Positive electrode active material having enhanced particle durability

Abstract

The present invention provides a positive electrode active material comprising Ni and having a particle durability in the range of 20 to 60, the particle durability being defined as (C×S×102) / G, wherein C is an Li site occupancy percentage of Ni2+ (hereinafter, Ni2+ occupancy rate), S is a span value calculated using (D90-D10) / D50 according to particle-size distribution (PSD), and G is a grain size (㎛).

Description

Cathode active material with enhanced particle durability The present invention relates to a positive electrode active material, and more specifically, to a material that essentially comprises Ni and has Ni within its crystal structure. 2+ The present invention relates to a positive electrode active material that exhibits excellent electrochemical properties through enhanced particle durability, defined by the Li site occupancy rate, Span value in PSD distribution, and crystal grain size, satisfying a specific numerical range. Conventional cathode active materials for lithium secondary batteries have primarily used lithium transition metal composite oxides, particularly Co; however, due to disadvantages in terms of cost and energy density, active research has recently been conducted on Ni-based cathode active materials, which are advantageous in terms of capacity. Although such Ni-based cathode active materials can achieve a high level of capacity, there is a problem in that cation mixing occurs, where some Ni ions occupy the sites of Li ions within the cathode active material, which leads to a decrease in capacity and a rapid deterioration in cycle characteristics during repeated charge-discharge cycles. Meanwhile, when manufacturing a positive electrode for a secondary battery, a rolling process is performed after the positive electrode active material is applied onto a current collector. However, due to the pressure applied during this process, stress accumulates inside the active material particles and cracks occur, resulting in the destruction of some active material particles. Consequently, side reactions in the electrolyte caused by the destroyed particle areas are triggered, accelerating the deterioration of cycle characteristics. Therefore, there is a high need in the industry for new technologies that can improve particle strength and cycle characteristics while maintaining the high energy density of nickel-based cathode active materials. The present invention aims to solve the problems of the prior art described above and technical challenges that have been requested over time. After conducting in-depth research and various experiments, the inventors of this application were able to establish a new relational equation that defines the correlation between the particle strength of a Ni-based cathode active material and certain factors. They confirmed that if the value derived from this relational equation satisfies a predetermined numerical range, it is possible to mitigate particle fracture occurring during the rolling process of the cathode active material and the resulting degradation of cycle characteristics, thereby completing the present invention. Accordingly, the positive active material according to the present invention is, It is characterized by containing Ni, and having a particle durability defined by the following equation 1 in the range of 20 to 60. Particle durability = (C×S×10 2 ) / G (1) In the above formula, C is Ni 2+ The percentage of Li sites occupied by (hereinafter, Ni 2+ (share) and; S is based on the PSD particle size distribution (D 90 -D 10 ) / D 50 It is a Span value calculated as; G is the crystal particle size (㎛). In the present invention, "particle durability" refers to the degree to which a particle is not destroyed by an applied external force, i.e., mechanical strength, and at the same time, the degree to which the crystal structure does not collapse during repeated charge-discharge cycles, i.e., chemical and / or physical bonding strength; it can be described as a unitless numerical value that comprehensively encompasses these factors. Therefore, high particle durability means that there is less particle breakage during rolling in the electrode manufacturing process, and the characteristics can be maintained for a longer period even when charge-discharge cycles are repeated. For example, as shown in the experimental example described below, when manufactured into a lithium secondary battery, a positive electrode active material with excellent cycle characteristics can be indirectly judged to have high mechanical strength, less breakage during rolling, and high particle durability. In the above relationship, each factor has a direct or indirect influence on particle strength. As can be confirmed in the experimental details described below, the present invention establishes an optimal relationship of physical properties to improve particle durability while securing the capacity characteristics of the cathode active material by controlling manufacturing process elements such as calcination temperature, calcination time, and the input amount of lithium raw material. Accordingly, a positive electrode active material satisfying the numerical range of particle durability defined in the present invention can be realized by controlling manufacturing process elements such as calcination temperature, calcination time, and the amount of lithium raw material input. For example, the higher the calcination temperature for manufacturing the cathode active material, the more heat is applied to the particles; in this case, particle growth is promoted and the crystal grain size increases, while the formation of the rock-salt phase is reduced, and Ni 2+ The share decreases. In addition, particle growth is promoted by the increase in heat, widening the particle size distribution, and consequently, the Span value increases. Conversely, the lower the firing temperature, the less heat is applied to the particles, and Ni 2+ While the share increases, the span value and grain size decrease. Since various manufacturing process elements, such as calcination time and the input amount of lithium raw materials, have a complex influence on the aforementioned factors determining particle durability, and because these factors do not fluctuate in the same trend as each manufacturing process element is controlled, it is important to improve particle strength and consequently cycle characteristics through appropriate coordination. For example, when a cathode active material is calcined at a low temperature for a long time, grain growth occurs slowly, forming primary and crystal grains and dense secondary grains, which can improve physical grain strength. However, Ni 2+ Despite the rapid increase in occupancy and the low grain breakage caused by rolling, the grains themselves are structurally unstable, making it difficult to achieve the desired level of cycle characteristics. The present invention relates to mechanical strength, which is predominantly influenced by the crystal grain size of the positive active material particles, overall particle density, which is influenced by the Span value, and Ni 2+ It is characterized by exhibiting superior electrochemical performance compared to conventional cathode active materials by satisfying a predetermined numerical range of particle durability, which is established based on mutual organic relationships such as the structural stability of the particle itself that is affected by the occupancy rate. However, the particle durability defined in the present invention is an indicator representing the optimal range for improving the particle strength and cycle characteristics of the cathode active material, and the degree of performance improvement and the numerical value of particle durability are not necessarily proportional. For example, if the particle durability of two different cathode active materials is 30 and 50, respectively, both active materials satisfy the numerical range presented in the present invention and are superior to active materials that fall outside this range; however, this does not mean that the active material with a particle durability of 50 necessarily has higher cycle characteristics. Therefore, the numerical range of particle durability from 20 to 60 defined in the above-mentioned Equation 1 can be considered as a range defining boundary values ​​for exhibiting the effects intended in the present invention, and particle durability values ​​exceeding this range cannot be considered as the cathode active material intended in the present invention. In addition, in the experimental details described below, only the difference in particle durability according to variations in calcination temperature and Li / Me was compared between the examples and comparative examples, but the methods for controlling the major factors determining particle durability are not limited to this. The cathode active material according to the present invention essentially includes Ni. The higher the Ni content included in the cathode active material, the more the energy density can be maximized. For example, by including at least 50 mol% of Ni based on the total transition metal content, it is possible to provide the improved particle strength desired in the present invention and the excellent cycle characteristics resulting therefrom while securing a certain level of capacity characteristics. In one preferred example, C may be in the range of 0.02 to 0.05 (or 2% to 5%), S may be in the range of 0.5 to 1.1, and G may be in the range of 0.02 to 0.10 μm (or 20 to 100 nm). First, Ni 2+ In relation to C, which represents the share, Ni within the crystal structure of the cathode active material 2+"Ni" is the proportion of the Li ion lattice structure occupied. 2+ "Occupancy" is one of the key factors determining the stability of the crystal structure. Generally, Ni 2+ While a higher occupancy rate leads to capacity degradation due to cation mixing within the crystal structure of the cathode active material, an appropriate level of cation mixing can actually enhance structural stability through the pillar effect, thereby suppressing the occurrence of additional cation mixing. Furthermore, the particle size generally decreases during the process of setting calcination temperature and Li / Me ratios to achieve an appropriate level of cation mixing; in this case, the lithium path is shortened, which can improve charge-discharge efficiency. Such Ni 2+ The occupancy rate can increase, for example, as the lithium / transition metal ratio (Li / Me) within the cathode active material decreases; this is because a lower ratio results in more empty Li sites within the crystal structure, making it more likely that Ni, which constitutes the majority of transition metals, will occupy them. Therefore, when C, which is the percentage of Ni ions among the total Li sites in the crystal structure, is within the specific range defined above, namely 0.02 to 0.05, it is possible to improve structural stability while minimizing the adverse effects of cation mixing. Second, regarding the Span value S, the Span value is generally an indicator of the uniformity of the particle size distribution in the particle size distribution of the cathode active material. Specifically, the larger the Span value, the wider the particle size distribution and the greater the variation between particle sizes. In this case, when an external force is applied to the particles, stress may concentrate towards the larger particles, and the particles may be more easily destroyed; therefore, it is desirable that the Span value not be excessively large. On the other hand, the smaller the Span value, the narrower the particle size distribution and the smaller the variation between particle sizes, so even when an external force is applied, stress is distributed evenly across a large number of particles; however, if the distribution is excessively uniform, the voids between particles are not sufficiently filled, which may actually lead to a decrease in energy density. Therefore, (D 90 -D 10 ) / D 50 In order for the Span value to exhibit appropriate physical properties, it is desirable to satisfy the range of 0.45 to 1.10 as defined above. Third, regarding G, the grain size (μm), grain size can be one of the most dominant factors affecting grain strength in cathode active materials. Generally, grain strength tends to increase as grain size decreases, because smaller grain sizes provide more grain boundaries, resulting in higher resistance to deformation. However, if the grain size is excessively small, an excess of grain boundaries actually lowers the threshold for the occurrence of internal defects or cracks. In other words, there is an upper limit to improving grain strength through the reduction of grain size. Conversely, if the grain size is excessively large, there are fewer grain boundaries, inter-grain bonding weakens, or defect migration becomes easier, which can make the material vulnerable to mechanical stress. Accordingly, conventionally, a method was used to suppress the movement of dislocations or defects by reducing the crystal grain size to improve the mechanical strength of particles or powders; however, since the conductivity of Li ions is also reduced in this case, controlling only the crystal grain size to control only the particle strength is not the best solution. Therefore, Ni 2+ In relation to the occupancy rate and particle size distribution, the crystal particle size G is preferably in the range of 0.02 to 0.10 μm, as defined above. For reference, the crystal particle size of particle durability defined in the present invention is a measurement value in nm converted to μm. The present invention may be particularly more preferable for a positive electrode active material containing 80 mol% or more of Ni based on the total transition metal content. Generally, as the Ni content in the cathode active material increases, the crystal grains grow rapidly during sintering, which can lengthen the migration path of Li and reduce efficiency characteristics. Additionally, the low porosity prevents sufficient buffering of external forces, resulting in a rapid decrease in mechanical strength. On the other hand, the cathode active material according to the present invention, despite its high Ni content, satisfies a predetermined range of particle durability, thereby enabling the realization of desired cycle characteristics through excellent particle strength even after the rolling process. Generally, as the Ni content increases, the phenomenon of structural stability degradation due to oxygen desorption can be exacerbated. Therefore, when an active material contains a high amount of Ni to secure capacity characteristics, the calcination temperature must be lowered for low-temperature calcination. However, this leads to a decrease in structural stability due to increased cation mixing and insufficient grain growth, thus limiting the ability to increase the Ni content to secure high capacity. In contrast, the cathode active material of the present invention can exhibit excellent particle strength, so it can be preferably applied even when the Ni content is high. In one specific example, the positive active material of the present invention may be configured to include the composition of the following chemical formula A. Li a (Ni w Co x Mn y D z ) b O c (A) In the above formula, 0.93≤a≤1.13, 0.5 <w<1, 0<x≤0.1, 0≤y≤0.4, 0≤z≤0.1, 0.93≤b≤1.13이고; D is one or more elements selected from the group consisting of Al, Zr, W, Ti, B, P, Si, Mg, Y, Cr, Ta, La, V, Nb, and Mo. In a desirable example, the condition w+x+y+z=1 can be applied. The positive active material of the present invention comprises at least 50 mol%, preferably 80 mol% or more, of Ni as defined above, and may optionally further comprise transition metals such as Co and Mn and / or additional elements. Specifically, the molar ratio of lithium to transition metal (Li / Me) may be 0.93 to 1.13. This can be controlled in relation to manufacturing process factors and Ni content, etc. For example, as the calcination temperature decreases, the ion diffusion power decreases, making it difficult to insert Li ions; therefore, Li / Me may be less than 1. If Li / Me is greater than 1 during low-temperature calcination, insufficient heat is applied, and Li ions on the surface side that are not inserted may form residual lithium, which can degrade electrochemical properties. Conversely, as the calcination temperature increases, the ion diffusion power increases, allowing sufficient insertion of Li ions even if Li is increased to 1 or more. However, since raising the calcination temperature excessively is undesirable because the cathode active material particles become close to single particles, an upper limit for Li / Me may be set according to the upper limit of the calcination temperature. Meanwhile, if a portion of the transition metal content in the cathode active material is substituted with Co, structural stability is further improved. However, if an excessive amount of transition metal is substituted, the effect of other transition metals may be excessively weakened, so it is desirable that the Co content be 10 mol% or less based on the total transition metal. Furthermore, in addition to improving the mechanical and chemical strength of the cathode active material by ensuring particle durability, if additional elements are added to the crystal structure, the desired characteristics can be further enhanced. For example, Al can further improve charge / discharge efficiency by improving surface resistance and lithium ion reactivity. Zr can improve structural stability and thermal properties, and enhance lifespan characteristics by suppressing structural collapse occurring at the particle surface through structural stabilization. W has excellent conductivity and reacts with residual lithium to improve interfacial characteristics by reducing byproducts and suppressing interfacial reactions, and can improve the discharge capacity, output characteristics, and lifespan characteristics of lithium secondary batteries. Ti can improve electrochemical properties and thermal stability, reduce structural instability such as side reactions with the electrolyte, and increase the surface protection effect of active material particles against electrolyte decomposition. B improves structural stability by enhancing particle strength, has the effect of suppressing cracks occurring inside the particles during life evaluation, and can improve the ionic conductivity of the active material. P can ensure structural stability and improve the stability and lifespan characteristics of lithium secondary batteries by reducing residual lithium. Si can improve the thermal stability of the active material, and Mg can suppress phase changes of the active material and enhance the protective effect on the surface of the active material against electrolyte decomposition. In another specific example, the positive active material of the present invention may be in the form of secondary particles in which a plurality of primary particles are aggregated. As mentioned above, if the particle durability satisfies a predetermined numerical range, sintering is possible at higher temperatures without being significantly constrained by the Ni content; however, as the sintering temperature increases, the crystal grain size is maximized, and ultimately, it may take the form of a single particle or a single particle formed by the aggregation of a small number of primary particles. However, in this case, the efficiency is reduced because the path of Li ions is long, and the capacity characteristics may also be inferior to those of secondary particles due to the low intrinsic density of the particles. In addition, the positive electrode active material of the present invention may have a tap density in the range of 1.9 to 2.6 g / cc. Tap density refers to the degree to which positive active material particles are densely arranged; a higher tap density means that the particles exist in a densely packed form, i.e., the space between the particles is narrow. While smaller interparticle voids allow for more cathode active material to be packed into the same volume, thereby improving energy density, applying external force may hinder interparticle movement or cause stress concentration, which can further intensify particle destruction. Therefore, considering the rolling process during electrode plate manufacturing, it is desirable that the tap density not be excessively high. Conversely, if the tap density is excessively low, it is difficult to secure a significant level of energy density. Since this tap density is determined by the degree of particle packing, it is closely related to the Span value. For example, the larger the Span value, the more small particles are present; as these particles fill the voids between large particles, the density of the cathode active material powder can be further improved, and the tap density can be higher. However, as mentioned above, an excessively high Span value can actually reduce the mechanical strength of the particles; therefore, it is desirable to set an optimal numerical range by considering the mutually inverse relationship between the two properties, and accordingly, the present invention proposes the tap density range described above. The present invention also provides a secondary battery characterized by including the above positive active material. Since the composition and manufacturing method of secondary batteries are known in the art, a detailed description thereof is omitted in this specification. As explained above, the positive active material of the present invention is a Ni-based positive active material within the Li site of the Ni-based positive active material. 2+Since the occupancy rate, the span value of the PSD distribution, and the grain size mutually satisfy specific conditions, high grain strength can be maintained, so the shape is firmly maintained even under pressure applied during the electrode manufacturing process and internal stress caused by repeated charging and discharging processes, and as a result, excellent cycle characteristics can be exhibited. FIG. 1 is an SEM image of the positive electrode active material according to Example 1 performed in Experimental Example 2 after 50 cycles; Figure 2 is an SEM image of the positive active material according to Comparative Example 1 after 50 cycles performed in Experimental Example 2. The present invention will be described further below with reference to embodiments thereof, but the scope of the invention is not limited by them. [Example 1] Ammonia water and caustic soda aqueous solutions were continuously supplied to an aqueous metal salt solution prepared by adding NiSO4, CoSO4, and MnSO4 as transition metal raw materials to distilled water in a molar ratio of 90:5:5 in a CSTR reactor, and co-precipitated for 2 hours at a stirring speed of 600 rpm and a reaction temperature of 50°C with an ammonia concentration in the reactor ranging from 4,000 to 7,000 ppm and a pH ranging from 11.4 to 11.7, so that the composition of Ni 0.90 Co 0.05 Mn 0.05 A transition metal precursor of (OH)2 was prepared. LiOH is mixed with the above precursor to achieve a molar ratio (Li / Me) of 0.97, and calcined at 610°C for 24 hours to obtain a composition of Li(Ni 0.90 Co 0.05 Mn 0.05 A positive electrode active material containing )O2 was prepared. [Example 2] A positive electrode active material was prepared in the same manner as in Example 1, except that the calcination temperature was changed to 700℃. [Example 3] A positive electrode active material was prepared in the same manner as in Example 1, except that the calcination temperature was changed to 730℃. [Example 4] A positive electrode active material was prepared in the same manner as in Example 1, except that the calcination temperature was changed to 760℃. [Example 5] A positive electrode active material was prepared in the same manner as in Example 1, except that the Li / Me ratio was changed to 1.02. [Example 6] A positive electrode active material was prepared in the same manner as in Example 5, except that 5,000 ppm of TiO2 was added when mixing LiOH with the precursor. [Example 7] A positive electrode active material was prepared in the same manner as in Example 1, except that the composition of the metal salt aqueous solution was changed to Ni:Co:Mn=60:10:30 when preparing the transition metal precursor. [Comparative Example 1] A positive electrode active material was prepared in the same manner as in Example 1, except that the Li / Me ratio was changed to 0.89. [Comparative Example 2] A positive electrode active material was prepared in the same manner as in Example 1, except that Li / Me was changed to 1.13. [Comparative Example 3] A positive electrode active material was prepared in the same manner as in Example 2, except that the Li / Me ratio was changed to 0.89. [Comparative Example 4] A positive electrode active material was prepared in the same manner as in Example 2, except that Li / Me was changed to 1.13. [Comparative Example 5] A positive electrode active material was prepared in the same manner as in Example 3, except that the Li / Me ratio was changed to 0.89. [Comparative Example 6] A positive electrode active material was prepared in the same manner as in Example 3, except that Li / Me was changed to 1.13. [Comparative Example 7] A positive electrode active material was prepared in the same manner as in Example 4, except that the Li / Me ratio was changed to 0.89. [Comparative Example 8] A positive electrode active material was prepared in the same manner as in Example 4, except that Li / Me was changed to 1.13. [Comparative Example 9] A positive electrode active material was prepared in the same manner as in Example 1, except that the calcination temperature was changed to 800℃. [Experimental Example 1] For the cathode active materials prepared in Examples 1 to 7 and Comparative Examples 1 to 9, respectively, under the following measurement conditions, Ni 2+ The occupancy rate, crystal particle size (measurement unit nm converted to μm), particle size distribution, tap density, etc. were each measured, and the results are shown in Table 1 below. <XRD 측정 조건> - Power Source: CuKα (Line Focus), Wavelength: 1.541836 Å - Control axis: 2θ / θ, Measurement method: Continuous, Counting unit: cps - Start angle: 10.0°, End angle:

[0220] 120.0°, Accumulation count: 1 time - Sampling width: 0.02°, Scan speed: 2° / min - Voltage: 40kV, Current: 30mA - Divergence slit: 0.3 mm, Divergence species limiting slit: 10 mm - Scattering slit: Open, Receiving slit: Open - Offset angle: 0° - Goniometer radius: 285 mm, Optical system: Focusing method - Attachment: ASC-48 - Slit: Slit for D / teX Ultra - Detector: D / teX Ultra - Incident Monochrome: CBO - Ni-Kβ filter: None - Rotation speed: 30 rpm < PSD (Particle Size Distribution) Measurement Conditions > - Measuring equipment: Microtrac S3500 Extended - Run Time: 30s - Flow Rate(%): 40% - Refraction index: 1.33 - Solvent: Distilled water - Analysis Mode: X100 - Sample amount: 0.0025g - Sample Injection Dispersant: 10% Sodium Hexamethaphosphate 1 ml - Sample input solvent: 40 ml distilled water - Sonication: 40KHz, 1min As shown in Table 1 above, the cathode active material of the examples is Ni 2+ It can be confirmed that the conditions of a occupancy rate of 0.02 to 0.05, a span value of 0.45 to 1.10, and a grain size of 0.02 to 0.10 μm are satisfied. Based on this, it can be seen that the calculated particle durability values ​​fall within the range of 20 to 60, and the tap density falls within the range of 2.11 g / cc to 2.58 g / cc. On the other hand, the cathode active materials of all comparative examples have particle durability values ​​of less than 20 or greater than 60, which is Ni 2+ It can be said that this is caused by some or all values ​​among the occupancy rate, span value, and grain size being excessively small or large. [Experimental Example 2] A positive active material slurry was prepared by mixing the positive active materials prepared in Examples 1 to 7 and Comparative Examples 1 to 9, respectively, with Super-P, a conductive material, and PVdF, a binder, in a solvent of N-methylpyrrolidone in a ratio of 93:5:2 (weight ratio). This slurry was then coated onto an aluminum current collector, dried at 120°C, and then rolled to produce a positive electrode. An electrode assembly was prepared by using lithium metal as the negative electrode and a porous polyethylene film as a separator between the positive electrode and the electrode assembly. The electrode assembly was placed inside a battery case, and an electrolyte was injected into the battery case to produce a lithium secondary battery. At this time, the electrolyte used was prepared by dissolving 1.0 M concentration lithium hexafluorophosphate (LiPF6) in an organic solvent composed of ethylene carbonate / dimethyl carbonate (mixed volume ratio of EC / DMC = 1:1). For each of the lithium secondary batteries prepared above, charging and discharging were performed under conditions of 0.1C 4.3V (charging) and 0.1C 2.7V (discharging), and 50 charging and discharging cycles were performed under conditions of 0.5C 4.3V (charging) and 1.0C 2.7V (discharging) at 45℃, and the results are shown in Table 2 below. As shown in Table 2 above, it can be seen that the lithium secondary batteries of the examples have a significant difference in cycle characteristics when compared to the lithium secondary batteries of the comparative examples. Specifically, when comparing Comparative Examples 1 and 2 against Example 1, Comparative Examples 3 and 4 against Example 2, Comparative Examples 5 and 6 against Example 3, and Comparative Examples 7 and 8 against Example 4 under mutually corresponding manufacturing conditions, the difference in cycle characteristics can be easily confirmed. For reference, FIG. 1 shows an SEM image of the positive electrode active material after 50 cycles according to Example 1, and FIG. 2 shows an SEM image of the positive electrode active material after 50 cycles according to Comparative Example 1. When referring to Figures 1 and 2 together, it can be seen that the cathode active material of Comparative Example 1 has many broken particles compared to the cathode active material of Example 1, which leads to increased side reactions with the electrolyte and deterioration of cycle characteristics. The present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without changing the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. A positive electrode active material characterized by containing Ni and having a particle durability defined by the following equation 1 in the range of 20 to 60: Particle durability = (C×S×10 2 ) / G (1) In the above formula, C is Ni 2+ The percentage of Li sites occupied by (hereinafter, Ni 2+ (share) and; S is based on the PSD particle size distribution (D 90 -D 10 ) / D 50 It is a Span value calculated as; G is the crystal particle size (㎛).

2. The positive active material according to claim 1, characterized in that C is in the range of 0.02 to 0.

05.

3. The positive active material according to claim 1, characterized in that S is in the range of 0.45 to 1.

10.

4. The positive active material according to claim 1, characterized in that G is in the range of 0.02 to 0.10 μm.

5. The positive electrode active material according to claim 1, characterized by containing 80 mol% or more of Ni based on the total transition metal content.

6. A positive active material according to claim 1, characterized by comprising the composition of the following chemical formula A: Li a (Ni w Co x Mr y D z ) b O c (A) In the above formula, 0.93≤a≤1.13, 0.5 <w<1, 0<x≤0.1, 0≤y≤0.4, 0≤z≤0.1, 0.93≤b≤1.13이고; D is one or more elements selected from the group consisting of Al, Zr, W, Ti, B, P, Si, Mg, Y, Cr, Ta, La, V, Nb, and Mo.

7. The positive active material according to claim 1, characterized in that it is in the form of secondary particles in which a plurality of primary particles are aggregated.

8. The positive electrode active material according to claim 1, characterized in that the tap density is in the range of 1.9 to 2.6 g / cc.

9. A secondary battery characterized by including a positive electrode active material according to claim 1.

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