Method for preparing cathode active material

Abstract

The present invention relates to a method for preparing a lithium iron phosphate-based cathode active material, the method comprising the steps of: dry-pulverizing iron phosphate (FePO4) and a carbon-containing coating raw material, separately; mixing a lithium-containing raw material, the pulverized iron phosphate, the pulverized carbon-containing coating raw material, and distilled water to prepare a reaction mixture; compressing the reaction mixture to process same into a pellet form; and firing the pellet-shaped reaction mixture to prepare a fired product, wherein the distilled water is mixed in an amount of 20 parts by weight or less with respect to 100 parts by weight of the total weight of the lithium-containing raw material, the pulverized iron phosphate, and the pulverized carbon-containing coating raw material.

Description

Method for manufacturing positive electrode active material

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0089614, filed July 8, 2024, the entire contents of which are incorporated herein by reference.

[0003]

[0004] Technology field

[0005] The present invention relates to a method for manufacturing a positive electrode active material.

[0006]

[0007] As technological development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which boast high energy density and voltage, long cycle life, and low self-discharge rates, are commercialized and widely used.

[0008] Lithium secondary batteries are composed of four major components: a cathode, an anode, a separator, and an electrolyte. Among these, the cathode active material contained in the cathode plays a significant role in determining the battery's capacity, output, and lifespan. Currently used cathode active materials include NCM-based cathode active materials containing nickel, cobalt, manganese, and / or aluminum, and LFP (lithium iron phosphate)-based cathode active materials. Meanwhile, improving the performance of cathode active materials is essential for lithium secondary batteries to achieve high energy density, output, and lifespan. Consequently, extensive research has been conducted recently to develop high-performance cathode active materials.

[0009] LFP-based cathode active materials, which are olivine-structured cathode active materials, have lower capacity than NCM-based cathode active materials, but they have the advantage of superior thermal stability and price competitiveness. However, LFP-based cathode active materials have problems due to high electrical resistance and low lithium ion diffusion. To solve these problems, research has been conducted, such as applying carbon coating and controlling the particle size to several hundred nm. However, applying carbon coating and controlling the particle size to several hundred nm inevitably requires wet grinding processes such as bead milling and spray drying processes, which not only require high energy for cathode active material synthesis, but also increase costs due to reduced yield. Therefore, a dry synthesis method that bypasses the wet grinding and spray drying processes is necessary, but this method has been pointed out as a disadvantage due to high resistance due to the uneven carbon coating.

[0010]

[0011] The present invention is intended to solve the above problems and to provide a method for manufacturing a lithium iron phosphate-based cathode active material capable of implementing an LFP-based cathode active material having a uniform carbon coating and low resistance.

[0012]

[0013] (1) The present invention provides a method for producing a lithium iron phosphate-based positive electrode active material, comprising the steps of: (A) dry-pulverizing iron phosphate (FePO4) and carbon-containing coating raw materials, respectively; (B) mixing lithium-containing raw materials, pulverized iron phosphate, pulverized carbon-containing coating raw materials, and distilled water to prepare a reaction mixture; (C) compressing the reaction mixture to form a pellet; and (D) firing the pellet-shaped reaction mixture to prepare a fired product; wherein the distilled water is mixed in an amount of 20 parts by weight or less based on 100 parts by weight of the total weight of the lithium-containing raw materials, pulverized iron phosphate, and pulverized carbon-containing coating raw materials.

[0014] (2) The present invention provides a method for manufacturing a lithium iron phosphate cathode active material, wherein, in the above (1), the carbon-containing coating raw material is at least one selected from the group consisting of sucrose, glucose, polyethylene glycol, polyvinyl alcohol, and polyvinyl acetate.

[0015] (3) The present invention provides a method for producing a lithium iron phosphate-based positive electrode active material, wherein, in step (A), the pulverization of iron phosphate in the above (1) or (2) is performed by airflow pulverization.

[0016] (4) The present invention provides a method for producing a lithium iron phosphate cathode active material, wherein, in any one of the above (1) to (3), the pulverization of the carbon-containing coating raw material in step (A) is performed by mechanical pulverization.

[0017] (5) In any one of (1) to (4), the pulverized iron phosphate has an average particle diameter (D 50 ) provides a method for manufacturing a lithium iron phosphate-based positive electrode active material having a particle size of 1.0㎛ or more and 2.0㎛ or less.

[0018] (6) The present invention provides a method for manufacturing a lithium iron phosphate-based positive electrode active material, wherein the pulverized iron phosphate has a span of 0.5 or more and 1.5 or less according to the following formula 1, in any one of (1) to (5).

[0019] [Formula 1]

[0020] Span = (D 90 -D 10 ) / D 50

[0021] (7) In any one of (1) to (6), the pulverized carbon-containing coating raw material has an apparent density (bulk density) of 500 kg / m 3 More than 700 kg / m 3 A method for manufacturing a lithium iron phosphate-based positive electrode active material is provided.

[0022] (8) The present invention provides a method for producing a lithium iron phosphate-based positive electrode active material, wherein the distilled water is mixed in an amount of 5 parts by weight or more and 15 parts by weight or less based on 100 parts by weight of the total weight of the lithium-containing raw material, the pulverized iron phosphate, and the pulverized carbon-containing coating raw material in any one of (1) to (7).

[0023] (9) The present invention provides a method for producing a lithium iron phosphate-based positive electrode active material, wherein the reaction mixture has a moisture content of 5 wt% or more and 25 wt% or less in any one of (1) to (8).

[0024] (10) The present invention provides a method for producing a lithium iron phosphate cathode active material, wherein, in any one of (1) to (9), when producing the reaction mixture, an M-containing raw material (M is at least one selected from the group consisting of V, Ti, Mn, Zn, Mo, Mg, and N) is further mixed.

[0025] (11) The present invention provides a method for producing a lithium iron phosphate positive electrode active material, wherein, in any one of (1) to (10), a silane compound is further mixed during the preparation of the reaction mixture.

[0026] (12) The present invention provides a method for producing a lithium iron phosphate positive electrode active material, wherein, in (11), the silane compound is mixed in an amount of 0.05 wt% or more and 0.2 wt% or less based on the total weight of the reaction mixture.

[0027] (13) In any one of (1) to (12), the compression in step (C) is 0.10 ton / cm 2 More than 1.0 ton / cm 2 A method for manufacturing a lithium iron phosphate-based positive electrode active material is provided, which is performed under the following pressure.

[0028] (14) The present invention provides a method for producing a lithium iron phosphate-based positive electrode active material, wherein the calcination is performed at a temperature of 600°C or higher and 800°C or lower in any one of (1) to (13).

[0029] (15) The present invention provides a method for manufacturing a lithium iron phosphate cathode active material, further comprising the step of (E) crushing the sintered product in any one of (1) to (14).

[0030]

[0031] The method for manufacturing a lithium iron phosphate-based cathode active material according to the present invention comprises dry-grinding iron phosphate (FePO4) and carbon-containing coating raw materials, respectively, mixing the lithium-containing raw materials, the pulverized iron phosphate, the pulverized carbon-containing coating raw materials, and a specific amount of distilled water to prepare a reaction mixture, and then compressing the reaction mixture to process it into a pellet form and then firing it, thereby not only preventing the sticking of the raw materials but also improving the reactivity of the raw materials, dissolving the carbon-containing coating raw materials in distilled water to uniformly form a coating layer, and improving the strength of the particles. Accordingly, a lithium iron phosphate-based cathode active material including a uniform carbon coating layer, low powder resistance, and improved particle strength can be effectively manufactured.

[0032] In addition, there is an effect of improving the resistance characteristics and output characteristics of the positive electrode and secondary battery including the positive electrode active material.

[0033]

[0034] Figure 1 is a SEM image (10K magnification) of the lithium iron phosphate-based positive electrode active material manufactured in Example 1.

[0035] Figure 2 is a SEM image (10K magnification) of the lithium iron phosphate-based positive electrode active material manufactured in Example 2.

[0036] Figure 3 is a SEM image (50K magnification) of the lithium iron phosphate-based positive electrode active material manufactured in Comparative Example 1.

[0037] Figure 4 is a SEM image (50K magnification) of the lithium iron phosphate-based positive electrode active material manufactured in Comparative Example 4.

[0038] Figure 5 is a STEM-EDS mapping image of the lithium iron phosphate cathode active material manufactured in Example 1.

[0039] Figure 6 is a STEM-EDS mapping image of C of the lithium iron phosphate cathode active material manufactured in Example 1.

[0040] Figure 7 is a STEM-EDS mapping image of Fe of the lithium iron phosphate cathode active material manufactured in Example 1.

[0041] Figure 8 is a STEM-EDS mapping image of the lithium iron phosphate cathode active material manufactured in Comparative Example 1.

[0042] Figure 9 is a STEM-EDS mapping image of C and Fe of the lithium iron phosphate cathode active material manufactured in Comparative Example 1.

[0043]

[0044] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0045] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best possible manner.

[0046] In this specification, it should be understood that terms such as “include,” “have,” or “have” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0047] In this specification, the term 'on' means not only when a configuration is formed directly on the top surface of another configuration, but also when a third configuration is interposed between these configurations.

[0048] In this specification, 'primary particle' means the smallest particle unit recognized when observing a positive electrode active material using a scanning electron microscope (SEM), and 'secondary particle' means a secondary structure formed by the aggregation of multiple primary particles.

[0049] In this specification, the average particle diameter (D 50 ) may be measured using a laser diffraction particle size measuring device (e.g., Malvern Panalytical, Mastersizer 3000). Specifically, it can be defined as the particle size corresponding to 50% of the volume cumulative distribution in the particle size distribution curve (graph curve of particle size distribution) of each particle obtained using a laser diffraction particle size measuring device. After dispersing the powder to be measured in a dispersion medium, the particle size distribution is calculated by measuring the difference in diffraction pattern according to particle size when the particles pass through the laser beam, and calculating the particle diameter at the point where the volume cumulative distribution according to the particle size in the measuring device is 50%, thereby measuring.

[0050] In this specification, the apparent density is measured according to the ISO 60 method.

[0051] In this specification, the 'moisture content' may be measured using a heating type moisture meter (e.g., MA100 from Sartorious). Specifically, after placing about 5 g of a sample on a sample dish in the device, the lid of the device is closed and the temperature of the sample dish is set to 110°C, thereby evaporating the moisture contained in the powder sample and measuring the degree of mass reduction. At this time, when the amount of mass reduction in the sample is 0.1 wt% or less, it is regarded as the point at which the mass no longer reduces, and this point is called a dried state. The moisture content may be expressed as a percentage (%) by measuring the mass of the sample before and after drying and expressing the difference in the mass (g) of the sample before and after drying with respect to the mass (g) of the sample before drying.

[0052]

[0053] Method for manufacturing lithium iron phosphate cathode active material

[0054] A method for manufacturing the positive electrode active material of the present invention is described.

[0055]

[0056] A method for producing a lithium iron phosphate-based cathode active material according to the present invention comprises the steps of (A) dry-pulverizing iron phosphate (FePO4) and a carbon-containing coating raw material, respectively; (B) mixing the lithium-containing raw material, the pulverized iron phosphate, the pulverized carbon-containing coating raw material, and distilled water to prepare a reaction mixture; (C) compressing the reaction mixture to process it into a pellet shape; and (D) firing the pellet-shaped reaction mixture to prepare a fired product; wherein the distilled water is mixed in an amount of 20 parts by weight or less based on 100 parts by weight of the total weight of the lithium-containing raw material, the pulverized iron phosphate, and the pulverized carbon-containing coating raw material.

[0057]

[0058] The present inventors have discovered that by performing steps (A) to (D) to manufacture a lithium iron phosphate-based positive electrode active material, not only can the fixation of raw materials be prevented, but also the reactivity of the raw materials can be improved, a coating layer can be uniformly formed, and the strength of the particles can be improved, thereby completing the present invention.

[0059] Meanwhile, if one of steps (A) to (C) is not performed, or if more than 20 parts by weight are mixed for 100 parts by weight of the total weight of the lithium-containing raw material, the pulverized iron phosphate, and the pulverized carbon-containing coating raw material, the raw materials may be fixed while being mixed unevenly, partial compositional unevenness may occur, which may increase resistance, the carbon coating layer may not be formed uniformly, and there is a problem of poor particle strength.

[0060] The lithium iron phosphate cathode active material according to the present invention described above can be manufactured by appropriately controlling the type of raw material, the mixing ratio of raw materials, the sintering and heat treatment times, etc.

[0061] Hereinafter, each step of the present invention will be described in detail.

[0062]

[0063] (A) Step

[0064]

[0065] The method for manufacturing a lithium iron phosphate-based positive electrode active material according to the present invention includes step (A) of dry-pulverizing iron phosphate (FePO4) and carbon-containing coating raw materials, respectively.

[0066] Specifically, the step (A) is a step of dry-grinding iron phosphate (FePO4) and carbon-containing coating raw materials, respectively, to produce pulverized iron phosphate and pulverized carbon-containing coating raw materials. The step (A) is a process of first pulverizing each raw material before mixing them, in which case the surface area of ​​the raw material increases, thereby improving reactivity.

[0067] Meanwhile, when manufacturing a cathode active material by mixing raw materials without first crushing them, there is a problem that the raw materials may be fixed while being mixed unevenly, and partial compositional unevenness may occur, resulting in increased resistance.

[0068] The above dry grinding is a grinding method that does not use water or liquid, and can significantly improve process costs and yield compared to wet grinding.

[0069]

[0070] According to one embodiment of the present invention, the carbon-containing coating raw material may be at least one selected from the group consisting of sucrose, glucose, polyethylene glycol, polyvinyl alcohol, and polyvinyl acetate. In particular, sucrose may be used when considering manufacturing cost and processability.

[0071]

[0072] The above step (A) is specifically a step of independently crushing iron phosphate (FePO4) and carbon-containing coating raw materials.

[0073] According to one embodiment of the present invention, the pulverization of iron phosphate in step (A) may be performed by air current pulverization. The air current pulverization may be performed by an air jet mill in which powder is pulverized by impact while forming an air current by air. The pulverization of iron phosphate may be performed for 0.1 to 2 hours under an ejection air pressure of 1 to 10 bar and a grinding air pressure of 0.5 to 2.0 bar. Specifically, the iron phosphate may be fed at a rate of 5 g / min using a single screw feeder, and pulverization may be performed under the above conditions.

[0074]

[0075] According to one embodiment of the present invention, the pulverization of the carbon-containing coating raw material in step (A) may be performed by mechanical pulverization. The mechanical pulverization may be performed by a rotary mill, a hammer mill, or the like, in a manner in which the powder is pulverized by colliding with a rotating device. The pulverization of the carbon-containing coating raw material may be performed at 500 to 2000 rpm for 0.5 to 2 hours.

[0076]

[0077] (B) Step

[0078] The method for manufacturing a positive electrode active material according to the present invention includes, after step (A), step (B) of preparing a reaction mixture by mixing a lithium-containing raw material, pulverized iron phosphate, pulverized carbon-containing coating raw material, and distilled water.

[0079] Specifically, the process involves mixing a small amount of raw materials and distilled water, dissolving the carbon-containing coating raw material in distilled water, but not mixing the raw materials in a slurry state, so that a uniform coating layer can be formed with relatively low energy, and the yield of the positive electrode active material can be improved.

[0080] Meanwhile, if distilled water is not mixed, there is a problem of high powder resistance because a uniform coating layer is not formed, and if distilled water is mixed in excessive amounts, the process cost and yield are inferior, and there is a problem of high powder resistance because a uniform coating layer is not formed.

[0081]

[0082] According to the present invention, the lithium-containing raw material may be, but is not limited to, Li2S, Li2S2, Li2S4, Li2S6, LiCl, LiBr, Li, Li3PS4, LiOH, Li2CO3, or a combination thereof.

[0083] The lithium-containing raw material may be mixed in an amount such that the resulting lithium iron phosphate compound has a composition represented by the chemical formula 1 described herein. For example, the lithium-containing raw material may be added such that the molar ratio (Li:Fe) of lithium (Li) contained in the lithium-containing raw material and iron (Fe) contained in the pulverized iron phosphate is 1.0 to 1.1:1, specifically 1.0 to 1.05:1. When the M-containing raw material is further mixed, the lithium-containing raw material may be added such that the molar ratio (Li:Fe+M) of the sum of the molar numbers of lithium (Li) contained in the lithium-containing raw material and iron (Fe) contained in the pulverized iron phosphate and M contained in the M-containing raw material is 1.0 to 1.1:1, specifically 1.0 to 1.05:1.

[0084]

[0085] According to one embodiment of the present invention, the pulverized iron phosphate has an average particle diameter (D 50 ) may be 1.0㎛ or more and 2.0㎛ or less. Specifically, the pulverized iron phosphate has an average particle diameter (D 50 ) may be 1.0㎛ or more, 1.10㎛ or more, 1.20㎛ or more, 1.30㎛ or more, 1.40㎛ or more, 1.50㎛ or more, 1.60㎛ or more, 1.70㎛ or more, 1.80㎛ or more, or 1.85㎛ or more, and may be 1.90㎛ or less, 1.95㎛ or less, or 2.0㎛ or less. The average particle diameter (D of the pulverized iron phosphate 50 ) is within the above range, the reactivity with lithium is high due to the small particle size, and as a result, the electrochemical properties of the manufactured positive electrode active material can be excellent.

[0086] According to one embodiment of the present invention, the pulverized iron phosphate may have a span of 0.5 or more and 1.5 or less according to Equation 1 described herein. Specifically, the span may be 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, or 1.0 or more, and 1.1 or less, 1.2 or less, 1.3 or less, 1.4 or less, or 1.5 or less. When the span is within the above range, the particle distribution may be uniform, and thus the electrochemical properties of the resulting positive electrode active material may be excellent.

[0087]

[0088] The above-mentioned pulverized carbon-containing coating raw material may be mixed in an amount of 8 parts by weight or more and 13 parts by weight or less, based on 100 parts by weight of the total weight of the lithium-containing raw material and the pulverized iron phosphate. When the mixing amount of the above-mentioned pulverized carbon-containing coating raw material is within the above range, a coating layer including carbon is appropriately formed on the surface of the resulting positive electrode active material, so that the energy density of the positive electrode active material is maintained while the conductivity can be improved.

[0089]

[0090] According to one embodiment of the present invention, the pulverized carbon-containing coating raw material has a bulk density of 500 kg / m 3 More than 700 kg / m 3 It may be as follows. Specifically, the apparent density of the above-mentioned pulverized carbon-containing coating raw material is 500 kg / m 3 Above, 510kg / m 3 Above, 520kg / m 3 Above, 530kg / m 3 Above, 540kg / m 3 or more than 550 kg / m 3 It can be more than 600kg / m 3 Below, 610kg / m 3 Below 620kg / m 3 Below, 630kg / m3 Below 640kg / m 3 Below 650kg / m 3 Below 660kg / m 3 Below 670kg / m 3 Below 680kg / m 3 Below 690kg / m 3 or less, or 700 kg / m 3 It may be as follows. When the apparent density of the pulverized carbon-containing coating raw material is within the above range, the surface area increases, and the contact surface with iron phosphate and lithium increases, enabling uniform coating, so there is an advantage of increasing the conductivity of the manufactured positive electrode active material. The apparent density is measured according to the ISO 60 method, and is evaluated by, for example, dropping the powder of the pulverized carbon-containing coating raw material into a 3.16 cc measuring container and measuring the weight.

[0091]

[0092] According to one embodiment of the present invention, the distilled water is mixed in an amount of 20 parts by weight or less based on 100 parts by weight of the total weight of the lithium-containing raw material, the pulverized iron phosphate, and the pulverized carbon-containing coating raw material. Specifically, the distilled water may be mixed in an amount of 5 parts by weight or more, or 10 parts by weight or more, and 20 parts by weight or less based on 100 parts by weight of the total weight of the lithium-containing raw material, the pulverized iron phosphate, and the pulverized carbon-containing coating raw material. When the mixing amount is within the above range, the carbon-containing coating layer is uniformly formed, thereby improving the powder resistance. In particular, when the mixing amount of the distilled water is 5 parts by weight or more and 15 parts by weight or less, the carbon-containing coating raw material is dissolved in the distilled water, but is not mixed in a slurry state, so that a uniform coating layer can be formed with relatively low energy, and the yield of the positive electrode active material can be improved. On the other hand, when the mixing amount of the distilled water exceeds 20 parts by weight, the carbon-containing coating layer is unevenly formed, which causes a problem of high powder resistance.

[0093]

[0094] According to one embodiment of the present invention, the reaction mixture may have a moisture content of 5 wt% or more and 25 wt% or less. Specifically, the reaction mixture may have a moisture content of 5 wt% or more, 10 wt% or more, and 22 wt% or less, 23 wt% or less, 24 wt% or less, or 25 wt% or less. When the moisture content is within the above range, the carbon-containing coating raw material is dissolved in distilled water, but the pulverized iron phosphate is present in a powder state, so that the reaction mixture is not present in a slurry state, so that a uniform coating layer can be formed with relatively low energy, and the yield of the positive electrode active material can be improved.

[0095]

[0096] According to one embodiment of the present invention, when preparing the reaction mixture, an M-containing raw material (M is at least one selected from the group consisting of V, Ti, Mn, Zn, Mo, Mg, and N) may be further mixed. Specifically, the M-containing raw material may be, but is not limited to, V2O5, TiO2, MnO, ZnO, MoO, MgO, NH4OH, or a combination thereof. The M-containing raw material may be mixed in an amount such that the composition of the resulting lithium iron phosphate compound has a composition represented by the chemical formula 1 described herein.

[0097] When the above reaction mixture includes an M-containing raw material (at least one selected from the group consisting of V, Ti, Mn, Zn, Mo, Mg, and N), M is doped into the resulting positive electrode active material, so that the charge / discharge capacity and rate characteristics can be further improved.

[0098]

[0099] According to one embodiment of the present invention, when preparing the reaction mixture, a silane-based compound may be further mixed. Specifically, the silane-based compound may be at least one selected from the group consisting of methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, tetramethoxysilane, tetraethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethylmethoxysilane, dimethylethoxysilane, diphenylmethoxysilane, diphenyldiethoxysilane, diphenyldimethoxysilane, or a combination thereof. When pelletizing the reaction mixture, the silane-based compound can increase the strength of the pellet, thereby further densifying the raw materials, and can improve the reactivity between the raw materials by increasing the contact area between the particles, and can enhance the particle strength.

[0100]

[0101] According to one embodiment of the present invention, the silane compound may be mixed in an amount of 0.05 wt% or more and 0.2 wt% or less based on the total weight of the reaction mixture. Specifically, the silane compound may be mixed in an amount of 0.05 wt% or more, 0.06 wt% or more, 0.07 wt% or more, 0.08 wt% or more, 0.09 wt% or more, or 0.1 wt% or more, and 0.15 wt% or less, or 0.2 wt% or less based on the total weight of the reaction mixture. When the mixing amount of the silane compound is within the above range, the strength of the pellets can be increased to further densify the raw materials without interfering with the formation of the coating layer, and the reactivity between the raw materials can be improved by increasing the contact area between the particles, and the particle strength can be improved.

[0102]

[0103] The mixing in step (B) may be performed by mechanical mixing. The mechanical mixing involves mixing powders using a rotating device, such as a rotary mill or hammer mill. The mixing may be performed at 500 to 2,000 rpm for 0.5 to 2 hours. In this case, the raw materials may be mixed more uniformly.

[0104]

[0105] (C) Step

[0106] The method for manufacturing a cathode active material according to the present invention includes, after step (B), step (C) of compressing the reaction mixture into pellets. For example, the reaction mixture may be compressed using a press to form pellets. In this case, the raw materials included in the reaction mixture are densified, increasing the contact area between particles, thereby enhancing the reactivity between the raw materials.

[0107] On the other hand, when firing without processing into pellet form, there is a problem of poor reactivity between raw materials because contact between raw materials does not occur well.

[0108]

[0109] According to one embodiment of the present invention, the compression in step (C) is 0.10 ton / cm 2 More than 1.0 ton / cm 2 It may be performed under the following pressure. Specifically, the compression is 0.10 ton / cm 2 Above, 0.15 tons / cm 2 Above, 0.20 tons / cm 2 or 0.25 tons / cm 2 Above, and 0.30 tons / cm 2 Below, 0.35 tons / cm 2 Below, 0.40 tons / cm 2 Below, 0.45 tons / cm 2 Below, 0.50 tons / cm 2Below, 0.80 tons / cm 2 Below, 0.85 tons / cm 2 Below, 0.95 tons / cm 2 or less, or 1.0 ton / cm 2 It may be performed under the pressure below. When the compression pressure is within the above range, the pellet shape is well maintained even after the pellet is removed from the mold, so that a more uniform result can be obtained.

[0110]

[0111] (D) Step

[0112] The method for manufacturing a positive electrode active material according to the present invention includes, after step (C), step (D) of manufacturing a sintered product by sintering the pellet-shaped reaction mixture.

[0113]

[0114] According to the present invention, the firing may be performed under an inert atmosphere to prevent side reactions with oxygen and moisture. For example, the firing may be performed under an argon atmosphere, a nitrogen atmosphere, or a helium atmosphere.

[0115]

[0116] According to one embodiment of the present invention, the firing is performed at 600°C. It may be performed at a temperature of 800°C or less. Specifically, the firing may be performed at a temperature of 600°C or more, 610°C or more, 620°C or more, 630°C or more, 640°C or more, or 650°C or more, and 750°C or less, 760°C or less, 770°C or less, 780°C or less, 790°C or less, or 800°C or less. When the firing temperature is within the above range, a primary particle size of an appropriate size can be obtained, thereby having the advantage of improving electrochemical properties.

[0117]

[0118] According to one embodiment of the present invention, the temperature maintenance time of the firing step may be 5 hours or more and 20 hours or less. When the firing time is within the above range, the powder resistance and rate characteristics are improved due to the uniform carbon coating.

[0119]

[0120] According to one embodiment of the present invention, after step (D), step (E) of crushing the sintered product may be further included.

[0121] The step of crushing the above-mentioned product is to increase the reactivity with lithium, and the average particle diameter (D) of the resulting lithium iron phosphate cathode active material is 50 ) can be performed so that it is 0.5㎛ to 3.0㎛.

[0122] According to one embodiment of the present invention, the pulverization in step (E) may be performed by air current pulverization. The air current pulverization may be performed by an air jet mill in a manner in which powder is pulverized by impact while forming an air current by air. The pulverization of the sintered product may be performed for 0.1 to 2 hours under an ejection air pressure of 1 to 10 bar and a grinding air pressure of 0.5 to 2.0 bar. Specifically, the sintered product may be fed at a rate of 5 g / min using a single screw feeder, and pulverization may be performed under the above conditions.

[0123]

[0124] According to the present invention, the resulting lithium iron phosphate-based positive electrode active material may be the lithium iron phosphate-based positive electrode active material according to the present invention described above. That is, the resulting lithium iron phosphate-based positive electrode active material may be a lithium iron phosphate-based positive electrode active material comprising a lithium iron phosphate-based compound; and a coating layer including carbon formed on the lithium iron phosphate-based compound; and having a powder resistance of 50ΩХcm or more and 200ΩХcm or less.

[0125]

[0126] Lithium iron phosphate cathode active material

[0127] Hereinafter, a lithium iron phosphate cathode active material manufactured using a manufacturing method according to the present invention will be described.

[0128] A lithium iron phosphate cathode active material manufactured by a manufacturing method according to the present invention includes a lithium iron phosphate compound; and a coating layer including carbon formed on the lithium iron phosphate compound; and has a powder resistance of 50ΩХcm or more and 200ΩХcm or less.

[0129] The above powder resistance is the volume resistance measured using a Hioki Rm3545 resistance measuring instrument while placing 5 g of powder into a 31 mm diameter circular 4-Point Probe (Gold Pin) mold and applying a force of 2000 kgf.

[0130] When the powder resistance of the positive electrode active material including a lithium iron phosphate compound and a coating layer including carbon formed on the lithium iron phosphate compound is 50ΩХcm or more and 200ΩХcm or less, the coating layer including carbon is uniformly formed on the lithium iron phosphate compound, thereby improving particle strength, and as a result of improving the electrical conductivity and ionic conductivity of the positive electrode active material, there is an effect of improving the capacity characteristics and resistance characteristics of a battery including the positive electrode active material.

[0131] Specifically, the powder resistance may be 50ΩХcm or more, 55ΩХcm or more, or 60ΩХcm or more, and 170ΩХcm or less, 180ΩХcm or less, 190ΩХcm or less, or 200ΩХcm or less. In this case, the lithium iron phosphate-based positive electrode active material has low resistance and excellent conductivity, thereby improving electrochemical characteristics. On the other hand, when the powder resistance of the lithium iron phosphate-based positive electrode active material exceeds 200ΩХcm, the positive electrode active material has high resistance, and the diffusion of lithium ions and the movement of electrons are reduced, so that there is a problem that the capacity characteristics and resistance characteristics of the battery including the positive electrode active material are poor, and when the powder resistance of the lithium iron phosphate-based positive electrode active material is less than 50ΩХcm, the coating layer is not formed uniformly, so that the particle strength of the positive electrode active material is poor, and there is a problem that the capacity characteristics are poor.

[0132]

[0133] The lithium iron phosphate-based cathode active material according to the present invention is manufactured by the method for manufacturing the lithium iron phosphate-based cathode active material according to the present invention described above, and has the characteristics of including a uniform carbon coating layer, low powder resistance, and improved particle strength. Accordingly, the performance of electrodes and batteries including the lithium iron phosphate-based cathode active material according to the present invention can be improved.

[0134] According to one embodiment of the present invention, the lithium iron phosphate compound may have a composition represented by the following chemical formula 1.

[0135] [Chemical Formula 1]

[0136] LiFe 1-x M x PO4

[0137] In the above chemical formula 1,

[0138] M is at least one selected from the group consisting of V, Ti, Mn, Zn, Mo, Mg, and N, and 0≤x<1.

[0139] The above lithium iron phosphate compound may be doped with M. Specifically, M may be at least one selected from the group consisting of V, Ti, Mn, Zn, Mo, Mg, and N. Although M is not essential, when it is included in an appropriate amount, the lattice structure and distance of the iron phosphate compound are changed, thereby increasing the diffusion of lithium ions, and consequently, the electrochemical characteristics of a battery including a positive electrode active material may be improved.

[0140] Meanwhile, the above x may be 0 or greater, and may be 0.1 or less, 0.2 or less, 0.3 or less, 0.4 or less, 0.5 or less, 0.6 or less, 0.7 or less, 0.8 or less, 0.9 or less, or less than 1. When x satisfies the above range, structural stability may be improved.

[0141]

[0142] According to one embodiment of the present invention, the lithium iron phosphate cathode active material has an average particle diameter (D 50 ) may be 0.5㎛ or more and 3.0㎛ or less. Specifically, the average particle diameter (D of the lithium iron phosphate-based positive electrode active material 50 ) may be 0.5㎛ or more, 0.6㎛ or more, 0.7㎛ or more, 0.8㎛ or more, 0.9㎛ or more, 1.0㎛ or more, 1.1㎛ or more, 1.2㎛ or more, 1.3㎛ or more, 1.4㎛ or more, or 1.5㎛ or more, and may be 2.0㎛ or less, 2.1㎛ or less, 2.2㎛ or less, 2.3㎛ or less, 2.4㎛ or less, 2.5㎛ or less, 2.6㎛ or less, 2.7㎛ or less, 2.8㎛ or less, 2.9㎛ or less, or 3.0㎛ or less. The average particle diameter (D of the lithium iron phosphate-based positive electrode active material 50 ) within the above range, there is an advantage of excellent electrochemical properties due to high reactivity with lithium due to the small particle size.

[0143]

[0144] According to one embodiment of the present invention, the coating layer may be uniformly coated on the surface of the lithium iron phosphate compound. The coating layer can improve electronic conductivity and ionic conductivity when electrons move during charging and discharging of a battery including a positive electrode active material. On the other hand, if the coating layer is not present, the positive electrode active material has high resistance, which causes problems with lithium ion diffusion and electron movement, and the particle strength is also poor.

[0145]

[0146] According to one embodiment of the present invention, the content of carbon included in the coating layer may be 1 wt% or more and 3 wt% or less based on the total weight of the lithium iron phosphate-based positive electrode active material in order to further improve electronic conductivity and ionic conductivity. The coating layer may be composed solely of carbon, and in this case, the content of the coating layer may be 1 wt% or more and 3 wt% or less based on the total weight of the lithium iron phosphate-based positive electrode active material.

[0147]

[0148] According to one embodiment of the present invention, the lithium iron phosphate-based compound may exist in the form of primary particles rather than in the form of secondary particles formed by agglomeration of primary particles. That is, the primary particles may not agglomerate but may exist separately. Accordingly, the lithium iron phosphate-based cathode active material according to the present invention may have the coating layer formed on the lithium iron phosphate-based compound in the form of primary particles. In this case, the coating layer may be in the form of a thin film.

[0149]

[0150] anode

[0151] Next, the anode according to the present invention will be described.

[0152] The positive electrode according to the present invention comprises a positive electrode active material layer comprising a positive electrode active material manufactured using the manufacturing method according to the present invention. Specifically, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and comprising the positive electrode active material. Since the positive electrode active material has been described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0153]

[0154] 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 µm to 500 µm, 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, the positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0155]

[0156] The above-mentioned positive electrode active material layer may include a conductive material and a binder together with the positive electrode active material. At this time, the positive electrode active material may be included in an amount of 80 wt% to 99 wt%, more specifically 85 wt% to 98.5 wt%, based on the total weight of the positive electrode active material layer, and excellent capacity characteristics may be exhibited within this range.

[0157]

[0158] 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 whiskers 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 type alone or a mixture of two or more types of these may be used. The conductive material may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0159]

[0160] 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 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0161]

[0162] The 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 can be manufactured by coating a composition for forming a positive electrode active material layer, which is manufactured by dissolving or dispersing the positive electrode active material and optionally a binder and a conductive material in a solvent, on a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive material are as described above. Alternatively, the positive electrode can be manufactured by casting the composition for forming a positive electrode active material layer on a separate support, and then laminating the film obtained by peeling it from the support on a positive electrode current collector.

[0163]

[0164] 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.

[0165]

[0166] lithium secondary battery

[0167] Next, a lithium secondary battery including a positive electrode including a lithium iron phosphate-based positive electrode active material manufactured by a manufacturing method according to the present invention is described.

[0168]

[0169] The present invention can manufacture an electrochemical device including the above-described positive electrode. The electrochemical device may be, specifically, a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

[0170]

[0171] The lithium secondary battery specifically includes 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. Since the positive electrode is the same as described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0172]

[0173] In addition, the lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0174]

[0175] In the above lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0176] 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.

[0177]

[0178] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0179]

[0180] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β (0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above 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.

[0181] The above negative electrode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0182]

[0183] 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 wt% 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, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0184]

[0185] 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, specifically, 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 whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0186]

[0187] The negative electrode active material layer may be manufactured by applying and drying a composition for forming a negative electrode active material layer prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the composition for forming a negative electrode active material layer on a separate support, and then laminating the film obtained by peeling it off from the support on a negative electrode current collector.

[0188]

[0189] 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 special 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, can 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. can also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength can be used, and can optionally be used in a single-layer or multi-layer structure.

[0190]

[0191] In addition, examples of the electrolyte used in the present invention 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.

[0192] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0193] As the organic solvent, any solvent that can serve as a medium through which ions involved in the electrochemical reaction of the battery can move may be used without particular limitation. Specifically, the organic solvent includes 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), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); Alcohol solvents such as ethyl alcohol, isopropyl alcohol, etc.; nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and 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, carbonate solvents are preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of a battery and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) 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.

[0194]

[0195] 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. The concentration of the lithium salt is preferably used within the range of 0.1 to 5.0 M, specifically, 0.1 to 3.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0196]

[0197] 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 additive may be included in an amount of 0.1 to 10 wt%, specifically, 0.1 to 5 wt%, based on the total weight of the electrolyte.

[0198]

[0199] As described above, a lithium secondary battery including a cathode active material according to the present invention exhibits excellent life characteristics and capacity 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).

[0200] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0201] The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0202] There is no particular limitation on the external shape of the lithium secondary battery of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0203] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

[0204]

[0205] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0206]

[0207] Examples and Comparative Examples

[0208] Example 1

[0209] FePO4 (G01X, Yacheng, China) is fed at a rate of 5 g / min using a single screw feeder and crushed for 1 hour under 5 bar of ejection air and 1.0 bar of grinding air using air jet mill equipment (Isac E&C, 4" size jet mill). The crushed FePO4 (average particle size (D) 50 ): 1.86㎛, span: 1.08) were prepared.

[0210] Sucrose (Deoksan Pharmaceutical, purity 99.6%) was ground in a mixer (Shinil Electronics, SFN-C656CS) at 2000 rpm for 1 hour, and the ground sucrose (apparent density: 590 kg / m 3 ) was prepared.

[0211] Li2CO3 (Tianqi) and the above-mentioned pulverized FePO4 were added to a mixer (Shinil Electronics, SFN-C656CS) so that the molar ratio of Li:Fe was 1.05:1, and the above-mentioned pulverized sucrose was added in an amount of 12 parts by weight based on 100 parts by weight of the total weight of the Li2CO3 and the above-mentioned pulverized FePO4, and the added raw materials were mixed at 2000 rpm for about 1 minute. Thereafter, distilled water was added in an amount of 10 parts by weight based on 100 parts by weight of the total weight of the lithium-containing raw material, the pulverized FePO4, and the pulverized sucrose, and mixed at 2000 rpm for about 1 minute to prepare a reaction mixture.

[0212] 3g of the above reaction mixture was put into a pellet die (Carver, Carver-3902) with a diameter of 31mm, and pressed with a force of 4 tons (pressure: 0.265 tons / cm 2 ) was processed into pellet form by applying vacuum.

[0213] After this, the pellet-shaped reaction mixture was fired at 700°C for 10 hours under a nitrogen atmosphere to produce a fired product, and the fired product was fed at a rate of 5 g / min using a single screw feeder and ground for 1 hour under ejection air 5 bar and grinding air 1.0 bar using air jet mill equipment (Isac E&C, 4" size jet mill), thereby producing a lithium iron phosphate-based positive electrode active material including a coating layer containing carbon.

[0214]

[0215] Example 2

[0216] Li2CO3 (Tianqi) and the pulverized FePO4 were added to a mixer (Shinil Electronics, SFN-C656CS) so that the molar ratio of Li:Fe was 1.05:1, and the pulverized sucrose was added in an amount of 12 parts by weight based on 100 parts by weight of the total weight of the Li2CO3 and the pulverized FePO4, and then a silane compound (A-187, MOMENTIVE) was mixed in an amount of 0.1% by weight based on the total weight of the reaction mixture, and the added raw materials were mixed at 2000 rpm for about 1 minute. Thereafter, distilled water was added in an amount of 10 parts by weight based on 100 parts by weight of the total weight of the lithium-containing raw material, the pulverized FePO4, and the pulverized sucrose, and the reaction mixture was mixed at 2000 rpm for about 1 minute, except that the reaction mixture was prepared in the same manner as in Example 1, thereby producing a lithium iron phosphate-based positive electrode active material including a coating layer containing carbon.

[0217]

[0218] Example 3

[0219] Li2CO3 (Tianqi) and pulverized FePO4 were added to a mixer (Shinil Electronics, SFN-C656CS) at a molar ratio of Li:Fe of 1.05:1, and the pulverized sucrose was added in an amount of 12 parts by weight based on 100 parts by weight of the total weight of the Li2CO3 and the pulverized FePO4, and the added raw materials were mixed at 2000 rpm for about 1 minute. Thereafter, distilled water was added in an amount of 20 parts by weight instead of 10 parts by weight based on 100 parts by weight of the total weight of the lithium-containing raw material, the pulverized FePO4, and the pulverized sucrose, and the reaction mixture was mixed at 2000 rpm for about 1 minute, except that the same procedure as in Example 1 was performed to prepare a lithium iron phosphate-based positive electrode active material including a coating layer containing carbon.

[0220]

[0221] Comparative Example 1

[0222] Li2CO3 (Tianqi) and the pulverized FePO4 manufactured in Example 1 were added to a mixer (Shinil Electronics, SFN-C656CS) so that the molar ratio of Li:Fe was 1.05:1, and the pulverized sucrose manufactured in Example 1 was added in an amount of 12 parts by weight based on 100 parts by weight of the total weight of the Li2CO3 and the pulverized FePO4, and the added raw materials were mixed at 2000 rpm for about 1 minute. Thereafter, distilled water was added in an amount of 30 parts by weight based on 100 parts by weight of the total weight of the lithium-containing raw material, the pulverized FePO4, and the pulverized sucrose, and the reaction mixture was mixed at 2000 rpm for about 1 minute, except that the same procedure as in Example 1 was performed to manufacture a lithium iron phosphate-based positive electrode active material including a coating layer containing carbon.

[0223]

[0224] Comparative Example 2

[0225] Li2CO3 (Tianqi) and the pulverized FePO4 manufactured in Example 1 were added to a mixer (Shinil Electronics, SFN-C656CS) so that the molar ratio of Li:Fe was 1.05:1, and the pulverized sucrose manufactured in Example 1 was added in an amount of 12 parts by weight based on 100 parts by weight of the total weight of the Li2CO3 and the pulverized FePO4, and the added raw materials were mixed at 2000 rpm for about 1 minute to prepare a reaction mixture. In this manner, a lithium iron phosphate-based positive electrode active material including a coating layer including carbon was manufactured.

[0226]

[0227] Comparative Example 3

[0228] Li2CO3 (Tianqi) and FePO4 (Yacheng, China, G01X) (average particle size (D)) were added to a mixer (Shinil Electronics, SFN-C656CS). 50 ): 2.34㎛, span: 1.39) was added so that the molar ratio of Li:Fe was 1.05:1, and sucrose (apparent density: 760 kg / m 3 ) was added in an amount of 12 parts by weight based on 100 parts by weight of the total weight of the Li2CO3 and the FePO4, and the added raw materials were mixed at 2000 rpm for about 1 minute to prepare a reaction mixture.

[0229] 3g of the above reaction mixture was put into a pellet die (Carver, Carver-3902) with a diameter of 31mm, and pressed with a force of 4 tons (pressure: 0.265 tons / cm 2 ) was processed into pellet form by applying vacuum.

[0230] After this, the pellet-shaped reaction mixture was fired at 700°C for 10 hours under a nitrogen atmosphere to produce a fired product, and the fired product was fed at a rate of 5 g / min using a single screw feeder and ground for 1 hour under ejection air 5 bar and grinding air 1.0 bar using air jet mill equipment (Isac E&C, 4" size jet mill), thereby producing a lithium iron phosphate-based positive electrode active material including a coating layer containing carbon.

[0231]

[0232] Comparative Example 4

[0233] The reaction mixture of Comparative Example 3 was fired at 700°C for 10 hours under a nitrogen atmosphere to produce a fired product, and the fired product was fed at a rate of 5 g / min using a single screw feeder and ground for 1 hour under ejection air 5 bar and grinding air 1.0 bar using an air jet mill device (Isac E&C, 4" size jet mill), thereby producing a lithium iron phosphate-based positive electrode active material including a coating layer containing carbon.

[0234]

[0235] Comparative Example 5

[0236] Li2CO3 (Tianqi) and FePO4 were added to a mixer (Shinil Electronics, SFN-C656CS) so that the molar ratio of Li:Fe was 1.05:1, and 12 parts by weight of the sucrose was added based on 100 parts by weight of the total weight of the Li2CO3 and the FePO4. The added raw materials were mixed at 2000 rpm for about 1 minute, and then added at a rate of 5 g / min using a single screw feeder and ground for 1 hour using an air jet mill (Isac E&C, 4" size jet mill) under an ejection air of 5 bar and a grinding air of 1.0 bar to prepare a ground reaction mixture.

[0237] 3g of the above reaction mixture was put into a pellet die (Carver, Carver-3902) with a diameter of 31mm, and pressed with a force of 4 tons (pressure: 0.265 tons / cm 2 ) was processed into pellet form by applying vacuum.

[0238] After this, the pellet-shaped reaction mixture was fired at 700°C for 10 hours under a nitrogen atmosphere to produce a fired product, and the fired product was fed at a rate of 5 g / min using a single screw feeder and ground for 1 hour under ejection air 5 bar and grinding air 1.0 bar using air jet mill equipment (Isac E&C, 4" size jet mill), thereby producing a lithium iron phosphate-based positive electrode active material including a coating layer containing carbon.

[0239]

[0240] Comparative Example 6

[0241] Li2CO3 (Tianqi) and FePO4 were added to the Bizmill equipment (Nanointech, XYREX UBM-1L-230) so that the molar ratio of Li:Fe was 1.05:1, and sucrose (apparent density: 760 kg / m 3 ) was added in an amount of 30 parts by weight based on 100 parts by weight of the total weight of the Li2CO3 and FePO4, and then distilled water was added in an amount of 250 parts by weight based on 100 parts by weight of the total weight of the lithium-containing raw material, FePO4, and sucrose. Thereafter, a reaction mixture was prepared by mixing at 1000 rpm for about 60 minutes.

[0242] The above reaction mixture and water were introduced into a bead mill (bead size: 0.3 mm, filling amount: 2 kg) at a total flow rate of 1 L / min, and ground for approximately 50 minutes at 3000 ppm to produce a ground reaction mixture. Then, the ground reaction mixture was spray-dried (inlet temperature 200°C, outlet temperature 90°C) using a spray drying device (Dongjin Kiyeon, DJE-005R) to produce a dried reaction mixture.

[0243] After this, the dried reaction mixture was fired at 700°C for 10 hours under a nitrogen atmosphere to produce a fired product, and the fired product was fed at a rate of 5 g / min using a single screw feeder and ground for 1 hour under ejection air 5 bar and grinding air 1.0 bar using an air jet mill device (Isac E&C, 4" size jet mill), thereby producing a lithium iron phosphate cathode active material including a coating layer containing carbon.

[0244]

[0245] Comparative Example 7

[0246] FePO4 (G01X, Yacheng, China) is fed at a rate of 5 g / min using a single screw feeder and crushed for 1 hour under 5 bar of ejection air and 1.0 bar of grinding air using air jet mill equipment (Isac E&C, 4" size jet mill). The crushed FePO4 (average particle size (D) 50 ): 1.86㎛, span: 1.08) were prepared.

[0247] Sucrose (Deoksan Pharmaceutical, purity 99.6%) was ground in a mixer (Shinil Electronics, SFN-C656CS) at 2000 rpm for 1 hour to prepare ground sucrose (apparent density: 590 kg / m3).

[0248] Li2CO3 (Tianqi) and the above-mentioned pulverized FePO4 were added to a mixer (Shinil Electronics, SFN-C656CS) so that the molar ratio of Li:Fe was 1.05:1, and the above-mentioned pulverized sucrose was added in an amount of 12 parts by weight based on 100 parts by weight of the total weight of the Li2CO3 and the above-mentioned pulverized FePO4, and the added raw materials were mixed at 2000 rpm for about 1 minute. Thereafter, distilled water was added in an amount of 10 parts by weight based on 100 parts by weight of the total weight of the lithium-containing raw material, the pulverized FePO4, and the pulverized sucrose, and mixed at 2000 rpm for about 1 minute to prepare a reaction mixture.

[0249] The reaction mixture was fired at 700°C for 10 hours under a nitrogen atmosphere to produce a fired product, and the fired product was fed at a rate of 5 g / min using a single screw feeder and ground for 1 hour under ejection air 5 bar and grinding air 1.0 bar using air jet mill equipment (Isac E&C, 4" size jet mill), thereby producing a lithium iron phosphate-based positive electrode active material including a coating layer containing carbon.

[0250]

[0251] Comparative Example 8

[0252] Li2CO3 (Tianqi) and FePO4 were added to a mixer (Shinil Electronics, SFN-C656CS) at a molar ratio of Li:Fe of 1.05:1, and distilled water was added to prepare a mixed solution with a solid content of 40 wt%. Sucrose (apparent density: 760 kg / m) was added to the mixed solution. 3 ) was added in an amount of 12 parts by weight based on 100 parts by weight of the total weight of the Li2CO3 and the FePO4 to prepare a reaction solution. The reaction solution was wet-milled for 50 minutes using a bead mill (capacity 5 L, circumferential speed 1 m / s, bead size 0.3 mm, bead filling ratio 80% by volume) to obtain a slurry (average particle size: 250 nm).

[0253] After the above slurry was dried through spray drying (inlet temperature: 230°C, outlet temperature: 95°C), the dried powder was fired at 700°C for 10 hours under a nitrogen atmosphere to produce a fired product, and the fired product was fed at a rate of 5 g / min using a single screw feeder and ground for 1 hour under ejection air 5 bar and grinding air 1.0 bar using air jet mill equipment (Isac E&C, 4" size jet mill), thereby producing a lithium iron phosphate-based positive electrode active material including a coating layer containing carbon.

[0254]

[0255] Whether FePO4 is crushed before mixing Whether sucrose is crushed before mixing Whether distilled water is mixed Whether pellets are processed Example 1○○○○ Example 2○○○○ Example 3○○○○ Comparative Example 1○○○(Excess)○Comparative Example 2○○X○Comparative Example 3XXXX○Comparative Example 4XXXXX Comparative Example 5X(Crushed after mixing)X(Crushed after mixing)X○Comparative Example 6XX○(Excess)X Comparative Example 7○○○X Comparative Example 8XXX

[0256] Experimental example

[0257] Experimental Example 1: Powder Resistance Evaluation

[0258] 5 g of each of the lithium iron phosphate-based positive electrode active materials manufactured in the above examples and comparative examples was placed in a circular 4-Point Probe (Gold Pin) mold with a diameter of 31 mm, and a force of 2000 kgf was applied. The volume resistivity was measured using a Hioki Rm3545 resistance measuring instrument, and the result was converted into powder resistivity (ΩХcm) and shown in Table 2 below.

[0259]

[0260] Experimental Example 2: Evaluation of particle size distribution

[0261] 20 mg of each lithium iron phosphate cathode active material manufactured in the above examples and comparative examples was dispersed in 5 ml of Triton X-100 (Sigma Aldrich), and then introduced into a laser diffraction particle size measuring device (Malvern Panalytical, Mastersizer 3000) to measure the average particle diameter (D) of the cathode active material. 50 ) were measured, and the results are shown in Table 2 below.

[0262] Sieving resistance (ΩХcm)Average particle size (D 50 )(㎛)Example 1651.7Example 2681.7Example 31651.7Comparative Example 13501.7Comparative Example 23701.9Comparative Example 331506.5Comparative Example 441505.5Comparative Example 54002.3Comparative Example 651.7Comparative Example 74102.3Comparative Example 8901.7

[0263] Through Table 2, it was confirmed that the lithium iron phosphate-based positive electrode active materials manufactured in Examples 1 to 3 had a powder resistance of 50ΩХcm or more and 200ΩХcm or less. On the other hand, it was confirmed that the lithium iron phosphate-based positive electrode active materials manufactured in Comparative Examples 1 to 5 and 7 had a powder resistance of more than 200ΩХcm, and the lithium iron phosphate-based positive electrode active material manufactured in Comparative Example 6 had a powder resistance of less than 50ΩХcm. This is because, when manufacturing the lithium iron phosphate-based positive electrode active materials of Examples 1 to 3, the iron phosphate (FePO4) and carbon-containing coating raw materials were first dry-pulverized, respectively, and then mixed with the lithium-containing raw material and a small amount of distilled water to prepare a reaction mixture, which was compressed and processed into a pellet form and then calcined, thereby preventing the sticking of the raw materials, significantly improving the reactivity of the raw materials, and uniformly forming a coating layer including carbon.

[0264]

[0265] Experimental Example 3: SEM Image Analysis

[0266] Using SEM (FEI, QUANTA 600), SEM images of each lithium iron phosphate-based positive electrode active material manufactured in the examples and comparative examples were taken, and the SEM images of each lithium iron phosphate-based positive electrode active material manufactured in examples 1 and 2, comparative example 1, and comparative example 4 are shown in FIGS. 1 to 4.

[0267]

[0268] Figure 1 is a SEM image (10K magnification) of the lithium iron phosphate-based positive electrode active material manufactured in Example 1.

[0269] Figure 2 is a SEM image (10K magnification) of the lithium iron phosphate-based positive electrode active material manufactured in Example 2.

[0270] Figure 3 is a SEM image (50K magnification) of the lithium iron phosphate-based positive electrode active material manufactured in Comparative Example 1.

[0271] Figure 4 is a SEM image (50K magnification) of the lithium iron phosphate-based positive electrode active material manufactured in Comparative Example 4.

[0272]

[0273] Through Figures 1 to 4, it was confirmed that the lithium iron phosphate-based positive electrode active materials manufactured in Examples 1 and 2 had a uniform particle size compared to the lithium iron phosphate-based positive electrode active materials manufactured in Comparative Examples 1 and 4.

[0274]

[0275] Experimental Example 4: STEM-EDS Analysis

[0276] Using STEM-EDS (ThermoFisher, Spectra 300), STEM-EDS mapping images of the lithium iron phosphate-based positive electrode active materials manufactured in the examples and comparative examples were obtained, and the STEM-EDS mapping images of the lithium iron phosphate-based positive electrode active materials manufactured in Example 1 and Comparative Example 1 are shown in FIGS. 5 to 9.

[0277] Specifically, measurements were made at an acceleration voltage of 200 kV, TEM Mode, and Beam Current of 1 to 1.5 nA.

[0278]

[0279] Figure 5 is a STEM-EDS mapping image of the lithium iron phosphate cathode active material manufactured in Example 1.

[0280] Figure 6 is a STEM-EDS mapping image of C of the lithium iron phosphate cathode active material manufactured in Example 1.

[0281] Figure 7 is a STEM-EDS mapping image of Fe of the lithium iron phosphate cathode active material manufactured in Example 1.

[0282] Figure 8 is a STEM-EDS mapping image of the lithium iron phosphate cathode active material manufactured in Comparative Example 1.

[0283] Figure 9 is a STEM-EDS mapping image of C and Fe of the lithium iron phosphate cathode active material manufactured in Comparative Example 1.

[0284]

[0285] Through Figures 5 to 9, it can be confirmed that a carbon coating layer is uniformly formed on the surface of the lithium iron phosphate-based positive electrode active material of Example 1.

[0286] In comparison, it was confirmed that a carbon coating layer was formed only at the boundary of the primary particles on the surface of the lithium iron phosphate-based positive electrode active material of Comparative Example 1.

[0287]

[0288] Experimental Example 5: Moisture content evaluation

[0289] In order to measure the moisture content present in the reaction mixtures prepared in the above examples and comparative examples, a heating type moisture meter (MA100, Sartorious) was used to measure the moisture content of each reaction mixture or reaction solution prepared in the examples and comparative examples, and the moisture content (moisture content (%)) of the reaction mixture or reaction solution is shown in Table 3 below.

[0290] Specifically, the reaction mixture (before drying) or reaction solution manufactured in the above examples and comparative examples was obtained, and about 5 g was placed in each sample dish in the device, and then the lid of the device was closed and the sample dish temperature was set to 110°C, thereby evaporating the moisture present in the reaction mixture or reaction solution and measuring the degree of mass reduction. At this time, when the amount of mass reduction in the sample is 0.1 wt% or less, it is considered as the point at which the mass no longer reduces, and this point is called a dried state.

[0291] The moisture content (χ), that is, the percentage difference between the mass (g) of the reaction mixture before drying and the mass (g) of the dried state (moisture content (%)) is shown in Table 3 below.

[0292]

[0293] Function rate (%) Example 111.1 Example 211.2 Example 321.5 Comparative Example 132.0 Comparative Example 21.2 Comparative Example 31.3 Comparative Example 41.3 Comparative Example 51.2 Comparative Example 640.1 Comparative Example 711.2 Comparative Example 840.2

[0294] Through Table 3, it was confirmed that the reaction mixtures prepared in Examples 1 to 3 had a moisture content of 5 wt% or more and 25 wt% or less. In contrast, it was confirmed that the reaction mixtures prepared in Comparative Examples 1, 6, and 8 had a moisture content of more than 25 wt%, and the reaction mixtures prepared in Comparative Examples 2 to 5 had a moisture content of less than 5 wt%.

[0295]

[0296] Experimental Example 6: Particle Strength Analysis

[0297] Using a nano indentation tester (TTX-NHT3, Anton Paar), the particle strength of each lithium iron phosphate-based positive electrode active material manufactured in the examples and comparative examples was derived, and the results are shown in Table 4 below.

[0298] Specifically, each of the lithium iron phosphate cathode active materials manufactured in the above examples and comparative examples was pelletized according to the ISO 14577 method, and then the manufactured pellet was placed on a glass plate, and force was applied using an indentor having a diameter of 45 μm, and the force applied by the indentor when the pellet was broken (pellet breaking force (N)) was measured, and the results are shown in Table 4 below.

[0299]

[0300] Breaking force of pellet (N) Example 120 Example 230 Example 310 Comparative Example 15 Comparative Example 25 Comparative Example 310 Comparative Example 40 Comparative Example 55 Comparative Example 60 Comparative Example 70 Comparative Example 80

[0301] Through Table 4, it was confirmed that the lithium iron phosphate-based positive electrode active materials manufactured in Examples 1 to 3 had a greater pellet breaking force, i.e., improved particle strength, compared to the lithium iron phosphate-based positive electrode active materials manufactured in Comparative Examples 1, 2, and 4 to 8.

[0302] Experimental Example 7: Battery Characteristics Evaluation

[0303] Each of the lithium iron phosphate-based positive electrode active materials manufactured in the above examples and comparative examples, carbon black as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder were mixed in a weight ratio of 96:2:2 in an N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. The above-mentioned positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to prepare a positive electrode.

[0304] An electrode assembly was manufactured using a lithium metal electrode as the negative electrode and a porous polyethylene separator interposed between the positive and negative electrodes. This was placed inside a battery case, and an electrolyte solution containing 1.0 M LiPF6 dissolved in an organic solvent containing ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a volume ratio of 3:4:3 was injected to manufacture a half-cell.

[0305] Using each half cell manufactured as described above, when charged to 3.65 V in CC (0.1 C)-CV (Cut-off current: 0.1 C) mode at 25 ℃ and then discharged to 2.5 V at 0.1 C, the initial charge / discharge capacity (mAh / g) and DCIR resistance (Ω) were measured and shown in Table 5 below.

[0306]

[0307] ClassificationCharge capacity (mAh / g)Discharge capacity (mAh / g)DCIR (Ω)Example 1156.5148.5105.1Example 2156.3148.4105.4Example 3155.2146.3110.7Comparative example 1152.3141.3118.4Comparative example 2152.5143.1119.0Comparative example 3116.2103.6218.5Comparative example 4108.594.3247.6Comparative example 5150.7142.6120.1Comparative example 6149.3145.5105.2Comparative example 7150.8142.8122.5Comparative example 8150.1146.1105.1

[0308] As shown in Table 5, in the case of batteries including the lithium iron phosphate-based positive electrode active materials manufactured in Examples 1 to 3, it was confirmed that not only was the initial charge / discharge capacity significantly superior to that of the batteries including the lithium iron phosphate-based positive electrode active materials manufactured in Comparative Examples 1 to 5 and 7, but also the resistance was significantly lower, and it was confirmed that the initial charge / discharge capacity was significantly superior to that of the lithium iron phosphate-based positive electrode active materials manufactured in Comparative Examples 6 and 8. This is because, as described above, the lithium iron phosphate-based positive electrode active materials manufactured in Examples 1 to 3 were manufactured by the method for manufacturing a lithium iron phosphate-based positive electrode active material according to the present invention, and thus included a uniform carbon coating layer and had low powder resistance.

Claims

1. (A) A step of dry grinding iron phosphate (FePO4) and carbon-containing coating raw materials, respectively; (B) a step of preparing a reaction mixture by mixing a lithium-containing raw material, pulverized iron phosphate, pulverized carbon-containing coating raw material, and distilled water; (C) a step of compressing the reaction mixture and processing it into a pellet form; and (D) a step of manufacturing a sintered product by sintering the reaction mixture in the form of pellets; A method for producing a lithium iron phosphate-based positive electrode active material, wherein the distilled water is mixed in an amount of 20 parts by weight or less based on 100 parts by weight of the total weight of the lithium-containing raw material, the pulverized iron phosphate, and the pulverized carbon-containing coating raw material.

2. In claim 1, A method for producing a lithium iron phosphate-based positive electrode active material, wherein the carbon-containing coating raw material is at least one selected from the group consisting of sucrose, glucose, polyethylene glycol, polyvinyl alcohol, and polyvinyl acetate.

3. In claim 1, A method for producing a lithium iron phosphate-based positive electrode active material, wherein the pulverization of iron phosphate in the above step (A) is performed by airflow pulverization.

4. In claim 1, A method for producing a lithium iron phosphate-based positive electrode active material, wherein the crushing of the carbon-containing coating raw material in the above step (A) is performed by mechanical crushing.

5. In claim 1, The above crushed iron phosphate has an average particle size (D 50 ) A method for manufacturing a lithium iron phosphate-based positive electrode active material having a particle size of 1.0㎛ or more and 2.0㎛ or less.

6. In claim 1, The above-mentioned pulverized iron phosphate is a method for manufacturing a lithium iron phosphate-based positive electrode active material having a span of 0.5 or more and 1.5 or less according to the following formula 1: [Formula 1] Span = (D 90 -D 10 ) / D 50 .

7. In claim 1, The above pulverized carbon-containing coating raw material has an apparent density (bulk density) of 500 kg / m 3 More than 700 kg / m 3 A method for manufacturing a lithium iron phosphate-based positive electrode active material as follows.

8. In claim 1, A method for producing a lithium iron phosphate-based positive electrode active material, wherein the distilled water is mixed in an amount of 5 parts by weight or more and 15 parts by weight or less, based on 100 parts by weight of the total weight of the lithium-containing raw material, the pulverized iron phosphate, and the pulverized carbon-containing coating raw material.

9. In claim 1, A method for producing a lithium iron phosphate-based positive electrode active material, wherein the above reaction mixture has a moisture content of 5 wt% or more and 25 wt% or less.

10. In claim 1, A method for producing a lithium iron phosphate cathode active material, wherein, when producing the above reaction mixture, an M-containing raw material (M is at least one selected from the group consisting of V, Ti, Mn, Zn, Mo, Mg, and N) is further mixed.

11. In claim 1, A method for producing a lithium iron phosphate-based positive electrode active material, wherein a silane compound is further mixed in the production of the above reaction mixture.

12. In claim 11, A method for producing a lithium iron phosphate cathode active material, wherein the above silane compound is mixed in an amount of 0.05 wt% or more and 0.2 wt% or less based on the total weight of the reaction mixture.

13. In claim 1, The compression in step (C) above is 0.10 ton / cm 2 More than 1.0 ton / cm 2 A method for producing a lithium iron phosphate-based positive electrode active material, the method being performed under the following pressure.

14. In claim 1, A method for producing a lithium iron phosphate-based positive electrode active material, wherein the above-mentioned calcination is performed at a temperature of 600°C or higher and 800°C or lower.

15. In claim 1, (E) A method for producing a lithium iron phosphate-based positive electrode active material, further comprising a step of crushing the above-mentioned product.

Images