Cathode active material for lithium secondary battery, preparation method therefor, and lithium secondary battery comprising same

Abstract

A cathode active material for a lithium secondary battery, according to one embodiment, comprises lithium nickel-based metal oxide particles, wherein it has been identified that a lithium nickel-based metal oxide has, on an X-ray diffraction (XRD) spectrum, a main peak of a (108) plane and a minor peak of the (108) plane, and a main peak of a (110) plane and a minor peak of the (110) plane, and an intensity ratio (I(110)_S / I(108)_S) of a minor peak intensity (I(110)_S) of the (110) plane to a minor peak intensity (I(108)_S) of the (108) plane can be 1.00 to 1.20.

Description

A positive electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same

[0001] The present invention relates 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. More specifically, the invention relates to a method for manufacturing a positive electrode active material for a lithium secondary battery in the form of a single particle, a positive electrode active material manufactured therefrom, and a lithium secondary battery including the same.

[0002] This application claims priority to Korean Patent Application No. 10-2024-0190608, filed on December 18, 2024, the entire contents of which 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 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, a method was 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 then applying it.

[0008] However, as primary particles grow from sub-micron to several micrometers in size, the increased diffusion distance of lithium ions leads to a problem where capacity and output decrease compared to polycrystalline materials of the same composition. In particular, for the manufacture of single-particle cathode materials, high-temperature sintering methods requiring firing at temperatures above 100°C are frequently adopted compared to multi-particle materials of the same composition; however, this sintering method results in severe capacity and output degradation due to the overdevelopment of specific planes during the grain growth process. This is because the planes where lithium enters and exits are relatively reduced, leading to a decrease in reaction sites and consequently restricting the insertion and extraction of lithium.

[0009] Therefore, there is a need to develop single-particle cathode active materials that exhibit desirable orientation by ensuring that the surfaces where lithium enters and exits develop together, rather than just specific surfaces becoming more developed.

[0010]

[0011] In this embodiment, we aim to provide a single-particle type positive electrode active material for a lithium secondary battery that can not only improve the capacity and charge / discharge efficiency of the battery but also exhibit excellent battery life characteristics, a method for manufacturing the same, and a lithium secondary battery including the same.

[0012] A positive electrode active material for a lithium secondary battery according to one embodiment comprises lithium nickel-based metal oxide particles, wherein the lithium nickel-based metal oxide has a main peak of the (108) plane, a volumetric peak of the (108) plane, a main peak of the (110) plane, and a volumetric peak of the (110) plane confirmed in an X-ray diffraction (XRD) spectrum, and the intensity ratio (I(110)_S / I(108)_S) of the volumetric intensity of the (110) plane (I(110)_S) to the volumetric intensity of the (108) plane (I(108)_S) may be 1.00 to 1.20.

[0013] A positive electrode for a lithium secondary battery according to another embodiment may include a positive electrode active material according to one embodiment.

[0014] A lithium secondary battery according to another embodiment may include a positive electrode according to one embodiment.

[0015] In these embodiments, as the orientation of the positive electrode active material is preferably formed, the insertion and extraction of lithium can occur smoothly, and resistance can be reduced by ensuring that the diffusion distance is not excessively increased.

[0016] Accordingly, the capacity, charge / discharge efficiency, and lifespan characteristics of a lithium secondary battery containing the positive electrode active material according to the present embodiment can be improved.

[0017] Figure 1 is an enlarged view of the X-ray diffraction analysis results of the positive electrode active material for a lithium secondary battery according to Example 1 and Comparative Example 1.

[0018] Figure 2 is the result of X-ray diffraction analysis of the positive electrode active material for a lithium secondary battery according to Example 1 and Comparative Example 1.

[0019] Figure 3 shows the X-ray diffraction analysis results of the positive electrode active material for a lithium secondary battery according to Reference Example 1, Reference Example 2 and Example 5.

[0020] Figure 4 is an SEM image of the positive electrode active material prepared according to Example 1.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0026] 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.

[0027] 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.

[0028]

[0029] Cathode active material for lithium secondary batteries

[0030] A positive electrode active material for a lithium secondary battery according to one embodiment comprises lithium nickel-based metal oxide particles, and the lithium nickel-based metal oxide can be identified on an X-ray diffraction (XRD) spectrum as a main peak (I(108)) of the (108) plane, a volume peak (I(108)_s) of the (108) plane, a main peak (I(110)) of the (110) plane, and a volume peak (I(110)_s) of the (110) plane.

[0031] In the present specification, I(108) represents the intensity of the main peak among the peaks corresponding to the (108) plane (peaks appearing in the range where 2θ is about 64.0 to 64.5°), and I(108)_s represents the intensity of the volume peak among the peaks corresponding to the (108) plane.

[0032] In the present specification, I(110) represents the intensity of the main peak among the peaks corresponding to the (110) plane (peaks appearing in the range where 2θ is about 64.5 to 65.5°), and I(110)_s represents the intensity of the volume peak among the peaks corresponding to the (110) plane.

[0033] In this case, the volumetric peak refers to a peak with a lower intensity compared to the main peak. Specifically, in a specific 2θ region, the "main peak" represents the peak with the maximum intensity, and the "volumetric peak" represents the peak with the second highest intensity, which is lower in intensity than the main peak. More specifically, the volumetric peak is identified at an angle of 0.1 to 0.5 degrees or 0.1 to 0.3 degrees away from the main peak (108) and the main peak (110). The more clearly the volumetric peak separates from the main peak, the more it indicates that the layered structure is well developed without structural defects.

[0034]

[0035] A positive electrode active material for a lithium secondary battery according to one embodiment comprises lithium nickel-based metal oxide particles, wherein the lithium nickel-based metal oxide has a main peak of the (108) plane, a volumetric value of the (108) plane, a main peak of the (110) plane, and a volumetric value of the (110) plane confirmed in an X-ray diffraction (XRD) spectrum, and the intensity ratio (I(110)_S / I(108)_S) of the volumetric value intensity of the (110) plane (I(110)_S) to the volumetric value intensity of the (108) plane (I(108)_S) may be 1.00 to 1.20. Specifically, the I(110)_S / I(108)_S may be 1.18 or less, 1.16 or less, 1.14 or less, or 1.12 or less.

[0036] A positive electrode active material satisfying the aforementioned range has a well-developed crystal structure, which can result in excellent electrochemical characteristics for a battery containing it. Conversely, if it falls below the aforementioned range, it may be a positive electrode active material that has not sufficiently secured entry and exit pathways for lithium, and if it exceeds the aforementioned range, it may be a case where particle growth has not been achieved in a desirable manner. Consequently, the electrochemical characteristics of a battery containing such a positive electrode active material may appear inferior.

[0037] More specifically, the above I(110)_S / I(108)_S may be 1.01 or greater or 1.03 or greater. In this case, the initial charge / discharge efficiency and rate characteristics may be better simultaneously.

[0038] The (108) peak and (110) peak, which exist at high angles of 60 degrees or more, have technical significance in that they can be used as representative indicators representing the powder properties of the cathode material compared to the main peak observed at low angles, as the error caused by handling is small.

[0039] In particular, the ratio of the intensity of the (108) peak and the (110) peak has technical significance in that it can confirm the degree of orientation of the single particle. When the (110) peak intensity is relatively high, it has a shape close to a sphere without orientation in a specific direction, and when the (108) peak intensity is high, it has orientation in the (003) plane direction and has a shape close to a plate. Therefore, when the (110) peak is strong and the shape close to a sphere, sufficient entry and exit paths for lithium can be secured through the (110) plane, and the diffusion distance during the process of lithium diffusing into the bulk is short, which can improve capacity and output characteristics. Conversely, when the (108) peak is strong, a shape close to a plate is formed, and the entry and exit surface of lithium is relatively reduced, which leads to a reduction in reaction sites, thereby restricting the insertion and extraction of lithium, and the diffusion distance increases during the process of lithium diffusing into the bulk, which can lead to a decrease in the capacity and output of the cathode material.

[0040]

[0041] In the lithium secondary battery positive electrode active material of the present embodiment, the lithium nickel-based metal oxide may have an intensity ratio (I(110) / I(108)) of the main peak intensity of the (110) plane (I(110)) to the main peak intensity of the (108) plane (I(108)) in the X-ray diffraction (XRD) spectrum of 1.01 or higher. Specifically, it may be 1.02 or higher or 1.03 or higher, and 1.20 or lower, 1.18 or lower, 1.16 or lower, 1.14 or lower, or 1.13 or lower.

[0042] A cathode active material satisfying the aforementioned range has a well-developed crystal structure, which can result in excellent electrochemical characteristics of a battery containing it. Conversely, if it falls below the aforementioned range, there may be limitations on lithium insertion and extraction, and if it exceeds the aforementioned range, particle growth may not be desirable. Consequently, the electrochemical characteristics of a battery containing such cathode active material may appear inferior.

[0043]

[0044] The positive electrode active material for a lithium secondary battery according to the present embodiment may include at least one of a single particle consisting of one primary particle and a quasi-single particle formed by the aggregation of the primary particle.

[0045] In this specification, “single particle” is a term used to distinguish it from cathode active material particles in the form of secondary particles formed by the aggregation of tens to hundreds of primary particles, which were conventionally used; it is a concept that includes a single particle consisting of one primary particle and aggregate particles of 30 or fewer primary particles. The “secondary particle” refers to an aggregate formed by the aggregation of primary particles through physical or chemical bonding between primary particles without an intentional aggregation or assembly process of the primary particles, i.e., a secondary structure.

[0046] In addition, “single particle” means a single particle composed of only one primary particle, and “quasi-single particle” means a single particle composed of multiple primary particles.

[0047] The above “primary particle” refers to a minimum particle unit that is distinguished as a single mass when the cross-section of the positive active material is observed through a scanning electron microscope (SEM), and may consist of a single crystal grain or multiple crystal grains.

[0048] As the positive electrode active material for a lithium secondary battery of this embodiment is composed of single particles, the particle strength is increased, which can suppress particle breakage during rolling and prevent cracks from forming between primary particles as charging and discharging are repeated. Additionally, the small specific surface area can reduce the amount of gas generated due to side reactions with the electrolyte. Furthermore, the rolling density can be increased during electrode manufacturing, thereby improving the energy density of the electrode.

[0049]

[0050] The above-mentioned positive electrode active material for a lithium secondary battery has an average particle size (D50) of 3.0 to 5.5 μm, and more specifically, 3.3 to 4.4 μm or 3.6 to 4.0 μm.

[0051] In this specification, the average particle size (D50) can be defined as the particle size corresponding to 50% of the volume accumulation in the particle size distribution curve. The average particle size (D50) can be measured, for example, using a laser diffraction method. The laser diffraction method generally enables the measurement of particle sizes ranging from the submicron region to several millimeters, and can obtain results with high reproducibility and high resolution.

[0052] As the average particle size of the positive electrode active material is sufficiently large as within the above range, the tap density can be further improved compared to conventional small particle size single particles, and consequently, the electrode density can be significantly improved. However, if the average particle size of the positive electrode active material is too large, the movement path of lithium ions becomes longer, which may degrade electrochemical characteristics such as capacity and output, so an upper limit is set as above.

[0053]

[0054] Meanwhile, the lithium nickel-based metal oxide may contain 60 mol% or more of nickel based on the total molar amount of transition metal, and more specifically, 70, 80, or 90 mol% or more. As the nickel content is included in such a high amount, high capacity characteristics can be achieved.

[0055]

[0056] In addition, the lithium nickel-based metal oxide comprises cobalt, manganese, and a doping element, and the doping element may comprise one or more selected from Al, Zr, Nb, Mo, W, Ti, Ce, Mg, P, V, Sr, and B. By further including the doping element in the positive electrode active material, the structural stability of the positive electrode active material can be improved, thereby extending the charge-discharge cycle life. Additionally, the electrical conductivity of the positive electrode active material can be improved, thereby enhancing the high-rate characteristics of the battery.

[0057]

[0058] The above-mentioned positive electrode active material may further include a coating layer comprising Co, Al, or a combination thereof on the lithium nickel-based metal oxide. By further including a coating layer of the above composition, the positive electrode active material can suppress adverse reactions with the electrolyte and improve the structural stability of the active material, thereby further improving battery life characteristics.

[0059]

[0060] The lithium nickel-based metal oxide according to this embodiment can be represented more specifically by the following chemical formula 1.

[0061] [Chemical Formula 1]

[0062] Li a [Ni x Co y Mn z M1 w1 M2 W2 ]O2

[0063] In the above chemical formula 1, 0.8≤a≤1.2, 0.60≤x<1, 0≤y≤0.4, 0≤z≤0.4, 0≤w1≤0.01, 0≤w2≤0.2, x+y+z+w1+w2=1, M1 is Zr, Al, B or a combination thereof, and M2 is Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr or a combination thereof.

[0064] In the lithium nickel-based metal oxide 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 cathode 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 cathode 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.

[0065] In the lithium nickel-based metal oxide of Chemical Formula 1 above, nickel may be included in an amount corresponding to x, i.e., 0.6≤x<1, 0.6≤x≤0.97, 0.80≤x≤0.97, or 0.90≤x≤0.97. 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 safety may decrease due to a decrease in the structural stability of the active material.

[0066] In the lithium nickel-based metal oxide of Chemical Formula 1 above, cobalt may be included in an amount corresponding to y, i.e., 0≤y≤0.4, 0≤y≤0.2, or 0≤y≤0.1. 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.

[0067] In the lithium nickel-based metal oxide of Chemical Formula 1 above, manganese may be included in an amount corresponding to z, i.e., 0 ≤ z ≤ 0.4. If the manganese content is too low, the production cost may increase and the stability of the active material may decrease. If the manganese content is too high, the capacity and output characteristics of the battery may decrease.

[0068] In the lithium nickel-based metal oxide of Chemical Formula 1 above, M1 may be included in an amount corresponding to w1, i.e., 0 ≤ w1 ≤ 0.01. At this time, M1 is a grain growth promoting element, which is Zr, Al, B, or a combination thereof.

[0069] In the lithium nickel-based metal oxide of Chemical Formula 1 above, M2 may be included in an amount corresponding to w2, i.e., 0≤w2≤0.2. At this time, M2 is an other doping element and is Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

[0070]

[0071] Method for manufacturing a positive electrode active material for a lithium secondary battery

[0072] A method for manufacturing a positive electrode active material for a lithium secondary battery according to another embodiment may include the steps of: preparing a transition metal precursor containing nickel; mixing the transition metal precursor and a lithium raw material to form a mixture; calcining the mixture after the first calcination; heat-treating the calcined product to form a lithium nickel-based metal oxide; and dissolving the lithium nickel-based metal oxide.

[0073] Hereinafter, a method for manufacturing a positive electrode active material for a lithium secondary battery according to the present embodiment will be described step by step.

[0074]

[0075] First, prepare a nickel-containing transition metal hydroxide.

[0076] The above transition metal hydroxide may be prepared as a positive electrode active material precursor by, for example, 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 solution.

[0077] At this time, the average particle size (D50) of the transition metal hydroxide may be 3 to 15 μm or 5 to 15 μm. When the average particle size of the transition metal hydroxide satisfies the above range, a single-particle lithium nickel-based metal oxide of medium particle size, which is the target of this embodiment, can be easily obtained.

[0078] 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.

[0079] 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.

[0080] The above manganese 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 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.

[0081] 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).

[0082] 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.

[0083] The above pH-adjusting solution acts as a precipitating agent or a pH adjuster and may include alkali compounds such as hydroxides of alkali metals or alkaline earth metals like NaOH, KOH, or Ca(OH)2, their hydrates, or combinations thereof. Meanwhile, the above pH-adjusting solution may also be used in the form of an aqueous solution, in which case water or a mixture of water and an organic solvent that is uniformly miscible with water (e.g., alcohol) may be used as the solvent. In this case, the above pH-adjusting solution may be added in an amount such that the pH of the reaction solution becomes 11 to 13.

[0084] The above co-precipitation reaction can be carried out under an inert atmosphere such as nitrogen or argon, at a temperature of 30 to 70°C, and at a pH of 11 to 13.

[0085] By the above process, particles of nickel-cobalt-manganese (-doping element) hydroxide are generated and precipitated in the reaction solution. The precipitated precursor particles can be separated by conventional methods, washed, and dried to obtain a precursor. The precursor may be a secondary particle formed by the aggregation of primary particles.

[0086] 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.

[0087] Meanwhile, the doping element may also be doped during the preparation stage of the anode active material precursor. In this case, the doping element can be doped into the precursor by additionally adding a doping raw material to a transition metal-containing solution and causing a co-precipitation reaction.

[0088]

[0089] Next, a mixture containing the above-mentioned transition metal hydroxide and lithium raw material is formed, then subjected to primary sintering and subsequent sintering, followed by heat treatment to form a lithium nickel-based metal oxide.

[0090] The above lithium raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and is not particularly limited as long as it is soluble in water. Specifically, the above lithium raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or a combination thereof, but is not limited thereto.

[0091]

[0092] Sintering is a heat treatment process for bonding cohesive particles through atomic-level mass transfer in a solid state, meaning it moves toward a thermodynamically more stable state by reducing free surface energy. Through this process, the energy of the system can be lowered and bond strength increased. At this time, the reduction in surface energy per unit area is achieved through densification, and the reduction in the total interfacial area is achieved through coarsening.

[0093] Generally, when sintering ceramic materials containing powders or fine particles with a large specific surface area, densification and particle growth occur simultaneously, making it difficult to precisely control the structure of the sintered body by controlling each sintering reaction. However, in this embodiment, a two-stage sintering process of main firing and post-firing is performed, and by controlling the orientation of single particles through the design of an optimal firing profile at each sintering stage, it is possible to manufacture an anode material with significantly improved capacity and output.

[0094] That is, the method for manufacturing an active material according to the present embodiment is carried out by dividing the calcination into two stages, and the temperature of the first calcination is higher than the temperature of the subsequent calcination. Specifically, the difference (T1-T2) between the temperature of the first calcination (T1) and the temperature of the subsequent calcination (T2) may be in the range of 50 to 350°C or 70 to 300°C.

[0095] Through high-temperature primary sintering, the number of primary particles within a single particle can be grown to an appropriate range. Through low-temperature post-sintering, crystal rearrangement can be induced to relieve the internal stress increased during high-temperature primary sintering, thereby reducing the nickel cation mixing phenomenon.

[0096] That is, as a conventional method for manufacturing single particles, the single-stage firing method involving high temperature and long-term firing had problems such as nickel cation mixing and the formation of rock salt impurities. On the other hand, in this embodiment, the above problems can be prevented through high-temperature main firing and low-temperature subsequent firing exhibiting the aforementioned temperature difference, and the number of primary particles within the single particle can be appropriately increased.

[0097] Specifically, the above-mentioned primary firing temperature may be 900 to 960°C, 900 to 950°C, or 905 to 945°C, and the above-mentioned secondary firing temperature may be 500 to 850°C, 550 to 845°C, or 600 to 840°C.

[0098] When the main firing temperature and the subsequent firing temperature each satisfy the above range, the aforementioned two-stage firing effect can be more preferably realized.

[0099]

[0100] Additionally, the above-mentioned main firing time may be shorter than the above-mentioned subsequent firing time. Specifically, the difference (t2-t1) between the holding time (t1) of the main firing temperature and the holding time (t2) of the subsequent firing temperature may be 3 to 10 hours or 4 to 9 hours.

[0101] That is, the main firing time, which is high temperature firing, can be shortened, and the subsequent firing time, which is low temperature firing, can be lengthened to more preferably realize the aforementioned two-stage firing effect.

[0102] Specifically, the holding time (t1) of the above-mentioned main firing temperature may be 1 hour to 5 hours or 1.5 hours to 4 hours, and the holding time (t2) of the above-mentioned subsequent firing temperature may be 4 hours to 15 hours or 6 hours to 12 hours.

[0103] When the main firing and subsequent firing times satisfy the above ranges, the aforementioned two-stage firing effect can be more preferably realized.

[0104] Specifically, the main sintering stage has a higher sintering temperature compared to the subsequent sintering stage, and through this process, particle growth based on mass transfer can be induced to synthesize a single-particle cathode active material. If the temperature and time of the main sintering are higher or longer than the optimal point, the particles grow in the (003) plane direction to achieve thermodynamic stability, resulting in a plate-like structure and a decrease in capacity and output.

[0105] In addition, through post-firing, internal stress generated during grain growth is relieved to develop a layered structure well and induce a densification reaction. By controlling the surface energy per unit area, the degree of development of the (003) plane and (110) plane can be finely controlled. Even during post-firing, just like with the main firing, if the temperature is higher than the optimal temperature or the firing time is longer, a specific plane (003) develops, causing a decrease in performance. Therefore, it is necessary to optimize the firing temperature and time within the aforementioned range.

[0106]

[0107] After the aforementioned firing, heat treatment may be performed at 220 to 400°C or 250 to 370°C. At this time, the holding time of the heat treatment temperature may be 3 to 7 hours or 4 to 6 hours.

[0108] A battery containing a positive electrode active material that has undergone heat treatment to satisfy the aforementioned range may exhibit excellent high-temperature life characteristics. Specifically, the capacity and output of a single particle can be improved by further developing the 110-plane direction through the heat treatment step to increase the diffusion coefficient of lithium.

[0109]

[0110] The above calcination can be performed under an oxygen or air atmosphere. Specifically, when calcined under an oxygen atmosphere, the local oxygen partial pressure increases, which can improve the crystallinity of the cathode active material.

[0111] Meanwhile, other doping elements can be doped during the lithium nickel-based metal oxide formation stage. In this case, other doping elements can be doped into the lithium nickel-based metal oxide by adding other doping raw materials during the formation of the mixture and calcining.

[0112]

[0113] Next, the above lithium nickel-based metal oxide is broken down to form a lithium nickel-based metal oxide in the form of a single particle.

[0114] During the main firing process, the fired body hardens due to inter-particle necking. Therefore, it is necessary to manufacture single particles with an average particle size of 3 micrometers or more by undergoing a grinding / crushing process using an air jet mill with strong grinding power. The air jet mill grinds the fired body by injecting compressed air through a high-pressure nozzle, and the desired particle size can be controlled by the rotational speed (rpm) of the classifying wheel.

[0115] Thus, a single-particle positive electrode active material according to the present embodiment can be obtained, and the intensity ratio of the peaks for the (110) plane and the (108) plane can be preferably formed. A detailed explanation regarding this is as described above.

[0116]

[0117] If necessary, after the above disintegration step, a step of forming a coating layer comprising Co, Al, or a combination thereof may be further included.

[0118] More specifically, a coating layer can be formed by mixing the above-mentioned single-particle lithium nickel-based metal oxide with a Co raw material, an Al raw material, or a combination thereof, and then heat-treating. The technical significance of forming the coating layer is as described above and is therefore omitted.

[0119]

[0120] anode

[0121] In another embodiment, it includes a current collector and a positive active material layer located on one side of the current collector and comprising a positive active material manufactured according to the above-described embodiment.

[0122] At this time, the rolling density of the anode may be 3.55 g / cc or more, more specifically in the range of 3.58 g / cc to 3.75 g / cc or 3.6 g / cc to 3.7 g / cc.

[0123] If the rolling density satisfies the above range, the energy density of the lithium secondary battery can be significantly improved. Therefore, when the cathode according to the present embodiment is applied to an electric vehicle, the driving range can be dramatically increased.

[0124] 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.

[0125] 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.

[0126] Meanwhile, the above positive active material layer may include a binder and a conductive material.

[0127] 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.

[0128] 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.

[0129] The above-mentioned anode can be manufactured according to a conventional anode manufacturing method, except for using the above-mentioned anode active material.

[0130] Specifically, the anode can be manufactured by applying a composition for forming an anode active material layer, comprising the aforementioned anode active material and optionally a binder, conductive material, or 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.

[0131] 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 allows for the dissolution or dispersion of 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.

[0132] Alternatively, the anode may be manufactured by casting the composition for forming the 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.

[0133]

[0134] lithium secondary battery

[0135] In another embodiment, a lithium secondary battery including the anode is provided.

[0136] Specifically, the lithium secondary battery may 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.

[0137] 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.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] The binder and conductive material mentioned above may be the same as those previously described in the anode.

[0142] 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.

[0143] 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.

[0144] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0145] 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.

[0146] 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.

[0147]

[0148] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0149]

[0150] Example 1

[0151] (1) Manufacturing of positive electrode active material

[0152] (Preparation of transition metal hydroxide) (Ni) with an average particle size (D50) of 7 μm according to a general coprecipitation method 0.62 Co 0.20 Mn 0.18 A hydroxide of the composition (OH)2 was prepared.

[0153] (Calcination) 200g of the above transition metal hydroxide was mixed with 92.1g of LiOH·H2O as a lithium raw material and 20.27g of ZrO as a dopant, and then the main calcination was performed at a temperature of 910℃ for 3 hours, and then 30.8g of Al(OH) as a dopant was added to 200g of the main calcination product and the subsequent calcination was performed at a temperature of 830℃ for 8 hours.

[0154] After (heat treatment), 180g of the post-fired product and 1.03g of boric acid, a coating agent, were mixed and then heat-treated at a temperature of 350℃ for 5 hours.

[0155] After (disintegration), the above-mentioned calcined product was disintegrated to form a single-particle lithium nickel-based metal oxide. At this time, the number of moles of lithium (Li), zirconium (Zr), and aluminum (Al) per 1 mol of transition metal in the lithium nickel-based metal oxide corresponds to 1.02, 0.001, and 0.005 mol, respectively.

[0156]

[0157] (2) Lithium secondary battery manufacturing

[0158] The slurry for electrode manufacturing was prepared by mixing the above-prepared cathode active material, conductive material (carbon black, Denka black), and binder (PVDF, KF1100) in a ratio of 96.25 : 1.5 : 2.25 wt%, and adding NMP (N-Methyl-2-pyrrolidone) to adjust the viscosity so that the solid content was approximately 65%. The prepared slurry was coated onto a 15 µm thick Al foil using a doctor blade and then dry-rolled. The electrode loading amount was 15.0 mg / cm². 2 It was, and the rolled density (25 ℃, 20 kN) was 3.6 g / cm³ 3 It was.

[0159] A coin cell was manufactured using an electrolyte of 1M LiPF6 in EC:DMC:EMC=3:4:3 (vol%) with 3.0 vol% of VC added relative to the total amount of the electrolyte, a PP separator, and a lithium anode (200 μm, Honzo metal).

[0160]

[0161] Examples 2 to 6 and Comparative Examples 1 to 6

[0162] A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the temperature and time conditions of the main firing, subsequent firing, and heat treatment were controlled during the firing and heat treatment steps as shown in Table 1.

[0163]

[0164] Table 1 below summarizes the active material manufacturing conditions of the above examples and comparative examples.

[0165]

[0166] Classification Main Firing Temperature (°C) Main Firing Time (h) Post-Firing Temperature (°C) Post-Firing Time (h) Heat Treatment Temperature (°C) Heat Treatment Time (h) Example 19 10383083505 Example 29 20365083505 Example 39 20283083505 Example 49 203650102805 Example 59 30265083505 Example 69 40265083505 Comparative Example 18 90365083505 Comparative Example 29 70365083505 Comparative Example 39 20340083505 Comparative Example 49 20390083505 Comparative Example 59 20365082005 Comparative Example 69 20365084505

[0167] Reference Example 1 and Reference Example 2

[0168] In the preparation of Example 5 above, a first intermediate material that underwent only the main firing was prepared as Reference Example 1, and a second intermediate material that underwent both the main firing and subsequent firing was prepared as Reference Example 2.

[0169] For Reference Example 1 and Reference Example 2 as well, the physical properties and electrochemical characteristics of the battery described below were confirmed, and the process of orientation control at each sintering and heat treatment step was confirmed.

[0170]

[0171] Experimental Example 1: Observation of SEM image of cathode active material

[0172] Figure 4 shows an SEM (scanning electron microscope) image of the positive electrode active material prepared according to Example 1, magnified 5,000 times.

[0173] Referring to Fig. 4, it was confirmed that the active material according to Example 1 is in the form of a single particle, rather than being formed by the aggregation of tens to hundreds of primary particles classified as conventional secondary particle shapes.

[0174] It was confirmed that the single particle of Example 1 had an average particle size of appropriate size, with the number of primary particles contained in the single particle being neither too small nor too large.

[0175]

[0176] Experimental Example 2: Evaluation of Physical Properties of Anode Active Material

[0177] The physical properties of the cathode active materials prepared according to the examples and comparative examples were evaluated, and the results are shown in Tables 2 and 3 below. The specific experimental methods are as follows.

[0178]

[0179] (1) XRD evaluation

[0180] The XRD data of the active material was measured using PANalytical’s XPERT-3 (X-ray diffraction) equipment and the pattern was analyzed to evaluate the peaks for the (108) plane and (110) plane.

[0181] 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 equipment, the detector was set to a LynxEye detector (opening=4.108°), the Divergence Slit was set to 0.38 mm, the Antiscatter Slit to na, and the Slit mode to Fixed.

[0182] I(108) represents the intensity of the main peak among the peaks corresponding to the (108) plane (peaks appearing in the range where 2θ is about 64.0 to 64.5°), and I(108)_s represents the intensity of the volume peak among the peaks corresponding to the (108) plane.

[0183] I(110) represents the intensity of the main peak among the peaks corresponding to the (110) plane (peaks appearing in the range where 2θ is about 64.5 to 65.5°), and I(110)_s represents the intensity of the volume peak among the peaks corresponding to the (110) plane.

[0184] In this case, the "boost" refers to a peak with a lower intensity compared to the main peak. More specifically, in a specific 2θ region, the "main peak" represents the peak with the maximum intensity, and the "boost" represents the peak with the second highest intensity, which is lower in intensity than the main peak.

[0185]

[0186] (2) Evaluation of residual lithium

[0187] After adding distilled water to the cathode active material, residual lithium was extracted using a stirrer, and the cathode active material powder and extract were separated using a filter. Subsequently, the residual lithium was evaluated by measuring the extract through neutralization titration using a Mettler Toledo potentiometric titrator.

[0188]

[0189] (3) Evaluation of average particle size (D50)

[0190] For the active material powder, the average particle size corresponding to 50% of the volume accumulation was measured using the laser diffraction method.

[0191]

[0192]

[0193] Classification I 108 I 108_s I 110 I 110_S I 110 / I 108 I 110_s / I 108_s Example 1 304801534434143170501.121.11 Example 2 202371095021720109501.071.04 Example 3 200001056621125103851.051.01 Example 4 198081091220433110021.031.00 Example 5 253131327628067142421.111.07 Example 6 221481172424329121801.101.04 Reference Example 1 176541073613781-0.78-Reference Example 2260401385327264137781.0470.99 Comparative Example 119673103541978899881.000.96 Comparative Example 2466042572038411207810.820.81 Comparative Example 3222451206120014102960.900.85 Comparative Example 4302101597324279127760.800.80 Comparative Example 5213651142920436104870.960.92 Comparative Example 6206441050420366102690.990.98

[0194] Classification Particle Size (um) Residual Lithium (ppm) D 50 LiOH Li2CO3 Total Example 1 3.9 29 234 75 339 8 Example 2 3.8 32 56 40 236 58 Example 3 3.8 29 824 10 339 2 Example 4 3.8 34 74 44 639 20 Example 5 3.9 21 62 10 22 318 4 Example 6 4.0 19 72 52 92 500 Reference Example 1 3.8 36 34 58 94 22 3 Reference Example 2 3.9 18 41 18 19 36 60 Comparative Example 1 3.5 500 129 56 79 57 Comparative Example 2 4.5 224 97 31 29 80 Comparative Example 3 3.7 43 89 228 86 677 Comparative Example 44.522377112947 Comparative Example 53.733234883811 Comparative Example 63.734134743887

[0195] Reference Example 1, Reference Example 2, and Example 5 were analyzed with reference to Table 2 and Figure 3 above. Figure 3 shows the results of X-ray diffraction analysis of the cathode active materials for lithium secondary batteries according to Reference Example 1, Reference Example 2, and Example 5. For reference, the degree of change in microstructure cannot be distinguished by micro-scale analysis using SEM images, but can be confirmed by changes in crystal structure using XRD. When analyzing Reference Example 1, the first intermediate material after performing the calcination, it can be seen that the I110 / I108 ratio is less than 1 because high temperature is required as a power source for grain growth when forming single particles through the calcination, causing the particles to grow in the 003 plane direction to ensure thermodynamic stability. Additionally, it is confirmed that I110_S is not yet measured.

[0196] When analyzing Reference Example 2, which is the second intermediate material after performing post-sintering, it can be seen that the degree of development of the (003) plane and (110) plane can be finely controlled by controlling the surface energy per unit area when inducing a densification reaction through post-sintering. Specifically, it is confirmed that by sintering at a lower temperature than the main sintering, the internal stress generated during the grain growth process in the main sintering is relieved and the (110) plane is developed, resulting in an I110 / I108 value of 1 or higher. In other words, the orientation of the single particle can be finely controlled primarily through the post-sintering process.

[0197] When analyzing Example 5, which has completed the final heat treatment step, it can be seen that the capacity and output of the single particle can be improved by increasing the diffusion coefficient of lithium through the final 3-step heat treatment step, thereby further developing the 110 plane direction. In addition, during this process, the volumetric strength ratio of the (110) plane and the (108) plane is formed within an appropriate range.

[0198]

[0199] Figure 2 is the result of X-ray diffraction analysis of a positive electrode active material for a lithium secondary battery according to Example 1 and Comparative Example 1, and Figure 1 is an enlarged view of Figure 2.

[0200] Referring to FIGS. 1 and 2 and Table 2 above, it was confirmed that the positive active material according to the embodiment with appropriately controlled process conditions exhibits main peaks and volumetric peaks for the (110) plane and the (108) plane. Specifically, it was confirmed that I(110)_s / I(108)_s satisfies 1.00 or more, and more specifically, corresponds to the range of 1.00 to 1.20.

[0201] In addition, the positive active material according to the example was found to satisfy an I(110) / I(108) ratio of 1.01 or higher, and more specifically, to be in the range of 1.03 to 1.20.

[0202] On the other hand, it was confirmed that the positive active material according to the comparative example did not satisfy the aforementioned range.

[0203]

[0204] Due to this difference, differences in the electrochemical characteristics of the battery containing the positive active material according to the example or comparative example appear as described below.

[0205] Meanwhile, referring to Table 3 above, Comparative Example 2, in which the main firing was performed at a higher temperature (970℃) than the example, and Comparative Example 4, in which the subsequent firing was performed at a higher temperature (900℃) than the example, showed a larger particle size (4.5μm or more) compared to the example.

[0206] In addition, Comparative Example 1, in which the main firing was performed at a lower temperature (890℃) than the example, and Comparative Example 3, in which the subsequent firing was performed at a lower temperature (400℃) than the example, showed a higher total residual lithium content (6000 ppm or more) compared to the example.

[0207] Meanwhile, in the case of Comparative Example 5, where the heat treatment temperature was too low, and Comparative Example 6, where the heat treatment temperature was too high, the particle size and total residual lithium were found to be appropriate, but as described below, the electrochemical properties were found to be inferior to those of the examples.

[0208]

[0209] Through the analysis of the aforementioned comparative example, it can be seen that the main firing temperature (T1) and the subsequent firing temperature (T2) satisfy the range according to the example, and the difference (T1-T2) satisfies the range of 50 to 350°C, and that the heat treatment should also be performed within an appropriate range. Specifically, when the positive electrode active material is manufactured according to the firing and heat treatment profile according to the example, the particle size of the positive electrode active material is appropriately formed and the residual lithium is controlled within a desirable range, thereby exhibiting excellent electrochemical characteristics as described below.

[0210]

[0211] Experimental Example 3: Evaluation of Battery Electrochemical Characteristics

[0212] The electrochemical characteristics of lithium secondary batteries prepared according to the examples and comparative examples were evaluated, and the results are shown in Table 4 below. The specific experimental methods are as follows.

[0213] (1) Evaluation of initial charge and discharge capacity and initial efficiency

[0214] After fabricating a lithium secondary battery half cell, a charge-discharge test was performed after aging it at 25°C for 12 hours. To evaluate the initial capacity, the reference capacity was set to 180 mAh / g, and the battery was charged to 4.34 V with a constant current of 0.2 C. Then, the voltage was switched to a constant voltage, and charging continued until the termination current reached 0.05 C. After a 10-minute rest time following charging, the battery was discharged until it reached 2.75 V with a constant current of 0.33 C, using a reference capacity of 180 mAh / g.

[0215]

[0216] (2) Evaluation of rate characteristics

[0217] The capacity evaluation was based on a reference capacity of 200 mAh / g, and the discharge capacity was measured by applying a CC / CV of 2.75 - 4.34 V and a 1 / 20 C cut-off, charging at 2.0 C and discharging at 0.1 C. Then, the initial room temperature discharge capacity was divided by the discharge capacity obtained by charging at 2 C and discharging at 0.1 C to derive the C-rate (2 C / 0.1 C) (%).

[0218]

[0219] (3) Evaluation of high-temperature life retention rate (45℃, 50 cycles)

[0220] The high-temperature life retention rate was determined by charging to 4.25V with a constant current of 0.5C at 45℃, then switching to a constant voltage and charging until the termination current reached 0.05C. After a 10-minute rest time following charging, the device was discharged with a constant current of 1.0C until it reached 2.5V. Fifty charge-discharge cycles were performed under these conditions, and the capacity retention rate of the 50th cycle was calculated relative to the first cycle.

[0221]

[0222] Classification Charging Capacity (mAh / g, 0.1C) Discharging Capacity (mAh / g, 0.1C) Initial Efficiency (%) C-rate (%) (2C / 0.1C) High Temperature Life Retention Rate (%, 50 cycles) Example 1 210.3193.491.990.397.6 Example 2 210.0192.391.689.997.2 Example 3 210.3192.091.389.897.5 Example 4 210.8191.690.989.597.5 Example 5 211.0191.690.889.897.6 Example 6 210.5192.491.490.897.0 Reference Example 1206.5185.190.089.096.0 Reference Example 2209.5188.090.090.696.5 Comparative Example 1209.2192.892.190.396.6 Comparative Example 2211.1189.590.089.097.8 Comparative Example 3209.5189.690.589.097.0 Comparative Example 4211.3189.489.690.097.5 Comparative Example 5208.2189.090.890.196.5 Comparative Example 6209.3189.890.789.296.6

[0223] Referring to Table 4, it was confirmed that in Examples 1 to 6, where the main peaks and volumetric peaks for the (110) plane and (108) plane are appropriately displayed, the electrochemical characteristics of capacity, efficiency, rate characteristics, and high-temperature life characteristics were all generally excellent. On the other hand, in Comparative Example 1, it was found that the high-temperature life retention rate was inferior to that of the present example.

[0224] In addition, it was confirmed that Comparative Examples 2 to 4 had a discharge capacity inferior to that of the Examples and a lower initial charge / discharge efficiency. In particular, Comparative Examples 2 and 3 were found to have rate characteristics that were as low as those of Reference Example 1.

[0225] In addition, it was confirmed that in the case of Comparative Examples 5 and 6, the charge / discharge capacity was inferior to that of the example, and the high-temperature life retention rate was also low.

[0226]

[0227] In short, the technical gist of this embodiment is that the orientation of the crystal is appropriately controlled to achieve excellent overall electrochemical characteristics of charge / discharge capacity, efficiency, rate characteristics, and lifespan characteristics.

[0228]

[0229] 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. Contains lithium nickel-based metal oxide particles, and In the X-ray diffraction (XRD) spectrum of the lithium nickel-based metal oxide, the main peak of the (108) plane, the volume of the (108) plane, the main peak of the (110) plane, and the volume of the (110) plane are identified, and The strength ratio (I(110)_S / I(108)_S) of the volumetric strength (I(108)_S) of the (110) plane to the volumetric strength (I(108)_S) of the (108) plane is 1.00 to 1.

20. Cathode active material for lithium secondary batteries.

2. In Paragraph 1, The above lithium nickel-based metal oxide has, in the X-ray diffraction (XRD) spectrum, an intensity ratio (I(110) / I(108)) of the main peak intensity of the (110) plane (I(110)) to the main peak intensity of the (108) plane (I(108)) is 1.01 or greater. Cathode active material for lithium secondary batteries.

3. In Paragraph 1, The lithium nickel-based metal oxide particles described above comprise at least one of a single particle consisting of one primary particle and a quasi-single particle formed by the aggregation of a plurality of primary particles. Cathode active material for lithium secondary batteries.

4. In Paragraph 1, The above lithium nickel-based metal oxide is a positive electrode active material for a lithium secondary battery containing 60 mol% or more of nickel based on the total molar amount of the transition metal.

5. In Paragraph 1, The above lithium nickel-based metal oxide has an average particle size (D50) in the range of 3.0 to 5.5 μm, Cathode active material for lithium secondary batteries.

6. In Paragraph 1, The above lithium nickel-based metal oxide contains cobalt, manganese, and doping elements, and The above doping element comprises one or more selected from Al, Zr, Nb, Mo, W, Ti, Ce, Mg, P, V, Sr, and B, Cathode active material for lithium secondary batteries.

7. In Paragraph 1, The above lithium nickel-based metal oxide is 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 M1 w1 M2 W2 ]O2 In the above chemical formula 1, 0.8≤a≤1.2, 0.60≤x<1, 0≤y≤0.4, 0≤z≤0.4, 0≤w1≤0.01, 0≤w2≤0.2, x+y+z+w1+w2=1, M1 is Zr, Al, B or a combination thereof, and M2 is Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr or a combination thereof.

8. A step of preparing a nickel-containing metal precursor; A step of forming a mixture by mixing the above metal precursor and lithium raw material; A step of forming a lithium nickel-based metal oxide by first calcining the above mixture at a temperature of 900 to 960°C, second calcining at a temperature of 500 to 850°C, and then heat-treating at 220 to 400°C; and The step of dissolving the above lithium nickel-based metal oxide; comprising Method for manufacturing a positive electrode active material for a lithium secondary battery.

9. In Paragraph 8, The difference (T1-T2) between the above primary firing temperature (T1) and the secondary firing temperature (T2) is in the range of 50 to 350℃. Method for manufacturing a positive electrode active material for a lithium secondary battery.

10. In Paragraph 8, The difference (t2-t1) between the holding time (t1) of the main firing temperature and the holding time (t2) of the subsequent firing temperature is 3 to 10 hours. Method for manufacturing a positive electrode active material for a lithium secondary battery.

11. In Paragraph 8, The holding time (t1) of the above-mentioned firing temperature is 1 hour to 5 hours. Method for manufacturing a positive electrode active material for a lithium secondary battery.

12. In Paragraph 8, The holding time (t2) of the above-mentioned post-sintering temperature is 4 to 15 hours. Method for manufacturing a positive electrode active material for a lithium secondary battery.

13. In Paragraph 8, The holding time of the above heat treatment temperature is 3 to 7 hours. Method for manufacturing a positive electrode active material for a lithium secondary battery 14. In Paragraph 8, The average particle size (D50) of the nickel-containing metal precursor is in the range of 3 to 15 μm. Method for manufacturing a positive electrode active material for a lithium secondary battery 15. A positive electrode for a lithium secondary battery comprising a positive electrode active material according to paragraph 1.

16. A lithium secondary battery comprising a positive electrode for a lithium secondary battery according to paragraph 15.

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