Cathode active material for secondary battery

Abstract

Cathode active material particles according to an embodiment of the present invention include a bulk region and a coating region, wherein the coating region includes cobalt (Co) and covers a portion of the surface of the bulk region. When a unit coating region refers to a closed coating region not connected to other coating regions on the surface of the bulk region, the cathode active material particles include one or more unit coating regions. When the shortest side drawn from the surface of the bulk region on a side surface of the unit coating region is referred to as a hypotenuse, the average length (S) of hypotenuses measured using Image J for a scanning electron microscope (SEM) image of the surface of the cathode active material particles may satisfy 40 nm ≤ S ≤ 70 nm.

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, coating form, etc., of a coating material containing cobalt (Co).

[0009] In particular, the present invention aims to provide a cathode active material with a controlled coating form that can improve battery performance when a non-washable cobalt (Co) coating method is applied to compensate for the disadvantages of water-washable 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 the coating region may cover a portion of the surface of the bulk region.

[0012] In a more preferred embodiment, when a unit coating region refers to a closed coating region on the surface of a bulk region that is not connected to other coating regions, the anode active material particles may include one or more unit coating regions.

[0013] In a more preferred embodiment, when measuring a scanning electron microscope (SEM) image of a positive electrode particle surface using Image J, the shortest side drawn from the surface of the bulk region on the side of the unit coating region is called the hypotenuse, and the average length (S) of the hypotenuse may be 40 nm ≤ S ≤ 70 nm.

[0014] As a more desirable embodiment, when a right triangle is drawn with the hypotenuse as the hypotenuse of the right triangle and the part touching the surface of the bulk area as the base, the average length (W) of the base of the right triangle and the average length (H) of the height may be 0.58 ≤ H / W ≤ 2.75.

[0015] As a more desirable embodiment, 30nm ≤ W ≤ 60nm may be used.

[0016] As a more desirable embodiment, 20nm ≤ H ≤ 50nm may be used.

[0017] 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 of ​​the coating region to the total area of ​​the one surface may be 50% to 98%.

[0018] In a more preferred embodiment, the average value of the coating area of ​​the unit coating region in the cathode active material particle is 2.0 μm 2 to 8.0 μm 2 It could be.

[0019] 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).

[0020] 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).

[0021] 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.

[0022] In a more preferred embodiment, the positive active material particle may consist of one single particle or may contain two to eight single particles aggregated together.

[0023] A positive electrode active material according to one embodiment of the present invention may include the positive electrode active material particles.

[0024]

[0025] 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.

[0026] 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.

[0027]

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

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

[0030]

[0031] Expressions such as "comprising" as used in this specification should be understood as open-ended terms implying the possibility of including other configurations.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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'.

[0037]

[0038] Meanwhile, the technical features described below relate to one embodiment that achieves the intended effect of the present invention described above.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] A positive electrode active material particle according to one embodiment of the present invention comprises a bulk region and a coating region.

[0043] First, the above bulk area will be explained.

[0044] In one embodiment, the bulk region may be a lithium composite oxide.

[0045] In one embodiment, the bulk region may be a lithium composite oxide containing nickel (Ni).

[0046] In one embodiment, the bulk region may be a lithium composite oxide containing nickel (Ni) and cobalt (Co).

[0047] In one embodiment, the lithium composite oxide can be represented by the following chemical formula 1.

[0048] [Chemical Formula 1]

[0049] Li a Ni x M1 y M2 1-x-y O2

[0050] 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-xyz≤0.5.

[0051] 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.

[0052] In one embodiment, x, which represents the mole% of nickel (Ni) relative to the mole% of the total transition metal excluding lithium (Li) in 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. While such high-nickel cathode active materials have the advantage of high energy density, the high Li / M ratio during the manufacturing of the cathode active material results in a high residual lithium content remaining in the cathode active material after calcination, causing difficulties in cell manufacturing due to gelation phenomena during the preparation of the electrode slurry. 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 a decrease in battery characteristics.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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).

[0057] 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).

[0058] 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.

[0059] In another aspect of the present invention, when a lithium composite oxide particle is coated according to one aspect of the invention, some of the coating elements may exist within the lattice structure of the primary particles contained within the lithium composite oxide particle. In this case, the coating elements are doped into the lithium composite oxide particle.

[0060] Meanwhile, the lithium composite oxide particles regarding the bulk region are defined to include all of the doped regions in this way.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] As described above, by controlling the dopant 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.

[0065] Next, the above-mentioned coating area is described.

[0066] In one embodiment, the coating region may be a region distinct from the lithium composite oxide particles, which is a bulk region.

[0067] 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.

[0068] In a more preferred embodiment, the coating region may include cobalt (Co).

[0069] In one embodiment, the cobalt (Co) is LiCoO within the coating region. 2, Li 1+a CoO2(1 <a<0.1) , Li1-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.

[0070] 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.

[0071] 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).

[0072] 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).

[0073] 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).

[0074] 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).

[0075] More preferably, the coating region may further include aluminum (Al), zirconium (Zr), and boron (B) in addition to cobalt (Co).

[0076] 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.

[0077] 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%.

[0078] 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%.

[0079] 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%.

[0080] 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.

[0081] The above coating area can cover a portion of the surface of the above bulk area.

[0082] In one embodiment, the positive active material particle may include one or more 'unit coating regions'.

[0083] 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.

[0084] In a more preferred embodiment, when measuring a scanning electron microscope (SEM) image of the surface of a positive electrode active material particle using Image J, the average length (S) of the hypotenuse may be 40 nm or more, 45 nm or more, 48 nm or more, 70 nm or less, 60 nm or less, 55 nm or less, or 52 nm or less, and more preferably 40 nm to 60 nm. By adjusting the average length (S) of the hypotenuse 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.

[0085] In the present invention, 'hypotenuse' refers to the shortest side drawn from the surface of the bulk area on the side of the unit coating area (see FIG. 1).

[0086] In the present invention, the 'average length of the hypotenuse (S)' refers to the average value of 10 to 15 hypotenuse lengths selected arbitrarily in 2 to 3 unit coating regions. Meanwhile, in the present invention, if the average value of 10 to 15 hypotenuse lengths selected arbitrarily in 2 to 3 unit coating regions satisfies the numerical range, it may be interpreted as corresponding thereto.

[0087] In a more preferred embodiment, when a right triangle is drawn with the hypotenuse as the hypotenuse of the right triangle and the part in contact with the surface of the bulk region as the base, regarding the average length (W) of the base of the right triangle and the average length (H) of the height, H / W may be 0.58 or more, 0.70 or more, 0.84 or more, 1.00 or more, 1.19 or more, 2.75 or less, 2.14 or less, or 1.73 or less, and more preferably 1.19 to 2.14. By satisfying 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.

[0088] At this time, the length of the base (W) refers to the length of the part in contact with the surface of the bulk area, and the length of the height (H) refers to the length of the part perpendicular to the base (see FIG. 1).

[0089] In the present invention, the 'average length of the base (W)' refers to the average value of 10 to 15 base lengths selected arbitrarily in 2 to 3 unit coating regions. Meanwhile, in the present invention, if the average value of 10 to 15 base lengths selected arbitrarily in 2 to 3 unit coating regions satisfies the numerical range, it may be interpreted as corresponding thereto.

[0090] In the present invention, the 'average height length (H)' refers to the average value of 10 to 15 height lengths selected arbitrarily in 2 to 3 unit coating areas selected arbitrarily. Meanwhile, in the present invention, if the average value of 10 to 15 height lengths selected arbitrarily in 2 to 3 unit coating areas selected arbitrarily satisfies the numerical range, it may be interpreted as corresponding thereto.

[0091] In a more preferred embodiment, W may be 30 nm or more, 35 nm or more, 38 nm or more, 60 nm or less, 50 nm or less, 45 nm or less, or 42 nm or less, and more preferably, 30 nm to 50 nm. By adjusting the average length (W) of the base 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.

[0092] In a more preferred embodiment, H may be 20 nm or more, 25 nm or more, 28 nm or more, 50 nm or less, 40 nm or less, 35 nm or less, or 32 nm or less, and more preferably, 20 nm to 40 nm. By adjusting the average length (H) of the height 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.

[0093] 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 50% or more, 60% or more, 70% or more, 80% or more, 98% or less, or 95% or less, and more preferably 80% to 96%. 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.

[0094] In the present invention, the coating area ratio was measured using the Image J program in a scanning electron microscope (SEM) image of one surface of a positive electrode active material particle. 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 above numerical range.

[0095] 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.

[0096] In a more preferred embodiment, the average value of the unit coating area in the cathode active material particles is 2.0 μm 2 Above, 3.0μm 2 Above, 8.0 μm 2 Below, 7.0μm 2 Less than 6.0 μm 2 Less than or equal to 5.0 μm 2 It can be, more preferably, 3.0 μm 2 to 5.0 μm 2 The present invention can further strengthen the coating structure and further improve the stability, lifespan, and output performance of the secondary battery by adjusting the unit coating area to the above numerical range.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] In a more preferred embodiment, the bulk material 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] A positive electrode active material according to one embodiment of the present invention may include a plurality of the positive electrode active material particles.

[0108] An anode according to one embodiment of the present invention comprises the anode active material.

[0109] 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.

[0110] A secondary battery according to one embodiment of the present invention comprises the positive electrode active material.

[0111] 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.

[0112]

[0113] Hereinafter, embodiments of the present invention will be described in more detail.

[0114]

[0115] Manufacturing of cathode active material

[0116] <Preparation Example 1-10>

[0117] 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.

[0118] 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.

[0119] Subsequently, a lithium composite oxide in the form of single particles was prepared by disintegration using a jet mill.

[0120] Next, Co(OH)2 0.5 to 4.3 mol%, ZrO2 0.2 mol%, and Al2O3 0.5 mol% were mixed in an O2 atmosphere at 700°C and heat-treated (secondary calcination) in an oxygen atmosphere for 12 hours to produce a cathode active material with a particle size of 3 μm to 4 μm.

[0121] <Preparation Example 11>

[0122] A lithium composite oxide in the form of a single particle was prepared in the same manner as in Preparation Examples 1 to 10 above, and then distilled water was added to the prepared lithium composite oxide to perform a first wash, and a 3.0 mol% aqueous cobalt sulfate solution was added and stirred for 5 minutes to perform a second wash while performing a cobalt (Co) coating.

[0123] Next, the washed lithium composite oxide was dried in an O2 atmosphere at 300°C.

[0124] Next, 0.1 mol% of ZrO2 and 0.1 mol% of Al(OH)3 were mixed in an O2 atmosphere at 700°C and heat-treated (secondary calcination) in an oxygen atmosphere for 12 hours to produce a cathode active material with a particle size of 3 μm to 4 μm.

[0125]

[0126] Manufacturing of lithium secondary batteries

[0127] 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.

[0128] 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.

[0129]

[0130] <Experimental Example 1> SEM Analysis and Measurement

[0131] For the surface of the cathode active material particles mixed with 3.0 mol% Co(OH)2 in Preparation Examples 1 to 10 above, FE-SEM was used to obtain particle surface images at a voltage of 2 kV using JSM-7610FPlus (JEOL), and the results are shown in FIG. 1 and FIG. 2.

[0132] In addition, the length of the hypotenuse at 10 points was measured using Image J on the SEM image of the surface of the above-mentioned cathode active material particles and is shown in Table 1 below.

[0133] In addition, a right triangle was drawn with the hypotenuse as the hypotenuse of the right triangle and the part touching the surface of the bulk area as the base, and the height (H) and the base length (W) were listed in Table 1 below.

[0134]

[0135] [Table 1]

[0136]

[0137]

[0138] <Experimental Example 2> Coating area, unit coating area, and number of unit coating regions

[0139] In scanning electron microscope (SEM) images of one surface of the cathode active material particles according to Preparation Examples 1 to 10 above, the coating area was measured using the Image J program and is shown in Table 2 below.

[0140] 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 2 below.

[0141] 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 2 below.

[0142]

[0143] [Table 2]

[0144]

[0145]

[0146] <Experimental Example 3> Lifespan Characteristics

[0147] 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 3 below.

[0148]

[0149] <Experimental Example 4> C-rate Measurement

[0150] 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 3 below.

[0151]

[0152] [Table 3]

[0153]

[0154]

[0155]

[0156]

Claims

1. Includes a bulk area; and a coating area; and The above coating region contains cobalt (Co), and The above coating area covers a portion of the surface of the bulk area, and When a unit coating region refers to a closed coating region on the surface of a bulk region that is not connected to other coating regions, the cathode active material particle comprises one or more unit coating regions, and When measuring a Scanning Electron Microscope (SEM) image of the surface of a positive electrode active material particle using Image J, where the shortest side drawn from the surface of the bulk region on the side of the unit coating region is called the hypotenuse, for the average length (S) of the hypotenuse, 40 nm ≤ S ≤ 70 nm, Cathode active material particles.

2. In Paragraph 1, When a right triangle is drawn with the above hypotenuse as the hypotenuse and the part touching the surface of the bulk area as the base, for the average length of the base (W) and the average length of the height (H) of the right triangle, 0.58 ≤ H / W ≤ 2.75, Cathode active material particles.

3. In Paragraph 2, 30nm ≤ W ≤ 60nm, Cathode active material particles.

4. In Paragraph 2, 20nm ≤ H ≤ 50nm, Cathode active material particles.

5. In Paragraph 1, In a scanning electron microscope (SEM) image of one surface of the above-mentioned 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 50% to 98%, 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-mentioned positive active material particle consists of a single particle, or Containing 2 to 8 aggregated single particles Cathode active material particles.

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

Images