Positive active material for lithium secondary battery, method for manufacturing the same, and lithium secondary battery including the same

Abstract

The present invention relates to a positive electrode active material for a lithium secondary battery, which is a lithium transition metal oxide containing an excess of lithium, an excess of nickel, and a buffer metal element, has a molar ratio of lithium to the lithium transition metal oxide of 1.02 to 1.1 and a molar ratio of nickel to transition metals of 0.75 or more, has a structure in which lithium layers and transition metal layers are alternately stacked as a basic framework, has some of the buffer metal elements in the transition metal layers substituted into the lithium layers and some of the lithium ions in the lithium layers substituted into the transition metal layers, thereby suppressing anisotropic shrinkage and expansion at the time of charging and discharging, and has a sphericity of 0.8 or more.

Description

Technical Field

[0001] This invention relates to positive electrode active materials for lithium secondary batteries, methods for manufacturing the same, and lithium secondary batteries comprising the same. Background Technology

[0002] As the application of lithium-ion batteries expands from small electronic devices to electric vehicles or energy storage devices, the demand for cathode materials with high energy density and excellent lifespan is increasing.

[0003] To achieve high energy density, traditional nickel-cobalt-manganese ternary NCM cathode materials have adopted the approach of increasing nickel content to increase capacity. However, there is a problem that the lifetime characteristics are degraded due to anisotropic expansion / contraction caused by the increase in nickel content.

[0004] In addition, lithium-rich layered cathode materials (Li) are being studied as a new generation of cathode materials. 1+x M-O2 (M-O2) has attracted much attention as a candidate group for next-generation cathode active materials due to its high lithium content and oxidation / reduction reactions of oxygen within its structure, resulting in very high charge / discharge capacity. However, it suffers from problems such as low actual discharge capacity after activation, low true density of the active material itself, and low actual energy density due to non-dense particle packing caused by plate-like crystal growth.

[0005] Therefore, a new type of cathode material is needed that can simultaneously achieve high energy density and excellent lifetime characteristics. Summary of the Invention

[0006] (a) Technical problems to be solved Therefore, the object of the present invention is to provide a novel positive electrode active material for lithium secondary batteries that can simultaneously achieve high energy density and excellent lifespan characteristics, a method for manufacturing the same, and a lithium secondary battery including the same.

[0007] (II) Technical Solution One embodiment of the present invention provides a positive electrode active material for lithium secondary batteries, which is a lithium transition metal oxide comprising excess lithium, excess nickel, and a buffer metal element. The molar ratio of lithium to the lithium transition metal oxide in the lithium transition metal oxide is 1.02 to 1.1, and the molar ratio of nickel to the transition metal is 0.75 or more. The lithium transition metal oxide has a basic structure of alternating lithium layers and transition metal layers. Some of the buffer metal elements in the transition metal layers are replaced into the lithium layers, and some of the lithium ions in the lithium layers are replaced into the transition metal layers, thereby suppressing anisotropic contraction and expansion during charging and discharging, and the sphericity is 0.8 or more.

[0008] The lithium transition metal oxide can be a secondary particle formed by the aggregation of multiple primary particles, and the average particle size of the primary particles can be less than 0.25 μm.

[0009] The average particle size (D50) of the secondary particles can be below 12 μm.

[0010] Furthermore, some nickel ions within the transition metal layer can be displaced into the lithium layer.

[0011] During charging and discharging, lithium ions can move through the lithium layer and the transition metal layer of the lithium transition metal oxide.

[0012] The buffer metal element can be a transition metal element that does not have atomic valence electrons in the d orbital.

[0013] The buffer metal element can be Ti, Nb, W, Zr, V, Cr, Mo, Ta, or a combination thereof.

[0014] The content of the buffer metal element can be 2 to 25 mol based on the total number of moles of transition metals.

[0015] The content of the buffer metal element can be 6 to 15 mol based on the total number of moles of transition metals.

[0016] The ratio of the peak intensity of the (003) plane to the peak intensity of the (104) plane (I(003) / I(104)) of the lithium transition metal oxide in X-ray diffraction analysis can be from 0.7 to 1.6.

[0017] During the first charging process of the lithium transition metal oxide until the termination voltage becomes 4.6V, the difference between the maximum and minimum values ​​of the c-axis lattice constant can be less than 0.6 Å.

[0018] During the first charging process of the lithium transition metal oxide until the termination voltage becomes 4.6V, the rate of change of the c-axis lattice constant can be less than 5%.

[0019] After the lithium transition metal oxide is charged during the first charging process until the termination voltage becomes 4.6V, the c-axis lattice constant can be above 13.8 Å.

[0020] The lithium transition metal oxide may exclude cobalt and manganese.

[0021] The lithium transition metal oxide can be represented by the following chemical formula 1.

[0022] [Chemical Formula 1] Li 1+x (Ni a M1 bM2 c ) 1-x O2 In the chemical formula 1, 0.02≤x≤0.1, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, and a+b+c=1. M1 is a buffer metal element, which is Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof. M2 is a dopant element, which is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

[0023] Another embodiment of the present invention provides a method for manufacturing a positive electrode active material for a lithium secondary battery, comprising: a step of mixing a nickel-containing transition metal compound, a buffer metal raw material, and a solvent to form a mixture; a step of spray drying the mixture to form a precursor; and a step of sintering the precursor and a lithium raw material to form a lithium transition metal oxide. In the step of forming the mixture, the amount of the nickel-containing transition metal compound is 75 mol% or more based on the total molar number of the nickel-containing transition metal compound and the buffer metal raw material. In the step of forming the lithium transition metal oxide, the amount of the lithium raw material is adjusted such that the molar ratio (Li / Me) of lithium relative to the total amount of transition metals included in the precursor is 1.05 to 1.25.

[0024] The nickel-containing transition metal compound can be Ni(OH)2, NiO, Ni2O3, or a combination thereof.

[0025] The buffer metal raw material can be an oxide, hydroxide, carbonate, sulfate, phosphate, or a combination thereof, including buffer metal elements.

[0026] The spray drying can be a process of spraying and drying using a spray dryer.

[0027] The precursor can be represented by any one of the following chemical formulas 2 to 5.

[0028] [Chemical Formula 2] (Ni a M1 b M2 c (OH)2 In the chemical formula 2, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, and a+b+c=1. M1 is a buffer metal element, which is Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof. M2 is a dopant element, which is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

[0029] [Chemical Formula 3] (Ni a M1 b M2 c CO3 In the chemical formula 3, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, and a+b+c=1. M1 is a buffer metal element, which is Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof. M2 is a dopant element, which is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

[0030] [Chemical Formula 4] (Ni a M2 C (OH)2·M1 b O d In the chemical formula 4, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, 2≤d≤3, and a+b+c=1. M1 is a buffer metal element, which is Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof. M2 is a dopant element, which is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

[0031] [Chemical Formula 5] (Ni a M2 c CO3·M1 b O d In the chemical formula 5, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, 2≤d≤3, and a+b+c=1. M1 is a buffer metal element, which is Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof. M2 is a dopant element, which is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

[0032] The sphericity of the precursor can be 0.8 or higher.

[0033] The precursor can be a secondary particle formed by the aggregation of multiple primary particles, and the average particle size (D50) of the secondary particles can be 3 to 12 μm.

[0034] The SPAN value of the precursor can be from 0.3 to 0.7.

[0035] The solvent may be water, ethanol, or a combination thereof.

[0036] The sintering can be carried out at a temperature of 650°C to 900°C.

[0037] Another embodiment of the present invention provides a positive electrode active material precursor for lithium secondary batteries, represented by any one of the following chemical formulas 2 to 5, and having a sphericity of 0.8 or higher.

[0038] [Chemical Formula 2] (Ni a M1 b M2 c (OH)2 In the chemical formula 2, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, and a+b+c=1. M1 is a buffer metal element, which is Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof. M2 is a dopant element, which is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

[0039] [Chemical Formula 3] (Ni a M1 b M2 c CO3 In the chemical formula 3, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, and a+b+c=1. M1 is a buffer metal element, which is Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof. M2 is a dopant element, which is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

[0040] [Chemical Formula 4] (Ni a M2 C (OH)2·M1 b O d In the chemical formula 4, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, 2≤d≤3, and a+b+c=1. M1 is a buffer metal element, which is Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof. M2 is a dopant element, which is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

[0041] [Chemical Formula 5] (Ni a M2 c CO3·M1 b O d In the chemical formula 5, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, 2≤d≤3, and a+b+c=1. M1 is a buffer metal element, which is Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof. M2 is a dopant element, which is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

[0042] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery comprising the above-described positive electrode active material.

[0043] Another embodiment of the present invention provides a lithium secondary battery including the positive electrode for the lithium secondary battery.

[0044] (III) Beneficial Effects According to one embodiment of the present invention, the positive electrode active material for lithium secondary batteries, by comprising excess nickel and excess lithium, can utilize not only nickel-based cation oxidation / reduction reactions but also anion (oxygen) oxidation / reduction reactions, thereby achieving capacity characteristics and high energy density.

[0045] Furthermore, according to one embodiment of the present invention, the positive electrode active material for a lithium secondary battery includes a buffer metal element, in which at least a portion of the lithium lattice sites within the lithium layer are replaced by the buffer metal element, thereby improving structural stability. This suppresses anisotropic contraction and expansion of the active material during charging and discharging, thereby achieving excellent lifetime characteristics.

[0046] Furthermore, according to one embodiment of the present invention, the positive electrode active material for lithium secondary batteries is manufactured by a wet spray drying process. As the sphericity is improved, the electrode density is increased, thereby maximizing the battery energy density. Moreover, due to the reduction in the dissolution of transition metals, the life characteristics can be further maximized. Attached Figure Description

[0047] Figure 1 This is a conceptual diagram of a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention.

[0048] Figure 2 This is a SEM image of the positive electrode active material precursor manufactured according to Example 1.

[0049] Figure 3 This is a SEM image of the positive electrode active material precursor manufactured according to Example 2.

[0050] Figure 4 This is a SEM image of the positive electrode active material precursor manufactured according to Example 3.

[0051] Figure 5 This is a SEM image of the positive electrode active material precursor manufactured according to Example 4.

[0052] Figure 6 This is an SEM image of the positive electrode active material manufactured according to Example 1.

[0053] Figure 7 This is an SEM image of the positive electrode active material manufactured according to Example 2.

[0054] Figure 8 This is an SEM image of the positive electrode active material manufactured according to Example 3.

[0055] Figure 9 This is an SEM image of the positive electrode active material manufactured according to Example 4.

[0056] Figure 10 The image shows an SEM image of the positive electrode active material manufactured according to Comparative Example 2.

[0057] Figure 11 The image shows an SEM image of the positive electrode active material manufactured according to Comparative Example 3.

[0058] Figure 12 The image shows an SEM image of the positive electrode active material manufactured according to Comparative Example 4.

[0059] Figure 13 The image shows an SEM image of the positive electrode active material manufactured according to Comparative Example 7. Detailed Implementation

[0060] The terms "first," "second," and "third," etc., are used to describe various parts, components, regions, layers, and / or segments, but are not limited thereto. These terms are only used to distinguish one part, component, region, layer, or segment from other parts, components, regions, layers, or segments. Therefore, without departing from the scope of the invention, the first part, component, region, layer, or segment described below may be referred to as the second part, component, region, layer, or segment.

[0061] The technical terms used herein are for reference only to specific embodiments and are not intended to limit the invention. The singular forms used herein include the plural forms unless the context clearly indicates otherwise. The word "comprising" as used in this specification embodies a particular feature, region, integer, step, operation, element, and / or component, and does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0062] When referring to one part as being "above" or "on top of" another part, it can be directly above or on the other part, or it can be accompanied by other parts. Conversely, when referring to one part as being "directly above" another part, no other parts are involved.

[0063] Unless otherwise defined, all terms, including technical and scientific terms used herein, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms as defined in commonly used dictionaries are further interpreted as having meanings consistent with relevant technical literature and current disclosure, and should not be construed as having ideal or highly formal meanings unless otherwise defined.

[0064] In addition, unless otherwise specified, % means weight, 1 ppm is 0.0001 weight.

[0065] In this specification, the term "combination thereof" as described in the Markush form means a mixture or combination of one or more of the groups of constituent elements described in the Markush form, meaning including any one or more of the groups of constituent elements.

[0066] The embodiments of the present invention will now be described in detail to enable those skilled in the art to readily implement the invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

[0067] 1. Positive electrode active material Figure 1 This is a conceptual diagram of a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention. Hereinafter, refer to... Figure 1 The positive electrode active material according to the present invention will be described.

[0068] According to one embodiment of the present invention, the positive electrode active material for a lithium secondary battery comprises a lithium transition metal oxide containing excess lithium, nickel, and a buffer metal element. This enables the simultaneous achievement of excellent capacity, high energy density, and lifetime characteristics.

[0069] Specifically, with lithium transition metal oxides containing excess lithium and nickel, not only nickel-based cationic oxidation / reduction reactions can be utilized, but also anionic (oxygen) oxidation / reduction reactions can be utilized, thereby enabling capacity characteristics and high energy density.

[0070] Furthermore, by incorporating buffer metal elements into lithium transition metal oxides, at least a portion of the lithium lattice sites within the lithium layer are replaced by these buffer metal elements, thereby improving structural stability. This suppresses anisotropic contraction and expansion of the active material during charging and discharging, resulting in excellent lifetime characteristics. Moreover, the buffer metal elements tend to be primarily located within the lithium layer, which coincides with the displacement of some nickel ions from the transition metal layer into the lithium layer due to the introduction of excess lithium, leading to a disordered cation-cation mixture structure. This disordered cation-cation mixture structure facilitates smooth lithium ion movement, thus also contributing to high capacity and high energy density.

[0071] More specifically, the lithium transition metal oxide according to the present invention can have a basic architecture of alternating layers of lithium and (represented by nickel) transition metal layers. In this case, the buffer metal element introduced into the lithium transition metal oxide tends to be located at lithium layer sites, so that at least a portion of the lithium sites within the lithium layers can be replaced by the buffer metal element. Simultaneously, the introduction of excess lithium can promote the displacement of nickel ions from the transition metal layers into the lithium layers. Furthermore, simultaneously, due to the introduction of excess lithium, some lithium ions within the lithium layers can be displaced into the transition metal layers.

[0072] That is, the lithium transition metal oxide according to the present invention can be a structure in which lithium ions, nickel ions and buffer metal elements are randomly mixed between the lithium layer and the transition metal layer.

[0073] In conventional layered lithium transition metal oxides, only lithium exists within the lithium layer, and only the transition metal exists within the transition metal layer. Even with partial exchange of positions between lithium and transition metal, electrochemical activity is typically reduced. Therefore, cathode material development aims to minimize this exchange. More specifically, even in conventionally composed cathode materials, nickel cations in the transition metal, due to their similar ionic radius to lithium ions, can occupy lithium sites within the lithium layer—a phenomenon commonly referred to as cation mixing. However, if nickel cations occupy lithium sites within the lithium layer, it hinders lithium ion movement, leading to electrochemical degradation such as reduced capacity and charge / discharge efficiency. Therefore, current technologies are being developed to minimize this cation mixing ratio.

[0074] Conversely, the lithium transition metal oxide according to the present invention can have a structure in which lithium ions within the lithium layer and nickel ions and buffer metal elements within the transition metal layer are disorderedly mixed, and simultaneously includes an excess of lithium compared to conventional compositions. Thus, during charging and discharging, lithium ions can move in three dimensions (i.e., insert and extract) not only through the lithium layer but also through the transition metal layer (unlike the conventional two-dimensional movement of lithium ions through only the lithium layer), thereby maximizing lithium ion mobility. As a result, the battery's capacity characteristics and energy density can be improved. In other words, the positional exchange between lithium and nickel typically reduces electrochemical activity, but the present invention facilitates lithium ion movement through the disordered positional exchange of buffer metal elements other than lithium and nickel, thereby maximizing the battery's capacity characteristics and energy density.

[0075] To achieve this structure in which lithium within the lithium layer and buffer metal elements within the transition metal layer are randomly mixed, an excess of lithium and an appropriate amount of buffer metal elements are required. Furthermore, as described later, the existence of this disordered cation-mixed structure can be confirmed by the ratio of the peak intensity of the (003) plane to the peak intensity of the (104) plane (I(003) / I(104)) during X-ray diffraction analysis, which is within the scope of this invention.

[0076] In this case, the buffer metal element can be a transition metal element that does not have atomic valence electrons in the d orbitals. When the buffer metal element is a transition metal element that does not have atomic valence electrons in the d orbitals, the buffer metal element in the transition metal layer can be easily replaced by lithium positions in the lithium layer.

[0077] More specifically, the buffer metal element may be Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof, but is not necessarily limited to this.

[0078] Furthermore, the lithium transition metal oxide according to the present invention can be a compound in which a solid solution phase of monoclinic Li2M1O3 (M1 being a buffer metal element) and rhombohedral LiMO2 (M being Ni and other doping elements) is mixed.

[0079] Furthermore, the sphericity of the lithium transition metal oxide according to the present invention can be 0.8 or higher, more specifically 0.85 or 0.9 or higher. With such improvement in sphericity, electrode density increases, thereby maximizing battery energy density. Initial efficiency is improved by reducing side reactions with the electrolyte, and lifetime characteristics are significantly improved by reducing transition metal dissolution due to decreased reactivity at high voltages. In this specification, sphericity refers to the degree to which a particle approximates a sphere, expressed numerically, and is the value obtained by dividing the circumference of a corresponding circle with the same area as the projected shape of the particle by the actual circumference of the particle's projected shape using a flow cytometry particle analyzer. This sphericity can be measured using an analyzer (Fluid Imaging Technologies, Flowcam 8100) for acquiring optical images and analysis software (visual spreadsheet).

[0080] Furthermore, the lithium transition metal oxide according to the present invention can be a secondary particle formed by the aggregation of multiple primary particles, wherein the average particle size of the primary particles can be less than 0.25 μm, more specifically less than 0.2 μm. Because the average particle size of the primary particles is sufficiently small, the lithium-ion migration length is shortened, thereby maximizing the capacity characteristics. In this specification, the average particle size of the primary particles can be measured by SEM imaging.

[0081] Furthermore, the average particle size (D50) of the secondary particles can be less than 12 μm, more specifically less than 11 or 10 μm. Because the average particle size of the secondary particles is sufficiently small, the electrolyte can effectively penetrate the interior, thereby improving rate performance. In this specification, the average particle size (D50) in the particle size distribution curve can be defined as the particle size corresponding to 50% of the cumulative volume. The average particle size (D50) can be measured, for example, using a laser diffraction method.

[0082] At this point, as described in the manufacturing method below, the sphericity, average particle size of primary particles, and average particle size (D50) of the lithium transition metal oxide can be easily obtained by using a spray drying process.

[0083] The composition of the lithium transition metal oxide according to the present invention will be described in more detail below.

[0084] In the lithium transition metal oxide according to the present invention, the molar ratio of lithium to lithium transition metal oxide can be from 1.02 to 1.1, more specifically from 1.03 to 1.06. If the molar ratio of lithium is too small, the utilization of anionic (oxygen) oxidation / reduction reactions is reduced, and almost no lithium substitution occurs within the transition metal layer, thus failing to achieve the aforementioned disordered mixed structure, and the improvement in capacity and energy density may be negligible. If the molar ratio of lithium is too large, phase stability problems may arise due to excessive occurrence of anionic (oxygen) oxidation / reduction reactions, potentially reducing lifetime characteristics. In particular, in the lithium transition metal oxide according to the present invention, considering the amount of lithium volatilized during the actual sintering process, the lithium content in the range is not added in small amounts, but can be adjusted so that the lithium content introduced into the actual lithium transition metal oxide reaches the range.

[0085] In the lithium transition metal oxide according to the present invention, the molar ratio of nickel to the transition metal is 0.75 or more, more specifically 0.80 or more. When the molar ratio of nickel to the transition metal meets the above range, the nickel-based cation oxidation / reduction reaction can be fully utilized, thereby improving capacity and energy density.

[0086] Furthermore, the content of the buffer metal element, based on the total moles of transition metals, can be 2 to 25 mol%, more specifically 6 to 15 mol%. If the content of the buffer metal element is too low, the improvement in lifetime, capacity, and energy density brought about by the introduction of the buffer metal element may be negligible. If the content of the buffer metal element is too high, the disordered mixing between the buffer metal and lithium will occur too severely, leading to the degradation of the layered crystal structure, which may instead deteriorate the lifetime, capacity, and energy density.

[0087] The physical properties of lithium transition metal oxides according to the present invention will be described in more detail below using X-ray diffraction analysis.

[0088] In X-ray diffraction analysis, the ratio of the peak intensity of the (003) plane to the peak intensity of the (104) plane (I(003) / I(104)) of the lithium transition metal oxide can be from 0.7 to 1.6, more specifically from 0.9 to 1.5. The ratio of the peak intensity of the (003) plane to the peak intensity of the (104) plane (I(003) / I(104)) can indicate the degree of mixing proportion of transition metal cations within the lithium layer; a smaller value indicates a larger mixing proportion of transition metal cations within the lithium layer. Since the lithium transition metal oxide according to the present invention replaces more buffer metal elements other than nickel within the lithium layer, the ratio of the peak intensity of the (003) plane to the peak intensity of the (104) plane (I(003) / I(104)) can be smaller compared to conventional cathode materials with typical compositions. However, if the ratio of the peak intensities of the (003) plane (I(003) / I(104)) is too small, it means that the content of buffer metal elements is too large, and the cation mixing occurs too severely, which may degrade lifetime characteristics, capacity characteristics and energy density.

[0089] Furthermore, the (before charging) c-axis lattice constant of the lithium transition metal oxide can be from 14.23 to 14.5 Å, more specifically from 14.3 to 14.42 Å. In the composition according to the invention, the (before charging) c-axis lattice constant can vary depending on the amount of buffer metal element introduced, and when the c-axis lattice constant meets the aforementioned range, the above-mentioned improvement in battery electrochemical characteristics can preferably be achieved.

[0090] Furthermore, during the first charging process of the lithium transition metal oxide until the termination voltage becomes 4.6V, the difference between the maximum and minimum values ​​of the c-axis lattice constant can be less than 0.6 Å, more specifically less than 0.55 Å or 0.5 Å.

[0091] Furthermore, during the first charging process of the lithium transition metal oxide until the termination voltage becomes 4.6V, the rate of change of the c-axis lattice constant can be less than 5%, more specifically less than 4.5%, 4%, or 3.5%. In this specification, the rate of change of the c-axis lattice constant can mean the percentage (%) of the difference between the maximum and minimum values ​​during charging relative to the maximum value of the c-axis lattice constant.

[0092] Furthermore, after the lithium transition metal oxide is charged during the first charging process until the termination voltage becomes 4.6V, the c-axis lattice constant can be above 13.8 Å, more specifically above 13.85 or 13.9 Å.

[0093] More specifically, the increase or decrease in the c-axis lattice constant during charging and discharging of lithium transition metal oxides can represent the degree of anisotropic expansion and contraction. Typically, as lithium transition metal oxides are charged, the c-axis lattice constant tends to increase first and then decrease. After charging, the resulting c-axis lattice constant may be smaller than the uncharged c-axis lattice constant.

[0094] At this point, with the introduction of a buffer metal element, the change in the c-axis lattice constant during charging can be reduced in the lithium transition metal oxide according to the present invention. Therefore, the trend of the c-axis lattice constant change can satisfy the aforementioned range. This improves the structural stability of the active material, thereby enhancing battery life characteristics.

[0095] Furthermore, the lithium transition metal oxide may exclude cobalt and manganese. Conventional cathode active materials, in order to improve capacity and lifetime characteristics, not only introduce nickel but also cobalt and manganese in appropriate levels. Conversely, the lithium transition metal oxide according to the present invention, by introducing excess lithium, excess nickel, and buffer metal elements, achieves excellent electrochemical characteristics even without cobalt and manganese. However, it goes without saying that the lithium transition metal oxide according to the present invention does not completely exclude the possibility of using cobalt and manganese.

[0096] The lithium transition metal oxide can be more specifically represented by the following chemical formula 1.

[0097] [Chemical Formula 1] Li 1+x (Ni a M1 b M2 c ) 1-x O2 In the chemical formula 1, 0.02≤x≤0.1, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, and a+b+c=1. M1 is a buffer metal element, which is Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof. M2 is a dopant element, which is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

[0098] The lithium transition metal oxide of Formula 1 may include lithium in an amount equivalent to 1+x, where x can be 0.02≤x≤0.1 or 0.03≤x≤0.06. If x is too small, almost no lithium substitution occurs within the transition metal layer, making it impossible to achieve the aforementioned disordered mixed structure, and the improvement in capacity and energy density may be negligible. If x is too large, excessive anionic (oxygen) oxidation / reduction reactions may cause phase stability problems, potentially reducing lifetime characteristics.

[0099] The lithium transition metal oxide of Formula 1 may include nickel in an amount equivalent to 'a', i.e., 0.75 ≤ a ≤ 0.98 or 0.85 ≤ a ≤ 0.94. If 'a' is too small, the nickel-based cation oxidation / reduction reaction cannot be fully utilized, potentially reducing capacity and energy density. If 'a' is too large, the content of the buffer metal element will decrease accordingly, as the improvement in lifetime, capacity, and energy density brought about by the introduction of the buffer metal element may be negligible.

[0100] In the lithium transition metal oxide of Formula 1, M1 may be included in an amount equivalent to b, i.e., 0.02 ≤ b ≤ 0.25 or 0.06 ≤ b ≤ 0.15. In this case, M1, as a buffer metal element, can be Ti, Nb, W, Zr, V, Cr, Mo, Ta, or combinations thereof. If b is too small, the improvement in lifetime, capacity, and energy density brought about by the introduction of the buffer metal element may be negligible. If b is too large, the content of the buffer metal element is too high, leading to excessive disordered mixing between the buffer metal and lithium, which may instead degrade lifetime, capacity, and energy density.

[0101] In the lithium transition metal oxide of chemical formula 1, M2 may be included in an amount equivalent to c, i.e., 0 ≤ c ≤ 0.1. In this case, M2, as a dopant element, can be Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc, or combinations thereof. The content of the dopant element can be appropriately selected and adjusted to achieve the doping effect within a range that does not degrade the electrochemical characteristics.

[0102] 2. Method for manufacturing positive electrode active material Another embodiment of the present invention provides a method for manufacturing a positive electrode active material for a lithium secondary battery, comprising: a step of mixing a nickel-containing transition metal compound, a buffer metal raw material, and a solvent to form a mixture; a step of spray drying the mixture to form a precursor; and a step of sintering the precursor and a lithium raw material to form a lithium transition metal oxide. In the step of forming the mixture, the amount of the nickel-containing transition metal compound is 75 mol% or more based on the total molar number of the nickel-containing transition metal compound and the buffer metal raw material. In the step of forming the lithium transition metal oxide, the amount of the lithium raw material is adjusted such that the molar ratio (Li / Me) of lithium relative to the total amount of transition metals included in the precursor is 1.05 to 1.25.

[0103] 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.

[0104] First, nickel-containing transition metal compounds, buffer metal raw materials, and solvents are mixed to form a mixture.

[0105] At this point, the amount of the nickel-containing transition metal compound added is 75 mol% or more, more specifically, 80 mol% or more, based on the total moles of the nickel-containing transition metal compound and the buffer metal raw material. Therefore, the nickel content in the lithium transition metal oxide, the final product, can be 75 mol% or more or 80 mol% or more, based on the total moles of the transition metal. Since the technical significance of adjusting the nickel content in the transition metal is the same as described above, it is omitted here.

[0106] Furthermore, the amount of the buffer metal raw material can be 2 to 25 mol%, based on the total moles of the transition metal precursor and the buffer metal raw material, and more specifically, 6 to 15 mol%. Since the technical significance of adjusting the content of the buffer metal raw material is the same as that of adjusting the content of the buffer metal element described above, it is omitted here.

[0107] In addition, the nickel-containing transition metal compound may be Ni(OH)2, NiO, Ni2O3 or a combination thereof, but is not necessarily limited to these.

[0108] Furthermore, the buffer metal raw material can be an oxide, hydroxide, carbonate, sulfate, phosphate, or a combination thereof, including the buffer metal element according to the present invention. In this case, the buffer metal element can be Ti, Nb, W, Zr, V, Cr, Mo, or Ta. For example, the buffer metal raw material can be TiO2, Ti(OH)2, Ti(CO3)2, Ti2(CO3)3, Ti[OCH(CH3)2]4, etc., but is not necessarily limited to these.

[0109] Furthermore, the solvent may be water, ethanol, or a combination thereof, but is not necessarily limited to these.

[0110] Furthermore, the mixing can be carried out by ball milling, but is not necessarily limited to this.

[0111] Furthermore, the mixing process can last for more than 24 hours. If the mixing time is too short, the various raw materials may not be mixed evenly, resulting in the oxidation / reduction reaction of oxygen not proceeding properly.

[0112] Next, the mixture is spray-dried to form a precursor.

[0113] The spray drying process improves the sphericity of lithium transition metal oxide particles. This improved sphericity leads to increased electrode density, which in turn maximizes battery energy density. Furthermore, it enhances initial efficiency by reducing side reactions with the electrolyte and significantly improves lifetime characteristics by minimizing transition metal dissolution due to reduced reactivity at high voltages.

[0114] At this point, the spray drying can be a process of spraying and drying via a spray dryer.

[0115] The precursor formed therefrom can be represented by any one of the following chemical formulas 2 to 5.

[0116] [Chemical Formula 2] (Ni a M1 b M2 c (OH)2 In the chemical formula 2, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, and a+b+c=1. M1 is a buffer metal element, which is Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof. M2 is a dopant element, which is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

[0117] [Chemical Formula 3] (Ni a M1 b M2 c CO3 In the chemical formula 3, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, and a+b+c=1. M1 is a buffer metal element, which is Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof. M2 is a dopant element, which is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

[0118] [Chemical Formula 4] (Ni a M2 C (OH)2·M1 b O d In the chemical formula 4, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, 2≤d≤3, and a+b+c=1. M1 is a buffer metal element, which is Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof. M2 is a dopant element, which is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

[0119] [Chemical Formula 5] (Ni a M2 c CO3·M1 b O d In the chemical formula 5, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, 2≤d≤3, and a+b+c=1. M1 is a buffer metal element, which is Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof. M2 is a dopant element, which is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

[0120] Furthermore, the precursor can be a secondary particle formed by the aggregation of multiple primary particles.

[0121] At this point, the sphericity of the precursor can be 0.8 or higher. As the sphericity of the precursor is improved, the sphericity of the final product, namely the lithium transition metal oxide, can be appropriately obtained within the scope of the present invention.

[0122] Furthermore, the average particle size (D50) of the precursor secondary particles can be from 3 to 12 μm. When the average particle size of the precursor secondary particles meets this range, it may have the advantage of ensuring appropriate capacity utilization and rate performance.

[0123] The SPAN value of the precursor can be from 0.3 to 0.7. When the SPAN value of the precursor meets the range, it may have the advantage of ensuring proper capacity utilization and rate performance. In this specification, the SPAN value refers to the value obtained by calculating particle size [particle size (D90) - particle size (D10)] / particle size (D50), where particle size (D90), particle size (D50), and particle size (D10) can be defined in the particle size distribution curve as corresponding to 90%, 50%, and 10% of the cumulative volume, respectively. Each particle size can be measured, for example, using a laser diffraction method.

[0124] Next, the precursor and lithium raw material are mixed and then sintered to form a lithium transition metal oxide.

[0125] At this point, the amount of lithium raw material added can be adjusted so that the molar ratio (Li / Me) of lithium relative to the total amount of transition metals included in the precursor is 1.05 to 1.25. Thus, a lithium transition metal oxide with a lithium-rich composition according to the present invention can be formed.

[0126] The lithium raw material can be any lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, as long as it is soluble in water, there are no particular restrictions. Specifically, the lithium raw material can be Li₂CO₃, LiNO₃, LiNO₂, LiOH, LiOH·H₂O, LiH, LiF, LiCl, LiBr, LiI, CH₃COOLi, Li₂O, Li₂SO₄, CH₃COOLi, Li₃C₆H₅O₇ or a combination thereof, but is not limited to these.

[0127] The sintering can be carried out at temperatures between 650°C and 900°C. If the sintering temperature is too low, the layered lithium transition metal oxide structure may not form well. If the sintering temperature is too high, the electrochemical properties may be degraded due to over-sintering.

[0128] Furthermore, the sintering process can last from 3 to 15 hours. If the sintering time is too short, the layered lithium transition metal oxide structure may not form well. If the sintering time is too long, the electrochemical properties may deteriorate due to over-sintering.

[0129] Furthermore, there are no particular restrictions on the atmosphere during sintering; for example, it can be carried out in an air or oxygen (O2) atmosphere.

[0130] 3. Positive electrode and lithium secondary battery Another embodiment of the present invention provides a positive electrode for a lithium secondary battery comprising the above-described positive electrode active material.

[0131] 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 aforementioned positive electrode active material.

[0132] The positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, it can be made of stainless steel, aluminum, nickel, titanium, sintered carbon, or materials with surface treatments of carbon, nickel, titanium, silver, etc., on aluminum or stainless steel surfaces. Furthermore, the positive electrode current collector can typically have a thickness of 3 to 500 μm, and the adhesion of the positive electrode active material can be improved by forming micro-protrusions on its surface. For example, it can be used in various forms such as thin films, sheets, foils, meshes, porous bodies, foams, and non-woven fabrics.

[0133] The positive electrode active material layer may include an adhesive and / or a conductive material together with the aforementioned positive electrode active material.

[0134] At this point, the adhesive serves to improve the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), PVDF-co-HFP copolymer, polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof. One or a mixture of two or more of these can be used, but the method is not limited thereto. The adhesive may comprise 1 to 30% by weight of the total weight of the positive electrode active material layer.

[0135] Furthermore, the conductive material is used to impart conductivity to the electrodes, and can be used without particular restrictions in the constructed battery as long as it does not cause chemical changes and has electronic conductivity. Specific examples include graphite such as natural or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lampblack, pyrolysis black, and carbon fiber; metal powders or fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, etc. One or a mixture of two or more of these can be used, but it is not limited to these. The conductive material is typically included in the total weight of the positive electrode active material layer in the range of 1 to 30% by weight.

[0136] The positive electrode can be manufactured using conventional positive electrode manufacturing methods, except for the positive electrode active material.

[0137] Specifically, the positive electrode can be manufactured by coating the aforementioned positive electrode active material and a positive electrode active material layer forming composition, selectively including a binder, conductive material, or solvent as needed, onto a positive electrode current collector, followed by drying and calendering. In this case, the types and amounts of the positive electrode active material, binder, and conductive material are the same as described above.

[0138] The solvent can be any solvent commonly used in this technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and may be one alone or a mixture of two or more of these. Considering the coating thickness and manufacturing yield of the slurry, the amount of solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, and to have a viscosity that exhibits excellent thickness uniformity during subsequent coating for manufacturing the positive electrode.

[0139] Alternatively, the positive electrode can also be manufactured by casting the positive electrode active material layer forming composition onto another support, and then laminating the thin film obtained by peeling it off from the support onto the positive electrode current collector.

[0140] Another embodiment of the present invention provides a lithium secondary battery including the above-described positive electrode for a lithium secondary battery.

[0141] More specifically, the lithium secondary battery may include a positive electrode, a negative electrode, a separator, and an electrolyte.

[0142] The lithium secondary battery may optionally further include a battery container housing the electrode assembly containing the positive electrode, negative electrode, and separator, and a sealing component for sealing the battery container.

[0143] The negative electrode may include a negative electrode current collector and a layer of negative electrode active material located on the negative electrode current collector.

[0144] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, it can be made of copper, stainless steel, aluminum, nickel, titanium, sintered carbon, materials with surface treatments of carbon, nickel, titanium, silver, etc., on the surface of copper or stainless steel, or aluminum-cadmium alloys. Furthermore, the negative electrode current collector can typically have a thickness of 3 to 500 μm. Similar to the positive electrode current collector, the bonding force of the negative electrode active material can be enhanced by forming micro-uneven surfaces on the current collector. For example, it can be used in various forms such as thin films, sheets, foils, meshes, porous bodies, foams, and non-woven fabrics.

[0145] The negative electrode active material layer may selectively include an adhesive and a conductive material together with the negative electrode active material. As an example, the negative electrode active material layer can be manufactured by coating a negative electrode active material layer forming composition comprising the negative electrode active material, and selectively an adhesive and a conductive material onto the negative electrode current collector and drying it, or by casting the negative electrode forming composition onto another support and then laminating a thin film obtained by peeling it off from the support onto the negative electrode current collector.

[0146] As the negative electrode active material, compounds capable of reversibly inserting and extracting lithium can be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fibers, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO2. βMetal oxides capable of doping and dedoping lithium, such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites including the aforementioned metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, may be used. Furthermore, a thin film of metallic lithium may also be used as the negative electrode active material. Additionally, both low-crystallinity carbon and high-crystallinity carbon may be used as carbon materials. Low-crystallinity carbon is represented by soft carbon and hard carbon, while high-crystallinity carbon is represented by amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitch, and high-temperature sintered carbon such as petroleum and coal tar pitch-derived cokes.

[0147] The adhesive and conductive material can be the same as those described above in the positive electrode section.

[0148] The separator isolates the negative and positive electrodes and provides a channel for lithium ion movement. Generally, any material used as a separator in lithium secondary batteries can be used without particular limitations, but materials with low resistance to electrolyte ion movement and excellent electrolyte moisture-holding capacity are particularly preferred. Specifically, porous polymer films can be used, such as porous polymer films made from polyolefin polymers like ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminates of two or more layers thereof. Alternatively, conventional porous nonwoven fabrics can be used, such as nonwoven fabrics made from high-melting-point glass fibers or polyethylene terephthalate fibers. Furthermore, to ensure heat resistance or mechanical strength, coated separators including ceramic components or polymeric materials can be used, selectively in single-layer or multi-layer structures.

[0149] Examples of electrolytes that can be used in the manufacture of lithium secondary batteries include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes, but are not limited to these.

[0150] Specifically, the organic liquid electrolyte may include organic solvents and lithium salts.

[0151] The organic solvent can be used without particular restriction as long as it can function as a medium for the movement of ions participating in the electrochemical reaction of the battery. Specifically, the following organic solvents can be used: 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; dimethyl carbonate (DMC), diethyl carbonate (DEC), methylethyl carbonate (MEC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate. Carbonate solvents such as PC; alcohol solvents such as ethanol and isopropanol; nitriles such as R-CN (where R is a C2 to C20 straight-chain, branched, or cyclic hydrocarbon group, and may include double bonds, aromatic rings, or ether bonds); amides such as dimethylformamide; dioxolane solvents such as 1,3-dioxolane; or sulfolane solvents, etc. Among these, carbonate solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate, etc.) with high ionic conductivity and high dielectric constant that can improve the charge-discharge performance of the battery and low viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) are more preferred. In this case, using a mixture of cyclic carbonates and linear carbonates at a volume ratio of about 1:1 to about 1:9 can result in an electrolyte exhibiting excellent performance.

[0152] The lithium salt can be used without particular restriction, as long as it is a compound capable of providing lithium ions for use in lithium secondary batteries. Specifically, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2 can be used as the lithium salt. The concentration of the lithium salt is preferably in the range of 0.1 to 2.0 M. If the concentration of the lithium salt is within this range, the electrolyte has suitable conductivity and viscosity, thus exhibiting excellent electrolyte performance, and lithium ions can move efficiently.

[0153] In addition to the electrolyte components, the electrolyte may further include, for purposes such as improving battery life characteristics, suppressing battery capacity reduction, and increasing battery discharge capacity, one or more haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glycol dimethyl ether (glyme), hexamethylphosphotriamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolides, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxyethanol, or aluminum trichloride, etc., as additives. In this case, the additives may be included in the electrolyte at a weight percentage of 0.1 to 5% relative to the total weight of the electrolyte.

[0154] As described above, lithium secondary batteries comprising the positive electrode active material according to the present invention stably exhibit excellent discharge capacity, output characteristics and capacity retention, and are therefore useful in portable devices such as mobile phones, laptops, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs).

[0155] Therefore, another embodiment of the present invention provides a battery module comprising the lithium secondary battery as a single cell and a battery pack comprising the same.

[0156] The battery module or battery pack can be used as a power source for any one or more medium to large-sized equipment selected from power tools; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0157] The embodiments of the present invention will be described in more detail below. However, the following embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to the following embodiments.

[0158] Example 1 (1) Manufacturing positive electrode active material (Mixing) Ni(OH)₂ powder, TiO₂ powder, and aqueous solvent were mixed and ball-milled for 120 hours to form a mixture. At this point, the molar ratio of Ni(OH)₂ powder to TiO₂ powder was 95:5.

[0159] (Spray drying) Subsequently, 1 wt% of citric acid was added to the mixture, and the mixture was sprayed through a spray dryer to produce a precursor with an average particle size (D50) of 12 μm, an SPAN value of 0.7, and a sphericity of 0.9.

[0160] (Sintering) Subsequently, in order to make the molar ratio (Li / Me) of the total amount of transition metals contained in the precursor to lithium 1.05 + 0.02 (however, +0.02 is an additional amount added to account for the amount of lithium volatilized during sintering, and the same applies to Examples 2 to 4 and Comparative Examples 1 to 7 below), the precursor and LiOH·H2O powder were mixed and sintered at 700°C for 10 hours under an O2 atmosphere to form Li 1.024 Ni 0.927 Ti 0.049 Lithium transition metal oxides composed of O2.

[0161] (2) Manufacturing lithium secondary batteries The slurry for electrode fabrication was prepared by mixing the aforementioned positive electrode active material, conductive material (carbon black, electrochemical acetylene black (denkablack)), and binder (PVDF, KF1100) in a ratio of 92.5:3.5:4 wt%, with the addition of NMP (N-methyl-2-pyrrolidone) to adjust the viscosity to a solid content of approximately 30%. The prepared slurry was then coated onto a 15 μm thick Al foil using a doctor blade and subsequently dried and calendered. The electrode loading was 14.6 mg / cm³. 2 The calendered density (25℃, 20kN) is 3.1 g / cm³. 3 .

[0162] The electrolyte used was a material in which 1 M LiPF6 was dissolved in EC:EMC = 3:7 (vol%), with 1.0 vol% VC and 0.5 wt% LiBF4 added relative to the total electrolyte. A button cell was manufactured using a PP separator and a lithium anode (200 μm, Honzo metal).

[0163] Example 2 Except for changing the molar ratio of Ni(OH)₂ powder to TiO₂ powder to 93:7 in the mixing step and changing the molar ratio of lithium to the transition metal contained in the precursor (Li / Me) to 1.07 + 0.02 in the sintering step, the same procedure as in Example 1 was followed to manufacture the positive electrode active material and the lithium secondary battery. At this time, the average particle size (D50) of the precursor was 12 μm, the SPAN value was 0.7, and the sphericity was 0.9.

[0164] Example 3 Except for changing the molar ratio of Ni(OH)₂ powder to TiO₂ powder to 90:10 in the mixing step and changing the molar ratio of lithium to the transition metal contained in the precursor (Li / Me) to 1.10 + 0.02 in the sintering step, the same procedures as in Example 1 were followed to manufacture the positive electrode active material and the lithium secondary battery. At this time, the average particle size (D50) of the precursor was 12 μm, the SPAN value was 0.7, and the sphericity was 0.9.

[0165] Example 4 Except for changing the molar ratio of Ni(OH)₂ powder to TiO₂ powder to 80:20 in the mixing step and changing the molar ratio of lithium to the transition metal contained in the precursor (Li / Me) to 1.20 ± 0.02 in the sintering step, the same procedure as in Example 1 was followed to manufacture the positive electrode active material and the lithium secondary battery. At this time, the average particle size (D50) of the precursor was 12 μm, the SPAN value was 0.7, and the sphericity was 0.9.

[0166] Comparative Example 1 (1) Manufacturing positive electrode active material (Mixture) Ni(OH)₂ powder, TiO₂ powder, and LiOH·H₂O powder were ball-milled to change the molar ratio of lithium to the total amount of transition metals contained in the Ni(OH)₂ powder and TiO₂ powder (Li / Me) to 1.05 + 0.02, forming a mixture. At this point, the molar ratio of Ni(OH)₂ powder to TiO₂ powder was 95:5.

[0167] (Sintering) Subsequently, the mixture was sintered at 700°C for 10 hours under an O2 atmosphere to form Li 1.024 Ni 0.927Ti 0.049 Lithium transition metal oxides composed of O2.

[0168] (2) Manufacturing lithium secondary batteries In addition to utilizing the positive electrode active material described above, a lithium secondary battery was manufactured in the same manner as in Example 1.

[0169] Comparative Example 2 Except that the molar ratio of lithium to the total amount of transition metal (Li / Me) was changed to 1.07+0.02 in the mixing step, and the molar ratio of Ni(OH)2 powder to TiO2 powder was changed to 93:7, the positive electrode active material and lithium secondary battery were manufactured in the same manner as in Comparative Example 1.

[0170] Comparative Example 3 Except that the molar ratio of lithium to the total amount of transition metal (Li / Me) was changed to 1.10+0.02 in the mixing step, and the molar ratio of Ni(OH)2 powder to TiO2 powder was changed to 90:10, the positive electrode active material and lithium secondary battery were manufactured in the same manner as in Comparative Example 1.

[0171] Comparative Example 4 Except that the molar ratio of lithium to the total amount of transition metal (Li / Me) was changed to 1.20+0.02 in the mixing step, and the molar ratio of Ni(OH)2 powder to TiO2 powder was changed to 80:20, the positive electrode active material and lithium secondary battery were manufactured in the same manner as in Comparative Example 1.

[0172] Comparative Example 5 Except that the molar ratio of lithium to the total amount of transition metal (Li / Me) was changed to 1.30+0.02 in the mixing step, and the molar ratio of Ni(OH)2 powder to TiO2 powder was changed to 70:30, the positive electrode active material and lithium secondary battery were manufactured in the same manner as in Comparative Example 1.

[0173] Comparative Example 6 Except that the molar ratio of lithium to the total amount of transition metal (Li / Me) was changed to 1.40+0.02 in the mixing step, and the molar ratio of Ni(OH)2 powder to TiO2 powder was changed to 60:40, the positive electrode active material and lithium secondary battery were manufactured in the same manner as in Comparative Example 1.

[0174] Comparative Example 7 Except that the molar ratio of lithium to the total amount of transition metal (Li / Me) was changed to 1.00+0.02 in the mixing step, and the molar ratio of Ni(OH)2 powder to TiO2 powder was changed to 100:0, the positive electrode active material and lithium secondary battery were manufactured in the same manner as in Comparative Example 1.

[0175] Comparative Example 8 Li(Ni) was produced using conventional methods. 0.6 Co 0.2- Mn 0.2 A lithium secondary battery was manufactured using a lithium transition metal oxide positive electrode active material composed of O2, and carried out in the same manner as in Example 1.

[0176] Comparative Example 9 Li(Ni) was produced using conventional methods. 0.8 Co 0.1 Mn 0.1 A lithium secondary battery was manufactured using a lithium transition metal oxide positive electrode active material composed of O2, and carried out in the same manner as in Example 1.

[0177] Comparative Example 10 Li(Ni) was produced using conventional methods. 0.9 Co 0.05- Mn 0.05 A lithium secondary battery was manufactured using a lithium transition metal oxide positive electrode active material composed of O2, and carried out in the same manner as in Example 1.

[0178] Comparative Example 11 Li was produced using conventional methods. 1.13 (Ni 0.3 Mn 0.57 A lithium secondary battery was manufactured using a lithium transition metal oxide positive electrode active material composed of O2, and carried out in the same manner as in Example 1.

[0179] Comparative Example 12 NiSO4, a nickel precursor, and TiSO4, a titanium precursor, were added to water in a molar ratio of 94:06 to prepare an aqueous solution of nickel-titanium hydroxide precursor. While stirring the aqueous solution, an aqueous solution of sodium hydroxide was slowly added dropwise to neutralize the precursor solution, precipitating Ni as a nickel-titanium hydrate. 0.94 Ti 0.06 (OH)2. LiOH was mixed in the precursor thus obtained to a molar ratio of 1.02 and sintered at 755°C for 30 hours in an oxygen atmosphere.

[0180] Experimental Example 1: SEM images of the positive electrode active material precursor and active material SEM (scanning electron microscope) images of the positive electrode active material precursors and active materials prepared according to Examples 1 to 4, and the positive electrode active materials prepared according to Comparative Examples 2 to 4 and 7 are shown below. Figures 2 to 13 middle.

[0181] Reference Figures 2 to 13In the examples where the spray drying process was applied, it was confirmed that the precursor and active material had excellent sphericity.

[0182] Conversely, in the case of active substances in Comparative Examples 2 to 4 and 7, which did not employ spray drying technology, a decrease in sphericity was confirmed.

[0183] Experimental Example 2: Evaluation of the physical properties of positive electrode active materials (1) Evaluation of peak intensity ratio of I(003) / I(104) by X-ray diffraction analysis After measuring the X-ray diffractometer, the peak intensity ratio (I(003) / I(104)) of the (003) and (104) diffraction peaks was determined from the obtained diffraction pattern results.

[0184] (2) Evaluation of the c-axis lattice constant variation curve during the first charging process After manufacturing button-shaped half-cells for each embodiment and comparative example, they were charged until the termination voltage reached 4.6V. The electrodes were then disassembled, and the c-axis lattice constant variation curves were evaluated. The c-axis lattice constant before charging, the maximum c-axis lattice constant during charging, and the minimum c-axis lattice constant after charging were also evaluated. The maximum value was selected as 4.4V based on in-situ XRD results confirming the voltage at which the maximum value was reached. Furthermore, the change in c-axis lattice constant was evaluated by the difference between the maximum and minimum values, and the rate of change of c-axis lattice constant was evaluated as a percentage of the change relative to the maximum value.

[0185] (3) Sphericity evaluation The sphericity was evaluated by dividing the circumference of the corresponding circle with the same area as the particle's projected shape by the actual circumference of the particle's projected shape using a flow cytometry particle analyzer. Measurements were then performed using an analyzer (Fluid Imaging Technologies, Flowcam 8100) for acquiring optical images and analysis software (visual spreadsheet).

[0186] (4) Evaluation of average particle size in primary particles The size of all primary particles constituting a secondary particle was separated from the SEM using image segmentation, and the average particle size of the primary particles was measured.

[0187] (5) Evaluation of secondary particle average size (D50) The average particle size (D50) of the secondary particles was measured using the laser diffraction method.

[0188] Table 1 (In Table 1, x, a, b, and c are lithium transition metal oxides with the chemical formula Li...) 1+x (Ni a Ti b M2 c ) 1-x O2, and the value is based on the premise that a+b+c=1. In this case, M2 is a dopant element other than Ti, which acts as a buffer metal element. Table 2 Referring to Tables 1 and 2, in the examples where excess lithium, nickel, and buffer metal element (Ti) were introduced, and a spray drying process was applied, it was confirmed that excellent sphericity was achieved, and the average primary particle size was appropriately obtained within the range specified according to the invention. Furthermore, in the examples, it was confirmed that the I(003) / I(104) value was smaller than that of a normally composed cathode material. Thus, it was confirmed that the lithium transition metal oxide according to the invention is a disordered mixed structure in which a large amount of nickel and buffer metal element are mixed at the lithium sites within the lithium layer. Furthermore, it was confirmed that the change in the c-axis lattice constant and its rate of change are small, and shrinkage during charging is minimized, resulting in a larger c-axis lattice constant value obtained after charging.

[0189] Conversely, in Comparative Examples 1 to 6, which introduced excessive amounts of lithium, nickel, and buffer metal (Ti) but did not employ spray drying, it was confirmed that the trend of the change in the c-axis lattice constant was similar to that of the Examples, but the sphericity decreased significantly, and the average particle size of the primary particles exceeded the range according to the present invention.

[0190] Furthermore, in the cases of Comparative Examples 7, 8 to 10 with typical compositions, or Comparative Example 11 with a lithium-rich composition without the introduction of buffer metal elements, it was confirmed that a larger I(003) / I(104) value was obtained. In addition, in the cases of Comparative Examples 7, 8 to 10 with typical compositions, it was confirmed that the change in the c-axis lattice constant and the rate of change were large, and that there was significant shrinkage during charging, resulting in a smaller c-axis lattice constant value obtained after charging.

[0191] Experimental Example 3: Evaluation of Electrochemical Characteristics of Lithium Secondary Batteries (1) First time (1) st ) and the second cycle (2 nd Cycle discharge capacity evaluation After fabricating the lithium-ion rechargeable battery half-cells, they were aged at 25°C for 12 hours, followed by charge-discharge tests at 45°C. To evaluate the initial capacity, using 200 mAh / g as the baseline capacity, the cells were charged at a constant current of 0.1C to 4.6V, then switched to a constant voltage and charged until the termination current reached 0.05C. After charging, following a 10-minute rest time, the cells were discharged at a constant current of 0.1C to 2.5V, using 200 mAh / g as the baseline capacity. Subsequently, the second cycle (2...) was evaluated. nd (cycle) discharge capacity.

[0192] (2) Evaluation of compressible electrode density Damage to the uncoated portion of the electrode was identified by adjusting the gap of the calender, thereby evaluating the calenderable electrode density.

[0193] (3) Average voltage evaluation The average voltage was evaluated by integrating the area at the lower end of the discharge curve and dividing it by the discharge capacity.

[0194] (4) Lifetime characteristics evaluation (45℃, 50 cycles) After fabricating the lithium-ion rechargeable battery half-cell, it was charged at 45°C with a constant current of 0.5C to 4.6V, then switched to a constant voltage and charged until the termination current reached 0.05C. After charging, following a 10-minute rest time, it was discharged at a constant current of 0.5C until it reached 2.5V. Fifty charge-discharge cycles were performed under these conditions, and the capacity retention rate of the 50th cycle relative to the first cycle was calculated.

[0195] (5) Battery energy density evaluation A secondary battery was designed using a pouch cell design. The density of electrodes made from various materials was considered, and the average voltage, capacity, and battery volume were calculated to evaluate the energy density. Here, electrode density was calculated using the weight of the electrode per unit area and the thickness exhibited at maximum rolling.

[0196] Table 3 Referring to Table 3, in the case of introducing excess lithium, nickel and buffer metal element (Ti) and applying spray drying process, it can be confirmed that the capacity, rollable electrode density, average voltage, lifetime characteristics and energy density are generally excellent.

[0197] In contrast, in the case of Comparative Example 7 with LiNiO2 composition, a significant decrease in lifetime characteristics and energy density can be confirmed.

[0198] Furthermore, in the case of a typical nickel-cobalt-manganese composition with a ratio of 8 to 10, a decrease in capacity, lifetime, and energy density can be confirmed.

[0199] Furthermore, in the case of Comparative Example 11, which has a lithium-rich composition but without the introduction of a buffer metal, it can be confirmed that 2 nd The discharge capacity, rollable electrode density and energy density decrease significantly, and the average voltage and lifetime characteristics deteriorate.

[0200] Furthermore, by comparing Comparative Examples 1 to 4 and Comparative Examples 5 to 6, it can be confirmed that when the excess lithium content and the amount of buffer metal element introduced are adjusted more appropriately, the electrochemical characteristics are more effectively achieved.

[0201] Furthermore, by comparing Example 1 with Comparative Example 1, Example 2 with Comparative Example 2, Example 3 with Comparative Example 3, and Example 4 with Comparative Example 4, it can be confirmed that when the excess lithium and the amount of buffer metal element introduced are the same, the capacity, lifetime and energy density are further maximized in the example where the sphericity is improved by applying the spray drying process.

[0202] Furthermore, it can be confirmed that in the case of Comparative Example 12, where the content of nickel and titanium relative to the total transition metals is similar to that of the present invention but cannot be considered as a lithium-rich composition, the capacity characteristics, average voltage, lifetime characteristics, and energy density are significantly degraded compared to the examples.

[0203] The preferred embodiments of the present invention have been described above, but the present invention is not limited thereto. Various modifications can be made within the scope of the claims, the specification and the drawings, which are of course also within the scope of the present invention.

[0204] Therefore, it can be said that the substantive scope of the invention is defined by the appended patent claims and their equivalents.

Claims

1. A positive electrode active material for lithium secondary batteries, characterized in that, The lithium secondary battery uses a lithium transition metal oxide as the positive electrode active material, which includes excess lithium, excess nickel, and buffer metal elements. The lithium transition metal oxide has a lithium molar ratio of 1.02 to 1.1 and a nickel molar ratio of 0.75 or higher. The lithium transition metal oxide has a basic architecture of alternating lithium layers and transition metal layers. Some buffer metal elements in the transition metal layers are replaced into the lithium layers, and some lithium ions in the lithium layers are replaced into the transition metal layers, thereby suppressing anisotropic contraction and expansion during charging and discharging. And the sphericity is above 0.

8.

2. The positive electrode active material for lithium secondary batteries according to claim 1, characterized in that, The lithium transition metal oxide is a secondary particle formed by the aggregation of multiple primary particles, and the average particle size of the primary particles is less than 0.25 μm.

3. The positive electrode active material for lithium secondary batteries according to claim 2, characterized in that, The average particle size (D50) of the secondary particles is less than 12 μm.

4. The positive electrode active material for lithium secondary batteries according to claim 1, characterized in that, Some of the nickel ions in the transition metal layer are replaced in the lithium layer.

5. The positive electrode active material for lithium secondary batteries according to claim 1, characterized in that, During charging and discharging, lithium ions move through the lithium layer and the transition metal layer in the lithium transition metal oxide.

6. The positive electrode active material for lithium secondary batteries according to claim 1, characterized in that, The buffer metal element is a transition metal element that does not have atomic valence electrons in the d orbital.

7. The positive electrode active material for lithium secondary batteries according to claim 1, characterized in that, The buffer metal element is Ti, Nb, W, Zr, V, Cr, Mo, Ta, or a combination thereof.

8. The positive electrode active material for lithium secondary batteries according to claim 1, characterized in that, The content of the buffer metal element is 2 to 25 mol based on the total number of moles of transition metals.

9. The positive electrode active material for lithium secondary batteries according to claim 1, characterized in that, The content of the buffer metal element is 6 to 15 mol based on the total number of moles of transition metals.

10. The positive electrode active material for lithium secondary batteries according to claim 1, characterized in that, The ratio of the peak intensity of the (003) plane to the peak intensity of the (104) plane (I(003) / I(104)) of the lithium transition metal oxide in X-ray diffraction analysis is 0.7 to 1.

6.

11. The positive electrode active material for lithium secondary batteries according to claim 1, characterized in that, During the first charging process of the lithium transition metal oxide until the termination voltage becomes 4.6V, the difference between the maximum and minimum values ​​of the c-axis lattice constant is less than 0.6 Å.

12. The positive electrode active material for lithium secondary batteries according to claim 1, characterized in that, During the first charging process of the lithium transition metal oxide until the termination voltage becomes 4.6V, the rate of change of the c-axis lattice constant is less than 5%.

13. The positive electrode active material for lithium secondary batteries according to claim 1, characterized in that, After the lithium transition metal oxide is charged during the first charging process until the termination voltage becomes 4.6V, the c-axis lattice constant is above 13.8 Å.

14. The positive electrode active material for lithium secondary batteries according to claim 1, characterized in that, The lithium transition metal oxide does not include cobalt and manganese.

15. The positive electrode active material for lithium secondary batteries according to claim 1, characterized in that, The lithium transition metal oxide is represented by the following chemical formula 1: [Chemical Formula 1] The 1+x (Nor a M1 b M2 c ) 1-x O2 In the chemical formula 1, 0.02≤x≤0.1, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, and a+b+c=1. M1 is a buffer metal element, which is Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof. M2 is a dopant element, which is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

16. A method for manufacturing a positive electrode active material for lithium secondary batteries, characterized in that, include: The step of mixing a nickel-containing transition metal compound, a buffer metal raw material, and a solvent to form a mixture; The step of spray drying the mixture to form a precursor; and The step involves mixing the precursor and lithium raw material and then sintering them to form a lithium transition metal oxide. In the step of forming the mixture, the amount of the nickel-containing transition metal compound added is 75 mol% or more based on the total molar number of the nickel-containing transition metal compound and the buffer metal raw material. In the step of forming the lithium transition metal oxide, the amount of the lithium raw material added is adjusted such that the molar ratio (Li / Me) of lithium relative to the total amount of transition metals included in the precursor is 1.05 to 1.

25.

17. The method for manufacturing the positive electrode active material for lithium secondary batteries according to claim 16, characterized in that, The buffer metal raw material is an oxide, hydroxide, carbonate, sulfate, phosphate, or a combination thereof that includes a buffer metal element.

18. The method for manufacturing the positive electrode active material for lithium secondary batteries according to claim 16, characterized in that, The spray drying refers to spraying and drying performed using a spray dryer.

19. The method for manufacturing the positive electrode active material for lithium secondary batteries according to claim 16, characterized in that, The precursor is represented by any one of the following chemical formulas 2 to 5, and has a sphericity of 0.8 or higher. [Chemical Formula 2] (Ni a M1 b M2 c )(OH)2 In the aforementioned chemical formula 2, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, and a+b+c=1. M1, as a buffer metal element, is Ti, Nb, W, Zr, V, Cr, Mo, Ta, or a combination thereof. M2, as a dopant element, is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc, or a combination thereof. [Chemical Formula 3] (Ni a M1 b M2 c CO3 In the aforementioned chemical formula 3, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, and a+b+c=1. M1, as a buffer metal element, is Ti, Nb, W, Zr, V, Cr, Mo, Ta, or a combination thereof. M2, as a dopant element, is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc, or a combination thereof. [Chemical Formula 4] (Ni a M2 C )(OH)2·M1 b O d In the aforementioned chemical formula 4, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, 2≤d≤3, and a+b+c=1. M1, as a buffer metal element, is Ti, Nb, W, Zr, V, Cr, Mo, Ta, or a combination thereof. M2, as a dopant element, is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc, or a combination thereof. [Chemical Formula 5] (Ni a M2 c CO3·M1 b O d In the chemical formula 5, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, 2≤d≤3, and a+b+c=1. M1 is a buffer metal element, which is Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof. M2 is a dopant element, which is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

20. The method for manufacturing the positive electrode active material for lithium secondary batteries according to claim 16, characterized in that, The precursor is a secondary particle formed by the aggregation of multiple primary particles, and the average particle size (D50) of the secondary particles is 3 to 12 μm.

21. The method for manufacturing the positive electrode active material for lithium secondary batteries according to claim 16, characterized in that, The SPAN value of the precursor is 0.3 to 0.

7.

22. A precursor for positive electrode active material in lithium secondary batteries, characterized in that, Represented by any one of the following chemical formulas 2 to 5, and having a sphericity of 0.8 or higher. [Chemical Formula 2] (Ni a M1 b M2 c )(OH)2 In the aforementioned chemical formula 2, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, and a+b+c=1. M1, as a buffer metal element, is Ti, Nb, W, Zr, V, Cr, Mo, Ta, or a combination thereof. M2, as a dopant element, is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc, or a combination thereof. [Chemical Formula 3] (Ni a M1 b M2 c CO3 In the aforementioned chemical formula 3, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, and a+b+c=1. M1, as a buffer metal element, is Ti, Nb, W, Zr, V, Cr, Mo, Ta, or a combination thereof. M2, as a dopant element, is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc, or a combination thereof. [Chemical Formula 4] (Ni a M2 C )(OH)2·M1 b O d In the aforementioned chemical formula 4, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, 2≤d≤3, and a+b+c=1. M1, as a buffer metal element, is Ti, Nb, W, Zr, V, Cr, Mo, Ta, or a combination thereof. M2, as a dopant element, is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc, or a combination thereof. [Chemical Formula 5] (Ni a M2 c CO3·M1 b O d In the chemical formula 5, 0.75≤a≤0.98, 0.02≤b≤0.25, 0≤c≤0.1, 2≤d≤3, and a+b+c=1. M1 is a buffer metal element, which is Ti, Nb, W, Zr, V, Cr, Mo, Ta or a combination thereof. M2 is a dopant element, which is Al, B, Y, Co, Mn, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

23. A positive electrode for a lithium secondary battery, characterized in that, include, The positive electrode active material according to any one of claims 1 to 15.

24. A lithium secondary battery, characterized in that, include, The positive electrode for a lithium secondary battery as described in claim 23.

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