Method for preparing positive active material for lithium secondary battery

Abstract

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

Description

Technology Field

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

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

[0004] The above lithium secondary battery is manufactured by using materials capable of reversible intercalation / deintercalation of lithium ions as positive and negative active materials, and adding an electrolyte for electrical and ion conduction.

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

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

[0007] However, nanoscaled lithium iron phosphate tends to aggregate easily due to intermolecular forces and grow into shapes unfavorable to energy density. Additionally, the carbon coating reduces the fluidity of lithium iron phosphate particles, which leads to a decrease in the density of the cathode active material.

[0008] As technology advances and the demand for lithium-ion batteries, including electric vehicles, increases rapidly, there is a growing need within related industries to increase the capacity of lithium-ion batteries, which is directly related to product usage time. The problem to be solved

[0010] In the lithium secondary battery market, while the growth of lithium secondary batteries for electric vehicles is acting as a driving force, the demand for cathode active materials used in lithium secondary batteries is also continuously changing, and in particular, the need for increased capacity of cathode active materials is gradually growing.

[0011] One objective of this specification is to provide a method for manufacturing an anode active material that is advantageous in terms of energy density, having a spherical, smooth shape and including a uniform carbon coating layer, in order to meet the demands of such markets.

[0012] In addition, the present specification aims to provide a positive electrode comprising a positive electrode active material manufactured according to the manufacturing method defined herein.

[0013] In addition, the present specification provides a lithium secondary battery using a positive electrode as defined herein. means of solving the problem

[0015] According to one aspect of the present specification, a positive electrode active material for a lithium secondary battery comprising a particulate material is provided, wherein the particulate material has a spherical shape, an amorphous carbon coating layer with a thickness of 1 to 500 nm is formed on at least a portion of the surface of at least a portion of the particulate material, and the average sphericity of the particulate material is 0.70 to 0.95.

[0016] Meanwhile, a cross-sectional SEM image of the above-mentioned positive active material may satisfy Equation 1 below:

[0017] [Equation 1]

[0018] (R m / r M )≤1.30

[0019] In the above equation, R m is the average of the radii of the smallest circles circumscribing the above particulate matter, and r M is the average radius of the largest circle inscribed in the above particulate matter.

[0020] In one embodiment, the compressed density of the positive active material may be 2.40 g / cc or higher.

[0021] Here, the 10 MPa powder resistance (ρ) of the positive active material 10 ) and 50 MPa powder resistance (ρ 50 The ratio of ) (ρ 10 / ρ 50 ) may be 1.40 or less.

[0022] In addition, the above particulate matter can be represented by the following chemical formula 1:

[0023] [Chemical Formula 1]

[0024] Li p M1 x M2 y A z P 1-z O4

[0025] In the above chemical formula, M1 is at least one selected from the group consisting of Fe, Mn, Ni, and Co, M2 is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Cr, Cu, Ga, Hf, In, K, La, Mg, Mo, Na, Nb, Nd, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr, A is at least one selected from the group consisting of C, Si, S, N, B, F, Cl, and I, and 0.5≤p≤1.5, 0 <x≤1, 0≤y<1, 0≤z<1, x+y=1이다.

[0026] Meanwhile, a compound represented by the following chemical formula 2 may be present on at least a portion of the surface of at least some of the particulate matter:

[0027] [Chemical Formula 2]

[0028] Li a M3 b O c

[0029] In the above chemical formula, M3 is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Hf, In, K, La, Mg, Mn, Mo, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr, and 0≤a≤10, 0 <b≤8, 2≤c≤13이다.

[0030] According to another aspect of the present specification, a method for manufacturing a positive electrode active material for a lithium secondary battery is provided, comprising: (a) mixing a lithium-containing raw material, a transition metal precursor, a carbon-based compound, and a dispersant to prepare a slurry; (b) grinding particles in the slurry; and (c) heat-treating the ground particles to obtain a lithium composite compound.

[0031] In one embodiment, at least one sub-raw material comprising an element selected from Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, F, Fe, Ga, Hf, I, In, K, La, Mg, Mo, N, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Si, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn and Zr may be additionally added to the slurry in step (a).

[0032] In addition, the above dispersant may be a polymer with a molecular weight of 1,000 to 40,000 g / mol.

[0033] In addition, the above dispersant may be a polymer with a pH of 3.0 to 8.0.

[0034] In one embodiment, the carbon atomic ratio of the carbon-based compound and the dispersant may be 5 to 8: 2 to 5.

[0035] In addition, in step (b) above, the solid content in the slurry may be ground so that the average particle size is 1.0 μm or less.

[0036] In addition, the above step (c) can be performed at a temperature in which the carbon-based compound and the dispersant are carbonized.

[0037] According to another aspect, a positive electrode comprising the above positive active material is provided.

[0038] According to another aspect, a lithium secondary battery using the above positive electrode is provided. Effects of the invention

[0040] According to the present specification, a spherical positive electrode active material having a smooth surface can be manufactured by including a carbon-based compound and a dispersant that satisfy specific conditions when manufacturing a lithium composite compound through the calcination of raw materials.

[0041] In addition, since the carbon coating layer is uniformly formed during the manufacture of the above-mentioned positive active material, a minimum amount of carbon-based compound can be used.

[0042] Accordingly, the above-mentioned cathode active material has a high press density, so it can have excellent energy density when applied to a cathode.

[0043] In addition, a method for manufacturing a positive electrode active material that can effectively exhibit these characteristics is provided.

[0044] In addition to the effects described above, the specific effects of this specification are described together with the specific details for implementing the matters described in this specification below. Brief explanation of the drawing

[0046] FIG. 1 schematically illustrates a method for calculating the properties of a particulate material according to one embodiment of the present specification; FIG. 2 shows a cross-sectional SEM image of a lithium composite compound according to one embodiment of the present specification. Specific details for implementing the invention

[0047] For convenience of understanding this specification, specific terms are defined herein. Unless otherwise defined herein, scientific and technical terms used herein shall have the meanings generally understood by those skilled in the art. Furthermore, unless specifically indicated in the context, terms in their singular form shall be understood to include their plural form, and terms in their plural form shall be understood to include their singular form.

[0049] Hereinafter, a positive electrode active material for a lithium secondary battery according to the present specification, a method for manufacturing the same, a positive electrode including the positive electrode active material, and a lithium secondary battery using the said positive electrode will be described in more detail.

[0051] Cathode active material for lithium secondary batteries

[0052] A positive electrode active material for a lithium secondary battery according to one aspect of the present specification is a positive electrode active material for a lithium secondary battery comprising a particulate material, wherein the particulate material has a spherical shape, and an amorphous carbon coating layer with a thickness of 1 to 500 nm is formed on at least a portion of the surface of at least a portion of the particulate material, and the average sphericity of the particulate material may be 0.70 to 0.95.

[0053] The above positive electrode active material may include a particulate material composed of a lithium complex compound capable of lithium intercalation / deintercalation.

[0054] In one embodiment, the particulate material may exist without forming any significant aggregates. In this case, the particulate material may have a spherical shape. Additionally, since the lithium composite compound is a particulate material having a smooth surface, the positive electrode active material may have excellent compressive density.

[0055] Here, the average particle size of the particulate material (wherein the average particle size of the particulate material may be the average major axis length of the particulate material) exists within the range of 0.01 to 5 μm, thereby enabling the realization of the optimal density of the anode manufactured using the anode active material according to various embodiments.

[0056] Meanwhile, in another example, the particulate material exists as a primary particle, and the primary particles may aggregate in multiple numbers to form a secondary particle. Here, the primary particle refers to a single grain or crystallite, and the secondary particle refers to an aggregate formed by the aggregation of multiple primary particles. In this case, the primary particle may have a spherical shape. Since the lithium composite compound is a particle having a smooth surface, the positive electrode active material may have excellent compressive density.

[0057] Voids and / or grain boundaries may exist between the primary particles constituting the secondary particles. The primary particles may form internal voids by being spaced apart from neighboring primary particles within the secondary particles. Additionally, the primary particles may form a surface existing within the secondary particles by coming into contact with internal voids rather than coming into contact with neighboring primary particles to form grain boundaries. Meanwhile, the surface of the primary particles existing on the outermost surface of the secondary particles that is exposed to the outside air forms the surface of the secondary particles.

[0058] Here, the average particle size of the primary particles (wherein the average particle size of the primary particles may be the average major axis length of the primary particles) exists within the range of 0.1 to 5 μm, thereby enabling the realization of the optimal density of the cathode manufactured using the cathode active material according to various embodiments. The average particle size of the secondary particles, which are aggregated from the primary particles, may vary depending on the number of aggregated primary particles, but generally may be 30.0 to 40.0 μm.

[0059] In another embodiment, the positive electrode active material may include a lithium composite compound existing in a single-crystal form with an average particle size of 0.1 μm or more.

[0060] In addition, the positive electrode active material may include a coating layer that covers at least a portion of the surface of the particulate material (e.g., the interface between the particulate materials) and / or the aggregate formed by the aggregation of the particulate materials.

[0061] Here, the coating layer may include a carbon layer and / or an oxide layer to improve the stability of the particulate material or to improve conductivity.

[0062] For example, the coating layer may exist to cover at least a portion of the exposed surface of the particulate material. Meanwhile, if the particulate material aggregates to form secondary particles, the coating layer may exist to cover at least a portion of the exposed surface of the primary particles located at the outermost edge of the secondary particles.

[0063] Accordingly, the coating layer may exist as a layer that continuously or discontinuously coats the surface of the particulate material and / or the secondary particles formed by the aggregation of the particulate material. If the coating layer exists discontinuously, it may exist in the form of an island.

[0064] In addition, when the particulate material forms an aggregate, the coating layer may exist not only at least a portion of the interface between the particulate materials and the surface of the secondary particles, but also in the internal pores formed inside the secondary particles.

[0065] The coating layer existing in this way can contribute to improving the electrochemical properties and stability of the positive electrode active material.

[0066] At this time, the coating layer may exist in the form of a solid solution that does not form a boundary with the particulate material and / or the secondary particles formed by the aggregation of the particulate material, but is not necessarily so.

[0067] Meanwhile, the thickness of the amorphous carbon coating layer formed on at least some of the surface of at least some of the particulate material may be 1 to 500 nm, for example, 1 nm, 2.5 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 50 nm, 75 nm, 100 nm, 125 nm, 150 nm, 175 nm, 200 nm, 225 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or a range between two of these values.

[0068] Here, the thickness of the carbon coating layer can be controlled according to the balance of fluidity and conductivity of the lithium composite compound.

[0069] In particular, the carbon coating layer has a small thickness variation, so the positive electrode active material can have excellent balance of fluidity and conductivity, which are in a complementary relationship.

[0070] Various known methods can be used to measure the thickness of the carbon coating layer. For example, it can be measured from TEM or SEM images, or determined from the results of line scanning of carbon in a specific direction from EDX analysis results. Such thickness may be the average value obtained after measuring at least three times.

[0071] Furthermore, the carbon coating layer can be uniformly formed on the surface of the lithium composite compound, which is a particulate material, to have a smooth surface texture. As a result, the compression density of the positive electrode active material can be increased.

[0072] Meanwhile, the synthesis conditions under which the carbon coating layer is uniformly formed can also influence the crystal growth of the particulate material to help form a spherical particle morphology. As a result, the average sphericity of the particulate material may be 0.70 to 0.95, for example, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, or a range between two of these values.

[0073] FIG. 1 schematically illustrates a method for calculating the properties of particulate matter according to one embodiment of the present specification.

[0074] In this specification, "sphericity" refers to the degree to which a particulate material approximates an ideal sphere. This sphericity can be obtained by plotting the smallest circle circumscribing each particle in a cross-sectional SEM image, and then dividing the cross-sectional area of ​​the particulate material by the area of ​​the plotted circle.

[0075] For example, referring to Figure 1 (a), the sphericity may mean the value of S1 / S2.

[0076] Meanwhile, the average of the above sphericity may be the average of values ​​calculated from at least 3, for example, 3, 5, 10, 15, 20, 25, or 50 particulate materials.

[0077] Olivine-based cathode materials are PO4 3-It is known to have low electrical conductivity due to strong covalent bonding. In addition, Li, which undergoes one-dimensional diffusion due to its crystal structure + Due to its characteristics, the ionic conductivity is low. To address this, it has been proposed to form a carbon coating layer and manufacture a nanoscaled cathode active material.

[0078] However, the amorphous carbon coating layer causes a decrease in the density of the cathode active material. Due to aggregation, nano-sized particles grow into angular shapes during calcination, which reduces flowability and similarly lowers the density of the cathode active material. This leads to a problem where the energy density per unit volume decreases.

[0079] On the other hand, the particulate material comprising the lithium composite compound according to the present specification comprises a uniform carbon coating layer. Furthermore, under conditions that form such a carbon coating layer, the lithium composite compound can grow into a spherical particulate material, thereby minimizing the reduction in density.

[0080] Meanwhile, a cross-sectional SEM image of the above-mentioned positive active material may satisfy Equation 1 below:

[0081] [Equation 1]

[0082] (R m / r M )≤ 1.30

[0083] In the above equation, R m is the average of the radii of the smallest circles circumscribing the above particulate matter, and r M is the average radius of the largest circle inscribed in the above particulate matter. For example, refer to (b) of Fig. 1.

[0084] Here, the above formula represents the ratio between the most protruding part and the most indented part of the particulate material. The smaller the value of the above formula, the more it may indicate that the particulate material is a uniform spherical particle.

[0085] In addition to the sphericity described above, the positive active material satisfying Equation 1 above has excellent flowability of the particulate material and can have a higher density.

[0086] Here, the average of the above formula may also be the average of values ​​measured for at least 3, for example, 3, 5, 10, 15, 20, 25, or 50 particulate materials.

[0087] In one embodiment, the compressive density of the positive active material may be 2.40 g / cc or higher, for example, 2.40 g / cc, 2.41 g / cc, 2.42 g / cc, 2.43 g / cc, 2.44 g / cc, 2.45 g / cc, 2.46 g / cc, 2.47 g / cc, 2.48 g / cc, 2.49 g / cc, 2.50 g / cc, 2.51 g / cc, 2.52 g / cc, 2.53 g / cc, 2.54 g / cc, 2.55 g / cc, 2.56 g / cc, 2.57 g / cc, 2.58 g / cc, 2.59 g / cc, 2.60 g / cc, or a range between two of these values ​​or 2.60 g / cc or higher.

[0088] A positive electrode active material satisfying the above range may have a relatively high energy density. This may be attributed to the shape and surface texture of the lithium composite compound, i.e., the particulate material, included in the positive electrode active material.

[0089] Here, the 10 MPa powder resistance (ρ) of the positive active material 10 ) and 50 MPa powder resistance (ρ 50 The ratio of ) (ρ 10 / ρ 50 ) may be 1.40 or less, for example, 1.40, 1.39, 1.38, 1.37, 1.36, 1.35, 1.34, 1.33, 1.32, 1.31, 1.30, 1.28, 1.27, 1.26, 1.25, 1.24, 1.23, 1.22, 1.21, 1.20, 1.19, 1.18, 1.17, 1.16, 1.15, or a range between two of these values.

[0090] A high ratio of such powder resistance may mean that, apart from compression density, conductivity is low without external pressure due to issues with the morphology or surface texture of the particulate material. Meanwhile, the cathode active material according to the present specification includes a uniform spherical particulate material, so that the ratio of 10 MPa powder resistance to 50 MPa powder resistance can satisfy the above range.

[0091] In addition, the above particulate matter can be represented by the following chemical formula 1:

[0092] [Chemical Formula 1]

[0093] Li p M1 x M2 y A z P 1-z O4

[0094] In the above chemical formula, M1 is at least one selected from the group consisting of Fe, Mn, Ni, and Co, M2 is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Cr, Cu, Ga, Hf, In, K, La, Mg, Mo, Na, Nb, Nd, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr, A is at least one selected from the group consisting of C, Si, S, N, B, F, Cl, and I, and 0.5≤p≤1.5, 0 <x≤1, 0≤y<1, 0≤z<1, x+y=1이다.

[0095] The above chemical formula 1 represents a lithium complex compound capable of intercalation / deintercalation of lithium, and may include lithium, a metal, and a phosphate.

[0096] For example, the above p may be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, or a range between two of these values, but is not limited thereto.

[0097] Meanwhile, the above x may include 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or a range between two of these values. In one example, the above x may be 0.5 or greater, but is not limited thereto.

[0098] In addition, the above y and z may each be 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.99, or include a range between two of these values, but are not limited thereto.

[0099] That is, LiFePO4, etc. can be represented by the above chemical formula 1. Meanwhile, the above lithium complex compound may further include a dopant. Here, the dopant can be represented by M2.

[0100] Meanwhile, a compound represented by the following chemical formula 2 may be present on at least a portion of the surface of at least some of the particulate matter:

[0101] [Chemical Formula 2]

[0102] Li a M3 b O c

[0103] In the above chemical formula, M3 is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Hf, In, K, La, Mg, Mn, Mo, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr, and 0≤a≤10, 0 <b≤8, 2≤c≤13이다.

[0104] The compound represented by Chemical Formula 2 above may exist separately from the amorphous carbon coating layer or may exist as a discontinuous phase within the continuous phase of the amorphous carbon coating layer. In one example, the compound represented by Chemical Formula 2 may form a coating layer. The coating layer may coat at least a portion of the surface of the particulate material continuously or discontinuously, and if the coating layer exists discontinuously, it may exist in the form of an island. Additionally, the coating layer may exist in the form of a solid solution that does not form a boundary with the particulate material, but is not necessarily so.

[0105] Meanwhile, even if a coating layer of the compound is present on at least a portion of the surface of the particulate material, it is desirable for the particulate material to maintain a spherical shape.

[0107] Method for manufacturing a positive electrode active material for a lithium secondary battery

[0108] A method for manufacturing a positive electrode active material for a lithium secondary battery according to another aspect of the present specification may include: (a) a step of preparing a slurry by mixing a lithium-containing raw material, a transition metal precursor, a carbon-based compound, and a dispersant; (b) a step of grinding particles in the slurry; and (c) a step of obtaining a lithium composite compound by heat-treating the ground particles.

[0109] Step (a) above is a step of preparing an aqueous solution slurry by mixing raw materials for manufacturing a lithium composite compound in water. Here, the lithium composite compound includes lithium composite phosphate, lithium composite oxide, etc.

[0110] The lithium-containing raw material used in step (a) above is intended to form a lithium composite compound used as a positive electrode active material, and may include lithium hydroxide, lithium carbonate, lithium nitrate, lithium phosphate, lithium fluoride, or lithium acetate.

[0111] The lithium compound above may be mixed such that the ratio of the number of atoms of lithium (Li) to the total number of atoms of metal elements other than lithium (Metal) in the slurry (Li / Metal) is in the range of 0.90 to 1.10, for example, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, or a range between two of these values. Alternatively, depending on the purpose, the ratio (Li / Metal) may be mixed such that it is in the range of 0.5 to 1.5, but is not limited thereto.

[0112] Meanwhile, the above transition metal precursor is a precursor material for a lithium complex compound containing one or more transition metal elements, and can form a lithium complex compound by reacting with a lithium-containing raw material.

[0113] The above transition metal precursor may include at least one transition metal such as iron, manganese, nickel, cobalt, vanadium, titanium, chromium, copper, zinc, etc., and at least one of elements such as phosphorus, oxygen, hydrogen, carbon, silicon, sulfur, nitrogen, boron, fluorine, chlorine, iodine, etc.

[0114] Meanwhile, the above transition metal precursor may include at least one transition metal and at least one anion.

[0115] Optionally, the transition metal precursor may be doped with a heterogeneous element. Here, the heterogeneous element may be at least one selected from Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, F, Fe, Ga, Hf, I, In, K, La, Mg, Mo, N, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Si, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr.

[0116] As an example, the transition metal precursor may be an iron complex hydroxide or iron complex oxide containing iron, or an iron complex phosphate containing iron and phosphorus, etc. For example, an iron complex hydroxide precursor can be prepared through a synthesis reaction in an aqueous solution containing iron raw materials.

[0117] More specifically, an iron complex hydroxide precursor can be prepared by stirring an aqueous solution containing an iron raw material, a phosphorus raw material, and an oxidizing agent, and adding a basic aqueous solution dropwise.

[0118] Here, the input amounts of the iron raw material, phosphorus raw material, and oxidizing agent may vary depending on the composition of the desired cathode active material. For example, when manufacturing LiFePO4, the iron raw material, phosphorus raw material, and oxidizing agent may be added such that the difference in input amounts between them is 5% or less on a molar basis, but is not limited thereto.

[0119] Meanwhile, a raw material containing a heterogeneous element may be optionally added to the above aqueous solution.

[0120] Examples of the aforementioned iron raw materials include ferrous sulfate, ferrous oxalate, ferric citrate, ferrous hydroxide, ferrous phosphate, ferric chloride, ferrous nitrate, ferric acetate, etc.

[0121] As the above-mentioned phosphorus raw materials, phosphoric acid, iron phosphate, lithium dihydrogen phosphate, lithium phosphate, ammonium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, phosphorus pentoxide, etc. may be used.

[0122] In addition, examples of the above oxidizing agents include hydrogen peroxide, glycolic acid, citric acid, ammonium persulfate, sodium persulfate, potassium persulfate, potassium permanganate, ammonium peroxydisulfate, nitric acid, chloric acid, chromic acid, manganese dioxide, ferric chloride, etc.

[0123] As the above basic aqueous solution, sodium hydroxide aqueous solution, ammonia aqueous solution, potassium hydroxide aqueous solution, etc., may be used.

[0124] In one embodiment, a hydroxide precursor can be prepared by adding a basic aqueous solution to an aqueous solution in which an iron raw material, a phosphorus raw material, and an oxidizing agent are added to pure water (DIW), and reacting it at a temperature of 40 to 80°C.

[0125] The above reaction may be carried out under inert conditions, for example, in a reaction system substituted with at least one inert gas selected from the group consisting of N2, Ar, He, Rn, Ne, and Xe, but is not limited thereto.

[0126] Meanwhile, if necessary, a raw material containing a foreign element can be added to dope the hydroxide precursor with a foreign element.

[0127] An iron complex oxide precursor can be produced by heat-treating the above iron complex hydroxide precursor.

[0128] In one example, an iron composite oxide precursor can be prepared by heat-treating an iron composite hydroxide precursor in a kiln at 400 to 700°C. Here, the heat treatment may be performed by heating in a kiln at a rate of 1 to 10°C per minute for 1 to 10 hours and then cooling, but is not limited thereto.

[0129] Using an iron composite oxide precursor prepared in this way, it is possible to form nano-primary particles having an olivine crystal structure.

[0130] Meanwhile, the above transition metal precursor may be represented by the chemical formula 3 below.

[0131] [Chemical Formula 3]

[0132] M1 x M2 y A z P 1-z O4

[0133] In the above formula, M1 is at least one selected from the group consisting of Fe, Mn, Ni, and Co, M2 is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Cr, Cu, Ga, Hf, In, K, La, Mg, Mo, Na, Nb, Nd, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr, A is at least one selected from the group consisting of C, Si, S, N, B, F, Cl, and I, and 0 <x≤1, 0≤y<1, 0≤z<1, x+y=1이다.

[0134] Here, the transition metal precursor represented by Chemical Formula 3 is a type of oxide precursor and can be prepared by heat treating a sulfate, carbonate, nitrate, acetate, silicate, phosphate, borate, fluoride, chloride, or hydroxide. For example, FePO4 is one of the non-limiting examples of Chemical Formula 3.

[0135] In one embodiment, at least one sub-raw material comprising an element selected from Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, F, Fe, Ga, Hf, I, In, K, La, Mg, Mo, N, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Si, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn and Zr may be additionally added to the slurry in step (a).

[0136] By additionally adding a sub-raw material in step (a) above, it is possible to dope elements not included in the transition metal precursor or adjust the proportion of elements included in the transition metal precursor.

[0137] Meanwhile, the carbon-based compound included in the slurry of step (a) above may be intended to form a carbon coating that improves the conductivity of the positive electrode active material. By minimizing the thickness of the carbon coating layer while increasing its uniformity, the decrease in flowability caused by amorphous carbon can be minimized and the conductivity of the positive electrode active material can be improved.

[0138] Here, examples of the above carbon-based compounds include, but are not limited to, sucrose, glucose, polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), colloidal carbon, citric acid, tartaric acid, glycolic acid, polyacrylic acid, adipic acid, glycine, and aminobenzoic acid.

[0139] In addition, the properties of the carbon-based compound forming the carbon coating layer can be controlled by controlling the properties of the carbon coating layer.

[0140] For example, the carbon-based compound may be a compound in which the proportion of the C element in the molecular structure is 30 to 60 wt%, for example, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, 40 wt%, 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45 wt%, 46 wt%, 47 wt%, 48 wt%, 49 wt%, 50 wt%, 51 wt%, 52 wt%, 53 wt%, 54 wt%, 55 wt%, 56 wt%, 57 wt%, 58 wt%, 59 wt%, 60 wt%, or a range between two of these values.

[0141] If a carbon-based compound is used in which the proportion of the C element satisfies the above range, a product with excellent yield and uniformity of carbon coating can be manufactured even when using the same amount of compound.

[0142] Meanwhile, since the above manufacturing method forms a carbon coating using a wet coating method, raw materials with sufficient solubility in water can be used.

[0143] Accordingly, the carbon-based compound may have a solubility in water at 25°C of 0 to 3,000 g / L, for example, 3,000 g / L, 2,750 g / L, 2,500 g / L, 2,250 g / L, 2,000 g / L, 1,750 g / L, 1,500 g / L, 1,250 g / L, 1,000 g / L, 750 g / L, 500 g / L, 250 g / L, 200 g / L, 150 g / L, 100 g / L, 50 g / L, or a range between two of these values.

[0144] Using carbon-based compounds with solubility within the above range can more easily form a uniform coating, but is not limited thereto.

[0145] Meanwhile, the carbon-based compound needs to be carbonized within the heat treatment temperature of step (c).

[0146] If uncarbonized carbon-based compounds remain in the cathode active material, conductivity improvement may be insufficient or unexpected side effects may occur.

[0147] In addition, the characteristics of the carbon coating formed may vary depending on the 25°C solubility of the carbon-based compound in water (B) and the ratio of element C (A). In particular, if the ratio (B / A) is 30 or more (unit omitted), for example, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45 or more, a more uniform and thin carbon coating layer can be formed.

[0148] In particular, if the value of B / A satisfies the above range and the slurry of step (a) is intended for manufacturing a lithium iron phosphate-based compound, a carbon coating layer of 1 to 500 nm can be uniformly formed.

[0149] Although the mechanism of action is not clearly known, it may be that the raw material of the lithium iron phosphate compound is sufficiently dispersed within a slurry containing both the carbon-based compound and the dispersant, satisfying conditions for forming a uniform carbon coating.

[0150] Meanwhile, as a means to minimize the aggregation of nano-sized particles, the slurry of step (a) may include a dispersant.

[0151] Crushed or nano-sized particles easily aggregate due to surface energy. Aggregated particles grow into angular shapes during the calcination process, which leads to a decrease in the density of the cathode active material. The dispersant can inhibit aggregation during particle growth by activating the interface and generating surface electrostatic forces. As a result, the particles grow into spherical shapes, which can improve density characteristics.

[0152] Furthermore, the dispersant can enable the carbon-based compound to form a more uniform carbon layer. In addition, the dispersant, as a carbon-based polymer, can be carbonized by heat treatment to form a uniform carbon coating layer in the final product. Therefore, the dispersant does not cause unnecessary side reactions inside the secondary battery containing the product.

[0153] Meanwhile, in order for the above-mentioned dispersant to form a carbon coating layer while having a sufficient particle dispersion effect, one having a specific molecular weight may be used.

[0154] Here, the dispersant is 1,000 to 40,000 g / mol, for example, 1,000 g / mol, 1,500 g / mol, 2,000 g / mol, 2,500 g / mol, 3,000 g / mol, 3,500 g / mol, 4,000 g / mol, 4,500 g / mol, 5,000 g / mol, 5,500 g / mol, 6,000 g / mol, 6,500 g / mol, 7,000 g / mol, 7,500 g / mol, 8,000 g / mol, 8,500 g / mol, 9,000 g / mol, 9,500 g / mol, 10,000 g / mol, 12,500 g / mol, 15,000 g / mol, 17,500 The polymer may have a molecular weight of g / mol, 20,000 g / mol, 22,500 g / mol, 25,000 g / mol, 27,500 g / mol, 30,000 g / mol, 32,500 g / mol, 35,000 g / mol, 37,500 g / mol, 40,000 g / mol, or a range between two of these values. Here, the molecular weight may be the weight-average molecular weight measured by GPC based on a polystyrene standard sample. If the molecular weight of the dispersant satisfies the above-described range, problems such as carbonization occurring too quickly during the heat treatment process or residue remaining in the final product can be prevented.

[0155] Meanwhile, the above dispersant has a pH of 3.0 to 8.0, for example, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, It may be a polymer with a range between two of these values, such as 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, or a range between two of these values.

[0156] If a dispersant satisfying the above characteristics is used, the synthesis reaction performed in the slurry of step (a) can be carried out smoothly.

[0157] The above-mentioned dispersant is not limited to any type as long as it satisfies the characteristics described above, but commercially available dispersants may include polyoxyethylene sorbitan monolaurate, polyether amine salt, polycarboxylic acid ammonium salt, modified polycarboxylic acid, etc.

[0158] Here, the amounts of the carbon-based compound and the dispersant added may vary depending on the composition of the cathode active material to be manufactured.

[0159] For example, since both the carbon-based compound and the dispersant can form a carbon coating layer, the ratio of the number of carbon atoms (C) to the total number of metal atoms other than lithium (Metal) in the slurry (C / Metal) is in the range of 0.30 to 0.70, for example, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.50, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57. 0.58, 0.59, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, or can be added to form a range between two of these values.

[0160] Meanwhile, the ratio of the carbon-based compound and the dispersant may vary depending on the target product.

[0161] In one embodiment, the carbon atomic ratio of the carbon-based compound and the dispersant may be 5 to 8 : 2 to 5, for example, 5 : 5, 5.25 : 4.75, 5.5 : 4.5, 5.75 : 4.25, 6 : 4, 6.25 : 3.75, 6.5 : 3.5, 6.75 : 3.25, 7 : 3, 7.25 : 2.75, 7.5 : 2.5, 7.75 : 2.25, 8 : 2, or a range between two of these, but is not limited thereto.

[0162] Next, step (b) is a step of grinding particles in the slurry. Here, lithium-containing raw materials, transition metal precursors, etc. may exist in particulate form in the slurry.

[0163] To grind the above particles, dry or wet dispersion mills such as a ball mill, a bead mill (beads commonly used to grind metallic raw materials such as Al beads, Fe beads, or Zr beads can be used), a vibratory mill, an attritor mill, an air jet mill, a disc mill, or an air classifier mill can be used.

[0164] In step (b) above, the average particle size of the solids in the slurry may be ground to 1.0 μm or less. That is, the average particle size of the particles ground in step (b) above may be 1.0 μm or less, for example, 1.0 μm, 0.9 μm, 0.8 μm, 0.7 μm, 0.6 μm, 0.5 μm, 0.4 μm, 0.3 μm, 0.2 μm, 0.1 μm, or a range between two of these values.

[0165] Meanwhile, after grinding in step (b) above, the slurry can be dried to obtain it in powder form. For example, the slurry can be dried through spray drying.

[0166] Spray drying, which is an example of the above drying, can be performed in a spray dryer. The spray dryer is not particularly limited to any spray drying device capable of producing dried particles with a shape close to spherical by spray drying the slurry containing the crushed particles, but may include an ultrasonic atomizer, a single-fluid spray nozzle atomizer, a two-fluid spray nozzle atomizer, an ultrasonic nozzle atomizer, a filter expansion droplet generator (FEAG), or a disc-type droplet generator.

[0167] The spray dryer may include a spray nozzle and a drying chamber, and the slurry is atomized into droplets of a predetermined size through the spray nozzle and sprayed into the drying chamber where a relatively high-temperature gas flow exists.

[0168] The raw material in the droplet sprayed into the drying chamber can be dried into particles with a shape close to spherical under the temperature environment inside the drying chamber.

[0169] Meanwhile, the dispersant included in the above slurry can suppress unnecessary aggregation of the particles during spray drying. As a result, particles with a shape close to spherical can be obtained.

[0170] Here, by adjusting the viscosity of the slurry after completing the grinding of step (b) above, the condensation time during drying can be shortened and the decrease in density due to moisture loss during drying can be minimized.

[0171] Moisture loss during drying can reduce particle density and form pores. As a result, particle strength decreases, and the stability of the cathode active material may be insufficient.

[0172] Meanwhile, if the viscosity of the above slurry is excessively high, fluidity decreases during drying, resulting in insufficient process efficiency and making it difficult to obtain spherical particles.

[0173] One of the means for controlling the viscosity of the above slurry is to add a binder.

[0174] Next, step (c) above may be a step of heat-treating the particles crushed in step (b) above to form a lithium composite compound.

[0175] During the heat treatment of step (c) above, the carbon-based compound and the dispersant may be carbonized to form a carbon coating layer. That is, step (c) above may be performed at a temperature in which the carbon-based compound and the dispersant are carbonized.

[0176] The heat treatment temperature of step (c) above may be 300 to 1,000°C, for example, 300°C, 350°C, 375°C, 400°C, 425°C, 450°C, 475°C, 500°C, 525°C, 550°C, 575°C, 600°C, 625°C, 650°C, 675°C, 700°C, 725°C, 750°C, 775°C, 800°C, 825°C, 850°C, 875°C, 900°C, 925°C, 950°C, 975°C, 1000°C, or a range between two of these values, and the heat treatment temperature may vary depending on the composition of the target anode active material.

[0177] More specifically, the heat treatment of step (c) above may be performed for 5 to 12 hours in a kiln maintaining an N2 atmosphere, increasing the temperature from 300 to 1,000°C at a rate of 1 to 10°C per minute. If the heat treatment temperature of step (c) above is less than 300°C, the calcination of the precursor proceeds insufficiently, resulting in insufficient crystal growth of the lithium composite compound or difficulty in forming a carbon coating layer. On the other hand, if the heat treatment temperature of step (c) above exceeds 1,000°C, thermal decomposition of the lithium composite compound may occur, leading to a decrease in particle strength or particle disintegration.

[0178] Optionally, before heat-treating the particles ground in step (b) in step (c), at least one sub-raw material comprising an element selected from Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, F, Fe, Ga, Hf, I, In, K, La, Mg, Mo, N, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Si, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr, and at least one selected from lithium-containing raw materials may be additionally added. The sub-raw material may be provided in at least one form selected from sulfates, carbonates, nitrates, acetates, chlorides, hydroxides, and oxides.

[0179] At this time, the content of the sub-raw material introduced in step (c) above may vary depending on the composition of the particles and the composition of the target positive active material.

[0180] Accordingly, when heat-treating the mixture of the particles and the sub-raw material in step (c) above, an element contained in the sub-raw material among the lithium composite compound may be doped or coated on at least a portion of the surface of the lithium composite compound.

[0181] Additionally, before or after performing step (c) above, disintegration, distribution, and / or washing processes may be performed on the lithium composite compound. These processes may utilize those typically performed.

[0183] lithium secondary battery

[0184] According to another aspect, a positive electrode may be provided comprising a positive current collector and a positive active material layer formed on the positive current collector. Herein, the positive active material layer may include a positive active material according to the various embodiments described above.

[0185] The above positive current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the above positive current collector may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesion of the positive active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0186] The above positive active material layer can be manufactured by applying a positive slurry composition, which includes a conductive material and optionally a binder together with the positive active material, to the positive current collector.

[0187] At this time, the positive active material may be included in an amount of 80 to 99 weight%, more specifically 85 to 98.5 weight%, based on the total weight of the positive active material layer. Excellent capacity characteristics may be exhibited when included within the above-mentioned content range, but it is not necessarily limited thereto.

[0188] The above conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxide such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above conductive material may be included in an amount of 0.1 to 15 weight% with respect to the total weight of the positive electrode active material layer.

[0189] The above binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above binder may be included in an amount of 0.1 to 15 weight% based on the total weight of the positive active material layer.

[0190] The above-described anode can be manufactured according to a conventional anode manufacturing method, except for using the above-described anode active material. Specifically, it can be manufactured by applying an anode slurry composition, prepared by dissolving or dispersing the above-described anode active material and optionally a binder and a conductive material in a solvent, onto an anode current collector, and then drying and rolling.

[0191] 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.

[0192] In addition, in another embodiment, the anode may be manufactured by casting the anode slurry composition onto a separate support and then laminating the film obtained by peeling off from the support onto an anode current collector.

[0193] In addition, according to another aspect, an electrochemical device including the anode described above may be provided. Specifically, the electrochemical device may be a battery, a capacitor, etc., and more specifically, a lithium secondary battery.

[0194] Specifically, the above lithium secondary battery may include a positive electrode, a negative electrode positioned opposite to the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode.

[0195] In addition, the above-mentioned lithium secondary battery may be provided as an anode-free secondary battery. Here, since the anode is the same as previously described, a detailed description is omitted for convenience, and only the remaining components not described above will be explained in detail below. Furthermore, the description regarding the anode to be described later should be understood as being based on the premise that an anode is present in the above-mentioned lithium secondary battery.

[0196] Meanwhile, the above lithium secondary battery may have the separator replaced with a solid electrolyte. In such cases, an electrode slurry composition in which a solid electrolyte is further added during the manufacture of the positive and negative electrodes may be used.

[0197] The above lithium secondary battery may optionally further include a battery container housing the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member sealing the battery container.

[0198] The above cathode may include a cathode current collector and a cathode active material layer located on the cathode current collector.

[0199] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0200] The above-mentioned cathode active material layer can be manufactured by applying a cathode slurry composition, which includes a conductive material and, if necessary, a binder, together with the above-mentioned cathode active material, to the above-mentioned cathode current collector.

[0201] As the above-mentioned negative electrode active material, a compound capable of reversible intercalation / deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO₂ β Examples include metal oxides capable of doping and dedoping lithium, such as (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Furthermore, the carbon material may include low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0202] The above-mentioned negative electrode active material may be included in an amount of 80 to 99 weight percent based on the total weight of the negative electrode active material layer.

[0203] The above binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1 to 10 weight percent based on the total weight of the negative active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0204] The above conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fiber or metal fiber; metal powder such as carbon fluoride, aluminum, or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxide such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0205] In one embodiment, the negative active material layer may be manufactured by applying a negative slurry composition, prepared by dissolving or dispersing a negative active material and optionally a binder and a conductive material in a solvent, onto a negative current collector and drying it, or by casting the negative slurry composition onto a separate support and then laminating the film obtained by peeling it off from the support onto a negative current collector.

[0206] In addition, in another embodiment, the negative active material layer may be manufactured by applying a negative slurry composition prepared by dissolving or dispersing a negative active material and optionally a binder and a conductive material in a solvent onto a negative current collector and drying it, or by casting the negative slurry composition onto a separate support and then laminating the film obtained by peeling it off from the support onto a negative current collector.

[0207] Meanwhile, in the above-mentioned lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator typically used in lithium secondary batteries can be used without special limitations, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0208] In addition, the electrolytes used in the above lithium secondary battery include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which can be used when manufacturing lithium secondary batteries, but are not limited to these.

[0209] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0210] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.In this case, using a mixture of cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent performance of the electrolyte.

[0211] The above lithium salt can be used without special limitations as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable to use the lithium salt within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and allow lithium ions to move effectively.

[0212] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1 to 5 weight percent based on the total weight of the electrolyte.

[0213] Meanwhile, the above electrolyte may include solid electrolytes such as solid polymer electrolytes, gel-type polymer electrolytes, and solid inorganic electrolytes.

[0214] A lithium secondary battery containing a solid electrolyte may omit the separator described above. However, since it is difficult for the electrolyte to penetrate into the positive and negative electrodes, the electrodes may be formed by mixing the solid electrolyte during their manufacture.

[0215] Meanwhile, the solid polymer electrolyte or gel-type polymer electrolyte may be a polymer resin in which a salt of a Group 1 or Group 2 metal ion used in a secondary battery is composited. For example, it may be a polymer resin added to a solvated lithium salt.

[0216] The above metal ion salts may include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2.

[0217] The above polymer resins include, for example, polyether-based polymers, polycarbonate-based polymers, acrylate-based polymers, polysiloxane-based polymers, phosphazene-based polymers, polyethylene derivatives, alkylene oxide derivatives such as polyethylene oxide, phosphate ester polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ionic dissociators, branched copolymers in which amorphous polymers such as PMMA, polycarbonate, polysiloxane (PDMS) to phosphazene are copolymerized as comonomers to a polyethylene oxide (PEO) main chain, comb-like polymers, and cross-linked polymer resins.

[0218] As solid inorganic electrolytes, sulfide-based solid electrolytes and oxide-based solid electrolytes can be widely used.

[0219] The sulfide-based solid electrolyte may be a material containing sulfur (S) and having the conductivity of Group 1 or Group 2 metal ions of the periodic table used in secondary batteries. For example, it may be a Li-PS-based glass or Li-PS-based glass ceramic having the conductivity of lithium ions.

[0220] Examples of the above sulfide-based solid electrolytes may include at least one selected from the group consisting of Li6PS5Cl, Li6PS5Br, Li6PS5I, Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2OP2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2S5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, and Li2S-GeS2-ZnS.

[0221] Meanwhile, oxide-based solid electrolytes may be materials containing oxygen (O) and having the conductivity of Group 1 or Group 2 metal ions of the periodic table used in secondary batteries. For example, LLTO-based compounds, Li6La2CaTa2O 12 , Li6La2ACaNb2O 12 , Li6La2ASrNb2O 12 , Li2Nd3TeSbO 12 , Li3BO 2.5 N 0.5 It may be at least one selected from the group consisting of Li9SiAlO8, LAGP-based compounds, LATP-based compounds, LISICON-based compounds, LIPON-based compounds, perovskite-based compounds, NASICON-based compounds and LLZO-based compounds.

[0222] As described above, since the lithium secondary battery containing the positive electrode active material stably exhibits excellent discharge capacity, output characteristics, and lifespan characteristics, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0223] There are no particular restrictions on the external shape of the above-mentioned lithium secondary battery, but it may be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape. In addition, the lithium secondary battery can be used not only as a battery cell used as a power source for small devices, but can also preferably be used as a unit cell in a medium-to-large battery module containing a plurality of battery cells.

[0224] According to another aspect, a battery module comprising the lithium secondary battery as a unit cell and / or a battery pack comprising the same may be provided.

[0225] The battery module or the battery pack may be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0227] The details described above will be explained in more detail below through examples. However, these examples are for illustrative purposes only and should not be interpreted as limiting the scope of this specification.

[0229] Preparation Example 1. Preparation of positive electrode active material

[0230] (1) Example 1

[0231] An aqueous solution of FeSO4·7H2O, H3PO4, and H2O2 in a molar ratio of 1:1:1 was prepared in a reactor. NaOH and NH4OH were added to the aqueous solution while stirring. At this time, the precursor was synthesized by maintaining the temperature inside the reactor at 60°C and introducing N2 gas. After the reaction was completed, the mixture was washed and dehydrated to obtain a transition metal hydroxide precursor with a composition of FePO4·xH2O.

[0232] The transition metal hydroxide precursor was heat-treated for 5 hours by heating a kiln in an N2 atmosphere at a rate of 2℃ / min and maintaining the temperature at 550℃. Afterward, the transition metal precursor was obtained by furnace cooling.

[0233] A slurry was prepared by mixing the above transition metal precursor, the lithium-containing raw material Li2CO3, the carbon-based compound glucose, and the dispersant polyoxyethylene (20) sorbitan monolaurate in such a ratio of carbon atoms to 7:3. Here, the lithium-containing raw material was weighed so that the Li / Metal molar ratio was 1.00, and the carbon content of the carbon-based compound and the dispersant was combined so that the C / Metal molar ratio was 0.6 (where Metal is the total sum of all metals excluding lithium). Subsequently, the precursor and raw material in the slurry were ground using a bead mill so that the D50 was 1.0 μm or less. Subsequently, the slurry was dried using a spray dryer (Dongjin Kiyon, DJE003R).

[0234] After heating the kiln in an N2 atmosphere at a rate of 2℃ / min, the mixture was heat-treated for 8 hours while maintaining the temperature at 850℃. Subsequently, the mixture was cooled in the furnace and classified to obtain a positive electrode active material containing lithium iron phosphate with a D50 of 30.0 to 40.0 μm.

[0235] The above-mentioned positive active material was ground using a Jet-Mill (Alpa, MQW03T) to obtain a final positive active material with an average particle size of 4.0 μm.

[0237] (2) Example 2

[0238] A positive electrode active material with an average particle size of 4.0 μm was prepared in the same manner as in Example 1, except that a polyether amine salt was used instead of polyoxyethylene (20) sorbitan monolaurate as a dispersant.

[0240] (3) Example 3

[0241] A positive electrode active material with an average particle size of 4.0 μm was prepared in the same manner as in Example 1, except that an ammonium polycarboxylate salt was used instead of polyoxyethylene (20) sorbitan monolaurate as a dispersant.

[0243] (4) Example 4

[0244] A positive electrode active material with an average particle size of 4.0 μm was prepared in the same manner as in Example 1, except that an aqueous solution of modified polycarboxylic acid (concentration 65-75 wt%) was used instead of polyoxyethylene (20) sorbitan monolaurate as a dispersant.

[0246] (5) Example 5

[0247] A positive electrode active material with an average particle size of 4.0 μm was prepared in the same manner as in Example 1, except that an aqueous solution of modified carboxylic acid (concentration 55 wt%) was used instead of polyoxyethylene (20) sorbitan monolaurate as a dispersant.

[0249] (6) Example 6

[0250] A positive electrode active material with an average particle size of 4.0 μm was prepared in the same manner as in Example 1, except that the carbon atomic ratio of the carbon-based compound and the dispersant was 5:5.

[0252] (7) Comparative Example 1

[0253] A positive electrode active material with an average particle size of 4.0 μm was prepared using the same method as in Example 1, except that the carbon atomic ratio of the carbon-based compound and the dispersant was 9:1.

[0255] (8) Comparative Example 2

[0256] A positive electrode active material with an average particle size of 4.0 μm was prepared using the same method as in Example 1, except that the carbon atomic ratio of the carbon-based compound and the dispersant was 3:7.

[0258] (9) Comparative Example 3

[0259] A positive electrode active material with an average particle size of 4.0 μm was prepared in the same manner as in Example 3 above, except that the carbon atomic ratio of the carbon-based compound and the dispersant was 9:1.

[0261] (10) Comparative Example 4

[0262] A positive electrode active material with an average particle size of 4.0 μm was prepared in the same manner as in Example 4 above, except that the carbon atomic ratio of the carbon-based compound and the dispersant was 9:1.

[0264] (11) Comparative Example 5

[0265] A positive electrode active material with an average particle size of 4.0 μm was prepared in the same manner as in Example 5 above, except that the carbon atomic ratio of the carbon-based compound and the dispersant was 9:1.

[0267] Experimental Example 1. Evaluation of particle characteristics of positive electrode active material

[0268] After obtaining cross-sectional FIB SEM images of each cathode active material prepared in Preparation Example 1 above, a circle containing each particle was drawn using an image program, and (actual particle cross-sectional area / area of ​​the drawn circle) was calculated. The same procedure was performed for 50 particles, and their average was taken as the sphericity.

[0269] Meanwhile, in the cross-sectional SEM image of each positive electrode active material, the smallest circumscribing circle and the largest inscribing circle for each particle are plotted, and the radius (R) of the smallest circumscribing circle m The radius of the largest circle inscribed within ) and (r M R, which is the ratio of the average of their radii m / r M Measured.

[0270] The manufacturing methods of the examples and comparative examples and the surface characteristics of the cathode active materials prepared therefrom are shown in Table 1 and Figure 2 below.

[0271] division carbon raw materials Dispersant Carbon raw material: Dispersant Spherical shape R m / r M Example 1 Glucose Polyoxyethylene (20) sorbitan monolaurate 7:3 0.83 1.08 Example 2 Glucose Polyether amine salt 7:3 0.77 1.22 Example 3 Glucose Polycarboxylic ammonium salt 7:3 0.81 1.17 Example 4 Glucose Modified Polycarboxylic acid, 65~75% 7:3 0.80 1.15 Example 5 Glucose Modified Polycarboxylic Acid, 55% 7:3 0.75 1.25 Example 6 Glucose Polyoxyethylene (20) sorbitan monolaurate 5:5 0.83 1.03 Comparative Example 1 Glucose Polyoxyethylene (20) sorbitan monolaurate 9:1 0.56 1.35 Comparative Example 2 Glucose Polyoxyethylene (20) sorbitan monolaurate 3:7 0.85 1.05 Comparative Example 3 Glucose Polycarboxylic ammonium salt 9:1 0.65 1.34 Comparative Example 4 Glucose Modified Polycarboxylic acid, 65~75% 9:1 0.67 1.37 Comparative Example 5 Glucose Modified Polycarboxylic Acid, 55% 9:1 0.51 1.40

[0273] Preparation Example 2. Preparation of a lithium secondary battery

[0274] A positive electrode slurry was prepared by dispersing 94 wt% of each positive electrode active material prepared according to Preparation Example 1, 3 wt% of artificial graphite, and 3 wt% of PVDF binder in 3.5 g of N-methyl-2-pyrrolidone (NMP). The positive electrode slurry was coated onto an aluminum (Al) thin film, which is a positive electrode current collector with a thickness of 20 μm, dried, and then rolled to produce a positive electrode.

[0275] A coin battery was manufactured according to a commonly known manufacturing process using a lithium foil as the counter electrode for the above positive electrode, a porous polyethylene film (Celgard 2300, thickness: 25 μm) as the separator, and a liquid electrolyte in which LiPF6 is present at a concentration of 1.15 M in a solvent mixed with ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7.

[0277] Experimental Example 2. Evaluation of Electrochemical Properties of Anode Active Material

[0278] After 1 g of each cathode active material specimen prepared in Preparation Example 1 above was placed into a pelletizer, the compression density was measured by applying pressure of 3 ton for 15 seconds and 5 ton for 15 seconds, and then measuring the volume of the pellet.

[0279] In addition, 1 g of the specimen was placed into a powder resistance measuring device (IEST, PRCD1100), and the powder resistance was measured by applying pressure of 10 MPa, 50 MPa, 90 MPa, and 130 MPa for 10 seconds each.

[0280] Electrochemical characteristics were measured by performing charge-discharge experiments on the coin battery prepared in Preparation Example 2 using an electrochemical analysis device (Toyo, Toscat 3100) at 25°C, with a voltage range of 2.0–3.65 V and a discharge rate of 0.1–5.0 C.

[0281] division 0.1C Initial Charge (mAh / g) 0.1C initial discharge (mAh / g) Compressed density (g / cc) Powder resistance (Ω·cm) 10 MPa 50 MPa 90 MPa 130 MPa Example 1 161.10 159.95 2.50 35.01 29.89 28.69 27.94 Example 2 160.74 158.99 2.43 37.98 31.6 30.11 29.27 Example 3 161.38 160.07 2.44 48.1 38.81 26.55 25.37 Example 4 161.64 159.78 2.48 28.17 21.01 20.72 20.62 Example 5 160.80 158.82 2.45 31.01 24.04 23.34 22.98 Example 6 162.45 160.11 2.48 34.51 27.47 26.37 25.72 Comparative Example 1 150.12 148.76 2.21 62.76 42.18 37.76 35.05 Comparative Example 2 141.44 138.66 2.16 96.19 65.16 59.21 56.14 Comparative Example 3 146.45 145.72 2.17 57.74 47.56 46.41 45.61 Comparative Example 4 144.23 142.37 2.13 86.95 75.75 72.76 70.64 Comparative Example 5 145.26 144.18 2.15 78.15 55.60 50.39 47.30

[0282] Although embodiments of this specification have been described above, those skilled in the art may modify and change this specification in various ways by adding, changing, deleting, or adding components, etc., without departing from the spirit of this specification as described in the claims, and such modifications and changes shall also be deemed to be included within the scope of the rights of this specification.

Claims

Claim 1 A positive electrode active material for a lithium secondary battery comprising particulate matter, wherein the particulate matter comprises particles existing without forming aggregates, the particulate matter has a spherical shape, an amorphous carbon coating layer with a thickness of 1 to 500 nm is formed on at least a portion of the surface of at least a portion of the particulate matter, the average sphericity of the particulate matter is 0.70 to 0.95, and the 10 MPa powder resistance (ρ) of the positive electrode active material 10 ) and 50 MPa powder resistance (ρ 50 The ratio of ) (ρ 10 / ρ 50 A positive electrode active material for a lithium secondary battery having a value of 1.40 or less. Claim 2 In claim 1, a positive electrode active material for a lithium secondary battery, wherein the cross-sectional SEM image of the positive electrode active material satisfies the following Equation 1: [Equation 1](R m / r M )≤1.30 In the above formula, R m is the average radius of the smallest circles circumscribing the above particulate matter, and r M is the average radius of the largest circle inscribed in the above particulate matter. Claim 3 A positive active material for a lithium secondary battery according to claim 1, wherein the compressed density of the positive active material is 2.40 g / cc or more. Claim 4 In claim 1, the particulate material is a positive electrode active material for a lithium secondary battery represented by the following chemical formula 1: [Chemical Formula 1]Li p M1 x M2 y A z P 1-z O4 In the above chemical formula, M1 is at least one selected from the group consisting of Fe, Mn, Ni, and Co; M2 is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Cr, Cu, Ga, Hf, In, K, La, Mg, Mo, Na, Nb, Nd, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr; A is at least one selected from the group consisting of C, Si, S, N, B, F, Cl, and I; and 0.5≤p≤1.5, 0 <x≤1, 0≤y<1, 0≤z<1, x+y=1이다. Claim 5 A positive electrode active material for a lithium secondary battery according to claim 1, wherein a compound represented by the following chemical formula 2 is present on at least a portion of the surface of at least a portion of the particulate material: [Chemical Formula 2]Li a M3 b O c In the above chemical formula, M3 is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Hf, In, K, La, Mg, Mn, Mo, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr, and 0≤a≤10, 0 <b≤8, 2≤c≤13이다. Claim 6 A method for manufacturing a positive electrode active material for a lithium secondary battery, comprising: (a) a step of preparing a slurry by mixing a lithium-containing raw material, a transition metal precursor, a carbon-based compound, and a dispersant; (b) a step of grinding particles in the slurry; and (c) a step of obtaining a lithium composite compound by heat-treating the ground particles; wherein the carbon atomic ratio of the carbon-based compound and the dispersant mixed in step (a) is 5 to 8: 2 to 5. Claim 7 A method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 6, wherein at least one sub-raw material comprising an element selected from Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, F, Fe, Ga, Hf, I, In, K, La, Mg, Mo, N, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Si, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn and Zr is further added to the slurry in step (a). Claim 8 A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein, in claim 6, the dispersant is a polymer with a molecular weight of 1,000 to 40,000 g / mol. Claim 9 A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein, in claim 6, the dispersant is a polymer with a pH of 3.0 to 8.

0. Claim 10 A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein, in step (b) above, the average particle size of the solid component in the slurry is 1.0 μm or less. Claim 11 A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein, in claim 6, step (c) is performed at a temperature in which the carbon-based compound and the dispersant are carbonized. Claim 12 A positive electrode comprising a positive electrode active material according to any one of paragraphs 1 to 5. Claim 13 A lithium secondary battery using a positive electrode according to Paragraph 12. Claim 14 delete Claim 15 delete

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