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

Abstract

To provide a positive electrode active material that can achieve high initial discharge capacity and initial charge-discharge efficiency, and long cycle-life characteristics, and a method for manufacturing the same.SOLUTION: A positive electrode active material includes: a first positive electrode active material including first lithium nickel-based composite oxide, and having a secondary particle form in which a plurality of primary particles are accumulated, wherein the average particle diameter D50 of the secondary particles is 10 μm to 25 μm; a second positive electrode active material including second lithium nickel-based composite oxide, and having a form similar to the former, wherein the average particle diameter D50 of the secondary particles is 0.5 μm to 8 μm; and a third positive electrode active material including third lithium nickel-based composite oxide, and having a form similar to the former, wherein the average particle diameter D50 of the secondary particles is 0.5 μm or 8 μm, and the secondary particles include needle-like primary particles. The content of nickel relative to the entire metal excluding lithium in the third lithium nickel-based composite oxide, is higher than the content of nickel relative to the entire metal excluding lithium in the second lithium nickel-based composite oxide.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a positive electrode active material, a method for producing the same, a positive electrode containing the same, and a lithium secondary battery.

Background Art

[0002] Lithium secondary batteries having a high energy density and being easy to carry are mainly used as driving power sources for mobile information terminals such as mobile phones, notebook computers, and smartphones. Recently, research has been actively conducted on using lithium secondary batteries having a high energy density as driving power sources or power storage power sources for hybrid vehicles and electric vehicles.

[0003] In order to realize a lithium secondary battery suitable for such applications, various positive electrode active materials have been studied. Among these, lithium nickel-based oxides, lithium nickel manganese cobalt composite oxides, lithium nickel cobalt aluminum composite oxides, lithium cobalt oxides, etc. are mainly used as positive electrode active materials. Nickel-based positive electrode active materials can achieve high capacity and high energy density and are materials that have been actively developed, but the synthesis method is relatively simple and there are limitations in improving the characteristics of the positive electrode active material through the process.

Summary of the Invention

Problems to be Solved by the Invention

[0004] To provide a positive electrode active material and a method for producing the same, which have a high initial discharge capacity and initial charge-discharge efficiency and can realize long-life characteristics.

Means for Solving the Problems

[0005] In one embodiment, it includes a first lithium nickel-based composite oxide and is in the form of secondary particles formed by aggregation of a plurality of primary particles, and the average particle diameter D of the secondary particles 50 is a first positive electrode active material of 10 μm to 25 μm, and includes a second lithium nickel-based composite oxide and is in the form of secondary particles formed by aggregation of a plurality of primary particles, and the average particle diameter D of the secondary particles50 is a second positive electrode active material having a size of 0.5 μm to 8 μm and contains a third lithium nickel-based composite oxide, and is in the form of secondary particles formed by aggregation of a plurality of primary particles. The average particle size D of the secondary particles 50 is 0.5 μm to 8 μm, and the secondary particles include a third positive electrode active material containing acicular primary particles, and the nickel content of the third lithium nickel-based composite oxide with respect to the total metal excluding lithium is higher than the nickel content of the second lithium nickel-based composite oxide with respect to the total metal excluding lithium. A positive electrode active material is provided. In another embodiment, the average particle size D 50 is a step of mixing a first nickel-based hydroxide having a size of 10 μm to 25 μm and a first lithium raw material, and mixing so that the molar ratio of lithium of the first lithium raw material to the total metal of the first nickel-based hydroxide is 1.09 or more, and then performing a first heat treatment; and the first heat treatment product and the average particle size D 50 is a step of mixing a second nickel-based hydroxide having a size of 0.5 μm to 8 μm and a second lithium raw material, and then performing a second heat treatment. A method for manufacturing a positive electrode active material is provided.

[0006] In another embodiment, a positive electrode for a lithium secondary battery including the above-described positive electrode active material is provided.

[0007] In another embodiment, a lithium secondary battery including the positive electrode, a negative electrode, and an electrolyte is provided.

Advantages of the Invention

[0008] The positive electrode active material manufactured according to one embodiment has high initial charge and discharge efficiency, and can achieve long life characteristics.

Brief Description of the Drawings

[0009]

Figure 1

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DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, specific embodiments will be described in detail so that those having ordinary knowledge in this technical field can easily implement them. However, the present invention can be implemented in various different forms and is not limited to the embodiments described herein.

[0011] The terms used herein are merely used to explain exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0012] Here, "these combinations" means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of components.

[0013] Here, terms such as "comprising", "including" or "having" are intended to specify the presence of implemented features, numbers, steps, components or combinations thereof, and should be understood not to preclude the presence or addition possibility of one or more other features, numbers, steps, components or combinations thereof in advance.

[0014] For the purpose of clearly showing various layers and regions in the drawings, the thickness is enlarged and shown, and the same drawing reference numerals are assigned to similar parts throughout the specification. When a part such as a layer, film, region, plate, etc. is "on" or "above" another part, this includes not only the case where it is "directly above" the other part, but also the case where there are other parts in between. Conversely, when a part is "directly above" another part, it means that there are no other parts in between.

[0015] Also, here, the "layer" includes not only the shape formed on the entire surface when observed in a plan view, but also the shape formed on a part of the surface.

[0016] The average particle size can be measured by methods widely known to those skilled in the art. For example, it can be measured with a particle size analyzer, or it can be measured from a transmission electron microscope image or a scanning electron microscope image. As another method, it can be measured using the dynamic light scattering method, data analysis is performed to count the number of particles for each particle size range, and then the average particle size value can be obtained based on this. Unless otherwise defined, the average particle size can mean the diameter D of the particle at which the cumulative volume is 50% by volume in the particle size distribution. 50 Also, unless otherwise defined, the average particle size can be obtained by measuring the sizes (diameter or major axis length) of more than 20 randomly selected particles from a scanning electron microscope image to obtain a particle size distribution, and taking the diameter D of the particle at which the cumulative volume is 50% by volume in the said particle size distribution as the average particle size. 50 It may also be taken as the average particle size.

[0017] Here, "or" is not interpreted in an exclusive sense. For example, "A or B" is interpreted to include A, B, A + B, etc.

[0018] "Metal" is interpreted as a concept including common metals, transition metals, and metalloids.

[0019] Positive electrode active material In one embodiment, a positive electrode active material for a lithium secondary battery including a first positive electrode active material, a second positive electrode active material, and a third positive electrode active material is provided. The first positive electrode active material includes a first lithium nickel-based composite oxide and has a secondary particle form in which a plurality of primary particles are aggregated, and the average particle diameter D of the secondary particles 50 is 10 μm to 25 μm. The second positive electrode active material includes a second lithium nickel-based composite oxide and has a secondary particle form in which a plurality of primary particles are aggregated, and the average particle diameter D of the secondary particles 50 is 0.5 μm to 8 μm. It includes a third lithium nickel-based composite oxide and has a secondary particle form in which a plurality of primary particles are aggregated, and the average particle diameter D of the secondary particles 50 is 0.5 μm to 8 μm, and the secondary particles include acicular primary particles. At this time, the nickel content in the third lithium nickel-based composite oxide with respect to the total metal excluding lithium is higher than the nickel content in the second lithium nickel-based composite oxide with respect to the total metal excluding lithium. Such a positive electrode active material can achieve high efficiency and long life characteristics.

[0020] The nickel-based cathode active material in the form of a mixture of large particles and small particles in the secondary particle form is generally manufactured by a method in which a large particle precursor, a small particle precursor, and a lithium raw material are simultaneously fired and then selectively coated. On the other hand, in one embodiment, as will be described later, a stepwise synthesis method is provided in which a large particle precursor and a lithium raw material are first mixed and fired, and then a small particle precursor and a lithium raw material are introduced here for secondary firing. At this time, when mixing the large particle precursor and the lithium raw material, by mixing lithium in excess at a certain level, lithium-rich large particles are synthesized, and by introducing a small particle precursor here and causing a reaction, it is induced that the lithium-rich large particles and a part of the small particle precursor react while contacting each other. As a result, the small particle precursor that has reacted with the lithium-rich large particles forms small particles having a higher nickel content than the small particle precursor by diffusion of nickel from the large particles into them. At this time, it is confirmed that the primary particles forming the secondary particles of these small particles have a needle-like shape. The small particles containing needle-like primary particles while increasing the nickel content in this way are referred to as the third cathode active material. There are also small particles that have the same nickel content as the small particle precursor and do not contain needle-like primary particles because they do not directly react with the lithium-rich large particles, and these are referred to as the second cathode active material. The large particles correspond to the first cathode active material.

[0021] According to the synthesis method according to one embodiment, the reactivity between the cathode active material precursor and the lithium raw material is further improved and the processability is improved. Also, the cathode active material synthesized by such a method is confirmed to have a higher initial discharge capacity, a significantly improved initial charge-discharge efficiency, and an improved life characteristic compared to the cathode active material manufactured by the existing manufacturing method.

[0022] The nickel content with respect to the total metal excluding lithium in the third lithium nickel-based composite oxide may be, for example, 1 mol% to 5 mol% higher than the nickel content with respect to the total metal excluding lithium in the second lithium nickel-based composite oxide, and may be, for example, 1 mol% to 4 mol%, or 2 mol% to 3 mol% higher.

[0023] The content of nickel in the third positive electrode active material increases compared to the precursor, and the contents of lithium and metal components other than nickel decrease. That is, the second lithium nickel-based composite oxide and the third lithium nickel-based composite oxide may further contain a metal M other than lithium and nickel. At this time, the content of metal M in the third lithium nickel-based composite oxide with respect to the total metal excluding lithium may be lower than the content of metal M in the second lithium nickel-based composite oxide with respect to the total metal excluding lithium. For example, it may be further lower by about 1 mol% to 5 mol%, 1 mol% to 4 mol%, or 2 mol% to 3 mol%.

[0024] Hereinafter, each positive electrode active material will be described in detail.

[0025] First positive electrode active material The first positive electrode active material contains a first lithium nickel-based composite oxide and has a secondary particle form in which a plurality of primary particles are aggregated. The average particle diameter D 50 of the secondary particles is 10 μm to 25 μm. The first positive electrode active material may be referred to as large grains or large particles. The average particle diameter D 50 of the secondary particles of the first positive electrode active material may be, for example, 10 μm to 20 μm, 10 μm to 18 μm, or 12 μm to 16 μm.

[0026] The shape of the secondary particles of the first positive electrode active material may be, for example, spherical, ellipsoidal, polyhedral, amorphous (irregular shape), or a combination thereof. For example, it may not be acicular. Here, the polyhedron refers to a three-dimensional figure having a plurality of corners such as a prism, a pyramid, and a frustum of a pyramid. The shape of the primary particles forming the secondary particles of the first positive electrode active material may be, for example, spherical, ellipsoidal, polyhedral, plate-like, amorphous, or a combination thereof. For example, it may not be acicular. Different from the third positive electrode active material, the first positive electrode active material may not contain acicular primary particles.

[0027] The nickel content in the first lithium nickel-based composite oxide with respect to 100 mol% of the total metals excluding lithium may be, for example, 50 mol% to 99 mol%, and may be, for example, 50 mol% to 90 mol%, 50 mol% to 80 mol%, 50 mol% to 70 mol%, 55 mol% to 70 mol%, or 55 mol% to 65 mol%. As an example, the first positive electrode active material may be a mid-nickel positive electrode active material containing 55 to 70 mol% of nickel.

[0028] The first lithium nickel-based composite oxide and the second lithium nickel-based composite oxide may have the same or different compositions from each other. Similarly, the first lithium nickel-based composite oxide and the third lithium nickel-based composite oxide may have the same or different compositions from each other. However, since there is a difference in nickel content between the second lithium nickel-based composite oxide and the third lithium nickel-based composite oxide, it can be said that their compositions are different from each other.

[0029] The first lithium nickel-based composite oxide is represented by Chemical Formula 1 as an example and may be represented by Chemical Formula 2 as a specific example. [Chemical Formula 1] Li a1 Ni x1 M 1 y1 O 2-b1 X b1

[0030] In the above Chemical Formula 1, 0.9 ≦ a1 ≦ 1.2, 0.5 ≦ x1 < 1, 0 < y1 ≦ 0.5, 0.9 ≦ x1 + y1 ≦ 1.1, and 0 ≦ b1 ≦ 0.1, and M 1 is one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S.

[0031] In the above Chemical Formula 1, 0.5 ≦ x1 ≦ 0.9 and 0.1 ≦ y1 ≦ 0.5, or 0.5 ≦ x1 ≦ 0.8 and 0.2 ≦ y1 ≦ 0.5, or 0.5 ≦ x1 ≦ 0.7 and 0.3 ≦ y1 ≦ 0.5, or 0.55 ≦ x1 ≦ 0.7 and 0.3 ≦ y1 ≦ 0.45 may be satisfied.

[0032] [Chemical Formula 2] Li a2 Ni x2 Co y2 M 2 z2 M 3 w2 O 2-b2 X b2

[0033] In the above Chemical Formula 2, 0.9 ≦ a2 ≦ 1.2, 0.5 ≦ x2 < 1, 0 < y2 ≦ 0.5, 0 < z2 ≦ 0.5, 0 ≦ w2 ≦ 0.1, 0.9 ≦ x2 + y2 + z2 + w2 ≦ 1.1, and 0 ≦ b2 ≦ 0.1, where M 2 is Al, Mn, or a combination thereof, and M 3 is one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S.

[0034] In the above Chemical Formula 2, 0.5 ≦ x2 ≦ 0.8, 0.1 ≦ y2 ≦ 0.4, 0.1 ≦ z2 ≦ 0.4, 0 ≦ w2 ≦ 0.1, or 0.5 ≦ x2 ≦ 0.7, 0.2 ≦ y2 ≦ 0.4, 0.1 ≦ z2 ≦ 0.3, 0 ≦ w2 ≦ 0.1, or 0.5 ≦ x2 ≦ 0.7, 0.1 ≦ y2 ≦ 0.3, 0.2 ≦ z2 ≦ 0.4, 0 ≦ w2 ≦ 0.1, or 0.5 ≦ x2 ≦ 0.6, 0.2 ≦ y2 ≦ 0.3, 0.2 ≦ z2 ≦ 0.3, 0 ≦ w2 ≦ 0.1 may be satisfied.

[0035] As an example, the first positive electrode active material may include core particles containing a first lithium nickel-based composite oxide, and a coating layer located on the surface of the core particles. The coating layer may include, for example, Al, B, Co, Mg, Si, Ti, V, W, Zn, Zr, or a combination thereof, and as an example, may include aluminum. With respect to 100% by weight of the total metal excluding lithium in the first positive electrode active material, the content of the coating element may be 0.1% by weight to 5% by weight, 0.1% by weight to 3% by weight, 0.1% by weight to 2% by weight, 0.1% by weight to 1% by weight, or 0.1% by weight to 0.9% by weight.

[0036] Second positive electrode active material The second positive electrode active material includes a second lithium nickel-based composite oxide and has a secondary particle form in which a plurality of primary particles are aggregated, and the average particle diameter D of the secondary particles 50 is characterized by being 0.5 μm to 8 μm. The second positive electrode active material may be expressed as small grains or small particles, and may be expressed as a part of the small grains. The average particle diameter D of the secondary particles of the second positive electrode active material 50 may be, for example, 0.5 μm to 6 μm, 1 μm to 5 μm, or 2 μm to 4 μm.

[0037] The second positive electrode active material can be meant to be such that the primary particles are not formed in a needle shape while maintaining the same composition as the small grain precursor. That is, unlike the third positive electrode active material, the secondary particles of the second positive electrode active material may not include needle-shaped primary particles. The shape of the primary particles of the second positive electrode active material may be, for example, spherical, ellipsoidal, polyhedral, plate-shaped, amorphous, or a combination thereof. The shape of the secondary particles of the second positive electrode active material may be, for example, spherical, ellipsoidal, polyhedral, amorphous, or a combination thereof, and may not be, for example, needle-shaped.

[0038] The content of nickel in the second lithium nickel-based composite oxide with respect to 100 mol% of the total metal excluding lithium may be, for example, 50 mol% to 99 mol%, and may be, for example, 50 mol% to 90 mol%, 50 mol% to 80 mol%, 50 mol% to 70 mol%, 55 mol% to 70 mol%, or 55 mol% to 65 mol%. As an example, the second positive electrode active material may be a mid-nickel positive electrode active material containing 55 to 70 mol% of nickel.

[0039] The second lithium nickel-based composite oxide may be represented by Chemical Formula 3 as an example, and may be represented by Chemical Formula 4 as a specific example. [Chemical Formula 3] Li a3 Ni x3 M 4 y3 O 2-b3 X b3

[0040] In the above Chemical Formula 3, 0.9 ≦ a3 ≦ 1.2, 0.5 ≦ x3 < 1, 0 < y3 ≦ 0.5, 0.9 ≦ x3 + y3 ≦ 1.1, and 0 ≦ b3 ≦ 0.1, and M 4 is one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S.

[0041] In the above Chemical Formula 3, 0.5 ≦ x3 ≦ 0.9 and 0.1 ≦ y3 ≦ 0.5, or 0.5 ≦ x3 ≦ 0.8 and 0.2 ≦ y3 ≦ 0.5, or 0.5 ≦ x3 ≦ 0.7 and 0.3 ≦ y3 ≦ 0.5, or 0.55 ≦ x3 ≦ 0.7 and 0.3 ≦ y3 ≦ 0.45 may also be acceptable.

[0042] [Chemical Formula 4] Li a4 Ni x4 Co y4 M 5 z4 M 6 w4 O 2-b4 X b4

[0043] In the above Chemical Formula 4, 0.9 ≦ a4 ≦ 1.2, 0.5 ≦ x4 < 1, 0 < y4 ≦ 0.5, 0 < z4 ≦ 0.5, 0 ≦ w4 ≦ 0.1, 0.9 ≦ x4 + y4 + z4 + w4 ≦ 1.1, and 0 ≦ b4 ≦ 0.1, and M 5 is Al, Mn, or a combination thereof, and M 6 is one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S.

[0044] In the above Chemical Formula 4, it may be 0.5 ≦ x4 ≦ 0.8, 0.1 ≦ y4 ≦ 0.4, 0.1 ≦ z4 ≦ 0.4, 0 ≦ w4 ≦ 0.1, or 0.5 ≦ x4 ≦ 0.7, 0.2 ≦ y4 ≦ 0.4, 0.1 ≦ z4 ≦ 0.3, 0 ≦ w4 ≦ 0.1, or 0.5 ≦ x4 ≦ 0.7, 0.1 ≦ y4 ≦ 0.3, 0.2 ≦ z4 ≦ 0.4, 0 ≦ w4 ≦ 0.1, or 0.5 ≦ x4 ≦ 0.6, 0.2 ≦ y4 ≦ 0.3, 0.2 ≦ z4 ≦ 0.3, 0 ≦ w4 ≦ 0.1.

[0045] As an example, the second positive electrode active material may include core particles containing a second lithium nickel-based composite oxide and a coating layer located on the surface of the core particles. The coating layer may include, for example, Al, B, Co, Mg, Si, Ti, V, W, Zn, Zr, or a combination thereof, and as an example, it may include aluminum. With respect to 100% by weight of the total metal excluding lithium in the second positive electrode active material, the content of the coating element may be 0.1% by weight to 5% by weight, 0.1% by weight to 3% by weight, 0.1% by weight to 2% by weight, 0.1% by weight to 1% by weight, or 0.1% by weight to 0.9% by weight.

[0046] Third positive electrode active material The third positive electrode active material includes a third lithium nickel-based composite oxide and is in the form of secondary particles formed by aggregation of a plurality of primary particles. The average particle size D of the secondary particles 50is from 0.5 μm to 8 μm, and the secondary particles include acicular primary particles. The third positive electrode active material may be expressed as small grains or small particles, and may be expressed as a part of small grains. The average particle diameter D of the secondary particles of the third positive electrode active material 50 may be, for example, from 0.5 μm to 6 μm, from 1 μm to 5 μm, or from 2 μm to 4 μm.

[0047] The third positive electrode active material can be said to be small grains formed by the reaction of lithium-rich large grains and small grain precursors while being in contact with each other in the method for producing a positive electrode active material described below. It can be said that the nickel content is further increased from the large grains and is higher than that of the small grain precursors, and the small grains have acicular primary particles. However, the secondary particles of the third positive electrode active material may not be acicular, and may be, for example, spherical, ellipsoidal, polyhedral, amorphous, or a combination thereof.

[0048] The content of nickel with respect to 100 mol% of the total metal excluding lithium in the third lithium nickel-based composite oxide may be, for example, from 50 mol% to 99 mol%, and may be, for example, from 50 mol% to 90 mol%, from 50 mol% to 80 mol%, from 50 mol% to 70 mol%, from 55 mol% to 70 mol%, or from 55 mol% to 65 mol%. As an example, the third positive electrode active material may be a mid-nickel positive electrode active material containing 55 to 70 mol% of nickel.

[0049] The third lithium nickel-based composite oxide is represented by Chemical Formula 5 as an example, and may be represented by Chemical Formula 6 as a specific example. [Chemical Formula 5] Li a5 Ni x5 M 7 y5 O 2-b5 X b5

[0050] In the above Chemical Formula 5, 0.9 ≦ a5 ≦ 1.2, 0.5 ≦ x5 < 1, 0 < y5 ≦ 0.5, 0.9 ≦ x5 + y5 ≦ 1.1, and 0 ≦ b5 ≦ 0.1, and M 7is one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S.

[0051] In the above Chemical Formula 5, 0.5 ≦ x5 ≦ 0.9 and 0.1 ≦ y5 ≦ 0.5, or 0.5 ≦ x5 ≦ 0.8 and 0.2 ≦ y5 ≦ 0.5, or 0.5 ≦ x5 ≦ 0.7 and 0.3 ≦ y5 ≦ 0.5, or 0.55 ≦ x5 ≦ 0.7 and 0.3 ≦ y5 ≦ 0.45 may be satisfied.

[0052] [Chemical Formula 6] Li a6 Ni x6 Co y6 M 8 z6 M 9 w6 O 2-b6 X b6

[0053] In the above Chemical Formula 6, 0.9 ≦ a6 ≦ 1.2, 0.5 ≦ x6 < 1, 0 < y6 ≦ 0.5, 0 < z6 ≦ 0.5, 0 ≦ w6 ≦ 0.1, 0.9 ≦ x6 + y6 + z6 + w6 ≦ 1.1, and 0 ≦ b6 ≦ 0.1, and M 8 is Al, Mn, or a combination thereof, and M 9 is one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S.

[0054] In the above Chemical Formula 6, 0.5 ≦ x6 ≦ 0.8, 0.1 ≦ y6 ≦ 0.4, 0.1 ≦ z6 ≦ 0.4, 0 ≦ w6 ≦ 0.1, or 0.5 ≦ x6 ≦ 0.7, 0.2 ≦ y6 ≦ 0.4, 0.1 ≦ z6 ≦ 0.3, 0 ≦ w6 ≦ 0.1, or 0.5 ≦ x6 ≦ 0.7, 0.1 ≦ y6 ≦ 0.3, 0.2 ≦ z6 ≦ 0.4, 0 ≦ w6 ≦ 0.1, or 0.5 ≦ x6 ≦ 0.6, 0.2 ≦ y6 ≦ 0.3, 0.2 ≦ z6 ≦ 0.3, 0 ≦ w6 ≦ 0.1 may be satisfied.

[0055] As an example, the third positive electrode active material may include core particles containing a third lithium nickel-based composite oxide and a coating layer located on the surface of the core particles. The coating layer may include, for example, Al, B, Co, Mg, Si, Ti, V, W, Zn, Zr, or a combination thereof, and as an example, may include aluminum. With respect to 100% by weight of the total metal excluding lithium in the third positive electrode active material, the content of the coating element may be 0.1% by weight to 5% by weight, 0.1% by weight to 3% by weight, 0.1% by weight to 2% by weight, 0.1% by weight to 1% by weight, or 0.1% by weight to 0.9% by weight.

[0056] With respect to 100% by weight in total of the first positive electrode active material, the second positive electrode active material, and the third positive electrode active material, the first positive electrode active material may be contained in an amount of 60% by weight to 85% by weight, or 70% by weight to 80% by weight, and the total amount of the second positive electrode active material and the third positive electrode active material may be 15% by weight to 40% by weight, or 20% by weight to 30% by weight. That is, the content of the large particles may be 60% by weight to 85% by weight, or 70% by weight to 80% by weight, and the content of the small particles may be 15% by weight to 40% by weight, or 20% by weight to 30% by weight. When the contents of the large particles and the small particles satisfy the above range, it is advantageous for the production of a high-efficiency and long-life positive electrode active material by the production method according to an embodiment.

[0057] The ratio of the second positive electrode active material to the third positive electrode active material is not particularly limited. For example, with respect to 100% by weight in total of the second positive electrode active material and the third positive electrode active material, the second positive electrode active material may be contained in an amount of 10% by weight to 90% by weight, and the third positive electrode active material may be contained in an amount of 10% by weight to 90% by weight. As a specific example, with respect to 100% by weight in total of the second positive electrode active material and the third positive electrode active material, the second positive electrode active material may be contained in an amount of 20% by weight to 80% by weight, or 30% by weight to 70% by weight, and the third positive electrode active material may be contained in an amount of 20% by weight to 80% by weight, or 30% by weight to 70% by weight. When the second positive electrode active material and the third positive electrode active material are mixed in an appropriate ratio, both the initial charge-discharge efficiency and the life characteristics can be improved.

[0058] Method for producing positive electrode active material In one embodiment, (i) a first nickel-based hydroxide having an average particle diameter D 50 of 10 μm to 25 μm is mixed with a first lithium raw material, and the mixture is heat-treated for the first time by mixing so that the molar ratio of lithium in the first lithium raw material to the total metal of the first nickel-based hydroxide is 1.09 or more; and (ii) a step of mixing the first heat-treated product with a second nickel-based hydroxide having an average particle diameter D 50 of 0.5 μm to 8 μm and a second lithium raw material and performing a second heat treatment is provided.

[0059] The first nickel-based hydroxide can be said to be a large particle precursor, and the second nickel-based hydroxide can be said to be a small particle precursor. According to the method, when the large particle precursor and the first lithium raw material are mixed, by designing the molar ratio of lithium to the metal to be 1.09 or more, lithium-rich large particles with a certain excess content of lithium can be formed in the first heat treatment process. By adding the small particle precursor and the second lithium raw material to such lithium-rich large particles and performing heat treatment again, a part of the small particle precursor can react in direct contact with the lithium-rich large particles. At this time, lithium diffuses and enters from the lithium-rich large particles, and small particles of lithium nickel oxide can be formed. The small particles thus formed had a higher nickel content than the small particle precursor and the primary particles were needle-shaped. This is understood to be the result of nickel diffusing and entering together when lithium diffuses to the small particle precursor on the surface of the lithium-rich large particles, and it is considered that the primary particles become needle-shaped due to such a diffusion mechanism. Such a third positive electrode active material can achieve a higher capacity, and the needle-shaped primary particles make the movement of lithium ions smoother, improving charge and discharge efficiency and output characteristics.

[0060] Generally, when manufacturing a nickel-based cathode active material, in the process of mixing and firing a cathode active material precursor and a lithium raw material, when the lithium raw material is introduced by designing the molar ratio of lithium to metal to be less than 1, secondary particles containing acicular primary particles are synthesized. In this case, there is a problem that the amount of lithium is small and the charge-discharge capacity decreases. On the contrary, the third cathode active material according to an embodiment receives lithium from lithium-rich large particles during the synthesis process, and lithium is also supplied through the second lithium raw material. Therefore, the amount of lithium does not decrease, and as a result, a high capacity can be realized.

[0061] The method for manufacturing the cathode active material is different from the existing synthesis method. Since the second lithium raw material is additionally introduced during the secondary heat treatment, the reactivity is further improved. Also, since the small particle precursor is supplied with lithium from the lithium-rich large particles, the reaction efficiency is also improved.

[0062] The molar ratio of lithium of the first lithium raw material to the entire metal of the first nickel-based hydroxide may be designed, for example, to be 1.09 to 1.2, 1.09 to 1.19, 1.09 to 1.15, or 1.09 to 1.12. When the lithium molar ratio satisfies the above range, lithium-rich large particles are effectively formed during the synthesis process, and as a result, a high-efficiency and long-life cathode active material can be manufactured.

[0063] The first nickel-based hydroxide is represented by Chemical Formula 11 as an example, and may be represented by Chemical Formula 12 as a specific example. [Chemical Formula 11] Ni x11 M 11 y11 (OH)2

[0064] In the above Chemical Formula 11, 0.9 ≦ a11 ≦ 1.2, 0.5 ≦ x11 < 1, 0 < y11 ≦ 0.5, 0.9 ≦ x11 + y11 ≦ 1.1, and 0 ≦ b11 ≦ 0.1, and M 11is one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, Y, W, Zn, and Zr, and X is one or more elements selected from F, P, and S.

[0065] In the above Chemical Formula 11, 0.5 ≦ x11 ≦ 0.9 and 0.1 ≦ y11 ≦ 0.5, or 0.5 ≦ x11 ≦ 0.8 and 0.2 ≦ y11 ≦ 0.5, or 0.5 ≦ x11 ≦ 0.7 and 0.3 ≦ y11 ≦ 0.5, or 0.55 ≦ x11 ≦ 0.7 and 0.3 ≦ y11 ≦ 0.45 may be satisfied.

[0066] [Chemical Formula 12] Ni x12 Co y12 M 12 z12 M 13 w12 (OH)2

[0067] In the above Chemical Formula 12, 0.9 ≦ a12 ≦ 1.2, 0.5 ≦ x12 < 1, 0 < y12 ≦ 0.5, 0 < z12 ≦ 0.5, 0 ≦ w12 ≦ 0.1, 0.9 ≦ x12 + y12 + z12 + w12 ≦ 1.1, and 0 ≦ b12 ≦ 0.1, and M 12 is Al, Mn, or a combination thereof, and M 13 is one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S.

[0068] In the above Chemical Formula 12, 0.5 ≦ x12 ≦ 0.8, 0.1 ≦ y12 ≦ 0.4, 0.1 ≦ z12 ≦ 0.4, 0 ≦ w12 ≦ 0.1, or 0.5 ≦ x12 ≦ 0.7, 0.2 ≦ y12 ≦ 0.4, 0.1 ≦ z12 ≦ 0.3, 0 ≦ w12 ≦ 0.1, or 0.5 ≦ x12 ≦ 0.7, 0.1 ≦ y12 ≦ 0.3, 0.2 ≦ z12 ≦ 0.4, 0 ≦ w12 ≦ 0.1, or 0.5 ≦ x12 ≦ 0.6, 0.2 ≦ y12 ≦ 0.3, 0.2 ≦ z12 ≦ 0.3, 0 ≦ w12 ≦ 0.1 may be satisfied.

[0069] In the first nickel-based hydroxide, the content of nickel relative to 100 mol% of the total metal may be, for example, 50 mol% to 99 mol%, and may be, for example, 50 mol% to 90 mol%, 50 mol% to 80 mol%, 50 mol% to 70 mol%, 55 mol% to 70 mol%, or 55 mol% to 65 mol%.

[0070] The first nickel-based hydroxide and the second nickel-based hydroxide may have the same or different compositions. The first nickel-based hydroxide and the second nickel-based hydroxide may each be produced by a general coprecipitation method.

[0071] The first nickel-based hydroxide may be secondary particles formed by aggregation of a plurality of primary particles, and the average particle size D of the secondary particles 50 may be, for example, 10 μm to 25 μm, 10 μm to 20 μm, 10 μm to 18 μm, or 12 μm to 16 μm.

[0072] The first lithium raw material may include lithium carbonate, lithium hydroxide hydrate, anhydrous lithium hydroxide, or a combination thereof.

[0073] When mixing the first nickel-based hydroxide and the first lithium raw material, a raw material of a doping element may be selectively added and the first heat treatment may be performed together.

[0074] The first heat treatment may be performed in an oxygen atmosphere, and may be performed, for example, at 750°C to 1000°C, 750°C to 900°C, or 800°C to 900°C, and may be performed for 4 hours to 24 hours.

[0075] It can be said that what is obtained by the first heat treatment is large particles containing a lithium nickel-based composite oxide, and it can be said that it is large particles containing a certain excess content of lithium.

[0076] The molar ratio of lithium in the second lithium raw material to the total metal of the second nickel-based hydroxide may be less than 1, for example, it may be 0.2 to 0.99, 0.4 to 0.9, or 0.6 to 0.8. By adjusting the lithium molar ratio of the second lithium raw material within the above range, the reactivity in the second heat treatment can be further improved, and finally a positive electrode active material with an appropriately adjusted lithium content can be obtained.

[0077] The second nickel-based hydroxide may be represented by Chemical Formula 13 as an example, and may be represented by Chemical Formula 14 as a specific example. [Chemical Formula 13] Ni x13 M 14 y13 (OH)2

[0078] In the above Chemical Formula 13, 0.9 ≦ a13 ≦ 1.2, 0.5 ≦ x13 < 1, 0 < y13 ≦ 0.5, 0.9 ≦ x13 + y13 ≦ 1.1, and 0 ≦ b13 ≦ 0.1, and M 14 is one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S.

[0079] In the above Chemical Formula 13, 0.5 ≦ x13 ≦ 0.9 and 0.1 ≦ y13 ≦ 0.5, or 0.5 ≦ x13 ≦ 0.8 and 0.2 ≦ y13 ≦ 0.5, or 0.5 ≦ x13 ≦ 0.7 and 0.3 ≦ y13 ≦ 0.5, or 0.55 ≦ x13 ≦ 0.7 and 0.3 ≦ y13 ≦ 0.45 may also be acceptable.

[0080] [Chemical Formula 14] Ni x14 Co y14 M 15 z14 M 16 w14 (OH)2

[0081] In the aforementioned Chemical Formula 14, 0.9 ≦ a14 ≦ 1.2, 0.5 ≦ x14 < 1, 0 < y14 ≦ 0.5, 0 < z14 ≦ 0.5, 0 ≦ w14 ≦ 0.1, 0.9 ≦ x14 + y14 + z14 + w14 ≦ 1.1, and 0 ≦ b14 ≦ 0.1, and M 15 is Al, Mn, or a combination thereof, and M 16 is one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S.

[0082] In the aforementioned Chemical Formula 14, it may be that 0.5 ≦ x14 ≦ 0.8, 0.1 ≦ y14 ≦ 0.4, 0.1 ≦ z14 ≦ 0.4, 0 ≦ w14 ≦ 0.1, or 0.5 ≦ x14 ≦ 0.7, 0.2 ≦ y14 ≦ 0.4, 0.1 ≦ z14 ≦ 0.3, 0 ≦ w14 ≦ 0.1, or 0.5 ≦ x14 ≦ 0.7, 0.1 ≦ y14 ≦ 0.3, 0.2 ≦ z14 ≦ 0.4, 0 ≦ w14 ≦ 0.1, or 0.5 ≦ x14 ≦ 0.6, 0.2 ≦ y14 ≦ 0.3, 0.2 ≦ z14 ≦ 0.3, 0 ≦ w14 ≦ 0.1.

[0083] The content of nickel in the second nickel-based hydroxide with respect to 100 mol% of the total metal may be, for example, 50 mol% to 99 mol%, and may be, for example, 50 mol% to 90 mol%, 50 mol% to 80 mol%, 50 mol% to 70 mol%, 55 mol% to 70 mol%, or 55 mol% to 65 mol%.

[0084] The second nickel-based hydroxide may be secondary particles formed by aggregation of a plurality of primary particles, and the average particle size D of the secondary particles 50 may be, for example, 0.5 μm to 8 μm, 0.5 μm to 6 μm, 1 μm to 5 μm, or 2 μm to 4 μm. The primary particles forming the secondary particles of the second nickel-based hydroxide do not have to be acicular. The acicular primary particles of the third positive electrode active material may be formed in the second heat treatment process.

[0085] The second lithium raw material may include lithium carbonate, lithium hydroxide hydrate, anhydrous lithium hydroxide, or a combination thereof.

[0086] The second heat treatment may be performed in an oxygen atmosphere. For example, it may be performed at 700°C to 900°C, or 750°C to 850°C, and may be performed for 4 hours to 24 hours.

[0087] As an example, the second heat treatment temperature may be lower than the first heat treatment temperature. By appropriately adjusting the temperatures of the first heat treatment and the second heat treatment, a high-efficiency and long-life positive electrode active material can be effectively manufactured.

[0088] The mixing ratio of the first nickel-based hydroxide and the second nickel-based hydroxide, which corresponds to the mixing ratio of large particles and small particles, may be, for example, a weight ratio of 60:40 to 85:15, or 70:30 to 80:20. When the first nickel-based hydroxide and the second nickel-based hydroxide are mixed at the above ratio, a high-efficiency and long-life positive electrode active material according to an embodiment can be effectively manufactured.

[0089] In one embodiment, in order to coat the positive electrode active material, when mixing the first heat treatment product, the second nickel-based hydroxide, and the second lithium raw material, the coating raw materials may be added together and subjected to a second heat treatment.

[0090] The coating raw materials may include Al, B, Co, Mg, Si, Ti, V, W, Zn, Zr, or a combination thereof, and may be in various compound forms such as oxides, hydroxides, nitrates, sulfates, etc. The content of the coating raw materials may be in the range where the coating element is 0.1 wt% to 5 wt%, or 0.1 wt% to 3 wt% with respect to 100 wt% of the metal excluding lithium in the final positive electrode active material.

[0091] As an example, the coating raw material may contain aluminum. For example, aluminum oxide particles may be used as the coating raw material. At this time, the aluminum raw material may be mixed so that the aluminum content is 0.1 part by weight to 2 parts by weight with respect to 100 parts by weight of the total metal excluding lithium in the entire first heat treatment product and the second nickel-based hydroxide. For example, it may be mixed so that the aluminum content is 0.1 part by weight to 1 part by weight, or 0.1 part by weight to 0.8 part by weight. When the aluminum coating is performed within the above range, the initial discharge capacity, the initial charge-discharge efficiency, and the life characteristics can all be improved.

[0092] The method for manufacturing the positive electrode active material may further include a crushing process after the first heat treatment and / or after the second heat treatment.

[0093] Positive electrode In one embodiment, a positive electrode for a lithium secondary battery including the above-described positive electrode active material is provided. For example, the positive electrode includes a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector. The positive electrode active material layer includes the above-described positive electrode active material and may selectively further include a binder, a conductive material, or a combination thereof.

[0094] Binder The binder serves to make the positive electrode active material particles adhere well to each other and make the positive electrode active material adhere well to the current collector. Representative examples of the binder include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc., but are not limited thereto.

[0095] Conductive material The conductive material is used to impart conductivity to the electrode, and in the battery being configured, any material can be used as long as it is an electron conductive material without causing a chemical change. Examples of the conductive material 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; or mixtures thereof.

[0096] The content of the binder and the conductive material may each be 0.5 wt% to 5 wt% based on 100 wt% of the positive electrode active material layer.

[0097] Al may be used as the positive electrode current collector, but is not limited thereto.

[0098] Lithium secondary battery In one embodiment, a lithium secondary battery including the positive electrode, negative electrode, and electrolyte described above is provided. As an example, the lithium secondary battery may include a positive electrode, a negative electrode, a separator positioned between the positive electrode and the negative electrode, and an electrolyte solution.

[0099] Lithium secondary batteries can be classified into cylindrical, prismatic, pouch, coin, etc. according to their form. FIGS. 1 to 4 are schematic views showing a lithium secondary battery according to an embodiment. It can be said that FIG. 1 is circular, FIG. 2 is prismatic, and FIGS. 3 and 4 are pouch-type battery forms. Referring to FIGS. 1 to 4, the lithium secondary battery 100 may include an electrode assembly 40 with a separator 30 interposed between a positive electrode 10 and a negative electrode 20, and a case 50 in which the electrode assembly 40 is incorporated. The positive electrode 10, negative electrode 20, and separator 30 may be impregnated with an electrolytic solution (not shown). The lithium secondary battery 100 may include a sealing member 60 for sealing 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, that is, a positive electrode tab 71 and a negative electrode tab 72, which serve as an electrical path for guiding the current formed by the electrode assembly 40 to the outside.

[0100] 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 may include a negative electrode active material and may further include a binder, a conductive material, or a combination thereof.

[0101] Negative electrode active material The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0102] As the substance capable of reversibly intercalating / deintercalating the lithium ions, a carbon-based negative electrode active material may be used, which may include, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-shaped, 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.

[0103] 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 may be used.

[0104] As the substance capable of doping and undoping lithium, an Si-based negative electrode active material or an Sn-based negative electrode active material may be used. As the Si-based negative electrode active material, 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 may be used. As the Sn-based negative electrode active material, Sn, SnO2, an Sn alloy, or a combination thereof may be used.

[0105] The silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle size D of the silicon-carbon composite particles 50It may be, for example, from 0.5 μm to 20 μm. According to one embodiment, the silicon-carbon composite may be in a form in which amorphous carbon is coated on the silicon particles and the surface of the silicon particles. For example, it may include secondary particles (cores) assembled from primary silicon particles and an amorphous carbon coating layer (shell) located on the surface of the secondary particles. The amorphous carbon is also located between the primary silicon particles. For example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be present dispersed in an amorphous carbon matrix.

[0106] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and an amorphous carbon coating layer located on the surface of the core. 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.

[0107] When the silicon-carbon composite contains silicon and amorphous carbon, the content of silicon may be from 10% by weight to 50% by weight based on 100% by weight of the silicon-carbon composite, and the content of amorphous carbon may be from 50% by weight to 90% by weight. Also, when the composite contains silicon, amorphous carbon, and crystalline carbon, the content of silicon may be from 10% by weight to 50% by weight based on 100% by weight of the silicon-carbon composite, the content of crystalline carbon may be from 10% by weight to 70% by weight, and the content of amorphous carbon may be from 20% by weight to 40% by weight.

[0108] Also, the thickness of the amorphous carbon coating layer may be from 5 nm to 100 nm. The average particle size D of the silicon particles (primary particles) 50may be from 10 nm to 1 μm, or may be from 10 nm to 200 nm. The silicon particles may exist alone as silicon, may exist in the form of a silicon alloy, or may exist in an oxidized form. The oxidized form of silicon can be represented by SiOx (0 < x < 2). At this time, the atomic content ratio of Si:O indicating the degree of oxidation may be from 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.

[0109] The Si-based negative electrode active material or the Sn-based negative electrode active material may be used in mixture with a carbon-based negative electrode active material. When the Si-based negative electrode active material or the Sn-based negative electrode active material is used in mixture with the carbon-based negative electrode active material, the mixing ratio may be from 1:99 to 90:10 by weight.

[0110] Binder The binder serves to well adhere the negative electrode active material particles to each other and to well adhere the negative electrode active material to the current collector. As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof may be used.

[0111] 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.

[0112] The aqueous binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0113] When an aqueous binder is used as the negative electrode binder, it may further contain a cellulose-based compound capable of imparting viscosity. As this cellulose-based compound, one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof may be mixed and used. As the alkali metal, Na, K, or Li may be used.

[0114] The dry binder is a polymer substance capable of being fibrillated, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof.

[0115] Conductive material The conductive material is used to impart conductivity to the electrode, and in the battery being configured, any material can be used as long as it is an electron conductive material that does not cause a chemical change. 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 containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0116] The content of the negative electrode active material may be 95% by weight to 99.5% by weight based on 100% by weight of the negative electrode active material layer, and the content of the binder may be 0.5% by weight to 5% by weight based on 100% by weight of the negative electrode active material layer. For example, the negative electrode active material layer may contain 90% by weight to 99% by weight of the negative electrode active material, 0.5% by weight to 5% by weight of the binder, and 0.5% by weight to 5% by weight of the conductive material.

[0117] Current collector The negative electrode current collector may contain, 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 may be in the form of a foil, a sheet, or a foam. The thickness of the negative electrode current collector may be, for example, 1 μm to 20 μm, may be 5 μm to 15 μm, or may be 7 μm to 10 μm.

[0118] Electrolyte The electrolyte for the lithium secondary battery may be, for example, an electrolytic solution, which may contain a non-aqueous organic solvent and a lithium salt.

[0119] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move. The non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0120] As carbonate solvents, 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. may be used. As ester solvents, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc. may be used. As ether solvents, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. may be used. Further, as ketone solvents, cyclohexanone, etc. may be used. As alcohol solvents, ethyl alcohol, isopropyl alcohol, etc. may be used, and as aprotic solvents, nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may contain a double bond, a benzene ring, or an ether group), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, 1,4-dioxolane, sulfolane, etc. may be used.

[0121] The non-aqueous organic solvent may be used alone or in combination of two or more. When used in combination of two or more, the mixing ratio can be appropriately adjusted according to the intended battery performance, which should be widely understood by those skilled in the art.

[0122] When using a carbonate solvent, a cyclic carbonate and a chain carbonate may be mixed and used, and the cyclic carbonate and the chain carbonate may be mixed at a volume ratio of 1:1 to 1:9.

[0123] The non-aqueous organic solvent may further contain an aromatic hydrocarbon-based organic solvent. For example, the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed and used at a volume ratio of 1:1 to 30:1.

[0124] The electrolytic solution may further contain vinyl ethyl carbonate, vinylene carbonate or an ethylene carbonate-based compound in order to improve the battery life.

[0125] Typical examples of the ethylene carbonate-based compound include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate and the like.

[0126] The lithium salt is a substance that dissolves in the organic solvent, acts as a source of lithium ions in the battery to enable the operation of a basic lithium secondary battery, and plays a role in promoting the movement of lithium ions between the positive electrode and the negative electrode. Typical examples of the lithium salt include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2)(x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFOB), lithium bis(oxalate)borate (LiBOB), and may contain one or more selected therefrom.

[0127] The concentration of the lithium salt 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 ionic conductivity and viscosity, so it can exhibit excellent performance and lithium ions can move effectively.

[0128] Separator Depending on the type of the lithium secondary battery, a separator may be present between the positive electrode and the negative electrode. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used, and it goes without saying that a mixed multilayer film such as a two-layer separator of polyethylene / polypropylene, a three-layer separator of polyethylene / polypropylene / polyethylene, or a three-layer separator of polypropylene / polyethylene / polypropylene may be used.

[0129] The separator may include a porous substrate and a coating layer located on one or both surfaces of the porous substrate and containing an organic substance, an inorganic substance, or a combination thereof.

[0130] The porous substrate may be a polyolefin such as polyethylene or polypropylene, a polyester such as polyethylene terephthalate or polybutylene terephthalate, a polyacetal, a polyamide, a polyimide, a polycarbonate, a polyether ketone, a polyaryl ether ketone, a polyether imide, a polyamide imide, a polybenzimidazole, a polyether sulfone, a polyphenylene oxide, a cyclic olefin copolymer, a polyphenylene sulfide, a polyethylene naphthalate, a glass fiber, Teflon (registered trademark), and polytetrafluoroethylene, any one polymer selected therefrom, or a polymer film formed of a copolymer or a mixture of two or more of these.

[0131] The porous substrate may have a thickness of about 1 μm to 40 μm. For example, it may have a thickness of 1 μm to 30 μm, 1 μm to 20 μm, 5 μm to 15 μm, or 10 μm to 15 μm.

[0132] The organic substance 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 (meth)acrylate and a structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof.

[0133] The inorganic substance 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 of the inorganic particles 50 may be from 1 nm to 2000 nm, for example, from 100 nm to 1000 nm, or from 100 nm to 700 nm.

[0134] The organic substance and the inorganic substance may be mixed and present in one coating layer, or may be present in a form in which a coating layer containing the organic substance and a coating layer containing the inorganic substance are laminated.

[0135] The thickness of each coating layer may be from 0.5 μm to 20 μm, for example, from 1 μm to 10 μm, or from 1 μm to 5 μm.

[0136] Hereinafter, examples and comparative examples of the present invention will be described. The following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples.

[0137] Example 1 1. Production of positive electrode active material The average particle size D of the large particle precursor 50 is a nickel-based composite hydroxide of about 19 μm (Ni 0.55 Co 0.24 Mn 0.21(OH)2) and Li2CO3 were mixed so that the molar ratio of Li / (Ni + Co + Mn) was 1.09, and the mixture was first heat-treated at 900 °C for 8 hours in an oxygen atmosphere. Then, after crushing and filtering, nickel-based composite hydroxide (Ni 50 with an average particle size D of about 2.7 μm 0.55 Co 0.24 Mn 0.21 (OH)2) was mixed so that the weight ratio of the large particle precursor to the small particle precursor was 80:20. With respect to the small particle precursor and Li, Li2CO3 was further added so that the molar ratio of Li / (Ni + Co + Mn) was 0.8, and the mixture was second heat-treated at 850 °C for 8 hours in an oxygen atmosphere. Then, after crushing and filtering, the final cathode active material was obtained.

[0138] Figure 5 is an SEM image of the final cathode active material manufactured in Example 1. In Figure 5, large particles (the first cathode active material) in the form of secondary particles formed by aggregation of a plurality of primary particles and small particles (the second cathode active material, the third cathode active material) with a smaller particle size than this and in the form of secondary particles formed by aggregation of a plurality of primary particles are observed. The average particle size D of the large particles measured through the SEM image 50 is about 19 μm, and the average particle size D of the small particles 50 is about 3 μm.

[0139] Figure 6 is an SEM image of a cross-section obtained by cutting the final cathode active material manufactured in Example 1 with a focused ion beam (FIB). In Figure 6, the upper large particles and five small particles below them are observed. Each small particle was designated as A1, A2, A3, A4, and A5. Through SEM-EDS quantitative analysis of the cross-section of each small particle, the contents of Ni, Co, and Mn were measured, and the results are shown in Table 1 below. SEM-EDS was analyzed using Philips' FEI Titan80-300 at an acceleration voltage of 15 kV.

[0140]

Table 1

[0141] Referring to FIG. 6 and Table 1, it is confirmed that the small particles A1 have primary particles forming secondary particles that are not in a needle-like structure and have the same Ni, Co, and Mn contents as the small particle precursor. Such small particles A1 correspond to the second positive electrode active material. In contrast, the small particles A2 to A5 contain primary particles with a needle-like shape in the secondary particles, and the Ni content appears to have increased by about 2 mol% to 3 mol% compared to the small particle precursor. At the same time, the contents of Co and Mn each became slightly lower than those of the small particle precursor. Such A2 to A5 correspond to the third positive electrode active material.

[0142] It is understood that as a result of a part of the introduced small particle precursor contacting the lithium-rich large particles and reacting with each other to receive lithium and nickel from the large particles and being synthesized, the nickel content increased and the primary particles were formed in a needle-like shape. The remaining part of the introduced small particle precursor is different from this, and it is understood that the nickel content is maintained as it is and the primary particles do not change into a needle-like shape and remain.

[0143] 2. Production of lithium secondary battery 98.5% by weight of the manufactured positive electrode active material, 1.0% by weight of a polyvinylidene fluoride binder, and 0.5% by weight of a carbon nanotube conductive material were mixed to produce a positive electrode active material layer slurry, which was coated on an aluminum foil current collector and dried and rolled to produce a positive electrode.

[0144] A structure was manufactured with a polytetrafluoroethylene separator interposed between the positive electrode and the lithium metal counter electrode, and after inserting this into a battery case, an electrolyte solution in which 1 M LiPF6 was dissolved in a solvent obtained by mixing ethylene carbonate and dimethyl carbonate at a volume ratio of 3:7 was injected, and a lithium secondary battery (half cell) was manufactured by a normal method.

[0145] Comparative Example 1 Apply the existing method of simultaneously firing the large-particle precursor, the small-particle precursor, and Li2CO3. That is, the large-particle precursor and the small-particle precursor are mixed at a weight ratio of 70:30, and Li2CO3 is mixed so that the molar ratio of Li / (Ni + Co + Mn) = 1.03 in relation to the whole of the large-particle precursor, the small-particle precursor, and Li. Except for performing only the first heat treatment at 900°C for 8 hours to obtain the final positive electrode active material according to Comparative Example 1, the positive electrode active material and the lithium secondary battery were manufactured in substantially the same manner as in Example 1.

[0146] Example 2 In Example 1, when mixing the large-particle precursor and Li2CO3, aluminum oxide was further added for Al doping so that aluminum was 0.14 parts by weight with respect to 100 parts by weight of the total metal excluding lithium in the large-particle precursor. Also, when adding the small-particle precursor and Li2CO3, aluminum oxide was further added so that aluminum was 0.1 parts by weight with respect to 100 molar parts of the total metal excluding lithium in the whole of the large-particle precursor and the small-particle precursor, and Al coating was performed by performing the second heat treatment. Except for this, the positive electrode active material and the lithium secondary battery were manufactured in substantially the same manner as in Example 1.

[0147] Comparative Example 2 In Comparative Example 1, when mixing the large-particle precursor, the small-particle precursor, and Li2CO3, aluminum oxide was further added for Al doping so that aluminum was 0.14 parts by weight with respect to 100 molar parts of the total metal excluding lithium in the whole of the large-particle precursor and the small-particle precursor. Also, after the first heat treatment, through the processes of crushing and filtering, aluminum oxide was further added so that aluminum was 0.1 parts by weight with respect to 100 molar parts of the total metal excluding lithium in the whole of the large-particle precursor and the small-particle precursor, and the second heat treatment was performed at 850°C for 8 hours to add Al coating. Except for this, the positive electrode active material and the lithium secondary battery were manufactured in substantially the same manner as in Comparative Example 1.

[0148] Comparative Example 3 In Example 2, a positive electrode active material and a lithium secondary battery were produced in substantially the same manner as in Example 2, except that when mixing the large-particle precursor and Li2CO3, the molar ratio of Li / (Ni + Co + Mn) was changed to 1.03.

[0149] The design details of the positive electrode active material production processes of Examples 1 and 2 and Comparative Examples 1 to 3 are briefly shown in Table 2 below. Also, the pellet densities of the final positive electrode active materials produced in Examples 1 and 2 and Comparative Examples 1 to 3 were measured and shown in Table 2 below. The pellet density was measured by putting 3 g of the positive electrode active material into a Mold (area: 1.298 cm 2 ), slowly inserting the Mold Bar into the Mold body, putting the Mold SET into a hydraulic press, applying pressure at 3 ton (Metric ton) for 30 seconds, and then measuring the height.

[0150] Evaluation Example 1: Evaluation of initial charge-discharge capacity, efficiency and life characteristics The lithium secondary batteries produced in Examples 1 and 2 and Comparative Examples 1 to 3 were charged at a constant current of 0.2C to 4.45V at 25°C and then at a constant voltage to 0.05C, and then discharged at 0.2C to 3.0V to perform initial charge and discharge. The initial charge capacity and initial discharge capacity are shown in Table 2 below, and the initial charge-discharge efficiency, which is the ratio of the latter to the former, is shown as efficiency in Table 2 below.

[0151] Next, cycles of charging at 1.0C and discharging at 1.0C in the voltage range of 3.0V to 4.45V at 45°C were repeated 50 times. The ratio of the discharge capacity in 50 cycles to the initial discharge capacity was calculated and shown as the life in Table 2 below.

[0152]

Table 2

[0153] Referring to Table 2, it is confirmed that in Example 1, the initial discharge capacity increased compared to Comparative Example 1, the initial charge-discharge efficiency increased significantly, and the life characteristics were also improved. Similarly, it was shown that in Example 2, the initial discharge capacity increased compared to Comparative Examples 2 and 3, the initial charge-discharge efficiency increased significantly, and the life characteristics were also improved.

[0154] In the case of Comparative Example 3, the stepwise firing method according to one embodiment was applied, and the content of Li input during the first heat treatment was reduced so that the molar ratio of Li to the total metal excluding lithium in the large-particle precursor was 1.03. In this case, since lithium-rich large particles were not sufficiently formed, small particles such as the third positive electrode active material were not formed, and as a result, it was confirmed that the initial discharge capacity did not increase much and the improvement effect of the initial charge-discharge efficiency hardly appeared.

[0155] Although the preferred embodiments have been described in detail above, the scope of the rights of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concepts defined in the following claims also belong to the scope of the rights of the present invention.

Explanation of Reference Numerals

[0156] 100: Lithium secondary battery 10: Positive electrode 11: Positive electrode lead tab 12: Positive electrode terminal 20: Negative electrode 21: Negative electrode lead tab 22: Negative electrode terminal 30: Separator 40: Electrode assembly 50: Case 60: Sealing member 70: Electrode tab 71: Positive electrode tab 72: Negative electrode tab

Claims

1. A first positive electrode active material including a first lithium nickel-based composite oxide and having a secondary particle form in which a plurality of primary particles are aggregated, and an average particle diameter D of the secondary particles 50 is from 10 μm to 25 μm, and A secondary particle form in which a plurality of primary particles are aggregated, including a second lithium nickel-based composite oxide, and an average particle size D of the secondary particles 50 is a second positive electrode active material of 0.5 μm to 8 μm, and It contains a third lithium nickel-based composite oxide and has a secondary particle form in which a plurality of primary particles are aggregated, and the average particle diameter D of the secondary particles 50 is from 0.5 μm to 8 μm, and the secondary particles include a third positive electrode active material containing acicular primary particles, A positive electrode active material in which the nickel content with respect to the total metal excluding lithium in the third lithium nickel composite oxide is higher than the nickel content with respect to the total metal excluding lithium in the second lithium nickel composite oxide.

2. The positive electrode active material according to claim 1, wherein the nickel content with respect to the total metal excluding lithium in the third lithium nickel composite oxide is 1 mol% to 5 mol% higher than the nickel content with respect to the total metal excluding lithium in the second lithium nickel composite oxide.

3. The second lithium nickel composite oxide and the third lithium nickel composite oxide further contain a metal M other than lithium and nickel, The positive electrode active material according to claim 1, wherein the content of the metal M with respect to the total metal excluding lithium in the third lithium nickel composite oxide is 1 mol% to 5 mol% lower than the content of the metal M with respect to the total metal excluding lithium in the second lithium nickel composite oxide.

4. The positive electrode active material according to claim 1, wherein the secondary particles of the third positive electrode active material are spherical, ellipsoidal, polyhedral, or amorphous (irregular shape), or a combination thereof, and are not needle-shaped.

5. The positive electrode active material according to claim 1, wherein the primary particles forming the secondary particles in the second positive electrode active material are spherical, ellipsoidal, polyhedral, plate-shaped, amorphous, or a combination thereof, and are not needle-shaped.

6. The positive electrode active material according to claim 1, wherein the third positive electrode active material is in contact with the first positive electrode active material or is positioned adjacent thereto.

7. The positive electrode active material according to claim 1, wherein the nickel content with respect to 100 mol% of the total metal excluding lithium in the first lithium nickel composite oxide, the nickel content with respect to 100 mol% of the total metal excluding lithium in the second lithium nickel composite oxide, and the nickel content with respect to 100 mol% of the total metal excluding lithium in the third lithium nickel composite oxide are each independently 50 mol% to 99 mol%.

8. The content of nickel with respect to 100 mol% of the total metal excluding lithium in the first lithium nickel-based composite oxide, the content of nickel with respect to 100 mol% of the total metal excluding lithium in the second lithium nickel-based composite oxide, and the content of nickel with respect to 100 mol% of the total metal excluding lithium in the third lithium nickel-based composite oxide are each independently 50 mol% to 70 mol%, the positive electrode active material according to claim 7.

9. The first lithium nickel-based composite oxide is represented by Chemical Formula 1, the second lithium nickel-based composite oxide is represented by Chemical Formula 3, and the third lithium nickel-based composite oxide is represented by Chemical Formula 5, the positive electrode active material according to claim 1. [Chemical Formula 1] Li a1 Ni x1 M 1 y1 O 2-b1 X b1 In the above Chemical Formula 1, 0.9 ≤ a1 ≤ 1.2, 0.5 ≤ x1 < 1, 0 < y1 ≤ 0.5, 0.9 ≤ x1 + y1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1, and M 1 is one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S. [Chemical Formula 3] Li a3 Ni x3 M 4 y3 O 2-b3 X b3 In the above chemical formula 3, 0.9 ≤ a3 ≤ 1.2, 0.5 ≤ x3 < 1, 0 < y3 ≤ 0.5, 0.9 ≤ x3 + y3 ≤ 1.1, and 0 ≤ b3 ≤ 0.1, and M 4 is one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S. [Chemical Formula 5] Li a5 Ni x5 M 7 y5 O 2-b5 X b5 In the above chemical formula 5, 0.9 ≦ a5 ≦ 1.2, 0.5 ≦ x5 < 1, 0 < y5 ≦ 0.5, 0.9 ≦ x5 + y5 ≦ 1.1, and 0 ≦ b5 ≦ 0.1, and M 7 is one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S.

10. With respect to a total of 100% by weight of the first positive electrode active material, the second positive electrode active material, and the third positive electrode active material, the first positive electrode active material is contained in an amount of 60% to 85% by weight, the total amount of the second positive electrode active material and the third positive electrode active material is 15% to 40% by weight, the positive electrode active material according to claim 1.

11. With respect to a total of 100% by weight of the second positive electrode active material and the third positive electrode active material, the second positive electrode active material is contained in an amount of 10% to 90% by weight, and the third positive electrode active material is contained in an amount of 10% to 90% by weight, the positive electrode active material according to claim 1.

12. Average particle diameter D 50 Mixing a first nickel-based hydroxide having an average particle diameter D of 10 μm to 25 μm and a first lithium raw material, and performing a first heat treatment by mixing them such that the molar ratio of lithium of the first lithium raw material to the total metal of the first nickel-based hydroxide is 1.09 or more; The first heat treatment product and the average particle size D 50 mixing a second nickel-based hydroxide having an average particle size D of 0.5 μm to 8 μm and a second lithium raw material and subjecting the mixture to a second heat treatment, a method for producing a positive electrode active material.

13. The molar ratio of lithium of the first lithium raw material with respect to the total metal of the first nickel-based hydroxide is 1.09 to 1.2, the method for producing a positive electrode active material according to claim 12.

14. The molar ratio of lithium of the second lithium raw material with respect to the total metal of the second nickel-based hydroxide is less than 1, the method for producing a positive electrode active material according to claim 12.

15. The first nickel-based hydroxide is represented by Chemical Formula 11, and the second nickel-based hydroxide is represented by Chemical Formula 13, the method for producing a positive electrode active material according to claim 12. [Chemical Formula 11] Ni x11 M 11 y11 (OH) 2 In the aforementioned Chemical Formula 11, 0.9 ≤ a11 ≤ 1.2, 0.5 ≤ x11 < 1, 0 < y11 ≤ 0.5, 0.9 ≤ x11 + y11 ≤ 1.1, and 0 ≤ b11 ≤ 0.1, and M 11 is one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S. [Chemical Formula 13] Ni x13 M 14 y13 (OH) 2 In the aforementioned Chemical Formula 13, 0.9 ≦ a13 ≦ 1.2, 0.5 ≦ x13 < 1, 0 < y13 ≦ 0.5, 0.9 ≦ x13 + y13 ≦ 1.1, and 0 ≦ b13 ≦ 0.1, and M 14 is one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S.

16. The first heat treatment is performed in a temperature range of 750°C to 1000°C, the second heat treatment is performed in a temperature range of 700°C to 900°C, the method for producing a positive electrode active material according to claim 12.

17. The mixing ratio of the first nickel-based hydroxide and the second nickel-based hydroxide is a weight ratio of 60:40 to 85:15, the method for producing a positive electrode active material according to claim 12.

18. The method for producing a positive electrode active material according to claim 12, wherein when mixing the first heat treatment product, the second nickel-based hydroxide, and the second lithium raw material, the coating raw materials are introduced together and second heat treatment is performed.

19. The coating raw material is an aluminum raw material, The method for producing a positive electrode active material according to claim 18, wherein the aluminum raw material is mixed such that the aluminum content is 0.1 part by weight to 2 parts by weight with respect to 100 parts by weight of the total metal excluding lithium in the entire first heat treatment product and the second nickel-based hydroxide.

20. The method for producing a positive electrode active material according to claim 12, wherein the method for producing the positive electrode active material further includes a pulverization process after the first heat treatment and / or after the second heat treatment.

21. A positive electrode for a lithium secondary battery, comprising the positive electrode active material according to any one of claims 1 to 11.

22. A lithium secondary battery, comprising the positive electrode according to claim 21, a negative electrode, and an electrolyte.

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