Positive electrode active material, method for preparing same, and positive electrode and lithium secondary battery comprising same

Abstract

The present invention provides a positive electrode active material, a method for preparing same, and a positive electrode and a lithium secondary battery comprising same, the material comprising a lithium iron phosphate manganese-based compound and having an orientation index (D) of 1.05 to 1.1 as calculated by Equation 1.

Description

Anode active material, method for manufacturing the same, anode including the same, and lithium secondary battery

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0175437 filed November 29, 2024 and Korean Patent Application No. 10-2025-0170823 filed November 12, 2025, and all contents disclosed in said documents are incorporated herein as part of this specification.

[0003] The present invention relates to a positive electrode active material capable of improving battery performance, a method for manufacturing the same, a positive electrode including the same, and a lithium secondary battery.

[0004] Recently, there have been attempts to apply lithium manganese iron phosphate (LMFP) with an olivine structure to lithium secondary batteries used as energy sources for electric vehicles (EVs), energy storage systems (ESS), and portable electronic devices.

[0005] The lithium iron phosphate manganese-based compound (hereinafter, LMFP-based compound) is a compound in which manganese is doped into a conventional lithium iron phosphate compound (hereinafter, LFP-based compound), and has the advantage of having a higher energy density and producing a high output compared to the above LFP-based compound.

[0006] However, LMFP-based compounds, during the repeated insertion and extraction of lithium in the battery's charging and discharging process, Fe 2+ / Fe 3+ and Mn 2+ / Mn 3+ Structural instability is high due to different potentials, and Mn 2+ and Mn 3+ Depending on the difference in diameter, the structure is prone to warping due to repeated charging and discharging, and Mn leaching from the active material 2+ There is a problem where battery performance and lifespan deteriorate rapidly due to this.

[0007] To address this, there have been attempts to improve physical properties by coating carbon (C) onto LMFP-based compounds, but there is a limit to the improvement in energy density because the proportion of the cathode active material decreases as the carbon content increases.

[0008] The present invention provides a positive electrode active material capable of improving battery performance by improving orientation characteristics, a method for manufacturing the same, a positive electrode including the same, and a lithium secondary battery.

[0009] According to one embodiment of the present invention for solving the above problem, the present invention provides a positive electrode active material comprising a lithium iron phosphate manganese-based compound, wherein the orientation index (D) calculated by the following mathematical formula 1 is 1.05 to 1.1.

[0010] [Mathematical Formula 1]

[0011] D = A / B

[0012] In the above formula,

[0013] A is the (101) / (020) peak intensity ratio (I) after rolling. 101 / I 020 ) and,

[0014] B is the (101) / (020) peak intensity ratio (I) before rolling. 101 / I 020 ) and,

[0015] I 101 is the (101) plane peak intensity in the X-ray diffraction (XRD) pattern, and

[0016] I 020 is the (020) plane peak intensity in the X-ray diffraction (XRD) pattern.

[0017] According to another embodiment of the present invention, a method for manufacturing the above-described positive electrode active material is provided, comprising the steps of: mixing a lithium-containing raw material, a manganese-containing raw material, an iron-containing raw material, and a phosphoric acid-containing raw material to prepare a mixture; calcining the mixture to obtain a lithium iron phosphate manganese-based compound; and jet milling the lithium iron phosphate manganese-based compound.

[0018] According to another embodiment of the present invention, a positive electrode comprising the positive electrode active material described above is provided.

[0019] According to another embodiment of the present invention, a lithium secondary battery comprising the anode described above is provided.

[0020] The positive electrode active material according to the present invention has a (101) plane peak intensity (I) derived from a lithium iron phosphate manganese-based compound in the X-ray diffraction (XRD) pattern. 101 ) and (020) plane peak intensity (I 020 By having the orientation index calculated using the ratio of ) exhibit characteristics that satisfy a predetermined range, battery characteristics such as charge / discharge efficiency and resistance can be improved.

[0021] Unless otherwise defined in this specification, all technical and scientific terms are used merely to describe exemplary embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the presence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0022] The present invention is capable of various modifications and may take various forms, and specific embodiments are illustrated and described in detail below. However, this is not intended to limit the invention to the specific disclosed forms, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0023] The technical terms used in this specification are intended merely to refer to specific embodiments and are not intended to limit the invention. Furthermore, the singular forms used herein include plural forms unless the phrases clearly indicate otherwise.

[0024] In this specification, the 'anode active material' may be a composition comprising a plurality of the above-described lithium iron phosphate manganese-based compounds.

[0025] In this specification, a 'primary particle' is a basic unit that forms a secondary particle, which is an aggregate of particles, and primary particles and secondary particles are distinguished by the presence or absence of particle aggregation. When multiple primary particles aggregate to form a secondary particle, a particle interface existing between the primary particles may exist within the secondary particle. The primary particle may refer to the smallest unit demarcated by the particle interface when observing the cathode active material using a scanning electron microscope (SEM). Additionally, the primary particle may refer to a particle in a state where the cathode active material containing secondary particles has been sufficiently crushed in a grinder or disperser.

[0026] In this specification, 'single particle' is a concept distinct from secondary particles formed by the aggregation of hundreds of primary particles. Specifically, it may be in the form of a single particle consisting of one primary particle, or in the form of secondary particles formed by the aggregation of several primary particles. For example, it may refer to a form consisting of 40 or fewer, 30 or fewer, 20 or fewer, 10 or fewer, or 5 or fewer primary particles. In this case, particle breakage can be prevented even at high electrode densities. Furthermore, compared to secondary particles formed by the aggregation of hundreds of primary particles, breakage during rolling is suppressed, enabling the realization of high energy density and preventing lifespan degradation caused by particle breakage.

[0027] In this specification, 'single crystal' refers to a particle form having a single crystal grain inside the particle. Alternatively, it may be a form that does not contain a crystal boundary inside the particle. Since the single crystal is distinguished by the number of crystals inside the particle, it is distinguished from the concept of a single particle defined based on the number of primary particles constituting the particle, regardless of the type and number of crystals inside. When the positive electrode active material is of the single-crystal type, structural stability is improved compared to the polycrystalline type, and lithium ion conductivity is enhanced, resulting in excellent high-speed charging characteristics.

[0028] In this specification, 'grain' refers to a region in a sample where atoms are arranged continuously and periodically in one direction. The grains can be analyzed using an Electron Backscatter Diffraction (EBSD) analyzer. Within a polycrystalline particle, multiple grains can be separated by grain boundaries.

[0029] In this specification, 'grain size' refers to the size of a region having an aligned atomic arrangement. This region is named as a single grain and forms a boundary with other grains. The average grain size can be quantitatively analyzed using X-ray diffraction analysis (XRD) by Cu Kα X-rays. Specifically, XRD data of the synthesized cathode active material is obtained using a Bruker D8 XRD instrument (Cu-target, voltage: 45kV, current: 40mA, 2θ: 10° to 100°), and structural analysis of the obtained data can be performed using the Rietveld refining method, a general structural analysis method, with Malvern Panalytical's Highscore software. The Rietveld refining method is a method in which a diffraction pattern is calculated from an initial structural model that the crystal structure of the materials may have, and this is compared with the measured diffraction pattern of the actual synthesized material. Various structure-related factors are introduced and their values ​​are changed to gradually and iteratively adjust the pattern until the two patterns match well. This method adopts an iterative approach that determines validity based on the difference between the calculated and measured patterns, repeating the process until the difference between the two patterns is minimized. Among the structure-related factors that can be introduced in this process, the crystal size can be derived using the full width at half maximum (FWHM) of each crystal plane appearing in the measured diffraction pattern.

[0030] In this specification, 'particle size' refers to the diameter of an individual particle. In cases where the particle is not spherical, it may refer to the diameter of a virtual, perfect sphere having the same volume as the particle. Alternatively, it may refer to the diameter of a virtual circle having the same area as the cross-section of the particle as confirmed by an optical microscope image, such as a scanning electron microscope; the maximum inscribed circle diameter that can be contained within the cross-section of the particle as confirmed by an optical microscope image; or the diameter of the smallest circle that completely encloses the cross-section of the particle as confirmed by an optical microscope image.

[0031] In this specification, 'mean particle size' refers to a statistical representative value representing a sample containing several particles. For example, it may be the number mean particle size calculated by dividing the sum of the diameters of individual particles by the number of particles, or the mean particle size (Dn) derived by a method using a particle size analyzer as described below.

[0032] The above method for measuring particle size may use a particle size analyzer (PSD) or a scanning electron microscope image analysis method.

[0033] The method using the particle size analyzer described above is a laser diffraction analysis method that irradiates a dispersion solution containing dispersed cathode active material with a laser and analyzes the pattern of scattered light using an optical model. It enables statistical analysis of the entire sample and allows for fast and automated analysis. By utilizing the particle size analyzer, it is possible to derive and analyze volume distribution curves or volume accumulation distribution curves that accumulate from smallest to largest particle sizes.

[0034] Unless otherwise stated in this specification, the particle size or average particle size may be measured using the particle size analyzer. For example, the average particle size of the positive electrode active material may be analyzed using a particle size analyzer on a dispersion in which the positive electrode active material is dispersed. Additionally, the average particle size of the lithium iron phosphate manganese-based compound may be analyzed using a particle size analyzer on a dispersion in which a positive electrode active material containing a plurality of lithium iron phosphate manganese-based compounds is dispersed. Unless otherwise stated in this specification, the average particle size of the lithium iron phosphate manganese-based compound may refer to the average particle size of the positive electrode active material.

[0035] In this specification, 'Dn' refers to the particle size at the n% point of the cumulative volume distribution according to particle size. That is, D 50 is the particle size at the 50% point of the cumulative volume distribution according to particle size, and D 90 The particle size at the 90% point of the cumulative volume distribution according to particle size is D 10 Dn is the particle size at the 10% point of the cumulative volume distribution according to particle size. The above Dn can be measured using the laser diffraction method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500 or Matersizer 3000) to calculate the particle size distribution by measuring the difference in diffraction patterns according to particle size as the particles pass through the laser beam. By calculating the particle diameters at the points corresponding to 10%, 50%, and 90% of the cumulative volume distribution according to particle size in the measuring device, D 10 , D 50 and D 90 It can measure.

[0036] The above scanning electron microscope image analysis method involves measuring the particle size of individual particles on the scanning electron microscope image of the positive electrode active material using image analysis software, etc. The actual morphology of the particles can be taken into account, and the particle sizes of primary and secondary particles distinguished in the scanning electron microscope image can be measured separately.

[0037] The present invention will be described in detail below.

[0038] One embodiment of the present invention relates to a positive electrode active material comprising a lithium iron phosphate manganese-based compound, wherein the positive electrode active material may satisfy an orientation index (D) calculated by the following mathematical formula 1 of 1.05 to 1.1.

[0039] [Mathematical Formula 1]

[0040] D = A / B

[0041] In the above formula,

[0042] A is the (101) / (020) peak intensity ratio (I) after rolling. 101 / I 020 ) and,

[0043] B is the (101) / (020) peak intensity ratio (I) before rolling. 101 / I 020 ) and,

[0044] I 101 is the (101) plane peak intensity in the X-ray diffraction (XRD) pattern, and

[0045] I 020 is the (020) plane peak intensity in the X-ray diffraction (XRD) pattern.

[0046] The above XRD pattern is the result of X-ray diffraction analysis (XRD) using Cu Kα X-rays on the anode, specifically XRD data of the anode analyzed using Bruker's D8 XRD equipment (Cu-target (1.54 Å, voltage: 45 kV, current: 40 mA, 2θ: 10° to 100°). In this case, the peak height appearing in the XRD pattern represents the peak intensity or peak strength.

[0047] The above (101) plane is a plane perpendicular to the lithium ion diffusion path (b-axis direction), and as the intensity of the (101) plane peak in the XRD pattern increases, the lithium ion diffusion path may experience resistance. The above (020) plane is a plane parallel to the lithium ion diffusion path (b-axis direction) within the lithium iron phosphate compound, and as the intensity of the (020) plane peak in the XRD pattern increases, the insertion / extraction of lithium ions becomes smoother, thereby improving electrochemical performance. Therefore, it is necessary to control the orientation of the (101) plane relative to the (020) plane so that it does not increase excessively.

[0048] Meanwhile, generally, when manufacturing a cathode using a cathode active material, the electrode density before the rolling process is approximately 1.4 g / cm³ 3 It exhibits a porosity of 55% or less (in other words, the porosity of the positive active material is 55% or more), but when rolling is performed, the electrode density is 2 to 3 g / cm³ 3 When the range increases, the porosity of the positive active material decreases to about 30% or less, and the orientation of the crystal structure changes. At this time, the electrode density of the lithium iron phosphate-based compound refers to the mass of the active material layer per unit volume of the electrode, and the unit volume of the electrode is the value obtained by multiplying the thickness of the active material layer excluding the current collector by the electrode area.

[0049] In particular, the above lithium iron phosphate manganese-based compound may have a higher peak intensity on the (101) plane and a lower peak intensity on the (020) plane due to the effect of preparation orientation during the rolling process. In order to simultaneously secure lithium ion migration / storage and structural stability at an appropriate level during the preparation orientation following the rolling, it is necessary to control the ratio of (101) / (020) peak intensity (B) before rolling and the ratio of (101) / (020) peak intensity (A) after rolling within a predetermined range.

[0050] Accordingly, the positive active material of the present invention has a (101) plane peak intensity (I) derived from the crystal structure of the lithium iron phosphate manganese-based compound in the XRD pattern. 101 ) and (020) plane peak intensity (I 020 When comparing the orientation of crystal planes before and after rolling of the anode using the ratio of ), it is adjusted to satisfy a predetermined range, thereby optimizing the lithium ion diffusion path and improving the electrochemical performance of the anode material.

[0051] Specifically, the (101) / (020) peak intensity ratio (I) after rolling 101 / I 020 Define ) as A, and the (101) / (020) peak intensity ratio (I) before rolling 101 / I 020 When ) is defined as B, the above A may be 0.85 to 1.5 and the above B may be 0.6 to 0.88.

[0052] That is, the above lithium iron phosphate manganese-based active material exhibits a (101) / (020) peak intensity ratio (B) of 0.6 to 0.88 before rolling in the XRD pattern, but 2 to 3 g / cm³ 3 The (101) / (020) peak intensity ratio (A) after the rolling process to achieve the electrode density may be 0.85 to 1.5, more specifically 0.85 to 1.2, 0.85 to 1.0, or 0.85 to 0.97.

[0053] Based on these A and B, the orientation index (D), i.e., A / B, calculated by the above mathematical formula 1 may be 1.05 to 1.1. More specifically, the orientation index (D) may be 1.08 to 1.1.

[0054] Within the range of the orientation index (D) above, the stability of the crystal structure is improved and an orientation that facilitates the movement and storage of lithium ions can be exhibited. Consequently, even if charging and discharging are repeated, changes in the anode are minimized, thereby enabling improved battery performance such as excellent charge-discharge efficiency and low resistance. If the value of the orientation index (D) above is less than 1.05, the value of A, which is the (101) / (020) peak intensity ratio after rolling, decreases, and the intended effect does not appear, making degradation likely. If the value of the orientation index (D) above exceeds 1.1, the lithium movement path within the anode becomes relatively longer, which reduces charge-discharge efficiency and may increase resistance. Such an orientation index (D) can be achieved by controlling the amount of carbon coating applied to the anode active material, the firing temperature, etc. In addition, the orientation index (D) may be affected by the average particle size of the lithium iron phosphate manganese-based compound included in the positive electrode active material, and the average particle size may be controlled through a grinding process such as jet milling so as not to include fine or large particles that may impede the crystal structure after rolling.

[0055] The lithium iron phosphate manganese-based compound included in the above-mentioned positive electrode active material may be in the form of primary particles, secondary particles formed by the aggregation of the primary particles, or a combination thereof.

[0056] In one embodiment of the present invention, the average particle size (D) of the lithium iron phosphate manganese-based compound is 50) may be 0.1㎛ to less than 0.9㎛, for example, 0.3㎛ or more, 0.4㎛ or more, 0.5㎛ or more, 0.6㎛ or more, 0.65㎛ or more, 0.68㎛ or more, or 0.71㎛ or more, and may be 0.89㎛ or less, 0.88㎛ or less, or 0.87㎛ or less. In particular, the above average particle size (D 50 When the value is between 0.65㎛ and 0.89㎛, the orientation index (D) calculated by Equation 1 is controlled within a predetermined range, thereby improving the stability of the crystal structure and enabling an orientation that facilitates the movement and storage of lithium ions. As a result, even if charging and discharging are repeated, changes in the anode are minimized, thereby enabling improved battery performance such as excellent charge-discharge efficiency and low resistance.

[0057] In one embodiment of the present invention, the lithium iron phosphate manganese-based compound may include an olivine structure. In this case, since it has strong PO bonds, it can prevent the crystal structure from collapsing during the charging and discharging process, thereby improving high-temperature stability. Additionally, since lithium ions mainly move along the b-axis within the olivine structure, the effect of the value calculated by the above-described Equation 1 may appear more prominently in the olivine structure. The olivine structure can be confirmed using XRD analysis.

[0058] In one embodiment of the present invention, the lithium iron phosphate manganese-based compound may be represented by the following chemical formula 1:

[0059] [Chemical Formula 1]

[0060] Li 1+y Fe a Mn b M c (PO4)

[0061] In the above chemical formula 1,

[0062] M is Mg, Al, Si, Ca, Sc, Ti, V, Cr, K, Co, Ni, Cu, Zn, Ga, Ge, As, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Ba, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, La, or a combination thereof, and

[0063] y, a, b, and c satisfy -0.1≤y<1, 0<a<1, 0<b<1, and 0≤c<1, respectively.

[0064] In the above chemical formula 1, M represents an element doped into a lithium iron phosphate manganese-based compound to obtain effects such as electrical conductivity and structural stability.

[0065] More specifically, M may be Mg, Al, Ti, V, Co, Ni, Zr, or a combination thereof. These elements are highly effective for improving lithium ion mobility characteristics or ensuring structural stability, and their effects can be further enhanced depending on the combination used. For example, when Mg is used as M, charge / discharge efficiency can be improved by enhancing lithium ion mobility characteristics, and stability can be improved by facilitating the control of particle growth of the manganese-based lithium iron phosphate compound. When Al is used as M, output characteristics can be improved by enhancing lithium ion conductivity and electrochemical reactivity. When Ti is used as M, thermal stability can be enhanced by improving structural stability. When V is used as M, durability can be improved by enhancing electrical conductivity, and power density can be increased when applied to lithium secondary batteries. When Zr is used as M, durability can be improved by increasing structural strength, and stability can be enhanced due to excellent compatibility with the electrolyte.

[0066] In addition, M may include one or more selected from the group consisting of V; and Mg, Al, Ti, and Zr. Specifically, it may be V and Mg; V and Al; V and Ti; or V and Zr. That is, when V is used together with other elements, the electrical conductivity enhancement effect of V and the effect of other elements complement each other, so that both electrochemical properties and stability properties can be improved.

[0067] If necessary, other elements may be included in addition to the elements described above to improve chemical or physical performance, and, for example, non-metallic elements such as F, S, and N may be additionally included.

[0068] In the above chemical formula 1, y may be 0 to 0.1 or 0 to 0.03, and when the above range is satisfied, structural stability may be improved.

[0069] In the above chemical formula 1, a can be 0.1 to 0.9, 0.15 to 0.85, or 0.2 to 0.8, and when the above range is satisfied, the crystal structure stability can be improved.

[0070] In the above chemical formula 1, b can be 0.1 to 0.5, 0.2 to 0.45, or 0.25 to 0.4, and when the above range is satisfied, side reactions can be reduced to ensure electrochemical stability, and thermal stability and structural stability can be improved.

[0071] In the above chemical formula 1, c may be 0.001 to 0.05, 0.001 to 0.02, or 0.001 to 0.01, and when satisfying the above range, electrical conductivity is improved, so that when applied to a battery, charge and discharge efficiency can be improved and the lattice structure is stabilized so that the movement of lithium ions can be smooth.

[0072] The above chemical formula 1 can satisfy a+b+c=1.

[0073] The above-mentioned lithium iron phosphate manganese-based compound may include a carbon coating layer. In this case, the electrical conductivity of the positive electrode active material may be improved.

[0074] The carbon source for forming the carbon coating layer may include one or more selected from the group consisting of pitch, carbon nanofibers, sucrose, glucose, polyethylene glycol, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), colloidal carbon, citric acid, tartaric acid, glycolic acid, polyacrylic acid, adipic acid, and glycine.

[0075] The carbon content included in the carbon coating layer may be 1 to 3 weight% based on the total weight of the lithium iron phosphate manganese-based compound. For example, it may be 1 weight% or more, 1.1 weight% or more, 1.2 weight% or more, 1.3 weight% or more, 1.4 weight% or more, 1.5 weight% or more, 1.6 weight% or more, 1.7 weight% or more, 1.8 weight% or more, 1.9 weight% or more, or 2 weight% or more, and 2.1 weight% or less, 2.2 weight% or less, 2.3 weight% or less, 2.4 weight% or less, 2.5 weight% or less, 2.6 weight% or less, 2.7 weight% or less, 2.8 weight% or less, 2.9 weight% or less, or 3 weight% or less. When the above content is satisfied, the electronic conductivity of the lithium iron phosphate manganese-based compound used as an active material can be improved, while the coating layer does not act as a resistor.

[0076] The thickness of the carbon coating layer may be in the range of 10 to 50 nm, 10 to 40 nm, or 10 to 30 nm. When the thickness is satisfied, the carbon coating layer may not act as a resistor while improving the electronic conductivity of the active material.

[0077] Another embodiment of the present invention relates to a method for manufacturing the above-mentioned positive electrode active material, wherein the method may include the steps of: mixing a lithium-containing raw material, a manganese-containing raw material, an iron-containing raw material, and a phosphoric acid-containing raw material to prepare a mixture; calcining the mixture to obtain a lithium iron phosphate manganese-based compound; and jet milling the lithium iron phosphate manganese-based compound.

[0078] In the manufacturing step of the above mixture, raw materials for forming a lithium iron phosphate manganese-based compound, namely, a lithium-containing raw material, a manganese-containing raw material, an iron-containing raw material, and a phosphoric acid-containing raw material, are mixed.

[0079] The above lithium-containing raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and is not particularly limited as long as it is soluble in water. Specifically, lithium carbonate (Li2CO3), lithium hydroxide (LiOH), and lithium nitrate (LiNO3) , It may be lithium acetate (CH3COOLi) and Li2(COO)2 or a combination thereof. Specifically, it may be lithium carbonate (Li2CO3), lithium hydroxide (LiOH), or a combination thereof.

[0080] The above manganese-containing raw materials are MnSO4 and MnPO4. 3, It may be at least one selected from the group consisting of MnPO4, MnCO3, MnFeO, Mn2O3, MnO2, Mn3O4, Mn(NO3)2, manganese acetate, manganese dicarboxylate, manganese citric acid, manganese fatty acid salts, oxyhydroxides, and manganese chloride halides, and one or more of these may be used.

[0081] The iron-containing raw material mentioned above may be iron sulfate (FeSO4), iron oxide (FeO), iron oxalate (FeC2O4), iron phosphate (FePO4), ferric phosphate {Fe3(PO4)2}, or a combination thereof. Preferably, iron phosphate may be used. In this case, chemical stability is high, and since the compound itself contains phosphoric acid, the use of additional phosphates can be reduced.

[0082] The above-mentioned phosphoric acid-containing raw materials include lithium phosphate (Li3PO4), lithium dihydrogen phosphate (LiH2PO4), ammonium dihydrogen phosphate ((NH4)2HPO4), ammonium monohydrogen phosphate (NH4H2PO4), phosphoric acid (H3PO4), etc., and these may be used alone or in a mixture of two or more. Preferably, ammonium dihydrogen phosphate or ammonium monohydrogen phosphate may be used. In this case, chemical reaction byproducts can be reduced and the pH of the reaction system can be stabilized.

[0083] The above mixture may include raw materials containing doping elements.

[0084] The above-mentioned raw material containing doping elements may include a doping element (M) comprising Mg, Al, Si, Ca, Sc, Ti, V, Cr, K, Co, Ni, Cu, Zn, Ga, Ge, As, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Ba, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, La, or a combination thereof. Meanwhile, to improve chemical or physical performance, other elements other than those described above may be included, and to improve electrochemical performance, non-metallic elements such as F, S, and N may also be included.

[0085] The above-mentioned raw material containing the doping element may be an oxide, chloride, nitrate, sulfate compound, oxalate compound, or a combination thereof of the doping element.

[0086] When the doping element is aluminum (Al), the raw material containing the doping element may be aluminum oxide (Al2O3), aluminum hydroxide (Al(OH)3), aluminum nitrate (Al(NO3)3), aluminum sulfate (Al2(SO4)3), aluminum dihydrogen acetate ((HO)2AlCH3CO2), aluminum monohydrogen acetate (HOAl(CH3CO2)2), aluminum acetate (Al(CH3CO2)3), aluminum halides, or a combination thereof. Preferably, aluminum hydroxide may be used. In this case, excessive temperature is not required during the doping process, and since no components other than water are detected as byproducts, it is environmentally friendly and allows for uniform doping.

[0087] When the doping element is vanadium (V), the raw material containing the doping element may be vanadium oxide. The vanadium oxide may be VO2, V2O3, V2O5, or a combination thereof. Preferably, it may be V2O5. V2O5 has high reactivity, which can improve doping efficiency, and since it has excellent heat resistance, it has the effect of stably maintaining the crystal structure of the lithium iron phosphate manganese-based compound during the calcination process.

[0088] When the doping element is magnesium (Mg), the raw material containing the doping element may be magnesium oxide (MgO), magnesium hydroxide {Mg(OH)2}, magnesium chloride (MgCl2), or a combination thereof. Preferably, magnesium oxide may be used. Magnesium oxide has excellent thermal stability, so it is maintained without decomposing even during high-temperature heat treatment, and has excellent dispersibility, which has the effect of excellent doping efficiency.

[0089] When the doping element is zirconium (Zr), the raw material containing the doping element may be zirconium oxide (ZrO2), zirconium chloride (ZrCl4), or a combination thereof. Preferably, zirconium oxide may be used. Zirconium oxide has excellent thermal stability, so it is maintained without decomposing even during high-temperature heat treatment, and it has excellent reactivity and doping efficiency.

[0090] When the above doping element is titanium (Ti), the raw material containing the above doping element may be titanium oxide (TiO2). Titanium oxide has excellent thermal stability, so it is maintained without decomposing even during high-temperature heat treatment, and has the effect of excellent reactivity.

[0091] The above mixture may additionally include a carbon source. The carbon source can form a carbon coating layer by being carbonized during the calcination step of the mixture.

[0092] The carbon source may be sucrose, glucose, polyethylene glycol, polyvinyl alcohol, polyvinyl acetate, or a combination thereof. Preferably, it may be sucrose, glucose, or polyethylene glycol. In this case, it has the effect of easily forming a carbon coating layer by thermally decomposing easily even at low temperatures. In addition, since sucrose is uniformly carbonized upon heat treatment and glucose is well soluble in water and easily adsorbed onto a lithium iron phosphate manganese-based compound, the carbon coating is uniformly formed and the microstructure is easy to control.

[0093] The above carbon source may be used in an amount of 3 to 15 parts by weight or 5 to 10 parts by weight based on 100 parts by weight of the mixture. When the above content is satisfied, a uniform carbon coating is possible, and the energy density of the anode can be improved.

[0094] If necessary, the mixture may be wet-ground to control particle size before calcination. For example, the mixture may be added to a solvent such as water or ethanol, and if necessary, a dispersant may be added to obtain a slurry; the slurry may then be wet-ground by feeding it into equipment such as a bead mill or ball mill and rotating it. The solid content of the slurry may be 10 to 40 weight%, 15 to 35 weight%, or 25 to 35 weight%, and satisfying the solid content prevents an increase in the viscosity of the slurry, thereby enabling the grinding process to be performed effectively. The mixture that has undergone the wet-ground process has an average particle size (D) of 0.3 to 1 μm or 0.3 to 0.6 μm. 50 It can represent ) and when this is satisfied, the reaction rate increases during the subsequent firing process and the formation and growth of the crystal structure can be performed stably.

[0095] The above wet-ground mixture may be dried to remove moisture or impurities before calcination. The drying may be performed for 10 minutes to 10 hours, 30 minutes to 5 hours, or 40 minutes to 3 hours at a temperature range of 50 to 300 ℃, 80 to 250 ℃, or 100 to 200 ℃. When the above drying conditions are satisfied, moisture and impurities can be sufficiently removed while preventing the mixture from undergoing thermal deformation.

[0096] The above calcination step can be performed at a temperature of 500°C to 900°C, specifically 650°C to 850°C, 680°C to 820°C, or 680°C to 710°C. When the above temperature range is satisfied, the raw material reacts sufficiently so that a crystal structure can be stably formed and excessive particle growth can be prevented. That is, under the above temperature conditions, the electrochemical characteristics and crystallinity of the positive active material can be improved.

[0097] The above firing can be performed for 1 to 50 hours, 2 to 20 hours, or 5 to 15 hours, and when the above firing time is satisfied, the effect of controlling the firing temperature described above can be secured without setting the firing temperature excessively.

[0098] In addition, an inert gas selected from argon (Ar), nitrogen (N2), or a combination thereof may be used during the above calcination. A reducing atmosphere may be created by adding a small amount of hydrogen (H2) to the inert gas. The reducing atmosphere may be advantageous for securing electrochemical properties by iron ions by easily controlling the oxidation state of the iron ions.

[0099] Subsequently, jet milling can be performed on the lithium iron phosphate manganese-based compound obtained through the above calcination.

[0100] The above-described jet milling is a method of performing grinding by filling a grinding chamber with raw materials and injecting high-pressure compressed air onto the raw materials using a spray nozzle, thereby inducing mutual collision between particles by the formed high-speed airflow, and enables grinding to a fine size without the incorporation of impurities.

[0101] The jet milling applied in the present invention can be performed by injecting compressed air using an injection nozzle with an inner diameter of 2 to 5 mm.

[0102] In addition, the jet milling can be performed under conditions of a spray speed of 300 rpm to 600 rpm, a feeding pressure of 2 bar to 5 bar, and a grinding pressure of 1 bar to 6 bar. If the spray speed is less than 300 rpm, productivity is low, and if it exceeds 600 rpm, large powder may be formed due to particle aggregation. If the feeding pressure is too low, backflow may occur. In addition, if the grinding pressure is less than 1 bar, large powder may be produced, and if it exceeds 6 bar, the generation of fine powder may impair operational stability.

[0103] Average particle size (D) of the above jet-milled lithium iron phosphate manganese-based compound 50 ) may be 0.1㎛ to less than 0.9㎛, for example, 0.3㎛ or more, 0.4㎛ or more, 0.5㎛ or more, 0.6㎛ or more, 0.65㎛ or more, 0.68㎛ or more, or 0.71㎛ or more, and may be 0.89㎛ or less, 0.88㎛ or less, or 0.87㎛ or less. In particular, the above average particle size (D 50 When the value is between 0.65㎛ and 0.89㎛, the orientation index (D) calculated by Equation 1 is controlled within a predetermined range, thereby improving the stability of the crystal structure and allowing for smooth orientation of lithium ion movement / storage. Consequently, even if charging and discharging are repeated, changes in the anode are minimized, thereby enabling improved battery performance such as excellent charge / discharge efficiency and low resistance.

[0104] Another embodiment of the present invention relates to a positive electrode comprising the positive electrode active material.

[0105] An anode according to one embodiment of the present invention can be manufactured by a process comprising the steps of forming an anode active material layer by coating and drying an anode active material composition comprising the anode active material, a binder, and a conductive material onto an anode current collector, and rolling.

[0106] Specifically, the above positive active material composition can be obtained in the form of a slurry by mixing and stirring a lithium iron phosphate manganese-based compound as an active material together with a binder and a conductive material in a solvent.

[0107] The above lithium iron phosphate manganese-based compound can be used in an amount of 80 to 99 weight%, specifically 85 to 98.5 weight%, based on the total weight of the positive electrode active material layer, and can exhibit excellent capacity characteristics when satisfying the above range.

[0108] 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 content of the above binder may be 0.1 to 15 weight% based on the total weight of the positive active material layer.

[0109] The above conductive material is used to impart conductivity to the electrode and can be used without special restrictions as long as it has electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fibers; metal powder or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The content of the above conductive material may be 0.1 to 15 weight% based on the total weight of the positive electrode active material layer.

[0110] 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.

[0111] In addition, the positive current collector may be used without special limitations as long as it is conductive and does not cause chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surfaces treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the 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 films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

[0112] Next, the above positive active material composition is coated and dried on a positive current collector to form a positive active material layer.

[0113] The above coating method is not particularly limited as long as it is a method commonly used in the field. For example, a coating method using a slot die may be used, and in addition, Meyer bar coating, gravure coating, immersion coating, spray coating, etc. may be used. Alternatively, the above positive active material layer may be manufactured by casting a positive active material composition onto a separate support and then laminating the film obtained by peeling it off from the support onto a positive current collector.

[0114] In addition, the above drying may be performed under conditions typically applied in the field. For example, the drying may be performed at a temperature of 130°C or lower.

[0115] The rolling of the positive electrode active material layer formed through the above coating and drying can be performed by a roll pressing method, and specifically, the electrode density after rolling is 2 to 3 g / cm³ 3It can be performed to the extent that the range is [described]. When the above conditions are satisfied, the preparation orientation of the lithium iron phosphate manganese-based compound included in the positive electrode active material layer is effectively carried out, and a stable olivine structure can be maintained.

[0116] Another embodiment of the present invention relates to an electrochemical device comprising the anode, specifically a lithium secondary battery.

[0117] 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.

[0118] Additionally, 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.

[0119] 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.

[0120] 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.

[0121] The above-mentioned cathode active material layer optionally includes a binder and a conductive material together with the cathode active material.

[0122] 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 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 and coal tar pitch-derived cokes.

[0123] The content of the above-mentioned negative electrode active material may be 80 to 99 weight% based on the total weight of the negative electrode active material layer.

[0124] 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.

[0125] 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, etc. may be used.

[0126] The above-mentioned cathode active material layer may be manufactured by applying a composition for forming a cathode active material layer, prepared by dissolving or dispersing a cathode active material and optionally a binder and a conductive material in a solvent, onto a cathode current collector and drying it, or by casting the composition for forming a cathode active material layer onto a separate support and then laminating the film obtained by peeling from the support onto a cathode current collector.

[0127] The above separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. It can be used without special limitations as long as it is typically used as a separator in a lithium secondary battery, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte wettability. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and it may optionally be used in a single-layer or multi-layer structure.

[0128] Examples of the above electrolytes that can be used in the manufacture of lithium secondary batteries include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., but are not limited to these.

[0129] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0130] 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-bonded aromatic 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 and 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.

[0131] The above lithium salt can be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably used within the range of 0.1 to 5.0 M, specifically 0.1 to 3.0 M. When the concentration of the lithium salt is satisfied, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0132] 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.

[0133] As described above, since the lithium secondary battery containing the positive electrode active material according to the present invention exhibits excellent lifespan and capacity 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).

[0134] 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.

[0135] 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.

[0136] There are no specific restrictions on the external shape of the above lithium secondary battery, but it may be a cylindrical type using a can, a prismatic type, a pouch type, or a coin type.

[0137] The above 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.

[0138] The present invention will be described in more detail below through examples. However, the following examples are intended to illustrate the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention, and the scope of the present invention is not limited only to these examples.

[0139] <Example 1>

[0140] Li2CO3, MnPO3, FePO4, and NH4H2PO4 were mixed such that the molar ratio of Li:Mn:Fe:PO4 was 1:0.3:0.7:1. Subsequently, 10 parts by weight of a 7:2 (wt% / wt%) mixture of glucose (GC) and polyethylene glycol (PEG) as carbon sources was mixed with 100 parts by weight of the total weight of the mixture. Water was added to prepare the mixture so that the solid content was 30 wt%.

[0141] The above mixture was wet-milled with a bead mill to obtain a slurry (average particle size D50: 0.421㎛), and then spray-dried (inlet temperature 235℃, outlet temperature 85℃, for 1 hour) to remove moisture.

[0142] Subsequently, by calcining for 10 hours under a nitrogen atmosphere and a calcination temperature of 700°C, a lithium iron phosphate manganese-based compound (LiMn) having a carbon layer 0.3 Fe 0.7 PO4)(Average particle size D 50 : 6.25㎛) was obtained.

[0143] The above-mentioned lithium iron phosphate manganese-based compound (average particle size D50: 6.25 μm) was prepared as the cathode active material, and jet milling was performed. At this time, jet milling was carried out under conditions of a spray nozzle of 4Φ, a feeding pressure of 5 bar, a grinding pressure of 2.5 bar, and a speed of 600 rpm, so that the average particle size (D 50 The size of ) was adjusted to 0.716㎛.

[0144] An anode slurry was obtained by mixing the above-mentioned pulverized lithium iron phosphate manganese-based compound, carbon black conductive material, and polyvinylidene fluoride (PVdF) binder in an N-methylpyrrolidone solvent at a weight ratio of 90:5:5. The anode slurry was coated onto one side of an aluminum current collector with a thickness of 12 μm and dried at 130°C for at least 20 minutes to form an anode active material layer (electrode density: 1.4 g / cm³). 3formed ).

[0145] Subsequently, the positive active material layer formed on the above current collector is rolled to an electrode density of 2.3 g / cm³ 3 The anode was manufactured by performing rolling to achieve this.

[0146] <Examples 2 and Comparative Examples 1 to 4>

[0147] The anode was manufactured using the same process, except that the conditions shown in Table 1 below were applied.

[0148]

[0149] Experimental Example 1: Measurement of Average Particle Size

[0150] 50 mg of each cathode active material powder prepared in the examples and comparative examples and 0.5 ml of a nonionic surfactant (Triton X-100) were mixed and dispersed in 50 ml of deionized water, then placed into a conical tube. The powders were dispersed for 5 minutes using an ultrasonic disperser to prevent aggregation, and then poured into an analysis beaker containing 450 ml of deionized water. The beaker was introduced into a laser diffraction particle size analyzer (Malvern Mastersizer 3000) to measure the difference in diffraction patterns according to particle size as the particles passed through the laser beam, thereby calculating the particle size distribution. By calculating the particle size at the point where the cumulative particle size distribution curve reaches 50%, D 50 Measured.

[0151] Experimental Example 2: XRD Analysis

[0152] For the anodes of the examples and comparative examples, the anode active material layer before rolling (electrode density 1.4 g / cm³) 3 ) and positive electrode active material layer after rolling (electrode density 2.3 g / cm³ 3X-ray diffraction (XRD) analysis using CuKα rays was performed on the electrode. The electrode density was determined by measuring the mass of the active material layer per unit volume of the electrode after manufacturing the electrode sample to a certain size, where the unit volume of the electrode is the value obtained by multiplying the thickness of the active material layer excluding the current collector by the electrode area.

[0153] Specifically, XRD analysis was performed using a Bruker D8 XRD instrument (Cu-target (1.54 Å, voltage: 45 kV, current: 40 mA, 2θ: 10° to 100°), and in the XRD diffraction patterns before and after rolling, the intensity (I of the peak corresponding to the (101) crystal plane (the peak with the greatest height among the peaks appearing at 2θ 19° to 21°) 101 The intensity (I) of the peak corresponding to the ) and (020) crystal planes (the peak with the greatest height among the peaks appearing at 2θ 29° to 32°) 020 After measuring ), the orientation index (D) was calculated using the following mathematical formula 1 and is shown in Table 1.

[0154] [Mathematical Formula 1]

[0155] In the above formula,

[0156] A is the (101) / (020) peak intensity ratio (I) after rolling. 101 / I 020 ) and,

[0157] B is the (101) / (020) peak intensity ratio (I) before rolling. 101 / I 020 ) and,

[0158] I 101 is the (101) plane peak intensity in the X-ray diffraction (XRD) pattern, and

[0159] I 020 is the (020) plane peak intensity in the X-ray diffraction (XRD) pattern.

[0160] Experimental Example 3: Battery Performance Evaluation

[0161] In the examples and comparative examples, an electrode assembly was prepared by using lithium metal as the anode and cathode, and interposing a porous polyethylene separator between the anode and cathode. After placing the electrode assembly inside a case, an electrolyte was injected into the case to produce a coin half cell. The electrolyte was prepared by dissolving 1 M concentration lithium hexafluorophosphate (LiPF6) in an organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 3:4:3.

[0162] The above-mentioned manufactured coin half battery was charged at 0.1C in CCCV mode at 25℃ until it reached 4.25V, and discharged at a constant current of 0.1C until it reached 2.5V, and the charging capacity, discharging capacity, and charge-discharging efficiency (%) (discharging capacity / charging capacity × 100) were evaluated.

[0163] In addition, the voltage drop over 60 seconds after the start of discharge was measured, and the discharge resistance was calculated by dividing this by the applied current value.

[0164] Process Conditions LMFP Average Particle Size (D 50, μm Orientation Result Cell Characteristics Carbon Coating (parts by weight) Sintering Temperature (°C) Jet Milling (feeding / grinding / rpm) ABD=A / B Charge Capacity (mAh / g) Discharge Capacity (mAh / g) Charge / Discharge Efficiency (%) Resistance (Ω) Comparative Example 110 (GC:PEG=8:2) 680 5bar / 1.5bar / 600rpm 0.958 0.99 0.80 1.24 314 5.81 38.69 5.118 8.6 Comparative Example 29 (GC:PEG=8:2) 740 5bar / 1.5bar / 500rpm 1.07 10.83 0.81 1.02 115 7.61 53.59 7.41 55.7 Comparative Example 39 (GC:PEG=8:2) 740 5bar / 1.5 bar / 400 rpm 0.90 10.8 20.78 1.046 157.6 153.497.3158.1 Comparative Example 411 (GC:PEG=8:2) 720 5 bar / 2.5 bar / 400 rpm 0.59 20.90 0.8 1.120 153.6 149.597.3139.3 Example 19 (GC:PEG=8:2) 700 5 bar / 2.5 bar / 600 rpm 0.71 60.97 0.88 1.10 157.6 154.598.0134.7 Example 29 (GC:PEG=8:2) 700 5 bar / 2 bar / 600 rpm 0.87 10.86 0.79 10.89 157 41 54 49 8.11 33 3.31) The LMFP average grain size is the grain size measured after jet milling.2) A is the (101) / (020) peak intensity ratio in the XRD pattern analyzed after rolling.3) B is the (101) / (020) peak intensity ratio in the XRD pattern analyzed before rolling.

[0165] From Table 1 above, Examples 1 and 2 effectively maintained a stable olivine structure by ensuring that preparation orientation, which creates orientation in the crystal structure during the rolling step, proceeded effectively. Consequently, the orientation index (D), i.e., the value of A / B calculated from the (101) / (020) peak intensity ratio (A) after rolling and the (101) / (020) peak intensity ratio (B) before rolling, satisfied the range of 1.05 to 1.1. This is achieved by controlling the carbon coating amount and calcination temperature during the preparation of the lithium iron phosphate manganese-based compound, and by changing the jet milling conditions to avoid including fine or large particles, with an average particle size (D 50 It is predicted that this is achieved by controlling ). In contrast, Comparative Example 1 is predicted to have a higher orientation index (D) as the A value increases, as the peak intensity in the (020) direction decreases after rolling due to the presence of particles with relatively large particle sizes as firing is performed at a relatively lower temperature than the example.

[0166] Comparative Examples 2 and 3 are predicted to not effectively achieve pre-alignment after rolling because, as sintering is performed at a relatively higher temperature than in the Examples, large particles with reduced crystallinity are present due to the occurrence of side reactions or the formation of incomplete crystal structures.

[0167] Meanwhile, in Comparative Example 4, a large amount of fine particles with low particle size is present, and as particle aggregation occurs during the electrode manufacturing process, it is predicted that the orientation index (D) deviates from a predetermined range due to the influence of aggregated particles.

[0168] Therefore, it can be confirmed that the coin half cell using the anode according to Examples 1 and 2 has higher charge / discharge efficiency and significantly lower discharge resistance compared to the cell using the anode of Comparative Examples 1 to 4. This is a result in which the electrode change of the anode according to Examples 1 and 2 is minimized compared to Comparative Examples 1 to 4.

Claims

1. Contains a lithium iron phosphate manganese-based compound, and A positive active material having an orientation index (D) of 1.05 to 1.1 calculated by the following mathematical formula 1: [Mathematical Formula 1] D = A / B In the above formula, A is the (101) / (020) peak intensity ratio (I) after rolling. 101 / I 020 ) and, B is the (101) / (020) peak intensity ratio (I) before rolling. 101 / I 020 ) and, I 101 is the (101) plane peak intensity in the X-ray diffraction (XRD) pattern, and I 020 is the (020) plane peak intensity in the X-ray diffraction (XRD) pattern.

2. In Paragraph 1, A positive active material having an orientation index (D) calculated by the above mathematical formula 1 of 1.08 to 1.

1.

3. In Paragraph 1, The above A is 0.85 to 1.5, and The above B is a positive active material having a value of 0.6 to 0.

88.

4. In Paragraph 3, The above A is a positive active material having a value of 0.85 to 0.

97.

5. In Paragraph 1, The above (101) plane peak appears at a diffraction angle (2θ) of 19° to 21°, and The above (020) plane peak appears at a diffraction angle (2θ) of 29° to 32°.

6. In Paragraph 1, Average particle size (D) of the above lithium iron phosphate manganese-based compound 50 ) is a positive electrode active material with a thickness of less than 0.1㎛ to 0.9㎛.

7. In Paragraph 6, Average particle size (D) of the above lithium iron phosphate manganese-based compound 50 ) is a positive active material having a thickness of 0.65㎛ to 0.89㎛.

8. In Paragraph 1, The above lithium iron phosphate manganese-based compound is a positive active material represented by the following chemical formula 1: [Chemical Formula 1] Li 1+y Fe a Mn b M c (PO4) In the above chemical formula 1, M is Mg, Al, Si, Ca, Sc, Ti, V, Cr, K, Co, Ni, Cu, Zn, Ga, Ge, As, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Ba, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, La, or a combination thereof, and y, a, b, and c satisfy -0.1≤y<1, 0<a<1, 0<b<1, and 0≤c<1, respectively.

9. In Paragraph 1, The above lithium iron phosphate manganese-based compound is a positive electrode active material comprising a carbon coating layer.

10. A step of preparing a mixture by mixing a lithium-containing raw material, a manganese-containing raw material, an iron-containing raw material, and a phosphoric acid-containing raw material; A step of obtaining a lithium iron phosphate manganese-based compound by calcining the above mixture; and A method for manufacturing a positive electrode active material according to any one of claims 1 to 9, comprising the step of jet milling the above-mentioned lithium iron phosphate manganese-based compound.

11. In Paragraph 10, A method for manufacturing an anode active material, wherein the above jet milling is performed under conditions of a spray speed of 300 rpm to 600 rpm, a feeding pressure of 2 bar to 5 bar, and a grinding pressure of 1 bar to 6 bar.

12. A positive electrode comprising a positive electrode active material according to any one of paragraphs 1 to 9.

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