Method for preparing positive electrode active material for lithium secondary battery

Abstract

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

Description

Method for manufacturing a cathode active material for a lithium secondary battery

[0001] The present specification relates to a method for manufacturing a positive electrode active material for a lithium secondary battery, and more specifically, to an environmentally friendly method for manufacturing a positive electrode active material for a lithium secondary battery having excellent electrical conductivity and energy density.

[0002]

[0003] Batteries store electricity by utilizing materials capable of electrochemical reactions in their anode and cathode. A representative example of such batteries is the lithium secondary battery, which stores electrical energy through the difference in chemical potential resulting from the intercalation / deintercalation of lithium ions between the anode and cathode.

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

[0005] Various materials are used as positive electrode active materials for lithium secondary batteries, and among them, lithium metal phosphate, such as lithium iron phosphate (LiFePO4), is widely used in the manufacture of lithium secondary batteries due to its excellent stability, ability to withstand many charge / discharge cycles, and relatively low manufacturing cost.

[0006] However, lithium iron phosphate suffers from low operating voltage and energy density. To address these shortcomings, lithium manganese iron phosphate (LMFP), which replaces some of the iron with manganese, has been proposed. However, lithium iron manganese phosphate suffers from low lithium ion diffusion speed and low electronic conductivity.

[0007] Meanwhile, conventional cathode active materials are manufactured by first synthesizing a precursor, then adding lithium and calcining. This process poses a problem: contaminants such as SOx and NOx are generated due to the components present in the raw materials used in precursor manufacturing. Furthermore, since lithium is added after the precursor is synthesized, dehydrated or dried, it presents disadvantages in terms of energy and yield.

[0008]

[0009] In the lithium secondary battery market, the growth of lithium secondary batteries for electric vehicles is driving the market, and the demand for cathode active materials used in lithium secondary batteries is also continuously changing, and in particular, the need to minimize costs in the production of cathode active materials is gradually increasing.

[0010] At the same time, the market is demanding positive electrode active materials with higher energy density and superior conductivity.

[0011] To meet the needs of such a market, the present specification aims to provide a method for manufacturing a positive electrode active material having excellent energy density and electronic conductivity without a process of synthesizing a separate precursor.

[0012] The purposes of the present invention are not limited to those mentioned above, and other unmentioned purposes and advantages of the present invention can be understood through the following description and will be more clearly understood through the embodiments of the present invention. Furthermore, it will be readily apparent that the purposes and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0013]

[0014] According to one aspect of the present specification, a method for producing a cathode active material for a lithium secondary battery is provided, comprising: (a) reacting an iron raw material and a phosphate raw material to produce a slurry containing an Fe-P complex; (b) reacting a manganese raw material and an Fe-P complex to produce a slurry containing an Fe-Mn-P complex; (c) adding a lithium raw material and a carbon raw material to the slurry and then drying the slurry to obtain a powder; and (d) heat-treating the powder to obtain a lithium complex compound.

[0015] In one embodiment, the iron source material may be at least one selected from the group consisting of Fe metal, FeOOH, Fe2O3, and Fe3O4.

[0016] Here, the phosphoric acid raw material may be at least one selected from the group consisting of H3PO4, Li3PO4, NH4H2PO4, and (NH4)2HPO4.

[0017] In addition, the above iron raw material and the above phosphoric acid raw material can be added so that the phosphorus element is 0.90 to 2.00 moles based on 1 mole of iron element.

[0018] Meanwhile, the manganese raw material may be at least one selected from the group consisting of Mn metal, MnCO3, Mn2O3, and Mn3O4.

[0019] Additionally, the manganese raw material may be added so that the manganese element is 1.00 to 2.00 moles based on 1 mole of iron element included in the Fe-P complex.

[0020] Meanwhile, at least one of the reactions in step (a) and step (b) can be performed at 50 to 150°C.

[0021] In addition, the above Fe-Mn-P complex is FePO4ㆍnH2O(0≤n≤9), FePO4 anhydride, Fe3(PO4)2, Fe2(HPO4)3, H 10 Mn5O 20It may include at least one selected from the group consisting of P4, MnPO4 and Mn3(PO4)2.

[0022] Here, the reaction of step (b) can be performed in the presence of an oxidizing agent.

[0023] In one embodiment, the oxidizing agent may be at least one selected from the group consisting of hydrogen peroxide, potassium permanganate, peroxyacetic acid, perbenzoic acid, sodium perborate, periodic acid, sodium percarbonate, potassium percarbonate, vanadium trioxide, ammonium chloride, ammonium phosphate, ferric chloride, hypochlorous acid, sodium hypochlorite, and dissolved ozone.

[0024] In addition, the lithium raw material of the step (c) may be added so that the ratio of the number of lithium atoms (Li) to the total number of metal elements other than lithium (Metal) in the slurry (Li / Metal) is 0.50 to 1.50.

[0025] In another embodiment, the carbon raw material of step (c) may be introduced so that the ratio of the number of carbon atoms (C) to the total number of metal atoms (Metal) of metal elements other than lithium in the slurry (C / Metal) is 0.25 to 0.75.

[0026] Here, in at least one of the steps (a) to (c), at least one sub-raw material including 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.

[0027] Additionally, before or after step (c), the solid content in the slurry may be pulverized to break up over-agglomerated particles.

[0028] As an example, the heat treatment in step (d) above can be performed under conditions of 500 to 950°C.

[0029] Here, the lithium complex compound obtained in the step (d) may include a first region in which Fe exists from the center to the surface but Mn does not exist, a second region in which a mixed structure of Fe and Mn exists, and a third region in which Mn exists but Fe does not exist.

[0030] Additionally, the sum of the thicknesses of the second region and the third region may be 0.5 to 2.0 ㎛.

[0031] In another example, after step (d), the step (e) may further include a step of pulverizing the lithium complex compound so that the average particle size becomes 1.0 μm or less.

[0032] According to this specification, the raw material can be more environmentally friendly as no harmful substances are generated during firing.

[0033] In addition, the cathode active material can be manufactured more economically and efficiently by excluding unnecessary dehydration or drying processes during the manufacture of the cathode active material.

[0034] In addition, the positive electrode active material manufactured by the above method may have excellent electrical conductivity and energy density.

[0035] In addition to the effects described above, the specific effects of this specification are described together with specific details for implementing the descriptions of the specification below.

[0036]

[0037] Figure 1 schematically illustrates element concentrations according to location in a positive electrode active material according to one aspect of the present specification;

[0038] FIG. 2 shows an SEM image of a positive electrode active material according to one embodiment of the present specification.

[0039]

[0040] To facilitate a better understanding of this specification, certain terms are defined herein for convenience. Unless otherwise defined herein, scientific and technical terms used herein shall have the meanings commonly understood by those of ordinary skill in the art. Furthermore, unless otherwise specified by context, singular terms shall be construed to include their plural forms, and plural terms shall be construed to include their singular forms.

[0041]

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

[0043]

[0044] Method for manufacturing positive electrode active material for lithium secondary batteries

[0045] A method for producing a cathode active material for a lithium secondary battery according to one aspect of the present disclosure may include: (a) a step of reacting an iron raw material and a phosphate raw material to produce a slurry containing an Fe-P complex; (b) a step of reacting a manganese raw material and an Fe-P complex to produce a slurry containing an Fe-Mn-P complex; (c) a step of adding a lithium raw material and a carbon raw material to the slurry and then drying the slurry to obtain a powder; and (d) a step of heat-treating the powder to obtain a lithium complex compound.

[0046] In the conventional method for producing a lithium phosphate complex compound, a precursor in the form of a phosphate is produced using sulfate or nitrate as a raw material, and then lithium is added and calcined to produce a cathode active material.

[0047] However, these manufacturing methods incur energy and yield losses during the dehydration and drying processes during precursor production. Furthermore, there is the problem of generating harmful substances such as SOx and NOx.

[0048] Meanwhile, the manufacturing method according to one aspect of the present specification can manufacture a positive electrode active material product of an equal or superior level while being environmentally friendly by not generating harmful substances such as SOx or NOx and excluding unnecessary dehydration or drying processes.

[0049] In addition, the manufacturing method according to one aspect of the present specification can suppress the formation of M2P2O7 (M=Fe or Mn) impurity phase.

[0050] When the Li reactivity is reduced due to the unstable MP phase during sintering, the M2P2O7 impurity phase may be generated. The M2P2O7 impurity phase can act as a resistor and reduce the output and capacity characteristics of the positive electrode active material. In addition, among the M2P2O7 impurity phases, Mn2P2O7 can cause Mn dissolution during charge and discharge, which can reduce battery stability.

[0051] The above step (a) is a step of forming an Fe-P complex by reacting an iron raw material and a phosphate raw material. Here, the iron raw material and the phosphate raw material may each be one type or two or more types.

[0052] The above iron raw material refers to a material containing iron element. For example, the iron raw material may be at least one selected from the group consisting of Fe metal, FeOOH, Fe2O3, and Fe3O4.

[0053] Meanwhile, when the raw material of the above step (a) further includes a transition metal M other than Fe, the Fe transition metal raw material and at least one selected from the group consisting of MSO4, HMPO4, MPO4, M3(PO4)2, (CH3COO)2M, M(NO3)2, MCO3, M2CO3, and MO2 may be further included as a transition metal raw material.

[0054] In addition, the phosphoric acid raw material includes an anion, salt, functional group, or ester derived from phosphoric acid. For example, the phosphoric acid raw material may be at least one selected from the group consisting of H3PO4, Li3PO4, NH4H2PO4, and (NH4)2HPO4.

[0055] Here, the ratio of the iron raw material and the phosphoric acid raw material can be mixed so that the phosphorus element is 0.90 to 2.00 mol based on 1 mol of iron element, for example, 0.90 mol, 0.95 mol, 1.00 mol, 1.05 mol, 1.10 mol, 1.15 mol, 1.20 mol, 1.25 mol, 1.30 mol, 1.35 mol, 1.40 mol, 1.45 mol, 1.50 mol, 1.55 mol, 1.60 mol, 1.65 mol, 1.70 mol, 1.75 mol, 1.80 mol, 1.85 mol, 1.90 mol, 1.95 mol, 2.00 mol, or a range between two of these values.

[0056] In the above step (a), iron ions and phosphate ions can react to form an Fe-P complex. For example, iron ions (Fe 3+ ) and phosphate ion (PO4 3- ) can form various Fe-P complexes when reacted. These metal complexes can include FePO4ㆍnH2O(0≤n≤9), FePO4 anhydride, Fe3(PO4)2, Fe2(HPO4)3, etc. Here, the Fe-P complex can also be formed in a precipitated form in the slurry. Meanwhile, among the Fe-P complexes, FePO4ㆍ2H2O can have the largest proportion.

[0057] Optionally, in the step (a), at least one sub-raw material including 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.

[0058] The above-mentioned sub-raw material can be introduced to dope a heterogeneous element into the Fe-P complex. The doped heterogeneous element can control the properties of the complex in a subsequent step or improve the performance of the positive electrode active material.

[0059] The above step (b) is a step of forming an Fe-Mn-P complex by reacting a manganese raw material with an Fe-P complex. Here, the manganese raw material may be one type or two or more types.

[0060] The above manganese raw material refers to a material containing the element manganese. For example, the manganese raw material may be at least one selected from the group consisting of Mn metal, MnCO3, Mn2O3, and Mn3O4.

[0061] Meanwhile, when the raw material of the above step (b) further includes a transition metal M other than Mn, the Mn transition metal raw material may further include at least one selected from the group consisting of MSO4, HMPO4, MPO4, M3(PO4)2, (CH3COO)2M, M(NO3)2, MCO3, M2CO3, and MO2 as a transition metal raw material.

[0062] Here, the ratio of the manganese raw material and the Fe-P complex may be mixed so that the manganese element is 1.00 to 2.00 mol based on 1 mol of iron element, for example, 1.00 mol, 1.05 mol, 1.10 mol, 1.15 mol, 1.20 mol, 1.25 mol, 1.30 mol, 1.35 mol, 1.40 mol, 1.45 mol, 1.50 mol, 1.55 mol, 1.60 mol, 1.65 mol, 1.70 mol, 1.75 mol, 1.80 mol, 1.85 mol, 1.90 mol, 1.95 mol, 2.00 mol, or a range between two of these values.

[0063] Meanwhile, at least one of the reactions of the above step (a) and the above step (b) is performed at 50 to 150°C, for example, 50°C, 52.5°C, 55°C, 57.5°C, 60°C, 62.5°C, 65°C, 67.5°C, 70°C, 72.5°C, 75°C, 77.5°C, 80°C, 82.5°C, 85°C, 87.5°C, 90°C, 92.5°C, 95°C, 97.5°C, 100°C, 102.5°C, 105°C, 107.5°C, 110°C, 112.5°C, 115°C, 117.5°C, 120°C, 122.5°C, 125°C, 127.5°C, 130°C, It can be performed at 132.5℃, 135℃, 137.5℃, 140℃, 142.5℃, 145℃, 147.5℃, 150℃ or a range between any two of these values.

[0064] Here, the reaction can be carried out while stirring the slurry for a time period ranging from 4 to 48 hours, for example, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, 36 hours, 38 hours, 40 hours, 42 hours, 44 hours, 46 hours, 48 ​​hours or a time period ranging between any two of these values.

[0065] In the above step (b), manganese ions can react with the Fe-P complex to form an Fe-Mn-P complex. In this reaction, the Fe-P complex acts as a kind of seed, so that the Fe-Mn-P complex can be coprecipitated.

[0066] The above Fe-Mn-P complex can be formed so that the structure of the Fe-P complex exists inside and the Mn-P structure exists on the surface. In other words, it can be a particulate material in the form of a structure with a high Fe concentration formed in the center and a low Fe concentration or no Fe at all on the surface.

[0067] For example, referring to Fig. 1, from the center (position 0) of the Fe-Mn-P complex toward the surface, a first region where Fe exists but Mn does not exist, a second region where a mixed structure of Fe and Mn exists, and a third region where Mn exists but Fe does not exist can be located.

[0068] Here, the thickness of the first region may be 3.0 to 5.0 ㎛, and the thickness of the second region and the third region may be 0.5 to 2.0 ㎛ or more, but is not limited thereto.

[0069] At least a portion of the first region and / or the second region may be maintained in an appropriate amount such that the content of the Fe2P phase, which does not come into contact with lithium during firing and thus has excellent electronic conductivity, is 0.2 to 0.9 wt%, for example, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, 0.5 wt%, 0.55 wt%, 0.6 wt%, 0.65 wt%, 0.7 wt%, 0.75 wt%, 0.8 wt%, 0.85 wt%, 0.9 wt%, or a range between any two of these values, based on 100 wt% of the lithium manganese iron phosphate phase.

[0070] For example, if the Fe-P complex is exposed to a strong reducing atmosphere during calcination, and the Fe2P phase is excessively formed, these may aggregate outside the particles, which may reduce the capacity of the positive electrode active material. At this time, the unstable MP phase may also cause the formation of the M2P2O7 impurity phase.

[0071] Meanwhile, when the Fe-Mn-P complex is formed so that the Mn-P complex structure exists inside and the Fe-P complex structure exists on the surface, the Fe2P phase is extremely suppressed, but the M2P2O7 impurity phase is formed, which increases the resistance and may reduce the capacity at high current or low temperature.

[0072] Alternatively, if the Fe raw material and the oxidizer are reacted after forming the Mn-P complex structure, the Fe-P complex structure may become unstable due to the oxidizer, causing an excessive amount of Fe2P phase to be formed, and at the same time, the M2P2O7 impurity phase may also increase, which may reduce the stability and capacity of the cathode material.

[0073] In the above step (b), various Fe-Mn-P complexes can be formed. These Fe-Mn-P complexes include FePO4ㆍnH2O(0≤n≤9), FePO4 anhydride, Fe3(PO4)2, Fe2(HPO4)3, H 10 Mn5O 20 It may include P4, MnPO4, Mn3(PO4)2, etc. Here, the Fe-Mn-P complex may be formed in a precipitated form in the slurry.

[0074] Optionally, in the step (b), at least one sub-raw material including 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.

[0075] The above-mentioned sub-raw material can be introduced to dope a heterogeneous element into the Fe-Mn-P complex. The doped heterogeneous element can control the reaction between the Mn of the Fe-P complex or adjust the properties of the manufactured positive electrode active material.

[0076] In particular, the reaction of step (b) may be carried out in the presence of an oxidizing agent. Examples of the oxidizing agent include, but are not limited to, at least one selected from the group consisting of hydrogen peroxide, potassium permanganate, peroxyacetic acid, perbenzoic acid, sodium perborate, periodic acid, sodium percarbonate, potassium percarbonate, vanadium trioxide, ammonium chloride, ammonium phosphate, ferric chloride, hypochlorous acid, sodium hypochlorite, and dissolved ozone.

[0077] Here, the oxidizing agent may be introduced after step (a) is completed. Referring to reaction scheme 1 below, in step (a), the Fe-P complex may be difficult to form in the presence of the oxidizing agent.

[0078] [Reaction Formula 1]

[0079] 1) 2FeOOH + 2H2O2→ 2Fe(OH)3+ O2

[0080] 2) Fe(OH)3→ FeOOH (200℃ dehydration)

[0081] Meanwhile, the step (c) may be a step of adding a lithium raw material and a carbon raw material to a slurry containing the Fe-Mn-P complex without a separate dehydration or drying process.

[0082] In addition, in the manufacturing method of lithium manganese iron phosphate compound using conventional precursors, if only the dehydration or drying process is excluded, sulfur (S) and nitrogen (N) compounds may be included in the slurry as impurities. These impurities are generated when SO is sintered. x , NO xIn addition to generating harmful substances, such as nitrous oxide, they can also impede the carbonization of carbon sources and the growth of olivine crystals. Furthermore, if these impurity-derived components remain in the cathode active material, they can generate gas within the battery, reducing stability.

[0083] The above lithium raw material may be for introducing lithium so that the Fe-Mn-P complex can function as a lithium positive electrode active material.

[0084] The lithium raw material of the step (c) may be added so that the ratio of the number of lithium atoms (Li) to the total number of metal atoms (Metal) of metal elements other than lithium in the slurry (Li / Metal) is 0.50 to 1.50, for example, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, or a range between any two of these values, but is not limited thereto.

[0085] Meanwhile, the carbon raw material added in step (c) may be used to form a carbon coating that improves the conductivity of the positive electrode active material. Minimizing the thickness of the carbon coating layer while increasing its uniformity can minimize the flowability degradation caused by amorphous carbon and improve the conductivity of the positive electrode active material.

[0086] For example, lithium manganese iron phosphate compound, which is an olivine-based cathode material, is PO4 3- Due to the strong covalent bonding, the electrical conductivity is relatively low. Also, due to its crystal structure, Li + It is known to have low ionic conductivity due to one-dimensional diffusion.

[0087] To overcome these shortcomings, Li is used in technology to improve conductivity by forming a carbon coating and nanoparticles. +Techniques have been proposed to improve diffusion.

[0088] However, the carbon coated in the conventional positive electrode active material exists in an amorphous phase, which may reduce the density of the positive electrode active material.

[0089] Additionally, conventional nano-sized particulate materials grow into angular particles due to agglomeration during the sintering process.

[0090] As a result, the reduced flowability and angular particle shape due to amorphous carbon can reduce the density of the positive electrode active material and lower the energy density of the final product.

[0091] On the other hand, the carbon coating layer formed by the above method can have a uniform and thin thickness. In addition, the carbon raw material can induce the lithium complex compound to grow into a spherical shape.

[0092] Meanwhile, the carbon raw material may be a compound in which the proportion of 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.

[0093] By using a carbon raw material having a ratio of C elements that satisfies the above range, a product with excellent yield and uniformity of carbon coating can be manufactured even when using the same content of compounds.

[0094] Examples of the above carbon raw material 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, aminobenzoic acid, etc.

[0095] In addition, by controlling the properties of the carbon raw material, the properties of the formed carbon coating layer can be controlled.

[0096] For example, by minimizing the thickness of the carbon coating layer in the positive electrode active material while increasing its uniformity, the flowability degradation caused by amorphous carbon can be minimized and the conductivity of the positive electrode active material can be improved.

[0097] As an example, the thickness of the carbon coating layer formed in the step (c) 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, but is not limited thereto.

[0098] In one embodiment, the carbon raw material of step (c) has a ratio of the number of carbon atoms (C) to the total number of metal atoms (Metal) of metal elements other than lithium in the slurry (C / Metal) of 0.25 to 0.75, for example, 0.25, 0.26, 0.27, 0.28, 0.29, 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, It can be injected so that it is 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, 0.71, 0.72, 0.73, 0.74, 0.75, or a range between any two of these values.

[0099] Optionally, in the step (c), at least one sub-raw material including 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.

[0100] The above-mentioned sub-raw material may be introduced to dope a heterogeneous element into the lithium composite compound. The doped heterogeneous element may improve the stability or conductivity of the positive electrode active material.

[0101] During the production of the above Fe-Mn-P composite, some solid particles may aggregate with each other. If at least some of these are over-agglomerated, it may be difficult to sufficiently react with the lithium source material or carbon source material.

[0102] Therefore, as needed, before or after step (c), the solid content in the slurry can be pulverized to break up the over-agglomerated particles.

[0103] Meanwhile, the above-described pulverization may be performed under conditions in which the Fe-Mn-P complex including the first region, the second region, and the third region described above is not broken, but over-agglomerated particles can be disintegrated. In the present specification, the term "unpulverized lithium complex compound" or "unpulverized state" does not simply refer to a lithium complex compound that has not undergone a pulverization process, but may also include a compound in which only over-agglomerated particles are disintegrated under conditions in which the Fe-Mn-P complex including the first region, the second region, and the third region is not broken even if it undergoes a pulverization process.

[0104] Additionally, the slurry may have a solids content of 20 to 50%, for example, but not limited to, 20%, 22.5%, 25%, 27.5%, 30%, 32.5%, 35%, 37.5%, 40%, 42.5%, 45%, 47.5%, 50%, or a range between any two of these values.

[0105] Meanwhile, the average particle diameter (D50) of the pulverized particles may be 1.0 ㎛ or less, for example, 1.0 ㎛, 0.95 ㎛, 0.90 ㎛, 0.85 ㎛, 0.80 ㎛, 0.75 ㎛, 0.70 ㎛, 0.65 ㎛, 0.60 ㎛, 0.55 ㎛, 0.50 ㎛, 0.45 ㎛, 0.40 ㎛, 0.35 ㎛, 0.30 ㎛, 0.25 ㎛, 0.20 ㎛, 0.15 ㎛, 0.10 ㎛, 0.05 ㎛ or a range between two of these values, but is not limited thereto.

[0106] To pulverize the particles, a dry or wet dispersion mill such as a ball mill, a bead mill (beads commonly used for pulverizing 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 disk mill or an air classifier mill can be used.

[0107] In one example, the grinding step can be performed in a milling machine comprising beads having a size of 0.1 to 1.5 mm, for example, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, 1 mm, 1.05 mm, 1.1 mm, 1.15 mm, 1.2 mm, 1.25 mm, 1.3 mm, 1.35 mm, 1.4 mm, 1.45 mm, 1.5 mm or a range between any two of these values. Here, the size can mean the diameter of the beads. If the above beads are not spherical, the diameter may refer to the diameter of the major axis.

[0108] Additionally, the milling machine may comprise beads in a range of 30 to 50% by volume, for example, 30%, 32.5%, 35%, 37.5%, 40%, 42.5%, 45%, 47.5%, 50%, or a range between any two of these values.

[0109] Meanwhile, in step (c), the slurry may be dried to obtain a powder form. For example, the slurry may be dried through spray drying. That is, the powder in step (d) may be a spray-dried product of the slurry ground in step (c).

[0110] Spray drying, which is an example of the above drying, can be performed in a spray dryer, and the spray dryer is not particularly limited to a spray drying device that can spray dry the slurry containing the pulverized particles to produce dried particles having a shape close to a sphere, but 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 disk-type droplet generator can be used.

[0111] 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.

[0112] The raw material in the droplets sprayed into the drying chamber can be dried into particles having a shape close to a spherical shape under the temperature environment in the drying chamber.

[0113] Meanwhile, if a specific carbon source material is included in the slurry, unnecessary agglomeration of the particles can be suppressed during spray drying. As a result, particles with a shape close to spherical can be obtained.

[0114] In one example, moisture loss during drying can reduce particle density and form pores. This can result in reduced particle strength and poor stability of the cathode active material.

[0115] Here, adjusting the viscosity of the slurry prior to drying can shorten the condensation time during drying and minimize the decrease in density due to moisture loss during drying. On the other hand, if the viscosity of the slurry is excessively high, fluidity is reduced during drying, resulting in poor process efficiency and difficulty in obtaining spherical particles. One means of adjusting the viscosity of the slurry is to add a binder.

[0116] Next, the step (d) may be a step of forming a lithium complex compound by heat-treating the powder dried in the step (c).

[0117] During the heat treatment in step (d), the carbon raw material may be carbonized to form a carbon coating layer. Therefore, the carbon raw material must be carbonized within the heat treatment temperature in step (d). If uncarbonized carbon compounds remain in the positive electrode active material, conductivity improvement may be insufficient or unpredictable side effects may occur.

[0118] The heat treatment in step (d) above can be performed at a maximum temperature of 500 to 950°C for 5 to 15 hours under an inert atmosphere. At this time, the maximum temperature can vary depending on the composition of the target positive electrode active material.

[0119] For example, the heat treatment may be performed at a maximum temperature of 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, or a range between any two of these values. Such heat treatment may be performed while maintaining the highest temperature for, for example, but not limited to, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, 11.5 hours, 12 hours, 12.5 hours, 13 hours, 13.5 hours, 14 hours, 14.5 hours, 15 hours or a time in between any two of these values.

[0120] When heat-treated at a temperature satisfying the above range, the density of the lithium complex compound can be excellent.

[0121] On the other hand, if the heat treatment temperature in step (d) is insufficient, the calcination of the precursor may proceed insufficiently, resulting in insufficient crystal growth of the lithium composite compound or difficulty in forming a carbon coating layer. Accordingly, the density of the lithium composite compound may decrease.

[0122] Meanwhile, if the heat treatment temperature in step (d) is excessively high, thermal decomposition of the lithium complex compound may occur, resulting in a decrease in particle strength or particle collapse.

[0123] Meanwhile, the heat treatment may be performed by increasing the temperature by 1 to 10°C per minute, for example, 1°C, 1.5°C, 2°C, 2.5°C, 3°C, 3.5°C, 4°C, 4.5°C, 5°C, 5.5°C, 6°C, 6.5°C, 7°C, 7.5°C, 8°C, 8.5°C, 9°C, 9.5°C, 10°C, or a range between two of these values ​​to reach the highest temperature.

[0124] Here, the inert atmosphere may be formed by replacing air with at least one inert gas selected from the group consisting of, for example, N2, Ar, He, Rn, Ne, and Xe, but is not limited thereto.

[0125] Most of the Fe-Mn-P complexes formed in step (b) above may take the form of hydrates. The crystal water of the Fe-Mn-P complexes formed in the form of hydrates can be removed and the crystals re-formed during the calcination process in step (d). This re-formation process generates moisture and consumes thermal energy. As a result, carbonization of the carbon raw material occurs at a relatively high temperature, and a more uniform carbon coating is formed, thereby improving conductivity.

[0126] Meanwhile, after the heat treatment in step (d), cooling can be performed while maintaining an inert atmosphere at a temperature of 150°C or lower. For example, the heat-treated lithium complex compound can be obtained by cooling.

[0127] In one example, the lithium complex compound obtained in step (d) may include a first region in which Fe is present from the center to the surface but Mn is not present, a second region in which a mixed structure of Fe and Mn is present, and a third region in which Mn is present but Fe is not present. In the lithium complex compound in an unpulverized state, the Fe2P phase may be present in at least a portion of the first region and / or the second region.

[0128] Here, the thickness of the first region may be 3.0 to 5.0 ㎛, for example, 3 ㎛, 3.25 ㎛, 3.5 ㎛, 3.75 ㎛, 4 ㎛, 4.25 ㎛, 4.5 ㎛, 4.75 ㎛, 5 ㎛, or a range between two of these values, and the thickness of the second region and the third region may be 0.5 to 2.0 ㎛ or more, for example, 0.5 ㎛, 0.75 ㎛, 1.0 ㎛, 1.25 ㎛, 1.5 ㎛, 1.75 ㎛, 2.0 ㎛, a range between two of these values, or 2.0 ㎛ or more, but is not limited thereto.

[0129] By heat-treating an Fe-Mn-P composite including the first region, second region, and third region described above together with a lithium source material, a lithium composite compound can be manufactured while minimizing the extreme suppression or excessive formation of the Fe2P phase. Furthermore, the first region, second region, and third region can exist in the heat-treated lithium composite compound.

[0130] Additionally, before or after performing step (d), a disintegration, distribution, and / or washing process may be performed on the lithium complex compound.

[0131] In one example, after step (d), a step (e) of pulverizing the lithium composite compound so that the average particle size becomes 1.0 μm or less may be further included. By pulverizing the lithium composite compound in which the Fe2P phase obtained according to the above-described method is distributed in an appropriate amount, a particulate material with a controlled particle size can be obtained.

[0132] In the above step (e), the particulate matter may be pulverized so that the average particle size is 1.0 ㎛ or less, for example, 1.0 ㎛, 0.9 ㎛, 0.8 ㎛, 0.7 ㎛, 0.6 ㎛, 0.5 ㎛, 0.4 ㎛, 0.3 ㎛, 0.2 ㎛, 0.1 ㎛, or a range between two of these values.

[0133] In another example, the average particle diameter (D50) of the pulverized particulate matter may be in the range of 0.5 to 0.7 μm, for example, 0.5 μm, 0.51 μm, 0.52 μm, 0.53 μm, 0.54 μm, 0.55 μm, 0.56 μm, 0.57 μm, 0.58 μm, 0.59 μm, 0.6 μm, 0.61 μm, 0.62 μm, 0.63 μm, 0.64 μm, 0.65 μm, 0.66 μm, 0.67 μm, 0.68 μm, 0.69 μm, 0.7 μm or a range between any two of these values.

[0134] The above-described particulate material, ground to have an average particle size within the above-described range, can be appropriately aggregated due to surface energy. As a result, the density characteristics of the positive electrode active material can be improved.

[0135] To pulverize the particles, a dry or wet dispersion mill such as a ball mill, a bead mill (beads commonly used for pulverizing 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 disk mill or an air classifier mill can be used.

[0136]

[0137] Cathode active material for lithium secondary batteries

[0138] According to another aspect of the present disclosure, a cathode active material for a lithium secondary battery includes a lithium composite compound capable of lithium intercalation / deintercalation, the lithium composite compound includes Fe and Mn, the lithium composite compound includes a plurality of particulate materials, and an Fe2P phase may be present in at least a portion of the particulate materials.

[0139] The above-mentioned positive electrode active material may include a particulate material composed of a lithium complex compound capable of lithium intercalation / deintercalation. Here, the particulate material may be a compound containing Fe and Mn as constituent elements. The particulate material may include a lithium manganese iron phosphate phase.

[0140] In one embodiment, the particulate material may exist without forming any significant aggregates. In this case, the particulate material may have a spherical shape. Furthermore, since the lithium composite compound is a particulate material with a smooth surface, the positive electrode active material may have excellent compression density.

[0141] Here, the average particle diameter of the particulate matter (here, the average particle diameter of the particulate matter may be the average major axis length of the particulate matter) is within the range of 0.01 to 5 ㎛, thereby enabling the implementation of an optimal density of a positive electrode manufactured using a positive electrode active material according to various embodiments.

[0142] Meanwhile, in another example, the particulate matter may exist as a primary particle, and the primary particles may aggregate into multiple secondary particles. 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 compression density.

[0143] The above particulate material may have an Fe2P phase present in at least some areas. The Fe2P phase has excellent electrical conductivity and can improve the performance of the positive electrode active material. In particular, the above effect can be more excellent when the Fe2P phase is uniformly positioned within the particulate material.

[0144] The Fe2P phase can be generated under excessively reducing or under-calcining conditions during the synthesis of the positive electrode active material, but the Fe2P phase generated in this manner can be unevenly distributed or located outside the particles, and can cause the crystal grains of the lithium complex compound to overgrow or rather inhibit crystal growth during the generation process.

[0145] Meanwhile, the above particulate material has high conductivity because the Fe2P phase is uniformly distributed inside the primary particles, and as a result, the capacity and rate characteristics of the positive electrode active material can be improved.

[0146] The above Fe2P phase can be confirmed using XRD Rietveld refinement. For example, the lithium manganese iron phosphate phase can be confirmed based on the JCPDS No. 74-0375 card having the orthorhombic Pnma space group, and the Fe2P phase can be confirmed based on the JCPDS No. 01-1200 card, but is not limited thereto. Meanwhile, the lithium manganese iron phosphate phase may mean all compound phases containing Li, Fe, Mn, P, and O simultaneously.

[0147] Here, the content of the Fe2P phase may be 0.2 to 0.9 wt%, for example, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, 0.5 wt%, 0.55 wt%, 0.6 wt%, 0.65 wt%, 0.7 wt%, 0.75 wt%, 0.8 wt%, 0.85 wt%, 0.9 wt%, or a range between any two of these values, based on 100 wt% of the lithium manganese iron phosphate phase included in the lithium complex compound. When the above range is satisfied, the positive electrode active material may have excellent conductivity and sufficient capacity.

[0148] In one example, the particulate material may be a finely divided lithium composite compound including a first region in which Fe is present but Mn is absent from the center to the surface, a second region in which a mixed structure of Fe and Mn is present, and a third region in which Mn is present but Fe is absent, or may be obtained by crushing the finely divided lithium composite compound. The finely divided lithium composite compound may be obtained by crushing the finely divided lithium composite compound in which the Fe2P phase is present in at least a portion of the first region and / or the second region. Meanwhile, the finely divided lithium composite compound may be, but is not limited to, a lithium composite compound including the first region, the second region, and the third region without undergoing a separate crushing process.

[0149] Here, the thickness of the first region may be 3.0 to 5.0 ㎛, for example, 3 ㎛, 3.25 ㎛, 3.5 ㎛, 3.75 ㎛, 4 ㎛, 4.25 ㎛, 4.5 ㎛, 4.75 ㎛, 5 ㎛, or a range between two of these values, and the thickness of the second region and the third region may be 0.5 to 2.0 ㎛ or more, for example, 0.5 ㎛, 0.75 ㎛, 1.0 ㎛, 1.25 ㎛, 1.5 ㎛, 1.75 ㎛, 2.0 ㎛, a range between two of these values, or 2.0 ㎛ or more, but is not limited thereto.

[0150] In one example, if the thicknesses of the first region, second region, and third region satisfy the above range, the particle material obtained through pulverization can have the performance improvement effect of increasing conductivity and capacity by a uniformly dispersed appropriate amount of Fe2P phase, while minimizing the performance degradation due to impurity phase.

[0151] In a non-limiting example, the particulate material may have a content of M2P2O7 phase (M=Fe or Mn) of 2.5 wt% or less, for example, 2.5 wt%, 2.25 wt%, 2 wt%, 1.75 wt%, 1.5 wt%, 1.25 wt%, 1 wt%, 0.75 wt%, 0.5 wt%, 0.25 wt%, 0.15 wt%, 0.05 wt%, an unmeasurable trace amount (nd), or a range between any two of these values, based on 100 wt% of the lithium manganese iron phosphate phase included in the lithium complex compound. The M2P2O7 phase may be identified using the XRD Rietveld method.

[0152] The M2P2O7 phase can act as a resistor, reducing the output and capacity characteristics of the cathode active material. Furthermore, among the M2P2O7 impurity phases, Mn2P2O7 can cause Mn dissolution during charge and discharge, thereby reducing battery stability.

[0153] In one example, the particulate matter may satisfy at least one of the conditions represented by Equations 1 to 3 below, but is not limited thereto.

[0154] [Formula 1]

[0155] 28.10 Å 2 ≤A p ≤28.74 Å 2

[0156] [Formula 2]

[0157] 62.40 Å 2 ≤B p ≤63.10 Å 2

[0158] [Formula 3]

[0159] 48.50 Å 2 ≤C p ≤49.20 Å 2

[0160] Here, the above A p C above p can be calculated using Equations 1' to 3' below.

[0161] [Formula 1']

[0162] A p =V c / l a

[0163] [Formula 2']

[0164] B p =V c / l b

[0165] [Formula 3']

[0166] C p =V c / l c

[0167] In the above formula, the V c is the unit cell volume of the above particulate matter, and l a , l b , l c Each represents the a-axis, b-axis, and c-axis diameter of the above particulate matter.

[0168] The above formulas 1 to 3 are cell characteristic values ​​representing the atomic arrangement of Fe and Mn in the particulate material, and may exhibit different cell characteristic values ​​when Fe-Mn is homogeneous, in a Mn rich phase, or in an Fe rich phase. When the above A' to C' characteristic values ​​satisfy the above-described range, the rate characteristics, life characteristics, and low-temperature characteristics of the positive electrode active material may be further improved. However, these values ​​are exemplary and may vary depending on the characteristics of the positive electrode active material. In addition, the lithium complex compound may be represented by the following chemical formula 1.

[0169] [Chemical Formula 1]

[0170] Li p Fe 1-x-y Mn x A y A' z P 1-z O w

[0171] In the above formula, A is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Cr, Cu, Ga, Hf, In, K, La, Mg, Mo, Na, Nb, Nd, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn and Zr, A' is at least one selected from the group consisting of C, Si, S, N, B, F, Cl and I, and 0.5≤p≤1.5, 0 <x<1, 0≤y<1, 0≤z<1, 0<w≤4이다.

[0172] The above chemical formula 1 represents a lithium complex compound capable of intercalating / deintercalating lithium, and may include lithium, a metal, and a phosphate.

[0173] For example, the above p may be, but is not limited to, 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 any two of these values.

[0174] Additionally, the above x, y and z may be, but are not limited to, 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 a range between any two of these values.

[0175] In addition, the above w may be, but is not limited to, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5, 3.75, 4 or a range between two of these values.

[0176] That is, LiFe 0.8 Mn 0.2 PO4, LiFe 0.5 Mn 0.5 PO4, etc. may be represented by the above chemical formula 1. Meanwhile, the lithium complex compound may further include a dopant. Here, the dopant may be represented by A and / or A'.

[0177] Here, the above chemical formula 1 may represent the average composition of the above lithium complex compound.

[0178] Meanwhile, 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., an interface between the particulate materials) and / or an aggregate formed by agglomeration of the particulate material.

[0179] 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.

[0180] For example, the coating layer may be present to cover at least a portion of the exposed surface of the particulate matter. Meanwhile, when the particulate matter aggregates to form secondary particles, the coating layer may be present to cover at least a portion of the exposed surface of the primary particles present at the outermost portion of the secondary particles.

[0181] Accordingly, the coating layer may exist as a layer that continuously or discontinuously coats the surface of the particulate matter and / or the secondary particles formed by agglomeration of the particulate matter. If the coating layer exists discontinuously, it may exist in the form of an island.

[0182] Additionally, when the particulate matter forms an aggregate, the coating layer may exist not only at the interface between the particulate matter and at least a portion of the surface of the secondary particle, but also in the internal pores formed inside the secondary particle.

[0183] The coating layer existing in this way can contribute to improving the electrochemical properties and stability of the positive electrode active material.

[0184] At this time, the coating layer may exist in the form of a solid solution that does not form a boundary with the particulate matter and / or the secondary particles formed by the agglomeration of the particulate matter, but this is not necessarily the case.

[0185] Meanwhile, the thickness of the amorphous carbon coating layer formed on at least a part of the surface of at least a part of the particulate matter 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.

[0186] Here, the thickness of the carbon coating layer can be controlled according to the balance of fluidity and conductivity of the lithium complex compound.

[0187] In particular, since the carbon coating layer has a small thickness deviation, the positive electrode active material can have excellent fluidity and conductivity, which are complementary in a balanced manner.

[0188] The thickness of the carbon coating layer can be measured using various known methods. For example, it can be measured from TEM or SEM images, or it can be determined from EDX analysis results obtained by line scanning of the carbon along a specific direction. This thickness can be the average of at least three measurements.

[0189] Furthermore, the carbon coating layer can be uniformly formed on the surface of the lithium composite compound, which is a particulate material, to provide a smooth surface texture. As a result, the compression density of the positive electrode active material can be increased.

[0190] Olivine-based cathode material is PO4 3- It is known that the electrical conductivity is low due to the strong covalent bonding. In addition, Li, which undergoes one-dimensional diffusion in the crystal structure, + Due to its characteristics, the ionic conductivity is low. To solve this problem, it has been proposed to form a carbon coating layer and manufacture a nano-sized positive electrode active material.

[0191] However, the amorphous carbon coating layer reduces the density of the cathode active material. Nanoparticles grow into angular shapes during sintering due to agglomeration, which reduces flowability and, similarly, the density of the cathode active material. This results in a reduction in energy density per unit volume.

[0192] In contrast, the particulate material comprising the lithium composite compound according to the present disclosure comprises a uniform carbon coating layer. Furthermore, under the conditions for forming this carbon coating layer, the lithium composite compound grows into a spherical particulate material, thereby minimizing density reduction.

[0193] Meanwhile, even if a coating layer of the compound exists on at least a portion of the surface of the particulate material, it is preferable that the particulate material maintain a spherical shape.

[0194]

[0195] lithium secondary battery

[0196] According to another aspect, a positive electrode may be provided, which includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. Here, the positive electrode active material layer may include a positive electrode active material manufactured according to a manufacturing method according to the various embodiments described above as a positive electrode active material.

[0197] The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change 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 positive electrode current collector may typically have a thickness of 3 to 500 ㎛, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesive strength of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0198] The above positive electrode active material layer can be manufactured by applying a positive electrode slurry composition including the positive electrode active material, a conductive material, and optionally a binder as needed, to the positive electrode current collector.

[0199] At this time, the positive electrode active material may be included in an amount of 80 to 99 wt%, more specifically 85 to 98.5 wt%, based on the total weight of the positive electrode active material layer. When included in the above-mentioned content range, excellent capacity characteristics may be exhibited, but the present invention is not necessarily limited thereto.

[0200] The conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. 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, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One of these may be used alone or a mixture of two or more may be used. The conductive material may be included in an amount of 0.1 to 15 wt% based on the total weight of the positive electrode active material layer.

[0201] The above binder serves to improve the adhesion between positive electrode active material particles and the adhesive strength between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The binder may be included in an amount of 0.1 to 15 wt% based on the total weight of the positive electrode active material layer.

[0202] The above positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material described above is used. Specifically, the positive electrode slurry composition, prepared by dissolving or dispersing the positive electrode active material described above and optionally a binder and a conductive agent in a solvent, is applied onto a positive electrode current collector, followed by drying and rolling.

[0203] The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0204] Additionally, in another embodiment, the positive electrode may be manufactured by casting the positive electrode slurry composition onto a separate support, and then laminating the resulting film onto a positive electrode current collector by peeling the film from the support.

[0205] In addition, according to another aspect, an electrochemical device including the above-described positive electrode may be provided. The electrochemical device may be specifically a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

[0206] The lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and electrolyte interposed between the positive electrode and the negative electrode.

[0207] In addition, the lithium secondary battery may be provided as an anode-free secondary battery. Here, since the anode is the same as described above, a detailed description thereof will be omitted for convenience, and only the remaining components not described above will be described in detail below. In addition, it should be understood that the description related to the anode described below is provided on the premise that the lithium secondary battery includes an anode.

[0208] Meanwhile, the lithium secondary battery may have a solid electrolyte replacing the separator. In such a case, an electrode slurry composition with additional solid electrolyte may be used during the manufacture of the positive and negative electrodes.

[0209] The above lithium secondary battery may optionally further include a battery container that houses an electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0210] The above negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0211] The negative electrode 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., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0212] The above negative electrode active material layer can be manufactured by applying a negative electrode slurry composition including the negative electrode active material, a conductive material, and optionally a binder as needed, to the negative electrode current collector.

[0213] As the negative electrode active material, a compound capable of reversible intercalation / deintercalation of lithium can 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 alloy, Sn alloy, or Al alloy; SiO β(0 < β < 2), metal oxides capable of doping and dedoping lithium, such as SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fiber-like forms, 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.

[0214] The above negative electrode active material may be included in an amount of 80 to 99 wt% based on the total weight of the negative electrode active material layer.

[0215] The above binder is a component that assists in 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 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0216] The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive agent is not particularly limited as long as it has conductivity and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0217] In one embodiment, the negative electrode active material layer may be manufactured by applying and drying a negative electrode slurry composition prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material, in a solvent on a negative electrode current collector, or by casting the negative electrode slurry composition on a separate support and then laminating the resulting film on a negative electrode current collector by peeling it off from the support.

[0218] In addition, in another embodiment, the negative electrode active material layer may be manufactured by applying and drying a negative electrode slurry composition prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material, in a solvent on a negative electrode current collector, or by casting the negative electrode slurry composition on a separate support and then laminating the resulting film on a negative electrode current collector by peeling it off from the support.

[0219] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without any particular restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure.

[0220] In addition, examples of the electrolyte used in the lithium secondary battery include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0221] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0222] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes, etc., can be used. Among these, a carbonate solvent is preferable, 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 linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.In this case, the performance of the electrolyte may be improved when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

[0223] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable that the concentration of the lithium salt be used within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0224] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 to 5 wt% based on the total weight of the electrolyte.

[0225] Meanwhile, the electrolyte may include a solid electrolyte such as a solid polymer electrolyte, a gel-type polymer electrolyte, or a solid inorganic electrolyte.

[0226] Lithium secondary batteries containing solid electrolytes may omit the aforementioned separator. However, since it is difficult for the electrolyte to penetrate the interior of the positive and negative electrodes, the solid electrolyte may be mixed to form the electrodes during their manufacture.

[0227] Meanwhile, the solid polymer electrolyte or gel polymer electrolyte may be a polymer resin complexed with a salt of a metal ion of Group 1 or Group 2 of the periodic table used in secondary batteries. For example, the polymer resin may be added to a solvated lithium salt.

[0228] Salts of the above metal ions may include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2.

[0229] The polymer resin includes, for example, polyether polymers, polycarbonate polymers, acrylate polymers, polysiloxane polymers, phosphazene polymers, polyethylene derivatives, alkylene oxide derivatives such as polyethylene oxide, phosphoric acid ester polymers, agitation lysine, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ionic dissociation groups, branched copolymers in which an amorphous polymer such as PMMA, polycarbonate, polysiloxane (PDMS) or phosphazene is copolymerized as a comonomer in a PEO (polyethylene oxide) main chain, comb-like polymers, and cross-linked polymer resins.

[0230] As solid inorganic electrolytes, sulfide-based solid electrolytes and oxide-based solid electrolytes can be broadly used.

[0231] The sulfide-based solid electrolyte may be a material containing sulfur (S) and having conductivity of metal ions of Group 1 or Group 2 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 conductivity of lithium ions.

[0232] Examples of the above sulfide-based solid electrolyte 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.

[0233] Meanwhile, the oxide-based solid electrolyte may be a material containing oxygen (O) and having the conductivity of a metal ion of Group 1 or Group 2 of the periodic table used in a secondary battery. For example, an LLTO-based compound, Li6La2CaTa2O 12 , Li6La2ACaNb2O 12 , Li6La2ASrNb2O 12 , Li2Nd3TeSbO 12 , Li3BO 2.5 N 0.5 , Li9SiAlO8, LAGP compounds, LATP compounds, LISICON compounds, LIPON compounds, perovskite compounds, NASICON compounds, and LLZO compounds may be at least one selected from the group consisting of:

[0234] As described above, a lithium secondary battery including the positive electrode active material stably exhibits excellent discharge capacity, output characteristics, and lifespan characteristics, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0235] There is no particular limitation on the external shape of the lithium secondary battery, but it may be in the form of a cylinder, square, pouch, or coin using a can. 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 be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

[0236] According to another aspect, a battery module including the lithium secondary battery as a unit cell and / or a battery pack including the same can be provided.

[0237] The above battery module or the battery pack can be used as a power source for one or more medium- to large-sized devices, including power tools; electric vehicles including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0238]

[0239] Hereinafter, the above-described matters will be described in more detail through examples. However, these examples are for illustrative purposes only, and the scope of this specification is not to be construed as being limited by these examples.

[0240]

[0241] Manufacturing Example 1. Manufacturing of positive electrode active material

[0242] (1) Example 1

[0243] In a reactor, FeOOH and 85 wt% H3PO4 were mixed so that the molar ratio of Fe to P was 1:2.55. Next, distilled water was added so that the FeOOH and H3PO4 in the slurry amounted to 40 wt% of the total weight. Thereafter, the slurry was stirred at 60°C for 8 hours to obtain a slurry containing an Fe-P complex. Here, an example of the reaction in which the Fe-P complex is formed can be referred to Reaction Scheme 2 below.

[0244] [Reaction Formula 2]

[0245] xFeOOH + yH3PO4→ Fe x (PO4) y ·nH2O

[0246] Mn3O4 and H2O2 were added to the above slurry so that the molar ratio of Fe, Mn, and H2O2 was 4:6:5. Afterwards, stirring was performed at 60°C for 8 hours to obtain a slurry containing an Fe-Mn-P complex. Here, an example of the reaction in which the Fe-Mn-P complex is formed can be referred to Reaction Scheme 3 below.

[0247] [Reaction Formula 3]

[0248] xMn3O4+ yH3PO4+ H2O2→ Mn 3x (PO4) z (HPO4) y-z ·nH2O

[0249] Li2CO3, a lithium raw material, and glucose, a carbon raw material, were added to the above slurry so that the molar ratio of Fe, Li, and C was 1:2.55:1, and a precipitate was obtained. Thereafter, the slurry was dried using a spray dryer (Dongjin Kiyeon, DJE003R).

[0250] The mixture was heat-treated in a N2 atmosphere furnace at a rate of 2°C / min and maintained at 650°C for 10 hours. After heat treatment, the mixture was pulverized using a jet mill to a D50 of 1.0 μm or less. After furnace cooling and classification, a cathode active material including lithium manganese iron phosphate was obtained.

[0251]

[0252] (2) Example 2

[0253] In a reactor, FeOOH and H3PO4 having a concentration of 85 wt% were mixed so that the molar ratio of Fe to P was 1:2.55. Next, distilled water was added so that the FeOOH and H3PO4 in the slurry amounted to 40 wt% of the total weight. Thereafter, the slurry was stirred at 60°C for 8 hours to obtain a slurry containing an Fe-P complex.

[0254] Mn3O4 and H2O2 were added to the above slurry so that the molar ratio of Fe, Mn, and H2O2 was 4:6:5. Afterwards, stirring was performed at 60°C for 8 hours to obtain a slurry containing an Fe-Mn-P complex.

[0255] Li2CO3, a lithium raw material, and glucose, a carbon raw material, were added to the above slurry so that the molar ratio of Fe, Li, and C was 1:2.55:1, and TiO2, a dopant, was added so that Ti was 0.4 mol% based on the total moles of the positive electrode active material, thereby obtaining a precipitate. Thereafter, the slurry was dried using a spray dryer.

[0256] The mixture was heat-treated in a N2 atmosphere furnace at a rate of 2°C / min and maintained at 650°C for 10 hours. After heat treatment, the mixture was pulverized using a jet mill to a D50 of 1.0 μm or less. After cooling and classifying, a cathode active material including lithium manganese iron phosphate was obtained.

[0257]

[0258] (3) Example 3

[0259] In a reactor, FeOOH and H3PO4 having a concentration of 85 wt% were mixed so that the molar ratio of Fe to P was 1:2.55, and TiO2 as a dopant was added so that Ti was 0.4 mol% based on the total moles of the positive electrode active material. Next, distilled water was added so that the FeOOH and H3PO4 in the slurry were 40 wt% of the total weight. Thereafter, the slurry was stirred at 60°C for 8 hours to obtain a slurry containing an Fe-P complex.

[0260] Mn3O4 and H2O2 were added to the above slurry so that the molar ratio of Fe, Mn, and H2O2 was 4:6:5. Afterwards, stirring was performed at 60°C for 8 hours to obtain a slurry containing an Fe-Mn-P complex.

[0261] Li2CO3, a lithium raw material, and glucose, a carbon raw material, were added to the above slurry so that the molar ratio of Fe, Li, and C was 1:2.55:1, thereby obtaining a precipitate. Thereafter, the slurry was dried using a spray dryer.

[0262] The mixture was heat-treated in a N2 atmosphere furnace at a rate of 2°C / min and maintained at 650°C for 10 hours. After heat treatment, the mixture was pulverized using a jet mill to a D50 of 1.0 μm or less. After cooling and classifying, a cathode active material including lithium manganese iron phosphate was obtained.

[0263]

[0264] (4) Example 4

[0265] In a reactor, FeOOH and H3PO4 having a concentration of 85 wt% were mixed so that the molar ratio of Fe to P was 1:2.55. Next, distilled water was added so that the FeOOH and H3PO4 in the slurry amounted to 40 wt% of the total weight. Thereafter, the slurry was stirred at 60°C for 8 hours to obtain a slurry containing an Fe-P complex.

[0266] To the above slurry, Mn3O4 and H2O2 were added so that the molar ratio of Fe, Mn, and H2O2 was 4:6:5, and TiO2 as a dopant was added so that Ti was 0.4 mol% based on the total mole number of the positive electrode active material. Thereafter, the slurry was further stirred at 60°C for 8 hours to obtain a slurry containing an Fe-Mn-P complex.

[0267] Li2CO3, a lithium raw material, and glucose, a carbon raw material, were added to the above slurry so that the molar ratio of Fe, Li, and C was 1:2.55:1, thereby obtaining a precipitate. Thereafter, the slurry was dried using a spray dryer.

[0268] The mixture was heat-treated in a N2 atmosphere furnace at a rate of 2°C / min and maintained at 650°C for 10 hours. After heat treatment, the mixture was pulverized using a jet mill to a D50 of 1.0 μm or less. After cooling and classifying, a cathode active material including lithium manganese iron phosphate was obtained.

[0269]

[0270] (5) Comparative Example 1

[0271] In a reactor, FeOOH and 85 wt% H3PO4, Mn3O4, and H2O2 were mixed so that the molar ratio of Fe, P, Mn, and H2O2 was 1:2.55:1.5:1.25. Next, distilled water was added so that the concentration of the aforementioned raw materials in the slurry became 40 wt% of the total weight. Thereafter, the slurry was stirred at 60°C for 24 hours to obtain a slurry.

[0272] Li2CO3, a lithium raw material, and sucrose, a carbon raw material, were added to the above slurry so that the atomic ratio of Fe, Li, and C was 1:2.55:1, and a precipitate was obtained. Thereafter, the slurry was dried using a spray dryer.

[0273] The mixture was heat-treated in a N2 atmosphere furnace at a temperature of 2°C / min and maintained at 650°C for 10 hours. After heat treatment, the mixture was pulverized using a jet mill to a D50 of 1.0 μm or less. After cooling and classifying, the positive electrode active material was obtained.

[0274]

[0275] (6) Comparative Example 2

[0276] In a reactor, FeOOH and H3PO4 with a concentration of 85 wt% were mixed so that the molar ratio of Fe and P was 1:2.55. Next, distilled water was added so that the FeOOH and H3PO4 in the slurry amounted to 40 wt% of the total weight. Thereafter, the mixture was stirred at 60°C for 8 hours to obtain a slurry.

[0277] Mn3O4 was added to the above slurry so that the molar ratio of Fe and Mn was 2:3. Afterwards, the slurry was obtained by additional stirring at 60°C for 8 hours.

[0278] Li2CO3, a lithium raw material, and glucose, a carbon raw material, were added to the above slurry so that the molar ratio of Fe, Li, and C was 1:2.55:1, thereby obtaining a precipitate. Thereafter, the slurry was dried using a spray dryer.

[0279] The mixture was heat-treated in a N2 atmosphere furnace at a temperature of 2°C / min and maintained at 650°C for 10 hours. After heat treatment, the mixture was pulverized using a jet mill to a D50 of 1.0 μm or less. After cooling and classifying, the positive electrode active material was obtained.

[0280]

[0281] (7) Comparative Example 3

[0282] Mn3O4, 85 wt% H3PO4, and H2O2 were added to the reactor so that the molar ratio of Mn, P, and H2O2 was 1:1.55:1.25. Next, distilled water was added so that the Mn3O4, H3PO4, and H2O2 in the slurry accounted for 40 wt% of the total weight. The mixture was stirred at 60°C for 8 hours to obtain a slurry.

[0283] FeOOH was added to the above slurry so that the molar ratio of Mn and Fe was 3:2. Afterwards, the slurry was obtained by additional stirring at 60°C for 8 hours.

[0284] Li2CO3, a lithium raw material, and glucose, a carbon raw material, were added to the above slurry so that the molar ratio of Fe, Li, and C was 1:2.55:1, thereby obtaining a precipitate. Thereafter, the slurry was dried using a spray dryer.

[0285] The mixture was heat-treated in a N2 atmosphere furnace at a temperature of 2°C / min and maintained at 650°C for 10 hours. After heat treatment, the mixture was pulverized using a jet mill to a D50 of 1.0 μm or less. After cooling and classifying, the positive electrode active material was obtained.

[0286]

[0287] (8) Comparative Example 4

[0288] In a reactor, FeOOH, H3PO4 with a concentration of 85 wt%, and lithium raw material Li2CO3 were mixed so that the molar ratio of Fe, P, and Li was 1:2.55:2.55. Next, distilled water was added so that the FeOOH, H3PO4, and Li2CO3 in the slurry amounted to 40 wt% of the total weight. Thereafter, the slurry was stirred at 60°C for 8 hours to obtain a slurry containing an Fe-P complex.

[0289] Mn3O4 and H2O2 were added to the above slurry so that the molar ratio of Fe, Mn, and H2O2 was 4:6:5. Afterwards, the slurry was obtained by additional stirring at 60°C for 8 hours.

[0290] Glucose, a carbon source material, was added to the above slurry so that the molar ratio of Fe and C was 1:1 to obtain a precipitate. Thereafter, the slurry was dried using a spray dryer.

[0291] The mixture was heat-treated in a N2 atmosphere furnace at a temperature of 2°C / min and maintained at 650°C for 10 hours. After heat treatment, the mixture was pulverized using a jet mill to a D50 of 1.0 μm or less. After cooling and classifying, the positive electrode active material was obtained.

[0292]

[0293] (9) Comparative Example 5

[0294] In a reactor, Mn3O4 and H3PO4 with a concentration of 85 wt% were mixed so that the molar ratio of Mn to P was 1:1.55. Next, distilled water was added so that the Mn3O4 and H3PO4 in the slurry amounted to 40 wt% of the total weight. Thereafter, the mixture was stirred at 60°C for 8 hours to obtain a slurry.

[0295] FeOOH and H2O2 were added to the above slurry so that the molar ratio of Fe, Mn, and H2O2 was 4:6:5. Afterwards, the slurry was obtained by additional stirring at 60°C for 8 hours.

[0296] Li2CO3, a lithium raw material, and glucose, a carbon raw material, were added to the above slurry so that the molar ratio of Fe, Li, and C was 1:2.55:1, thereby obtaining a precipitate. Thereafter, the slurry was dried using a spray dryer.

[0297] The mixture was heat-treated in a N2 atmosphere furnace at a temperature of 2°C / min and maintained at 650°C for 10 hours. After heat treatment, the mixture was pulverized using a jet mill to a D50 of 1.0 μm or less. After cooling and classifying, the positive electrode active material was obtained.

[0298]

[0299] Experimental Example 1. Characteristics of the positive electrode active material

[0300] Each cathode active material manufactured according to Manufacturing Example 1 was analyzed by XRD using the Rietveld refining method to confirm the ratio of lithium manganese iron phosphate (LMFP) phase, Fe2P phase, and Mn2P2O7 phase, and the results are shown in Table 1 below. Meanwhile, SEM images of Example 1 and Comparative Example 4 are shown in Fig. 2.

[0301] Classification Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 LMFP (wt%) 99.4199.4899.5499.5496.5296.2796.4587.5789.12 Fe2P (wt%) 0.590.520.460.460.070.980.057.106.60 Mn2P2O7 (wt%) 0.000.000.000.003.412.753.505.334.28

[0302] Additionally, the unit cell volume (Cell volume; V) of each positive electrode active material manufactured according to Manufacturing Example 1 was determined from the XRD results. c ), a-axis length (l) a ), b-axis length (l) b ), c-axis length (l) c ) and A according to the following equations 1' to 3' p Inland C p After calculating the cell characteristic values, the results are shown in Table 2 below.

[0303] [Formula 1']

[0304] A p =V c / l a

[0305] [Formula 2']

[0306] B p =V c / l b

[0307] [Formula 3']

[0308] C p =V c / l c

[0309] Classification Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5A p (Å 2 )28.6028.6728.6228.6628.7528.1128.6628.1829.38B p (Å 2 )62.9563.0863.0063.0763.0862.4863.0762.0463.67C p (Å 2 )49.0749.1649.1049.1449.1648.4049.2448.4549.93

[0310] Referring to Table 1 and Table 2, Fe2P can be formed when excessively reduced by carbon at high temperatures.

[0311] In addition, when the MP phase is unstable, as in the comparative example, the M2P2O7 phase (M=Fe or Mn) may be generated due to the decrease in Li reactivity during sintering. The M2P2O7 phase acts as a resistor, lowering the output characteristics and also reducing the capacity. Among these, Mn2P2O7 may cause the elution of Mn during charge and discharge, which may lower the battery stability.

[0312] Meanwhile, cell characteristic values ​​may vary depending on the atomic arrangement of Fe and Mn. For example, Fe-Mn may exhibit different cell characteristic values ​​in a homogeneous, Mn-rich phase, or Fe-rich phase, respectively.

[0313] The positive electrode active material manufactured in the example was 28.10 Å 2 ≤A p ≤28.74 Å 2 , 62.40 Å 2 ≤B p ≤63.10 Å 2 , 48.50 Å 2 ≤C p ≤49.20 Å 2 It can be confirmed that it has a range of .

[0314]

[0315] Manufacturing Example 2. Manufacturing of a lithium secondary battery

[0316] A positive electrode slurry was prepared by dispersing 94 wt% of each positive electrode active material manufactured according to Manufacturing 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 applied to an aluminum (Al) thin film as a positive electrode current collector with a thickness of 20 μm, dried, and roll pressed to prepare a positive electrode.

[0317] A coin cell was manufactured according to a commonly known manufacturing process using a lithium foil as a counter electrode for the above anode, a porous polyethylene film (Celgard 2300, thickness: 25 ㎛) as a separator, and a liquid electrolyte containing LiPF6 at a concentration of 1.15 M in a solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3:7.

[0318]

[0319] Experimental Example 2. Characteristic Evaluation of Positive Electrode Active Materials

[0320] In Manufacturing Example 2, a charge / discharge experiment was performed on a coin cell using an electrochemical analyzer (Toyo, Toscat 3100) at 25°C, a voltage range of 2.0 to 3.65 V, and a discharge rate of 0.1 to 5.0 C, to measure the discharge capacity. Charge / discharge was performed 100 times repeatedly at a voltage range of 2.0 to 3.65 V and a current of 1.0 C, and the life characteristics were evaluated as the ratio of the 100th discharge capacity to the initial capacity. In addition, a charge / discharge experiment was performed at -20°C, a voltage range of 2.0 to 3.65 V, and a discharge rate of 0.1 C, and the analysis results are shown in Table 3 below.

[0321] ClassificationExample 1Example 2Example 3Example 4Comparative Example 1Comparative Example 2Comparative Example 3Comparative Example 4Comparative Example 50.1 C Discharge capacity (mAh / g)152.5153.7152.1153.5143.1138.1147.6128.5121.65 C Discharge capacity (mAh / g)122126.3124.3124.5100.298.1107.78179.5100 cycles life (%)98.499.599.198.788.187.586.980.082.4-20℃0.1 C Discharge capacity (mAh / g)129.9130.0134.7134.8108.6109.6106.1106.0109.9

[0322] Referring to Tables 1 to 3 and Fig. 2, it can be confirmed that in the positive electrode active material according to the example, the Fe2P phase with excellent electrical and ionic conductivity is uniformly distributed, so that it has high conductivity and sufficient capacity. On the other hand, in the positive electrode active material of the comparative example, the Fe2P phase is present in an extremely small amount, so that the performance is not improved, or as can be seen in Fig. 2, the Fe2P phase is aggregated on the outside of the particles, or an excessive amount is present, so that the conductivity and capacity are reduced.

[0323] Above, the embodiments of this specification have been described, but a person having ordinary skill in the art will be able to modify and change this specification in various ways by adding, changing, deleting or adding components, etc., within the scope that does not depart from the spirit of this specification described in the claims, and this is also considered to be included within the scope of the rights of this specification.

Claims

1. (a) A step of producing a slurry containing an Fe-P complex by reacting an iron raw material and a phosphoric acid raw material; (b) a step of reacting a manganese raw material and an Fe-P complex to produce a slurry containing an Fe-Mn-P complex; (c) a step of adding a lithium raw material and a carbon raw material to the slurry and then drying the same to obtain a powder; and (d) a step of heat-treating the above powder to obtain a lithium complex compound; including, A method for producing a positive electrode active material for a lithium secondary battery.

2. In paragraph 1, The above iron raw material is at least one selected from the group consisting of Fe metal, FeOOH, Fe2O3 and Fe3O4. A method for producing a positive electrode active material for a lithium secondary battery.

3. In paragraph 1, The above phosphoric acid raw material is at least one selected from the group consisting of H3PO4, Li3PO4, NH4H2PO4 and (NH4)2HPO4. A method for producing a positive electrode active material for a lithium secondary battery.

4. In paragraph 1, The above iron raw material and the above phosphoric acid raw material are added so that the phosphorus element is 0.90 to 2.00 moles based on 1 mole of iron element. A method for producing a positive electrode active material for a lithium secondary battery.

5. In paragraph 1, The above manganese raw material is at least one selected from the group consisting of Mn metal, MnCO3, Mn2O3 and Mn3O4. A method for producing a positive electrode active material for a lithium secondary battery.

6. In paragraph 1, The above manganese raw material is added so that the manganese element is 1.00 to 2.00 moles based on 1 mole of iron element included in the Fe-P complex. A method for producing a positive electrode active material for a lithium secondary battery.

7. In paragraph 1, At least one of the reactions of step (a) and step (b) is performed at 50 to 150°C. A method for producing a positive electrode active material for a lithium secondary battery.

8. In paragraph 1, The above Fe-Mn-P complex is FePO4ㆍnH2O(0≤n≤9), FePO4 anhydride, Fe3(PO4)2, Fe2(HPO4)3, H 10 Mn5O 20 Containing at least one selected from the group consisting of P4, MnPO4 and Mn3(PO4)2, A method for producing a positive electrode active material for a lithium secondary battery.

9. In paragraph 1, The reaction of step (b) above is carried out in the presence of an oxidizing agent, A method for producing a positive electrode active material for a lithium secondary battery.

10. In paragraph 9, The above oxidizing agent is at least one selected from the group consisting of hydrogen peroxide, potassium permanganate, peroxyacetic acid, perbenzoic acid, sodium perborate, periodic acid, sodium percarbonate, potassium percarbonate, vanadium trioxide, ammonium chloride, ammonium phosphate, ferric chloride, hypochlorous acid, sodium hypochlorite and dissolved ozone. A method for producing a positive electrode active material for a lithium secondary battery.

11. In paragraph 1, The lithium raw material of the above step (c) is added so that the ratio of the number of lithium atoms (Li) to the total number of metal atoms (Metal) of metal elements other than lithium in the slurry (Li / Metal) is 0.50 to 1.

50. A method for producing a positive electrode active material for a lithium secondary battery.

12. In paragraph 1, The carbon raw material of the above step (c) is added so that the ratio of the number of carbon atoms (C) to the total number of metal atoms (Metal) of metal elements other than lithium in the slurry (C / Metal) is 0.25 to 0.

75. A method for producing a positive electrode active material for a lithium secondary battery.

13. In paragraph 1, In at least one step of the above (a) to (c) steps, at least one sub-raw material including 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 additionally added to the slurry. A method for producing a positive electrode active material for a lithium secondary battery.

14. In paragraph 1, Before or after the above step (c), the solid content in the slurry is crushed to break up the over-agglomerated particles. A method for producing a positive electrode active material for a lithium secondary battery.

15. In paragraph 1, The heat treatment in step (d) above is performed under conditions of 500 to 950°C. A method for producing a positive electrode active material for a lithium secondary battery.

16. In paragraph 1, The lithium complex compound obtained in the above step (d) includes a first region in which Fe exists from the center to the surface but Mn does not exist, a second region in which a mixed structure of Fe and Mn exists, and a third region in which Mn exists but Fe does not exist. A method for producing a positive electrode active material for a lithium secondary battery.

17. In paragraph 16, The sum of the thicknesses of the second and third regions is 0.5 to 2.0 ㎛. A method for producing a positive electrode active material for a lithium secondary battery.

18. In paragraph 1, After step (d) above, (e) further comprising a step of pulverizing the lithium complex compound so that the average particle size becomes 1.0 ㎛ or less. A method for producing a positive electrode active material for a lithium secondary battery.

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