Positive electrode active material, preparation method thereof, positive electrode including the same, and rechargeable lithium batteries

Abstract

To provide a positive electrode active material that is structurally stable, has no residual impurities, does not increase resistance, and exhibits a long cycle-life by proposing a method for effectively preparing a high-nickel-based positive electrode active material in a form of a single particle at a relatively low firing temperature without utilizing an alkaline grain growth accelerator, and for reducing aggregation between single particles, thereby making the overall preparing process simple and economical.SOLUTION: A positive electrode active material includes a layered lithium nickel-based composite oxide, wherein, based on 100 mol% of a total mole of metals excluding lithium, a nickel content is greater than or equal to 60 mol%, an aluminum content is 0.8 mol% to 1.5 mol%, a zirconium content is 0.1 mol% to 0.3 mol%, a ratio of the aluminum content relative to the zirconium content (AI / Zr) is greater than or equal to 5. Also, disclosed are a positive electrode active material in a form of a single particle with an average particle diameter D50 of 1 μm to 4 μm, a preparation method thereof, a positive electrode including the same and a rechargeable lithium battery.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. High-nickel-based positive electrode active materials having a nickel content of about 80 mol% or more can achieve a high energy density and have been actively developed recently, but they have limitations such as various problems such as structural deterioration due to charge and discharge, surface side reactions with the electrolyte, and deterioration due to particle cracks. Accordingly, development of a positive electrode active material that realizes a high energy density and long life characteristics is required.

[0004] As a high-nickel-based positive electrode active material that realizes high capacity, a secondary particle form in which a plurality of primary particles aggregate has generally been mainly used. Recently, however, a single particle form has been studied in order to realize long life and reduce the amount of gas generation. However, increasing the firing temperature to produce single particles causes problems such as an increase in the aggregation phenomenon between particles and a decrease in productivity. Research has been proposed to introduce an alkaline particle growth promoter during single particle synthesis in order to eliminate aggregation between particles and lower the firing temperature. However, there is a problem that the remaining particle growth promoter acts as a resistance in the positive electrode after firing and reduces the life. When passing through a washing process to remove the remaining particle growth promoter and residual salts, there are problems such as an increase in manufacturing cost and a complication of the process.

Summary of the Invention

Problems to be Solved by the Invention

[0005] A method is proposed for effectively producing a single particle form of a high-nickel-based positive electrode active material at a relatively low firing temperature without using an alkaline particle growth promoter, and a method is proposed in which aggregation between particles is reduced and the overall manufacturing process is simple and economical. Thereby, a positive electrode active material that is structurally stable, does not leave impurities, does not increase resistance, and can achieve long life is proposed.

Means for Solving the Problems

[0006] In one embodiment, based on 100 mol% of the total metal excluding lithium, the nickel content is 60 mol% or more, the aluminum content is 0.8 mol% to 1.5 mol%, the zirconium content is 0.1 mol% to 0.3 mol%, and the ratio of the aluminum content to the zirconium content (Al / Zr) is 5 or more. It includes a layered lithium nickel-based composite oxide, and provides a positive electrode active material in the form of single particles with an average particle size D 50 of 1 μm to 4 μm.

[0007] In another embodiment, a nickel precursor and M 1A coprecipitation reaction of a precursor is carried out to prepare a nickel-based composite hydroxide having fine pores inside the particles, and the nickel-based composite hydroxide, a lithium raw material, an aluminum raw material, and a zirconium raw material are mixed and heat-treated to obtain a layered lithium nickel-based composite oxide, and a hollow secondary particle having pores inside is manufactured as a secondary particle formed by aggregation of a plurality of primary particles, and the secondary particle is pulverized to obtain a positive electrode active material. A method for manufacturing a positive electrode active material includes the above M 1 is one or more elements selected from B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zn. With respect to the total 100% by weight of the entire metal of the nickel-based composite hydroxide, aluminum in the aluminum raw material, and zirconium in the zirconium raw material, the aluminum content of the aluminum raw material is 0.8 mol% to 1.5 mol%, and the zirconium content of the zirconium raw material is 0.1 mol% to 0.3 mol%, and the ratio (Al / Zr) of the aluminum content to the zirconium content is 5 or more. Provided is a method for manufacturing a positive electrode active material.

[0008] In another embodiment, a positive electrode for a lithium secondary battery including the above-described positive electrode active material is provided.

[0009] In another embodiment, a lithium secondary battery including the positive electrode, a negative electrode, and an electrolyte is provided.

Advantages of the Invention

[0010] The single-particle-form high-nickel-based positive electrode active material according to one embodiment can be synthesized by a simple method at a relatively low heat treatment temperature, and since no alkyl lithium-based particle growth promoter or the like is used during the synthesis process, no residue remains, the resistance does not increase, and the long-life characteristics of the lithium secondary battery can be realized structurally stably.

Brief Description of the Drawings

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[0012] 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.

[0013] 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.

[0014] Here, "these combinations" means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of components.

[0015] Here, terms such as "comprising", "including", or "having" are intended to specify the presence of the 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.

[0016] For the purpose of clearly showing various layers and regions in the drawings, the thickness is enlarged, and the same drawing reference numerals are given 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.

[0017] Here, the "layer" includes not only the shape formed on the entire surface but also the shape formed on a part of the surface when observed in a plan view.

[0018] The average particle diameter 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 also 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, and after performing data analysis to count the number of particles for each particle size range, the average particle diameter value can be obtained based on this. Unless otherwise defined, the average particle diameter is the diameter D of the particle with a cumulative volume of 50% by volume in the particle size distribution. 50 can be meant. Also, unless otherwise defined, the average particle diameter is 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 with a cumulative volume of 50% by volume in the particle size distribution 50 as the average particle diameter.

[0019] Here, "or" is not interpreted in an exclusive sense. For example, "A or B" is interpreted to include A, B, A + B, etc.

[0020] "Metal" is interpreted as a concept including general metals, transition metals, and metalloids.

[0021] Positive electrode active material In one embodiment, based on 100 mol% of the total metal excluding lithium, the nickel content is 60 mol% or more, the aluminum content is 0.8 mol% to 1.5 mol%, the zirconium content is 0.1 mol% to 0.3 mol%, and the ratio of the aluminum content to the zirconium content (Al / Zr) is 5 or more. It includes a layered lithium nickel-based composite oxide, and provides a cathode active material in the form of single particles with an average particle diameter D 50 of 1 μm to 4 μm.

[0022] The positive electrode active material can be effectively synthesized even by relatively low-temperature heat treatment, is economical and advantageous for mass production, and can achieve excellent life characteristics due to its high structural stability.

[0023] Here, a single particle means that it exists alone without having a grain boundary inside the particle and consists of one particle, and can mean a single particle, a monolith structure or a single structure or non-aggregated particles existing in a morphological phase where the particles do not aggregate with each other. As an example, it may be a single crystal. The single particles may exist alone or the single particles may be aggregated with each other. For example, 2 to 9 single particles may be aggregated and in contact with each other.

[0024] In one embodiment, the single particles may exist alone or 5 or fewer single particles may adhere to each other.

[0025] The average particle size D of the single particles according to one embodiment 50 is 1 μm to 4 μm, and for example, it may be 1.5 μm to 4 μm, 2 μm to 4 μm, or 2 μm to 3.8 μm. The single particles satisfying the particle size range can structurally stabilize and increase the energy density of the positive electrode, and can improve the long-life characteristics of the lithium secondary battery. Here, the average particle size is, for example, by measuring the particle size (particle size, major axis length, or length of the major axis) of any 20 or more particles in a scanning electron microscope image to obtain a particle size distribution, and here, the size D of the particle where the cumulative volume is 50% by volume 50 may be calculated.

[0026] The above-mentioned layered lithium nickel-based composite oxide may be a high-nickel-based oxide in which the nickel content is 60 mol% or more based on 100 mol% of the total metal excluding lithium. The nickel content may be, for example, 65 mol% or more, 70 mol% or more, 75 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more, and may also be 99 mol% or less or 98 mol% or less with respect to 100 mol% of the total metal excluding lithium in the above-mentioned layered lithium nickel-based composite oxide.

[0027] The above-mentioned layered lithium nickel-based composite oxide is characterized by containing aluminum and zirconium as a kind of dopant in specific contents in addition to nickel. The aluminum content is 0.8 mol% to 1.5 mol% with respect to 100 mol% of the total metal excluding lithium, and may be, for example, 0.8 mol% to 1.4 mol%, 0.8 mol% to 1.3 mol%, or 0.9 mol% to 1.2 mol%. The zirconium content is 0.1 mol% to 0.3 mol% with respect to 100 mol% of the total metal excluding lithium, and may be, for example, 0.1 mol% to 0.2 mol%.

[0028] Also, the ratio (Al / Zr) of the aluminum content to the zirconium content in the above-mentioned layered lithium nickel-based composite oxide is characterized by being 5 or more, and may be, for example, 5 to 20, 5 to 15, or 5 to 10. When the content ratio of aluminum to zirconium satisfies the above range, it is possible to synthesize at a relatively low firing temperature without using, for example, an alkaline particle growth additive in the synthesis process, and high structural stability enables the realization of long-life characteristics.

[0029] As a specific example, the above-mentioned layered lithium nickel-based composite oxide is represented by the following Chemical Formula 1. [Chemical Formula 1] Li a1 Ni x1 M 1 y1 Al z1 Zrw1 O 2-b1 X b1

[0030] In the above Chemical Formula 1, 0.9 ≤ a1 ≤ 1.2, 0.6 ≤ x1 ≤ 0.991, 0 ≤ y1 ≤ 0.391, 0.008 ≤ z1 ≤ 0.015, 0.001 ≤ w1 ≤ 0.003, 0.9 ≤ x1 + y1 + z1 + w1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1, and M 1 is one or more elements selected from B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zn, and X is one or more elements selected from F, P, and S.

[0031] In the above Chemical Formula 1, 0.9 ≤ a1 ≤ 1.1, 0.9 ≤ a1 ≤ 1.05, or 0.9 ≤ a1 ≤ 1 may also be possible. Also, 0.7 ≤ x1 ≤ 0.991 and 0 ≤ y1 ≤ 0.291, or 0.8 ≤ x1 ≤ 0.991 and 0 ≤ y1 ≤ 0.191, or 0.9 ≤ x1 ≤ 0.991 and 0 ≤ y1 ≤ 0.091 may also be possible. The Al content z1 may be, for example, 0.008 ≤ z1 ≤ 0.014, 0.008 ≤ z1 ≤ 0.013, or 0.009 ≤ z1 ≤ 0.012. The Zr content w1 may be, for example, 0.001 ≤ w1 ≤ 0.002.

[0032] In Chemical Formula 1, 5 ≤ z1 / w1 is satisfied, and for example, 5 ≤ z1 / w1 ≤ 20, 5 ≤ z1 / w1 ≤ 15, or 5 ≤ z1 / w1 ≤ 10 may also be possible.

[0033] As a more specific example, the above layered lithium nickel-based composite oxide is represented by the following Chemical Formula 2. [Chemical Formula 2] Li a2 Ni x2 Co v2 M 2 y2 Al z2 Zr w2 O 2-b2 X b2

[0034] In the above Chemical Formula 2, 0.9 ≦ a2 ≦ 1.2, 0.6 ≦ x2 < 0.991, 0 < v2 ≦ 0.391, 0 ≦ y2 ≦ 0.391, 0.008 ≦ z2 ≦ 0.015, 0.001 ≦ w2 ≦ 0.003, 0.9 ≦ x2 + v2 + y2 + z2 + w2 ≦ 1.1, and 0 ≦ b2 ≦ 0.1, and M 2 is one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zn, and X is one or more elements selected from F, P, and S.

[0035] In the above Chemical Formula 2, 5 ≦ z2 / w2 is satisfied, and for example, 5 ≦ z2 / w2 ≦ 20, 5 ≦ z2 / w2 ≦ 15, or 5 ≦ z2 / w2 ≦ 10 may be satisfied.

[0036] Method for manufacturing positive electrode active material In one embodiment, (i) a coprecipitation reaction of a nickel precursor and an M 1 precursor is performed to prepare a nickel-based composite hydroxide having fine pores inside the particles, and (ii) the nickel-based composite hydroxide, a lithium raw material, an aluminum raw material, and a zirconium raw material are mixed and heat-treated to produce a hollow secondary particle having pores inside as a secondary particle formed by aggregation of a plurality of primary particles and containing a layered lithium nickel-based composite oxide, and (iii) the secondary particle is pulverized to obtain a positive electrode active material, and a method for producing a positive electrode active material is provided.

[0037] The M 1 precursor, where M 1 is one or more elements selected from B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zn. With respect to the total of 100% by weight of the entire metal of the nickel-based composite hydroxide, the aluminum, and the zirconium of the zirconium raw material, the aluminum content of the aluminum raw material is 0.8 mol% to 1.5 mol%, the zirconium content of the zirconium raw material is 0.1 mol% to 0.3 mol%, and the ratio of the aluminum content to the zirconium content (Al / Zr) satisfies 5 or more.

[0038] According to the manufacturing method, it is possible to effectively manufacture a high-nickel-based cathode active material in single-particle form at a relatively low firing temperature and by a simple method without adding an alkaline grain growth promoter or a flux, etc., and productivity and economy can be improved.

[0039] It can be said that when the nickel-based composite hydroxide and the lithium raw material are mixed and heat-treated in the manufacturing method, both the aluminum raw material and the zirconium raw material are charged and fired. At this time, the aluminum raw material and the zirconium raw material are understood to act as a dopant and as a grain growth promoter. When the aluminum raw material and the zirconium raw material are charged, this can promote grain growth and effectively synthesize single particles at a temperature lower than that of existing single-particle synthesis methods, thereby suppressing particle aggregation and improving productivity. Existing alkaline grain growth promoters and fluxes have the problem of acting as resistance in the cathode and reducing the lifespan due to remaining after firing, but the aluminum raw material and the zirconium raw material are used as a dopant for the cathode active material and do not remain on the surface of the cathode active material particles, thereby improving the lifespan characteristics.

[0040] Hereinafter, the manufacturing method of the cathode active material will be specifically described.

[0041] It can be said that the nickel-based composite hydroxide is a precursor of the cathode active material and can be synthesized through a coprecipitation reaction. In the coprecipitation reaction, the nickel precursor may be a hydroxide, oxide, nitrate, sulfate, carbonate, or a combination thereof of nickel. M 1 The precursor may be a hydroxide, oxide, nitrate, sulfate, carbonate, or a combination thereof containing the M 1 element.

[0042] In the coprecipitation reaction, the nickel precursor and M 1Complexing agents and pH adjusters may also be used in addition to the precursors. The complexing agent plays a role in regulating the reaction rate of the formation reaction of the precipitate in the coprecipitation reaction. For example, it may contain ammonium hydroxide (NH 4 OH), citric acid, or a combination thereof. The concentration of the complexing agent may be 0.1 to 1.5 M, for example, 0.1 to 1.4 M, or 0.5 to 1.4 M. The pH adjuster plays a role in controlling the pH of the reactants. For example, it may contain sodium hydroxide (NaOH), sodium carbonate (Na 2 CO 3 ), sodium oxalate (Na 2 C 2 O 4 ) or a combination thereof.

[0043] The coprecipitation reaction may include a first step that reacts in a pH range of 11 to 12 and a second step that reacts at a pH lower than the first step. The pH of the first step may be, for example, 11.5 to 12, 11.6 to 11.9, or 11.7 to 11.8, and can be said to be a kind of pore formation step. The second step is a step that reacts at a pH lower than the pH of the first step and can be said to be a kind of particle growth step. By changing the pH in two or more steps, the synthesis rate can be changed, and as a result, a nickel-based composite hydroxide having fine pores inside the particles can be obtained. The pH of the second step may be, for example, 10 to 11.9, 10.5 to 11.7, 11 to 11.7, 11.2 to 11.6, or 11.3 to 11.6. The difference between the pH of the first step and the pH of the second step may be, for example, 0.1 to 1.5, for example, 0.1 to 1.0, 0.1 to 0.8, 0.1 to 0.6, 0.1 to 0.5, 0.1 to 0.3, or 0.1 to 0.2.

[0044] The first step may be carried out for 6 to 12 hours, or 8 to 10 hours. The second step may be carried out for 10 to 30 hours, 15 to 25 hours, or 18 to 24 hours.

[0045] The produced nickel-based composite hydroxide is represented by, for example, Chemical Formula 11.

[0046] [Chemical Formula 11] Ni x11 M 1 y11 (OH) 2 In the above Chemical Formula 11, 0.6 ≦ x11 ≦ 1, 0 ≦ y11 ≦ 0.4, and 0.9 ≦ x11 + y11 ≦ 1.1, and M 1 is one or more elements selected from B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zn.

[0047] In Chemical Formula 11, it may be 0.7 ≦ x11 ≦ 1, 0 ≦ y11 ≦ 0.3, or 0.8 ≦ x11 ≦ 1, 0 ≦ y11 ≦ 0.2, or 0.9 ≦ x11 < 1, 0 < y11 ≦ 0.1.

[0048] As a specific example, the nickel-based composite hydroxide is represented by the following Chemical Formula 12. [Chemical Formula 12] Ni x12 Co v12 M 2 y12 (OH) 2

[0049] In the above Chemical Formula 12, 0.6 ≦ x12 < 1, 0 < v12 ≦ 0.4, 0 ≦ y1 ≦ 0.4, and 0.9 ≦ x12 + v12 + y12 ≦ 1.1, and M 2 is one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zn.

[0050] The nickel-based composite hydroxide is in particulate form. As an example, the particles may include an interior containing a large number of fine pores and an exterior surrounding the interior and having a dense structure. Here, the interior of the nickel-based composite hydroxide particles can mean a region that is 50 to 70% by volume, for example, 60% by volume, of the total volume of the particles, or can mean the remaining region excluding the exterior, which is a region within 3 μm from the outermost contour, of the total distance from the particle center to the surface.

[0051] By using such a nickel-based composite hydroxide having fine pores inside the particles, a cathode active material in the form of hollow secondary particles can be effectively obtained. In this case, during the pulverization process, the secondary particles are easily pulverized, and good single particles can be obtained.

[0052] The nickel-based composite hydroxide may, as an example, be non-crystalline, which can be confirmed through X-ray diffraction analysis.

[0053] Among the methods for manufacturing the cathode active material, in the process of (ii), the lithium content of the lithium raw material may be 0.9 to 1.2 mole parts, for example, 0.9 to 1.1 mole parts, or 0.9 to 1.05 mole parts, relative to a total of 1 mole part of the total amount of metals in the nickel-based composite hydroxide, the aluminum in the aluminum raw material, and the zirconium in the zirconium raw material. As an example, it may exceed 1 mole part and be less than 1.1 mole parts, for example, 1.01 to 1.04 mole parts. By appropriately adjusting the molar ratio of the lithium raw material, a cathode active material in the form of single particles having a stable structure and good quality can be manufactured.

[0054] The lithium raw material may be, for example, lithium hydroxide, lithium carbonate, lithium sulfate, lithium nitrate, or a combination thereof. As an example, it may be anhydrous lithium hydroxide.

[0055] With respect to a total of 100% by weight of the entire metal of the nickel-based composite hydroxide, aluminum of the aluminum raw material, and zirconium of the zirconium raw material, the aluminum content of the aluminum raw material is designed to be 0.8 mol% to 1.5 mol%, and the zirconium content of the zirconium raw material is designed to be 0.1 mol% to 0.3 mol%. The aluminum content of the aluminum raw material may be, for example, 0.8 mol% to 1.4 mol%, 0.8 mol% to 1.3 mol%, or 0.9 mol% to 1.2 mol%. The zirconium content of the zirconium raw material may be, for example, 0.1 mol% to 0.2 mol%.

[0056] At the same time, the ratio of the aluminum content to the zirconium content (Al / Zr) is designed to be 5 or more, and may be, for example, 5 to 20, 5 to 15, or 5 to 10.

[0057] As described above, it is understood that the aluminum raw material and the zirconium raw material act as raw materials for dopants and also serve as grain growth accelerators, and by introducing them within the above content ranges, it is possible to obtain single particles in an optimal state.

[0058] As an example, the aluminum raw material may be an aluminum oxide, specifically Al 2 O 3 It may also be so. Further, as an example, the zirconium raw material may be a zirconium oxide, specifically ZrO 2 It may also be so.

[0059] The method for manufacturing a positive electrode active material according to an embodiment can be heat-treated at a temperature lower than that of existing single-particle synthesis methods. That is, even when heat treatment is performed at a relatively low temperature, it is possible to obtain a positive electrode active material in a desired single-particle form with a good morphology. As a result, the process becomes simpler, the economy is improved, and the problem of particle aggregation is also reduced, improving productivity and processability. The heat treatment may be performed, for example, at a temperature of 900 °C or lower, or 890 °C or lower, 850 °C or lower, or 810 °C or lower, and may be performed, for example, at 700 °C to 900 °C, 710 °C to 890 °C, 730 °C to 850 °C, or 750 °C to 810 °C.

[0060] The heat treatment may be performed in an oxidizing gas atmosphere, and may be performed, for example, for 4 hours to 20 hours, 5 hours to 15 hours, or 6 hours to 12 hours.

[0061] In the method for manufacturing a positive electrode active material according to an embodiment, even when an alkali-based grain growth promoter or a flux is not added during the process of mixing a nickel-based composite hydroxide, a lithium raw material, an aluminum raw material, and a zirconium raw material and performing heat treatment. As a result, an increase in resistance due to the residue after heat treatment can be prevented, thereby improving the life characteristics of the lithium secondary battery. Since there is no need to add a step of removing the residue, the processability and economy can be improved.

[0062] Through the heat treatment, hollow secondary particles containing a layered lithium nickel-based composite oxide can be obtained. At this time, the primary particles forming the secondary particles have sufficiently grown and crystallized into single crystals by the addition of the aluminum raw material and the zirconium raw material, and the secondary particles have a hollow structure having internal pores, so that they can be easily pulverized in the subsequent pulverization step.

[0063] The average particle size D of the obtained secondary particles 50 may be 10 μm to 20 μm, and may be, for example, 10 μm to 18 μm, or 12 μm to 16 μm. The average particle size D of the secondary particles 50It may be measured through a SEM image.

[0064] The average particle size D of the primary particles forming the secondary particles 50 may be from 1 μm to 4 μm, for example, from 1.5 μm to 4 μm, from 2 μm to 4 μm, or from 2 μm to 3.8 μm. The average particle size D of the primary particles 50 may be measured through a SEM image of the surface of the secondary particles.

[0065] The size of the pores inside the secondary particles may be approximately from 1 μm to 9 μm, for example, from 2 μm to 8 μm, from 3 μm to 7 μm, etc. The size of the pores inside the secondary particles may be measured by a SEM image of the cross-section of the secondary particles and may mean the length of the major axis of the pores.

[0066] The obtained layered lithium nickel-based composite oxide may be represented by Chemical Formula 1, and the description of Chemical Formula 1 is as described above.

[0067] In (iii) of the method for producing the positive electrode active material, pulverizing the secondary particles means breaking the secondary particles, and it can be understood as a process in which the primary particles that formed the secondary particles are separated from each other to become single individual particles. Through the pulverization process, the average particle size D 50 of single particles in the range of 1 μm to 4 μm can be obtained for the high nickel-based positive electrode active material.

[0068] According to the manufacturing method, by using a nickel-based composite hydroxide with fine pores formed inside as a precursor, it is possible to obtain a lithium nickel-based composite oxide in the form of hollow secondary particles after heat treatment, and thereby it is possible to produce single particles by easily pulverizing the secondary particles. Moreover, when mixing the nickel-based composite hydroxide and the lithium raw material and performing heat treatment, by introducing both the aluminum raw material and the zirconium raw material and performing heat treatment, it is possible to form single primary particles of sufficient size at a relatively low temperature of 900 °C or lower, and it is possible to obtain secondary particles in which such primary particles are aggregated, and by pulverizing this, it is possible to obtain a desired single-particle positive electrode active material with a good form.

[0069] The pulverization may be performed using a jet mill or an air classifier mill (ACM) equipment. When pulverizing with a jet mill, the air pressure can be appropriately adjusted so that the bulk density of the pulverized product becomes about 0.2 to 0.5 g / cm 3 For example, it can be adjusted to 2 to 8 bar, or 4 to 6 bar. The pulverization process may be performed for, for example, 10 minutes to 120 minutes, and may be performed for, for example, 10 minutes to 80 minutes, 10 minutes to 60 minutes, or 20 minutes to 50 minutes.

[0070] The method for manufacturing a positive electrode active material according to one embodiment may further include reheat treatment after the pulverization. The reheat treatment may be performed in an oxidizing gas atmosphere, for example, at 500 °C to 900 °C, or 600 °C to 800 °C, or 650 °C to 750 °C.

[0071] The method for manufacturing the positive electrode active material may include mixing the resultant product pulverized after the pulverization and a coating raw material, and then performing reheat treatment. Thereby, it is possible to obtain single particles coated with a desired material.

[0072] The coating raw material is not particularly limited. For example, it may be a raw material of one or more elements selected from Al, B, Co, Mg, V, Zn, and Zr, and may be a hydroxide, oxide, sulfate, nitrate, or carbonate containing the above elements.

[0073] The positive electrode active material obtained through the above manufacturing method contains a lithium nickel-based composite oxide, and the average particle size D 50 may include single particles with a size of 1 μm to 4 μm. As an example, it may include a mixture of unground hollow secondary particles and ground single particles.

[0074] 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, and the positive electrode active material layer may include the above-described positive electrode active material.

[0075] Here, the positive electrode active material contains a layered lithium nickel-based composite oxide in which the nickel content is 60 mol% or more, the aluminum content is 0.8 mol% to 1.5 mol%, the zirconium content is 0.1 mol% to 0.3 mol%, and the ratio of the aluminum content to the zirconium content (Al / Zr) is 5 or more, based on 100 mol% of the total metal excluding lithium. The positive electrode active material layer has an average particle size D 50 and contains the positive electrode active material in the form of single particles with a size of 1 μm to 4 μm.

[0076] As an example, the positive electrode active material layer may include a first positive electrode active material in the form of single particles and a second positive electrode active material in the form of secondary particles. At this time, the second positive electrode active material can mean unground hollow secondary particles, and the first positive electrode active material may mean single particles formed by grinding the second positive electrode active material.

[0077] In the positive electrode active material layer, based on a total of 100% by weight of the first positive electrode active material and the second positive electrode active material, the first positive electrode active material may be contained in an amount of 5% to 60% by weight, and the second positive electrode active material may be contained in an amount of 40% to 95% by weight. That is, the weight ratio of the first positive electrode active material to the second positive electrode active material may be 5:95 to 60:40, for example, 10:90 to 50:50, 20:80 to 40:60, but is not particularly limited.

[0078] The positive electrode active material layer may further selectively contain a binder, a conductive material, or a combination thereof.

[0079] Binder The binder serves to well adhere the positive electrode active material particles to each other and also to well adhere the positive electrode active material 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, polymers 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.

[0080] Conductive material The conductive material is used to impart conductivity to the electrode, and in the battery being constructed, any electron conductive material that does not cause a chemical change can be used. Examples of the conductive material include carbon-based substances such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, carbon nanotube; metal-based substances in the form of metal powder or metal fiber containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0081] The contents of the binder and the conductive material may each be 0.5% by weight to 5% by weight based on 100% by weight of the positive electrode active material layer.

[0082] As the positive electrode current collector, Al may be used, but is not limited thereto.

[0083] Lithium secondary battery In one embodiment, a lithium secondary battery including the above-described positive electrode, negative electrode, and electrolyte 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 electrolytic solution.

[0084] Lithium secondary batteries can be classified into cylindrical, rectangular, pouch, coin, etc. depending on their form. FIGS. 1 to 4 are schematic views showing a lithium secondary battery according to one embodiment, and it can be said that FIG. 1 is circular, FIG. 2 is rectangular, 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 having 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 that seals the case 50 as shown in FIG. 1. Further, 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.

[0085] Negative electrode The negative electrode may include a current collector and a negative electrode active material layer positioned on the current collector, may include a negative electrode active material, and may further include a binder, a conductive material, or a combination thereof.

[0086] 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 undoping lithium, or a transition metal oxide.

[0087] Examples of the material capable of reversibly intercalating / deintercalating lithium ions include carbon-based negative electrode active materials, 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.

[0088] As the alloy of 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.

[0089] As the material capable of doping and undoping lithium, an Si-based negative electrode active material or an Sn-based negative electrode active material may be used. Examples of the Si-based negative electrode active material include 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. Examples of the Sn-based negative electrode active material include Sn, SnO 2 , an Sn alloy, or a combination thereof.

[0090] The silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle size D of the silicon-carbon composite particles 50 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 silicon particles are coated with amorphous carbon on 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 may also be located between the primary silicon particles, and for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be present dispersed in an amorphous carbon matrix.

[0091] The silicon-carbon composite may further contain 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.

[0092] 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. Further, 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.

[0093] 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 particles with a cumulative volume of 50% by volume in the particle size distribution.

[0094] 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 and the carbon-based negative electrode active material are used in mixture, the mixing ratio may be from 1:99 to 90:10 by weight.

[0095] 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.

[0096] 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.

[0097] 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, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0098] When using an aqueous binder 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, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof may be mixed and used. As the alkali metal, Na, K, or Li may be used.

[0099] 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.

[0100] Conductive material The conductive material is used to impart conductivity to the electrode, and in the battery being configured, any electron conductive material that does not cause a chemical change can be used. Specific examples include carbon-based substances such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, carbon nanotube; metal-based substances in the form of metal powder or metal fiber containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0101] 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.

[0102] 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, sheet, or foam. The thickness of the negative electrode current collector may be, for example, 1 μm to 20 μm, or may be 5 μm to 15 μm, or 7 μm to 10 μm.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] The non-aqueous organic solvent can be used alone or in a mixture of two or more. When used in a mixture 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.

[0107] 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.

[0108] 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.

[0109] The electrolytic solution may further contain vinyl ethyl carbonate, vinylene carbonate or an ethylene carbonate-based compound in order to improve the battery life.

[0110] 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.

[0111] 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 LiPF 6 、LiBF 4 、LiSbF 6 、LiAsF 6 、LiClO 4 、LiAlO 2 、LiAlCl 4 、LiPO 2 F 2 、LiCl、LiI、LiN(SO 3 C 2 F 5 ) 2 、Li(FSO 2 ) 2 N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC 4 F 9 SO 3 、LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2)(where x and y are integers from 1 to 20), and may contain one or more selected from lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFOB), and lithium bis(oxalate)borate (LiBOB).

[0112] The concentration of the lithium salt is preferably used in 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.

[0113] Separator A separator may be present between the positive electrode and the negative electrode depending on the type of the lithium secondary battery. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more of these 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.

[0114] The separator may include a porous substrate and a coating layer located on one or both sides of the porous substrate and containing an organic substance, an inorganic substance, or a combination thereof.

[0115] 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, polyether imide, polyamide imide, polybenzimidazole, polyether sulfone, 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.

[0116] The porous substrate may have a thickness of about 1 μm to 40 μm, for example, a thickness of 1 μm to 30 μm, 1 μm to 20 μm, 5 μm to 15 μm, or 10 μm to 15 μm.

[0117] The organic matter may include a (meth)acrylic copolymer containing a first structural unit derived from (meth)acrylamide and at least one of a second structural unit derived from (meth)acrylic acid or (meth)acrylate and a second structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof.

[0118] The inorganic matter is Al 2 O 3 SiO 2 TiO 2 SnO 2 CeO 2 MgO, NiO, CaO, GaO, ZnO, ZrO 2 Y 2 O 3 SrTiO 3 BaTiO 3 Mg(OH) 2 and may include inorganic particles selected from boehmite and combinations thereof, but is not limited thereto. The average particle size D of the inorganic particles 50It may be 1 nm to 2000 nm, for example, 100 nm to 1000 nm, or 100 nm to 700 nm.

[0119] The organic matter and the inorganic matter may be mixed and present in one coating layer, or may be present in a form in which a coating layer containing organic matter and a coating layer containing inorganic matter are laminated.

[0120] 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.

[0121] 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.

[0122] Example 1 1. Manufacture of positive electrode active material (1) Manufacture of nickel-based composite hydroxide A nickel-based composite hydroxide having fine pores inside the particles was produced through the following coprecipitation method. Nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in distilled water as a solvent so that the molar ratio was Ni:Co:Mn = 95:4:1 to prepare a metal raw material mixed solution. As a complexing agent, an aqueous ammonia (NH 4 OH) dilution and sodium hydroxide (NaOH) were prepared as a pH adjuster. The concentration of the aqueous ammonia was 10% by weight, and the concentration of the sodium hydroxide was 20% by weight. The metal raw material mixed solution, aqueous ammonia, and sodium hydroxide prepared inside the reactor were each charged.

[0123] After adjusting the pH inside the reactor to 11.75 and stirring for 10 hours (first step), the pH was lowered to 11.55 and stirred for 22 hours (second step) to generate a difference in synthesis rate between the inside and outside of the particles, and a nickel-based composite hydroxide having fine pores inside the particles was synthesized.

[0124] The slurry solution in the reactor was filtered, washed with high-purity distilled water, and then dried in a hot air oven at 180 °C for 24 hours to obtain a nickel-based composite hydroxide (Ni 0.95 Co 0.04 Mn 0.02 (OH) 2 ) having a hollow structure. It can be said that the obtained nickel-based composite hydroxide is in the form of secondary particles formed by the aggregation of a plurality of primary particles. The average particle diameter D 50 of the secondary particles measured through the SEM image was about 13.2 μm.

[0125] (2) Manufacture of positive electrode active material The prepared nickel-based composite hydroxide was mixed with anhydrous lithium hydroxide, Al 2 O 3 , and ZrO 2 . At this time, an anhydrous lithium salt was mixed so that the molar ratio of lithium to the total metal of the nickel-based composite hydroxide was 1.05. Also, with respect to the total of 100 mol% of the total metal of the nickel-based composite hydroxide, Al of Al 2 O 3 , and Zr of ZrO 2 , Al 2 O 3 was mixed so that Al was 1 mol%, and ZrO 2 was mixed so that Zr was 0.1 mol%.

[0126] This mixture was heat-treated at 810 °C for 8 hours in an oxygen atmosphere. The heat-treated product was confirmed to have a composition of Li 1.00 Ni 0.939 Co 0.04 Mn 0.01 Al 0.01 Zr 0.001 O 2 and to be in the form of hollow secondary particles. The SEM image of the surface of this secondary particle is shown in Figure 5. The average particle diameter D 50 of the secondary particles measured through SEM was about 13.5 μm, the average particle diameter D 50 of the primary particles forming the secondary particles was about 2.7 μm, and the size of the pores inside the secondary particles was about 4 μm.

[0127] The heat-treated product was pulverized in a jet mill with an air pressure of about 5 bar for 20 minutes to obtain a positive electrode active material in the form of single particles, and the SEM image thereof is shown in FIG. 6.

[0128] 2. Manufacture of lithium secondary battery 98.5% by weight of the produced 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, dried and rolled to produce a positive electrode. The produced positive electrode has a pulverized positive electrode active material in the form of single particles.

[0129] 97.5% by weight of a graphite negative electrode active material, 1.5% by weight of carboxymethyl cellulose, and 1% by weight of styrene-butadiene rubber were mixed in an aqueous solvent to produce a negative electrode active material layer slurry. The negative electrode active material layer slurry was coated on a copper foil current collector and dried and rolled to produce a negative electrode.

[0130] Using a polytetrafluoroethylene separator, an electrolyte in which 1M LiPF 6 was dissolved in a solvent in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 3:7 was used to produce a lithium secondary battery by a conventional method.

[0131] Example 2 In the production of the positive electrode active material, except that ZrO 2 O 3 of Al and ZrO 2 of Zr were mixed so that Zr was 0.2 mol% with respect to a total of 100 mol% of the entire metal of the nickel-based composite hydroxide, the positive electrode active material and the lithium secondary battery were produced in substantially the same manner as in Example 1. 2 FIG. 7 is an SEM image of the surface of the secondary particles produced in Example 2, and FIG. 8 is an SEM image of the pulverized single particles. The average particle diameter D of the secondary particles of one Example 2 measured through SEM

[0132] FIG. 7 is an SEM image of the surface of the secondary particles produced in Example 2, and FIG. 8 is an SEM image of the pulverized single particles. The average particle diameter D of the secondary particles of one Example 2 measured through SEM 50is about 14 μm, and is the average particle size D of the primary particles forming secondary particles 50 is confirmed to be about 2.7 μm.

[0133] Comparative Example 1 In the production of the positive electrode active material, except for not mixing ZrO 2 a positive electrode active material and a lithium secondary battery were produced in substantially the same manner as in Example 1. FIG. 9 is an SEM image of the surface of the secondary particles produced in Comparative Example 1.

[0134] In the case of Comparative Example 1, the primary particles forming the secondary particles did not crystallize into a sufficient size during the heat treatment process at 810° C., and the secondary particles were not pulverized during the jet mill process.

[0135] Comparing FIG. 9 of Comparative Example 1 with FIG. 5 of Example 1 and FIG. 7 of Example 2, under the same heat treatment temperature condition of 810° C., during the heat treatment, Al 2 O 3 , ZrO 2 is introduced at a certain content to perform Al and Zr doping, it can be confirmed that grain growth, that is, the growth of primary particles or the crystallization of primary particles is promoted.

[0136] Comparative Example 2 In the production of the positive electrode active material, with respect to the total 100 mol % of the entire metal of the nickel-based composite hydroxide, Al of Al 2 O 3 , and Zr of ZrO 2 , except that ZrO 2 is mixed so that Zr becomes 0.3 mol %, a positive electrode active material and a lithium secondary battery were produced in substantially the same manner as in Example 1. Comparative Example 2 is a case where the Al / Zr ratio is 3.33 and less than 5. FIG. 10 is an SEM image of the surface of the secondary particles produced in Comparative Example 2.

[0137] In the case of Comparative Example 2, it was confirmed that the primary particles overgrew and the initial charge / discharge capacity, efficiency, and life characteristics decreased.

[0138] Example 3 The positive electrode active material and the lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the heat treatment temperature was changed from 810 °C to 790 °C in the manufacture of the positive electrode active material.

[0139] FIG. 11 is an SEM image of the surface of the secondary particles manufactured in Example 3. The secondary particles were pulverized with a jet mill to obtain a positive electrode active material in the form of single particles.

[0140] Example 4 The positive electrode active material and the lithium secondary battery were manufactured in substantially the same manner as in Example 2, except that the heat treatment temperature was changed from 810 °C to 790 °C in the manufacture of the positive electrode active material.

[0141] FIG. 12 is an SEM image of the surface of the secondary particles manufactured in Example 4. The secondary particles were pulverized with a jet mill to obtain a positive electrode active material in the form of single particles.

[0142] Comparative Example 3 The positive electrode active material and the lithium secondary battery were manufactured in substantially the same manner as in Comparative Example 1, except that the heat treatment temperature was changed from 810 °C to 790 °C in the manufacture of the positive electrode active material.

[0143] FIG. 13 is an SEM image of the surface of the secondary particles manufactured in Comparative Example 3. Also in the case of Comparative Example 3, during the heat treatment process at 790 °C, the primary particles did not crystallize into a sufficient size, and the secondary particles were not pulverized during the jet mill process.

[0144] Even when comparing FIG. 13 of Comparative Example 3 with FIG. 11 of Example 3 and FIG. 12 of Example 4, under the same heat treatment temperature condition of 790 °C, during heat treatment, Al 2 O 3 , ZrO 2 was introduced at a certain content and Al and Zr doping were performed, it was confirmed that grain growth was promoted.

[0145] Example 5 The positive electrode active material and the lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the heat treatment temperature was changed from 810°C to 890°C in the manufacture of the positive electrode active material.

[0146] Figure 14 is an SEM image of the surface of the secondary particles manufactured in Example 5. The secondary particles were pulverized with a jet mill to obtain a positive electrode active material in the form of single particles.

[0147] Example 6 The positive electrode active material and the lithium secondary battery were manufactured in substantially the same manner as in Example 2, except that the heat treatment temperature was changed from 810°C to 890°C in the manufacture of the positive electrode active material.

[0148] Figure 15 is an SEM image of the surface of the secondary particles manufactured in Example 6. The secondary particles were pulverized with a jet mill to obtain a positive electrode active material in the form of single particles.

[0149] Comparative Example 4 The positive electrode active material and the lithium secondary battery were manufactured in substantially the same manner as in Comparative Example 1, except that the heat treatment temperature was changed from 810°C to 890°C in the manufacture of the positive electrode active material.

[0150] Figure 16 is an SEM image of the surface of the secondary particles manufactured in Comparative Example 4. Also in the case of Comparative Example 4, during the heat treatment process at 890°C, the particles did not crystallize into a sufficient size, and the secondary particles were not pulverized during the jet mill process.

[0151] Comparing Figure 16 of Comparative Example 4 with Figure 14 of Example 5 and Figure 15 of Example 6, even under the same heat treatment temperature condition of 890°C, it can be confirmed that the grain growth is promoted by introducing Al 2 O 3 and ZrO 2 at a certain content for Al and Zr doping.

[0152] Evaluation Example 1: Evaluation of life characteristics The lithium secondary batteries manufactured in Example 1, Example 2, and Comparative Example 1 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. Next, cycles of charging at 1.0C and discharging at 1.0C in the voltage range of 3.0V to 4.45V were repeated 30 times at 45°C. The ratio of the discharge capacity in each cycle to the initial discharge capacity is shown in Fig. 17. Referring to Fig. 17, in the case of Comparative Example 1, it can be confirmed that the single crystallization of the positive electrode active material was not performed, and the capacity retention rate decreased rapidly as the cycle was performed. On the other hand, it can be seen that Example 1 and Example 2 achieve excellent life characteristics.

[0153] As described above, the preferred embodiments have been described in detail. However, the scope 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 present invention.

Explanation of reference numerals

[0154] 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. The layered lithium-nickel composite oxide has a nickel content of 60 mol % or more, an aluminum content of 0.8 mol % to 1.5 mol %, and a zirconium content of 0.1 mol % to 0.3 mol %, based on 100 mol % of all metals excluding lithium, and the ratio of the aluminum content to the zirconium content (Al / Zr) is 5 or more, Average particle size D 50 The positive electrode active material has a single particle form with a particle size of 1 μm to 4 μm.

2. The positive electrode active material according to claim 1 , wherein the positive electrode active material is in the form of one separated single particle or two to nine single particles attached to each other.

3. The positive electrode active material according to claim 1 , wherein the layered lithium nickel composite oxide is represented by Chemical Formula 1: [Chemical formula 1] Li a1 N x1 M 1 y1 A z1 Zhr w1 O 2-b1 X b1 (In the above Chemical Formula 1, 0.9≦a1≦1.2, 0.6≦x1≦0.991, 0≦y1≦0.391, 0.008≦z1≦0.015, 0.001≦w1≦0.003, 0.9≦x1+y1+z1+w1≦1.1, and 0≦b1≦0.1; M 1 is one or more elements selected from B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zn, and X is one or more elements selected from F, P, and S.

4. A positive electrode current collector; A positive electrode comprising: a positive electrode active material layer located on the positive electrode current collector and comprising the positive electrode active material according to claim 1 .

5. The positive electrode active material layer is The second positive electrode active material may further include a second positive electrode active material having a secondary particle form formed by agglomeration of a plurality of primary particles, The second positive electrode active material includes a layered lithium-nickel-based composite oxide having a nickel content of 60 mol % or more, an aluminum content of 0.8 mol % to 1.5 mol %, a zirconium content of 0.1 mol % to 0.3 mol %, and a ratio of the aluminum content to the zirconium content (Al / Zr) of 5 or more, based on 100 mol % of the total metals excluding lithium, and the secondary particles have a hollow structure having pores therein, and the average particle diameter D of the primary particles constituting the secondary particles is 1.0 mol %. 50 The positive electrode of claim 4, wherein the thickness is from 1 μm to 4 μm.

6. The positive electrode according to claim 5 , wherein the layered lithium nickel composite oxide of the second positive electrode active material is represented by Chemical Formula 1: [Chemical formula 1] Li a1 N x1 M 1 y1 A z1 Zhr w1 O 2-b1 X b1 (In the above Chemical Formula 1, 0.9≦a1≦1.2, 0.6≦x1≦0.991, 0≦y1≦0.391, 0.008≦z1≦0.015, 0.001≦w1≦0.003, 0.9≦x1+y1+z1+w1≦1.1, and 0≦b1≦0.1; M 1 is one or more elements selected from B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zn, and X is one or more elements selected from F, P, and S.

7. The average particle size D of the secondary particles of the second positive electrode active material 50 The positive electrode of claim 5 , wherein the thickness is 10 μm to 20 μm.

8. The positive electrode of claim 7 , wherein the size of the internal pores of the secondary particles of the second positive electrode active material is 1 μm to 9 μm.

9. 6. The positive electrode of claim 5, wherein the first positive electrode active material is included in an amount of 5 wt% to 60 wt% and the second positive electrode active material is included in an amount of 40 wt% to 95 wt%, based on a total weight of the first positive electrode active material and the second positive electrode active material being 100 wt%.

10. Nickel precursor and M 1 A nickel-based composite hydroxide having micropores inside the particles is prepared by subjecting the precursors to a coprecipitation reaction; The nickel-based composite hydroxide, a lithium raw material, an aluminum raw material, and a zirconium raw material are mixed and heat-treated to produce hollow secondary particles having pores therein, the secondary particles being formed by agglomeration of a plurality of primary particles and including a layered lithium-nickel-based composite oxide; The secondary particles are pulverized, A method for producing a positive electrode active material, comprising obtaining a positive electrode active material, Said M 1 is one or more elements selected from B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zn; the aluminum content of the aluminum raw material is 0.8 mol % to 1.5 mol %, the zirconium content of the zirconium raw material is 0.1 mol % to 0.3 mol %, and a ratio of the aluminum content to the zirconium content (Al / Zr) is 5 or more, relative to a total of 100 weight % of all metals of the nickel-based composite hydroxide, the aluminum of the aluminum raw material, and the zirconium of the zirconium raw material.

11. 11. The method of claim 10, wherein the coprecipitation reaction includes a first step in which the reaction is performed in a pH range of 11 to 12, and a second step in which the reaction is performed at a pH lower than that of the first step.

12. The nickel-based composite hydroxide is represented by chemical formula 11, [Chemical formula 11] Ni x11 M 1 y11 (OH) 2 (In the above formula 11, 0.6≦x11<1, 0<y1≦0.4, and 0.9≦x11+y11≦1.1; M 1 is one or more elements selected from B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zn. The nickel-based composite hydroxide is non-crystalline, The method for producing a positive electrode active material according to claim 10, wherein the nickel-based composite hydroxide is in a particulate form, and the particulate includes an interior portion containing a large number of micropores and an exterior portion surrounding the interior portion and having a dense structure.

13. The lithium content of the lithium raw material is 0.9 to 1.2 molar parts per 1 molar part of the total of all the metals of the nickel-based composite hydroxide, the aluminum of the aluminum raw material, and the zirconium of the zirconium raw material; and The aluminum raw material is aluminum oxide, The method for producing a positive electrode active material according to claim 10 , wherein the zirconium raw material is a zirconium oxide.

14. The heat treatment is carried out in an oxidizing gas atmosphere at 700° C. to 900° C., and The method for producing a positive electrode active material according to claim 10, wherein an alkali-based grain growth promoter is not added during the process of mixing and heat-treating the nickel-based composite hydroxide, the lithium raw material, the aluminum raw material, and the zirconium raw material.

15. The layered lithium nickel composite oxide is represented by chemical formula 1, [Chemical formula 1] Li a1 N x1 M 1 y1 A z1 Zhr w1 O 2-b1 X b1 (In the above Chemical Formula 1, 0.9≦a1≦1.2, 0.6≦x1≦0.991, 0≦y1≦0.391, 0.008≦z1≦0.015, 0.001≦w1≦0.003, 0.9≦x1+y1+z1+w1≦1.1, and 0≦b1≦0.1; M 1 is one or more elements selected from B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zn, and X is one or more elements selected from F, P, and S. The average particle diameter D of the secondary particles 50 is between 10 μm and 20 μm, The average particle size D of the primary particles constituting the secondary particles 50 is between 1 μm and 4 μm, The method of claim 10, wherein the size of the pores inside the secondary particles is 1 μm to 9 μm.

16. The grinding is carried out in a jet mill or an air classifier grinder for 10 to 120 minutes; and The method for producing a positive electrode active material further includes a heat treatment after the grinding, The method for producing a positive electrode active material according to claim 10, wherein the re-heat treatment is carried out at 500° C. to 900° C. in an oxidizing gas atmosphere.

17. After the pulverization, the pulverized product is mixed with a coating material and then reheated; and The method for producing a positive electrode active material according to claim 16, wherein the coating raw material is a raw material of one or more elements selected from Al, B, Co, Mg, V, Zn, and Zr.

18. The obtained positive electrode active material had an average particle size D 50 The method for producing a positive electrode active material according to claim 10, wherein the positive electrode active material comprises single particles having a size of 1 μm to 4 μm.

19. The obtained positive electrode active material was Average particle size D 50 A first positive electrode active material in the form of a single particle having a particle size of 1 μm to 4 μm; a second positive electrode active material in the form of secondary particles formed by agglomeration of a plurality of primary particles, The average particle size D of the secondary particles of the second positive electrode active material 50 is 10 μm to 20 μm, and the average particle diameter D of the primary particles constituting the secondary particles is 50 The method for producing a positive electrode active material according to claim 10, wherein the thickness of the first electrode is 1 μm to 4 μm.

20. The positive electrode according to claim 4 , A negative electrode; and an electrolyte.

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