Positive electrode active material for lithium secondary battery, method for preparing same, and lithium secondary battery

Abstract

The present invention provides a positive electrode active material for a lithium secondary battery, the positive electrode active material for a lithium secondary battery being a positive electrode active material containing a lithium metal oxide, and the positive electrode active material for a lithium secondary battery satisfying formula 1. [Formula 1] Charge Transfer Resistance (RCT) < = 30 Omega (In Formula 1, RCT is based on a value measured by Electrochemical Impedance Spectroscopy (EIS) for a coin-type half cell including a positive electrode to which the positive electrode active material is applied).

Description

Technical Field

[0001] This invention relates to a positive electrode active material for lithium secondary batteries, its preparation method, and lithium secondary batteries. Background Technology

[0002] Rechargeable batteries are batteries that can be repeatedly charged and discharged. With the development of the information communication and display industries, rechargeable batteries are widely used as power sources for portable electronic communication devices such as portable cameras, mobile phones, and laptops. Furthermore, battery packs incorporating rechargeable batteries are being developed for use as power sources in environmentally friendly vehicles such as electric cars.

[0003] Secondary batteries can be categorized into, for example, lithium secondary batteries, nickel-cadmium batteries, and nickel-metal hydride batteries. Among them, lithium secondary batteries have high operating voltage and energy density per unit weight, and are advantageous for charging speed and lightweight design.

[0004] Lithium metal oxides are widely used as positive electrode materials for lithium secondary batteries.

[0005] In the case of lithium metal oxides, a large amount of residual lithium will exist on their surface, so research and development related to washing processes to remove residual lithium are underway. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] One technical problem of the present invention is to provide a positive electrode active material for lithium secondary batteries that has reduced residual lithium and improved conductivity.

[0008] One technical problem of the present invention is to provide a method for preparing a positive electrode active material for lithium secondary batteries, the method being able to reduce the loss rate of the positive electrode material and improve the removal rate of residual lithium.

[0009] One technical problem of the present invention is to provide a lithium secondary battery with improved capacity and lifespan characteristics.

[0010] (II) Technical Solution

[0011] The present invention provides a positive electrode active material for lithium secondary batteries, the positive electrode active material for lithium secondary batteries comprising lithium metal oxide and satisfying the following formula 1.

[0012] [Formula 1]

[0013] Charge transfer resistance (R) CT ≤30Ω

[0014] In Equation 1, R CTThe values ​​are based on measurements obtained by electrochemical impedance spectroscopy (EIS) of a coin-shaped half-cell, including a positive electrode incorporating the aforementioned positive electrode active material.

[0015] In some embodiments, the content of residual lithium present on the surface of the lithium metal oxide may be less than 5000 ppm.

[0016] In some embodiments, the positive electrode active material for the lithium secondary battery may further include a coating formed on at least a portion of the surface of the lithium metal oxide, the coating may include an inorganic material containing at least one of a metallic element, a quasi-metallic element, and a non-metallic element.

[0017] In some embodiments, the metallic element may include at least one selected from aluminum, tungsten, cobalt, zirconium, molybdenum, niobium, and titanium, the metalloid element may include boron, and the nonmetallic element may include sulfur.

[0018] In some implementations, the inorganic material may comprise tungsten.

[0019] In some implementations, the content deviation of inorganic matter throughout the entire area of ​​the coating can be less than 10%.

[0020] In some embodiments, the content deviation of tungsten-containing inorganic matter throughout the entire area of ​​the coating may be less than 10%.

[0021] This invention provides a method for preparing a positive electrode active material for lithium secondary batteries, the method comprising: preparing a primary lithium metal oxide; and treating the primary lithium metal oxide with flake ice.

[0022] In some implementations, the primary lithium metal oxide may be treated without the use of water or water vapor.

[0023] In some embodiments, the average crystal size of the flake ice can be from 0.05 mm to 0.5 mm.

[0024] In some embodiments, in the processing using the flake ice, 1 to 3 parts by weight of the flake ice can be used relative to 100 parts by weight of the primary lithium metal oxide.

[0025] In some implementations, the processing using the flake ice can be carried out in a temperature range of -35°C to 35°C.

[0026] In some embodiments, during the processing using the flake ice, the primary lithium metal oxide and the flake ice can be added to a mixer and mixed.

[0027] In some embodiments, in the process of using the flake ice, the primary lithium metal oxide and inorganic material can be added to a mixer and mixed, and then the flake ice can be added and mixed.

[0028] In some embodiments, the inorganic material may contain at least one of a metallic element, a quasi-metallic element, and a non-metallic element.

[0029] In some implementations, the mixing time from the addition of the primary lithium metal oxide and the inorganic material to the addition of the flake ice can be from 3 minutes to 15 minutes.

[0030] In some embodiments, the amount of the inorganic material added to the mixer may be from 1,000 ppm to 9,000 ppm per 1 kg of the primary lithium metal oxide.

[0031] In some embodiments, the preparation method may further include the step of calcining the treated primary lithium metal oxide more than once to obtain lithium metal oxide.

[0032] In some implementations, the loss rate (%) of lithium metal oxide according to Formula 2 below can be less than 0.5%.

[0033] [Equation 2]

[0034]

[0035] In Formula 2, A1 is the amount of lithium metal oxide that has undergone calcination, and A2 is the amount of graded lithium metal oxide obtained by sieving the calcined lithium metal oxide using a 325-mesh sieve.

[0036] The present invention provides a lithium secondary battery, the lithium secondary battery comprising a positive electrode containing the above-mentioned positive electrode active material and a negative electrode disposed opposite to the positive electrode.

[0037] (III) Beneficial Effects

[0038] The positive electrode active material for lithium secondary batteries according to embodiments of the present invention can have improved conductivity and can reduce the amount of residual lithium present on the surface.

[0039] The method for preparing positive electrode active material for lithium secondary batteries according to an embodiment of the present invention can reduce the loss rate of positive electrode material and can fully remove residual lithium present on the surface of the positive electrode active material.

[0040] The lithium secondary battery according to the embodiments of the present invention can achieve improved capacity and lifespan characteristics.

[0041] The positive electrode active material for lithium secondary batteries and the lithium secondary battery containing the positive electrode active material of the present invention can be widely used in green technology fields such as electric vehicles, battery charging stations, and other battery-based solar power generation and wind power generation. The positive electrode active material for lithium secondary batteries and the lithium secondary battery containing the positive electrode active material of the present invention can be used in eco-friendly electric vehicles and hybrid vehicles, which prevent climate change by suppressing air pollution and greenhouse gas emissions. Attached Figure Description

[0042] Figure 1 This is a schematic process flow diagram of a method for preparing a positive electrode active material for a lithium secondary battery according to an exemplary embodiment.

[0043] Figure 2 An example image of ice flakes.

[0044] Figure 3 This is a schematic plan view of a lithium secondary battery according to an exemplary embodiment.

[0045] Figure 4 This is a schematic cross-sectional view of a lithium secondary battery according to an exemplary embodiment.

[0046] Figure 5 Nyquist plot of a coin-type half-cell using the positive electrode active material according to Example 1 and Comparative Example 1.

[0047] Explanation of reference numerals in the attached figures:

[0048] 100: Positive electrode; 105: Positive electrode current collector

[0049] 107: Positive electrode lead; 110: Positive electrode active material layer

[0050] 120: Negative electrode active material layer; 125: Negative electrode current collector

[0051] 127: Negative lead; 130: Negative electrode

[0052] 140: Diaphragm; 150: Electrode assembly

[0053] 160: Casing Detailed Implementation

[0054] Hereinafter, with reference to the accompanying drawings, exemplary embodiments of the present invention will be described in detail so that those skilled in the art can readily implement them. However, these are merely exemplary, and the present invention is not limited to the exemplary embodiments described.

[0055] <Positive electrode active materials for lithium secondary batteries>

[0056] The positive electrode active material according to an exemplary embodiment of the present invention comprises a lithium metal oxide. The lithium metal oxide satisfies Formula 1 below, therefore the positive electrode using the positive electrode active material can have improved conductivity and reduced surface interfacial resistance.

[0057] [Formula 1]

[0058] Charge transfer resistance (R) CT ≤30Ω

[0059] In Equation 1, R CT The values ​​are based on measurements obtained by electrochemical impedance spectroscopy (EIS) of a coin-shaped half-cell, including a positive electrode incorporating the aforementioned positive electrode active material.

[0060] R CT It can be, for example, below 29Ω, below 28Ω, or below 27Ω, and can also be above 20Ω.

[0061] The positive electrode can be formed, for example, by coating a positive electrode slurry containing the positive electrode active material onto a positive electrode current collector and then drying under reduced pressure or by drying and calendering. Therefore, the positive electrode may include a positive electrode current collector and a layer of positive electrode active material.

[0062] Measuring R CT The mass of the positive electrode active material layer per unit area can be 9 mg / cm³. 2 Up to 11 mg / cm 2 For example, it could be 10 ± 0.5 mg / cm³ 2 .

[0063] Measuring R CT The density of the positive electrode mixture can be 3.4 g / cm³. 3 Up to 3.6 g / cm 3 For example, it could be 3.5 ± 0.1 g / cm³. 3 .

[0064] Measuring R CT The total thickness of the positive electrode can be from 45 μm to 55 μm, for example, from 48 μm to 52 μm or 50 ± 1 μm.

[0065] The positive current collector may include metal foil, metal plate, etc. The metal foil or metal plate may include, for example, stainless steel, iron, aluminum, copper, germanium, nickel, titanium or magnesium, or alloys of two or more of them.

[0066] The positive electrode slurry may further include at least one selected from, for example, binders, conductive materials, and solvents.

[0067] As a non-limiting example, the adhesive may include, for example, organic adhesives such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, and polymethyl methacrylate, and water-based adhesives such as styrene-butadiene rubber (SBR). These may be used alone or in combination of two or more. The adhesive may be used with a thickener (e.g., carboxymethyl cellulose (CMC)).

[0068] As a non-limiting example, the conductive material may include, for example, linear conductive materials, point conductive materials, or both linear and point conductive materials. The linear conductive material may include, for example, carbon nanotubes (CNTs), which may include single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), multi-walled carbon nanotubes (MWCNTs), rope carbon nanotubes, etc.

[0069] The solvent may include, for example, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc.

[0070] In the positive electrode slurry, the content of the positive electrode active material can be from 80% to 98% by weight, based on the total weight of solids.

[0071] In the positive electrode slurry, the content of the binder can be, for example, from 1% to 10% by weight or from 1% to 5% by weight, based on the total weight of solids.

[0072] In the positive electrode slurry, the content of the conductive material can be, for example, from 1% to 10% by weight or from 1% to 6% by weight, based on the total weight of solids.

[0073] The total weight of solids in the cathode slurry can be from 65% to 90% by weight.

[0074] The coin-shaped half-cell may include, for example, a positive electrode, a separator, a negative electrode, and an electrolyte. The separator may be a porous separator, for example, a polyethylene-based separator. The negative electrode may be, for example, lithium metal, and the electrolyte may contain, for example, a lithium salt.

[0075] For the aforementioned coin-type half-cell, for example, it is possible to set the frequency from 10 to 10 mV with an amplitude of 10 mV while the state of charge (SOC) is at 100%. 5 The frequency was varied from Hz to 0.1 Hz, and an AC voltage was applied simultaneously. R was measured by electrochemical impedance spectroscopy. CT .

[0076] The voltage of the coin-type half-cell when the state of charge (SOC) is 100% can be, for example, 4.3V.

[0077] In some embodiments, the lithium metal oxide may be represented by the following chemical formula 1.

[0078] [Chemical Formula 1]

[0079] Li x Ni a Co b M c O y

[0080] In chemical formula 1, M can be at least one of Al, Zr, Ti, B, Mg, Mn, Ba, Si, Y, W, and Sr, and can be 0. <x≤1.1,2≤y≤2.02,0≤a≤1,0≤b≤1,0≤c≤1,0<a+b+c≤1。

[0081] The chemical structure of Formula 1 represents the bonding relationships contained in the layered or crystalline structure of the lithium metal oxide, without excluding the introduction of other additional elements.

[0082] For example, the lithium metal oxide may further include auxiliary elements to enhance the chemical stability of the active material or the layered / crystal structure. These auxiliary elements may be further incorporated into the layered / crystal structure and bonded together with the main active element; this should also be understood as including within the scope of the chemical structure represented by Formula 1.

[0083] As a non-limiting example, the auxiliary element may be one or more elements selected from, for example, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, and Zr.

[0084] In some implementations, the positive electrode active material may be in single-particle form.

[0085] In this specification, "single particle" can refer to a single-crystal particle without grain boundaries, and / or a particle composed of 2 to several tens (e.g., less than 20, less than 10, or 2 to 5) of such single-crystal particles. This concept encompasses particles with fewer than 10 grain boundaries visible when observed, for example, using a scanning electron microscope (SEM) at a magnification of 4000x to 20000x.

[0086] The single particle is different from an aggregate, i.e., a secondary particle or polycrystalline particle, which is composed of hundreds of single crystal particles.

[0087] The average particle size of the single-particle positive electrode active material is smaller than that of the polycrystalline form, and the amount of residual lithium on the surface is relatively large. Therefore, the physical properties of the final positive electrode active material may vary significantly depending on the washing method. The residual lithium may include, for example, lithium hydroxide (LiOH), lithium carbonate (Li2CO3), etc.

[0088] For the positive electrode active material according to the exemplary embodiment, unlike water washing methods using water or water vapor, or non-water washing methods without using water, ice flakes are used for washing, so that the positive electrode active material can be an active material in a state that effectively removes residual lithium while preventing surface damage.

[0089] In some embodiments, the residual lithium content on the surface of each 1 kg of the lithium metal oxide can be less than 5000 ppm. Therefore, gelation, solidification, battery swelling, and gas generation caused by residual lithium and side reactions with the electrolyte can be suppressed or reduced.

[0090] The residual lithium content present on the surface of the lithium metal oxide can be, for example, less than 4500 ppm, less than 3000 ppm, or less than 2400 ppm.

[0091] As a non-limiting example, the content of residual lithium present on the surface of each 1 kg of the lithium metal oxide may be more than 1000 ppm.

[0092] In some embodiments, the content of LiOH present on the surface of the lithium metal oxide can be, for example, from 500 ppm to 2000 ppm.

[0093] In some embodiments, the content of Li2CO3 present on the surface of the lithium metal oxide can be, for example, from 500 ppm to 2000 ppm.

[0094] In some embodiments, the positive electrode active material may further comprise a coating formed on at least a portion of the surface of the lithium metal oxide, the coating comprising an inorganic substance containing at least one of a metallic element, a quasi-metallic element, and a non-metallic element.

[0095] The inorganic material may be, for example, an oxide or hydroxide containing the above-mentioned elements.

[0096] In some embodiments, the metallic element may include aluminum, tungsten, cobalt, zirconium, molybdenum, niobium and / or titanium, the metalloid element may include boron, and the nonmetallic element may include sulfur.

[0097] In one embodiment, the inorganic material may comprise tungsten, for example, tungsten oxide. The tungsten oxide may include, for example, WO3.

[0098] Therefore, the conductivity of the positive electrode active material can be further improved.

[0099] In one embodiment, the inorganic material may include, for example, amorphous Al2O3, lithium aluminum oxide, AlOOH, Al(OH)3, amorphous lithium boron oxide, LiBO, Li2BO2, Li2B4O7, Li4BO3, CoOOH, Nb2O5, etc.

[0100] In some embodiments, the content deviation of inorganic matter throughout the entire region of the coating can be less than 10%. The content of the inorganic matter can be measured by energy-dispersive X-ray spectroscopy (EDS). The peak intensity of the inorganic matter in the EDS spectrum can be measured, and the difference between the average peak intensity and the highest or lowest peak intensity, expressed as a percentage, can be calculated. The value calculated thereby can be defined as the deviation.

[0101] In one embodiment, the content deviation of tungsten-containing inorganic matter throughout the entire region of the coating may be less than 10%. This deviation can be, for example, a value obtained by calculating, as a percentage, the difference between the average peak intensity and the highest or lowest peak intensity of WO3 in an EDS spectrum.

[0102] The content deviation of the inorganic substance can be, for example, less than 9% or less than 8%, and the smaller the lower limit, the better.

[0103] In some embodiments, the content of inorganic matter in the positive electrode active material can be from 1000 ppm to 9000 ppm or from 2000 ppm to 6000 ppm per 1 kg of the lithium metal oxide. Therefore, the positive electrode active material can be further stabilized.

[0104] The specific surface area of ​​the lithium metal oxide can be, for example, 0.05 m². 2 / g or higher. Under these conditions, smooth lithium-ion migration can be ensured.

[0105] The average particle size of the lithium metal oxide in single-particle form can be, for example, 1 μm to 9 μm, 1 μm to 7 μm, or 2 μm to 4 μm. The average particle size can refer to D... 50 .

[0106] The thickness of the coating can be, for example, 10 nm to 200 nm or 20 nm to 100 nm.

[0107] <Preparation Method of Positive Electrode Active Material for Lithium Secondary Batteries>

[0108] Figure 1 This is a schematic process flow diagram of a method for preparing a positive electrode active material for a lithium secondary battery according to an exemplary embodiment.

[0109] A method for preparing a positive electrode active material for a lithium secondary battery according to an exemplary embodiment includes: preparing a primary lithium metal oxide (S10); and treating the primary lithium metal oxide with flake ice (S20). Therefore, residual lithium on the surface of the primary lithium metal oxide can be effectively removed without damaging the surface, and the loss rate of the primary lithium metal oxide (hereinafter, simply referred to as the positive electrode material) during the preparation process can be reduced.

[0110] In the preparation method of the positive electrode active material according to the exemplary embodiment, the primary lithium metal oxide may not be treated with water or water vapor.

[0111] In some implementations, the primary lithium metal oxide may be in single-particle form.

[0112] Single-particle positive electrode active materials have relatively small average particle size. Therefore, when washing with water during the preparation process or washing with a small amount of water and high-speed rotation without water, the loss rate of the positive electrode material may increase, and the surface damage of the positive electrode material may increase.

[0113] In addition, the amount of residual lithium in the single-particle form of positive electrode active material is relatively large. Therefore, when washing with water vapor or by dry coating during the preparation process, the residual lithium may not be completely removed.

[0114] Figure 2This is an exemplary image of flake ice. The flake ice can refer to ice shaved into thin flakes, which can be prepared using a flake ice machine. As a non-limiting example, the flake ice can be prepared using a snowflake ice machine (NSD-151MW) from Nakanzo International, etc.

[0115] In some embodiments, the average crystal size of the flake ice can be from 0.05 mm to 0.5 mm. The average crystal size of the flake ice can refer to, for example, the average of the maximum and minimum lengths of the diameter passing through the center of the crystal of the flake ice. As a non-limiting example, the average crystal size of the flake ice can be measured using an optical microscope or the like.

[0116] The average thickness of the flake ice can be, for example, 0.1 mm or more.

[0117] In some embodiments, during the treatment using the flake ice, 1 to 3 parts by weight of the flake ice can be used relative to 100 parts by weight of the primary lithium metal oxide. Therefore, residual lithium on the surface of the primary lithium metal oxide can be sufficiently removed, and lithium detachment within the layered structure can be prevented. Furthermore, after the treatment using the flake ice is completed, the amount of water (e.g., moisture content) contained in the primary lithium metal oxide can be reduced compared to washing methods using water or steam.

[0118] In some implementations, the treatment using the flake ice can be carried out in a temperature range of -35°C to 35°C or 5°C to 25°C. Therefore, the treatment of the primary lithium metal oxide can be performed smoothly.

[0119] In some embodiments, the primary lithium metal oxide and the flake ice can be added to and mixed in a mixer to treat the primary lithium metal oxide using the flake ice. As a non-limiting example, the mixer can be a drum blender, a V-type blender, a bin blender, a ribbon blender, a twin-screw blender, etc.

[0120] For example, the primary lithium metal oxide can be added to the mixer, followed by the flake ice. The mixer can be operated before or simultaneously with the addition of the aforementioned substances.

[0121] The first mixing of the primary lithium metal oxide and the flake ice can be carried out at a rotational speed of 60 rpm to 600 rpm. Therefore, surface damage can be suppressed while preventing the agglomeration of the primary lithium metal oxide.

[0122] In the method for preparing the positive electrode active material according to the exemplary embodiment, unlike washing using a non-water washing method, high-speed mixing is not required, thus surface damage to the primary lithium metal oxide can be suppressed and the generation of micropowder can be prevented.

[0123] In some implementations, the first mixing can be carried out for 3 to 15 minutes. Therefore, changes in the crystal structure within the primary lithium metal oxide can be prevented, and residual lithium on the surface can be effectively removed.

[0124] In some embodiments, the primary lithium metal oxide and inorganic material may be added to the mixer and mixed, and then the flake ice may be added and mixed.

[0125] The primary lithium metal oxide and the inorganic material can be added to the mixer simultaneously or sequentially.

[0126] The second mixing of the primary lithium metal oxide and the inorganic material before adding the flake ice can be carried out at a rotational speed of, for example, 1000 rpm to 2000 rpm.

[0127] The third mixing, which involves mixing the primary lithium metal oxide, the inorganic material, and the flake ice, can be carried out at a rotational speed of, for example, 60 rpm to 600 rpm.

[0128] In some embodiments, the inorganic material may comprise at least one of a metallic element, a quasi-metallic element, and a nonmetallic element. The inorganic material is as described above in this specification.

[0129] In some embodiments, the amount of the inorganic material added to the mixer may be from 2000 ppm to 6000 ppm per 1 kg of the primary lithium metal oxide.

[0130] In some embodiments, the mixing time from the addition of the primary lithium metal oxide and inorganic material to the addition of the flake ice (i.e., the second mixing time) can be from 3 minutes to 15 minutes. This stabilizes the crystal structure and surface of the primary lithium metal oxide.

[0131] In some implementations, the third mixing time may be the same as the first mixing time.

[0132] In the method for preparing the positive electrode active material according to the exemplary embodiment, the treated primary lithium metal oxide can be calcined more than once to obtain lithium metal oxide.

[0133] The treated primary lithium metal oxide can be calcined, for example, once, twice, or three times.

[0134] The treated primary lithium metal oxide can be placed in a calcining furnace, for example, by heat treatment under an oxygen atmosphere.

[0135] As a non-limiting example, the calcination can be carried out at 200°C to 600°C for 2 to 7 hours.

[0136] In some implementations, the loss rate (%) of lithium metal oxide according to Formula 2 below can be less than 0.5%.

[0137] [Equation 2]

[0138]

[0139] In Equation 2, A1 is the amount of lithium metal oxide that has undergone calcination, and A2 is the amount of graded lithium metal oxide obtained by sieving the calcined lithium metal oxide using a 325-mesh sieve.

[0140] Therefore, the method for preparing the positive electrode active material according to the exemplary embodiment can further reduce the degree of loss of the positive electrode material.

[0141] For example, the loss rate (%) of lithium metal oxide can be less than 0.4% or less than 0.3%, and the smaller the lower limit of the loss rate, the better.

[0142] The lithium metal oxide that has undergone calcination is sieved using a 325-mesh sieve to obtain lithium metal oxide that passes through the sieve and can be used as a positive electrode active material for lithium secondary batteries.

[0143] According to the existing washing methods described above, the primary lithium metal oxides may agglomerate during the washing process, or some of them may become pasty due to insufficient water drainage during the sieving process, resulting in a relatively large amount of lithium metal oxides remaining on the screen.

[0144] In the method for preparing the positive electrode active material according to the exemplary embodiment, the lithium metal oxide that has undergone calcination is graded by sieving with a sieve, thereby obtaining graded lithium metal oxide.

[0145] The screen can be, for example, a 325-mesh screen.

[0146] <Lithium secondary batteries>

[0147] Figure 3 This is a schematic plan view of a lithium secondary battery according to an exemplary embodiment. Figure 4 This is a schematic cross-sectional view of a lithium secondary battery according to an exemplary embodiment.

[0148] A lithium secondary battery according to an exemplary embodiment includes a positive electrode 100 comprising the aforementioned positive electrode active material for lithium secondary batteries and a negative electrode disposed opposite to the positive electrode 100. Therefore, the lithium secondary battery can achieve improved capacity and lifespan characteristics.

[0149] The positive electrode 100 is as described above in this specification. The positive electrode 100 may include a positive electrode current collector 105 and a positive electrode active material layer 110 disposed on at least one side of the positive electrode current collector 105. The positive electrode 100 may include, for example, a structure in which the positive electrode active material layer 110 is stacked on the positive electrode current collector 105.

[0150] In some implementations, the mass of the positive electrode active material layer 110 per unit area of ​​the positive electrode 100 can be 8.0 mg / cm². 2 Up to 13.0 mg / cm 2 9.0 mg / cm 2 Up to 11.0 mg / cm 2 Or 9.5 mg / cm 2 Up to 10.5 mg / cm 2 .

[0151] In some implementations, the mixture density of cathode 100 can be 3.0 g / cm³. 3 Up to 3.8 g / cm 3 For example, it could be 3.4 g / cm³. 3 Up to 3.6 g / cm 3 .

[0152] In some embodiments, the thickness of the positive current collector 105 can be, for example, 10 μm to 30 μm or 10 μm to 20 μm.

[0153] In some embodiments, the thickness of the positive electrode active material layer 110 can be, for example, 30 μm to 70 μm, 40 μm to 60 μm, or 45 μm to 55 μm.

[0154] The negative electrode 130 may include a negative electrode current collector 125 and a negative electrode active material layer 120 disposed on one or both sides of the negative electrode current collector 125.

[0155] The negative electrode current collector 125 may include, for example, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, etc. The thickness of the negative electrode current collector 125 may be, for example, 10 μm to 50 μm.

[0156] The negative electrode active material layer 120 may contain a negative electrode active material. The negative electrode active material may include, for example, carbon-based materials such as crystalline carbon, amorphous carbon, carbon composites, carbon fibers, etc.; lithium metal; lithium alloys; silicon (Si)-containing substances or tin (Sn)-containing substances, etc. These may be used alone or in combination of two or more.

[0157] The amorphous carbon may include hard carbon, soft carbon, coke, mesocarbon microbead (MCMB), mesophase pitch-based carbon fiber (MPCF), etc.

[0158] The crystalline carbon may include graphite-based carbons such as natural graphite, artificial graphite, graphitized coke, graphitized MCMB, graphitized MPCF, etc.

[0159] The lithium metal may include pure lithium metal and / or lithium metal formed with a protective layer for suppressing dendrite growth, etc.

[0160] The elements contained in the lithium alloy may include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, indium, etc. These may be used alone or in combination of two or more.

[0161] The silicon-containing substance may include Si, SiO x (0 < x < 2), SiO doped with metal x (0 < x < 2), silicon-carbon composites, etc.

[0162] The metal may include lithium and / or magnesium, and SiO doped with metal x (0 < x < 2) may include metal silicate.

[0163] In an exemplary embodiment, a separator 140 may be disposed between the positive electrode 100 and the negative electrode 130. The separator 140 may be arranged to prevent a short circuit between the positive electrode 100 and the negative electrode 130 and allow the flow of ions. For example, the thickness of the separator may be 10 μm to 20 μm.

[0164] For example, the separator 140 may include a porous polymer membrane or a porous non-woven fabric.

[0165] The porous polymer membrane may include polyolefin-based polymers such as ethylene polymers, propylene polymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers. These may be used alone or in combination of two or more.

[0166] The porous nonwoven fabric may include high-melting-point glass fibers, polyethylene terephthalate fibers, etc.

[0167] The diaphragm 140 may also include a ceramic-based material. For example, inorganic particles may be coated on or dispersed in the polymer membrane to improve heat resistance.

[0168] The diaphragm 140 may have a single-layer or multi-layer structure comprising the aforementioned polymer membrane and / or nonwoven fabric.

[0169] According to an exemplary embodiment, the battery cell can be defined by a positive electrode 100, a negative electrode 130, and a separator 140, and an electrode assembly 150 can be formed, for example, by stacking multiple battery cells. For example, the electrode assembly 150 can be formed by winding, stacking, z-folding, stack-folding, etc. of the separator 140.

[0170] The electrode assembly 150 can be housed together with the electrolyte in the housing 160, thereby defining a lithium secondary battery. According to an exemplary embodiment, the electrolyte can be a non-aqueous electrolyte.

[0171] Non-aqueous electrolytes may contain a lithium salt as the electrolyte and an organic solvent. For example, the lithium salt may be made from Li... + X - This is represented, for example, by the anion (X) of the lithium salt. - ), can be exemplified by F - Cl - ,Br - I - NO3 - N(CN)2 - BF4 - ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2- 、(CF3)5PF - 、(CF3)6P - 、CF3SO3 - 、CF3CF2SO3 - 、(CF3SO2)2N - 、(FSO2)2N - 、CF3CF2(CF3)2CO - 、(CF3SO2)2CH - 、(SF5)3C - 、(CF3SO2)3C - 、CF3(CF2)7SO3 - [[ID=Y]] - 、CH3CO2 - 、SCN - 、(CF3CF2SO2)2N - etc.

[0172] ​The organic solvent may be, for example, propylene carbonate (PC), ethylene carbonate (EC), butene carbonate, diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, vinylene carbonate, methyl acetate (MA), ethyl acetate (EA), n-propylacetate (n-PA), 1,1-dimethylethyl acetate (DMEA), methyl propionate (MP), ethyl propionate (EP), ethyl fluoroacetate (FEA), ethyl difluoroacetate (DFEA), ethyl trifluoroacetate (TFEA), dibutyl ether, tetraethylene glycol dimethyl ether (TEGDME), and diethylene glycol dimethyl ether. These include ether (DEGDME), dimethoxyethane, tetrahydrofuran (THF), 2-methyltetrahydrofuran, ethyl alcohol, isopropyl alcohol, dimethyl sulfoxide, acetonitrile, diethoxyethane, sulfolane, γ-butyrolactone, propylene sulfite, etc. These can be used alone or in combination of two or more.

[0173] The non-aqueous electrolyte may further contain additives. These additives may include, for example, cyclic carbonate compounds, fluorinated carbonate compounds, sulfonyl lactone compounds, cyclic sulfate compounds, cyclic sulfite compounds, phosphate compounds, borate compounds, etc. These may be used alone or in combination of two or more.

[0174] The cyclic carbonate-based compound may include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), etc.

[0175] The fluorinated carbonate compounds may include fluoroethylene carbonate (FEC), etc.

[0176] The sulfonyl compounds may include 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, etc.

[0177] The cyclic sulfate-based compounds may include 1,2-ethylene sulfate, 1,2-propylene sulfate, etc.

[0178] The cyclic sulfite-based compounds may include ethylene sulfite, butylene sulfite, etc.

[0179] The phosphate-based compounds may include lithium difluorobis-oxalato phosphate, lithium difluorophosphate, etc.

[0180] The borate-based compounds may include lithium bis(oxalate) borate, etc.

[0181] In some embodiments, a solid electrolyte can be used instead of the non-aqueous electrolyte. In this case, the lithium secondary battery can be made into an all-solid-state battery. Furthermore, a solid electrolyte layer can be disposed between the positive electrode 100 and the negative electrode 130 instead of the separator 140.

[0182] The solid electrolyte may include a sulfide-based electrolyte. As a non-limiting example, the sulfide-based electrolyte may include Li₂S-P₂S₅, Li₂S-P₂S₅-LiCl, Li₂S-P₂S₅-LiBr, Li₂S-P₂S₅-LiCl-LiBr, Li₂S-P₂S₅-Li₂O, Li₂S-P₂S₅-Li₂O-LiI, Li₂S-SiS₂, Li₂S-SiS₂-LiI, Li₂S-SiS₂-LiBr, Li₂S-SiS₂-LiCl, Li₂S-SiS₂-B₂S₃-LiI, Li₂S-SiS₂-P₂S₅-LiI, Li₂S-B₂S₃, and Li₂S-P₂S₅-Z. m Sn (m and n are positive numbers, Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p and q are positive numbers, M is P, Si, Ge, B, Al, Ga, or In), Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), Li 7-x PS 6-x I x (0≤x≤2), etc. These can be used individually or in combination of two or more.

[0183] In one embodiment, the solid electrolyte may further include oxide-based amorphous solid electrolytes such as Li2O-B2O3-P2O5, Li2O-SiO2, Li2O-B2O3, and Li2O-B2O3-ZnO.

[0184] like Figure 3 and Figure 4 As shown, the tabs (positive tab and negative tab) can protrude from the positive current collector 105 and negative current collector 125 belonging to each cell and extend to one side of the housing 160. The tabs can be fused to said side of the housing 160 to form electrode leads (positive lead 107 and negative lead 127) extending to or exposed outside the housing 160.

[0185] The lithium secondary battery can be manufactured in shapes such as cylindrical, prismatic, pouch, or coin, for example, using a can.

[0186] The embodiments of the present invention will be further described below with reference to specific experimental examples. The embodiments and comparative examples included in the experimental examples are for illustrative purposes only and are not intended to limit the scope of the claims.

[0187] Example 1

[0188] Preparation of primary lithium metal oxides

[0189] NiSO4, CoSO4, and MnSO4 were added and mixed in a molar ratio of 6:1:3 to distilled water that had been bubbled with N2 for 24 hours to remove internal dissolved oxygen. The mixture was then added to a reactor at 50°C, and NaOH and NH3·H2O were added as precipitating and chelating agents, respectively, for a co-precipitation reaction for 48 hours to obtain transition metal precursors. The average particle size (D) of the obtained transition metal precursors was [not specified].50 The particle size is 3 μm, and the chemical formula is Ni. 0.6 Co 0.1 Mn 0.3 (OH)2.

[0190] The transition metal precursor was dried at 80°C for 12 hours, and then dried at 110°C for 12 hours.

[0191] Lithium carbonate and the transition metal precursor were added to a mixer at a ratio of 1.05:1 and mixed for 5 minutes. The resulting mixture was placed in a calcining furnace under an oxygen atmosphere and heated to 850°C at a rate of 2°C / min, and calcined at 850°C for 10 hours. During the heating and calcination process, oxygen was continuously introduced into the calcining furnace at a flow rate of 20 mL / min.

[0192] The calcination furnace was then allowed to cool naturally to room temperature. The resulting contents were then pulverized and classified using an air jet mill to obtain LiNi. 0.6 Co 0.1 Mn 0.3 O2 represents primary lithium metal oxide in single-particle form (average particle size (D) 50 ): 3μm).

[0193] Formation and washing of inorganic coatings

[0194] Using a mixer, the primary lithium metal oxide and tungsten oxide (WO3) powder are mixed for 10 minutes. The amount of tungsten oxide (WO3) powder added is 4000 ppm per 1 kg of the primary lithium metal oxide.

[0195] After mixing the primary lithium metal oxide and tungsten oxide (WO3) powder for 10 minutes, 2.04 parts by weight of flake ice were added relative to 100 parts by weight of the primary lithium metal oxide. The flake ice was prepared using a Nakanzo International snowflake ice maker (NSD-151MW).

[0196] At 25°C, the primary lithium metal oxide, the tungsten oxide (WO3) powder, and the flake ice are mixed for 10 minutes.

[0197] The washed primary lithium metal oxide was placed in a calcining furnace under an oxygen atmosphere and heated to 400°C at a rate of 2°C / min, and calcined at 400°C for 5 hours.

[0198] The calcined lithium metal oxides are sieved using a 325-mesh sieve to obtain graded lithium metal oxides.

[0199] At this point, the loss rate (%) of lithium metal oxide is calculated based on the amount of lithium metal oxide that has undergone calcination and the amount of lithium metal oxide remaining on the screen.

[0200] Example 2

[0201] Lithium metal oxide was obtained by the same method as in Example 1, except that cobalt oxyhydroxide (CoOOH) was used instead of tungsten oxide (WO3) powder.

[0202] Example 3

[0203] Lithium metal oxide was obtained by the same method as in Example 1, except that niobium oxide (Nb2O5) was used instead of tungsten oxide (WO3) powder.

[0204] Comparative Example 1

[0205] Lithium metal oxide was obtained by the same method as in Example 1, except that flake ice was not added.

[0206] Comparative Example 2

[0207] Lithium metal oxide was obtained by the same method as in Example 1, except that flake ice was not added, and an inorganic coating was formed after the primary lithium metal oxide was treated with a gas containing water vapor as follows.

[0208] <Washing using water vapor>

[0209] The prepared primary lithium metal oxide is placed into the calcining furnace, and the internal temperature of the calcining furnace is set to 300°C. Oxygen is injected into the calcining furnace at a flow rate of 100 mL / min through a water supply source (distilled water in a water tank).

[0210] The oxygen is converted into a gas containing moisture when passing through the water tank. The gas containing moisture is injected into the calcining furnace and converted into a gas containing water vapor, thereby treating the primary lithium metal oxide loaded into the calcining furnace with water vapor.

[0211] The steam treatment is carried out for 6 hours, followed by drying at 80°C for 1 hour to obtain washed primary lithium metal oxide.

[0212] At this time, the amount of water vapor injected into the calcining furnace is 1.01 parts by weight relative to 100 parts by weight of the primary lithium metal oxide.

[0213] <Formation of Inorganic Coatings>

[0214] Washed primary lithium metal oxide and 800 ppm tungsten oxide (WO3) powder were added to a dry high-speed mixer and mixed for 5 minutes. The resulting mixture was placed in a calcination furnace under an oxygen atmosphere and heated to 400°C at a heating rate of 2°C / min, and calcined at 400°C for 5 hours.

[0215] The calcined lithium metal oxides are sieved using a 325-mesh sieve to obtain graded lithium metal oxides.

[0216] Comparative Example 3

[0217] Lithium metal oxide was obtained using the same method as in Example 1, except that a small amount of liquid water was added instead of flake ice.

[0218] At this point, the amount of liquid water added to the mixer is 7.53 parts by weight relative to 100 parts by weight of the primary lithium metal oxide.

[0219] Comparative Example 4

[0220] Lithium metal oxide was obtained by the same method as in Example 1, except that flake ice was not added, and an inorganic coating was formed after washing the primary lithium metal oxide with liquid water as follows.

[0221] Washing with water

[0222] 1 kg of the primary lithium metal oxide was added to a reactor containing 1 kg of distilled water and stirred for 10 minutes to obtain a slurry. The obtained slurry was filtered through a vacuum flask and dried in a vacuum oven at 180°C for 12 hours to obtain washed primary lithium metal oxide.

[0223] <Formation of Inorganic Coatings>

[0224] Washed primary lithium metal oxide and tungsten oxide (WO3) powder were mixed for 10 minutes. The resulting mixture was placed in a calcination furnace under an oxygen atmosphere and heated to 400°C at a heating rate of 2°C / min. The mixture was then calcined at 400°C for 5 hours.

[0225] The calcined lithium metal oxides are sieved using a 325-mesh sieve to obtain graded lithium metal oxides.

[0226] Experimental Example

[0227] <The Manufacturing of the Positive Electrode>

[0228] Using the lithium metal oxides (hereinafter referred to as positive electrode active materials) prepared in Examples 1 to 3 and Comparative Examples 1 to 4 above, a positive electrode was manufactured according to the following method.

[0229] Prepare a mixture of positive electrode active material, carbon-based conductive material (acetylene black (Denka Black)) and polyvinylidene fluoride (PVDF) in a weight ratio of 96:2:2 (total mass of 10g).

[0230] The mixture and N-methylpyrrolidone are added to a mixer (THINKY MIXER, ARE-310) and mixed to prepare a positive electrode active material slurry.

[0231] The positive electrode active material slurry is coated onto an aluminum foil with a thickness of 20 μm by bar coating, dried at room temperature, and then dried under vacuum conditions at 120°C. The slurry is then rolled and stamped (Φ14) to manufacture the positive electrode.

[0232] The thickness, length, and width of the prepared positive electrode are measured using a micrometer, its volume is calculated, and the density of the positive electrode mixture is measured using the weight value of the positive electrode active material layer.

[0233] The electrochemical impedance spectrum of a coin-type half-cell is affected by the following three physical properties of the positive electrode. Therefore, the positive electrodes according to the above embodiments and comparative examples are manufactured in a manner that makes the following three physical properties the same.

[0234] - Mass (loading) of positive electrode active material layer per unit area: 10 ± 0.5 (mg / cm²) 2 )

[0235] - Total thickness of the positive electrode: 50±2μm (approximately 20μm for the current collector and approximately 30μm for the positive electrode active material layer)

[0236] - Mixture density: 3.5 ± 0.1 g / cm³ 3 )

[0237] <Manufacturing of Coin-Type Half-Cells>

[0238] Prepare a 1.2 mm thick lithium metal as the negative electrode.

[0239] The positive and negative electrodes prepared above are notched into circular shapes with diameters of Φ14 and Φ16, respectively, and stacked. A porous membrane (polyethylene with a thickness of 13μm) cut into Φ19 is placed between the positive and negative electrodes to form a battery cell.

[0240] The cell was placed in an outer casing material with a diameter of 20 mm and a height of 3.2 mm, electrolyte was injected, and the casing was assembled to manufacture a coin-shaped half-cell (CR2032). It was then aged for 12 hours to allow the electrolyte to penetrate the cell. The electrolyte used was 1M LiPF6 with a mixed solvent of EC / EMC (30 / 70; volume ratio).

[0241] Experimental Example 1: Evaluation of Initial Charge / Discharge Capacity and Capacity Retention

[0242] The charge / discharge capacity of the coin cell half-cell was evaluated using a charge / discharge tester (manufacturer: TOYO, model: TOYO-3100).

[0243] The coin-shaped half-cell manufactured as described above was left to stand for 24 hours until the open circuit voltage (OCV) stabilized. Then, it was charged at a constant current (CC) of 0.1C at room temperature (25°C) until the voltage reached 4.4V. Afterward, it was charged at a constant voltage (CV) of 4.4V until the charging current reached 0.05C. This process was repeated once, and the initial charge capacity was measured.

[0244] Afterward, the coin-shaped half-cell was left to stand for 10 minutes, and then discharged at a constant current of 0.1C to 3.0V. The discharge was repeated once, and the initial discharge capacity was measured.

[0245] Subsequently, at 45°C, 50 cycles of CC-CV charging (0.5C, 4.4V, 0.05C cut-off) and discharging (1.0C, 3.0V) were repeated. The capacity retention rate was evaluated as the percentage obtained by dividing the discharge capacity measured in the 50th cycle by the initial discharge capacity in the 1st cycle.

[0246] The results are shown in Table 1 below.

[0247] Experimental Example 2: Charge Transfer Resistance (R) CT Evaluation

[0248] The initial charge capacity and initial discharge capacity of the coin-shaped half-cell manufactured as described above were measured using the same method as in Experimental Example 1.

[0249] Subsequently, the coin-shaped half-cell was charged at room temperature (25°C) using a constant voltage and constant current charging method, with a charging voltage of 4.3V and a charging current of 0.2C. The coin-shaped half-cell was charged to 100% state of charge (SOC) (4.3V) and then the voltage was fixed. After transferring the coin-shaped half-cell to a low-temperature (-5°C) chamber, an electrochemical impedance spectroscopy was obtained using an impedance measurement device (a potentiostat from NeoScience). At this point, the frequency was adjusted from 10 mV with an amplitude of 10 mV. 5 The Hz frequency is changed to 0.1Hz while an AC voltage is applied.

[0250] The Nyquist plot is obtained based on the impedance spectrum. Figure 5 The diagram shows a Nyquist plot of a coin-type half-cell including a positive electrode with a positive electrode active material prepared according to Example 1.

[0251] Mathematical fitting is performed on the small and large semicircles on the Nyquist plot to calculate R. SEI and R CT At this point, the resistance value obtained from the semicircle (small semicircle) generated in the high-frequency region represents R. SEI The resistance value obtained from the semicircle (large semicircle) generated in the low-frequency region represents R. CT .

[0252] R based on the semicircle generated in the high-frequency region SEI It can represent the resistance caused by solid electrolytes, based on the semicircular R generated in the low-frequency region. CT It can represent the charge transfer resistance during the charge movement process at the positive electrode interface.

[0253] The results are shown in Table 1 below.

[0254] Experimental Example 3: Evaluation of Coating Uniformity

[0255] For the positive electrode active materials prepared in Examples 1 to 3 and Comparative Examples 1 to 4 above, SEM images were captured at 20,000x magnification using a scanning electron microscope (SEM) under an accelerating voltage of 10kV.

[0256] Energy-dispersive X-ray spectroscopy (EDS) using scanning electron microscopy was employed at a pulse throughput of 60 eV / count and a working distance of 10 mm. EDS spectra were obtained based on SEM images. The average peak intensity and highest peak intensity of WO3 were calculated by averaging 10 randomly selected points from the spectra. The tungsten peak was then normalized to the Pt peak intensity of the Pt coating (2.05 keV).

[0257] The results are shown in Table 2 below.

[0258] Experimental Example 4: Evaluation of the content of residual lithium on the surface

[0259] The content of residual lithium on the surface of the positive electrode active materials prepared in Examples 1 to 3 and Comparative Examples 1 to 4 was measured as follows.

[0260] 2.5 g of the positive electrode active material and 100 g of deionized water were added to a 250 mL flask and stirred at 400 rpm for 10 minutes. The resulting dispersion was filtered through a vacuum flask to obtain 100 g. The filtered dispersion was added to an autotitrator, and the contents (ppm) of LiOH and Li₂CO₃ in the dispersion were measured based on the pH titration chart obtained by autotitration with 0.1 N HCl, referring to the Warder Method. The sum of the measured LiOH and Li₂CO₃ contents was evaluated as the amount of residual lithium on the surface.

[0261] The results are shown in Table 2 below.

[0262] Experimental Example 5: Evaluation of the Loss Rate of Lithium Metal Oxides

[0263] The lithium metal oxides that underwent calcination treatment in Examples 1 to 3 and Comparative Examples 1 to 4 were sieved using a 325-mesh sieve to obtain graded lithium metal oxides.

[0264] At this point, the loss rate (%) of lithium metal oxide is calculated based on the amount of lithium metal oxide that has undergone calcination and the amount of lithium metal oxide remaining on the screen.

[0265] The results are shown in Table 2 below.

[0266] [Table 1]

[0267]

[0268] [Table 2]

[0269]

[0270] According to Tables 1 and 2, in the positive electrode active materials according to Examples 1 to 3, surface damage is reduced, residual lithium is sufficiently removed, and a more uniform coating is formed. Therefore, the positive electrode active materials according to Examples 1 to 3 have improved conductivity, and side reactions caused by residual lithium are suppressed. Consequently, the capacity and lifetime characteristics of coin-type half-cells incorporating positive electrodes using the positive electrode active materials of Examples 1 to 3 are improved. Furthermore, in Examples 1 to 3, the loss rate of lithium metal oxide is reduced.

[0271] According to Comparative Example 1, the positive electrode active material has the highest residual lithium content, therefore the capacity and lifespan characteristics of the coin-type half-cell that includes the positive electrode active material of Comparative Example 1 are low.

[0272] In the positive electrode active material according to Comparative Example 2, the residual lithium on the surface was not sufficiently removed, resulting in insufficient capacity and lifetime characteristics of the coin-type half-cell using the positive electrode active material of Comparative Example 2. Furthermore, in Comparative Example 2, the loss rate of lithium metal oxide increased.

[0273] According to Comparative Example 3, surface damage and micronization occurred in the positive electrode active material. Therefore, the capacity and lifetime characteristics of the coin-type half-cell using the positive electrode active material of Comparative Example 3 were insufficient. Furthermore, in Comparative Example 3, the loss rate of lithium metal oxide was relatively high.

[0274] In the positive electrode active material according to Comparative Example 4, surface damage caused by liquid water occurred most frequently, a large amount of lithium was detached from the layered structure, and the water content in the active material was high. Therefore, the coin-type half-cell using the positive electrode active material of Comparative Example 4 had the lowest high-temperature capacity retention. Furthermore, in Comparative Example 4, the loss rate of lithium metal oxide was the highest.

Claims

1. A positive electrode active material for lithium secondary batteries, comprising lithium metal oxide, The positive electrode active material for the lithium secondary battery satisfies the following formula 1: [Formula 1] Charge transfer resistance (R) CT ≤30Ω In Equation 1, R CT The values ​​are based on measurements obtained by electrochemical impedance spectroscopy (EIS) of a coin-shaped half-cell, including a positive electrode incorporating the aforementioned positive electrode active material.

2. The positive electrode active material for lithium secondary batteries according to claim 1, wherein, The residual lithium content present on the surface of the lithium metal oxide is less than 5000 ppm.

3. The positive electrode active material for lithium secondary batteries according to claim 1, wherein, The positive electrode active material for the lithium secondary battery further comprises a coating, the coating being formed on at least a portion of the surface of the lithium metal oxide, the coating comprising an inorganic substance containing at least one of a metallic element, a quasi-metallic element, and a non-metallic element.

4. The positive electrode active material for lithium secondary batteries according to claim 3, wherein, The metallic element comprises at least one selected from aluminum, tungsten, cobalt, zirconium, molybdenum, niobium, and titanium; the metalloid element comprises boron; and the nonmetallic element comprises sulfur.

5. The positive electrode active material for lithium secondary batteries according to claim 3, wherein, The inorganic material contains tungsten.

6. The positive electrode active material for lithium secondary batteries according to claim 3, wherein, The inorganic content deviation is less than 10% throughout the entire area of ​​the coating.

7. The positive electrode active material for lithium secondary batteries according to claim 5, wherein, The content deviation of tungsten-containing inorganic matter in the entire area of ​​the coating is less than 10%.

8. A method for preparing a positive electrode active material for lithium secondary batteries, comprising the following steps: Prepare primary lithium metal oxides; and The primary lithium metal oxide was treated with flake ice.

9. The method for preparing the positive electrode active material for lithium secondary batteries according to claim 8, wherein, The primary lithium metal oxide is not treated with water or water vapor.

10. The method for preparing the positive electrode active material for lithium secondary batteries according to claim 8, wherein, The average crystal size of the flake ice is 0.05 mm to 0.5 mm.

11. The method for preparing the positive electrode active material for lithium secondary batteries according to claim 8, wherein, In the processing using the flake ice, 1 to 3 parts by weight of the flake ice are used relative to 100 parts by weight of the primary lithium metal oxide.

12. The method for preparing the positive electrode active material for lithium secondary batteries according to claim 8, wherein, The processing using the flake ice is carried out in a temperature range of -35°C to 35°C.

13. The method for preparing the positive electrode active material for lithium secondary batteries according to claim 8, wherein, In the process of using the flake ice, the primary lithium metal oxide and the flake ice are added to a mixer and mixed.

14. The method for preparing the positive electrode active material for lithium secondary batteries according to claim 8, wherein, In the process of using the flake ice, the primary lithium metal oxide and inorganic matter are added to a mixer and mixed, and then the flake ice is added and mixed.

15. The method for preparing the positive electrode active material for lithium secondary batteries according to claim 14, wherein, The inorganic material contains at least one of a metallic element, a quasi-metallic element, and a non-metallic element.

16. The method for preparing the positive electrode active material for lithium secondary batteries according to claim 14, wherein, The mixing time from the addition of the primary lithium metal oxide and the inorganic material to the addition of the flake ice is 3 to 15 minutes.

17. The method for preparing the positive electrode active material for lithium secondary batteries according to claim 14, wherein, The amount of the inorganic material added to the mixer is 1000 ppm to 9000 ppm per 1 kg of the primary lithium metal oxide.

18. The method for preparing the positive electrode active material for lithium secondary batteries according to claim 8, wherein, The method further includes the step of calcining the treated primary lithium metal oxide more than once to obtain lithium metal oxide.

19. The method for preparing the positive electrode active material for lithium secondary batteries according to claim 18, wherein, The loss rate of lithium metal oxide, expressed as a percentage, according to Equation 2 below is less than 0.5%: [Equation 2] In Formula 2, A1 is the amount of lithium metal oxide that has undergone calcination, and A2 is the amount of graded lithium metal oxide obtained by sieving the calcined lithium metal oxide using a 325-mesh sieve.

20. A lithium secondary battery, comprising: The positive electrode comprises the positive electrode active material for lithium secondary batteries as described in claim 1; as well as The negative electrode is positioned opposite to the positive electrode.

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