Cathode active material, and cathode and lithium secondary battery comprising same

Abstract

The present invention relates to: a single-particle cathode active material; and a cathode and a lithium secondary battery, each comprising same. The cathode active material comprises: a single-particle lithium transition metal oxide; and a coating portion comprising cobalt formed on the single-particle lithium transition metal oxide, wherein, in an XPS spectrum, a ratio (ICarbonate / IMetal-O) of the intensity (ICarbonate) of a peak (289eV to 291eV) corresponding to C 1s to the intensity (IMetal-O) of a peak (525eV to 530eV) corresponding to O 1s core-level is greater than 0.10 and not more than 0.18.

Description

Cathode active material and cathode and lithium secondary battery containing the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0041065, filed March 26, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a cathode active material and a cathode and a lithium secondary battery containing the same, and more particularly, to a cathode active material in the form of a single particle and a cathode and a lithium secondary battery containing the same.

[0005]

[0006] With the recent increase in technological development and demand for mobile devices and electric vehicles, the demand for secondary batteries as an energy source is rapidly increasing.

[0007] A lithium secondary battery is generally composed of a positive electrode, a negative electrode, a separator, and an electrolyte, and the positive electrode and negative electrode include an active material capable of intercalation and deintercalation of lithium ions.

[0008] Meanwhile, the cathode active materials used in lithium secondary batteries typically take the form of spherical secondary particles, formed by the aggregation of hundreds of submicron-sized fine primary particles. However, secondary particle-type cathode active materials suffer from the problem of battery performance deterioration as the secondary particles break apart as the primary particles separate during repeated charge / discharge cycles.

[0009] To solve these problems, active development of single-particle type positive electrode active materials is underway. However, when manufacturing single-particle type positive electrode active materials, firing at a higher temperature is required than when manufacturing secondary particle type positive electrode active materials, which increases the proportion of NiO reduction layers on the particle surface. On the other hand, when the proportion of NiO reduction layers on the surface of positive electrode active materials increases, problems such as increased resistance of the battery, decreased capacity, and decreased output occur. Accordingly, a surface treatment technology capable of controlling the NiO reduction layer is required.

[0010]

[0011] The object of the present invention is to provide a cathode active material in the form of a single particle capable of implementing a battery with improved capacity characteristics, initial efficiency, and lifespan characteristics, and a cathode and a lithium secondary battery including the same.

[0012]

[0013] To solve the above problem, the present invention provides a cathode active material in the form of a single particle and a cathode and a lithium secondary battery including the same.

[0014]

[0015] (1) The present invention comprises a lithium transition metal oxide in the form of a single particle; and a coating part including cobalt formed on the lithium transition metal oxide in the form of a single particle; and in the XPS spectrum, the intensity (I) of the peak (525 eV to 530 eV) corresponding to the O 1s core-level Metal-O ) intensity of the peak (289 eV to 291 eV) corresponding to C 1s (I Carbonate ) ratio (I Carbonate / I Metal-O ) provides a single particle type positive electrode active material having a particle size of more than 0.10 and less than 0.18.

[0016] (2) In the present invention, in the above (1), the positive electrode active material in the form of a single particle has an average particle diameter (D 50) provides a positive electrode active material in the form of a single particle having a particle size of 0.1㎛ to 10㎛.

[0017] (3) The present invention provides a single particle type positive electrode active material in the above (1) or (2), wherein the single particle type positive electrode active material is in the form of agglomeration of 50 or less primary particles composed of 10 or less single crystal grains.

[0018] (4) The present invention provides a single particle type positive electrode active material in any one of the above (1) to (3), wherein the single particle type lithium transition metal oxide is a lithium composite transition metal oxide containing nickel (Ni), cobalt (Co), and manganese (Mn).

[0019] (5) The present invention provides a single particle type positive electrode active material in any one of the above (1) to (4), wherein the single particle type lithium transition metal oxide has a composition represented by the following chemical formula 1.

[0020] [Chemical Formula 1]

[0021] Li a Ni b Co c Mn d M 1 e O2

[0022] In the above chemical formula 1,

[0023] M 1 is at least one selected from Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, Sn, Y, Zn, F, P and S,

[0024] 0.9≤a≤1.1, 0.8≤b<1.0, 0 <c<0.2, 0<d<0.2, 0≤e≤0.1, b+c+d+e=1이다.

[0025] (6) The present invention provides a single particle type positive electrode active material, wherein the coating part comprises a cobalt-containing coating layer; and LiCoO2 in the form of islands discontinuously formed on the surface, in any one of the above (1) to (5).

[0026] (7) The present invention provides a positive electrode active material in the form of a single particle in a region of 5 nm to 100 nm from the surface of the positive electrode active material toward the center in any one of (1) to (6) above, wherein the coating portion is a region of 5 nm to 100 nm from the surface of the positive electrode active material toward the center.

[0027] (8) The present invention provides a positive electrode comprising a positive electrode active material according to any one of (1) to (7).

[0028] (9) The present invention provides a lithium secondary battery including a positive electrode according to (8).

[0029]

[0030] The cathode active material in the form of a single particle according to the present invention includes a coating portion containing cobalt, and in the XPS spectrum, the intensity (I) of the peak (525 eV to 530 eV) corresponding to the O 1s core-level Metal-O ) intensity of the peak (289 eV to 291 eV) corresponding to C 1s (I Carbonate ) ratio (I Carbonate / I Metal-O ) is greater than 0.10 and less than 0.18, and the NiO reduction layer and residual lithium existing on the surface of the positive electrode active material are reduced due to the cobalt coating portion having uniform coverage, so that the capacity characteristics, initial efficiency, and life characteristics of the battery including the same can be improved.

[0031]

[0032] Figure 1 is an XPS spectrum of the positive electrode active materials of Examples 1 to 2 and Comparative Examples 1 to 5.

[0033] Figure 2 is element mapping data of a cross-sectional sample of the positive electrode active material of Example 1.

[0034] Figure 3 is an SEM image of the positive electrode active material of Example 2.

[0035] Figure 4 is an SEM image of the positive electrode active material of Comparative Example 3.

[0036] Figure 5 is crystal analysis data of the positive electrode active material of Example 1.

[0037]

[0038] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best possible manner.

[0039] It should be understood that the terms “include,” “comprising,” or “having” used in this specification are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0040] The term "on" in this specification means not only when a configuration is formed directly on top of another configuration, but also when a third configuration is interposed between these configurations.

[0041] In this specification, the term "single-particle positive electrode active material" refers to a positive electrode active material composed of 50 or fewer primary particles, as opposed to a spherical secondary particle positive electrode active material formed by agglomeration of hundreds of primary particles manufactured by a conventional method. Specifically, the single-particle positive electrode active material in the present invention may be a single particle composed of one primary particle, or may be a secondary particle in which 2 to 50, 2 to 40, 2 to 30, 2 to 20, 2 to 15, 2 to 10, or 2 to 5 primary particles are aggregated. In this case, "primary particle" refers to the smallest particle unit recognized when the positive electrode active material is observed through a scanning electron microscope.

[0042] Meanwhile, the primary particle may be composed of 10 or fewer single crystal grains, and the grains can be analyzed using an electron backscatter diffraction (EBSD) analyzer, LG Chem's Advanced Material DX program, etc. The single crystal grain is a unit indicated by the same color in the electron backscatter diffraction (EBSD) Euler map data of one positive electrode active material particle and the crystal analysis data processed by the DX program, and is a grain in which no grain boundary exists within the grain.

[0043] In this specification, the average particle diameter (D 50 ) means the particle size based on 50% of the volume cumulative particle size distribution of the positive electrode active material or lithium transition metal oxide powder. The average particle diameter (D 50) can be measured using a laser diffraction method. For example, after dispersing the positive electrode active material powder in a dispersion medium, it can be measured by introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), irradiating it with ultrasonic waves of about 28 kHz at an output of 60 W, obtaining a volume cumulative particle size distribution graph, and then finding the particle size corresponding to 50% of the volume cumulative amount.

[0044] In this specification, the average particle diameter (D) of single crystal grains EBSD ) refers to the particle size at 50% of the volume cumulative particle size distribution of single crystal grains obtained through EBSD analysis using SEM. The EBSD analysis may be performed by obtaining images using SEM-EBSD equipment (e.g., FEI Quanta200-EDAX Velocity super OIM 8) and analyzing them using image analysis software (EDAX OIM Analysis).

[0045]

[0046] Hereinafter, the present invention will be described in detail.

[0047]

[0048] positive electrode active material

[0049]

[0050] The present invention comprises a lithium transition metal oxide in the form of a single particle; and a coating part including cobalt formed on the lithium transition metal oxide in the form of a single particle; and in the XPS spectrum, the intensity (I) of the peak (525 eV to 530 eV) corresponding to the O 1s core-level Metal-O ) intensity of the peak (289 eV to 291 eV) corresponding to C 1s (I Carbonate ) ratio (I Carbonate / I Metal-O ) provides a single particle type positive electrode active material having a particle size of more than 0.10 and less than 0.18.

[0051]

[0052] The present inventors have found that a positive electrode active material is in the form of a single particle and includes a coating portion containing cobalt; and in the XPS spectrum, the intensity (I) of the peak (525 eV to 530 eV) corresponding to the O 1s core-level Metal-O ) intensity of the peak (289 eV to 291 eV) corresponding to C 1s (I Carbonate ) ratio (I Carbonate / I Metal-O ) is greater than 0.10 and less than 0.18, the NiO reduction layer and residual lithium existing on the surface of the positive electrode active material are reduced due to the uniform cobalt coating, so that the performance of the battery including it, particularly the capacity characteristics, initial efficiency and life (cycle) characteristics are improved, and the present invention has been completed. In the XPS spectrum, the intensity (I) of the peak (525 eV to 530 eV) corresponding to the O 1s core-level Metal-O ) intensity of the peak (289 eV to 291 eV) corresponding to C 1s (I Carbonate ) ratio (I Carbonate / I Metal-O ) can be more specifically greater than 0.10, greater than 0.11, greater than 0.12, greater than 0.13, greater than 0.14, or greater than 0.15, and less than or equal to 0.18.

[0053] Meanwhile, in the XPS spectrum, the intensity (I) of the peak (525 eV to 530 eV) corresponding to the O 1s core-level Metal-O ) intensity of the peak (289 eV to 291 eV) corresponding to C 1s (I Carbonate ) ratio (I Carbonate / I Metal-O ) is less than 0.10, the coating part including cobalt is not uniformly formed at an appropriate level, and thus the uniformity is reduced, and there is a problem that the performance of the battery including it is not improved. In addition, in the XPS spectrum, the intensity (I) of the peak (525 eV to 530 eV) corresponding to the O 1s core-level Metal-O) intensity of the peak (289 eV to 291 eV) corresponding to C 1s (I Carbonate ) ratio (I Carbonate / I Metal-O ) is 0.18 or higher, the coating part containing cobalt penetrates into the interior at an excessive level compared to the surface part, and there is a problem that the performance of the battery is not improved due to the inferiority of the surface area of ​​the active material.

[0054]

[0055] According to the present invention, the positive electrode active material in the form of single particles has an average particle diameter (D 50 ) may be 0.1㎛ to 10㎛. Specifically, the average particle diameter (D) of the positive electrode active material in the form of a single particle 50 ) may be 0.1㎛ or more, 1.0㎛ or more, 2.0㎛ or more, 3.0㎛ or more, or 4.0㎛ or more, and may be 5.0㎛ or less, 6.0㎛ or less, 7.0㎛ or less, 8.0㎛ or less, 9.0㎛ or less, or 10.0㎛ or less. In this case, the rolling ratio of the battery including the positive electrode active material in the form of a single particle can be increased, thereby further improving the performance of the battery.

[0056] According to the present invention, the positive electrode active material in the form of a single particle may be in the form of primary particles composed of 10 or fewer single crystal grains aggregated into 50 or fewer, specifically 30, 20, 10, or 5 or fewer. In this case, the capacity and resistance performance of the battery can be improved, and cracks occurring within the particles during repeated charge and discharge can be reduced. At this time, the single crystal grains have an average particle diameter (D EBSD ) may be 0.1㎛ to 10㎛. Specifically, the average particle diameter (D) of the single crystal grains EBSD ) may be 0.1㎛ or more, 1.0㎛ or more, or 2.0㎛ or more, and may be 5.0㎛ or less, 6.0㎛ or less, 7.0㎛ or less, 8.0㎛ or less, 9.0㎛ or less, or 10.0㎛ or less.

[0057]

[0058] According to the present invention, the lithium transition metal oxide in the form of a single particle may be a lithium composite transition metal oxide containing nickel (Ni), cobalt (Co), and manganese (Mn). In this case, the lithium transition metal oxide in the form of a single particle may contain nickel (Ni) in an amount of 80 mol% or 85 mol% or more among all metals excluding lithium.

[0059] According to the present invention, the lithium transition metal oxide in the form of a single particle may have a composition specifically represented by the following chemical formula 1.

[0060] [Chemical Formula 1]

[0061] Li a Ni b Co c Mn d M 1 e O2

[0062] In the above chemical formula 1,

[0063] M 1 is at least one selected from Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, Sn, Y, Zn, F, P and S,

[0064] 0.9≤a≤1.1, 0.8≤b<1.0, 0 <c<0.2, 0<d<0.2, 0≤e≤0.1, b+c+d+e=1이다.

[0065] The above b refers to the atomic fraction of nickel among metal elements other than lithium in the lithium transition metal oxide, and may be 0.8 or more, or 0.85 or more, and may be 0.95 or less, or 0.98 or less.

[0066] The above c refers to the atomic fraction of cobalt among metal elements excluding lithium in the lithium transition metal oxide, and may be 0.01 or more, 0.1 or less, or 0.2 or less.

[0067] The above d refers to the atomic fraction of manganese among metal elements other than lithium in the lithium transition metal oxide, and may be 0.01 or more, 0.1 or less, or 0.2 or less.

[0068] The above e is M among the metal elements excluding lithium in the lithium transition metal oxide. 1 It refers to the elemental fraction of an element, which can be 0 or greater, 0.02 or less, 0.05 or less, or 0.1 or less.

[0069]

[0070] In the present invention, the coating part is a layer formed when cobalt diffuses toward the center from the surface of the lithium transition metal oxide in the form of a single particle when mixing the lithium transition metal oxide in the form of a single particle and the cobalt raw material and then performing a heat treatment. Therefore, the composition of the coating part is similar to the composition of the lithium transition metal oxide in the form of a single particle included in the positive electrode active material of the present invention, but the proportion of cobalt in the total metal excluding lithium is higher than that of the lithium transition metal oxide in the form of a single particle. Meanwhile, when cobalt diffuses toward the center from the surface of the lithium transition metal oxide in the form of a single particle, Ni present in the lithium transition metal oxide in the form of a single particle may be replaced with Co, and the coating part may have the same structure as the lithium transition metal oxide in the form of a single particle, that is, a layered structure.

[0071]

[0072] According to the present invention, the coating portion may include a cobalt-containing coating layer and LiCoO2 in the form of islands discontinuously formed on the surface. That is, the coating portion may include a cobalt-containing coating layer in the form of a thin film and LiCoO2 in the form of islands discontinuously formed on the surface.

[0073] Meanwhile, the island-shaped LiCoO2 may not entirely cover the surface of the positive electrode active material, but may be partially dispersed and distributed. That is, the island-shaped LiCoO2 may be discontinuously formed over an area of ​​20% to 50% of the total surface area of ​​the positive electrode active material.

[0074]

[0075] According to the present invention, the coating portion may be a region of 5 nm to 100 nm in the center direction from the surface of the positive electrode active material. Specifically, the coating portion may be a region of 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm in the center direction from the surface of the positive electrode active material.

[0076] In this specification, the coating portion is a region from the surface of the positive electrode active material to a point where the Co content measured through a TEM-EDX experiment exceeds 1.1 times the average Co content (mol%) of the entire positive electrode active material. At this time, the TEM-EDX experiment is performed by making a thin film sample with a thickness of 100 nm to 200 nm using a positive electrode active material powder using a Helios G4 UX FIB equipment of FEI Corporation, and then using a Titan G2 80-200 ChemiSTEM equipment of FEI Corporation and an EDX (in-column super-X Energy Dispersive X-ray spectroscopy) unit (ChemiSTEM technology), measuring the X-ray spectrum of elements at each location of the sample and comparing the intensities to obtain a molar ratio (mol%) value for each element.

[0077]

[0078] The cathode active material according to the present invention comprises the steps of (A) preparing a mixture by dry mixing a lithium transition metal oxide in the form of single particles and a cobalt raw material; and (B) heat-treating the mixture at a temperature of more than 700°C and less than 780°C; wherein the lithium transition metal oxide in the form of single particles can be produced by a method for producing a cathode active material in the form of single particles in which the molar ratio of lithium to all metals except lithium (Li:M) is 1.01 to 1.07:1, but is not limited thereto.

[0079] The cathode active material according to the present invention can be manufactured by appropriately controlling the mixing method (dry mixing), the type of precursor (lithium transition metal oxide), the temperature at which the mixture is heat-treated, as well as the type of cobalt raw material.

[0080]

[0081] Hereinafter, the method for manufacturing the positive electrode active material is described in more detail.

[0082]

[0083] (A) Step

[0084] The above step (A) is a step of preparing a mixture by dry mixing lithium transition metal oxide and cobalt raw material in the form of single particles.

[0085]

[0086] In the above step (A), the lithium transition metal oxide in the form of single particles has an average particle diameter (D 50 ) may be 0.1㎛ to 10㎛. At this time, the positive electrode active material in the form of a single particle may be in the form of primary particles composed of 10 or fewer single crystal grains aggregated into 50 or fewer.

[0087] The lithium transition metal oxide in the form of a single particle of the above step (A) can be manufactured by mixing a positive electrode active material precursor (e.g., transition metal hydroxide, transition metal oxyhydroxide, etc.), a lithium raw material (e.g., lithium carbonate (Li2CO3), lithium hydroxide (LiOH), LiNO3, CH3COOLi, Li2(COO)2, etc.), and optionally a doping element (e.g., Y, Zr, Al) raw material, and calcining at a high temperature. At this time, the calcination may be a single-stage calcination or a multi-stage calcination. Meanwhile, when the calcination is a two-stage calcination, the lithium raw materials may be mixed all before the first calcination, or may be mixed separately before the first calcination and before the second calcination. Meanwhile, the calcination may be performed at a temperature of 700°C to 900°C in an oxygen atmosphere.

[0088]

[0089] According to the present invention, the lithium transition metal oxide in the form of a single particle may have a composition represented by the following chemical formula 2. In this case, lithium is sufficiently provided, so that a coating portion including cobalt formed on the resulting positive electrode active material can be well formed.

[0090] [Chemical Formula 2]

[0091] Li a2 Ni b2 Co c2 Mn d2 M 2 e2 O2

[0092] In the above chemical formula 1,

[0093] M 2 is at least one selected from Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, Sn, Y, Zn, F, P and S,

[0094] 1.01≤a2≤1.07, 0.8≤b2<1.0, 0 <c2<0.2, 0<d2<0.2, 0≤e2≤0.1, b2+c2+d2+e2=1이다.

[0095]

[0096] According to the present invention, in the step (A), the lithium transition metal oxide in the form of single particles and the cobalt raw material may be mixed so that the molar ratio (M:Co) of cobalt (Co) contained in the cobalt raw material to the transition metal (M) contained in the lithium transition metal oxide is 1:0.01 to 0.10. When the content of the cobalt raw material is within the above range, a coating portion including cobalt is appropriately formed, so that the performance of the battery can be further improved.

[0097] The above cobalt raw material may be an acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or oxyhydroxide containing cobalt. For example, it may be Co(OH)2, Co2O3, etc., and preferably Co(OH)2. On the other hand, when a highly reactive material, such as Co3O4, Co(OH)3, cobalt acetate, etc., is used as the cobalt raw material, there may be a problem in that too much Co penetrates inside, resulting in almost no coating portion containing cobalt.

[0098]

[0099] According to the present invention, the mixing in step (A) may be a dry mixing process. That is, the powdered cobalt raw material may be simply mixed with the lithium transition metal oxide in single particle form, without the use of a solvent. This process can simplify the process, reducing costs, and also produce a positive electrode active material of uniform quality.

[0100]

[0101] Meanwhile, in the step (A), in addition to the lithium transition metal oxide and cobalt raw material in the form of single particles, a raw material containing a coating element may be additionally mixed, and the metal elements included in the raw material containing the coating element may be Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Sn, Y, Zn, Ce, F, P, and S, etc. The raw material containing the coating element may be an acetate, a nitrate, a sulfate, a halide, a sulfide, a hydroxide, an oxide, or an oxyhydroxide containing the metal element. For example, when the metal element is Al, which can further improve the lifespan and thermal stability of the cathode material, Al(OH)3, etc. may be used, and when the metal element is B, boric acid (H3BO3), etc. may be used.

[0102]

[0103] (B) Step

[0104] The above step (B) is a step of heat-treating the mixture at a temperature exceeding 700°C and less than 780°C. Through this, a coating is formed as cobalt diffuses toward the center from the surface of the lithium transition metal oxide in the form of a single particle, and at the same time, island-shaped LiCoO2 is discontinuously formed on the surface of the positive electrode active material. In particular, when the heat treatment temperature is within the above range, Co existing externally in the LiCoO2 phase appropriately penetrates into the positive electrode active material during the heating process, and in the XPS spectrum, the intensity (I) of the peak (525 eV to 530 eV) corresponding to the O 1s core-level Metal-O ) intensity of the peak (289 eV to 291 eV) corresponding to C 1s (I Carbonate ) ratio (I Carbonate / I Metal-O ) may be greater than 0.10 and less than or equal to 0.18.

[0105]

[0106] The heat treatment of step (B) may be performed at a temperature exceeding 700°C and less than 780°C. Specifically, the heat treatment temperature may be 700°C or higher, 710°C or higher, or 720°C or higher, and may be 740°C or lower, 750°C or lower, 760°C or lower, 770°C or lower, or lower than 780°C. When the heat treatment temperature is within the above range, a coating portion including cobalt is appropriately formed, so that the life characteristics of the battery can be further improved.

[0107] Meanwhile, when the heat treatment temperature is 700℃ or lower, there is a problem that cobalt cannot diffuse toward the center from the surface of the lithium transition metal oxide due to the low temperature, and only remains in the form of islands. In addition, when the temperature is 780℃ or higher, Co existing externally in the LiCoO2 phase penetrates into the positive electrode active material in large quantities during the heating process, and there is a problem that the life characteristics of the battery are reduced depending on the surface heat level.

[0108] The heat treatment in step (B) above can be performed for 2 to 12 hours to ensure productivity and uniformity of plasticity. Specifically, the heat treatment in step (B) above can be performed for 2 or more, 6 hours, 9 hours, or 12 hours or less.

[0109]

[0110] Meanwhile, in the step (A), when a coating element-containing raw material is additionally mixed in addition to the single-particle lithium transition metal oxide and cobalt raw material, specifically, when an aluminum raw material is additionally mixed, the method for manufacturing a cathode active material according to the present invention may further include a step of performing a secondary heat treatment after the step (B). At this time, the heat treatment of step (B) and the secondary heat treatment may be performed continuously. That is, after the heat treatment of step (B), the temperature may be adjusted to a temperature for the secondary heat treatment without lowering it to room temperature, and then the secondary heat treatment may be performed immediately. The secondary heat treatment may be performed at a temperature of 450°C to 550°C so that the aluminum is appropriately coated, but is not limited thereto.

[0111]

[0112] anode

[0113] In addition, the present invention can provide a positive electrode including the positive electrode active material.

[0114] Specifically, the positive electrode includes a positive electrode current collector, and a positive electrode active material layer positioned on at least one surface of the positive electrode current collector and including the positive electrode active material described above.

[0115] The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 µm to 500 µm, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesive strength of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0116]

[0117] The above positive electrode active material layer may include a conductive material and a binder together with the positive electrode active material.

[0118] At this time, the positive electrode active material may be included in an amount of 80 wt% to 99 wt%, more specifically 85 wt% to 98 wt%, based on the total weight of the positive electrode active material layer. When included in the above content range, excellent capacity characteristics can be exhibited.

[0119] At this time, the conductive material is used to provide conductivity to the electrode, and in the battery to be constructed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like, and one type alone or a mixture of two or more types thereof may be used. The conductive material may be included in an amount of 1 wt% to 30 wt% based on the total weight of the positive electrode active material layer.

[0120]

[0121] The above binder serves to improve the adhesion between positive electrode active material particles and the adhesive strength between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The binder may be included in an amount of 1 wt% to 30 wt% based on the total weight of the positive electrode active material layer.

[0122]

[0123] The positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material described above is used. Specifically, the positive electrode can be manufactured by coating a composition for forming a positive electrode active material layer, which is manufactured by dissolving or dispersing the positive electrode active material and optionally a binder and a conductive material in a solvent, on a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive material are as described above. Alternatively, the positive electrode can be manufactured by casting the composition for forming a positive electrode active material layer on a separate support, and then laminating the film obtained by peeling it from the support on a positive electrode current collector.

[0124] The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0125]

[0126] lithium secondary battery

[0127] In addition, the present invention can manufacture an electrochemical device including the positive electrode. The electrochemical device may be a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

[0128] The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is the same as described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0129] In addition, the lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0130]

[0131] In the above lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0132] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0133]

[0134] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0135] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β(0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fiber-like forms, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0136] The above negative electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of the negative electrode active material layer.

[0137]

[0138] The above binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0139] The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive agent is not particularly limited as long as it has conductivity and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0140]

[0141] The negative electrode active material layer may be manufactured by applying and drying a composition for forming a negative electrode active material layer prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the composition for forming a negative electrode active material layer on a separate support, and then laminating the film obtained by peeling it off from the support on a negative electrode current collector.

[0142]

[0143] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without special restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure.

[0144]

[0145] In addition, examples of the electrolyte used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0146] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0147] As the organic solvent, any solvent that can serve as a medium through which ions involved in the electrochemical reaction of the battery can move may be used without particular limitation. Specifically, the organic solvent includes ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); Alcohol solvents such as ethyl alcohol, isopropyl alcohol, etc.; nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes, etc. can be used. Among these, carbonate solvents are preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of a battery and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferable.In this case, the performance of the electrolyte may be improved when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

[0148]

[0149] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. It is preferable that the concentration of the lithium salt be used within the range of 0.1M to 2.0M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0150]

[0151] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrolyte.

[0152]

[0153] As described above, a lithium secondary battery including a cathode active material according to the present invention stably exhibits excellent discharge capacity, initial efficiency, and lifespan characteristics, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0154] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0155] The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0156] There is no particular limitation on the external shape of the lithium secondary battery of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0157] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

[0158]

[0159] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0160]

[0161] Manufacturing example

[0162] Manufacturing Example 1: Manufacturing of lithium transition metal oxide in single particle form

[0163] Ni 0.885 Co 0.035 Mn 0.08 It has a composition represented by (OH)2 and an average particle diameter (D 50 ) is a positive electrode active material precursor of 4㎛, Al(OH)3, LiOH, mixed in an amount such that the molar ratio of (Ni+Co+Mn):Al:Li is 1:0.005:1.05, and a plastic product is manufactured by first firing at a temperature of 880°C for 18 hours in an oxygen atmosphere, and the plastic product is pulverized, and then second firing is performed at a temperature of 820°C for 22 hours in an oxygen atmosphere to produce Li 1.05 Ni 0.88 Co 0.035 Mn 0.08 Al 0.005 A lithium transition metal oxide in the form of a single particle having a composition represented by O2 was prepared.

[0164]

[0165] Manufacturing Example 2: Manufacturing of lithium transition metal oxide in single particle form

[0166] Ni 0.885 Co 0.035 Mn 0.08 It has a composition represented by (OH)2 and an average particle diameter (D 50 ) is a positive electrode active material precursor of 4㎛, Al(OH)3, LiOH, mixed in an amount such that the molar ratio of (Ni+Co+Mn):Al:Li is 1:0.005:1.03, and a plastic product is manufactured by first firing at a temperature of 880°C for 18 hours in an oxygen atmosphere, and the plastic product is pulverized, and then a second firing is performed at a temperature of 820°C for 22 hours in an oxygen atmosphere to produce Li 1.03 Ni 0.88 Co 0.035 Mn 0.08 Al 0.005 A lithium transition metal oxide in the form of a single particle having a composition represented by O2 was prepared.

[0167]

[0168] Examples and Comparative Examples

[0169] Example 1

[0170] In Manufacturing Example 1, a single particle type lithium transition metal oxide was prepared by mixing 2 mol% of powder type Co(OH)2 (Huayou Cobalt Co., Ltd.) (mixing so that the molar ratio of Co contained in Co(OH)2 to the transition metal (Ni+Co+Mn+Al) contained in the lithium transition metal oxide ((Ni+Co+Mn+Al):Co)) was 1:0.02), and Al(OH)3 was mixed at a level of 500 ppm based on the lithium transition metal oxide to prepare a mixture. The mixture was first heat-treated at a temperature of 720°C for 3 hours in an oxygen atmosphere, and then second heat-treated at a temperature of 500°C for 3 hours in an oxygen atmosphere to prepare Li 1.03 Ni 0.86 Co 0.055 Mn 0.08 Al 0.005 A positive electrode active material in the form of a single particle (average particle size: 4.0 μm) having a composition represented by O2 was manufactured.

[0171]

[0172] Example 2

[0173] A positive electrode active material in the form of a single particle (average particle size: 4.0 μm) was manufactured in the same manner as in Example 1, except that the primary heat treatment temperature was adjusted to 740°C.

[0174]

[0175] Comparative Example 1

[0176] The lithium transition metal oxide in the form of a single particle manufactured in Manufacturing Example 1 was first heat-treated at a temperature of 720°C for 3 hours in an oxygen atmosphere, and then second heat-treated at a temperature of 500°C for 3 hours in an oxygen atmosphere to obtain Li 1.05 Ni 0.88 Co 0.035 Mn 0.08 Al 0.005 A positive electrode active material in the form of a single particle (average particle size: 4.0 μm) having a composition represented by O2 was manufactured.

[0177]

[0178] Comparative Example 2

[0179] A mixture was prepared by mixing 2 mol% of powdered Co(OH)2 (Huayou Cobalt Co., Ltd.) with the lithium transition metal oxide in the form of a single particle manufactured in Manufacturing Example 2 and mixing Al(OH)3 at a level of 500 ppm based on the lithium transition metal oxide. The mixture was first heat-treated at a temperature of 720°C for 3 hours in an oxygen atmosphere, and then second heat-treated at a temperature of 500°C for 3 hours in an oxygen atmosphere to obtain Li 1.01 Ni 0.86 Co 0.055 Mn 0.08 Al 0.005 A positive electrode active material in the form of a single particle (average particle size: 4.0 μm) having a composition represented by O2 was manufactured.

[0180]

[0181] Comparative Example 3

[0182] A positive electrode active material in the form of a single particle (average particle size: 4.0 μm) was manufactured in the same manner as in Example 1, except that the primary heat treatment temperature was adjusted to 700°C.

[0183]

[0184] Comparative Example 4

[0185] A positive electrode active material in the form of a single particle (average particle size: 4.0 μm) was manufactured in the same manner as in Example 1, except that the primary heat treatment temperature was adjusted to 780°C.

[0186]

[0187] Comparative Example 5

[0188] In Manufacturing Example 1, a single particle type lithium transition metal oxide was prepared by mixing 0.67 mol% of powder type Co3O4 (Zumwi) (mixing so that the molar ratio of Co contained in Co3O4 to the transition metal (Ni+Co+Mn+Al) contained in the lithium transition metal oxide ((Ni+Co+Mn+Al):Co)) was 1:0.02), and Al(OH)3 was mixed at a level of 500 ppm based on the lithium transition metal oxide to prepare a mixture. The mixture was first heat-treated at a temperature of 720°C for 3 hours in an oxygen atmosphere, and then second heat-treated at a temperature of 500°C for 3 hours in an oxygen atmosphere to prepare Li 1.03 Ni 0.86 Co 0.055 Mn 0.08 Al 0.005 A positive electrode active material in the form of a single particle (average particle size: 4.0 μm) having a composition represented by O2 was manufactured.

[0189]

[0190] Comparative Example 6

[0191] The lithium transition metal oxide in the form of single particles manufactured in Manufacturing Example 1 and cobalt sulfate heptahydrate (CoSO4·7H2O) were mixed (mixed so that the molar ratio of Co contained in CoSO4·7H2O to the transition metal (Ni+Co+Mn+Al) contained in the lithium transition metal oxide ((Ni+Co+Mn+Al):Co)) was 1:0.02), and then wet precipitation was performed using LiOH (7 mol%) as a precipitant with 100% purified water, and stirring was performed for 20 minutes. Afterwards, the mixture obtained through the filtering and drying process was first heat-treated at a temperature of 720°C for 3 hours under an oxygen atmosphere, and then second heat-treated at a temperature of 500°C for 3 hours under an oxygen atmosphere to obtain Li 1.03 Ni 0.86 Co 0.055 Mn 0.08 Al 0.005 A positive electrode active material in the form of a single particle (average particle size: 4.0 μm) having a composition represented by O2 was manufactured.

[0192]

[0193] Experimental example

[0194] Experimental Example 1: Analysis of positive electrode active material

[0195] - XPS spectrum analysis of positive electrode active material

[0196] Using XPS (Thermo Fisher Scientific Inc., K-Alpha), XPS spectra (survey & narrow scan data) of each of the positive electrode active materials of Examples 1 to 2 and Comparative Examples 1 to 6 were obtained under the following conditions, and these were subjected to qualitative and quantitative analysis.

[0197] (1) Initial Survey Conditions

[0198] - Scan interval binding energy: 0~1360 eV

[0199] - Step Size: 1 eV

[0200] - Per point dwell time: 20 ms

[0201] - Number of Scans: 15

[0202] - Pass Energy: 200 eV

[0203] (2) Narrow (Snapshot) condition

[0204] - Scan section binding energy: 20.80 eV

[0205] - Step Size: 0.16 eV

[0206] - Per point dwell time: 1 s

[0207] - Number of Scans: 10~30

[0208] - Pass Energy: 151.2 eV

[0209] (3) Narrow (Scan) condition

[0210] - Scan section binding energy: 15~20 eV

[0211] - Step Size: 0.1 eV

[0212] - Per point dwell time: 50 ms

[0213] - Number of Scans: 4~20

[0214] - Pass Energy: 20 eV

[0215]

[0216] For the surface in the beam-irradiated state, after identifying the main components through an initial survey, a narrow spectrum for each component was obtained in snapshot mode, and then a narrow scan was obtained at one point per sample (for binding state analysis). Binding energy was corrected based on the hydrocarbon peak of C 1s (C-C bond, 284.8 eV) and analyzed.

[0217] The XPS spectrum of each cathode active material is shown in Fig. 1, and the intensity (I) of the peak (525 eV to 530 eV) corresponding to the O 1s core-level in the XPS spectrum Metal-O ) intensity of the peak (289 eV to 291 eV) corresponding to C 1s (I Carbonate ) ratio (I Carbonate / I Metal-O ) are shown in Table 1 below. 2-1 and 2-2 of Fig. 1 are data corresponding to Examples 1 and 2, respectively, and 1-1 to 1-5 are data corresponding to Comparative Examples 1 to 5, respectively.

[0218] Category I Carbonate / I Metal-O Example 10.15 Example 20.16 Comparative Example 10.03 Comparative Example 20.05 Comparative Example 30.09 Comparative Example 40.20 Comparative Example 50.08 Comparative Example 60.24

[0219]

[0220] - Analysis of positive electrode active material morphology and Co element

[0221] The morphology of the positive electrode active material coating portion of Example 1 was confirmed using STEM-EDS (FEI Titan G2 80-200 ChemiSTEM w / super-XEDS system) and STEM-HAADF (FEI Titan G2 80-200 ChemiSTEM w / DCOR+Cs-corrector) (acceleration voltage: 200 kV). In addition, Co, Ni, Mn, and Al element mapping data of the cross-sectional sample of the positive electrode active material of Example 1 were obtained, and this is shown in Fig. 2.

[0222] Additionally, SEM images of the positive electrode active materials of Example 2 and Comparative Example 3 were obtained using a scanning electron microscope (SEM, Thermo Fischer Scientific, accelerating voltage: 6 kV), and these are shown in FIGS. 3 and 4, respectively.

[0223] Referring to FIGS. 2 to 4, it can be confirmed that the positive electrode active material according to the embodiment has a cobalt-containing coating layer and a discontinuously formed island-shaped LiCoO2 present simultaneously on the surface. In addition, it can be confirmed that the positive electrode active material according to the embodiment has a coating portion formed in the shape of a coating layer with improved coverage compared to the positive electrode active material of Comparative Example 3.

[0224] Meanwhile, the cross-section sample of the positive electrode active material was prepared by Ar ion milling for 2 hours using FIB (Thermo Fisher Scientific G4 UX FIB) (acceleration voltage: 30 kV).

[0225]

[0226] - Crystal analysis of positive electrode active material particles

[0227] Using a scanning electron microscope (SEM, Thermo Fischer Scientific, accelerating voltage: 6 kV, magnification: 3000x), an SEM image of the positive electrode active material of Example 1 was obtained, and crystal analysis was performed using the Advanced Material DX program of LG Chem. Specifically, the SEM image was processed with the DX program, and single crystal grains in the image were displayed in the same color based on the crystal grain boundaries within the particles. Fig. 5 is crystal analysis data of the positive electrode active material of Example 1. A single crystal grain is a unit displayed in the same color in the DX program, and is a grain in which no crystal grain boundary exists within the grain.

[0228] Referring to FIG. 5, it can be confirmed that the positive electrode active material particles of Example 1 are single crystal grains expressed in different colors, primary particles in which single crystal grains are aggregated into 10 or fewer, or secondary particles in which primary particles in which single crystal grains are aggregated into 10 or fewer.

[0229]

[0230] Experimental Example 2: Battery Characteristics Evaluation

[0231] (Half-cell manufacturing)

[0232] Each of the positive electrode active materials manufactured in Examples 1 to 2 and Comparative Examples 1 to 6, the carbon black (Denka, DenkaBlack) conductive agent, the dispersant (BM730H), and the PVdF (Kureha, KF1300) binder were added to an N-methylpyrrolidone (NMP) (Daejung Chemicals & Metals) solvent at a weight ratio of 95:2:0.2:2.8 to manufacture a composition for forming a positive electrode active material layer.

[0233] The composition for forming the positive electrode active material layer was applied to one surface of an aluminum foil current collector having a thickness of 20 ㎛, and dried at a temperature of 130°C for 1 hour to form a positive electrode active material layer. Subsequently, the positive electrode was manufactured by rolling using a roll pressing method so that the porosity of the positive electrode active material layer became 20% by volume after rolling.

[0234] A half-cell was manufactured using lithium metal as the cathode together with the above-mentioned positive electrode.

[0235] (Monocell manufacturing)

[0236] Each of the positive electrode active materials manufactured in Examples 1 to 2 and Comparative Examples 1 to 6, the carbon black (Denka, DenkaBlack) conductive agent, the dispersant (BM730H), and the PVdF (Kureha, KF1300) binder were added to an N-methylpyrrolidone (NMP) (Daejung Chemicals & Metals) solvent at a weight ratio of 95:2:0.2:2.8 to manufacture a composition for forming a positive electrode active material layer.

[0237] The composition for forming the positive electrode active material layer was applied to one surface of an aluminum foil current collector having a thickness of 20 ㎛, and dried at a temperature of 130°C for 1 hour to form a positive electrode active material layer. Subsequently, the positive electrode was manufactured by rolling using a roll pressing method so that the porosity of the positive electrode active material layer became 20% by volume after rolling.

[0238] A negative electrode was prepared in which a negative electrode active material layer including graphite was formed on one surface of a Cu foil current collector having a thickness of 10 ㎛.

[0239] A mono-cell was manufactured using the above positive and negative electrodes.

[0240] (Evaluation of initial characteristics of the battery)

[0241] The half-cells manufactured above were each charged at 25℃ with a constant current (CC) of 0.1C until the voltage reached 4.25V, and then charged at a constant voltage (CV) of 4.25V until the charge current reached 0.05mAh (cut-off current), left for 20 minutes, and then discharged at a constant current of 0.1C until the voltage reached 2.5V. The initial charge capacity and initial discharge capacity were measured, and the initial efficiency was calculated, which is shown in Table 2 below. For reference, the DCIR value is a value calculated by dividing the difference between the voltage at 60 seconds and the initial voltage while discharging at a constant current of 0.1C by the applied current.

[0242] (Evaluation of battery life characteristics)

[0243] The monocells manufactured above were each charged at 25℃ with a constant current (CC) of 0.3C until 4.2V, then charged at a constant voltage (CV) of 4.2V until the charge current became 0.05mAh (cut-off current), left for 20 minutes, and then discharged at a constant current of 0.3C until 2.5V. This charge-discharge cycle was repeated twice. After this, the cells were recharged at a constant current of 0.3C in the discharged state, and after completing the room temperature output measurement using the Hybrid Pulse Power Characterization (HPPC) protocol, they were charged at a constant current of 0.3C until 4.2V in a 45℃ oven, and then charged at a constant voltage of 4.2V until the charge current became 0.05mAh (cut-off current). After that, it was left for 20 minutes, and then one charge-discharge cycle was performed at a constant current of 0.3 C to discharge until the voltage reached 2.5 V. After that, it was charged at a constant current of 0.5 C to 4.2 V, and then charged at a constant voltage of 4.2 V until the charge current reached 0.05 mAh (cut-off current), and then left for 20 minutes, and then the charge-discharge cycle of discharging at a constant current of 1.0 C to 2.5 V was repeated 300 times. At this time, the percentage of the discharge capacity of the 300th cycle to the discharge capacity of the first cycle was defined as the capacity retention rate, and is shown in Table 2 below. In addition, the percentage of the DICR value of the 300th cycle to the DCIR value of the first cycle was defined as the resistance increase rate, and is shown in Table 2 below.

[0244]

[0245] Initial charge capacity (mAh / g) Initial discharge capacity (mAh / g) Initial efficiency (%) Capacity retention rate (%) Resistance increase rate (%) Example 1231.5206.189.090.144.5 Example 2231.1206.589.389.634.6 Comparative example 1230.9204.488.588.767.4 Comparative example 2231.4204.988.589.251.4 Comparative example 3232.1205.788.789.458.0 Comparative example 4231.6205.588.789.048.8 Comparative example 5231.1204.988.789.260.1 Comparative example 6230.8206.489.488.542.2

[0246] Referring to Table 2, it can be confirmed that the batteries including the positive electrode active materials of Examples 1 and 2 have superior initial discharge capacity, initial efficiency, capacity retention rate, and resistance increase rate compared to the batteries including the positive electrode active materials of the comparative examples.

[0247] As a result, a lithium transition metal oxide in the form of a single particle; and a coating part including cobalt formed on the lithium transition metal oxide in the form of a single particle; and in the XPS spectrum, the intensity (I) of the peak (525 eV to 530 eV) corresponding to the O 1s core-level Metal-O ) intensity of the peak (289 eV to 291 eV) corresponding to C 1s (I Carbonate ) ratio (I Carbonate / I Metal-O ) in the case of a battery including a positive electrode active material according to the present invention having a value of 0.10 or more and 0.18 or less, the NiO reduction layer and residual lithium present on the surface of the positive electrode active material are reduced, so it can be confirmed that the capacity characteristics, initial efficiency, and life characteristics of the battery are excellent.

Claims

1. Lithium transition metal oxide in single particle form; and A coating portion including cobalt formed on the lithium transition metal oxide in the form of a single particle; In the XPS spectrum, the intensity (I) of the peak (525 eV to 530 eV) corresponding to the O 1s core-level Metal-O ) intensity of the peak (289 eV to 291 eV) corresponding to C 1s (I Carbonate ) ratio (I Carbonate / I Metal-O ) is a single particle type positive electrode active material having a particle size of 0.10 or more and 0.18 or less.

2. In claim 1, The above single particle type positive electrode active material has an average particle diameter (D 50 ) A positive electrode active material in the form of a single particle having a size of 0.1㎛ to 10㎛.

3. In claim 1, The above single-particle type positive electrode active material is a single-particle type positive electrode active material in which primary particles composed of 10 or fewer single crystal grains are aggregated into 50 or fewer.

4. In claim 1, The above single particle type lithium transition metal oxide is a single particle type positive electrode active material that is a lithium composite transition metal oxide containing nickel (Ni), cobalt (Co), and manganese (Mn).

5. In claim 1, The above single particle type lithium transition metal oxide is a single particle type positive electrode active material having a composition represented by the following chemical formula 1: [Chemical Formula 1] Li a Ni b Co c Mr d M 1 e O2 In the above chemical formula 1, M 1 is at least one selected from Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, Sn, Y, Zn, F, P and S, 0.9≤a≤1.1, 0.8≤b<1.0, 0 <c<0.2, 0<d<0.2, 0≤e≤0.1, b+c+d+e=1이다.

6. In claim 1, The above coating portion is a single particle type positive electrode active material including a cobalt-containing coating layer; and island-shaped LiCoO2 discontinuously formed on the surface.

7. In claim 1, The above coating portion is a single particle-shaped positive electrode active material in a region of 5 nm to 100 nm from the surface of the positive electrode active material toward the center.

8. A positive electrode comprising a positive electrode active material according to claim 1.

9. A lithium secondary battery comprising a positive electrode according to claim 8.

Images