Positive electrode active material for secondary battery

Abstract

A positive electrode active material according to one aspect of the present invention comprises a lithium composite oxide containing nickel (Ni), and comprises a coating material containing cobalt (Co) and boron (B), wherein the occupancy of Ni inserted into the Li 3a site of the positive electrode active material based on Rietveld analysis by X-ray diffraction may be 1.4% or less.

Description

Cathode active material for secondary batteries

[0001] The present invention relates to a positive electrode active material for a secondary battery comprising a lithium composite oxide containing nickel (Ni), and more specifically, to a positive electrode active material in which thermal stability, lifespan characteristics, and output characteristics are all improved when applied to a secondary battery by controlling the coating composition, coating method, bulk composition, etc., in a lithium composite oxide containing nickel (Ni) coated with cobalt (Co) and boron (B), thereby controlling the values ​​regarding crystal structure and thermal stability.

[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] Meanwhile, lithium composite oxides containing nickel have a problem in that thermal stability decreases as the Ni content increases.

[0007] In addition, lithium composite oxides containing nickel have a problem in that their lifespan characteristics at room temperature and high temperature deteriorate rapidly as the Ni content increases due to increased structural instability caused by Li / Ni cation mixing, physical disintegration of internal particles caused by microcracks, and intensified depletion of electrolyte.

[0008]

[0009] The present invention aims to provide a cathode active material with improved lifespan and output characteristics by controlling the crystal structure and thermal stability values ​​through controlling the coating composition, coating method, bulk composition, etc., of a lithium composite oxide containing nickel (Ni).

[0010]

[0011] A positive electrode active material according to one embodiment of the present invention comprises a lithium composite oxide containing nickel (Ni) and a coating material containing cobalt (Co) and boron (B), and from Rietveld analysis by X-ray diffraction, the nickel occupancy (Ni occupancy) inserted into the Li 3a sites of the positive electrode active material may be 1.4% or less.

[0012] In a more preferred embodiment, the a-axis length of the anode active material obtained from Rietveld analysis by X-ray diffraction may be 2.8782 Å to 2.8795 Å.

[0013] In a more preferred embodiment, the c-axis length of the anode active material obtained from Rietveld analysis by X-ray diffraction may be 14.2000 Å to 14.2030 Å.

[0014] In a more preferred embodiment, when the anode active material is analyzed by differential scanning calorimetry (DSC), the temperature at which the peak with the maximum heat flow appears may be 218°C to 280°C.

[0015] In a more preferred embodiment, the maximum heat flow at the temperature at which the maximum heat flow peak appears when the anode active material is analyzed by differential scanning calorimetry (DSC) may be 1000 J / g or less.

[0016] In a more preferred embodiment, the temperature at which weight loss begins to appear during thermogravimetric analysis (TGA) of the cathode active material may be 215°C to 280°C.

[0017] In a more preferred embodiment, the temperature at which the weight loss peak is at its highest point during thermogravimetric analysis (TGA) of the cathode active material may be 225°C to 280°C.

[0018] In a more preferred embodiment, the coating material may further include one or more selected from aluminum (Al) and zirconium (Zr).

[0019] In a more preferred embodiment, the coating material may further include aluminum (Al) and zirconium (Zr).

[0020] In a more preferred embodiment, the cathode active material particles included in the cathode active material comprise a bulk region and a coating region including the coating material, and the bulk region may be doped with one or more selected from aluminum (Al), zirconium (Zr), and cobalt (Co).

[0021] In a more desirable embodiment, the bulk region may not be doped with boron (B).

[0022] As a more preferred embodiment, boron (B) may be included in an amount of 0.01 mol% to 3.0 mol% based on the total amount of the cathode active material.

[0023] In a more preferred embodiment, the average particle size (D50) of the positive active material particles included in the positive active material may be 2.0 μm to 6.0 μm.

[0024] In a more preferred embodiment, the lithium composite oxide particles included in the cathode active material may consist of one single particle or two to eight single particles in contact.

[0025] A method for manufacturing a positive electrode active material according to one embodiment of the present invention may include the step of heat-treating a mixture comprising a positive electrode active material precursor and a lithium-containing compound to produce a lithium composite oxide; the step of first coating the produced lithium composite oxide with a first coating material comprising a cobalt (Co)-containing compound; and the step of second coating the first coating material with a second coating material comprising a boron (B)-containing compound at a temperature of 300°C to 400°C.

[0026]

[0027] As an effect, the present invention provides a positive electrode active material in which the crystal structure and thermal stability are controlled, while simultaneously improving both lifespan characteristics and output characteristics.

[0028]

[0029] Figure 1 is an SEM image of the surface of a positive electrode active material particle according to one embodiment of the present invention.

[0030] FIG. 2 is a differential scanning calorimetry (DSC) analysis graph of a positive electrode active material according to one embodiment of the present invention.

[0031] Figure 3 is a thermogravimetric analysis (TGA) graph of a positive electrode active material according to one embodiment of the present invention.

[0032]

[0033] Expressions such as "comprising" as used in this specification should be understood as open-ended terms implying the possibility of including other configurations.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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'.

[0039]

[0040] Meanwhile, the technical features described below relate to one embodiment that achieves the intended effect of the present invention described above.

[0041] 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 providing a positive electrode active material in which the values ​​regarding crystal structure and thermal stability are controlled when applied to a secondary battery, while simultaneously improving both lifespan characteristics and output characteristics.

[0042] 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.

[0043] 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.

[0044] First, a positive electrode active material according to one embodiment of the present invention will be described.

[0045] A positive electrode active material according to one embodiment of the present invention may include 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, problems of reduced thermal stability and structural instability caused by Li / Ni cation mixing may be exacerbated due to the high Ni content. The present invention can resolve these problems, which are particularly exacerbated in high-nickel (high-Ni) cathode active materials.

[0053] 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.

[0054] 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.

[0055] In one embodiment, the positive electrode active material particles included in the positive electrode active material may include a bulk region and a coating region including the coating material.

[0056] In one embodiment, the bulk region and the coating region may be distinct regions.

[0057] Meanwhile, when a lithium composite oxide particle according to one embodiment of the present invention is coated, some of the coating elements may exist within the lattice structure of the primary particles included in the lithium composite oxide particle. This is described as the lithium composite oxide particle being doped, and the lithium composite oxide particle with respect to the bulk region is defined to include all of the regions thus doped.

[0058] In another aspect, 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.

[0059] In a more preferred embodiment, the positive electrode active material may include a coating material comprising cobalt (Co) and boron (B).

[0060] Meanwhile, the present invention may include cobalt (Co) and boron (B) as coating materials according to a coating method in which a coating material containing cobalt (Co) is first coated, and then boron (B) is coated at low temperature. In this case, a positive electrode active material can be provided in which the crystal structure is more stabilized, the thermal stability value is controlled, and at the same time, both the lifespan characteristics and the output characteristics are improved.

[0061] In one embodiment, in a scanning electron microscope (SEM) image of a surface of a positive electrode active material particle included in the positive electrode active material, the ratio of the coating area of ​​the coating region to the total area of ​​the surface may be 5% or more, 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 100% or less, 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less, and more preferably may be 50% to 98%.

[0062] 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 the cathode active material particle.

[0063] 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 10 at% or more, 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.

[0064] In a more preferred embodiment, the coating material may further include one or more selected from aluminum (Al) and zirconium (Zr).

[0065] In one embodiment, the aluminum (Al) and / or zirconium (Zr) may be coated together during the cobalt (Co) coating.

[0066] In a more preferred embodiment, the coating material may further include aluminum (Al) and zirconium (Zr).

[0067] In one embodiment, the coating material may further include one or more selected from titanium (Ti), magnesium (Mg), zinc (Zn), molybdenum (Mo), iron (Fe), nickel (Ni), barium (Ba), tungsten (W), strontium (Sr), yttrium (Y), niobium (Nb), vanadium (V), tantalum (Ta), silicon (Si), and fluorine (F).

[0068] In a more preferred embodiment, based on the total amount of the cathode active material, boron (B) may be included in an amount of 0.01 mol% or more, 0.1 mol% or more, 3.0 mol% or less, 2.0 mol% or less, or 1.0 mol% or less, and more preferably in an amount of 0.1 mol% to 1.0 mol%.

[0069] In one embodiment, the present invention heat-treats the boron (B) separately at a low temperature after the cobalt (Co) coating, so that the introduced boron (B) is not doped into the lattice structure of the particles and can be entirely contained in the coating area.

[0070] In a more preferred embodiment, the bulk region may be doped with one or more selected from aluminum (Al), zirconium (Zr), and cobalt (Co).

[0071] In the present invention, 'doping' means that an element is present within the lattice structure of the primary particles of the lithium composite oxide.

[0072] Meanwhile, in the present invention, the aluminum (Al) and / or zirconium (Zr) can be doped into the lattice structure of the primary particles when a precursor in the form of a hydroxide or oxide is heat-treated with a lithium-containing compound at 800°C to 840°C.

[0073] In addition, as one embodiment, cobalt (Co) can be doped into the lattice structure of the primary particles when heat-treated at 680°C to 720°C to first coat the lithium composite oxide.

[0074] In a more preferred embodiment, the bulk region may be doped with two or more selected from aluminum (Al), zirconium (Zr), and cobalt (Co).

[0075] In a more preferred embodiment, the bulk region may be doped with aluminum (Al), zirconium (Zr), and cobalt (Co).

[0076] Meanwhile, as a more desirable embodiment, the bulk region may not be doped with boron (B).

[0077] In one embodiment, the present invention heat-treats the boron (B) separately at a low temperature after the cobalt (Co) coating, so that the introduced boron (B) may not be doped into the bulk region.

[0078] As described above, the present invention can control the crystal structure and thermal stability by controlling the coating composition, coating method, bulk composition, etc. of the cathode active material, and simultaneously improve both lifespan characteristics and output characteristics.

[0079] In a more preferred embodiment, the nickel occupancy (Ni occupancy) inserted into the Li 3a sites of the anode active material from Rietveld analysis by X-ray diffraction may be 1.4% or less, 1.2% or less, 1.0% or less, 0.8% or less, or 0.5% or more. In the present invention, as the nickel occupancy (Ni occupancy) inserted into the Li 3a sites is controlled within the above numerical range, the degree of cation mixing and the crystal structure are controlled, thereby reinforcing the bulk structure and further improving thermal stability, lifespan characteristics, and output characteristics.

[0080] Meanwhile, in the present invention, XRD analysis is performed using a Bruker D8 Advance diffractometer with Cu-Kα radiation (1.540598 Å) to obtain 0.02 in the 2θ range of 10-80° (2θ). o Measure at step intervals.

[0081] In a more preferred embodiment, the a-axis length of the anode active material obtained from Rietveld analysis by X-ray diffraction may be 2.8782 Å or more, 2.8783 Å or more, 2.8784 Å or more, 2.8795 Å or less, 2.8790 Å or less, or 2.8787 Å or less. In the present invention, as the a-axis length obtained from Rietveld analysis by X-ray diffraction is adjusted to the above numerical range, the degree of cation mixing and the crystal structure are controlled, thereby reinforcing the bulk structure and further improving thermal stability, lifespan characteristics, and output characteristics.

[0082] In a more preferred embodiment, the c-axis length obtained from Rietveld analysis by X-ray diffraction of the anode active material may be 14.2000 Å or more, 14.2010 Å or more, 14.2030 Å or less, or 14.2020 Å or less. In the present invention, as the c-axis length obtained from Rietveld analysis by X-ray diffraction is adjusted to the above numerical range, the degree of cation mixing and the crystal structure are controlled, thereby reinforcing the bulk structure and further improving thermal stability, lifespan characteristics, and output characteristics.

[0083] In a more preferred embodiment, when performing thermal analysis of the cathode active material by differential scanning calorimetry (DSC), the temperature at which the peak with maximum heat flow appears may be 218°C or higher, 220°C or higher, 225°C or higher, 280°C or lower, 250°C or lower, or 230°C or lower. In the present invention, as the temperature at which the peak with maximum heat flow appears is controlled to the above numerical range, thermal stability, lifespan characteristics, and output characteristics can be further improved.

[0084] In a more preferred embodiment, the maximum heat flow at the temperature at which the peak of maximum heat flow appears during thermal analysis by differential scanning calorimetry (DSC) of the cathode active material may be 1000 J / g or less, 900 J / g or less, or 800 J / g or less. In the present invention, as the maximum heat flow is controlled within the above numerical range, thermal stability, lifespan characteristics, and output characteristics can be further improved.

[0085] In a more preferred embodiment, the temperature at which weight loss begins to appear during thermogravimetric analysis (TGA) of the cathode active material may be 215°C or higher, 220°C or higher, 280°C or lower, 250°C or lower, or 230°C or lower. In the present invention, as the temperature at which weight loss begins to appear is controlled to the above numerical range, thermal stability, lifespan characteristics, and output characteristics can be further improved.

[0086] In a more preferred embodiment, the temperature at which the weight loss peak reaches its highest point during thermogravimetric analysis (TGA) of the cathode active material may be 225°C or higher, 230°C or higher, 280°C or lower, or 250°C or lower. In the present invention, as the temperature at which the weight loss peak reaches its highest point is controlled within the above numerical range, thermal stability, lifespan characteristics, and output characteristics can be further improved.

[0087] In one aspect, the lithium composite oxide particles included in the cathode active material of the present invention may be in the form of multiple particles of secondary particles formed by the aggregation of primary particles. For example, the secondary particles may consist of 2 to 10 primary particles, 10 to 100, 100 to 1000, 1000 to 10000, or 10000 or more.

[0088] The primary particle and the secondary particle may each independently have a rod shape, an elliptical shape, and / or an irregular shape.

[0089] In one embodiment, the average major axis length of the primary particle may be 0.1 μm or more, 0.5 μm or more, 1 μm or more, 10 μm or less, 5 μm or less, or 3 μm or less.

[0090] In one embodiment, the average aspect ratio (major axis length / minor axis length) of the primary particle may be 1.0 or more, 1.2 or more, 1.5 or more, 2.0 or more, 10.0 or less, 7.0 or less, or 5.0 or less.

[0091] In one embodiment, the secondary particle is spherical in shape, and the average diameter (D50) may be 1 μm or more, 5 μm or more, 10 μm or more, 30 μm or less, 20 μm or less, or 15 μm or less.

[0092] 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.

[0093] In another aspect of one embodiment, the lithium composite oxide particles may be single particles, and if the single particles consist of one crystallite, they may be in a single crystal form, and the average diameter (D50) of the single particles may be 0.1 μm or more and 30 μm or less.

[0094] In a more preferred embodiment, the average particle size (D50) of the cathode 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.

[0095] Meanwhile, in this case, the lithium composite oxide particles included in the above-mentioned cathode active material may be particles formed by contacting at least one single particle. Here, a single particle refers to a primary particle.

[0096] In a more preferred embodiment, the lithium composite oxide particle 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.

[0097] In one aspect, when the lithium composite oxide particle consists 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 consist of a single particle with a size of 3.0 μm to 4.0 μm.

[0098] In one aspect, when the lithium composite oxide particles are included in contact with 2 to 8 single particles, 2 to 8 single particles of 1 μm or more, 3 μm or less, or 2 μm or less may be included in contact.

[0099] 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.

[0100] Next, a method for manufacturing an anode active material according to one embodiment of the present invention will be described.

[0101] By the manufacturing method described below, the characteristics regarding the coating structure, bulk structure, and thermal stability of the cathode active material particles of the present invention are controlled, and a cathode active material with improved thermal stability, lifespan, and output characteristics can be manufactured when applied to a secondary battery. More specifically, by performing a 'sequential, dual-temperature process' in which coating materials performing different functions are applied sequentially under their respective optimal temperature conditions, a cathode active material in which the characteristics regarding the coating structure, bulk structure, and thermal stability of the particles are controlled can be manufactured. First, to manufacture the cathode active material, a step of manufacturing a lithium composite oxide by heat-treating a mixture containing a cathode active material precursor and a lithium-containing compound can be performed.

[0102] At this time, more preferably, a doping element may be heat-treated together with the mixture, and the doping element mixed together may be one or more selected from aluminum (Al) and zirconium (Zr), and more preferably may be aluminum (Al) and zirconium (Zr).

[0103] At this time, the heat treatment temperature may be 800℃ to 840℃.

[0104] Next, a step of first coating the prepared lithium composite oxide with a first coating material containing a cobalt (Co)-containing compound can be performed.

[0105] The first coating material may further include one or more selected from aluminum (Al) containing compounds and zirconium (Zr) containing compounds in addition to the cobalt (Co) containing compound, and more preferably may include both aluminum (Al) containing compounds and zirconium (Zr) containing compounds.

[0106] At this time, more preferably, the first coating heat treatment temperature may be 680℃ to 720℃.

[0107] Meanwhile, more preferably, the first coating material is a dry material, and the first coating can be performed by a dry coating method.

[0108] More preferably, the molar content of cobalt (Co) introduced in the first coating step may be 0.5 mol% to 5.0 mol% relative to the total amount of the cathode active material.

[0109] More preferably, the molar content of aluminum (Al) introduced in the first coating step may be 0.1 mol% to 1 mol% relative to the total anode active material.

[0110] More preferably, the molar content of zirconium (Zr) introduced in the first coating step may be 0.05 mol% to 0.5 mol% relative to the total amount of the cathode active material.

[0111] Next, the step of applying a second coating can be performed by heat-treating the first coating material with a second coating material containing a boron (B)-containing compound at a temperature of 300°C to 400°C, more preferably 320°C to 380°C.

[0112] Meanwhile, more preferably, the boron (B) containing compound is a dry material, and the second coating can be performed by a dry coating method.

[0113] More preferably, the molar content of boron (B) introduced in the second coating step may be 0.01 mol% or more, 0.1 mol% or more, 3.0 mol% or less, 2.0 mol% or less, or 1.0 mol% or less relative to the total amount of the cathode active material, and more preferably may be 0.1 mol% to 1.0 mol%.

[0114] A positive electrode active material according to one embodiment of the present invention may include a plurality of the positive electrode active material particles.

[0115] An anode according to one embodiment of the present invention comprises the anode active material.

[0116] 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.

[0117] A secondary battery according to one embodiment of the present invention comprises the positive electrode active material.

[0118] 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.

[0119]

[0120] Hereinafter, embodiments of the present invention will be described in more detail.

[0121]

[0122] Manufacturing of cathode active material

[0123] <Example 1>

[0124] 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.

[0125] A lithium composite oxide was prepared by uniformly mixing 1.03 wt% LiOH·H2O, 30.11 wt% Al(OH)3 and 20.178 wt% ZrO 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.

[0126] Subsequently, a lithium composite oxide in the form of single particles was prepared by disintegration using a jet mill.

[0127] Next, a first coating material was prepared by mixing Co(OH)2 3.18 wt%, Al(OH)3 0.55 wt%, and ZrO2 0.178 wt% in an O2 atmosphere at 700°C and heat-treating (secondary firing) in an oxygen atmosphere for 12 hours.

[0128] Next, the first coating material was mixed with 0.3 wt% of H3BO3 at 350°C in an O2 atmosphere and heat-treated (third firing) for 12 hours to obtain a second coating material, which is an anode active material with a particle size of 3 μm to 4 μm.

[0129]

[0130] <Example 2>

[0131] In the above Example 1, when preparing the first coating material, instead of mixing Co(OH)23.18wt%, Al(OH)30.55wt%, and ZrO20.178wt%, Co(OH)23.18wt%, TiO20.55wt%, and ZrO20.178wt% were mixed and heat-treated (secondary firing), except otherwise, the procedure was carried out in the same manner as in the above Example 1.

[0132]

[0133] <Example 3>

[0134] In the above Example 1, except that when preparing the first coating material, heat treatment (secondary firing) was performed at 720°C instead of heat treatment (secondary firing) at 700°C, the rest of the procedure was carried out in the same manner as in the above Example 1.

[0135]

[0136] <Comparative Examples 1-1 to 1-3>

[0137] In the above Examples 1 to 3, except that the second coating was not performed after the first coating was prepared, the rest of the procedures were carried out in the same manner as in Examples 1 to 3 to prepare Comparative Examples 1-1 to 1-3.

[0138]

[0139] <Comparative Example 2>

[0140] In the above Example 1, the procedure was carried out in the same manner as Example 1, except that the first coating preparation step was omitted and 0.3 wt% of H3BO3 was mixed with the pulverized lithium composite oxide and heat-treated (third calcination) at 350°C.

[0141]

[0142] <Comparative Example 3>

[0143] In the above Example 1, the above procedure was carried out in the same manner as Example 1, except that Co(OH)2, Al(OH)3, ZrO2, and H3BO3 were simultaneously mixed with a lithium composite oxide and then heat-treated in a single step at 700°C.

[0144]

[0145] manufacturing of coin batteries

[0146] An anode slurry was prepared by dispersing 94 wt% of the respective anode active material, 3 wt% of synthetic graphite, and 3 wt% of the PVDF binder prepared according to each example and comparative example in 3.5 g of N-methyl-2-pyrrolidone (NMP). The anode slurry was coated onto an aluminum (Al) thin film serving as an anode current collector with a thickness of 20 μm, dried, and then roll-pressed to produce an anode. The loading level of the anode was 7 mg / cm². 2 and the electrode density is 3.2 g / cm³ 3 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 a liquid 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.

[0147]

[0148] <Experimental Example 1> SEM Analysis

[0149] For the cathode active material particles according to the above example, an image of the particle surface was obtained using FE-SEM JSM-IT8800 (JEOL) at a voltage of 2 kV, and then shown in FIG. 1.

[0150]

[0151] <Experimental Example 2> XRD Analysis

[0152] For the cathode active materials of the above examples and comparative examples, the a-axis length, c-axis length, and nickel occupancy (Ni occupancy) inserted into the Li 3a sites obtained from Rietveld analysis by X-ray diffraction were measured and listed in Table 1 below.

[0153] The above XRD analysis was performed using a Bruker D8 Advance diffractometer with Cu-Kα radiation (1.540598 Å) to obtain 0.02 in the 2θ range of 10–80° (2θ). o It was measured at step intervals.

[0154]

[0155]

[0156]

[0157]

[0158] According to Table 1 above, compared to the comparative example, it was confirmed that the a-axis length and c-axis length increased and the Ni share decreased.

[0159]

[0160] <Experimental Example 3> DSC Analysis

[0161] The results of the DSC analysis are shown in Figure 2 and Table 2 below.

[0162] In the present invention, DSC analysis was performed as follows.

[0163] The above-mentioned coin battery was disassembled in a charged state of 100% SOC, or after 0.1C charging / discharging and then again in a 0.1C charged state to obtain a positive electrode active material.

[0164] DSC was measured using the TA instrument Q50.

[0165] Approximately 1.8 to 2.0 mg of sample was weighed and placed in a 250 μL Al crucible (flat-bottomed aluminum pan with one pin-hole lid), and one pinhole was made. Subsequently, the sample was heated from 40°C to 360°C at a rate of 5°C / min while measuring DSC. During the measurement, Ar gas was supplied to the inside of the instrument at a rate of 50 mL / min to prevent the ingress of oxygen and other gases.

[0166]

[0167] Table 2

[0168]

[0169]

[0170] <Experimental Example 4> TGA Analysis

[0171] The results of the TGA analysis are shown in Figure 3 and Table 3 below.

[0172] In the present invention, TGA analysis was performed as follows.

[0173] The above-mentioned coin battery was disassembled in a charged state of 100% SOC, or after 0.1C charging / discharging and then again in a 0.1C charged state to obtain a positive electrode active material.

[0174] TGA analysis was performed using a thermogravimetric analyzer (Netzsch, TGA-MS TG209 F1 Libra - QMS403 Aeolos Quadro).

[0175] A sample of approximately 10.0 mg of the obtained cathode active material was weighed, and the weight loss was measured at a heating rate of 10℃ / min from 25℃ to 350℃ under an Ar atmosphere at atmospheric pressure.

[0176]

[0177] Table 3

[0178]

[0179]

[0180] <Experimental Example 4> Lifespan Characteristics

[0181] For the coin batteries according to the above examples and comparative examples, 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 4 below.

[0182]

[0183] <Experimental Example 5> C-rate Measurement

[0184] For the coin batteries according to the above examples and comparative examples, 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 4 below.

[0185]

[0186] Table 4

[0187]

Claims

1. A lithium composite oxide containing nickel (Ni), comprising, A coating material comprising cobalt (Co) and boron (B), and From Rietveld analysis by X-ray diffraction, the nickel occupancy (Ni occupancy) inserted into the Li 3a sites of the cathode active material is 1.4% or less, Cathode active material.

2. In Paragraph 1, The a-axis length obtained from Rietveld analysis by X-ray diffraction is 2.8782 Å to 2.8795 Å, Cathode active material.

3. In Paragraph 1, In thermal analysis by differential scanning calorimetry (DSC), the temperature at which the peak of maximum heat flow appears is between 218°C and 280°C, Cathode active material.

4. In Paragraph 1, In thermal analysis by differential scanning calorimetry (DSC), the maximum heat flow at the temperature where the peak of maximum heat flow appears is 1000 J / g or less, Cathode active material.

5. In Paragraph 1, In thermogravimetric analysis (TGA), the temperature at which weight loss begins to appear is between 215°C and 280°C, Cathode active material.

6. In Paragraph 1, In thermogravimetric analysis (TGA), the temperature at which the weight loss peak reaches its highest point is between 225°C and 280°C, Cathode active material.

7. In Paragraph 1, The above coating material further comprises one or more selected from aluminum (Al) and zirconium (Zr), Cathode active material.

8. In Paragraph 1, The above coating material further comprises aluminum (Al) and zirconium (Zr), Cathode active material.

9. In Paragraph 1, The positive electrode active material particles included in the above positive electrode active material include a bulk region and a coating region including the coating material, and The above bulk region is doped with one or more selected from aluminum (Al), zirconium (Zr), and cobalt (Co). Cathode active material.

10. In Paragraph 9, The above bulk region is not doped with boron (B), Cathode active material.

11. In Paragraph 1, Based on the total amount of the above-mentioned cathode active material, boron (B) is included in an amount of 0.01 mol% to 3.0 mol%, Cathode active material.

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

13. In Paragraph 1, The lithium composite oxide particles included in the above-mentioned cathode active material consist of a single particle, or 2 to 8 single particles contained in contact, Cathode active material.

14. In the method for manufacturing a positive electrode active material according to claim 1, A step of preparing a lithium composite oxide by heat-treating a mixture containing a positive electrode active material precursor and a lithium-containing compound; A step of first coating the above-prepared lithium composite oxide with a first coating material comprising a cobalt (Co)-containing compound; and A step comprising: heat-treating the first coating material with a second coating material containing a boron (B)-containing compound at a temperature of 300°C to 400°C to perform a second coating; Method for manufacturing positive electrode active material.

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