Cathode active material for lithium secondary battery, manufacturing method of the same and lithium secondary battery comprising the same

Abstract

The present invention relates to a positive electrode active material for a lithium secondary battery comprising a lithium metal oxide particle having a single-particle nickel (Ni)-containing layered crystal structure and a coating layer located on the surface of the lithium metal oxide particle, wherein the degree of single particle formation is 50 to 75% and the fine particle generation rate having a particle size of 1.0 μm or less is 2.1% or less when a pressure of 4.52 tonf / cm2 is applied.

Description

Technology Field

[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. Background Technology

[0003] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMnO4, etc.), and lithium iron phosphate compounds (LiFePO4) have been used as cathode active materials for lithium secondary batteries. Among these, lithium cobalt oxide has the advantage of high operating voltage and excellent capacity characteristics, but it is difficult to apply it commercially to large-capacity batteries due to the high cost and unstable supply of cobalt, which is the raw material. Lithium nickel oxide has poor structural stability, making it difficult to achieve sufficient lifespan characteristics. Meanwhile, lithium manganese oxide has the problem of poor capacity characteristics despite excellent stability. Accordingly, lithium composite transition metal oxides containing two or more transition metals have been developed to compensate for the problems of lithium transition metal oxides containing Ni, Co, or Mn alone; among these, lithium nickel cobalt manganese oxide containing Ni, Co, and Mn is widely used in the field of electric vehicle batteries.

[0004] Conventional lithium nickel cobalt manganese oxide was generally in the form of spherical secondary particles formed by the aggregation of tens to hundreds of primary particles. However, in the case of lithium nickel cobalt manganese oxide in the form of secondary particles, there are problems such as particle breakage where primary particles detach during the rolling process in cathode manufacturing, and cracks occurring inside the particles during the charging and discharging process. If particle breakage or cracking occurs in the cathode active material, the contact area with the electrolyte increases, leading to increased gas generation and active material degradation due to side reactions with the electrolyte, which in turn reduces lifespan characteristics.

[0005] Furthermore, there has been a recent increase in demand for high-output, high-capacity batteries, such as those for electric vehicles. Consequently, there is a trend toward gradually increasing the nickel content in cathode active materials (so-called "high-nickel"). While increasing the nickel content in the cathode active material improves initial capacity characteristics, the highly reactive Ni... +4 There is a problem in that the excessive generation of ions causes structural collapse of the cathode active material, which increases the degradation rate of the cathode active material, leading to reduced lifespan characteristics and decreased battery safety.

[0006] To solve the above problem, a technology has been proposed to manufacture a cathode active material in the form of a single particle rather than a secondary particle by increasing the calcination temperature during the production of lithium nickel cobalt manganese oxide. In the case of a cathode active material in the form of a single particle, the contact area with the electrolyte is smaller compared to conventional cathode active materials in the form of secondary particles, so there are fewer side reactions with the electrolyte, and the particle strength is excellent, resulting in less particle breakage during electrode manufacturing. Therefore, when a cathode active material in the form of a single particle is applied, there are advantages such as reduced gas generation and excellent lifespan characteristics.

[0007] However, in order to obtain a final cathode active material in the form of mild single particles, a disintegration process is required to break up the aggregation of particles after the calcination process to obtain lithium metal oxide particles. At this time, as the disintegration process conditions change slightly, various physical properties such as the degree of aggregation of single particles, particle size distribution, and particle strength may change, and consequently, the energy density, resistance characteristics, lifespan characteristics, and safety of the active material may change drastically. The problem to be solved

[0009] Accordingly, one objective of the present invention is to provide a single-particle type positive electrode active material for a lithium secondary battery having excellent energy density, resistance characteristics, lifespan characteristics, and safety, a method for manufacturing the same, and a lithium secondary battery including the same. means of solving the problem

[0011] One embodiment of the present invention comprises lithium metal oxide particles having a nickel (Ni)-containing layered crystal structure in a single-particle form and a coating layer located on the surface of said lithium metal oxide particles, wherein the degree of single particle formation is 50 to 75% and 4.52 tonf / cm² 2 A positive electrode active material for a lithium secondary battery is provided, wherein the generation rate of fine particles with a particle size of 1.0 μm or less is 2.1% or less when pressure is applied.

[0012] The above positive active material may have a volume-based average particle size (D50) of 3.5 to 4.8 μm.

[0013] The above-mentioned positive active material exhibits a single-peak distribution when analyzing the volume-based particle size distribution curve, and may have a full width at half maximum (FWHM) of 1.86 to 2.7 μm.

[0014] The above positive active material may have a SPAN value of 0.8 or less based on the number.

[0015] The above positive active material may have a tap density of 2.0 g / cc or more.

[0016] The above positive active material may have a residual lithium content of 2900 ppm or less.

[0017] The nickel content in the above lithium metal oxide may be 80 mol% or more based on the total molar amount of metal excluding lithium.

[0018] The coating layer may contain Co, Al, B, or a combination thereof.

[0019] The above coating layer may include a first coating layer containing Co and Al and a second coating layer located on the first coating layer and containing B.

[0020] The above lithium metal oxide can be represented by the following chemical formula 1.

[0021] [Chemical Formula 1]

[0022] Li a [Nix Co y Mn z M w ]O2

[0023] In the above chemical formula 1, 0.8≤a≤1.3, 0.8≤x<1, 0≤y≤0.2, 0≤z≤0.2, 0≤w≤0.2, x+y+z+w=1, and M is Zr, Al, B, Y, Ti, Nb, W, V, Cr, Mo, Ta, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc, or a combination thereof.

[0025] Another embodiment of the present invention provides a method for manufacturing a positive electrode active material for a lithium secondary battery, comprising the steps of: mixing a nickel (Ni)-containing metal precursor and a lithium raw material, and then calcining at a temperature of 740 to 840°C to form a lithium metal oxide; desquashing the lithium metal oxide to form a desquashed material having an average particle size (D50) of 5 to 9 μm; finely crushing the desquashed material to form a lithium metal oxide in the form of a single particle having a single particle size of 50 to 75%; and forming a coating layer on the lithium metal oxide.

[0026] The above-mentioned desiccation can be performed at a stirring speed of 8,000 to 18,000 rpm.

[0027] The above-mentioned crushing can be performed at a crushing pressure of 1.5 to 3.5 bar.

[0028] The above firing can be performed as high-temperature single-stage firing and low-temperature two-stage firing within a single firing profile.

[0029] After the step of forming the lithium metal oxide in the form of a single particle, the method may further include a step of classifying the lithium metal oxide.

[0030] Through the above classification, particles with a particle size exceeding 44 μm can be removed.

[0032] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery comprising the aforementioned positive electrode active material.

[0033] Another embodiment of the present invention provides a lithium secondary battery comprising a positive electrode for the lithium secondary battery. Effects of the invention

[0035] In one embodiment of the present invention, the positive electrode active material for a lithium secondary battery has a single particle form, and as the degree of single particle formation is precisely controlled, excellent energy density, resistance characteristics, lifespan characteristics, and safety can be achieved. Brief explanation of the drawing

[0037] Figure 1 is an SEM image of the positive electrode active material prepared according to Example 1. Figure 2 is an SEM image of the positive electrode active material prepared according to Example 2. Figure 3 is an SEM image of the positive electrode active material prepared according to Comparative Example 1. Figure 4 is an SEM image of the positive electrode active material prepared according to Comparative Example 2. Figure 5 is an SEM image of the positive electrode active material prepared according to Comparative Example 3. Figure 6 is an SEM image of the positive electrode active material prepared according to Comparative Example 4. Specific details for implementing the invention

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0043] 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.

[0044] 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.

[0046] 1. Cathode active material

[0047] A positive electrode active material for a lithium secondary battery according to one embodiment of the present invention comprises lithium metal oxide particles in the form of single particles. The positive electrode active material in the form of single particles has a smaller specific surface area compared to conventional secondary particles, which reduces the amount of gas generated due to side reactions with the electrolyte, and has a higher particle strength, which can suppress particle breakage during rolling and reduce the occurrence of cracks due to repeated charging and discharging. Accordingly, it has the advantage of superior lifespan and safety compared to secondary particles.

[0048] In this specification, "single particle" is a term used to distinguish from a positive active material particle in the form of a secondary particle formed by the aggregation of tens to hundreds of primary particles that were conventionally used, and is a concept that includes a single particle consisting of one primary particle and an aggregate particle of 30 or fewer primary particles.

[0049] In addition, "secondary particles" refers to aggregates formed by the aggregation of tens to hundreds of primary particles through physical or chemical bonding between primary particles without any intentional aggregation or assembly process of the primary particles, i.e., secondary structures.

[0050] In addition, "primary particle" refers to the smallest particle unit that is distinguished as a single mass when the cross-section of the positive electrode active material is observed through a scanning electron microscope (SEM), and it may consist of a single crystal grain or multiple crystal grains. In addition, "crystal grain" refers to a distinct region in which atoms within the primary particle form a lattice structure in a specific direction.

[0051] Meanwhile, the nickel content in the lithium metal oxide according to the present invention may be 80 mol% or more based on the total molar amount of metal excluding lithium, and more specifically, 85 mol% or more. As the nickel content in the lithium metal oxide is included in such a high amount (so-called "high nickel"), it is possible to achieve a high capacity of the battery.

[0052] In addition, the lithium metal oxide according to the present invention includes a coating layer located on the surface of lithium metal oxide particles. Accordingly, as the positive electrode active material includes the coating layer, degradation of the positive electrode active material and gas generation caused by side reactions between the electrolyte and the lithium metal oxide are suppressed, thereby further improving the lifespan and safety of the battery.

[0053] However, in order to manufacture a lithium metal oxide in the form of a moderate single particle, a disintegration process is required after the calcination process for forming the lithium metal oxide. The inventors have conducted repeated research on disintegration process conditions that can achieve excellent energy density, resistance characteristics, lifespan characteristics, and safety of the cathode active material in the form of a single particle. As a result, they discovered that when disintegration is performed in two stages of coarse disintegration and fine disintegration, and each disintegration process condition is appropriately controlled, the overall physical properties of the cathode active material, such as the degree of single particle formation, are optimized, and accordingly, excellent energy density, resistance characteristics, lifespan characteristics, and safety are achieved, thereby completing the present invention.

[0055] Specifically, the positive electrode active material according to the present invention has a single particle magnetization degree of 50 to 75%, and more specifically, 55 to 74%.

[0056] In this specification, "single particle size" is a physical property that quantitatively indicates the degree of single particle size of a positive electrode active material, and refers to the ratio (%) of the number of single particles consisting of 1 to 3 primary particles among the total number of positive electrode active material particles when the positive electrode active material powder is observed with an SEM image at a magnification of 5000x. At this time, it should be noted that the number of primary particles within the positive electrode active material particles refers to the number of primary particles observed visually in the SEM image, which is a two-dimensional image, rather than the actual number of primary particles within the positive electrode active material particles in three dimensions.

[0057] If the degree of single particle size of the positive electrode active material is too small, the number of particles consisting of four or more primary particles among the active material particles becomes too large, and the uncoated primary particle interface region increases, which may reduce the coating effect (i.e., the effect of improving lifespan characteristics) and increase resistance. If the degree of single particle size of the positive electrode active material is too large, the coating effect (i.e., the effect of improving lifespan characteristics) may be good, but the tap density of the positive electrode active material may drop too low, which may reduce the energy density of the battery.

[0058] In addition, when the degree of single-particle formation of the positive electrode active material satisfies the above range, the particle strength is maximized, and when a predetermined pressure is applied to the particles of the positive electrode active material (which may correspond to a rolling process during the manufacturing of the positive electrode), the generation of fine particles due to particle breakage can be reduced, and the residual lithium content can be lowered. Accordingly, the safety of the battery can be maximized by preventing gas generation caused by fine particles or residual lithium. The inventors believe that in the case of a positive electrode active material having an appropriate degree of single-particle formation, most of the aggregated particles that can be broken are broken and exist as single particles, so particle breakage does not occur when measuring particle breakage, and thus the particle strength appears to be high. On the other hand, in the case of a positive electrode active material having a low degree of single-particle formation, the aggregated particles that are not broken are easily broken when measuring particle breakage, resulting in a low particle strength measurement; and in the case of a positive electrode active material having too high a degree of single-particle formation, the strength of the fine particles generated when not broken is weak, resulting in a low particle strength measurement. The correlation between the degree of single-particle formation and residual lithium is that as the degree of single-particle formation increases, the reaction surface area between the residual lithium present at the particle interface and the coating material expands, facilitating the reaction and allowing for lower residual lithium levels. However, if the micro-disintegration is strengthened to achieve a degree of single-particle formation beyond an appropriate level, the specific surface area of ​​the cathode active material increases, leading to a reaction with air and potentially an increase in residual lithium.

[0059] Therefore, when the degree of single-particle magnetization of the positive electrode active material satisfies the above range, energy density, resistance characteristics, lifespan characteristics, and safety can be uniformly and excellently realized.

[0061] In addition, the positive electrode active material according to the present invention has a value of 4.52 tonf / cm 2When pressure is applied, the generation rate of fine particles with a particle size of 1.0 μm or less can be 2.1% or less, and more specifically, 2.0% or less. Accordingly, when a predetermined pressure is applied to the positive electrode active material particles (which may correspond to a rolling process during positive electrode manufacturing), the generation of fine particles due to particle breakage can be reduced, and as a result, gas generation caused by fine particles can be prevented, thereby maximizing the safety of the battery.

[0062] More specifically, the above fine powder generation rate can be calculated by placing 3.0 g of positive active material powder into a mold with a radius of 0.65 cm, applying a force of 6.0 ton using a Carver Press machine, and measuring the volume percentage of fine powder with a particle size of 1.0 μm or less using a particle size analyzer.

[0064] In addition, the positive electrode active material according to the present invention may have a volume-based average particle size (D50) of 3.5 to 4.8 μm, and more specifically, 3.6 to 4.5 μm. If the average particle size (D50) of the positive electrode active material is too small, the density of the positive electrode active material may decrease, and thus the energy density may decrease. If the average particle size (D50) of the positive electrode active material is too large, the lithium ion migration path may become too long, which may cause the capacity characteristics to deteriorate too much, thereby causing the energy density to decrease and the resistance characteristics to deteriorate. Therefore, when the average particle size (D50) of the positive electrode active material satisfies the above range, excellent resistance characteristics and energy density can be achieved.

[0065] Meanwhile, in this specification, the volume-based average particle size (D50) can be defined as the particle size corresponding to 50% of the volume-cumulative amount in the particle size distribution curve. The average particle size (D50) can be measured, for example, using a laser diffraction method.

[0067] In addition, the positive electrode active material according to the present invention may exhibit a single-peak distribution when analyzing the volume-based particle size distribution curve. In this case, the full width at half maximum (FWHM) of the volume-based particle size distribution curve may be 1.86 to 2.7 μm, and more specifically, 1.9 to 2.5 μm. The full width at half maximum of the volume-based particle size distribution curve may be affected by the degree of disintegration during the disintegration process for manufacturing single particles after the formation of the lithium metal oxide. In this case, if the full width at half maximum (FWHM) of the volume-based particle size distribution curve of the positive electrode active material is too large, it means that disintegration has not occurred sufficiently, and the average particle size (D50) of the positive electrode active material may become too large, which may result in a decrease in capacity, energy density, or resistance characteristics. If the full width at half maximum (FWHM) of the volume-based particle size distribution curve of the positive electrode active material is too small, it means that disintegration has occurred too much, and the average particle size (D50) of the positive electrode active material may become too small, which may result in a decrease in energy density. Therefore, when the full width at half maximum (FWHM) in the volume-based particle size distribution curve of the cathode active material satisfies the above range, both energy density and resistance characteristics can be uniformly and excellently realized.

[0068] Meanwhile, in this specification, the volume-based particle size distribution curve and its full width at half maximum can be derived using a laser diffraction method.

[0070] In addition, the positive electrode active material according to the present invention may have a number-based SPAN value of 0.8 or less, and more specifically, 0.78 or less. The inventors confirmed that when the number-based SPAN value of the positive electrode active material is minimized as within the above range, the energy density and resistance characteristics are uniformly excellent. The inventors believe that this is because the fine particles and coarse particles that adversely affect battery characteristics are reduced as the SPAN value decreases.

[0071] Meanwhile, in this specification, the number-based SPAN value refers to a value obtained by calculating the particle size [number-based particle size (D90) - number-based particle size (D10)] / number-based particle size (D50), and the number-based particle size (D90), number-based particle size (D50), and number-based particle size (D10) can be defined as particle sizes corresponding to 90%, 50%, and 10% of the cumulative number amount in the particle size distribution curve. Each of the above particle sizes can be measured, for example, using a laser diffraction method.

[0073] In addition, the cathode active material according to the present invention may have a tap density of 2.0 g / cc or more. Accordingly, when implementing a cathode, the density of the cathode composite is improved, and the energy density can be maximized.

[0074] In this specification, the tap density of the positive active material can be determined by placing 10 g of positive active material powder into a cylinder with a diameter of 19.1 mm, applying a force of 108 N, and measuring the height of the cylinder.

[0076] In addition, the positive electrode active material according to the present invention may have a residual lithium content of 2900 ppm or less. Since the residual lithium (LiOH and / or Li2CO3) content of the positive electrode active material is sufficiently low as in the above range, the generation of gas due to side reactions between the residual lithium and the electrolyte is reduced, thereby improving the safety of the battery.

[0078] Meanwhile, the coating layer according to the present invention may contain Co, Al, B, or a combination thereof.

[0079] In terms of a more desirable implementation of the effect of improving lifespan characteristics, the coating layer may contain all of Co, Al, and B.

[0080] More specifically, the coating layer may include a first coating layer containing Co and Al and a second coating layer located on the first coating layer and containing B. When the stacked structural relationship of the coating layers containing Co, Al, and B is as described above, there may be an advantage in that the surface of the positive electrode active material is stabilized, thereby obtaining a higher charge / discharge capacity and lifespan. The coating layer of the stacked structure may be obtained by forming a lithium metal oxide in the form of a single particle, then mixing the lithium metal oxide with a Co coating raw material and an Al coating raw material together, and then performing a first coating heat treatment to form a first coating layer, and then mixing in a B raw material, and then performing a second coating heat treatment to form a second coating layer.

[0082] Meanwhile, the lithium metal oxide according to the present invention can be represented more specifically by the following chemical formula 1.

[0083] [Chemical Formula 1]

[0084] Li a [Ni x Co y Mn z M w ]O2

[0085] In the above chemical formula 1, 0.8≤a≤1.3, 0.8≤x<1, 0≤y≤0.2, 0≤z≤0.2, 0≤w≤0.2, x+y+z+w=1, and M is Zr, Al, B, Y, Ti, Nb, W, V, Cr, Mo, Ta, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc, or a combination thereof.

[0086] In the lithium metal oxide of Chemical Formula 1 above, lithium may be included in an amount corresponding to a, i.e., 0.8 ≤ a ≤ 1.3. 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.

[0087] In the lithium metal oxide of Chemical Formula 1 above, nickel may be included in an amount corresponding to x, i.e., 0.8≤x<1. When the nickel content satisfies the above range, it is possible to achieve a high capacity of the battery.

[0088] In the lithium metal oxide of Chemical Formula 1 above, cobalt may be included in an amount corresponding to y, i.e., 0 ≤ y ≤ 0.2. If the cobalt content is too low, grain size growth may be inhibited and output characteristics may be degraded. If the cobalt content is too high, manufacturing costs may increase and reversible capacity may decrease.

[0089] In the lithium metal oxide of Chemical Formula 1 above, manganese may be included in an amount corresponding to z, i.e., 0 ≤ z ≤ 0.2. 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.

[0090] In the lithium metal oxide of Chemical Formula 1 above, the other doping element M may be included in an amount corresponding to w, i.e., 0≤w≤0.2. In this case, M may be Zr, Al, B, Y, Ti, Nb, W, V, Cr, Mo, Ta, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc, or a combination thereof. The content of the doping element may be appropriately selected to achieve other doping effects.

[0092] 2. Method for manufacturing positive electrode active material

[0093] Various physical properties of the aforementioned positive electrode active material, including the degree of single particle size, can vary sharply depending on the calcination temperature and disintegration process conditions during the calcination process, and this can ultimately have a significant impact on the energy density, resistance characteristics, lifespan characteristics, and safety of the positive electrode active material. Below, a method for manufacturing a positive electrode active material for a lithium secondary battery according to another embodiment of the present invention will be described.

[0094] Another embodiment of the present invention provides a method for manufacturing a positive electrode active material for a lithium secondary battery, comprising the steps of: mixing a nickel (Ni)-containing metal precursor and a lithium raw material, and then calcining at a temperature of 740°C to 840°C to form a lithium metal oxide; desquashing the lithium metal oxide to form a desquashed material having an average particle size (D50) of 5 to 9 μm; finely crushing the desquashed material to form a lithium metal oxide in the form of a single particle having a single particle size of 50 to 75%; and forming a coating layer on the lithium metal oxide.

[0095] Hereinafter, a method for manufacturing a positive electrode active material for a lithium secondary battery according to another embodiment of the present invention will be described in detail step by step.

[0097] First, a nickel (Ni)-containing metal precursor and a lithium raw material are mixed, and then calcined at a temperature of 740°C to 840°C to form a lithium metal oxide.

[0098] The nickel (Ni)-containing metal precursor may be, more specifically, a nickel (Ni)-containing metal hydroxide.

[0099] The above metal precursor may be prepared by co-precipitating a metal-containing solution containing, for example, nickel raw material, manganese raw material, or cobalt raw material by adding a complexing agent-containing solution and a pH adjuster-containing solution.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] The above metal-containing solution may be prepared by adding a nickel raw material, a manganese raw material, or a cobalt 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).

[0104] 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.

[0105] The above pH-adjusting solution serves as a precipitating agent or a pH regulator 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 10 to 13.

[0106] 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 10 to 13.

[0107] By the above process, particles of nickel (or manganese-cobalt) 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.

[0108] At this time, the molar ratio of nickel, cobalt, or manganese in the precursor can be controlled by adjusting the concentration of the nickel raw material, the cobalt raw material, or the manganese raw material. That is, the concentrations of the nickel raw material, the cobalt raw material, and the manganese raw material can be controlled so that the molar ratio of nickel, cobalt, or manganese in the final product, the lithium metal oxide, falls within the range according to the present invention.

[0109] 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.

[0110] At this time, the above firing can be performed at a temperature of 740℃ to 840℃.

[0111] More specifically, the above firing can be performed as a high-temperature first-stage firing and a low-temperature second-stage firing within a single firing profile.

[0112] The above high-temperature first-stage firing can be performed at a temperature of 800 to 840°C, and the above low-temperature second-stage firing can be performed at a temperature of 740 to 800°C.

[0113] When the firing profiles of high-temperature first-stage firing and low-temperature second-stage firing, and the first-stage and second-stage firing temperatures, respectively satisfy the above ranges, the degree of single-particle formation of the anode active material, the average particle size (D50), and other physical properties can be more appropriately realized within the range according to the present invention. In particular, according to the present invention, good electrochemical performance can be secured by promoting single-particle formation of particles in high-temperature first-stage firing and stabilizing structural instability at high temperatures in low-temperature second-stage firing.

[0115] Next, the lithium metal oxide is desquashed to form a desquashed material having an average particle size (D50) of 5 to 9 μm.

[0116] Next, the above-mentioned deslicing material is further deslicing to form a single-particle lithium metal oxide having a single-particle degree of 50 to 75%.

[0117] The disintegration process according to the present invention is carried out by two-stage disintegration of crude disintegration and unreintegration as described above.

[0118] Through decomposition, weak bonds between primary particles can be broken, and the average particle size (D50) of the lithium metal oxide can be primarily controlled to the above range. When the average particle size (D50) of the lithium metal oxide is primarily controlled to the above range, the final average particle size (D50) of the lithium metal oxide through a subsequent decomposition process can be appropriately realized to the range according to the present invention.

[0119] Through undisintegration, strong bonds between primary particles can be disintegrated, so the degree of single particle formation of the positive electrode active material can be appropriately realized within the range according to the present invention, and the average particle size (D50) of the lithium metal oxide can be appropriately realized within the range according to the present invention.

[0120] Since strong bonds between primary particles cannot be broken by only decomposition, the degree of single particle formation of the positive active material cannot be improved to the range according to the present invention, and the average particle size (D50) of the positive active material cannot be reduced to the range according to the present invention.

[0121] Therefore, when the disintegration is performed as a two-stage disintegration of crude disintegration and microdisintegration, the degree of single particle size and average particle size (D50) of the positive electrode active material, as well as other physical properties, can be appropriately realized within the range according to the present invention.

[0122] At this time, the above-mentioned deliquescence can be performed at a stirring speed of 8,000 to 18,000 rpm, and more specifically, at a stirring speed of 16,000 to 18,000 rpm. If the stirring speed during deliquescence is too slow, the average particle size (D50) of the obtained deliquescence material may be obtained too large. If the stirring speed during deliquescence is too fast, the average particle size (D50) of the obtained deliquescence material may be obtained too small. This may reduce the deliquescence efficiency during the subsequent unreacted deliquescence process, and thus the degree of single particle formation of the cathode active material, the average particle size (D50), and other physical properties may deviate from the range according to the present invention.

[0123] In addition, the above-mentioned crushing can be performed at a crushing pressure of 1.5 to 3.5 bar, and more specifically, at a crushing pressure of 1.8 to 3.2 bar. When the crushing pressure during crushing satisfies the above range, the degree of single particle size and average particle size (D50) of the anode active material, as well as other physical properties, can be appropriately realized within the range according to the present invention.

[0124] The above-mentioned desalination can be performed, for example, by a rotor mill process.

[0125] The above-mentioned undissolved fragmentation can be performed, for example, by a jet mill process.

[0126] When the crude disintegration and microdisintegration processes are performed in the above process manner, crude disintegration, which breaks weak bonds between primary particles, and microdisintegration, which breaks strong bonds between primary particles, can be performed more easily. Accordingly, all physical properties, including the degree of single particle size and average particle size (D50) of the cathode active material, can be appropriately realized within the range according to the present invention. Furthermore, when microdisintegration is performed by a jet mill process, fine particles are filtered through a cyclone to a bag filter, and large particles are repeatedly crushed and collected, thereby minimizing the SPAN value based on the number of cathode active materials to the range according to the present invention.

[0128] If necessary, after the step of forming the lithium metal oxide in the form of a single particle, a step of classifying the lithium metal oxide may be further included.

[0129] At this time, through the above classification, large particles with a particle size exceeding 44 μm can be removed, and accordingly, the SPAN value based on the number of final products can be more easily realized within the range according to the present invention.

[0130] The above classification can be performed, for example, using an ultrasonic classifier.

[0131] In this case, the mesh size of the ultrasonic classifier may be 325 to 400 mesh, which can be converted to a size of 37 to 44 μm. When the mesh size of the ultrasonic classifier satisfies the above range, the removal of particles within the above particle size range can be implemented more easily.

[0133] Next, a coating layer is formed on the lithium metal oxide.

[0134] In this case, the coating layer according to the present invention may contain Co, Al, B, or a combination thereof. For a more preferred implementation of the lifespan characteristic improvement effect, the coating layer may contain all of Co, Al, and B.

[0135] More specifically, the coating layer may include a first coating layer containing Co and Al and a second coating layer located on the first coating layer and containing B. When the stacking structure relationship of the coating layers containing Co, Al, and B is as described above, the surface of the positive active material is stabilized, which may provide the advantage of obtaining a higher charge / discharge capacity and lifespan.

[0136] The above-described laminated coating layer can be obtained by forming a lithium metal oxide in the form of a single particle, then mixing the lithium metal oxide with a Co raw material and an Al raw material together, and then performing a first coating heat treatment to form a first coating layer, then mixing a B raw material, and then performing a second coating heat treatment to form a second coating layer.

[0137] The first coating heat treatment can be performed at a temperature of 620 to 720°C. When the temperature of the first coating heat treatment satisfies the above range, Co and Al coatings are efficiently formed, and the coating effect (improvement of life characteristics) can be more preferably realized.

[0138] The second coating heat treatment can be performed at a temperature of 250 to 350°C. When the second coating heat treatment temperature satisfies the above range, the B coating is efficiently formed, and the coating effect (effect of improving lifespan characteristics) can be more preferably realized.

[0139] The above Co coating raw material may be, for example, Co(OH)2.

[0140] The above Al raw material may be, for example, Al(OH)3.

[0141] The above B raw material may be, for example, B(OH)3.

[0142] When the Co raw material, Al raw material, and B raw material are each as described above, the coating is efficiently performed within the range of the first coating heat treatment temperature and the second coating heat treatment temperature, so that the effect of improving the lifespan characteristics of the anode active material can be more preferably realized.

[0144] By appropriately controlling the above series of active material manufacturing process conditions, the various physical properties of the obtained positive electrode active material, including the degree of single particle size and average particle size (D50), can be appropriately realized within the range according to the present invention. As a result, the energy density, resistance characteristics, lifespan characteristics, and safety of the positive electrode active material can be uniformly and excellently realized.

[0146] 3. Anodes and Lithium Secondary Batteries

[0147] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery comprising the aforementioned positive electrode active material.

[0148] More specifically, the anode may include an anode current collector and an anode active material layer disposed on the anode current collector and comprising the aforementioned anode active material.

[0149] The above positive current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the above positive current collector may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the positive current collector to increase the adhesion of the positive active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0150] The above positive active material layer may include a binder and / or a conductive material together with the aforementioned positive active material.

[0151] 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.

[0152] In addition, the conductive material is used to impart conductivity to the electrode, and in the battery being constructed, any material that possesses electronic conductivity without causing chemical changes may be used without any particular limitations. 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. 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 percent relative to the total weight of the positive electrode active material layer.

[0153] The above-mentioned anode can be manufactured according to a conventional anode manufacturing method, except for using the above-mentioned anode active material.

[0154] 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.

[0155] 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.

[0156] 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.

[0158] Another embodiment of the present invention provides a lithium secondary battery comprising a positive electrode for a lithium secondary battery as described above.

[0159] More specifically, the above lithium secondary battery may include a positive electrode; a negative electrode; a separator; and an electrolyte.

[0160] The above lithium secondary battery may optionally further include a battery container that accommodates the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

[0161] The above cathode may include a cathode current collector and a cathode active material layer located on the cathode current collector.

[0162] 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.

[0163] 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.

[0164] 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.

[0165] The binder and conductive material mentioned above may be the same as those previously described in the anode.

[0167] The above separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. It can be used without special restrictions as long as it is typically used as a separator in a lithium secondary battery, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte wettability. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and it may optionally be used in a single-layer or multi-layer structure.

[0169] The above electrolytes include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which can be used in the manufacture of lithium secondary batteries, but are not limited to these.

[0170] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0171] 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.

[0172] 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.

[0173] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, haloalkylene carbonate-based compounds like difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexamethylphosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1 to 5 weight% based on the total weight of the electrolyte.

[0174] As described above, since the lithium secondary battery containing the positive electrode active material 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).

[0175] Accordingly, another embodiment of the present invention provides a battery module comprising the lithium secondary battery as a unit cell and a battery pack comprising the same.

[0176] The above battery module or battery pack can be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0178] The embodiments of the present invention will be described in more detail below through examples. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited by the following examples.

[0180] Example 1

[0181] (1) Manufacturing of positive electrode active material

[0182] (Mixed) Ni 0.98 Co 0.01 Mn 0.01 A mixture was formed by mechanically mixing a precursor of (OH)2 composition and LiOHH2O in a mixer such that the molar ratio of lithium to the transition metal of the precursor (Li / M) was 1.02.

[0183] After (calcination), the above mixture was calcined in an oxygen atmosphere at a temperature of 825°C for 5 hours and at a temperature of 760°C for 8 hours to form lithium metal oxide.

[0184] After (decomposition), the lithium metal oxide was decomposed using a rotor mill at a stirring speed of 18,000 rpm to form a decomposed material. At this time, the average particle size (D50) of the obtained decomposed material was 6.8 μm.

[0185] After (undissolved), lithium metal oxide in the form of single particles was formed by dissolving the particles using a jet mill with a grinding pressure of 2 bar.

[0186] After (classification), the lithium metal oxide was classified using an ultrasonic classifier with a mesh size of 325 (44 μm) to remove particles with a particle size greater than 44 μm.

[0187] The composition of the obtained lithium metal oxide is LiNi 0.98 Co 0.01 Mn 0.01 It was O2.

[0188] After (coating), the obtained lithium metal oxide was mixed with Co(OH)2 and Al(OH)3, and then a first coating heat treatment was performed at a temperature of 660°C to form a first coating layer containing Co and Al. After that, the lithium metal oxide with the first coating layer formed was mixed with B(OH)3, and then a second coating heat treatment was performed at a temperature of 310°C to form a second coating layer containing B.

[0189] (2) Lithium secondary battery manufacturing

[0190] The slurry for electrode manufacturing was prepared by mixing the above-prepared cathode active material, conductive material (carbon black, Denka black), and binder (PVDF, KF9700) in a ratio of 95.0 : 2.0 : 3.0 wt%, and adding NMP (N-Methyl-2-pyrrolidone) to adjust the viscosity so that the solid content was approximately 60%. The prepared slurry was coated onto a 20 µm thick Al foil using a doctor blade and then dry-rolled. The electrode loading amount was 16.0 mg / cm². 2 It was, and the rolled density (25 ℃, 20 kN) was 3.5 g / cm³3 It was.

[0191] A coin cell was manufactured using an electrolyte of 1M LiPF6 in EC:DMC:DEC=1:2:1 (vol%) with 2.0 vol% of VC added relative to the total amount of the electrolyte, a PP separator, and a lithium anode (400 μm, Neba metal).

[0193] Example 2

[0194] A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the crushing step was performed at a grinding pressure of 3 bar.

[0196] Comparative Example 1

[0197] A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the unresolved crushing step was not performed and the unresolved crushed material was classified.

[0199] Comparative Example 2

[0200] A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the crushing step was performed at a grinding pressure of 1 bar.

[0202] Comparative Example 3

[0203] A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the crushing step was performed at a grinding pressure of 4 bar.

[0205] Comparative Example 4

[0206] A positive electrode active material and a lithium secondary battery were prepared in the same manner as in Example 1, except that the crushing step was performed at a grinding pressure of 5 bar.

[0208] Table 1 below summarizes the process conditions of the examples and comparative examples.

[0209] plasticity profile Seaweed processing Deliquescence stirring speed (rpm) Average particle size of deliquents (D50, μm) Classification process Undissolved process Classification process Undissolved crushing pressure (bar) Comparative Example 1 (825℃, 5h)-(760℃, 8h) rotor mill 18000 6.8 Ultrasonic classification - - - Comparative Example 2 (825℃5h)-(760℃8h) rotor mill 18000 6.8 - Jet Mill Ultrasonic classification 1 Example 1 (825℃5h)-(760℃8h) rotor mill 18000 6.8 - Jet Mill Ultrasonic classification 2 Example 2 (825℃5h)-(760℃8h) rotor mill 18000 6.8 - Jet Mill Ultrasonic classification 3 Comparative Example 3 (825℃5h)-(760℃8h) rotor mill 18000 6.8 - Jet Mill Ultrasonic classification 4 Comparative Example 4 (825℃5h)-(760℃8h) rotor mill 18000 6.8 - Jet Mill Ultrasonic classification 5

[0210] Tables 2 and 3 below summarize the results of the evaluation of the physical properties of the cathode active material and the electrochemical characteristics of the lithium secondary battery according to Experimental Example 2 and Experimental Example 3 described below.

[0211] Single-particle size (%) Tap density (g / cc) Differential generation rate (%) Residual lithium (ppm) Volume-based PSD Full Width at Half Maximum (FWHM, μm) Span value LiOH Li2CO3 Total Dmin D50 Dmax Volume basis Based on the number Comparative Example 1 41.3 2.011 2.17 1818 1175 2993 2.1 6.8 31.1 4.12 1.26 1.07 Comparative Example 2 41.4 2.037 2.18 1996 946 2942 2.1 5.1 18.5 2.92 0.97 0.86 Example 1 65.7 2.022 1.67 1982 653 2635 1.8 4.2 13.1 2.23 0.86 0.77 Example 2 73 2.007 1.99 2006 862 2868 1.5 3.7 11 1.91 0.82 0.77 Comparative Example 3 77.4 1.905 1.95 1889 1027 2916 1.3 3.4 11 1.83 0.81 0.84 Comparative Example 4 78.6 1.862 2.55 2124 1049 3173 0.9 3.1 9.3 1.83 0.83 0.98

[0212] Initial charging capacity (mAh / g) Initial discharge capacity (mAh / g) Initial efficiency (%) Room temperature resistance (Ω) Energy density (Wh / L) Lifespan characteristics (%) Comparative Example 1 251 218.3 87.00% 38.5 1701 92.70% Comparative Example 2 253.3 220.5 87.00% 38 1740 93.10% Example 1 252.6 220 87.10% 37.1 1723 94.10% Example 2 253.5 220.5 87.00% 36.8 1715 94.20% Comparative Example 3 253.7 221.5 87.30% 37.3 1635 94.40% Comparative Example 4 252.8 221.1 87.40% 36.3 1594 94.70%

[0214] Experimental Example 1: Evaluation of SEM Images of Anode Active Material

[0215] Scanning electron microscope (SEM) images of the positive electrode active materials prepared according to Examples 1 to 2 and Comparative Examples 1 to 4 were evaluated and are shown in Figures 1 to 6, respectively.

[0216] Referring to FIGS. 1 to 6, it was confirmed that the positive active materials of the examples and comparative examples exhibited a single-particle form.

[0218] Experimental Example 2: Evaluation of Physical Properties of Anode Active Material

[0219] (1) Single-particle magnetization

[0220] When the cathode active material powder was observed with a SEM image at 5000x magnification, the ratio (%) of the number of single particles consisting of 1 to 3 primary particles among the total number of cathode active material particles was measured and evaluated. The number of primary particles within the cathode active material particles refers to the number of primary particles observed visually in the SEM image, which is a two-dimensional image, rather than the actual number of primary particles within the cathode active material particles in three dimensions.

[0221] (2) Differential generation rate (4.52 tonf / cm²) 2 Generation rate of fine particles with a diameter of 1.0 μm or less upon application of pressure)

[0222] After placing 3.0 g of positive active material powder into a mold with a radius of 0.65 cm, a force of 6.0 tons was applied using a Carver Press machine, and the volume percentage of fine particles with a particle size of 1.0 μm or less was measured using a particle size analyzer to evaluate the fine particle generation rate.

[0223] (3) Tap density

[0224] Tap density was measured using the Micromeritics Geopyc1365 instrument. Specifically, 10g of cathode active material powder was placed into a cylinder with a diameter of 19.1mm, and the tap density was determined by applying a force of 108N and measuring the height of the cylinder.

[0225] (4) Residual lithium

[0226] 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 filtering device. Subsequently, the residual lithium was evaluated by measuring the extract through neutralization titration using a Metrohm potentiometer.

[0227] (5) Particle size related properties

[0228] For the active material powder, the volume-based particle size (Dmin), particle size (D50), particle size (Dmax), full width at half maximum (FWHM) on the volume-based particle size distribution curve, volume-based SPAN value, and number-based SPAN value were evaluated using the laser diffraction method. At this time, the SPAN value was derived by calculating [particle size (D90) - particle size (D10)] / particle size (D50).

[0230] Experimental Example 3: Evaluation of Electrochemical Characteristics of Lithium Secondary Battery

[0231] (1) Evaluation of initial capacity and initial efficiency

[0232] After fabricating a lithium secondary battery half cell, it was aged at 25°C for 10 hours, and then a charge-discharge test was performed at 25°C. To evaluate the initial capacity, the reference capacity was set to 200 mAh / g, and the battery was charged to 4.25V with a constant current of 0.2C. Then, the voltage was switched to a constant voltage, and charging continued until the terminal current reached 0.005C. After a rest time of 20 minutes following charging, the battery was discharged until it reached 2.5V with a constant current of 0.2C and a reference capacity of 200 mAh / g.

[0233] (2) Evaluation of room temperature resistance characteristics

[0234] After fabricating a lithium secondary battery half cell, it was charged to 4.25V at 25℃ with a constant current of 0.2C, then switched to a constant voltage and charged until the termination current reached 0.005C. After a rest time of 20 minutes following charging, discharge was performed with a constant current of 0.2C. At this time, the impedance was measured after 1 minute had passed since discharge to evaluate the resistance characteristics.

[0235] (3) Energy density evaluation

[0236] After fabricating a lithium secondary battery half cell, it was charged to 4.25V at 25℃ with a constant current of 0.2C, then switched to a constant voltage and charged until the termination current reached 0.005C. After a rest time of 20 minutes following charging, it was discharged with a constant current of 0.2C. At this time, the energy density was evaluated by dividing the value obtained by multiplying the discharge capacity by the average voltage by the tap density measurement value.

[0237] (4) High-temperature life characteristics evaluation (45℃, 50 cycles)

[0238] After fabricating a lithium secondary battery half cell, it was charged to 4.25V at 45℃ with a constant current of 0.5C, then switched to a constant voltage and charged until the termination current reached 0.05C. After a rest time of 20 minutes following charging, it 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.

[0240] Referring to Tables 1 to 3, in the case of Examples 1 and 2, where the general process conditions, such as the calcination temperature and process conditions during decomposition and non-decomposition, were controlled within the range according to the present invention, it was confirmed that the general physical properties, including the degree of single particle size, tap density, and volume-based average particle size (D50) of the cathode active material, were appropriately realized within the range according to the present invention. As a result, it was confirmed that the resistance characteristics, energy density, lifespan characteristics, and safety of the lithium secondary battery were all excellently realized. The effect of improving the safety of the lithium secondary battery can be confirmed by the fact that the fine particle generation rate of the cathode active material is sufficiently low.

[0241] On the other hand, in the case of Comparative Example 1, as a result of not performing the pulverization process, it was confirmed that the degree of single particle size of the cathode active material was too small, the fine particle generation rate was too high, the residual lithium content increased slightly, and the volume-based average particle size (D50), volume-based full width at half maximum (FWHM), and number-based SPAN value were obtained too large. Furthermore, it was confirmed that the resistance characteristics, energy density, and lifespan characteristics of the lithium secondary battery deteriorated compared to the example. Meanwhile, a decrease in the safety of the battery was predicted due to the high fine particle generation rate of the cathode active material.

[0242] In the case of Comparative Example 2, as a result of the grinding pressure being too low during non-disintegration, it was confirmed that the degree of single particle size of the cathode active material was too low, the fine particle generation rate was too high, and the volume-based average particle size (D50), volume-based full width at half maximum (FWHM), and number-based span value were obtained too large. Furthermore, it was confirmed that the resistance characteristics and lifespan characteristics of the lithium secondary battery deteriorated compared to the example. A decrease in the safety of the battery was predicted due to the high fine particle generation rate of the cathode active material.

[0243] In the case of Comparative Examples 3 and 4, as a result of the grinding pressure being too high during non-disintegration, it was confirmed that the degree of single particle size of the cathode active material was too small, the tap density was small, the volume-based average particle size (D50) and volume-based full width at half maximum (FWHM) were small, and the number-based SPAN value was too large. Furthermore, it was confirmed that the energy density of the lithium secondary battery was significantly degraded compared to the examples. Meanwhile, in the case of Comparative Example 4, in addition to this, it was confirmed that the fine particle generation rate and residual lithium were too high. Through this, a decrease in the safety of the battery was predicted.

[0245] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention.

[0246] Therefore, the substantive scope of the present invention shall be defined by the appended claims and their equivalents.

Claims

Claim 1 It comprises lithium metal oxide particles having a single-particle nickel (Ni)-containing layered crystal structure and a coating layer located on the surface of said lithium metal oxide particles, wherein the coating layer comprises a first coating layer containing Co and Al and a second coating layer located on said first coating layer containing B, the degree of single particle size is 50 to 75%, and 4.52 tonf / cm² 2 A positive electrode active material for a lithium secondary battery having a fine particle generation rate of 2.1% or less with a particle size of 1.0 μm or less when pressure is applied, a volume-based average particle size (D50) of 3.5 to 4.8 μm, and a tap density of 2.0 g / cc or more. Claim 2 delete Claim 3 A positive electrode active material for a lithium secondary battery according to claim 1, which exhibits a unimodal distribution when analyzing the volume-based particle size distribution curve and has a full width at half maximum (FWHM) of 1.86 to 2.7 μm. Claim 4 A positive electrode active material for a lithium secondary battery having a number-based SPAN value of 0.8 or less, according to claim 1. Claim 5 delete Claim 6 A positive electrode active material for a lithium secondary battery having a residual lithium content of 2,900 ppm or less, according to claim 1. Claim 7 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the nickel content in the lithium metal oxide is 80 mol% or more based on the total molar amount of metal excluding lithium. Claim 8 delete Claim 9 delete Claim 10 In claim 1, the lithium 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 Mn z M w ]O2 In the above chemical formula 1, 0.8≤a≤1.3, 0.8≤x<1, 0≤y≤0.2, 0≤z≤0.2, 0≤w≤0.2, x+y+z+w=1, and M is Zr, Al, B, Y, Ti, Nb, W, V, Cr, Mo, Ta, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof. Claim 11 A method for manufacturing a positive electrode active material for a lithium secondary battery, comprising the steps of: mixing a nickel (Ni)-containing metal precursor and a lithium raw material, and then calcining to form a lithium metal oxide; desquashing the lithium metal oxide using a rotor mill to form a desquashing material having an average particle size (D50) of 5 to 9 μm; finely crushing the desquashing material using a jet mill at a grinding pressure of 1.5 to 3.5 bar to form a lithium metal oxide in the form of single particles having a single particle size of 50 to 75%; and forming a coating layer on the lithium metal oxide, wherein the calcination is performed as a high-temperature first-stage calcination at a temperature of 800 to 840°C and a low-temperature second-stage calcination at a temperature of 740 to 800°C within a single calcination profile. Claim 12 In claim 11, the above-mentioned desiccant is a method for manufacturing a positive electrode active material for a lithium secondary battery, wherein the desiccant is performed at a stirring speed of 8,000 to 18,000 rpm. Claim 13 delete Claim 14 delete Claim 15 A method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 11, further comprising the step of classifying the lithium metal oxide after the step of forming the lithium metal oxide in the form of a single particle. Claim 16 A method for manufacturing an anode active material according to claim 15, wherein large particles with a particle size exceeding 44 μm are removed through the above classification. Claim 17 A positive electrode for a lithium secondary battery comprising the positive electrode active material of claim 1. Claim 18 A lithium secondary battery comprising a positive electrode for a lithium secondary battery according to claim 17.

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