Positive electrode active material powder, and positive electrode and lithium secondary battery comprising same

Abstract

The present invention relates to: a positive electrode active material powder including particles containing a lithium iron phosphate-based compound, wherein the particles containing a lithium iron phosphate-based compound have an average particle diameter (D50) of 250-500 nm and an average grain size (Dc) of 90-180 nm, and the value (X) calculated by Equation 1 described in the present specification is 10-50 nm; and a positive electrode and a lithium secondary battery which comprise the positive electrode active material powder.

Description

Positive electrode active material powder, a positive electrode and a lithium secondary battery including the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0132874 filed on September 30, 2024, and all contents disclosed in the document of said Korean Patent Application are incorporated herein as part of this specification.

[0003]

[0004] Technology field

[0005] The present invention relates to a positive electrode active material powder, a positive electrode containing the same, and a lithium secondary battery.

[0006]

[0007] With the increasing technological development and demand for mobile devices, the demand for rechargeable batteries as an energy source is rapidly rising. Among these rechargeable batteries, lithium-ion batteries, which possess high energy density and voltage, long cycle life, and low self-discharge rates, have been commercialized and are widely used.

[0008] Lithium secondary batteries consist of four major components: a positive electrode, a negative electrode, a separator, and an electrolyte. Among these, the positive electrode active material, which is included in the positive electrode, plays a significant role in determining the battery's capacity, output, and lifespan. Currently used positive electrode active materials include NCM-based positive electrode active materials containing nickel, cobalt, manganese, and / or aluminum, and LFP (lithium iron phosphate)-based positive electrode active materials. Meanwhile, improving the performance of the positive electrode active material is essential for lithium secondary batteries to have high energy density, output, and lifespan; consequently, much research is currently being conducted to develop high-performance positive electrode active materials.

[0009] With the recent expansion of lithium-ion battery applications, active development is underway for NCM-based cathode active materials with increased nickel content to enhance energy density, particularly capacity. However, NCM-based cathode active materials with increased nickel content suffer from reduced thermal stability due to structural instability associated with the high nickel content. In contrast, LFP-based cathode active materials, which feature an olivine structure, offer the advantages of superior thermal stability and price competitiveness, despite having a lower capacity compared to NCM-based materials. However, batteries containing LFP-based materials have lower operating voltage and specific capacity compared to those containing NCM-based materials, resulting in lower energy density. Additionally, LFP-based materials exhibit low electron conductivity, and phase changes during charging and discharging lead to reduced electrochemical efficiency.

[0010] Accordingly, there is a need for development to improve the performance of LFP-based cathode active materials.

[0011]

[0012] The present invention aims to solve the above-mentioned problems and to provide a positive electrode active material powder capable of improving the capacity and rate characteristics of a battery.

[0013] In addition, the present invention aims to provide a positive electrode and a lithium secondary battery having excellent capacity and rate characteristics, including the positive electrode active material powder as described above.

[0014] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0015]

[0016] (1) The present invention comprises particles containing a lithium iron phosphate-based compound, and the particles containing the lithium iron phosphate-based compound have an average particle size (D 50) is 250 nm or more and 500 nm or less, and the average grain size (D c The present invention provides a positive electrode active material powder having a length of 90 nm or more and 180 nm or less, and a value (X) calculated by the following formula 1 having a length of 10 nm or more and 50 nm or less.

[0017] [Equation 1]

[0018] X=D 50 / (D 50 / D c ) 3

[0019] In the above Equation 1, D 50 is the average particle size [nm], and D c is the average grain size [nm].

[0020] (2) The present invention, in the above (1), wherein the average particle size (D 50 ) provides a positive electrode active material powder having a diameter of 280 nm or more and 450 nm or less.

[0021] (3) The present invention, in (1) or (2), wherein the average size (D) of the crystal grains is the average size (D) of the crystal grains. c ) provides a positive electrode active material powder having a length of 110 nm or more and 170 nm or less.

[0022] (4) The present invention, in any one of (1) to (3), wherein (D 50 / D c ) 3 It provides a positive electrode active material powder having a value of 5 or more and 20 or less.

[0023] (5) The present invention provides a positive electrode active material powder in which, in any one of (1) to (4), the lithium iron phosphate compound has a manganese (Mn) content of 40 mol% or more and 70 mol% or less among all metals excluding lithium.

[0024] (6) The present invention provides a positive electrode active material powder in which, in any one of (1) to (5), the lithium iron phosphate compound has a composition represented by the following chemical formula 1.

[0025] [Chemical Formula 1]

[0026] Li 1+y Fe 1-p-q Mn p M 1 q (PO4)

[0027] In the above chemical formula 1, M 1 is one or more selected from the group consisting of Al, Mg, Ni, Co, Ti, Mo, Ga, Cu, V, Nb, Zr, Ce, In, Zn, Na, Si, Ca, B, and Y, and -0.1≤y≤0.1, 0.4≤p≤0.7, 0≤q≤0.1.

[0028] (7) The present invention provides a positive electrode active material powder in which, in any one of (1) to (6), the lithium iron phosphate compound comprises vanadium (V).

[0029] (8) The present invention provides a positive electrode active material powder in which, in any one of (1) to (7), the particles containing the lithium iron phosphate compound include primary particles having a particle size (D') obtained from an SEM image of 150 nm or more and 400 nm or less, and contain 60 volume% or more of the primary particles with respect to the total volume of the positive electrode active material powder.

[0030] (9) The present invention provides a positive electrode active material powder in which, in any one of (1) to (8), the particles containing the lithium iron phosphate-based compound further include a coating portion containing carbon (C) formed on the lithium iron phosphate-based compound.

[0031] (10) The present invention provides a positive electrode active material powder according to (9), wherein the carbon (C) content included in the coating portion is 1.2% by weight or more and 2.5% by weight or less with respect to the total weight of the positive electrode active material powder.

[0032] (11) The present invention provides a positive electrode active material powder in which, in any one of (1) to (10), the particles containing the lithium iron phosphate compound are in the form of primary particles.

[0033] (12) The present invention provides a positive electrode comprising a positive electrode active material powder according to any one of (1) to (11).

[0034] (13) The present invention provides a lithium secondary battery comprising a positive electrode according to (12) above.

[0035]

[0036] The positive electrode active material powder according to the present invention comprises particles containing a lithium iron phosphate-based compound, and by controlling the particle size of the particles containing the lithium iron phosphate-based compound and the particle size of the crystal grains within the particles, the capacity and rate characteristics can be improved.

[0037] Accordingly, the performance of the positive electrode and secondary battery including the above positive electrode active material, particularly capacity and rate characteristics, can be improved.

[0038]

[0039] Hereinafter, the present invention will be described in more detail to aid in understanding the invention.

[0040] Terms and words used in this specification and claims shall not be interpreted as being limited to their ordinary or dictionary meanings, but shall be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0041] In this specification, terms such as 'comprising,' 'having,' or 'having' are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0042] In this specification, the term "on" means not only cases where one configuration is formed on the immediate upper surface of another configuration, but also cases where a third configuration is interposed between these configurations.

[0043] In this specification, the primary particle form is a concept contrasted with the secondary particle form formed by the aggregation of hundreds of primary particles manufactured by conventional methods, and may be a single particle consisting of one primary particle, or may be formed by the aggregation of two or more, 10 or fewer, 20 or fewer, 30 or fewer, 40 or fewer, or 50 or fewer primary particles due to inevitable aggregation during the process.

[0044] In this specification, the secondary particle form may be a form formed by aggregating more than 50 primary particles as a result of manufacturing by a conventional method.

[0045] In this specification, 'average particle size (D 50 )' can be defined as the particle diameter corresponding to 50% of the cumulative volume distribution in the particle size distribution curve (graph curve of the particle size distribution). The above average particle diameter is calculated by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500), measuring the difference in diffraction patterns according to particle size as the particles pass through a laser beam to calculate the particle size distribution, and calculating the particle diameter at the point where it is 50% of the cumulative volume distribution according to particle diameter in the measuring device, thereby D 50 It can measure.

[0046] In this specification, 'single crystal' refers to a crystal in a state that does not contain grain boundaries within the grain.

[0047] In this specification, 'grain' means a particle unit having substantially the same crystal orientation.

[0048] In this specification, 'average grain size (D c)' can be quantitatively analyzed using X-ray diffraction analysis (XRD) by Cu Kα X-rays. Specifically, the average size of the crystal grains can be quantitatively analyzed by placing the particle to be measured into a holder, irradiating the particle with X-rays, and analyzing the resulting diffraction grating. Sampling was prepared by placing a powder sample of the particle to be measured into a recessed groove in the center of a general powder holder, smoothing the surface using a slide glass, and ensuring the sample height was level with the edge of the holder. Then, X-ray diffraction analysis was performed using a Bruker D8 Endeavor (light source: Cu-Kα rays, wavelength: 1.54 Å) equipped with a LynxEye XE-T position-sensitive detector, under conditions of a step size of 0.02° for the FDS 0.5° and 2θ = 10° to 80° range. For the measured data, Rietveld refinement was performed considering the charge at each site (metal ions at transition metal sites are +3, and Ni ions at Li sites are +2) and cation mixing. During size analysis, instrumental brodadening was considered using the Fundamental Parameter Approach (FPA) implemented in the Bruker TOPAS program, and all peaks within the measurement range were used for fitting. Peak shape was fitted using only the Lorenzian contribution as the First Principle (FP) among the peak types available in TOPAS, without considering strain.

[0049] In this specification, the particle size (D') corresponding to each of the n primary particles present in the SEM image can be verified by processing the scanning electron microscope (SEM) image with an image processing program (LG Chem, DX program). Specifically, it can be measured from a two-dimensional segmentation image divided by primary particle units obtained by image processing using an artificial intelligence model. The segmentation image can be obtained by acquiring a scanning electron microscope (SEM) image of the cathode active material powder to be measured, inputting the acquired scanning electron microscope image into a U-NET structure or the like to generate a boundary image, removing the boundary from the scanning electron microscope (SEM) image based on the boundary image to generate a boundary removal image, identifying a plurality of objects included in the boundary removal image, and then segmenting the SEM image into primary particle units based on the plurality of objects. The particle size of the primary particles may be calculated by determining the area of ​​each primary particle through the number of pixels corresponding to each of the n primary particles present in the segmentation image, and by using the radius of a circle having an area equal to the area of ​​each primary particle present in the segmentation image. The magnification of the scanning electron microscope (SEM) image used for image analysis is preferably 10K to 30K, and specifically, 20K is preferred. In this case, the boundary distinction is clear, and the representativeness of the analysis value can be guaranteed. If the magnification is low, the resolution for each particle is reduced, making it difficult to distinguish the boundary; if the magnification is high, the number of populations is small, raising concerns that the representativeness of the analysis value may be reduced. To ensure the representativeness of the population, the particle size of each primary particle may be calculated using three or more scanning electron microscope (SEM) images taken from different parts.

[0050]

[0051] In this specification, the carbon (C) content (weight%) with respect to the total weight of the cathode active material powder may be measured through TC-IC (Total Carbon-Inorganic Carbon) analysis, which is a subtraction method using a carbon analyzer (Primacs, Skalar Analytical). Specifically, it is a method of measuring total carbon and inorganic carbon and calculating the difference value as organic carbon.

[0052]

[0053] positive electrode active material powder

[0054] Hereinafter, the positive active material powder according to the present invention will be described.

[0055] The positive electrode active material powder according to the present invention comprises particles containing a lithium iron phosphate-based compound, and the particles containing the lithium iron phosphate-based compound have an average particle size (D 50 ) is 250 nm or more and 500 nm or less, and the average grain size (D c ) is 90nm or more and 180nm or less, and the value (X) calculated by Equation 1 below is 10nm or more and 50nm or less.

[0056] [Equation 1]

[0057] X=D 50 / (D 50 / D c ) 3

[0058] In the above Equation 1, D 50 is the average particle size [nm], and D c is the average grain size [nm].

[0059] Lithium iron phosphate-based compounds have low electrical conductivity, so when used as positive electrode active materials, there is a problem of increased internal resistance of the battery. As a result, the battery capacity decreases as the polarization potential increases when the battery circuit is closed. In addition, lithium iron phosphate-based compounds have a lower density than conventional positive electrode active materials, so there is a limitation in that the energy density of the battery cannot be sufficiently increased. Also, since they typically have the form of secondary particles assembled from primary particles, there is a problem of low output characteristics due to high interfacial resistance between primary particles.

[0060] The positive active material powder of the present invention has an average particle size (D 50 ) is 250 nm or more and 500 nm or less, and the average grain size (D c By including particles comprising a lithium iron phosphate-based compound having a length of 90 nm or more and 180 nm or less, and a value (X) calculated by Formula 1 described in this specification having a length of 10 nm or more and 50 nm or less, the effect of improving the capacity and rate characteristics of a battery to which the same is applied is achieved by securing a lithium ion transport path while minimizing the resistance of the grain boundaries.

[0061] On the other hand, if the positive electrode active material powder does not contain particles containing a lithium iron phosphate-based compound, there is a problem with the lifespan characteristics of the battery containing it being inferior. Furthermore, the positive electrode active material powder contains particles containing a lithium iron phosphate-based compound, and the average particle size (D) of the particles containing the lithium iron phosphate-based compound is 50 If ) is less than 250 nm, there is a problem where the grain boundaries of the particles act as resistance, and if it exceeds 500 nm, there is a problem where the lithium ion migration path becomes long, resulting in inferior lithium ion conductivity. In addition, the average grain size (D) of the crystal grains of the particles containing the above lithium iron phosphate-based compound cIf the value is less than 90 nm, there is a problem where the grain boundaries act as resistance because the number of crystal grains is excessive, and if it is greater than 180 nm, there is a problem where the diffusion path of lithium ions within the crystal grains is lengthened, resulting in inferior electrochemical characteristics. In addition, if the value (X) calculated by Equation 1 described in this specification is less than 10 nm or greater than 50 nm, there is a problem where the grain boundaries of the particles or crystal boundaries act as resistance, or the movement and diffusion path of lithium ions is lengthened, resulting in inferior capacity characteristics and rate characteristics of the battery containing it.

[0062] Specifically, the positive electrode active material powder of the present invention comprises particles containing a lithium iron phosphate-based compound, and the particles containing the lithium iron phosphate-based compound have an average particle size (D 50 ) is 250 nm or more and 500 nm or less. Specifically, the particles containing the above lithium iron phosphate-based compound have an average particle size (D 50 The average particle size (D) may be 250 nm or more, 260 nm or more, 270 nm or more, or 280 nm or more, and may be 450 nm or less, 460 nm or less, 470 nm or less, 480 nm or less, 490 nm or less, or 500 nm or less. 50 When ) is within the above range, the grain boundaries of the particles act as resistance while controlling the movement path of lithium ions, thereby improving the capacity and rate characteristics of the battery containing it.

[0063] And, the particles containing the above lithium iron phosphate-based compound have an average grain size (D c ) is 90 nm or more and 180 nm or less. Specifically, the particle containing the above lithium iron phosphate-based compound has an average grain size (D c ) may be 90 nm or more, 100 nm or more, or 110 nm or more, and may be 170 nm or less, or 180 nm or less. The average size of the crystal grains (D cWhen ) is within the above range, the number of crystal grains exists in an appropriate amount, so that the diffusion path of lithium ions is controlled while minimizing the resistance of the crystal grain boundaries, thereby improving the capacity and rate characteristics of the battery containing it.

[0064] In the present invention, the average particle size (D) of particles containing a lithium iron phosphate-based compound 50 ) and average grain size (D c The relationship was evaluated and expressed as a parameter represented by Equation 1 above. The value (X) calculated by Equation 1 as implied in the present invention is the average particle size (D) of the particles containing the lithium iron phosphate-based compound. 50 ) and average grain size (D c It is a value controlled according to ). Specifically, Equation 1 above is a parameter that quantifies the relative size of crystal grains within a particle using the average particle diameter measured by a Particle Size Analyzer (PSA) and the average grain size [nm]. D 50 is the average particle size [nm] measured by a Particle Size Analyzer (PSA), D c Defined as the average grain size [nm], (D 50 / D c ) 3 The number of crystal grains contained within the particle, measured by a Particle Size Analyzer (PSA), was estimated in three dimensions, and D 50 / (D 50 / D c ) 3 By calculating, the size of the crystal grains within a single particle recognized when measured by a particle size analyzer was relatively quantified.

[0065] In addition, the particles containing the lithium iron phosphate-based compound have a value (X) calculated by Formula 1 described in this specification that is 10 nm or more and 50 nm or less. Specifically, the particles containing the lithium iron phosphate-based compound may have a value (X) calculated by Formula 1 described in this specification that is 10 nm or more, 15 nm or more, or 20 nm or more, and may be 45 nm or less, or 50 nm or less. When the value (X) calculated by Formula 1 described in this specification is within the above range, the particle size and crystal grain size can be controlled to minimize the resistance of grain boundaries and crystal grain boundaries while controlling the lithium ion path, thereby improving the capacity characteristics and rate characteristics of the battery containing the same.

[0066]

[0067] According to one embodiment of the present invention, the average particle size (D 50 ) may be 280 nm or more and 450 nm or less. The above average particle size (D 50 When ) is within the above range, the grain boundaries of the particles act as resistance while controlling the movement path of lithium ions, thereby improving the capacity and rate characteristics of the battery containing it.

[0068]

[0069] According to one embodiment of the present invention, the average size (D) of the crystal grains c ) may be 90 nm or more and 170 nm or less. The average size of the crystal grains (D c When ) is within the above range, the number of crystal grains exists in an appropriate amount, so that the diffusion path of lithium ions is controlled while minimizing the resistance of the crystal grain boundaries, thereby improving the capacity and rate characteristics of the battery containing it.

[0070]

[0071] According to one embodiment of the present invention, the above (D 50 / D c ) 3may be 5 or more and 20 or less. Specifically, the above (D 50 / D c ) 3 may be 5 or more, 6 or more, 7 or more, or 8 or more, and may be 19.9 or less, or 20 or less. The above (D 50 / D c ) 3 When the above range is within, the particle size and crystal grain size can be controlled to minimize the resistance caused by grain boundaries and crystal grain boundaries, while controlling the lithium ion pathways, thereby improving the capacity characteristics and rate characteristics of the battery containing the same.

[0072]

[0073] According to one embodiment of the present invention, the lithium iron phosphate-based compound may have a manganese (Mn) content of 40 mol% or more and 70 mol% or less among the total metals excluding lithium. Specifically, the lithium iron phosphate-based compound may have a manganese (Mn) content of 40 mol% or more, 45 mol% or more, 50 mol% or more, or 55 mol% or more, and may have a manganese (Mn) content of 60 mol% or less, 65 mol% or less, or 70 mol% or less. When the manganese (Mn) content is within the above range, it has the effect of improving capacity characteristics and output characteristics, while improving the life characteristics of a battery containing the same.

[0074]

[0075] According to one embodiment of the present invention, the lithium iron phosphate-based compound may have a composition represented by the following chemical formula 1.

[0076] [Chemical Formula 1]

[0077] Li 1+y Fe 1-p-q Mn p M 1 q (PO4)

[0078] In the above chemical formula 1,

[0079] M 1It is one or more selected from the group consisting of Al, Mg, Ni, Co, Ti, Mo, Ga, Cu, V, Nb, Zr, Ce, In, Zn, Na, Si, Ca, B, and Y, and

[0080] -0.1≤y≤0.1, 0.4≤p≤0.7, 0≤q≤0.1.

[0081] The above y may be between -0.1 and 0.1. When y satisfies the above range, high capacity characteristics can be achieved and by-products during manufacturing can be minimized.

[0082] The above p is the mole fraction of manganese (Mn) among all metals excluding lithium in the lithium iron phosphate compound, and may be 0.4 or more and 0.7 or less. Specifically, the above p may be 0.4 or more, 0.45 or more, 0.5 or more, or 0.55 or more, and may be 0.6 or less, 0.65 or less, or 0.7 or less. When p is within the above range, the charge / discharge voltage range is widened, and the energy density may be increased.

[0083] The above q is M among the total metals excluding lithium in the lithium complex transition metal oxide. 1 The mole fraction of q may be 0 or greater, or 0.1 or less. Specifically, q may be 0 or greater, greater than 0, 0.001 or greater, 0.002 or greater, or 0.003 or greater, and may be 0.01 or less, 0.02 or less, 0.03 or less, 0.04 or less, 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, or 0.1 or less. When q is within the above range, ionic conductivity and electrical conductivity may be improved.

[0084]

[0085] According to one embodiment of the present invention, the lithium iron phosphate-based compound may include vanadium (V). In this case, since vanadium exists in a form with an oxidation state of +5, the a and b-axis lattice constants of the unit cell of the lithium iron phosphate-based compound are reduced, thereby reducing the overall lattice volume. Accordingly, the mobility and electron conductivity of lithium ions are improved.

[0086]

[0087] According to one embodiment of the present invention, the particles containing the lithium iron phosphate-based compound may comprise primary particles having a particle size (D') obtained from an SEM image of 150 nm or more and 400 nm or less, comprising 60 volume% or more with respect to the total volume of the cathode active material powder. Specifically, the particles containing the lithium iron phosphate-based compound may comprise primary particles having a particle size (D') obtained from an SEM image of 150 nm or more and 400 nm or less, more specifically, primary particles having a particle size (D') obtained from an SEM image of 170 nm or more and 250 nm or less, comprising 60 volume% or more, 65 volume% or more, 70 volume% or more, or 75 volume% or more, and 85 volume% or less, 90 volume% or less, or 100 volume% or less with respect to the total volume of the cathode active material powder. When the particles containing the above lithium iron phosphate-based compound contain primary particles within the above volume range, wherein the particle size (D') obtained from the SEM image is 150 nm or more and 400 nm or less, the rate characteristics, capacity characteristics, and life characteristics of the battery containing the same can be improved.

[0088]

[0089] According to one embodiment of the present invention, the particle comprising the lithium iron phosphate-based compound may further comprise a coating portion comprising carbon (C) formed on the lithium iron phosphate-based compound.

[0090] In addition, according to one embodiment of the present invention, the content of carbon (C) included in the coating portion may be 1.2% by weight or more and 2.5% by weight or less with respect to the total weight of the positive electrode active material powder. Specifically, the content of carbon (C) included in the coating portion may be 1.2% by weight or more, 1.5% by weight or more, or 1.8% by weight or more, and 2.5% by weight or less with respect to the total weight of the positive electrode active material powder. When the content of carbon (C) included in the coating portion is within the above range, the rolling density can be improved while improving the electron conductivity of the positive electrode active material.

[0091]

[0092] According to one embodiment of the present invention, the particles containing the lithium iron phosphate-based compound may be in the form of primary particles. Specifically, the particles containing the lithium iron phosphate-based compound may be single particles consisting of one primary particle, or they may be formed by the aggregation of two or more, ten or fewer, twenty or fewer, thirty or fewer, forty or fewer, or fifty or fewer primary particles due to inevitable aggregation during the process. When the particles containing the lithium iron phosphate-based compound are in the form of primary particles, the effect is to secure a lithium ion migration path while minimizing the resistance of grain boundaries, thereby improving the capacity and rate characteristics of the battery to which the same is applied.

[0093]

[0094] The positive electrode active material powder according to the present invention may be manufactured by a manufacturing method comprising: (A) mixing a lithium raw material, a phosphate raw material, and an iron raw material, and optionally further mixing a doping element raw material (e.g., vanadium, etc.) to prepare a mixture; (B) wet-grinding the mixture with a bead mill to prepare a slurry; (C) calcining the slurry to prepare a calcined product; and (D) grinding the calcined product; but is not limited thereto.

[0095]

[0096] The physical properties of the lithium iron phosphate-based cathode active material according to the present invention can be achieved by appropriately controlling the presence or absence and amount of doping element raw material input, the amount of carbon coating raw material used, the calcination temperature, and the grinding conditions during the manufacture of the cathode active material, but are not limited thereto. For example, in step (B) or step (C), a carbon coating raw material and a dispersant may be further mixed into the mixture.

[0097]

[0098] The above lithium raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide. Specifically, the above lithium raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, etc.

[0099] The above phosphoric acid raw material may be FePO4, H3PO4, NH4H2PO4, (NH4)2HPO4, P2O5, etc.

[0100] The above iron raw material may be an iron-containing phosphate, sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide. Specifically, the above iron raw material may be FePO4, FeSO4, FeC2O4·2H2O, FeCl2, etc.

[0101] The above-mentioned phosphoric acid raw material and iron raw material may be the same. For example, it may be iron phosphate (FePO4).

[0102]

[0103] The above carbon coating raw material can provide a coating portion containing carbon by calcination, and accordingly, the electrical conductivity of the positive electrode active material powder can be improved. The above carbon coating raw material may be sucrose, glucose, lactose, starch, oligosaccharide, polyoligosaccharide, fructose, cellulose, pitch, vinyl resin, cellulose resin, phenolic resin, pitch resin, tar resin, polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, citric acid, ammonium citrate, etc. Specifically, the above carbon coating raw material may be sucrose or pitch.

[0104] The carbon coating raw material may be added in an amount of 3 parts by weight or more and 20 parts by weight or less, specifically 5 parts by weight or more and 10 parts by weight or less, based on 100 parts by weight of the total weight of the lithium raw material, phosphate raw material, iron raw material, and doping element raw material. In this case, the carbon coating raw material is utilized as a material for the oxidation-reduction reaction that proceeds during the process of forming lithium iron phosphate crystals, and an appropriate amount of carbon is coated to improve conductivity.

[0105] The above dispersant may be a carbon-containing compound, specifically, polyethylene glycol (PEG).

[0106]

[0107] The above doping element raw material may be a phosphate, sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, oxide, hydroxide, or oxyhydroxide containing the above doping element, and in this case, the above doping element may be one or more selected from the group consisting of Al, Mg, Ni, Co, Ti, Mo, Ga, Cu, V, Nb, Zr, Ce, In, Zn, Na, Si, Ca, B, and Y. Specifically, when the above doping element is vanadium, it may be vanadium oxide, etc.

[0108]

[0109] When preparing the mixture in step (A) above, the mixture can be prepared by further mixing manganese raw materials.

[0110] The above manganese raw material may be a manganese-containing phosphate, iron phosphate, sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide.

[0111] The above manganese raw material, phosphoric acid raw material, and iron raw material may be the same. For example, Mn α Fe (1-α) PO4 (where 0 < α < 1.0) may be used.

[0112]

[0113] The above lithium raw material, phosphate raw material, iron raw material, doping element raw material and / or manganese raw material can be mixed in an amount such that the lithium iron phosphate-based compound included in the resulting cathode active material powder has a composition represented by Chemical Formula 1.

[0114]

[0115] The mixing of the above raw materials may be wet mixing or dry mixing.

[0116] If the above mixing is a wet mixing, water may be used as a solvent, and after simply mixing the raw materials in water, the mixed solution is milled in a bead mill (conditions: 20~40Hz, use of beads of size 0.3~1㎛, D 50 It may be mixed by wet grinding with a thickness of <225~232nm, Dmax<484~658nm).

[0117]

[0118] Meanwhile, in the case of wet mixing, a dried powder (mixture) can be obtained by finally spray drying.

[0119]

[0120] The above calcination can be performed at a temperature of 650°C to 800°C. In this case, through the optimized calcination temperature, appropriate primary particles are formed and no impurities are formed, thereby enabling the production of a positive electrode active material powder with high rolling density and low resistance, and enabling the production of a positive electrode active material powder in which the value (X) calculated by Equation 1 described in this specification is within a specific range. Additionally, the process may include calcination while maintaining the temperature at 400°C to 500°C for 30 minutes to 2 hours during the heating process. In this case, a positive electrode active material powder in which the value (X) calculated by Equation 1 described in this specification is within a specific range can be produced.

[0121]

[0122] Average particle size (D of lithium iron phosphate-based cathode active material) 50 The average grain size and the presence or amount of doping element raw materials are influenced by various process conditions. Specifically, the presence or absence and amount of doping element raw materials, the amount of carbon coating raw materials used, the calcination temperature, and grinding conditions act in combination. Generally, as the calcination temperature and time increase, the average grain size (D) 50 ) and the average size of the crystal grains may increase. Also, under grinding conditions, the larger the grinding particle size, the greater the average particle diameter (D 50 ) may increase. The more carbon coating raw material is used, the more the carbon hinders particle growth, so the average particle size (D 50 The average size of the crystal grains and the doping element raw materials may decrease. Although the mechanisms of action of doping element raw materials differ depending on the element, for example, in the case of V, Ti, and Mg, they affect the crystal structure by substituting into metal sites. Consequently, the size of the crystal grains may change.

[0123]

[0124] The above calcination may be performed under an inert atmosphere. Specifically, the above calcination may be performed under a nitrogen atmosphere.

[0125]

[0126] The grinding of the above-mentioned sintered product may be performed, for example, using a jet mill under conditions of a feeding pressure of 1.5 to 10 bar and a grinding pressure of 0.5 to 5.0 bar. If the feeding pressure is higher than the grinding pressure, the difference in pressure is not a significant issue. Specifically, it may be performed using a jet mill under conditions of a feeding pressure of 6 bar and a grinding pressure of 1.5 bar.

[0127] As a result of grinding the above-mentioned sintered product, most of the particles may be in the form of primary particles by grinding the sintered product which is in the form of secondary particles. Specifically, it may be a single particle consisting of one primary particle, or it may include some particles formed by the aggregation of two or more, ten or fewer, twenty or fewer, thirty or fewer, forty or fewer, or fifty or fewer primary particles due to inevitable aggregation during the process.

[0128]

[0129] anode

[0130] Next, the anode according to the present invention will be described.

[0131] The anode according to the present invention comprises an anode active material layer comprising an anode active material powder according to the present invention. Specifically, the anode comprises an anode current collector and an anode active material layer formed on the anode current collector and comprising the anode active material powder. Since the anode active material powder has been described above, a detailed explanation is omitted, and only the remaining components are described in detail below.

[0132]

[0133] 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 μm 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.

[0134]

[0135] The above positive active material layer may include a conductive material and a binder together with the positive active material powder. In this case, the positive active material powder may be included in an amount of 80% to 99% by weight, more specifically 85% to 98.5% by weight, based on the total weight of the positive active material layer, and may exhibit excellent capacity characteristics within this range.

[0136]

[0137] 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 whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above conductive material may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0138]

[0139] The above binder serves to improve adhesion between positive active material particles and adhesion between the positive active material powder 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% by weight based on the total weight of the positive active material layer.

[0140]

[0141] The above-described anode may be manufactured according to a conventional anode manufacturing method, except for using the above-described anode active material powder. Specifically, it may be manufactured by applying a composition for forming an anode active material layer, prepared by dissolving or dispersing the above-described anode active material powder and, optionally, a binder and a conductive material in a solvent, onto an anode current collector, followed by drying and rolling. At this time, the types and contents of the anode active material powder, binder, and conductive material are as described above. Alternatively, the above-described anode may be manufactured by casting the composition for forming an anode active material layer onto a separate support, and then laminating the film obtained by peeling from the support onto an anode current collector.

[0142]

[0143] 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.

[0144]

[0145] lithium secondary battery

[0146] Next, a lithium secondary battery according to the present invention will be described.

[0147]

[0148] The present invention can manufacture an electrochemical device comprising the anode. Specifically, the electrochemical device may be a battery, a capacitor, etc., and more specifically, a lithium secondary battery.

[0149]

[0150] Specifically, the above lithium secondary battery comprises a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is identical to the one described above, a detailed description is omitted, and only the remaining components are described in detail below.

[0151]

[0152] In addition, the 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.

[0153]

[0154] In the above lithium secondary battery, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0155] 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 μm 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.

[0156]

[0157] The above-mentioned cathode active material layer optionally includes a binder and a conductive material together with the cathode active material.

[0158]

[0159] 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; and SiO₂ βExamples 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.

[0160] The above-mentioned negative electrode active material may be included in an amount of 80% to 99% by weight relative to the total weight of the negative electrode active material layer.

[0161]

[0162] 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% by weight relative to 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.

[0163]

[0164] 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, specifically 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 whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0165]

[0166] The above-mentioned negative electrode active material layer may be manufactured by applying and drying a composition for forming a negative electrode active material layer, prepared by dissolving or dispersing a negative electrode active material and optionally a binder and a conductive material in a solvent, or by casting the composition for forming a negative electrode active material layer onto a separate support and then laminating the film obtained by peeling from the support onto a negative electrode current collector.

[0167]

[0168] 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 may 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.

[0169]

[0170] In addition, the electrolytes used in the present invention may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which are usable when manufacturing lithium secondary batteries, but are not limited to these.

[0171] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0172] 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; aromatic hydrocarbon-based solvents such as benzene and fluorobenzene; and carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl 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-directing ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, carbonate-based solvents are 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.

[0173]

[0174] 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 above 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 above lithium salt is preferably used within the range of 0.1 to 5.0 M, specifically 0.1 to 3.0 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 lithium ions can move effectively.

[0175]

[0176] 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 10 weight%, specifically 0.1 to 5 weight%, based on the total weight of the electrolyte.

[0177]

[0178] As described above, since the lithium secondary battery containing the positive electrode active material powder according to the present invention exhibits excellent resistance 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).

[0179] Accordingly, according to another embodiment of the present invention, a battery module comprising the lithium secondary battery as a unit cell and a battery pack comprising the same are provided.

[0180] 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.

[0181] The external shape of the lithium secondary battery of the present invention is not particularly limited, but can be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape.

[0182] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also preferably be used as a unit cell in a medium-to-large battery module comprising a plurality of battery cells.

[0183]

[0184] 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.

[0185]

[0186] Examples and Comparative Examples

[0187] Example 1

[0188] Li2CO 3, MnCO3, FePO4, V2O5, and NH4H2PO4 were mixed such that the molar ratio of Li:Mn:Fe:V:PO4 was 1.02:0.6:0.39:0.01:0.6, and then water was added to achieve a solid content concentration of 20 wt% to prepare a mixture.

[0189] Sucrose in the above mixture Li2CO 3, MnCO3, FePO4, V2O5 and NH4H2PO4 are mixed in an amount of 5 parts by weight per 100 parts by weight of the total weight, and polyethylene glycol (PEG) is added to Li2CO 3, MnCO3, FePO4, V2O5 and NH4H2PO4 are mixed at 0.5 parts by weight per 100 parts by weight of the total weight, and then wet-ground using a bead mill (grounding conditions: D 50 A slurry was prepared by <225nm, Dmax<484nm).

[0190] After spray-drying the above slurry (inlet temperature 200°C, outlet temperature 100°C), it is placed in a graphite refractory box and heated from room temperature to 425°C at a rate of 5°C / min under a nitrogen atmosphere. Subsequently, it is subjected to primary firing at 425°C for 1 hour, heated from 425°C to 700°C at a rate of 5°C / min, and subjected to secondary firing at 700°C for 10 hours to produce a fired product in the form of secondary particles, which is then ground with a jet mill to obtain a product in the form of primary particles, and LiMn 0.6 Fe 0.39 V 0.01 Particles (anode active material powder) containing a lithium iron phosphate-based compound having a composition represented by PO4 and a carbon (C) coating portion formed thereon were prepared.

[0191]

[0192] Example 2

[0193] A slurry was prepared by performing the same procedure as in Example 1, except that glucose, rather than sucrose, was mixed into the mixture prepared in Example 1.

[0194] After spray-drying the above slurry (inlet temperature 200℃, outlet temperature 100℃), it is placed in a graphite refractory box and fired at 750℃ under a nitrogen atmosphere for 10 hours to produce a fired product in the form of secondary particles, and then ground with a jet mill to obtain a product in the form of primary particles, and LiMn 0.6 Fe 0.39 V 0.01 Particles (anode active material powder) containing a lithium iron phosphate-based compound having a carbon (C) coating portion formed thereon and a composition represented by PO4 were prepared. At this time, the anode active material powder contains 60 volume% of the particles containing the lithium iron phosphate-based compound relative to the total volume.

[0195]

[0196] Example 3

[0197] Li2CO 3, MnCO3, FePO4, V2O5, MgO, and NH4H2PO4 were mixed such that the molar ratio of Li:Mn:Fe:V:Mg:PO4 was 1.02:0.58:0.40:0.01:0.01:1.0, and then water was added to achieve a solid content concentration of 20 wt% to prepare a mixture.

[0198] Sucrose in the above mixture Li2CO 3, MnCO3, FePO4, V2O5, MgO, and NH4H2PO4 are mixed at 0.035 parts by weight per 100 parts by weight of the total weight, and polyethylene glycol (PEG) is added to Li2CO 3, MnCO3, FePO4, V2O5, MgO, and NH4H2PO4 were mixed at 0.005 parts by weight per 100 parts by weight of the total weight, and then wet-ground using a bead mill (grounding conditions: D 50A slurry was prepared by <232nm, Dmax<658nm).

[0199] The above slurry is spray-dried (inlet temperature 180°C, outlet temperature 95°C) to produce a spray-dried product, and pitch is mixed at a ratio of 0.01 parts by weight per 100 parts by weight of the total weight of the spray-dried product. The mixture is then placed in a graphite refractory container and heated from room temperature to 730°C at a rate of 15°C / minute under a nitrogen atmosphere. Subsequently, a primary firing is performed at a temperature of 750°C for 5 hours to produce a fired product in the form of secondary particles, which is then ground with a jet mill to obtain a product in the form of primary particles and LiMn 0.58 Fe 0.4 V 0.01 Mg 0.01 Particles (anode active material powder) containing a lithium iron phosphate-based compound having a composition represented by PO4 and a carbon (C) coating portion formed thereon were prepared.

[0200]

[0201] Comparative Example 1

[0202] Sucrose to the mixture prepared in Example 1, Li2CO 3, MnCO3, FePO4, V2O5 and NH4H2PO4 are mixed in an amount of 5 parts by weight per 100 parts by weight of the total weight, and single-walled carbon nanotubes other than polyethylene glycol (PEG) are Li2CO 3, MnCO3, FePO4, Except for mixing V2O5 and NH4H2PO4 at 0.5 parts by weight per 100 parts by weight of the total weight, the procedure was carried out in the same manner as Example 1, and the LiMn is in the form of primary particles. 0.6 Fe 0.39 V 0.01 Particles (anode active material powder) containing a lithium iron phosphate-based compound having a composition represented by PO4 and a carbon (C) coating portion formed thereon were prepared.

[0203]

[0204] Comparative Example 2

[0205] Wet grinding of Example 1 (Grinding conditions: D 50 Wet grinding under different conditions (grinding conditions: D <225nm, Dmax<484nm) and other conditions (grinding conditions: D 50 Except for the fact that <358nm, Dmax<1414nm), the procedure was performed in the same manner as Example 1, and the primary particle form is LiMn 0.6 Fe 0.39 V 0.01 Particles (anode active material powder) containing a lithium iron phosphate-based compound having a composition represented by PO4 and a carbon (C) coating portion formed thereon were prepared.

[0206]

[0207] Comparative Example 3

[0208] Li2CO, not the mixture prepared in Example 1 3, Except for preparing a mixture by mixing MnCO3, FePO4, MgO, and NH4H2PO4 such that the molar ratio of Li:Mn:Fe:Mg:PO4 is 1.02:0.6:0.39:0.01:0.6, and then mixing with water to achieve a solid content concentration of 20 wt%, the procedure was carried out in the same manner as Example 1, resulting in a primary particle form and LiMn 0.6 Fe 0.39 V 0.01 Particles (anode active material powder) containing a lithium iron phosphate-based compound having a composition represented by PO4 and a carbon (C) coating portion formed thereon were prepared.

[0209]

[0210] Comparative Example 4

[0211] Sucrose to the mixture prepared in Example 1, Li2CO 3, MnCO3, FePO4, V2O5 and NH4H2PO4 are mixed in a ratio of 2 parts by weight to 100 parts by weight of the total weight, and then wet-ground using a bead mill (grounding conditions: D 50 A first slurry was prepared by (<225nm, Dmax<484nm).

[0212] After spray-drying the above first slurry (inlet temperature 200°C, outlet temperature 100°C), placing it in a graphite refractory container and calcining it at a temperature of 600°C for 1 hour under a nitrogen atmosphere to produce a compound in the form of secondary particles, and then grinding it with a jet mill to produce a compound in the form of primary particles.

[0213] Sucrose to the above compound Li2CO 3, MnCO3, FePO4, V2O5 and NH4H2PO4 are mixed in a ratio of 3 parts by weight to 100 parts by weight of the total weight, water is added to achieve a solid content of 20 wt%, and then wet-ground using a bead mill (grounding conditions: D 50 A second slurry was prepared by (<225nm, Dmax<484nm).

[0214] After spray-drying the above second slurry (inlet temperature 200°C, outlet temperature 100°C), placing it in a graphite refractory box and firing it at a temperature of 700°C for 10 hours under a nitrogen atmosphere to produce a fired product in the form of secondary particles, and then grinding it with a jet mill to obtain a product in the form of primary particles, and LiMn 0.6 Fe 0.39 V 0.01 Particles (anode active material powder) containing a lithium iron phosphate-based compound having a composition represented by PO4 and a carbon (C) coating portion formed thereon were prepared.

[0215]

[0216] Experimental Example

[0217] Experimental Example 1: Measurement of Average Particle Size

[0218] For each cathode active material powder prepared in the above examples and comparative examples, the average particle size (D) was measured using a PSA (Microtrac, S3500). 50 ) was measured, and the results are shown in Table 1 below.

[0219]

[0220] Experimental Example 2: Analysis of Average Grain Size

[0221] For each cathode active material powder prepared in the above examples and comparative examples, after XRD measurement, the average grain size (D c ) is shown in Table 1 below.

[0222] At this time, the XRD measurement was performed using Bruker’s AXS D8 Endeavor, and 0.5g to 1.5g of positive active material particles were taken from each positive active material powder and measured at a scan speed of 0.2° / sec from 2θ 10° to 80° under conditions of Cu-Kα line (wavelength 1.54 Å), acceleration voltage 40 kV, and current 40 mA.

[0223] And, the value (X) according to Formula 1 described in this specification and (D 50 / D c ) 3 The results were calculated and shown in Table 1 below.

[0224]

[0225] Classification average particle size (D 50 Average grain size (D)[nm] c ) [nm](D 50 / D c ) 3 X [nm] Example 1 310145.19.831.8 Example 2 432159.319.921.7 Example 3 328163.28.140.4 Comparative Example 1 25281.329.88.5 Comparative Example 2 70015592.17.6 Comparative Example 3 32048.8282.01.1 Comparative Example 4 280169.14.561.7

[0226] Through Table 1 above, the cathode active material powders of Examples 1 to 3 comprise particles containing a lithium iron phosphate-based compound, and the particles containing the lithium iron phosphate-based compound have an average particle size (D 50 ) is 250 nm or more and 500 nm or less, and the average grain size (D cIt was confirmed that ) is 90 nm or more and 180 nm or less, and the value (X) calculated by Equation 1 described in this specification is 10 nm or more and 50 nm or less. In addition, the cathode active material of Examples 1 and 2 is (D 50 / D c ) 3 It was confirmed that the value was between 5 and 20. On the other hand, it was confirmed that the positive active material powder of Comparative Examples 1 to 3 had a value (X) calculated by Formula 1 described in this specification of less than 10 nm, and the positive active material of Comparative Example 4 had a value (X) calculated by Formula 1 described in this specification of greater than 50 nm.

[0227] And, the positive electrode active material powder of Comparative Example 2 has an average particle size (D) of particles containing a lithium iron phosphate-based compound. 50 It was confirmed that ) is less than 250 nm, and the average grain size (D) of the crystal particles containing the lithium iron phosphate-based compound in the cathode active material powders of Comparative Examples 1 and 3 was D c It was confirmed that ) is less than 90 nm, and the cathode active material powders of Comparative Examples 1 to 3 are (D 50 / D c ) 3 α is greater than 20, and the positive active material powder of Comparative Example 4 is (D 50 / D c ) 3 It was confirmed that it is less than 5.

[0228] Through examples and comparative examples, the value (X) according to Formula 1 described herein, (D 50 / D c ) 3 , average grain size (D c ) and average particle size (D 50 It can be seen that ) is a technical characteristic that appears when manufacturing a positive electrode active material by complexly controlling the calcination step, calcination and calcination temperature, calcination time, and the amount of raw material input.

[0229]

[0230] Experimental Example 3: SEM Image Analysis

[0231] SEM images (approx. 20K magnification) of the cathode active material powders prepared in the above examples and comparative examples were obtained using an SEM (JEOL, JSM7610F-plus), and the particle size (D') and particle size distribution of the primary particles of the cathode active material powders prepared in the examples and comparative examples were calculated using an image processing program (LG Chem, DX program).

[0232] Specifically, SEM images (approx. 20K magnification) of the cathode active material powders prepared in the examples and comparative examples were obtained using an SEM (JEOL, JSM7610F-plus), and a two-dimensional segmentation image was obtained by dividing the boundaries of the primary particles present in the SEM image and displaying them in random colors using an image processing program (LG Chem, DX program). A particle size distribution curve of the primary particles (graph curve of the particle size distribution) was obtained from the segmentation image, and using the particle size distribution curve, the percentage of the cumulative volume distribution of primary particles with a particle size (D') of 150 nm or more and 400 nm or less obtained from the SEM image (volume %) of primary particles with D' of 150 nm or more and 400 nm or less was calculated, and the results are shown in Table 2 below.

[0233] Volume (Volume %) of primary particles with D' being 150 nm or more and 400 nm or less Example 185 Example 278 Example 383 Comparative Example 173 Comparative Example 265 Comparative Example 347 Comparative Example 458

[0234] Through Table 2, it was confirmed that the particles containing lithium iron phosphate-based compounds in the cathode active material powders of Examples 1 to 3 contain primary particles with a particle size (D') obtained from SEM images ranging from 150 nm to 400 nm in an amount of 60 vol% or more relative to the total volume of the cathode active material powder. On the other hand, it was confirmed that the particles containing lithium iron phosphate-based compounds in the cathode active material powders of Comparative Examples 3 and 4 contain primary particles with a particle size (D') obtained from SEM images ranging from 150 nm to 400 nm in an amount of less than 60 vol% relative to the total volume of the cathode active material powder.

[0235]

[0236] Experimental Example 4: Analysis of Carbon (C) Content

[0237] 1 g of each cathode active material powder prepared in the above examples and comparative examples is taken to prepare an analysis sample. Using a carbon analyzer (Primacs, Skalar Analytical), the analysis sample is subjected to high-temperature combustion oxidation at 1,100°C to convert the carbon present in the sample into CO2, which is then measured using an NDIR detector. IC is detected by the acidification in which inorganic carbon is converted into CO2 in the IC reactor. Data is collected using Windows-based PRIMACS MCS software, and the TOC (Total Organic Carbon) concentration of the sample is calculated using the formula TC-IC=TOC. Regarding the carbon (C) present in the analysis sample, the carbon (C) content (weight%) relative to the total weight of the cathode active material is shown in Table 3 below.

[0238]

[0239] Carbon (C) Content (Weight%) Example 11.97 Example 22.13 Example 32.43 Comparative Example 12.34 Comparative Example 22.04 Comparative Example 31.64 Comparative Example 42.27

[0240] Through Table 3, it was confirmed that the carbon content included in the coating portion of the positive active material powders of Examples 1 to 3 is 1.2% by weight or more and 2.5% by weight or less relative to the total weight of the positive active material powder.

[0241] Experimental Example 5: Evaluation of Battery Characteristics

[0242] Coin-type half-battery manufacturing

[0243] An anode slurry was prepared by mixing 90 wt% of the anode active material powder prepared in the above examples and comparative examples, 5.0 wt% of carbon black as a conductive material, and 5.0 wt% of polyvinylidene fluoride (PVDF) as a binder in an N-methylpyrrolidone (NMP) solvent. The anode slurry prepared above was coated on one side of an aluminum current collector, dried at 100°C, and then rolled to produce an anode.

[0244] An electrode assembly was manufactured by using a lithium metal electrode as the negative electrode and interposing a porous polyethylene separator between the positive and negative electrodes. This was placed inside a battery case, and a coin-type half-cell was manufactured by injecting an electrolyte solution in which 1.0 M LiPF6 was dissolved in an organic solvent mixed with ethylene carbonate (EC):ethyl methyl carbonate (EMC):diethyl carbonate (DEC) in a volume ratio of 3:4:3.

[0245]

[0246] Initial charge / discharge capacity evaluation

[0247] Using the coin-type half-cell manufactured as described above, the battery was charged to 4.25 V at 25 ℃ using the CC (0.1C)-CV (Cut-off current: 0.05C) method, left for 20 minutes, and then discharged to 2.5 V using the CC (0.1C) method to measure the charge / discharge capacity (mAh / g). The measured charge capacity (mAh / g) and discharge capacity (C 0.1 ) (mAh / g) is shown in Table 4 below.

[0248]

[0249] Rate characteristic evaluation

[0250] Using the above coin-type half-cell, it was charged to 4.25 V at 25 ℃ using the CC (4C)-CV (Cut-off current: 0.05C) method, left for 20 minutes, and then discharged to 2.5 V using the CC (1C) method, and the discharge capacity (C1) (mAh / g) at this time was measured. Then, the discharge capacity (C at a discharge rate of 0.1C) 0.1 The percentage (C1 / C) of the discharge capacity (C1) at a discharge rate of 1C with respect to ) 0.1 The )(%) was calculated, and the results are shown in Table 4 below.

[0251]

[0252] Classification Charging Capacity (mAh / g) Discharging Capacity (C 0.1 )(mAh / g)C1 / C 0.1 (%) Example 1 152.9 150.8 85.4 Example 2 150.1 146.8 83.7 Example 3 155.1 150.4 85.9 Comparative Example 1 142.2 136.3 78.7 Comparative Example 2 138.9 134.2 80.1 Comparative Example 3 127.5 125.8 82.0 Comparative Example 4 146.2 141.2 78.0

[0253] Through Table 4 above, it was confirmed that the charge / discharge capacity and rate characteristics of the battery prepared with the positive active material powder of Examples 1 to 3 were superior to those of the battery prepared with the positive active material powder of Comparative Examples 1 to 4.

Claims

1. Contains particles containing a lithium iron phosphate-based compound, and The particles containing the above lithium iron phosphate-based compound are in the form of primary or secondary particles, and have an average particle size (D 50 ) is 250 nm or more and 500 nm or less, and the average grain size (D c A positive electrode active material powder having a length of 90 nm or more and 180 nm or less, and a value (X) calculated by Formula 1 below of 10 nm or more and 50 nm or less: [Equation 1] X=D 50 / (D 50 / D c ) 3 In the above Equation 1, D 50 is the average particle size [nm] measured by a Particle Size Analyzer (PSA), and D c is the average grain size [nm].

2. In Claim 1, The above average particle size (D 50 ) is a positive electrode active material powder having a diameter of 280 nm or more and 450 nm or less.

3. In Claim 1, The average size of the above grains (D c ) is a positive electrode active material powder having a length of 110 nm or more and 170 nm or less.

4. In Claim 1, The above (D 50 / D c ) 3 A positive electrode active material powder having a value of 5 or more and 20 or less.

5. In Claim 1, The above lithium iron phosphate-based compound is a positive electrode active material powder having a manganese (Mn) content of 40 mol% or more and 70 mol% or less among the total metals excluding lithium.

6. In Claim 1, The above lithium iron phosphate-based compound is a positive electrode active material powder having a composition represented by the following chemical formula 1: [Chemical Formula 1] Li 1+y Fe 1-p-q Mn p M 1 q (PO4) In the above chemical formula 1, M 1 It is one or more selected from the group consisting of Al, Mg, Ni, Co, Ti, Mo, Ga, Cu, V, Nb, Zr, Ce, In, Zn, Na, Si, Ca, B, and Y, and -0.1≤y≤0.1, 0.4≤p≤0.7, 0≤q≤0.

1.

7. In Claim 1, The above lithium iron phosphate-based compound is a positive electrode active material powder containing vanadium (V).

8. In Claim 1, The positive electrode active material powder comprising the above-mentioned lithium iron phosphate-based compound particles, wherein the particles have a particle size (D') obtained from an SEM image of 150 nm or more and 400 nm or less, and contain 60 volume% or more of primary particles relative to the total volume of the positive electrode active material powder.

9. In Claim 1, A positive electrode active material powder comprising particles containing the above-mentioned lithium iron phosphate-based compound, further comprising a coating portion containing carbon (C) formed on the above-mentioned lithium iron phosphate-based compound.

10. In Claim 9, A positive electrode active material powder having a carbon (C) content of 1.2% by weight or more and 2.5% by weight or less with respect to the total weight of the positive electrode active material powder.

11. In Claim 1, The positive electrode active material powder, wherein the particles containing the above lithium iron phosphate-based compound are in the form of primary particles.

12. An anode comprising an anode active material powder according to any one of claims 1 to 11.

13. A lithium secondary battery comprising a positive electrode according to claim 12.