Cathode active material, method for manufacturing same, and cathode and lithium secondary battery comprising same

Abstract

The present invention relates to a cathode active material capable of enhancing the performance of a lithium secondary battery, a method for manufacturing same, and a cathode and a lithium secondary battery comprising same, the anode active material comprising: a lithium composite transition metal oxide including both a Li2MnO3 phase and a LiMO2 (where, M is an element of Ni, Mn, or a combination thereof); and a coating layer containing a compound composed of vanadium (V) and oxygen (O) on the lithium composite transition metal oxide, wherein the lithium composite transition metal oxide has a composition represented by chemical formula 1 described in the present specification, and the content of vanadium (V) contained in the coating layer is 90 ppm to 2,500 ppm with respect to the total weight of the lithium composite transition metal oxide.

Description

Positive electrode active material, method for producing the same, and positive electrode and lithium secondary battery including the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0116360, filed September 1, 2023, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a positive electrode active material, a method for producing the same, and a positive electrode and a lithium secondary battery including the same.

[0005]

[0006] Lithium secondary batteries are composed of four major components: a cathode, an anode, a separator, and an electrolyte. Among these, the cathode active material contained in the cathode plays a significant role in determining the battery's capacity, output, and lifespan. For lithium secondary batteries to achieve high energy density, output, and lifespan, improving the performance of the cathode active material is essential. Consequently, extensive research has been conducted recently to develop high-performance cathode active materials.

[0007] Li-rich layered oxide, a type of cathode active material, is a mixed phase of Li2MnO3 phase and LiMO2 (where M is an element including Ni, Mn, Co or a combination thereof) phase, and has a high operating voltage (>3.5 V vs. Li / Li). + ) has the characteristic of providing a very large capacity of 250 mAh / g. Therefore, the lithium-excess oxide is attracting attention as a high-capacity cathode active material.

[0008] However, the lithium-excess oxide has problems that arise due to its structural characteristic of having two phases mixed together. Specifically, when a battery containing the lithium-excess oxide is operated under high voltage, there is a problem that irreversible capacity loss occurs in the first formation process, resulting in reduced efficiency, and during charge / discharge cycles, the layered structure changes to a spinel structure and then to a rock salt structure, resulting in voltage fading, increased resistance, and the generation of O2 gas.

[0009] Additionally, the rising price of cobalt, a raw material used in lithium-excess oxides, is also emerging as a significant issue. The price of cobalt is expected to continue to rise, necessitating the development of cathode active materials with reduced cobalt content.

[0010] Therefore, it is necessary to secure a technology to improve the capacity characteristics, resistance characteristics, life characteristics and economic feasibility of the lithium-excess oxide.

[0011]

[0012] [Prior Art Literature]

[0013] [Patent Document]

[0014] (Patent Document 1) Korean Patent Publication No. 10-2014-0025102

[0015]

[0016] The present invention is intended to solve the above problems, and to provide a cathode active material and a method for manufacturing the same, which can improve the capacity characteristics, resistance characteristics, and life characteristics of a battery and reduce costs.

[0017] In addition, the present invention seeks to provide a cathode and secondary battery having excellent capacity characteristics and resistance characteristics, a relatively low resistance increase rate, and being economical, including the cathode active material as described above.

[0018]

[0019] (1) The present invention provides a cathode active material comprising a lithium composite transition metal oxide simultaneously including a Li2MnO3 phase and a LiMO2 (wherein M is an element including Ni, Mn or a combination thereof) phase; and a coating layer including a compound composed of vanadium (V) and oxygen (O) on the lithium composite transition metal oxide; wherein the lithium composite transition metal oxide has a composition represented by the following chemical formula 1, and the content of vanadium (V) included in the coating layer is 90 ppm to 2,500 ppm based on the total weight of the lithium composite transition metal oxide.

[0020] [Chemical Formula 1]

[0021] Li 1+x Ni a Mn b M 1 c O2

[0022] In the above chemical formula 1, M 1 is at least one selected from the group consisting of Zr, Al, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, Na and Pt, and 0 <x≤0.5, 0<a≤0.5, 0.5≤b<1, 0≤c≤0.01이다.

[0023] (2) The present invention provides a positive electrode active material in the above (1), wherein the lithium composite transition metal oxide has a composition represented by the following chemical formula 2.

[0024] [Chemical Formula 2]

[0025] αLi2Mn (1-p) M 2 p O3·βLiNi q Mn r M 2 s O2

[0026] In the above chemical formula 2, M 2is at least one selected from the group consisting of Zr, Al, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, Na, and Pt, and 0<α≤0.5, 0<β≤1, 0≤p≤0.01, 0 <q≤0.8, 0<r≤0.8, 0≤s≤0.01이고, q+r+s=1이다.

[0027] (3) The present invention provides a positive electrode active material in (1) or (2) above, wherein b is 0.5 to 0.75.

[0028] (4) The present invention provides a positive electrode active material according to any one of the above (1) to (3), wherein the coating layer includes V2O5.

[0029] (5) The present invention provides a positive electrode active material in any one of the above (1) to (4), wherein the content of the coating layer is 0.01 part by weight to 0.1 part by weight with respect to 100 parts by weight of the lithium composite transition metal oxide.

[0030] (6) In any one of the above (1) to (5), the positive electrode active material has an average particle diameter (D 50 ) provides a positive electrode active material having a diameter of 1.0㎛ to 15.0㎛.

[0031] (7) The present invention provides a method for producing a positive electrode active material according to claim 1, comprising the steps of: (A) mixing a composite transition metal hydroxide and a lithium (Li)-containing raw material and calcining them to produce a lithium composite transition metal oxide; and (B) mixing the lithium composite transition metal oxide and a vanadium (V)-containing raw material and then heat-treating them to form a coating layer comprising a compound composed of vanadium (V) and oxygen (O) on the lithium composite transition metal oxide; wherein the heat treatment is performed at a temperature of 400°C to 600°C.

[0032] (8) The present invention provides a method for manufacturing a positive electrode active material in the above (7), wherein the vanadium (V)-containing raw material is V2O5.

[0033] (9) The present invention provides a method for producing a positive electrode active material, wherein, in the above (7) or (8), the vanadium (V)-containing raw material is mixed so that the vanadium (V) content is 100 ppm to 2,500 ppm with respect to the total weight of the lithium composite transition metal oxide.

[0034] (10) The present invention provides a method for manufacturing a positive electrode active material, wherein in any one of the above (7) to (9), the heat treatment in step (B) is performed under an oxygen atmosphere.

[0035] (11) The present invention provides a method for manufacturing a positive electrode active material, wherein the coating layer comprises V2O5 in any one of the above (7) to (10).

[0036] (12) The present invention provides a positive electrode comprising a positive electrode active material according to any one of (1) to (6).

[0037] (13) The present invention provides a lithium secondary battery including a positive electrode according to (12) above.

[0038]

[0039] The cathode active material of the present invention comprises a lithium composite transition metal oxide having a composition represented by the chemical formula 1 described herein, which simultaneously includes a Li2MnO3 phase and a LiMO2 (wherein M is an element including Ni, Mn or a combination thereof) phase; and a coating layer including a compound composed of vanadium (V) and oxygen (O) on the lithium composite transition metal oxide; wherein the content of vanadium (V) included in the coating layer satisfies a specific numerical range, thereby implementing the effects of improving lithium ion absorption and release performance, electrical conductivity and structural stability. Accordingly, the performance of the cathode active material, the cathode including the cathode and the lithium secondary battery, for example, capacity characteristics, resistance characteristics, life characteristics, etc., can be improved, and there is the effect of reducing cost.

[0040] In addition, according to the method for manufacturing a positive electrode active material of the present invention, the positive electrode active material described above can be effectively manufactured.

[0041]

[0042] Figure 1 shows XRD data of each of the positive electrode active materials manufactured in Examples 1 and 2.

[0043]

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

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

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

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

[0048] In this specification, 'average particle diameter (D 50 )' can be defined as the particle size corresponding to 50% of the volume cumulative distribution in the particle size distribution curve (graph curve of particle size distribution). The above average particle size is calculated by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., S3500 of Microtrac), and measuring the difference in diffraction pattern according to particle size when the particles pass through the laser beam, and calculating the particle diameter at the point where it becomes 50% of the volume cumulative distribution according to the particle size in the measuring device, thereby obtaining D 50 can be measured.

[0049]

[0050] positive electrode active material

[0051] Hereinafter, the positive electrode active material according to the present invention will be described.

[0052] The cathode active material according to the present invention comprises a lithium composite transition metal oxide including both a Li2MnO3 phase and a LiMO2 (wherein M is an element including Ni, Mn or a combination thereof) phase; and a coating layer including a compound composed of vanadium (V) and oxygen (O) on the lithium composite transition metal oxide; wherein the lithium composite transition metal oxide has a composition represented by the following chemical formula 1, and the content of vanadium (V) included in the coating layer is 90 ppm to 2,500 ppm based on the total weight of the lithium composite transition metal oxide.

[0053] [Chemical Formula 1]

[0054] Li 1+x Ni a Mn b M 1 c O2

[0055] In the above chemical formula 1,

[0056] M 1 is at least one selected from the group consisting of Zr, Al, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, Na and Pt,

[0057] 0 <x≤0.5, 0<a≤0.5, 0.5≤b<1, 0≤c≤0.01이다.

[0058] Lithium-rich layered oxide, a type of positive electrode active material, is a mixed phase in which Li2MnO3 phase and LiMO2 phase (where M is an element including Ni, Mn, Co or a combination thereof) phase are mixed. When Co is included, Co acts as an impurity, which reduces the capacity characteristics of a secondary battery including lithium-rich layered oxide and has the problem of high manufacturing costs.

[0059] The present inventors have conducted repeated research to solve the above problems and have confirmed that by including a coating layer containing a compound composed of vanadium (V) and oxygen (O) instead of Co in the lithium-excess oxide, lithium ion absorption and release performance can be improved, thereby improving capacity characteristics, resistance characteristics can be improved by increasing electrical conductivity, and lifespan characteristics can be improved by enhancing structural stability. Accordingly, they have found that the capacity characteristics, resistance characteristics, lifespan characteristics, and economic feasibility of existing lithium-excess oxides can be improved, and the present invention has been completed.

[0060] Above M 1 is a doping element, specifically the above M 1 It may be at least one selected from the group consisting of Zr, Al, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, Na and Pt. The above M 1 Although it is not essential, if included in an appropriate amount, the particle shape of the positive electrode active material can be improved and the stability of the crystal structure can be enhanced.

[0061] The above x may be greater than 0, 0.1 or more, 0.2 or more, or 0.3 or more, and may be 0.4 or less, or 0.5 or less. When x satisfies the above range, the Li2MnO3 phase and the LiMO2 phase are formed in an appropriate ratio, so that high-capacity characteristics can be realized.

[0062] The above a may be greater than 0, greater than or equal to 0.2, or greater than or equal to 0.3, and may be less than or equal to 0.4, or less than or equal to 0.5. When a satisfies the above range, high energy density may be exhibited, thereby realizing high-capacity characteristics.

[0063] The above b may be 0.5 or more, or 0.55 or more, and may be 0.6 or less, 0.7 or less, 0.8 or less, 0.9 or less, or less than 1. When b satisfies the above range, high energy density is exhibited, so that high-capacity characteristics can be realized. In particular, when b is 0.5 to 0.75, the Li2MnO3 phase and the LiMO2 phase are formed in an appropriate ratio, so that high-capacity characteristics can be realized.

[0064] The above c may be 0 or more, or 0.003 or more, and may be 0.005 or less, 0.007 or less, or 0.01 or less. When c satisfies the above range, the particle shape of the positive electrode active material may be improved and the stability of the crystal structure may be enhanced.

[0065] The above lithium composite transition metal oxide may not contain cobalt (Co). In this case, there is a cost-saving effect and the performance of a lithium secondary battery can be improved without containing cobalt.

[0066] According to the present invention, the content of vanadium (V) included in the coating layer may be 90 ppm to 2,500 ppm based on the total weight of the lithium composite transition metal oxide. Specifically, the content of vanadium (V) included in the coating layer may be 90 ppm or more, 950 ppm or less, 1,950 ppm or less, 2,000 ppm or less, or 2,500 ppm or less based on the total weight of the lithium composite transition metal oxide. When the content of vanadium (V) is within the above range, the coating layer formed on the lithium composite transition metal oxide improves electrical conductivity and reduces side reactions between the positive electrode active material and the electrolyte, thereby improving capacity characteristics, resistance characteristics, and life characteristics of a battery including the positive electrode active material. When the content of the vanadium (V) is less than 90 ppm, the coating layer is not sufficiently formed on the lithium composite transition metal oxide, resulting in poor electrical conductivity and poor lifespan characteristics due to the failure to reduce side reactions between the positive electrode active material and the electrolyte. When the content of the vanadium (V) exceeds 2,500 ppm, the coating layer is formed excessively and unevenly, resulting in resistance and poor lifespan characteristics.

[0067]

[0068] The coating layer comprising the compound composed of vanadium (V) and oxygen (O) may be in the form of partially covering at least a portion of the lithium composite transition metal oxide, i.e., a region of the lithium composite transition metal oxide, or covering the entire region. The shape of the coating layer may be an island type, a film type, or a combination thereof, but the shape of the coating layer is not limited thereto.

[0069] The structure of the coating layer including the compound composed of the above vanadium (V) and oxygen (O) may include a layered structure, an olivine structure, an orthorhombic structure, a monoclinic structure, etc., but does not include a spinel structure.

[0070]

[0071] According to one embodiment of the present invention, the lithium composite transition metal oxide may have a composition represented by the following chemical formula 2.

[0072] [Chemical Formula 2]

[0073] αLi2Mn (1-p) M 2 p O3·βLiNi q Mn r M 2 s O2

[0074] In the above chemical formula 2,

[0075] M 2 is at least one selected from the group consisting of Zr, Al, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, Na and Pt,

[0076] 0<α≤0.5, 0<β≤1, 0≤p≤0.01, 0 <q≤0.8, 0<r≤0.8, 0≤s≤0.01이고, q+r+s=1이다.

[0077] Above M 2 is a doping element, specifically the above M 2 M may be at least one selected from the group consisting of Zr, Al, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, Na and Pt. 2 Although not necessarily included, if included in an appropriate amount, the particle shape of the positive electrode active material can be improved and the stability of the crystal structure can be enhanced.

[0078] The above α refers to the molar ratio of Li2MnO3 phase in the lithium composite transition metal oxide, and may be greater than 0, 0.4 or more, or 0.43 or more, and may be 0.47 or less, 0.48 or less, or 0.5 or less. When α satisfies the above range, a high energy density per unit volume is exhibited, so that high-capacity characteristics can be realized. In addition, the capacity characteristics, resistance characteristics, and life characteristics of the battery including the positive electrode active material can be further improved.

[0079] The above 1-p is the molar ratio of Mn among all metals excluding lithium in Li2MnO3.

[0080] The above p is M among all metals except lithium on Li2MnO3 2 The molar ratio may be 0 or more, 0.002 or more, 0.004 or more, or 0.006 or more, and 0.008 or less, or 0.01 or less. M 2 Although not essential, if included in an appropriate amount, the particle shape of the positive electrode active material can be improved and the stability of the crystal structure can be enhanced. In addition, it can exhibit high energy density and realize high-capacity characteristics.

[0081] The above β refers to the molar ratio of LiMO2 phase in the lithium composite transition metal oxide, and may be greater than 0, 0.2 or more, or 0.4 or more, and may be 0.6 or less, 0.8 or less, or 1 or less. When β satisfies the above range, a high energy density per unit volume can be exhibited, thereby realizing high-capacity characteristics. In addition, the capacity characteristics, resistance characteristics, and life characteristics of a battery including a positive electrode active material can be further improved.

[0082] The above q is the molar ratio of nickel (Ni) among the total metals excluding lithium in the LiMO2 phase, and may be greater than 0, 0.4 or more, or 0.5 or more, and may be 0.6 or less, 0.7 or less, or 0.8 or less. When q satisfies the above range, a high energy density is exhibited, and high-capacity characteristics can be realized.

[0083] The above r is the molar ratio of manganese (Mn) among all metals excluding lithium in the LiMO2 phase, and may be greater than 0, 0.3 or more, or 0.4 or more, and may be 0.5 or less, 0.6 or less, or 0.8 or less. When r satisfies the above range, a high energy density is exhibited, and high-capacity characteristics can be realized.

[0084] The above s is M among all metals except lithium in LiMO2 2 The molar ratio may be 0 or more, 0.002 or more, 0.004 or more, or 0.006 or more, and 0.008 or less, or 0.01 or less. M 2 Although not necessarily included, if included in an appropriate amount, the particle shape of the positive electrode active material can be improved and the stability of the crystal structure can be enhanced.

[0085] In the above chemical formula 2, q, r, and s are q+r+s=1.

[0086]

[0087] According to one embodiment of the present invention, the coating layer may include V2O5. In this case, structural stability can be improved, structural changes of the particles can be minimized, and life characteristics can be improved. Specifically, the coating layer may be composed solely of V2O5, or may be a mixture of V2O5 and LiMn2O4.

[0088]

[0089] According to one embodiment of the present invention, the content of the coating layer may be 0.01 part by weight or more, 0.015 part by weight or more, or 0.017 part by weight or more, and may be 0.018 part by weight or less, 0.02 part by weight or less, 0.05 part by weight or less, or 0.1 part by weight or less, based on 100 parts by weight of the lithium composite transition metal oxide. When the content of the coating layer is within the above range, the energy density per volume of the positive electrode active material is maintained, and lithium ion absorption and release performance, electrical conductivity, and structural stability are improved, thereby improving the capacity characteristics, resistance characteristics, and life characteristics of a battery including the positive electrode active material.

[0090]

[0091] According to one embodiment of the present invention, the positive electrode active material has an average particle diameter (D 50 ) may be 1.0㎛ or more, 2.0㎛ or more, 3.0㎛ or more, or 4.0㎛ or more, and may be 10.0㎛ or less, 11.0㎛ or less, 12.0㎛ or less, 13.0㎛ or less, 14.0㎛ or less, or 15.0㎛ or less. The average particle diameter (D 50 ) is within the above range, excellent electrode density can be achieved and structural stability can be improved.

[0092]

[0093] Method for manufacturing positive electrode active material

[0094] Next, a method for manufacturing the positive electrode active material of the present invention will be described. The method for manufacturing the positive electrode active material of the present invention is a method for manufacturing the positive electrode active material according to the present invention.

[0095]

[0096] (A) a step of mixing a composite transition metal hydroxide and a lithium (Li)-containing raw material and calcining them to produce a lithium composite transition metal oxide; and (B) a step of mixing the lithium composite transition metal oxide and a vanadium (V)-containing raw material and then heat-treating them to form a coating layer including a compound composed of vanadium (V) and oxygen (O) on the lithium composite transition metal oxide.

[0097] According to the present invention described above, the type of raw material, the mixing ratio of raw materials, the firing temperature, the firing and heat treatment temperature increase rate, the firing and heat treatment time, etc. can be appropriately controlled to manufacture the product.

[0098]

[0099] Hereinafter, each step of the present invention will be described in detail.

[0100] (A) Step

[0101] It includes the step (A) of producing a lithium composite transition metal oxide by mixing and calcining a composite transition metal hydroxide and a lithium (Li)-containing raw material.

[0102] The above complex transition metal hydroxide can be produced through a coprecipitation reaction by introducing a complex transition metal aqueous solution, an ammonium cation complex, and a basic compound into a reactor.

[0103] The above-mentioned complex transition metal aqueous solution can be prepared by dissolving a transition metal-containing raw material in a solvent such as water. For example, it can be prepared by dissolving a nickel (Ni)-containing raw material and a manganese (Mn)-containing raw material in water. In addition, if necessary, the above-mentioned complex transition metal aqueous solution can further include a metal-containing raw material.

[0104] The above nickel (Ni) containing raw material is NiSO 4,At least one selected from the group consisting of NiO, Ni(OH)2, NiOㆍOH, NiCO3ㆍ2Ni(OH)2ㆍ4H2O, NiC2O4ㆍ2H2O, Ni(NO3)2ㆍ6H2O, fatty acid nickel, and nickel halides may be used, and a mixture of one or two or more of these may be used. Considering the strong base used to control pH during the coprecipitation reaction, specifically, NiSO4 may be used.

[0105] The above manganese (Mn)-containing raw material may be at least one selected from the group consisting of MnSO4, MnCO3, Mn2O3, MnO2, Mn3O4, Mn(NO3)2, manganese acetate, manganese dicarboxylate, manganese citrate, manganese salts of fatty acid manganese, oxyhydroxides, and halides of manganese chloride, and a mixture of one or two or more of these may be used. Considering the strong base used to control pH during the coprecipitation reaction, specifically, MnSO4 may be used.

[0106] Nickel (Ni)-containing raw materials and manganese (Mn)-containing raw materials can be used in appropriate amounts considering the content of each metal element in the composite transition metal hydroxide being manufactured.

[0107] Meanwhile, the ammonium cation complex forming agent may include at least one compound selected from the group consisting of NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and NH4CO3, and may be introduced into the reactor in the form of a solution in which the compound is dissolved in a solvent. At this time, as the solvent, water or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water may be used.

[0108] The basic compound may be at least one compound selected from the group consisting of NaOH, KOH, and Ca(OH)2, and may be introduced into the reactor in the form of a solution in which the compound is dissolved in a solvent. At this time, the solvent may be water, or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water.

[0109] When a complex transition metal aqueous solution, an ammonium cation complex forming agent, and a basic compound are introduced into a reactor as described above, precursor particles in the form of a complex transition metal hydroxide are generated due to a coprecipitation reaction between the transition metal ions in the complex transition metal aqueous solution and the hydroxide ions of the basic compound.

[0110] The above co-precipitation reaction may be carried out for 50 to 90 hours. In this time range, the crystallinity of the precursor particles is controlled to a sufficient degree.

[0111] At this time, the basic compound can be added in an amount such that the pH of the reaction solution becomes within the desired range.

[0112] Once the precursor particles are formed by the above method, the particles are separated from the reaction solution to obtain a complex transition metal hydroxide. Specifically, the reaction solution is filtered to separate the particles, and then the separated particles are washed and dried to obtain a complex transition metal hydroxide. At this time, processes such as grinding and / or classification may also be performed as needed.

[0113] The above complex transition metal hydroxide containing nickel and manganese is Ni x1 Mn y1 M 3 z1 (OH)2(M above 3is at least one selected from the group consisting of Zr, Al, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, Na and Pt, and 0 <x1≤0.5, 0.5≤y1<1, 0≤z1≤0.01이다.)로 표시되는 조성을 가질 수 있다.

[0114] The above lithium (Li)-containing raw material may be at least one selected from the group consisting of LiOH, Li2CO3, LiNO3, LiNO2, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li acetate, Li dicarboxylic acid, Li citrate, Li fatty acid, alkyl lithium, and lithium halides, and a mixture of one or two or more of these may be used. Specifically, when heat treatment at a high temperature of about 910°C is considered, LiOH may be used.

[0115] The above mixing can be done by dry mixing or wet mixing. When mixing each component through dry mixing, the firing process can be performed without a separate drying process. When mixing each component through wet mixing, the mixture can be prepared by adding it to a solvent, specifically water, or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water, or a solution containing each raw material, specifically an aqueous solution, is prepared, and then the mixed components are mixed and spray-dried before the firing process is performed. Each raw material and composite transition metal hydroxide can be used in an appropriate amount considering the content of each metal element in the lithium composite transition metal oxide to be finally manufactured.

[0116] According to the present invention, in the step (A), a composite transition metal hydroxide containing nickel and manganese and a lithium (Li)-containing raw material without containing cobalt can be mixed in an amount such that the raw material has a composition represented by the chemical formula 1.

[0117] The above firing can be performed under an air atmosphere. In this case, the firing atmosphere is easily maintained and is advantageous from an economic perspective.

[0118] The above sintering may be performed at a temperature of 700°C or higher, 750°C or higher, 800°C or higher, 850°C or higher, or 900°C or higher, and 950°C or lower, or 1,000°C or lower. In the above temperature range, an appropriate ratio of Li2MnO3 phase and LiMO2 phase (wherein M is an element including Ni, Mn, or a combination thereof) can be formed.

[0119] The above calcination can be performed for 7 to 10 hours. Within the above time range, the crystallinity of the lithium composite transition metal oxide particles is sufficiently controlled, which is advantageous for lithium ion transport.

[0120]

[0121] (B) Step

[0122] Thereafter, the step (B) includes mixing the lithium composite transition metal oxide and the vanadium (V)-containing raw material and then heat-treating the mixture to form a coating layer including a compound composed of vanadium (V) and oxygen (O) on the lithium composite transition metal oxide.

[0123]

[0124] The above vanadium (V)-containing raw material may be at least one selected from the group consisting of V2O5, vanadium sulfide, vanadium acetylacetonate, and vanadium oxidizer, and a mixture of one or two or more thereof may be used. Specifically, considering economic feasibility and fairness, V2O5 may be used.

[0125]

[0126] The above vanadium (V)-containing raw material may be mixed so that the vanadium (V) content is 100 ppm or more, and 950 ppm or less, 1,000 ppm or less, 1,500 ppm or less, 2,000 ppm or less, or 2,500 ppm or less, based on the total weight of the lithium composite transition metal oxide.

[0127]

[0128] The above heat treatment may be performed at a temperature of 400°C or higher, 450°C or higher, or 500°C or higher, and 550°C or lower, or 600°C or lower. By performing the heat treatment in this manner, sufficient heat energy required for coating can be supplied. If the heat treatment temperature is lower than 400°C, sufficient heat energy required for coating is not supplied, and thus the coating layer may not be formed. If the heat treatment temperature is higher than 600°C, not only the vanadium (V)-containing raw material but also the lithium composite transition metal oxide may be over-sintered, thereby forming a secondary phase.

[0129]

[0130] When the above lithium composite transition metal oxide and the vanadium (V)-containing raw material are mixed and then heat-treated in the above temperature range, a coating layer including a compound composed of vanadium (V) and oxygen (O) can be formed on the lithium composite transition metal oxide. The coating layer including the compound composed of vanadium (V) and oxygen (O) may partially cover at least a portion of the lithium composite transition metal oxide, that is, a region of the lithium composite transition metal oxide, or may be in the form of covering the entire region. The shape of the coating layer may be an island type, a film type, or a combination thereof, but the shape of the coating layer is not limited thereto. The structure of the coating layer including the compound composed of vanadium (V) and oxygen (O) may include a layered structure, an olivine structure, an orthorhombic structure, a monoclinic structure, etc., but a spinel structure is not applicable.

[0131]

[0132] The above heat treatment may be performed under an oxygen atmosphere. In this case, an oxidizing atmosphere is created, which may be suitable for forming a coating layer including a compound composed of vanadium (V) and oxygen (O).

[0133]

[0134] The above coating layer may include V2O5. In this case, lithium ion absorption and release performance, electrical conductivity, and structural stability are improved, thereby improving the capacity characteristics, resistance characteristics, and lifespan characteristics of a battery including a positive electrode active material. Specifically, the coating layer may be composed solely of V2O5 or may be a mixed form of V2O5 and LiMn2O4.

[0135]

[0136] anode

[0137] Next, the anode according to the present invention will be described.

[0138] The positive electrode according to the present invention comprises a positive electrode active material layer comprising the positive electrode active material according to the present invention. Specifically, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and comprising the positive electrode active material. Since the positive electrode active material has been described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0139]

[0140] The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 µm to 500 µm, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesive strength of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0141]

[0142] The above-mentioned positive electrode active material layer may include a conductive material and a binder together with the positive electrode active material. At this time, the positive electrode active material may be included in an amount of 80 wt% to 99 wt%, more specifically 85 wt% to 98.5 wt%, based on the total weight of the positive electrode active material layer, and excellent capacity characteristics may be exhibited within this range.

[0143]

[0144] The conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One type alone or a mixture of two or more types of these may be used. The conductive material may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0145]

[0146] The above binder serves to improve the adhesion between positive electrode active material particles and the adhesive strength between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The binder may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0147]

[0148] The positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material described above is used. Specifically, the positive electrode can be manufactured by coating a composition for forming a positive electrode active material layer, which is manufactured by dissolving or dispersing the positive electrode active material and optionally a binder and a conductive material in a solvent, on a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive material are as described above. Alternatively, the positive electrode can be manufactured by casting the composition for forming a positive electrode active material layer on a separate support, and then laminating the film obtained by peeling it from the support on a positive electrode current collector.

[0149]

[0150] The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0151]

[0152] lithium secondary battery

[0153] Next, a lithium secondary battery according to the present invention will be described.

[0154]

[0155] The present invention can manufacture an electrochemical device including the above-described positive electrode. The electrochemical device may be, specifically, a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

[0156]

[0157] The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is the same as described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0158]

[0159] In addition, the lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0160]

[0161] In the above lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0162] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0163]

[0164] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0165]

[0166] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β(0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fiber-like forms, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0167] The above negative electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of the negative electrode active material layer.

[0168]

[0169] The above binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0170]

[0171] The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, specifically, 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0172]

[0173] The negative electrode active material layer may be manufactured by applying and drying a composition for forming a negative electrode active material layer prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the composition for forming a negative electrode active material layer on a separate support, and then laminating the film obtained by peeling it off from the support on a negative electrode current collector.

[0174]

[0175] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without special restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, can be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. can also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength can be used, and can optionally be used in a single-layer or multi-layer structure.

[0176]

[0177] In addition, examples of the electrolyte used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0178] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0179] As the organic solvent, any solvent that can serve as a medium through which ions involved in the electrochemical reaction of the battery can move may be used without particular limitation. Specifically, the organic solvent includes ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); Alcohol solvents such as ethyl alcohol, isopropyl alcohol, etc.; nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes, etc. can be used. Among these, carbonate solvents are preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of a battery and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferable.In this case, the performance of the electrolyte may be improved when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

[0180]

[0181] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably used within the range of 0.1 to 5.0 M, specifically, 0.1 to 3.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0182]

[0183] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additive may be included in an amount of 0.1 to 10 wt%, specifically, 0.1 to 5 wt%, based on the total weight of the electrolyte.

[0184]

[0185] As described above, a lithium secondary battery including a cathode active material according to the present invention exhibits excellent resistance characteristics and capacity characteristics, and has a relatively low resistance increase rate, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0186] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0187] The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0188] There is no particular limitation on the external shape of the lithium secondary battery of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0189] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

[0190]

[0191] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0192]

[0193] Manufacturing example

[0194] Manufacturing Example 1

[0195] A 2.4 M complex transition metal aqueous solution was prepared by dissolving NiSO4 and MnSO4 in deionized water so that the molar ratio of nickel:manganese was 0.35:0.65. The inlet pipes for the complex transition metal aqueous solution and the 25 wt% NaOH aqueous solution were each connected to a 10 L continuous stirred tank reactor. 2.6 L of deionized water and 3.5 mL of a 25 wt% NaOH aqueous solution were added to the reactor, maintained at 50°C, and stirred at 150 rpm to prepare the initial pH of the solution to 12.0 to 13.0 (based on 25°C conversion). In addition, N2 gas was purged at 2 L / min to remove dissolved oxygen and create a non-oxidizing atmosphere inside the reactor. After that, while stirring at 1,000 rpm, the composition ratio of the gas input inside the reactor is changed from N2 100% to N2: atmosphere ratio from 99.5:0.5 to 85.0:15.0 to form a weak oxygen atmosphere, and the complex transition metal aqueous solution is continuously input into the reactor at a flow rate of 0.85 L / hr. The amount of NaOH input and the RPM are adjusted so that the pH reaches 10.0 to 11.0 within 1 to 2 hours from the start of the reaction, thereby generating complex transition metal hydroxide seeds with a size of 0.1 to 1 μm. After that, the co-precipitation reaction is performed while maintaining the pH at 10.0 to 11.0 for 80 hours to grow the complex transition metal hydroxide particles, and the input of raw materials is stopped when the target particle size (4 μm) is reached. After that, the particles are separated from the reaction solution, washed with water, and dried to form Ni. 0.35 Mn 0.65 A complex transition metal hydroxide having the composition (OH)2 was prepared.

[0196]

[0197] Manufacturing Example 2

[0198] By adjusting the amount of NaOH input and the RPM to reach pH 10.0 to 11.0 within 1 to 2 hours from the start of the reaction, complex transition metal hydroxide seeds with a size of 3 to 5 μm are generated. Afterwards, the co-precipitation reaction is performed while maintaining the pH at 10.0 to 11.0 for 60 hours to grow complex transition metal hydroxide particles, and when the target particle size (10 μm) is reached, the raw material input is stopped, and the same method as in Manufacturing Example 1 is performed to produce Ni 0.35 Mn 0.65 A complex transition metal hydroxide having the composition (OH)2 was prepared.

[0199]

[0200] Examples and Comparative Examples

[0201] Example 1

[0202] LiOH and Ni prepared in Manufacturing Example 1 0.35 Mn 0.65 (OH)2 was mixed so that the molar ratio of Li:(Ni+Mn) was 1.32:1, and calcined at 910℃ under air atmosphere, Li 1.14 Ni 0.3 Mn 0.56 A lithium composite transition metal oxide having a composition represented by O2 was prepared. At this time, the lithium composite transition metal oxide had a composition of 0.47(Li2MnO3)·1.0(LiNi 0.51 Mn 0.49 It has a composition represented by O2).

[0203] After mixing the lithium composite transition metal oxide and V2O5, a heat treatment was performed at 500°C in an oxygen atmosphere to produce a positive electrode active material in which a coating layer including V2O5 was formed on the lithium composite transition metal oxide. At this time, the V2O5 was mixed so that the vanadium (V) content was 100 ppm based on the total weight of the lithium composite transition metal oxide.

[0204]

[0205] Example 2

[0206] A positive electrode active material was manufactured in the same manner as in Example 1, except that V2O5 was mixed so that the content of vanadium (V) was 1,000 ppm based on the total weight of the lithium composite transition metal oxide.

[0207]

[0208] Example 3

[0209] A positive electrode active material was manufactured in the same manner as in Example 1, except that V2O5 was mixed so that the content of vanadium (V) was 2,000 ppm based on the total weight of the lithium composite transition metal oxide.

[0210]

[0211] Example 4

[0212] LiOH and Ni prepared in Manufacturing Example 2 0.35 Mn 0.65 (OH)2 was mixed so that the molar ratio of Li:(Ni+Mn) was 1.31:1, and calcined at 910 ℃ under air atmosphere, Li 1.13 Ni 0.3 Mn 0.57 A lithium composite transition metal oxide having a composition represented by O2 was prepared. At this time, the lithium composite transition metal oxide had a composition of 0.43(Li2MnO3)·1.0(LiNi 0.51 Mn 0.49 It has a composition represented by O2).

[0213] After mixing the lithium composite transition metal oxide and V2O5, a heat treatment was performed at 500°C in an oxygen atmosphere to produce a positive electrode active material in which a coating layer including V2O5 was formed on the lithium composite transition metal oxide. At this time, the V2O5 was mixed so that the vanadium (V) content was 100 ppm based on the total weight of the lithium composite transition metal oxide.

[0214]

[0215] Example 5

[0216] A positive electrode active material was manufactured in the same manner as in Example 4, except that V2O5 was mixed so that the content of vanadium (V) was 1,000 ppm based on the total weight of the lithium composite transition metal oxide.

[0217]

[0218] Example 6

[0219] A positive electrode active material was manufactured in the same manner as in Example 4, except that V2O5 was mixed so that the content of vanadium (V) was 2,000 ppm based on the total weight of the lithium composite transition metal oxide.

[0220]

[0221] Comparative Example 1

[0222] LiOH and Ni prepared in Manufacturing Example 1 0.35 Mn 0.65 (OH)2 was mixed so that the molar ratio of Li:(Ni+Mn) was 1.32:1, and calcined at 910 ℃ under air atmosphere, Li 1.14 Ni 0.3 Mn 0.56 A lithium composite transition metal oxide having a composition represented by O2 was prepared.

[0223]

[0224] Comparative Example 2

[0225] A positive electrode active material was manufactured in the same manner as in Example 1, except that V2O5 was mixed so that the content of vanadium (V) was 50 ppm based on the total weight of the lithium composite transition metal oxide.

[0226]

[0227] Comparative Example 3

[0228] A positive electrode active material was manufactured in the same manner as in Example 1, except that V2O5 was mixed so that the content of vanadium (V) was 3,000 ppm based on the total weight of the lithium composite transition metal oxide.

[0229]

[0230] Experimental example

[0231] Experimental Example 1: XRD Analysis

[0232] XRD measurements were performed on each of the positive electrode active materials manufactured in the above examples and comparative examples. The XRD data for each of the positive electrode active materials manufactured in Examples 1 and 2 are shown in Fig. 1.

[0233]

[0234] Figure 1 shows XRD data of each of the positive electrode active materials manufactured in Examples 1 and 2.

[0235]

[0236] At this time, the XRD was measured by collecting 2g to 3g of positive electrode active material particles from each positive electrode active material powder, and using Cu-Kα rays (wavelength 1.54 Å), at an acceleration voltage of 40 kV / 40 mA, at a scan speed of 0.2° / sec, in a 2θ range of 15° to 80° using an X-ray diffraction analysis method.

[0237] Through Fig. 1, it was confirmed that the positive electrode active materials manufactured in Examples 1 and 2 simultaneously included a Li2MnO3 phase and a LiMO2 (wherein M is an element including Ni, Mn, or a combination thereof) phase. Specifically, it was confirmed that the Li2MnO3 phase was included with a small peak existing at 20° to 23°, and it was confirmed that the LiMO2 (wherein M is an element including Ni, Mn, or a combination thereof) phase was included with a large peak existing at 18°.

[0238]

[0239] Experimental Example 2: ICP Analysis

[0240] Each of the lithium composite transition metal oxides and the positive electrode active material manufactured in Examples 1 to 6 and Comparative Examples 1 to 3 was taken in an amount of 0.1 g, 1 ml of hydrochloric acid was added, and the positive electrode active material was dissolved by heating. Thereafter, a small amount of hydrogen peroxide was added to promote the reaction, completely dissolving the positive electrode active material to prepare a solution. Next, the solution was diluted with deionized water so that the total volume of the solution became 10 ml to prepare an analysis sample. Using an ICP device (Perkin Elmer, OPTIMA 7300DV), the weight ratio of the constituent elements present in the analysis sample was measured, and the composition of the lithium composite transition metal oxide and the content (ppm) of vanadium (V) included in the coating layer are shown in Table 1 below.

[0241] Lithium complex transition metal oxide composition V content (ppm) Example 1 Li 1.14 Ni 0.3 Mn 0.56 O297 Example 2Li 1.14 Ni 0.3 Mn 0.56 O2985 Example 3Li 1.14 Ni 0.3 Mn 0.56 O21,968 Example 4Li 1.13 Ni 0.3 Mn 0.57 O2100 Example 5Li 1.13 Ni 0.3 Mn 0.57 O2991 Example 6Li 1.13 Ni 0.3 Mn 0.57 O21,973 Comparative Example 1Li 1.14 Ni 0.3 Mn 0.56 O2-Comparative Example 2Li 1.14 Ni 0.3 Mn 0.56 O245 Comparative Example 3Li 1.14 Ni 0.3 Mn 0.56 O22,957

[0242] Through Table 1, it was confirmed that the compositions of Examples 1 to 6 are represented by the chemical formula 1, and the content of vanadium (V) included in the coating layer is 90 ppm to 2,500 ppm with respect to the total weight of the lithium composite transition metal oxide.

[0243] Experimental Example 3: Measurement of the content of the coating layer

[0244] The content of vanadium (V) included in the coating layer of Example 1 was measured by performing ICP-MS (Inductively Coupled Plasma-Mass Spectrometer) analysis.

[0245] As a result of calculating the contents of vanadium oxide and lithium vanadium oxide included in the coating layer by reverse calculation from the content of vanadium (V) obtained from the measurement results, it was confirmed that the content of the coating layer in Example 1 was 0.0178 parts by weight for 100 parts by weight of lithium composite transition metal oxide.

[0246]

[0247] Experimental Example 4: Measurement of the average particle size of the positive electrode active material

[0248] In order to measure the average particle size of the positive electrode active material particles manufactured in Examples 1 to 6 and Comparative Examples 1 to 3, the particle size of the positive electrode active material produced in Examples 1 to 6 and Comparative Examples 1 to 3 was measured using PSA (Microtrac, S3500), and the results are shown in Table 2 below.

[0249] Average particle size (D) 50 )(㎛)Example 14.07Example 24.09Example 34.07Example 49.59Example 59.61Example 69.58Comparative Example 14.08Comparative Example 24.08Comparative Example 34.07

[0250] Through Table 2, the above positive electrode active material has an average particle diameter (D 50 ) was confirmed to be 1.0㎛ to 15.0㎛.

[0251] Experimental Example 5: Battery Characteristics Evaluation

[0252] Coin-type half-cell manufacturing

[0253] A positive electrode slurry was prepared by mixing 97.5 wt% of each of the positive electrode active materials manufactured in Examples 1 to 6 and Comparative Examples 1 to 3, 1.0 wt% of Super P as a conductive agent, and 1.5 wt% of polyvinylidene fluoride (PVDF) as a binder in an N-methylpyrrolidone (NMP) solvent. The prepared positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to prepare a positive electrode.

[0254] An electrode assembly was manufactured using a lithium metal electrode as the negative electrode and a porous polyethylene separator interposed between the positive and negative electrodes. This was placed inside a battery case, and a coin-type half-cell was manufactured by injecting an electrolyte solution containing 1 M LiPF6 dissolved in an organic solvent containing ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a volume ratio of 3:4:3.

[0255]

[0256] Battery Characteristics Evaluation

[0257] Using the coin-type half-cells containing the positive electrode active materials manufactured in Examples 1 to 6 and Comparative Examples 1 to 3, an activation process (formation) was performed, and then the cells were charged (0.33C) in a CC-CV manner to 4.4 V at 25°C, and then discharged (0.33C) in a CC manner to 2.5 V to perform an initial charge-discharge process, and the charge-discharge capacity and resistance at this time were measured. The measured charge-discharge capacity (mAh / g) and resistance (Ω) are shown in Table 3 below.

[0258] After charging (0.33C) to 4.4 V at 25 ℃ in a CC-CV manner, and then discharging (0.33C) to 2.5 V in a CC manner, one cycle was defined as a cycle, and a total of 30 cycles of charging and discharging were repeated. After measuring the resistance in the first and 30th cycles, the percentage of the resistance in the 30th cycle with respect to the resistance in the first cycle (resistance increase rate (%)) is shown in Table 3 below.

[0259] Charge and discharge of the first cycle @ 0.33C Resistance increase rate (%) Charge capacity (mAh / g) Discharge capacity (mAh / g) Resistance (Ω) Example 1 214.5 203.8 4 0.36 134.8 Example 2 216.1 205.4 3 9.78 131.0 Example 3 215.2 205.0 4 0.80 139.4 Example 4 215.3 203.0 3 8.18 118.2 Example 5 216.1 204.9 3 7.50 112.2 Example 6 214.9 203.2 3 8.66 119.2 Comparative example 1214.2 202.4 4 1.74 143.6 Comparative example 2213.7200.742.35142.8 Comparative example 3211.8198.745.8155.3

[0260] As shown in Table 3, in the case of batteries including the positive electrode active materials of Examples 1 to 6, in which the coating layer includes a compound composed of vanadium (V) and oxygen (O) and the content of vanadium (V) included in the coating layer is 90 ppm to 2,500 ppm with respect to the total weight of the lithium composite transition metal oxide, it was confirmed that the charge / discharge capacity and resistance in the first cycle were superior to the battery including the positive electrode active material of Comparative Example 1 that did not include the coating layer and the battery including the positive electrode active materials of Comparative Examples 2 and 3 in which the content of vanadium (V) included in the coating layer was less than 90 ppm or more than 2,500 ppm with respect to the total weight of the lithium composite transition metal oxide. In comparison, it was confirmed that the batteries including the positive electrode active materials of Comparative Examples 1 to 3 had a problem in which the resistance increase rate was significantly high in the 30th cycle. In conclusion, it can be seen that the positive electrode active material according to the present invention can improve the charge / discharge capacity and electrical conductivity of a battery, and that the structural change is not significant even during charge / discharge cycles.

Claims

1. A lithium composite transition metal oxide comprising a Li2MnO3 phase and a LiMO2 phase (wherein M is an element including Ni, Mn or a combination thereof); and a coating layer comprising a compound composed of vanadium (V) and oxygen (O) on the lithium composite transition metal oxide; The above lithium composite transition metal oxide has a composition represented by the following chemical formula 1, A positive electrode active material in which the content of vanadium (V) included in the coating layer is 90 ppm to 2,500 ppm based on the total weight of the lithium composite transition metal oxide: [Chemical Formula 1] Li 1+x Ni a Mr b M 1 c O2 In the above chemical formula 1, M 1 is at least one selected from the group consisting of Zr, Al, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, Na and Pt, 0 <x≤0.5, 0<a≤0.5, 0.5≤b<1, 0≤c≤0.01이다.

2. In claim 1, The above lithium composite transition metal oxide is a positive electrode active material having a composition represented by the following chemical formula 2: [Chemical Formula 2] αLi2Mn (1-p) M 2 p O3·βLiNi q Mn r M 2 s O2 In the above chemical formula 2, M 2 is at least one selected from the group consisting of Zr, Al, Re, V, Cr, Fe, Ga, Si, B, Ru, Ti, Nb, Mo, Mg, W, Na and Pt, 0<α≤0.5, 0<β≤1, 0≤p≤0.01, 0 <q≤0.8, 0<r≤0.8, 0≤s≤0.01이고, q+r+s=1이다.

3. In claim 1, The above b is a positive electrode active material of 0.5 to 0.

75.

4. In claim 1, The above coating layer is a positive electrode active material containing V2O5.

5. In claim 1, A positive electrode active material having a content of the coating layer of 0.01 to 0.1 parts by weight based on 100 parts by weight of the lithium composite transition metal oxide.

6. In claim 1, The above positive electrode active material has an average particle diameter (D 50 ) A positive electrode active material having a diameter of 1.0㎛ to 15.0㎛. 7.(A) A step of mixing and calcining a composite transition metal hydroxide and a lithium (Li)-containing raw material to produce a lithium composite transition metal oxide; and (B) a step of mixing the lithium composite transition metal oxide and a vanadium (V)-containing raw material and then heat-treating the mixture to form a coating layer comprising a compound composed of vanadium (V) and oxygen (O) on the lithium composite transition metal oxide; A method for producing a positive electrode active material according to claim 1, wherein the heat treatment is performed at a temperature of 400°C to 600°C.

8. In claim 7, A method for manufacturing a positive electrode active material in which the above vanadium (V)-containing raw material is V2O5.

9. In claim 7, A method for producing a positive electrode active material, wherein the above vanadium (V)-containing raw material is mixed so that the vanadium (V) content is 100 ppm to 2,500 ppm with respect to the total weight of the lithium composite transition metal oxide.

10. In claim 7, A method for manufacturing a positive electrode active material, wherein the heat treatment in the above step (B) is performed under an oxygen atmosphere.

11. In claim 7, A method for manufacturing a positive electrode active material, wherein the above coating layer comprises V2O5.

12. A positive electrode comprising a positive electrode active material according to any one of claims 1 to 6.

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

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