Precursor of positive electrode active material, positive electrode active material, and method for producing positive electrode active material

Abstract

To provide a method for maximizing energy density by improving density and increasing capacity per volume while maintaining a high capacity effect of a lithium-manganese-rich positive electrode active material, and to provide a positive electrode active material precursor therefor, a method for producing a positive electrode active material, and a positive electrode active material.SOLUTION: Provided are a method of preparing a positive electrode active material, a precursor of a positive electrode active material, and a lithium-manganese-rich positive electrode active material, the method including preparing a nickel-manganese-based oxide by first heat-treating a nickel-manganese-based hydroxide having a manganese content of 34 mol% to 50 mol% based on 100 mol% of total metal at a temperature of 500 °C or less, and obtaining a lithium-manganese-rich positive electrode active material containing a lithium nickel-manganese-based composite oxide by mixing the nickel-manganese-based oxide with a lithium raw material such that a molar ratio of lithium of the lithium raw material to total metal of the nickel-manganese-based oxide is greater than 1 and 2 or less and second heat-treating the mixture.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a precursor of a positive electrode active material, a positive electrode active material, a method for producing a positive electrode active material, and a lithium secondary battery. [Background technology]

[0002] Lithium-manganese-rich (LMR) materials, used as positive electrode active materials for lithium secondary batteries, are layered-structure positive electrode active materials that contain an excess of lithium and a relatively high manganese content. In addition to capacity generation through the oxidation-reduction of existing transition metals, LMR materials also use a new principle called oxygen oxidation-reduction (O-redox), which allows them to generate high capacity while also containing a high proportion of low-cost manganese, drawing attention as an ultra-low-cost next-generation positive electrode active material.

[0003] However, LMR materials have a low specific gravity for LiNiO2, which has a high theoretical density, and a high specific gravity for LiMnO2 and Li2MnO3, which have low theoretical densities. As a result, the theoretical density is lower than that of conventional nickel-based positive electrode active materials. Therefore, even if high capacity (capacity per weight) is achieved, the advantages of capacity per volume, i.e., energy density, are diluted. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention provides a method for maximizing energy density by improving the density and increasing the capacity per volume while maintaining the high capacity effect of a lithium-manganese-rich positive electrode active material, and provides a method for manufacturing a positive electrode active material precursor and a positive electrode active material, as well as the positive electrode active material. [Means for solving the problem]

[0005] In one embodiment of the present invention, there is provided a method for producing a positive electrode active material, comprising: subjecting a nickel-manganese hydroxide having a manganese content of 34 mol % to 50 mol % relative to 100 mol % of total metals to a first heat treatment at a temperature of 500°C or less to produce a nickel-manganese oxide; mixing the nickel-manganese oxide with a lithium raw material so that the molar ratio of lithium in the lithium raw material to total metals in the nickel-manganese oxide is greater than 1 and less than 2; and subjecting the mixture to a second heat treatment to obtain a lithium-manganese-rich positive electrode active material containing a lithium nickel-manganese composite oxide.

[0006] In another embodiment, a positive electrode active material precursor is provided, which contains a nickel-manganese oxide having a manganese content of 34 mol% to 50 mol% relative to 100 mol% of all metals, and in which, in X-ray diffraction analysis, the peak half-width at the (012) crystal plane of the R-3 space group is 0.5 to 3.

[0007] In yet another embodiment, the present invention provides a lithium-manganese-rich positive electrode active material containing a lithium nickel-manganese composite oxide in which the manganese content is 34 mol % to 50 mol % relative to 100 mol % of all metals, and in which, in X-ray diffraction analysis, the ratio of the peak intensity of the (003) crystal plane to the peak intensity of the (104) crystal plane of the R-3m space group is 0.86 to 1.1. [Effects of the Invention]

[0008] The present invention can provide a lithium-manganese-rich positive electrode active material that has improved capacity and density, and maximized capacity and energy density per volume. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 2] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 3]1 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 4] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 5] 1 is a scanning electron microscope (SEM) image of the hydroxide precursor of Comparative Example 1. [Figure 6] 1 is a scanning electron microscope (SEM) image of the hydroxide precursor of Comparative Example 1. [Figure 7] 1 is a SEM image of the oxide precursor of Example 1. [Figure 8] 1 is a SEM image of the oxide precursor of Example 1. [Figure 9] 1 is a SEM image of the oxide precursor of Example 3. [Figure 10] 1 is a SEM image of the oxide precursor of Example 3. [Figure 11] 1 is a SEM image of the oxide precursor of Comparative Example 2. [Figure 12] 1 is a SEM image of the oxide precursor of Comparative Example 2. [Figure 13] 1 is an X-ray diffraction analysis (XRD) of the hydroxide precursor of Comparative Example 1. [Figure 14] 1 is an XRD diagram of the oxide precursor of Example 1. [Figure 15] 1 is an XRD diagram of the oxide precursor of Example 3. [Figure 16] 1 is an XRD diagram of the oxide precursor of Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] Although the present invention may be embodied in many different forms, it is not limited to the embodiments set forth herein.

[0011] The terms used herein are merely used to describe exemplary embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless otherwise clearly indicated in the context.

[0012] As used herein, "combinations thereof" refers to mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like of compositions.

[0013] It should be understood that the terms "comprise," "include," "comprise," or "have" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but do not preclude the possible presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0014] In the drawings, thicknesses of various layers and regions are exaggerated for clarity, and similar parts are designated by the same reference numerals throughout the specification. When a layer, film, region, plate, or other part is said to be "on" or "above" another part, this includes not only the case where it is "directly on" another part, but also the case where there is another part between them. Conversely, when a part is said to be "directly on" another part, it means that there is no other part between them.

[0015] Furthermore, the term "layer" as used herein includes not only shapes formed on the entire surface when observed in a plan view, but also shapes formed on a portion of the surface.

[0016] The average particle size can be measured by a method well known to those skilled in the art, for example, by using a particle size analyzer or by using a transmission electron microscope or a scanning electron microscope. Alternatively, the average particle size can be calculated by measuring using a dynamic light scattering method and then counting the number of particles in each particle size range through data analysis. Unless otherwise defined, the average particle size is the diameter (D) of particles whose cumulative volume is 50% by volume in the particle size distribution. 50) and, unless otherwise defined, the average particle size is the diameter (D) of the particle that makes up 50% of the cumulative volume in the particle size distribution obtained by measuring the size (diameter or length of the major axis) of 20 or more particles randomly selected from a scanning electron microscope image. 50 ) can be taken as the average particle size.

[0017] Here, "or" is not to be construed in an exclusive sense; for example, "A or B" is to be construed as including A, B, A+B, etc.

[0018] The term "metal" is understood to include general metals, transition metals, and metalloids (semimetals).

[0019] Method for producing positive electrode active material In one embodiment, a method for producing a positive electrode active material includes first heat-treating a nickel-manganese hydroxide having a manganese content of 34 mol% to 50 mol% relative to 100 mol% of total metals at a temperature of 500°C or less to produce a nickel-manganese oxide, and then mixing the nickel-manganese oxide with a lithium source so that the molar ratio of lithium in the lithium source to total metals in the nickel-manganese oxide is greater than 1 and less than 2, followed by second heat-treating the resulting mixture to obtain a lithium-manganese-rich positive electrode active material containing a lithium nickel-manganese composite oxide. This method can provide a lithium-manganese-rich positive electrode active material with high capacity and density and improved energy density.

[0020] Generally, the easiest way to increase the density of a cathode active material is to increase particle size and reduce the porosity. However, unlike nickel-rich cathode active material precursors, lithium-manganese-rich cathode active materials have drawbacks, such as difficulty in controlling the synthesis conditions through the co-precipitation process and difficulty in increasing particle density. For example, precursors for lithium-manganese-rich cathode active materials are typically prepared from either carbonate-based or hydroxide-based raw materials. Carbonate-based raw materials have a low impurity content after the co-precipitation reaction, making it easy to control the reaction and particle shape. However, they have drawbacks, such as the rapid growth rate of secondary particles compared to primary particles, making it difficult to reduce the porosity. Hydroxide-based raw materials are advantageous for increasing density due to the high sphericity of secondary particles and low porosity. However, Mn(OH)2 tends to grow into needle, lamellar, or plate-like shapes, making it difficult to synthesize a high-density precursor. They also have drawbacks, such as difficult reaction control, the easy generation of impurities, and poor reproducibility.

[0021] In one embodiment, a lithium-manganese-rich cathode active material is manufactured by calcining a hydroxide precursor at a low temperature to obtain an oxide precursor, and then mixing the oxide precursor with a lithium source and performing a secondary calcination. Here, the term "hydroxide precursor" refers to a precursor of a cathode active material having a metal hydroxide composition, while the term "oxide precursor" refers to a precursor of a cathode active material having a metal oxide composition. The oxide precursor, which has a manganese to total metal molar ratio of 50% or less, is subjected to a primary heat treatment at a temperature of 500°C or less to produce an oxide precursor. This oxide precursor is then mixed with a lithium source and subjected to a secondary heat treatment, thereby improving both capacity and density, thereby improving capacity per volume. The oxide precursor according to one embodiment has a significantly increased specific surface area compared to the hydroxide precursor, which improves reactivity with the lithium source, and this is understood to contribute to the improved density and capacity of the lithium-manganese-rich cathode active material.

[0022] In one embodiment of the method for preparing a positive electrode active material, the nickel-manganese hydroxide refers to a hydroxide precursor, and is characterized by having a manganese content of 34 mol% to 50 mol% relative to 100 mol% of the total metals. The manganese content in the hydroxide precursor may be 35 mol% to 50 mol%, 36 mol% to 50 mol%, 38 mol% to 50 mol%, 40 mol% to 50 mol%, or 45 mol% to 50 mol% relative to 100 mol% of the total metals, for example, 35 mol%, 40 mol%, 45 mol%, or 50 mol%. When a hydroxide precursor having a manganese molar ratio within the above range is used, the oxide precursor prepared by the method of this embodiment has a significantly increased specific surface area. Therefore, a positive electrode active material prepared using the hydroxide precursor can achieve high capacity and simultaneously exhibit high pellet density, thereby improving energy density. For example, when a nickel-manganese hydroxide having a manganese content of more than 50 mol% relative to the total metal is used as a precursor, the specific surface area of ​​the oxide precursor produced by the method of one embodiment may not increase or may increase only slightly, and the pellet density of the synthesized cathode active material may not increase or may be small, and the capacity per weight may not increase, resulting in no improvement in capacity per volume. In one embodiment, a method for simultaneously improving capacity and density is proposed when producing a lithium-manganese-rich cathode active material using a precursor having a manganese content of 34 mol% to 50 mol%.

[0023] The nickel-manganese hydroxide is, for example, represented by the following chemical formula 11. [Chemical formula 11] Ni y11 Mn z11 M 11 1-y11-z11 (OH)2

[0024] In Chemical Formula 11, 0.5≦y11≦0.66, 0.34≦z11≦0.5, and M 11is one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, or Zr.

[0025] In the formula 11, for example, 0.5≦y11≦0.6, 0.4≦z11≦0.5, or 0.5≦y11≦0.55, 0.45≦z11≦0.5.

[0026] The average particle size (D 50 ) may be, for example, 2 μm to 18 μm, specifically 3 μm to 15 μm, 4 μm to 13 μm, or 5 μm to 12 μm. When the particle size range is satisfied, a lithium-manganese-rich cathode active material with high density and capacity can be effectively produced by the method of one embodiment. Here, the average particle size may be determined by measuring the sizes (e.g., particle size, major axis, or major axis length) of approximately 20 random particles from an SEM image of the precursor, obtaining a particle size distribution, and then taking the size of the particles that make up 50% of the cumulative volume as the average particle size.

[0027] The primary heat treatment temperature is preferably 500°C or less, e.g., 250°C to 500°C, 300°C to 500°C, 350°C to 500°C, or 400°C to 500°C, e.g., 400°C, 450°C, or 500°C. By performing the primary heat treatment within this temperature range, the specific surface area of ​​the oxide precursor can be significantly increased, effectively producing a lithium-manganese-rich cathode active material with improved density and capacity. If the primary heat treatment temperature is outside this range, e.g., exceeds 500°C, the resulting oxide precursor will have a significantly reduced specific surface area compared to oxide precursors obtained by heat treatment at 500°C or higher. The resulting cathode active material will have a relatively low pellet density, which may result in a poor capacity per volume.

[0028] The primary heat treatment may be performed in an oxygen atmosphere or an air atmosphere for 1 to 10 hours, for example, 2 to 9 hours, or 4 to 8 hours. When these conditions are met, an oxide precursor with a high specific surface area can be effectively produced, and a cathode active material with high density and capacity can be effectively produced.

[0029] The molar ratio of lithium in the lithium raw material to the total metals in the nickel-manganese oxide precursor is 1.06 to 2, for example, 1.06 to 1.8, 1.06 to 1.6, 1.06 to 1.5, 1.1 to 1.45, 1.1 to 1.4, 1.1 to 1.3, 1.1 to 1.2, 1.2 to 1.8, 1.2 to 1.5, or 1.3 to 1.45, and may be, for example, 1.12. By appropriately designing the molar ratio of lithium to metals, it is possible to produce a lithium-manganese-rich positive electrode active material with high capacity and density.

[0030] The lithium source may be lithium hydroxide, lithium carbonate, lithium sulfate, lithium nitrate, or a combination thereof, and an example thereof may be anhydrous lithium hydroxide.

[0031] When anhydrous lithium hydroxide is used as the lithium raw material, the amount of raw material charged in the synthesis process of the cathode active material can be increased, improving production per hour, and the amount of unnecessary gas and moisture generated during heat treatment can be reduced, improving processability and improving the quality of the cathode active material.In addition, by eliminating the input of unnecessary heavy materials such as H2O, the heat treatment yield can be increased, improving productivity.

[0032] As an example, the anhydrous lithium hydroxide (LiOH) has an average particle size (D 50 After drying, hydrated lithium hydroxide (LiOH·HO) with an average particle size (D 50The anhydrous lithium hydroxide can be produced by pulverizing the starting material so that the average particle size (D) of the hydrated lithium hydroxide is about 3 μm to 30 μm. The anhydrous lithium hydroxide can be produced by pulverizing once after drying, without pulverizing before drying. The drying can be carried out, for example, under vacuum conditions at a temperature range of 50°C to 200°C for 0.5 to 20 hours. 50 ) is, for example, about 450 μm to 550 μm, 480 μm to 500 μm, and the average particle size (D 50 ) may be about 3 μm to 25 μm or about 5 μm to 20 μm.

[0033] According to this method for producing anhydrous lithium hydroxide, the process for obtaining anhydrous lithium salt is simple, optimal process conditions can be maintained, and the conversion rate to Li2CO3 is low (5% or less), making it possible to obtain high-purity anhydrous lithium hydroxide. After anhydrous lithium hydroxide is pulverized, the powder's fluidity rapidly decreases, making it generally very difficult to perform additional processing after pulverization. For example, when the pulverized material is dried, the heat generated during drying causes the fine particles to become entangled and agglomerate, necessitating an additional pulverization process. However, the high agglomeration strength of the particles makes pulverization difficult. Furthermore, as the number of processes increases, the conversion rate to Li2CO3 increases due to the increase in specific surface area, making it difficult to obtain high-quality anhydrous lithium hydroxide. According to one embodiment of the method for producing anhydrous lithium hydroxide, anhydrous lithium hydroxide is dried under specific conditions and then pulverized once to a specific size, making the process simple and allowing for the production of high-quality anhydrous lithium hydroxide. Furthermore, additional processing steps can be easily performed after pulverization.

[0034] In one embodiment of the method for manufacturing a positive electrode active material, the second heat treatment may be performed at a temperature of 950° C. or higher, for example, 950° C. to 1100° C., 975° C. to 1050° C., or 975° C. to 1000° C., for example, 950° C., 975° C., or 1000° C. The second heat treatment may be performed for 1 second to 48 hours, for example, 4 hours to 42 hours, 8 hours to 36 hours, 12 hours to 32 hours, or 18 hours to 28 hours.

[0035] When a hydroxide precursor and a lithium source are mixed and calcined as in conventional methods, increasing the calcination temperature can grow particles, reducing the porosity of the cathode active material and increasing pellet density. However, the increased particle size can have the opposite effect of increasing resistance and reducing capacity, limiting the calcination temperature. Therefore, the optimal calcination temperature must be set relatively low, ultimately making it difficult to simultaneously increase capacity and pellet density. On the other hand, in one embodiment, a process for preparing a lithium-manganese-rich cathode active material by mixing an oxide precursor and a lithium source and performing a secondary heat treatment can be performed at a higher calcination temperature than when a hydroxide precursor is used, thereby increasing pellet density and improving capacity. This is presumably because the large specific surface area of ​​the oxide precursor facilitates the reaction between the oxide precursor and the lithium source, resulting in the synthesis of a lithium-manganese-rich cathode active material with a layered crystalline structure with fewer defects and superior conductivity properties. Therefore, in the method for manufacturing a cathode active material according to one embodiment, the secondary heat treatment may be performed at a temperature range of 950°C or higher, or 1000°C or higher, thereby producing a cathode active material having high pellet density and capacity, and improved capacity per volume.

[0036] Positive electrode active material precursor In one embodiment, a precursor having a metal oxide composition is provided as a precursor for a lithium-manganese-rich cathode active material. The cathode active material precursor according to one embodiment contains a nickel-manganese oxide with a manganese content of 34 mol% to 50 mol% relative to 100 mol% of the total metals, and is characterized by an X-ray diffraction peak half-width of 0.5 to 3 in the (012) crystal plane of the R-3 space group. This oxide precursor can be obtained by a primary heat treatment in the method for manufacturing a cathode active material described above. The crystal structure of the oxide precursor corresponds to the R-3 space group, and can be said to have a (012) crystal plane belonging to the R-3 space group, a (104) crystal plane belonging to the R-3 space group, and / or a (024) crystal plane belonging to the R-3 space group. This distinguishes the final cathode active material from one having a crystal structure of the R-3m space group.

[0037] Specifically, unlike hydroxide precursors, the oxide precursor may exhibit peaks at multiple positions in 2θ values, such as (22-27)°, (30-35)°, and (49-52)°, in X-ray diffraction analysis. The peak half-width at the (012) crystal plane of the R-3 space group, corresponding to a 2θ value of (22-27)°, may be 0.5 to 3, e.g., 1 to 3, or 1.5 to 2.5. The peak half-width at the (104) crystal plane of the R-3 space group, corresponding to a 2θ value of (30-35)°, may be 0.5 to 3, e.g., 1 to 3, or 1 to 2. The peak half-width at the (024) crystal plane, corresponding to a 2θ value of (49-52)°, may be 0.5 to 2, e.g., 1 to 2, or 1.5 to 2. The specific surface area of ​​the positive electrode active material precursor is 10 m 2 / g~50m 2 / g, for example, 15m 2 / g~40m 2 / g, 18m 2 / g~38m 2 / g, or 20m 2 / g~35m 2 / g. The oxide precursor according to one embodiment is prepared by calcining a hydroxide precursor within a specific temperature range and conditions, and is characterized by having a significantly increased specific surface area compared to the hydroxide precursor. This significantly increased specific surface area of ​​the oxide precursor increases the reactivity of the oxide precursor with a lithium source, which is understood to improve both the capacity and density of the synthesized cathode active material.

[0038] The average particle size (D 50 ) may be, for example, 2 μm to 18 μm, specifically 3 μm to 15 μm, 4 μm to 13 μm, or 5 μm to 12 μm. When the above particle size range is satisfied, a lithium-manganese-rich cathode active material with high density and capacity can be effectively produced by the method of one embodiment. Here, the average particle size may be determined by measuring the sizes (e.g., particle size, major axis, or major axis length) of approximately 20 random particles from an SEM image of the precursor, obtaining a particle size distribution, and then taking the size of the particles that make up 50% of the cumulative volume as the average particle size.

[0039] The oxide precursor is, for example, represented by Chemical Formula 21. [Chemical formula 21] Ni y21 Mn z21 M 21 1-y21-z21 O3

[0040] In Chemical Formula 21, 0.5≦y21≦0.66, 0.34≦z21≦0.5, and M 21 is one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, or Zr.

[0041] In the formula 21, for example, 0.5≦y21≦0.6, 0.4≦z21≦0.5, or 0.5≦y21≦0.55, 0.45≦z21≦0.5.

[0042] positive electrode active material In one embodiment, a lithium-manganese-rich cathode active material is provided that is manufactured by the above-described method and has high density and capacity, and has improved capacity per volume and energy density. The cathode active material according to one embodiment includes a lithium nickel-manganese composite oxide having a manganese content of 34 mol% to 50 mol% relative to 100 mol% of all metals excluding lithium, and is characterized in that, in X-ray diffraction analysis, the ratio of the peak intensity of the (003) crystal plane to the peak intensity of the (104) crystal plane in the R-3m space group satisfies 0.86 to 1.1.

[0043] The crystal structure of the positive electrode active material corresponds to the R-3m space group, which distinguishes it from the oxide precursor described above, which has a crystal structure of the R-3 space group. For example, the (104) crystal plane of the R-3m space group and the (104) crystal plane of the R-3 space group should be understood to be different crystal planes. The positive electrode active material can be said to have the (104) crystal plane of the R-3m space group and / or the (003) crystal plane of the R-3m space group.

[0044] Specifically, the positive electrode active material may have a ratio of the peak intensity of the (003) crystal plane to the peak intensity of the (104) crystal plane of the R-3m space group in X-ray diffraction analysis of 0.86 to 1.1, 0.86 to 1.04, or 0.90 to 0.99.

[0045] In an X-ray diffraction analysis of the positive electrode active material, the (104) crystal plane peak half width of 0.310 to 0.340 and the (003) crystal plane peak half width of 0.150 to 0.165 in the R-3m space group may be obtained.

[0046] The positive electrode active material may have a ratio of the c-axis lattice constant to the a-axis lattice constant of 4.951 to 4.953 as determined by X-ray diffraction analysis.

[0047] The average particle size (D 50) may be, for example, 2 μm to 18 μm, specifically 3 μm to 15 μm, 4 μm to 13 μm, or 5 μm to 12 μm. Here, the average particle size may be determined by measuring the sizes (e.g., particle size, major axis, or length of the major axis) of approximately 20 random particles from an SEM image of the positive electrode active material, obtaining a particle size distribution, and then taking the size of particles that make up 50% of the cumulative volume as the average particle size.

[0048] The pellet density of the positive electrode active material may be 2.7 g / cc or more, for example, 2.85 g / cc or more, 2.85 g / cc to 3.00 g / cc, or 2.90 g / cc to 2.95 g / cc. The positive electrode active material according to an embodiment may achieve a higher pellet density than conventional lithium-manganese-rich positive electrode active materials, thereby exhibiting a higher capacity per volume.

[0049] The capacity per volume of the positive electrode active material is 520 mAh / cc or more, for example, 554 mAh / cc or more, 554 mAh / cc to 565 mAh / cc, or 558 mAh / cc to 563 mAh / cc.

[0050] The lithium-manganese-rich positive electrode active material is characterized in that it exhibits capacity through the oxidation-reduction reaction of transition metals while simultaneously exhibiting capacity through the oxidation-reduction reaction of oxygen.

[0051] The lithium-manganese-rich positive electrode active material is, for example, represented by Chemical Formula 1. [Chemical formula 1] a[Li 1+x (Ni y Mn z M 1 1-y-z ) 1-x O2]+(1-a)[b(LiNi j Mn k M 1 1-j-k O2)+c(Li2Mn w M 1 1-w O3)]

[0052] In the above chemical formula 1, 0≦a≦1, 0.03≦x≦0.2, 0.50≦y≦0.66, 0.34≦z≦0.50, 0 <b<1、0<c<1、0.50≦j≦1.0、0.50≦k≦1.0、0.9≦w≦1.0およびM 1 is one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, or Zr.

[0053] In the above formula 1, [Li 1+x (Ni y Mn z M 1 1-y-z ) 1-x O2] indicates a solid-solution phase, and [b(LiNi j Mn k M 1 1-j-k O2)+c(Li2Mn w M 1 1-w O3) can be said to exhibit a composite phase. That is, the compound represented by Chemical Formula 1 can be said to have either a solid solution phase or a composite phase structure.

[0054] Here, a solid solution can be defined as a solid mixture in which different elements are completely and uniformly mixed, with other elements incorporated and uniformly distributed in the solid crystal, resembling a solution where solute is uniformly distributed in a solvent. A solid solution can be a compound with a new property formed by the strong mutual relationship of two or more individual components, having a continuum quasi-isostructural nature. The solid solution is homogeneous, has a nearly identical composition, and can have a single phase or a single crystal structure. In contrast, a composite is formed by bonding two or more materials, consisting of materials with different physical properties, and the materials maintain a physically distinguishable state. A composite is heterogeneous, can have two or more compositions, and can have two or more phases or crystal structures.

[0055] The lithium-manganese-rich cathode active material according to one embodiment can be said to be a material with an additional solid solution phase in addition to the composite phase, for example, a material in which the composite and the solid solution coexist, or a material in which the composite and the solid solution coexist competitively. In this case, in Chemical Formula 1, the value of a can be 0 < a < 1. The lithium-manganese-rich cathode active material is, for example, 0.3[Li 1.13 Ni 0.44 Mn 0.44 O2]+0.7[0.61(LiNi 0.72 Mn 0.28 O2)+0.26(Li2MnO3)], represented by 0.15[Li 1.13 Ni 0.57 Mn 0.30 O2]+0.85[0.61(LiNi 0.94 Mn 0.06 O2)+0.26(Li2MnO3)], represented by 0.41[Li 1.09 Ni 0.46 Mn 0.46 O2]+0.59[0.85(LiNi 0.56 Mn 0.44 O2)+0.10(Li2MnO3], or 0.43[Li1.05 Ni 0.48 Mn 0.48 O2] + 0.57 [0.85(LiNi 0.56 Mn 0.44 O2) + 0.10(Li2MnO3)], but is not limited to this.

[0056] In one embodiment, the lithium-manganese-rich positive electrode active material may have a molar ratio of lithium to all metals excluding lithium of, for example, 1.1 or more and 1.2 or less.

[0057] In Chemical Formula 1, (1+x) is the molar ratio of lithium, and (1+x) / (1-x) is the ratio of the lithium content to the total metal content excluding lithium. In Chemical Formula 1, the range of x is 0.03≦x≦0.2, and may be, for example, 0.03≦x≦0.15, 0.03≦x≦0.13, 0.03≦x≦0.11, or 0.03≦x≦0.09.

[0058] In an embodiment of the lithium-manganese-rich positive electrode active material, the cobalt content relative to 100 mol % of all metals excluding lithium may be 0 mol % to 1 mol %, or 0 mol % to 0.1 mol %, or 0 mol % to 0.01 mol %.

[0059] positive electrode In one embodiment, a positive electrode using the above-described positive electrode active material is provided. The positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, the positive electrode active material layer including the above-described lithium-manganese-rich positive electrode active material. The positive electrode active material layer may further include other types of positive electrode active materials in addition to the above-described positive electrode active material, and may optionally further include a binder, a conductive material, or a combination thereof.

[0060] binder The binder serves to firmly adhere the positive electrode active material particles to each other and to firmly adhere the positive electrode active material to the current collector. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0061] Conductive material The conductive material is used to impart electrical conductivity to the electrode, and any material that is electron-conductive and does not cause chemical changes in the battery that is constructed can be used. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0062] The content of the binder and the conductive material may be 0.5% by weight to 5% by weight, respectively, relative to 100% by weight of the positive electrode active material layer.

[0063] The positive electrode current collector may be made of Al, SUS (stainless steel), or the like, but is not limited to these.

[0064] Lithium secondary battery In one embodiment, a lithium secondary battery is provided that employs the above-described positive electrode active material. The lithium secondary battery can include a positive electrode containing the lithium-manganese-rich positive electrode active material, a negative electrode, and an electrolyte. The lithium secondary battery can be a lithium ion battery employing a liquid electrolyte, or an all-solid-state secondary battery or semi-solid-state secondary battery employing a solid electrolyte. For convenience, the configuration of the lithium ion battery will be described in detail below.

[0065] Lithium secondary batteries can be classified into cylindrical, prismatic, pouch, and coin types depending on their shape. FIGS. 1 to 4 are schematic diagrams showing lithium secondary batteries according to an embodiment, with FIG. 1 showing a cylindrical battery, FIG. 2 showing a prismatic battery, and FIGS. 3 and 4 showing pouch-type batteries. Referring to FIGS. 1 to 4, a lithium secondary battery 100 may include an electrode assembly 40 having a positive electrode 10 and a negative electrode 20 with a separator 30 interposed therebetween, and a case 50 in which the electrode assembly 40 is housed. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). The lithium secondary battery 100 may include a sealing member 60 that seals the case 50, as shown in FIG. 1. Also, in FIG. 2, the lithium secondary battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As shown in FIGS. 3 and 4, the lithium secondary battery 100 may include electrode tabs 70, i.e., a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical paths for conducting the current generated in the electrode assembly 40 to the outside.

[0066] negative electrode The negative electrode may include a current collector and a negative electrode active material layer located on the current collector. The negative electrode active material layer includes a negative electrode active material and may further include a binder, a conductive material, or a combination thereof.

[0067] negative electrode active material The negative electrode active material includes a material capable of reversibly inserting / extracting lithium ions, lithium metal, a lithium metal alloy, a material capable of being doped with and dedoped from lithium, or a transition metal oxide.

[0068] As the substance capable of reversibly inserting / desorbing the lithium ions, a carbon-based negative electrode active material can be used, which can include, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical or fibrous natural graphite, or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0069] As the alloy of the lithium metal, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn can be used.

[0070] As the substance capable of doping and undoping lithium, an Si-based negative electrode active material or a Sn-based negative electrode active material can be used. The Si-based negative electrode active material can be silicon, a silicon-carbon composite, SiOx (0 < x < 2), an Si-Q alloy (where Q is an element selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, for example, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof), or a combination thereof. The Sn-based negative electrode active material can be Sn, SnO2, a Sn alloy, or a combination thereof.

[0071] The silicon-carbon composite can be a composite of silicon and amorphous carbon. The average particle size (D of the silicon-carbon composite particles 50) may be, for example, 0.5 μm to 20 μm. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles, and the surfaces of the silicon particles may be coated with amorphous carbon. For example, it may include secondary particles (cores) formed by granulating primary silicon particles, and an amorphous carbon coating layer (shell) located on the surfaces of the secondary particles. The amorphous carbon may also be located between the primary silicon particles, for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0072] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core including crystalline carbon and silicon particles, and an amorphous carbon coating layer located on the core surface. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. Examples of the amorphous carbon include soft carbon, hard carbon, mesophase pitch carbide, and calcined coke.

[0073] When the silicon-carbon composite contains silicon and amorphous carbon, the silicon content may be 10 to 50% by weight and the amorphous carbon content may be 50 to 90% by weight, based on 100% by weight of the silicon-carbon composite.Alternatively, when the composite contains silicon, amorphous carbon, and crystalline carbon, the silicon content may be 10 to 50% by weight, the crystalline carbon content may be 10 to 70% by weight, and the amorphous carbon content may be 20 to 40% by weight, based on 100% by weight of the silicon-carbon composite.

[0074] The thickness of the amorphous carbon coating layer may be 5 nm to 100 nm. 50 ) can be 10 nm to 1 μm, or 10 nm to 200 nm. The silicon particles may be present as silicon alone, in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon is SiO xIt can be represented by (0 < x < 2). At this time, the ratio of the atomic content of Si:O indicating the degree of oxidation can be 99:1 to 33:67. In this specification, unless otherwise defined, the average particle size (D 50 ) means the diameter of the particle with a cumulative volume of 50% by volume in the particle size distribution.

[0075] The Si-based negative electrode active material or the Sn-based negative electrode active material can be used by mixing with a carbon-based negative electrode active material. When the Si-based negative electrode active material or the Sn-based negative electrode active material and the carbon-based negative electrode active material are used in combination, the mixing ratio can be 1:99 to 90:10 by weight ratio.

[0076] Binder The binder plays a role of making the negative electrode active material particles adhere well to each other and making the negative electrode active material adhere well to the current collector. As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof can be used.

[0077] Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0078] The aqueous binder can be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluorine rubber, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene-propylene-diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0079] When an aqueous binder is used as the negative electrode binder, a cellulose-based compound that can impart viscosity may be further included. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof. The alkali metal may be sodium, potassium, or lithium.

[0080] The dry binder can be a fiberizable polymeric material such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0081] Conductive material The conductive material is used to impart conductivity to the electrode and can be any material that is electron-conductive and does not cause chemical changes in the battery. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0082] The content of the negative electrode active material may be 95% to 99.5% by weight, and the content of the binder may be 0.5% to 5% by weight, relative to 100% by weight of the negative electrode active material layer. For example, the negative electrode active material layer may contain 90% to 99% by weight of the negative electrode active material, 0.5% to 5% by weight of the binder, and 0.5% to 5% by weight of the conductive material.

[0083] current collector The negative electrode current collector can include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof, and can be in the form of a foil, sheet, or foam. The thickness of the negative electrode current collector can be, for example, 1 μm to 20 μm, 5 μm to 15 μm, or 7 μm to 10 μm.

[0084] electrolyte The electrolyte for a lithium secondary battery can be, for example, an electrolytic solution, which can include a non-aqueous organic solvent and a lithium salt.

[0085] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reactions of the battery can migrate, and can be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0086] Examples of carbonate solvents that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. Examples of ester solvents that can be used include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc. Examples of ether solvents that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Examples of ketone solvents that can be used include cyclohexanone. Examples of alcohol solvents that can be used include ethyl alcohol and isopropyl alcohol. Examples of aprotic solvents that can be used include nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes.

[0087] The non-aqueous organic solvent may be used alone or in combination of two or more kinds. When a mixture of two or more kinds is used, the mixing ratio may be appropriately adjusted depending on the desired battery performance, which is widely understood by those skilled in the art.

[0088] When a carbonate-based solvent is used, a cyclic carbonate and a chain carbonate can be mixed and used, and the cyclic carbonate and the chain carbonate can be mixed in a volume ratio of 1:1 to 1:9.

[0089] The non-aqueous organic solvent may further include an aromatic hydrocarbon organic solvent. For example, a carbonate solvent and an aromatic hydrocarbon organic solvent may be mixed in a volume ratio of 1:1 to 30:1.

[0090] The electrolyte may further contain vinyl ethyl carbonate, vinylene carbonate or ethylene carbonate based compounds to improve the battery life.

[0091] Representative examples of the ethylene carbonate compounds include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and cyanoethylene carbonate.

[0092] Lithium salts are substances that dissolve in organic solvents and act as a source of lithium ions within the battery, enabling basic lithium secondary battery operation and facilitating the movement of lithium ions between the positive and negative electrodes. Representative examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (x and y are integers of 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFOB), and lithium bis(oxalato)borate (LiBOB).

[0093] The concentration of the lithium salt is preferably within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within this range, the electrolyte has appropriate ionic conductivity and viscosity, thereby exhibiting excellent performance and allowing lithium ions to migrate effectively.

[0094] Separator Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators may be made of polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more of these. Of course, mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0095] The separator may include a porous substrate and a coating layer including an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0096] The porous substrate may be a polymer membrane formed of any one polymer selected from polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyaryl ether ketone, polyetherimide, polyamide imide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon (registered trademark), and polytetrafluoroethylene, or a copolymer or mixture of two or more of these polymers.

[0097] The porous substrate can have a thickness of about 1 μm to 40 μm, for example, 1 μm to 30 μm, 1 μm to 20 μm, 5 μm to 15 μm, or 10 μm to 15 μm.

[0098] The organic material may include a (meth)acrylic copolymer including a first structural unit derived from (meth)acrylamide and a second structural unit including at least one of a structural unit derived from (meth)acrylic acid or a (meth)acrylate and a structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof.

[0099] The inorganic material may include, but is not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof. The average particle size (D 50 ) is 1 nm to 2000 nm, and can be, for example, 100 nm to 1000 nm, or 100 nm to 700 nm.

[0100] The organic material and the inorganic material may be mixed in one coating layer, or may be stacked in a coating layer containing an organic material and a coating layer containing an inorganic material.

[0101] The thickness of each of the coating layers may be 0.5 μm to 20 μm, for example, 1 μm to 10 μm, or 1 μm to 5 μm.

[0102] Examples of the present invention and comparative examples are described below. The following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples.

[0103] Comparative Example 1 1. Production of positive electrode active material A mixed metal solution was prepared by dissolving nickel sulfate (NiSO4·6H2O) and manganese sulfate (MnSO4·H2O) in distilled water as a solvent to give a molar ratio of Ni:Mn = 50:50. Ammonia water (NH4OH) and sodium hydroxide (NaOH) were prepared as a precipitant to form the complex compound.

[0104] Ammonia water with a concentration of 0.25M was placed in the reactor, and the stirring power was 3.0 kW / m 3 The reaction was initiated by adding the metal raw material mixed solution and complexing agent at a rate of 142 ml / min and 34 ml / min, respectively, at a reaction temperature of 50°C. The reaction was continued for 30 hours while adding NaOH to maintain the pH. The reaction was terminated when the average size of the resulting particles reached approximately 10 μm. The resulting product was washed and then dried with hot air at approximately 150°C for 24 hours to obtain the hydroxide precursor, nickel-manganese hydroxide (Ni 0.5 Mn 0.5 (OH)2) was prepared.

[0105] Produced Ni 0.5 Mn 0.5 (OH)2 and LiOH were mixed so that the molar ratio of Li / (Ni+Mn) was 1.12, and the mixture was heat-treated in an oxygen atmosphere at 1000°C for 24 hours to produce a lithium-manganese rich positive electrode active material.

[0106] 2. Manufacturing of lithium secondary batteries (half cells) 96 wt% of the prepared positive electrode active material, 2 wt% of polyvinylidene fluoride binder, and 2 wt% of carbon nanotube conductive material were mixed to prepare a positive electrode active material layer slurry, which was then coated on an aluminum foil current collector, dried, and rolled to prepare a positive electrode. At this time, the loading level of the positive electrode active material layer was 10 mg / cm. 2 and the density of the final rolled cathode is about 3.5 g / cc.

[0107] The fabricated positive electrode and lithium counter electrode were inserted into a battery case with a polytetrafluoroethylene separator between them, and an electrolyte solution prepared by dissolving 1M LiPF6 in a solvent made by mixing ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in a volume ratio of 2:4:4, to which 1.5 wt% vinylene carbonate had been added, was poured into the case, and a lithium secondary battery was fabricated in a conventional manner.

[0108] Example 1 In the production of the positive electrode active material of Comparative Example 1, Ni 0.5 Mn 0.5 A positive electrode active material and a lithium secondary battery were manufactured in substantially the same manner as in Comparative Example 1, except that (OH)2 was first heat-treated in an oxygen atmosphere at 400°C for 6 hours to prepare a nickel-manganese-based oxide, and the prepared nickel-manganese-based oxide was mixed with LiOH so that the molar ratio of Li / (Ni+Mn) was 1.12. The mixture was then secondly heat-treated in an oxygen atmosphere at 1000°C for 24 hours to prepare a lithium-manganese-rich positive electrode active material according to Example 1.

[0109] Example 2 A positive electrode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the primary heat treatment temperature was changed to 450°C.

[0110] Example 3 A positive electrode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the primary heat treatment temperature was changed to 500°C.

[0111] Comparative Example 2 A positive electrode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the primary heat treatment temperature was changed to 600°C.

[0112] Table 1 below shows the design details of Examples 1 to 3 and Comparative Examples 1 and 2, as well as the analysis results of the precursor, the positive electrode active material, and the battery.

[0113] [Table 1]

[0114] Evaluation example 1: Observation of precursor surface by SEM The hydroxide precursor of Comparative Example 1 (Ni 0.5 Mn 0.5SEM images of the oxide precursor of Example 1 are shown in Figures 5 and 6, and SEM images of the oxide precursor of Example 3 are shown in Figures 9 and 10, and SEM images of the oxide precursor of Comparative Example 2 are shown in Figures 11 and 12.

[0115] 5 to 12, it can be seen that the hydroxide precursor of Comparative Example 1 has a different surface shape from the oxide precursors of Examples 1 and 2 and Comparative Example 2. Furthermore, when comparing the oxide precursors of Examples 1 and 2 with the oxide precursor of Comparative Example 2, it can be seen that the surface shape changes depending on the primary heat treatment temperature.

[0116] Evaluation example 2: Precursor specific surface area analysis The specific surface area of ​​the hydroxide precursor of Comparative Example 1 and the BET specific surface areas of the oxide precursors of Examples 1 to 3 and Comparative Example 2 were measured and are shown in Table 1 above.

[0117] The BET specific surface area can be measured by a nitrogen gas adsorption method using, for example, a MOUNTECH HM model-1208 specific surface area analyzer. Specifically, approximately 0.3 g of a sample is heated in a nitrogen atmosphere at 300°C in a pretreatment device for 1 hour, then further pretreated at 300°C for 15 minutes in a specific surface area analyzer, cooled to the temperature of liquid nitrogen, and saturated adsorbed with a gas mixture of 30% nitrogen and 70% He. The sample is then heated to room temperature, the amount of desorbed gas is measured, and the specific surface area can be calculated from the obtained results using a conventional BET method.

[0118] Referring to Table 1, the specific surface areas of the oxide precursors according to Examples 1 to 3 are much larger than those of the precursors according to Comparative Examples 1 and 2, reaching 10 m 2 / g or more, e.g., 20m 2It can be seen that the specific surface area is greater than or equal to 1 / g. When an oxide precursor is obtained by calcining a hydroxide precursor at a low temperature, the specific surface area of ​​the oxide precursor is significantly greater than that of the hydroxide precursor. This indicates that the reactivity between the oxide precursor and the lithium source is improved during the process of mixing and calcining the precursor with the lithium source, thereby achieving high capacity (capacity per weight) while simultaneously improving density and significantly improving capacity per volume. Furthermore, as in Comparative Example 2, it was confirmed that the specific surface area of ​​the oxide precursor decreases when the calcination temperature exceeds a certain level. This indicates that an oxide precursor with a high specific surface area can be synthesized by designing an appropriate calcination temperature.

[0119] Evaluation example 3: X-ray diffraction analysis of precursor X-ray diffraction analysis was carried out on the hydroxide precursor of Comparative Example 1, the oxide precursors of Examples 1 and 3, and the oxide precursor of Comparative Example 2, and the results are shown in FIGS. 13 to 16, respectively.

[0120] X-ray diffraction analysis was carried out using a Powder XRD (D8 Advance) device manufactured by Bruker under the following conditions.

[0121] -X-ray wavelength: 1.5406Å (CuK α 1) -Slit conditions: Divergence Slit 0.5°, Scattering Slit 0.5°, Receiving Slit 0.20mm -Scan conditions: Continuous scan, 10°≦2θ≦80°, 0.01° / step, 1.27° / min, total measurement time 55 min.

[0122] 13 to 16, the XRD patterns for the hydroxide precursor and the oxide precursor are different from each other. The XRD patterns for the oxide precursors of Examples 1 and 3 show numerous peaks, such as (22-27)°, (30-35)°, and (49-52)°, which were not present in Comparative Example 1. The half-widths of the peaks (2θ = 22-27°, 30-35°, and 49-52°) corresponding to the (012) crystal plane, (104) crystal plane, and (024) crystal plane of the R-3 space group in the XRD patterns for the oxide precursors of Examples 1 and 3 and Comparative Example 2 were measured and are shown in Table 1. Table 1 indicates that the half-widths for the (012) crystal plane, (104) crystal plane, and (024) crystal plane of the oxide precursors of Examples 1 and 3 are 0.5 to 3, 0.5 to 3, and 0.5 to 2, respectively.

[0123] Evaluation example 4: Evaluation of positive electrode active material properties The average particle size (D 50 ) and pellet density (P / D) were measured and shown in Table 1 above. X-ray diffraction analysis was used to analyze the ratio of the peak intensity of the (003) crystal plane to the peak intensity of the (104) crystal plane of the R-3m space group, the ratio of the c-axis lattice constant to the a-axis lattice constant, and the peak half-widths for the (003) crystal plane and the (104) crystal plane, respectively, and these results are shown in Table 1 above.

[0124] Here, the average particle size (D 50 ) was obtained by measuring the size (diameter or major axis length) of more than 20 particles randomly selected from a scanning electron microscope image to obtain a particle size distribution, and the diameter of the particle whose cumulative volume was 50% by volume in the particle size distribution was taken as the average particle size.

[0125] The pellet density was measured by placing 3 g of sample in a mold (area: 1.298 cm 2 The mold set was placed in a hydraulic press, and the mold bar was fitted into the mold body. The mold set was then pressed at a pressure of 3 tons (metric ton) for 30 seconds to pelletize the mixture, followed by measurement.

[0126] Referring to Table 1 above, it can be seen that the pellet densities of the positive electrode active materials of Examples 1 to 3 were improved compared to Comparative Examples 1 and 2.

[0127] Furthermore, XRD analysis of the positive electrode active materials of Examples 1 to 3 reveals that the ratio of the peak intensity of the (003) crystal plane to the peak intensity of the (104) crystal plane of the R-3m space group satisfies 0.86 to 1.1, the half-width of the (104) crystal plane peak of the R-3m space group satisfies the range of 0.310 to 0.340, the half-width of the (003) peak satisfies the range of 0.150 to 0.165, and the ratio of the c-axis lattice constant to the a-axis lattice constant satisfies 4.951 to 4.953.

[0128] Evaluation example 5: Battery characteristic evaluation The lithium secondary batteries produced in Examples 1 to 3 and Comparative Examples 1 and 2 were charged to 4.7 V at a constant current of 0.1 C at 25° C., then maintained at a voltage until the current value reached 0.05 C, and then discharged at a constant current of 0.1 C to 2.5 V, thereby carrying out a first charge-discharge. Next, the batteries were charged to 4.45 V at a constant current of 0.2 C at 25° C., then maintained at a voltage until the current value reached 0.05 C, and then discharged at a constant current of 0.2 C to 2.5 V, thereby carrying out a second charge-discharge.

[0129] The charge capacity in the first cycle and the discharge capacity in the second cycle are shown in Table 1, and the ratio of the latter to the former is expressed as the reversible discharge capacity ratio. The pellet density of the positive electrode active material is multiplied by the discharge capacity in the second cycle to express the capacity per volume in Table 1.

[0130] Referring to Table 1, it can be seen that in Examples 1 to 3, the discharge capacity in the second cycle was high and the pellet density was high, so the capacity value per volume obtained by multiplying these values ​​was improved compared to Comparative Examples 1 and 2.

[0131] The value obtained by subtracting the average discharge voltage at 50 cycles from the average discharge voltage at the first cycle is shown as the voltage drop in Table 1. The average discharge voltage was calculated by integrating the area under the discharge voltage curve (voltage-capacity graph) and then dividing that value by the discharge capacity.

[0132] Referring to Table 1, it can be seen that Examples 1 to 3 exhibit voltage drop values ​​at levels equal to or greater than those of the comparative example.

[0133] The analysis results regarding the secondary heat treatment temperature will be explained below.

[0134] Comparative Example 3 A positive electrode active material and a lithium secondary battery were manufactured in substantially the same manner as in Comparative Example 1, except that the heat treatment temperature was changed to 950°C.

[0135] Example 4 A positive electrode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the first heat treatment temperature was 500°C and the second heat treatment temperature was 975°C.

[0136] Example 5 A positive electrode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the first heat treatment temperature was 500°C and the second heat treatment temperature was 950°C.

[0137] The analytical results for Comparative Example 3 and Comparative Example 1 are shown in Table 2, and the analytical results for Examples 3 to 5 are shown in Table 3 below. The charge / discharge conditions and the measurement methods for each evaluation item are as described above. In Tables 2 and 3, the high-temperature life was calculated by repeating 50 cycles under the same conditions as in Evaluation Example 5, except that after the first and second charge / discharge, charging from 45°C to 4.45V at a constant current of 0.2C, the voltage was maintained until the current value reached 0.05C, and then discharging to 2.5V at a constant current of 0.2C, and the charge / discharge C rate was changed to 1C, and the ratio of the 50th discharge capacity to the initial discharge capacity at 1C was calculated.

[0138] [Table 2]

[0139] [Table 3]

[0140] Referring to Table 2 above, when a hydroxide precursor is used, the pellet density can be increased by increasing the calcination temperature, but this results in a problem of a decrease in capacity (e.g., second cycle discharge capacity). As a result, the optimal calcination temperature must be set to a relatively low temperature, making it difficult to simultaneously increase capacity and pellet density.

[0141] Referring to Table 3 above, it can be seen that when an oxide precursor is used, the calcination temperature can be increased, thereby increasing both the capacity and pellet density, and thus improving the capacity per volume, unlike the comparative example in Table 2. Furthermore, it can be seen that, because the calcination is performed at a relatively higher temperature than when a hydroxide precursor is used, it is possible to synthesize a lithium-manganese-rich cathode active material with high pellet density and capacity.

[0142] The analysis results for different average particle sizes will be explained below.

[0143] Example 6 Hydroxide precursor Ni 0.5 Mn 0.5 (OH)2 as the average particle size (D 50 ) of the final positive electrode active material is about 6.5 μm. 50 A positive electrode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 3, except that the thickness of the porous layer was adjusted to about 6.8 μm.

[0144] Comparative Example 4 A cathode active material and a lithium secondary battery were prepared in substantially the same manner as in Example 6, except that instead of preparing an oxide precursor as in Comparative Example 1, a hydroxide precursor and a lithium raw material were mixed and heat-treated at 1000°C.

[0145] The following Table 4 shows the analytical results for Example 6 and Comparative Example 4. Similarly, the charge / discharge conditions and the measurement methods for each evaluation item are as described above.

[0146] [Table 4]

[0147] Referring to Table 4, the same principle applies to a cathode active material having an average particle size of 6.8 μm. In Example 6, the specific surface area of ​​the oxide precursor is significantly increased. When a lithium-manganese-rich cathode active material is synthesized using this, the capacity and density are all improved. Compared to Comparative Example 4, the first charge capacity, second discharge capacity, reversible discharge capacity ratio, and capacity per volume are also improved.

[0148] Although the preferred embodiments have been described in detail above, the scope of the present invention is not limited to these, and various modifications and improvements made by those skilled in the art using the basic concepts defined in the claims also fall within the scope of the present invention. [Explanation of symbols]

[0149] 100 Lithium secondary battery 10 positive electrode 11 Positive electrode lead tab 12 Positive terminal 20 negative electrode 21 Negative electrode lead tab 22 Negative terminal 30 Separator 40 Electrode assembly 50 cases 60 Sealing member 70 Electrode tab 71 Positive electrode tab 72 Negative electrode tab

Claims

1. A nickel-manganese-based hydroxide having a manganese content of 34 mol% to 50 mol% relative to 100 mol% of the total metal is subjected to a primary heat treatment at a temperature of 500°C or less to prepare a nickel-manganese-based oxide; The nickel-manganese-based oxide and the lithium raw material are mixed so that the molar ratio of lithium in the lithium raw material to the total metal of the nickel-manganese-based oxide is greater than 1 and less than 2, and then subjected to a second heat treatment; A method for producing a positive electrode active material, comprising obtaining a lithium-manganese-rich positive electrode active material containing a lithium nickel-manganese composite oxide.

2. The method for producing a positive electrode active material according to claim 1, wherein the primary heat treatment is performed at a temperature in the range of 400° C. to 500° C. for 1 hour to 10 hours.

3. 2. The method for producing a positive electrode active material according to claim 1, wherein a molar ratio of lithium in the lithium raw material to the total metal of the nickel-manganese oxide precursor is 1.06 to 2.

4. 4. The method for producing a positive electrode active material according to claim 3, wherein a molar ratio of lithium in the lithium raw material to the total metal of the nickel-manganese oxide precursor is 1.1 to 1.

3.

5. The method for producing a positive electrode active material according to claim 1 , wherein the lithium raw material includes lithium hydroxide.

6. The method for manufacturing a positive electrode active material according to claim 1 , wherein the second heat treatment is performed at a temperature of 950° C. or higher.

7. 2. The method for producing a positive electrode active material according to claim 1, wherein the specific surface area of ​​the nickel-manganese oxide is larger than the specific surface area of ​​the nickel-manganese hydroxide.

8. The specific surface area of ​​the nickel-manganese hydroxide is 10 m 2 / g or less, The specific surface area of ​​the nickel-manganese oxide is 10 m 2 The method for producing a positive electrode active material according to claim 7 , wherein the SiO 2 content is 1 / g or more.

9. 2. The method for producing a positive electrode active material according to claim 1, wherein the nickel-manganese oxide has a peak half width of 0.5 to 3 on a (012) crystal plane of the R-3 space group, a peak half width of 0.5 to 3 on a (104) crystal plane of the R-3 space group, and a peak half width of 0.5 to 2 on a (024) crystal plane of the R-3 space group, as determined by X-ray diffraction analysis.

10. The average particle size (D 50 2. The method for producing a positive electrode active material according to claim 1, wherein the particle size is 2 μm to 18 μm, the pellet density is 2.7 g / cc or more, and the capacity per volume is 520 mAh / cc or more.

11. The nickel-manganese oxide contains 34 mol% to 50 mol% of manganese relative to 100 mol% of the total metals, A positive electrode active material precursor, in which the peak half width at the (012) crystal plane of the R-3 space group is 0.5 to 3 in X-ray diffraction analysis.

12. The positive electrode active material precursor according to claim 11, wherein, in X-ray diffraction analysis, the positive electrode active material precursor has a peak half width of 0.5 to 3 on a (104) crystal plane of the R-3 space group and a peak half width of 0.5 to 2 on a (024) crystal plane of the R-3 space group.

13. The specific surface area of ​​the positive electrode active material precursor is 10 m 2 / g to 50m 2 / g, and the average particle size (D 50 12. The positive electrode active material precursor according to claim 11, wherein the particle size is 2 μm to 18 μm.

14. a lithium-manganese-rich positive electrode active material containing a lithium nickel-manganese composite oxide in which the manganese content is 34 mol% to 50 mol% relative to 100 mol% of all metals excluding lithium; A lithium-manganese-rich positive electrode active material, in which the ratio of the peak intensity of the (003) crystal plane to the peak intensity of the (104) crystal plane of the R-3m space group in X-ray diffraction analysis is 0.86 to 1.

1.

15. The positive electrode active material has an X-ray diffraction analysis in which the half width of the (003) crystal plane peak of the R-3m space group is 0.150 to 0.165, and the half width of the (104) crystal plane peak of the R-3m space group is 0.310 to 0.

340. The lithium-manganese-rich positive electrode active material of claim 14.

16. 15. The lithium-manganese-rich positive electrode active material of claim 14, wherein the ratio of the c-axis lattice constant to the a-axis lattice constant is 4.951 to 4.953 in X-ray diffraction analysis.

17. The average particle size (D 50 15. The lithium-manganese-rich cathode active material of claim 14, wherein .gamma. is 2 μm to 18 μm.

18. 15. The lithium-manganese-rich cathode active material of claim 14, wherein the cathode active material has a pellet density of 2.7 g / cc or more and a capacity per volume of 520 mAh / cc or more.

19. The lithium-manganese-rich positive electrode active material according to claim 14, wherein the positive electrode active material exhibits capacity due to oxidation-reduction reactions of all of the transition metal and oxygen.

20. The lithium-manganese-rich positive electrode active material of claim 14, represented by Chemical Formula 1: [Chemical formula 1] [L) 1+x (N y Mn ｚ M １ １－ｙ－ｚ ) １－ｘ O ２ ]+(1-a)[b(L-& ｊ Mn ｋ M １ １－ｊ－ｋ O ２ )+c(L- ２ Mn ｗ M １ １－ｗ O ３ )] In the formula 1, 0≦a≦1, 0.03≦x≦0.2, 0.50≦y≦0.66, 0.34≦z≦0.50, 0<b<1, 0<c<1, 0.50≦j≦1.0, 0.50≦k≦1.0, 0.9≦w≦1.0, and M １ is one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, or Zr.

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