Cathode active material for secondary battery

Abstract

A positive electrode active material particle according to one aspect of the present invention includes a host material and a first coating material, the first coating material containing zirconium (Zr), and the first coating material may be dot-shaped in a scanning electron microscope image on one surface of the positive electrode active material particle.

Description

Technical Field

[0001] The present invention relates to positive electrode active material particles and a positive electrode active material for a secondary battery including the same, and more particularly, to a positive electrode active material capable of significantly improving the stability, charge / discharge capacity, and efficiency characteristics of a secondary battery when applied to the secondary battery by controlling the composition, coating method, coating form, etc. of a zirconium (Zr)-containing coating material included in a lithium composite oxide. Background Art

[0002] With the development of portable mobile electronic devices such as smart phones, MP3 players, and tablet computers, the demand for secondary batteries capable of storing electric energy has increased explosively.

[0003] In particular, with the emergence of electric vehicles, large and medium-sized energy storage systems, and portable devices requiring high energy density, the demand for lithium secondary batteries is increasing.

[0004] As a lithium composite oxide included in a positive electrode active material, the material that has recently attracted the most attention is lithium nickel (manganese / aluminum) cobalt oxide Li(Ni x Co y( Mn / Al) z )O2 (where x, y, and z are the atomic fractions of the oxide constituent elements, respectively, 0 < x ≤ 1, 0 < y ≤ 1, 0 < z ≤ 1, and 0 < x + y + z ≤ 1).

[0005] Compared with LiCoO2, which has been actively studied and used as a positive electrode active material in the past, this positive electrode active material can be used at a higher voltage, and thus has the advantages of high capacity and low cost due to the relatively low Co content.

[0006] However, during the charge / discharge process of this lithium composite oxide, volume changes occur as lithium ions are inserted and extracted.

[0007] During charge / discharge, the primary particles of the lithium composite oxide undergo a sharp volume change, or cracks occur in the secondary particles as the charge / discharge is repeated, or there are problems such as crystal structure collapse or crystal structure phase change.

[0008] In order to compensate for these disadvantages, as a positive electrode active material for a secondary battery, the demand for a high-nickel-based positive electrode active material with a high nickel (Ni) content relative to the total metal content excluding lithium (Li) has started to increase. Summary of the Invention

[0009] Technical Problem

[0010] The present invention aims to provide a positive electrode active material that, by controlling the composition, coating method, coating morphology, etc. of the coating material containing zirconium (Zr), can significantly improve the stability, charge-discharge capacity and efficiency characteristics of secondary batteries when applied to them.

[0011] In particular, the present invention aims to provide a positive electrode active material that can improve battery performance when using a non-water-washing coating method to overcome the disadvantages of water-washing coating with a coating liquid, and which controls the composition, coating method, and coating morphology of the coating material.

[0012] Solution to the problem

[0013] According to one aspect of the present invention, the positive electrode active material particles comprise a host material and a first coating material, wherein the first coating material may comprise zirconium (Zr).

[0014] As a more preferred aspect, in a scanning electron microscope (SEM) image of one surface of the positive electrode active material particles, the first coating material may be in the form of dots.

[0015] As a more preferred aspect, the first coating material may comprise at least one selected from ZrO2 and lithium zirconium oxide.

[0016] As a more preferred aspect, the molar percentage of zirconium (Zr) contained in the positive electrode active material particles may be between 0.01 mol% and 1.0 mol% relative to the positive electrode active material particles.

[0017] As a more preferred aspect, the positive electrode active material particles may comprise 3 to 20 of the first coating material.

[0018] As a more preferred aspect, the average particle size (D50) of the first coating material contained in the positive electrode active material particles may be between 50 nm and 150 nm.

[0019] As a more preferred aspect, the positive electrode active material particles further include a second coating material, which may include cobalt (Co).

[0020] As a more preferred aspect, the second coating material may be applied to a portion of the surface of the body material.

[0021] As a more preferred aspect, in a scanning electron microscope (SEM) image of one surface of the positive electrode active material particles, the coating area ratio of the second coating material can be between 30% and 98% relative to the total area of ​​the surface.

[0022] As a more preferred aspect, the average particle size (D50) of the positive electrode active material particles may be between 1.0 μm and 6.0 μm.

[0023] As a more preferred aspect, the host material may consist of a single crystal particle or may contain two to eight contacting single crystal particles.

[0024] According to a more preferred aspect of the invention, the positive electrode active material may comprise the positive electrode active material particles.

[0025] The effects of the invention

[0026] As an effect, the present invention provides a positive electrode active material that reduces the amount of gas generated, which directly affects the lifespan reduction, and suppresses direct contact between the surface and the electrolyte, thereby achieving higher stability and enhanced main structure and coating structure.

[0027] As an effect, the present invention provides a positive electrode active material that can significantly improve the stability, charge / discharge capacity and efficiency characteristics of secondary batteries. Attached Figure Description

[0028] Figure 1 This is a SEM image of the surface of positive electrode active material particles according to an embodiment of the present invention.

[0029] Figure 2 This is a SEM image of the surface of positive electrode active material particles according to an embodiment of the present invention.

[0030] Figure 3 This is a SEM image of the surface of positive electrode active material particles according to an embodiment of the present invention. Detailed Implementation

[0031] The terms “include” and similar expressions used in this specification should be understood as including other open-ended terms that could constitute possibilities.

[0032] As used in this specification, "preferred" and "preferred" refer to embodiments of the invention that provide specific advantages under specific conditions.

[0033] However, this is not intended to exclude other embodiments from the scope of the present invention.

[0034] Furthermore, the singular forms used in the specification and appended claims are intended to include the plural forms unless the context clearly indicates otherwise.

[0035] That is, the technical characteristics of a single particle may refer to the technical characteristics of multiple particles, or they may refer to the average technical characteristics of multiple particles.

[0036] The numerical ranges used in this specification include lower and upper limits, all values ​​within that range, increments logically derived from the form and width of the defined range, all double-qualified values, and all possible combinations of upper and lower limits of numerical ranges qualified in different forms.

[0037] Unless otherwise defined, values ​​outside the defined range that may arise due to experimental error or rounding are also included within the defined range.

[0038] The meanings of '≤', 'above' or 'below' as used in this specification may be replaced by the meanings of '<', 'exceeding' or 'not full'.

[0039] In addition, the following technical features are one aspect of achieving the above-mentioned objective effect of the present invention.

[0040] That is, according to one aspect of the positive electrode active material of the present invention, by including the technical features of the following aspect, the main structure and coating structure of the particles can be further strengthened, and the stability, charge and discharge capacity and efficiency characteristics of the secondary battery can be significantly improved.

[0041] This invention relates to positive electrode active material particles for secondary batteries and positive electrode active materials comprising a plurality of such particles.

[0042] The secondary battery of the present invention is not limited in type as long as it can convert external electrical energy into chemical energy for storage and reuse.

[0043] For example, the present invention may relate to positive electrode active materials for lithium-ion secondary batteries.

[0044] According to one aspect of the present invention, the positive electrode active material particles may comprise a host material and a first coating material.

[0045] First, let's describe the main material.

[0046] As one aspect, the host material may be a lithium composite oxide.

[0047] In one respect, the host material may be a lithium composite oxide containing nickel (Ni).

[0048] As one aspect, the main body region may be a lithium composite oxide comprising nickel (Ni) and cobalt (Co).

[0049] In one respect, the lithium composite oxide can be represented by the following chemical formula 1.

[0050] [Chemical Formula 1] Li a Ni x M1 y M2 1-x-y O2

[0051] 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 and combinations thereof, and 0.9≤a≤1.2 and 0.1≤x<1.0, 0.0≤y≤0.5, and 0.0≤1-xy ≤0.5.

[0052] As one aspect, in the above chemical formula 1, the molar percentage of lithium (Li) relative to the total molar percentage of transition metals other than lithium (Li) can be 0.9 or more, 1.0 or more, 1.2 or less, 1.1 or less, or 1.05 or less.

[0053] In one aspect, in the above-mentioned chemical formula 1, x, which represents the molar percentage of nickel (Ni) relative to the total molar percentage of transition metals other than lithium (Li), 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. In particular, the present invention may be a high-Ni oxide with x being 0.5 or more.

[0054] This high-nickel cathode active material has the advantage of high energy density. However, due to the high Li / M ratio during preparation, the residual lithium content in the cathode active material after sintering is relatively high, leading to gelation during electrode slurry preparation and causing difficulties in battery manufacturing. To address this, a water washing process has been introduced to remove residual lithium, but the cathode surface is damaged during washing, resulting in a decrease in battery performance.

[0055] Furthermore, due to the high Ni content, the structure becomes unstable, and the reaction between the particle surface and interface and the electrolyte increases. During repeated charge and discharge processes, a large amount of gas is released, leading to a decrease in lifetime characteristics. This invention can solve these more serious problems in high-Ni cathode active materials.

[0056] As one aspect, in the above chemical formula 1, when y represents the molar percentage of cobalt (Co) relative to the total molar percentage of transition metals other than lithium (Li), y may be less than 0.5, less than 0.4, less than 0.3, less than 0.2, or less than 0.1.

[0057] As one aspect, in the above chemical formula 1, when y represents the molar percentage of Al and / or Mn relative to the total molar percentage of transition metals other than lithium (Li), y may be less than 0.5, less than 0.4, less than 0.3, less than 0.2, less than 0.1, more than 0.1, more than 0.2, or more than 0.3.

[0058] As a more preferred aspect, the main body region may be doped with at least one element 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).

[0059] More preferably, the main region may be doped with at least one element selected from cobalt (Co), zirconium (Zr), barium (Ba), strontium (Sr), aluminum (Al) and titanium (Ti).

[0060] In preparing the positive electrode active material of the present invention, lithium composite oxide can be prepared by heat-treating the hydroxide precursor and the lithium compound.

[0061] At this point, by heat-treating the dopant elements together, they can be uniformly doped into the lattice structure of the primary particles.

[0062] As another implementation method, when coating lithium composite oxide particles, some of the coating elements may be present in the lattice structure of the primary particles contained within the lithium composite oxide particles.

[0063] In this case, the coating element can be doped into the lithium composite oxide particles.

[0064] Furthermore, the lithium composite oxide particles of the host material are defined as containing all of these doped elements.

[0065] As one aspect, zirconium (Zr) is a coating element used in the preparation of lithium composite oxides, and it can also be doped into the lattice structure of primary particles during coating heat treatment.

[0066] As one aspect, cobalt (Co) is a coating element used in the preparation of lithium composite oxides, and it can also be doped into the lattice structure of primary particles during coating heat treatment.

[0067] As one aspect, aluminum (Al) is a coating element used in the preparation of lithium composite oxides, and it can also be doped into the lattice structure of primary particles during coating heat treatment.

[0068] By controlling the dopants and main body composition as described above, the present invention can further strengthen the main body structure and further improve the stability, charge / discharge capacity and efficiency characteristics of the secondary battery.

[0069] Next, the first coating material will be described.

[0070] In one respect, the first coating material may be a region distinct from the lithium composite oxide particles that are the host material.

[0071] In one aspect, the first coating material may comprise zirconium (Zr), and in a scanning electron microscope (SEM) image of a surface of the positive electrode active material particles, the first coating material may be dot-shaped (see...). Figure 1 ).

[0072] This invention confirms that by coating zirconium (Zr) in a dot pattern, the coating structure can be further strengthened, and the stability, charge / discharge capacity, and efficiency characteristics of the secondary battery can be further improved.

[0073] In addition, in this invention, the scanning electron microscope (SEM) image is a particle surface FE-SEM image obtained using a JSM-IT8800 (JEOL) at a voltage of 2kV.

[0074] As a more preferred aspect, the first coated material may exhibit the highest brightness in a low-angle backscattered electron (LABE) mode scanning electron microscope (SEM) image of one surface of the positive electrode active material particles (see [link to image]). Figure 1 ).

[0075] This difference in brightness may be due to variations in the type and density of the coating elements.

[0076] In this invention, the scanning electron microscope (SEM) image is obtained by measuring the particle surface using a voltage of 2 kV in low-angle backscatter electron (LABE) mode.

[0077] As a more preferred aspect, the first coating material may comprise ZrO2 and / or lithium zirconium oxide.

[0078] As a more preferred aspect, the molar percentage of zirconium (Zr) contained in the positive electrode active material particles may be more than 0.01 mol%, more than 0.05 mol%, more than 0.1 mol%, less than 1.0 mol%, less than 0.5 mol%, less than 0.4 mol%, less than 0.3 mol%, less than 0.2 mol%, or less than 0.15 mol%, more preferably, between 0.05 mol% and 0.2 mol%.

[0079] The present invention confirms that, considering the above-described coating morphology of zirconium (Zr), when included in the stated molar content, the charge / discharge capacity and efficiency characteristics of the secondary battery can be further improved.

[0080] As a more preferred aspect, the positive electrode active material particles may contain 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, less than 20, less than 19, less than 18, less than 17, less than 16, less than 15, less than 14, less than 13, less than 12, less than 11, or less than 10 of the first coating material.

[0081] By including the number of the first coating material within the above-mentioned numerical range, the present invention can further strengthen the coating structure and further improve the charge and discharge capacity and efficiency characteristics of the secondary battery.

[0082] As a more preferred aspect, the average particle size (D50) of the first coating material contained in the positive electrode active material particles may be 50 nm or more, 60 nm or more, 70 nm or more, 80 nm or more, 150 nm or less, 140 nm or less, or 130 nm or less, more preferably, between 70 nm and 130 nm.

[0083] By adjusting the average particle size (D50) of the first coating material within the aforementioned range, the present invention can further enhance the coating structure and further improve the charge and discharge capacity and efficiency characteristics of the secondary battery.

[0084] In addition, in the present invention, the average particle size (D50) of the first coating material is converted using the scale at the same magnification of the SEM image x20.0K, and then the diameters of arbitrarily selected 5 to 15 first coating materials are measured using the Image J program and the average value is calculated.

[0085] In addition, in the present invention, if the average value of the diameters of arbitrarily selected 5 to 15 first coating materials satisfies the above numerical range, it can be interpreted as conforming to the range.

[0086] By controlling the composition, morphology, etc. of the first coating material as described above, the present invention can further strengthen the coating structure and further improve the stability, charge-discharge capacity, and efficiency characteristics of the secondary battery.

[0087] As one aspect, the positive electrode active material particles may further include a second coating material, and the second coating material may include cobalt (Co).

[0088] As one aspect, the cobalt (Co) in the coating material may exist in the form of LiCoO2, Li 1+a CoO2 (0 < a < 1) , Li 1- b CoO2 (0 < b < 1), Co q O r (0 < q < 10, 0 < r < 10), and / or Co(OH)2, etc.

[0089] As one aspect, by using the EP-EDS (Energy Profiling-Energy Dispersive X-Ray Spectroscopy) method for measuring the average elemental concentration from the surface of the positive electrode active material particles to the electron beam penetration depth irradiated with an acceleration voltage of 1 kV, the average concentration of cobalt (Co) element in the second coating material can 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.

[0090] As one aspect, in addition to cobalt (Co), the second coating material may further include at least one selected from the group consisting of 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).

[0091] More preferably, the second coating material may contain, in addition to cobalt (Co), at least one selected from aluminum (Al), zirconium (Zr), boron (B), tungsten (W), yttrium (Y) and titanium (Ti).

[0092] More preferably, the second coating material may contain aluminum (Al) in addition to cobalt (Co).

[0093] More preferably, considering the coating method, coating composition and coating morphology of the present invention, when cobalt (Co), zirconium (Zr) and aluminum (Al) are coated on the host material, the charge and discharge capacity and efficiency characteristics can be further improved.

[0094] By controlling the composition of the second coating material as described above, the present invention can further enhance the coating structure and further improve the stability, charge / discharge capacity and efficiency characteristics of the secondary battery.

[0095] As a more preferred aspect, the second coating material may be applied to a portion of the surface of the body material.

[0096] As a more preferred aspect, in a scanning electron microscope (SEM) image of one surface of the positive electrode active material particles, the coating area ratio of the second coating material relative to the total area of ​​one surface can be 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 98% or less, or 95% or less, more preferably, between 80% and 96%.

[0097] By adjusting the coating area ratio of the second coating material within the above-mentioned numerical range, the present invention can further enhance the coating structure and further improve the stability, charge / discharge capacity, and efficiency characteristics of the secondary battery.

[0098] In this invention, the coating area ratio is measured using the ImageJ program on a scanning electron microscope (SEM) image of one surface of the positive electrode active material particles.

[0099] Furthermore, in this invention, if the coating area ratio measured on one surface of any selected positive electrode active material particle satisfies the above-mentioned numerical range, it can be interpreted as conforming to the range.

[0100] In addition, unlike the wet process of immersing active material particles in a coating liquid, the present invention can achieve the above-mentioned coating area and morphology by adjusting the coating content, heat treatment temperature and time, particle size, etc., during the dry coating process in the second heat treatment without water washing process.

[0101] In particular, in order to overcome the disadvantages of water-wash coating using coating liquid, the present invention controls the composition of coating material, coating method and coating morphology when applying non-water-wash coating method, so as to further improve battery performance.

[0102] As a more preferred aspect, the thickness of the second coating material, measured vertically from the surface of the host material, can be between 1 nm and 100 nm, more preferably between 20 nm and 60 nm.

[0103] In this invention, the thickness of the second coating material is determined by measuring the thickness of the second coating material at arbitrarily selected 10 points and calculating the average value after obtaining a cross-sectional SEM image of the lithium composite oxide using a JSM-7610FPlus (JEOL) at 2kV.

[0104] Furthermore, in this invention, if the thickness of the second coating material at any arbitrarily selected 10 points meets the above-mentioned numerical range, it can be interpreted as conforming to the range.

[0105] By controlling the coating method and coating morphology of the second coating material as described above, the present invention can further strengthen the coating structure and further improve the stability, charge / discharge capacity and efficiency characteristics of the secondary battery.

[0106] In addition, as an aspect, the first coating material may be present on the surface of the host material or on the surface of the second coating material.

[0107] According to one aspect of the present invention, the average particle size (D50) of the positive electrode active material particles may be 1.0 μm or more, 2.0 μm or more, 2.5 μm or more, 3.0 μm or more, 6.0 μm or less, 5.5 μm or less, 5 μm or less, or 4.5 μm or less, more preferably, between 3.0 μm and 4.0 μm.

[0108] In this invention, the average diameter (D50) is the particle size at the 50% point of the cumulative area distribution of the particle size, which can be measured using the laser diffraction method.

[0109] Specifically, after the powder to be tested is dispersed in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measurement device. When the particles pass through the laser beam, the particle size distribution is calculated by measuring the difference in diffraction patterns based on the particle size.

[0110] Additionally, the host material may be a particle formed by the contact of at least one single-crystal particle. Here, a single-crystal particle refers to a primary particle.

[0111] As a more preferred aspect, the host material may be composed of a single crystal particle, or may be composed of 8 or fewer, 7 or fewer, 6 or fewer, 5 or fewer, 4 or fewer, 3 or fewer, or 2 or fewer single crystal particles in contact.

[0112] In one aspect, when the host material is composed of a single crystal particle, the average particle size (D50) may be 2.0 μm or more, 2.5 μm or more, 3.0 μm or more, 6.0 μm or less, 5.5 μm or less, 5 μm or less, or 4.5 μm or less. More preferably, it may be composed of a single crystal particle with an average particle size of 3.0 μm to 4.0 μm.

[0113] In one aspect, when the host material comprises 2 to 8 contacting single crystal particles, it may be composed of 2 to 8 single crystal particles with a diameter of 1 μm or larger, a diameter of 3 μm or smaller, or a diameter of 2 μm or smaller.

[0114] In one respect, the aspect ratio (longest major axis / shortest minor axis) of the single crystal particle can be greater than 1, greater than 2, less than 3, less than 2, less than 1.5, less than 1.2 or less than 1.1.

[0115] According to one aspect of the present invention, the positive electrode active material may comprise a plurality of said positive electrode active material particles.

[0116] According to one aspect of the invention, the positive electrode comprises the positive electrode active material.

[0117] In addition to using the aforementioned positive electrode active material, the positive electrode may have a known structure and may be manufactured according to known manufacturing methods.

[0118] Adhesives, conductive agents, and solvents are not subject to special restrictions as long as they can be used on the positive current collector of a secondary battery.

[0119] A secondary battery according to one aspect of the present invention comprises the positive electrode active material.

[0120] The secondary battery may specifically include a positive electrode, a negative electrode disposed opposite to the positive electrode, and an electrolyte located between the positive electrode and the negative electrode, but it is not particularly limited as long as it can be used as a secondary battery.

[0121] The embodiments of the present invention will now be described in more detail.

[0122] Preparation of positive electrode active materials

[0123] <Example 1>

[0124] A NiCoMn(OH)2 hydroxide precursor of lithium complex oxide (Ni:Co:Mn = 95:2:3 (at%)) was synthesized using a known co-precipitation method with nickel sulfate, cobalt sulfate, and manganese sulfate.

[0125] Next, the hydroxide precursor and LiOH (Li / (Ni+Co+Mn) mol ratio = 1.05) were mixed and heat-treated at 790°C for 12 hours in an O2 atmosphere (one-time calcination) to obtain lithium composite oxide.

[0126] Subsequently, the lithium composite oxide in the form of single crystal particles was prepared by using jet-Mill fragmentation.

[0127] Next, under an O2 atmosphere at 700°C, 3 mol% Co(OH)2, 0.1 mol% ZrO2, and 0.1 mol% Al2O3 relative to the lithium composite oxide particles were mixed and heat-treated in an oxygen atmosphere for 12 hours (secondary sintering) to prepare positive electrode active materials with particle sizes of 3 μm to 4 μm.

[0128] <Example 2>

[0129] In Example 1 above, except that 3 mol% of Co(OH)2 and 0.1 mol% of ZrO2 were used instead of 3 mol% of Co(OH)2, 0.1 mol% of ZrO2 and 0.1 mol% of Al2O3, the rest was the same as in Example 1, and a positive electrode active material was prepared.

[0130] <Example 3>

[0131] In Example 1 above, except that 3 mol% of Co(OH)2 and 0.5 mol% of ZrO2 were used instead of 3 mol% of Co(OH)2, 0.1 mol% of ZrO2 and 0.1 mol% of Al2O3, the rest was the same as in Example 1, and a positive electrode active material was prepared.

[0132] <Comparative Example 1>

[0133] In Example 1 above, except that 3 mol% of Co(OH)2 and 0.1 mol% of TiO2 were used instead of 3 mol% of Co(OH)2, 0.1 mol% of ZrO2 and 0.1 mol% of Al2O3, the rest was the same as in Example 1, and a positive electrode active material was prepared.

[0134] <Comparative Example 2>

[0135] In Example 1 above, except that 3 mol% of Co(OH)2 and 0.5 mol% of TiO2 were used instead of 3 mol% of Co(OH)2, 0.1 mol% of ZrO2, and 0.1 mol% of Al2O3, the rest was the same as in Example 1, and a positive electrode active material was prepared.

[0136] <Comparative Example 3>

[0137] In Example 1 above, except that 3 mol% of Co(OH)2 and 0.1 mol% of Al2O3 were used instead of 3 mol% of Co(OH)2, 0.1 mol% of ZrO2 and 0.1 mol% of Al2O3, the rest was the same as in Example 1, and a positive electrode active material was prepared.

[0138] <Comparative Example 4>

[0139] In Example 1 above, except that 3 mol% of Co(OH)2 and 0.5 mol% of Al2O3 were used instead of 3 mol% of Co(OH)2, 0.1 mol% of ZrO2, and 0.1 mol% of Al2O3, the rest was the same as in Example 1, and a positive electrode active material was prepared.

[0140] <Comparative Example 5>

[0141] In Example 1 above, except that 3 mol% Co(OH)2, 0.1 mol% TiO2 and 0.1 mol% Al2O3 were used to replace 3 mol% Co(OH)2, 0.1 mol% ZrO2 and 0.1 mol% Al2O3, the rest was the same as in Example 1, and a positive electrode active material was prepared.

[0142] Preparation of lithium secondary batteries

[0143] A positive electrode slurry was prepared by dispersing 96 wt% of each positive electrode active material, 2 wt% of artificial graphite, and 2 wt% of PVDF binder prepared according to the above preparation example in 8 g of N-methyl-2-pyrrolidone (NMP).

[0144] The above-mentioned positive electrode slurry was uniformly coated on an aluminum foil with a thickness of 15 μm and vacuum dried at 135 °C to prepare a positive electrode for lithium secondary batteries.

[0145] A button cell was prepared using the above-mentioned positive electrode as the working electrode, lithium foil as the counter electrode, a porous polyethylene membrane (Celgard 2300, thickness: 25μm) as the separator, and an electrolyte with a LiPF6 concentration of 1.15M in a solvent of ethylene carbonate and ethyl methyl carbonate mixed in a volume ratio of 3:7.

[0146] <Experimental Example 1> SEM Analysis

[0147] The surface images of the positive electrode active material particles from Example 1 were obtained using a FE-SEM JSM-IT8800 (JEOL) at 2kV and are shown below. Figures 1 to 3 .

[0148] <Experimental Example 2> Measurement of the average particle size (D50) of Zr white spots

[0149] For the surface of the positive electrode active material particles in Example 1 above, the units were converted using a scale bar with the same magnification of SEM image x20.0K. The diameters of 7 to 12 first coating materials were measured using ImageJ program and the average value was calculated. The results are shown in Tables 1 to 3 below.

[0150] Table 1

[0151] Table 2

[0152] Table 3

[0153] <Experimental Example 3> Charge and Discharge Capacity and Efficiency

[0154] For the lithium secondary batteries of the above examples and comparative examples, charge / discharge experiments were conducted using an electrochemical analysis apparatus (Toyo, Toscat-3100) at 25°C, a voltage range of 3.0V to 4.3V, and a discharge rate of 0.1C. The initial charge capacity and initial discharge capacity were measured, and the efficiency was calculated. The results are shown in Table 4 below.

[0155] Table 4

Claims

1. A positive electrode active material particle, comprising: Main materials; And a first coating material; wherein the first coating material comprises zirconium, and in a scanning electron microscope image of one surface of the positive electrode active material particles, the first coating material is dotted.

2. The positive electrode active material particles as described in claim 1, wherein, The first coating material contains at least one selected from ZrO2 and lithium zirconium oxide.

3. The positive electrode active material particles as described in claim 1, wherein, The molar percentage of zirconium contained in the positive electrode active material particles is from 0.01 mol% to 1.0 mol% relative to the positive electrode active material particles.

4. The positive electrode active material particles as described in claim 1, wherein, The positive electrode active material particles comprise 2 to 20 of the first coating material.

5. The positive electrode active material particles as described in claim 1, wherein, The average particle size (D50) of the first coating material contained in the positive electrode active material particles is 50 nm to 150 nm.

6. The positive electrode active material particles as described in claim 1, wherein, The positive electrode active material particles also include a second coating material, which includes cobalt.

7. The positive electrode active material particles as described in claim 6, wherein, The second coating material is applied to a portion of the surface of the main material.

8. The positive electrode active material particles as described in claim 6, wherein, In a scanning electron microscope image of one surface of the positive electrode active material particles, the coating area of ​​the second coating material is 30% to 98% relative to the total area of ​​the surface.

9. The positive electrode active material particles as described in claim 1, wherein, The average particle size (D50) of the positive electrode active material particles is 1.0 μm to 6.0 μm.

10. The positive electrode active material particles as described in claim 1, wherein, The main material is composed of one single crystal particle, or of two to eight contacting single crystal particles.

11. A positive electrode active material comprising the positive electrode active material particles as described in claim 1.

Images