru, Ir, or a combination thereof.

15. A positive electrode for a lithium secondary battery comprising the positive electrode active material of paragraph 1.

16. A lithium secondary battery comprising the positive electrode for a lithium secondary battery of Article 15.

17. Step of preparing a metal precursor containing nickel; A step of mixing the above metal precursor, lithium raw material and first Al raw material, and then performing a first firing to form a first fired product; and Comprising a step of forming lithium metal oxide by secondary firing of the above primary fired product, A method for manufacturing a cathode active material for a lithium secondary battery.

18. In paragraph 17, A method for manufacturing a positive electrode active material for a lithium secondary battery, comprising mixing the above-mentioned primary sintered material and the second Al raw material and then performing a second sintering to form a lithium metal oxide.

19. In paragraph 18, A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein the ratio of the input amounts of the first Al raw material and the second Al raw material (first Al raw material: second Al raw material) is 80:20 to 60:

40.

20. In paragraph 17, A method for producing a positive electrode active material for a lithium secondary battery, wherein the lithium metal oxide formed above has a concentration gradient in which Al increases and then decreases from the center of the particle to the outermost surface.

21. In paragraph 20, A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein the maximum concentration point of Al in the lithium metal oxide particles formed above exists within a region within 0.755 R from the center of the particle, when the distance from the center of the particle to the outermost surface is R.

22. In paragraph 18, A method for producing a positive electrode active material for a lithium secondary battery, wherein the sum of the input amounts of the first Al raw material and the second Al raw material is controlled so that the content of Al in the lithium metal oxide is 0.8 to 3.0 mol% based on the total mole number of metals excluding lithium.

23. In paragraph 18, A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein the first Al raw material and the second Al raw material are each independently Al(OH)3, Al2O3, Al2(SO4)3, Al(NO)3, AlCl3, or a combination thereof.

24. In paragraph 17, A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein the first sintering temperature is 650 to 750°C.

25. In paragraph 17, A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein the secondary firing temperature is 680 to 780°C.

26. In paragraph 17, A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein the first sintering temperature is lower than the second sintering temperature.

27. In paragraph 17, A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein the first and second firing times are each independently performed for 2 to 12 hours.

28. In paragraph 17, After the step of forming the above lithium metal oxide, A method for manufacturing a positive electrode active material for a lithium secondary battery, further comprising the step of mixing the lithium metal oxide and the B raw material and then performing a coating heat treatment to form a B-containing coating layer.

29. In paragraph 28, A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein the above coating heat treatment is performed at a temperature of 250 to 350°C.

Images