Positive electrode active material for secondary battery

Abstract

Positive electrode active material particles according to an aspect of the present invention comprise a bulk region and a coating region, the coating region containing cobalt (Co), wherein on a scanning electron microscope (SEM) image of one surface of the positive electrode active material particles, the ratio of the coating area of the coating region to the total area of the one surface may be 83% to 96%.

Description

Cathode active material for secondary batteries

[0001] The present invention relates to positive electrode active material particles and a positive electrode active material for a secondary battery containing the same, and more specifically, to a positive electrode active material that significantly improves the stability, lifespan, and output performance of a secondary battery when applied by controlling the composition, coating method, and coating form of a coating material containing cobalt (Co) of a lithium composite oxide.

[0002]

[0003] With the advancement of portable mobile electronic devices such as smartphones, MP3 players, and tablet PCs, the demand for rechargeable batteries capable of storing electrical energy is increasing explosively. In particular, the demand for lithium-ion batteries is rising due to the emergence of electric vehicles, medium-to-large energy storage systems, and portable devices requiring high energy density.

[0004] As a lithium composite oxide included in cathode active materials, the material currently receiving the most attention is lithium nickel (manganese / aluminum) cobalt oxide (Li(Ni x Co y( Mn / Al) z )O2(wherein x, y, and z are each the atomic fractions of independent oxide composition elements, 0 <x≤1, 0<y≤1, 0<z≤1, 및 0<x+y+z≤1)이다. 이 양극활물질 재료는 그동안 양극활물질로서 활발히 연구되고 사용되어 왔던 LiCoO2보다 고전압에서 사용되기 때문에 고용량을 내는 장점이 있고, Co 함량이 상대적으로 적기 때문에 저가격이라는 장점이 있다.

[0005] However, these lithium composite oxides undergo volume changes due to the intercalation and deintercalation of lithium ions during charging and discharging. There are problems such as the primary particles of the lithium composite oxide rapidly changing in volume during charging and discharging, cracks occurring in the secondary particles due to repeated charging and discharging, or the collapse of the crystal structure or phase transition of the crystal structure.

[0006] To compensate for these drawbacks, the demand for high-nickel cathode active materials for secondary batteries, which have a high nickel (Ni) content relative to the total metal content excluding lithium (Li), has begun to increase.

[0007]

[0008] The present invention aims to provide a positive electrode active material that significantly improves the stability, lifespan, and output performance of a secondary battery when applied to a secondary battery by controlling the composition, coating method, and coating form of a coating material containing cobalt (Co).

[0009] In particular, the present invention aims to provide a positive electrode active material with a controlled coating area ratio that can improve battery performance when a non-washing cobalt (Co) coating method is applied to compensate for the disadvantages of washing coating using a coating solution.

[0010]

[0011] A positive electrode active material particle according to one embodiment of the present invention comprises a bulk region and a coating region, wherein the coating region comprises cobalt (Co), and in a scanning electron microscope (SEM) image of one surface of the positive electrode active material particle, the ratio of the coating area of ​​the coating region to the total area of ​​one surface may be 83% to 96%.

[0012] In a more preferred embodiment, the cathode active material particle comprises one or more unit coating regions, wherein the unit coating region refers to a closed coating region not connected to other coating regions on the surface of the bulk region, and the average value of the area of ​​the unit coating region is 3.0 μm 2 to 8.0 μm 2 It could be.

[0013] In a more preferred embodiment, the number of unit coating regions in the positive electrode active material particles may be 1 to 10.

[0014] In a more preferred embodiment, the average value of the slope of the perimeter of the closed coating area on the surface of the bulk area may be 70° or less.

[0015] In a more preferred embodiment, the average value of the thickness of the coating region measured in a vertical direction from the surface of the bulk region may be 20 nm to 60 nm.

[0016] In a more preferred embodiment, the coating region may further include one or more selected from aluminum (Al), zirconium (Zr), boron (B), tungsten (W), yttrium (Y), and titanium (Ti).

[0017] In a more preferred embodiment, the bulk region may be doped with one or more elements selected from cobalt (Co), zirconium (Zr), barium (Ba), strontium (Sr), aluminum (Al), and titanium (Ti).

[0018] In a more preferred embodiment, the average particle size (D50) of the positive active material particles may be 2.0 μm to 6.0 μm.

[0019] In a more preferred embodiment, the bulk region may consist of one single particle or may contain two to eight single particles in contact.

[0020] A positive electrode active material according to one embodiment of the present invention may include the positive electrode active material particles.

[0021]

[0022] As an effect, the present invention provides an anode active material with increased stability and reinforced bulk and coating structures, while suppressing direct contact between the surface and the electrolyte to reduce the amount of gas generated that directly affects the reduction of lifespan.

[0023] As an effect, the present invention provides a positive electrode active material that significantly improves the stability, lifespan, and output performance of a secondary battery.

[0024]

[0025] Figure 1 is an SEM image of the surface of a positive electrode active material particle according to one manufacturing example of the present invention.

[0026] Figure 2 is an SEM image of the surface of a positive electrode active material particle according to one manufacturing example of the present invention.

[0027]

[0028] Expressions such as "comprising" as used in this specification should be understood as open-ended terms implying the possibility of including other configurations.

[0029] As used herein, "preferably" and "preferably" refer to embodiments of the present invention that can provide certain advantages under certain conditions. However, it is not intended to exclude other embodiments from the scope of the present invention.

[0030] Furthermore, the singular form used in the specification and the appended claims may be intended to include the plural form unless specifically indicated otherwise in the context. That is, a technical feature of a single particle may mean a technical feature of multiple particles, or may be intended to mean an average technical feature of multiple particles.

[0031] The numerical ranges used in this specification include lower and upper limits and all values ​​within the range, increments logically derived from the form and width of the defined range, all of which are limited values, and all possible combinations of upper and lower limits of numerical ranges limited in different forms.

[0032] Unless otherwise specifically defined in this specification, values ​​outside the numerical range that may occur due to experimental error or rounding are also included in the defined numerical range.

[0033] The meanings of '≤', 'greater than or equal to', or 'less than or equal to' as described in this specification may be replaced with the meanings of '<', 'greater than', or 'less than'.

[0034]

[0035] Meanwhile, the technical features described below relate to one embodiment that achieves the intended effect of the present invention described above.

[0036] That is, the positive electrode active material according to one embodiment of the present invention includes the technical features according to one embodiment described below, thereby further strengthening the bulk structure and coating structure of the particles and significantly improving the performance of the stability, lifespan, and output of the secondary battery.

[0037] The present invention relates to positive electrode active material particles for a secondary battery and a positive electrode active material comprising a plurality of such particles.

[0038] The secondary battery of the present invention is not limited to any type as long as it is a battery that converts external electrical energy into the form of chemical energy for storage and reuse. As an example, the present invention may relate to a positive electrode active material for a lithium-ion secondary battery.

[0039] A positive electrode active material particle according to one embodiment of the present invention comprises a bulk region and a coating region.

[0040] First, the above bulk area will be explained.

[0041] In one embodiment, the bulk region may be a lithium composite oxide.

[0042] In one embodiment, the bulk region may be a lithium composite oxide containing nickel (Ni).

[0043] In one embodiment, the bulk region may be a lithium composite oxide containing nickel (Ni) and cobalt (Co).

[0044] In one embodiment, the lithium composite oxide can be represented by the following chemical formula 1.

[0045] [Chemical Formula 1]

[0046] Li a Ni x M1 y M2 1-x-y O2

[0047] In the above chemical formula 1, M1 is selected from the group consisting of cobalt (Co), manganese (Mn), aluminum (Al) and combinations thereof, and M2 is selected from the group consisting of Zr, Mn, Al, B, S, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, Na, K, Hf, Ta, Cu, Ta and combinations thereof, and 0.9≤a≤1.2 and 0.1≤x<1.0, 0.0≤y≤0.5, and 0.0≤1-xyz≤0.5.

[0048] In one embodiment, in the above chemical formula 1, a, which represents the mole% of lithium (Li) relative to the mole% of the total transition metal excluding lithium (Li), may be 0.9 or more, 1.0 or more, 1.2 or less, 1.1 or less, or 1.05 or less.

[0049] In one embodiment, x, which represents the mole% of nickel (Ni) relative to the mole% of the total transition metal excluding lithium (Li) in the above chemical formula 1, may be 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more, and in particular, the present invention may be a high-nickel (high-Ni) oxide in which x is 0.5 or more.

[0050] While these high-nickel cathode active materials have the advantage of high energy density, the high Li / M ratio during manufacturing results in a high residual lithium content remaining in the cathode active material after calcination, which causes gelation during the preparation of the electrode slurry, making cell manufacturing difficult. Accordingly, a washing process is introduced to remove residual lithium, but there is a problem in that the cathode surface is damaged during the washing process, leading to reduced battery performance.

[0051] In addition, due to the high Ni content, the structure becomes unstable and there is a problem where lifespan characteristics deteriorate as a large amount of gas is released during repeated charge-discharge processes due to increased reactions with the electrolyte at the particle surface and interface. The present invention can resolve this problem, which is particularly exacerbated in high-nickel (high-Ni) cathode active materials.

[0052] In one embodiment, in the above chemical formula 1, where y represents the mole% of cobalt (Co) relative to the mole% of the total transition metal excluding lithium (Li), y may be 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[0053] In one embodiment, in the above formula 1, where y represents the mol% of Al and / or Mn relative to the mol% of the total transition metal excluding lithium (Li), y may be 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, 0.1 or less, 0.1 or more, 0.2 or more, or 0.3 or more.

[0054] In a more preferred embodiment, the bulk region may be doped with one or more elements selected from cobalt (Co), zirconium (Zr), barium (Ba), strontium (Sr), titanium (Ti), aluminum (Al), niobium (Nb), vanadium (V), molybdenum (Mo), boron (B), yttrium (Y), tungsten (W), magnesium (Mg), zinc (Zn), iron (Fe), tantalum (Ta), silicon (Si), and fluorine (F).

[0055] More preferably, the bulk region may be doped with one or more elements selected from cobalt (Co), zirconium (Zr), barium (Ba), strontium (Sr), aluminum (Al), and titanium (Ti).

[0056] When manufacturing the cathode active material of the present invention, a lithium composite oxide can be prepared by heat-treating a hydroxide precursor and a lithium compound. At this time, the doping element can be uniformly doped into the lattice structure of the primary particles by heat-treating together.

[0057] In another aspect of the aspect, when lithium composite oxide particles are coated, some of the coating elements may exist within the lattice structure of the primary particles contained within the lithium composite oxide particles. In this case, the coating elements may be doped into the lithium composite oxide particles.

[0058] Meanwhile, the lithium composite oxide particles regarding the bulk region are defined to include all of the doped regions in this way.

[0059] In one embodiment, cobalt (Co) is a coating element that is coated after preparing a lithium composite oxide, and can be doped during the coating heat treatment and exist within the lattice structure of the primary particles.

[0060] In one embodiment, aluminum (Al) is a coating element that is coated after the lithium composite oxide is prepared, and can be doped during the coating heat treatment and exist within the lattice structure of the primary particles.

[0061] In one embodiment, zirconium (Zr) is a coating element that is coated after preparing a lithium composite oxide, and can be doped during the coating heat treatment and exist within the lattice structure of the primary particles.

[0062] As described above, by controlling the doping element and bulk composition, the present invention can further strengthen the coating structure and further improve the performance of the stability, lifespan, and output of the secondary battery.

[0063] Next, the above-mentioned coating area is described.

[0064] In one embodiment, the coating region may be a region distinct from the lithium composite oxide particles, which is a bulk region.

[0065] When lithium composite oxide particles according to one embodiment of the present invention are coated, a portion of the coating element may form a coating region where a coating material is present. This coating material may exist on the surface of secondary particles of the lithium composite oxide particles and / or at the grain boundaries between primary particles of the lithium composite oxide. In this case, the grain boundaries between primary particles refer to a region that includes both the space between primary particles and the surface of said primary particles.

[0066] In a more preferred embodiment, the coating region may include cobalt (Co).

[0067] In one embodiment, the cobalt (Co) is LiCoO within the coating region. 2, Li 1+a CoO2(1 <a<0.1) , Li 1-b CoO2(1 <b<0.1) , Co q O r( 0 <q<10, 0<r<10) , It can exist in the form of and / or Co(OH)2, etc.

[0068] In one embodiment, the average concentration of the cobalt (Co) element measured by EP-EDS (Energy Profiling-Energy Dispersive X-Ray Spectroscopy), which measures the average concentration of the element from the surface of the positive active material particle to the depth penetrated by the electron beam irradiated with an acceleration voltage of 1 kV on the coating area of ​​the surface of the positive active material particle, may be 20 at% or more, 30 at% or more, 40 at% or more, 50 at% or more, 80 at% or less, 70 at% or less, 60 at% or less, 50 at% or less, 40 at% or less, or 30 at% or less.

[0069] In a more preferred embodiment, the coating region may further include one or more selected from aluminum (Al), titanium (Ti), zirconium (Zr), magnesium (Mg), zinc (Zn), molybdenum (Mo), iron (Fe), nickel (Ni), barium (Ba), tungsten (W), strontium (Sr), yttrium (Y), niobium (Nb), vanadium (V), boron (B), tantalum (Ta), silicon (Si), and fluorine (F), in addition to cobalt (Co).

[0070] More preferably, the coating region may further include one or more selected from aluminum (Al), zirconium (Zr), boron (B), tungsten (W), yttrium (Y), and titanium (Ti) in addition to cobalt (Co).

[0071] More preferably, the coating region may further include one or more selected from aluminum (Al), zirconium (Zr), and boron (B) in addition to cobalt (Co).

[0072] More preferably, the coating region may further include two or more selected from aluminum (Al), zirconium (Zr), and boron (B) in addition to cobalt (Co).

[0073] More preferably, the coating region may further include aluminum (Al), zirconium (Zr), and boron (B) in addition to cobalt (Co).

[0074] Meanwhile, as an example, the molar content of each coating element and / or doping element included in the cathode active material may be 5.0 mol% or less, 3.0 mol% or less, or 1.0 mol% or less.

[0075] For example, if aluminum (Al) is included in the above-mentioned cathode active material, the content of aluminum (Al) relative to the total content of the cathode active material may be 1.0 mol% to 2.0 mol%.

[0076] For example, if zirconium (Zr) is included in the above-mentioned cathode active material, the content of zirconium (Zr) relative to the total content of the cathode active material may be 0.1 mol% to 1.0 mol%.

[0077] For example, if the above-mentioned cathode active material contains barium (Ba), the content of barium (Ba) relative to the total content of the cathode active material may be 0.05 mol% to 0.15 mol%.

[0078] The present invention can further strengthen the coating structure and further improve the performance of the stability, lifespan, and output of the secondary battery by controlling the coating composition as described above.

[0079] In a more preferred embodiment, in a scanning electron microscope (SEM) image of one surface of the positive electrode active material particle, the ratio of the coating area to the total area of ​​the one surface may be 96% or less, 95% or less, 93% or less, 90% or less, 83% or more, 85% or more, 87% or more, or 90% or more. By adjusting the coating area ratio to the above numerical range, the present invention can further strengthen the coating structure and further improve the performance of the stability, lifespan, and output of the secondary battery.

[0080] In the present invention, the coating area ratio was measured using the Image J program on a scanning electron microscope (SEM) image of one surface of a positive electrode active material particle.

[0081] Meanwhile, in the present invention, the coating area ratio can be interpreted as corresponding if the coating area ratio measured on one surface of an arbitrarily selected positive electrode active material particle satisfies the numerical range.

[0082] Meanwhile, unlike a wet process in which active material particles are immersed in a coating solution, the present invention can achieve the coating area and shape by controlling the coating content, heat treatment temperature and time, particle size, etc., through a dry coating process during secondary heat treatment without a washing process.

[0083] In particular, the present invention controls the composition of the coating material, the coating method, and the coating form so that battery performance can be further improved when a non-washing coating method is applied to compensate for the disadvantages of washing coating using a coating solution.

[0084] In one embodiment, the positive active material particle may include one or more 'unit coating regions'.

[0085] The above unit coating area refers to a closed coating area on the surface of the bulk area that is not connected to other coating areas.

[0086] More preferably, the average value of the unit coating area is 3.0 μm 2 Above, 3.2μm 2 Above, 3.5μm 2 Above, 8.0μm 2 Below, 7.0μm 2 Below, 6.0μm 2 Below, 5.0μm 2 Below, 4.5μm 2 Below, 4.0μm 2 Less than or equal to 3.8 μm 2 It may be less than or equal to, and more preferably 3.0 μm 2 to 5.0 μm 2 The following may be possible. By adjusting the unit coating area to the above numerical range, the present invention can further strengthen the coating structure and further improve the stability, lifespan, and output performance of the secondary battery.

[0087] In the present invention, the average value of the unit coating area is calculated by arbitrarily selecting 2 to 5 unit coating areas on a scanning electron microscope (SEM) image. Meanwhile, in the present invention, if the average value of the arbitrarily selected 2 to 5 unit coating area satisfies the numerical range, it can be interpreted as corresponding thereto.

[0088] In a more preferred embodiment, the number of unit coating regions in the cathode active material particles may be 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or fewer, 9 or fewer, 8 or fewer, 7 or fewer, 6 or fewer, 5 or fewer, 4 or fewer, 3 or fewer, or 2 or fewer. By adjusting the number of unit coating regions to the above numerical range, the present invention can further strengthen the coating structure and further improve the performance of stability, lifespan, and output of the secondary battery.

[0089] In a more preferred embodiment, the average value of the thickness of the coating region measured in a vertical direction from the surface of the bulk region may be 20 nm or more, 30 nm or more, 60 nm or less, or 50 nm or less.

[0090] In the present invention, the average value of the thickness of the coating area was calculated by obtaining a cross-sectional SEM image of the lithium composite oxide at a voltage of 2 kV using JSM-7610FPlus (JEOL), and then measuring the thickness of the coating area at 10 randomly selected points. Meanwhile, in the present invention, if the average value of the thickness of the coating area at 10 randomly selected points satisfies the numerical range, it can be interpreted as corresponding to this.

[0091] Meanwhile, the closed coating region may have a shape other than an island-shaped protrusion, an island, and / or an uneven shape (see FIG. 2).

[0092] In a more preferred embodiment, when looking at the inclined plane around the perimeter of the closed coating region, the average value of the slope of the inclined plane around the perimeter of the closed coating region on the surface of the bulk region may be 70° or less, 60° or less, 50° or less, or 40° or more. By adjusting the slope to the above numerical range, the present invention can further strengthen the coating structure and further improve the stability, lifespan, and output performance of the secondary battery.

[0093] In the present invention, the average value of the slope of the perimeter of the closed coating region was calculated by measuring the slope of 10 randomly selected points of the closed coating region in a scanning electron microscope (SEM) image of one surface of the cathode active material particle. Meanwhile, in the present invention, if the average value of the slope of 10 randomly selected points satisfies the numerical range, it can be interpreted as corresponding to this.

[0094] As described above, by controlling the coating method and coating type, the present invention can further strengthen the coating structure and further improve the stability, lifespan, and output performance of the secondary battery.

[0095] According to one embodiment of the present invention, the average particle size (D50) of the positive active material particles may be 2.0 μm or more, 2.5 μm or more, 3.0 μm or more, 6 μm or less, 5.5 μm or less, 5 μm or less, or 4.5 μm or less, and more preferably, 3.0 μm to 4.0 μm.

[0096] In the present invention, the average diameter (D50) is the particle size at the 50% point of the cumulative area distribution according to particle size, and this can be measured using the laser diffraction method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device, and the particle size distribution can be calculated by measuring the difference in diffraction patterns according to particle size as the particles pass through the laser beam.

[0097] Meanwhile, the bulk region of the above-mentioned positive active material particle may be a particle formed by contacting at least one single particle. Here, the single particle refers to a primary particle.

[0098] In a more preferred embodiment, the bulk region may consist of one single particle, or may contain eight or fewer, seven or fewer, six or fewer, five or fewer, four or fewer, three or fewer, or two or fewer single particles in contact.

[0099] In one aspect, when the bulk region is composed of a single particle, the average particle size (D50) may be 2.0 μm or more, 2.5 μm or more, 3.0 μm or more, 6 μm or less, 5.5 μm or less, 5 μm or less, or 4.5 μm or less, and more preferably, may be composed of a single particle with a size of 3.0 μm to 4.0 μm.

[0100] In one aspect, when the bulk region contains 2 to 8 single particles in contact, 2 to 8 single particles of 1 μm or more, 3 μm or less, or 2 μm or less may be contained in contact.

[0101] In one embodiment, the aspect ratio (longest major axis / shortest minor axis) of the single particle may be 1 or more, 2 or more, 3 or less, 2 or less, 1.5 or less, 1.2 or less, or 1.1 or less.

[0102] A positive electrode active material according to one embodiment of the present invention may include a plurality of the positive electrode active material particles.

[0103] An anode according to one embodiment of the present invention comprises the anode active material.

[0104] Except for using the aforementioned positive active material, the positive electrode may have a known structure and be manufactured according to a known manufacturing method. The binder, conductive material, and solvent are not particularly limited thereto as long as they can be used on the positive current collector of a secondary battery.

[0105] A secondary battery according to one embodiment of the present invention comprises the positive electrode active material.

[0106] The above secondary battery may specifically include a positive electrode, a negative electrode positioned opposite to the positive electrode, and an electrolyte between the positive electrode and the negative electrode, but is not particularly limited thereto as long as it can be used as a secondary battery.

[0107]

[0108] Hereinafter, embodiments of the present invention will be described in more detail.

[0109]

[0110] Manufacturing of cathode active material

[0111] <Preparation Examples 1 to 10>

[0112] NiCoMn(OH)2 hydroxide precursors (Ni:Co:Mn = 95:2:3 (at%)) of lithium composite oxides were synthesized through a known co-precipitation method using nickel sulfate, cobalt sulfate, and manganese sulfate.

[0113] A lithium composite oxide was prepared by uniformly mixing 1.02 mol% LiOH·H2O, 30.5 mol% Al(OH)20.2 mol% ZrO20.2 mol% and 20.1 mol% Ba(OH)20.9 mol% with the above-prepared precursor and heat-treating (first calcination) at 800°C to 840°C for 24 hours in a box-shaped calcination furnace into which oxygen is introduced.

[0114] Subsequently, a lithium composite oxide in the form of single particles was prepared by disintegration using a jet mill.

[0115] Next, a cathode active material with a particle size of 3 μm to 4 μm was prepared by mixing Co(OH)2 0.5 to 4.3 mol%, ZrO2 0.2 mol%, and Al2O3 0.5 mol% relative to the lithium composite oxide particles at 700°C to 720°C in an O2 atmosphere and heat-treating (secondary calcination) in an oxygen atmosphere for 12 hours.

[0116]

[0117] Manufacturing of lithium secondary batteries

[0118] A cathode slurry was prepared by dispersing 96 wt% of the cathode active material prepared according to the above preparation example, 2 wt% of artificial graphite, and 2 wt% of PVDF binder in 8 g of N-methyl-2-pyrrolidone (NMP). The cathode slurry was uniformly coated onto an aluminum thin film with a thickness of 15 μm and vacuum dried at 135°C to produce a cathode for a lithium secondary battery.

[0119] A coin battery was manufactured using a lithium foil as the counter electrode for the above positive electrode, a porous polyethylene film (Celgard 2300, thickness: 25 μm) as the separator, and an electrolyte in which LiPF6 is present at a concentration of 1.15 M in a solvent mixed with ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7.

[0120]

[0121] <Experimental Example 1> SEM Analysis

[0122] For the cathode active material particles according to the above manufacturing example, FE-SEM obtained particle surface images using a JSM-7610FPlus (JEOL) at a voltage of 2 kV, and the results are shown in FIG. 1 and FIG. 2.

[0123]

[0124] <Experimental Example 2> Coating Area

[0125] In a scanning electron microscope (SEM) image of one surface of a positive electrode active material particle, the coating area was measured using the Image J program and is shown in Table 1 below.

[0126]

[0127] <Experimental Example 3> Unit Coating Area and Number of Unit Coating Areas

[0128] The average value of the area of ​​2 to 5 randomly selected unit coating regions was measured on a scanning electron microscope (SEM) image of one surface of a positive electrode active material particle and is shown in Table 1 below.

[0129] In addition, scanning electron microscope (SEM) images were analyzed on all surfaces of the cathode active material particles to measure the number of unit coating regions, which are shown in Table 1 below.

[0130]

[0131] <Experimental Example 4> Lifespan Characteristics

[0132] For the lithium secondary battery according to the above manufacturing example, 50 charge / discharge cycles were performed under 1C / 1C conditions within a driving voltage range of 2.0V to 4.6V at 25℃, and the ratio of the discharge capacity at the 50th cycle to the initial discharge capacity (cycle capacity retention rate) was measured and is shown in Table 2 below.

[0133]

[0134] <Experimental Example 5> C-rate Measurement

[0135] For the lithium secondary battery according to the above manufacturing example, the output efficiency (C-rate) of 1.0C / 0.1C was measured through charge-discharge experiments using an electrochemical analyzer (Toyo, Toscat-3100) at 25℃, a voltage range of 2.5V to 4.25V, and a discharge rate of 0.1C to 1.0C, and is shown in Table 2 below.

[0136]

[0137] [Table 1]

[0138]

[0139]

[0140] [Table 2]

[0141]

Claims

1. Includes a bulk area; and a coating area; and The above coating region contains cobalt (Co), and In a scanning electron microscope (SEM) image of one surface of a positive electrode active material particle, the ratio of the coating area of ​​the said coating region to the total area of ​​the said surface is 83% to 96%, Cathode active material particles.

2. In Paragraph 1, The above-mentioned positive active material particles include one or more unit coating regions, and When the above unit coating region refers to a closed coating region on the surface of the bulk region that is not connected to other coating regions, the average value of the area of ​​the unit coating region is 3.0 μm 2 to 8.0 μm 2 person, Cathode active material particles.

3. In Paragraph 2, The number of unit coating regions in the above-mentioned positive electrode active material particles is 1 to 10, Cathode active material particles.

4. In Paragraph 2, The average value of the slope of the inclined plane around the perimeter of the closed coating region on the surface of the bulk region is 70° or less, Cathode active material particles.

5. In Paragraph 1, The average value of the thickness of the coating region measured in a vertical direction from the surface of the bulk region is 20 nm to 60 nm, Cathode active material particles.

6. In Paragraph 1, The above coating region further comprises one or more selected from aluminum (Al), zirconium (Zr), boron (B), tungsten (W), yttrium (Y), and titanium (Ti). Cathode active material particles.

7. In Paragraph 1, The above bulk region is doped with one or more elements selected from cobalt (Co), zirconium (Zr), barium (Ba), strontium (Sr), aluminum (Al), and titanium (Ti), Cathode active material particles.

8. In Paragraph 1, The average particle size (D50) of the above positive active material particles is 2.0 μm to 6.0 μm, Cathode active material particles.

9. In Paragraph 1, The above bulk region consists of a single particle, or 2 to 8 single particles contained in contact, Cathode active material particles.

10. Comprising positive electrode active material particles according to claim 1, Cathode active material.

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