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

Abstract

The present invention relates to a method for manufacturing a cathode active material, the method comprising: a step of mixing a lithium compound, a transition metal oxide, and a metal oxide to prepare a mixture; and a calcination step of calcining the mixture to prepare a lithium transition metal oxide, wherein the transition metal oxide contains 40-70 mol% of Ni with respect to the total transition metals, the calcination step is performed through a two-stage temperature maintenance section, a temperature of a first temperature maintenance section is 700-800 °C, and a temperature of a second temperature maintenance section is 800-900 °C.

Description

Method for manufacturing positive electrode active material, positive electrode active material, positive electrode and lithium secondary battery containing the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 2024-0067171, filed May 23, 2024, and Korean Patent Application No. 2025-0043502, filed April 3, 2025, the entire contents of which are incorporated herein by reference.

[0003]

[0004] Technology field

[0005] The present invention relates to a method for manufacturing a positive electrode active material, a positive electrode active material, a positive electrode including the same, and a lithium secondary battery.

[0006]

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

[0008] Lithium transition metal oxides such as lithium cobalt oxide such as LiCoO2, lithium nickel oxide such as LiNiO2, lithium manganese oxide such as LiMnO2 or LiMn2O4, and lithium iron phosphate oxide such as LiFePO4 have been developed as positive electrode active materials for lithium secondary batteries, and recently, Li[Ni a Co b Mn c ]O2, Li[Ni a Co b Al c ]O2, Li[Ni a Co b Mn c Al d] Lithium composite transition metal oxides containing two or more transition metals, such as O2, have been developed and are widely used.

[0009] Meanwhile, with the recent increase in demand for high-capacity batteries used in electric vehicles, etc., development of high-nickel (High-Ni) cathode active materials with improved capacity characteristics by increasing the nickel content in lithium composite transition metal oxides to 70 mol% or more is actively underway.

[0010] However, as the nickel content increases, the cation mixing (Niocc) becomes more severe, and depending on the degree of this intensification, a large amount of lithium (Li) residue is generated. Most of this Li residue is composed of compounds of LiOH and Li2CO3, which causes the problem of gelation during the manufacture of the positive electrode paste and gas generation during charge and discharge after the electrode manufacture. The residual Li2CO3 not only increases the swelling of the cell, reducing the cycle, but also causes the battery to swell.

[0011] Accordingly, as a means to solve the above problems, research is being conducted on a method for manufacturing a cathode active material and a cathode active material that can improve cation mixing and residual lithium.

[0012]

[0013] [Prior Art Literature]

[0014] [Patent Document]

[0015] (Patent Document 1) KR 2019-0044451 A

[0016]

[0017] The problem to be solved by the present invention is to provide a method for manufacturing a cathode active material, which can solve the problem of intensified cation mixing occurring in conventional cathode active materials, and reduce the amount of residual lithium present on the surface of the cathode active material, thereby solving the problem of reduced stability due to gas generation, etc., and a cathode active material, a cathode including the cathode active material, and a lithium secondary battery.

[0018]

[0019] The present invention provides a method for manufacturing a positive electrode active material, a positive electrode active material, a positive electrode including the same, and a lithium secondary battery.

[0020] (1) The present invention provides a method for producing a positive electrode active material, comprising the steps of mixing a lithium compound, a transition metal oxide, and a metal oxide to produce a mixture, and the sintering step of sintering the mixture to produce a lithium transition metal oxide, wherein the transition metal oxide contains Ni in an amount of 40 mol% or more and 70 mol% or less among the total transition metal, and the sintering step is performed through two temperature maintenance sections, the temperature of the first temperature maintenance section being 700°C or more and 800°C or less, and the temperature of the second temperature maintenance section being 800°C or more and 900°C or less.

[0021] (2) The present invention provides a method for manufacturing a positive electrode active material, wherein, in the above (1), the metal oxide includes at least one oxide selected from the group consisting of ZrO2, ZnO, Nb2O5, MgO, Fe2O3, V2O5, WO3, SiO, SiO2, and Sn2O3.

[0022] (3) The present invention provides a method for manufacturing a positive electrode active material, wherein, in (1) or (2), the metal oxide is mixed in an amount of 0.01 wt% or more and 1.0 wt% or less based on the total weight of the mixture.

[0023] (4) The present invention provides a method for manufacturing a positive electrode active material, wherein the transition metal oxide contains Ni in an amount of 50 mol% or more and 60 mol% or less among the total transition metals in any one of (1) to (3).

[0024] (5) The present invention provides a method for manufacturing a positive electrode active material, wherein the transition metal oxide comprises at least one transition metal selected from the group consisting of Ni, Co, and Mn, in any one of the above (1) to (4).

[0025] (6) The present invention provides a method for producing a positive electrode active material, wherein the transition metal oxide is represented by the following chemical formula 1 in any one of (1) to (5).

[0026] [Chemical Formula 1]

[0027] Ni a1 Co b1 Mn c1 M d1 (O)4

[0028] In the above chemical formula 1,

[0029] M may include at least one selected from the group consisting of Al, Zr, Mg, Zn, Y, Fe, W and Ti, and 0.4≤a1≤0.7, 0 <b1≤0.6, 0<c1≤0.6, 0≤d1≤0.2, a1+b1+c1+d1 = 1이다.

[0030] (7) The present invention provides a method for manufacturing a positive electrode active material, wherein the first temperature maintenance section and the second temperature maintenance section are performed continuously in any one of the above (1) to (6).

[0031] (8) The present invention provides a method for manufacturing a positive electrode active material, wherein, in any one of the above (1) to (7), the heating rate before reaching the second temperature maintenance section from the first temperature maintenance section is 3.0°C / min or more and 7.0°C / min or less.

[0032] (9) The present invention provides a positive electrode active material comprising a lithium transition metal oxide of nickel (Ni), cobalt (Co), and manganese (Mn), wherein the lithium transition metal oxide has a nickel (Ni) content of 40 mol% or more and 70 mol% or less among the total transition metal content, a residual lithium content of 0.80 wt% or less based on the total content of the positive electrode active material, and a cation mixture of 2.0% or more and 2.4% or less.

[0033] (10) The present invention provides a positive electrode active material according to (9) above, wherein the average particle diameter (D50) of the positive electrode active material is 13 ㎛ or more and 19 ㎛ or less.

[0034] (11) The present invention provides a positive electrode active material according to (9) or (10), wherein the residual lithium includes at least one material selected from the group consisting of LiOH and Li2CO3.

[0035] (12) The present invention provides a positive electrode for a secondary battery including a positive electrode active material according to (9) to (11).

[0036] (13) The present invention provides a lithium secondary battery including a positive electrode according to (12) above.

[0037]

[0038] According to the method for manufacturing a positive electrode active material of the present invention, a positive electrode active material can be manufactured that maintains high charge / discharge capacity and efficiency, while resolving the degree of intensification of cation mixing and reducing the amount of residual lithium present on the surface of the positive electrode active material, thereby resolving the problem of reduced stability due to gas generation, etc.

[0039]

[0040] Figure 1 is an SEM photograph showing the oxidized precursor of Example 1 and the non-oxidized precursor of Comparative Example 3.

[0041] Figure 2 is an SEM photograph of the positive electrode active materials of Example 1, Comparative Example 2, and Comparative Example 3.

[0042]

[0043] Hereinafter, the present invention will be described in more detail to facilitate understanding. The terms and words used in this specification and claims should not be interpreted based on their conventional or dictionary meanings. Based on the principle that the inventor can appropriately define the concepts of terms to best explain his or her invention, they should be interpreted in a way that aligns with the technical spirit of the present invention.

[0044] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0045] In this specification, it should be understood that the terms “include,” “comprising,” or “having” 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.

[0046] In the present invention, the term 'primary particle' means the smallest particle unit that can be distinguished as a single lump when observing the cross-section of a positive electrode active material through a scanning electron microscope (SEM), and may be composed of multiple crystal grains.

[0047] In the present invention, the term 'single particle form' includes both a single particle form of the positive electrode active material and / or the lithium transition metal composite oxide and a pseudo-single particle form in which two or more and less than or equal to 100 particles are aggregated. That is, the single particle form of the positive electrode active material and / or the single particle form of the lithium transition metal composite oxide of the present invention may include at least one selected from the group consisting of single particles and particles in which two or more and less than or equal to 100 primary particles are aggregated.

[0048] In the present invention, the term "secondary particle" refers to a secondary structure formed by the agglomeration of multiple primary particles. Specifically, it refers to a form in which a number of primary particles exceeds the number of primary particles contained in the single particle form. The average particle diameter of the secondary particles can be measured using a particle size analyzer.

[0049] In the present invention, the term 'average particle diameter (D 50 )' means the particle size at the 50% point of the volume cumulative distribution according to particle size. 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 from Microtrac), and measuring the difference in diffraction pattern according to particle size when the particles pass through the laser beam to calculate the particle size distribution, and calculating the particle diameter at the point where it becomes 50% of the volume cumulative distribution according to particle size in the measuring device, thereby obtaining D 50 can be measured.

[0050]

[0051] Method for manufacturing positive electrode active material

[0052] The present invention provides a method for producing a positive electrode active material, comprising the steps of mixing a lithium compound, a transition metal oxide, and a metal oxide to produce a mixture, and the sintering step of sintering the mixture to produce a lithium transition metal oxide, wherein the transition metal oxide contains Ni in an amount of 40 mol% or more and 70 mol% or less among the total transition metal, and the sintering step is performed through two temperature maintenance sections, the temperature of the first temperature maintenance section being 700°C or more and 800°C or less, and the temperature of the second temperature maintenance section being 800°C or more and 900°C or less.

[0053] The method for manufacturing a positive electrode active material of the present invention may include a mixing step of mixing each precursor and additive and a firing step of firing the mixture.

[0054] First, a mixture is prepared by mixing a lithium compound, a transition metal oxide, and a metal oxide. Here, the lithium compound is a reactant for reacting with the transition metal precursor to form a lithium transition metal oxide. For example, the lithium compound is a compound containing lithium, and is not particularly limited as long as it can be used as a lithium source. For example, the lithium compound may be at least one selected from the group consisting of lithium carbonate (Li2CO3), lithium hydroxide (LiOH), lithium nitrate (LiNO3), and lithium hydrate (LiOH·H2O).

[0055] In addition, the transition metal oxide is a transition metal precursor and a reactant for reacting with the lithium compound to form a lithium transition metal oxide. For example, the transition metal oxide may include one or more transition metals selected from the group consisting of nickel, cobalt, and manganese.

[0056] In the above mixing step, the ratio of the lithium compound to the transition metal oxide may be 0.9 or more and 1.3 or less, and for example, the ratio of the lithium mole number may be 0.9 or more, 0.93 or more, 0.95 or more, 0.97 or more, 1.01 or more, 1.02 or more, 1.03 or more, 1.04 or more, 1.05 or more, 1.06 or more, 1.07 or more, 1.3 or less, 1.27 or less, 1.25 or less, 1.2 or less, 1.17 or less, 1.15 or less, 1.13 or less, 1.1 or less, 1.09 or less, 1.08 or less. Since the lithium compound has a characteristic of volatilizing at high temperatures, a relatively excessive amount must be added based on the transition metal oxide so that the reaction can sufficiently occur. Therefore, it is preferable that the lithium compound be mixed with the transition metal oxide within the above ratio range.

[0057] The above transition metal oxide may contain nickel (Ni) in an amount of 40 mol% or more and 70 mol% or less among the total transition metals. For example, the transition metal oxide may contain nickel in an amount of 40 mol% or more, 45 mol% or more, 50 mol% or more, 55 mol% or more, 70 mol% or less, 65 mol% or less, or 60 mol% or less among the total transition metals, and specifically, may contain nickel in an amount of 50 mol% or more and 60 mol% or less. In addition, the transition metal precursor mixed in the manufacturing method of the present invention may be an oxide rather than a hydroxide. Here, when the transition metal precursor is a precursor in the form of an oxide rather than a transition metal hydroxide, the structure of the lithium transition metal oxide formed by the reaction of the lithium compound and the transition metal precursor in the first temperature range can be stabilized, thereby suppressing the remaining lithium impurities and increasing the Ni occupancy rate (Niocc) at the 3a site.

[0058] Conventional cathode active materials with high nickel content exhibit high capacity characteristics, but as the nickel content in the cathode active material increases, cation mixing may increase, and the cation mixing may be caused by Li having similar ionic radii. + and Ni 2+ This refers to the phenomenon of changing each other's positions to form a decision. In the case of lithium nickel cobalt oxide, Ni 3+ , Co 3+ The ions of the back are Li + Because of the large size difference, the possibility of cation mixing is low. However, among nickel ions, Ni has an oxidation number of +2. 2+ The ions have a similar size to lithium ions, making it easy for cation mixing to occur. 2+ When ions are mixed in the lithium layer, the layered crystal structure does not develop properly, so the structural stability of the active material is reduced, and Ni present in the lithium layer 2+The movement of lithium ions is hindered by ions, resulting in a decline in battery performance. The above cation mixing induces a phase transformation of lithium transition metal oxides, resulting in the formation of an excess of lithium transition metal oxides having a metastable phase or rock-salt phase in addition to the originally intended layered structure. In this way, the coexistence of an excess of lithium composite oxides having a phase other than the layered structure with the lithium composite oxide having the layered structure can lead to the deterioration of the positive electrode active material.

[0059] In order to prevent this phenomenon of increasing cation mixing, the inventor of the present invention mixed a transition metal oxide as a precursor in the manufacturing method of the present invention and controlled the content of nickel contained in the transition metal oxide. In addition, the inventor of the present invention attempted to solve the problem of an additional increase in the amount of residual lithium that may occur due to the high bonding force between metals and oxygen, although the discharge efficiency can be increased by using a transition metal oxide, and thus developed a method for manufacturing a cathode active material having a high level of charge / discharge capacity and efficiency by using a continuous two-stage firing method within a specific temperature range in the firing step, thereby reducing the cation mixing and the amount of residual lithium as a result.

[0060] According to one embodiment of the present invention, a method for manufacturing a positive electrode active material is provided, wherein the transition metal oxide includes at least one transition metal selected from the group consisting of nickel (Ni), cobalt (Co), and manganese (Mn).

[0061] According to one embodiment of the present invention, a method for manufacturing a positive electrode active material is provided, wherein the transition metal oxide is represented by the following chemical formula 1.

[0062] [Chemical Formula 1]

[0063] Ni a1 Co b1 Mn c1 M d1 (O)4

[0064] In the above chemical formula 1, M may include at least one selected from the group consisting of Al, Zr, Mg, Zn, Y, Fe, W and Ti, and 0.4≤a1≤0.7, 0 <b1≤0.6, 0<c1≤0.6, 0≤d1≤0.2, a1+b1+c1+d1 = 1이다.

[0065] Specifically, in the chemical formula 1, 0.5≤a1≤0.6, 0.2≤b1≤0.4, 0.2≤c1≤0.4, 0≤d1≤0.2, a1+b1+c1+d1 = 1. That is, the content of nickel may be contained in an amount of 50 mol% or more and 60 mol% or less, and in this case, cation mixing may be suppressed to have a high level of capacity and efficiency.

[0066] The metal oxide additive mixed with the lithium compound and the transition metal oxide in the above mixing step is a substance having a different reactivity with the lithium compound compared to the transition metal oxide, and is introduced as a doping source doped on the surface or / and inside of the lithium transition metal oxide, and can also serve as a calcination catalyst capable of promoting the reaction between the lithium compound and the transition metal oxide in the calcination step described below.

[0067] According to one embodiment of the present invention, the metal oxide may include at least one oxide selected from the group consisting of ZrO2, ZnO, Nb2O5, MgO, Fe2O3, V2O5, WO3, SiO, SiO2 and Sn2O3, and for example, may include ZrO2 or ZnO, and specifically, may include ZrO2.

[0068] Additionally, according to one embodiment of the present invention, the metal oxide may be mixed in an amount of 0.01 wt% or more and 1.0 wt% or less based on the total weight of the mixture. For example, the metal oxide may be mixed at 0.01 wt% or more, 0.05 wt% or more, 0.1 wt% or more, 0.15 wt% or more, 0.2 wt% or more, 0.25 wt% or more, 0.3 wt% or more, 0.35 wt% or more, 0.4 wt% or more, 0.45 wt% or more, 0.5 wt% or more, 1.0 wt% or less, 0.95 wt% or less, 0.9 wt% or less, 0.85 wt% or less, 0.8 wt% or less, 0.75 wt% or less, 0.7 wt% or less, 0.65 wt% or less, or 0.6 wt% or less based on the total weight of the mixture, and specifically, may be mixed at 0.05 wt% or more and 0.5 wt% or less. When the above metal oxides are mixed within the above range, a high level of capacity of the lithium secondary battery can be maintained while simultaneously improving the reactivity between the lithium compound and the transition metal oxide.

[0069] The above lithium compound, transition metal oxide and metal oxide additive can be mixed by a dry and wet mixing process, and general mixing can be performed for uniform mixing.

[0070] Next, the method for manufacturing a positive electrode active material of the present invention includes a firing step of firing the mixture manufactured in the mixing step to form a lithium transition metal oxide. The firing step is performed through a two-stage temperature maintenance section. The two-stage temperature maintenance section is composed of a first temperature maintenance section and a second temperature maintenance section. At this time, the temperature of the first temperature maintenance section is 700°C or more and 800°C or less, and the temperature of the second temperature maintenance section is 800°C or more and 900°C or less.

[0071] When manufacturing a cathode active material using a lithium transition metal oxide, there was a problem in that lithium impurities, such as lithium oxide (Li2O), lithium hydroxide (LiOH), lithium carbonate (Li2CO3), and lithium carbide (Li2C), did not react with the transition metal oxide and remained. In particular, in the case of a conventional active material with a high nickel content, there was a problem in that more lithium impurities remained on the surface of the cathode active material than when manufacturing the cathode active material using a different type of lithium oxide.

[0072] In order to solve the above problem, the inventor of the present invention studied a method to suppress residual lithium impurities by increasing the reactivity between a lithium compound and a transition metal oxide, and thus prepared a mixture in which a metal oxide additive was mixed in addition to a lithium compound and a transition metal oxide, and caused the mixture to pass through a two-stage temperature maintenance section.

[0073] Therefore, by using a transition metal oxide as a transition metal precursor in the mixing step, it is possible to suppress cation mixing, add a metal oxide, and calcinate in a two-stage calcination method to reduce the amount of lithium residue, and stably maintain the structure of the lithium transition metal oxide, thereby improving the performance of the battery.

[0074] The temperature of the first temperature maintenance section is 700°C or more and 800°C or less. For example, the temperature of the first temperature maintenance section may be 700°C or more, 710°C or more, 720°C or more, 730°C or more, 740°C or more, 800°C or less, 790°C or less, 780°C or less, or 770°C or less. During the first temperature maintenance section, a lithium compound and a transition metal oxide react, and when the temperature is maintained in the above range, the reaction can sufficiently occur to form a lithium transition metal oxide. Generally, in the case of a non-oxidizing precursor, i.e., a transition metal hydroxide, the M(OH)2 form is maintained up to about 300°C, and thereafter, a spinel (M3O4) phase and a rock salt phase are formed. On the other hand, in the case of transition metal oxides, the reaction occurs slightly later than in non-oxidizing precursors, and Li2CO3 remains at a higher temperature, so it is desirable to maintain the above temperature range in the first temperature maintenance section.

[0075] In addition, the temperature of the second temperature maintenance section is 800°C or more and 900°C or less. For example, the temperature of the first temperature maintenance section may be 900°C or more, 810°C or more, 820°C or more, 830°C or more, 840°C or more, 850°C or more, 860°C or more, 870°C or more, 900°C or less, 890°C or less, or 880°C or less. The second temperature maintenance section can improve the crystallinity of the lithium transition metal oxide formed by the reaction of the lithium compound and the transition metal oxide, and stabilize the structure. In addition, the second temperature maintenance section can additionally react unreacted residual lithium after firing in the first temperature maintenance section. The cathode active material, whose structure is stabilized by the second temperature maintenance section, can smoothly move lithium ions during the charging and discharging process, and thus can have a high level of charging and discharging capacity and high efficiency.

[0076] According to one embodiment of the present invention, the first temperature maintenance section and the second temperature maintenance section may be performed continuously. A temperature raising step to reach the second temperature maintenance section may be included in the first temperature maintenance section, but both the first temperature maintenance section and the second temperature maintenance section may be performed in a single firing step. Specifically, after the firing step according to the first temperature maintenance section, a separate processing step is performed and then a second firing according to the second temperature maintenance section is not performed, but the second temperature maintenance section may be performed continuously after the first temperature maintenance section within a single firing step. The second temperature maintenance section is intended to react unreacted lithium residues in the first temperature maintenance section and further stabilize the structure, and is preferably performed immediately after the first temperature maintenance section.

[0077] Meanwhile, the maintenance time of the first temperature maintenance section may be 3 hours or more and 7 hours or less. The maintenance time of the first temperature maintenance section may vary depending on the average particle size of the transition metal oxide and the temperature of the first temperature maintenance section. In addition, the maintenance time of the second temperature maintenance section may be 5 hours or more and 15 hours or less. The maintenance time of the second temperature maintenance section may vary depending on the degree of crystal growth and the degree of structural stability of the lithium transition metal oxide.

[0078] According to one embodiment of the present invention, a method for manufacturing a positive electrode active material is provided, wherein a heating rate before reaching a second temperature maintenance section in a first temperature maintenance section is 3.0°C / min or more and 7.0°C / min or less. For example, the heating temperature may be 3.0°C / min or more, 3.5°C / min or more, 4.0°C / min or more, 4.5°C / min or more, 5.0°C / min or more, 7.0°C / min or less, 6.5°C / min or less, 6.0°C / min or less, or 5.5°C / min or less. This is to rapidly additionally react unreacted lithium residue in the first temperature maintenance section, and therefore may vary in consideration of the type of mixture, the average particle size of the transition metal precursor content, the amount of lithium residue measured by XRD, etc.

[0079] According to one embodiment of the present invention, the firing step can be performed in an oxygen, anhydrous air, nitrogen (N2) or argon (Ar) atmosphere.

[0080]

[0081] positive electrode active material

[0082] The method for manufacturing a positive electrode active material described above may be one of several methods for manufacturing the positive electrode active material described below. The positive electrode active material of the present invention will now be described.

[0083] The present invention provides a cathode active material comprising a lithium transition metal oxide of nickel (Ni), cobalt (Co), and manganese (Mn), wherein the lithium transition metal oxide has a nickel (Ni) content of 40 mol% or more and 70 mol% or less among the total transition metal content, and a residual lithium content of 0.80 wt% or less among the total content of the cathode active material.

[0084] The content of the nickel may be, for example, 50 mol% or more, 55 mol% or more, 70 mol% or less, 65 mol% or less, or 60 mol% or less based on the total content of the transition metal, and the positive electrode active material of the present invention can have high capacity characteristics and reduce cation mixing by including nickel in the above range.

[0085] According to one embodiment of the present invention, the lithium transition metal oxide may have a ratio of the number of moles of lithium to the total number of moles of transition metal (Li / Me) of 0.9 or more and 1.3 or less, and for example, the ratio of the number of moles of lithium may be 0.9 or more, 0.93 or more, 0.95 or more, 0.97 or more, 1.01 or more, 1.02 or more, 1.03 or more, 1.04 or more, 1.05 or more, 1.06 or more, 1.07 or more, 1.3 or less, 1.27 or less, 1.25 or less, 1.2 or less, 1.17 or less, 1.15 or less, 1.13 or less, 1.1 or less, 1.09 or less, or 1.08 or less. The lithium transition metal oxide may have excellent charge / discharge capacity when it has Li / Me in the above range.

[0086] According to one embodiment of the present invention, the lithium transition metal oxide of the present invention may have a composition represented by the following chemical formula 2.

[0087] [Chemical Formula 2]

[0088] Li x Ni a1 Co b1 Mn c1 M d1 (O)4

[0089] In the above chemical formula 1, M may include at least one selected from the group consisting of Al, Zr, Mg, Zn, Y, Fe, W and Ti, and 0.9≤x≤1.3, 0.4≤a1≤0.7, 0 <b1≤0.6, 0<c1≤0.6, 0≤d1≤0.2, a1+b1+c1+d1 = 1이다.

[0090] According to one embodiment of the present invention, x is a molar ratio of lithium to a transition metal in a lithium transition metal composite oxide, which may be 0.9 or more, 0.95 or more, or 1.0 or more, and may also be 1.1 or less, 1.07 or less, 1.05 or less, or 1.03 or less.

[0091] According to one embodiment of the present invention, the a1 may be a molar ratio of nickel (Ni), and may be 0.4 or more, 0.45 or more, 0.5 or more, 0.55 or more, 0.7 or less, 0.65 or less, or 0.6 or less.

[0092] According to one embodiment of the present invention, the b1 may be a molar ratio of cobalt (Co), and may be greater than 0, 0.1 or more, 0.15 or more, 0.2 or more, 0.25 or more, 0.6 or less, 0.55 or less, 0.5 or less, 0.45 or less, or 0.4 or less.

[0093] According to one embodiment of the present invention, the c1 may be a molar ratio of manganese (Mn), and may be greater than 0, 0.1 or more, 0.15 or more, 0.2 or more, 0.6 or less, 0.55 or less, 0.5 or less, 0.45 or less, or 0.4 or less.

[0094] According to one embodiment of the present invention, the content of residual lithium relative to the total content of the positive electrode active material may be 0.80 wt% or less. The residual lithium may include one or more materials selected from the group consisting of LiOH and Li2CO3, and for example, the content of the residual lithium may be 0.8 wt% or less, 0.79 wt% or less, 0.77 wt% or less, 0.75 wt% or less, 0.73 wt% or less, 0.71 wt% or less, or 0.7 wt% or less. In addition, the residual content of Li2CO3 among the residual lithium may be 0.5 wt% or less, 0.48 wt% or less, 0.46 wt% or less, 0.44 wt% or less, 0.42 wt% or less, or 0.4 wt% or less, and the residual content of LiOH may be 0.32 wt% or less, 0.31 wt% or less, 0.3 wt% or less, 0.28 wt% or less, 0.27 wt% or less, 0.25 wt% or less, 0.23 wt% or less, or 0.2 wt% or less. When the above ranges are satisfied, by making a certain level of lithium residue exist, the amount of gas generated during the operation of the lithium secondary battery can be reduced and the stability can be improved. In addition, in the process of coating the positive electrode active material, the residual lithium can participate in the reaction to smoothly form a coating layer.

[0095] According to one embodiment of the present invention, a positive electrode active material is provided, wherein the average particle diameter (D50) of the positive electrode active material is 13 ㎛ or more and 19 ㎛ or less. For example, the average particle diameter of the positive electrode active material may be 13.0 ㎛ or more, 13.3 ㎛ or more, 13.5 ㎛ or more, 13.7 ㎛ or more, 14.0 ㎛ or more, 14.3 ㎛ or more, 14.5 ㎛ or more, 14.7 ㎛ or more, 14.9 ㎛ or more, 15.0 ㎛ or more, 19.0 ㎛ or less, 18.9 ㎛ or less, 18.7 ㎛ or less, 18.5 ㎛ or less, 18.3 ㎛ or less, 18.1 ㎛ or less, 18.0 ㎛ or less, 17.7 ㎛ or less, 17.5 ㎛ or less, 17.3 ㎛ or less, 17.1 ㎛ or less, 17.0 ㎛ or less.

[0096] According to one embodiment of the present invention, the positive electrode active material is provided with a cation mixing of 2.0% or more and 2.4% or less. For example, the positive electrode active material may have a cation mixing of 2.0% or more, 2.05% or more, 2.1% or more, 2.15% or more, 2.2% or more, 2.22% or more, 2.4% or less, 2.39% or less, 2.37% or less, 2.36% or less, 2.35% or less, 2.31% or less, 2.3% or less, 2.27% or less, 2.25% or less, 2.24% or less, and specifically, may be 2.2% or more and 2.25% or less. The cation mixing is the occupancy (or content) of Ni inserted into the Li 3a site (Ni occ ) can be confirmed by measuring it through Rietveld refinement of the X-ray diffraction pattern. When the above range of cation mixing is satisfied, lithium ions can move smoothly, so that a high level of efficiency can be achieved, and further, deformation of the positive electrode active material can be suppressed during operation of the lithium secondary battery, thereby increasing structural stability.

[0097]

[0098] anode

[0099] In addition, the present invention can provide a positive electrode for a lithium secondary battery including a positive electrode active material manufactured by the above-described method.

[0100] Specifically, the positive electrode includes a positive electrode current collector, and a positive electrode active material layer positioned on at least one surface of the positive electrode current collector and including the positive electrode active material described above.

[0101] The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 ㎛ to 500 ㎛, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesive strength of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0102] The above positive electrode active material layer may include a conductive material and a binder together with the positive electrode active material.

[0103] The above positive electrode active material may be included in an amount of 80 wt% to 99 wt%, more specifically 85 wt% to 98 wt%, based on the total weight of the positive electrode active material layer. When included in the above content range, excellent capacity characteristics may be exhibited.

[0104] 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 of these may be used alone or a mixture of two or more may be used. The conductive material may be included in an amount of 1 wt% to 30 wt% based on the total weight of the positive electrode active material layer.

[0105] 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 1 wt% to 30 wt% based on the total weight of the positive electrode active material layer.

[0106] The above-described 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 active material layer forming composition, which is manufactured by dissolving or dispersing the above-described positive electrode active material and optionally a binder and a conductive agent in a solvent, is applied onto 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 agent are as described above.

[0107] 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 composition for forming the active material layer, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0108] Additionally, in another method, the positive electrode may be manufactured by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating the resulting film on a positive electrode current collector by peeling it off from the support.

[0109]

[0110] lithium secondary battery

[0111] In addition, the present invention can manufacture an electrochemical device including the positive electrode. The electrochemical device may be a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, specifically 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive agent is not particularly limited as long as it has conductivity and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0125] 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.

[0126] The above lithium salt can be used without any special limitation as long as it is a compound that can provide lithium ions used in a lithium secondary battery. Specifically, the above lithium salt is 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 above lithium salt concentration is preferably used within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, so that it can exhibit excellent electrolyte performance, and lithium ions can move effectively.

[0127] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrolyte.

[0128] As described above, a lithium secondary battery including a cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and lifespan characteristics, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0129] Accordingly, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0130] 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.

[0131] 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.

[0132] 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.

[0133]

[0134] 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.

[0135]

[0136] Example 1

[0137] Lithium raw material (LiCO3) and transition metal precursor ((Ni 0.55 Co 0.25 Mn 0.2 )3O4) were mixed so that the final Li / Me(Ni, Co, Mn) molar ratio was 1.07, and 0.6 wt% of metal oxide (ZrO2) was added based on the combined weight of the lithium compound and transition metal precursor, and then placed in a planetary mixer and mixed at 1000 rpm for 10 minutes to prepare a mixture.

[0138] The above mixture was heated to 740°C at a rate of 4°C / min by box heat treatment, then maintained at 740°C for 5 hours as a first temperature maintenance section and fired, then further heated to 880°C at a rate of 4°C / min, then maintained at 880°C for 8 hours as a second temperature maintenance section and fired to produce a cathode active material.

[0139]

[0140] Example 2

[0141] A positive electrode active material was manufactured in the same manner as in Example 1, except that the first temperature maintenance section was maintained at 700°C.

[0142]

[0143] Example 3

[0144] A positive electrode active material was manufactured in the same manner as in Example 1, except that the first temperature maintenance section was maintained at 700°C and the second temperature maintenance section was maintained at 870°C.

[0145]

[0146] Comparative Example 1

[0147] A positive electrode active material was manufactured in the same manner as in Example 1, except that the first temperature maintenance section was maintained at 660°C.

[0148]

[0149] Comparative Example 2

[0150] A positive electrode active material was manufactured in the same manner as in Example 1, except that the first temperature maintenance section was not set and firing was performed at 880°C for 8 hours.

[0151]

[0152] Comparative Example 3

[0153] Ni as a transition metal precursor 0.55 Co 0.25 Mn 0.2 A positive electrode active material was manufactured in the same manner as in Example 1, except that (OH)2 was used.

[0154]

[0155] Comparative Example 4

[0156] As a transition metal precursor (Ni 0.98 Co 0.01 Mn 0.01 )3O4 was used and the first temperature maintenance section was maintained at 700°C and the second temperature maintenance section was maintained at 870°C, and the positive electrode active material was manufactured in the same manner as in Example 1.

[0157]

[0158] Comparative Example 5

[0159] As a transition metal precursor (Ni 0.5 Co 0.2 Mn 0.3 )3O4 was used, and the first temperature maintenance section was maintained at 820°C and the second temperature maintenance section was maintained at 870°C, and the positive electrode active material was manufactured in the same manner as in Example 1.

[0160]

[0161] Comparative Example 6

[0162] A positive electrode active material was manufactured in the same manner as in Example 1, except that the second temperature maintenance section was maintained at 930°C.

[0163]

[0164] Comparative Example 7

[0165] A positive electrode active material was manufactured in the same manner as in Example 1, except that no metal oxide (ZrO2) was added.

[0166]

[0167] Comparative Example 8

[0168] Lithium raw material (LiCO3) and transition metal precursor ((Ni 0.90 Co 0.06 Mn 0.04 )3O4) were mixed so that the final Li / Me(Ni, Co, Mn) molar ratio was 1.06, and metal oxides (ZrO2, Al(OH)3, TiO2) were added in amounts of 0.6 wt%, 2.5 wt%, and 0.5 wt%, respectively, based on the combined weight of the lithium compound and transition metal precursor, and then placed in a planetary mixer and mixed at 1000 rpm for 10 minutes to prepare a mixture.

[0169] The above mixture was heated to 650°C at a rate of 4°C / min by box heat treatment, then maintained at 650°C for 3 hours as a first temperature maintenance section and fired, then further heated to 750°C at a rate of 4°C / min, then maintained at 750°C for 6 hours as a second temperature maintenance section and fired to produce a cathode active material.

[0170]

[0171] Experimental Example 1 - ICP Analysis

[0172] Each of the positive electrode active materials manufactured in the above examples and comparative examples was taken in an amount of 0.1 g, and 1.5 ml of 0.1 M hydrochloric acid was added and heated to 80°C to dissolve the positive electrode active material. Thereafter, a small amount of hydrogen peroxide was added to completely dissolve the positive electrode active material to prepare a solution. Next, the solution was diluted with ion-exchanged water to a total volume of 30 ml, and this was diluted 10 times again to prepare an analysis sample. Using an ICP device, the weight ratio of the constituent elements present in the analysis sample was measured, and the composition of the positive electrode active material is shown in Table 1 below.

[0173] Example 1 of composition of a classification system 1.07 Ni 0.55 Co 0.20 Mn 0.25 O4 Example 2Li 1.07 Ni 0.55 Co 0.20 Mn 0.25 O4 Example 3Li 1.07 Ni 0.55 Co 0.20 Mn 0.25 O4 Comparative Example 1Li 1.07 Ni 0.55 Co 0.20 Mn 0.25 O4 Comparative Example 2Li 1.07 Ni 0.55 Co 0.20 Mn 0.25 O4 Comparative Example 3Li 1.07 Ni 0.55 Co 0.20 Mn 0.25 O4 Comparative Example 4Li 1.07 Ni 0.98 Co 0.01 Mn 0.01 O4 Comparative Example 5Li 1.07 Ni 0.55 Co 0.20 Mn 0.25 O4 Comparative Example 6Li 1.07 Ni 0.55 Co 0.20 Mn 0.25 O4 Comparative Example 7Li 1.07 Ni 0.55 Co 0.20 Mn 0.25 O4 comparison example 8Li 1.07 Ni 0.90 Co 0.06 Mn 0.04 O4

[0174] As shown in Table 1 above, it was confirmed that the positive electrode active material manufactured according to the present invention has a nickel (Ni) content of 40 mol% or more and 70 mol% or less among the total transition metal content.

[0175]

[0176] Experimental Example 2 - Measurement of Lithium Residue

[0177] The positive electrode active material powder manufactured in the examples and comparative examples was dissolved in water and then titrated with hydrochloric acid. The contents of LiOH and Li2CO3 contained in the positive electrode active material powder are shown in Table 2.

[0178]

[0179] Experimental Example 3 - Evaluation of Charge-Discharge Characteristics

[0180] Lithium secondary batteries were manufactured using the positive electrode active materials manufactured in the above examples and comparative examples, respectively.

[0181] Specifically, the positive electrode active material, carbon black conductive material, and PVDF binder manufactured in the above examples and comparative examples were mixed in a weight ratio of 95:2.5:2.5 in an N-methylpyrrolidone solvent to manufacture a positive electrode composite, which was then applied to one surface of an aluminum current collector, dried at 100°C, and rolled to manufacture a positive electrode.

[0182] Lithium metal was used as the cathode.

[0183] An electrode assembly was manufactured by interposing a porous polyethylene separator between the positive and negative electrodes manufactured as described above, and the electrode assembly was placed inside a case, and a liquid electrolyte was injected into the case to manufacture a lithium secondary battery. At this time, the liquid electrolyte was manufactured by dissolving 1.0 M lithium hexafluorophosphate (LiPF6) in an organic solvent composed of ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate (mixed volume ratio of EC / DMC / EMC = 3 / 4 / 3).

[0184] Each lithium secondary battery half cell manufactured as described above was charged at 0.2 C in CCCV mode at 25 ℃ until 4.35 V, and discharged to 2.5 V at a constant current of 0.05 C. The charge and discharge were considered as one cycle, and the charge / discharge capacity and charge / discharge efficiency of the first cycle were measured. The results are shown in Table 2 below.

[0185]

[0186] Experimental Example 4 - Niocc Measurement

[0187] The occupancy (or content) of Ni metal inserted into the Li 3a site of the positive electrode active materials manufactured according to the examples and comparative examples was measured through Rietveld refinement of X-ray diffraction patterns. The measurement results are shown in Table 2 below.

[0188] ClassificationLi2CO3(wt%)LiOH(wt%)Total content(wt%)Charge capacity(mAh / g)Discharge capacity(mAh / g)Charge / discharge efficiencyNioccExample 10.440.270.70200.9189.094.02.24Example 20.460.280.75201.5189.694.12.25Example 30.480.310.79202.6189.893.72.36Comparative example 10.560.270.83200.7183.891.62.20Comparative example 20.570.310.88201.8187.592.92.29Comparative example 30.280.300.59203.1187.192.12.58Comparative example 40.5780.581.158243.5214.588.11.87Comparative example 50.0950.1870.282200.4183.091.33.44Comparative example 60.630.290.93200.6185.092.22.22Comparative example 70.670.290.96201.5186.992.72.36Comparative example 80.2250.3130.538239.6221.592.52.12

[0189] Referring to Table 2, it can be confirmed that the positive electrode active materials of Examples 1 to 3 manufactured according to the manufacturing method of the present invention have lithium residual amount and Niocc within the range of the present invention, thereby reducing gas generation and improving structural stability while having excellent charge / discharge efficiency. On the other hand, in the case of Comparative Examples 1 and 2, which exceeded the lower limit of the range of the present invention in the first temperature maintenance section or did not set the first temperature maintenance section, the lithium residual amount exceeded the range of the present invention, and the charge / discharge efficiency was inferior to that of the examples.

[0190] In addition, in the case of Comparative Example 3, which used a hydroxide precursor as a transition metal precursor, excessive cation mixing occurred, resulting in poor battery performance compared to the examples, and in the case of Comparative Example 4, which is high nickel and has a nickel content range outside the range of the present invention, the lithium residue increased excessively, resulting in significantly reduced battery performance.

[0191] In addition, in the case of Comparative Example 5, which is outside the upper limit of the first temperature maintenance section range of the present invention, and Comparative Example 6, which is outside the upper limit of the second temperature maintenance section range of the present invention, it can be confirmed that the lithium residual amount or Niocc value is outside the range of the present invention, and the charge / discharge efficiency is inferior to that of the examples.

[0192] In addition, in the case of Comparative Example 7, which does not include a metal oxide, it can be confirmed that the lithium residual amount value is outside the range of the present invention, and thus the charge / discharge efficiency is inferior to that of the example.

[0193] In addition, in the case of Comparative Example 8, where the content of nickel (Ni) among the total transition metal content exceeded 70 mol%, it was confirmed that the charge / discharge efficiency was inferior to that of the example.

Claims

1. A step of preparing a mixture by mixing a lithium compound, a transition metal oxide, and a metal oxide; and Comprising a calcination step of calcining the above mixture to produce a lithium transition metal oxide, The above transition metal oxide contains Ni in an amount of 40 mol% or more and 70 mol% or less among the total transition metals, A method for manufacturing a positive electrode active material, wherein the above-mentioned firing step is performed through two temperature maintenance sections, the temperature of the first temperature maintenance section being 700°C or more and 800°C or less, and the temperature of the second temperature maintenance section being 800°C or more and 900°C or less.

2. In claim 1, A method for manufacturing a cathode active material, wherein the metal oxide comprises at least one oxide selected from the group consisting of ZrO2, ZnO, Nb2O5, MgO, Fe2O3, V2O5, WO3, SiO, SiO2, and Sn2O3.

3. In claim 1, A method for manufacturing a positive electrode active material, wherein the metal oxide is mixed in an amount of 0.01 wt% or more and 1.0 wt% or less based on the total weight of the mixture.

4. In claim 1, A method for manufacturing a positive electrode active material, wherein the above transition metal oxide contains Ni in an amount of 50 mol% or more and 60 mol% or less among the total transition metals.

5. In claim 1, A method for manufacturing a cathode active material, wherein the above transition metal oxide comprises at least one transition metal selected from the group consisting of Ni, Co, and Mn.

6. In claim 1, A method for manufacturing a positive electrode active material, wherein the above transition metal oxide is represented by the following chemical formula 1. [Chemical Formula 1] Ni a1 Co b1 Mr c1 M d1 (O)4 In the above chemical formula 1, M may include at least one selected from the group consisting of Al, Zr, Mg, Zn, Y, Fe, W and Ti, and 0.4≤a1≤0.7, 0 <b1≤0.6, 0<c1≤0.6, 0≤d1≤0.2, a1+b1+c1+d1 = 1이다.

7. In claim 1, A method for manufacturing a positive electrode active material, wherein the first temperature maintenance section and the second temperature maintenance section are performed continuously.

8. In claim 1, A method for manufacturing a positive electrode active material, wherein the heating rate before reaching the second temperature maintenance section in the first temperature maintenance section is 3.0 ℃ / min or more and 7.0 ℃ / min or less.

9. Contains lithium transition metal oxides of nickel (Ni), cobalt (Co), and manganese (Mn). The above lithium transition metal oxide has a nickel (Ni) content of 40 mol% or more and 70 mol% or less among the total transition metal content, The content of residual lithium is 0.80 wt% or less compared to the total content of the positive electrode active material, A cathode active material having a cation mixture of 2.0% or more and 2.4% or less.

10. In claim 9, A positive electrode active material having an average particle diameter (D50) of 14 ㎛ or more and 19 ㎛ or less.

11. In claim 9, A cathode active material wherein the residual lithium comprises at least one substance selected from the group consisting of LiOH and Li2CO3.

12. A cathode for a secondary battery comprising a cathode active material according to claim 9.

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

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