Cathode active material and preparation method therefor

Abstract

Provided are: a cathode active material having improved capacity characteristics and effects of inhibiting metal leaching; and a preparation method therefor, wherein the cathode active material comprises particles of a lithium composite oxide, wherein the lithium composite oxide comprises manganese and a doping element, an average Mn-O (manganese-oxygen) bond length in the lithium composite oxide is less than 2.55 Å, and the sphericity of the particles of the lithium composite oxide is 0.49-0.8. As such, through the preparation of the cathode active material, the structural and thermal stability of a battery may be simultaneously improved, and accordingly, the battery performance in terms of capacity and lifespan may be improved.

Description

Cathode active material and method for manufacturing the same

[0001] The present application claims the benefit of priority based on Korean Patent Application No. 10-2025-0006502 filed January 16, 2025 and Korean Patent Application No. 10-2026-0008486 filed January 16, 2026, and includes all contents disclosed in the documents of said Korean patent applications as part of the specification.

[0002] The present invention relates to a positive electrode active material and a method for manufacturing the same. Specifically, it relates to a positive electrode active material with controlled Mn-O (manganese-oxygen) bond length and a method for manufacturing the same. More specifically, the invention relates to a positive electrode active material comprising lithium composite oxide particles, wherein the lithium composite oxide comprises manganese and a doping element, the average Mn-O (manganese-oxygen) bond length within the lithium composite oxide is less than 2.55 Å, and the degree of sphericity of the lithium composite oxide particles is 0.49 to 0.8, and a method for manufacturing the same.

[0003] With the increasing technological development and demand for mobile devices, the demand for rechargeable batteries as an energy source is rapidly rising. Among these rechargeable batteries, lithium-ion batteries, which possess high energy density and voltage, long cycle life, and low self-discharge rates, have been commercialized and are widely used.

[0004] Lithium transition metal oxides are used as cathode active materials for lithium secondary batteries; among these, lithium cobalt composite metal oxides such as LiCoO2 have been primarily used due to their high operating voltage and excellent capacity characteristics. However, LiCoO2 has very poor thermal properties due to the descaling of its crystal structure following lithium delithiation, and because it is expensive, there are limitations to its mass use as a power source in fields such as electric vehicles.

[0005] As materials to replace lithium cobalt composite metal oxides, lithium manganese composite metal oxides (such as LiMnO2 or LiMn2O4), lithium iron phosphate compounds (such as LiFePO4), or lithium nickel composite metal oxides (such as LiNiO2) have been developed. Among these, research on cathodes utilizing high-nickel (High Ni) cathode active materials, which exhibit excellent capacity characteristics, has been actively conducted. However, high-nickel cathode active materials have problems such as poor thermal stability; if an internal short circuit occurs due to external pressure during charging, the cathode active material itself decomposes, leading to battery rupture and ignition.

[0006] Accordingly, nickel-cobalt-manganese-based lithium composite metal oxides (hereinafter simply referred to as 'NCM-based lithium oxides') in which some of the nickel is replaced with manganese, cobalt, or aluminum have been developed. However, due to the use of cobalt and an excess amount of nickel, manufacturing costs increase, and metals such as manganese leaches out during battery operation, causing a decrease in lifespan characteristics.

[0007] Accordingly, lithium iron phosphate compounds (hereinafter simply referred to as 'LFP-based lithium composite materials') are attracting attention as cathode active materials because they not only exhibit superior high-temperature stability compared to LiCoO2 but also superior chemical and structural stability compared to NCM-based lithium oxides, and offer economic advantages due to their low-cost raw materials.

[0008] However, LFP-based lithium composite materials have lower electrical conductivity and lower driving voltage compared to other lithium composite metal oxides, which limits the provision of capacity characteristics. Although stability has been improved compared to NCM-based lithium oxides, there is still a problem of reduced lifespan characteristics due to the leaching of metals contained in the active material, such as manganese and iron.

[0009] Accordingly, there is a need to develop a cathode active material and a method for manufacturing the same that can achieve high capacity by overcoming the disadvantages of NCM-based lithium composite transition metal oxides, ensuring stability, and improving battery characteristics.

[0010] [Prior Art Literature]

[0011] [Patent Literature]

[0012] (Patent Document 1) Chinese Patent Publication No. 17080388

[0013] The objective of the present invention is to provide a positive electrode active material having improved capacity characteristics and metal leaching during battery operation, wherein the positive electrode active material comprises lithium composite oxide particles, wherein the lithium composite oxide comprises manganese and a doping element, the average Mn-O (manganese-oxygen) bond length in the lithium composite oxide is less than 2.55 Å, and the sphericity of the lithium composite oxide particles is 0.49 to 0.8.

[0014] Another objective of the present invention is to provide a method for manufacturing the positive electrode active material.

[0015] A first aspect of the present invention provides a positive electrode active material comprising lithium composite oxide particles, wherein the lithium composite oxide comprises manganese and a doping element, the average Mn-O (manganese-oxygen) bond length in the lithium composite oxide is less than 2.55 Å, and the degree of sphericity of the lithium composite oxide particles is 0.49 to 0.8.

[0016] In one embodiment of the present invention, the content of the doping element in the lithium composite oxide is 0.5 mol% to 5 mol% based on the total number of moles of the transition metal in the lithium composite oxide.

[0017] In one embodiment of the present invention, the doping element is selected from the group consisting of V, Al, Ni, Co, Mg, Nb, Mo, W, Ti, Sr, Zr, B, Y, Ru, Rh, Pd, Pt, Zn and combinations thereof.

[0018] In one embodiment of the present invention, the content of an element having an oxidation number of 3 or less in the doping element is 20 mol% to 100 mol% based on the total number of moles of the element in the doping element.

[0019] In one embodiment of the present invention, the lithium composite oxide has a PF factor of 1 or more, represented by the following [Formula 1].

[0020] [Equation 1]

[0021] PF factor = [ (A × B) / C] × 100

[0022] In Equation 1 above, A is the degree of sphericity of the lithium composite oxide particles, B is the average particle size (μm) of the lithium composite oxide particles, and C is the BET specific surface area (m²) of the lithium composite oxide particles. 2 / g) is.

[0023] In one embodiment of the present invention, the lithium composite oxide comprises a carbon coating layer.

[0024] In one embodiment of the present invention, the carbon coating layer has a layered structure comprising a first layer and a second layer, wherein the first layer comprises an amorphous carbon-based material and the second layer comprises a crystalline carbon-based material.

[0025] In one embodiment of the present invention, the carbon content in the coating layer is 1% to 10% by weight based on the total weight of the lithium composite oxide.

[0026] In one embodiment of the present invention, the lithium composite oxide comprises a lithium iron phosphate-based compound.

[0027] In one embodiment of the present invention, the lithium composite oxide is represented by the following [Chemical Formula 1].

[0028] [Chemical Formula 1]

[0029] Li 1+a Fe 1-x-y Mn x M y PO4

[0030] In the above chemical formula 1,

[0031] The above M is selected from the group consisting of V, Al, Ni, Co, Mg, Nb, Mo, W, Ti, Sr, Zr, B, Y, Ru, Rh, Pd, Pt, Zn and combinations thereof, and

[0032] The above a, x, and y are each -0.1≤a≤0.1, 0<x≤0.7, and 0≤y≤0.1.

[0033] A second aspect of the present invention is a method for manufacturing a positive electrode active material comprising a lithium composite oxide, wherein the lithium composite oxide comprises manganese and a doping element, the average Mn-O (manganese-oxygen) bond length in the lithium composite oxide is less than 2.55 Å, the sphericity of the lithium composite oxide particles is 0.49 to 0.8, and the manufacturing method comprises the step of mixing a composite oxide raw material containing manganese, a doping element raw material, and a lithium raw material, and then calcining.

[0034] In one embodiment of the present invention, the firing is performed at 500°C to 900°C for 5 to 15 hours.

[0035] In one embodiment of the present invention, the step of mixing and then calcining a composite oxide raw material containing manganese, a doping element raw material, and a lithium raw material comprises (1) a step of mixing a composite oxide raw material containing manganese, a doping element raw material, and a lithium raw material, and (2) a step of mixing and then calcining the mixture with a carbon coating raw material.

[0036] In one embodiment of the present invention, step (2) includes (S1) mixing the mixture with a first carbon coating raw material and then firing to produce a first fired product, and (S2) mixing the first fired product with a second carbon coating raw material and then firing.

[0037] In one embodiment of the present invention, the mixing in step (S2) is dry mixing.

[0038] The positive electrode active material according to the present invention is a positive electrode active material comprising lithium composite oxide particles, wherein the lithium composite oxide comprises manganese and a doping element, the average Mn-O (manganese-oxygen) bond length in the lithium composite oxide is less than 2.55 Å, and the sphericity of the lithium composite oxide particles is 0.49 to 0.8, and has excellent characteristics in terms of capacity and prevention of metal leaching of the positive electrode active material.

[0039] When applied to batteries, these characteristics can improve battery performance, such as increasing capacity and lifespan characteristics.

[0040] [Fig. 1] is an image showing the SEM analysis results of an active material according to Example 1 of the present invention.

[0041] [Fig. 2] is an image showing the process of evaluating the degree of sphericity using the SEM analysis results of the active material according to Example 1 of the present invention.

[0042] The present invention will be described in more detail below.

[0043] Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention. Accordingly, the configurations described in the embodiments described in this specification are merely one preferred embodiment of the invention and do not represent all of the technical spirit of the invention; therefore, it should be understood that various equivalents and modifications capable of replacing them may exist at the time of filing this application.

[0044] In this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0045] In this specification, "%" means weight percent unless otherwise explicitly indicated.

[0046] Where measurement conditions and methods are not specifically described for the physical properties described in this specification, said physical properties are measured according to measurement conditions and methods generally used by a person skilled in the art in the relevant technical field.

[0047]

[0048] The present invention will be described in detail below.

[0049]

[0050] positive electrode active material

[0051] The present invention provides a positive electrode active material.

[0052] In one embodiment of the present invention, the positive active material comprises lithium composite oxide particles.

[0053] The above lithium composite oxide is a material containing lithium, transition metals, etc., capable of lithium ion insertion and extraction during battery operation, and may be a lithium cobalt-based composite metal oxide; a lithium manganese-based composite metal oxide; a lithium nickel-based composite metal oxide; a lithium iron phosphate-based compound, or a combination thereof, but is not limited thereto as long as it is a material commonly used in cathode active materials in the relevant technical field.

[0054] When these lithium composite oxide particles are included in the cathode active material, excellent chemical and structural stability is achieved, so improvements in stability and lifespan characteristics can be expected when applied to batteries.

[0055] In one embodiment of the present invention, the lithium composite oxide is a lithium composite manganese oxide.

[0056] In one embodiment of the present invention, the lithium composite oxide comprises manganese and a doping element.

[0057] By including manganese in the above lithium composite oxide, high capacity characteristics and ease of operation at high voltages can be expected.

[0058] The above doping element is included in small amounts within the cathode active material to improve the electrical conductivity, chemical or structural stability, and capacity retention of the cathode active material. Examples include metals such as yttrium (Y), zirconium (Zr), titanium (Ti), magnesium (Mg), aluminum (Al), or vanadium (V), or elements that can behave like transition metals such as boron (B), but are not limited to those commonly used in the relevant technical field.

[0059] The above lithium composite oxide can improve the stability and electrical conductivity of the positive electrode active material by including doping elements, and accordingly, the capacity and lifespan characteristics of the battery containing the above positive electrode active material can also be improved.

[0060] In one embodiment of the present invention, the content of the doping element in the lithium composite oxide is 0.5 mol% to 5 mol% based on the total number of moles of the transition metal in the lithium composite oxide. Specifically, the content of the doping element is 0.5 mol% or more, 0.6 mol% or more, 0.7 mol% or more, 0.8 mol% or more, 0.9 mol% or more, 1 mol% or more, 1.1 mol% or more, 1.2 mol% or more, 1.3 mol% or more, 1.4 mol% or more, 1.5 mol% or more, 1.6 mol% or more, 1.7 mol% or more, or 1.8 mol% or more, and 5 mol% or less, 4.5 mol% or less, 4 mol% or less, 3.5 mol% or less, 3 mol% or less, 2.9 mol% or less, 2.8 mol% or less, 2.7 mol% or less, 2.6 mol% or less, 2.5 mol% or less, 2.4 mol% or less, 2.3 mol% or less, 2.2 mol% or less, 2.1 mol% or less, 2 mol% or less, or 1.9 mol% or less, and 0.5 The content may be from 5 mol% to 1 mol%, from 4 mol%, or from 1.5 mol% to 2.5 mol%. When the content of the doping element satisfies the above range, sites substituted with the doping element in the lithium composite oxide can be formed to an appropriate degree to improve structural stability and capacity characteristics.

[0061] In one embodiment of the present invention, the doping element is selected from the group consisting of V, Al, Ni, Co, Mg, Nb, Mo, W, Ti, Sr, Zr, B, Y, Ru, Rh, Pd, Pt, Zn and combinations thereof.

[0062] In one embodiment of the present invention, the doping element is selected from the group consisting of V, Al, Mg, Ti, Zr, B, Y, and combinations thereof.

[0063] In one embodiment of the present invention, the doping element is selected from the group consisting of V, Mg, and combinations thereof.

[0064] A lithium composite oxide according to one embodiment of the present invention includes a doping element selected from the group above, so that the doping element is stably substituted within the structure of the lithium composite oxide, thereby improving the chemical and structural stability of the cathode active material including the lithium composite oxide, and furthermore, the capacity characteristics can also be improved.

[0065] In one embodiment of the present invention, the doping element comprises a non-reactive metal.

[0066] The above-mentioned non-reactive metal refers to a metal whose oxidation state does not change during battery operation, and which does not participate in the electrochemical reactions occurring during battery operation. For example, it may be selected from the group consisting of Al, Mg, Mo, W, Zr, Ru, Rh, Pd, Pt, and combinations thereof, but is not limited thereto if it is a metal commonly known in the relevant technical field as a metal whose oxidation state does not change during battery operation.

[0067] When a lithium composite oxide contains a transition metal, particularly manganese, distortion occurs in the structure of the lithium composite oxide due to changes in the oxidation state of the transition metal resulting from electrochemical reactions during battery operation. When such distortion occurs, problems arise such as structural stability of the battery and deterioration of lifespan characteristics due to issues like the leaching of the transition metal. A lithium composite oxide according to one embodiment of the present invention includes a non-reactive metal as a doping element, thereby allowing the doping element to be placed within the lithium composite oxide crystal. This enables the suppression of distortion in the crystal structure caused by changes in the oxidation state of manganese. Accordingly, the stability and lifespan characteristics of the battery can be improved.

[0068] In one embodiment of the present invention, the content of the non-reactive metal in the lithium composite oxide is 0.1 mol% to 5 mol% based on the total molar amount of the transition metal in the lithium composite oxide. Specifically, the content of the non-reactive metal is 0.1 mol% or more, 0.2 mol% or more, 0.3 mol% or more, 0.4 mol% or more, 0.5 mol% or more, 0.6 mol% or more, 0.7 mol% or more, 0.8 mol% or more, 0.9 mol% or more, or 1 mol% or more, 5 mol% or less, 4.5 mol% or less, 4 mol% or less, 3.5 mol% or less, 3 mol% or less, 2.5 mol% or less, 2 mol% or less, 1.5 mol% or less, 1.4 mol% or less, 1.3 mol% or less, 1.2 mol% or less, or 1.1 mol% or less, and may be 0.1 mol% to 5 mol%, 0.1 mol% to 3 mol%, or 0.5 mol% to 1.5 mol%. When the content of the above-mentioned non-reactive metal satisfies the above range, the stability of the positive electrode active material containing the lithium composite oxide can be improved within a range where the electrochemical reaction required for battery operation can be smoothly exhibited.

[0069] In one embodiment of the present invention, the content of the non-reactive metal in the doping element is 20 mol% to 100 mol% based on the total number of moles of the element in the doping element. Specifically, the content of the non-reactive metal is 20 mol% or more, 25 mol% or more, 30 mol% or more, 35 mol% or more, 40 mol% or more, or 45 mol% or more, and 100 mol% or less, 99 mol% or less, 95 mol% or less, 90 mol% or less, 85 mol% or less, 80 mol% or less, 75 mol% or less, 70 mol% or less, 65 mol% or less, 60 mol% or less, 55 mol% or less, or 50 mol% or less, and may be 20 mol% to 100 mol%, 30 mol% to 80 mol%, or 40 mol% to 70 mol%. When the content of the above-mentioned non-reactive metal satisfies the above range, the reduction in the structural stability enhancement effect that may occur due to other elements included in the doping element affecting the substitution of the non-reactive metal within the lithium composite oxide can be minimized.

[0070] In one embodiment of the present invention, the non-reactive metal is a metal having an oxidation number of 3 or less.

[0071] In one embodiment of the present invention, the non-reactive metal is magnesium (Mg).

[0072] In one embodiment of the present invention, the doping element comprises a metal having an oxidation number of 3 or less. The metal having an oxidation number of 3 or less can be appropriately placed within the lithium composite oxide crystal as described above, and since there is almost no change in the oxidation number due to battery operation, it can exhibit the effect of improving the stability and lifespan characteristics of the battery.

[0073] In one embodiment of the present invention, the content of the metal having an oxidation state of 3 or less in the lithium composite oxide is 0.1 mol% to 5 mol% based on the total molar amount of transition metal in the lithium composite oxide. Specifically, the content of the metal having an oxidation number of 3 or less is 0.1 mol% or more, 0.2 mol% or more, 0.3 mol% or more, 0.4 mol% or more, 0.5 mol% or more, 0.6 mol% or more, 0.7 mol% or more, 0.8 mol% or more, 0.9 mol% or more, or 1 mol% or more, 5 mol% or less, 4.5 mol% or less, 4 mol% or less, 3.5 mol% or less, 3 mol% or less, 2.5 mol% or less, 2 mol% or less, 1.5 mol% or less, 1.4 mol% or less, 1.3 mol% or less, 1.2 mol% or less, or 1.1 mol% or less, and may be 0.1 mol% to 5 mol%, 0.1 mol% to 3 mol%, or 0.5 mol% to 1.5 mol%. When the content of the metal having an oxidation number of 3 or less satisfies the above range, the stability of the positive electrode active material containing the lithium composite oxide can be improved within a range where the electrochemical reaction required for battery operation can be smoothly exhibited.

[0074] In one embodiment of the present invention, the content of the metal having an oxidation number of 3 or less in the doping element is 20 mol% to 100 mol% based on the total number of moles of the element in the doping element. Specifically, the content of the metal having an oxidation number of 3 or less is 20 mol% or more, 25 mol% or more, 30 mol% or more, 35 mol% or more, 40 mol% or more, or 45 mol% or more, 100 mol% or less, 99 mol% or less, 95 mol% or less, 90 mol% or less, 85 mol% or less, 80 mol% or less, 75 mol% or less, 70 mol% or less, 65 mol% or less, 60 mol% or less, 55 mol% or less, or 50 mol% or less, and may be 20 mol% to 100 mol%, 30 mol% to 80 mol%, or 40 mol% to 70 mol%. When the content of the metal with an oxidation number of 3 or less satisfies the above range, the reduction in the effect of improving structural stability that may occur due to other elements included in the doping element affecting the substitution of the metal with an oxidation number of 3 or less in the lithium composite oxide can be minimized.

[0075] In one embodiment of the present invention, the metal having an oxidation number of 3 or less is magnesium (Mg).

[0076] In one embodiment of the present invention, the doping element comprises a reactive metal.

[0077] Unlike the non-reactive metal, the above-mentioned reactive metal participates in electrochemical reactions that occur during battery operation, causing a change in oxidation number, and is selected from a group consisting of transition metals corresponding to groups 4 to 10 of the periodic table and combinations thereof.

[0078] By including the above-mentioned reactive metal in the lithium composite oxide, the ionic conductivity, structural and thermal stability, etc., of the positive electrode active material containing the lithium composite oxide can be improved, and accordingly, battery performance such as capacity and lifespan characteristics of the battery containing the lithium composite oxide can be improved.

[0079] In one embodiment of the present invention, the reactive metal is selected from the group consisting of V, Ni, Co, Zn and combinations thereof.

[0080] In one embodiment of the present invention, the reactive metal is vanadium (V).

[0081] In one embodiment of the present invention, the content of the reactive metal in the lithium composite oxide is 0.1 mol% to 3 mol% based on the total molar amount of the transition metal in the lithium composite oxide. Specifically, the content of the reactive metal is 0.1 mol% or more, 0.2 mol% or more, 0.3 mol% or more, 0.4 mol% or more, 0.5 mol% or more, 0.6 mol% or more, 0.7 mol% or more, 0.8 mol% or more, 0.9 mol% or more, or 1 mol% or more, 3 mol% or less, 2.5 mol% or less, 2 mol% or less, 1.5 mol% or less, 1.4 mol% or less, 1.3 mol% or less, 1.2 mol% or less, or 1.1 mol% or less, and may be 0.1 mol% to 3 mol%, 0.1 mol% to 2 mol%, or 0.5 mol% to 1.5 mol%. When the content of the above-mentioned reactive metal satisfies the above range, the positive electrode active material containing the lithium composite oxide can exhibit easy electrical conductivity and stability for battery operation.

[0082] In one embodiment of the present invention, the content of the reactive metal in the doping element is 10 mol% to 70 mol% based on the total number of moles of the elements in the doping element. Specifically, the content of the reactive metal may be 10 mol% or more, 15 mol% or more, 20 mol% or more, 25 mol% or more, 30 mol% or more, 35 mol% or more, or 40 mol% or more, 70 mol% or less, 65 mol% or less, 60 mol% or less, 55 mol% or less, 50 mol% or less, or 45 mol% or less, and may be 10 mol% to 70 mol%, 20 mol% to 70 mol%, or 40 mol% to 60 mol%. When the content of the reactive metal satisfies the above range, the reduction in the improvement effect, such as electrical conductivity and stability, which may occur due to other elements included in the doping element affecting the action of the reactive metal, can be minimized.

[0083] In one embodiment of the present invention, the doping element comprises a non-reactive metal and a reactive metal.

[0084] In one embodiment of the present invention, the content of the non-reactive metal in the doping element is 80 to 200 parts by weight based on 100 parts by weight of the reactive metal in the doping element. Specifically, the content of the non-reactive metal is 80 parts by weight or more, 85 parts by weight or more, 90 parts by weight or more, 90 parts by weight or more, 95 parts by weight or more, 100 parts by weight or more, 105 parts by weight or more, 110 parts by weight or more, 115 parts by weight or more, or 120 parts by weight or more, based on 100 parts by weight of the reactive metal in the doping element; 200 parts by weight or less, 195 parts by weight or less, 190 parts by weight or less, 185 parts by weight or less, 180 parts by weight or less, 175 parts by weight or less, 170 parts by weight or less, 165 parts by weight or less, 160 parts by weight or less, 155 parts by weight or less, 150 parts by weight or less, 145 parts by weight or less, 140 parts by weight or less, 135 parts by weight or less, 130 parts by weight or less, or 125 parts by weight or less; and 80 parts by weight to 200 parts by weight, 90 It may be in parts by weight to 180 parts by weight or in parts by weight to 110 parts by weight to 150 parts by weight. When the content of the non-reactive metal satisfies the above range, performance degradation caused by mutual reaction between the non-reactive metal and the reactive metal is suppressed, and the effects of suppressing crystal structure distortion due to the inclusion of the non-reactive metal and improving battery capacity and lifespan characteristics due to the inclusion of the reactive metal can be appropriately exhibited.

[0085] In one embodiment of the present invention, the doping element includes a metal having an oxidation number of 3 or less and a reactive metal.

[0086] In one embodiment of the present invention, the average Mn-O (manganese-oxygen) bond length in the lithium composite oxide is less than 2.55 Å. Specifically, the above average Mn-O (manganese-oxygen) bond length is less than 2.55 Å, 2.54 Å or less, 2.53 Å or less, 2.52 Å or less, 2.51 Å or less, or 2.5 Å or less; is 1 Å or more, 1.5 Å or more, 2 Å or more, 2.1 Å or more, 2.2 Å or more, 2.3 Å or more, 2.4 Å or more, 2.41 Å or more, 2.42 Å or more, 2.43 Å or more, 2.44 Å or more, 2.45 Å or more, 2.46 Å or more, 2.47 Å or more, 2.48 Å or more, or 2.49 Å or more; is less than 2.55 Å, 2.4 Å or more, less than 2.55 Å, or 2.48 Å to 2.52 Å. When the Mn-O (manganese-oxygen) bond length satisfies the above range, structural distortion of the lithium composite oxide, particularly Jahn-Teller distortion caused by changes in the oxidation state of manganese occurring during battery operation, can be mitigated, and accordingly, manganese leaching due to battery operation can be suppressed and the chemical and structural stability of the cathode active material containing the lithium composite oxide can be improved.

[0087] In one embodiment of the present invention, the degree of sphericity of the lithium composite oxide particles is 0.49 to 0.8. Specifically, the degree of sphericity may be 0.49 or higher, 0.5 or higher, 0.51 or higher, 0.52 or higher, or 0.53 or higher, 0.8 or lower, 0.75 or lower, 0.7 or lower, 0.65 or lower, 0.6 or lower, 0.59 or lower, 0.58 or lower, 0.57 or lower, 0.56 or lower, 0.55 or lower, or 0.54 or lower, and may be 0.49 to 0.8, 0.49 to 0.7, or 0.5 to 0.6. When the degree of sphericity satisfies the above range, it is easy to control the specific surface area of ​​the lithium composite oxide particles according to the particle size, the energy density of the cathode active material including the lithium composite oxide particles can be improved, and the insertion and extraction of lithium ions can be smoothly performed.

[0088] In one embodiment of the present invention, the average particle size of the lithium composite oxide particles is 0.1 μm to 3 μm. Specifically, the average particle size is 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, 0.31 μm or more, 0.32 μm or more, 0.33 μm or more, or 0.34 μm or more, 3 μm or less, 2.5 μm or less, 2 μm or less, 1.5 μm or less, 1 μm or less, 0.9 μm or less, 0.8 μm or less, 0.7 μm or less, 0.6 μm or less, 0.5 μm or less, 0.4 μm or less, 0.39 μm or less, 0.38 μm or less, 0.37 μm or less, 0.36 μm or less, or 0.35 μm or less, and may be 0.1 μm to 3 μm, 0.3 μm to 2 μm, or 0.34 μm to 1 μm. When the above average particle size satisfies the above range, it can exhibit an energy density suitable for battery utilization.

[0089] In one embodiment of the present invention, the specific surface area of ​​the lithium composite oxide particles is 10 m² 2 / g to 20 m 2 / g. Specifically, the above specific surface area is 10 m² 2 / g or more, 10.5 m 2 / g or more, 11 m 2 / g or more, 11.5 m 2 / g or more, 12 m 2 / g or more, 12.5 m 2 / g or more, 13 m 2 / g or more, 13.5 m 2 / g or more, 14 m 2 / g or more, 14.5 m 2 / g or more, 15 m 2 / g or more, 15.5 m 2 / g or more or 16 m 2 / g or more, and 20 m 2 / g or less, 19.5 m 2 / g or less, 19 m 2 / g or less, 18.5 m 2 / g or less, 18 m 2 / g or less, 17.5 m 2 / g or less, 17 m 2 / g or less or 16.5 m 2 / g or less, and 10 m 2 / g to 20 m 2 / g, 12 m 2 / g to 18 m 2 / g or 15 m 2 / g to 16.5 m 2 It may be / g. When the above specific surface area satisfies the above range, the lithium composite oxide particles exhibit a specific surface area that allows lithium ions to move smoothly, while simultaneously suppressing side reactions with the electrolyte occurring at the surface.

[0090] In one embodiment of the present invention, the lithium composite oxide has a PF factor represented by the following [Formula 1] of 1 or more. Specifically, the PF factor is 1 or more, 1.05 or more, 1.1 or more, 1.15 or more, or 1.2 or more, 3 or less, 2.5 or less, 2 or less, 1.9 or less, 1.8 or less, 1.7 or less, 1.6 or less, 1.5 or less, 1.4 or less, or 1.3 or less, and may be 1 to 3, 1 to 2, or 1.1 to 1.5.

[0091] [Equation 1]

[0092] PF factor = [ (A × B) / C] × 100

[0093] In Equation 1 above, A is the degree of sphericity of the lithium composite oxide particles, B is the average particle size (μm) of the lithium composite oxide particles, and C is the BET specific surface area (m²) of the lithium composite oxide particles. 2 / g) is.

[0094] The above PF factor is a value that evaluates the suitability of a positive electrode active material containing the above lithium composite oxide particles for battery application related to particle characteristics such as the surface shape of the above lithium composite oxide particles. When the above PF factor satisfies the above range, the shape of the above particles is formed to be suitable for battery application, thereby exhibiting an effect of suppressing side reactions with the electrolyte and metal leaching. Accordingly, when the positive electrode active material containing the above particles is applied to a battery, battery performance such as the capacity and lifespan characteristics of the battery can be improved.

[0095] In one embodiment of the present invention, the lithium composite oxide comprises a lithium iron phosphate-based compound.

[0096] The above lithium iron phosphate-based compound is an LFP-based lithium composite oxide, and as oxygen atoms and phosphorus atoms form strong covalent bonds in the PO4 tetrahedral structure forming an olivine structure, it has high structural stability against volume changes caused by charging and discharging of the battery compared to other lithium composite oxides such as NCM-based lithium oxide, and has the characteristic of maintaining high thermal stability because oxygen atoms are not easily detached due to thermal decomposition. Accordingly, as the particle according to one embodiment of the present invention contains the above lithium iron phosphate-based compound as a core, the phenomenon of capacity reduction caused by the collapse of the crystal structure resulting from overcharging of the positive electrode active material is small, and gas generation is small, so the stability is excellent, thereby ensuring the stability of the battery, especially the stability required for large batteries.

[0097] In one embodiment of the present invention, the lithium iron phosphate-based compound further comprises elements such as manganese (Mn). By substituting a portion of the iron in the lithium iron phosphate-based compound with manganese or the like, the insertion and extraction of lithium ions occur smoothly, thereby improving the capacity and efficiency of the battery, particularly the efficiency at high voltage.

[0098] In one embodiment of the present invention, the lithium composite oxide is represented by the following [Chemical Formula 1].

[0099] [Chemical Formula 1]

[0100] Li 1+a Fe 1-x-y Mn x M y PO4

[0101] In the above chemical formula 1, M is selected from the group consisting of V, Al, Ni, Co, Mg, Nb, Mo, W, Ti, Sr, Zr, B, Y, Ru, Rh, Pd, Pt, Zn and combinations thereof.

[0102] In one embodiment of the present invention, a is -0.1 ≤ a ≤ 0.1. Specifically, a may be -0.1 ≤ a ≤ 0.1, -0.08 ≤ a ≤ 0.08, or -0.05 ≤ a ≤ 0.05.

[0103] In one embodiment of the present invention, x is 0 < x ≤ 0.7. Specifically, x may be 0 < x ≤ 0.7, 0.1 ≤ x ≤ 0.6, or 0.2 ≤ x ≤ 0.4.

[0104] In one embodiment of the present invention, y is 0≤y≤0.1. Specifically, y may be 0≤y≤0.1, 0≤y≤0.08, or 0≤y≤0.05.

[0105] In one embodiment of the present invention, the lithium composite oxide comprises a carbon coating layer. The term "coating layer" refers to one formed on the outer surface of the lithium composite oxide.

[0106] A lithium composite oxide according to one embodiment of the present invention includes the carbon coating layer on the outer surface, thereby allowing for easy control of particle size and shape. Even if the lithium composite oxide is a material with low electrical conductivity, such as an LFP-based lithium composite material, it can improve electrochemical properties to enhance the capacity characteristics and operation at high voltage of the positive electrode active material containing the particles.

[0107] In one embodiment of the present invention, the coating layer comprises an amorphous carbon-based material and a crystalline carbon-based material.

[0108] The above-mentioned amorphous carbonaceous material refers to a carbonaceous material having an irregular arrangement without a specific crystal structure. Similarly, a crystalline carbonaceous material refers to a carbonaceous material having a specific arrangement. The presence or absence of amorphous or crystalline properties can be evaluated through methods capable of analyzing the crystal structure within the material. For example, this can be evaluated through phase analysis using a transmission electron microscope (TEM).

[0109] When the coating layer includes an amorphous carbon-based material, it can provide ion migration pathways to contribute to capacity characteristics and improve structural stability through a flexible structure. Additionally, when a crystalline carbon-based material is included along with the amorphous carbon-based material, it can contribute to improving battery performance by enhancing the strength of active material particles and simultaneously lowering powder resistance through improved electrical conductivity.

[0110] In one embodiment of the present invention, the coating layer has a layered structure including a first layer and a second layer.

[0111] In one embodiment of the present invention, the first layer comprises an amorphous carbon-based material, and the second layer comprises a crystalline carbon-based material.

[0112] When the coating layer includes a layered structure as described above, the benefits intended for the amorphous structure of each amorphous carbon-based material and the crystalline structure of the crystalline carbon-based material can be clearly manifested, and phase separation that may occur due to the mixing of each material can be prevented. The presence or absence of such a layered structure can be evaluated using a transmission electron microscope, etc.

[0113] In one embodiment of the present invention, the amorphous carbon-based material comprises an oxygen-containing carbon-based material.

[0114] The oxygen-containing carbon-based material mentioned above refers to a carbon-based material that contains oxygen atoms within a carbon chain or contains oxygen-containing functional groups such as hydroxyl groups, ether groups, or ester groups. By including the oxygen-containing carbon-based material, the coating layer forms a physical or chemical bond with the lithium composite oxide in the core, thereby facilitating particle growth and contributing to the electrochemical properties of the active material.

[0115] The inclusion of oxygen elements within the carbon chain means that carbon and oxygen elements are mixed together to form a chain, similar to etheric substances.

[0116] The presence of oxygen-containing carbon-based materials within the coating layer can be determined by the presence or absence of (-C=O) or (-CO-) bonds or oxygen-containing functional groups such as (-OH) or (-C(=O)-O-) within the coating layer. The presence or absence of such bonds or functional groups can be evaluated using spectra capable of analyzing the bonding relationships between elements within the material, such as Nuclear Magnetic Resonance Spectroscopy (NMR) or Infrared Spectroscopy (IR). For example, as a result of analyzing the coating layer of the cathode active material using IR, the 1650 cm⁻¹ region, which corresponds to the (-C=O) bond region... -1 to 1850 cm -1 If a peak is observed in the vicinity, the corresponding coating layer can be evaluated as containing an oxygen-containing carbon-based material.

[0117] In one embodiment of the present invention, the oxygen-containing carbon-based material comprises an oxygen element within a carbon chain and comprises an oxygen-containing functional group.

[0118] In one embodiment of the present invention, the crystalline carbon-based material comprises an aromatic carbon-based material.

[0119] The above-mentioned aromatic carbonaceous material refers to a carbonaceous material containing an aromatic ring. By including the above-mentioned aromatic carbonaceous material, the coating layer can contribute to the electrochemical properties of the active material and can improve powder properties such as powder resistance by controlling the interactions between carbonaceous materials within the coating layer.

[0120] Whether an aromatic carbonaceous material is included in the coating layer can be determined by the presence or absence of an aromatic ring in the coating layer. The evaluation method is similar to the evaluation method for the inclusion of an oxygen-containing carbonaceous material, and, for example, 1If a peak is observed in the region of aromatic rings between 6.5 ppm and 8 ppm as a result of analyzing the surface of the cathode active material with H-NMR, the coating layer can be evaluated as containing an aromatic carbon-based material.

[0121] In one embodiment of the present invention, the coating layer comprises an oxygen-containing carbon-based material and an aromatic carbon-based material.

[0122] In one embodiment of the present invention, the amorphous carbon-based material or oxygen-containing carbon-based material is derived from sugars or vinyl polymer compounds.

[0123] The above sugars or vinyl polymer compounds may be, for example, sucrose; glucose; cellulose; lactose; polyvinyl alcohol; polyvinylpyrrolidone; or a combination thereof, but are not limited thereto as long as they are materials that can improve the electrochemical properties of the particles and form physical or chemical bonds with the material in the lithium composite oxide to control the growth of the particles during the manufacturing process of the positive electrode active material.

[0124] In one embodiment of the present invention, the crystalline carbonaceous material or aromatic carbonaceous material is derived from a polycyclic aromatic hydrocarbon compound.

[0125] The above polycyclic aromatic hydrocarbon compound may be, for example, pyrine; naphthalene; anthracene; coronine; or a combination thereof, or coal-based pitch; petroleum-based pitch; or a combination thereof containing such, but can improve the electrochemical properties of the particles and the sp of carbon in the coating layer 2 Any material capable of improving the characteristics regarding the insertion and extraction of lithium ions within the positive electrode active material and suppressing side reactions with the electrolyte by controlling the degree of binding is not limited thereto.

[0126] In one embodiment of the present invention, the carbon content in the coating layer is 1% to 10% by weight based on the total weight of the lithium composite oxide. Specifically, it may be 1% or more by weight, 2% or more by weight, 3% or more by weight, or 4% or more by weight; 10% or less by weight, 9% or less by weight, 8% or less by weight, 7% or less by weight, 6% or less by weight, or 5% or less by weight; or 1% to 10% by weight, 1% to 8% by weight, or 2% to 5% by weight. When the carbon content satisfies the above range, the carbon coating layer is formed evenly, allowing for smooth insertion and extraction of lithium and facilitating easy control of the electrochemical properties of the positive electrode active material.

[0127]

[0128] Method for manufacturing positive electrode active material

[0129] The present invention provides a method for manufacturing a positive electrode active material.

[0130] In one embodiment of the present invention, a method for manufacturing a positive electrode active material comprising a lithium composite oxide, wherein the lithium composite oxide comprises manganese and a doping element, the average Mn-O (manganese-oxygen) bond length in the lithium composite oxide is less than 2.55 Å, and the degree of sphericity of the lithium composite oxide particles is 0.49 to 0.8.

[0131] In one embodiment of the present invention, the manufacturing method is a method for manufacturing the anode active material described above.

[0132] In one embodiment of the present invention, a method for manufacturing a positive electrode active material comprises the step of mixing a complex oxide raw material containing manganese, a doping element raw material, and a lithium raw material, and then calcining.

[0133] The above mixing is not particularly limited as long as it is a method commonly used in the relevant technical field. The above mixing is intended to uniformly disperse various raw materials and can be carried out by mixing methods such as acoustic mixing.

[0134] The above-mentioned composite oxide raw material containing manganese refers to a compound containing manganese and the corresponding element as a raw material for transition metals, etc., that constitutes a lithium composite oxide. For example, it may be an acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or oxyhydroxide of each transition metal within the raw material. Specifically, it may be a hydroxide or an oxide, but is not limited thereto as long as it is commonly used in the relevant technical field for manufacturing cathode active materials.

[0135] In one embodiment of the present invention, the composite oxide raw material further comprises an iron raw material.

[0136] In one embodiment of the present invention, the composite oxide raw material further comprises a phosphoric acid raw material.

[0137] The above doping raw material may also be an acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or oxyhydroxide of each doping element within the raw material, and specifically may be a hydroxide or oxide, but is not limited thereto as long as it is commonly used for manufacturing cathode active materials in the relevant technical field.

[0138] The above lithium raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, etc. For example, Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or a mixture thereof may be used, and one of these alone or a mixture of two or more may be used. Specifically, it may be Li2CO3 or LiOH, but is not limited thereto as long as it is commonly used in the relevant technical field for the manufacture of cathode active materials.

[0139] In one embodiment of the present invention, the lithium raw material is Li2CO3.

[0140] In one embodiment of the present invention, the firing in the manufacturing method is performed at 500°C to 900°C. Specifically, the firing is performed at 500°C or higher, 550°C or higher, 600°C or higher, 650°C or higher, 700°C or higher, or 750°C or higher, and is performed at 900°C or lower, 850°C or lower, or 800°C or lower, and can be performed at 500°C to 900°C, 600°C to 900°C, or 700°C to 800°C.

[0141] In one embodiment of the present invention, the firing in the manufacturing method is performed for 5 to 15 hours. Specifically, it may be performed for 5 hours or more, 6 hours or more, 7 hours or more, 8 hours or more, 9 hours or more, or 10 hours or more, 15 hours or less, 14 hours or less, 13 hours or less, 12 hours or less, or 11 hours or less, and may be performed for 5 to 15 hours, 6 to 14 hours, or 8 to 12 hours.

[0142] When the above calcination temperature and calcination time satisfy the above range, the calcined product produced by the calcination can have a strength suitable for improving the structural stability of the cathode active material, and the transition metal and doping element can react effectively with lithium to achieve appropriate crystal growth.

[0143] In one embodiment of the present invention, the step of mixing and then calcining the composite raw material containing manganese, the doping element raw material, and the lithium raw material comprises (1) the step of mixing the composite raw material containing manganese, the doping element raw material, and the lithium raw material, and (2) the step of mixing and then calcining the mixture with the carbon coating raw material.

[0144] In one embodiment of the present invention, step (1) comprises: (1-1) a step of preparing a composite mixture by mixing a composite raw material containing manganese and a doping element raw material; and (1-2) a step of preparing a lithium composite oxide raw material by mixing the transition metal mixture and a lithium raw material.

[0145] If the above step (1) is performed over two steps (1-1) and (1-2), the composite raw material containing manganese, the doping raw material, and the lithium raw material can be mixed more uniformly.

[0146] The above carbon coating raw material refers to a material capable of forming a coating layer on the outer surface of the lithium composite oxide by mixing it with the above lithium composite oxide raw material.

[0147] The mixing in step (2) above is not particularly limited as long as it is a method commonly used in the relevant technical field. The mixing is intended to uniformly disperse various raw materials and can be performed by a milling process such as ball milling or jet milling.

[0148] In one embodiment of the present invention, the mixing in the manufacturing method is performed through a milling process.

[0149] In one embodiment of the present invention, the carbon coating layer comprises a compound selected from the group consisting of sugars or vinyl polymer compounds, polycyclic aromatic hydrocarbon compounds, and combinations thereof.

[0150] In one embodiment of the present invention, step (2) includes (S1) mixing the mixture with a first carbon coating raw material and then firing to produce a first fired product, and (S2) mixing the first fired product with a second carbon coating raw material and then firing.

[0151] In one embodiment of the present invention, the first carbon coating raw material in step (S1) is a sugar or a vinyl polymer compound.

[0152] In one embodiment of the present invention, the firing in step (S1) is performed at 500°C to 900°C. Specifically, the firing is performed at 500°C or higher, 550°C or higher, 600°C or higher, 650°C or higher, 700°C or higher, or 750°C or higher, and is performed at 900°C or lower, 850°C or lower, or 800°C or lower, and can be performed at 500°C to 900°C, 600°C to 900°C, or 700°C to 800°C.

[0153] In one embodiment of the present invention, the firing in step (S1) is performed for 5 to 15 hours. Specifically, it may be performed for 5 hours or more, 6 hours or more, 7 hours or more, 8 hours or more, 9 hours or more, or 10 hours or more, 15 hours or less, 14 hours or less, 13 hours or less, 12 hours or less, or 11 hours or less, and may be performed for 5 to 15 hours, 6 to 14 hours, or 8 to 12 hours.

[0154] When the above-mentioned firing temperature and firing time satisfy the above range, the coating layer is evenly formed on the outer surface of the lithium composite oxide, allowing for smooth insertion and extraction of lithium ions, and the carbon within the coating layer can exhibit a bonding degree suitable for battery application.

[0155] In one embodiment of the present invention, the mixing of the mixture of step (S1) and the first carbon coating raw material means mixing directly with the first carbon coating raw material without a pretreatment process between the mixture of the composite raw material containing manganese, the doping element raw material, and the lithium raw material prior to the mixing.

[0156] The mixing in step (S1) above is not particularly limited as long as it is a method commonly used in the relevant technical field. The mixing is intended to uniformly disperse various raw materials and may be performed using a milling process such as ball milling or jet milling.

[0157] In one embodiment of the present invention, the mixing in step (S1) is performed through a ball milling process.

[0158] In one embodiment of the present invention, the mixing in step (S1) is wet mixing.

[0159] In one embodiment of the present invention, the second carbon coating raw material in step (S2) is a polycyclic aromatic hydrocarbon compound.

[0160] In one embodiment of the present invention, the firing in step (S2) is performed at 650°C to 850°C. Specifically, the firing may be performed at 650°C or higher, 700°C or higher, or 750°C or higher, at 850°C or lower, or at 800°C or lower, or at 650°C to 850°C, 700°C to 850°C, or 750°C to 800°C.

[0161] In one embodiment of the present invention, the firing in step (S2) is performed for 5 to 15 hours. Specifically, it may be performed for 5 hours or more, 6 hours or more, 7 hours or more, 8 hours or more, 9 hours or more, or 10 hours or more, 15 hours or less, 14 hours or less, 13 hours or less, 12 hours or less, or 11 hours or less, and may be performed for 5 to 15 hours, 6 to 14 hours, or 8 to 12 hours.

[0162] When the above-mentioned firing temperature and firing time satisfy the above range, the coating layer is evenly formed on the outer surface of the lithium composite oxide, allowing for smooth insertion and extraction of lithium ions, and the carbon within the coating layer can exhibit a bonding degree suitable for battery application.

[0163] The mixing in step (S2) above is not particularly limited as long as it is a method commonly used in the relevant technical field. The mixing is intended to uniformly disperse various raw materials and may be performed by a milling process such as ball milling or jet milling.

[0164] In one embodiment of the present invention, the mixing in step (S2) is performed through a jet milling process.

[0165] In one embodiment of the present invention, the mixing in step (S2) is dry mixing.

[0166] The above dry mixing refers to mixing solid substances by physical or chemical methods without the addition of solvents or the like for mixing. For example, this may be performed by methods such as mortar mixing, but is not limited to any method that can evenly mix each substance.

[0167] In the case of wet mixing, which involves diluting the carbon coating raw material with an organic solvent, etc., additional coating and drying processes are generally included to ensure uniform coating of the carbon coating raw material. Since a grinding process is also necessarily involved, fine particles are generated above a certain level during the manufacturing process. However, unlike wet mixing, dry mixing allows for uniform coating of the carbon coating raw material without additional coating and drying processes. Therefore, compared to wet mixing, process convenience is increased, and rolling density can be improved as fine particles are not generated. When particle size distribution and rolling density are improved in this way, the energy density of the positive active material increases, thereby improving the capacity characteristics and stability of the battery containing the positive active material. Accordingly, when dry mixing is performed in step (2), the manufacturing process becomes more convenient, and the performance and stability of the battery containing the manufactured positive active material are also improved.

[0168]

[0169] anode

[0170] The present invention also provides an anode.

[0171] In one embodiment of the present invention, the anode comprises the anode active material described above.

[0172] In one embodiment of the present invention, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode active material.

[0173] The above-mentioned anode may be manufactured according to a conventional anode manufacturing method, except for using the above-mentioned anode active material. For example, the above-mentioned anode may be manufactured by dissolving or dispersing the components constituting the anode active material layer, namely the anode active material, a conductive material and / or a binder, etc., in a solvent to produce an anode composite, applying the anode composite to at least one surface of an anode current collector, and then drying and rolling; or by casting the anode composite onto a separate support and then laminating the film obtained by peeling it off from the support onto an anode current collector.

[0174] In one embodiment of the present invention, the positive current collector may include a highly conductive metal, and is not particularly limited as long as it allows the positive active material layer to adhere easily and is non-reactive within the voltage range of the battery. The positive current collector may be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. Additionally, the positive current collector may typically have a thickness of 3 μm to 500 μm, and may form fine irregularities on the surface of the current collector to increase the adhesion of the positive active material. It may be used in various forms, such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0175] In one embodiment of the present invention, the positive active material layer may include, together with the positive active material, a conductive material and a binder as needed. In this case, the positive active material may be included in an amount of 80% to 99% by weight, more specifically 85% to 98.5% by weight, based on the total weight of the positive active material layer, and may exhibit excellent capacity characteristics within this range.

[0176] In one embodiment of the present invention, the conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it has electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fibers; metal powder or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The conductive material may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0177] In one embodiment of the present invention, the binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and polymers in which hydrogens thereof are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above binder may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive active material layer.

[0178] In one embodiment of the present invention, the solvent may be a solvent generally used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of solvent used is sufficient to dissolve or disperse the cathode active material, conductive material, binder, and dispersant, taking into account the coating thickness of the slurry and the manufacturing yield, and to have a viscosity that can exhibit excellent thickness uniformity when coated for cathode manufacturing thereafter.

[0179]

[0180] lithium secondary battery

[0181] The present invention provides a lithium secondary battery.

[0182] In one embodiment of the present invention, the lithium secondary battery includes the anode described above.

[0183] In one embodiment of the present invention, the lithium secondary battery comprises the anode described above; a cathode; a separator interposed between the anode and the cathode; and an electrolyte. Additionally, the lithium secondary battery may optionally further comprise a battery container housing an electrode assembly of the anode, cathode, and separator described above, and a sealing member sealing the battery container.

[0184] In one embodiment of the present invention, the cathode may comprise a cathode current collector and a cathode active material layer located on the cathode current collector.

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

[0186] In one embodiment of the present invention, the negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material.

[0187] In one embodiment of the present invention, the negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and aqueous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO₂ β Examples include metal oxides capable of doping and dedoping lithium, such as (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Furthermore, the carbon material may include low-crystallinity carbon and high-crystallinity carbon. Representative examples of the above low-crystallinity carbon include soft carbon and hard carbon, and representative examples of the above high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes. The above negative electrode active material may be included in the negative electrode active material layer in an amount of 80% to 99% by weight based on the total weight of the negative electrode active material layer.

[0188] In one embodiment of the present invention, the binder of the negative electrode active material layer is a component that assists in the bonding between the conductive material, the active material, and the current collector, and can typically be added to the negative electrode active material layer in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0189] In one embodiment of the present invention, the conductive material of the negative electrode active material layer may be added to the negative electrode active material layer in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer, as a component for further improving the conductivity of the negative electrode active material. Such a conductive material is not particularly limited as long as it possesses conductivity without causing chemical changes in the battery. For example, the conductive material may be graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon; metal powders such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives.

[0190] In one embodiment of the present invention, the cathode may be manufactured by applying and drying a composition for forming a cathode active material layer, prepared by dissolving or dispersing a cathode active material and optionally a binder and a conductive material in a solvent, onto a cathode current collector, or by casting the composition for forming a cathode active material layer onto a separate support and then laminating the film obtained by peeling from the support onto a cathode current collector.

[0191] In one embodiment of the present invention, the separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. It can be used without special limitations as long as it is a separator typically used in lithium secondary batteries, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like 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, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and it may optionally be used in a single-layer or multi-layer structure.

[0192] In one embodiment of the present invention, the electrolyte may be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc., which are usable in the manufacture of a lithium secondary battery, but is not limited thereto. As a specific example, the electrolyte may include an organic solvent and a lithium salt.

[0193] In one embodiment of the present invention, the organic solvent may be used without 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 be an ester-based solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; an ether-based solvent such as dibutyl ether or tetrahydrofuran; a ketone-based solvent such as cyclohexanone; or an aromatic hydrocarbon-based solvent such as benzene or fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.

[0194] In one embodiment of the present invention, the lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, as the anion of the lithium salt, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - The lithium salt may be at least one selected from the group consisting of LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable to use the lithium salt within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0195] In one embodiment of the present invention, in addition to the electrolyte components, the electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in the electrolyte in an amount of 0.1% to 5% by weight relative to the total weight of the electrolyte.

[0196] A lithium secondary battery comprising a positive electrode active material according to one embodiment of the present invention stably exhibits excellent capacity characteristics, output characteristics, and lifespan characteristics, and is therefore useful in fields such as portable devices like mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0197] There are no specific restrictions on the external shape of the above lithium secondary battery, but it may be a cylindrical type using a can, a prismatic type, a pouch type, or a coin type.

[0198] A lithium secondary battery according to one embodiment of the present invention can be used not only as a battery cell used as a power source for a small device, but can also preferably be used as a unit cell in a medium-to-large battery module comprising a plurality of battery cells.

[0199] Accordingly, in one 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.

[0200] In one embodiment of the present invention, the battery module or battery pack may be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0201] Specific embodiments of the present invention are presented below. However, the embodiments described below are merely for the purpose of specifically illustrating or explaining the present invention and do not limit the present invention. Furthermore, details not described herein can be sufficiently technically inferred by a person skilled in the art, so their description is omitted.

[0202]

[0203] Examples

[0204]

[0205] <Example 1>

[0206] (1) Manufacturing of primary fired products

[0207] MnCO3 (Alweal), FePO4 (Yacheong), and NH4H2PO4 (Sigma Aldrich) were used as composite oxide raw materials for the cathode active material in a molar ratio of 6:4:6. V2O5 (Sigma Aldrich) and MgO (Sigma Aldrich) were added as doping element raw materials to the composite oxide raw materials, respectively, after mixing with the composite oxide raw materials, so that their molar percentages were 0.8 mol% and 1 mol% of the total transition metal contained in the mixture, and then mixed. Subsequently, Li2CO3 (Daebo) was added so that the molar ratio of lithium (Li) to the total transition metal (Me) contained in the mixture of the composite oxide raw materials and doping element raw materials (Li / Me) was 1.02, and further mixing was performed.

[0208] The above mixture was fed into a planetary bead milling device (Nanointec, NPM-1L) along with 3% by weight of sucrose (manufactured by Sigma Aldrich) based on the total weight of the mixture, and then ground and mixed to prepare the mixture. The ball milling device contains 2 kg of ZrO2 balls having a particle size of 0.3 mm.

[0209] The above mixture is dried in a spray dryer (BUCHI B-290 Mini Spray Dryer) at an inlet temperature of 170°C and an outlet temperature of 95°C, and then calcined at 700°C for 10 hours under a nitrogen atmosphere using a graphite crucible (Jungmin Industrial Co., Ltd.) to form a single layer of Li as a coating layer. 1.02 Mn 0.6 Fe 0.4 V 0.008 Mg 0.01 A primary sintered product having a composition of PO4 was manufactured.

[0210] (2) Preparation of positive electrode active material

[0211] The above primary fired product was fed into a jet milling device (manufactured by Isaac E&C, 04-626c-WC Micron Master) and ground at a pressure of 1.5 bar. Subsequently, the ground primary fired product was mixed with pitch (RX-120) using an experimental blender to prepare a mixture. The pitch was added to the total mixture at a content of 1 weight%.

[0212] The above mixture was calcined at 750°C for 5 hours under a nitrogen atmosphere using a graphite crucible (manufactured by Jungmin Industrial Co., Ltd.) to produce an olivine-structured positive electrode active material in which a double layer of a first layer containing an amorphous carbon-based material and a second layer containing a crystalline carbon-based material was formed as a coating layer.

[0213]

[0214] <Example 2>

[0215] The product was prepared in the same manner as in Example 1, except that V2O5 and MgO were each mixed with the above-mentioned composite oxide raw material as doping element raw materials and added such that their molar amounts were 1.1 mol% and 1 mol% with respect to the total transition metal contained in the mixture, and polyvinylpyrrolidone (PVP, Thermo Fischer Scientific) was added at 3 wt% instead of sucrose.

[0216]

[0217] <Comparative Example 1>

[0218] It was manufactured in the same manner as Example 1, except that a single layer was formed instead of a double layer as a coating layer.

[0219]

[0220] <Comparative Example 2>

[0221] It was manufactured in the same manner as Example 1, except that sucrose was added at 1 weight% instead of pitch.

[0222]

[0223] <Comparative Example 3>

[0224] It was prepared in the same manner as Example 1, except that V2O5 was mixed with the above-mentioned complex oxide raw material as a doping element raw material and added so that the molar amount was 2 mol% relative to the total transition metal contained in the mixture.

[0225]

[0226] <Comparative Example 4>

[0227] It was prepared in the same manner as Example 1, except that doping and coating were not performed.

[0228]

[0229] Experimental Example

[0230]

[0231] <Experimental Example 1: PF Factor Analysis>

[0232] (1) Sphericity analysis

[0233] The circularity of the positive electrode active material prepared in the above examples and comparative examples was derived through the following [Equation 2].

[0234] [Equation 2]

[0235] Circularity = ( 4π × Area ) / Perimeter 2

[0236] In Equation 2 above, the area and perimeter refer to the area and perimeter of the positive electrode active material particles. These values ​​are derived from the area and perimeter of the particles by using the image analysis program SEM-DX on the two-dimensionalized images obtained by scanning electron microscope (SEM, JEOL JSM-7800F prime) of the particles as shown in [Fig. 1] and [Fig. 2]. Specifically, they were derived by analyzing three or more SEM images.

[0237] (2) Particle size analysis

[0238] Particle size (D) corresponding to 50% of the cumulative volume distribution of the cathode active material prepared in the above examples and comparative examples 50 The particle size was measured using a particle size analyzer (Malvern, Mastersizer 3000). Specifically, the cathode active material was introduced into the analyzer and irradiated with ultrasound of approximately 28 kHz at an output of 60 W, and then the particle size was calculated based on the volumetric cumulative distribution in the measuring device.

[0239] (3) BET specific surface area analysis

[0240] The BET specific surface area of ​​the cathode active material prepared in the above examples and comparative examples is the BET specific surface area of ​​the cathode active material measured by the BET method, specifically calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using BELSORP-mini II from Microtrac BEL.

[0241] (4) PF factor analysis

[0242] The PF factor of the cathode active material prepared according to the above examples and comparative examples is a value expressed by the following [Equation 1], and the sphericity of the cathode active material derived above, D 50 It is a value calculated using the BET specific surface area and with the units removed.

[0243] [Equation 1]

[0244] PF factor = [ (A × B) / C] × 100

[0245] In the above Equation 1,

[0246] A is the degree of sphericity of the above lithium composite oxide particles, and

[0247] B is the average particle size (μm) of the lithium composite oxide particles, and

[0248] C is the BET specific surface area (m²) of the lithium composite oxide particles. 2 / g) is.

[0249] The sphericity, average particle size, BET specific surface area, and PF factor derived through the above process are shown in [Table 1] below.

[0250]

[0251] Sphericity Average particle size (㎛) BET specific surface area (m²) 2 / g)PF factor Example 10.53 10.36 15.8 0 1.21 Example 20.52 90.34 16.39 1.10 Comparative Example 10.48 60.32 19.0 10.82 Comparative Example 20.48 30.33 18.52 0.86 Comparative Example 30.52 10.32 16.53 1.00 Comparative Example 40.50 30.35 17.7 0 0.99

[0252]

[0253] <Experimental Example 2: Evaluation of Mn-O Bond Length>

[0254] The Mn-O bond lengths of the cathode active materials prepared in the above examples and comparative examples were measured using XPS (X-ray photoelectron spectroscopy, Thermo Fischer Scientific, Nexsa). To measure the Mn-O lengths, the active material samples were filled into a powder holder, the holder was secured onto copper foil using carbon tape, and then loaded into the measurement equipment. After loading, the loadlock inside the equipment was evacuated, and measurements were performed according to the K-Alpha standard operating procedure (SOP-0524-ok). A survey scan was performed on the sample surface, followed by a qualitative analysis. Based on the results of the qualitative analysis, three points within the sample were selected, and a narrow scan for each element was performed at each of these points to conduct a quantitative analysis. To derive the bonding states between each element from the results of the quantitative analysis, P 2p PO4 3- The binding energy in the quantitative analysis results was corrected based on the binding energy of 133.6 eV. Subsequently, the Mn-O length was derived from the corrected Mn-O binding energy using Density Functional Theory (DFT). The average Mn-O bond length derived by the above method is shown in [Table 2] below.

[0255]

[0256] Average Mn-O bond length (Å) Example 1 2.50 Example 2 2.51 Comparative Example 12.46 Comparative Example 22.46 Comparative Example 3 2.55 Comparative Example 4 2.48

[0257]

[0258] As shown in [Table 2] above, the Mn-O bond length of Comparative Example 4, which did not undergo doping or coating, differs from the Examples and Comparative Examples that underwent doping or coating, and it can be confirmed that the value changes depending on the presence or content of doping or coating in each Example and Comparative Example. Accordingly, it can be seen that the Mn-O bond length of the cathode active material can satisfy the target range by adjusting the conditions within the manufacturing method.

[0259] Furthermore, as shown in [Table 1] above, it can be confirmed that not only the Mn-O bond length but also characteristics such as sphericity, specific surface area, and PF factor change depending on the conditions within the manufacturing method.

[0260]

[0261] <Experimental Example 3: Evaluation of Dosage Characteristics>

[0262] (1) Manufacturing of batteries

[0263] Using the positive active materials prepared in the examples and comparative examples, a positive slurry was prepared by mixing each of the positive active materials, a carbon black conductive material, and a polyvinylidene fluoride (PVDF) binder in a ratio of 90:5:5 in an N-methylpyrrolidone (NMP) solvent (manufactured by Taisho Chemical Co., Ltd.). The positive slurry was applied to one side of an aluminum current collector (manufactured by Tianjin Co., Ltd.), dried at 130°C, and rolled to produce a positive electrode.

[0264] A lithium metal electrode (manufactured by Welcos) was used as the negative electrode, and an electrode assembly was manufactured by interposing a porous polyethylene separator (manufactured by LG Chem) between the positive electrode and the negative electrode. After placing the electrode assembly inside a battery case, an electrolyte was injected into the case to manufacture a half-cell. At this time, the electrolyte was prepared by adding 2 wt% of vinylene carbonate (VC) to an organic solvent mixed with ethylene carbonate (EC) (manufactured by GTHR), ethyl methyl carbonate (EMC) (manufactured by GTHR), and diethyl carbonate (DEC) (manufactured by GTHR) in a volume ratio of 1:2:1, and dissolving 1.0 M LiPF6 therein.

[0265] (2) Evaluation of capacity characteristics

[0266] For each half-cell containing the positive active material prepared in the examples and comparative examples prepared in this manner, charging was performed at 25°C in CC-CV mode at a rate of 0.1 C-rate until it reached 4.25 V, and then discharging was performed at a rate of 0.1 C-rate until it reached 2.5 V. The initial discharge capacity was measured and is shown in [Table 3] below.

[0267]

[0268] <Experimental Example 4: Evaluation of Elution Amount>

[0269] For each battery containing the positive electrode active material prepared in the examples and comparative examples prepared as described above, activation was performed by charging at 45°C in CC-CV mode at a rate of 0.1 C-rate until it reached 4.2 V. Subsequently, charging in CC / CV mode at a rate of 0.5 C-rate until it reached 4.2 V, followed by discharging in CC mode at a rate of 1 C-rate until it reached 2.5 V, was defined as one cycle. After 200 cycles and 400 cycles, respectively, the batteries were disassembled, and the leached Mn and Fe leached amounts were evaluated through ICP (Inductively Coupled Plasma) (iCAP-PRO, Thermo Fischer Scientific). At this time, the above-mentioned elution amount was measured after disassembling the battery and storing it in a sealed solution for 4 weeks in 4 mL of an electrolyte prepared by dissolving 1.0 M LiPF6 in an organic solvent mixed with ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7, and evaluated using the metal deposited on the negative electrode. The elution amount evaluated in the above manner is shown in [Table 3] below.

[0270]

[0271] Initial Discharge Capacity (mA·h / g) 200 Cycle Elution Amount (ppm) 400 Cycle Elution Amount (ppm) MnFe MnFe Example 1 148.165910215 Example 2 150.7861112319 Comparative Example 1 145.81211518224 Comparative Example 2 148.11071315621 Comparative Example 3 148.888819626 Comparative Example 4 143.11302223534

[0272]

[0273] As shown in [Table 1] to [Table 3] above, when a battery is manufactured using the positive active material of Example 1 and Example 2, which contains manganese and doping elements, has an average Mn-O (manganese-oxygen) bond length of less than 2.55 Å, and has a particle sphericity of 0.49 to 0.8, it can be confirmed that excellent capacity and lifespan characteristics are exhibited.

[0274] In the case of the positive active materials of Comparative Examples 1 and 2, the average Mn-O (manganese-oxygen) bond length is less than 2.55 Å, but the degree of sphericity of the particles is outside the range of 0.49 to 0.8. When compared to Examples 1 and 2, which satisfy the range of sphericity, it can be seen that the amount of leaching from the battery can be controlled when the degree of sphericity within the above range is satisfied.

[0275] In addition, Comparative Example 1 includes a coating layer consisting of a single layer, and in the case of Comparative Example 2, the second layer includes an amorphous carbon-based material rather than a crystalline carbon-based material, so the PF factor is less than 1. It can be seen that, as with the cathode active material of Example 1 and Example 2, the coating layer must include a first layer containing an amorphous carbon-based material and a second layer containing a crystalline carbon-based material to show a PF factor of 1 or more.

[0276] In particular, seeing that Comparative Example 1, which includes a single-layer coating layer, exhibits a lower discharge capacity compared to the batteries manufactured using the positive active materials of Examples 1 and 2, which include the first and second layers, it can be seen that the capacity characteristics of the battery can be further improved if the coating layer includes the first and second layers.

[0277] Furthermore, when comparing the leaching amount of a battery manufactured using the positive active material of Example 1 and Example 2, which has a PF factor of 1 or more, and a battery manufactured using the positive active material of Comparative Example 1 and Comparative Example 2, which has a PF factor of less than 1, it can be seen that the PF factor must be 1 or more to effectively improve the leaching of metal generated during battery operation.

[0278] Accordingly, it can be seen that the PF factor, which represents the correlation between the shape of the positive electrode active material particles and the amount of metal leaching that occurs during battery operation, is an indicator that can effectively evaluate the degree of metal leaching in a battery containing the positive electrode active material.

[0279] In addition, when a battery manufactured using the positive active material of Comparative Example 3, in which the content of an element with an oxidation number of 3 or less in the doping element falls outside the range of 20 mol% to 100 mol% based on the total molar amount of the element in the doping element, shows a decent amount of Mn and Fe leaching at 200 cycles, but the amount of leaching increased sharply at 400 cycles, it can be seen that Examples 1 and 2, in which the content of an element with an oxidation number of 3 or less in the doping element satisfies the range of 20 mol% to 100 mol% based on the total molar amount of the element in the doping element, can continuously maintain the effect of preventing metal leaching even during long-term battery operation.

[0280] Furthermore, the battery manufactured using the positive active material of Comparative Example 4, which does not contain doping elements, exhibits the lowest discharge capacity and the highest leaching amounts of Mn and Fe, indicating that the capacity and lifespan characteristics of the battery can be improved only if the positive active material contains doping elements. In addition, it can be seen that the characteristics of Examples 1 and 2, such as Mn-O bond length, sphericity, specific surface area, and PF factor, have the most suitable range for improving battery performance.

[0281] Therefore, it can be seen that when a battery is manufactured using the positive active material of Example 1 and Example 2, which contains manganese and doping elements, has an average Mn-O (manganese-oxygen) bond length of less than 2.55 Å, and has a particle sphericity of 0.49 to 0.8, not only the capacity characteristics of the battery but also the problem of metal leaching within the battery can be improved, and thus the lifespan characteristics can also be improved. Furthermore, it can be seen that when a positive active material having a PF factor of 1 or more, which represents the correlation between the shape of the positive active material particles and the amount of metal leaching occurring during battery operation, is used in the battery, or when a coating layer comprising a first layer containing an amorphous carbon-based material and a second layer containing a crystalline carbon-based material is formed, the capacity characteristics and the improvement of the metal leaching are more effectively observed.

[0282]

[0283] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

Claims

As a positive electrode active material comprising lithium composite oxide particles, The above lithium composite oxide contains manganese and doping elements, and The average Mn-O (manganese-oxygen) bond length in the above lithium composite oxide is less than 2.55 Å, and The degree of sphericity of the lithium composite oxide particles is 0.49 to 0.8, Positive active material. In claim 1, The content of the doping element in the lithium composite oxide is 0.5 mol% to 5 mol% based on the total moles of the transition metal in the lithium composite oxide. Positive active material. In claim 1, The above doping element is selected from the group consisting of V, Al, Ni, Co, Mg, Nb, Mo, W, Ti, Sr, Zr, B, Y, Ru, Rh, Pd, Pt, Zn and combinations thereof, Positive active material. In claim 1, The content of an element having an oxidation number of 3 or less within the doping element is 20 mol% to 100 mol% based on the total moles of the elements within the doping element. Positive active material. In claim 1, The above lithium composite oxide is one having a PF factor of 1 or more, represented by the following [Formula 1], Positive active material. [Equation 1] PF factor = [ (A × B) / C] × 100 In the above Equation 1, A is the degree of sphericity of the above lithium composite oxide particles, and B is the average particle size (μm) of the lithium composite oxide particles, and C is the BET specific surface area (m²) of the lithium composite oxide particles. 2 / g) is. In claim 1, The above lithium composite oxide comprises a carbon coating layer, Positive active material. In claim 6, The carbon coating layer has a layered structure including a first layer and a second layer, and The first layer above comprises an amorphous carbon-based material, and The above second layer comprises a crystalline carbon-based material, Positive active material. In claim 6, The carbon content in the coating layer is 1% to 10% by weight based on the total weight of the lithium composite oxide. Positive active material. In claim 1, The above lithium composite oxide comprises a lithium iron phosphate-based compound, Positive active material. In claim 1, The above lithium composite oxide is represented by the following [Chemical Formula 1], Positive active material. [Chemical Formula 1] Li 1+a Fe 1-x-y Mn x M y PO4 In the above chemical formula 1, The above M is selected from the group consisting of V, Al, Ni, Co, Mg, Nb, Mo, W, Ti, Sr, Zr, B, Y, Ru, Rh, Pd, Pt, Zn and combinations thereof, and The above a, x, and y are each -0.1≤a≤0.1, 0<x≤0.7, and 0≤y≤0.

1. A method for manufacturing a positive electrode active material comprising a lithium composite oxide, The above lithium composite oxide contains manganese and doping elements, and The average Mn-O (manganese-oxygen) bond length in the above lithium composite oxide is less than 2.55 Å, and The degree of sphericity of the above lithium composite oxide particles is 0.49 to 0.8, and The above manufacturing method comprises the step of mixing a complex oxide raw material containing manganese, a doping element raw material, and a lithium raw material, and then calcining. Method for manufacturing positive electrode active material. In claim 11, The above firing is performed at 500℃ to 900℃ for 5 to 15 hours, Method for manufacturing positive electrode active material. In claim 11, The step of mixing the above-mentioned complex oxide raw material containing manganese, the doping element raw material, and the lithium raw material, and then calcining, (1) A step of mixing a complex oxide raw material containing manganese, a doping element raw material, and a lithium raw material; (2) A step of mixing the above mixture with the carbon coating raw material and then firing; including, Method for manufacturing positive electrode active material. In claim 13, The above step (2) is, (S1) A step of mixing the above mixture with the first carbon coating raw material and then firing to produce a first fired product; and (S2) A step of mixing the above first fired product with the second carbon coating raw material and then firing; including, Method for manufacturing positive electrode active material. In claim 14, The mixing in the above step (S2) is a dry mixing, Method for manufacturing positive electrode active material.

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