Cathode active material for lithium secondary battery, and lithium secondary batterty comprising same

Abstract

A cathode active material for a lithium secondary battery, according to the present invention, is in the form of single particles, wherein the cathode active material may satisfy expression 1 in the present specification.

Description

Cathode active material for lithium secondary batteries and lithium secondary battery including the same

[0001] The present embodiments relate to a positive electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same.

[0002] The present application claims priority to Korean Patent Application No. 10-2024-0130351, filed September 26, 2024 and Korean Patent Application No. 10-2024-0130352, filed September 26, 2024, the entire contents of said prior applications are incorporated herein by reference.

[0003] Recently, the demand for IT mobile devices, small power drive systems (e-bikes, small EVs, etc.), and Energy Storage Systems (ESS) has been increasing explosively. Consequently, the development of high-capacity and high-energy-density secondary batteries to power these devices is actively underway worldwide. To manufacture such high-capacity batteries, high-capacity cathode materials must be used.

[0004] Among existing layered cathode active materials, LiNiO2 has the highest capacity, but commercialization is difficult due to structural collapse occurring easily during charging and discharging and low thermal stability caused by oxidation state issues.

[0005] To solve this problem, other stable transition metals (Co, Mn, etc.) must be substituted at the unstable Ni sites, and for this purpose, ternary NCM systems with Co and Mn substituted have been developed.

[0006] Conventional NCM-based cathode active materials are composed of secondary particles formed by the aggregation of primary particles. However, cathode materials composed of secondary particles formed by the aggregation of primary particles ranging in size from tens of nanometers to several micrometers have a large specific surface area of ​​powder, resulting in a large surface area in contact with the electrolyte, which leads to a high potential for gas generation. Additionally, there is a problem where the lifespan characteristics deteriorate because the secondary particles break into primary particles during the electrode rolling process due to the weak strength of the secondary particles.

[0007] To solve this problem, a method has been proposed to manufacture a cathode material in the form of a single particle with 20 or fewer primary particles clustered together, rather than in the form of a secondary particle with tens to hundreds of primary particles clustered together, by maximizing the size of the primary particles and applying it. However, in this case, a rock salt structure is formed on the surface of the particles, which causes a problem of degraded electrochemical performance of the cathode active material.

[0008] Furthermore, if the degree of single-grainization is defined solely by crystal size in XRD analysis, there is a limitation in that it cannot simultaneously represent the electrochemical performance and stability of the single-crystal material.

[0009] Therefore, there is a need to develop cathode active materials capable of increasing battery life stability while simultaneously exhibiting excellent electrochemical characteristics, such as charge / discharge capacity, by performing analyses at different levels on single-particle cathode materials to derive appropriate physical properties.

[0010] In this embodiment, the present invention aims to provide a positive electrode active material for a lithium secondary battery and a lithium secondary battery comprising the same, wherein the electrochemical properties and stability are improved when the strain within the particle satisfies a specific range in a positive electrode active material in the form of a single particle.

[0011] A positive electrode active material for a lithium secondary battery according to one embodiment may be a positive electrode active material for a lithium secondary battery in the form of a single particle, satisfying the following Equation 1.

[0012] [Equation 1]

[0013] 0.000160 ≤ Strain(e0) ≤ 0.000182

[0014] In the above Equation 1, Strain (e0) is measured using the Rietveld refinement method in TOPAS (Version 6) in the X-ray diffraction pattern of the positive active material, and may represent the strain of the crystal structure within the positive active material particles.

[0015] A method for manufacturing a positive electrode active material for a lithium secondary battery according to another embodiment comprises the steps of: preparing a transition metal precursor containing 50 to 70 mol% of nickel based on the total molar amount of the transition metal; mixing the transition metal precursor and a lithium raw material and then calcining to form a lithium transition metal oxide; and dissolving the lithium transition metal oxide to form a positive electrode active material for a lithium secondary battery, wherein the calcination may be performed at a temperature of 930 to 982.5°C and in an oxygen atmosphere of 35 to 100 vol%.

[0016] A lithium secondary battery according to another embodiment may include a positive electrode for a lithium secondary battery comprising the positive electrode active material according to one embodiment.

[0017] According to the present embodiment, by appropriately controlling the manufacturing process of a positive electrode active material for a lithium secondary battery, a positive electrode active material can be manufactured in which the strain of the crystal structure within the particles satisfies a specific range. Accordingly, a positive electrode active material with improved electrochemical properties, such as high charge / discharge capacity, excellent high-temperature lifespan, and a low resistance increase rate, can be realized.

[0018] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0019] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0020] When it is stated that one part is "above" or "on" another part, it may be directly above or on the other part, or other parts may be involved in between. In contrast, when it is stated that one part is "directly above" another part, no other parts are interposed in between.

[0021] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0022] Also, unless otherwise specified, % means mol%.

[0023] In this specification, the term “combination(s) of these” described in the Markush-type expression means one or more mixtures or combinations selected from the group consisting of the components described in the Markush-type expression, and means including any one or more selected from the group consisting of said components.

[0024] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0025]

[0026] Cathode active material for lithium secondary batteries

[0027] As mentioned above, there is a need to derive appropriate physical properties of the single-particle cathode active material.

[0028] Accordingly, in this embodiment, an anode active material was realized in which the strain of the crystal structure within the particle satisfies a specific range, thereby deriving appropriate physical properties of the anode active material.

[0029] Specifically, the positive electrode active material for a lithium secondary battery according to one embodiment may be a positive electrode active material for a lithium secondary battery in the form of a single particle.

[0030] In this specification, the single particle may include at least one of a single crystal structure consisting of a single particle and a structure in which 2 to 20 or 2 to 10 particles are clustered together, which is distinguished as a single mass when the cross-section of the powder is observed through a scanning electron microscope.

[0031] At this time, the above positive active material may be a positive active material for a lithium secondary battery that satisfies Formula 1 below.

[0032] [Equation 1]

[0033] 0.000160 ≤ Strain(e0) ≤ 0.000182

[0034] In the above Equation 1, Strain(e0) refers to the strain of the crystal structure within the particles of the positive active material.

[0035] In this specification, “strain” refers to the degree of deformation in the microstructure within the particles of the positive active material. Strain can be measured using X-ray diffraction (XRD). Specifically, when X-rays are irradiated onto a sample, some of them undergo diffraction, so the strain of the crystal structure of the positive active material can be analyzed by measuring the diffraction angle and intensity.

[0036] Depending on the functional model applied to the deformation extension of XRD data, the strain

[0037] It can be measured in two types: Strain L or Strain(e0), and the specific meaning of each strain and the relationship between the two strains are as described below.

[0038] The above Strain (e0) may be a value derived by refining all of the Cry Size L, G and Strain L, G measured through XRD. More specifically, it may refer to a strain obtained by applying Gaussian and Lorentzian strain expansion and deriving a single value defined in Balzar (Voigt function model of diffraction line expansion). For the Voigt function model of diffraction line expansion, refer to Microstructure Analysis of Diffraction, RL Snyder, HJ Bunge and J. Fiala, International Union of Crystallography, 1999 and Balzar (2004).

[0039] The above strain L may be derived from the following function (1).

[0040] <Function (1)>

[0041] βtot cosθ = Cε sinθ + Kλ / L

[0042] If we view the above function as a linear function with cosθ as the y value and sinθ as the x value, Cε becomes the slope of the linear function and Kλ / L becomes the intercept. In this case, the Strain L value can be derived by calculating ε using Cε=4ε.

[0043]

[0044] The above Strain(e0) has technical significance in that it contains more accurate information about the appropriate strain within the layered structure through the aforementioned refinement process.

[0045] The above Strain(e0) may be 0.000160 to 0.000182, and specifically, may be 0.000162 to 0.000182, 0.000163 to 0.000181, 0.000164 to 0.000181, or 0.000165 to 0.000180.

[0046] Cases exceeding the aforementioned range correspond to cases where the strain of the crystal structure within the grain is high. In this case, as the defects within the layered structure increase, they act as blockages. Consequently, the movement of lithium ions (Li+ ions) is kinetically disadvantageous, which can lead to an inferior electrochemical capacity.

[0047] On the other hand, if it falls below the aforementioned range, the defect rate decreases as the strain of the crystal structure within the grain decreases, resulting in relatively high repulsion between layers. Consequently, slip occurs between layers at high pressures, which can lead to higher grain fracture, reduced grain strength, and inferior discharge capacity.

[0048]

[0049] A positive active material according to one embodiment may be a positive active material for a lithium secondary battery that satisfies Formula 2 below.

[0050] [Equation 2]

[0051] 0.65 [nm*m 2 / g] ≤ (Strain(e0)*XS*BET / Strain L) ≤ 1.18 [nm*m 2 / g]

[0052] In the above Equation 1,

[0053] Strain L refers to the first strain within the particle in the positive active material, and

[0054] Strain(e0) refers to the second strain within the particle in the positive active material, and

[0055] BET is the BET specific surface area of ​​the positive active material [m² 2 It means / g],

[0056] XS represents the crystal grain size [nm] of the positive active material.

[0057]

[0058] The above (Strain(e0)*XS*BET / Strain L) relationship has technical significance in that it includes information regarding the ratio of appropriate strains within a layered structure, as well as information regarding excellent single-grainedness and specific surface area. For reference, it is difficult to exhibit the excellent effects according to the present invention if only some of the strain, specific surface area, or grain size satisfy the desirable range, and the excellent effects are confirmed as described below only when the above relationship satisfies the desirable range according to the present invention.

[0059] More specifically, as the strain within the particle increases, defects within the layered structure increase, and these defects act as blockages. Consequently, the movement of lithium ions (Li+ ions) is kinetically disadvantageous, which tends to cause an inferiority in electrochemical capacity.

[0060] However, lower strain does not necessarily lead to superior effects. While lower strain within the particles can enhance the properties of the layered structure and result in high electrochemical capacitance, a layered structure with low defects exhibits relatively high repulsion between layers. Consequently, under high pressure, this causes slip between layers, leading to greater particle fracture. In other words, an appropriate strain within the solid solution can play a role in increasing particle strength.

[0061] These characteristics can be confirmed by analyzing the relationship composed of strain ratio, grain size, and BET specific surface area.

[0062] The above (Strain(e0)*XS*BET / Strain L) is 0.65 nm*m 2 / g to 1.18 nm*m 2 It can be / g, specifically 0.65 nm*m 2 / g to 1.17 nm*m 2 / g, 0.65 nm*m 2 / g to 1.16 nm*m 2 / g, 0.660 nm*m 2 / g to 1.155 nm*m 2 / g or 0.6700 nm*m 2 / g to 1.1510 nm*m 2 / g can be.

[0063] The positive electrode active material satisfying the above range can ensure excellent crystallinity by forming a desirable specific surface area as deformation occurs appropriately within the layered structure, while simultaneously growing the grain size ideally.

[0064] If the value exceeds or falls below the aforementioned range, structural damage to the cathode material may be induced, leading to a decrease in electrochemical performance. More specifically, if the value exceeds the aforementioned range, particle fracture may be high and charge / discharge efficiency may be poor; if the value falls below the aforementioned range, a large amount of residual lithium may remain due to reasons such as insufficient lithiation, and problems such as reduced charge / discharge capacity or a high rate of resistance increase may occur.

[0065]

[0066] According to one embodiment, the range of Strain L may be 0.031 to 0.065, and specifically, 0.033 to 0.064, 0.034 to 0.062, or 0.035 to 0.060.

[0067] If the value exceeds the aforementioned range, defects occurring between the layered structures may cause resistance in lithium movement, resulting in low charge / discharge capacity. On the other hand, if the value falls below the aforementioned range, the formation of a high layered structure may cause repulsion between oxygen layers, leading to particle breakage.

[0068]

[0069] In the cathode active material according to one embodiment, (XS*BET) is 249 to 262 nm*m 2 It may be in the range of / g, specifically 249 to 262 nm*m 2 / g, 249 to 262 nm*m 2 / g, or 249 to 262 nm*m 2 It can be / g.

[0070] At this time, the above BET is the BET specific surface area of ​​the positive active material [m² 2 It means / g],

[0071] The above XS refers to the crystal grain size [nm] of the positive active material.

[0072]

[0073] A positive electrode active material satisfying the above range can secure excellent crystallinity by forming a desirable specific surface area and simultaneously growing the grain size ideally. Accordingly, when satisfying the aforementioned range, excellent discharge capacity can be exhibited, while simultaneously displaying excellent resistance, high-temperature lifespan, and resistance increase characteristics.

[0074]

[0075] In addition, the BET specific surface area of ​​the above-mentioned cathode active material is 0.50 to 0.90 m² 2 / g range, more specifically 0.55 to 0.87 m 2 / g, 0.60 to 0.85 m 2 / g, 0.65 to 0.83 m 2 / g, or 0.71 to 0.82 m 2 It can be / g.

[0076] By implementing the above BET specific surface area within the aforementioned range, the risk of gas generation can be significantly reduced.

[0077]

[0078] In this specification, “crystallite” refers to a particle unit having a regular atomic arrangement. The crystallite size can be measured using X-ray diffraction (XRD).

[0079] According to one embodiment, the grain size (Xs) may be 250 to 500 nm, specifically 290 to 440 nm, 300 to 420 nm, 310 to 400 nm, or 320 to 350 nm.

[0080] If it falls below the aforementioned range, the grain size within the single particle does not grow sufficiently, which may lead to a problem of deterioration in grain strength and lifespan characteristics, and if it exceeds the range, a problem of reduced charge / discharge capacity may occur.

[0081]

[0082] In addition, the positive electrode active material for the lithium secondary battery may contain 50 to 70 mol% of nickel (Ni) based on the total molar amount of transition metals. If the nickel content is too high, there may be a thermal propagation issue and the cost may increase. However, if the nickel content is too low, the capacity may be too low. Therefore, the positive electrode active material according to the present invention has a nickel content of 50 to 70 mol%, which allows for excellent thermal stability and reduced manufacturing costs while achieving an appropriate capacity.

[0083] More specifically, it can be represented by the following chemical formula 1.

[0084] [Chemical Formula 1]

[0085] Li a [Ni x Co y Mn z M w ]O2

[0086] In the above chemical formula 1, 0.8≤a≤1.2, 0.5≤x≤0.7, 0.05≤y≤0.2, 0≤z≤0.4, 0≤w<0.03, x+y+z+w=1, and M is Zr, Y, B, Al, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr or a combination thereof.

[0087] In the positive electrode active material of Chemical Formula 1 above, lithium may be included in an amount corresponding to a, i.e., 0.8 ≤ a ≤ 1.2. If a is too small, the capacity may decrease, and if a is too large, the strength of the calcined positive electrode active material may increase, making it difficult to grind, and the amount of gas generated may increase due to an increase in lithium by-products. Considering the effect of improving the capacity characteristics of the positive electrode active material by controlling the lithium content and the balance of sinterability during the manufacture of the active material, the lithium may more preferably be included in an amount of 0.9 ≤ a ≤ 1.1.

[0088] In the positive electrode active material of Chemical Formula 1 above, nickel may be included in an amount corresponding to x, i.e., 0.5≤x≤0.7. As previously mentioned, if the nickel content is too low, it may be difficult to achieve high capacity of the battery, and if the nickel content is too high, the battery life and thermal safety may decrease due to reduced structural stability of the active material, and manufacturing costs may increase.

[0089] In the positive electrode active material of Chemical Formula 1 above, the content of cobalt corresponding to y may be 0.05 ≤ y ≤ 0.2. If the cobalt content is too low, it may be difficult to simultaneously achieve sufficient rate characteristics and high powder density of the active material. If the cobalt content is too high, the cost of raw materials increases overall and the reversible capacity may decrease.

[0090] In the positive active material of Chemical Formula 1 above, manganese may be included in an amount corresponding to z, i.e., 0≤z≤0.4 or 0.1≤z≤0.4. If the manganese content is too low, the production cost may increase and the stability of the positive active material may decrease. If the manganese content is too high, the capacity and output characteristics of the battery may decrease.

[0091] In the positive active material of Chemical Formula 1 above, the positive active material may specifically include Zr and Y, and the total content of Zr and Y is 3,000 to 5,800 ppm based on the weight of the positive active material, and more specifically, may be 4,000 to 5,200 ppm or 4,200 to 5,000 ppm. If the content is below the above range, the particle size growth may be negligible, and if the content exceeds the above range, an excess amount of elements may be distributed at the precursor interface during the calcination process, which may instead inhibit the particle size growth. Therefore, when the total content of Zr and Y satisfies the above range, the size of the single particles within the positive active material can be formed within an appropriate range.

[0092]

[0093] In addition, a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention may include a coating layer on the surface of the positive electrode active material. Specifically, the coating layer may include Al, W, Co, V, Ti, Nb, Ce, B, P, or a combination thereof.

[0094] More specifically, the coating layer comprises Al and W, and the ratio of the content of W to the content of Al (W / Al) may be greater than 0 and less than or equal to 4.0, more specifically, in the range of greater than 0.5 and less than or equal to 3.5.

[0095] Satisfying the above content ratio offers the advantage of improved discharge capacity and high-temperature lifespan. If the above content ratio is exceeded, there is a problem in that the improvement in high-temperature lifespan is reduced due to the formation of unstable LiWOx on the surface of the positive active material or at the interface between single-particle positive active materials.

[0096]

[0097] Method for manufacturing a positive electrode active material for a lithium secondary battery

[0098] In another embodiment of the present invention, a method for manufacturing a positive electrode active material for a lithium secondary battery is provided, comprising the steps of: preparing a transition metal precursor containing 50 to 70 mol% of nickel based on the total molar amount of the transition metal; mixing the transition metal precursor and a lithium raw material and then calcining to form a lithium transition metal oxide; and dissolving the lithium transition metal oxide to form a positive electrode active material for a lithium secondary battery in the form of a single particle, wherein the calcination is performed at a temperature of 930 to 982.5°C and under conditions of 35 to 100 vol% oxygen atmosphere.

[0099] Hereinafter, a method for manufacturing a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention will be described step by step.

[0100] First, a transition metal precursor containing 50 to 70 mol% of nickel based on the total molar amount of the transition metal is prepared.

[0101] The above nickel-containing transition metal precursor is not particularly limited, but may be, for example, a transition metal hydroxide.

[0102] The above transition metal hydroxide may be prepared by co-precipitating a transition metal-containing solution containing a nickel raw material and optionally a cobalt raw material or a manganese raw material by adding a complexing agent-containing solution and a pH adjusting agent-containing solution to the transition metal-containing solution.

[0103] The above nickel raw material is not particularly limited as long as it is used in the industry for manufacturing a cathode active material precursor. For example, the above nickel raw material may be a nickel-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, it may be NiSO4, NiSO4·6H2O, Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, nickel fatty acid salt, nickel halide, or a combination thereof, but is not limited thereto.

[0104] The above-mentioned cobalt raw material is not particularly limited as long as it is used in the industry for the manufacture of cathode active material precursors. For example, the above-mentioned cobalt raw material may be a cobalt-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, CoSO₄ 4, It may be CoSO4·7H2O, Co(OH)2, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, or a combination thereof, but is not limited thereto.

[0105] The above manganese raw material is not particularly limited as long as it is used in the industry for manufacturing cathode active material precursors. For example, the above manganese raw material may be a manganese-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof. Specifically, it may be a manganese salt such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylate, manganese citrate, and manganese fatty acid, manganese oxide such as Mn2O3, MnO2, and Mn3O4, oxyhydroxide, manganese chloride, or a combination thereof, but is not limited thereto.

[0106] The above transition metal-containing solution may be prepared by adding a nickel raw material and optionally a cobalt raw material or a manganese raw material to a solvent, specifically water, or a mixture of water and an organic solvent that can be uniformly mixed with water (e.g., alcohol).

[0107] The above-mentioned complexing agent-containing solution performs the role of forming a complex, and may include, for example, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or a combination thereof as the complexing agent, but is not limited thereto. Meanwhile, the above-mentioned complexing agent-containing solution may be used in the form of an aqueous solution, and in this case, water or a mixture of water and an organic solvent that is uniformly miscible with water (e.g., alcohol, etc.) may be used as the solvent.

[0108] At this time, the molar ratio of nickel, cobalt, and manganese in the precursor can be controlled by adjusting the concentrations of the nickel raw material, cobalt raw material, and manganese raw material.

[0109] Accordingly, the nickel content in the transition metal precursor may be 50 to 70 mol% based on the total molar amount of the transition metal.

[0110] In addition, the content of cobalt in the transition metal precursor may be 5 to 20 mol% based on the total molar amount of the transition metal.

[0111] In addition, the manganese content in the transition metal precursor may be 10 mol% or more based on the total molar amount of the transition metal, and more specifically, may be 15 mol% to 50 mol%, 20 mol% to 50 mol%, 25 mol% to 50 mol%, 25 mol% to 45 mol%, or 25 mol% to 40 mol%.

[0112] The technical significance of controlling the nickel, cobalt, and manganese content in transition metal precursors is as previously described and is therefore omitted.

[0113] In addition, in the step of preparing a first mixture by mixing the transition metal precursor and the lithium raw material, a doping raw material may be further included. Specifically, the doping raw material may be a Zr raw material and a Y raw material.

[0114] The above Zr raw material may be Zr(SO4)2, ZrS2, ZrO2, Zr(NO3)4, or a combination thereof, but is not necessarily limited thereto.

[0115] The above Y raw material may be Y(SO4)2, Y2(SO4)3, Y2O3, Y(NO3)3, or a combination thereof, but is not necessarily limited thereto.

[0116]

[0117] Next, the above transition metal precursor and lithium raw material are mixed and then calcined to obtain a lithium transition metal oxide. Specifically, a lithium metal oxide can be obtained through a single calcination. At this time, single calcination may mean performing a first calcination under a single condition without changing calcination conditions, such as temperature, during the calcination.

[0118] It can be characterized by being performed continuously at the same temperature without including a cooling or grinding step in the middle of the firing process in a single firing process, thereby suppressing the reaction between external moisture and the fired product, suppressing the increase in residual lithium, suppressing the degradation of the active material due to over-firing, and structurally stabilizing the active material.

[0119]

[0120] Conventionally, to form a single-particle lithium metal oxide, the process was carried out by calcining for a long time at a high temperature of 990°C or higher; however, in this case, there was a problem in which the electrochemical properties of the active material deteriorated due to nickel cation mixing and the formation of rock salt impurities caused by over-calcining. On the other hand, the manufacturing method according to the present invention can prevent the above problems by controlling the calcination temperature or time.

[0121] Specifically, the above firing temperature may be 930 to 982.5°C, 930 to 980°C, 935 to 980°C, 935 to 975°C, 940 to 970°C, or 950 to 965°C.

[0122] If the calcination temperature is lower than the above range, the growth of individual particles within the lithium transition metal oxide is reduced, and lithium transition metal oxide in the form of individual particles may not be easily formed. If the primary calcination temperature is too high, under-calcination occurs, and electrochemical properties such as the capacity of the active material may deteriorate, particularly as the rock-salt structure crystal phase increases within the surface of the positive electrode active material.

[0123]

[0124] Specifically, the firing time may be a total of 8 to 35 hours, a total of 10 to 30 hours, a total of 11 to 25 hours, or a total of 11.5 to 25 hours. In this case, the total time may include the time of the heating section, the firing temperature holding section, and the cooling section. More specifically, the time of the firing temperature holding section may be 8 to 13 hours or 8.4 to 12.2 hours.

[0125] By satisfying the above range, particle strength can be increased, and there may be the advantage of increased production volume.

[0126]

[0127] More specifically, it is desirable to perform the process within the aforementioned temperature and time ranges, as this allows for the stabilization of the crystal structure of the positive electrode active material. Additionally, it is desirable because lithium byproducts remaining on the surface of the metal oxide decompose due to heat and diffuse into the interior of the metal oxide, thereby reducing the amount of lithium remaining on the surface; furthermore, as the lithium ions react with the surface of the metal oxide to form a stable layered structure, the surface structure of the metal oxide is stabilized, which in turn offers the advantage of improving the resistance and lifespan characteristics of the battery.

[0128]

[0129] Specifically, the atmosphere during the above-mentioned calcination may be an oxygen atmosphere of 35 to 100 vol%, or 35.3 to 100 vol%. At this time, the remainder other than oxygen in the atmosphere for performing calcination may be a gas used by a person skilled in the art when calcining a nickel-containing active material. For example, it may be air, nitrogen, or a mixture thereof.

[0130] When the above atmosphere conditions are satisfied, a positive active material satisfying the appropriate range of Formula 1 in this specification can be calcined. In addition, if the oxygen atmosphere range is lower than the above range, the formation of a layered crystal structure is not well achieved, which may result in a significant degradation of electrochemical properties, and if the oxygen atmosphere range is higher than the above range, the process cost may be excessively high, making it difficult to perform the process economically.

[0131]

[0132] A method for manufacturing a positive electrode active material for a lithium secondary battery according to the present invention includes the step of crushing a lithium metal oxide to obtain a positive electrode active material in the form of a single particle or in which 1 to 20 of the single particles are aggregated.

[0133] The above crushing may be performed using compressed air at a crushing pressure of 1.0 to 3.0 bar.

[0134] The above disintegration can be performed after cooling the calcined lithium transition metal oxide to 50 to 200°C. Cooling to the above cooling temperature can suppress the reaction between external moisture and the calcined product and suppress the increase in residual lithium.

[0135] The above-mentioned disintegration can be performed by methods commonly practiced in the industry, for example, using rotary mills, jet mills, ball mills, fin mills, bead mills, or roll mills, but in particular, it can be performed using a jet mill, more specifically, an air jet mill using compressed air. At this time, the grinding pressure can be performed at a grinding pressure of 1.0 to 3.0 bar, specifically 1.3 to 2.9 bar or 1.5 to 2.8 bar. The above-mentioned disintegration can be performed by adjusting the grinding pressure according to the cohesive force between single particles depending on the calcination temperature or time during the calcination, but when performed within the above range, the generation of fine particles due to unnecessary particle breakage is suppressed, thereby suppressing side reactions with the electrolyte during operation when the electrode containing the above-mentioned positive active material is included in a secondary battery, and separation between sufficiently grown particles can be performed, thereby realizing the stability of the positive active material in the desired single particle form.

[0136] Additionally, after the step of obtaining a single-particle form of a positive active material through the above-mentioned disintegration, the method may further include the step of mixing the single-particle form of the positive active material and a coating raw material, and then heat-treating to obtain a positive active material having a coating layer formed on its surface. At this time, the technical definition, significance, and characteristics of the coating layer are as described above, and the heat treatment may be performed at 400 to 500°C, more specifically at 410 to 450°C, and for 5 to 8 hours.

[0137]

[0138] anode

[0139] In another embodiment of the present invention, a positive electrode is provided comprising a current collector and a positive electrode active material layer located on one surface of the current collector and comprising a positive electrode active material manufactured according to the above embodiment.

[0140] The characteristics of the positive active material constituting the above positive active material layer are the same as those previously described. Therefore, a detailed description of the positive active material will be omitted.

[0141] The above current collector may be, for example, made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treated with carbon, nickel, titanium, silver, etc.

[0142] Meanwhile, the above positive active material layer may include a binder and a conductive material.

[0143] At this time, the binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the positive current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof. One of these alone or a mixture of two or more may be used, but is not limited thereto. The binder may be included in an amount of 1 to 30 weight% based on the total weight of the positive active material layer.

[0144] In addition, the conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. 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, thermal black, and carbon fibers; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used, but is not limited thereto. The conductive material may typically be included in an amount of 1 to 30 weight% relative to the total weight of the positive electrode active material layer.

[0145] Except for being manufactured to fall within the above range, the above anode may be manufactured according to a conventional anode manufacturing method.

[0146] Specifically, the anode may be manufactured by applying a composition for forming an anode active material layer, which optionally includes a binder, a conductive material, or a solvent as needed, onto an anode current collector, followed by drying and rolling. At this time, the types and contents of the anode active material, binder, and conductive material are as described above.

[0147] The above solvent may be a solvent commonly used in the relevant technical field, such as dimethylsulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it has a viscosity that dissolves or disperses the anode active material, conductive material, and binder, taking into account the coating thickness of the slurry and the manufacturing yield, and subsequently provides excellent thickness uniformity when coated for anode manufacturing.

[0148] Alternatively, the anode may be manufactured by casting a composition for forming an anode active material layer onto a separate support, and then laminating the film obtained by peeling off from the support onto an anode current collector.

[0149]

[0150] lithium secondary battery

[0151] In another embodiment, a lithium secondary battery including the anode is provided.

[0152] The above lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite to the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as described above. Additionally, the lithium secondary battery may optionally further include a battery container housing an electrode assembly comprising the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container.

[0153] In the above lithium secondary battery, the negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0154] The above-mentioned negative 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., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0155] The above-mentioned cathode active material layer may optionally include a binder and a conductive material together with the cathode active material. The above-mentioned cathode active material layer may be manufactured, as an example, by applying a composition for forming a cathode active material layer, comprising a cathode active material and optionally a binder and a conductive material, onto a cathode current collector and drying it, or by casting the composition for forming a cathode onto a separate support and then laminating the film obtained by peeling it off from the support onto a cathode current collector.

[0156] As the above-mentioned 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 alloys, Sn alloys, or Al alloys; metal oxides capable of doping and dedoping lithium, such as SiOβ (0 ≤ β ≤ 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the above-mentioned metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the above-mentioned negative electrode active material. Furthermore, the carbon material may include both low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, 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.

[0157] The binder and conductive material mentioned above may be the same as those previously described in the anode.

[0158] Next, depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used, and a mixed multilayer film such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0159] In addition, regarding the above lithium secondary battery, the electrolyte may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which are usable when manufacturing a lithium secondary battery, but is not limited to these.

[0160] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0161] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having C2 to C20 structures and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.In this case, using a mixture of cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent performance of the electrolyte.

[0162] The above lithium salt can be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and allow lithium ions to move effectively.

[0163] As described above, since the lithium secondary battery including the positive electrode according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0164]

[0165] Preferred embodiments and comparative examples of the present invention are described below. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0166]

[0167] Preparation of positive electrode active material

[0168] Example 1

[0169] Ni so that the molar ratio of lithium to the transition metal (Li / M) of the (mixed) precursor becomes 1.05 0.6Co 0.1 Mn 0.3 A precursor of (OH)2 composition and Li2CO3 were introduced into a mixer, and doping raw materials ZrO2 and Y2O3 were introduced and mechanically mixed to form a mixture such that the content of Zr and Y in the active material was 3000 ppm and 1500 ppm, respectively.

[0170] After (calcination and disintegration), the mixture was maintained at 960°C for 10 hours under an oxygen atmosphere of 50–70 vol%. After single calcination through heat treatment for a total of 22 hours, including a heating phase, a calcination temperature holding phase, and a heating phase, the mixture was naturally cooled to form a lithium transition metal oxide. Subsequently, the lithium metal oxide was disintegrated using an air jet mill to obtain a single-particle cathode active material. The composition of the obtained cathode active material is Li 1.06 Ni 0.6 Co 0.1 Mn 0.3 It was O2.

[0171] (Coating and heat treatment) When mixing the obtained positive active material with coating raw materials Al2O3 and WO3, Al and W were added at 1500 ppm and 3000 ppm of the total weight of the mixture, respectively, mixed in a mixer, and then heat-treated at 410°C for 6 to 7 hours to obtain a positive active material having a coating layer containing Al and W formed on its surface.

[0172]

[0173] Examples 2 to 7 and Comparative Examples 1 to 11

[0174] A positive electrode active material was prepared in the same manner as in Example 1, except that the calcination and disintegration conditions were adjusted as shown in Table 1 below. At this time, the remainder of the calcination atmosphere other than oxygen was air (dry air). For reference, in Table 1 below, calcination time refers to the calcination temperature holding time.

[0175]

[0176] Sintering Conditions Heat Treatment Atmosphere Disintegration Sintering Temperature (°C) Holding Time (Hour) Heat Treatment Temperature (°C), Time Oxygen Content (vol%) Grinding Pressure (bar) Example 1 9 35 10 410, 7h 35.40% 2 Example 2 9 45 8.4 410, 7h 35.40% 2.7 Example 3 9 45 10 410, 6h 42.50% 1.5 Example 4 9 45 12.2 410, 6h 42.50% 2 Example 5 9 70 11.5 410, 7h 100.00% 1.8 Example 6 9 75 10 410, 7h 100.00% 1.5 Example 7 9 80 10 410, 7h 100.00% 2.3 Comparative Example 1 9 45 10 410, 6h 0.00% 3.9 Comparative Example 2950 10410, 7h 0.00% 5 Comparative Example 3950 10410, 6h 25.50% 5 Comparative Example 4945 10410, 6h 31.60% 3.8 Comparative Example 5950 8.4410, 6h 31.60% 3.8 Comparative Example 6945 10410, 7h 35.40% 3.5 Comparative Example 7950 10410, 7h 35.40% 4.1 Comparative Example 8955 10410, 7h 35.40% 5 Comparative Example 9945 10410, 6h 39.20% 2 Comparative Example 10970 10410, 7h 100.00% 2 Comparative Example 11985 13410, 7h100.00%3.7

[0177] Experimental Example 1: Analysis of Cathode Active Material via XRD

[0178] The strain and grain size of the cathode active material can be confirmed using X-ray diffraction (XRD). At this time, X-ray diffraction patterns were extracted and analyzed using a D8 Endeavor (BRUKER) instrument.

[0179] Specifically, after uniformly loading the positive active material in powder form into a sample holder, X-rays were generated by applying a voltage of 40 kV and a current of 40 mA to an X-ray Generator (Cu, 1.54 Å), and the X-ray diffraction pattern was measured in a 2θ region between 10 and 90 degrees with a step size of 0.01° and a scan speed of approximately 5.8° / min. At this time, when using the XRD (Bruker, D8 Endeavor), the detector was set to the LynxEye detector (opening=4.108°), the Divergence Slit was set to 0.5°, the Antiscatter Slit to na, and the Slit mode to Fixed.

[0180] (TOPAS - Rietveld refinement settings)

[0181] Background - Chebychev check, Order 5, 1 / x Bkg Check

[0182] Instrument - Goniometer radii 200.5 (Primary & Secondary)

[0183] - Linear PSD - LPSD 4.11 Fix, FDS 0.5 Fix, Beam spill 20 Fix

[0184] - Full Axial Model check - Source 12 Fix, Sample 20 Fix, RS 12 Fix, Prim 4.1 Fix, Sec 4.1 Fix N Beta 30

[0185] Correction - Sample displacement check (Refine)

[0186] - LP factor 0 Fix

[0187] Miscellaneous - Conv. Steps 1, Start 15, Finish 80

[0188] Structure - Spacegroup R-3m, LiNi 0.6 Co 0.1 Mn 0.3 O2

[0189]

[0190] The grain size and strain (Strain L) and strain (e0) were determined using the Rietveld refinement method on TOPAS (Version 6) based on the X-ray diffraction pattern of the cathode active material measured by the above method. The results are shown in Table 2 below. Unmeasured data are indicated by -.

[0191]

[0192] XS[nm] Strain(e0) Strain L Example 1 30 80.0001750.059489 Example 2 29 80.000169 - Example 3 339 0.0001670.041309 Example 4 320 0.0001740.046587 Example 5 321 0.0001720.044269 Example 6 348 0.0001650.035936 Example 7 318 0.000180 - Comparative Example 1 265 0.0002030.084352 Comparative Example 2 233 0.0002740.113938 Comparative Example 32410.0002400.108117 Comparative Example 42610.0002110.08649 Comparative Example 52700.0002010.078068 Comparative Example 62730.0002090.072543 Comparative Example 72580.0002240.089944 Comparative Example 82420.0002470.111428 Comparative Example 93210.0001870.04052 Comparative Example 103260.000152- Comparative Example 112850.0001840.069975

[0193] Referring to Table 2 above, it can be seen that the example satisfies the range of Strain (e0) from 0.000160 to 0.000182, and the comparative example does not satisfy the range.

[0194]

[0195] Experimental Example 2: BET Specific Surface Area Measurement

[0196] The specific surface area of ​​the cathode active material prepared according to the examples and comparative examples was measured using the BET method (Surface area and Porosity analyzer, Micromertics Tristar II). Specifically, 4.0 g of the cathode active material prepared in the examples and comparative examples was subjected to vacuum heat treatment at 300°C for 2 hours and cooling for 1 hour, after which nitrogen gas was adsorbed and desorbed onto the surface of the active material, and the amount of adsorption was measured at each partial pressure to determine the specific surface area of ​​the material. Along with the BET specific surface area results, the value obtained by multiplying the XS (grain size) derived as described above by the BET specific surface area is shown in Table 3 below.

[0197]

[0198] BET specific surface area [m 2 / g](XS*BET) [nm*m 2 / g](Strain(e0)*XS*BET / Strain L) [nm*m 2 / g] Example 1 0.74227.920.6705 Example 2 0.75223.50 - Example 3 0.77261.031.0553 Example 4 0.81259.200.9681 Example 5 0.74237.540.9229 Example 6 0.72250.561.1504 Example 7 0.73232.14 - Comparative Example 10.89235.850.5676 Comparative Example 20.99230.670.5547 Comparative Example 31.03248.230.5510 Comparative Example 40.93242.730.5922 Comparative Example 50.81218.700.5631 Comparative Example 60.8218.400.6292 Comparative Example 70.83214.140.5333 Comparative Example 80.95229.900.5096 Comparative Example 90.82263.221.2148 Comparative Example 100.71231.46 Comparative Example 110.78222.300.5845

[0199] Referring to Tables 2 and 3 above, the example has 0.65 nm*m for (Strain(e0)*XS*BET / Strain L). 2 / g to 1.18 nm*m 2It can be confirmed that the range of / g is satisfied, and the comparative example does not satisfy the said range. As described below, the above relationship has technical significance in that it can simultaneously represent electrochemical performance and stability and simultaneously includes information on the degree of single-grain formation, strain, and crystal structure.

[0200] For the cathode active materials according to Examples 3, 4, and 6, (XS*BET) is 249 to 262 nm*m 2 It can be confirmed that / g is satisfied. When this range is satisfied, as described below, excellent discharge capacity can be exhibited, while resistance, high-temperature life, and resistance increase characteristics can be simultaneously displayed excellently.

[0201]

[0202] Experimental Example 3: Measurement of Residual Lithium

[0203] 100 g of distilled water was added to 5 g of the cathode active material prepared according to the examples and comparative examples, and the mixture was stirred at 800 rpm for 5 minutes using a stirrer to extract residual lithium. The mixture was then filtered to separate the cathode active material powder from the extract. Subsequently, the extract was measured by neutralization titration using a T50 model titrator from METTLER TOLEDO. The results are shown in Table 4 below.

[0204] In Table 4 below, LH represents residual LiOH, LC represents residual Li2CO3, and Total represents the sum of LH and LC. By measuring residual lithium, gas generation or explosion of the battery, or gallation occurring during electrode fabrication, can be predicted or prevented, thereby allowing these factors to be taken into account during battery manufacturing.

[0205]

[0206] LH[wt%]LC[wt%]Total[wt%] Example 1 0.05 0.14 0.19 Example 2 0.04 0.18 0.22 Example 3 0.04 0.12 0.16 Example 4 0.04 0.14 0.19 Example 5 0.05 0.13 0.17 Example 6 0.03 0.13 0.17 Example 7 0.03 0.16 0.19 Comparative Example 10.05 0.18 0.22 Comparative Example 20 .060.210.27 Comparative Example 30.060.180.24 Comparative Example 40.060.160.21 Comparative Example 50.050.160.21 Comparative Example 60.060.160.22 Comparative Example 70.050.170.22 Comparative Example 80.050.240.30 Comparative Example 90.040.140.18 Comparative Example 100.030.150.18 Comparative Example 110.040.180.22

[0207] It was confirmed that the total residual lithium in the positive electrode active material according to the example is 0.22 wt% or less, whereas in the case of Comparative Examples 1 to 3 and Comparative Example 8, it exceeds this.

[0208] Accordingly, it is expected that a battery using the positive electrode active material according to the present embodiment can prevent gas generation or explosion, and gallation that occurs during electrode fabrication.

[0209] However, in the case of the comparative example, even if the total residual lithium satisfies 0.22 wt% or less, it was confirmed that electrochemical properties such as charge / discharge capacity, high-temperature life, or resistance increase rate were impaired as described below.

[0210]

[0211] Experimental Example 4: Evaluation of Electrochemical Properties via Coin Cell

[0212] To evaluate the physical properties and electrochemistry of the positive electrode active materials according to the examples and comparative examples, coin cells were manufactured as follows.

[0213] Specifically, a positive electrode active material, a polyvinylidene fluoride binder (product name: KF9700), and a conductive material (acetylene black FX35, Denka) were mixed in a weight ratio of 95.0:3.0:2.0, and this mixture was added to an N-methyl-2-pyrrolidone solvent so that the solid content was about 60 wt% to prepare a positive electrode active material slurry.

[0214] The above slurry was coated onto an aluminum foil (Al foil, thickness: 20 μm), which serves as an anode current collector, using a doctor blade, and an anode was manufactured by drying and rolling. The loading amount of the anode was approximately 15–16 mg / cm², and the rolling density was approximately 3.5 g / cm³. 3 It was.

[0215] A 2032 coin cell was manufactured by a conventional method using the above-mentioned anode, lithium metal cathode (thickness 400 μm, NEBA), electrolyte, and polyethylene separator. The electrolyte was prepared by dissolving 1M LiPF6 in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) (mixing ratio EC:DMC:DEC = 1:2:1 volume%) to prepare a mixed solution, and then adding 2 weight% of vinylene carbonate (VC) to it.

[0216]

[0217] Evaluation of initial capacity and room temperature resistance

[0218] After fabricating the coin cell, it was aged at 25°C for 10 hours, and then a charge / discharge test was conducted at 25°C. To evaluate the discharge capacity, 200 mAh / g was used as the reference capacity, and the cell was charged to 4.4V with a constant current of 0.1C. Then, the voltage was switched to a constant voltage, and charging continued until the termination current reached 0.05C. After a 10-minute rest time following charging, the initial capacity was measured by discharging with a constant current of 0.1C until it reached 2.5V. The room temperature resistance (Direct current internal resistance, DCIR) was calculated by measuring the voltage value 60 seconds after applying the discharge current from a state charged to 4.4V, and then calculating '(Voltage before current application - Voltage after 60 seconds of current application) / Applied current'.

[0219]

[0220] Output Characteristics Evaluation

[0221] Afterwards, the device was charged at 0.5C using the same method and discharged in sequence at 0.33C, 1C, and 2C, and three charge-discharge cycles were performed. Then, the measured 2C discharge capacity was divided by the 0.1C discharge capacity to calculate the output characteristics.

[0222]

[0223] High-temperature life characteristics evaluation

[0224] For the lifespan characteristics, the coin cell, which had been evaluated at room temperature, was aged at a high temperature (45℃) for 1 hour, then charged to 4.4V with a constant current of 0.2C, switched to a constant voltage, and continued charging until the termination current reached 0.05C. After charging, a rest time of 10 minutes was taken, and then discharged at a constant current of 0.2C until it reached 2.5V to stabilize the capacity before the lifespan evaluation.

[0225] Afterward, the device was charged to 4.4V with a constant current of 0.5C, then switched to a constant voltage and continued charging until the termination current reached 0.05C, followed by a 10-minute rest period, and then discharged with a constant current of 1C until it reached 2.5V, repeating this process 50 times. The life characteristics were calculated as the discharge capacity measured in 50 cycles as a percentage (%) of the discharge capacity measured in one cycle.

[0226] Evaluation of resistance increase rate characteristics

[0227] The rate of increase in resistance measured after 50 cycles relative to the resistance measured once was converted into a percentage (%). Resistance (DC internal resistance, DCIR) was calculated by measuring the voltage value after 60 seconds of applying a discharge current while charged to 4.4V, and then calculating '(voltage before current application - voltage after 60 seconds of current application) / applied current'.

[0228]

[0229] The electrochemical properties derived from this are listed in Table 5 below.

[0230]

[0231] Charging Capacity [mAh / g] Discharging Capacity [mAh / g] Efficiency Resistance [Ω] 2C / 0.1C Output Characteristics High Temperature Life [%] Resistance Increase Rate Example 1 2 17.1 196.3 90.30% 22.3 87.60% 95.90% 71.10% Example 2 2 17.1 196.3 90.20% 22.1 88.00% 96.30% 68.10% Example 3 2 18.1 197.3 90.40% 21.0 87.70% 95.50% 79.10% Example 4 2 17.6 197.6 90.80% 21.8 88.10% 95.90% 75.70% Example 5 2 18.1 196.2 90.00 %22.186.80%96.00%69.20%Example 6217.8196.490.20%19.987.60%95.80%79.90%Example 7217.5196.090.10%21.587.20%95.60%82.00%Comparative Example 1214.0194.090.70%22.387.30%95.70%87.40%Comparative Example 2216.9196.290.50%23.086.40%95.30%89.00 %Comparison Example 3 216.9 196.2 90.50% 23.686.10% 95.30% 94.40% Comparison Example 4 217.5 196.2 90.20% 24.687.30% 95.90% 85.10% Comparison Example 5 215.01 93.9 90.20% 24.286.70% 95.90% 82.90% Comparison Example 6 217.1 196.6 90.50% 21.987.10% 95.30% 85.50% Comparison Example 7 217.01 96.6 90.60% 2 2.387.00%95.10%83.60%Comparative Example 8217.2196.890.60%22.586.70%95.00%99.20%Comparative Example 9217.1196.690.60%21.385.90%95.40%86.70%Comparative Example 10217.3195.690.00%22.687.00%95.70%74.70%Comparative Example 11216.0194.790.10%23.186.10%95.10%82.50%

[0232] It was confirmed that the positive electrode active material according to the example has a charge capacity of 217.1 mAh / g or more and a discharge capacity of 196.0 mAh / g or more, with an efficiency of 90.0% or more, while simultaneously exhibiting excellent resistance, output characteristics, high-temperature life, and resistance growth rate.

[0233] In particular, in the case of Examples 3, 4, and 6, it was confirmed that excellent discharge capacity was displayed while resistance, high-temperature life, and resistance increase characteristics were simultaneously exhibited to be even better.

[0234] Therefore, through a comparison between the example and the comparative example, it can be confirmed that the positive electrode active material according to the example and the battery containing it are electrochemically excellent and simultaneously have excellent stability.

[0235]

[0236] The present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without changing the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. As a positive electrode active material for a lithium secondary battery in the form of a single particle, That which satisfies Equation 1 below, Cathode active material for lithium secondary batteries: [Equation 1] 0.000160 ≤ Strain(e0) ≤ 0.000182 In Equation 1 above, Strain (e0) is measured using the Rietveld refinement method in TOPAS (Version 6) on the X-ray diffraction pattern of the positive active material, and represents the strain of the crystal structure within the positive active material particles.

2. In Paragraph 1, The above positive active material satisfies the following Equation 2, Cathode active material for lithium secondary batteries: [Equation 2] 0.65 [nm*m 2 / g] ≤ (Strain(e0)*XS*BET / Strain L) ≤ 1.18 [nm*m 2 / g] In Equation 1 above, Strain L, Strain(e0), and XS are values ​​measured by X-ray diffraction (XRD), and Strain L refers to the first strain within the particle in the positive active material, and Strain(e0) refers to the second strain within the particle in the positive active material, and BET is the BET specific surface area [m²] of the positive electrode active material measured by the BET method. 2 It means / g], XS represents the crystal grain size [nm] of the positive active material.

3. In Paragraph 2, The range of the above Strain L is 0.031 to 0.065, Cathode active material for lithium secondary batteries.

4. In Paragraph 1, The BET specific surface area of ​​the above positive active material is 0.50 to 0.90 m² 2 / g thing, Cathode active material for lithium secondary batteries.

5. In Paragraph 1, The crystal grain size of the above-mentioned positive active material is in the range of 250 to 500 nm, Cathode active material for lithium secondary batteries.

6. In Paragraph 1, In the above-mentioned cathode active material, the range of (XS*BET), which is the product of the grain size and the BET specific surface area, is 249 to 262 nm*m 2 / g thing, Cathode active material for lithium secondary batteries.

7. In Paragraph 1, The above positive active material contains 50 to 70 mol% of nickel (Ni) based on the total molar amount of transition metals, Cathode active material for lithium secondary batteries.

8. In Paragraph 1, A positive electrode active material for a lithium secondary battery represented by the following chemical formula 1: [Chemical Formula 1] Li a [Ni x Co y Mr z M w ]O2 In the above chemical formula 1, 0.8≤a≤1.2, 0.5≤x≤0.7, 0.05≤y≤0.2, 0≤z≤0.4, 0≤w≤0.2, x+y+z+w=1, and M is Zr, Y, B, Al, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr or a combination thereof.

9. In Paragraph 1, The above positive active material includes Zr and Y, and The total content of the above Zr and Y is in the range of 3,000 to 5,800 ppm based on the weight of the above positive active material, Cathode active material for lithium secondary batteries.

10. In Paragraph 1, The above positive active material includes a coating layer on its surface, and The coating layer comprises Al, W, Co, V, Ti, Nb, Ce, B, P, or a combination thereof. Cathode active material for lithium secondary batteries.

11. In Paragraph 10, The above coating layer comprises Al and W, and The ratio of W content to Al content (W / Al) is in the range greater than 0 and less than or equal to 4.0, Cathode active material for lithium secondary batteries.

12. A step of preparing a transition metal precursor containing 50 to 70 mol% of nickel based on the total molar amount of the transition metal; A step of forming a lithium transition metal oxide by mixing the above transition metal precursor and lithium raw material and then calcining; and The method includes the step of breaking down the above lithium transition metal oxide to form a positive electrode active material for a lithium secondary battery, and The above calcination is performed at a temperature of 930 to 982.5°C and in an oxygen atmosphere of 35 to 100 vol%, Method for manufacturing a positive electrode active material for a lithium secondary battery.

13. In Paragraph 12, The above firing is performed as a single firing, and The above firing is performed for a total of 8 to 35 hours, Method for manufacturing a positive electrode active material for a lithium secondary battery.

14. In Paragraph 12, The above crushing is performed at a crushing pressure of 1.0 to 3.0 bar, Method for manufacturing a positive electrode active material for a lithium secondary battery.

15. A cathode for a lithium secondary battery comprising a cathode active material according to any one of claims 1 to 11, Lithium secondary battery.