Positive electrode active material and lithium secondary battery using the same

Abstract

The present specification relates to a method for manufacturing a positive electrode active material for a lithium secondary battery, and more specifically, to a positive electrode active material for a lithium secondary battery having excellent electrical conductivity and energy density, a method for manufacturing the same, a positive electrode including the same, and a secondary battery.

Description

Technology Field

[0001] This specification relates to a method for manufacturing a positive electrode active material for a lithium secondary battery, and more specifically, to a method for manufacturing a positive electrode active material for a lithium secondary battery having excellent electrical conductivity and energy density. Background Technology

[0003] A battery stores electrical power by using materials capable of electrochemical reactions at the positive and negative electrodes. A representative example of such a battery is the lithium secondary battery, which stores electrical energy based on the difference in chemical potential when lithium ions intercalate or deintercalate at the positive and negative electrodes.

[0004] The above lithium secondary battery is manufactured by using materials capable of reversible intercalation / deintercalation of lithium ions as positive and negative active materials, and by filling an organic electrolyte or a polymer electrolyte between the positive and negative electrodes.

[0005] Various materials are used as cathode active materials for lithium secondary batteries, and among them, lithium metal phosphates, such as lithium iron phosphate (LiFePO4), are widely used in the manufacture of lithium secondary batteries because they possess excellent stability and the ability to withstand many charge / discharge cycles while having relatively low manufacturing costs.

[0006] However, lithium iron phosphate has the disadvantage of low ionic conductivity and electrical conductivity because, due to its olivine crystal structure, lithium ions can only diffuse in one dimension. Accordingly, there have been technical attempts to improve this by nano-sizing lithium iron phosphate particles and coating them with carbon.

[0007] However, nanoscaled lithium iron phosphate tends to aggregate easily due to intermolecular forces and grow into shapes that are unfavorable to energy density.

[0008] In addition, the carbon coating reduces the fluidity of lithium iron phosphate particles, which leads to a decrease in the density of the cathode active material.

[0009] As technology advances and the demand for lithium-ion batteries, including electric vehicles, increases rapidly, there is a growing need within related industries to increase the capacity of lithium-ion batteries, which is directly related to product usage time. The problem to be solved

[0011] In the lithium secondary battery market, while the growth of lithium secondary batteries for electric vehicles is acting as a driving force, the demand for cathode active materials used in lithium secondary batteries is also continuously changing, and in particular, the demand for increased cathode active material capacity is gradually growing.

[0012] In order to meet these market demands, the present specification aims to provide a method for manufacturing a positive electrode active material that has a bimodal particle size distribution including subatomic particles and alleles and is advantageous in terms of energy density.

[0013] In addition, the present specification aims to provide a positive electrode comprising a positive electrode active material manufactured according to the manufacturing method defined herein.

[0014] In addition, the present specification provides a lithium secondary battery using a positive electrode as defined herein. means of solving the problem

[0016] According to one aspect of the present specification, a positive electrode active material for a lithium secondary battery is provided, comprising a lithium composite compound capable of intercalation / deintercalation of lithium, wherein the lithium composite compound comprises a plurality of particulate materials, and the particulate materials have a bimodal particle size distribution comprising a first lithium composite compound that is a fine particle and a second lithium composite compound that is an allotrope, and at least some of the particulate materials have an amorphous carbon coating layer with a thickness of 1 to 500 nm formed on at least some of the surface.

[0017] Meanwhile, the particle size distribution of the above particulate matter may have a fine particle peak in the range of 1.0 μm or less and a large particle peak in the range of 1.5 to 5.0 μm.

[0018] Here, the difference between the center points of the subatomic peak and the allele peak may be 1.8 to 4.5 μm.

[0019] In addition, the proportion of fine particles with a particle size of 1.0 μm or less among the particulate matter may be 10 to 50 volume%, and the proportion of large particles with a particle size of 1.5 to 5.0 μm among the particulate matter may be 50 to 90 volume%.

[0020] In particular, the volume ratio of elementary particles and conglomerates among the above particulate matter may be 0.1 to 0.5:1.

[0021] Meanwhile, the above-mentioned positive active material may have a compressed density of 2.35 to 2.65 g / cc and an energy density of 1,300 to 1,400 Wh / L.

[0022] In one embodiment, the lithium complex compound may be represented by the following chemical formula 1:

[0023] [Chemical Formula 1]

[0024] Li p M x A y A' z P 1-z O w

[0025] In the above formula, M is at least one selected from the group consisting of Fe, Mn, Ni, and Co; A is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Cr, Cu, Ga, Hf, In, K, La, Mg, Mo, Na, Nb, Nd, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr; A' is at least one selected from the group consisting of C, Si, S, N, B, F, Cl, and I; and 0.5≤p≤1.5, 0 <x≤1, 0≤y<1, 0≤z<1, 0<w≤4, x+y=1이다.

[0026] According to another aspect of the present specification, a method for manufacturing a positive electrode active material for a lithium secondary battery is provided, comprising: (a) mixing a lithium-containing raw material, a transition metal precursor, and a carbon-based compound to prepare a slurry; (b) grinding particles in the slurry such that the average particle size (D50) is 0.5 to 0.7 μm; and (c) heat-treating the ground particles to obtain a bimodal lithium composite compound.

[0027] In one embodiment, the ratio of the number of atoms of lithium (Li) to the total number of atoms of metal elements other than lithium (Metal) in the slurry of step (a) (Li / Metal) may be 0.90 to 1.10.

[0028] Meanwhile, the ratio of the number of carbon atoms (C) to the total number of metal atoms other than lithium (Metal) in the slurry of step (a) above (C / Metal) may be 0.30 to 0.70.

[0029] In addition, at least one sub-raw material comprising an element selected from Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, F, Fe, Ga, Hf, I, In, K, La, Mg, Mo, N, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Si, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn and Zr may be additionally added to the slurry in step (a).

[0030] In one example, step (b) above may be performed in a milling machine containing beads of size 0.1 to 1.5 mm.

[0031] According to another aspect, a positive electrode comprising the above positive active material is provided.

[0032] According to another aspect, a lithium secondary battery using the above positive electrode is provided. Effects of the invention

[0034] According to the present specification, when manufacturing a lithium composite compound through the calcination of raw materials, a bimodal cathode active material containing both small particles and alleles can be manufactured in a single synthesis process.

[0035] In addition, when manufacturing the above-mentioned positive active material, both large and small particles can be formed at the same calcination temperature, so a uniform carbon-based coating layer can be formed with a minimum amount of carbon-based compounds.

[0036] Accordingly, the above-mentioned positive active material has a high press density and can have excellent energy density.

[0037] In addition to the effects described above, the specific effects of this specification are described together with the specific details for implementing the matters described in this specification below. Brief explanation of the drawing

[0039] FIG. 1 is an SEM image of a positive electrode active material manufactured according to one example of the present specification. Specific details for implementing the invention

[0040] For convenience of understanding this specification, specific terms are defined herein. Unless otherwise defined herein, scientific and technical terms used herein shall have the meanings generally understood by those skilled in the art. Furthermore, unless specifically indicated in the context, terms in their singular form shall be understood to include their plural form, and terms in their plural form shall be understood to include their singular form.

[0042] Hereinafter, a positive electrode active material for a lithium secondary battery according to the present specification, a method for manufacturing the same, a positive electrode including the positive electrode active material, and a lithium secondary battery using the positive electrode will be described in more detail.

[0044] Cathode active material for lithium secondary batteries

[0045] A positive electrode active material for a lithium secondary battery according to one aspect of the present specification is a positive electrode active material comprising a lithium composite compound capable of intercalation / deintercalation of lithium, wherein the lithium composite compound comprises a plurality of particulate materials, and the particulate materials have a bimodal particle size distribution comprising a first lithium composite compound that is a fine particle and a second lithium composite compound that is an allotrope, and at least some of the particulate materials may have an amorphous carbon coating layer with a thickness of 1 to 500 nm formed on at least some of the surface.

[0046] The above positive electrode active material may include a particulate material composed of a lithium complex compound capable of lithium intercalation / deintercalation.

[0047] The above particulate material includes lithium composite compounds with different particle sizes and may exist without forming any distinct aggregates. In this case, the above particulate material may have a spherical shape. Furthermore, since the lithium composite compound is a particulate material having a smooth surface, the above positive active material may have excellent compressive density.

[0048] Here, the average particle size of the particulate material (wherein the average particle size of the particulate material may be the average major axis length of the particulate material) exists within the range of 0.4 to 5.0 μm, thereby enabling the realization of the optimal density of the anode manufactured using the anode active material according to various embodiments.

[0049] Meanwhile, the above particulate material may have a bimodal particle size distribution including a first lithium complex compound which is a subatomic particle and a second lithium complex compound which is an allotrope.

[0050] In this case, as the voids between the alleles can be filled by subatomic particles with a relatively small average particle size, the integration density of the lithium complex compound within a unit volume is improved, thereby increasing the energy density per unit volume.

[0051] Here, the fine particles may refer to particulate matter having a particle size of 1.0 μm or less, for example, 1.0 μm, 0.95 μm, 0.9 μm, 0.85 μm, 0.8 μm, 0.75 μm, 0.7 μm, 0.65 μm, 0.6 μm, 0.55 μm, 0.5 μm, 0.45 μm, 0.4 μm, or a range between two of these values.

[0052] Meanwhile, the above-mentioned coarse has a particle size of 1.5 to 5.0 μm, for example, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4.0 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, 4.6 μm, It may refer to particulate matter with a size of 4.7 µm, 4.8 µm, 4.9 µm, 5.0 µm, or a range between two of these values.

[0053] The above-described lithium composite compound may include materials with particle sizes outside the aforementioned range, but must include peaks in the particle size distribution at least within the particle size ranges of the aforementioned alleles and the above-described subparticles. Here, a peak refers to a maximum point in the particle size distribution.

[0054] That is, in one example, the particulate material may have a small particle peak in the range of 1.0 μm or less and a large particle peak in the range of 1.5 to 5.0 μm.

[0055] In addition, in one example, the particulate matter may not only include peaks in the above range of elementary and alleles, but the majority of the particulate matter (e.g., 90 volume% or more) may all fall within the above range.

[0056] Meanwhile, the difference between the center points of the above-mentioned particle peak and the above-mentioned allele peak, i.e., the two maximum points, may be 1.8 to 4.5 μm, for example, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4.0 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, or a range between two of these values.

[0057] If the distance between the above-mentioned subatomic peak and the allele peak satisfies the above range, a positive electrode active material with even better compression density can be obtained.

[0058] The above nanoscaled subatomic particle is Li + The capacity of the cathode active material can be improved by shortening the diffusion distance. However, nano-sized particles can increase the specific surface area of ​​the lithium composite compound, which may cause a decrease in the density of the cathode active material. However, unnecessary dark pores caused by the high specific surface area of ​​the nano-sized particles can be minimized by mixing them with covalent particles.

[0059] In addition, conventional nano-sized particles grow into angular shapes during calcination due to aggregation, resulting in poor flowability; however, since the first lithium composite compound is a spherical particle with excellent flowability, the positive electrode active material can have a high compression density.

[0060] In addition, the proportion of fine particles with a particle size of 1.0 μm or less among the particulate matter may be 10 to 50 volume%, and the proportion of coarse particles with a particle size of 1.5 to 5.0 μm among the particulate matter may be 50 to 90 volume%. In one example, the proportion of fine particles may be 10 volume%, 12.5 volume%, 15 volume%, 17.5 volume%, 20 volume%, 22.5 volume%, 25 volume%, 27.5 volume%, 30 volume%, 32.5 volume%, 35 volume%, 37.5 volume%, 40 volume%, 42.5 volume%, 45 volume%, 47.5 volume%, 50 volume%, or a range between two of these values. Meanwhile, the proportion of the above alleles may be 50 volume%, 52.5 volume%, 55 volume%, 57.5 volume%, 60 volume%, 62.5 volume%, 65 volume%, 67.5 volume%, 70 volume%, 72.5 volume%, 75 volume%, 77.5 volume%, 80 volume%, 82.5 volume%, 85 volume%, 87.5 volume%, 90 volume%, or a range between two of these values.

[0061] If the ratio of subatomic particles to alleles falls within the range mentioned above, the compressive strength of the positive electrode active material can be further increased.

[0062] This means that relatively bulky alleles occupy most of the volume, while elementary particles are located in the spaces between the alleles, thereby minimizing unnecessary voids.

[0063] In particular, the volume ratio of elementary particles and conglomerates among the above particulate matter may be 0.1 to 0.5:1.

[0064] If the above conditions are satisfied, the subatomic particles can fill the voids between alleles while simultaneously minimizing aggregation among them. As a result, the cathode active material can have high compression density and excellent conductivity.

[0065] Meanwhile, the above-mentioned positive active material may have a compressed density of 2.35 to 2.65 g / cc and an energy density of 1,300 to 1,400 Wh / L.

[0066] The above-mentioned cathode active material has a compressed density, for example, 2.35 g / cc, 2.36 g / cc, 2.37 g / cc, 2.38 g / cc, 2.39 g / cc, 2.4 g / cc, 2.41 g / cc, 2.42 g / cc, 2.43 g / cc, 2.44 g / cc, 2.45 g / cc, 2.46 g / cc, 2.47 g / cc, 2.48 g / cc, 2.49 g / cc, 2.5 g / cc, 2.51 g / cc, 2.52 g / cc, 2.53 g / cc, 2.54 g / cc, 2.55 g / cc, 2.56 g / cc, 2.57 g / cc, 2.58 g / cc, 2.59 g / cc, 2.6 g / cc, It may be 2.61 g / cc, 2.62 g / cc, 2.63 g / cc, 2.64 g / cc, 2.65 g / cc, or a range between two of these values, or 2.65 g / cc or higher.

[0067] The above-mentioned cathode active material has an energy density of, for example, 1,300 Wh / L, 1,305 Wh / L, 1,310 Wh / L, 1,315 Wh / L, 1,320 Wh / L, 1,325 Wh / L, 1,330 Wh / L, 1,335 Wh / L, 1,340 Wh / L, 1,345 Wh / L, 1,350 Wh / L, 1,355 Wh / L, 1,360 Wh / L, 1,365 Wh / L, 1,370 Wh / L, 1,375 Wh / L, 1,380 Wh / L, 1,385 Wh / L, 1,390 Wh / L, 1,395 Wh / L, 1,400 Wh / L, or two of these. The value may be in the range between 1,400 Wh / L or higher.

[0068] As described above, the positive electrode active material has a uniform and smooth surface and can have a high compression density by including a lithium composite compound having a uniform spherical particle shape in a bimodal particle size distribution.

[0069] At the same time, the above positive active material minimizes the decrease in conductivity between each particulate material so that the energy density can satisfy the above range.

[0070] In conventional cathode active materials, mixing microparticles and coarse particles can improve compressive density, but energy density tends to decrease due to reduced conductivity. For example, including coarse particles with excessively large particle sizes leads to reduced conductivity and a tendency for capacity to decrease. Furthermore, while nanoparticles can improve conductivity, they lower the density of the cathode active material, which may result in insufficient energy density.

[0071] In one example, the lithium complex compound can be represented by the following chemical formula 1.

[0072] [Chemical Formula 1]

[0073] Li p M x A y A' z P 1-z O w

[0074] In the above formula, M is at least one selected from the group consisting of Fe, Mn, Ni, and Co; A is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Cr, Cu, Ga, Hf, In, K, La, Mg, Mo, Na, Nb, Nd, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr; A' is at least one selected from the group consisting of C, Si, S, N, B, F, Cl, and I; and 0.5≤p≤1.5, 0 <x≤1, 0≤y<1, 0≤z<1, 0<w≤4, x+y=1이다.

[0075] The above chemical formula 1 represents a lithium complex compound capable of intercalation / deintercalation of lithium, and may include lithium, a metal, and a phosphate.

[0076] For example, the above p may be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, or a range between two of these values, but is not limited thereto.

[0077] Meanwhile, the above x may include 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or a range between two of these values. In one example, the above x may be 0.5 or greater, but is not limited thereto.

[0078] In addition, the above y and z may each be 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.99, or include a range between two of these values, but are not limited thereto.

[0079] That is, LiFePO4, etc. can be represented by the above chemical formula 1. Meanwhile, the above lithium complex compound may further include a dopant. Here, the dopant may be represented as A and / or A'.

[0080] The composition of the above lithium composite compound may vary depending on the composition of the raw material used in manufacturing and the type and composition of the sub-raw material additionally used therein.

[0081] Meanwhile, since the first lithium complex compound, which is a subatomic particle, and the second lithium complex compound, which is an allotrope, are manufactured simultaneously within a single calcination process, they may have the same components.

[0082] That is, both the first lithium complex compound and the second lithium complex compound can be represented by the chemical formula 1.

[0083] However, even if manufactured in the same calcination process, the ratio between each component may vary because the degree of crystal growth differs.

[0084] Nevertheless, in one example, the first lithium complex compound and the second lithium complex compound may have the same composition, but are not limited thereto.

[0085] In addition, the positive active material may include a coating layer that covers at least a portion of the particulate material.

[0086] It is known that the amorphous carbon coating layer of a conventional positive electrode active material causes a decrease in the density of the positive electrode active material. However, the amorphous carbon coating layer coated on the particulate material can induce a uniform particle surface, thereby minimizing the decrease in the density of the positive electrode active material.

[0087] Here, the coating layer may include a carbon layer and / or an oxide layer to improve the stability of the particulate material or to improve conductivity.

[0088] For example, the coating layer may exist to cover at least a portion of the exposed surface of the particulate material.

[0089] Accordingly, the coating layer may exist as a layer that coats the surface of the particulate material continuously or discontinuously. If the coating layer exists discontinuously, it may exist in the form of an island.

[0090] The coating layer existing in this way can contribute to improving the electrochemical properties and stability of the positive electrode active material.

[0091] In particular, it is known that lithium iron phosphate-based cathode active materials, which have low electrical conductivity, can compensate for this through a carbon coating. The carbon coating layer exists in an amorphous state and can serve as a pathway for electrons.

[0092] Furthermore, the carbon coating layer can be uniformly formed on the surface of the lithium composite compound, which is a particulate material, to have a smooth surface texture. As a result, the compression density of the positive electrode active material can be increased.

[0093] However, a non-uniform carbon coating layer can form an amorphous matrix on the surface of particulate matter, which can degrade characteristics such as the BET specific surface area, compressive density, and energy capacity of the cathode active material.

[0094] Conventionally, it was necessary to apply separate process conditions for the manufacture of coarse particulate materials. Therefore, to manufacture a bimodal cathode active material containing a homogeneous carbon coating layer, it was necessary to manufacture small particles and coarse particles separately, mix them, and then perform an additional carbon coating. Alternatively, small particle precursors and coarse precursors were manufactured separately, mixed, calcined, and then carbon coated. As a result, carbon under the same conditions was coated onto small particles / coarse particles or small particle precursors / coarse precursors with different surface states, leading to the formation of a non-uniform coating layer.

[0095] On the other hand, the above-mentioned positive active material, which is manufactured in a bimodal form according to local overgrowth, is synthesized from a single raw material and composed of the same components, and the carbon coating layer formed by controlling the surface to be coated is uniform.

[0096] Here, the thickness of the amorphous carbon coating layer formed on the surface of at least some of the particulate composition may be 1 to 500 nm, for example, 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, 8.5 nm, 9 nm, 9.5 nm, 10 nm, 12.5 nm, 15 nm, 17.5 nm, 20 nm, 22.5 nm, 25 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or a range between two of these values.

[0097] Here, the thickness of the carbon coating layer can be controlled according to the balance of fluidity and conductivity of the lithium composite compound.

[0098] In particular, the carbon coating layer has a small thickness variation, so the positive electrode active material can have excellent balance of fluidity and conductivity, which are in a complementary relationship.

[0099] Various known methods can be used to measure the thickness of the carbon coating layer. For example, it can be measured from TEM or SEM images, or determined from the results of line scanning of carbon in a specific direction from EDX analysis results. Such thickness may be the average value obtained after measuring at least three times.

[0100] Meanwhile, even if the coating layer on the surface of the first lithium composite compound and the coating layer on the surface of the second lithium composite compound are formed in the same firing process, the thickness of the coating layer may differ because the size of the particulate material being coated is different. However, depending on the conditions, the thickness of each coating layer may be the same.

[0101] In one example, the content of the carbon coating layer may be 0.5 to 5.0 wt% based on the total weight of the lithium composite compound, for example, 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, 3.5 wt%, 4.0 wt%, 4.5 wt%, 5.0 wt%, or a range between two of these values.

[0102] In one example, since the carbon coating layer is formed in the same process, the carbon content of the positive active material may be 1.0 to 2.0 weight percent, but is not limited thereto.

[0103] If the above-mentioned positive active material has a carbon content within the above range, the decrease in density can be suppressed while improving conductivity.

[0104] When the carbon content of the surface coating layer of the conventional positive electrode active material is in the low range as described above, the surface becomes non-uniform, resulting in reduced density and insufficient improvement in conductivity.

[0105] On the other hand, the above-mentioned positive active material can form a uniform coating layer on both small particles and large particles by utilizing local overgrowth.

[0106] Meanwhile, a compound represented by the following chemical formula 2 may be present on at least a portion of the surface of at least some of the particulate matter:

[0107] [Chemical Formula 2]

[0108] Li a M' b O c

[0109] In the above chemical formula, M' is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Hf, In, K, La, Mg, Mn, Mo, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr, and 0≤a≤10, 0 <b≤8, 2≤c≤13이다.

[0110] The compound represented by Chemical Formula 2 above may exist separately from the amorphous carbon coating layer, or may exist as a discontinuous phase within the continuous phase of the amorphous carbon coating layer.

[0111] In one example, the compound represented by the above chemical formula 2 can form a coating layer. The coating layer can coat at least a portion of the surface of the particulate material continuously or discontinuously, and if the coating layer exists discontinuously, it may exist in the form of an island.

[0112] In addition, the coating layer may exist in the form of a solid solution that does not form a boundary with the particulate material, but is not necessarily so.

[0113] Meanwhile, even if a coating layer of the compound is present on at least a portion of the surface of the particulate material, it is desirable for the particulate material to maintain a spherical shape.

[0115] Method for manufacturing a positive electrode active material for a lithium secondary battery

[0116] A method for manufacturing a positive electrode active material for a lithium secondary battery according to one aspect may include: (a) a step of preparing a slurry by mixing a lithium-containing raw material, a transition metal precursor, and a carbon-based compound; (b) a step of grinding particles in the slurry so that the average particle size (D50) is 0.5 to 0.7 μm; and (c) a step of heat-treating the ground particles to obtain a bimodal lithium composite compound.

[0117] Step (a) above is a step of preparing an aqueous solution slurry by mixing raw materials for manufacturing a lithium composite compound in water. Here, the lithium composite compound includes lithium composite phosphate, lithium composite oxide, etc.

[0118] The lithium-containing raw material used in step (a) above is intended to form a lithium composite compound used as a positive electrode active material, and lithium hydroxide, lithium carbonate, lithium nitrate, lithium phosphate, lithium fluoride, or lithium acetate may be used.

[0119] Here, the lithium compound may be mixed such that the ratio of the number of atoms of lithium (Li) to the total number of atoms of metal elements other than lithium (Metal) in the slurry (Li / Metal) is in the range of 0.90 to 1.10, for example, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, or a range between two of these values. Alternatively, depending on the purpose, the ratio (Li / Metal) may be mixed such that it is in the range of 0.5 to 1.5, but is not limited thereto.

[0120] Meanwhile, the above transition metal precursor is a precursor material for a lithium complex compound containing one or more transition metal elements, and can form a lithium complex compound by reacting with a lithium-containing raw material.

[0121] The above transition metal precursor may include at least one transition metal such as iron, manganese, nickel, cobalt, vanadium, titanium, chromium, copper, zinc, etc., and at least one of elements such as phosphorus, oxygen, hydrogen, carbon, silicon, sulfur, nitrogen, boron, fluorine, chlorine, iodine, etc.

[0122] Meanwhile, the above transition metal precursor may include at least one transition metal and an anion.

[0123] Optionally, the transition metal precursor may be doped with a heterogeneous element. Here, the heterogeneous element may be at least one selected from Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, F, Fe, Ga, Hf, I, In, K, La, Mg, Mo, N, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Si, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr.

[0124] As an example, the transition metal precursor may be an iron complex hydroxide or iron complex oxide containing iron, or an iron complex phosphate containing iron and phosphorus, etc. For example, an iron complex hydroxide precursor can be prepared through a synthesis reaction in an aqueous solution containing iron raw materials.

[0125] As an example, an iron complex hydroxide precursor can be prepared by stirring an aqueous solution containing an iron raw material, a phosphorus raw material, and an oxidizing agent, and adding a basic aqueous solution dropwise.

[0126] Here, the input amounts of the iron raw material, phosphorus raw material, and oxidizing agent may vary depending on the composition of the desired cathode active material. For example, when manufacturing LiFePO4, the iron raw material, phosphorus raw material, and oxidizing agent may be added such that the difference in input amounts between them is 20% or less on a molar basis, but is not limited thereto.

[0127] In another example, the molar ratio of the iron raw material, the phosphorus raw material, and the oxidizing agent may be 0.8~1.2 : 0.8~1.2 : 0.8~1.2, respectively, but is not limited thereto.

[0128] Meanwhile, a raw material containing a heterogeneous element may be optionally added to the above aqueous solution.

[0129] Examples of the aforementioned iron raw materials include ferrous sulfate, ferrous oxalate, ferric citrate, ferrous hydroxide, ferrous phosphate, ferric chloride, ferrous nitrate, ferric acetate, etc.

[0130] Meanwhile, the above-mentioned phosphorus raw materials may include phosphoric acid, iron phosphate, lithium dihydrogen phosphate, lithium phosphate, ammonium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, phosphorus pentoxide, etc.

[0131] In addition, examples of the above oxidizing agents include hydrogen peroxide, glycolic acid, citric acid, ammonium persulfate, sodium persulfate, potassium persulfate, potassium permanganate, ammonium peroxydisulfate, nitric acid, chloric acid, chromic acid, manganese dioxide, ferric chloride, etc.

[0132] As the above basic aqueous solution, sodium hydroxide aqueous solution, ammonia aqueous solution, potassium hydroxide aqueous solution, etc., may be used.

[0133] A hydroxide precursor can be prepared by adding the above basic aqueous solution to an aqueous solution in which an iron raw material, a phosphorus raw material, and an oxidizing agent are added to pure water (DIW), and reacting the solution at a temperature of 40 to 80°C, for example, 40°C, 42.5°C, 45°C, 47.5°C, 50°C, 52.5°C, 55°C, 57.5°C, 60°C, 62.5°C, 65°C, 67.5°C, 70°C, 72.5°C, 75°C, 77.5°C, 80°C, or a temperature in the range between two of these values.

[0134] The above reaction may be carried out under inert conditions, for example, in a reaction system substituted with at least one inert gas selected from the group consisting of N2, Ar, He, Rn, Ne, and Xe, but is not limited thereto.

[0135] Meanwhile, if necessary, a raw material containing a foreign element can be added to dope the hydroxide precursor with a foreign element.

[0136] An iron complex oxide precursor can be produced by heat-treating the above iron complex hydroxide precursor.

[0137] Here, the iron composite oxide precursor can be prepared by heat-treating the iron composite hydroxide precursor in a kiln at a maximum temperature of 400 to 700°C, for example, 400°C, 425°C, 450°C, 475°C, 500°C, 525°C, 550°C, 575°C, 600°C, 625°C, 650°C, 675°C, 700°C, or between two of these values ​​for 3 to 10 hours, for example, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours, or between two of these values, but is not limited thereto.

[0138] Meanwhile, the heat treatment may be performed by increasing the temperature at a rate of 1 to 5°C per minute, for example, 1°C, 1.5°C, 2°C, 2.5°C, 3°C, 3.5°C, 4°C, 4.5°C, 5°C, or a range between two of these values, so as to reach the maximum temperature. Additionally, the heat-treated precursor may be obtained by furnace cooling.

[0139] Using an iron composite oxide precursor prepared in this way, it is possible to form nano-primary particles having an olivine crystal structure.

[0140] As a specific example, the iron composite oxide precursor may be prepared by a method comprising: (i) a step of preparing an iron composite hydroxide precursor by introducing a basic aqueous solution into a reaction system comprising an iron raw material, a phosphorus raw material, and an oxidizing agent; and (ii) a step of preparing an iron composite oxide precursor by heat-treating the iron composite hydroxide precursor, but is not limited thereto.

[0141] In another example, the above transition metal precursor may be represented by the chemical formula 3 below.

[0142] [Chemical Formula 1]

[0143] M x A y A' z P 1-z O w

[0144] In the above formula, M is at least one selected from the group consisting of Fe, Mn, Ni, and Co; A is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Cr, Cu, Ga, Hf, In, K, La, Mg, Mo, Na, Nb, Nd, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr; A' is at least one selected from the group consisting of C, Si, S, N, B, F, Cl, and I; and 0 <x≤1, 0≤y<1, 0≤z<1, 0<w≤4, x+y=1이다

[0145] Here, the transition metal precursor represented by Chemical Formula 3 is a type of oxide precursor and can be prepared by heat treating a sulfate, carbonate, nitrate, acetate, silicate, phosphate, borate, fluoride, chloride, or hydroxide. For example, FePO4 is one of the non-limiting examples of Chemical Formula 1.

[0146] Meanwhile, the carbon-based compound included in the slurry of step (a) above may be intended to form a carbon coating that improves the conductivity of the positive electrode active material. By minimizing the thickness of the carbon coating layer while increasing its uniformity, the decrease in flowability caused by amorphous carbon can be minimized and the conductivity of the positive electrode active material can be improved.

[0147] For example, lithium iron phosphate compounds, which are olivine-based cathode materials, are PO4 3- Due to its strong covalent bonds, its electrical conductivity is relatively low. In addition, due to its crystal structure, Li + It is known that it undergoes one-dimensional diffusion and has low ionic conductivity.

[0148] As a means to overcome these drawbacks, a technology that improves conductivity by forming a carbon coating and Li through nanoparticle formation + Technology to improve diffusion has been proposed.

[0149] However, in conventional positive electrode active materials, the coated carbon exists in an amorphous phase, which can reduce the density of the positive electrode active material.

[0150] In addition, conventional nano-sized particulate materials grow into angular particles due to aggregation during the calcination process.

[0151] As a result, reduced flowability due to amorphous carbon and angular particles reduce the density of the cathode active material, which can lower the energy density of the final product.

[0152] On the other hand, since the carbon coating layer of the above method is formed satisfying specific ratios and specific temperature conditions, it can have a uniform and thin thickness. In addition, the particulate material can be induced to grow into a spherical shape.

[0153] Examples of the above carbon-based compounds include, but are not limited to, sucrose, glucose, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), colloidal carbon, citric acid, tartaric acid, glycolic acid, polyacrylic acid, adipic acid, glycine, and aminobenzoic acid.

[0154] In addition, the properties of the carbon-based compound forming the carbon coating layer can be controlled by controlling the properties of the carbon coating layer.

[0155] Meanwhile, there is a method of mixing particles of different sizes to increase the density of the positive electrode active material.

[0156] For example, it is known that a positive electrode active material exhibiting a bimodal particle distribution mixed to have two peaks in the particle size distribution graph can have a high density.

[0157] Conventionally, to manufacture such a positive electrode active material, two materials with different average particle sizes were mixed.

[0158] However, in this method, since the lithium complex compound is synthesized at a high calcination temperature during the manufacture of the allotrope, the carbon-based compound is lost during calcination, resulting in differences in the characteristics of the carbon-based coating between the allotrope and the subparticle. Additionally, a larger amount of the carbon-based compound was required to form the carbon-based coating layer.

[0159] Meanwhile, the above manufacturing method was derived by taking into account the fact that some particles locally overgrow during a firing process under specific conditions.

[0160] That is, by using specific process conditions and a slurry to induce abnormal growth of some particulate matter, a positive electrode active material exhibiting a bimodal particle distribution can be manufactured in a single calcination process.

[0161] By applying this method, high-density bimodal cathode active materials can be manufactured without the need to separately produce fine particles and large particles.

[0162] In addition, since the above-mentioned positive active material is synthesized under the same conditions, the composition of the covalent and subparticles and the characteristics of the carbon coating layer may be identical or at least similar.

[0163] By minimizing the thickness of the carbon coating layer in the cathode active material while increasing its uniformity, the decrease in flowability caused by amorphous carbon can be minimized and the conductivity of the cathode active material can be improved.

[0164] For example, the carbon-based compound is in a range where the ratio of the number of carbon atoms (C) to the total number of metal atoms other than lithium (Metal) in the slurry (C / Metal) is 0.30 to 0.70, for example, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.50, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59. 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, or a range between two of these values ​​can be added.

[0165] However, carbon-based compounds can suppress local overgrowth of particles depending on the ratio. Accordingly, the content of the carbon-based compound in the slurry may be 0.45 to 0.55 mol%, for example, 0.45 mol%, 0.46 mol%, 0.47 mol%, 0.48 mol%, 0.49 mol%, 0.5 mol%, 0.51 mol%, 0.52 mol%, 0.53 mol%, 0.54 mol%, 0.55 mol%, or a range between two of these values.

[0166] When manufacturing a positive electrode active material using a slurry containing carbon-based compounds within the above range, local overgrowth may occur to the extent that the particulate material can have a bimodal form.

[0167] Meanwhile, the carbon-based compound may be a compound in which the proportion of the C element in the molecular structure is 30 to 60 wt%, for example, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, 40 wt%, 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45 wt%, 46 wt%, 47 wt%, 48 wt%, 49 wt%, 50 wt%, 51 wt%, 52 wt%, 53 wt%, 54 wt%, 55 wt%, 56 wt%, 57 wt%, 58 wt%, 59 wt%, 60 wt%, or a range between two of these values.

[0168] If a carbon-based compound is used in which the proportion of the C element satisfies the above range, a product with excellent yield and uniformity of carbon coating can be manufactured even when using the same amount of compound.

[0169] Since the above manufacturing method forms a carbon coating using a wet coating method, it is necessary to use raw materials with sufficient solubility in water.

[0170] Accordingly, the carbon-based compound may have a solubility in water at 25°C of 0 to 3,000 g / L, for example, 3,000 g / L, 2,750 g / L, 2,500 g / L, 2,250 g / L, 2,000 g / L, 1,750 g / L, 1,500 g / L, 1,250 g / L, 1,000 g / L, 750 g / L, 500 g / L, 250 g / L, 200 g / L, 150 g / L, 100 g / L, 50 g / L, or a range between two of these values.

[0171] Using carbon-based compounds with solubility within the above range can more easily form a uniform coating, but is not limited thereto.

[0172] In addition, the carbon-based compound needs to be carbonized within the heat treatment temperature of step (c). If uncarbonized carbon-based compound remains in the cathode active material, conductivity improvement may be insufficient or unexpected side effects may occur.

[0173] In addition, the characteristics of the carbon coating formed may vary depending on the 25°C solubility of the carbon-based compound in water (B) and the ratio of element C (A). In particular, if the ratio (B / A) is 30 or more (unit omitted), for example, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45 or more, a more uniform and thin carbon coating layer can be formed.

[0174] In particular, if the value of B / A satisfies the above range and the slurry of step (a) is intended for manufacturing a lithium iron phosphate-based compound, a carbon coating layer of 1 to 500 nm can be uniformly formed.

[0175] In one embodiment, at least one sub-raw material comprising an element selected from Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, F, Fe, Ga, Hf, I, In, K, La, Mg, Mo, N, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Si, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn and Zr may be additionally added to the slurry in step (a).

[0176] By additionally adding a sub-raw material in step (a) above, it is possible to dope elements not included in the transition metal precursor or adjust the proportion of elements included in the transition metal precursor.

[0177] Next, step (b) is a step of grinding particles in the slurry. Here, lithium-containing raw materials, transition metal precursors, etc. may exist in particulate form in the slurry.

[0178] Meanwhile, the average particle size (D50) of the particles ground in step (b) above may be 0.5 to 0.7 μm, for example, 0.5 μm, 0.51 μm, 0.52 μm, 0.53 μm, 0.54 μm, 0.55 μm, 0.56 μm, 0.57 μm, 0.58 μm, 0.59 μm, 0.6 μm, 0.61 μm, 0.62 μm, 0.63 μm, 0.64 μm, 0.65 μm, 0.66 μm, 0.67 μm, 0.68 μm, 0.69 μm, 0.7 μm, or a range between two of these values.

[0179] The particles, ground to have an average particle size within the range described above, can be aggregated in an appropriate amount due to surface energy. The aggregated particles undergo localized overgrowth during the calcination process, which leads to the bimodalization of the cathode active material. As a result, the density characteristics of the cathode active material can be improved.

[0180] In one example, step (b) above may be performed in a milling machine containing beads having a size of 0.1 to 1.5 mm, e.g., 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, 1 mm, 1.05 mm, 1.1 mm, 1.15 mm, 1.2 mm, 1.25 mm, 1.3 mm, 1.35 mm, 1.4 mm, 1.45 mm, 1.5 mm, or a range between two of these values. Here, the size may refer to the diameter of the beads. If the above bead is not spherical, the above diameter may refer to the diameter of the major axis.

[0181] Meanwhile, the milling machine may contain beads in a volume of 30 to 50 percent, for example, 30 percent, 32.5 percent, 35 percent, 37.5 percent, 40 percent, 42.5 percent, 45 percent, 47.5 percent, 50 percent, or a range between two of these values.

[0182] In addition, the slurry fed into the milling machine may have a solid content of 20 to 50%, for example, 20%, 22.5%, 25%, 27.5%, 30%, 32.5%, 35%, 37.5%, 40%, 42.5%, 45%, 47.5%, 50%, or a range between two of these values.

[0183] To grind the above particles, dry or wet dispersion mills such as a ball mill, a bead mill (beads commonly used to grind metallic raw materials such as Al beads, Fe beads, or Zr beads can be used), a vibratory mill, an attritor mill, an air jet mill, a disc mill, or an air classifier mill can be used.

[0184] In one example, the milling machine may be a nanomill containing Zr balls.

[0185] In this way, local overgrowth of particulate matter can be induced by using a slurry having a specific size of solid content and a controlled concentration of carbon-based compounds.

[0186] Meanwhile, the slurry can be dried after grinding in step (b) to obtain it in powder form. For example, the slurry can be dried through spray drying. That is, the ground particles in step (c) may be the slurry obtained in step (b) that has been spray-dried.

[0187] Spray drying, which is an example of the above drying, can be performed in a spray dryer. The spray dryer is not particularly limited to any spray drying device capable of producing dried particles with a shape close to spherical by spray drying the slurry containing the crushed particles, but may include an ultrasonic atomizer, a single-fluid spray nozzle atomizer, a two-fluid spray nozzle atomizer, an ultrasonic nozzle atomizer, a filter expansion droplet generator (FEAG), or a disc-type droplet generator.

[0188] The spray dryer may include a spray nozzle and a drying chamber, and the slurry is atomized into droplets of a predetermined size through the spray nozzle and sprayed into the drying chamber where a relatively high-temperature gas flow exists.

[0189] The raw material in the droplet sprayed into the drying chamber can be dried into particles with a shape close to spherical under the temperature environment inside the drying chamber.

[0190] Meanwhile, if a specific carbon-based compound is included in the above slurry, unnecessary aggregation of the particles can be suppressed during spray drying. As a result, particles with a shape close to spherical can be obtained.

[0191] Here, by adjusting the viscosity of the slurry after completing the grinding of step (b) above, the condensation time during drying can be shortened and the decrease in density due to moisture loss during drying can be minimized.

[0192] Moisture loss during drying can reduce particle density and form pores. As a result, particle strength decreases, and the stability of the cathode active material may be insufficient.

[0193] Meanwhile, if the viscosity of the above slurry is excessively high, fluidity decreases during drying, resulting in insufficient process efficiency and making it difficult to obtain spherical particles.

[0194] One of the means for controlling the viscosity of the above slurry is to add a binder.

[0195] Next, step (c) above may be a step of heat-treating the particles crushed in step (b) above to form a lithium composite compound.

[0196] During the heat treatment of step (c) above, the carbon-based compound can be carbonized to form a carbon coating layer.

[0197] The heat treatment of step (c) above may be performed for 5 to 15 hours at a maximum temperature of 750 to 950°C under an inert atmosphere. At this time, the maximum temperature may vary depending on the composition of the target positive active material.

[0198] More specifically, the heat treatment of step (c) above can be performed for 5 to 15 hours by increasing the temperature from 750 to 950°C at a rate of 1 to 10°C per minute while maintaining an inert atmosphere in a kiln.

[0199] The heat treatment of step (c) above may be performed at 750 to 950°C, for example, 750°C, 775°C, 800°C, 825°C, 850°C, 875°C, 900°C, 925°C, 950°C, or in a range between two of these values.

[0200] If heat treatment is performed at a temperature satisfying the above range, local coagulation can be easily achieved.

[0201] On the other hand, if the heat treatment temperature of step (c) above is less than 750°C, the calcination of the precursor proceeds insufficiently, which may result in insufficient crystal growth of the lithium composite compound or difficulty in forming a carbon coating layer. Consequently, local overgrowth of the lithium composite compound is suppressed, and a bimodal cathode active material may not be produced.

[0202] In addition, if the heat treatment temperature of step (c) above exceeds 950℃, thermal decomposition of the lithium composite compound may occur, resulting in a decrease in particle strength or particle disintegration. Alternatively, all of the lithium composite compounds may become coarse.

[0203] Meanwhile, the heat treatment may be performed by increasing the temperature by 1 to 10°C per minute, for example, 1°C, 1.5°C, 2°C, 2.5°C, 3°C, 3.5°C, 4°C, 4.5°C, 5°C, 5.5°C, 6°C, 6.5°C, 7°C, 7.5°C, 8°C, 8.5°C, 9°C, 9.5°C, 10°C, or a range between two of these values.

[0204] In addition, the heat treatment may be performed while maintaining the maximum temperature for a period of time of 15 hours or less, for example, 15 hours, 14.5 hours, 14 hours, 13.5 hours, 13 hours, 12.5 hours, 12 hours, 11.5 hours, 11 hours, 10.5 hours, 10 hours, 9.5 hours, 9 hours, 8.5 hours, 8 hours, 7.5 hours, 7 hours, 6.5 hours, 6 hours, 5.5 hours, 5 hours, or a range between two of these values.

[0205] Here, the above-mentioned inert atmosphere may be composed by replacing air with at least one inert gas selected from the group consisting of N2, Ar, He, Rn, Ne, and Xe, for example, but is not limited thereto.

[0206] Meanwhile, after the heat treatment of step (c) above, cooling can be performed while maintaining an inert atmosphere at a temperature of 150°C or lower.

[0207] Here, if an inert atmosphere is maintained during the cooling of the lithium composite compound, oxidation is prevented and it can be manufactured into a bimodal cathode active material.

[0208] Optionally, before heat-treating the particles ground in step (b) in step (c), at least one sub-raw material comprising an element selected from Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, F, Fe, Ga, Hf, I, In, K, La, Mg, Mo, N, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Si, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr, and at least one selected from lithium-containing raw materials may be additionally added. The sub-raw material may be provided in at least one form selected from sulfates, carbonates, nitrates, acetates, chlorides, hydroxides, and oxides.

[0209] At this time, the content of the sub-raw material introduced in step (c) above may vary depending on the composition of the particles and the composition of the target positive active material.

[0210] Accordingly, when heat-treating the mixture of the particles and the sub-raw material in step (c) above, an element contained in the sub-raw material among the lithium composite compound may be doped or coated on at least a portion of the surface of the lithium composite compound.

[0211] Additionally, before or after performing step (c) above, disintegration, distribution, and / or washing processes may be performed on the lithium composite compound.

[0213] lithium secondary battery

[0214] According to another aspect, a positive electrode may be provided comprising a positive current collector and a positive active material layer formed on the positive current collector. Here, the positive active material layer may comprise a positive active material manufactured according to the manufacturing method according to the various embodiments described above as the positive active material.

[0215] 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 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.

[0216] The above positive active material layer can be manufactured by applying a positive slurry composition, which includes a conductive material and optionally a binder together with the positive active material, to the positive current collector.

[0217] At this time, the positive active material may be included in an amount of 80 to 99 weight%, more specifically 85 to 98.5 weight%, based on the total weight of the positive active material layer. Excellent capacity characteristics may be exhibited when included within the above-mentioned content range, but it is not necessarily limited thereto.

[0218] The above 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 fiber; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxide 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. The above conductive material may be included in an amount of 0.1 to 15 weight% with respect to the total weight of the positive electrode active material layer.

[0219] The above binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the 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, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above binder may be included in an amount of 0.1 to 15 weight% based on the total weight of the positive active material layer.

[0220] The above-described anode can be manufactured according to a conventional anode manufacturing method, except for using the above-described anode active material. Specifically, it can be manufactured by applying an anode slurry composition, prepared by dissolving or dispersing the above-described anode active material and optionally a binder and a conductive material in a solvent, onto an anode current collector, and then drying and rolling.

[0221] The above solvent may be a solvent commonly used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it has a viscosity that dissolves or disperses the anode active material, conductive material, and binder, taking into account the coating thickness of the slurry and the manufacturing yield, and subsequently provides excellent thickness uniformity when coated for anode manufacturing.

[0222] In addition, in another embodiment, the anode may be manufactured by casting the anode slurry composition onto a separate support and then laminating the film obtained by peeling off from the support onto an anode current collector.

[0223] In addition, according to another aspect, an electrochemical device including the anode described above may be provided. Specifically, the electrochemical device may be a battery, a capacitor, etc., and more specifically, a lithium secondary battery.

[0224] Specifically, the above lithium secondary battery may include a positive electrode, a negative electrode positioned opposite to the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode.

[0225] In addition, the above-mentioned lithium secondary battery may be provided as an anode-free secondary battery. Here, since the anode is the same as previously described, a detailed description is omitted for convenience, and only the remaining components not described above will be explained in detail below. Furthermore, the description regarding the anode to be described later should be understood as being based on the premise that an anode is present in the above-mentioned lithium secondary battery.

[0226] Meanwhile, the above lithium secondary battery may have the separator replaced with a solid electrolyte. In such cases, an electrode slurry composition in which a solid electrolyte is further added during the manufacture of the positive and negative electrodes may be used.

[0227] The above lithium secondary battery may optionally further include a battery container housing the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member sealing the battery container.

[0228] The above cathode may include a cathode current collector and a cathode active material layer located on the cathode current collector.

[0229] 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.

[0230] The above-mentioned cathode active material layer can be manufactured by applying a cathode slurry composition, which includes a conductive material and, if necessary, a binder, together with the above-mentioned cathode active material, to the above-mentioned cathode current collector.

[0231] As the above-mentioned negative electrode active material, a compound capable of reversible intercalation / 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; and SiO₂ β Examples include metal oxides capable of doping and dedoping lithium, such as (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, 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 negative electrode active material. Furthermore, the carbon material may include 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.

[0232] The above-mentioned negative electrode active material may be included in an amount of 80 to 99 weight percent based on the total weight of the negative electrode active material layer.

[0233] The above binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1 to 10 weight percent based on the total weight of the negative active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0234] The above conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fiber or metal fiber; metal powder such as carbon fluoride, aluminum, or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxide such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0235] In one embodiment, the negative active material layer may be manufactured by applying a negative slurry composition, prepared by dissolving or dispersing a negative active material and optionally a binder and a conductive material in a solvent, onto a negative current collector and drying it, or by casting the negative slurry composition onto a separate support and then laminating the film obtained by peeling it off from the support onto a negative current collector.

[0236] In addition, in another embodiment, the negative active material layer may be manufactured by applying a negative slurry composition prepared by dissolving or dispersing a negative active material and optionally a binder and a conductive material in a solvent onto a negative current collector and drying it, or by casting the negative slurry composition onto a separate support and then laminating the film obtained by peeling it off from the support onto a negative current collector.

[0237] Meanwhile, in the above-mentioned lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator typically used in lithium secondary batteries can be used without special limitations, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. 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 may optionally be used in a single-layer or multi-layer structure.

[0238] In addition, the electrolytes used in the above lithium secondary battery 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 when manufacturing lithium secondary batteries, but are not limited to these.

[0239] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0240] 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 2 to 20 carbon atoms 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.

[0241] The above lithium salt can be used without special limitations 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. It is preferable to use the lithium salt 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.

[0242] 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, a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, 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 percent based on the total weight of the electrolyte.

[0243] Meanwhile, the above electrolyte may include solid electrolytes such as solid polymer electrolytes, gel-type polymer electrolytes, and solid inorganic electrolytes.

[0244] A lithium secondary battery containing a solid electrolyte may omit the separator described above. However, since it is difficult for the electrolyte to penetrate into the positive and negative electrodes, the electrodes may be formed by mixing the solid electrolyte during their manufacture.

[0245] Meanwhile, the solid polymer electrolyte or gel-type polymer electrolyte may be a polymer resin in which a salt of a Group 1 or Group 2 metal ion used in a secondary battery is composited. For example, it may be a polymer resin added to a solvated lithium salt.

[0246] The above metal ion salts may include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2.

[0247] The above polymer resins include, for example, polyether-based polymers, polycarbonate-based polymers, acrylate-based polymers, polysiloxane-based polymers, phosphazene-based polymers, polyethylene derivatives, alkylene oxide derivatives such as polyethylene oxide, phosphate ester polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ionic dissociators, branched copolymers in which amorphous polymers such as PMMA, polycarbonate, polysiloxane (PDMS) to phosphazene are copolymerized as comonomers to a polyethylene oxide (PEO) main chain, comb-like polymers, and cross-linked polymer resins.

[0248] As solid inorganic electrolytes, sulfide-based solid electrolytes and oxide-based solid electrolytes can be widely used.

[0249] The sulfide-based solid electrolyte may be a material containing sulfur (S) and having the conductivity of Group 1 or Group 2 metal ions of the periodic table used in secondary batteries. For example, it may be a Li-PS-based glass or Li-PS-based glass ceramic having the conductivity of lithium ions.

[0250] Examples of the above sulfide-based solid electrolytes may include at least one selected from the group consisting of Li6PS5Cl, Li6PS5Br, Li6PS5I, Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2OP2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2S5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, and Li2S-GeS2-ZnS.

[0251] Meanwhile, oxide-based solid electrolytes may be materials containing oxygen (O) and having the conductivity of Group 1 or Group 2 metal ions of the periodic table used in secondary batteries. For example, LLTO-based compounds, Li6La2CaTa2O 12 , Li6La2ACaNb2O 12 , Li6La2ASrNb2O 12 , Li2Nd3TeSbO 12 , Li3BO 2.5 N 0.5 It may be at least one selected from the group consisting of Li9SiAlO8, LAGP-based compounds, LATP-based compounds, LISICON-based compounds, LIPON-based compounds, perovskite-based compounds, NASICON-based compounds and LLZO-based compounds.

[0252] As described above, since the lithium secondary battery containing the positive electrode active material stably exhibits excellent discharge capacity, output characteristics, and lifespan characteristics, 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).

[0253] There are no particular restrictions on the external shape of the above-mentioned lithium secondary battery, but it may be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape. In addition, the lithium secondary battery can be used not only as a battery cell used as a power source for small devices, but can also preferably be used as a unit cell in a medium-to-large battery module containing a plurality of battery cells.

[0254] According to another aspect, a battery module comprising the lithium secondary battery as a unit cell and / or a battery pack comprising the same may be provided.

[0255] The battery module or the battery pack may 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.

[0257] The details described above will be explained in more detail below through examples. However, these examples are for illustrative purposes only and should not be interpreted as limiting the scope of this specification.

[0259] Experimental Example 1. Evaluation of characteristics according to the particle size distribution of the cathode active material

[0260] The characteristics of the positive electrode active material were evaluated by controlling its particle size distribution.

[0261] The cathode active materials used in the experiment all had the same composition of LiFePO4, except for differences in particle size; they were prepared by mixing iron phosphate precursors of different particle sizes and calcining them together with lithium raw materials to obtain a bimodal distribution.

[0263] (1) Comparison based on the size of the opposites

[0264] A LiFePO4 cathode active material was prepared with a small particle peak at a particle size of 1 μm and large particle peaks at 3 μm, 5.5 μm, and 8 μm, respectively. As the particle size of the large particles increased, the compressive density increased, but the capacity decreased. It appears that conductivity decreases as particle size increases, and as a result, the capacity decreases.

[0266] (2) Comparison based on particle size

[0267] LiFePO4 cathode active materials were prepared with small particle peaks at particle sizes of 0.3 μm, 0.65 μm, and 1 μm, and a large particle peak at 3 μm. There was no significant difference between the cathode active materials with small particle peaks at 0.65 μm and 1 μm, but the compressive density decreased in the cathode active material with a peak at 0.3 μm. This appears to be due to aggregation occurring between very small particles.

[0269] Preparation Example 1. Preparation of positive electrode active material

[0270] (1) Examples and Comparative Examples

[0271] In the reactor, FePO4 precursor in oxide state, lithium-containing raw material Li2CO3, and carbonaceous compound sucrose (C 12 H 22 O 11A slurry was prepared by mixing 0.46~0.54 mol% of lithium (Li) and metals other than lithium (Metal). Here, the mixture was prepared such that the molar ratio (Li / Metal) of lithium (Li) and metals other than lithium was 1.00. Zirconia balls with a size of 0.3~2.0 mm were filled into a nano mill to fill 40% of the internal space of the nano mill, and then the slurry was ground. Subsequently, the slurry was dried using a spray dryer (Dongjin Kiyon, DJE003R).

[0272] The above mixture was heat-treated for 8 hours at a rate of 2°C / min in a N2 atmosphere and maintained at 850°C. Afterward, the mixture was heat-treated by furnace cooling and classification to obtain an anode active material containing lithium iron phosphate with an average particle size of 20.0 to 40.0 μm.

[0273] The obtained positive active material was ground using a Jet-Mill (Alpa, MQW03T) to obtain a final positive active material with an average particle size of 1.0 to 3.0 μm.

[0274] division Zirconia ball size (mm) Firing temperature (°C) Carbon input amount (C / Metal mol ratio) Microparticle peak (㎛) Allele peak (㎛) Small particle / large particle volume ratio Example 1 beads 0.3 850 0.46 0.53 2.9 0.33:1 Example 2 beads 0.3 850 0.50 0.5 2.64 0.38:1 Example 3 beads 0.3 850 0.54 0.42 2.19 0.40:1 Example 4 beads 0.5 850 0.46 0.63 3.2 0.30:1 Example 5 beads 0.5 850 0.50 0.58 3.11 0.34:1 Example 6 beads 0.5 850 0.54 0.55 2.89 0.35:1 Example 7 beads 1.0 850 0.46 0.88 3.84 0.20:1 Example 8 beads 1.0 850 0.50 0.74 3.51 0.22:1 Example 9 beads 1.0 850 0.54 0.67 3.26 0.27:1 Comparative Example 1 beads 2.0 850 0.46 1.51 4.15 0.08:1 Comparative Example 2 beads 2.0 850 0.54 1.26 3.82 0.06:1 Comparative Example 3 beads 1.0 850 0.30 1.47 4.1 0.03:1 Comparative Example 4 beads 1.0 850 0.60 1.32 2.4 0.3:1 Comparative Example 5 beads 0.3 850 0.30 0.61 3.64 0.7:1 Comparative Example 6 beads 0.3 850 0.60 0.35 1.58 2.0:1

[0276] Cross-sectional SEM images of the cathode active materials prepared in Examples 1, 4, and 8 and Comparative Examples 1, 4, and 6 are shown in Figure 1.

[0278] Preparation Example 2. Preparation of a lithium secondary battery

[0279] A positive electrode slurry was prepared by dispersing 94 wt% of each positive electrode active material prepared according to Preparation Example 1, 3 wt% of artificial graphite, and 3 wt% of PVDF binder in 3.5 g of N-methyl-2-pyrrolidone (NMP). The positive electrode slurry was coated onto an aluminum (Al) thin film, which is a positive electrode current collector with a thickness of 20 μm, dried, and then rolled to produce a positive electrode.

[0280] A coin battery was manufactured according to a commonly known manufacturing process using a lithium foil as the counter electrode for the above positive electrode, a porous polyethylene film (Celgard 2300, thickness: 25 μm) as the separator, and a liquid electrolyte in which LiPF6 is present at a concentration of 1.15 M in a solvent mixed with ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7.

[0282] Experimental Example 2. Evaluation of Electrochemical Characteristics of a Lithium Secondary Battery

[0283] For the coin battery in Preparation Example 2, charge-discharge experiments were performed using an electrochemical analyzer (Toyo, Toscat 3100) at 25°C, with a voltage range of 2.0–3.65 V and a discharge rate of 0.1–5.0 C, to measure the initial charge capacity and initial discharge capacity. Compression density was measured by weighing 3 g of positive active material onto a pelletizer and pressurizing it at 4.5 tons for 5 seconds.

[0284] division 0.1C Initial Charge (mAh / g) 0.1C Initial Discharge (mAh / g) Compressed density (g / cc) Energy density (Wh / L) Example 1 163.46 161.79 2.46 1353.21 Example 2 163.24 162.33 2.40 1324.61 Example 3 162.53 161.57 2.38 1307.42 Example 4 163.35 160.95 2.49 1362.60 Example 5 163.20 161.70 2.43 1335.97 Example 6 162.12 160.52 2.41 1315.30 Example 7 162.57 159.50 2.50 1355.75 Example 8 161.48 159.54 2.44 1323.54 Example 9 161.48 159.62 2.41 1307.93 Comparative Example 1 155.12 150.16 2.50 1276.36 Comparative Example 2 158.20 155.10 2.44 1286.71 Comparative Example 3 149.61 145.88 2.55 1264.78 Comparative Example 4 162.55 159.47 2.31 1252.48 Comparative Example 5 150.84 146.97 2.49 1244.25 Comparative Example 6 163.92 162.92 2.25 1246.34

[0285] Although embodiments of this specification have been described above, those skilled in the art may modify and change this specification in various ways by adding, changing, deleting, or adding components, etc., without departing from the spirit of this specification as described in the claims, and such modifications and changes shall also be deemed to be included within the scope of the rights of this specification.

Claims

Claim 1 A positive electrode active material comprising a lithium composite compound capable of lithium intercalation / deintercalation, wherein the lithium composite compound comprises a plurality of spherical particulate materials, the particulate materials have a bimodal particle size distribution comprising a first lithium composite compound that is a small particle and a second lithium composite compound that is an allotrope, the particle size distribution of the particulate materials has a small particle peak in the range of 1.0 μm or less and an allotrope peak in the range of 3.0 to 5.0 μm, the difference between the center points of the small particle peak and the allotrope peak is 1.8 to 4.5 μm, the volume ratio of the small particle and the allotrope among the particulate materials is 0.27 or more and less than 0.5 : 1, and at least some of the particulate materials have an amorphous carbon coating layer with a thickness of 1 to 500 nm formed on at least some of their surfaces. Claim 2 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the proportion of fine particles having a particle size of 1.0 μm or less among the particulate material is 10 to 50 volume%, and the proportion of large particles having a particle size of 1.5 to 5.0 μm among the particulate material is 50 to 90 volume%. Claim 3 A positive electrode active material for a lithium secondary battery according to claim 1, having a compressive density of 2.35 to 2.65 g / cc and an energy density of 1,300 to 1,400 Wh / L. Claim 4 In claim 1, the lithium composite compound is a positive electrode active material for a lithium secondary battery represented by the following chemical formula 1: [Chemical Formula 1]Li p M x A y A' z P 1-z O w In the above formula, M is at least one selected from the group consisting of Fe, Mn, Ni, and Co; A is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Cr, Cu, Ga, Hf, In, K, La, Mg, Mo, Na, Nb, Nd, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr; A' is at least one selected from the group consisting of C, Si, S, N, B, F, Cl, and I; and 0.5≤p≤1.5, 0 <x≤1, 0≤y<1, 0≤z<1, 0<w≤4이다. Claim 5 (a) a step of preparing a slurry by mixing a lithium-containing raw material, one type of transition metal precursor, and a carbon-based compound; (b) a step of grinding particles in the slurry so that the average particle size (D50) is 0.5 to 0.7 μm; and (c) a step of heat-treating the ground particles to obtain a bimodal lithium composite compound; wherein the content of the carbon-based compound in the slurry is 0.45 to 0.55 mol%. Claim 6 A method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 5, wherein the ratio of the number of atoms of lithium (Li) to the total number of atoms of metal elements other than lithium (Metal) in the slurry of step (a) (Li / Metal) is 0.90 to 1.

10. Claim 7 A method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 5, wherein the ratio of the number of carbon atoms (C) to the total number of atoms of metal elements other than lithium (Metal) in the slurry of step (a) (C / Metal) is 0.30 to 0.

70. Claim 8 A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein, in step (a) above, at least one sub-raw material comprising an element selected from Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, F, Fe, Ga, Hf, I, In, K, La, Mg, Mo, N, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Si, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn and Zr is further added to the slurry. Claim 9 A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein, in claim 5, step (b) is performed in a milling machine containing beads having a size of 0.1 to 1.5 mm. Claim 10 A positive electrode comprising a positive electrode active material according to any one of paragraphs 1 to 4. Claim 11 A lithium secondary battery using a positive electrode according to Paragraph 10. Claim 12 delete Claim 13 delete Claim 14 delete Claim 15 delete

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